• ETRI Journal
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• 제36권4호
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• pp.537-544
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• 2014

In this paper, we present a new inter-carrier interference (ICI) self-cancellation scheme - namely, ISC scheme - for orthogonal frequency-division multiplexing systems to reduce the ICI generated from phase noise (PHN) and residual frequency offset (RFO). The proposed scheme comprises a new ICI cancellation mapping (ICM) scheme at the transmitter and an appropriate method of combining the received signals at the receiver. In the proposed scheme, the transmitted signal is transformed into a real signal through the new ICM using the real property of the transmitted signal; the fast-varying PHN and RFO are estimated and compensated. Therefore, the ICI caused by fast-varying PHN and RFO is significantly suppressed. We also derive the carrier-to-interference power ratio (CIR) of the proposed scheme by using the symmetric conjugate property of the ICI weighting function and then compare it with those of conventional schemes. Through simulation results, we show that the proposed ISC scheme has a higher CIR and better bit error rate performance than the conventional schemes.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1999년도 유체기계 연구개발 발표회 논문집
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• pp.221-226
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• 1999

Three-dimensional flow analysis and numerical optimization methods are presented for the design of an axial-flow fan. Steady, Incompressible, three-dimensional Reynolds-averaged Wavier-Stokes equations are used as governing equations, and standard k-$\epsilon$ turbulence model is chosen as a turbulence model. Governing equations are discretized using finite volume method. Steepest descent method, conjugate gradient method and BFGS method are compared to determine the searching directions. Golden section method and quadratic fit-sectioning method are tested for one dimensional search. Objective function is defined as a ratio of generation rate of the turbulent kinetic energy to pressure head. Sweep angle distributions are used as design variables.

• Communications for Statistical Applications and Methods
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• 제29권4호
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• pp.471-486
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• 2022

Autoregressive moving average (ARMA) models involve nonlinearity in the model coefficients because of unobserved lagged errors, which complicates the likelihood function and makes the posterior density analytically intractable. In order to overcome this problem of posterior analysis, some approximation methods have been proposed in literature. In this paper we first review the main analytic approximations proposed to approximate the posterior density of ARMA models to be analytically tractable, which include Newbold, Zellner-Reynolds, and Broemeling-Shaarawy approximations. We then use the Kullback-Leibler divergence to study the relation between these three analytic approximations and to measure the distance between their derived approximate posteriors for ARMA models. In addition, we evaluate the impact of the approximate posteriors distance in Bayesian estimates of mean and precision of the model coefficients by generating a large number of Monte Carlo simulations from the approximate posteriors. Simulation study results show that the approximate posteriors of Newbold and Zellner-Reynolds are very close to each other, and their estimates have higher precision compared to those of Broemeling-Shaarawy approximation. Same results are obtained from the application to real-world time series datasets.

• 한국정보처리학회논문지
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• 제1권1호
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• pp.14-22
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• 1994

본 논문은 스미스의 베이지안 소프트웨어 신뢰도 성장모형을 기반으로 테스팅 단계에서의 소프트웨어 신뢰도에 대한 두가지 베이즈 추정량에 그에 대한 평가 알고 리즘을 제안하는데 목적이 있다. 그 방법으로 사전정보 클래스로서 일양사전분포보다 더 일반적인 베타사전분포 BE(a.b)를 사용하였다. 그 연구 과정으로 베이지안 추정절 차에 있어서 제곱오차결손함수와 해리스결손함수를 고려하고, 컴퓨터 시뮬레이션을 통 해서 소프트웨어 신뢰도에 대한 베이즈추정량들과 그에 따른 알고리즘을 이용하여 평 균자승오차 성능을 비교한다. 연구 결과로써 a가 크면 클수록 그리고 b가 적으면 적을 수록 해리스결손함수하의 소프트웨어 신뢰도의 베이즈추정량이 평균자승오차 성능의 관점에서는 더욱 유효하고, a 가 b보다 더 클 때 공액사전분포인 베타사전분포상의 소 프트웨어 신뢰도의 베이즈추정량이 비정보사전분포인 일양사전분포상에서 소프트웨어 신뢰도의 베이즈추정량보다는 성능이 더 좋다는 결론을 얻는다.

• 터널과지하공간
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• 제17권2호
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• pp.119-127
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• 2007

임계면법을 적용하여 횡등방성 암석의 강도이방성을 해석하는 방법을 제안하였다. 암석의 파괴는 Hoek-Brown 파괴기준을 따르는 것으로 가정하였다. Hoek-Brown의 경험적 파괴기준식에 대응되는 Mohr 포착선식을 이용하고 강도상수인 m과 s를 방향에 따른 스칼라 함수로 정의하여 이방성 파괴함수를 구성하였다. 이방성 파괴함수를 최대고 하는 임계면의 방향을 찾기 위하여 직접 최적화기법의 하나인 공액구배법을 적용하였다. 횡등방성 안석에 대한 기존 이방성 강도모델이 대부분 삼축압축실험과 동일한 응력조건에서만 적용할 수 있는데 반하여 이 연구에서 제안된 방법은 일반적인 3차원 응력조건에도 쉽게 적용할 수 있다는 장점을 가지고 있다. 삼축압축실험의 모사를 통하여 얻어진 삼축압축강도와 파괴면의 경사에 분석을 통하여 제안된 방법의 적합성을 검토하였다.

• Journal of Mechanical Science and Technology
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• 제20권9호
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• pp.1390-1398
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• 2006

A gerotor pump is suitable for oil hydraulics of machine tools, automotive engines, compressors, constructions and other various applications. In particular the pump is an essential machine element that feeds lubricant oil in an automotive engine. The subject of this paper is the theoretical analysis of internal lobe pump whose the main components are the two rotors. Usually the outer one is characterized by lobes with a circular shape, while the inner rotor profile is determined as a conjugate to the other. For this reason the first topic presented here is the definition of the geometry of the rotors starting from the design parameters. The choice of these parameters is subject to some limitations in order to limit the pressure angle between the rotors. Now we will consider the design optimization. The first step is the determination of the instantaneous flow rate as a function of the design parameter. This allows us to calculate three performance indexes commonly used for the study of positive displacement pumps the flow rate irregularity, the specific flow rate, and the specific slipping. These indexes are used to optimize the design of the pump and to obtain the sets of optimum design parameter Results obtained from the analysis enable the designer and manufacturer of the oil pump to be more efficient in this field.

• 한국연소학회지
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• 제10권3호
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• pp.25-33
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• 2005

Fast-time instability is investigated for diffusion flames with Lewis numbers greater than unity by employing the numerical technique called the Evans function method. Since the time and length scales are those of the inner reactive-diffusive layer, the problem is equivalent to the instability problem for the $Li\tilde{n}\acute{a}n#s$ diffusion flame regime. The instability is primarily oscillatory, as seen from complex solution branches and can emerge prior to reaching the upper turning point of the S-curve, known as the $Li\tilde{n}\acute{a}n#s$ extinction condition. Depending on the Lewis number, the instability characteristics is found to be somewhat different. Below the critical Lewis number, $L_C$, the instability possesses primarily a pulsating nature in that the two real solution branches, existing for small wave numbers, merges at a finite wave number, at which a pair of complex conjugate solution branches bifurcate. For Lewis numbers greater than $L_C$, the solution branch for small reactant leakage is found to be purely complex with the maximum growth rate found at a finite wave number, thereby exhibiting a traveling nature. As the reactant leakage parameter is further increased, the instability characteristics turns into a pulsating type, similar to that for L < $L_C$.

• 한국가축번식학회지
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• 제20권2호
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• pp.215-221
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• 1996

This study was carried out to develop an immunoassay for the diagnosis of the pregnancy and ovarian function of domestic animals. Using 2E92C10 monoclonal antibody(McAb) generated against estrone-3-glucuronide(E1-3-G) and appeared a high cross-reactivity with estrone-3-sulfate(E1-3-S), chemiluminesence immunoassay (CIA) to detect E1-3-S was developed. 2E92C10 McAb cross-reacted with E1-3-S (30%) was purified from ascites fluid using protein G sepharose gel column. The purity of purified antibody fraction was monitored by SDS-PAGE and was better compared to that of crude ascite fluid. The soild and liquid phase CIA for E1-3-S were established utilizing 2E92C10 antibody and E1-3-G-ABEI conjugate used as a tracer. As the results, the titer of 2E92C10 antibody was 5g/ml in soild phase and 1:2000 in liquid phase. The sensitivity on soild and solid phase CIA were about 200 pg/ml. These results indicate that CIA for measurement of E1-3-S was successfully developed by using ant-E1-3-G McAb cross-reacted with E1-3-S and could be usefully used to research this area.

• Smart Structures and Systems
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• 제17권5호
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• pp.753-771
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• 2016

This paper addresses the free and transient responses of a SDOF linear complex stiffness system by making use of the Hilbert transform and the convolution integral. Because the second-order differential equation of motion having the complex stiffness give rise to the conjugate complex eigen values, its time-domain analysis using the standard time integration scheme suffers from the numerical instability and divergence. In order to overcome this problem, the transient response of the linear complex stiffness system is obtained by the convolution integral of a green function which corresponds to the unit-impulse free vibration response of the complex system. The damped free vibration of the complex system is theoretically derived by making use of the state-space formulation and the Hilbert transform. The convolution integral is implemented by piecewise-linearly interpolating the external force and by superimposing the transient responses of discretized piecewise impulse forces. The numerical experiments are carried out to verify the proposed time-domain analysis method, and the correlation between the real and imaginary parts in the free and transient responses is also investigated.

• 한국정밀공학회지
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• 제23권4호
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• pp.124-131
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• 2006

A gerotor pump is suitable for oil hydraulics of machine tools, automotive engines, compressors, constructions and other various applications. Especially the pump is an essential machine element of an automotive engine to feed lubricant oil. The subject of this paper is the theoretical analysis of internal lobe pump whose the main components are the rotors: usually the outer one is characterized by lobes with circular shape, while the inner rotor profile is determined as conjugate to the other. For this reason the first topic presented here is the definition of the geometry of the rotors starting from the design parameters. The choice of these parameters is subject to some limitations in odor to limit the pressure angle between the rotors. Now we will consider the design optimization. The first step is the determination of the instantaneous flow rate as a function of the design parameter. This allows us to calculate three performance indexes commonly used far the study of positive displacement pumps: the flow rate irregularity, the specific flow rate, and the specific slipping. These indexes are used to optimize the design of the pump and to obtain the sets of optimum design parameter. Results obtained from the analysis enable the designer and manufacturer of oil pump to be more efficient in this field, and the system could serve as a valuable one for experts and as a dependable training aid for beginners.