• 한국재료학회지
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• 제24권11호
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• pp.610-616
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• 2014

In this study, we investigated the precipitation behavior of the R-phase precipitated at the initial stage of aging and its effect on the pitting corrosion of 25%Cr-7%Ni-4%Mo super duplex stainless steel. The R-phase in super duplex stainless steel was mainly precipitated at the interface of ferrite/austenite phases and inside of the ferrite phase during the initial stage of aging, and it was transformed into the ${\sigma}$-phase with an increase in aging time. The ferrite phase was decomposed into a new austenite phase and ${\sigma}$-phase. The R phase was an intermetallic compound, which represented a lower Ni and higher Mo than the matrix, and also had a higher Mo and Cr concentration than the ${\sigma}$ phase. With an increasing aging time, the pitting potential $E_p$ was increased slowly by the precipitation of the R-phase, and it was then steeply decreased by the precipitation of the ${\sigma}$-phase. The R-phase was decreased the pitting potential, but its effect was smaller than effect of ${\sigma}$-phase.

• 전기학회논문지
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• 제64권1호
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• pp.182-187
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• 2015

In the three-phase power system, when any one-phase or two-phases is open-phase, the unbalanced current flows and the single-phase power supplies to three-phase loads. Specially, motor coil and transformer coil receive over-current. As a result, great damage as well as electrical fire can occur to the power system. In order to improve these problems, this paper proposes that an open-phase detection device is designed by a new algorithm using electric potential difference between the resultant voltage of neutral point and ground, and a control circuit topology of open-phase protector is composed of highly efficient semiconductor devices. It improves response speed and reliability. The control algorithm circuit also operates the cut-off of a conventional residual current protective device (RCD) which flows an enforced leakage current to ground wire at open-phase accident. Furthermore, time delay circuit is added to prevent the incapable operation of open-phase protector about instantaneous open-phase not open-phase fault. The time delay circuit improves more reliability.

• Management Science and Financial Engineering
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• 제7권2호
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• pp.73-90
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• 2001

This paper presents the reliability models for redundant systems composed of repairable components whose failure time and repair time distributions are phase-type. It is shown that the distribution of time to system failure is also phase-type. The dependency between components are considered and integrated into the model by the used of the rate adjustment factor. The phase-type representation is constructed for the system through algebraic operations on the parameters of components\` failure time and repair time distributions and the corresponding rate adjustment factors. Types of system structures considered are parallel, k-out-of-N system with load sharing scheme and standby system with operation priority.

• ETRI Journal
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• 제25권4호
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• pp.238-246
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• 2003

This paper introduces the modeling and analysis of a discrete-time, two-phase queueing system for both exhaustive batch service and gated batch service. Packets arrive at the system according to a Bernoulli process and receive batch service in the first phase and individual services in the second phase. We derive the probability generating function (PGF) of the system size and show that it is decomposed into two PGFs, one of which is the PGF of the system size in the standard discrete-time Geo/G/1 queue without vacations. We also present the PGF of the sojourn time. Based on these PGFs, we present useful performance measures, such as the mean number of packets in the system and the mean sojourn time of a packet.

• 대한한의학원전학회지
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• 제22권3호
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• pp.271-289
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• 2009

This thesis intend to help the eastern medical doctor to understand body condition from interpretation of perspirations(汗出) in daily time cycle. The conclusion is followed. 1. In most Eastern Medical classic and clinic literatures, the time of fever and perspirations are described as a result of disease's position at human body. Following this description, in daytime the perspirations must come from the Gi phase and night time the perspirations must come from the blood phase. Because in daytime the skin pores are opening and the defensive Gi is going out to the superficial portion of the body. In night time the skin pores are shutting and the defensive Gi is going in to the five solid organs. So a sweat in daytime comes out from the Gi phase and superficial portion of the body. And in night time comes out from the blood phase and five solid organs. But in recent real clinic cases, in daytime, there are so many perspirations from the five solid organs. Comparatively, the perspirations from the superficial portion of body are very little. And in same daytime perspirations, when the heat pathogens mixed with moist, the symptom revelation time delay to the afternoon. Therefore it can be concluded that the time of perspirations are combination of disease's Gi or blood phase and characteristics of pathogens. The position of disease at human body cannot simply judge the symptom revelation time. 2. The exchange of climate following time cycle of a day effect to the condition of human body. At same time it activates or not activates the pathogens in human body. So we can consider the kinds and characteristics of pathogens by distinguishing the symptom revelation time. In general differentiation of syndromes[辨證] pathogen's kinds and location are generally judged. By understanding the characteristics of pathogen, doctor can devise more correct and delicate prescription.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2010년도 춘계 학술논문 발표대회 2부
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• pp.103-108
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• 2010

The purpose of this study is to analyze of the risk factors for oversea plants construction projects. For this study, risk factors data from related literature review, research organization and construction company was researched and classified under each EPC phases. In addition, a questionnaire survey by plant experts was conducted for analysis of risk weight and costs and time impact on each EPC phases. The results of this study are as follows: First, a detail design errors(engineering phase), a equipment procurement plan(procurement phase), and exchange rate fluctuations(construction phase) were analyzed the highest weight factors. Second, a financing plan(engineering phase), quantity take-off bill(procurement phase), and exchange rate fluctuations(construction phase) were analyzed the highest cost impact factors. Third, detail design errors(engineering phase), a equipment procurement plan(procurement phase), and schedule management errors(construction phase) were analyzed the highest time impact factors.

• 열처리공학회지
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• 제25권2호
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• pp.74-79
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• 2012

This study has been carried out to investigate the precipitation behavior of ${\chi}$ phase and effect of ${\chi}$ phase precipitation on the impact toughness of 25%Cr-7%Ni-4%Mo super duplex stainless steel. It was proved that the ${\chi}$ phase was a intermetallic compound, which represented the higher chromium and molybdenum concentration than the matrix phases, and also showed the higher molybdenum concentration than the ${\sigma}$ phase. The ${\chi}$ phase was precipitated at the interface between ferrite and austenite or inside the ferrite matrix in the early stage of aging. The number of ${\chi}$ phase precipitates increased with increasing aging time, however, after showing the maximum value, the number was decreased due to the gradual transformation of ${\chi}$ phase into ${\sigma}$-phase. Aging ferrite phase was decomposed by the $r^2$ phase and ${\sigma}$-phase. Impact toughness rapidly decreased with time in the initial stage of aging at ${\chi}$ phase start to precipitate. Thus, the impact toughness was greatly influence for the precipitation of ${\chi}$ phase.

• 한국전기전자재료학회논문지
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• 제16권4호
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• pp.343-350
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• 2003

Using Bi$_2$Sr$_2$Ca$_2$.$_2$Cu$_3$ $O_{x}$ powders prepared by solid state reaction and spray drying method, the nucleation and growth behaviors of superconducting and second phases were investigated during isothermal heat treatment. When the spray drying power was used in contrast with solid state reaction powder, Bi$_2$Sr$_2$Ca$_2$.$_2$Cu$_3$ $O_{x}$ (2223) phase could be formed at the relatively shot time and second phases were much bigger. Quantitative analysis showed that as the heat treatment time increased, more Bi$_2$Sr$_2$Ca$_2$.$_2$Cu$_3$ $O_{x}$ (2212) changed to 2223 and the major second phase was changed from (Sr,Ca)$_{14}$Cu$_{24}$ $O_{x}$(14:24) to (Sr,Ca)$_2$Cu$_1$ $O_{x}$ (2:l). The superconducting phase formed at the relatively short time 14:24 phase. Following the Bi-free phase of 14:24 Phase, but long time was needed in places far from the 14:24 phase. Following the formation of the 2212 phase near the 14:24 phase, the 2223 phase nucleated preferentially at the interface between the 2212 and 14:24 phases. The preferential nuclcation of 2223 was explained by its structural similarity and low Interfacial energy with both the Bi-free and 2212 Phases.12 Phases.

• 한국자동차공학회논문집
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• 제3권1호
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• pp.1-12
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• 1995

Isothermal and thermal-mechanical fatigue characteristics of 12Cr heat resisting steel used for high temperature applications were investigated including hold time effects. Isothermal low cycle fatigue test at $600^{\circ}C$ and in-phase, out-of-phase thermal-mechanical fatigue test at 350 to $600^{\circ}C$ were conducted using smooth cylindrical hollow specimen under strain-control with total strain ranges from 0.006 to 0.015. Regardless of thermal-mechanical and isothermal fatigue tests, cyclic softening behavior was observed and much more pronounced in the thermal-mechanical fatigue tests with hold times due to the stress relaxation during the hold time. The phase difference between temperature and strain in thermal-mechanical fatigue tests resulted in significantly shorter fatigue life for out-of-phase compared to in-phase. The differences in fatigue lives were dependent upon the magnitudes of plastic strain ranges and mean stresses. During the hold time in the strain-controlled fatigue tests, the increase in the plastic strain range and the stress relaxation were observed. It appeared that the increase in plastic strain range per cycle and the introduction of creep damage made important contributions to the reduction of thermal-mechanical fatigue life with hold time, and the life reduction tendency was more remarkable in the in-phase than in the out-of-phase thermal-mechanical fatigue. Isothermal fatigue tests performed under the combination of fast and slow strain rates at $600^{\circ}C$ showed that the fatigue life decreased as the strain rate and frequency decreased,especially for the low strain ranges.

• Bulletin of the Korean Chemical Society
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• 제34권8호
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• pp.2353-2357
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• 2013

The objective of this study was to develop a simple, less time-consuming and accurate sampling technique based on solid-phase sorption with activated carbon as the sorbents. The results from solid-phase sorption techniques were compared to that from a conventional solvent impinger-based technique to confirm the efficacy of the proposed method. The laboratory results indicated that the solid-phase sorption method was suitable for the determination of siloxanes as the measured concentrations were similar to that from a solvent impinge method. The data from solid-phase sorption method showed excellent recovery and reproducibility while the sampling was less labor intensive and less time consuming than the solvent impinge method. Following the laboratory tests, the solid-phase sorption technique was successfully applied to sampling biogas from a field site. This study shows that the activated carbon-based solid-phase sorption can be a reliable and less time-consuming option for the sampling and collection of siloxanes under various different landfill conditions.