• International Journal of Automotive Technology
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• 제8권2호
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• pp.165-177
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• 2007

Predictions of diesel particulate filtration are typically made by modeling of a particle collection, and providing particle trapping levels in terms of a pressure drop. In the present study, a series of single channel diesel particulate filter (DPF) experiments are conducted, the pressure traces are inversely analyzed and essential filtration parameters are deducted for model closure. A DPF filtration model is formulated with a non-linear description of soot cake regression. Dependence of soot cake porosity, packing density, permeability, and soot density in filter walls on convective-diffusive particle transportation is examined. Sensitivity analysis was conducted on model parameters, relevant to the mode of transition. Soot cake porosity and soot packing density show low degrees of dispersion with respect to the Peclet number and have asymptotes at 0.97 and $70\;kg/m^3$, respectively, at high Peclet number. Soot density in the filter wall, which is inversely proportional to filter wall Peclet number, controls the filtration mode transition but exerts no influence on termination pressure drop. The percolation constant greatly alters the extent of pressure drop, but is insensitive to volumetric flow rate or temperature of exhaust gas at fixed operation mode.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권10호
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• pp.3945-3964
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• 2015

Since the decentralized structure and the blindness of a large-scale wireless network make it difficult to collect the real-time channel state or other information from random distributed relays, a fundamental question is whether it is feasible to perform the relay selection without this knowledge. In this paper, a Slotted ALOHA based Greedy Relay Selection (SAGRS) scheme is presented. The proposed scheme allows the relays satisfying the user's minimum transmission request to compete for selection by randomly accessing the channel through the slotted ALOHA protocol without the need for the information collection procedure. Moreover, a greedy selection mechanism is introduced with which a user can wait for an even better relay when a suitable one is successfully stored. The optimal access probability of a relay is determined through the utilization of the available relay region, a geographical region consisting of all the relays that satisfy the minimum transmission demand of the user. The average number of the selection slots and the failure probability of the scheme are analyzed in this paper. By simulations, the validation and the effectiveness of the SAGRS scheme are confirmed. With a balance between the selection slots and the instantaneous rate of the selected relay, the proposed scheme outperforms other random access selection schemes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권9호
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• pp.3034-3055
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• 2014

Wireless Sensor Networks have extensively been utilized for ambient data collection from simple linear structures to dense tiered deployments. Issues related to optimal resource allocation still persist for simplistic deployments including linear and hierarchical networks. In this work, we investigate the case of dimensioning parameters for linear and tiered wireless sensor network deployments with notion of providing extended lifetime and reliable data delivery over extensive infrastructures. We provide a single consolidated reference for selection of intrinsic sensor network parameters like number of required nodes for deployment over specified area, network operational lifetime, data aggregation requirements, energy dissipation concerns and communication channel related signal reliability. The dimensioning parameters have been analyzed in a pipeline monitoring scenario using ZigBee communication platform and subsequently referred with analytical models to ensure the dimensioning process is reflected in real world deployment with minimum resource consumption and best network connectivity. Concerns over data aggregation and routing delay minimization have been discussed with possible solutions. Finally, we propose a node placement strategy based on a dynamic programming model for achieving reliable received signals and consistent application in structural health monitoring with multi hop and long distance connectivity.

• 대한공간정보학회지
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• 제10권3호
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• pp.71-77
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• 2002

유역선정과 하도망구축에서 최근에 수치표고모델을 많이 이용한다. 수치표고모델생성방법은 지형측량, 사진측량, 지형도, 위성영상에 의한 방법등이 있다. 정확한 수치표고모델의 추출은 처리방법과 원시자료의 해상력, 공간해상도 등에 많이 의존한다. 그러나 위성영상 촬영시기상조건, 자연환경 등 여러 요인으로 인해 최상의 품질의 위성영상을 얻을 수 없고 또한 스테레오영상의 촬영시기가 다르기 때문에 자동생성 DEM에는 많은 오류를 포함하게 된다. 본 논문은 Kompsat 영상을 이용하여 수치표고모델을 형성하여 유역해석에 있어서 실시간 해석이 가능하도록 자료를 제공하는데 그 목적이 있다.

• 한국게임학회 논문지
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• 제13권2호
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• pp.111-118
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• 2013

미군은 이기종간 워게임 환경통합과 최단시간 모의환경 생성을 위해 SE-CORE와 공통가상 환경을 개발하고 발전시키고 있다. 한국도 실정에 맞는 SEDRIS 연구 등을 진행하고 있지만 여전히 풀어야 할 문제가 많다. 이 연구는 합성자연환경에서 수작업으로 행해지는 객체 배치 과정을 이미지 채널 정보를 통해 반자동화 하는 방법을 제안하고 있으며, 이는 합성환경 생성을 빠르게 하고 이기종간 자료공유를 수월하게 할 수 있게 한다. 향후 추가적인 연구가 진행되면 다양한 정보수집 장치로부터 입력된 자료들을 합성전장환경에 적용할 수 있는 자동화 기술 개발도 가능할 것으로 보인다.

• 대한원격탐사학회지
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• 제35권1호
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• pp.39-55
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• 2019

In this study, we have proposed an improved method to detect forest fires by correcting the reflected signals of day images using the middle-wavelength infrared (MWIR) channel. The proposed method is allowed to remove the reflected signals only using the image itself without an existing data source such as a land-cover map or atmospheric data. It includes the processing steps for calculating a solar-reflected signal such as 1) a simple correction model of the atmospheric transmittance for the MWIR channel and 2) calculating the image-based reflectance. We tested the performance of the method using the MODIS product. When compared to the conventional MODIS fire detection algorithm (MOD14 collection 6), the total number of detected fires was improved by approximately 17%. Most of all, the detection of fires improved by approximately 30% in the high reflection areas of the images. Moreover, the false alarm caused by artificial objects was clearly reduced and a confidence level analysis of the undetected fires showed that the proposed method had much better performance. The proposed method would be applicable to most satellite sensors with MWIR and thermal infrared channels. Especially for geostationary satellites such as GOES-R, HIMAWARI-8/9 and GeoKompsat-2A, the short acquisition time would greatly improve the performance of the proposed fire detection algorithm because reflected signals in the geostationary satellite images frequently vary according to solar zenith angle.

• 지구물리와물리탐사
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• 제7권4호
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• pp.245-250
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• 2004

단일 채널 해양 탄성파탐사 자료의 2차원 탄성파 단면도에 수평거리 보정을 적용하여 탄성파 단면도의 수평축을 거리 단위로 표현하였다. 수평축을 거리 단위로 표시함으로써 탐사선의 운항 속력이 변할 경우 나타나는 수평 거리 왜곡 현상을 상당히 해소할 수 있었다. 수평거리 보정을 위하여 탄성파 자료의 각 트레이스에 저장된 GPS 위치 정보와 자료 취합 윈도우를 이용하였다. 자료 취합 윈도우의 최소 길이는 탐사선의 속력과 발파 간격에 의해 결정하였으며, 최대 길이는 1차 프레넬대 반경을 이용하여 결정하였다. 자료 취합 윈도우의 길이를 결정함에 있어 수평 해상도와 중합의 효과를 동시에 고려하였다. 수평거리 보정 과정을 적용하여 실제 지층구조와 유사하다고 생각되는 2차원 탄성파 단면도를 작성할 수 있었다.

• International Journal of Air-Conditioning and Refrigeration
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• 제9권4호
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• pp.10-16
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• 2001

An experimental study for free convective heat transfer in a thermal diode type enclosure is presented. The thermal diode is a device which allows heat to be transferred in one direction by convection due to density difference of the fluid, and consists of a rectangular-paralle-logrammic enclosure with a guide vane. It is used as heat collection system of solar energy due to its simple construction and low cost. Experimental parameters were guide vane thickness, the inclination angles of the parallelogrammic enclosure, and the lengths of the rectangular enclosure part. The parameter range of the flux Rayleigh numbers was $2.4\times{10}^8$~$9.8\times{10}^8$. The heat transfer rate of this system was shown 10~47% higher than that of other earlier research results without the guide vane. The correlation for fixed $\phi=60^\circ$ was obtained, Nu=0.0037(Ra^*)^{0.429}(d^*)^ {0.050}(Lr/H)^{0.0415}$.

• 유통과학연구
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• 제11권11호
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• pp.89-99
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• 2013

Purpose - The purpose of this research was to examine the regulation and distribution channel of second-hand goods in cross-border trade in order to propose methods of protecting consumers through the international standardization of the intensifying second-hand trade and resource recycling. Research design, data, methodology - This study first defines several concepts relevant to research in international second-hand goods. Second, a questionnaire and interviews were conducted with manufacturers of second-hand toner cartridges and automobile parts to identify the current status of export and manufacturing. Results - The study proposes the international standardization of second-hand goods and waste to protect consumers and promote efficient resource recycling. Conclusions - The results of the study reveal that second-hand goods (except automobiles) do not have an HSK code to use for import/export data collection. Though used car exports are declining, used cars are increasing. Collecting data on used car parts is impossible because the buyers purchase and ship the second-hand parts.

• 한국물환경학회지
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• 제25권5호
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• pp.651-660
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• 2009

Detailed flow analysis in river is essential to increase the accuracy of water quality simulation since flow variation depends on many factors such as cross sections, channel slopes, and bed materials. In the QUAL2E stream water quality simulation model, the hydraulic coefficients are assigned to the reach that is collection of computational element using the hydraulic coefficient. This study developed a module that can incorporate the results of non-uniform flow analysis and assign such information to each individual element. Model application focused on the upstream of the Hoengseong reservoir including the reservoir where significant flow change is expected. Comparing with original QUAL2E model the developed module improved the result of water quality simulation without considering the relation of flow velocity and flow depth in terms of flow rates.