• 제목/요약/키워드: AP1000

검색결과 52건 처리시간 0.026초

점탄성유체의 저항 및 열전달 감소현상과 퇴화의 영향에 관한 연구 (A Study on the Drag and Heat Transfer Reduction Phenomena and Degradation Effects of the Viscoelastic Fluids)

  • 엄정섭;전찬열;유상신
    • 설비공학논문집
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    • 제2권1호
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    • pp.37-48
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    • 1990
  • The drag and heat transfer reduction phenomena and degradation effects of drag reducing polymer solutions which are known as the viscoelastic fluids are investigated experimentally for the turbulent circular tube flows. Two stainless steel tubes are used for the experimental flow loops. Aqueous solutions of Polyacrylamide Separan AP-273 with concentrations from 300 to 1000 wppm are used as working fluids. Flow loops are set up to measure the friction factors and heat transfer coefficients of test tubes in the once-through system and the recirculating flow system. Test tubes are heated by power supply directly to apply constant heat flux boundary conditions on the wall. Capillary tube viscometer and falling ball viscometer are used to measure the viscous characteristics of fluids and the characteristic relaxation time of a fluid is determined by the Powell-Eyring model. The order of magnidude of the thermal entrance length of a drag reducing polymer solution is close to the order of magnitude of the laminar entrance length of Newtonian fluids. Dimensionless heat transfer coefficients of the viscoelastic non-Newtonian fluids may be represented as a function of flow behavior index n and newly defined viscoelastic Graetz number. As degradation continues viscosity and the characteristic relaxation time of the testing fluids decrease and heat transfer coefficients increase. The characteristic relaxation time is used to define the Weissenberg number and variations of friction factors and heat transfer coefficients due to degradation are presented in terms of the Weissenberg number.

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IS THE PEGASUS DWARF GALAXY A MEMBER OF THE LOCAL GROUP?

  • Lee, Myung-Gyoon
    • 천문학회지
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    • 제28권2호
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    • pp.169-175
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    • 1995
  • Deep V I CCD photometry of the Pegasus dwarf irregular galaxy shows that the tip of the red giant branch (RGB) is located at I = $21.15{\pm}0.10$ mag and (V - I) = $1.58{\pm}0.03$. Using the I magnitude of the tip of the RGB (TRGB), the distance modulus of the Pegasus galaxy is estimated to be $(m\;-\;M)_o\;=\;25.13{\pm}0.11$ mag (corresponding to a distance of d = $1060{\pm}50$ kpc). This result is in a good agreement with the recent distance estimate based on the TRGB method by Aparicio [1994, ApJ, 437, L27],$ (m\;-\;M)_o$ = 24.9 (d = 950 kpc). However, our distance estimate is much smaller than that based on the Cepheid variable candidates by Hoessel et al.[1990, AJ, 100, 1151], $(m\;-\;M)_o\;=\;26.22{\pm}0.20$ (d = $1750{\pm}160$ kpc) mag. The color-magnitude diagram illustrates that the Cepheid candidates used by Hoessel et al.are not located in the Cepheid instability strip, but in the upper part of the giant branch. This result shows that the Cepheid candidates studied by Hoessel et al.are probably not Cepheids, but other types of variable stars. Taking the average of our distance estimate and Aparicio's, the distance to the Pegasus galaxy is d= $1000{\pm}80$ kpc. Considering the distance and velocity of the Pegasus galaxy with respect to the center of the Local Group, we conclude that the Pegasus galaxy is probably a member of the Local Group.

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Performance analysis of automatic depressurization system in advanced PWR during a typical SBLOCA transient using MIDAC

  • Sun, Hongping;Zhang, Yapei;Tian, Wenxi;Qiu, Suizheng;Su, Guanghui
    • Nuclear Engineering and Technology
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    • 제52권5호
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    • pp.937-946
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    • 2020
  • The aim in the present work is to simulate accident scenarios of AP1000 during the small-break loss-of-coolant accident (SBLOCA) and investigate the performance and behavior of automatic depressurization system (ADS) during accidents by using MIDAC (The Module In-vessel Degradation severe accident Analysis Code). Four types of accidents with different hypothetical conditions were analyzed in this study. The impact on the thermal-hydraulic of the reactor coolant system (RCS), the passive core cooling system and core degradation was researched by comparing these types. The results show that the RCS depressurization becomes faster, the core makeup tanks (CMT) and accumulators (ACC) are activated earlier and the effect of gravity water injection is more obvious along with more ADS valves open. The open of the only ADS1-3 can't stop the core degradation on the basis of the first type of the accident. The open of ADS1-3 has a great impact on the injection time of ACC and CMT. The core can remain intact for a long time and the core degradation can be prevent by the open of ADS-4. The all results are significant and meaningful to understand the performance and behavior of the ADS during the typical SBLOCA.

토끼 위 근위부의 비-아드레날린 비-콜린성 이완반응의 포타슘 체널에 의한 접합전 조절작용 (Prejunctional Modulation of Non-adrenergic Non-cholinergic Relaxation of the Rabbit Proximal Stomach by Potassium Channels)

  • 홍은주;박미선;박상일;김명우;최수경;홍승철
    • 약학회지
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    • 제41권4호
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    • pp.399-406
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    • 1997
  • The effects of different $K^+$ channel blockers were investigated on the non-adrenergic non-cholinergic (NANC) relaxations in the circular muscle of the rabbit proximal stomach. Non-selective blockers of $K^+$ channels, 4-aminopyridine (4-AP, 3~30${\mu}M$) and tetraethylammonium (TEA, 100~1000${\mu}M$) significantly enhanced the NANC relaxations in a concentration-dependent manner. The enhancement was more prominent for the NANC relaxations induced by the electric field stimulation (EFS) with lower frequencies. Blockers of large conductance $Ca^{2+}$-activated $K^+$ channels, charybdotoxin and iberiotoxin, a blocker of small conduntance $Ca^{2+}$-activated $K^+$ channels, apamin and a blocker of ATP-sensitive $K^+$ channels, glibenclamide had no effect on the NANC relaxations, respectively. Exogeneous administration of nitric oxide (NO, 1~30${\mu}M$) caused concentration-dependent relaxations which showed a similarity to those obtained with EFS. None of the $K^+$ channel blockers had an effect on the concentration-dependent relaxation in response to NO. These results suggest that prejunctional $K^+$ channels regulate the release of NO from the NANC nerve in the rabbit proximal stomach as the inhibition of prejunctional $K^+$ channels increases the NANC relaxation induced by the EFS.

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The development of high fidelity Steam Generator three dimensional thermal hydraulic coupling code: STAF-CT

  • Zhao, Xiaohan;Wang, Mingjun;Wu, Ge;Zhang, Jing;Tian, Wenxi;Qiu, Suizheng;Su, G.H.
    • Nuclear Engineering and Technology
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    • 제53권3호
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    • pp.763-775
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    • 2021
  • The thermal hydraulic performances of Steam Generator (SG) under both steady and transient operation conditions are of great importance for the safety and economy in nuclear power plants. In this paper, based on our self-developed SG thermal hydraulic analysis code STAF (Steam-generator Thermalhydraulic Analysis code based on Fluent), an improved new version STAF-CT (fully Coupling and Transient) is developed and introduced. Compared with original STAF, the new version code STAF-CT has two main functional improvements including "Transient" and "Fully Three Dimensional Coupling" features. In STAF-CT, a three dimensional energy transferring module is established which can achieve energy exchange computing function at the corresponding position between two sides of SG. The STAF-CT is validated against the international benchmark experiment data and the results show great agreement. Then the U-shaped SG in AP1000 nuclear power plant is modeled and simulated using STAF-CT. The results show that three dimensional flow fields in the primary side make significant effect on the energy source distribution between two sides. The development of code STAF-CT in this paper can provide an effective method for further SG high fidelity research in the nuclear reactor system.

An improved time-domain approach for the spectra-compatible seismic motion generation considering intrinsic non-stationary features

  • Feng Cheng;Jianbo Li;Zhixin Ding;Gao Lin
    • Nuclear Engineering and Technology
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    • 제55권3호
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    • pp.968-980
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    • 2023
  • The dynamic structural responses are sensitive to the time-frequency content of seismic waves, and seismic input motions in time-history analysis are usually required to be compatible with design response spectra according to nuclear codes. In order to generate spectra-compatible input motions while maintaining the intrinsic non-stationarity of seismic waves, an improved time-domain approach is proposed in this paper. To maintain the nonstationary characteristics of the given seismic waves, a new time-frequency envelope function is constructed using the Hilbert amplitude spectrum. Based on the intrinsic mode functions (IMFs) obtained from given seismic waves through variational mode decomposition, a new corrective time history is constructed to locally modify the given seismic waves. The proposed corrective time history and time-frequency envelope function are unique for each earthquake records as they are extracted from the given seismic waves. In addition, a dimension reduction iterative technique is presented herein to simultaneously superimpose corrective time histories of all the damping ratios at a specific frequency in the time domain according to optimal weights, which are found by the genetic algorithm (GA). Examples are presented to show the capability of the proposed approach in generating spectra-compatible time histories, especially in maintaining the nonstationary characteristics of seismic records. And numerical results reveal that the modified time histories generated by the proposed method can obtain similar dynamic behaviors of AP1000 nuclear power plant with the natural seismic records. Thus, the proposed method can be efficiently used in the design practices.

In-depth investigation of natural convection thermal characteristics of BALI experiment through Eulerian computational fluid dynamics code and comparison with Lagrangian code

  • Hyeongi Moon;Sohyun Park;Eungsoo Kim;Jae-Ho Jeong
    • Nuclear Engineering and Technology
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    • 제56권1호
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    • pp.9-18
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    • 2024
  • In-vessel retention through external reactor vessel cooling (IVR-ERVC) is a severe accident management (SAM) strategy that has been adopted and used in many nuclear reactors such as AP1000, APR1400, and light water reactor etc. Some reactor accidents have raised concerns about nuclear reactors among residents, leading to a decrease in residents' acceptability and many studies on SAM are being conducted. Experiments on IVR-ERVC are almost impossible due to its specificity, so fluid characteristics are analyzed through BALI experiments with similar condition. In this study, computational fluid dynamics (CFD) via Reynolds-averaged Navier-Stokes (RANS) and large eddy simulation (LES) for BALI experiments were performed. Steady-state CFD analysis was performed on three turbulence models, and SST k-ω model was in good agreement with the experimental measurement temperature within the maximum error range of 1.9%. LES CFD analysis was performed based on the RANS analysis results and it was confirmed that the temperature and wall heat flux for depth was consistent within an error range of 1.0% with BALI experiment. The LES CFD analysis results were compared with those of the Lagrangian-based solver. LES matched the temperature distribution better than SOPHIA, but SOPHIA calculated the position of boundary between stratified layer and convective layer more accurately. On the other hand, Lagrangian-based solver predicted several small eddy behaviors of the convective layer and LES predicted large vortex behavior. The vibration characteristics near the cooling part of the BALI experimental device were confirmed through Fast Fourier Transform (FFT) investigation. It was found that the power spectral density for pressure at least 10 times higher near the side cooling than near the top cooling.

수종의 수복재의 불소 적용법에 따른 불소 유리에 관한 비교 연구 (COMPARATIVE STUDY ON FLUORIDE RELEASE AND RE-UPTAKE CAPACITY OF SEVERAL FLUORIDE-RELEASING RESTORATIVE MATERIALS)

  • 이연호;유승호;김종수
    • 대한소아치과학회지
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    • 제33권1호
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    • pp.25-34
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    • 2006
  • 불소는 구강내에서 치아 우식의 예방 및 초기 우식의 재광화를 유도하기 위한 목적으로 널리 사용되고 있으며, 불소가 유리되는 수복물을 이용하게 되면, 수복물 주위의 이차 우식 및 구강내의 우식 감수성을 감소시킬 수 있다. 현재 소아치과 영역에서 주로 사용되고 있는 불소유리 수복재로는, 전통적인 글라스 아이오노머와 레진 강화형 글라스 아이오노머, 컴포머 등이 있는데, 본 연구에서는 현재 소아치과 영역에서 많이 사용되고 있는 불소를 유리하는 수복재의 불소 유리량 및 불소 적용방법에 따른 불소유리량의 변화를 비교하고 확인하고자 한다. 복합레진으로 $Z-250^{TM}$ (Group I)과 컴포머로 $Dyract^{(R)}$ AP(Group II) 레진 강화형 글라스 아이오노머로 Fuji II $LC^{(R)}$ (Group III), 자가중합형 글라스 아이오노머로 Fuji IX GP $Fast^{(R)}$(Group IV)를 실험대상으로 선정하였다. 각 재료별로 동일한 크기의 디스크를 제작하여, 31일 동안 매일 새로운 용액으로 교환하면서 불소 유리량을 측정하였다(실험 I). 이후 수복재료별로 불소 적용 방법에 따라 4군으로 나누는데, A군은 대조군(No treatment)으로, B군은 불소가 함유된 치약(500ppm, Stages, $Oral-B^{(R)}$, Holland)을 3분간 3회 적용하고, C군은 1.23% APF Foam(1000ppm, Sultan Topex, #31150, Canada)을 1회 적용하며, D군은 B군과 동일한 치약을 3회 적용하고, 1.23% APF Foam을 1회 적용하였다. 불소 적용 후 7일 동안 불소 유리량을 측정하였다(실험 II). 실험 I에서, 실험 개시일부터 7일까지 불소 유리량이 급속히 감소하고, 이후 일정한 불소 유리량을 보였다. III군 (Fuji II-$LC^{(R)}$)과 IV군 (Fuji IX GP $Fast^{(R)}$)이 다른 군에 비해 높은 불소 유리량을 보였으며, III군과 IV군 사이에서는 유의한 차이를 보이지 않았다. 실험 II에서, 불소 적용 후 II, III, IV군에서 불소 유리 량이 증가한 양상을 보이는데, II군에서는 불소 적용 후 2일, III군에서는 5일, IV군에서는 4일부터 초기 불소 유리량 수준으로 돌아갔다.

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고지방식이에 의한 흰쥐의 시상하부 Neuropeptide Y-면역반응 신경세포와 장내 Cajal 세포의 변화 (Changes in Neuropeptide Y-Immunoreactive Cells in the Hypothalamus and Cajal Interstitial Cells in the Small Intestine of Rats with High-Fat Diet)

  • 문지영;문경래;박상기;정윤영;김은영
    • Pediatric Gastroenterology, Hepatology & Nutrition
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    • 제14권2호
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    • pp.171-180
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    • 2011
  • 목 적: 고지방식이를 섭취한 흰쥐에서 식이 유발인자인 NPY와 장내 운동 조절인자인 Cajal 간질세포의 변화를 관찰하고자 하였다. 대상 및 방법: 동일 연령의 Sprague-Dawley계 수컷 흰쥐를 임의로 대조군(7마리)과 고지방식이군(7마리)으로 분리한 후, 대조군에는 일반 흰쥐 사료를 충분히 섭취시켰으며, 고지방식이군에게는 60% kcal 지방이 포함된 사료(중앙실험동물센터)를 6주 동안 물과 함께 충분히 섭취하도록 하였다. 6주 후 시상하부 조직 절편에 rabbit polyclonal NPY (1 : 1000, Abcam)항체를 반응시키고, 소장의 조직 절편에 rabbit polyclonal c-kit (1 : 400, Neuromics)항체를 반응시켜서 면역조직화학 검사를 시행하였다. 결 과: 고지방식이군의 시상하부에서 NPY의 면역 반응성이 강하게 나타났으며, 특히 PVN에서 NPY의 면역 반응 세포수의 증가를 관찰할 수 있었다. 고지방식이군에서 소장의 Auerbach's plexus 부위의 Cajal 간질 세포의 면역 반응성이 떨어졌으며, 환상근과 종주근 내 Cajal 간질 세포 수도 현저히 감소하였다. 결 론: 고지방식이를 섭취한 흰쥐에서 시상하부 NPY 면역반응 신경세포수와 발현의 증가는 NPY의 저항성과 관련되며, 소장에서 Cajal 간질 세포의 감소는 장운동의 이상을 초래할 수 있음을 나타낸다.

광중합형 수복용 복합레진의 기계적 성질에 미치는 수중침적과 Thermal Cycling의 영향 (Effect of Immersion in Water and Thermal Cycling on the Mechanical Properties of Light-cured Composite Resins)

  • 배태성;김태조;김효성
    • 대한의용생체공학회:의공학회지
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    • 제17권3호
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    • pp.327-336
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    • 1996
  • This study was performed to investigate the effec% of immersion in water and thermal cycling on the mechanical peoperties of light cured restorative composite resins. Five commerically available light-cured composite resins(Photo Clearfil A : CA, Lite-Fil A . LF, Clearril Photo Posterior CP, Prisms AP.H.. PA, 2100 : ZH) were unto The specimens of 12 m in diameter and 0.7 m in thickness were made, and an immersion in $37^{\circ}C$ water for 7 days and a thermal cycling of 1000 cycles at 15 second dwell time each in $5^{\circ}C$ and $55^{\circ}C$ baths were performed. Biaxial flexure test was conducted using the ball-on-three-ball method at the crosshead speed of 0.5mm/min. In order to investigate the deterioration of composite resins during the thermal cycling test, Weibull analysis for the biaxial flexure strengths was done. Fracture surfaces and the surfaces before and after the thermal cycling test were examined by SEM. The highest Weibull modulus value of 10.09 after thermal cycling tests which means the lowest strength variation, was observed in the CP group, and the lowest value of 4.47 was obsered in the LF Group. Biaxial flexure strengths and Knoop hardness numbers significantly decreased due to the thermal cycling ($\textit{p}$< 0.01), however, they recovered when specimens were drie4 The highest biaxial flexure strength of 125.65MPa was observed in the ZH group after the thermal cycling test, and the lowest value of 64.86MPa was observed in the CA group. Biaxial flexure strengths of ZH and CP groups were higher than those of PA, CF, and CA groups after thermal cycling test($\textit{p}$< 0.05). Knoop hardness numbers of CP group after the thermal cycling test was the highest(95.47 $\pm$ 7.35kg/$mm^2$) among the samples, while that of CA group was the lowest(30.73 $\pm$ 2.58kg/$mm^2$). Knoop hardness numbers showed the significant differences between the CP group and others after the thermal cycling test(($\textit{p}$< 0.05). Fracture surfaces showed that the composite resin failure developed along the matrix resin and the filler/resin interface region, and the cracks propagated in the conical shape from the maximum tensile stress zone.

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