Torque and efficiency maximization for a wave energy harvesting turbine: an approach to modify multiple design variables

Multiple design variables modifications are carried out for a bidirectional flow turbine used in an oscillating water column wave energy converter to enhance its performance by maximizing the peak torque‐coefficient (TC) and the corresponding efficiency (EFF), which are the objective functions of this problem. The Latin hypercube sampling technique selects samples from a designed space created by the design parameters defined for the blade sweep and aerofoil profile thickness modifications. The objective function values are obtained by solving Reynolds‐averaged Navier–Stokes equations and are approximated by surrogate models. The models help in generating populations of the genetic algorithm, which finally produces a set of optimal designs in a Pareto optimal front. Only two extreme designs among the five clustered points are further evaluated by solving Reynolds‐averaged Navier–Stokes equations to cross‐check the validity of the optimization steps. It is found that the TC is increased by 33% and the EFF is decreased by 5% at one extreme cluster point, while the other extreme point gives that both the TC and the EFF are higher by 1.8% and 2.9%, respectively, as compared with the reference geometry. The optimal geometry has a wider operating range, which is an important parameter to get continuous power from a wave energy converter. Copyright © 2016 John Wiley & Sons, Ltd.     

Authentication systems: A literature review and classification

One of the most important parts of any system is authentication. Appreciated as the first and the last line of defense in the great majority of cases, authentication systems can usually prevent the kleptomaniac from unauthorized accessing to users’ data. However, the traditional text-based password is still used in many websites and applications which are vulnerable to different kinds of attacks. Accordingly, there exist some other alternative ways to boost this traditional method. In this study, we classified and identified different types of authentication systems in a variety of platforms. Their usage, similarity, usability, performance and drawbacks were discussed. The goal of this study is to provide useful, classified information with the aim of understanding of how different authentication systems work and of what their usability and drawbacks are to the readers.     

4- and 6-GS/s 4-bit frequency-translating hybrid ADCs in 90-nm CMOS

Two frequency-translating hybrid analog-to-digital converters (FTH-ADCs) are implemented using building blocks that are designed and fabricated in a 90-nm CMOS technology. These blocks include a mixer, a filter, and an ADC that are cascaded to build each analog processing path of the FTH-ADC. The mixer-filter path is designed with sufficient linearity and signal-to-noise-and-distortion ratio (SNDR) to accommodate for the desired resolution of the path ADC. A 4-bit flash ADC structure is used in each path. This path has a signal bandwidth of 0.5 GHz and frequency-translates the input signal into baseband and digitizes it with the sample rate of 2 GHz. Multiple such mixer-filter-ADC paths are then combined together with proper mixing frequencies in order to implement two- and three-channel ADC systems. The two- and three-channel systems have overall input bandwidths of 2 and 3 GHz and effective conversion rates of 4 and 6 GS/s, respectively, while maintaining their single-path resolution across their entire input bandwidths. The implemented architecture provides an extendible solution to improve the speed of ADCs by incorporating them in an FTH-ADC architecture.     

Emerging drying techniques for food safety and quality: A review

The new trends in drying technology seek a promising alternative to synthetic preservatives to improve the shelf-life and storage stability of food products. On the other hand, the drying process can result in deformation and degradation of phytoconstituents due to their thermal sensitivity. The main purpose of this review is to give a general overview of common drying techniques with special attention to food industrial applications, focusing on recent advances to maintain the features of the active phytoconstituents and nutrients, and improve their release and storage stability. Furthermore, a drying technique that extends the shelf-life of food products by reducing trapped water, will negatively affect the spoilage of microorganisms and enzymes that are responsible for undesired chemical composition changes, but can protect beneficial microorganisms like probiotics. This paper also explores recent efficient improvements in drying technologies that produce high-quality and low-cost final products compared to conventional methods. However, despite the recent advances in drying technologies, hybrid drying (a combination of different drying techniques) and spray drying (drying with the help of encapsulation methods) are still promising techniques in food industries. In conclusion, spray drying encapsulation can improve the morphology and texture of dry materials, preserve natural components for a long time, and increase storage times (shelf-life). Optimizing a drying technique and using a suitable drying agent should also be a promising solution to preserve probiotic bacteria and antimicrobial compounds.     

Synthesis of zinc oxide nanoparticles reinforced clay and their applications for removal of Pb (Ⅱ) ions from aqueous media

The aim of the study was to synthesize zinc oxide nanoparticles (ZnONPs) composite with clay by a novel route and then to explore the capability of composite of ZnONPs and silty clay (SC) as adsorbents for Pb (Ⅱ) eradication from aqueous media by batch adsorption method. The effect of different operating factors like temperature, pH, dose and time of contact on the adsorption process were studied to optimize the conditions. Langmuir, Freundlich, Dubinin–Radushkevich (D-R) and Temkin isotherms were applied for the interpretation of the process. The R2 and q values obtained from Langmuir model suggested that the process is best interpreted by this model. The values of adsorption capacity (qm) noted were 12.43 mg·g-1 and 14.54 mg·g-1 on SC and ZnONPs-SC respectively. The kinetic studies exposed that pseudo second order (PSO) kinetics is followed by the processes suggesting that more than one steps are involved to control the rate of reactions. Various thermodynamic variables such as change in free energy (ΔGΘ), change in enthalpy (ΔHΘ) and change in entropy (ΔSΘ) were calculated. Thermodynamic data suggested that Pb (Ⅱ) adsorption on SC and ZnONPs-SC are spontaneous, endothermic and feasible processes.     

Effectively designed shell‐tube heat exchangers considering cost minimization and energy management

Cost optimization, which is expressed as a set of analytical variables, is a key objective in economic design approaches of shell‐and‐tube heat exchangers. This study has provided new design techniques based on tube bundle effect on the economic optimization design of shell‐and‐tube heat exchangers. Also the objective of this paper is to develop the cost estimating for the new modified shell‐and‐tube heat exchangers by introducing new objective functions. According to the results the best configuration choice will obviously be the one with the least irreversibility, that is, with the lowest exergy destruction rate and lower annual capital cost. Also, the combined reduction of annual capital investment and operating cost by the new design technique led to a decrease in the overall costs of about 10% to 24% in comparison with original design. So the proposed design technique shows potential for improvement and economic optimization of shell‐and‐tube heat exchangers.     

Feasibility study for Tehran Research Reactor power upgrading

The present work is concerned with a power upgrading study of Tehran Research Reactor (TRR). The upgrading study is aimed at investigating the possibility of raising power of the TRR from the current level of 5 MW_th to a higher level without violating the original thermal-hydraulic safety criteria. The existing core, comprising 22 standard fuel elements and five control fuel elements, is used for the analyses. Different reactor thermal powers (5–11 MW) and different core coolant flow rates (500–921 m³/h) are considered. It is shown that, for the present core, this goal could be achieved safely by gradually opening the butterfly control valve until the desired coolant flow rate is reached. The TRR power could be upgraded up to around 7.5 MW_th with the total power peaking factor maintained at less than or equal to 3.0.     

Practical OEICs based on the monolithic integration of GaAs-InGaPLEDs with commercial GaAs VLSI electronics

Recent advances in the epitaxy-on-electronics (EoE) integration process, which combines commercial GaAs VLSI electronics with conventional epitaxial growth and fabrication to produce complex, monolithic optoelectronic integrated circuits (OEICs), have resulted in improved integrated light-emitting diodes (LEDs), eliminated any impact on the preexisting electronics, and increased the robustness of the integration process. An EoE-integrated OEIC combining a photodetector, electronics, and LED is presented which demonstrates the capability of this technology to now satisfy practical optoelectronic systems requirements