Exact analysis of unsteady convective diffusion in Casson fluid flow in an annulus – Application to catheterized artery

Summary The dispersion of a solute in the flow of a Casson fluid in an annulus is studied. The generalized dispersion model is employed to study the dispersion process. The effective diffusion coefficient, which describes the whole dispersion process in terms of a simple diffusion process, is obtained as a function of time, in addition to its dependence on the yield stress of the fluid and on the annular gap between the two cylinders. It is observed that the dispersion coefficient changes very rapidly for small values of time and becomes essentially constant as time takes large values. In non–Newtonian fluids the steady state is reached at earlier instants of time when compared to the Newtonian case and the time taken to reach the steady state is seen to depend on the values of the yield stress. It is observed that a decrease in the annular gap inhibits the dispersion process for all times both in Newtonian as well as in non–Newtonian fluids. When the yield stress is 0.05, depending upon the size of the annular gap (0.9–0.7) the reduction factor in the dispersion coefficient varies in the range 0.58–0.08. The application of this study for understanding the dispersion of an indicator in a catheterized artery is discussed.     

Junction reinforced pressurized spherical shell with a conical nozzle

In this paper, an analytical solution to the problem of a junction reinforced spherical shell with a conical nozzle under internal pressure is presented. The stresses are determined using Reissner's shallow spherical shell equations together with the solutions corresponding to the conical nozzle in terms of Bessel functions. The reinforcement and the conical nozzle are considered as an elastic discontinuity in the spherical shell causing perturbations in the undisturbed membrane state of stress in the spherical shell. After checking many limiting cases for which analytical or other solutions are available, the computer software developed is applied to a wide range of discontinuity parameters to assess their influence on the stress concentrations. Outside reinforcement is found to be more beneficial compared to inside reinforcement. The method presented is applicable to a wide range of discontinuity dimensions including those for which Esslinger's or Geckler's approximation is not applicable.     

Mechanistically based fatigue-damage evolution model for brittle matrix fibre-reinforced composites

An analysis of the fatigue-damage evolution process through prediction of stiffness drop in brittle matrix unidirectional composites reinforced with continuous stiff fibres is presented. The drop in stiffness of the composite is calculated by partitioning the total damage between the components of the composite, namely the matrix, the fibre, and the interface. Predictions of drop in stiffness are validated for different fatigue test conditions in borosilicate glass-ceramic matrix-Nicalon fibre-reinforced composites. In addition, fatigue test results from other composite systems, such as LASII-Nicalon and aluminosilicate-Nicalon, are examined in the light of this model.     

Finite element modelling of crack propagation in elastic-plastic media

Materials which are cyclically stressed by sliding indenters often undergo fatigue wear, as surface breaking vertical cracks and subsurface horizontal cracks propagate causing eventual loss of material. In this study, the authors model crack propagation in an elastic-plastic material using finite element techniques, and consider the influence of friction, elasticity, plasticity and degree of penetration on the J-integral at the tip of a vertical crack. Crack propagation directions are estimated using J-integral maxima as the determining variable. It is found that the J-integral values, as a measure of strain energy release rate, can be used to estimate the crack propagation angle. Its main advantage lies in the fact that it considers both modes (I, II) of crack propagation. Using the J-integral values, one finds that, in the absence of friction between the indenter and the material, the vertical crack is equally prone to propagation at both 45 and 135° angles. However, one notices that the vertical crack favours the direction opposite to the direction of rolling for non-zero values of friction, i.e. 135°. The effects of both the crack depth and the crack tip plasticity are also investigated. It is found that any experimental findings suggestive of crack orientations closer to the horizontal in the direction opposite to the sliding direction are probably a result of shallow vertical asperities or higher crack tip plasticity.     

Transition metal-based cathodes for hydrogen evolution in alkaline solution: Electrocatalysis on nickel-based ternary electrolytic codeposits

Nickel-molybdenum-iron, nickel-molybdenum-copper, nickel-molybdenum-zinc, nickel-molybdenum-cobalt, nickel-molybdenum-tungsten and nickel-molybdenum-chromium ternary codeposits, obtained through electrodeposition on mild steel strips have been characterized with the objective of qualitatively comparing and assessing their electrocatalytic activities as hydrogen electrodes in alkaline solution. It has been concluded that their electrocatalytic effects for the hydrogen evolution reaction (h.e.r.) rank in the following order: Ni–Mo–Fe>Ni–Mo–Cu>Ni–Mo–Zn>Ni–Mo–Co Ni–Mo–W>Ni–Mo–Cr>Ni-plated steel. Further investigations on these electrocatalysts have revealed that the cathodic overpotential contribution to the electrolysis voltage can be brought down by 0.3 V when compared with conventional steel cathodes. The best and most stable hydrogen evolving cathode of these, namely Ni–Mo–Fe, exhibited an overpotential of about 0.187 V for over 1500 h of continuous electrolysis in 6 M KOH at 300 mA cm^–2 and 353 K. The salient features of the codeposits, such as physical characteristics, chemical composition, current-potential behaviour and the varying effects of the catalytic activation method were analysed with a view to correlating the micro-structural characteristics of the coatings with the hydrogen adsorption process. The stability under open circuit conditions, the tolerance to electrochemical corrosion and the long term stability of Ni–Mo–Fe codeposit cathodes were very encouraging. An attempt to identify the pathway for the h.e.r. on these codeposit cathodes was made, in view of the electrochemical parameters obtained experimentally.     

Biodegradable polymeric injectable implants for long‐term delivery of contraceptive drugs

Development of injectable, long‐lasting, contraceptive drug delivery formulations, and implants are highly desired to avoid unplanned pregnancies while improving patient compliance and reducing adverse side effects and treatment costs. The present study reports on the fabrication and characterization of two levonorgestrel (LNG) microsphere injectable formulations. Poly(?‐caprolactone) (PCL) with 12.5% and 24% (w/w) LNG were fabricated into microspheres, measuring 300 ± 125 µm, via the oil‐in‐water (o/w) emulsion solvent evaporation technique. Formulations showed sustained drug release up to 120 days. FTIR, XRD, DSC, and TGA confirmed the absence of LNG chemical interaction with PCL as well as its molecular level distribution. The in vitro release of LNG was calculated to be Fickian diffusion controlled and properly characterized. The inclusion of multiple elevated release temperatures allowed for the application of the Arrhenius model to calculate drug release constants and representative sampling intervals, demonstrating the use of elevated temperatures for accelerated‐time drug release studies. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46068.     

A Three Layered Peer-to-Peer Energy Efficient Protocol for Reliable and Secure Data Transmission in EAACK MANETs

The wireless body sensor network (WBSN) an extensive of WSN is in charge for the detection of patient’s health concerned data. This monitored health data are essential to be routed to the sink (base station) in an effective way by approaching the routing technique. Routing of tremendous sensed data to the base station minimizes the life time of the network due to heavy traffic occurrence. The major concern of this work is to increase the lifespan of the network which is considered as a serious problem in the wireless network functionalities. In order to recover this issue, we propose an optimal trust aware cluster based routing technique in WBSN. The human body enforced for the detection of health status is assembled with sensor nodes. In this paper, three novel schemes namely, improved evolutionary particle swarm optimization (IEPSO), fuzzy based trust inference model, and self-adaptive greedy buffer allocation and scheduling algorithm (SGBAS) are proposed for the secured transmission of data. The sensor nodes are gathered to form a cluster and from the cluster, it is necessary to select the cluster head (CH) for the effective transmission of data to nearby nodes without accumulation. The CH is chosen by considering IEPSO algorithm. For securable routing, we exhibit fuzzy based trust inference model to select the trusted path. Finally, to reduce traffic occurrence in the network, we introduce SGBAS algorithm. Experimental results demonstrate that our proposed method attains better results when compared with conventional clustering protocols and in terms of some distinctive QoS determinant parameters.     

Compact light-emitting-diode sun photometer for atmospheric optical depth measurements

A new compact light-emitting diode (LED) sun photometer, in which a LED is used as a spectrally selective photodetector as well as a nonlinear feedback element in the operational amplifier, has been developed. The output voltage that is proportional to the logarithm of the incident solar intensity permits the direct measurement of atmospheric optical depths in selected spectral bands. Measurements made over Ahmedabad, India, show good agreement, within a few percent, of optical depths derived with a LED as a photodetector in a linear mode and with a LED as both a photodetector and a feedback element in an operational amplifier in log mode. The optical depths are also found to compare well with those obtained simultaneously with a conventional filter photometer.