高压水射流除垢机理研究

本文根据流体力学的基本方程－积分形式的能量方程、连续性方程和动量方程，推导出高压水射流作用在管壁污垢上的应力计算公式，从理论上分析了高压水射流除垢机理，提出了根据不同管垢的耐压强度极限应力设计喷嘴结构及射流压力选择的理论方法，对现场应用具有重要指导意义，本文所述理论方法及计算公式未见有公开文献报道。     

Response of promiscuously nodulating soybean to N and P fertilization andBradyrhizobium inoculation in a ferruginous tropical soil (Haplustalf)

Field trials were conducted at Samaru, Nigeria over a three-year period (1986–88) to study the effects of N and P fertilization on the response of promiscuously nodulating soybean toBradyrhizobium japonicum inoculation in a ferruginous tropical soil. Phosphorus fertilization enhanced nodulation, while N fertilization had no consistent effect on nodulation. Both N and P increased dry matter production. Seed yields were not influenced by the application of N. However, P increased seed yields in two out of three years. Response of seed yield to P fertilization was significant up to 26.4 kg P ha^–1.Bradyrhizobium inoculation consistently enhanced nodulation while it increased seed yield in only one out of three years. Results demonstrate that P is an important nutrient for soybean production in ferruginous tropical soils. The roles of promiscuously nodulating soybean in the maintenance of tropical soil fertility are discussed.     

The roles of nitrogen,phosphorus and Potassium in the production of sugarcane in South Africa

The amounts of N and K fertilizers used in the South African sugar industry have increased dramatically in the past four decades, due partly to an increase in the area under sugarcane but also to large increases in the amounts of N and K fertilizers applied per hectare. There has also been an increase in the amount of P fertilizer used but this has been more gradual. The main fertilizer carriers for cane and their relative efficiency are discussed. During this period there has been considerable research into the nutrient requirements of sugarcane. Correlations established between soil and leaf analysis and crop responses to N, P and K fertilizers, and their effects on cane quality, are reviewed. While fertilizer recommendations based on soil and leaf analysis have provided a useful guide for determining the nutrient requirements of cane, they are continually being modified in the light of current research.     

Liquid-Phase Transport During Removal of Organic Binders in Injection-Molded Ceramics

A method has been developed for calculating hydraulic pressures induced by thermal expansion of liquid binders early in the removal cycle, when evaporative losses are negligible and fully saturated conditions prevail. Specific results were obtained for flat compacts containing a common wax binder, mixed with varying amounts of low-density polyethylne. In general, these results show how the risk of hydraulic fracture increases with heating rate and compact thickness. Although pressures are minimal when the binder consists entirely of wax, the continual addition of polyethylene eventually gives rise to unacceptable risk levels, even for relatively thin compacts. Binder removal at elevated temperatures is considered subsequently. In this case, vapor pressures eventually approach a critical level, thereby allowing mass removal by evaporation to overcome the effect of thermal expansion in maintaining full saturation. With the onset of void formation, the developing capillary pressure supersedes hydraulic pressure as the driving force in liquid transport. Besides representing capillary flow, the present formulation also accounts for thermal degradation of the binder during removal. The resulting system of equations was solved numerically for a variety of representative debinding conditions. Predictions for flat compact containing a balanced wax/polyethylene binder indicate that thermal degradation of the polyethylene can give rise to a marked improvement in debinding rates. It turns out, however, that this enhancement is far more effective in thinner compacts.     

微波消解ICP-AES法测定高碳铬铁中铬锰磷

用微波消解法,配合电感耦合等离子体原子发射光谱技术,选择适宜的工作条件,建立定量测定高碳铬铁中铬、锰、磷的方法。结果表明,此法快速、准确,回收率在90.9%~101.2%之间,相对标准偏差不大于2.84%。     

微通道板双面抛光过程材料去除特性研究

材料去除率是表征双面抛光加工效率的重要参数,也是影响工件表面质量的关键因素。基于双面抛光加工中工件运动过程的分析,通过向量法构建了工件上任一点的运动轨迹及其相对速度的数学模型。运用Preston模型,建立双面抛光过程中材料去除特性方程,并辅助计算机软件模拟了不同工艺条件下的材料去除特性。最后,通过微通道板的双面抛光实验,研究了不同工艺参数下的材料去除量,验证了理论模拟的正确性。     

深小孔脉冲电解加工精度控制研究

为了实现电解加工深小孔的精度控制,建立线性去除率动态数学模型,分析影响动态方程的工艺参数,通过在镍基合金上进行电解加工深小孔试验,分析了脉冲宽度、工具电极进给速度、工具电极绝缘层有无裸露对深小孔加工精度的影响。结果表明：采用较大的脉冲宽度、较大的工具电极进给速度、绝缘层覆盖全部工具电极,有利于提高孔的加工精度。     

部分子孔径缺光对夏克-哈特曼波前传感器波前复原的影响

对比研究缺光子孔径斜率置零复原法和缺光子孔径去除复原法的波前复原误差。首先研究了单子孔径缺光的情况,分析表明:缺光子孔径斜率置零法的波前复原误差呈现随子孔径中心相对全口径中心的半径的增大而增大的规律,即孔径中心部分的缺光子孔径的复原误差小,孔径边沿缺光子孔径的复原误差大;而缺光子孔径去除法的波前复原误差在孔径上分布比较均匀并且较小。缺光的子孔径数目增加后,波前复原误差也随之增加。对比研究了多子孔径缺光的情况,结果表明缺光子孔径去除复原法虽然计算量大,但波前复原误差要小得多。     

Dual-Antenna RF CMOS Front-End for Interferer Removal in Ultra-Wideband Systems

Many ultra-wideband (UWB) systems are challenged by strong jammers and narrowband interferers. Using two antennas, we demonstrate a robust UWB radio frequency (RF) front-end design in a 0.25 μm mixed-signal complementary metal oxide semiconductor (CMOS) technology. The proposed realization is capable of adaptively removing a high-power, narrowband interferer early in the receiver chain avoiding front-end saturation and preserving UWB signal power. The early interferer removal resulting in interferer-free demodulation is based on the least mean squares (LMS) algorithm and achieved through a novel combiner low-noise amplifier and noise optimized filtering. Circuit level RF simulations of the proposed circuitry indicate a maximum improvement in signal-to-interference ratio of 39.6 dB.     

Creating an Air‐Stable Sulfur‐Doped Black Phosphorus‐TiO2 Composite as High‐Performance Anode Material for Sodium‐Ion Storage

With the increasing demand for low cost, long lifetime, high energy density storage systems, an extensive amount of effort has recently been focused on the development of sodium‐ion batteries (SIBs), and a variety of cathode materials have been discovered. However, looking for the most suitable anode material for practical application is a major challenge for SIBs. Herein, a high capacity sulfur‐doped black phosphorus‐TiO₂ (TiO₂‐BP‐S) anode material for SIBs is first synthesized by a feasible and large‐scale high‐energy ball‐milling approach, and its stability in air exposure is investigated through X‐ray photoelectron spectroscopy. The morphology of TiO₂‐BP‐S is characterized using transmission electron microscopy, indicating that the TiO₂ nanoparticles produce P? Ti bonds with BP. The TiO₂‐BP‐S composite with P? S and P? Ti bonds exhibits excellent stability in air and the superior electrochemical performance. For example, the discharge specific capacity is up to 490 mA h g^?1 after 100 cycles at 50 mA g^?1, and it remains at 290 mA h g^?1 after 600 cycles at 500 mA g^?1. Meanwhile, the scientific insight that the formation of stable P? S and P? Ti bonds can provide a guide for the practical large‐scale application of SIBs in other titanium base and black phosphorus materials is looked forward.