Sensitivity importance‐based robust optimization of structures with incomplete probabilistic information

Robust design optimization (RDO) is usually performed by minimizing the nominal value of a performance function and its dispersion considering equal importance to each individual gradient of the performance function. However, it is well known that all gradients are not equally important. An efficient sensitivity importance‐based RDO technique is proposed in the present study for optimum design of structures characterized by bounded uncertain input parameters. The basic idea of the proposed RDO formulation is to improve the robustness of a performance function by using a new gradient index that utilizes the importance factors proportional to the importance of the gradients of the performance function. The same concept is also extended to the constraints. To enhance the robustness of the constraints, the constraint functions are also modified by using the importance factor proportional to the importance of the associated gradient of the constraint. Because all the variables are not equally important to capture the presence of uncertainty, an improved robust solution is obtained by the proposed approach compared with the conventional RDO approach. The present formulation is illustrated with the help of three informative examples. The results are compared with the conventional RDO results to study the effectiveness of the proposed RDO approach. Copyright © 2012 John Wiley & Sons, Ltd.     

Estimation of heat transfer coefficient and friction factor in the transition flow with low volume concentration of Al2O3 nanofluid flowing in a circular tube and with twisted tape insert

Experiments to evaluate heat transfer coefficient and friction factor for flow in a tube and with twisted tape inserts in the transition range of flow with Al₂O₃ nanofluid are conducted. The results showed considerable enhancement of convective heat transfer with Al₂O₃ nanofluids compared to flow with water. It is observed that the equation of Gleninski applicable in transitional flow range for single-phase fluids showed considerable deviation when compared with values obtained with nanofluid. The heat transfer coefficient of nanofluid flowing in a tube with 0.1% volume concentration is 23.7% higher when compared with water at number of 9000. Heat transfer coefficient and pressure drop with nanofluid has been experimentally determined with tapes of different twist ratios and found to deviate with values obtained from equations developed for single-phase flow. A regression equation is developed to estimate the Nusselt number valid for both water and nanofluid flowing in the transition flow Reynolds number range in circular plain tube and with tape inserts. The maximum friction factor with twisted tape at 0.1% nanofluid volume concentration is 1.21 times that of water flowing in a plain tube.     

Thermal distribution analysis of rectangular fin considering multiboiling heat transfer modes

In this investigation, a numerical method is used to compute the thermal distribution analysis of a rectangular fin with surface emissivity and internal heat generation. Here, the thermal conductivity, heat generation, emissivity at the surface, and coefficient of heat transfer depend on temperature linearly. The role of four distinct multiboiling heat transfer modes such as laminar film boiling (condensation), laminar convection, turbulent convection, and nucleate boiling are discussed in detail and the corresponding outcomes are displayed graphically. Isolated (insulated) and convective tip boundary conditions for the fin tip are employed in this study. The solution is obtained using shooting technique involving Runge Kutta Fehlberg method. It is emphasized that the thermal distribution shows a diminishing trend for the convective tip condition compared to the insulated tip. In addition to this, it is illustrated that laminar film boiling and laminar convection are two effective modes of heat transfer in comparison with turbulent convection and nucleate boiling for a finned surface in boiling liquids. The study on fin efficiency shows that fin efficiency increases with the increase in internal heat generation number.     

Flow and thermal analysis of Oldroyd 8 constant fluid in a porous channel

The present research is based on the thermal and flow properties of the viscoelastic Oldroyd 8 constant fluid in an upright microchannel. The energy and momentum equations were solved with the support of temperature Jump and velocity slip boundary conditions. To measure the irreversibility rate of the flow system, the acquired results of velocity and thermal equations were used. To crack the current mathematical model problem, the numerical Runge–Kutta–Fehlberg method was used. With the aid of graphs, the effect of physical parameters such as thermal radiation, thermal-dependent heat source, Joule heating, fluid parameters, velocity slip, and temperature Jump parameters on the fluid flow, thermal energy, and system entropy generation was discussed. Fluid parameters have different effects on the velocity profile. The Grashof and Hartmann numbers demonstrate opposite effects on the momentum field. The thermal energy of the system reduces with thermal radiation and temperature Jump factor. The thermal radiation, Hartmann number, and temperature Jump parameters reduce the system's irreversibility rate. With the Brinkman number and temperature Jump parameter, the irreversibility ratio increases.     

Gold nanoparticle-based method for detection of calcium carbide in artificially ripened mangoes (Magnifera indica)

A new approach was developed for a simple and easy colorimetric detection assay to detect the use of calcium carbide in artificial ripening of fruits. Residues of arsenic on the fruit surface were used as an indicator for this. Use of calcium carbide in artificial ripening has been banned in many countries including India. In the present study, we have used a gold nanoparticle (AuNP)-based colorimetric detection method for determination of artificial ripening of fruits. ICP-MS analysis showed the presence of higher amounts of arsenic on fruits ripened using calcium carbide. Lauryl sulphate (LS)-capped AuNP aggregates in the presence of arsenic, replacing the LS, resulting in a colour change from red to purple. Hence, the developed method can be used for easy and rapid detection of use of calcium carbide in artificial ripening of fruits.     

Investigation of Different Gas Sensor-Based Artificial Olfactory Systems for Screening <Emphasis Type="Italic">Salmonella typhimurium</Emphasis> Contamination in Beef

Two different electronic nose systems (metal oxide and conducting polymer based) were used to identify Salmonella typhimurium contaminated beef strip loin samples (stored at two temperatures). The sensors present in the two systems were ranked based on their Fisher criteria of ranking to evaluate their importance in discriminant analysis. The most informative sensors were then used to develop linear discriminant analysis and quadratic discriminant analysis-based classification models. Further, sensor signals collected from both the sensor systems were combined to improve the classification accuracies. The developed models classified meat samples based on the Salmonella population into “No Salmonella” (microbial counts < 0.7 log₁₀ cfu/g) and “Salmonella inoculated” (microbial counts ≥ 0.7 log₁₀ cfu/g). The performances of the developed models were validated using leave-1-out cross-validation. Classification accuracies of 80% and above were observed for the samples stored at 10 °C using the sensor fusion approach. However, the classification accuracies were relatively low for the meat samples stored at 4 °C when compared to the samples stored at 10 °C. The results indicate that the electronic nose systems could be effectively used as a first stage screening device to identify the meat samples contaminated with S. typhimurium.     

Transformation of two-line ferrihydrite to goethite and hematite as a function of pH and temperature

Under oxic aqueous conditions, two-line ferrihydrite gradually transforms to more thermodynamically stable and more crystalline phases, such as goethite and hematite. This temperature- and pH-dependent transformation can play an important role in the sequestration of metals and metalloids adsorbed onto ferrihydrite. A comprehensive assessment of the crystallization of two-line ferrihydrite with respect to temperature (25, 50, 75, and 100 °C) and pH (2, 7, and 10) as a function of reaction time (minutes to months) was conducted via batch experiments. Pure and transformed phases were characterized by X-ray diffraction (XRD), X-ray absorption near-edge spectroscopy (XANES), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The rate of transformation of two-line ferrihydrite to hematite increased with increasing temperature at all pHs studied and followed first-order reaction kinetics. XRD and XANES showed simultaneous formation of goethite and hematite at 50 and 75 °C at pH 10, with hematite being the dominant product at all pHs and temperatures. With extended reaction time, hematite increased while goethite decreased, and goethite reaches a minimum after 7 days. Observations suggest two-line ferrihydrite transforms to hematite via a two-stage crystallization process, with goethite being intermediary. The findings of this study can be used to estimate rates of crystallization of pure two-line ferrihydrite over the broad range of temperatures and pH found in nature.     

Exploration of irreversibility and thermal motion of a nanoliquid with the Newton boundary condition by using the Darcy–Forchheimer rule

This study has been conducted to focus on magnetohydrodynamic flow of a nanoliquid through a microchannel in the presence of a magnetic field. In this article, carbon nanotubes suspended in an aqueous medium were our considered fluid, and we focused on both singlewall and multiwall carbon nanotubes. The numerical calculations have been made via the fourth- and fifth-order Runge–Kutta–Fehlberg method. The flow of the nanoliquid in a microchannel with porosity has been scrutinized with the existence of mutual effects, like, the nanoparticle volume fraction, suction or injection, thermal-dependent heat source, convective boundary conditions, Darcy friction factor, and thermal motion of the nanoparticles. The influence of every major parameter on the profile of momentum, temperature, and entropy generation has been displayed graphically, and we discuss their physical aspects. The numerical outcomes demonstrated that the momentum profile augmented with the buoyancy force, angle of inclination, and Darcy number. Thermal energy was enriched with the heat source parameter, Darcy number, and Hartmann number. The irreversibility rate declined with the volume fraction of nanoparticle and radiation parameter, while it increases with the buoyancy force, Eckert parameter, and Darcy friction factor.     

Analysis of second law on Eyring‐Powell nanoliquid flow in a vertical microchannel considering magnetic field and convective boundary

Studies related to enhancing heat transfer has attained much attention of researchers to avail optimized heat‐transfer devices. High viscous fluids are of great importance as they are widely used in petroleum products, organic chemistry, coating, printing, and so forth. In this study, heat transfer mechanism driven by Eyring‐Powell nanoliquid flow in a vertical microchannel is examined. Impact of considering buoyancy force, magnetic field, and convective boundary on the thermal system is demonstrated. The modeled nondimensional equations are computed by using the Runge‐Kutta‐Fehlberg method. The vital roles of thermophoresis and Brownian motion are discussed in detail. The significance of second law analysis for thermal systems is presented. The causes of irreversibilities in a microchannel due to Eyring‐Powell nanoliquid flow is also demonstrated in the current research study. The upshots of the current investigations are visualized through graphical elucidation. It is established that minimization of entropy generation can be achieved by enhancing the mechanism of thermophoresis. The convective boundary helps in transmitting heat from the thermal system to the ambience hence the lower thermal field is attained.