• 품질경영학회지
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• 제47권1호
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• pp.33-46
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• 2019

Purpose: This study proposed a DEA (Data Envelopment Analysis)-based stepwise benchmarking target selection for inefficient DMU (Decision Making Unit) to improve its efficiency gradually to reach most efficient frontier considering resource (DEA inputs and outputs) improvement preferences. Methods: The proposed method proceeded in two steps. First step evaluates efficiency of DMUs by using DEA, and an evaluated DMU selects benchmarking targets of HCU (Hypothesis Composit Unit) or RU (Real Unit) considering resource improvement preferences. Second step selects stepwise benchmarking targets of the inefficient DMU. To achieve this, this study developed a new DEA model, which can select a benchmarking target of an inefficient DMU in considering inputs or outputs improvement preference, and suggested an algorithm, which can select stepwise benchmarking targets of the inefficient DMU. Results: The proposed method was applied to 34 international ports for validation. In efficiency evaluation, five ports was evaluated as most efficient port, and the remaining 29 ports was evaluated as relative inefficient port. When port 34 was supposed as evaluated DMU, its can select its four stepwise benchmarking targets in assigning the preference weight to inputs (berth length, total area of pier, CFS, number of loading machine) as (0.82, 1.00, 0.41, 0.00). Conclusion: For the validation of the proposed method, it applied to the 34 major ports around the world and selected stepwise benchmarking targets for an inefficient port to improve its efficiency gradually. We can say that the proposed method enables for inefficient DMU to establish more effective and practical benchmarking strategy than the conventional DEA because it considers the resource (inputs or outputs) improvement preference in selecting benchmarking targets gradually.

• Advances in nano research
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• 제10권4호
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• pp.359-371
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• 2021

A tumor immune interaction is a main topic of interest in the last couple of decades because majority of human population suffered by tumor, formed by the abnormal growth of cells and is continuously interacted with the immune system. Because of its wide range of applications, many researchers have modeled this tumor immune interaction in the form of ordinary, delay and fractional order differential equations as the majority of biological models have a long range temporal memory. So in the present work, tumor immune interaction in fractional form provides an excellent tool for the description of memory and hereditary properties of inter and intra cells. So the interaction between effector-cells, tumor cells and interleukin-2 (IL-2) are modeled by using the definition of Caputo fractional order derivative that provides the system with long-time memory and gives extra degree of freedom. Moreover, in order to achieve more efficient computational results of fractional-order system, a discretization process is performed to obtain its discrete counterpart. Furthermore, existence and local stability of fixed points are investigated for discrete model. Moreover, it is proved that two types of bifurcations such as Neimark-Sacker and flip bifurcations are studied. Finally, numerical examples are presented to support our analytical results.

• Advances in nano research
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• 제10권5호
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• pp.449-460
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• 2021

Flexoelectricity is an interesting materials' property that is more touchable in small scales. This property beside the sandwich structures placed in the center of scientists' attention due to their extraordinary effects on the mechanical properties. Furthermore, in the passage of decades, more elaborated sandwich structures took into consideration results from using honeycomb core. This kind of structure, inspiring from honeycomb core, provides more stiffness to weight ratio, which plays a crucial role in different industries. In this paper, based on the Love-Kirchhoff's hypothesis, Hamilton's principle, modified couple stress theory and Fourier series analytical method, equations of motion for a sandwich plate containing a honeycomb core integrated by two face-sheets have derived and solved analytically. The equations of both face sheets have derived by flexoelectricity consideration. Moreover, it should be noticed that the whole structure rests on the visco-Pasternak foundation. Conducting current research provided an acceptable and throughout study based on flexoelectricity to address the effect of materials' characteristics, length-scale parameter, aspect, and thickness ratios and boundary conditions on the natural frequency of honeycomb sandwich plates. Also, based on the presented figures and tables, there is a close agreement between previous studies and recent work. Due to the high ratio of strength to weight, current model analyzing is capable of taking into account for different vehicles' manufacturing in a high range of industries.

• Advances in nano research
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• 제10권3호
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• pp.221-234
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• 2021

During the previous few years, phenomenon of bioconvection along with the use of nanoparticles showed large number of applications in technological and industrial field. This paper analyzed the bioconvection phenomenon in magnetohydrodynamic boundary layer flow of a Powell-Eyring nanoliquid past a stretchable cylinder with Cattaneo-Christov heat flux. In addition, the impacts of chemical reaction and heat generation/absorption parameter are considered. By the use of appropriate transformation, the governing PDEs (nonlinear) have been transformed and formulated into nonlinear ODEs. The resulting nonlinear ODEs subjected to relevant boundary conditions are solved analytically through homotopy analysis method which is programmed in Mathematica software. Graphical and numerical results versus physical quantities like velocity, temperature, concentration and motile microorganism are investigated under the impact of physical parameters. It is noted that velocity profile enhances as the curvature parameter A and Eyring-Powell fluid parameter M increases but a decline manner for large values of buoyancy ratio parameter Nr and bio-convection Rayleigh number Rb. In the presence of Prandtl number Pr, Eyring-Powell fluid parameter M and heat absorption parameter ��, temperature profile decreases. Nano particle concentration profile increases for increasing values of magnetic parameter Ha and thermophoresis parameter Nt. The motile density profile has revealed a decrement pattern for higher values of bio-convection Lewis number Lb and bio-convection peclet number Pe. This study may find uses in bio-nano coolant systems, advance nanomechanical bio-convection energy conversion equipment's, etc.

• Advances in nano research
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• 제14권4호
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• pp.375-389
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• 2023

In this study, free vibration analysis of functionally graded (FG) porous truncated conical shell panels reinforced by graphene platelets (GPLs) has been investigated for the first time. Additionally, the effect of three different types of porosity distribution and five different types of GPLs patterns on dynamic response of the shell are also studied. Halpin-Tsai micromechanical model and Voigt's rule are used to determine Young modulus, shear modulus and Poisson's ratio with mass densities of the shell, respectively. The main novelties of present study are: applying 3D elasticity theory and the finite element method in conjunction with Rayleigh-Ritz method to give more accurate results unlike other simplified shell theories, and also presenting a general 3D solution in cylindrical coordinate system that can be used for analyses of different structures such as circular, annular and annular sector plates, cylindrical shells and panels, and conical shells and panels. A convergence study is performed to justify the correctness of the obtained solution and numerical results. The impact of porosity and GPLs patterns, the volume of voids, the weight fraction of graphene nanofillers, semi vertex and span angles of the cone, and various boundary conditions on natural frequencies of the functionally graded panel have been comprehensively studied and discussed. The results show that the most important parameter on dynamic response of FG porous truncated conical panel is the weight fraction of nanofiller and adding 1% weight fraction of nanofiller could increase 57% approximately the amounts of natural frequencies of the shell. Moreover, the porosity distribution has great effect on the value of natural frequency of structure rather than the porosity coefficient.

• 분석과학
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• 제20권4호
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• pp.339-346
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• 2007

높은 염색성과 형광성을 나타내는 ninhydrin 유도체를 탐색하기 위하여 잠재지문 검출제로서 ninhydrin 유도체들과 glycine 분자와의 반응성에 관한 분자 홀로그래피적인 HQSPR 모델을 유도하고 정량적으로 검토하였다. Ninhydrin의 반응성은 ${\varepsilon}LUMO$ 에너지가 중요한 요인이었으며, ninhydrin 유도체들과 glycine 분자 사이의 경계분자궤도(FMO) 상호작용으로부터 궤도조절반응에 의한 친핵성 반응이 전하조절반응에 의한 친전자성 반응보다 우세하였다. 기여도 분석결과, benzo 고리상 강한 전자끌게로서 meta-치환체가 ninhydrin의 반응성을 증가시켰으며 HQSPR 및 QSPR 모델에 의하여 5,6-dinitroninhydrin 분자는 비 치환체보다 3배 이상의 반응성을 향상시킬것으로 예측되었다.

• Structural Engineering and Mechanics
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• 제89권1호
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• pp.1-11
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• 2024

This article introduces a novel analytical model for examining the impact of porosity on shear correction factors (SCFs) in functionally graded porous beams (FGPB). The study employs uneven and logarithmic-uneven modified porosity-dependent power-law functions, which are distributed throughout the thickness of the FGP beams. Additionally, a modified exponential-power law function is used to estimate the effective mechanical properties of functionally graded porous beams. The correction factor plays a crucial role in this analysis as it appears as a coefficient in the expression for the transverse shear stress resultant. It compensatesfor the assumption that the shear strain is uniform across the depth of the cross-section. By applying the energy equivalence principle, a general expression for static SCFs in FGPBs is derived. The resulting expression aligns with the findings obtained from Reissner's analysis, particularly when transitioning from the two-dimensional case (plate) to the one-dimensional case (beam). The article presents a convenient algebraic form of the solution and provides new case studies to demonstrate the practicality of the proposed formulation. Numerical results are also presented to illustrate the influence of porosity distribution on SCFs for different types of FGPBs. Furthermore, the article validates the numerical consistency of the mechanical property changesin FG beams without porosity and the SCF by comparing them with available results.

• 지역연구
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• 제34권2호
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• pp.3-19
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• 2018

본 연구의 목적은 우리나라 의료자원의 임상적 성과에 대한 효율성을 종단적으로 관찰하는 데 있다. 이를 위하여, 2006년부터 2013년까지 우리나라 16개 시도의 연령 표준화 사망률을 산출변수로, 의사, 전문의, 수술, 의료기관, 상급종합병원비율, 만성질환 진료 실인원, 만성질환 내원일 수를 투입변수로 정하고, 이를 이용한 의료성과 및 의료자원에 대한 집계자료를 구축하여 패널확률프론티어모형을 분석방법으로 적용하였다. 또한 시도별 인구사회학적, 사회경제적 특성, 의료자원 분포 특성 변수인 실업률, 노인인구비율, 1인당 GRDP, 종합병원 대비 상급종합병원 비율이 패널확률프론티어모형 분석 결과를 바탕으로 도출된 기술적 효율성에 미치는 영향을 추가적으로 살펴보았다. 이때 오차항의 이분산과 자기상관을 고려한 패널모형을 적용하였다. 주요 분석 결과는 다음과 같다. 첫째, 임상적 성과에 대해서는 의사, 전문의와 같은 공급 측면의 인적 의료자원과 단위 인구당 만성질환 진료 실인원과 같은 수요 측면의 요인이 각각 유의한 영향력을 미치는 것으로 나타났다. 둘째, 투입요소 시변 마모 모형 적용 결과 각 투입요소별 기술 결합 효율성 추정치는 임상적 성과 효율성이 지역별로 59~70%로 나타났다. 셋째. 임상적 성과에 영향을 미치는 투입요소의 기술적 효율성 추정치는 분석기간 동안 모든 지역에서 미세하게 증가하는 추세가 도출된 반면, 증가 추세는 미세하게 감소하였다. 넷째, 지역의 노인인구비율과 1인당 GRDP는 기술적 효율성 수치에 유의한 정(+)적 영향력을 미치는 것으로 나타났다. 지역별 각 효율성의 차이는 투입요소인 의료자원의 지역별 차이와 이의 결합과 지역의 인구사회학적, 사회경제적 특성 등에 기인한 것으로서, 지역별로 임상적 성과에 영향을 미치는 의료자원의 공급 편중과 수요의 접근성 차이, 인구구조와 경제적 차이가 복합적으로 작용함에 따른 기술적 효율성 차이가 다르게 나타나고 있음을 보였다는 점에 본 연구의 의의가 있다.

• 벤처혁신연구
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• 제1권2호
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• pp.35-46
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• 2018

국내 자동차부품기업의 효율성 분석에 대한 연구들은 투입자산 대비 매출액등 성과창출의 크기를 산출변수로 하는 연구들이 대다수였다. 그러나 기업의 성과지표인 매출액, 영업이익, 당기순이익 등은 비용구조와 직접적인 연관이 있고, 이러한 비용구조는 기업의 자산구조와 자본구조의 변동에 의해 영향을 받는다. 결국, 적절한 투자를 통해 효율적 경영성과를 창출하는 것은 효율적 자본조달이 동시에 이루어 져야 할 것이다. 본 연구는 이러한 점에 착안하여 현대기아자동차에 차제부품을 납품하는 1차 협력업체 33개를 대상으로 기업이 창출한 매출액등 성과지표 대비 조달자본의 효율성을 측정하고자 한다. 효율성을 평가하는 방법 중 비모수적 방법으로 가장 널리 사용되고 있는 것이 선형계획법에 기반한 DEA모형이다, 그러나, 효율적 프론티어에 기반한 DEA모형은 효율성에 하향적 영향을 주는 변수를 그대로 사용할 수 없는 한계를 지니고 있다. 이로 인해 자본조달과 관련된 차입금, 총부채등에 대한 변수를 직접적으로 고려하기에는 부적합하다. 본 연구에서는 한계점을 개선하기 위해 Worst Practice DEA를 이용하여 자본조달 측면의 효율성을 측정하였으며 국내 자동차 부품기업의 자본조달 측면의 효율성 개선 방향을 제시하였다.

• 지역연구
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• 제36권1호
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• pp.51-67
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• 2020

본 연구는 건축물대장, 주민등록대장 등 공공빅데이터의 활용성을 탐구하기 위해, 비교적 간단한 구조를 가진 맨큐-와일(MW)모형을 활용해 1인당 주거면적 추정을 시도하였다. 그 결과 공공빅데이터를 활용하여 정기조사 방식에 버금가는 모형을 수립할 수 있고, 기존 정기조사 방식으로는 어려웠던 기초자치단체별 모형수립도 가능함을 확인할 수 있었다. 공공빅데이터로부터 일반단독주택과 다세대주택 샘플을 판별하는 과정을 설계하여, 10세 연령대별 1인당 주거면적을 추정하고, 인구주택총조사, 주거실태조사 등 기존 정기조사 자료를 활용한 결과와 비교해 일치시킨 후, 서울시 25개 자치구별 1인당 주거면적을 도출하였다. 공공빅데이터는 지식영역을 확장시켜주는 장점이 있지만 본래의 작성의도와 다른 목적으로 생성된 자료를 활용한다는 점에서 근본적 한계는 존재한다. 또 개인정보 접근이라는 어려운 과정은 분석을 보다 신중히 진행해야 하는 부담을 주고, 비식별화를 거친 자료를 분석함에 따라 연구설계가 어려워지는 문제도 있다. 향후 공공빅데이터가 기존 통계조사를 보완하거나 대체할 수도 있도록 가공하는 방법 등에 대한 꾸준한 연구가 필요할 것으로 보인다.