Microprocessor-Based Speed Control System for High-Accuracy Drives

A digital speed control system for a dc motor with a pulse tachogenerator for speed sensing is described. A microprocessor is used for fast speed measurement with a response time constant of the order of 8 ms and a resolution of 0.0125 percent of the top speed. This has become possible because of the principle of obtaining the latest speed value based on the previous speed value. This paper describes the principle of speed measurement and control, the flowchart, and the experimental results. A closed-loop speed holding accuracy of ±0.025 percent of the top speed is obtained.     

Bioavailability of Heavy Metals in Soil: Impact on Microbial Biodegradation of Organic Compounds and Possible Improvement Strategies

Co-contamination of the environment with toxic chlorinated organic and heavy metal pollutants is one of the major problems facing industrialized nations today. Heavy metals may inhibit biodegradation of chlorinated organics by interacting with enzymes directly involved in biodegradation or those involved in general metabolism. Predictions of metal toxicity effects on organic pollutant biodegradation in co-contaminated soil and water environments is difficult since heavy metals may be present in a variety of chemical and physical forms. Recent advances in bioremediation of co-contaminated environments have focussed on the use of metal-resistant bacteria (cell and gene bioaugmentation), treatment amendments, clay minerals and chelating agents to reduce bioavailable heavy metal concentrations. Phytoremediation has also shown promise as an emerging alternative clean-up technology for co-contaminated environments. However, despite various investigations, in both aerobic and anaerobic systems, demonstrating that metal toxicity hampers the biodegradation of the organic component, a paucity of information exists in this area of research. Therefore, in this review, we discuss the problems associated with the degradation of chlorinated organics in co-contaminated environments, owing to metal toxicity and shed light on possible improvement strategies for effective bioremediation of sites co-contaminated with chlorinated organic compounds and heavy metals.     

Performance and emission characteristics of a diesel engine using Calophyllum Inophyllum biodiesel blends with TiO2 nanoadditives and EGR

An experimental investigation was carried out to evaluate the performance and emission characteristics of a single cylinder diesel engine by using Calophyllum Inophyllum biodiesel blends with TiO₂ nano additives and exhaust gas recirculation (EGR). The Calophyllum Inophyllum biodiesel-diesel blend was prepared by mixing 20% of Calophyllum Inophyllum biodiesel with 80% diesel (B20) in volumetric approach. The TiO₂ nanoparticles were dispersed into a B20 fuel with a dosage of 40?ppm to prepare the B2040TiO₂ fuel sample. The tests were conducted on a diesel engine by using B20, B2040TiO₂, B20?+?20%EGR, B2040TiO₂?+?20% EGR fuel samples at different load conditions. The brake thermal efficiency of B2040TiO₂, B2040 TiO₂?+?20%EGR fuels increased by 3.1%, 2.5%, and decreased by 1.8% for B20?+?20%EGR fuel compared to the B20 fuel at full load condition. The CO and HC emissions were reduced with the addition of TiO₂ nano particles to the B20 fuel and increased with the EGR method compared to the B20 fuel. The smoke emissions were increased by 16.23% and 12% for the B20?+?20%EGR and B2040TiO₂?+?20%EGR fuel samples compared to the B20 fuel at full load condition. The NOx emissions were reduced with the EGR technique and increased with the addition of TiO₂ nanoparticles to the biodiesel blend compared to the B20 fuel. It is concluded that Calophyllum Inophyllum biodiesel blend (B20) with the addition of TiO₂ nano particles and EGR technique exhibits better engine performance and reduced emissions compared to the other fuels.     

Paal–Knorr synthesis of pyrroles: from conventional to green synthesis

The pyrrole molecular framework is found in a large number of natural and synthetic compounds of great importance. Since functionalized pyrroles are essential for the progress of many branches of science, its synthesis by simple, efficient and eco-friendly routes are particularly attractive in modern organic and bio-organic chemistry. To this end, a number of synthetic methods have been developed, in which the Paal–Knorr pyrrole synthesis stands out to be the easiest route to synthesize pyrroles. In spite of the efficiency, Paal–Knorr synthesis of pyrroles is considered limited by harsh reaction conditions, such as prolonged heating in acid, which may degrade sensitive functionalities in many potential precursors. Through this route almost all dicarbonyls can be converted to their corresponding heterocycles and therefore it is a synthetically valued process. To address the adverse issues this reaction route has undergone numerous modifications recently and today it can be said that this reaction route is a prominent green route for the synthesis of pyrroles. This review is a tour from the evolution and application of this harsh synthetic route to the eco-friendly greener route developed for the synthesis of pyrroles.     

Dislocation creep in particle-strengthened systems

A model for climb-controlled creep in two-phase materials is proposed which invokes the presence of a back-stress for providing the necessary mobile dislocations for creep. It is shown that by incorporating this stress in the creep equation it is possible to reduce both the activation energy for creep and the stress exponents to values normally observed in single-phase materials. Creep data on TD nickel and yttriated superalloy when analysed on this basis confirm the applicability of this model.     

Preconditioned Krylov solvers for BEA

The performance of a number of preconditioned Krylov methods is analysed for a large variety of boundary element formulations. Low- and high-order element, two-dimensional (2-D) and three-dimensional 3-D, regular, singular and hypersingular, collocation and symmetric Galerkin, single- and multi-zone, thermal and elastic, continuous and discontinuous boundary formulations with and without condensation are considered. Preconditioned Conjugate Gradient (CG) solvers in standard form and a form effectively operating on the normal equations (CGN), Generalized Minimal Residual (GMRES), Conjugate Gradient Squared (CGS) and Stabilized Bi-conjugate Gradient (Bi-CGSTAB) Krylov solvers are employed in this study. Both the primitive and preconditioned matrix operators are depicted graphically to illustrate the relative amenability of the alternative formulations to solution via Kryiov methods, and to contrast and explain their computational performances. A notable difference between 2-D and 3-D BEA operators is readily visualized in this manner. Numerical examples are presented and the relative conditioning of the various discrete BEA operators is reflected in the performance of the Krylov equation solvers. A preconditioning scheme which was found to be uncompetitive in the collocation BEA context is shown to make iterative solution of symmetric Galerkin BEA problems more economical than employing direct solution techniques. We conclude that the preconditioned Krylov techniques are competitive with or superior to direct methods in a wide range of boundary formulated problems, and that their performance can be partially correlated with certain problem characteristics.     

Controlled Electrodeposition of Gold on Graphene: Maximization of the Defect‐Enhanced Raman Scattering Response

A reliable method to prepare a surface‐enhanced Raman scattering (SERS) active substrate is developed herein, by electrodeposition of gold nanoparticles (Au NPs) on defect‐engineered, large area chemical vapour deposition graphene (GR). A plasma treatment strategy is used in order to engineer the structural defects on the basal plane of large area single‐layer graphene. This defect‐engineered Au functionalized GR, offers reproducible SERS signals over the large area GR surface. The Raman data, along with X‐ray photoelectron spectroscopy and analysis of the water contact angle are used to rationalize the functionalization of the graphene layer. It is found that Au NPs functionalization of the “defect‐engineered” graphene substrates permits detection of concentrations as low as 10^?16 m for the probe molecule Rhodamine B, which offers an outstanding molecular sensing ability. Interestingly, a Raman signal enhancement of up to ≈10⁸ is achieved. Moreover, it is observed that GR effectively quenches the fluorescence background from the Au NPs and molecules due to the strong resonance energy transfer between Au NPs and GR. The results presented offer significant direction for the design and fabrication of ultra‐sensitive SERS platforms, and also open up possibilities for novel applications of defect engineered graphene in biosensors, catalysis, and optoelectronic devices.