• Steel and Composite Structures
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• 제45권6호
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• pp.839-850
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• 2022

This paper presents an analytical solution to study the combined effect of non-local and stretching effect on the vibration of advanced functionally graded (FG) nanoplates. A new quasi-3D plate theory is presented; there are only five unknowns and any shear correction factor is used. A new displacement field with a new shear warping function is proposed. The equilibrium equations of the FG nanoplates are obtained using the Hamilton principle and solved numerically using the Navier technique. The material properties of functionally graded nanoplates are presumed to change according to the power-law distribution of ceramic and metal constituents. The numerical results of this work are compared with those of other published results to indicate the accuracy and convergence of this theory. Hence, a profound parameterstudy is also performed to show the influence of many parameters of the functionally graded nanoplates on the free vibration responses is investigated.

• Structural Engineering and Mechanics
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• 제84권6호
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• pp.783-798
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• 2022

This study attempts to investigate the impact of thickness stretching and nonlinear hygro-thermo-mechanical loading on the bending behavior of FG beams. Young's modulus, thermal expansion, and moisture concentration coefficients vary gradually and continuously according to a power-law distribution in terms of the volume fractions of the constituent materials. In addition, the interaction between the thermal, mechanical, and moisture loads is involved in the governing equilibrium equations. Using the present developed analytical model and Navier's solution technique, the numerical results of non-dimensional stresses and displacements are compared with those obtained by other 3D theories. Furthermore, the present analytical model is appropriate for investigating the static bending of FG beams exposed to intense hygro-thermo-mechanical loading used for special technical applications in aerospace, automobile, and civil engineering constructions.

• 천문학회보
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• 제44권2호
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• pp.73.4-73.4
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• 2019

Most of the galaxy mass is known to be occupied by dark matter. However, it is difficult to directly measure the mass and distribution of dark matter in a galaxy. Recently, the velocity dispersion of the stellar population in a galaxy's center has been suggested as a possible probe of the mass of the dark matter halo. In this study, we test and verify this hypothesis using the kinematics of the satellite galaxies of isolated galaxies. We use the Friends-of-Friends (FoF)algorithm to build a catalog of primary galaxies and their satellite galaxies from the Sloan Digital Sky Survey (SDSS) DR 12. We calculate the dynamical mass of the primary galaxies from the velocity dispersion of their satellite galaxies. We then investigate the correlation between the dynamical mass and the central velocity dispersion of the primary galaxies. The stellar velocity dispersion of the central host galaxies has a strong linear correlation with the velocity dispersion of their satellite galaxies. Also, the stellar velocity dispersion of the central galaxy is strongly correlated with the dynamical mass of the galaxy, which can be described as a power law. The results of this study show that the central velocity dispersion of the primary galaxies is a good proxy for tracing the mass of dark matter halo.

• Steel and Composite Structures
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• 제44권5호
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• pp.633-649
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• 2022

This paper is first implemented with the bending behavior of three-dimensional functionally graded (3DFG) plates in the framework of level set-based topology optimization (LS-based TO). Besides, due to the suitable properties of the current design domain, the thin-plate spline (TPS) is recognized as a RBF to construct the LS function. The overall mechanical properties of the 3DFG plate are assessed using a power-law distribution scheme via Mori-Tanaka micromechanical material model. The bending response is obtained using the first-order shear deformation theory (FSDT). The mixed interpolation of four elements of tensorial components (MITC4) is also implemented to overcome a well-known shear locking problem when the thickness becomes thinner. The Hamilton-Jacobi method is utilized in each iteration to enforce the necessary boundary conditions. The mathematical formulas are expressed in great detail for the LS-based TO using 3DFG materials. Several numerical examples are exhibited to verify the efficiency and reliability of the current methodology with the previously reported literature. Finally, the influences of FG materials in the optimized design are explained in detail to illustrate the behaviors of optimized structures.

• Steel and Composite Structures
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• 제49권6호
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• pp.603-614
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• 2023

In this paper, frequency analysis of curved functionally graded (FG) nanobeam by consideration of deepness effect has been studied. Differential transform method (DTM) has been used to obtain frequency responses. The nonlocal theory of Eringen has been applied to consider nanoscales. Material properties are supposed to vary in radial direction according to power-law distribution. Differential equations and related boundary conditions have been derived using Hamilton's principle. Finally, by consideration of nonlocal theory, the governing equations have been derived. Natural frequencies have been obtained using semi analytical method (DTM) for different boundary conditions. In order to study the effect of deepness, the deepness term is considered in strain field. The effects of the gradient index, radius of curvature, the aspect ratio, the nonlocal parameter and interaction of aforementioned parameters on frequency value for different boundary conditions such as clamped-clamped (C-C), clamped-hinged (C-H), and clamped-free (C-F) have been investigated. In addition, the obtained results are compared with the results in previous literature in order to validate present study, a good agreement was observed in the present results.

• 무역상무연구
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• 제45권
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• pp.191-238
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• 2010

The purpose of this paper is to make research on the trend of the worldwide medical device market, the trend of the medical device market in the major foreign countries, the present status of the medical device industry in Korea and Gangwon area, the present status of export competitive power and the SWOT analysis of competitive power of the medical device industry in Gangwon area, and the strengthening methods of export competitive power of the medical device industry in Gangwon area. As the research method, the questionaire for the strengthening of export competitive power of the medical device industry in Gangwon area was carried out from August 13 to Otober 22, 2009. The worldwide medical device market in 2008 is estimated at USD 210.2 billion, with the United States being the largest market, followed closely by Japan and Western Europe. In 2006, the worldwide export amount of medical devices recorded USD 121.1 billion and the worldwide import amount of medical devices recorded USD 126.3 billion. As of the end of 2008, the number of Korea's medical device manufacturers expanded to 1,726. The production amount of Korea's medical device industry in 2008 recorded 2,525 billion won, and the domestic market volume of medical devices in 2008 recorded 3,618 billion won. Korea's export amount of medical devices in 2008 recorded USD 1,132 million and recorded a 9.67% growth compared to the previous year, and the import amount of medical devices recorded USD 2,123 million and recorded a 1.43% reduction compared to the previous year. As of the end of 2008, the number of Gangwon area's medical device manufacturers expanded to 81. The production amount of Gangwon area's medical industry in 2008 recorded 380 billion won, and Gangwon area's export amount of medical devices recorded USD 269 million and recorded a 0.25% reduction compared to the previous year, and the import amount of medical devices recorded USD 3 million and recorded a 39.63% reduction compared to the previous year. According to the result analysis of the questionaire for the strengthening of export competitive power of medical device industry in Gangwon area(August 13~October 22, 2009), the competing country of the export medical device is the United States being the highest ranking. Comparing to the collective competitive power level 100 of the competing country, the collective competitive level of the export medical device is 60 below and 70-80 below being the highest ranking. Comparing to the quality level 100 of the United States, EU and Japan, the quality level of the export medical device is 80-90 below being the highest ranking. Comparing to the design level 100 of the United States, EU and Japan, the design level of the export medical device is 90-100 below being the highest ranking. Comparing to the technology level 100 of the United States, EU and Japan, the technology level of the export medical device is 80-90 below being the highest ranking. According to the SWOT analysis of competitive power of medical device industry in Gangwon area, the strength is the abundant expert manpower of the medical device in Wonju area. The weakness is the fragility of the brand recognition of the medical device industry. The opportunity is the demand increase of the new medical device owing to the advanced age of population. The threat is the difficulty of entry into overseas market owing to the request of the new specification certification of the medical device. In order to strengthen the export competitive power of the medical device industry in Gangwon area, the following measures should be taken by the government, local self-government body, related organization and medical device industry : the development of new technology and design, the enhancement of brand recognition. the acquisition of the foreign specification certification, the building of overseas distribution channel and after sales service channel, the positive participation in overseas medical device exhibition and opening of medical device exhibition, the training of expert manpower, the strengthening of overseas marketing, and the application of FTA and the establishment of counter measures against FTA. In conclusion, the medical device industry in Gangwon area has the difficulty in the entry into the overseas market owing to the shortage of overseas marketing capability. Therefore, the government and local self-government body should make the intensive and systematical support for overseas marketing of the medical device industry. For the support of overseas marketing, the government and local self-government body should provide positively the support of expenses for the acquisition of foreign specification certification, the support of participation in the overseas medical device exhibition, the despatch of market development mission, the increase of the support amount for R&D investment fund, and the training of expert manpower of medical devices.

• Wind and Structures
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• 제30권4호
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• pp.433-450
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• 2020

The strong turbulence characteristic of typhoon not only will significantly change flow field characteristics surrounding the large-scale wind turbine and aerodynamic force distribution on surface, but also may cause morphological evolution of coast dune and thereby form sand storms. A 5MW horizontal-axis wind turbine in a wind power plant of southeastern coastal areas in China was chosen to investigate the distribution law of additional loads caused by wind-sand coupling movement of coast dune at landing of strong typhoons. Firstly, a mesoscale Weather Research and Forecasting (WRF) mode was introduced in for high spatial resolution simulation of typhoon "Megi". Wind speed profile on the boundary layer of typhoon was gained through fitting based on nonlinear least squares and then it was integrated into the user-defined function (UDF) as an entry condition of small-scaled CFD numerical simulation. On this basis, a synchronous iterative modeling of wind field and sand particle combination was carried out by using a continuous phase and discrete phase. Influencing laws of typhoon and normal wind on moving characteristics of sand particles, equivalent pressure distribution mode of structural surface and characteristics of lift resistance coefficient were compared. Results demonstrated that: Compared with normal wind, mesoscale typhoon intensifies the 3D aerodynamic distribution mode on structural surface of wind turbine significantly. Different from wind loads, sand loads mainly impact on 30° ranges at two sides of the lower windward region on the tower. The ratio between sand loads and wind load reaches 3.937% and the maximum sand pressure coefficient is 0.09. The coupling impact effect of strong typhoon and large sand particles is more significant, in which the resistance coefficient of tower is increased by 9.80% to the maximum extent. The maximum resistance coefficient in typhoon field is 13.79% higher than that in the normal wind field.

• 한국지구과학회지
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• 제30권7호
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• pp.845-854
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• 2009

북한의 풍력발전 가능성을 조사하기 위한 첫 단계로 북한 지역에서의 30년 동안의 27개 지점의 지상관측자료 중 풍속과 풍향 자료를 이용하여 이 지역에서의 기후학적 바람 자원을 분석하였다. 바람자원 분석을 위해 풍속의 확률 밀도함수를 Weibull 함수로 가정하여 접근하였다. 지표로부터 50 m 고도에서 연중 평균 풍속이 4.0 m/s 이상인 지역은 대체적으로 개마고원 지역과 황해도 해안 지역이었다. 이 지역들은 비교적 바람 자원이 풍부한 것으로 나타났다. 풍속이 5 m/s 이상을 유지하는 지속시간이 가장 긴 계절은 봄이었고, 짧은 계절은 여름이었다. 관측 지점 중 장진과 양덕이 지속시간이 가장 길고 평균 풍속도 가장 큰 곳이었다.

• 대한기계학회논문집B
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• 제36권3호
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• pp.301-307
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• 2012

정밀한 물질분배기관인 인체 기관지의 기능을 이해하기 위해서는 호흡에서 발생하는 다양한 유동 및 형상 조건에서 압력손실특성을 파악하는 것이 필수적이다. 본 연구는 기관지 구조의 기본 단위인 분지관의 층류 흡기유동 압력손실을 수치해석을 통해 확인하였다. 인체 기관지에 대한 관찰에서 보고되는 비대칭 형상과 유량분배비율 범위 안에서 압력손실계수 K 는 Re 와 관의 길이만의 함수로 다음과 같이 표현이 가능하며 $K{\propto}Re^{-1}(\frac{L}{d})^{3/4}$, Re<100, $K{\propto}Re^{-1/2}\(\frac{L}{d}\)^{1/2}$, $Re\geq100$, 이는 대칭 분지관의 관계식과 동일한 것이다. 연속분지로 입구 유속분포가 편향될 경우 분지관 압력손실의 변화는 4% 미만이었으며 분지가 반복될수록 그 차이는 줄어들어 무시할 만하였다.

• 한국산학기술학회논문지
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• 제21권11호
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• pp.465-476
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• 2020

본 연구에서는 사회연결망 분석 기법을 활용해 무역 분야 연구의 동향과 지식구조를 입체적으로 파악했다. 이를 위해 2003년부터 2019년까지 국제통상연구, 무역학회지, Journal of Korea Trade의 3개 학술지에 수록된 1797개의 논문에서 4840개의 주제어를 추출해 분석을 실시했다. 분석 결과, 무역 연구의 주제어 분포는 다른 지적 네트워크와 마찬가지로 뚜렷한 멱함수 분포를 나타냈다. 학술지에 따라 상위 주제어에 다소의 차이가 나타났는데, Total Factor Productivity, Economic Growth, Korea-US FTA는 국제통상연구에서만 상위에 랭크됐다. Global Value Chain, Trust는 2011~2019년 기간에 새롭게 연구자들의 관심을 끈 주제어로 부상한 것으로 나타났다. E-Trade, WTO, Internationalization은 관심도가 근년에 올수록 줄어들었다. 기존 무역 분야 연구동향 분석은 서술적 방법에 의한 질적 분석이 대종을 이뤘으나, 본 연구는 사회 연결망 분석 기법을 활용한 양적 분석이라는 점에 의미가 있다.