• 한국수자원학회논문집
• /
• 제42권4호
• /
• pp.331-341
• /
• 2009

본 연구에서는 generalized logistic(GL) 분포의 최우도 추정량(maximum likelihood estimate)에 대한 불확실성 추정을 위하여 사용되는 관측정보행렬(observed information matrix)과 Fisher 정보행렬(Fisher information matrix)의 정확도를 비교해 보고자 하였다. 타 분포형에 대한 기존의 연구결과에서 표본의 크기가 클 경우 매개변수 추정시 관측정보행렬이 동시에 추정되어 계산시간도 단축되고 Fisher 정보행렬의 정확도와도 차이도 거의 없어 관측정보행렬의 사용이 추천된 바 있으나, 최근 사용이 증가되고 있는 GL 분포에 대한 연구결과는 아직 전무한 실정이며 기존 연구문헌의 결과를 토대로 구체적인 연구 없이 관측정보행렬을 사용하고 있는 상황이다. 따라서 본 연구에서는 이를 위해 모의실험을 수행하였으며, 모의 결과 최우도법에 의한 매개변수의 분산 및 공분산은 기존의 연구 결과와 비슷한 결과를 보이나, quantile에 대한 불확실성 추정에는 관측정보행렬보다 Fisher 정보행렬의 사용이 더 적절할 것으로 판단되었다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제14권7호
• /
• pp.3057-3075
• /
• 2020

End-to-end network delay plays an vital role in distributed services. This delay is used to measure QoS (Quality-of-Service). It would be beneficial to know all node-pair delay information, but unfortunately it is not feasible in practice because the use of active probing will cause a quadratic growth in overhead. Alternatively, using the measured network delay to estimate the unknown network delay is an economical method. In this paper, we adopt the state-of-the-art matrix completion technology to better estimate the network delay from limited measurements. Although the number of measurements required for an exact matrix completion is theoretically bounded, it is practically less helpful. Therefore, we propose an online adaptive sampling algorithm to measure network delay in which statistical leverage scores are used to select potential matrix elements. The basic principle behind is to sample the elements with larger leverage scores to keep the traits of important rows or columns in the matrix. The amount of samples is adaptively decided by a proposed stopping condition. Simulation results based on real delay matrix show that compared with the traditional sampling algorithm, our proposed sampling algorithm can provide better performance (smaller estimation error and less convergence pressure) at a lower cost (fewer samples and shorter processing time).

• Bulletin of the Korean Chemical Society
• /
• 제32권6호
• /
• pp.2093-2096
• /
• 2011

• Transactions on Electrical and Electronic Materials
• /
• 제6권6호
• /
• pp.284-288
• /
• 2005

We have systematically studied the superconducting properties and flux pinning enhancement of $(Y_{0.33}Sm_{0.33}Nd_{0.33})\;Ba_2Cu_3O_y$ [(YSN)-123] composite oxides by melt growth process in air. A sample prepared by this method showed well-textured microstructure, and $(Y_{0.33}Sm_{0.33}Nd_{0.33})\;BaCuO_5$ [(YSN)211] nonsuperconducting particles were uniformly dispersed in large (YSN) 123 superconducting matrix. The sample showed a sharp superconducting transition at 91 K. The magnetization measurements of the (YSN)-123 sample exhibited the enhanced flux pinning, compared with $YBa_2Cu_3O_y$ (Y-123) sample without Sm and Nd. Critical current densities of (YSN)-123 sample was $2.5{\times}10^4 A/cm^2$ at 2 T and 77 K.

• Coupled systems mechanics
• /
• 제11권2호
• /
• pp.133-149
• /
• 2022

The accurate prediction of elastoplasticity under prescribed workloads is essential in the optimization of engineering structures. Mechanical experiments are carried out with the goal of obtaining reliable sets of material parameters for a chosen constitutive law via inverse identification. In this work, two sample geometries made of high strength steel plates were evaluated to determine the optimal configuration for the identification of Ludwik's nonlinear isotropic hardening law. Finite element model updating(FEMU) was used to calibrate the material parameters. FEMU computes the parameter changes based on the Hessian matrix, and the sensitivity fields that report changes of computed fields with respect to material parameter changes. A sensitivity analysis was performed to determine the influence of the sample geometry on parameter identifiability. It was concluded that the sample with thinned gauge region with a large curvature radius provided more reliable material parameters.

• 한국자동차공학회논문집
• /
• 제4권2호
• /
• pp.173-182
• /
• 1996

An analytical model has been developed to predict the elastic properties of a filled resin reinforced by chopped fibers, a three-phase composite such as a filled sheet molding compound(SMC). In the model the matrix material and fillers form an effective matrix. The effective matrix is then considered to be reinforced with long fibers lying in the sheet plane but randomly oriented in the plane. Expressions for the resulting transversely isotropic composite properties are explicitly presented. Using this model, the Young's and shear moduli are calculated for the SMC sample with filler weight fraction of 35% and fiber content of 30%. The same properties are also determined experimentally. The agreement between the calculated and measured elastic moduli is found to be very good for the in-plane properties. However, the out-of-plane properties show a large difference because the effect of voids is not taken into account in the model.

• 대한의용생체공학회:의공학회지
• /
• 제27권6호
• /
• pp.310-317
• /
• 2006

Extensive research with polarimetry and Mueller matrix has been done for chemical measurements and possible cancer detection. However, the effect of thermally denatured biological tissue on polarization changes is not well known. The purpose of this study is to characterize polarization changes in collagen due to thermal denaturation. The variations in polarized state caused by thermal damage were investigated by obtaining the Mueller matrix elements of collagen sample at multiple thermal damage levels. The changes in birefringence of denatured collagen were also investigated. This information could be used to determine the extent of thermal damage level of clinically heat treated tissues.

• Journal of Photoscience
• /
• 제8권2호
• /
• pp.83-86
• /
• 2001

Structural analyses of oligosaccharide-malononitrile derivatives were conducted by matrix-assisted laser desorption/ionization post-source decay (MALDI-PSD) analysis in positive ion mode. The malononitrile derivatives of oligosaccharides, which were developed for highly sensitive detection of multi-component oligosaccharides by negative ion electrospray ionization mass spectrometry (ESI MS), were detected by positive-ion MALDI with the detection limit of 2 pmol level from the crude derivatization sample. The used matrix affected drastically the analytical results of oligosaccharide-malononitrile derivative by matrix-assisted laser desoprtion/ionization mass spectrometry (MALDI MS). The malononitrile derivatization of oligosaccharide also affect the patterns of MALDI-PSD spectra and give much more structural information than the free oligosaccharide.

• 산업경영시스템학회지
• /
• 제35권3호
• /
• pp.155-162
• /
• 2012

This study proposes an integrated approach that uses both a fuzzy service FMEA (failure mode and effect analysis) and HOQ (house of quality) matrix algebra in designing and improving a service system. The fuzzy service FMEA methodology applies the customer satisfaction to the fuzzy RPN model. We fuzzify only the service satisfaction that consist in two failure factors, intangible service and tangible service, to more effectively assess the customer satisfactions on service encounters. Proposed fuzzy service satisfactions with triangle membership function are defuzzified by using the Fuzzy Inference System, and these are eventually identified the ranks on the potential fail points. HOQ matrices are constructed from cause-effect relationships. It is possible for these relationship matrix to find a linear approximation solution on the engineering attributes. Thus, in order to demonstrate how the proposed methods work, practical sample of the A/S part in S Electronic Co. provides for the ranking of the engineering attributes which has been successfully implemented.

• 반도체디스플레이기술학회지
• /
• 제3권1호
• /
• pp.31-34
• /
• 2004

We develop Mueller-matrix spectroscopic ellipsometry based on dual compensator configuration. This technique is very powerful for measuring surface anisotropy in nano-scale, especially when materials show depolarization. Dual-rotating compensator configuration is adopted with the rotational ratio of 5:3 originally developed by Collins et al[1]. The instrument can provide 250-point spectra over the wavelength range from 230 nm to 820 nm in one irradiance waveform with minimum acquisition time of Tc=10 s. In this work, the results obtained in transmission modes are presented for the initial attempt. We present calibration procedures to diagnose the system from the utilized data collected in transmission mode without sample. We expect that the instrument will have important applications in thin films and surfaces that have anisotropy and inhomogeneity.