Effect of matrix on the ballistic impact of aramid fabric composite laminates by armor piercing projectiles

Ballistic impact performance of aramid fiber fabric‐epoxy and aramid fiber fabric‐polypropylene (PP)‐based composite laminates has been studied against 7.62 mm armor piercing projectiles. Twaron® was used as aramid fiber fabric in the composites. Role of matrix on the damage pattern has been investigated by impacting the composites of different thickness with projectiles having different strike velocity (SV). Ballistic limit (BL) for each composite has been estimated through correlation of SV and residual velocity (RV) of the projectile by usual V₅₀ method. Ballistic limit was found to vary linearly with composite laminate thickness. Twaron®‐PP composites exhibited higher ballistic limit compared toequivalent thickness of Twaron®‐epoxy composites. Epoxy‐based composites exhibited localized damage mode compared to a global mode of failure in PP‐based composites. Scanning electron microscopy revealed that fibers in Twaron®‐epoxy composites failed largely by shear while tensile mode of failure was observed for Twaron®–PP composites. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Sedimentological control on Mn, and other trace elements, in groundwater of the Bengal delta

To reveal what controls the concentration and distribution of possibly hazardous (Mn, U, Se, Cd, Bi, Pb) and nonhazardous (Fe, V, Mo, PO(4)) trace elements in groundwater of the Bengal delta, we mapped their concentrations in shallow groundwater (<60 mbgl) across 102 km(2) of West Bengal. Only Mn is a potential threat to health, with 55% of well water exceeding 0.3 mg/L, the current Indian limit for drinking water in the absence of an alternate source, and 75% exceeding the desirable limit of 0.1 mg/L. Concentrations of V are <3 μg/L. Concentrations of U, Se, Pb, Ni, Bi, and Cd, are below WHO guideline values. The distributions of Fe, Mn, As, V, Mo, U, PO(4), and δ(18)O in groundwater reflect subsurface sedimentology and sources of water. Areas of less negative δ(18)O reveal recharge by sources of evaporated water. Concentrations of Fe, As, Mo, and PO(4) are high in palaeo-channel groundwaters and low in palaeo-interfluvial groundwaters. Concentrations of U, V, and Mn, are low in palaeo-channel groundwaters and high in palaeo-interfluvial groundwaters. Concentrations of Fe and Mn are highest (18 and 6 mg/L respectively) at dual reduction-fronts that form strip interfaces at depth around the edges of palaeo-interfluvial aquifers. The fronts form as focused recharge carries dissolved organic carbon into the aquifer margins, which comprise brown, iron-oxide bearing, sand. At the Mn-reduction front, concentrations of V and Mo reach peak concentrations of 3 μg/L. At the Fe-reduction front, concentrations of PO(4) and As reach concentrations 3 mg/L and 150 μg/L respectively. Many groundwaters contain >10 mg/L of Cl, showing that they are contaminated by Cl of anthropogenic origin and that organic matter from in situ sanitation may contribute to driving reduction.     

The Geometry of the 2 × 2 Matt Weave Part II: Validation of Theoretical Models

For the validation of theoretical models, experiments were suitably designed to generate a realistic set of data. Relations between the corresponding characteristic geometrical parameters exhibited a good correspondence with those of point contact model of 2×2 Matt Weave (MRP). Finally the study with distributive contact model (MRD) suggests, the necessity of a hybrid model incorporating typical features of MRP (curvature constraint) and MRD (distributive force constraint).     

Antibacterial properties of polypropylene textiles modified by poly(2-(N,N-dimethyloamino ethyl) methacrylate)

Polypropylene nonwoven fabrics samples were modified using poly(2-(N,N-dimethyloamino ethyl) methacrylate) (PDAMA) and silver-containing layers. The structure of the material after modification was confirmed using scanning electron mocroscope, energy-dispersive X-ray spectroscopy, Fourier Transfer Infrared Spectroscopy (FTIR), and electro-kinetic measurements. It was found that samples with external PDAMA layers have excellent activity against Staphylococcus aureus under dynamic contact conditions. In contrast, samples finished with deposited silver showed little antimicrobial effect. Antibacterial tests conducted under static conditions showed no antibacterial activity irrespective of the deposited layers.     

Quantum drift-diffusion model for IMPATT devices

Quantum correction is necessary on the classical drift-diffusion (CLDD) model to predict the accurate behavior of high frequency performance of ATT devices at frequencies greater than 200 GHz when the active layer of the device shrinks in the range of 150–350 nm. In the present work, a quantum drift-diffusion model for impact avalanche transit time (IMPATT) devices has been developed by incorporating appropriate quantum mechanical corrections based on density-gradient theory which macroscopically takes into account important quantum mechanical effects such as quantum confinement, quantum tunneling, etc. into the CLDD model. Quantum potentials (synonymous as Bohm potentials) have been incorporated in the current density equations as necessary quantum mechanical corrections for the analysis of millimeter-wave (mm-wave) and Terahertz (THz) IMPATT devices. It is observed that the large-signal (L-S) performance of the device is degraded due to the incorporation of quantum corrections into the model when the frequency of operation increases above 200 GHz; while the effect of quantum corrections are negligible for the devices operating at lower mm-wave frequencies.     

Effect of sodium chloride replacement and apple pulp inclusion on the physico-chemical, textural and sensory properties of low fat chicken nuggets

The effect of 40 percent sodium chloride replacement with salt substitute blend (potassium chloride, citric acid, tartaric acid and sucrose) and incorporation of apple pulp, at the levels of 8 (Treatment I), 10 (Treatment II) and 12 (Treatment III) g/100 g of formulation, on the various quality characteristics of low fat chicken nuggets was investigated. Emulsion and product pH values were significantly higher (P < 0.01) for the control when compared to treatments. Salt replacement and apple pulp addition resulted in significantly lower (P < 0.05) emulsion stability and cooking yield. Among low salt and low fat nuggets, the product with 12 g/100 g apple pulp had the highest moisture percent. Protein and ash contents were significantly lower (P < 0.01) in treatment products, whereas moisture protein ratio was higher. Incorporation of apple pulp significantly increased (P < 0.01) dietary fibre content, redness, yellowness and chroma index of the product. Textural properties of the products significantly decreased (P < 0.01) with substitution of common salt and addition of apple pulp. Sensory evaluation showed significant reduction (P < 0.01) in texture and overall acceptability scores of treatment products; however, scores were in the range of very good.     

Inhibitive effect of polyacrylamide grafted with fenugreek mucilage on corrosion of mild steel in 0.5 M H2SO4 at 35°C

The inhibitive effect of polyacrylamide grafted with fenugreek mucilage, a natural grade polysaccharide, on the corrosion of mild steel in 0.5M H₂SO₄ has been investigated by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy. An inhibition efficiency of 78% has been obtained at a concentration as low as 1 ppm and efficiency as high as 96% at 100 ppm. The polarization studies reveal that it acts as a predominantly cathodic inhibitor. The adsorption of this inhibitor on the mild steel surface obeys a Langmuir adsorption isotherm. The deposited films on the electrode surface have been analyzed by using microscopic techniques. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Homeopathic remedy for arsenic toxicity?: Evidence-based findings from a randomized placebo-controlled double blind human trial

Millions of people are at risk of groundwater arsenic contamination, but supply of arsenic-free drinking water is grossly inadequate. The present study was intended to examine if a potentized homeopathic remedy reportedly showing ameliorating potentials in people inhabiting high-risk arsenic-contaminated areas but drinking arsenic-free water, can also ameliorate arsenic toxicity in subjects living in high-risk arsenic-contaminated areas, and drinking arsenic-contaminated water. This pilot study was conducted on 20 males and 19 females of village Dasdiya (arsenic contaminated) who initially agreed to act as volunteers; but as many as 14, mostly placebo-fed subjects, later dropped out. 18 volunteers, 14 males and 4 females, from a distant village, Padumbasan (arsenic-free), served as negative controls. In a double blind placebo-controlled study, a potentized remedy of homeopathic Arsenicum Album-30 and its placebo (Succussed Alcohol-30) were given randomly to volunteers. Arsenic contents in urine and blood and several widely accepted toxicity biomarkers and pathological parameters in blood were analyzed before and after 2 months of administration of either verum or placebo. Elevated levels of ESR, creatinine and eosinophils and increased activities of AST, ALT, LPO and GGT were recorded in arsenic exposed subjects. Decreased levels of hemoglobin, PCV, neutrophil percentages, and GSH content and low G-6-PD activity were also observed in the arsenic exposed people. The administration of "verum" appeared to make positive modulations of these parameters, suggestive of its ameliorative potentials. Most of the subjects reported better appetite and improvement in general health, thereby indicating possibility of its use in remote arsenic-contaminated areas as an interim health support measure to a large population at risk.     

Synthesis,Characterization and Properties of New Semifluorinated Poly(arylene ether phosphine oxide)s

Bis(4‐fluoro‐3‐trifluoromethylphenyl)phenylphosphine oxide is synthesized and six new poly(arylene ether)s are prepared by nucleophilic displacement of the fluorine atom on the benzene ring by several diphenols under basic conditions. The products show very high glass transition temperatures of up to 252 °C and very good thermal stabilities of up to 490 °C for 5% weight loss. The polymers display very low heat release rates in the microscale combustion calorimeter test, suggesting good flame retardance. All polymers are soluble in a wide range of organic solvents. Transparent thin films cast from dichloromethane exhibit tensile strengths up to 54 MPa, a modulus of elasticity up to 0.97 GPa and elongation at break up to 47% depending on their exact repeating unit structures.

     

Geometry of chip formation in circular end milling

Machining along continuous circular tool-path trajectories avoids tool stoppage and even feed rate variation. This helps particularly in high-speed milling by reducing the effect of the machine tool mechanical structure and cutting process dynamics. With the increase in popularity of this machining concept, the need for detailed study of a valid chip formation in circular end milling is becoming necessary for accurate kinematic and dynamic modeling of the cutting process. In this paper, chip formation during circular end milling is studied with a major focus on feed per tooth and undeformed chip thickness along with their analytical derivations and numerical solutions. At first, the difference in the feed per tooth formulation for end milling along linear and circular tool-path trajectories is presented. In the next step, valid formulation of the undeformed chip thickness in circular end milling is derived by considering an epitrochoidal tooth trajectory with a wide range of the tool-path radius. The complex transcendental equations encountered in the derivation are dealt with, by a case-based approach to obtain closed-form analytical solutions. The analytical solutions of undeformed chip thickness are validated with results of numerical simulations of tool and tooth trajectories for circular end milling and also compared to the linear end milling. The close resemblance between analytical and numerical calculations of the undeformed chip thickness in circular end milling suggests validity of the proposed analytical formulations. As a case study, the cutting forces in circular end milling are calculated based on the derived chip thickness formulations and an existing mechanistic model. The calculation results reiterate the need of taking into account adjusted feed per tooth and valid chip thickness formulations in circular end milling, especially for small tool-path radii, for more realistic process modeling.