回转体头部压力分布规律及其对转捩点的影响

以圆头回转体为研究对象,头部线型采用双参数椭圆曲线,利用面元法求解绕流势流流场,利用F.W.Scholkemeier的积分方法,确定该压力分布下的层流边界层,利用P.S.Granville方法求解边界层转捩点.通过变换头部线型参数,以最小压力系数绝对值的下降方向为搜索方向,研究不同头型压力分布的变化规律及其对转捩点的影响.结果表明:最小压力系数绝对值越小的头型其最小压力点离头部驻点的距离越近;不同头型的转捩点不光与其压力分布有关,而且还与其头部长径比有关.     

2D Bi2O2Te Semiconductor with Single-Crystal Native Oxide Layer

Following logic in the silicon semiconductor industry, the existence of native oxide and suitable fabrication technology is essential for 2D semiconductors in planar integronics, which are surface-sensitive to typical coating technologies. To date, very few types of integronics are found to possess this feature. Herein, the 2D Bi₂O₂Te developed recently is reported to possess large-area synthesis and controllable thermal oxidation behavior toward single-crystal native oxides. This shows that surface-adsorbed oxygen atoms are inclined to penetrate across [Bi₂O₂]_n²ⁿ⁺ layers and bond with the underlying [Te]_n²ⁿ⁻ at elevated temperatures, transforming directly into [TeO₄]_n²ⁿ⁻ with the basic architecture remaining stable. The oxide can be adjusted to form in an accurate layer-by-layer manner with a low-stress sharp interface. The native oxide Bi₂TeO₆ layer (bandgap of ≈2.9 eV) exhibits visible-light transparency and is compatible with wet-chemical selective etching technology. These advances demonstrate the potential of Bi₂O₂Te in planar-integrated functional nanoelectronics such as tunnel junction devices, field-effect transistors, and memristors.     

The rim zone of cement-based materials – Barrier or fast lane for chemical degradation?

Sophisticated evaluation models for the long-term stability of cement-based systems demand a precise knowledge of the mechanisms of deterioration reactions, particularly respecting a permanent exposure to aqueous environments. Commonly, insights into these mechanisms are deduced from long-term investigations. However, these chemical reactions start immediately after exposure to aggressive environments causing rapid changes of composition and structure. Consequently, properties of its rim zone change, which affects transport processes in aqueous solutions. In laboratory experiments, the influence of these surface processes on the stability of cement-based materials exposed to different chloride solutions was studied as a function of time and temperature. Analysis of compositional and structural changes beneath the surface reveal the role of crystalline covering layers for chemical resistance. Such layers are often described as protective barriers. However, these processes in the rim zone can accelerate chemical degradation and subsequently reduce the resilience of the cement-based materials to aggressive aqueous environments.     

Production of perovskite-like La1−xCaxMnO3+δ ferromagnetic thin films by electrochemical reduction

Ferromagnetic and perovskite-like thin films (<1m) of La1–xCaxMnO3+ have been routinely prepared by heat treatment of an amorphous La–Ca–Mn precursor. The precursor was electrodeposited cathodically in the absence of oxygen and water onto polished silver substrates from a nonaqueous solution of the components' nitrates. Analysis by X-ray diffraction and SQUID magnetometry shows these materials exhibit the appropriate structural and magnetic phases indicative of colossal magnetoresistance.     

The renaming problem in shared memory systems: An introduction

Exploring the power of shared memory communication objects and models, and the limits of distributed computability are among the most exciting research areas of distributed computing. In that spirit, this paper focuses on a problem that has received considerable interest since its introduction in 1987, namely the renaming problem. It was the first non-trivial problem known to be solvable in an asynchronous distributed system despite process failures. Many algorithms for renaming and variants of renaming have been proposed, and sophisticated lower bounds have been proved, that have been a source of new ideas of general interest to distributed computing. It has consequently acquired a paradigm status in distributed fault-tolerant computing.In the renaming problem, processes start with unique initial names taken from a large name space, then deciding new names such that no two processes decide the same new name and the new names are from a name space that is as small as possible.This paper presents an introduction to the renaming problem in shared memory systems, for non-expert readers. It describes both algorithms and lower bounds. Also, it discusses strong connections relating renaming and other important distributed problems such as set agreement and symmetry breaking.     

工业软测量模型结构与输入变量选择的研究

针对过程工业中难以直接测量的变量建立其软测量模型,对于实现关键指标的在线监测和实时控制具有十分重要的意义.变量的选择直接关系到神经网络软测量模型的预测性能,针对现有输入变量和网络结构选择方法在工业应用中的不足,提出了一种基于敏感度分析的方法来确定网络输入变量集和前馈神经网络隐含层节点个数,并建立了高密度聚乙烯(HDPE...     

Comparison of the RF MEMS switches with dielectric layers on the bridge’s lower surface and on the transmission line

Previously, we proposed that the dielectric layer of RF MEMS switch can be fabricated either on the transmission line, as traditional switches, or on the lower surface of the bridge. This paper presents a detailed comparison of the RF MEMS switches with different positions of dielectric layer. Through theoretically analyzing the physical model of fringing capacitance, it is revealed that different positions of dielectric layer can result in different switch capacitances. Therefore, the change of d...     

PS对剪贴图层创建图层样式的方法

该文介绍了设计Logo时对剪贴图层创建图层样式的方法。     

集散控制系统网络结构的研究

为了提高集散控制系统通信的可靠性、稳定性、抗干扰性和可扩展性,降低集散控制系统通信的故障率,提出了一种基于工业以太网的网络通信方式,并验证了该通信网络的可行性。该网络是一种采用分布式、冗余式、立体式的多层次网络结构。此结构使网络的负荷均匀分配,降低了网络的故障率,并使集散控制系统的网络向开放化、信息化的方向发展。     

Discharge properties and chemical stability of SrZrO films

Abstract— MgO thin film is currently used as a surface protective layer for dielectric materials because MgO has a high resistance during ion sputtering and exhibits effective secondary electron emission. The secondary‐electron‐emission coefficient γ of MgO is high for Ne ions; however, it is low for Xe ions. The Xe content of the discharge gas of PDPs needs to be raised in order to increase the luminous efficiency. Thus, the development of high‐γ materials replacing MgO is required. The discharge properties and chemical surface stability of SrO containing Zr (SrZrO) as the candidate high‐γ protective layer for noble PDPs have been characterized. SrZrO films have superior chemical stability, especially the resistance to carbonation because of the existence of a few adsorption sites due to their amorphous structure. The firing voltage is 60 V lower than that of MgO films for a discharge gas of Ne/Xe = 85/15 at 60 kPa.