Simulation of thermal state of containers with spent nuclear fuel: multistage approach

The safe thermal conditions of spent nuclear fuel storage are the important component of complex safety of the dry spent nuclear fuel storage facility. The multistage approach for numerical definition of thermal fields in storage containers with spent fuel assemblies is proposed. The approach is based on solving of the series of the conjugate heat transfer problems with different geometrical detailing. The developed approach is used for estimation of thermal state of ventilated containers with spent nuclear fuel of WWER‐1000 reactors of Zaporizhska nuclear power plant. The results of the thermal calculations for single‐placed container on open‐site storage platform were presented. The safety of containers usage in normal and extreme ambient temperatures was proven. Copyright © 2015 John Wiley & Sons, Ltd.     

Ukrainian dietary bakery product with selenium-enriched yeast

Bread is a most important food product and source of selenium in Ukraine. However, low content of selenium in wheat flour from north and northwest regions of Ukraine does not ensure the recommended consumption of selenium. Daily intake of selenium by the population of North Ukraine is below recommended allowance. The aim of this research was to study the production of the dietary rolls with selenium-enriched yeast for the population of North Ukraine. The study showed that to obtain bakery yeast of good quality, concentration of sodium hydroselenite in the medium for yeast cultivation should be in the range from 2 to 5 μg Se/ml. Under these concentrations of selenium in medium, specific growth rate and biomass yield as well as bakery properties of the yeast Saccharomyces cerevisiae did not differ from the parameters of yeast, grown in the medium without selenium. Maturation of the selenium-enriched yeast improved their bakery properties. The 100 g wheat roll prepared with selenium-enriched yeast contained 50 μg Se (25% of the recommended daily allowance) in the form of selenomethionine, which is the best form of selenium for human consumption. These rolls can be used as a dietary product to reach recommended daily consumption of selenium by the population of North Ukraine and Chernobyl region.     

Transverse conductivity of unidirectional fibrous composite with interface arc cracks

A complete solution of the conductivity problem has been obtained for the finite and infinite arrays of circular inclusions with interface arc cracks regarded as the models of fibrous composite with interface damage. By combining the multipole expansion technique with newly derived theoretical results, the model boundary-value problem has been reduced to a linear set of algebraic equations. An exact and finite form expression of the effective conductivity tensor has been found by integrating the local fields over the representative cell volume. The numerical data are given which show an accuracy and numerical efficiency of the proposed method and discover the way and extent to which the conductivity of fibrous composite is affected by the interface debonding.     

Ultra-stable nanoparticles of CdSe revealed from mass spectrometry

Nanoparticles under a few nanometres in size have structures and material functions that differ from the bulk because of their distinct geometrical shapes and strong quantum confinement. These qualities could lead to unique device applications. Our mass spectral analysis of CdSe nanoparticles reveals that (CdSe)(33) and (CdSe)(34) are extremely stable: with a simple solution method, they grow in preference to any other chemical compositions to produce macroscopic quantities. First-principles calculations predict that these are puckered (CdSe)(28)-cages, with four- and six-membered rings based on the highly symmetric octahedral analogues of fullerenes, accommodating either (CdSe)(5) or (CdSe)(6) inside to form a three-dimensional network with essentially heteropolar sp(3)-bonding. This is in accordance with our X-ray and optical analyses. We have found similar mass spectra and atomic structures in CdS, CdTe, ZnS and ZnSe, demonstrating that mass-specified and macroscopically produced nanoparticles, which have been practically limited so far to elemental carbon, can now be extended to a vast variety of compound systems.     

Computational fluid dynamics modeling of the flow in a laboratory membrane filtration cell operated at low recoveries

Scaled-down models of industrial filtration units are often used in laboratory studies of membrane processes. Knowledge of the flow field and shear stresses at the membrane surface is vital for the accurate interpretation of bench scale experiments. In this paper, we present results of computational fluid dynamics modeling of the flow within the SEPA CF flat sheet membrane filtration cell operated at low recoveries. The problem was formulated as the steady-state isothermal laminar flow of incompressible Newtonian fluid. Pressure, velocity, and shear stress distributions were computed with resolution for different average inlet velocities. Flow was found to be unidirectional over most of the channel area with exception of the corners of the channel. Stagnation areas in dead ends of inlet and outlet tubes and in the channel areas behind duct entries as well as local regions of high shear in duct-channel transition areas were observed. The relation between the highest shear rate created in this geometry and the average inlet velocity is given.     

电磁复合场协同激光熔覆制备TiBw/Ti网状结构复合涂层

目的利用电磁复合场(EMCF)辅助激光熔覆制备TiB_w/Ti网状结构复合涂层,探索电磁场对涂层组织结构的影响。方法以TiB_2∶Ti=1∶1(摩尔比)的混合粉末为熔覆材料,TC4作为基板材料,通过外加电磁复合场进行激光熔覆试验。通过扫描电子显微镜(SEM)观察洛伦兹力方向对熔覆层组织结构的影响,利用X射线衍射仪(XRD)和维氏显微硬度计分析施加电磁复合场前后熔覆层的相组成和硬度分布。结果未施加电磁复合场的熔覆层组织主要为细针状、粗棒状和颗粒状组织。而施加电磁复合场后,熔覆层出现了网状结构,而且方向向下的洛伦兹力可使涂层内部形成空间间距更大的网状结构。此外,单独施加稳态磁场后,熔覆层只出现细针状和粗棒状组织。电磁复合场施加前后熔覆层硬度与基体相比,均有很大的提高。但未施加电磁复合场的熔覆层硬度变化幅度较大;施加电磁复合场后,随着距熔覆层表面距离的增加,硬度的变化幅度比较平缓。结论在洛伦兹力作用下,可得到TiB_w/Ti网状结构的复合涂层,电磁复合场使TiB_w/Ti网状结构强化相均匀分布,同时提高涂层的显微硬度。     

Influence of oxygen on the tool wear in machining

High temperatures generated in machining are known to facilitate oxidation wear. A controlled atmosphere chamber was developed to investigate the effects of oxygen on tool wear and high speed machining tests were conducted on air and in argon. Cemented carbide, cermet and cubic boron nitride tooling was used on alloyed steel, hardened tool steel and superalloy Alloy 718. Machining in argon resulted in higher flank wear, higher cutting forces, and larger tool–chip contact length on the rake face. However, in hard machining, argon atmosphere reduced rake cratering. Transmission electron microscopy of tools worn on air showed formation of nanocrystalline Al₂O₃ film on the rake when machining aluminium containing Alloy 718, while no oxide films was detectable in the other cases.     

Synthesis and Properties of Novel Surface Active Monomers Based on Derivatives of 4‐Hydroxybutyric Acid and 6‐Hydroxyhexanoic Acid

Novel surface active maleate and methacrylate monomers based on derivatives of ω‐hydroxy carboxylic acids have been synthesized. The monomers are comprised of hydrophobic alkyl chains and hydrophilic poly(ethylene glycol), quaternary ammonium, sulfonate and carboxylic fragments. Synthesized monomers sufficiently reduce surface tension at the aqueous solution‐air interface. The copolymerization of synthesized monomers with 5‐tert‐butylperoxy‐5‐methyl‐2‐hexene‐3‐yne monomer and N‐vinylpyrrolidone in solvent and emulsion copolymerization of synthesized peroxide containing surface active monomer with styrene have been carried out. The synthesized surface active monomers have been shown to be suitable emulsifiers for obtaining polystyrene colloid dispersions. It has been ascertained that the surface active copolymers obtained can form stable interpolyelectrolyte complexes with oppositely charged polymers.     

Incorporation of cellulose nanocrystals and reactive surfactants for improved pressure-sensitive adhesive performance

Pressure-sensitive adhesives (PSAs), which achieve instantaneous adhesion with the application of light pressure, are used in a large range of commodity applications. In this work, PSAs enriched with cellulose nanocrystals (CNCs) and stabilized with a reactive surfactant (Hitenol AR-1025, AR) were synthesized via in situ emulsion polymerization. Incorporation of CNCs into AR-stabilized PSAs lead to improvements of peel strength, shear strength, and loop tack with significant increases observed at a CNC concentration of 0.75 parts per hundred monomer (phm). A comparative investigation of PSAs stabilized with reactive (AR) and non-reactive (sodium dodecyl sulfate) surfactant revealed that the enhanced performance can be attributed to the synergistic combination of CNCs and reactive surfactant, as only modest improvements can be attributed to surfactant type. In contrast to previous studies that report a trade-off in adhesive properties, we present a well-rounded PSA with exceptional peel strength, shear strength, and loop tack.