珍珠镀镍的电镀工艺参数优化

通过正交试验确定了珍珠镀镍的最佳工艺条件,制备出了效果优良的珍珠镍镀层,提高了镀层的珠光外观和耐腐蚀性．通过金相显微镜照片和电化学技术表征（交流阻抗技术和Tafel曲线测试）对单层珍珠镀镍、单层光亮镀镍和双层珍珠镀镍（光亮镍上施镀珍珠镍）的性能进行了对比．结果表明：双层珍珠镀镍更加均匀致密;单层珍珠镍的耐腐蚀性优于双层珍珠镀镍;双层珍珠镀镍的耐腐蚀性优于单层光亮镀镍．     

The experimental investigation of a pulse tube refrigerator with a ‘L’ type pulse tube and two orifice valves

In order to simplify the structure of the cold end of the pulse tube refrigerator (PTR) and have a better utilization of the cold energy of the system, a single stage four-valve pulse tube refrigerator (FVPTR) with a ‘L’ type pulse tube structure and two orifice valves at the hot end of pulse tube has been constructed. Verification experiments show that a two-orifice valve structure gives different adjustments to the gas flow rate of the hot end of the pulse tube than that of the one-orifice valve structure, a lowest temperature of 72 K was obtained at a frequency of 2.5 Hz under a system average pressure of 1.6 MPa with 200 mesh bronze screens as regenerator material, 20 mesh copper screens as stuffing material of heat exchanger. Due to the difficulty in manufacturing the thin ‘L’ type pulse tube, the wall thickness of the pulse tube in the experiment is relatively bigger than that of the ordinary pulse tube, which resulted in relatively big system loss and affected the minimum temperature of the system to a certain degree.     

Band diagram for low-k/Cu interconnects: The starting point for understanding back-end-of-line (BEOL) electrical reliability

The starting point for describing the electrostatic operation of any semiconductor device begins with a band diagram illustrating changes in the semiconductor Fermi level and the alignment of the valence and conduction bands with other interfacing semiconductors, insulating dielectrics and metal contacts. Such diagrams are essential for understanding the behavior and reliability of any semiconductor device. For metal interconnects, the band alignment between the metal conductor and the insulating intermetal and interlayer dielectric (ILD) is equally important. However, relatively few investigations have been made. In this regard, we have investigated the band alignment at the most common interfaces present in traditional single and dual damascene low-k/Cu interconnect structures. We specifically report combined X-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy (REELS) measurements of the Schottky barrier present at the ILD and dielectric Cu capping layer (CCL) interfaces with the Ta(N) via/trench Cu diffusion barrier. We also report similar measurements of the valence and conduction band offsets present at the interface between a-SiN(C):H dielectric CCLs and low-k a-SiOC:H ILDs (porous and non-porous). The combined results point to metal interfaces with the CCL having the lowest interfacial barrier for electron transport. As trap and defect states in low-k dielectrics are also important to understanding low-k/Cu interconnect reliability, we additionally present combined electron paramagnetic resonance (EPR) and electrically detected magnetic resonance (EDMR) measurements to determine the chemical identity and energy level of some electrically active trap/defect states in low-k dielectrics. Combined with the photoemission derived band diagrams, the EPR/EDMR measurements point to mid-gap carbon and silicon dangling bond defects in the low-k ILD and CCL, respectively, playing a role in electronic transport in these materials. We show that in many cases the combined band and defect state diagrams can explain and predict some of the observed reliability issues reported for low-k/Cu interconnects.     

Cooling rate effects on the microstructure evolution in the βo zones of cast Ti–45Al–8.5Nb–(W,B, Y) alloy

The cooling rate effects on the β_o → ω_o phase transformation in Ti–45Al–8.5Nb–(W, B, Y) (at.%) alloy were investigated by annealing the alloy at 950 °C followed by different cooling methods. The morphology and the distribution of the ω-related phases were analyzed by TEM. The amount and morphology of the ω-related phases are very sensitive to the cooling rate. The ω-related phases could not be resolved in the water-quenched sample whereas it grew into nano-particles in the air-cooled sample. In the furnace-cooled sample, the ω_o phase with B8₂ structure grew into micron-sized particles and occupied the whole β_o area. The nucleation of the ordered ω embryos can be explained by the well accepted displacive mechanism because of the instability of the β_o(B2) structure, accompanied by a short-range diffusion process between neighboring {111}_βo planes. However, the growth of the ω-related phases is controlled by a long-range diffusion process. Due to ready nucleation and growth, the ordered ω formation is bound to occur in as-cast and heat-treated high Nb–TiAl alloys.     

Fuel choices in rural Maharashtra

We report on and analyze the results of an energy use survey in two tribal villages in rural Maharashtra, India. Though there is significant heterogeneity between the effects of the variables in the two villages there are some robust results. We find modest evidence for the ‘energy ladder’ hypothesis and that use of higher quality energy sources reduces total energy use, ceteris paribus. Income elasticities of fuel use are small. Additionally, we demonstrate that household size, stove ownership, and season influence energy choices. However, the effects of improved stoves are small and not consistent across the villages.     

Sensory characterisation of food and beverage stimuli containing β-ionone and differences between individuals by genotype for rs6591536

The aroma compound β-ionone is present in many fruits and vegetables and their derived products. Odour profiles at different β-ionone concentrations and perceived contributions of β-ionone to food/beverage flavour have only been partially established, and they generally do not extend to differences among individuals who vary in their sensitivity to the odour. Recent research has identified rs6591536, a single nucleotide polymorphism (SNP) located in the coding region of the odorant receptor OR5A1 as responsible for major differences in ability to detect β-ionone odour. In Study 1, using trained sensory panellists (n = 12), odour profiles were obtained for a range of β-ionone concentrations and compared across sensitivity groups defined by genotypes for rs5691536 (GG/AG or AA). A similar comparative approach was used in Studies 2 and 3, where participants (n = 104 and 158) characterised food/beverage stimuli containing added β-ionone using check-all-that-apply questions. The concentration of β-ionone required to elicit perception of the ‘floral’, ‘rose/violet’ and ‘aromatic/fragrant’ characteristics typically associated with β-ionone depended on the background fruit flavour (apple, raspberry, orange) and/or the product type (juice, jelly). It also differed among people classified as more sensitive (“sensitive”) and more insensitive (“insensitive”) to the odour of β-ionone. Perception of negative aspects of β-ionone (incl. ‘sour, acid, vinegar’, ‘sharp, pungent’, ‘soap’, ‘chemical’, ‘artificial’, ‘aftertaste’, ‘woody’) was encountered in all studies, but with varying frequency depending on concentration of added β-ionone and whether participants were “sensitive” or “insensitive” to β-ionone. There was some evidence in Study 3 that perception of β-ionone flavour was masked by the fruity flavours of the test products and that changes in ‘sweet’ and ‘fruity’ were associated with β-ionone spike concentration. Overall, this research suggests a need to consider genotype-encoded sensitivity together with other variables when measuring human flavour perception.     

Design of Ag nanograting for broadband absorption enhancement in amorphous silicon thin film solar cells

Light trapping is one of the key issues to improve the light absorption and increase the efficiency of thin film solar cells. The effects of the triangular Ag nanograting on the absorption of amorphous silicon solar cells were investigated by a numerical simulation based on the finite element method. The light absorption under different angle and area of the grating has been calculated. Furthermore, the light absorption with different incident angle has been calculated. The optimization results show that the absorption of the solar cell with triangular Ag nanograting structure and anti-reflection film is enhanced up to 96% under AM1.5 illumination in the 300–800 nm wavelength range compared with the reference cell. The physical mechanisms of absorption enhancement in different wavelength range have been discussed. Furthermore, the solar cell with the Ag nanograting is much less sensitive to the angle of incident light. These results are promising for the design of amorphous silicon thin film solar cells with enhanced performance.     

钢管地聚物混凝土柱轴向重复受压性能试验研究

为探究钢管地聚物混凝土柱轴向重复受压性能，制作了4根钢管地聚物混凝土中长柱和8根钢管地聚物混凝土短柱，对其进行了轴向重复受压试验，观察结构的行为表现及破坏模式，分析其荷载 位移曲线、骨架曲线、特征荷载与位移、延性、刚度退化曲线、荷载 残余位移曲线、耗能等内容。结果表明：钢管地聚物混凝土中长柱破坏模式为典型的弹塑性破坏，而短柱则为材料破坏；长径比不同，试件的荷载 位移曲线变化趋势略有不同，但其刚度退化曲线变化规律类似；地聚物混凝土强度、外套钢管壁厚、长径比，对试件的承载能力、平均压缩力和耗能能力影响显著。研究结果表明钢管地聚物混凝土承载能力良好，为其试验研究和工程应用提供了参考。     

Prototype,control system architecture and controlling of the hexapod legs with nonlinear stick-slip vibrations

The paper introduces the constructed prototype of the hexapod robot designed based on the biomechanics of insects for inspection and operation applications as well as for different research investigations related to the walking robots. A detailed discussion on the design and realization of mechanical construction, electronic control system and devices installed on the robot body are presented. Moreover, the control problem of the robot legs is studied in detail. In order to find the relationship between movements commonly used by insects legs and stable trajectories of mechanical systems, first we analyze different previous papers and leg movements of real insects. Next, we are focus on the control the robot leg with several oscillators working as a so-called Central Pattern Generator (CPG) and we propose other model of CPG based on the oscillator describing stick-slip induced vibrations. Some advantages of the proposed model are presented and compared with other previous applied mechanical oscillators with help of numerical simulations performed for both single robot leg and the whole robot. In order to confirm the mentioned numerical simulations, the conducted real experiments are described and some interesting results are reported. Both numerical and experimental results indicate some analogies between the characteristics of the simulated walking robot and animals met in nature as well as the benefits of the proposed stick-slip vibrations as a CPG are outlined. Our research work has been preceded by a biological inspiration, scientific literature review devoted to the six-legged insects met in nature as well as various prototypes and methods of control hexapod robots which can be found in engineering applications.     

Effect of thermal stresses on the microstructure of the continuous cooling TiAl alloys

A series of continuous cooling tests were performed on TiAl alloys using a Gleeble3500 machine to investigate the effect of thermal stresses on the microstructure. The results show that macroscopic thermal stresses promote correlated nucleation of γ lamellae. The trend of the dominance of one twin-group γ variants in local regions is weakened, and the γ/γ interfaces tend to be true twin and pseudotwin boundaries rather than 120° rotational faults under macroscopic thermal stresses. Meanwhile, thermal-induced deformation generated under the effect of both microscopic and macroscopic thermal stresses results in numerous low angle grain boundaries (LAGBs) and dislocations. The LAGBs and dislocations distribute heterogeneously among lamellar colonies and phases. No mechanical twins are observed due to the low strain and low strain rate characteristics of the thermal-induced deformation. These findings could shed light on understanding and preventing the cracking of TiAl components during cooling process.