• The Journal of Asian Finance, Economics and Business
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• 제5권1호
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• pp.11-16
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• 2018

This research examines the alternative ways of estimating the coefficient of non-diversifiable risk, namely beta coefficient, in Capital Asset Pricing Model (CAPM) introduced by Sharpe (1964) that is an essential element of assessing the value of diverse assets. The non-parametric methods used in this research are the robust Least Trimmed Square (LTS) and Maximum likelihood type of M-estimator (MM-estimator). The Jackknife, the resampling technique, is also employed to validate the results. According to finance literature and common practices, these coecients have often been estimated using Ordinary Least Square (LS) regression method and monthly return data set. The empirical results of this research pointed out that the robust Least Trimmed Square (LTS) and Maximum likelihood type of M-estimator (MM-estimator) performed much better than Ordinary Least Square (LS) in terms of eciency for large-cap stocks trading actively in the United States markets. Interestingly, the empirical results also showed that daily return data would give more accurate estimation than monthly return data in both Ordinary Least Square (LS) and robust Least Trimmed Square (LTS) and Maximum likelihood type of M-estimator (MM-estimator) regressions.

• 한국경영과학회지
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• 제41권3호
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• pp.23-36
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• 2016

We consider a model that minimizes the total cost incurred by assigning available weapons to existing targets in order to reduce enemy threats, which is called the weapon target assignment problem (WTAP). This study addresses the stochastic versions of WTAP, in which data, such as the probability of destroying a target, are given randomly (i.e., data are identified with certain probability distributions). For each type of random data or parameter, we provide a stochastic optimization model on the basis of the expected value or scenario enumeration. In particular, when the probabilities of destroying targets depending on weapons are stochastic, we present a stochastic programming formulation with a simple recourse. We show that the stochastic model can be transformed into a deterministic equivalent mixed integer programming model under a certain discrete probability distribution of randomness. We solve the stochastic model to obtain an optimal solution via the mixed integer programming model and compare this solution with that of the deterministic model.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권3호
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• pp.891-910
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• 2021

Previous QoS-aware service composition methods mainly focus on how to generate composite service with the optimal QoS efficiently for a single request. However, in the real application scenarios, there are multiple service requests and multiple service providers. It is more important to compose services with suboptimal QoS and maintain the load balance between services. To solve this problem, in this paper, we propose a service composition method, named as dynamically change and balancing composition method (DCBC). It assumes that the QoS of service is not static, and the services can adjust the value of QoS to gain more opportunities to be selected for composition. The method mainly includes two steps, which are the preprocessing step and the service selection step. In the preprocessing step, a backward global best QoS calculation is performed which regarding the static and dynamic QoS respectively; then guided by the global QoS, the feasible services can be selected efficiently in the service selection step. The experiments show that the DCBC method can not only improve the overall quality of composite services but also guarantee the fulfill ratio of requests and the load balance of services.

• Journal of the Korean Statistical Society
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• 제32권3호
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• pp.299-309
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• 2003

Let ${\pi}_1,...,{\pi}_{k}$k($\geq$2) independent logistic populations such that the cumulative distribution function (cdf) of an observation from the population ${\pi}_{i}$ is $$F_{i}\;=\; {\frac{1}{1+exp{-\pi(x-{\mu}_{i})/(\sigma\sqrt{3})}}},\;$\mid$x$\mid$<\;{\infty}$$ where ${\mu}_{i}(-{\infty}\; < \; {\mu}_{i}\; <\; {\infty}$ is unknown location mean and ${\delta}^2$ is known variance, i ＝ 1,..., $textsc{k}$. Let ${\mu}_{[k]}$ be the largest of all ${\mu}$'s and the population ${\pi}_{i}$ is defined to be 'good' if ${\mu}_{i}\;{\geq}\;{\mu}_{[k]}\;-\;{\delta}_1$, where ${\delta}_1\;>\;0$, i = 1,...,$textsc{k}$. A selection procedure based on sample median is proposed to select a subset of $textsc{k}$ logistic populations which includes all the good populations with probability at least $P^{*}$(a preassigned value). Simultaneous confidence intervals for the differences of location parameters, which can be derived with the help of proposed procedures, are discussed. If a population with location parameter ${\mu}_{i}\;<\;{\mu}_{[k]}\;-\;{\delta}_2({\delta}_2\;>{\delta}_1)$, i ＝ 1,...,$textsc{k}$ is considered 'bad', a selection procedure is proposed so that the probability of either selecting a bad population or omitting a good population is at most 1­ $P^{*}$.

• 조명전기설비학회논문지
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• 제30권2호
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• pp.1-10
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• 2016

A system which provides multispectral near-IR and visible gray images of objects is constructed and an algorithm is derived to acquire a natural color image of objects from the gray images. A color image of 24 color patches is obtained by recovering their CIE (International Commission on Illumination) LAB color coordinates $L^*$, $a^*$, $b^*$ from their gray images using the algorithm based on polynomial regression. The system is composed of a custom-designed LED illuminator emitting multispectral near-IR illuminations, fluorescent lamps and a monochrome digital camera. Color reproducibility of the algorithm is estimated in CIELAB color difference ${\Delta}E^*_{ab}$. And as a result, if yellow and magenta color patches with around 10 ${\Delta}E^*_{ab}$ are disregarded, the average ${\Delta}E^*_{ab}$ is 2.9, and this value is within the acceptability tolerance for quality evaluation for digital color complex image.

• Advances in concrete construction
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• 제13권5호
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• pp.367-376
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• 2022

Theoretical study of vibration distinctiveness of rotating cylindrical are examined for three volume fraction laws viz.: polynomial, exponential and trigonometric. These laws control functionally graded material composition in the shell radius direction. Functionally graded materials are controlled from two or more materials. In practice functionally graded material comprised of two constituent materials is used to form a cylindrical shell. For the current shell problem stainless steel and nickel are used for the shell structure. A functionally graded cylindrical shell is sanctioned into two types by interchanging order of constituent materials from inner and outer side for Type I and Type II cylindrical shell arrangement. Fabric composition of a functionally graded material in a shell thickness direction is controlled by volume fraction law. Variation of power law exponent brings change in frequency values. Influence of this physical change is investigated to evade future complications. This procedure is capable to cater any boundary condition by changing the axial wave number. But for simplicity, numerical results have been evaluated for clamped- simply supported rotating cylindrical shells. It has been observed from these results that shell frequency is bifurcated into two parts: one is related to the backward wave and other with forward wave. It is concluded that the value of backward frequency is some bit higher than that forward frequency. Influence of volume fraction laws have been examined on shell frequencies. Backward and forward frequency curves for a volume fraction law are upper than those related to two other volume fraction laws. The results generated furnish the evidence regarding applicability of present shell model and also verified by earlier published literature.

• 응용통계연구
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• 제24권6호
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• pp.1249-1257
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• 2011

비모수적 결측치 대치법인 k-최근접 이웃(k-Nearest Neighbors; KNN) 대치법을 개선한 적응 최근접 이웃(Adaptive Nearest Neighbor; ANN) 대치법과 순차 k-최근접 이웃(Sequential k-Nearest Neighbor; SKNN) 대치법의 장점들을 결합한 순차 적응 최근접 이웃(Sequential Adaptive Nearest Neighbor; SANN) 대치법을 제안하고자 한다. 이 방법은 ANN 대치법의 장점인 자료의 국소적 특징을 반영할 뿐 아니라, SKNN 대치법과 같이 결측값 대치가 이루어진 개체를 다음 결측값을 대치할 때 사용함으로써 효율성에 개선이 있을 것으로 기대한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권1호
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• pp.452-472
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• 2019

Most existing wavelet-based multiplicative watermarking methods are affected by geometric attacks to a certain extent. A serious limitation of wavelet-based multiplicative watermarking is its sensitivity to rotation, scaling, and translation. In this study, we propose an image watermarking method by using dual-tree complex wavelet transform with a multi-objective optimization approach. We embed the watermark information into an image region with a high entropy value via a multiplicative strategy. The major contribution of this work is that the trade-off between imperceptibility and robustness is simply solved by using the multi-objective optimization approach, which applies the watermark error probability and an image quality metric to establish a multi-objective optimization function. In this manner, the optimal embedding factor obtained by solving the multi-objective function effectively controls watermark strength. For watermark decoding, we adopt a maximum likelihood decision criterion. Finally, we evaluate the performance of the proposed method by conducting simulations on benchmark test images. Experiment results demonstrate the imperceptibility of the proposed method and its robustness against various attacks, including additive white Gaussian noise, JPEG compression, scaling, rotation, and combined attacks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권2호
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• pp.1003-1019
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• 2019

Threshold ring signature scheme enables any t entities from N ring members to spontaneously generate a publicly verifiable t-out-of-N signature anonymously. The verifier is convinced that the signature is indeed generated by at least t users from the claimed group, but he cannot tell them apart. Threshold ring signatures are significant for ad-hoc groups such as mobile ad-hoc networks. Based on the lattice-based ring signature proposed by Melchor et al. at AFRICRYPT'13, this work presents a lattice-based threshold ring signature scheme, employing the technique of message block sharing proposed by Choi and Kim. Besides, in order to avoid the system parameter setup problems, we proposed a message processing technique called "pad-then-permute", to pre-process the message before blocking the message, thus making the threshold ring signature scheme more flexible. Our threshold ring signature scheme has several advantages: inherits the quantum immunity from the lattice structure; has considerably short signature and almost no signature size increase with the threshold value; provable to be correct, efficient, indistinguishable source hiding, and unforgeable.

• Natural Product Sciences
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• 제25권3호
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• pp.244-247
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• 2019

A new isoprenylated stilbene, flavestinK (1) together with two known isoprenylated stilbenes, flavestin B (2), flavestin G (3), and two isoprenilated flavanones, 4-O-methyl-8-isoprenylnaringenin (4) and 8-isoprenyl-5,7-dihydroxyflavanone (5) were isolated from the leaves of Macaranga recurvata Gage. All of the structures have been determined based on HRESIMS, 1D and 2D NMR spectral data. All of the isolated compounds were evaluated for their cytotoxicity against three human cancer cells (HeLa, T47D and WiDr). Compound 1 showed higher activity than doxorubicin against HeLa cells with $IC_{50}$ value of $13.1{\mu}g/mL$.