• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.1
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• pp.63-69
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• 2006

This study deals with the friction welding of A2024- T6 to A6061- T6; The friction time was variable conditions under the conditions of spindle revolution of 2000rpm, friction pressure of 50MPa, upset pressure of 100MPa, and upset time of 5.0seconds. Under these conditions, the microstructure of weld interface, tensile fracture surface and mechanical tests were studied, of friction weld, and so the results were as follows. 1. When the friction time was 1.5seconds under the conditions, the maximum tensile strength of the friction weld happened to be 292MPa, which is $94.2\%$ of the base material's tensile strength(310MPa). At the same condition, the maximum shear strength was 2l2MPa, which is equivalent to $103\%$ of the base material's shear strength (205MPa). 2. At the same condition, the maximum vickers hardness was Hv 146 at A2024- T6 nearby weld interface, which is higher Hv3 than condition of the friction time 0.5seconds, and the maximum vickers hardness was Hvl20 from weld interface of A6061-T6, which is higher Hv28 then base material's. 3. The results of microstructure analysis show that the structures of two base materials have fractionized and rearranged along a column due to heating and axial force during friction, which has affected in raising hardness and tensile strength.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.1068-1072
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• 1997

This work deals with on investigation the influence of various additives to a base stock cutting fluid in order to develop a better deep hold drilling. This investigation has been aiming at developing an oil which gives a maximum cutting efficiency at a minimum wear rate of the tool and the guiding pads. The purpose of study is to analyze how guide pad of tools, workpiece and the change of contained quantity of extreme pressure additive in cutting fluids have effects on the hold over size of cutting hole, surface roughness of workpiece,wear rates of guide pad and roundness during the deep hole machining of SM55C with solid BTA drill by using BTA drilling system through experiment. Conclusion reached is as follows. It has been proved that the contained quantity of surphur more affects machinability than that of extreme pressure additive of chlorine of cutting fluid in BTA drilling during Deep Hole Drilling. Considering its base oil, the the contained quantity of extreme pressure assitive of surphur can be different, but it's judged that the range of 1.5 ~ 2.0% is suitable to machinability for workpiece in BTA drilling. Regarding guide pad, it's judged that the reduction of wear is possible in propotion to the contained quantity of exrreme pressure additive of chlorine against supporting of cutting force and Bumishing operation of machining parts in cutting.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.6
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• pp.524-534
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• 2013

Gasoline direct injection(GDI) engine has a high thermal efficiency, but it has a problem to increase carbon emissions such as soot and $CO_x$. In this study, the objective is to analyze numerically a problem for adding the hydrogen during the intake stroke so as to reduce the injected amount of gasoline in GDI engines. For selection of the base model, the cylinder pressure of simulation is matched to experimental data. The numerical analysis are carried out by a CFD model with the hydrogen addition of 2%, 3% and 4% on the volume basis. In the case of 3% hydrogen addition, the injected gasoline amount is only changed to match the maximum pressure of simulation to that of the base model for additional study. It is found that the combustion temperature and pressure increase with the hydrogen addition. And NO emission also increases because of the higher combustion temperature. $CO_x$ emissions, however, are reduced due to the decrease of injected gasoline amount. Also, as the injected gasoline amount is reduced for the same hydrogen addition ratio, the gross indicated work is no significant, But NO and $CO_x$ emissions are considerably decreased. On the order hand, $CO_x$ emissions of two cases are more decreased and their gross indicated works are higher obtained than those of the base model.

• Journal of the Korean Society of Safety
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• v.19 no.4 s.68
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• pp.109-116
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• 2004

The dynamic behavior of the rectangular liquid storage structure is known to be greatly influenced by fluid-structure interaction. By mounting the liquid storage structure on the properly designed base isolators, dynamic response of the superstructure can be reduced. However, base isolators inevitably incur large displacement of the structure to the ground ·ind may give adverse effects on the sloshing height. This paper presents the analysis method for fluid-structure-isolator interaction in base-isolated rectangular liquid storage structures. In the method, the irrotational motion of invicid and incompressible ideal fluid is expressed by analytic solutions and the superstructure and isolators are properly modeled by finite element and bilinear model. Free surface sloshing motion, hydrodynamic pressure acting on the wall and structural response are obtained by the presented method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.26-28
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• 1996

A high power SiGe HBT has been fabricated using APCVD(Atmospheric Pressure Chemical Vapor Deposition) and its perfermanoe has been analysed. The composition of Ge in the SiGe base was graded from 0% at the emitter-base junction to 20% at the base-collector junction. As a base electrode, titanium disilicide(TiSi$_2$) was used to reduce the extrinsic base resistance. The SiGe HBT with an emitter area of 2$\times$8${\mu}{\textrm}{m}$$^2$typically has a cutoff frequency(f$_{T}$) of 7.0GHz and a maximun oscillation frequency(f$_{max}$) of 16.1GHz with a pad de-embedding. The packaged high power SiGe HBT with an emitter area of 2xBx80${\mu}{\textrm}{m}$$^2$typically shows a cutoff frequency of 4.7GHz and a maximun oscillation frequency of 7.1GHz at Ic of 115mA.A.A.

• Proceedings of the KWS Conference
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• 2000.10a
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• pp.192-195
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• 2000

This paper describes a fundamental investigation of the friction welding condition for pure copper/pure titanium and the effect of friction time, upset pressure on the mechanical and metallurgical properties of friction welding. Under the constant upset pressure, the tensile strength make a little difference with an increase in friction time. At the constant friction time, the tensile strength increased with an increase in upset pressure. The tensile fracture of Cu to Ti joint occurred in Cu base material near interface.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.36-37
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• 2003

Three-dimensional numerical analysis of the flow around rectangular cylinders with various side ratios, D/H, from 0.2 to 2.0 is carried out for Reynolds number of 1000 by using multi-directional finite difference method in multi-grid. The predicted results are well compared with the experimental data. It is found that fluid dynamics characteristics alternate between high pressure mode. and low pressure mode of the base pressure for rectangular cylinder of D/H=0.2-0.6.

• Journal of Welding and Joining
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• v.3 no.2
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• pp.27-34
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• 1985

The mechanical properties and bonding mechanism of aluminum, copper and mild steel have been determined in cold pressure welding. The brittle cover layer to be established by scratch-brushing plays an important role in bond strength and has an influence on the threshold of deformation. The cold pressure welding was achieved at 54% of height reduction in A1-A1, 75% in Cu-Cu, 56% in Al-Cu, and 74% in Cu-steel. The height reduction at which the bond strength of weld interface was the same as the tensile strength of base metal should be over 76% in Al-Al, 82% in Cu-Cu, and 78% in Al-Cu.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.05b
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• pp.635-640
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• 1995

Two techniques for the verification of the phase separation in ferrite phase of primary pressure bounary component materials, the primary cause of thermal aging embrittlement, are presented. Data base of room-temperature Charpy V-notch impact energy during reactor service was estimated as a measure of the degree of embrittlement. The serviceable period of CF-3 and CF-8 alloys as the primary pressure boundary components may be acceptably extended for 60 years of lifetime. However, the integrity of CF-8M alloys can be degraded seriously after several years of service in the nuclear reactor.

• Journal of Trauma and Injury
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• v.18 no.2
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• pp.127-134
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• 2005

Purpose: Currently, there is a variety of systems available for predicting prognosis of trauma patients such as trauma score, Injury severity score (ISS) and acid-base variables. But it is not clear that the initial acid-base variables are predictors of prognosis in trauma patients at the emergency department. The objective of this study is to compare the base deficit, lactate and strong ion gap as an early predictor of mortality in trauma patients. Methods: Retrospective record review of 136 trauma patients needed to admit to intensive care unit via emergency department (June 2004 to February 2005). Data included age, injury mechanism, ISS, Revised trauma score (RTS), Multiple organ dysfunction score (MODS), Acute physiology and chronic health evaluation III (APACHE III), Glasgow coma scale (GCS), laboratory profiles, calculated anion gap and strong ion gap. Patients were divided into survivors and non-survivors, shock group and non-shock group with comparison by t-test;significance was assumed for p<0.05. Correlation between acid-base variables and mean arterial blood pressure (MABP) was evaluated. Results: There was a significant difference between the RTS (p=0.00), APACHE III (p=0.00), MODS (p=0.00), GCS (p=0.00) of survivors and non-survivors. There was no significant difference between the ISS (p=0.082), lactate (p=0.541), base excess (p=0.468) and SIG (p=0.894) of survivors and non-survivors. There was a significant difference between the RTS (p=0.023), APACHE III (p=0.002), lactate (p=0.000), base excess (p=0.000) and SIG (p=0.000) of shock and non-shock group. There was no significant difference between the ISS (p=0.270), MODS (p=0.442) and GCS (p=0.432) of shock and non-shock group. The base excess was most correlated to MABP (r2=0.150). Conclusion: Initial base deficit, serum lactate and SIG are not predictors of mortality in moderate to severe trauma patients. Initial base deficit, serum lactate and SIG are correlated with the mean arterial blood pressure in trauma patients in emergency department.