• 한국추진공학회:학술대회논문집
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• 한국추진공학회 1998년도 제10회 학술강연회논문집
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• pp.15-15
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• 1998

The problem of the impingement of a sonic or a supersonic jet on a flat surface has not only wide applications but has also interesting and very complex flow phenomena. The main applications of this impinging jet include prediction of solid surface erosion, design of launcher systems, stage separation of multi-stage rocket system, V/STOL operations, thermal spray system, and manufacturing technologies of materials. Much have been learned about the supersonic impinging jet flow field but many fundamental questions have not been answered satisfactorily. The problem encompasses many facets of fluid dynamics which, in combination, present the compressibility effect and the viscous-inviscid interaction, coupled with flow separation and reattachment. What is more, there are many flow parameters that have on the impinging jet flow field, for example, Mach number, Reynolds number, pressure ratio, distance between the nozzle exit and flat plate, jet shock structure, nozzle diameter and etc. Thus the existing data on the supersonic impinging jet flow present considerable disagreement in which quantitative comparison between one result and another is often impossible.

• 항공우주시스템공학회지
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• 제6권2호
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• pp.23-27
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• 2012

The evaluation of simulation models against ADS-33 quantitative rotorcraft handling qualities metrics has, in the past, been a time consuming effort, involving many individual analyses in both the time and frequency domains. Manual tuning of control system parameters to meet handling qualities and performance specifications has been cumbersome and complicated. Performing rigorous trade-off studies for numerous variations in the control system is too time consuming to be practicable. With the complex interaction of time- and frequency based specifications for the closed- and broken-loop responses, it is difficult to know if the design makes the most effective use of the available control power. The Control Designer's Unified Interface (CONDUIT) software makes possible rapid optimization and trade-offs of design configurations against handling qualities specifications.

• 물과 미래
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• 제23권1호
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• pp.89-98
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• 1990

유역 수문학에 있어서 하도망의 지형학적 특성을 하천유출해석에 적용시키는 방법을 지형학적 순간단위도를 이용해서 검토하였다. 유역의 지형학적 특성은 Shreve link분류법과 Kirkby가 제안한 거리함수를 이용하여 정량적으로 표현 하였다. 거리함수는 해석적으로 유도된 확률모델로서 Weibull분포를 사용하였으며, 분석대상유역에 대한 거리함수의 확률모델과 하도망으 구조적 특성 및 기타 지형인자등을 분석하였다.

• 한국건설관리학회논문집
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• 제5권5호
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• pp.93-100
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• 2004

For accurate construction contract time estimation, few parameters are more significant than crew production rates and factors affecting the rates. However, statistical analysis techniques for finding such factors are not always simple mainly because there are many factors and the interaction between factors is not well quantitatively understood. This paper presents methodology of identifying factors driving crew production rates. The methodology is further demonstrated with representative data collected by the author from 13 on-going highway constructions. Three factors were identified as statistically significant drivers of Cap crew production rate: 'Cap Size (m3/ea)'; 'Cap Length (m)'; and 'Cap Shape (Rectangle vs. Inverted 'T')'. It was also found that the production rates are best explained by a multiple regression model with two of the drivers; 'Cap Size' and 'Cap Shape'.

• Journal of Electrical Engineering and Technology
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• 제9권4호
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• pp.1196-1201
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• 2014

This paper presents an exploration on the effect of wind turbine contribution to the frequency control of individual systems that can be used for efficient power production in India. The research includes the study of Permanent Magnet Synchronous Generator (PMSG), in wind farms. The WTs are tested for inertia and for droop responses with intelligent fuzzy logic controllers (FLC) that choose Double Input Single Output (DISO) strategy that automatically sets gain constants, as well as combined responses for the WTs. Quantitative analyses are presented for the WTs for benefits and drawbacks including appropriate selection parameters. The analysis includes inertia, droop and combined inertia, droop schemes. The reconnaissance also incorporates inertia with FLC, droop with FLC, inertia and droop with FLC schemes for detailed study of WTs, so as to forecast and achieve proper frequency control. Moreover, the analysis provides the best suited method for frequency control in PMSG.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 학술대회 논문집 전문대학교육위원
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• pp.102-105
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• 2002

In this paper, the electron transport characteristics in $CF_4$ has been analysed over the E/N range 1${\sim}$300 [Td] by a two-term approximation Boltzmann equation method and by a Monte Carlo simulation. The motion has been calculated to give swarm parameters for the electron drift velocity, longitudinal diffusion coefficient, the ratio of the diffusion coefficient to the mobility, electron ionization and attachment coefficients, effective ionization coefficient, mean energy, collision frequency and the electron energy distribution function. The swarm parameter from the swarm study are expected to serve as a critical test of current theories of low energy electron scattering by atoms and molecules, in particular, as well as crucial information for quantitative simulations of weakly ionized plasmas.

• 한국연소학회지
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• 제9권3호
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• pp.1-9
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• 2004

This study is aimed to characterize the combustion behavior of solid fuel in the various types of the combustors: stoker, rotary kiln and fluidized bed type combustors. Three different types of reduced-scale combustors are introduced, and temperatures and flue gas compositions are measured for various fuel sizes, water contents, initial temperature, and air flow rates. In case of the rotary kiln combustor, effects of rotating speed of the combustor are also investigated. Mean carbon conversion time (MCCT) and flame propagation rate (FPR) are used for the quantitative analysis. It is revealed that the reaction rates of the fuel are significantly influenced by the fuel characteristics, type of the combustors and air flow rate. Major design parameters for each type of the combustors are summarized through the reduced-scaled model analysis.

• 한국자동차공학회논문집
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• 제12권1호
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• pp.55-60
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• 2004

Residual gas acts as a diluent which results in reducing the in-cylinder temperature as well as the flame speed, significantly affecting fuel economy, NOx emissions and combustion stability. Therefore it is important to determine the residual gas fraction as a function of the engine operating parameters accurately. However, the determination of the residual gas fraction is very sophisticated due to the unsteady state of induction and exhaust process. There has been little work toward the development of a generally applicable model for quantitative predictions of residual gas fraction. In this paper, a simple model for calculating the residual gas fraction in SI engines was suggested. The amount of fresh air was evaluated through AFR and fuel consumption. After this, from the intake temperature and pressure, the amount of total cylinder-charging gas was estimated. The residual gas fraction was derived by comparing the total charging and fresh air. This results coincide with measured EGR value very well.

• 한국자기공명학회논문지
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• 제6권2호
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• pp.142-154
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• 2002

One of the oldest, still unsolved, and often ignored problems in magnetic resonance remains the issue of how to observe undistorted, normal one-dimensional spectra where the frequencies and their relative intensities represent faithfully the distribution of spins and sites in the sample within the magnet. Often distortions in these parameters are accepted, as the price of sensitivity enhancement, or because it is unclear just how these distortions might be avoided. Surprisingly enough, the problem is exacerbated by the use of modern techniques of pulsed Fourier transform NMR. Noise spectroscopy is an approach to solving the problem of distorted NMR spectra, which is largely under appreciated; it promises virtually "unlimited" distortionless bandwidths without costly hardware investments. Nonetheless, its exploitation remains limited. We will discuss why noise spectroscopy belongs in the arsenal of tricks spectroscopists should be aware of, show examples where its use is essential if accurate, quantitative NMR is to be expected, and discuss some recent approaches which extend its applicability yet further, particularly in solid state NMR and in applications to quadrupolar nuclear spins.

• 산업공학
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• 제11권2호
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• pp.125-137
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• 1998

A new vehicle design approach coupled with an ergonomic human model was proposed in the study. The seating package layout of a vehicle is very important to the driving comfort, and it has been one of the primary ergonomic research areas since the past 30 years. The diverse and interrelated design factors of seating package layout in the limited workspace make designers often neglect many parameters related with drivers which differ in their anthropometric characteristics. It is due to the lack of the proper tools by which the designer can easily apply several ergonomic design guidelines to the vehicle design. In this study. an iterative package layout procedure was developed, and the effectiveness of an ergonomic human model was examined in this procedure. A discomfort function was developed for the quantitative evaluation of the driving posture. This study clearly demonstrates that the package layout using an ergonomic human model is very helpful to improve the usability and driving comfort of the drivers or passengers.