• Structural Engineering and Mechanics
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• v.51 no.5
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• pp.867-891
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• 2014

An equivalent single layer trigonometric shear deformation theory taking into account transverse shear deformation effect as well as transverse normal strain effect is presented for static flexure of cross-ply laminated composite and sandwich plates. The inplane displacement field uses sinusoidal function in terms of thickness coordinate to include the transverse shear deformation effect. The cosine function in thickness coordinate is used in transverse displacement to include the effect of transverse normal strain. The kinematics of the present theory is much richer than those of the other higher order shear deformation theories, because if the trigonometric term (involving thickness coordinate z) is expanded in power series, the kinematics of higher order theories (which are usually obtained by power series in thickness coordinate z) are implicitly taken into account to good deal of extent. Governing equations and boundary conditions of the theory are obtained using the principle of virtual work. The closed-form solutions of simply supported cross-ply laminated composite and sandwich plates have been obtained. The results of present theory are compared with those of the classical plate theory (CPT), first order shear deformation theory (FSDT), higher order shear deformation theory (HSDT) of Reddy and exact three dimensional elasticity theory wherever applicable. The results predicted by present theory are in good agreement with those of higher order shear deformation theory and the elasticity theory.

• Journal of Distribution Science
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• v.13 no.9
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• pp.47-57
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• 2015

Purpose - The aim of this paper is to investigate the explanatory power of the Pecking-order theory (the cost of financing increases with asymmetric information) among Korean retail firms from the perspective of debt capacity. According to the Pecking-order theory, a firm's first preference is to use internal funds for its capital needs, its next preference is the issuance of debt, and its last preference is the issuance of equity; this is due to the information asymmetry problem between existing shareholders and investors. However, prior empirical studies, such as Lemmon and Zender (2010), argue that the entire sample test for the Pecking-order theory could be misleading due to the different levels of debt issuance capability of each of the individual firms; in fact, they confirm that the explanatory power of the Pecking-order theory improves after taking into account the differences in debt capacity of the U.S. firms they examined. This paper implements a case study approach among Korean retail firms to examine the relationship between debt capacity and the explanatory power of the Pecking-order theory in Korea. Research design, data, and methodology - This study uses the sample of public retail firms on the Korea Composite Stock Price Index (KOSPI) from the time period of 1990 to 2013. We gather related financial and accounting statements from the financial information firm WISEfn. Credit rating information is provided by the Korea Investor Service. We employ the models of Lemmon and Zender (2010) and Son and Kim (2013) to measure a firm's debt capacity. Their logit models use the rating dummy variable as a dependent variable and incorporate other firm characteristics as independent variables to estimate debt capacity. To test the Pecking-order theory, we adopt variants of the financing deficit model of Shyam-Sunder and Myers (1999). In the test of the Pecking-order theory, we consider all of the changes in total debt obligations, current debt obligations, and long-term debt obligations. Results - Our main contribution to the literature is our confirmation of the predicted relationship between debt capacity and the explanatory power of the Pecking-order theory among Korean retail firms. The coefficients on financing deficits become greater as a firm's debt capacity improves. This is consistent with the results of Lemmon and Zender (2010). The coefficients on the square of the financing deficits are also negative for the firms in the largest debt capacity group, which is also consistent with the predictions in prior literature. Conclusions - This study takes a case study approach by examining Korean retail firms. We confirm that the Pecking-order theory explains the capital structure of retail firms more appropriately, after taking into account the debt capacity of each firm. This result suggests the importance of debt capacity consideration in the testing of the Pecking-order theory. Our result also implies that there has been a potential underestimation of the explanatory power of the Pecking-order theory in existing studies.

• Journal of Power Electronics
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• v.10 no.6
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• pp.621-627
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• 2010

This paper presents a TSMST (Theory - Simulation - Measurement - Simulation - Theory) method for power electronics laboratory. The method successfully integrates theory, simulation and measurement, thus enabling better integration of student's knowledge and better usage of inadequate number of laboratory hours. Students are attracted with relatively simple tasks to be solved and modern, but economical laboratory equipment. A significant part of the assignments can be made at home, thus lowering the pressure on students to finish the tasks on time. The proposed method is described on three basic examples explaining characteristic phases of the TSMST method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.4 s.119
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• pp.448-454
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• 2007

In this paper, the game theory based power control for CDMA system is studied, which has attained intensive interest as a core artificial intelligent technology fur cognitive Radio and its efficiency is evaluated using performance metrics such as system throughput and fairness. Utility Function for joint user centric and network centric power control is defined and simulation results show that game theory based power control is far better than closed loop power control. The contribution of this raper is to formalize the game theory based power control toward the cognitive radio that recognizes and adapts to the radio communication environments.

• Journal of applied mathematics & informatics
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• v.26 no.1_2
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• pp.337-347
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• 2008

Based on social welfare maximum theory, the optimal scale of power plants entering generation power market being is researched. A static non-cooperative game model for short-term optimization of power plants with different cost is presented. And the equilibrium solutions and the total social welfare are obtained. According to principle of maximum social welfare selection, the optimization model is solved, optimal number of power plants entering the market is determined. The optimization results can not only increase the customer surplus and improve power production efficiency, but also sustain normal profits of power plants and scale economy of power production, and the waste of resource can also be avoided. At last, case results show that the proposed model is efficient.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.6
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• pp.678-682
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• 1999

In this paper, we propose the algorithm which can control active power and reactive power independently in Battery Energy Storage System. The proposed algorithm is based on the instantaneous power theory that the inner product of the voltage vector and current vector represents the active power and the cross product of those represents the reactive power, and it can control active power and reactive power independently. To verify the validity of the proposed algorithm, we make model of the real power system in th KERI and simulate this algorithm. As a result of this simulation, we verified that the proposed algorithm can control active power and reactive power independently.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2481-2483
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• 1999

This paper proposed the p-q-r coordinate system where the instantaneous active power p, and the two instantaneous reactive powers $q_{q}$, $q_{r}$ were defined. The three power components are linearly independent, so the compensation for the two instantaneous reactive powers leads to control the two components of the current space vector. With the theory, the neutral current of a three-phase four-wire system can be eliminated by only compensating the instantaneous reactive power using no energy storage element.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.888-893
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• 1998

In practice, not only the load current but also the load voltage may contain asymmetric and harmonic components. Instantaneous power using p-q theory is analyzed to have compensation of reactive power, harmonics and asymmetry at the same time. In this paper, the limitation of p-q theory by using only shunt or series active filter is analyzed. A new scheme is proposed to solve the above issues.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.445-450
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• 2008

The primary role of traction power systems is to provide reliable and continuous electrical energy to satisfy traction loads. AC traction substation transforms power from generation company and supply the power to the electric railway power line. Forced outage rate(FOR) of the equipment of substation should be used in the evaluation. This paper proposes the fast and easy way to evaluate by using Bayes' theory when a new equipment is added to the existing substation facility.

• Journal of the Optical Society of Korea
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• v.8 no.4
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• pp.149-155
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• 2004

Newly developed modal transmission-line theory(MTLT) is used to analyze rigorously the optical power distribution in grating-assisted directional couplers(GADCs) with three guiding channels. By defining a novel coupling efficiency ${\eta}$ amenable to the rigorous analytical solutions of modal transmission-line theory, we explicitly evaluate the power coupling and distribution of TM modes. The results reveal that the incident power is sensitively partitioned through three output channels in terms of such grating parameters as the grating period, the duty cycle, and the operating wavelength.