气升式内环流生物反应器中液体的返混

本文采用了柯尔莫哥洛夫（Ｋｏｌｍｏｇｏｒｏｆｆ）各向同性湍流理论模拟气升式环流反应器中粘性非牛顿流体在上升段及下降段中的轴向返混，在应用该理论分析反应器的行为时，对环流反应器的输入功进行了推算，导出了非牛顿流体系统中的特征长度和特征速度，并且以此为基础进一步分析和推导了非牛顿流体中液相轴向返混系数的表达式。     

An effective splitting-and-recombination micromixer with self-rotated contact surface for wide Reynolds number range applications

It is difficult to mix two liquids on a microfluidic chip because the small dimensions and velocities effectively prevent the turbulence. This paper describes two 2-layer PDMS passive micromixers based on the concept of splitting and recombining the flow that exploits a self-rotated contact surface to increase the concentration gradients to obtain fast and efficient mixing. The designed micromixers were simulated and the mixing performance was assessed. The mixers have shown excellent mixing efficiency over a wide range of Reynolds number. The mixers were reasonably fabricated by multilayer soft lithography, and the experimental measurements were performed to qualify the mixing performance of the realized mixer. The results show that the mixing efficiency for one realized mixer is from 91.8% to 87.7% when the Reynolds number increases from 0.3 to 60, while the corresponding value for another mixer is from 89.4% to 72.9%. It is rather interesting that the main mechanism for the rapid mixing is from diffusion to chaotic advection when the flow rate increases, but the mixing efficiency has not obvious decline. The smart geometry of the mixers with total length of 10.25 mm makes it possible to be integrated with many microfluidic devices for various applications in μ-TAS and Lab-on-a-chip systems.     

Distributed Expert-Based Information Systems: An interdisciplinary approach

An international workshop on Distributed Expert-Based Information Systems (DEBIS) was held at Rutgers University in March 1987. The aims of the workshop were to discuss problems and issues in the design of such systems, and to develop research and implementation strategies for them. The workshop attendees discussed both models and implementations of DEBIS. A prototypical implementation operates on one or more workstations and connects an end-user to an information source after invoking multiple expert functions. The design of these functions depends in part on careful study of end-user and search intermediary behavior. Such studies suggest a dozen basic functions which must be incorporated in a DEBIS. including ones to model the user, generate search strategies, and manage the interface. The favored methods of implementation use blackboards to simplify communications between functional modules. Two large systems, I³R and CODER, have been developed which illustrate the complexity but also the feasibility of DEBIS.     

Flow of DNA solutions in a microfluidic gradual contraction

The flow of λ-DNA solutions in a gradual micro-contraction was investigated using direct measurement techniques. The effects on DNA transport in microscale flows are significant because the flow behavior is influenced by macromolecular conformations, both viscous and elastic forces dominate inertial forces at this length scale, and the fully extended length of the molecule approaches the characteristic channel length w_c (L/w_c ∼ 0.13). This study examines the flow of semi-dilute and entangled DNA solutions in a gradual planar micro-contraction for low Reynolds numbers (3.7 × 10⁻⁶< Re < 3.1 × 10⁻¹) and high Weissenberg numbers (0.4 < Wi < 446). The semi-dilute DNA solutions have modest elasticity number, El = Wi/Re = 55, and do not exhibit viscoelastic behavior. For the entangled DNA solutions, we access high elasticity numbers (7.9 × 10³< El < 6.0 × 10⁵). Video microscopy and streak images of entangled DNA solution flow reveal highly elastic behavior evidenced by the presence of large, stable vortices symmetric about the centerline and upstream of the channel entrance. Micro-particle image velocimetry measurements are used to obtain high resolution, quantitative velocity measurements of the vortex growth in this micro-contraction flow. These direct measurements provide a deeper understanding of the underlying physics of macromolecular transport in microfluidic flow, which will enable the realization of enhanced designs of lab-on-a-chip systems.     

改进的大纯滞后过程预测函数控制算法

提出了预测函数控制（PFC）与PID控制结合的新方法．并针对典型工业过程控制．分析了预测函数控制的基本原理和特点。基于Smith预估器．给出了工业过程控制中改进的预测函数控制算法,并用MATLAB进行仿真实验．仿真结果也表明其对被控系统有良好的鲁棒性、抑制干扰能力和跟踪性能。     

Audience management,online turbulence and lurking in social networking services: A transactional process of stress perspective

In social networking services (SNSs), users’ unclear understanding of the large and invisible audience increases the chances of online turbulence, which is a key source of SNS-induced stress. This growing phenomenon has gained increasing attention in academia and industry due to the undesirable consequences for users and SNS platforms. In this study, we draw from the transactional model of stress to examine how audience management strategies impact online turbulence and lead to neglected unintended audience concern and lurking. We also investigate the role of self-monitoring as a stress inhibitor. We test our model with data collected from 301 SNS users. The results show that the four types of audience management strategies have different effects on online turbulence, which significantly impacts neglected unintended audience concern especially when users have high self-monitoring skills. We believe that this work contributes, both from scientific and practical standpoints, to the understanding of the interventions and stressful responses of online turbulence in SNSs.     

A probabilistic approach to polycrystalline plasticity part II: applications

Using our constitutive theory for polycrystalline plasticity, we have calculated characteristic yield conditions for several sample materials in which the dependence of the dislocation velocity on stress is given by an empirical power function. The shape of the yield surfaces for these materials varies resembling that of von Mises when the stress exponent is small and that of Tresca when the exponent is large. Additional examples illustrate the ability of the proposed theory to model such phenomena as the development of anisotropy during plastic deformation, material hardening and softening, the occurrence of upper and lower yield points, and a Bauschinger effect.     

Investigation of the heat transfer of a non-Newtonian fluid flow in an axisymmetric channel with porous wall using Parameterized Perturbation Method (PPM)

In the present article Parameterized Perturbation Method (PPM) is used to obtain the solutions of momentum and heat transfer equations of non-Newtonian fluid flow in an axisymmetric channel with porous wall for turbine cooling applications. The validity of the results of PPM solution were verified by comparison with numerical results obtained using a fourth order Runge–Kutta method. These comparisons reveal that Parameterized Perturbation Method is a powerful approach for solving this problem. The analytical investigation is carried out for different governing parameters namely, Reynolds number, injection Reynolds number, Prandtl number and power law index. The results show that skin friction coefficient increases with increase of Reynolds number, especially at high Reynolds numbers. Also it can be found that Nusselt number has direct relationship with Reynolds number, Prandtl number and power law index.     

Identification and characterization of a novel 2R,3R-Butanediol dehydrogenase from Bacillus sp. DL01

Background2R,3R-butanediol dehydrogenase (R-BDH) and other BDHs contribute to metabolism of 3R/3S-Acetoin (3R/3S-AC) and 2,3-butanediol (2,3-BD), which are important bulk chemicals used in different industries. R-BDH is responsible for oxidizing the hydroxyl group at their (R) configuration. Bacillus species is a promising producer of 3R/3S-AC and 2,3-BD. In this study, R-bdh gene encoding R-BDH from Bacillus sp. DL01 was isolated, expressed and identified.ResultsR-BDH exerted reducing activities towards Diacetyl (DA) and 3R/3S-AC using NADH, and oxidizing activities towards 2R,3R-BD and Meso-BD using NAD⁺, while no activity was detected with 2S,3S-BD. The R-BDH showed its activity at a wide range of temperature (25°C to 65°C) and pH (5.0–8.0). The R-BDH activity was increased significantly by Cd²⁺ when DA, 3R/3S-AC, and Meso-BD were used as substrates, while Fe²⁺ enhanced the activity remarkably at 2R,3R-BD oxidation. Kinetic parameters of the R-BDH from Bacillus sp. DL01 showed the lowest K_m, the highest V_max, and the highest K_cat towards the racemic 3R/3S-AC substrate, also displayed low K_m towards 2R,3R-BD and Meso-BD when compared with other reported R-BDHs.ConclusionsThe R-BDH from Bacillus sp. DL01 was characterized as a novel R-BDH with high enantioselectivity for R-configuration. It considered NAD⁺ and Zn²⁺ dependant enzyme, with a significant affinity towards 3R/3S-AC, 2R,3R-BD, and Meso-BD substrates. Thus, R-BDH is providing an approach to regulate the production of 3R/3S-AC or 2,3-BD from Bacillus sp. DL01.How to cite: Elmahmoudy M, Elfeky N, Zhongji P, et al. Identification and characterization of a novel 2R,3R-Butanediol Dehydrogenase from Bacillus sp. DL01. Electron J Biotechnol 2021;49. https://doi.org/10.1016/j.ejbt.2020.11.002     

基于Fluent模拟的独头巷道通风流场分析

运用通风安全学和流体力学理论,建立独头巷道压入式通风的湍流模型。利用Fluent软件模拟独头巷道通风流场,并用Tecplot软件进行后处理,显示其速度矢量图。模拟显示了独头巷道的射流规律,模拟结果与理论相符,为独头巷道的通风研究提供了一条新的途径。     

Air flow separation at high speed

The resistance coefficient of a body moving in a fluid depends on Reynolds Number R, Mach Number M and the parameter $\text{gL}\text{U}{}^2$, which is customarily neglected in view of small weight of the air. Here L denotes a characteristic length; U denotes the body's speed of translation. The author points that dimensional deduction of this parameter does not limit it to the acceleration of gravity, and that the resistance coefficient is affected by the general acceleration to which the air is subjected. Evaluation of the acceleration of the air flowing about spheres puts this parameter in the form $\text{L}\text{R}$, where the characteristic length L is interpreted as the mean free molecular path. Large and small spheres were found to have widely different values of the pressure coefficient $\text{Δp}\text{q}$ for the same Reynolds Number or Mach Number. Here Δp denotes the difference in pressure between front stagnation point and the rear portion of the sphere, and q denotes the dynamic pressure. The plot of $\text{Δp}\text{q}$ against the parameter $\text{L}\text{R}$ removes this confusion. The low values of $\text{Δp}\text{q}$ are found to be associated with $\text{L}\text{R}$ below a certain critical value, and high values of $\text{Δp}\text{q}$ with $\text{L}\text{R}$ above the critical value, which apparently indicates the condition under which the flow separation takes place. Attention is called to the effect of air pressure on the separation as shown by the parameter $\text{L}\text{R}$, and its possible bearing on the drag in high altitude flying.     

导叶式多点绕流流量计叶片翼型选型研究

基于差压测速原理,设计一种新型导叶式多点绕流流量计,该流量计可作为水泵的前置导叶安装于水泵进水流道出口位置.为减小水力损失、优化水泵进口流态,取得最佳测量效果,利用流体动力学通用计算软件Fluent,基于雷诺平均纳维-斯托克斯方程（RANS）、k-ε双方程湍流模型和SIMPLEC算法,对10个设计方案的导叶叶片翼型进行了CFD计算和分析.通过对水力损失、流速分布状态和叶片表面压力规律的比较,决定选择方案14的叶片翼型作为后续研究的基础.     

项目组合管理对新产品开发绩效的影响:高管参与的中介效应

基于组织信息加工理论,以高管参与为中介变量,以技术动荡性为调节变量,构建项目组合管理实践对新产品开发绩效的影响关系模型。对来自不同行业的169位项目经理和公司高管开展实证研究发现,项目组合管理实践对新产品开发绩效有间接的正向促进作用;高管参与在项目组合管理实践与新产品开发绩效间发挥完全中介作用。技术动荡对项目组合管理实践与新产品开发绩效关系有负向调节作用,低技术动荡条件下,项目组合管理实践对新产品开发绩效有显著的直接影响,高管参与的中介效应不明显。     

高新技术企业研发人员跨界行为何以激励探索式创新？——一个有调节的中介效应模型

运用资源依赖理论，构建研发人员跨界行为、知识重构影响企业探索式创新的有调节的中介效应模型，运用259份有效问卷通过层次回归、bootstrap等数据分析方法进行实证分析，研究研发人员跨界行为对探索式创新的影响机制并进一步证明环境动荡性的调节作用。研究结果表明，研发人员跨界行为能够显著提高高新技术企业探索式创新；研发人员跨界行为对探索式创新的影响主要通过知识重构介导；环境动荡性增强了研发人员跨界行为对探索式创新的影响。     

Ultra-small hollow ternary alloy nanoparticles for efficient hydrogen evolution reaction

Hollow nanoparticles with large specific surface area and high atom utilization are promising catalysts for the hydrogen evolution reaction (HER). We describe herein the design and synthesis of a series of ultra-small hollow ternary alloy nanostructures using a simple one-pot strategy. The same technique was demonstrated for hollow PtNiCu nanoparticles, hollow PtCoCu nanoparticles and hollow CuNiCo nanoparticles. During synthesis, the displacement reaction and oxidative etching played important roles in the formation of hollow structures. Moreover, our hollow PtNiCu and PtCoCu nanoparticles were single crystalline, with an average diameter of 5 nm. Impressively, ultra-small hollow PtNiCu nanoparticles, containing only 10% Pt, exhibited greater electrocatalytic HER activity and stability than a commercial Pt/C catalyst. The overpotential of hollow PtNiCu nanoparticles at 10 mA cm⁻² was 28 mV versus reversible hydrogen electrode (RHE). The mass activity was 4.54 A mg_Pt⁻¹ at −70 mV versus RHE, which is 5.62-fold greater than that of a commercial Pt/C system (0.81 A mg_Pt⁻¹). Through analyses of bonding and antibonding orbital filling, density functional theory calculations demonstrated that the bonding strength of different metals to the hydrogen intermediate (H^*) was in the order of Pt > Co > Ni > Cu. The excellent HER performance of our hollow PtNiCu nanoparticles derives from moderately synergistic interactions between the three metals and H^*. This work demonstrates a new strategy for the design of low-cost and high-activity HER catalysts.     

The coefficient of resistance as a function of Reynolds number for solids of various shapes

The purpose of the present article is twofold. First it is an attempt to show the usefulness of the degree of true sphericity as an expression for shape of rock particles. Second it is intended as a background for a new, analytical, sedimentographic method to be given in a forthcoming paper. Any radical variation in shape influences the numerical value of the degree of true sphericity and affects the size of the surface area, the size of the largest cross-sectional area and the degree of circularity of a great number of cross-sections of a solid. These factors determine to a large extent the settling velocity of that solid. The resistance of wholly submerged bodies, as a theoretical foundation for determining the coefficient of resistance as a function of Reynolds number for solids of different degree of sphericity, is discussed. The influence of the degree of circularity on the resistance is then shown by graphs constructed on the basis of available data. Formulæ for calculating the coefficient of resistance and Reynolds number are introduced and their practical value demonstrated by graphic illustrations. The sedimentological significance and usefulness of the results are discussed.     

一种企业研发团队复杂网络平台体系架构

针对现有复杂网络软件难以支撑企业研发团队分析的问题,建立一个灵活、可扩展的关系网络的展示环境和可视化分析环境,提炼出研发团队复杂网络映射方案、表示方案,通过特征指标关联反映研发团队复杂网络的内在本质,形成以行为为准则的复杂网络动态演化机制,为企业研发团队的复杂网络分析提供一个具有复杂网络建模、分析展示系统、指标特征关联、网络动态演化4个层面的专业平台架构。     

Tracking structural evolution: operando regenerative CeOx/Bi interface structure for high-performance CO2 electroreduction

Unveiling the structural evolution and working mechanism of catalysts under realistic operating conditions is crucial for the design of efficient electrocatalysts for CO₂ electroreduction, yet remains highly challenging. Here, by virtue of operando structural measurements at multiscale levels, it is identified under CO₂ electroreduction conditions that an as-prepared CeO₂/BiOCl precatalyst gradually evolves into CeO_x/Bi interface structure with enriched Ce³⁺ species, which serves as the real catalytically active phase. The derived CeO_x/Bi interface structure compared to pure Bi counterpart delivers substantially enhanced performance with a formate Faradaic efficiency approaching 90% for 24 hours in a wide potential window. The formate Faradaic efficiency can be further increased by using isotope D₂O instead of H₂O. Density functional theory calculations suggest that the regenerative CeO_x/Bi interfacial sites can not only promote water activation to increase local ^*H species for CO₂ protonation appropriately, but also stabilize the key intermediate ^*OCHO in formate pathway.     

建立基于RS ＆ LS的图书馆自组织管理研究

传统直线制图书馆组织的两大弊端：缺乏对快速变化环境的适应能力和及时响应读者需要的能力,因此,传统理念的局限呼唤新的管理范式。自组织理论的特点和优势为图书馆管理创新提供了新的视角和方法,文中不仅分析了图书馆组织具有构成耗散结构的三个条件,即开放性、非线性和非平衡性;而且还针对自组织耗散结构的三个优势研究了进行针对性图书馆自组织管理的相应措施。     

战略型企业家精神与自主创新:一个研究框架

自主创新能力提高对企业建立持续竞争优势至关重要。基于战略型企业家精神观点和组织学习理论,提出一个关于战略导向、组织学习、环境动态性与包容性及自主创新间关系的理论分析框架。分析认为,资源导向与机会导向会通过不同的组织学习方式影响企业自主创新能力,环境动态性与包容性影响组织学习对自主创新能力的影响效果,战略型企业家精神的培育、探索性学习与应用性学习的平衡发展对企业自主创新能力提高至关重要。