• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권3호
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• pp.101-106
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• 2003

The high temperature superconductor transformers gain interests from the industries. This paper described construction and test results of 10㎸A HTS transformer Three phase transformer with double pancake windings were constructed. To reduce the leakage magnetic field, secondary coil were placed between the two primary coils. BSCCO-2223 wire. silicon sheet steel core and FRP cryostats were used to construct the transformer. Three coils were stacked in one cryostat. Two double pancake coils were connected in series for the primary coil and one double pancake coil was used for the secondary coil. Total number of turns of the primary winding and the secondary winding were 112turns and 98urns, respectively, The rated voltages of each winding were 440/220V. The rated currents of each winding were 13.1/26.2A. After the tests of basic properties of the three phase HTS transformer using no-load test, short-circuit test and full-load test, continuous operation of 100 hours with pure resistive load has been carried out. Test results proved over-load capability and reliability of the HTS transformer.

• Journal of Advanced Marine Engineering and Technology
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• 제31권1호
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• pp.51-57
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• 2007

In process of reinforced concrete (RC) box structure. the heat of hydration may cause serious thermal cracking. In order to eliminate hydration heat of mass concrete. this paper reports results of hydration heat control in mass concrete structure using the pulsating heat pipe. There were three RC box molds($1.2{\times}l.8{\times}2.4m^3$) which shows a difference as compared with each other. One was not equipped with pulsating heat pipe. The others were equipped with pulsating heat pipe. All of them were cooled with natural air convection. The pulsating heat pipe was composed of serpentine type copper pipe with 10 turns (outer diameter: 4mm. inner diameter: 2.8mm). The working fluid was R-22 and its charging ratio was 40% by volume. The conditions such as the number of turns. the length and the pitch of the pulsating heat pipe and the size of concrete structure were changed. Based on these experiments, it was confirmed that this construction method using pulsating heat pipe was effective to remove hydration heat of mass concrete structure and thus it was possible to prevent harmful thermal crack and construction Period and costs of concrete structure would be cut down.

• The Plant Pathology Journal
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• 제25권2호
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• pp.172-178
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• 2009

To obtain global gene expression profiles of Arabidopsis thaliana by acid stress, seedlings were subjected to low pH stress. Using Affymetrix AH1 chips covering 24,000 genes, we analyzed gene expression patterns. Fifty-four genes were up-regulated, and 38 were down-regulated more than 3-fold after 2 h of acid stress (pH 3.0). Several defense and abiotic stress-related genes were recognized among the up-regulated genes and peroxidase and extensin genes were identified among the down-regulated genes. After 12 h treatment, relatively fewer genes showed changed expression, indicating that plants seem to adjust themselves to this abiotic stress. Most of the up-regulated genes are already known to be involved in abiotic stress responses and pathogen attacks, especially wounding. However, down-regulated genes for the members of extensins and peroxidases are specific to the acid treatment. These results suggest that acid treatment turns on genes involved in stress responses, especially in wounding and turns off genes very specific for the acid stress.

• 대한기계학회논문집A
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• 제31권1호
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• pp.43-49
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• 2007

A new electric coil design methodology using the notion of topology optimization is developed. The specific design problem in consideration is to find optimal coil configuration that maximizes the Lorentz force under given magnetic field. Topology optimization is usually formulated using the finite element method, but the novel feature of this method is that no such partial differential equation solver is employed during the whole optimization process. The proposed methodology allows the determination of not only coil shape but also the number of coil turns which is not possible to determine by any existing topology optimization concept and to perform single coil strand identification algorithm. The specific applications are made in the design of two-dimensional fine-pattern focusing coils of an optical pickup actuator. In this method, the concept of equivalent magnetizing current is utilized to calculate the Lorentz force, and the optimal coil configuration is obtained without any initial layout. The method is capable of generating the location and shape of turns of coil. To confirm the effectiveness of the proposed method in optical pickup applications, design problems involving multipolar permanent magnets are considered.

• 한국생산제조학회지
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• 제23권4호
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• pp.408-412
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• 2014

An electromagnetic launching system presents a viable projectile propulsion alternative with low cost and minimal environmental drawbacks. A coil gun system propels a projectile using an electromagnetic force and the system is mainly employed in military weapon systems and space launch systems. In this paper, we perform optimization design to improve the muzzle velocity by analyzing the sensitivity. The muzzle velocity, which is the most important design function variable, is affected by design variables including the number of axial turns in the electromagnetic coil, number of radial turns in the electromagnetic coil, initial distance between the projectile and the coil, inner radius of the electromagnetic coil, and length of the projectile. An orthogonal arrays matrix is configured, and a finite element analysis is performed utilizing the commercial electromagnetic analysis software MAXWELL. The muzzle velocity of the optimal design is 62.4% greater than that of the initial design.

• 한국추진공학회지
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• 제15권1호
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• pp.1-10
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• 2011

가스연소와 촉매연소 실험을 통해 열교환 연소기의 연소 및 소염한계에 대하여 레이놀즈 수에 적용하여 성능평가를 수행하였으며, 마이크로 스케일 연소 장치에 대한 적용 가능성에 대해 살펴보았다. 본 논문에서는 연소기의 특성을 살펴보기 위해 나선형 연소기의 물리적 크기와 회전수를 변화시킨 스위스롤 연소기를 제작하여 실험을 수행하였다. 또한 연소가스 분석을 통한 연소효율에 대해서도 살펴보았다. 실험 결과를 바탕으로 스위스롤 연소기의 최적 작동상태에 대해서도 분석하였다.

• 한국전자파학회논문지
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• 제19권5호
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• pp.501-505
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• 2008

이 논문에서는 휴대 장치의 지상파 DMB용 안테나로 다중 권선 loop 안테나를 제안한다. 제안된 안테나는 크기가 작으면서도 지상파 DMB 대역에서 충분한 수신 전력을 확보하도록 권수는 80회, 그리고 직경은 4 mm로 하였으며, 또한 높은 전달 함수 특성을 갖도록 품질 계수를 1로 하였다. 제작된 안테나는 길이가 30 mm로 소형이며, 이득은 약 -15 dBd로 길이 190 mm의 상용 지상파 DMB 모노폴 안테나와 비슷한 수신 능력을 가짐을 측정을 통해 확인하였다.

• 한국초전도ㆍ저온공학회논문지
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• 제4권1호
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• pp.99-104
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• 2002

This study deals with the optimal design of a DC reactor type high-Tc superconducting fault current limiter(SFCL). The condition in which the cost function is minimized under given constraints is one of the things to be first considered in developing SFCLS. This condition is a group of the values corresponding to the variables the cost function depends on. In this paper, the length of tape was taken as a dependent variable, the inductance of DC reactor and the turns ratio of magnetic core reactors as independent variables. For the SFCL available at the level of 6.6kV-200A, we examined 4 cases; at the fault times of 80msec, 50msec, 30msec and 10msec. Since thyristors would be utilized instead of diodes, we chose the result at 10msec as the basic data. Considering safety factor 30%, our optimal design was decided to be the inductance 570mH, the critical current over 620A, the turns ratio 0.89 and the fault time within 20msec.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제5권4호
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• pp.316-321
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• 2005

We designed and implemented fish robots for various purposes such as autonomous navigation, maneuverability control, posture balancing and improvement of quick turns in a tank of 120 X 120 X 180cm size. Typically, fish robots have 30-50 X 15-25 X 10-20cm dimensions; length, width and height, respectively. It is essential to have the ability of quick and smooth turning to avoid collision with obstacles or walls of the water pool at a close distance. Infrared distance sensors are used to detect obstacles, magneto-resistive sensors are used to read direction information, and a two-axis accelerometer is mounted to compensate output of direction sensors. Because of the swing action of its head due to the tail fin movement, the outputs of an infrared distance sensor contain a huge amount of noise around true distances. With the information from accelerometers and e-compass, much improved distance data can be obtained by fuzzy logic based estimation. Successful swimming and smooth turns without collision demonstrated the effectiveness of the distance estimation.

• 한국음향학회지
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• 제16권1호
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• pp.67-75
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• 1997

본 논문에서는 CDMA 이동국 시스템의 고주파 수신부를 구현하기 위한 시스템 파라메타에 대하여 이동국 최소 규격인 IS-98-A를 기준으로 고찰하였으며, 이 규격을 만족시키기 위한 수신감도와 잡음지수의 관계, 그리고 프레임 오율과 비트 오율과의 관계를 분석하였다. 시뮬레션 결과, 이동국의 수신감도에 적합한 수신기의 최대 잡음지수는 퀄컴사에서 언급하는 규격보다 3dB 정도 여유를 갖는 약 11dB를 나타내었다. 또한 각 부호율에 대한 통화채널의 Eb/Nt와 프레임 오율과의 관계를 통화채널 속도를 가변하여 시험하고, LNA에서 IMD가 가장 중요한 변수라는 사실을 검증하기 위한 상호변조 스퓨리어스에 대한 시험을 LNA를 항상 ON시킨 경우와 ON/OFF시킨 경우 두가지로 나누어 시험하였다.