• The Journal of the Korea Contents Association
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• v.11 no.1
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• pp.34-41
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• 2011

At present wireless internet access service is available through the 3G network, mobile WiMAX and WiFi anytime and anywhere. In this environment where there are various networks, users should be able to select specific networks depending on different situations. And it is necessary to provide mobility support between homogeneous and between heterogenous networks. Given this situation, the many proposals have been presented to link 3G, which has the largest service area among various networks, with mobile WiMAX(IEEE 802.16e), or with WiFi(IEEE 802.11). But, recently, with the increasing volume of wireless internet use and wireless internet data, due to the advents of net-book, e-book and smart phone, the service area of WiFi and mobile WiMAX has rapidly expanded. Especially, the availability of real-time application such as internet phone has led to the relative shrinking of the proportion of 3G mobile communication network giving conventional voice service, and enlargement of those of wireless internet access networks like WiFi and mobile WiMAX. This paper suggests a handover scheme based on PMIPv6, whitch support mobility between WiFi and mobile WiMAX, and minimizes handover delay. In this scheme, the mobile node has a dual stack structure composed of two interfaces-WiFi and mobile WiMAX. Since WiFi dose not support mobility, it is suggested that the mobile node have the capacity to deal with handover signaling between gateway in case of handover between homogeneous networks. This handover scheme, suggested comparing with current handovers between homogeneous networks, has proved, in its analytic evaluation, to be able to reduce handover, transmission, and signaling overhead.

• Journal of Korean Society of Transportation
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• v.22 no.7 s.78
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• pp.7-16
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• 2004

The homogeneous road section is defined as one consisted of similar traffic characteristics focused on demand and supply. The criteria, in the aspect of demand, are the diverging rate and the ratio of green time to cycle time at signalized intersection, and distance between the signalized intersections. The criteria, in that or supply, are the traffic patterns such as traffic volume and its speed. In this study, the effective method to generate valuable data, pointing out the problems of removal method of obscure data, is proposed using data collected from Gonjiam IC to Jangji IC on the national highway No.3. Travel times are collected with licence matching method and traffic volume and speed are collected from detectors. Futhermore, the method of selecting homogeneous road section is proposed considering demand and supply aspect simultaneously. This method using outlier filtering algorithm can be applied to generate the travel time forecasting model and to revise the obscured of missing data transmitting from detectors. The point and link data collected at the same time on the rational highway can be used as a basis predicting the travel time and revising the obscured data in the future.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.4
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• pp.97-103
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• 2001

Accuracy of a machined part is determined by the relative motion between the cutting tool and the workpiece. One of the important factors which affects the relative motion is the geometric errors of a machine tool. In this study, firstly, geometric errors are measured by laser interferometer, and the positioning error of each control point selected uniformly on the control surface CAD model can be estimated from th oirm shaping model and geometric error data base. Where a form shaping function is derived from the link of homogeneous transformation matrix. Secondly, control points are shifted to the estimated amount of positioning errors. A new control surface is modeled with NURBS(Non Uniform Rational B-Spline) surface approximation to the shifted control points. By generating tool paths to the redesigned control surface, we reduce the machining error quite.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.115-119
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• 1999

Ba$_2Cu_3O_{7-{\delta}}$ (YBCO) thin films were deposited by pulsed laser deposition using differently prepared targets: One was a conventionally solid-state sintered (SSS) target and the other was a modified melt-textured grown (MTC) target. Compared with SSS targets, MTG targets showed a well-connected microstructure consisting of much larger grains and the surface was Bess roughened with the cumulative laser incidence. YBCO films deposited from MTC targets showed a denser and smoother surface of the basal film than the case of SSS targets. The investigations of ${\alpha}$-axis outgrowths in the films indicated that the deposition using MTG targets would result in a more homogeneous and stable film growth as compared to the SSS targets. Also, TEM analysis revealed that the film deposited from MTG targets had a less granular microstructure that would reduce weak-link effects in the film.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.882-885
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• 2008

Recently, various types of wireless networks have been proliferated. Bluetooth, IEEE 802.11 WLAN, 802.16e Mobile WiMAX (or Wibro) and 3G celluar networks are some examples. Accordingly, research on seamless mobility support mechanisms among homogeneous or heterogeneous networks has drawn significant interests. This paper examines recent research efforts on seamless mobility support mechanisms from link to transport layer. Yet, no single solution meets all the requirements for supporting the seamless mobility and it seems hard to tell which layer is the most appropriate one for supporting mobility. This area is still wide open and needs further research.

• The Research Journal of the Costume Culture
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• v.5 no.4
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• pp.32-43
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• 1997

Deprivation of means to study the cultures and history of the natives of Bering Strait in their own lands, gives us and especially U. S. A. and Russia-where the objective regions of this study is pertained to-the great suffering of intellectual and aesthetic losses. Throughout 20th century, as political and economic forces prevailed, it became increasingly difficult for both Natives and outsiders to see this region as having common past. In such difficult circumstances, United Nations Council for Environmental Development held at Rio de Janeiro, Brasil in June, 1992 started out to give obligations to present environmental future. With such trend getting stronger and being in demand, this study is also focussed on coincides with such environmental matters and differs from man centered western civilization which ruled th environment rather than to harmonize with it. Through the studies of fashions and cultural materials of this region, it was able to identify the great similarities between Northwestern Alaska and Northeastern Siberia. Especially in the clothing materials of this region\`s toy dolls, it was possible to confirm that both side of Bering Strait possessed similar culture. Although both side had similar environment, in the past its peoples began to be seen as separated and alienated aligned only with their current political state-Russia and U. S. A. Through this study, it was able to see diversity of the peoples and thir languages but also close cultural and historical ties that link them very closely together. This study verified such similarities and common characteristics through close examination of Native clothing and decorations and other traditions of Siberian Natives such as Yupik, Chukchi, Koryak, Even, Amur River peoples and Nivkh; and Alaskan Natives such as Inupiag, Yupik, Alutiig, Aleut, Athapaskan, and Tlingit.

• Journal of KSNVE
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• v.6 no.2
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• pp.163-177
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• 1996

An investigation on thermohydraulic stability of flow oscillations in the CANada Deuterium Uranium-600(CANDU-6) heat transport system has been conducted. Flow oscillations in reactor coolant loops, comprising two heat sources and two heat sinks in series, are possibly caused by the response of the pressure to extraction of fluid in two-phase region. This response consists of two contributions, one arising from mass and another from enthalpy change in the two-phase region. The system computer code used in the investigation os SOPHT, which is capable of simulating steady states as well as transients with varying boundary conditions. The model was derived by linearizing and solving one-dimensional, homogeneous single- and two-phase flow conservation equations. The mass, energy and momentum equations with boundary conditions are set up throughout the system in matrix form based on a node-link structure. Loop stability was studied under full power conditions with interconnecting the two compressible two phase regions in the figure-of-eight circuit. The dominant function of the interconnecting pipe is the transfer of mass between the two-phase regions. Parametric survey of loop stability characteristics, i. e., damping ratio and period, has been made as a function of geometrical parameters of the interconnection line such as diameter, length, height and orifice flow coefficient. The stability characteristics with interconnection line has been clarified to provide a simple criterion to be used as a guide in scaling of the pipe.

• The KIPS Transactions:PartC
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• v.9C no.4
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• pp.589-596
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• 2002

Tn the data transmission service of the mobile host, it is needed to reduce the bandwidth and to make a reliable error recovery. there are two appropriate methods in that. One is FEC which retransmits the parity of error recovery, in case of happening of the loss after forming the parity of error recovery by grouping original data. The other is local recovery based on server which can block the implosion of transmission. The use of FEC and local recovery based on server at the same time enables the reliable multicast. This paper suggests algorithm that recovers the loss by FEC and local recovery based on server through the solution of the problems about triangle routing, tunnel convergence by dividing mobile host into two parts-the sender and the receiver. This model about the loss of algorithm tested the efficiency of performance by the homogeneous independent loss, the heterogeneous independent loss, the shared source link loss model. The suggested algorithm confirms effectiveness in the environment where there are much data and many receivers in mobile host.

• Journal of Communications and Networks
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• v.18 no.3
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• pp.364-374
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• 2016

With vast amounts of spectrum available in the millimeter wave (mmWave) band, small cells at mmWave frequencies densely deployed underlying the conventional homogeneous macrocell network have gained considerable interest from academia, industry, and standards bodies. Due to high propagation loss at higher frequencies, mmWave communications are inherently directional, and concurrent transmissions (spatial reuse) under low inter-link interference can be enabled to significantly improve network capacity. On the other hand, mmWave links are easily blocked by obstacles such as human body and furniture. In this paper, we develop a multi-hop relaying transmission (MHRT) scheme to steer blocked flows around obstacles by establishing multi-hop relay paths. In MHRT, a relay path selection algorithm is proposed to establish relay paths for blocked flows for better use of concurrent transmissions. After relay path selection, we use a multi-hop transmission scheduling algorithm to compute near-optimal schedules by fully exploiting the spatial reuse. Through extensive simulations under various traffic patterns and channel conditions, we demonstrate MHRT achieves superior performance in terms of network throughput and connection robustness compared with other existing protocols, especially under serious blockage conditions. The performance ofMHRT with different hop limitations is also simulated and analyzed for a better choice of the maximum hop number in practice.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.7
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• pp.1037-1047
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• 2001

In this paper, the capacity for the reverse link of the imperfect power controlled DS/CDMA hierarchical cellular system is analyzed considering imperfect sectorization in shadowing environment. Unlike the theoretical assumption, the power control of the DS/CDMA hierarchical cellular system is not perfect. Therefore, we consider various parameters such as the imperfect power control, the imperfect sectorization, the processing gain and the number of microcell interferers, which cause the capacity variation of the DS/CDMA hierarchical cellular system. It is shown that the capacity of DS/CDMA hierarchical cellular system is decreased according to the increase of the deviation of the imperfect power control, the overlapped angle, the power ratio between macrocell and microcell and to the decrease of processing gain, the number of microcell interfering users. Also, it is observed that the hierarchical cellular system can increase the user capacity from 1.54 to 3.89 times compared to the homogeneous macro-cellular system.