关键词： 工程机械   冲击破碎   系统开发   旋转机构   爆破冲击   机构设计  

摘要： 为提高破碎动力头工作效率,在研究冲击破碎机理的基础上,通过岩石冲击破碎动力学试验分析,应用能量传递守恒原理,开发设计了一种新型的具有旋转冲击功能特征的液、气压混合冲击破碎机械,其创新之处是该机械打破传统的单作用直线冲击破碎观念,通过增加液压旋转冲击机构,实现钎杆冲击时既产生轴向冲击力又产生径向离心力的合成冲击效果,达到了更加高效的破碎目的,该设计获得国家发明专利。

关键词： 汽油发动机   单缸发动机   工程机械   产品线   养护机械   上市   宝马  

摘要： 2018年11月28日,美国发动机专家百力通公司在上海宝马展上发布了全新的先锋单缸发动机产品线,旨在为全球轻型工程机械和养护机械提供革命性的动力。在本次亚洲工程机械盛会上,百力通展示了刚上市不久的先锋200发动机(单缸6.5hp)以及将于2019年上市的先锋400发动机(单缸13hp)。百力通还将在接下来的2年时间内推出先锋160和先锋300发动机。

关键词： 机器人   黄蜂   独立电影   机械   种源   《变形金刚》   迈克尔   人气  

摘要： 要说这几年的机器人电影中,迈克尔贝的电影《变形金刚》系列算是最红的了,不过电影版走了一条跟系列漫画和动画完全不同的路线,从豆瓣8.1的第一部一路下滑到只有4.8的第五部,得罪了几乎所有原著粉,路人观众评价也是毁誉参半,但不可否认的是,它依然捧红了一个人气角色“大黄蜂(Bumblebee)”。今年十二月,大黄蜂的独立电影在北美上映,不但再次体现了它的人气爆棚,还吸了不少的新粉。

关键词： 铁路   机械动力设备   维修  

摘要： 介绍了上海机车检修段的设备与车间现状,从四方面分析了实施铁路机械动力设备委外修的原因:新设备新技术自主维修难度大,维修人员与任务量之间矛盾突出,专业技术人才数量少、素质不高,控制设备维修成本。介绍了实施委外修的具体方案与成效,并进行了生产成本对比。最后给出了铁路机械动力设备实施委外修在各阶段的相关建议。

关键词： Mitochondrial fusion   Mitochondria] fission   Mitophagy   MFN2   OPA1   YME1L1   MSTO1   FBXL4   DNM1L   MFF   PINK1   PRKN  

摘要： Mitochondria are dynamic organelles that undergo fusion, fission, movement, and mitophagy. These processes are essential to maintain the normal mitochondrial morphology, distribution, and function. Mitochondrial fusion allows the exchange of intramitochondrial material, whereas the fission process is required to replicate the mitochondria during cell division, facilitate the transport and distribution of mitochondria, and allow the isolation of damaged organelles. Mitochondrial mobility is essential for mitochondrial distribution depending on the cellular metabolic demands. Mitophagy is needed for the elimination of dysfunctional and damaged mitochondria to maintain a healthy mitochondria] population. The mitochondrial dynamic processes are mediated by a number of nuclear-encoded proteins that function in mitochondrial transport, fusion, fission, and mitophagy. Disorders of mitochondrial dynamics are caused by pathogenic variants in the genes encoding these proteins. These diseases have a high clinical variability, and range in severity from isolated optic atrophy to lethal encephalopathy. These disorders include defects in mitochondrial fusion (caused by pathogenic variants in MFN2, OPA1, YME1L1, MSTO1, and FBXL4), mitochondrial fission (caused by pathogenic variants in DNM1L and MFF), and mitochondrial autophagy (caused by pathogenic variants in PINK1 and PRKN). In this review, the molecular machinery and biological roles of mitochondrial dynamic processes are discussed. Subsequently, the currently known diseases related to mitochondrial dynamic defects are presented.

关键词： Redox dynamics   Model   Glutathione   Cysteine   Embryo   Organogenesis  

摘要： Precise control of the glutathione/glutathione disulfide (GSH/GSSG) redox balance is vital for the developing embryo, but regulatory mechanisms are poorly understood. We developed a novel, mechanistic mass-balance model for GSH metabolism in the organogenesis stage (gestational day 10.0-11.13) rat conceptus predicting the dynamics of 8 unique metabolites in 3 conceptal compartments: the visceral yolk sac (VYS), the extra-embryonic fluid (EEF) and the embryo proper (EMB). Our results show that thiol concentrations in all compartments are well predicted by the model. Protein synthesis is predicted to be a major efflux pathway for all amino acid precursors of GSH synthesis and an essential model element. Our model provides quantitative insights in the transport fluxes and enzymatic fluxes needed to maintain thiol redox balances under normal physiological conditions. This is crucial to further elucidate the mechanisms through which chemical exposure can perturb redox homeostasis, causing oxidative stress, and potentially birth defects.

关键词： deformation   ductility   elastic constants   first principles theory   fracture mechanics/toughness  

摘要： In this study, first-principles calculations were performed to study the stability, mechanical property, electronic structure and lattice dynamics of beta-Si-3(C-x,N1-x)(4) silicon carbonitride. The solubility of carbon in beta-Si-3(C-x,N1-x)(4) having a stable structure is shown to be about 15 at.%. Within the limit of solubility, an increase in carbon concentration in beta-Si-3(C-x,N1-x)(4) will lead to a decrease in the Young's modulus and density and an increase in the Poisson's ratio. The study of deformation behavior shows that the most likely slip system of {1100} [0001] is on prismatic plane rather than on basal plane. This feature of beta-Si-3(C-x,N1-x)(4) is similar to WC. In addition, the ductility and fracture toughness of beta-Si-3(C-x,N1-x)(4) can be optimized by controlling the carbon concentration. The improvement in ductility and fracture toughness can be attributed to the formation of metallic bonds by the incorporation of carbon atoms. The lattice dynamics study shows that the structural stability of beta-Si-3(C-x,N1-x)(4) is controlled by energy stability criteria under stress-free condition. In the stressed state, the structural stability of beta-Si-3(C-x,N1-x)(4) is controlled by the elastic stability criteria. Subsequently, the beta-Si-3(C-x,N1-x)(4) solid solution was prepared by self-propagating high-temperature synthesis (SHS), and the carbon-concentration-dependent mechanical properties were consistent with the first-principles calculations. The maximum fracture toughness of 10.4 MPa.m(0.5) was obtained in beta-Si-3(C-x,N1-x)(4) at carbon concentration of 5 wt%, which means that the solid solution toughening can be used as a supplement to crack bridging toughening and phase transition toughening for ceramic toughening. The results obtained in this study reveal that the beta-Si-3(C-x,N1-x)(4) solid solution is a promising candidate for high-speed ceramic bearings.

关键词： Free energy   QM/MM   Ions   Chemical calculations   Hydration  

摘要： A recently proposed thermodynamic integration (TI) approach formulated in the framework of quantum mechanical/molecular mechanical molecular dynamics (QM/MM MD) simulations is applied to study the structure, dynamics, and absolute intrinsic hydration free energy Delta(s) G degrees(M+,wat) of the Li+ ion at a correlated ab initio level of theory. Based on the results, standard values (298.15 K, ideal gas at 1 bar, ideal solute at 1 molal) for the absolute intrinsic hydration free energy G degrees(H+,wat), of the proton, the surface electric potential jump chi degrees(wat) upon entering bulk water, and the absolute single-electrode potential V degrees(H+,wat) of the reference hydrogen electrode are calculated to be -1099.9 +/- 4.2 ***(-1), 0.13 +/- 0.08 V, and 4.28 +/- 0.04 V, respectively, in excellent agreement with the standard values recommended by HUnenberger and Reif on the basis of an extensive evaluation of the available experimental data (-1100 +/- 5 ***(-1), 0.13 +/- 0.10 V, and 4.28 +/- 0.13 V). The simulation results for Li+ are also compared to those for Na+ and K+ from a previous study in terms of relative hydration free energies Delta Delta(s) G degrees(M+,wat) and relative electrode potentials Delta V degrees(M+,wat). The calculated values are found to agree extremely well with the experimental differences in standard conventional hydration free energies Delta Delta(s)G(M+,wat)(center dot) and redox potentials Delta Delta(H) V degrees(M+,wat). The level of agreement between simulation and experiment, which is quantitative within error bars, underlines the substantial accuracy improvement achieved by applying a highly demanding QM/MM approach at the resolution-of -identity second -order Moller-Plesset perturbation (RIMP2) level over calculations relying on purely molecular mechanical or density functional theory (DFT) descriptions. A detailed analysis of the structural and dynamical properties of the Li+ hydrate indicates that a correct descriptio

关键词： DNB/DNB center dot- and DNB/DNB2- model systems   antioxidants   kinetics and mechanism for interactions   cyclic voltammetry   PM3 calculations  

摘要： Here we are presenting complete electrochemical studies on redox activities of 1,2-dinitrobenzene (DNB) in the presence of antioxidants-quercetin, morin, rutin, ascorbic acid and beta-carotene. Bimolecular rate constants (k(2)), antioxidant activities (K-a) and diffusion coefficients (D-o) were evaluated from changes in voltammeric responses and electrochemical parameters in the presence of antioxidant's concentrations. Theoretical charge calculations by PM3 parameterization were done which further justified our experimental electrochemical work and proposed scavenging mechanism. Present findings were also compared in details with our previously reported studies on 1,3- and 1,4-dinitrobenzene systems for their interactions with antioxidants.

关键词： in situ liquid cell TEM   dynamics of self-assembly   cluster growth   Brownian force   van der Waals force   hydrodynamic drag force   and steric hindrance force  

摘要： Superlattice structures formed by nanoparticle (NP) self-assembly have attracted increasing attention due to their potential as a class of nanomaterials with enhanced physicochemical properties tailored by the assembly structure. However, many key questions remain regarding the correlation between the dynamics of individual NPs and emerging superlattice patterns. Here we investigated the self-assembly of gold NPs by employing in situ transmission electron microscopy equipped with direct detection camera capabilities, which enabled us to track the rapid motion of individual nanoparticles in real time. By calculating the contributions of Brownian, van der Waals, hydrodynamic, and steric hindrance forces, we obtained a quantitative evaluation of the competitive interactions that drive the assembly process. Such competition between forces over various separations is critical for the kinetics of cluster growth, leading to the superlattice formation. Brownian motion resulted in the formation of small-sized clusters, whose growth dynamics was characterized as reaction-limited aggregation. Subsequently, at relative short-range particle separations, van der Waals force overrode the Brownian force and dominantly drove the assembly process. When the particles were in close proximity, a delicate balance between van der Waals and steric hindrance forces led to an unexpected dynamic nature of the assembled superlattice. Our study provides a fundamental understanding of coupling energetics and dynamics of NPs involved in the assembly process, enabling the control and design of the structure of nanoparticle superlattices.