Experimental and numerical investigations on effect of reverse flow on transient from forced circulation to natural circulation

Li, Mingrui,Chen, Wenzhen,Hao, Jianli,Li, Weitong Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.9

In a sudden shutdown of primary pump or coolant loss accident in a marine nuclear power plant, the primary flow decreases rapidly in a transition process from forced circulation (FC) to natural circulation (NC), and the lower flow enters the steam generator (SG) causing reverse flow in the U-tube. This can significantly compromise the safety of nuclear power plants. Based on the marine natural circulation steam generator (NCSG), an experimental loop is constructed to study the characteristics of reverse flow under middle-temperature and middle-pressure conditions. The transition from FC to NC is simulated experimentally, and the characteristics of SG reverse flow are studied. On this basis, the experimental loop is numerically modeled using RELAP5/MOD3.3 code for system analysis, and the accuracy of the model is verified according to the experimental data. The influence of the flow variation rate on the reverse flow phenomenon and flow distribution is investigated. The experimental and numerical results show that in comparison with the case of adjusting the mass flow discontinuously, the number of reverse flow tubes increases significantly during the transition from FC to NC, and the reverse flow has a more severe impact on the operating characteristics of the SG. With the increase of flow variation rate, the reverse flow is less likely to occur. The mass flow in the reverse flow U-tubes increases at first and then decreases. When the system is approximately stable, the reverse flow is slightly lower than obverse flow in the same U-tube, while the flow in the obverse flow U-tube increases.

High‑frequency response current direct demodulation method for sensorless control of interior permanent magnet synchronous motor drives

Wenzhen Li,Jinglin Liu,Chao Gong 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.5

Sensorless schemes are mainly used in fault-tolerant control of interior permanent magnet synchronous motor (IPMSM) drives. Traditional sensorless methods with injection of high-frequency (HF) carrier signals into the stationary reference frame have a stable performance. However, phase shifts caused by conventional high-pass filters (HPFs) decrease the estimation accuracy. Besides, the demodulation process is usually complicated, which increases the difficulty of application. To solve these problems, this study presents an HF-induced current direct demodulation method. Rotor position angle can be solved from the sampled currents at adjacent moments without demodulation signals. Therefore, the errors related to filters in the rotor position estimation are eliminated. Besides, the efficiency of the demodulation algorithm is improved. Furthermore, an online compensation method for cross-saturation effect is proposed. Experimental results verify that the proposed strategy can obtain an accurate rotor position with good steady-state and dynamic performance.

The anti-tumor efficacy of 20(S)-protopanaxadiol, an active metabolite of ginseng, according to fasting on hepatocellular carcinoma

Wenzhen Li,YifanWang,Xinbo Zhou,Xiaohong Pan,Junhong Lu,Hongliu Sun,Zeping Xie,Shayan Chen,Xue Gao 고려인삼학회 2022 Journal of Ginseng Research Vol.46 No.1

Background: 20(S)-protopanaxadiol (20(S)-PPD), one of the main active metabolites of ginseng, performs a broad spectrum of anti-tumor effects. Our aims are to search out new strategies to enhance anti-tumor effects of natural products, including 20(S)-PPD. In recent years, fasting has been shown to be multifunctional on tumor progression. Here, the effects of fasting combined with 20(S)-PPD on hepatocellular carcinoma growth, apoptosis, migration, invasion and cell cycle were explored. Methods: CCK-8 assay, trypan blue dye exclusion test, imagings photographed by HoloMonitorTM M4, transwell assay and flow cytometry assay were performed for functional analyses on cell proliferation, morphology, migration, invasion, apoptosis, necrosis and cell cycle. The expressions of genes on protein levels were tested by western blot. Tumor-bearing mice were used to evaluate the effects of intermittent fasting combined with 20(S)-PPD. Results: We firstly confirmed that fasting-mimicking increased the anti-proliferation effect of 20(S)-PPD in human HepG2 cells in vitro. In fasting-mimicking culturing medium, the apoptosis and necrosis induced by 20(S)-PPD increased and more cells were arrested at G0-G1 phase. Meanwhile, invasion and migration of cells were decreased by down-regulating the expressions of matrix metalloproteinase (MMP)-2 and MMP-9 in fasting-mimicking medium. Furthermore, the in vivo study confirmed that intermittent fasting enhanced the tumor growth inhibition of 20(S)-PPD in H22 tumor-bearing mice without obvious side effects. Conclusion: Fasting significantly sensitized HCC cells to 20(S)-PPD in vivo and in vitro. These data indicated that dietary restriction can be one of the potential strategies of chinese medicine or its active metabolites against hepatocellular carcinoma.

Investigation on reverse flow characteristics in U-tubes under two-phase natural circulation

Chu, Xi,Li, Mingrui,Chen, Wenzhen,Hao, Jianli Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.5

The vertically inverted U-tube steam generator (UTSG) is widely used in the pressurized water reactor (PWR). The reverse flow behavior generally exists in some U-tubes of a steam generator (SG) under both single- and two-phase natural circulations (NCs). The behavior increases the flow resistance in the primary loop and reduces the heat transfer in the SG. As a consequence, the NC ability as well as the inherent safety of nuclear reactors is faced with severe challenges. The theoretical models for calculating single- and two-phase flow pressure drops in U-tubes are developed and validated in this paper. The two-phase reverse flow characteristics in two types of SGs are investigated base on the theoretical models, and the effects of the U-tube height, bending radius, inlet steam quality and primary side pressure on the behavior are analyzed. The conclusions may provide some promising references for SG optimization to reduce the disadvantageous behavior. It is also of significance to improve the NC ability and ensure the PWR safety during some accidents.

Identification and Partial Characterization of an Alanine Aminotransferase Gene CsAlaAT2 in Response to Shade in Tea (Camellia sinensis)

Wang Jinhe,Chen Wenzhen,Li Yuanda,Zhao Xiuxiu,Xiang Qinzheng,Li Min 한국식물학회 2021 Journal of Plant Biology Vol.64 No.1

Alanine contributes to the taste and nutritional quality of tea and is an important member of alanine metabolism catalyzed by alanine aminotransferase (AlaAT, EC 2.6.1.2). However, the molecular mechanism underlying alanine metabolism in tea plants has not been fully elucidated. In this study, an increase in enzyme activity of AlaAT2 was detected in vitro, and the alanine aminotransferase activity was higher level in leaves than that in other tissues of tea plant, while the CsAlaAT2 transcription was high in leaves and root. Using phylogenetic analysis, an alanine aminotransferase gene CsAlaAT2 was identified as a member of group C, which was located in the mitochondrion. Additionally, the molecular mass of CsAlaAT2 protein was found to be approximately 53 kDa by SDS-PAGE and western blotting. The CsAlaAT2 expression level and the alanine content in photosynthetic tissues increased in response to the shade treatment. Furthermore, the involvement of CsAlaAT2 in alanine biosynthesis was confirmed based on transient suppression assays in tea leaves, and the alanine content and CsAlaAT2 transcript level decreased when CsAlaAT2 expression was suppressed in tea leaves. Thus, this study suggests that CsAlaAT2 is essential for the alanine metabolism in tea plants grown and its response to shade.

The Changes of Absorption and Catalytic Capacity on Reduced Graphene Oxide After Electron Beam Irradiation

Peng Liu,Wei Qi,Wenzhen An,Longlong Tian,Zhan Li,Xiaolei Chen,Wang-Suo Wu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2015 NANO Vol.10 No.3

As is well-known, porous nanomaterials have attracted increasing attention recently, and graphene-related materials (such as porous graphene) have been studied both experimentally and theoretically. Almost all researches are focused on nanoelectronics, supercapacitors, multifunctional membrances, bio-applications or others. Consequently, in order to understand the differences between porous graphene and normal graphene at adsorption and catalytic property, in this experiment, with the removal of metal ion (152Eu(III)) and organic matter (gallic acid) and reduction of 4-nitrophenol (4-NP) by NaBH4 as model reactions, a systematic investigation into the adsorptive performance as well as catalytic activity of graphene with or without electron beam irradiation exposure had been carried out. As the results showed, compared with the reduction of pristine graphene oxidized (R-GO), the reduction of graphene oxidized with electron beam irradiation exposure (100 MGy, about 2 h, radiation graphene oxide (R-RGO)) had many irregular defects caused by lack of atoms; the adsorptive performance of the R-RGO increased for metals but decreased for organic matter. However, the adsorption rate of the R-RGO was lower for metals, but higher for organic matter than that of the R-GO. In addition, the results also showed that the R-RGO had a better catalytic capacity than the R-GO.

Apigenin Suppresses the IL-1β-Induced Expression of the Urokinase-Type Plasminogen Activator Receptor by Inhibiting MAPK-Mediated AP-1 and NF-κB Signaling in Human Bladder Cancer T24 Cells

Xia, Yong,Yuan, Miaomiao,Li, Shinan,Thuan, Ung Trong,Nguyen, Thi Thinh,Kang, Taek Won,Liao, Wenzhen,Lian, Sen,Do Jung, Young ACS AMERICAN CHEMICAL SOCIETY 2018 Journal of agricultural and food chemistry Vol.66 No.29

Manganese-based hollow nanoplatforms for MR imaging-guided cancer therapies

Shuang Liang,Guangfu Liao,Wenzhen Zhu,Li Zhang 한국생체재료학회 2022 생체재료학회지 Vol.26 No.3

Theranostic nanoplatforms integrating diagnostic and therapeutic functions have received considerable attention in the past decade. Among them, hollow manganese (Mn)-based nanoplatforms are superior since they combine the advantages of hollow structures and the intrinsic theranostic features of Mn2+. Specifically, the hollow cavity can encapsulate a variety of small-molecule drugs, such as chemotherapeutic agents, photosensitizers and photothermal agents, for chemotherapy, photodynamic therapy (PDT) and photothermal therapy (PTT), respectively. After degradation in the tumor microenvironment (TME), the released Mn2+ is able to act simultaneously as a magnetic resonance (MR) imaging contrast agent (CA) and as a Fenton-like agent for chemodynamic therapy (CDT). More importantly, synergistic treatment outcomes can be realized by reasonable and optimized design of the hollow nanosystems. This review summarizes various Mn-based hollow nanoplatforms, including hollow MnxOy, hollow matrix-supported MnxOy, hollow Mn-doped nanoparticles, hollow Mn complex-based nanoparticles, hollow Mn-cobalt (Co)-based nanoparticles, and hollow Mn-iron (Fe)-based nanoparticles, for MR imaging-guided cancer therapies. Finally, we discuss the potential obstacles and perspectives of these hollow Mn-based nanotheranostics for translational applications. Graphical AbstractMn-based hollow nanoplatforms such as hollow MnxOy nanoparticles, hollow matrix-supported MnxOy nanoparticles, Mn-doped hollow nanoparticles, Mn complex-based hollow nanoparticles, hollow Mn-Cobased nanoparticles and hollow Mn-Fe-based nanoparticles show great promise in cancer theranostics.

Effect of Tension Temperature on the Anisotropy of Tensile Behavior for Az31 Alloys: A Visco-Plastic Self-Consistent Analysis

Wenke Wang,Jaimyun Jung,Chao Cui,Wenzhen Chen,Yang Yu,Peng Li,Wencong Zhang,Renlong Xiong,김형섭 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.4

In this work, the anisotropy variation of tensile flow stress for AZ31 magnesium alloys was investigated at various temperaturesand tensile strains with the help of the visco-plastic self-consistent model. The results showed that the anisotropyof flow stress was weakened with the increase of tensile temperature, while such anisotropy presented a slightly increasingstage first and then a continuously decreasing stage with the increase of tensile strain. During the tension deformation, theactivations of basal slip and tension twinning, together contributed to the development of a (0002)//LD (LD: loading direction)type texture. In contrast, the activations of prismatic slip produced a ⟨10–10⟩//LD type texture. Such texture variationsinfluenced the Taylor factors, but did not cause significant differences in the flow stress. By comparison, the difference inthe macroscopic average resolved shear stress, which was calculated according to the critical resolved shear stress of eachdeformation mode and their respective activation fractions, decreased significantly with the increase of tensile temperatureor tensile strain. This was the major reason for the decline of the tension deformation behavior anisotropy.

Paternal Behaviors and Adolescents' Academic Motivation at Low, Moderate, and High Levels of Students' Achievement in Mainland China

Cho, Won Jee,Bush, Kevin R.,Xia, Yan,Wilson, Stephan M.,Li, Wenzhen,Peterson, Gary W. Korean Association of Child Studies 2014 Child studies in Asia-Pacific context Vol.3 No.2

The purpose of this study was to examine group differences in paternal behaviors (i.e., paternal connection, paternal punitiveness, and paternal knowledge) within and across three academic achievement levels-low, moderate, and high, and to explore the effects of paternal behaviors on the academic motivation of Chinese adolescents within these three achievement groups. Analyses of variance (ANOVAs) indicated that adolescents with low achievement perceived their fathers as more punitive than teens with moderate and high academic achievement. Regression analyses also revealed that paternal punitiveness (negative) and paternal knowledge (positive) were significant predictors of academic motivation for teens with low levels of academic achievement; while paternal punitiveness was a significant negative predictor of academic motivation among adolescents with moderate achievement. In contrast, for adolescents with high achievement, paternal connection was a positive significant predictor of academic motivation. The present findings provide some evidence that the impact of parental behaviors on teen's motivation varies across adolescent academic achievement levels, which may prove useful for professionals working with fathers to help target the most effective parenting behaviors to foster academic motivation.