• The Korean Journal of Physiology and Pharmacology
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• v.20 no.1
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• pp.53-62
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• 2016

Mesenchymal stem cells (MSCs) in the bone marrow and other somatic tissues reside in an environment with relative low oxygen tension. Cobalt chloride ($CoCl_2$) can mimic hypoxic conditions through transcriptional changes of some genes including hypoxia-inducible factor-$1{\alpha}$ (HIF-$1{\alpha}$) and vascular endothelial growth factor (VEGF). This study evaluated the potential role of $CoCl_2$ preconditioning on multi-lineage differentiation of C3H/10T1/2, a murine MSC line to understand its possible molecular mechanisms in vitro. $CoCl_2$ treatment of MSCs markedly increased HIF-$1{\alpha}$ and VEGF mRNA, and protein expression of HIF-$1{\alpha}$. Temporary preconditioning of MSCs with $CoCl_2$ induced up-regulation of osteogenic markers including alkaline phosphatase, osteocalcin, and type I collagen during osteogenic differentiation, followed by enhanced mineralization. $CoCl_2$ also increased chondrogenic markers including aggrecan, sox9, and type II collagen, and promoted chondrocyte differentiation. $CoCl_2$ suppressed the expression of adipogenic markers including $PPAR{\gamma}$, aP2, and $C/EBP{\alpha}$, and inhibited adipogenesis. Temporary preconditioning with $CoCl_2$ could affect the multi-lineage differentiation of MSCs.

• Journal of the Korean Society for Heat Treatment
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• v.26 no.6
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• pp.306-316
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• 2013

Microstructure and fracture behavior of a multi-phase low-density steel were investigated. After hot-rolling and heat treatment, the microstructure of low-density steel was composed of coarse ferrite grains and elongated bands which include second phases such as austenite, martensite and ${\kappa}$-carbide depending on holding time during isothermal heat treatment. After tensile test, microcracks were observed at martensite or ${\kappa}$-carbide interface in the elongated bands. Coarse ferrite grains showed cleavage fracture behavior regardless of second phase. The cleavage fracture of ferrite could be attributed to their coarse grain size and solute atoms that increase ductile-to-brittle transition temperature of ferrite. Despite of the tendency of cleavage fracture in coarse ferrite grains, a specimen having coarse spheroidized ${\kappa}$-carbide particles in the elongated bands showed high total elongation of 30%. Thus, the easiness of plastic deformation in the elongated band seems to play an important role in retardation of cleavage crack formation in coarse ferrite grains.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.5392-5395
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• 2013

Application of electric wheelchair, sort of wheelchair which is playing important role in transporting patients and old people, has been increasing. In this study, we designed the electric wheelchairs' driving system. Using the multi-step gear, the driving system can get great power, even though the small capacity of motors. First, we designed the multi-step gear, test its bending strength and contact strength, as well as verified its performance. We installed 'B-type electric brake(Multiple plate clutch, Anti-magnetization) in same axle of the driving system, so it is possible to stop under huge torque and small size. Using this driving system of the multi-step gear which we designed, it's possible to improve driving gear efficiency 30% up and create the high-competitive electric wheelchair. And, it is easy to repair and control.

• ETRI Journal
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• v.38 no.5
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• pp.922-933
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• 2016

IP header compression schemes offer a valuable measure for bandwidth preservation. Such schemes have been practically implemented in infrastructure-based IP networks for point-to-point links. However, minimal research and practical implementation efforts have been conducted in the direction of an IP header compression strategy that can meet the peculiar requirements of multi-hop ad hoc wireless networks. In this paper, we present a practically implemented multi-hop IP header compression scheme using the Robust Header Compression (ROHC) protocol suite. The scheme runs on a novel identifier (ID) based networking architecture, known as an ID-based ad hoc network (IDHOCNET). IDHOCNET additionally solves a number of bottlenecks of pure IP-based ad hoc networks that have emerged owing to IP address auto-configuration service, distributed naming and name resolution, and the role of an IP address as an identifier at the application layer. The proposed scheme was tested on a multi-hop test bed. The results show that the implemented scheme has better gain and requires only O (1) ROHC contexts.

• Journal of the Korean Society of Costume
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• v.61 no.7
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• pp.101-109
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• 2011

The present research aims to suggest the design of a new direction that copes with the changing environment. For example, the design for outdoor wear can be made through various methods that allows it to be worn for anytime and anywhere. Also, the research aimed to seek a development direction of outdoor wear design with environment-friendly expanded function that handles unpredictable environmental changes. The analysis of this research is as follows. First, it can be said that the trend of the outdoor wear design according to climate and environment changes is a design that seeks an efficient and rational role in functional aspects such as complex multi-functionality and minimum decorations as well as enhancing economic efficiency. Second, the outdoor wear design provides the optimal climate for the human body even in a continuously changing artificial environment. Its easy and comfortable function also helps to keep defense from possible risk elements. Lastly, this research seeks interactions among design, the body and environment. It also tries shape change using buttons and zippers, etc. according to expansion of a structural form of clothes as multi-functionality and versatility tools, and seeks a design form that can be reconstructed. The research that geared toward environmental changes should be further progressed in order to produce apparel that have efficient adaptability of any climate situations.

• Membrane and Water Treatment
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• v.2 no.2
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• pp.105-119
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• 2011

This study presents the tests of an Immersed Membrane BioReactor (IMBR) equipped with a draft tube and focuses on the influence of hydrodynamic conditions on membrane fouling in a pilot-scale using a hollow fiber membrane module of ZW-10 under ambient conditions. In this system, the cross-flow velocities across the membrane surface were induced by a cylindrical draft-tube. The relationship between cross-flow velocity and aeration strength and the influence of the cross-flow on fouling rate (under various hydrodynamic conditions) were investigated using Multi-Dimension Scaling (MDS) analysis. MDS technique is especially suitable for samples with many variables and has relatively few observations, as the data about Membrane Bio-Reactor (MBR) often is. Observations and variables are analyzed simultaneously. According to the results, a specialized form of MDS, CoPlot enables presentation of the results in a two dimensional space and when plotting variables ratio (output/input) rather than original data the efficient units can be visualized clearly. The results indicate that: (i) aeration plays an important role in IMBR performance; (ii) implementing the MDS approach with reference to the variables ratio is consequently useful to characterize performance changes for data classification.

• Smart Structures and Systems
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• v.12 no.3_4
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• pp.235-250
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• 2013

Optimal sensor placement (OSP) technique plays a key role in the structural health monitoring (SHM) of large-scale structures. According to the mathematical background and implicit assumptions made in the triaxial effective independence (EfI) method, this paper presents a novel multi-dimensional OSP method for the Canton Tower focusing on application demands. In contrast to existing methods, the presented method renders the corresponding target mode shape partitions as linearly independent as possible and, at the same time, maintains the stability of the modal matrix in the iteration process. The modal assurance criterion (MAC), determinant of the Fisher Information Matrix (FIM) and condition number of the FIM have been taken as the optimal criteria, respectively, to demonstrate the feasibility and effectiveness of the proposed method. Numerical investigations suggest that the proposed method outperforms the original EfI method in all instances as expected, which is looked forward to be even more pronounced should it be used for other multi-dimensional optimization problems.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.469-472
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• 2004

There have been numerous accelerated aging laboratory tests for evaluating suitability of polymeric materials and devices. Aging test for materials and its full scale device has been conducted, but poor correlation of aging test such as service experience were observed. Service experience plays a key role in the utility section of composite insulators. A meaningful and reliable accelerated aging test is needed for evaluating composite insulator. During the service these insulators are subjected to aging stress such as humidity, pollution, and electrical field, and erosion and tracking of the weathershed occurs. This paper presents the criteria of reliability evaluation and evaluation facilities for 22.9 kV suspension composite insulator. We adopt the criteria of reliability evaluation consist of two test methods. One is CEA tracking wheel test for examining the tracking and erosion performance of composite insulator. The other is multi-stress aging test for examining effects of environmental factors such as UV, temperature, humidity, etc on composite insulator.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.1
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• pp.35-57
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• 2014

Multi-criteria decision making (MCDM) algorithms play an important role in ensuring quality of service in an integrated HetNets (Heterogeneous Networks). The primary objective of this paper is to develop a multi-criteria vertical handoff decision algorithm (VHDA) for best access network selection in an integrated Wireless Local Area Network (WLAN)/Universal Mobile Telecommunications System (UMTS)/Worldwide Interoperability for Microwave Access (WiMAX) system. The proposed design consists of two parts, the first part is the evaluation of an Analytic Hierarchy Process (AHP) to decide the relative weights of handoff decision criteria and the second part computes the final score of the weights to rank network alternatives using Simple Additive Weighting (SAW). SAW ranks the network alternatives in a faster and simpler manner than AHP. The AHP-SAW mathematical model has been designed, evaluated and simulated for streaming video type of traffic. For other traffic type, such as conversational, background and interactive, only simulation results have been discussed and presented in brief. Simulation results reveal that the hierarchical modelling and computing provides optimum solution for access network selection in an integrated environment as obtained results prove to be an acceptable solution to what could be expected in real life scenarios.

• Journal of the Earthquake Engineering Society of Korea
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• v.23 no.6
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• pp.301-309
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• 2019

A methodology to assess seismic fragility of a nuclear power plant (NPP) using a conditional mean spectrum is proposed as an alternative to using a uniform hazard response spectrum. Rather than the single-scenario conditional mean spectrum, which is the conventional conditional mean spectrum based on a single scenario, a multi-scenario conditional mean spectrum is proposed for the case in which no single scenario is dominant. The multi-scenario conditional mean spectrum is defined as the weighted average of different conditional mean spectra, each one of which corresponds to an individual scenario. The weighting factors for scenarios are obtained from a deaggregation of seismic hazards. As a validation example, a seismic fragility assessment of an NPP containment structure is performed using a uniform hazard response spectrum and different single-scenario conditional mean spectra and multi-scenario conditional mean spectra. In the example, the number of scenarios primarily influences the median capacity of the evaluated structure. Meanwhile, the control frequency, a key parameter of a conditional mean spectrum, plays an important role in reducing logarithmic standard deviation of the corresponding fragility curves and corresponding high confidence of low probability of failure (HCLPF) capacity.