Chemical Design of Palladium‐Based Nanoarchitectures for Catalytic Applications

Palladium (Pd) plays an important role in numerous catalytic reactions, such as methanol and ethanol oxidation, oxygen reduction, hydrogenation, coupling reactions, and carbon monoxide oxidation. Creating Pd‐based nanoarchitectures with increased active surface sites, higher density of low‐coordinated atoms, and maximized surface coverage for the reactants is important. To address the limitations of pure Pd, various Pd‐based nanoarchitectures, including alloys, intermetallics, and supported Pd nanomaterials, have been fabricated by combining Pd with other elements with similar or higher catalytic activity for many catalytic reactions. Herein, recent advances in the preparation of Pd‐based nanoarchitectures through solution‐phase chemical reduction and electrochemical deposition methods are summarized. Finally, the trend and future outlook in the development of Pd nanocatalysts toward practical catalytic applications are discussed.     

Cell responses to physical forces,and how they inform the design of tissue-engineered constructs for bone repair: a review

The fields of biomaterials and bone tissue engineering continue to grow, due in part to new advances in materials science but also to the increasingly broad understanding of how the human body responds to implanted materials. For a long time the goal of the biomaterials scientist was to develop materials that supported healing and were biocompatible, but over time a better understanding of how the body responds to implanted materials has been achieved. The concept of mechanotransduction, which involves mechanical forces applied to the cell, the conversion of those forces into a biochemical signal, the transmission of signals to cells, and the resulting cell response, has blossomed over the past 20 years or so. Here we review how cells, specifically those of the skeletal system, respond to different types of physical forces, how these responses manifest themselves as changes and adaptations within the skeletal system, and how investigators go about evaluating these responses in the laboratory. We also review how these approaches and lessons learned inform the development of novel strategies for bone tissue engineering, toward healing bone defects with biomaterials.     

Optimisation of cutting parameters for minimizing carbon emission and maximising cutting quality in turning process

Modern manufacturing systems are faced with the challenge of reducing the carbon emission related to manufacturing technologies. Machining centres consume large amounts of energy and as a consequence; carbon emissions are generated owing to this consumption. This paper presents a design of experiment work related to the optimisation of machining factors in the turning process of aluminium alloys. Carbon emission and surface quality were concurrently optimised. A set of experimental scenarios was set using a Box–Behnken design and the response surface methodology was applied to get the regression model for the carbon emission and surface roughness during turning process. The relationship between factors and the responses (carbon emission and surface quality) was investigated using surface plots. Furthermore, the desirability function method using the Response Optimizer tool in MINITAB and goal programming methodology was used to obtain the values of the parameters that achieved minimum surface roughness and a minimum quantity of carbon emission.     

Scattering of waves by a soft–hard half-plane between isorefractive medium

The scattering of plane waves by a soft–hard half-plane residing between isorefractive medium is studied. The scattered geometrical optics fields are obtained by subtracting the initial geometrical optics fields from the total geometrical optics waves. The diffracted fields are determined by considering the structure of the scattered geometrical optics waves. The uniform expressions for the diffracted fields are derived. The behaviour of the total waves is investigated numerically.     

矿井水过流表面超疏水涂层的制备及其阻垢机理研究

在矿井水淡化过程中,因其水质的硬度较高,导致设备、管道表面结垢,影响制水的效率,提高制水成本.通过喷涂法在不锈钢316基体表面制备超疏水涂层,开展CaCO3结垢对比试验研究,通过扫描电镜(SEM)、X射线衍射仪(XRD)分析样品表面的结垢物成分,发现无超疏水涂层表面CaCO3的形态为少量菱形晶体与典型的方解石,有超疏水涂层的316不锈钢表面的形态为针状和花状文石,质地松软;并首次通过成核理论,分析超疏水涂层的阻垢机理,确定超疏水涂层的成核功;同时研究温度、流速对CaCO3结垢性能的影响,开展动态、静态对比试验发现,当流速一定时,温度越高CaCO3结垢速率越大,当温度一定时,流速越大CaCO3结垢速率越小.该方法在矿井水过流表面的阻垢、自清洁方面展现出了良好的应用前景.     

Grey and black optical solitary waves,and modulation instability analysis to the perturbed nonlinear Schrödinger equation with Kerr law nonlinearity

This paper addresses the nonlinear Schrödinger equation (NLSE) with Kerr law nonlinearity and perturbation terms in optical fibre. A class of grey and black optical solitary wave solutions of this equation are retrieved by adopting an appropriate solitary wave ansatz solution. These types of solitary waves play a vital role in understanding various physical phenomena in nonlinear systems. This lead to a constraint condition on the solitary wave parameters which must hold for the solitary waves to exist. Moreover, the modulation instability (MI) analysis of the model is studied by employing the concept of linear-stability analysis (LSA) and the MI gain spectrum is got. Physical interpretations of the acquired results are demonstrated. It is hoped that the results reported in this paper can enrich the nonlinear dynamical behaviours of the equation.     

A Laser-Induced Mo2CTx MXene Hybrid Anode for High-Performance Li-Ion Batteries

MXenes, a fast-growing family of two-dimensional (2D) transition metal carbides/nitrides, are promising for electronics and energy storage applications. Mo₂CT_x MXene, in particular, has demonstrated a higher capacity than other MXenes as an anode for Li-ion batteries. Yet, such enhanced capacity is accompanied by slow kinetics and poor cycling stability. Herein, it is revealed that the unstable cycling performance of Mo₂CT_x is attributed to the partial oxidation into MoO_x with structural degradation. A laser-induced Mo₂CT_x/Mo₂C (LS-Mo₂CT_x) hybrid anode has been developed, of which the Mo₂C nanodots boost redox kinetics, and the laser-reduced oxygen content prevents the structural degradation caused by oxidation. Meanwhile, the strong connections between the laser-induced Mo₂C nanodots and Mo₂CT_x nanosheets enhance conductivity and stabilize the structure during charge–discharge cycling. The as-prepared LS-Mo₂CT_x anode exhibits an enhanced capacity of 340 mAh g⁻¹ vs 83 mAh g⁻¹ (for pristine) and an improved cycling stability (capacity retention of 106.2% vs 80.6% for pristine) over 1000 cycles. The laser-induced synthesis approach underlines the potential of MXene-based hybrid materials for high-performance energy storage applications.     

Backstepping approach for design of PID controller with guaranteed performance for micro-air UAV

Flight controllers for micro-air UAVs are generally designed using proportional-integral-derivative (PID) methods, where the tuning of gains is difficult and time-consuming, and performance is not guaranteed. In this paper, we develop a rigorous method based on the sliding mode analysis and nonlinear backstepping to design a PID controller with guaranteed performance. This technique provides the structure and gains for the PID controller, such that a robust and fast response of the UAV (unmanned aerial vehicle) for trajectory tracking is achieved. First, the second-order sliding variable errors are used in a rigorous nonlinear backstepping design to obtain guaranteed performance for the nonlinear UAV dynamics. Then, using a small angle approximation and rigorous geometric manipulations, this nonlinear design is converted into a PID controller whose structure is naturally determined through the backstepping procedure. PID gains that guarantee robust UAV performance are finally computed from the sliding mode gains and from stabilizing gains for tracking error dynamics. We prove that the desired Euler angles of the inner attitude controller loop are related to the dynamics of the outer backstepping tracker loop by inverse kinematics, which provides a seamless connection with existing built-in UAV attitude controllers. We implement the proposed method on actual UAV, and experimental flight tests prove the validity of these algorithms. It is seen that our PID design procedure yields tighter UAV performance than an existing popular PID control technique.     

Synthesis of a side chain liquid crystalline polycarbonate with a chiral backbone

We report the experimental demonstration of a novel and environmentally benign supercritical carbon dioxide (ScCO₂) technique that yields an optically active, side chain liquid crystalline polycarbonate in a single‐step reaction. The obtained polymer is worthwhile, since it is highly stereoregular and can find applications in an enlarged mesomorphic temperature range compared to its acrylic analogues. The synthesized materials were characterized by IR, ¹H‐NMR, and ¹³C‐NMR, while the thermal properties were measured by DSC. Polarized optical micrograph and wide angle X‐ray diffraction were used for the mesogenic property characterization of the copolymer. The transfer chirality from the backbone to the mesophase is demonstrated on the optical microscopy textures. Being consistent with the ¹³C‐NMR, X‐ray implies an ordered polymeric structure. The DSC analysis of the copolymer indicates that the T_i (the clearing point temperature) value does not change dramatically, whereas a pronounced decrease in T_g (the glass transition temperature) value is observed from that of its acrylic analogues. Hence, the obtained polymer exhibits another practical benefit by widening the mesomorphic temperature range. This study is the insightful combination of material processing and chemical design that elucidates the advantages of ScCO₂ application, in terms of liquid crystallinity and the tacticity of the obtained polymer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1915–1921, 2006