Abstract

Blades are the very important components of wind turbines in order to convert wind energy to mechanical or

electrical energy. Therefore, the aerodynamic forces acting on the horizontal wind turbine blades have an important role in

their performance. The objective of this paper is to investigate the aerodynamic characteristics and power generation

properties for a NREL PHASE VI wind turbine blade. For this purpose, an analysis procedure based on the Blade Element

Method (BEM) is demonstrated for a horizontal-axis wind turbine model (HAWT), and the methodology approach is discussed

in detail throughout this paper. In this study, a Math Lab code has been developed for analyzing a model of Horizontal-Axis

Wind Turbine (HAWT) in order to display aerodynamic behaviour on the blade. The NACA S809 airfoil was selected for the

analysis of the wind turbine blade, where the tip and root losses proposed by Prandtl are also executed. The calculated results

are validated using Q-Blade commercial software at rated wind speed of 10 m/s and show that the BEM is a good method of

aerodynamic investigation of a HAWT blade

In this work,we investigate Frobenius companion matrices with entries from the ring of integers modulo a prime number. We introduce a mapping 𝝍to construct a directed graph, where vertices represent these matrices and edges are defined by 𝝍. Our analysis focuses on the structure and properties of this directed graph, including vertex degrees, cycles, and connected components, in relation to theeigenvalues of the matrices

Surface properties of prosthodontic polymer impression materials, such as hardness, roughness, and accuracy, are crucial for the accurate replication of oral structures in restorative dentistry. To evaluate the surface properties by using different types of polymer impression materials commonly used in dentistry and analyze their surface characteristics. Materials and methods: Forty -five samples of materials were used, including alginate (irreversible hydrocolloid), condensation silicone (putty) and addition silicone (putty), study was conducted at the advanced medical polymer group in the Libyan Polymer Research Center to evaluate the surface properties of prosthodontic polymer impression materials. Three evaluation methods were used: Shore hardness testing, surface roughness testing, and dimensional accuracy measurements. Data analysis included mean, standard deviation, and One-way ANOVA calculations. Alginate has a lower hardness compared to addition silicone (putty) and condensation silicone (putty). The ANOVA test for surface roughness showed no significant differences among the materials, with a p-value of 0.027. For shore hardness, there were no significant differences among the materials, with a p-value of 0.000. The ANOVA test for dimensional accuracy showed no significant differences among the different periods for alginate, condensation silicone (putty) and addition silicone (putty), with p-values of 0.000 respectively. The study concluded that alginate had the lowest hardness and roughness compared to condensation silicone (putty) and addition silicone (putty). There are no significant differences among the material surface properties (Shore hardness and surface roughness) but not in dimensional accuracy among the materials. This information provides valuable insights for dental professionals working with impression material. 

Abstract

This project investigated the stresses developed in a thick-walled cylinder for rocket motor case

under internal pressure. Stress analysis used the finite element method with ANSYS software for

rocket motor case selection. This study focus on structural elastic analysis of thick-walled pressure

vessels since it is a common design practice to aim at maintaining the induced stresses within the

elastic region. However, pressure vessels operate under complex environments such as high

pressure which may lead to gross plastic deformation and subsequent failure. In process, the

pressure vessel is pressurized beyond the yield point. As a result, the conventional elastic analysis

will not be applicable at internal pressures above the yield point. Therefore, it is important to

examine the structural integrity of a thick-walled pressure vessel in both elastic and plastic state

of the material.

In this study, FE static structural analysis of a presumably untracked thick-walled solid rocket

motor case has been presented, where stress distribution within the motor case wall and the

resulting material deformation were investigated using ANSYS 19.2. Motor case has been designed

with uniform model of the same internal and external diameter, and motor case with diameter

change at both sides is modeled to investigate the effect of the diameter change or shape

discontinuity on the resulting of stresses and deformation using ANSYS program by applying

internal pressure varying from 50 Bars to 350 Bar. Von Mises yield criteria were used by ANSYS

program and calculated Von Mises stresses were compared; the results are close for elastic

analysis. The results show that the Von Mises stresses was high for discontinues shape of motor

case compared by the uniform motor case (constant thickness).

It has been noted the wide spread of the use of composite materials due to their specific strength that made them the best alternative to many other materials,However, the high cost of synthetic fibers represents an obstacle to the use of composite materials in most applications. Therefore, research has tended to test natural fibers, which are the ideal solution for using composite materials in many industries such as furniture, flooring, decoration, and others. This paper concerned with the study of natural composite materials made of Libyan almond shells. Three different sizes of ground almond shells were studied: large size in the form of grains, medium size, and the small size (powder form). These crushed peels were mixed with the resinous polyester resin in four proportions: ratio of 80: 20, 60: 40, 40: 60, and 20: 80. Three basic tests were conducted to investigate the mechanical properties of the samplesIt has been noted the wide spread of the use of composite materials due to their specific strength that made them the best alternative to many other materials, However, the high cost of synthetic fibers represents an obstacle to the use of composite materials in most applications. Therefore, research has tended to test natural fibers, which are the ideal solution for using composite materials in many industries such as furniture, flooring, decoration, and others. This paper concerned with the study of natural composite materials made of Libyan almond shells. Three different sizes of ground almond shells were studied: large size in the form of grains, medium size, and the small size (powder form). These crushed peels were mixed with the resinous polyester resin in four proportions: ratio of 80:20, 60:40, 40:60, and 20:80. Three basic tests were conducted to investigate the mechanical properties of the samples: impact test, tensile test, and flexural test. The results showed that samples made of almond peels in a powder form exhibits the best results among all other kind of specimens for three mentioned tests of mechanical properties.