Perpendicular-to-grain compression behaviour of screw reinforced timber and a novel application of digital image correlation

This project investigates various factors which influence the behaviour of a timber roof structure designed by Smith & Wallwork Engineers. The first part of the project focused on material of sweet chestnut, where Digital Image Correlation (DIC) was employed to obtain values for the shear modulus. DIC was able to implement the shear field test method prescribed in BS EN 408:2010, along with two new methods developed based on additional information available through DIC. These methods were accurate, fast to implement, and potentially more robust than the shear field test method. A method to estimate the true value of the Timoshenko shear coefficient was also developed. The second section of the project involved physical testing of portions of the roof structure to investigate the behaviour of screw-reinforced and unreinforced timber loaded perpendicular to grain. Together with finite element modelling, it was noticed that a key aspect of the connection's behaviour was the axial force transfer between overlapping screws via shear in the timber, and the resulting relative displacement between the screws. A simple spring model was developed to characterise the compression stiffness of the roof which can now be used in reverse to calculate the forces due to moisture expansion or contraction

The rotational stiffness of cross-laminated timber half-lap joints

Half-lap joints in cross-laminated timber are often conservatively assumed to have no rotational stiffness, preventing applications where the cross-joint stiffness could be utilised. The stiffness of a typical half-lap joint was derived from static four point bend tests, with experiments carried out through a combination of laboratory testing and finite element modelling. A simplified calculation method was developed to predict the rotational stiffness from the joint configuration and material properties. This was incorporated into a spreadsheet design tool for use by the industry partner

Acute leukaemoid reaction following cardiac surgery

Chronic myelomonocytic leukaemia is an atypical myeloproliferative disorder with a natural history of progression to acute myeloid leukaemia, a complex and poorly understood response by the bone marrow to stress. Cardiac surgery activates many inflammatory cascades and may precipitate a systemic inflammatory response syndrome. We present a case of undiagnosed chronic myelomonocytic leukaemia who developed rapidly fatal multi-organ dysfunction following cardiac surgery due to an acute leukaemoid reaction

Reliability of measuring abductor hallucis muscle parameters using two different diagnostic ultrasound machines

<p>Abstract</p> <p>Background</p> <p>Diagnostic ultrasound provides a method of analysing soft tissue structures of the musculoskeletal system effectively and reliably. The aim of this study was to evaluate within and between session reliability of measuring muscle dorso-plantar thickness, medio-lateral length and cross-sectional area, of the abductor hallucis muscle using two different ultrasound machines, a higher end Philips HD11 Ultrasound machine and clinically orientated Chison 8300 Deluxe Digital Portable Ultrasound System.</p> <p>Methods</p> <p>The abductor hallucis muscle of both the left and right feet of thirty asymptomatic participants was imaged and then measured using both ultrasound machines. Interclass correlation coefficients (ICC) with 95% confidence intervals (CI) were used to calculate both within and between session intra-tester reliability. Standard error of the measurement (SEM) calculations were undertaken to assess difference between the actual measured score across trials and the smallest real difference (SRD) was calculated from the SEM to indicate the degree of change that would exceed the expected trial to trial variability.</p> <p>Results</p> <p>The ICCs, SEM and SRD for dorso-plantar thickness and medial-lateral length were shown to have excellent to high within and between-session reliability for both ultrasound machines. The between-session reliability indices for cross-sectional area were acceptable for both ultrasound machines.</p> <p>Conclusion</p> <p>The results of the current study suggest that regardless of the type ultrasound machine, intra-tester reliability for the measurement the abductor hallucis muscle parameters is very high.</p

Multi-scale hydro-morphodynamic modelling using mesh movement methods

Abstract: Hydro-morphodynamic modelling is an important tool that can be used in the protection of coastal zones. The models can be required to resolve spatial scales ranging from sub-metre to hundreds of kilometres and are computationally expensive. In this work, we apply mesh movement methods to a depth-averaged hydro-morphodynamic model for the first time, in order to tackle both these issues. Mesh movement methods are particularly well-suited to coastal problems as they allow the mesh to move in response to evolving flow and morphology structures. This new capability is demonstrated using test cases that exhibit complex evolving bathymetries and have moving wet-dry interfaces. In order to be able to simulate sediment transport in wet-dry domains, a new conservative discretisation approach has been developed as part of this work, as well as a sediment slide mechanism. For all test cases, we demonstrate how mesh movement methods can be used to reduce discretisation error and computational cost. We also show that the optimum parameter choices in the mesh movement monitor functions are fairly predictable based upon the physical characteristics of the test case, facilitating the use of mesh movement methods on further problems

Review of Suspended Sediment Transport Mathematical Modelling Studies

YesThis paper reviews existing studies relating to the assessment of sediment concentration profiles within various flow conditions due to their importance in representing pollutant propagation. The effects of sediment particle size, flow depth, and velocity were considered, as well as the eddy viscosity and Rouse number influence on the drag of the particle. It is also widely considered that there is a minimum threshold velocity required to increase sediment concentration within a flow above the washload. The bursting effect has also been investigated within this review, in which it presents the mechanism for sediment to be entrained within the flow at low average velocities. A review of the existing state-of-the-art literature has shown there are many variables to consider, i.e., particle density, flow velocity, and turbulence, when assessing the suspended sediment characteristics within flow; this outcome further evidences the complexity of suspended sediment transport modelling

Flood Suspended Sediment Transport: Combined Modelling from Dilute to Hyper-concentrated Flow

YesDuring flooding, the suspended sediment transport usually experiences a wide-range of dilute to hyper-concentrated suspended sediment transport depending on the local flow and ground con-ditions. This paper assesses the distribution of sediment for a variety of hyper-concentrated and dilute flows. Due to the differences between hyper-concentrated and dilute flows, a linear-power coupled model is proposed to integrate these considerations. A parameterised method combining the sediment size, Rouse number, mean concentration, and flow depth parameters has been used for modelling the sediment profile. The accuracy of the proposed model has been verified against the reported laboratory measurements and comparison with other published analytical methods. The proposed method has been shown to effectively compute the concentration profile for a wide range of suspended sediment conditions from hyper-concentrated to dilute flows. Detailed com-parisons reveal that the proposed model calculates the dilute profile with good correspondence to the measured data and other modelling results from literature. For the hyper-concentrated profile, a clear division of lower (bed-load) to upper layer (suspended-load) transport can be observed in the measured data. Using the proposed model, the transitional point from this lower to upper layer transport can be calculated precisely

The adhesive properties of pyridine-terminated self-assembled monolayers

The atomic force microscopy (AFM) adhesion force behaviour and contact angle titration behaviour of self-assembled monolayers (SAMs) presenting surface pyridine and substituted pyridine moieties has been investigated as a function of pH and electrolyte concentration. The pKas of the pyridine moieties were modified through the incorporation of fluorine, chlorine and bromine substituents in the pyridyl ring. Contact angle titration and AFM adhesion force measurements were performed using aqueous phosphate buffered saline solutions over the pH range 3–9, and at concentrations of 150 mM and 0.1 mM. AFM adhesion force measurements were performed using a clean Si3N4 pyramidal-tipped AFM cantilever

Identification of multiple root disease resistant wheat germplasm against cereal nematodes and dryland root rot and their validation in regions of economic importance

História da literatura portuguesa coordenada por Giulia Lanciani - primeiras páginas de um total pp. 7-108)História literária do século XVIII portuguêsGoverno de Portuga