Effect of torch angle on arc properties and weld pool shape in stationary GTAW

In this paper, a three dimensional numerical simulation is performed on a stationary arc to study the effect of torch angle in gas tungsten arc welding (GTAW) of SS304 stainless steel. A comparison has been made to investigate 90o and 70o torch angles and analyze the effect on arc and weld pool shape. Current density, heat flux and gas shear stress are calculated in the arc region and are used as input to the workpiece to determine the weld pool. Buoyancy and Marangoni shear also affect the weld pool shape and are taken into account. The computed and experimental results are observed symmetric for 90o torch angle. For 70o torch angle, current density and hence the heat flux due to electron contribution is found the maximum behind and heat flux due to conduction and convection is found the maximum ahead of the electrode tip in the welding direction. This makes the maximum of total heat flux symmetric along the arc center. Heat flux due to conduction and convection decreases as the torch angle decreases resulting in a shallow weld pool. The nonsymmetric “w” shaped weld pool is developed by the combined effect of the gas shear and Marangoni convection. It is found that for 70o torch angle, the weld pool becomes non-symmetric, shallow and wide ahead of the electrode tip in the welding direction. The numerical weld pool shapes are verified through experiments

On Channels with Composite Rough Surfaces at Terahertz Frequencies

The paper preliminarily examines the influence of diffuse reflection by composite rough surfaces in ultra-broadband terahertz (THz) communication channels across 300 GHz (0.3 THz) to 310 GHz (0.31 THz) frequency spectrum. At terahertz frequencies, diffuse reflection tends to be higher due to the increased surface roughness and this surface roughness causes an additional attenuation even in a specular direction of reflection (by the amount that is scattered into non-specular directions). Two most famous modeling approaches, Rayleigh-Rice (R-R) and Beckmann-Kirchhoff (B-K) theories are employed to account for the surface scattering and compared by demonstrating the multipath channel transfer function (CTF) dynamics for line-of-sight (LoS) and non-line-of-sight (NLoS) conditions in a simple office environment. The R-R vector perturbation approach predicts diffuse reflection from optically smooth surfaces (σ h /λ≪1), whilst classical B-K theory in addition attempts to predict the angular distribution of the scattered field from very rough surfaces (σ h /λ≪1). The composite rough surfaces considered in this work have a Gaussian probability density of height and a Gaussian correlation function. Based on these results, it is concluded that the rough surface scattering effects are enhanced at terahertz frequencies and the scattering phenomena show a significant impact, especially in NLoS configuration

Religion as a barrier to the use of student loans for higher education:a community‐based participatory study with Somalis living in England

The unwillingness of the Somali community to finance higher education has largely gone unnoticed within the academic literature and government policy documents. This study explores the role of religion and the influence of Shari'ah scholars on the use of interest‐bearing student loans within the Somali community. In the absence of any theoretical framework on this topic, we explore the multiple socioeconomic factors that may influence the attitude, perception of need, motivation and action of using student loans for higher education, by proposing the UK Somali Muslims Acceptance of Interest‐bearing Student Loan Model. This is also a community‐based participatory study that actively involved Somali community members in exploring and interpreting the results. This was achieved through regular consultations with the sampled Somali Muslim communities within the UK. Our results contribute to the broader debate on the effect of cultural, religious and social values of marginalised communities on inclusion and widening access policies for higher education. The findings reemphasise that people sharing the same location do not necessarily share the same level of opportunities for higher education because of the intersectionality of race, religion, gender and class. The results also show the complexity of the issue of exclusion and the atheoretical nature of student loans as a financial instrument for improving financial inclusion and widening access to higher education among Somali residents in England

Atmospheric Attenuation Analysis in Indoor THz Communication Channels

In this paper, we study the terahertz (THz) transmission channels from 100 GHz (0.1 THz) to 1000 GHz (1 THz) by including the effects of frequency-dependent atmospheric attenuation and diffuse reflection (non-specular scattering) due to surface roughness for short-range indoor wireless communications. First and foremost, the ITU-R Rec. P. 676-8 model has been used for this study to compute the effects of water-vapor content in the atmosphere by demonstrating the multipath channel transfer function (CTF) dynamics for line-of-sight (LoS) and non-line-of-sight (NLoS) scenarios in a simple realistic office environment. Then, the indoor multipath propagation and its impact considering rough surfaces has been investigated employing the classical Beckmann-Kirchhoff (B-K) model by using our self-developed ray tracing algorithm (RTA). Finally, the relative received power and contribution of the diffusely scattered power at 300 GHz has been illustrated at each scenario point with different surface roughness to predict the achievable signal-to-noise ratio

HEAT TRANSFER MODELING OF METAL DEPOSITION EMPLOYING WELDING HEAT SOURCE

ABSTRAC

Monitoring health status and quality assessment of leaves using terahertz frequency

The demand for effective use of water resources has increased due to ongoing global climate transformations in the agriculture science sector. Cost-effective and timely distributions of the appropriate amount of water are vital not only to maintain a healthy status of plants leaves but to drive the productivity of the crops and achieve economic benefits. This paper presents a novel, and non-invasive machine learning (ML) driven approach using terahertz waves with a swissto12 material characterization kit (MCK) in the frequency range of 0.75 to 1.1 THz in real-life digital agriculture interventions, aiming to develop a feasible and viable technique for precise estimation of water content (WC) in plants leaves on different days. For this purpose, multi-domain features are extracted from frequency, time, time-frequency domains using observations data to incorporate three different machine learning algorithms such as support vector machine, (SVM), K-nearest neighbour (KNN) and decision-tree (D-Tree). The results demonstrate SVM outperformed other classifiers using 10-fold and leave-one-observations-out cross-validation for different days classification with an overall accuracy of 98.8%, 97.15%, and 96.82% for coffee, pea-shoot, and spinach leaves respectively. In addition, using SFS technique, coffee showed a significant improvement of 15%, 11.9%, 6.5% in computational time for SVM, KNN and D-tree. For pea-shoot, 21.28%, 10.01%, and 8.53% of improvement was noticed in operating time for SVM, KNN and D-Tree classifiers. Lastly, in baby-spinach leaf, SVM exhibited an upgrade of 21.28%, 10.01%, and 8.53% was noticed in operating time for SVM, KNN and D-Tree classifiers and which eventually enhanced the classification accuracy. Thus, the proposed method incorporating ML using terahertz waves can be beneficial for precise estimation of WC in leaves and can provide prolific recommendations and insights for farmers to take proactive actions in relations to plants health monitoring

Low-Rank Multi-Channel Features for Robust Visual Object Tracking

Kernel correlation filters (KCF) demonstrate significant potential in visual object tracking by employing robust descriptors. Proper selection of color and texture features can provide robustness against appearance variations. However, the use of multiple descriptors would lead to a considerable feature dimension. In this paper, we propose a novel low-rank descriptor, that provides better precision and success rate in comparison to state-of-the-art trackers. We accomplished this by concatenating the magnitude component of the Overlapped Multi-oriented Tri-scale Local Binary Pattern (OMTLBP), Robustness-Driven Hybrid Descriptor (RDHD), Histogram of Oriented Gradients (HoG), and Color Naming (CN) features. We reduced the rank of our proposed multi-channel feature to diminish the computational complexity. We formulated the Support Vector Machine (SVM) model by utilizing the circulant matrix of our proposed feature vector in the kernel correlation filter. The use of discrete Fourier transform in the iterative learning of SVM reduced the computational complexity of our proposed visual tracking algorithm. Extensive experimental results on Visual Tracker Benchmark dataset show better accuracy in comparison to other state-of-the-art trackers

Identification of systemic immune response markers through metabolomic profiling of plasma from calves given an intra-nasally delivered respiratory vaccine

International audienceVaccination procedures within the cattle industry are important disease control tools to minimize economic and welfare burdens associated with respiratory pathogens. However, new vaccine, antigen and carrier technologies are required to combat emerging viral strains and enhance the efficacy of respiratory vaccines, particularly at the point of pathogen entry. New technologies, specifically metabolomic profiling, could be applied to identify metabolite immune-correlates representative of immune protection following vaccination aiding in the design and screening of vaccine candidates. This study for the first time demonstrates the ability of untargeted UPLC-MS metabolomic profiling to identify metabolite immune correlates characteristic of immune responses following mucosal vaccination in calves. Male Holstein Friesian calves were vaccinated with Pfizer Rispoval® PI3 + RSV intranasal vaccine and metabolomic profiling of post-vaccination plasma revealed 12 metabolites whose peak intensities differed significantly from controls. Plasma levels of glycocholic acid, N-[(3α,5β,12α)-3,12-Dihydroxy-7,24-dioxocholan-24-yl]glycine, uric acid and biliverdin were found to be significantly elevated in vaccinated animals following secondary vaccine administration, whereas hippuric acid significantly decreased. In contrast, significant upregulation of taurodeoxycholic acid and propionylcarnitine levels were confined to primary vaccine administration. Assessment of such metabolite markers may provide greater information on the immune pathways stimulated from vaccine formulations and benchmarking early metabolomic responses to highly immunogenic vaccine formulations could provide a means for rapidly assessing new vaccine formulations. Furthermore, the identification of metabolic systemic immune response markers which relate to specific cell signaling pathways of the immune system could allow for targeted vaccine design to stimulate key pathways which can be assessed at the metabolic level

Static and vibration analysis of functionally graded beams using refined shear deformation theory

Static and vibration analysis of functionally graded beams using refined shear deformation theory is presented. The developed theory, which does not require shear correction factor, accounts for shear deformation effect and coupling coming from the material anisotropy. Governing equations of motion are derived from the Hamilton's principle. The resulting coupling is referred to as triply coupled axial-flexural response. A two-noded Hermite-cubic element with five degree-of-freedom per node is developed to solve the problem. Numerical results are obtained for functionally graded beams with simply-supported, cantilever-free and clamped-clamped boundary conditions to investigate effects of the power-law exponent and modulus ratio on the displacements, natural frequencies and corresponding mode shapes

Axial-flexural coupled vibration and buckling of composite beams using sinusoidal shear deformation theory

A finite element model based on sinusoidal shear deformation theory is developed to study vibration and buckling analysis of composite beams with arbitrary lay-ups. This theory satisfies the zero traction boundary conditions on the top and bottom surfaces of beam without using shear correction factors. Besides, it has strong similarity with Euler–Bernoulli beam theory in some aspects such as governing equations, boundary conditions, and stress resultant expressions. By using Hamilton’s principle, governing equations of motion are derived. A displacement-based one-dimensional finite element model is developed to solve the problem. Numerical results for cross-ply and angle-ply composite beams are obtained as special cases and are compared with other solutions available in the literature. A variety of parametric studies are conducted to demonstrate the effect of fiber orientation and modulus ratio on the natural frequencies, critical buckling loads, and load-frequency curves as well as corresponding mode shapes of composite beams