Isolation and characterization of seven quorum quenching bacteria for biofouling control in MBR

Recently, interspecies quorum quenching (QQ) by bacteria has been reported as a novel approach in biofouling control in membrane bioreactor (MBR) for wastewater treatment. In this study, seven QQ bacteria, named RO1 to RO7, were isolated from fouling reverse osmosis (RO) membrane and were encapsulated in the microbial filters for biofouling control in MBR. Results showed that all isolates have extracellular QQ activity, and RO1 to RO6 were characterized as heat-stable enzymatic degradation of N-acyl homoserine lactones (AHLs), while RO7 was mainly pH-dependent. Analysis of the 16S rRNA gene indicated that RO7 was a species of Pseudomonas sp., others belonged to the species of Bacillus, Stenotrophomonas maltophilia and Delftia tsuruhatensis, respectively. Then, the microbial filters encapsulated each isolate were applied in a laboratory-scaled MBR and proved the substantial inhibition effect on membrane biofouling except for RO7, indicating that QQ bacteria employing enzymes to degrade AHLs have great potential in biofouling control in MBR.     

A two-phase variable neighbourhood search algorithm for assembly line worker assignment and balancing problem type-II: an industrial case study

The assembly line worker assignment and balancing problem type-II (ALWABP-2) occurs when workers and tasks (where task times depend on workers’ skills) are to be simultaneously assigned to a fixed number of workstations with the goal of minimising the cycle time. In this study, a two-phase variable neighbourhood search (VNS) algorithm is proposed to solve the ALWABP-2 due to the NP-hard nature of this problem. In the first phase of the algorithm, a VNS approach is applied to assign tasks to workstations with the aim of minimising the cycle time while in the second phase, a variable neighbourhood descent method is applied to assign workers to workstations. The performance of the proposed algorithm is tested on well-known benchmark instances. In addition, the proposed algorithm has been used to solve a real case study from a consumer electronics company that manufactures LCD TVs. The results show that the algorithm is superior to the methods reported in the literature in terms of its higher efficiency and robustness. Furthermore, the algorithm is easy to implement and significantly improves the performance of the final assembly line for the investigated LCD TV real case study.     

Measurement Uncertainty Budget of the PMV Thermal Comfort Equation

Fanger’s predicted mean vote (PMV) equation is the result of the combined quantitative effects of the air temperature, mean radiant temperature, air velocity, humidity activity level and clothing thermal resistance. PMV is a mathematical model of thermal comfort which was developed by Fanger. The uncertainty budget of the PMV equation was developed according to GUM in this study. An example is given for the uncertainty model of PMV in the exemplification section of the study. Sensitivity coefficients were derived from the PMV equation. Uncertainty budgets can be seen in the tables. A mathematical model of the sensitivity coefficients of \(T_{\mathrm{a}}\), \(h_{\mathrm{c}}\), \(T_{\mathrm{mrt}}\), \(T_{\mathrm{cl}}\), and \(P_{\mathrm{a}}\) is given in this study. And the uncertainty budgets for \(h_{\mathrm{c}}\), \(T_{\mathrm{cl}}\), and \(P_{\mathrm{a}}\) are given in this study.     

5-5′型木质素二聚体高温热解微观化学反应机理研究

选用5-5′键型连接的木质素二聚体为研究对象,基于B3LYP/6-31g基组和密度泛函理论(DFT)对其进行了高温热解微观化学反应机理研究,设计了5-5′型木质素二聚体高温热解反应的5条初反应路径,并在分析初反应结果的基础上设计了7条次反应路径,对每条路径的反应物及其产物进行了结构优化,计算了1500K温度下每条反应路径的热力学及动力学参数。结果表明,5-5′型木质素苯环位上的甲氧基具有很强的活性,甲氧基中O-CH3键以及Caromatic-OCH3键较易断裂;通过计算得出初反应的R3、R4反应焓变较小,分别为192.7kJ/mol和270.5kJ/mol,认为该热解反应的主反应路径以R3及R4为主;该热解反应得到的最终产物有3-4,二羟基甲苯、对羟基甲苯、2-乙烯-4-甲基-3,5-二烯环己酮、甲烷、甲醇及甲醛。     

微晶纤维素表面接枝对苯二胺的制备及其荧光性能

以微晶纤维素(MCC)为原料,高碘酸钠(NaIO4)为氧化剂首先制备了双醛纤维素(DAC),进而与对苯二胺(PPDA)进行小分子接枝反应,得到对苯二胺改性的微晶纤维素。通过红外光谱、热重分析、示差扫描量热仪和荧光显微镜分别表征了MCC氧化和接枝前后样品的变化,以及产物的荧光性能。结果表明,MCC经高碘酸钠氧化,可选择性地将C2、C3键的羟基氧化成醛基;对苯二胺接枝于DAC后可形成碳氮双键,具有明显的荧光效应。     

功率超声在金属熔体成形中的作用效应及其可视化研究进展

主要介绍功率超声在金属熔体成形领域中的作用,详述了超声在铸造成形、辅助焊接成形中细化晶粒、除气除杂、强化焊缝、减小残余应力、促进界面润湿等方面的应用和作用机理。针对超声空化气泡的高速摄影及金属熔体中晶体生长的同步辐射X射线成像观察的研究进展,提出将高速摄影与同步辐射X射线成像结合起来,通过原位观察方法研究超声波与液态金属媒质的相互作用机理,为进一步促进超声在金属熔体成形中的应用提供理论指导。     

电流密度对微/纳结构电铸成型模芯质量的影响

利用多物理场耦合分析软件COMSOL Multiphysics,模拟微/纳结构电铸过程中阴极表面的电场分布,研究不同电流密度下微/纳结构表面的电场分布及电铸层生长前沿情况。仿真结果表明:采用较低的初始电流密度,可有效改善微/纳结构生长前沿铸层厚度的均匀性。选用纳米光阑和纳米柱阵列2种微/纳结构母板进行电铸实验,将初始电流密度从4A/dm2调至1A/dm2,纳米光阑母板成型最大误差60nm降至±20nm之内。通过合理设置初始电流密度、增强阴极表面溶液流动强度等措施,纳米柱阵列模芯特征直径尺寸误差由6.27%下降至2.49%,有效提高电铸模芯的复制质量。     

Molybdenum Carbide‐Decorated Metallic Cobalt@Nitrogen‐Doped Carbon Polyhedrons for Enhanced Electrocatalytic Hydrogen Evolution

Electrocatalytic hydrogen evolution reaction (HER) based on water splitting holds great promise for clean energy technologies, in which the key issue is exploring cost‐effective materials to replace noble metal catalysts. Here, a sequential chemical etching and pyrolysis strategy are developed to prepare molybdenum carbide‐decorated metallic cobalt@nitrogen‐doped porous carbon polyhedrons (denoted as Mo/Co@N–C) hybrids for enhanced electrocatalytic hydrogen evolution. The obtained metallic Co nanoparticles are coated by N‐doped carbon thin layers while the formed molybdenum carbide nanoparticles are well‐dispersed in the whole Co@N–C frames. Benefiting from the additionally implanted molybdenum carbide active sites, the HER performance of Mo/Co@N–C hybrids is significantly promoted compared with the single Co@N–C that is derived from the pristine ZIF‐67 both in alkaline and acidic media. As a result, the as‐synthesized Mo/Co@N–C hybrids exhibit superior HER electrocatalytic activity, and only very low overpotentials of 157 and 187 mV are needed at 10 mA cm^?2 in 1 m KOH and 0.5 m H₂SO₄, respectively, opening a door for rational design and fabrication of novel low‐cost electrocatalysts with hierarchical structures toward electrochemical energy storage and conversion.     

A Two‐Stage Annealing Strategy for Crystallization Control of CH3NH3PbI3 Films toward Highly Reproducible Perovskite Solar Cells

The solvent‐engineering method is widely used to fabricate top‐performing perovskite solar cells, which, however, usually exhibit inferior reproducibility. Herein, a two‐stage annealing (TSA) strategy is demonstrated for processing of perovskite films, namely, annealing the intermediate phase at 60 °C for the first stage then at 100 °C for the second stage. Compared to conventional direct annealing temperature (DHA) at 100 °C, using this strategy, MAPbI₃ films become more controllable, leading to superior film uniformity and device reproducibility with the champion device efficiency reaching 19.8%. More specifically, the coefficient of variation of efficiency for 49 cells is reduced to 5.9%, compared to 9.8% for that using DHA. The TSA process is carefully studied using Fourier transform infrared spectroscopy, X‐ray diffraction, and UV–vis absorption spectroscopy. It is found that in comparison with DHA the formation of hydrogen bonding and crystallization of perovskite are much slower and can be better controlled when using TSA. The improvements in film uniformity and device reproducibility are attributed to: 1) controllable MAPbI₃ crystal growth stemming from the progressive formation of hydrogen bonding between methylammonium and halide; 2) suppression of intermediate phase film dewetting, which is believed to be due to its decreased mobility at the initial low‐temperature annealing stage.     

Hierarchical CdS Nanorod@SnO2 Nanobowl Arrays for Efficient and Stable Photoelectrochemical Hydrogen Generation

An efficient photoanode based on CdS nanorod@SnO₂ nanobowl (CdS NR@SnO₂ NB) arrays is designed and fabricated by the preparation of SnO₂ nanobowl arrays via nanosphere lithography followed by hydrothermal growth of CdS nanorods on the inner surface of the SnO₂ nanobowls. A photoelectrochemical (PEC) device constructed by using this hierarchical CdS NR@SnO₂ NB photoanode presents significantly enhanced performance with a photocurrent density of 3.8 mA cm^?2 at 1.23 V versus a reversible hydrogen electrode (RHE) under AM1.5G solar light irradiation, which is about 2.5 times higher than that of CdS nanorod arrays. After coating with a thin layer of SiO₂, the photostability of the CdS NR@SnO₂ NB arrays is greatly enhanced, resulting in a stable photoanode with a photocurrent density of 3.0 mA cm^?2 retained at 1.23 V versus the RHE. The much improved performance of the CdS NR@SnO₂ NB arrays toward PEC hydrogen generation can be ascribed to enlarged surface area arising from the hierarchical nanostructures, improved light harvesting owing to the NR@NB architecture containing multiple scattering centers, and enhanced charge separation/collection efficiency due to the favorable CdS–SnO₂ heterojunction.