• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1999년도 춘계 학술대회논문집
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• pp.186-191
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• 1999

An Euler solver is developed to predict accurate aerodynamic data such as lift coefficient, drag coefficient, and moment coefficient. The conservation law form of the compressible Euler equations are used in the generalized curvilinear coordinates system. The Euler solver uses a finite volume method and the second order Roe's flux difference splitting scheme with min-mod flux limiter to calculate the fluxes accurately. An implicit scheme which includes the boundary conditions is implemented to accelerate the convergence rate. The multi-block grid is integrated into the flow solver for complex geometry. The flowfields are analyzed around NACA 0012 airfoil in the cases of $M_{\infty}=0.75,\;\alpha=2.0\;and\;M_{\infty}=0.80,\;\alpha=1.25$. The numerical results are compared with other numerical results from the literature. The final goal of this research is to prepare a robust and an efficient Navier-Stokes solver eventually.

• The Journal of Asian Finance, Economics and Business
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• 제8권12호
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• pp.19-29
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• 2021

This study aims to measure financial inclusion and examine its impact on income inequality in a panel of 18 Asian countries over the period 1997-2017. Two alternative approaches for developing financial inclusion index are used: one approach following the methodology of Sarma (2008), while the other is the Dynamic Factor Model (DFM)-based index. The impact of individual indicators and index of financial inclusion on inequality in income is analyzed. The Generalized Method of Moment (GMM) approach is used for empirical analysis. The results indicate that micro-level financial inclusion has a weak negative and statistically significant impact on income inequality. Macro-level index and all individual indicators of financial inclusion do not affect income inequality in the selected sample of economies. The income inequality issues have different natures and cannot be fixed by financial inclusion only. It needs holistic structural reforms to enable fair distribution of income and make an equitable financial system. Financial inclusion is a relatively less important intervention tool regarding fixing the issue of income inequality. This is one of the first studies that used the DFM method for financial inclusion indices construction.

• The Journal of Asian Finance, Economics and Business
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• 제7권11호
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• pp.195-204
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• 2020

The aim of this study is to estimate the impact of ownership structure on the performance of listed firms in transition economy. Buiding upon agency theory, hypotheses on such relationship are proposed. A detailed panel data of 502 non-financial companies listed on Ho Chi Minh Stock Exchange and Hanoi Stock Exchange over the period from 2013 to 2018, and the system generalized method of moment estimation are employed to test the proposed hypotheses. To ensure the reliability of data, this study excludes companies that violate information disclosure regulations or that are subject to special supervision by the State Securities Commission of Vietnam. Some firms with inadequate information, firms that lack the financial data required for creating variable or firms that have inconsistent construction are also re-screened. We only collect the data of enterprises that have ownership structure of two or more components. Estimation results reveal that state ownership has an U-shaped relationship with the performance of Vietnamese listed firms, while foreign ownership and the degree of ownership concentration have an inverted U-shaped relationship with listed firms' performance. The article provides governance implications that Vietnamese listed firms should decrease state ownership and foreign ownership to improve firm performance in order to boost investors' confidence.

• The Journal of Asian Finance, Economics and Business
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• 제7권10호
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• pp.555-569
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• 2020

This study examines the impact of corporate tax, a fiscal measure along with trade liberalization and research and development on total factor productivity for a panel of 153 industrial firms listed on the Pakistan Stock Exchange over the period 1997-2017. For empirical analysis, we employ the system generalized method of moment estimator. In the first step, we estimate industrial production function and the results reveal that raw material, industrial labour force and energy play vital role in enhancing industrial production. Whereas, industrial capital exerts negative impact on industrial output. We also measured total factor productivity using the production elasticities. In the second step, we examine the impact of corporate tax, trade liberalization and research and development on total factor productivity. The results indicate that higher level of corporate tax exerts negative impact on total factor productivity. The findings reveal that higher corporate taxation discourages industrial firms to undertake research and development thereby exerting adverse impact on total factor productivity of firms. The impact of trade liberalization proxied by average tariff is positive while customs duty and sales tax negatively impact firm-level total factor productivity. These findings provide useful insights for managers, investors and policy makers in Pakistan.

• The Journal of Asian Finance, Economics and Business
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• 제8권1호
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• pp.45-52
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• 2021

The capital structure is one of the hot financial topics among researchers and scholars. Its importance comes from the fact that capital structure is closely related to companies' ability to meet different stakeholders' needs. A suitable capital structure will boost the business and create a competitive advantage in the context of fierce competition. Many companies choose an optimal debt level based on the trade-off between interest and debt costs. This study aimed to test the existence of trade-off theory in capital structure, the case of Vietnam's real estate companies, which are growing very fast recently. Instead of considering constant optimal leverage to test the trade-off model, we take advantage of the dynamic capital structure determined by growth opportunities, profitability, tax incentives, tangibility, liquidity, and firm size. The dynamic panel data regression was estimated by the system Generalized Method of Moment (Sys-GMM). The empirical evidence showed that real estate companies listed in the Vietnamese stock market might change their leverage toward a target capital structure determined by influential factors in a long-term perspective. In particular, the debt-to-asset ratio will change by approximately 14 percent, positively, in response to the difference between the current debt-to-asset ratio and the dynamic target debt-to-asset ratio.

• The Journal of Asian Finance, Economics and Business
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• 제9권5호
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• pp.355-363
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• 2022

The debt maturity structure has a significant impact on a company's financial situation. Any debt maturity structure decisions substantially impact investment decisions due to changes in capital cost and dividend decisions due to cash flow consequences. This study used the system generalized method of moment (Sys-GMM) to investigate the debt maturity structure of real estate companies listed on the Ho Chi Minh Stock Exchange (HOSE) in the duration from 2008 to 20019. It found that the firm size, liquidity, and tangible assets affected the decision on debt maturity structure. The tangible asset had the most significant impact on the possibility for companies to access long-term loans. This finding revealed that the majority of the real estate companies listed on HOSE borrowed money from banks. Such decisions are most likely affected by the collateral. Another finding of the study is that financial institutions had a major impact on loan maturity structure, whereas the effects of the financial market were negligible. Besides, the real estate companies listed on HOSE seemed not to pay attention to changes in inflation, economic growth, and institutional qualities when deciding on the debt maturity structure.

• Current Applied Physics
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• 제18권12호
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• pp.1465-1472
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• 2018

The magnetic and optical properties of Ce-doped ZnO systems have been widely demonstrated, but the effects of different strains of Ce-doped ZnO systems remain unclear. To solve these problems, this study identified the effects of biaxial strain on the electronic structure, absorption spectrum, and magnetic properties of Ce-doped ZnO systems by using a generalized gradient approximation + U (GGA + U) method with plane wave pseudopotential. Under unstrained conditions, the formation energy decreased, the system became stable, and the doping process became easy with the increase in the distances between two Ce atoms. The band gap of the systems with different strains became narrower than that of undoped ZnO without strain, and the absorption spectra showed a red shift. The band gap narrowed, and the red shift became weak with the increase of compressive strain. By contrast, the band gap widened, and the red shift became significant with the increase of tensile strain. The red shift was significant when the tensile strain was 3%. The systems with -1%, 0%, and 1% strains were ferromagnetic. For the first time, the magnetic moment of the system with -1% strain was found to be the largest, and the system showed the greatest beneficial value for diluted magnetic semiconductors. The systems with -3%, -2%, 2%, and 3% strains were non-magnetic, and they had no value for diluted magnetic semiconductors. The ferromagnetism of the system with -1% strain was mainly caused by the hybrid coupling of Ce-4f, Ce-5d, and O-2p orbits. This finding was consistent with Zener's Ruderman-Kittel-Kasuya-Yosida theory. The results can serve as a reference for the design and preparation of new diluted magnetic semiconductors and optical functional materials.

• 한국자기학회지
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• 제25권2호
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• pp.31-38
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• 2015

최근에 전자구조 계산으로 반쪽금속성을 가진다는 것이 확인된 4원 호이슬러 화합물인 CoFeCrGa와 CoFeCrGe의 (001)표면에서 반쪽금속성의 유지여부와 표면자성을 Full-potential Linearized Augmented Plane Wave 에너지띠 계산방법을 통해 연구하였다. 이를 위해 두 화합물 모두에서 각기 CoFe와 CrGa, 그리고 CrGe로 끝나는 (001)표면을 모두 고려하였다. 계산된 상태밀도로부터 두 화합물의 두가지 절단표면계 모두에서 반쪽금속성이 유지되지 못함을 알았다. 다만 CoFeCrGa에서 CrGa(001) 표면계는 그 상태밀도로부터 거의 반쪽금속성을 가짐을 알았다. 두 계에서 표면이나 표면 밑층의 Co나 Fe, 그리고 Cr 원자의 자기모멘트는 계에 따라 상당히 다른 값을 가졌다.

• 한국자기학회지
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• 제18권6호
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• pp.206-210
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• 2008

최근의 연구에 따르면 체심입방구조(bcc)를 가지는 Rh은 상자성 상태와 약간의 에너지 차를 보이며 강자성체가 된다고 한다. 이 연구에서는 bcc Rh(001) 표면의 전자구조와 자성을 일반기울기 근사 하에서 총퍼텐셜 선형보강 평면파 에너지 띠 계산방법을 이용하여 연구하였다. 표면의 자성상태는 강자성상태를 가졌으며, unrelaxed 된 경우에 표면층의 자기모멘트는 $0.48{\mu}B$로 덩치상태의 $0.43{\mu}B$에 비해 증진되었으나, 표면 바로 밑층의 자기모멘트는 $0.23{\mu}B$으로 상당히 줄어들었다. 총에너지 및 원자힘 계산을 통해 relaxed 된 구조를 구하였는데, 이 때 표면 층은 안쪽으로, 표면 바로 밑층은 바깥 쪽으로 이동하여 원래의 층간격보다 약 7.0% 줄어들었다. 이러한 층간 간격 변화는 표면 자성을 약화시켜, 표면층과 표면 바로 밑층의 자기모멘트를 $0.36{\mu}B$ 및 $0.14{\mu}B$로 줄어들게 하였다.

• 경영과정보연구
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• 제33권3호
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• pp.21-33
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• 2014

본 연구는 최근에 해외직접투자의 결정요인으로써 간주되고 있는 투자대상국의 지적재산권 보호의 영향에 관하여 실증분석 하였다. 2000부터 2008년까지 미국의 다국적기업들을 대상으로 고정효과 모형(FEM)과 시스템 GMM을 사용하여 분석한 결과, 지적재산권 보호의 변화는 미국 다국적기업으로부터의 해외직접투자를 유입에 있어서 긍정적인 영향을 미치는 반면에, 지적재산권 보호의 정도는 유의적인 영향을 제공하지 않았다. 소득수준을 기준으로 고소득국가와 저소득국가로 나누어 실시한 추가 분석결과에서 역시 지적재산권 보호의 변화만이 저소득국가에서의 미국 다국적기업의 투자에 긍정적인 영향을 미치는 것으로 나타났다. 패널자료의 특성상 오차항의 이분산성(heteroscedasticity)을 고려하여 전체 투자대상국을 상대로 FGLS와 PCSE 분석을 실시한 결과에서도 지적재산권 보호의 변화만이 해외직접투자의 유입에 긍정적인 영향을 미치고 있음을 알 수 있으며, 동일한 방법으로 고소득국가와 저소득국가로 나누어 추가분석을 실시한 결과에서는, 저소득국가에서만 미국 다국적기업의 해외직접투자 유입에 유의적으로 긍정적인 영향을 제공하고 있음을 보여주었다. 이러한 결과는 투자대상국의 지적재산권 보호의 수준보다는 변화가 해외직접투자의 유입에 영향을 제공하는 것으로써, 특히 저소득국가가 미국 다국적 기업의 해외직접투자를 유입하기 위하여 지적재산권 보호의 변화에 대한 중요성을 시사한다.