• Proceedings of the KSR Conference
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• 2007.11a
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• pp.734-743
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• 2007

The KTX station is one of special generators that produce a lot of trips caused by special land use such as university, airport, and super shopping mall. Special generators need special attention in developing travel demand models since the standard trip generation and distribution model in the conventional four-step approach do not provide reliable estimates of their travel patterns. New modeling approach, activity-based model, considering travel behavior of person, seem to be more appropriate for those special generators. Thus, this study introduces a spatial-temporal activity-based approach and how activity-based approach can be applied to estimation of travel demand at KTX stations.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.75-75
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• 2010

3D 패키징 기술은 전기소자의 소형화, 고용량화, 저전력화, 높은 신뢰성등의 요구와 함께 그 중요성이 대두대고 있다. 이러한 3D 패키징의 연결방법은 와이어 본딩 또는 플립칩등의 기존의 방법에서 TSV(Through Silicon Via)를 이용하여 적층하는 방법이 주목받고 있다. TSV는 기존의 와이어 본딩과 비교하여 고집적도, 빠른 신호전달, 낮은 전력소비 등의 장점을 가지고 있어 많은 연구가 진행되고 있다. TSV의 세부 공정 중 비아필링(Via filling)기술은 I/O수 증가와 미세피치화에 따른 비아(Via) 직경의 감소 및 종횡비(Via Aspect Ratio)증가로 인해 기존 필링 공정으로는 한계가 있다. 기존의 비아 홀(Via hole)에 금속을 필링하기 위한 방법으로 전기도금법이 많이 사용되고 있으나, 전기도금법은 전기도금액 조성, 첨가제의 종류, 전류밀도, 전류모드 등에 따라 결과물에 큰 차이가 발생되어, 최적공정조건의 도출이 어렵다. 또한 20um이하의 비아직경과 높은 종횡비로 인하여 충진시 void형성등의 문제점이 발생하기도 한다. 본 연구에서는 용융솔더와 진공을 이용하여 비아를 필링시켰다. 이 방법은 관통된 비아가 형성된 웨이퍼 양단에 압력차를 주어, 작은 직경을 갖는 비아 홀의 표면장력을 극복하고, 용융상태의 솔더가 관통된 비아 홀 내부로 필링되는 방법이다. 관통 비아홀이 형성 된 웨이퍼 위에 솔더페이스트를 $250^{\circ}C$이상 온도를 가해 용융상태로 만든 후 웨이퍼 하부에 진공을 형성하여 필링하는 방법과 용융솔더를 노즐을 통하여 위쪽으로 유동시켜 그 위에 비아홀이 형성된 웨이퍼를 접촉하고 웨이퍼 상부에 진공을 형성하여 필링하는 방법으로 실험을 각각 실시하였다. 이 때, 웨이퍼 두께는 100um이하이며 홀 직경은 20, 30um, 웨이퍼 상부와 하부의 진공차는 약 0.02~0.08Mpa, 진공 유지시간은 1~3s로 실시하여 최적 조건을 고찰하였다. 각 조건에 따른 필링 후 단면을 전자현미경(FE-SEM)을 통해 관찰하였다. 실험 결과 0.04Mpa 이상에서 1s내의 시간에 모든 비아홀이 기공(Void)없이 완벽하게 필링되는 것을 관찰하였으며 이 결과는 기존의 방법에 비하여 공정시간을 감소시켜 생산성이 대폭 향상 될 수 있는 방법임을 확인하였다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.11
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• pp.30-40
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• 2001

In this paper, we propose a dynamic slot allocation algorithm for efficient transmission of VBR services in wireless ATM networks. The proposed algorithm is based on a hybrid dynamic parameter(DP) control which combines the strength of in-band control and out-of-band control by considering the variation characteristics of buffer length in distributed mobile terminals. This algorithm consists of four sub-algorithms: dynamic parameter determination algorithm, dynamic parameter transmission algorithm, estimation algorithm of the number of request slots, and prorated-allocation algorithm. As the proposed allocation algorithm based on the hybrid DP control scheme can offer nearly precise MAC level estimations of the requirements for each VBR, the algorithm makes it possible to obtain ideal allocation efficiency. The allocation efficiency of the algorithm is shown by numerical analysis. Simulation results show that the proposed algorithm has better performance than conventional schemes in terms of allocation efficiency, delay and cell loss ratio under VBR traffic.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.918-931
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• 2013

The conventional object tracking techniques using PTZ camera detects object movements by analyzing acquired image. However, this technique requires expensive hardware devices to perform a complex image processing. And it is occasionally hard to detect object movements, if an acquired image is low quality or image acquisition is impossible. In this paper, we proposes a smart security CCTV system applying to wireless sensor network technique based on IEEE 802.15.4 standard to overcome the problems of conventional object tracking technique, which enables to track suspicious objects by detecting object movements and GPS data in sensor node. This system enables an efficient control of PTZ camera to observe a wide area, decreasing image processing complexity. Also, wireless sensor network is implemented using mesh networks to increase the efficiency of installing sensor node.

• Journal of Korea Multimedia Society
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• v.9 no.9
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• pp.1107-1117
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• 2006

In this paper, a load balancing method using ring network structure in the Grid database is proposed. In the Grid database, generally, data is replicated for performance and availability. And, user's request is transferred to node and processed in that node which has target data. But, in such environment, a decline of performance can be occurred because unbalanced workload. A traditional research is proposed to solve unbalanced load problem. However, the Grid database has a number of systems and user's request always changes dynamically. Therefore, a traditional research can not be applied. The proposed method connects each node which has a same replicated data through ing network structure. If workload is overflowed in some node, user's request is transferred to a linked node which has a target data. And, this node stops another request processing until workload is decreased. Then, it changes the link structure through sending a message to a previous node, to stop request forwarding from a previous node. This paper shows a proposed method increases performance than existing research through performance evaluation and is more suitable for a complex and dynamic environment.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.2D
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• pp.159-166
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• 2012

During concrete placement, the formwork structure supports the weight of concrete mass. The complexity of the operation can cause concentrated workloads, which in turn brings about a collapse of the temporary structure. As a countermeasure, the operation needs to be constantly monitored to maintain safety and prevent accidents. This paper presents a USN (Ubiquitous Sensor Network)-based safety monitoring system for formwork construction. The system takes advantage of ubiquitous technology in monitoring the behavior of the formwork structure such as deflection, load weight, and tilting. The collected data are sent to the host computer wirelessly for real time monitoring. The data can be then compared with the allowed limits on guidelines. The comparison can indicate whether the concrete placement operation is executed in a safe condition.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.6
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• pp.466-473
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• 2011

The buoyancy and initial momentum fluxes make near-field dominated by buoyant jet when thermal discharge releases underwater. In order to estimate prediction capabilities of those near-field phenomena, non-hydrostatic RANS applied CFD(Computational Fluid Dynamic) model was used. Condition of model was composed based on past laboratory experiments. Numerical simulations carried out for the horizontal buoyant jet in the stagnant flow and vertical buoyant jet into crossflow. The results of simulation are compared with the terms of trajectory and dilution rate of laboratory experiments and analytic model(CorJET) results. CFD model showed a good agreement with them. CFD model can be appropriate for assessment of submerged thermal discharge effect because CFD model can resolve the limitations of near-field analytic model and far-field quasi 3D hydrodynamic model. The accuracy and capability of the CFD model is reviewed in this study. If the computational efficiency get improved, CFD model can be widely applied for simulation of transport and diffusion of submerged thermal discharge.

• Tunnel and Underground Space
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• v.13 no.2
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• pp.100-107
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• 2003

Deformation is found by an external force in the rock which has internal stress. So, deformation is increased in time what is stressed under constant load. Rock materials collapse suddenly in a long period when the creep rate increases slightly. So mechanical deformability of the ground is an essential condition for determination of long term safety in structures. The result of analysis in 40%, 50%, 60%, 70% of constant load in creep test, strain velocity constants $\alpha$ and ${\gamma}$ increase with load increasement. Griggs equation is more exact than Li and Xia, Singh equation, and G$_2$of a flow constant by Burger's model decreases with stress increasement, but η$_1$,η$_2$and G$_1$ manifest irregularly in this study.

• Fire Science and Engineering
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• v.28 no.1
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• pp.31-36
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• 2014

Recently, the safety assessments with using the various evacuation programs are performed for improving the performance of fire and evacuation safety in the building. Generally, the evacuation programs can simulate the human behavior in fire situation by applying the variation of the movement speed and Fractional Effective Dose (FED) index in the smoke. However, if the simulation is performed without optional setting around the fire, the agents do not avoid the fire and they move through the fire. Therefore in this study, we define the radiative repulsion force which exists between the fire and the agents. Moreover, we modify the Helbing's movement model by adding the radiative repulsion force. As a result of the modified movement model, all agents move around the fire and they do not enter the upper bound area of radiative heat flux, $2.4kW/m^2$. From these results, we verified the reliability of the modified movement model.

• Journal of Korea Water Resources Association
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• v.37 no.6
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• pp.499-507
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• 2004

In this study, the fully coupled SWAT-MODFLOW model is developed by using the type of embedment MODFLOW in SWAT. Since SWAT model has semi distributed features, its groundwater component can't consider distributed parameters such as hydraulic conductivity, storage coefficient and spatially variable natures such as distribution of groundwater heads and pumping rate and so forth. The main purpose of this study is to overcome these limitations. This linkage is completed considering the interaction between stream network and aquifer to reflect boundary flow. To correspond HRU in SWAT to grid in MODFLOW, HRU-GRID conversion tool using DEM is newly suggested. As groundwater recharge of MODFLOW can be estimated accurately by SWAT model, the reliability of groundwater discharge and total runoff of watershed could be greatly enhanced.