期刊文献+
共找到4,821篇文章
< 1 2 242 >
每页显示 20 50 100
聚N-烷基丙烯酰胺类凝胶及其温敏特性 被引量:33
1
作者 金曼蓉 吴长发 +2 位作者 张桂英 刘培毅 侯薇 《高分子学报》 SCIE EI CAS CSCD 北大核心 1995年第3期321-326,共6页
研制成功5种聚N-烷基丙烯酰胺类温敏凝胶:聚N-异丙基丙烯酰胺(PNIPA),聚N-异丙基丙烯酰胺+甲基丙烯酰胺(PNIPA/MAA),聚N,N-二乙基丙烯酰胺(PNDEA),聚N-正丙基丙烯酰胺(PNNPA),聚N... 研制成功5种聚N-烷基丙烯酰胺类温敏凝胶:聚N-异丙基丙烯酰胺(PNIPA),聚N-异丙基丙烯酰胺+甲基丙烯酰胺(PNIPA/MAA),聚N,N-二乙基丙烯酰胺(PNDEA),聚N-正丙基丙烯酰胺(PNNPA),聚N,N-二乙基丙烯酰胺+N-叔丁基丙烯酰胺(PNDEA/NTBA),并系统研究了这些凝胶的温敏相交特性.以聚N-异丙基丙烯酰胺(PNIPA)凝胶相交特性为基础的凝胶萃取过程对牛血清白蛋白和兰葡聚糖溶液的浓缩实验表明,凝胶萃取对于浓缩和制备贵重生化制品是很有效的. 展开更多
关键词 烷基内丙烯酰胺 凝胶 温敏性 萃取分离
下载PDF
终端区进场交通流广义跟驰行为与复杂相变分析 被引量:28
2
作者 张洪海 杨磊 +1 位作者 别翌荟 尹苏皖 《航空学报》 EI CAS CSCD 北大核心 2015年第3期949-961,共13页
空中交通流特性分析是空中交通流理论研究的重要内容,是空中交通管理的重要依据。基于终端区交通流混杂动力特征,采用模糊逻辑方法提出了航空器动态期望间隔控制策略,运用"刺激-反射"跟驰理论和局域先到先服务(FCFS)的原则建... 空中交通流特性分析是空中交通流理论研究的重要内容,是空中交通管理的重要依据。基于终端区交通流混杂动力特征,采用模糊逻辑方法提出了航空器动态期望间隔控制策略,运用"刺激-反射"跟驰理论和局域先到先服务(FCFS)的原则建立了终端区交通流广义跟驰模型,并基于NetLogo构建了终端区交通流多智能体仿真平台,结合广州白云机场(ZGGG)02R跑道进场实例,演析了终端区进场交通系统涌现行为,揭示了交通流的速度、密度和流量3个基本参数之间的相互关系,发掘了空中交通蕴含的自由态、畅行态、亚稳态、伪拥塞态和同步态等5个演变相态,剖析了不同交通组织、间隔标准和流控策略下交通流的相变规律。研究成果可为丰富完善空中交通流理论奠定部分基础,为科学管控空中交通提供重要基础支撑。 展开更多
关键词 空中交通管理 交通流 跟驰行为 特性参数 相变 终端区
原文传递
大型繁忙机场场面离场交通流拥堵特征分析 被引量:15
3
作者 杨磊 胡明华 +1 位作者 尹苏皖 张洪海 《航空学报》 EI CAS CSCD 北大核心 2016年第6期1921-1930,共10页
阐明机场场面交通流时空演变规律,揭示离场交通流拥堵机理是科学制定场面交通流管控策略的重要基础。采用元胞传输机理论,建立线性滑行道元胞、机坪发散/交叉元胞、汇聚元胞的交通流传输模型,并基于NetLogo系统动力学仿真平台,以广州白... 阐明机场场面交通流时空演变规律,揭示离场交通流拥堵机理是科学制定场面交通流管控策略的重要基础。采用元胞传输机理论,建立线性滑行道元胞、机坪发散/交叉元胞、汇聚元胞的交通流传输模型,并基于NetLogo系统动力学仿真平台,以广州白云国际机场为例验证了模型的有效性,进而推演分析了离场交通流基础相变特征及其影响机理。研究表明,场面离场交通流存在自由态、亚稳态、拥堵累积态和拥堵死锁态4种基础相态,指出调节与进场率相协调的推出率是有效控制离场交通流密度,缓解场面拥堵的重要手段。研究结果可为大型繁忙机场场面交通智能管控提供一定的理论基础和决策参考。 展开更多
关键词 机场 交通流 元胞传输机 NETLOGO 相变 空中交通管理
原文传递
Industrial Application of a Deep Purification Technology for Flue Gas Involving Phase-Transition Agglomeration and Dehumidification 被引量:12
4
作者 Jianmin Liu Fahua Zhu Xiuyuan Ma 《Engineering》 2018年第3期416-420,共5页
A moist plume forms when the flue gas emitted from wet desulfurization equipment exits into the ambi- ent air, resulting in a waste of water resources and visual pollution. In addition, sulfur trioxide (SO3), water ... A moist plume forms when the flue gas emitted from wet desulfurization equipment exits into the ambi- ent air, resulting in a waste of water resources and visual pollution. In addition, sulfur trioxide (SO3), water with dissolved salts, and particles in the wet flue gas form secondary pollution in the surrounding atmosphere. In this study, a deep purification technology for flue gas involving phase-transition agglom- eration and dehumidification (PAD) is proposed. This deep purification technology includes two technical routes: the integrated technology of phase-transition agglomeration and a wet electrostatic precipitator (PAW); and the integrated technology of phase-transition agglomeration and a mist eliminator (PAM). Industrial applications of PAW and PAM were carried out on 630 and 1000 MW coal-fired units, respectively. The results show that the average amount of recycled water obtained from wet flue gas by means of PAD is more than 4 g.(kg.℃)-1 Decreasing the wet flue gas temperature by 1.5-5.3 ℃ allows 5%-20% of the moisture in the flue gas to be recycled; therefore, this process could effectively save water resources and significantly reduce water vapor emissions. In addition, the moist plume is effectively elim- inated. With the use of this process, the ion concentration in droplets of flue gas is decreased by more than 65%, the SO3 removal efficiency from flue gas is greater than 75%, and the removal efficiency of par- ticulate matter is 92.53%. 展开更多
关键词 Moist plume phase-transition agglomeration DEHUMIDIFICATION Dissolved salts SO3 Particulate matter
下载PDF
前驱体物相转变对浆态床合成甲醇催化剂活性的影响 被引量:11
5
作者 李忠 郭启海 +3 位作者 张小兵 郑华艳 范辉 谢克昌 《高等学校化学学报》 SCIE EI CAS CSCD 北大核心 2009年第11期2215-2221,共7页
采用并流共沉淀法,通过考察老化温度,研究CuO/ZnO/A l2O3催化剂前驱体晶相及组成的变化对浆态床催化合成甲醇的反应活性的影响.结果表明,前驱体的物相转变对浆态床合成甲醇活性影响显著,单斜晶系锌孔雀石(Cu,Zn)2CO3(OH)2和斜方晶系绿... 采用并流共沉淀法,通过考察老化温度,研究CuO/ZnO/A l2O3催化剂前驱体晶相及组成的变化对浆态床催化合成甲醇的反应活性的影响.结果表明,前驱体的物相转变对浆态床合成甲醇活性影响显著,单斜晶系锌孔雀石(Cu,Zn)2CO3(OH)2和斜方晶系绿铜锌矿(Cu,Zn)5(CO3)2(OH)6晶体是产生高活性催化剂的主要物相.随着Cu2+/Zn2+进入Zn5(CO3)2(OH)6/Cu2CO3(OH)2晶格,离子同晶取代量增加,催化剂前驱体中形成了固定铜锌比的锌孔雀石和绿铜锌矿物相.焙烧后催化剂比表面积增大,CuO-ZnO固溶体协同作用加强,浆态床催化合成甲醇的活性提高. 展开更多
关键词 CuO/ZnO/Al2O3 催化剂 前驱体 物相转变 浆态床 甲醇合成
下载PDF
冻土中冻结锋面移动的影响因素 被引量:7
6
作者 吴礼舟 许强 黄润秋 《湖南科技大学学报(自然科学版)》 CAS 北大核心 2010年第4期51-53,共3页
冻结中的固液相变过程是冻土冻胀研究的一个基础.根据热传导理论,对半无限土体的热传导模型进行分析,将冻土分为已冻土和未冻土两个区,对固液相变以及冻结锋面的移动进行研究,探索影响冻土温度分布的因素,研究含水量、干密度和土的类型... 冻结中的固液相变过程是冻土冻胀研究的一个基础.根据热传导理论,对半无限土体的热传导模型进行分析,将冻土分为已冻土和未冻土两个区,对固液相变以及冻结锋面的移动进行研究,探索影响冻土温度分布的因素,研究含水量、干密度和土的类型对温度场及冻结锋面移动速率的作用.同时根据冻结锋面的移动规律,建立了冻胀量随时间的关系式.最后,通过算例,结果表明含水量和干密度对冻土温度分布产生不小的影响,尤其是含水量,含水量越大,冻结锋面移动越快.含水量对冻土温度分布的影响最大,其次是干密度,土类型的影响最小.分析显示冻胀过程中温度与冻胀的影响作用明显,含水量是一重要因素,对冻胀量的影响是非常显著的. 展开更多
关键词 冻土 温度场 固液相变 冻结锋面 冻胀量 含水量
原文传递
Opinion Spreading with Mobility on Scale-Free Networks 被引量:6
7
作者 郭强 刘建国 +3 位作者 汪秉宏 周涛 陈兴文 姚玉华 《Chinese Physics Letters》 SCIE CAS CSCD 2008年第2期773-775,共3页
A continuum opinion dynamic model is presented based on two rules. The first one considers the mobilities of the individuals, the second one supposes that the individuals update their opinions independently. The resul... A continuum opinion dynamic model is presented based on two rules. The first one considers the mobilities of the individuals, the second one supposes that the individuals update their opinions independently. The results of the model indicate that the bounded confidence εc, separating consensus and incoherent states, of a scale-free network is much smaller than the one of a lattice. If the system can reach the consensus state, the sum of all individuals' opinion change Oc(t) quickly decreases in an exponential form, while if it reaches the incoherent state finally, Oc(t) decreases slowly and has the punctuated equilibrium characteristic. 展开更多
关键词 SCIENCE BASIC RESEARCH SMALL-WORLD NETWORKS COMPLEX NETWORKS phase-transition SZNAJD MODEL DYNAMICS OPTIMIZATION ROBUSTNESS EVOLUTION
下载PDF
两种相变型多功能纳米粒的制备及体外特性比较 被引量:7
8
作者 唐琴 朱深银 +5 位作者 常淑芳 崔健毓 田中华 孙江川 王志刚 邱峰 《中国介入影像与治疗学》 CSCD 北大核心 2016年第10期636-641,共6页
目的制备包裹吲哚菁绿(ICG)及不同相变材料[全氟正戊烷(PFP)或全氟己烷(PFH)]的两种相变型多功能纳米粒,比较其理化性质、稳定性及体外相变特性。方法采用改良的双乳化法制备包裹ICG及液态PFP或PFH的乳酸-羟基乙酸(PLGA)纳米粒(分别称为... 目的制备包裹吲哚菁绿(ICG)及不同相变材料[全氟正戊烷(PFP)或全氟己烷(PFH)]的两种相变型多功能纳米粒,比较其理化性质、稳定性及体外相变特性。方法采用改良的双乳化法制备包裹ICG及液态PFP或PFH的乳酸-羟基乙酸(PLGA)纳米粒(分别称为IPNPs、IHNPs),比较两者的一般特性、稳定性及热致相变、光致相变、声致相变和光声成像能力,采用MTT法检测光致相变所需能量的细胞毒性。结果IPNPs及IHNPs粒径分别为(490.53±36.96)nm及(512.23±38.52)nm,电位分别为(-14.40±1.40)mV及(-13.97±1.61)mV,二者差异无统计学意义(P均>0.05);二者形态、吸收光谱也均无明显差异,于37℃储存24h均较稳定;IPNPs热致相变、光致相变及声致相变所需能量均低于IHNPs,且IPNPs光声及超声成像增强能力高于IHNPs。经能使IPNPs及IHNPs发生相变的激光能量辐照后,MH7A细胞存活率分别为(95.34±7.96)%,(54.92±6.11)%,二者差异有统计学意义(P<0.05)。结论 IPNPs是更适于诊疗一体化应用的多功能纳米粒。 展开更多
关键词 多功能纳米粒 氟碳化合物 相变 成像
下载PDF
Cellular automaton model considering headway-distance effect 被引量:4
9
作者 胡守信 高坤 +1 位作者 汪秉宏 陆玉凤 《Chinese Physics B》 SCIE EI CAS CSCD 2008年第5期1863-1868,共6页
This paper presents a cellular automaton model for single-lane traffic flow. On the basis of the Nagel-Schreckenberg (NS) model, it further considers the effect of headway-distance between two successive cars on the... This paper presents a cellular automaton model for single-lane traffic flow. On the basis of the Nagel-Schreckenberg (NS) model, it further considers the effect of headway-distance between two successive cars on the randomization of the latter one. In numerical simulations, this model shows the following characteristics. (1) With a simple structure, this model succeeds in reproducing the hysteresis effect, which is absent in the NS model. (2) Compared with the slow-tostart models, this model exhibits a local fundamental diagram which is more consistent to empirical observations. (3) This model has much higher efficiency in dissolving congestions compared with the so-called NS model with velocitydependent randomization (VDR model). (4) This model is more robust when facing traffic obstructions. It can resist much longer shock times and has much shorter relaxation times on the other hand. To summarize, compared with the existing models, this model is quite simple in structure, but has good characteristics. 展开更多
关键词 traffic flow headway-distance phase-transition fundamental diagram
下载PDF
Physical Nanoindentation: From Penetration Resistance to Phase-Transition Energies 被引量:3
10
作者 Gerd Kaupp 《Advances in Materials Physics and Chemistry》 2019年第6期103-122,共20页
-The ISO standard 14577 is challenged for its violation of the energy law, its wrong relation of normal force FN with impression depth h, and for its iterative treatments. The solution of this dilemma is the use of sa... -The ISO standard 14577 is challenged for its violation of the energy law, its wrong relation of normal force FN with impression depth h, and for its iterative treatments. The solution of this dilemma is the use of sacrosanct simplest calculation rules for the loading parabola (now FN = kh3/2) giving straight lines for cones, pyramids and wedges. They provide the physical penetration resistance hardness k with dimension [Nm-3/2] and allow for non-iterative calculations with closed formulas, using simple undeniable calculation rules. The physically correct FN versus h3/2 plot is universally valid. It separates out the most common surface effects and reveals gradients. It provides unmatched precision, including reliability checks of experimental data. Regression analysis of FN versus h3/2 plots reveals eventual unsteadiness kink phase-transition onset with the transition-energy. This is shown for all kinds of solid materials, including salts, silicon, organics, polymers, composites, and superalloys. Exothermic and endothermic single and consecutive multiple phase-transitions with their surface dependence are distinguished and the results compared in 5 Tables. The sharp phase-transition onsets and the transition energies provide unprecedented most important materials’ characteristics that are indispensable for safety reasons. ISO ASTM is thus urged to thoroughly revise ISO 14577 and to work out new standards for the mechanically (also thermally) stressed materials. For example, the constancy of the first phase-transition parameters must be controlled, and materials must only be admitted for maximal forces well below the first phase-transition onset. Such onset loads can now be easily calculated. The nevertheless repeated oppositions against the physical analysis of indentations rest on incredibly poor knowledge of basic mathematics, errors that are uncovered. The safety aspects caused by the present unphysical materials’ parameters are discussed. 展开更多
关键词 ENERGY Law VIOLATION ISO-14577 Challenge Calculation Rules for Indentations phase-transition ONSET and ENERGY Multiple transitions Safety Problems
下载PDF
Liquid-Liquid Structure Transition in Metallic Melts: Experimental Evidence by Viscosity Measurement 被引量:3
11
作者 王玉青 武玉琴 边秀房 《Chinese Physics Letters》 SCIE CAS CSCD 2007年第7期2028-2031,共4页
Temperature dependence of viscosity for more than ten kinds of metallic melts is analysed based on viscosity measurements. An obvious turning point is observed on the Arrhenius curves. Since viscosity is one of the ph... Temperature dependence of viscosity for more than ten kinds of metallic melts is analysed based on viscosity measurements. An obvious turning point is observed on the Arrhenius curves. Since viscosity is one of the physical properties sensitive to structure, its discontinuous change with temperature reveals the possible liquidliquid structure transition in the metallic melts. Furthermore, an integrated liquid structure transition diagram of the Sn-Bi system is presented. The universality of liquid-liquid structure transition is also discussed simply. 展开更多
关键词 phase-transition HIGH-DENSITY WATER ORDER
下载PDF
MEMS-actuated terahertz metamaterials driven by phase-transition materials
12
作者 Zhixiang Huang Weipeng Wu +5 位作者 Eric Herrmann Ke Ma Zizwe A.Chase Thomas A.Searles M.Benjamin Jungfleisch Xi Wang 《Frontiers of Optoelectronics》 EI CSCD 2024年第2期23-32,共10页
The non-ionizing and penetrative characteristics of terahertz(THz)radiation have recently led to its adoption across a variety of applications.To effectively utilize THz radiation,modulators with precise control are i... The non-ionizing and penetrative characteristics of terahertz(THz)radiation have recently led to its adoption across a variety of applications.To effectively utilize THz radiation,modulators with precise control are imperative.While most recent THz modulators manipulate the amplitude,frequency,or phase of incident THz radiation,considerably less progress has been made toward THz polarization modulation.Conventional methods for polarization control suffer from high driving voltages,restricted modulation depth,and narrow band capabilities,which hinder device performance and broader applications.Consequently,an ideal THz modulator that offers high modulation depth along with ease of processing and operation is required.In this paper,we propose and realize a THz metamaterial comprised of microelectromechanical systems(MEMS)actuated by the phase-transition material vanadium dioxide(VO_(2)).Simulation and experimental results of the three-dimensional metamaterials show that by leveraging the unique phase-transition attributes of VO_(2),our THz polarization modulator offers notable advancements over existing designs,including broad operation spectrum,high modulation depth,ease of fabrication,ease of operation condition,and continuous modulation capabilities.These enhanced features make the system a viable candidate for a range of THz applications,including telecommunications,imaging,and radar systems. 展开更多
关键词 METAMATERIALS MEMS THZ VO_(2) phase-transition material
原文传递
Real and Fitted Spherical Indentations 被引量:2
13
作者 Gerd Kaupp 《Advances in Materials Physics and Chemistry》 2020年第10期207-229,共23页
Spherical indentations that rely on original date are analyzed with the physically correct mathematical formula and its integration that take into account the radius over depth changes upon penetration. Linear plots, ... Spherical indentations that rely on original date are analyzed with the physically correct mathematical formula and its integration that take into account the radius over depth changes upon penetration. Linear plots, phase-transition onsets, energies, and pressures are algebraically obtained for germanium, zinc-oxide and gallium-nitride. There are low pressure phase-transitions that correspond to, or are not resolved by hydrostatic anvil onset pressures. This enables the attribution of polymorph structures, by comparing with known structures from pulsed laser deposition or molecular beam epitaxy and twinning. The spherical indentation is the easiest way for the synthesis and further characterization of polymorphs, now available in pure form under diamond calotte and in contact with their corresponding less dense polymorph. The unprecedented results and new possibilities require loading curves from experimental data. These are now easily distinguished from data that are “fitted” to make them concur with widely used unphysical Johnson’s formula for spheres (“<span style="white-space:nowrap;"><em>P</em> = (4/3)<em>h</em><sup>3/2</sup><em>R</em><sup>1/2</sup><em>E</em><sup><span style="white-space:nowrap;">&#8727;</span></sup></span>”) not taking care of the <em>R/h</em> variation. Its challenge is indispensable, because its use involves “fitting equations” for making the data concur. These faked reports (no “experimental” data) provide dangerous false moduli and theories. The fitted spherical indentation reports with radii ranging from 4 to 250 μm are identified for PDMS, GaAs, Al, Si, SiC, MgO, and Steel. The detailed analysis reveals characteristic features. 展开更多
关键词 Spherical Indentations Correct Formula phase-transition Onset Pressure False Johnson Formula Detection of Data Fittings
下载PDF
载Fe_3O_4及液态氟碳高分子纳米粒的制备及其体外相变与双模态显影 被引量:3
14
作者 赵雅静 王志刚 +2 位作者 冉海涛 郑元义 王冬 《中国医学影像技术》 CSCD 北大核心 2015年第4期483-487,共5页
目的探讨载Fe3O4同时包裹液态全氟己烷(PFH)的高分子造影剂的制备并评价其体外相变与双模态显影能力。方法采用乳化法制备可相变的磁性造影剂,检测其粒径、电荷、表面形态及内部结构,对不同浓度的纳米粒溶液行MR扫描并用原子吸收光谱... 目的探讨载Fe3O4同时包裹液态全氟己烷(PFH)的高分子造影剂的制备并评价其体外相变与双模态显影能力。方法采用乳化法制备可相变的磁性造影剂,检测其粒径、电荷、表面形态及内部结构,对不同浓度的纳米粒溶液行MR扫描并用原子吸收光谱法测量各样品中Fe浓度;用加热法激发纳米粒相变,显微镜观察相变后产生的微泡,在造影模式下观察造影剂相变后增强超声显影能力。结果成功制备出可相变磁性Fe3O4/聚乳酸/羟基乙酸[PLGA]/PFH纳米粒。体外MR显像表明其能明显降低T2*WI信号强度。当加热5min温度升高至55~65℃,纳米粒相变产生微泡,且可明显增强超声显影。结论制备的可相变磁性造影剂能明显降低T2*WI信号强度,加热可发生相变,增强超声显影,可为多模态成像技术的发展奠定一定的实验基础。 展开更多
关键词 磁共振成像 相变 纳米粒 超声检查 造影剂
下载PDF
Sn_(62)Pb_(36)Ag_2焊料的微结构粗化 被引量:1
15
作者 叶润清 罗乐 《功能材料与器件学报》 CAS CSCD 1999年第4期327-331,共5页
在焊料的浸镀及表面贴装过程中,发现Sn62Pb36Ag2 焊料的微结构粗化,并且可焊性很差。金相研究发现:Sn62Pb36Ag2 合金焊料在熔体状态保温较长时间以及冷却速率较慢,均会促进焊料的微结构粗化。其机理为焊料中... 在焊料的浸镀及表面贴装过程中,发现Sn62Pb36Ag2 焊料的微结构粗化,并且可焊性很差。金相研究发现:Sn62Pb36Ag2 合金焊料在熔体状态保温较长时间以及冷却速率较慢,均会促进焊料的微结构粗化。其机理为焊料中生成较多的Ag3Sn 和Cu6Sn5 等金属间化合物,消耗了合金焊料中的部分锡,使焊料组成偏离共晶点,从而最终导致富铅相偏析。组成偏离及微结构粗化致使焊料在铜上的润湿性降低,并影响焊料的可焊性。 展开更多
关键词 SnPbAg焊料 焊接 相变 微结构
原文传递
Cluster-size dependent randomization traffic flow model 被引量:1
16
作者 高坤 汪秉宏 +1 位作者 付传技 陆玉凤 《Chinese Physics B》 SCIE EI CAS CSCD 2007年第11期3483-3493,共11页
In order to exhibit the meta-stable states, several slow-to-start rules have been investigated as modification to Nagel-Schreckenberg (NS) model. These models can reproduce some realistic phenomena which are absent ... In order to exhibit the meta-stable states, several slow-to-start rules have been investigated as modification to Nagel-Schreckenberg (NS) model. These models can reproduce some realistic phenomena which are absent in the original NS model. But in these models, the size of cluster is still not considered as a useful parameter. In real traffic, the slow-to-start motion of a standing vehicle often depends on the degree of congestion which can be measured by the clusters' size. According to this idea, we propose a cluster-size dependent slow-to-start model based on the speed- dependent slow-to-start rule (VDR) model. It gives expected results through simulations. Comparing with the VDR model, our new model has a better traffic efficiency and shows richer complex characters. 展开更多
关键词 traffic flow slow-to-start JAM phase-transition hysteresis effect
下载PDF
Fluctuation of the Download Network 被引量:1
17
作者 韩定定 刘锦高 马余刚 《Chinese Physics Letters》 SCIE CAS CSCD 2008年第2期765-768,共4页
The scaling behaviour of fluctuation for a download network we investigated a few years ago based upon Zhang's Econophysics web page is presented. A power law scaling, namely σ~〈f〉^α exists between the dispersio... The scaling behaviour of fluctuation for a download network we investigated a few years ago based upon Zhang's Econophysics web page is presented. A power law scaling, namely σ~〈f〉^α exists between the dispersion a and average flux 〈f〉 of the download rates. The fluctuation exponent α is neither 1/2 nor 1, which were claimed as two universal fluctuation classes in previous publication, while it varies from 1/2 to 1 with the time window in which the download data are accumulated. The crossover behaviour of fluctuation exponents can be qualitatively understood by the external driving fluctuation model for a small-size system or a network traffic model which suggests congestion as the origin. 展开更多
关键词 phase-transition ION COLLISIONS
下载PDF
Finite Element Method on Shape Memory Alloy Structure and Its Applications 被引量:1
18
作者 Bo Zhou Zetian Kang +1 位作者 Zhiyong Wang Shifeng Xue 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2019年第5期125-135,共11页
It is significant to numerically investigate thermo-mechanical behaviors of shape memory alloy(SMA)structures undergoing large and uneven deformation for they are used in many engineering fields to meet special requir... It is significant to numerically investigate thermo-mechanical behaviors of shape memory alloy(SMA)structures undergoing large and uneven deformation for they are used in many engineering fields to meet special requirements To solve the problems of convergence in the numerical simulation on thermo-mechanical behaviors of SMA structures by universal finite element software.This work suppose a finite element method to simulate the super-elasticity and shape memory effect in the SMA structure undergoing large and uneven deformation.Two scalars,named by phase-transition modulus and equivalent stiffness,are defined to make it easy to establish and implement the finite element method for a SMA structure.An incremental constitutive equation is developed to formulate the relationship of stress,strain and temperature in a SMA material based on phase-transition modulus and equivalent stiffness.A phase-transition modulus equation is derived to describe the relationship of phase-transition modulus,stress and temperature in a SMA material during the processes of martensitic phase transition and martensitic inverse phase transition.A finite element equation is established to express the incremental relationship of nodal displacement,external force and temperature change in a finite element discrete structure of SMA.The incremental constitutive equation,phase-transition modulus equation and finite element equation compose the supposed finite element method which simulate the thermo-mechanical behaviors of a SMA structure.Two SMA structures,which undergo large and uneven deformation,are numerically simulated by the supposed finite element method.Results of numerical simulation show that the supposed finite element method can effectively simulate the super-elasticity and shape memory effect of a SMA structure undergoing large and uneven deformation,and is suitable to act as an effective computational tool for the wide applications based on the SMA materials. 展开更多
关键词 Shape memory alloy Incremental CONSTITUTIVE EQUATION Finite element EQUATION phase-transition MODULUS APPLICATIONS
下载PDF
基于时段及过渡区域的KICA间歇过程监测方法 被引量:2
19
作者 谢晓庆 王建林 +1 位作者 赵利强 于涛 《计算机与应用化学》 CAS CSCD 北大核心 2014年第10期1250-1256,共7页
针对间歇过程时段的切换存在过渡区域,同时,间歇过程数据有着强非线性的特点,提出一种基于时段及过渡区域的KICA间歇过程监测方法。该方法基于MPCA及k-means聚类算法对间歇过程进行子时段划分,并基于第一主元贡献率差值识别时段间的过... 针对间歇过程时段的切换存在过渡区域,同时,间歇过程数据有着强非线性的特点,提出一种基于时段及过渡区域的KICA间歇过程监测方法。该方法基于MPCA及k-means聚类算法对间歇过程进行子时段划分,并基于第一主元贡献率差值识别时段间的过渡区域,在此基础上,对稳定时段建立统一KICA监测模型,而过渡区域针对各时刻滑动窗口进行KICA建模监测。将该方法应用于青霉素发酵过程在线监测,实验结果表明,相比sub..PCA监测方法,本文基于时段及过渡区域的KICA监测方法能更及时、准确的检测到过渡区域的异常。 展开更多
关键词 核独立成分分析 主成分分析 时段及过渡区域 间歇过程 在线监测
原文传递
异多核金属三键(W≡C)有机化合物的红外和拉曼光谱研究 被引量:2
20
作者 许振华 A Mayr 《光谱学与光谱分析》 SCIE EI CAS CSCD 北大核心 2000年第5期702-703,共2页
五种 (Ⅰ ,Ⅱ ,Ⅲ ,Ⅳ ,Ⅴ )异多核金属钨三键W≡C金属有机化合物的红外和拉曼光谱研究表明 ,由于N和P原子为强的σ 给予体和弱的π 接受体 ,在金属原子上分别引入含N或P的功能基团 (TMEDA或DPPE)将降低金属三键 (W≡C)的键强度 ,W≡C... 五种 (Ⅰ ,Ⅱ ,Ⅲ ,Ⅳ ,Ⅴ )异多核金属钨三键W≡C金属有机化合物的红外和拉曼光谱研究表明 ,由于N和P原子为强的σ 给予体和弱的π 接受体 ,在金属原子上分别引入含N或P的功能基团 (TMEDA或DPPE)将降低金属三键 (W≡C)的键强度 ,W≡C伸缩振动νW≡C 波数下降。化合物Ⅲ的压力调制红外和拉曼光谱显示 ,在 2 0kbar压力附近存在一压力诱导相变。低压相区高的压力灵敏度dv/dp(0 75cm-1·kbar-1)和高压相区很低的压力灵敏度 (0 0 8cm-1·kbar-1)指出 ,对W≡C键存在两种压力效应 ,一种是正常的 ,W≡C键强度随压力增加而增强 ,伸缩振动 νW≡C 波数增加 ;另一种是随着压力增加 ,从W到COπ 轨道反馈增加 ,导致W≡C键强度减弱 ,伸缩振动νW≡C 波数下降。 展开更多
关键词 红外光谱 拉曼光谱 异多核金属三键有机化合物
下载PDF
上一页 1 2 242 下一页 到第
使用帮助 返回顶部