A proposed model for frequency tuned antennas used in mobile communication systems

The antenna is considered as one of the most fundamental elements in wireless communication systems, especially in mobile devices. Desirable specifications of antennas include covering wide range of operating frequencies, while maintaining high quality of system performance over the whole range of operating frequencies. Therefore, the ability of tuning the resonant frequency of the antenna without altering its physical dimensions would be highly recommended in up-and-coming designs of antennas in mobile devices. This research work proposes a model for tuning the operating frequency of the inverted F-antenna over a reasonably wide range of frequencies, via altering the electromagnetic properties of its ferrite material. In this proposed model, it will be shown that the electronic control of the permeability of the ferrite material of the antenna leads effectively to a significant shift in its resonant frequency, and hence to an overall improvement in the performance of the communication system

La radiación-γ mantiene la calidad de la mantequilla de vaca

This investigation aims to study the use of gamma irradiation for keeping the quality of cows’ butter. Fresh butter samples were exposed to gamma irradiation at doses of 0, 2.5 and 5 kGy followed by refrigerated storage and the effects of these treatments on the microbiological aspects and lipid characteristics of butter samples were studied. Moreover, fatty acid profiles and unsaponifiable matter constituents were determined by gas chromatographic analysis, while the stability of butter was determined by rancimat. The results indicated that gamma irradiation at 2.5 kGy dose reduced the counts of total bacteria, lipolytic bacteria, coliforms, molds and yeasts, however, these counts gradually increased during cold storage. Also irradiation at 5 kGy dose greatly reduced the total bacterial count which gradually increased upon storage, while completely eliminated the other determined microorganisms. Irradiation treatments increased the acid value and peroxide value of butter, while the iodine number was not altered. Moreover, gas chromatographic analysis showed that gamma irradiation slightly increased the total volatile fatty acids, total saturated fatty acids and total hydrocarbons, while slightly decreased the total unsaturated fatty acids and total sterols. In addition, irradiation of butter decreased its stability as determined by rancimat and upon storage of both irradiated and non irradiated butter samples, the acid value gradually increased, while a flexuous changes in the peroxide value were observed. The present study proved that 2.5 and 5 kGy gamma irradiation doses could keep the quality of cows’ butter and increased its shelf life at 4±1ºC for 8 and 12 weeks as compared to 4 weeks for non irradiated butter (based on the visual appearance of mold growth on the surface of samples) without any effects on its sensory properties.En esta investigación se estudió el uso de la radiación gamma para mantener la calidad de la mantequilla de vaca. Muestras de mantequilla fresca fueron expuestas a diferentes dosis de radiación gamma (0, 2.5 y 5 kGy) y guardadas en frío. Se determinaron parámetros microbiológicos y lipídicos, incluyendo el análisis de ácidos grasos y constituyentes del insaponificable mediante cromatografía gaseosa, y la estabilidad de la mantequilla por rancimat. Los resultados indicaron que la radiación gamma a la dosis de 2.5 kGy reducía el número total de bacterias, bacterias lipolíticas, coliformes, hongos y levaduras, aunque la recuperación era gradual con el tiempo de almacenamiento. A la dosis de 5 kGy, el efecto sobre el número total de bacterias fue más acentuado, hubo una recuperación gradual, pero el resto de microorganismos estudiados desaparecieron completamente. Los tratamientos de irradiación aumentaron la acidez y los peróxidos en la mantequilla, sin alterar el índice de yodo. La radiación gamma aumentó ligeramente el total de ácidos grasos volátiles, de ácidos grasos saturados y de hidrocarburos; mientras que redujo ligeramente el total de ácidos grasos insaturados y el de esteroles. La irradiación de la mantequilla afectó negativamente su estabilidad, aumentando gradualmente la acidez tanto en las muestras irradiadas como en las no irradiadas. Con el presente estudio se demuestra que la irradiación gamma a las dosis de 2.5 y 5 kGy podría mantener la calidad de la mantequilla de vaca e incrementar su vida útil si se mantiene a 4±1ºC durante 8 y 12 semanas cuando se compara con la mantequilla no irradiada y almacenada durante 4 semanas (basado en la apariencia visual del crecimiento de hongos en la superficie de las muestras), sin efectos sobre las propiedades sensoriales

A new approach for solving systems of fractional differential equations via natural transform

In this paper, A new method proposed and coined by the authors as the natural variational iteration  transform method(NVITM) is utilized to solve linear and nonlinear systems of fractional differential equations. The new method is a combination of natural transform method and variational iteration method. The solutions of our modeled systems are calculated in the form of convergent power series with easily computable components. The numerical results shows that the approach is easy to implement and accurate when applied to various linear and nonlinear systems of fractional differential equations

Review: The Stochastic Approach and Systems of Index Numbers

The main objective of the paper is to review a number of widely used multilateral index numbers for International comparisons of purchasing power parities (PPPs) and real incomes that can be derived using the stochastic approach. The paper discuss that price index numbers from commonly used methods like the Ikleacute, the Rao-weighted, and an additive multilateral system are all estimators of the parameters of the countryndashproductndashdummy (CPD) model. The paper also presents the method of moments (MOM) as an approach to estimate PPPs under the stochastic approach and shows how the GearyndashKhamis system of multilateral index numbers is a method of moments estimator of the parameters of the CPD model.nbs

Development of Hot Equal Channel Angular Processing (ECAP) consolidation technique in the production of Boron Carbide(B4C)-Reinforced Aluminium Chip (AA6061)-based composite

The production of metal matrix composites (MMCs) through recycled materials is a cost-saving process. However, the improvement of the mechanical and physical properties is another challenge to be concerned. In this study, recycled aluminium 6061 (AA6061) chips reinforced with different volumetric fractions of boron carbide (B4C) were produced through hot equal channel angular processing (ECAP). Response surface methodology (RSM) was carried out to investigate the dependent response (compressive strength) with independent parameters such as different volumetric fractions (5-15%) of added contents of B4C and preheating temperature (450 – 550°C). Also, the number of passes were examined to check the effect on the mechanical and physical properties of the developed recycled AA6061/B4C composite. The results show that maximum compressive strength and hardness of recycled AA6061/B4C were 59.2 MPa and 69 HV respectively at 5% of B4C contents. Likewise, the density and number of pores increased, which were confirmed through scanning electron microscope (SEM) and atomic force microscopes (AFM) analysis. However, the number of passes enhanced the mechanical and physical properties of the recycled AA6061/B4C composite. Therefore, the maximum compressive strength and hardness achieved were 158 MPa and 74.95 HV for the 4th pass. Moreover, the physical properties of recycled AA6061/B4C composite become denser of 2.62 g/cm3 at the 1st pass and 2.67 g/cm3 for the 4th pass. Thus, it can be concluded that the B4C volumetric fraction and number of passes have a significant effect on recycled AA6061 chips

Hot extrusion followed by a hot ecap consolidation combined technique in the production of Boron Carbide (B4C) reinforced with aluminium chips (AA6061) composite

A new and promising MMC approach to the reduction of pollution, greenhouse effects, and emissions is to develop a technology related to materials composite forming. Hot extrusion followed by hot ECAP is a combination of solid-state recycling method (direct recycling) that consists of chip preparations, cold compaction, and hot extrusion, followed by the ECAP process. The developed process is used to consolidate the chips for direct chip recycling purposes without the remelting phase. In this study, finished or semi-finished products from B4C-reinforced particles and AA6061 aluminium chips were produced. The samples made by hot extrusion were compared with samples obtained from hot extrusion followed by the hot ECAP process in terms of mechanical properties. Additional plastic deformation by hot ECAP after hot extrusion significantly increased the mechanical properties of the MMC compared with the samples obtained from the hot extrusion only. The density and microstructure of the samples were also determined

High frequency of SEN virus infection in thalassemic patients and healthy blood donors in Iran

<p>Abstract</p> <p>Background</p> <p>SEN virus is a blood-borne, circular ssDNA virus and possessing nine genotypes (A to I). Among nine genotypes, SENV-D and SENV-H genotypes have the strong link with patients with unknown (none-A to E) hepatitis infections. Infection with blood-borne viruses is the second important cause of death in thalassemic patients. The aim of this study was to determine the frequency of SENV-D and SENV-H genotypes viremia by performing nested-PCR in 120 and 100 sera from healthy blood donors and thalassemic patients in Guilan Province, North of Iran respectively. Also, to explicate a possible role of SEN virus in liver disease and established changes in blood factors, the serum aminotransferases (ALT and AST) and some of the blood factors were measured.</p> <p>Results</p> <p>Frequency of SENV-D, SENV (SENV-H or SENV-D) and co-infection (both SENV-D and SENV-H) viremia was significantly higher among thalassemic patients than healthy individuals. Frequency of SENV-H viremia was significantly higher than SENV-D among healthy individuals. In comparison to SENV-D negative patients, the mean of mean corpuscular hemoglobin was significantly higher in SENV-D positive and co-infection cases (<it>P </it>< 0.05). The means of AST and ALT were significantly higher in thalassemic patients than healthy blood donors, but there were not any significant differences in the means of the liver levels between SENV-positive and -negative individuals in healthy blood donors and thalassemic patients. High nucleotide homology observed among PCR amplicon's sequences in healthy blood donors and thalassemic patients.</p> <p>Conclusions</p> <p>The high rate of co-infection shows that different genotypes of SENV have no negative effects on each other. The high frequency of SENV infection among thalassemic patients suggests blood transfusion as main route of transmission. High frequency of SENV infection in healthy individuals indicates that other routes rather than blood transfusion also are important. Frequency of 90.8% of SENV infection among healthy blood donors as well as high nucleotide homology of sequenced amplicons between two groups can probably suggest that healthy blood donors infected by SENV act partly as a source of SENV transmission to the thalassemic patients. In conclusion, SENV-D isolate in Guilan Province may be having a pathogenic agent for thalassemic patients.</p

The effect of solid-State processes and heat treatment on the properties of AA7075 aluminum waste recycling nanocomposite

Direct solid-states, such as hot extrusion and equal channel angular pressing (ECAP), are alternative and efficient solid-state processes for use in recycling aluminium scrap. These processes utilise less energy and are eco-friendly. Ceramic particles such as ZrO2 are suggested as alternatives in the production of metal composites. This study investigated and optimised the effects of various parameters of reinforced ZrO2 nanoparticles on the mechanical and physical properties via response surface methodology (RSM). These parameters were the volume fraction (VF), preheating temperature (T), and preheating time (t). The effects of these parameters were examined before and after the heat treatment condition and ECAP. Each parameter was evaluated at varying magnitudes, i.e., 450, 500, and 550 °C for T, 1, 2, and 3 h for t, and 1, 3, and 5% for VF. The effect that process variables had on responses was elucidated using the factorial design with centre point analysis. T and VF were crucial for attaining the optimum ultimate tensile strength (UTS) and microhardness. Reducing VF increased the mechanical properties to 1 vol% of oxide. The maximum hardness of 95 HV was attained at 550 °C, 1.6 h, and 1 vol% ZrO2 with a density of 2.85 g/cm3 and tensile strength of 487 MPa. UTS, density, and microhardness were enhanced by 14%, 1%, and 9.5%, respectively. Additionally, the hot extrusion parameters and ECAP followed by heat treatment strengthened the microhardness by 64% and density by 3%. Compression pressure and extrusion stress produced in these stages were sufficient to eliminate voids that increased the mechanical properties

Response Surface Methodology (RSM) implementation in zro particles reinforced aluminium chips by Hot Equal Channel Pressing (ECAP)

In recent years, the interest on solid-state recycling of aluminum chips increases over the years due to the less energy consumption of the process. This research studies the quantitative effects of preheating temperature and volume fraction of Zirconium Dioxide when it is reinforced to the Aluminum alloy AA6061 on its mechanical properties. The parameters of the experiment are preheating temperature and volume fraction of ZrO . Temperature are varied between 450 and 550 ℃ according to the boundary parameters. The volume fraction of ZrO consists of 5, 10 and 15% of the reinforcement. Increasing the volume fraction of ZrO correlates with the increase of mechanical and physical properties. Design of Experimental with factorial design was implemented to analyse the magnitude of response on the mechanical properties from the variable of parameters. The preheating temperature was revealed to be the most significant factor affecting the yield strength and the microhardness of the composite followed by the volume fraction of ZrO . It is revealed that the most optimum temperature is 550 ℃ and the optimum percentage of volume fraction is 9.28%. Both highest microhardness and yield strength were obtained from these optimum temperatures. Scanning Electron Microscope (SEM) revealed on how elongation in Zirconia chips is affected by the amount of ZrO reinforcement. Energy Dispersive Spectroscopy (EDS) analysis performed revealed on the arbitrary weight out of total weight for every element in the composite such as Al, Zr, O and Si