• The Journal of Asian Finance, Economics and Business
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• 제8권7호
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• pp.55-66
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• 2021

The purpose of this study is to analyze the relationship and effects of variables both directly and indirectly (e.g., investment (INV), government expenditure (GE), unemployment rate (UR), economic growth (EG), and income inequality). The analytical phases consist, first, to transform the data using the Log Natural (Ln) method. Second, to check normality and multicollinearity of data. Third, to test direct effects of variables (government expenditure and investment effect on the unemployment rate and economic growth; investment on government expenditure; economic growth on unemployment rate; economic growth and unemployment rate on income inequality). Fourth, to test indirect effects using Sobel test, which involves UR and EG as intervening variable. Fifth, to test hypotheses with p-value < 0.05. The results of the study reveal that, of the 12 relationships, statistics show that 11 variations of the association have significant positive and negative effects. Theoretically, the different characters and goals of GE and INV in each country will have a different impact on EG and UR goals. The study provides an input, especially for the government. To create optimal EG through GE and INV, it is necessary to allocate budgets to industrial sectors that can absorb a massive labor force and to new economic growth sectors.

• 한국환경과학회지
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• 제31권7호
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• pp.637-652
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• 2022

In this study, the contributions of emissions (foreign and domestic) and atmospheric physical and chemical processes to PM_2.5 concentrations were evaluated during a high PM_2.5 episode (March 24-26, 2018) observed on the Jeju Island in the spring of 2018. These analyses were performed using the community multi-scale air quality (CMAQ) modeling system using the brute-force method and integrated process rate (IPR) analysis, respectively. The contributions of domestic emissions from South Korea (41-45%) to PM_2.5 on the Jeju Island were lower than those (81-89%) of long-range transport (LRT) from China. The substantial contribution of LRT was also confirmed in conjunction with the air mass trajectory analysis, indicating that the frequency of airflow from China (58-62% of all trajectories) was higher than from other regions (28-32%) (e.g., South Korea). These results imply that compared to domestic emissions, emissions from China have a stronger impact than domestic emissions on the high PM_2.5 concentrations in the study area. From the IPR analysis, horizontal transport contributed substantially to PM_2.5 concentrations were dominant in most of the areas of the Jeju Island during the high PM_2.5 episode, while the aerosol process and vertical transport in the southern areas largely contributed to higher PM_2.5 concentrations.

• 전기전자학회논문지
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• 제26권2호
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• pp.150-159
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• 2022

본 논문에서는 증강현실(AR) 당구 콘텐츠를 위한 물리 시뮬레이션을 제안한다. 제안하는 증강현실 당구 콘텐츠에 대한 물리 시뮬레이션의 특징은 다음과 같다. 먼저, 증강현실 환경에서 실제와 비슷한 당구공의 움직임을 구현하기 위해 당구공에 적용되는 힘과 관성모멘트 계산을 하여 물리식을 도출한다. 다음에 타격 지점에 대한 가상 당구공의 회전과 관련된 가상 당구공의 속도와 각속도를 구한다. 다음으로, 가상 당구공의 움직임 궤적이 실제 당구공과 비슷한 움직임을 구현하기 위하여 입사벡터, 법선벡터, 반사벡터 등의 물리식을 도출하게 된다. 이러한 방정식을 증강현실 환경에 적용하여 AR 당구 콘텐츠를 구현할 수 있다. 이러한 물리 시뮬레이션은 사용자가 가상 당구대를 사용하여 실제와 유사함을 느낄 수 있도록 하며 실제 환경과 상호 작용하게 돕는다. 실험 결과 실제 당구공의 경로와 가상 당구공의 경로 사이의 정확도 범위는 97.75%~99.11%로 계산됐다. 따라서 본 논문에서 제안하는 증강현실 당구 콘텐츠에 대한 물리 시뮬레이션의 성능은 실제 당구공의 경로와 유사함을 확인하였다.

• Safety and Health at Work
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• 제11권4호
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• pp.458-465
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• 2020

Background: The aim of this study was to analyze the interaction between neck and/or wrist pain and hand grip strength (HGS) and to investigate factors (age, sex, neck disorders, and carpal tunnel syndrome) influencing the HGS of industrial quality proofing workers (N = 145). Methods: Standardized questionnaires [Neck Disability Index (NDI), Boston Carpal Tunnel Questionnaire] were used to evaluate existing neck and/or wrist pain. HGS measurements were performed in different wrist positions. Results: Significant differences between participants with and without neck pain were found in different wrist positions, in neutral wrist position right [without neck pain (n = 48) 46.34 (43.39 - 49.30); with neck pain (n = 97) 38.46 (36.20 - 40.72), F_(1,144) = 16.82, p < 0.001, ŋ_p² = 0.11] and left [without neck pain 44.06 (41.19 - 46.94); with neck pain 37.36 (35.13 - 39.58), F_(1,144) = 12.70, p < 0.001, ŋ_p² = 0.08]. A significant difference between participants with and without wrist pain was found for neutral wrist position right [without wrist pain (n = 105) 42.53 (40.37 - 44.70); with wrist pain (n = 40) 37.24 (33.56 - 40.91), F_(1,144) = 6.41, p = 0.01, ŋ_p² = 0.04]. Regression analysis showed significant results especially for steps two (age and weight, NDI) and three (age and weight, NDI, Boston Carpal Tunnel Questionnaire) for neutral position right (R² = 0.355, R² = 0.357, respectively). Conclusion: Neck pain has an impact on HGS but should be evaluated in consideration of age and sex.

• Wind and Structures
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• 제35권2호
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• pp.83-92
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• 2022

When the rolling stocks run on the curve, the external rail has to be lifted to a certain level to balance the centrifugal force acting on the train body. Under such a situation, passengers may feel uncomfortable, and the slanted vehicle has the potential overturning risks at high speed. This paper conducted a wind tunnel test in an annular wind tunnel with φ=3.2 m based on a 1/20^th scaled high-speed train (HST) model. The sensitivity of Reynolds effects ranging from Re = 0.37×10⁶ to Re = 1.45×106 was tested based on the incoming wind from U=30 m/s to U=113 m/s. The wind speed covers the range from incompressible to compressible. The impact of roll angle ranging from γ=0° to γ=4° on train aerodynamics was tested. In addition, the boundary layer development was also analyzed under different wind speeds. The results indicate that drag and lift aerodynamic coefficients gradually stabilized and converged over U=70 m/s, which could be regeared as the self-similarity region. Similarly, the thickness of the boundary layer on the floor gradually decreased with the wind speed increase, and little changed over U=80 m/s. The rolling moment of the head and tail cars increased with the roll angle from γ=0° to γ=4°. However, the potential overturning risks of the head car are higher than the tail car with the increase of the roll angle. This study is significant in providing a reference for the overturning assessment of HST.

• 자원ㆍ환경경제연구
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• 제31권3호
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• pp.393-417
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• 2022

전력시장 도매가격인 전력계통한계가격(System Marginal Price, SMP)의 급등락은 발전 사업자들의 재생에너지 및 기존 신규 발전설비에 대한 투자 결정을 변경하거나 지연시켜 에너지 정책 실현에 부정적인 영향을 미칠 수 있다. 이 연구는 2016~2020년 시간별 데이터를 활용하여 우리나라 SMP 주간 실현 변동성을 측정하고 결정요인을 파악함으로써 SMP 급등락 현상에 대한 정보 제공을 목적으로 한다. 국면전환(regime-switching)을 베이지안 변수선택(Bayesian stochastic selection) 모형에 적용하여 추정한 결과, SMP 고변동·저변동 국면 모두에서 기저 발전인 석탄 및 원자력 발전과 재생에너지인 태양광 발전의 증가는 SMP 변동성을 심화시키고, 가스발전량과 LNG 가격 변화는 고변동 국면에서만 SMP 변동성을 감소시키는 것으로 나타났다. 이러한 결과는 탄소 중립이나 에너지 전환 정책에 따른 재생에너지의 점진적인 확대가 SMP 변동성을 확대할 수 있지만, 재생에너지의 간헐성을 보완하기 위한 가스발전의 증가나 탄소 중립을 위한 석탄발전 감축은 SMP 변동성 증가를 상쇄시키는 역할을 할 수 있음을 시사한다.

• 문화기술의 융합
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• 제8권6호
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• pp.435-439
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• 2022

2022년 2월 24일, 우크라이나-러시아 전쟁이 발발했다. 이 전쟁에서 특이한 현상들이 발생하고 있는데, 그중에 하나가 2차 세계대전 이후 장군들의 전사율이 가장 높다는 것이다. 이것은 우크라이나군이 러시아군의 장군들만을 제거하는 핀셋작전을 전개하고 있기 때문이다. 이를 위해, 우크라이나군은 군사정보팀이라는 특수작전 부대를 운용하고 있는데, 이들은 자체, 미군·나토군, 민간 등의 자산을 융복합하여 다영역에서 활용함으로써 시너지를 창출하고 있다. 특히, 이들은 스타링크를 활용하여 '감시-결심-타격' 활동을 실시간 초연결함으로써 생존성과 작전효용성을 극대화하고 있다. 한국군 또한 다양한 특수작전부대를 보유하고 있고, 한반도에는 대량살상무기 위협이 내재되어 있다. 따라서 우크라이나군에서 운용하는 군사정보팀의 조직편성, 무기체계 및 운용 방법은 한국군이 미래 위협을 상쇄하는데 방향성을 제공할 수 있다.

• Design & Manufacturing
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• 제16권4호
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• pp.34-39
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• 2022

Sustained economic development around the world is accelerating resource depletion. Research and development of secondary batteries that can replace them is also being actively conducted. Secondary batteries are emerging as a key technology for carbon neutrality. The core of an electric vehicle is the battery (secondary battery). Therefore, in this study, the temperature change by the heat source of the hammer and the rotational speed (rpm) of the abrasive disc of the Classifier Separator Mill (CSM) was repeatedly calculated and analyzed using the heat flow simulation STAR-CCM+. As the rotational speed (rpm) of the abrasive disk increases, the convergence condition of the iteration increases. Under the condition that the inlet speed of the Classifier Separator Mill (CSM) and the heat source value of the disc hammer are the same, the disc rotation speed (rpm) and the hammer temperature are inversely proportional. As the rotational speed (rpm) of the disc increases, the hammer temperature decreases. However, since the wear rate of the secondary battery material increases due to the strong impact of the crushing rotational force, it is determined that an appropriate rpm setting is necessary. In CSM (Classifier Separator Mill), it is judged that the flow rate difference is not significantly different in the direction of the pressure outlet (Outlet 1) right above the classifier wheel with the fastest flow rate. Because the disc and hammer attachment technology is adhesive, the attachment point may deform when the temperature of the hammer rises. Therefore, it is considered necessary to develop high-performance adhesives and other adhesive technologies.

• 수산해양기술연구
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• 제59권3호
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• pp.261-263
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• 2023

Recently, universities of fisheries and institutions related to fisheries are actively carrying out a project to build new fisheries training ships. These new fisheries training ships are significantly larger in size and longer in length than the previous ships. In addition, these new ships basically have space that can accommodate more than 100 crew and passenger. On the other hand, they are excluded from IMO maneuverability evaluation since the size of these ships are still less than 100 m in length (LBP). These results have had an impact on the study of maneuverability of fishing vessels including the fisheries training ships. Against these backgrounds, the authors conducted a study to estimate the maneuvering characteristics of fisheries training ship Baek-Kyung according to depth in order to prepare a maneuvering characteristic index that enables the large fisheries training ships to navigate more safely using a modified empirical formula. It was confirmed that the maneuvering characteristics of Baek-Kyung changed significantly as the values of the hydrodynamic force coefficients changed as the water depth gradually decreased from around 1.5 (approx. 8 m in depth) of the ratio of the water depth to the ship draft. The results of this study will not only help navigators understand the maneuvering characteristics of Baek-Kyung, but also serve as an indicator when navigating in shallow water. In addition, the accumulation of these results will serve as a basis for future study on maneuverability of fishing vessel types.

• Structural Engineering and Mechanics
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• 제86권1호
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• pp.119-137
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• 2023

The purpose of this research is to assess the performance of CBN and ceramic tools during the dry turning of gray cast iron EN GJL-350. During the turning operation, the variable machining parameters are cutting speed, feed rate, depth of cut and type of the cutting material. This contribution consists of two sections, the first one deals with the performance evaluation of four materials in terms of evolution of flank wear, surface roughness (2D and 3D) and cutting forces. The focus of the second section is on statistical analysis, followed by modeling and optimization. The experiments are conducted according to the Taguchi design L₃₂ and based on ANOVA approach to quantify the impact of input factors on the output parameters, namely, the surface roughness (Ra), the cutting force (Fz), the cutting power (Pc), specific cutting energy (Ecs). The RSM method was used to create prediction models of several technical factors (Ra, Fz, Pc, Ecs and MRR). Subsequently, the desirability function approach was used to achieve a multi-objective optimization that encompasses the output parameters simultaneously. The aim is to obtain optimal cutting regimes, following several cases of optimization often encountered in industry. The results found show that the CBN tool is the most efficient cutting material compared to the three ceramics. The optimal combination for the first case where the importance is the same for the different outputs is Vc=660 m/min, f=0.116 mm/rev, ap=0.232 mm and the material CBN. The optimization results have been verified by carrying out confirmation tests.