Digital Instrumentation of Slowly Moving Arcs

The slowly moving arc has been instrumented for position and velocity. A practical arc model has been used that has particular application to the needs of industry. Analog circuitry has been developed that interfaces the arc plant with a digital computer. A computer strategy has been applied for time-average filtering without losing the resolution capability of the computer's A/D converter. Through digital differentiation, arc velocity signals are obtained of a quality adequate for industrial control. The entire system is oriented towards the low-priced computer increasingly available in industry. Appendix I contains the flow chart for implementing this instrumentation on a computer. Appendix II presents a simple mathematical model of the instrumentation system.     

Managing arcs in large area sputtering applications

Arc detection and power supply response technology have evolved over the years to provide significant enhancement to virtually all thin film sputtering processes. While arcing can vary in severity and process impact it is generally accepted that arcs will occur, at some level, through the course of a typical deposition. The complexity of arc detection and response has grown as thin films continue to scale becoming increasingly sensitive to the particles arcs generate. Effective optimization of arc handling requires an understanding of both the nature of, and the contributors to, arcs that are occurring. Minimizing the impact of arcs requires an appropriate response that considers their characteristics and the elements that influence or interact with these characteristics. This study evaluates many of the key factors that influence arc rate, arc energy and arc persistence in large area sputtering applications. Interactions between arc behaviors and methods used to handle them are shown to offer key insight for methods extending beyond arc handling and into what is now called arc management. Ultimately, optimized arc management offers promise for controlling the factors that affect arc formation and persistence. This, in the end, allows for more intelligent response to the arcs that occur and better control over the impact arcs have on the deposition being performed.     

A scanning electron microscope study of the role of copper oxide layers on arc cathode erosion rates

The results are described of scanning electron microscopy of copper surfaces covered initially with oxide films of thickness from 2.5 to 340 nm, which have been the cathodes of electric arcs. The objective of the work has been to learn more about the mechanisms of electrical conduction through oxide films on non-refractory arc cathodes, electron emission into the arc and the erosion of the cathode. It is the latter aspect upon which this paper concentrates. Cathode erosion is a major problem when arcs rotate over electrode surfaces for very long times in certain industrial processes. Erosion rates are calculated here using SEMs, both for stationary 4.5 A arcs of duration 1ec, and for higher current arcs which were magnetically driven once over the cathode surface. Making allowance for the effect of current, these erosion rates are shown to be similar in magnitude and in their variation with oxide thickness, and reasons for this are given. Comparison is then made with erosion rates measured by weight loss for long-duration rotating arcs. In the light of the new data given here, it is now possible to understand better the remarkable changes which have occurred for long-duration arcs when varying arc velocity, water-cooling flow rate and arcing duration.     

Forced convective heat and mass transfer of a water droplet (effects of vapour concentration)

Abstract

Numerically controlled flame cutting machines used in shipyards are generally equipped only with line‐segment and circle‐arc moving capabilities. This paper attacks the problem of how to approximate a given curve of arbitrary shape by a sequence of line‐segments and circle‐arcs. The given curve is represented by the cubic spline interpolation curve formed by a set of net points on the curve. An efficient method based on the nature of cubic spline is then provided to approximate the interpolation curve by a sequence of linesegments and circle‐arcs. This method has been practically employed by the China Shipbuilding Co. in production line. In order to save storage and expedite the approximation, an effective method is also provided for selecting a near minimal set of net points whose cubic spline interpolation curve can adequately represent the actual given curve. Although the techniques are developed for shipbuilding purpose, they can find applications in other fields.     

Tri-Arc与Tandem双丝电弧焊的工作原理对比分析

目的 介绍一种称为Tri-Arc的新型双丝电弧焊接方法。方法 将Tri-Arc双丝电弧焊与应用较广的Tandem双丝电弧焊的系统构成和焊接电流波形进行对比分析。结果 Tri-Arc和Tandem两种双丝电弧焊接方法所使用的双丝焊枪相近,双电源相位同步控制和U/I脉冲控制方式类似。Tri-Arc和Tandem两种双丝电弧焊接方法的差异在于:Tandem双丝电弧焊的2个电弧是相对独立的,而Tri-Arc双丝电弧焊的2个电弧是相互耦合的,因此Tri-Arc双丝电弧焊又具有旁路耦合电弧的某些特点。结论 这种新型的Tri-Arc双丝电弧焊不仅具有与Tandem双丝电弧焊一样的高焊丝熔敷率,而且具有比Tandem双丝电弧焊更低的焊接热输入。     

八心圆弧拟合椭圆误差的理论解析及最优解

在数控加工领域,由于加工刀具一般采用的是球刀,因此在加工非圆的曲面时采用的是用圆弧拟合的方法转换成圆弧加工,理论拟合精度决定了加工误差;圆弧拟合椭圆有无数解,针对八心圆弧拟合椭圆没有准确的误差算法导致拟合椭圆的精度较模糊这一问题,根据图形学理论提出了等差拟合弧的概念,确定了八心圆弧拟合椭圆的定解区间,导出了拟合椭圆的八心圆弧法向误差超越方程解析式,并用二分法求解,在AutoCAD环境下应用Visual LISP语言编程,求解出根据法向误差确定八心圆弧拟合椭圆的最小误差带,从而确定八心圆弧拟合椭圆的最优解,使八心圆弧是否可以拟合给定形状公差的椭圆有了准确的判断依据.     

DELIVERY OF SUBSTANCES INTO CELLS AND TISSUES USING A PARTICLE BOMBARDMENT PROCESS

Biologists commonly wish to introduce a wide range of substances into living cells. Such substances include biological stains, proteins (antibodies or enzymes), and genetic material (either RNA or DNA). The cell membrane and, in the case of plant ceils, the cell wall pose formidable barriers which exclude many macromolecules. The concept of particle bombardment has been put forward as a universal mechanism for transporting substances into any living cell. An acceleration device has been designed and constructed which can accelerate small tungsten particles (1 to 4 urn in diameter) to velocities of about 1,000 to 2,000 ft/sec. We have found that these particles can penetrate cell walls and membranes and enter cells in a nonlethal manner. Thousands of cells can be penetrated simultaneously, in situ, as they occur in tissues. Particle bombardment has been shown to be effective in delivering foreign substances into a variety of plant species, including onion, tobacco, corn, and rice. This new method of delivering macromolecules into living cells and tissues should have diverse scientific applications.     

A cautious minimum variance controller with ARIMA disturbances

This article investigates a Cautious Minimum Variance (CMV) control approach for controlling industrial process variability when the model parameters are estimated from data and subject to uncertainty. CMV control has a number of advantages over traditional robust control methods. It incorporates probabilistic, as opposed to deterministic, measures of parameter uncertainty, which are more consistent with the statistical methods typically used to estimate industrial process models. CMV control is also more consistent with the objective of minimizing process variability, since parameter uncertainty is treated simply as an additional source of variation. CMV results have previously been derived for the case where the process disturbance follows a first-order integrated moving average model. This work extends the results to autoregressive moving average and autoregressive integrated moving average disturbances.     

Water distribution at solid/liquid interfaces visualized by frequency modulation atomic force microscopy

Interfacial phenomena at solid/water interfaces play an important role in a wide range of industrial technologies and biological processes. However, it has been a great challenge to directly probe the molecular-scale behavior of water at solid/water interfaces. Recently, there have been tremendous advancements in frequency modulation atomic force microscopy (FM-AFM), enabling its operation in liquids with atomic resolution. The high spatial and force resolutions of FM-AFM have enabled the visualization of one-dimensional (1D) profiles of the hydration force, two-dimensional (2D) images of hydration layers and three-dimensional (3D) images of the water distribution at solid/water interfaces. Here I present an overview of the recent advances in FM-AFM instrumentation and its applications to the study of solid/water interfaces.     

Velocity–Moisture Relationships for Sandy Soils: Experimental Results and Data Analysis

Many techniques have been proposed in recent years for in situ soil characterization, and among them, acoustic methods have been revealed to be particularly promising. These methods are based on measurements of the propagation velocities of seismic, sonic, and ultrasonic waves. However, in granular and porous mediums, velocities depend on the state of the saturation of the soil in a complex and not yet fully understood way. In this paper, a refined mathematical model to account for the effects of many soil properties such as porosity, bulk modulus, and pressure on acoustic wave velocity is proposed and investigated. The model has been validated by an experimental comparison between the measured and calculated values of velocities, using a kind of sand of known characteristics. A custom measurement system has been developed and realized for this purpose. The proposed model has potential applications in various areas, including geothermal resource evaluation, petroleum exploration, environmental protection, and archaeological and cultural site protection.     

Gefilterte Bogenbeschichtung – alte Probleme und neue Lösungen

Currently, the vacuum arc deposition (VAD) technique is well established in industry, primarily to deposit wear protective hard coatings such as metal nitrides and carbides onto tools and components. From the beginning of the industrial development of the vacuum arc deposition, it was obvious that the emission of macroparticles or droplets is a fundamental drawback of this coating technology. The emission is caused by the highly dynamic process of plasma generation and limits the fields of application significantly. Different methods have been proposed to minimize the macroparticle flux to the substrate surface. But the only way to hinder droplets from reaching the substrate reliable is to separate the plasma from particles by using curved magnetic fields. This filtered arc technique has proven its superiority of depositing high quality films compared to conventional arc applications in numerous laboratory tests. Current demands have stimulated new developments at the Fraunhofer IWS of more compact and higher productive filtered arc sources. One important application of ultra thin protective films is the topcoat on hard disks. In order to increase the storage density, the head‐to‐media spacing as well as the thickness of the overcoat has been reduced continuously. Until now, the thickness of the sputtered films was reduced to about 4 nm. The limit for this technology seems to be achieved. Filtered arc deposition is one of the most promising candidates for the deposition of thinner films – down to 1.3 nm with an even improved mechanical and chemical resistance. Another application area is the manufacturing of metallic lines and interconnections with high aspect ratios in the deep sub‐micron region in microelectronics. The excellent properties of this new filtered source for the deposition of conducting lines in microelectronics were been demonstrated. Actually, the technology for the subsequent deposition of barrier films and conducting wires is under development. Besides the micro technologies, there are a lot of applications requiring higher quality but not (yet) such a perfect film surface. Therefore, using a quite simple filter design – the so‐called Venetian blind filter – a filter unit was developed which can be used at the common industrial vacuum arc deposition machines. The filter does not reduce the deposition area, so the standard deposition processes can be used furthermore. With this filter, the number of droplets can reduced dramatically. A plasma transmission through the filter of approximately 20 % could be measured. Such filter module was realized and is in use now.     

Numerical modeling of electric arcs

Thermal plasmas generated by electric arc discharges between various types of electrodes or by plasmatrons have many well-established-and numerous potential-applications in extractive metallurgy, materials processing and high temperature chemistry. The current is from below 100 A in welding arcs to above 100 kA in electric arc furnaces (EAF) for steel-making and submerged arc furnaces (SAF) for production of silicon alloys. AC as well as DC is used. To improve process understanding and equipment design a number of simulation models have been developed, reaching higher levels of sophistication as more computer capacity has become available. This report reviews the state-of-the-art of arc simulation and discusses some important problems and challenges for future modelling work-in particular on high currents and AC operation. The perspective is the metallurgical and chemical engineers' demand for practical simulation models-not the physicist's very stringent approach.     

The railgun force in the presence of secondary arcs

A model of the railgun forces in the presence of a secondary arc has been developed. The model approximates the railgun rails as parallel, circular, cross-sectional wires, and the armature and secondary arc as filaments. The classical railgun force equation has been generalized, and its correspondence to an equivalent electrical circuit has been identified. It is shown that the forces tend to drive the primary and secondary arcs together or apart, depending on their separation and the magnitude of the currents flowing in the primary and secondary arcs     

Water distribution at solid/liquid interfaces visualized by frequency modulation atomic force microscopy

Abstract

Interfacial phenomena at solid/water interfaces play an important role in a wide range of industrial technologies and biological processes. However, it has been a great challenge to directly probe the molecular-scale behavior of water at solid/water interfaces. Recently, there have been tremendous advancements in frequency modulation atomic force microscopy (FM-AFM), enabling its operation in liquids with atomic resolution. The high spatial and force resolutions of FM-AFM have enabled the visualization of one-dimensional (1D) profiles of the hydration force, two-dimensional (2D) images of hydration layers and three-dimensional (3D) images of the water distribution at solid/water interfaces. Here I present an overview of the recent advances in FM-AFM instrumentation and its applications to the study of solid/water interfaces.     

Superharte amorphe Kohlenstoffschichten

Carbon films are distinguished by their special properties and the broad structural spectrum. Amorphous carbon films with dominating tetragonal bonds (ta‐C films) represent a high potential for tribological applications by their combination of superhardness and low adhesion. With the pulsed vacuum arc methods there are now industrial technologies available for the deposition of these promising protective coatings.     

A Method of Measuring the Duration of Arc Discharge Supplied with AC and DC Power Source

This paper describes a simple method of measuring the duration of an arc and/or the integrated are duration in a series of arcs supplied with ac and dc power source. This new method is based on the conversion of the arc duration into the time during which the larger generated power between the electrical contacts exist. The prototype equipment is constructed by using four IC products, a clock oscillator, and a digital counter; it is very simple, handy, accurate, and easy to deal with. The equipment can measure the duration of widely fluctuating arcs without changing the measuring ranges, whenever one arc, the reignition of arc and a series of arcs occur between the electrical contacts.     

Numerical investigations of arc behaviour in gas metal arc welding using ANSYS CFX

Current numerical models of gas metal arc welding (GMAW) are trying to combine magnetohydrodynamics (MHD) models of the arc and volume of fluid (VoF) models of metal transfer. They neglect vaporization and assume an argon atmosphere for the arc region, as it is common practice for models of gas tungsten arc welding. These models predict temperatures above 20 000 K and a temperature distribution similar to tungsten inert gas (TIG) arcs. However, current spectroscopic temperature measurements in GMAW arcs demonstrate much lower arc temperatures. In contrast to TIG arcs they found a central local minimum of the radial temperature distribution. The paper presents a GMAW arc model that considers metal vapour and which is in a very good agreement with experimentally observed temperatures. Furthermore, the model is able to predict the local central minimum in the radial temperature and the radial electric current density distributions for the first time. The axially symmetric model of the welding torch, the work piece, the wire and the arc (fluid domain) implements MHD as well as turbulent mixing and thermal demixing of metal vapour in argon. The mass fraction of iron vapour obtained from the simulation shows an accumulation in the arc core and another accumulation on the fringes of the arc at 2000 to 5000 K. The demixing effects lead to very low concentrations of iron between these two regions. Sensitive analyses demonstrate the influence of the transport and radiation properties of metal vapour, and the evaporation rate relative to the wire feed. Finally the model predictions are compared with the measuring results of Zielińska et al.     

Synthesis of carbon nanotubes

Carbon nanotubes play a fundamental role in the rapidly developing field of nanoscience and nanotechnology because of their unique properties and high potential for applications. In this article, the different synthesis methods of carbon nanotubes (both multi-walled and single-walled) are reviewed. From the industrial point of view, the chemical vapor deposition method has shown advantages over laser vaporization and electric arc discharge methods. This article also presents recent work in the controlled synthesis of carbon nanotubes with ordered architectures. Special carbon nanotube configurations, such as nanocoils, nanohorns, bamboo-shaped and carbon cylinder made up from carbon nanotubes are also discussed.     

Polypropylene/glass fibre 3D-textile reinforced composites for automotive applications

Textile-reinforced thermoplastic composites offer huge application potentials for a rapid manufacturing of components with versatile possibilities of integrating functions. However, an application of these new materials requires the knowledge of the directional dependent material properties. In this study, results are presented concerning selected relevant load cases for industrial applications. For the new group of multi-layered flat bed weft-knitted glass fibre/polypropylene composites (MKF-GF/PP), tensile tests under different temperatures and test velocities have been carried out as well as Charpy impact tests, open hole tension tests and dynamic-mechanical analysis. The mechanical properties of MKF-GF/PP and unidirectional GF/PP composites with tailored fibre surface and interphase, respectively, have been compared to those of woven GF/PP composites and GF/PP composites made of non-crimp fabrics (NCF) as a benchmark.     

The Possibility of Using Rail-Gun Arcs for Cleaning Metal Surfaces

Results are given of theoretical and experimental investigations of the physical characteristics of a free electric arc moving in a self-magnetic field along metal surfaces of different shapes contaminated by dielectric deposits. Similarly to welding, a direct-action arc is used, when the material being cleaned is one of the electrodes stabilizing the electric arc. Compared to plasmotrons, a facility using rail-gun arcs may exhibit a higher specific heat flux. This enables one to attain higher efficiency and capacity by reducing the loss of heat for heating the plate to be cleaned. Experiments are performed with steel samples contaminated by paraffin films. Data are obtained on the rate of arc propagation and its geometric characteristics, on the heat flux to the electrode being cleaned, on the cleaning capacity at different amplitudes of current, and on the thickness of paraffin coating. The basic possibility of removing dielectric deposits from metal surfaces with the aid of electric-arc treatment is demonstrated.