检索结果-南通市图书馆

Bandgap characteristics analysis and graded design of a novel metamaterial for flexural wave suppression

在线全文

学校读者我要写书评

暂无评论

applied Mathematics and Mechanics(English Edition) 2025年第1期46卷 1-24页

作者： Fan YANG Zhaoyang MA Xingming GUO Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai Institute of Applied Mathematics and Mechanics School of Mechanics and Engineering ScienceShanghai University Shanghai institute of Aircraft Mechanics and Control

A novel elastic metamaterial is proposed with the aim of achieving lowfrequency broad bandgaps and bandgap regulation. The band structure of the proposed metamaterial is calculated based on the Floquet-Bloch theorem, and the boundary modes of each bandgap are analyzed to understand the effects of each component of the unit cell on the bandgap formation. It is found that the metamaterials with a low elastic modulus of ligaments can generate flexural wave bandgaps below 300 Hz. Multi-frequency vibrations can be suppressed through the selective manipulation of bandgaps. The dual-graded design of metamaterials that can significantly improve the bandgap width is proposed based on parametric studies. A new way that can regulate the bandgap is revealed by studying the graded elastic modulus in the substrate. The results demonstrate that the nonlinear gradient of the elastic modulus in the substrate offers better bandgap performance. Based on these analyses, the proposed elastic metamaterials can pave the way for multi-frequency vibration control, low-frequency bandgap broadening, and bandgap tuning.

关键词：

Response of needle dark respiration of Pinus koraiensis and Pinus sylvestriformis to elevated CO_2 concentra-tions for four growing seasons’ exposure

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China Earth Sciences 2007年第4期50卷 613-619页

作者： ZHOU YuMei1. HAN ShiJie1. ZHANG HaiSen1. XIN LiHua2 & ZHENG JunQiang1.1.institute of {1. ecology, Chinese Academy of Sciences, Shenyang 1.001., China 2 Shenyang Agricultural University, Shenyang 1.01.1. China 1. institute of applied ecology Chinese Academy of Sciences Shenyang 110016 China 2. Shenyang Agricultural University Shenyang 110161 China

The long-term effect of elevated CO2 concentrations on needle dark respiration of two coniferous spe- cies—Pinus koraiensis and Pinus sylvestriformis on the Changbai Mountain was investigated using open-top chambers. P. koraiensis and P. sylvestriformis were exposed to 700, 500 μmol·mol-1.CO2 and ambient CO2 (approx. 350 μmol·mol-1. for four growing seasons. Needle dark respiration was meas- ured during the second, third and fourth growing seasons’ exposure to elevated CO2. The results showed that needle dark respiration rate increased for P. koraiensis and P. sylvestriformis grown at elevated CO2 concentrations during the second growing season, could be attributed to the change of carbohydrate and/or nitrogen content of needles. Needle dark respiration of P. koraiensis was stimu- lated and that of P. sylvestriformis was inhibited by elevated CO2 concentrations during the third growing season. Different response of the two tree species to elevated CO2 mainly resulted from the difference in the growth rate. Elevated CO2 concentrations inhibited needle dark respiration of both P. koraiensis and P. sylvestriformis during the fourth growing season. There was consistent trend be- tween the short-term effect and the long-term effect of elevated CO2 on needle dark respiration in P. sylvestriformis during the third growing season by changing measurement CO2 concentrations. How- ever, the short-term effect was different from the long-term effect for P. koraiensis. Response of dark respiration of P. koraiensis and P. sylvestriformis to elevated CO2 concentrations was related to the treatment time of CO2 and the stage of growth and development of plant. The change of dark respiration for the two tree species was determined by the direct effect of CO2 and long-term acclimation. The prediction of the long-term response of needle dark respiration to elevated CO2 concentration based on the short-term response is in dispute.

关键词： elevated CO2 concentration long-term short-term dark respiration Pinus koraiensis Pinus sylvestriformis

PREDETERMINATION STEM WOOD QUALITY WITH THE BRANCH WOOD INDEX OF KOREAN PINE

在线全文

学校读者我要写书评

暂无评论

Journal of Northeast Forestry University 1992年第1期3卷 54-61页

作者： Luan ShujieInstitudc of applied {1. Academia SinicaYang RuopengShenyang institute of Technology 1. Institude of applied {1. Academia Sinica China 2. Shenyang institute of Technology China

Predetermination of growth ring wood quality was a *** the method ofgrowth ring wood quality analysis,correlation ship of variation between the wood quality andecological condition of forest growth is exlained with the theory of quantification,According to in-dex of quantification model,the variation of forests growth and wood quality is *** pa-per discribed the correlationship between branch wood and stem wood of growth ring wood quality,according to quantification index to infer the stemwood quality by the branchwood qualitypredeterminning stemwood quality,this lead to a new way for wood quality predetermlnation.

关键词： frontier branch WOOD quantification forests Northeast beginning hardness precious Correlation

Multi boron-doping effects in hard carbon toward enhanced sodium ion storage

在线全文

学校读者我要写书评

暂无评论

Journal of Energy Chemistry 2025年第1期100卷 730-738页

作者： Peng Zheng Wang Zhou Ying Mo Biao Zheng Miaomiao Han Qin Zhong Wenwen Yang Peng Gao Lezhi Yang Jilei Liu College of Materials Science and Engineering Hunan Joint International Laboratory of Advanced Materials and Technology for Clean Energy Hunan Province Key Laboratory for Advanced Carbon Materials and Applied Technology Hunan University Greater Bay Area institute for Innovation Hunan University Changsha Research institute of Mining & Metallurgy Co. LTD.

Hard carbon （HC） has been considered as promising anode material for sodium-ion batteries （SIBs）.The optimization of hard carbon’s microstructure and solid electrolyte interface （SEI） property are demonstrated effective in enhancing the Na+storage capability,however,a one-step regulation strategy to achieve simultaneous multi-scale structures optimization is highly ***,we have systematically investigated the effects of boron doping on hard carbon’s microstructure and interface chemistry.A variety of structure characterizations show that appropriate amount of boron doping can increase the size of closed pores via rearrangement of carbon layers with improved graphitization degree,which provides more Na+storage ***-situ Fourier transform infrared spectroscopy/electrochemical impedance spectroscopy （FTIR/EIS） and X-ray photoelectron spectroscopy （XPS） analysis demonstrate the presence of more BC3and less B–C–O structures that result in enhanced ion diffusion kinetics and the formation of inorganic rich and robust SEI,which leads to facilitated charge transfer and excellent rate *** a result,the hard carbon anode with optimized boron doping content exhibits enhanced rate and cycling *** general,this work unravels the critical role of boron doping in optimizing the pore structure,interface chemistry and diffusion kinetics of hard carbon,which enables rational design of sodium-ion battery anode with enhanced Na+storage performance.

关键词： X ray photoelectron spectroscopy

Some Results on Default Logic

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 Computer Science & Technology 1994年第3期9卷 267-274页

作者：张明义 1. institute of {1. Mathematics Guizhou Academy of Sciences 550001 Guiyang

In the previous paper, some important properties of extensions of general default theories were given. In order to further explore default logic, a characterization of extensions is presented. And a class of defaults, so-called Auto-compatible Default Theory, is also iotroduced. All these essentially develop the theories of Reiter and his followers.

关键词： Default theory extension compatible subset of defaults auto-compatible default theory

Arsenobetaine and thio-arsenic species in marine macroalgae and herbivorous animals: Accumulated through trophic transfer or produced in situ?

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2016年第11期28卷 131-139页

作者： Simon Foster William Maher Ecochemistry Laboratory Institute for Applied Ecology University of Canberra

Arsenobetaine（AB） and thio-arsenoribosides were measured in common macroalgae species（8 phaeophyta, 4 rhodophyta and 2 chlorphyta）, along the Australian south east coast line. As well, arsenic species profiles were measured for two common marine herbivores, the sea urchin Centrostephanus rodgersii and the fish Odax cyanomelas that graze on these macroalgae to understand if trophic transfer of these species would account for their presence in marine herbivores. AB was found in seven of the fourteen macroalgae species investigated but does not contributed significantly to any of the macroalgae arsenic content（0.01.1.2 μg/g）. AB was found in only two of the brown macroalgae and all the red and green macroalgae（with the exception of Corallina officinalis）. Thio-arsenic species were found sporadically, but not in high concentrations in any of the macroalgae *** present in macroalgae is likely to be associated with epiphytic organisms while thio-arsenoribosides are likely to be produced by decaying parts of damaged macroalgae.A laboratory feeding experiment in which the herbivorous gastropod, Austrocochlea constricta, was fed macroalgae containing thio-arsenoribosides for a 24 hr period every three days showed that these are readily accumulated over a short period. Thio-arsenoribosides in herbivores are therefore probably obtained through trophic transfer. Some AB is also obtained through trophic transfer; however, the presence of trimethylated arsonioribosides,a hypothesized precursor of AB formation in herbivores, suggests that some AB is produced within herbivores from the transformation of arsenoribosides accumulated from their diet.

关键词： Arsenobetaine Arsenic Metabolism Thio-arsenosugars Macroalgae Gastropods

Physical entropy, information entropy and their evolution equations

在线全文

学校读者我要写书评

暂无评论

Science China Mathematics 2001年第10期44卷 1331-1339页

作者：邢修三 1. Department of applied Physics Beijing Institute of Technology 100081 Beijing China

Inspired by the evolution equation of nonequilibrium statistical physics entropy and the concise statistical formula of the entropy production rate, we develop a theory of the dynamic information entropy and build a nonlinear evolution equation of the information entropy density changing in time and state variable space. Its mathematical form and physical meaning are similar to the evolution equation of the physical entropy: The time rate of change of information entropy density originates together from drift, diffusion and production. The concise statistical formula of information entropy production rate is similar to that of physical entropy also. Furthermore, we study the similarity and difference between physical entropy and information entropy and the possible unification of the two statistical entropies, and discuss the relationship among the principle of entropy increase, the principle of equilibrium maximum entropy and the principle of maximum information entropy as well as the connection between them and the entropy evolution equation.

关键词： statistical entropy entropy evolution equation entropy diffusion formula for entropy production rate disorder

The nonlinear standing wave inside the space of liquid

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2010年第3期53卷 496-503页

作者： WANG ChengHui & LIN ShuYu institute of {1. Acoustics, Shaanxi Normal University, Xi’an 71.062, China 1. institute of {1. Acoustics Shaanxi Normal University Xi’an 710062 China

Based on the basic equations of hydrodynamics, the nonlinear acoustic wave equation is obtained. By taking into account the boundary condition and properties of nonlinear standing wave, the equation is solved through perturbation method, and the stable expressions of fundamental wave and second harmonic are presented. The sound pressures in an ultrasonic cleaner are measured by hydrophones, and the relationship between the received voltages of hydrophones and the output voltages of the ultrasonic generator is researched. The study shows the existence of the nonlinear effect of liquid and analyzes the frequency spectrum of the received signals by hydrophones, by which the fundamental wave, second and high order harmonics are found coexisting in the bounded space filled with liquids. The theory and experimental results testify the existence of the nonlinear standing wave in liquid. Owing to the restricted applicability of perturbation method, the theoretical results of the fundamental wave and second harmonic are good only for the weak nonlinear phenomenon.

关键词： nonlinear acoustic wave equation nonlinear standing wave perturbation method fundamental wave second harmonic

ON THE CHARACTERISTICS OF applied MATHEMATICS

在线全文

学校读者我要写书评

暂无评论

applied Mathematics and Mechanics(English Edition) 1991年第1期12卷 67-69页

作者：秦元勋 1. institute of {1. Mathematics Academia Sinica Beijing

In this paper, four aspects of particular characteristics of applied Mathematics different from those of Pure Mathematics are summarized by comparison. These aspects concern the origin of problems, method of problem s... 详细信息

关键词： pure mathematics applied mathematics characteristics