Design and commissioning of a high magnetic field muon spin relaxation spectrometer at the ISIS pulsed neutron and muon source

The high magnetic field (HiFi) muon instrument at the ISIS pulsed neutron and muon source is a state-of-the-art spectrometer designed to provide applied magnetic fields up to 5 T for muon studies of condensed matter and molecular systems. The spectrometer is optimised for time-differential muon spin relaxation studies at a pulsed muon source. We describe the challenges involved in its design and construction, detailing, in particular, the magnet and detector performance. Commissioning experiments have been conducted and the results are presented to demonstrate the scientific capabilities of the new instrument.     

Electron beam melting of gamma titanium aluminide and investigating the effect of EBM layer orientation on milling performance

Electron beam melting (EBM) is one of the growing processes of additive manufacturing technology (AMT) to fabricate 3D parts from various difficult-to-process materials such as titanium alloys. A major limitation of the EBM process is the poor surface finish of the produced parts which ultimately demands a subsequent subtractive method (secondary finishing operation) to improve the surface finish for shaping the part to be fit for-end use applications where high surface finish is commonly required. With respect to the EBM layer build direction, the fabricated part has different orientations with varying surface characteristics. Therefore, in order to perform secondary finishing operation (e.g., milling) there are different choices of EBM part orientation to select the direction of tool feed. In this research, 3D parts of titanium alloy (gamma titanium aluminide; γ-TiAl) are additively manufactured through EBM process. The effect of EBM layer/part orientation on the milling performance is further investigated in terms of surface finish improvement and edge chipping evaluation. It has been observed that the EBM layer/part orientation with respect to milling tool feed direction (TFD) plays a vital role in milling performance. Thus, a care must be taken to select the appropriate tool feed direction and layer/part orientation in order to achieve maximum surface finish with minimum edge chipping. The results revealed the vertical milling can be adopted as a secondary finishing operation to be performed on EBM produced parts of γ-TiAl and it allows to significantly improve the poor surface finish generated by EBM (R_a 31 μm). Furthermore, among the available part orientation choices, the part orientation in which the milling tool is fed across the EBM layer build direction is the best orientation resulting into high surface finish (R_a 0.12 μm) with relatively smooth edges (minimum chipping-off).     

A Novel Model for Predicting the Dense Phase Behavior of 3D Gas‐Solid Fluidized Beds

A novel phenomenological discrete bubble model was developed and tested for prediction of the hydrodynamic behavior of the dense phase of a 3D gas‐solid cylindrical fluidized bed. The mirror image technique was applied to take into account the effects of the bed wall. The simulation results were validated against experimental data reported in the literature that were obtained by positron emission particle tracking. The time‐averaged velocity profiles of particles predicted by the developed model were found to agree well with experimental data. The initial bubble diameter had no significant influence on the time‐averaged circulating pattern of solids in the bed. The model predictions clearly indicate that the developed model can fairly predict the hydrodynamic behavior of the dense phase of 3D gas‐solid cylindrical fluidized beds.     

Single drop behaviour in a high shear granulator

The wet granulation process starts when a liquid drop makes contact with the powder bed. In a powder bed, drops are subjected to centripetal and gravitational forces. These forces may affect the size and shape of the drop as it is incorporated into the bed. The majority of experiments studying droplet behaviour have been performed on static bed surfaces. This paper seeks to demonstrate droplet behaviour during the initial contact stage with a dynamic powder bed representative of that occurring during high shear granulation. Particle image velocimetry (PIV) is used to determine droplet and powder bed surface velocities. Due to inclination of powder bed part of drop de-accelerate slowly moved downward while other parts remain attached to powder bed this result in their deformation and breakage. Amount of deformation of drop and span of area where it occurred was increased as drop was added farther from the outer edge of the mixer. This paper shows that the binder drop may deform or break in high shear granulator depending on its initial impact position. This will affect size distribution and other properties of nuclei.     

Assessment and Characterization of Welded Mild Steel (E-6013) Using Ultrasonic Testing and Hilbert Huang Transform

Russian Journal of Nondestructive Testing - All welded parts undergo aging once operated at elevated temperatures. Exposures of structures on elevated temperatures adversely affect the material...     

Prediction of the self-diffusion coefficients in aqueous KCl solution using molecular dynamics: A comparative study of two force fields

Molecular dynamic simulation was used to calculate the self-diffusion coefficients of ions in aqueous KCl solution. The simulations were performed for enough time (12 ns) in the form of all-atom to determine the accurate values of the self-diffusion coefficients. The values of the self-diffusion coefficients were calculated by Einstein equation. Two different force fields of Dang and Deublein were employed in the simulations, and we found that at low ion concentration (equal or less than 3mol/(kg of H₂O)), the Dang force field is more accurate for prediction of the selfdiffusion coefficient of K⁺ ions and Deublein force field is more accurate for Cl^? ions. An Arrhenius type equation was used to model the temperature dependence of the self-diffusion coefficients and the diffusion activation energies at different ion concentrations were reported.     

Hybrid modeling approach to market deployment planning: an application to a natural disaster relief supply business venture

In today’s fast-paced global economy, entrepreneurs increasingly tend to holistically design their business ventures during the early stages of business creation. This tendency highlights the need for an efficient and systematic approach to market deployment planning due to the dynamic and complex nature of current markets and the evolving significance of global strategic positioning. Traditional market expansion planning is no longer adequate for fast-paced contexts. This paper introduces a hybrid modelling approach in order to develop a market deployment roadmap. Based on market pertinent databases, the proposed approach uses self-organising maps for market clustering and an optimisation model for market deployment road mapping within each cluster. The approach is illustrated through its application to market deployment road mapping for a business venture specialising in natural disaster supply relief. Dealing with real case studies with exploiting the vast database have not received much attention in disaster relief planning context. Hence, this study provides a novel contribution to humanitarian relief planning considering the role of the business ventures in relief operation and their business model simultaneously.     

Microscopic interpretation of granule strength in liquid media

This paper reports experimental studies illustrating the effects of partially wetting liquids on the mechanical strength of model granules composed of autoadhesive polystyrene particles. The liquids were prepared by mixing different amounts of isopropanol with pure water and their wetting behaviour was characterised by contact angle measurements on polystyrene surfaces and also by their surface tensions. The strength of the granules was measured by diametric compression while being immersed in the liquid media. The Young's modulus and yield stress were inferred from the compression data using elasto-plastic contact mechanics theory. A reduction in the granule strength was observed at a ‘critical’ isopropanol concentration, which was interpreted in terms of solvation forces. Existing micromechanical models of particle assemblies were examined in order to interpret the dependence of the mechanical properties on the wetting behaviour of the liquid environment. The work provides a basis for understanding some of the factors that are important in the dispersion and dissolution of granules in liquid media.     

Thermal conductivity of InAs quantum dot stacks using AlAs strain compensating layers on InP substrate

The growth and thermal conductivity of InAs quantum dot (QD) stacks embedded in GaInAs matrix with AlAs compensating layers deposited on (1 1 3)B InP substrate are presented. The effect of the strain compensating AlAs layer is demonstrated through Atomic Force Microscopy (AFM) and X-ray diffraction structural analysis. The thermal conductivity (2.7 W/m K at 300 K) measured by the 3ω method reveals to be clearly reduced in comparison with a bulk InGaAs layer (5 W/m K). In addition, the thermal conductivity measurements of S doped InP substrates and the SiN insulating layer used in the 3ω method in the 20–200 °C range are also presented. An empirical law is proposed for the S doped InP substrate, which slightly differs from previously presented results.     

Composite insulators and their aging: An overview

The aging (biological deterioration) is a major problem of composite insulators now-a-days. The main thing in aging is to predict how, when and with what speed it occurs and under what conditions it can lead to failure and what overall average expected life of a composite insulator is. For this a lot of researches have been done. This review summarizes the methods of artificial field testing (aging), natural testing, standards the developed for aging, techniques of analysis, results achieved until now about various parameters from various locations, handling guidelines and a conclusion on what is further needed.