基于MAS的勤务维修协同任务分配策略（英文）

飞机的勤务过程是一个资源约束的多人协同问题,任务分配是协同的基础。现有的关于勤务维修协同的研究还比较有限。针对以上问题,以单机勤务任务为研究对象,基于MAS构建飞机勤务维修任务分配的动态模型,综合考虑了任务时间窗、任务执行者时间要求、勤务任务执行成本、勤务任务需求能力等多重因素,以最短的时间和最低的成本完成单机勤务任务为双重优化目标,通过遗传算法与最短路算法相结合得到了勤务任务的最优分配方案及执行顺序。实例验证表明所提出的模型和算法对于勤务维修协同任务分配切实可行,对于机务人员的勤务维修管理具有指导性的意义。     

基于改进蚁群算法的多机器人任务分配

研究了多机器人系统的任务分配方法,多机器人多任务分配是一个NP问题.针对多机器人系统在动态环境下自主任务分配问题,综合考虑任务约束及机器人的执行任务能力,采用了一种改进的蚁群算法,解决多机器人系统全局最优任务分配问题.通过对基本蚁群算法和改进的算法的仿真,验证了改进的算法实现了全局近似最优的任务分配.     

基于模糊层次分析决策的产品协同开发任务分配研究

在分析产品协同开发任务分配需求的基础上,建立了任务分配的评价指标体系;介绍了模糊层次分析决策的数学方法,并以某产品协同开发任务分配为例,采用时间、质量、成本作为一级评价指标,人员的工作效率、技术水平、协作能力、工作经验、人员兴趣、工作态度、人员工资和协作费用等为二级评价指标,建立了支持产品协同开发任务分配的多层评价模型;运用模糊层次分析综合决策方法对其进行评价,实现了产品协同开发的人员任务分配;最后基于COM组件技术,实现了产品协同开发任务分配工具的软件原型,它具有界面友好、操作方便、计算快捷等特点.     

裂纹检出概率对飞机结构维修间隔影响的研究

针对飞机结构裂纹检测的不完备性,考虑到疲劳裂纹具有时间延迟的特性,对Goranson模型进行改进,提出了基于时间的裂纹检出概率模型。并在此基础上建立了以复检间隔和首检间隔系数为变量,单位时间维修成本最小为目标函数的飞机结构维修间隔优化模型。通过裂纹检出概率模型中参数的变化对优化模型进行仿真计算,分析了裂纹检查概率对飞机结构维修间隔优化结果的影响情况,结果显示裂纹检出概率对维修间隔有显著的影响,其变化趋势与实际情况相符,表明提出的裂纹检出概率模型能够有效地应用于飞机结构维修间隔的优化与确定。     

基于任务可用度的设备维修建模与优化研究

设备故障停机导致的总损失成本包括设备维修成本和生产任务损失成本。为减少多设备混联生产系统中设备故障停机带来的总损失成本,以设备停机总损失成本最小化为目标,综合考虑设备失效率和修复率两方面因素,建立了基于设备任务可用度的维修成本模型。探讨了利用遗传蚁群算法对模型进行优化求解的方法。最后以发动机凸轮机加工线设备为例,验证了所建模型的有效性。     

基于免疫蚁群优化算法的仓储任务调度北大核心

针对仓储机器人群的多目标任务分配问题,以最小距离成本为目标,建立了仓储机器人群调度方案的数学模型。以免疫算法为基础,提出了一种免疫蚁群优化算法。通过融合、改进免疫算法和蚁群算法,弥补了免疫算法因冗余信息多导致的迭代时间长、收敛速度慢以及蚁群算法初期信息素积累时间较长,速度慢的缺陷,提高了算法的效率。再多次进行对比实验,从算法运行时间,机器人群的距离成本角度验证了改进算法的可行性。     

考虑人力资源约束的串联系统机会维修策略优化

针对多部件串联系统维修存在人力资源约束的问题，提出一种考虑人力资源配置的机会维修策略模型。针对部件在使用过程中受外部环境影响发生劣化的特点，引入役龄回退因子和故障率递增因子，建立单部件的预防性维修策略。引入机会维修思想，以机会维修系数作为优化变量，对系统的维修策略进行组合优化，在维修人员有限的条件下确定维修任务的配置以及系统的停机时间，进一步构建考虑人力资源约束的串联系统机会维修策略模型。最后，针对算例进行建模，通过元胞自动机算法应用MATLAB进行仿真分析，获得系统的最优机会维修方案。结果显示：考虑机会维修的策略相比传统的预防性维修可有效降低维修成本13.6%,提高系统的可用度2.05%,考虑人力资源约束的机会维修策略相比人员无约束的机会维修策略可有效降低维修成本7.3%,此时经济效益最高。     

求解大规模生产排程问题的一种快捷算法

生产排程是一类复杂而困难的系统性问题，但其对多品种小批量企业的生产效率以及经济效益的提高有着至关重要的作用。文章针对生产排程时效性差的算法瓶颈，设计了一套基于交货期的快捷排程算法。算法的基本思想是将加工任务先分配到具体的设备上，然后根据任务的加工时间为每个设备提供一个排程方案。该算法体系包括绝对最优方案确定、任务分配、依次排队、二次排程和条件汇报5个模块，其中依次排队是该算法的核心。该算法具有寻优合理、速度快等优点，但同时也有只适宜以交货期为目标的缺点。     

基于多个系统因素控制图的预防维修决策模型研究

以控制图经济性模型为基础,增加预防维修的成本及时间两个参数变量,构建基于多个系统因素的均值控制图的预防维修决策模型。设定控制图警戒区域为维修窗口,当样本落于警戒区域时就执行预防维修决策。对模型进行算例分析,在单位时间期望损失成本最低时算出模型的各类参数值,发现此时若不考虑预防维修则单位时间期望损失成本会增大,说明基于多重系统因素均值控制图的预防维修决策模型对降低制造企业总成本是有效的。     

基于多重约束模型的折弯工序规划算法

针对复杂折弯件的加工提出了一种基于多重约束模型的工序规划算法。该算法采用启发式搜索中的A*算法将工序规划转换为一般化的最短路径搜寻问题,并使用基于可行性、尺寸精度和生产效率的多重约束模型来优化搜索过程。基于该算法实现了一套工艺规划系统,通过对该系统的测试表明,该算法执行效率高,稳定性好,能够有效减少复杂折弯件的规划时间,尤其对于无法完成最终折弯的工件,规划时间会大幅缩短。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.