• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.1
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• pp.8-20
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• 2013

This paper deals with the concept design of HVDC system for controlling AC network reactive power. HVDC system can control active power and reactive power and the control concept of reactive power is similar to SVC(Static Var Compensator). Reactive power is controlled by adjusting firing angle of HVDC system under the condition that AC filters are switched. Reactive power depends on AC voltage condition, considering the steady-state and transient state to maintain the stable operation of AC network in the viewpoint of voltage stability. Therefore, in the design stage of HVDC, the reactive power required in the AC network must be considered. For the calculation of operation angle in HVDC system, the expected reactive power demand and supply status is examined at each AC system bus. The required reactive power affects the determination of the operation angle of HVDC. That is, the range of "control deadband" of operation angle should have the capability supplying the required reactive power. Finally, the reactive power control concepts is applied to 1GW BTB Pyeongtaek-Dangjin HVDC system.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1859-1864
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• 2004

An effective methodology is reported for the optimal design of multisite batch production/transportation and storage networks under uncertain demand forecasting. We assume that any given storage unit can store one material type which can be purchased from suppliers, internally produced, internally consumed, transported to or from other plant sites and/or sold to customers. We further assume that a storage unit is connected to all processing and transportation stages that consume/produce or move the material to which that storage unit is dedicated. Each processing stage transforms a set of feedstock materials or intermediates into a set of products with constant conversion factors. A batch transportation process can transfer one material or multiple materials at once between plant sites. The objective for optimization is to minimize the probability averaged total cost composed of raw material procurement, processing setup, transportation setup and inventory holding costs as well as the capital costs of processing stages and storage units. A novel production and inventory analysis formulation, the PSW(Periodic Square Wave) model, provides useful expressions for the upper/lower bounds and average level of the storage inventory. The expressions for the Kuhn-Tucker conditions of the optimization problem can be reduced to two sub-problems. The first yields analytical solutions for determining lot sizes while the second is a separable concave minimization network flow subproblem whose solution yields the average material flow rates through the networks for the given demand forecast scenario. The result of this study will contribute to the optimal design and operation of large-scale supply chain system.

• Plant Journal
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• v.10 no.4
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• pp.35-41
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• 2014

The height and capacity of the thermal storage tank can be decided by the altitude and heat load of the heat supply area. Evaporation in heat pipe can be prevented by pressurizing it with the hydraulic head of the thermal storage tank. In addition, it absorbs the expanded volume from the temperature changes and supplies water to the pipelines in case of the shortage of water. One of the most important roles of the thermal storage tank is a stable heat supply facility. It can control the heat demand by accumulating the surplus heat and supplying in changing heat demand time. The purpose of this thesis is to be helpful for the operation and maintenance of the thermal storage tanks. The study has been carried out for 18 thermal storage tanks, which have been used polyurethane foam as insulation, among 27 tanks in district heating plants. The characteristics of the insulation materials, the reasons for the damages of the insulation and how impact the insulation damages to the corrosion of the thermal storage tank have been studied.

• Journal of Technology Innovation
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• v.26 no.4
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• pp.173-198
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• 2018

In this paper, we analyze the determinants of the adoption of industrial robots using the data from 42 countries, and thereby examine the factors underlying the rapid expansion of industrial robots in Korea. To this end, the industrial robot data for the years 2001-2016 were drawn from the World Robotics dataset of the International Federation of Robotics (IFR). The explanatory variables included labor market environment variables and innovation capacity variables extracted from the dataset of the relevant international organizations. For data analysis, the Arellano-Bond dynamic panel analysis was performed to control for the endogeneity problem of some explanatory variables. The empirical results confirmed the exceptionally rapid expansion of industrial robots in Korea as compared to other countries, even when considering the national income level, employment cost, and innovation capacity. This phenomenon could be attributed to both the demand-side and supply-side factors. For one thing, changes in the labor market environment, such as an increase in employment costs, have led to an increase of the corporate demand for industrial robots. For another, the supply-side factors, such as an increase in the capital intensity and innovation capacity of companies, have also contributed to the widespread adoption of industrial robots.

• Journal of Electrical Engineering and Technology
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• v.13 no.3
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• pp.1069-1078
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• 2018

Demand response (DR) programs give opportunity to consumers to manage their electricity bills. Besides, distribution system operator (DSO) is interested in using DR programs to obtain technical and economic benefits for distribution network. Since small consumers have difficulties to individually take part in the electricity market, an entity named demand response provider (DRP) has been recently defined to aggregate the DR of small consumers. However, implementing DR programs face challenges to fairly allocate benefits and payments between DRP and DSO. This paper presents a procedure for modeling the interaction between DRP and DSO based on a bilevel programming model. Both DSO and DRP behave from their own viewpoint with different objective functions. On the one hand, DRP bids the potential of DR programs, which are load shifting and load curtailment, to maximize its expected profit and on the other hand, DSO purchases electric power from either the electricity market or DRP to supply its consumers by minimizing its overall cost. In the proposed bilevel programming approach, the upper level problem represents the DRP decisions, while the lower level problem represents the DSO behavior. The obtained bilevel programming problem (BPP) is converted into a single level optimizing problem using its Karush-Kuhn-Tucker (KKT) optimality conditions. Furthermore, point estimate method (PEM) is employed to model the uncertainties of the power demands and the electricity market prices. The efficiency of the presented model is verified through the case studies and analysis of the obtained results.

• Korean Journal of Construction Engineering and Management
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• v.4 no.3 s.15
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• pp.85-94
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• 2003

The goal of enterprises is to make a profit. They should change and evolve themselves according to various customers' demand and developing information technology. The construction industry has not been used to such a change of business environment, although it has a long history. So it needs a new management system that accepts the various demands of construction participants and keeps pace with the evolving environment where is replaced by high-valued one. In this point, this research's objective is to apply SCM which shows visible outcome in the manufacturing industry, to the construction industry. This study regards the concept of SCM not as a simple management method, but as a comprehensive one. In other words, SCM is composed of three viewpoints; control, organization and information technology. SCM is to improve process by new management method, to benefit each other by strategical cooperation among participants, and to make information delivery and saving system for maintaining the relationship.

• Journal of Mechanical Science and Technology
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• v.16 no.12
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• pp.1633-1642
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• 2002

Uninterrupted power supply has become indispensable during the maintenance task of active electric power lines as a result of today's highly information-oriented society and increasing demand of electric utilities. The maintenance task has the risk of electric shock and the danger of falling from high place. Therefore it is necessary to realize an autonomous robot system using electro-hydraulic manipulator because hydraulic manipulators have the advantage of electric insulation. Meanwhile it is relatively difficult to realize autonomous assembly tasks particularly in the case of manipulating flexible objects such as electric lines. In this report, a discrete event control system is introduced for automatic assembly task of electric lines into sleeves as one of the typical task of active electric power lines. In the implementation of a discrete event control system, LVQNN (linear vector quantization neural network) is applied to the insertion task of electric lines to sleeves. In order to apply these proposed control system to the unknown environment, virtual learning data for LVQNN is generated by fuzzy inference. By the experimental results of two types of electric lines and sleeves, these proposed discrete event control and neural network learning algorithm are confirmed very effective to the insertion tasks of electric lines to sleeves as a typical task of active electric power maintenance tasks.

• Korean Institute of Interior Design Journal
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• v.20 no.2
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• pp.156-166
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• 2011

A studio type urban lifestyle housing was recently introduced as a new urban multi-housing typology. It was particularly created to meet the increasing housing demand of one-person households due to the population change and the shortage of housing supply. However, some concerns have been raised, because the government's policy has been focused on expanding housing supply by easing certain legal regulations in construction. Poorly planned and managed urban lifestyle housings might degrade living conditions for one-person households and ultimately harm urban environments. As such, this research is conducted to investigate the design characteristics of the studio type urban lifestyle housing from selected construction precedents in Seoul. Critical evaluations are made for the facilities and uses in site plans, unit plans, and shared public spaces. As a result, problem areas are found in the lack of design varieties, privacy protection in units, control of natural environment conditions, and the absence of community spaces. Improvement strategies can be suggested by comparing with some overseas' housing precedents: Design variations can be extended through flexible structure, facility, and furniture systems. Privacy and natural environment can be controled through the integration of interior space configurations and exterior envelope systems. The housing policy needs to be reconsidered to improve a variety in design, residents' social interaction, security, and management. Thereby, the studio type urban lifestyle housing should be holistically approached in terms of design and policy to enrich urban living experiences by residents and communities.

• Transactions of the Korean hydrogen and new energy society
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• v.15 no.4
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• pp.324-332
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• 2004

According to the rapid depletion of the fossil fuels, the electricity and hydrogen will gradually take charge of the future energy supply. Especially, in order to control the supply and demand of electricity, energy storage medium is necessary and this could be solved by the combination of water electrolysis and fuel cell. Although electricity can be generated from such alternative energies as hydropower, nuclear, solar, and wind-power resources, alternative energy storage medium is also required since regenerative energies, solar and wind-powers, are intermittent energy resources. In this regard, hydrogen production from water electrolysis was recognized as a superb method for electricity storage. In this work, the current development and economic status of alkaline, solid polymer, and high temperature electrolysis were reviewed, and then the practical use of water electrolysis technology were discussed.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.5
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• pp.554-561
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• 2014

Hybrid wind Diesel stand-alone power systems are considered economically viable and effective to create balance between production and load demand in remote areas where the wind speed is considerable for electric generation, and also, electric energy is not easily available from the grid. In Wind diesel hybrid system, the wind energy system is the main constitute and diesel system forms the back up. This type of hybrid power system saves fuel cost, improves power capacity to meet the increasing demand and maintains the continuity of supply in the system. Problem we face in this system is that even after producing enough power through wind turbine system, considerable portion of this power needs to be dumped due to short term oversupply of power and to maintain the frequency within close tolerances. As a result remaining portion of total energy supplied comes from the diesel generator to overcome the temporal energy shortage. This scenario decreases the overall efficiency of hybrid power system. In this study, efficient Simulink modeling for wind-diesel hybrid system is proposed and some simulations study is carried out to verify the feasibility of the proposed scheme.