• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.1
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• pp.27-35
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• 1998

This study describes the influence of combustion parameters on the nitric oxide emission, such as injection timing, air flow rate, injected amount of fuel, and compression ratio of engine. In order to determine the influence factors on the nitric oxide emission, the experiment were investigated with various parameters of engine cycle. According to the results of this study, the retardation of injection timing and the increases of airflow rate, and the decreases of fuel injection amount reduce the nitric oxide concentration in the exhaust emissions. Also, the increases of compression ration of engine increase in the concentration of nitric oxide formation in the combustion chamber. The results of this study give a guideline to decrease the nitric oxide formation by using the simulation program.

• Journal of Advanced Marine Engineering and Technology
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• v.19 no.2
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• pp.36-46
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• 1995

In this paper, fatigue crack propagation behaviors were investigated experimentally for the materials, carbon steel forgings (SF45A, SF50A, SF60A) which are used in the marine propeller shaft. The results obtained are as follows: The number of cycles required to grow crack length 1.30mm from microcrack initiation was about 60% of the total fatigue life. Fatigue crack propagation rate was expressed by the equation d(2a)/dN_B 2a/$N_f$ and the result was agreed well with the experimented data. And the equation d(2a)/dN=$C{\sigma}_a^m(2a)^n$ was evaluated also. Obtained material property m and n are 3~5 and 1-1.5 respectably, and the result was reasonably agreed to the data obtained from experiments.

• Journal of Applied Reliability
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• v.17 no.2
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• pp.150-158
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• 2017

Purpose: The RAM objective is a very important factor that has a great effect on the improvement of the operation ration during the operation maintenance and the reduction of the life cycle cost. It is used as a design criterion during the system development, and its sufficiency should be evaluated during its test evaluation. Method: This study analyzed the cases related to RAM objective setting and suggested the improvement measures. Result: The base data for RAM objective is OMS/MP, which needs to be drawn up under the supervision of the requirement military, and a high-accuracy operating availability should be set through ALDT calculation which reflects the military logistics support environment. In addition, data collection necessary for RAM objective and RAM analysis should be made by supplementing the input data of DELIIS. Conclusion: This study suggests improvement of RAM objective considering for the weapon system.

• Journal of Power System Engineering
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• v.19 no.6
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• pp.82-88
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• 2015

In this paper, cycle performance analysis of two-stage compression and one-stage expansion refrigeration system applied various refrigerants is presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include degree of superheating and subcooling, compressor efficiency, evaporation temperature, condensing temperature, mass flow rate ration into inter-cooler, effectiveness of internal heat exchanger. The main results were summarized as follows : The COP of two-stage compression and 1-stage expansion refrigeration system increases with the increasing subcooling, mass flow rate ration of inter-cooler, evaporation temperature, but decreases with the increasing condensing temperature and superheating degree. Therefore, subcooling degree, mass flow rate ratio of inter-cooler of two-stage compression and 1-stage expansion using substitute refrigerant have an effect on COP of this system. The COP of alternative refrigerants was higher than the COP of R22 in this study, although the COP of some mixed refrigerants were lower than COP of R22.

• Korean Journal of Agricultural Science
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• v.44 no.3
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• pp.392-399
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• 2017

The present study was conducted to investigate the effects of different dietary proteins as fraction-enriched protein, defined by Cornell net carbohydrates and protein system (CNCPS), on in vivo ruminal fermentation pattern and blood metabolites in Holstein steers fed total mixed ration (TMR) containing 17.2% crude protein. Four ruminally cannulated Holstein steers in a $4{\times}4$ Latin square design consumed TMR only (control) and TMR with rapeseed meal (AB1), soybean meal (B2), and perilla meal (B3C). Each protein was substituted for 23.0% of crude protein in TMR. Rumen digesta were taken through ruminal cannula at 1 h interval during the feeding cycle in order to analyze ruminal pH, ammonia-N, and volatile fatty acids (VFA). Plasma metabolites in blood taken via the jugular vein after the rumen digesta sampling were analyzed. Feeding perilla meal significantly (p < 0.05) decreased mean ruminal pH compared with control and the other protein feeding groups. Compared with control, feeding protein significantly (p < 0.05) increased ruminal ammonia-N concentration except for AB1. Statistically (p > 0.05) similar total VFA appeared among control and the supplemented groups. However, control, AB1, and B2 showed higher (p < 0.05) acetate concentrations than B3C, and propionate was vice versa. CNCPS fractionated protein significantly (p < 0.05) affected concentrations of albumin and total protein in blood; i.e. plasma albumin was lower for control and B2 groups than AB1 and B3C groups. Despite lack of significances (p > 0.05) in creatinine and blood urea nitrogen, AB1 and B2 groups were numerically higher than the others.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.225-230
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• 2005

It is theoretically known that recuperator can bring a significant increase in thermal efficiency of the gas turbine unit, but it also has disadvantages such as pressure loss in the flow channel, thermal stress and increase in weight. Therefore it is necessary to consider all pros and cons of this equipment in view of economic aspects throughout its life cycle. Recuperator has been applied mostly in the power ranges of $20\sim300kW$ class industrial units but hasn't been used as a larger power generation unit except for naval applications in mid twentieth century. Present paper considered the applicability of a recuperator cycle in term of pressure loss, part load aspects for power generation purpose.

• Korean Chemical Engineering Research
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• v.51 no.6
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• pp.677-684
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• 2013

A mixed refrigerant cycle (MRC) has been widely used in liquefaction of natural gas because it is simple and easily operable with reasonable equipment costs. One of the important techniques in MRC is selection of a refrigerant mixture and decision of its optimum mixing ratio. In this work, it is examined whether mixture components (refrigerants) and their mixing ratio influence performance of general MRC processes. In doing this, mixture design and response surface method, which are well-known statistical techniques, are used to find optimal mixture refrigerants and their optimal mixing ratio that minimize total energy consumption of the entire liquefaction process. A MRC process using several refrigerants and various mixing ratios is simulated by Aspen HYSYS and mixture design and response surface method are implemented using Minitab. According to the results, methane ($C_1$), ethane ($C_2$), propane ($C_3$) and nitrogen ($N_2$) are selected as best mixture refrigerants and the determined mixture ratio (mole ration) can reduce total energy consumption by up to 50%.

• Korean Journal of Community Nutrition
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• v.5 no.1
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• pp.120-129
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• 2000

Very little is known about the relation between isoflavone intake and menopausal symptoms in Korean woman To find the effects and correlations between these factors, questionnaires(maternal factors, menopausal symptoms) anthropometric measurement, 24hr dietary recalls, and urinary isoflavones analysis were conducted in 100 postmenopausal women residing in the Kyunggi-do rural area. The average age hight and weight of the subject were 61.5 years, 153.6 cm and 56.2kg. The average age at menarche, menopause, and menstrual cycle were 16.7 years, 47.2 years, 29.8 years, respectively. Most of the postmenopausal women experienced mildly menopausal symptoms. The mean calorie, protein and calcium intake were 1417.6 kcal(74.7% of the Korean RDA) 53.2 g(88.6% of the Korean RDA) and 454.0mg(65.6% of the Korean RDA) respectively. The ration of energy from carbohydrate, protein, and fat was 68: 15: 17 The average isoflavone intake from soy foods was 27.27 mg. The major food source of the isoflavone were soybeans and soybean curd. The average urinary isoflavone excretion was 2. 78nmol/mg Cr and showed significant positive correlation with isoflavone intake. Isoflavone intake from soy foods had a negative correlation with the severity of menopausal symptoms. Therefore, soy foods which contain isoflavone may have a protective effect on menopausal symptoms of women in Korea.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.4
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• pp.15-22
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• 2002

As the emission regulations on the automobiles have been increasingly stringent, precise control of air/fuel ration is one of the most important issues on the gasoline engines. Although many researches have been carried out to identify the fuel transport phenomena in the port fuel injection gasolines, mixture preparation in the cylinder has not been fully understood due to the complexity of fuel film behavior, In this paper, the mixture preparation during cold engine start is studied by using a Fast Response Flame ionization Detector.(FRFID) In order to estimate the transportation of injected fuel from the intake port into cylinder, the wall wetting fuel model was used. The two coefficient($\alpha$,$\beta$) of the wall-wetting fuel model was determined from the measured fuel mass that was inducted into the cylinder at the first cycle after injection cut-in. $\alpha$( ratio of directly inducted fuel mass into cylinder from injected fuel mass) and $\beta$ (ratio of indirectly inducted fuel mass into cylinder from wall wetted fuel film on the wall) was increased with increasing cooling water temperature. To reduce a air/fuel ratio fluctuation during cold engine start, the appropriate fuel injection rate was obtained from the wall wetting fuel model. Result of air/fuel ratio control, air/fuel excursion was reduced.

• Asian-Australasian Journal of Animal Sciences
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• v.30 no.3
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• pp.347-354
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• 2017

Objective: The effects of the pre- and postpartum supplementation of cows with Se on their plasma P4 concentrations after calving were investigated. Methods: Thirty-four Holstein cows were used to investigate the effects of dietary selenium supplementation on the postpartum recovery of the luteal function in cows. Selenium-rich yeast (containing 300 ppm selenium) was mixed with total mixed ration fed to 17 pregnant cows from 30 days before they were due to calve (10 g yeast daily) to 100 days after calving (20 g yeast daily). The control cows (n = 17) were fed the same amount of ordinary yeast. The cows' plasma progesterone concentrations were determined every two days using an enzyme immunoassay after calving. Results: Feed intake (total digestive nutrient, crude protein), milk production, body weight and the biochemical properties of blood plasma did not differ between the two groups; however, the plasma selenium concentrations of the supplemented animals were significantly greater than those of the controls at and after calving. The postpartum plasma progesterone concentrations of the selenium-yeast-supplemented group increased earlier than those of the control group. Moreover, during the estrus cycle after the 3rd ovulation or ovulation with estrus between 60 to 80 days after calving, the selenium-supplemented cows exhibited greater progesterone concentrations than the control cows. Conclusion: Selenium supplementation promotes the postpartum progesterone production of cows.