• Journal of KIISE:Computer Systems and Theory
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• v.33 no.9
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• pp.699-708
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• 2006

Bus splitting technique reduces bus energy by placing modules with frequent communications closely and using necessary bus segments in communications. But, previous bus splitting techniques can not be used in MPSoC platform, because it uses cache coherency protocol and all processors should be able to see the bus transactions. In this paper, we propose a bus splitting technique for MPSoC platform to reduce bus energy. The proposed technique divides a bus into several bus segments, some for private memory and others for shared memory. So, it minimizes the bus energy consumed in private memory accesses without producing cache coherency problem. We also propose a task allocation technique considering cache coherency protocol. It allocates tasks into processors according to the numbers of bus transactions and cache coherence protocol, and reduces the bus energy consumption during shared memory references. The experimental results from simulations say the bus splitting technique reduces maximal 83% of the bus energy consumption by private memory accesses. Also they show the task allocation technique reduces maximal 30% of bus energy consumed in shared memory references. We can expect the bus splitting technique and the task allocation technique can be used in multiprocessor platforms to reduce bus energy without interference with cache coherency protocol.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.3
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• pp.343-351
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• 2018

Renewable energy sources has drawn considerable attention as clean energy sources because of changing public attitudes regarding greenhouse gas and fine dust. Recently, in this respect, the government provides the drivers of electric vehicles with various benefits such as tax reduction, financial incentives and free parking from the public to the private sector. Plug-in electric vehicles are the most common in the private sector. Otherwise, different types of battery-based buses in the public sector are being developed, and there are three main types of charging: plug-in, battery swapping and wireless. Therefore, economic assessment of charging types in each bus route is required in order to facilitate the use of battery-based buses instead of the existing CNG buses. In this paper, net present value(NPV) and B/C ratio of charging types are evaluated in consideration of the bus schedule, the cost of charging station, and the life cycle of battery, etc. per each bus route. In case study, main bus routes in Daegu City are simulated with the proposed evaluation method to validate the eco-bus project.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.311-315
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• 1998

Load Flow calculation methods can usually be divided into Gauss-Seidel method, Newton-Raphson method and decoupled method. Load flow calculation is a basic on-line or off-line process for power system planning, operation, control and state analysis. These days Newton-Raphson method is mainly used since it shows remarkable convergence characteristics. It, however, needs considerable calculation time in construction and calculation of inverse Jacobian matrix. In addition to that, Newton-Raphson method tends to fail to converge when system loading is heavy and system has a large R/X ratio. In this paper, matrix equation is used to make algebraic expression and then to solve load flow equation and to modify above defects. And it preserve certain part of Jacobian matrix to shorten the time of calculation. Application of mentioned algorithm to 14 bus, 39 bus, 118 bus systems led to identical result and the number of iteration got by Newton-Raphson method. The effect of time reduction showed about 28%, 30%, at each case of 39 bus, 118 bus system.

• ETRI Journal
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• v.34 no.4
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• pp.553-563
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• 2012

Serial peripheral interface (SPI) has been identified as a bottleneck in many wireless sensing systems today. SPI is used almost universally as the physical connection between the microcontroller unit (MCU) and radios, storage devices, and many types of sensors. Virtually all wireless sensor nodes today perform up to twice as many bus transactions as necessary to transfer a given piece of data, as an MCU must serve as the bus master in all transactions. To eliminate this bottleneck, we propose the master-handoff protocol. After the MCU initiates reading from the source slave device and writing to the sink slave device, the MCU as a master becomes a slave, and either the source or the sink slave becomes the temporary master. Experiment results show that this master-handoff technique not only cuts the data transfer time in half, but, more importantly, also enables a superlinear energy reduction.

• Journal of Hydrogen and New Energy
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• v.32 no.6
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• pp.431-441
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• 2021

UAE is first country in Middle East to approve UN Paris Climate Agreement. Ministry of Climate Change and Environment of UAE announced National Climate Change Plan for carbon reduction to replace 24% by clean energy. Dubai open its first hydrogen station in UAE and Middle East in 2017, and Abu Dhabi planed to open second hydrogen station in 2019 but not realized. Korean government announced hydrogen economy roadmap in 2019 and various hydrogen cooperation are realized between UAE, Korea, Germany, USA, and Japan. MOU between Ministry of State of UAE and Ministry of Land, Infrastructure and Transport of Korea in 2019 for the cooperation of hydrogen city. This study propose strategies for the 'Hydrogen Based Public Transport in UAE' by the support of Korea government considering various stakeholder.

• Current Photovoltaic Research
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• v.11 no.1
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• pp.34-37
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• 2023

Solar energy had become the main energy industry of renewable energy along with hydroelectric power generation. One of the technologies that contributed to the popularization of photovoltaic power and the decrease in the unit price of photovoltaic modules was the large-area solar cell. However, as the area increased, the light receiving area increased and the current value increased accordingly. Since power loss occurs when the current value was large, the number of busbar was increased to increase the current collection rate, and a technology to lower the current value through half-cutting was developed. The bus bar of the solar cell served as a passage through which the generated current was transmitted. This was because when the number of busbar decreases, the moving distance of electrons increased, so the amount of power generation decreases and when it increases, shadows occured. An important aspect of the electrode design was the optimal balance of these busbars and number of fingers. Therefore, in this study, the characteristics of the solar cell according to the number of front bus bars of the large-area solar cell were simulated using Griddler 2,5 pro. After selecting the number of busbar with the best characteristics, the difference was compared by varying the number of fingers and a better direction for the number of cutting was presented.

• Journal of the Korean institute of surface engineering
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• v.49 no.5
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• pp.447-453
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• 2016

In this study, we intended to extend the life of electropolishing solution through the reduction of electric resistance by improving the electrolysis efficiency. The optimum conditions were obtained by half round bus bar and Taguchi method. As the main control factors in the electropolishing process, current density, polishing time, electrolyte temperature and flow rate were selected. The electrolyte temperature was the most significant to the electrolysis efficiency. The optimum conditions for the life extension of electropolishing solution were as follows: current density, $45A/dm^2$; polishing time, 6 min; electrolyte temperature, $70^{\circ}C$; flow rate, 11 L/min. As a results of ANOVA of SN ratios, it was found that the electrolyte temperature was significant factor at the 90% confidence level.

• International Journal of Automotive Technology
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• v.2 no.2
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• pp.39-45
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• 2001

Hydrogen is seen as one of the important energy vectors of the next century. Hydrogen as a renewable energy source, provides the potential for a sustainable development particularly in the transportation sector. Hydrogen driven vehicles reduce both local as well as global emissions. The laboratory of transporttechnology (University of Gent) converted a GM/Crusader V-8 engine for hydrogen use. Once the engine is optimised, it will be built in a low-floor midsize hydrogen city bus for public demonstration. For a complete control of the combustion process and to increase the resistance to backfire (explosion of the air-fuel mixture in the inlet manifold), a sequential timed multipoint injection of hydrogen and an electronic management system is chosen. The results as a function of the engine parameters (ignition timing. injection timing and duration, injection pressure) we given. Special focus is given to topics related to the use of hydrogen as a fuel: ignition characteristics (importance of electrode distance), quality of the lubricating oil (crankcase gases with high contents of hydrogen), oxygen sensors (very lean operating conditions), noise reduction (configuration and length of inlet pipes). The advantages and disadvantages of a power regulation only by the air to fuel ratio (as for diesel engines) against a throttle regulation (normal gasoline or gas regulation) are examined. Finally the goals of the development of the engine are reached: power output of 90 kW, torque of 300 Nm, extremely low emission levels and backfire-safe operation.

• Journal of Korean Society of Transportation
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• v.28 no.1
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• pp.25-38
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• 2010

In this study, the real on-road driving data were analyzed to draw the various characteristics related to idling of vehicles. The results revealed that the average idling time of a city bus corresponds to 30.9% of the total daily driving time. Among this, for about 21.6% of the total daily driving time, it is available that an engine can be halted while the vehicle stops. It is a daytime when the portion of time, for which idling stop is available, is peak. Due to idling stop, an increase of turnaround was not found throughout this analysis. When a city bus stops at a traffic right, idling periods were long enough to execute the idling stop, during which an engine halts. Whereas, during the idling time for bus stops, the idling periods were not so long enough to execute idling stop. Deceleration periods among the total turnarounds of a city bus occupies about 24.7%, during which, for about 30%, a deceleration maintains for more than four seconds. Thus, using the energy during deceleration period, which then can be recovered from braking energy, it was also found that a hybrid system can be effectively implemented to a city bus.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.4
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• pp.361-367
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• 2014

This paper is related to a new solar power conditioner for a built-in step-up chopper function. In the first step-up chopper proposed solar PV power conditioner for mutually connected in series with the input voltage of the bypass diodes are respectively connected to the positive terminal should install the mutual boosting chopper diode connected in series with the boost chopper switching element between the two power supply and at the same time the first and the second was connected to a second diode and a resonance inductor and a snubber capacitor in series with each other. And the common connection point between the bypass diode and the step-up chopper and the step-up chopper diode common connection point of the switching elements of the input voltage was set to the boost inductor for storing energy. In addition, between the step-up chopper and the step-up chopper diode and a switching element of a joint connection point of the first auxiliary diode and the second common connection point of the auxiliary diode was provided, the resonance capacitor. Between the step-up chopper and the step-up chopper diode and a switching element of a joint connection point and the common connection point of the resonance inductor snubber capacitor and connecting the third secondary diode, between two power supply lines is characterized by configuring the DC link capacitor bus lines in parallel. Therefore, it is possible to suppress the switching loss through, DC link bus lines, as well as there could seek miniaturization and weight reduction of the power conditioner itself by using a common capacitor of the non-polar non-polar electrolytic capacitor having a capacitor, the service life of the circuit can be extended and it is possible to greatly reduce the loss can be greatly improve the reliability of the product and the operation of the product itself.