• Journal of the Microelectronics and Packaging Society
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• 제14권1호
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• pp.33-38
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• 2007

We studied a bonding at low temperature using polymer bump and Non-Conductive Adhesive (NCA), and studied the reliability of the polymer bump/Al pad joints. The polymer bumps were formed on oxidized Si substrates by photolithography process, and the thin film metals were formed on the polymer bumps using DC magnetron sputtering. The substrate used was AL metallized glass. The polymer bump and Al metallized glass substrates were joined together at $80^{\circ}C$ under various pressure. Two NCAs were applied during joining. Thermal cycling test ($0^{\circ}C-55^{\circ}C$, cycle/30 min) was carried out up to 2000 cycles to evaluate the reliability of the joints. The bondability was evaluated by measuring the contact resistance of the joints through the four point probe method, and the joints were observed by Scanning Electron Microscope (SEM). The contact resistance of the joints was $70-90m{\Omega}$ before the reliability test. The joints of the polymer bump/Al pad were damaged by NCA filler particles under pressure above 200 MPa. After reliability test, some joints were electrically failed since thinner metal layers deposited at the edge of bumps were disconnected.

• Korean journal of applied entomology
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• 제39권1호
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• pp.31-41
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• 2000

Community analysis of oribatid mites was conducted in Namsan and Kwangreung coniferous forests which have been received by different degrees of environmental pressures through urbanization processes. Oribatid mites were sampled in the litter and soil layer of study sites from May 1993 to October 1994. Although two sites have been under similar weather condition, seasonal changes in oribatid mites density did not show a synchronized pattern. Density in spring and summer showed stable pattern with low fluctuations, but unstable pattern in autumn between 1993 and 1994. And these patterns were highly correlated with precipitation. The density and species number were higher in the litter layer than in the soil layer and showed no typical seasonal changes. The dominant species were Scheloribates latipes (1 l.78%), Pergalumna altera (8.92%), Eohypochthonius crassisetiger (7.58%), Scheloribates sp. (6.89%) and Suctobelbella yezoensis (5.04%) in Namsan, and Ceratozetes japonicus (25.72%), Punctoribates punctum (14.15%), Trichogalumna nipponica (10.96%) and Ramusella sengbuschi (5.08%) in Kwangreung. The number of species with high constany were 10 and 18 in Namsan and Kwangreung, respectively. Namsan showed the feature of urban forests. In analysis of species diversity, species richness was significantly higher in Kwangreung than in Namsan, while shannon (H') and evenness index (J') were higher in Namsan than in Kwangreung. The values of shannon index (H') in Namsan and Kwangreugn were 2.83 and 2.62, respectively and evenness index (J') were 0.78 and 0.67, respectively. The value of similarity index between two sites was 0.68.

• Journal of the Korean Geotechnical Society
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• 제17권4호
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• pp.289-299
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• 2001

본 연구는 균질 및 2개층 비균질지반에서 사질토지반 상에 놓인 정방형 기초의 극한지지력과 침하에 대하여 고찰하였다. 본 연구는 얕은기초의 거동에 대한 정방형 기초의 크기, 지반 상대밀도, 기초 폭에 대한 상부층의 두께 비(H/B), 상부층 아래 경계면의 경사($\theta$) 그리고 지반강성비의 영향을 규명하기 위하여 모형실험을 수행하였다. 동일 상대밀도에서 지지력 계수($N_{{\gamma}}$)는 일정하지 않으며 기초 폭에 직접적으로 관련되며 지지력계수는 기초 폭이 증가함에 따라 감소하였다. 기초크기의 영향과 구속압력의 영향을 고려하는 Ueno 방법에 의한 극한지지력의 예측값은 고전적인 지지력 산정식보다 더 잘 일치하며 그 값은 실험값의 65% 이상으로 나타났다. $\theta$=$0^{\circ}$인 2개층 지반의 결과에 근거하여, 극한지지력에 대한 하부층 지반의 영향을 무시할 수 있는 한계 상부층 두께는 기초 폭의 2배로 결정되었다. 그러나, 73%의 상부층 상대밀도인 경우는 침하비($\delta$B) 0.05 이하에서만 이 결과가 유효하였다. 경계면이 경사진 2개층 지반의 결과에 근거하여, 상부층의 상대밀도가 느슨할수록 그리고 상부층의 두께가 클수록 극한지지력에 대한 경계면 경사의 영향은 크지 않는 것으로 나타났다. 경계면의 경사가 증가함에 따른 극한침하량의 변화는 경계면이 수평인 경우($\theta$=$0^{\circ}$)를 기준으로 0.82~1.2(상부층 $D_{r}$=73%인 경우) 그리고 0.9~1.07(상부층 $D_{r}$=50%인 경우) 정도로 나타났다.Markup Language 문서로부터 무선 마크업 언어 문서로 자동 변환된 텍스트를 인코딩하는 경우와 같이 특정한 응용 분야에서는 일반 문자열에 대한 확장 인코딩 기법을 적용할 필요가 있을 수 있다.mical etch-stop method for the etching of Si in TMAH:IPA;pyrazine solutions provides a powerful and versatile alternative process for fabricating high-yield Si micro-membranes. the RSC circle, but also to the logistics system in the SLC circle. Thus, the RSLC model can maximize combat synergy effects by integrating the RSC and the SLC. With a similar logic, this paper develops "A Revised System of Systems with Logistics (RSSL)" which combines "A New system of Systems" and logistics. These tow models proposed here help explain several issues such as logistics environment in future warfare, MOE(Measure of Effectiveness( on logistics performance, and COA(Course of Actions) for decreasing mass and increasing velocity. In particular, velocity in logistics is emphasized.

• Korean Chemical Engineering Research
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• 제49권6호
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• pp.816-822
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• 2011

Pervaporation is known to be a low energy consumption process since it needs only an electric power to maintain the permeate side in vacuum. Also, the pervaporation is an environmentally clean technology because it does not use the third material such as an entrainer for either an azeotropic distillation or an extractive distillation. In this study, Silicalite-1 particles are hydrothermally synthesized and polydimethylsiloxane(PDMS)-zeolite composite membranes are prepared with a mixture of synthesized Silicalite-1 particles and PDMS-polymer. They are used to separate n-butanol from its aqueous solution. Pervaporation characteristics such as a permeation flux and a separation factor are investigated as a function of the feed concentration and the weight % of Silicalite-1 particles in the membrane. A 1,000 $cm^3$ aqueous solution containing butanol of low mole fraction such as order of 0.001 was used as a feed to the membrane cell while the pressure of the permeation side was kept about 0.2~0.3 torr. When the butanol concentration in the feed solution was 0.015 mole fraction, the flux of n-butanol significantly increased from 14.5 g/ $m^2$/hr to 186.3 g/$m^2$/hr as the Silicalite-1 content increased from 0 wt% to 10 wt%, indicating that the Silicalite-1 molecular sieve improved the membrane permselectivity from 4.8 to 11.8 due to its unique crystalline microporous structure and its strong hydrophobicity. Consequently, the concentration of n-butanol in the permeate substantially increased from 0.07 to 0.15 mole fraction. This composite membrane could be potentially appliable for separation of n-butanol from insitu fermentation broth where n-butanol is produced at a fairly low concentration of 0.015 mole fraction.

• Transactions of the Korean Society of Mechanical Engineers B
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• 제35권10호
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• pp.981-987
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• 2011

In this study, single cylinder engine experiment was carried out to investigate combustion characteristics spray guided direct injection spark ignition engine. In the result of engine experiment, it was shown that flammable window of injection timing was existed. The combustion efficiency increased with retarding injection timing, reaching a peak value, subsequent to decrease again. These results were likely due to the effect of ambient pressure on stratified-premixed mixture preparation. 150 bar injection pressure condition and retarded injection timing from the best combustion efficiency injection timing showed the highest IMEP value due to the advanced combustion phase of the maximum combustion efficiency condition. HC emission showed same trend of combustion efficiency, and smoke emission was increased as injection timing was retarded due to the increased locally rich area in the high ambient pressure. NOx emission showed decreasing trend as injection timing was retarded. This is likely due to the maximum in-cylinder temperature was decreased with retarded combustion phase.

• Transactions of the Korean Society of Mechanical Engineers B
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• 제35권8호
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• pp.781-787
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• 2011

We design a four-stage propane-refrigerant centrifugal compressor for an LNG plant. Using a commercial code, we aerodynamically designed the compressor at each design point of the corresponding stages. We estimated the one-dimensional aerodynamic design output and the three-dimensional shape of the impeller flow passage via three-dimensional flow analysis. In particular, we discuss in detail the flow characteristics of the impeller and the vaneless diffuser passages of the fourth-stage compressor in terms of the velocity fields, the pressure, and the entropy distributions of the flow passages. We include the flow effects of the tip clearance flow, because at this stage the rotating speed and total inlet pressure are higher than those at the other compressor stages are. We carried out performance tests of the designed compressor stages using propane as a refrigerant in the LNG cycle. The practical evaluation could lead to design enhancements in the future.

• Journal of the Korean Society for Railway
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• 제18권1호
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• pp.8-14
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• 2015

This paper describes a prediction method for micro-pressure wave emitted from a tunnel on the Kyung-bu high-speed railway. Pressure and micro-pressure wave were measured simultaneously to obtain some constants for the prediction method. The change of a micro-pressure wave were analyzed according to the speed of the train, the track bed type, and the distance from a tunnel portal. At a train speed of 300km/h, the micro-pressure wave of 4.0km long ballast track tunnel is about 7.5Pa; that of 3.3km long slab track tunnel is about 14.3Pa The strength of the micro-pressure wave decreases in inverse proportion to the distance and becomes about 0.5~1.0Pa at a point of 100m from the tunnel exit. Micro-pressure waves were predicted using the formula with the obtained the constants. Using a comparison between the predicted data and field measurement data, it was confirmed that micro-pressure wave can be predicted easily through the prediction formula.

• Journal of Aerospace System Engineering
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• 제12권2호
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• pp.7-14
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• 2018

In this study, a new check valve was studied to improve the load pressure of a brake system with a small piezoelectric-hydraulic pump. During the pressurization process, the steady-state pressure at the load is affected by the ratio of the cross-sectional area of the check valve the chamber pressure and load pressure. Since the flow path cover of the check valve is made wider than the cross-sectional area of the output flow to prevent backflow, a method of reducing the area ratio is proposed for a higher load pressure by mounting an additional mass to a thin plate spring type check valve. To identify the effect of mounting an additional mass to the existing check valve on the load pressure, a simple brake system with a small piezoelectric-hydraulic pump was modeled using a commercial code AMESim. The AMESim modeling was verified by comparing the simulation results with the experimental results of the pump the existing check valve. The additional mass was added to the verified AMESim modeling and higher load pressure was able to be obtained through simulation. The 35% performance improvement in load pressure identified by carrying out pressurization test of the brake system after adopting the new check valve the small piezoelectric-hydraulic pump.

• The Journal of the Petrological Society of Korea
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• 제26권4호
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• pp.385-398
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• 2017

Jiri Mountain lies in the southwestern portion of the Yeongnam massif, which is one of the Precambrian basement massifs of the Korean Peninsular, consisting essentially of high-grade metamorphic rocks. The geology of the area mainly consists of Paleoproterozoic metasedimentary migmatitic gneisses, granitic gneisses which are classified into granitic gneiss, (K-feldspar porphyroblastic) granitic gneiss and quartzo-feldspathic gneiss, charnockite and anorthosite based on their occurrence and petrographic characteristics. The ages obtained from these rocks mainly span a narrow range between ca. 1,876 and 1,856 Ma although inherited cores of zircons from massive granite gneiss yielded much older age spectrum (>2,029 Ma). The age of major metamorphism is ca. 1850-1840 Ma and the metamorphic condition obtained from mineral assemblages and geothermobarometers is about 4-6 kb and up to $700-750^{\circ}C$. These results indicate that in the area intense granitic magmatism and metamorphism occurred in the deep crust during Paleoproterozoic orogeny. Some younger age of charnockite (1,856-1,865 Ma) and anorthosite (1,861-1,862 Ma) might indicate the beginning of intraplate rifting leading to felsic and mafic magmatism just after the orogeny. In conclusion, the rocks in the Jiri Mountain area which formed at a mid to deep crustal zone provide us windows into the deep crust.

• The Journal of the Acoustical Society of Korea
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• 제39권4호
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• pp.303-317
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• 2020

Extracorporeal Shock Wave Therapy (ESWT) is an innovative treatment in chronic musculoskeletal pain management and cardiovascular diseases. In this study, we surveyed the acoustic shock wave outputs from the domestically used focal type ESWT devices. The survey data were collected through 30 technical documents registered to the Ministry of Food and Drug Safety (MFDS), Rep. Korea. The results show that the focusing geometry varies largely, 5 mm to 65 mm in the focal length, 3 mm to 30 mm in focal width, and 4 mm to 108 mm in focal depth. The maximum positive pressure (P+) ranges from 7 MPa to 280 MPa, the focal Energy Flux Density (EFD) from 0.0035 mJ/㎟ to 35 mJ/㎟, and the energy per pulse (E) from 0.737 mJ to 80.86 mJ. All domestic PE-type (five) and one EM-type domestic devices included in the analysis of the correlation between P+ and EFD are shown to be far beyond the usual ranges and do not comply with expected correlation so that the reliability of their data was suspected. For the suspected, post-performance tests are required by a recognized testing agency. MFDS guidelines need to be revised so that the pass criteria for the shock wave acoustic outputs can be based on the clinical tests for indications.