期刊文献+
共找到1,047篇文章
< 1 2 53 >
每页显示 20 50 100
Study for the Forming Principle of Logix Gear Tooth Profile and Its Mesh Performance 被引量:3
1
作者 Lee Leckseng Linda Lee 《厦门大学学报(自然科学版)》 CAS CSCD 北大核心 2002年第S1期91-92,共2页
In recent years, a new type of gear named Logix gea r was developed. Actually, the tooth profile of this new type of gear is composed of lots of micro-segment involute curves, and on the profile, there exist lots of p... In recent years, a new type of gear named Logix gea r was developed. Actually, the tooth profile of this new type of gear is composed of lots of micro-segment involute curves, and on the profile, there exist lots of points, which their relative curvatures are equal to zero. This can result in the sliding coefficient smaller between two meshed Logix gears, and the mesh ch aracteristic becomes almost rolling transmission from sliding transmission accor dingly. So, this new type of gear has lots of advantages such as higher contact intensity, longer useful life and can easily realize power transfer of bigger tr ansmission ratio than standard involute gear. Study results showed that the cont act fatigue strength is 3 times larger, the bend fatigue strength is 2.5 times l arger, and the minimum tooth number can be decreased to 3, much smaller than tha t of standard involute gear. In this paper, following studies had been done: 1) The formation principle of Logix gear tooth profile was studied. The theoreti cal models describing the geometrical formations of this type of gear and its re lative Logix rack had been deduced. 2) While cutting a Logix gear, its tooth profile is decided by its normal tooth profile of Logix rack. Besides the basic parameters of standard involute gear, L ogix rack has its own specific parameters such as preliminary pressure angle, re lative pressure angle, and preliminary referential circle radius etc. So, the in fluence of connatural parameters of Logix rack on the tooth profile of Logix gea r had been farther studied. Reasonable selection for these parameters had been d iscussed. 3) Several kinds of transition curves for gear’s tooth profile had been introdu ced, its selection used by Logix gear had been described, and also its mathemati cal description model had been deduced. 4) The mesh theories of Logix gears had been developed. It had been proved that the transmission performance between Logix gears coincides with E-W theorem as that of ordinary standard involute gears. The formula calculating superposition coefficient was deduced according to its definition. Different from standard inv olute gears, the parameter of gear number has no effect on the superposition coe fficient of the Logix gears. Accordingly, bigger ratio transmission can be acqui red by means of decreasing the gear number, and its minimum gear number can be r eached to 3, much smaller than the minimum gear number of ordinary standard invo lute gear: 14~17. This is very important to realize the miniaturization of prod uction design. 5) The CAD special software was developed to design all kinds of Logix gears, an d a solid design example was offered. To sum up, by means of above study, the system info about Logix gear had been de veloped and enriched. This has most significant impact on its widely promotion a nd practical application, on the improvement of carrying capacity, miniaturizati on, and life of kinetic transmission products. 展开更多
关键词 Logix gear forming principle mesh performance big transmission ratio
下载PDF
Metaphysics Z 17’s Ontological Deduction of the Ε■δο■as Principle and Primary Substance through the Analysis of the Becoming
2
作者 Fernando A.Riofrío 《Journal of Philosophy Study》 2019年第1期16-42,共27页
This research represents another of the various different versions of the Hylomorphism of the third millennium(some closer and some less close to the thought of Aristotle).Its aim is to find the most profound and basi... This research represents another of the various different versions of the Hylomorphism of the third millennium(some closer and some less close to the thought of Aristotle).Its aim is to find the most profound and basic intrinsic explanation of the being of the sense-perceptible substance,by means of a systematic approach to the theory of substance developed in the central books of Aristotle's Metaphysics.The theory of substance is based on the hylomorphic conception of the sense-perceptible substance,and reaches its culmination in Chapter 17 of Metaphysics Book Zeta,where Aristotle develops the definitive deeper argument that demonstrates the essence of substance.The argument is developed through a rigorous analysis of the sense-perceptible thing and its elements during the existence of the thing and after its corruption.The result obtained by this analysis is that none of the material components of a sense-perceptible thing,nor the sum of all of them,explain the constitution of the sense-perceptible thing,or its nature.And the final conclusion is that there exists an entity distinct from all of the material components,which is the arrangement and the essence of the sense-perceptible thing,that is,its form.The form also emerges as the primary cause of the being of the sense-perceptible thing and the primary substance,because it acts as the cause of matter and of the hylomorphic compound,and possesses the characters of substantiality in the maximum degree,being separate(τōχωριστòν)and being"a this"(τò?τóδετι).To take another angle,the soul is the form of biological organisms and man;and this investigation ends by establishing how the Aristotelian argument applies to a biological organism,and demonstrates that the soul is the first cause of this and the primary substance,by means of the distinction of the proximate matter and remote matter of the living being. 展开更多
关键词 PRIMARY substance definition of substance form matter Hylomorphism BECOMING CAUSE ARISTOTLE
下载PDF
Politeness Principle and the Choice of Address Forms in Intercultural Communication
3
作者 TIAN Yan-ping(Foreign Languages Department,Qinghai Normal University,Xining 810008,China) 《海外英语》 2011年第9X期289-290,共2页
This paper makes a tentative study of the politeness strategies stressed in the choice of address forms in Chinese,American and Japanese culture under the guidance of Politeness Principle by Brown and Levinson.Through... This paper makes a tentative study of the politeness strategies stressed in the choice of address forms in Chinese,American and Japanese culture under the guidance of Politeness Principle by Brown and Levinson.Through a comprehensive analysis,It is concluded that the major function of English address forms is to indicate solidarity and realize positive politeness,In contrast,both Chinese and Japanese address forms emphasize deference and help achieve negative politeness;It is the author's hope that a better understanding of these addressing rules in different cultures will benefit effective use of these languages and help avoid miscommunication in intercultural communication. 展开更多
关键词 POLITENESS principle ADDRESS formS positive POLITENESS negative POLITENESS INTERCULTURAL communication
下载PDF
The application of formative assessment in college oral English teaching 被引量:1
4
作者 陈宏 《Sino-US English Teaching》 2011年第2期77-81,共5页
Teaching assessment is one of the most important components of college English teaching. The traditional assessment system over emphasizes the summative assessment, which used examinations as the main assessment metho... Teaching assessment is one of the most important components of college English teaching. The traditional assessment system over emphasizes the summative assessment, which used examinations as the main assessment method. Formative assessment focuses on the process assessment during the practice of teaching. It is integrated in the teaching and learning process and cannot be separated as evaluation. The formative assessment aims to confirm the students' potential, develop their ability in study and strengthen the students' confidence and the spirit of cooperation. It is also a method intended to generate feedback on performance to improve and accelerate teaching and learning effectively. Based on some theories, this paper states the importance of the application of formative assessment in college oral English teaching. It also introduces some principles and measures to apply this assessment. The reasonable and effective application can promote college oral English teaching. 展开更多
关键词 formative assessment college oral English teaching principleS APPLICATION
下载PDF
^(15)N NMR Spectroscopic Study on Nitrogen Forms in Humic Substances of Soils 被引量:2
5
作者 WEN QIXIAO, ZHUO SUNENG and CHENG LILI (Institute of Soil Science, the Chinese Academy of Sciences, P.O. Box 821, Nanjing 210008 (China)) 《Pedosphere》 SCIE CAS CSCD 2001年第1期1-9,共9页
Nitrogen forms of humic substances from a subalpine meadow soil, a latentic red soil and a weathered coal and the effect of acid hydrolysis on N structures of soil humic substances were studied by using 15N cross-pola... Nitrogen forms of humic substances from a subalpine meadow soil, a latentic red soil and a weathered coal and the effect of acid hydrolysis on N structures of soil humic substances were studied by using 15N cross-polarization magic angle spinning nuclear magnetic resonance (CPMAS NMR) spectroscopy. Of the detectable 15N-signal intensity in the spectra of soil humic substances 71%-79% may be attributed to amide groups, 10%-18% to aromatic/aliphatic amines and 6%~11% to indole- and pyrrole-like N. Whereas in the spectrum of the fulvic acid from weathered coal 46%, at least, of the total 15N-signal intensity might be assigned to pyrrole-like N, 14% to aromatic/aliphatic ammes, and the remaining intensities could not be assigned with certainty. Data on nonhydrolyzable residue of protein-sugar mixture and a 15N-labelled soil fulvic acid confirm the formation of nonhydrolyzable heterocyclic N during acid hydrolysis. Project (No. 39790100) supported by the National Natural Science Foundation of China. 展开更多
关键词 forms of N humic substances mineral soils 15N CPMAS NMR weathered coal
下载PDF
FORM INVARIANCE AND NOETHER SYMMETRICAL CONSERVED QUANTITY OF RELATIVISTIC BIRKHOFFIAN SYSTEMS
6
作者 罗绍凯 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2003年第4期468-478,共11页
A form invariance of the relativistic Birkhoffian system is studied, and the conserved quantities of the system are obtained. Under the infinitesimal transformation of groups, the definition and criteria of the form i... A form invariance of the relativistic Birkhoffian system is studied, and the conserved quantities of the system are obtained. Under the infinitesimal transformation of groups, the definition and criteria of the form invariance of the system were given. In view of the invariance of relativistic Pfaff_Birkhoff_ D'Alembert principle under the infinitesimal transformation of groups, the theory of Noether symmetries of the relativistic Birkhoffian system were constructed. The relation between the form invariance and the Noether symmetry is studied, and the results show that the form invariance can also lead to the Noether symmetrical conserved quantity of the relativistic Birkhoffian system under certain conditions. 展开更多
关键词 RELATIVITY Birkhoffian system Pfaff_Birkhoff_ D'Alembert principle form invariance Noether symmetry conserved quantity
下载PDF
Connection between the Principles of Thermodynamics and the Conservation Laws: Physical Meaning of the Principles of Thermodynamics
7
作者 L. I. Petrova 《Journal of Applied Mathematics and Physics》 2018年第12期2697-2704,共8页
It has been shown that the first principle of thermodynamics follows from the conservation laws for energy and linear momentum. And the second principle of thermodynamics follows from the first principle of thermodyna... It has been shown that the first principle of thermodynamics follows from the conservation laws for energy and linear momentum. And the second principle of thermodynamics follows from the first principle of thermodynamics under realization of the integrating factor (namely, temperature) and is a conservation law. The significance of the first principle of thermodynamics consists in the fact that it specifies the thermodynamic system state, which depends on interaction between conservation laws and is non-equilibrium due to a non-commutativity of conservation laws. The realization of the second principle of thermodynamics points to a transition of the thermodynamic system state into a locally-equilibrium state. Phase transitions are examples of such transitions. 展开更多
关键词 SKEW-SYMMETRIC Differential formS Conservation LAWS First principle of theRMODYNAMICS Realization of Integrating Factor the Second principle of theRMODYNAMICS the Entropy
下载PDF
Vegetative Reproduction through Green Cuttings of the Introduced Form <i>Weigela florida</i>f. “<i>Bristol ruby</i>” (Caprifoliaceae) in the Conditions of the Tashkent Botanical Garden (Uzbekistan)
8
作者 Dilovar A. Khamraeva Nargiza K. Rakhimova Eldor E. Temirov 《American Journal of Plant Sciences》 2021年第7期994-1001,共8页
For the first time, work was carried out on the vegetative reproduction of <i><span style="font-family:Verdana;">Weigela florida </span></i><span style="font-family:Verdana;&q... For the first time, work was carried out on the vegetative reproduction of <i><span style="font-family:Verdana;">Weigela florida </span></i><span style="font-family:Verdana;">f.</span><i> </i><span style="font-family:Verdana;">“</span><i><span style="font-family:Verdana;">Bristol Rubru</span></i><span style="font-family:Verdana;">” (Caprifoliaceae) was introduced into the Tashkent Botanical Garden (Uzbekistan) through green branches. As a result of the research conducted, it was noted that the vegetative reproduction possibil</span><span><span style="font-family:Verdana;">ities of the “</span><i><span style="font-family:Verdana;">Bristol Ruby</span></i><span style="font-family:Verdana;">” form of </span><i><span style="font-family:Verdana;">Weigela florida</span></i><span style="font-family:Verdana;"> were high. W</span></span><span style="font-family:Verdana;">hen placed on stimulants of two types (kornevin, heteroauxin), it became known that kornevin stimulants are effective in taking root. It was found that the effective way to multiply this form by green branches in a vegetative way—when placed on the stimulator of kornevin from the middle part of the rod, the indicators of root extraction of the cuttings were 93.3%, which is more effective than other options. When vegetative reproduction of this decorative form, it is recommended that the seedlings come to the standard state in 3 - 4 years and the root extraction indicators are high—this is its use as the second row shrubs in the case of growing on strongly saline soils in the conditions of Uzbekistan. The cultivation of green cuttings of the form in the fog showed that they are more effective than in the open ground.</span> 展开更多
关键词 form Weigela florida f. Bristol Ruby (Caprifoliaceae) Vegetative Reproduction Green Shoots Growth Regulators Biologically Active substances Tashkent Botanical Garden Uzbekistan Introduction
下载PDF
相对论Birkhoff系统的形式不变性与Noether守恒量 被引量:8
9
作者 罗绍凯 《应用数学和力学》 EI CSCD 北大核心 2003年第4期414-422,共9页
研究相对论Birkhoff系统的形式不变性,寻求系统的守恒量。在群的无限小变换下,给出相对论Birkhoff系统的形式不变性的定义和判剧。基于相对论Pfaff-Birkhoff-D’Alembert原理在群的无限小变换下的变形形式,建立相对论Birkhoff系统的Noet... 研究相对论Birkhoff系统的形式不变性,寻求系统的守恒量。在群的无限小变换下,给出相对论Birkhoff系统的形式不变性的定义和判剧。基于相对论Pfaff-Birkhoff-D’Alembert原理在群的无限小变换下的变形形式,建立相对论Birkhoff系统的Noether对称性理论。通过研究形式不变性与Noether对称性之间的关系,得到相对论Birkhoff系统的守恒量。研究结果表明:在一定的条件下,相对论Birkhoff系统的形式不变性导致Noether对称性的守恒量。 展开更多
关键词 相对论 BIRKHofF系统 Pfaff-Birkhoff-D'Alembert原理 形式不变性 NOEtheR对称性 守恒量
下载PDF
LOWER INEQUALITIES OF HEAT SEMIGROUPS BY USING PARABOLIC MAXIMUM PRINCIPLE 被引量:1
10
作者 胡二彦 《Acta Mathematica Scientia》 SCIE CSCD 2012年第4期1349-1364,共16页
Using parabolic maximum principle, we apply the analytic method to obtain lower comparison inequalities for non-negative weak supersolutions of the heat equation associated with a regular strongly p-local Dirichlet fo... Using parabolic maximum principle, we apply the analytic method to obtain lower comparison inequalities for non-negative weak supersolutions of the heat equation associated with a regular strongly p-local Dirichlet form on the abstract metric measure space. As an application we obtain lower estimates for heat kernels on some Riemannian manifolds. 展开更多
关键词 Dirichlet form parabolic maximum principle heat kernel
下载PDF
Vertical migration through faults and hydrocarbon accumulation patterns in deepwater areas of the Qiongdongnan Basin 被引量:4
11
作者 WANG Zhenfeng LIU Zhen +4 位作者 CAO Shang SUN Zhipeng ZUO Qianmei WANG Yahui HE Weijun 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2014年第12期96-106,共11页
In the Qiongdongnan Basin, faults are well developed.Based on the drilling results, the traps controlled two or more faults are oil-rich. However, when only one fault cut through the sand body, there is no sign for hy... In the Qiongdongnan Basin, faults are well developed.Based on the drilling results, the traps controlled two or more faults are oil-rich. However, when only one fault cut through the sand body, there is no sign for hy-drocarbon accumulation in the sandstone. In terms of this phenomenon, the principle of reservoir-forming controlled by fault terrace is proposed, i.e., when the single fault activates, because of the incompressibility of pore water, the resistance of pore and the direction of buoyancy, it is impossible for hydrocarbon to ac-cumulate in sandstone. But when there are two or more faults, one of the faults acts as the spillway so the hydrocarbon could fill in the pore of sandstone through other faults. In total five gas bearing structures and four failure traps are considered, as examples to demonstrate our findings. According to this theory, it is well-advised that south steep slope zone of Baodao-Changchang Depression, south gentle slope zone of Lingshui Depression, north steep slope zone of Lingshui Depression, and north steep slope zone of Baodao Depression are the most favorable step-fault zones, which are the main exploration direction in next stage. 展开更多
关键词 principle of reservoir-forming controlled by fault terrace gas bearing structures step-fault zone Qiongdongnan Basin
下载PDF
Evaluation of glass forming ability of alloys
12
作者 Anhui CAI Ye PAN Guoxiong SUN 《China Foundry》 SCIE CAS 2005年第1期1-6,共6页
Key step of exploiting a new type BMG (Bulk Metallic Glass) is quickly judging GFA (Glass Forming Ability) of the alloys. The mole melting heats of BMGs are calculated using the weighted averages principle. The reliab... Key step of exploiting a new type BMG (Bulk Metallic Glass) is quickly judging GFA (Glass Forming Ability) of the alloys. The mole melting heats of BMGs are calculated using the weighted averages principle. The reliability and limitation of Trg criterion for GFA are discussed. The reason why Trg of BMGs is larger than 0.5 is discussed. Two new criteria for GFA, ΔHmg and ΔGg, are proposed. GFA sequence of BMGs is calculated using the ΔHmg criterion, the result agrees with that of A. Inoue and the Rc criterion. Furthermore, as an example, the Rc of the alloys developed by Chuang DONG et al is calculated using the ΔHmg and ΔGg. The ascending sequence of these alloys calculated with the ΔHmg criterion agrees with that of Chuang DONG et al. On the contrary, the result by the ΔGg criterion is in contrary with Chuang DONG et al, indicating that the ΔHmg criterion is better and more convenient than the ΔGg criterion. Calculation showed that the optimum ΔHmg is -15.16 kJ/mol. 展开更多
关键词 bulk metallic GLASSES glass formING ability weighted AVERAGES principle GFA CRITERION
下载PDF
Natural Selection and Thermodynamics of Biological Evolution
13
作者 Georgi P. Gladyshev 《Natural Science》 2015年第3期117-126,共10页
The author of this article proposes that the representation of Charles Darwin and Alfred Wallace’s theory on “variation and selection” in the living world is a reflection of the action of hierarchical thermodynamic... The author of this article proposes that the representation of Charles Darwin and Alfred Wallace’s theory on “variation and selection” in the living world is a reflection of the action of hierarchical thermodynamics. Hierarchical thermodynamics is based on the law of temporal hierarchies and on the principle of substance stability. This principle enables the transmission of thermodynamic information between lower and higher structural hierarchies, in both forward and reverse direction: from nucleic acids to higher structural hierarchies and back. The principle of substance stability, in fact, is the main dynamical and thermodynamic mechanism of natural selection. It is alleged that the natural selection of atoms, molecules, organisms, populations, and other hierarchical structures takes place under the action of a variety of internal factors within organisms and the external environmental factors that can be considered as tropisms. Forms (design) of living organisms are formed as a result of spontaneous and non-spontaneous processes that lead to the adaptation of living systems to the environment. The selection is carried out as a result of the impacts of different energy types and the principle of substance stability at all levels of hierarchical structures. Actions of tropisms are presented by various members of the generalized Gibbs equation. 展开更多
关键词 NATURAL Selection HIERARCHICAL theRMODYNAMICS principle of substance Stability the ORIGIN of Life Evolution
下载PDF
An XPS Study of Nitrogen Structures in Soil Humic Substances
14
作者 WEN QIXIAO, CHENG LILI and CHEN BIYUN Institute of Soil Science, the Chinese Academy of Sciences, Nanjing 210008 (China) 《Pedosphere》 SCIE CAS CSCD 2001年第4期321-326,共6页
X-ray photoelectron spectroscopy (XPS) was applied to examine the N structures of soil humic substances and some of their analogues. It was found that for soil humic substances XPS method gave similar results as those... X-ray photoelectron spectroscopy (XPS) was applied to examine the N structures of soil humic substances and some of their analogues. It was found that for soil humic substances XPS method gave similar results as those obtained by 15N CPMAS NMR (cross-polarization magic-angle spinning nuclear magnetic resonance) method. 70%~86% of total N in soil humic substances was in the form of amide, and 6%~13% was presented as amines, with the remaining part as heterocyclic N. There was no difference in the distribution of the forms of N between the humic substances from soils formed over hundreds or thousands of years and the newly formed ones. For fulvic acid from weathered coal and benzoqu inone- (N H-4 )-2 S O-4 polymer the XPS results deviated significantly from the 15N CPMAS NMR data. 展开更多
关键词 distribution of N forms 15N CPMAS NMR soil humic substances XPS.
下载PDF
The “3 Genomic Numbers” Discovery: How Our Genome Single-Stranded DNA Sequence Is “Self-Designed” as a Numerical Whole
15
作者 Jean-Claude Perez 《Applied Mathematics》 2013年第10期37-53,共17页
This article proves the existence of a hyper-precise global numerical meta-architecture unifying, structuring, binding and controlling the billion triplet codons constituting the sequence of single-stranded DNA of the... This article proves the existence of a hyper-precise global numerical meta-architecture unifying, structuring, binding and controlling the billion triplet codons constituting the sequence of single-stranded DNA of the entire human genome. Beyond the evolution and erratic mutations like transposons within the genome, it’s as if the memory of a fossil genome with multiple symmetries persists. This recalls the “intermingling” of information characterizing the fractal universe of chaos theory. The result leads to a balanced and perfect tuning between the masses of the two strands of the huge DNA molecule that constitute our genome. We show here how codon populations forming the single-stranded DNA sequences can constitute a critical approach to the understanding of junk DNA function. Then, we suggest revisiting certain methods published in our 2009 book “Codex Biogenesis”. In fact, we demonstrate here how the universal genetic code table is a powerful analytical filter to characterize single-stranded DNA sequences constituting chromosomes and genomes. We can then show that any genomic DNA sequence is featured by three numbers, which characterize it and its 64 codon populations with correlations greater than 99%. The number “1” is common to all sequences, expressing the second law of Chargaff. The other 2 numbers are related to each specific DNA sequence case characterizing life species. For example, the entire human genome is characterized by three remarkable numbers 1, 2, and Phi = 1.618 the golden ratio. Associated with each of these three numbers, we can match three axes of symmetry, then “imagine” a kind of hyperspace formed by these codon populations. Then we revisit the value (3-Phi)/2 which is probably universal and common to both the scale of quarks and atomic levels, balancing and tuning the whole human genome codon population. Finally, we demonstrate a new kind of duality between “form and substance” overlapping the whole human genome: we will show that—simultaneously with the duality between genes and junk DNA—there is a second layer of embedded hidden structure overlapping all the DNA of the whole human genome, dividing it into a second type of duality information/redundancy involving golden ratio proportions. 展开更多
关键词 Genetic Code CODON Populations Junk DNA Cancer Genomics Chromosomal Translocations Genomes Diversity Chromosomes Diversity WHOLE Human GENOME DNA SEQUENCE “Phi” the Golden Ratio Fibonacci NUMBERS Information theory SYMMETRY Cellular Automata Chargaff’s CODON Level SYMMETRY principle Fractal Self-Similarity “e” Euler’s Number “Pi” form and substance Redundancy Encryption
下载PDF
Mathematical theory of signal analysis vs. complex analysis method of harmonic analysis
16
作者 QIAN Tao ZHANG Li-ming 《Applied Mathematics(A Journal of Chinese Universities)》 SCIE CSCD 2013年第4期505-530,共26页
We present recent work of harmonic and signal analysis based on the complex Hardy space approach.
关键词 Mobius transform Blaschke form mono-component Hardy space adaptive Fourier decomposi-tion rational approximation rational orthogonal system time-frequency distribution digital signal processing uncertainty principle higher dimensional signal analysis in several complex variables and the Clifford algebrasetting.
下载PDF
Folk Gestalt --Research on the Cultural Philosophy of the Folk Revival in The Book of Songs
17
作者 Jiang Xia 《学术界》 CSSCI 北大核心 2014年第3期297-301,共5页
Visual perception is researched both in psychology and in the aesthetic field,and understanding of the principle of visual perception is important for the aesthetic mechanism. T his paper explains the Gestalt psycholo... Visual perception is researched both in psychology and in the aesthetic field,and understanding of the principle of visual perception is important for the aesthetic mechanism. T his paper explains the Gestalt psychology from the perspective of the fu,bi and xing of T he Book of Songs,illustrating the cognitive rules and characteristics of visual perception as w ell as the processing and understanding mode of the brain w hen visual information enters.Besides,this paper emphasizes the basic principle of gestalt and how to use the principle of visual perception. Based on the research by Z hou Z henhao,this paper attempts to explore the coding of the visual elements such as fu,bi and xing inT he Book of Songs,w hich can be treated as the element task for researching the cultural psychology in C hina. 展开更多
关键词 文化心理 诗经 格式塔心理学 视觉感知特性 民间 哲学 民俗 视觉元素
下载PDF
超高压在植物活性物质提取中的应用研究进展
18
作者 王菁 乔勇进 +4 位作者 柳洪入 王晓 叶章颖 林思敏 王春芳 《农业工程学报》 EI CAS CSCD 北大核心 2024年第18期272-282,共11页
植物中含有多种活性物质,并具有抗氧化、抗菌、免疫调节、抗炎等多重功效,如何从植物中快速、高效、环保地提取活性物质一直以来是食品、医药、化妆品等行业最重要的研究领域之一。超高压技术作为一种非热加工技术,近年来被广泛研究用... 植物中含有多种活性物质,并具有抗氧化、抗菌、免疫调节、抗炎等多重功效,如何从植物中快速、高效、环保地提取活性物质一直以来是食品、医药、化妆品等行业最重要的研究领域之一。超高压技术作为一种非热加工技术,近年来被广泛研究用于食品加工、提取等方面。超高压提取技术的应用提高了植物活性物质的提取率,缩短了提取时间,可作为一种替代传统固液萃取植物活性化合物的方法。该文重点综述了超高压技术的发展历程及其在植物提取方面的发展应用,超高压提取原理与提取工艺,及其在黄酮、多酚、多糖等多种活性物质提取中的应用,与传统热回流提取方法相比,超高压提取技术可以在常温或较低温度下进行,可有效缩短提取时间,提高生物活性,降低能耗。但超高压在提取植物活性物质方面的应用还面临超高压提取理论基础不完善,提取物生物活性研究有待深入、设备成本高等诸多挑战,有必要探索超高压与其他提取方法相结合的协同提取作用,进一步揭示该技术所涉及的工作机制,以期为深入应用超高压技术提取植物活性物质提供理论参考。 展开更多
关键词 超高压 活性物质 提取原理 提取工艺 应用
下载PDF
基于不同绕组形式双定子低速大转矩永磁直驱电机转矩脉动的分析与抑制
19
作者 刘佶炜 狄冲 +1 位作者 李仕豪 鲍晓华 《电工技术学报》 EI CSCD 北大核心 2024年第12期3646-3657,共12页
双定子低速大转矩永磁直驱电机(DLHPMDM)具有高转矩密度和高效率等优点,是传统低速大转矩传动系统的良好替代方案。DLHPMDM可以看作由内、外两台电机构成的整体。绕组形式选择不仅直接影响内、外电机的转矩性能,内、外电机不同绕组形式... 双定子低速大转矩永磁直驱电机(DLHPMDM)具有高转矩密度和高效率等优点,是传统低速大转矩传动系统的良好替代方案。DLHPMDM可以看作由内、外两台电机构成的整体。绕组形式选择不仅直接影响内、外电机的转矩性能,内、外电机不同绕组形式的组合还会改变内、外电机输出转矩的叠加效果,最终影响DLHPMDM的转矩脉动水平。首先,基于双定子电机的转矩叠加原理,提出一种抑制DLHPMDM转矩脉动的设计方法,采用解析法分析内、外电机反电动势谐波相位差如何影响纹波转矩的叠加效果,并对内定子采用不同绕组形式时DLHPMDM的转矩性能进行仿真分析和初步验证。其次,考虑到绕组谐波引起的谐波电流对转矩脉动的影响,采用以电压源为激励的有限元分析进一步验证了内、外电机选用合理的绕组形式组合时,内、外电机纹波转矩的叠加削减作用能够有效降低DLHPMDM的转矩脉动。最后,采用转矩脉动最低的设计方案试制了一台DLHPMDM样机并完成相关实验,实验结果验证了分析的准确性。 展开更多
关键词 双定子永磁直驱电机 绕组形式 转矩叠加原理 纹波转矩 转矩脉动
下载PDF
Kirchhoff弹性杆分析动力学的准坐标表达 被引量:3
20
作者 薛纭 刘延柱 《力学季刊》 CSCD 北大核心 2006年第4期550-556,共7页
作为DNA的力学模型,依据Kirchhoff动力学比拟思想建立的弹性细杆的分析力学方法已从静力学深入到动力学。由于静力学平衡微分方程与刚体动力学相当,因此,弹性细杆动力学的分析力学方程必是以弧坐标和时间为双自变量的偏微分方程。以横... 作为DNA的力学模型,依据Kirchhoff动力学比拟思想建立的弹性细杆的分析力学方法已从静力学深入到动力学。由于静力学平衡微分方程与刚体动力学相当,因此,弹性细杆动力学的分析力学方程必是以弧坐标和时间为双自变量的偏微分方程。以横截面的形心速度以及弯扭度和角速度沿主轴的分量为准速度,定义了准坐标,导出了准坐标的微分和变分运算的交换关系。从Hamilton原理出发,利用准坐标的微分和变分运算的交换关系,导出了Kirchhoff弹性杆动力学准坐标下的Boltzmann-Hamel方程,并由此导出Lanrange方程。指出了Boltzmann-Hamel方程显式即为弹性杆动力学的Kirchhoff方程。定义关于弧坐标和时间的正则变量和Hamilton函数,导出Boltzmann-Hamel方程的正则形式。本文结果是以弹性杆静力学和刚性杆动力学为其特例。作为例子,建立了垂挂的在重力作用下作平面运动的弹性细杆的动力学微分方程以说明本文方法的应用。 展开更多
关键词 Kirchhoff弹性杆动力学 HAMILTON原理 准坐标 Boltzmann-Hamel方程 正则形式
下载PDF
上一页 1 2 53 下一页 到第
使用帮助 返回顶部