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# FAQ about Basic Facts, Safety and Security Clarifications of Liquefied Natural Gas

This section is structured in the form of answers to frequently asked questions (FAQ) about LNG posed by those with little or no previous understanding of the LNG industry.

## Background of LNG

Liquefied Natural Gas (LNG) is the liquid form of natural gas. LNG is a natural gas, just like the gas produced and delivered by pipelines to energy markets around the world.

It is called liquefied natural gas because it is a liquid. When natural gas is cooled at atmospheric pressure to very low temperatures (about -162 °C, or about -260 °F, depending on the composition of the natural gas) it condenses into a liquid. The critical temperature and pressure of natural gas are around -82 °C and 46 bar, again depending upon the exact composition of the gas.

Natural gas is composed primarily of methane (typically at least 90 %), but may also contain some heavier hydrocarbons such as ethane, propane, or butane, and typically less than 1 % nitrogen. Prior to liquefaction natural gas is typically conditioned to remove any oxygen, carbon dioxide, sulfur com-pounds, other trace impurities (such as mercury), and water. Removal of these impurities eases the handling of the LNG formed by minimizing corrosion or damage to materials used for its containment.

### Why LNG?

It typically takes about 600 m3 of natural gas to yield 1 m3 of LNG, with 1 tonne of LNG holding the energy equivalent of some 50,000 cubic ft of natural gas. Exact conversions depend upon the composition of the natural gas in question. It is the large contraction in volume from the gaseous state to the liquid state that makes LNG much easier and more economical to transport over large distances and store in large quantities.

### Is LNG explosive?

LNG is not at all explosive or flammable in its liquid state.

### What happens when LNG is warmed?

As LNG vapor warms above -160 °F (-106.7 °C), it becomes lighter than air and will rise and disperse rather than collect near the ground. However, it is not explosive unless flammable concentrations of gas occur in enclosed or otherwise confined spaces.

### How much energy does it take to make LNG from natural gas?

Typically about 10 to 20 % of gas delivered into an LNG supply chain is consumed in the process and transportation facilities. This is comparable with long-distance high-pressure gas pipelines.

### What are the advantages of storing gas as LNG?

LNG facilities offer two clear advantages over alternative gas storage options:

• Because LNG facilities can be located above ground, operators and/or owners have many more opportunities for locating LNG facilities in comparison with traditional underground gas storage alternatives that depend on underground geological conditions such as depleted reservoirs, aquifers, and salt caverns;
• LNG facilities are often constructed with a higher degree of “deliverability” (the amount of gas the facility can send out under peak conditions relative to stock in inventory) than traditional underground storage facilities. This deliverability provides the opportunity to meet demand spikes, sometimes called “needle peaks.”

### What is the history of LNG?

LNG has been used for more than 50 years, especially in Asia, Europe, and the United States. Improved technology is now making it more economical to produce, transport, and store LNG in large quantities. These economies of scale have opened up wider markets for its use where it can compete effectively on price with other sources of fuel.

LNG fed by gas from large gas fields remote from gas markets has become an increasingly attractive alternative to oil or piped gas (natural gas transported from its country of origin through pipelines). Natural gas as a “clean” source of energy is becoming the fuel of choice or preference in many regions if significant volumes can be brought reliably and at competitive prices into a market enabling it to compete with coal, oil, and petroleum products for power generation and industrial and commercial fuels.

Read also: Fundamentals of Liquefied Natural Gas

There is an increasing need globally for diversification of energy supplies due to politics, eco¬nomics, and reserves. LNG carriers can be diverted to a number of LNG consuming countries easily providing higher confidence in security of supply for major gas-importing nations.

### How can we keep LNG cold?

LNG is stored in large insulated tanks that are designed to minimize any heat ingress. The insulation of the tanks, as efficient as it is, does not keep the temperature of LNG at cryogenic temperatures by itself. LNG will stay at near constant temperature if kept at constant pressure. This phenomenon is called auto-refrigeration.

As long as the LNG vapor boil-off is allowed to leave the tank in a safe and controlled manner, the auto-refrigeration process will keep the temperature constant. This vaporization loss is typically collected as it leaves the tank and either reliquefied, sent to the gas line connecting to a gas distribution network, or used as fuel on the site or to power an LNG carrier ship.

### What are the differences between LNG and LPG or LNG and NGL?

All are light liquid hydrocarbons that can be used as fuel. To most nonengineers, the terminology is confusing. Liquefied petroleum gas (LPG) is composed primarily of propane (upward of 95 %) and smaller quantities of butane. This is quite different from the primarily methane composition of LNG. LPG is used primarily as residential fuel, petrochemical feedstock and often is used as vehicle fuel. In fact LPG is a cleaner burning liquid fuel than gasoline.

Natural gas liquid (NGL) is a light hydrocarbon mixture that may also consist of ethane, propane, butane and traces of condensate (heavier gasoline range hydrocarbon) components. Ethane can be used for petrochemical production and the remaining portion can be sold as LPG.

LPG can be maintained as a liquid by means of elevated pressure alone or by chilling to tem-peratures to around -40 °C. On the other hand, it is not possible to liquefy natural gas (methane) at ambient temperature even at elevated pressure.
Despite perceived safety concerns, LNG is also safer to handle than LPG in most circumstances. Because LPG is heavier than air, it “hangs” low to the ground if leaks occur in storage facilities. A leaked, low-lying cloud of LPG is more easily ignited than LNG. In contrast, LNG vapor (primarily methane) is lighter than air. As a result, the revaporized gas stream in an uncontained condition typically floats away into the atmosphere and poses a much lower threat of fire or explosion.

### What are the sources of LNG?

Qatar, Indonesia, Australia, Malaysia, Trinidad, Algeria and Nigeria are leading exporters of LNG. There are in total some nineteen countries that export LNG. LNG is imported by many countries and in particularly large quantities by Japan and South Korea and some European countries with China and India increasing their demand for LNG quite rapidly.

Growth in LNG applications depends on expansion of current facilities and new construction and infrastructure investment along the LNG supply chains. The industry has experienced growth of some 7.5 % per year for the past 20 years and investment commitments suggest this rate of growth will continue for the next decade at least.

The continued expansion and diversification of LNG supply indicates that sources of LNG will become more readily available in gas consuming markets around the world. The emergence of new LNG import markets in South America (i.e., Argentina, Brazil, and Chile) and the Middle East (i.e., Dubai, Kuwait) in recent years is testament to the diversification of the industry.

Floating regasification and LNG storage units have enabled smaller markets to secure LNG imports quickly (i.e. in less than a year) without building land-based LNG receiving terminals. This approach has now become popular with countries seeking to import occasional or seasonal LNG cargoes.

Demand for LNG is expected to increase as emission restrictions favor gas over coal for power gen-eration, and gas supply companies make inroads into niche markets such as road vehicular fuel, as a marine vessel fuel, and as LNG replaces propane as a fuel for facilities not connected to the pipeline gas grid.

## LNG supply chain

The LNG supply chain includes all the facility and equipment involved in taking natural gas from an underground reservoir, liquefying it, and transporting to an end-user customer of natural gas.

That supply chain is typically long in terms of distance and expensive in terms of the capital costs of the equipment and facility involved. The components of the supply chain typically include:

• Gas field production infrastructure;
• Feed gas pipeline to gas processing and conditioning plant;
• A large-scale refrigeration plant involving heat exchangers to liquefy the feed gas;
• LNG storage and port loading facilities: everything must be kept cold;
• LNG marine tankers;
• LNG receiving terminal including port unloading, LNG storage, regasification, and gas sendout compression facilities;
• Connection to a natural gas transmission and distribution network to deliver gas to customers;
• In some cases distribution of LNG by truck to small, remote off-grid gas customers.

### Can LNG compete commercially with pipeline gas?

Yes. An LNG supply chain (i.e., gas field development, liquefaction plant, transportation by LNG carrier, LNG terminal) is generally set up when pipeline transmission is too expensive due to the long distances involved or the technical/political difficulties of pipeline construction, or to enable the gas to be delivered to more than one geographic market location. LNG supply chains are much more flexible than gas pipelines, being able to serve different markets at different times and to avoid the political and geopolitical instability of transit countries that transcontinental gas pipelines have to deal with.

### What are the commercial terms?

In traditional LNG markets, buyers and sellers are generally linked by long-term contracts (i.e., 10 to 25 years duration typically) for predefined quantities of LNG produced in a liquefaction plant and received at an LNG terminal specified in the contract.

There are usually penalties for the customer not taking the contracted quantitiesdtake-or-pay. The contracts usually specify a price often linked to benchmark gas prices or to other fuel (crude oil) prices or inflated from an initial floor price.

Rapidly growing short-term markets are changing this as more uncontracted LNG carrier vessels enter the market. However, the LNG market will remain dominated by long-term contracts for the foreseeable future. Short-term LNG cargo sales amount to about 15 % of the overall LNG supply.

## LNG regasification terminals

An LNG regasification terminal is where the LNG is delivered to the end users, which typically comprises the LNG unloading jetty and LNG storage and sendout facility, along with heating to reconvert LNG back to natural gas. The regasification process is a heating process typically using ambient temperature heat sources. Most terminals use seawater for heating, and in some terminals ambient air is also used. In cold climate regions, fuel gas is necessary to supplement heating during the winter months.

The LNG terminals typically unload the LNG shipment in 10 to 12 hours, in order to minimize the docking times for the ships and reduce the operating cost of the ship.

### How are terminals designed?

All LNG storage facility designs must comply with stringent regulations as required by national planning legislation codes (e.g., in the United States: the US Department of Transportation (DOT)’s safety standards in Title 49 Code of Federal Regulations (CFR) Part 193dLiquefied Natural Gas Facilities: Federal Safety Standards and National Fire Protection Association (NFPA) 59Ad Standard for the Production, Storage, and Handling of LNG).

In accordance with safety standards, vapor dispersion distances must be calculated to determine how far downwind a natural gas cloud could travel from an onshore storage facility and still be flammable. As required by these regulations, these exclusion zones must not reach beyond a property line where other development could occur.

Since a fire would burn with intense heat, each onshore LNG container and LNG transfer system must also have thermal exclusion zones established in accordance with prevailing safety standards. These exclusion zones must be legally controlled by the LNG facility operator, or a government agency, to ensure adequate separation between members of the public and the heat from a fire.

## Seismic design requirements

LNG facilities must meet stringent standards to ensure public safety and plant reliability in the event of an earthquake. Extensive studies of the geological conditions and earth history of a proposed LNG site are required to determine appropriate design loads on the critical components of the LNG plant, such as the design of the LNG storage tanks.

### What gas markets do LNG regasification facilities serve?

Some LNG facilities have the flexibility to participate in several markets at once. For example, some fill both base load and peak shaving roles. Some also provide LNG for commercial vehicle fuel which is growing in demand since the LNG fuel cost is significantly less than petroleum fuel that has been escalating in price.

### How long can LNG be stored at LNG regasification terminals?

Scheduling for both the arrival of the LNG shipment and the dispatch of the regasified product generally is necessary to maintain an optimum operation of the LNG facility. A balance of multiple sources of LNG supply and storage capacity to match the variations in consumption is essential to minimize the inventory shortages that might be brought about by weather or tanker-scheduling problems.

Typically, the regasified LNG is sent out to customers on a routine schedule under a contract that calls for a set daily volume. Consequently, the LNG may be in storage at a marine import terminal for only a few days and, depending on the terms of individual contracts and the time of the year, is seldom held for more than a few months, unless it is held only for emergency back-up.

### What is an LNG peak shaving plant?

Such facilities typically involve a small liquefaction unit linked with a large LNG storage tank and gas sendout facilities to a gas distribution network capable of responding to gas demand peaks or supply crises. However, some peak shaving plants receive their LNG in liquid form by ship or by truck from other LNG facilities and do not have liquefaction facilities of their own.

Typically, gas is taken from a pipeline supply and liquefied and stored as LNG at the peak shaving plant. LNG remains in storage for several months and in most cases is only used to supply the extreme demand periods or needle peaks of just a few days each winter.

Peak shaving plants are used by gas utilities and regional pipeline companies as a means of storing gas in liquid form for peak periods and emergency backup. They are usually located at strategic points within the supply network to enable rapid delivery of gas to key markets.

### Are there air emissions from an LNG regasification terminal?

During the operation of an LNG regasification terminal, atmospheric emissions are mainly combustion emissions resulting from the burning sulfur-free natural gas.

LNG terminals are typically subject to regulations set by a government environment agency. Authorization for a specified level of emissions is typically granted by such agencies once they are satisfied that best available techniques are being employed in the operation and the terminal to eliminate, minimize, and render harmless any resultant emissions to the environment.

## LNG’s safety records

The LNG industry has a long and excellent safety record, due to strict industrial safety standards applied worldwide. Up to 2012 there have been some 50,000 LNG carrier voyages, without a sig¬nificant accident or safety problem (i.e., loss of containment) either in port or on the high seas.

Two major accidents have impacted the LNG industry:

• Cleveland LNG storage facility, located in the United States, in 1944;
• and, Skikda liquefaction plant, located in Algeria, in 2004. These incidents are described together in the following, with lessons learned.

In most jurisdictions “safety case” and environmental impact study” reports are required by the government’s regulatory authorities before consent for building an LNG facility is granted. The safety case considers all aspects of management, handling facilities, and operation of the plant, particularly on potential accidents and how major accidents would be prevented. Fires are more likely at lique¬faction plants than regasification terminals, but are extremely rare; for example, a fire shut down the seventh train of the Malaysian MLNG Tiga plant (Bintulu), with a capacity of 3.4 MTPA, for seven months.

As part of the safety case and environmental impact studies, “credible” LNG spill incidents are the subject of risk analyses to review and assess the suitability of the site and the design of an LNG facility and any access waterway and road network. Modern LNG facilities are designed and operated such that persons not involved in the operation of the facility (including ships) that are outside the clearly designated safety and exclusion zones would not be at risk should these credible incidents occur. Rapid response planning to potential incidents by emergency services and training of responders is also part of the safety systems put in place for LNG facilities.

### What caused the Cleveland LNG tank failure in 1944?

The East Ohio Gas Company built the world’s first LNG peak shaving facility in Cleveland in 1941. It consisted of three small spherical LNG storage tanks covered by cork insulation and a mild steel outer shell. The tanks were supported by uninsulated mild steel legs. The facility adjoined a residential neighborhood. The facility was run without incident until 1944, when a larger new tank was added. Since stainless steel alloys were scarce because of shortages resulting from World War II, the new tank was built using a toro-segmented design using low-nickel content (3.5 %) alloy steel.

Shortly after going into service, on October 20, 1944, the tank failed. LNG spilled into the street and storm sewer system where vaporizing gas ultimately met an ignition source and ignited. The resultant fire killed 128 people.

The US Bureau of Mines investigation (1946) that followed showed that the accident was due to the low-temperature embrittlement of the inner shell of the cylindrical tank. The inner tank was made of 3.5 %-nickel steel, a material now known to be susceptible to brittle fracture at LNG storage tem¬perature (-260 °F). Had the fourth Cleveland tank been built using appropriate materials, the investi¬gation concluded that the tragic accident would not have happened. LNG tanks constructed around the world of 9 %-nickel steel have never had a brittle crack failure over decades of subsequent operations.

Clearly there is no reason why such an accident should be repeated.

### What caused the Skikda liquefaction train fire in 2004?

On January 19, 2004, a leak in the hydrocarbon refrigerant system at one of the natural gas liquefaction units (Train 40) in Skikda, Algeria formed a vapor cloud that was ingested into the inlet of the combustion fan of a steam boiler. The hydrocarbon acted as increased fuel to the boiler causing a rapidly rising pressure within the steam generating equipment. The rapidly rising pressure quickly exceeded the capacity of the boiler’s safety valve and the steam drum ruptured, tearing apart the boiler fire box and housing. The flames from the boiler firebox ignited the leaked refrigerant gas, which was confined by the equipment and structures in the area producing an explosion and an ensuing fire.

The explosion, along with the shrapnel from the ruptured steam drum, caused further damage to the process piping and pressure vessels in the immediate area leading to additional flammable fluid release. The fire took eight hours to extinguish. The explosions and fire destroyed a portion of the LNG plant and caused 27 deaths and injury to 72 more. No one outside the plant was injured nor were the LNG storage tanks damaged by the hydrocarbon explosions.

A joint report issued by the US Federal Energy Regulatory Commission (FERC) and the US Department of Energy (DOE) was issued in April 2004. The findings in that report indicate that:

• There were ignition sources in the process area;
• There was a lack of “typical” automatic equipment shutdown devices required by modern design codes;
• There was a lack of hazard detection devices, which should have provided advanced warning of the refrigerant leak and helped to prevent the explosion.

While Skikda liquefaction trains 10, 20, and 30 had been upgraded in the late 1990s, Skikda train 40 was, in fact, of an obsolete design and scheduled for demolition at the time of the incident. Train 40 was originally built in 1981 and not well maintained. The poor maintenance, obsolete design, and poor general condition of Skikda train 40 suggest that such an incident should not be repeated in a modern liquefaction plant. Nevertheless, the incident highlights the need for comprehensive maintenance schedules and appropriate hazard detection systems at LNG facilities.

### What other serious incidents have occurred at LNG regasification terminals?

In addition to Cleveland, there have been two other incidents attributed to LNG.

A construction accident on Staten Island in 1973 has been cited by some parties as an “LNG accident” because the construction crew was working inside an (empty, warm) LNG tank.

In another case, the failure of an electrical seal on an LNG pump in 1979 permitted gas (not LNG) to enter an enclosed building. A spark of indeterminate origin caused an explosion in the building. As a result of that incident, the electrical code was revised for the design of electrical seals used with all flammable fluids under pressure.

This record suggests that LNG offers a safe and reliable source of natural gas and facilities can be located close to urban areas with confidence that they do not pose https://sea-man.org/lng-safety.htmlsignificant safety risks.

## LNG carriers

LNG carriers have double-hulled containment systems to limit loss of containment in cases of collision or grounding. LNG carrier safety equipment includes sophisticated radar and positioning systems that alert the crew to other traffic and hazards around the ship. A number of distress systems and beacons will automatically send out signals if the ship is in difficulty. The cargo system safety features include an extensive instrumentation package that safely shuts down the system if it starts to operate out of predetermined parameters.

Ships are also equipped with gas and fire detection systems. Crews are extensively trained to maintain high levels of onboard safety and how to handle emergency situations if they should arise.

Three LNG cargo tank types currently used in LNG carrier ships are self-supporting spherical, self¬supporting prismatic SPB, and membrane. The membrane tanks are the most common in vessels built over the past decade and very few vessels have been built with self-supporting prismatic tanks, although there is renewed interest in such designs for floating liquefaction vessels.

For all cargo tank types, penetrating one or more LNG cargo tanks in a collision or grounding requires the penetration of all of the following:

• The ship’s outer hull;
• The 3-meter or so space between the outer and inner hulls (the water ballast tanks);
• The inner hull;
• The insulation system around the LNG cargo tank;
• The secondary containment of the individual LNG cargo tank;
• The insulation system around the primary containment;
• The primary containment vessel wall of the individual LNG cargo tank.

### What are the sizes of an LNG carrier and an LNG terminal?

LNG import terminals are equipped with storage tanks capable of holding at least one tanker load of LNG, and most modern facilities typically have a capacity of at least two tanker loads.

Modern large LNG carrier ships or tankers commonly hold some 145,000 cubic meters of LNG in liquid form, which equates to about 3 Bcf (about 80 mcm) in gaseous form. LNG vessels range in capacity from 19,000 to 265,000 m3. The largest (Q-max) vessels of up to 265,000 m3 have come into service since 2008 as part of Qatar’s LNG supply chains.

LNG carriers are large double-hulled ships, several hundred meters in length, which travel at average speeds of 17 to 20 knots (18 knots is 33 km/h). It takes around 10 hours to fill an LNG tanker with a capacity of 120,000 m3. Larger vessels require higher capacity loading infrastructure to enable rapid loading of cargoes.

Although the storage tanks at an LNG marine terminal often function as LNG storage facilities, the principal operation of an import terminal is not for gas storage, but rather for receiving the water-borne LNG imports and then regasifying LNG for shipment via pipelines to customers.

### Have LNG carrier groundings and collisions occurred?

Very few incidents involving LNG ships have occurred and those that have occurred have not resulted in loss of containment. The following example illustrates the robustness of these vessels and that the piercing or breaching an LNG ship tanks is extremely difficult.

In 1979, the El Paso Paul Kayser, loaded with about 125,000 m3 of LNG, was steaming out of the Mediterranean Sea from an Algerian port. It was traveling at approximately 19 knots off the coast of Gibraltar when it struck a rock outcropping below surface and gouged a 750-foot long scar in its hull. This serious marine incident did not involve a loss of cargo, nor did it result in a breach of an LNG tank. The grounding did not even penetrate the outer hull. Another ship was brought alongside; the cargo was pumped out of the El Paso Paul Kayser into the second ship. The El Paso Paul Kayser was righted and sent to the shipyard for repairs and eventually returned to service.

## LNG spills

In order to be ignited, LNG must first be vaporized (heated and returned to a vapor state), mixed with between 5 to 15 % air, and come in contact with an ignition source.

Were LNG to be released onto the ground as a consequence of a leak from a storage tank, the heat from the ground surface would initially cause very rapid boiling of the LNG. As the ground cools the boiling rate of the LNG would reduce. The amount of vapor formed would be in direct proportion to the amount of LNG released, the rate of release, and the surface area covered in the release.

In an unconstrained open-air environment the cold gas vapor will condense most of the water (humidity) in the surrounding air forming a white vapor cloud. If unhindered, the cloud will drift in the direction of the wind, further mixing with the air and picking up heat from both the ground and the air as it moves. As the vapor cloud warms up, it will become buoyant (lighter than air) and rise into the atmosphere where typically it will gradually disperse without ignition.

LNG released on water acts very similarly to the initial release on land. Assuming a large volume of water, the vapor formation rate will remain high as the surface water that is cooled by the LNG sinks and is replaced by warmer water.

Hence, in unconstrained scenarios spilled LNG should not typically ignite. Ignition is possible only in certain zones of an LNG vapor cloud where mixing with air would produce a flammable gas in the to 15 % concentration in air range. At the center of the cloud the air quantity is too low for ignition; at the outer limits of the cloud the air quantity is too high for ignition. Natural gas has an auto-ignition temperature range of approximately 590 °C to 650 °C (1 100 °F to 1 200 °F), which is higher than LPG and significantly higher than gasoline. Those other fuels also ignite with lower concentrations in air. For example, gasoline has a lower flammability limit (LFL) of only 1.4 % and propane is 2.1 %, meaning that both can be ignited with significantly lower concentrations in air than natural gas (which has an LFL of 5 %). If the limited flammable portion of a natural gas vapor cloud in an unconstrained environment met an ignition source, it would burn but not explode.

In order for the ignition of an LNG vapor cloud to result in an explosion, the gas must first be uniformly mixed with air in the 5 to 15 % range, confined in an enclosed space, and then ignited through contact with an ignition source. It is extremely unlikely that such conditions could all occur together in a modern LNG facility.

### What are the likely impacts of large LNG spills?

Over the course of the past decade Sandia National Laboratories (New Mexico, USA) have conducted a series of detailed risk analysis studies and provided safety guidance associated with the conse¬quences of a large LNG spill over water from a marine vessel. The studies examine the vulnerability of LNG tankers and the impact of an intentional or accidental event that spills a large amount of LNG into a carrier or onto the water. As part of the research, Sandia in December 2009 intentionally set a very large LNG fire in a 120 meter-diameter pool in New Mexico that was made for that purpose. The test LNG spill was 83 m in diameter and created a 56 m diameter fire. The test also showed that the fire would likely stay attached to the ship instead of floating away.

Modeling associated with Sandia’s 2011 studies showed that about 40 % of spilled LNG could stay within the ship, causing cryogenic and heat damage. At high temperatures the strength of the steel on the ship is much reduced. On the other hand the extreme cold temperature of LNG is likely to cause fractures in all structural elements in and around the ship that come into contact with LNG. The largest intentional breach events modeled would cause significant damage and make the vessel unseaworthy. The study considered a wide range of events, including shoulder-fired weapons, stinger missiles, backpack explosives, underwater events, and small aircraft.

The estimated thermal hazard distances, even from a pool fire associated with the largest capacity LNG carriers in operation, involve significant impacts to public safety and property contained within approximately 500 m of a spill, with lower public health and safety impacts at distances beyond approximately 1 600 m. However, the studies found that pool fire and vapor dispersion hazard distances are significantly influenced by site-specific environmental, topographical, climatic, and operational conditions including the breach and spill size.

### What should be done if there is spill from an LNG delivery truck?

Truck loading and transport of LNG carries a higher risk than normal pipeline delivery, but involves a relatively small, limited amount of LNG. First responders need to be trained to treat such a spill because pouring water on an LNG pool results in a large increase in LNG vaporization. A better approach is to confine a spill with quick, simple methods such as placing sand bags in ditches.

Application of firefighting foam is not too effective once an LNG pool fire is ignited, but it can limit the evaporation rate of a pool prior to ignition. Blocking traffic is important to reduce ignition sources from hot engines and mufflers. If ignition occurs, an explosion is very unlikely unless the vaporized LNG cloud drifts indoors into buildings.

### What are the safety concerns of LNG spills?

Because of its cryogenic temperature (atmospheric boiling point approximately -260 °F), LNG poses exposure concerns to employees, facility structure, and equipment. The design and operation of LNG terminals minimize ignition sources; thus, cryogenic exposure is more likely than a fire incident. This is particularly true in the high-pressure processing areas where the fluid inventory is lower but where the higher pressure creates greater potential for cryogenic exposure.
Cryogenic exposure can cause freeze burns to employees. Gas from LNG vaporization is extremely cold and can produce irreparable burns on delicate tissues such as those of the eyes. Therefore unprotected parts of the body should not be allowed to touch uninsulated pipes or vessels containing LNG.

The cold LNG vapor can also cause embrittlement to carbon steel, thus possibly resulting in structural failure. Protection from cryogenic exposure with insulation, as well as from fire exposure, is installed in the facility. Protective measures should be chosen that are effective for both fire and cryogenic exposure.

The other safety concern is asphyxiation. The normal oxygen content of air is 20.9 % in volume. Atmosphere containing less than 18 % are potentially asphyxiant. In the case of gas leakage, the high concentration of gas can cause nausea or dizziness from anoxia. In an LNG facility, oxygen and hydrocarbon content of the atmosphere are constantly monitored to detect any gas leakage. For maintenance of equipment, the operator is equipped with instruments to ensure sufficient oxygen is present before entry to any equipment.

### How would an LNG facility be safeguarded against damages from an LNG spill?

Direct contact of LNG with structural steel can rapidly cool the material to below embrittlement temperature and may quickly cause failure in a short time. For this reason, the construction and protection system material is selected to withstand cold temperatures and must comply with the most stringent LNG safety standards. Insulation, shielding, and detection systems are provided in the facility to limit the volume of LNG release and mitigate the spread of LNG over a greater area. In the United States, NFPA-59A is one of the key design documents for the design of the LNG facilities. In Europe, BS EN-1473 is normally used. Both US NFPA-59A (2009) and BS EN-1473 (2007) require that equipment and structures whose failure would result in incident escalation must be protected from cryogenic embrittlement.

## Security for LNG facilities and ships

Each country has its own regulations and agencies responsible for marine vessel security. For example, in the United States FERC is among several federal agencies overseeing the security of LNG terminals and peak shaving plants. The Coast Guard has responsibility for LNG shipping and marine terminal security. DOT’s Pipeline and Hazardous Materials Safety Administration (PHMSA) and the Department of Homeland Security’s Transportation Security Administration (TSA) have security authority for LNG peak shaving facilities. In addition to federal agencies, state and local authorities provide security assistance at LNG facilities.

Security measures for both onshore and offshore portions of marine terminals are required by Coast Guard regulations under the Maritime Transportation Security Act. Requirements for maintaining security of LNG import terminals are in the Coast Guard regulations at 33 CFR Part 105. The Coast Guard keeps other ships and boats from getting near LNG vessels while in transit or docked by enforcing Regulated Navigation Areas and security zones. The Coast Guard performs a number of important security and safety checks before allowing an General information and Rules for Ships carrying LNG and LPGLNG tanker to enter a port and unload its LNG. Facilities are required to have a written security plan and an emergency response plan. FERC, DOT, and the Coast Guard require LNG companies to contact and coordinate procedures with local response organizations.

## Risk of terrorism adds new dimension to LNG safety risk

The LNG business has an admirable safety record overall but a whole new dimension has been introduced since the terrorist attacks of September 11, 2001.

By their nature, LNG import terminals are likely to be near centers of population, and issues of public protection and public acceptance of new terminal proposals have high community profiles.

How much LNG could conceivably be released in a major incident? How quickly and how far might the pool spread? How fast does it vaporize to gaseous methane? And, what is the maximum size and intensity of any resulting fire? These are the questions typically addressed in accessing the potential impact of terrorist attacks. These are questions typically addressed in the planning, siting and design of modern LNG import terminals.

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text:
# Magnetic Field Orientations in Star Formation

##### Posted on Jan 12, 2022
$\def\MCF{\mathrm{MCF}} \def\pixel{\mathrm{pixel}} \def\cm{\mathrm{cm}} \def\mag{\mathrm{mag}} \def\trs{\mathrm{trs}} \def\small{\mathrm{small}} \def\large{\mathrm{large}}$

Understanding star formation rates (SFRs) is a central goal of modern star formation models, which mainly involve gravity, turbulence and, in some cases, magnetic fields (B-fields).

However, a connection between B-fields and SFRs has never been observed.

A comparison between the surveys of SFRs and a study of cloud-field alignment shows consistently lower SFRs per solar mass for clouds almost perpendicular regulator of SFRs.

The perpendicular alignment possesses a significantly higher magnetic flux than the parallel alignment and thus a stronger support of the gas against self-gravity. This results in overall lower masses of the fragmented components, which are in agreement with lower SFRs.

Clouds with a similar mass and age can have different SFRs, as shown in the following figure.

Figure 2 correlates the SFRmass$^{-1}$ with the cloud-field angles and shows that large-angle clouds hava consistently lower values of SFRmass$^{-1}$. Perform the permutation tests and Spearman rank correlation tests to determine the significance of this trend.

The dynamical importance of magnetic fields in molecular clouds has been increasingly recognized, as observational evidence has accumulated. However, how a magnetic field affect star formation is still unclear.

Typical star formation models still treat a magnetic fields as an isotropic pressure, ignoring the fundamental property of dynamically important magnetic fields: their directions.

Their previous work: which demonstrate how the mean magnetic field orientation relative to the global cloud elongation can affect cloud fragmentation.

The paper shows that the mass cumulative function (MCF) of a cloud is also regulated by the field orientation.

• A cloud elongated closer to the field direction tends to have a shallower MCF

The authors have conducted a series of studies on the connections between molecular cloud fragmentation and cloud-field offset (i.e., the misalignment between the ambient magnetic field direction and the cloud elongation).

• Li et al. (2013): The discovery of bimodal cloud-field offsets
• study 13 nearby Gould Belt molecular clouds and revealed that the long axes of a cloud tend to align either perpendicularly (large cloud-field offset) or in parallel (small cloud-field offset) to the mean directions of the ambient magnetic field
• a possible effect of the cloud-field offset on cloud fragmentation is due to the magnetic flux

The present study considers the effect of the cloud-field offset on the mass portion of gas in high density.

### Data

• same catalogue of Gould belt molecular clouds as in Li et al. (2017)
• use the dust extinction maps to construct the MCFs
• a resolution of 1’
• select clouds within 500pc, which limits the distance variation between 150 and 450 pc to restrict the effect from different spatial resolutions.

only use pixels with extinction higher than $A_{V_{trs}}$, the “transition density” of the column density probability density functions (N-PDFs), to construct the MCFs

MCF is the amount of cloud mass that is above a given dust extinction, $\tilde A_V$,

$\MCF(\hat A_V) = \mu m_HC\sum_{\pixel (A_V>\tilde A_V)} A_V \times A_{\pixel}$

where

• $\mu=1.37$ is the mean molecular weight
• $m_H$ is the mass of hydrogen
• $A_\pixel = [D(cm)\times R(rad)]^2$ is the area of one pixel
• $C=1.37\times 10^{21}\cm^{-2}\mag^{-1}$

The MCF slope is defined by

$\text{MCF slope} = \left\vert \frac{\log(M_{trs})-\log (0.1M_\trs)}{A_{V\trs}-A_{V0.1}}\right\vert = \frac{1}{\vert A_{V\trs} - A_{V0.1}}$

### Results

• molecular clouds with larger cloud-field offsets show steeper slopes

study the degree of significance of the correction between MCF slopes and cloud-field offsets

$H_0: \mu_{\small} = \mu_{\large}\qquad H_1:\mu_\small > \mu_\large$

where $\mu_\small$ is the average MCF slope of the molecular clouds with cloud-field offsets < 45 degrees.

By the non-parametric permutation test, the resulting $p$-value is 0.01.

### MCF slope uncertainties

The potential uncertainties in the MCF slopes arising from

• extinction measurement uncertainty
• line of sight (LOS) contamination
• MCF bin width
• spatial resolution
• $A_{V\trs}$ uncertainty
• $A_V$ range adopted for the MCF slope measurements

Published in categories Note

format: plain


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# Backing Up Central¶

Having a data backup strategy is a critical part of running a web service like ODK Central. Backups should go to a system in a different physical location from where Central is installed in order to prevent data loss across a broad range of scenarios. Many cloud providers offer backup strategies that run automatically. If you are an experienced system administrator, you may want to set up your own backups of the PostgreSQL database that contains all of Central's data. One strategy for doing this is to configure a separate database server. If you don't already have a server-wide backup system in place and don't want to set up your own database backup, Central provides a managed backup system to Google Drive.

## Managed backups¶

ODK Central features an optional off-site backup system to keep your data safe. For each backup, we extract all your data (including user accounts, forms, and submissions), we encrypt it so that only you can access it, and we send the encrypted result to your Google Drive account for safekeeping. We send data to Google Drive because it is a service that many people already use, it is easy to set up, and it is relatively inexpensive. Because backups are encrypted, Google can't see their contents. However, you should verify that policies and laws that govern your project allow this usage.

To see your current managed backups status, navigate to ‣ System at the top of the Central management website. You should see a status page for backups that looks something like this:

## Setting up backups¶

1. To set up a new automated backup, click on the Set up now button on the right.

Tip

If you see a Terminate button instead of a Set up now button, you already have an automated backup configured. Right now, you can only have one automated backup scheduled at a time. If you wish to change where the backup is saved, you will need to terminate the old one before creating a new one.

2. You'll be asked to enter an optional passphrase. This passphrase is what the server will use to encrypt your backups. You will be unable to restore the backup without the passphrase, exactly as you type it in here. If you leave this field blank, we will still encrypt your backup data but anybody will be able to decrypt it by doing nothing more than leaving the passphrase blank.

4. Once you press Allow, you will see a screen in the popup which contains a lengthy code, and instructions to copy and paste it back into "your application." Copy the code, switch back to the ODK Central website, and paste it into the Confirmation text box. Press Next to confirm it.

5. The setup box should close and you should see a message telling you Success! Automated backups are now configured.

6. Backups are scheduled to run once a day, at 02:00 server local time. If more than 24 hours pass without a backup completing successfully, you'll want to double check that everything has been correctly set up.

Tip

You can verify your Google Drive usage on the Drive storage page. You may want to periodically remove older backups to free up space.

## Performing an immediate backup¶

It is possible to immediately download a backup of your database to your own computer. As of Central v1.1, you will still need to have managed backups configured in order to access this functionality in the web management interface. Once you do, you will see a button Download Backup Now next to the Terminate button near the top.

Clicking this button will perform an immediate backup and download the result to your computer. This process can take some time, and it is normal for data to download quite slowly for many minutes before it gets faster. Take care in using this feature particularly if you have a lot of data and traffic, as performing a backup while a lot of data is being saved to the database can cause a lot of slowdown.

You can also use the API to download a backup without configuring managed backups.

## Restoring a backup¶

Restoring a backup to a Central instance will entirely replace all of its data with the backup. Please be very sure you are restoring to the right place with the right backup snapshot before proceeding.

Note

You cannot restore a backup to an older version of Central. For example, if you create a backup from Central v1.0, you cannot restore it to Central v0.9.

1. The first thing you'll have to do is download your backup from Google Drive, which you can do from the Google Drive website. You will find the backups in a folder called ODK Backups. Each file is a single backup snapshot, and each snapshot should be titled backup-{date}T{time}Z.zip.

2. Once you have the file on your local computer, you will have to transfer that backup snapshot file to your ODK Central server. If you don't know how to do this, and you used our DigitalOcean installation guide, please see their instructions on how to transfer a file to a Droplet.

3. Once the file is on the server itself, you'll need to log back into it, like you did when you first set up the server.

Tip

If you used our DigitalOcean installation steps but can't quite remember how to do this, we suggest reviewing the login steps.

4. Now you'll want to put it in a special place where it can be used by the restore tool: /data/transfer. If, for example, you uploaded the file to /root/backup-2018-01-01T00:00:00Z.zip, you'll want to run this command in order to move it:

mv /root/backup-2018-01-01T00:00:00Z.zip /data/transfer/

5. Now you need to run the restore script. Please note again that all data on this server is about to be replaced by the backup snapshot data! Anybody currently using the server will be kicked off and all changes made since the last backup will be lost. When you are sure you wish to proceed, run the following commands:

cd
cd central
docker-compose exec service node /usr/odk/lib/bin/restore.js /data/transfer/backup-2018-01-01T00:00:00Z.zip 'SECRET_PASSPHRASE'

You'll have to replace the filename following /data/transfer with your own snapshot filename, and the text SECRET_PASSPHRASE with the passphrase you typed when backups were first set up. If you did not set up a passphrase, immediately press Enter after you have finished putting the :file.zip filename in:

docker-compose exec service node /usr/odk/lib/bin/restore.js /data/transfer/backup-2018-01-01T00:00:00Z.zip

6. The server will think for a while, and then print some more instructions. You will have to refresh any browser windows you have open to ODK Central to proceed. If you run into error messages at this step, please read them carefully and then seek help on the ODK Forum if you are not sure what to do.


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# How do you find the vertex of a parabola  y= -3[x-6]^2-3 ?

Jul 18, 2015

The vertex is at color(red)((6,-3).

#### Explanation:

$y = - 3 {\left(x - 6\right)}^{2} - 3$

The vertex form for the equation of a parabola is

$y = a {\left(x - h\right)}^{2} + k$, where ($h , k$) is the vertex of the parabola.

By comparing the two equations, we see that $h = 6$ and $k = - 3$.

The vertex is at ($6 , - 3$).


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## Monday, March 25, 2013

### The Physiology/Life-history Nexus: life history a la Ricklefs and Wikelski (2002)

Ricklefs and Wikelski (2002) present a conceptual model linking genotypes, phenotypes, performance, and demography to evolutionary responses in the context of the environment.

It is a little mushy because they define life-history in as a set of ... physiological adaptations, and then argue that "physiology mediates the relationship between life-history and the environment" (R&W p. 463).

Demography refers to traits of populations, where the state variable is typically population size, N, and we may characterized rates of change of N due to birth rates, death rates and migration. In contrast, life history refers to traits of individuals, especially individual probabilities of survival and death, lifespan, and the sizes and number of offspring in one bout of reproduction and over an organism's lifetime.

I think they take it for granted that their readers know that life history refers literally to the history of "significant" events in the life of an average individual of a population, focused exclusively on those events, such as clutch size or lifespan, that govern population demographic rates. For instance, different life history stages refer to elements of a life cycle are relatively recognizably distinct, and which might be characterized by different probabilities of death or survival, birth, or different average fecundities. Thus distinct life history stages are characterized by individuals having different properties. The study of life histories includes the study of traits of individuals related directly to survival and reproduction. The traits of interest most commonly include:
• lifespan and senescence;
• age at maturity;
• metamorphosis between stages;
• age-specific or stage-specific probabilities of survival or death;
• number of seeds, eggs, or offspring per bout of reproduction (e.g., mast event, clutch, or litter);
• semelparity vs. iteroparity
• average size of individual seeds, eggs, or offspring;
• body size.
Life history strategies are set of these traits that seem to us to optimize fitness in a particular context. For instance, r-selection is a life history strategy characterized by early onset of reproduction and large numbers of offspring and which often maximizes fitness in highly unpredictable environments. This strategy can maximize fitness when adult survival (and therefore future reproduction) is unpredictable. At the other end of the r vs. K-selection continuum, K-selected species are characterized by delayed onset of reproduction, and multiple bouts of reproduction (iteroparity). The K-selected strategy tends to maximize fitness in predictable environments. These two life history strategies seem to represent to ends of a continuum in which many of the above life history traits seem to covary.

The study of life histories focuses on the proximate (e.g., phsyiological) and ultimate (evolutionary) causes of variation and covariation in the above traits.

Non-sequitor: Why do we have the impression that aggregate properties (ecosystem variables, diversity, N) exhibit patterns and are suitable objects of study? (I ask this, I think, because of Ricklefs' focus on individuals and species).

The five principles of Ricklefs and Wikelski (2002):
1. individuals respond to variation in their environments.
2. responses are constrained by the allocation of limited resources among competing functions,
3. individual organisms assume alternative physiological states at different stages in their life cycles because these states are incompatible.
4. individuals might also assume different states as phenotypic responses to the environment,
5. the assumption of one or another state can be modulated by demography, especially reproductive value (future reproductive potential).
Specific points
•  It seems to me that their primary point is that we need to study physiology in order to understand life history.
• I could not determine whether they were implying that the environment caused covariation in life history traits, or the covariation was due primarily to physical constraints on different components of organisms' physiologies.
• Figures I and II in Box 1 seems orthogonal or perpendicular to life history traits. That is, we might imagine that a particular life history strategy such as r-selected traits occupies the phenotype box but different points on the r-K continuum lie perpendicular to the figure, extending out of and into the page.
• I thought it was odd that they chose to not mention tradeoffs that might arise through "simple" laws of conservation of matter and energy.

## Thursday, March 7, 2013

### Organisms are built in four dimensions

Here is, I think, one observation, expressed in various and complementary ways:
• All species exhibit an average relative fitness, w, of approximately $w = 1$.
• On average, all organisms leave approximately one descendent.
• Over its lifetime, an organism does the work (joules) required to leave approximately one descendent.
• Over its lifetime, an organism must do the work required to build another organism of the same size.
Let
• A be the total amount of work required to produce a descendent.
• R be the rate of that work, and
• T be the time over which the work is done, then
RT = A

My "observation" above implies that A depends strongly on body size: It takes longer to build a large organism.

A 3-D organism has to propagate itself through time, at a velocity sufficient to maintain and replicate itself. The 4-D integral of that mass-time event is directly proportional to the mass of the organism. The rate or velocity measured at any instant in time, $t$, will be a 3-D slice of the 4-D mass-time event. As the event is proportional to the size (mass or volume) of the organism, the 3-D slice will scale to the 3/4 power of the 4-D event or size of the organism.

## Sunday, November 11, 2012

### Thinking like an ecologist

Here is some advice for budding young ecologists--useful or not useful?

## Monday, September 3, 2012

### A blueprint for ecology

Scheiner (and Willig's) general theory of ecology
Scheiner 2012, QRB; Scheiner and Willig 2011 monograph

#### Domain

The spatial and temporal patterns of the distribution and abundance or organisms, including causes and consequences.

#### Principles

1. Organisms are distributed unevenly in space and time.
2. Organisms interact with their abiotic and biotic environments.
3. Variation in the characteristics of organisms results in heterogeneity of ecological patterns and processes.
4. The distributions of organisms and their interactions depend on contingencies.
5. Environmental conditions are heterogeneous in space and time.
6. Resources are finite and heterogeneous in space and time.
7. Birth rates and death rates are a consequence of interactions with the abiotic and biotic environment.
8. The ecological properties of species are the result of evolution.

## Stevens' general theory of ecology

#### Domain

Life: its constituent entities, causes, and consequences.

#### Principles

1. All entities are systems, with some internal complexity.
2. All entities change.
3. Some entities may have inputs and outputs.
4. All rates of change, including inputs and outputs, are influenced directly by physical factors.
5. Some entities interact.
6. All observers must choose specific temporal and spatial scales at which to make observations.

## Sunday, June 10, 2012

### Basic desiderata (Jaynes)

From E.T. Jaynes with G.L. Bretthorst (2003) Probability theory: the logical of science. Cambridge University Press, Cambridge.

Consider that we build a robot that thinks like us, except that it cannot make qualitative judgements. It can use only Aristotelian logic. What sort of fundamental desirable properties would its thinking have?

Desiderata I.   Degrees of plausibility are represented by real numbers.

Desiderata II.  Qualitative correspondence with common sense.

Desiderata III. Consistency:
• IIIa. If a conclusion can be reasoned out in more than one way, then every plausible way must lead to the same result.
• IIIb. The robot always takes into account all of the evidence it has relevant to a question. It does not arbitrarily ignore some of the information, basing its conclusions only on what remains. In other words, it is not ideological.
• IIIc. The robot always represents equivalent states of knowledge by equivalent plausibility assignments. That is, if in two problems the robot's state of knowledge is the same (except perhaps for the labeling of propositions), then it must assign the same plausibilities in both.
....

I (HS) will note that IIIb makes this robot a Bayesian, just like the rest of us.

## Sunday, June 3, 2012

### Will Bayesian statistics become too easy?

A Bayesian approach to statistical inference has become increasing popular since the advent of increased desktop computing power and the development of tailored software. This is a really really good thing. However, I am concerned that it may, in the not very distant future, become too easy, and too much like frequentist methods as they are currently learned and used by life science undergraduate and graduate students. I am concerned that, in order to make Bayesian methods more accessible, they will be dumbed-down --made too easy-- and their value lost.
Part of the benefit of a Bayesian approach is that it more accurately reflects how Science is done. In a nutshell, the Bayesian approach consists of
1. Prior beliefs: ideas, knowledge, and explicit assumptions about our system,
2. Collection of new data.
3. Using the new data to update our beliefs.
The result of a Bayesian analysis is not a simple yes-no, significant-not significant kind of answer, but rather a probability distribution that reflects our most informed guesses about our variable of interest.

I believe that there are two potential pitfalls in the over simplification of a Bayesian analysis. I believe that the less serious of these pitfalls concerns the results, the posterior distribution of each model parameter. Each of these distributions is really a massive collection of independent guesses at the parameters of interest, given all of our assumptions and the newly collected data. Thus the result is not "an answer" but rather thousands of answers, with some answers more likely than others. In our efforts to satisfy ourselves, editors, and readers, we may try too hard to simplify our results.

Although we may try too hard to simplify our results, I think there is a greater danger that we will try to simplify the prior knowledge and that assumptions that we start with. In my limited experience, ecologists and statisticians are very quick to fall back into the use of the "uninformative prior," as if this is somehow "unbiased." Statisticians recognize that all priors come with a point of view, so there is no such thing as an objective uninformative prior, sometimes more accurately called a reference prior. However, I see us taking the lazy route too often and using a supposedly unbiased reference prior that reduces the tendency to take seriously the literature we read. Lots of data will overwhelm a weak prior. However, it is my experience that priors derive their weakness out of our tendency to not take seriously the quantitative nature of our literature.

As evidence that Bayesian analyses can be made easy, I can point to the numerous specialized programs for population genetics and phylogenetics that are based upon Bayesian approaches. I have seen many students use these with very little notion of what they are doing.

As learning in general is essentially a Bayesian process, my fears are not too serious. Nonetheless, ecologists need to take their priors seriously. Statisticians can help by encouraging us to make our beliefs both informed and explicit. In the end, it will only strengthen our science.

## Tuesday, May 29, 2012

### What are the fundamental units in E & E?

Part of the trick to unifying or connecting things is to figure out what the “things” are that can be connected and need connecting. Here I list the elements or “things” that are at the core of ecology and which need connection. We should think of these as the primary state variables of the most distinct subdisciplines:
• Ecosystem variables: elements tracked by ecosystem scientists, such as carbon, or nitrogen; these might be described by the mean, variance and dynamics of grams per meter squared.
• Individual physiological rates: elements tracked by physiologists, such as body mass, resting and active metabolic rates, or the fat reserves in migratory songbirds.
• Populations: elements tracked by population and community ecologists, and evolutionary biologists; these might be tracked as the mean and variance and the dynamics of N, the number of individuals.
• Genes: the elements tracked by evolutionary biologists; these tend to be tracked by either copy number, N, or frequency, p.

We can use similar conceptual and mathematical tools and equations to study all of these. Complicating factors are numerous and in many cases shared across subdisciplines. For instance, one could study “disturbance” in any of these subdisciplines, but but it is the consequence of disturbance that is usually of primary interest. The physical landscape is an important factor as well, whether in landscape ecology, metapopulation dynamics, or in niche partitioning. Again, it is the consequence of the landscape more than the landscape itself which is usually of primary interest.

These elements (ecosystem variables, populations and genes) can be and often are linked in classic levels of biological organisation (e.g., cells, tissues, organs, organ systems, etc.). While this is a comfortable approach, it is not the best we can do. This LBO approach requires the instructor to create all the meaning, connection, and disciplinary thinking and structure. Instead, the Core Elements approach reinforces the type of disciplinary thinking of of ecology and evolutionary biology generally.

The primary cross-cutting feature of these elements that scientists tend to study are statics and dynamics, corresponding to pattern and process. For each element type, we can measure a static pattern such as the amounts of carbon in the atmosphere and the oceans, the abundance an invasive species in its introduced range and its native range, or the relative frequency of rare genotypes in the wild. By the same token, we can measure the dynamics or processes of a system, such as the rate of flow of carbon from the atmosphere to the oceans, how metabolic rate varies with body mass, population growth rate of an invasive species, or changes in particular allele frequency in response to El Nino events.

We often equate pattern with description and process with mechanism, but this is a misleading distinction. We can describe patterns and processes, and use either of such descriptions in either hypothesis-generation or hypothesis falsification/confirmation.


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Homework Help: Speed of an exiting gas from a pressured deposit

1. Sep 5, 2008

Kasper_NYC

Hi,

Please, what is the formula to calculate the speed (velocity) of an exiting flow of gas from a pressured deposit?

For example, it is supposed a deposit, that contains gas CO2, at 10 atmospheres of pressure (980.665 KPa), with a density of 18.7 Kg/m^3, at 288.15 K (59 F) of temperature. The molar mass of the CO2 is 0.044 Kg/mol.

How much would be the speed (velocity) during the first second of an exiting flow of gas from the deposit to the atmosphere, through a 10 cm diameter hole made in the deposit, being the exterior atmosphere at 1 atmosphere of pressure and 288.15 K of temperature as well?

Please, image a hypothetical huge deposit, so the loss of mass of the first second exiting gas doesn’t make any perceptible difference in the density of the total mass of the deposit (so neither the pressure changes), and doesn’t matter any other variable as humidity, external wind, resistance or viscosity.

I have been several days looking for this formula, and I couldn’t find it. Any link will help.

PS - [[ Maybe this is ridicules, but I supposed that the difference of 9 atmospheres of pressure, it is similar to the energy that a mass of 1 cubic meter of water will have when falls vertically 90 meters. (1 atmosphere of pressure it is similar than the hydrostatic pressure at 10 meters of depth in water). So I supposed that the speed of the exiting gas will be similar to the speed you get in a free fall of 90 meters. I estimated 42.02 m/s. But I am afraid this is completely wrong. ]].

2. Sep 6, 2008

Irid

Well, you just calculate the force:

$$F = P S$$

Then, according to a modified version of Newton's 2nd law,

$$F = v\frac{\Delta m}{\Delta t} = \rho S v \frac{\Delta x}{\Delta t} = \rho S v^2$$

And so, the velocity is

$$v = \sqrt{\frac{P}{\rho}}$$

3. Sep 7, 2008

Kasper_NYC

Hi Irid,

Thanks for your answer. Before you answer me I posted also in other forum in order to compare results. This problem seems to be a little bite tricky.

I have tried the formula you suggested and I have got this:

$$P$$: 980665 Pa
$$\rho$$: 18.7 Kg/m$$\overline{}3$$

$$\nu$$ = 229 m/s

http://en.wikipedia.org/wiki/Choked_flow

Being all of them relatives to "Chocked Flow", that I think is what the problem is going about.

I have tried two of them, getting a similar result that "Krchwey" answered in the other forum: approximately 16 Kg/s that means a volume of 0.8556 m^3, that will results in a speed flow of 109 m/s approximately.

This is the formula I have used:

Q = C A [K d P]^(1/2) [2/(K+1)]^(K+1)/(2K-2)

C= 0.72
A= 0.007853981 m^2
K= Cp/Cv = 815 / 626 = 1.3 J/Kg
d= 18.7 Kg/m^3

Q = 0.005654866 * 4882.608 * 0.585227 = 16.158 Kg/s

My result is a little bite different, but is close.

Still I am confused, and I am not sure if this is the correct answer. I have to check everything again, and I will let you know.


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# texstudio macro for next or previous label

In texstudio there exist two menus by which one can add the \ref{} with reference previous or next label. However, the usage of such a command is more encountered when referencing to equations, where the \eqref{} should be applied instead. Therefore, it would be more appropriate if it inserts the key of the next or previous label.

Ex. consider the case:

$$\label{ZEqnNum448683} \begin{array}{l} {\mathop{\min }\limits_{x} \mathop{\sum }\limits_{k}^{} |y_{k}^{+} -y_{k}^{-} |+|z_{k}^{+} -z_{k}^{-} |} \end{array}$$

I need a shortcut to insert just the key, i.e. ZEqnNum448683 into my text when writing above or bellow this equation.

• \mathop{\min } should be \min and \mathop{\sum } should be \sum (they are mathop already) you only need \limits here as array is being used instead of a multi-line math display environment such as align – David Carlisle Dec 24 '17 at 15:15
• Thank you. they were generated by MathType I really don't follow what it does! – Hamid Dec 24 '17 at 16:16

Here's one way:

## Insert Key of Next Label:

%SCRIPT
var LineNo = cursor.lineNumber(), ColNo = cursor.columnNumber();
cursor.movePosition(1,cursorEnums.End, cursorEnums.KeepAnchor);
var myText = cursor.selectedText();
var regEx = /\\label{(.*)}/
var match = regEx.exec(myText);

cursor.moveTo(LineNo, ColNo);
if (match && match[1]){
editor.insertText(match[1])
}

## Insert Key of Previous Label:

%SCRIPT
var LineNo = cursor.lineNumber(), ColNo = cursor.columnNumber();
cursor.movePosition(1,cursorEnums.Start, cursorEnums.KeepAnchor);
var myText = cursor.selectedText();
var regEx = /\\label{(.*)}/
var match = regEx.exec(myText);

cursor.moveTo(LineNo, ColNo);
if (match && match[1]){
editor.insertText(match[1])
}

Assign these to their own respective keyboard shortcuts. In the gif below, I show briefly how to implement these two macros. (Under Macros -> Edit Macros -> Add)

## Test MWE

\documentclass[]{article}

\begin{document}
$$\label{BeforeLabel} x = y$$

% Test here:
\eqref{} % Next key
\eqref{} % Previous key

$$\label{AfterLabel} a = b$$
\end{document}


text:
# Tag Info

18

You should take a look at the possibility to name groups in regex patterns; your match pattern can then be a oneliner: const string pattern = @"^(?<name>\w+)$(?<index>\d+)$$"; Match match = Regex.Match(command[2], pattern); if (match.Success) { string featureName = match.Groups["name"].Value; int index = int.Parse(match.... 12 One possible place you can improve performance is here: const string pattern = @"$(.*?)$"; var query = command[2]; var matches = Regex.Matches(query, pattern); //Gets anything inside the brackets index = Convert.ToInt32(matches[0].Groups[1].Value); //should be an int featureName = command[2].Substring(0, command[2].IndexOf('[')).ToUpper(); You're ... 7 Why would you want to use Regular Expressions anyway if the base format of the string is always the same? Name[Number] seems like an easy pattern. Just iterate through the characters one by one and store all characters in the first string until you reach the first bracket. Then store the numbers in the second string (until you reach the closing bracket). ... 4 Hash all string constants I'm presuming you only have a limited number of keywords ("move", "vertex" etc.). Hash all of those with something fast - CRC32 is perfectly adequate. Split the string into space-separated tokens, as usual, and calculate the hash of the first and second tokens. Then you just need to compare the calculated hash with the hashes of ... 4 Instead of throwing away that list of GovernmentCsvRecord objects after converting it to a StringCsv list, you could keep it around so you don't have to read the csv file again if the IsNumericFile check fails. It looks like you can validate the list of GovernmentCsvRecord objects directly instead of first converting them to StringCsv objects. However, with ... 3 Here's one: number_regex = re.compile( r'^[-+]?(?:(?:(?:[1-9](?:_?\d)*|0+(_?0)*)|(?:0[bB](?:_?[01])+)' r'|(?:0[oO](?:_?[0-7])+)|(?:0[xX](?:_?[0-9a-fA-F])+))' r'|(?:(?:(?:\d(?:_?\d)*)?(?:\.(?:\d(?:_?\d)*))|(?:\d(?:_?\d)*)\.)' r'|(?:(?:(?:\d(?:_?\d)*)|(?:(?:\d(?:_?\d)*)?(?:\.(?:\d(?:_?\d)*))' r'|(?:\d(?:_?\d)*)\.))(?:[eE][-+]?(?:\d(?:_?\d)*... 3 Your expression looks just fine, maybe we would slightly modify that to: ^[+-]?((\d+(\.\d+)?)|(\.\d+))$ for failing these samples, 3., 4., for instance, just in case maybe such samples might be undesired. Other than that, you have some capturing groups that I'm guessing you'd like to keep those. Test the capturing groups with re.finditer import re ...

3

The first obvious optimization would be to not call Regex.Matches(string, string) which compiles the regular expression every single time. Compiling the regex is an expensive operation. Instead, create a Regex (which compiles the expression exactly once) and keep it around during your several thousand invocations. That should by itself do the trick (because,...

2

Well, your regex solution is obviously badly broken - it will fail if the attributes are in a different order, if they are separated by newlines, if they are delimited by single quotes, etc etc. If you try to replace it with a more correct regex (it will never be 100% correct of course) then you are quite likely to lose some of this speed - perhaps ...

2

On my windows 10 laptop, I ran your program on a dummy log file under the python profiler using the command line: python -m cProfile -s cumulative loggrep.py "speech" \data\test.log The dummy log file has about 4.3 Mbytes of text spread across about 100k lines comprising 32772 log entries. The search pattern was "speech", which occured 444 times. ...

1

Pre-compilation In theory, you're going to want to call this function more than once. That means that you only want to pay the cost of regex compilation once, and you should move your re.compile calls out of the function, setting your regex variables in the module's global scope. Type-hinting s is s: str, and char is (I think) also char: str. 'Removed ...

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text:
This is a graded in-class assignment with peer review. One submission per group on paper. Do a clean work, your style will be evaluated too. Take a snapshot of your work after peer review. Check the details of peer review guidelines on Bilgi Learn.

# Question 1

A boutique shop offers three types of breads; olive, rye and white. 15% of its customers buy olive bread, 55% rye bread and the rest white bread. What is the probability that the first 10 customers of the shop buys 2 olive, 5 rye and 3 white bread?

# Question 2

An urn contains 32 balls; 18 red, 14 white. If I take 8 balls randomly from the urn, what is the probability of getting 4 red balls?

# Question 3

A UNICEF activist asks bypassers to contribute to their efforts. Each of her attempts has a 10% chance of success. What is the probability that she got the first contribution at the 10th attempt?

# Question 4

Suppose there are 10 cards in a deck numbered from 1 to 10. If I draw four cards out of the deck without putting them back, what is the probability that they are in increasing order (e.g. 3-4-5)?

# Question 5

A tennis player has the probability of 0.15 to ace a serve (i.e. he serves and gets the point without the opponent touching the ball) at each shot. His trainer challenged him that he will pay the square of the aces he makes out of 10 serves (e.g. if he serves 8 aces out of 10, the trainer pays him $$8^2 = 64TL$$). But, if he serves less than or equal to 6 aces, the player should pay the trainer 5 TL for each ace he missed (e.g. 4 aces 6 misses, player pays up 6*5 = 30TL).

1. What is the maximum amount of money he can get?
2. What is the expected earnings of the player?
3. What is the variance of his earnings?


text:
- Current Issue - Ahead of Print Articles - All Issues - Search - Open Access - Information for Authors - Downloads - Guideline - Regulations ㆍPaper Submission ㆍPaper Reviewing ㆍPublication and Distribution - Code of Ethics - For Authors ㆍOnline Submission ㆍMy Manuscript - For Reviewers - For Editors
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 J. Korean Math. Soc. 1998 Vol. 35, No. 1, 1—257
 Strong-max cyclic submodules Chin-Hong Park MSC numbers : 16D99 J. Korean Math. Soc. 1998 Vol. 35, No. 1, 1—9
 Norm estimate for a certain maximal ppeator Jong-In Lee and Yoon Jae Yoo MSC numbers : Primary 42B25 J. Korean Math. Soc. 1998 Vol. 35, No. 1, 11—21
 Assouad Dimension : antifractal metrization, Porous sets, and homogeneous measures Jouni Luukkainen MSC numbers : Primary 54F45; Secondary 28A75 J. Korean Math. Soc. 1998 Vol. 35, No. 1, 23—76
 A central limit theorem for functionals of level overshoot by a Gaussian field with dependence Tae Il Jeon MSC numbers : 60F05 J. Korean Math. Soc. 1998 Vol. 35, No. 1, 77—83
 The Riemann problem for a system of conservation laws of mixed type (I) Choon-Ho Lee MSC numbers : 35L45, 35L65 J. Korean Math. Soc. 1998 Vol. 35, No. 1, 85—114
 Optimal problem of regular cost function for retarded system Jong-Yeoul Park, Jin-Mun Jeong, and Young-Chel Kwun MSC numbers : Primary 49B20; Secondary 93C20 J. Korean Math. Soc. 1998 Vol. 35, No. 1, 115—126
 A Basis of the space of meromorphic quadratic differentials on Riemann surfaces J. H. Keum and M. K. Lee MSC numbers : 14H55 J. Korean Math. Soc. 1998 Vol. 35, No. 1, 127—134
 A collision avoidance control problem for moving objects and a robot arm Junhong Ha and Jito Vanualailai MSC numbers : 65L07, 93-04, 73B52 J. Korean Math. Soc. 1998 Vol. 35, No. 1, 135—148
 Homology of the triple loop space of the exceptional Lie group $F_4$ Younggi Choi and Seonhee Yoon MSC numbers : 55R20, 55S12 J. Korean Math. Soc. 1998 Vol. 35, No. 1, 149—164
 Selection theorems with $n$-connectedness In-Sook Kim MSC numbers : 54C65, 54C60, 55M20 J. Korean Math. Soc. 1998 Vol. 35, No. 1, 165—175
 Weighted Bloch spaces in $\Bbb{C}^n$ Kyong Taik Hahn and Ki Seong Choi MSC numbers : 32H25, 32E25, 30C40 J. Korean Math. Soc. 1998 Vol. 35, No. 1, 177—189
 Iterative process with errors for $m$-accretive operators J. H. Baek, Y. J. Cho, and S. S. Chang MSC numbers : 47H17, 47H06, 47H10 J. Korean Math. Soc. 1998 Vol. 35, No. 1, 191—205
 On selfsimilar and semi-selfsimilar processes with independent increments Ken-iti Sato and Kouji Yamamuro MSC numbers : 60G18, 60J30 J. Korean Math. Soc. 1998 Vol. 35, No. 1, 207—224
 Genus distributions for bouquets of dipoles Jin Hwan Kim and Jaeun Lee MSC numbers : 05C10 J. Korean Math. Soc. 1998 Vol. 35, No. 1, 225—235
 The generalized normal state space and unital normal completely positive map Sa Ge Lee MSC numbers : 46.L.10 J. Korean Math. Soc. 1998 Vol. 35, No. 1, 237—257


text:
Volume 340 - The 39th International Conference on High Energy Physics (ICHEP2018) - Parallel: Formal Theory
Prediction for the Cosmological Constant and Constraints on SUSY GUTS: Status Report for Resummed Quantum Gravity
B.F.L. Ward
Full text: pdf
Published on: August 02, 2019
Abstract
We give a status report on the theory of resummed quantum gravity. We recapitulate the use of our resummed quantum gravity approach to Einstein's general theory of relativity to estimate the value of the cosmological constant as $\rho_\Lambda=(0.0024{\mathrm{eV}})^4$. The estimate is made in the context of the Planck scale cosmology formulation of Bonanno and Reuter. We discuss the constraints on susy GUT models that follow from the closeness of the estimate to experiment. Various consistency checks on the calculation are addressed and we use the Heisenberg uncertainty principle to remove a large part of the remaining uncertainty in our estimate of $\rho_\Lambda$.
DOI: https://doi.org/10.22323/1.340.0620
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