Suspension and Mixing Characterization of Intermittent Agitation Modes in DASGIP Bioreactors

Intermittent agitation strategies have been increasingly used for a range of process development applications, i.e., to modulate physical cues, to improve stem cell differentiation yields, and to control hydrodynamic shear stresses in microcarrier suspension; however, there is a distinct lack of characterization. Both continuous and intermittent agitation modes in relation to suspension and mixing dynamics within a DASGIP bioreactor were characterized. Suspension dynamics were found to be affected by microcarrier porosity and the degree of settling was found to be more pronounced at the top of the bioreactor. Mixing time characterization showed a marked improvement in mixing efficiency for intermittent agitation, with an overall dependence on the timing of tracer insertion.     

Suspension stability and sintering influence on yttria-stabilized zirconia fabricated by colloidal processing

The stability of nano-zirconia 3YSZ powder in suspension was extensively studied by the colloidal method, and the optimum sintering temperature of the green sample fabricated through slip casting was determined. Zirconia suspensions with 10 vol% powder loading were prepared with distilled water, and HNO₃ was used to adjust the pH of the suspension to pH 1–6. All of the suspensions were subjected to sedimentation test, and the results showed that the suspensions adjusted to pH 2 had the lowest sediment volume. This finding indicates that a suspension with pH 2 produces higher packing density. Viscosity test was carried out for the suspensions added with dispersant ranging from 0.3 wt% to 0.7 wt% polyethyleneimine (PEI) with and without pH adjustment. The suspension containing 0.5 wt% PEI with pH 2 adjustment produced the lowest viscosity because of interparticle bond breakage in the aggregates, thus forming colloidally stable suspensions. The zirconia suspension containing 0.5 wt% PEI and whose pH was adjusted to pH 2 was chosen to be slip casted into cylindrical shape. Green samples were sintered at various sintering temperatures that ranged from 1100 °C to 1500 °C through a two-step sintering method. The sample sintered at 1500 °C was found to be porosite-free, and its highest relative density was 99.6% of the theoretical density. Morphological studies detected pores in the microstructure of the samples sintered at low sintering temperatures (1100 and 1200 °C). By contrast, the samples sintered at 1400 and 1500 °C were fully densified. However, the grain size of the sample sintered at 1500 °C was 230 nm, which indicated excessive grain growth. The Vickers hardness of the sample sintered at 1400 °C was found to be highest (12.9 GPa) and comparable to results found in the literature.     

Convective mass exchange between flows in a valve-pulsatory apparatus with permeable partition

A mathematical model of convective mass exchange between flows in a valve-pulsatory apparatus with permeable partition is proposed. The mass exchange between flows of aqueous Na₂CO₃ solution and distilled water, or pearlite suspension in water and aqueous solution of NaCl was studied on a pilot apparatus.     

麦尔兹石灰窑悬挂缸耐火材料的技术改进

从结构和原材料分析华塑公司3座麦尔兹石灰窑悬挂缸浇注料脱落的原因,提出了技术改进方案,介绍了具体处理措施及改进后的效果。     

无轴承异步电机逆变器设计及试验研究

阐述了无轴承异步电机基本工作原理,并根据其悬浮和控制要求设计了硬件控制系统,给出了硬件电路图,通过实验得到试验波形。实验表明设计的硬件电路可以作为无轴承电机驱动的通用逆变器电路,且性能可靠。基于本硬件电路,通过DSP软件调节PID参数可实现无轴承异步电机的悬浮及旋转。     

气－固悬浮体两相流流体力学描述

根据两相流体力学的基本原理，提出了描述悬浮体两相流过程的数学模型。通过对装置上内径为φ１０８ｍｍ。管高３９５ｍｍ的垂直管轴向压降。气体、固体颗粒速度的测定及比较计算值与实测值的误差，修正粒群的阻力系数后得出的结果，说明模拟公式能满足工程应用的要求。并讨论了参数的影响。关键词     

Review of suspension and solution precursor plasma sprayed thermal barrier coatings

As one of the promising methods that can be employed to fabricate high-performance thermal barrier coatings (TBCs), suspension plasma spraying (SPS) or solution precursor plasma spraying (SPPS) has received significant attention in academic research. Enhanced performances have been shown in the SPS-/SPPS-coatings due to their special microstructures, such as uniformly distributed micro-pores, vertical cracks or columnar structures. Since there are more complexities than conventional plasma spraying methods, many works have been devoted to study the mechanism and properties of SPS-/SPPS-coatings during the past decades. In this work, the latest development of SPS or SPPS is reviewed in order to discuss some key issues in terms of preparation of suspension or solution precursor, injection mode of liquid phase, interaction between liquid and plasma jet, microstructure of as-sprayed coatings and corresponding deposition mechanism. Meanwhile, the potential application of SPS or SPPS in some new-type TBCs is introduced at the end of this paper.     

基于SIMULINK的物料悬浮速度仿真研究

SIMULINK是MATLAB重要的组件之一，它为模拟动态系统提供了交互式程序，允许用户在屏幕上绘制框图来模拟系统。并能够动态地控制该系统。本文基于上述软件工具，设计一个模糊逻辑控制器，并应用于球形物料悬浮速度的仿真计算。从建立系统的仿真模型到仿真结果的图形化处理变得非常简单、直观和方便。     

Design of suspension and swing arm for improved shock resistance in the micro optical disk drives

One of the trends on information storage device is focused on the development of micro optical disk with optical flying head (OFH). The OFH in the small form factor ODD consists of optical slider, suspension, swing arm, and so on. In order for a slider with OFH to be successfully implemented in the system, the shock performance of the head-gimbal assembly should be guaranteed for mobile applications. We design development model of suspension and swing arm for improved shock resistance using topology optimization and shape optimization. The objective of the suspension design is to decrease the equivalent mass with increasing first torsional frequency. The objective of the swing arm design is mass reduction for reducing power consumption and fast access time. In this paper, we suggest a design method for the improvement of the dynamic performance of suspension and swing arm for the OFH considering shock characteristics.     

316L不锈钢粉末的凝胶注模成形

本文对316L不锈钢粉的凝胶注模成形工艺进行了研究,分析了影响浆料流变性和凝胶化时间的因素,以及单体含量对固化胶体性状的影响.结果表明:加入聚丙烯酰胺作为分散剂可以显著降低浆料的黏度,使不锈钢粉体的固相体积分数达到54%,满足注凝成形的要求;单体的浓度对固化胶体的性质有很大的影响;引发剂和催化剂的加入量越大,聚合诱导期越短.在最佳形成工艺条件下,凝胶注模成形出的不锈钢坯体性能优良,组织均匀,生坯的抗弯强度可达38MPa,烧结体的相对密度达95%,屈服强度可达160MPa,并可成形出形状复杂的较大尺寸的不锈钢坯体.