课程文献中心 更多>>

关键词： 离合器   支承钉   负荷特性  

摘要： 支承钉在离合器中起支点和连接作用。对于支承钉结构的盖总成来说,支承钉所产生的变形对负荷特性的影响是比较大的,本文我们就讨论支承钉对离合器盖总成的负荷特性的影响。

关键词： Ball mill   Gear transmission   Kriging   Genetic algorithm   Global optimization   Reliability design  

摘要： This paper aims to improve the global optimization operation efficiency in engineering by establishing the Kriging model to simplify the calculated mathematics model. In the case of the large ball mill, this paper presents in detail the application of the stress-strength distribution interference theory to calculate the reliability of gear transmission, establishes the Kriging model for function fitting, and uses genetic algorithm to globally optimize the volume and reliability of large ball mill gear transmission. The optimal result based the Kriging model is contrasted with the Monte Carlo Method in terms of calculation accuracy, greatly improving the efficiency of calculation. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： birds   development   early life effects   genetic assimilation   genetic modules   heterochrony   internal factors   natural selection   ovarian follicles  

摘要： Why different bird species lay different numbers of eggs is a question that has long been associated with factors external to the organism, that is, factors which operate on inherited variation in clutch size through the action of natural selection. Yet, while external factors are important, the extent of what is evolutionarily possible rests with the mechanisms developed by birds for clutch-size control. Hitherto neglected, these mechanisms generate factors internal to the organism that are central to the origin of evolutionary change. They are related to the fact that a species-specific range of clutch size arises from the differential survival of pre-ovulatory follicles undergoing growth when the signal causing egg laying to end reaches the ovary. Herein, I examine three internal factors that, together with external factors, could impact the evolution of avian clutch size. Each factor acts by changing either the number of pre-ovulatory follicles present in the ovary at the time of follicular disruption or the timing of this event. These changes to clutch size can be explained by the concept of heterochrony. In light of this, the role of phenotypic plasticity and genes determining clutch size is discussed. Finally, to account for the origin of evolutionary change in clutch size, I detail an hypothesis involving a process similar to Waddington's theory of genetic assimilation.

关键词： PIEZOELECTRIC actuators   ACTUATORS   ELECTRIC actuators   FLEXURE   SCIENTIFIC apparatus & instruments   RESEARCH  

摘要： This paper presents the development of a new compact three-axis compliant stage employing piezoelectric actuators and a new flexure structure. A proposed stage works out-of-plane (Z, theta(x), theta(y)) direction. The stage consists of 4 amplification flexures mounted piezoelectric actuators. New structure of flexure reduces height and enhances dynamic performance of stage. To certify excellent performance of the stage, comparison accomplished between conventional amplification flexure and new compact bridge type flexure. Modeling and optimal design of new type nano positioning stage performed. The optimal design is executed on the geometric parameters of the proposed flexure structure using Sequential Quadratic Programming. Experiments are carried out to verify the static and dynamic performance of the stage. The proposed out-of-plane nano-positioning stage has a Z-directional motion range 190 mu m and a theta(x), theta(y)-directional motion range +/- 2 mrad. The resolution of the stage is 4 nm, 40 nrad, and 40 nrad in the Z-, theta(x)-, and theta(y)-directional motions, respectively. The size of stage is 150 x 150 x 30 mm(3). (c) 2013 AIP Publishing LLC.

关键词： CENTRIFUGAL force   MAGNETIC clutches   CHEMICAL processes   SEALING (Technology)   RADIOCHEMISTRY   MANUFACTURING processes  

摘要： Two alternative designs of a hermetically sealed extractor, the drive of which utilizes a cylindrical magnetic clutch, are examined. In the first version, the driving half coupling is internal, and the driven half coupling external. In the second version, the driving half coupling is external, and the driven internal. It is shown that as the extractor based on the first design begins to accelerate with use of a frequency regulator that permits smooth variation in current frequency, the maximum angle of mismatch between the half couplings of the magnetic clutch is less then 0.5p rad. The proposed design of the extractor has been tested at an establishment manufacturing radiochemical products, and placed in experimental- industrial service.

关键词： Inflammation   Cell loss   Seizures   Toll-like receptors   Antiinflammatory drugs   Status epilepticus   Glia   Epileptogenesis  

摘要： We studied whether pharmacological blockade of the IL-1 beta-mediated signaling, rapidly activated in forebrain by epileptogenic injuries, affords neuroprotection in two different rat models of status epilepticus (SE). As secondary outcome, we measured treatment's effect on SE-induced epileptogenesis. IL-1 beta signaling was blocked by systemic administration of two antiinflammatory drugs, namely human recombinant IL-1 receptor antagonist (anakinra), the naturally occurring and clinically used competitive IL-1 receptor type 1 antagonist and VX-765 a specific non-peptide inhibitor of IL-1 beta, cleavage and release. Antiinflammatory drugs were given 60 min after antiepileptic (AED) drug-controlled SE induced by pilocarpine, or 180 min after unrestrained electrical SE, for 7 days using a protocol yielding therapeutic drug levels in brain. This drug combination significantly decreased both IL-1 beta expression in astrocytes and cell loss in rat forebrain. Neuroprotection and the antiinflammatory effect were more pronounced in the electrical SE model. Onset of epilepsy, and frequency and duration of seizures 3 months after electrical SE were not significantly modified. Transcriptomic analysis in the hippocampus showed that the combined treatment did not affect the broad inflammatory response induced by SE during epileptogenesis. In particular, the treatment did not prevent the induction of the complement system and Tolllike receptors, both contributing to cell loss and seizure generation. We conclude that the IL-1 beta signaling represents an important target for reducing cell loss after SE. The data highlight a new class of clinically tested agents affording neuroprotection after a delayed post-injury intervention. Earlier blockade of this rapid onset inflammatory pathway during SE, or concomitant treatment with antiinflammatory drugs targeting additional components of the broad inflammatory response to SE, or cotreatment with AEDs, is likely to be required for optimiz

关键词： MAGNETIC clutches   SEALING (Technology)   PERMANENT magnets   PUMPING machinery   COMPRESSORS   MIXING machinery  

摘要： A technique for selection and design of magnetic clutches with highly coercive permanent magnets (barium oxide magnets or magnets produced from such alloys of rare-earth elements as samarium-cobalt and neodymium-iron-boron) for sealed machines (pumps, compressors, mixers) is presented.

关键词： Research Article  

摘要： Winning the war against invasive species requires early detection of invasions. Compared to terrestrial invaders, aquatic species often thrive undetected under water and do not garner notice until too late for early action. However, fortunately for managers, apple snails (Family Ampullariidae, Genus Pomacea) provide their own conspicuous sign of invasion in the form of vibrantly colored egg clutches. Managers can potentially use egg clutches laid in the riparian zone as a means of early detection and species identification. To facilitate such efforts, we quantified differences in characteristics (length, width, depth, mass, egg number) of field-laid clutches for the two most common invasive species of apple snail, P. canaliculata and P. maculata, in native and non-native populations. Pomacea canaliculata native and non-native populations differed noticeably only in width. Native P. maculata clutches possessed significantly greater width, mass and eggs numbers compared with native P. canaliculata. Non-native P. maculata clutches significantly exceeded all other populations in all measured characteristics. Consequently, these traits may successfully distinguish between species. Fecundity data also allowed us to develop models that accurately estimated the number of eggs per clutch for each species based on clutch dimensions. We tested one, two and three dimensional models of clutches, including rendering a clutch as either a complete ellipsoid or an ellipsoid intersected by a cylinder to represent the oviposition site. Model comparisons found the product of length and depth, with a different function for each population, best predicted egg number for both species. Comparisons of egg number to clutch volume and mass implied non-native P. canaliculata may be food limited, while non-native P. maculata appeared to produce such enormous clutches by having access to greater nutrients than the native population. With these new tools, researchers and managers can quickly iden

关键词： 双离合器   节能   液压系统   AMESim  

摘要： 对湿式双离合变速器节能型液压系统组成及其工作原理进行了分析,并利用AMESim软件对离合器压力控制系统进行仿真研究,明确该系统的工作原理与工作特性。通过台架实验验证了仿真模型的正确性,为下一步控制策略的制定及控制系统的开发提供依据。

关键词： V型带   离合器   功能的应用  

摘要： 利用V型带传递动力在机械设计中得到广泛应用。在农业机械中人们利用V型带的特性,使V型带既用来传递动力,又用来切断动力,起到一个离合器的作用。