7xxx系铝合金热处理的进展

7xxx系合金是基于Al-Zn-Mg（-Cu）系的可热处理的锻铝合金，广泛应用于高性能航空结构和运输部件。除了受成分、铸造和形变热处理影响外，材料性能的平衡明显受到其所经历的热处理方式的影响。描述了均匀化、固溶处理、淬火、时效对7xxx系高强合金组织和性能的影响。总结了在Monash大学进行的有关厚板产品的生产工艺，包括从均匀化到最终的时效处理，以及通过控制微观组织特征，比如弥散体、粗粒子、精细析出相、晶粒结构和晶界特征，来实现组织与性能的平衡。重点陈述了相关方法，如通过高温热处理溶解不需要的粗粒子、基于连续冷却析出行为的淬火敏感性变化、通过实验与建模来研究时效包括一步时效、两步时效、三步时效。对每种情况下的组织与性能都进行研究。     

Heuristic dynamic programming-based learning control for discrete-time disturbed multi-agent systems

Owing to extensive applications in many fields, the synchronization problem has been widely investigated in multi-agent systems. The synchronization for multi-agent systems is a pivotal issue, which means that under the designed control policy, the output of systems or the state of each agent can be consistent with the leader. The purpose of this paper is to investigate a heuristic dynamic programming (HDP)-based learning tracking control for discrete-time multi-agent systems to achieve synchronization while considering disturbances in systems. Besides, due to the difficulty of solving the coupled Hamilton– Jacobi–Bellman equation analytically, an improved HDP learning control algorithm is proposed to realize the synchronization between the leader and all following agents, which is executed by an action-critic neural network. The action and critic neural network are utilized to learn the optimal control policy and cost function, respectively, by means of introducing an auxiliary action network. Finally, two numerical examples and a practical application of mobile robots are presented to demonstrate the control performance of the HDP-based learning control algorithm.     

Friction and Wear Behavior of Resin/Graphite Composite under Dry Sliding

The friction and wear behavior of resin/graphite composite has been investigated using a pin-on-disc configuration under dry sliding condition. The results showed that the resin/graphite composite exhibited much better mechanical and tribological properties compared with the unimpregnated graphite. The friction coefficient was reduced by addition of furan resin, which could also prevent the"dusting" wear at loads more than 15 MPa. The steady and lubricated transfer film was easily formed on the counterpart surface due to the interaction of furan resin and wear debris of graphite, which was useful to reduce the wear rate of the resin/graphite composite. The composite is highly promising for mechanical sealing application and can be used at high load for long time sliding.     

Sintering behavior and properties of SiC/Si3N4 composite

SiC/Si3N4 composite was pressureless sintered using self-propagating high-temperature combustion synthesis a-Si3N4 powder and appropriate amount of b-SiC powder. Both of the sintering additive systems were used,which were YAN(Y2O3–Al2O3–AlN) and YN(Y2O3–AlN).The influences of b-SiC content on sintering behavior of SiC/Si3N4 composite were investigated. The results show that the density, shrinkage, bending strength, hardness, and fracture toughness of the samples with two sintering additive systems increase first with the increase of the contents of b-SiC and then decrease even when b-SiC contents continually increase. The tendency of weight loss of the samples is opposite. The b-SiC content of the samples with the best mechanical properties is different in two systems. For YAN system, the best mechanical properties of the samples are gained when b-SiC content reaches 10 %, while as for YN system it is 5 %. The properties of YN samples are superior to YAN samples. J phase(2Y2O3 Si2N2O) forms in YN system easily. A small amount of M phase(Y2O3Si3N4) is observed in YAN system.     

Increasing ionic conductivity in Li0.33La0.56TiO3thin-films via optimization of processing atmosphere and temperature

As a promising solid electrolyte for thin-film lithium batteries,the amorphous Li_0.33La_0.56TiO₃(LLTO)thin film has gained great interest.However,enhancing ionic conductivity remains challenging in the field.Here,a systematical study was performed to improve the ionic conductivity of sputter-deposited LLTO thin films via the optimization of processing atmosphere and temperature.By combining the optimized oxygen partial pressure(30%),annealing temperature(300℃),and annealing atmosphere(air),an amorphous LLTO thin film with an ionic conductivity of 5.32910^-5·S·cm^-1 at room temperature and activation energy of 0.26 eV was achieved.The results showed that,first,the oxygen partial pressure should be high enough to compensate for the oxygen loss,but low enough to avoid the abusive oxygen scattering effect on lithium precursors that results in a lithium-poor composition.The oxygen partial pressure needs to achieve a balance between lithium loss and oxygen defects to improve the ionic conductivity.Second,a proper annealing temperature reduces the oxygen defects of LLTO thin films while maintaining its amorphous state,which improves the ionic conductivity.Third,the highest ionic conductivity for the LLTO thin films that were annealed in air(a static space without a gas stream)occurs because of the decreased lithium loss and oxygen defects during annealing.These findings show that the lithium-ion concentration and oxygen defects affect the ionic conductivity for amorphous LLTO thin films,which provides insight into the optimization of LLTO thin-film solid electrolytes,and generates new opportunities for their application in thinfilm lithium batteries.     

Petroleum substitution, greenhouse gas emissions reduction and environmental benefits from the development of natural gas vehicles in China

This study develops a bottom-up model to quantitatively assess the comprehensive effects of replacing traditional petroleum-powered vehicles with natural gas vehicles (NGVs) in China based on an investigation of the direct energy consumption and critical air pollutant (CAP) emission intensity, life-cycle energy use and greenhouse gas (GHG) emission intensity of NGV fleets. The results indicate that, on average, there are no net energy savings from replacing a traditional fuel vehicle with an NGV. Interestingly, an NGV results in significant reductions in direct CAP and life-cycle GHG emissions compared to those of a traditional fuel vehicle, ranging from 61% to 76% and 12% to 29%, respectively. Due to the increasing use of natural gas as a vehicle fuel in China (i.e. approximately 28.2 billion cubic metres of natural gas in 2015), the total petroleum substituted with natural gas was approximately 23.8 million tonnes (Mt), which generated a GHG emission reduction of 16.9 Mt of CO₂ equivalent and a CAP emission reduction of 1.8 Mt in 2015. Given the significant contribution of NGVs, growing the NGV population in 2020 will further increase the petroleum substitution benefits and CAP and GHG emission reduction benefits by approximately 42.5 Mt of petroleum-based fuel, 3.1 Mt of CAPs and 28.0 Mt of GHGs. By 2030, these benefits will reach 81.5 Mt of traditional petroleum fuel, 5.6 Mt of CAPs and 50.5 Mt of GHGs, respectively.     

Protection Performance of Plasma Sprayed Al2O3-13 wt%TiO2 Coating Sealed with an Organic-inorganic Hybrid Agent

An organic-inorganic hybrid sealing agent was fabricated and used in the plasma sprayed Al₂O₃-13 wt%TiO₂ coating,and conventional silicone agent was also used for comparison.Protection performance of the coatings was comprehensively evaluated based on both anti-corrosion and anti-biofouling properties.The results reveal that the sealing treatment is remarkably useful to decrease the porosity of the coating,and the porosity of the coating sealed with the hybrid ag...     

Estimation method of state-of-charge for lithium-ion battery used in hybrid electric vehicles based on variable structure extended kalman filter

Since the main power source of hybrid electric vehicle(HEV) is supplied by the power battery, the predicted performance of power battery, especially the state-of-charge(SOC) estimation has attracted great attention in the area of HEV. However, the value of SOC estimation could not be greatly precise so that the running performance of HEV is greatly affected. A variable structure extended kalman filter(VSEKF)-based estimation method, which could be used to analyze the SOC of lithium-ion battery in the fixed driving condition, is presented. First, the general lower-order battery equivalent circuit model(GLM), which includes column accumulation model, open circuit voltage model and the SOC output model, is established, and the off-line and online model parameters are calculated with hybrid pulse power characteristics(HPPC) test data. Next, a VSEKF estimation method of SOC, which integrates the ampere-hour(Ah) integration method and the extended Kalman filter(EKF) method, is executed with different adaptive weighting coefficients, which are determined according to the different values of open-circuit voltage obtained in the corresponding charging or discharging processes. According to the experimental analysis, the faster convergence speed and more accurate simulating results could be obtained using the VSEKF method in the running performance of HEV. The error rate of SOC estimation with the VSEKF method is focused in the range of 5%to 10%comparing with the range of 20%to 30%using the EKF method and the Ah integration method. In Summary, the accuracy of the SOC estimation in the lithium-ion battery cell and the pack of lithium-ion battery system, which is obtained utilizing the VSEKF method has been significantly improved comparing with the Ah integration method and the EKF method. The VSEKF method utilizing in the SOC estimation in the lithium-ion pack of HEV can be widely used in practical driving conditions.     

Enhanced Mn2+ solidification and NH4+-N removal from electrolytic manganese metal residue via surfactants

Electrolytic manganese metal residue (EMMR) harmless treatment has always lacked a low-cost and quick processing technology. In this study, surfactants, namely tetradecyl trimethylammonium chloride (TTC), sodium dodecyl benzene sulfonate (SDBS), sodium lignin sulfonate (SLS), and octadecyl trimethylammonium chloride (OTC), were used in the solidification of Mn²⁺ and removal of NH₄⁺-N from EMMR. The Mn²⁺ and NH₄⁺-N concentrations under different reaction conditions, Mn²⁺ solidification and NH₄⁺-N removal mechanisms, and leaching behavior were studied. The results revealed that the surfactants could enhance the Mn²⁺ solidification and NH₄⁺-N removal from EMMR, and the order of enhancement was as follows: TTC > SDBS > OTC > SLS. The NH₄⁺-N and Mn²⁺ concentrations were 12.3 and 0.05 mg·L^-1 with the use of 60.0 mg·kg^-1 TTC under optimum conditions (solid–liquid ratio of 1.5:1, EMMR to BRM mass ratio of 100:8, temperature of 20 ℃, and reaction duration of 12 h), which met the integrated wastewater discharge standard (GB8978-1996). Mn²⁺ was mainly solidified as Mn(OH)₂, MnOOH and MnSiO₃, and NH₄⁺-N in EMMR was mostly removed in the form of ammonia. The results of this study could provide a new idea for cost-effective EMMR harmless treatment.     

变频调速技术及其在刮板输送机中的应用

针对分析变频调速技术的功能、特点,并详细阐述变频调速技术在刮板输送机启动阶段、运输阶段、控制阶段的具体应用。该技术在某煤矿SG-1000/2×270型刮板输送机上的应用效果表明:应用变频调速技术,不仅可实现刮板输送机的变频启动,使启动平缓,而且可降低对轮皮子的摩擦,有效降低能耗和电耗。