• Restorative Dentistry and Endodontics
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• 제13권1호
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• pp.53-67
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• 1988

An investigation was carried out to compare the pulp responses against a few type of composite and streptococcus mutans contamination under the zinc oxide eugenol cement, and also confirmed pulpal responses of various composites with or without base. Seventy eight teeth from 6 dogs were employed and divided into 6 groups. Class V cavities were prepared on each tooth routinely with low speed dental engine. Paper disc about 0.3mm thick was immersed in the BHI broth in which streptococcus mutans had been enriched and the disc was inserted on the cavity floor prior to filling. Scotch bond puls Silux as Bis-GMA system composite resin and Helimolar as urethane system composite resin were adopted. Control group: Zinc-Oxide Eugenol cement filling Experimental groups: Group 1. Scotch bond + Silux filling with Dycal base Group 2. Heliomolar filling with Dycal base Group 3. Scotch bond + Silux filling without base Group 4. Heliomolar filling without base Group 5. Streptococcus mutans application. All cavities were sealed with thick ZOE cement to avoid marginal leakage. Postoperative intervals of 1, 2, 3, 4, 5 and 6 weeks teeth were carefully extracted, processed and stained with Hematoxylin and Eosin. The results were as follows: 1. S. mutans application group and composites without any base showed more severe pupal response than control group and dyca based groups. 2. The experimental group of S. mutans application showed severe response in the early stage compared to the two groups of composite resin without base, but no significant difference was found following periods. 3. The difference of pulpal response is not significant between Bis-GMA system and urethane system. 4. Streptococcus mutans application group and composites without base groups showed the evidence of histologic recovery at the six week cases and the large amount of reparative dentin was the prominent feature. 5. Pulp responses against every material were inclined to normal according to the time elapsed.

• 한국자동차공학회논문집
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• 제25권1호
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• pp.66-73
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• 2017

In this work, graphene platelets were introduced into wax in an automotive electronic controlled thermostat for the purpose of enhancing its thermal-conductive property and improving response performance. Graphene content ranging from 10 % to 20% was added into and mixed with the wax to investigate the effect of graphene amounts on the performance of an automotive electronic controlled thermostat in terms of response time, hysteresis and melting temperature. The experimental results revealed that graphene in wax contributed to a reduction in the response time and hysteresis of an automotive electronic controlled thermostat. As a consequence, important improvement in thermal sensitivity, full lift, melting temperature and hysteresis were obtained. The thermal response of wax with graphene content of 20 % was improved by 25 %, as compared to that of wax with Cu content of 20 %. Hysteresis of wax with graphene was reduced by $0.6^{\circ}C$ as compared to that of wax with Cu content. The melting temperature of wax is lowered and hysteresis is also improved with increased graphene content of wax in an electronic controlled thermostat. We hope that this study can help further the transition of nano-fluid technology from small-scale research laboratories to industrial application in the automotive sector.

• 대한기계학회논문집B
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• 제30권6호
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• pp.553-559
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• 2006

Most diesel injector, which is currently used in high-pressure common rail fuel injection system of diesel engine, is driven by the solenoid coil energy for its needle movement. The main disadvantage of this solenoid-driven injector is a high power consumption, high power loss through solenoid coil and relatively fixed needle response's problem. In this study, a prototype piezo-driven injector, as a new injector mechanism driven by piezoelectric energy based on the concept of inverse piezo-electric effect, has been designed and fabricated to know the effect of piezo-driven injection processes on the diesel spray structure and internal nozzle flow. Firstly we investigated the spray characteristics in a constant volume chamber pressurized by nitrogen gas using the back diffusion light illumination method for high-speed temporal photography and also analyzed the inside nozzle flow by a fully transient simulation with cavitation model using VOF(volume of fraction) method. The numerical calculation has been performed to simulate the cavitating flow of 3-dimensional real size single hole nozzle along the injection duration. Results were compared between a conventional solenoid-driven injector and piezo-driven injector, both equipped with the same micro-sac multi-hole injection nozzle. The experimental results show that the piezo-driven injector has short injection delay and a faster spray development and produces higher injection velocity than the solenoid-driven injector. And the predicted simulation results with the degree of cavitation's generation inside nozzle for faster needle response In a piezo-driven injector were reflected to spray development in agreement with the experimental spray images.

• 한국통신학회논문지
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• 제27권11C호
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• pp.1064-1073
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• 2002

본 논문에서는 프로토콜 개발 도구를 이용하여 Wireless Application Protocol (WAP) 포럼에서 제안하는 무선 트랜잭션 프로토콜(Wireless Transaction Protocol: WTP)을 구현하였다. 또한, 서버모델, coroutine 모델 및 activity-thread 모델에 따라 개발도구의 지원없이 직접 개발된 WTP 구현물들과 그 성능을 비교 분석하였다. 우선 Unified Modeling Language (UML)을 사용하여 프로토콜의 요구사항을 분석함과 동시에 프로토콜 엔진의 구조를 정의하였으며, 이를 기반으로 Specification and Description Language (SDL)을 사용하여 프로토콜 엔진을 상세 설계한 후, 코드 자동 생성기를 이용하여 WTP 구현물을 생성하였다. 구현물의 성능을 분석한 결과, 3,000개 이하의 클라이언트가 동시에 접속할 경우에는 트랜잭션 처리율(throughput)과 트랜잭션 처리 지연시간(system response time) 측면에서 기존의 세 가지 모델을 이용하여 직접 개발한 프로토콜 엔진과 그 성능이 대등함을 알 수 있었다. 그러나, 5,000개 이상의 클라이언트가 동시에 접속할 경우 트랜잭션 성공률은 약 10%까지 급격히 감소하고 트랜잭션 처리 지연시간은 1,500㎳까지 증가하였는데, 이는 프로토콜 개발도구를 사용한 경우에 구현물의 크기가 약 62% 증가하면서 프로토콜 처리시간 증가로 인한 것이다. 그러나, 이러한 실험 결과는 실험에 사용된 PC 서버의 사양을 고려할 때 호스트의 과부하로 인한 것이며, 부하분산 기능이 제공되는 실제 환경에서는 프로토콜 개발 도구를 사용하지 않고 직접 개발한 프로토콜 엔진과 거의 대등한 성능을 보였다.

• 대한기계학회논문집A
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• 제21권11호
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• pp.1957-1964
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• 1997

Torsional vibration is to vibrate strongly when the ignition pulses of the engine is excited with natural frequency of driveline. Torsional vibration like this can cause various noises as rattle and booming. For this study multi-degree of freedom analysis model of torsional vibration, which is combined with mass moment of inertia and torsional spring, was developed toward two wheel drive, four wheel drive and torsional vibration characteristics were compared and analyzed through the natural frequences, mode shapes and frequency response characteristics which was acquired by the simulation of it. The pertinence of that model was proved by the field test and the outcome of the simulations coincided with feeling test. Therefore, four wheel drive simulation model is considered to be useful thing for reducing torsional vibration of driveline and developing full-time four wheel drive vehicles.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.265-270
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• 2005

This paper presents a new attitude stabilization and control of an unmanned helicopter based on neural network compensation. A systematic derivation on the dynamics of an unmanned small-scale helicopter is performed. Combined rotor-fuselage-tail dynamics is derived in body-fixed reference frame with its origin at the C.G. of the helicopter. And the resulting nonlinear equation of motion consists of 6-DOF air vehicle dynamics as well as the rotor flapping and engine torque equations. A simulation model was modified using the existing simulator for an unmanned helicopter dynamic model, which reflects the unmanned test helicopter(CNUHELI). The dynamic response of the refined model was compared with the flight test data. It can be shown that a good coincidence was accomplished between the real unmanned helicopter system and the mathematical model. This dynamic model was linearized for classical controller design using small perturbation method. A Neuro-PD control system was designed for both longitudinal and lateral flight modes, and the results were compared with the PD-only control response. Simulation results show that the proposed Neuro-PD control system demonstrates better performance.

• Computers and Concrete
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• 제1권3호
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• pp.303-324
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• 2004

The Component-Based Software Development (CBSD) has established itself as a sound paradigm in the software engineering discipline and has gained wide spread acceptance in the industry. The CBSD relies on the availability of standard software components for encapsulation of specific functionality. This paper presents the framework for the development of a software component for the design of general member cross-sections. The proposed component can be used in component-based structural engineering software or as a stand-alone program developed around the component. This paper describes the use-case scenarios for the component, its design patterns, object models, class hierarchy, the integrated and unified handling of cross-section behavior and implementation issue. It is expected that a component developed using the proposed patterns and model can be used in analysis, design and detailing packages to handle reinforced concrete, partially prestressed concrete, steel-concrete composite and steel sections. The component can provide the entire response parameters of the cross section including determination of geometric properties, elastic stresses, flexural capacity, moment-curvature, and ductility ratios. The component can also be used as the main computational engine for stand-alone section design software. The component can be further extended to handle the retrofitting and strengthening of cross-sections, shear and torsional response, determination of fire-damage parameters, etc.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.772-777
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• 2006

An acoustic finite element model of a bridge is developed to evaluate the noise generated by the traffic-induced vibration of the bridge. The dynamic response of a multi-girder bridge, modeled by a 3-dimensional frame element model, is analyzed with a 3-axle(8DOF) truck model and a 5-axle(l3DOF) semi-trailer. The flat plate element is used to analyze the acoustic pressure due to the fluid-structure interactions between the vibrating surface and contiguous acoustic fluid medium. The radiation fields of noise with a specified distribution of vibrating velocity and pressure on the structural surface are also computed using the Kirchhoff-Helmholtz integral. In an attempt to illustrate the influence of the structural vibration noise of a bridge to total noise level around the bridge, the random function is used to generate the vehicle noise source including the engine noise and the rolling noise interacting between the road and tire. Among the diverse parameters affecting the dynamic response of bridge, the vehicle velocity, the vehicle weight, the spatial distribution of the road surface roughness, the stiffness degradation of the bridge and the variation of the air temperature changing the air density are found to be the main factors that increase the level of vibration noise. Consequently, The amplification rate of noise increases with the traveling speed and the vehicle weight.

• 대한기계학회논문집A
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• 제21권12호
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• pp.2081-2089
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• 1997

Accurate positioning of the throttle valve of a gasoline engine is required to implement various systems such as traction control system(TCS), cruise control system and drive-by-wire system. In this research, position control system has been developed for the throttle actuator system that uses one throttle actuation for small volume and DC servo motor for fast response. In order to drive the DC motor, PWM signal generator and PWM amplifier were built and interfaced to the motor and controller. Also, time delay control(TDC) law has been used as a basic control algorithm. A method of varying the reference model of the TDC according to the size of change in target throttle angle is proposed here. The simulation and experimental results show that both overshoot prevention and fast response are achieved by the TDC technique with this variable reference model.

• 한국자동차공학회논문집
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• 제5권3호
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• pp.191-201
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• 1997

Accurate positioning of a throttle valve is required to implement the traction control system(TCS) which improves acceleration performance in slippery roads. In this research, position control system is developed for the main throttle actuator(MTA) system which uses one throttle actuation for small volume and DC servo motor for fast response. In order to drive DC motor, PWM signal generator and PWM amplifier were built and interfaced to the motor and controller. Digital PID control law is used as basic control algorithm. In order to prevent overshoot and improve accuracy, velocity profiles are generated and implemented whenever the targer throttle angle is given from the TCS controller. Thanks to velocity profiles, the control performance was very good and only one set of PID gains was used to cover the entire operating range. Also, the resolution of position is about 0.4$^{\circ}C$, which is better than that of stepping motor also used as throttle actuator in some products. The response time of the developed system is also fast enough to implement the engine control based TCS algorithm.