• STI Policy Review
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• 제6권1호
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• pp.1-23
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• 2015

Based on the work of Anand et al. (2013) we measure inclusive income growth, which combines growth in gross domestic product (GDP) per capita and growth in the equity of the income distribution. Extending the work of Causa et al. (2014), we estimate a dynamic simultaneous structural equations model of GDP per capita and inclusive income on panel data for 63 countries over the 1990-2013 period. We estimate both equations in error correction form by difference GMM (generalized method of moments). Among the explanatory variables of the level and the distribution of GDP per capita we include R&D (research and development) expenditure per capita. In OECD countries we obtain a large positive effect of R&D on GDP. R&D is found to have a positive effect on the social mobility index but its impact on the income equity index at first decreases, then switches around to become slightly positive in the long run. In non- OECD countries, R&D is found to decrease inclusive income, mostly through a negative growth effect but also because of a slightly increasing income inequity effect.

• 산경연구논집
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• 제6권4호
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• pp.27-37
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• 2015

Purpose - This study first explores the possible dynamic relationship between ownership structure and firm performance using a panel of 4,900 Chinese-listed small- and medium-sized enterprises (SMEs) from 1999 to 2012. Research design, data, and methodology - We address this issue through a dynamic panel model using a method of moments (GMM) technique and dynamic simultaneous equations to alleviate the potential endogenous problem: unobserved heterogeneity, simultaneity, and dynamic endogeneity. Results - Under the framework of dynamic endogeneity, firm performance has a significantly positive influence on ownership, but not vice versa. Ownership and performance can be explained by their owned lagged values, respectively. Moreover, intertemporal endogeneity exists among ownership, investment, and performance through the application of system dynamic equations, which implies that the relationship among ownership structure, investment, and firm performance is dynamic by nature. Conclusions - This study also significantly contributes to a better understanding of dynamic corporate governance by providing further empirical evidence from the largest capital market in the Asian region.

• 대한산업공학회지
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• 제24권4호
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• pp.475-483
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• 1998

Structural changes in an economy system bring about serious problems in establishing economic policies. The boom of middle-east export, the oil shock, and the recent dollar crisis in Korean economy are such examples. Hence, it is necessary to identify and estimate those structural changes. This study focuses on an output and price and analyzes structural changes in aggregate demand and supply. The aggregate demand and supply structures are described by conventional dynamic simultaneous equations model, where each structural change is represented by dummy variables and estimated by the proposed Bayesian method. By applying this model to Korean output and price, structural changes in the aggregate demand and supply are analyzed.

• 대한산업공학회지
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• 제23권3호
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• pp.545-557
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• 1997

This paper deals with dynamic optimal pricing for new products by a firm which maximizes the discounted profit stream of it's own in a duopoly. The problem is constructed as differential games and dynamic optimization theory. Cost is assumed to decline as time goes on. A modified customer's choice model is formulated as a diffusion model and we solve a dynamic optimization problem by adopting the diffusion model. Since this paper focus on deriving real prices not showing a time trend, we formulate recursive form equations of costate variables(shadow price) and a simultaneous equation of price. Hence we derive a dynamic optimal pricing model for using in real market. In particular, we construct a dynamic optimal pricing model in the case that there are benefits from not only new subscribers but also previous subscribers. We analyze instant camera market in U.S.A(1976-1985) by utilizing the above model.

• 응용통계연구
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• 제11권1호
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• pp.65-81
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• 1998

많은 실증분석에 사용되고 있는 연립방정식모형은 연구대상분야의 구조를 더욱 현실에 가깝게 표현하고 또 상세한 분석을 위해 점차 복잡해지고 대형화되어 가는 추세다. 그러나 이러한 다중방정식체계의 설정시, 각 회귀방정식이 결합되어 동시에 추정될 때 발생할 수도 있는 모형체계의 구조적 불안정성으로 인해 추정된 모형의 사용 및 그에 따른 분석은 오류를 가져올 수 있다. 특히 시뮬레이션 수행이 무의미해질 가능성이 있음에도 연립방정식모형을 사용하는 대부분의 연구들이 이러한 모형의 구조적 안정성문제를 간과하고 있는 실정이다. 따라서 본 연구에서는 동태적 관점에서 모형체계의 안정성 진단을 위한 조건을 제시하여 보고, 실제의 연립방정식모형을 예로 들어 적용시켜 본 후 그 결과가 모형의 구조적 특징에 관해 어떠한 유용한 정보를 제공하여 주는가를 추가로 분석하여 보았다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1996년도 봄 학술발표회 논문집
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• pp.111-118
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• 1996

Dynamic load models which show the practical behavior of truss bridge subjected to moving train load are presented. Three basically approaches are available for evaluating structural response to dynamic effects : moving force, moving mass, and influence moving force and mass. Simple warren truss bridge model is selected in this research, and idealized lumped mass system, modelled as a planar structure. In the process of dynamic analysis, the uncoupled equation of motion is derived from simultaneous equation of the motion of truss bridge and moving train load. The solution of the uncoupled equations of motion is solved by Newmark-$\beta$ method. The results show that dynamic response of moving mass and static analysis considering the impact factor specified in the present railway bridge code was nearly the same. Generally, the dynamic response of moving force is somewhat greater than that of moving mass. The dynamic load models which are presented by this study are obtained relatively adequate load model when apply to a truss bridge.

• Steel and Composite Structures
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• 제9권5호
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• pp.473-497
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• 2009

For the spatially coupled free vibration analysis of composite box beams resting on elastic foundation under the axial force, the exact solutions are presented by using the power series method based on the homogeneous form of simultaneous ordinary differential equations. The general vibrational theory for the composite box beam with arbitrary lamination is developed by introducing Vlasov°Øs assumption. Next, the equations of motion and force-displacement relationships are derived from the energy principle and explicit expressions for displacement parameters are presented based on power series expansions of displacement components. Finally, the dynamic stiffness matrix is calculated using force-displacement relationships. In addition, the finite element model based on the classical Hermitian interpolation polynomial is presented. To show the performances of the proposed dynamic stiffness matrix of composite box beam, the numerical solutions are presented and compared with the finite element solutions using the Hermitian beam elements and the results from other researchers. Particularly, the effects of the fiber orientation, the axial force, the elastic foundation, and the boundary condition on the vibrational behavior of composite box beam are investigated parametrically. Also the emphasis is given in showing the phenomenon of vibration mode change.

• Journal of Mechanical Science and Technology
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• 제17권6호
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• pp.844-853
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• 2003

In this paper, a dynamic analysis of the reciprocating compression mechanism of a small refrigeration compressor is performed. In the problem formulation of the mechanism dynamics, the viscous frictional force between the piston and the cylinder wall is considered in order to determine the coupled dynamic behaviors of the piston and the crankshaft. Simultaneous solutions are obtained for the equations of motion of the reciprocating mechanism and the time-dependent Reynolds equations for the lubricating film between the piston and the cylinder wall and for the oil films on the journal bearings. The hydrodynamic forces of the journal bearings are calculated by using a finite bearing model along with the Gumbel boundary condition. A Newton-Raphson procedure is employed in solving the nonlinear equations for the piston and crankshaft. The developed computer program can be used to calculate the complete trajectories of the piston and the crankshaft as functions of the crank angle under compressor-running conditions. The results explored the effects of the radial clearance of the piston, oil viscosity, and mass and mass moment of inertia of the piston and connecting rod on the stability of the compression mechanism.

• 대한기계학회논문집A
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• 제26권12호
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• pp.2647-2655
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• 2002

This research presents an analytical model to investigate the stability due to the ball bearing waviness i n a rotating system supported by two ball bearings. The stiffness of a ball bearing changes periodically due to the waviness in the rolling elements as the rotor rotates, and it can be calculated by differentiating the nonlinear contact forces. The linearized equations of motion can be represented as a parametrically excited system in the form of Mathieu's equation, because the stiffness coefficients have time -varying components due to the waviness. Their solution can be assumed as a Fourier series expansion so that the equations of motion can be rewritten as the simultaneous algebraic equations with respect to the Fourier coefficients. Then, stability can be determined by solving the Hill's infinite determinant of these algebraic equations. The validity of this research is proved by comparing the stability chart with the time responses of the vibration model suggested by prior researches. This research shows that the waviness in the rolling elements of a ball bearing generates the time-varying component of the stiffness coefficient, whose frequency is called the frequency of the parametric excitation. It also shows that the instability takes place from the positions in which the ratio of the natural frequency to the frequency of the parametric excitation corresponds to i/2 (i=1,2,3..).

• 응용통계연구
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• 제27권5호
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• pp.797-808
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• 2014

건전성과 신뢰성이 높은 기업에 선별 투자가 이루어지면 이는 기업의 가치 상승으로 이어지므로 상위 등급의 기업 가치 변동 간 상관성 및 동적 특성에 대한 연구의 필요성이 증대하게 되었다. 본 연구에서는 증권거래소 분류 기업지배구조 등급별 주식수익의 중장기 변동성향을 분석하기 위한 연립방정식 통계모형을 설정하였다. 외생적 충격에 의해 등급별 주식수익에 일어난 변화는 시간이 흐르면서 완만히 조정되어 가는 구조적 특징을 공통적으로 가지고 있으며, 변동 과정이나 성향도 등급 간에 별다른 차이가 없는 것으로 판명되었다.