检索结果-南通市图书馆

Theoretical Investigation for the Abstraction Reaction of H with (CH_3)_3GeH

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2002年第12期13卷 1227-1230页

作者： qing Zhu zhang chun sheng wang Yue shu GU School of Chemistry and Chemical Engineering Shandong UniversityJinan 250100

ion reaction of H atom with (CH3)3GeH has been studied using ab initio molecular orbital theory. The kinetics calculation has been deduced using the canonical variational transition state theory (CVT) with the small-curvature tunneling correction method (SCT) over the temperature range of 200-3000 K. The CVT/SCT rate constants exhibit typical non-Arrhenius behavior, and a three-parameter rate-temperature formula has been fitted as follows: k=6.66×10-18T2.33 exp(-60.3/T) (in units of cm3 molecule-1 s-1).

关键词： Trimethylgermane ab initio calculation variational transition state rate constants.

Theoretical Studies on the Abstraction Reaction of Atomic O(^3p) with Si2H6

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2002年第7期13卷 662-665页

作者： qing Zhu zhang chun sheng wang Shao Kun wang Yue shu GU School of Chemistry and chemical engineering Shandong UniversityJinan 250100

ion reaction of O (3P) with Si2H6 has been studied theoretically. Two transition states of 3A and 3A symmetries have been located for this abstraction reaction. Geometries have been optimized at the UMP2 level with 6-311G+(d) basis set. G3MP2 has been used for the final single-point energy calculation. The rate constants have been calculated over a wide temperature range of 200~3000 K using canonical variational transition-state theory (CVT) with small curvature tunneling effect (SCT). The calculated CVT/SCT rate constants match well with the experimental value.

关键词： O (3P) disilane ab initio calculation variational transition state rate constants.

Design parameter optimization method for a prestressed steel structure driven by multi-factor coupling

在线全文

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2024年第7期18卷 1066-1083页

作者： Guo-liang SHI Zhan-sheng LIU De-chun LU qing-Wen zhang Majid DEZHKAM Ze-Qiang wang Faculty of Architecture Civil and Transportation EngineeringBeijing University of TechnologyBeijing 100124China The Key Laboratory of Urban Security and Disaster Engineering of the Ministry of Education Beijing University of TechnologyBeijing 100124China Beijing Building Construction Research Institute Co. Ltd.Beijing 100039China

To achieve efficient structural design,it is crucial to reduce the cost of materials while ensuring structural *** study proposes an optimization method for design parameters(DPs)in a prestressed steel structure driven by multi-factor *** accomplish this,a numerical proxy model of prestressed steel structures is established with integration of DPs and mechanical parameters(MPs).A data association-parameter analysis-optimization selection system is established.A correlation between DPs and MPs is established using a back propagation(BP)neural *** correlation provides samples for parameter analysis and optimization *** are used to characterize the safety of the *** on the safety grade analysis,the key DPs that affect the mechanical properties of the structure are obtained.A mapping function is created to match the MPs and the key *** optimal structural DPs are obtained by setting structural materials as the optimization objective and safety energy as the constraint *** theoretical model is applied to an 80-m-span gymnasium and verified with a scale test physical *** MPs obtained using the proposed method are in good agreement with the experimental *** with the traditional design method,the design cycle can be shortened by more than 90%.Driven by the optimal selection method,a saving of more than 20% can be achieved through reduction of structural material ***,the cross-sectional dimensions of radial cables have a substantial influence on vertical *** initial tension and cross-sectional size of the upper radial cable exhibit the most pronounced impact on the stress distribution in that *** initial tension and cross-sectional size of the lower radial cable hold the greatest sway over the stress distribution in that cable.

关键词： structure design association relationship performance analysis optimum selection experimental verification

Risk factors for Clostridioides difficile infection in children and adolescents with inflammatory bowel disease: a systematic review and meta-analysis

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

World Journal of Pediatrics 2022年第1期18卷 27-36页

作者： sheng-Bo Fang Yan-qing Song chun-Yan zhang Li-Bo wang Department of Pharmacy First Hospital of Jilin UniversityChangchunChina Department of Pediatric Gastroenterology Unit First Hospital of Jilin University71 Xinmin StreetChangchun130021China

Background Risk factors and consequences associated with Clostridioides difficile infection(CDI)in children and adolescents with inflammatory bowel disease(IBD)are still *** conduct a systematic review and meta-analysis to assess risk factors and outcomes associated with CDI in children and adolescents with *** PubMed,EMBASE and Cochrane Library databases were searched from inception to 24th February,*** investigating risk factors,bowel surgery rate in pediatric IBD patients with and without CDI were ***-effects model was used for calculating summary ***–Ottawa scale(NOS)was used for quality *** Fourteen studies,comprising 17,114 patients,were *** was a significant association between 5-aminosalicylic acid(5-ASA)use and CDI[odds ratio(OR)=1.95,95%confidence interval(CI)1.26–3.03],with minimal heterogeneity(I^(2)=0.00%).Increased risk of active disease(OR=4.66,95%CI 2.16–10.07)were associated with CDI in those studies performed in high quality score(NOS>6)and significantly higher CDI rates in studies conducted outside USA(OR=2.94,95%CI 1.57–5.58).The bowel surgery rate in IBD with CDI was 3.8–57.1%,compared to that in IBD without CDI(0–21.3%).All studies were of moderate to high *** 5-ASA use and active disease might be risk factors associated with CDI in children and adolescents with *** surgery rates associated with CDI in IBD patients varied ***-scale clinical studies on CDI in children and adolescents with IBD are still needed to verify risk factors and outcomes.

关键词： Adolescent Children Clostridioides difficile infection Inflammatory bowel disease

Microstructure evolution of Ti5Si3 in Cu-Ti-Si alloys

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

China Foundry 2020年第4期17卷 286-292页

作者： qing Liu Xiao-cui zhang Qiang wang Wen-zhi Miao chun-yan Li hai-min Ding School of Energy Power and Mechanical EngineeringNorth China Electric Power UniversityBaoding 071003China State Grid Shandong Electric Power Maintenance Company Jinan 250021China Hebei Key Laboratory of Electric Machinery Health Maintenance&Failure Prevention North China Electric Power UniversityBaoding 071003China

The Cu-Ti-Si alloys containing in-situ formed Ti5Si3 are prepared. In order to clarify the Ti5Si3 formation processes and its microstructure characteristics, the as-cast and deeply etched Cu-Ti-Si alloys with different compositions and cooling rates were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). It is found that the eutectic Ti5Si3 phases in Cu-Ti-Si alloys are rod-like with hexagonal cross section which tend to intertwine with each other to form a firm skeleton like a bird nest structure which can make the alloys keep their original shape even after etching off the Cu matrix. In addition, there is Cu in the center of many Ti5Si3 rods, resulting in a core-shell structure. With the increase of the cooling rate, Ti5Si3 distributes more uniformly, and the diameter of Ti5Si3 significantly decreases, with a minimum size of less than 100 nm, while the aspect ratio of Ti5Si3 increases.

关键词： microstructures Cu alloys Ti5Si3 intermetallic compounds

Relationship between Crystal Structure of Inclusions and Formation of Acicular Ferrites

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2016年第6期23卷 586-592页

作者： Zhi-min cui Li-guang ZHU Yuan-liang LI qing-jun zhang chun-liang YAN Wen-ling MO School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Analysis and Testing Center North China University of Science and Technology College of Metallurgy and Energy North China University of Science and Technology Hebei Provincial Key Laboratory of Inorganic Nonmetallic Materials North China University of Science and Technology Yi sheng College North China University of Science and Technology

The formation mechanism of intragranular ferrites with acicular morphology was *** ferrites were characterized by scanning electron *** results showed that the ferrites had an acicular structure with radial,symmetrical,and acicular laths,and that the inclusions were the nucleation sites of the intragranular acicular *** electron microscopy（TEM）was used to characterize the *** results of TEM with energy dispersive spectroscopy and TEM-selected area electron diffraction indicated that the complex inclusions consisted of Ti-Al complex oxides and *** jagged edges of the complex inclusions can be ascribed to the effects of the crystal *** stabilization energy U of the coordination polyhedron growth units varies with the type of connection according to the calculation results.A larger Ucorresponds to more stable growth units,which induces the preferentially oriented growth of inclusions,at which point acicular ferrites are formed.

关键词： nucleation dispersive preferentially stabilization characterize rutile ferrite anatase grains symmetrical

Preventive effect of tetramethylpyrazine on intestinal mucosal injury in rats with acute necrotizing pancreatitis

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2006年第39期12卷 6386-6390页

作者： Jian-Xin zhang sheng-chun Dang Jian-Guo Qu Xue-qing wang Department of General Surgery the Affiliated Hospital of Jiangsu University Zhenjiang 212001 Jiangsu Province China

AIM： To evaluate the role of microcirculatory disorder （MCD） and the therapeutic effectiveness ;of tetramethylpyrazine （TMP） on intestinal mucosa injury in rats with acute necrotizing pancreatitis （ANP）.METHODS： A total of 192 Sprague-Dawley rats were randomly divided into three groups： normal control group （C group）, ANP group not treated with TMP （P group）, ANP group treated with TMP （T group）. An ANP model was induced by injection of 50 g/L sodium taurocholate under the pancreatic membrane （4 mL/kg）. C group received isovolumetric injection of 9 g/L physiological saline solution using the same method. T group received injection of TMP （10 mL/kg） via portal vein. Radioactive biomicrosphere technique was used to measure the blood flow at 0.5, 2, 6 and 12 h after the induction of ANP. Samples of pancreas, distal ileum were collected to observe pathological changes using a validated histology score. Intestinal tissues were also used for examination of myeloperoxidase （MPO） expressed intraceUularly in azurophilic granules of neutrophils.RESULTS： The blood flow was significantly lower in P group than in C group （P 〈 0.01）. The pathological changes were aggravated significantly in P group. The longer the time, the severer the pathological changes. The intestinal MPO activities were significantly higher in P group than in C group （P 〈 0.01）. The blood flow of intestine was significantly higher in T group than in P group after 2 h （P 〈 0.01）. The pathological changes were alleviated significantly in T group. MPO activities were significantly lower in T group than in P group （P 〈 0.01 or P 〈 0.05）. There was a negative correlation between intestinal blood flow and MPO activity （r = -0.981, P 〈 0.01） as well as between intestinal blood flow and pathologic scores （r = -0.922, P 〈 0.05）.CONCLUSION： MCD is an important factor for intestinal injury in ANP. TMP can ameliorate the condition of MCD and the damage to pancreas and intestine.

关键词： Acute necrotizing pancreatitis Microcirculation Tetramethylpyrazine Intestinal mucosal injury

Study on the Influencing Factors of the Permittivity Estimation Method Considering Antenna Layout Based on Lunar Penetrating Radar

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2022年第10期22卷 11-23页

作者： Rui-Gang wang Yan Su Zong-Yu zhang qing zhang Chen-Di Liu Tian-sheng Hong shu-Ning Liu Wei Du shun Dai chun-Yu Ding chun-Lai Li National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China School of Astronomy and Space Science Universty of Chinese Academy of SciencesBeijing 100049China The 54th Research Institute of China Electronics Technology Group Corporation Shijiazhuang 050081China Institute of Moon-base Exploration and Observation Institute of Advance StudyShenzhen UniversityShenzhen 518060China

The permittivity of lunar regolith is crucial for further processing and interpretation of radar *** conventional hyperbolic fitting method ignores the antenna height and spacing and has a significant error at a shallow *** the new method that considers the layout of the antenna,the influencing factors have not been *** this paper,we studied the influence of the position of the hyperbola peak and time zero on the new method for permittivity *** simulation results show that when the input errors of time zero,abscissa and ordinate of the hyperbolic peak are±2 ns,±0.02 m and±0.2 ns respectively,the average errors of the calculated results by points within 1 m from the hyperbolic peak are 10.0%,16.7%and 38.2%,*** improve the accuracy,we used the average results by points that are horizontally more than 1 m away from the hyperbola ***,we calculated the permittivity of the lunar regolith by the new method based on Lunar Penetrating Radar *** average permittivity of the lunar regolith is estimated to be 3.3±1.2.

关键词： Moon-techniques radar astronomy-techniques image processing

Better use of experience from other reservoirs for accurate production forecasting by learn-to-learn method

在线全文

学校读者我要写书评

暂无评论

Petroleum Science 2024年第1期21卷 716-728页

作者： Hao-Chen wang Kai zhang Nancy Chen Wen-sheng Zhou Chen Liu Ji-Fu wang Li-Ming zhang Zhi-Gang Yu Shi-Ti cui Mei-chun yang China University of Petroleum(East China) 66 Changjiang West RoadQingdao West Coast New AreaQingdao266580ShandongChina University of Calgary 2500 University Dr NWCalgaryT2N 1N4AlbertaCanada qingdao University of Technology Qingdao266071ShandongChina State Key Laboratory of Offshore Oil Exploitation Beijing100028China CNOOC Research Institute Ltd. Beijing100028China CNPC Tarim Oilfield Branch Company Korla841000XinjiangChina National Engineering Laboratory for Exploration and Development of Low-Permeability Oil and Gas Fields Xi'an710000ShaanxiChina Sinopec Matrix Co. LTDQingdao266000ShandongChina

To assess whether a development strategy will be profitable enough,production forecasting is a crucial and difficult step in the *** development history of other reservoirs in the same class tends to be studied to make predictions ***,the permeability field,well patterns,and development regime must all be similar for two reservoirs to be considered in the same *** results in very few available experiences from other reservoirs even though there is a lot of historical information on numerous reservoirs because it is difficult to find such similar *** paper proposes a learn-to-learn method,which can better utilize a vast amount of historical data from various ***,the proposed method first learns how to learn samples before directly learning rules in ***,by utilizing gradients from networks with independent parameters and copied structure in each class of reservoirs,the proposed network obtains the optimal shared initial parameters which are regarded as transferable information across different *** on that,the network is able to predict future production indices for the target reservoir by only training with very limited samples collected from reservoirs in the same *** cases further demonstrate its superiority in accuracy to other widely-used network methods.

关键词： Production forecasting Multiple patterns Few-shot learning Transfer learning