Water droplet spreading and recoiling upon contact with thick-compact maltodextrin agglomerates

BACKGROUND: The food and pharmaceutical industries handle a number of compounds in the form of agglomerates which must be put into contact with water for rehydration purposes. In this work, liquid‐solid interaction between water and maltodextrin thick–compact agglomerates was studied at different constituent particle sizes for two compression forces (75 and 225 MPa). RESULTS: Rapid droplet spreading was observed which was similar in radius to the expected one for ideal, flat surfaces. Contact angle determinations reported oscillations of this parameter throughout the experiments, being indicative of droplet recoiling on top of the agglomerate. Recoiling was more frequent in samples obtained at 225 MPa for agglomerate formation. Agglomerates obtained at 75 MPa exhibited more penetration of the water. Competition between dissolution of maltodextrin and penetration of the water was, probably, the main mechanism involved in droplet recoiling. Micrographs of the wetting marks were characterized by means of image analysis and the measurements suggested more symmetry of the wetting mark at higher compression force. CONCLUSION: Differences found in the evaluated parameters for agglomerates were mainly due to compaction force used. No significant effect of particle size in recoiling, penetration of water into the agglomerate, surface texture and symmetry was observed. Copyright © 2011 Society of Chemical Industry     

紧密纺与普通环锭纺纱线性能的对比研究

通过实验，比较了紧密纺纱线与普通环锭纺纱线的性能。紧密纺纱线能在采用较低捻度的条件下显著减少3mm以上的毛羽数，一些柔软度要求较高的产品则不宜采用紧密纺的纱线。     

曲线牵伸上销对紧密纺成纱条干影响的探讨

细纱机后区牵伸形式影响成纱条干.对现有的细纱机后区牵伸形式进行分析,介绍了曲线牵伸上销对后区牵伸形式的影响,并对普通紧密纱和曲线牵伸上销纱线进行了测试,结果表明曲线牵伸上销对14.6tex和9.8 tex的紧密纺成纱条干改善明显,但7.3tex的紧密纺成纱条干恶化.     

紧凑型接地极用均流电阻器的研制及应用

大功率均流电阻器的研制对于有效提高特高压直流下紧凑型接地极的性能具有重要作用.该电阻器采用具有较低正电阻温度系数的合金作为电阻材料,电阻体结构采用环绕式,整体布置采用多层框架式结构.主要基于单元电阻体并联方法和内建反馈机制实现电流扩充和阻值稳定,完成了紧凑型接地极用均流电阻器的研制和并联均流控制,并成功运用于紧凑型接地极中,运行良好,能够满足实际工程需要.均流电阻器的成功研制为紧凑型接地极的技术突破与应用奠定了坚实的基础.     

Thermo-physical characterization of binder and feedstock for single and multiphase flow of PIM 316L feedstock

A thorough knowledge of the material properties of the feedstock and binder system is essential for successful powder injection moulding (PIM) as well as for numerical simulation. In view of the above, characterization of a developed binder system and feedstock has been reported in this paper for processing of 316L stainless steel powder through PIM route. The binder system consists of paraffin wax, stearic acid and low-density polyethylene. The feedstock comprises of 316L stainless steel powder and the above binder system. The thermal, physical and rheological characteristics of the binder system and feedstock have been investigated separately along with binder removal technique from the injection-moulded green compact. The thermal characterization revealed the semi-crystalline nature having distinct melting and solidification range for both the binder and feedstock. Data from DSC and TGA show that injection of the feedstock should be carried out above 102 °C (i.e. the upper melting temperature) but below 154 °C as beyond which the binder components paraffin wax and stearic acid start degrading and mould temperature should be below 57 °C. The binder and feedstock are found as shear-thinning fluid as viscosity decreases with the increase in shear strain rate and temperature. However, the viscosity of the binder is more sensitive to shear strain rate and temperature compared to that of the feedstock.     

Research on polycrystalline diamond compact (PDC) with low residual stress prepared using nickel-based additive

Polycrystalline diamond compact (PDC) with low residual stress was synthesized using nickel-based additive (Ni₇₀Mn₂₅Co₅) as sintering solvent at high temperature/pressure (HTHP). A systematic study of the residual stress in a polycrystalline diamond (PCD) layer was performed using micro-Raman spectroscopy. The stress was measured by determining the Raman shift and was approximated as being biaxial to calculate the magnitudes of stress. Sintering process parameters such as temperature, the diamond size and content of binder additive were all found to affect residual stress levels. The sample with low stress measured on the surface of PCD is compressive and has an average value of 0.10 GPa. Scanning electron microscopy (SEM) analysis of morphology shows that the dense microstructure with diamond-diamond (D-D) direct bonding has formed in the PCD layer. X-ray diffraction (XRD) performed in the cross-section of PCD confirmed the presence of diamond, nickel-based alloy, WC and Co_xW_xC.     

界面结构对PDC抗冲击性能的影响

本文采用重陀倾斜式方法测试了不同界面结构的PDC的抗冲击韧性,并对PDC冲击破坏机理进行了讨论,对界面结构以及其它因素对PDC抗冲击性能的影响进行了探讨和研究.结果表明:重陀倾斜式方法能够较好地反应PDC钻头工作时的实际受力情况;在同一工艺参数下,PDC层与硬质合金基体之间的界面结构对PDC的抗冲击性能影响很大;随着界...     

高温高压下新型金刚石/碳化硅热沉材料的热导率研究

本文针对国内外对高导热、低热膨胀系数的热沉材料需求,以金刚石为基体、硅粉为添加物,用国产六面顶压机在5.1 GPa,1 350～1 650℃的条件下,采用高压固液渗透法合成出金刚石/碳化硅陶瓷热沉材料,并对高压烧结体的相组成、密度与热导率进行了分析.研究结果表明:初始材料中硅含量、烧结时间与温度对烧结体的成分以及密度有...     

基于液压转角伺服的液压关节研究

针对液压机器人关节研究中存在关节径向尺寸过大,运动范围偏小,控制精度有限等问题,提出了一种阀芯径向力平衡、伺服肓区小的液压转角伺服阀来解决该问题,设计了对应的液压转角伺服阀,并基于该液压转角伺服阀设计了液压关节.该液压关节尺寸小、力矩大.仿真实验结果证明该液压关节响应快,运动平稳性与稳定性好,运动精度高,带负载能力强.     

带有文丘里反向流动转向器的紧凑型气动式脉冲射流泵(英文)

A compact pneumatic pulse-jet pump with a Venturi-like reverse flow diverter,which consists of a nozzle and diffuser,is designed for lifting and transporting a hazardous fluid through a narrow mounting hole.The pumping performance for a liquid mixture or a liquid-solid mixture is examined in terms of the effects of liquid viscosity,particle mass concentration,lifting height,and compression pressure.Results reveal that the pumping performance of the compact pneumatic pulse-jet pump is controlled by jet inertia and the flow resistance of the riser tube positioned after the diffuser.The capacity of the compact pneumatic pulse-jet pump increases with compression pressure and decreases with liquid viscosity.However,even for a liquid mixture with a high viscosity of 7.38 mPa·s,a pumping capacity of 170.7 L·h-1 was observed.For a liquid mixture,two dimensionless indices of performance were found to be the ratio of Euler numbers Euout/EuDV and the suction factor q.As the liquid-solid mixture was lifted to elevation of 6.74 m by the compact pump,the particle size distributions of the liquid-solid mixture in the tank and from the riser tube outlet were determined by a particle size analyzer and found to coincide well.