Effect of Ambient Conditions on Insulation Strength of High Voltage Protection Devices

Overvoltage protection devices are the most important apparatuses in the power networks which decrease the cost of power network designing. High voltage protection devices such as spark gaps, surge arrestors, and pin & cap insulators are needed in a power system to protect the system from overvoltage by deflecting the cross-currents. In designing a power system, it is necessary to consider the strength of protection devices under different ambient conditions. Protection devices should be tested under different voltages to ensure the reliability of the power system. In this paper, the experimental activities were performed on the investigation of the performance of the spark gaps, arresters and contaminated insulator strings under impulse lightning voltage in High Voltage Lab at Mississippi State University and results are obtained consistently. For this test, IEEE standards were considered to accord the ambient conditions at laboratory with standards

Novel considerations for lightning strike damage mitigation of Carbon Fiber Reinforced Polymer Matrix (CFRP) composite laminates

Lightning current with high amplitude disseminates through the body of aircraft and causes physical damages including the delamination and puncture of materials. Also , such high-amplitude and high-frequency current could interfere with electronic devices through electromagnetic coupling with the conductive interfaces of an airplane. Hence, robust protection against lighting strike is essential in the aerospace industry. Carbon Fiber Reinforced Polymer (CFRP) Matrix Composites have become significant alternatives to conventional metal-base materials. Despite the superior physical and structural properties of CFRP composites, these materials are vulnerable to lightning strikes due to the low electrical conductivity compared to the metal counterpart. Many researchers have been working on the lightning strike damage mitigation of CFRP composites by increasing the electrical conductivity of materials. Conventional methods are adding conductive layers such as metal foil and copper mesh to the composite structures. These layers are added to the composite structure during the manufacturing process and are placed at the top layer for the effective bypassing of lightning current to the ground. While adding the conductive layers reduces the lightning strike damage significantly, the industry is more interested in using conductive nanofillers to prevent the corrosion of metal layers in contact with carbon fibers and to avoid the higher weight of conductive layers than nanofillers. The lightning damage mitigation methods are studied by applying lightning strike current to the CFRP composites using an impulse current generator. Conventional lightning strike damage tolerance of CFRP composites are prone to misinterpretation. The risk of misinterpretation originates from the lack of standards clearly defining testbed design requirements including electrode size and ground electrode edge configuration. In this dissertation, the effects of testbed configuration including discharge and ground electrode on lightning strike damage evaluation studies are demonstrated. Finite element analysis is applied to perform the simulations through the COMSOL Multiphysics to validate the experimental test results. Furthermore, after improving the testbed design, carbon black was added to the CFRP composites as a cost-effective additive for lightning strike damage mitigation performance. Correlations between lightning strike damage intensity and the added carbon black fillers as well as with other additive nanofillers are reported

Comparison of Three Chaotic Meta-heuristic Algorithms for the Optimal Design of Truss Structures with Frequency Constraints

The main reasons for the success of using chaos maps in meta-heuristic algorithms are fast optimization of non-linear and non-convex problems. One of these cases is the control of the natural frequencies of structures to prevent the destructive and dangerous phenomenon of resonance. Natural frequencies have useful information about the dynamic behavior of structures, and by applying dynamic constraints, a significant improvement is achieved in the optimal design of structural weight. Applying frequency limits with traditional and gradient-based methods is very difficult and time-consuming, and in most cases, the calculation process stops at local optima. Recent research shows that chaos maps play a major role in escaping from local optima and reaching global optima. By combining these maps with meta- heuristic algorithms, while avoiding premature convergence, the access to global optima is accelerated and improved, and the ideal state of balance between the exploration and exploitation stages is realized. Today, chaotic algorithms are widely accepted by researchers and are considered as a challenging topic. In a recent research, six chaotic meta- heuristic algorithms have been investigated for the formation and improvement of results with the optimal design of truss structures. In this part the chaotic algorithms include Chaotic Water Evaporation Optimization (CWEO), Chaotic Tug-of-War Optimization (CTWO) and Chaotic Thermal Exchange Optimization (CTEO) are examined

Determining the Effectiveness of Kinesio Taping on Balance in Athletes with Acute Sprain and Chronic Ankles Instable

چکیده مقدمه: بیشتر افرادی که دچار اسپرین خارجی مچ پا می شوند، به طور کامل بهبود نمی یابند و اختلال در تعادل، یکی از رایجترین مشکلاتی است که برای این افراد آسیب دیده بروز می کند. با توجه به آنکه بانداژ ورزشی کینزیوتیپ (Athletic kinesio Tape) به عنوان یک روش درمانی جدید معرفی شده و در طب ورزشی کاربرد پیداکرده است، هدف تحقیق حاضر بررسی اثر کینزیوتیپ بر تعادل ورزشکاران مبتلا به بی ثباتی مزمن و اسپرین حاد مچ پا می باشد. مواد و روش ها: در این مطالعه شبه تجربی 26 ورزشکار مرد ( 14 نفر با بی ثباتی مزمن: میانگین سن 1/2±4/21، BMI 1/3±3/22 و 12 نفر با اسپرین حاد مچ پا: میانگین سن3/2±7/20، BMI 7/2±4/22 ) در شرایط عادی مورد ارزیابی تعادل داینامیک با تست تعادل گردش ستاره ((SEBT در دو وضعیت با کینزیوتیپ به روش ترکیبی اصلاح عملکردی – مکانیکال و بدون بانداژ قرار گرفتند. برای بررسی اثرکینزیوتیپ از آزمون T با سطح معنی داری

Machine Learning Methods for Geotechnical Site Characterization and Scour Assessment

publishedVersio

Determination of optimum feeding rate expressed as percent of body weight in Persian sturgeon, Acipenser persicus

The present study was conducted to determine the best feeding rates expressed as percent of body weight in Persian sturgeon fingerlings at different body weights. Eighteen fiberglass tanks each holding 30 fingerlings with an average initial body weight of 19.45 ± 0.5 g were used in this experiment. Six different feeding trials (1, 2, 3, 4, 5 and 6 percent of body weight) were employed and each trial was run in three replicates through a period of 60 days (4 periods of 15 days). The results were analyzed using Statgragh software and compared using Duncan test. The optimum recommended feeding rate was 4 percent of body weight for an increase of body weight from 19.5 to 31g and 3 percent of body weight for an increase of body weight from 33 to 47g. For an increase in body weight from 47 to 90g the recommended feeding rate was 3 percent of body weight. The recommended doses are subject to alteration with variation in water temperature

Line search algorithms for locally Lipschitz functions on Riemannian manifolds

This paper presents line search algorithms for finding extrema of locally Lipschitz functions defined on Riemannian manifolds. To this end we generalize the so-called Wolfe conditions for nonsmooth functions on Riemannian manifolds. Using ε-subgradient-oriented descent directions and the Wolfe conditions, we propose a nonsmooth Riemannian line search algorithm and establish the convergence of our algorithm to a stationary point. Moreover, we extend the classical BFGS algorithm to nonsmooth functions on Riemannian manifolds. Numerical experiments illustrate the effectiveness and efficiency of the proposed algorithm