Radiation Heat Transfer and Vapor Shielding in a Two-Dimensional Model of an Electrothermal Plasma Source

Electrothermal (ET) plasma discharges are emerging as valuable mechanisms for pellet injection in magnetic confinement fusion reactors. They have been shown to be capable of achieving the required pellet velocities and pellet launch frequencies required for edge localized mode control. Another advantage of ET plasma discharges is their ability to simulate fusion disruption events by depositing large heat fluxes on exposed materials. A deeper understanding of the heat transfer processes occurring in ET plasma discharges will aid in this particular application. ET plasma discharges involve the passage of high currents (order of tens of kA) along the axis of a narrow, cylindrical channel. As the current passes through the channel, radiant heat is transferred from the plasma core to the capillary wall. Ablated particles eventually fill the plasma channel and the partially ionized plasma is ejected. It is well known that the ablated material separating the plasma core from the ablating surface can act as a vapor shield and limit the radiation heat flux reaching the ablating surface. In this work, the results from a two-dimensional simulation model for ET plasma discharges are presented. The simulation of the plasma in a two-dimensional domain combined with the diffusion approximation for radiation heat transfer is shown to successfully simulate the effects of the vapor shield layer that develops inside these devices.     

The reuse of machining knowledge to improve designer awareness through the configuration of knowledge libraries in PLM

The nature of competition induces the need to constantly improve and perform better. For global aerospace manufacturers, this is as timely an epithet as ever as market forces urge for more growth, better financial return and market position. The macroeconomic aspect is compounded by the growth of product complexity and the need for higher product quality, hence the drive to reduce waste places emphasis upon production costs and the need to improve product performance. This paper focuses upon a rapid development and deployment method that enables the capture and representation of machining knowledge so that it may be shared and reused by design engineers to accelerate the design-make process. The study and mapping of information and knowledge relationships are described and put forward as a lightweight ontology. From this, a set of knowledge document templates were created to facilitate the capture, structuring and sharing of machining knowledge within a collaborative multidisciplinary aerospace engineering environment. An experimental pilot system has been developed to test and demonstrate that knowledge document templates can accelerate the sharing of machining knowledge within an industrial product lifecycle management environment. The results are discussed to provide a case for further development and application within the product domain.     

Solution of sparse positive definite systems on a shared-memory multiprocessor

Algorithms and software for solving sparse symmetric positive definite systems on serial computers have reached a high state of development. In this paper, we present algorithms for performing sparse Cholesky factorization and sparse triangular solutions on a shared-memory multiprocessor computer, along with some numerical experiments demonstrating their performance on a Sequent Balance 8000 system.Research was supported by the Applied Mathematical Sciences Research Program of the Office of Energy Research, U.S. Department of Energy under contract DE-AC05-84OR21400 with Martin Marieta Energy Systems, Inc., by the U.S. Air Force Office of Scientific Research under contract AFOSR-ISSA-85-00083 and by the Canadian Natural Sciences and Engineering Research Council under grants A8111 and A5509.     

Effect of preheating on the mechanical properties of tough pitch copper made from copper scraps

When hot rolled tough pitch copper is made from copper scraps, lead is intentionally or unintentionally added to the melt. The major role of this lead seems to be the removal of metallic tin by the formation of PbO–SnO₂. A continuously cast and hot rolled copper rod was preheated at temperatures between 673–1173 K for 1 h prior to cold drawing. The maximum diameter of the PbO–SnO₂, of 1–2 μm, was obtained by preheating at 873 K. This preheating temperature also produced the maximum decrease in the recrystallization temperature and the maximum electrical conductivity of the 89.4% cold drawn wire within the investigated experimental range. This can be attributed to a decrease in the dissolved impurity concentration due to the growth of PbO–SnO₂ particles at that temperature. The decrease in recrystallization temperature enhanced the room temperature multiple upset weldability. When preheated at 1173 K, Zn₂SnO₄ particles were formed, but the recrystallization temperature increased and the electrical conductivity decreased due to the dissolution of PbO–SnO₂. This revised version was published online in November 2006 with corrections to the Cover Date.     

Occurrence of Exophiala werneckii on salted freshwater fish Osteoglossum bicirrhosum

Fungal contamination occurred on the salted Amazonian fish Osteoglossum bicirrhosum which were air dried in the shade. The human pathogenic fungus Exophiala werneckii was recovered as the sole contaminant from all salted fish. It was implicated for the first time as a halophilic saprophyte causing food spoilage.     

基于遗传算法及仿真技术的服装生产流水线平衡

针对大部分服装企业存在生产流水线编制效率较低以及生产周期长的普遍现象,提出一种服装工序编排方案自动生成和单件流生产线仿真运行的方法。首先分析服装生产工序编排方法和影响因素,采用拓扑方法和遗传算法相结合,在MatLab(R2016b)软件中建立自动优化模型,实现工序的自动编排;然后考虑服装生产数量和生产线设备情况,采用仿真技术,在Plant Simulation仿真软件中,根据实际生产对工序编排方案进行流水线仿真运行,得出直观可视的仿真结果,实现流水线平衡再优化。生产实例验证表明,流水线编制效率为90.8%,比原有效率提高12.8%,节省流水线编排方案在投产前的平衡调试时间,生产周期缩短。     

上海房产展的空间游戏

空间的形式是人定义的。正因为是人定义的，所以形式就有可能因为创造者或使用者的想法不同而改变。可是事实通常并非如此，我们今天所看见的所有空间形式差不多都被制式化了。所以，所谓的有理想的空间创造者穷其一生都在努力想要改变既有的形式事实，但是，事实却很困难。因此，大多数设计师过了四十不惑的年纪，碍于残酷现实的考量，不是转行或变成管理者，就是任它去了，业主想要什么就给什么了。我认识的设计师实在是没几个人像我这过了半百的老设计师，还这么自以为是地坚守自己设计的信仰侦操。我自以为自己是少数的特例，从创造来说，我应该才起步吧。     

An intelligent online fault diagnostic scheme for nonlinear systems

An online fault diagnostic scheme for nonlinear systems based on neurofuzzy networks is proposed in this paper. The scheme involves two stages. In the first stage, the nonlinear system is approximated by a neurofuzzy network, which is trained offline from data obtained during the normal operation of the system. In the second stage, residual is generated online from this network and is modelled by another neurofuzzy network trained online. Fuzzy rules are extracted from this network, and are compared with those in the fault database obtained under different faulty operations, from which faults are diagnosed. The performance of the proposed intelligent fault scheme is illustrated using a two-tank water level control system under different faulty conditions .     

基于遗传算法的UPFC模糊阻尼控制器参数优化及与梯度下降法的比较

设计了一种统一潮流控制器（UPFC）模糊辅助控制器,能够阻尼互联系统之间功率低频振荡．分别使用遗传算法和梯度下降法实现了模糊阻尼控制器（FDC）的参数优化。建立了UPFC的频域模型,给出了主控制和辅助控制的框图。推导了模糊阻尼控制器参数优化的公式。互联多机系统算例显示了2种优化方法都具有很好的收敛性。且结果吻合,同时由这2种方法优化的阻尼控制器能够很好地阻尼系统的功率振荡。且比传统的基于线性系统设计的辅助控制器在不同的系统运行方式和振荡模式下具有更好的鲁棒性。