• 산업기술연구
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• 제17권
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• pp.79-85
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• 1997

This paper describes a control for the high performance induction motor drive system with a wide speed operating range and proposes a robust control method independent of motor parameter variation. For the operation below the rated speed, the high performance control is achieved by using the indirect field-oriented control with a speed sensor. In the high speed regain, the field weakening region with a large variation in motor parameters, the motor drive system can obtain the robustness to motor parameter variation by switchover to the direct field-oriented control. Also, the sensorless speed control using estimated speed is achieved in very high speed region that the utilization of speed sensor pulses is limited. And from experiments using high performance 32bit DSP for 2.2[kW] and 22[kW] laboratory induction motor drive systems, it is verified that the proposed opration algorithm provided a good performance.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1583_1584
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• 2009

Reverberation chamber have become a common tool in radiated susceptibility and emission testing of electronic equipment. In a reverberation chamber, internal electromagnetic fields are mixed by metallic stirrer. Due to elimination of Polarization characteristic in reverberation chamber, electromagnetic wave reached to EUT all aspect angle. Hence, Field distribution in overmode reverberation chamber can be presented by chi-square distribution. Field uniformity in reverberation chamber have to satisfy standard deviation below 3dB and is influenced by mechanical stirrer. This paper investigates relationship between change of stirrer parameter and field uniformity in reverberation chamber.

• 한국전자파학회논문지
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• 제13권2호
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• pp.164-169
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• 2002

본 논문에서는 300~3000 MHz 의 주파수 영역에서 동작하는 근역장 측정 프로브를 설계하여 제작하였다. 설계 파라미터는 프로브에 대한 등가회로를 이용하여 추출하였으며 S파라미터를 이용한 수치해석을 통해 그 특성을 예측하였다. 제작된 프로브는 3.25 mm 길이의 다이폴 안테나와 제로 바이어스 쇼트키 다이오드, 고저항 전송 선으로 구성되어 있으며 TEM 셀을 이용하여 성능을 확인하였다.

• 대한기계학회논문집A
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• 제21권1호
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• pp.164-172
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• 1997

Two parameter technique that uses far-field stress and displacement distributions was applied to composite laminates in order to calculate mode II energy release rate, $G_{II}$ . The $G_{II}$ calculated by two parameter technique was compared with that calculated from the crack closure method to inspect the effectiveness of two parameter technique. Sensitivity study of two parameter technique to the crack extension size was also performed. The results showed that both methods produced comparable $G_{II}$ results. In particular, it was found that although the crack closure method was affected by the crack extension size, the two parameter technique was less affected by the crack extension size.

• Steel and Composite Structures
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• 제43권2호
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• pp.221-228
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• 2022

Two-dimensional stagnation point slip flow of a Casson fluid impinging normally on a flat linearly shrinking surface is considered. The modeled PDEs are changed into nonlinear ODEs through appropriate nonlinear transformations.The flow is assumed to be steady and incompressible, with external magnetic field acting on it. Similarity transformation is utilized to investigate the behavior of many parameters for heat and velocity distributions using truncation approach.The influence of buoyancy parameter, slip parameter, shrinking parameter, Casson fluid parameter on the heat profile. The effect of the magnetic parameter on the streamwise velocity profile is also investigated.

• 드라이브 ㆍ 컨트롤
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• 제10권3호
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• pp.27-33
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• 2013

Solenoid valve has used in various industrial field extensively. A solenoid valve has different size, shape and method of operation accordantly to industrial field. Many researchers study on kinds of solenoid valve such as flow rate, dynamic, magnetic field, valve shape and operating method. But the flow rate characteristic and dynamic response time performance on the diaphragm valve are not studied. This paper describes the flow rate characteristic and dynamic response time performance on the diaphragm valve. At first, the diaphragm valve is simulated in AMESim simulation tool. AMESim model found that an effect of valve performance depends on parameter. The parameter is the diaphragm orifice area. And the performance test bench confirms the effect in this parameter. Finally, it finds out the flow rate characteristic and dynamic response time performance on the diaphragm valve.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.158-167
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• 2008

The quality control of compacted fills has been carried out by evaluating relative densities and coefficients of soil reaction. These measures have several limitations regarding repeatability and reliability of field measurements, and difficulties to use in the fills including large grain size as gravels and boulders. Also, the density is not directly related to the design parameter such as resilient modulus. A preliminary investigation for the usage of the stiffness as a control measure has been carried out. In the laboratory, the stiffness (P-wave velocity) was measured during compaction tests. The stiffness at the optimal moisture content was proposed to use a target control parameter likewise maximum dry density. A field method to match the target stiffness was also proposed by considering easiness of the method and availability of equipment. The most phenomenal feature of the method is that the control parameter (stiffness) is closely related to resilient modulus and can be consistently used from the design stage to the field control during construction.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(2)
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• pp.217-220
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• 2001

Modified Materka-Kacprzak 대신호 MODFET(modulation-doped field-effect transistor) model을 사용하여 GaN(gallium nitride) MODFET 대신호 모델링을 수행하였다. Dambrine(3)이 제안한 방법에 따라 45㎒에서 40㎒의 주파수 범위에 걸쳐 S-parameter 및 DC특성을 측정하였으며, 측정결과를 토대로 cold FET 방법［4］에 의해 측정된 기생성분들을 de-embedding 함으로써 소신호 파라미터를 추출하였고, 추출된 소신호 파라미터는 함수를 사용하여 측정결과를 재현하는 맞춤함수 모델의 일종인 modified Materka 모델을 사용하여 모델링하였다. 수행된 대신호 모델링을 검증하기 위하여 모델링된 GaN MODFET의 DC 및 S-파라미터, 전력특성을 측정값과 각각 비교해 보았을 때 비교적 일치하고 있음을 보여서 GaN 대신호 모델링을 검증하였으며, modified Materka 모델이 GaN MODFET 대신호 모델링에 유용하게 사용될 수 있음을 보였다.

• Structural Engineering and Mechanics
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• 제66권2호
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• pp.237-248
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• 2018

This study presents the investigation of wave dispersion characteristics of a magneto-electro-elastic functionally graded (MEE-FG) nanosize beam utilizing nonlocal strain gradient theory (NSGT). In this theory, a material length scale parameter is propounded to show the influence of strain gradient stress field, and likewise, a nonlocal parameter is nominated to emphasize on the importance of elastic stress field effects. The material properties of heterogeneous nanobeam are supposed to vary smoothly through the thickness direction based on power-law form. Applying Hamilton's principle, the nonlocal governing equations of MEE-FG nanobeam are derived. Furthermore, to derive the wave frequency, phase velocity and escape frequency of MEE-FG nanobeam, an analytical solution is employed. The validation procedure is performed by comparing the results of present model with results exhibited by previous papers. Results are rendered in the framework of an exact parametric study by changing various parameters such as wave number, nonlocal parameter, length scale parameter, gradient index, magnetic potential and electric voltage to show their influence on the wave frequency, phase velocity and escape frequency of MEE-FG nanobeams.

• Structural Engineering and Mechanics
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• 제71권6호
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• pp.669-682
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• 2019

We in this article study nonlinear thermal buckling of bi-directional functionally graded beams in the theoretical frameworks of nonlocal strain graded theory. To begin with, it is assumed that the effective material properties of beams vary continuously in both the thickness and width directions. Then, we utilize a higher-order shear deformation theory that includes a physical neutral surface to derive the size-dependent governing equations combining with the Hamilton's principle and the von $K{\acute{a}}rm{\acute{a}}n$ geometric nonlinearity. It should be pointed out that the established model, containing a nonlocal parameter and a strain gradient length scale parameter, can availably account for both the influence of nonlocal elastic stress field and the influence of strain gradient stress field. Subsequently, via using a easier group of initial asymptotic solutions, the corresponding analytical solution of thermal buckling of beams is obtained with the help of perturbation method. Finally, a parametric study is carried out in detail after validating the present analysis, especially for the effects of a nonlocal parameter, a strain gradient length scale parameter and the ratio of the two on the critical thermal buckling temperature of beams.