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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

Chain Dynamics Heterogeneity in Plasticized Poly(vinyl butyral)(PVB) as Elucidated by Solid-State NMR

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Chinese Journal of Polymer Science 2024年第1期42卷 113-124,I0010页

作者： Jing lv Xu Chen Zi-Shuo Wu Ya-Hui Li Wei Chen National Synchrotron Radiation Laboratory Anhui Provincial Engineering Laboratory of Advanced Functional Polymer FilmCAS Key Laboratory of Soft Matter ChemistryUniversity of Scienceand Technology of ChinaHefei 230026China

The chain dynamics heterogeneity of the poly(vinyl butyral)(PVB) plasticized by triethylene glycol bis(2-ethylhexa noate)(TEG-EH) was investigated by various solid-state NMR *** plasticized PVB shows two domains in distinct molecular dynamics differences,namely,rigid and soft domains,where the latter is the plasticizer-rich *** time domain low field NMR was first used to investigate the dynamics heterogeneity of the plasticized PVB,and the results show the decreasing activated energy of components in the soft domain of plasticized PVB(E_a=20.2 kJ/mol) as compared with that of the pristine one(E_a=24.3 kJ/mol).Detailed dynamics heterogeneity was obtained by high-field NMR with site-specific *** quadrupole-echo ~2H-NMR was adopted to elucidate the dynamics heterogeneity of the vinyl alcohol(VA) units,where only the hydroxyl group of VA is *** ~1H-^(13)C WISE NMR spectra show that there is not much difference in the mobility of the VB unit in PVB with and without plasticizer,whereas the glass transition temperature differed by approximately 53℃.This is further supported by Torchia's T_1 relaxation *** origin of such an unusual phenomenon is attributed to the critical role of the remaining VA(~22%) in the soft domain,where the VA units locally aggregate through hydrogen ***,the existence of a mobility gradient in the VB unit has been ***,the mobility difference for VB with different stereo-geometry(meso or racemic conformation) is observed for the first *** indicates the importance of modulating the ratio of meso over racemic VB for controlling the macroscopic perfo rmance of PVB.

关键词： Poly(vinyl butyral) Dynamics heterogeneity Plasticizer Solid state NMR

The GNSS PWV retrieval using non-observation meteorological parameters based on ERA5 and its relation with precipitation

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Geodesy and Geodynamics 2024年第3期15卷 302-313页

作者： Weifeng Yang Zhiping Chen Kaiyun lv Pengfei Xia Tieding Lu School of Surveying and Geoinformation Engineering East China University of TechnologyNanchang 330013China Key Laboratory of Mine Environmental Monitoring and Improving around Poyang Lake of Ministry of Natural Resources East China University of TechnologyNanchang 330013China State Key Laboratory of Geodesy and Earth's Dynamics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan 430077China Jiangxi Province Engineering Research Center of Surveying Mapping and Geographic InformationNanchang 330025China School of Geodesy and Geomatics Wuhan UniversityWuhan 430079China

The pressure and temperature significantly influence precipitable water vapor(PWV) retrieval. Global Navigation Satellite System(GNSS) PWV retrieval is limited because the GNSS stations lack meteorological sensors. First, this article evaluated the accuracy of pressure and temperature in 68 radiosonde stations in China based on ERA5 Reanalysis data from 2015 to 2019 and compared them with GPT3model. Then, the accuracy of pressure and temperature calculated by ERA5 were estimated in 5 representative IGS stations in China. And the PWV calculated by these meteorological parameters from ERA5(ERA5-PWV) were analyzed. Finally, the relation between ERA5-PWV and precipitation was deeply explored using wavelet coherence analysis in IGS stations. These results indicate that the accuracy of pressure and temperature of ERA5 is better than the GPT3 model. In radiosonde stations, the mean BIAS and MAE of pressure and temperature in ERA5 are-0.41/1.15 hpa and-0.97/2.12 K. And the mean RMSEs are 1.35 hpa and 2.87 K, which improve 74.77% and 40.58% compared with GPT3 model. The errors of pressure and temperature of ERA5 are smaller than the GPT3 model in bjfs, hksl and wuh2, and the accuracy of ERA5-PWV is improved by 18.77% compared with the GPT3 model. In addition, there is a significant positive correlation between ERA5-PWV and precipitation. And precipitation is always associated with the sharp rise of ERA5-PWV, which provides important references for rainfall prediction.

关键词： ERA5 GNSS Precipitable water vapor Precipitation Wavelet coherence analysis

Oligomeric donor with appropriate crystallinity for organic solar cells

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Chinese Chemical Letters 2024年第2期35卷 289-294页

作者： Kaiming Yang Min lv Yanhong Chang Kun Lu Zhixiang Wei CAS Key Laboratory of Nanosystem and Hierarchical Fabrication CAS Center for Excellence in NanoscienceNational Center for Nanoscience and TechnologyBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Department of Environmental Science and Engineering University of Science and Technology BeijingBeijing 100083China Beijing Key Laboratory of Resource Treatment of Typical Industrial Pollutants Beijing 100083China

Improving the performance of all-small-molecule organic solar cells(ASM-OSCs)largely depends on the design and application of novel donors with appropriate *** molecular conjugation is an effective method for regulating molecular stacking and *** this work,we successfully designed and synthesized two novel acceptor-donor-donor-donor-acceptor(A-D-D-D-A)type oligomeric donors with three dithieno[2,3-d:2′,3′-d′]benzo[1,2-b:4,5-b']dithiophene(DTBDT)as the central unit,named as 3DTBDT-Cl and 3DTBDT,depending on with and without chlorine substitution on the thiophene side *** found that the introduction of chlorine atoms makes the blend films display stronger crystallinity but with large-scale phase separation morphology and more defects,which eventually leads to a power conversion efficiency(PCE)of only 10.83%,whereas the blend films based 3DTBDT with appropriate crystallinity achieved 13.74%*** with 3DTBDT-Cl/L8-BO,the 3DTBDT/L8-BO films exhibited a nanoscale bi-continuous interpenetrating network morphology with a smaller domain size and more suitable crystallinity,which guarantees the corresponding devices obtained more efficient exciton dissociation,efficient charge transport,reduced bimolecular recombination,and performed more balanced carrier *** results demonstrated that regulating the crystallinity of oligomeric donors to obtain the desired phase separation morphology in the blend films could facilitate further improving the performance of ASM-OSCs.

关键词： Linked donor unit Oligomeric donors Crystallinity regulation Organic solar cells

Theoretical and experimental investigation of the resonance responses and chaotic dynamics of a bistable laminated composite shell in the dynamic snap-through mode

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Applied Mathematics and Mechanics(English Edition) 2024年第4期45卷 581-602页

作者： Meiqi WU Pengyu lv Hongyuan LI Jiale YAN Huiling DUAN Wei ZHANG State Key Laboratory for Turbulence and Complex Systems Department of Mechanics and Engineering ScienceBIC-ESATCollege of EngineeringPeking UniversityBeijing 100871China Nanchang Innovation Institute of Peking University Nanchang 330096China Department of Mechanics Guangxi UniversityNanning 530004China

The dynamic model of a bistable laminated composite shell simply supported by four corners is further developed to investigate the resonance responses and chaotic *** existence of the 1:1 resonance relationship between two order vibration modes of the system is *** resonance response of this class of bistable structures in the dynamic snap-through mode is investigated,and the four-dimensional(4D)nonlinear modulation equations are derived based on the 1:1 internal resonance relationship by means of the multiple scales *** Hopf bifurcation and instability interval of the amplitude frequency and force amplitude curves are *** discussion focuses on investigating the effects of key parameters,e.g.,excitation amplitude,damping coefficient,and detuning parameters,on the resonance *** numerical simulations show that the foundation excitation and the degree of coupling between the vibration modes exert a substantial effect on the chaotic dynamics of the ***,the significant motions under particular excitation conditions are visualized by bifurcation diagrams,time histories,phase portraits,three-dimensional(3D)phase portraits,and Poincare ***,the vibration experiment is carried out to study the amplitude frequency responses and bifurcation characteristics for the bistable laminated composite shell,yielding results that are qualitatively consistent with the theoretical results.

关键词： bistable laminated composite shell dynamic snap-through mode Hopf bifurcation chaotic dynamics vibration experiment

Waist subcutaneous soft tissue metastasis of rectal mucinous adenocarcinoma: A case report

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World Journal of Clinical Cases 2024年第14期12卷 2412-2419页

作者： Zi-Xing Gong Guo-Lei Li Wen-Min dong Zhao Xu Rui Li Wen-Xia lv Jing Yang Zhong-Xin Li Wei Xing Department of General Surgery Hebei Provincial Hospital of Chinese MedicineShijiazhuang 050011Hebei ProvinceChina Department of Medical Imaging Hebei Provincial Hospital of Chinese MedicineShijiazhuang 050011Hebei ProvinceChina Department of Pathology Hebei Provincial Hospital of Chinese MedicineShijiazhuang 050011Hebei ProvinceChina Department of Gastroendoscopy Hebei Provincial Hospital of Chinese MedicineShijiazhuang 050011Hebei ProvinceChina Gastrointestinal Disease Diagnosis and Treatment Center The First Hospital of Hebei Medical UniversityShijiazhuang 050000Hebei ProvinceChina

BACKGROUND Rectal mucinous adenocarcinoma(MAC)is a rare pathological type of rectal can-cer with unique pathological features and a poor *** is difficult to diag-nose and treat early because of the lack of specific manifestations in some aspects of the *** common metastatic organs of rectal cancer are the liver and lung;however,rectal carcinoma with metastasis to subcutaneous soft tissue is a rare *** SUMMARY In this report,the clinical data,diagnosis and treatment process,and postope-rative pathological features of a patient with left waist subcutaneous soft tissue masses were retrospectively *** patient underwent surgical treatment after admission and recovered well after *** final pathological diagnosis was rectal MAC with left waist subcutaneous soft tissue *** Subcutaneous soft tissue metastasis of rectal MAC is rare,and it can suggest that the tumor is disseminated,and it can appear even earlier than the primary ma-lignant tumor,which is occult and leads to a missed diagnosis and misdiagnosis *** a subcutaneous soft tissue mass of unknown origin appears in a patient with rectal cancer,a ma-lignant tumor should be considered.

关键词： Colorectal cancer Rectal mucinous adenocarcinoma Cancer metastasis Subcutaneous soft tissue Hematogenous Case report

Introducing hydroxyl groups to tailor the d-band center of Ir atom through side anchoring for boosted ORR and HER

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Journal of Energy Chemistry 2024年第3期90卷 144-151,I0005页

作者： Qing lv Meiping Li Xiaodong Li Xingru Yan Zhufeng Hou Changshui Huang Science Center for Material Creation and Energy Conversion School of Chemistry and Chemical EngineeringInstitute of Frontier and Interdisciplinary ScienceShandong UniversityJinan 250100ShandongChina Institute of Chemistry Chinese Academy of ScienceBeijing 100191China State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhou 350002FujianChina

Tuning the coordination atoms of central metal is an effective means to improve the electrocatalytic activity of atomic ***,iridium(Ir) is proposed to be asymmetrically anchored by sp-N and pyridinic N of hydrogen-substituted graphdiyne(HsGDY),and coordinated with OH as an Ir atomic catalyst(Ir_(1)-N-HsGDY).The electron structures,especially the d-band center of Ir atom,are optimized by these specific coordination ***,the as-synthesized Ir_(1)-N-HsGDY exhibits excellent electrocatalytic performances for oxygen reduction and hydrogen evolution reactions in both acidic and alkaline *** from the unique structure of HsGDY,IrN_(2)(OH)_(3) has been developed and demonstrated to act as the active site in these electrochemical *** those indicate the fresh role of the sp-N in graphdiyne in producing a new anchor way and contributing to promote the electrocatalytic activity,showing a new strategy to design novel electrochemical catalysts.

关键词： Oxygen reduction reaction D-band center Graphdiyne Hydroxyl group Electrocatalysis

Early postoperative complications after transverse colostomy closure,a retrospective study

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World Journal of Gastrointestinal Surgery 2024年第3期16卷 807-815页

作者： Fei Liu Xiao-Juan Luo Zi-Wei Li Xiao-Yu Liu Xu-Rui Liu Quan lv Xin-Peng Shu Wei Zhang dong Peng Department of Gastrointestinal Surgery The First Affiliated Hospital of Chongqing Medical UniversityChongqing 400016China Endoscopy Center The First Affiliated Hospital of Chongqing Medical UniversityChongqing 400012China

BACKGROUND Ostomy is a common surgery usually performed to protect patients from clinical symptoms caused by distal anastomotic leakage after colorectal cancer(CRC)surgery and perforation or to relieve intestinal *** To analyze the complications after transverse colostomy *** Patients who underwent transverse colostomy closure from Jan 2015 to Jan 2022 were retrospectively enrolled in a single clinical *** differences between the complication group and the no complication group were *** regression analyses were conducted to find independent factors for overall complications or incision *** A total of 102 patients who underwent transverse colostomy closure were enrolled in the current ***(68.6%)patients underwent transverse colostomy because of CRC related *** complications occurred in 30(29.4%)patients and the most frequent complication occurring after transverse colostomy closure was incision infection(46.7%).The complication group had longer hospital stays(P<0.01).However,no potential risk factors were identified for overall complications and incision *** The most frequent complication occurring after transverse colostomy closure surgery in our center was incision *** operation time,interval from transverse colostomy to reversal,and method of anastomosis might have no impact on the postoperative *** should pay more attention to aseptic techniques.

关键词： Transverse colostomy closure Surgery Complications A single clinical centre Risk factors

Spherical Bi_(2)O_(3)/ATO catalyst with N_(2)pre-reduction electrocatalytic reduction of CO_(2)to formic acid

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Journal of Environmental Sciences 2024年第6期140卷 331-340页

作者： Junying Yi Yuli Chen dongze Lai Bihong lv Xiaomin Wu Guohua Jing Department of Environmental Science&Engineering College of Chemical EngineeringHuaqiao UniversityXiamenFujian 361021China

To achieve carbon neutrality,the Chinese government needs to gain a comprehensive understanding of the sources and drivers of greenhouse gas(GHG)emissions,particularly at the county *** County in eastern China is a typical example of an industrial transformation from quarrying to a low-carbon *** study analyzed the decoupling types and structural characteristics of GHG emissions and the driving factors of carbon dioxide(CO_(2))emissions in the Anji from 2006 to 2019,and explored the differences between countylevel and provincial-level or city-level *** was observed that energy-related activities are the main source of GHG emissions in Anji and that economic development is the driving factor behind the increasing CO_(2)***,industrial transformation and upgradation coupled with the alternative use of clean energy limit the growth of GHG *** study details the GHG emissions of county during the industrial transformation stage and provides corresponding policy recommendations for county governments.

关键词： N_(2)prereduction CO_(2)electroreduction Bi_(2)O_(3)/ATO catalyst Formate