• 한국ITS학회 논문지
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• 제8권3호
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• pp.1-10
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• 2009

버스지체시간은 버스노선의 교통여건이 반영되어 나타나는 결과로서 버스도착시간을 예측하는데 있어 중요한 요소이다. 이에 본 연구에서는 다양한 변수를 사용하지 않아도 되는 마코브 체인을 이용하여 분석 정류장간 전이확률행렬표를 생성하고 이를 이용하여 버스지체시간을 예측하였다. 본 연구를 통하여 기존연구의 한계점인 정류장별 계획된 버스도착 시간이 존재하지 않은 경우에 대하여 배차시간을 이용한 버스지체시간 산출방법을 제시함으로서 기존연구의 한계점을 극복하였으며, 또한 정류장별 버스지체시간을 예측하기 위해 정의한 정류장간 버스지체의 전이는 동질하다는 귀무가설을 대웅표본 T검정을 통하여 채택함으로서 사용한 가정이 95% 신뢰수준에서 유의하다는 것을 확인하였다. 이를 통하여 향후마코브 체인을 이용하여 버스도착시간 예측이 가능할 것으로 판단된다.

• BMB Reports
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• 제57권6호
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• pp.273-280
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• 2024

Cancer cells metastasize to distant organs by altering their characteristics within the tumor microenvironment (TME) to effectively overcome challenges during the multistep tumorigenesis. Plasticity endows cancer cell with the capacity to shift between different morphological states to invade, disseminate, and seed metastasis. The epithelial-to-mesenchymal transition (EMT) is a theory derived from tissue biopsy, which explains the acquisition of EMT transcription factors (TFs) that convey mesenchymal features during cancer migration and invasion. On the other hand, adherent-to-suspension transition (AST) is an emerging theory derived from liquid biopsy, which describes the acquisition of hematopoietic features by AST-TFs that reprograms anchorage dependency during the dissemination of circulating tumor cells (CTCs). The induction and plasticity of EMT and AST dynamically reprogram cell-cell interaction and cell-matrix interaction during cancer dissemination and colonization. Here, we review the mechanisms governing cellular plasticity of AST and EMT during the metastatic cascade and discuss therapeutic challenges posed by these two morphological adaptations to provide insights for establishing new therapeutic interventions.

• 대한전자공학회논문지SP
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• 제38권6호
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• pp.692-702
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• 2001

본 논문에서는 표준화 영상부호화기에서 사용할 수 있는 새로운 블럭정합 방식을 제안하였다. 제안방식은 기존 방식처럼 광역-협역 탐색방식을 사용하는 방식이 아닌, 미리 선정된 각 후보에 대하여 SAD 누적추이를 사용하여 움직임 벡터를 찾는 방식이다. 확산누적배열(dispersed accumulation matrix)의 제안으로 SAD 추이곡선의 선형성(linearity)을 높여서 누적 초기에 가능성 낮은 후보를 제거하였다. 이를 토대로 고속 슬라이스 경쟁 블럭정합 방식을 제안하였다. 후보선출단계와 후보경쟁단계를 통하여 최종 움직임 벡터를 생성하였으며, 국부최소값에 빠질 확률을 줄이는 동시에 불필요한 연산을 감소시켰다. 기존의 고속 블럭정합 방법들에 비하여 연산량은 10%∼70%가 줄었으며, 18%∼35%의 실제 수행시간이 감소되었다. 평균 MAD는다양한 테스트영상에 대하여 항상 우수하였으며, 전역탐색의 결과에 가장 가까운 결과를 나타내었다.

• Composites Research
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• 제16권3호
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• pp.41-48
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• 2003

본 연구에서는 고온 산화분위기 하에서 탄소/탄소 복합재료의 내산화 특성 향상을 위해 사용된 이규화 몰리브덴(MoSi$_2$)의 함량(0. 4, 12. 그리고 20 wt%)에 따른 복합재료의 충격특성에 관하여 고찰하였다. 결과로서, MoSi$_2$가 함침된 탄소/탄소 복합재료는 이를 함유하지 않은 것에 비하여 충격특성 향상의 원인이 되는 탄소섬유와 매트릭스 수지간의 계면결합력 증가를 가져왔으며, 특히 12 wt% MoSi$_2$가 현재의 시스템에서 가장 우수한 충격특성을 나타내었다. 이는 복합재료 내의 탄소섬유, 필러, 그리고 매트릭스 수지간의 계면 접착력의 증가를 가져오는 90$0^{\circ}C$ 전후에서 MoSi$_2$의 취성­연성 전이(BDT) 작용 때문이라 사료된다.

• 한국축산식품학회지
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• 제32권5호
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• pp.627-634
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• 2012

This study was carried out to investigate the physical and thermal properties of ${\kappa}$-carrageenan (${\kappa}$-car) gel added whey protein isolate (WPI) as a cryoprotectant. The concentration of ${\kappa}$-carrageenan was fixed at 0.2 wt%. The mean ice crystal size of the WPI/${\kappa}$-car was decreased according to increasing whey protein isolate concentration. The temperature of gel-sol (Tg-s) and sol-gel (Ts-g) transition of WPI/${\kappa}$-car maxtrix was represented in the order of 3.0, 0.2, 5.0 and 1.0 wt%. In addition, the transition temperature of gel-sol of WPI in sucrose solution were showed in order of 1.0, 5.0, 0.2 and 3.0 wt% depending on whey protein isolate concentration. The shape of ice crystal was divided largely into two types, round and rectangular form. 1.0 wt% WPI/${\kappa}$-car matrix at pH 7 and 9 showed minute and rectangular formation of ice crystals and whey protein isolate in sucrose solution at a concentration of 1.0 wt% WPI/${\kappa}$-car matrix at pH 3 and 5 showed relatively large size and round ice crystals. The ice recrystallization characteristics and cryprotective effect of ${\kappa}$-carrageenan changed through the addition of different concentrations of whey protein isolate. It seems that the conformational changes induced interactions between whey protein isolate and ${\kappa}$-carrageenan affected ice recrystallization.

• 한국통신학회논문지
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• 제36권6C호
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• pp.361-367
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• 2011

본 논문에서는 효율적인 영상 암호화를 위해 NBCA(Null Boundary CA)에 기초한 여원 MLCA(Maximum Length Cellular Automata)와 2D CAT(Two-Dimensional Cellular Automata Transform)를 이용한 암호화 방법을 제안한다. 암호화 방법은 먼저, Wolfram Rule 행렬에 의해 전이행렬 T를 생성한다. 그 후, 암호화하려는 원영상에 생성된 전이 행렬 T를 곱하여 원 영상의 픽셀 값을 변환한다. 또한 변환된 원 영상을 여원 벡터 F와 XOR 연산하여 여원 MLCA가 적용된 영상으로 변환한다. 다음, 게이트웨이 값을 설정하여 2D CAT 기저함수를 생성한다. 그리고, 여원 MLCA가 적용된 영상에 생성된 기저함수를 곱하여 2D CAT 암호화를 한다. 마지막으로 안정성 분석을 통하여 제안한 방법이 높은 암호화 수준의 성질을 가졌음을 검증한다.

• 로봇학회논문지
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• 제12권1호
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• pp.42-54
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• 2017

Using an inverse of the geometric Jacobian matrix is one of the most popular ways to control robot manipulators, because the Jacobian matrix contains the relationship between joint space velocities and operational space velocities. However, the control algorithm based on Jacobian matrix has algorithmic singularities: The robot manipulator becomes unstable when the Jacobian matrix loses rank. To solve this problem, various methods such as damped and filtered inverse have been proposed, but comparative studies to evaluate the performance of these algorithms are insufficient. Thus, this paper deals with a comparative analysis of six representative singularity avoidance algorithms: Damped Pseudo Inverse, Error Damped Pseudo Inverse, Scaled Jacobian Transpose, Selectively Damped Inverse, Filtered Inverse, and Task Transition Method. Especially, these algorithms are verified through computer simulations with a virtual model of a humanoid robot, THORMANG, in order to evaluate tracking error, computational time, and multiple task performance. With the experimental results, this paper contains a deep discussion about the effectiveness and limitations of each algorithm.

• 한국재료학회지
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• 제25권3호
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• pp.119-124
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• 2015

This paper investigates the change of the percolation threshold in the carbon powder-filled polystyrene matrix composites based on the experimental results of changes in the resistivity and relative permittivity of the carbon powder filling, the electric field dependence of the current, and the critical exponent of conductivity. In this research, the percolation behavior, the critical exponent of resistivity, and electrical conduction mechanism of the carbon powder-filled polystyrene matrix composites are discussed based on a study of the overall change in the resistivity. It was found that the formation of infinite clusters is interrupted by a tunneling gap in the volume fraction of the carbon powder filling, where the change in the resistivity is extremely large. In addition, it was found that the critical exponent of conductivity for the universal law of conductivity is satisfied if the percolation threshold is estimated at the volume fraction of carbon powder where non-ohmic current behavior becomes ohmic. It was considered that the mechanism for changing the gaps between the carbon powder aggregates into ohmic contacts is identical to that of the connecting conducting phases above the percolation threshold in a random resister network system. The electric field dependence is discussed with a tunneling mechanism. It is concluded that the percolation threshold should be defined at this volume fraction (the second transition of resistivity for the carbon powder-filled polystyrene matrix composites) of carbon powder.

• Advances in materials Research
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• 제8권4호
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• pp.337-359
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• 2019

Shape Memory Polymer Composites (SMPC) have gained popularity over the last few decades due to its flexible shape memory behaviour over wide range of strains and temperatures. In this paper, non-linear bending analysis has been carried out for SMPC beam under the application of uniformly distributed transverse load (UDL). Simplified C⁰ continuity Finite Element Method (FEM) based on Higher Order Shear Deformation Theory (HSDT) has been adopted for flexural analysis of SMPC. The numerical solutions are obtained by iterative Newton Raphson method. Material properties of SMPC with Shape Memory Polymer (SMP) as matrix and carbon fibre as reinforcements, have been calculated by theory of volume averaging. Effect of temperature on SMPC has been evaluated for numerous parameters for instance number of layers, aspect ratio, boundary conditions, volume fraction of carbon fiber and laminate stacking orientation. Moreover, deflection profile over unit length and behavior of stresses across thickness are also presented to elaborate the effect of glass transition temperature (T_g). Present study provides detailed explanation on effect of different parameters on the bending of SMPC beam for large strain over a broad span of temperature from 273-373K, which encompasses glass transition region of SMPC.

• Computers and Concrete
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• 제12권1호
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• pp.1-18
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• 2013

This paper presents an actual microstructure-based numerical method to investigate the mechanical properties of concrete at mesoscopic level. Digital image processing technique is used to capture the concrete surface image and generate the actual 3-phase microstructure of the concrete, which consists of aggregate, matrix and interfacial transition zones. The microstructure so generated is then transformed into a mesh or grid for numerical analysis. A finite difference code FLAC2D is used for the numerical analysis to simulate the mechanical responses and failure patterns of the concrete. Several cases of concrete with different degrees of material heterogeneity and under different compression loading conditions have been analysed. From the numerical results, the effects of the internal material heterogeneities as well as the external confining stresses are studied. It is shown that the material heterogeneities arising from the presence of different phases and the existence of interfacial transition zones have great influence on the overall mechanical behaviour of concrete and that the numerically simulated behaviour of concrete with or without confining stresses applied agrees quite well with the general observations reported in the literature.