• 한국자동차공학회논문집
• /
• 제13권3호
• /
• pp.24-34
• /
• 2005

The automobile seat must satisfy various safety regulations for the passenger's safety. In many design practices, each component is independently designed by concentrating on a single related regulation. However, since multiple regulations can be involved in a seat component, there may be design confliction among the various safety regulations. Therefore, a new design methodology is required to effectively design an automobile seat. The axiomatic approach is employed for considering multiple regulations. The Independence Axiom is used to define the overall flow of the seat design. Functional requirements (FRs) are defined by safety regulations and components of the seat are classified into groups which yield design Parameters (DPs). The classification is carried out to have independence in the FR-DP relationship. Components in a DP group are determined by using orthogonal away of the design of experiments (DOE). Numerical analyses are utilized to evaluate the safety levels by using a commercial software system for nonlinear transient finite element analysis.

• Journal of the Korean Data and Information Science Society
• /
• 제26권1호
• /
• pp.31-39
• /
• 2015

본 논문은 확률효과모형에서 사영에 근거한 분산성분을 구하는 방법을 다루고 있다. 분산성분을 추정하기 위한 ANOVA방법에서 제곱합의 계산에 사영을 이용하는 방법을 제시하고 있다. 분산성분을 구하기 위한 사영의 이용은 모형행렬에 의한 사영공간을 분산성분별 제곱합을 얻기 위한 상호직교하는 부분공간들로 분할하게 된다. 부분공간들로 분할하기 위해 모형행렬 X로의 사영에 단계별 방법(stepwise procedure)을 적용하여 해당하는 공간으로의 사영행렬을 구하는 방법을 다루고 있다. 단계별 방법에 의해 주어지는 부분공간들의 직교성으로 인해 사영행렬의 곱은 영행렬로 주어지는 성질을 갖는다. 단계별 방법에 의한 순차적 사영은 해당하는 공간으로의 사영행렬에 대한 확인과 사영행렬의 구조를 파악할 수 있는 이점이 있다. 또한 분산성분의 추정을 위한 제1종 제곱합을 구하기 위한 방법으로 유용하다.

• 대한기계학회논문집B
• /
• 제25권11호
• /
• pp.1500-1508
• /
• 2001

This paper represents the importance of dependent variables in non-orthogonal curvilinear coordinates just as the importance of those variables of convective scheme and turbulence model in computational fluid dynamics. Each of Cartesian, physical covariant and physical contravariant velocity components was tested as the dependent variables of momentum equations in the staggered grid system. In the flow past a circular cylinder, the results were computed to use each of three variables and compared to experimental data. In the skewed driven cavity flow, the results were computed to check the grid dependency of the variables. The results used in Cartesian and physical contravariant components of velocity in cylinder flow show the nearly same accuracy. In the case of Cartesian and contravariant component, the same number of vortex was predicted in the skewed driven cavity flow. Vortex strength of Cartesian component case has about 30% lower value than that of the other two cases.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제11권2호
• /
• pp.939-951
• /
• 2019

A novel empirical mode decomposition strategy based on Fourier transform and band-pass filter techniques, contributing to efficient instantaneous vibration analyses, is developed in this study. Two key improvements are proposed. The first is associated with the adoption of a band-pass filter technique for intrinsic mode function sifting. The primary characteristic of decomposed components is that their bandwidths do not overlap in the frequency domain. The second improvement concerns an attempt to design narrowband constraints as the essential requirements for intrinsic mode function to make it physically meaningful. Because all decomposed components are generated with respect to their intrinsic narrow bandwidth and strict sifting from high to low frequencies successively, they are orthogonal to each other and are thus suitable for an instantaneous frequency analysis. The direct Hilbert spectrum is employed to illustrate the instantaneous time-frequency-energy distribution. Commendable agreement between the illustrations of the proposed direct Hilbert spectrum and the traditional Fourier spectrum was observed. This method provides robust identifications of vibration modes embedded in vibration processes, deemed to be an efficient means to obtain valuable instantaneous information.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2008년도 춘계학술대회 논문집
• /
• pp.109-117
• /
• 2008

In this study, a method predicting the displacement responseof structures from the measured dynamic strain signal is proposed by using a mode decomposition technique. Dynamic loadings including wind and seismic loadings could be exerted to the bridge. In order to examine the bridge stability against these dynamic loadings, the prediction of displacement response is very important to evaluate bridge stability. Because it may be not easy for the displacement response to be acquired directly on site, an indirect method to predict the displacement response is needed. Thus, as an alternative for predicting the displacement response indirectly, the conversion of the measured strain signal into the displacement response is suggested, while the measured strain signal can be obtained using fiber optic Bragg-grating (FBG) sensors. To overcome such a problem, a mode decomposition technique was used in this study. The measured strain signal is decomposed into each modal component by using the empirical mode decomposition(EMD) as one of mode decomposition techniques. Then, the decomposed strain signals on each modal component are transformed into the modal displacement components. And the corresponding mode shapes can be also estimated by using the proper orthogonal decomposition(POD) from the measured strain signal. Thus, total displacement response could be predicted from combining the modal displacement components.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2004년도 추계학술대회논문집
• /
• pp.695-698
• /
• 2004

STSAT RWA (Reaction Wheel Assembly) micro-vibration is measured using KISTLER dynamic plate that can provide the time signals of three orthogonal forces and torques simultaneously up to 400Hz. In the post-processing, measured data are evaluated with respect to the wheel spin rate in both time and frequency domains, and the static/dynamic unbalances are evaluated from the extracted first harmonic component. Also the friction torque profile at each wheel speed is estimated from the measured data. Several higher order harmonic components are observed, that comes from its rotor shape as well as the wheel bearing characteristics. One of the most peculiar characteristics of this wheel is that the dynamic properties of two radial unbalance components are much different from each other as the RWA mounting configuration on a spacecraft is different from conventional RWA mounting configuration. Rocking mode is not appeared below 400Hz for all operating speed because the wheel size is very small. The post-processed results will be used for jitter analysis of STSAT due to RWA micro-vibration.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제13권5호
• /
• pp.2434-2453
• /
• 2019

To improve the separation performance of time-frequency overlapped radar and communication signals from a single channel, this paper proposes an effective separation method based on an improved empirical wavelet transform (EWT) that introduces a fast boundary detection mechanism. The fast boundary detection mechanism can be regarded as a process of searching, difference optimization, and continuity detection of the important local minima in the Fourier spectrum that enables determination of the sub-band boundary and thus allows multiple signal components to be distinguished. An orthogonal empirical wavelet filter bank that was designed for signal adaptive reconstruction is then used to separate the input time-frequency overlapped signals. The experimental results show that if two source components are completely overlapped within the time domain and the spectrum overlap ratio is less than 60%, the average separation performance is improved by approximately 32.3% when compared with the classic EWT; the proposed method also improves the suitability for multiple frequency shift keying (MFSK) and reduces the algorithm complexity.

• 한국작물학회지
• /
• 제63권4호
• /
• pp.360-377
• /
• 2018

The levels of 12 isoflavones were measured in soybean (Glycine max (L.) Merrill) sprouts of 68 genetic varieties from three countries (China, Japan, and Korea). The isoflavone profile differences were analyzed using data mining methods. A principal component analysis (PCA) revealed that the CSRV021 variety was separated from the others by the first two principal components. This variety appears to be most suited for functional food production due to its high isoflavone levels. Partial least squares discriminant analysis (PLS-DA) and orthogonal projections to latent structures discriminant analysis (OPLS-DA) showed that there are meaningful isoflavone compositional differences in samples that have different countries of origin. Hierarchical clustering analysis (HCA) of these phytochemicals resulted in clusters derived from closely related biochemical pathways. These results indicate the usefulness of metabolite profiling combined with chemometrics as a tool for assessing the quality of foods and identifying metabolic links in biological systems.

• Journal of the Optical Society of Korea
• /
• 제7권4호
• /
• pp.211-215
• /
• 2003

Statistical characteristics of the backscattered light from turbid tissues obtained by polarizationsensitive optical coherence tomography are investigated. The amplitude of the backscattered light is found to faithfully follow the Rayleigh distribution predicted by the scattering theory of electromagnetic waves in random media. The probability density function of the phase difference between the two orthogonal polarization components of the backscattered light is explicitly derived and then verified in comparison with the experimental data measured from in-vitro tissues of porcine ligament.

• ETRI Journal
• /
• 제26권6호
• /
• pp.622-634
• /
• 2004

In this paper, we discuss the design problem and the robustness of space-frequency trellis codes (SFTCs) for multiple input multiple output, orthogonal frequency division multiplexing (MIMO-OFDM) systems. We find that the channel constructed by the consecutive subcarriers of an OFDM block is a correlated fading channel with the regular correlation function of the number and time delay of the multipaths. By introducing the first-order auto-regressive model, we decompose the correlated fading channel into two independent components: a slow fading channel and a fast fading channel. Therefore, the design problem of SFTCs is converted into the joint design in both slow fading and fast fading channels. We present an improved design criterion for SFTCs. We also show that the SFTCs designed according to our criterion are robust against the multipath time delays. Simulation results are provided to confirm our theoretic analysis.