Eco-friendly tape casting of borosilicate glass/Al2O3 sheets for LTCC applications

This work reports the innovative development of a borosilicate glass/Al₂O₃ tape for LTCC applications using an eco-friendly aqueous tape casting slurry. Polyvinylpyrrolidone (PVP) and polyacrylic acid (PAA) were the respective dispersants, while carboxymethyl cellulose (CMC) and styrene acrylic emulsion (SA) were the respective binders. The results showed that PVP was more suitable than PAA as the dispersant for the aqueous casting slurry, and that 1.5 wt% PVP would achieve well dispersion of CABS glass/Al₂O₃ powder in the aqueous slurry. Moreover, a small amount of 2.0 wt% CMC binder could yield smooth CABS glass/Al₂O₃ tapes crack free. A high-quality CABS glass/Al₂O₃ tape with a smooth surface was made from an aqueous slurry containing 1.5 wt% PVP dispersant, 2.0 wt% CMC binder, and 2.0 wt% PEG-400 plasticizer. The density, tensile strength, and surface roughness of the green tape were 2.05 g/cm³, 0.87 MPa, and 148 nm, respectively. The resulting CABS glass/Al₂O₃ composites sintered at 875 °C exhibited a bulk density of 3.14 g/cm³, a dielectric constant of 8.09, a dielectric loss of 1.0 × 10^?3, a flexural strength of 213 MPa, a thermal expansion coefficient of 5.30 ppm/^°C, and a thermal conductivity of 3.2 W m^?1 K^?1, thus demonstrating its broad prospects in LTCC applications.     

Evaluation of turbulent forced convection of non-Newtonian aqueous solution of CMC/CuO nanofluid in a tube with twisted tape inserts

The present paper investigates the turbulent flow and heat transfer of non-Newtonian aqueous solution of Carboxymethyl cellulose (CMC) and CuO nanoparticles in a plain tube and also tube with twisted tape inserts. The aqueous solution of CMC and CuO/CMC nanofluid show a shear-thinning (pseudo-plastic) rheological behavior, resulting in a higher viscosity than that of water. The consistency index and the power law index are evaluated based on available experimental data. The single phase approach with temperature dependent thermo-physical properties is applied to simulate the nanofluid flow and heat transfer. Simulation results are presented at different nanoparticle concentrations and twisted tape ratios. Only an axial flow is identified in the plain tube whereas both axial and swirl flows are detected in the tube with twisted tape inserts. The turbulence kinetic energy in the tube with twisted tapes is significantly higher than that in the plain one, which is useful for non-Newtonian fluid with higher viscosity. Also, the temperature fields in the tube with twisted tapes are disturbed relative to those in the plain one, due to stronger turbulence intensity and better fluid mixing. Higher amounts of nanoparticles concentration and lower twist ratios, giving maximum values of total efficiency, display the advantage of using non-Newtonian nanofluid in the tube with twisted tape inserts rather than non-Newtonian base fluid in the plain one.     

Analysis of the flow field,thermal performance,and heat transfer augmentation in circular tube using different dimple geometrical configurations with internal twisted-tape insert

In this study, a numerical investigation for the fluid flow field analysis using different configuration dimple parameters in conjunction with an internal type insert in pipe is carried out. The effects of the dimple diameters with a center twisted tape on the flow pattern, pressure drop, friction factor, and heat transfer characteristics are investigated. The influence of the latter device on heat performance and thermal-hydraulic performance evaluation factor (PEF) were carried out in a pipe for fully developed flow with range for fully developed flow with range of Reynolds number (Re) of 1573 and 23 592. Experiments with numerical models are performed using different dimpled dimeters by inserting twisted tapes. The outcomes observe that the qualitative analysis for flow fields such as static pressure, dynamic pressure, velocity magnitude, wall shear stress, and turbulent kinetic energy as well as the quantities analysis for pressure drop, heat transfer coefficient friction factor, and Nu number in dimpled pipe fitted with twisted tape are greater than plain pipe. This is because using these devices cause more secondary flow, swirl flow, and flow mixing that lead to higher turbulence, which, in turn, enhance the overall heat transfer. The results indicated that the lower and higher values of thermal PEF are about 0.78 and 1.6, respectively, at the dimple dimmers of 1 mm.     

5ESS-2000型电话交换机计费磁带的制作

介绍了5ESS-2000型电话交换机的计费方式、计费磁带的制作方法及其相关注意事项。     

应用“三小”技术及中深孔爆破技术实现岩巷快速掘进

在岩巷掘进施工中,通过使用“三小”和“中深孔爆破”技术,峻德煤矿在2002年创造出了4个百米掘进队,而且成本材料均有所降低,效益可观,此项技术工艺值得进一步推广。     

皮带轮的结构设计

从力学的角度解释了皮带轮中部凸起的原因 ,着重分析了高速皮带轮中部凸起的各种形式和具体的凸起数值 ,从而完善了皮带轮的结构设计 ,为皮带轮在实际中的应用奠定了理论基础。     

煤矿主提升胶带输送机改造技术

主要介绍了东峡煤矿主提升胶带输送机的改造依据及设计构思、实施过程以及解决的技术关键.主提升胶带输送机在不增加带强、带宽的基础上,保证皮带机运行的安全系数的前提下,增加了皮带机总功率,提高了带速,增加了运输能力,达到了预期目标.     

一起带式输送机输送带跑偏事故分析及对策

对刚换上一条防撕裂新带式输送机在试运行时,由于输送带浮在面上无法落槽而产生忽左忽右的跑偏进行分析,指出了托辊对输送带运行所产生的摩擦力,在输送带运行中起到平衡作用以及不落槽所采取的解决办法。     

丁基橡胶防水密封胶粘带发展现状及标准化

介绍了丁基橡胶防水密封胶粘带的产品特点、国内外产品的发展状况和标准化情况，概述了丁基橡胶防水密封胶粘带行业标准的要点和有关技术问题。     

一种混凝土养护的新技术

介绍一种新兴的混凝土养护技术,并通过比较传统的混凝土包覆洒水、养护剂养护等方法,显示出该新技术在提高混凝土抗压强度、改善混凝土外观和表面密实度、降低表面孔隙率和透水率等方面的特点,说明该技术不但好于已有养护剂养护的效果,更比传统的包覆洒水养护方法,节水环保、省人工维护,提高效率。