检索结果-南通市图书馆

Asymmetric Drying and Wetting Trends in Eastern and Western China

在线全文

学校读者我要写书评

暂无评论

Advances in Atmospheric Sciences 2024年第2期41卷 221-232页

作者： Wen WU fei ji Shujuan HU Yongli HE College of Atmospheric Sciences Lanzhou UniversityLanzhou 730000China Collaborative Innovation Center for Western Ecological Safety Lanzhou UniversityLanzhou 730000China

As an important factor that directly affects agricultural production, the social economy, and policy implementation,observed changes in dry/wet conditions have become a matter of widespread concern. However, previous research has mainly focused on the long-term linear changes of dry/wet conditions, while the detection and evolution of the non-linear trends related to dry/wet changes have received less attention. The non-linear trends of the annual aridity index, obtained by the Ensemble Empirical Mode Decomposition(EEMD) method, reveal that changes in dry/wet conditions in China are asymmetric and can be characterized by contrasting features in both time and space in China. Spatially, most areas in western China have experienced transitions from drying to wetting, while opposite changes have occurred in most areas of eastern China. Temporally, the transitions occurred earlier in western China compared to eastern China. Research into the asymmetric spatial characteristics of dry/wet conditions compensates for the inadequacies of previous studies, which focused solely on temporal evolution;at the same time, it remedies the inadequacies of traditional research on linear trends over centennial timescales. Analyzing the non-linear trend also provides for a more comprehensive understanding of the drying/wetting changes in China.

关键词： aridity index EEMD dry/wet conditions asymmetric evolution

Long-term trend of oceanic surface carbon in the Northwest Pacific from 1958 to 2017

在线全文

学校读者我要写书评

暂无评论

Acta Oceanologica Sinica 2022年第5期41卷 90-98页

作者： Xuanliang ji fei Chai Peng Xiu Guimei Liu Key Laboratory of Research on Marine Hazards Forecasting National Marine Environmental Forecasting CenterMinistry of Natural ResourcesBeijing100081China State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of OceanographyMinistry of Natural ResourcesHangzhou310012China School of Marine Sciences University of MaineOronoME04469USA State Key Laboratory of Tropical Oceanography South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou510301China

Contrasting decrease and increase trends of sea surface temperature(SST)have been documented in the western Subarctic(WSA)and the rest of the Northwest Pacific(NWP)from 1958 to 2017,***,more(less)total carbon dioxide(TCO_(2))due to ocean cooling(warming)is transported to the surface,which leads to increase(decrease)of oceanic surface partial pressure of carbon dioxide(pCO_(2)).With the combined influence of the rising atmospheric carbon dioxide(CO_(2))level and changing ocean conditions,a prominent increase in oceanic surface pCO_(2) occurred with different rates of increase in summer and winter in the *** oceanic surface pCO_(2) is mainly controlled by the variation of TCO_(2) at the interdecadal timescale and by SST at the seasonal *** results also indicate that increasing SST tends to strengthen the capability of ocean in absorbing anthropogenic CO_(2) in the NWP,while ocean’s uptaking ability is weakened in the cooling area of the WSA.

关键词： sea surface temperature oceanic surface pCO_(2) ocean cooling(warming) control factor

Analytical study on the dynamic displacement response of a curved track subjected to moving loads

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2013年第12期14卷 867-879页

作者： Ke-fei LI Wei-ning LIU Valeri MARKINE Zhi-wei HAN School of Civil Engineering Beijing Jiaotong University Beijing MTR Construction Administration Corporation Railway Engineering Group Faculty of Civil Engineering and Geosciences Delft University of Technology

A closed-form out-of-plane dynamic displacement response of a curved track subjected to moving loads was *** track structure was modeled as a planar curved Timoshenko beam periodically supported by the double-layer spring-damping *** general dynamic displacement response induced by the moving loads along the curve on the elastic semi-infinite space was firstly obtained in the frequency domain,according to the Duhamel integral and the dynamic reciprocity *** the case of the periodic curved track structure subjected to moving loads,the dynamic displacement equation was simplified into a form of summation within the basic track cell instead of the *** transfer function for the curved track was expressed in the form of a transfer *** and series moving loads were involved in the calculation *** the verification of the analytical model,the mid-span vertical deflection of a simply support curved beam subjected to moving load was recalculated and compared with the same case in the *** research results indicate that:under the same moving loads,the displacement response of the curved track decreases slightly with the increasing track radius,and the displacement response of the curved track with the radius greater than or equal to 600 m is almost equivalent to the displacement response of the straight track;the frequency spectrum of the curved track is more abundant than that of the straight track,which may result in more wheel-rail resonance and rail corrugation in the curved lines.

关键词： Curved track Moving loads Dynamic displacement Analytical solution Transfer function

Hydrodynamic performance of flexible risers subject to vortex-induced vibrations

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2013年第1期25卷 156-164页

作者： ZHANG Hui YANG jian-min XIAO Long-fei LU Hai-ning State Key Laboratory of Ocean Engineering Shanghai Jiaotong University

The Vortex-Induced Vibration （VIV） displacements are determined from both the measured accelerations and strains in a series of VIV experiments. Based on the results, the forces in the longitudinal, transversal and tangential directions are estimated by using the finite element method with and without considering the interactions between adjacent elements. The numerical simulation indicates that the method considering the interactions performs better in the estimation of the forces. The component of the transversal force in phase with the acceleration is associated with the added mass coefficient. The estimated added mass coefficients take abnormally high values at the locations where the displacements are small. An improved formula based on the L＇Hospital＇s rule is pro- posed to deal with this problem. The results show the advantage of this formula in estimating the added mass coefficients at the loca- tions with small VIV displacements.

关键词： Vortex-Induced Vibration (VIV) flexible risers hydrodynamic force added mass coefficient

Integrated agronomic practices management improved grain formation and regulated endogenous hormone balance in summer maize (Zea mays L.)

在线全文

学校读者我要写书评

暂无评论

Journal of Integrative Agriculture 2020年第7期19卷 1768-1776页

作者： YU ning-ning ZHANG ji-wang LIU Peng ZHAO Bin REN Bai-zhao State Key Laboratory of Crop Biology Ministry of Science and Technology/College of AgronomyShandong Agricultural UniversityTai’an 271018P.R.China

Compared with single agronomic practices management during grain formation, knowledge about integrated agronomic practices management on grain-filling characteristics and physiological function of endogenous hormones was limited. In order to clarify this issue, two field experiments, integrated agronomic practices management(IAPM), T1(local conventional cultivation practices), T2(an optimized combination of cropping systems and fertilizer treatment), T3(treatment based on high-yield studies), and T4(further optimized combination of cropping systems and fertilizer treatment), and nitrogen rate testing(NAT)(four nitrogen rates, 0, 129.0, 184.5, and 300.0 kg N ha–1) were performed with summer maize hybrid Zhengdan 958(ZD958). Results showed that with increased nitrogen rate, the endogenous hormone balance was promoted and the grain-filling characteristics were improved sufficiently to resulting in a significant increase in grain yield. However, the grain-filling characteristics deteriorated and yield was reduced with excessive nitrogen fertilization. However, IAPM could promote hormone balance and improve grain filling characteristic. The indole-3-acetic acid(IAA), zeatin riboside(ZR), and gibberellin(GA3) contents under T2 and T4 treatments were higher and the abscisic acid(ABA) content was lower, and the ZR and GA3 contents under T3 were higher than those under T1. Those resulted in the maximum grain-filling rate(Wmax) and the active grain-filling period(P) under T2, T3 and T4 were significantly increased than those under T1, and hence promoted kernel weight and grain yield. So IAPM promoted hormone balance by improving tillage model, optimizing fertilizer rate and fertilization period, appropriately increasing planting density and delaying harvest, which promoted grain filling rate and lengthened active grain-filling period, finally increased grain yield.

关键词： grain fling endogenous hormone integrated agronomic practices management summer maize

Sol–gel derived porous ultra-high temperature ceramics

在线全文

学校读者我要写书评

暂无评论

Journal of Advanced Ceramics 2020年第1期9卷 1-16页

作者： fei LI Xiao HUANG ji-Xuan LIU Guo-Jun ZHANG State Key Laboratory for Modification of Chemical Fibers and Polymer Materials Institute of Functional MaterialsDonghua UniversityShanghai 201620China Institute for the Conservation of Cultural Heritage Shanghai UniversityShanghai 200444China

Ultra-high temperature ceramics(UHTCs)are considered as a family of nonmetallic and inorganic materials that have melting point over 3000℃.Chemically,nearly all UHTCs are borides,carbides,and nitrides of early transition metals(e.g.,Zr,Hf,Nb,Ta).Within the last two decades,except for the great achievements in the densification,microstructure tailoring,and mechanical property improvements of UHTCs,many methods have been established for the preparation of porous UHTCs,aiming to develop high-temperature resistant,sintering resistant,and lightweight materials that will withstand temperatures as high as 2000℃for long periods of *** the synthesis methods for porous UHTCs,sol–gel methods enable the preparation of porous UHTCs with pore sizes from 1 to 500μm and porosity within the range of 60%–95%at relatively low *** this article,we review the currently available sol–gel methods for the preparation of porous ***,foaming,and solvent evaporation methods are described and compared in terms of processing–microstructure *** properties and high temperature resistance of sol–gel derived porous UHTCs are ***,directions to future investigations on the processing and applications of porous UHTCs are proposed.

关键词： sol–gel ultra-high temperature ceramics porous ceramics processing microstructure

Viscous numerical examination of hydrodynamic forces on a submerged horizontal circular cylinder undergoing forced oscillation

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2019年第5期31卷 887-899页

作者： Bin Teng Hong-fei Mao De-zhi ning Chong-wei Zhang State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China

As a classical topic,the hydrodynamic forces on a submerged horizontal cylinder undergoing forced oscillation have been widely studied based on potential flow ***,the fluid viscosity and the flow rotation may play an important role when the oscillation amplitude of the circular cylinder is large,and large discrepancy will occur between the potential flow simulation and the experimental *** study focuses on the study of hydrodynamic forces on a submerged horizontal circular cylinder undergoing forced oscillation by means of a viscous fluid numerical wave tank(NWT)*** accuracy of the numerical model is validated against available experimental *** comparisons between the hydrodynamic forces on the circular cylinder predicted by the viscous fluid model and the potential flow model are conducted to show the viscous effects on the hydrodynamic *** the study on the flow fields,the mechanism of the viscous effects is explained by the vortex *** basic reason for the difference between the results based on the viscous fluid theory and the potential flow theory is revealed by analyzing the force components.

关键词： Submerged horizontal circular cylinder forced oscillation hydrodynamic forces vortex effect

Species bias and spillover effects in scientific research on Carnivora in China

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

Zoological Research 2021年第3期42卷 354-361页

作者： Zhi-ning Wang Li Yang Peng-fei Fan Lu Zhang School of Life Sciences Sun Yat-Sen UniversityGuangzhouGuangdong 510275China

Scientific research provides essential information for conservation of threatened *** deficiency due to insufficient research impedes the design of conservation plans,and research bias may mistakenly direct limited resources to low biodiversity regions or less threatened ***,we conducted a systematic review of published papers,grants,and graduate student training on carnivorans in China to identify species bias and research ***,we collected intrinsic and extrinsic features of carnivorans,and identified features that impact research intensity using generalized linear *** found that the amount of research on carnivorans increased markedly after 2000,but species bias *** and big cats received the greatest research attention,while most small-and medium-sized carnivorans received little attention,thus showing the 80-20 *** with a higher level of endemism and protection under Chinese law received more *** an animal conservation icon in China,the giant panda(Ailuropoda melanoleuca)attracted more than 50%of overall carnivoran research ***,the giant panda also showed spillover effects,i.e.,post-doctoral graduates who studied the giant panda shifted their research focus to other species after graduation,which may help improve research on other ***,to improve and strengthen Carnivora research and conservation,we suggest investing greater effort in species of less concern,training of more graduate students,and reinforcing academic *** such actions are not taken,many carnivoran species will continue being data deficient and threatened.

关键词： Ailuropoda melanoleuca Carnivora Conservation Research bias 80-20 phenomenon

CeO_(2)-supported Fe,Co and Ni toward CO_(2) hydrogenation:Tuning catalytic performance via metal-support interaction

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2023年第6期41卷 926-932,I0005页

作者： Bolang Li fei Wang Kai Li Ping ning Min Chen Changbin Zhang Faculty of Environmental Science and Engineering Kunming University of Science and TechnologyKunming 650500China National-Regional Engineering Center for Recovery of Waste Gases from Metallurgical and Chemical Industries Kunming University of Science and TechnologyKunming 650500China State Key Joint Laboratory of Environment Simulation and Pollution Control Research Center for Eco-Environment SciencesChinese Academy of SciencesBeijing 100085China University of Chinese Academy of Sciences Beijing 100049China

The chemical transformation of CO_(2) produces carbon compounds that can be used as precursors for the production of chemicals and ***,we investigated the activity and selectivity of the transition metals(Fe,Co,and Ni)supported on CeO_(2) catalyst for CO_(2) hydrogenation at atmospheric *** found that Ni/CeO_(2) shows the highest CO_(2)conversion compared with Fe/CeO_(2) and Co/CeO_(2).Besides,Co/CeO_(2)and Ni/CeO_(2) exhibit nearly 100%CH_(4)selectivity while Fe/CeO_(2) inclines to produce *** characterization results show that the metal-support interaction order is Fe/CeO_(2)>Co/CeO_(2)>Ni/CeO_(2),the weak metal-support inte raction over Ni/CeO_(2)benefits the activation of H_(2) and then promotes the activity of CO_(2) ***,in situ DRIFTS results demonstrate that monodentate formate species rather than bidentate formate are the active *** main route of CO_(2) hydrogenation to CH_(4) is that CO_(2) is firstly transformed to m-HCOO*and then direct hydrogenation of the m-HCOO*to CH_(4).This study provides insights into the understanding of the mechanisms of CO_(2) hydrogenation on CeO_(2)based catalysts.

关键词： Ni CeO_(2) Metal-support interaction CO_(2)hydrogenation Rare earths