A linear model of elasto-plastic and adhesive contact deformation

Rigorous non-linear models of elasto-plastic contact deformation are time-consuming in numerical calculations for the distinct element method (DEM) and quite often unnecessary to represent the actual contact deformation of common particulate systems. In this work a simple linear elasto-plastic and adhesive contact model for spherical particles is proposed. Plastic deformation of contacts during loading and elastic unloading, accompanied by adhesion are considered, for which the pull-off force increases with plastic deformation. Considering the collision of a spherical cohesive body with a rigid flat target, the critical sticking velocity and coefficient of restitution in the proposed model are found to be very similar to those of Thornton and Ning’s model. Sensitivity analyses of the model parameters such as plastic, elastic, plastic-adhesive stiffnesses and pull-off force on work of compaction are carried out. It is found that by increasing the ratio of elastic to plastic stiffness, the plastic component of the total work increases and the elastic component decreases. By increasing the interface energy, the plastic work increases, but the elastic work does not change. The model can be used to efficiently represent the force-displacement of a wide range of particles, thus enabling fast numerical simulations of particle assemblies by the DEM.     

Variable Sets and Fuzzy Rating Interval for Water Allocation Options Assessment

Optimal water allocation is an important means of improving water use efficiency. However, since water allocation options are usually characterized by multi-region, multi-principle and multi-criterion factors, decision-makers often have difficulty in making objective decisions using them because the many available water allocation options often make the ratings of the options so close to be ranked. This study present a hierarchy variable sets (VS) model, based on the single-layer variable sets model, for ranking the water allocation options of Jining City, China. The ratings of the options are evaluated using a fuzzy rating interval (FRI) that can overcome homogenization in the ratings. The structure of the model presented in this study is clear with a simple procedure of computation and the result is rational. The case study used illustrates that this model can help decision-makers know the rating of water allocation options partially and overall. The computed result from this model appears more convincing than a previous water allocation approach for the city based on the maximum entropy principle.     

Detection of lysozyme magnetic relaxation switches based on aptamer-functionalized superparamagnetic nanoparticles

Magnetic relaxation switch (MRSw) detection is based on aggregate formation or dissociation when magnetic nanoparticles (MNPs) bind to target molecules. In the aggregated state, the dephasing rate of nearby proton spins is higher than in the dispersed state, resulting in a decrease in the spin-spin relaxation time, T(2). In this work, an MRSw-based nanosensor for lysozyme (Lys) protein detection was achieved using iron oxide nanoparticles conjugated with either Lys aptamer or linker DNA, which can hybridize with the extended part of the aptamer to form clusters. Upon the addition of Lys, the aptamers bind with their targets, leading to disassembly of clusters and an increase in T(2). A detection limit in the nanomolar range was achieved for Lys detection in both buffer and human serum. The determination of Lys level in different types of cancer cell lysates was also performed to demonstrate detection in real clinical samples.     

An e-government framework for assessing readiness for public sector e-procurement in a lower-middle income country

ABSTRACT

Governments globally are leveraging information and communication technology (ICT) growth towards improving the quality of public procurement services for socio-economic development. However, the extent of its application differs across nations. Notwithstanding the extant theoretical and empirical literature on IT for development, knowledge on how to assess readiness for adopting a full e-procurement system in the public sector of lower and lower-middle income countries (LMICs) begs for understanding. With the narrative of Ghana, we address this gap by drawing on the institutional and economic theory and the United Nations E-Government Development Index towards a holistic framework beyond the dyad of linear website functionalities and internet focus of prior e-government adoption models. Elite interviews gathered from multiple cases from Ghana’s public sector reveals the key readiness determinants for a full public sector e-procurement system. This study has significant implications for shaping the process-oriented management of government e-procurement projects towards socio-economic development in LMICs amid their complex institutional and socio-technical environments.     

Numerical Simulation Software for Oil Sand Slurry Flow in Flexible Pipelines

In order to optimize the hydraulic transportation system efficiency and cost in the surface extraction of Athabasca oil sand deposits in Canada, there is a desire to extend the hydraulic transport system to production faces in oil sands mines using mobile train of Flex-Rite-based flexible pipelines. Hydraulic transportation system based on flexible-pipe arrangement has been shown to be more competitive than the dump-truck transportation system. This flexible arrangement introduces a unique set of hydraulic transport problems which needs rigorous modeling, experimentation, and analysis to understand the system production capacities and efficiency. Part of the work presented here is an attempt to provide multiphase oil sand slurry simulation and modeling by developing a slurry flow simulator, a graphical user interface-based software, for Flex-Rite flexible-pipe train, a form of hydraulic transportation system. Such software provides a tool/platform for rigorous experimentation and analysis of flow and production capacities.     

Photopolymerization kinetics of poly(acrylate)-clay composites using polymerizable surfactants

Photopolymerization kinetics of polymer-clay nanocomposite systems utilizing polymerizable quaternary ammonium surfactants as dispersants were systematically investigated to determine the effects of surfactant type and clay morphology on polymerization behavior. For these studies, either polymerizable surfactants were mixed into a clay-monomer system or the surfactants were ionically anchored to clay surfaces and added to the monomer for in situ photopolymerization. Higher photopolymerization rates are observed with increasing polymerizable surfactant concentration, while no significant change or decreases in polymerization rate occur with incorporation of non-polymerizable surfactants. The higher rates observed for polymerizable surfactant systems are due to lower apparent termination rate parameters stemming from immobilization of the surfactants. For clay that is modified with ionically bonded quaternary ammonium surfactants, polymerization rates decrease in both polymerizable and non-polymerizable organoclay systems with increasing concentration, but this decrease is much smaller when polymerizable organoclays are utilized. For the same organoclay concentration, higher polymerization rates and double bond conversions result with increasing polymerizable surfactant concentration via cation exchange. Significant increases in polymerization rate also occur with increasing degree of clay exfoliation.     

Housing and the elderly in Singapore – financial and quality of life implications of ageing in place

In spite of the unprecedented success of publichousing in Singapore, the rapid rate at whichthe population is greying is causing housingstress in the matured Housing and DevelopmentBoard (HDB) estates. Although new housingoptions such as studio apartments are beingprovided by the public sector while a recentlyformed housing cooperative is developing aretirement village, the majority of the elderlyin Singapore prefer to age in place,notwithstanding the imbalance between thedemands of their homes and the functioninglevel of the elderly persons' physical andbiological systems. This implies that homemodification, rather than new-built elderlyhousing, may be a more pragmatic solution tothe elderly Singaporeans' housing problems thatcould also improve their quality of life. Since85% of the population of Singapore live inpublic housing, this paper examines the typesof home modifications that could be carried outto the existing stock of public housing so asto create a suitable living environment for theelderly. In addition, the paper considers thehousing finance predicaments of the elderlySingaporean and explores possible financinginstruments that could be implemented tosupport home modifications for Singapore'sgreying population. The paper concludes thatsince home modification(s) could improve thequality of life of the elderly persons morethan specialised housing, public funds shouldbe diverted from building new specialisedhousing to home modification(s) for elderlyhome owners.