• Bulletin of the Korean Mathematical Society
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• v.50 no.2
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• pp.353-373
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• 2013

In this paper, a class of delayed predator-prey models of prey migration and predator switching is considered. By analyzing the associated characteristic transcendental equation, its linear stability is investigated and Hopf bifurcation is demonstrated. Some explicit formulae for determining the stability and the direction of the Hopf bifurcation periodic solutions bifurcating from Hopf bifurcations are obtained by using the normal form theory and center manifold theory. Some numerical simulations for justifying the theoretical analysis are also provided. Finally, biological explanations and main conclusions are given.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.239-242
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• 2000

Symbiotic evolutionary algorithms are stochastic search algorithms that imitate the biological coevolution process through symbiotic interactions. In the algorithms, the fitness evaluation of an individual requires first selecting symbiotic partners of the individual. The symbiotic partner effects the change of individual's fitness and search direction. In this study we are to analyze how much partnering strategies can influence the performance of the algorithms. For this goal extensive experiments are carried out to compare the performance of partnering strategies. The NKC model and the binary string covering problem are used as the test-bed problems. The experimental results indicate that there does not exist statistically significant difference in their performance.

• Journal of Biomedical Engineering Research
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• v.7 no.2
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• pp.133-138
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• 1986

Abstract In a conventional digital sector scan system in the ultrasound medical imaging, the sampling space is in the polar coordinates while the display space is in the cartesian coordinates, which necessitates a coordinate transformation process resultion process resulting the overall system very complex and bulky. In this paper we propose a new architecture of the Digital-Scan-Converter (DSC) for the ultrasound sector scan system in which sampling space is the same as the display space, so the data are displayed as they are acquired without any interpola- tion process required. To implement the above real time DSC. two frequency synthesizes with very high switching time and a low-pass filter are required. The former determines the precise location of the data points and the latter fills the gap betw- een pixels in the horizontal direction.

• Journal of Biomedical Engineering Research
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• v.21 no.3 s.61
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• pp.279-283
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• 2000

After ACL reconstruction. abrasion or wear of graft appeared frequently because of contact stresses between femoral tunnel and ACL. To minimize these problems. optimal shape of femoral tunnel is necessary. In this study. we evaluate friction force by degree of wear due to abrasion of soft tissue and develop 3-dimensional FEM model using ANSYS 5.5.1 version to analyze stress growths between femoral tunnel and ACL, We conclude that femoral tunnel angle must be slacked parallel to tunnel direction to minimize contact stress.

• Asian-Australasian Journal of Animal Sciences
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• v.12 no.3
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• pp.449-459
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• 1999

Non-conventional roughage (NCR) is shrub and tree fodders, crop residues and agroindustrial oy-products which is not commonly used as livestock feed traditionally and commercially. Eventhough many sources of NCR is available, the farmers perceptions on NCR not only vary from country to country in tropical and sub-tropical Asian-Australasian countries, but also vary from region to region within the country. Chemical composition and nutritive value of NCR are not only vary from species to species but also vary between species within the genera, between provenances/cultivars within the species and such variations are affected by season, climatic zone, topography and land utilization. The nutritive value of NCR can be improved by physical, chemical and biological treatments and conservation. Feeding NCR to ruminant and non-ruminant is not only improve performance of the livestock but also economically feasible. Future direction of NCR is inventarization, exchange information through NCR information centre, integration with either agrisilvicultural, agrisilvipastoral or silvipastoral system, and use of genetic engineering to produce high quality NCR that ultimately become conventional roughage for agroindustry and agribissiness.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.127-130
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• 1997

Phase-contrast(PC) methods have been used for quantitative measurements of velocity and volume flow rate. In addition, phase contrast cine magnetic resonance imaging (MRI) combines the flow dependent contrast of PC MRI with the ability of cardiac cine imaging to produce images throughout the cardiac cycle. In this method, the through-plane velocity has been encoded generally. However, the accuracy of the flow data can be reduced by the effect of flow direction, finite slice thickness, resolution, pulsatile flow pattern, and so on. In this study we calculated the error caused by misalignment of tomographic plane and flow directon. To reduce this error and encode the velocity for more complex flow, we suggested 3 directional velocity encoding method.

• The Journal of Fisheries Business Administration
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• v.12 no.2
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• pp.73-100
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• 1981

Fisheries resources, due to their intrinsic biological -density dependent, and socio- economic -common property nature, might yield the sustained benefits to the society involved, depending on the degree to which the social management scheme, pursuing the optimum yield from each of them, is framed. And besides, the success or failure of the management on them would, with no doubt, lead parallelly to the direction on scientific study of "Natural Resource Economics." Thus the objectives of the management, to ensue the best use of these society's resource, should underlie the technical, economic, ana social efficiency all together to meet the maximization of society's benefits from yields, taking account of managerial efficiency. And those multiple conflicts need communications between biologists, social scientists, and managers given tile mandate, tobe coordinated to arrive at a unique value weighed, through the well-ordered system approach and resulting timely decision-making which accommodates dynamical fisheries aspects and varying social purposes. purposes.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.486-491
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• 2005

There come various types of robot with researches for mobile robot. This paper introduces the multi-joint snake robot having 16 degree of freedom and composing of eight-axis. The biological snake robot uses the forward movement friction and the proposed artificial snake robot uses the un-powered wheel instead of the body of snake. To determine the enable joint angle of each joint, the controller inputs are considered such as color and distance using PC Camera and ultra-sonic sensor module, respectively. The movement method of snake robot is sequential moving from head to tail through body. The target for movement direction is decided by a certain article be displayed in the PC Camera. In moving toward that target, if there is any obstacle then the snake robot can avoid by itself. In this paper, we show the method of snake robot for tracing the target with experiment.

• Animal cells and systems
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• v.12 no.1
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• pp.1-9
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• 2008

In the developing limb, chondrogenesis is an important prerequisite for the formation of cartilage whose template is required for bone formation. Chondrogenesis is a tightly regulated multi-step process, including mesenchymal cell recruitment/migration, prechondrogenic condensation of the mesenchymal cells, commitment to the chondrogenic lineage, and differentiation into chondrocytes. This process is controlled exquisitely by cellular interactions with the surrounding matrix and regulating factors that initiate or suppress cellular signaling pathways and transcription of specific genes in a temporal-spatial manner. Understanding the cellular and molecular mechanisms of chondrogenesis is important not only in the context of establishing basic principle of developmental biology but also in providing research direction toward preventive and/or regenerative medicine. Here, I will overview the current understanding of cellular and molecular mechanisms contributing to prechondrogenic condensation processes, the crucial steps for chondrogenesis, focusing on cell-cell and cell-matrix interactions.

• Journal of Mechanical Science and Technology
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• v.16 no.3
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• pp.344-353
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• 2002

A reliable computational heat transfer model has been investigated to define the heat transfer characteristics of a spray column direct contact heat exchanger, which is often utilized in the process involving counterflows for heat and mass transfer operations. Most of the previous studies investigated are one-dimensional unsteady solutions based on rather fragmentary experimental data. Development of a multidimensional numerical model and a computational algorithm are essential to analyze the inherent multidimensional characteristics of a direct contact heat exchanger. The present study has been carried out numerically and establishes a solid simulation algorithm for the operation of a direct contact heat exchanger. Operational and system parameters such as the speed and direction of working fluid droplets at the injection point, and the effects of aspect ratio and void fraction of continuous fluid are examined thoroughly as well to assess their influence on the performance of a spray column.