Effect of refrigerated storage temperature on the viability of probiotic micro-organisms in yogurt

The effect of refrigerated storage temperature was studied at 2, 5 and 8°C on the viability of probiotics in ABY ( Lactobacillus acidophilus, Bifidobacterium lactis BB-12 and yogurt bacteria. Bulgaricus , i.e. Streptococcus thermophilus and Lactobacillus delbrueckii ssp. Bulgaricus ) probiotic yogurt. The study was carried out during a 20-day refrigerated storage period to identify the best storage temperature(s). Also, the viability change of the probiotic micro-organisms was analysed at 5-day intervals throughout the refrigerated storage period. After 20 days, storage at 2°C resulted in the highest viability of L. acidophilus , whereas for Bifidobacterium lactis the highest viability was obtained when yogurt was stored at 8°C.     

利用晶粒尺寸构建本构方程模拟AA1070铝的热变形行为

对原有Johnson-Cook本构模型中的项进行修正,提出一种新的现象学的、基于经验的本构模型.该模型可用于描述和预测具有不同初始晶粒尺寸的AA1070铝在热加工过程中的流变应力.该模型考虑热软化、应变速率硬化、应变硬化、初始晶粒尺寸及其相互影响,能够正确模拟具有不同应变、应变速率和初始晶粒尺寸AA1070铝的高温行为...     

Design of multi-objective damping controller for gate-controlled series capacitor

This paper proposes an optimization procedure based on eigenvalues to carry out the stabilization function of the Gate-Controlled Series Capacitor (GCSC) in a power system. It is aimed to provide a reliable damping framework by means of a GCSC based multi-objective damping controller. The proposed method employs Particle Swarm Optimization (PSO) to search for optimal parameter settings of a widely used multi-objective lead-lag damping controller. The eigenvalue analysis is considered as the cornerstone of the performed studies in order to investigate the multi-objective methodology in which the unstable or lightly damped modes are scheduled to effectively shift to some prescribed stability zones in the s-plane. The effectiveness of the suggested approach in damping local and interarea oscillations modes in a multi-machine power system, over a wide range of loading conditions, is confirmed through eigenvalue analysis and time simulation.     

Energy supply for water electrolysis systems using wind and solar energy to produce hydrogen: a case study of Iran

Due to acute problems caused by fossil fuels that threaten the environment, conducting research on other types of energy carriers that are clean and renewable is of great importance. Since in the past few years hydrogen has been introduced as the future fuel, the aim of this study is to evaluate wind and solar energy potentials in prone areas of Iran by the Weibull distribution function (WDF) and the Angstrom-Prescott (AP) equation for hydrogen production. To this end, the meteorological data of solar radiation and wind speed recorded at 10 m height in the time interval of 3 h in a five-year period have been used. The findings indicate that Manjil and Zahedan with yearly wind and solar energy densities of 6004 (kWh/m²) and 2247 (kWh/m²), respectively, have the greatest amount of energy among the other cities. After examining three different types of commercial wind turbines and photovoltaic (PV) systems, it becomes clear that by utilizing one set of Gamesa G47 turbine, 91 kg/d of hydrogen, which provides energy for 91 car/week, can be produced in Manjil and will save about 1347 L of gasoline in the week. Besides, by installing one thousand sets of X21-345 PV systems in Zahedan, 20 kg/d of hydrogen, enough for 20 cars per week, can be generated and 296 L of gasoline can be saved. Finally, the RETScreen software is used to calculate the annual CO₂ emission reduction after replacing gasoline with the produced hydrogen.     

Cross-focusing of two chirped Gaussian laser beams and THz wave generation in plasmas of multi-ion species under a weakly relativistic and ponderomotive regime

The generation of terahertz (THz) waves via the beating of two high-intensity chirped Gaussian lasers in a multi-ion-species plasma is numerically studied by taking into account the weak relativistic and ponderomotive regime of interaction. The coupled differential equations for beamwidth parameters are extracted by introducing the dielectric function of such plasma and using WKB and paraxial ray approximations. The amplitude of THz radiation at beat frequency resulting from the nonlinear current density induced by the beat ponderomotive force of the cross-focusing of beams was obtained. The impacts of the chirp frequency parameter, initial laser intensity and initial ionic species density (specifically, the presence of singly and doubly charged ions) in the plasma on THz generation were discussed. Our numerical results reveal that THz radiation generation strongly depends on the chirp frequency parameter. A specific range of chirp frequencies exists for self-focusing as well as THz generation with a 'turning point', where the THz emission reaches its maximum value. The results show that the strength of self-focusing and consequently the generated THz radiation are reduced by increasing the density of doubly charged ionic species in the plasma due to the suppression of the nonlinear effects.