Electrochemical Behavior Assessment of Micro- and Nano-Grained Commercial Pure Titanium in H<Subscript>2</Subscript>SO<Subscript>4</Subscript> Solutions

In this study, the electrochemical behavior of commercial pure titanium with both coarse-grained (annealed sample with the average grain size of about 45 µm) and nano-grained microstructure was compared by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Mott-Schottky analysis. Nano-grained Ti, which typically has a grain size of about 90 nm, is successfully made by six-cycle accumulative roll-bonding process at room temperature. Potentiodynamic polarization plots and impedance measurements revealed that as a result of grain refinement, the passive behavior of the nano-grained sample was improved compared to that of annealed pure Ti in H₂SO₄ solutions. Mott-Schottky analysis indicated that the passive films behaved as n-type semiconductors in H₂SO₄ solutions and grain refinement did not change the semiconductor type of passive films. Also, Mott-Schottky analysis showed that the donor densities decreased as the grain size of the samples reduced. Finally, all electrochemical tests showed that the electrochemical behavior of the nano-grained sample was improved compared to that of annealed pure Ti, mainly due to the formation of thicker and less defective oxide film.     

3D characterisation of indentation induced sub-surface cracking in silicon nitride using FIB tomography

In this study, a combination of 3D FIB tomography and incremental surface polishing has been used to characterize cracking beneath 0.5 kg and 1 kg Vickers indentations on silicon nitride. It is shown that a half-penny cracking regime exists even for low indentation loads with c/a ratios < 2 indicating that the c/a ratio cannot reliably be used to predict sub-surface crack morphology. For the first time, the presence of deep lateral cracks interconnected with radial cracks was also observed surrounding indentations of low loads on silicon nitride, and it is likely that these could contribute to material removal via spalling.     

Combined Flow over Weir and under Gate

Problems related to sedimentation and deposition can be minimized by using a system where weirs and gates are combined. Given its applications, the hydraulics of simultaneous flow over weir and under gate, in particular, the determination of the stage–discharge relationship, is of interest. Although previous approaches have been based on regression or dimensional analysis, the current work describes a physically based approach. Models of sharp-edged weirs and gates with no lateral contraction are combined. To calibrate and validate the proposed model, experiments have been carried out in a laboratory flume applying different submergence conditions. It was found that the model is able to predict the stage–discharge relationship with reasonable accuracy.     

Multi-walled carbon nanotube/nanostructured zirconia composites: Outstanding mechanical properties in a wide range of temperature

Multi-walled carbon nanotube (MWCNT)/nanostructured zirconia composites with a homogenous distribution of different MWCNT quantities (ranging within 0.5-5 wt.%) were developed. By using Spark Plasma Sintering we succeeded in preserving the MWCNTs firmly attached to zirconia grains and in obtaining fully dense materials. Moreover, MWCNTs reduce grain growth and keep a nanosize structure. A significant improvement in room temperature fracture toughness and shear modulus as well as an enhanced creep performance at high temperature is reported for the first time in this type of materials. To support these interesting mechanical properties, high-resolution electron microscopy and mechanical loss measurements have been carried out. Toughening and creep hindering mechanisms are proposed. Moreover, an enhancement of the electrical conductivity up to 10 orders of magnitude is obtained with respect to the pure ceramics.     

Notes for Contributors /

Abstract

The aim of this study was to depict a framework for development of integrated intelligent human engineering environment in complex critical systems. Conventional health, safety and environment (HSE) are a widely used approach to enhance reliability and safety of complex systems. The integrated health, safety, environment and ergonomics management system (HSEE‐MS) is defined however as integration of conventional HSE with ergonomics.

To show the need for and superiority of HSEE over conventional HSE, a gas treatment company in Iran was studied. Evaluation of ergonomics was carried out by 195 male employees responding to questionnaires.

The integrated HSEE system introduces a unique, effective and systemic mechanism, which integrates the structure of the human and organizational systems with a conventional HSE system. It is utilized to enhance reliability, availability, maintainability and safety through the proposed integrated framework of this study.     

Computation of the autocovariances of stationary arma processes

Autoregressive-moving average (ARMA) models are often used for the purpose of forecasting a time series. As an aide to chosing a model, use is made of the autocorrelation function which is estimated from the data. If the only interest in the model is for forecasting purposes, then it is not necessary to compute the autocorrelation function associated with the chosen model. For this reason, a method for computation of the autocorrelation function is not usually included in the software used for identifying ARMA models. However, there are applications of ARMA models where it is important to compute the autocovariance function.

This paper contains an algorithm and a listing of a FORTRAN program which computes the autocovariance directly from the solution to the difference equations which govern its behavior.     

Characterisation of spray‐dried microparticles containing iron coated by pectin/resistant starch

Iron is one of three major minerals in human body. However, the iron deficiency is a medical problem in developed and underdeveloped countries due to its poor oral absorption or insufficient iron intake. Encapsulation could solve problems associated with oral iron consumption. Various advantages including low cost, biodegradability, biocompatibility and large‐scale production have been included in the current study. In a modified encapsulation method, iron microparticles were prepared using low methoxy pectin and resistant starch during spray drying. Covalent and hydrogen bonds were formed between iron and pectin and between polymers, respectively. Particles sized 3.5 ± 1.14 μm and showed spherical shapes. The yield of particles was 72.07%, and solubility and loading efficiency were 33.64% ± 0.88 and 34.79%, respectively. In conclusion, using iron as a cross‐linker of pectin molecules resulted in microparticles with appropriate properties of lowering organoleptic changes and a better bioavailability especially in dairy‐based products for food fortification.