检索结果-南通市图书馆

tensile deformation of fine-grained mg at 4K,78K and 298K

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of magnesium and Alloys 2024年第6期12卷 2534-2556页

作者： m.Walag A.Kula p.Noga t.tokarski G.Cios m.Niewczas AGH University of Krakow Faculty of Non-Ferrous MetalsKrakowPoland AGH University of Krakow Academic Centre for Materials and NanotechnologyKrakowPoland materials Science and Engineering McMaster UniversityHamiltonCanada

the impact of grain size,ranging from 0.9μm to 9μm,on the mechanical properties of commercially pure mg is investigated at temperatures of 4K,78K,and *** mechanisms governing plastic flow are influenced by both grain size and *** 4K and 78K,dominant deformation modes in mg involve dislocation glide and extension twinning,regardless of grain *** interactions between basal and non-basal dislocations and dislocations with grain boundaries promote an unusually high rate of work hardening in the plastic regime,leading to premature *** yield stress follows the Hall-petch relationshipσ_(y)∼k/√d,with the slope k increasing with decreasing *** 298K,in addition to dislocation glide and twinning,grain boundary sliding(GBS)becomes significant in samples with grain sizes below 3μm,considerably enhancing the material’s *** activation provides an additional recovery mechanism for dislocations accumulating at grain boundaries,facilitating their absorption during sliding and *** ofσrelationship suggests that the basal slip is the dominant dislocation mode in mg at *** grain size suppresses dislocation activity and twinning and increases GBS,resulting in lowerandσ*** conventional deformation modes coupled with enhanced GBS yields stress softening,breaking down the Hall-petch relationship in mg below 3μm grain size,leading to an inverse Hall-petch *** work reports new data on the strength,ductility,work hardening and fracture behaviour,and their variations with mg grain size across different temperature regimes.

关键词： polycrystalline mg mechanical properties Deformation mechanisms Work-hardening texture evolution Cryogenic temperatures Hall-petch relationship

在线全文

学校读者我要写书评

暂无评论

根瘤菌-豆科植物共生固氮的分子生物学

核农学报 1986年第4期2卷 1-8页

作者： R.C.Van den Bos t.m.p.schetgens 尤崇杓张大达宋未荷兰瓦格宁根农业大学分子生物学系中国农业科学院原子能利用研究所

本综述着重讨论根瘤菌及其豆科植物宿主在共生固氮作用中的几个重要问题。根瘤菌和豆科植物在根瘤发育过程中的相互作用。根瘤菌在根瘤的植物细胞中分化成类菌体,使空气中的 N_2还原成 NH_4^+用作宿主植物的营养来源。文中还介绍了几种... 详细信息

本综述着重讨论根瘤菌及其豆科植物宿主在共生固氮作用中的几个重要问题。根瘤菌和豆科植物在根瘤发育过程中的相互作用。根瘤菌在根瘤的植物细胞中分化成类菌体,使空气中的 N_2还原成 NH_4^+用作宿主植物的营养来源。文中还介绍了几种适用于根瘤菌基因操作以进行共生固氮研究的分子遗传学技术。

关键词：根瘤菌属植物细胞启动区类菌体豆科植物共生固氮生物固氮分子生物学

multi-scale habitat influences sprainting and group size of a freshwater-obligate smooth-coated otter(Lutrogale perspicillata) in tungabhadra Otter Conservation Reserve, India

在线全文

学校读者我要写书评

暂无评论

Ecological processes 2024年第1期13卷 159-175页

作者： Ankit moun p.Ramesh Kumar m.malathi priya t.Ramesh Riddhika Kalle Sálim Ali Centre for Ornithology and Natural History Deputy Conservator of Forests Bellary Territorial Forest Division Deputy Conservator of Forests Working Plan and Survey and Research WingBellary Territorial Forest Division Centre for Functional Biodiversity University of Kwa Zulu-Natal

Background the impact of changing land-use patterns and associated anthropogenic threats on scale-dependent habitat use of semi-aquatic mustelids in scent-marking and social behaviour can provide important insights into the habitat ecology of smooth-coated otters(Lutrogale perspicillata).methods We sampled 180 stream segments(100–400 m) as spatial replicates of 60 1-km2 sites to record indirect evidence(i.e. spraints and mass latrine sites) and group sizes of smooth-coated otters along the tungabhadra Otter Conservation Reserve(tOCR) during the dry season. to quantify habitat, we recorded stream characteristics, riparian vegetation, and anthropogenic disturbances at the local scale, and hydro-environmental characteristics and land uses at the landscape scale. Using markovian-chain detection and occupancy models, we assessed the multi-scale habitat use of otters in their selection of suitable areas for scent-marking based on repeated presence-absence data on spraint/latrine locations along the tOCR. We further used linear regression techniques to explore relationships between the number of individuals in smooth-coated otter group and hydro-environmental characteristics, spraint/latrine encounter rate, anthropogenic pressure, land cover, topography, and *** At the local scale, the probability of spraint deposition and group size decreased with anthropogenic disturbance while the probability of spraint detections decreased with grass cover. At the landscape scale, the probability of otter site use for spraint deposition and group sizes increased in southeast flowing streams. Spraint deposition increased with the proportion of sugarcane fields, whereas in contrast, group size decreased with proportion of sugarcane *** Our findings highlight the first empirical evidence on multi-scale habitat use of a southern Indian population of smooth-coated otters in an inland freshwater ecosystem surrounded by the scrub jungle–agriculture matrix. We sug

关键词： presence-absence modelling Inland river Freshwater ecosystem Semi-aquatic mammal Smooth-coated otter

Radiative decays D*(s)→ D(s)γ in covariant confined quark model

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese physics C 2024年第2期48卷 45-56页

作者： C.t.tran m.A.Ivanov p.Santorelli Q.C.Vo Department of physics HCMC University of Technology and EducationVo Van Ngan 1700000 Ho Chi Minh CityVietnam Bogoliubov Laboratory of theoretical physics Joint Institute for Nuclear Research141980 DubnaRussia Dipartimento di Fisica"E.pancini" Universitàdi Napoli Federico ⅡComplesso Universitario di Monte S.AngeloVia CintiaEdificio 680126 NapoliItaly Istituto Nazionale di Fisica Nucleare Sezione di Napoli80126 NapoliItaly University of Science 700000 Ho Chi Minh CityVietnam

Radiative decays D((s))*→D((s))γare revisited in light of new experimental data from the BaBar and BESⅢ*** radiative couplings gD*Dγencoding nonperturbative QCD effects are calculated in the framework of the covariant confined quark model developed by *** compare our results with other theoretical studies and experimental *** couplings(in GeV-1)|g(D*+D+γ)|=0.45(9)and|g(D*0D0γ)|=1.72(34)calculated in our model agree with the corresponding experimental data|g(D*+D+γ)|=0.47(7)and|g(D*0D0γ)|=1.77(16).the most interesting case is the decay Ds*→Dsγ,for which a recent prediction based on light-cone sum rules at next-to-leading order|gDs*Dsγ|=0.60(19)deviates from the first(and only to date)lattice QCD result|gDs*Dsγ|=0.11(2)at nearly3σ.Our calculation yields|gDs*Dsγ|=0.29(6),which falls somehow between the two mentioned results,although it is larger than those predicted in other studies using quark models or QCD sum rules.

关键词： covariant quark model radiative decay charmed meson

A novel approach to study generalized coupled cubic Schrödinger-Korteweg-de Vries equations

在线全文

学校读者我要写书评

暂无评论

Journal of Ocean Engineering and Science 2024年第1期9卷 13-24页

作者： Lanre Akinyemi p.Veeresha m.t.Darvishi Hadi Rezazadeh mehmet Senol Udoh Akpan Department of mathematics Lafayette CollegeEastonPAUSA Department of mathematics Christ Deemed to be UniversityBengaluru 560029India Department of mathematics Razi UniversityKermanshah 67149Iran Faculty of Engineering technology Amol University of Special Modern TechnologiesAmolIran Department of mathematics Nev¸s ehir HacıBekta¸s Veli UniversityNev¸s ehirTurkey Drexel University Department of MathematicsPhiladelphiaPAUSA

the Kortewegde Vries(KdV)equation represents the propagation of long waves in dispersive media,whereas the cubic nonlinear Schrödinger(CNLS)equation depicts the dynamics of narrow-bandwidth wave packets consisting of short dispersive waves.A model that couples these two equations seems in-triguing for simulating the interaction of long and short waves,which is important in many domains of applied sciences and engineering,and such a system has been investigated in recent *** work uses a modified Sardar sub-equation procedure to secure the soliton-type solutions of the generalized cubic nonlinear Schrödinger-Korteweg-de Vries system of *** various selections of arbitrary parameters in these solutions,the dynamic properties of some acquired solutions are represented graph-ically and *** particular,the dynamics of the bright solitons,dark solitons,mixed bright-dark solitons,W-shaped solitons,m-shaped solitons,periodic waves,and other soliton-type *** re-sults demonstrated that the proposed technique is highly efficient and effective for the aforementioned problems,as well as other nonlinear problems that may arise in the fields of mathematical physics and engineering.

关键词： CNLS equation modiﬁed Sardar sub-equation method KdV equation Solitons Long and short waves

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

美国页岩油气地质特征及勘探开发进展

石油勘探与开发 2024年第4期51卷 807-828页

作者： mCmAHON t p LARSON t E ZHANG t SHUStER m 美国德克萨斯大学奥斯汀分校杰克逊地质科学学院经济地质局奥斯汀78758-4445德克萨斯州美国

基于美国页岩油气勘探开发历程的回顾,对主要页岩盆地的地质演化、主要页岩层系的油气地质特征及勘探开发进展进行系统梳理和总结。美国重要页岩盆地的富烃页岩主要发育于6个地质时期:中奥陶世、中—晚泥盆世、早石炭世(中—晚密西西比... 详细信息

基于美国页岩油气勘探开发历程的回顾,对主要页岩盆地的地质演化、主要页岩层系的油气地质特征及勘探开发进展进行系统梳理和总结。美国重要页岩盆地的富烃页岩主要发育于6个地质时期:中奥陶世、中—晚泥盆世、早石炭世(中—晚密西西比世)、早二叠世、晚侏罗世和晚白垩世(塞诺曼期—土伦期),构造沉积环境主要包括克拉通内盆地、前陆盆地和被动大陆边缘盆地。古生界富烃页岩主要分布于以下6个盆地:阿巴拉契亚盆地(尤蒂卡页岩和马塞勒斯页岩)、阿纳达科盆地(伍德福德页岩)、威利斯顿盆地(巴肯页岩)、阿卡马盆地(费耶特维尔页岩)、沃思堡盆地(巴内特页岩)和二叠盆地(狼营组和斯帕瑞组/骨泉组页岩)。中生界富烃页岩主要发育在西墨西哥湾盆地(海恩斯维尔组和鹰滩组)和落基山盆地群(以丹佛和粉河盆地的尼尔布拉勒组页岩为主)。通过对各页岩区带的详细分析发现,页岩的岩相和矿物成分存在差异,“页岩储层”并非只是页岩,很多情况下页岩油气还产自粉砂岩和碳酸盐岩等多种岩石类型。美国的页岩油气资源丰富,页岩油地质资源量超过0.246×1012 t,页岩气地质资源量超过290×1012 m3。在开启“页岩革命”的水平井水力压裂技术出现之前,美国经过了长达20年的勘探开发实践和理论技术积累。自2007年至2023年,美国页岩油气产量从约11.2×104t/d油当量增加到超过300.0×104t/d油当量,2017年页岩油气产量超过了常规油气,2023年在油气总产量中的占比增加到60%以上。页岩油气的开发主要得益于钻完井技术的改进,“立体开发”的攻关,以及重复压裂、提高原油采收率和“U”形井等技术的应用。基于美国丰富的页岩资源基础和技术的不断进步,页岩油气的产量将继续为全美的油气生产做出更大贡献。

关键词：美国页岩油页岩气页岩储层非常规储层油气产量资源评价

同方期刊数据库

QCD sum rule study of J^(p)=1^(±)exotic states with two heavy quarks in the molecular picture

在线全文

学校读者我要写书评

暂无评论

Chinese physics C 2024年第6期48卷 31-37页

作者： t.m.Aliev S.Bilmis m.Savcı Department of physics Middle East Technical UniversityAnkara06800Turkey tUBItAK ULAKBIm Ankara06510Turkey

In this study,the spectroscopic parameters of exotic molecular states composed of mesons containing two heavy quarks(scalar-axial and pseudoscalar-axial meson combinations)are investigated within the QCD sum *** findings reveal that molecular states containing charm quarks do not form bound states,whereas states with b-quarks can form exotic molecular *** observation has significant implications for understanding the structure of these exotic states.

关键词： QCD sum rules exotic mesons molecular states

Analysis of strong decays of SU(3)partners ofΩ(2012)baryon

在线全文

学校读者我要写书评

暂无评论

Chinese physics C 2024年第8期48卷 34-41页

作者： t.m.Aliev S.Bilmis m.Savci Department of physics Middle East Technical UniversityAnkara 06800Turkey tUBItAK ULAKBIm Ankara 06510Turkey

We estimate the coupling constants and decay widths of the SU(3)partners of theΩ(2012)hyperon,as discovered by the BELLE Collaboration,using the distribution amplitudes of the octet baryons within the light cone sum rules *** study includes a comparison of the obtained results for the relevant decay widths with those derived within the framework of the flavor SU(3)*** observe a good agreement between the predictions of both ***,our result on the decay width ofΩ→ΞK is compatible with the existing experimental result within the uncertainties of the model *** results can provide helpful insights for determining the nature of the SU(3)partners of theΩ(2012)baryon.

关键词： coupling constants light cone sum rule hyperon

Distribution, health and ecological risk assessments of trace elements in Nigerian oil sands

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

Acta Geochimica 2024年第1期43卷 59-71页

作者： Odunayo t.Ore Festus m.Adebiyi Department of Chemistry Obafemi Awolowo UniversityIle-Ife 220005Nigeria Department of Chemical Sciences Achievers UniversityOwoNigeria

the Nigerian oil sands represent the largest oil sand deposit in Africa, yet there is little published information on the distribution and potential health and ecological risks of trace elements in the oil resource. In the present study, we investigated the distribution pattern of 18trace elements(including biophile and chalcophile elements) as well as the estimated risks associated with exposure to these elements. the results of the study indicated that Fe was the most abundant element, with a mean concentration of 22,131 mg/kg while Br had the lowest mean concentration of 48 mg/kg. the high occurrence of Fe and ti suggested a possible occurrence of ilmenite(Fe tiO_(3)) in the oil sands. Source apportionment using positive matrix factorization showed that the possible sources of detected elements in the oil sands were geogenic, metal production, and crustal. the contamination factor, geo-accumulation index, modified degree of contamination, pollution load index, and Nemerow pollution index indicated that the oil sands are heavily polluted by the elements. Health risk assessment showed that children were relatively more susceptible to the potentially toxic elements in the oil sands principally via ingestion exposure route(HQ > 1E-04). Cancer risks from inhalation are unlikely due to CR t ingestion and dermal contact pose severe risks(CR > 1E-04). the high concentrations of the elements pose serious threats due to the potential for atmospheric transport, bioaccessibility, and bioavailability.

关键词： Biophile Chalcophile Oil sand Risk assessment trace element