影响复摆颚式破碎机传动质量的肘板纯滚动力学条件

通过分析传力角与动颚摆动角、传力角与机构压力角、机架与肘板摩擦角的关系,推导复摆颚式破碎机主要传递运动部件——肘板作纯滚动无滑动的力学条件。结果表明,传力角与压力角互为余角,即α+δ=90°,肘板机构纯滚动而无滑动的条件是δ≤φ,保证肘板纯滚动而无滑动的条件与肘板的摆角无关。

直齿轮纯扭转模型弹性动力学分析

为研究非线性因素对直齿轮纯扭转模型弹性动力学的影响,根据达朗贝尔原理,采用微位移思想,建立4自由度直齿轮纯扭转动力学模型.首先,通过Runge-Kutta法结合时间离散法求解系统在齿轮啮合误差、时变啮合刚度和啮合间隙等非线性因素影响下的时变方程,得到系统振动的响应以及对应频谱图.其次,结合非线性特性分析理论,通过改变系统的啮合刚度、激励频率和齿侧间隙,获得系统动态响应的全局分岔图和最大Lyapunov指数.然后,综合运用时间历程曲线、相空间轨线、Poincáre映射图和功率谱,定量和定性分析系统的周期运动、拟周期运动和混沌运动.最后,考虑非线性因素耦合作用对系统的影响,为齿轮传动系统的非线性特性分析提供一套较为完整的方法.

钢管自应力混凝土构件纯弯力学性能研究

采用ABAQUS有限元软件计算分析了钢管自应力混凝土纯弯构件的力学性能,并作了试验验证,在此基础上,分析了钢管自应力混凝土纯弯构件受力过程中的弯矩-挠度关系以及钢管和混凝土间的相互作用。讨论了在初始自应力影响下,钢管自应力混凝土的力学性能。结果表明,在相同条件下,钢管自应力混凝土比普通钢管混凝土的纵向应力分布更加均匀,弹性工作阶段有所增长,抗弯承载力也得到了提高,但当自应力水平达到某一数值后,抗弯承载力有一定程度的下降。

石屑代替河砂配置预应力混凝土梁纯弯力学性能试验

混凝土具有能源消耗高、能效低等缺点,特别是细骨料作为其重要组成部分,主要采用自然界中的天然砂。在某些工程中,由于种种条件限制无法取得符合要求的河砂。结合工程,探讨了用石屑代替河砂配置预应力混凝土的可行性,并进行了力学试验研究。通过与普通预应力混凝土受力性能进行对比,得出高强石屑混凝在预应力构件中具有良好的受力性能。

几种跳频码的混沌动力学特性及预测分析

利用动力系统方法研究了几种跳频码 (m序列 ,RS序列 ,非线性序列及混沌序列 )的动力学特性 (相关维数与最大李雅普诺夫指数 ) ,结果表明了跳频码表现出混沌的特征。最后根据遗传算法确定前馈神经网络的结构 ,并利用该神经网络模型对这几种序列做了预测分析。实验结果表明 ,该模型能成功地预测跳频码 。

RV减速器5自由度纯扭转模型非线性特性分析

为了研究旋转向量(RV)减速器中非线性因素对系统动态特性的影响,以集中质量块代替各部件,以弹簧连接表述各部件间的关系,采用达朗贝尔原理和微位移思想,建立简化的5自由度纯扭转RV减速器动力学模型.对模型动力学方程进行坐标变换和无量纲化处理,并采用结合时间离散法的龙格-库塔法求解此非线性时变方程,得到系统在启动和稳定过程中各部件的动态响应曲线以及整体传动误差和对应频谱图.研究传动过程中多种非线性因素对系统动态特性的影响,并搭建RV减速器动力性能综合检测实验平台,得到在输入轴转速为10 r/min,行星架负载为30 N·m情况下的系统传动误差和对应频谱图.实验结果与理论结果较为一致,说明纯扭转模型建立和求解正确,为RV减速器动力学发展提供一定理论基础.

Preparation of high purity ruthenium nitrosyl nitrate from spent Ru-Zn/ZrO_(2)catalyst

Preparation of high purity ruthenium nitrosyl nitrate using spent Ru-Zn/ZrO_(2)catalyst was studied,including melting and leaching to obtain potassium ruthenate solution,reduction,dissolving,concentrating and drying to obtain ruthenium trichloride,nitrosation and hydrolysis to obtain ruthenium nitrosyl hydroxide,removing of K^(+)and Cl^(-),and neutralization with nitric acid.The effects of temperature,concentration,time and pH on the yield and purity of intermediates and final product were studied,and the optimum process conditions were obtained.The yield of ruthenium nitrosyl nitrate is 92%,the content of ruthenium in high purity product is 32.16%,and the content of Cl^(-)and K^(+)are much less than 0.005%.The reaction kinetics of ruthenium nitrosyl chloride to ruthenium nitrosyl hydroxide was studied.The reaction orders of Ru(NO)Cl_(3)at 40,55 and 70℃are 0.39,0.37 and 0.39,respectively,while those of KOH are 0.16,0.15 and 0.17,respectively.The activation energy is-2.33 k J/mol.

番茄酱生产线自动除杂选果装置的研制及试验

番茄酱厂依靠大量人力捡拾清除杂质,费时费工,效率低,食品卫生也难以保障。研制可替代人工清理杂草及杂质的自动除杂选果装置,主要由支架、滚筒、防滑花纹传送带、侧挡板、挡杂板、电动机、减速机、光电传感器及自控系统构成。通过试验分析,当除杂选果机工作角度在25°~45°时,装置选果率和除杂率高,且番茄滚落速度快,适合连续处理大量含杂质原料,几乎可以达到100%的果料与非果料杂质的分离。

基于PMCM模型的裂缝滑移与宽度计算

通过介绍纯力学裂缝模型,得到一种可以计算钢筋混凝土构件的宽度与滑移的方法,分析了纯力学裂缝模型的相容关系、平衡关系、本构关系以及裂缝处刚度削减方法,同时确定纯力学裂缝模型参数值,得到与实验值更为接近的数值模拟值。

对我国优秀投篮手单手原地跳投动作结构持征的分析

一、前言单手原地跳投是投篮技术教学与训练的核心内容,它既是一项应用性技术,又是掌握多种形式跳投技术的基础。然而,长期以来人们对投篮技术的研究大部分是属于定性方面的分析和论述,少数的定量分析又多是局限于对球出手后某些抛物体运动规律的纯力学研究上,

降低炮孔压力是减少中硬以下岩石爆破成本的一种手段

按照纯力学的观点,每个炸药包都会产生一种炮孔峰值压力(p_b),这种压力正好不能压碎(粉碎或塑性变形)周围岩石。在p_b超出临界值的地方,一些炸药能量直接消耗在压碎周围的岩石上。随着岩石动态压缩破裂应变(ε_c)的减小,p_b也就减小。

Mechanical responses, texture and microstructural evolution of high purity aluminum deformed by equal channel angular pressing

Ultrafine-grained(UFG) high purity aluminum exhibits a variety of attractive mechanical properties and special deformation behavior. Equal channel angular pressing(ECAP) process can be used to easily and effectively refine metals. The microstructure and microtexture evolutions and grain boundary characteristics of the high purity aluminum(99.998%) processed by ECAP at room temperature are investigated by means of TEM and EBSD. The results indicate that the shear deformation resistance increases with repeated EACP passes, and equiaxed grains with an average size of 0.9 μm in diameter are formed after five passes. Although the orientations distribution of grains tends to evolve toward random orientations, and microtextures(80°, 35°, 0°),(40°, 75°, 45°) and(0°, 85°, 45°) peak in the sample after five passes. The grain boundaries in UFG aluminum are high-angle geometrically necessary boundaries. It is suggested that the continuous dynamic recrystallization is responsible for the formation of ultrafine grains in high purity aluminum. Microstructure evolution in the high purity aluminum during ECAP is proposed.

Effect of refining processes on inclusions and mechanical properties of cast Al-2Li-2Cu-0.2Zr alloy

The effect of different refining processes on inclusions and mechanical properties of cast Al-2Li-2Cu-0.2Zr alloy was investigated, including two-stage hexachloroethane (C2Cl6) refining process, two-stage rotating gas bubbling refining process and two-stage composite refining process. It was found that the two-stage composite refining process, which combined C2Cl6 and rotating gas bubbling, can significantly improve the melt purity and mechanical properties of cast Al-2Li-2Cu-0.2Zr alloy. Compared to the unrefined alloy, the volume fraction of gas porosity defects and slag inclusions decreased from 1.47% to 0.12%, and the yield strength, ultimate tensile strength and elongation of as-quenched alloy increased from 113 MPa,179 MPa and 3.9% to 142 MPa, 293 MPa and 18.1%, respectively. C2Cl6 was first utilized to degas and remove large size slag inclusions before lithium addition, and then the rotating gas bubbling was utilized to do the further degassing and remove the suspended fine inclusions after lithium addition. The two-stage composite refining process can take advantage of two methods and get the remarkable refining effect.

基于气温的浮冰侧向融化速率参数化方案实验研究

为定量探究影响冰层侧向融化的主导因素,并简化冰层侧向融化速率参数化方案,在实验室模拟了无风、静水、无辐射、纯热力学条件下纯水冰的融化过程,测量了冰层的侧向融化量,并记录了融化期间实验室气温、冰面皮温、水温及冰温等要素。观测结果表明,无辐射纯热力学条件下冰层侧向融化整体较均匀,侧向上层和下层融化速率相对中间层较快;相关性分析结果表明,气温与水温、冰温、冰面皮温之间都有很好的线性相关;信息流结果表明,气温是影响冰层侧向融化的最主要因素;最后通过拟合建立了用气温表征冰层侧向融化速率的参数化方案,并与前人的方案进行了比较,结果显示本文参数化方案模拟效果较好,所得标准偏差最小,为0.08 mm/h,达到了简化参数的目的。

Graphdiyne as Hydrogen Purification Membrane

The permselectivity of H2/O2, H2/N2, H2/CO, and H2/CH4 mixtures passing a graphdiyne membrane is studied by molecular dynamics simulations. At pressure range of 0.047-4.5 GPa, H2 can pass the graphdiyen membrane quickly, while all the O2, N2, CO, and CH4 molecules are blocked. At pressure of 47 kPa, the hydrogen flow is 7 mol/m^2s. With increase of pressure, the hydrogen flow goes up, and reaches maximum of 6×10^5 mol/m^2s at 1.5 GPa. Compared to other known membranes, graphdiyne can be used for means of hydrogen purification with the best balance of high selectivity and high permeance.

Effect of annealing temperature on microstructure and mechanical properties of cold-rolled commercially pure titanium sheets

The strength of traditional commercially pure titanium(CP-Ti) alloys often fails to meet the demand of structural materials. In order to enhance their mechanical properties, the cold-rolled CP-Ti alloys were annealed at different temperatures, and the recrystallization behavior and texture evolution were investigated. It was found that the bimodal microstructure(equiaxed and elongated grains) was formed after partial recrystallization, and the corresponding sample exhibited an excellent combination of ultimate tensile strength(702 MPa) and total elongation(36.4%). The recrystallization nucleation of CP-Ti sheets occurred preferentially in the high strain and the high-angle grain boundaries(HAGBs) regions. Meanwhile, the internal misorientations of the deformed heterogeneous grains increased and transformed into HAGBs, which further promoted the recrystallization nucleation. The main recrystallization texture was basal TD-split texture transformed from cold-rolled basal RD-split texture, and the oriented nucleation played a dominated role during recrystallization.

Microstructure and thermal stability of sintered pure tungsten processed by multiple direction compression

Multiple direction compression(MDC)was conducted on sintered pure tungsten(99.9%,mass fraction)with different reductions at 1423 K.The microstructure,microhardness and thermal stability of the MDC-processed samples were studied by X-ray diffraction(XRD),electron backscattered diffraction(EBSD)and differential scanning calorimetry(DSC)compared with those of the initial sintered tungsten.The results show that the dislocation density increases significantly with the reduction of MDC,ranging from 3.08×1014 m-2 for the initial sintered tungsten to 8.08×1014 m-2 for the tungsten after MDC with the reduction of 50%.The average grain size decreases from 83.8 to 14.7μm and the microhardness value increases from HV0.2 417 to HV0.2 521.The recrystallization temperature for the tungsten samples processed by MDC is approximately constant at around 1600 K.The MDC of sintered tungsten results in a decrease of grain size concurrent with an increase of uniformly distributed nucleation sites,which leads to the improvement of the thermal stability.

纯钛板力学性能与其影响因素的数学关系研究

通过对纯钛板力学性能的长期研究,确定了其与坯料化学成分及热处理工艺参数的数学关系,并且提出了可以根据铸锭化学成分和退火温度来推测钛板性能的算法,可以推算退火后的强度和延伸率,从而为生产工艺的合理制定提供了指导,确保钛板性能可以满足相关标准和合同要求。

Evolution of Cooperation in Public Goods Games

We investigate the evolution of cooperation with evolutionary public goods games based on finite populations, where four pure strategies： cooperators, defectors, punishers and loners who are unwilling to participate are considered. By adopting approximate best response dynamics, we show that the magnitude of rationality not only quantitatively explains the experiment results in [Nature （London） 425 （2003） 390], but also it will heavily influence the evolution of cooperation. Compared with previous results of infinite populations, which result in two equilibriums, we show that there merely exists a special equilibrium cooperation. In addition, we characterize that loner＇s and the relevant high value of bounded rationality will sustain payoff plays an active role in the maintenance of cooperation, which will only be warranted for the low and moderate values of loner＇s payoff. It thus indicates the effects of rationality and loner＇s payoff will influence the cooperation. Finally, we highlight the important result that the introduction of voluntary participation and punishment will facilitate cooperation greatly.

基于稳定气流法对莱氏现象的探究

本文利用稳定气流来模拟液滴下蒸汽层的方法,实现了莱顿弗罗斯特现象。对不同黏度的液滴,观察了其稳定状态、不规则振动、星形振荡和液滴的破裂(烟囱现象:指液体下方的气泡上涌,突破液滴的中心,导致液滴破碎的现象)。通过实验数据分析总结,给出了液滴体积与气体流速的关系,以及不同黏滞系数液滴对气流流速的影响。同时,由计算机软件建立模型,模拟了实验过程。通过实验可以发现,莱顿弗罗斯特现象的产生只依赖于纯流体动力学机制,而与热效应无关。