Browsing by Author "Chang, YS"

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A component-based, reconfigurable mobile agent system for context-aware computing
(2002)
Chiao, HT
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Cheng, MC
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Chang, YS
;
Yuan, SM
;
資訊工程學系
In the near future, people can use various kinds of portable terminal devices, such as PDAs or smart phones, to access,the information on Internet at any time, in any place, for supporting their daily life. Personal mobile agents can help those people to search, to filter, to analyze, or to translate the large amount of Internet information. Since the context of a user may vary frequently, the way a personal mobile agent process the Internet information must adapt to the context change. However, we think that the current mainstream mobile agent platforms, such as the IBM Aglet and the IKV++ Grasshopper, are not good enough for developing context-aware applications. Hence, we propose a Component-based, Reconfigurable Mobile Agent (CRMA) system, which is designed for context-aware computing. It offers downloadable user-interface modules on terminal devices for application to adapt the characteristics of various terminal devices. In addition, on agent side, CRMA provides a reconfigurable agent-programming framework, which uses component-based pipelines to perform context-aware data-processing operations. This not only simplifies the programming task for dynamically reconfiguring an agent's behavior to adapt the context change, but also improves the reusability of agent software. In the end of this paper, we will propose a context-aware meta-search service to demonstrate how to use CRMA to develop a context-aware application.
A fault-tolerant object service on CORBA
(1997)
Sheu, GW
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Chang, YS
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Liang, DR
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Yuan, SM
;
Lo, W
There are more and more COSS (Common Object Service Specification) on CORBA (Common Object Request Broker Architecture) that is announced by the OMG (Object Management Group), bur no common specification about fault-tolerance exists now. In this paper, we propose a ''warm stand-by'' replication approach. When an object (primary object) is invoked, it will invoke a secondary object, and the primary object will log the messages and checkpoint the state to the secondary object periodically. If the primary object fails, the secondary object can take over by way of client executing a few operations to change secondary object's mode to primary's. Following the style of COSS, we define four interfaces and provide class implementations that can help programmers write programs with fault-tolerant capability. The whole model has been implemented on Orbix, which is a full implementation of CORBA specification.
A new development environment for an event-based distributed system
(2003-08-01)
Hsiao, TY
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Perng, NC
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Lo, W
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Chang, YS
;
Yuan, SM
The rapid growth of data exchange on the Internet has created many critical problems that require an answer. Traditional data exchange systems based on client/server communication models are less scalable and incur especially high maintenance cost in the data exchange domain. For these reasons, many researchers have switched their interest to asynchronous communication models. Although Message-Oriented Middleware (MOM) is a middle-tier infrastructure that links operating systems and applications, such asynchronous communication APIs supported by middleware vendors are usually hard to use. For these reasons, in this study, we present a new development environment for asynchronous communication platforms which we term Ghostwriter. The keyword for our development environment is 'easy', that is, easy to,use, easy to develop, and easy to deploy. Therefore, many researchers have switched their interest to asynchronous communication models. In addition, learning about and implementing the functions of the asynchronous communication's clients in Ghostwriter environment is simple. Other benefits are a lower technical learning curve, help for concentrate on system design, has easily reusable components, and easily integrated applications. (C) 2003 Elsevier Science B.V. All rights reserved.
A new multi-search engine for querying data through an Internet search service on CORBA
(2000-09-01)
Chang, YS
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Yuan, SM
;
Lo, W
;
資訊工程學系
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Department of Computer Science
Search engines are important but generally far from ideal tools of the World Wide Web (WWW). Many researchers therefore prefer to use meta-brokers to construct multi-search engines (MSE). However, these have no uniform programming interfaces, which makes tying them with other search engines difficult. Moreover, for an application that needs a search service capability, querying them is difficult. To reduce that difficulty, we propose in this paper an Internet search service (ISS) based on common object request broker architecture (CORBA) that follows the style of common object service specification (COSS). We design a multi-search engine based on ISS, which we term Octopus. For a system developer, because of its uniformity of interface, Octopus easily ties with any search engine. Equally, for an application programmer, the ISS offers a clear interface for application programs to search for information or mine data from the Internet. We demonstrate our approach to designing multi-search engines through ISS by tying two search engine agents, Yahoo and Alta Vista, with Octopus and show how CORBA clients query them. Programmers may use this interface to construct their search engine agents or query a search engine agent in their applications. (C) 2000 Elsevier Science B.V. All rights reserved.
A unified interface for integrating information retrieval
(2001-09-01)
Chang, YS
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Ho, MH
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Yuan, SM
;
資訊工程學系
;
Department of Computer Science
In this paper, we propose a unified interface and a flexible architecture for querying various information sources on the Internet and the WWW using both a popular object model and a data model. We propose an Integrated Information Retrieval MR) service based on the Common Object Service Specification (COSS) for Common Object Request Broker Architecture (CORBA) and apply the Document Type Definition (DTD) of eXtensible Mark-up Language XML) to define the metadata of information sources for sharing the ontology between mediator and wrappers, The objective of using the IIR design is not only to provide programmers with a uniform interface for coding a software application that can query a variety of information sources on the Internet, but also to create a flexible and extensible environment that easily allows system developers to add new or updated wrappers to the system. (C) 2001 Elsevier Science B.V. All rights reserved.
A unified, adjustable, and extractable biological data mining-broker
(2003)
Ho, MH
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Chang, YS
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Cheng, MC
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Li, KL
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Yuan, SM
The document formats of biological data sources typically are more versatile and more complicated than the traditional data sources. It is hard to efficiently retrieve useful information from biological data sources by traditional information retrieval technologies. In this paper, we propose a unified, adjustable, and extractable Biological Data Mining-Broker mechanism. Based on XML methodology, the mechanism provides a federated forum model to overcome the heterogeneities of both form and meaning from those different diverse biological data sources. Furthermore, the mechanism also utilizes the feedback-based direct raw and meaningful extracted cache technique to improve the efficiency and accuracy of the system. The experimental results show that our proposed system has good performance, and it is a good choice for biological data mining process with multiple heterogeneous data sources, different mining applications, and knowledge analysts. It is highly useful for target discovery and bioinformatics research projects.
A wrapper generator for integrated information retrieval.
(2002)
Ho, MH
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Chang, YS
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Sun, WC
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Yuan, SM
;
資訊工程學系
In the paper, we propose an XML-based framework for automatic wrapper generation.. Different,from the previous approaches, the wrapper generated within this framework is supported to the unified interface for the meta-search information retrieval system based on the Internet Search Service with CORBA standard. Taking advantages of the great compatibilities of CORBA and XML, the user can easily: develop his information gathering application for a. new search engine or any other information source from-the-Internet in a short period. The major contribution of this paper is, to, provide a CORBA and XML compliant solution of wrapper generator supported to unified interface for the information retriever. It is fast, easy and efficient to design a,, uniform-interface-ready wrapper for information retrieval application by the framework presented in,this paper.
An Information Store and Retrieval Facility on CORBA
(2000)
Lo, W
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Chang, YS
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Chou, CL
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Sheu, RK
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Yuan, SM
In this paper, we propose an Information Storage and Retrieval Facility based on the CORBA. This facility provides information search, retrieval and storage service. To define these services, we referred the Z39.50 and defined a set of interfaces by CORBA IDL. In addition, other information storage respect services, such as information update, information update notify, and information version control etc., and more other services, such as initial service, close service, and search command forward and distribution etc., were provided in this facility. Based on this facility, programmer can add the capability of query Z39.50 server into applications and also can integrate various data sources and provide an uniform interface. Finally, we also implement an experimental library management system to verify our design.
CFMS - A collaborative file management system on WWW
(2000)
Sheu, RK
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Cheng, MC
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Chang, YS
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Yuan, SM
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Tsai, J
The increasing complexity and geographical separation of design data, tools and teams have demanded for a collaborative and distributed management environment. In this paper we present a practical system, the CFMS, which is designed to manage collaborative files on WWW. Wherever remote developers are, they can navigate the evolutions and relationships between target files, check in and check out them conveniently on web browsers using CFMS. The capabilities of CFMS include the two-level navigation mechanism for version selection, the relationship model that conceptually manages the relationships between physical files as well as the prefix-based naming scheme that can uniquely identify requested objects.
CODEX: Content-oriented data EXchange model on CORBA
(2003-08-01)
Chang, YS
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Wu, RS
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Liang, KC
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Yuan, SM
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Yang, M
Asynchronous Data Exchange (ADE) is useful in Electronic Data Interchange (EDI). It needs a well-defined mechanism to support data buffing, dispatching, and filtering. ADE is more flexible, extensible and scalable than the synchronous one. CORBA Event Service, announced by OMG, offers an easy-to-use, abstract and generic communication mechanism, while providing message delivering, dispatching and buffering by way of introducing the concept of event channels. However, it lacks some practical data exchange functions. This paper proposes the design and implementation of a system named CODEX (stand for Content-Oriented Data EXchange system), which combines the XML features and the functionality of CORBA (which stands for Common Object Request Broker Architecture) Event Service. The CODEX system equips functions of primitive data type checking, message classification, content filtering and source/destination screening. Application developers can focus more on business functions, instead of caring about the detail of data exchange. The concept and architecture of the content-oriented data exchange, provided by CODEX, can be applied to other practical computing fields in the large-scale, loosely coupled distributed computing environments. (C) 2003 Elsevier Science B.V. All rights reserved.
Design and implementation of IIPC locking facility
(1999)
Chang, YS
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Yuan, SM
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Chiao, HD
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Chiu, CH
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Tsay, WP
In the most of operating system or distributed operating system, Inter-Process Communication (IPC) is an important mechanism. Most existing IPC synchronization facilities provide only mutual exclusion type of semantic, which greatly reduces the parallelism of concurrent programs and decreases the performance. This paper proposes an intra- and inter-processes locking facility, which is a useful tool promoting the parallelism of concurrent programs. it contains two-level locking facility; the first level deals with thr ead's synchronization its the same process, and the second level handles thread's synchronization in different processes. Both are implemented in the form of DLL on the Windows NT. Beside, we compare the performance of this facility with Windows NT's synchronization objects. The result is obviously that IIPC locking facility has better performance than traditional synchronization objects.
Design and implementation of multi-threaded object request broker
(1998)
Chang, YS
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Lo, W
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Wang, CJ
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Yuan, SM
;
Liang, DR
Distributed object-oriented computing model is the next logical step to develop distributed applications. In recent year, several object models have been proposed, such as COM/DCOM, CORBA, and JAVA Bean etc. In CORBA, which is announced by OMG, object request broker is a software bus to connect applications and object components. In addition, multi-threaded programming is a well-known technique to improve the performance of applications. In CORBA environment, clients can invoke the remote objects that are shared. If those objects are single-threaded it will affect the performance of system by the large distributed applications. In this paper we will depict in detail the design and implementation of multi-threaded object request broker based on the CORBA. Our ORE nas implemented atop Windows NT and underlying TCP protocol. Finally, we will compare our system's performance with IONA's Orbix, which is a well-known commercial product, in both one-way and two-way request.
EMARE: An Email-based Mobile Agent Runtime Environment for information retrieval on the Internet
(2004)
Ho, MH
;
Chang, YS
;
Yuan, SM
;
資訊工程學系
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Department of Computer Science
Most of current information retrieval systems are deployed on high-speed network and high-power environment. For those great increasingly popular mobile devices with low-speed network and low-power environment, to intensively retrieve the information on the Internet is difficult. In this paper, we propose a framework named EMARE (stand for E-mail based Mobile Agent Runtime Environment) to solve the difficulty EMARE provides users to retrieve desired information via mobile devices over the Internet. The mobile device can be a mobile phone, PDA, or handheld PC Take advantage of the compatibility of the e-mail protocol, EMARE can be uniformly accessed by those versatile devices. Furthermore, we, in the proposed framework, also utilize mobile agent technologies to enhance the ability of mobile devices. The experiments show that EMARE is an ideal mobile computing framework with cost-effective communications, unified user interface, and ease-of-deployment features.
ESD protection design to overcome internal damage on interface circuits,of a CMOS IC with multiple separated power pins
(2004-09-01)
Ker, MD
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Chang, CY
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Chang, YS
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電機學院
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College of Electrical and Computer Engineering
This paper reports a real case of electrostatic discharge (ESD) improvement on a complementary metal oxide semiconductor integrated circuit IC product with multiple separated power pins. After ESD stresses, the internal damage have been found to locate at, the interface circuit connecting between different circuit blocks with different power supplies. Some ESD designs have been implemented to rescue this IC product to meet the required ESD specification. By adding only an extra ESD clamp N-channel metal oxide semiconductor with a channel width of 10 mum between the interface node and the ground line, the human-body-model (HBM) ESD level of this IC product can be improved from the original 0.5 to 3 kV. By connecting the separated vertical sync signal (VSS) power lines through the ESD conduction circuit to a common VSS ESD bus realized by the seal ring, the HBM ESD level of the enhanced version IC product with 12 separated power supplies pairs can be significantly improved from original 1 kV up to > 5 kV, without noise coupling issue.
ESD protection design to overcome internal damages on interface circuits of CMOS IC with multiple separated power pins
(2002)
Ker, MD
;
Chang, CY
;
Chang, YS
;
電機學院
;
College of Electrical and Computer Engineering
This paper reports a real case for ESD level improvement on a CMOS IC product with multiple separated power pins. After ESD stress, the internal damage has been found and located at the interface circuit connecting different circuit blocks with different power supplies. Some ESD designs are implemented to rescue this IC product to meet the required ESD specification. By adding only an extra ESD clamp NMOS with a channel width of 10 mum between the interface node and ground line, the HBM ESD level of this IC product can be improved from the original 0.5 kV to 3 kV. By connecting the separated VSS power lines through the ESD conduction circuit to a common VSS ESD bus realized by the seal ring, the HBM ESD level of the second version IC product with 12 separated power supplies pairs can be significantly improved from the original 1 kV up to > 5 kV, without noise coupling issue.
Experience in building a real-time extension library for Java
(2002-11-01)
Chiao, HT
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Kao, SHJ
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Chang, YS
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Huang, ST
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Yuan, SM
For building real-time control programs on PC controllers, we designed and implemented a real-time extension library to enhance the Java virtual machine that was already available in the real-time operating system we used. Our extension library has the following advantages: First, the underlying Java virtual machine needs no modification to accommodate it. Second, this extension library is easily ported to any other priority-based real-time operating system. Third, the core of this extension library is basically derived from a subset of the Real-Time Specification for Java (RTSJ) standard, and thus our real-time control program can be moved to a forthcoming RTSJ-compliant Java virtual machine without much difficulty. In brief, our work may help suggest ways of implementing RTSJ, or the notion of (degrees of) "minimal" compliance/support of RTSJ based on non-RTSJ Java virtual machines. In this paper, we will show the requirement, application programming interface, and implementation of this extension library, and discuss its influence on timing.
High speed performance of 850 nm silicon-implanted AlGaAs/GaAs vertical cavity emitting lasers
(2004-03-01)
Kuo, HC
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Chang, YS
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Lai, FY
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Hseuh, TH
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Chu, LT
In this paper, we report a high speed performance of silicon-implanted vertical surface emitting lasers (VCSELs) with the aperture size 6x6 mum(2). These VCSELs exhibit kink-free current-light output with threshold currents similar to1.14 mA, and the slope efficiencies similar to0.5 W/A. The eye diagram of VCSEL operating at 10 Gb/s with 6 mA bias and 6 dB extinction ratio shows very clean eye. The rise time is 29 ps and fall time is 41 ps with jitter (p-p) = 21 ps. We have accumulated life test data up to 1000 h at 70 degreesC/10 mA. (C) 2003 Elsevier Ltd. All rights reserved.
High-speed modulation of 850 nm InGaAsP/InGaP strain-compensated VCSELs
(2003-07-10)
Kuo, HC
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Chang, YS
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Lai, FY
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Hsueh, TH
;
Laih, LH
High performance 850 um InGaAsP/InGaP strain-compensated vertical cavity surface emitting lasers (VCSELs) are demonstrated with superior output characteristics and modulation bandwidths up to 12.5 Gbit/s from 25 to 85degreesC.
Improvement of high speed performance for 10-Gb/s 850-nm VCSELs using InGaAsP/InGaP strain-compensated MQWs
(2004)
Chang, YS
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Kuo, HC
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Lai, FI
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Chang, YA
;
Laih, LH
We present in this paper the MOCVD growth and characterization of high performance 850nm InGaAsP/InGaP strain-compensated MQWs vertical-cavity surface-emitting lasers (VCSELs). These VCSELs exhibit superior characteristics, with threshold currents similar to0.4 mA, and slope efficiencies similar to 0.6 mW/mA. The threshold current change is less than 0.2 mA and the slope efficiency drops by less than similar to30% when the substrate temperature is raised from room temperature to 85degreesC. These VCSELs also demonstrate high speed modulation bandwidth up to 12.5Gbit/s from 25degreesC to 85degreesC.
InP/InGaAlAs distributed Bragg reflectors grown by low-pressure metal organic chemical vapor deposition
(2003-04-01)
Lu, TC
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Tsai, JY
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Chu, JT
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Chang, YS
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Wang, SC
Long-wavelength vertical cavity surface emitting lasers (VCSELs) are considered the best candidate for the future low-cost reliable light sources in fiber communications. However, the absence of high refractive index contrast in InP-lattice-matched materials impeded the development of 1.3-1.5 mum VCSELs. Although wafer fusions provided the alternative approaches to integrate the InP-based gain materials with the GaAs/AlAs materials for their inherent high refractive index contrast, the monolithic InP-based lattice-matched distributed Bragg reflectors (DBRs) are still highly attractive and desirable. In this report, we demonstrate InP/InGaAlAs DBRs with. larger refractive index contrast than InP/InGaAsP and InAlAs/InGaAlAs DBRs. The switching between InP and InGaAlAs layers and growth rate control have been done by careful growth interruption technique and accurate in situ optical monitoring in low-pressure metal organic chemical vapor deposition. A 35 pairs 1.55 mum centered InP/InGaAlAs DBRs has the stopband of more than 100 nut and the highest reflectivity of more than 99%. A VCSEL structure incorporating 3 5 pairs InP/InGaAlAs DBR as the bottom mirror combined with a 2lambda thick periodic gain cavity and 10 pairs SiO2/TiO2 top dielectric mirrors was fabricated. The VCSELs lased at 1.56 mum by optical pumping at room temperature with the threshold pumping power of 30 mW. (C) 2002 Elsevier Science B.V. All rights reserved.