• Title/Summary/Keyword: pre-conditioning

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Numerical Analysis of Partial Cavitaing Flow Past Axisymmetric Cylinders (축대칭 실린더형상 주위 부분공동 유동의 전산해석)

  • Kim, Bong-Su;Lee, Byung-Woo;Park, Warn-Gyu;Jung, Chul-Min
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.33 no.2
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    • pp.69-78
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    • 2009
  • Cavitating flow simulation is of practical importance for many hydraulic engineering systems, such as pump, turbine, nozzle, injector, etc. In the present work, a solver for cavitating flow has been developed and applied to simulate the flows past axisymmetric cylinders. Governing equations are the two-phase Navier-Stokes equations, comprised of continuity equation of liquid and vapor phase. The momentum equation is in the mixture phase. The solver employed an implicit, dual time, preconditioned algorithm in curvilinear coordinates. Computations were carried out for three axisymmetric cylinders: hemispherical, ogive, and caliber-0 forebody shape. Then, the present calculations were compared with experiments and other numerical results to validate the present solver. Also, the code has shown its capability to accurately simulate the re-entrant jet phenomena and ventilated cavitation. Hence, it has been found that the present numerical code has successfully accounted for cavitating flows past axisymmetric cylinders.

An experimental study on heat transfer characteristics in a vertical micro-fin tube during evaporation process of carbon dioxide flowing upward (이산화탄소의 마이크로 핀관 내 상향유동 증발열전달 특성에 관한 연구)

  • Kim, Yong-Jin;Cho, Jin-Min;Kim, Min-Soo
    • Proceedings of the SAREK Conference
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    • 2007.11a
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    • pp.247-251
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    • 2007
  • Because of the ozone layer depletion and global warming, new alternative refrigerants are being developed. In this study, evaporation heat transfer characteristics of carbon dioxide flowing upward in a vertical micro-fin tube have been investigated by experiment. Before a test section, a pre-heater is installed to adjust the inlet quality of the refrigerant to a desired value. The micro-fin tube with outer diameter of 5 mm and length of 1.44 m was selected as the test section. The test was conducted at mass fluxes of 318 to $530\;kg/m^2s$, saturation temperature of -5 to $5^{\circ}C$, and heat fluxes of 15 to $30\;kW/m^2$. As the vapor quality increases, the heat transfer coefficients of carbon dioxide are increased, and the heat transfer coefficients increase when the heat fluxes and saturation temperatures increase, and there was not much of influence of mass flux on the heat transfer coefficients.

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Evaluation of Natural Ventilation Performance using the Multi-Functional Floor Heating System (다기능온돌시스템을 이용한 자연환기성능 평가)

  • Cho, Dong-Woo;Yu, Ki-Hyung;Yu, Jung-Yeon;Jung, Hae-Kwon
    • Proceedings of the SAREK Conference
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    • 2007.11a
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    • pp.105-112
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    • 2007
  • Recently developed raised floor heating system is not only capable of basic function to reduce noise between floors, but also is a multi-functional floor heating system enabling natural ventilation. The procedure of this system for natural ventilation is to import outdoor air through bottom space of the floor heating system, circulate indoor space and discharge it out of ceiling. In winter, powerless natural ventilation is possible with buoyancy effect caused by temperature difference between outdoor and indoor. And it also allows saving of energy by importing pre-heated air in bottom space of the floor heating system. To evaluate ventilation performance of this system, on-site measurement was conducted in 2 test laboratories, and the nominal air change rate was satisfied as 0.4$\sim$0.8 h-1 under the condition of outdoor temperature $5^{\circ}C{\sim}-5^{\circ}C$, which was evaluated as highly possible to be applied as a natural ventilation system in multi-family houses.

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Pre-study for the improvement of air filtration performance in the air handling unit of subway station (도시철도 지하역사 공기조화기의 미세먼지 저감성능 개선을 위한 사전연구)

  • Kang, Joong-Goo;Shin, Chang-Heon;Bae, Sung-Joon;Kwon, Soon-Bark;Kim, Se-Young;Han, Seok-Yoon
    • Proceedings of the SAREK Conference
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    • 2008.11a
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    • pp.541-545
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    • 2008
  • Particulate matter (PM) is one of the major indoor air pollutants especially in the subway station in Korea. In order to remove PM in the subway station, several kinds of PM removal system such as roll-filter, auto-washable air filter, demister, and electrostatic precipitator re used in the air handling unit (AHU) of subway station. However, those systems are faced to operation and maintenance problems since the filter-regeneration unit consisting of electrical or water jet parts is malfunctioned due to the high load of particulates and the filter material needs periodic replacement. In this study, we surveyed the particle removal systems in order to develop the new system of particle removing can be adopted in the current AHU of subway station.

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High Yielding [18F]Fluorination Method by Fine Control of the Base

  • Lee, Sang-Ju;Oh, Seung-Jun;Chi, Dae-Yoon;Moon, Dae-Hyuk;Ryu, Jin-Sook
    • Bulletin of the Korean Chemical Society
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    • v.33 no.7
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    • pp.2177-2180
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    • 2012
  • New [$^{18}F$]F-fluorination methods using a minimized amount of precursor has been developed by controlling the base concentration. In the first method, pre-conditioning of the anion exchange cartridge with $K_2CO_3$ solution or water was carried out. The trapped [$^{18}F$]fluoride on the cartridge was then eluted by KOMs or KOTf solution. [$^{18}F$]F-Fluorination could be performed without additional base. In the second method, the QMA cartridge was preconditioned with KOMs solutions. Trapped [$^{18}F$]fluoride on the QMA was then eluted with KOMs and additional base, such as KOH, $K_2CO_3$, and $KHCO_3$, was added into the reaction vessel. Method 1 showed a [$^{18}F$]F-incorporation yield of 20.9% for [$^{18}F$]FLT synthesis with 5 mg of precursor. Unlike method 1, a [$^{18}F$]F-incorporation yield of 91.4% was achieved from the same amount of precursor in method 2.

A Study of Dance Movement Training on the Wellness of young Women (율동적 동작 훈련이 젊은 여성의 Wellness에 미치는 영향)

  • ;Lou Heber
    • Journal of Korean Academy of Nursing
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    • v.25 no.3
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    • pp.538-548
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    • 1995
  • Exercises are achievement oriented, the process is frequently perceived as hard and difficult Participants drop out from exercise programs in the middle of the training period. Dance movement, which is the deliberate and systematic use of movement, is enjoyable during the movement and provides opportunities for persons to express them-selves. Regular long term dance movement may in-duce a training effect with a decreased drop out rate. Dance movement could be one way to attain wellness, however, there have been few studies to evaluate both physiological and psychological aspects of dance movement. This study focused on evaluating the effects of dance movement training on body weight, resting blood pressure and heart rate, limb circumference and strength, stress response and subjective feelings. This quasi-experimental study was designed as a nonequivalent control group pre test -post test study. Ten healthy fe-male subjects, aged between 19 and 31 years volunteered for an eight week dance movement program. Ten healthy female subjects, between 19 and 21 years of age paticipated as controls. None of the subjects had performed regular physical activity for six months prior to the study. Dance movement was created with reference to Heber's movement guide. The Dance movement program consisted of approximately 30 minutes of dance, three days per week, for eight weeks. During each 30 minute work out, there were approximately 5 minutes of warm-up dancing, 20 minutes of conditioning dance and 5 minutes of cool-down dancing. The intensity for the conditioning phase was at between 60% and 65% of age-adjusted maximum heart rates. Body weight, resting blood pressure and heart rate, circumference of mid upper arm, mid thigh and mid calf, muscle strength of upper and lower limb, physical and psychological response to stress were measured prior to, and following the experimental treatment. Body weight was measured by digital weight scale(Kyung In Corp., Korea). Resting systolic and diastolic blood pressure were measured by sphygmomanometer, Resting heart rate was measured for one minute in a relaxed sitting position using the radial artery. Circumference of mid upper arm, mid thigh and mid calf was determined by tape measure. Muscle strength of the upper extremities was measured by a grip dynamometer (Takei Corp. No.1857, Japan) and that of the extremities was measured by the length of time the leg could be held at 45° Physical and psychological responses to stress were measured using the Symptoms of Stress (SOS)Scale. Paticipants in the dance movement were interviewed by the facilitator following the eight weeks, and their thematic responses about the dance movement were recorded. Following the eight week dance movement train-ing, body weight decreased significantly, circumference of mid thigh and mid calf increased. The length of time leg - raising could be held tended to increase following the dance movement training. Resting systolic and resting heart rate showed a tendency to decrease. Total mean score of stress response tended to de-crease, and mean score of habitual patterns, do-pression, anxiety / fear, anger and cognitive disorganization decreased remarkably following the eight week dance movement. Thematic responses about the dance movement were positive following the training.

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Effect of NaF iontophoresis and Nd:YAG laser irradiation on the abrasion-resistance of root surface (불화나트륨 이온도포와 Nd:YAG laser 조사가 치근면 내마모성에 미치는 영향)

  • Kim, Chin-Dok;Yum, Chang-Yup;Kim, Song-Uk;Kim, Byung-Ock;Han, Kyung-Yoon
    • Journal of Periodontal and Implant Science
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    • v.27 no.4
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    • pp.819-828
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    • 1997
  • The purpose of this study was to evaluate the abrasion-resistance of root surface after NaF iontophoresis, Nd:YAG laser irradiation and combined treatment 50 anterior teeth with flat interproximal root surface that had been extracted due to periodontal destruction were selected. All teeth were treated by the same procedure as conventional periodontal root treatment, such as scaling and root planing, root conditioning with tetracycline HCI(lOOmg/ml, 5min). The pre-treatment weight of each tooth was measured by a dial scale(SHIMADEU Co, LIBROR EB-220HU, capacity 220.000 g, Japan). All teeth were divided into 5 groups as follows: Nd:YAG laser irradiation(group 1, 1 W, 100 mJ, 10Hz, fiberoptic-root surface distance=5mm, $10\;sec.{\times}6times$, EL.EN.EN060, Italy): NaF iontophoresis(group 2, $150{\mu}A$, 4 min}: Nd:YAG laser irradiation following NaF iontophoresis(group 3): NaF iontophoresis following Nd:YAG laser irradiation(group 4): No treatment(control group). Electric toothbrushing (Oral-B, Brown Co, Germany) was conducted during 1 hour($lO\;min.{\times}6\;times$). Subsequently post-treatment weight was remeasured by the same method as pre-treatment weight measurement. The difference of abrasion rate among all groups was statistically analyzed by ANOVA(SAS program). Following results were obtained: 1. The abrasion rate was significantly lower in Nd:YAG laser irradiation group than NaF iontophoresis group(p < 0.001). 2. The abrasion rate was significantly lower in combined groups of Nd:YAG laser irradiation and NaF iontophoresis than either Nd:YAG laser irradiation group or NaF iontophoresis group(p < 0.001). 3. There was no significant difference in abrasion rate according to application order in the combined groups(p > 0.05). 4. The abrasion rate was significantly lower in all experimental groups than control group(p < 0.001). The results suggest that combined treatment of Nd:YAG laser irradiation and NaF iontophoresis on exposed root surface after periodontal therapy can enhance the abrasion-resistance of root surface and may inhibit the root caries development.

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SPECTROPHOTOMETRIC ANALYSIS OF THE INFLUENCE OF METAL SUBSTRATE ON THE COLOR OF CERAMIC (금속하부구조물이 도재의 색조에 미치는 영향에 대한 분광측색분석)

  • Lee Su-Ok;Woo Yi-Hyung;Choi Dae-Gyun;Kwon Keung-Rok
    • The Journal of Korean Academy of Prosthodontics
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    • v.41 no.2
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    • pp.148-159
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    • 2003
  • Statement of problem Metal-ceramic restorations have been used extensively by dental clinicians for nearly 40 years. Strength an functional ability of metal-ceramic restorations are proved to be satisfying, However esthetics and biocompatibility of metal alloy which is used in metal-ceramic restoration is not ideal. Using pure gold as an alternative, have advantage of esthetics, biocompatibility over conventional metal alloy. But there had been little article which studied on the color effect of pure gold on fual porcelain color. Purpose The purpose of this study was to spectrophotometrically evaluate the difference between color of metal alloy(Au-Pt, Ni-Cr) and pure gold, during color masking procedure with opaque porcelain and to analyze the differences, Material and Methods Three types of metal - base metal(Ni-Cr), high gold alloy(Au-Pt), pure gold(GES) - specimen were fabricated 1cm in diameter. Four steps were established - after finishing, after pre-coditioning, after application of first opaque porcelain(0.08mm in thickness), after application of second opaque porcelain(0.15mm in thickness)- and tested color with spectrophotometer every each steps and analyzed with $CIEL^*a^*b^*$ color order system. One-Way ANOVA test was used to and out if there were significant differences between groups tested and Shaffe multiple comparison was used to identify where the differences were. Results 1. After finishing and pre-conditioning, pure gold(GES) group showed most high values in $L^*,a^*,b^*$. 2. After application of first opaque porcelain(0.08mm in thickness), after application of second opaque porcelain(0.15mm in thickness), pure gold(GES) group showed the least difference in $L^*,a^*,b^*$ values and the lowest ${\Delta}E$ value(${\Delta}E$=0.63). 3. After application of first opaque porcelain and after application of second opaque porcelain differences that were significant (P<0.05) between groups were found only in $a^*$ values. 4. Base metal alloy group showed the lowest $a^*$ value in test after application of first opaque porcelain and the highest value in test after application of first opaque porcelain Conclusion Pure gold group and high gold group showed higher $a^*$ values than base metal group when tested after 0.08mm thickness of opaque porcelain was applied and pure gold group showed much similar $L^*,a^*,b^*$ values between 0.08mm thickness and 0.15mm thickness of opaque porcelain. This meant that pure gold was more easily masked by opaque porcelain than the other two groups.

The Effects Of The Dietary Microbial Phytase Supplementation In Juvenile Olive Flounder, Paralichthys olivaceus And Juvenile Korean Rockfish, Sebastes schlegeli Fed Soybean Meal-Based Diets

  • Gwangyeol Yu;Kyungmin Han;Park, Semin;Sungchul C. Bai
    • Proceedings of the Korean Aquaculture Society Conference
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    • 2003.10a
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    • pp.70-70
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    • 2003
  • This study was conducted to determine the effects of the dietary microbial phytase (P) supplementation on growth performance and bioavailability of phosphorus in juvenile olive flounder, Paralichthys olivaceus and juvenile Korean rockfish, Sebastes schlegeli fed soybean meal-based diets. Nine experimental diets were formulated to be isonitrogenous and isocalolic to contain 50.0%crude protein (CP) and 16.7kJ, 48.6% crude protein (CP) and 16.0kJ available energy/g without the dietary phytase supplementation for olive flounder and Korean rockfish, respectively : 100% fish meal (FM); 70% FM + 30% soybean meal (SM); 70% FM + 30% SM + Phytase(P) 1000U/kg diet; 70% FM + 30% SM + P 2000U/kg diet; 70% FM + 30% SM with phytase-treated (Ptre) P 1000U/kg diet; 60% FM + 40% SM; 60% FM + 40% SM + P 1000U/kg diet; 60% FM + 40% SM + P 2000U/kg diet; 60% PM + 40% SM with Ptre P 1000U/kg diet. After two weeks of the conditioning period, triplicate groups of 25 fish initially averaging 6.15$\pm$0.04g, was randomly distributed into the aquarium for olive flounder, and 20 fish initially averaging 7.25$\pm$0.04g was randomly distributed into the aquarium for Korean rockfish. After 8 weeks feeding trials, there was no significant difference on weight gain fish fed between 100% FM and 70% FM+30%SM with Ptre P 1000U in olive flounder and Korean rockfish. Apparent phosphorus digestibility fish fed phytase supplemental diets were significantly higher than those of fish fed phytase non-supplemental diets in olive flounder and Korean rockfish. Therefore, these results indicated that pre-treated soybean meal with phytase 1000U could replace fishmeal up to 30% for the maximum growth of juvenile olive flounder and Korean rockfish. Phytase supplementation could improve apparent digestibility of phosphorus in olive flounder and Korean rockfish fed soybean meal based diets.

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Effects of Flight Conditions on IR Signature from Aircraft Exhaust Plume (비행조건에 따른 항공기 배기플룸의 IR 신호 특성)

  • Go, Gun-Yung;Kim, Man-Young;Baek, Seung-Wook
    • Journal of the Korean Society of Propulsion Engineers
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    • v.16 no.5
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    • pp.58-66
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    • 2012
  • The IR signature and radiative base heating from an aircraft plume have been important factors for aircraft survivability in modern battle fields. In order to enhance the aircraft survivability and reduce the base heating, infrared signatures emitted from an aircraft exhaust plume should be determined. In this work, therefore, IR signatures and radiative base heating characteristics are examined in the plume exhausted from the aircraft with operating at altitude of 5 km in M=0.9 and 1.6, respectively. As a result, it is found that the particular wavelength IR signature has high spectral characteristics because of $H_2O$ and $CO_2$ gases in the plume, and the radiative heat flux coming into the base plane increases with higher Mach number and shorter distance.