Modelling, testing and design, of a surface piercing propeller drive

In collaboration with Marinetech South Ltd., Defence, Evaluation and Research Agency, Haslar and Teignbridge Propellers Ltd.Available from British Library Document Supply Centre-DSC:DXN036584 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Singlets and reflection symmetric spin systems

We rigorously establish some exact properties of reflection symmetric spin systems with antiferromagnetic crossing bonds: At least one ground state has total spin zero and a positive semidefinite coefficient matrix. The crossing bonds obey an ice rule. This augments some previous results which were limited to bipartite spin systems and is of particular interest for frustrated spin systems.Comment: 11 pages, LaTeX 2

Tensile force monitoring on large winch-assist forwarders operating in British Columbia

The forest industry around the world is facing common challenges in accessing wood fiber on steep terrain. Fully mechanized harvesting systems based on specialized machines, such as winch-assist forwarders, have been specifically developed for improving the harvesting perfor- mances in steep grounds. While the mechanization process is recognized as a safety benefit, the use of cables for supporting the machine traction needs a proper investigation. Only a few studies have analyzed the cable tensile forces of winch-assist forwarders during real operations, and none of them focused on large machines normally used in North America. Consequently, a preliminary study focused on tensile force analysis of large winch-assist forwarders was conducted in three sites in the interior of British Columbia during the fall of 2017. The results report that in 86% of the cycles, the maximum working load of the cable was less than one-third of the minimum breaking load. The tensile force analysis showed an expected pattern of minimum tensile forces while the forwarders were traveling or unloading on the road site and high tensile forces when operating on steep trails, loading or traveling. Further analysis found that the maximum cycle tensile forces occurred most frequently when the machines were moving uphill, independently of whether they were empty or loaded. While the forwarders were operating on the trails, slope, travel direction, and distance of the machines from the anchor resulted statistically significant and able to account for 49% of tensile force variability. However, in the same conditions, the operator settings accounted for 77% of the tensile force variability, suggesting the human factor as the main variable in cable tensile force behavior during winch-assist operations

Asymptotic forms for hard and soft edge general β\beta conditional gap probabilities

An infinite log-gas formalism, due to Dyson, and independently Fogler and Shklovskii, is applied to the computation of conditioned gap probabilities at the hard and soft edges of random matrix $\beta$-ensembles. The conditioning is that there are $n$ eigenvalues in the gap, with $n \ll |t|$, $t$ denoting the end point of the gap. It is found that the entropy term in the formalism must be replaced by a term involving the potential drop to obtain results consistent with known asymptotic expansions in the case $n=0$. With this modification made for general $n$, the derived expansions - which are for the logarithm of the gap probabilities - are conjectured to be correct up to and including terms O$(\log|t|)$. They are shown to satisfy various consistency conditions, including an asymptotic duality formula relating $\beta$ to $4/\beta$.Comment: Replaces v2 which contains typographical errors arising from a previous unpublished draf

eInk versus paper: exploring the effects of medium and typographic quality on recall and reading speed

This study compares the effects of reading from paper and an eInk display on recall and reading speed alongside the effects of changes in typographic quality (fluent and disfluent conditions). Both medium and typographic quality were between-subject variables resulting in four groups of participants. Each participant was timed while they read one text. They then completed a general questionnaire before answering multiple-choice questions evaluating their recall of the content they had read. Comparable reading speeds for paper and eInk were recorded and these were slower for disfluent conditions. Improved typographic quality significantly enhanced recall on eInk, whereas for paper participants who read the disfluent condition recalled more. These findings suggest that typographic quality has a significant effect on reading, which is also influenced by the medium. Although recall was better in the disfluent paper condition, some caution should be observed in translating this into recommendations that would result in more effortful reading

A random matrix decimation procedure relating β=2/(r+1)\beta = 2/(r+1) to β=2(r+1)\beta = 2(r+1)

Classical random matrix ensembles with orthogonal symmetry have the property that the joint distribution of every second eigenvalue is equal to that of a classical random matrix ensemble with symplectic symmetry. These results are shown to be the case $r=1$ of a family of inter-relations between eigenvalue probability density functions for generalizations of the classical random matrix ensembles referred to as $\beta$-ensembles. The inter-relations give that the joint distribution of every $(r+1)$-st eigenvalue in certain $\beta$-ensembles with $\beta = 2/(r+1)$ is equal to that of another $\beta$-ensemble with $\beta = 2(r+1)$. The proof requires generalizing a conditional probability density function due to Dixon and Anderson.Comment: 19 pages, 1 figur

Numerical computation of fluid properties at nano/meso scales.

Engineering systems are increasingly being developed with dimensions within the micro to nano scale. Mature simulation schemes are available for large scale systems (> 0.5mum) in the form of continuum mechanics, and for small scale systems (< 50nn). However, there is to simulation scheme that covers the middle, meso scale, range between them. The work presented in this thesis focuses on the development of a computational framework focused on fluid systems on the nano- meso scale, with characteristic dimensions between 50nm and 500nm. Existing methods approach the meso scale either with approximated molecular behaviour from the 'top down', or directly modelling molecular physics from the 'bottom up'. Top down approaches have the disadvantage of only including known behaviour with some statistical variations to approximate chaotic behavior. Bottom up approaches model the fluid from a molecular physics model, but fail to capture bulk fluid behaviour and are computationally expensive. The approach developed in this thesis, covers the middle ground between continuum and molecular simulation scales. A molecular physics model is used to govern the behaviour of the fluid, and is surrounded by a set of meso scale boundary conditions, providing an accurate and efficient fluid model. Bulk fluid behaviour is extracted in the form of ensemble property distributions in a versatile grid-like implementation, allowing the fluid properties to be calculated from first principles accurately and efficiently. Each part of the developed method is validated separately. The physics model is compared with published results of simulations at molecular scales, as there is insufficient information for meso scale fluid systems. The bulk ensemble property collection scheme is fully explored by means of a parametric study. Case studies are presented to highlight how bulk fluid properties, such as velocity, temperature and pressure, can be examined as distributions in time and space over the flow field in channel flow systems. The approach developed in this thesis opens the door to accurate and efficient meso scale fluid simulation. This work has also identified the next step to widen and improve the abilities for meso scale fluids to be fully investigated

Leu628 of the KIX domain of CBP is a key residue for the interaction with the MLL transactivation domain

AbstractPhysical interaction between the transactivation domain (TAD) of the mixed-lineage leukemia protein (MLL) and the KIX domain of the cyclic-AMP response element binding protein (CREB) binding protein (CBP) is necessary for MLL-mediated transcriptional activation. We show by alanine-scanning mutagenesis that hydrophobic surface residues of KIX, especially L628, are energetically important for binding the MLL TAD. NMR studies of the KIX-L628A mutant suggest that L628 plays a crucial role in conformational transitions at the MLL binding site, necessary for high affinity interactions with MLL. Unexpectedly, MLL also binds to the c-Myb/phosphorylated kinase-inducible domain of CREB (pKID) site of KIX, highlighting the complex nature of interactions involving intrinsically disordered transcriptional activators.Structured summaryMINT-8044564, MINT-8044580, MINT-8044598, MINT-8044616, MINT-8044634, MINT-8044656:Cbp (uniprotkb:P45481) and MLL (uniprotkb:Q03164) bind (MI:0407) by isothermal titration calorimetry (MI:0065)MINT-8044696:Cbp (uniprotkb:P45481) and MLL (uniprotkb:Q03164) bind (MI:0407) by nuclear magnetic resonance (MI:0077

Effective spin-wave action for ordered Heisenberg antiferromagnets in a magnetic field

We derive the effective long-wavelength Euclidean action for the antiferromagnetic spin-waves of ordered quantum antiferromagnets subject to a uniform magnetic field. We point out that the magnetic field dependence of the spin-wave dispersion predicted by the usual O(3)-quantum nonlinear sigma model disagrees with spin-wave theory. We argue that the nonlinear sigma model does not take into account all relevant spin-wave interactions and derive a modified effective action for the long-wavelength spin-waves which contains an additional quartic interaction. At zero temperature the corresponding vertex is relevant in the renormalization group sense below three dimensions.Comment: 4 pages, 1 eps figure; proceedings of the symposium on "Spin- and charge-correlations in molecule-based materials", October 2005, Koenigstein (Taunus), German