Plasma sprayed titanium coatings with/without a shroud

Abstract: Titanium coatings were deposited by plasma spraying with and without a shroud. The titanium coatings were then assessed by scanning electron microscopy. A comparison in microstructure between titanium coatings with and without the shroud was carried out. The results showed that the shroud played an important role in protecting the titanium particles from oxidation. The presence of the shroud led to a reduction in coating porosity. The reduction in air entrainment with t he shroud resulted in better heating of the particles, and an enhanced microstructure with lower porosity in the shrouded titanium coatings were observed compared to the air plasma sprayed counterpart

Analysis of contact mechanics in micro flexible rolling

Micro flexible rolling is a new microforming method by online controlling and adjusting the roll gap to make various strip thickness in the submillimeter range. The micro flexibly rolled strips can be divided into three zones of the thicker zone, the thinner zone and the transition zone after experiencing the upward and downward rolling processes. However, it is tough to achieve the final target thickness especially in the transition zone due to a number of issues relating to the contact mechanics such as the change in the central neutral point/zone, the touch at the edges of the work rolls, the elastic deformation of the work rolls, the roll bite arc modifications in real time and the tribological conditions. All of these factors have significant influences on flatness, profile and surface finish of the rolled products, as well as the rolling forces. In the current work, a new model has been developed in order to clarify the micro flexible rolling process. This model considers a non-circular contact arc which includes an elastic loading region at the start of the roll gap, a plastic reduction region with backward slip, a central flattened region without slip, the plastic reduction region with forward slip, and an elastic unloading region at the end of the roll gap. In this study, the effect of speed ratio (the ratio of the lifting speed and the rolling speed) on the dimensions and the rolling forces along the transition zones is investigated. The contact mechanics in the micro flexible rolling are systematically analysed. The simulation results are found to be in line with the experimental ones, which means that the developed model with high precision is suitable for the analysis of the micro flexible rolling process

Accuracy Enhancement with Processing Error Prediction and Compensation of a CNC Flame Cutting Machine Used in Spatial Surface Operating Conditions

This study deals with the precision performance of the CNC flame-cutting machine used in spatial surface operating conditions and presents an accuracy enhancement method based on processing error modeling prediction and real-time compensation. Machining coordinate systems and transformation matrix models were established for the CNC flame processing system considering both geometric errors and thermal deformation effects. Meanwhile, prediction and compensation models were constructed related to the actual cutting situation. Focusing on the thermal deformation elements, finite element analysis was used to measure the testing data of thermal errors, the grey system theory was applied to optimize the key thermal points, and related thermal dynamics models were carried out to achieve high-precision prediction values. Comparison experiments between the proposed method and the teaching method were conducted on the processing system after performing calibration. The results showed that the proposed method is valid and the cutting quality could be improved by more than 30% relative to the teaching method. Furthermore, the proposed method can be used under any working condition by making a few adjustments to the prediction and compensation models

Adsorption models of hybridization and post-hybridisation behaviour on oligonucleotide microarrays

Analysis of data from an Affymetrix Latin Square spike-in experiment indicates that measured fluorescence intensities of features on an oligonucleotide microarray are related to spike-in RNA target concentrations via a hyperbolic response function, generally identified as a Langmuir adsorption isotherm. Furthermore the asymptotic signal at high spike-in concentrations is almost invariably lower for a mismatch feature than for its partner perfect match feature. We survey a number of theoretical adsorption models of hybridization at the microarray surface and find that in general they are unable to explain the differing saturation responses of perfect and mismatch features. On the other hand, we find that a simple and consistent explanation can be found in a model in which equilibrium hybridization followed by partial dissociation of duplexes during the post-hybridization washing phase.Comment: 26 pages, 6 figures, some rearrangement of sections and some additions. To appear in J.Phys.(condensed matter

Measurement of vibrational energy flow in a plate with high energy flow boundary crossing using electronic speckle pattern interferometry

The measurement of vibrational energy flow is an important tool in understanding the vibrational behaviour of structures. In the past, because of transducer constraints, the measurement of vibrational energy flow was mostly restricted to single point measurements. However, recent developments in advanced laser measurement techniques, such as electronic speckle pattern interferometry (ESPI), have gained interest in applying two-dimensional, multi-point measurement techniques to the estimation of vibrational energy flow. This paper addresses the measurement of vibrational energy flow in a plate by using an ESPI based vibrational energy flow measurement technique. A radially symmetric bending wave plate vibration model is introduced and theoretical expressions for energy-based quantities are derived. To assess the accuracy of the measurement method, these theoretical quantities are compared to synthetic results derived from the ESPI energyflowmeasurement technique. The ESPI measurement technique is also applied to an experimental ‘infinite’ plate. Thus, a specially designed experimental apparatus was constructed so as to minimise undesired wave reflections in the plate and, thus, achieve a high energy flow boundary crossing at the edges of the plate. To reduce the effect of optical noise contamination on the ESPI measured out-of-plane plate displacement data, optimal filters were applied prior to the vibrational energy flow computation. To appraise the accuracy of the experimental method, measured vibrational power on the plate is compared with measured vibrational input power. A difference of less than 1 dB between both quantities indicates that vibrational energy flow within a rectangular plate that contains radially symmetric wave propagation can be measured to a good degree of accuracy if appropriate filtering is applied

Development, Properties, and Applications of CVD Diamond-Based Heat Sinks

Heat sink is an essential component to nanoelectronics, microelectronics, and optoelectronics applications because it allows the thermal management of devices such as integrated circuits (ICs), microelectromechanical systems (MEMSs), and graphic unit processing. There are different materials being employed for heat sink production. Among them, diamond has stood out due to its excellent chemical and physical properties. This book chapter focuses on the development, properties, and applications of CVD diamond heat sinks. It covers the basic concepts of heat conduction applied to CVD diamond as a heat sink material and its production as freestanding CVD wafers of polycrystalline CVD diamond, since the literature about this topic is extensive, giving the reader a comprehensive overview. We will comprise the use and potential widening of applications of in CVD diamond heat sink technology, providing the reader with a substantial background at the current development of solutions and new frontiers in the practical use of CVD diamond thermal management devices

Implementation of an actuator line method for aerodynamic analysis of horizontal axis wind turbines

In this study, the NREL Phase VI turbine has been investigated using a computer code developed in C and ncoupled to Ansys Fluent. First the general theory has been explained and then the structure of the code has been presented. An ALM algorithm, coupled with a Blade Element Momentum (BEM) routine for the initialization of the loads, has been validated and proposed as an alternative to a full CFD analysis

Development of lumped parameters models for aerostatic gas bearings

L'abstract è presente nell'allegato / the abstract is in the attachmen