• Journal of Korea Trade
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• v.26 no.7
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• pp.1-18
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• 2022

Purpose - Recent international studies have largely focused on measuring the welfare gains from increased trade varieties. To adequately capture the variety gains, it is of importance to estimate the elasticity of substitution between varieties of trade goods because it is one of the key parameters to determine the magnitude of the variety gains. Using the import data of South Korea, this paper shows that the elasticities vary substantially across the estimators, which affects the magnitude of the gains from trade. Design/methodology - Empirical studies working on the gains from trade variety have heavily depended on the estimation methods for the elasticity of substitution between trade varieties, developed by Feenstra (1994) and refined by Broda and Weinstein (2006). We estimate and compare the estimated elasticities for 8,945 HS 10 goods of South Korea, obtained from the three estimation methods: Feenstra's weighted least square (F-WLS), Feenstra's feasible generalized least square (F-FGLS), and Broda and Weinstein's feasible generalized least square (BW-FGLS). Findings - Using the estimated elasticities from the F-FGLS, considered as a suitable estimator, A typical Korean consumer saved 228 dollars per year by the greater access to new import varieties. This leads to gains from imported variety of 2.06% of GDP. In 2017, a typical Korean consumer would gain by 611 dollars, compared with 2000. China is the country with the largest contribution (28.4%), followed by Japan and USA. About 50% of all the welfare gains come from the imports from the three main trade partners. The Southern Asian countries are more important to the South Korean welfare gain than the Western European countries. Originality/value - Existing studies have chosen one of the methods without any criterion for the choice and then estimated the elasticities of substitution between varieties of trade goods. This paper focuses on the estimation specifications and methods as the cause of the disparity in estimated elasticities and welfare gains from trade variety. According to the Ramsey RESET and White tests, the F-FGLS estimates are relatively better compared to the F-WLS and BW-FGLS estimates. As another contribution, this paper provides the first measure of the welfare gains from trade variety for South Korea, using the estimated elasticities of substitution between trade varieties.

• International Journal of Contents
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• v.3 no.3
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• pp.20-25
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• 2007

Standards impact the economy in various ways. Moreover, intense competition exists between a variety of standards in this era of globalization. This paper quantifies the economic effect of multiple standards in the Information Communications and Technology (ICT) sector. Thus, it identifies and specifies which standard applies when economic gains exist. A model is developed which quantifies the magnitude of the economic effect of multiple standards as compared with a single standard or no standard. The model allows for both the micro- and macroeconomic gains from standardization to be quantified. Preliminary estimates indicate that at the macro level the multiple standards multiplier is approximately three. That is for every dollar invested, the gain is on the order of three dollars. Although not as robust. preliminary results indicated a similar economic gain at the micro level Overall, multiple standards dominate a single standard. This paper applies the model to IMT-2000, an example of multiple standards, to demonstrate this approach to quantify the standards economic effect.

• Environmental and Resource Economics Review
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• v.17 no.1
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• pp.23-49
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• 2008

In this paper, we estimate whether changes in the economic environment a firm operates in affects technical efficiency. Since efficiency gains can manifest themselves in a variety of ways, we estimate for efficiency gains on annual generating plants input demand for expenses and fuel use. We find that generating plants reduced their workers and costs respectively by 6.8% in 1999 and 37.9% in 2001. However, they didn't show any systematic caloric consumption changes facing various economic environmental shocks. These results suggest that restructuring brought efficiency gains by replacing regulated monopoly with a more competitive firms in the context of the Korean electricity market.

• Proceedings of the KIEE Conference
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• 2004.10a
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• pp.173-175
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• 2004

This paper presents a novel design of a self tuning PI controller of induction motor using fuzzy control. In this approach, the fuzzy tuning of a PI controller gains is achieved through fuzzy rules deduced from many robustness simulation tests applied to several induction motors, for a variety of operating conditions such as response to speed command from standstill, step load torque application and speed variations, with nominal parameters and an changed rotor resistance, self inductance and inertia. Simulation results on a speed controller of induction motor are presented to show the effectiveness of the proposed gain tuner. And this controller is better than the fixed gains one in terms of robustness, even under great variations of operating conditions and load disturbance.

• Journal of Communications and Networks
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• v.17 no.6
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• pp.549-557
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• 2015

Mobile cellular networks are becoming increasingly complex to manage while classical deployment/optimization techniques and current solutions (i.e., cell densification, acquiring more spectrum, etc.) are cost-ineffective and thus seen as stopgaps. This calls for development of novel approaches that leverage recent advances in storage/memory, context-awareness, edge/cloud computing, and falls into framework of big data. However, the big data by itself is yet another complex phenomena to handle and comes with its notorious 4V: Velocity, voracity, volume, and variety. In this work, we address these issues in optimization of 5G wireless networks via the notion of proactive caching at the base stations. In particular, we investigate the gains of proactive caching in terms of backhaul offloadings and request satisfactions, while tackling the large-amount of available data for content popularity estimation. In order to estimate the content popularity, we first collect users' mobile traffic data from a Turkish telecom operator from several base stations in hours of time interval. Then, an analysis is carried out locally on a big data platformand the gains of proactive caching at the base stations are investigated via numerical simulations. It turns out that several gains are possible depending on the level of available information and storage size. For instance, with 10% of content ratings and 15.4Gbyte of storage size (87%of total catalog size), proactive caching achieves 100% of request satisfaction and offloads 98% of the backhaul when considering 16 base stations.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.11 no.4
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• pp.91-101
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• 2016

This research focused on searching the specialized factors which affect the cyber universities' performance. This research was approached from three perspective of professor, graduation and employment, and brand image to embody the cyber universities' performance. We drew five factors of contents variety, contents quality, practical orientation of contents, lecture presence, and learning management as the Influencing factors of cyber universities' performance. We proved our research model by analyzing 170 questionnaires which were completed by college students who were studying at cyber universities in China. The results of analysis are showed as below: 1) The level of contents variety can affect the cyber universities' performance; higher level gains better outcomes. 2) The level of contents quality can affect the cyber universities' performance; better quality gains better outcomes. 3) The level of practical orientation of contents can affect the cyber universities' performance; the higher the better. 4) The level of lecture presence can affect the cyber universities' performance; the stronger the better. 5) The level of learning management can affect the cyber universities' performance; the higher the better.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.4
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• pp.31-40
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• 2013

This paper proposes a performance improvement of synchronous generator using exciter control with field coils parameter estimation technique. In general, the generator excitation system controller uses the PID controller. When the Field winding impedance changed, the PID gains must be changed. General method is difficult to apply varying capacity of the synchronous generator. The proposed control method determine automatically measure the internal impedance of the synchronous generator's exciter and configure the controller. This method can be applied regardless of the generator capacity. So it is possible to apply a variety of synchronous generator systems. The validity of the proposed algorithm is verified by simulations and experiments.

• The Korean Journal of Financial Management
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• v.8 no.2
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• pp.165-208
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• 1991

This paper develops an intertemporal general equilibrium model of asset pricing with taxes under the noisy and the incomplete information structure and examines theoretically the stochastic behavior of general equilibrium asset prices in a one-good, production, and exchange economy in continuous time markets. The important features of the model are its integration of real and financial markets and the analysis of the effects of differential tax rates between ordinary income and capital gains. The model developed here can provide answers to a wide variety of questions about stochastic structure of asset prices and the effect of tax on them.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1847-1852
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• 2003

Ultrasonic motors have many excellent performances. A variety of ultrasonic motors has been developed and used as an actuator in motion control systems. However, this motor has nonlinear characteristics. Therefore, it is difficult to achieve the precise position control system incorporating with the ultrasonic motor. This paper describes a position control scheme for traveling-wave type ultrasonic motor using a pseudo-derivative control with feedforward gains (PDFF) controller designed by the coefficient diagram method (CDM). The PDFF control system satisfies both the tracking and regulation performances, which are the most important for the precise position control system. The CDM is shown to be an efficient and simple method to design the parameters of PDFF controller. The effectiveness of the proposed control system is demonstrated by experiments.

• Genomics & Informatics
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• v.7 no.3
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• pp.148-151
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• 2009

Generally, larger sample size leads to a greater statistical power to detect a significant difference. We may increase the sample size for both case and control in order to obtain greater power. However, it is often the case that increasing sample size for case is not feasible for a variety of reasons. In order to look at change in power as the ratio of control to case varies (1:1 to 4:1), we conduct association tests with simulated data generated by PLINK. The simulated data consist of 50 disease SNPs and 300 non-disease SNPs and we compute powers for disease SNPs. Genetic Power Calculator was used for computing powers with varying the ratio of control to case (1:1, 2:1, 3:1, 4:1). In this study, we show that gains in statistical power resulting from increasing the ratio of control to case are substantial for the simulated data. Similar results might be expected for real data.