• Transactions of the Korean hydrogen and new energy society
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• v.22 no.4
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• pp.481-487
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• 2011

A fuel cell vehicle using a polymer electrolyte membrane fuel cell (PEM FC) as power source produces electric power by consuming the fuel, hydrogen. The unconsumed hydrogen is recirculated and reused to gain higer stack efficiency and to maintain the humidity in the anode side of the stack. So it is needed considering fuel efficiency to recirculated hydrogen. In this study, the indirect hydrogen recirculation flow rate measurement method for fuel cell vehicle is presented. By modeling of a convergent nozzle ejector and a hydrogen recirculation blower for the hydrogen recirculation of a PEM FC, the hydrogen recirculation flow rate was calculated by means of the mass balance and heat balance at Anode In/Outlet.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.4
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• pp.96-103
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• 2007

In this paper, we present a novel and numerically efficient algorithm for high resolution TOA(Time Of Arrival) estimation under indoor radio propagation channels. The proposed algorithm is not dependent on the structure of receivers, i.e, it can be used with either coherent or non-coherent receivers. The TOA estimation algorithm is based on a high resolution frequency estimation algorithm of Minimum-norm. The efficiency of the proposed algorithm relies on numerical analysis techniques in computing signal or noise subspaces. The algorithm is based on the two step procedures, one for transforming input data to frequency domain data and the other for estimating the unknown TOA using the proposed efficient algorithm. The efficiency in number of operations over other algorithms is presented. The performance of the proposed algorithm is investigated by means of computer simulations.. Throughout the analytic and computer simulation results, we show that the proposed algorithm exhibits superior performance in estimating TOA estimation with limited computational cost.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.403-406
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• 2008

In this paper proposes a novel tracking algorithm regarding the power loss when operating a tracking system for a rapidly changing insolation to improve the power of PV tracking system. In case of tracking an azimuth and altitude of the sun in realtime, therefore, the actual PV power is less increasing than the power of tracking system fixed a specific position. To reduce the power loss, this paper proposes a nonel control algorithm of the tracking system. The paper is analyzed efficiency about conventional PV tracking method, comparing proposed algorithm with high performance method. We show propriety of proposed algorithm by means of the demonstrable study.

• Archives of design research
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• v.14
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• pp.63-74
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• 1996

By study the basic elements and the development process of the visual identity design, We have the aims in this study to help the design study groups in the country to develop a VI design system with a high degree of efficiency. We clarified the strategic position which the individual basic elements occupy in the visual communication process, by studying the individual function and the character of the basic elements which construct the keynote of VI design system, and the mutual relations among them. Also, we presented in this study the systematic and resonable approaching means in the design development process for the VI system with a high degree of efficiency.

• Journal of the korean Society of Automotive Engineers
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• v.8 no.4
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• pp.13-23
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• 1986

The power of an international combustion engine depends on its ability to inhale air whether it is naturally aspirated or turbocharged. The use of fuel injection allows engine efficiency to be increased through a more even distribution of the air/fuel ratio throughout the engine's operation range. The theoretical value for complete combustion in an engine is commonly refered to as stoichiometric, which means that we require 14.7 parts of air to 1 part of gasoline. This stoichiometric ratio can be more closely maintained with electronically controlled fuel injection than it can with carburetion. Because of the greater efficiency of the engine using fuel injection, a horse power increase of at least 10% is produced over its carburetor version. In addition, better fuel economy and less exhaust emissions are also obtained.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.1981-1983
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• 1998

The principle of the MHD generation is based on Faraday's law of induction that a eletromotive force(u ${\times}$ B) is generated when the working gas of velocity u flows a channel in which magnetic field of strength(B) exists. In MHD power generation system, enthalpy of the working gas is converted to electric power directly through expansion in generator channel. It means that electric power can be generated without moving mechanical linkage such as turbine blades. There are two types in the MHD generator; linear type Faraday and disk type hall generator. Disk type hall generator is the main target of this paper. Isentropic efficiency and enthalpy extraction rate of disk type shock tube driven hall generator is discussed here.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.05a
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• pp.109-110
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• 2006

Nanocrystalline $TiO_2$ electrode were prepared by spray-printing in order to efficiency and improved fill factor. Different compositions of nanocrystalline $TiO_2$ pastes are described, based on $TiO_2$ powder made by ourselves. The produced by spray printing $TiO_2$ films were compare with the produced by squeeze printing $TiO_2$ films and was studied in the light of static I-V characteristics. The produced $TiO_2$ films are extensively characterized by means of spectroscopy(Ramon, XRD) and microscopy(FE-SEM).

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.615-622
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• 2002

In this paper, the modification of double projection method for the adaptive analysis of Element-free Galerkin(EFG) method were proposed. As results of the double projection method, the smoothed error profile that is adequate for adaptive analysis was obtained by re-projection of error that means the differences of EFG stress and projected stress. However, it was found that the efficiency of double projection method is degraded as increase of the numerical integration order. Since, the iterative refinement to single step error estimation made the same effect as increasing of integration order, the application of the iterative refinement base on double projection method could be produced the inadequately refined analysis model. To overcome this defect, a modified scheme of double projection were proposed. In the numerical example, the results did not show degradation of double projection effect in iterative refinement and the efficiency of proposed scheme were proved.

• International Journal of High-Rise Buildings
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• v.6 no.2
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• pp.177-185
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• 2017

This research suggests the most effective way for improving energy efficiency in tall buildings is a "fabric-first" approach. This involves optimizing the performance of the building form and envelope as a first priority, with additional technologies a secondary consideration. The paper explores a specific fabric-first energy standard known as "Passivhaus". Buildings that meet this standard typically use 75% less heating and cooling. The results show tall buildings have an intrinsic advantage in achieving Passivhaus performance, as compared to low-rise buildings, due to their compact form, minimizing heat loss. This means high-rises can meet Passivhaus energy standards with double-glazing and moderate levels of insulation, as compared to other typologies where triple-glazing and super-insulation are commonplace. However, the author also suggests that designers need to develop strategies to minimize overheating in Passivhaus high-rises, and reduce the quantity of glazing typical in high-rise residential buildings, to improve their energy efficiency.

• The Journal of Korea Robotics Society
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• v.6 no.3
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• pp.230-236
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• 2011

In previous researches, the self-stability was studied for the spring-mass model and the two segment leg model. In these researches, it was presented that the spring-mass model has the self-stable region at relatively high speed running and the two segment leg model has the self-stable region at relatively low speed running. If the model was run in the self-stable region, the cost of transport is zero ideally. That is, actually, only the energy loss is needed to compensate for running. This means that the energy efficiency is high, running in the self-stable region. We want to have high energy efficiency at low and high speed running. So, in this paper, we propose the design direction of the three segment leg having the self-stable region at low and high speed running. And we prove the self-stable region of the three segment leg designed by the proposed design direction.