This paper is aimed at improving the output voltage waveform of a single phase PWM inverter. Two approaches is proposed, the first approach is based on selected harmonic elimination (SHE) of order up to 7th harmonic, for minimising harmonic distortion and modulating amplitude of the fundamental component of the output voltage waveform. For the first time, the Levenberg-Marquardt algorithm (LMA) is used for determining the switching angles of the inverter switches. The second approach is based on ripple current minimisation using LMA. A simulation model is developed using PSIM for the inverter to verify the proposed approaches. An experimental system was implemented to demonstrate the effectiveness of the proposed approaches by using PIC16F877 microcontroller. Analysis of the voltage THD as influenced by the amplitude modulation index is made using MATLAB based on the computed switching angles.

Natural convection in a differentially-heated enclosure is studied, with emphasis on the role of thermophoresis force and slip/drift velocity on particle surface with respect to the main flow. In nanofluid literature, thermophoresis force has been either neglected or erroneous expressions have been used to model its effect. Here, a sufficiently accurate expression for thermophoresis coefficient in liquid solutions and mixtures, backed with a theoretical foundation is introduced and used. A two-phase lattice Boltzmann method (LBM) is employed to capture the slip velocity created by Brownian, thermophoresis and gravitational forces. At Ra = 106 and particle volume concentration of 5%, the nanofluid Nu number is 13% higher than that of the pure fluid, where 5% out of 13% of the enhancement is due to the thermophoresis effect.

One of the most important problems Egypt is facing nowadays is saving and controlling the limited available quantity of water and its quality for irrigation and other purposes. Such goals may be achieved through different types of diversion head structures across the river and in the entrance of other carrying canals. The construction of diversion head structures, which usually causes many technical problems, should have the objective of solving and overcoming to protect the structure from failure. The main problem occurs downstream. Such structures have the harmful effect of converting the potential energy gained in the upstream side to a kinetic energy in the downstream side. This energy must be dissipated shortly and safely as near as possible to the head structure to avoid its destructive effect. The hydraulic jump is the most effective tool for the dissipation of water energy, accelerating the forming of the hydraulic jump downstream such structures became essential for achieving our main goal. Using energy dissipaters on the soled apron in the downstream side of the structures was the main technique for accelerating the hydraulic jump formation and dissipating great amount of the residual harmful kinetic energy occurring downstream head structures. So early, many researchers investigated different types, shapes, and arrangements of such dissipaters to evaluate its efficiency in dissipating the water energy and accelerating the forming of the hydraulic jump. In fact, in our present study we will try to investigate some other shapes of energy dissipaters, which have not been studied enough, by evaluating its positive technical impact on: (i) percentage value of dissipating kinetic water energy; (ii) percentage value of increasing the dissolved oxygen (DO) content in the irrigation water, and improving its quality. The study is proposed to be held in the irrigation and hydraulic laboratory of the Civil department, Faculty of Engineering, Assiut University, using a movable bed tilting channel 20 m long, 30 cm wide, and 50 cm high, using fourteen types of curved dissipaters with different arrangements as shown in Table 2. It is worth mentioning that, in this first part of our paper, we will introduce a comparative analysis for the efficiency of different types of energy dissipaters available in the literature review. The most effective types of the previously studied dissipaters will be put in a comparison with our new dissipaters from the two above mentioned points of view, and the results will be presented in the second part of this paper later.

Haulage drifts play a vital role in providing personnel and equipment access to ore extraction areas for mine production. Thus, their stability is of crucial importance during the life of a mine plan. Many Canadian mines use longhole mining methods or one of its variants. These methods require access to the orebody through haulage drifts on multiple levels. This paper examines the stability of mine haulage drifts with respect to planned mining sequence. A case study of an underground mine is presented. The case study examines #1 Shear East of the Garson Mine in Sudbury, Ontario. A two-dimensional, elastoplastic, finite difference model (FLAC 2D) is developed for a haulage drift situated 1.5 km below surface in the footwall of the orebody. The stability of the haulage drift is evaluated in terms of the spread of yield zones into the rockmass due to nearby mining activities. The performance of the drift stability is evaluated at various mining stages, employing the Random Monte Carlo technique in conjunction with finite difference modelling to study the probability of unsatisfactory performance of the drift. The results are presented and categorized with respect to probability, instability, and mining stage. RÉSUMÉ Les galeries de halage jouent un rôle vital permettant l'accès des operateurs et de l'équipement dans les zones d'extraction . Ainsi, leur stabilité est d'une importance cruciale au cours de la vie de la mine. Plusieurs mines canadiennes utilisent la méthode d'exploitation long-trous ou une de ses variantes. Ces méthodes nécessitent l'accès à la zone minéralisée à travers les galeries de halage sur plusieurs niveaux. Ce document examine la stabilité des galereis de halage des mines en fonction en considérant la séquence minière prévue. Une étude de cas de la zone n ° 1 de cisaillement Est, de la mine souterraine Garson à Sudbury, Ontario, est présentée. Un modèle de différence finie de deux dimensions élastoplastique (FLAC 2D) est développé pour une galerie de halage située à 1,5 km sous la surface (in the footwall of the orebody). La stabilité de la galerie de halage est évaluée en termes de l'extension des zones de rendement dans la masse rocheuse en raison des activités minières à proximité et par rapport à un système de soutien de roche primaire comprenant 2,4 m et 2,1 m de résine coulis barres dans le dos de dérive et les murs de dérive, respectivement . La performance de la stabilité de la galerie est évaluée à différentes étapes de minages , en employant la méthode aléatoire de Monte Carlo en conjonction avec le logiciel de modélisation de différences finies FLAC 2D pour étudier la probabilité d'un rendement insatisfaisant de la stabilité de la galerie. Les résultats sont présentés et classés selon la probabilité, l'instabilité, et l'étape de l'exploitation minière.