• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.43.1-43.1
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• 2010

In the crystalline silicon solar cells, the full area aluminum_back surface field(BSF) is routinely achieved through the screen-printing of aluminum paste and rapid firing. It is widely used in the industrial solar cell because of the simple and cost-effective process to suppress the overall recombination at the back surface. However, it still has limitations such as the relatively higher recombination rate and the low-to-moderate reflectance. In addition, it is difficult to apply it to thinner substrate due to wafer bowing. In the recent years, the dielectric back-passivated cell with local back contacts has been developed and implemented to overcome its disadvantages. Although it is successful to gain a lower value of surface recombination velocity(SRV), the series resistance($R_{series}$) becomes even more important than the conventional solar cell. That is, it is a trade off relationship between the SRV and the $R_{series}$ as a function of the contact size, the contact spacing and the geometry of the opening. Therefore it is essential to find the best compromise between them for the high efficiency solar cell. We have investigated the optimal design for the local back contact by using PC1D simulation.

• Journal of Drive and Control
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• v.17 no.2
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• pp.45-54
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• 2020

The IMV is a combination of four two-way valve systems which replace a conventional four-way spool valve to improve efficiency mostly in excavator hydraulics. As the environmental regulations for construction equipment have tightened, some overseas advanced companies have released commercial excavators in which the MCV is implemented with the IMVs. Development of the IMV type MCV relies on the control algorithm as well as the robust performance of proportional flow control valves. In this study, the IMV controller was designed and verified with experiments for the excavator working unit, which determines the IMV mode of operation and the extent of the valve opening in consideration of the load conditions on hydraulic actuators. First, the open-loop controller was designed with a joystick command vs. a PSV reference current map comprising several control parameters in to compensate for the different flow characteristics and non-linearities of two-way flow control valves. Second, the closed-loop controller was designed with the PI control fed by the actuator displacement and outputs actuator percent effort equivalent to the operator's joystick command. Finally, the performance of the IMV type MCV was verified with the trajectory control of position references derived from the energy consumption test standard. Experimental results showed the control performance of the IMV developed in this study, and suggest that future studies to be conducted to advance technical progress.

• Journal of Information Technology Services
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• v.15 no.3
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• pp.97-114
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• 2016

One of the key success factors for the intelligent IT service which is characterized by personalization and automation, is to obtain relevant data from either sensors or data storage for reasoning, analyzing and forecasting. The availability of the open data sources such as public portal sites remarkably increases the efficiency and quality of the intelligent IT service. However, with the condition that not all data in the existing public or private sites are opened or have various types of openness, it prohibits the value of utilization. For these reasons, it is highly required to evaluate the extent of openness of data storage. However, there are only a few studies which explore the factors which affect the degree of data openness with respect to intelligent IT services. Hence, this study aims to propose an evaluation model including the indices to evaluate a process of opening data for the intelligent IT service from a viewpoint of data utilization process. The indices are applied to evaluate the actual multinational websites, which provide public data for verification. We also discuss the implications of the evaluation according to the results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.3
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• pp.738-750
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• 1994

The load-sensing hydraulic system which was developed to improve energy efficiency of conventional hydraulic systems has its own properties. The instability of system responses, linearity of a servo valve, robustness for variation of external load, and dynamic interference between hydraulic motors are such properties which have much to do with control properties of the system. The load-sensing hydraulic system has instability tendancy because the load-sensing mechanism makes a positive feedback loop between the motor part and the pump part. A flow property of the servo valve can be said to be linear because the flow through the valve has nothing to do with a load pressure and the flow is strictly proportional to a valve opening which is adjusted by a valve command signal. The resultant control property can be said to be robust because the steady-state control performance is independent to the load actuated on the motor shaft. In the case when one pump simultaneously drives more than two hydraulic motors, the pump outlet pressure is determined by a hydraulic motor of the largest load pressure among all of the hydraulic motors, and, thus, the other motors are dominated by the largest load pressure. That is, the other motors can be said to be interfered by the motor of the largest load pressure.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.9
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• pp.36-47
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• 1999

Three-way catalyst converter, cleaning up the exhaust gas contamination of SI engine, has the best efficiency when A/F ratio is near the stoichiometry . The feedback control using oxygen sensors in the exhaust manifold has limits caused by the system delays. So the accurate measurement of air flow rate to an engine is essential to control the fuel injection rate especially on transient condition like the rapid throttle opening and closing. To measure the rapid change of flow rates. the air flow meter for the engine requires quick response, flow reversal detection, and linearity . Tjhe proposed integration type air flow meter (IFM), composed of an ultrasonic flow meter with an integration circuit, has significantly improved the measurement accuracy of air mass inducted through the throttle body. The proposed control method estimated the air mass at the cylinder port using the measured air mass at the throttle . For the fuel dynamic model, the two constant fuel model is introduced . The control parameters from air and fuel dynamics are tuned to minimize the excursion of the air fuel ratio. As a result A/F ratio excursion can be reduced within 5% when throttle rapidly opens and closes at the various engine conditions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.6
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• pp.584-589
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• 2009

As the automobile energy efficiency stands out an important matter of interest, the magnetic engine valve system receives attention. It has an advantage of no engine power leakage in opening and closing the valve. Moreover, it generates much bigger force than the piezo actuator system, so it can be a good alternative system of the cam and camshaft system. However, since the valve system is not light enough, it is necessary to make its weight reduce. In this study, topology optimization is applied to find the optimal shape of the armature in a magnetic valve system combined with the finite element analysis for the magnetic field analysis. The result is used to obtain a concept design. The adjoint variable method is employed in order to calculate the design sensitivity of the magnetic driving force in the armature component mostly to reduce the computational time during the repeated sensitivity calculation. The sequential linear programming is employed for the optimization algorithm.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.864-870
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• 2005

Hydraulic excavators have been popular devices in construction field because of its multi-workings and economic efficiency. The mathematical models of excavators have many nonlinearities because of nonlinear opening characteristics and dead zone of main control valve, oil temperature variation, etc. The objective of this paper is to develop a simulator for hydraulic excavator using AMESim. Components and whole circuit are expressed graphically. Parameters and nonlinear characteristics are inputted in text style. From the simulation results, fixed spring stiffness of MCV can't satisfy accuracy of spool displacement under whole P-Q diagrams. Closed loop type MCV containing proportional gain is proposed in this paper that can reduce displacement error. The ability of closed loop MCV is verified through comparing with normal type MCV using AMESim simulator. The simulator can be used to forecastexcavator behavior when new components, new mechanical attachments, hydraulic circuit changes, and new control algorithm are applied. The simulator could be a kind of development platform for various new excavators.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.868-869
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• 2011

Domestic Foreign automaker's are focused on the high-efficiency, low emission cars development. On the way, the hybrid car is the first priority. Hybrid electric vehicle battery pack configurations, EV Relay one of the key components of the engine driving, to assist in the drive motor to supply electrical energy to the battery is a device for opening and closing of the output device. EV Relay determine the longevity and the replacement cycle, The EV Relay environmental conditions and duty cycle considering the reliability tests are essential requirements of many automotive companies to respond to RFQ, this test is essential. This paper using Maxwell Software for Prediction of the Ev Relay impulse, the theoretical data to obtain the impulse to develop methods for mechanical testing after to take advantage of it.

• Journal of Korean Institute of Industrial Engineers
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• v.12 no.2
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• pp.21-31
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• 1986

Consider a capacitated facility location problem in which the demands of customers are all equal and so are the capacities of facilities. Under the restriction that each customer's uniform demand be met by exactly one facility, the objective is to select a set of facilities to open, and to assign customer's demand to them so as to minimize the total cost which includes fixed costs of opening facilities as well as variable assignment costs. The problem is modelled as a pure zero-one program which may be viewed as a variant of well-known capacitated facility location problems. The purpose of this study is to develop efficient computational procedures for solving the pure zero-one facility location problems. Due to the special structure of our zero-one location problem with uniform demand, it can be converted to a location problem with the unimodular property. A Lagrangean relaxation algorithm is developed to solve the location problem. The algorithm is made efficient by employing a device which exploits the special structure of a surrogate constraint. The efficiency of the algorithm is analyzed through computational experiments with some test problems.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.430-433
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• 2009

The development of large-scale environmental friendly livestock complex in the reclaimed tideland is one of different alternatives to increase the competitiveness of internal livestock industry against an international opening markets as DDA and FTA in agricultural field. Recently, it is possible to introduce an environmental friendly livestock complex in the reclaimed tideland by an amendment of the acts for agricultural land. However more studies that are on the basis of nitrogen and phosphorus mass balance need to preserve the agricultural environments as the quality of agricultural water and soil in rural area. In this study, the reference for feasibility study is Whaong reclaimed tideland which located at Whaseong city, Gyeonggi Province, and a basic concept of environmental friendly livestock complex is the production of forage crops with the supply of liquid fertilizer and the production of bioenergy such as biogas by the recycling of pig slurry as a resource. The mass balance of nitrogen based on between forage crops such as maize, barley and liquid fertilizer supplied at the reclaimed tideland, and also it was estimated an economical efficiency as anaerobic digestion plant for treating pig slurry of $100m^3/day$ introduce in an environmental friendly livestock complex.