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.     

Perspective: Arnheim and In-Between Solutions.

Arnheim wrote extensively about perspective and percepts that were "in between" correct perception of objects and projected shapes. We apply Arnheim's views to a Renaissance piazza of square tiles. We show the kind of formalization to which the analysis leads and give a formula applicable to a perspective picture as an example. We argue that Arnheim was answering the Gestalt phenomenological question "why the world looks as it does" with comments that, happily, are also a solution to the Realist question "how perception lets us know about the world." Like Renaissance writers, Arnheim recognized that perspective had strict limits. Both the Gestalt and the Realist perception theories give accounts of the effects of perspective and both argue perspective constancy is widespread in perception, but Arnheim is correct that it operates within strict limits. We conclude that perception uses an approximation to perspective. The approximation is close under many circumstances but it produces what Arnheim called "in-between" percepts (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

From informing to remembering: ubiquitous systems in interactive museums

Museums are excellent locations for testing ubiquitous systems; the Exploratorium in San Francisco offers a unique and challenging environment for just such a system. An important design consideration is how users switch between virtual and physical interactions.     

High molecular weight waxes from Short Path Distillates of vacuum residue

Short Path Distillates of vacuum residue (boiling above 545 °C) is taken as feedstock for this study. Wax from this fraction is separated by solvent extraction method using methyl iso-butyl ketone (MIBK) as solvent. Both wax and the feedstock are characterised with the help of ASTM and IP procedures. Separated wax is fractionated at different temperatures, say 0–30 °C using MIBK as solvent. High temperature gas chromatography (HTGC) technique is used to study the distribution of alkane carbon number in all the fractions. It is observed that the wax contains very high molecular weight hydrocarbons as high as C₆₇H₁₃₆. HTGC technique as well as the Differential Scanning Calorimetry (DSC) indicates that all the fractions of the wax contain two types of hydrocarbons, one having high molecular weight alkanes (> 600) and another having low mol. wt. alkanes (~ 400). Thermal analysis by DSC technique further indicates that the wax is microcrystalline in nature having a low degree of crystallinity, 17%, as evidenced by XRD studies. Both high and low molecular weight waxes can also be separated based on their solubility characteristics.     

On critical criteria for shifting towards plastic strain localization during explosive cladding of Inconel 625 on low-carbon steel

The present study aims at detecting the critical criteria and corresponding critical impact energy for initiation of strain localization during explosive cladding of the Inconel 625 superalloy as a cladding material and low-carbon steel as a substrate. The results do not reveal adiabatic shear bands, which are the main signs of strain localization, within the superalloy in all studied impact energies up to 205 kJ. At impact energies greater than 78–114 kJ, strain localization is observed in low-carbon steel, and microcracks develop within the adiabatic shear bands. The Johnson-Cook model is used to explains the results obtained and to study the thermomechanical behavior of materials.     

Preparation and microwave characterization of PTFE/PEEK blends

Present paper describes the preparation and characterization of the PTFE / PEEK blends. The surface morphology of different volume percentage of PTFE/PEEK blends is investigated using Scanning Electron Microscopy. The permittivity and loss tangent of the blends up to 40 MHz are studied using a Precision Impedance Analyzer. The variation of permittivity with respect to temperature (τ_εr) of the composite blends are also measured in the 0–100°C temperature region using a microprocessor controlled hot and cold chamber. The microwave dielectric properties of the polymer blends are studied in the X‐band (8.2–12.4 GHz) region by waveguide cavity perturbation technique using a Vector Network Analyzer. Rectangular cavity resonator is used to measure the complex permittivity of the PTFE/PEEK blends. Different modeling approaches are used to predict the theoretical permittivity of the blends and the results are compared with the experimental values. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Capillary and venous blood estrogen in pregnancy

Total estrogens in the third trimester of pregnancy were measured in matched samples of venous and capillary blood serum. A close correlation was observed between capillary blood estrogens (CBE) and venous blood estrogens (VBE). After establishing norms for CBE during the third trimester of normal pregnancy, the parameter was assessed for its use in high-risk pregnancy in comparison with VBE. In 96.6% of the 59 high-risk pregnancy cases studied, the conclusions drawn about the fetoplacental unit on the basis of CBE and VBE were similar.     

Multicomponent Petasis‐borono Mannich Preparation of Alkylaminophenols and Antimicrobial Activity Studies

In this work we report the antibacterial activity of alkylaminophenols. A series of such compounds was prepared by a multicomponent Petasis‐borono Mannich reaction starting from salicylaldehyde and its derivatives. The obtained compounds were tested against a large panel of microorganisms, Gram‐positive and Gram‐negative bacteria, and a yeast. Among the several tertiary amine derivatives tested, indoline‐derived aminophenols containing a nitro group at the para‐phenol position showed considerable activity against bacteria tested with minimal inhibitory concentrations as low as 1.36 μm against Staphyloccocus aureus and Mycobacterium smegmatis. Cytotoxicity of the new para‐nitrophenol derivatives was observed only at concentrations much higher than those required for antibacterial activity.