text:
# Classification of Casting MCQ Quiz - Objective Question with Answer for Classification of Casting - Download Free PDF

Last updated on Dec 22, 2022

## Latest Classification of Casting MCQ Objective Questions

#### Classification of Casting Question 1:

In which casting operation is an expandable pattern used?

1. Centrifugal
2. Slush
3. Squeeze
4. Investment

Option 4 : Investment

#### Classification of Casting Question 1 Detailed Solution

Explanation:

Investment Casting:

The process "Full - mould casting" also called "Cavity Less Casting" or "Investment Casting" or "Disposable pattern casting" is a variant of sand casting in the sense that the process utilizes an expendable pattern, which instead of being removed from the mould gets burnt and evaporated when the molten metal is poured into the mould.

The pattern material is expanded polystyrene foam.

Since the pattern gets destroyed in the process, the method is mainly used for product research in the foundry industry and for one - of - a kind complex casting. The method is also known as the "Lost Foam" process.

Slush casting:
Slush casting is a variation of the permanent mold process in which the metal is permitted to remain in the mold only until a shell of the desired thickness has formed. The mold is then inverted and the remaining liquid is poured out. Used for Hollow chin casting, toys, decorative items, statues, lampshades, thin section ornaments, etc.

Squeeze casting:

It is a process that is a combination of gravity and pressurized casting. In this process, molten metal is poured into a pre-heated die. When the filling is complete, a ram is used to slowly apply high pressure to the molten metalhead.

Centrifugal casting:

Molten metal is introduced into a rotating sand, metal, or graphite mould, and held against the mould wall by centrifugal force until it is solidified. Used for Hollow pipes, large bushings, gun barrels, etc.

#### Classification of Casting Question 2:

Which of the following is permanent mould casting process?

1. Centrifugal casting
2. Investment casting
3. Vacuum casting
4. Shell moulding

Option 1 : Centrifugal casting

#### Classification of Casting Question 2 Detailed Solution

Explanation:

Metal casting

It is defined as the process in which molten metal is poured into a mould that contains a hollow cavity of a required geometrical shape and allowed to cool down to form a solidified part.

There are basically three types of moulds used in casting:

1) Temporary mould

• Sand moulding
• Shell moulding
• Full moulding
• Investment moulding
• CO2 moulding

2) Permanent mould

• Centrifugal moulding
• Die moulding
• Slush moulding
• Squeeze moulding

3) Continuous casting

#### Classification of Casting Question 3:

Disk shaped parts are manufactured by ______

1. Centrifugal casting
2. Semi-centrifugal casting
3. Investment casting
4. Sand Casting

Option 2 : Semi-centrifugal casting

#### Classification of Casting Question 3 Detailed Solution

Explanation:

Semi - centrifugal Casting:

• When the moulds prepared by any of the techniques under expendable or permanent moulds are rotated about the central vertical axis and the casting is symmetrical about the axis of rotating that is the axis of the casting coincides with the axis of rotation), the process is called as "Semi-centrifugal casting".
• The centrifugal force aids the flow of the molten metal from a central feeding sprue and can thereby produce a somewhat more dense structure as compared to conventional sand casting.
• Casting shapes can be more complicated than true centrifugal casting Cores are used if central hole is needed, the spinning speed being considerably less than that for true centrifugal casting.
• An advantage of the process is that stack moulding can be used to cast many parts at the same time.

Product applications:

• Disk-shaped parts: wheels, rings, rollers, sheaves, pulleys, flywheels, gear blanks, Trubo-supercharger diaphragm disks and steel railroad wheels etc.

Centrifugal casting :

This is a process where the mould is rotated rapidly about its central axis as the metal is poured into it. Because of the centrifugal force, a continuous pressure will be acting on the metal as it solidifies. The slag, oxides and other inclusion being lighter get separated from the metal and segregates towards the centre. There three main types of centrifugal casting processes. They are :

1. True centrifugal casting: Horizontal or vertical axis of rotation
2. Semi centrifugal casting
3. Centrifuging

True centrifugal casting:

• The mould is rotated about a horizontal or a vertical axis and the molten metal is held against the walls of the mould by centrifugal force until it solidifies.
• The mould is rotated about a horizontal or a vertical axis. As it is rotating molten metal is held against the walls of the mould. Now, true centrifugal casting is used for the production of cylindrical hollow parts.
• Long parts are produced using a horizontal centrifugal casting process.
• Heavy parts whose diameter is more important than the length, are produced using a vertical centrifugal casting process.
• Usually, the centrifugal casting method is used for casting articles of symmetrical shape about the horizontal axis
• Cast iron and steel pipes, gun barrel are produced by this method., gun barrel

#### Classification of Casting Question 4:

In the CO2 method of core making, ______ is used as the binder.

1. water glass
2. synthetic resins
3. urea-formaldehyde
4. phenol formaldehyde

Option 1 : water glass

#### Classification of Casting Question 4 Detailed Solution

Explanation:

Core Sand:

• The core sand mainly consists of silica sand and an organic binder, with very little, if any, clay content.
• The presence of clay in core sand reduces its permeability and collapsibility.
• The core sand may contain small percentages of other constituents also, to enhance its properties.
• The common organic binders used in core sands include core oils, dextrin, cereals, sulfite liquor, molasses, resins and other commercial binding materials.
• The main ingredients of core oils are vegetable oils, for example linseed oil and corn oil. To these may be added: fish oil, petroleum oils and coal tar.
• Core oils impart sufficient strength and good collapsibility. In the CO2, method of core making, water glass (sodium silicate) is used as the binder.

#### Classification of Casting Question 5:

Low-pressure casting is a type of ______.

1. semi-permanent casting process
2. temporary mould casting process
3. expendable mould casting process
4. permanent mould casting process

Option 4 : permanent mould casting process

#### Classification of Casting Question 5 Detailed Solution

Explanation:

Casting:

Casting is one of the oldest manufacturing processes. It is the first step in making most of the products. A cast product or casting is produced by the pouring of molten metal into a mold where it then solidifies into a geometric shape. In other instances, molten metal is injected into a die having a cavity in the desired shape of the part.

Types of casting processes:

The three primary casting processes are:

1. Expendable mold/reusable pattern
2. Expendable mold/expendable pattern
3. Permanent mold/no pattern

1) Expendable mold/reusable pattern:

The expendable mold/reusable pattern method includes the sand mold, plaster mold, and ceramic mold casting. Sand mold casting is the most common with virtually no limit to the size of casting that can be made. Though not very precise in dimension or detail, sand mold casting is the least expensive.

2) Expendable mold/expendable pattern:

The expendable mold/expendable pattern method includes investment casting and evaporative foam casting. Investment casting is also known as the “lost-wax process” because the pattern material, wax, is consumed during the mold-making process. Some plastics may also be substituted for the more commonly used wax.

3) Permanent mold/no pattern:

Permanent mold/no pattern casting is initially very expensive in producing the mold, but such molds, machined out of metal or graphite, can be reused thousands of times.

Cores are also made of metal, but if sand is used then called semi-permanent mold casting.

Three variations of this method include

• Permanent-mold casting
• Die casting
• Centrifugal casting

The permanent mold method, because of the chilling effects of the molds, produces parts of superior mechanical properties, close tolerances, and smooth finishes. The method is well suited for casting nonferrous materials.

Low-pressure casting:

In the earlier casting process, metal flow in the mold cavity is by gravity pull, but in low-pressure casting, liquid metal is forced into the cavity under low pressure, app. 0.1 MPa, from beneath the surface so that metal flow is upward.

## Top Classification of Casting MCQ Objective Questions

#### Classification of Casting Question 6

In centrifugal casting method, ________ core is used.

1. sand
2. no
3. ferrous
4. Non-ferrous

Option 2 : no

#### Classification of Casting Question 6 Detailed Solution

Explanation:

Core:

• Cores are used to get the internal cavity in the castings.
• Cores are placed into the mould after the removal of the casting. These are made up of sand are used in permanent moulds also.
• The cores are surrounded by molten metal and therefore subjected to severe thermal and mechanical conditions.
• Core sand should be of higher strength than the moulding sand.

Centrifugal casting:

• In centrifugal casting, molten metal is poured into the revolving metallic mould.
• The molten metal falling into the centre of the mould at the axis of its rotation is whirled out by the power of centrifugal force towards the periphery and the impurities being lighter in weight, are left behind at the centre.
• Due to the application of centrifugal force, the casting is completely free from any porosity defect, denseness and strength are high and these castings have been proved as strong as forgings.
• Metal is filled due to centrifugal action hence hollow parts is produced without using core in this method.
• No gating element is used process is used to produce hollow cylindrical objects (symmetrical) in mass production without using core.

Application:

• Hollow cylindrical pipes.
• Gun barrels.
• Large size bushes.
• Propeller shafts.

#### Classification of Casting Question 7

Which one of the following casting processes produces the products with better surface finish?

1. Sand casting
2. Hot die casting
3. Investment casting
4. Cold die casting

Option 3 : Investment casting

#### Classification of Casting Question 7 Detailed Solution

Explanation:

Casting: It is a manufacturing process in which liquid material is filled into the mould, which contains a hollow cavity of the desired shape and then allowed to solidify. The solidified part is known as a casting, which injected or broken out of the mould to complete the process.

Investment casting:

• The investment casting process also called the lost-wax process begins with the production of wax replicas or patterns of the desired shape of the castings
• It is preferred where intricate shapes are required like jewellery, sewing machines, firearms, surgical and dental devices, turbine blades, gear impeller, hand tools, cranks, and levers.

Sand casting:

Steps involved in sand casting are:

• Make the pattern. The material of the pattern can be wood metal or plastic.
• With the help of a pattern prepare the mould and necessary cores.
• Melt the metal or alloy to be cast.
• Pour the molten metal or alloy into the mould cavity.
• Allow the molten metal to cool and solidify.
• Remove the casting from the mould. This operation is called a shakeout.
• Remove the defects if any and if possible.

Product application includes metallic components, taps, tools, and many more.

Centrifugal casting:

• This is a process where the mold is rotated rapidly about its central axis as the metal is poured into it. Because of the centrifugal force, continuous pressure will be acting on the metal as it solidifies.
• The slag, oxides, and other inclusions being lighter gets separated from the metal and segregates toward the center.
• There are three main types of centrifugal casting processes. They are,
• True centrifugal casting,
• Semi-centrifugal casting, and
• Centrifuging.

Die casting:

• Die casting is a moulding process in which the molten metal is injected under high pressure and velocity into a split mould die.
• It is also called pressure die casting.
• The split mould used under this type of casting is reusable.

Some parts produced by die-casting even do not require machining after casting or may require only light machining to achieve the desired dimensions.

#### Classification of Casting Question 8

A true centrifugal casting operation needs to be performed horizontally to make copper tube sections with outer diameter of 250 mm and inner diameter of 230 mm. The value of acceleration due to gravity, g = 10 m/s2. If a G-factor (ratio of centrifugal force to weight) of 60 is used for casting the tube, the rotational speed required is _____ rpm (round off to the nearest integer).

#### Classification of Casting Question 8 Detailed Solution

Concept:

G-factor is the ratio of centrifugal force to weight:

$$G =\frac{F_c}{mg} = \frac{mr\omega^2}{mg}$$

Calculation:

Given:

G-factor = 60, do = 250 mm = 0.25 m, g = 10 m/s2

$$G =\frac{F_c}{mg} = \frac{mr\omega^2}{mg}$$

For horizontal centrifugal casting, the outer radius is considered during the calculation.

$$G = \frac{mr\omega^2}{mg} = \frac{d_o}{2g}\left ( \frac{2\pi N}{60}\right )^2$$= 60

N = $$\sqrt{\frac{2\times60\times10}{0.25}}\times\frac{60}{2\pi}$$

N = 661.93 $$\approx$$ 662 rpm

#### Classification of Casting Question 9

Blow molding process to produce object such as bottles & floatable objects can be applied to only

1. Thermo setting plastics
2. Thermo plastics
3. Lamented plastics
4. Reinforced plastics

Option 2 : Thermo plastics

#### Classification of Casting Question 9 Detailed Solution

Explanation:

Blow Molding:

This is the most common method for manufacturing hollow articles from thermoplastics.

The most simple products and articles that are made by blow moulding are bottles, ventilation ducts, suitcases and fuel tanks for automobiles.

Thermoplastic:

• Plastics that can be deformed easily upon heating and can be bent easily.
• Linear polymers and a combination of linear and cross-linked polymers come under thermoplastics.
• Example: PVC, nylon, polythene, etc.

Thermosetting Plastics

• Plastics that cannot be softened again by heating once they are moulded.
• Heavily cross-linked polymers come under the category of thermosetting plastics.
• Thermosetting plastics have high melting points and tensile strength.
• Thermosetting plastic is high in molecular weight.
• High melting points and tensile strength signifies it is weldable plastic.
• Example: Bakelite, melamine, etc.

#### Classification of Casting Question 10

Gears are casted by-

1. Permanent mould casting
2. Slush casting
3. Centrifugal casting
4. All of the options

Option 1 : Permanent mould casting

#### Classification of Casting Question 10 Detailed Solution

Explanation:

Metal casting

• It is defined as the process in which molten metal is poured into a mould that contains a hollow cavity of a required geometrical shape and allowed to cool down to form a solidified part.
• There are basically three types of moulds used in casting:
1. Temporary mould
• Sand moulding
• Shell moulding
• Full moulding
• Investment moulding
• CO2 moulding
2. Permanent mould
• Centrifugal moulding
• Die moulding
• Slush moulding
• Squeeze moulding
3. Continuous casting

Die casting

• Die casting is a moulding process in which the molten metal is injected under high pressure and velocity into a split mould die.  It is also called pressure die casting.
• The split mould used under this type of casting is reusable.
• The gears are manufactured by this process

Advantages of the die casting process:

1. High production rate.
2. High accuracy in part dimensions.
3. Smooth surface finish for minimum mechanical finishing.
4. Ability to make many intricate parts such as hole opening slot trademark number etc.
5. Much thinner wall sections can be produced which can’t be produced by other casting methods.

Slush casting

• Slush casting is a variation of the permanent mold process in which the metal is permitted to remain in the mold only until a shell of the desired thickness has formed.
• The mould is then inverted and the remaining liquid is poured out.
• Used for Hollow chin casting, toys, decorative items, statues, lampshades, thin section ornaments etc.

Centrifugal casting

• In centrifugal casting, the metal is always pushed outward because of centrifugal force hence there is no need of a core for making the concentric hole.

#### Classification of Casting Question 11

In carbon dioxide moulding process, the binder used is:

1. Sodium bentonite
2. Calcium bentonite
3. Sodium silicate
4. Phenol formaldehyde

Option 3 : Sodium silicate

#### Classification of Casting Question 11 Detailed Solution

Explanation:

• This process is called the sodium silicate moulding process because, in this process, the refractory material is coated with a sodium-based binder.
• In this process, CO2 gas is passed through the core or mould. The CO2 chemically reacts with the odium silicate to cure or harden the binder.

#### Classification of Casting Question 12

A hot chamber die casting machine melts non-ferrous alloys which has a uniqueness of _______.

1. high temperature and pressure is used
2. melting pot may have any location
3. melting pot is separate from the machine
4. melting pot is an integral part of the machine

Option 4 : melting pot is an integral part of the machine

#### Classification of Casting Question 12 Detailed Solution

Explanation:

Hot-chamber die casting:

• It has a melting furnace as a part of the machine.
• It is used for low melting point metals such as Zn and Sn.
• It has greater molten metal contamination.
• Reduces time to deliver the liquid metal.

Cold – Chamber die casting:

• In this casting method, the furnace is separated from the casting unit.
• It is used to produce high melting point material casting.
• The force required to move the liquid metal into the die will be high when compared to hot chamber die casting.
• Brass, Copper Aluminium and Magnesium is commonly cold die-casting metals.

#### Classification of Casting Question 13

The most commonly used method for making Jewellery is:

1. Sand casting
2. Centrifugal casting
3. Die casting
4. Investment casting

Option 4 : Investment casting

#### Classification of Casting Question 13 Detailed Solution

Explanation:

Investment casting:

• The investment casting process also called the lost-wax process begins with the production of wax replicas or patterns of the desired shape of the castings
• It is preferred where intricate shapes are required like jewellery, sewing machines, firearms, surgical and dental devices, turbine blades, gear impeller, hand tools, cranks, and levers.

The investment casting process or lost wax process has the following steps:

1. Produce expendable wax, plastic, or polystyrene patterns.
2. Assemble these patterns onto a gating system
3. Investing or covering the pattern assembly with a refractory slurry
4. Melting the pattern assembly to remove the pattern material
5. Firing the mould to remove the last traces of the pattern material
6. Pouring molten metal
7. Knockout, cutoff, and finishing

As in this casting, the pattern disappears so this is also known as lost pattern casting.

Centrifugal casting:

• This is a process where the mold is rotated rapidly about its central axis as the metal is poured into it. Because of the centrifugal force, continuous pressure will be acting on the metal as it solidifies.
• The slag, oxides, and other inclusions being lighter gets separated from the metal and segregates toward the center.
• There are three main types of centrifugal casting processes. They are,
• True centrifugal casting,
• Semi-centrifugal casting, and
• Centrifuging.

Die casting:

• Die casting is a moulding process in which the molten metal is injected under high pressure and velocity into a split mould die.
• It is also called pressure die casting.
• The split mould used under this type of casting is reusable.

Advantages of the die casting process

1. High production rate.
2. High accuracy in part dimensions.
3. Smooth surface finish for minimum mechanical finishing.
4. Ability to make many intricate parts such as hole opening slot trademark number etc.
5. Much thinner wall sections can be produced which can’t be produced by another casting.
6. methods.

Some parts produced by die-casting even do not require machining after casting or may require only light machining to achieve the desired dimensions.

#### Classification of Casting Question 14

In casting process the molten metal when poured into mould, it will make a direct contact with __________.

1. backing sand
2. facing sand
3. core sand
4. parting sand

Option 2 : facing sand

#### Classification of Casting Question 14 Detailed Solution

Explanation:

Various type of materials is used in foundaries for the manufacturing of casting moulds. One of the essential constituents is sand. They are of many types which are mentioned below.

 Sand Properties Facing sand This sand is used directly next to the surface of the pattern and comes into contact with the molten metal when the mould is poured. It is subjected to severest conditions and must possess, therefore, high strength and refractoriness. This sand provides smoother casting surface. Baking sand This sand is used to back-up the facing sand and to fill the whole volume of the flask. Old repeatedly used sand is used for this purpose. System sand In mechanised foundries, where machine moulding is employed a so called “system sand” is used to fill the whole flask. The strength, refractoriness of the sand must be higher than that of backing sand. Parting sand This sand is used to prevent adhering of two halves of mould surfaces in each moulding box when they are separated. To ensure good parting, moulds surface should be treated with parting sand. Parting sand is sprinkled on the pattern surface to avoid its sticking and permits easy withdrawal from the mould.

#### Classification of Casting Question 15

Which of the following are advantages of die casting over sand casting?

1. Higher melting temperature metals
2. Higher production rates
3. Larger parts can be cast
4. Mold cannot be reused

Option 2 : Higher production rates

#### Classification of Casting Question 15 Detailed Solution

Explanation:

Die Casting:

• Die casting is a moulding process in which the molten metal is injected under high pressure and velocity into a split mould die.
• It is also called pressure die casting.
• The split mould used under this type of casting is reusable.

Advantages of the die casting process

1. High production rate.
2. High accuracy in part dimensions.
3. Smooth surface finish for minimum mechanical finishing.
4. Ability to make many intricate parts such as hole opening slot trademark number etc.
5. Much thinner wall sections can be produced which can’t be produced by another casting.
6. methods.

Some parts produced by die-casting even do not require machining after casting or may require only light machining to achieve the desired dimensions.

Sand casting:

Steps involved in sand casting are:

• Make the pattern. The material of the pattern can be wood metal or plastic.
• With the help of a pattern prepare the mould and necessary cores.
• Melt the metal or alloy to be cast.
• Pour the molten metal or alloy into the mould cavity.
• Allow the molten metal to cool and solidify.
• Remove the casting from the mould. This operation is called a shakeout.
• Clean and finish the casting which improves the surface appearance of the casting This operation is called fettling.
• Remove the defects if any and if possible.

Product application includes metallic components, taps, tools, and many more.


text:
miun.sePublikationer
Ändra sökning
Avgränsa sökresultatet
45678910 301 - 350 av 774
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
• apa
• ieee
• modern-language-association-8th-edition
• vancouver
• Annat format
Fler format
Språk
• de-DE
• en-GB
• en-US
• fi-FI
• nn-NO
• nn-NB
• sv-SE
• Annat språk
Fler språk
Utmatningsformat
• html
• text
• asciidoc
• rtf
Träffar per sida
• 5
• 10
• 20
• 50
• 100
• 250
Sortering
• Standard (Relevans)
• Författare A-Ö
• Författare Ö-A
• Titel A-Ö
• Titel Ö-A
• Publikationstyp A-Ö
• Publikationstyp Ö-A
• Äldst först
• Nyast först
• Disputationsdatum (tidigaste först)
• Disputationsdatum (senaste först)
• Standard (Relevans)
• Författare A-Ö
• Författare Ö-A
• Titel A-Ö
• Titel Ö-A
• Publikationstyp A-Ö
• Publikationstyp Ö-A
• Äldst först
• Nyast först
• Disputationsdatum (tidigaste först)
• Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
• 301.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Embodied energy and CO2 emission of wood- and concrete-framed buildings in Sweden: 2nd World Biomass Conference, Rome, Italy2004Konferensbidrag (Övrigt vetenskapligt)
• 302.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Variability in energy and carbon dioxide balances of wood and concrete building materials2006Ingår i: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 41, nr 7, s. 940-951Artikel i tidskrift (Refereegranskat)

A variety of factors affect the energy and CO2 balances of building materials over their lifecycle. Previous studies have shown that the use of wood for construction generally results in lower energy use and CO2 emission than does the use of concrete. To determine the uncertainties of this generality, we studied the changes in energy and CO2 balances caused by variation of key parameters in the manufacture and use of the materials comprising a wood- and a concrete-framed building. Parameters considered were clinker production efficiency, blending of cement, crushing of aggregate, recycling of steel, lumber drying efficiency, material transportation distance, carbon intensity of fossil fuel, recovery of logging, sawmill, construction and demolition residues for biofuel, and growth and exploitation of surplus forest not needed for wood material production. We found the materials of the wood-framed building had lower energy and CO2 balances than those of the concrete-framed building in all cases but one. Recovery of demolition and wood processing residues for use in place of fossil fuels contributed most significantly to the lower energy and CO2 balances of wood-framed building materials. We conclude that the use of wood building material instead of concrete, coupled with greater integration of wood by-products into energy systems, would be an effective means of reducing fossil fuel use and net CO2 emission to the atmosphere.

• 303.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Joanneum Research, Graz, Austria. Force Consulting Ltd, Rotorua, New Zealand.
Preface - Special issue: Efficient USE of biomass for mitigating climate change2006Ingår i: Mitigation and Adaptation Strategies for Global Change, ISSN 1381-2386, E-ISSN 1573-1596, Vol. 11, nr 5-6, s. 933-934Artikel i tidskrift (Refereegranskat)
• 304.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Substituting Fossil Fuels with Biomass1996Ingår i: Energy Conversion and Management, ISSN 0196-8904, Vol. 37, nr 6/8, s. 1211-1216Artikel i tidskrift (Refereegranskat)
• 305.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
Efficient Use of Forest Resources2003Ingår i: International Nordic Bioenergy Conference, September 3-5, 2003, Finland, 2003, s. 165-170Konferensbidrag (Övrigt vetenskapligt)
• 306. Gutman, I.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Estimating and approximating the total pi-electron energy of benzenoid hydrocarbons2000Ingår i: Zeitschrift fur Naturforschung A-A Journal of Physical Sciences, ISSN 0932-0784, E-ISSN 1865-7109, Vol. 55, nr 5, s. 507-512Artikel i tidskrift (Refereegranskat)

Lower and upper bounds as well as approximate formulas for the total pi-electron energy (E) of benzenoid hydrocarbons are deduced, depending only on the number of carbon atoms (n) and number of carbon-carbon bonds (m). These are better than the several previously known (n, m)-type estimates and approximations for E.

• 307. Gwinner, G.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Influence of magnetic fields on electron-ion recombination at very low energies2000Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 84, nr 21, s. 4822-4825Artikel i tidskrift (Refereegranskat)

Radiative recombination (inverse photoionization) is believed to be well understood since the beginning of quantum mechanics. Still, modern experiments consistently reveal excess recombination rates at very low electron-ion center-of-mass energies. In a detailed study on recombination of F and C ions with magnetically guided electrons we explored the yet unexplained rate enhancement, its dependence on the magnetic field B, the electron density n(e), and the beam temperatures T-perpendicular to and T-parallel to. The excess scales as T-perpendicular to(-1/2) and, surprisingly, as T-parallel to(-1/2), increases strongly with B, and is insensitive to n(e). This puts strong constraints on explanations of the enhancement.

• 308. Hansson, O
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Arbetstillfredsställelse i kundteam: en fallstudie på Frigoscandia Distribution AB (examensarbete)2002Rapport (Övrigt vetenskapligt)
• 309.
Luleå University of Technology.
Luleå University of Technology. Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
How successful Swedish organisations achieve sustaniable health2005Ingår i: International Journal of Management Practice, ISSN 1477-9064, E-ISSN 1741-8143, Vol. 1, nr 3, s. 233-250Artikel i tidskrift (Refereegranskat)

The costs connected to the rapidly increasing sick leaves have risen to alarming levels in Sweden and, for instance, Norway and the Netherlands. To find out how to handle the situation on an organizational level, a case study of two organizations has been carried out, which are recognized and have been awarded for their excellence in methodologies for decreasing the number of sick leaves. One is a small manufacturing company and the other one is a large public health care organization. Both organizations are non-hierarchical with responsibility and authority delegated to different groups. The data collection has mainly been carried out through brainstorming in groups, structured in tree diagrams, complemented by interviews. Important working methods for mangers are low-prestige, visibility and functioning as coaches with activities aimed at building relations. On the basis of the result of this study, suggestions are presented which are considered possible for others to adopt.

• 310.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Kompostering av organiskt avfall i jämtländsk glesbygd - en förstudie1998Rapport (Övrigt vetenskapligt)
• 311. Havila, V
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
International business-relationship triads2004Ingår i: International Marketing Review, ISSN 0265-1335, E-ISSN 1758-6763, Vol. 21, nr 2, s. 172-186Artikel i tidskrift (Refereegranskat)

• 312. Hayderer, G.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Threshold for Potential Sputtering of LiF1999Ingår i: Physical Review Letters, ISSN 0031-9007, Vol. 83, nr 19, s. 3948-3951Artikel i tidskrift (Refereegranskat)

• 313. He, J H
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Research progress on biomass fuel ethanolManuskript (Övrig (populärvetenskap, debatt, mm))

Advances of domestic and overseas biomass fuel ethanol is outlined in this paper. Having evaluated its economic, energy, environmental and social benefits, thereafter its importance as a part of Chinese energy strategy had been confirmed. Finally, a feasible scheme for fuel ethanol production from biomass in large scale is suggested, used for reference.

• 314.
Huazhong University of Science and Technology, Wuhan, 430074, China.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
A study on latent heat storage exchangers with the high-temperature phase-change material2001Ingår i: International Journal of Energy Research, ISSN 0363-907X, Vol. 25, nr 4, s. 331-341Artikel i tidskrift (Refereegranskat)

This paper presents a theoretical analysis and an experimental test on a shell-and-tube latent heat storage exchanger. The heat exchanger is used to recover high temperature waste heat from industrial furnaces and off-peak electricity. It can also be integrated into a renewable energy system as an energy storage component. A mathematical model describing the unsteady freezing problem coupled with forced convection is solved numerically to predict the performance of the heat exchanger. It provides a basis for optimum design of the heat exchanger. The experimental study on the heat exchanger is carried out under various operating conditions. Effects of various parameters, such as the inlet temperature, the mass flow rate, the thickness of the phase change material and the length of the pipes, on the heat transfer performance of the unit are discussed by combining with theoretical prediction. Criterion for analyzing and evaluating the performance of heat exchanger is also proposed.

• 315.
Umeå universitet.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Resultat och erfarenheter av nationella prov på gymnasiet2000Ingår i: Dokumentation av 11:e Matematikbiennalen, Göteborg 27-29 januari 2000: tid för matematik, Göteborg: Nationellt centrum för matematikutbildn., Univ. , 2000, s. 679-Konferensbidrag (Övrigt vetenskapligt)
• 316. Hemmers, O.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Dipole and nondipole angular-distribution effects in valence photoemission from neon2002Ingår i: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, Vol. 123, nr 2-3, s. 257-264Artikel i tidskrift (Refereegranskat)

Nondipole angular-distribution parameters γ and δ for neon 2s and 2p photoelectrons have been measured and are compared to all available theoretical data. The agreement is very good throughout the 150-1200 eV photon-energy range studied. Furthermore, the neon 2p dipole angular-distribution parameter β and the 2s to 2p cross-section ratio have been measured throughout the same photon-energy range. The agreement between theoretical data and experiment is excellent.

• 317.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Aspects of predicting fracture in paper with the cohesive zone model combined with an elastic-plastic material model with kinematical hardening2004Rapport (Övrigt vetenskapligt)
• 318.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Determination of the cohesive stress-displacement relation aimed at prediction of fracture in paper2003Rapport (Övrigt vetenskapligt)
• 319. Hemp, John
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Problems in the Theory and Design of Electromagnetic Flowmeters for Dielectric Fluids: Part 1: Experimental Assessment of Static Charge Noise Levels and Signal-to-Noise Ratio2002Ingår i: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 13, nr 4, s. 143-145Artikel i tidskrift (Refereegranskat)

This paper reports on experimental measurements of electrode signal noise spectra in an electromagnetic flowmeter designed for

flow measurement of the dielectric liquid BP180. The design of the flowmeter tube and the detection electronics is described.

Dependence of the noise spectra on flow rate, electrode dimensions and particle content of the liquid is reported. Implications for

flowmeter tube design and for the choice of frequency of operation to achieve reasonable signal-to-noise ratios are explained.

• 320. Holm, P
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Solidification Experiments in Mirror Furnaces Flown in a GAS Payload on Space Shuttle STS-1082003Ingår i: Proceedings of the 16th ESA Symposium on European Rocket and Balloon Programmes and Related Research, 2003, s. 113-117Konferensbidrag (Övrigt vetenskapligt)

Solidification Experiments in Mirror Furnaces Flown in a GAS Payload on Space Shuttle STS-108

• 321.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Cross-country Skiing Biomechanics using the AnyBody Modeling System2007Ingår i: ANSYS Conference & 25th CADFEM Users´ Meeting 2007, Dresden, 2007Konferensbidrag (Refereegranskat)
• 322.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Optimering av biomekaniska system2001Ingår i: SMD 01 - Svenska mekanikdagar Linköping 11-13 juni 2001: Svenska mekanikdagar (2001 : Linköping), Stockholm: Svenska nationalkommittén för mekanik , 2001, s. 195-Konferensbidrag (Övrigt vetenskapligt)
• 323.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Using Double‐Poling Simulations to Study the Load Distribution between Teres Major and Latissimus Dorsi2007Ingår i: Science and Nordic Skiing, Oxford: Meyer & Meyer Sport, 2007, s. 81-89Konferensbidrag (Refereegranskat)
• 324.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
VerOpt - MATLAB Driven Versatile Optimization2001Ingår i: Program and proceedings for the Nordic MATLAB Conference Oslo, October 17-18, 2001, Trondheim: Comsol , 2001, s. 207-212Konferensbidrag (Övrigt vetenskapligt)

VerOpt, a MATLAB driven versatile optimization environment, enables the choice of a suitable optimization routine, parallelization over TCP/IP and the use of external solvers. VerOpt is the result of working towards the creation of a versatile yet effective environment for applied optimization studies. This paper presents the concepts behind VerOpt, including how and why we use parallelization, and the lessons learnt when using external solvers. The paper also gives a comparison of implemented optimization routines when applied to test problems. Currently, links to three external solvers are implemented. Two of them come from the commercial software market for engineering solutions: ANSYS (version 5.6 University High), a general purpose FE-code and C-MOLD (version 2000.7.1), a code for injection molding. The third solver is from the academic world, AnyBody, a code for biomechanical studies. The implemented optimization routines referred to are Method of Moving Asymptotes (MMA), Simulated Annealing (SA) and a genetic algorithm (GA). The MMA is a gradient-based algorithm whereas the other two can be classified as stochastic. The results of the comparison of the implemented optimization routines, in which �fmincon� from the MATLAB Optimization Toolbox is also used, show that MMA is generally the fastest routine, but does not always find the best solution. However, in test cases when parallelization is used the comparison is not ideal, since the parallelization procedures for the algorithms are not equivalent. When optimization routines are based on numerically computed gradients, such as MMA, they are embarrassingly parallel. This is because the gradients are independent of each other, which makes it possible to compute them simultaneously, but on different processors. For a stochastic routine such as SA a different approach is needed. In our case we have used a simple form of domain decomposition. An interesting result is that, in the test case involving ANSYS, we found that using ANSYS alone, as solver as well as optimizer, did not give such a good solution as using VerOpt. A clear future development is to add a greater number of different types of optimization routines. A possible future development is to transform VerOpt into something that is more akin to a regular style MATLAB Toolbox. Irrespective of this development, VerOpt will be a significant aid for education as well as research in applied optimization. It will also serve the authors as the environment for further research in the fields of injection molding and biomechanics.

• 325.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
A biomechanical model of a double-poling skier2003Ingår i: International Society of Biomechanics XIXth Congress, 6-11 July 2003, Dunedin, New Zealand, CD ROM - Abstracs and Proceeding, Dunedin, N.Z: University of Otago , 2003Konferensbidrag (Refereegranskat)

Up till now, very little has been done in the field of cross-country skiing biomechanics using numerical techniques. This paper presents a biomechanical model of a double-poling skier that is created with the use of AnyBody, a general body-modeling and optimization software. As an aid to validate the model, a physical experiment is performed. An elite female skier is video-taped while using a double-poling ergometer. This experiment provides measurements of movement and poling power. Simulation results agree well with an experiment concerning muscle activation sequences (Nilsson and Holmberg, 2000). However, when simulation results and measured poling power are compared, agreement is not good. This means that further work on the biomechanical model is needed before it can be validated as a good representation of reality. Still, the method shows potential, and the present model could be used for initial studies of the double-poling technique. When the model is validated, it could provide a very useful tool in the quest for gold medals and perhaps, more importantly, for the prevention of injuries.

• 326.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Efficient use of wood - a comparison between chemical and mechanical pulping2005Ingår i: Proceedings of the 14th European Biomass Conference and exhibition: Biomass for Energy, Industry and Climate Protection, Florence: ETA - Renewable energies , 2005Konferensbidrag (Övrigt vetenskapligt)

The pulp and paper industry is energy intensive and consumes large amounts of wood. Here, the total biomass use is estimated for the production of one tonne paper in a cradle-to-factory gate scope, assuming that all energy, including electricity and motor fuels, are produced from forest biomass. We consider the production of newsprint made from mechanical pulp; lightweight coated paper from a mixture of mechanical and chemical pulp; and fine paper from chemical pulp, under Swedish conditions. The results indicate that chemical pulp papers require less biomass resources per tonne of paper produced than do mechanical pulp papers. For mechanical pulp papers, external electricity requires the largest part of the biomass. Motor fuel production accounts in no case for more than 10%. Between 27% and 38% of the total biomass used is embodied in the paper product, indicating that waste paper recovery options are important.

• 327.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Biomass use in chemical and mechanical pulping with biomass-based energy supply2007Ingår i: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 52, nr 2, s. 331-350Artikel i tidskrift (Refereegranskat)

The pulp and paper industry is energy intensive and consumes large amounts of wood. Biomass is a limited resource and its efficient use is therefore important. In this study, the total amount of biomass used for pulp and for energy is estimated for the production of several woodfree (containing only chemical pulp) and mechanical (containing mechanical pulp) printing paper products, under Swedish conditions. Chemical pulp mills today are largely self-sufficient in energy while mechanical pulp mills depend on large amounts of external electricity. Technically, all energy used in pulp- and papermaking can be biomass based. Here, we assume that all energy used, including external electricity and motor fuels, is based on forest biomass. The whole cradle-to-gate chain is included in the analyses. The results indicate that the total amount of biomass required per tonne paper is slightly lower for woodfree than for mechanical paper. For the biomass use per paper area, the paper grammage is decisive. If the grammage can be lowered by increasing the proportion of mechanical pulp, this may lower the biomass use per paper area, despite the higher biomass use per unit mass in mechanical paper. In the production of woodfree paper, energy recovery from residues in the mill accounts for most of the biomass use, while external electricity production accounts for the largest part for mechanical paper. Motor fuel production accounts for 5–7% of the biomass use. The biomass contained in the final paper product is 21–42% of the total biomass use, indicating that waste paper recovery is important. The biomass use was found to be about 15–17% lower for modelled, modern mills compared with mills representative of today's average technology.

• 328. Holmberg,, Jonas M
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Efficient wood use - a comparison between chemical and mechanical pulping2005Ingår i: Biomass for energy, industry and climate protection :: 14th European Biomass Conference & Exhibition ; proceedings of the international conference held in Paris, France, 17 - 21 October 2005, [Florence]: ETA-Renewable Energies, , 2005Kapitel i bok, del av antologi (Övrigt vetenskapligt)

The pulp and paper industry is energy intensive and consumes large amounts of wood. Here, the total biomass use is estimated for the production of one tonne paper in a cradle-to-factory gate scope, assuming that all energy, including electricity and motor fuels, are produced from forest biomass. We consider the production of newsprint made from mechanical pulp; lightweight coated paper from a mixture of mechanical and chemical pulp; and fine paper from chemical pulp, under Swedish conditions. The results indicate that chemical pulp papers require less biomass resources per tonne of paper produced than do mechanical pulp papers. For mechanical pulp papers, external electricity requires the largest part of the biomass. Motor fuel production accounts in no case for more than 10%. Between 27% and 38% of the total biomass used is embodied in the paper product, indicating that waste paper recovery options are important.

• 329.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Systems aspects on new energy technologies in the pulp and paper industry2007Ingår i: Proceedings. 3rd International Green Energy Conference IGEC-III June 18 - 20, 2007 Västerås, Sweden, 2007Konferensbidrag (Refereegranskat)

Concerns about energy security, energy prices, and the impact of energy use on the global climate have put focus on ways to reduce CO2 emissions and oil dependency. In this paper we examine consequences of new energy technologies in the pulp and paper industry and estimate the costs for achieving certain CO2 emissions and oil use reductions with different pulp mill technologies. Stand-alone production of electricity and transportation fuel from biomass is included to balance the systems compared, so that they produce the same CO2 emission and oil use reductions. The technologies considered are black liquor gasification (BLG) with electricity and motor fuels production in chemical pulp mills and increased energy efficiency in mechanical pulp mills. The entire production chain from the extraction of primary resources is included in the analysis. Changes in the production chain are assumed to affect energy production on the margin. The technology alternatives are evaluated with respect to five parameters: Net CO2 emission, oil use, primary energy use, biomass use and monetary cost. We find that BLG in chemical pulp mills is favourable compared to stand-alone production of fuels and electricity from biomass. If both CO2 emission reductions and oil use reductions are to be achieved, it is more efficient to implement BLG with motor fuels production and stand-alone electricity production from biomass, than to implement BLG with electricity production and stand-alone production of motor fuels. Increased energy efficiency in refining of thermomechanical pulp is found to achieve CO2 savings more efficiently than stand-alone production of electricity from biomass.

• 330.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Mittuniversitetet, Fakulteten för humanvetenskap, Institutionen för hälsovetenskap.
The role of triceps in double poling biomechanics, an introductory study2007Ingår i: Proceedings of the 4th International Congress on Science and Skiing (2007). St. Cristoph am Aarlberg, Austria., 2007Konferensbidrag (Övrigt vetenskapligt)
• 331.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
A Darcy law for quasi-periodic porous media and optimal design of composite materials1996Ingår i: Proceedings of international Conference on Composites Engineering ICCE/3: 21-25/7 -96, New Orleans, LA, USA, 1996, s. 363-364Konferensbidrag (Övrigt vetenskapligt)
• 332.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
A model for non-linear nonstationary heat conduction in composites with many small nonperiodic perforations1997Ingår i: Proceedings of International Conference on Composites Engineering ICCE/4: 6-12/7, 1997, Hawaii, USA, 1997, s. 435-344Konferensbidrag (Övrigt vetenskapligt)
• 333.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Homogenization applied to some problems in mechanics1993Licentiatavhandling, monografi (Övrigt vetenskapligt)
• 334.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Homogenization in various kinds of quasi-periodic domains1995Rapport (Övrigt vetenskapligt)
• 335.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Homogenization of parabolic equations: an alternative approach and some corrector type results.1997Ingår i: Applications of Mathematics, ISSN 0862-7940, Vol. 42, nr 5, s. 321-343Artikel i tidskrift (Refereegranskat)

We extend and complete some quite recent results by Nguetseng and Allaire concerning two-scale convergence. In particular, a compactness result for a certain class of parameterdependent functions is proved and applied to perform an alternative homogenization procedure for linear parabolic equations with coefficients oscillating in both their space and time variables. For different speeds of oscillation in the time variable, this results in three cases. Further, we prove some corrector-type results and benefit from some interpolation properties of Sobolev spaces to identify regularity assumptions strong enough for suck results to hold.

• 336.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
On homogenization and correctors for elliptic equations with mixed boundary conditions in periodic domains1995Rapport (Övrigt vetenskapligt)
• 337.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
On homogenization applied to Stokes flow in porous media. A brief discussion of geometrical modelling and possible applications1992Ingår i: Proceedings of the Industrial Mathematics Week: Trondheim August 1992, Department of Mathematical Sciences, NTH, 1992, s. 152-159Konferensbidrag (Övrigt vetenskapligt)
• 338.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
On homogenization theory and its application to optimal micro-design of composite materials1994Rapport (Övrigt vetenskapligt)
• 339.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
On homogenization theory and its application to optimal micro-design of composite materials1994Ingår i: Proceedings of International Conference on Composites Engineering ICCE/1: New Orleans, LA, USA, Aug 28-31, 1994, 1994, s. 749-750Konferensbidrag (Övrigt vetenskapligt)
• 340.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Some modes of convergence and their application to homogenization and optimal composites design1996Doktorsavhandling, monografi (Övrigt vetenskapligt)

In this thesis, we develop, extend, apply, and discuss a number of methods for the study of limits of sequences of functions and operators. The connection between the notion of two-scale convergence and more general concepts of convergence is investigated and some alternative classes of admissible test functions are characterized. These techniques are extended into compactness results suitable to prove homogenization and corrector results for linear parabolic equations. A further refinement of these methods, together with a characterization of the limits of certain sequences of parameter-dependent functions which has been subject to extension from a quite general class of periodic domains, is introduced. This provides an efficient tool for the homogenization of e.g. nonlinear evolution heat conduction in heterogeneous materials which vibrate with high frequencies or are perforated by periodically arranged nonconducting holes. Moreover, we prove compactness and homogenization for sequences of solutions of linear elliptic and monotone parabolic equations defined in some classes of nonperiodic domains and derive a Darcy's law for a type of nonperiodic porous media. In the linear elliptic case the convergence is strengthened by means of correctors. Finally, we present some numerical results for homogenized stiffness of fibre composites and demonstrate how homogenization techniques for elasticity in composite materials and for liquid flow in porous media can be combined with recent optimization techniques to obtain optimal layout of composite materials.

• 341.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
The concept of parabolic two-scale convergence, a new compactness result and its application to homogenization of evolution partial differential equations1994Rapport (Övrigt vetenskapligt)
• 342.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Theorie des skis paraboliques1998Ingår i: L'Entraineur de ski alpin, ISSN 0983-9305, Vol. 27, nr septArtikel i tidskrift (Övrigt vetenskapligt)
• 343.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik. Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
On the determination of limits for some sequences of functions and differential operators2006Ingår i: Canadian Applied Mathematics Quarterly, ISSN 1073-1849, Vol. 14, nr 3, s. 299-329Artikel i tidskrift (Refereegranskat)

This article deals with homogenization methods, namely two-scale convergence and Hconvergence, with the aim of comparing their efficiency in studying composite materials. Analytic examples are given to illustrate both methods. While compensated compactness allows one to determine the limit of a product of two weakly converging sequences under additional assumptions on the derivatives, two-scale convergence takes advantage of underlying oscillations of solution sequences and H-convergence is concerned with the operator behaviour. Special attention is paid to periodic homogenization as this case yields the most involved results. Numerical experiments are used to investigate open questions in H-convergence dealing with the possible relaxation of some convergence hypotheses. Partial results are established in this respect.

• 344.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
A homogenization procedure for computing effective moduli and micro stresses in elastic composite materials1992Ingår i: Composites Part B: Engineering, ISSN 1359-8368, Vol. 2, nr 4, s. 249-259Artikel i tidskrift (Refereegranskat)
• 345.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
On a convergence result for sequences of functions with multiple scales2006Ingår i: Proceedings of the 9th WSEAS international conference on applied mathematics, Istanbul. Turkey., Aten: WSEAS press , 2006Konferensbidrag (Refereegranskat)
• 346.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
On the characterization of effective properties in highly heterogeneous media2005Ingår i: IASME transactions / International ASsociation of Mechanical Engineers, ISSN 1790-031X, Vol. 2, s. 177-179Artikel i tidskrift (Refereegranskat)

We discuss methods related to homogenization theory and G-convergence for the computation of effective properties in heterogeneous materials. Especially we investigate a method to detect deviations from the arithmetic mean in heterogeneous materials that are not necessarily periodic.

• 347.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
On the characterization of G-limits by means of some generalized two-scale techniques: Paper presented at the 26th Midwest-Pacific Differential Equations Conference, October 15-17, 2005, University of Alberta Edmonton, Alberta, Canada2005Konferensbidrag (Refereegranskat)

G-convergence usually deals with the convergence of sequences of elliptic or parabolic operators. When the convergence of the sequence of operators is strong enough, it is trivial to determine the $G$-limit. Other cases need sophisticated techniques for this aim, where the most well investigated case is periodic homogenization. The main tool of today for this purpose has become the so called two-scale convergence method by Nguetseng. This approach relies on a fundamental compactness result which says that for any bounded sequence $\left\{ u_{h}\right\}$ in $L^{2}\left( \Omega \right)$ there is $u_{0}\in L^{2}\left( \Omega \times Y\right)$ such that \begin{equation*} \dint\nolimits_{\Omega }u_{h}(x)\tau _{h}v(x)dx\rightarrow \dint\nolimits_{\Omega} \dint\nolimits_{Y}u_{0}(x,y)v(x,y)dxdy\end{equation*}% for any $v\in X=L^{2}(\Omega ;C_{\sharp }(Y))$ up to a subsequence, where% \begin{equation*} \tau _{h}v(x)=v(x,\frac{x}{\varepsilon _{h}}),\varepsilon _{h}\rightarrow 0% \text{.}\end{equation*} For gradients of sequences $\left\{ u_{h}\right\}$ bounded in $H^{1}\left( \Omega \right)$ the deviation from the week limit can be made explicit in terms of a local gradient $\nabla _{y}u_{1}$, $u_{1}\in L^{2}(\Omega;H_{\sharp }^{1}(Y))$, and this is the key to the characterization of the $G$%-limit. Similar techniques can be developed for other choices of the maps $\tau _{h}$ and admissible spaces $X$ which do not necessarily depend on any periodicity assumptions. We study such examples with respect to the possible appearance of residual terms corresponding to $\nabla _{y}u_{1}$ in periodic homogenization. In particular $G$-limits for problems, where the matrices defining the operators are generated by a kind of modified Hilbert-Schmidt operators, are investigated with respect to such deviations.

• 348.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
On the convergence of some pairs of weakly convergent sequences: Presented at the Applmath05 Fourth conference on applied mathematics and scientific computing June 19-24 Brijuni Island, Croatia2005Konferensbidrag (Övrigt vetenskapligt)
• 349.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
On the convergence of some sequences of oscillating functionals2006Ingår i: WSEAS transactions on mathematics, ISSN 1109-2769, Vol. 5, nr 8, s. 951-956Artikel i tidskrift (Refereegranskat)

We study an intermediate case between the two-scale convergence of Nguetseng and the more general concept of scale convergence of Mascarenhas and Toader. Suitable assumptions to provide scale convergence with some of the most essential properties of two-scale convergence are identified. Some aspects of the characterization of limits for sequences of gradients are discussed briefly.

• 350.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
On the characterization of effective properties in highly heterogeneous media (Proc.)2005Ingår i: Proceedings of the WSEAS HEAT '06, FLUID '06 : Elounda, Agios Nikolaos, Crete Island, Greece, August 21 - 23, 2006 ; 4th IASME/WSEAS International Conference on Heat Transfer, Thermal Engineering and Environment, 4th IASME/WSEAS International Conference on Fluid Mechanics and Aerodynamics Elounda, Greece, 2006, Elounda, Greece,, 2005, , s. -Konferensbidrag (Refereegranskat)

We discuss methods related to homogenization theory and G-convergence for the computation of effective properties in heterogeneous materials. Especially we investigate a method to detect deviations from the arithmetic mean in heterogeneous materials that are not necessarily periodic.

45678910 301 - 350 av 774
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
• apa
• ieee
• modern-language-association-8th-edition
• vancouver
• Annat format
Fler format
Språk
• de-DE
• en-GB
• en-US
• fi-FI
• nn-NO
• nn-NB
• sv-SE
• Annat språk
Fler språk
Utmatningsformat
• html
• text
• asciidoc
• rtf

format: plain


text:
# Thread: Can I replace paragraphs using sed?

1. Registered User
Join Date
Aug 2003
Posts
4

## Unanswered: Can I replace paragraphs using sed?

Hi,
I have this problem and I wish to know is there an easy way to solve it.

I have a file containing in it couples of lines with a specific format (among many other lines).
The format of the couples look like that:
rocks 20
books 12

or:
rocks 32
books 7

etc..
the numbers follow rocks and books could be any numbers.

I want to get 4 numbers as parameters and than to check these couples at the file for a match, if there is a match than the numbers of these certain couples at the file should be replace.

example:

the file a.txt starts here
the numbers
is it true
rocks 20
books 12
yes
I want to be there
rocks 12
books 20
rocks 65
books 17
why is it
rocks 20
books 12
so difficult
rocks 20
books 78
the file a.txt ends here

Now if I get the parameters : 20 12 100 200

than it means that I should look for the couples:
rocks 20
books 12
and change them to:
rocks 100
books 200

the file after the changes should look like that:

the file a.txt starts here
the numbers
is it true
rocks 100
books 200
yes
I want to be there
rocks 12
books 20
rocks 65
books 17
why is it
rocks 100
books 200
so difficult
rocks 20
books 78
the file a.txt ends here

Is it possible to use the sed command in order to search for a pattern of 2 lines with the first 2 numbers :
rocks 20
books 12

and than to replace them with the last 2 numbers?
rocks 100
books 200

I need to know is there a short easy way with sed or should I write scripts to solve that,

Join Date
Jun 2002
Location
UK
Posts
525
I'm not entirely sure what you are trying to do but I think I get the jist of it.

The following example would do the sort of thing you are asking using awk. Just pass in the type (rocks or books), the existing count and the replacement count.

awk '$1==type &&$2==count {sub(/.*/,newCount,$2)}{print}' type=rocks count=40 newCount=100 < yourFile In sed, you would want to control the parameters using the shell. The example below assumes that the type and the count are separated by a single space and that there is no leading or trailing whitespace. type=rocks; count=40; newCount=100 sed "/^$type $count$/s/$count/$newcount/" < yourFile

3. Registered User
Join Date
Aug 2003
Posts
4
Originally posted by Damian Ibbotson
I'm not entirely sure what you are trying to do but I think I get the jist of it.

The following example would do the sort of thing you are asking using awk. Just pass in the type (rocks or books), the existing count and the replacement count.

awk '$1==type &&$2==count {sub(/.*/,newCount,$2)}{print}' type=rocks count=40 newCount=100 < yourFile In sed, you would want to control the parameters using the shell. The example below assumes that the type and the count are separated by a single space and that there is no leading or trailing whitespace. type=rocks; count=40; newCount=100 sed "/^$type $count$/s/$count/$newcount/" < yourFile
Hello damian,

However the most important thing is that the two lines appear one after the other
and only in that format exactly :
rocks 12
books 20

than, if that is the situation, I want to replace these 2 lines to:
rocks 100
books 200

If for example the line:
rocks 12

appears and not followed by the line:
books 20

than I don't want to change it at all.

I wanted to know whether sed can find a pattern of 2 lines:
rocks 12
books 20

and replace it by
rocks 100
books 200

Regards meirav

Join Date
Jun 2002
Location
UK
Posts
525
Here's a rather low-tech method using a sed script. I've included some comments to help you see what's going on.

Save to a file and execute using sed -f yourSedFile yourInputFile

----------------------------------------------------------------

#if pattern space matches "rocks 20"
/rocks 20/ {
#append next line of input to pattern space
N
#if pattern space matches "books 30"
/books 30/ {
#perform substitutions
s/rocks 20$$.*$$books 30/rocks 88\1books 77/
}
}

-----------------------------------------------------------------

Join Date
Jun 2002
Location
UK
Posts
525
A slight tweak so that "rocks 20XXXX" wouldn't also get changed.

/rocks 20$/ { N /books 30$/ {
s/rocks 20$$.*$$books 30/rocks 88\1books 77/
}
}

6. Registered User
Join Date
Aug 2003
Posts
4

## Can I find&replace paragraphs using sed command?

Hello damian,

Thanks a lot for the answer it works perfectly!
I have for you 2 more questions:

1. Is there a way to pass the 4 numbers as parameters? ( if not, I thought to
write a script that will build the sed file every time with the numbers I will give it).

2. I wrote a C - shell script (attached below) which does the same,
but when I compare the running time of your sed file to my script,
both on a 1M size of file.
well it took yours - 2 seconds while 7 minutes to mine,
do you know why the big difference?

Regards meirav

The command line is:

>Convert_lines num1 num2 num3 num4

Convert_lines:

#!/usr/local/bin/tcsh –f

cat a.txt | convert $1$2 $3$4

Convert:

#!/usr/bin/tcsh -f

set line1 = ( $< ) set line2 = ($< )

\rm tmp.txt

touch tmp.txt

while ( ${#line2} != 0 ) if (${#line1} == 2 && ${#line2} == 2 ) then if ($line1[1] =~ "rocks" && $line2[1] =~ "books” &&$line1[2] =~ $1 &&$line2[2] =~ $2 ) then set line1=("$line1[1] $3") set line2=("$line2[1] $4") echo "$line1" >> tmp.txt

echo "$line2" >> tmp.txt set line1=($< )

set line2=( $< ) else echo "$line1" >> tmp.txt

set line1 = ( $line2 ) set line2=($< )

endif

else

echo "$line1" >> tmp.txt set line1 = ($line2 )

set line2=( $< ) endif end echo "$line1" >> tmp.txt

Join Date
Jun 2002
Location
UK
Posts
525
If you place double quotes around your sed command, the shell will evaluate it first and expand any shell variables.

--------------------------------------------------------------------------
# sedUsingTheShell.sh

rocksVal=20
booksVal=30
newRocksVal=88
newBooksVal=77

sed "
/rocks ${rocksVal}$/ {
N
/books ${booksVal}$/ {
s/rocks ${rocksVal}$$.*$$books${booksVal}/rocks ${newRocksVal}\1books${newBooksVal}/
}
}" < yourFile

---------------------------------------------------------------------------

As to why yours is slower...

I'm not familar with tcsh but generally shells are notoriously slow when implementing a 'while read' type construct. I won't claim to understand why because I don't. Sed on the other hand, is notoriously quick.

It would probably be a little quicker if you executed it like this...

convert_lines var1 var2 var3 var4 < inputFile

The use of 'cat' is unnecessary.

Last edited by Damian Ibbotson; 08-14-03 at 10:17.

8. Registered User
Join Date
Aug 2003
Posts
4

## Can I find&replace paragraphs using sed command?

Hello Damian,

The script works just excellent.
I tested it on 100MB files and it runs very fast.

Thanks a lot
Best regards meirav

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•


text:
# Likely-silly question on Gaussian Processes: can/should they be scale()'d?

As the title notes, I assume this is a silly idea since I’ve never seen it implemented, but to set the stage, consider the following Gaussian Process model:

``````data{
int<lower=2> n_xy ;
vector[n_xy] y ;
array[n_xy] real x ;
}
parameters{
real grand_mean ;
real<lower=0> noise_amplitude ;
real<lower=0> gp_amplitude ;
real<lower=0> gp_lengthscale ;
vector[n_xy] gp_helper ;
}
transformed parameters{
// gp: latent (noiseless) GP
vector[n_xy] gp = (
cholesky_decompose(
x
, gp_amplitude
, gp_lengthscale
)
, gp_amplitude * 1e-5 //jitter
)
)
* gp_helper
) ;
}
model{
// Priors:
grand_mean ~ ... ;
noise_amplitude ~ ... ;
gp_amplitude ~ ... ;
gp_lengthscale ~ ... ;
// gp_helper must be ~ std_normal()
gp_helper ~ std_normal() ;
// Likelihood:
y ~ normal( grand_mean + gp , noise_amplitude ) ;
}
``````

So we have some data `y` measured at known locations on some 1D space `x`, and we want to account for both gaussian measurement noise as well as a smooth effect of measurement location, with the magnitude of these factors represented by the `*_amplitude` parameters, and smoothness of the latter factor represented by the `gp_lengthscale` parameter. The possibility of a non-zero grand mean for measurements is placed in an explicit `grand_mean` parameter.

While the above computes `gp` using `gp_exp_quad_cov()` and supplying an amplitude parameter, an equivalent (but probably slightly less efficient) model is:

``````...
transformed parameters{

// gp_: latent (noiseless) GP with unit-amplitude
vector[n_xy] gp_ = (
cholesky_decompose(
x
, 1.0
, gp_lengthscale
)
,  1e-5 //jitter
)
)
* gp_helper
) ;

// gp: latent (noiseless) GP
vector[n_xy] gp = gp_ * gp_amplitude ;

}
...
``````

What becomes clear in this latter formulation is that there’s an assumption of sorts that, for `gp_amplitude` to play it’s role in scaling the latent vector, `gp_` is expected to have a consistent variance, ideally unit variance as we then get to interpret `gp_amplitude` as the standard deviation of the latent gp. And presumably the conditioning of `gp_helper` with `std_normal()` in the model block is intended to contribute to ensuring a consistent variance of `gp_`, but in my playing `gp_` can nonetheless have rather variable variances even when all parameters other than `gp_helper` are fixed.

So it occurs to me then that one can easily enforce a unit variance by:

``````...
transformed parameters{

// gp_: latent (noiseless) GP with unit-amplitude
vector[n_xy] gp_ = ...;
gp_ = gp_ / sd(gp_) ;

// gp: latent (noiseless) GP
vector[n_xy] gp = gp_ * gp_amplitude ;

}
``````

And similarly, one could additionally enforce a zero mean via:

``````...
transformed parameters{

// gp_: latent (noiseless) GP with unit-amplitude
vector[n_xy] gp_ = ...;
gp_ = ( gp_- mean(gp_) ) / sd(gp_) ;

// gp: latent (noiseless) GP
vector[n_xy] gp = gp_ * gp_amplitude ;

}
``````

With `gp_` constrained to a zero-mean-&-unit-variance vector in this way, I feel like the model is more “straightforward” as a data generating process whereby the GP part solely speaks to the wiggliness of the effect of `x` on `y`, while `gp_amplitude` deterministically encodes the magnitude of this effect with a mean centered on zero so that it is deterministically isolated from other factors in the model (ex. `grand_mean`). We lose the ability for the GP to diverge from our explicit model formulation (ex. I don’t think the constrained version would fit well if there were additionally a linear effect of `x`; we’d have to explicitly add that effect whereas the unconstrained version could find regions of the parameter space that implicitly reflect a linear effect of `x`), but that’s arguably a benefit in forcing us (if doing a proper workflow) to detect and add the missing pieces as explicit structure rather than letting the unconstrained GP’s flexibility try to find it.

Not constraining in this way means that, for example, areas of the parameter space where `gp_` has a non-zero mean are less well identified from areas of the parameter space where `gp_` has a zero mean but `grand_mean` is non-zero. Similarly, without the constraints, areas of the parameter space where `gp_` has a lower variance are less well identified from areas of the parameter space where `gp_amplitude` has a lower variance.

So why don’t folks do this with GPs? Does the enforcement of zero-mean-&-unit-variance of the latent process induce some sort of pathology? So far in my playing I haven’t encountered anything obvious, but possibly I’m not exploring properly?

Oh! After thinking a bit, I wonder if the constrained parameterization doesn’t eliminate identifiability as I conveyed above, but instead shoves it all into `gp_`? For example, the zero-mean constraint means that whenever some elements of `gp_` are high, the others must be low, and ditto with the unit-variance constraint. But I wonder if this is a more appropriate/tractable kind of non-identifiability as the specific shapes of the data should inform strongly in that regard?

Or maybe the constraing-transform on `gp_` makes for identifiability issues between `gp_` and `gp_helper`?

Tagging some GP-knowledgeable folks that might weigh in to set me straight; @avehtari @rtrangucci @rok_cesnovar @betanalpha @spinkney @Niko

1 Like

This may or may not be helpful for a given model, but what it isn’t is a gaussian process. Recall that by definition every finite-dimensional projection of a gaussian process is specified by a multivariate normal density function. Introducing those constraints modified those finite-dimensional projections and hence the implicit infinite dimensional object that is being represented.

An immediate practical consequence of this models over a different number of input points will no longer be consistent. Adding a new variable requires either changing the constraint on the initial variables, and hence their probabilistic behavior, or forcing the new variable to a fixed value. Similarly removing a variable requires modifying the constraints and hence the behavior of the other variables.

Besides the math are introducing constraints like this a good idea? I don’t personally think so. The mean and variance implied by a gaussian process determine ensemble expectations, not the behavior of any one functional realization. A set of output values from a function modeled with a zero-mean gaussian process prior will not in general average out to zero. Indeed concentration of measure arguments tell us that the typical realizations will exhibit fluctuations that pull the average away from zero. Again the mean and variance are relevant to the ensemble expectation of many functional realizations, not any one.

Of course one can always implement these constraints as a new, heuristic prior model that deviates from a gaussian process, but then one has to argue that new model is appropriate for the given analysis. These kinds of constraints often seem to be helpful superficially (indeed they’re often recommended as a hack for multi-factor modeling) but I find that they cause more trouble than they’re worth.

3 Likes