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.
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.
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.
15655721
The Worst-case Analysis of the MULTIFIT Algorithm for Scheduling Nonsimultaneous Parallel Machines
Abstract In this paper we consider the nonsimultaneous multiprocessor scheduling problem, or NMSP for short. The NMSP is a makespan minimization scheduling problem which involves the nonpreemptive assignment of independent jobs on m parallel machines with different starting times. It is well known that the longest processing time (LPT) algorithm and the modified LPT(MLPT) algorithm yield schedules with makespans bounded by 3 2 − 1 2m and 4/3 times the optimum makespan, respectively. In this paper, we show that the best known worst-case performance bound, 4/3 of the MLPT, is tight by constructing a worst-case example. Then, we employ the bin-packing heuristic algorithm called the MULTIFIT to solve the NMSP and show that the makespan of the schedule generated by the MULTIFIT algorithm is bounded by 9/7+2−k times the optimum makespan, where k is the selected number of the major iterations in the MULTIFIT. This worst-case bound of the MULTIFIT algorithm is, so far, the best bound for the NMSP and the tightness of the bound is still an open question.
15437086
A framework of a visual language with dynamic specification
The behavior of complex software may be changed depending on the external environment such as user profile, available resources, input data, time, and so on. Design of such dynamic software in conventional languages needs extra effort to keep consistency among behaviors for all states. We propose an object oriented visual language for dynamic software and its visualized specification with dynamics presentation. The language supports dynamic behavior according to both time-dependent and time-independent external states based on dynamic objects. In the visualized specification, we present uniform dynamics presentation for all elements in the language based on three concepts of snapshot, overlap and sweep.
20494586
The implementation of a secure and pervasive multimodal Web system architecture
While most users currently access Web applications from Web browser interfaces, pervasive computing is emerging and offering new ways of accessing Internet applications from any device at any location, by utilizing various modes of interfaces to interact with their end users. The PC and its back-end servers remain important in a pervasive system, and the technology could involve new ways of interfacing with a PC and/or various types of gateways to back-end servers. In this research, cellular phone was used as the pervasive device for accessing an Internet application prototype, a multimodal Web system (MWS), through voice user interface technology. This paper describes how MWS was developed to provide a secure interactive voice channel using an Apache Web server, a voice server, and Java technology. Securing multimodal applications proves more challenging than securing traditional Internet applications. Various standards have been developed within a context of Java 2 Micro Edition (J2ME) platform to secure multimodal and wireless applications. In addition to covering these standards and their applicability to the MWS system implementation, this paper also shows that multimodal user-interface page can be generated by using XSLT stylesheet which transforms XML documents into various formats including XHTML, WML, and VoiceXML.
28778874
A Framework for Intelligent Visual Interface Design for Database Systems
We propose a framework for intelligent visual interface design for database systems supporting visual querying aided by a user model consisting of three components: the class stereotype, the user signature and the system model. An approach for multiparadigmatic visualization is then suggested, in order to achieve seamless integration of different interaction paradigms. Our hypothesis is that such a three-component user model captures the essential characteristics of the user, and enhances human-task interaction. A system architecture and an experimental testbed for model-aided visual querying is then proposed.
23414354
An iconic query system with intensional feedback capabilities
In recent years the issue of the interaction between casual users and database systems has become increasingly important. Moreover, the introduction of multimedia and distributed databases has necessitated the design of querying systems capable of reducing unnecessary and costly accesses. The authors address these issues by proposing a visual query system based on (1) the extensive utilization of icons and natural language in order to facilitate the access and the understanding of the database and (2) the use of knowledge, or the intensional part of the database, in order to reduce the physical access to the actual data (extensional part). In their query system the perception of the database structure is made particularly easy by introducing the concept of generalized attribute.<<ETX>>