Energy-Efficient Clustering Mechanism of Routing Protocol for Heterogeneous Wireless Sensor Network Based on Bamboo Forest Growth Optimizer

In wireless sensor networks (WSN), most sensor nodes are powered by batteries with limited power, meaning the quality of the network may deteriorate at any time. Therefore, to reduce the energy consumption of sensor nodes and extend the lifetime of the network, this study proposes a novel energy-efficient clustering mechanism of a routing protocol. First, a novel metaheuristic algorithm is proposed, based on differential equations of bamboo growth and the Gaussian mixture model, called the bamboo growth optimizer (BFGO). Second, based on the BFGO algorithm, a clustering mechanism of a routing protocol (BFGO-C) is proposed, in which the encoding method and fitness function are redesigned. It can maximize the energy efficiency and minimize the transmission distance. In addition, heterogeneous nodes are added to the WSN to distinguish tasks among nodes and extend the lifetime of the network. Finally, this paper compares the proposed BFGO-C with three classic clustering protocols. The results show that the protocol based on the BFGO-C can be successfully applied to the clustering routing protocol and can effectively reduce energy consumption and enhance network performance.     

New possibilities for materials science with STED microscopy

Up to now, STED microscopy has been mainly used to study biological systems. However with the development of the technique, many benefits are expected in materials science for imaging 1D, 2D or 3D nanomaterials. We review here the use of STED microscopy in materials science, its challenges, and opportunities.     

Radiation forces of a dielectric medium plate induced by a Gaussian beam

Based on the angular spectrum method, we investigate the radiation forces on a finite-size dielectric medium plate induced by a Gaussian beam. The formulas for the radiation force along longitudinal and transverse direction are derived, and numerically calculation is performed. It is shown that for the finite-size dielectric medium plate, the radiation forces exerted by the Gaussian beam is dependent upon the angle and position of a single ray striking on the plate and the intensity of light. Our numerical results indicate that if we choose the appropriate parameters there will be enough transverse forces to overcome the gravity force, making the plate move upwards.     

First-principles study of intrinsic defect properties in hexagonal BN bilayer and monolayer

The formation energies and transition energy levels of intrinsic defects in hexagonal BN (h-BN) bilayer and monolayer have been studied by first-principles calculations based on density functional theory. Our calculated results predict that excellent intrinsic p-type and n-type conductivities are very difficult to be realized in h-BN bilayer and monolayer. This is because of the high formation energies of acceptor-like defects (≥4.6 eV ) and the rather deep transition energy levels of donor-like defects (≥2.0 eV ). In order to obtain h-BN layers with more efficient p-type and n-type conductivity, extrinsic doping using foreign impurities is necessary.     

Non-negative infrared patch-image model: Robust target-background separation via partial sum minimization of singular values

To further enhance the small targets and suppress the heavy clutters simultaneously, a robust non-negative infrared patch-image model via partial sum minimization of singular values is proposed. First, the intrinsic reason behind the undesirable performance of the state-of-the-art infrared patch-image (IPI) model when facing extremely complex backgrounds is analyzed. We point out that it lies in the mismatching of IPI model’s implicit assumption of a large number of observations with the reality of deficient observations of strong edges. To fix this problem, instead of the nuclear norm, we adopt the partial sum of singular values to constrain the low-rank background patch-image, which could provide a more accurate background estimation and almost eliminate all the salient residuals in the decomposed target image. In addition, considering the fact that the infrared small target is always brighter than its adjacent background, we propose an additional non-negative constraint to the sparse target patch-image, which could not only wipe off more undesirable components ulteriorly but also accelerate the convergence rate. Finally, an algorithm based on inexact augmented Lagrange multiplier method is developed to solve the proposed model. A large number of experiments are conducted demonstrating that the proposed model has a significant improvement over the other nine competitive methods in terms of both clutter suppressing performance and convergence rate.     

Van der Waals Effects on semiconductor clusters

Van der Waals (vdW) interactions play an important role on semiconductors in nanoscale. Here, we utilized first‐principles calculations based on density functional theory to demonstrate the growth mode transition from prolate to multiunit configurations for Ge_n (n = 10–50) clusters. In agreement with the injected ion drift tube techniques that “clusters with n < 70 can be thought of as loosely bound assemblies of small strongly bound fragments (such as Ge₇ and Ge₁₀),” we found these stable fragments are connected by Ge₆, Ge₉, or Ge₁₀ unit (from bulk diamond), via strong covalent bonds. Our calculated cations usually fragment to Ge₇ and Ge₁₀ clusters, in accordance with the experiment results that the spectra Ge₇ and Ge₁₀ correspond to the mass abundance spectra. By controlling a germanium cluster with vdW interactions parameters in the program or not, we found that the vdW effects strengthen the covalent bond from different units more strikingly than that in a single unit. With more bonds between units than the threadlike structures, the multiunit structures have larger vdW energies, explaining why the isolated nanowires are harder to produce. © 2015 Wiley Periodicals, Inc.     

Promotion of photocatalytic steam reforming of methane over Ag~0/Ag~+-SrTiO_3

Methane(CH_4) is not only used as a fuel but also as a promising clean energy source for hydrogen generation.The steam reforming of CH4(SRM) using photocatalysts can realize the production of syngas(CO+H_2) with low energy consumption.In this work,Ag~0/Ag~+-loaded SrTi03 nanocomposites were successfully prepared through a photodeposition method.When the loading amount of Ag is 0.5 mol%,the atom ratio of Ag~+ to Ag~0 was found to be 51:49.In this case,a synergistic effect of Ago and Ag~+ was observed,in which Ago was proposed to improve the adsorption of H_2 O to produce hydroxyl radicals and enhance the utilization of light energy as well as the separation of charge carriers.Meanwhile,Ag~0 was regarded as the reduction reaction site with the function of an electron trapping agent.In addition,Ag~+adsorbed the CH4 molecules and acted as the oxidation reaction sites in the process of photocatalytic SRM to further promote electron-hole separation.As a result,0.5 mol% Ag-SrTi03 exhibited enhancement of photocatalytic activity for SRM with the highest CO production rate of 4.3 μmol g~(-1) h~(-1),which is ca.5 times higher than that of pure SrTi03.This work provides a facile route to fabricate nanocomposite with cocatalyst featuring different functions in promoting photocatalytic activity for SRM.