Abstract: The mission abilities of unmanned aerial vehicles (UAVs) under complex environments will be improved by autonomous swarm formations. The coexistence of multiple aircrafts raises a series of problems, such as growing difficulties in coordinated managements. As a result, the design of the UAV swarm formation coordinated autonomous control algorithm is an urgent and crux problem. During the process of collective flight in bird flocks, complex and orderly collective behaviors emerges after the cooperation among individuals based on simple behavior rules. Due to the agreement between the autonomous, coordinated and intelligent control requirements of UAV swarm formations and the characteristic of bird flock collective flight such as adjacent interactions, group stabilities and environment adaptions, the study on the mechanism of collective flight in bird flocks and the mapping relationship between bird flocks and UAV swarm systems will give a feasible way to solve the UAV swarm formation coordinated autonomous control problem.
Abstract: Based on the measured in-situ stress data of the metal mining area in China, 165 sets of data were finally adopted after optimized treatment, which basically covers the distribution area of the main metal mines in the Chinese mainland. The characteristics of in-situ stress field in the buried depth of the metal mining area in China were presented by regression analysis method, and the stability of the fault of the metal mining area in China was discussed from the ground stress. The results show that the vertical principal stress, the maximum horizontal principal stress and the minimum horizontal principal stress in the metal mining area of Chinese mainland generally increase linearly with the depth. The difference between maximum and minimum horizontal principal stresses (Δσ) increases with the depth, but the regularity is not significant. The ratio of maximum horizontal principal stress to vertical principal stress (Kh,max), the ratio of minimum horizontal principal stress to vertical principal stress (Kh,min) and the ratio of average horizontal stress to vertical principal stress (Kh,av) mainly concentrate in the interval of 1. 00 to 2. 50, 0. 50 to 1. 50, and 1. 00 to 2. 00, respectively. With the increase of depth, the variation amplitudes of the three lateral pressure coefficients decrease gradually:Kh,max, Kh,min and K h,av tend to 1. 83, 0. 80 and 1. 31, respectively. The ratio of maximum horizontal principal stress to minimum horizontal principal stress has no obvious regularity with the depth, and the values mainly concentrate from 1. 5 to 2. 0, approximate to normal distribution. Metal mining area has the possibility of fault slip when the depth is less than 500 m, and the reverse fault has the possibility of sliding while the strike slip fault is in a relatively stable state when the depth is more than 500 m.
Abstract: To understand the precise mechanism by what the soot is removed when the triple point passed over the smoked inner wall foil or smoked end-on glass and promote the research on spinning detonation structure, smoked end-on glasses and inner wall smoked foils were established to record the trajectories of triple-shock Mach intersections of spinning detonation. Detonation records of unstable, a little stable and very stable premixed mixtures were obtained in wall foils and end-on glasses. Smoked end-on glass of 2H2 + O2 + 3Ar gave clear records. Sing-head spinning detonation records of 2H2 + O2 + 3Ar indicates that the internal structure of the spinning detonation is not stable while the inner wall results are similar. The cause why soot can be adsorbed on foils and glasses is one factor. Another factor is that reaction characteristics performance of different mixtures should be considered according to above experimental results. The soot can be removed when bond energy is bigger than adsorption energy between the soot and the foil or glass surface. What's more, the carbon molecules particles in detonation front reaction may lead to carbon accumulation and affect the records. In another hand, the strength of reflected shock wave may affect the clarity of the records. Finally, the precise mechanism is affected by characteristics of mixtures. Using appropriate surface roughness and soot particle size according to mixtures characteristics can give satisfying detonation structure records.
Abstract: To realize the accurate and scientific optimization of mining production scheduling for underground metal mines, a mathematic model based on 0-1 integer programming was constructed in view of the characteristics of mining process, such as decentralized production sites, complex production organization and difficulty in controlling the quality of the ore. After the requirements of economic index and spatial sequence relationship being analyzed, an optimization model was proposed which constrained by the yield balance, ore-drawing capacity and combination of high and low grade, aiming at the minimum grade deviation. The optimal mining schedule for underground mines was obtained by computer technology and integer programming to meet the operating procedure, mining sequence, production capacity and other factors. The optimization model was verified by a case in a large gold mine. The optimal solution, expressed by the Gantt chart, indicates that the model is not only meaningful to guide the completion of production tasks in underground mine operation scheduling, but also meets the requirements of continuity and equilibrium of operation scheduling.
Abstract: By chemical composition analysis, X-ray diffraction (XRD), optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) and other measurements, the process mineralogy of Jinchuan nickel slag in a settlement furnace was studied, including the mineral composition, structure, embedded features, distribution of Fe, Ni, Cu, and Co. The results show that the phase composition of the slag includes hortonolite and glass, a few Cu-Ni sulphide, chalcocite and magnetite. The structure of the slag is single, and the Cu-Ni sulphide is distributed in the silicate irregularly. The irons are mainly located in the hortonolite, nickel and copper are mainly located in the Cu-Ni sulphide, and there is no independent minerals about cobalt, which is in the form of isomorphism in other minerals. The recovery of valuable metals from the slag can use deep reduction process or hydrometallurgy.
Abstract: To investigate the leaching characteristic of alkaline copper dioxide ore by ammonia producing bacteria, the influence of the ammonia producing bacteria on the ore during the process was analyzed. To expose the possible influence factor, the shaking flask leaching test was carried out by putting alkaline cupric oxide ore from Yunnan separately into five kinds of leaching solutions, such as bacteria-containing, bacteria-removing inoculums and ammonia solution. Experimental results indicate that the bacteria have a strong ability at producing ammonia and the highest ammonia mass concentration reaches 8. 93 g·L-1. Ammonia production is positively correlated with the content of bacteria. The bacteria leach mineral mainly through producing ammonia, besides, the bacteria and their metabolites can also effect. The leaching capacity is in the order of bacteria ammonia > bacteria > bacterial metabolites, and the ratio of the three is 12:5:4.
Abstract: The as-cast structure of high-silicon steel ingots under different cooling conditions was studied in this paper. It is found that the as-cast structure of the ingot is formed mainly by coarse columnar crystals, especially in the water cooling ingot, and the ratio is reaches as 90%. The dendrite tip growth kinetic coefficients and Gauss distribution parameters for 3D-CAFE simulation were determined according to the compositions of high-silicon steel and the results of as-cast structure. Then the solidification process of high-silicon steel under different cooling conditions was simulated by 3D-CAFE method. The results show that the temperature field under air cooling is more uniform, the mushy zone is broader, and it exhibits a transitional solidification pattern, however, which shows a layered solidification pattern under water cooling. The flow field under air cooling is more stable than that under water cooling, there is a remarkable suction region within the feeder head of the air cooling ingot, and this phenomenon is not observed in the water cooling one. The CAFE results including both morphology and grain size show a good agreement with the results from experiments. Moreover, the influence of superheat on the solidification structures was researched to find that the ratio and quantity of equiaxed structures increase with the decrease of the superheat, and the grain size becomes finer.
Abstract: Aiming at the steelmaking process of IF steel in Han-Steel, the relationship between key parameters and the defects of the rolled sheet was investigated, and the correlation among the parameters was also analyzed through the logic regression analysis, correlation statistics, descriptive statistics and other methods in the statistical software SPSS. The results show that the probability of inclusion defects in the rolled sheet reduces in the steelmaking process of IF steel when the end-point temperature of BOF is controlled in the range of 1695-1700℃, the oxygen blow amount below 250 m3, the holding time in the range of 30-40 min and the oxygen content before adding aluminum below 3. 9×10-4. Besides, the improvement measures were carried out and the results show that the optimization measures can reduce the inclusion defects of rolled IF steel sheet.
Abstract: The leaching experiments of zinc from mixed sulfide-oxide lead and zinc ore were performed in NH3-(NH4)2SO4 solution with ammonium persulfate as an oxidant under atmospheric pressure and relatively low temperature. The effects of stirring speed, lixiviants, oxidant concentration and reaction temperature on the leaching rate of zinc were studied. The results show that under the optimal conditions, the leaching rate of zinc can reach 93. 2%, and nearly no other metal ions enter into lixivium during the leaching process, which shows that this ammoniacal leaching system has a high efficiency and selectivity. This is significant to simplify the following purification process and product preparation process. Leaching kinetics indicates that the oxidative leaching of zinc could be represented by a shrinking core model with product layer diffusion and the activation energy for the dissolution reaction is calculated as 17. 89 kJ·mol-1.
Abstract: The recovery of copper and cyanide from high concentration wastewater was conducted by electrodeposition with high basicity. The effect of hypophosphite dosage and temperature on recycling copper and cyanide from wastewater was investigated. The linear cyclic voltammetry, potentiostatic electrolysis and X-ray diffraction analysis were used to research the anodic reaction and precipitate phase, the mechanisms of cyanide decomposition and hypophosphite inhibition were also analyzed. The experiment of cyanide leaching of gold was done in residual liquid after electrolysis. The results indicate that the damage of cyanide is effectively suppressed by hypophosphite. The inhibitory effect is enhanced gradually with increasing temperature. The Cu2+ forming on the anode surface is the main reason to degrade cyanide. Hypophosphite restrains cyanide from degradation by preferential oxidation. The tail liquid has no effect on leaching of gold, and the copper-cyanide wastewater can be comprehensively recovered the valuable metals and cyanide by electrodeposition.
Abstract: A thermal-mechanical coupling model of a copper cooling stave with variable slag coating was founded based on thermal elastic mechanics, and the influence of the gas temperature, the cooling system, the materials of insert bricks, and the properties of the slag on the stave life and the stability of the adherent dross was analyzed from the view point of the stress distribution of the stave body and the slag-brick interface. The results show that the increase of the gas temperature linearly improves the stress of stave body and reduces the stability of the adherent dross meanwhile. The stress of the stave body and the stability of the adherent dross both decrease at first and then increase when the slag coating thickness increases, and the slag coating thickness should be controlled between 30 to 60 mm. The increase of water velocity incurs tiny growth of the stress of the stave body, while the stability of the adherent dross is enhanced. The stress of the stave body is weakly reduced with the increase of water temperature, but the stability of the adherent dross decreases heavily meanwhile. The increase of the heat conductivity of insert bricks and the decrease of the heat expansion coefficient of the slag significantly reduce the stress of the stave body and enhance the stability of the adherent dross.
Abstract: The effects of chloride concentration and dissolved oxygen on the high-temperature electrochemical corrosion behaviors of 304 stainless steel sheets were investigated in simulated pressurized water reactor (PWR) primary water. The results of potentiodynamic polarization measurements reveal that the chloride ion mainly affects the second passivation region under high potential, but little effect under low potential. Oxide film chemical content analysis by X-ray photoelectron spectroscopy (XPS) shows that the second passivation properties are closely related to the Fe/Cr ratio of the oxide film. Electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) results show that, when the chloride ion concentration increases, the oxide film resistance decreases, the size of oxide particles and the gap between oxide particles on the outer layer increases and the corrosion resistance decreases. Besides, with the increase of dissolved oxygen, the corrosion potential increases, the passive current density decreases, the passive potential region shrinks, and the oxide film resistance gradually increases.
Abstract: MnO/reduced graphene oxide (MnO/rGO) composites synthesized through freeze-drying following annealing were used as anode materials for lithium ion batteries. At 500 mA·g-1, the MnO/rGO composite exhibits a reversible capacity as high as 830 mAh·g-1 and the specific capacitance remains at 805 mAh·g-1 after 160 discharge/charge cycles, demonstrating excellent cycling stability. It also shows good rate capacities and delivers a specific capacity of 412 mAh·g-1 at 2. 0 A·g-1 after 225 cycles at different rates. The rGO increases the electrical conductivity and provides space to accommodate the volume expansion of MnO during charge/discharge. The extra capacity, over the theoretical value of MnO, is attributed to the formation of higher oxidation state manganese according to the charge-voltage derivative analysis of the galvanostatic charge-discharge curves. A higher tendency to further oxidize Mn(Ⅱ) in the MnO/rGO composite maybe result in the extra oxygen source provided by rGO during the electrode reaction. The simple and green synthetic protocol and the excellent electrochemical performance demonstrate the great potential of the MnO/rGO composite anode in large scale production and applications.
Abstract: A copper/titanium bimetallic composite pipe with high interfacial bonding quality was manufactured by the high-temperature rotary swaging forming, and then was processed by the floating-plug drawing process. The forming ability of drawing process and the effect of drawing process on the microstructure and properties of the product were mainly investigated. The results show that the floating plug drawing, especially the wall-reduction drawing, has a great destructive effect on the bonding interface of the pipe, which results in that it is difficult to carry out multi-pass continuous drawing, and single pass drawing volume should not reach over 30%. The annealing at 575℃ for 70 min has little effect on the diffusion of interfacial elements, but it can reduce the work hardening and residual stress. This process makes the pipe's average peel strength increase from 7. 8 N·mm-1 (worked state) to 17. 1 N·mm-1 (annealed state), which considerably improves the subsequent drawing performance of the pipe. A reasonable drawing forming process for the copper/titanium composite pipe was made based on the strict control of drawing wall-reduction, and a capillary size pipe with an excellent bonding property was successfully prepared.
Abstract: The friction and wear properties of ultrafine grain Ti-8Mo-3Fe alloy fabricated by mechanical alloying (MA) and subsequent spark plasma sintering (SPS) were investigated in SBF simulated body fluid. It was compared with those of as-SPSed micron size grain Ti-8Mo-3Fe alloy and as-casted Ti and TC4 alloy. The results show that ultrafine grain Ti-8Mo-3Fe alloy with high density and uniform microstructure can be fabricated by MA-SPS, and the alloy mainly consists of β-Ti phase and a small amount of α-Ti phase. The average grain size is 1. 5 μm, and the microhardness is 448 HV. In the same wear condition, the wear degree of ultrafine grain Ti-8Mo-3Fe alloy is significantly lower than those of micro-crystalline Ti-8Mo-3Fe, as-casted Ti, and TC4 alloy, so it has the lowest wear volume and stable friction coefficient. Ultrafine grain Ti-8Mo-3Fe alloy is mainly characterized by abrasive wear, but micro-crystalline Ti-8Mo-3Fe, as-casted Ti and TC4 alloy are characterized by abrasive and adhesion wear.
Abstract: For enhancing the corrosion resistance of the T6-aged high-strength Al alloys with higher strength, retrogression and reaging (RRA) treatments were used to optimize the morphologies, sizes, distribution of precipitates, especially grain boundary precipitates (GBPs). The effects of different retrogression treatments on the microstructures and mechanical properties were studied so as to gain suitable RRA process for 7B50 Al alloy plates. It is found that increasing the retrogression temperature or time will promote the coarsening of transgranular and intergranular precipitates in the center and surface layers of 7B50 Al alloy plates as well as the precipitation of stable η-MgZn2 phase, which will decrease the strength and raise the conductivity. The retrogression temperature will greatly affect the strength and conductivity. The continuously distributed GBPs induced by T6 aging become discontinuous after RRA treatment, accompanying with slightly increasing sizes of transgranular precipitates. Based on the strength and conductivity of the center and surface layers, 165℃/6 h is the suitable retrogression process for 7B50 Al alloy plates. However, the severe deformation of the surface grains compared to that of the central grains caused by hot rolling leads to a higher content of subgrains or substructures in the surficial grains, which promotes the surface layer to quickly reach the peak aging, and the subsequent retrogression treatment results in much more stable η phase in the surface layer. The formation of stable η phase as well as the coarsening or growth of transgranular precipitates could be mainly responsible for the strength difference between the surface and center layers. Although there are some differences about the grain structures between the surface and center layers after quenching/RRA treatments with some local subgrain growth, the positive impact of RRA treatment to the strength is apparently unable to compare with the obvious strength reduction caused by early precipitation of stable η phase in the surface layer. Thus, the RRA treatment cannot relieve the property difference between the center and surface layers of 7B50 Al alloy plates, but it can make the strength and conductivity of the center and surface layers to concurrently meet some working requirements.
Abstract: A novel process for preparation of a carbon molecular sieve (CMS) was proposed. With coconut shell char as a carbon precursor and phenol formaldehyde resin (PF) as a binder, the process consists of a series of stages, i. e., forming, carbonization, activation with steam, and two-step chemical vapor deposition with benzene as a carbon source. The CMS has been used as an adsorbent in pressure swing adsorption (PSA) of air for N2 production. The evaluation method of CMS based on PSA was developed by introducing a couple of analysis items including the amount of the effluent desorption gas in PSA and the O2 concentration in it. In this way, the development of the effective volume and size of the micropores of CMS during the preparation stages could be followed and controlled on purpose. The coconut shell-based CMS prepared by this method has a superior compressive strength and a comparable PSA performance to those commercial CMSs.
Abstract: In order to grasp the resistance characteristics of gas-liquid two-phase flow in stick venturi scrubbers, based on the multiphase flow theory, a three-dimensional CFD model was established. The impacts of stick spacing, air flow and liquid-gas ratio on the pressure loss were studied, and a resistance characteristic model was established. The relationship among stick spacing, air flow and liquid-gas ratio was obtained based on the resistance characteristic model. The results show that the pressure loss between the venturi bar layer and the lower cylinder increases in power exponent with the decrease of stick spacing and the increase of air flow, and it increases in linear with the increase of liquid-gas ratio. The pressure loss of the upper cylinder increases in quadratic with the increase of air flow. The max error between the resistance characteristic model and experimental data is 16. 88%, which verifies the model effectiveness.
Abstract: Aiming at the requirement for voltage regulation with a 18-pulse autotransformer-rectifier, a novel step-down 18-pulse topology was designed and optimized based on the advantage of present topologies. The primary extended winding of the step-down 18-pulse autotransformer-rectifier was connected with the winding tap of the phase shift secondary winding to reduce the transformer input voltage. Considering the influence caused by the position change of the connecting tap between the primary extended windings and secondary phase shift windings on the autotransformer performance, transformer voltage ratio and winding tap position were regarded as variables. A universal design formula was derived and simulation analysis was carried out to obtain the optimal connection tap position with the minimum equivalent capacity of the step-down autotransformer under the same voltage ratio. Finally, the rationality of the design is verified by experiments.
Abstract: A layer-by-layer evolution strategy was proposed to deal with the premature convergence of swarm intelligence as a collaborator with other existing researches based on pre-experiments and simple proofs. For promoting the precision of solution and eviting the premature convergence, the self-adaption system was constructed on the basis of the primal algorithm, operations such as compression, selection and re-initialization using the technology of layer-by-layer, and the social information was used including the compressed research space and the optimal solution. The improvements of precision of solution and the vitality of terminal individuals can be found in results of simulation experiments with benchmark functions.
Monthly, started in 1955 Supervising institution：Ministry of Education Sponsoring Institution：University of Science and Technology Beijing Editorial office：Editorial Department of Chinese Journal of Engineering Publisher：Science Press Chairperson：Ren-shu Yang Editor-in-Chief：Ai-xiang Wu ISSN 2095-9389CN 2095-9389
