• Journal of the Korean Society for Precision Engineering
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• v.21 no.7
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• pp.53-61
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• 2004

Condenser tube which is used for a cooling system of automobiles is mainly manufactured by conform extrusion. However, direct extrusion using porthole die in comparison with conform extrusion has many advantages such as improvement of productivity, reduction of production cost etc. In general, the porthole die extrusion process is useful for manufacturing long tubes with hollow sections and consists of three stages(dividing, welding and forming stages). Especially, Porthole die for producing condenser tube is very complex. Thus, in order to obtain the detailed mechanics, to assist in the design of proper die shapes and sizes, and to improve the quality of products, porthole die extrusion should be analyzed in as non-steady state as possible. This paper describes FE analysis of non-steady state porthole die extrusion for producing condenser tube with multi-hole through 3D simulation in the non-steady state during the entire process to evaluate detailed metal flow, temperature distribution, welding pressure and extrusion load. Also to validate FE simulation of porthole die extrusion, a comparison of simulation and experiment results was presented in this paper.

• Journal of Digital Forensics
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• v.12 no.3
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• pp.55-70
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• 2018

With the diversification of mobile devices, the development of web technologies, and the popularization of the cloud, an internet-centric web OS that is not dependent on devices has become necessary. Chromebooks are mobile devices in the form of convertible laptops featuring a web OS developed by Google. These Web OS mobile devices have advantages of multi-user characteristics of the same device and storage and sharing of data through internet and cloud, but it is easy to collect and analyze evidence from the forensic point of view because of excellent security and easy destruction of evidence not. In this paper, we propose an evidence collection procedure and an analysis method considering the cloud environment by dividing the Chromebook, which is a web OS mobile device popularized in the future, into user and administrator modes.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.7
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• pp.225-234
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• 2021

This research aimed to investigate the key factors affecting student satisfaction and loyalty in selected private universities in Cambodia. The study implemented a quantitative survey designed and guided by seven hypotheses to test the causal relationships among variables, such as academic experience, faculty services, campus life, social integration, student support facilities, student satisfaction, university image, and student loyalty. The research applied a multi-stage sampling technique of probability procedures to guarantee the presence of the research population. Confirmatory Factor Analysis (CFA) and Structural Equation Modeling (SEM) were applied for data analysis to test the hypotheses model. The collected survey totaled 543 from three universities. The purposive sampling methods were used to select the three target universities, based on their reputation, the number of students, year of establishment, and the recognition from the Ministry of Education, Youth, and Sport. The stratified random sampling method was employed to select target respondents for data collection by dividing the population into subgroups to ensure a random sample. The results showed that student support facilities, campus life, and social integration, faculty services, and university image play very important roles in the satisfaction and loyalty of the students in three universities.

• The Journal of Information Systems
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• v.30 no.2
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• pp.165-188
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• 2021

Purpose This study was conducted to identify the multidimensional role of institutional mechanisms in the linear relationship of satisfaction, trust and repurchase intention, which are used as an important concept in the research of e-commerce. To this end, a research model was proposed by combining concepts which are the concept of perceived effectiveness of institutional mechanisms for overall e-commerce environment(e.g., PEEIM) and the concep of perceived effectiveness of institutional structures(e.g., PEIS) of a specific marketplace based on the social cognitive theory. Design/methodology/approach This study was conducted by dividing the data into two groups to identify institutional mechanisms and trust-building relationships according to the institutional contexts inherent in e-commerce. The institutional contexts were set up for the top two online companies and the bottom two online companies according to the results of the open market brand assessment from 2018 to 2019 in South Korea. Findings The result of this study found that PEIS had a direct impact on trust in both high and low groups respectively whereas PEEIM presented different paradoxical results in high and low groups. In the relationship between the satisfaction and the trust in the vendor of the high group, PEEIM showed negative moderating effects but in the relationship between the trust and the repurchase intention of the low group PEEIM showed positive moderating effects.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.75-77
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• 2021

In order to find objects in an image through deep learning technology, an image dataset for learning is required. In order to increase the recognition rate of objects, a large amount of image learning data is required. It is difficult for individuals to build large amounts of datasets because it is expensive. This paper introduces a method for more easily constructing an image dataset including several sides of an object by photographing a rotating image. A method of constructing a dataset by placing an object on a rotating plate, photographing it, and dividing and synthesizing the captured images according to the needs is proposed.

• Progress in Superconductivity and Cryogenics
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• v.25 no.4
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• pp.45-49
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• 2023

CORC, which is being studied as one of the conductors for large currents, is manufactured by symmetrically arranging several strands of high-temperature superconducting wires on a cylindrical former. It allows current to flow evenly between wires and has the advantage of being manufactured in a multi-layer structure to increase current capacity. In order to apply CORC to AC power devices, it is necessary to review the material of the former, which is the frame around which the superconducting wire is wound. In the case of metal formers, they are difficult to apply because eddy currents are generated in the former, and they do not have the flexibility to be manufactured into coils by winding them with CORC. In this paper, we compare and analyze the magnetization loss caused by an external alternating magnetic field of Litz wire, which is being considered as a former material for CORC, with the results from formers made of other materials. In addition, we experimentally examine the effect of reducing magnetization loss due to an external magnetic field in CORC using a split wire made by dividing a high-temperature superconducting wire into two using an etching method, and in CORC made with a non-split wire.

• Journal of Korea Soil Environment Society
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• v.5 no.1
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• pp.3-12
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• 2000

The multi-region model, to describe preferential flow, is an equation representing solute transport in soils by dividing soil into numerous pore groups and using the hydraulic properties of the soil. As the model partial differential equation (PDE) is solved numerically with finite difference methods. a modified equivalent partial differential equation(MEPDE) of the partial differential equation of the multi-region model is derived to analyze the accuracy and consistency of the solution of the model PDE and the Von Neumann method is used to analyze the stability of the finite difference scheme. The evaluation obtained from the MEPDE indicated that the finite difference scheme was found to be consistent with the model PDE and had the second order accuracy The stability analysis is performed to analyze the model PDE with the amplification ratio and the phase lag using the Von Neumann method. The amplification ratio of the finite difference scheme gave non-dissipative results with various Peclet numbers and yielded the most high values as the Peclet number was one. The phase lag showed that the frequency component of the finite difference scheme lagged the true solution. From the result of the stability analysis for the model PDE, it is analyzed that the model domain should be discretized in the range of Pe < 1.0 and Cr < 2.0 to obtain the more accurate solution.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.36 no.2
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• pp.13-24
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• 2020

This study derives the characteristics of the private external space planning in multi-family housing through the analysis of the good case built after 2000 in Europe. First, the cases were categorized into block or block perimeter, linear and point type to examine the relationship between the type of building in urban context and the location of private external space. By block or block perimeter and linear type, private external spaces are planned in the inner courtyards or open space between buildings used as common space for residents, inducing communications between neighbors. And the direction of private external space depends on the arrangement of the building mass in urban context. In the classification as point type, there are many cases, where private external spaces are arranged in all directions, connected almost all interior spaces. Second, based on the above results, the planned characteristics of the private external space are derived by dividing it into three categories: intermediated space between inside and outside, intermediate space between private and public /individual and collective space and the identity of the intermediate space. (1) In most cases, direction, size of enclosed area and location of private extern space is designed to fit the surrounding context, so residents can perceive as much of the assets of the surrounding environment as possible, and it can be used as an extended area of living space. In another cases, it is divided into various sub-areas to experience the spatial transition from inside to outside or vice versa. 2) The private external space, which is placed in a courtyard or in a collective open space, is partially enclosed and blocked, allowing interaction with the neighbors without pressure. Along the street, they are designed to allow residents to experience the vitality of the city and to be formative element of the facade, which could confidently reveal the lifestyle and taste of residents. 3) By some of point types, which facade is three-demensional layer as a habitable external space, the private external space is very flexible for use. This intermediate space is composed of diverse spaces for various needs, or it has generous size with positional conditions connected with all interior spaces to be used multi-functional.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.8
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• pp.102-116
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• 2009

There have been lots of researches for H.264/AVC performance enhancement on a multi-core processor. The enhancement has been performed through parallelization methods. Parallelization methods can be classified into a task-level parallelization method and a data level parallelization method. A task-level parallelization method for H.264/AVC decoder is implemented by dividing H.264/AVC decoder algorithms into pipeline stages. However, it is not suitable for complex and large bitstreams due to poor load-balancing. Considering load-balancing and performance scalability, we propose a horizontal data level parallelization method for H.264/AVC decoder in such a way that threads are assigned to macroblock lines. We develop a mathematical performance expectation model for the proposed parallelization methods. For evaluation of the mathematical performance expectation, we measured the performance with JM 13.2 reference software on ARM11 MPCore Evaluation Board. The cycle-accurate measurement with SoCDesigner Co-verification Environment showed that expected performance and performance scalability of the proposed parallelization method was accurate in relatively high level

• Journal of Korea Water Resources Association
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• v.51 no.4
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• pp.301-311
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• 2018

Recently, the flood inundation caused by heavy rainfall in urban area is increasing due to global warming. The variability of climate change is described in the IPCC 5th report (2014). The precipitation pattern and hydrological system is varied by climate change. Since the heavy rainfall surpassed the design capacity of the pipeline, it caused great damage in metropolitan cities such as Seoul and Busan. Inundation in urban area is primarily caused by insufficient sewer capacity and surplus overflow of river. Inundation in urban area with concentrated population is more dangerous than rural and mountains areas, because it is accompanied by human casualties as well as socio-economic damage to recover destruction of roads, brides and underground spaces. In addition, various factors such as an increase in impervious area, a short time of concentration to outlet, and a shortage of sewer capacity's lack increase flooding damage. In this study, flood inundation analysis was conducted for vulnerable areas using XP-SWMM. Also, three structural flood prevention measures such as drainage pipeline construction, detention reservoir construction, and flood pumping station construction are applied as flood damage prevention alternatives. The flood data for each alternative were extracted by dividing the basin by grid. The Spatial Compromise Programming are applied using flood assessment criteria, such as maximum inundation depth, inundation time, and construction cost. The purpose of this study is to reflect the preference of alternatives according to geographical condition even in the same watershed and to select flood defense alternative considering regional characteristics.