• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.12 no.3
• /
• pp.439-445
• /
• 2001

In this paper, we propose a method that can minimize time-error when a commercial rubidium atomic clock is used as a portable reference clock. A linear interpolation method which was widely used is not based upon long-term stability, but our new method is considered to reduce time error. The comparison results between two method have shown that time error of our new approach considering with long-term stability is better than that of linear interpolation method within observation duration about one and half days. In addition, when the role of a rubidium atomic clock as a portable reference clock is completed within 12 hours, our new method can provide at most maximum time-error of 10 ns which is shorter than 15 ns in conventional method.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.20 no.4
• /
• pp.305-313
• /
• 2000

To determine detection capabilities of locating steel bars and delamination inside concrete, commercially available nondestructive testing (NDT) equipments have been tested. The equipments include two radar systems and two electromagnetic method systems. The inclusions are a 19 mm diameter steel bar and 50 mm thick delamination embedded at different cover depths from the surface of concrete specimens. For the steel bar, attempts were made to determine the size of the bars by changing the diameter of the bars. A sample result of measuring horizontal spacing between doubly reinforced bars is presented in this paper. Experimental results on various measurement cases are discussed. Application of numerical modeling technique for the simulation of radar measurements and improved output display of radar measurements are also presented.

• 한국HCI학회:학술대회논문집
• /
• 2007.02a
• /
• pp.174-181
• /
• 2007

정보 검색의 결과로 나타나는 요약문을 스니펫(snippet)이라 한다. 사용자는 자신이 원하는 정보를 얻기 위해 문서를 검색하는데, 이 때 스니펫은 사용자가 원하는 문서를 찾는데 중요한 역할을 한다. 본 논문에서는 정보검색 분야에서 높은 성능을 보이는 유사 적합성 피드백을 자동 문서 요약에 맞게 적용하여 높은 성능의 스니펫 생성 시스템을 구현한다. 우선, 사용자의 질의가 포함된 문장들을 일차적으로 요약 문장 후보로 추출한다. 그리고 추출된 문장 후보로부터 명사들을 질의 후보로 고려한다. 각 문장이 질의의 포함 여부에 따라 문장의 적합성을 판단하게 되고, 유사 적합성 피드백 확률 모델에 적용한 후 질의 후보들의 가중치를 추정하여 가중치 순위를 통해 확장할 질의들을 결정한다. 확장된 질의들과 기존의 질의들의 가중치를 합산하여 각 문장의 순위를 매기게 되고 가장 높은 순위의 문장들이 스니펫으로 제시된다. 논문에서 제안한 기법은 추가적인 핵심 질의들을 자동으로 확장하여 중요한 문장을 추출할 수 있다. 이 연구를 위해서 일반 상용 정보 검색 서비스에서 제공하는 스니펫을 수집하였고 이들의 정확도와 시스템의 정확도를 비교하였다. 실험 결과를 통해 살펴본 제안된 시스템의 성능은 상용 정보 검색기에서 제공되고 잇는 스니펫의 정확도 보다 우수한 성능을 보였다.

• Applied Chemistry for Engineering
• /
• v.8 no.2
• /
• pp.230-236
• /
• 1997

Polyurethane dispersions(PUD) were prepared from IPDI, PBEAG and PTMG as respectively ester type and ether type polyols and DMPA as anionic site. The effect of composition and type of polyols on the particle size of PUD and mechanical, thermal properties of PUD cast film were investigated. As the PTMG contents in mixed polyols increased, the particle size asymptotically increased and tensile strength showed a mild drop followed by a mild increase. This results from the incompatibility of two polyols, which was possibly identified by DSC analysis.

• Proceedings of the KIEE Conference
• /
• 2005.07b
• /
• pp.1719-1721
• /
• 2005

현재 지구 환경 오염에 관한 관심이 증가하면서, 공해가 없는 자연 에너지원에 대한 연구가 많이 진행되고 있다. 그 중에서도 태양전지 분야중 염료감응형 태양전지(DSC)는 Si계 태양전지와 비교하여 낮은 제조비용등 여러 가지 이유로 최근 많은 연구가 진행되고 있다. 따라서 DSC 발전 시스템의 효율 향상이 요구된다. 본 연구에서는 태양전지 분야 중에서 독립적인 발전설비가 필요한 도서 및 산간 지역에 전력을 안정적으로 공급할 수 있는 소형발전용의 설비로 "전압 및 전류의 피드백을 통한 DSC Cell의 독립전원의 안정화"에 관해 연구하였다. DSC Cell측의 DC입력을 받아 Boost Converter로 승압 후 Full Bridge 인버터를 사용하여 단상 220V 60Hz의 상용전원으로 변환하였다. 여기서는 32Bit 마이크로프로세서인 DSP TMS320F2812의 A/D변환기능을 이용하여 Boost Converter의 스위칭과 Full Bridge 인버터의 스위칭을 제어하였다. 특히 TMS320F2812의 RTC(Real Time Clock)를 이용하여 출력전압의 안정성 향상에 주목적을 두었다. 실험결과 출력단에서는 220V 변동범위 0.2% 주파수 60Hz의 상용전원을 얻었으며, 프로그램의 개선을 통하여 출력전압의 변동범위를 감소시켜야 될 것이다.

• Journal of Convergence for Information Technology
• /
• v.9 no.3
• /
• pp.30-35
• /
• 2019

An unattended recording system based on smartphone based image image tracking is rapidly developing. Among the existing products, a system that automatically tracks and rotates the object to be photographed using an infrared signal is very expensive for general users. Therefore, this paper proposes a mobile unattended recording system that enables automatic recording by anyone who uses a smartphone. The system consists of a commercial mobile camera, a servomotor that moves the camera from side to side, a microcontroller to control the motor, and a commercial wireless Bluetooth Earset for video audio input. In this paper, we designed a system that enables unattended recording through image tracking using smartphone.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.21 no.2
• /
• pp.131-138
• /
• 2011

The previous FPGA cluster systems for a brute force search of DES keyspace have showed cost efficient performance, but the research on optimized implementation of the DES algorithm on a single FPGA has been insufficient. In this paper, the optimized DES implementation for a single FPGA of the commercial FPGA cluster system with 77 Xilinx Virtex5-LX50 FPGAs is proposed. Design space exploration using the number of pipeline stages in a DES core, the number of DES cores and the maximum clock frequency of a DES core is performed which leads to integrating 16 DES cores running at 333MHz. Also low power design is applied to reduce the loss of performance caused by limitation of power supply on each FPGA which results in fitting 8 DES cores running at 333MHz. When the proposed DES implementations would be used in the FPGA cluster system, it is estimated that the DES key would be found at most 2.03 days and 4.06 days respectively.

• Journal of the Korean Institute of Gas
• /
• v.18 no.5
• /
• pp.6-11
• /
• 2014

To optimize the design of fuel cylinder for LNG vehicles, we introduced the design parameters of the inner and the outer tank of the vessel support structure by analyzing the structural characteristics of conventional design. We selected the inner and outer diameter of the hollow support bars and a dimension of the inner structure of the vessel among the design parameters for design optimization. In this study the temperature distribution and thermal stress of the support structure were evaluated by using the utility program as MSC/MARC. The evaluation criteria are first mode natural frequency, total transferred energy through support structure and thermal stress. The developed design satisfied the design criteria and it was made of prototype. The prototype was verified through three-dimensional vibration testing and thermal performance test.

• Journal of Korea Association of Health Promotion
• /
• v.4 no.1
• /
• pp.95-103
• /
• 2006

Purpose: With remarkable increase in the prevalence of childhood obesity, nonalcoholic fatty liver disease increased, The aim of this study is to evaluate the prevalence of the increase liver enzymes, lipid levels and fasting blood glucose level in normal and obese children. Methods: A total of 2206 elementary students were grouped according to obesity index; normal group and obesity group(mild, moderate, severe). Aspartate aminotransferase(AST, SGOT) and alanine aminotrausferase(ALT, SGPT) were measured with tota1 cholesterol, triglyceride and fasting blood glucose. Results: Compared with the 2.7% of ALT > 50 IU/L in normal group, obese groups showed significantly higher prevalence; 6.7% in mild obesity group, 11.8% in moderate group and 15.0% in severe group. The prevalence of hypertriglyceremia was 12,4% in normal weight group, which is significantly lower than obesity group(mild obesity group 24.8%, moderate and severe 32.1% each). Conclusion: The prevalence of nonalcoholic fatty liver increased along with severity of obesity. Of Nutritional assessment, intervention, and preferably prevention are necessary for health promotion elementary students.

• Aerospace Engineering and Technology
• /
• v.3 no.2
• /
• pp.183-190
• /
• 2004

The performance analysis of a fuel pump for a liquid rocket engine has been performed numerically on its design condition. A commercial three-dimensional Navier-Stokes flow solver has been used for the computation. All of the fuel pump components - inducer, impeller, volute and secondary flow passages - are included in computation for the accurate estimation of the leakage flow rate which affects the performance and axial thrust. A pitchwise-averaged mixing plane method was used on the boundaries among the fuel pump components to save computational time. The predicted overall performance satisfied the design requirement. However, the axial thrust exceeded a permissible limit. In order to reduce the axial thrust, the secondary flow passage design has been changed. With this change, the axial thrust level has been reduced to 30% as compared with the original value.