Synthesis and ceramization of polycarbosilane containing beryllium简

Polycarbosilane containing beryllium （BPCS） precursors was prepared by the reaction of polycarbosilane （PCS） with beryllium acetylacetone （Be （acac）2）. The analysis of structures and components of BPCS demonstrates that their main structures are basically the same as PCS. Ceramization of BPCS precursors shows that BPCS precursors are organic below 600 °C and inorganic at 800 °C. At 1400 °C, BPCS precursors convert into silicon carbide ceramics. The ceramization of different beryllium content precursors were studied, which show that beryllium plays an important role in the inhibition of crystalline grain growth of β-SiC at high temperature and it can adjust the dielectric constant of silicon carbide ceramics.     

Optimization of ultrasonic elastography by coded excitation and transmit-side multi-frequency compounding简

To improve the quality of ultrasonic elastography, by taking the advantage of code excitation and frequency compounding, a transmitting-side multi-frequency with coded excitation for elastography （TFCCE） was proposed. TFCCE adopts the chirp signal excitation scheme and strikes a balance in the selection of sub-signal bandwidth, the bandwidth overlap and the number of sub-strain image based on theoretical derivation, so as to further improve the quality of elastic image. Experiments have proved that, compared with the other optimizing methods, the elastographyic signal-to-noise ratio（Re-SN） and contrast-to-noise ratio（Re-CN） are improved significantly with different echo signal-to-noise ratios （ReSN） and attenuation coefficients. When ReSN is 50 dB, compared with short pulse, Rc-SN and Re-CN obtained by TFCCE increase by 53% and 143%, respectively. Moreover, in a deeper investigation （85-95 mm）, the image has lower strain noise and clear details. When the attenuation coefficient is in the range of 0-1 dB/（cm.MHz）, Re-SN and Re-CN obtained by TFCCE can be kept in moderate ranges of 5〈Re-SN〈6.8 and 11.4〈Re-CN〈15.2, respectively. In particular, for higher tissue attenuation, the basic image quality cannot be ensured with short pulse excitation, while mediocre quality strain figure can be obtained by TFCCE. Therefore, the TFCCE technology can effectively improve the elastography quality and can be applied to ultrasonic clinical trials.     

Exploration and determination of the principles of rotary-percussive underground slimhole drilling简

A possibility of the efficient use of rotary percussive drilling to provide drilling smaller diameter holes (40–70 mm) both in mining and prospecting is disclosed herein. A new construction designed for the nipple thread connection is described. The relative amplitude variation, change of power pulse time and energy in their propagation throughout the drilling tool are determined. A possibility of the efficient power pulse transfer along the drill string to the rock destruction tools with new nipple connections which allow automating the make-up and breakout system of drill pipe was supported by experiments.     

Shadow detection combining characters of human vision简

A shadow detection method using pulse couple neural network inspired by the characters of human visual system is proposed.More precisely,lateral inhibition of human vision and coefficient of variation are combined together to improve the pulse couple neural network.Shadow detection is considered to be a shadow region segmentation problem.Experiment shows that the presented method is consistent with human vision compared to shadow detection methods based on HSV and pulse couple neural network（PCNN） by both subjective and objective assessments.     

Bioleaching of low-grade copper sulfide ores by Acidithiobacillus ferrooxidans and AcidithiobacillusThiooxidans简

The grown conditions of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans were investigated,and then experiments were conducted to research the bioleaching behaviors of crude ore of copper sulfide and hand-picked concentrates of chalcopyrite by Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans.The experimental results show that the bacteria grow best when the temperature is（30±1） °C and the pH value is 2.0.The bacteria concentration is 2.24×107 mL-1 in this condition.It is found that the copper extraction yield is affected by the inoculum size and the pulp density and the extraction yield increases as the inoculum size grows.The bioleaching rates reach their highest point in sulfide copper and chalcopyrite with a pulp density of 5% and 10%,respectively.Column flotation experiments of low-grade copper sulfide ores show that the bioleaching recovery reaches nearly 45% after 75 days.     

Mechanism of ultrasonic-pulse electrochemical compound machining based on particles简

The electric double layer with the transmission of particles was presented based on the principle of electrochemistry. In accordance with this theory, the cavitation catalysis removal mechanism of ultrasonic-pulse electrochemical compound machining （UPECM） based on particles was proposed. The removal mechanism was a particular focus and was thus validated by experiments. The principles and experiments of UPECM were introduced, and the removal model of the UPECM based on the principles of UPECM was established. Furthermore, the effects of the material removal rate for the main processing parameters, including the particles size, the ultrasonic vibration amplitude, the pulse voltage and the minimum machining gap between the tool and the workpiece, were also studied through UPECM. The results show that the particles promote ultrasonic-pulse electrochemical compound machining and thus act as the catalyzer of UPECM. The results also indicate that the processing speed, machining accuracy and surface quality can be improved under UPECM compound machining.     

Direct reduction of carburized pre-reduced pellets by microwave heating简

A new iron-making process using carburized pre-reduced iron ore pellets and microwave heating is investigated. The pre-reduced pellets, with a porous structure, and fine particles are carburized homogeneously at 400-650 ℃ in a CO atmosphere. The carburized carbon not only acts reaction as a reduction agent, but also absorbs microwave in the reduction process. Hence, the carburized pre-reduced pellets can be rapidly reduced by microwave heating. There are three procedures involved in the process, namely, gas-based pre-reduction, low-temperatttre carburization and deep reduction by microwave heating. Carburized pre-reduced iron ore pellets show a rapid temperature rise that is twice as fast as the results for pre-reduced pellets in the laboratory. This not only improves the efficiency of the microwave heating, but also accelerates the reduction of iron oxides. The temperature of the pre-reduced pellets rises to 1050 ℃ in 45 min when the carburization rate is 2.02%, and the metallization rate and compressive strength reach 94.24% and 1725 N/pellet, respectively.     

Effects of MgO on densification and consolidation of oxidized pellets简

The calcined magnesite was utilized as a kind of MgO bearing additive to produce MgO bearing pellets. The effects of MgO on densification and consolidation of pellets were investigated. The experimental results show that, at the same process parameters, the porosity and pore size distribution of green pellets have no evident relation with the MgO bearing additive, pore size of green pellets is between 15 μm and 35 μm and the porosity of green pellets is about 34%. There is a densification and consolidation phenomenon during the induration process; the pore size and porosity of product pellets decrease gradually; and the structure of product pellets becomes dense. MgO makes a negative effect on the densification and consolidation of product pellets, the densification ratio of pellets decreases from 46.3% to 28.6% with the addition of MgO bearing additive from 0 to 2.0 %. The porosity and the pore size of product pellets increase gradually with the increase of MgO content; When the mass fraction of MgO bearing additive increases from 0 to 2.0%, the pore size of product pellet increases and the pore size distributes in a large range. Also, the porosity increases from 18.61% to 24.06%.     

Mechanical,piezoelectric and some thermal properties of (B3) BP under pressure简

Some compounds of group III-V semiconductor materials exhibit very good piezoelectric, mechanical, and thermal properties and their use in surface acoustic wave （SAW） devices operating specially at GHz frequencies. These materials have been appreciated for a long time due to their high acoustic velocities, which are important parameters for active microelectromechanical systems （MEMS） devices. For this object, first-principles calculations of the anisotropy and the hydrostatic pressure effect on the mechanical, piezoelectric and some thermal properties of the （B3） boron phosphide are presented, using the density functional perturbation theory （DFPT）. The independent elastic and compliance constants, the Reuss modulus, Voigt modulus, and the shear modulus, the Kleinman parameter, the Cauchy and Born coefficients, the elastic modulus, and the Poisson ratio for directions within the important crystallographic planes of this compound under pressure are obtained. The direct and converse piezoelectric coefficients, the longitudinal, transverse, and average sound velocity, the Debye temperature, and the Debye frequency of （B3） boron phosphide under pressure are also presented and compared with available experimental and theoretical data of the literature.     

Spontaneous combustion tendency of fresh and pre-oxidized sulfide ores简

Three representative sulfide ore samples were collected from typical metal mines,and their corresponding pre-oxidized products were obtained under nature environment.The thermal behaviors of each sample at heating rates of 5,10,15 and 20 °C/min in air flow from ambient temperature to 800 °C were studied by simultaneous thermal analysis and the TG/DSC curves before and after the pre-oxidation were compared.By the peak temperature of DTG curves,the whole reaction process for each sample was divided into different stages,and the apparent activation energies were calculated by the Ozawa-Flynn-Wall method.The results show that the reaction process of each sample after pre-oxidation is more complex,with quicker reaction rates,fewer heat production quantities,and higher or lower ignition-points.The apparent activation energies decrease from 364.017-474.228 kJ/mol to 244.523- 333.161 kJ/mol.Therefore,sulfide ores are more susceptible to spontaneous combustion after the pre-oxidation.     

Enantioselective extraction of clorprenaline enantiomers with hydrophilic selector of sulfobutylether-β-cyclodextrin by experimentand modeling简

Enantioselective extraction of hydrophobic clorprenaline （CPE） enantiomers from organic phase to aqueous phases with sulfobutylether-β-cyclodextrin （SBE-β-CD） as the selector was investigated with insight into a number of important process variables, such as the type of organic solvent, concentration of selector, pH, and temperature. Equilibrium of the extraction system was modeled using a reactive extraction modcl with a homogeneous aqueous phase reaction. The important parameters of this model were determined experimentally. The physical distribution coefficients for molecular and ionic CPE were determined as 0.3 and 8.93, respectively. The equilibrium constants of the complexation reaction with SBE-β-CD were determined as 152 and 110 L/mol for R- and S-CPE, respectively. Results show that the experimental data agree with the model predictions perfectly. Comprehensively considering the experiment and model, the extraction conditions are optimized and the best extraction conditions are： pH of 6.0, SBE-β-CD concentration of 0.04 tool/L, and temperature of 5 ℃, providing the enantioselectivity （a） of 1.25, the fraction of R-CPE （φR） in aqueous phase of 0.71 and performance factor （pf） of 0.025.     

Fabrication and thermal performance of grooved-sintered wick heat pipe简

Some novel grooved-sintered composite wick heat pipes（GSHP） were developed for the electronic device cooling.The grooved-sintered wicks of GSHP were fabricated by the processes of oil-filled high-speed spin forming and solid state sintering.The wick could be divided into two parts for liquid capillary pumping flow：groove sintered zone and uniform sintered zone.Both of the thermal resistance network model and the maximum heat transfer capability model of GSHP were built.Compared with the theoretical values,the heat transfer limit and thermal resistance of GSHP were measured from three aspects：copper powder size,wick thickness and number of micro grooves.The results show that the wick thickness has the greatest effect on the thermal resistance of GSHP while the copper powder size has the most important influence on the heat transfer limit.Given certain copper powder size and wick thickness,the thermal resistance of GSHP can be the lowest when micro-groove number is about 55.     

Evaluating ultrasound signals of carbon steel fatigue testing using signal analysis approaches简

The application of ultrasound techniques to monitor the condition of structures is becoming more prominent because these techniques can detect the early symptoms of defects such as cracks and other defects. The early detection of defects is of vital importance to avoid major failures with catastrophic consequences. An assessment of an ultrasound technique was used to investigate fatigue damage behaviour. Fatigue tests were performed according to the ASTM E466-96 standard with the attachment of an ultrasound sensor to the test specimen. AISI 1045 carbon steel was used due to its wide application in the automotive industry. A fatigue test was performed under constant loading stress at a sampling frequency of 8 Hz. Two sets of data acquisition systems were used to collect the fatigue strain signals and ultrasound signals. All of the signals were edited and analysed using a signal processing approach. Two methods were used to evaluate the signals, the integrated Kurtosis-based algorithm for z-filter technique （I-kaz） and the short-time Fourier transform （STFT）. The fatigue damage behaviour was observed from the initial stage until the last stage of the fatigue test. The results of the I-kaz coefficient and the STFT spectrum were used to explain and describe the behaviour of the fatigue damage. I-kaz coefficients were ranged from 60 to 61 for strain signals and ranged from 5 to 76 for ultrasound signals. I-kaz values tend to be high at failure point due to high amplitude of respective signals. STFT spectrogram displays the colour intensity which represents the damage severity of the strain signals. I-kaz technique is found very useful and capable in assessing both stationary and non-stationary signals while STFT technique is suitable only for non-stationary signals by displaying its spectrogram.     

Propagation simulation and dilatancy analysis of rock joint using displacement discontinuity method简

A revised displacement discontinuity method （DDM） program is developed for the simulation of rock joint propagation and dilatancy analysis. The non-linear joint model used in the program adopts Barton-Bandis normal deformation model, Kulhaway shear deformation model and Mohr-Coulomb criterion. The joint propagation criterion is based on the equivalent stress intensity factor which can be obtained by regression analysis. The simulated rock joint propagation accords well with the existing knowledge. The closure and opening ofj oint is investigated by DDM, and it is shown that if the opening volume of propagated joint is larger than closure volume of the old joint, the joint dilatancy occurs. The dilatancy condition is mainly controlled by the normal stiffness of the rock joint. When the normal stiffness is larger than the critical value, joint dilatancy occurs. The critical normal stiffness of rock joint changes with the joint-load angle, and joint dilatancy is most possible to occur at 30°.     

Modeling,identification and compensation for geometric errors of laser annealing table简

In order to improve the process precision of an XY laser annealing table, a geometric error modeling, and an identification and compensation method were proposed. Based on multi-body system theory, a geometric error model for the laser annealing table was established. It supports the identification of 7 geometric errors affecting the annealing accuracy. An original identification method was presented to recognize these geometric errors. Positioning errors of 5 lines in the workspace were measured by a laser interferometer, and the 7 geometric errors were identified by the proposed algorithm. Finally, a software-based error compensation method was adopted, and a compensation mechanism was developed in a postprocessor based on LabVIEW. The identified geometric errors can be compensated by converting ideal NC codes to actual NC codes. A validation experiment has been conducted on the laser annealing table, and the results indicate that positioning errors of two validation lines decreased from ±37 μm and ±33 μm to±5 μm and ±4.5 μm, respectively. The geometric error modeling, identification and compensation method presented in this work can be straightforwardly extended to any configurations of 2-dimensional worktable.     

Mathematical model of slotting manufacture and simulation for cosine gears简

A slotting method for cosine gears was proposed by using the involute cutter based on the conjugate theories of digital surface and gear meshing. The slotting model between the cosine tooth surface represented by discrete points and the cutter figuration determined by analytic function was built for their geometrical relationship and conjugate motion during the machining process. Conjugate points in the cutter section corresponding to the discrete points on the cosine gear tooth surface and the conjugate movements were solved. By using the flexible control of the CNC procedure, the active control of the cutting trace of the slotting cutter was accomplished and the envelop forming of the cosine gear was obtained. Based on the software C＋＋ and Matlab, the computer aided manufacturing （C;AM） system of the cosine gear was developed, and the simulation of the slotting process was accomplished. Several examples were provided to illustrate the approach. The result of the simulation demonstrates that the proposed slotting method is feasible.     

Modeling and control for hydraulic transmission of unmanned ground vehicle简

Variable pump driving variable motor （VPDVM） is the future development trend of the hydraulic transmission of an unmanned ground vehicle （UGV）. VPDVM is a dual-input single-output nonlinear system with coupling, which is difficult to control High pressure automatic variables bang-bang （HABB） was proposed to achieve the desired motor speed. First, the VPDVM nonlinear mathematic model was introduced, then linearized by feedback linearization theory, and the zero-dynamic stability was proved. The HABB control algorithm was proposed for VPDVM, in which the variable motor was controlled by high pressure automatic variables （HA） and the variable pump was controlled by bang-bang. Finally, simulation of VPDVM controlled by HABB was developed. Simulation results demonstrate the HABB can implement the desired motor speed rapidly and has strong robustness against the variations of desired motor speed, load and pump speed.     

Modelling and simulation of contact force in cold rotary forgin简

Cold rotary forging is an advanced and complex metal forming technology with continuous local plastic deformation. Investigating the contact force between the dies and the workpiece has a great significance to improve the life of the dies in cold rotary forging. The purpose of this work is to reveal the contact force responses in cold rotary forging through the modelling and simulation. For this purpose, a 3D elastic-plastic dynamic explicit FE model of cold rotary forging is developed using the FE code ABAQUS/Explicit. Through the modelling and simulation, the distribution and evolution of the contact force in cold rotary forging is investigated in detail. The experiment has been conducted and the validity of the 3D FE model of cold rotary forging has been verified. The results show that： 1） The contact force distribution is complex and exhibits an obvious non-uniform characteristic in the radial and circumferential directions; 2） The maximum contact force between the upper die and the workpiece is much larger than that between the lower die and the workpiece; 3） The contact force evolution history is periodic and every period experiences three different stages; 4） The total normal contact force is much larger than the total shear contact force at any given time.     

Preparation of amorphous nano-boron powder with high activity by combustion synthesis简

The preparation process of amorphous nanometer boron powders through combustion synthesis was investigated, and the effects of the reactant ratio, the heating agent and the milling rate on the activity and particle size of amorphous boron powders were studied. The results show that the boron powders exist in the form of an amorphous phase which has the crystallinity lower than 30.4%, and the panicle size of boron powder decreases with an increase of the high-energy ball milling rate. The purity of amorphous boron powder is 94.8% and panicle sizes are much smaller than 100 nm when the mass ratio of B2O3/Mg/KClO3 is 100：105：17 and the ball milling time is 20 min with the milling rate of 300 r/min. At the same time, the amorphous boron nano-fibers appear in the boron powders.     

Sticking of iron ore pellets in direct reduction with hydrogen and carbon monoxide: Behavior and prevention简

A series of reduction experiments of iron ore pellets with hydrogen,carbon monoxide and their mixture were carried out in a laboratory scale shaft furnace.The sticking behavior accompanying reduction of iron ore pellets was investigated.And morphology of the sticking interface forming during reduction was analyzed by SEM equipped with EDS.In order to evaluate the effects of the temperature and gas composition on sticking properties,reduction of iron ore pellets were conducted at 800-1000 ℃.The results show that the sticking strength of the pellets increases with temperature,however,decreases with hydrogen content in reducing gas.For an efficient shaft furnace operation in direct reduction（DR）,relative prevention of sticking such as coating of pellets was also developed to solve sticking problem.The results show that CaO is a suitable material for the coating method.