• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.4
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• pp.284-288
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• 2013

Power MOSFETs(Metal Oxide Semiconductor Field Effect Transistor) operate as energy control semiconductor switches. In order to reduce energy loss of the device during switch-on state, it is essential to increase its conductance. We have experimental results and explanations on the doping profile dependence of the electrical behavior of the vertical MOSFET. The device is fabricated as $8.25{\mu}m$ cell pitch and $4.25{\mu}m$ gate width. The performances of device with various p base doping concentration are compared at Vth from 1.77 V to 4.13 V. Also the effect of the cell structure on the on-resistance and breakdown voltage of the device are analyzed. The simulation results suggest that the device optimized for various applications can be further optimized at power device.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.3
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• pp.217-225
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• 2008

A new micro reformer system consisted of a micro reformer, a microcombustor and a micro evaporator was studied experimentally and computationally. In order to satisfy the primary requirements for designing the microcombustor integrated with a micro evaporator, i.e. stable burning in a small confinement and maximum heat transfer through a wall, the present microcombustor is simply cylindrical to be easily fabricated but two-staged (expanding downstream) to feasibly control ignition and stable burning. Results show that the aspect ratio and wall thickness of the microcombustor substantially affect ignition and thermal characteristics. For the optimized design conditions, a premixed microflame was easily ignited in the expanded second stage combustor, moved into the smaller first stage combustor, and finally stabilized therein. A micro reformer system integrated with a modified microcombustor based on the optimized design condition was fabricated. For a typical operating condition, the designed micro reformer system produced 22.3 sccm hydrogen (3.61 W in LHV) in an overall efficiency of 12%.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.6
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• pp.498-504
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• 2008

Metal-reducing bacterium, Geobacter sulfurreducens is available for mediator-less microbial fuel cell (MFC) because it has biological nanowires(pili) which transfer electrons to outside the cell. In this study, in the anode chamber of the MFC system using G. sulfurreducens, the concentrations of NaCl, sodium phosphate and sodium bicarbonate as electrolytes were mainly optimized for the generation of electricity from acetate. 0.4%(w/v) NaClO and 0.5M $H_2SO_4$ could be utilized for the sterilization of acrylic plates and proton exchange membrane (major construction materials of the MFC reactor), respectively. When NaCl concentration in anode phosphate buffer increased from 5 to 50 mM, power density increased from 6 to $20\;mW/m^2$. However, with increasing sodium phosphate buffer concentration from 5 to 50 mM, power density significantly decreased from 18 to $1\;mW/m^2$. Twenty-four mM sodium bicarbonate did not affect electricity generation as well as pH under 50 mM phosphate buffer condition. Optimized anode chamber of MFC using G. sulfurreducens generated relatively high power density ($20\;mW/m^2$) with the maximum coulombic efficiency (41.3%).

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.473-478
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• 2005

Active suspension system improves ride quality with optimized suspension force, generated by electric, hydrolic or pneumatic power and controlled by micro-processor under various operation condition of train, while Semi-Active susepsion system provides optimized and controlled characteristics of suspensions such as damping coefficient without external energy. The benefits fo Semi-Active suspension are no required power source and to be made compact with lower cost. Train with narrow gauge could be more unstable than one for normal or wide gauge, and it could be more vibrated than others one by external force such as aerodynamic force and track irregularity. So, the reduced ride quality could be improved with appling with Semi-active suspension system. In this report, the Semi-Active suspension system for narrow gauge train shall be proposed and to prepare the Roller Rig test of this train, integration of system, development of control algorithm and confirmation of its performance with simulation tool would be taken.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.52-55
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• 1997

This paper discusses an automatic visual-servoing system, in which a laser and a CCD camera are used for imaging the pattern of joint groove. The algorithm used here is simple and robust to find out the gap width and gap center. As a consequence, the speed of algorithm is very fast and optimized. A feature of this system is that it processes only by summing the vertical line and horizontal line of screen without any image preprocessing in order to get the energy information of lines alternatively. It is practical and useful for the system requiring a fast process time of vision.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.11A
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• pp.891-901
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• 2003

This paper presents low-power asynchronous barrel shifters for variable length encoders and decoders useful in portable applications using multimedia standards. Our approach is to create multi-level asynchronous barrel shifters optimized for the skewed shift control statistics often found in these codecs. For common shifts, data passes through one level, whereas for rare shifts, data passes though multiple levels. We compare our optimized designs with the straightforward asynchronous and synchronous designs. Both pre- and Post-layout HSPICE simulation results indicate that, compared to their synchronous counterparts, our designs provide over a 40% savings in average energy consumption for a given average performance.

• Korean Institute of Interior Design Journal
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• v.16 no.5
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• pp.81-88
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• 2007

Energy consumption has been increased world widely, and the energy retain is one of the most important economic alternatives. These tendencies expand the nuclear power plants not only quantitatively but also qualitatively. Despite of the increasing construction of nuclear power plants and related facilities, every system in main control room(MCR) has been designed and administered solely based on the safety-first principles because of the specificity of nuclear industry. However, recent main control rooms started with the concept that the operators' performance could be optimized though the organic interrelation between human, machine, and environments. Now, it has been recognised in the scope of Ergonomics and Space Design which acknowledge our living spaces as Man-Environment Interface and this change connotes the MCR spaces should be special spaces rather than ordinary spaces. This research investigated domestic and foreign nuclear power plants' MCRs to suggest basic alternatives which can be applied to future MCR. With the review of characteristics of MCR, an integration of interior design, lighting and Ergonomics was explored and classified as types. Futhermore, the classification of environmental characteristics within the relationships between human, machine, and environments was developed through the case analysis of nuclear power plants. The results of this study will provide a basis of space design for system environments that the high level of safety and function are extremely important.

• Journal of Power Electronics
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• v.15 no.2
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• pp.469-478
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• 2015

In order to promote the application of switched reluctance machines (SRM) in electric vehicles (EVs), the braking torque closed-loop control of a SRM is proposed. A hysteresis current regulator with the soft chopping mode is employed to reduce the switching frequency and switching loss. A torque estimator is designed to estimate the braking torque online and to achieve braking torque feedback. A feed-forward plus saturation compensation torque regulator is designed to decrease the dynamic response time and to improve the steady-state accuracy of the braking torque. The turn-on and turn-off angles are optimized by a genetic algorithm (GA) to reduce the braking torque ripple and to improve the braking energy feedback efficiency. Finally, a simulation model and an experimental platform are built. The simulation and experimental results demonstrate the correctness of the proposed control strategy.

• Journal of Energy Engineering
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• v.21 no.1
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• pp.75-80
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• 2012

In this paper a realistic bounding method for flooding analysis following rupture of large size of thanks and piping is defined. Mass and energy release during main feedwater line break accident is analyzed with RETRAN code. It is modeled that the main feed water control valve is closed in 5.0 seconds after reactor trip. In result of the analysis, largest mass and energy is discharged at 70% reactor power. The flood sources for main feedwater room are calculated when piping failure occurs in the high energy line and medium energy line. Based on the result of flood level (1.43m), it is investigated that all of the safety-related environmental qualification equipments are well located above the flood level.

• KIPS Transactions on Computer and Communication Systems
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• v.3 no.5
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• pp.151-154
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• 2014

An energy of applications had consumed through the complexed inter-action with operating systems, run-time environments, compiler, and applications on various mobile devices. In these days, challenged researches are studying to reduce of energy consumptions that uses energy-oriented high-level and low-level compiler techniques on mobile devices. In this paper, we intented to reduce an energy consumption of Java mobile applications that applied a list instruction scheduling for energy dissipation from dalvik bytecode which extracted Android dex files. Through this works, we can construct the optimized power and energy environment on mobile devices with the limited power supply.