• Bulletin of the Korean Space Science Society
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• 2007.10a
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• pp.139-143
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• 2007

Electric propulsion has become a cost effective and sound engineering solution for many space applications. The success of SMART-1 and MUSES-C developed by European Space Agency (ESA) and Japan Aerospace Exploration Agency (JAXA) each proved that even small spacecraft could accomplish planetary mission with electric propulsion systems. A small electric propulsion system which is Hall effect thruster like SMART-1 is under development by SaTReC and GDPL (Glow Discharge Plasma Lab.) in KAIST for the next microsatellite, STSAT-3. To achieve optimized propulsion system, it is very necessary to understand plasma motions of Hall effect thruster. In this paper, we try to approach comprehensive plasma model with the particle simulation complementary to Particle In Cell (PIC) simulation. We think these two different approaches will help experimenters to optimize Hall effect thruster performances.

• Journal of Korean Society of Forest Science
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• v.79 no.3
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• pp.330-342
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• 1990

One might have a retrospect on the relationship between the forest and human being from the viewpoint of ecological perspective. It is no doubt that most of the fossil humans should have lived on the forest and the latter provided foods and shelters for humans from their beginning stages, Since the so-called agricultural revolution, humans have extensively started to exploit the forest which had beer, their cradle. The industrial revolution has created another situation against the forest in terms of the quality of ecosystem. These two revolutions have set up the so-called civilization which seems to have been based on the sacrificial oblation of the forest. The cradle for human being has been kept exterminating for the shake of "economic development and miracle." This might be a synoptic history of relationships between the forest and human beings in a sense. designates the behavioral aspects of human being against the forest and people consider the forest only as exploitable resource in this context, and the latter means that people live on the forest and strive to adapt the order of forest ecosystem. The resourcism has developed a strategy of colonialism to exploit the forest and provided a winner's position for the human beings against the forest, This idea and behavioral perspective seems to have started the backfire against the exploiter who is the owner of the civilization. However, there are different philosophies and ideas to view the relationship between the forest and human beings. People within the forest who are mostly considered as "primitives" still keep their idea of the ontology of the forest. There is a theoretical assumption of the "socionatural system" to look into the ecosystem. The forest could be viewed in the above frame of analysis. There are five variables : environment, resource, technology, organization, and ideology. Ideological aspect of the forest can be explained in the context of belief systems. Forest has a meaning of religion and rituals and people within the forest should admire it in anyway of religious reasons. This aspect of the forest cannot be separated from the environmental aspect of the forest. People within the forest acknowledge and practice the above idea. People outside the forest have lost the idea, however, at the cost of acquiring the civilization. They have expelled themselves from the forest and divided the socionatural system of the forest by way of colonialism. The efforts like agroforestry and social forestry would be strategies for recovering the idea of ontology of the forest as well as the sense of community including the forest and human being. People within the forest will be a prospective model for the future socionatural system of the forest for the people outside the forest. At this point, an ecological anthropologist can work with the forest specialists.

• Korean Journal of Social Welfare
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• v.57 no.4
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• pp.67-90
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• 2005

The purpose of this study is to analyze factors to affect low fertility and to investigate its implications to social welfare. For the purpose, I surveyed 360 married women and men in Gyeongnam province, and employed multi-regression, logistic regression model to process the data. I analyzed factors to influence low fertility in three aspects: demographic feature, socio-economic status, and personal sense of value. The results of analysis can be summarized as follows: (1) the period of marriage in demographic feature, income level in social economic status, and the necessity of children in personal sense of value are important factors to affect the current fertility level, (2) period of marriage, total numbers of children, gender of the first child are determining the future childbirth in demographic feature. Secondly, income level is interrelated to the future childbirth in socio-economic status. Thirdly, in the aspect of personal values, how much one needs to get married, how much one prefers son to daughter, how much one relies on one's children to realize one's dream are interrelated to the future childbirth, (3) the cost of bringing up a child as well as he expense of private education, lacking of a day nursery, and economic difficulty are causes to make people to postpone or give up childbirth. These results suggest that development of population policy to promote women's social participation and to strengthen family welfare as well as social welfare is necessary. These also implicates that if we pursue integrated policies on women, childcare, and education, we can get much more effective population welfare policy.

• The KIPS Transactions:PartD
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• v.8D no.6
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• pp.665-672
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• 2001

ITA (Information Technology Architecture) satisfies the requirements of information system, supports the information used in the institution's business to guarantee the interoperability and security, and analyzes the components of information system. ITA consists of EA (Enterprise Architecture), TRM (Technical Reference Manual) and SP (Standard Profile). The SP, one of the major components of ITA, is a set of information technology standards. In this paper, to construct and utilize the ITA, we mention the applications of information technology about the SP system implementation based on the TRM. The SP management system implemented in this paper is the first trial in Korea, and designs the software with object oriented programming languages such as JSP and Java. Moreover the basic and detailed specification based on the UML notation, system design using the component and system design pattern consisting of software architectures enhance the software reusability. And the constructed system in this paper shows less maintenance cost by using the public softwares such as Linux system, Korean DBMS, Apache and Tomcat, etc. Finally, the system includes the SP reference system which is used in the other institutions and cannot be found in other institutions. Also it includes the additional diverse service modules which support the subsequent processing for the establishment and revision of standards via internet.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.11
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• pp.594-603
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• 2018

Recently, according to the development of measurement techniques, it has become possible to take complicated and time-consuming field measurements in a simple and convenient manner. In this background, this study estimated the tension of cables under ambient vibration using minimized measurement and signal processing. The VBDM using video-only by low-cost equipment was used as a minimized measurement. An estimation of the natural frequency using the mirror frequency concept was also proposed to solve the shortage of frequency band in this case. Furthermore, the FDD method was adopted for a natural frequency estimation in the ambient vibration related to field application. Experimental studies using a cable-stayed bridge model were carried out to examine the properties of the mirror frequency and the applicability of FDD with the proposed minimized system. The results showed that FDD for ambient vibration also works properly in an estimation of the natural frequency using the minimized system. In addition, the mirror frequency concept can allow a high natural frequency estimation even in a distorted signal by low-speed recording, which can overcome the limit of the minimized system. Overall, the proposed minimized system can be effective for the tension estimations of a cable under ambient vibration.

• Journal of the Korean Society of Radiology
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• v.13 no.2
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• pp.185-192
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• 2019

DXA is the most commonly used BMD examination equipment with the best performance on reflecting the biological alteration with tiny change of bone density. In spite of the importance of the quality control to maintain the accuracy and precision of the examination, considerable number of hospitals are not conducting QC due to the difficulty and high cost of the phantom product. This study develops the cross revision phantom with 3D printer and the change of the degree of infilling filaments which can be readily secured, and provides the usefulness assessment of the developed phantom by comparing with existing products. The Hounsfield Units of ABS, TPU, PLA, 30% Cu-PLA, and 30% Al-PLA are assessed. The Hounsfield Units result at infilling rate 100% was $-149.74{\pm}2.36$, $-55.62{\pm}7.14$, $-7.68{\pm}3.82$, $87.53{\pm}1.07$, and $1795.20{\pm}16.15$. The L1, L2, L3 BMD of 3D printing phantom with linear regression model were $0.620{\pm}0.010g/cm^2$, $1.092{\pm}0.025g/cm^2$, $1.554{\pm}0.026g/cm^2$ which are statistically relevant to the existing phantom products. This result provides the base line data for various medical phantom produce and capability of proper quality control of DXA equipment.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.7
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• pp.918-925
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• 2017

Multiple reflections on exterior equipment with complex shape on naval ships cause unexpectedly high Radar Cross Section (RCS) distributions, and the directions of reradiated electromagnetic waves are hard to predict. Therefore, the optimum arrangement of exterior equipments should be considered according to the Radar Absorbing Structure (RAS) method. In this paper, the optimum arrangement for exterior equipments was determined to reduce multiple reflections and RCS even with complex shapes. The sequential descending arrangement method was used to establish an optimum arrangement algorithm. An LCS-2 type model was selected for optimum exterior equipment arrangements. In order to reduce computational cost, RCS distributions and multiple reflection path analysis of exterior equipments was carried out to select exterior equipments for optimum arrangement, and an optimum arrangement was determined to find positions with minimum RCS values. Also, the RCS reduction effect was analyzed using detectable radar range.

• Journal of Technology Innovation
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• v.27 no.2
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• pp.37-71
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• 2019

How has the passenger car's architecture evolved? In the meantime, the discussions on the car architecture have been mixed, i.e., integral, modular, and the coexistence of two types. Therefore, in this study, we aim to develop two indices can measure the degree of modularization of passenger car and its all modules using global trade data. By applying the indices to the framework of architecture positioning that reflects the hierarchical structure of a product, we examined that the degree of modularization of the passenger car architecture has been enhanced. Meanwhile, the degree of modularization differs across the modules that make up the car. Specifically, we observed the higher degree of modularization in front-end, cockpit and seat modules. Whereas, we found that body module had a relatively low degree of modularization. In particular, we observed that the platform of passenger car has notably modularized due to carmakers' efforts to achieve model diversification and reduction of cost and period in new product development at the same time. Interestingly, we showed that three modules, i.e., engine, chassis (relatively less modularized), and transmission (relatively highly modularized), had a different level of modularization, even if they commonly make up the platform. We contribute to the suggestion for analytical approaches that examine the degree of modularization and its progress longitudinally. In addition, we propose the necessity of decomposition of a system into elements in a study of product architecture, considering the possibly distinctive progress of modularization across the elements.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.4
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• pp.626-631
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• 2019

The policy-making and technological development for the supply expansion of eco-friendly automobiles has been continuing, but the internal combustion engines still accounts for about 95%. Also, in order to meet the stricter emission regulations of internal combustion engines based on fossil fuels, the proportion of after-treatments for vehicles and (ocean going) vessels is gradually increasing. This study is a basic study for the post-Euro-VI exhaust response of CNG buses, and it is to investigate the basic characteristics according to Pd substitution transition metal effect, catalyst volume effect and space velocity. A catalysts was prepared and tested using a model gas reactor. The NGOC catalyst with 3Pd exhibited the highest catalytic activity with 22% at $300^{\circ}C$, 48% at $350^{\circ}C$ and about 75% at $500^{\circ}C$. 3Co NGOC containing 3wt% of transition metal was excellent in oxidation ability, and it was small in size of 2nm, and the degree of catalyst dispersion was improved and de-NO/CO conversion was high. The volume of the NGOC-LNT-SCR catalyst system was optimal in the combination of 1.5+0.5+0.5 with a total score of 165, considering $de-CH_4/NOx$ performance and catalyst cost. For SV $14,000h^{-1}$, the $CH_4$ reduction performance was the highest at about 20%, while the SV $56,000h^{-1}$ was the lowest at about 5%. If the space velocity is small, the flow velocity decreases and the time remaining in the catalyst volume become long, so that the harmful gas was reduced.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.1-12
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• 2021

Technologies for an MVDC(medium voltage direct current) distribution system are being considered as an effective alternative to overcome the interconnection delay issues of PV systems. However, the implementation of a DC distribution system might lead to economic problems because of the development of DC devices. Therefore, this paper deals with the scale of a PV plant based on its capacity and proposes hosting-capacity models for PV systems to establish a network to evaluate the feasibility of an MVDC distribution system. The proposed models can be classified as AC and DC distribution systems by the power-supply method. PV systems with hundreds of MW, dozens of MW, and a few MW can be categorized as large-scale, medium-scale, and small-scale models, respectively. This paper also performed modeling for an economic evaluation of MVDC distribution system by considering both the cost of AC and DC network construction, converter replacement, operation, etc. The profit was composed of the SMP and REC rate of a PV plant. A simulation for economic evaluation was done for the MVDC distribution system using the present worth and equal-principal costs repayment method. The results confirmed that the proposed model is a useful tool to evaluate economic issues of a DC distribution system.