The measurement of shear compliances for oriented polyethylene terephthalate sheet

Two techniques have been used to measure the shear compliances of one-way drawn uniplanar-axially-oriented polyethylene terephthalate (PET) sheet, draw ratio 51; a torsional method for all three compliancesS ₄₄,S ₅₅ andS ₆₆, and a recently-developed simple-shear method forS ₄₄ andS ₆₆. The two techniques gave values for the compliances in common which agreed very well. An examination of end effects in torsion has also been made. The determination of the three shear compliances complete the determination of all nine independent compliances for this PET sheet. The overall mechanical anisotropy has been considered in the light of existing structural information, and comparison made with the elastic constants of isotropic PET and a highly oriented PET fibre on the basis of the single-phase aggregate model.     

An analysis of the mechanics of solid phase extrusion of polymers

An analysis is presented for the mechanics of the hydrostatic extrusion of polymers in the solid phase through a conical die. The analysis starts with the lower bound solution proposed by Hoffman and Sachs and includes the effects of strain, strain rate and pressure on the deformation behaviour. It is proposed that this involves knowledge of the tensile stress-strain-strain rate relationships for each polymer, and it is shown how such information for polyethylene and polyoxymethylene can be used to explain the observed behaviour of these materials in the solid-phase extrusion process.List of Symbols die cone semi-angle - normal stress coefficient of tensile flow stress - d ₀ initial diameter of billet - d _f die exit diameter - axial strain rate (plug flow) - _red shear strain (redundant strain) incurred on crossing die entry or exit boundary - _N In R _N=2ln (d ₀/d _f) nominal true strain in extrusion - _{f red}+ _N - L cot - normal stress coefficient of friction at die/billet interface - P experimental extrusion pressure=total work done per unit volume of material - P _F work done per unit volume against billet-die friction - P _I ideal deformation work done per unit volume of material - P _R total redundant work done per unit volume - P _W=P–P _I extra work required to overcome friction, pressure and redundant strain effects - r ₀ initial radius of billet - r _f die exit radius - r material radius at a point in the deformation zone - R _N=(r ₀/r _f)² nominal extrusion ratio - R=(r ₀/r)² extrusion ratio at a point in the deformation zone - ₀() axial tensile flow stress - _f() process flow stress path, related to die strain and strain rate fields - _h tensile haul-off stress - _x, _y die stresses in deformation zone - ₁, ₂ shear yield stress of material at die entry and exit boundaries, respectively - v _x axial velocity - v _f extrudate velocity at die exit     

A study of ergonomics factors in washbasin design

A 4-week UNESCO-sponsored mission to the Department of Architecture, Karadeniz Technical University in Eastern Turkey, gave an opportunity to apply ergonomics techniques to some aspects of that country's domestic washbasin design. The study was intended to provide experience in questionnaire design and administration, in the application of psycho-physical methods, and to highlight the importance of determining user characteristics and preferences with regard to the built environment. A field study elicited information on dimensions and positioning of existing wash-basins and ancillary equipment and the opinions of users as to the suitability of these features in relation to the activities performed. A laboratory study, using an adjustable rig permitting variation in the heights of basin, taps and mirror/shelf, followed. The data obtained on preferred heights of these items led to the conclusions that basin height should be increased to between 95 and 100 cm to satisfy the majority of users; tap height above the basin should be reduced to about 11 cm; the shelf and lower edge of a mirror sited above the basin should be 136 cm above the floor; and a clear space of 110 cm should be available between the front of the basin and a wall or other obstruction. Suggestions on other design aspects of the bathroom, resulting from the study, are discussed.     

Economic Costs of Sustaining Water Supplies: Findings from the Rio Grande

Water claims in many of the world??s arid basins exceed reliable supplies. Water demands for irrigation, urban use, the environment, and energy continue to grow, while supplies remain constrained by unsustainable use, drought and impacts of climate change. For example, policymakers in North America??s Upper Rio Grande Basin face the challenge of designing plans for allocating the basin??s water supplies efficiently and fairly to support current uses and current environments. Managers also seek resilient institutions that can ensure adequate supplies for future generations. This paper addresses those challenges by designing and applying an integrated basin-scale framework that accounts for the basin??s most important hydrologic, economic, and institutional constraints. Its unique contribution is a quantitative analysis of three policies for addressing long term goals for the basin??s reservoirs and aquifers: (1) no sustainability for water stocks, (2) sustaining water stocks, and (3) renewing water stocks. It identifies water use and allocation trajectories over time that result from each of these three plans. Findings show that it is hydrologically and institutionally feasible to manage the basin??s water supplies sustainably. The economic cost of protecting the sustainability of the basin??s water stocks can be achieved at 6?C11 percent of the basin??s average annual total economic value of water over a 20?year time horizon.     

Distributed computing for carbon footprint reduction by exploiting low-footprint energy availability

Low carbon footprint energy sources such as solar and wind power typically suffer from unpredictable or limited availability. By globally distributing a number of these renewable sources, these effects can largely be compensated for. We look at the feasibility of this approach for powering already distributed data centers in order to operate at a reduced total carbon footprint. From our study we show that carbon footprint reductions are possible, but that these are highly dependent on the approach and parameters involved. Especially the manufacturing footprint and the geographical region are critical parameters to consider. Deploying additional data centers can help in reducing the total carbon footprint, but substantial reductions can be achieved when data centers with nominal capacity well below maximum capacity redistribute processing to sites based on renewable energy availability.     

Near-infrared photodetection with a diruthenium complex having redox-switchable wavelength response

We report on the electrochromic behavior of a dinuclear ruthenium complex, which provides high environmental stability together with an intense absorption maximum at 1237 nm in solution in its +3 oxidation state. To verify its optoelectronic properties, we used this complex as the photoactive material in a planar photodetector prototype for near-infrared light pulses, succeeding in the detection of a train of light pulses at a wavelength of 1280 nm.     

Keeping It Real: A Grounded Theory Study of African American Clients Engaging in Counseling at a Community Mental Health Agency.

Few studies have examined African American clients' subjective experiences in counseling from their perspective. This study used a constructivist paradigm, grounded theory methodology, and dimensional analysis to develop a model of clients' subjective experiences in counseling. Derived from clients' perspectives, the model suggests that the African American participants in this study engaged in an ongoing assessing process. Initially, they assessed client-therapist match, which was influenced by 3 factors: salience of Black identity, court involvement, and ideology similarity between client and therapist. These clients then assessed their safety in therapy and their counselor's effectiveness simultaneously. Clients in turn used information obtained from their assessing process to monitor and manage their degree of self-disclosing along a continuum. The model has important implications for future research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of the measurement frequency on the elastic anisotropy of fibre laminates

Static tests and ultrasonic measurements (2.25 MHz) have been carried out on a series of composite laminates of glass fibres in a polypropylene matrix. A range of angle ply laminates were prepared for this study, with laminate angles θ of ±0, 10, 20, 30 and 40^∘. The high frequency measurements were made using the ultrasonic immersion technique, which allows the determination of a complete set of the elastic constants of a material. The relationship between the ultrasonically determined elastic constants of the angle ply laminates was found to be in excellent agreement with theoretical predictions, as previously validated for carbon fibre/epoxy angle ply laminates. A comparison between the ultrasonic and statically measured values was made for two of the angle ply laminates (θ = 0 and 20^∘). It was found that the static values were lower than those measured at ultrasonic frequency, particularly those constants that were more matrix dominated (for example the transverse moduli of the laminates). Measurements on a pure polypropylene sample at both testing frequencies confirmed that the change in matrix properties with frequency was the cause of this difference. The change in properties with test frequency is likely to be much larger in this system than in other composite materials because the glass transition temperature of polypropylene is close to ambient temperature. Dynamic mechanical tests (1 Hz) were carried out on a sample of pure polypropylene to assess this effect. We also give an appropriate method of estimating the dependence of glass transition temperature on frequency. The results for polypropylene are compared with those for other commonly used polymer matrix materials: epoxy resin, nylon and polyetheretherketone (PEEK): DMTA measurements were also made on these samples. The effect of test frequency on matrix properties, for the glass/PP laminates, was further investigated by examining the relationship of the Poisson's ratios with laminate angle using a mixture of ultrasonic experiments and theoretical predictions. Previously we have shown that the degree of anisotropy between the reinforcing fibre and the matrix phase is paramount in determining whether the material will show a negative Poisson's ratio at a critical laminate angle. The ultrasonic measurements carried out in this study on the glass/PP laminates showed a minimum in one of the Poisson's ratio at a laminate angle of 32°, but the value did not become negative. However, theoretical predictions showed that for a static frequency measurement (1 Hz), where the matrix is softer and hence the anisotropy of each laminate ply is higher, the laminate will show a negative Poisson's ratio with a minimum at a laminate angle of around 28°.     

Numerical inversion of multidimensional Laplace transforms by the Laguerre method

Numerical transform inversion can be useful to solve stochastic models arising in the performance evaluation of telecommunications and computer systems. We contribute to this technique in this paper by extending our recently developed variant of the Laguerre method for numerically inverting Laplace transforms to multidimensional Laplace transforms. An important application of multidimensional inversion is to calculate time-dependent performance measures of stochastic systems. Key features of our new algorithm are: (1) an efficient FFT-based extension of our previously developed variant of the Fourierseries method to calculate the coefficients of the multidimensional Laguerre generating function, and (2) systematic methods for scaling to accelerate convergence of infinite series, using Wynn's ε-algorithm and exploiting geometric decay rates of Laguerre coefficients. These features greatly speed up the algorithm while controlling errors. We illustrate the effectiveness of our algorithm through numerical examples. For many problems, hundreds of function evaluations can be computed in just a few seconds.     

The Effect of the Length of To-Be-Remembered Lists and Intervening Lists on Free Recall: A Reexamination Using Overt Rehearsal.

In 3 experiments, the authors investigated the effects of to-be-remembered (TBR) and intervening list length on free recall to determine whether selective rehearsal could explain the previous finding that recall was affected only by TBR list length. In Experiments 1 (covert rehearsal) and 2 (overt rehearsal), participants saw 5- and 20-word lists and had to recall the list prior to that last presented list. In Experiment 3, either 1 or 2 lists were presented, and recall of TBR list was postcued. Recall proportion decreased with increased TBR list length. Moreover, the authors found extended recency effects when recall was replotted by when words were last rehearsed (Experiments 2 and 3) and an effect of intervening list length when rehearsal was reduced (Experiment 3). (PsycINFO Database Record (c) 2010 APA, all rights reserved)