• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2006.11a
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• pp.702-707
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• 2006

There have been certain extent of material inventory in construction site because of difficulties in ordering by small quantity, strategy of securing future requirements and prevention of delay. However, carrying these inventory entails a financial cost called inventory holding cost and decrease construction productivity, so proper inventory management in construction industry is important for construction efficiency and cost reduction. This study tries to find analytical method of inventory management. It includes ordering decision which decide how much to order and when to order. Setting these strategies including deciding safety inventory, input and ouput variability are able to controled.

• Journal of Internet Computing and Services
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• v.8 no.2
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• pp.77-87
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• 2007

A typical VOD service allows that a number of remote clients playback a desired video from a large collection of videos stored in one or more video servers. The main bottleneck for a VOD service is the network bandwidth connecting to the VOD server to the client due to the high bandwidth requirements. Many previous researches have shown that VOD server can be greatly improved through the use of multicast, broadcast, or P2P scheme. Broadcast is one of the most efficient techniques because it can transmit a stream to many users without additional network bandwidth. But the broadcast has long latency time. In order to overcome the drawback, in this paper, we propose P2Prefix broadcast scheme that can solve the service latency time, which is the problem of broadcast scheme, by using P2P caching as well as minimizing the client buffer requirement.

• The Journal of the Korea Contents Association
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• v.10 no.1
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• pp.68-77
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• 2010

In this paper, we propose a new log buffer management scheme considering the accessibility of the data. Our proposed scheme evaluates the worth of the merge of log blocks. It conducts the merge operations between infrequently updated data and the data blocks and postpones as much as possible the merge operations between frequently updated data and the data blocks. As a result, the proposed method prevents the unnecessary merge operations, reduces the number of the erase operations, and improves the utilization of the flash memory storage. In order to show the superiority of the proposed scheme, we compare it with BAST and FAST. It is shown through performance evaluation that the proposed method achieves about 25% and 65% performance improvements over BAST and FAST on average in terms of the number of the erase operations.

• Journal of Korea Water Resources Association
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• v.47 no.9
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• pp.743-752
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• 2014

Delay time for groundwater recharge means the travel time from the bottom of soil layer to groundwater through vadose zone after infiltration from rainfall. As it is difficult to measure delay time, we suggested an empirical formula which is derived by using linear regression between altitude and delay time. For the regression analysis, 4 major gauging watersheds were chosen (Hancheon, Kangjeongcheon, Oedocheon, Cheonmicheon) with 18 measured groundwater level stations. To verify this empirical formula, derived equation from linear reservoir theory was applied to compute delay time and to compare estimated amounts of groundwater recharge using both methods. The result showed good agreement. Furthermore, if derived empirical formula would be linked with SWAT model, the spatial time delay effect in the watershed could be reflected properly.

• The Journal of the Acoustical Society of Korea
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• v.36 no.1
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• pp.23-29
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• 2017

A concept of a VSA (Virtual Source Array) is the method for an acoustic spatio-temporal focus at a selected location in the outbound direction with respect to the VSA without the need of a probe source as combines a TRP (Time-Reversal Processing) and time-delay and beam-steering. However, in TRP using the VSA concept, it is limited to the critical angle and the short distances relevant to the VSA. In this paper, the waveguide invariant theory is applied to the VSA concept to refocus the received field at ranges greater other than the critical angle and the short ranges by shifting the focused field. The suggested method is verified via numerical simulation, and the results show that the robust acoustic focusing is achieved on the selected location regardless of the limitation on the conventional VSA concept.

• Journal of Digital Contents Society
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• v.15 no.1
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• pp.1-9
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• 2014

Delay-Tolerant Network (DTN) is an asynchronous networking technology that has been deployed for the networking environment in which steady communication paths are not available, and therefore it stores receiving data in a data storage and forward them only when the communication links are established. DTN can be applied to sensor networks and mobile ad-hoc network (MANET) as well as space communication that supports data transmissions among satellites. In DTN networking environments, it is very important to secure a scheme that has relatively low routing overhead and high reliability, so that it can enhance the overall routing speed and performance. In order for achieving efficient data transmissions among the nodes that have comparatively periodic moving patterns, this paper proposes a time information based DTN routing scheme which is able to predict routing paths. From the simulation results using Omnet++ simulation tools, it has been verified that the proposed time information based DTN routing algorithm shows satisfied levels of routing speed and routing reliability even with lower routing overheads.

• Korean Journal of Construction Engineering and Management
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• v.5 no.2 s.18
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• pp.194-201
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• 2004

Core-wall construction method is applied in many high-rise building constructions. This is caused by the advantages of the method such as the effect of saved construction cost and shortened period. However, the analysis study of planning practice for core-wall construction shows matters take place during core-wall construction, such as increasing in construction cost and period. These matters result from the limited work space leading to low productivity, the activity interference leading to increasing in period, additional temporary work cost and time, and delayed concrete pour activity. A large part of these can be prevented taking place by very detailed and most careful core-wall construction plan. Therefore, this study suggests improvement directions of core-wall construction planning process focused on the cooperation system of a contractor between a sub-contractor and the process.

• 월간 기계설비
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• s.241
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• pp.38-51
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• 2010

6시 15분, 모 설비건설업체 김과장의 스마트폰 알람이 울렸다. 6시에 맞춰놓은 알람이 15분이나 늦게 울린 것이다. 침대에서 뒤척인 정도를 측정해 가장 얕은 잠을 자고있는 최적의 기상시간에 깨워주는 스마트폰 수면 앱을 켜놓고 잔 김과장. 어젯밤 뒤척이다 늦게 잠드는 바람에 스마트폰이 김과장의 최적수면상태를 체크하여 15분 지연된 뒤 깨워준 것이다. 김과장은 자리에서 일어나자마자 오전 중에 있을 공사현장 미팅을 생각해 냈다. 중요한 미팅이라 늦으면 큰일이다. 15분이나 늦게 일어나는 바람에 아침은 걸러야했다. 김과장은 간단히 씻고 난 후 실시간으로 버스 운행 정보를 알려주는 스마트폰 앱을 클릭한다. 5분 후면 버스가 집 앞 버스정류장에 도착한다. 이 버스를 놓치면 15분을 기다려야 한다. 급히 신발을 신고 버스 정류장으로 내달리는 김과장. "휴!"겨우 버스를 탔다. 이제 지하철을 한 번만 갈아타면 된다. 갈아탄 지하철 안에서 김과장은 이메일을 확인한다. 현장에서 자재를 발주해 달라는 이메일이 도착해 있다. 오후에는 자재 발주를 해야 한다. 그러나 오전의 현장미팅이 지연될 수 있으니 지금 발주하는게 좋겠다. 명함관리용 앱을 활용해 자재업체 담당자를 검색하여 전화를 건다. 좀 이른 시간인지 담당자가 전화를 받지 않는다. 김과장은 즉시 자재업체 담당자에게 물품 출고 요청 이메일을 보낸다. 물론 물품내역은 스마트폰 안에 저장된 파일을 통해서다. 모 설비건설업체 김과장의 아침 출근길 단면을 들여다보았다. 스마트폰을 이용해 출근길 버스 및 지하철 속에서도 이메일을 확인하고 물품 출고를 지시한다. 과거에는 사무실에서만 할 수 있었던 일들이 스마트폰이 보편화 되면서 언제 어디서든 움직이면서 업무처리가 가능하게 됐다. 이처럼 스마트폰이 모바일 인터넷 대중화 시대를 열고 있다. 올해 국내 시장에는 약 400만명이 넘는 스마트폰 사용자가 생겨날 것이며 앞으로 더욱 가속화될 전망이다. 스마트폰은 $\triangle$실시간 $\triangle$정보소통의 확장 $\triangle$공간극복 등의 특성을 바탕으로 개인과 기업, 더불어 사회를 변화시킬 전망이다. 통신 플랫폼 패러다임이 변화되고 있는 것이다. 거대한 물결처럼 밀려오는 이러한 변화에 기민하게 대처하지 못하면 개인이든 기업이든 낙오될 수밖에 없다. 건설산업 분야 역시 인터넷 등 통신망을 통해 사업홍보와 시장개척은 물론 각종 업무의 전산처리 등 그 활용 범위가 급증하고 있다. 이제 건설업계도 스마트폰 패러다임에서 비껴나갈 수는 없다. 본지는 스마트폰이 가져온 환경변화와 그 활용범위에 대해 살펴본다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.3
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• pp.391-398
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• 2018

There are many problems caused by data sharing between general heterogeneous digital devices due to various interfaces. To solve this problem, this paper proposes heterogeneous data sharing with cloud service and mobile through D2D communication that supports communication between different devices. The proposed technique is used to reduce the load on the server to perform data synchronization. Also, in order to minimize data latency caused by data replication between different devices, a technique to enhance the speed of data writing with copying only the modified parts in the chunk list is adopted and cloud service model integrated with mobile environment is realized in order to minimize the network bandwidth consumed for synchronization for data sharing. Therefore, it is possible to share data in different spaces efficiently with maintaining data integrity and minimizing latency in data.

• Tunnel and Underground Space
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• v.27 no.3
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• pp.121-131
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• 2017

We studied the time-dependent behaviors of rock and concrete materials by conducting the static and dynamic long-term strength tests. In particular, acoustic emission(AE) signals generated while the tests were analyzed and used for the long-term stability evaluation. In the static subcritical crack growth test, the long-term behavior and AE characteristics of Mode I and Mode II were investigated. In the dynamic long-term strength test, the fatigue limit and characteristics of generation of AE were analyzed through cyclic four points bending test. The graph of the cumulative AE hits versus time showed a shape similar to that of the creep curve with the first, second and third stages. The possibility for evaluating the static and dynamic long-term stability of rock and concrete is presented from the log - log relationship between the slope of the secondary stage of cumulative AE hits curve and the delayed failure time.