• New & Renewable Energy
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• v.2 no.2 s.6
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• pp.50-59
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• 2006

An experimental and numerical study is carried out to investigate the performance and the efficiency humidifying Membrane Electrolyte Assembly and having the double-layered catalyst in a fuel cell system which is taken into account the physical and thermal concept. Based on the principals of the problem, the equation of electronic charge conservation equation, gas-phase continuity equation, and mass balance equation are used for the numerical calculation. A unit cell for $200cm^2$ MEA is assembled and measured for finding better operational situation. After finding the optimal condition, 10 cell stacked PEMFC is fabricated. For the performance evaluation, V-I and power curves are examined in detail by changing the condition of humidity, temperature, pressure, thickness of catalyst and oxidant. It is found that the power is maximized around 500W at 80A.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.5
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• pp.447-455
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• 2023

SAE J2601, hydrogen fueling protocols, proposes two charging methods. The first is the table-based fueling protocol, and the second is the MC formula-based fueling protocol. Among them, MC formula-based fueling protocol calculates and supplies the target pressure and pressure ramp rate (PRR) using the pre-cooling temperature of the hydrogen and the physical parameters of the tank in the vehicle. The coefficient of the MC formula for deriving MC varies depending on the physical parameters of the tank in the vehicle. However, most studies use the MC coefficient derived from SAE J2601 as it is, despite the difference in the physical parameters of the tank applied to the study and the tank used to derive the MC coefficient from SAE J2601. In this study, the MC coefficient was derived by applying the hydrogen tank currently used, and the difference with the fueling performance using the MC coefficient proposed in SAE J2601 was verified. In addition, the difference was confirmed by comparing and analyzing the fueling performance of the table-based method currently used in hydrogen fueling stations and the MC formula-based method using MC coefficient derived in this study.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.7
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• pp.2914-2935
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• 2016

With the increasing popularization of cloud computing, how to reduce physical energy consumption and increase resource utilization while maintaining system performance has become a research hotspot of virtual machine deployment in cloud platform. Although some related researches have been reported to solve this problem, most of them used the traditional heuristic algorithm based on greedy algorithm and only considered effect of single-dimensional resource (CPU or Memory) on energy consumption. With considerations to multi-dimensional resource utilization, this paper analyzed impact of multi-dimensional resources on energy consumption of cloud computation. A multi-dimensional resource constraint that could maintain normal system operation was proposed. Later, a novel virtual machine deployment method (NVMDM) based on improved particle swarm optimization (IPSO) and Euclidean distance was put forward. It deals with problems like how to generate the initial particle swarm through the improved first-fit algorithm based on resource constraint (IFFABRC), how to define measure standard of credibility of individual and global optimal solutions of particles by combining with Bayesian transform, and how to define fitness function of particle swarm according to the multi-dimensional resource constraint relationship. The proposed NVMDM was proved superior to existing heuristic algorithm in developing performances of physical machines. It could improve utilization of CPU, memory, disk and bandwidth effectively and control task execution time of users within the range of resource constraint.

• Proceedings of the KIEE Conference
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• 1997.07c
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• pp.1121-1123
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• 1997

The control strategy for damping analysis of STATCON is derived based on an energy function of the power system equation. The center-of-angle(COA) coordinated system by a simple equivalent physical system is used and the control law for this system is induced for FACTS devices as TCSC and STATCON. Damping results from the transient performance simulations carried out on the model system.

• Journal of Energy Engineering
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• v.14 no.2 s.42
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• pp.98-104
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• 2005

Pannier-arrangement condensers are usually adopted in the turbine generator units of combined cycle power plants. Optimization of operating performance and economy is an important goal, which requires accurate understanding of flow and heat transfer effects in the condenser. The tube bundle arrangement and steam flow behaviors of pannier-arrangement condensers are very different from those of common condensers. The physical model for existing numerical simulation program of condenser is refined by constructing the correlations for flow resistance and condensation heat exchange coefficient in which the influences of steam flow direction are considered according to available experimental data. The adaptability of the developed physical model and simulation program of pannier-arrangement condenser is verified with available experimental data.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.4
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• pp.16-23
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• 2011

Since the first lighting light source was invented, lighting has turned into superior-quality lighting considering the amenity of occupants, and the characteristics of a light source has developed rapidly. So this research confirmed the lighting performance of a dimmer control system and an ON-OFF control system via the existing light source, and analyzed the basic lighting environment of Permanent Supplementary Artificial Lighting of Interiors(PSALI) through the physical comparison and evaluation of a LED lamp substituted for a fluorescent lamp used in a dimmer control system, showing that the lighting physical quantity characteristics of an ON-OFF control system and a dimmer control system are similar to each other and that they are effective in terms of energy saving. Besides, it was shown that introducing a LED light source to a dimmer control system improves lighting environments and largely reduces energy consumption.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.2
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• pp.42-49
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• 1997

This experimental study was performed to find fuel property variations of the ultrasonic energy adding gasoline and improve the spray characteristics of the multipoint injector for EFI engine. The cause and effect of the characteristic improvement of the ultrasonic energy adding fuel was found out by the chemical structure analysis (NMR, IR), distillation and viscosity test. The results are obtained that the chemical property of gasoline organizition was changed aromatics to paraffins and branch index as the physical characteristics of gasoline were improved by ultrasonic energy. There were higher distillation and lower viscosity in ultrasonic energy adding gasoline.

• Carbon letters
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• v.15 no.1
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• pp.38-44
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• 2014

This paper reports the effect of adding reduced graphene oxide (RGO) as a conductive material to the composition of an electrode for capacitive deionization (CDI), a process to remove salt from water using ionic adsorption and desorption driven by external applied voltage. RGO can be synthesized in an inexpensive way by the reduction and exfoliation of GO, and removing the oxygen-containing groups and recovering a conjugated structure. GO powder can be obtained from the modification of Hummers method and reduced into RGO using a thermal method. The physical and electrochemical characteristics of RGO material were evaluated and its desalination performance was tested with a CDI unit cell with a potentiostat and conductivity meter, by varying the applied voltage and feed rate of the salt solution. The performance of RGO was compared to graphite as a conductive material in a CDI electrode. The result showed RGO can increase the capacitance, reduce the equivalent series resistance, and improve the electrosorption capacity of CDI electrode.

• Journal of Internet Computing and Services
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• v.15 no.3
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• pp.1-10
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• 2014

The cloud computing paradigm introduced pay-per-use models in which IT services can be created and scaled on-demand. However, service providers are still concerned about the constraints imposed by their physical infrastructures. In order to keep the required QoS and achieve the goal of upholding the SLA, virtualized resources must be efficiently consolidated to maximize system throughput while keeping energy consumption at a minimum. Using ANN, we propose a predictive SLA-aware approach for consolidating virtualized resources in a cloud environment. To maintain the QoS and to establish an optimal trade-off between performance and energy efficiency, the server's utilization threshold dynamically adapts to the physical machine's resource consumption. Furthermore, resource-intensive VMs are prevented from getting underprovisioned by assigning them to hosts that are both capable and reputable. To verify the performance of our proposed approach, we compare it with non-optimized conventional approaches as well as with other previously proposed techniques in a heterogeneous cloud environment setup.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.4
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• pp.309-316
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• 2009

The effect of gas diffusion layers (GDLs) on the freeze/thaw condition durability in polymer electrolyte fuel cells (PEFCs) were investigated. For this purpose, three kinds of GDLs, such as, felt, paper and cloth types with different basic properties have been first prepared, then the changes in the properties and performance of cells was observed during the freeze/thaw cycles ranging from -30 to $70^{\circ}C$. The performance evaluations were conducted by using the single cells consisting of different GDLs. The performance degradation and the cell resistance increase could be directly correlated. The physical destruction of electrode was shown by SEM analysis. The mechanically supporting ability on the interface between the cell components can help enhancing the durability of PEFCs in the freeze/thaw condition.