• Title/Summary/Keyword: concavity

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Stochastic convexity in Markov additive processes and its applications (마코프 누적 프로세스에서의 확률적 콘벡스성과 그 응용)

  • 윤복식
    • Journal of the Korean Operations Research and Management Science Society
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    • v.16 no.1
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    • pp.76-88
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    • 1991
  • Stochastic convexity (concavity) of a stochastic process is a very useful concept for various stochastic optimization problems. In this study we first establish stochastic convexity of a certain class of Markov additive processes through probabilistic construction based on the sample path approach. A Markov additive process is abtained by integrating a functional of the underlying Markov process with respect to time, and its stochastic convexity can be utilized to provide efficient methods for optimal design or optimal operation schedule wide range of stochastic systems. We also clarify the conditions for stochastic monotonicity of the Markov process. From the result it is shown that stachstic convexity can be used for the analysis of probabilitic models based on birth and death processes, which have very wide applications area. Finally we demonstrate the validity and usefulness of the theoretical results by developing efficient methods for the optimal replacement scheduling based on the stochastic convexity property.

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The Optimal Environmental Tax Rates in the Generalized Utilitarian Social Welfare Function (일반적인 사회후생함수 모형에서의 최적환경세 추정에 관한 연구)

  • Lho, Sangwhan
    • Environmental and Resource Economics Review
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    • v.11 no.4
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    • pp.689-706
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    • 2002
  • This paper makes some contributions on optimal environmental taxes in the generalized utilitarian social welfare function. It is not to suggest as to appropriate environmental tax rates but to contribute the direction of environmental tax policy. The tax rates depend on parameters of individual utility function (CES utility function) and social welfare function and income tax rate. The major findings are that, as the elasticity of substitution between labor and leisure and the concavity of social welfare function increase, both the optimal tax rates and the government demogrants rise. And, as the parameter of environmental pollution in the individual utility function increases, the optimal tax rates also increase. For the future study, this model involves the income tax and the capital tax as endogenous variables and the wage changes due to international trade.

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Sensory substitution in perceiving architectural surfaces

  • Kim, Young-Kil;Young, Rockefeller-S.L.
    • Proceedings of the Korean Operations and Management Science Society Conference
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    • 1992.04b
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    • pp.573-580
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    • 1992
  • 인공건물의 평면특성에 대한 시각을 통한 인지를 청각으로 대체했을 경우의 인지능력을 측정하였다. 정상적으로 시각(visual)을 이용하겠으나, 시각 장애자의 경우는 청각(auditory) 또는 촉각(tactile) 또는 두가지 모두를 사용하게 된다. Psychophysical approach를 사용하여 모의평면에 대한 인지능력을 JND단위로 측정하였다. 청각적인 신호를 관찰자에게 제공하기 위해 전자장치(electronic ranging device)가 고안되었다. 이 장치는 목표물까지의 거리를 초음파의 이동시간으로 측정하여 음의세기(sound level)로 발생시켜 준다. 관찰자는 이 음의 세기를 듣고 거리를 추정하고 물표의 방향은 이 장비를 쥔 손의 방향, 즉, proprioceptive cue를 이용하게 된다. 세가지 task에 대한 실험은 평면의 slantness, 두 평면이 교차하는 모서리의 크기, 두 평면사이의 공간(aperture size)등에 대한 인지능력의 측정실험이다. 실험결과를 보면, 관찰자는 시각신호 대신에 청각신호를 사용할 수 있는 능력이 있는 것으로 나타났다. 세가지 task별 JND측정치는 slant angle 6도, 모서리의 concavity 10도, angular aperature size 3-5도로 나타났다. 이 결과는 정상인이 시각을 이용한 인지능력과 큰 차이가 없음을 보여주고 있다.

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Developent of Scanning and Registration Methods Using Tooling Balls (툴링볼을 이용한 측정 및 레지스트레이션 방법 개발)

  • 김용환;윤정호;이관행
    • Korean Journal of Computational Design and Engineering
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    • v.4 no.1
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    • pp.60-68
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    • 1999
  • In reverse engineering (RE) sustems, the quality of the data aquisition process is crucial to the accuracy of the reverse engineered three dimensional computer-aided design (CAD) model. However, these tasks are predominantly done manually, and little work has been done to improve the efficiency of scanning by determining the minimum number of scans and the optimal scanning directions. In this paper, new scanning and registration methods using tooling balls are developed to assist in determining the optimal parameter for these processes. When the object to scanned has no concavity, attaching path of the object and its bounding rectangle are used for optimal scanning and registration. Then minimum number of tooling balls and their positions are calculated automatically. In the case of concave parts, the scanning plan should include a complete scan of the concave area. With the surface normal vector and the scanning direction, the minimum degree of rotating the part can be calculated. But the maximum rotation should be restricted in order to prevent occlusion of the part. Finally tow sample part ar scanned based on the proposed methods and the results are discussed.

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SOME REMARKS ON THE DIMENSIONS OF THE PRODUCTS OF CANTOR SETS

  • Kim, Jin-Oh
    • Journal of the Chungcheong Mathematical Society
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    • v.23 no.2
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    • pp.231-236
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    • 2010
  • Using the properties of the concave function, we show that the Hausdorff dimension of the product $C_{\frac{a+b}{2},\frac{a+b}{2}}{\times}C_{\frac{a+b}{2},\frac{a+b}{2}}$ of the same symmetric Cantor sets is greater than that of the product $C_{a,b}{\times}C_{a,b}$ of the same anti-symmetric Cantor sets. Further, for $1/e^2$ < a, b < 1/2, we also show that the dimension of the product $C_{a,a}{\times}C_{b,b}$ of the different symmetric Cantor sets is greater than that of the product $C_{\frac{a+b}{2},\frac{a+b}{2}}{\times}C_{\frac{a+b}{2},\frac{a+b}{2}}$ of the same symmetric Cantor sets using the concavity. Finally we give a concrete example showing that the latter argument does not hold for all 0 < a, b < 1/2.

Implementation of a Portable Identification System using Iris Recognition Techniques (홍채인식을 이용한 정보보안을 위한 휴대용 신분인식기 개발)

  • Joo, Sang-Hyun;Yang, Woo-Suk
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.11 no.5
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    • pp.107-112
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    • 2011
  • In this paper, we introduce the implementation of the security system using iris recognition. This system acquires images with infrared camera and extracts the 2D code from a infrared image which uses scale-space filtering and concavity. We examine the system by (i) extract 2D code and (ii) compare the code that stored on the server (iii) measure FAR and FRR using pattern matching. Experiment results show that the proposed method is very suitable.

MONOTONE ITERATION SCHEME FOR IMPULSIVE THREE-POINT NONLINEAR BOUNDARY VALUE PROBLEMS WITH QUADRATIC CONVERGENCE

  • Ahmad, Bashir;Alsaedi, Ahmed;Garout, Doa'a
    • Journal of the Korean Mathematical Society
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    • v.45 no.5
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    • pp.1275-1295
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    • 2008
  • In this paper, we consider an impulsive nonlinear second order ordinary differential equation with nonlinear three-point boundary conditions and develop a monotone iteration scheme by relaxing the convexity assumption on the function involved in the differential equation and the concavity assumption on nonlinearities in the boundary conditions. In fact, we obtain monotone sequences of iterates (approximate solutions) converging quadratically to the unique solution of the impulsive three-point boundary value problem.

Holostephanus metorchis (Digenea: Cyathocotylidae) from Chicks Experimentally Infected with Metacercariae from a Fish, Pseudorasbora parva, in the Republic of Korea

  • Seo, Min;Guk, Sang-Mee;Chai, Jong-Yil;Sim, Seo-Bo;Sohn, Woon-Mok
    • The Korean Journal of Parasitology
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    • v.46 no.2
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    • pp.83-86
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    • 2008
  • Holostephanus metorchis (Digenea: Cyathocotylidae) is a parasite of birds, transmitted by freshwater fishes. H. metorchis adults were recovered from chicks experimentally infected with metacercariae collected from freshwater fishes, Pseudorasbora parva. The metacercariae were oval, surrounded with thick fibrous capsules. In adult flukes, the holdfast organ occupied the ventral concavity, and the anterior testis did not reach the level of the ventral sucker. Based on these morphological characteristics, these flukes were identified as H. metorchis.

ON NONSMOOTH OPTIMALITY THEOREMS FOR ROBUST OPTIMIZATION PROBLEMS

  • Lee, Gue Myung;Son, Pham Tien
    • Bulletin of the Korean Mathematical Society
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    • v.51 no.1
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    • pp.287-301
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    • 2014
  • In this paper, we prove a necessary optimality theorem for a nonsmooth optimization problem in the face of data uncertainty, which is called a robust optimization problem. Recently, the robust optimization problems have been intensively studied by many authors. Moreover, we give examples showing that the convexity of the uncertain sets and the concavity of the constraint functions are essential in the optimality theorem. We present an example illustrating that our main assumptions in the optimality theorem can be weakened.

Paradoxical Herniation after Decompressive Craniectomy for Acute Subdural Hematoma

  • Cho, Hyun;Kim, Choong-Hyun;Kim, Jae-Hoon;Kim, Jae-Min
    • Journal of Korean Neurosurgical Society
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    • v.40 no.1
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    • pp.51-53
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    • 2006
  • Decompressive craniectomy is usually performed to relieve raised intracranial pressure[ICP] caused by various intracranial lesions. A 67-year-old man presented with acute subdural hematoma and traumatic intracerebral hematoma. The patient underwent a decompressive craniectomy. Four weeks later, the patient presented with acute neurological deterioration. Brain computed tomographic[CT] scans revealed the marked concavity of the brain at the site of the craniectomy and associated with midline shift which was reversed by cranioplasty. We report an unusual case of cerebral herniation from intracranial hypotension after decompressive craniectomy for a traumatic subdural hematoma. The cranioplasty may be helpful to prevent paradoxial cerebral herniation.