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Flow excitation mechanisms of unbalanced impeller forces after pump power-trip of ultra-high head pump-turbines

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Science China(Technological Sciences) 2024年第5期67卷 1602-1611页

作者： FU XiaoLong LI Deyou LV JingWei yANG Biao wang HongJie WEI XianZhu School of Energy Science and Engineering Harbin Institute of TechnologyHarbin150001China State Key Laboratory of Hydro-Power Equipment Harbin Institute of Large Electrical MachineryHarbin150040China

To elucidate the dynamic mechanisms of unbalanced impellers in ultra-high head pump-turbines(PTs),this study employed a one-and three-dimensional coupled method to simulate the pump power-trip(PPT)process of an ultra-high head *** investigation revealed two novel pulsation frequency components,denoted as fDVand fINFT,associated with impeller *** pulsation intensities of these components were markedly higher than those of rotor-stator interaction frequency components in ultra-high head ***,the fDVcomponents exhibited pulsations at 1–2 times the rated rotation frequency of the impeller,spanning the entire transition ***,the fINFTcomponents constituted a complex frequency band with various frequency values,primarily occurring near conditions(q=0,n=0,M=0,and d M/dt=0).These two pulsation frequency components were predominantly linked to the unsteady evolution of dean vortices inside the volute and complex transitions of the flow pattern within the impeller,*** is crucial to note that these unbalanced flow-induced impeller axial forces can elevate the risk of accidents where the rotor is subjected to significant upwind axial *** findings offer valuable insights into mitigating the risk of rotor lifting due to axial forces during PT events in ultra-high head PTs.

关键词： ultra-high head pump-turbine pump power-trip unbalanced impeller forces pressure pulsations flow pattern transitions

Existence of Multiple Normalized Solutions for Schr?dinger-Choquard Equation with Mixed Nonlinearities

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Acta Mathematicae Applicatae Sinica 2024年

作者： Li-qin TANG Li wang Jun wang School of Mathematics Sun Yat-sen University Department of Basic Courses Hefei University of economics College of Science East China Jiaotong University

This paper considers the existence of multiple normalized solutions of the following SchrodingerChoquard equation where c,ε,μ> 0,N≥3,α∈(0,N),(N+α)/N <q <1+(α+2)/N

This paper considers the existence of multiple normalized solutions of the following SchrodingerChoquard equation where c,ε,μ> 0,N≥3,α∈(0,N),(N+α)/N q y Ekeland:s variational principle and truncated skill.

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青藏高原及其周边新近纪综合地层、生物群与古地理演化

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中国科学：地球科学 2024年第4期54卷 1343-1378页

作者：邓涛方小敏李强王世骐吴飞翔侯素宽马姣江左其杲孙丹辉郑妍史勤勤孙博阳李录中国科学院古脊椎动物与古人类研究所中国科学院脊椎动物演化与人类起源重点实验室北京100044 中国科学院生物演化与环境卓越创新中心北京100044 中国科学院大学地球与行星科学学院北京100049 中国科学院青藏高原研究所中国科学院青藏高原地球科学卓越创新中心北京100101 北京大学地球与空间科学学院造山带与地壳演化教育部重点实验室北京100871

青藏高原在新近纪的显著隆升对东亚乃至全球的气候环境产生了巨大的影响,因此,建立青藏高原新近纪地层框架对地球科学各领域的研究都有重要的意义.国际新近纪年代地层系统以海相为标准,分为中新统的6个阶和上新统的2个阶.新生代以来,陆... 详细信息

青藏高原在新近纪的显著隆升对东亚乃至全球的气候环境产生了巨大的影响,因此,建立青藏高原新近纪地层框架对地球科学各领域的研究都有重要的意义.国际新近纪年代地层系统以海相为标准,分为中新统的6个阶和上新统的2个阶.新生代以来,陆相地层在陆地上所占的比例迅速增加,到新近纪时已远远超过海相地层,在青藏高原及其周边地区几乎全部为陆相地层.中国的中新统包括5个阶,上新统包括2个阶,除中中新统的通古尔阶以15Ma为底界外,其余各阶都与对应的国际海相阶具有相同的古地磁定义和时限.哺乳动物化石在新生代陆相地层的划分对比中占有非常重要的地位,在新近系尤其倚重于啮齿类、食肉类、长鼻类、奇蹄类和偶蹄类化石.青藏高原有不少地层出露好且富含哺乳动物化石的盆地,新近系谢家阶和灞河阶的底界层型剖面分别位于西宁盆地和临夏盆地,并有精细的古地磁定年与哺乳动物化石相互配合,其余各阶的底界在青藏高原也可以有效确定.东亚地区许多哺乳动物首现属出现在青藏高原及其周边地区,在东北缘的临夏盆地和西南缘的西瓦立克地区尤为典型,其中,西瓦立克的原恐象Prodeinotherium首现于中新统底界,旧大陆最早的三趾马Hipparion首现于临夏盆地的灞河阶底界.对青藏高原及其周缘地区新生代沉积物及其所含的哺乳动物化石进行的牙釉质和古土壤碳氧同位素分析重建了气候环境背景及植被发育特征,发现其既与全球变化相关,又有地区性的特点.根据碳同位素变化得到的晚中新世C4植物扩张事件证据来自于青藏高原南缘,但形成鲜明对比的是,多个食草哺乳动物类群和古土壤碳酸盐及有机质的δ13C指示在青藏高原北缘直到新近纪末期仍然缺少明确或显著的C4植物信号.δ^(18)O分析显示在新生代存在几次重大的气候变化事件,尤其是晚中新世末期约7Ma的δ^(18)O正漂指示了青藏高原南北两侧向更干旱环境的转变.青藏高原在晚中新世的强烈隆升强化了海陆热力对比,由此加强了季风环流并导致C4植被在南亚扩张,但能够为中国北方带来大气降水和C4植物适宜气候的东亚夏季风还不足以影响到青藏高原北部地区.青藏高原在中新世整体上已上升至海拔3000m左右,成为阻碍大型哺乳动物交流的屏障;至上新世达到4000m以上的现代海拔高度,由此形成冰冻圈环境,导致冰期动物群祖先类型出现.

关键词：青藏高原新近系陆相地层哺乳动物化石古地磁

Crack Initiation Mechanism of Z3CN20.09M Duplex Stainless Steel during Corrosion Fatigue in Water and Air at 290 °C

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Journal of Materials Science & Technology 2015年第11期31卷 1144-1150页

作者： H.C.Wu B.yang y.Z.Shi q.Gao y.q.wang State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Collaborative Innovation Center of Universal Iron & Steel Technology School of Materials Science and Engineering Anhui University of Technology

The crack initiation mechanism of a Z3CN20.09M duplex stainless steel （DSS） during corrosion fatigue （CF） in water and air at 290 ℃ was investigated by using a CF cracking machine and a scanning electron microscopy （SEM）. The cracks were initiated successively at the persistent stip bands （PSBs）, phase boundaries （PBs） and pitting corrosion points （PCPs） of the specimens when they were tested in water at 290 ℃, while in airat 290 ℃ the cracks were only initiated at the PSBs and PBs. And the cracks were found mainly to initiate at the PSBs and PBs when the specimens were tested in water and air at 290 ℃, respectively. The results also reveal that the cracks were likely to be initiated at the first 20% of fatigue life of the specimens tested in water at 290 ℃. However, the cracks were not found until 50% of fatigue life when tested in air at 290 ℃. Moreover, the crack numbers of the specimens tested in water at 290 ℃ were much more than those tested in air at 290 ℃.

关键词： Duplex stainless steel Corrosion fatigue Crack initiation High temperature water

Comparison of the clinical effects of dual-modality endoscopy and traditional laparotomy for the treatment of intra-and extrahepatic bile duct stones

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World Journal of Gastrointestinal Surgery 2024年第3期16卷 759-767页

作者： Wei wang Hui Xia Bin Dai Department of Hepatobiliary Surgery Wuhan No.1 HospitalWuhan 430030Hubei ProvinceChina

BACKGROUND Bile duct stones(BDSs)may cause patients to develop liver cirrhosis or even liver ***,the success rate of surgical treatment for intrahepatic and extrahepatic BDSs is not satisfactory,and there is a risk of postoperative *** To compare the clinical effects of dual-modality endoscopy(duodenoscopy and laparoscopy)with those of traditional laparotomy in the treatment of intra-and extrahepatic *** Ninety-five patients with intra-and extrahepatic BDSs who sought medical services at Wuhan No.1 Hospital between August 2019 and May 2023 were selected;45 patients in the control group were treated by traditional laparotomy,and 50 patients in the research group were treated by dual-modality *** following factors were collected for analysis:curative effects,safety(incision infection,biliary fistula,lung infection,hemobilia),surgical factors[surgery time,intraoperative blood loss(IBL)volume,gastrointestinal function recovery time,and length of hospital stay],serum inflammatory markers[tumor necrosis factor(TNF)-α,interleukin(IL)-6,and IL-8],and oxidative stress[glutathione peroxidase(GSH-Px),superoxide dismutase(SOD),malondialdehyde(MDA),and advanced protein oxidation products(AOPPs)].RESULTS The analysis revealed markedly better efficacy(an obviously higher total effective rate)in the research group than in the control *** addition,an evidently lower postoperative complication rate,shorter surgical duration,gastrointestinal function recovery time and hospital stay,and lower IBL volume were observed in the research ***,the posttreatment serum inflammatory marker(TNF-α,IL-6,and IL-8)levels were significantly lower in the research group than in the control *** with those in the control group,the posttreatment GSH-Px,SOD,MDA and AOPPs in the research group were equivalent to the pretreatment levels;for example,the GSH-Px and SOD levels were significantly higher,while the MDA and AOPP levels were

关键词： Dual-modality endoscopy Traditional laparotomy Intra-and extrahepatic bile duct stones Clinical efficacy

UPLC-q-TOF/MS-Based Serum Metabolomics Reveals Potential Anti-tumor Mechanism of Banxia Xiexin Decoction in Colorectal Cancer Mice

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Chinese Journal of Integrative Medicine 2024年第7期30卷 623-632页

作者： yUE yin-zi LI Ming-xuan wang Xiao-hui qIN yuan-yuan wang ya-hui TAN Jin-hua SU Lian-lin yAN Shuai Department of General Surgery Suzhou TCM Hospital Affiliated to Nanjing University of Chinese MedicineSuzhou215009China School of Pharmacy Nanjing University of Chinese MedicineNanjing210023China Department of General Surgery Bayinguoleng Mongolian Autonomous Prefecture People’s HospitalXinjiang Uygur Autonomous RegionKorla841000China Department of Pharmacy Suzhou TCM Hospital Affiliated to Nanjing University of Chinese MedicineSuzhou215009China Department of Anorectal Surgery Suzhou TCM Hospital Affiliated to Nanjing University of Chinese MedicineSuzhou215009China

Objective To clarify the potential mechanism of Banxia Xiexin Decoction(BXD)on colorectal cancer(CRC)from the perspective of *** Forty male C57BL/6 mice were randomly divided into normal control(NC),azoxymethane/dextran sulfate sodium(AOM/DSS)model,low-dose BXD(L-BXD),high-dose BXD(H-BXD)and mesalamine(MS)groups according to a random number table,8 mice in each *** cancer model was induced by AOM/*** was administered daily at doses of 3.915(L-BXD)and 15.66 g/kg(H-BXD)by gavage for consecutive 21 days,and 100 mg/kg MS was used as positive *** the entire modeling cycle,colon length of mice was measured and quantity of colorectal tumors were *** spleen and thymus index were determined by calculating the spleen/thymus weight to body *** cytokine and changes of serum metabolites were analyzed by enzyme-linked immunosorbent assay kits and ultra performance liquid chromatography.q.adrupole/time-of-flight mass spectrometry(UPLC-q/TOF-MS),*** Notably,BXD supplementation protected against weight loss,mitigated tumor formation,and diminished histologic damage in mice treated with AOM/DSS(Py enzymes,and improved the spleen and thymus index(Py related to D-glutamine and D-glutamate metabolism,phenylalanine,tyrosine and tryptophan biosynthesis,arginine biosynthesis,nitrogen metabolism and so *** BXD exerts partial protective effects on AOM/DSS-induced CRC by reducing inflammation,protecting organism immunity ability,and regulating amino acid metabolism.

关键词： colorectal cancer metabolomics ultra performance liquid chromatography.q.adrupole/time-of-flight mass spectrometry azoxymethane dextran sulfate sodium Banxia Xiexin Decoction Chinese medicine

Distributed Resource Allocation in Dispersed Computing Environment Based on UAV Track Inspection in Urban Rail Transit

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Computers, Materials & Continua 2024年第7期80卷 643-660页

作者： Tong Gan Shuo Dong Shiyou wang Jiaxin Li Division of Consulting Beijing Metro Consultancy Corporation Ltd.Beijing100037China Department of Computer and Communication Engineering University of Science and Technology BeijingBeijing100083China

With the rapid development of urban rail transit,the existing track detection has some problems such as low efficiency and insufficient detection coverage,so an intelligent and automatic track detectionmethod based onUAV is urgently needed to avoid major safety *** the same time,the geographical distribution of IoT devices results in the inefficient use of the significant computing potential held by a large number of *** a result,the Dispersed Computing(DCOMP)architecture enables collaborative computing between devices in the Internet of Everything(IoE),promotes low-latency and efficient cross-wide applications,and meets users’growing needs for computing performance and service *** paper focuses on examining the resource allocation challenge within a dispersed computing environment that utilizes UAV inspection ***,the system takes into account both resource constraints and computational constraints and transforms the optimization problem into an energy minimization problem with computational *** Markov Decision Process(MDP)model is employed to capture the connection between the dispersed computing resource allocation strategy and the system ***,a method based on Double Deep q-Network(DDqN)is introduced to derive the optimal ***,an experience replay mechanism is implemented to tackle the issue of increasing *** experimental simulations validate the efficacy of the method across various scenarios.

关键词： UAV track inspection dispersed computing resource allocation deep reinforcement learning Markov decision process

Effects of oxygen vacancy on bond ionicity,lattice energy,and microwave dielectric properties of CeO_(2) ceramics with yb^(3+) substitution

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Journal of Advanced Ceramics 2024年第2期13卷 247-254页

作者： Mingan Shi Shuyang Ma wangsuo Xia ying wang Jinzi yu Haitao Wu School of Materials Science and Physics China University of Mining and TechnologyXuzhou 221008China School of Environment and Material Engineering Yantai UniversityYantai 264005China

Novel yb_(x)Ce_(1-x)O_(2-0.5x)(x=0-0.8)ceramics,designed by replacing Ce^(4+)with yb^(3+)ions were prepared by conventional oxide reaction,and the structural stability of the cubic fluorite structure was assessed using lattice energy and ionic properties of Ce/yb-O *** oxygen vacancy caused by unequal substitution,which played a decisive role in bond ionicity and lattice energy,was analyzed experimentally by XPS and also theoretically by first *** yb_(x)Ce_(1-x)O_(2-0.5x) ceramics maintain a stable cubic fluorite structure when x≤0.47,corresponding to the minimum lattice energy of 4142 kJ/mol with the lowest ionicity as ƒ_(i)=87.57%.For microwave dielectric properties,when the yb_(x)Ce_(1-x)O_(2-0.5x)(x=0-0.4)ceramics are pure phase,the porosity-corrected permittivity is dependent on the bond *** q×ƒ values are related to the lattice energy and grain *** temperature coefficient of resonance frequency has been analyzed using bond *** the yb_(x)Ce_(1-x)O_(2-0.5x)(x=0.5-0.8)ceramics are multiple phases,the microwave dielectric properties are associated with the phase composition and grain growth.

关键词： structure stability bond ionicity oxygen vacancy electronic localization function(ELF)

Distributed Cooperative Secondary Voltage Control in an Unbalanced Microgrid

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CSEE Journal of Power and Energy Systems 2024年第1期10卷 222-234页

作者： Xiangzhen yang Haixi Zhao Mengke Duan yan Du Haining wang Jian Zhang School of Electrical Engineering and Automation Hefei University of TechnologyHefei 23009China

The negative-sequence reactive power-conductance(q^(−)-G) droop control strategy is a conventional method to compensate for the output unbalanced voltages in an islanded ***, the conflict between unbalanced voltage compensation and negative-sequence reactive power sharing, caused bythe impedance mismatching of distribution lines and distributedgenerators, has not been solved only by.q.(−)-G droop *** this paper, a distributed cooperative secondary unbalancedvoltage control strategy is proposed to decrease the outputvoltage unbalance factor (VUF) of each droop-controlled DG,as well as to further enhance the negative-sequence reactivepower sharing effectiveness among DGs by properly shiftingup and down the q^(−)-G droop characteristics of each *** algorithm for adaptive VUF weight coefficient is proposedto better suppress VUF under severe imbalance ***, a negative-sequence small-signal model of an MGunder an unbalanced condition, considering the communicationdelay time of the proposed SUVC, is established to analyze thesystem’s stability and transient performance under the influenceof some critical parameters. Finally, the effectiveness of theproposed strategy is validated by the simulation results froma real-time emulator of StarSim HIL.

关键词： Distributed cooperative control MG negativesequence reactive power starsim real-time platform time delay voltage unbalance compensation