检索结果-南通市图书馆

Frontiers of structural and Civil Engineering 2024年第6期18卷 899-917页

作者： Huong-Giang Thi HOANG Hai-Van Thi mAI Hoang Long NGUyEN Hai-Bang ly University of Transport Technology Hanoi 100000Vietnam

Complex modulus(G^(*))is one of the important criteria for asphalt classification according to AAsHTO m320-10,and is often used to predict the linear viscoelastic behavior of asphalt *** addition,phase angle(φ)characterizes the deformation resilience of asphalt and is used to assess the ratio between the viscous and elastic *** is thus important to quickly and accurately estimate these two *** purpose of this investigation is to construct an extreme gradient boosting(XGB)model to predict G^(*)andφof graphene oxide(GO)modified asphaltat medium and high *** data sets are gathered from previously published experiments,consisting of 357 samples for G^(*)and 339 samples forφ,and the se are used to develop the XGB model using nine inputs representing theasphalt binder *** findings show that XGB is an excellent predictor of G^(*)andφof GO-modified asphalt,evaluated by the coefficient of determination R^(2)(R^(2)=0.990 and 0.9903 for G^(*)andφ,respectively)and root mean square error(RmsE=31.499 and 1.08 for G^(*)andφ,respectively).In addition,the model’s performance is compared with experimental results and five other machine learning(mL)models to highlight its *** the final step,the shapley additive explanations(sHAP)value analysis is conducted to assess the impact of each input and the correlation between pairs of important features on asphalt’s two physical properties.

关键词： complex modulus phase angle graphene oxide asphalt extreme gradient boosting machine learning

Do aeolian deposits and sand encroachment intensity shape patterns of vegetation diversity and plant functional traits in desert pavements?

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

Journal of Arid Land 2023年第6期15卷 667-694页

作者： m'hammed BOUALLALA souad NEFFAR lyès BRADAI Haroun CHENCHOUNI Laboratory of saharan Natural Resources Faculty of Sciences and TechnologyUniversity of Ahmed DraiaAdrar 01000Algeria Department of Nature and Life sciences Faculty of Exact Sciences and Nature and Life SciencesUniversity of TebessaTebessa 12002Algeria Laboratory Water and Environment University of TebessaTebessa 12002Algeria Laboratory of saharan Bioresources Preservation and Valorization Faculty of Nature and Life SciencesUniversity of Kasdi MerbahOuargla 30000Algeria Department of Forest management Higher National School of ForestsKhenchela 40000Algeria Laboratory of Natural Resources and management of sensitive Environments University of Oum-El-BouaghiOum-El-Bouaghi 04000Algeria

The effects of sand encroachment on composition,diversity,and functional patterns of vegetation in drylands are rarely studied,and yet addressing these aspects is important to deepen our understanding of the biodiversity *** study aimed to investigate the effect of sand encroachment on plant functional biodiversity of desert pavements(gravel deserts)in the sahara Desert of *** were sampled and analyzed in three desert pavements with different levels of sand encroachment(LsE)and quantity of aeolian deposits(low,LLsE;medium,mLsE;and high,HLsE).Within the sample-plot area(100 m^(2)),density of every plant species was identified and total vegetation cover was *** taxonomic and functional diversity were analyzed and compared between *** showed that 19 plant species in desert pavements were classified into 18 genera and 13 *** and Poaceae were the most important *** species Anabasis articulata(Forssk)*** LLsE desert pavements with 11 species,whereas Thymelaea microphylla Coss.&Durieu ex *** Calobota saharae(C&D)Boatwr.&van Wyk were dominant species of desert pavements with mLsE(14 species)and HLsE(10 species),*** highest values of species richness and biodiversity were recorded in desert pavements with mLsE,while low values of these ecological parameters were obtained in desert pavements with *** pavements with LLsE were characterized with the highest values of species *** communities were dominated by chamaephytes,anemochorous,arido-active,and competitive stress-tolerant *** increase in LsE along the gradient from LLsE to HLsE induced significant changes in plant community variables including decreases in plant density,plant rarity,lifeform composition,morphological type,and aridity *** pavements with HLsE favor the degradation of vegetation and trigger biodiversity erosion.

关键词： desert pavements hot and arid rangeland plant diversity land degradation sand encroachment plant functional trait sahara Desert

multiply Charged Anions,maximum Charge Acceptance,and Higher Electron Affinities of molecules,superatoms,and Clusters

在线全文

学校读者我要写书评

暂无评论

物理化学学报 2018年第6期34卷 675-682页

作者： VON sZENTPály László Institut fur Theoretische Chemie Universitat Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany.

The addition of electrons to form gas-phase multiply charged anions(mCAs)normally requires sophisticated experiments or *** this work,the factors stabilizing the mCAs,the maximum electron uptake of gas-phase molecules,X,and the electronic stability of mCAs X^(Q-),are *** drawbacks encountered when applying computational and/or conceptual density functional theory(DFT)to mCAs are *** develop and test a different model based on the valence-state *** in DFT,the electronic energy,E(N,v_(ex)),is a continuous function of the average electron number,N,and the external potential,v_(ex),of the *** valence-state-parabola is a second-order polynomial that allows extending E(N,v_(ex))to dianions and higher *** model expresses the maximum electron acceptance,Q_(max),and the higher electron affinities,A_Q,as simple functions of the firstelectron affinity,A_1,and the ionization energy,I,of the"ancestor"***,the maximum electron acceptance is Q_(max,calc)=1+12A_1/7(I-A_1).The ground-state parabola model of the conceptual DFT yields approximately half of this value,and it is termed Q_(max,Gs)=?+A_1/(I-A_1).A large variety of molecules are evaluated including fullerenes,metal clusters,super-pnictogens,super-halogens(OF_3),super-alkali species(OLi_3),and neutral or charged transition-metal complexes,AB_(m )L_n^(0/+/-).The calculated second electron affinity A_(2,calc)=A_1-(7/12)(I-A_1)is linearly correlated to the literature references A_(2,lit) with a correlation coefficient R=0.998.A_2 or A_3 values are predicted for further 24 *** appearance sizes,n_(ap)^(3-),of triply charged anionic clusters and fullerenes are calculated in agreement with the literature.

关键词： multiply charged negative ions Their appearance sizes second electron affinity Third electronaffinity Conceptual density-functional theory Valence-state parabola model of electronegativity

multi-exponential model to describe pressure-dependent P-and s-wave velocities and its use to estimate the crack aspect ratio

在线全文

学校读者我要写书评

暂无评论

Journal of Rock mechanics and Geotechnical Engineering 2022年第2期14卷 385-395页

作者： mihály Dobróka Norbert Péter szabó Tünde Edit Dobróka mátyás Krisztián Baracza Department of Geophysics University of MiskolcMiskolc-Egyetemváros3515Hungary mTA-mE Geoengineering Research Group University of MiskolcMiskolc-Egyetemváros3515Hungary Research Institute of Applied Earth sciences University of MiskolcMiskolc-Egyetemváros3515Hungary

We present new quantitative model describing the pressure dependence of acoustic P-and s-wave *** that a variety of individual mechanisms or defects(such as cracks,pore collapse and grain crushing)can contribute to the pressure-dependent change of the wave velocity,we order a characteristic pressure to all of them and allow a series of exponential terms in the description of the(Pand s-waves)velocity-pressure *** estimate the parameters of the multi-exponential rock physical model in inversion procedures using laboratory measured P-and s-wave velocity *** is known,the conventional damped least squares method gives acceptable results only when one or two individual mechanisms are *** the number of exponential terms leads to highly nonlinear ill-posed inverse *** to this reason,we develop the spectral inversion method(sIm)in which the velocity amplitudes(the spectral lines in the characteristic pressure spectrum)are only considered as *** characteristic pressures(belonging to the velocity amplitudes)are excluded from the set of inversion unknowns,instead,they are defined in a set of fixed positions equidistantly distributed in the actual interval of the independent variable(pressure).Through this novel linear inversion method,we estimate the parameters of the multi-exponential rock physical model using laboratory measured P-and s-wave velocity *** characteristic pressures are related to the closing pressures of cracks which are described by well-known rock mechanical relationships depending on the aspect ratio of elliptical *** gives the possibility to estimate the aspect ratios in terms of the characteristic pressures.

关键词： multi-exponential rock physical model spectral inversion method(sIm) Crack aspect ratio Characteristic pressures

A Positron study of Hysteresis Temperature in Ti-Ni Alloy

在线全文

学校读者我要写书评

暂无评论

Journal of materials science & Technology 1996年第6期12卷 470-472页

作者： Wang, JC Qin, Gy Zhang, GL Zheng, WH Chen, ly Gu, m ACAD sINICA SHANGHAI INST NUCL RESSHANGHAI 201800PEOPLES R CHINA TONGJI UNIV DEPT PHYSSHANGHAI 200092PEOPLES R CHINA

For Ti-Ni alloy, it is exceedingly difficult; to prepare an element that has a desired and defined hysteresis temperature for its preparing process is not perfect at present. Because the mechanism of transformation in Ti-Ni has not been fully clarified, it is far more exceedingly difficult to explain the hysteresis temperature only by using the traditional metal physics techniques. But position annihilation seems to be a suitable method for it. The positron annihilation measurements show that the hysteresis temperature may be controlled mainly by the relative fraction of the defects contained in a two-way shape memory element.

关键词： Titanium alloys

m-Quarterphenyl detected in the aerosols of Pearl River Delta and preliminary study on its environmental significance

在线全文

学校读者我要写书评

暂无评论

Chinese science Bulletin 1997年第13期42卷 1107-1110页

作者： Cheng, y Fu, Jm shen, Gy min, ys Le, sC Chan, ly Guangzhou Institute of Geochemistry Chinese Academy of Sciences Guangzhou 510640 China Guangdong state Kay Lab. Environ. P. Chinese Academy of Sciences Guangzhou 510640 China Department of Civil Engineer Hongkong University Hong Kong

m-QUARTERPHENyL, also nominated as 5′-phenyl-1, 1′: 3′1″-terphenyl, is one of the four-ringpolycyclic aromatic hydrocarbons （PAHs） with its four rings meta-linked together with C—Cbonds. Its molecular formula is Csub>18sub>Hsub>24sub> and its molecular weight 306. m-Quarterphenyl and other kinds of quarterphenyls as well as terphenyls have been de-tected in aerosols by Beemaert by use of GC-ms. Tong, and Karasek and Tong ana-

关键词： m-quarterphenyl aerosol environmental significance Pearl River Delta.

PREPARATION　AND　CHARACTERIZATION　OF　NIOBIUm－CONTAINING　DImOlyBDO－15－TUNGsTODIPHOs－PHORIC　sALT

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 1996年第2期7卷 199-200页

作者： Gong, J Qu, ly NE NORmAL UNIV DEPT CHEMCHANGCHUN 130024PEOPLES R CHINA

Preparation of P2W15m15mo2NbO627- was reported in the paper. It was characterized by elementry analysis, IR,UV, polarography, 183 W-NmR and XPD spectra. All results showed the structure of the heteropoly anion was the...

关键词：

ROLLING DEFORmATION LAW OF ALUmINIUm ALLOy CLAD sHEET

在线全文

学校读者我要写书评

暂无评论

中国有色金属学会会刊：英文版 1999年第2期9卷 77-81页

作者： Zhou, HZ Wang, ly Huang, GJ sW Aluminium Fabricat Plant Chongqing 401326 Peoples R China Chongqing Univ Dept Met & Mat Engn Chongqing 400044 Peoples R China

１ＩＮＴＲＯＤＵＣＴＩＯＮＡｌＳｉ／ＡｌＭｎｔｒｉｌａｙｅｒｂｒａｚｅｄｃｌａｄａｌｕｍｉｎｉｕｍｓｈｅｅｔｉｓｔｈｅｍａｉｎｍａｔｅｒｉａｌｆｏｒｍａｋｉｎｇｅｖａｐｏｒａｔｏｒａｎｄｃｏｏｌｅｒｉｎｔｈ... 详细信息

１ＩＮＴＲＯＤＵＣＴＩＯＮＡｌＳｉ／ＡｌＭｎｔｒｉｌａｙｅｒｂｒａｚｅｄｃｌａｄａｌｕｍｉｎｉｕｍｓｈｅｅｔｉｓｔｈｅｍａｉｎｍａｔｅｒｉａｌｆｏｒｍａｋｉｎｇｅｖａｐｏｒａｔｏｒａｎｄｃｏｏｌｅｒｉｎｔｈｅａｉｒｃｏｎｄｉｔｉｏｎｅｒｏｆ...

关键词： aluminium alloyclad sheetrolling deformationdeformation lawcan be divided into 3 stages: free (slip or nonrestraining) deformation stage partial restraining (partial clad) deformation stage full restraining (full clad) deformation stage.

Positron study of Origin of Thermoelastic martensitestabilization for a Cu-Zn-Al Alloy

在线全文

学校读者我要写书评

暂无评论

Journal of materials science & Technology 1996年第5期12卷 377-380页

作者： Wang, JC shao, ZC Zhang, GL Zheng, WH yu, FH Chen, ly Gu, m ACAD sINICA SHANGHAI INST NUCL RESSHANGHAI 201800PEOPLES R CHINA TONGJI UNIV DEPT PHYSSHANGHAI 200092PEOPLES R CHINA

A series of Cu-23Zn-10Al (at pet) alloy specimens subjected to different heat-treatment processes have been studied by means of Doppler broadening technique of positron annihilation combined with mechanical test. Results show that the mechanism of quenched-in vacancies, instead of the other suggested ones, plays a dominant role in thermoelastic martensite stabilization of Cu-based shape memory alloy. Knowing the character of the movement of quenched-in vacancies and eliminating them as rapidly as possible are the basis for further optimizing heat-treatment process to obtain desired shape memory performance.

关键词： shape memory effect

Effect of Austenite Ageing on martensitic Transformation

在线全文

学校读者我要写书评

暂无评论

Journal of materials science & Technology 1997年第6期13卷 508-514页

作者： Chen, QZ Wu, XF Wei, ly Ke, J Univ sci & Technol Beijing Dept Mat Phys Beijing 100083 Peoples R China

The effect of austenite ageing on martensite transformation in an iron and nickel alloy was studied. Attention was paid to the variation of dislocation configurations in austenite before martensite transformation, The clusters or precipitates produced during austenite ageing and the alteration of dislocation configurations affect together the consequent martensite transformation. Dispersed fine clusters and precipitates cripple nucleus role of special dislocation configurations and drop m-s. Coarse precipitates make m-g rise again. Densely piled up dislocations in nuclei lead to rise of m-s. All the changes in austenite are of benefit to small martensite plates.

关键词： Iron alloys