• Transactions of The Korea Fluid Power Systems Society
• /
• 제5권4호
• /
• pp.26-31
• /
• 2008

This paper deals with the issue of position tracking control of a clamp-cylinder for injection moulding machine with electric-hydrostatic drives. A fixed displacement pump is utilized in combination with AC motor in order to directly control a clamp-cylinder. A clamp-cylinder may be required to operate under a variety of operating conditions. Therefore, robust control performance is important in position tracking control applications. In order to accommodate mismatches between the real plant and the model used for controller design, discrete-time sliding mode control is developed by combining a velocity feedforward loop. From tracking control experiments, it is shown that significant reduction in position tracking error is achieved through the use of sliding mode control.

• Information and Communications Magazine
• /
• 제31권3호
• /
• pp.85-95
• /
• 2014

통신 사업자들은 과거에 통신 사업자 주도의 Walled Garden 형태의 제한적인 컨텐츠 서비스 제공 및 음성 중심의 시대에서 트래픽의 증가에 비례하는 수익의 증가를 경험하였다. 그러나 스마트폰의 보급과 함께 사용자들이 필요한 컨텐츠에 직접 접속하는 개방형 서비스의 수용 및 데이터 중심의 시대로 전환되면서 통신 사업자의 수익은 처리 트래픽의 증가에 비례 하지 않고 정체되어 있고 모바일 데이터 폭증에 따른 망 인프라 투자 및 유지보수 비용을 계속 늘려야 하는 상황에 직면하게 되었다. 본 고에서는 통신 사업자들의 이러한 국면을 타개하기 위한 제도적, 사업적 그리고 기술적인 해결책 중에서 기술적인 측면의 한 분야로 평가되고 있는 클라우드 기지국 전반에 대하여 살펴본다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• 제14권9호
• /
• pp.726-730
• /
• 2001

Temperature stabilities of dielectric constraints and resonant frequencies of the substrates are very important in piezoelectric ceramics oscillators and filters. In this study, it was investigated temperature stability of the length-extensional vibration mode of Pb(Zr$\_$y/Ti$\_$1-y/)O$_3$+x[wt%]Cr$_2$O$_3$ ceramics. The mode can be utilized in fabricating ultra-small 455 kHz IF devices. Addition of Cr$_2$O$_3$ in morphotrophic phase PZT decreased the variations of dielectric constant, electro-mechanical coupling factor k$\_$31/ and resonant frequency by thermal shock. As additive weight of Cr$_2$O$_3$increased, the temperature coefficient of resonant frequency changed from positive number to negative one. And the composition tith temperature coefficient of resonant frequency was shifted to the one with increased Cr$_2$O$_3$ additive weigh by thermal aging.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• 제38권3호
• /
• pp.68-68
• /
• 2001

본 논문에서는 3GPP와 ETSI에서 IMT-2000의 음성부호화 방식 표준안으로 채택한 AMR 음성부호화 알고리즘을 분석하고 C 컴파일러와 어셈블리 언어를 이용한 최적화 과정을 거친 후, 고정 소수점 DSP 칩인 TMS320C6201을 이용하여 실시간 구현하였다. 구현된 codec의 프로그램 메모리는 약 31.06 kWords, 데이터 RAM 메모리는 약 9.75 kWords, 그리고 데이터 ROM 메모리는 약 19.89 kWords 정도를 가지며, 한 프레임(20 ms)을 처리하는데 약 4.38 ms가 소요되어 TMS320C6201 DSP 칩의 전체 가용한 clock의 21.94%만 사용하여도 충분히 실시간으로 동작 가능함을 확인하였다. 또한, DSP 보드상에서 구현한 결과가 ETSI에서 공개한 ANSI C 소스 프로그램의 수행 결과와 일치함을 검증하였고, 구현된 AMR 음성부호화기를 sound I/O 모듈과 결합하여 실험한 결과, 어떠한 음질의 왜곡이나 지연 없이 실시간으로 충분히 동작함을 확인하였다. 마지막으로, Host I/O와 LAN 케이블을 이용하여 AMR 음성부호화 알고리즘을 통한 쌍방간 실시간 통신을 full-duplex 모드로 확인하였다.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• 제31A권8호
• /
• pp.62-71
• /
• 1994

A novel semiconductor device is proposed to be used as a processing element for the implementation of pulse-mode neural networks which consists of alternating n' GaAs quantum wells and undoped AlGaAs barriers sandwitched between n' GaAs cathode and P' GaAs anode and in simple circuit in conjunction with a parallel capacitive and resistive load the trigger circuit generates neuron-like pulse train output mimicking the function of axon hillock of biological neuron. It showed the sigmoidal relationship between the frequency of the pulse-train and the applied input DC voltage. In conjunction with MQWIMD the various neural circuits are proposed especially a neural chip monolithically integrated with photodetectors in order to perfrom the pattern recognition.

• Proceedings of the KSR Conference
• /
• 한국철도학회 2006년도 추계학술대회 논문집
• /
• pp.31-34
• /
• 2006

A new continuum damage theory (CDT) has been proposed by Lee et al. (1996) based on the SEEP. The CDT has the apparent advantage over the other related theories because the complete constitutive law can be readily derived by simply replacing the virgin elastic stiffness with the effective orthotropic elastic stiffness obtained by using the proposed continuum damage theory. In this paper, the CDT is evaluated by the numerical experiment comparing the mode shapes and natural frequencies of a square plate containing a small line-through crack with those of the same plate with a damaged site replaced with the effective orthotropic elastic stiffness computed by using the CDT.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 한국전기전자재료학회 1999년도 추계학술대회 논문집
• /
• pp.549-552
• /
• 1999

We have developed an novel vertical-alignment (VA) - $\pi$ cell mode that provides a wide viewing angle and fast response times for negative dielectric anisotropy nematic liquid crystal (NLC) on a homeotropic polyimide (PI) surfaces. We had the good voltage-transmittance curves and low driving voltages were achieved with the novel VA - $\pi$ cell mode without negative compensation film. Iso-viewing angle characteristics using the novel VA - $\pi$ cell mode without negative compensation film of NLC was also successfully observed. As well a fast response time of 31.7ms for the novel VA - $\pi$ cell mode was measured. Consequently, It is seen that by using the novel VA - $\pi$ cell mode the iso-viewing angle, fast response time, and low driving voltage characteristics can be achieved.

• Journal of the Korean Society of Safety
• /
• 제13권3호
• /
• pp.24-31
• /
• 1998

Variable thickness plates are commonly encountered in the majority of mechanical/structural components of industrial applications. And, as a result of the unsymmetry of the structure or the load and the anisoptropy of the materials, the cracks in engineering structures are generally subjected to combined stresses. In spite of considerable practical interest, however, a few fracture mechanics study on combined mode crack in a variable thickness plate have carried out. In this respect, combined mode I/III stress intensity factors $K_I$ and $K_III$ at the crack tip for a variable thickness plate were obtained by 3-dimensional finite element analysis. Variable thickness plates containing a central slant crack were chosen. The parameters used in this study were dimensionless crack length $\lamda$, crack slant angle $\alpha$, thickness ratio $\beta$ and width ratio $\omega$. Stress intensity factors were calculated by crack opening displacement(COD) and crack tearing displacement(CTD) method.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• 제51권6호
• /
• pp.260-264
• /
• 2002

We developed LD Pumped Nd:$VVO_4$ microchip laser with the cavity length of 1mm. The microchip laser output was 87.5㎽ at the wavelength of 1063.9nm with the input power of 241㎽ at the wavelength of 809nm. The slope efficiency was 40.7% and the threshold input power was 31.1㎽. We have also defined input power limit for the single longitudinal mode operation theoretically. It was 2.5 times larger than that of threshold input intensity. According to the results of simulation, the Nd:YVO$_4$ microchip laser can be operated with the maximum output of 15㎽ for the single longitudinal mode up to the input power of 77.75㎽.

• Proceedings of the KIPE Conference
• /
• 전력전자학회 2015년도 전력전자학술대회 논문집
• /
• pp.31-32
• /
• 2015

본 논문은 FAC (Forward converter Active Clamp) 회로를 통해 변압기 자화인덕턴스에 저장된 에너지를 셀 밸런싱에 재사용하는 Active Clamp Forward converter 기반 셀 밸런싱 회로를 제안한다. 제안 회로는 클램프 커패시터의 충전 균형으로 스위치를 전압 스파이크로부터 보호하고 전력손실을 초래할 수 있는 변압기의 자기포화를 방지할 수 있다. 제안한 셀 밸런싱 회로는 RCD 포워드 셀 밸런싱 컨버터 보다 더 높은 전력 전달 효율과 낮은 전압 스트레스를 갖는다. 제안한 액티브 셀 밸런싱 회로는 동시에 모든 셀이 균등화 되도록 작동하므로, 셀밸런싱 시간이 짧다. 본 논문에서는 제안 회로의 배터리 상태에 따른 제어모드를 설명하고 회로의 타당성 검증을 위해 Powersim 사(社)의 Psim 시뮬레이션 연구를 수행하였다.