Yingilng Bao

Zhejiang University of Technology

Using the Advanced Research Weather Research and Forecasting (WRF) model, its performance of modeling radiation feature and finding a reasonable combination of model schemes for the simulation of radiation over Badain Jaran Desert was evaluated. These simulations were performed in 9-days (11th-19th of August, 2009) under different weather condition...

The impacts of inhomogeneity of the oasis interior on the oasis self-maintenance mechanism are investigated by using the mesoscale model MM5 (the fifth-generation Pennsylvania State University National Center for Atmospheric Research (NCAR) mesoscale model) with satellite observations of land use types, vegetation fraction and surface-layer soil mo...

Mesoscale meteorological modeling is an important tool to help understand the energy budget of the oasis. While basic dynamic and thermodynamic processes for oasis self-maintaining in the desert environment is well investigated, influence of heterogeneous landscapes of oasis interior on the processes are still important and remain to be investigate...

The radiation budget and surface energy over the Jinta oasis were simulated by WRF mesoscale meteorological model which combined with satellite-derived underlying surface land use-types and vegetation types. The model results were verified by experiment of "Theoretical study and observations of water-energy exchange and planetary boundary on inhomo...

A computational model is developed to predict the temperature profile over an organic coating on a metal surface as a result of the action of a moving flame. The deflection of the flame as it impinges on the surface is simulated and its consequent heat transfer to the polymer is determined. The scanning action of the flame across the substrate is q...

Silicon nitride decomposes before it can melt, and so thermal spraying of pure silicon nitride powder is impracticable. To address this difficulty, feedstock powder for plasma spray deposition has been developed in which each particle is a composite of silicon nitride in a low temperature borosilicate glass matrix. The research showed that the sili...

The high temperatures and velocities of plasma jets give them uniquely high heat transfer coefficients and the ability for extremely rapid heat transfer. These characteristics have been applied to use plasma scanning to sinter aluminosilicate films prepared by sol–gel processing. The critical thickness, up to which crack-free films can be obtained,...

Silicon nitride composite powders have been prepared in which each individual powder particle contains submicron silicon nitride particles completely encapsulated in a glass matrix. This necessitated raising the sintering temperature as the silicon nitride content increased in order to reduce the viscosity of the glass and enhance the Darcian flow....

Silicon nitride does not melt but decomposes at 1900°C and so thermal spraying of pure silicon nitride powder is impracticable. However, the use of silicon nitride and other non-oxide ceramics as thick, thermally sprayed coatings has considerable engineering potential owing to their unique combination of properties. This research shows that embeddi...

Some albedo parameterizations of SZA dependence were evaluated in a simple land surface model BATS using in situ data over Gobi and Desert. Results indicate schemes of SZA dependence can improve the modeling of surface albedo in different degree in diurnal variation and values. Compared with the observations, methods of modified BRDF and B from Wan...

Thermal-spray processes involve many sources of uncertainty: the feedstock powder has a wide particle size distribution, the powder particles leave the powder injection nozzle in a variety of angles and velocities and enter a thermal jet that has enormous temperature and velocity gradients. Particles of various sizes therefore travel through the ga...

In plasma spraying, the size and initial velocity of indivdual feedstock particles injected into the flame are essentially random variables within the fairly wide ranges of the injection conditions and powder characteristics. As a result, the motion and heating of particles cannot be specified in a deterministic manner and so a simulation based on...

The temperature of the substrate and coating during thermal spraying may have a significant effect on coating quality, especially for low-temperature materials such as polymers. The temperature must be high enough to thermally activate the necessary interfacial bonding mechanisms but low enough to avoid degradation of the coating material or of the...

A Lagrangian two-phase flow approach has been used to simulate the gas flow and simultaneously the motion and heating of particles in a plasma jet. This enables the interaction between the gas flow and feedstock powder particles to be investigated during the plasma spraying of engineering coatings. An essential element of the Lagrangian two-phase f...

Ultra-high molecular weight polyethylene (UHMWPE) has remarkable properties in the bulk state and has substantial potential for use as a protective coating on metals. However, the molecular architecture responsible for these exceptional properties also causes difficulties in the formation of coatings by thermal spraying. This paper studies the effe...

Plasma-sprayed coatings are formed by the impact and accumulation of feedstock particles with random sizes, temperatures and velocities on the surface of a substrate. The simulation results obtained for a single particle are not able to represent the behaviour of the feedstock in the process. A statistical analysis is required to describe this stoc...

The temperature of a substrate during thermal spraying may have a significant influence on the quality of coatings, especially for low-temperature materials such as polymers. The temperature must be high enough to thermally activate the interfacial bonding mechanisms but low enough to avoid degradation of the coating material or the substrate surfa...

A computational model has been developed to simulate the deposition of enamel on steel substrates by the use of plasma spraying. The model predicts the temperature profiles of the feedstock particles during their flight in the gas jet and the concurrent heating of the substrate. A process window is predicted for enamel deposition in terms of plasma...

Non-oxide ceramics, such as silicon nitride, have a unique combination of high strength, toughness, wear resistance, thermal and chemical stability. However, the use of these materials as thick protective coatings on engineering components has been severely restricted by their decomposition behavior. Silicon nitride, for instance, does not melt but...

Ultra-high molecular weight polyethylene (UHMWPE) has remarkable properties in the bulk state and has substantial potential for use as a protective coating on metals. However, the molecular architecture responsible for these exceptional properties also causes difficulties in the formation of coatings by flame spraying. This paper studies two UHMWPE...

The motion and heating of a single particle in a plasma jet is strongly influenced by the feedstock injection conditions and can be predicted using computational modelling as described in the literature. In practice, however, the size and initial velocity of a given particle are essentially random variables within the fairly wide limits of the inje...

A theoretical model based on a CFD (computational fluid dynamics) methodology has been developed to simulate the motion and heating of particles in a plasma jet during plasma spraying. The particle motion and heat transfer equations are solved semianalytically using a prediction-correction method, taking into account phase changes during heating. T...

In this paper, a quantitative model of the viscous behavior of two-phase particles hitting a substrate is used to optimize a plasma spraying process for silicon-nitride composite layers. The model is derived from the observed behavior of Si3N4-YAS (Y2O3-Al2O3-SiO2) layers and provides a basis for further study of ceramic-matrix composite layers. Pa...

A ball-milled mixture of glass and alumina powders has been plasma sprayed to produce alumina-glass composite coatings. The coatings have the unique advantage of a melted, ceramic secondary phase parallel to the surface in an aligned plateletlike-composite structure. The alumina raises the hardness from 300 HV for pure glass coatings to 900 HV for...

Jets produced in conventional atmospheric plasma spraying are inevitably heterogeneous due to the mechanics of a rapid gas flow entering a stagnant environment. The resulting high air content together with considerable velocity and temperature variations will adversely affect the quality of coatings. This paper applies a CFD code to simulate the ef...

The behaviour of glass coatings during thermal spray deposition is fundamentally different from that of metal and ceramic coatings because quench stresses can berelaxed during spraying. However, the expansion coefficient mismatch between the coating and the steel substrate remains an important source of residual stress and this paper investigates t...

Experimental measurements have been carried out with the aim of investigating the residual stresses generated during plasma spray deposition of glass composite coatings. The research shows that the behaviour of these materials is fundamentally different from metals and ceramics. The quench stress in the glass composites can be eliminated by plasma-...

A ball-milled mixture of glass and alumina powders has been plasma sprayed to produce alumina-glass composite coatings. The coatings have the unique advantage of a melted ceramic secondary phase parallel to the surface in an aligned platelet composite structure. The alumina raises the hardness from 300HV for pure glass coatings to 900HV for a 60wt%...

Experimental measurements have been carried out with the aim of investigating the residual stresses generated during plasma spray deposition of glass composite coatings. The research shows that the behaviour of these materials is fundamentally different from metals and ceramics. The quench stress in the glass composites can be eliminated by plasma-...

A high-intensity, plasma-sputter negative-ion source based on the use of RF power for plasma generation has been developed that can be operated in either pulsed or dc modes. The source utilizes a high-Q, self-igniting, inductively coupled antenna system, operating at 80 MHz that has been optimized to generate Cs-seeded plasmas at low pressures (ty...

A multi-sample Cs sputter negative-ion source, equipped with a conical-geometry, W-surface-ionizer has been designed and fabricated that permits sample changes without disruption of on-line accelerator operation. Sample changing is effected by actuating an electro-pneumatic control system located at ground potential that drives an air-motor-driven...

This paper investigates the degradation of polymers during thermal spraying with special reference to the changes in molar mass. A study is carried out on the degradation of polymethylmethacrylate (PMMA) during plasma spraying. The infrared spectroscopy showed that the coating did not lead to any significant chemical reactions. However, the gel per...

Experimental work has shown that enamel frits can be plasma sprayed but there is a tendency for cracks to form in the deposits. This investigation indicates that cracking is due to the development of residual stresses during deposition. Theoretical analysis and in-situ experimental measurements show that the residual stresses in enamel coatings are...

An investigation has been undertaken on the analysis of residual stress in glass coatings during plasma spraying. Theoretical analysis and in-situ experimental measurements show that the residual stresses in glass coatings are particularly sensitive to the heat input from the plasma flame, since this can raise the temperature to above the glass tra...

Kinetic and heat transfer analysis have been undertaken in order to predict the decomposition of polymer feedstock particles during thermal spraying. Thermogravimetric measurements indicated that the decomposition of PMMA had an order of reaction of unity and an activation energy of 135 kJ mol-1. The polymer decomposition temperature is shown to be...

An investigation has been undertaken on the analysis of residual stress in glass coatings during plasma spraying. Theoretical analysis and in-situ experimental measurements show that the residual stresses in glass coatings are particularly sensitive to the heat input from the plasma flame, since this can raise the temperature to above the glass tra...

PMMA coatings have been applied to steel by plasma spraying. The work shows that the polymer decomposition temperature is a function of the particle residence time in the plasma and is much higher than in conventional polymer processing. The analysis indicates that realistic prediction of the temperature profiles of in-flight polymer particles can...

Heat transfer theory has been used to predict the influence of process parameters on the decomposition of in-flight particles and deposited layers during the thermal spraying of polymer coatings. The methodology is applicable to all polymers and the generic family of thermal spray processes, including plasma, combustion flame, and high-velocity oxy...

The adhesion of plasma sprayed polyamide and PMMA coatings to steel depends markedly on the plasma arc power, the spraying distance and the substrate temperature. Each of these process parameters shows an optimum value with respect to adhesion. The underlying reason for this behaviour is the pronounced sensitivity of polymers to temperature. Heat t...

Experimental work has been undertaken to investigate the importance of the temperature of the substrate during deposition on the coating-adhesion of plasma sprayed borosilicate glass coatings. The work shows that the measured adhesion increases markedly with substrate temperature up to 400°C above which no further major increase takes place. Heat t...

Magnesium hydroxide is shown to dehydrate endothermically to magnesium oxide over a similar temperature range to that of the thermal degradation of polyamide. The extent of dehydration in plasma spraying is shown to be a function of particle size. However the research indicates that the use of magnesium hydroxide as a filler in plasma sprayed polya...

Plasma spray deposition of epoxies under normal conditions produces coatings with low wear resistance. The research shows that the difficulty in achieving satisfactory properties is a result of the rapid heat flow from the coating to the substrate, which suppresses the crosslinking reaction. The results indicate that the use of substrate preheating...

A heat transfer analysis has been undertaken to predict the influence of process parameters on the decomposition of in-flight particles and deposited layers during thermal spraying of polymer coatings. The theoretical analysis shows that polymers are unique in developing large temperature gradients, which accelerates the degradation of the surface...

A heat transfer analysis has been undertaken to predict the temperature profiles of in-flight polymer particles in a plasma jet. It shows that the development of large temperature gradients below the surface of particles during plasma spraying is a distinctive characteristic of polymers and is primarily due to their low rate of internal heat conduc...

Optimisation of thermal spraying, as for generic polymers, produces thermosets in the uncured condition with unsatisfactory engineering properties. The present paper develops a theoretical process modelfor thermoset reactive deposition, based on heat transfer mechanisms, which enables temperature profiles to be generated as a function of process va...

The production of ceramic-polymer and metal-polymer matrix composite coatings by plasma spray deposition has been studied. The work involves the co-deposition of alumina, magnesium hydroxide, silica and stainless steel with nylon by simultaneous powder injection into the plasma jet. The results show that dense deposits with sound bonding between th...

Glass-polyamide composite coatings have been successfully plasma sprayed on to steel by simultaneous injection of glass and polyamide particles into the plasma jet. The deposition conditions were selected such that the polyamide melts in the jet in order to provide the matrix, whereas the glass remains solid to avoid overheating the polymer. The de...

The feasibility of plasma spray deposition of polyamide 11 on steel has been investigated. The conditions for he preparation of high integrity deposits have been established by the control of precursor powder injection,torch traverse speed, and arc power. The optimal deposition conditions are designed to produce complete particle melting in the pla...

Nylon 11 coatings up to 2mm in thickness have been successfully deposited by plasma spraying. The work showed that control of the torch traverse speed and arc power were essential for the production of sound coatings. The coating quality deteriorated rapidly for torch traverse speeds below 100mms-1 due to thermal degradation, under the conditions u...

The beta-lactamase crude extract of Bacteroides fragilis 55 was chromatographed with DEAE-sepharose CL-6B and sephadex G-100. The partial purified enzyme proteins was further purified by cutting the band on PAGE in which the beta-lactamase was distinguishable from other proteins by our method of fluorescent staining. Using purified preparations to...

Bacteroides fragilis 55 from clinical specimens was selected at random for beta-lactamase investigation of physico-chemical and enzymological properties. The enzyme was characterized as a cell-associated cephalosporinase with some penicillinase activity, the molecular weight of the enzyme being 43,000 and the pI 4.95. It could be inhibited by cefox...