A parallel approach of the inverse kinematics solutions for robots using a transputer network

This article presents a parallel method for computing inverse kinematics solutions for robots with closed-form solutions moving along a straight line trajectory specified in Cartesian space. Zhang and Paul's approach¹ is improved for accuracy and speed. Instead of using previous joint positions as proposed by Zhang and Paul, a first order prediction strategy is used to decouple the dependency between joint positions, and a zero order approximation solution is computed. A compensation scheme using Taylor series expansion is applied to obtain the trajectory gradient in joint space to replace the correction scheme proposed by Zhang and Paul. The configuration of a Mitsubishi RV-M1 robot is used for the simulation of a closed-form inverse kinematics solutions. An Alta SuperLink/XL with four transputer nodes is used for parallel implementation. The simulation results show a significant improvement in displacement tracking errors and joint configuration errors along the straight line trajectory. The computational latency is reduced as well. The modified approach proposed in this work is more accurate and faster than Zhang and Paul's approach for robots with closed-form inverse kinematics solutions. © 1996 John Wiley & Sons, Inc.     

Orientation of graphitic planes during annealing of “dip deposited” amorphous carbon film: A carbon K-edge X-ray absorption near-edge study

Annealing effect of amorphous carbon thin films on Si(1 0 0) substrates is studied by normal incidence and angle dependent carbon K-edge X-ray absorption near-edge structure (XANES) spectroscopy. The angle dependence of the XANES signal shows that the graphitic basal planes are oriented perpendicular to the surface when the film is annealed at 1000 °C. Micro-Raman spectroscopy reveals two well-separated bands the D band at 1355 cm⁻¹ and G band at ∼1600 cm⁻¹, and their I_D/I_G intensity ratio indicates the formation of more graphitic film at higher annealing temperatures. X-ray diffraction pattern of 1000 °C temperature annealed film confirms the formation of graphite structure.     

Kinetics and mechanism of iodide-film growth on lead-effect of short-circuiting and higher-valent dopant

The effect of a higher-valent dopant like Sb on the iodination rate of lead under normal and short-circuit conditions in iodine pressure of 0.615–6.578 kPa and in the temperature range of 423–523 K has been investigated. Like pure Pb, Sb-doped Pb also follows the parabolic law of film growth. The isothermal parabolic rate constants are found to be enhanced due to the presence of Sb. The iodine-vapor-pressure dependence of the isothermal parabolic rate constant has been observed to be k_ppI ₂ ^1/2 . This has been explained on the consideration of electron-hole migration across the film as the rate-limiting step. The activation energy for iodination of Sb-doped Pb under normal condition is estimated to be 64 kJ · mol^–1 in an iodine pressure of 0.615 kPa. The rate of iodide-film growth has been found to increase considerably under a short-circuit mode of experiments. Such observations have been explained with the concept of ion migration as the rate-limiting step for the film-growth process. The iodine pressure dependence of rate constants under short-circuit conditions is observed to be k_pI ₂ ^1/3 , associated with an activation energy value of 51 kJ mol^–1. The effect of putting additional resistances in series to the short-circuit Pt path during iodination of Sb-doped Pb is found to be similar to that observed for pure Pb. Results of the present study have been explained considering the prevalence of Schottky-Wagner type of point defects in the lead-iodide film. Wagner's electrochemical potential gradient has been confirmed to be the main driving force for the film-growth process. Iodide films have been characterized by SEM, EDS, EPMA, XRD, and AES analyses to substantiate the kinetics results.     

My words for your pizza: An analysis of persuasive narratives in online crowdfunding

We analyze charity requests registered on the Random Acts of Pizza online community and examine the content of postings and non-content characteristics to identify features that are associated with the success of donation. We find that the presence of rational and credible appeals in a message increases the likelihood of receiving a donation, whereas the mere presence of negative emotional appeal does not do so. Our research is useful for those who like to make persuasive charity requests on online platforms.     

Control and Simulation of a Current-Fed Linear Inductor Machine

A self-controlled, current-fed inverter excited linear inductor machine is described, in which the field current and inverter switching angles are programmed such that the machine operates at constant air-gap flux and unity displacement factor under all operating conditions. The machine can operate in wide speed range and constant predetermined torque is developed during both motoring and regeneration. The control incorporates overlap angle compensation for the inverter and permits modulation of inverter firing angle with resolution of a fraction of a degree. The dynamic d-q axis model of the machine with the power converters and the proposed control strategy has been simulated on a hybrid computer, and static and dynamic performance have been studied in detail. The control circuit has been designed and tested with a 112-kW prototype inductor machine. The experimental results give good agreement with the theory and with simulation.     

Silicone Rubber Compatibilized Syndiotactic Polystyrene and Thermotropic Liquid Crystalline Polymer (Vectra A950) Blend

Blends of syndiotactic polystyrene (s-PS), thermotropic liquid crystalline polymer (Vectra A-950), and silicone rubber with two different loading levels, have been prepared through melt processing in internal mixer at 285°C. Silicone rubber was used as a compatibilizer for this blend system. The effect of silicon rubber on crystalline, dynamic mechanical, rhelogical, thermal properties, and phase morphology of the (s-PS/TLCP) blend has been investigated in details. With the addition of compatibilizer the viscosity of the blend system increased to an order of magnitude. Dynamic mechanical analysis (DMTA) and differential scanning calorimetry (DSC) results showed that the glass transition temperature (T_g) of the blend, in presence of silicone rubber, shifted towards lower temperature region. From FTIR analysis it is evident that the ‘C=O’ stretching frequency has shifted towards lower side. SEM analysis suggested that, the TLCP domain size is reduced in ternary blend in comparison to binary blend system.     

Host-Assisted Delivery of a Model Drug to Genomic DNA: Key Information from Ultrafast Spectroscopy and in silico Study

Drug delivery to a target without adverse effects is one of the major criteria for clinical use. Herein, we have made an attempt to explore the delivery efficacy of SDS surfactant in a monomer and micellar stage during the delivery of the model drug, Toluidine Blue (TB) from the micellar cavity to DNA. Molecular recognition of pre-micellar SDS encapsulated TB with DNA occurs at a rate constant of k₁ ∼652 s⁻¹. However, no significant release of encapsulated TB at micellar concentration was observed within the experimental time frame. This originated from the higher binding affinity of TB towards the nano-cavity of SDS at micellar concentration which does not allow the delivery of TB from the nano-cavity of SDS micelles to DNA. Thus, molecular recognition controls the extent of DNA recognition by TB which in turn modulates the rate of delivery of TB from SDS in a concentration-dependent manner.     

Half-of-the-sites reactivity of F235C {lambda}-repressor: implications for the structure of the whole repressor

A site-directed mutation, F235C, was created at the penultimateresidue of the -repressor. Measurement of dimer–monomerdissociation constant suggested that dimer–monomer dissociationof the mutant repressor is similar to that of the wild-type.Affinity towards a single operator O_R1 is also similar to thatof the wild-type repressor. The mutant repressor gene in a multi-copyplasmid confers immunity towards infection by a cI^- lambda phage,suggesting preservation of functional integrity. Far-UV circulardichroism spectra show no major change in the secondary structure.Fluorescence quenching experiments, however, suggest increasedexposure of some tryptophan residues. The urea denaturationprofile indicates decreased stability of a part of the C-terminaldomain. Under non-denaturing conditions, cysteine-235 showshalf-of-the-sites reactivity, i.e. on average only one out oftwo cysteine-235 residues in the dimer shows reactivity towardssulfhydryl reagents. Fluorescence energy transfer between randomlylabeled donor and acceptor fluorescent probes indicates thatonly one sulfhydryl per dimer is reactive, suggesting true half-of-the-sitesreactivity. The structural role of the C-terminal tail in thewhole repressor dimer is discussed.     

Silicate-based polymer-nanocomposite membranes for polymer electrolyte membrane fuel cells

Proton-exchange membrane fuel cells have emerged as a promising emission free technology to fulfill the existing power requirements of the 21st century. Nafion^® is the most widely accepted and commercialized membrane to date and possesses excellent electrochemical properties below 80 °C, under highly humidified conditions. However, a decrease in the proton conductivity of Nafion^® above 80 °C and lower humidity along with high membrane cost has prompted the development of new membranes and techniques. Addition of inorganic fillers, especially silicate-based nanomaterials, to the polymer membrane was utilized to partially overcome the aforementioned limitations. This is because of the lower cost, easy availability, high hydrophilicity and higher thermal stability of the inorganic silicates. Addition of silicates to the polymer membrane has also improved the mechanical, thermal and barrier properties, along with water uptake of the composite membranes, resulting in superior performance at higher temperature compared to that of the virgin membrane. However, the degrees of dispersion and interaction between the organic polymer and inorganic silicates play vital roles in improving the key properties of the membranes. Hence, different techniques and solvent media were used to improve the degrees of nanofiller dispersion and the physico-chemical properties of the membranes. This review focuses mainly on the techniques of silicate-based nanocomposite fabrication and the resulting impact on the membrane properties.     

Influence of a mixed Al2O3+Cr2O3 superficial coating on the non-isothermal oxidation behavior of Fe and Fe-Cr alloys

The non-isothermal oxidation behavior of electrolytic-grade iron and Fe-Cr alloys in dry air has been studied using linear heating rates of 6 K/min, 10 K/ min, and 15 K/min up to a final temperature of 1273–1473 K. Some of the iron and iron-chromium alloy samples were given a surface treatment by dipping them in an aqueous solution containing both Cr and Al ions before their oxidation studies. This pretreatment has resulted in improved oxidation resistance and scale adherence as depicted by no scale rupture even after a second thermal cycle. Mass changes were recorded gravimetrically, and scales have been characterized by SEM, EPMA, and x-ray diffraction analyses.