A study of the climate of Egypt with special reference to agriculture

This thesis contains a study of the climate of Egypt with special reference to agriculture. It is organised in three main sections. The main body of the thesis, beginning with Chapter 3 (Temperatures in Egypt), deals with surface, earth and water temperatures in detail. Analysis of daily maximum temperatures at selected stations during the 15 year period (1960 - 1974) showed that spring is the period during which the frequency and severity of hot spells is greatest. Analysis of precipitation over Egypt showed that the rainy season in Egypt occurs between October and May and the maximum rainfall over the coastal Mediterranean region occurs in January, but in Middle and Upper Egypt this maximum occurs in October and May. Evaporation and evapotranspiration was estimated using the Penman equation and the Thornthwaite formula for selected stations in Egypt. These indicated that the evaporation and evapotranspiration values for each month are very high at Aswan, Kharga and Dakhla stations, in comparison to Alexandria and Tanta. The main weather features which are sufficient to specify what is called Khamsin weather have been analysed. These are excessively high surface temperatures and extremely low humidities, associated with the invasion of south and south-east winds which produce rising dust and duststorms. It is also seen that there are two types of Khamsin depressions. The first originates over the Atlantic and the second forms to the south of the Atlas mountains. Factor analysis techniques have been used to classify the climate of Egypt. The results showed that the climate of Egypt can basically be divided into two climatic zones. The first comprises the Mediterranean Coastal area, including the Delta. The second zone covers the rest of the country south of Cairo. Multiple regression equations have been used to explain the relationships between the crop yields and selected climatic variables. The results derived show that the multiple regression equations analysing climatic data have good predictive qualities in terms of annual yields

Pool Boiling Heat Transfer from Aluminum Alloy Circular Surface Using Al2O3 and CuO Water Based Nano-fluids

The present work aims to study the effect of nano-particles volume fraction of nano-fluid on the heat transfer during pool boiling with different values of heat flux. The concentration ratios by volume in demineralized water are taken as 0.02 %, 0.20 %, 0.40 %, 0.60, and 0.80 % for Al2O3 nano-particles and 0.02 %, 0.06 %, and 0.20 % for CuO nano-particles. Heat transfer coefficients for pool boiling were established experimentally for different values of volume fraction and heat flux. The heating element is made from an aluminum alloy (AL 6061) with a circular smooth surface of 100 mm diameter and 10 mm thickness. The nano-particles porous layer that builds up during boiling is observed by a scanning electron microscope of the heated surface before and after the boiling. The results demonstrate that the heat transfer rate depends on the concentration ratios and heat flux. Using nano-particles decreases the pool boiling heat transfer in comparison with demineralized water. Due to the deposition of nano-particles on the heated surface, lower heat transfer is obtained for a lower bubble departure compared with demineralized water for the small wall superheat

A comparative review of three different power inverters for DC–AC applications

This paper presents a comparative review of three different widely used power inverters, namely the conventional six-switch inverter; the reduced switch count four-switch inverter; and the eight-switch inverter. The later inverter can be reconfigured as a neutral-point diode-clamped inverter at the failure of one inverter leg. The three power inverters are compared and discussed with respect to cost, complexity, losses, common mode voltage, and control techniques. The paper is intended to serve as a guide regarding selecting the appropriate inverter for each specific application. Simulation results are presented to demonstrate the performance of the three power inverters, followed by a comprehensive comparison between the three power inverters

Model predictive current control for a low-cost shunt active power filter

Performance of a three-phase shunt active power filter (SAPF) relies on the capability of the controller to track the reference current. Therefore, designing an accurate current controller is crucial to guarantee satisfactory SAPF operation. This paper presents a model predictive current controller (MPCC) for a low-cost, four switch, shunt active power filter for power quality improvement. A four switch, B4, converter topology is adopted as an SAPF, hence offering a simple, robust, and low-cost solution. In addition, to further reduce the overall cost, only two interfacing filter inductors, instead of three, are used to eliminate switching current ripple. The proposed SAPF model MPCC is detailed for the implementation, where simulation and experimental results validate the effectiveness of the proposed control algorithm showing a 20% improvement in total harmonic distortion compared with a conventional hysteresis band current controller

Synthesis and antimicrobial activity of some penicillin and cephalosporin derivatives

196-19

Some Properties of Special Magnetic Curves

In the theory of curves, a magnetic field generates a magnetic flow whose trajectories are curves called magnetic curves. This paper aims at studying some properties for these curves which corresponding to the Killing magnetic fields in the 3-dimensional Euclidean space. We investigate the trajectories of the magnetic fields called $T$-magnetic and $e$-magnetic curves, also we give some characterizations of these curves. In addition, we determine all magnetic curves for new spherical images of a spherical curve and finally, we defray some examples to confirm our main results

Power density improvement due to rotor flux screens in an SRM with a higher number of rotor poles than stator poles

This paper studies the performance of screened switched reluctance motors (SRMs) with a number of rotor poles higher than the number of stator poles. Flux (conducting) screens are electrically conducting, non-magnetic materials like aluminum or copper. These screens fill the interpolar rotor air gaps decreasing the unaligned inductance, and thereby increasing the output torque. In addition, flux screens result in a cylindrical rotor structure which minimizes windage losses especially at high speeds. The paper investigates the effect of the flux screens thickness and material on the SRM performance including output torque, power and phase current. A modified flux tube approach for estimating the unaligned inductance of screened SRM is proposed. Finite element analysis results for different screen cases confirm the effectiveness of conducting screens in improving the torque, hence power capability, of switched reluctance motors

Metabolic Syndrome and Cardiovascular Risk Factors in Obese Adolescent

BACKGROUND: Childhood and adolescent obesity is associated with insulin resistance, abnormal glucose metabolism, hypertension, dyslipidemia, inflammation, liver disease, and compromised vascular function. The purpose of this study was to determine the prevalence of cardiovascular risk factor abnormalities and metabolic syndrome in a sample of obese adolescent as prevalence data might be helpful in improving engagement with obesity treatment in future. The high blood lipid levels and obesity are the main risk factors for cardio vascular diseases. Atherosclerotic process begins in childhood.AIM: This study aimed to investigate the relationship between obesity in adolescent and their blood lipids levels and blood glucose level.METHODS: This study was conducted with 100 adolescents of both gender age 12-17 years and body mass index (BMI) greater than 95th percentiles and 100 normal adolescents as control group. The blood samples were collected from all adolescents after overnight fasting (10 hours) to analyze blood lipids (Total cholesterol, high density lipoprotein, low density lipoprotein) and hematological profile (Hemoglobin, platelets and red blood cell, C reactive protein and fasting blood glucose.RESULTS: There were statistical difference between the two groups for red blood cells (P<0.001), Hemoglobin (P < 0.001) and platelets (P = 0.002), CRP (P = 0.02). Positive correlation was found between the two groups as regards total cholesterol (P = 0.0001), P value was positive for HDL (P = 0.005 and Atherogenic index P value was positive (P = 0.002). Positive correlation was found between the two group as regards fasting blood glucose (P = 0.001).CONCLUSION:  Saturated fat was associated with elevated lipid levels in obese children. These results reinforce the importance of healthy dietary habits since child-hood in order to reduce the risks of cardiovascular diseases in adulthood

Improving postharvest storage of fresh artichoke bottoms by an edible coating of Cordia myxa gum

This study aimed to prolong the shelf life of fresh-cut artichoke (Cynara scolymus L.) bottoms under refrigerated conditions (2 °C and 95 % RH) for a period of 9 d. Fresh artichoke bottoms were subjected to an edible coating of Cordia myxa gum (Cg) supplemented with or without calcium dichloride (CaCl2) 1 %, or ascorbic acid (AsA) 1 %. The key postharvest quality parameters which were investigated were weight loss, browning, polyphenol oxidase activity (PPO), firmness, vitamin C, and total phenolic compounds (TPC). Moreover, the microbial load of artichoke bottoms during the storage was also measured which comprised of total aerobic mesophilic and psychrotrophic bacteria, fungi, and E. coli. Results indicated that edible coating with Cg, when supplemented with CaCl2 or AsA, had a significant positive effect on weight loss, vitamin C, and TPC. Browning and PPO activities were significantly inhibited by Cg supplemented with AsA. The mesophilic and psychrotrophic bacterial count was significantly reduced in the presence of CaCl2 with or without Cg. For moulds and E. coli control, again Cg in combination with CaCl2 seems to be the most effective treatment. Hence, based on these findings, it can be recommended that postharvest coating Cg supplemented with CaCl2 could be a new application for delaying browning and extending the shelf-life of artichoke bottoms during refrigerated storage. Further research and development are required in commercial settings to test and scale the application of Cg in fresh-cut artichoke bottom industry