Effect of warping-pretwist coupling on the natural vibration of torsionally clamped-pinned thin-walled open-profile bars

Exact natural frequencies are determined for the torsional vibration of pretwisted thin-walled open-profile bars having torsionally clamped and pinned end restraints. The equation of motion and boundary conditions are derived from a multifilament model of a pretwisted thin-walled bar undergoing warp deformation and a moderately large twist about the elastic axis. Closed-form torsional frequencies and mode shapes are derived from the linear terms of the resulting non-linear equations. As the length-to-leg ratio (L/b) and leg-to-thickness ratio (b/t) of typical open-profile bars are varied, the individual and collective effects of warping and pretwist on the non-dimensional torsional frequencies are demarcated. In addition, the closed-form solutions offered here reveal considerable destiffening of the torsional frequencies due to warping-pretwist coupling present in thin-walled bars having pretwisted, unsymmetrical, open-profiles and torsionally clamped and pinned end restraints. This coupling effect, which have been ignored in thin-walled bar vibration theories hitherto, is brought out by the Wagner effect and warping shear stresses acting on the profiles.     

The practitioner perspective on the modeling of pedagogy and practice

Abstract   The promotion of e-learning in policies internationally has led to questions about how best to employ technology in support of learning. A range of models has since been developed that attempts to relate pedagogy to technology. However, research into the effectiveness of such models in changing teaching practice is sparse, and work that compares these models to practitioners' own representations of their practice is absent. The study described here involved asking practitioners to model their own practice, and to compare these with a model developed by a government organization. Practitioners were adept at using existing models and repurposing them to suit their own context. Our research provided evidence of broad acceptance of the existing model with practitioners, but indicated that practitioners would take this tool and remodel it for their own contexts of learning to make it meaningful, relevant and useful to them.     

A biochemical microdevice with an integrated chemiluminescence detector

By taking advantage of both the semiconductor properties and the advanced micromachining possibilities of silicon, integration of back-side photodiodes with a microfluidic channel network on a single substrate is accomplished. The resulting microsystem has all fluidic and electrical connections on one side of the chip. Hermetic sealing by anodic bonding is greatly facilitated by the simple topography on the front-side of the chip. To test the chemical functionality and performance of the device a chemiluminescence-based detection scheme is implemented. The introduction and control of the necessary chemical solutions is achieved using a flow injection analysis approach. Hydrogen peroxide is used as a model compound; injected plugs with concentrations in the range of 100 μM to 1 mM are successfully detected.     

ICT and operations outsourcing in banking

Outsourcing of ICT (Information and communications technology) and Operations services has reappeared on the agenda of top management in European banking. As a contribution to this important topic, McKinsey & Company has carried out a comprehensive survey, based primarily on 70 interviews with executives of banks and providers. Key topics analyzed are: the relevance of outsourcing to address current challenges in banking; the value created by outsourcing and the barriers to its successful implementation; the degree of viability of outsourcing across specific services and functions; and likely developments in the outsourcing market. In addition, industry best practices have been collected and synthesized.     

Thermal properties of fats and oils

Summary 1. The heat content of a quickly chilled sample, and that of a slowly chilled and tempered sample, of almost completely hydrogenated cottonseed oil, has been measured over a temperature range within which there is in each case complete transformation of the oil from a solid to a liquid form. 2. Heat capacity data have been calculated for the liquid oil and for the quickly chilled and the tempered solid oil. Equations expressing the changes in heat capacity with temperature have been derived. A correlation of the heat capacity data on highly hydrogenated cottonseed oil and similar data previously obtained on unhydrogenated cottonseed oil, and on partially hydrogenated oil, in both liquid and solid states, is presented. 3. The heat of fusion calculated for the quickly chilled and for the tempered solid oil is given. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Context-aware environments: from specification to implementation

Abstract: This paper deals with the problem of implementing a context model for a smart environment. The problem has already been addressed several times using many different data- or problem-driven methods. In order to separate the modelling phase from implementation, we first represent the context model by a network of situations. Then, different implementations can be automatically generated from this context model depending on user needs and underlying perceptual components. Two different implementations are proposed in this paper: a deterministic one based on Petri nets and a probabilistic one based on hidden Markov models. Both implementations are illustrated and applied to real-world problems.     

Investigations of Flow Conditions and Solidification in Continuous Casting Moulds by Advanced Simulation Techniques

Concerning further improvement of product quality in continuous casting, advanced simulation techniques are successfully used to investigate and optimise the complex flow and temperature conditions and the physical phenomena related to them. The work presented here focuses on the mould and discusses the corresponding application of selected mathematical and physical simulation techniques. Transient numerical simulations considering multiphase flow conditions and solidification with mould oscillation provide detailed information on the so‐called solidified hook formation directly below the meniscus. Concerning mould powder performance, the numerical simulation approach is carried out considering the flux flow in the meniscus region in order to obtain information e.g. on the mould powder consumption. With physical model investigations performing simultaneous and time dependent measurements of flow field and mould level behaviour, an optimised SEN design for the thin slab casting could be developed, which allows significantly higher casting velocities and yield, respectively. Operational plant trials confirm these results.