• 한국전자파학회논문지
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• 제17권11호
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• pp.1040-1049
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• 2006

본 논문에서는 광대역 동축-마이크로스트립 선로에서 전송 손실을 최소화하는 수직 트랜지션(transition)의 설계 기법을 제안하였다. 동축-마이크로스트립 선로의 수직 트랜지션은 동축 선로와 인쇄 회로 기판이 수직으로 연결되는 구조로서 인쇄형 안테나 혹은 마이크로스트립 기판을 사용하는 마이크로파 송수신 장치 등에 널리 사용된다. 제안한 설계 방법은 넓은 대역폭을 가지면서 전송 손실을 최소화하는 방법으로, 접지 개구면(ground aperture)의 지름, 프로브(probe)의 지름, 접지 개구면의 오프셋과 스텁(stub) 길이를 설계 변수로 설정하여, 시뮬레이션을 통하여 설계 값을 구하였다. 동축 선로와 마이크로스트립 기판은 일반적으로 널리 사용되는 SMA 커넥터와 PTFE 재질의 두께 0.254, 0.508 및 0.787 mm 기판을 사용하였다. 시뮬레이션 결과로부터 구한 설계 변수 값들을 입증하기 위하여 SMA 동축 커넥터와 0.787 mm 두께의 기판을 사용하여 수직 트랜지션 시험 블록을 제작하였다. 이 트랜지션의 특성을 측정한 결과 $0.05{\sim}20GHz$주파수 범위에서 반사 계수가 -22 dB 이하이고, 전송 손실이 0.45 dB 이하인 만족할만한 결과를 얻었다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.335-338
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• 1998

This paper presents calculated results for the infinite phased arrays of the probe-fed rectagualr microstrip patches. A numerical model that is based on a rigorous Green's function and galerkin solutionsis is described. In an arbitrary scan plane, the input impedance and the input reflection coefficient versus the scand angle are calculated. The effects of substrate parameters on the phased arry antenna are considered. The scan blindness phenomenon due to the surface wave is observed and the input impedance bandwidth in the arbitrary scan plane is calculated.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2465-2470
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• 2007

We have analyzed the three-dimensional thermal conduction in anisotropic materials using nonsymmetric-Fourier transforms. And a complete theoretical treatment of the photothermal deflection spectroscopy has been performed for thermal conductivity measurement in anisotropic medium. Thermal conductivity tensor was determined by the deflection angle and phase angle with the relative position between the heating and probe beams. The influence of the parameters, such as modulation frequency of the heating beam, the thermal conductivity tensor, was investigated.

• 비파괴검사학회지
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• 제9권1호
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• pp.106-110
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• 1989

Bolting degradation problems in primary coolant pressure boundary applications have become a major concern in the nuclear industry. In the bolts concerned, the failure mechanism was either corrosion wastage(loss of bolt diameter) or stress-corrosion cracking.(3) Here the manual ultrasonic testing of RPV(Reactor Pressure Vessel) and RCP(Reactor Coolant Pump) stud has been performed. But it is difficult to detect indications because examiner can not exactly control the rotation angle and can not distinguish the indication from signals of bolt. In many cases, the critical sizes of damage depth are very small(1-2 mm order). At critical size, the crack tends to propagatecompletly through the bolt under stress, Resulting in total fracture.(3) Automatic stud scanner for studs(bolts) was developed because the precise measurement of bolt diameter is required in this circumstance. By use of this scanner, the rotation angle of probe was exactly controlled and the exposure time of radiations was reduced.

• 대한전기학회논문지
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• 제40권6호
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• pp.590-597
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• 1991

Ion reflective index and sheet resistance in the silicon oblique range smaller than 8 degree and optimization of annealing temperature have been studied. A four point probe was used to obtain the sheet resistance after annealing, while high resolution SIMS was used to determine the Boron and Fluorine atomic profiles before and after annealing. Experimental results and theory of ion reflective index are compared. Ion reflective index was found to decrease according to increasing an ion oblique angle. We introduce a simple analytical model ion reflection, concidering the Rutherford scattering model. This result can not be explained by the conventional Gaussian model.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.41-46
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• 2002

Flow field downstream of an inducer was measured to see the flow and performance characteristics of a turbopump inducer. A large axisymmetric collector instead of a volute casing was installed to obtain circumferentially uniform flow - without interaction of the inducer and the volute. A conventional 3-hole probe was used to measure the flow. At inducer exit axial component of absolute velocity decreased on hub region with decrease in flow rate. Tangential velocity component static pressure, and total pressure increased from hub to tip. Relative flow angle from tangential direction was a little higher than outlet blade angle at flow coefficient $\varphi$=0.087 and 0.073. Dynamic pressure was $53\%$ of the mean total pressure at inducer exit at $\varphi$=0.073.

• 한국산업융합학회 논문집
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• 제8권4호
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• pp.221-226
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• 2005

This paper presents a hybrid method for recognizing the faces by using zero mean and principal component analysis. Zero mean is applied to reduce the 1st order statistics to data nonlinearities. PCA is also used to derive an orthonormal basis which directly leads to dimensionality reduction, and possibly to feature extraction of face image. The proposed method has been applied to the problems for recognizing the 20 face images(10 persons * 2 scenes) of 324*243 pixels from Yale face database. The 3 distances such as city-block, Euclidean, negative angle are used as measures when match the probe images to the nearest gallery images. The experimental results show that the proposed method has a superior recognition performances(speed, rate). The negative angle has been relatively achieved more an accurate similarity than city-block or Euclidean.

• 한국유체기계학회 논문집
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• 제6권4호
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• pp.38-44
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• 2003

Flow field downstream of an inducer was measured to see the flow and performance characteristics of a turbopump inducer. A large axisymmetric collector instead of a volute casing was installed to obtain circumferentially uniform flow - without interaction of the inducer and the volute. A conventional 3-hole probe was used to measure the flow. At inducer exit, axial component of absolute velocity decreased on hub region with decrease in flow rate. Tangential velocity component, static pressure, and total pressure increased from hub to tip. Relative flow angle from tangential direction was a little higher than outlet blade angle at flow coefficient ${\phi}=0.087$ and 0.073. Dynamic pressure was $53\%$ of the mean total pressure at inducer exit at ${\phi}=0.073$.

• 대한기계학회논문집B
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• 제26권12호
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• pp.1747-1755
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• 2002

A complete theoretical treatment of the photothermal displacement technique has been performed for thermal diffusivity measurement in semi-infinite solid materials. The influence of the parameters, such as radius and modulation frequency of the heating beam and the thermal diffusivity, was studied. Usually, thermal diffusivity was determined by the deformation angle and phase angle as the relative position between the heating and probe beams. In this study, we proposed the simple analysis method based on the real part of deformation gradient as the relative position between two beams. It is independent in the parameters such as power of heating beam, absorption coefficient, reflectivity, Poisson's ratio, and thermal expansion coefficient.

• 한국산업융합학회 논문집
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• 제8권3호
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• pp.143-148
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• 2005

This paper presents a hybrid method for recognizing the faces by using principal component analysis(PCA) and fixed-point independent component analysis(FP-ICA). PCA is used to whiten the data, which reduces the effects of second-order statistics to the nonlinearities. FP-ICA is applied to extract the statistically independent features of face image. The proposed method has been applied to the problems for recognizing the 20 face images(10 persons * 2 scenes) of 324*243 pixels from Yale face database. The 3 distances such as city-block, Euclidean, negative angle are used as measures when match the probe images to the nearest gallery images. The experimental results show that the proposed method has a superior recognition performances(speed, rate). The negative angle has been relatively achieved more an accurate similarity than city-block or Euclidean.