• International Journal of Highway Engineering
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• v.12 no.3
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• pp.17-26
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• 2010

Maintenance of the roads and bridges is a major issue for all road administrators around the world, and various initiatives are being implemented in each region for the purpose of controlling the ever increasing road maintenance cost while ensuring the safety of the vehicles driving. Efforts for such initiatives have also been made in Asia and initiatives for managing heavy-weight vehicles have recently gained momentum in Korea and Japan. We have developed a technology for unevenly installing bar-shaped sensors (piezo quartz sensors) to enable dynamic axle load measurement at a highly accurate level, and have estimated our measurement accuracy of axle load/gross weight, etc. on an actual road. The measurement accuracy of the axle load/gross weight varies significantly depending on the number of sensors installed. In our implementation, the target accuracy was set to below ${\pm}5%$ for gross weight measurement so that automatic regulation can be applied. We have achieved our target by installing 8-point measurement system. However, to have this technology widely accepted, it was necessary to reduce the system size so that it can be easily implemented. Therefore, we have estimated the relationship between the measurement accuracy and the system size (number of measurement points), and have come up with the proposal of 3-point measurement as an optimum number of measurement points, and have estimated its performance on an actual road. Additionally, we evaluated the relationship between the measurement accuracy and vehicle velocity.

• Journal of KIISE
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• v.41 no.10
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• pp.762-773
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• 2014

As the web of data is increasingly producing large RDFS datasets, it becomes essential in building scalable reasoning engines over large triples. There have been many researches used expensive distributed framework, such as Hadoop, to reason over large RDFS triples. However, in many cases we are required to handle millions of triples. In such cases, it is not necessary to deploy expensive distributed systems because logic program based reasoners in a single machine can produce similar reasoning performances with that of distributed reasoner using Hadoop. In this paper, we propose a scalable RDFS reasoner using logical programming methods in a single machine and compare our empirical results with that of distributed systems. We show that our logic programming based reasoner using a single machine performs as similar as expensive distributed reasoner does up to 200 million RDFS triples. In addition, we designed a meta data structure by decomposing the ontology triples into separate sectors. Instead of loading all the triples into a single model, we selected an appropriate subset of the triples for each ontology reasoning rule. Unification makes it easy to handle conjunctive queries for RDFS schema reasoning, therefore, we have designed and implemented RDFS axioms using logic programming unifications and efficient conjunctive query handling mechanisms. The throughputs of our approach reached to 166K Triples/sec over LUBM1500 with 200 million triples. It is comparable to that of WebPIE, distributed reasoner using Hadoop and Map Reduce, which performs 185K Triples/sec. We show that it is unnecessary to use the distributed system up to 200 million triples and the performance of logic programming based reasoner in a single machine becomes comparable with that of expensive distributed reasoner which employs Hadoop framework.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.223.2-223.2
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• 2010

용융탄산염 연료전지(MCFC)는 $650^{\circ}C$에서 작동하는 고온형 연료전지 시스템이다. 이 시스템은 천연가스 등을 개질하여 생산된 수소를 바로 전기로 생산할 수 있는 시스템으로 열효율이 높으며, 현재 대체 발전시스템으로 각광을 받고 있다. MCFC는 개질방식에 따라 내부개질 방식과 외부개질 방식이 있다. 내부개질 방식은 수소를 생산하는 개질기가 스택내부에 장착된 형식으로 천연가스를 스택내부에서 개질하여 바로 전기를 생산하는 방식이다. 이 내부개질반응에 사용되는 촉매로는 알루미나에 담지된 니켈(Ni) 계열촉매이 주로 쓰이고 있다. 또한 내부개질촉매의 형태는 작은 원주형의 촉매형태로 성형되어 사용된다. 이 성형된 촉매의 크기가 바로 내부개질 스택의 크기를 결정하는 중요한 요소이다. 그래서 촉매의 크기는 되도록이면 작게 성형하는 것이 중요하다. 그러나 촉매의 크기가 너무 작으면 촉매를 성형하는데 큰 어려움이 생기게 된다. 본 연구에서는 니켈 촉매를 공침법이 아닌 균일용액침전법을 이용하여 제조하였으며, 이 촉매를 이용하여 지름이 약 2 mm 이하로 촉매를 압출성형하는 방법을 연구하였다. 먼저 요소(urea)를 이용한 균일용액침전법으로 촉매를 제조하였다. 최적의 촉매 합성조건을 살펴보기 위해서, 반응 온도를 80, 85, 90, 95, $100^{\circ}C$로 변화 시키면서 제조된 촉매의 특성을 살펴보았다. 그리고 촉매의 적절한 니켈 양을 알아보기 위해서 니켈의 양을 30, 40, 50, 60, 70 wt%로 변화 시켰으며, 조촉매로 사용되는 MgO 양을 5, 10, 15, 20 wt%로 변화 시켜서 제조된 촉매의 특성을 살펴보았다. 물성을 비교하기 위해서, X-선 회절분석(XRD) 및 TPR, 물리화학흡착을 하였다. 그 결과 침전반응온도가 $80^{\circ}C$에서 촉매가 가장 좋은 물성을 보였으며, 우수한 개질성능을 보였다. 그리고 촉매 활성물질인 니켈의 함량은 50 wt% 정도가 가장 적절한 함량이었으며, MgO의 함량이 15 wt%일 때 가장 우수한 물성과 개질 성능을 보여주었다. 이 촉매들은 공침법으로 제조된 상용촉매와 비교하였을 때, 보다 우수한 물성과 개질성능 보였다. 그래서 이 촉매를 균일침전법을 이용하여 대량으로 제조한 다음 압출성형 방법을 이용하여 촉매를 원주형으로 제조하였다. 먼저 제조된 촉매는 별도의 분쇄작업(볼밀 혹은 제트밀)을 거치지 않아도 입자사이즈가 약 $4{\mu}m$ 수준이 나오도록 촉매 제조조건을 조절 하였다. 그리고 소량의 Methyl cellulose(MC) 바이더와 물만 사용하여 촉매를 혼합한 다음 스크류 압출기를 이용하여 촉매를 성형하였다. 이 촉매는 지름이 약 2 mm 이하로 제조할 수 있었으며, 기계적 강도는 타정기로 성형한 상용촉매보다 우수하였다. 그리고 촉매 성능 또한 상용촉매와 비교하였을 때, 우수한 성능 보였다. MCFC용 내부개질 촉매로 균일용액침전법을 사용한 촉매가 적합하다고 판단되며, 압출성형에도 적합하다고 판단되었다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.618-624
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• 2017

In Seoul and most metropolitan cities, urban trains are delayed due to high congestion during commute times. The delay effect of passengers boarding and disembarking is also significant. In this study, a wide passenger door system was developed as a way to improve the scheduled speed of urban trains by decreasing the passengers' flow time. The door size was defined experimentally to shorten the entrance time. The optimum door size was also determined to improve the stop precision performance of the train while considering the interference effect with peripheral devices. Because the change in door size changes the structural characteristics of the vehicle, the structural stability of a train was analyzed numerically. A prototype of the wide door system was made, and the proposed design was verified using functional and endurance tests. The systematic development process can be used as design data for door size definition and system production when applying a wide door to improve the scheduled speed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.3
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• pp.572-579
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• 2009

A monitoring system needs many parameters to increase devices for monitoring data and to support various services. In particular, monitoring the status of a device in a wireless mobile environment has a difficulty in displaying multi data in a limited screen size, and transfer of the status data of a device into a network is largely related with network traffic. The research aims at designing a control board that collects data in order to effectively manage a greenhouse environment system. Also, the research tries to appropriately operate devices, environment data monitoring, and the control of each device by realizing a multiplexed interface based on a web. Thus, in the case in which a distributed client was a computer, monitoring and control were obtained with a web browser through the Lab VIEW web server of a server or local control module in order to effectively monitor and control according to the status of a user. In the case in which a client was a PDA, application of a wireless mobile considering the scale and data processing capacity of a displayer was connected. As a result of the research, we could confirm a satisfactory outcome from the viewpoint of a human-centered design by supplying adaptability and mobility according to the environment of a user.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.12
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• pp.5622-5632
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• 2011

This paper presents the simulation design and analysis of Integrated Logistics System(ILS) which is operated by using the AGV(Automated Guided Vehicle). To maximize the operation performances of ILS with AGV, many parameters should be considered such as the number, velocity, and dispatching rule of AGV, part types, scheduling, and buffer sizes. We established the design of experiment in a way of Orthogonal Array in order to consider (1)maximizing the throughput; (2)maximizing the vehicle utilization; (3)minimizing the congestion; and (4)maximizing the Automated Storage and Retrieval System(AS/RS) utilization among various critical factors. Furthermore, we performed the optimization by using the simulation-based analysis and Evolution Strategy(ES). As a result, Orthogonal Array which is conducted far fewer than ES significantly saved not only the time but the same outcome when compared after validation test on the result from the two methods. Therefore, this approach ensures the confidence and provides better process for quick analysis by specifying exact experiment outcome even though it provides small number of experiment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.72-72
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• 2009

본 연구에서는 Photoconductor materials 기반의 평판형 X-ray Detector film 제작에 관한 연구를 수행하였다. 기존의 광도전성 물질로 사용되어 오던 비정질 셀레늄(Amorphous seleinum; a-Se) 기반의 디지털 방사선 검출기 보다 높은 신호 및 동작 특성을 가지는 Mercury Iodide(HgI2)와 열적, 전기적 특성이 안정적이며, 소자의 동작특성이 우수한 Lead Oxide(PbO) 기반의 X-ray Detector film의 개발에 있어서 각각 HgI2 및 PbO 두 물질 층을 적정비율에 맞추어 제작함으로써 최적의 X-ray Detector를 구현하고자 하였다. 이는 빠른 영상획득을 통해 기존의 방식이 가지는 문제점을 해결하고 의료기기 디지털화를 구현할 수 있는 차세대 시스템을 개발하고자 하는 것이다. 본 연구에서는 기존의 진공증착법의 두꺼운 대면적 필름의 제조가 어려운 문제점을 해결하고자 Particle In Binder method(PIB) 방법을 이용하여 $3"{\times}3"$사이즈의 두께 $200{\mu}m$의 다결정의 Photoconductor 필름을 제조하여 전기적 특성을 평가하였다. 제작된 필름의 전기적 특성을 dark current, X-선 sensitivity와 SNR(Signal to -Noise Rate) 등을 측정하여 정량적으로 평가 하였다. 기준 실험으로 진행한 DG 2.1 바인더를 사용한 single-HgI2 층에서 보다 높은 sensitivity 값을 보였지만 높은 dark current로 인해 SNR이 떨어지는 결과를 볼 수 있었다. 본 연구에서 제시하는 두 Photoconductor material의 Soaking method를 이용한 실험에서는 single-HgI2에 해당하는 높은 sensitivity 및 저감된 dark current로 인해 높은 SNR 값을 획득하였다. 하지만 습도와 같은 주변 환경에 의한 재현성 문제로 인한 신호값의 불안정성에 대한 문제점도 남아 있으므로, 차후 최적화된 material 제작 공정을 위한 연구가 꾸준히 진행 되어져야 할 것이다.

• Journal of Digital Contents Society
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• v.16 no.4
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• pp.605-613
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• 2015

This paper addresses the problem to make sparse the projection matrix in pattern recognition method. Recently, the size of computer program is often restricted in embedded systems. It is very often that developed programs include some constant data. For example, many pattern recognition programs use the projection matrix for dimension reduction. To improve the recognition performance, very high dimensional feature vectors are often extracted. In this case, the projection matrix can be very big. Recently, RSR(roated sparse regression) method[1] was proposed. This method has been proved one of the best algorithm that obtains the sparse matrix. We propose three methods to improve the RSR; outlier removal, sampling and elastic net RSR(E-RSR) in which the penalty term in RSR optimization function is replaced by that of the elastic net regression. The experimental results show that the proposed methods are very effective and improve the sparsity rate dramatically without sacrificing the recognition rate compared to the original RSR method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.9 s.100
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• pp.957-963
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• 2005

This paper presents technique of wideband TIA for optical communication systems using TSMC 0.25 ${\mu}m$ CMOS RF-Mixed mode. In order to improve bandwidth characteristics of an TIA, we use active inductor shunt peaking to cascode and common-source configuration. The result shows the 37 mW and 45 mW power dissipation with 2.5 V bias and 61 dB$\Omega$ and 61.4 dB$\Omega$ transimpedance gain. And the -3 dB bandwidth of the TIA is enhanced from 0.8 GHz to 1.45 GHz in cascode and 0.61 GHz to 0.9 GHz in common-source. And the input noise current density is $5 pA/\sqrt{Hz}$ and $4.5 pA/\sqrt{Hz}$, and -10 dB out put return loss is obtained in 1.45 GHz. The total size of the chip is $1150{\times}940{\mu}m^2$.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.3
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• pp.88-97
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• 2012

To measure the traffic pollutants with high temporal and spatial resolution under real conditions, a mobile emission laboratory (MEL) was designed. The equipment of the mini-van provides gas phase measurements of CO, NOx, CO2 and THC (Total hydrocarbon), and number density & size distribution measurements of fine and ultra-fine particles by a fast mobility particle sizer (FMPS) and a condensation particle counter (CPC). The inlet sampling port above the bumper enables the chasing of different type of vehicles. This paper introduces the technical details of the MEL and presents data from the experiment in which a MEL chases a city bus fuelled by diesel, DME and Bio-diesel. The dilution ratio was calculated by the ratio of ambient NOx and tail-pipe NOx. Most particles from the bus fuelled by diesel were counted under 300 nm and the peak concentration of the particles was located between 30 and 60 nm. However, most particles in the exhaust of the bus fuelled by DME were nano-particles (diameter: less than 50 nm). The bus fuelled by Bio-diesel shows less particle emissions compare to diesel bus due to the presence of the oxygen in the fuel.