• Journal of the Korea Computer Industry Society
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• v.2 no.2
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• pp.165-180
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• 2001

This study is on the design and performance evaluation of a multi medium access control(MAC) protocol for multimedia access in the wireless ATM network. In general, MAC protocols for multimedia data transmission are classified into the fixed slot allocation algorithm that allocates base-station slots equally over terminals, and the dynamic slot allocation algorithm that with flexible penetration. The conventional slot allocation algorithms assign slots based on the average bandwidths required for various services types. Although the algorithms have a wide bandwidth for real-time-variant services, the slots are being wasted due the service types. To improve the slot waste problem, this thesis proposes a method that minimizes the waste by assigning variable slots based on the most appropriate bandwidth after a base-station analyzes the service type requested from terminals.

• Journal of Communications and Networks
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• v.10 no.3
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• pp.351-361
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• 2008

This paper presents a delay-margin based traffic engineering (TE) approach to provide end-to-end quality of service (QoS) in multi-protocol label switching (MPLS) networks using differentiated services (DiffServ) at the link level. The TE, including delay, class, and route assignments, is formulated as a nonlinear optimization problem reflecting the inter-class and inter-link dependency introduced by DiffServ and end-to-end QoS requirements. Three algorithms are used to provide a solution to the problem: The first two, centralized offline route configuration and link-class delay assignment, operate in the convex areas of the feasible region to consecutively reduce the objective function using a per-link per-class decomposition of the objective function gradient. The third one is a heuristic that promotes/demotes connections at different links in order to deal with concave areas that may be produced by a trunk route usage of more than one class on a given link. Approximations of the three algorithms suitable for on-line distributed TE operation are also derived. Simulation is used to show that proposed approach can increase the number of users while maintaining end-to-end QoS requirements.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.8
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• pp.768-772
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• 2008

Today's microprocessor normally includes several processing cores to reduce the energy consumption without losing performance. In this paper, data transfer ordering mechanism can be efficiently used for cache coherence solution in unidirectional ring interconnect. RING-DATA ORDER combines the simplicity of GREEDY-ORDER and the performance of RING-ORDER. RING-DATA ORDER can be easily applicable to multicore processor with unidirectional ring interconnect.

• Journal of Information Processing Systems
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• v.5 no.2
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• pp.97-104
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• 2009

In this paper we propose a Differentiated Services Based Admission Control and Routing Algorithm for IPv6 (ACMRA). The basic DiffServ architecture lacks an admission control mechanism, the injection of more QoS sensitive traffic into the network can cause congestion at the core of the network. Our Differentiated Services Based Admission Control and Routing Algorithm for IPv6 combines the admission control phase with the route finding phase, and our routing protocol has been designed in a way to work alongside DiffServ based networks. The Differentiated Services Based Admission Control and Routing Algorithm for IPv6 constructs label switched paths in order to provide rigorous QoS provisioning. We have conducted extensive simulations to validate the effectiveness and efficiency of our proposed admission control and routing algorithm. Simulation Results show that the Differentiated Services Based Admission Control and Routing Algorithm for IPv6 provides an excellent packet delivery ratio, reduces the control packets' overhead, and makes use of the resources present on multiple paths to the destination network, while almost each admitted flow shows compliance with its Service Level Agreement.

• Journal of Fisheries and Marine Sciences Education
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• v.26 no.5
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• pp.966-978
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• 2014

Currently, majority small ship's clutch for power transmission to propeller relies on multi plate hydraulic clutch regardless its size. Most of the small ships do not have a spare equipments of clutch. Furthermore, many ship engineers do not have an ability as well as enough experience to solve this problem related to the hydraulic clutch during the voyage. Therefore, any small problems cause many serious marine accidents. Once the clutch has problem, almost of all ships can not sail by itself anymore and it must be towed by salvage boat, maritime police ships, or fish guidance boat etc. In this case, all the accidents will be categorized as a marine accident and they all need to go through marine accident court inquiries. In this study, an understanding of each crew on hydraulic clutch system has been profoundly measured. Furthermore, the knowledge on an emergency navigation protocol of each crew has been also profoundly checked. Additionally, various surveys on hydraulic clutch classes has been performed and its satisfaction of crews on this topic have been carefully checked based on various feedback from students who took these courses. All of the above data from this study will be used to reduce marine accidents in current marine industry.

• International Journal of Vascular Biomedical Engineering
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• v.3 no.1
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• pp.23-29
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• 2005

We developed a three dimensional cardiac tissue model based on human cardiac cell and mono-domain approximation for action potential propagation. The human myocyte model proposed by ten Tusscher et al. (TNNP model) (2004) for cell electrophysiology and a mono-domain method for electric wave propagation are used to simulate the cardiac tissue propagation mechanism using a finite element method. To delineate non-homogeneity across cardiac tissue layer, we used three types of cardiac cell models. Ansiotropic effect of action potential propagation is also considered in this study. In this 3D anisotropic cardiac tissue with three cell layers, we generated a reentrant wave using S1-S2 protocol. Computational results showed that the reentrant wave was affected by the anisotropic properties of the cells. To test the reentrant wave under pathological state, we simulated a hypertopic model with non-excitable fibroblasts in stochastic manner. Compared with normal tissue, the hypertropic tissue result showed another center of reentrant wave, indicating that the wave pattern can be more easily changed from regular with a concentric focus to irregular multi-focused reentrant waves in case of patients with hypertrophy.

• IEIE Transactions on Smart Processing and Computing
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• v.3 no.1
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• pp.28-34
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• 2014

Recently, ultrasound therapy has become a new and effective treatment for many brain diseases. Therefore, skull-mimicking phantoms have been developed to simulate the skull and brain tissue of a human and allow further research into ultrasound therapy. In this study, the suitability of various skull-mimicking materials(HDPE, POM C, Acrylic) for studies of brain-tumor treatments was evaluated using focused ultrasound. The acoustic properties of three synthetic resins were measured. The skull-mimicking materials were then combined with an egg white phantom to observe the differences in the ultrasound beam distortion according to the type of material. High-intensity polyethylene was found to be suitable as a skull-mimicking phantom because it had acoustic properties and a denatured-area shape that was close to those of the skull,. In this study, a skull-mimicking phantom with a multi-layer structure was produced after evaluating several skull-mimicking materials. This made it possible to predict the denaturation in a skull in relation to focused ultrasound. The development of a therapeutic protocol for a range of brain diseases will be useful in the future.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.6
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• pp.588-594
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• 2010

In a multi-hop wireless sensor network, broadcasting is an elementary operation to support command message sending, route discovery and other application tasks. Broadcasting by flooding may cause serious redundancy, contention, and collision in the network, which is referred to as the broadcast storm problem. Many broadcasting schemes have been proposed to give better performance than simple flooding in wireless sensor network. How to decide whether re-broadcast or not also poses a dilemma between reach ability and efficiency under different host densities. In this paper, we present popular broadcasting schemes, which can reduce re-broadcast packets and improve SRB(Saved ReBroadcast). Simulation results show different levels of improvement over the simple flooding scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11B
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• pp.722-729
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• 2005

Ethernet passive optical networks (EPONs) are an emerging access network technology which has a point-to-multipoint topology. EPONs operate point-to-multipoint in the OLT-ONU direction, and point-to-point in the ONU-OLT direction. To support point-to-point emulation and shared LAM emulation, EPONs use multi-point control protocol (MPCP). The MPCP uses logical link identification (LLID) field for frame tagging and filtering between the OLT and ONUs. In this paper, I propose logical-group identification (LGID) for logical link-based multicasting or VLAN services in EPONs. Using LGID with new frame tagging and filtering rules, EPONs support differentiated multimedia broadcasting or multicasting services. Additionally, EPONs can support logical link-based VLAN services that divides ONUs into several subsets.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.1
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• pp.32-43
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• 2000

In this paper, we investigate the existing medium access control (MAC) protocols to integrate the voice and data services in packet-based CDMA networks and furthermore, propose a new approach to circumvent the operational limits inherent in them. We propose the $P^2R$-CDMA (Prioritized Packet Reservation Code Division Multiple Access) protocol for the uplink in the synchronous multi-code CDMA system, which employs the centralized frame-based slot reservation along with the dynamic slot assignment in the base station using the QoS-oriented dynamic priority of individual terminal. The simulation results show that, as compared with the existing scheme based on the adaptive permission probability control (APC), the proposed approach can significantly improve the system capacity while guaranteeing the real-time requirement of voice service.