排序方式: 共有37条查询结果,搜索用时 279 毫秒
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S. Vaynman R. S. Guico M. E. Fine S. J. Manganello 《Metallurgical and Materials Transactions A》1997,28(5):1274-1276
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Copper-precipitation hardening in a non-ferromagnetic face-centered cubic austenitic steel 总被引:1,自引:0,他引:1
Dieter Isheim Semyon Vaynman Morris E. Fine David N. Seidman 《Scripta materialia》2008,59(12):1235-1238
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Alexandre Dolgui Semyon Potryasaev Boris Sokolov Marina Ivanova Frank Werner 《国际生产研究杂志》2020,58(7):2184-2199
Recently, the applications of Blockchain technology have begun to revolutionise different aspects of supply chain (SC) management. Among others, Blockchain is a platform to execute the smart contracts in the SC as transactions. We develop and test a new model for smart contract design in the SC with multiple logistics service providers and show that this problem can be presented as a multi-processor flexible flow shop scheduling. A distinctive feature of our approach is that the execution of physical operations is modelled inside the start and completion of cyber information services. We name this modelling concept ‘virtual operation’. The constructed model and the developed experimental environment constitute an event-driven dynamic approach to task and service composition when designing the smart contract. Our approach is also of value when considering the contract execution stage. The use of state control variables in our model allows for operations status updates in the Blockchain that in turn, feeds automated information feedbacks, disruption detection and control of contract execution. The latter launches the re-scheduling procedure, comprehensively combining planning and adaptation decisions within a unified methodological framework of dynamic control theory. The modelling complex developed can be used to design and control smart contracts in the SC. 相似文献
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We consider fourth order accurate compact schemes, in both space and time, for the second order wave equation with a variable speed of sound. We demonstrate that usually this is much more efficient than lower order schemes despite being implicit and only conditionally stable. Fast time marching of the implicit scheme is accomplished by iterative methods such as conjugate gradient and multigrid. For conjugate gradient, an upper bound on the convergence rate of the iterations is obtained by eigenvalue analysis of the scheme. The implicit discretization technique is such that the spatial and temporal convergence orders can be adjusted independently of each other. In special cases, the spatial error dominates the problem, and then an unconditionally stable second order accurate scheme in time with fourth order accuracy in space is more efficient. Computations confirm the design convergence rate for the inhomogeneous, variable wave speed equation and also confirm the pollution effect for these time dependent problems. 相似文献
6.
Flux development for lead-free solders containing zinc 总被引:1,自引:0,他引:1
New lead-free solders containing zinc are promising candidates to replace near-eutectic tin-lead solders because the solders
melt at lower temperatures than Sn-Ag-base solders. They also possess good mechanical and fatigue properties and are less
expensive. However, the contact angle on copper for Sn-Zn solders is high when fluxes used for Sn-Pb solders are utilized.
A novel approach for flux development to improve wetting of copper surfaces by tin-zinc eutectic solder was developed: tin
containing organic compounds, which decomposes at soldering temperatures and produces metallic tin on surfaces to be soldered
was added to several specially formulated fluxes. This process improves wetting of copper surfaces by molten tin-zinc eutectic
solder. Fluxes were developed that give a contact angle as low as 20°. 相似文献
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This paper is devoted to serial production lines consisting of producing and inspection machines that obey the Bernoulli reliability and Bernoulli quality models. Such production lines are encountered in automotive assembly and painting operations where the downtime is relatively short and the defects are due to uncorrelated random events. For these systems, this paper develops analytical methods for performance analysis, bottleneck identification, and design. In addition, insights into the nature of bottlenecks in such systems are provided, and an empirical rule for placing an inspection machine that maximises the production rate of non-defectives is formulated. 相似文献
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Ekaterina Skolotneva Kseniia Tsygurina Semyon Mareev Ekaterina Melnikova Natalia Pismenskaya Victor Nikonenko 《International journal of molecular sciences》2022,23(10)
It is known that ammonium has a higher permeability through anion exchange and bipolar membranes compared to K+ cation that has the same mobility in water. However, the mechanism of this high permeability is not clear enough. In this study, we develop a mathematical model based on the Nernst–Planck and Poisson’s equations for the diffusion of ammonium chloride through an anion-exchange membrane; proton-exchange reactions between ammonium, water and ammonia are taken into account. It is assumed that ammonium, chloride and OH− ions can only pass through membrane hydrophilic pores, while ammonia can also dissolve in membrane matrix fragments not containing water and diffuse through these fragments. It is found that due to the Donnan exclusion of H+ ions as coions, the pH in the membrane internal solution increases when approaching the membrane side facing distilled water. Consequently, there is a change in the principal nitrogen-atom carrier in the membrane: in the part close to the side facing the feed NH4Cl solution (pH < 8.8), it is the NH4+ cation, and in the part close to distilled water, NH3 molecules. The concentration of NH4+ reaches almost zero at a point close to the middle of the membrane cross-section, which approximately halves the effective thickness of the diffusion layer for the transport of this ion. When NH3 takes over the nitrogen transport, it only needs to pass through the other half of the membrane. Leaving the membrane, it captures an H+ ion from water, and the released OH− moves towards the membrane side facing the feed solution to meet the NH4+ ions. The comparison of the simulation with experiment shows a satisfactory agreement. 相似文献
10.
The effects of (a) 0.5 wt.% of Pd addition, and (b) aging on mechanical and fatigue properties of eutectic solder (63Sn37Pb)
were investigated. The creep rate of eutectic solder at room temperature is not affected by Pd addition. However, at 80°C,
solder containing Pd creeps slower than Sn-Pb eutectic. Strain rate dramatically affects yield and tensile stress of eutectic
solder with Pd as it does for the binary solder. Isothermal fatigue life of solder at 25°C is essentially not changed by Pd
addition. The microstructure of Pd-containing solder consisted of polyhedral grains of (Pb), (Sn), and a dispersion of PdSn4 intermetallic. Significant microstructural changes and interphase interface phenomena take place during creep deformation
at 25 and 80°C. Ambient aging for seven years leads to solder softening and to moderate increase in isothermal fatigue life. 相似文献