http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
The Effects of Multinational Enterprises Investment in the Nontraded Sector of Developing Economies
Abera Gelan 중앙대학교 경제연구소 2004 Journal of Economic Development Vol.29 No.2
This paper draws attention to the implications of multinational enterprises (MNEs) investment in the nontraded sector of a developing host country when their investment is characterized by the transmission of superior technology, but also draws on the local capital market to secure factors of production. In a simple general equilibrium model, we show that once the MNEs control the nontraded sector, their activities generate disturbing results for the host country’s economy. In particular, the host country may experience reduced total employment and real national income as a result of their investment. The cause for such unsettling outcomes is directly related to the MNEs utilization of their sector-specific stock of knowledge-based assets in the production of nontraded goods.
Gezaei Abera, A.,Song, Sung-Jin,Kim, Hak-Joon,Kishore, M.B.,Lee, Teak-Gyu,Kang, Sung-Sik Elsevier 2018 The International journal of pressure vessels and Vol.168 No.-
<P><B>Abstract</B></P> <P>Ultrasonic nondestructive testing plays an important role in structural integrity monitoring of dissimilar metal weld (DMW) structures in pressure vessels and piping of nuclear power plants. Inspection of DMW components is too complicated due to its anisotropic behavior to ultrasonic beam propagation. Many researchers are working rigorously to model the grain orientation and ultrasonic beam skewing in DMW structures but still not completely resolved yet. This paper is intended to estimate the grain orientation with the help of numerical simulation for a given asymmetric DMW component with specified scatterers. The DMW is fabricated from austenite stainless steel and carbon steel base metals with austenite stainless steel filler metal using Gas Tungsten-Arc Welding. To study this research a finite element method (FEM) based numerical simulation has been used to exactly evaluate the grain structure. This model mainly depends on the elasticity matrix which is a function of the grain orientation and attenuation of ultrasonic energy of the weld. Iterative measurement of grain orientation using macrograph of the etched weldment with 5 × 5mm mesh size was carried out then the attenuated elasticity matrix was fed into the FEM COMSOL software model as input parameter. Result obtained from numerical simulation (time of flight and amplitude) are validated with the experimental result and good agreement (above 0.8 correlation coefficient) have been observed at higher iterations. This macro-graphic information based numerical model shows the potential to predict the grain orientation of DMW.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Motivation to DMW components to qualitatively improve the mechanical properties of structures and to radically increase its application. </LI> <LI> Measure the grain structure from macro-graphic of DMW prepared by etching to find easiest practical way of defect prediction. </LI> <LI> Estimate the grain orientation with the help of numerical simulation for a given asymmetric DMW component with specified scatterers. </LI> <LI> Grain orientation modeling plays an important role in distinguishing defect signal during practical DMW testing and optimization of signal to noise ratio during ultrasonic testing. </LI> <LI> This opens advanced mathematical modeling of grain orientation to simplify ultrasonic testing in DMW for wide spread application in safety and micro structural integrity of pressure vessels and other heterogeneous anisotropic solids. </LI> </UL> </P>
김민송,김재남,Tullu Abera Shiffraw,송우진,강범수 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.11
본 논문에서는 쿼드로터형 드론에 적용한 카본 복합재 튜브 로터-암의 진동특성을 분석하였다. Rayleigh’s Method를 이용하여 상용 복합재 튜브의 탄성계수를 획득하고, 고유진동수에 대한 이론 및 유한요소해석, 실험 결과를 비교하였다. Circular Type 카본 튜브의 직경, 길이 및 끝단 질량의 변화에 따른 고유진동수를 측정하여 해석의 신뢰성을 검증하였다. 이를 통해, 실제 드론 플랫폼에 적용한 Octagonal Type의 카본 튜브 로터-암의 탄성계수와 진동특성을 확인하였다. This paper presents the vibration characteristics of a carbon fiber tube rotor-arm which was applied to quad rotor type drone. A young’s modulus of the tube was evaluated using the Rayleigh’s method then a natural frequency of the carbon fiber tube obtained from analytical formulation was compared with the experimental and numerical values. This natural frequency was measured to verify the reliability of a numerical analysis that varies with the diameter and length of the tube as well as a mass on the tip of the tube. Finally, vibration characteristics and material property of rotor-arm of octagonal type carbon fiber tube was confirmed on a drone platform.