期刊文献+
共找到2,377篇文章
< 1 2 119 >
每页显示 20 50 100
Evaluation of Technical Education by Using a Modern Structured MOODLE Laboratory Course, in Relation to Recent Data
1
作者 Gerasimos Vlassopoulos George Albert Karikas +4 位作者 Efstathia Papageorgiou Ioannis Psaromiligkos Niki Giannouli Pigi Vlassopoulou Petros Karkalousos 《Journal of Intelligent Learning Systems and Applications》 2024年第3期316-339,共24页
E-learning platforms support education systems worldwide, transferring theoretical knowledge as well as soft skills. In the present study high-school pupils’, and adult students’ opinions were evaluated through a mo... E-learning platforms support education systems worldwide, transferring theoretical knowledge as well as soft skills. In the present study high-school pupils’, and adult students’ opinions were evaluated through a modern structured MOODLE interactive course, designed for the needs of the laboratory course “Automotive Systems”. The study concerns Greek secondary vocational education pupils aged 18 and vocational training adult students aged 20 to 50 years. The multistage, equal size simple random cluster sample was used as a sampling method. Pupils and adult students of each cluster completed structured 10-question questionnaires both before and after attending the course. A total of 120 questionnaires were collected. In general, our findings disclosed that the majority of pupils and adult students had significantly improved their knowledge and skills from using MOODLE. They reported strengthening conventional teaching, using the new MOODLE technology. The satisfaction indices improved quite, with the differences in their mean values being statistically significant. 展开更多
关键词 Information and communication Technologies (IcT) Distance Learning E-Learning students Opinions Education in Greece I.c.T. in Greece sTUDENTs Pupils Adults Adult students MOODLE MOOc (V.H.s.) Vocational High schools (s.H.V.T.) schools of Higher Vocational Training VOcATIONAL Profession Interactive Lessons courses Training Laboratory course secondary Education Automotive systems car systems
下载PDF
INFINITELY MANY SOLUTIONS FOR ELLIPTIC SYSTEMS WITH STRONGLY INDEFINITE VARIATIONAL STRUCTURE 被引量:1
2
作者 刘朝霞 《Acta Mathematica Scientia》 SCIE CSCD 2010年第1期55-64,共10页
Based on the multiplicity results of Benci and Fortunato [4], we consider some elliptic systems with strongly indefinite quadratic part, and establish the existence of infinitely many nontrivial solutions in a suitabl... Based on the multiplicity results of Benci and Fortunato [4], we consider some elliptic systems with strongly indefinite quadratic part, and establish the existence of infinitely many nontrivial solutions in a suitable family of products of fractional Sobolev spaces. 展开更多
关键词 semilinear elliptic systems variational functional (P.s.)c sequence criticalpoint
下载PDF
LINEAR ACTIVE STRUCTURES AND MODES (Ⅱ) —DISCRETE SYSTEMS AND BEAMS
3
作者 王永刚 龚靖School of Civil Engineering and Mechanics +10 位作者 Xi'an Jiaotong University Xi'an 710049 P.R.China Department of Civil Engineering Northeast China Institute of Electric Power Jilin 132012 P.R.China 张景绘School of Civil Engineering and Mechanics Xi'an Jiaotong University Xi'an 710049 P.R.China 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2004年第8期854-862,共9页
The basic concepts about the active structures and some attributes of the modes were presented in paper “Liner Active Structures and Modes]( I) ". The characteristics of the active discrete systems and active be... The basic concepts about the active structures and some attributes of the modes were presented in paper “Liner Active Structures and Modes]( I) ". The characteristics of the active discrete systems and active beams were discussed, especially, the stability of the active structures and the orthogonality of the eigenvectors. The notes about modes were portrayed by a model of a seven-storeyed building with sensors and actuators. The concept of the adjoint active structure was extended from the discrete systems to the beams that were the representations of the continuous structures. Two types of beams with different placements of the measuring and actuating systems were discussed in detail. One is the beam with the discrete sensors and actuators, and the other is the beam with distributed sensor and actuator function. The orthogonality conditions were derived with the modal shapes of the active beam and its adjoint active beam. An example shows that the variation of eigenvalues with feedback amplitude for the homo-configuration and non-homo-configuration active structures. 展开更多
关键词 I) ". The characteristics of the active discrete systems and active beams were discussed especially the stability of the active structures and the orthogonality of the eigenvectors. The notes about modes were portrayed by a model of a seven-s
下载PDF
Effect of C/S Ratio on Morphology and Structure of Hydrothermally Synthesized Calcium Silicate Hydrate 被引量:11
4
作者 何永佳 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2011年第4期770-773,共4页
The samples of the C-S-H series were synthesized by hydrothermal reaction of fumed silica, CaO and deionized water at initial C/S ratios between 1.0-1.7. Phase composition and structural and morphology characteristics... The samples of the C-S-H series were synthesized by hydrothermal reaction of fumed silica, CaO and deionized water at initial C/S ratios between 1.0-1.7. Phase composition and structural and morphology characteristics of C-S-H samples were analyzed by XRD, IR and SEM. The experimental results showed that the d-spacing of (002), (110) and (020) decreased, the d-spacing of (200) increased, and the d-spacing of (310) varied randomly, the polymerization of silica tetrahedra of C-S-H decreased, and morphology of C-S-H samples varied from sheet shapes to long reticular fibers as C/S ratio increased. 展开更多
关键词 calcium silicate hydrate c/s ratio MORPHOLOGY structure hydrothermal synthesis
下载PDF
A welding document management software package based on a Client/Server structure 被引量:4
5
作者 魏艳红 杨春利 王敏 《China Welding》 EI CAS 2003年第1期72-77,共6页
According to specifications for Welding Procedure Qualification of ASME IX Section and Chinese code, JB 4708 2000, a software package for managing welding documents has been rebuilt. Consequently, the new software pa... According to specifications for Welding Procedure Qualification of ASME IX Section and Chinese code, JB 4708 2000, a software package for managing welding documents has been rebuilt. Consequently, the new software package can be used in a Limited Area Network (LAN) with 4 different levels of authorities for different users. Therefore, the welding documents, including DWPS (Design for Welding Procedure Specifications), PQRs (Procedure Qualification Records) and WPS (Welding Procedure Specifications) can be shared within a company. At the same time, the system provides users various functions such as browsing, copying, editing, searching and printing records, and helps users to make decision of whether a new PQR test is necessary or not according to the codes above as well. Furthermore, super users can also browse the history of record modification and retrieve the records when needed. 展开更多
关键词 c/s structure welding procedure qualification DATABAsE LAN
下载PDF
Effect of Polymer on Morphology and Structure of Calcium Silicate Hydrate Prepared via Precipitation Method 被引量:3
6
作者 吕林女 PING Bing +3 位作者 何永佳 HE Liu WU Xi HU Shuguang 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2014年第3期504-506,共3页
The effects of polyaerylamide (PAM) and polyvinyl alcohol (PVA) on morphology and structure of calcium silica~ hydrate with C/S 1.0-1.7 prepared via precipitation in solution were investigated by XRD, FT-IR and TE... The effects of polyaerylamide (PAM) and polyvinyl alcohol (PVA) on morphology and structure of calcium silica~ hydrate with C/S 1.0-1.7 prepared via precipitation in solution were investigated by XRD, FT-IR and TEM techniques. The results show that incorporation of the polymers decreased the order degree, increased the interlayer spacing and disturbed the layered stacking of C-S-H. Interlayer spacing expansion depended on C/S ratios and type of polymer. Interlayer spacing expansion had a minimum at C/S 1.0 and a maximum at C/S 1.3 and 1.5. Interlayer spacing expansion of PAM was bigger than that of PVA with the same C/S. C-S-H added with PVA mainly exhibited foil-like and fibrillar morphology. The fibrils were of variable length from a few tens of nanometers to a few hundreds of nanometers. Fibrils or foils seemed to be longer in the presence of PVA. 展开更多
关键词 c-s-H MORPHOLOGY structure POLYAcRYLAMIDE polyvinyl alcohol
下载PDF
Electronic Structure and Optical-absorption Properties of C-, N-, and S-doped BiOCl: the First-principles Calculations
7
作者 YAO Wen-Zhi YAO Jian-Bin +1 位作者 ZHANG Xia MA Ya-Hao 《Chinese Journal of Structural Chemistry》 SCIE CAS CSCD 2019年第4期509-523,共15页
Impurity formation energy, electronic structure, and photocatalytic properties of C-, N-, or S-doped BiOCl are investigated by density-functional theory plus U calculations(DFT + U). Results show that the doping effec... Impurity formation energy, electronic structure, and photocatalytic properties of C-, N-, or S-doped BiOCl are investigated by density-functional theory plus U calculations(DFT + U). Results show that the doping effect of S is better than that of C or N on the tunable photocatalytic activities of BiOCl. At low concentration, S-doped BiOCl systems are the most stable under Bi-rich growth conditions because of their lower impurity-formation energy. Compared with the electronic structures of S-doped BiOCl, C-or N-doped BiOCl have relatively deeper impurity energy levels appearing in their band gap(except Bi_(36)O_(35)NCl_(36)), which may act as photogenerated carrier-recombination centers and reduce photocatalytic activity. At high concentration, S is substituted on the O lattice site system, whereas some S 3p states mix with the valence band; this mixture leads to an obvious band-gap decrease and continuum-state formation above the valence-band edge of BiOCl. Such activity is advantageous to photochemical catalysis response. Compared with pure Bi OCl and a low-concentration S-doped system, a high-concentration S-doped system shows an obvious redshift on the absorption edge and has better photocatalytic O_2 evolution performance. 展开更多
关键词 BiOcl c N s DOPING the FIRsT-PRINcIPLEs electronic structures VIsIBLE light absorption
下载PDF
SYNTHESIS AND STRUCTURE OF COMPLEX(PPh3)_2Ni[S_2C=C(CN)_2]
8
作者 Zi Xiang HUANG Shao Fang LU Jian Quan HUANG Jin Ling HUANG State Key Laboratory of Structural Chemistry and Fujian Institute of Research on the Structure of Matter,Chinese Academy of Sciences,Fuzhou 350002 《Chinese Chemical Letters》 SCIE CAS CSCD 1992年第12期1023-1024,共2页
(PPh_3)_2Ni(i-mnt),(i-mnt=S_2C=C(CN)_2),Mr=613.43,monoclinic,Pn,a=9.167(3),b=10.872(3), c=18.209(7) ,β=101.46(3)°,V=1779(1) ,Z=2,Dc=1.15 g/cm^3,λ(Moka)=0.71069 ,μ=7.67 cm^(-1), F(000)=648,T=296K,final R=0.060,... (PPh_3)_2Ni(i-mnt),(i-mnt=S_2C=C(CN)_2),Mr=613.43,monoclinic,Pn,a=9.167(3),b=10.872(3), c=18.209(7) ,β=101.46(3)°,V=1779(1) ,Z=2,Dc=1.15 g/cm^3,λ(Moka)=0.71069 ,μ=7.67 cm^(-1), F(000)=648,T=296K,final R=0.060,Rw=0.073 for 1909 observed reflections with Ⅰ≥3σ(Ⅰ).The complex adopts a square planar geometry as its coordination unit,the mean Ni-S and Ni-P distances are 2.216 and 2.221 ,respectivety. 展开更多
关键词 cN s2c=c sYNTHEsIs AND structure OF cOMPLEX NI PPH3
下载PDF
Effect of solid solution modification on structure and properties of dicalcium silicate
9
作者 王政 李家和 张玉珍 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2008年第1期77-79,共3页
In the paper, dicalcium silicate (C2S) was modified to obtain higher performance, and the solutionizing pattern of BaSO4 in cement clinker was analyzed theoretically. According to experimental results, solutionizing o... In the paper, dicalcium silicate (C2S) was modified to obtain higher performance, and the solutionizing pattern of BaSO4 in cement clinker was analyzed theoretically. According to experimental results, solutionizing of BaSO4in cement clinker improved crystal plane distance of C2S as well as the relations of coordination. The performance tests show that the strength of C2S modified by BaSO4 changes and the reactivity of C2S increases significantly. 展开更多
关键词 solid solution crystal structure REAcTIVITY c2s
下载PDF
Systemic lupus erythematosus combined with primary hyperfibrinolysis and protein C and protein S deficiency:A case report
10
作者 Yi-Xuan Liao Yan-Fei Guo +2 位作者 Yu-Xia Wang Ai-Hua Liu Chun-Li Zhang 《World Journal of Clinical Cases》 SCIE 2021年第8期2008-2014,共7页
BACKGROUND Systemic lupus erythematosus(SLE)is an autoimmune disease characterized by systemic involvement and multiple autoantibodies in the serum.Patients with protein C(PC)and protein S(PS)deficiency are prone to t... BACKGROUND Systemic lupus erythematosus(SLE)is an autoimmune disease characterized by systemic involvement and multiple autoantibodies in the serum.Patients with protein C(PC)and protein S(PS)deficiency are prone to thrombosis.In contrast,patients with primary hyperfibrino-lysis tend to bleed.CASE SUMMARY A 52-year-old female patient with bilateral pleural effusion was diagnosed with"tuberculous pleurisy"and treated with anti-tuberculosis drugs and prednisone.The coagulation-related laboratory results showed decreased fibrinogen,PC activity,PS activity,and antithrombinШactivity.The immune-related laboratory results showed positive antinuclear antibody,anti-Smith antibody,anticardiolipin antibody(ACL),anti-β2-glycoprotein I antibody(aβ2GPI)and direct Coomb’s test and decreased complement 3 and complement 4.Thoracoscopy was performed and bloody pleural fluid was drained.Pathology of the pleural biopsy showed lymphocytes,plasma cells,and a few eosinophils in adipose and fibrous connective tissue.Results of whole exome sequencing of blood showed no genetic mutations suggesting the presence of hereditary hematological diseases.The patient was finally diagnosed with SLE and primary hyperfibrinolysis,and was treated with prednisolone,hydroxychloroquine,and compound cyclophosphamide.CONCLUSION PC and PS deficiency in SLE might be related to ACL and aβ2GPI.SLE and primary hyperfibrinolysis can coexist in one patient,with both a risk of thrombosis and a risk of bleeding. 展开更多
关键词 systemic lupus erythematosus Primary hyperfibrinolysis Antiphospholipid antibody Protein c deficiency Protein s deficiency case report
下载PDF
Structures that should be Described in Higher-Symmetry, Centrosymmetric Space Groups. Part 1. The Disordered Structures of [(CH_3CH_2)_4N]_3{[(SCH_2CH_2S)MoS_3]_2Fe}, [(CH_3CH_2)_4N]_2{[S_2CN(C_2H_5)_2]_4Fe_4S_4} and [(CH_3CH_2)_4N]_3{[(SCH_2C
11
《Chinese Journal of Structural Chemistry》 SCIE CAS CSCD 2000年第6期405-410,共6页
关键词 scH2cH2s)Mos3 cH3cH2 c2H5 s2cN structures of Fe
下载PDF
Independent and Combined Effect of Some Soil Tillage Systems on Nitrogen and Carbon Concentration in Soil Structural Units of Haplic Chernozems
12
作者 Margarita Nankova Peter Yankov 《Journal of Agricultural Science and Technology(B)》 2015年第7期465-476,共12页
This paper aimed at studying the effect of different types of soil tillage systems on the change of total carbon (C) and nitrogen (N) in the soil structural units of different size after dry structural analysis of... This paper aimed at studying the effect of different types of soil tillage systems on the change of total carbon (C) and nitrogen (N) in the soil structural units of different size after dry structural analysis of soil. The research was carried out in a 6-field rotation system (grain maize-wheat-sunflower-wheat-bean-wheat) at the end of the 2nd rotation. Six out of 24 soil tillage systems were selected; they were applied independently and in combination in the crop rotation. After that, they were compared to the system with constant deep plowing. So a total of seven soil tillage systems were investigated. The selected systems for main soil tillage were the following: plowing (control variant), disking, cutting, nil tillage (direct sowing), plowing-disking, plowing-nil tillage, disking-nil tillage. Three depths of 0-10, 10-20 and 20-30 cm were studied, as well as soil structural units were of the following sizes: 〉 10 mm, 10-5, 5-3, 3-1, 1-0.25 mm and 〈 0.25 mm. As a result of systematic implementation of different soil tillage systems, higher N and C concentrations were established by the layers according to constant plowing. Constant disking and its alternation with nil tillage increased the total N concentration with 15.6% and 11.1%, respectively, in comparison with the constant plowing. The same was valid for C concentration in soil, but the highest increase was established in the variants with constant cutting and nil tillage. The exceeding was with 14.0% and 13.2%, in comparison to constant plowing. The redistribution of N and C depending on the structural soil units was most expressed in the 0-10 cm and 10-20 cm layers. The highest amounts of C and N were found in the soil units with size less than 5 mm, mainly in the 〈 0.25 mm fraction. At depth of 20-30 cm, the role of the size of soil structural units for C and N redistribution decreased strongly. The values of C/N ratio were moderate only under the use of constant disking. This index was low under all other soil tillage systems. The correlation of total N with C in soil was high, positive and significant depending on the size of structural soil units and the tillage systems, as average for the investigated factors in this experiment. The minimal tillage and the tillage without turning of soil, used independently and in combination, had the highest contribution to preserving the organic matter in the haplic Chernozems of Dobrudzha region. 展开更多
关键词 soil tillage systems soil c total soil N soil structural units.
下载PDF
CRYSTAL STRUCTURE OF SEVEN-COORDINATE ZIRCONOCENE COMPLEX (CH_3C_5H_4) Zr(S_2CNBz_2)_3 (Bz=CH_2C_6H_5)
13
作者 Zhi Qiang WANG Shi Wei LU +1 位作者 He Fu GUO Niag Hai HU 《Chinese Chemical Letters》 SCIE CAS CSCD 1991年第11期863-864,共2页
(CH_3C_5H_4)Zr(S_2CNBz_2)_3, Mr=987.55, space group P1, a=13.002(4), b=13.659(3), c=29.685(8); α=100.72(2)~o,β=97.23(2)~o, γ=105.36(2)~o; V=4909(2)~3, Z=4, Dc=1.34gcm^(-3), Mo-K(λ=0.71073A) radiation, μ=5.0cm^(-1... (CH_3C_5H_4)Zr(S_2CNBz_2)_3, Mr=987.55, space group P1, a=13.002(4), b=13.659(3), c=29.685(8); α=100.72(2)~o,β=97.23(2)~o, γ=105.36(2)~o; V=4909(2)~3, Z=4, Dc=1.34gcm^(-3), Mo-K(λ=0.71073A) radiation, μ=5.0cm^(-1), R=0.069, Rw=0.078 for 6100 reflections. The title complex has pentagonal bipyramid configuration in which the zirconium atom is coordinated by one CH_3C_5H_4 group and three bidentate dibenzyldithiocarbamate ligands. 展开更多
关键词 cH3c5H4 cRYsTAL structure OF sEVEN-cOORDINATE ZIRcONOcENE cOMPLEX s2cNBz2 Bz=cH2c6H5 ZR Bz
下载PDF
CRYSTAL STRUCTURE OF FIVE-COORDINATE ZIRCONOCENE COMPLEX CP_2ZrCl(S_2CNBz_2) (Bz=C_6H_5CH_2)
14
作者 Zhi Qiang WANG Shi Wei LU +1 位作者 He Fu GUO Ning Hai HU 《Chinese Chemical Letters》 SCIE CAS CSCD 1991年第11期865-866,共2页
Cp;ZrCl(S;CNBz;) is a five-coordinate bent zirconocene in which the dibenzyldithiocarbamate is a bidentate ligand (Zr-Cl 2.549(1)A; Zr-C 2.489-2.533; Zr-S 2.667(1), 2.734(1); Zr-Cl-S1 137.6(1);; Zr-Cl-S2 73.... Cp;ZrCl(S;CNBz;) is a five-coordinate bent zirconocene in which the dibenzyldithiocarbamate is a bidentate ligand (Zr-Cl 2.549(1)A; Zr-C 2.489-2.533; Zr-S 2.667(1), 2.734(1); Zr-Cl-S1 137.6(1);; Zr-Cl-S2 73.3(1);). 展开更多
关键词 Bz=c6H5cH2 Zr cP cRYsTAL structure OF FIVE-cOORDINATE ZIRcONOcENE cOMPLEX cP2Zrcl Bz s2cNBz2 cH
下载PDF
Crystal Structure of Phenol,2-[4(S)-4-Dihydro-4-benzyl-2-ozazolinyl]
15
作者 罗梅 周仕明 +3 位作者 张家海 庞文民 尹浩 胡克良 《Chinese Journal of Structural Chemistry》 SCIE CAS CSCD 2010年第6期947-949,共3页
The compound phenol,2-[4(S)-4,5-dihydro-4-phenyl-2-ozazolinyl(1,C15H13NO2) was synthesized with a simple,one step method free of water and air.It was obtained in a moderate yield from the reaction of 2-hydroxybenz... The compound phenol,2-[4(S)-4,5-dihydro-4-phenyl-2-ozazolinyl(1,C15H13NO2) was synthesized with a simple,one step method free of water and air.It was obtained in a moderate yield from the reaction of 2-hydroxybenzonitrile with optically active amino alcohol in chloroben-zene under dry,anaerobic conditions.It belongs to the orthorhombic system,space group P212121 with a = 5.786(5),b = 10.730(5),c = 19.722(5),C15H13NO2,Mr = 239.26,V = 1224.4(12)3,Z = 4 and Dc = 1.298 mg/m3.The final R = 0.0324 for 1627 observed reflections with Ⅰ 〉 2σ(Ⅰ) and Rw = 0.0826 for all data.The structure of compound 1 was determined by X-ray diffraction,NMR and HRMS. 展开更多
关键词 OXAZOLINE PHENOL 2-[4(s)-4 5-dihydro-4-phenyl-2-ozazolinyl c15H13NO2) crystal structure
下载PDF
Analyze Obama’s State of the Union 2015——From the Perspective of Halliday’s Systemic Functional Grammar
16
作者 加峰 《海外英语》 2019年第21期265-266,共2页
The present study uses textual function of metafunction in Halliday’s Systemic Functional Grammar as the theoretical framework,focusing on Thematic structures of political discourses.This thesis moves on to analyze t... The present study uses textual function of metafunction in Halliday’s Systemic Functional Grammar as the theoretical framework,focusing on Thematic structures of political discourses.This thesis moves on to analyze the State of the Union Address and its Chinese version from the perspective of a contrastive study,aiming to find out English-Chinese translation approaches.The study findings give rise to two implications for E-C translation in Obama’s Address For one thing,a thematic structure,without any change of word orders,can be directly translated into a SV pattern in a topic-comment structure.For another,it has to be restructured into non-SV patterns.It helps to apply the strategy in the target text of Obama’s State of the Union Address. 展开更多
关键词 Halliday’s systemic Functional GRAMMAR THEMATIc structure sTATE of the UNION ADDREss
下载PDF
基于C/S架构和物联网技术的可移动医疗设备共享调配系统的设计与应用 被引量:2
17
作者 王杰 薛博宇 +2 位作者 徐云华 张琛 顾伟 《中国医疗设备》 2024年第1期85-91,共7页
目的 设计一个可移动医疗设备高效管理与临床科室共享调配相结合的医疗设备共享管理平台,实现可移动医疗设备使用的全过程管理。方法 基于C/S架构,利用物联网技术优化整合现有医疗设备大数据资源,结合医院需求,构建可移动医疗设备共享... 目的 设计一个可移动医疗设备高效管理与临床科室共享调配相结合的医疗设备共享管理平台,实现可移动医疗设备使用的全过程管理。方法 基于C/S架构,利用物联网技术优化整合现有医疗设备大数据资源,结合医院需求,构建可移动医疗设备共享调配系统,实现医疗设备共享管理、预约借用、统计分析等核心功能。通过比较系统上线前后呼吸机调配次数、平均调配时间、呼吸机使用率、单台呼吸机日均收入4个指标,分析系统应用效果。结果 系统上线后,呼吸机调配次数明显增加、平均调配时间明显降低,呼吸机使用率、单台呼吸机日均收入明显升高,且差异均有统计学意义(P﹤0.05),表明系统对提高呼吸机调配效率与使用效率有促进作用。结论 可移动医疗设备共享调配系统优化了医院设备管理流程,实现了医疗资源的统一调配,有效满足临床紧急抢救时医疗设备调配使用的相关需求,提高了医疗设备周转率以及设备管理人员的工作效率,有助于医院节约人员成本、降低采购费用,为医院管理者制定相关决策提供数据支撑。 展开更多
关键词 可移动医疗设备 物联网 c/s架构 设备共享 管理系统
下载PDF
纳米C-S-H/PCE对蒸养UHPC力学性能增强机理研究
18
作者 伍勇华 易昂 +2 位作者 何娟 匡玉峰 原毅冰 《硅酸盐通报》 CAS 北大核心 2024年第8期2797-2805,共9页
目前超高性能混凝土(UHPC)制品的力学性能有待进一步提升,采用纳米C-S-H/PCE对UHPC进行增强在理论上是一种可行的技术途径。本文研究了蒸养条件下掺入以聚羧酸(PCE)为分散剂的纳米水化硅酸钙(C-S-H/PCE)对UHPC力学性能的影响,通过测试... 目前超高性能混凝土(UHPC)制品的力学性能有待进一步提升,采用纳米C-S-H/PCE对UHPC进行增强在理论上是一种可行的技术途径。本文研究了蒸养条件下掺入以聚羧酸(PCE)为分散剂的纳米水化硅酸钙(C-S-H/PCE)对UHPC力学性能的影响,通过测试水化热、水化产物、微观形貌和孔结构等对其机理进行了分析。结果表明,掺入3.0%(质量分数)纳米C-S-H/PCE可以显著提高蒸养UHPC的抗压强度和抗折强度。掺入纳米C-S-H/PCE可以促进UHPC的早期水化,生成更多的水化硅酸钙(C-S-H)凝胶,使水化放热温峰增高,并缩短达到水化温峰的时间。掺入纳米C-S-H/PCE可有效改善蒸养UHPC的孔结构,在掺量为3.0%(质量分数)时总孔隙率最小,有害孔比例最低。该研究可为纳米C-S-H/PCE在蒸养UHPC中的应用提供参考。 展开更多
关键词 纳米c-s-H/PcE 超高性能混凝土 孔结构 水化放热 蒸汽养护
下载PDF
基于剩余电流和不平衡电流突变向量比的TN-C-S系统漏电故障检测方法 被引量:4
19
作者 翟国亮 梁栋 +3 位作者 王玮 徐丙垠 高海洋 尚同同 《中国电机工程学报》 EI CSCD 北大核心 2024年第5期1726-1736,I0005,共12页
TN-C-S系统在我国应用广泛,但由于固有剩余电流大,无法区分负荷投切和故障引起的剩余电流变化,漏电总保和中保无法投运,存在安全隐患。针对该问题,提出一种基于剩余电流和不平衡电流突变量之比的漏电故障保护方法。首先,分析剩余电流回... TN-C-S系统在我国应用广泛,但由于固有剩余电流大,无法区分负荷投切和故障引起的剩余电流变化,漏电总保和中保无法投运,存在安全隐患。针对该问题,提出一种基于剩余电流和不平衡电流突变量之比的漏电故障保护方法。首先,分析剩余电流回路,剩余电流和不平衡电流突变量之比在单相接地故障发生时刻突变,在负荷投切时不变。其次,基于中性线阻抗和接地阻抗不会发生突变的特征,计算故障电流突变量幅值,以故障电流突变量幅值越限作为故障判别依据,实现漏电故障检测。仿真及试验证明,所提方法可有效区分负荷投切和漏电故障,实现大幅值固有剩余电流下的漏电故障检测,在单支路和多支路系统中的检测灵敏度分别为70、150 mA,满足TN-C-S系统多级漏电保护的灵敏度要求。 展开更多
关键词 TN-c-s系统 漏电保护 剩余电流 不平衡电流 突变向量
下载PDF
An Web Client System Design and Implementation for IOS Platform
20
作者 Haixia Peng Hai Zhao Chuan Lin 《Journal of Software Engineering and Applications》 2013年第1期38-42,共5页
For current physical examination and medical institutions, the majority of Medical projects need a long time to get the result, this wastes user too much time. In order to solve this problem, this paper presents a pro... For current physical examination and medical institutions, the majority of Medical projects need a long time to get the result, this wastes user too much time. In order to solve this problem, this paper presents a program to achieve viewing the results of examination anytime or anywhere with the help of cell phone applications software. The program proposed to solve the problem that user have to wait for the medical test results for a long time and cause the time waste, compared to the programs which using e-mail, SMS and mailing report card to inform the user the results, this one is to be more efficient, while also better meet user and medical institutions’ requirements. In addition, in order to test the practicality and feasibility of the program, with IOS devices as the material basis, this paper constructs a Web client system, based on the GPRS technology, we can realize the data communications between the Web server and a client which is the workbench IOS devices. Through testing, we can proof this Web client system has certain practical and development value, with the physical examination institutions become popular gradually, I believe that this design ideas of the system will be used extensively in the medical system, and also will bring a person more convenient. 展开更多
关键词 WEB cLIENT systems IOs MEDIcAL Institutions c/s Mode AsIHTTPRequest
下载PDF
上一页 1 2 119 下一页 到第
使用帮助 返回顶部