Volume Conservation Controversy of the Variable Parameter Muskingum–Cunge Method

The study analyzes the volume conservation problem of the variable parameter Muskingum–Cunge (VPMC) method for which some remedial solutions have been advocated in recent literature. The limitation of the VPMC method to conserve volume is brought out by conducting a total of 6,400 routing experiments. These experiments consist of routing a set of given hypothetical discharge hydrographs for a specified reach length in uniform rectangular and trapezoidal channels using the VPMC method, and comparing the routed solutions with the corresponding benchmark solutions obtained using the full Saint-Venant equations. The study consisted of 3,200 routing experiments carried out each in uniform rectangular and trapezoidal channel reaches. Each experiment was characterized by a unique set of channel bed slope, Manning’s roughness coefficient, peak discharge, inflow hydrograph shape factor, and time to peak. A parallel study was carried out using an alternate physically based variable parameter Muskingum discharge hydrograph (VPMD) routing method proposed by Perumal in 1994 under the same routing conditions, and the ability of both the VPMC and VPMD methods to reproduce the benchmark solutions was studied. It is brought out that within its applicability limits, the VPMD method is able to conserve mass more accurately than the VPMC method. The reason for the better performance of the former over the latter method is attributed to the physical basis of its development. It is argued that adoption of artificial remedial measures to overcome the volume conservation problem makes the VPMC method semiempirical in nature, thereby losing the fully physically based characteristics of the method. The paper also dwells on the problems of negative initial outflow or dip in the beginning of the Muskingum solution, and the negative value of the Muskingum weighting parameter. Besides, the effect of incorporating the inertial terms in the estimation of Muskingum parameters and their impact on the overall Muskingum routing solutions is addressed by conducting another set of 6,400 numerical experiments using both the VPMC and VPMD methods.     

Synthesis and biodegradability of starch-g-ethyl methacrylate/sodium acrylate/sodium silicate superabsorbing composite

A new superabsorbent composite polymer (SAP) has been prepared by graft copolymerization reaction using starch, ethyl methacrylate (EMA), benzoyl peroxide (BPO) as initiator and sodium acrylate as crosslinking agent. Further, it is observed that the composite doped with sodium silicate exhibits higher waterabsorbency as the silicate can well disperse in the water and enter into the network structure of the composite, thereby increasing the porosity of the composite. Sodium acrylate plays an important role as the crosslinker forming a network structure of the superabsorbent composite. The composite was characterized by IR, TGA, and XRD methods. The biodegradability of these valuable novel materials was evaluated for their industrial and commercial importance. The surface morphology was compared by scanning electron microscopy (SEM) before and after biodegradation of the composite.     

Multiwalled carbon nanotube‐filled ethylene acrylic elastomer nanocomposites: Influence of ionic liquids on the mechanical,dynamic mechanical,and dielectric properties

Electrically conductive nanocomposites based on ethylene acrylic elastomer (AEM) and multiwalled carbon nanotube (MWNT) have been successfully prepared. Before mixing the MWNT is dispersed in ethanol in presence of ionic liquids such as 1‐methyl‐3‐octylimidazolium chloride (MOIC) and 1‐allyl‐3‐methyl imidazolium chloride (AMIC). Uniform dispersion of MWNT in the nanocomposites is achieved in presence of ionic liquid, which is confirmed by the high‐resolution transmission electron microscopic (HRTEM) microphotographs. The tensile strength increases up to 6 phr of MWNT loading and above that it decreases. However, the tensile strength increases due to the incorporation of ionic liquid assisted dispersed MWNT. It is observed from the dynamic mechanical analysis (DMA) that the storage modulus (E′) and glass transition temperature (T_g) of AEM matrix increase by incorporation of MWNT. The E′ also increases and the tan δ_max marginally decreases due to the incorporation of dispersed MWNT in presence of ionic liquids. The dielectric relaxation characteristic properties of AEM/MWNT nanocomposites such as dielectric permittivity (ε′), AC conductivity (σ_ac), impedance (Z^*) have been studied as a function of frequency (10¹−10⁶ Hz) in presence of ionic liquids. The ε′ and σ_ac increase with increasing the MWNT loading due to the easy orientation of dipoles and formation of interconnected conductive networks in the nanocomposites. The electromagnetic interference shielding effectiveness (EMISE) is studied in the X‐band frequency range of 8 to 12 GHz, which significantly improved with increase in MWNT loading. POLYM. COMPOS., 37:2568–2580, 2016. © 2015 Society of Plastics Engineers     

Development of ionic and non‐ionic natural gum‐based bigels: Prospects for drug delivery application

Recently, much attention has been focused on the development of gel based formulations for controlled drug delivery applications. Herein, we report the effect of the ionic (gum acacia) and the non‐ionic (guar gum) gums on the properties of the bigels prepared with fluid‐filled organogels. The microscopic study suggested the presence of flocculated structure in guar gum bigel, whereas, a de‐flocculated structure was observed in gum acacia bigel. Infrared spectroscopy suggested the presence of polysaccharides in the bigels. The mechanical properties of the guar gum bigel were better than gum acacia bigel. The conductivity and the release properties suggested superior properties of gum acacia bigel. This indicated that the ionic nature of acacia bigel played a major role in controlled drug delivery, making it a potential bigel for desired pharmaceutical applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42561.     

Microtribology and Friction-Induced Material Transfer in Layered MoS2 Nanoparticles Sprayed on a Steel Surface

Frictional performance of molybdenum disulfide (MoS₂) particles sprayed on a substrate is investigated in a ball-on-disc tribometer. The ability of large (~2 μm) and small (~50 nm) particles to generate low-friction transfer film is investigated with a view to elucidate the requirement for film formation. Particle migration, particle stability in the contact region, oxidation potential, and particle adhesion to the substrate are explored within a span of operating parametersp; normal load, and sliding velocity. It is found that the larger particles are able to migrate to the contact to raise a homogeneous but nonuniform low-friction transfer film that flows plastically to yield large contact areas, which aid in wear protection. Within the present load and speed range, the inability of small particles to stay in the contact region and undergo basal slip militates against the formation of a low-friction transfer film.     

Elemental imaging of kidneys of adult rats exposed to uranium acetate

Concern about the toxicity of depleted uranium for military use has increased recently. Renal toxicity is the hallmark effect of uranium exposure. However, the dynamics and distribution of uranium in the kidney are not well understood. Here, we determined the precise distribution of uranium and essential elements in the rat kidney using microbeam scanning particle-induced X-ray emission (micro-PIXE) and synchrotron radiation X-ray fluorescence (SR-XRF).Uranium accumulation in the rat kidney reached a maximum at 1 day after the subcutaneous (s.c.) administration of 2 mg U/kg of uranium acetate and then gradually decreased. At 3 h after administration, uranium was distributed mainly in the proximal tubules of the inner zone of the cortex and in the outer stripe of the outer medulla, and absorbed by the proximal tubule epithelium. Iron was localized more in the inside of the outer medulla than uranium, while phosphorus, potassium, sulfur and zinc were equally distributed in the cortex and the outer stripe of the outer medulla. At 3 days after administration, the number of apoptotic cells increased and cells were lost from the proximal tubules. Uranium was detectable mainly in the outer stripe of the outer medulla at 15 days, suggesting that the renal distribution of uranium is site-selective and causes site-specific renal lesions.     

CFD Analysis of Steady Laminar Natural Convection Heat Transfer from a Pin Finned Isothermal Vertical Plate

Heat transfer behavior with both the conductive and nonconductive fins have been analyzed by examining variations of the local and average Nusselt numbers in two‐dimensional flow. The main objective of this study is to quantify and compare the natural convection heat transfer enhancement of fin array with different fin aspect ratio and at different angles of inclination. It is found that significant heat transfer augmentation is obtained for both conductive and nonconductive fins. For conductive fins 20% higher augmentation factor is obtained when the fin aspect ratio is 6, angle of inclination is 60° and the pitch‐to‐length ratio is 0.2. For nonconductive fins, 10% higher augmentation factor is obtained when fin aspect ratio is 8, angle of inclination is 45° and pitch‐to‐length ratio at 0.5. A general correlation has been developed to predict the average Nusselt number and heat transfer augmentation factor for conductive and nonconductive fin arrays as a function of different fin configurations.     

Thermo‐oxidative stability of new‐generation base oils

Thermo‐oxidation of base oils is the primary cause of lubricant degradation and engine failure during use. Degradation is mainly due to high‐temperature oxidation and thermal decomposition near the piston ring zone, forming oxygenated compounds that polymerise to form high‐molecular‐weight insoluble deposits. New‐generation base oils are found to be more stable towards oxidation and deposit formation due to the absence of aromatics and polynaphthenes. However, compatibility with antioxidants and other additives is now of greater concern because of the poor solvency of these oils. With the increase in the purity of the oil, sometimes the oxidation performance is poor in comparison to group I oils, mainly due to the removal of sulphur compounds, which act as natural antioxidants. Thermal techniques, such as differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), are emerging as fast and accurate methods for determining the thermo‐oxidative stability of base oils and their additive blends, making it possible to measure the oxidation induction time, incipient oxidation temperature, and deposit‐forming tendency. The objective of this work is to evaluate the thermo‐oxidative stability of new‐generation group II/III base oils without antioxidant additives, using DSC and TGA. The kinetics of base oil oxidative degradation are studied using different heating rates. The data obtained from thermal techniques are correlated with the micro‐oxidation data obtained from the Penn State Micro‐Oxidation (PSMO) test. The response of a typical antioxidant additive, zinc dialkyldithiophosphate, towards oxidative degradation of base oils has also been studied.     

Blends of low‐density polyethylene and liquid crystalline polymer

Blends of low‐density polyethylene (LDPE) and a glass‐filled thermotropic liquid crystalline polymer (LCP‐g) have been prepared by melt mixing techniques. The thermal transitions, dynamic behavior, morphology and crystalline properties of the blends have been measured by DSC, DMTA, SEM and XRD respectively. The crystallinity decreased with increase in LCP‐g content in the blends. At higher levels of LCP‐g, crystal growth is favored in the PE phase. From DSC, it is found that the thermal stability of the blends increased with the LCP‐g content. The variation of storage modulus, loss modulus and stiffness as a function of blend ratio suggested the phase inversion at the 40–50% level of LCP‐g in the blend. SEM studies revealed that with the increase in LCP‐g content, the flow of the matrix was restricted.     

Round-to-hexagon drawing through straightly converging dies: an application of the SERR technique

The modelling of metal forming processes in recent years has brought the development of different analytical and/or numerical techniques. The SERR technique is eminently suitable for analyzing drawing/extrusion of sections having re-entrant corners. However, in its present form, it cannot be used to analyse forming processes where the deformation zone has curved boundaries, since the elementary regions will no longer remain rigid. The present study is an endeavor to remodel this technique so that it can handle round billets. The circular cross section of the round billet is approximated by a regular polygon of equal area and the number of sides of the polygon is progressively increased until convergence of the drawing stress is achieved. As a test, the drawing of hexagon section bars from round billets through the straightly converging dies is analyzed