An analytical approach for free vibration and transient response of functionally graded piezoelectric cylindrical panels subjected to impulsive loads

In this article, the free vibration and dynamic response of simply supported functionally graded piezoelectric cylindrical panel impacted by time-dependent blast pulses are analytically investigated. Using Hamilton’s principle, the equations of motion based on the first-order shear deformation theory are derived. Also, Maxwell’s electricity equation is taken as one of the governing equations. Three sets of electric surface conditions including closed circuit and two mixtures of closed and open circuit surface conditions are considered. By introducing an analytical approach and using the Fourier series expansions, the Laplace transform and Laplace inverse method, the solution of unknown variables are obtained in the real time domain based on a combination of system frequencies. Finally, the effects of various electric surface conditions, geometric parameters and the material power law index on the free vibration and transient response of functionally graded piezoelectric cylindrical panels subjected to various impulsive loads are examined in detail.     

A Study on the Effect of Process Parameters on the Properties of Joint in TLP-Bonded Inconel 738LC Superalloy

Optimization of transient liquid phase (TLP)-bonding variables is essential to achieve a joint free from deleterious intermetallic constituents and with appropriate mechanical properties. In this study, TLP bonding of IN-738LC superalloy was performed using AMS 4777 filler metal. The influence of gap size and bonding parameters (temperature and time) was investigated on the joint microstructure and its properties. In cases where the holding time was insufficient for complete isothermal solidification, the residual liquid transformed to non-equilibrium eutectic microconstituents consisting of nickel-rich boride, chromium-rich boride, and γ solid solution phases. The eutectic width decreased with the increase of holding time and the increase in initial gap size resulted in thicker eutectic width in the samples bonded at the same temperature and for equivalent holding times. The time of complete isothermal solidification decreased with the increase in bonding temperature to 1100°C, which was consistent with the models based on the diffusion-induced solid/liquid interface motion. Microhardness and shear strength tests were used to investigate the mechanical properties of the bonds. In the bonding condition in which isothermal solidification was not accomplished completely, the eutectic constituent with the highest hardness in the bond region was the preferential failure source. The results showed that homogenized joints had the highest shear strength.     

Optimized coordination of brakes and active steering for a 4WS passenger car

Optimum coordination of individual brakes and front/rear steering subsystems is presented. The integrated control strategy consists of three modules. A coordinated high-level control determines the body forces/moment required to achieve vehicle motion objectives. The body forces/moment are allocated to braking and steering subsystems through an intermediate unit, which integrates available subsystems based on phase plane notion in an optimal manner. To this end, an optimization problem including several equality and inequality constraints is defined and solved analytically, such that a real-time implementation can be realized without the use of numeric optimization software. A low-level slip-ratio controller works to generate the desired longitudinal forces at small longitudinal slip-ratios, while averting wheel locking at large slip-ratios. The efficiency of the suggested approach is demonstrated through computer simulations.     

Enhancing differential evolution with role assignment scheme

As one of the most popular evolutionary algorithms, differential evolution (DE) has been used for solving a wide range of real-world problems. The performance of DE highly depends on the chosen mutation strategy and control parameter settings. Although the conventional trial-and-error procedure can be used to elaborately select the proper strategy and to tune the parameter values, this procedure is often very time-consuming and is not suitable for practitioners without a priori experience. To tackle this problem, DE with a novel role assignment (RA) scheme is proposed in this paper. In the RA scheme, both the fitness information and positional information of individuals are utilized to dynamically divide the population into several groups. Each group is considered as a role, which has its own mutation strategy and parameter settings and is expected to play a different role in the evolution process. To verify the performance of our approach, experiments are conducted on 23 well-known benchmark functions. Results show that our approach is better than, or at least comparable to, several state-of-the-art DE variants.     

Antimicrobial activity of Zataria multiflora Boiss. essential oil incorporated with whey protein based films on pathogenic and probiotic bacteria

The antimicrobial potential of whey protein isolate (WPI) edible films containing 1–4% (v/v) Zataria multiflora Boiss. essential oil (EO) on food‐borne pathogenic bacteria (Escherichia coli, Salmonella enteritidis, Staphylococcus aureus and Bacillus cereus) and probiotic bacteria (Lactobacillus acidophilus, Lactobacillus rhamnosus, Lactobacillus plantarum and Lactobacillus casei subsp. casei) was evaluated. WPI films incorporated with 2% (v/v) of this EO inhibited the growth of all tested pathogenic bacteria and gram‐negative bacteria were more sensitive than gram‐positive bacteria. Incorporation of the EO at higher than 2% (v/v) showed significant antimicrobial effects (P < 0.05) for S. enteritidis and L. acidophilus. The growth of all probiotic lactic acid‐producing bacteria also inhibited when 2% of the EO was added. Comparison of an image processing‐based method with conventional method for measuring of inhibitory effects of edible films exhibited high correlations (R² ≥ 0.876) between the two methods. These results revealed that Z. multiflora Boiss. EO is a good antimicrobial additive for some food applications when included into WPI edible films.     

An integrated design methodology based on the use of group AHP-DEA approach for measuring lean tools efficiency with undesirable output

The selection of lean tools is one of the crucial factors for decision makers and practitioners in a competitive environment. A few efforts have been made based on problem selection. Conversely, numerical studies have been done on analytical hierarchy process (AHP)–data envelopment analysis (DEA) as well as DEA-undesirable variables separately. Thus, there is a shortage of lean practitioners as well as the methods involved. The present research aims at integrating AHP and DEA with desirable and undesirable factors to evaluate the lean tools and techniques and to rank the aspect of efficacy. We suggest a logical procedure to measure the efficacy of lean tools on leanness and to prioritize them as decision makers. In this extensive research, we apply the integrated multicriteria decision-making approach, including the hybrid groups AHP and DEA models with desirable and undesirable variables, to assess the relative efficiency of lean manufacturing tools and techniques. Case studies are used to demonstrate the lean implementation in companies while being validated by a panel of experts. The integration of these approaches has created synergy and shown to be even more powerful. Thus, the proposed integrated AHP-DEA model can evaluate and rank different alternatives while considering desirable and undesirable variables in the production processes.     

Dynamic Thermal Postbuckling Analysis of Piezoelectric Functionally Graded Cylindrical Shells

Dynamic thermal postbuckling behavior of functionally graded cylindrical shells with surface-bonded piezoelectric actuators subjected to the combined action of thermal load and applied actuator voltage is analyzed using an incremental numerical technique. The shell is graded across the thickness according to a power law form function. The material properties of the functionally graded cylindrical shells are considered to be temperature dependent. The theoretical formulations are based on the classical shell theory with Sanders' nonlinear kinematic relations. Then, using Hamilton's principle, equations of motion are derived for the piezoelectric FGM cylindrical shell. A finite difference based method combined with the Runge–Kutta method is employed to predict the postbuckling equilibrium paths, and the dynamic buckling temperature difference is detected according to Budiansky's stability criterion. Numerical results are presented to demonstrate the effects of the applied actuator voltage, shell geometry, volume fraction exponent of FGM, and the temperature dependency of the material properties on the postbuckling behavior of the shell. The results for simpler states are validated with the known data in the literature.     

Automated setup planning in CAPP: a modified particle swarm optimisation-based approach

Comprehensive process planning is the key technology for linking design and the manufacturing process and is a rather complex and difficult task. Setup planning has a basic role in computer-aided process planning (CAPP) and significantly affects the overall cost and quality of machined parts. This paper presents a generative system and particle swarm optimisation algorithm (PSO) approach to the setup planning of a given part. The proposed approach and optimisation methodology analyses constraints such as the TAD (tool approach direction), the tolerance relation between features and feature precedence relations, to generate all possible process plans using the workshop resource database. Tolerance relation analysis has a significant impact on setup planning to obtain part accuracy. Based on technological constraints, the PSO algorithm approach, which adopts the feature-based representation, optimises the setup planning using cost indices. To avoid becoming trapped in local optima and to explore the search space extensively, several new operators have been developed to improve the particles’ movements, combined into a modified PSO algorithm. A practical case study is illustrated to demonstrate the effectiveness of the algorithm in optimising the setup planning.     

Highly selective and sensitive voltammetric sensor based on modified multiwall carbon nanotube paste electrode for simultaneous determination of ascorbic acid,acetaminophen and tryptophan

A carbon-paste electrode modified with multiwall carbon nanotubes (MWCNTs) was used for the sensitive and selective voltammetric determination of ascorbic acid (AA) in the presence of 3,4-dihydroxycinnamic acid (3,4-DHCA) as mediator. The mediated oxidation of AA at the modified electrode was investigated by cyclic voltammetry (CV), chronoamperommetry and electrochemical impedance spectroscopy (EIS). Also, the values of catalytic rate constant (k), and diffusion coefficient (D) for AA were calculated. Using square wave voltammetry (SWV), a highly selective and simultaneous determination of AA, acetaminophen (AC) and tryptophan (Trp) has been explored at the modified electrode. The modified electrode displayed strong function for resolving the overlapping voltammetric responses of AA, AC and Trp into three well-defined voltammetric peaks. In the mixture containing AA, AC and Trp, the three compounds can well separate from each other with potential differences of 200, 330 and 530 mV between AA and AC, AC and Trp and AA and Trp, respectively, which was large enough to determine AA, AC and Trp individually and simultaneously.     

A comparative study on some properties of wood plastic composites using canola stalk,Paulownia, and nanoclay

In this research, the reinforcing effect of fillers including canola stalk, paulownia and nanoclay, in polypropylene (PP) has been investigated. In the sample preparation, 50 wt% of lignocellulosic materials and 0, 3, and 5 wt% of nanoclay particles were used. The results showed that while flexural and tensile properties were moderately enhanced by the addition of nanoclay in the matrix, notched Izod impact strengths decreased dramatically. However, with increase in the nanoclay content (5 wt%), the flexural and tensile properties decreased considerably. The mechanical properties of composites filled with paulownia are generally greater than canola stalk composites, due to the higher aspect ratio. The thickness swelling and water absorption of the composites significantly decreased with the increase in nanoclay loading. Except tensile modulus, the differences between the type of fibrous materials and nanoclay contents had significant influence on physicomechanical properties. Morphologies of the composites were analyzed using transmission electron microscopy (TEM) and X‐ray diffraction (XRD), and the results showed increased d‐spacing of clay layers indicating enhanced compatibility among PP, clay, and lignocellulosic material. TEM micrographs also confirmed that the composites containing 3 wt% nanoclay had uniform dispersion and distribution of clay layers in the polymer matrix. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013