Interpretation of infinite shear rate viscosity and a nonuniform heat sink/source on a 3D radiative cross nanofluid with buoyancy assisting/opposing flow

With respect to bionomical concerns and energy security, the performance of refrigeration systems should be enriched, which can be done by improving the characteristics of working liquids. Nanoliquids have attracted interest in the fields of engineering and industry due to their prominent thermophysical characteristics. Researchers have used nanoliquids as working liquids and noticed significant fluctuations in thermal execution. In this study,  our prime aim was to study the impact of thermal radiation and varying thermal conductivity on a cross-nanofuid with the addition of a nonuniform heat sink–source, chemical process, and activation energy (AE) together with effects of assisting and opposing buoyancy. Furthermore, the relationship of zero-mass flux together with the mechanism of thermophoresis and Brownian motion is considered. Traditionalistic transformations gave the ordinary differential equations (ODEs), which are further dealt with the approach of the Shooting Scheme to change the boundary value problem (BVP) into an initial value problem (IVP) and a numerical comparison is made with the Matlab solver package bvp4c. Bvp4c is based upon a collocation scheme, which yields numeric outcomes for nonlinear ODEs with IVP. Impacts of the involved parameters on mass transfer profile, heat, and momentum fields are shown through graphs. Mass transfer of the cross nanofluid increases with increasing values of AE parameter. Values of physical quantities like drag forces, rate of transport of heat and mass in the case of assisting/opposing flow are tabulated. The drag force magnitudes are greater for enhancing values of M, a, and n, while on the other hand, the opposing tendency is seen for We₁ and We₂. The magnitude of the rate of heat transport (Nusselt number) falls for greater values of m, σ, δ, and N_t, but in contrast, it accelerates for E, Pr, and n.     

Magnetic properties of maraging steels in relation to nickel concentration

Magnetic properties of maraging steels have been investigated as a function of nickel concentration. The alloys nickel content varied from 12 to 24 wt pct, while other alloying constituents were kept at a level maintained in the 18Ni-2400 MPA-grade maraging steel. The magnetic properties were determined following aging for 1 hour in the temperature range of 450 °C to 750 °C. In every alloy investigated, the coercive field increased with aging temper-ature, reaching a maximum around 670 °C ± 30 °C. The saturation magnetization values were lowest around temperatures where maximum coercive field was observed. The coercive field increased from ∼55 to ∼ 175 Oe (∼4380 to ∼ 13,900 amp/meter) and the corresponding sat-uration magnetization decreased from ∼18,500 to ∼ 4000 G (∼1.85 to ∼0.4 T) in the alloys containing 12 and 24 wt pct Ni, respectively. The reverted austenite increased from 25 vol pct at 12 wt pct Ni to 100 vol pct at 24 wt pct Ni. The hardness and Charpy impact strength of the alloys have also been determined. An attempt has been made to correlate magnetic properties with different phase transformations occurring in maraging steels.     

Mechanical stability and magnetic properties of austenite

Austenitic alloys have been produced by additional alloying in maraging steel grade 18 Ni at 2400 MPa. The concentration of Mo, Ni and Co was increased individually until the martensite start temperature M _s, was suppressed below ambient value. Charpy impact strength, tensile strength and magnetic properties were determined. The impact strength in the annealed condition ranged between 260 to 294 J. In alloys where martensitic transformation occurred following quenching in liquid nitrogen, the impact strength dropped appreciably and was found to be in the range 120–216 J. The tensile strengths of the austenite and martensite phases ranged between 680 to 890 and 1030 to 1100 MPa, respectively. It was observed that the austenite phase transformed to martensite in the region that under went plastic deformation during Charpy and tensile testing. The degree of transformation incorporated, varied as a function of composition. The magnetic properties of the austenite phases were typical of a very weak magnetic material. The coercive field and saturation magnetization values were in the range 1034–2387 Am^–1 and 1.6–2.9 T, respectively. In contrast to the general observation, the austenite phase containing high Co exhibited ferromagnetic behaviour. The coercive field and saturation magnetization of ferromagnetic austenite was 1034 Am^–1 and 11 T, respectively.     

Numerical assessment of the mechanical stability in vertical,directional and horizontal wellbores

In this research the stability of wellbore is evaluated in seven different stress regimes and diverse orientations using FLAC3D software. The normalized yielded zone area (NYZA, i.e., the ratio of surrounding yielded cross-sectional area to initial area of wellbore) is determined for different mud pressures as well as diverse orientations of wellbore. By means of MATLAB software the best curve is fitted to the recorded points and then the optimized mud pressure is calculated using these plots. The optimized orientation is selected considering these data. Finally the mud pressure resulted from this method was compared with the mud pressure obtained from the Mogi-Coulomb criterion and then with the fields data. The minimum allowable mud pressure obtained from the NYZA criterion is close to actual data and the value obtained from the Mogi-Coulomb criterion. Hence, the NYZA is considered to be an appropriate criterion for wellbore stability analysis.     

An enhanced scheme for mutual authentication for healthcare services

With the advent of state-of-art technologies, the Telecare Medicine Information System (TMIS) now offers fast and convenient healthcare services to patients at their doorsteps. However, this architecture engenders new risks and challenges to patients' and the server's confidentiality, integrity and security. In order to avoid any resource abuse and malicious attack, employing an authentication scheme is widely considered as the most effective approach for the TMIS to verify the legitimacy of patients and the server. Therefore, several authentication protocols have been proposed to this end. Very recently, Chaudhry et al. identified that there are vulnerabilities of impersonation attacks in Islam et al.'s scheme. Therefore, they introduced an improved protocol to mitigate those security flaws. Later, Qiu et al. proved that these schemes are vulnerable to the man-in-the-middle, impersonation and offline password guessing attacks. Thus, they introduced an improved scheme based on the fuzzy verifier techniques, which overcome all the security flaws of Chaudhry et al.'s scheme. However, there are still some security flaws in Qiu et al.'s protocol. In this article, we prove that Qiu et al.'s protocol has an incorrect notion of perfect user anonymity and is vulnerable to user impersonation attacks. Therefore, we introduce an improved protocol for authentication, which reduces all the security flaws of Qiu et al.'s protocol. We also make a comparison of our protocol with related protocols, which shows that our introduced protocol is more secure and efficient than previous protocols.     

Graphene Oxide‐Based Lamella Network for Enhanced Sound Absorption

Noise is an environmental pollutant with recognized impacts on the psychological and physiological health of humans. Many porous materials are often limited by low sound absorption over a broad frequency range, delicacy, excessive weight and thickness, poor moisture insulation, high temperature instability, and lack of readiness for high volume commercialization. Herein, an efficient and robust lamella‐structure is reported as an acoustic absorber based on self‐assembled interconnected graphene oxide (GO) sheets supported by a grill‐shaped melamine skeleton. The fabricated lamella structure exhibits ≈60.3% enhancement over a broad absorption band between 128 and 4000 Hz (≈100% at lower frequencies) compared to the melamine foam. The enhanced acoustic absorption is identified to be structure dependent regardless of the density. The sound dissipation in the open‐celled structure is due to the viscous and thermal losses, whereas it is predominantly tortuosity in wave propagation and enhanced surface area for the GO‐based lamella. In addition to the enhanced acoustic absorption and mechanical robustness, the lamella provides superior structural functionality over many conventional sound absorbers including, moisture/mist insulation and fire retardancy. The fabrication of this new sound absorber is inexpensive, scalable and can be adapted for extensive applications in commercial, residential, and industrial building structures.     

Aerodynamics and heat transfer during coating of tablets in two-dimensional spouted bed

The two-dimensional spouted bed has been pointed out in recent research works as an improved configuration of spouted beds. The main advantages in relation to the conventional spouted beds are the easy construction and scale-up. In this work we begin the study of coating of tablets in two-dimensional spouted beds. An experimental system was constructed and the data obtained were used to determine the values of maximum pressure drop, minimum spout flowrate and gas-to-particle heat transfer coefficient, for 36 process conditions. The experimental results have been correlated with process and geometrical parameters.     

Dynamic Prediction based Multi Queue (DPMQ) drop policy for probabilistic routing protocols of delay tolerant network

Two most important issues should be considered to achieve data delivery in DTN networking: routing protocols for the network and intelligent buffer management policy for everyone node in the network. The routing scheme decides which messages should be forwarded when nodes meet, and the buffer management policy determines which message is purged when the buffer overflows in a node. This study proposes a buffer management policy named as Dynamic Prediction based Multi Queue (DPMQ) for probabilistic routing protocols. It works by classification of local buffer into three queues of messages, which are DCTL, HPTL and LPTL. The simulation results have proven that the DPMQ performs well as compared to DLA, DOA, MOFO, LIFO, LEPR and LIFO in terms of reducing the message relay, message drop, hop counts average and overhead while rising in the delivery probability.     

Comparative production of xylanase and the liberation of xylooligosaccharides from lignocellulosic biomass by Aspergillus brasiliensis BLf1 and recombinant Aspergillus nidulans XynC A773

We investigated the simultaneous production of xylanase and the liberation of xylooligosaccharides in rice husk solid‐state cultivations of Aspergillus brasiliensis BLf1 and by the recombinant Aspergillus nidulans XynC A773 strain. The bioprocess was optimised by experimental fractional design and response surface analysis. Results show that both fungi strains produced xylanases and their activities were dependent on the addition of basal medium, moisture content and the interactions between particle size and inoculum size, producing maximum xylanase activities of 230.7 U g^?1 substrate for A. brasiliensis, and 187.9 U g^?1 substrate for A. nidulans XynC. Xylooligosaccharides were liberated in the same cultures, with concentrations up to 17.6 mg g^?1 and 23.9 mg g^?1 of substrate for A. brasiliensis and A. nidulans XynC, respectively, both strains presenting similar profiles, with xylose residues varying from X3 to X6. These results suggest the possibility of lowering production costs of enzymes for food applications and oligosaccharides.