• Proceedings of the KWS Conference
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• 2009.11a
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• pp.37-37
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• 2009

Due to their high corrosion resistance and improved mechanical properties super-duplex stainless steel (SDSS) are extensively used in petrochemical plants such as facilities in modern oil platform and off-shore process equipment. It is well known that the best mechanical and corrosion resistance properties of super-duplex stainless steel are obtained with a microstructure having approximately equal amounts of austenite and ferrite. And it is also known that sigma($\sigma$), chi($\chi$), secondary austenite(${\gamma}2$), chromium carbides and nitride affected adversely their properties. Therefore these phases must be avoided. However, effects of succeeding weld thermal cycle on the change of microstructure of weldment at multi-pass weld were not seldom experimentally researched. Therefore in the present work, the change of weldmetal microstructure and the effect of microstructure on pitting corrosion property at $40^{\circ}C$ by succeeding each weld thermal cycle were researched. The thermal history of root side was measured experimentally and the change of microstructure of root weld according to thermal cycle of each weld layer was evaluated. And the relationship between microstructure of root weld and pitting corrosion property at $40^{\circ}C$ was also investigated. Results of the present work are show as below. 1. The ferrite contents of root weld are gradually reduced by succeeding weld thermal cycle. 2. The 2nd phases such as sigma($\sigma$), chi($\chi$), secondary austenite(${\gamma}2$), chromium carbides and nitride are increased gradually by succeeding weld thermal cycle. 3. The pitting corrosion was detected in root weld part and weight loss by pitting corrosion is increased in proportional to the time exposed over $600^{\circ}C$ of the root weld. 4. The succeeding weld thermal cycles affect the microstructure of the former weldments and promote the formation of 2nd phases. That is, the more succeeding welds are added, the more 2nd phases are gradually increased. Consequently, it is thougth that this adversely affects pitting corrosion property.

• Journal of Environmental Science International
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• v.13 no.5
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• pp.449-467
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• 2004

Interannual and decadal scale changes in body size of Pacific saury, catch and catch per unit effort were examined to investigate the environmental effects on the stock structure and abundance in the Tsushima Warm Current region. Interannual changes in thermal conditions are responsible for the different occurrence (catch) rates of sized group of the fish. Changes in body size due to environmental variables lead the stock to be homogeneous during the period of high abundance, while one of the reminder cohorts supports the stock during the period of low level of abundance. Migration circuits of two cohorts of saury stock are hypothesized on the basis of short life span and spatio-temporal changes of the stock structure in normal environmental conditions. Changes in upper ocean structure and production cycles by the decadal scale climate changes lead changes in stock structure and recruitment, resulting in the fluctuation of saury abundance. Hypothesized mechanism of the effects of climate changes on stock structure and abundance is illustrated on the basis of changes in thermal regime and production cycle.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.11
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• pp.699-707
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• 2017

This study presents a comparative thermodynamic analysis of subcritical and transcritical organic Rankine cycles for the recovery of low-temperature heat sources considering nine substances as the working fluids. The effects of the turbine inlet pressure, source temperature, and working fluid on system performance were all investigated with respect to metrics such as the temperature distribution of the fluids and pinch point in the heat exchanger, mass flow rate, and net power production, as well as the thermal efficiency. Results show that as the turbine inlet pressure increases from the subcritical to the supercritical range, the mismatch between hot and cold streams in the heat exchanger decreases, and the net power production and thermal efficiency increase; however, the turbine size per unit power production decreases.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.6
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• pp.192-199
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• 2002

Largely, there are three kinds of the design criteria of piping system in petrochemical plant. The first is on the pipe thickness in accordance with the design pressure of piping system. The second is on the static state evaluation by thermal growth and the other is on the dynamic evaluation by piping vibration. According to the ASME B31.3 code, the internal pressure design thickness fur straight pipe shall be calculated as a code formula. And the static design by thermal displacement is defined 7000 cycles of fatigue life in operating the piping system with a design condition. However, the dynamic design evaluation in comparative with small displacements of high frequencies to the static condition has not established clearly the method, yet. So, this study purposes to present the trial of a proposal of dynamic design criterion on the basis of static design method.

• Journal of Powder Materials
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• v.5 no.2
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• pp.145-153
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• 1998

W-Cu alloy is attractive to thermal managing materials in microelectronic devices because of its good thermal properties. The metal injection molding (MIM) of W-Cu systems can satisfy the need for mass production of the complex shaped W-Cu parts in semiconductor devices. In this study, the application of MIM process of the mechanically alloyed (MA) W-Cu composite powders, which had higher sinterability were investigated. The MA W-Cu powders and reduction treated (RT) powders were injected by using of the multicomponent binder system. The multi-stage debinding cycles were adopted in $N_2$ and $H_2$ atmosphere. The isostatic repressing treatment was carried out in order to improve the relative density of brown parts. The brown part of RT W-Cu composite powder sintered at 110$0^{\circ}C$ had shown the higher sinterability compared to that of MA powder. The relative sintered density of all specimens increased to 96% by sintering at 120$0^{\circ}C$ for 1 hour. The relationship between green density and the sintering behavior of MA W-Cu composite powder was analyzed and discussed on the basis of the nanostructured characteristics of the MA W-Cu composite powder.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.12
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• pp.1283-1288
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• 2004

Metal-ferroelectric-insulator-semiconductor(WFIS) capacitors using rapid thermal annealed LiNbO$_3$/AlN/Si(100) structure were fabricated and demonstrated nonvolatile memory operations. The capacitors on highly doped Si wafer showed hysteresis behavior like a butterfly shape due to the ferroelectric nature of the LiNbO$_3$ films. The typical dielectric constant value of LiNbO$_3$ film in the MFIS device was about 27, The gate leakage current density of the MFIS capacitor was 10$^{-9}$ A/cm$^2$ order at the electric field of 500 kV/cm. The typical measured remnant polarization(2P$_{r}$) and coercive filed(Ec) values were about 1.2 $\mu$C/cm$^2$ and 120 kV/cm, respectively The ferroelectric capacitors showed no polarization degradation up to 10$^{11}$ switching cycles when subjected to symmetric bipolar voltage pulses of 1 MHz. The switching charges degraded only by 10 % of their initial values after 4 days at room temperature.e.

• Proceedings of the Korean Aquaculture Society Conference
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• 2004.05a
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• pp.169-171
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• 2004

Interannual and decadal scale body size of Pacific saury, catch and catch per unit effort were examined to investigate the environmental effects on the stock structure and abundance in the Tsushima Warm Current region. Interannual changes in thermal conditions are responsible for the different occurrence (catch) rates of sized group of the fish. Changes in body size due to environmental variables lead the stock to be homogeneous during the period of high abundance, while one of the reminder cohorts supports the stock during the period of low level of abundance. Migration circuits of two cohorts of saury stock are hypothesized on the basis of short life span and spatio-temporal changes in stock structure in normal environmental conditions. Changes in upper ocean structure and production cycles by the decadal scale climate changes lead changes in stock structure and recruitment, resulting in the fluctuation of saury abundance. Hypothesized mechanism of the effects of climate changes on the stock structure and abundance is illustrated on the basis of changes in thermal regime and production cycle.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.2
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• pp.239-244
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• 2011

Nano Imprint Lithography(NIL) is technique for copying a pattern from stamp with nano size pattern in order to replicated the materials. It is very important to demold in order to make NIL process effectively. Self Assembled Monolayers(SAM) coater is manufactured by means of decreasing surface energy with the stamp surface treatment to improve release characteristics. Manufactured device contains tilting and rotation option for increasing process life time by coating on the sidewall of the pattern in stamp. The stamp coated with optimized tilting angle $30^{\circ}$ and rotation speed of 10rpm has more imprinting cycles than the stamping coated without tilting and rotation. Effective SAM coating on the sidewall of the pattern in stamp will improve by 50% of process life time.

• Journal of Welding and Joining
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• v.32 no.3
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• pp.74-80
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• 2014

Due to environmental regulations (RoHS, WEEE and ELV) of the European Union, electronics and automotive electronics have to eliminate toxic substance from their devices and system. Especially, reliability issue of lead-free solder joint is increasing in car electronics due to ELV (End-of-Life Vehicle) banning from 2016. We have prepared engine control unit (ECU) modules soldered with Sn-40Pb and Sn-3.0Ag-0.5Cu (SAC305) solders, respectively. Degradation characteristics of solder joint strength were compared with various conditions of automobile environment such as cabin and engine room. Thermal cycle test (TC, $-40^{\circ}C$ ~ ($85^{\circ}C$ and $125^{\circ}C$), 1500 cycles) were conducted with automotive company standard. To compare shear strength degradation rate with eutectic and Pb-free solder alloy, we measured shear strength of chip components and its size from cabin and engine ECU modules. Based on the TC test results, finally, we have known the difference of degradation level with solder alloys and use environmental conditions. Solder joints degradation rate of engine room ECU is superior to cabin ECU due to large CTE (coefficient of thermal expansion) mismatch in field condition. Degradation rate of engine room ECU is 50~60% larger than cabin room electronics.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.4
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• pp.47-52
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• 2001

Pb-free wave soldering process of AC Adapter was implemented by six sigma method using Sn-Cu-Ni type solder. The solder joint appearance, microstructural change, a lift-off phenomenon and reliability were evaluated through thermal shuck test. $(Cu,Ni)_6/Sn_5$-type intermetallic compound of which thickness is about 5 $\mu\textrm{m}$ was found at solder joint between Sn-Cu-Ni solder and copper land. After applying the thermal shock test of as-soldered product up to 750 cycles, no crack was fecund at the solder joint. The newly developed product was superior to conventional one in terms of productivity and reliability.