A Level Set Algorithm for Tracking Discontinuities in Hyperbolic Conservation Laws II: Systems of Equations

A level set algorithm for tracking discontinuities in hyperbolic conservation laws is presented. The algorithm uses a simple finite difference approach, analogous to the method of lines scheme presented in [36]. The zero of a level set function is used to specify the location of the discontinuity. Since a level set function is used to describe the front location, no extra data structures are needed to keep track of the location of the discontinuity. Also, two solution states are used at all computational nodes, one corresponding to the real state, and one corresponding to a ghost node state, analogous to the Ghost Fluid Method of [12]. High order pointwise convergence was demonstrated for scalar linear and nonlinear conservation laws, even at discontinuities and in multiple dimensions in the first paper of this series [3]. The solutions here are compared to standard high order shock capturing schemes, when appropriate. This paper focuses on the issues involved in tracking discontinuities in systems of conservation laws. Examples will be presented of tracking contacts and hydrodynamic shocks in inert and chemically reacting compressible flow.     

Controlled Synthesis and Stability of Co@SiO2 Aqueous Colloids

Magnetic nanoparticles have emerged as an important class of functional nanostructures with potential applications of magnetic resonance imaging, drug targeting, and bio-conjugation. We have developed a modified sol–gel approach to synthesize stable and well-dispersed magnetic Co@SiO₂ nanoparticles with improved control over shell thickness and larger core diameters. These well-defined Co@SiO₂ core–shell nanoparticles exhibit useful magnetic properties, and the protective silica shell allows them to be surface modified for bioconjugation for various biomedical applications. The core–shell nanoparticles were characterized by transmission electron microscopy, energy-dispersive spectroscopy, elemental mapping, and the line compositional analyses to demonstrate that uniform individually isolated core–shell nanoparticles are obtained through the improved synthetic route.     

Prediction of cumulative fatigue damage

The life of a component subjected to a constant stress can be determined using the S-N diagram. Prediction of cumulative fatigue damage or fatigue life of a component subjected to a given stress sequence of varying amplitude is difficult, if not impossible. Miner's rule and Kramer's equation can predict cumulative fatigue damage with a reasonable degree of accuracy for limited cases. The development of Kramer's equation was studied and a modification suggested. Cumulative fatigue data generated using aluminium alloys 2011-T3 and 2024-T4, were analysed using Miner's, Kramer's and the modified equations. While Miner's rules and Kramer's equation predict cumulative fatigue damage with tolerable error for a few cases, the modified equation has shown close agreement between the experimental and theoretical values of fatigue life or cumulative fatigue damage for the materials studied in this investigation.     

Numerical simulation of mixed convective 3D flow of a chemically reactive nanofluid subject to convective Nield's conditions with a nonuniform heat source/sink

The present investigation aims to explore the influence of a mixed convection and nonuniform heat source/sink on unsteady flow of a chemically reactive nanofluid driven by a bidirectionally expandable surface. Convective heat transport phenomenon is used to maintain the temperature of the surface. Moreover, zero mass flux is also accounted at the surface such that the fraction of nanomaterial maintains itself on strong retardation. The governing nonlinear set of partial differential equations is transformed into a set of ordinary differential equations via a suitable combination of variables. The Keller‐Box scheme has been incorporated to make a numerical inspection of the transformed problem. The spectacular impacts of the pertinent constraints on thermal and concentration distributions are elucidated through various plots. Graphical outcomes indicate that the thermal state of nanomaterial and nanoparticles concentration are escalated for elevated amounts of Biot number, porosity parameter and nonuniform heat source/sink constraints. Furthermore, it is also seen that escalating amounts of unsteady parameter, temperature controlling indices, Prandtl number, and expansion ratio parameter reduce the thermal and concentration distributions. Numerical results for the rate of heat transference have been reported in tabular form. The grid independence approach is used to verify the convergence of the numerical solution and the CPU run time is also obtained to check the efficiency of the numerical scheme adopted for finding the solution.     

Decentralized Dynamic Event-Triggered Communication and Active Suspension Control of In-Wheel Motor Driven Electric Vehicles with Dynamic Damping

This paper addresses the co-design problem of decentralized dynamic event-triggered communication and active suspension control for an in-wheel motor driven electric vehicle equipped with a dynamic damper. The main objective is to simultaneously improve the desired suspension performance caused by various road disturbances and alleviate the network resource utilization for the concerned in-vehicle networked suspension system. First, a T-S fuzzy active suspension model of an electric vehicle under dynamic damping is established. Second,a novel decentralized dynamic event-triggered communication mechanism is developed to regulate each sensor's data transmissions such that sampled data packets on each sensor are scheduled in an independent manner. In contrast to the traditional static triggering mechanisms, a key feature of the proposed mechanism is that the threshold parameter in the event trigger is adjusted adaptively over time to reduce the network resources occupancy. Third, co-design criteria for the desired event-triggered fuzzy controller and dynamic triggering mechanisms are derived. Finally, comprehensive comparative simulation studies of a 3-degrees-of-freedom quarter suspension model are provided under both bump road disturbance and ISO-2631 classified random road disturbance to validate the effectiveness of the proposed co-design approach. It is shown that ride comfort can be greatly improved in either road disturbance case and the suspension deflection, dynamic tyre load and actuator control input are all kept below the prescribed maximum allowable limits, while simultaneously maintaining desirable communication efficiency.     

Green synthesised zinc oxide nanostructures through Periploca aphylla extract shows tremendous antibacterial potential against multidrug resistant pathogens

To grapple with multidrug resistant bacterial infections, implementations of antibacterial nanomedicines have gained prime attention of the researchers across the globe. Nowadays, zinc oxide (ZnO) at nano‐scale has emerged as a promising antibacterial therapeutic agent. Keeping this in view, ZnO nanostructures (ZnO‐NS) have been synthesised through reduction by P. aphylla aqueous extract without the utilisation of any acid or base. Structural examinations via scanning electron microscopy (SEM) and X‐ray diffraction have revealed pure phase morphology with highly homogenised average particle size of 18 nm. SEM findings were further supplemented by transmission electron microscopy examinations. The characteristic Zn–O peak has been observed around 363 nm using ultra‐violet–visible spectroscopy. Fourier‐transform infrared spectroscopy examination has also confirmed the formation of ZnO‐NS through detection of Zn–O bond vibration frequencies. To check the superior antibacterial activity of ZnO‐NS, the authors'' team has performed disc diffusion assay and colony forming unit testing against multidrug resistant E. coli, S. marcescens and E. cloacae. Furthermore, protein kinase inhibition assay and cytotoxicity examinations have revealed that green fabricated ZnO‐NS are non‐hazardous, economical, environmental friendly and possess tremendous potential to treat lethal infections caused by multidrug resistant pathogens.Inspec keywords: nanomedicine, zinc compounds, II‐VI semiconductors, wide band gap semiconductors, nanoparticles, scanning electron microscopy, X‐ray diffraction, antibacterial activity, transmission electron microscopy, particle size, Fourier transform infrared spectra, ultraviolet spectra, visible spectra, enzymes, biochemistry, molecular biophysics, microorganisms, drugs, toxicology, bonds (chemical), semiconductor growth, nanofabrication, vibrational modesOther keywords: green synthesised zinc oxide nanostructures, Periploca aphylla extract, antibacterial potential, multidrug resistant pathogens, multidrug resistant bacterial infections, antibacterial nanomedicines, P. aphylla aqueous extract, structural examinations, scanning electron microscopy, X‐ray diffraction, pure phase morphology, homogenised average particle size, SEM, transmission electron microscopy, Fourier‐transform infrared spectroscopy, bond vibration frequency, antibacterial activity, disc diffusion assay, colony forming unit testing, S. marcescens, E. cloacae, E. coli, ultraviolet‐visible spectroscopy, protein kinase inhibition assay, cytotoxicity, lethal infections, ZnO     

Analysis of the decoupled uplink downlink technique for varying path loss exponent in multi-tier HetNet

In this paper, the impact of varying path loss exponent (PLE) on user association probability, decoupled uplink coverage probability as well as decoupled uplink average spectral efficiency in downlink uplink decoupled (DUDe) multi-tier heterogeneous networks, is investigated. We investigate the effect of the difference in path loss exponents in both macro and small cell environments over uplink network performance. It is assumed that the mobile user connected to the macro base station experience different path loss exponent as compared to when connected to small base station. It is observed that the difference of path loss exponents in both cases has significant effect on the user association probability, decoupled uplink coverage probability as well as decoupled uplink average spectral efficiency. Moreover, in order to further support key findings and make sound comparison between coupled and DUDe performance in varying PLE environment, generalized analytical expressions for coupled association probabilities, along with coupled uplink coverage probability and coupled uplink average spectral efficiency have been derived. The analytical results evaluated in this paper are compared with the computer simulation and found in good agreement. Our analysis shows that decoupling technique performs suboptimal for cases where the environments around macro and small base stations are different with respect to each other. The work explained in this paper highlights the limitation of applying DUDe technique in realistic conditions where the PLEs of cellular tiers are not exactly equal to one another.

     

Qualitative response of safety injection system for a large size break in the reactor coolant system cold leg

Safety injection system, accumulator injection system and residual heat removal system of CHASNUPP-1 were simulated using the computer code APROS. We observed the qualitative response of the simulated system during injection and re-circulation phases after LOCA. During rapid depressurization of SRC system due to leakage, these systems started coolant injection in the SRC system as per plant requirement. Different thermal-hydraulic parameters of the respective systems are presented and discussed. Results obtained are in good agreement with the reported document of the reference power plant.     

Designing zinc oxide nanostructures (nanoworms,nanoflowers, nanowalls,and nanorods) by pulsed laser ablation technique for gas-sensing application

In this study, pulsed laser ablation technique, also known as pulsed laser deposition (PLD), is used to design and grow zinc oxide (ZnO) nanostructures (nanoworms, nanowalls, and nanorods) by template/seeding approach for gas-sensing applications. Conventionally, ZnO nanostructures used for gas-sensing have been usually prepared via chemical route, where the 3D/2D nanostructures are chemically synthesized and subsequently plated on an appropriate substrate. However, using pulsed laser ablation technique, the ZnO nanostructures are structurally designed and grown directly on a substrate using a two-step temperature-pressure seeding approach. This approach has been optimized to design various ZnO nanostructures by understanding the effect of substrate temperature in the 300-750°C range under O₂ gas pressure from 10-mTorr to 10 Torr. Using a thin ZnO seed layer as template that is deposited first at substrate temperature of ~300°C at background oxygen pressure of 10 mTorr on Si(100), ZnO nanostructures, such as nanoworms, nanowalls, and nanorods (with secondary flower-like growth) were grown at substrate temperatures and oxygen background pressures of (550°C and 2 Torr), (550°C and 0.5 Torr), and (650°C and 2 Torr), respectively. The morphology and the optical properties of ZnO nanostructures were examined by Scanning Electron Microscope (SEM-EDX), X-ray Diffraction (XRD), and photoluminescence (PL). The PLD-grown ZnO nanostructures are single-crystals and are highly oriented in the c-axis. The vapor-solid (VS) model is proposed to be responsible for the growth of ZnO nanostructures by PLD process. Furthermore, the ZnO nanowall structure is a very promising nanostructure due to its very high surface-to-volume ratio. Although ZnO nanowalls have been grown by other methods for sensor application, to this date, only a very few ZnO nanowalls have been grown by PLD for this purpose. In this regard, ZnO nanowall structures are deposited by PLD on an Al₂O₃ test sensor and assessed for their responses to CO and ethanol gases at 50 ppm, where good responses were observed at 350 and 400°C, respectively. The PLD-grown ZnO nanostructures are very excellent materials for potential applications such as in dye-sensitized solar cells, perovskite solar cells and biological and gas sensors.     

Synthesis,characterization and thermal dissociation of 2‐butoxyethanol‐blocked diisocyanates and their use in the synthesis of isocyanate‐terminated prepolymers

A series of blocked diisocyanates has been synthesized from toluene diisocyante (TDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), 4,4′‐diphenylmethane diisocyanate (MDI) and 2‐butoxyethanol. The synthesis of blocked diisocyanate adducts was confirmed by Fourier transform infrared, ¹H NMR, electron impact mass spectrometry and nitrogen analysis. Differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and carbon dioxide evolution were used to determine the minimum de‐blocking temperatures. De‐blocking temperatures determined by these three techniques were found to be in the order DSC > TGA > CO₂ evolution. The effect of different metal catalysts on thermal de‐blocking reaction of the blocked diisocyanates was studied, using the carbon dioxide evolution method. It was found that iron(III) oxide has the maximum catalytic activity on de‐blocking. The solubility of the blocked diisocyanate adducts was determined in different solvents. The study revealed that at 30 °C blocked IPDI and HDI adducts show better solubility than adducts based on TDI and MDI. Isocyanate‐terminated prepolymers of blocked diisocyanates and hydroxyl‐terminated polybutadiene (HTPB) were prepared. The storage stability and gelation times of the prepolymers were studied. Results showed that all the diisocyanate‐HTPB compositions are stable at 50 °C for more than three months. However, aliphatic diisocyanate‐HTPB compositions require greater gelation time than aromatic diisocyanate‐HTPB compositions at their respective de‐blocking temperatures. Copyright © 2007 Society of Chemical Industry