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Publications (7)17.94 Total impact

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    ABSTRACT: In metal cutting processes, an effective monitoring system, which depends on a suitably developed scheme or set of algorithms can maintain machine tools in good condition and delay the occurrence of tool wear. In this paper, an approach is developed for fault detection and diagnosis based on an observer model of an uncertain linear system. A robust observer is designed, using the derived uncertain linear model, to yield the necessary and key information from the system. Subsequently, it is used as a state (tool wear) estimator, and fault detection is carried out by using the observed variables and cutting force. The developed approach is applied to milling machine center. Several linear models are identified based on different working conditions. A dominant model plus uncertain terms is derived from these model set and used as an observer. Threshold values are proposed for detecting the fault of the milling machine. Examples taken from experimental tests shown that the developed approach is effective for the fault detection. The approach can be used for fault detection of failures arising from sensor or actuator malfunction.
    No preview · Article · Mar 2007 · International Journal of Machine Tools and Manufacture
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    ABSTRACT: There is a growing trend in developing the wireless machine-to-machine (M2M) communication for factory automation. Currently, most wireless protocols for infrastructureless mobile ad-hoc networks focus on the mobility issue and are mainly suitable for narrowband radio devices. The mechanisms for route update and discovery that work well for wireless mobile ad-hoc networks prove to be redundant and instead add to processing overheads in a static wireless factory setting. This paper presents the development and implementation of a new wireless routing protocol, Bluewave, that caters specifically to wireless communication between machines in a factory setting. Bluewave utilizes features of Bluetooth technology when performing the route setup. The merits of the proposed protocol, in terms of shorter initialization time and route setup time, are duly discussed. A case study illustrating the application of Bluewave to an online condition-based maintenance scenario is presented. Experimental results obtained are furnished to show the viability of Bluewave in industrial automation
    No preview · Article · Dec 2006 · IEEE Transactions on Industrial Informatics
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    Kok Kiong Tan · Han Leong Goh
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    ABSTRACT: The use of the electronic spreadsheet as a modeling and simulation tool in the engineering fields is increasingly popular with an increasing number of tertiary institutions, including spreadsheet as a teaching resource in the core curriculum of these fields. Concurrently, the dramatic improvement in Internet speed allows certain course material to be delivered online, facilitating electronic-learning (E-learning). E-learning frees students from the restriction of time, although they are still largely constrained by space to the nearest wired computer. However, the boundary of computing has expanded with the advance in wireless communication; now numerous handheld mobile devices (e.g., personal digital assistants (PDAs) and cellular phones) are available that will allow computing to be accomplished on the move. In turn, this wireless trend has contributed to move E-learning toward mobile learning (M-learning). Based on the previously mentioned trends, this paper presents the development, implementation, and evaluation of a mobile spreadsheet-based Proportional, Integral, Derivative (PID) control simulation system that aims to enhance the learning of the student in the field of control engineering. The system has been used in an industrial control system course at the National University of Singapore (NUS), Singapore. The mobile spreadsheet system developed is able to work with most handheld mobile devices, including the cellular phone. The methods and difficulties (e.g., limited storage space and small screen display of a cellular phone) involved in the development of the system will be duly discussed. Feedback from students that is used to assess the usefulness of the system will be released to share the benefits of such an M-learning system
    Preview · Article · Jun 2006 · IEEE Transactions on Education
  • Han Leong Goh · Kok Kiong Tan
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    ABSTRACT: Years have lapsed since the inauguration of the first Wireless Application Protocol (WAP) application. One of the main reasons for the lukewarm response so far may be attributed to the lack of a “Killer” application. Many companies and developers have attempted to replicate email services (an Internet Killer appplication) within the WAP realm, but till now, no significant success has been reported. This paper will first discuss on the key functions which are lacking in the present WAP-email service, and which are arguably necessary if a much larger user base is to be attracted to these services. A new system will be proposed which can enable the user to send files residing in a remote personal computer (PC) as attachments to his emails using WAP-enabled mobile devices. The implementation of the system will be presented in details. Issue relating to the connection to various types of email servers and the security of the system will also be addressed in the paper.
    No preview · Article · May 2005 · Computers & Electrical Engineering
  • K.K. Tam · H.L. Goh
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    ABSTRACT: Session Initiation Protocol (SIP) is a new and emerging protocol that is used to establish and release the connection between two end systems. It is used in preference to the older H323 protocol. Both protocols provide a similar set of services but SIP is much simpler because it has less logical components. This paper describes the implementation of a VoIP application using SIP as the handshaking protocol. The implementation of the SIP is performed with the aid of Libsip++ library from Columbia University. The audio signal is transmitted via the Microsoft's Windows API. The VoIP system was created using Delphi 5.0. As the Lipsip++ was created using Microsoft's C++ 6.0, some incompatibility problem arises. There will be a section discussing these problems and it's solution. The VoIP system consists of a SIP server and two user agent. The SIP server is linked to a HTTP server to facilitate the update of user configuration via Internet. This paper will also introduce a new function called chatboard that will facilitate users with speech handicap.
    No preview · Conference Paper · Jan 2003
  • K.K. Tan · Y.L. Lim · H.L. Goh
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    ABSTRACT: This paper presents the development of a system to perform remote adaptive control and automation within a home. Based on an Internet model, it allows users to control and monitor a simulated lock device remotely using a commonly available web browser. Using Sun Microsystem's Jini Technology, the lock device is able to adaptively interact with other devices to form a network of services. This paper describes the research on various technology standards to build a smart home facilitating remote control and self-adapting to new devices. It will also presents the hardware setup, software design considerations and the strength and limitations of the system. Despite some limitations imposed by the hardware, the system proves to be a viable model for future home remote adaptive control and monitoring.
    No preview · Conference Paper · Jan 2003
  • X. J. Xu · H. L. Goh · K. S. Siow · L. M. Gan
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    ABSTRACT: Two polymerizable ionic surfactants sodium 4-(ω-acryloyloxyalkyl)oxy benzene sulfonate (SABS-n, n = 8 or 10) have been synthesized and polymerized. Their critical micelle concentrations (CMC) were determined to be 9.40 × 10-3 M and 2.02 × 10-3 M at 25 °C for SABS-8 and SABS-10, respectively. The rate of micellar polymerization of SABS-8 or SABS-10 was found to be proportional to half an order of the concentration of ammonium persulfate (APS) and first order of the surfactant concentration. Their activation energies of micellar polymerization were relatively low, that is, 58.2 kJ mol-1 for SABS-8 and 45.4 kJ mol-1 for SABS-10. The monomer reactivity ratios for emulsion copolymerization of SABS-8 (M1) and styrene (M2) were determined to be r1 = 0.47 and r2 = 3.91. These emulsion copolymerizations produced small latex particles ranging from 16 to 30 nm in diameter. XPS analysis shows that SABS-8 was significantly enriched on the surface of latex particles, for example, 63.4% surface coverage on latex particles by 16 wt % SABS-8 in the feed composition. The surface coverage of about 20% polymerized surfactant on the surface of latex particles was found to be sufficient to stabilize latexes under heating at 70 °C for at least one month.
    No preview · Article · Sep 2001 · Langmuir