Drag coefficient of flow around a sphere: Matching asymptotically the wide trend

An empirical relationship of drag coefficient of flow around a sphere is developed for the entire range of Particle Reynolds numbers reported in the literature from Stokes regime to the condition when turbulent boundary layer prevails. The relationship is obtained using an approach to match asymptotically the wide trend of drag coefficient. The matching approach, which relies on dividing the wide trend into smaller segments that can be combined into an overall relationship, employs regression techniques and thus warrants the best-fit accuracy results. The relationship is calibrated with experimental data available in the literature covering the entire range for Reynolds numbers up to ~ 10⁶. For Reynolds values greater than 10⁶, the relationship renders a drag coefficient of 0.2. The performance of the relationship is tested and compared with other suitable models found in the literature. This relationship is also transformed into an explicit expression for settling velocity calculations.     

高速宽带取样-滤波数字化系统中高斯滤波器的设计

本文基于频域逼近的方法提出了高斯滤波器的设计理论,得出了带宽归一化的各阶高斯滤波器的通用计算公式。并对高斯滤波器的数字化时间窗口、回复时间参数等进行了计算。     

Domestic and Industrial Wastewater Treatment with Ozonated Activated Sludge

Poor sludge settleability is a problem encountered in many activated sludge wastewater treatment plants. This study was aimed at combatting the unwanted biological growths at the root of this phenomenon with ozone. Ozone dosed directly into the aeration basins of small activated sludge pilot plants treating both domestic and synthetic fuel wastewaters led to a substantial reduction of the bulking problem even at dosages as low as 6 to 10 mg/L. Ozone did not interfere in the delicate nutrient removal processes and significantly enhanced effluent quality.     

Geotechnical behavior of uranium mill tailings from Saskatchewan,Canada

This paper investigates the geotechnical behavior of uranium mill tailings from Saskatchewan, Canada.The 4% tailings were well-graded with 29% fines whereas the 5% and 6% tailings were gap-graded with 49% fines. All samples exhibited a negligible strength(0.4 k Pa) up to 60% solids, followed by a rapid increase. The 4% tailings exhibited a lower rate and amount of settlement than 5% and 6% tailings. The kidecreased from 10~(-2)to 10~(-4)m/s with a decrease in eifrom 16 to 4 and a decrease in ef from 8 to 4 such that 4% tailings showed one order of magnitude lower values than the 5% and 6%tailings. The settling potential decreased ten times(50%–5%) for 4% tailings and four times(60%–15%)for 5% and 6% tailings. The effective stress increased from 80 to 260 Pa in the settling tests. The 4%tailings were less prone to segregation when compared with 5% and 6% tailings. The average solids content after settling was 35% for 4% tailings, 40% for 5% tailings and 39% for 6% tailings with a solids content deviation of ±3%, ±8%, ±6%, respectively. All materials were essentially non-segregating at 40%initial solids.     

Improved Image Based Visual Servoing with Parallel Robot

The position regulation problem of an eye-in-hand type of parallel robot based pointing systems (PRBPS) is considered in this paper. A fuzzy logic system is first designed to compensate for the uncertainties of the parallel robot and the uncertainty of the image Jacobian, then a hybrid controller (HC) including the image-based nonlinear controller and the adaptive supervisory fuzzy logic controller (ASFLC) is derived by using the Lyapunov direct method to realize the position regulation (PR). The stability of the closed-loop system in the Lyapunov sense is proven theoretically. The fuzzy scaling matrix is combined with the HC to improve the performance of the control system. The simulation results demonstrate that the PRBPS realizes PR with very good robustness to the parameter uncertainties, and the control input torques and settling time are reduce greatly in the case of large initial feature errors.     

A 10-bit 300-MS/s asynchronous SAR ADC with strategy of optimizing settling time for capacitive DAC in 65 nm CMOS

A 10-bit 300-MS/s asynchronous SAR ADC in 65 nm CMOS is presented in this paper. To achieve low power, binary-weighed capacitive DAC is employed without any digital correction or calibration. Consequently, settling time for the capacitive DAC would be a dominant limiting factor for the ADC operating speed. A novel architecture is proposed to optimize the settling time for the capacitive DAC, which depends merely on the on-resistance of switches and the capacitance of unit capacitor and irrelevant to the resolution. Therefore, high-speed high-resolution SAR ADC is possible. What is deserved to highlight is that the architecture improves the ADC performance at a fraction of the cost, with only some capacitors and control logic added. Post-layout simulation has been made for the SAR ADC. At a 1.2-V supply voltage and a sampling rate of 300 MS/s, it consumes 1.27 mW and achieves an SNDR of 60 dB, an SFDR of 67.5 dB, with the Nyquist input. The SAR ADC occupies a core area of 450×380 μm².     

渤海湾盆地铲形正断层及其次级断层组合成因

渤海湾盆地铲形正断层及其反向分支断层组合可分为５类，它们的形成过程取决于断层形态，控制断层形态的因素包括岩石力学性质，沉积压实，地层压力等非构造因素，正是这些因素时复杂变化造成亚样式多样性和千姿百态的断层分布。     

沉淀池数值模拟技术的研究进展与评论

在水处理应用当中的沉淀池数值模拟研究近些年取得了很大的进展.自20世纪70年代,国外的研究人员开始进行许多沉淀池场方面的试验研究与数值模拟工作,在试验测量方面进行了原型池与模型池的测量,包括对速度场与浓度场都进行了许多的测量工作.国内于近几年也开始开展一些数值模拟研究工作,但试验测量方面的工作几乎没有.数值模拟技术尚未能很好地发展到实际工程应用的阶段.对模型的最新进展、所需解决的关键性问题进行了总结.     

An experimental study of the relationship between settling flocs and eroded flocs of kaolinite in aqueous media

Aspects of the relationship between flocs in suspension and those held in a cohesive sediment bed were investigated experimentally using an erosion rig with kaolinite as the sample material under different medium conditions. The critical shear-stress, τ_c, required to initiate the erosion were measured, and the floc sizes of the eroded products (d_E) were analysed in situ using macro-photography. Factors such as age, density, pH and ionic strength were investigated. Separate experiments were performed to measure the floc size in the settling zone (d_A). The results show that the floc sizes from the above two different measurements show the same variance with respect to physico-chemical (pH and ionic strength) changes in the environment. This work has been very successful in showing the relationship between the flocs in suspension and those eroded from a bed of sediment, so one property can be predicted from knowledge of another.     

Optimization of Settling Behavior for an Efficient Solvent‐Extraction Process for Biobased Components

Extraction is a downstream process option in biobased processes. Because knowledge of phase‐separation behavior is essential for designing efficient separation processes, this study investigates the settling and coalescence behavior of biobased extraction systems by using a standard laboratory‐scale settling cell. The influence of different buffer media and Escherichia coli cells on coalescence was determined for the reactive extraction of hexane‐1,6‐diamine with isostearic acid and di(2‐ethylhexyl)phosphoric acid by using kerosene and oleyl alcohol as diluents. As a result, an increasing pH value of the buffer significantly increases the settling time. The presence of E. coli cells hinders phase separation of the investigated systems, in particular, with dispersed organic phases.