• 대한의용생체공학회:의공학회지
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• 제27권3호
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• pp.117-124
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• 2006

Recently, active research has been going on to measure the elastic modulus of human soft tissue with medical ultrasound imaging systems for the purpose of diagnosing cancers or tumors which have been difficult to detect with conventional B-mode imaging techniques. In this paper, a real-time ultrasonic elasticity imaging system is implemented in software on a Pentium processor-based ultrasonic diagnostic imaging system. Soft tissue is subjected to external vibration, and the resulting tissue displacements change the phase of received echoes, which is in turn used to estimate tissue elasticity. It was confirmed from experiment with a phantom that the implemented elasticity imaging system could differentiate between soft and hard regions, where the latter is twice harder than the former, while operating at an adequate frame rate of 20 frames/s.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.1128-1133
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• 2003

A gas driven heat pump (GHP) core design comprises internal combustion engine, compressors incorporated to a cooling/heating system, rubber mountings and belt transmissions. Main excitation farces are generated by an engine, compressors themselves and belt fluctuation. It leads to high vibration level of the mount that can cause damage of GHP elements. Therefore an appropriate design of the mounting system is crucial in terms of reliability and vibration reduction. In this paper oscillation of the engine mount is explored both experimentally and analytically. Experimental analysis of natural frequencies and operational frequency response of the GHP engine mounting system enables to create simplified model for numerical and analytical investigations. It is worked out criteria f3r vibration abatement of the isolated structure. Influence of bracket stiffness between engine and compressors, suspension locations and damper performance is investigated. Ways to reduce excitation forces and improve dynamic performance of the engine-compressor mounting system are considered from these analyses. Implementation of the proposed approach permits to choose appropriate rubber mountings and their location as well as joining elements design A phase matching technique can be employed to control forces from main exciters. It enables to changing vibration response of the structure by control of natural modes contribution. Proposed changes lead to significant vibration reduction and can be easily utilized in engineering practice.

• 정보교육학회논문지
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• 제16권1호
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• pp.61-70
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• 2012

본 연구에서는 창의적 문제해결 수업을 멀티미디어공학의 특성에 맞는 교과과정으로 정착시키기 위한 새로운 시도로 3D 인터랙티브 저작도구인 앨리스를 사용하여 설계프로젝트를 진행하였다. 그 결과, 수업에서 요구하는 창의적 문제해결의 각 단계가 구체적으로 구현됨으로써 앨리스를 활용한 설계프로젝트가 멀티미디어공학부의 창의적 문제해결 수업에서의 학습목표를 달성하는데 적절함을 보였다.

• 산업기술연구
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• 제20권B호
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• pp.155-162
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• 2000

Although Fuzzy Logic Controller(FLC) adopted three terms as input gives better performance, FLC is in general composed of two-term control because of the difficulty in the construction of fuzzy rule base. In this paper, a three-term FLC which is similar to PID control but acts as a nonlinear controller is proposed. To reduce the complexity of the rule base design and to increase efficiency. a simplified fuzzy PID control is induced from a hybrid velocity/position type PID algorithm by sharing a common rule base for both fuzzy PI and fuzzy PD parts. It is simple in structure, easy in implementation, and fast in calculation. The phase plane technique is applied to obtain the rule base for fuzzy two-term control and the resultant rule base is Macvicar-Whelan type. And the membership function is a Gaussian function. The frequency response information is used in tuning of the membership functions. Also a tuning strategy for the scaling factors is proposed based on the relationship between PID gain and the scaling factors. Simulation results show better performance and the effectiveness of the proposed method.

• Journal of Gastric Cancer
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• 제17권3호
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• pp.193-203
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• 2017

The implementation of national cancer screening has increased the detection rates of early gastric cancer (EGC) in Korea. Since the successful introduction of laparoscopic gastrectomy for gastric cancer in the early 1990s, this technique has demonstrated improved short-term outcomes without compromising long-term oncologic results. It is associated with reduced pain, shorter hospitalization, reduced morbidity rates, better cosmetic outcomes, and equivalent mortality rates as those for open surgery. Laparoscopic gastrectomy improves patients' quality of life (QOL) and provides favorable prognosis. Single-incision laparoscopic gastrectomy (SILG) is one extremely minimally invasive method, theoretically offering improved cosmetic results, less postoperative pain, and earlier recovery after surgery than conventional multiport laparoscopic gastrectomy. In this context, SILG is thought to be an optimal method to promote and maximize patients' QOL in the acute postoperative phase. However, the technical difficulties of this procedure have limited its use. Since the first report describing single-incision distal gastrectomy in 2011, only 16 studies to date have evaluated SILG. Most of these studies have focused on the technical feasibility and safety of SILG because its long-term outcomes have not been reported. This article reviews the advantages and limitations of SILG.

• 한국안전학회지
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• 제25권6호
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• pp.75-80
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• 2010

본 논문에서는 일반용 전기설비 중에서 전기안전관리의 사각지대로 분류되는 보안등 전기설비를 대상으로 전기안전요소들을 계측하고 원격 모니터링 할 수 있는 보안등 원격점검시스템을 개발하였다. 단말기에서 센싱하는 누설전류는 위상차 측정법을 이용한 저항성분 누설전류(Igr) 측정 알고리즘을 이용하였으며, 계측데이터 전송을 위한 중계기와 MMI에서 모니터링 할 수 있는 시스템을 제작하였으며, Igr 누설전류 검출 알고리즘의 타당성을 확인하기 위해 실험실 기반의 성능시험으로 누설전류의 안정도를 확인하였다.

• 한국정보통신학회논문지
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• 제8권6호
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• pp.1147-1152
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• 2004

논문에서는 다양한 표준을 지원하는 NTSC, PAL 복합 영상 부호화기의 설계 및 구현에 관한 내용이다. 복합 영상 부호화기는 ITU-R BT.601 4:2:2, ITU-R BT.656, RGB중 하나의 입력을 받아서 NTSC, PAL등의 S-video 신호와 복합 영상 신호로 바꾸어 준다. 하드웨어 복잡도를 줄이기 위해서 곱셈기를 사용하지 않는 구조로 설계하였다. 명암 신호와 색차 신호를 위한 디지털 필터의 bit width는 하드웨어 설계 시 발생할 수 있는 오차를 1 least significant bit (LSB) 이하가 되도록 정하여 양질의 복합 영상 신호를 만들 수 있도록 하였다. 제안된 영상 부호화기는 Altera FPGA인 APEX20K600EBC652-3을 이용하여 실시간 검증을 수행하였다.

• 한국군사과학기술학회지
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• 제13권6호
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• pp.1058-1063
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• 2010

In this paper, we designed self-frequency synchronizing circuit using image rejection mixer(IRM) and single-sideband(SSB) up-converter which can effectively eliminate the image frequencies occurred in multi-channel super-heterodyne receivers and help us to match inter-channel phase. Also the self-frequency synchronizing circuit simplifies system because there need no extra devices for making intermediate frequency(IF) by creating the local signal within several nanoseconds by means of generating the same frequency of IF signal and modulating radio frequency(RF) signal. We adopt the limiting amplifier for the purpose of protecting the circuit from spurious signals which come from the front end side having wide instantaneous bandwidth characteristics and constantly injecting same level into the input local signal of IRM. The IRM we fabricated has image rejection ratio of 27dB, which is good over 7dB for foreign company's. Also, the SSB up-converter we fabricated has 1dB compression point of 18dBm, which is good over 16dB for foreign company's. And the size is compact about one-forth.

• Journal of Electrical Engineering and Technology
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• 제8권2호
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• pp.354-358
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• 2013

This paper discusses the analysis of arc conductance in a gas circuit breaker (GCB) during current interruption process and the investigation method of the interruption capability. There are some limitations in the application of the computational fluid dynamics (CFD) for the implementation of an arc model around the current zero, despite the fact that it gives good results for the high-current phase arc. In this study, we improved the accuracy in the analysis of the interruption performance by attempting the method using CFD and a mathematical arc model. The arc conductance at 200 ns before current zero (G-200ns) is selected as the indicator to predict the current interruption of the Short Line Fault (SLF). Finally, the proposed method is verified by applying to the actual circuit breakers which have different interruption performances.

• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.800-811
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• 2018

This paper presents a regenerative braking control scheme for Switched Reluctance Machine (SRM) drive in Electric Vehicles (EVs). The main purpose is to maximize the recovered energy during battery charging by taking into account the nonlinear physical characteristics of the Switched Reluctance Machine. The proposed regenerative braking method employs the back-EMF in the generation process as a complicated position-dependent voltage source. The proposed maximum power recovery (MPR) operation of the regenerative braking is first based on the maximization of the extracted power from the machine and then the maximization of the power transferred to the battery. The maximum power extraction (MPE) from SRM is based on maximizing the energy conversion ratio by the calculation of the optimum PWM switching duty cycle, turn-on, and turn-off angles. By using the impedance matching theorem that allows the maximum power transfer (MPT) of the MPE, the proposed MPR is achieved. The parametric averaged value modeling of the machine phase currents in the chopping control mode is used for MPR realization. By following this model, a nonlinear equivalent input resistance is derived for the battery internal resistance matching. The effectiveness of the proposed regenerative braking method is demonstrated through simulation results and experimental implementation.