Flow and transmission characteristics of the multistage hydrogen Knudsen pump in the micro-power system

The multistage hydrogen Knudsen pump based on the thermal transpiration effect has exciting application prospects for hydrogen transport in the micro-power system. The multistage hydrogen Knudsen pump with the silica microchannel is beneficial to its temperature control, which can accurately provide hydrogen transport and storage for the micro-power system. In this paper, the model of the multistage hydrogen Knudsen pump with the silica microchannel is established. The effects of the microchannel height, width and parallel number on the flow and transmission characteristics of the multistage hydrogen Knudsen pump are studied by using the method of N–S equations with the slip boundary. The temperature difference, Knudsen number, thermal transpiration effect, maximum mass flow rate, maximum pressure difference and performance curve under different microchannel parameters are analyzed in detail. The results show that the thermal transpiration effect increases with the microchannel height and decreases with the microchannel width. As the number of parallel microchannels increases, the microchannel is closer to the silicon cantilever, and the thermal transpiration effect becomes stronger. The pumping performance increases with the microchannel height, width and parallel number. The pressurization performance increases with the microchannel height and parallel number. The research results have important guiding significance for the application and design of the multistage hydrogen Knudsen pump in the micro-power system.     

Elastic mimicry of elasto-plastic responses

A range of successively more elaborate elastic models is developed, with responses that in many ways mimic those of plastic specimens under load. The bilinear stiffness of a simple one degree-of-freedom elastic prop, which experiences a symmetric point of bifurcation, is first used to model the fundamental elasto-plastic response: the introduction of an imperfection corresponds to the Ramberg-Osgood approximation, rounding off the bilinearity. Upper and lower yield points are reproduced by a model termed the elastic hook, in which an elastic spring of the first model is itself replaced by an elastic prop with a bilinear stiffness. Finally, the normality relation of incremental plasticity theory is reproduced by two props at right-angles: responses are also traced for two hooking models in this configuration, for which no real comparison in plasticity theory seems to exist at present.     

Simulation in public sector management: a case study

We detail the development and application of a simulation model to aid decision making concerning the procedures followed in the Office of Film and Literature Classification, by forecasting the effects of possible management initiatives. The major variables are — the number of censors, the volume of publications to be classified (with special emphasis on computer technology publications) and the procedures, in particular, the number of censors with decision-making powers. A model of the system was developed using Extend; a simulation software package designed to aid decision support. This model was used to investigate the utilization of "decision-makers", and to identify and locate the bottlenecks, in the system under a number of different scenarios suggested by the client. There is also the flexibility to include additional duties that might be imposed on the Office.     

Exact solutions of the cubic–quintic Swift–Hohenberg equation and their bifurcations

Many systems of physical interest may be modelled by the bistable Swift–Hohenberg equation with cubic–quintic nonlinearity. We construct a two-parameter family of exact meromorphic solutions of the time-independent equation and use these to construct a one-parameter family of exact periodic solutions on the real line. These are of two types, differing in their symmetry properties, and are connected via an exact heteroclinic solution. We use these exact solutions as initial points for numerical continuation and show that some of these lie on secondary branches while others fall on isolas. The approach substantially enhances our understanding of the solution space of this equation.     

Flattening: An efficient approach to improving the performance of conventional MINs

Numerous conventional interconnection networks have been designed in a way in which they use indirect or multistage topologies. The reason behind this idea is the fact that such topologies can minimize the network hop count. However, the constraints of technology and packaging have given impetus for fundamental changes in the approach to designing topologies. Increasing the radix of the network׳s routers lowers the total cost of the network, which is related to the number of routers׳ pins and connectors. This increase also results in lowering the power consumption, which plays a crucial role in the performance. Kim, Dally and Abts have provided a cost-efficient topology for high-radix networks, named the flattened Butterfly. They have shown that this approach is comparable to the conventional Butterfly networks with regard to cost. It is much the same as a Folded-Clos topology in terms of the performance per cost ratio under adversarial traffic, whilst under benign traffic, the flattened Butterfly has approximately twice this ratio. In this paper, we have generalized the idea of flattening to all Delta networks, in addition to some non-Delta ones such as Beneš and Clos. Moreover, the conditions on which multistage networks can be converted to the flattened ones have been generally provided. All the mentioned networks have also been compared with another cost-efficient topology, named the HyperX, in order to gain deep insight into the key facets of the microarchitecture of high-radix networks. On the other hand, advances in designing digital circuits and reduction in their size rely upon knowledge in nano-electronics for refinements of the standard copper interconnect technology. This copper interconnects have become a major performance bottleneck in Multistage Interconnection Network (MIN) platforms. Consequently, a minor contribution of this paper is the performance assessment of the aforementioned networks using the Carbon NanoTube (CNT) technology under trace-driven and synthetic traffic patterns; inasmuch as this technology has been introduced as one of the six most important architectures in future digital systems. CNT is considered to be a promising technology in the design and fabrication of the next-generation chips since it is capable of handling extremely high current densities for a long time without considerable performance degradation. Although the comparative study of different networks with various parameters is the main goal, it should be taken into consideration that in some situations, these parameters provide similar conditions in different networks. As such, they can be combined with an efficient method to present a simple model. Finally, we have used data mining in order to reach a unified and meaningful performance parameter.     

水平井分段压裂裂缝间距优化技术研究

在水平井分段压裂设计中,裂缝间距的选取是一项十分重要的内容。针对目前裂缝间距选择方法不完善的问题,从极限泄油半径、产能模拟、岩石可压性、压裂工艺特点、储层厚度等方面进行了研究,得到五种优化裂缝间距的方法,可为现场应用提供理论参考。     

抑制行波管多级降压收集极二次电子发射的工艺研究

利用自行设计制造的一台抑制行波管多级降压收集极（MDC）二次电子发射的专用设备,分别对无氧铜片样品与无氧铜MDC进行了离子束表面改性的工艺研究。结果表明,表面改性后无氧铜表面二次电子发射系数可以得到大幅度的降低,有效提高空间行波管MDC的效率及整管效率。     

Finite element analysis of a multi-stage axisymmetric forging process having a spring-attached die for controlling metal flow lines

In this paper, a computer simulation technique for the forging process having a spring-attached die is presented. A penalty rigid-viscoplastic finite element method is employed together with an iterative force-balancing method, in which convergence is achieved when the forming load and the spring reaction force are in equilibrium within the user-specified allowable accuracy. The force balancing is controlled by adjusting the velocity of the spring-attached die. To minimize the number of iterations, a velocity estimating scheme is proposed. Two application examples found in the related company are given in order to emphasize the significance of metal flow lines for quality control and to investigate the effects of spring-attached dies on the metal flow lines as well as the decrease in forming load.     

A multistage system of microbial fed-batch fermentation and its parameter identification

In fed-batch fermentation of glycerol bio-dissimilation to 1,3-propanediol (1,3-PD) by Klebsiella pneumoniae, glycerol and alkali are fed into the reactor to provide nutrient and maintain a suitable environment for cells growth. Taking the feeding process as a time-continuous process, we present a nonlinear multistage dynamical system to formulate the fed-batch fermentation. In view of the big errors between experimental data and computational values, a parameter identification model is established. Finally, an improved Nelder–Mead simplex search method is developed to seek the unknown parameters in the model. Numerical simulations show that the multistage dynamical system can describe the fed-batch process better, compared with the previous results.     

Multilevel fuzzy relational systems: structure and identification

 Existing fuzzy relational equations (FRE) typically possess an evident single-level structure, where no consequence part of the rule being modeled, is used as a fact to another rule. Corresponding to multistage fuzzy reasoning, a natural extension of traditional fuzzy relational systems (FRS) is to introduce some intermediate levels of processing governed by enhanced FRE's so that the structure resulted becomes multilevel or multistage. Three basic multilevel FRS structures, namely, incremental, aggregated, and cascaded, are considered in this paper and they correspond to different reasoning mechanisms being frequently used by human beings in daily life. While the research works on multilevel FRS are sparse and our ability to solve a system of multilevel FRE's in a purely analytical manner is very limited, we address the identification problem from an optimization approach and introduce three fuzzy neural models. The proposed models consist of single-level FRS modules that are arranged in different hierarchical manners. Each module can be realized by Lin and Lee's fuzzy neural model for implementing the Mamdani fuzzy inference. We have particularly addressed the problem of how to distribute the input variables to different (levels of) relational modules for the incremental and aggregated models. In addition, the new models can learn a complete multistage fuzzy rule set from stipulated data pairs using structural and parameter learning. The effectiveness of the multilevel models has been demonstrated through various benchmarking problems. It can be generally concluded that the new models are distinctive in learning, generalization, and robustness.