The equilibrium lattice parameters, electronic structure, bulk modulus, Debye temperature, heat capacity and Gibbs energy of TiB and TiB2 were investigated using the pseudopotential plane-wave method based on density functional theory (DFT) and the improved quasi-harmonic Debye method. The results show that the total density of states (DOS) of TiB2 is mainly provided by the orbit hybridization of Ti-3d and B-2p states, and the total DOS of TiB is mainly provided by the hybrids bond of Ti-3d and B-2p below the Fermi level and Ti-Ti bond up to the Fermi level. The Ti-B hybrid bond in TiB2 is stronger than that in TiB. Finally, the enthalpy of formation at 0 K, heat capacity and Gibbs free energy of formation at various temperatures were determined. The calculated results are in excellent agreement with the available experimental data.
Numerical simulation based on a new regularized phase field model was presented to simulate the dendritic shape of a non-isothermal alloy with strong anisotropy in a forced flow. The simulation results show that a crystal nucleus grows into a symmetric dendrite in a free flow and into an asymmetry dendrite in a forced flow. As the forced flow velocity is increased, both of the promoting effect on the upstream arm and the inhibiting effects on the downstream and perpendicular arms are intensified, and the perpendicular arm tilts to the upstream direction. With increasing the anisotropy value to 0.14, all of the dendrite arms tip velocities are gradually stabilized and finally reach their relative saturation values. In addition, the effects of an undercooling parameter and a forced compound flow on the faceted dendrite growth were also investigated.
A novel technique of introducing gas bubble stirring during solidification was studied to prepare Al-Si semi-solid slurry. The microstructure evolution of the slurry during slow cooling process after stirring was investigated. The effects of the solidification rate on the microstructure of the semi-solid slurry were investigated under three different solidification conditions. The results show that fine non-dendritic slurry can be obtained using the gas bubble stirring method. Ripening and coarsening of primary Al grains are observed during the slow cooling process, and at last coarsened eutectic Si appears. Primary Al grains with different sizes and eutectic Si are obtained, corresponding to three different solidification rates.
Anodic oxide films of titanium alloy Ti-10V-2Fe-3Al were sealed in calcium acetate solution. The morphology and composition of the sealed films were investigated using scanning electron microscopy (SEM), atomic force microscope (AFM) and energy dispersive spectroscopy (EDS). The results show that the sealing process makes the anodic oxide films more uniform. Elemental calcium is presented through the whole depth of the anodic oxide films. The roughness of the anodic oxide films is reduced after the sealing process. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization were used to study the corrosion behavior of the anodic oxide films. It is revealed that the sealing process improves the corrosion resistance of the anodic oxide film of titanium alloy Ti-10V-2Fe-3Al.
A fine-grained TiAl alloy with a composition of Ti-45Al-5Nb-1.5Cr-0.2W (mole fraction, %) with multiphases was prepared by spark plasma sintering (SPS) and heat-treating at 1 100 °C for 48 h. The relationship among sintering temperature, microstructure and fracture toughness were investigated by X-ray diffractometry (XRD), optical microscopy (OM), scanning electron microscopy (SEM) and mechanical testing. The results show that microstructure of the bulk alloy depends on the sintering temperature strongly, and the main phase TiAl and few phases Ti3Al and niobium solid solution (Nbss) are observed in the SPS bulk samples. In the heat-treatment condition, the lamellar and Nbss phase can provide significant toughening by plastic strengthening, interface decohension, crack branch and crack bridge mechanisms. The fracture mode of the SPS TiAl composite samples is intergranular rupture and cleavage fracture.
For the drum of hot rolling coiler is prone to be easily destroyed, the type of MMU-5G abrasion tester was applied to revealing the friction and wear behavior. The morphology observation by scanning electron microscope (SEM) demonstrates the wear mechanism of the drum, and the test data of the influence coefficient of the normal pressure, relative sliding speed and surface lubrication conditions acted on the linear rate of the wear could be obtained by the regression method. A calculation model, which considers the factors of the structure of the drum, coiling tension and coiling strip specifications, was established by the combination method to predict the wear life of the drum. Then the practical production data was applied into this model and the analysis result was in good accordance with that of actual production.
Both experimental and mechanical analyses were carried out to investigate the characteristics of thickness distribution for tailor-welded tube (TWT) hydroforming with dissimilar thickness. Then, the effects of weld-seam position and thickness difference were also revealed. A multiple-diameter tube was formed to reveal the characteristics and the regularity of thickness distribution during TWT hydroforming. It is indicated that there are obvious fluctuations in thickness distribution though the TWTs have the same expansion ratio. The thinning ratio of thinner tube is bigger than that of thicker tube especially in the zone closed to the weld-seam. The difference in thinning ratio between two tube segments can reach 9%. Consequently, sudden and large fluctuation of thickness appears in the zone nearby the weld-seam. The difference in thinning ratio between thinner and thicker tubes enlarges as the thickness difference increases, but improves as length ratio increases. Different strain states are the main reason to induce nonuniform thickness distribution. The difference in thickness is the main reason to induce different strain states on thinner and thicker tubes.
Diamond films were deposited on high-speed steel substrates by hot filament chemical vapor deposition (HFCVD) method. To minimize the early formation of graphite and to enhance the diamond film adhesion, a WC-Co coating was used as an interlayer on the steel substrates by high velocity oxy-fuel spraying. The effects of methane content on nucleation, quality, residual stress and adhesion of diamond films were investigated. The results indicate that the increasing methane content leads to the increase in nucleation density, residual stress, the degradation of quality and adhesion of diamond films. Diamond films deposited on high-speed steel (HSS) substrate with a WC-Co interlayer exhibit high nucleation density and good adhesion under the condition of the methane content initially set to be a higher value (4%, volume fraction) for 30 min, and then reduced to 2% for subsequent growth at pressure of 3 kPa and substrate temperature of 800 °C.
In order to improve the electrochemical hydrogen storage performance of the Mg2Ni-type electrode alloys, Mg in the alloy was partially substituted by La, and the nanocrystalline and amorphous Mg2Ni-type Mg20−xLaxNi10 (x=0, 2) alloys were synthesized by melt-spinning technique. The microstructures of the as-spun alloys were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical hydrogen storage properties of the experimental alloys were tested. The results show that no amorphous phase is detected in the as-spun Mg20Ni10 alloy, but the as-spun Mg18La2Ni10 alloy holds a major amorphous phase. As La content increases from 0 to 2, the maximum discharge capacity of the as-spun (20 m/s) alloys rises from 96.5 to 387.1 mA·h/g, and the capacity retaining rate (S20) at the 20th cycle grows from 31.3% to 71.7%. Melt-spinning engenders an impactful effect on the electrochemical hydrogen storage performances of the alloys. With the increase in the spinning rate from 0 to 30 m/s, the maximum discharge capacity increases from 30.3 to 135.5 mA·h/g for the Mg20Ni10 alloy, and from 197.2 to 406.5 mA·h/g for the Mg18La2Ni10 alloy. The capacity retaining rate (S20) of the Mg20Ni10 alloy at the 20th cycle slightly falls from 36.7% to 27.1%, but it markedly mounts up from 37.3% to 78.3% for the Mg18La2Ni10 alloy.
The dissolution behavior of CaO-MgO-SiO2 glass fiber was investigated by scanning electron microscopy (SEM), Fourier-transform infrared spectrometer (FTIR) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) using in-vitro tests. The results show that the soaked fiber is surrounded by an outer calcium-magnesium silicate hydrated layer, and there exists a balancing function between the formation and abscission of the hydrated layer during the dissolution process. The concentrations of leached ions increase constantly, and the mass loss of the fibers and pH changes of the solution are found to rise rapidly during the initial dissolution process, then their increasing rates are controlled by the balancing function of the hydrated layer at the subsequent dissolution stages. The dissolution rate constant and time for complete dissolution are estimated to be 274 ng/(cm2·h) and 15.2 d, respectively, presenting preferable biosolubilities.
The effects of Al2O3 addition on both the sintering behavior and microwave dielectric properties of PbO-B2O3-SiO2 glass ceramics were investigated by Fourier transform infrared spectroscope (FTIR), differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that with the increase of Al2O3 content the bands assigned to [SiO4] nearly disappear. Aluminum replaces silicon in the glass network, which is helpful for the formation of boron-oxygen rings. The increase of the transition temperature Tg and softening temperature Tf of PbO-B2O3-SiO2 glass ceramics leads to the increase of liquid phase precipitation temperature and promotes the structure stability in the glasses, and consequently contributes to the decreasing trend of crystallization. Densification and dielectric constants increase with the increase of Al2O3 content, but the dielectric loss is worsened. By contrast, the 3% (mass fraction) Al2O3-doped glass ceramics sintered at 725 °C have better properties of density ρ=2.72 g/cm3, dielectric constant ɛr=6.78, dielectric loss tan δ=2.6×10−3 (measured at 9.8 GHz), which suggest that the glass ceramics can be applied in multilayer microwave devices requiring low sintering temperatures.
The synthesis of Al2O3-coated and uncoated LiMn2O4 by solid-state method and fabrication of LiMn2O4/graphite battery were described. The structure and morphology of the powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The electrochemical and overcharge performances of Al2O3-coated and uncoated LiMn2O4 batteries were investigated and compared. The uncoated LiMn2O4 battery shows capacity loss of 16.5% after 200 cycles, and the coated LiMn2O4 battery only shows 12.5% after 200 cycles. The uncoated LiMn2O4 battery explodes and creates carbon, MnO, and Li2CO3 after 3C/10 V overcharged test, while the coated LiMn2O4 battery passes the test. The steadier structure, polarization of electrode and modified layer are responsible for the safety performance.
A simple and rapid strategy to construct laccase biosensor for determination of catechol was investigated. Magnetic multiwalled carbon nanotubes (MMCNT) which possess excellent capability of electron transfer were prepared by chemical coprecipitation method. Scanning electron microscope (SEM) and vibrating sample magnetometer (VSM) were used to identify its surfacetopography and magnetization, respectively. Laccase was immobilized on the MMCNT modified magnetic carbon paste electrode by the aid of chitosan/silica (CS) hybrid membrane. Using current-time detection method, the biosensor shows a linear response related to the concentration of catechol in the range from 10−7 to 0.165×10−3 mol/L. The corresponding detection limit is 3.34×10−8 mol/L based on signal-to-noise ratios (S/N) ≥3 under the optimized conditions. In addition, its response current retains 90% of the original after being stored for 45 d. The results indicate that this proposed strategy can be expected to develop other enzyme-based biosensors.
Gp96, a member of HSP90 family, is a versatile molecular chaperone with various newly-discovered functions, for example to serve as a low affinity, high capacity calcium binding protein, a natural adjuvant for therapeutic cancer vaccines, a tumor rejection antigen, an immune regulator to pathological cell death. Its multi-functional and structural characteristics make it also an interesting target to develop antibody-based therapeutics. However, its low immunogenicity to mice, because of its high-sequence similarity among different species, is an obstacle to obtain valuable monoclonal antibodies (MAbs). This is a common problem for any low immunogenic proteins, whose sequences share close identity between mice and other species. Here, a new strategy of priming was employed by swine endogenous full-length gp96 and then boosting by E. coli-system heterologously expressed gp96 N-terminal fragment (N-355) to generate MAbs. Twelve different highly-specific MAbs against swine/human endogenous gp96 were successfully obtained. The binding activities of these MAbs were confirmed by enzyme-linked immunosorbent assay (ELISA), Western blot (WB), immunofluorescence and flow cytometry analysis. This provides some important reagents for further research and potential therapeutics. The methods employed can be used for MAb production of any sequence-highly-conserved proteins between mice and swine/human (or any other species).
The thermal decomposition process of basic magnesium carbonate was investigated. Firstly, Basic magnesium carbonate was prepared from magnesite, and the characteristics of the product were detected by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Subsequently, the thermal decomposition process of basic magnesium carbonate in air was studied by thermogravimetry-differential thermogravimetry (TG-DTG). The results of XRD confirm that the chemical composition of basic magnesium carbonate is 4MgCO3·Mg(OH)2·4H2O. And the SEM images show that the sample is in sheet structure, with a diameter of 0.1–1 μm. The TG-DTG results demonstrate that there are two steps in the thermal decomposition process of basic magnesium carbonate. The apparent activation energies (E) were calculated by Flynn-Wall-Ozawa method. It is obtained from Coats-Redfern’s equation and Malek method that the mechanism functions of the two decomposition stages are D3 and A1.5, respectively. And then, the kinetic equations of the two steps were deduced as well.
Magnesium oxysulfate (MgSO4·5Mg(OH)2·2H2O) flake powders with an average diameter of 2 μm and a thickness of 0.052 μm were prepared using magnesium sulfate and sodium hydroxide as raw materials by hydrothermal synthesis process. The composition, morphology and structural features of the hydrothermal products were examined with X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The experimental results indicate that in the conditions of n(NaOH)/n(MgSO4) of 1.25, the dosage of w(Na3PO4) crystal additives of 1.0% w(MgSO4), stirring for 5 h at 180 °C, the morphology of MgSO4·5Mg(OH)2·2H2O products is flaky and laminar, which is a kind of complex magnesium single-crystal. The recycling of MgSO4 mother liquor was also investigated to make a full use of the materials and reduce disposal. The results prove that there is no adverse effect on the yield and purity of the products.
Silver nano-particles with average diameter of about 60 nm were compacted in a high-strength mold under different pressures at 523 K to produce nano-structured Ag solid materials. The structure and characteristic of the nano-structured Ag solid materials (NSS-Ag) were studied using X-ray diffraction (XRD), scanning electron microscope (SEM) and Raman spectrometer. The NSS-Ag could be used as highly efficient surface-enhanced Raman scattering (SERS) active substrates. The common probe molecules Rhodamine 6G (R6G, 1×10−10 mol/L) were used to test the SERS activity on these substrates at very low concentrations. It is found that the SERS enhancement ability is dependent on the density of NSS-Ag. When the relative density of NSS-Ag is 83.87%, the materials reveal great SERS signal.
The selective catalytic reduction reaction belongs to the gas-solid multiphase reaction, and the adsorption of NH3 and NO on CuO/γ-Al2O3 catalysts plays an important role in the reaction. Performance of the CuO/γ-Al2O3 catalysts was explored in a fixed bed adsorption system. The catalysts maintain nearly 100% NO conversion efficiency at 350 °C. Comprehensive tests were carried out to study the adsorption behavior of NH3 and NO over the catalysts. The desorption experiments prove that NH3 and NO are adsorbed on CuO/γ-Al2O3 catalysts. The adsorption behaviors of NH3 and NO were also studied with the in-situ diffusion reflectance infrared Fourier transform spectroscopy methods. The results show that NH3 could be strongly adsorbed on the catalysts, resulting in coordinated NH3 and NH4+ NO adsorption leads to the formation of bridging bidentate nitrate, chelating bidentate nitrate, and chelating nitro. The interaction of NH3 and NO molecules with the Cu2+ present on the CuAl2O4 (100) surface was investigated by using a periodic density functional theory. The results show that the adsorption of all the molecules on the Cu2+ site is energetically favorable, whereas NO bound is stronger than that of NH3 with the adsorption site, and key information about the structural and energetic properties was also addressed.
The influence of temperature and mass fraction of Pluonic F127 on the rheological properties of polyvinyl butyric (PVB)/Pluronic F127/polyethylene glycol (PEG) 200 blend systems was investigated by a rotational rheometer with parallel plates. The results show that the blend systems approach homogeneous state at 140, 150 and 160 °C while the rheological properties of the blend systems significantly deviate from the homogeneous systems at 120 °C. Shear thinning behavior is observed for all the blend systems at different temperatures and is enhanced by increasing Pluronic F127 content. The complex viscosity, storage modulus, loss modulus, zero-shear activation energy and flow recovery of the blend systems increase with the increase of Pluronic F127 content. There is a crossing point for the loss modulus and the storage modulus of each sample at high frequency, which is called specified frequency (SF). The loss modulus is larger than the storage modulus when the frequency is less than the SF, and when frequency is more than SF, the loss modulus is smaller than the storage modulus.
Inclusion behavior of oxybutynin (OBN) with hydroxypropyl-β-cyclodextrin (HP-β-CD) was investigated by ultraviolet absorption spectrum and fluorescence spectrum. A reliable determination of the complex stoichiometry was provided by the continuous variation technique. Alcohol was added to further investigate the mechanism of the inclusion behavior. Thermodynamic constants ΔG, ΔH and ΔS for inclusion interaction of OBN and HP-β-CD were determined. The results show that host-guest complex with molar ratio of 1:1 is formed, and inclusion stability constant between OBN and HP-β-CD is 54.9 L/mol determined by ultraviolet spectrum and 11.1 L/mol determined by fluorescence spectrum. OBN has weak binding ability with HP-β-CD in aqueous solution (stability constant <102 L/mol) and addition of alcohol leads to a decrease of stability constant, which indicates that the hydrophobic force contributes to the inclusion process. ΔG, ΔH and ΔS are all less than zero, which indicates that the inclusion process is a spontaneous and exothermic process.
A set of water powered excavation test system was developed for the comprehensive performance testing and evaluation of water powered percussive rock drill indoors. The whole system contains hydraulic power section, electronic control system, test and data acquisition system, and assistant devices, such as guideway and drilling bench. Parameters of the water powered percussive rock drill can be obtained by analyzing testing data, which contain impact energy, front and back cavity pressure, pressure and flow in each working part, drilling velocity, frequency and energy efficiency etc. The system is applied to test the self-designed water powered percussive rock drill SYYG65. The parameters of water powered percussive rock drill with impact pressure of about 8.9 MPa are 58.93 J for impact energy, and 8.97% for energy efficiency, which prove the effectiveness of system.
A new visual method for quantitative measurement of frothers effect and flotation efficiency was presented. A self-designed electrolytic cell was chosen as the reaction environment with sodium chloride (NaCl) as the electrolyte. Constant current, supplied by a self-designed power supplier and fixed cathode and anode equipment, guaranteed the constant bubble volume per unit time. Even aperture of the cathode material guaranteed the original bubbles size to be uniform. Bubble generating equipment was connected with a microscopical camera. Statistic data collected by high speed charge-coupled device (CCD) and processed by software Sigmascan and Matlab could reflect bubble characteristics. The efficiency of dipropylene glycol monomethyl ether (DPM) and tripropylene glycol n-butyl ethel (TPnB) were measured at the same condition, and 2×10−4 mol/L and 5×10−2 mol/L were found to be the inflexions of bubble size changes.
In order to utilize the spontaneous accumulation of heat (SAH) reasonably and obtain the high quality sinter with low energy consumption, a lower fuel consumption modeling based on raw materials of a certain steel works was built. An air-flow segregation feeding (ASF) experimental equipment was designed to simulate strand feeding process and calculate the lower fuel consumption quantity. Compared with baseline test, the ASF experimental equipment was adopted. The results of sinter pot tests show that the solid fuel consumption is lower than that in baseline test, which is decreased by 5.8%. Meanwhile, other sinter indexes, such as pan yeild, tumbler strength and strand productivity are improved. The mineralogical examination indicates that the mineral compositions and micostructures are improved in sinter.
The influence of sulfur content in raw materials on oxidized pellets was studied. The results show that most sulfur exists in the form of elementary sulfur in pyrite cinder, and over 95% sulfur is removed in producing pyrite cinder oxidized pellets. The compressive strength of fired pellets drops from 3 186 N to 2 405 N when the ratio of pyrite cinder increases from 40% to 70% under the conditions of preheating at 900 °C for 9 min and firing at 1 230 °C for 15 min. The porosity and microstructures of fired pellets prove that the higher ratio of pyrite cinder is given, and the more holes and cracks are achieved, leading to the better reducibility index (RI) and reduction swelling index (RSI), and the lower compressive strength of fired pellets and the worse reduction degradation index (RDI).
Eleven acid mine drainage (AMD) samples were obtained from southeast of China for the analysis of the microbial communities diversity, and the relationship with geochemical variables and spatial distance by using a culture-independent 16S rDNA gene phylogenetic analysis approach and multivariate analysis respectively. The principle component analysis (PCA) of geochemical variables shows that eleven AMDs can be clustered into two groups, relative high and low metal rich (RHMR and RLMR) AMDs. Total 1 691 clone sequences are obtained and the detrended correspondence analysis (DCA) of operational taxonomic units (OTUs) shows that, γ-Proteobacteria, Acidobacteria, Actinobacteria, Cyanobacteria, Firmicutes and Nitrospirae are dominant species in RHMR AMDs. In contrast, α-Proteobacteria, β-Proteobacteria, Planctomycetes and Bacteriodetes are dominant species in RLMR AMD. Results also show that high-abundance putative iron-oxidizing and only putative sulfur-oxidizing microorganisms are found in RHMR AMD. Multivariate analysis shows that both geochemical variables (r=0.429 3, P=0.037 7) and spatial distance (r=0.321 3, P=0.018 1) are significantly positively correlated with microbial community and pH, Mg, Fe, S, Cu and Ca are key geochemistry factors in shaping microbial community. Variance partitioning analysis shows that geochemical variables and spatial distance can explain most (92%) of the variation.
In order to reduce the pollution of Cl2 and HCl released during extracting vanadium from stone coal by sodium chloride roasting, a modified salt-roasting process was proposed by adding calcined lime in roasting process followed by H2SO4 leaching. The effects of parameters including roasting temperature, roasting time, addition mass ratio of NaCl, calcined lime upon leaching rate of vanadium and curing rate of chlorine were investigated, and the effects of leaching time and leaching temperature on leaching rate of vanadium were also studied. The results show that the vanadium leaching rate and the curing rate of chlorine are 67.3% and 51.5% (mass fraction), respectively, at roasting temperature of 750 °C, roasting time of 4 h, 15% sodium chloride and 8% (mass fraction) calcined lime, leaching temperature of room temperature, and leaching time of 4 h.
Grate fly ash and fluidized bed fly ash mixed with glass cullet additive respectively were melted in the electronic arc-furnace. The product, arc-melting slag, was further treated by crushing, pressing and heat treatment in order to make the glass-ceramics. The crystallization behaviors of the produced glass-ceramics were examined by differential thermal analysis (DTA), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Results show that main crystalline phase of the glass-ceramics from grate fly ash is wollastonite (CaSiO3) with small amount of diopside (Ca(Mg,Al)(Si,Al)2O6), and that from fluidized bed fly ash is diopside (Ca(Mg,Al)(Si,Al)2O6). It is found that the glass-ceramics sintered at 850 °C and 1 000 °C from grate fly ash and fluidized bed fly ash respectively have the optimal physical, mechanical and chemical characteristics. Glass-ceramics samples, produced from incinerator fly ash with desirable properties and the low leaching concentration of heavy metals, can be the substitute of nature materials such as marble, granite and porcelain tiles.
A novel sorting system based on one degree of freedom (DOF) tendon based parallel manipulator (TBPM) for high value waste processing was presented and designed. In order to control the motion of loads, nonlinear state feed forward control algorithm in the tendon length coordinate was used. Considering the system redundancy and actuation behavior, algorithms of optimal tension distribution and forward kinematics were designed. Then, the simulation experiments of motion control were implemented. The results demonstrate that the proposed TBPM translation system performs robust capacities. It can transfer the loads 1 m away within 1.5 s. With further optimization, the translation duration can be further reduced to be about 1 s and the optimized translation is followed with 43.59 m/s2 maximum acceleration. The translation errors at the aim position remain below 0.4 mm.
The stability and reliability of a tilting index table should be considered at the design stage. A design method for the lightweight and improvement of the stability of the structure in a tilting index table was proposed using a commercial analysis program, ANSYS Workbench 12, by analyzing the static-thermal characteristics of the developed high-accuracy tilting index table at its design stage. The results of the performed structural analysis show that the maximum stress is generated at the stock tail part. An optimum design for the stock tail part was carried out to reduce the maximum stress and deformation. Also, the design variables were determined by considering the support of the stock tail part for the C-axis body. In the comparison of the results before and after the optimization, the maximum deformation and stress are improved by 2.8% and 8%, respectively.
During five-axis machining of impeller, the excessive local interference avoidance leads to inconsistency of cutter posture, low quality of machined surface and increase of processing time. Therefore, in order to improve the efficiency of five-axis machining of impellers, it is necessary to minimize the cutter posture changes and create a continuous tool path while avoiding interference. By using an MC-space algorithm for interference avoidance, an MB-spline algorithm for continuous control was intended to create a five-axis machining tool path with excellent surface quality and economic feasibility. A five-axis cutting experiment was performed to verify the effectiveness of the continuity control. The result shows that the surface shape with continuous method is greatly improved, and the surface roughness is generally favorable. Consequently, the effectiveness of the suggested method is verified by identifying the improvement of efficiency of five-axis machining of an impeller in aspects of surface quality and machining time.
The effects of cyanidation conditions on gold dissolution were studied by artificial neural network (ANN) modeling. Eighty-five datasets were used to estimate the gold dissolution. Six input parameters, time, solid percentage, P80 of particle, NaCN content in cyanide media, temperature of solution and pH value were used. For selecting the best model, the outputs of models were compared with measured data. A fourth-layer ANN is found to be optimum with architecture of twenty, fifteen, ten and five neurons in the first, second, third and fourth hidden layers, respectively, and one neuron in output layer. The results of artificial neural network show that the square correlation coefficients (R2) of training, testing and validating data achieve 0.999 1, 0.996 4 and 0.998 1, respectively. Sensitivity analysis shows that the highest and lowest effects on the gold dissolution rise from time and pH, respectively. It is verified that the predicted values of ANN coincide well with the experimental results.
The effects of geometry on mechanical properties in woven fabric composites were explored. Two types of composites, including one-layered and two-layered composites, were designed and studied. For one-layered composites, inter-strand gap effects on the mechanical properties were studied, while three cases of geometries with inter-strand gaps in two-layered composites were evaluated. A woven fiber micromechanics analytical model called MESOTEX was employed for theoretical simulation. The predicted results show that the inter-strand gap and simple variation of the strand positions in a repeating unit cell significantly affect the mechanical properties of woven fabric composites.
In order to obtain the determining method of the installing angle and decrease the performance indices (cutting force and wearing rate) of the pick, the relationships among the installing angles (impact angle, inclination angle and the skew angle) were studied, and the static model of installing angles of the pick was built. The relationships among the impact angle, the tip angle of pick and the kinematics parameters of the pick were built, too. Moreover, the mechanic models of the maximum clearance angle and the wearing angle of the pick were set up. To research the relationships of the installing angles and the change law of the wearing angle along with the kinematics parameters, the simulation was done. In order to verify the correctness of the models, the cutting experiments were done by employing two picks with different pick tip angles. The results indicate that, the cutting force is the smallest when the direction of the resultant force of pick follows its axis, and the relationship derived among the installing angles should be satisfied. In addition, to decrease the cutting force and the wearing of the pick, the tip angle of pick should not be larger than the half of the difference between the minimum wearing angle and the impact angle of the pick, and the clearance angle must not be less than zero.
To denoise the diffusion weighted images (DWIs) featured as multi-boundary, which was very important for the calculation of accurate DTIs (diffusion tensor magnetic resonance imaging), a modified Wiener filter was proposed. Through analyzing the widely accepted adaptive Wiener filter in image denoising fields, which suffered from annoying noise around the edges of DWIs and in turn greatly affected the denoising effect of DWIs, a local-shift method capable of overcoming the defect of the adaptive Wiener filter was proposed to help better denoising DWIs and the modified Wiener filter was constructed accordingly. To verify the denoising effect of the proposed method, the modified Wiener filter and adaptive Wiener filter were performed on the noisy DWI data, respectively, and the results of different methods were analyzed in detail and put into comparison. The experimental data show that, with the modified Wiener method, more satisfactory results such as lower non-positive tensor percentage and lower mean square errors of the fractional anisotropy map and trace map are obtained than those with the adaptive Wiener method, which in turn helps to produce more accurate DTIs.
An efficient calibration algorithm for an ambulatory audiometric test system is proposed. This system utilizes a personal digital assistant (PDA) device to generate the correct sound pressure level (SPL) from an audiometric transducer such as an earphone. The calibrated sound intensities for an audio-logical examination can be obtained in terms of the sound pressure levels of pure-tonal sinusoidal signals in eight-banded frequency ranges (250, 500, 1 000, 2 000, 3 000, 4 000, 6 000 and 8 000 Hz), and with mapping of the input sound pressure levels by the weight coefficients that are tuned by the delta learning rule. With this scheme, the sound intensities, which evoke eight-banded sound pressure levels by 5 dB steps from a minimum of 25 dB to a maximum of 80 dB, can be generated without volume displacement. Consequently, these sound intensities can be utilized to accurately determine the hearing threshold of a subject in the ambulatory audiometric testing environment.
The high pressure waves generated due to muzzle blast flow of tank gun during firing is a critical issue to examine. The impulsive noise from the gun has various negative effects such as damage of human bodies, damage of structures, creating an environmental, social problem and also military problems such as exposure of location of troops. This high pressure impulsive sound, generated during the blast flow, was studied and attenuated. An axisymmetric computational domain was constructed by employing Spalart Allmaras turbulence model. Approximately 90% of pressure and 20 dB of sound level are reduced due to the use of the three baffle silencer at the muzzle end of the gun barrel, in comparison with the tank gun without silencer. Also, the sound pressure level at different points in the ambient region shows the same attenuation in results. This study will be helpful to understand the blast wave characteristics and also to get a good idea to design silencer for large caliber weapon system.
A novel control strategy for three-phase shunt active power filter (SAPF) was proposed to improve its performance under non-ideal mains voltages. The approach was inspired by our finding that the classic instantaneous reactive power theory based algorithm was unsatisfactory in terms of isolating positive sequence fundamental active components exactly under non-ideal mains voltages. So, a modified ip-iq reference current calculation method was presented. With usage of the new method, not only the positive sequence but also the fundamental active current components can be accurately isolated from load current. A deadbeat closed-loop control model is built in order to eliminate both delay error and tracking error between reference voltages and compensation voltages under unbalanced and distorted mains voltages. Computer simulation results show that the proposed strategy is effective with better tracking ability and lower total harmonic distortion (THD). The strategy is also applied to a 10 kV substation with a local electrolysis manganese plant injecting a large amount of harmonics into the power system, and is proved to be more practical and efficient.
To promote the modeling standardization process of the integrated circuits, an improved electrical simulation model for a direct power injection (DPI) setup which was used to measure the conducted immunity of a 16-bit microcontroller to radio frequency aggression was investigated. Based on the existing model of the same microcontroller, the PDN module was modified by adding the core, PLL and A/D network models, which could reflect the actual electric distribution situation within the microcontroller more accurately. By comparing the simulation results with the measurement results, the effectiveness of the modified model can be improved to 500 MHz, and its uncertainty is within ±1.8 dB (±2 dB is acceptable). Then, to improve the simulation accuracy of the complete model in the high frequency range, the I/O model which contained the dynamic and nonlinear characteristics reflecting the variation of the internal impedance of the microcontroller with increasing the frequency of the external noise was introduced. By comparing the simulation results with the measurement results, the effectiveness of the second modified model can be improved up to 1.4 GHz with the uncertainty of ±1.8 dB. Thus, a conclusion can be reached that the proposed model can be applied to a much wider frequency range with a smaller uncertainty than the latest model of the similar type. Furthermore, associated with the electromagnetic emission testing platform model, the PDN module can also be used to predict the electromagnetic conducted and radiated emission characteristics. This modeling method can also be applied to other integrated circuits, which is very helpful to the standardization of the IC electromagnetic compatibility (EMC) modeling process.
A single poly EEPROM cell circuit sharing the deep N-well of a cell array was designed using the logic process. The proposed cell is written by the FN tunneling scheme and the cell size is 41.26 μm2, about 37% smaller than the conventional cell. Also, a small-area and low-power 512-bit EEPROM IP was designed using the proposed cells which was used for a 900 MHz passive UHF RFID tag chip. To secure the operation of the cell proposed with 3.3 V devices and the reliability of the used devices, an EEPROM core circuit and a DC-DC converter were proposed. Simulation results for the designed EEPROM IP based on the 0.18 μm logic process show that the power consumptions in read mode, program mode and erase mode are 11.82, 25.15, and 24.08 μW, respectively, and the EEPROM size is 0.12 mm2.
Comparison and data analysis with the similarity measures and entropy for fuzzy sets were carried out. The distance proportional value between the fuzzy set and the corresponding crisp set was considered by the fuzzy entropy. The relation between the similarity measure and the entropy for fuzzy set was also analyzed. The fuzzy entropy was reformulated as the dissimilarity measure. Furthermore, crisp set having the minimum uncertainty with respect to the corresponding fuzzy set was also proposed. Finally, derivation of a similarity measure from entropy with the help of total information property was derived. A simple example shows the relation between similarity measure and fuzzy entropy, in which the summation of similarity measure and fuzzy entropy represents a constant value.
The gradual hybrid anti-worm (GHAW) was presented. It changed its confrontation scheme in real time according to the percentage of vulnerable hosts present in the network. For GHAW, its process of countering malicious internet worms was modeled. The performance of GHAW on two factors was also estimated: confronting validity against worms and consumption of network resources. Factors governing its performance, specifically the transformation threshold and the transformation rate, were analyzed. The simulation experiments show that GHAW has dynamical adaptability to changes of network conditions and offers the same level of effectiveness on confronting internet worms as the divide-and-rule hybrid anti-worm, with significantly less cost to network resources. The experiments also indicate that the transformation threshold is the key factor affecting the performance of GHAW.
The robust guaranteed cost sampled-data control was studied for a class of uncertain nonlinear systems with time-varying delay. The parameter uncertainties are time-varying norm-bounded and appear in both the state and the input control matrices. By applying an input delay approach, the system was transformed into a continuous time-delay system. Attention was focused on the design of a robust guaranteed cost sampled-data control law which guarantees that the closed-loop system is asymptotically stable and the quadratic performance index is less than a certain bound for all admissible uncertainties. By applying Lyapunov stability theory, the theorems were derived to provide sufficient conditions for the existence of robust guaranteed cost sampled-data control law in the form of linear matrix inequalities (LMIs), especially an optimal state-feedback guaranteed cost sampled-data control law which ensures the minimization of the guaranteed cost was given. The effectiveness of the proposed method was illustrated by a simulation example with the asymptotically stable curves of system state under the initial condition of x(0)=[0.679 6 0].
In response to the deficiencies of BitTorrent, the concept of density radius was proposed, and the distance from the maximum point of radius density to cluster center as a cluster radius was taken to solve the too large cluster radius resulted from the discrete points and to reduce the false positive rate of early recognition algorithms. Simulation results show that in the actual network environment, the improved algorithm, compared with K-means, will reduce the false positive rate of early identification algorithm from 6.3% to 0.9% and has a higher operational efficiency.
A new scheduling algorithm called deferrable scheduling with time slice exchange (DS-EXC) was proposed to maintain the temporal validity of real-time data. In DS-EXC, the time slice exchange method was designed to further defer the release time of transaction instances derived by the deferrable scheduling algorithm (DS-FP). In this way, more CPU time would be left for lower priority transactions and other transactions. In order to minimize the scheduling overhead, an off-line scheme was designed. In particular, the schedule for a transaction set is generated off-line until a repeating pattern is found, and then the pattern is used to construct the schedule on-line. The performance of DS-EXC was evaluated by sets of experiments. The results show that DS-EXC outperforms DS-FP in terms of increasing schedulable ratio. It also provides better performance under mixed workloads.
A support vector machine (SVM) forecasting model based on rough set (RS) data preprocess was proposed by combining the rough set attribute reduction and the support vector machine regression algorithm, because there are strong complementarities between two models. Firstly, the rough set was used to reduce the condition attributes, then to eliminate the attributes that were redundant for the forecast, Secondly, it adopted the minimum condition attributes obtained by reduction and the corresponding original data to re-form a new training sample, which only kept the important attributes affecting the forecast accuracy. Finally, it studied and trained the SVM with the training samples after reduction, inputted the test samples re-formed by the minimum condition attributes and the corresponding original data, and then got the mapping relationship model between condition attributes and forecast variables after testing it. This model was used to forecast the power supply and demand. The results show that the average absolute error rate of power consumption of the whole society and yearly maximum load are 14.21% and 13.23%, respectively, which indicates that the RS-SVM forecast model has a higher degree of accuracy.
The finite element method was used to solve fluid dynamic interaction problems between the crust and mantle of the Earth. To consider different mechanical behaviours, the lithosphere consisting of the crust and upper mantle was simulated as fluid-saturated porous rocks, while the upper aesthenospheric part of the mantle was simulated as viscous fluids. Since the whole lithosphere was computationally simulated, the dynamic interaction between the crust and the upper mantle was appropriately considered. In particular, the mixing of mantle fluids and crustal fluids was simulated in the corresponding computational model. The related computational simulation results from an example problem demonstrate that the mantle fluids can flow into the crust and mix with the crustal fluids due to the resulting convective flows in the crust-mantle system. Likewise, the crustal fluids can also flow into the upper mantle and mix with the mantle fluids. This kind of fluids mixing and exchange is very important to the better understanding of the governing processes that control the ore body formation and mineralization in the upper crust of the Earth.
A new method was presented to determine the safety factor of wall stability against overturning based on pseudo-dynamic approach. In this time-dependent method, the actual dynamic effect with variation of time and propagation of shear and primary wave velocities through the backfills was considered. Planar failure surface was considered behind the retaining wall. The results were compared with those obtained from Mononobe-Okabe theory. It is found that there is a higher value of safety factor by the present dynamic analysis. The effects of wall inclination, wall friction angle, soil friction angle and horizontal and vertical seismic coefficients on the overturning stability of retaining wall were investigated. The parametric study shows that both horizontal and vertical seismic accelerations have decreasing effect on the overturning stability of retaining wall.
The required reinforcement force to prevent instability and the yield acceleration of reinforced slopes are computed under seismic loading by applying the kinematic approach of limit analysis in conjunction with the pseudo-dynamic method for a wide range of soil cohesion, friction angle, dilation angle and horizontal and vertical seismic coefficients. Each parameter threatening the stability of the slope enhances the magnitude of the required reinforcement force and vice versa. Moreover, the yield acceleration increases with the increase in soil shear strength parameters but decreases with the increase in the slope angle. The comparison of the present work with some of the available solutions in the literatures shows a reasonable agreement.
In the view of the disadvantages of complex method (CM) and electromagnetism-like algorithm (EM), complex electromagnetism-like hybrid algorithm (CEM) was proposed by embedding complex method into electromagnetism-like algorithm as local optimization algorithm. CEM was adopted to search the minimum safety factor in slope stability analysis and the results show that CEM holds advantages over EM and CM. It combines the merits of two and is more stable and efficient. For further improvement, two CEM hybrid algorithms based on predatory search (PS) strategies were proposed, both of which consist of modified algorithms and the search area of which is dynamically adjusted by changing restriction. The CEM-PS1 adopts theoretical framework of original predatory search strategy. The CEM-PS2 employs the idea of area-restricted search learned from predatory search strategy, but the algorithm structure is simpler. Both the CEM-PS1 and CEM-PS2 have been demonstrated more effective and efficient than the others. As for complex method which locates in hybrid algorithm, the optimization can be achieved at a convergence precision of 1×10−3, which is recommended to use.
In the reliability analysis of slope, the performance functions derived from the most available stability analysis procedures of slopes are usually implicit and cannot be solved by first-order second-moment approach. A new reliability analysis approach was presented based on three-dimensional Morgenstern-Price method to investigate three-dimensional effect of landslide in stability analyses. To obtain the reliability index, Support Vector Machine (SVM) was applied to approximate the performance function. The time-consuming of this approach is only 0.028% of that using Monte-Carlo method at the same computation accuracy. Also, the influence of time effect of shearing strength parameters of slope soils on the long-term reliability of three-dimensional slopes was investigated by this new approach. It is found that the reliability index of the slope would decrease by 52.54% and the failure probability would increase from 0.000 705% to 1.966%. In the end, the impact of variation coefficients of c and f on reliability index of slopes was taken into discussion and the changing trend was observed.