Damage Threshold of Ni Thin Film by Terahertz Pulses

Damage in a thin nickel film irradiated by subpicosecond pulses of terahertz (THz) radiation in the range of 1–3 THz at electric-field strengths up to 20 MV/cm at the center of a focal spot is observed. The damage threshold fluence is evaluated for single-pulse experiments. The damage pattern induced by multiple THz pulses has the appearance of a complex periodic structure in the form of elongated channels of metal film discontinuity that are perpendicular to the in-plane electric field direction of THz radiation.     

The effect of TiO2 nanotube morphological engineering and ZnS quantum dots on the water splitting reaction: A theoretical and experimental study

Ordered arrays of TiO₂ nanotubes with smooth and rippled morphologies were prepared by one-step titanium oxidation in NH₄F and ethylene glycol solution. The samples were then decorated with ZnS using a microwave-assisted solvothermal method. The experiments under constant or pulsed applied voltage resulted in smooth and rippled TiO₂material morphologies, respectively. Field emission scanning electron microscopy, incident photon-to-current efficiency, linear sweep voltammetry and electrochemical impedance spectroscopy were used to investigate the structure and morphology of the TiO₂ nanotubes, along with their photoelectrochemical activity in the water splitting reaction. An envelope function was proposed to correlate the anisotropic morphologies and broad distribution of mobility due to the random nature of charge carrier transport. The smooth and rippled morphologies were evaluated using the transmission line model. First-principles quantum mechanical calculations based on the density functional theory at the B3LYP level are conducted to obtain a better understanding of optical properties of TiO₂.     

Evaluation of the minimum face clearance of a high-speed gas-lubricated bearing with Navier slip boundary conditions under random excitations

Motivated by ongoing developments in aero-engine technology, a model for a coupled gas-lubricated bearing is developed in terms of an extended dynamical system. A slip boundary condition, characterised by a slip length, is incorporated on the bearing faces which can be relevant for operation in non-ideal extreme conditions, notably where external vibrations or disturbances could destabilise the bearing. A modified Reynolds equation is formulated to model the gas flow, retaining the effects of centrifugal inertia which is increasingly important for high-speed operation, and is coupled to the structural equations; spring-mass-damper systems model the axial stator and rotor displacements. A novel model is developed corresponding to a bearing experiencing an external random force to evaluate the resulting induced displacements of the bearing components. The minimum face clearance is obtained from a mapping solver for the modified Reynolds equation and structural equations simultaneously. In the case of random excitations, the solver is combined with a Monte Carlo technique. Evaluation of the average value of the minimum gap and the probability of the gap reaching a prescribed tolerance are provided. Extensive insight is given on the effect of key bearing parameters on the corresponding bearing dynamics.     

Simplified partitioning model to simulate high pressure under-expanded jet flows impinging vertical obstacles

Various reduced-order models have been developed to quickly model high pressure underexpanded jets. One example is the two-layer partitioning model which was developed to model underexpanded jets, but it has not been evaluated for high pressure jets with obstacles in the jet flow region. This research describes an improved two-layer partitioning model based on the Abel-Noble equation of state that is applied here to model horizontal jet flows impacting a vertical obstacle with validations against high pressure gas experiments, full CFD simulations and a revised notional nozzle model based on the Abel-Noble equation of state. The improved two-layer partitioning model accurately predicts the gas concentrations on the obstacle for a 15 MPa underexpanded jet while consuming much less computational resources and time compared with the full CFD simulation.     

Hydrogen storage in Zr0.9Ti0.1(Ni0.5Cr0.5-xVx)2 Laves phase,with x = 0, 0.125, 0.25, 0.375, 0.5. A theoretical approach

Density functional calculations were performed on Zr_0.9Ti_0.1(Ni_0.5Cr_0.5-xV_x)₂ Laves Phase, with x = 0, 0.125, 0.25, 0.375 and 0.5, in order to study its H absorption capacity. Binding energy, electronic structure and bonding were analyzed for the intermetallic compound with different V content and increasing amounts of hydrogen.The optimized geometry was found in good agreement with experimental data of the C14 Laves phase. Hydrogen locates preferentially in A₂B₂ tetrahedral sites in the AB₂ matrix (A = Zr, Ti; B = Ni, Cr, V) but AB₃ and B₄sites are also stable. The volume of the intermetallic and the H binding energy increases with vanadium content. Theoretically H absorption is possible up to 4.5 H/F.U. but the strongest binding energy is achieved with 3 H/F. U.The main contribution to density of states is due to d states of all components of the structure and an H-metal bonding is observed in the range ?10 to ?4 eV.     

Fermented and malted millet products in Africa: Expedition from traditional/ethnic foods to industrial value-added products

With the prevalent food insecurity in Africa, there is a growing need to utilize the available crops to develop nutritious, affordable and palatable food for the populace. Millet is critical in this role, relative to its abundance in the continent and good nutritional composition. For ages, fermentation and malting have been traditionally used to transform millet into variety of produce. A paradigm shift has however occurred over the years, giving birth to new commercially available products. This review thus appraises and gives an overview of traditional and modern fermented and malted products. Although, millet has been diversified to several products, its major food uses are still restrained to traditional consumers and largely remains underutilized. Considering the potential embedded in this grain, it is important to explore this crop through the application of appropriate modern fermentation and malting technologies. This will ensure the availability of ready to eat (RTE) and ready to use (RTU) food products and to a large extent address the incessant food security challenges plaguing Africa.     

Development of an immunochromatographic assay for the β-adrenergic agonist feed additive zilpaterol

Zilpaterol is a β-adrenergic agonist feed additive approved in the United States to increase weight gain and improve feed efficiency of cattle. A zilpaterol immunochromatographic assay was developed as an economical and user-friendly rapid detection method for zilpaterol and validated using urine and tissue samples derived from animal studies. The assay sensitivity was 1.7–23.2 ng g^?1 or mL^?1 across a variety of feed and animal matrices and did not cross-react with clenbuterol or ractopamine. No sample pre-treatment of cattle and sheep urine was needed, but horse urine and feed required dilution; skeletal muscle required solvent extraction prior to testing. Of 32 incurred sheep urine samples tested, zilpaterol content was correctly identified in all but 2 samples. Horse urine containing >10 ng mL^?1 of incurred zilpaterol residue (n = 48) was correctly identified as zilpaterol positive. The assay correctly identified 0-day withdrawal sheep muscle samples as zilpaterol positive and the control and longer withdrawal day sheep muscle samples as negative. Zilpaterol was demonstrated to be stable in horse urine when stored at ?20°C for 7 years.     

Solidification of Be-free Ni-based dental alloy

A novel, Nb- and Si-rich and Be-free Ni-based alloy was cast by two methods of investment casting and continuous casting to study the microstructure evolution during solidification and its mechanical properties. The solidification of the alloy started with the primary crystallization of FCC-γ, followed by a binary eutectic reaction, with the formation of a heterogeneous constituent: FCC-γ+G-phase, which replaced the low-melting eutectic (FCC-γ+NiBe) in the Be-bearing alloys. AlNi₆Si₃ and γ′ formed during the terminal stages of solidification by investment casting, while the formation of AlNi₆Si₃ was suppressed by continuous casting. The Scheil solidification model agreed very well with the experimental results.     

利用Sn-Ag-Ti活性焊料直接活化软焊接合Al_(0.3)CrFe _(1.5)MnNi_(0.5)高熵合金与6061铝合金（英文）

高熵合金Al_(0.3)Cr Fe_(1.5)Mn Ni_(0.5)(HEA)具有许多特殊性能。在大气环境、接合温度为250℃保持60 s的条件下,以Sn3.5Ag4Ti为活性焊料对HEA/HEA及HEA/6061-Al进行直接活性软焊接合,并对其进行显微组织及剪力强度分析。实验结果显示,在接合过程中,高熵合金中所有元素缓慢扩散进入连接区域。HEA/HEA和HEA/6061-Al样品的剪切强度分别为(14.20±1.63)和(15.70±1.35)MPa。HEA/6061-Al样品的断裂面呈显明显的半脆性断裂特征。     

Al-7Si-0.35Mg-xCu合金的品质系数和热裂敏感性（英文）

研究铜添加量(0.5%、1%、1.5%、2%、3%,质量分数)对A356合金的品质系数(Q_i)和热裂敏感性(HTS)的影响。结果显示,当铜添加量达到1.5%时,Q_i增加了约10%,这可能是由于富铜的Al_2Cu相和AlMgCuSi化合物的固溶强化和弥散硬化。然而,继续提高Cu添加量到3%,Q_i反而降低了近12%,这很可能是因为显微组织中脆性富Cu金属间化合物和微孔体积的增加导致抗拉强度和伸长率降低。用约束杆铸造法测试A356合金的热裂敏感性,结果显示随着铜含量的增加,其HTS也增加。热分析结果表明,铜拓宽了合金的凝固范围,进而降低了其流动性,增加了糊状合金暴露在热裂易感区的时间。高铜合金热裂表面的SEM也表明,其表面粗糙,且存在枝晶间/晶粒间微裂纹,这也证明了在凝固后期,合金萌生了热裂,没有足够的裂纹修复时间。