Evidence of nano-galvanic couple formation on in-situ formed nano-aluminum amalgam surfaces for passivation-bypassed water splitting

Reaction of Al metal with water is a well-known technique for large scale production of hydrogen. However, this method suffers from kinetic limitations due to formation of a passivation layer on Al, preventing optimal operations. Using high resolution Scanning Kelvin Probe Force Microscopy (SKPFM), we show the origin of formation of 'nano-galvanic couple' on in situ formed nano-aluminum amalgam surfaces in a water splitting system; passivation based limitations are completely bypassed in this approach. Furthermore, they offer an opportunity to beneficiate and recover mercury in contaminated water. The nano-galvanic corrosion due to substantial lateral variation in surface contact potential is responsible for the observed high throughput of hydrogen production (720 mL/min per 0.5 g Al salt). It may be noted that this process fares better than in situ prepared nano-Al based hydrogen production, wherein 600 mL/min of hydrogen is obtained for 0.5 g Al salt. Investigations using Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) provide evidence for passivation-bypassed hydrolysis and favourable kinetics for in situ derived nano-AlHg hydrolytic agents (when compared to nano-Al). This study, to the best of our knowledge, reports the first direct proof of nano-galvanic couple formation on in-situ prepared nanoaluminum amalgam surface; paving a direct way to overcome the long standing passivation problem in Al hydrolysis. It is found that the hydrogen production rate and standard deviation (SD) of the contact potential of nanoaluminum amalgam are directly related to the rate of addition of the reducing agent, offering an opportunity for kinetic control for the in situ hydrolytic process.     

Adaptive force–environment estimator for manipulators based on adaptive wavelet neural network

This study focuses on the accurate tracking control and sensorless estimation of external force disturbances on robot manipulators. The proposed approach is based on an adaptive Wavelet Neural Network (WNN), named Adaptive Force-Environment Estimator (WNN-AFEE). Unlike disturbance observers, WNN_AFEE does not require the inverse of the Jacobian transpose for computing the force, thus, it has no computational problem near singular points. In this scheme, WNN estimates the external force disturbance to attenuate its effects on the control system performance by estimating the environment model. A Lyapunov based design is presented to determine adaptive laws for tuning WNN parameters. Another advantage of the proposed approach is that it can estimate the force even when there are some parametric uncertainties in the robot model, because an additional adaptive law is designed to estimate the robot parameters. In a theorem, the stability of the closed loop system is proved and a general condition is presented for identifying the force and robot parameters. Some suggestions are provided for improving the estimation and control performance. Then, a WNN-AFEE is designed for a planar manipulator as an example, and some simulations are performed for different conditions. WNN_AFEE results are compared attentively with the results of an adaptive force estimator and a disturbance estimator. These comparisons show the efficiency of the proposed controller in dealing with different conditions.     

The dynamic effect of Micro-MHD convection on bubble grown at a horizontal microelectrode

Relatively low efficiency is the biggest obstacle to the popularization of water electrolysis, which is a particularly feasible way to produce super-pure hydrogen. Imposing a magnetic field can increase the hydrogen production efficiency of water electrolysis. However, the enhancement's detailed mechanism still lacks an insightful understanding of the bubbles' micro vicinity. Our recent work aims to understand why the micro-magnetohydrodynamic (MHD) convection hinders single bubbles' detachment on the microelectrode. A water electrolysis experiment by microelectrode is performed under an electrode-normal magnetic field, and dynamic analysis of the single bubble growing on microelectrodes is performed. The variation of bubble diameter with time in the presence or absence of the magnetic field was measured, and the forces acting on the bubble were quantified. The result shows that the micro-MHD convection, induced by Lorentz force, can give rise to a downward hydrodynamic pressure force that will not appear in large-scale MHD convection. This force can be of the same magnitude as the surface tension, so it dramatically hinders bubbles' detachment. Besides, the Kelvin force provides a new potential way for further improving the efficiency of water electrolysis.     

Experimental investigation of the effects of contraction on tsunami-induced forces and pressures on a box section bridge

Many bridges that lie within possible tsunami inundation zones are critical links in transport networks. Some efforts have been made to determine the effects of tsunamis on bridges, but only a limited range of published design guidelines are available. Therefore, it is necessary to further investigate the effects of tsunamis on bridges. In the current study, physical modeling experiments were carried out to measure bore impact forces and pressures for various tsunami bore strengths on a bridge deck with different abutment types (wing wall and spill-through) and different opening and submergence ratios. The experiments were conducted in a wave flume with dimensions of 14 × 1.2 × 0.8 m (length × width × height), equipped with an automatic gate designed to generate a tsunami bore. The horizontal and vertical forces showed an increasing trend with increasing submergence ratio for both types of abutment. However, the horizontal force showed a decreasing trend as the opening ratio decreased, while the vertical force initially increased as the opening ratio decreased, until it reached a peak value, and then it started to decrease. The overall shapes of the results for both types of abutment are similar, with higher values for spill-through abutments due to their lower energy dissipation rates. Based on the experimental data, empirical equations are proposed for estimation of tsunami loads as a function of opening and submergence ratios.     

Structural analysis of greenhouses: A case study in Turkey

This study was carried out to determine the structural and functional characteristics of the greenhouses in greenhouse enterprises of Turkey. Greenhouse enterprises are widely common along the Marmara, Aegean and Mediterranean cost lines. Marmara region was selected as the study area since it is the pioneering region and has large areas allocated to greenhouses, and has various greenhouse types. Information about greenhouse types, material properties, placement, and arrangement of greenhouses in the study area was gathered by a questionnaire; then greenhouses in enterprises were divided into groups based on cover material, load bearing materials and directional placement. A total of four types of greenhouse with the most economic cross-section, one from each group, were selected and load acting on structural members of greenhouses were calculated. Loads acting on beams of each greenhouse were analysed by Force Method and Moment Distribution Method. The results obtained were compared statistically to determine the best methodology for structural analysis of greenhouses. As a result, no statistical difference was found between moments and shear forces obtained from both methods. However, a difference occurred based on greenhouse types and it was determined that the values obtained for trussed block greenhouse were higher than the other ones.     

形式追随函数 ——数字模拟生物细胞镶嵌形态法则的仿生建筑形体生成

本文通过观察生物的细胞镶嵌形 态,发现其形成的法则——正十四面体镶 嵌,并通过数字技术予以模拟,生成数字仿 生建筑形体,并将其与对应的另一十四面体 与十二面体镶嵌的传统建筑形体分别进行结 构受力分析,通过数据明确指出仿生建筑形 体在结构和实际建造方面的优势和不足。     

Energiedissipation und Energieflüsse während des Tablettiervorganges

The tableting process causes a temperature increase due to dissipation of energy. Therefore, with time the temperature of the tablets and the tablet press increases. Depending on the calculated tablet temperature, this temperature increase is discussed for different compression forces and lubricant concentrations. Two different measurement techniques are presented and compared.