• Structural Engineering and Mechanics
• /
• 제29권4호
• /
• pp.411-422
• /
• 2008

In the present study, free vibration analysis of thick annular plates is analyzed by discrete singular convolution method. The Mindlin plate theory is employed. The material is isotropic, homogeneous and obeys Hook's law. In this paper, discrete singular convolution method is used for discretization of equations of motion. Axisymmetric frequency values are presented illustrating the effect of radius ratio and thickness to radius ratio of the annular plate. The influence of boundary conditions on the frequency characteristics is also discussed. Comparing results with those in the literature validates the present analysis. It is shown that the obtained results are very accurate by this approach.

• 한국통신학회논문지
• /
• 제39A권1호
• /
• pp.12-18
• /
• 2014

In this paper, a new peak-to-average power ratio (PAPR) reduction method for spatial modulation(SM) is presented. By using the matrix with all non-zero elements to precode the signals before transmitting, the transmit power is scattered over all transmit antennas for achieving the goal of PAPR reduction. If this matrix is also an unitary matrix, the distribution of transmit power over transmit antennas will be uniform and it also could retain the characteristic of avoiding inter channel interference (ICI) due to the orthogonality of unitary matrix. In case of a non-ideal amplifier, the proposed method can produce a considerable improvement that increases with a number of transmit antennas in performance. Furthermore, the new scheme achieves an identical performance with conventional one in the case of ideal amplifier.

• 한국자동차공학회논문집
• /
• 제7권8호
• /
• pp.43-54
• /
• 1999

The effects of equivalence ratio and pressure on burnt gas temperature in premixed fuel rich propane-oxygen-inert gas combustion are investigated over the wide ranges of equivalence ration from 1.5 to 2.7 and pressure from 0.1 to 7 MPa by using a specially designed disk -type constant-voume combustion chamber, The premixtures are simultaneously ignited by eight spark plugs located on the circumference of combustion chamber with 45 degree interals. The eight converging flames compress the end gases to high pressures. The burnt gas temperature is meausured by the nmodifie dtow-colr pyrometry method. The transmissivity in the chamber center during the final stage of combustion at the hightest pressure is meausred by in situ laser extinction method. It is found that a temperature difference between the burnt gas temperature measured by mofidied and conventrational two-color method is 10 to 20 K, but the accuracy of the modified two-color methdo is higher if the local transmissivity in observed region is uniform , and the combustion at higher pressures results gas density conditions and the burnt gas temperature increases as the volume fraction of argon is increased because the specific heat of argon is lower compared to that of nitrogen with a constant equivalence ratio.

• 설비공학논문집
• /
• 제22권8호
• /
• pp.523-529
• /
• 2010

We investigate two-dimensional laminar flow around rectangular cylinders placed in a uniform stream. Numerical simulations are performed, using finite volume method, in the ranges of $50{\leq}Re{\leq}150$ and $0.1{\leq}W/H{\leq}1.0$, where Re and W/H are the Reynolds number and the width-to-height ratio, respectively. The immersed boundary method is used to handle the rectangular cylinder in a rectangular grid system. Comparisons with the previous results show good agreement in Strouhal number, drag and lift coefficient. The present study reports the detailed information of flow structure at different width-to-height ratios in the ranges of $50{\leq}Re{\leq}150$.

• Steel and Composite Structures
• /
• 제12권2호
• /
• pp.129-147
• /
• 2012

In this paper, the thermal buckling analysis of rectangular composite laminated plates is investigated using the Differential Quadrature (DQ) method. The composite plate is subjected to a uniform temperature distribution and arbitrary boundary conditions. The analysis takes place in two stages. First, pre-buckling forces due to a temperature rise are determined by using a membrane solution. In the second stage, the critical temperature is predicted based on the first-order shear deformation theory. To verify the accuracy of the method, several case studies were used and the numerical results were compared with those of other published literatures. Moreover, the effects of several parameters such as aspect ratio, fiber orientation, modulus ratio, and various boundary conditions on the critical temperature were examined. The results confirm the efficiency and accuracy of the DQ method in dealing with this class of engineering problems.

• 말소리와 음성과학
• /
• 제2권2호
• /
• pp.63-68
• /
• 2010

A new version of sequential probability ratio test (SPRT) which has been investigated in utterance-length control is proposed to obtain uniform response results in speaker verification (SV). Although SPRTs can obtain fast responses in SV tests, differences in the performance may occur depending on the compositions of consonants and vowels in the sentences used. In this paper, a fast sequential probability ratio test (FSPRT) method that shows consistent performances at all times regardless of the compositions of vocalized sentences for SV will be proposed. In generating frames, the FSPRT will first conduct SV test processes with only generated frames without any overlapping and if the results do not satisfy discrimination criteria, the FSPRT will sequentially use frames applied with overlapping. With the progress of processes as such, the test will not be affected by the compositions of sentences for SV and thus fast response outcomes and even consistent performances can be obtained. Experimental results show that the FSPRT has better performance to the SPRT method while requiring less complexity with equal error rates (EER).

• Wind and Structures
• /
• 제24권4호
• /
• pp.307-331
• /
• 2017

Free transverse vibration of shear deformable super-elliptical plates with uniform thickness was studied based on Mindlin plate theory using finite element method. Quadrilateral isoparametric elements were used in the paper. Sensitivity analysis was made to determine the influence of the thickness, the aspect ratio, and the shape of the plate on the natural frequency. Accuracy of the results computed in the current study was validated by comparing them with the solutions available in the literature. The results reveal that the frequencies of clamped super-elliptical plates lie in the range bounded by elliptical and rectangular plates irrespective of the aspect ratio, and furthermore, the frequency decreases if the super-elliptical power increases. A similar trend was observed for simply supported plates with high aspect ratio. The free vibration response for the first and the second symmetric-antisymmetric (SA) modes were found to be different for high aspect ratio. The results reveal that using insufficient number of degrees of freedom results in finding a totally different relation between the super-elliptical power and the frequency.

• Journal of the Korean Data and Information Science Society
• /
• 제12권2호
• /
• pp.125-143
• /
• 2001

We, in this paper, propose a kernel estimator of hazard ratio with censored survival data. The uniform consistency and asymptotic normality of the proposed estimator are proved by using counting process approach. In order to assess the performance of the proposed estimator, we compare the kernel estimator with Cox estimator and the generalized rank estimators of hazard ratio in terms of MSE by Monte Carlo simulation. Two examples are illustrated for our results.

• KIEAE Journal
• /
• 제2권3호
• /
• pp.33-38
• /
• 2002

The intermediate range of temperatures($100{\sim}300^{\circ}C$) which can be achieved with CPCs(Compound Parabolic Concentrators) without tracking device provides both economic and thermal advantages for solar collector design. The present paper summarizes critical design considerations for CPC with cylindrical absorber and its optical performance using ray tracing program. Concentration ratios vary as acceptance half angle, ratio of reflector height to aperture width and ratio of reflector area to aperture area. This effects showed that the concentration ratio was increased as acceptance angle but optimum ratio of reflector height to aperture width existed at critical value. As a result of ray tracing, solar ray losses was maximized at acceptance half angle and this problem was solved by increasing absorber tube diameter. The concentrating flux distribution on the absorber surface was uniform but peak flux existed.

• 한국정보전자통신기술학회논문지
• /
• 제12권4호
• /
• pp.380-386
• /
• 2019

본 논문은 이송방식에 따른 혼합비율을 비교하기 위하여 동일 점도를 가지는 원재료를 사용하여 100 사이클 동안 주재료와 부재료의 투입량 오차를 측정하고 분석하였다. 측정 결과 피스톤 펌프 방식에서는 주재료와 부재료의 투입량 오차는 0g에서 3g까지 변화의 폭이 컸으며, 최대 오차비율은 10.3%로 큰 편차를 보였다. 듀얼-스크류 회전방식에서는 0.01g에서 0.4g으로 최대 오차 비율이 0.41%로 투입량 오차가 거의 발생하지 않았으며, 공정 사이클이 증가함에도 거의 균등하게 투입됨을 알 수 있었다. 듀얼-스크류 회전방식 이액형 혼합시스템을 이용하여 원재료의 점도가 다른 3종류의 액상 실리콘을 사용하여 100 사이클 동안의 주재료와 부재료의 투입량을 측정하고 분석하였다. 그 결과 적용한 원재료의 점도에 관계없이 평균 오차가 0.75g, 오차 비율은 1% 미만으로 측정되었으며, 동일 점도를 갖는 원재료를 사용했을 때 피스톤 펌프 방식의 평균 오차 비율은 4.09 %로 측정되었다. 이 결과는 듀얼-스크류 회전방식을 적용한 실험에서 일정한 혼합비율로 주재료와 부재료가 투입됨을 알 수 있었다.