Scaling of activation energy for macroscopic flow in poly(ethylene glycol) solutions: Entangled – Non-entangled crossover

We postulate an empirical scaling equation, which accurately describes flow of polymer solutions, complimenting the paradigm of length-scale-dependent viscosity. We investigated poly(ethylene glycol) aqueous solutions and observed an exponential dependence of viscosity on the hydrodynamic radius of a single coil R_h divided by the correlation length ξ. Properties of the system changed abruptly with the onset of chain entanglement at concentration corresponding to ξ = R_h. We propose a single equation valid for all the investigated systems, analyze the physical meaning of parameters appearing therein and discuss the impact of chain entanglement. Viscous flow is treated as an activated process, following the Eyring rate theory. We show that the difference of activation energy for flow between pure solvent and polymer solution, ΔE_a, is a function of concentration, whose derivative has a discontinuity at the crossover concentration. For dilute PEG solutions ΔE_a takes values of up to several kJ/mol and is proportional to the intrinsic viscosity. We successfully apply the scaling approach to the diffusive motion of a protein (aldolase) in solutions of 25 kg/mol PEO (concentrations of 2–20%), investigated by fluorescence correlation spectroscopy (FCS). A significant difference in the influence of crowding on translational and rotational motion of the protein is revealed.     

Design,analysis and test of a model turbine blade for a wave basin test of floating wind turbines

Froude scaling is a generally reliable way to design models of floating wind turbines for wave basin testing. However, the resulting rotor thrust of the model is far lower than the Froude-scaled value of a full-size turbine, because the reduction in Reynolds number decreases the lift coefficients and increases the drag coefficients (the Reynolds number scaling effect). A 1/50th scale model wind turbine based on a NREL-5MW reference turbine is examined here. To mitigate the Reynolds number scaling effect in the model, the original aerofoils of the reference turbine (DU series and NACA 64-618) were replaced by an aerofoil at a low Reynolds number (NACA 4412). Such a model with aerofoil-adjusted blades was used in the mathematical optimization of rotor thrust. The design objective was to guarantee that while the rotor thrust of the model equalled the Froude-scaled rotor thrust of the reference, the smallest chord lengths were achieved, considering the weight control in building the model blade. The distribution of chord lengths fitted a fourth-order polynomial curve, and the distribution of twist angles along the blade fitted a second-order polynomial curve. The eight coefficients of the two curves were chosen as optimization variables, and pattern search method was used to solve the optimization model. The model blade was designed at zero pitch angle and further tested in FAST, a fully coupled simulation tool. A model test was conducted using the optimized blade geometry in the State Key Laboratory of Ocean Engineering in Shanghai, China, and the thrusts were compared with the predicted values.     

Step scaling and behaviour selection in a constrained set of manual material handling transfers

Predictive biomechanical analysis of manual material handling (MMH) transfers is dependent on accurate prediction of foot locations relative to the task. Previous studies have classified common acyclic stepping patterns used during those transfer tasks, but the influence of walking distance prior to the transfer is not well understood. Twenty men and women performed transfers for a minimum of six different delivery distance conditions. The number of steps used by the participants ranged from two to seven. A theoretical framework for idealised step-scaling strategies is proposed and compared with the experimental data. The maximum observed increase in step length prior to delivery was 1.43 times the nominal step length calculated for each participant. The data suggest that although participants can scale their steps to facilitate the use of a single terminal stance at the transfer, the majority of participants chose to utilise a combination of stepping strategies if the preferred contralateral lead foot strategy could not be easily implemented.

Practitioner summary: Accurate foot placements are needed for predictive biomechanical analysis of MMH. A laboratory study investigated the influence of previous step positions on MMH. A flexible step-scaling strategy, in which step lengths and strategy were varied, suggests that analysis based on simulated movements should consider multiple lifting postures.     

热管锅炉效率下降原因分析及处理措施

分析贵溪冶炼厂冶炼烟气制酸转化工序的热管锅炉换热效率降低的原因，主要是热管中产生了不凝性气体及水垢。对二系列低温锅炉的下降管进行了疏通清理并煮炉，去除水垢；对一系列中温锅炉热管进行了在线管内工质更换检修。换热管经过处理后换热效率得到了明显提高，延长了热管的使用寿命，热管锅炉运行稳定。     

Shapiro不等式的指数推广

利用Holder不等式，Young不等式和幂平均不等式建立了Shapiro不等式的指数推广形式．所得结果改进和推广了最近文献的一些相应结果．     

Designing Experiments for Causal Networks

Causal networks are directed graphs representing cause-effect relationships and are multiple-response generalizations of Ishikawa's cause–effect diagrams. Emphasizing tolerance design applications, this article describes an algorithm for designing suitable experiments when the factors and responses are organized as a causal network. The causal network is transformed into a so-called causal map, which represents all factors and responses as points in a common D-dimensional metric space. The design approach is algorithmic, optimizing the entropy criterion due to Wynn. This criterion is applied to maximize dispersion among the multiple responses, using a distance-in-space coefficients model. A key constraint is for the blocks to be self-contained; this implies that each block can be analyzed without reference to other blocks. This is to be complemented by a unified, all-block analysis. The resulting designs are evaluated for efficiency, response dispersion, and resolution V column rank. Particular attention is given to skewing each block by shifting one or a few factors off-center.     

超临界机组腐蚀、结垢和积盐分析及处理对策

超临界及超超临界发电机组近十几年成为我国主力发电机组,超临界及超超临界机组设备在运行中出现了与亚临界机组设备不同的腐蚀结垢问题。笔者介绍了湖北省超临界发电机组在运行中产生的腐蚀、结垢及汽轮机叶片的积盐情况,并对该情况产生的原因进行了分析和探讨,并提出了对策和解决措施。     

关于丢番图方程sum from i=1 to k (a_ix_i~(m_i/n_i)=x~(m/n)

根据整系数整指数丢番图方程∑ki=1aixini=ym,有含参数一般解的一个充分条件 ,作者就推广型整系数有理分数指数丢番图方程∑ki=1aiximini=ymn 进行研究 ,给出该方程有参数一般解的一个充分条件 ,并得到它的一族含参整数解 .     

Opportunities for economies of scale with alkaline electrolyzers

Large alkaline electrolyzer installations are typically modular and do not exhibit significant economies of scale. Substantial capital cost reductions are possible if electrolyzer stacks utilize equipment common to each modular installation. This work analyzes the possible capital cost reduction arising from the use of common equipment. Established chemical engineering techniques are used to determine the capital cost curves for the major electrolyzer subsystems for installations ranging from one to fifty units. The major equipment found in large-scale alkaline electrolyzers – like those electrolyzers used in the DOE's Hydrogen Analysis (H₂A) program – is reviewed and the associated cost scaling exponents are discussed. The common equipment is scaled up to meet the flow rates and processing requirements of large, multi-electrolyzer systems. The capital costs of the scaled electrolyzer systems are calculated and compared to standard modular systems. It is shown that scaling the compressors, the gas holding tanks, the transformers and the balance of plant equipment can reduce the capital costs by as much as 60% for the best-case scenario and 25% for the worst-case scenario. It was also found that simply using large compressors common to each electrolyzer has the greatest impact on capital cost reduction.