• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.2
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• pp.97-107
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• 2017

This study is the second investigation on the steady flow characteristics of an SI engine with a semi-edge combustion chamber as a function of the port shape with varying evaluation positions. For this purpose, the planar velocity profiles were measured from 1.75B, 1.75 times of bore position apart from the bottom of head, to 6.00B positions using particle - image velocimetry. The flow patterns were examined with both a straight and a helical port. The velocity profiles, streamlines, and centers of swirl were almost the same at the same valve lift regardless of the measuring position, which is quite different from the case of the pent-roof combustion chamber. All the eccentricity values of the straight port were out of distortion criterion 0.15 through the lifts and the position. However, the values of the helical port exceeded the distortion criterion by up to 4 mm lift, but decreased rapidly above the 3.00B position and the 5 mm lift. There always existed a relative offset effect in the evaluation of the swirl coefficient using the PIV method due to the difference of the ideal impulse swirl meter velocity profile assumption, except for the cylinder-center-base estimation that was below 4 mm of the straight port. Finally, it was concluded that taking the center as an evaluation basis and the assumption about the axial velocity profile did not have any qualitative effect on swirl evaluation, but affected the value owing to the detailed profile.

• International Area Studies Review
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• v.16 no.3
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• pp.293-321
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• 2012

This study aims to examine how institutions has been formed to deepen interdependence and to keep check in trade on the border regions of East Sea Rim between the macro structure and micro behaviors. The transitional nations such as China, Russia, and North Korea adjacent to the East Sea Rim exhibits unique characteristics in terms of transaction governance structure. While the regional economy in northeast China is still overwhelmed by the stated-owned enterprises(SOEs), it strongly encourages the private economic trade to form institutional economy through the border trade port and peddler trade market. Thus trade is shaped by the mixed governance. In far east Russia, whereas the SOEs are in charge of exporting oil, gas etc., private firms and small scale traders are importing household items, so that it can also be called as the mixed governance, while informal social networks simultaneously work. In North Korea, for the trade, since the firms are mainly required to have the permits from the different levels of government, it is regarded as the hierarchical governance. The institutional economics seems to well explain the changing agencies and their influence on the trade among the regions in the East Sea Rim.

• The Korean Journal of Archival Studies
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• no.23
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• pp.45-86
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• 2010

This thesis is performed to suggest an objective and effective optimization plan of appraisal for archival values. Even though saving all of archives and records and passing them to descendants would be a strong preservation method, but preservation expenses cannot be ignored. Additionally the appraisal for archives is completed by selecting and preserving high-value records, preserving all of records seems not to be effective. In this aspects archivists have tried to find the appraisal standard to ensure the objectivity of it, however, existing studies cannot bring out positive method because of focusing on analyzing only theoretical analysis on appraisal. This study divides appraisal for archives in 3 steps; inquiry for the records creators, appraisal of archivists, appraisal of appraisal experts, and suggests the standard to increase objectivity and confidency of appraisal. The optimization plan of appraisal for archival values with the results of this thesis would influence on the revitalization of reappraisal for the archives in repository and archive of Korea.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.9
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• pp.382-389
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• 2019

A novel folding process is proposed using a repeated cold-die forging and annealing to form a sterling silver ring. Sterling silver plate was cut into a doughnut shape, and lattices with 0.43-mm line-width were imprinted on it. The sample was folded by forging using dies with slopes of $45^{\circ}$, $60^{\circ}$, and $75^{\circ}$ and annealing. For comparison, samples were also fabricated without annealing. Strain was identified by measuring the length of lattices. Vernier calipers, a Vickers hardness tester, an optical microscope, and a UV-VIS colorimeter were used to determine the size, hardness, microstructure, and body color. Without annealing, cracks occurred. However, successful deformation was possible when annealing was used. The results of macro strain measurements show that the outer diameter and width decreased, while the inner diameter and thickness increased after the final process. The maximum strain was increased 0.128 toward the parallel direction. The Vickers hardness decreased after annealing and increased after the folding process. The microstructure results showed that the grain size increased after annealing but decreased after folding. The color difference based on the Lab index was under 10 for all processes. Eventually, a doughnut-shaped silver plate was successfully deformed into a ring shape by the folding process.

• Food Science and Industry
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• v.53 no.2
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• pp.235-247
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• 2020

Current status of the domestic food industry and major issues are reviewed, and some problems derived from the R&D aspect are analyzed. Particularly, the role of the public sector and the direction of R&D are presented in order to enhance the vitality of the food industry and strengthen the competitiveness of small and medium-sized businesses. At first, the government needs to provide a consistent R&D roadmap through macroscopic coordination, and public institutes and private companies should come up with practical and concrete collaborative measures. It is also necessary to set the investment direction for food R&D in the public sector, taking into account the strategic importance of core technology and the global level difference, targeting on basic research and public platform technology. More efforts to discover agendas focused on food technology and link them to large-scale R&D projects are urgently needed to solve national and social problems through food research.

• Korean Journal of Legislative Studies
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• v.24 no.1
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• pp.135-170
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• 2018

The recent success of populist parties and candidates in the US and European countries leads to a massive amount of empirical research on populism, a deviant form of representative democracy. Much ink has been spilled to define populism and to identify the causes of its rise and continued success in democratic political system. However, little is known about populist attitudes of individual voters. Using a large-scale online survey fielded in the context of the South Korean presidential election in 2017, this study examines (1) what determines populist attitudes of South Korean voters and (2) how populist attitudes are associated with evaluations of political parties, candidates, and political issues. Statistical analysis reveals that people high on populism are more likely to support an underdog left-wing political party and its presidential candidate, and are less likely to support policies implemented or proposed under the auspices of the Park Geun-hye administration. These findings do not necessarily suggest the inherent affinity between populism and left-wing ideology; rather, it implies populist attitudes happened to appear in 2017, in reactions to lack of confidence in the previous government.

• New Physics: Sae Mulli
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• v.68 no.12
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• pp.1302-1307
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• 2018

The crystallographic, electrical and magnetic behaviors of magnetite powder in the vicinity of its Verwey transition were investigated in this study. Magnetite was prepared by synthesizing a nanoparticle precursor and then annealing it at $800^{\circ}C$ for 1 h under a dynamic vacuum. Crystallographic and morphology analyses were done by using scanning electron microscope (SEM) and X-ray diffraction (XRD). The electrical and the magnetic properties were examined by using $M{\ddot{o}}ssbauer$ spectroscopy, vibrating sample magnetometer (VSM) and resistivity measurement. Both the magnetic moment and the resistivity showed discontinuous changes at the Verwey transition temperature ($T_V$). The temperature dependence of magnetic anisotropy constant showed a monotonic decrease with increasing temperature, with slight dip near $T_V$. $M{\ddot{o}}ssbauer$ spectra showed the superposition of two sextets, one from the tetrahedral (A) and the other from the octahedral (B) sites. The results revealed that identical charge states existed in the B site at temperatures both above and below $T_V$. A coordination crossover resulted in a transition from an inverse to a normal spinel at or close to $T_V$.

• Analyses & Alternatives
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• v.7 no.1
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• pp.45-81
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• 2023

This paper examines how Korean economy has been asymmetrically changed after economics crises. The three crises during the last three decades, covid19, global financial crisis, and currency crisis, have deteriorated the economic inequalities of Korea in various ways. First, manufacture industry has been affected larger by economic crises, but recovered fast. The shocks in service sector were small but persist longer or were permanent. Second, although the covid19 spreaded out more to the capital area, the negative economic shock was greater in the non-capital region. That is, the crisis in the capital region transferred or amplified to the other region. Third, the inequality between permanent and temporary workers became worse after crises. Fourth, the sluggish small business growth problem became more serious during the covid19. In order to overcome the industrial and labor inequality, it is desirable to government strategy for economic development from focusing on high value-added industry to a balanced growth for all industry and region. To this end, governemt support should be asymmetric. That is, it should focus on indirect support such as regulatory reforms in the high value-added and private-led industries, and, for small business related service sector and non-capital region which have had limited opportunity of renovation and growth, the more active effort of government and government-driven gowth strategy would be desirable.

• Korean Journal of Environmental Biology
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• v.40 no.1
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• pp.99-111
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• 2022

Vegetation is the basis for biodiversity conservation and sustainable development. In the Environmental Impact Assessment (EIA), which is the most direct and efficient policy measure to prevent degradation of nature, vegetation-related assessment has limitations as it is not based on quantitative and scientific methods. In addition, it focuses on the presence of protected species; hence, it does not take into account the role of vegetation as a habitat on a wide-area scale. As a way to overcome these limitations, this study aims to contribute to the quantification and advancement of future EIA on vegetation. Through the review of previous studies, core areas, connectivity, and vegetation condition were derived as the items to be dealt within the macroscopic aspect of vegetation impact assessment. Each item was spatially constructed using land cover maps and satellite imageries, and time series change analysis was performed. As a result, it was found that vegetation has been continuously deteriorating due to development in all aspects, and in particular, development adversely affects not only the inside of the project site but also the surrounding area. Although this study suggested the direction for improvement of the EIA in the vegetation sector based on data analysis, a more specific methodology needs to be established in order to apply it to the actual EIA process. By actively utilizing various environmental spatial data, the impact of the development on the natural ecosystem can be minimized.

• Applied Chemistry for Engineering
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• v.34 no.3
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• pp.285-290
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• 2023

Poly-lactic acid (PLA) is the most promising polymer in additive manufacturing as an alternative to acrylonitrile butadiene styrene (ABS). Since it is produced from renewable resources such as corn starch and sugar beets, it is also biocompatible and biodegradable. However, PLA has a couple of issues that limit its use. First, it has a comparatively low glass transition temperature of around 60 ℃, such that it exhibits low thermal resistance. Second, PLA has low impact strength because it is brittle. Due to these problems, scientists have found methods to improve the crystallinity and ductility of PLA. Polyethylene glycol (PEG) is one of the most studied plasticizers for PLA to give it chain mobility. However, the blend of PLA and PEG becomes unstable, and phase separation occurs even at room temperature as PEG is self-crystallized. Thus, it is necessary to investigate the optimal mixing ratio of PLA-PEG at the molecular scale. In this study, molecular dynamics will be conducted with various ratios of L-type PLA (PLLA) or DL-type PLA-PEG (PDLA-PEG) systems by using BIOVIA Materials Studio.