In the present study, rapidly solidified ribbons of Al87Ni7Cu3 Nd3 metallic glass was prepared by using melt spinning. Devitrification process of the totally amorphous ribbons was investigated by high temperature X-ray diffraction analysis, combining with differential scanning calorimetry, under continuous and isothermal heating regime. The X-ray diffraction intensity and full width at the half maximum (FWHM) were analyzed to investigate the increase of crystallized amount and growth of α-Al crystal particles. The results show that under continuous heating regime, the metallic glass devitrifies via two main stages: primary crystallization, resulting in two-phase mixture of α-Al plus residual amorphous phase, and secondary crystallization, corresponding to rapid precipitation of some inter-metallic phases in the form of dispersion or eutectic mixture. Under isothermal heating regime, only Al crystal precipitates from the Al-rich amorphous matrix at low temperature, and when heating at 280 °C only Al crystal precipitates within a short time, and then Al8Cu4Nd forms, followed by Al3Ni, in the residual amorphous phase. When heating at higher temperature or for longer time, Al11Nd3 forms, the amorphous phase disappears, and the ribbons develop into polycrystalline morphologies with multiply phase mixture of α-Al, Al8Cu4Nd, Al3Ni, and Al11Nd3.
In order to improve the process of co-reduction of oxide powder, a new mechano-thermal process was designed to produce high-dispersed W-Cu composite powder by high temperature oxidation, short time high-energy milling and reduction at lower temperature. The particle size, oxygen content and their sintering abilities of W-Cu composite powder in different conditions were analyzed. The results show that after a quick milling of the oxide powder for about 3–10 h, the reduction temperature of the W-Cu oxide powder can be lowered to about 650 °C from 700–750 °C owning to the lowering of particle size of the oxide powder. The average particle size of W-Cu powder after reduction at 650 °C is about 0.5 µm smaller than that reduced at 750 °C. After sintering at 1 200 °C for 1 h in hydrogen atmosphere, the relative density and thermal conductivity of final products (W-20Cu) can attain 99.5% and 210 W · m−1 · K−1 respectively.
In order to improve the friction-wear properties of the C/C composites for aircraft brake pairs, the friction behavior of samples with infiltrating Si was investigated. The influence of Si smearing thickness on friction properties was studied in detail. The results show that with the increase of Si smearing thickness and β-SiC content, the friction coefficient reduces from 0.40 to 0.30; the linear wear of stators from 2.0 µm to 18.9 µm per cycle, and that of rotors increases from 1.4 µm to 22.6 µm per cycle; mass wear of stators increases from 20.6 mg to 126.9 mg per cycle, and that of rotors increases from 13.7 mg to 166.2 mg per cycle. On the other hand, when a large number of inhomogeneous β-SiC particulates are performed, friction surfaces of the samples flake off layer by layer and many nicks are observed.
Burnt lime and serpentine were incorporated into the sinter mix to improve high iron and low silica sintering. Optimization of how to use burnt lime including dosage of burnt lime, moisture of sinter mix, hydrating and granulation time was performed. Evaluations of sinter characteristics including sinter mineralogy, reducibility, low temperature reduction degradation, softening and melting down properties were carried out. Compared with the results of traditional process in base case, the tumbling index (TI) is increased by 1.53%–2.33% through proportioning high ratio of burnt lime or adding serpentine in the sinter mix. It is shown that effective granulation, better permeability and improved high temperature reactivity in the sinter bed are achieved, resulting in an increase in 3.13%–5.10% calcium ferrite occurring in acicular and columnar shape and decrease in glass phase, and with the reducibility index(RI) being increased by 1.65%–3.25%.
Electrochemical behaviors of Zn-Fe alloy and Zn-Fe-TiO2 composite electrodeposition in alkaline zincate solutions were studied respectively by the methods of linear potential sweep and cyclic voltammetry. From the results it can be concluded that Zn shows under potential deposition, Zn-Fe alloy codeposition is anomalous codeposition and Zn-Fe alloy cathode polarization is increased with the introduction of additive. From the view point of electrochemistry, the reasons that the content of Fe in the Zn-Fe coating changes with the composition of the electrolyte and the process conditions altering and the relationship between the content of Fe and the appearance of the coating are interpreted. The cathode polarization of Zn-Fe alloy codeposition is enhanced obviously with addition of additive. In the course of composite electrodeposition, TiO2 has less promotion to electrodeposition of zinc ions than to iron ions, while the electrodeposition of iron ions improves the content of TiO2 in composite coating, which is in agreement with the results of process experiments.
A stable polyradical, poly (2,2,6,6-tetramethylpiperidinyloxy methacrylate)(PTMA), was synthesized, and its structure was determined by infrared, ultraviolet-visible, and ESR spectroscopy. Cyclic voltammograms of the PTMA polyradical electrodes were obtained by using a three-electrode cell at a scan rate of 5 mV/s within a potential range of 3.2–4.0 V. The results show that the shape of oxidation peak is very similar to that of reduction peak, and oxidation peak current is equal to the corresponding reduction peak current, which suggest that PTMA possesses an excellent reversibility. The difference of the anodic peak potential (Ea,p=3.66 V, vs Li/Li+) and cathodic peak potential(Ec,p=3.58 V, vs Li/Li+) is estimated at 80 mV, which is extremely less than that of the other organic positive materials in lithium second batteries such as organosulfide compounds, leading to a capability for high current capability in the charging and discharging process of the battery. The maximum discharge specific capacity of PTMA is 78.4 mA · h/g at the constant discharge current of 0.3 mA (0.2 C rate), the coulombic efficiency is about 95%, and the charging and discharging curves of the batteries have an obvious plateau at 3.65 V and 3.56 V, respectively. The discharging specific capacity of the battery decreased is about 2% after 100 cycles. The PTMA/Li button batteries exhibite an excellent stability.
A modified wet chemical route for low-temperature syntheiss of the calcium stannate CaSnO3, a potential material for dielectric applications is reported. Firstly, a precursor CaSn(OH)6 was prepared using tin tetrachloride, calcium chloride and sodium hydroxide at room temperature. Then the precursor was annealed at relatively low temperature of 600 °C to obtain CaSnO3. The phase identification, thermal behavior and surface morphology of the samples were characterized by element analysis, X-ray diffraction (XRD), thermo-gravimetric (TG) analysis and derivative thermo-gravimetric (DTG) analysis, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) in detail. The results show that CaSnO3 obtained by this method possesses a cubic perovskite structure with average grain size of 5 µm.
A high performance liquid chromatography (HPLC) method was established for simultaneous determination of geniposidic acid, chlorogenic acid and geniposide in eucommia. Detection at 240 nm with a reversed-phase column, CH3OH volume fraction, acidic additive and pH value of mobile phase were studied for their effects on the separability of the compounds. The most suitable separation was obtained with isocratic gradient elution system using CH3OH-H2O-H3PO4 (12.00 : 87.96 : 0.04, volume ratio) at a flow-rate of 1.0 mL/min. Under the experimental conditions, the capacity factors of three compounds are in 3–13. The sample is separated rightly. The analysis time is 30 min and the retention time of geniposidic acid, chlorogenic acid and geniposide are 6.7 min, 10.5 min and 21 min, respectively.
The nanoparticles of polylactide (PLA) and poly(lactide-co-glycolide) (PLGA) were prepared by the binary organic solvent diffusion method. The yield, particle size and size distribution of these nanoparticles were evaluated. The yield of nanoparticles prepared by this method is over 90%, and the average size of the nanoparticles is between 130–180 nm. In order to clarify the effect of the organic solvent used in the system on nanoparticle yield and size, the cloud points of PLA and PLGA were examined by cloud point titration. The results indicate that the yields of nanoparticles increase with the increase of ethanol in the acetone solution and attain the maximum at the cloud point of ethanol, while the size of nanoparticles decreases with the increase of ethanol in the acetone solution and attains the minimum at the cloud point of ethanol. The optimal composition ratio of binary organic solvents coincides to that near the cloud point and the optimal condition of binary organic solvents can be predicted.
Paclitaxel in southern yew tree was quantitatively determined by high performance liquid chromatography (HPLC) with ODS-C18 column. A mixture of CH3OH-H2O-CH3COOH(volume ratio: 55 : 44 : 1) is used as mobile phase and UV detection is carried out at 227 nm, and the column temperature is 20°C. The results show that there is a good linear relationship between the area of paclitaxel and the concentration of the sample in the range 50–500 mg/L for paclitaxel. The corresponding regression equation is Y=13021.7+1.01×106X, r=0.9990. The average recovery is 95.3% and the relative standard deviation is 2.08%.
A new specimen geometry—the double edge-cracked Brazilian disk and a relevant fracture analysis by weight function method are proposed for the investigation of rock fracture caused by compression-shear loading. Not only can the mixed mode fracture with any ratio of KI/KII be achieved, but also the pure mode II crack extension can be obtained. The combined mode fracture analysis for this geometry shows that diametral compression in the farfield can induce a compression-shear stress state in the singular stress field ahead of crack tips. Experimental investigations conducted on marble specimens show that the pure mode II crack extension can be obtained when the dimensionless crack length a>0.7 and the inclined crack angle 5°⩽ϕ⩽40°. Normalized mode I and mode II stress intensity factors decrease from −0.45 and 2.47 at ϕ=5° to −1.65 and 1.52 at ϕ=40°, respectively. The strains at three points of specimen are also measured in order to investigate the influence of stress singularity on initial crack extension. The results show that the principal orientations of strain at three points are very stable in the loading process. The derived formulae are quite explicit, and the specimen geometry is easy to fabricate and convenient to achieve the pure mode II crack extension. Therefore, it can hopefully be used to obtain mode II fracture toughness of rock.
Based on the detailed geological investigation and record of galleries and drill holes, a new idea has been advanced that granodiorite is earlier than quartz monzodiorite porphyry. Both of them are products of two different magmatic intrusive activities. The analysis results of trace elements show that the Sr content is beyond any other crustal rock and the Th content is beyond that of Ta. The whole-rock analysis indicates that rockbody is rich in CaO and poor in K2O. In the composition of Pb istope of rockbody, the ratio of 207Pb to 204Pb is less than 15.60. All these show that the magma mainly comes from the upper mantle. Ti,Zr,Cr,Nb trace elements and the relation between the Gardini index(τ) and the Rittmann index(σ) indicate that the rockbodies are formed in the orogenic belt and island arc tectonic setting. The summation (ΣREE) and the characteristic value (m(La)/m(Yb) of the rare earth elements show that the original rock is alkalic basalt. The analysis of the characteristic values of REE and the quantitative modeling calculation indicate that the rock-forming process is dominated by mixed crystallization. According to the analysis on the rock-forming order, magmatic source, tectonic setting and rock-forming process, combined with the achievements of regional rock-controlling structures and division of sublayer of crust, it is believed that Fenghuangshan rock body derives from the deep-seated alkalic basalt magma. The rock-forming process has undertaken sialic and calcareous assimilation and contamination of two different degrees. The rock-forming model belongs to the typical assimilation and fractional cryatalization mechanism.
The pit limit optimization is discussed, which is one of the most important problems in the combined mining method, on the basis of the economic model of ore-blocks. A new principle of the limit optimization is put forward through analyzing the limitations of moving cone method under such conditions. With a view to recovering as much mineral resource as possible and making the maximum profit from the whole deposit, the new principle is to maximize the sum of gain from both open-pit and underground mining. The mathematical models along the horizontal and vertical directions and modules for software package (DM&MCAD) have been developed and tested in Tonglushan Copper Mine. It has been proved to be rather effective in the mining practice.
There exist three problems in the calculation of lateral vibration of the train-track time-variant system at home and abroad and the method to solve them is presented. Spatially coupling vibration analysis model of traintrack time-variant system is put forward. Each vehicle is modeled as a multi-body system with 26 degrees of freedom and the action of coupler is also considered. The track structure is modeled as an assembly of track elements with 30 degrees of freedom, then the spatially coupling vibration matrix equation of the train-track time-variant system is established on the basis of the principle of total potential energy with stationary value and the “set-in-right-position” rule. The track vertical geometric irregularity is considered as the excitation source of the vertical vibration of the system, and the hunting wave of car bogie frame is taken as the excitation source of lateral vibration of the system. The spatially coupling vibration matrix equation of the system is solved by Wilson-ϑ direct integration method. The approximation of the calculated results to the spot test results demonstrates the feasibility and effectiveness of the presented analysis method. Finally, some other vibration responses of the system are also obtained.
A set of analytical equations for the variation of the axial force along depth and the pile-top load-settlement curve were established, using tri-linear softening model to pile-side soil and bilinear hardening model to pile-end soil. Influences of the pile-side and pile-end soil behavior on the load-settlement curve were discussed, indicating that the lowering reason for the variation step degree of the axial force along depth is the softening of the pile-side soil to result in the side friction lowering when the pile-top load is increased. To verify the reliability of this method, the parameters used in calculation are obtained from the test in Zhuzhou area. The obtained results are then compared with the tested results. Contrast shows that the calculated results and the tested values are very close, which illustrates that the proposed method is reliable.
An optimal PID controller with incomplete derivation is proposed based on fuzzy inference and the genetic algorithm, which is called the fuzzy-GA PID controller with incomplete derivation. It consists of the off-line part and the on-line part. In the off-line part, by taking the overshoot, rise time, and settling time of system unit step response as the performance indexes and by using the genetic algorithm, a group of optimal PID parameters K*p, T*i, and T*i are obtained, which are used as the inital values for the on-line tuning of PID parameters. In a on-line part, based on K*p, T*i, and T*d and according to the current system error e and its time derivative, a dedicated program is written, which is used to optimize and adjust the PID parameters on line through a fuzzy inference mechanism to ensure that the system response has optimal dynamic and steady-state performance. The controller has been used to control the D. C. motor of the intelligent bionic artificial leg designed by the authors. The result of computer simulation shows that this kind of optimal PID controller has excellent control performance and robust performance.
A soft-measuring approach is presented to measure the flux of liquid zinc with high temperature and causticity. By constructing mathematical model based on neural networks, weighing the mass of liquid zinc, the flux of liquid zinc is acquired indirectly, the measuring on line and flux control are realized. Simulation results and industrial practice demonstrate that the relative error between the estimated flux value and practical measured flux value is lower than 1.5%, meeting the need of industrial process.
An Approximate Voronoi Boundary Network is constructed as the environmental model by way of enlarging the obstacle raster. The connectivity of the path network under complex environment is ensured through building the second order Approximate Voronoi Boundary Network after adding virtual obstacles at joint-close grids. This method embodies the network structure of the free area of environment with less nodes, so the complexity of path planning problem is reduced largely. An optimized path for mobile robot under complex environment is obtained through the Genetic Algorithm based on the elitist rule and re-optimized by using the path-tightening method. Since the elitist one has the only authority of crossover, the management of one group becomes simple, which makes for obtaining the optimized path quickly. The Approximate Voronoi Boundary Network has a good tolerance to the imprecise a priori information and the noises of sensors under complex environment. Especially it is robust in dealing with the local or partial changes, so a small quantity of dynamic obstacles is difficult to alter the overall character of its connectivity, which means that it can also be adopted in dynamic environment by fusing the local path planning.
The probability model is used to analyze the fault tolerance of mesh. To simplify its analysis, it is assumed that the failure probability of each node is independent. A 3-D mesh is partitioned into smaller submeshes, and then the probability with which each submesh satisfies the defined condition is computed. If each submesh satisfies the condition, then the whole mesh is connected. Consequently, the probability that a 3-D mesh is connected is computed assuming each node has a failure probability. Mathematical methods are used to derive a relationship between network node failure probability and network connectivity probability. The calculated results show that the 3-D mesh networks can remain connected with very high probability in practice. It is formally proved that when the network node failure probability is bounded by 0.45%, the 3-D mesh networks of more than three hundred thousand nodes remain connected with probability larger than 99%. The theoretical results show that the method is a powerful technique to calculate the lower bound of the connectivity probability of mesh networks.
A prediction method to obtain harmonic reference for active power filter is presented. It is a new use of the adaptive predictive filter based on FIR. The delay inherent in digital controller is successfully compensated by using the proposed method, and the computing load is not very large compared with the conventional method. Moreover, no additional hardware is needed. Its DSP-based realization is also presented, which is characterized by time-variant rate sampling, quasi synchronous sampling, and synchronous operation among the line frequency, PWM generating and sampling in A/D unit. Synchronous operation releases the limitation on PWM modulation ratio and guarantees that the electrical noises resulting from the switching operation of IGBTs do not interfere with the sampled current. The simulation and experimental results verify the satisfactory performance of the proposed method.
This paper discusses two industrial control applications using advanced control techniques. They are the optimal-tuning nonlinear PID control of hydraulic systems and the neural predictive control of combustor acoustic of gas turbines. For hydraulic control systems, an optimal PID controller with inverse of dead zone is introduced to overcome the dead zone and is designed to satisfy desired time-domain performance requirements. Using the adaptive model, an optimal-tuning PID control scheme is proposed to provide optimal PID parameters even in the case where the system dynamics is time variant. For combustor acoustic control of gas turbines, a neural predictive control strategy is presented, which consists of three parts: an output model, output predictor and feedback controller. The output model of the combustor acoustic is established using neural networks to predict the output and overcome the time delay of the system, which is often very large, compared with the sampling period. The output-feedback controller is introduced which uses the output of the predictor to suppress instability in the combustion process. The above control strategies are implemented in the SIMULINK/dSPACE controller development environment. Their performance is evaluated on the industrial hydraulic test rig and the industrial combustor test rig.
The objective of the architecture is to make agent promptly and adaptively accomplish tasks in the real-time and dynamic environment. The architecture is composed of elementary level behavior layer and high level behavior layer. In the elementary level behavior layer, the reactive architecture is introduced to make agent promptly react to events; in the high level behavior layer, the deliberation architecture is used to enhance the intelligence of the agent. A confidence degree concept is proposed to combine the two layers of the architecture. An agent decision making process is also presented, which is based on the architecture. The results of experiment in RoboSoccer simulation team show that the proposed architecture and the decision process are successful.