16514620
SIMD architecture for job shop scheduling problem solving
Job shop is a typical environment for manufacturing high-variety and low-volume discrete parts. Good scheduling is critical and challenging to the competitiveness of job shops. The Lagrangian relaxation neural network (LRNN) provides an approach of quantifiable quality and successful industrial applications. To further speed up scheduling for large-scale problems, in this paper, the parallelism of the LRNN approach is exploited for hardware implementation. New designs include a SIMD architecture, its associated instruction set and detailed circuits. Logic level simulation of the circuit design shows consistent schedules with those obtained by a software implementation. The hardware implementation is expected to have a one to two orders speed-up over the software one.
43612588
Priority-Based Internet Access Control for Fairness Improvement and Abuse Reduction
In this paper, we exploit a prioritized-service architecture and apply a priority based traffic control scheme to reduce abusive Internet access, improve fairness among users and study users' behavior under a prioritized service for Internet access. The Internet access by dormitory users of National Taiwan University (NTU) serves as a conveyer problem. There are two classes of service. The regular class has a volume quota for each user, which is designed to meet majority users' essential demands while limiting abusive usage of quality service. The custody class is lower in service priority with no volume quota limitation. Our mathematical models for design and analysis include individual and aggregate user demand models and a network performance model. The priority control scheme is implemented over an existing NTU dormitory network with additions of a QoS router, a meter reading server, an accounting server and a user interface server. The control leads to 48.9% reduction in average packet drop rate, 42.2% improvement in a fairness measure, reduction of abusive Internet access by 57.82% and 145.09% Internet access increase in majority users. Such results are quite consistent with predictions of our mathematical models.
44477744
Efficient selection of scheduling rule combination by combining design of experiment and ordinal optimization-based simulation
In a fab with heterogeneous machine groups, the number of scheduling policies grows in a combinatorial way because each machine group has its specific dispatching rules. In this paper, we design a fast simulation methodology by an innovative combination of the notions of ordinal optimization (OO) and design of experiments (DOE) to efficiently select a good scheduling policy for fab operation, Instead of finding the exact performance among scheduling policies, our approach compares their relative orders of performance to a specified level of confidence. The DOE method is exploited to largely reduce the number of scheduling policies to be evaluated by the OO-based simulation. Simulation results of applications to scheduling wafer fabrications show that most of the OO-based DOE simulations require 2 to 3 orders of magnitude less computation time than those of traditional approach, and the speedup is up to 7,000 times in certain cases.
613728
Dynamic scheduling rule selection for semiconductor wafer fabrication
We exploit the speed of an ordinal optimization (OO)-based simulation tool designed by Hsieh et al. (1999) to investigate dynamic selection of scheduling rules for semiconductor wafer fabrication (FAB). Although a scheduling rule is a combination of loading wafer release and dispatching rules, this paper specifically focuses on dispatching when significant amount of wafers-in-process are held due to engineering causes and when major machine failures occur. Four prominent dispatching rules combined with the wafer release policy of workload regulation constitute a basic set of rule options. The dispatching rule may be weekly selected based on FAB states over a four-week horizon. A total of 756 rule options are then evaluated and ranked by the OO-based simulation tool under the performance index of mean cycle time and throughput rate. Results demonstrate the value of dynamic rule selection for uncertainty handling, the insightful selection of good rules and the needs for further research.
27879646
Location-Based Services for Tourism Industry: An Empirical Study
To cope with the fact of high competitiveness in tourism industry, some travel agencies are adopting the strategy of providing relatively more abundant and higher quality services to their clients. Since prior research has found that lack of information is one of the main barriers for people to travel, provide location-based information to people visiting and staying at a new location should be useful and valuable. This research attempts to find out travelers’ attitude toward location-based service (LBS). “What factors will affect the travelers’ willingness to adopt this new service” is what we tried to find out in this research. Our findings shows that perceived usefulness, perceived ease of use, and security & privacy are associated with travelers’ attitude toward using LBS, but location information, context awareness, and device functions are not. Our findings can be referenced by tourism industry for the purpose of the design and development of successful business applications to catch the revolutionary opportunity and benefit of LBS.
18088728
Order Consolidation for Batch Processing
We consider the batch processing of orders where either whole or part of a single order or a specific pair of different orders may be grouped in a batch with a fixed capacity. The problem can be modelled by a graph G = (V,E), where each node v$${\in}$$V corresponds to an order, its weight w(v) corresponds to the amount of ordered quantity and a pair of orders, say u and v may be grouped in a batch if there exists the edge (u,v) $${\in}$$E. The objective is to maximize the number of batches filled up to its capacity $$\lambda$$. In this paper, we prove that the problem is NP-hard and, moreover, that no PTAS exists unless P = NP. Then, an optimal algorithm is developed with running time O(|V|log |V|) for the special case when G is a tree.
28061461
An entity-relationship approach to schema evolution
A dynamically evolving information system supports changes to its database schema in order to facilitate the needs of new application programs. This paper presents an approach to schema evolution through changes to the entity-relationship schema of a database. This approach has the advantage of being closer to the designer's perception of data, rather than to the logical database schema which describes how data are stored in the database. The underlying database structure is re-organized, if necessary, to accommodate new data without the changes affecting existing objects. In this way and through the construction of views, modifications of existing programs are avoided while all objects in the database are accessible to all application programs, both new and old. Thus, the invariance of the programs' interface is preserved by the views.<<ETX>>
15015492
Undoing Code Transformations in an Independent Order
A transformation applied to optimize or parallelize a program may be found to be ineffective, or may be made invalid by code changes. In this paper, we present a technique to remove such transformations. The order of undoing the transformations is independent of the application order. The technique uses post conditions of a transformation to determine whether the transformation can be immediately removed. Transformations that affect the immediate removal of a transformation must be identified and removed. Other transformations made invalid by the removal of a transformation must also be undone. The technique employs inverse primitive actions, making the technique transformation independent. The enabling and disabling interactions of transformations are used to drive the process, thereby reducing redundant analysis when undoing transformations.
16824799
A heuristic method for self‐healing ring design in a single‐homing cluster
In this paper, we consider a SONET (Synchronous Optical NETwork) USHR (Uni‐directional Self‐Healing Ring) design problem for a single‐homing cluster, i.e., a cluster with a single designated hub. The problem is formulated as a nonlinear integer programming problem and a branch and bound heuristic method based on the Lagrangian relaxation and subgradient optimization technique is proposed to handle the problem. In solving any ring design problem, we should deal with two different aspects of the ring design, namely, the ring routing aspect and the ring loading aspect. Both of these two aspects are well integrated and represented in our model. Such an integrated formulation has not been proposed in the existing literature mainly due to its computationally intractable complexity. In order to cope with such complexity, a preprocessing technique for reducing the complexity and several branch and bound strategies are proposed. The efficiency of the proposed method is tested through computational experiments. For the computational experiments, test problems are generated using the data obtained from the actual topologies in Seoul, Korea. The computational experiments show that the proposed method yields near‐optimum designs within reasonable computation time.