• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.590-599
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• 2006

In this study, Liquefaction characteristics of saturated sand under various dynamic loadings such as sinusoidal loading, increasing wedge loading, and real earthquake loading were investigated focusing on the dissipated energy. From the results of cyclic triaxial test, liquefaction resistance strength was calculated by the concept of energy according to the type of input loading. Liquefaction resistance strength was expressed in accumulated dissipated energy calculated from stress-strain curve(hysteresis loop). The dissipated energy according to loading type was compared and the energy-based evaluation was proposed. The procedures are presented in terms of normalized energy demand(NED), normalized energy capacity(NEC), and factor of safely, where NED is the load imparted to the soil by the loading(both amplitude and duration), NEC is the demand required to induce liquefaction, and factor of safely is defined as the ratio of NEC and NED.

• The Transactions of the Korea Information Processing Society
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• v.6 no.10
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• pp.2790-2796
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• 1999

In video-on-demand systems, the I.O bandwidth of video servers is the critical resource which contributes to increase in latency. Several approaches: bridging, piggybacking are used to reduce the I/O demand on the video server through sharing. Batching delays the requests for the different videos for a batching window so that more requests for the same video arriving during the current batching window may be served using the same stream. In this paper, we propose an adaptive reservation-based batching policy which dynamically reserves video server capacity for popoular videos according to video server loads. The performance of the proposed policy is evaluated through a simulation, and is compared with simple batching and static reservation-based batching policies. As the result, we know that the adaptive reservation-based batching policy more improves service ratio and average waiting time than simple batching and simple reservation-based batching policy more improves service ratio and average waiting time than simple batching and simple reservation-based batching polices.

• Journal of KIISE:Computer Systems and Theory
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• v.30 no.5_6
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• pp.223-231
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• 2003

Video-on-Demand (VOD) service needs high resource consumption because of high bandwidth and long playback duration which are characteristics of multimedia. Various techniques such as Patching and Channel-Reserving Patching have been proposed to reduce the demand on the network-I/O bandwidth. Patching allows new clients to join an existing multicast for realization of true VOD, and Channel-Reserving Patching reserves the part of total channel capacity of video server in order to serve the requests for popular videos on which requests of users concentrate. To improve the performance of Channel-Reserving Patching, we propose the method that determines the reserved channel capacity of video server for the popular videos in this paper. The performance of our method is evaluated in terms of average servile latency, defection ratio and fairness through simulation, and is compared with those of Patching and another Channel-Reserving Patching.

• Earthquakes and Structures
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• v.8 no.6
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• pp.1277-1297
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• 2015

Post-tensioned precast segmental bridge columns have shown high level of strength and ductility, and low residual displacement, which makes them suffer minor damage after earthquake loading; however, there is still lack of confidence on their lateral response against severe seismic loading due in part to their low energy dissipation capacity. This study investigates the influence of major design factors such as post-tensioning force level, strands position, columns aspect ratio, steel jacket and mild steel ratio on seismic performance of self-centring segmental bridge columns in terms of lateral strength, residual displacement and lateral peak displacement. Seismic analyses show that increasing the continuous mild steel ratio improves the lateral peak displacement of the self-centring columns at different levels of post-tensioning (PT) forces. Such an increase in steel ratio reduces the residual drift in segmental columns with higher aspect ratio more considerably. Suggestions are proposed for the design of self-centring segmental columns with various aspect ratios at different target drifts.

• Journal of Korean Society of Transportation
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• v.27 no.6
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• pp.167-176
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• 2009

Several travel demand management schemes have been used for controlling overloaded traffics on urban area. To maximize efficiency of the travel management, traffic manager has to set target level that we try to arrive in advance, and then to find optimal variable to attain this goal. In this regard, this paper presents two travel demand management models, expressed by mathematical program, and also presents their solution algorithms. The first is to find optimal travel demand for origin-destination (OD) pair, based on average travel time between the OD pair, and the second is based on the ratio of volume over capacity on congested area. An example is given to test the models.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.7
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• pp.303-308
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• 2001

This paper presents algorithm to plan construction and expanding of substation considering contingency accidents by proposing utilization factor according to configuration of substation bank system. In this paper, firstly, proper sphere of supply area by each district which could be standardized with respect to its supply capacity is established under assumption of long term load forecasting. Secondly, goal of utilization ratio based on configuration of substation bank was set to keep reliability by remaining sound bank when it happen to one bank accidents. Finally, it is set up for optimal construction and expanding of substation considering economy and reliability simultaneously about substation to exceed these ratio. To verify proposed algorithm, at first, after adopting a part of Kangnam area in Seoul as area for testing, it is divided into several regions for this area according to power branches of power utility. Secondly, by deriving correlation factor between load demand and economic indicators in these region respectively, the regional load forecasting was performed with economic growth and city plan scenario. Finally, based on the predicted load demand by region and land use data which is identified from air-photographic, the load demand by district was predicted. Also, planning for substation considering contingency is formulated to expand taking into account computing utilization factor which is based on configuration of substation bank respectively.

• Journal of the Korea Society of Computer and Information
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• v.22 no.7
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• pp.1-7
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• 2017

As the capacity of NAND flash module increases, the amount of RAM increases for caching and maintaining the FTL mapping information. In order to reduce the amount of mapping information managed in the RAM, a demand-based address mapping method stores the entire mapping information in the flash and some valid mapping information in the form of cache in the RAM so that the RAM can be used efficiently. However, when cache miss occurs, it is necessary to read the mapping information recorded in the flash, so overhead occurs to translate the address. If the RAM space is not enough, the cache hit ratio decreases, resulting in greater overhead. In this paper, we propose a method using two tables called TPMT(Translation Page Mapping Table) and SMT(Segmented Translation Page Mapping Table) to utilize both temporal locality and spatial locality more efficiently. A performance evaluation shows that this method can improve the cache hit ratio by up to 30% and reduces the extra translation operations by up to 72%, compared to the TPM scheme.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.2
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• pp.69-80
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• 1998

The optimal reservoir storage capacity is needed to be determined at the stage of reservoir planning. The reservoir storage capacity should be based on water balance between demand and supply, and meet the water deficity during the growing season. However, the optimal reservoir storage capacity should be determined considering benefit-cost analysis for the project. In this study, Two models are developed. The one is the RSOM(Reservoir Storage Optimization Model), that is consisted by three submodels, MROPER (Modified Reservoir OPERation model), RESICO(REservoir SIze and the construction COst computation) model. And the other is the BECA(BEnefit-Cost Anaysis) model. For model application, three districts, Chungha, Ipsil and Edong were selected. The relative difference of B/C ratio between project planning data and estimation by RSOM is 17.9, 15.0 and 7.3% respectively, which may be applicable for water resources development feasibility planning.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.239-241
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• 2010

Performance evaluation for an air conditioning system is conducted at a specified test conditions. One is low temperature and the other is high temperature condition. Most of the manufactures tried to improve the performance at higher outdoor temperature. One of the reasons is that the customer wants to get ore capacity at high temperature climate. To cope with these kinds of demand, manufactures are tried to achieve higher capacity at high temperature with minimum power consumption even with same size of the system. Consequently, previous studies on performance of the air conditioning system are focused on capacity and performance improvement at high outdoor temperature.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.844-849
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• 2006

The electric facilities for subway stations require reliable and safe electricity in spite of their load increases rapidly. Nevertheless, Korea Electrical Safety Corporation reports that the accidents of independent electric facilities increased greatly from 4,632 cases in 1998 to 6,024 in 1999 and 6,776 cases in 2000, while the ratio of the accidents related with transformers grew gradually. As it is, it is deemed very important to minimize the spreading effects of the electric system accidents and thereby, enhance reliability of the electric supply as well as its safety. According to the fact that the electric facilities for subway stations are important for the public safety and conveniences, it should be careful to set their capacity instead of simply applying the general capacity standard to them, and thereby, improve their economy as well as prevent their accidents. With such a basic conception in mind, this study is aimed at analyzing the characteristics of the electric load in the subway stations and thereupon, suggesting some guidelines for setting of the electric facility capacity for subway stations in terms of optimal operation and safety.