Solid Particle Erosion Behavior of WC-CoCr Nanostructured Coating

In the present study, solid particle erosion resistance of high-velocity oxy-fuel (HVOF)-sprayed WC-CoCr coatings was evaluated. Erosion testing was conducted using alumina (Al₂O₃) powder as the erodent with three different impact angles (30, 60, and 90°) and impact velocity was kept constant. The coatings were deposited using two different powders; one was composed of conventional WC particles and second one contained nanoscale particles mixed with CoCr binder material. Erosion testing was carried out at room temperature using an air-jet erosion test setup. The effect of varying impact angles was studied and discussed with the help of scanning electron microscopy images of worn surfaces of coatings. The results showed that coating properties like microhardness and fracture toughness have a strong influence on the erosion behavior. During erosion testing, material was removed by fracturing and pullout of WC grains from the binder matrix. The morphology of the eroded surface also showed cutting, lip, and groove formation in the binder matrix caused by the repetitive impacts of erodent particles. It was observed that coating with nano-WC grains exhibited higher erosion resistance compared to conventional coating.     

Enhanced antibacterial activity of bifunctional Fe3O4-Ag core-shell nanostructures

We describe a simple one-pot thermal decomposition method for the production of a stable colloidal suspension of narrowly dispersed superparamagnetic Fe₃O₄-Ag core-shell nanostructures. These biocompatible nanostructures are highly toxic to microorganisms. Antimicrobial activity studies were carried out on both Gram negative (Escherichia coli and Proteus vulgaris) and Gram positive (Bacillus megaterium and Staphylococcus aureus) bacterial strains. Efforts have been made to understand the underlying molecular mechanism of such antibacterial actions. The effect of the core-shell nanostructures on Gram negative strains was found to be better than that observed for silver nanoparticles. The minimum inhibitory concentration (MIC) values of these nanostructures were found to be considerably lower than those of commercially available antibiotics. We attribute this enhanced antibacterial effect of the nanostructures to their stability as a colloid in the medium, which modulates the phosphotyrosine profile of the bacterial proteins and arrests bacterial growth. We also demonstrate that these core-shell nanostructures can be removed from the medium by means of an external magnetic field which provides a mechanism to prevent uncontrolled waste disposal of these potentially hazardous nanostructures.      

Removal of Pb(II) ions from aqueous solution by adsorption using bael leaves (Aegle marmelos)

Biosorption of Pb(II) on bael leaves (Aegle marmelos) was investigated for the removal of Pb(II) from aqueous solution using different doses of adsorbent, initial pH, and contact time. The maximum Pb loading capacity of the bael leaves was 104 mg g^?1 at 50 mg L^?1 initial Pb(II) concentration at pH 5.1. SEM and FT-IR studies indicated that the adsorption of Pb(II) occurs inside the wall of the hollow tubes present in the bael leaves and carboxylic acid, thioester and sulphonamide groups are involved in the process. The sorption process was best described by pseudo second order kinetics. Among Freundlich and Langmuir isotherms, the latter had a better fit with the experimental data. The activation energy E_a confirmed that the nature of adsorption was physisorption. Bael leaves can selectively remove Pb(II) in the presence of other metal ions. This was demonstrated by removing Pb from the effluent of exhausted batteries.     

A three-dimensional micromechanical model to predict the viscoelastic behavior of woven composites

Polymer matrix based cloth composites are increasingly used in engineering applications. For such composites, significant viscoelastic behavior can be observed for dynamic load conditions. The viscoelastic effect is primarily due to the polymeric matrix used as most of the fibers used in structural applications are elastic. Matrix does not show a major contribution in the axial properties of composites, thus in the traditional modeling its viscoelastic nature is often ignored. However, the effective out of plane properties are influenced by the matrix material and exhibit significant damping characteristics. Therefore, a complete three-dimensional (3-D) model considering the viscoelastic nature of matrix is needed for better understanding of cloth composites. An analytical 3-D micromechanical model based on classical laminate theory (CLT) is verified, in this paper for the prediction of effective elastic and viscoelastic properties of a cloth composite. The method is shown to be accurate. This model is extended to the viscoelastic regime with the use of Laplace transform and correspondence principle. Prony series coefficients for composite cloth are obtained for different volume fractions of fibers in yarn. It is observed from the hysteresis plots that dissipation in out of plane normal and shear modes is significantly higher than the normal directions.     

Cactus cladode polysaccharide as cryoprotectant in frozen Paneer (Indian Cottage Cheese)

The study investigated the optimisation of freezing conditions for Paneer (Indian cottage cheese) incorporated with cactus cladode polysaccharide as cryoprotectant. The freezing rate of both natural and commercial cryoprotectant‐containing samples varied significantly. The optimised (2% natural cryoprotectant) Paneer sample had about 44% moisture content, 14% protein, 16% carbohydrate and 22% fat. Freezing time of optimised Paneer sample packed in metalised polyester was 40 min. The study concluded that Paneer incorporated with 2% cactus cladode polysaccharide, packaged using metalised polyester and frozen with packaged immersion freezing method, had the least freezing time (40 min) and retained better texture during freezing.     

Bayes estimation of reliability in stress-strength model of Weibull distribution with equal scale parameters

The paper provides a Bayesian approach to inference about the reliability in a multicomponent stress-strength system. We consider Bayes' estimator of the system reliability from data consisting of a random sample from the stress distribution and one from the strength distribution when the two distributions are Weibull with equal and known scale parameters. The estimator of λ, ratio of two shape parameters, is also considered. The proposed estimators can be compared with the maximum likelihood estimators (mles). However, the comparison is carried out for single component stress-strength system and the Monte Carlo efficiencies are obtained. It is found that the proposed estimators are better than the corresponding mles.     

Multifunctional greener additives for lubricating oil

In an anticipation to produce biodegradable additives with multifunctional performance for a cost‐effective lubricant composition, copolymers are synthesized by incorporating rice bran oil, peanut oil, β‐pinene in the backbone of isodecyl acrylate through microwave irradiation method using AIBN (azobisisobutyronitrile) as radical initiator. The prepared polymers are characterized by spectral techniques (IR, NMR) and SEC‐GPC analysis, thermal stability was determined by thermogravimetric analysis. Performance of the polymers as antiwear (AW), pour point depressant (PPD), viscosity modifier/viscosity index improver (VII) in different mineral base oils (SN1 and SN2) were done by standard ASTM methods. Biodegradability test of the polymers was carried out by disk diffusion (DD) and soil burial test methods. The copolymers of rice bran oil showed better viscosity index values and AW property, whereas the copolymers of peanut oil found to be most effective as PPD. Copolymers with higher concentration of green units showed better performance as viscosity modifier, pour point depressant and AW performance along with excellent biodegradability. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers     

A Dual-Band Circularly Polarized Hexagonal Ring Antenna for Handheld RFID Readers

In this paper, a compact, lightweight, low-profile dual-band circularly polarized antenna is presented for handheld radio frequency identification (RFID) readers. The proposed antenna consists of two concentric hexagonal rings and a feed network printed on different layers of the dielectric substrate. The antenna configuration exploits a stacked-coupled technique for gain enhancement and single-port feeding for easy manufacturing. The center frequencies of the two resonating bands are 0.92 GHz (UHF) and 2.45 GHz (ISM). The antenna exhibits circular polarization characteristics in both the resonating bands, therefore encountering the losses due to polarization mismatch and increasing the tag detection reliability. A prototype of the proposed RFID antenna is simulated and fabricated, and experimental results are in close agreement. The peak antenna gain is 3.3 dB and 5 dB in the UHF and ISM bands, respectively. The overall size of the RFID antenna is 80 mm?×?80 mm?×?7.76 mm.

     

Analysis of Traffic Impact on Proposed Congestion Control Scheme in AODV

Wireless Personal Communications - Congestion is a noteworthy problem in Mobile Ad hoc Network, which occurs when number of users increases and a node carries data more than its capacity. In this...     

Free space and user proximity analysis of octaband monopole MIMO/diversity antenna for modern handset applications

In this article, a comprehensive study of the compact octaband monopole MIMO/diversity antenna is carried out in the free space and user proximity. The radiating structure of the proposed antenna consists of a driven element which is directly fed with microstrip line and a parasitic element. However, the designed antenna provides of 730‐885 MHz at lower frequency side and 1670‐2740 MHz at higher frequency side. Further, to reduce the mutual coupling between two antenna elements, a folded T‐shaped structure is designed of electrical length λ/4 at 0.8 GHz and attached to the ground plane. This structure helps in isolation improvement up to the level of ?12 dB from ?6 dB. The folded structure of T‐shaped provides compactness to the proposed antenna. Thereafter, three kinds of user proximity named as Talk mode, Data mode, and Read mode along with mobile phone are studied. Moreover, the specific absorption rate (SAR) is calculated and found well below the standard limit of FCC and European standard. Finally, the proposed antenna is fabricated and tested. The measured results are in close agreement with simulated results.