Effect of Surface Roughness and Structure Features on Tribological Properties of Electrodeposited Nanocrystalline Ni and Ni/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Coatings

Metal matrix composite coatings obtained by electrodeposition are one of the ways of improving the surfaces of materials to enhance their durability and properties required in different applications. This paper presents an analysis of the surface topography, microstructure and properties (residual stresses, microhardness, wear resistance) of Ni/Al₂O₃ nanocomposite coatings electrodeposited on steel substrates from modified Watt’s-type baths containing various concentrations of Al₂O₃ nanoparticles and a saccharin additive. The residual stresses measured in the Ni/Al₂O₃ coatings decreased with an increasing amount of the co-deposited ceramics. It was established that the addition of Al₂O₃ powder significantly improved the coatings’ microhardness. The wear mechanism changed from adhesive-abrasive to abrasive with a rising amount of Al₂O₃ particles and coating microhardness. Nanocomposite coatings also exhibited a lower coefficient of friction than that of a pure Ni-electrodeposited coating. The friction was found to depend on the surface roughness, and the smoother surfaces gave lower friction coefficients.     

Visualizing Thermally Activated Memristive Switching in Percolating Networks of Solution-Processed 2D Semiconductors

Memristive systems present a low-power alternative to silicon-based electronics for neuromorphic and in-memory computation. 2D materials have been increasingly explored for memristive applications due to their novel biomimetic functions, ultrathin geometry for ultimate scaling limits, and potential for fabricating large-area, flexible, and printed neuromorphic devices. While the switching mechanism in memristors based on single 2D nanosheets is similar to conventional oxide memristors, the switching mechanism in nanosheet composite films is complicated by the interplay of multiple physical processes and the inaccessibility of the active area in a two-terminal vertical geometry. Here, the authors report thermally activated memristors fabricated from percolating networks of diverse solution-processed 2D semiconductors including MoS₂, ReS₂, WS₂, and InSe. The mechanisms underlying threshold switching and negative differential resistance are elucidated by designing large-area lateral memristors that allow the direct observation of filament and dendrite formation using in situ spatially resolved optical, chemical, and thermal analyses. The high switching ratios (up to 10³) that are achieved at low fields (≈4 kV cm⁻¹) are explained by thermally assisted electrical discharge that preferentially occurs at the sharp edges of 2D nanosheets. Overall, this work establishes percolating networks of solution-processed 2D semiconductors as a platform for neuromorphic architectures.     

Melanocyte pigmentation stiffens murine cardiac tricuspid valve leaflet

Pigmentation of murine cardiac tricuspid valve leaflet is associated with melanocyte concentration, which affects its stiffness. Owing to its biological and viscoelastic nature, estimation of the in situ stiffness measurement becomes a challenging task. Therefore, quasi-static and nanodynamic mechanical analysis of the leaflets of the mouse tricuspid valve is performed in the current work. The mechanical properties along the leaflet vary with the degree of pigmentation. Pigmented regions of the valve leaflet that contain melanocytes displayed higher storage modulus (7–10 GPa) than non-pigmented areas (2.5–4 GPa). These results suggest that the presence of melanocytes affects the viscoelastic properties of the mouse atrioventricular valves and are important for their proper functioning in the organism.     

地下机动车道空气质量标准和设计通风量计算方法

分析了机动车排放的主要污染物,探讨了地下机动车道可借鉴应用的空气质量标准.通过分析机动车在地下车道内的运行特点,研究了地下车道的分类及不同分类下的通风量计算指标.给出了地下车道设计通风量的计算公式,通过实例论证了地下空间采用稀释污染物计算方法的必要性.     

Differences in safety belt use by race

The purpose of the study was to identify daytime differences in safety belt use by race. Safety belt use was investigated in a direct observation survey of drivers and front-outboard passengers throughout Michigan. Data were weighted to calculate statewide safety belt use rates by race. Race was assessed visually by trained observers. The study showed that motor vehicle occupants identified as Black had significantly lower safety belt use than those occupants identified as White or Other.     

Palm oil deodorizer distillate as toughening agent in polylactide packaging films

Polylactide (PLA) is the most used biodegradable and biobased food packaging polymer for rigid containers and films. However, its low ductility is a hurdle for increasing its applications in flexible food packaging. A solution is the use of additives. Palm oil deodorizer distillate (PODC) is revealed to be an excellent additive promoting PLA ductility. PODC is a by‐product of vegetable oil refining, which is available in stable quality and in sufficient amounts. Amorphous PLA/PODC blends had an elongation at break of around 130% and that of semi‐crystalline blends was still around 55% compared to the initial 5% of neat PLA. At the same time the PLA rigidity and high glass transition temperatures were kept. PODC was also a very efficient processing aid, allowing for film blow extrusion. The blends were stable in properties during six months without exudation. They complied with legal norms of Food Contact Materials (EU 10/2011) and induced no sensorial alteration of packed food. Therefore PODC is a very interesting alternative to common plasticizers for the production of flexible PLA packaging films. © 2016 Society of Chemical Industry     

Dynamics and Selectivity of N<Subscript>2</Subscript>O Formation/Reduction During Regeneration Phase of Pt-Based Catalysts

The formation of N₂O has been studied by means of isothermal lean-rich experiments at 150, 180 and 250 °C over Pt–Ba/Al₂O₃ and Pt/Al₂O₃ catalysts with H₂ and/or C₃H₆ as reductants. This allows to provide further insights on the mechanistic aspects of N₂O formation and on the influence of the storage component. Both gas phase analysis and surface species studies by operando FT-IR spectroscopy were performed. N₂O evolution is observed at both lean-to-rich (primary N₂O) and rich-to-lean (secondary N₂O) transitions. The production of both primary and secondary N₂O decreases by increasing the temperature. The presence of Ba markedly decreases secondary N₂O formation. FT-IR analysis shows the presence of adsorbed ammonia at the end of the rich phase only for Pt/Al₂O₃ catalyst. These results suggest that: (i) primary N₂O is formed when undissociated NO in the gas phase and partially reduced metal sites are present; (ii) secondary N₂O originates from reaction between adsorbed NH₃ and residual NO_x at the beginning of the lean phase. Moreover, N₂O reduction was studied performing temperature programming temperature experiments with H₂, NH₃ and C₃H₆ as reducing agents. The reduction is completely selective to nitrogen and occurs at temperature higher than 250 °C in the case of Pt–Ba/Al₂O₃ catalyst, while lower temperatures are detected for Pt/Al₂O₃ catalyst. The reactivity order of the reductants is the same for the two catalysts, being hydrogen the more efficient and propylene the less one. Having H₂ a high reactivity in the reduction of N₂O, it could react with N₂O when the regeneration front is developing. Moreover, also ammonia present downstream to the H₂ front could react with N₂O, even if the reaction with stored NO_x seems more efficient.     

Advances in speech transcription at IBM under the DARPA EARS program

This paper describes the technical and system building advances made in IBM's speech recognition technology over the course of the Defense Advanced Research Projects Agency (DARPA) Effective Affordable Reusable Speech-to-Text (EARS) program. At a technical level, these advances include the development of a new form of feature-based minimum phone error training (fMPE), the use of large-scale discriminatively trained full-covariance Gaussian models, the use of septaphone acoustic context in static decoding graphs, and improvements in basic decoding algorithms. At a system building level, the advances include a system architecture based on cross-adaptation and the incorporation of 2100 h of training data in every system component. We present results on English conversational telephony test data from the 2003 and 2004 NIST evaluations. The combination of technical advances and an order of magnitude more training data in 2004 reduced the error rate on the 2003 test set by approximately 21% relative-from 20.4% to 16.1%-over the most accurate system in the 2003 evaluation and produced the most accurate results on the 2004 test sets in every speed category.