Search

The composition and microstructure of silicon nitride fibers after heat-treatment at elevated temperatures were investigated by XRD, NMR, XPS, SEM and TEM analyses. The results show that as-received fibers consisted of amorphous silicon nitride, and a little Si-C-O structure. During heat-treatment process, α-Si3N4 and β-Si3N4 formed resulting from the crystallization of amorphous silicon nitride, and the formation of β-SiC derived from the decomposition of Si-C-O structure. As heat-treated temperature increased from 1400oC to 1600oC, the above phenomenon become obvious, indicating that the fiber would possess high serving life with serving temperature lower than 1400oC. The tensile strength of fibers stays stable when heat-treated temperature was below 1200oC, while the strength retention of fibers sharply decreased to 50% after heat-treatment at 1400°C.

The microstructure and texture evolution of the as-cast and hot rolled grain-oriented silicon steel strips was investigated, and the precipitation of the inhibitors of the hot rolled strips was clarified. The results showed that the microstructure of the as-cast strip was characterized by coarse columnar grains with strong {001} fiber texture. The microstructure of hot rolled strips was composed of ferrite and pearlite and the microstructure was gradually refined with increasing hot rolling reduction. In the hot rolled strips, α and γ fiber textures were enhanced at the expense of initial {001} fiber texture and Goss texture was generated in the surface and sub-surface layer with increasing hot rolling reduction. Besides, a great number of dispersed MnS particles with the size of 20-30nm were observed in the hot rolled strips. These MnS particles could act as the effective inhibitors during the second recrystallization annealing of the grain-oriented silicon steel.

In order to efficiently fabricate dense three-dimensional carbon fiber reinforced mullite matrix composites (3D C/mullite), two kinds of Al2O3-SiO2sols with high solid content were used as raw materials. The ceramic yield and mullitization behavior of the sols and the densification process were investigated. It is indicated that the two sols have proper solid content and ceramic yield and can be completely transformed into mullite at 1573K, which make them be able to prepare composites. 3D C/mullite composites with a porosity of ∼25% were prepared by repeating less than 20 cycles of infiltration-drying-heating of sols, and the microstructures and mechanical properties were examined. The results suggest that the sol with smaller particle size derived composites exhibit well-sintered dense matrix and physically stronger interfacial bonding, which are beneficial to improve load-bearing and load-transferring capacity of matrix. As a result, this composites show much higher mechanical properties. The flexural strength and modulus are 2.4 times and 1.3 times as those of the sol with larger particle size derived composites, respectively.

we report the fabrication and microstructure of Ge-Sb-S-CsCl chalcogenide glass containing β-GeS2 nanocrystals. A Ge-Sb-S-CsCl chalcogenide base glass with the better crystalline ability is first fabricated by melt-quenching method, and a further careful thermal process has led to the formation of β-GeS2 nanocrystals in the glass. Transmission electron microscopy showed that the size of β-GeS2 nanocrystals with nearly monodisperse spherical shape ranges from 30 to 45 nm in the glass. Powder X-ray diffraction results confirm that the β-GeS2 nanocrystals are of high crystallization with orthorhombic phase. Energy dispersive spectroscopy is employed for the information of nanocrystals glass composition. It is worthwhile to note that the obtained Ge-Sb-S-CsCl chalcogenide glass containing β-GeS2 nanocrystals still keeps higher transmittance in mid- and far- infrared spectral region.

Accurate wind speed prediction is of significance to improve the ability to coordinate operation of a wind farm with a power system and ensure the safety of power grid operation. According to the randomness and volatility of wind speed, it is put forward that a WD_GA_LS_SVM short-term wind speed combination prediction model on basis of Wavelet decomposition (WD), Genetic alogorithms (GA) optimization and Least squares support vector machine (LS_SVM). Short-term wind speed prediction is carried out and compared with the neural network prediction model with use of the measured data of a wind farm. The results of error analysis indicate the combination prediction model selected is of higher prediction accuracy.

In order to broaden the absorbing bandwidth of radar-absorbing materials (RAMs), a type of sandwich-structure RAMs (SSRAMs) derived from a Salisbury absorber and comprising two dielectric layers and one resistive sheet was investigated. In this paper, the impedance characteristics of the SSRAMs were analysed and the mechanisms of broadening microwave-absorbing bandwidth were interpreted using a Smith chart. In order to realise the study’s SSRAMs, plain-woven glass fibre fabric and silicon carbide (SiC) fibre fabric with low electrical resistivity were employed as reinforcements of the dielectric layers and lossy layer, respectively. The microwave-absorbing properties of the SSRAMs were measured and compared with simulated results. The results showed that the experimental and simulated results were in good agreement, that the SSRAMs had better wideband microwave-absorbing properties and that the microwave-absorbing bandwidth at reflectivity below −10 dB can reach 11.6 GHz.

The finite element method to obtain the stiffness of MEMS (Micro-Electro-Mechanical Systems) accelerometer is difficult to give an exact expression, so a new method to analyze the stiffness of MEMS accelerometer was purposed. Both Mechanics and electricity analysis were used to calculate the stiffness of vacuum microelectronic accelerometer developed in our laboratory, and the control and detection circuits were design according to the result. Finally, the sensitivity, linearity and other performance were measured through the static gravitational field experiments; the least squares curve fitting correlation coefficient 0.9999 and linear 0.9%. The result shows that this method to analyze the stiffness of the stiffness of vacuum microelectronics accelerometer is correct and feasible, and this method can also be applied to other MEMS accelerometer with symmetrical structure and electrostatic force balance mode.

Aimed at the problems existed in remote monitoring system of shearer, this paper put forward a new remote control strategy of shearer based on virtual reality (VR) to achieve control visualization and automation of equipment in coal face. Firstly, after analysed the control demands of shearer in the automatic coal face, an overall scheme of coal mining machine virtual control system was put forward, its working principle and main composition were introduced also. Secondly, the methods and procedures for VR-based remote control system for shearer using Quest3D, such as virtual control platform, logic control, data transmission and communication were described. Finally, the experiments were carried out to validate and evaluate those technologies. The experimental result show that the VR techniques were the effective and efficient way to carry out remote control of mining equipment and to improve safety and reliability of production in coal mine.

Three-dimensional carbon fiber reinforced mullite composites (3D-Cf/mullite) were fabricated by sol-gel method with diphasic mullite sol as raw materials. SiC interfacial coatings were deposited by polycarbosilane infiltration and pyrolysis before sol-gel process. The as-fabricated composites showed 285.7MPa in flexural strength, relatively close to 277.6MPa of those without coatings. After treated at 1300°C and 1500°C in Ar atmosphere for 1h, the retention rates of flexural strength were 80.0% and 69.9%, respectively, which showed a great improvement compared to the composites without coatings. This was attributed to the prevention of carbothermal reduction between carbon fiber and matrix by SiC coatings.

An Fe-3wt% Si as-cast strip was produced by twin-roll strip casting process. The as-cast strip was hot rolled at 1150°C by one pass of 20% reduction and coiled at 550°C. The tensile test was carried out and the elongation was measured. The microstructure and texture of the coiled strip and the fracture surface morphology of the tensile samples were characterized. It is found that the microstructure of the as-cast strip was characterized by columnar ferrite grains with pronounced {001} fiber texture and martensite. The microstructure of coiled strip consisted of ferrite grains and pearlite, and the texture was mainly characterized by {001} fiber texture. The necking was absent during the tensile test and the elongation of coiled strip was as low as 12%. The fracture surfaces of the tensile samples mainly exhibited cleavage fracture mode with coarse cleavage facets and some ligaments.

In order to research the influence of bolt pretension on the flexible flange joints stiffness further, ANSYS finite element model was built on the basis of experimental investigations, and was used to research the influence of bolt pretension on the axial rigidity, shear rigidity and bending rigidity. The calculation results indicated that the axial rigidity, shear rigidity and bending rigidity were all increased along with the increase of bolt pretension, and the increase of axial rigidity was most obvious.

Distributed resources and microgrids may be designed for power supply in some area. AC-DC or DC-AC conversions are required in microgrids because of DC distributed resources, e.g. photovoltaic arrays. In this paper some factors are considered for determining the voltage grades of microgrids, both AC grid and DC grid, according to comprehensive analysis of microgrid design and operation. The factors include microgrid or distributed resource capacity, efficiency, cost, safety and so on. The line length, microgrid capacity and economic impacts are taken into account for selecting the voltage grade to connect the microgrid into the distribution system. Further, suitable AC and DC voltage grades are selected for residential and commercial application with some microgrid cases.

The development of wind power and PV has provided an important force for the development of Micro-Network under the islanding state. This paper first gives component model of different part of micro-network. Then show the method of sampling. Moreover, display the assessment of reliability under islanding state. Finally, give the conclusion on the evaluation of the isolated island.

The graphite reserves are 1146452300 tons in Heilongjiang Province, and its industry technology development reflect three aspects: graphite mining and selecting technology, processing technology, tailings utilization technology. The existing problems of graphite industry in Heilongjiang Province are: non-standard mining and management, small and scattered enterprise scale, backward technology, short deep processing industry chain, the lack of skilled personnel. Strategies of graphite industry development include: scientific planning, government guiding and investment, the adjustment of product structure, the proportion improvement of deep processing products.

Field emission accelerometer work in vacuum environment, the negative exponential relationship between the current and the distance of the cathode and anode electrode make the accelerometer has high sensitivity and serious non-linearity. A system simulation method by using SIMULINK tools was put forward, and the system simulation model was proposed. The system simulation was carried out under low vacuum and high vacuum environment. On the guidance of the simulation result, the circuit was designed and the performance of accelerometer was tested. The result indicated that the accelerometer have good linearity and sensitivity.

In order to solve the problems of failing to record, query, count and manage the production process data caused by the domestic industrial furnace industry configuration interface only focusing on the real-time data and status monitoring and control of the input parameters, this paper introduces an industrial furnace data management system based on WinCC user archive, and describes the systems principle, process and characteristics applications. This paper makes use of an industrial furnace data management system based on WinCC user archive to record the production process data, and query, count, manage and obtain the temperature curve, and help to improve production efficiency and production quality control, which have some promotional value.

This project put forward a kind of new low-cost real-time monitoring system of carbon dioxide. First, this equipment guides the gas into the device of chemical reaction by using step motor and measures the change of the gas’s volume which is guided into the device of chemical reaction after the reaction between the CO2 and NaOH by using the data-acquisition unit. Then, it processes data with Freescale MC9S12XS128 MCU and calculates the concentration of the CO2, in the meantime sends the data to the PC system by APC220V 3.0 wireless module, then using PC system makes the real time control over the concentration of the CO2 come true. Finally, detecting concentration accurately and steadily is achieved.

This paper presents an in-depth economic analysis on Photovoltaic power generation (PV) project. The research is based on nine business and technical proposals which with different investment operational pattern and different distributed generation (DG) integration technology of PV project. An all-life-cycle benefit/cost (B/C) assessment methods was used to assess the feasibility of the project. Through the accurately simulate of an annual PV output and load curves from typical time, received electric power and energy balance calculations and revenue forecast results. And then different operators’ electricity price benefits based on china’s complex tariff mechanism was estimated in this paper, while the initial PV panel investment, operation and maintenance, distribution network investment and losses of PV projects were calculated. Finally, through the PI value come to the best business model. Calculation results show that if power grid enterprise as the PV power producer, and use of virtual power plant technology for DG integration means more investment value than other business mode.

As for those high piers of bridge that constructed crossing sea and clough, the p-delta effect is evident; Looking upon present situation over the domestic and foreign research, stipulated laws on p-delta effect are various. Research shows that computing upper pier displacement by energy method was simple and versatile for different load case in comparing with other methods, and neglecting p-delta effect often underestimated the disadvantageous state when the pier is high; also, lateral loads like wind and seismic force further aggravate the pier state.

The thermocouple is extremely wide application in temperature measurement. The active sensor has the advantages of simple structure, wide measuring range, high precision, signal stability and other advantages and is widely used in the detection of furnace and pipeline temperature. The author analyzes the theory of measurement of thermocouple, and put forward a kind of originality of thought. According to this idea, the author derives several laws of thermocouple, and finds that a simple estimation method. Finally, some of the common thermocouple method measurement results are given.

High volume fraction SiCp/Al composites were milled in ultrasonic longitudinal high frequency vibration milling and conventional milling in this experiment. Meanwhile, the form of wear and wear mechanism of PCD milling tools were investigated. In addition, the relationship between the maximum wear of PCD milling tool and the length of milling were obtained. The results show that it is mainly flank wear of PCD cutting tool under the same milling parameters, which are caused due to hard points wear and thermal and chemical wear. Furthermore, the wear of PCD cutting tool by the ultrasonic vibration milling is smaller than that obtained by the conventional milling.

In this paper an improved image segmentation algorithm based on watershed transform is presented. Firstly the normalized cut method and watershed transform are explained and analyzed. Secondly the idea of the improved algorithm and the main formula are explained. We consider the area and perimeter when we merge adjacent regions. We define a new weight value and discuss the value of the parameterαandβ. Finally the experiment result is presented. The new algorithm reduces the nodes and the computational demand of the common normalized cut technique.

With the rapid development of national transportation, many bridges with higher and higher piers crossing sea and clough are constructed. The p-delta effect of tall piers in bridge is so evident that can not be ignored to assure the absolute safety of bridge. Research shows that, in comparison with other ways, energy analysis was simple and versatile for different load combinations in computing upper pier displacement, and neglecting p-delta effect often underestimated the disadvantageous state when the pier is high.

This paper proposes a dynamical performance-ranking method to predict the relative performance of soccer robot based on the mechanical analysis with energy materials. Introduce Fuzzy-PID control arithmetic in the soccer robot control system apply, make some mechanical analyses, give control system hardware compose and software achieve method. The experiment result shows that the design of robot soccer system is stable, reliability is high, and expansibility is strong.

This paper studies a new approach to developing AutoCAD in MFC with ActiveX Automation technology. It successfully solved the problem that development visions of Object ARX are not correspondent. It analyzed the application of dispatch interface in IDispatch technology and VARIANT type data in depth. In addition, it gave out practical cases in which this approach is used and particularly discussed the method for using blocks and searching through diagram objects. This designing realized the automatic designing of engineering drawing and automatic extracting of information.

In order to realize more compact and in particular cost-effective spectrometers MOEMS technology offers attractive possibilities. Based Littrow spectrometer structure for the near-IR, a micro mirror grating spectrometer has been designed and developed. The ZEMAX was used for designed this structure. The resolution of this design is 10nm, the spectral range from 900nm to 1400nm. A scanning micro mirror is the key element of this IR spectrometer set-up. This micro mirror is driven by electromagnetic force. Before fix the micro mirror, it was calibrated. Meanwhile, for reducing the cost of this system, the silicon silt was designed and fabricated. For resolution testing of this spectral system, we used one light correction filters finished this experiment. The test result has shown the resolution of this spectrometer is16.8nm. Finally, the relation between the spectral line scanning characteristic and wavelength spectral resolution was discussed.

This paper describes a practical method of Online Risk Assessment (ORA) on urban power system. It includes a set of models for online risk analysis of urban power system, the Online Probabilistic Risk Indices (OPRI) & their arithmetic, and the models for computing parameters varying with operating conditions which are used for Probabilistic Risk Indices calculation. The ability of the method can provide operators in control center the near term identification on security level, weak point, and riskiest event of urban power system. Further more, the system architecture of Online Risk Assessment (ORA) is presented, which is the preparation of software implementation of Online Risk Assessment System (ORAS) on Urban Power System

We selecte two bentonite products: activated clay and organo-bentonite, and introduce the related content of them like industrial applications, technology and raw materials of producting at the same time. After that, we choose the preparation processes of activated clay and organo-bentonite. Choose conditions of the prepared samples, arranging test methods by orthogonal test program, and preparing of the activated clay and organo-bentonite samples in accordance with the different test conditions. Finally, we draw this conclusion according to the test analysis and demonstration results. We propose the recommendations of the development of activated clay and organo-bentonite by Hongquan bentonite, pointing out that the shortcomings of this study and proposing pilot study of future.

Expressway is developed quickly in China, but its construction is seriously affected by the un-uniform deformation of the subgrade. The basic concepts of post- treatment and pre- treatment on freeway subgrade are firstly discussed in this article, and then a conclusion that Post- treatment Method can obviously reduce the after-work sink is gained, which may be used as a practical reference for lighting the un-uniform deformation of thick-filled subgrade in soft-soil area.

The design and machining of globoidal cam is difficult,because the shape of working surface is complex,and the curved surface of its space is undevelopable. Based on the above reasons,we proposed the parametric Modeling method for globoidal cam based on CATIA/CAA. Through the secondary development of CATIA,we realized the parameterized modeling of globoidal cam using the modelling mothods based on the feature model,it made the design process simplified,improved the efficiency of design,provided a new solution for the design of globoidal cam.

Based on the experimental results of three steel fiber reinforced high-strength concrete frame exterior joint under the low cycle loading, the numerical simulation by nonlinear finite element method was adopted to analyze their behaviors and to explore the influence of axial compressive ratio on seismic capacity of the joint. The results indicate that the increase of the axial compressive ratio enhances the restriction role to the joint core area concrete, slows down the degeneration degree of shearing-resistance capacity and stiffness, enhances the shearing-resistance capacity of the core area, the joint ductility and the energy dissipation capacity. The finite element analysis coincides well with the experimental results. In finite element analysis, steel fiber was equated with micro-reinforcement, and then put evenly into the concrete unit. Compared with the test results, the method of taking the steel fiber and concrete as a holistic model was thus validated.

Silver-loaded maifanite prepared at different particle sizes (60 mesh~200 mesh) and light calcining temperatures (100°C~800°C) of maifanite, different AgNO3solution concentrations (0.025 mol•L-1~0.300 mol•L-1) and pH values (2~7) were researched, simultaneously antibacterial ability of silver-loaded maifanite was investigated. Results indicate that the appropriate conditions of preparing silver-loaded maifanite are that particle size is 200 mesh, light calcining temperature is 100°C, AgNO3concentration is 0.1 mol•L-1at pH=7, and then the silver-loading amount of maifanite gained at this conditions is 1.27wt%; antimicrobial ability of silver-loaded maifanite decreases with increase of light calcining temperature.

Multi-ribbed frame grid (hereinafter referred to as MRFG) is the important part of Multi-ribbed composite wall and consisted of outer frame and ribbed grid. The reinforcement in column of outer frame is the main influence factor on the performance of MRFG. In this study, a MRFG specimen under laterally cyclic and axial loading in literature is numerically simulated with 5 kinds of different reinforcement ratio in column of outer frame, by a general finite element software and user-defined material model. The influence of different reinforcement ratio in column of outer frame on the mechanical behavior of MRFG has been discussed.

In order to determine the minimum thickness of cutting under different cutting condition of aluminum alloy materials 2A12 of micro-milling, research the size effect caused by the cutting edge radius and few microns per tooth in micro-milling process. Using thermal coupling model of Johnson-Cook as a material model of the workpiece, using Johnson-Cook shear failure of the law as part of the failure criteria, using coupled plane strain thermal units and hybrid adaptive grid technology to mesh, the friction between the tool and workpiece take the amendment Coulomb's law that combine with the sliding friction areas and areas of the adhesive friction, to the micro-milling by nonlinear and elastic-plastic finite element simulation. Through finite element analysis, the ratio of minimum radius of thickness to the cutting edge tool radius under different conditions of cutting speed and cutter blade was got, the size effect, stress field and cutting force under different cutting depth was got, and comparing and analysis the results, getting the various factors impact on the size effect of micro-milling, it provide a basis for the actual processing.

Thermochromic vanadium dioxide (VO2) exhibits a semi-conducting to metallic phase transition at about 68°C, involving strong variations in electrical and optical properties. A simple method was proposed to prepare VO2 thin films from easily gained V2O5 thin films. The detailed thermodynamic calculation was done and the results show that V2O5 will decompose to VO2 when the post annealing temperature reaches 550°C at the atmospheric pressure of less than 0.06Pa. The initial V2O5 films were prepared by sol-gel method on fused-quartz substrates. Different post annealing conditions were studied. The derived VO2 thin film samples were characterized using X-ray diffraction and X-ray photoelectron spectroscopy. The electrical resistance and infrared emissivity of VO2 thin films under different temperatures were measured. The results show that the VO2 thin film derived from the V2O5 thin film annealed at 550°C for 10 hours is pure dioxide of vanadium without other valences. It was observed that the resistance of VO2 thin film with thickness about 600nm can change by 4 orders of magnitude and the 7.5-14μm emissivity can change by 0.6 during the phase transition.

The pyrophyllite used in this study was from Taishun County(Wenzhou,China). The surface of pyrophyllite was modified by coating with N-(n-butyl)-3-aminopropyltrimethoxysilane (BAPTS) coupling agent and utility of the BAPTS-modified pyrophyllite was investigated as an adsorbent for removal of Pb(II) ions from aqueous solutions. XRD and SEM analysis were used to characterise the surface modification. It can be clearly observed that the pyrophyllite looses its aculeated surface structure and gains more smooth morphology. It was observed that the BAPTS -modified pyrophyllite adsorbed approximately 94.50% of Pb(II) ions at an initial concentration of 10 mg/l and an amount of BAPTS of 2.0%.

To study the deformation and fracture form of double-deck metal cylindrical tube under inside-explosive loading，the numerical simulation of the deformation and fracture process of double-deck metal cylindrical tube under inside-explosive loading of TNT was performed by LS-DYNA, and the fragment number and mass statistics software code is developed. The results showed that, with different length of TNT and detonating position the fragment number and mass is greatly different . The result can be a consult to some practicalities like the cannonball exploded in the gun barrel during shoot.