• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2006.05a
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• pp.202-205
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• 2006

Recently, high vacuum pumps are widely used in the semi-conduction and liquid-crystal display ( LCD ) process. The composite-type high vacuum pumps are widely used in the various processes. In this study, the pumping performance of composite-type molecular pumps has been investigated experimentally. The experimented pumps are a compound molecular pump ( CMP ) and hybrid molecular pump ( HMP ). The CMP consists with helical-type drag pump, at lower part, and with turbomolecular pump ( TMP ), at upper part. The HMP consists with disk-type drag pump, at lower part, and with TMP, at upper part. The experiments are performed in the outlet pressure of $0.2\;{\sim}\;533\;Pa$. We have measured the ultimate pressure, compression ratio, and pumping speed

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.11
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• pp.1359-1367
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• 2004

The demand of vacuum pump has been increased in the process of semi-conduct manufacturing, as a core component. The response of the system for vacuum pump performance test can be utilized to assess the system and to obtain the reliability of the apparatus for the test. The system consists of gas supply tank, pressure chamber, measurement chamber and transmission line. Transient analysis for compressible fluid has been conducted to evaluate the dynamic characteristic of the volume terminated transmission line. Numerical approach based on the method of characteristics is used for the analysis. The response is evaluated with the important parameters for the system: i.e., length and diameter of the line, volume of the terminal tank. Using the numerical results, pumping speeds are calculated and then compared to the experimental results.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.95-97
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• 1995

A superconducting current generator, or a superconducting rectifier(SCR) is used as a current source to energize a superconducting magnets in SMES, MRI. We selected a full-wave SCR among various SCR models and analyzed its operational characteristics by computer simulation. In process of pumping the current, the improvement of performance is dependent on how much bigger the open resistance of the switch is in comparison to load coil impedance when one of two switches become active. Faster transfer can he seen in resistive commutation mode by shortening the time elapsed for the resistance to arrive at certain level from zero state. Although recovery time for the switch has no direct effect on current pumping, optimal switch design is needed to increasing operational frequency.

• KCID journal
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• v.14 no.1
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• pp.67-79
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• 2007

Concrete repair and reinforcement is a complex process, presenting unique challenges very different from those experience in the field of construction. The purpose of this study is to analyze the pattern and mechanism of deteriorations in irrigation and drainage structure. Damage and deteriorated structures are classified with several types. This provides a survey of crack repair methods, including a summary of the procedures that are being used. It is systematically evaluated with the disintegration on irrigation & drainage structure; drainage sluice gate, pumping station, drainage pumping station. Following the evaluation of the irrigation & drainage structure, a suitable repair and reinforcing procedure can be selected based on this report

• Journal of Korean Society on Water Environment
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• v.32 no.3
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• pp.253-260
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• 2016

To reduce energy consumption in wastewater treatment plants (WWTPs), renewable energy applications such as small hydropower, solar energy, and wind energy are popular. However, it should be noticed that energy originated from operation of wastewater treatment process can be reduced through optimized operation based on analysis of factors affecting energy. In this research, the relationship to the various operational variables and influent factors was explored using correlation analysis and decision tree algorithm. Due to the non-linear characteristics of the process, it was difficult to find clear linear patterns through correlation analysis. However, decision tree algorithm showed its usefulness in uncovering hidden patterns that consume energy. As operational factors, influent flowrate, the amount of aeration, nitrate recycling pumping rate, and sludge wasting pumping rate were selected as important factors. For environmental factors associated with influent compositions and removal rate, BOD and T-N removal rate were selected as significant factors.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.105-106
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• 2008

As a carrier of malaria and sneak of blood, mosquitoes are an unpleasant insect. However, there are several unknown natural secretes related with mosquitoes. Among them, we focused on the blood sucking process of a female mosquito. The main objective of this study is to understand the mosquito's blood sucking mechanism that can be used to resolve the problem encountered in the injection or transport of infinitesimal biological fluids in a micro-chip. At first, the velocity fields of blood-sucking flow in a proboscis were measured using a micro-particle image velocimetry (PIV) technique. The velocity signals of flow in the proboscis show periodic variation. This seems to be resulted from the beating of the pharyngeal pump which works as driving power. To analyze the pumping mechanism, the temporal variation of the pharyngeal pump was visualized using the synchrotron X-ray micro-imaging technique. The volume variation was estimated by the help of digital image processing techniques. Once the main mechanism of blood sucking process was found, a effective micro-pumping system with high efficiency would be developed in near future.

• Advances in environmental research
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• v.1 no.2
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• pp.125-142
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• 2012

Clean development mechanism (CDM) validity study was conducted to suggest better and more adaptable CDM scenario on water treatment plant (WTP). Potential four scenarios for CDM project; improvement of intake pumping efficiency, hydro power plant construction, solar panel construction and system optimization of mechanical mixing process were evaluated on S-WTP in Korea. Net present value (NPV) of each scenario was estimated based on sensitivity analysis with the variable factors to investigate the CDM validity percentile. Hydro power plant construction was the best option for CDM business with 97.76% validity and $1,127,069 mean profit by 9,813 $tonsCO_2e$/yr reduction. CDM validity on improvement of intake pumping efficiency was 90.2% with $124,305 mean profit by huge amount of $CO_2$ mitigation (10,347 $tonsCO_2e$/yr). System optimization of mechanical mixing process reduced 15% of energy consumption (3,184 $tonsCO_2e$/yr) and its CDM validity and mean profit was 77.25% and $23,942, respectively. Solar panel construction could make the effect of 14,094 $tonsCO_2$ mitigation annually and its CDM validity and mean profit was 64.68% and $228,487, respectively.

• Current Optics and Photonics
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• v.3 no.3
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• pp.248-255
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• 2019

Spherical $CeO_2:Ho^{3+}/Yb^{3+}$ particles were synthesized using spray pyrolysis, and the upconversion (UC) properties were investigated with changing the preparation conditions and the infrared pumping power. The resulting particles had a size of about $1{\mu}m$ and hollow structure. The prepared $CeO_2:Ho^{3+}/Yb^{3+}$ particles exhibited intense green emission due to the $^5F_4/^5S_2{\rightarrow}^5I_8$ transition of $Ho^{3+}$ and showed weak red or near-IR peaks. In terms of achieving the highest UC emission, the optimal concentrations of $Ho^{3+}$ and $Yb^{3+}$ were 0.3% and 2.0%, respectively. The UC emission intensity of prepared $CeO_2:Ho^{3+}/Yb^{3+}$ particles had a linear relationship with crystallite size and concentration quenching was caused by dipole-dipole interaction between the same ions. Based on the dependency of UC emission on the pumping power, the observed green upconversion was achieved through a typical two-photon process and concluded that the main energy transfer from $Yb^{3+}$ to $Ho^{3+}$ was involved in the ground-state adsorption (GSA) process.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.3
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• pp.312-320
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• 2019

In this paper, we design a 512Kb eFlash IP using 110nm eFlash cells. We proposed eFlash core circuit such as row driver circuit (CG/SL driver circuit), write BL driver circuit (write BL switch circuit and PBL switch select circuit), read BL switch circuit, and read BL S/A circuit which satisfy eFlash cell program, erase and read operation. In addition, instead of using a cross-coupled NMOS transistor as a conventional unit charge pump circuit, we propose a circuit boosting the gate of the 12V NMOS precharging transistor whose body is GND, so that the precharging node of the VPP unit charge pump is normally precharged to the voltage of VIN and thus the pumping current is increased in the VPP (boosted voltage) voltage generator circuit supplying the VPP voltage of 9.5V in the program mode and that of 11.5V in the erase mode. A 12V native NMOS pumping capacitor with a bigger pumping current and a smaller layout area than a PMOS pumping capacitor was used as the pumping capacitor. On the other hand, the layout area of the 512Kb eFlash memory IP designed based on the 110nm eFlash process is $933.22{\mu}m{\times}925{\mu}m(=0.8632mm^2)$.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.787-790
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• 2012

In downtown, construction noise related claims are the most important issues. Sometimes noise related claims halt the construction process. Therefore, Introduction of noise reduction measures is common to construction process with a loud noise. This case is about concrete pouring for mat foundation of super tall building. Concrete pouring process using High Pressure Pumping machine causes high noise level in the vicinity of area. And large number of transit-mixer truck cause traffic congestion. This paper introduces effort and process to prevention of construction noise claims on massive scale concrete pouring.