Aluminum-carbon nanotube nanocomposite for silicon solar cell back metallization

With the global push towards having thinner silicon solar cells, the bowing problem arising from the thermal mismatch between the Aluminum electrode and the Silicon wafer in the cell becomes more critical. The thinner the cells the more the bowing and the higher the probability of cracking and hence yield losses and lower cell efficiency. The main objective of this work was to explore the effect of introducing CNT into the composition of the Al paste in order to reduce the Coefficient of Thermal Expansion (CTE) of the resulting composite and hence reduce the bowing problem. Two types of samples were produced: Cylindrical and Wafer samples. The first consisted of 26 compacted and sintered at 500oC powders of the following consistencies: Un-Milled Al, Milled Al, 2%, 5% and 10% CNT-Al. CTE was measured by a Dilatometer DIL 801, TA instruments device. Electrical Performance was measured for the same samples via varying the voltage and measuring the current, then calculated the resistance taking the latter as an indicator for the Resistivity. In both tests, it was found that the 10% CNT-Al samples gave the highest results: in terms of CTE, it resulted in around 20% reduction, and in case of electrical performance, it increased the resistivity by around 3.8%. For the wafer samples, Un-Milled Al, Milled Al and 10% CNT-Al powder-based pastes were prepared using a patented recipe that was modified for the current work, and then the pastes were printed using Spin Coating technique on 9 wafers which were heated at 160oC for around 3 hours. A Contactless Wafer Geometry Gauge device was used to measure the bow and warp. Bow results were inconclusive, however the warping revealed promising results as it was clearly shown that the 10% CNT-Al paste caused the lowest warp per unit thickness of paste printed, average warp to Al paste layer thickness ratios for all 3 pastes were 0.59, 0.35 and 0.24 for the Un-Milled Al, Milled Al and 10% CNT-Al pastes respectively. SEM images of the Top & cross-sectional views of the wafer showed that while the Un-Milled Al and 10% CNT-Al wafers provided an almost uniform layer, the thickness of the layer of the Milled Al paste was relatively irregular due to employing irregular techniques of printing and un-even powder particle size

Existence, uniqueness and approximation of solutions to the stochastic Landau-Lifshitz-Gilbert equation on the real line

The Landau-Lifshitz-Gilbert(LLG) equation is a partial differential equation describing the motion of magnetic moments in a ferromagnetic material. In the theory of ferromagnetism, an important problem is to study noise-induced transitions between different equilibrium states. Hence, the LLG equation needs to be modified in order to incorporate random fluctuations into the dynamics of the magnetisation. Including the noise effects in the theory of evolution of magnetic moments requires a proper study of the stochastic version of the LLG equation. The aim of this thesis is to lay foundation of the theory of the stochastic LLG equation for magnetic nanowire of infinite length that is widely used in physics to study the dynamics of the domain walls. The deterministic version of this equation has been intensely studied in recent years due its importance for fabrication of magnetic devices. It is customary to study the nanowire of infinite length. This approach allows for relatively simple mathematical description and at the same time provides a useful approximation of the wires of finite length. Firstly, we propose a semi-discrete finite difference method to find approximate solutions to the stochastic LLG equation on the real line. Then, we transform the discretised equation into a partial differential equation with random coefficients, without the It\^o term, to prove the convergence of approximate solutions. We deduce the existence and uniqueness of a global unique strong solution to the stochastic problem on the whole real line. The main novelty of our approach is that we prove the existence of pathwise solutions, unique for each given in advance trajectory of the noise. Secondly, in order to solve numerically the stochastic LLG equation on real line, we truncate the infinite line into a bounded interval. We consider the stochastic problem on a bounded interval $[-L,L]$ with physically relevant homogeneous Neumann boundary conditions and we show that when $L$ tends to infinity, the solution of the problem on a bounded interval converges to the solution of the original stochastic problem on real line. We also provide pathwise error estimates depending on $L$. Finally, in order to solve the stochastic LLG equation numerically we propose a fully-discrete finite difference scheme based on the midpoint rule for the stochastic LLG equation on a bounded interval. We perform first numerical experiments which shows that the fully-discrete solutions converge to the solution of the stochastic problem on a bounded interval $[-L,L]$ for vanishing discretisation parameters. Next, we implement a numerical experiment which validates the convergence of the solution on a bounded interval $[-L,L]$ to the solution on real line when $L$ is large enough

Caractérisation à grande échelle d'un signal 60 GHz dans un environnement minier confiné

Les télécommunications sans fil ont connu un grand intérêt et succès depuis plusieurs années grâce à leur facilité de déploiement par rapport aux télécommunications filaires, leur support de la mobilité des nœuds communiquant et leur souplesse d'utilisation par les usagers. Le problème actuel des télécommunications sans fil est de pouvoir assurer des débits élevés de transmission capable de supporter des applications fortement gourmande en bande passante. Pour relever ces défis plusieurs solutions sont proposées. Parmi elle la montée en fréquence vers le spectre des ondes millimétriques. Cette approche est à la base de notre étude qui porte un intérêt particulier à l'étude de la propagation d 'un signal 60 GHz dans un dans un milieu confiné en mettant en œuvre un sondeur de canal pour ses ondes millimétriques. Les résultats des mesures à grande échelle d'un signal à 60 GHZ sont étudiés dans plusieurs scénarios : visibilité directe, et en visibilité obstruée en utilisant comme obstacle un être humain, dans un environnement de laboratoire et dans un milieu souterrain minier. Les résultats montrent une différence considérable dans l'atténuation de canal pour ces différents scénarios. Ce travail a été effectué en partie au laboratoire de recherche en communications souterraine LRTCS à Val-d'Or, Canada et pour la partie expérimentation sous terre dans la mine de CANMET. Wireless communications have been a great interest and success for several years because of their infrastructure simplicity compared to wired telecommunications, their important terminal mobility, and also their flexibility of operation by users. The current problem of wireless telecommunications is being able to provide high transmission rates capable of supporting intensive applications consuming bandwidth. To meet these challenges, several solutions are proposed. Among them the rise in frequency to millimetre wave spectrum. This approach is the basis of our study that has a particular interest in the study of signal propagation in 60 GHz in a confined environment by implementing a channel sounder for its millimetre wave. The measurement results of a large-scale signal at 60 GHz are studied in several scenarios: Line of Sight and obstructed Line of sight using a human being as an obstacle in a laboratory environment and in an underground mining environment. The results show a considerable difference in the channel attenuation for these different scenarios. This work was done in part at the Underground Communications Research Laboratory LRTCS in Val-d'Or, Canada and the part of experimentation in underground CANMET mine

A rare breed: Wild-type braf and ighv expression in a 29 year old lady with classical hairy cell leukemia

The V600 BRAF mutation has been described as a key mutation in the pathogenesis of classical hairy cell leukemia (c-HCL) cases without expression of a mutant immunoglobulin heavy chain (IgHV). Here we present a rare case of c-HCL with neither V600 BRAF mutation nor the aforementioned IgHV variant successfully treated with cladribine and review the current literature on its use in women of childbearing age/pregnancy

Thymic Rejuvenation: Are We There Yet?

Vaccination is an appealing form of immunotherapy for frail senior patients. However, several studies have shown that in contrast to younger adults, older patients do not effectively respond to vaccines. This phenomenon is greatly attributed to immunosenescence, a hallmark of aging defined by a general decline in immunity caused by thymic involution. Historically, the study of thymic involution brought to attention several factors and components involved in thymopoiesis, as contributors to the phenomena. Depicting the underlying cause(s) of the dramatic changes in the production and properties of the naïve T-cell pool in the event of acute thymic injury or due to inovulation can therefore, help focus the efforts on the best strategy to reverse or overcome these hurdles. Here, we discuss some of the well-studied approaches for rejuvenating the thymus, and introduce interleukin-(IL) 21 as the most recent thymo-stimulatory agent in the field

Multi-variable Constrained Control Approach for a Three-Dimensional Eel-like Robot

International audienceIn this paper, a multi-variable feedback design for the 3D movement of an eel-like robot is presented. Such a robot is under construction in the context of a national French robotic project. The proposed feedback enables the tracking of a desired 3D position of the eel's head as well as the stabilization of the rolling angle. The control design is based on a recently developed reduced model that have been validated using a 3D complete continuous model. Several scenarios are proposed to assess the efficiency of the proposed feedback law

Plasmablastic Lymphoma: Case Report of Prolonged Survival of an Advanced Human Immunodeficiency Patient and Literature Review

Clinical Practice Points. Plasmablastic lymphoma (PBL) is a rare and highly aggressive variant of diffuse large B cell lymphoma with median survival of advanced stage patients varying between 6 and 15 months in previous reports. We report here a human immunodeficiency virus-infected patient surviving over 12 years following treatment for advanced PBL with EPOCH chemotherapy and intrathecal therapy. This case highlights the potential for improved survival in PBL with intensive chemotherapy. Further, literature review suggests promising prospects utilizing novel targeted therapies to increase the rate of prolonged responses

Investigation of numerical dissipation in classical and implicit large eddy simulations

The quantitative measure of dissipative properties of different numerical schemes is crucial to computational methods in the field of aerospace applications. Therefore, the objective of the present study is to examine the resolving power of Monotonic Upwind Scheme for Conservation Laws (MUSCL) scheme with three different slope limiters: one second-order and two third-order used within the framework of Implicit Large Eddy Simulations (ILES). The performance of the dynamic Smagorinsky subgrid-scale model used in the classical Large Eddy Simulation (LES) approach is examined. The assessment of these schemes is of significant importance to understand the numerical dissipation that could affect the accuracy of the numerical solution. A modified equation analysis has been employed to the convective term of the fully-compressible Navier–Stokes equations to formulate an analytical expression of truncation error for the second-order upwind scheme. The contribution of second-order partial derivatives in the expression of truncation error showed that the effect of this numerical error could not be neglected compared to the total kinetic energy dissipation rate. Transitions from laminar to turbulent flow are visualized considering the inviscid Taylor–Green Vortex (TGV) test-case. The evolution in time of volumetrically-averaged kinetic energy and kinetic energy dissipation rate have been monitored for all numerical schemes and all grid levels. The dissipation mechanism has been compared to Direct Numerical Simulation (DNS) data found in the literature at different Reynolds numbers. We found that the resolving power and the symmetry breaking property are enhanced with finer grid resolutions. The production of vorticity has been observed in terms of enstrophy and effective viscosity. The instantaneous kinetic energy spectrum has been computed using a three-dimensional Fast Fourier Transform (FFT). All combinations of numerical methods produce a k−4 spectrum at t∗=4 , and near the dissipation peak, all methods were capable of predicting the k−5/3 slope accurately when refining the mesh

Changes of Radial Diffusivity and Fractional Anisotopy in the Optic Nerve and Optic Radiation of Glaucoma Patients

Purpose of this study was to evaluate with diffusion-tensor imaging (DTI) changes of radial diffusivity (RD) and fractional anisotropy (FA) in the optic nerve (ON) and optic radiation (OR) in glaucoma and to determine whether changes in RD and FA correlate with disease severity. Therefore, glaucoma patients and controls were examined using 3T. Regions of interest were positioned on RD and FA maps, and mean values were calculated for ON and OR and correlated with optic nerve atrophy and reduced spatial-temporal contrast sensitivity (STCS) of the retina. We found, that RD in glaucoma patients was significantly higher in the ON (0.74 ± 0.21 versus 0.58 ± 0.17·10−3 mm2 s−1; P < 0.05) and OR (0.79 ± 0.23 versus 0.62 ± 0.14·10−3 mm2 s−1; P < 0.05) compared to controls. Aside, FA was significantly decreased (0.48 ± 0.15 versus 0.66 ± 0.12 and 0.50 ± 0.20 versus 0.66 ± 0.11; P < 0.05). Hereby, correlation between changes in RD/FA and optic nerve atrophy/STCS was observed (r > 0.77). In conclusion, DTI at 3 Tesla allows robust RD and FA measurements in the ON and OR. Hereby, the extent of RD increase and FA decrease in glaucoma correlate with established ophthalmological examinations

Optimal network reconfiguration in active distribution networks with soft open points and distributed generation

Copyright © 2019 by the authors. In this study, we allocated soft open points (SOPs) and distributed generation (DG) units simultaneously with and without network reconfiguration (NR), and investigate the contribution of SOP losses to the total active losses, as well as the effect of increasing the number of SOPs connected to distribution systems under different loading conditions. A recent meta-heuristic optimization algorithm called the discrete-continuous hyper-spherical search algorithm is used to solve the mixed-integer nonlinear problem of SOPs and DGs allocation, along with new NR methodology to obtain radial configurations in an efficient manner without the possibility of getting trapped in local minima. Further, multi-scenario studies are conducted on an IEEE 33-node balanced benchmark distribution system and an 83-node balanced distribution system from a power company in Taiwan. The contributions of SOP losses to the total active losses, as well as the effect of increasing the number of SOPs connected to the system, are investigated to determine the real benefits gained from their allocation. It was clear from the results obtained that simultaneous NR, SOP, and DG allocation into a distribution system creates a hybrid configuration that merges the benefits offered by radial distribution systems and mitigates drawbacks related to losses, power quality, and voltage violations, while offering a far more efficient and optimal network operation. Also, it was found that the contribution of the internal loss of SOPs to the total loss for different numbers of installed SOPs is not dependent on the number of SOPs and that loss minimization is not always guaranteed by installing more SOPs or DGs along with NR. One of the findings of the paper demonstrates that NR with optimizing tie-lines could reduce active losses considerably. The results obtained also validate, with proper justifications, that SOPs installed for the management of constraints in LV feeders could further reduce losses and efficiently address issues related to voltage violations and network losses