• Journal of the Korea Safety Management & Science
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• v.6 no.1
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• pp.125-133
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• 2004

Greeting the globalization and information period of 21C, the improvement of the distributional system structure and modernization of publishing distribution are the seriously required periodic assignments for the publishing industry that is a national knowledge and culture industry to be equipped with the core competitiveness. First, it is to found a large distributional organization that is able to provide total logistics services in time that is essential to the publishing company and bookstore. Second, it is to have a logistics service to act up to the variable requirements of customers such as publishing companies and bookstores under the rapidly changing distribution environment. Third, it is to provide the standardized information of publishing distribution. It is needed to establish a total distributional center in collaboration to satisfy the requirements of publishing industry as above. By doing this work, structure of the publishing distribution system can be improved and its constitution can be strengthen, and it is possible not only to construct a stable supply system but also to realize an information-based system in the publishing industry with the construction of information system and its utilization. Furthermore, the application of RFID in the publishing distribution is essentially required to provide the symbolic model and logistics infrastructure into the 'Paju publishing culture information industrial complex'. It could be possible by growing the international recognition regarding distribution environment and strengthening the international competitiveness in the period of the ""Open door".

• Journal of the Korean Society of Industry Convergence
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• v.21 no.1
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• pp.29-36
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• 2018

Low pressure casting process for unidirectional carbon fiber reinforced aluminum (UD-CF/Al) composites which is an infiltration route of molten Al into porous UD-CF preform has been a cost-effective way to obtain metal matrix composites (MMCs) but, easy to cause non-uniform fiber distribution as CF clustering. Such clustered CFs have been a problem to decrease the density and thermal conductivity (TC) of composites, due to the existence of pores in the clustered area. To obtain high thermal performance composites for heat-sink application, the relationship between fiber distribution and porosity has to be clearly investigated. In this study, the CF distribution was evaluated with quantification approach by using two-dimensional spatial distribution method as local number 2-dimension (LN2D) analysis. Note that the CFs distribution in composites sensitively changed by sizes of Cu bridging particles between the CFs added in the UD-CF preform fabrication stage, and influenced on only $LN2D_{var}$ values.

• Journal of the Korean Data and Information Science Society
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• v.9 no.2
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• pp.289-298
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• 1998

We investigate the distribution of likelihood ratio test(LRT) of null hypothesis a sample is from single gamma with unknown shape and scale against the alternative hypothesis a sample is from a mixture of two gammas, each with unknown scale and unknown (but equal) scale. To obtain stable maximum likelihood estimates(MLE) of a mixture of two gamma distributions, the EM(Dempster, Laird, and Robin(1977))and Modified Newton(Jensen and Johansen(1991)) algorithms were implemented. Based on EM, we made a simple structure likelihood equation for each parameter and could obtain stable solution by Modified Newton Algorithms. Simulation study was conducted to investigate the distribution of LRT for sample size n = 25, 50, 75, 100, 50, 200, 300, 400, 500 with 2500 replications. To determine the small sample distribution of LRT, I considered the model of a gamma distribution with shape parameter equal to 1 + f(n) and scale parameter equal to 2. The simulation results indicate that the null distribution is essentially invariant to the value of the shape parameter. Modeling of the null distribution indicates that it is well approximated by a gamma distribution with shape parameter equal to the quantity $0.927+1.18/\sqrt{n}$ and scale parameter equal to 2.16.

• Journal of Korean Society of Transportation
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• v.28 no.6
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• pp.159-166
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• 2010

Trip distribution is to connect travel demand for each OD pair based on travel cost, trip production and attraction derived from trip generation step. In real world the travel cost is a function of travel demand, but existing models could not fully consider such functional relation between travel cost and demand, which leads to an equilibrium in trip distribution model. This paper proves the equilibrium trip distribution by using gravity model. In order to obtain such equilibrium this paper also presents a solution algorithm based on fixed point theorem. The algorithm will be tested with an example and confirmed the equilibrium solution of trip distribution.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2208-2218
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• 2017

To resolve overload in a distribution system, a distribution system operator (DSO) often performs a load transfer using normally open tie points and switches in the distribution line. During this process, the distribution system is momentarily operated in closed-loop operation. A closed-loop current in the distribution system can cause a power failure due to excess breaking current in the circuit breakers and reclosers. Therefore, it is necessary to calculate the closed-loop current exactly. However, if there are a large number of distributed generation (DG) systems in the distribution system, such as energy storage systems (ESS), they might obstruct the closed-loop operation based on bidirectional power flow. For quick and precise operation of a closed-loop system, the ESS has to regulate the power generation while satisfying closed-loop operation in the worst cases. We propose a strategy for balanced power regulation of an ESS. Simulations were carried out using PSCAD/EMTDC, and the results were compared with calculation results.

• Journal of the Korean Society of Safety
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• v.33 no.2
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• pp.14-20
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• 2018

In this study, we analyze the current status of major disasters in distribution works and propose safety measures through the distribution live-line work method and electric shock risk assessment. The result of analyzing the ratio of electric shocks to the occurrence of industrial accidents in the recent 13 years shows that the death rate is higher than other industries, especially the construction industry occupying most of the disaster, and it is higher than the collapse disaster. We analyze statistic data of 101 victims selected as core words of live work, distribution line, pole and 22.9 kV in the investigation report of major accident of electric shock fatal from 2001 to 2014. The safety measure was established through the risk assessment of the distribution method using the standard model of the risk assessment based on the results of electric shock analysis on the distribution line. In order to prevent the electric shock accident which is recently being discussed, the risk assessment procedure were carried out in the above-mentioned 22.9kV special high voltage live-line operation method. We derived the risk reduction plan for the distribution line from the results of the major accidents statistic and demonstration of the line works.

• Journal of Communications and Networks
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• v.18 no.5
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• pp.688-698
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• 2016

In this paper, we investigate the achievable sum rate and energy efficiency of downlink massive multiple-input multiple-output antenna systems with zero-forcing precoding, by taking into account the randomness of user locations. Specifically, we propose two types of non-uniform user distributions, namely, center-intensive user distribution and edge-intensive user distribution. Based on these user distributions, we derive novel tight lower and upper bounds on the average sum rate. In addition, the impact of user distributions on the optimal number of users maximizing the sum rate is characterized. Moreover, by adopting a realistic power consumption model which accounts for the transmit power, circuit power and signal processing power, the energy efficiency of the system is studied. In particular, closed-form solutions for the key system parameters, such as the number of antennas and the optimal transmit signal-to-noise ratio maximizing the energy efficiency, are obtained. The findings of the paper suggest that user distribution has a significant impact on the system performance: for instance, the highest average sum rate is achieved with the center-intensive user distribution, while the lowest average sum rate is obtained with the edge-intensive user distribution. Also, more users can be served with the center-intensive user distribution.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.2042-2048
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• 2014

In medium voltage electrical distribution networks, reforming the loss reduction is important, and in line with this, the issue of system engineering and use of proper equipment Expansion of distribution systems results in higher system losses and poor voltage regulation. Therefore, an efficient and effective distribution system has become more important. So, proper selection of conductors in the distribution system is crucial as it determines the current density and the resistance of the line. Evaluation of aging conductors for losses and costs imposed in addition to the careful planning of technical and economic networks can be identified in the network design. In this paper the use of imperialist competitive algorithm; genetic algorithm; is proposed to optimal branch conductor selection and reconstruction in radial distribution systems planning. The objective is to minimize the overall cost of annual energy losses and depreciation on the cost of conductors to improve productivity given the maximum current carrying capacity and acceptable voltage levels. Simulations are carried out on 69-bus radial distribution network using genetic algorithm approaches to show the accuracy as well as the efficiency of the proposed solution technique.

• Journal of Distribution Science
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• v.18 no.5
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• pp.61-70
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• 2020

Purpose: The aim of this paper is to investigate whether labor unions are the main determinants of advertising expenditures and whether market competition has an impact on the relation between labor unions and advertising expenditures, focusing on distribution firms. Research design, data, and methodology: Using 914 observations of KOSPI market from 2001 to 2009 in distribution firms, this paper examines whether labor union is related to advertising expenditures, focusing on distribution firms. For this, this paper employs not only OLS regressions method but also 2SLS regressions method in which Female_Ratio(percentage of female employees) is used as instrumental. Results: This paper finds that in the distribution firms, labor union, as a major stakeholder of the company is, in terms of statistic, negatively associated with advertising expenditures. Also, market competition, in this paper, doesn't have real impact on the relation between labor unions and advertising expenditures. Conclusions: This paper presents the influence of labor unions, as a major factor in determining advertising expenditures. An executive who understands that as the amount of advertising expenditure increases, the total pie of wages to be attributed to the members of labor union will decrease.

• Journal of Distribution Science
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• v.18 no.9
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• pp.5-11
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• 2020

Purpose: We sought to investigate the operation status of internal accounting control systems in the distribution and service industries and verify whether investing in internal accounting personnel significantly influences the quality of the companies' financial reporting. Research design, data and methodology: We identified descriptive statistics and performed a univariate analysis. Furthermore, a regression analysis verified the impact of investing in internal accounting personnel on the absolute value of discretionary accruals, a proxy for financial reporting quality. Results: Distribution and service companies allocated a significantly higher number of accountants to their internal accounting control systems than companies in other industries. We also confirmed that the absolute value of discretionary accruals significantly decreased as the average working experience of internal accounting personnel in distribution and service companies, in months, increased. Conclusions: In this study, we confirmed that distribution and service companies are devoting efforts to establishing internal accounting control systems and found that financial reporting quality is more effectively controlled as companies allocate more experienced personnel in their internal accounting control system.