• Nuclear Engineering and Technology
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• v.15 no.4
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• pp.236-247
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• 1983

Analyzed are the the DNBR(Departure from Nucleate Boiling Ratio) sensitivities to variations in various PWR operating parameters utilizing the Korea Nuclear Unit 1(KNU-1) design and operating data. Studied parameters in the analysis are core power level, system pressure, core inlet flow rate, core inlet temperature, enthalpy rise hot channel factor, and axial power peaking factor and axial offset. The calculations are performed using the steady state and transient thermal-hydraulics computer program, COBRA-IV-K, which is the revised version of COBRA-IV-i that has been adapted, partially modified and verified at KAERI. A reference case is established based on the design and operating condition of the KNU-1 reactor core, and this provides a basis for the subsequent sensitivity analysis. From the calculation results it is concluded that the most sensitive parameter in the DNBR thermal design is the coolant core inlet temperature while the axial power peaking factor is the least sensitive.

• Journal of the Korean Society of Industry Convergence
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• v.20 no.2
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• pp.105-113
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• 2017

Recently the direct injection diesel engine is the most efficient one available for road vehicles, so this fundamental advantage suggests the compression injection diesel engine are a wise choice for future development efforts. The compression ignition diesel engine, with its bigger compression ratios if compared to the SI engine, offers a higher thermodynamic efficiency, also additionally the diesel engine with its less pumping losses due to the throttled intake charge as in a SI engine has higher fuel economy. But the largest obstacle to the success of this engine is meeting emission standards for Nitric oxides and particulate matter while maintain fuel consumption advantage over currently available engines. Thus its use should be largely promoted, however, diesel engine emits more Nitric oxides and particulate matter than other competing one. There has been a trade-off between PM and NOx, so efforts to reduce NOx have increased PM and vice versa, but trap change this situation and better possibility emerge for treating NOx emission with engine related means, such as injection timing, equivalence ratio, charge composition, and engine speed. The common rail direct injection system is able to adjust the fuel injection timing in a compression ignition engine, so this electronically controlled injection system can reduce the formation of NOx gas without increase in soot. In this study it is designed and used the engine test bed which is installed with turbocharge and intercooler. In addition to equipped using CRDI by controlling injection timing with mapping modulator, it has been tested and analyzed the engine performance, combustion characteristics, and exhaust emission as operating parameters.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.75-82
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• 2021

Low-temperature combustion (LTC) strategies, such as HCCI (Homogeneous Charge Compression Ignition), PCCI (Premixed Charge Compression Ignition), and RCCI (Reactivity Controlled Compression Ignition), have been developed to effectively reduce NOx and PM while increasing the thermal efficiency of diesel engines. Through numerical analysis, this study examined the effects of the injection timing and two-stage injection ratio of diesel fuel, a highly reactive fuel, on the performance and exhaust gas of RCCI engines using gasoline as the low reactive fuel and diesel as the highly reactive fuel. In the case of two-stage injection, combustion slows down if the first injection timing is too advanced. The combustion temperature decreases, resulting in lower combustion performance and an increase in HC and CO. The injection timing of approximately -60°ATDC is considered the optimal injection timing considering the combustion performance, exhaust gas, and maximum pressure rise rate. When the second injection timing was changed during the two-stage injection, considering the combustion performance, exhaust gas, and the maximum pressure increase rate, it was judged to be optimal around -30°ATDC. In the case of two-stage injection, the optimal result was obtained when the first injection amount was set to approximately 60%. Finally, a two-stage injection rather than a single injection was considered more effective on the combustion performance and exhaust gas.

• Journal of the Korean GEO-environmental Society
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• v.12 no.10
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• pp.63-72
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• 2011

The high capacity bi-directional pile load test is an optimum pile load test method for high-rised buildings. Especially, a high pressure and double-acting bi-directional pile load testing, a special type of the high capacity bi-directional pile load test, is the most practical way to overcome limitations of loading capacities and constraints of field conditions, which was judged to be a very useful test method for requiring high loading capacities. Total of 2 high capacity bi-directional pile load tests(P-1 and P-2) were conducted in high-rised building sites in Korea. Based on the field load test results, the sufficiency ratio of loading capacities to design loads for P-1 and P-2 were 3.3 and 2.1, respectively. For P-2, the load test could not verify the design load if 1-directional loads applied slightly smaller than the actual applied load. Also, high capacity bi-directional pile load tests were difficult to determine an ultimate state of ground or piles, although the loads were applied until their maximum loads. Hence, finite element analyses were conducted to determine their ultimate states by calibrating and extrapolate with test results.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.6
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• pp.541-554
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• 2023

The utilization of underground spaces in relation to tunnels and energy/waste storage is on the rise. To ensure the stability of underground spaces, it is crucial to reinforce rock fractures and discontinuities. Discontinuities, such as joints, can weaken the strength of the rock and lead to groundwater inflow into underground spaces. In order to enhance the strength and stability of the area around these discontinuities, rock grouting techniques are employed. However, during rock grouting, it is impossible to visually confirm whether the grouting material is being smoothly injected as intended. Without proper injection, the expected increases in strength, durability, and degree of consolidation may not be achieved. Therefore, it is necessary to predict in advance whether the grouting material is being injected as designed. In this study, we aimed to assess the injection performance based on injection variables such as the water/cement mixture ratio, injection pressure, and injection flow using UDEC (Universal Distinct Element Code) numerical program. Additionally, numerical results were validated by the lab experiment. The results of this study are expected to help optimize variables such as injection material properties, injection time, and pump pressure in the grouting design in the field.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.8
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• pp.1311-1319
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• 2004

The purpose of this study was to compare the serum lipid level, blood sugar and blood pressure in vegetarians and non-vegetarians. The subjects of the study were 127 Buddhist nuns (age: 23∼79 y) from Oonmoon Temple in Choungdo district Gyeongsang Bookdo province and 118 Buddhist nuns practicing Zen meditation at Soodeok Temple in Yeosan district Chongcheong Namdo province. For control subjects, 235 healthy female adults (age: 23∼79 y) were selected. They were the nurses in the Gyeongsang National University Hospital, teachers and housekeepers living in Jinju, Gyeongsang Namdo province. The period of this study was from October 1996 to February 1997. The contents were consisted of food consumption survey, anthropometric measurement, estimated amount of energy expenditure, physical activity and clinical examination. The mean ages of the subjects were 44.2 y for vegetarians and 40.5 y for non-vegetarians, respectively. Average body mass index (BMI) of vegetarians and non-vegetarians were 22.47 and 21.08, WHR 0.85 and 0.84, percentage of body fat 28.79 and 26.55 respectively. The average duration of vegetarian diet of the vegetarians was 13.16 y. Levels of total cholesterol, LDL-cholesterol, atherogenic index (AI), diastolic blood pressure, blood sugar and HDL-cholesterol were significantly higher (p<0.01) in non-vegetarians than those of vegetarians. In both of subjects, levels of TG, total cholesterol, LDL-cholesterol, atherogenic index (AI) and systolic blood pressure were significantly higher (p<0.01) with an increment of age and the vegetarians showed a lower ratio of rise than the non-vegetarians. Levels of serum TG, LDL-cholesterol and AI were utmost in the 60 s and declined in the 70 s. Consequently, vegetarian diet can be considerably effective in reducing the level of the risk factors causing cardiovascular disease.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.510-515
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• 2011

The pyrolytic reaction of 1,1-dichloroethylene($CH_2CCl_2$) has been conducted to investigate thermal decomposition of chlorocarbon and product formation pathways under hydrogen reaction environment. The reactions were studied in a isothermal tubular flow reactor at 1 atm total pressure in the temperature range $650{\sim}900^{\circ}C$ with reaction times of 0.3~2.0 sec. A constant feed molar ratio $CH_2CCl_2:H_2$ of 4:96 was maintained through the whole experiments. Complete decay(99%) of the parent reagent, $CH_2CCl_2$ was observed at temperature near $825^{\circ}C$ with 1 sec. reaction time. The important decay of $CH_2CCl_2$ under hydrogen reaction environment resulted from H atom cyclic chain reaction by abstraction and addition displacement. The highest concentration (28%) of $CH_2CHCl$ as the primary product was observed at temperature $700^{\circ}C$, where up to 46% decay of $CH_2CCl_2$ was occurred. The secondary product, $C_2H_4$ as main product was detected at temperature above $775^{\circ}C$. The one less chlorinated ethylene than parent increase with temperature rise subsequently. The HCl and dechlorinated hydrocarbons such as $C_2H_4$, $C_2H_6$, $CH_4$ and $C_2H_2$ were the main products observed at above $825^{\circ}C$. The important decay of $CH_2CCl_2$ resulted from H atom cyclic chain reaction by abstraction and addition displacement. The important pyrolytic reaction pathways to describe the features of reagent decay and intermediate product distributions, based upon thermochemical and kinetic principles, were suggested.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.1
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• pp.97-106
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• 2011

Purpose: This review article was written to theoretically compare the depressing force (pressure, adhesion) to the cornea between when the spherical lenses were being tightly and flat fitted. Methods: Mathematical equations and their numerical solution programs (model) were formulated to calculate the depressing (adhesion) force to the cornea by both the tightly and flat fitted contact lenses. Based on this proposed model the effects of parameters characterizing a contact lens such as BCs, diameters, edge shape and corneal shape (ratio of long and short corneal axis, p) on the depressing force to the cornea were predicted/analyzed in both tightly and flat fitting regimes. Results: Corneal adhesion increased as the corneal p-value increased. Adhesion increase caused by the increased p-value was much larger in flat fitted case than in tight fitted one. Corneal adhesion reduced abruptly as the BC increased in flat fitting regimes while the adhesion rise was insignificant in tight fitting ones. Reduction in corneal adhesion due to lens-size increase was predicted to be insignificant in both tight and flat fitting regimes. Both the lens edge shape (edge angle) and thickness were relevant only in tight fitting regime. Corneal adhesion increased as the increased with tight-fitted lenses. As the thickness of tight fitted lenses increased, corneal adhesion inversely decreased. Conclusions: The two most significantly affecting the depressing force to cornea were found to be the degree of corneal bending toward the periphery and the BCs of lenses.

• The Korean Journal of Emergency Medical Services
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• v.11 no.2
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• pp.51-66
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• 2007

Purpose: With a view to providing basic data to develop cardiopulmonary resuscitation education suitable for elementary students, the cardiopulmonary resuscitation education was conducted to grasp students' knowledge, skills accuracy and the attitude change before and after the education. Methods: Convenience sampling was made on fourth and fifth graders(total-35 students) of S elementary school located in K city, Chungcheongnam-do, and this was a pre-experiment research designed before and after choosing a single group. In terms of methods, specifically we, researchers ; 1) Handed out questionnaires to students directly to make them fill in firsthand and collected the questionnaires. 2) Utilized PPT materials based on 2005 AHA guideline and DVD materials of AHA, to give students theoretical education of cardiopulmonary resuscitation. We used Anne/SkillReporter$^{(R)}$ torso produced by Leardal Inc, and Little Anne to conduct practical education individually. 3) Asked students to give Anne/SkillReporter$^{(R)}$ torso cardiopulmonary resuscitation five times with the ratio of 30 : 2, and then one of researchers filled in the evaluation sheet individually. 4) Evaluated the accuracy of students' ability to perform the resuscitation based on the record of Anne/SkillReporter$^{(R)}$ integrated printer(which was the objective tool to grasp students' skills accuracy). 5) Gave out questionnaires to make students fill them in and then collected them. after completing the practical evaluation. Results: 1) In case of the attitude about cardiopulmonary resuscitation, Students' confidency rose from 19.28%(before the education) to 93.57(after the education)- which is a positive change. 2) As the result of the education, some elementary students scored 11 points (full score-16 points), up from 5 points before the education, in terms of the knowledge about cardiopulmonary resuscitation. The average point also reached 13.14 points(after the education), jump from 8.37(before the education), which was the rise of 29.8%. 3) When it comes to the practical performance, the skills accuracy was 80.93% on average, and the calculation method was as follows: total items were 16, and each item was marked form 0 to 2 points, meaning the full score was 32 points. The minimum score was 19 points and the maximum was 32($M{\pm}SD=25.90{\pm}2.88$), which was calculated based on percentage. 4) Regarding skills accuracy, respiration accuracy(%)($M{\pm}SD=30.20{\pm}27.16$) was higher than pressure accuracy(%) ($M{\pm}SD=15.34{\pm}25.27$). Conclusion: The result showed that students' attitude on cardiopulmonary resuscitation changed positively. and meaningful difference(p = .00) existed in the change of students' knowledge. In terms of skills accuracy. chest compression and airway control showed high accuracy, but the result of Anne/SkillReporter$^{(R)}$ performance showed that the accuracy of chest compression was lower than that of mouth-to-mouth resuscitation.

• The Korean Journal of Emergency Medical Services
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• v.12 no.1
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• pp.17-26
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• 2008

Purpose : With a view to providing basic data to develop basic cardiopulmonary resuscitation education suitable for female college students, the basic cardiopulmonary resuscitation education was conducted to grasp students' knowledge, skill accuracy and the attitude change before and after the education. Methods : Convenience sampling was made on first graders(total-38 students) of K college located in K city, Chungcheongnam-do, and this was a preliminary research designed before and after choosing a single group. In terms of methods, the researchers as specified ; 1) Handed out questionnaires to students directly to make them fill in firsthand and collected the questionnaires. 2) Utilized Power Point materials based on 2005 AHA guideline and used Anne/Skill Reporter$^{(R)}$ torso produced by Leardal Inc, and Little Anne$^{(R)}$ to conduct practical education individually. 3) Asked students to give Anne/Skill Reporter$^{(R)}$ torso basic cardiopulmonary resuscitation five times with the ratio of 30:2, and then one of researchers filled in the evaluation sheet individually. 4) Evaluated the accuracy of students' ability to perform the resuscitation based on the record of Anne/Skill Reporter$^{(R)}$ integrated printer(which was the objective tool to grasp students' skills accuracy). 5) Gave out questionnaires to make students fill them in and then collected them, after completing the practical evaluation. Results : 1) In case of the attitude(confidence) about basic cardiopulmonary resuscitation, students' confidency rose from 14%(before the education) to 55.5%(after the education)- which was a positive change. 2) In case of the attitude(educational necessity) about basic cardiopulmonary resuscitation, students' confidency rose from 94.7%(before the education) to 100%(after the education)- which was a positive change. 3) As a result of the education, some female college students' scored knowledge about basic cardiopulmonary resuscitation. The average point also reached 88.95%(after the education), jump from 63.51%(before the education), which was the rise of 25.44%. 4) Regarding skill accuracy, pressure accuracy(%)($M{\pm}SD=91.37{\pm}14.16$) was higher than respiration accuracy(%)($M{\pm}SD=61.55{\pm}26.13$). Conclusion : The result showed that students' attitude(confidence, on basic cardiopulmonary resuscitation changed positively, and meaningful difference(p= .000) existed in the change of students' knowledge. Anne/Skill Reporter$^{(R)}$ performance showed that the accuracy of mouth-to-mouth resuscitation was lower than that of chest compression.