Mathematical modelling of abrasive waterjet footprints for arbitrarily moving jets: Part I—single straight paths

It is notoriously well-known that abrasive waterjet milling (AWJM) is difficult to perform controlled-depth owing to variable geometries of the footprints that depends not only on jet energy and the exposure time upon the workpiece, but also on the orientation of the jet relative to the target surface. An attempt is made to develop a model that can be generally applied to different machine system and to predict individual jet footprints that are one of the key steps for controlled-depth AWJM. To address this, the paper breaks new ground in geometrical modelling of AWJM with the benefit of having few variables for predicting the footprints obtained under the following conditions: (i) any time exposures (i.e. V_f, jet feed speeds); (ii) jet orientations (θ) relative to the target surface; (iii) arbitrarily moving straight jet-paths (β). These conditions reflect the real industrial conditions under which the process is run. The geometrical model results in a non-linear partial differential equation, a method to evaluate the material specific erosion rate from the characteristics of a shallow trench obtained experimentally using high jet feed speeds. Under these conditions, the governing equations can be linearised and solved analytically.The model validation for full profile of trenches generated at various tilt angles (θ=70-90°), jet feed rates (V_f=500-1000 mm/min) and jet path directions (β=0-270°) indicates that a high degree of accuracy (mean of the residuals R_M<3% and root-mean-square error of residuals R_RMS<6%) has been achieved. This innovative footprint modelling approach has the key advantage of being independent of the properties of the workpiece material and/or machine setup, since it calibrates the specific etching rate. By considering any orientation of the jet plume vector relative to the target surface, this approach becomes a powerful tool for the development of advanced jet path strategies to enable AWJM of complex geometries.     

Formulation and characterisation of nanosuspension of herbal extracts for enhanced antiradical potential

Nanotechnology is a promising technique to increase the bioavailability of herbal medicines. This paper presents the nanosuspension approach for increasing the aqueous solubility and thereby bioactivity of important herbal extracts. Nanosuspensions of the seeds of three plants extract (Silybum marianum, Elettaria cardamomum and Coriandrum sativum) were prepared by using polyvinyl alcohol (1.5% w/v) as a stabiliser. Prepared nanoparticles were characterised by scanning electron microscope. Activity of nanosuspension formulation was assessed by using four in vitro antioxidant assays. S. marianum, E. cardamomum and C. sativum particle size was observed to fall in range of 446.1 ± 112.6, 456.63 ± 339.2 and 432.1 ± 172.8 nm, respectively, most of the particles were having spherical shape and smooth topology. These synthesised nanoparticles were found to be more effective against quenching free radical than their crude extracts and standards [butylated hydroxyl toluene and ascorbic acid]. C. sativum nanosuspension showed most free radical scavenging potential against 2,2-diphenyl-1-picrylhdrazyl (DPPH) and superoxide free radical scavenging assays (IC₅₀ 0.59 ± 0.01 and 0.81 ± 0.11 mg/ml). S. marianum nanosuspension was found to be most effective against DPPH radicals scavenging (IC₅₀ 0.34 ± 0.02 mg/ml). It was concluded that nanosuspension of herbal medicines potentiates the antioxidant potential.     

Model-based design verification for embedded systems through SVOCL: an OCL extension for SystemVerilog

Model Based System Engineering (MBSE) is a renowned approach in the context of embedded systems development. It is frequently used to deal with the structural and behavioral aspects of system design. However, the verification of system design is generally performed in isolation. It is particularly true in the context of assertion based verification. Consequently, there is a huge gap between system design and its verification that seriously effects the productivity and time-to market objectives. Therefore, in this research, we target to reduce this gap by exploiting the features of MBSE and SystemVerilog assertions (SVA’s). This article introduces a novel MBSE approach to model the design verification aspects of embedded systems, along with the system design (structural and behavioral aspects). We propose SystemVerilog in Object Constraint Language (SVOCL), an OCL temporal extension for SystemVerilog, to represent the design verification requirements by means of SVA’s. As a part of research, SVOCL transformation engine has been developed to generate SVA’s code in order to automate the design verification of embedded systems. The application of SVOCL has been validated through four case studies.     

Thermal behaviour of polyethylene‐block‐poly(methyl methacrylate) block copolymer: effect of multiple heating and cooling rates versus mathematical artefact

The melting and crystallization behaviours of a polyethylene‐block‐poly(methyl methacrylate) (PE‐b‐PMMA) diblock copolymer and a PE homopolymer were investigated using multiple heating and cooling rate differential scanning calorimetry (DSC) experiments, and modelling of the crystallization kinetics and lamellar thickness distribution. This new model was first validated applying literature and experimental data. The model‐predicted morphology (n = 3.2) closely matched the spherulitic morphology (n = 3), which was determined using polarized optical microscopy. For each experimental cooling rate, the model predicted diblock copolymer crystallinity that well matched the entire DSC crystallinity curve, notably for an Avrami–Erofeev index of n = 2; and apparent crystallization activation energy that hardly varied with the cooling rates used, relative crystallinity (α), and crystallization temperature or time. This disfavours the concept of variable activation energy. The use of the right crystallization model and parameter estimation algorithm is important for addressing the mathematical artefact. Under non‐isothermal cooling, the PE‐b‐PMMA diblock copolymer, as per the model prediction, crystallized without confinement (n ≠ 1), preserving the cylindrical structure. From the characteristic shapes of the crystallization function f(α(T)) versus 1/T and crystallization rate versus α plots, the resulting T_cmax and narrow α_max range can guide the search for an appropriate crystallization model. The overall treatment illustrated in this study is not restricted to a PE homopolymer and a PE‐b‐isotactic PMMA block copolymer. It can be generally applied to crystalline homopolymers and copolymers (alternating, random and block), as well as their blends. The block copolymers and blends can be crystalline–amorphous as well as crystalline–crystalline. © 2014 Society of Chemical Industry     

Recent Developments in Epoxy/Graphite,Epoxy/Graphene,and Epoxy/Graphene Nanoplatelet Composites: A Comparative Review

Development in graphite, graphene, and graphene nanoplatelet composites with epoxy matrix is presented here. Graphite and its modified forms propose exclusive properties to composites. Graphene has developed as subject of huge scientific attention due to excellent electron transport, mechanical properties, and high surface area. When combined appropriately with epoxy, these atomically thin carbon sheets can expressively progress physical properties even at very small loading. Epoxy/graphene nanoplatelet nanocomposite with enhanced properties was also reported. We summarized and compared electrical, thermal, and mechanical properties of epoxy composites derived from these three nanofillers. Potential of carbon fillers with epoxy matrix is also discussed.     

Recent Developments in Different Types of Flame Retardants and Effect on Fire Retardancy of Epoxy Composite

In this review, main focus is on the different types of fire retardants, their properties, and pertinent potential. Both inorganic (titania, silica, and zinc oxide) and organic (graphite, graphene, and graphene nanoplatelet) compounds have been discussed as flame inhibitors. Among various sorts of fire retardants, halogen-based flame inhibitors possess outstanding features. Consequently influence of fire retardant on the performance of epoxy composite has been discussed. It was noted that significant enhancement occurs by addition of organic and inorganic fillers in epoxy matrix. However, halogen additives impart better flame resistance to epoxy composite. Toward the end of this review, potential of halogen-containing fire retardant is discussed.