Browsing by Author "Cheng, CW"

Now showing 1 - 5 of 5

iNetwork - a GSM compliant IF-based communication platform
(2000)
Cheng, CW
;
Liu, WC
;
Chung, CG
;
資訊工程學系
;
Department of Computer Science
Enterprise communication systems require data, voice, and mobile communication services. However, the cost to maintain many disparate networks is high. We propose iNetwork, an IF-based communication system complied with GSM to provide these services at an integrated platform Furthermore, an iNetwork system can cooperate with other iNetwork, Internet, PSTN or GSM systems to provide global services.
Rules markup for automatic deployment of information security policies
(2001)
Hwang, JJ
;
Cheng, CW
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
Information security policies define directive principles for information security management. These policies must be implemented in access control models. Role-Based Access Control (RBAC) is a paradigm, with which security policies can be developed from the perspectives of executive officers. Because "role" is tile core part of organizational dynamics, RBAC can provide a vision of adaptive information security management. In organizations, rights are assigned to proper roles and users (employees) are assigned responsibilities of certain roles. With the RBAC model, the function of information and network security can be managed in a flexible way, and better meet tile needs of doing business. XML (eXtensible Markup Language) offers a standard mean for information exchange, and must also be applicable to the exchange of definitions and contents of ACl for distributed applications. In this paper, we propose a classification of rules, which are the base of setting information policies. We also provide two sets of languages in XML: AML (Authorization Markup Language) to formulate these rules, and AUCL (AUthorization Code Language) to express access control information.
Suppression of buoyancy-driven vortex flow resulting from a low speed jet impinging onto a heated disk in a vertical cylinder by cylinder top tilting
(2004-07-01)
Hsieh, JC
;
Cheng, CW
;
Lin, TF
;
機械工程學系
;
Department of Mechanical Engineering
Buoyancy-driven vortex flow resulting from a low speed round gas jet impinging vertically downwards onto a heated horizontal circular disk confined in an adiabatic vertical cylindrical chamber can be strong and even unstable as the buoyancy-to-inertia ratio exceeds certain critical level. An experiment combining flow visualization and temperature measurement is conducted in the present study to explore the suppression of the above buoyancy-driven vortex gas flow by inclining the top of the cylindrical chamber. The chamber top is chosen to incline linearly in the radial direction so that the mean flow in the wall-jet region is accelerated and meanwhile the effective buoyancy signified by the local Rayleigh number reduces in that direction. Specifically, in the present experiment. the disk-to-chamber top separation distance decreases from 20.0 mm at the jet axis to 10.0 mm at the chamber side. Tests are conducted for the jet flow rate varied from 1.0 to 5.0 slpm (standard liter per minute) and the jet-to-disk temperature difference varied from 0 to 35.0 degreesC for two injection pipes with diameter 10.0 and 22.1 mm for the chambers with horizontal and inclined tops. The results from the flow visualization indicate that the chamber top inclination can effectively suppress the unstable buoyancy-induced vortex roll and the temporal flow oscillation at high buoyancy-to-inertia ratios. However, the effects of the chamber top inclination on the inertia-driven rolls are much milder. The non-monotonic air temperature distribution in the radial direction is found to result from the unique vortex flow structure in the chamber. A universal criterion based on the local flow and thermal conditions in the wall-jet region for the onset of the buoyancy-driven roll is proposed. To quantify the characteristics of the vortex flow in the chamber with the inclined top, empirical correlations have been proposed for the size and location of the vortex rolls. (C) 2004 Elsevier Ltd. All rights reserved.
The design of a signaling system in an enterprise network system
(2003)
Cheng, CW
;
Liu, WC
;
Chung, CG
;
資訊工程學系
;
Department of Computer Science
An enterprise communication system has the requirements of data, voice, and mobile communications. We have proposed iNetwork as an enterprise-based communication system that integrates GSM services and IP network resources to establish a low cost communication environment. In this paper we discuss the design of signaling system in iNetwork system, and study the performance and efficiency of iNetwork by investigating the call setup time and mis-routing events. The resultant design has less routing stages than the original design of GSM and it can avoid bandwidth wastage and enhances the utilization of network resources.
Utilizing 3G/WLAN dual-mode terminals to enhance the efficiency of mobile number portability service
(2006-06-01)
Cheng, CW
;
Chung, CG
;
交大名義發表
;
National Chiao Tung University
Querying routing information is all-call-based during the process of translating portable numbers. Long delays in database searches make portable number translation the bottleneck of providing mobile number portability (NP) service. In this article we propose the mitigation of the traffic load through querying an NP database (NPDB) to alleviate the portable number translation delay. We also present a mechanism that utilizes the routing information on dual-mode MSs to alleviate the traffic load of NPDB and thus enhances the efficiency of mobile NP service. To conclude, we evaluate the performance of the proposed mechanism by simulation.