An improved model of thin cylindrical piezoelectric layers between isotropic elastic media

AbstractRadially polarized piezoelectric fibers are now considered to be used in smart composites. The piezoelectric layers in these fibers are generally anisotropic in the transverse direction and therefore difficult to analyze when dynamic loads are involved. The present paper presents a theoretical study of the dynamic behavior of radially polarized cylindrical piezoelectric layers between isotropic elastic media. A new interphase model is developed to provide simple yet accurate evaluation of the dynamic response of such anisotropic elastic layers. Unlike the traditional interface-spring model, the current interphase model satisfies the equations of motion of the layers and can provide reliable prediction of the stress and displacement. A comparison between the developed model, the interface-spring model and the finite element analysis is conducted. The results clearly show the advantages of the current model over the traditional interface-spring model in simulating anisotropic layers. Numerical examples based on this interphase model for different interphase thicknesses, loading frequencies and material combinations are presented to evaluate the dynamic behavior of multilayered elastic media

Spatio-temporal variations of macrobenthic fauna in Lake Nasser khors, Egypt

AbstractSpatial and temporal variations of macrobenthic fauna in Lake Nasser khors, were studied at four subsequent seasons during 2013. Khor Tushka West recorded the highest average number (597Org./m2). It was decreased at khor Kursku (112Org./m2) and Kalabsha (105Org./m2) while it reached the lowest at khor Wadi Abyad (65Org./m2). The highest average number was recorded during spring (447Org./m2). It decreased during winter (174Org./m2) and summer (151Org./m2), then reached the lowest during autumn (107Org./m2). Annelida, Arthropoda and Mollusca were the most dominant groups in the lake during the study being 72.65%, 26.09% and 1.35%, respectively. The highest number of species (16) was observed at khor Kalabsha. This may be due to its nature of sandy bottom. Biological indices showed high richness values of all the studies khors except khor Tushka West.These low values of indices may be due to the dominance of Annelids species especially, Limnodrilus spp. and Branchiura sowerbyi. There is a positive correlation between these species and total annelids with all physico-chemical parameters. The analysis of variance between the different khors based on the main macrobenthic groups showed a highly significant value (p<0.001)

Irrigation and drainage in the new millennium

Presented at the 2000 USCID international conference, Challenges facing irrigation and drainage in the new millennium on June 20-24 in Fort Collins, Colorado.Includes bibliographical references.A field study was conducted at Mashtul Pilot Area MPA (260 feddans' 1 feddan = 4200 m2) situated at north Zagazig to evaluate the performance of the long term constructed subsurface drainage system. The evaluation of grades, alignment and clogging of drain lines can give an indication of the system performance and efficiency. Three drainage units served by the same collector were selected. Four 30 m interval PVC lateral pipes were installed at different depths. The results revealed that, the collector drain slopes were either steep or flat while the overall slope of the collector drain was considered steep for about 45.50% of the sections and flat for the rest. On the other hand, some sections showed an inverse slope which can cause a decrease in the discharge rate. The regularity was classified as good for about 82% of the sections and moderate for the rest. The slope of the lateral drains was correct for 41.7% of those under study (12 lateral drains), steep for 16.60%, and flat for the rest, and the regularity was classified as poor except lateral number 71 which had moderate regularity in the first approach while, in the second approach 41.67% had moderate regularity and poor for the rest. Also the deviation of the drain pipes from the straight line was generally larger than pipe diameter. Consequently, air entrapment and sedimentation resulted. The results also indicated that, the average height of sedimentation inside lateral drains was 12.70 mm (618.30 gm/m drain length) while for collector drains, sediment was in 22.88% of pipe diameter. The average reduction in discharge capacity due to sedimentation for laterals and collectors upstream and downstream parts were 17.17%, 32.80% and 17.60% respectively. Also using Manning, Visser and Wesseling equations leads to different safety factors

On the pseudo-incident wave technique for interacting inhomogeneities in electromechanical problems

The current paper presents the Pseudo-Incident Wave method for the theoretical treatment of the dynamic interaction between general inhomogeneities in advanced piezoelectric structures. Instead of simulating the response of such complicated systems using purely numerical or analytical methods, the current technique will take the advantages of the accuracy and reliability of analytical solutions and the flexibility of numerical methods. Using this method the original interaction problem is reduced to the solution of coupled single inhomogeneity problems, for which analytical solutions or simpler numerical solutions could be derived. By considering the consistency condition between different inhomogeneities, the steady state dynamic solution of multiple interaction problems can be formulated in terms of coupled single inhomogeneity solutions. The current method is very general and can provide reliable simulation of complicated interaction problems. Numerical examples are presented to illustrate the effectiveness of the Pseudo-Incident Wave method in simulating dynamic interaction between general inhomegeneities under complicated geometries

Modulation of L-arginine-induced acute pancreatitis by meloxicam and/or L-carnitine in rats

Background: Acute pancreatitis (AP) is an inflammatory disease, where oxidative stress, subsequently inflammatory mediators activation play a pivotal role. Currently, no definite treatment exists and therapy is mainly supportive that directed to inhibit local pancreatic injury and systemic inflammatory complications. This study is presented to explore whether anti-inflammatory and/or antioxidant drug could ameliorate L-arginine-induced AP.Methods: Rats were sub-grouped randomly into five groups. Control group, AP was provoked by a single intraperitoneal injection of L-arginine (250 mg/100g), rat treated with meloxicam (4 mg/kg, IP), animals treated with L-carnitine (500 mg/kg, IP), and rats were treated with both meloxicam and L-carnitine. All treatments were once daily for 7 consecutive days and started 1 hr later after L-arginine administration. Serum and tissues samples were prepared for biochemical analysis. Histopathological examination for the other pancreatic tissues was done.Results: L-arginine significantly elevated serum activity of amylase and lipase enzymes, while notably reduced serum calcium level. Moreover, L-arginine markedly increased the pancreatic tissues content of tumor necrosis factor-α, malondialdehyde, and nitric oxide. In addition, L-arginine significantly increased pancreatic activity of myeloperoxidase, while markedly depleted glutathione level. Treatment with either meloxicam or L-carnitine significantly attenuated L-arginine-induced biochemical changes. On the other hand, co-administration of both meloxicam and carnitine has an ameliorative effect greater than each drug alone.Conclusion: Treatment with both meloxicam and L-carnitine is a more effective than each of them alone which is attributed to augmentation their antioxidant, anti‑inflammatory effects

Irrigation and drainage in the new millennium

Presented at the 2000 USCID international conference, Challenges facing irrigation and drainage in the new millennium on June 20-24 in Fort Collins, Colorado.Includes bibliographical references.Current global population growth rates require an increase in agricultural food production of about 40-50% over the next thirty to forty years, in order to maintain present levels of food intake. To meet the target, irrigated agriculture must play a vital role, in fact the FAO estimates that 60% of future gains will have to come from irrigation. The practice of controlling drainage involves the extension of on-farm water management to include drainage management. With the integration of irrigation and drainage management, the water balance can be managed to reduce excess water losses and increase irrigation efficiencies. Controlled drainage is relatively new and there are many theoretical and practical issues to be addressed. The technique involves maintaining high water table in the soil profile for extended periods of time, requiring careful management to ensure that crop growth is not affected by anaerobic conditions. A fieldwork programme has been investigated to test controlled drainage in the Nile Delta, where water resources are stretched to the limit. Water saving is essential in the next 20 years. Pressures from the fixed Nile water allocation, population growth, industry and other sectors and the horizontal expansion programme mean that this need is urgent. One crop season has been completed at a site in the Western Nile Delta using simple control devices in the subsurface drainage system. This paper discusses the potential benefits of controlled drainage to save water in agricultural areas such as the Nile Delta, and presents findings from the first crop season

Transient Investigation of the Critical Abstraction Rates in Coastal Aquifers: Numerical and Experimental Study

This research investigated the transient saltwater upconing in response to pumping from a well in a laboratory-scale coastal aquifer. Laboratory experiments were completed in a 2D flow tank for a homogeneous aquifer where the time evolution of the saltwater wedge was analysed during the upconing and the receding phase. The SEAWAT code was used for validation purposes and to thereafter examine the sensitivity of the critical pumping rate and the critical time (the time needed for the saltwater to reach the well) to the well design and hydrogeological parameters. Results showed that the critical pumping rate and the critical time were more sensitive to the variations of the well location than the well depth. The critical time increased with increasing the location and depth ratios following a relatively linear equation. For all the configurations tested, the lowest critical pumping rate was found for the lower hydraulic conductivity, which reflects the vulnerability of low permeability aquifers to salinization of pumping wells. In addition, higher saltwater densities led to smaller critical pumping rate and shorter critical time. The influence of the saltwater density on the critical time was more significant for wells located farther away from the initial position of the interface. Moreover, increasing the dispersivity induced negligible effects on the critical pumping rate, but reduced the critical time for a fixed pumping rate

Protective Effects of Simvastatin, a Lipid Lowering Agent, against Oxidative Damage in Experimental Diabetic Rats

The present study was undertaken to evaluate the possible protective effects of simvastatin (SMV) against oxidative stress in streptozotocin- (STZ)-induced diabetic rats. Diabetes was induced experimentally in rats by i.p. injection of STZ in a dose of 60 mg/kg bwt. After 5 weeks of STZ injection, there were apparent reductions in the animal body weight and significant increase in blood glucose, HbA1c, urea, creatinine, AST, ALT, and lipid profiles with a concomitant decrease in total hemoglobin, plasma glutathione and vitamin C as compared to the control group. The treatment with SMV at a dose (10 mg/kg, orally) normalized all the above-mentioned biochemical parameters in STZ-induced diabetic rats. In vitro studies confirmed the free radical scavenging and antioxidant activity of SMV. Therefore, the present results revealed that SMV has a protective effect against STZ-induced oxidative damage by scavenging the free radicals generation and restoring the enzymatic and nonenzymatic antioxidant systems

Assessment of Emissions from Cement Plants Using AERMOD Modeling

Coal combustion generates many gases and emissions which are harmful to public health and the environment. So, it is necessary to assess the health risks for the people living in the nearby cement plants that use coal as a fuel. In this article, a health risk assessment HRA was carried out concerning the air emissions from a cement plant in the heavy industry area located at Beni Suef governorate - Egypt. The article handles the assessment of the health risks for pollutants classified as non-carcinogenic i.e. sulfur dioxide - mercury and the health risks for pollutants classified as carcinogenic i.e. arsenic – chromium VI. An Air dispersion modeling program AERMOD is used to measure and evaluate long and short terms health impacts to expect the concentration of pollutants at the ground level within 30 km radius of the studied cement plant. The emissions measurements findings are used as input to the model in addition to some factors such as meteorology and surrounding terrain. Consequently, the program can implement simulations for the emissions concentration level of the mentioned pollutants and their effects on the population at Jazirat Abu Salih village, which is 10 km far from the studied cement plant. The results for mentioned pollutants concentrations levels matched with acceptance and safe levels of ambient air quality standards. In addition, the increment lifetime cancer risk ILCR by inhalation was calculated for arsenic and chromium and all results conformed with the safe and accepted limits