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971.
通过对华北平原地区旱作大田作物田间灌溉方式的调查研究,发现传统的地面灌水方法存在着蒸发量大、深层渗漏多,水分利用效率低,田间灌水均匀度差等问题。为了提高旱作大田的水分利用效率,提出一种新的灌溉新技术——旱作膜袋灌,实现适时适量精细控制灌溉。通过试验研究,膜袋灌能够较好地提高大田作物的田间水分利用效率,避免沟灌、畦灌等传统地面灌水方法存在的棵间蒸发和深层渗漏,同时也能够解决滴灌、微润灌、喷灌等灌水方法易堵塞、系统复杂、田间工程量大和经济成本高等问题,对现代的高效节水农业具有重要的现实意义。 相似文献
972.
Shape memory NiTi-based thin films approximately 2 μm thick were deposited onto Si (100) substrates at room temperature by simultaneous DC magnetron sputter deposition from separate elemental Ni and Ti targets. The effect of composition on film structure, surface morphology, transformation temperature and mechanical behavior was studied using variable temperature X-ray diffraction, atomic force microscopy, electrical resistivity, and nanoindentation. The films showed the expected shape memory and superelasticity behavior corresponding to the different film compositions, comparable with bulk properties. The transformation from the low temperature martensitic phase to the high temperature parent phase takes place above room temperature in Ti-rich and near-equiatomic films, and below room temperature in Ni-rich films. Mechanical properties of films investigated at room temperature by a series of nanoindentations at mN loads (indentation depth < 200 nm) with a spherical indenter demonstrate superelasticity in Ni-rich material and martensitic deformation for Ti-rich and near-equiatomic compositions. 相似文献
973.
974.
《Journal of Adhesion Science and Technology》2013,27(12):1397-1410
This paper describes the preparation and wetting properties of two-component self-assembled monolayers (SAMs) obtained by the competitive adsorption of one short-chain (HS(CH2)10Sh) and one long-chain (HS(CH2)21Lg) alkanethiol onto gold from dilute ethanolic solutions. The four possible combinations of the tail groups CH3 and CH2OH were investigated: Sh = CH3/Lg = CH2OH, Sh = CH2OH/Lg = CH3, Sh = CH2OH/Lg = CH2OH, and Sh = CH3/Lg = CH,. The compositions of these SAMs are not the same as the compositions of the solutions from which they were formed. Although the relationship between the composition of the SAM and the composition of the solution suggests that some phase separation may be occurring within the SAM, contact angles with water and hexadecane show that significant disorder still remains in the interfacial region. 相似文献
975.
Ilaria Adamo Valeria Diella Alessandro Pavese Pietro Vignola Fernando Francescon 《Journal of the European Ceramic Society》2013,33(15-16):3387-3395
The system Na-feldspar (F) and kaolinite (K) was investigated at temperatures of interest in ceramic applications (1200–1280 °C) to study the effects of F/K ratios by weight and crystallinity degree of kaolinite on the final product, micro-structural features and mullite-glass Gibbs energy of formation (ΔGeff). Mullite and glass are the dominant phases; in general, the higher the temperature, the larger the former. An F/K increase promotes the formation of glass and secondary mullite, appearing along with the primary one. ΔGeff was modelled by α(T) × (F/K)2 + β(T) × F/K + γ(T), α, β and γ being linear functions of temperature whose coefficients were determined by fitting the ΔGeff-theoretical to the ΔGeff-obtained from the measured phase compositions. ΔGeff is less affected by temperature than by F/K, whose increase shifts equilibrium towards glass phases. The ΔGeff-curves for ordered and disordered kaolinite intersect one another at F/K ~0.5, a ratio close to that used in industrial practice. 相似文献
976.
This article presents results of an experimental study on the flow characteristics of a pilot-size screw conveyor dryer (SCD). In particular, the effects of granular solids flow rate (15.2–206 kg/h) and screw speed (10.8–28 rpm) on the residence time distribution (RTD) were studied using sand as the model material. The RTD was measured using a dynamic step change in the solids flow rate. Parameters such as solids holdup, degree of fullness, mean residence time, and uniformity of the discharge flow were studied. The solids holdup and hence the degree of fullness was found to decrease with increase in the screw speed and decrease with the solids flow rate. The mean residence time was found to decrease with an increase in the screw speed, as expected. The screw speed and the solids flow rate strongly affected the discharge uniformity. An optimum value of the degree of fullness was observed with regard to the solids flow rate. Over the operating range examined, the solids flow pattern was close to plug flow, as indicated by high values of N and Pe number. 相似文献
977.
The effect of different types of compounds commonly found in diesel fuel (e.g., paraffins, naphthenes, and aromatics), as well as their chemical structure (e.g., branched versus linear paraffins) on fuel reforming has been investigated. Diesel reforming is very complicated because diesel is a complex mixture of hundreds of compounds with greatly different reactivities. The syngas production rates at the same conditions were observed in this order: paraffins > naphthenes ? aromatics. Additionally, the type of reforming performed (OSR, CPOX, or SR) as well as the process parameters (space velocity and reaction temperature) significantly affected the syngas production rates as well as carbon formation. The reactivity of one fuel component can affect the conversion pattern of others, e.g., overall yields from the reforming of a fuel mixture are not additive of yields from individual fuel components, rather the more reactive component is consumed first. Furthermore, the type of substituent in aromatics and naphthenes, the carbon chain length in n-paraffins, branching in paraffins, and degree of aromatic saturation affect the overall hydrocarbon conversion, syngas selectivity, and carbon formation. The presence of sulfur compounds in the fuel caused significant drops in H2 yields compared to CO yields. 相似文献
978.
通过化学成分设计和生产过程控制,经过对产品性能的检验,25MnV钢各项物理检验指标均满足技术条件要求.确定了25MnV钢的炼钢工艺制度. 相似文献
979.
980.
简要介绍了WZDQ30C型真空加压气淬炉的结构及其特点,总结了在调诗过程中的一些体会,对典型软磁材料进行了真空热处理并测定了热处理后的磁性能。 相似文献