Synthesis and characterization of some novel copolymer resins. III

In continuation of our endeavor to develop synthetic resins of improved properties and performance, we report here the synthesis of mixed copolymer resins by the condensation of resorcinol, aniline, and formaldehyde with ortho-, meta-, and para-phenylenediamine separately. The resins were characterized by infrared (IR) and thermogravimetric analysis (TGA). The mixed copolymer resins were found to have superior thermal stability over conventional phenol–CH₂O and resorcinol–CH₂O resins. The solubility behavior of the resins showed that they are resistant to common solvents. However, they are soluble in concentrated H₂SO₄ and HNO₃, but insoluble in concentrated HCl. © 1998 John Wiley & Sons, Inc. J Appl Polm Sci 68: 2183–2187, 1998     

Age-Dependent Contributions of NMDA Receptors and L-Type Calcium Channels to Long-Term Depression in the Piriform Cortex

In the hippocampus, the contributions of N-methyl-D-aspartate receptors (NMDARs) and L-type calcium channels (LTCCs) to neuronal transmission and synaptic plasticity change with aging, underlying calcium dysregulation and cognitive dysfunction. However, the relative contributions of NMDARs and LTCCs in other learning encoding structures during aging are not known. The piriform cortex (PC) plays a significant role in odor associative memories, and like the hippocampus, exhibits forms of long-term synaptic plasticity. Here, we investigated the expression and contribution of NMDARs and LTCCs in long-term depression (LTD) of the PC associational fiber pathway in three cohorts of Sprague Dawley rats: neonatal (1–2 weeks), young adult (2–3 months) and aged (20–25 months). Using a combination of slice electrophysiology, Western blotting, fluorescent immunohistochemistry and confocal imaging, we observed a shift from an NMDAR to LTCC mediation of LTD in aged rats, despite no difference in the amount of LTD expression. These changes in plasticity are related to age-dependent differential receptor expression in the PC. LTCC Cav1.2 expression relative to postsynaptic density protein 95 is increased in the associational pathway of the aged PC layer Ib. Enhanced LTCC contribution in synaptic depression in the PC may contribute to altered olfactory function and learning with aging.     

Flocculation of Textile Wastewater by Plantago psyllium Mucilage

The ability of a low cost flocculating material, Plantago psyllium mucilage, for removal of solid waste from textile effluent has been successfully investigated. Standard jar test method has been used in this study. The effects of polymer dose, contact time and pH on the %‐removal of solid waste are reported. An increase in polymer dose up to a certain level increases solid waste removal. The maximum suspended solid removal, ≈ 90%, was seen after 5 h at pH 4.0, while the maximum removal of dissolved solids, ≈ 68%, takes 3 h at pH 7.0. The optimal dosage was found to be 1.6 mg/L. X‐ray diffractograms of pure polymer and solid waste from effluent before and after treatment were obtained to suggest the interaction of the waste material with the mucilage.     

Optoelectronic properties and Seebeck coefficient in SnSe thin films

SnSe thin films of thickness 180 nm have been deposited on glass substrates by reactive evaporation at an optimized substrate temperature of 523±5 K and pressure of 10^-5 mbar. The as-prepared SnSe thin films are characterized for their structural, optical and electrical properties by various experimental techniques. The p-type conductivity, near-optimum direct band gap, high absorption coefficient and good photosensitivity of the SnSe thin film indicate its suitability for photovoltaic applications. The optical constants, loss factor, quality factor and optical conductivity of the films are evaluated. The results of Hall and thermoelectric power measurements are correlated to determine the density of states, Fermi energy and effective mass of carriers and are obtained as 2.8×10¹⁷cm^-3, 0.03 eV and 0.05 m₀ respectively. The high Seebeck coefficient≈7863 μV/K, reasonably good power factor≈7.2×10^-4 W/(m·K²) and thermoelectric figure of merit≈1.2 observed at 42 K suggests that, on further work, the prepared SnSe thin films can also be considered as a possible candidate for cryogenic thermoelectric applications.     

A simple nonlinear PD controller for integrating processes

Many industrial processes are found to be integrating in nature, for which widely used Ziegler–Nichols tuned PID controllers usually fail to provide satisfactory performance due to excessive overshoot with large settling time. Although, IMC (Internal Model Control) based PID controllers are capable to reduce the overshoot, but little improvement is found in the load disturbance response. Here, we propose an auto-tuning proportional-derivative controller (APD) where a nonlinear gain updating factor α continuously adjusts the proportional and derivative gains to achieve an overall improved performance during set point change as well as load disturbance. The value of α is obtained by a simple relation based on the instantaneous values of normalized error (e_N) and change of error (Δe_N) of the controlled variable. Performance of the proposed nonlinear PD controller (APD) is tested and compared with other PD and PID tuning rules for pure integrating plus delay (IPD) and first-order integrating plus delay (FOIPD) processes. Effectiveness of the proposed scheme is verified on a laboratory scale servo position control system.     

An improved auto-tuning scheme for PID controllers

An improved auto-tuning scheme is proposed for Ziegler–Nichols (ZN) tuned PID controllers (ZNPIDs), which usually provide excessively large overshoots, not tolerable in most of the situations, for high-order and nonlinear processes. To overcome this limitation ZNPIDs are upgraded by some easily interpretable heuristic rules through an online gain modifying factor defined on the instantaneous process states. This study is an extension of our earlier work [Mudi RK., Dey C. Lee TT. An improved auto-tuning scheme for PI controllers. ISA Trans 2008; 47: 45–52] to ZNPIDs, thereby making the scheme suitable for a wide range of processes and more generalized too. The proposed augmented ZNPID (AZNPID) is tested on various high-order linear and nonlinear dead-time processes with improved performance over ZNPID, refined ZNPID (RZNPID), and other schemes reported in the literature. Stability issues are addressed for linear processes. Robust performance of AZNPID is observed while changing its tunable parameters as well as the process dead-time. The proposed scheme is also implemented on a real time servo-based position control system.     

Graft copolymerization with new class of acidic peroxo salts as initiators. I. Grafting of acrylamide onto cotton–cellulose using potassium monopersulfate,catalyzed by co(II)

Graft copolymerization of acrylamide (AM) onto cotton–cellulose has been studied using a new class of acidic peroxo-salt “potassium monopersulfate” as initiator catalyzed by Co(II). It is observed that the graft yield is influenced by the reaction time, temperature, and concentrations of the monomer, catalyst, initiator, at fixed weight of the polymer. Maximum graft yield (30.8%) is obtained at 40°C under nitrogen atmosphere for the concentrations of monomer 1.2M; initiator 4.83 × 10^?3M; Co(II) 5 × 10^?4M for 4 h of reaction time. The graft copolymers after proper purification have been subjected to IR analysis, testing of their water-retention properties, rot resistance, tensile properties, and behavior towards acids and alkalies. The results of such analysis are compared with the base. Suitable mechanism for the graft copolymerization is suggested and grafting rate has been evaluated.     

Study on Flocculation Efficiency of Okra Gum in Sewage Waste Water

Okra gum, a polysaccharide consisting of D ‐galactose, L ‐rhamnose and L ‐galacturonic acid is used as food additive. In the present investigation, the flocculation efficiency of okra gum for the treatment of sewage waste water is tested. The flocculation study has been done by standard jar test method. The effect of polymer dose, contact time and pH on the per cent removal of solid waste is reported. Okra gum is found to be very effective and to be comparable with commercial flocculants. X‐ray analysis of the flocs is also reported to support the interaction of sewage waste with the gum.     

Failure Analysis of Cast Iron Trunk Main in Cleveland, Ohio

This article describes the failure analyses of a 30??-diameter cast iron main that failed suddenly at the bell?Cspigot joint in Cleveland, Ohio in March 2008. The main had been operating largely without problems since its installation in 1880. The failure was analyzed using three models developed previously, each of which considered a specific failure mechanism candidate, namely (a) operational load or static analysis, (b) joint failure due to ground movement (settlement), and (c) fatigue failure. Operational load analysis clearly showed that while the factor of safety was significantly reduced in the presence of a concrete vault installed in 2002 just above the pipe, the margin of safety was still sufficient for the main to have performed safely. Ground movement analysis of the jointed pipe showed that the construction of the concrete vault above the joint of the 30??-cast iron main subjected the joint to rotation, which might have ultimately cracked the bell leading to failure. Under this circumstance, two failure scenarios are possible: namely, (a) additional rotation was large enough to cause the bell to split, or (b) additional rotation was sufficient to induce a minor crack in the bell but fatigue (repeated) loading caused the crack to grow over time until the combination of crack length and loading was sufficient to cause the bell to eventually split. The color differences along the fracture surfaces indicated that the fracture occurred in two distinct stages. This observation suggests that the second scenario is more plausible than the first.