检索结果-南通市图书馆

Artificial molecular machines that can perform work

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2018年第10期61卷 1261-1273页

作者： Qiaochun Wang Dizhi Chen he tian Key Laboratory for Advanced Materials and Institute of Fine Chemicals School of Chemistry and Molecular Engineering East China University of Science and Technology

An artificial molecular machine consists of molecule or substituent components jointed together in a specific way so that their mutual displacements could be initiated using appropriate outside stimuli. Such an ability of performing mechanical motions by consuming external energy has endowed these tiny machines with vast fascinating potential applications in areas such as actuators, manipulating atoms/molecules, drug delivery, molecular electronic devices, etc. To date, although vast kinds of molecular machine archetypes have been synthesized in facile ways, they are inclined to be defined as switches but not true machines in most cases because no useful work has been done during a working cycle. More efforts need to be devoted on the utilization and amplification of the nanoscale mechanical motions among synthetic molecular machines to accomplish useful tasks. here we highlight some of the recent advances relating to molecular machines that can perform work on different length scales, ranging from microscopic levels to macroscopic ones.

关键词： molecular machines molecular motors rotaxanes catenanes switches

Climate Change and Ecological Projects Jointly Promote Vegetation Restoration in Three-River Source Region of China

在线全文

学校读者我要写书评

暂无评论

Chinese Geographical Science 2021年第6期31卷 1108-1122页

作者： he Xiaohui YU Yipin CUI Zepeng he tian School of Geoscience and Technology Zhengzhou UniversityZhengzhou450001China College of Chemistry Zhengzhou UniversityZhengzhou450001China School of Water Conservancy Engineering Zhengzhou UniversityZhengzhou450001China

As the source of the Yellow River,Yangtze River,and Lancang River,the Three-River Source Region(TRSR)in China is very important to China’s ecological *** recent decades,TRSR’s ecosystem has degraded because of climate change and human ***,a range of ecological projects were initiated by Chinese government around 2000 to curb further *** research shows that the vegetation of the TRSR has been initially restored over the past two decades,but the respective contribution of ecological projects and climate change in vegetation restoration has not been ***,we used the Moderate Resolution Imaging Spectroradiometer(MODIS)Enhanced Vegetation Index(EVI)to assess the spatial-temporal variations in vegetation and explore the impact of climate and human actions on vegetation in TRSR during 2001–*** results showed that about 26.02%of the TRSR had a significant increase in EVI over the 18 yr,with an increasing rate of 0.010/10 yr(Phe *** trend analysis indicated vegetation restoration was jointly promoted by climate and human actions,and the promotion of human actions was greater compared with that of climate,with relative contributions of 59.07%and40.93%,***,the degradation of vegetation was mainly caused by human actions,with a relative contribution of71.19%.Partial correlation analysis showed that vegetation was greatly affected by temperature(r=0.62,Phe relatively sufficient moisture but lower temperature in ***,the establishment of nature reserves and the implementation of the Ecological Protection and Restoration Program(EPRP)improved vegetation,and the first stage EPRP had a better effect on vegetation restoration than the second *** findings identify the driving factors of vegetation change and lay the foundation for subsequent effective management.

关键词： Three-River Source Region of China climate change Enhanced Vegetation Index(EVI) vegetation change human actions

An efficient method of addressing ectopic beats:new insight into data preprocessing of heart rate variability analysis

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2011年第12期12卷 976-982页

作者： Feng WEN Fang-tian he College of Life Science Zhejiang University Hangzhou 310027 China ECG Department Sir Run Run Shaw Hospital School of Medicine Zhejiang University Hangzhou 310016 China

heart rate variability(HRV) analysis is affected by ectopic *** efficient method was proposed to deal with the ectopic *** method was based on trend correlation of the heart timing *** of R-R interval(RRI) value at ectopic beat time was constructed by the weight calculation and the slope estimation of preceding normal *** type of ectopic beat was detected and replaced by the predictor of *** performance of the simulated signal after ectopic correction was tested by the standard value using power spectrum density(PSD) estimation,whereas the results of clinical data with ectopic beats were compared with the adjacent ectopic-free *** result showed the frequency indexes after ectopy corrected had less error than other methods with the test of simulated signal and clinical *** indicated our method could improve the PSD estimation in HRV *** method had advantages of high accuracy and real time properties to recover the sinus node modulation.

关键词： Frequency domain Ectopic beat heart rate variability(HRV) Power spectrum density

Preparation and Properties of Doped Lanthanum Gallate Film on a Ni/SDC Porous Anode Support

在线全文

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2006年第5期22卷 643-646页

作者： he Qiang he tian-min PEI Li JI Yuan College of Physics Jilin University Changchun 130023 P. R. China

A 65. 8-μm dense doped lanthanum gallate La0.8Sr0.2 Ga0.85 Mg0.15 O2.825（LSGM）film was prepared on a porous Ni/SDC（samarium doped ceria, Ce0.8Sm0.2O1.9 ） anode support by colloid susponsion deposition with incomplete crystallization LSGM powder as a starting material. The phase composition and micromorphology of the LSGM film were characterized by X-ray diffraction and scanning electron microscopy. The electrical properties of the LSGM film and the performances of the LSGM film solid oxide fuel cell were also analyzed. The results show that beth the dense LSGM film on the porous anode support, and the required phase composition of the LSGM film were obtained simultaneously by sintering at 1400 ℃ for 6 h. The adhesion between the LSGM film and the porous anode support is very strong. The electrical conductivities of the LSGM film on the porous anode support are 0. 113 and 0. 173 S/cm at 800 and 850℃, respectively. The maximum output power density of the LSGM film cell is 177 mW/cm^2 at 700℃.

关键词： Doped lanthanum gallate Film Electrical property Solid oxide fuel cell Anode support

Most recent advances on enzyme-activatable optical probes for bioimaging

在线全文

学校读者我要写书评

暂无评论

Aggregate

Aggregate 2021年第2期2卷 28-61页

作者： Ju Mei he tian Key Laboratory for Advanced Materials Feringa Nobel Prize Scientist Joint Research CenterInstitute of Fine ChemicalsJoint International Research Laboratory for Precision Chemistry and Molecular EngineeringSchool of Chemistry and Molecular EngineeringEast China University of Science&TechnologyShanghaiChina

Enzymes are essential biological elements that play vital roles in many key cellular events and physiological *** dysregulation of enzyme activity broadly occurs in a large number of diseases ranging from inflammation to neurodegenerative disorders to *** imaging allows accurate and noninvasive visualization of biological analytes/physiological processes of interest closely linked to human health at different *** various imaging modalities,optical imaging stands out benefited from its high sensitivity,excellent spatiotemporal resolution,real-time mode,and facile *** optical probes specifically activatable by disease-relevant enzymes have sprung *** comparison to the“always-on”counterparts,the“off-on”imaging probes activated by enzymes hold great promise for precise diagnosis of diseases at early stage with high target-to-background ratio,dramatically improved specificity,and significantly enhanced ***,the most recent advances in optical probes activatable by enzymes for biosensing and bioimaging are briefly reviewed emphasizing their molecular design,working mechanism,and biomedical ***,some important prospects and the current challenges to fully implement the potential of enzyme-activatable probes for precise and efficient theranostics in life science are also pointed out to hopefully arouse new insights into the development of new generation of theranostics.

关键词： aggregation-induced emission bioimaging chemiluminescence enzyme-activatable near-infrared fluorescence photoacoustic theranostics

Airborne sparse flight array SAR 3D imaging based on compressed sensing in frequency domain

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 Systems Engineering and Electronics 2023年第1期34卷 56-67页

作者： tian he DONG Chunzhu YIN Hongcheng YUAN Li Science and Technology on Electromagnetic Scattering Laboratory Bejing Insititute of Environment FeaturesBeijing 100854China

In airborne array synthetic aperture radar(SAR), the three-dimensional(3D) imaging performance and cross-track resolution depends on the length of the equivalent array. In this paper, Barker sequence criterion is used for sparse flight sampling of airborne array SAR, in order to obtain high cross-track resolution in as few times of flights as possible. Under each flight, the imaging algorithm of back projection(BP) and the data extraction method based on modified uniformly redundant arrays(MURAs) are utilized to obtain complex 3D image pairs. To solve the side-lobe noise in images, the interferometry between each image pair is implemented, and compressed sensing(CS) reconstruction is adopted in the frequency domain. Furthermore, to restore the geometrical relationship between each flight, the phase information corresponding to negative MURA is compensated on each single-pass image reconstructed by CS. Finally,by coherent accumulation of each complex image, the high resolution in cross-track direction is obtained. Simulations and experiments in X-band verify the availability.

关键词： three-dimensional(3D)imaging synthetic aperture radar(SAR) sparse flight interferometry compressed sensing(CS)

Use of the epitaxial MTBs as a 1D gate(Lg=0.4 nm)for the construction of scaling down two-dimensional field-effect transistors

在线全文

学校读者我要写书评

暂无评论

Journal of Semiconductors 2024年第10期45卷 1-2页

作者： Youla Yang Daixuan Wu he tian tian-Ling Ren School of Integrated Circuit Tsinghua UniversityBeijing 100083China School of Instrument Science and Technology Xi'an Jiaotong UniversityXi'an 710049China

In recent years,there has been a significant increase in research focused on the growth of large-area single *** et al.[1]recently achieved the growth of large-area monolayers of transition-metal chalcogenides through assisted *** quality of molecular beam epitaxy(MBE)-grown two-dimensional(2D)materials can be greatly enhanced by using sacrificial species deposited simultaneously from an electron beam evaporator during the growth *** technique notably boosts the nucleation rate of the target epitaxial layer,resulting in large,homogeneous monolayers with improved quasiparticle lifetimes and fostering the development of epitaxial van der Waals ***,micrometer-sized silver films have been formed at the air-water interface by directly depositing electrospray-generated silver ions onto an aqueous dispersion of reduced graphene oxide under ambient conditions[2].

关键词： silver epitaxial dimensional

Simulation of MoS_(2)stacked nanosheet field effect transistor

在线全文

学校读者我要写书评

暂无评论

Journal of Semiconductors 2022年第8期43卷 41-45页

作者： Yang Shen he tian tianling Ren School of Integrated Circuits and Beijing National Research Center for Information Science and Technology(BNRist) Tsinghua UniversityBeijing 100084China

Transition metal dichalcogenides are nowadays appealing to researchers for their excellent electronic *** stacked nanosheet FET(NSFET)based on MoS_(2)are proposed and studied by Poisson equation solver coupled with semiclassical quantum correction model implemented in Sentaurus *** is found that,the 2D stacked NSFET can largely suppress short channel effects with improved subthreshold swing and drain induced barrier lowering,due to the excellent electrostatics of 2D MoS_(2).In addition,small-signal capacitance is extracted and *** MoS_(2)based NSFET shows great potential to enable next generation electronics.

关键词： MoS_(2) stacked nanosheet GAA TCAD simulation

A Comparative Study on Emulsion Polymerization Processes of Styrene Initiated by Water-soluble and Oil-soluble Initiators

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2019年第2期37卷 142-148页

作者： Xiao-Jing Liu Yu-he tian Yang-Cheng Lu State Key Laboratory of Chemical Engineering Department of Chemical Engineering Tsinghua University

The solubility of initiator determines its distribution and the roles played in emulsion polymerization as well as the final products, but this is still lack of systematic investigation. The present work focuses on this issue by comparing the kinetic behaviors and product properties of styrene emulsion polymerization initiated by 2,2-azoisobutyronitrile(AIBN) and potassium persulphate(KPS).Compared to KPS-initiated emulsion polymerization, the AIBN-initiated polymerization was found to be insensitive to the type of emulsifier, and have high polymerization rate as well as narrow molecular weight distribution and particle size distribution. This result indicates the effective free radicals are generated in micelles or colloids, which could decrease the proportion of homogeneous nucleation and make the process and product more controllable. As a consequence, there is a linear relationship between molecular weight of product and AIBN concentration in lg-lg coordinate. It provided a reference for the preparation of latexes with specified molecular weight and supported the possibility of the coexistence of multiple free radicals in one micelle or colloid when using oil-soluble initiator.

关键词： Emulsion polymerization Oil-soluble initiator Water-soluble initiator Styrene Reaction mechanism