An ant colony optimization approach to multi-objective optimal design of symmetric hybrid laminates for maximum fundamental frequency and minimum cost

An ant colony optimization algorithm for optimum design of symmetric hybrid laminates is described. The objective is simultaneous maximization of fundamental frequency and minimization of cost. Number of surface and core layers made of high-stiffness and low-stiffness materials, respectively, and fiber orientations are the design variables. Optimal stacking sequences are given for hybrid graphite/epoxy-glass/epoxy laminated plates with different aspect ratios and number of plies. The results obtained by ant colony optimization are compared to results obtained by a genetic algorithm and simulated annealing. The effectiveness of the hybridization concept for reducing the weight and keeping the fundamental frequency at a reasonable level is demonstrated. Furthermore, it is shown that the proposed ant colony algorithm outperforms the two other heuristics.     

Laminar convection in the annulus of a double-pipe with triangular fins

A steady and laminar convective flow has been numerically simulated in the fully-developed annular region of a finned double-pipe subjected to the constant heat flux boundary condition imposed at the inner-pipe wall. Finite element method has been employed in this study. Friction factor and Nusselt number have been studied as flow characteristics against variations in the ratio of radii of the inner and the outer pipes, the fin height, the fin half angle and the number of fins. The results show significant enhancement in the heat transfer rate in both the cases when sufficient pumping power is available and when it is not. The minimum and maximum increase in the product of friction factor and Reynolds number relative to the finless geometry is more than one time and more than 40 times respectively while gain in the relative value of Nusselt number lies in the range 1–177. This provides an evidence of more than four times enhancement in the heat transfer coefficient relative to that in the pressure loss as a result of extended fin surfaces.     

Rapid and efficient hand gestures recognizer based on classes discriminator wavelet networks

Multimedia Tools and Applications - The vision based on hand gesture recognition is one of the key challenges in behavior understanding and computer vision. It offers to machines the possibility of...     

Optimum section selection procedure for horizontal axis tidal stream turbines

Stochastic behavior of renewable energy sources forces designers to optimize the energy converters for the purpose of capturing the maximum amount of available energy. The performance of horizontal axis wind and tidal turbines mainly depends on the geometrical properties such as chord and twist distributions and also the types of sections which are utilized along the blade. The purpose of presented paper is introducing a procedure which can be utilized in order to select the optimum sections for horizontal axis tidal turbines for the purpose of increasing the turbine performance. The presented procedure also can be applied for horizontal axis wind turbines. For the purpose of evaluating the performance of the proposed method, two design types (chord and twist distributions) of tidal turbines are selected as case studies. Power coefficient is considered as objective function, and three types of hydrofoils namely NACA63-8xx, NACA44xx, and RISO-A1-xx are selected as candidate solutions. A blade element momentum theory model is used for calculating the power coefficient. The discrete ant colony optimization algorithm is selected as optimization tool. The results indicate that the utilization of the proposed method will considerably decrease the required process time for obtaining the optimum sections across the blade span, and also it is shown that using different types of sections across the blade span can increase the power coefficient of the turbine. The importance of the proposed method will be significant when various types of hydrofoils and airfoils can be considered as candidate sections across the blade span.

     

One-step electroless deposition of Pd/Pt bimetallic microstructures by galvanic replacement on copper substrate and investigation of its performance for the hydrogen evolution reaction

A facile and one-step method for fabrication of Pd/Pt bimetallic microstructure using galvanic replacement reaction is presented. This electroless deposition was performed without any additive reagent via simple immersion of the copper sheet in cation aqueous solution of Pd and Pt. The as-prepared electrode was characterized by using the techniques of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and cyclic voltammetry and tested for the hydrogen evolution reaction (HER) in the acidic media. Comparison of the HER on the Pd/Pt bimetallic catalysts with different Pd:Pt percentage compositions indicated that the Pd₆₀Pt₄₀ catalyst had the highest HER activity among all the Pd/Pt catalysts and a better performance than the pure Pt. The effects of galvanic replacement time and concentration of H₂SO₄ on the catalytic activity of as-prepared electrode for HER were comparatively investigated.     

Seasonal performance of a central air conditioner in Dhahran, Saudi Arabia. A computer simulation study

Seasonal performance of four standard, residential-sized, central air conditioners in a typical hot and humid climate of Gulf environment was measured. A computer model was developed to stimulate the residential building cooling loads and the resulting seasonal energy consumption. For an average 100 m² residence located in Dhahran, equipped with a 17.6 kW air conditioner, simulations show a consumption of ≈22200 kWh of electricity for space cooling over 2600 operation hours, this being within 13% of the measured value. The seasonal performance of three lower capacity (10.5, 12.3 and 14.0 kW) air conditioners for the same duty was also predicted. With the 14.0 kW capacity unit the electricity consumption is reduced by ≈ kWh and can satisfy the load for 96.6% of the time. The smallest (10.5kW) of the four systems can supply the house cooling load for only ≈78% of the time with a seasonal energy consumption of 17 350 kWh.     

A robust digital audio watermarking scheme based on DWT and Schur decomposition

The vulnerability of digital audio signals for different types of risks requires an imperceptible and robust digital audio watermarking scheme. In this research, we propose creating one such imperceptible and robust hybrid watermarking scheme based on a discrete wavelet transform (DWT) and Schur decomposition hybrid method. The proposed scheme embeds the foreground bits of the watermarking image into the least significant bit of the diagonal coefficients of the triangular matrix S generated from Schur decomposition. Schur decomposition is applied on the second sub-band HL₂ generated from applying a second-level 2D-Haar DWT on the first channel of the original audio signal. We analyze the proposed digital audio watermarking scheme’s performance in terms of signal to noise ratio (SNR), objective difference grades (ODG), and subjective difference grades (SDG) that resulting 81.43, 4.78 and 0.184, respectively. The resulting of payload capacity, NC, and BER are as high as 319.29 bps, 0.9911, and 0.0135, respectively. Experimental results confirm that the proposed scheme is inaudible and robust against common types of attacks such as Gaussian noise, re-quantization, re-sampling, low-pass filter, high-pass filter, echo, MP3 compression, and cropping. In comparison with state-of-the-art audio watermarking schemes, the proposed scheme’s performance is superior in term of imperceptibility, robustness, and data payload size.

     

Analysis of a three-phase to seven-phase transformer under unbalanced input

Microsystem Technologies - In the recent past, multiphase power generation, power transmission, and multiphase drive system are the main focus of research due to their several advantages over...     

Interlaminar stresses in thick rectangular laminated plates with arbitrary laminations and boundary conditions under transverse loads

In the present study, interlaminar stresses resulting from bending of thick rectangular laminated plates with arbitrary laminations and boundary conditions are analyzed analytically based on a three-dimensional multi-term extended Kantorovich method (3DMTEKM). Using the principle of minimum total potential energy, three systems of coupled ordinary differential equations with non-homogeneous boundary conditions are obtained. Then an iterative procedure is established to achieve analytical solution. The results obtained from this theory are compared with those of analytical solutions existing in the literature. It is found that the present results have excellent agreements with those obtained by layerwise theory. The results show that the multi-term EKM converges within only three terms of trial functions and the single-term EKM is not able to estimate the local interlaminar stresses near the boundaries of laminates. Finally, the power of the present approach in obtaining the interlaminar stresses in thick rectangular laminated plates with general types of boundary conditions and lay-ups is examined.     

Fabrication of bimetallic Cu/Pt nanoparticles modified glassy carbon electrode and its catalytic activity toward hydrogen evolution reaction

The film of poly(8-hydroxyquinoline) was formed by cyclic voltammetery method on the surface of glassy carbon electrode and poly(8-hydroxyquinoline) modified glassy carbon electrode, p(8-HQ)MGCE, was prepared. Cu²⁺ ion was adsorbed on the polymer matrix due to complexation with 8-hydroxyquinoline units Copper nanoparticles were deposited onto p(8-HQ)MGCE by applying potential and prepared copper nanoparticles galvanic replaced with platinum to fabricate poly(8-hydroxyquinoline)–Pt/Cu composite on the surface of GCE. Stripping voltammetery of Cu in aqueous 0.1 M KSCN + Britton–Robinson buffer, pH = 2.0, solution was used to quantify the copper present on the electrode surface. The amount of platinum was estimated from the electrooxidation peak of Pt in aqueous 0.1 M H₂SO₄ solution. The nature of Cu/Pt–p(8-HQ) on the surface of GCE was characterized by scanning electron microscopy. Cu/Pt–p(8-HQ) modified GCE can be used as a convenient conducting substrate for electrocatalytic hydrogen evolution reaction (HER). The effects of different parameters such as number of cycles, replacement time, scan rate of potential, and etc were investigated to obtaining optimum condition for HER.