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Aiming at the problem that the localization algorithm based on received signal strength indication is difficult to dynamically track the parameter change in the complex environment of coal mines. In order to improve the accuracy of the mine personnel positioning, this paper proposes a method to use the improved gravitational search algorithm to position the underground personnel in the weighted centroid positioning. Utilizing the long distance path loss model got the distance between the beacon nodes and unknown nodes, and then through the weighted centroid localization algorithm performed the unknown node positioning. Finally, the improved GSA-PSO optimized the preliminary location results and parameters. Experimental results show the proposed method can improve both the positioning accuracy effectively and the adaptive ability of changeful environment.

Abstract. The method of mapping function was first proposed by Henrick et al. [J. Comput. Phys. 207:542-547 (2005)] to adjust nonlinear weights in [0,1] for the fifth order WENO scheme, and through which the requirement of convergence order is satisfied and the performance of the scheme is improved. Different from Henrick’s method, a concept of piecewise polynomial function is proposed in this study and corresponding WENO schemes are obtained. The advantage of the new method is that the function can have a gentle profile at the location of the linear weight (or the mapped nonlinear weight can be close to its linear counterpart), and therefore is favorable for the resolution enhancement. Besides, the function also has the flexibility of quick convergence to identity mapping near two endpoints of [0,1], which is favorable for improved numerical stability. The fourth-, fifth- and sixth-order polynomial functions are constructed correspondingly with different emphasis on aforementioned flatness and convergence. Among them, the fifth-order version has the flattest profile. To check the performance of the methods, the 1-D Shu-Osher problem, the 2-D Riemann problem and the double Mach reflection are tested with the comparison of WENO-M, WENO-Z and WENO-NS. The proposed new methods show the best resolution for describing shear-layer instability of the Riemann problem, and they also indicate high resolution in computations of double Mach reflection, where only these proposed schemes successfully resolved the vortex-pairing phenomenon. Other investigations have shown that the single polynomial mapping function has no advantage over the proposed piecewise one, and it is of no evident benefit to use the proposed method for the symmetric fifth-order WENO. Overall, the fifth-order piecewise polynomial and corresponding WENO scheme are suggested for resolution improvement.

The paper presents a new single-port robotic manipulator system (SiromanS) for brain tumor removal surgery. SiromanS is designed to minimize the size of surgical incisions compared to those needed for existing brain tumor removal surgeries. SiromanS consists of two robotic arms, a stereo-endoscope with a light source, and a cylindrical insertion part to house the arms and the endoscope. The stereo-endoscope is used to provide a 3D view of the surgical site to surgeons. The insertion part possesses three channels, through which the two robotic arms and the stereo-endoscope are integrated into SiromanS. One robotic arm of SiromanS has a gripper end-effector and the other has a suction end-effector to remove the brain tumor. This paper presents the robotic arm controlled by a wire-driven mechanism for distal dexterous motion and its miniaturization, and illustrates an actuating module that is separable from the robotic arm for sterilization and tool exchange. The forward/inverse kinematics analysis is also presented. A series of experimental results show that SiromanS’ performance capabilities are promising for brain surgery applications.

In studies on instabilities of flowfield in rotating detonation, one of the most common concerns is the instability at the slip line originating from the conjunction of the detonation wave and oblique shock. Using Euler equations associated with 7-species-and-8-reaction finite-rate chemical reaction model of hydrogen/air mixtures, further studies are performed to simulate the 2-D rotating detonation, and the flow mechanism of instability at the slip line is investigated in depth. The results show that the distinct wake profile exists at the slip line, which is different from the typical mixing layer. Analysis indicates that the generation of wake is caused by the transition shock between the detonation wave and oblique shock. Because of the wake profile, the vorticity distribution therein appears in a double-layer layout, and different evolution exist in different vorticity layers. Based on the velocity profile across the slip line, the analysis by the linear stability theory is made, and two unstable modes which have different shape profiles and phase velocities are found. Discrete Fourier transformation is utilized to analyze the numerical results, and similar shape profiles are obtained. A general coincidence in velocity of vortex movement is also attained between the theoretical predictions and simulations. Investigations show that the wake instability is responsible for the unstable mechanism, and corresponding unstable structures differs from the canonical ones in typical mixing layers.

Air-stable atomically thick copper nanosheets are prepared and used for selective electrochemical reduction of CO2 into CO., The electrochemical conversion of CO2 and H2O into syngas using renewably generated electricity is an attractive approach to simultaneously achieve chemical fixation of CO2 and storage of renewable energy. Developing cost-effective catalysts for selective electroreduction of CO2 into CO is essential to the practical applications of the approach. We report a simple synthetic strategy for the preparation of ultrathin Cu/Ni(OH)2 nanosheets as an excellent cost-effective catalyst for the electrochemical conversion of CO2 and H2O into tunable syngas under low overpotentials. These hybrid nanosheets with Cu(0)-enriched surface behave like noble metal nanocatalysts in both air stability and catalysis. Uniquely, Cu(0) within the nanosheets is stable against air oxidation for months because of the presence of formate on their surface. With the presence of atomically thick ultrastable Cu nanosheets, the hybrid Cu/Ni(OH)2 nanosheets display both excellent activity and selectivity in the electroreduction of CO2 to CO. At a low overpotential of 0.39 V, the nanosheets provide a current density of 4.3 mA/cm2 with a CO faradaic efficiency of 92%. No decay in the current is observed for more than 22 hours. The catalysts developed in this work are promising for building low-cost CO2 electrolyzers to produce CO.

The largest Ln-Fe metal cluster [Gd

Since the first introduction of the weighted essentially non-oscillatory (WENO) scheme in [1], the efficient implementation in [2] made the algorithm applicable to realistic problems. Despite the success, some analytic outcomes of the scheme were still called in question. It were Henrick et al. [3] who first pointed out that WENO5 failed to pertain the fifth-order accuracy at the critical point where f′ j = 0. They further proposed the necessary and sufficient conditions for a scheme to obtain the order. In order to provide remedies for WENO5, Henrick et al. [3] proposed a carefully designed mapping function, through which the difference between the nonlinear weight and its linear counterpart will usually have the order of Δx3. The corresponding scheme was called as WENO-M, and the improvement on resolution was shown through the comparison with WENO5.

A versatile system combining chemotherapy with photothermal therapy for cancer cells using Pd nanosheet-covered hollow mesoporous silica nanoparticles is reported. While the hollow mesoporous silica core can be used to load anticancer drugs (i.e., doxorubicin) for chemotherapy, the Pd nanosheets on the surface of particles can convert NIR light into heat for photothermal therapy. More importantly, the loading of Pd nanosheets on hollow mesoporous silica nanospheres can dramatically increase the amount of cellular internalization of the Pd nanosheets: almost 11 times higher than the unloaded Pd nanosheets. The as-prepared nanocomposites efficiently deliver both drugs and heat to cancer cells to improve the therapeutic efficiency with minimal side effects. Compared with chemotherapy or photothermal therapy alone, the combination of chemotherapy and phototherapy can significantly improve the therapeutic efficacy, exhibiting a synergistic effect.

The design and synthesis of hollow/yolk-shell mesoporous structures with catalytically active ordered mesoporous shells can infuse new vitality into the applications of these attractive structures. In this study, we report that hollow/yolk-shell structures with catalytically active ordered mesoporous aluminosilica shells can be easily prepared by using silica spheres as the silica precursors. By simply treating with a hot alkaline solution in the presence of sodium aluminate (NaAlO(2)) and cetyltrimethylammonium bromide (CTAB), solid silica spheres can be directly converted into high-quality hollow mesoporous aluminosilica spheres with perpendicular pore channels. On the basis of the proposed formation mechanism of etching followed by co-assembly, the synthesis strategy developed in this work can be extended as a general strategy to prepare ordered mesoporous yolk-shell structures with diverse compositions and morphologies simply by replacing solid silica spheres with silica-coated nanocomposites. The reduction of 4-nitrophenol with yolk-shell structured Au@ordered mesoporous aluminosilica as the catalyst has clearly demonstrated that the highly permeable perpendicular pore channels of mesoporous aluminosilica can effectively prevent the catalytically active yolk from aggregating. Furthermore, with accessible acidity, the yolk-shell structured ordered mesoporous aluminosilica spheres containing Pd yolk exhibit high catalytic activity and recyclability in a one-pot two-step synthesis involving an acid catalysis and subsequent catalytic hydrogenation for desired benzimidazole derivative, which makes the proposed hollow ordered aluminosilica spheres a versatile and practicable scaffold for advanced catalytic nanoreactor systems.

Lightly dispersed palladium Catalysts made from atomically dispersed metal atoms on oxide supports can exhibit very high per atom activity. However, the low loadings needed to prevent metal particle formation can limit overall performance. Liu et al. stably decorated titanium oxide nanosheets with relatively high loadings of single palladium atoms by reducing the ions with ultraviolet light and ethylene glycol. These catalysts cleaved H 2 into atoms and were highly effective for hydrogenating alkenes and aldehydes. Science , this issue p. 797

通讯作者地址: Zheng, NF (通讯作者) Xiamen Univ, State Key Lab Phys Chem Solid Surfaces, Collaborat Innovat Ctr Chem Energy Mat, Xiamen 361005, Peoples R China.

Green tea dietary supplements (GTDS) are the fourth most popular dietary supplement (DS) in the US. However, taken in excess, they have been shown to result in liver damage. The Dietary Supplement Health and Education Act (DSHEA) of 1994 designated dietary supplements as foods and charged the FDA to regulate their manufacturing. More recently, Current Good Manufacturing Practices (cGMP) and Standard Reference Materials (SRMs) have been developed. In this chapter, we summarize the DSHEA and related regulations, discuss some of the health benefits and concerns related to GTDS, as well as review the literature regarding their analysis. The literature suggests that the amount and type of catechins vary widely in GTDS from manufacturer to manufacturer, and batch to batch from the same manufacturer. In addition, some GTDS do not have catechins present, and the amount of catechins and caffeine in the GTDS often differs greatly from manufacturers’ claims.

Firstly we propose a theoretical method to increase the speed-up ratio in parallel test generation based on fault partitioning. Based on this method, a new fault partitioning approach-Backward Fault Partitioning based on Output fan-in Cones (BFPOC)-is presented which combines the relevant fault identification and shortest path sensitization. In addition, BFPOC is compared via experiments with the approach of Toward Fault Partitioning based on Input fan-out Cones (TFPIC) proposed by Bannerjee (1994) and the widely used method-Equal Distance Partitioning of Fault Sequence (EDPFS) respectively. The results show that in a large-scale parallel processing environment, BFPOC can obtain higher speed-up ratio than the other two approaches.

Hollow mesoporous silica spheres have recently attracted increasing attention. However, effective synthesis of uniform hollow mesoporous spheres with controllable well-defined pore structures for fundamental research and practical applications has remained a significant challenge. In this work, a straightforward and effective "cationic surfactant assisted selective etching" synthetic strategy was developed for the preparation of high-quality hollow mesoporous silica spheres with either wormhole-like or oriented mesoporous shell. The as-prepared hollow mesoporous silica spheres have large surface area, high pore volume, and controllable structure parameters. Our experiments demonstrated that cationic surfactant plays critical roles in forming the hollow mesoporous structure. A formation mechanism involving the etching of solid SiO(2) accelerated by cationic surfactant followed by the redeposition of dissolved silica species directed by cationic surfactant is proposed. Furthermore, the strategy can be extended as a general strategy to transform silica-coated composite materials into yolk-shell structures with either wormhole-like or oriented mesoporous shell.