• Journal of the Korean Society of Manufacturing Process Engineers
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• v.2 no.2
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• pp.98-105
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• 2003

In the experimental study, wire EDM was conducted for cold die steel by changing the Wire electrode, peak discharge current and number of finish cut. From the micro structure analysis of SEM photographs, the size of irregular welded and added component on the EDMed surface is decreasing and size of EDMed plane surface is increasing as the decreasing peak current and increasing number of finish cut. From the analysis of coating effect, Zn component is highly contained in Br and Zn Wire EDMed surface and copper component is highly contained in Br and Al wire EDMed surface. Hardness values are Increasing as the increasing peak current and decreasing the number of finish cut The value of hardness is decreasing as Cu, Al, Zn and Br wire electrode because of the residual austenite effect of solid solution copper on solidification, and finally EDMed surface has the highest hardness values for every wire electrode. Yield strength values becomes larger and bending strength values become smaller due to the increasing the hardness. These results are increased as increasing brittleness with hardness.

• ETRI Journal
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• v.36 no.4
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• pp.635-642
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• 2014

Three-dimensional integrated circuits (3D ICs) implement heterogeneous systems in the same platform by stacking several planar chips vertically with through-silicon via (TSV) technology. 3D ICs have some advantages, including shorter interconnect lengths, higher integration density, and improved performance. Thermal-aware design would enhance the reliability and performance of the interconnects and devices. In this paper, we propose thermal-aware floorplanning with min-cut die partitioning for 3D ICs. The proposed min-cut die partition methodology minimizes the number of connections between partitions based on the min-cut theorem and minimizes the number of TSVs by considering a complementary set from the set of connections between two partitions when assigning the partitions to dies. Also, thermal-aware floorplanning methodology ensures a more even power distribution in the dies and reduces the peak temperature of the chip. The simulation results show that the proposed methodologies reduced the number of TSVs and the peak temperature effectively while also reducing the run-time.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.202-202
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• 2011

Diagnostics of plasma density is a key factor for monitoring plasma processing. Various probes are invented to measure plasma density and cut-off probe is a one of the most promising diagnostics tool for measuring plasma density. However, at the low density or high pressure the cut-off probe cannot clearly resolve the cut-off peak. Several reasons make this problem: Cut-off likes peaks caused by cavity resonances and weaken transmission spectrum signal at high pressure. Recently, You et al., have researched mechanism of cut-off probe and we improve the cut-off reliability and sensitivity base on that research. Modified cut-off antenna is adapted and bias cut-off probe method is tried. These experiment results have good agreement with the previous study and show good measurement characteristics.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.181-181
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• 2012

The microwave probe for measuring plasma density is widely used for its advantages: First, it is not affected by the reactive gas. Second, it can measure local plasma parameters such as plasma density, plasma potential and plasma temperature. Third, it is simple and robust. A cut-off probe is the one of the most promising microwave probe. Recently, Kim et al. reveals the physics of the cut-off probe but the effect of the sheath on the determination of the plasma density is not explained. In this presentation, for taking account of sheath effects on determination of plasma density from the cut-off peak, a simplified circuit modeling and an E/M simulation are conducted. The results show that occupation ratio of sheath volume between two tips of the cut-off probe and subsequence pressure condition mainly change position of the cut-off peak with respect to plasma frequency. Magnitude of relative voltage taken on the impedance of sheath and the impedance of bulk plasma can explain this effect. Furthermore, effects of gap size, tip radius, and tip length ware revealed based on above analysis.

• Journal of the Korean Society of Safety
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• v.19 no.2
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• pp.21-25
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• 2004

This study deals with the characteristics of wire-cut EDM(Electrical Discharge Machining)process in aluminum alloys. Besides 2 series and 7 series of aluminum alloys for aerospace applications, porous aluminum is tested, which is used for sound absorbing matherial and interior and exterior material of building. Jinyoung JW-30 wire cutting machine was used in this experiment. Tap wate passed a filter and ionization was used as the discharging solution. An immerision method was applied as a cooling method because it separates chips effectively and machinability is good even with low value of electric current. The speed of fabrication was estimated by measuring the travel distance of the work piece and time spent for the movement. As pulse-on-time increased the fabrication speed decreased. On the other hand, as peak voltage of peak current increased the fabrication speed increased. In general 7075 aluminum alloy resulted in higher fabrication speed.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.142-142
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• 2011

Microwave diagnostics method for plasma science and engineering is vigorous research area for its good characteristics such as high sensitivity, reliability, and broad measurement spectrum from low density plasma to high density. We investigate mechanism of microwave probes (hairpin, impedance and absorbtionf probe) and apply it for interpretation of full transmitted spectrum of cutoff probe. Mechanism of the spectrum having same key roles of I-V curve of Langmuir probe is not exactly revealed yet in spite of its importance. This study elucidates physics behind it using a circuit model and E/M wave simulation. Circuit model reveals exact cut-off peak frequency taking account of a collision frequency and a plasma frequency and it enable precise diagnostics of plasma densty from low pressure to high pressre. Cut-off like peaks have been obstacle for choosing cut-off peak is analyzed by E/M simulation and one of cutoff like peaks made by probe holder used for acquire plasma density with cutoff peak applying the hairpin relation. Furthermore, phase difference method for plasma density is conducted. This method uses a single microwave frequency source and it is low-priced.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1045-1047
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• 1992

Photovoltaics is considered to be one of the most promising technologies which can greatly contribute to future energy supply because of a large, secure, essentially inexhaustible and broadly available resource - sunlight. However, recent progresses in photovoltaics make also possible its short-term practical application in some areas. Among them the solar air conditionner powered by photovoltaic system attracts considerable interest due to its main advantage which consists in the reduction of drastically increasing electricity peak load in summer season. In this review paper our current study on the solar air conditionner will be briefly summarized.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.152-159
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• 1999

YBa$_2Cu_3O_{7-{\delta}}$ (YBCO) films grown on CeO$_2$-buffered r-cut sapphire substrates (CbS's) were prepared and their structural and electrical properties were measured. Post-annealed CeO$_2$ films were used as buffer layers for the experiments. It turned out that the YBCO films grown on post-annealed CbS's had the rms roughness of less than 20 ${\AA}$ and peak-to-peak roughness of about 30 ${\AA}$ when the YBCO film thickness was 3000 ${\AA}$. Meanwhile, YBCO films on in-situ grown CeO$_2$ buffer layers on r-cut sapphire substrates appeared to have the peak-to-peak roughness of more than 450 ${\AA}$. X-ray diffraction data revealed that the YBCO flms were epitaxially grown along the c-axis with the typical FWHM of(005) ${\theta}$ -2 ${\theta}$ peak about 0. 16 $^{\circ}$ and ${\Delta}$ ${\omega}$ of the (005) peak about 0.5 $^{\circ}$. T$_c$ > 87 K, ${\Delta}$T < 1 K and R(look)/R(100K) ${\ge}$3 were observed from the YBCO films. Applicability of the YBCO films for high-frequency applications was described.

• Journal of Korean Ophthalmic Optics Society
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• v.6 no.1
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• pp.101-105
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• 2001

It was measured the transmittance and the reflectance by tie dip method using the UV cut lens' UV solution. The half point and the edge wavelength of the transmittance were wry well applied to the eqution of a dip time dependence. $$W=W_0+A_1{e}{x}{p}[-(x-x_1)/t_1]$$ The half point wavelength of the transmittance shifted from 358 nm to 408 nm and the edge wavelength moved from 340 nm to 398 nm. The more dip time had long the less intensity of main reflectance peak-380 nm was small and shifted to long wavelength regions. And the component peak of UV solution began to show in dip time-10 min.

• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.135-136
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• 2012

Renewable energy is getting more important due to its alternative usage of fossil fuel. This paper discusses the system using Peak-cut alagorithm of solar power which takes great proportion in renewable energy. It also proves the validity of this system by simulation and experiment.