检索结果-南通市图书馆

Integrability of auto-B?cklund transformations and solutions of a torqued ABS equation

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2021年第7期73卷 42-46页

作者： Xueli Wei Peter h van der Kamp da-jun Zhang Department of Mathematics Shanghai UniversityShanghai 200444China Department of Mathematics and Statistics La Trobe UniversityVictoria 3086Australia

An auto-B?cklund transformation for the quad equation Q1_(1) is considered as a discrete equation,called h2^(a),which is a so called torqued version of *** equations h2^(a) and Q1_(1) compose a consistent cube,from which an auto-B?cklund transformation and a Lax pair for h2^(a) are *** generally it is shown that auto-B?cklund transformations admit auto-Backlund *** the auto-Backlund transformation for h2^(a)we derive a seed solution and a one-soliton *** this solution it is seen that h2^(a) is a semi-autonomous lattice equation,as the spacing parameter q depends on m but it disappears from the plane wave factor.

关键词： auto-Bocklund transformation consistency Lax pair soliton solution torqued ABS equation semi-autonomous

Superconducting fluctuation induced conductance corrections near a pair-breaking quantum phase transition in doubly connected ultrathin cylinders of Al

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2020年第3期63卷 89-97页

作者： Ke Zhang ZongLi Wang da Xu YaZhe Wang h.Wang Ying Liu Department of Physics Zhejiang UniversityHangzhou 310027China Key Laboratory of Artificial Structures and Quantum Control(MOE)and Shanghai Center for Complex Physics School of Physics and AstronomyShanghai Jiao Tong UniversityShanghai 200240China Materials Research Institute and Department of Physics Pennsylvania State UniversityUniversity ParkPA 16802USA Collaborative Innovation Center of Advanced Microstructures Nanjing 210093China

We report measurements on ultrathin,doubly connected superconducting cylinders of Al that exhibit a destructive regime,which refers to the loss of superconductivity in a doubly connected superconductor near applied half flux quanta due to the sample topology and the small size of the sample.A depairing quantum phase transition(QPT)between a superconducting and metallic state tuned by the magnetic flux enclosed in the quasi one-dimensional(1D)cylinder was found at the onset of the destructive *** on magnetic flux and temperature dependent sample resistance as well as current-voltage characteristics revealed the presence of both thermally activated and quantum phase slips near the depairing *** the superconducting side of the QPT,thermally activated phase slips as described by the Langer-Ambegaokar and McCumber-halperin(LAMh)theory were found to describe the sample resistance as the system was pushed towards the QPT by a magnetic field applied along the cylinder ***,deviation from this behavior was found at low temperatures,signaling the presence of the quantum phase *** importantly,we observed a highly unusual negative slope in the resistance versus temperature curves on the metallic side of the QPT as predicted by the diagrammatic calculation of the dc conductivities in a 1D system near a depairing *** work suggests that fluctuations from both the phase and the amplitude of the superconducting order parameter are important for the superconductor-to-metal depairing QPT.

关键词： mesoscopic superconductor quantum phase transition superconducting fluctuation

Coordinated Regulation of Tissue Type Plasminogen Activator and Plasminogen Activator Inhibitor Type-1 Gene Expression in hypophysectomized Rat Ovaries During GnRha-Induced Ovulation

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 1994年第7期37卷 820-830页

作者：刘以训刘奎彭晓蓉 T.ny State Key Laboratory of Reproductive Biology and Department of Endocrinology Institute of ZoologyAcademia Sinica Unit for Applied Cell and Molecular Biology Umea University

In this study we have demonstrated that both granulosa and theca-interstitial cells of hy-pophysectomized rat ovaries are capable of synthesizing tPA and *** of a GnRh agonist canmarkedly induce these gene expressions in the ovary in a cell-specific and time-coordinated manner,so that asurge of tPA mRNA and its activity in both granulosa and theca-interstitial cells was obtained just prior ***-interstitial cells make PAI-1 become the most active in the *** the amount PAI-1mRNA and its activity in the cells reach the maximum level 6 h before the tPA *** contrast,granulosacells produce only a little amount of PAI-1 (most increase tPA activity),and both PAI-1 mRNA and activityin the cells reach the maximum after *** coordinated regulation of tPA and PAI-1 in the ovarymay fine-tune the peak of tPA activity which may be important for the regulation of the ovulatory *** changes of tPA and PAI-1 in the ovarian cells of hypophysectomized rats during GnRha-induced ovula-tion are similar to that in intact rats during hCG-induced ovulation,suggesting that the ovulatory process canbe modulated by different regulatory signals mediated by influencing the coordinated expression of both tPAand PAI-1.

关键词： GnRh agonist hypophysectomized rat ovulation tPA PAI-1

Bi-capon beamforming for MIMO radar based on rank-reduced correlation matrix

在线全文

学校读者我要写书评

暂无评论

The Journal of China Universities of Posts and Telecommunications 2013年第1期20卷 85-90页

作者： hE Jie FENG da-zheng Nicolas h. Younan MA Lun School of Information Engineering Chang'an University National Laboratory of Radar Signal Processing Xidian University Department of Electrical and Computer Engineering Mississippi State University

A bi-capon beamforming （BCB） algorithm for multi-input multi-output （MIMO） radar is developed on the basis of correlation domain. By vectorizing the echo matrix and its transpose, the conventional capon cost function is transformed into bi-capon quadratic functions. By calculating two lower dimensional weight vectors with sub-matrices of the correlation matrix, BCB can significantly decrease the computational complexity and the requirement of training samples. In the presence of short data records, BCB can achieve better interference suppression performance than fully adaptive capon algorithm. Simulation results are presented to demonstrate the effectiveness of the proposed method.

关键词： MIMO radar capon beamforming correlation complexity performance

Preparation of MCM-41 in Industrial Scale and Its Application in heavy Oil Processing

在线全文

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2002年第2期18卷 169-174页

作者： Jianwen da Tiancun Xiao Jianming Su Xingzhong Xu Malcolm L.h.Green Research Institute of Qilu Petrochem.Corp. Zibo 255400China The Wolfson Catalysis Centre Inorganic Chemistry LaboratoryUniversity of OxfordSouth Parks RoadOxfordOX13QRUK

A series of MCM 41 molecular sieves have been prepared on an industrial scale, and the effect of preparation factors such as aging temperature, ph values on the structure and pore distribution of the MCM 41 product have been studied by using X ray diffraction(XRD), thermogravimetric(TG) and electron microscopy(TEM). It is shown that the ph values have a significant effect on the crystallinity of the synthesized product. Under proper conditions, the MCM 41 prepared on an industrial scale has the same performance as the samples prepared on an Lab scale. The prepared MCM 41 was used as a modifier of zeolite Y for fluid catalytic cracking(FCC) of residual oil. It is shown that the addition of the MCM 41 in the zeolite Y catalyst increases the pore size, and surface area of the catalysts, which helps to increase the yield of gasoline and diesel and decrease the production of gaseous product and carbon deposition in the catalyst. The better performance of the MCM 41 modified zeolite Y catalyst is believed to be due to its adjustment on the acidity and increase of the pore size.

关键词： MCM-41 Industrial scale synthesis FCC catalyst

A comprehensive study on the processing of Co:ZnO nanostructured ceramics:Defect chemistry engineering and grain growth kinetics

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2023年第7期138卷 221-232页

作者： R.T.da Silva J.M.Morbec G.Rahman h.B.de Carvalho Universidade Federal de Ouro Preto-UFOP Ouro PretoMG 35400-000Brazil School of Chemical and Physical Sciences Keele UniversityKeele ST55BGUnited Kingdom Department of Physics Quaid-i-Azam UniversityIslamabad 45320Pakistan Universidade Federal de Alfenas-UNIFAL Alfenas 37130-000Brazi

In this report,we present a systematic study on the preparation of Co:ZnO ceramics via a standard solid-state route from different Co precursors(Co_(3)O_(4),CoO,and metallic Co)and atmospheres(O_(2)and Ar).Particular emphasis is given to defect chemistry engineering and the sintering growth ***-principles calculations based on density functional theory are employed to determine the formation en-ergy of the main point defects in ZnO and Co:ZnO *** on the theoretical results,a set of chemical reactions is *** microstructural characterization is also performed to determine the degree of Co incorporation into the ZnO *** samples prepared in Ar atmosphere and metal-lic Co present the highest Co solubility limit(lower apparent Co incorporation activation energy)due to the incongruent ZnO *** of the parameters of the sintering growth kinetics reveals that Co_(3)O_(4)is the best sintering additive to achieve larger grain sizes,and possible higher densi-ties,in both sintering atmospheres,while metallic Co is the best to achieve the smallest grain size with higher Co concentration and homogeneous spatial distribution for a subsequent reduction of *** results show that the sintering in O_(2)effectively promotes zinc vacancies in the ZnO structure,while the sintering in Ar promotes zinc interstitial *** findings contribute to understanding the preparation of Co-doped ZnO ceramics and the sintering growth kinetics,which may improve the state of the art in processing the material at both bulk and nanometric scales.

关键词： Multifunctionality Zinc oxide Defect engineering Growth kinetics

Autoregressive neural networks with exogenous variables for indoor temperature prediction in buildings

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

Building Simulation 2021年第1期14卷 165-178页

作者： Benoit Delcroix Jérôme Le ny Michel Bernier Muhammad Azam Bingrui Qu Jean-Simon Venne Department of Mechanical Engineering Polytechnique Montréal2500 Chemin de PolytechniqueMontréalQCH3T 1J4Canada Department of Electrical Engineering and GERAD Polytechnique Montréal2500 Chemin de PolytechniqueMontréalQCH3T 1J4Canada Smart Building Lab BrainBox AIMontréalQCCanada

Thermal models of buildings are helpful to forecast their energy use and to enhance the control of their mechanical ***,these models are building-specific and require a tedious,error-prone and time-consuming development effort relying on skilled building energy *** to white-box and gray-box models,data-driven(black-box)models require less development time and a minimal amount of information about the building *** this paper,autoregressive neural network models are compared to gray-box and black-box linear models to simulate indoor *** models are trained,validated and compared to actual experimental data obtained for an existing commercial building in Montreal(QC,Canada)equipped with roof top units for air *** show that neural networks mimic more accurately the thermal behavior of the building when limited information is available,compared to gray-box and black-box linear *** gray-box model does not perform adequately due to its under-parameterized nature,while the linear models cannot capture non-linear phenomena such as radiative heat transfer and ***,the neural network models outperform the alternative models in the presented application,reaching a coefficient of determination R2 up to 0.824 and a root mean square error down to 1.11℃,including the error propagation over time for a 1-week period with a 5-minute *** considering a 50-hour time horizon,the best neural networks reach a much lower root mean square error of around 0.6℃,which is suitable for applications such as model predictive control.

关键词： thermal model building simulation experimental validation multi-layer perceptron linear vs.non-linear black-box vs.gray-box

Selective conversion of CO_(2)to CO using earth abundant tin modified copper gas diffusion electrodes

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

Materials Reports(Energy) 2023年第2期3卷 154-163,I0004页

作者： Preetam K.Sharma Shahid Rasul da Li Eileen h.Yu Department of Chemical Engineering Loughborough UniversityLoughboroughLE113TUUK Faculty of Engineering and Environment Northumbria UniversityEllison PlNewcastle Upon TyneNE18STUK State Key Laboratory of Urban Water Resource and Environment School of EnvironmentHarbin Institute of TechnologyHarbin150090China

Earth-abundant copper-tin(CuSn)electrocatalysts are potential candidates for cost-effective and sustainable production of CO from electrochemical carbon dioxide reduction(eCO_(2)R).however,the requirement of highoverpotential for obtaining reasonable current,low Faradaic efficiencies(FE)and low intrinsic catalytic activities require the optimisation of the CuSn nanoarchitecture for the further advancement in the *** the current work,we have optimised Sn loading on Cu gas diffusion electrodes(GDEs)by electrochemical spontaneous *** with various Sn loadings were tested in a three-chamber GDE reactor to evaluate their CO_(2)reduction *** best performance of 92%CO Faradaic efficiency at a cathodic current density of 120 mA cm^(-2)was obtained from the 20 min Sn deposited Cu_(2)O sample operated at-1.13 V *** electrocatalyst had~13%surface coverage of Sn on Cu GDE surface,and had Sn in oxide form and copper in metallic *** catalyst also showed stable performance and was operable for>3 h under chronoamperometric *** surface of the GDE reduces from Cu2O to Cu during eCO_(2)R and goes further reconstruction during the eCO_(2)*** study demonstrates the potential of Cu-Sn for selective CO production at high current densities.

关键词： Electrochemical CO_(2)reduction Cu-Sn binary Catalyst Optimising loading Selective CO production Surface reconstruction

Effect of Cu-ZnO-Al_2O_3 supported on h-ferrierite on hydrocarbons formation from CO hydrogenation

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

Chinese Journal of Catalysis 2016年第3期37卷 378-388页

作者： J.h.Flores M.E.h.Maia da Costa M.I.Pais da Silva 里约热内卢天主教大学生物化学系里约热内卢天主教大学物理系

Methanol synthesis catalysts based on Cu, Zn and Al were prepared by three methods and subsequently mixed with h-ferrierite zeolite in an aqueous suspension to disperse the catalysts over the support. These materials were characterized by X-ray diffraction, N2 adsorption, transmission electron microscopy, temperature programmed reduction, Nh3 and h2 temperature-programmed desorption, and X-ray photoelectron spectroscopy. They were also applied to the CO hydrogenation reaction to produce dimethyl ether and hydrocarbons. The catalysts were prepared by coprecipitation under low and high supersaturation conditions and by a homogeneous precipitation method. The preparation technique was found to affect the precursor structural characteristics, such as purity and crystallinity, as well as the particle size distribution of the resulting catalyst. Low supersaturation conditions favored high dispersion of the Cu species, increasing the methanol synthesis catalyst＇s metallic surface area and resulting in a homogeneous particle size distribution. These effects in turn were found to modify the zeolite properties, promoting both a low micropore volume and blockage of the zeolite acid sites. The effect of the methanol synthesis catalyst on the reaction was verified by the correlation between the Cu surface area and the CO conversion rate.

关键词： Methanol synthesis catalyst Low supersaturation precipitation high supersaturation precipitation Syngas hydrotalcite hydrocarbon Dimethyl ether