Optimization of structural parameters for spatial flexible redundant manipulators with maximum ratio of load to mass

Optimization of structural parameters aimed at improving the load carrying capacity of spatial flexible redundant manipulators is presented in this paper. In order to increase the ratio of load to mass of robots, the cross-sectional parameters and constructional parameters are optimized respectively. The cross-sectional and configurational parameters are optimized simultaneously. The numerical simulation of a 4R spatial manipulator is performed. The results show that the load capacity of robots has been greatly improved through the optimization strategies proposed in this paper.

Structural Characteristics and Mechanical Properties of Rock Mass in the Field of Tianwan Nuclear Power Plant, China

The structural characteristics and mechanical properties of the rock mass are important parts of the feasibility study on the nuclear power engineering field. In this study, by means of in situ investigation and statistics, the structural plane and joint fissure features of the rock mass were analyzed and discussed at different plots and different depth scopes in the Tianwan Nuclear Power engineering field, the rock mass integrality and its weathered degree were evaluated respectively, and especially, the unfavorable geological phenomena of strongly-weathered cystid existing in the field were studied. According to the results of indoor rock mechanical tests, in combination with drilling, the shallow seismic prospecting, sonic logging and point load tests, the statistical results of physical and mechanical indices of rocks at key plots of the field were analyzed, and the design parameters of the field were calculated. It provided scientific basis for the foundation design of the nuclear power plant.

In-Plane and Out-of-Plane Mechanical Properties of Zero Poisson’s Ratio Cellular Structures for Morphing Application

Intelligent structures like zero Poisson’s ratio(ZPR)cellular structures have been widely applied to the engineering fields such as morphing wings in recent decades,owing to their outstanding characteristics including light weight and low effective modulus. In-plane and out-of-plane mechanical properties of ZPR cellular structures are investigated in this paper. A theoretical method for calculating in-plane tensile modulus,in-plane shear modulus and out-of-plane bending modulus of ZPR cellular structures is proposed,and the impacts of the unit cell geometrical configurations on in-plane tensile modulus,in-plane shear modulus and out-of-plane bending modulus are studied systematically based on finite element(FE)simulation. Experimental tests validate the feasibility and effectiveness of the theoretical and FE analysis. And the results show that the in-plane and out-of-plane mechanical properties of ZPR cellular structures can be manipulated by designing cell geometrical parameters.

Solution of the Nucleon Structure Problem from a Field Theory of Fermions and Bosons and the Origin of the Proton Stability

A bound state formalism derived from a fermion-boson symmetric Lagrangian has been used to calculate the nucleon masses, the charge neutrality of the neutron, the magnetic moments and the electromagnetic form factor ratios μpGEp/GMpand μnGEn/GMn. A quantitative description is obtained, assuming a mixing of a scalar bound state of 3(f f¯)fstructure with its corresponding vector (f f¯)fstate (f indicating massless elementary fermions). Only a few parameters are needed, mainly fixed by energy and momentum conservation. The nucleon stability is explained by an extra binding in the confinement potential, negative for electric and positive for magnetic binding of the proton, and opposite for the neutron. The stronger electric extra binding of the proton allows a decay of the neutron to proton and electron.

The Mystery behind the Fine Structure Constant Contracted Radius Ratio Divided by the Mass Ratio? A Possible Atomist Interpretation

This paper examines various alternatives for what the fine structure constant might represent. In particular, we look at an alternative where the fine structure constant represents the radius ratio divided by the mass ratio of the electron, versus the proton as newly suggested by Koshy [1], but derived and interpreted here based on Haug atomism (see [2]). This ratio is remarkably close to the fine structure constant, and it is a dimensionless number. We also examine alternatives including the proton mass divided by the Higgs mass, which appears to be another possible candidate for what the fine structure constant might represent.

Effect of Al_(2)O_(3)/SiO_(2) mass ratio and CaO content on viscosity and structure of slag for pyrometallurgical processing of spent automotive catalysts

The effect of Al_(2)O_(3)/SiO_(2) mass ratio and CaO content on the viscosity and structure of the CaO-Al_(2)O_(3)-SiO_(2)-6MgO-1.5ZrO_(2)-1.5CeO_(2) slag was investigated.The results show that with the increase in Al_(2)O_(3)/SiO_(2) mass ratio,the viscous flow units within the slag gradually change from Si-O-Si to Al-O-Al and Al-O-Si.Furthermore,the substitution of Al_(2)O_(3) for SiO_(2) leads to the transformation of Si-O bonds towards weaker Al-O bonds,which weaken the bond strength of the aluminosilicate networks,thus leading to a decrease in the viscosity of slag.The increase in CaO content effectively promotes the depolymerization of the aluminosilicate networks,resulting in a significant decrease in the viscosity of the slag.The slag with Al_(2)O_(3)/SiO_(2) of 0.7-1.5 and CaO of 30 wt.%shows promise as the reference slag system for the Fe-collection smelting of spent automotive catalysts due to its good comprehensive performance.

Molecular Structures and Mechanical Properties of Microbe Rapid Coagulation Natural Rubber

In this work,molecular structures,dynamic mechanical properties and glass transition temperatures of microbe coagulated natural rubber（NR） samples were analyzed by using pyrolysis gas chromatography-mass spectrometry（py-GC/MS）,rubber process analyzer（RPA） and dynamic mechanical thermal analysis（DMA）.And the cross-linked network structures and mechanical properties of the corresponding NR vulcanizates were further determined by using nuclear magnetic resonance（NMR） crosslink density spectrometer（XLDS-15） and universal testing machines.The results show that NR raw rubber produced by rapidly coagulated with microorganism exhibits a simple molecular structure composition and good dynamic mechanical properties,and the corresponding NR vulcanizates possess the aggregation structure of high cross-linked density,a high glass transition temperature of-61.5 ℃ and high mechanical properties（tensile strength reaches 25.2 MPa）,as compared with that coagulated with acetic acid.

EFFECTS OF STOICHIOMETRIC RATIO ON STRUCTURE AND ELECTRODE PERFORMANCE OF HYDROGEN STORAGE ALLOYS

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Highly Accurate Relations between the Fine Structure Constant and Particle Masses, with Application to Its Cosmological Measurement

Highly accurate algebraic relations between the fine structure constant a and a wide range of particle masses are given, ranging from Δa/a = (2.1 ±0.1)×10-7 to Δa/a = (-2.7 ±0.3 ±0.6)×10-8, and with a very large standard deviation, ranging to Δa/a = -5.5×10-9. The analysis is based on empirical relations that exist among some particle masses, and also on several theoretical assumptions, of which the most significant is that the electromagnetic contribution to the electron’s mass is finite, and given by f ameb, where f is a dimensionless parameter that is shown to be equal to 1.032409810 (63), and where meb is the electron’s “bare mass.” The relations for a and f are homogeneous degree zero in the particle masses. The relations for f in terms of particle masses are found by trial and error. A quadratic equation is given relating a to f and me/mp. This equation is used in the application to cosmological measurements of a, and , where it is shown that, to a few percent accuracy, δa/a ≈ -δμ/μ. This relation can serve to test the validity of measurements of a and μ.

轻质高强混凝土制备与性能分析

基于轻质高强混凝土竞赛,文中对我国企业和高校制备轻质高强混凝土的能力进行了调研和分析,对46家企业、19家高校制备的轻质高强混凝土配合比、抗压强度、劈裂强度、粗骨料含量进行汇总、测试和分析,探究了原材料品质、配合比参数对混凝土力学性能和结构效率系数(强度容重比)的影响。分析结果表明,基于对轻质高强混凝土微观结构与宏观性能关系的理解,通过原材料选择、配合比设计和粗骨料优化等措施,在容重不大于1500 kg/m^(3)的控制条件下,轻质高强混凝土的抗压强度可达120 MPa,结构效率系数世界领先,达83.2 kPa/(kg·m^(-3))。文中所展示的轻质高强混凝土制备方法和材料性能,对轻质高强混凝土制备和建筑行业发展有促进作用。

黏结性富油煤热解油气析出规律及物性演变特征

黏结性富油煤受热产生的软化、熔融现象可能导致井筒堵塞和地层扰动,这是原位热解需考虑的重要因素。在300~700℃下对黏结性富油煤热解,考察油气析出规律和组成性质,分析半焦的物性演变特征及其对原位热解的指示意义。结果表明,焦油产率在500℃取得最大值7.75%,此时<300℃轻质组分含量最高(32.2%),且焦油成分在400~500℃变化显著,酚类和芳烃含量分别呈现增大和降低趋势。煤样的软化温度和固化温度分别为389和455℃,使半焦的宏观孔率度在≥400℃时由不足10%增至约50%,而微观孔隙结构仅在600~700℃高温脱气阶段更发达;半焦导热系数随温度先减小后增大,并在400℃达到最小值0.06 W/(m·℃)。黏结性富油煤原位热解面临通道堵塞、挥发分析出受阻和煤层导热速率偏慢等潜在问题,可尝试采用具有破黏效应的压裂支撑剂或近临界水原位转化技术加以解决。

基于参数化建模的负泊松比微结构性能分析与优化

为提高分析微结构单胞结构参数对其力学性能影响的效率,提出一种基于ABAQUS二次开发的参数化建模方法。该文以双箭头负泊松比微结构为研究对象:基于ABAQUS二次开发设计参数化建模的图形用户界面(GUI),且采用3D打印方法制造样件开展准静态压缩试验,以验证上述参数化平台所建立有限元模型的准确性;基于此,建立峰值力和比吸能的响应面模型,采用NSGA-Ⅱ多目标遗传优化算法,以峰值力最小、比吸能最大为目标,以θ_(1)、θ_(2)、T_(L)、T_(M)为设计变量,对微结构的冲击性能进行优化,获得最优的微结构拓扑参数。与优化前微结构的冲击性能进行对比分析,结果表明峰值力降低了14.36%,比吸能增加了33.72%。

某工程连廊及不规则悬挑结构振动舒适度分析与控制

针对某工程连廊及不规则悬挑结构,基于MIDAS/Gen软件建立有限元仿真分析模型,按照国内外相关规范,验算结构正常使用时各人行荷载工况下的舒适度。针对不满足要求的结构,开展基于调谐质量阻尼器(TMD)的振动控制分析,并对无控制状态及振动控制后的计算结果进行对比。结果表明:连廊及悬挑结构在人行荷载激励下部分工况下竖向加速度响应超过规范限值,最大可达0.9839m/s^(2),采用TMD系统进行减振控制后,结构加速度响应得到有效降低;对于超限工况,TMD有效减振率在69%以上,最高减振率达90.82%,平均减率为85.59%。

新型蝙蝠型负泊松比微结构非充气轮胎设计

为解决传统充气轮胎易爆胎、易刺破等问题,提出一种新型蝙蝠形微结构(bat-shaped cellular structure,BSCS)非充气轮胎。首先,推导了BSCS微元胞的相对密度、单位质量吸能和峰值力的理论力学模型,并开展准静态压缩试验验证了力学模型和有限元仿真模型的准确性。然后,建立了BSCS非充气轮胎有限元模型,并利用准静态压缩试验验证了轮胎有限元模型的准确性。最后,对非充气轮胎开展接地性能、三向刚度、模态分析、侧偏特性和稳态滚动的仿真分析,其中径向刚度为151.37 N/mm、侧向刚度为281.88 N/mm、纵向刚度为686.05 N/mm。仿真结果表明,所提出的BSCS非充气轮胎具有优异的力学承载性和可靠性,为非充气轮胎的设计提供了新的思路。

岩体结构面循环剪切设备和剪切力学特性的研究现状及展望

总结了岩体结构面在循环荷载作用下的力学特性若干重要问题的研究进展,包括4个方面:(1)岩体结构面表面形态信息;(2)岩体结构面循环剪切试验设备;(3)循环剪切试验影响因素;(4)结构面力学特性的描述与表征。在对现有研究成果进行评述的基础上指出了需要解决的问题和今后的发展方向。目前,结构面粗糙度描述缺乏统一的评判标准,在单向剪切中足以模拟地震动荷载的剪切设备仍有待进一步研发,且法向循环加载试验,特别是切向和法向循环荷载耦合剪切试验还有待研究,此外针对循环加载试验,仍缺乏一个完备的理论能够综合考虑所有影响因素;结构面的变形和强度公式如何选择也是一个较难解决的问题。研发新的动态、多自由度循环剪切设备,进行完备的循环剪切变形和强度公式研究是岩体结构面动态剪切问题研究的必由之路。希望本文可为今后的相关工作提供一定的参考和依据。

炼焦煤成焦机理再认识:“衍构成焦机理”的提出

深度认识煤质特性、探究炼焦煤成焦机理是开发精细化配煤炼焦技术的关键。传统成焦机理仅宏观地解释了炼焦煤炭化过程中的塑性和黏结现象,缺乏对煤转变为焦炭所涉及的化学反应的深层次认识。基于此,从分子水平阐述了炼焦煤成焦特性的演化机制并提出了“衍构成焦机理”,其核心观点是:煤的焦化本质是煤分子在温度作用下发生的一系列化学反应;成焦过程中的一切宏观特性都取决于煤基体的瞬态空间结构,即“结构决定性质”;炼焦过程中传热传质条件的动态变化将影响煤的热转化行为进而影响成焦特性和焦炭质量,即“环境影响行为”。基于煤分子结构特性及热解过程中共价键的断裂和重建规律,重点分析了炼焦煤的流动性、膨胀性及其演化机制,探究了煤分子空间结构重排与焦炭强度的内在联系。流动性源于煤中弱共价键的断裂,终于芳香碎片的交联缩聚。在流动过程中,煤热解碎片以分子链段的形式向孔穴相继跃迁并封闭孔隙,形成了包含塑性层和部分煤层及半焦层的低透气带,限制了挥发分的释放从而产生了膨胀压力;同时,碳基质结构发生重排,取向性增加,sp^(2)杂化和sp^(3)杂化形式的碳原子的空间排布方式决定了焦炭的强度。加热速率的合理调控将明显改善焦炭强度并实现焦化过程节能降耗。“衍构成焦机理”是对传统煤成焦机理的补充和延伸,以期为现代煤焦化工业精细化发展提供理论指导和技术支撑。

直链/支链比对青稞淀粉凝胶与消化性的影响

为深入探讨不同直链/支链比例对淀粉凝胶特性和消化行为的影响,本研究选取糯青稞和普通青稞品种,通过提取淀粉并复配制备直链/支链比例8%、14%、20%、25%的青稞淀粉,比较其在结晶结构、糊化特性、凝胶特性以及消化性方面的差异。结果表明,直链/支链比例未改变青稞淀粉的晶型,但直链/支链比例的增加降低了结晶度,使淀粉内部结构更紧密、双螺旋结构更稳定。同时,随着直链/支链比例的增加,淀粉糊化时的峰值黏度(3296~4226 mPa·s)逐渐降低、回生值(481.67~1604.33 mPa·s)逐渐增加。流变学结果表明,淀粉存在弱凝胶行为(G′>G″),淀粉凝胶的弹性行为增强会增加硬度和咀嚼度。消化特性方面,直链/支链比例的增加会增加抗性淀粉含量,降低快速消化淀粉含量、淀粉消化率和预估血糖生成指数。本研究结果对开发具有特定工业用途的功能性“定制”青稞淀粉具有一定的理论价值。

基于竞聚率设计制备组成均匀的聚羧酸减水剂

基于实验得到的聚羧酸减水剂(PCE)共聚单体的竞聚率数据,采用控制转化率和补加活泼单体相结合的方法,结合理论计算和实际测定结果,确定了活泼单体丙烯酸(AA)补加时间及补加量,使其在共聚过程中始终与大单体异丁烯基聚乙二醇醚(MAPEG)组成保持基本不变,以保证聚合反应不同时间段生成的共聚物组成和结构与设计值一致。为系统研究控制工艺的准确性和可靠性,将其与传统投料工艺反应过程中所得产物的组成对比,考察了控制共聚物组成对分散性能的影响。结果表明,基于竞聚率的控制工艺制备PCE过程中,分段补加消耗较快的AA抑制了AA和MAPEG在共聚物瞬时组成的变化幅度,共聚物的平均酸醚比[n(AA)/n(MAPEG)]分别为2.8、3.8、4.8,基本接近设计酸醚比(3.0、4.0、5.0);其制备的PCE平均主链长度及主链上羧基含量、大单体含量较高,使PCE覆盖面积和吸附层厚度增大,从而提升了水泥净浆初始流动度和流动保持性能。

闪蒸纺UHMWPE/HDPE共混纤维的制备及性能研究

为提高闪蒸纺纤维束的力学强度,将力学性能更为优异的超高相对分子质量聚乙烯(UHMWPE)与高密度聚乙烯(HDPE)共混,通过闪蒸纺丝方法制备UHMWPE/HDPE共混纤维束,采用扫描电子显微镜、差示扫描量热仪、X射线衍射仪和万能试验机等探究UHMWPE的引入对共混纤维束形貌、熔融结晶行为、聚集态结构和力学性能的影响。结果表明:闪蒸纺丝制备HDPE/UHMWPE共混纤维束时,随着纺丝液中UHMWPE质量分数由1%增至5%,溶液黏度增大,共混纤维束单丝直径逐渐增大,当UHMWPE质量分数为7%时,纺丝液会因黏度过大而无法纺丝;随着UHMWPE含量的增加,HDPE/UHMWPE共混纤维束的结晶度和取向度降低,力学性能增大,当纺丝液中UHMWPE质量分数为5%时,共混纤维束结晶度和取向因子分别为74.2%和0.46,拉伸强度为118.9 MPa,较纯HDPE纤维束提高了84.9%。

内凹-星型三维负泊松比结构设计及冲击吸能特性

负泊松比结构因其反常的变形机制在缓冲吸能领域具有可观的应用前景。该文设计并表征了一种参数可调的新型负泊松比结构。采用理论和数值模拟相结合的研究手段,系统地研究了结构的静/动态力学性能和吸能特性。研究结果表明:新结构具有较好的力学性能和参数可调性;在静态压缩条件下,新型蜂窝结构具有更高的刚度和更优异的吸能性能,其比吸能值是内凹型蜂窝结构的2.64倍,是星型蜂窝结构的3.89倍;在动态冲击条件下,内凹-星型结构的吸能性能在低速时优于两种传统蜂窝结构(内凹和星型),在中高速时其吸能优势有所退化,与内凹型蜂窝结构相当,但远高于星型蜂窝结构。