• International Journal of Precision Engineering and Manufacturing
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• v.9 no.2
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• pp.23-27
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• 2008

As a biofuel source, direct photosynthetic/metabolic biofuel cells (DPBFC) use cyanobacteria whose photosynthesis and metabolization reactions can convert light energy to electricity, In our previous work, we fabricated a prototype micro-DPBFC that could generate a peak current density of $36{\mu}A/cm^{2}$ and a maximum power density of $270nW/cm^{2}$. In this study, we improve on the previous results by using carbon micro electromechanical systems (C-MEMS), formed from the pyrolysis of patterned photoresist, to fabricate carbon electrodes of an arbitrary shape and controlled porosity to increase the surface area. With these new C-MEMS electrodes, the maximum power density of the micro-DPBFC was $516nW/cm^{2}$, a performance twice as good as the results of our previous work.

• Journal of the Korean institute of surface engineering
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• v.22 no.4
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• pp.197-206
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• 1989

The Composition and throwing power-of Pb-Sn alloy deposits are investigated in tems of the pulse parameters in pulse plating. Microhardness and intermal srress of alloy deposots are measured. The current efficiency of pulse plating is lower than that of D.C.plating while cathode overpotential and macro-throwing power noticebly increase with increasing peak current density. The Pb content of P.C. plated alloy deposits with increasing average current density, is relatively lower than of D.C. plated deposits at the same average current density. The internal stress of Pb-Sn alloy is not detected and the microhardness are 9.0kg/mm2 and 11kg/mm2 for D.C. plated P.C. plated deposits, respectively.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.6
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• pp.85-88
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• 2009

This paper shows a reasonable power density, that was made by the systematic and statistical way considering actual conditions, such as investigated power consumption capacity for the year and peak power, contract power for the last 5 years of each customer for 23 general customers all data obtained by AMR. In this dissertation, it is necessary to analyze the key features from the investigated data. It made an analysis of the feature parameters, such as average, standard deviation, median, maximum, minimun and load factor.

• Proceedings of the KIEE Conference
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• 2002.04a
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• pp.139-142
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• 2002

A resonant type voltage source and power device and a control method using Pulse Density Modulation(PDM) power control and Pulse Width Modulation(PWM) voltage control for Ozone Generator are described. For the stability of discharge in the generating tube, it is desirable that the peak apply voltage is constant. The PDM power control is employed for sustaining the voltage constant at any generating tube input power. Moreover, to avoid the influence of input AC voltage fluctuation etc., PWM voltage control with generating tube peak voltage feedback is used. Both functions were confirmed by the experiment with 6.5[kHz], 1.8[kW] inverter and generating tube. The effect of input synchronous PDM method for input current stabilizing is confirmed also.

• Korean Journal of Applied Biomechanics
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• v.15 no.4
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• pp.117-129
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• 2005

The purpose of this study was to characterize the impact shock wave and its attenuation, and the kinematic response of the lower extremity's joints to the impact shock during downhill running in which the lower extremity's extensor acts dominantly. For this study, fifteen subjects(mean age:$27.08{\pm}4.39$; mass:$76.30{\pm}6.60$; height:$177.25{\pm}4.11$) were required to run on the 0% grade treadmill and downhill grades of 7%, and 15% in random at speed of their preference. When the participant run, acceleration at the tibia and the sacrum and kinematic data of the lower extremity were collected for 20s so as to provide at least 5 strides for analysis at each grade. Peak impact accelerations were used to calculate shock attenuation between the tibia and sacrum in time domain at each grade. Fast Fourier transformation(FFT) and power spectral density(PSD) techniques were used to analyze impact shock factors and its attenuation in the frequency domain. Joint coordinate system technique was used to compute angular displacement of the ankle and knee joint in three dimension. The conclusions were drawn as fellows: 1. Peak impact accelerations of the tibia and sacrum in downhill run were greater than that of 0% grade run, but no significant between conditions. Peak shock of PSD resembled also in pattern of peak impact acceleration. The wave of impact shock attenuation between the tibia and sacrum decreased with increasing grade, but didn't find a significant difference between grade conditions. 2. Adduction/abduction, flexion/extention, and internal/external rotation of the ankle and knee joints at support phase between grade conditions didn't make much difference. 3. At grade of 7% and 15%, there were relationship between the knee of the flexion/extension movement and peak impact acceleration during heel strike and found also it in the ankle of plantar/dorsiflexion at grade of 15%.

• Journal of Radiation Protection and Research
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• v.22 no.4
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• pp.309-317
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• 1997

The measured radioactivity of gamma-emitting radionuclides in each radioactive waste drum using the non-destructive waste assay method is underestimated than real radioactivity in radioactive waste drum because the gamma-rays are attenuated within the medium. Therefore, the measured radioactivity should be corrected for the attenuation of gamma-rays. For the correction of the attenuation of gamma-rays, the attenuation correction method should be applied differently by considering the distribution and density of medium in radioactive wastes drum generated from nuclear power plants. In this study, the model drums were fabricated for simulating five types of radioactive waste drums generated from nuclear power plant and the optimum methods of the attenuation correction were experimentally determined to analyze the activity of radionuclides in the waste drum accurately using the segmented gamma scanning system. With the determination of the attenuation correction methods from the experimental results the transmission method and the average density method for the miscellaneous waste drum, the transmission method and the differential peak absorption method for the shielded miscellaneous waste drum were used to measure the density of medium in waste drums. Also, the average density method and the differential peak absorption method for the spent resin drum, the paraffin solidified drum, and the spent filter drum were used.

• Korean Journal of Applied Biomechanics
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• v.27 no.4
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• pp.263-268
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• 2017

Objective: The purpose of this study was to show differences in impact variables between treadmills with (treadmills B, C, and D) and treadmills without a shock-absorbing function (treadmill A) to propose the development of a treadmill with improved or added shock-absorbing function to reduce impact shock. Method: Thirteen male students in their twenties who had habitual rear foot strike during running ran on four treadmills at 2.67 m/sec while ankle and neck acceleration data were collected. The magnitude of the ankle and neck acceleration peaks and peak positive ankle acceleration were calculated. The power spectral density of each signal was calculated to transform the ankle and neck accelerations in the frequency domain. Results: The peak positive ankle acceleration on treadmill B was significantly lesser than that on treadmills A and D, and that on treadmill C was significantly less than that on treadmill A (p < .01). Peak positive neck acceleration was not statistically different between the treadmills. The frequencies of the peak power of the ankle and neck acceleration signal within the lower and higher frequency ranges were not statistically different between the treadmills. The signal power magnitude of the ankle in higher frequency ranges on treadmill B was significantly less than that on treadmills A, C, and D (p < .01). The signal power magnitude of the ankle in higher frequency ranges was not statistically different between the treadmills. The signal power magnitudes of the neck acceleration signal within the lower and higher frequency ranges were not statistically significantly different between the treadmills. Conclusion: Our results indicate that the shock-absorbing function of a treadmill plays a role in reducing impact shock. Therefore, in future treadmill development, shock-absorbing function should be improved or incorporated to reduce impact shock to the body.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.6
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• pp.916-926
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• 1994

A high frequency and soft-switched AC-to-DC rectifier employing a series-type resonant circuit is proposed to overcome the disadvantages of the conventional peak-rectifying circuit. Using the proposed rectifier, the high power factor and low harmonic currents are obtained in the AC line. Furthermore, several advantages such as the high power density and wide output voltage range can be available. Through the simulation and experimental results, the usefulness of the proposed rectifier is verified.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.4
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• pp.281-286
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• 2019

Raman spectra of a-C:H thin films deposited with an unbalanced magnetron sputtering system showed that the G peak shifted to a higher wavenumber as the target power density increased and $I_D/I_G$ ratio increased from 0.902 to 1.012. Moreover, the transmittance of a-C:H films fabricated at 60 nm tended to decrease with increasing target power density; at 550 nm in the visible light region, the transmittance decreased from 69% to 58%. The rms surface roughness values of the a-C:H thin films decreased with increasing target power density, and varied from 1.11 nm to 0.71 nm. In order to achieve efficient light trapping, the light scattering at the rough interface must be enhanced. Consequently, the surface roughness of the thin film will decrease with the target power density. Further, the refractive index and reflectivity of the a-C:H thin films increased with increasing target power density; however, the Brewster angle decreased with the target power density. Hence, dye-sensitized solar cells using an a-C:H antireflective coating increased the CE, $V_{OC}$, and $J_{SC}$ by approximately 8.6%, 5.5%, and 4.5%, respectively.

• Transactions on Electrical and Electronic Materials
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• v.13 no.2
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• pp.69-72
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• 2012

In this study, deposition of low-dielectric constant SiOC(H) films by conventional plasma-enhanced chemical vapor deposition (PECVD) were investigated through various characterization techniques. The results show that, with an increase in the plasma power density, the relative dielectric constant (k) of the deposited films decreases whereas the refractive index increases. This is mainly due to the incorporation of organic molecules with $CH_3$ group into the Si-O-Si cage structure. It is as confirmed by FT-IR measurements in which the absorption peak at 1,129 $cm^{-1}$ corresponding to Si-O-Si cage structure increases with power plasma density. Electrical characterization reveals that even after fast thermal annealing process, the leakage current density of the deposited films is in the order of $10^{-11}$ A/cm at 1.5 MV/cm. The reliability of the SiOC(H) film is also further characterized by using BTS test.