Calcium deficient hydroxyapatite by precipitation: Continuous process by vortex reactor and semi-batch synthesis

Precipitation of calcium deficient hydroxyapatite nanoparticles in an environmentally benign manner by using only dilute solutions of calcium hydroxide and phosphoric acid without pH adjustment and addition of other chemicals, and water, being the only by-product was investigated by using continuous flow Vortex Reactor (VR) and Semi-Batch Reactor (SBR). The effect of hydrodynamics by changing the Reynolds number of the jets providing residence times of 8.4 ms to 4.37 s for VR, and by changing the stirrer speed between 100 rpm (Re = 2656) and 1000 rpm (Re = 26560) for SBR, on the particle size, particle size distribution, and morphology of the particles was investigated for both systems. It has been shown that it is possible to produce pure phase hydroxyapatite nanoparticles in the desired morphology by changing production system, without resorting to additives. While VR produced rod-like particles with the crystallite size around 4 nm, SBR produced spherical particles with the crystallite size of around 5 nm.     

A facile co-solvent strategy for preparation of graphene nanoplatelet powder: An industrially viable innovative approach

We report an industrially viable promising approach to produce micrometer-sized multilayer graphene nanoplatelet powder (MGNP) in a scalable quantity via microwave-assisted exfoliation of graphite (MEG) and fragmented into MGNP through liquid-phase exfoliation in the co-solvent mixture by kitchen mixer (KM). KM allows rapid delaminating MEG into MGNP by shear force dominated exfoliation. Majority of MGNPs are with a diameter of few micrometers and thickness is in nanometers. MGNP are crystalline with very limited defects was confirmed by Raman measurements and transmission electron microscopy. This process transforms, more than 86% of graphite flakes into MGNP. This advanced approach opens a new pathway to produce MGNP in bulk quantity as it is feasible, rapid, and cost-effective.     

Non-equilibrium particle motion in the vicinity of a single blade

The motion of sand particles close to a single moving blade was investigated using Positron Emission Particle Tracking (PEPT) during the period in which the free bed surface profile was evolving to an equilibrium shape. The area affected by the blade was divided into active and inactive regions and these were analysed separately. The characteristic heart-shape of the active region in the plan view was determined. An approximately 10-particle-diameter wide velocity transition zone is found between the two regions. While the tracer particle is in the inactive region moving away from the blade, the time dependence of the axial displacement is well described by a logarithmic relationship. The probability of particle movement towards the centre of the blade was quantified using a “central tendency” index. The calculated central tendency shows maxima at each side of the blade. The separation of the two maxima, which indicates the width of the active region, increases with fill level but is independent of rotational speed.     

AMBE-1000声码器接口电路设计方法

DVSI公司的AMBE-1000声码器芯片是一款高性能的全双工、实时语音压缩编解码芯片,可以应用于卫星通信、保密通信、视频会议等领域.文中简要介绍AMBE-1000声码器的A/D-D/A接口以及信道接口的工作原理;结合实例分别给出了AMBE-1000声码器与PCM编解码器MC14LC5480的A/D-D/A接口电路、与单片机AT89C51的信道接口电路的设计方法;最后指出了电路设计中应该注意的问题.     

油气润滑系统在四切分轧制技术上的应用

本文介绍了油气润滑技术的工作原理及特点，阐述了该系统在四切分轧制技术上的应用与延伸。     

哈尔滨炼油厂MTBE装置试生产

介绍了哈尔滨炼油厂ＭＴＢＥ装置的工艺路线、新技术的应用及特点；催化剂的装填及应用情况；总结了生产过程中遇到的一系列问题及解决办法；探索了平稳生产的新徐径，以保证装置安全、平稳、长周期运行；同时对反应器操作温度、催化蒸馏塔操作压力、原料中醇烯比等因素对异丁烯转化率及ＭＴＢＥ产品的影响做了简单的总结。     

家庭智能终端系统的硬件设计与实现

随着生活水平的提高,人们对居住环境的舒适性、安全性要求不断提高。家庭自动化、智能化已经成为自动化领域的一个发展热点。本文将当前比较先进的ARM技术运用到家庭智能终端系统的开发上,设计实现了一个既适合当前家庭需要又符合今后发展方向的家庭智能终端体系结构,较好地解决了绝大多数智能家居系统所普遍存在的实时性差、安全性低等问题。     

Analysis and Optimization of Noise in Bipolar RF Harmonic Mixers

A noise analysis of bipolar harmonic mixers (BHM) used for direct-conversion receivers is presented in this paper. Analytical and simulated results for the transfer function of the mixer are presented. Simple analytical expressions describing noise contribution from all sources are derived. Estimation of flicker noise quite agrees with harmonic-balance simulation results. Based on the derived expressions, total time average noise power spectral density (PSD) at the output is compared with simulation results. For the recommended regions of operation, error is less than 20%. The overall BHM noise figure (NF) is calculated and optimized based on a simple extracted formula. Errors introduced by analysis remain within a 1.5-dB margin with respect to simulation results. The validity of analysis for high frequencies is justified. The effect of flicker noise coefficient on the overall mixer NF is compared for different available processes.     

圆筒混合机振动和粘漏料问题及解决办法

对圆筒混合机长期未得彻底解决的振动、大型零部件寿命短、筒体内壁粘料、进料漏斗堵料与漏料等问题进行了原因分析；根据宝钢烧结分厂的实践经验提出了解决办法。     

铸型尼龙改性的研究进展

铸型尼龙产品广泛地用于各种机械零件，改性后的铸型尼龙，可克服其自身的缺点，满足工业应用的要求。文章就我国近年来在铸型尼龙改性研究方面的情况及不同的改性方法做了详细的介绍。