火花氢离子源的等离子体特性研究

提出了氢离子源等离子体的一维动态CRAM(collisional radiative atomic and molecular)模型,计算了非平衡态(NTE)下等离子体中分子、电子、离子、基态原子、激发态原子共9种粒子浓度以及电场强度、气体温度和电子温度在一个脉冲内随时间和轴向空间的分布.计算表明:氢离子源中粒子分布在轴向极不均匀,阳极附近有很高的粒子浓度;氢原子离子占总离子数的93.9%,与文献值相符;巴耳末系谱线强度与文献值符合较好.     

A Mathematical Analysis of the Glow and Dark Space Regions in Positive Corona

The authors present a mathematical analysis of the electric field, current density, and charge density in the entire airgap in positive dc corona in cylindrical geometry. The currents are found using the Townsend breakdown theory and the Sarma empirical equation for the ionization coefficient in air. Since the ionization coefficient is a function of the local field intensity and the electric field distribution depends on the ionization process, an iterative numerical method was used. White-head's empirical formula describing the conductor surface onset field intensity as a function of the conductor radius was used to establish the field intensity at the point in the gap where the ionization process begins. The results show good agreement with available experimental data on particle-charging.     

离子束增强沉积氮化硅薄膜生长及其性能研究

用离子束增强沉积技术合成了氮化硅薄膜并研究了薄膜的组分、性能和结构.结果表明,离子束增强沉积生长的氮化硅薄膜的组分比,可借助于调节氮离子和硅原子到达率之比加以控制.在合适条件下生长的氮化硅薄膜,其红外吸收特征峰在波数为840cm~(-1)附近,光折射率在2.2到2.6之间,其组分为Si_3N_4用RBS、AES、TEM、SEM、ED及扩展电阻,测量和观察生成的氮化硅薄膜的组分深度分布及结构.发现,离子束增强沉积制备的氮化硅薄膜,存在着表面富硅层、氮化硅沉积层及混合过渡层这样的多层结构.薄膜呈球状或方块状堆积.基本上是无定形相,但局部可观察到单晶相的存在.离子束增强沉积制备的氮化硅薄膜中的含氧量比不用离子束辅助沉积的显著减少.     

Corona as a Means of Minimizing the Electric Current Surge from a DC High-Voltage Terminal

It is often necessary to reduce the total energy released by an accidental spark discharge from a dc high-voltage terminal. The paper presents the results obtained with two experimental setups designed to investigate the effects of inserting a corona element in series with such terminals. The spark discharge onto a 23-cm diameter spherical probe was measured for the same terminal voltage with and without the corona element. Depending on the capacitances of the high-voltage circuit and of the corona element, and on the corona current-voltage characteristics, the reduction of the spark energy may reach one order of magnitude or more.     

A High-Voltage Isolator for Conductive Liquids

In certain manufacturing operations, and particularly in electrostatic spray-coating, portions of a conductive liquid line may be exposed to a high potential. To localize the high potential, a new isolation system has been developed that allows the continuity of the conductive liquid to be broken and insulated by a gas medium. Experiments show that potential differences up to 100 kV may be successfully isolated over a distance of 10 cm.     

The Concept of Operational Rank Extractor

An operational rank extractor (ORE) is introduced in this paper as an operational amplifier having rank extractors at its inputs. This versatile building block can implement a variety of nonlinear transfer functions such as a dead-zone amplifier, a limiter, a full-wave rectifier, and a tri-state comparator (including hysteretic behavior). A 6-input circuit has been implemented in a 2 m CMOS process. The total silicon area is 460 × 100m², and the circuit dissipates 0.7 mW from a single 5 V supply. Various circuit configurations are analyzed theoretically, and experimental results are also provided.     

Supervisory control and data acquisition for virtual enterprise

The new manufacturing paradigms, such as agile manufacture and lean production, are leading industrial countries towards the new generation of concurrent enterprises involving virtual enterprise architecture and concurrent engineering extended methodology. Continuing adaptation to the market can only be achieved efficiently if the planning and control processes are both optimized horizontally (Automatic Control Systems) and vertically (Management Control Systems). The desired improvement in performance and the realization of global enterprise objectives require a tight integration of the units of the enterprise. The close monitoring of the operational performance of various plants, manufacturing shop-floors/cells/machines, as well as their associated instrumentation and control is of increasing strategic importance. Failures can lead to increased costs and reduced product quality, consistency and production, and to plant shutdowns and increased environmental impact. There is a real need for advanced monitoring technologies to be applied, and their potential demonstrated, on complex industrial plants. The planning and scheduling of manufacturing systems integrated into virtual enterprise architectures requires the implementation of new General Master Production Planning and Scheduling techniques and Supervisory Control and Data Acquisition (SCADA) functions. This paper discusses some key issues on the SCADA-oriented open system for virtual enterprise architecture.     

Dental Enamel Quality and Black Tooth Stain: A New Approach and Explanation by using Raman and AFM Techniques

This contribution takes in account investigation of dental enamel regarding “quality” of hydroxyapatite material involved in the mineralization process. Areas damaged by black stain were investigated in order to evaluate changes in chemical composition as compared to those of healthy dental enamel.

Different sectors on tooth surfaces were analyzed using micro-Raman spectroscopy. The integral areas of ν₁ (960 cm^?1) phosphate peak as well as of B-type carbonate peak ν₂ (1070 cm^?1) were obtained to investigate structural differences between the specimens (healthy/unhealthy enamel tooth and different sectors on unhealthy surface tooth). A complete list of chemical specimens involved in chemical processes on dental enamel surface was obtained by Energy Dispersive x-rays (EDX) investigation.

It was noticed that mineralized carbonate peak at 1070 cm^?1 decreased significantly for unhealthy tooth enamel or spots areas (as fluorite groups), suggesting that carbonate ions are easily dissolved in the presence of fluoride.

The present study is confirming an organic origin for the dental “black stain.” The “black stain” is the result of a complex generation process from the damaged enamel, thus explaining their reappearance after the mechanical removing. A possible model for the “black stain” generation process is advanced.