• 제목/요약/키워드: Drop Time

검색결과 1,139건 처리시간 0.033초

CEFR control rod drop transient simulation using RAST-F code system

  • Tuan Quoc Tran;Xingkai Huo;Emil Fridman;Deokjung Lee
    • Nuclear Engineering and Technology
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    • 제55권12호
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    • pp.4491-4503
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    • 2023
  • This study aimed to verify and validate the transient simulation capability of the hybrid code system RAST-F for fast reactor analysis. For this purpose, control rod (CR) drop experiments involving eight separate CRs and six CR groups in the China Experimental Fast Reactor (CEFR) start-up tests were utilized to simulate the CR drop transient. The RAST-F numerical solution, including the neutron population, time-dependent reactivity, and CR worth, was compared against the measurement values obtained from two out-of-core detectors. Moreover, the time-dependent reactivity and CR worth from RAST-F were verified against the results obtained by the Monte Carlo code Serpent using continuous energy nuclear data. A code-to-code comparison between Serpent and RAST-F showed good agreement in terms of time-dependent reactivity and CR worth. The discrepancy was less than 160 pcm for reactivity and less than 110 pcm for CR worth. RAST-F solution was almost identical to the measurement data in terms of neutron population and reactivity. All the calculated CR worth results agreed with experimental results within two standard deviations of experimental uncertainty for all CRs and CR groups. This work demonstrates that the RAST-F code system can be a potential tool for analyzing time-dependent phenomena in fast reactors.

수포작용제(HD) 분석을 위한 단일방울 미세농축법 연구 (Single Drop Microextraction for Analysis of Mustard Gas(HD))

  • 박양기;김성기;손병훈;박명주
    • 한국군사과학기술학회지
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    • 제11권2호
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    • pp.95-100
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    • 2008
  • A fast, simple, inexpensive, and reproducible sample preparation for extraction and analysis of HD in water was studied using single-drop microextraction(SDME) and GC-MS. Operation parameters, such as extraction solvent, extraction time were optimized. The optimized conditions were $1\{mu}L$ trichloroethylene and 10 min extraction time. In these conditions, about 42 times higher enrichment factor(EF) was obtained. The detection limit of HD was $1\{mu}g/L$, and the precision expressed as relative standard deviation was about 9.0%.

활성탄을 충전한 흡착탑에서 벤젠 회수를 위한 세정공정의 연구 (A Study on Cleaning Process for Benzene Recovery in Activated Carbon Bed)

  • 강성원;민병훈;서성섭
    • 한국응용과학기술학회지
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    • 제19권2호
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    • pp.108-116
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    • 2002
  • Experimental Study was carried out for benzene desorption by purge gas or evacuation in an activated carbon bed. As purge gas flow rate increased, desorption rate increased due to the higher interstitial linear gas velocity. For various purge gas flow rates, desoption curves almost got together if they were plotted against dimensionless time. At a higher flow rate, mass transfer zone became narrower. Temperature drop in the bed was more fast and severe at higher flow rates and higher outer temperature. It was found out that desorption was almost completed when the temperature in the drop of the bed returned to the initial temperature before temperature drop. Desorption by vacuum purge was completed in shorter time than desorption by purge gas. Countercurrent purge was more effective than cocurrent purge.

경험모델을 이용한 충격기류식 여과집진기의 적정 탈진압력 예측 (The Prediction of Optimal Pulse Pressure Drop by Empirical Static Model in a Pulsejet Bag Filter)

  • 서정민;박정호;임우택;강점순;조재환
    • 한국환경과학회지
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    • 제21권5호
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    • pp.613-622
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    • 2012
  • A pilot-scale pulse-jet bagfilter was designed, built and tested for the effects of four operating conditions (filtration velocity, inlet dust concentration, pulse pressure, and pulse interval time) on the total system pressure drop, using coke dust from a steel mill factory. Two models were used to predict the total pressure drop according to the operating conditions. These model parameters were estimated from the 180 experimental data points. The empirical model (EM) with filtration velocity, areal density, inlet dust concentration, pulse interval time and pulse pressure shows the best correlation coefficient (R=0.971) between experimental data and model predictions. The empirical model was used as it showed higher correlation coefficient (R=0.971) compared to that of the Multivariate linear regression(MLR) (R=0.961). The minimum pulse pressure predicted by empirical model (EM) was 5kg/$cm^2$.

전류 감지 회로를 이용한 빠른 과도응답특성을 갖는 capless LDO 레귤레이터 (Capless Low Drop Out Regulator With Fast Transient Response Using Current Sensing Circuit)

  • 정준모
    • 전기전자학회논문지
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    • 제23권2호
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    • pp.552-556
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    • 2019
  • 본 논문에서는 전류 제어 회로를 이용하여 load Transient response 특성을 향상시킨 capless LDO(low drop-out) 레귤레이터를 제안하였다. LDO 레귤레이터 내부의 오차증폭기와 패스 트랜지스터 사이에 전류 조절 회로를 두어 전압 라인에 들어오는 전류특성을 개선시켜 기존의 LDO 레귤레이터보다 향상된 transient 응답특성을 갖는다. 제안된 회로는 cadence의 virtuoso, spectre 시뮬레이터를 이용하여 0.18 um 공정에서 특성을 분석하였다. 실험 결과에 따르면, 제안된 회로 구성을 이용한 LDO의 load transient response는 기존 LDO과 비교하여 부하 전류가 rising time인 경우 1.954 us에서 1.378 us, falling time인 경우 19.48 us에서 13.33 us으로 약 29%, 28% 개선된 응답속도를 가진다.

Effects of an Elastic AFO on the Walking Patterns of Foot-drop Patients with Stroke

  • Hwang, Young-In
    • 대한물리의학회지
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    • 제15권1호
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    • pp.1-9
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    • 2020
  • PURPOSE: Many patients with stroke have difficulties in walking with foot-drop. Various types of ankle-foot orthoses (AFOs) have been developed, but their weight needs to be reduced with the assistance of the ankle dorsiflexor. Therefore, an elastic AFO (E-AFO) was devised that not only improves the stability and flexibility of the ankle but also assists with ankle dorsiflexion while walking. This study examined the effects of an E-AFO, on the walking patterns of foot-drop patients with stroke. METHODS: Fourteen patients walked with and without an E-AFO, and the gait parameters were assessed using the GAITRite system. The spatiotemporal data on the gait patterns of stroke patients with foot-drop were compared using paired t-tests; the level of statistical significance was set to α<.05. RESULTS: No significant differences were observed in the velocity (p=.066) and affecte+d step length (p=.980), but the affected and less-affected stance (p=.022, p=.002) and swing time (p=.012, p=.005) were significantly different. The E-AFO produced a significant difference in the less-affected step length (p=.032). CONCLUSION: The E-AFO has a significant effect on the walking patterns of individuals with foot-drop and stroke. The E-AFO could be a useful assistive device for gait training in stroke patients.

루버형 휜을 가진 휜관형 열교환기의 착상현상 연구 (Study on the Frosting Phenomenon of the Fin and Tube Heat Exchanger with a Louvered Fin)

  • 김정국;코야마 시게루;쿠와하라 켄;박병덕
    • 한국산업융합학회 논문집
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    • 제11권4호
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    • pp.157-163
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    • 2008
  • The present study investigated the pressure drop and the total frost mass of the louvered fin type heat exchanger, which is widely used at the air-conditioning system. The pressure drop due to the frosting phenomenon and the total frost mass were investigated by changing the wet bulb temperature condition of the inlet air. Hence the brain of 55wt% was used as a cooling solution instead of a common refrigerant. The temperature difference between the brine and the tube outside wall at the outlet of heat exchanger was $10^{\circ}C$, at maximum, higher than that at the inlet of heat exchanger. As the wet bulb temperatures were increased, the pressure drop was linearly increased due to the increment of frost mass. And the increment of heat exchange rate was smaller than that of inlet air enthalpy due to the increment of frost mass. The pressure drop of air side was rapidly increased due to the progress of frosting phenomena. The run time that the pressure drop occurred rapidly was decreased by the growth of frost.

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잎담배 및 제품담배의 재떨어짐에 관한 연구 (Ash Drop Measuring on Tobacco Leaf Grades and Brand Cigarettes)

  • 양범호;안대진;조시형;제병권;김시몽;김병구
    • 한국연초학회지
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    • 제26권2호
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    • pp.117-125
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    • 2004
  • In this study, we have investigated the natural and puffing combustibility of cigarette brands and the compulsory ash-drop, and analysed factors related to the materials. Cigarette combustibility was greatly affected by the tobacco weight in cigarettes rod. Combustion rate of 4AOR cigarette made by flue-cured tobacco was 5.02 $^{mm}/_{min}\;and\;10\%$ faster than 1BO cigarette. Combustion pattern has interrelation with sugars, chlorine and ash contents among tobacco components. Combustion rate of 4DL, flue-cured tobacco was 55 seconds faster than 1CL tobacco extremely much in sugars contents, and ash drop was maintained at $21\%$ longer. Combustion time and burning rate were fast in cigarette made by expanded tobacco slice and tobacco stem and the formation of ash was poor. The length of puffed ash drop of expanded tobacco slice and tobacco stem were 18.6 mm and 25.2 mm and these forced ash drop length were 3.8 mm and 4.9 mm respectively. Puffed burning rate of general cigarette was $14.3\%$ faster than static burning rate and super slim type cigarettes was $21.3\%$ faster. Combustion rate and ash drop of domestic and foreign cigarette brands were quite different depending on tar level and cigarette types. The lower tar level, the faster combustion rate and the shorter ash drop.

연구용 원자로의 정지봉 장치 성능에 미치는 인자 분석과 성능 시험 (Performance test and factor analysis on the performance of shutoff units with the research reactor)

  • 김경련;김석범;고재명;문균영;박종호
    • 한국유체기계학회 논문집
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    • 제10권2호
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    • pp.41-45
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    • 2007
  • The shutoff unit was designed to provide rapid insertion of neutron absorbing material into the reactor core to shutdown the reactor quickly and also to withdraw the absorber slowly to avoid a log-rate trip. Four shutoff units were installed on the HANARO reactor but the half-core test facility was equipped with one shutoff unit. The reactor trip or shutdown is accomplished by four shutoff units by insertion of the shutoff rods. The shutoff rod(SOR) is actuated by a directly linked hydraulic cylinder on the reactor chimney, which is pressurized by a hydraulic pump. The rod is released to drop by gravity, when triplicate solenoid valves are de-energized to vent the cylinder. The hydraulic pump, pipe and air supply system are provided to be similar with the HANARO reactor. The shutoff rod drops for 647mm stroke within 1.13 seconds to shut down the reactor and it is slowly inserted to the full down position, 700mm, with a damping. We have conducted the drop test of the shutoff rod in order to show the performance and the structural integrity of operating system of the shutoff unit. The present paper deals with the 647mm drop time and the withdrawal time according to variation of the pool water temperature, the water level and the core flow.

A Study on the Design and Electrical Characteristics Enhancement of the Floating Island IGBT with Low On-Resistance

  • Jung, Eun-Sik;Cho, Yu-Seup;Kang, Ey-Goo;Kim, Yong-Tae;Sung, Man-Young
    • Journal of Electrical Engineering and Technology
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    • 제7권4호
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    • pp.601-605
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    • 2012
  • Insulated Gate Bipolar Transistors(IGBTs) have received wide attention because of their high current conduction and good switching characteristics. To reduce the power loss of IGBT, the onstate voltage drop should be lowered and the switching time should be shortened. However, there is trade-off between the breakdown voltage and the on-state voltage drop. The FLoatingIsland(FLI) structure can lower the on-state voltage drop without reducing breakdown voltage. In this paper, The FLI IGBT shows an on-state voltage drop that is 22.5% lower than the conventional IGBT, even though the breakdown voltages of each IGBT are almost identical.