• Korean Journal of Mineralogy and Petrology
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• v.34 no.2
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• pp.121-131
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• 2021

Magnesium (Mg) present in carbonate minerals as impurities has been used as a geochemical proxy to infer the environmental conditions where the minerals precipitated. The reliability of Mg geochemical proxies requires fundamental understanding of Mg incorporation into minerals based on accurate speciation of Mg ²⁺ in the crystal structure, which is determined mainly by application of X-ray absorption spectroscopy (XAS). However, high uncertainties are involved in interpreting the XAS spectra of minerals containing trace amount of Mg ²⁺. Because density function theory (DFT) can predict an XAS spectrum for a crystal structure, DFT calculations can reduce the uncertainties in the interpretation of the XAS spectrum. In this study, we calculated ab initio Mg K-edge absorption spectra of Mg silicates and (hydr)oxides based on DFT and analyzed the correlation between the calculated spectra and Mg structural parameters. Our ab initio Mg K-edge absorption spectra well reproduced the key features of the experimental spectra. The absorption-edge positions of the calculated spectra showed the weak positive correlation with the average Mg-O bond distance or Mg effective coordination number. The current study shows that DFT-based core-level spectroscopy method is a powerful tool in providing standard Mg K-edge spectra of diverse Mg minerals and determining the Mg chemical species within carbonate minerals.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.403-412
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• 2021

Despite strengthening requirements for fire retardancy and applied buildings of insulation panels, the number of fires and influence of damage have increased. In this study, the thermal effects were evaluated as the separation distances, and three types of EPS panel, glass wool panel, and gypsum board panel were then selected. Temperature sensors on the panels were installed vertically from the ground. The fire source on the lamination layer of lumber was ignited by changes in the separation distances (0 cm, 25 cm, 50 cm) from the panels. The test results suggested that the maximum temperature was 349 ℃ in the EPS panel. The inside/outside shape changes were limited by the height of the low and middle positions until the critical point of a 25 cm separation distance. Furthermore, the combustion marks appeared after 500 s on average, and then the EPS panel with a high fire strength showed a broad "U type" pattern, glass wool panel, and gypsum board panel showed medium or narrow "V type" pattern. Therefore, the acquired data can provide valuable information for evaluating the fire risks and verifying fire investigation from buildings composed of these insulation panels.

• The Journal of the Acoustical Society of Korea
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• v.40 no.4
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• pp.330-336
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• 2021

In bistatic sonar operation, the scattering strength of a sonar target is characterized by the probe signal frequency, the aspect angle and the bistatic angle. Therefore, the target detection and identification performance of the bistatic sonar may vary depending on how the positions of the target, sound source, and receiver are changed during sonar operation. In this study, it was evaluated which variable is advantageous to change by comparing the target identification performance between the case of changing the aspect angle and the case of changing the bistatic angle during the operation. A scenario of identifying a hollow sphere and a cylinder was assumed, and performance was compared by classifying two targets with a support vector machine and comparing their accuracy using a finite element method-based acoustic scattering simulation. As a result of comparison, using the scattering strength defined by the frequency and the bistatic angle with the aspect angle fixed showed superior average classification accuracy. It means that moving the receiver to change the bistatic angle is more effective than moving the sound source to change the aspect angle for target identification.

• Korean Journal of Labor Studies
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• v.24 no.2
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• pp.29-59
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• 2018

This paper examines the achievements and limitations of the Moon Jae-In administration's first-year policies on non-standard employment in the public sector of Korea. The most remarkable achievement was that the transition rate of non-standard to standard positions reached the highest historical level of 42.1 percent, mainly by including for the first time temporary agency workers as a target of those policies. There also have been many steps taken to relax the qualification for transition, reduce the number of exception clauses, and expand union participation. In contrast, policy measures to address problems of low wages and inequality were very limited and not significantly different from those of previous administrations. As a result, the success of the policy paradigm shift pursued by Moon's administration will be determined by how aggressive measures are being taken in the next policy steps to improve such problems of low wages and inequality.

• Journal of Navigation and Port Research
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• v.42 no.6
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• pp.469-477
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• 2018

Most of the current administrative names and locations for the names of places in the Nanjung diary have since been confirmed. However, a disagreement ensued among translators or researchers over Anpyeon-do (Baleum-do) islet recorded in Admiral Yi Sun-Shin's diary. Anpyeon-do was first recorded in the diary on October 11, 1597. It is credited to be the location where Yi Sun-shin and Chosun Naval Fleet stayed when sailing along the Southwestern coast of the Korean Peninsula after the battle of Myeongnyang. However, Anpyeon-do's exact geographical location has never been accurately confirmed. To accurately locate the islet, this study compared the direction and position of geographical locations observed in the Anpeon-do site match to actual geographical positions and directions. In addition, the direction and position of the geographical locations observed in the newly explored islands and mountains were evaluated with regard to how they correspond to the actual Anpeon-do. As a result, we concluded that the real location of Anpyeon-do recorded in the Nanjung diary is the Maebong mountain in Anjwa-do.

• Korean Journal of Heritage: History & Science
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• v.52 no.1
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• pp.148-169
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• 2019

The purpose of this paper is to understand characteristics and trends of calligraphy styles through the analysis of handwriting. Renowned Calligraphy of Korea (海東名迹, Haedong Myeongjeok) is the first collection of famous Korean calligraphers' masterpieces and was published by Shin Gongje (申公濟, 1469-1536) in the early sixteenth century. While my previous studies have focused on analyzing the publishing backgrounds of and differences among the wood block editions and stone-carved editions of the various remaining copies of Renowned Calligraphy of Korea, this study examines the calligraphy style in the early Joseon period as represented within the collection itself. This study tries to identify the aspects of style transitions among two categories of calligraphy: (1) the calligraphy style of scribes who were in charge of documentation in the central administrative institutions (館閣) and (2) the calligraphy style passed down among the Goryeong Shin clan (高靈申氏). This study verifies that various styles which emerged based on the influence of the revivalism of the late Yuan dynasty gained acceptance in the early Joseon period while the traditional Wang Xizhi style was still in use. The most notable revelation of this study is that the calligraphy style of Kangli Naonao (康里??), a Yuan dynasty calligrapher from a remote region to the west of China, appears to have become acceptable during this period. Indeed, various Yuan dynasty styles were flowing into Korea during the late Goryeo and the early Joseon period that stand in contrast to Zhao Mengfu's "pine-snow calligraphy style." Finally, the authenticity of the Eo Sukguan (魚叔權)'s record in A Storyteller's Miscellany (稗官雜記, Paegwanjapgi) is reviewed in this study. Eo claims that writing attributed to Park Gyeong in Renowned Calligraphy of Korea was actually Shin Jageon's. However, the analysis of the relationship between Shin and Park based on their backgrounds and their political positions suggests that Eo's claim is not valid.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.649-656
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• 2019

Flux cored arc welding (FCAW), which is used widely in many fields, such as shipyards, bridge structures, construction machinery, and plant industry, is an alternative to shielded metal arc welding (SMAW). FCAW is used largely in the welding of carbon and alloy steel because it can be welded in all poses and obtain excellent quality in the field under a range of working conditions. In this study, the mechanical properties of welded parts were analyzed after different welding of SS400 and SM490A using FCAW. The following conclusions were drawn. The tensile test results satisfied the KS standard tensile strength in the range of 400~510 N/mm2 in all welding positions. The bending test confirmed that most of the specimens did not show surface breakage or other defects during bending and exhibited sufficient toughness, even after plastic deformation. The hardness test results were lower than the standard value of 350 Hv of KS B 0893. Similar to the hardness test, were greater than the KS reference value. The macro test revealed no internal flaws, non-metallic inclusions, bubbles or impurities on the entire cross section of the weld, and there were no concerns regarding lamination.

• Journal of the Korean Regional Science Association
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• v.35 no.2
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• pp.19-31
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• 2019

There have been a growing number of studies that show huge discrepancies between individuals' perceptions of relative economic position and the economic position based on the reported income in the survey. If this is the case, it is expected that the impact of perceived income status on individual happiness can be different from that of objective income status based on the reported income. The aim of this study is to investigate the factors affecting the discrepancies between perception and reality with respect to relative income status, focusing on the 'Reference group theory'. This study also tries to extend existing knowledge of the relative status on the happiness level of individuals, by examining how individual's happiness can be changed by providing the accurate information about their objective income level. There are systematic biases in perceived income status. A majority of people who actually rank in the lower part of income ladder place themselves in higher positions, while a significant portion of rich individuals underestimate their actual income status. Secondly, the misperception about the income distribution is affected by a variety of individual, household characteristics and reference group income. Thirdly, providing individuals with accurate information has a considerable effect on their happiness level.

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.2
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• pp.90-97
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• 2019

Purpose: Previous studies related with occlusal contact area were limited that interocclusal thickness level or the method of measurement has not been accurate in measuring. The purpose of this study was to investigate the relation between head posture and occlusal contact area using photo occlusion analysis. Materials and Methods: 54 subjects with complete dentition (44 men, 10 women / 23 to 33 years of age) were included. To identify the relationship between head posture and occlusal contact area, subjects took interocclusal record in maximal intercuspal position with three different positions(supine position ($0^{\circ}$) / inclined position ($45^{\circ}$) / upright position ($90^{\circ}$)) on the dental unit chair. Occlusal contact area was analyzed using photo occlusion analysis. Statistical analyses were performed with SPSS ver.25.0 at 95% confidence interval. Results: Head posture has no significant effect on the changes of occlusal contact area (P > 0.05). Conclusion: When interocclusal relation is stable, head posture does not change a interocclusal record because head posture has no significant effect on occlusal contact area. Analysis of occlusal contact area using photo occlsion analysis device is useful due to its material property and simplicity.

• Korean Journal of Construction Engineering and Management
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• v.20 no.1
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• pp.124-132
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• 2019

Notwithstanding the crucial contribution of international construction industry in the national economy, previous studies on international construction contracts had mainly focused either on trend investigation or market share analysis at a point of time. Fundamentally, the international construction industry is fragmented due to its project-based nature, is heterogeneous that has to involve different firms from diverse fields, and tends to be dynamic according to macroeconomic conditions. Therefore, the combination of static and dynamic analyses is necessary to understand its underlying structure. This study analyzes the market structure of international construction contracts using the data of 9,173 projects awarded by Korean construction firms from 2000 to 2017. Industry-level performance data is analyzed both in static (market concentration) and dynamic (market mobility and instability) methods, and detailed methodology is also provided. Consequently, the static analysis result shows that the competition among Korean construction firms has been more intensified, and the dynamic analysis result indicates that market positions of Korean construction firms are unstable and vulnerable in most of the regions and the sectors. The combination of static and dynamic indices is found to be helpful to understand the underlying aspects of market structure and can be utilized as an effective strategic reference in the highly competitive market.