미세특징에 따른 복합재료의 특성해석

김태우 국민대학교 생산기술연구소 2004 공학기술논문집 Vol.27 No.-

Studies on the transverse properties were made for the unidirectional composite under uniaxial loading. The unidirectional composites, with fibers regularly arranged in square pattern, have been known to display different mechanical behavior depending on the fiber/matrix interface characteristics. The present study employed finite element analysis technique, which enabled modeling of the unit-cell for the composite with different types of interface bonding. The stress-strain curves were obtained as a function of fiber volume fraction and bonding type. The resulting decrease of the elastic stiffness for the weakly-bonded composite was caused by the progressive debonding at the fiber/matrix interface with incremental loading.

바렉터 다이오드를 이용한 높은 격리도를 갖는 Diplexer 스위치 설계 및 구현

박준석,강명수 국민대학교 생산기술연구소 2004 공학기술논문집 Vol.27 No.-

In this paper, using diplexer structure and varactor diode controlled by reverse bias voltage for diplexer switch gives possibilities to improve isolation and current characteristics. I have newly designed switch with high isolation by application varactor diode corresponding to capacitor of diplexer. The low-pass filter for proposed tunable diplexer passes the microwave signal in the bandwidth for wireless cellular network systems and high-pass filter passes it in the bandwidth for wireless personal communication services (PCS) network systems. As the capacitance of the low-pass filter increases, the cut-off frequency can be moved to low frequency, so that the switch is on state in cellular bandwidth and off state in the PCS bandwidth, in contrast to, as the capacitance for attenuation characteristic of high-pass filter increases, it can be moved to high frequency, so that the switch is off state and on state in the cellular bandwidth, it is possible to improve isolation and current consumption characteristics by application diplexer design methods and varactor diode. I expect that the tunable diplexer circuit and design methods should be able to find applications on MMIC and low temperature copired ceramic (LTCC).

Steer-By-Wire 시스템의 Fault-Tolerant 기술 개발

김재석,이운성 국민대학교 생산기술연구소 2004 공학기술논문집 Vol.27 No.-

The Steer-By-Wire (SBW) system replaces complex mechanical linkages of the current steering system with electric motors, sensors, and electronic control units. However, the SBW system should guarantee its safety before commercialization, and therefore, a reliable and robust fault-tolerant technology has to be implemented. This paper presents fault-tolerant control strategy for a reliable and safe SBW system and proposes a fault-tolerant SBW control system integrating SBW control algorithms, fault-detection algorithms, and reconfiguration algorithms. Based on careful analysis on propagation effects of sensor faults, a reliable fault-tolerant control strategy has been developed. The fault-tolerant controller consists of a fault detection part that monitors and defects faults in the steering wheel and road wheel sensors, and a reconfiguration part that switches to normal sensor signal based on fault detection information. It has been demonstrated that the proposed algorithm detects sensor faults accurately and enables reliable steering control under various dynamic fault situations.

Single-Stage Single-Switched Rectifier/Regulator with Magnetic Coupled Nondissipative Snubber

Kim, Joong-Soo,Roh, Chung-Wook,Hong, Sung-Soo,Sakong, Sug-Chin 국민대학교 생산기술연구소 2004 공학기술논문집 Vol.27 No.-

This paper presents a new single-stage single-switched forward converter with magnetic coupled nondissipative snubber, which gives the good power factor correction (PFC), low current harmonic distortion, and tight output voltage regulation. The proposed converter features the low switch current and voltage stresses, essential for the design of a single-stage power factor correction converter. The prototype shows that the IEC 1000-3-2 requirements are met satisfactorily with nearly unity power factor. This proposed converter with magnetic coupled nondissipative snubber is particularly suited for power supply applications with low power level.

실험적 모델과 인공신경망을 사용한 소독부산물 생성예측

손진식 국민대학교 생산기술연구소 2004 공학기술논문집 Vol.27 No.-

Water treatment facilities face new challenges with regard to maintaining disinfectants as well as reducing disinfection by-products(DBPs). The need to control DBPs in water treatment facilities has stimulated the development of various models including empirical models, kinetic based models, and artificial neural networks (ANN). In order to evaluate the appropriate models for simulating DBPs, several attempts have been made to compare an empirical based model and ANN simulations using bench-scale experiment data. The empirical based model is considered a powerful modeling tool in simulating DBPs. ANN Simulation also provides a potential modeling tool in predicting DBP formation. The external evaluation of these models is further needed by using full-scale monitoring data.

치과용 Ti-Pd합금의 개발연구

김민주,이진형 국민대학교 생산기술연구소 2004 공학기술논문집 Vol.27 No.-

It is difficult to cast pure titanium by usual dental casting method, because titanium has a high melting temperature and high chemical reactivity with mold material and air at high temperatures. Developing new titanium alloys that have lower melting points and less reactivity may solve these problems. Ti-Pd alloy has a great potential for dental casting alloys. The purpose of this study is to investigate the effects of Pd in titanium on mechanical properties, microstructure and phase transformation behaviours in dentistry. CP-Ti, Ti-15wt%Pd, Ti-25wt%Pd and Ti-35wt%Pd were cast into phosphate bonded Al₂0₃/SiO₂ investment by using an argon arc melting/centrifugal castings machine. The following results were obtained; Ti and Ti-Pd alloys investigated had good castability by argon arc melting/centrifugal castings method. The phase as cast state were all alpha Ti in CP-Ti, mostly alpha Ti with some Ti₂Pd in Ti-15wt%Pd, all beta Ti in Ti-25wt%Pd and mostly Ti₂Pd with some alpha Ti in Ti-35wt%Pd. Ti-25wt%Pd alloy had an adequate mechanical properties for dental applications, but as-cast phase decompose above 490℃.

이산화탄소를 이용한 냉방시스템의 성능 해석 시뮬레이션

박종환,박경근 국민대학교 생산기술연구소 2003 공학기술논문집 Vol.26 No.-

Simulation and performance analysis of a carbon dioxide air cooling system is made. The air cooling system using carbon dioxide consists of compressor, gas-cooler, expansion device and evaporator. Loss and efficiency model is applied for compressor analysis and effectiveness-NTU method is utilized for heat exchanger analysis. Changing compressor outlet pressure, gas-cooler inlet air temperature or evaporator inlet air temperature, its effect on system performance is examined. It is found that there is an optimum compressor outlet pressure which gives a maximum COP. It is also noted that COP decreases as the gas-cooler inlet air temperature increases and as the evaporator inlet air temperature decreases.

원자층 증착기를 이용한 ZrO₂박막의 제조 및 특성 연구

김지영,박노헌 국민대학교 생산기술연구소 2004 공학기술논문집 Vol.27 No.-

SiO₂ as a dielectric of gate structure for CMOS has been facing the scaling limitation due to direct tunneling current and reliability problems. ZrO₂ has been suggested as an alternative gate dielectric material for ULSI CMOS devices due to its thermal stability and high dielectric constant. Since atomic layer deposition (ALD) has several features such as excellent uniformity, accuracy and easiness of thickness control and conformal film formation, ALD is one of the most suitable method for deposition of the gate dielectrics. In this study, ZrO₂ thin films on Si substrate were grown by ALD using a metal-organic precursor, zirconium t-butoxide. We investigated the effects of oxidizer on the characteristics of the ZrO₂ films.

TiC 입자강화 Al기 복합재료에 관한 연구

심호섭,이세영,조수연,양형렬,김형철,권훈 국민대학교 생산기술연구소 2002 공학기술논문집 Vol.25 No.-

The tensile properties and microstructures of Al composites reinforced with TiC particulates fabricated by pressureless infiltration method were investigated. Under the nitrogen atmosphere spontaneous infiltration of the molten Al alloy into the TiC powder bed occurred. The distribution of TiC particles in the composites was relatively uniform. A1N and MgAl₂O₄ were formed both control alloy and composites as a reaction product. During fabrication of Al-Mg/TiC composites Al₄C₃, Al_(18)Ti₂Mg₃, Ti₂AlC, Al₃Ti and TiAl were formed as a result of the interfacial reaction between Al alloy matrix and TiC particles. Fine AlN particles during composite and control alloy fabrication were formed by the in-situ reaction, which led to higher tensile and yield strengths than that of commercial Al alloy.

탄화물 입자 강화 7075 Al 합금 기지 복합재료의 미끄럼마멸 특성 연구

강석하,박형철,강신철,김용석 국민대학교 생산기술연구소 2002 공학기술논문집 Vol.25 No.-

Effects of the type and volume fraction of carbide-particle-reinforcements on dry sliding wear behavior of 7075 Al alloy matrix composites were investigated. SiC, TiC and B₄C reinforced 7075 Al alloy matrix composites were manufactured by a pressureless infiltration technique and wear tested. Wear tests were carried out using a pin-on-disk wear tester with varying loads of 3N-160N at a constant sliding velocity of 0.2m/s. AISI 52100 bearing steel ball was a counterpart of the composites. Wear resistance of the composites was always higher than that of the monolithic alloy except the TiC reinforced 7075 Al matrix composite. The resistance increased with the increase of volume fraction of the reinforcing particles. Among the composites, the TiC reinforced composite had the lowest wear resistance and the B4C reinforced composite showed the highest wear resistance.