• 소음진동
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• 제10권3호
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• pp.430-436
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• 2000

The cross-flow fans have been widely used to constitute the air moving systems in many air-ventilating and air-conditioning units. The cross-flow fan system has many design parameters which have crucial influence on the performance and the noise characteristics of the units. As a result there are many difficulties in the design stage of the system and the general design guide has not been sufficiently established yet. This study presents the experimental results of the parametric investigation of some chosen design parameters which are directly related to the shape of the stabilizer the profile of the scroll casing and the diffusion angle of the flow exit. The results are expressed in terms of the fan performance and the specific sound pressure level characteristics. Some parameters have been found to have crucial effects on the system performance/noise characteristics and should be considered with care in the design stage.

• 한국유체기계학회 논문집
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• 제9권6호
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• pp.35-44
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• 2006

Operation conditions of a reheat cycle gas turbine for a combined cycle power plant was analyzed. Based on measured performance parameters of the gas turbine, a performance analysis program predicted component characteristic parameters such as compressor air flow, compressor efficiency, efficiencies of both the high and low pressure turbines, and coolant flows. The predicted air flow and its variation with the inlet guide vane setting were sufficiently accurate. The compressor running characteristic in terms of the relations between air flow, pressure ratio and efficiency was presented. The variations of the efficiencies of both the high and low pressure turbines were also presented. Almost constant flow functions of both turbines were predicted. The current methodology and obtained data can be utilized for performance diagnosis.

• 한국분무공학회지
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• 제5권2호
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• pp.68-74
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• 2000

A this experimental study is executed to analyze spray characteristics for air-shrouded injector and 4hole 2spray type injector used in a gasoline engine. Since spray parameters including spray penetration and angle, SMD, and atomization characteristics are very important to increase the engine performance, the image processing algorithm for measuring the non-spherical spray diameter is developed. Spray characteristics of the air-shrouded injector(2hole 2spray) and 4hole-2spray injector are analyzed respectively by this digital image processing method. Effective spray characteristics to injectors is derived from this experimentation and obtained the design guide for gasoline injector.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.443-446
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• 1997

This paper raises issues in testing the absorption coefficients of sound-absorptive samples in the standing wave tube according to the Korean standard of KS F 2814. The code does not consider any effect of air-damping during test. This limitation has been shown to yield much variation of sound absorption coefficients for recent sample tests whose coefficients are less than 10 %. An improved method of calculating the sound absorption coefficients is proposed in this work and its effectiveness in real test is also illustrated. Finally, the guide line for the modification of our national standard code KS F 2814 is suggested for the future.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.1243-1248
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• 2009

This paper introduces the methode to improve the indoor air quality for Korea Tilting train express(TTX). TTX operates more than 80,000km in commercial line and in the near future service is expected. To improve air quality effective heat and cooling system is proposed. Also according to the ministry of environment guide line, major factor component are selected to Co2(carbon dioxide) and Pm10(particle matter). The database of the vital factor was accumulated by the various case of operation environment. Finally, optimal air condition controling device is developed and installed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 학술대회 논문집 전문대학교육위원
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• pp.6-8
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• 2002

Generally in solar air conditioning system, the diode rectifier is used to build up DC link voltage from AC source. The diode rectifier is simple and cheap but it brings out the problems of low power factor and plentiful harmonics at the AC source. Also It can degrade the utilization rate of solar energy because the reverse of power flow cannot be made. Hence, in this paper to overcome the peak power problems in summer and to endure good AC input characteristics, solar air conditioning system using the PWM converter is proposed. A high input power factor of 97[%] and an efficiency of 98[%] are also obtained. The harmonic guide lines of proposed rectifier is no interfered with inverter switching, resulting in a simple, reliable and low cost ac to dc converters in comparison with the boost type current improving circuits.

• 대한방사선치료학회지
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• 제10권1호
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• pp.69-77
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• 1998

When a high energy photon beam is used to treat lesions located in the upper respiratory air passages or in maxillary sinus, the beams often must traverse an air cavity before it reaches the lesion. Because of this traversal of air, it is not clear that the surface layers of the lesion forming the air-tumor tissue interface will be in a state of near electronic equilibrium; if they are not, underdosing of these layers could result. Although dose corrections at large distances beyond an air cavity are accountable by attenuation differences, perturbations at air-tissue interfaces are complex to measure or calculate. This problem has been investigated for 4MV and 10MV X-ray beams which are becoming widely available for radiotherapy with linear accelerator. Markus chamber was used for measurement with variouse air cavity geometries in X-ray beams. Underdosing effects occur at both the distal and proximal air cavity interface. The magnitude depended on geometry, energy, field sizes and distance from the air-tissue interfaces. As the cavity thickness increased, the central axis dose at the distal interface decreased. Increasing field size remedied the underdosing, as did the introduction of lateral walls. Fellowing a $20{\times}2{\times}2\;cm^3$\;air\;cavity,\;4{\times}4\;cm\;field\;there\;was\;an\;11.5\%\;and\;13\%\;underdose\;at\;the\;distal\;interface,\;while\;a\;20{\times}20{\times}2\;cm^3\;air\;cavity\;yielded\;a\;24\%\;and\;29\%$ loss for the 4MV and 10MV beams, respectively. The losses were slightly larger for the 10MV beams. The measurements reported here can be used to guide the development of new calculation models under non-equilibrium conditions. This situation is of clinical concern when lesions such as larynx and maxillary carcinoma beyond air cavities are irradiated.

• 한국자동차공학회논문집
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• 제13권2호
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• pp.72-82
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• 2005

The objective of this paper is to describe the optimization of design parameters in a large-sized commercial bus heater system by using CFD(computational fluid dynamics) analysis and Taguchi method. In order to obtain the best combination of each control factor which results in a desired performance of heater system, the parameter design of the Taguchi method is adopted for the robust design considering the dynamic characteristic. The research activity may be divided into four phases. The first one is analyzing the problem, i.e., ascertaining the influential factors. In the second phase the levels were set in such a way that their variation would significantly influence the response. In the third phase the experimental runs were designed. In the final phase the planned runs were carried out numerically to evaluate the optimal combination of factors which is able to provide the best response. In this study, eight factors were considered for the analysis: one with two level and seven with three level combinations comprising the $L_{18}(2^1{\times}3^7)$ orthogonal array. The results of this study can be summarized as follows ; (i)The optimum condition of control factor is a set of <$A_2\;B_1\;C_3\;D_3\;E_1\;F_2\;G_3\;H_2$> where A is shape of the outer fin, B is pitch of the outer fin, C is height of the outer fin, D is the inner fin number, E is the inner fin height, F is length of the flame guide, G is diameter of the heating element and H is clearance between air guide and heating element. (ii)The heat capacity of heated discharge air under the optimum condition satisfies the equation y=0.6M w here M is a signal factor. (iii)The warm-up rate improves about three times, more largely as com pared with the current condition, which results in about 9.2minutes reduction.

• 한국정밀공학회지
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• 제30권11호
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• pp.1217-1224
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• 2013

In this paper, a hand exoskeleton actuated by air muscles(soft hand exoskeleton) is introduced. Some soft hand exoskeletons have already been developed to overcome the defects of hand exoskeletons based on linkage and pneumatic piston system-they are usually bulky and do not have enough degree of freedom(DOF). However, soft hand exoskeletons still have defects. Their motions are not precise as linkage based hand exoskeletons, because their actuator, such as air muscle is made of soft materials. So we developed a new linkage which is not bulky and has redundant DOF. It is combined with air muscle in a specific way so that it acts as a guide when air muscle is actuated. Some experiments were conducted to evaluate the validity and usability of our hand exoskeleton.

• 한국항공우주학회지
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• 제41권7호
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• pp.539-546
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• 2013

항공기용 터보팬 엔진에서 압축기 성능이 단 시간에 변화가 클 경우, 이를테면 항공기가 이륙하는 상황에서와 같이 엔진 회전속도(RPM)를 공회전(idle) 상태에서 최대로 증가 시킬 때, 항공기의 엔진 성능이 급격하게 변화하므로 압축기 내에서 서지현상이 발생할 수 있다. 본 연구에서는 서지현상 발생 방지를 그 목적으로 하였다. Simulink를 이용하여 특정 상황에서 압축기 내에 일어나는 동적 움직임을 모사하였다. 연료유량을 입력값으로 하고 그에 따른 RPM, 공기유량은 전달함수로 나타냈으며, NPSS를 통해서 획득한 압축기 성능 맵을 통해 서지마진을 출력하였다. 서지마진을 기준 값 10%와의 차이를 PD제어하여 IGV(Inlet Guide Vane)각을 변화시킴으로써 즉, VIGV를 이용하여 압축기 내의 서지라인과 운용점 사이의 마진을 증가시켜 서지현상이 발생하는 것을 방지하였다.