Effect of milling on the anisotropic grain growth in a sintered Ba5Nb4O15 specimen and its effect on microwave dielectric properties

In this study, relationships between the processing, microstructure, and properties of barium niobate (Ba₅Nb₄O₁₅) are investigated. The milling of a Ba₅Nb₄O₁₅ powder in water is effective with respect to size reduction. However, after milling in water, BaCO₃ is formed within the slurry. With the increase in the amount of BaCO₃ formed, the aspect ratio of the elongated Ba₅Nb₄O₁₅ grains increases. The formation of the elongated Ba₅Nb₄O₁₅ grains prohibits the densification. Hence, the microwave dielectric properties, including permittivity and quality factor, are poor because of the low density. In addition, milling in ethanol is carried out for comparison: A lower amount of BaCO₃ is formed after milling in ethanol; the extent of anisotropic grain growth is thus reduced.     

Mediated Electrochemistry to Mimic Biology's Oxidative Assembly of Functional Matrices

Biology uses diffusible oxidants to perform functions that range from signaling to matrix assembly, and these oxidation chemistries offer surprising selectivities. Here, it is reported that mediated electrochemistry can access the richness of such oxidation chemistries. Specifically, electrode‐imposed voltage inputs are used to locally generate oxidized mediators that can diffuse into polymer solutions and induce the formation of covalent bonds for the deposition and functionalization of hydrogels at the electrode surface. Depending on the mediator's redox potential (E⁰), it is possible to “gate” the voltage inputs to target specific residues (e.g., thiols or amines) and oxidation chemistries. Further, mediators of varying E⁰ offer different reactivities and thus allow control of reaction‐diffusion rates to modulate the hydrogel's crosslink density and mechanical properties. Importantly, this mediated oxidation can be performed under physiologically relevant conditions to preserve labile biological functionalities (e.g., cell viability and protein function). Finally, it is demonstrated that protein fusion tags can be engineered to have “targetable” amino acid residues that enable protein function to be oxidatively conjugated to electrodeposited hydrogels. In summary, mediated electrochemistry can engage orthogonal oxidation chemistries to create functionalized matrices and thus mediated electrochemistry should add important capabilities to the electrofabrication toolbox.     

Physical study of room‐temperature‐cured epoxy/thermally reduced graphene oxides with various contents of oxygen‐containing groups

In this study, the effects of different oxygen‐containing group contents in thermally reduced graphene oxides (TRGs) for enhancing the physical properties of epoxy nancomposites was examined. The epoxy/TRG nanocomposites (ETNs) were prepared by a room temperature curing method in the presence of TRGs containing different oxygen‐containing groups and were then characterized by Fourier transform infrared spectroscopy. TRG contents with higher oxygen‐containing group contents (ca 33%) were found to show better dispersion capability in the epoxy matrix than TRGs with lower oxygen‐containing group contents (ca 11%) based on morphological observations by transmission electron microscopy. The better dispersion capability of TRGs with higher oxygen‐containing group contents in ETN membranes was found to lead to significantly enhanced mechanical strength, thermal stability and thermal conductivity based on measurements of dynamic mechanical analysis, tensile tests, thermogravimetric analysis and by the transient plane source technique. © 2014 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry     

Role of mass transfer in overall substrate removal rate in a sequential aerobic sludge blanket reactor treating a non-inhibitory substrate

A laboratory study was undertaken to explore the role of mass transfer in overall substrate removal rate and the subsequent kinetic behavior in a glucose-fed sequential aerobic sludge blanket (SASB) reactor. At the organic loading rates (OLRs) of 2-8 kg chemical oxygen demand (COD)/m³-d, the SASB reactor removed over 98% of COD from wastewater. With an increase in OLR, the average granule diameter (d_p = 1.1-1.9 mm) and the specific oxygen utilization rate increased; whereas biomass density of granules and solids retention time decreased (13-32 d). The intrinsic and apparent kinetic parameters were evaluated using break-up and intact granules, respectively. The calculated COD removal efficiencies using the kinetic model (incorporating intrinsic kinetics) and empirical model (incorporating apparent kinetics) agreed well with the experimental results, implying that both models can properly describe the overall substrate removal rate in the SASB reactor. By applying the validated kinetic model, the calculated mass transfer parameter values and the simulated substrate concentration profiles in the granule showed that the overall substrate removal rate is intra-granular diffusion controlled. By varying different d_p within a range of 0.1-3.5 mm, the simulated COD removal efficiencies disclosed that the optimal granular size could be no greater than 2.5 mm.     

关于狭义相对论的修正以及新引力理论的方案

相对论存在一定的局限性.狭义相对论适用于电磁的相互作用.没有强有力的证据显示狭义相对论也适用于其它3种基本相互作用.至少在弱相互作用中,中微子可能是超光速粒子.物理学需采取多种时间的定义,一种推广伽利略变换的时间值得进一步研究.广义相对论很大程度上是一种数学理论.作为物理学的引力理论,它存在很多基本缺陷.检验广义相对论一些天文实验,误差很大,需要重新分析.笔者将讨论一种新引力理论的方案.它的引力场方程与电磁理论的麦克斯韦方程十分相似.     

Ambient‐Stable,Annealing‐Free,and Ambipolar Organic Field‐Effect Transistors Based on Solution‐Processable Poly(2,2′‐bis(trifluoromethyl)biphenyl‐alt‐2,5‐divinylthiophene) without Long Alkyl Side Chains

An ambipolar conjugated polymer CF₃‐PBTV, poly(2,2′‐bis(trifluoromethyl)biphenyl‐alt‐2,5‐divinylthiophene), consisting of thienylenevinylene as the donor and trifluoromethyl‐substituted biphenyl as the acceptor has been successfully synthesized. CF₃‐PBTV shows solution‐processability without electrically insulating long alkyl side chains. Grazing incidence X‐ray diffraction results suggest a nearly equal population of flat‐on and end‐on domains in CF₃‐PBTV thin film. The excellent ambipolarity of CF₃‐PBTV is demonstrated by well‐equivalent charge mobilities of 0.065 and 0.078 cm² V^?1 s^?1 for p‐ and n‐channel, respectively. The organic field‐effect transistors (OFET) also shows very high on/off ratio (≈10⁷) which is attributed to the relatively large bandgap and low‐lying highest occupied molecular orbital (HOMO) of CF₃‐PBTV. The OFET performance barely changes after the device is stored in ambient conditions for 90 days. The ambient‐stability is attributed to the enhanced oxidative stability from its low‐lying HOMO and the better moisture resistance from its fluorine contents. The performance of CF₃‐PBTV based OFET is annealing independent. It is noteworthy that the solution‐processable, ambipolar, and thienylenevinylene‐containing conjugated polymer without any long alkyl side chains is reported for the first time. And to the best of our knowledge, it is the first ambient‐stable, annealing‐free OFET with well‐equivalent ambipolarity.     

Cascaded Mirror Array: design and demonstration of low-cost light-weight digital scanning

Microsystem Technologies - A new digital scanning approach is proposed and its feasibility is demonstrated. The Cascaded Mirror Array applies an array of reflectors, with each reflector movable...