The Amorphous-Crystal Interface in Silicon: a Tight-Binding Simulation

The structural features of the interface between the cystalline and amorphous phases of Si solid are studied in simulations based on a combination of empirical interatomic potentials and a nonorthogonal tight-binding model. The tight-binding Hamiltonian was created and tested for the types of structures and distortions anticipated to occur at this interface. The simulations indicate the presence of a number of interesting features near the interface. The features that may lead to crystallization upon heating include chains with some defects, most prominently dimers similar to those on the Si(001) 2x1 reconstructed free surface. Within the amorphous region order is lost over very short distances. By examining six different samples with two interfaces each, we find the energy of the amorphous-crystal interface to be 0.49 +/- 0.05 J/m^2Comment: Submitted to Phys. Rev.

Polyethersulfone/HFO mixed matrix membrane for enhanced oily wastewater rejection

The recent growth of oil and gas industry has led to the increase of oily wastewater release. Membrane technology has been in the spotlight in recent advancement to treat the oily wastewater. Fouling due to surfactant adsorption and/or oil droplets plugging the pore has become one of the major hindrances in most of the research on oily wastewater treatment. In this work, self-synthesized hydrous ferric dioxide nanoparticles (HFO NPs) via chemical precipitation method were incorporated in polyethersulfone (PES) to fabricate a novel nanocomposite mixed matrix membranes (MMMs) for ultrafiltration (UF). The morphologies and physicochemical properties of prepared HFO NPs and MMMs were characterized using Scanning Electron Microscopy (SEM) and Transmission electron microscope (TEM), contact angle goniometer, before further subjected to water permeation test and oil rejection test. It was found that contact angle of membrane decreased remarkably with an increase in HFO nanoparticle loading from 70° to 38° at which proved its improved hydrophilicity which led to a significant rise in permeate flux, achieving 168.06 L/m2h bar in comparison to 63.67 L/m2h bar shown by the plain PES membrane. Total rejection of oil (100% rejection) demonstrated by the MMMs has confirmed the superior potential of PES/HFO UF membrane for total purification of oily wastewater especially to be reused in oilfield and refinery processes as well as to be released to the environment

Size versus truthfulness in the house allocation problem

We study the House Allocation problem (also known as the Assignment problem), i.e., the problem of allocating a set of objects among a set of agents, where each agent has ordinal preferences (possibly involving ties) over a subset of the objects. We focus on truthful mechanisms without monetary transfers for finding large Pareto optimal matchings. It is straightforward to show that no deterministic truthful mechanism can approximate a maximum cardinality Pareto optimal matching with ratio better than 2. We thus consider randomized mechanisms. We give a natural and explicit extension of the classical Random Serial Dictatorship Mechanism (RSDM) specifically for the House Allocation problem where preference lists can include ties. We thus obtain a universally truthful randomized mechanism for finding a Pareto optimal matching and show that it achieves an approximation ratio of eovere-1. The same bound holds even when agents have priorities (weights) and our goal is to find a maximum weight (as opposed to maximum cardinality) Pareto optimal matching. On the other hand we give a lower bound of 18 over 13 on the approximation ratio of any universally truthful Pareto optimal mechanism in settings with strict preferences. In the case that the mechanism must additionally be non-bossy, an improved lower bound of eovere-1 holds. This lower bound is tight given that RSDM for strict preference lists is non-bossy. We moreover interpret our problem in terms of the classical secretary problem and prove that our mechanism provides the best randomized strategy of the administrator who interviews the applicants

An Update of Roof Bolt Research at the University of Wollongong

The influence of surface profile on load transfer mechanisms of bolts has been studied under both the constant normal stiffness (CNS) and constant normal load (CNL) conditions. Testing under CNS condition was conducted in a specially constructed constant normal stiffness shearing apparatus, whereby the flattened surface of a bolt section was pulled against the image of cast resin sample under constant stiffness conditions. Testing under CNL conditions included the conventional pull testing of an encapsulated section of bolt anchored in a borehole, and the short encapsulation push test. The conventional pull testing involved pull testing of three different profiled bolts in three different diameter holes. The pull tests were carried out both insitu and in the laboratory. Parameters examined, in addition to bolt surface profile, were the resin annulus thickness and the effectiveness of resin mixing in the hole. The credibility of push testing, in short steel cylinder sleeves, was examined by pulling the bolt out of the cylindrical sleeve instead of pushing. Also tested in short sleeve, was the possibility of changing the load transfer capability of a bolt by changing its surface profile. A numerical simulation study has recently been incorporated to enhance the current programme of research carried out at the School of Civil, Mining and Environmental Engineering, The University of Wollongong. The numerical study included the modeling of both the short encapsulation push/ pull test as well as shear stress simulation across joints. The conclusions drawn were that the bolt surface profile is an important parameter affecting the load transfer capacity of the bolt/rock interface, that the anchorage strength of resin encapsulation is influenced by the effectiveness of resin mixing, and the annulus thickness, and the short encapsulation push test underestimates the peak shear load and peak load displacement

A New Technique to Determine the Load Transfer Capacity of Resin Anchored Bolts

This paper describes a new technique to evaluate the load transfer capacity of different resin anchored rock bolts. With an increasing number of rock bolts currently being introduced into the Australian market for use in a variety of ground conditions, a new technique to determine bolt load transfer capacity is necessary. The assessment of the performance bolt with regard to load transfer mechanisms is conducted in the laboratory under Constant Normal Stiffness (CNS) conditions. This method of testing is considered as being a realistic way of evaluating bolt surface roughness as the tests are carried out under different confining pressures thus accommodating the changes in ground conditions such as high horizontal stress while allowing for surface dilations due to rubbing of rough surfaces against each other

Integrating vocational training in culinary arts and Islamic studies at juvenile rehabilitation centres: Malaysian experience

The Juvenile Rehabilitation Centres (JRC) in Malaysia aims to provide shelter, counselling and skills training to juveniles specifically for those who wish to transform themselves from the regrettable misdeeds they have committed. At JRCs, an integrated Culinary Vocational Training and Islamic education forms part of their training curriculum. The skills acquired should enable trainees to secure jobs upon completion of training. However, there are some training institutions that lack systematic training structures resulting in trainees becoming less skilful in both vocational and Islamic education. The objective of this research is to identify the effectiveness of an integrated Culinary and Islamic Education curriculum implemented at JRCs in Malaysia. This is a descriptive survey and data was obtained using questionnaire and interview. Respondents comprised 92 trainees, four managers, four culinary trainers and four Islamic education teachers, all from four different JRCs. The findings show that the trainees are happy with their trainings that brought about positive effects for them. Some suggestions have been made to provide improvements in the implementation of the course among them the inclusion of prayers in the Islamic education syllabus

Averting Behavior Framework for Perceived Risk of Yersinia enterocolitica Infections

The focus of this research is to present a theoretical model of averting actions that households take to avoid exposure to Yersinia enterocolitica in contaminated food. The cost of illness approach only takes into account the value of a cure, while the averting behavior approach can estimate the value of preventing the illness. The household, rather than the individual, is the unit of analysis in this model, where one household member is primarily responsible for procuring uncontaminated food for their family. Since children are particularly susceptible and live with parents who are primary decision makers for sustenance, the designated household head makes the choices that are investigated in this paper. This model uses constrained optimization to characterize activities that may offer protection from exposure to Yersinia enterocolitica contaminated food. A representative household decision maker is assumed to allocate family resources to maximize utility of an altruistic parent, an assumption used in most research involving economics of the family