Experimental verification of pH localization mechanism of particle consolidation at the electrode/solution interface and its application to pulsed DC electrophoretic deposition (EPD)

Experimental measurement and verification of the pH localization at the electrode/solution interface was conducted during continuous and pulsed DC electrophoretic deposition (EPD) from aqueous solution. Application of pulsed DC enabled controlling bubble incorporation and obtaining bubble-free deposits during electrophoretic deposition (EPD) from aqueous suspension. The pH localization at the electrode/solution interface on application of electric field was attributed as the underlying mechanism of particle consolidation during continuous as well as pulsed EPD. The suspension pH tends to shift towards isoelectric point (i.e.p.) leading to spontaneous coagulation of particles at the electrode. Application of continuous DC tends to attain the i.e.p. faster and closer compared to pulse DC leading to maximum deposit yield. The kinetics and closeness of attainment of pH towards i.e.p. decreased progressively with decreasing pulse size resulting in a corresponding decrease in deposit yield.     

Electrophoretic deposition of doped ceria in anti-gravity set-up

An innovative anti-gravity set-up has been designed and fabricated to consolidate doped ceria powder by electrophoretic deposition. In this set-up, the charged ceramic powders dispersed in non-aqueous suspension moved upward in opposite direction to gravity under the influence of an external applied field and were consequently deposited on the lower face of upper electrode placed horizontally parallel above the counter electrode. Electrophoretic deposition using this innovative technique was found more superior to the conventional electrophoretic deposition using vertically arranged electrodes where a very broad particle size range was used. The deposit thus obtained predominantly contained finer particles which can move relatively easily against gravity. It enabled formation of homogeneous compact films. This paper presents the results of detailed investigation on the effect of different process parameters such as concentration of particles, duration, addition of charge modifier etc. on forming a deposit. A comparison of deposition yield in anti-gravity set-up vis-à-vis conventional set-up is also presented.     

A Novel Method Based on Capillary Suction Time (CST) for Assessment of Dispersion Characteristics of Suspensions

This paper presents the applicability of a simple and novel technique based on capillary suction time (CST) to characterize the dispersibility of suspension. The method is simple, rapid, and requires little experience. It has been shown to be extremely useful for comparing the dispersibility during preparation of a stable suspension of ceramic powder with high solids loading. The method has also been found to be suitable for obtaining homogeneous suspensions of maximum stability. The dispersibility of particles in any suspension has been assessed with respect to the condition at point of zero charge (pH_pzc). A quantitative measure of the dispersibility has been proposed in term of a dispersion ratio (DR). According to this proposition, the suspension is in a state of dispersion when the value of DR is more than unity, whereas it is in a flocculated state when the value of DR is less than unity.     

Visual–Motor Coordination Using a Quantum Clustering Based Neural Control Scheme

Visual–Motor Coordination is a problem considered analogous to the hand-eye coordination in biological systems. In this work we propose a novel approach to this problem using Quantum Clustering and an extended Kohonen's Self-Organizing Feature Map (K-SOFM). This facilities the use of the method in varying workspaces by considering the joint angles of the robot arm. Unlike previous work, where a fixed topology for the input space is considered, the proposed approach determines a topology as the workspace varies. Quantum Clustering is a method which constructs a scale-space probability function and uses the Schroedinger equation and its lowest eigenstate to obtain a potential whose minimum gives the cluster centers. It transforms the input space into a Hilbert space, where it searches for its minimum. The motivation of this work is to identify the implicit relationship existing between the end-effector positions and the joint angles through Quantum Clustering and Neural Network methods to fine-tune the system to correctly identify the mapping.     

Electrophoretic deposition of alumina on stainless steel from non-aqueous suspension

Electrophoretic deposition of alumina on stainless steel has been investigated. The influence of different organic media and deposition parameters such as solid concentration, applied voltage and time of deposition on deposit yield has been evaluated. Maximum deposit yield was obtained for solvent media that imparts highest magnitude of surface charge on alumina in suspension. The deposit yield increased linearly with concentration of alumina powder in suspension, and applied voltage following Hamakers law. A similar linearity in yield was observed at short deposition times, but a deviation in linearity was observed at higher time of deposition, which is attributed to the shielding effect of the deposited layers and accumulation of ions at the electrode, and depletion of powder in the suspension with progress in deposition.     

Organocatalytic Highly Enantioselective Synthesis of β‐Formyl‐α‐hydroxyphosphonates

The cross‐aldol reaction between enolizable aldehydes and α‐ketophosphonates was achieved for the first time by using 9‐amino‐9‐deoxy‐epi‐quinine as the catalyst. β‐Formyl‐α‐hydroxyphosphonates were obtained in high to excellent enantioselectivities. The reaction works especially well with acetaldehyde, which is a tough substrate for organocatalyzed cross‐aldol reactions. The products were demonstrated to have anticancer activities.     

Variable-gain controllers for nonlinear systems using the T-S fuzzy model.

This correspondence proposes two novel control schemes with variable state-feedback gain to stabilize a Takagi-Sugeno (T-S) fuzzy system. The T-S fuzzy model is expressed as a linear plant with nonlinear disturbance terms in both schemes. In controller I, the T-S fuzzy model is expressed as a linear plant around a nominal plant arbitrarily selected from the set of linear subsystems that the T-S fuzzy model consists of. The variable gain then becomes a function of a gain parameter that is computed to neutralize the effect of disturbance term, which is, in essence, the deviation of the actual system dynamics from the nominal plant as the system traverses a specific trajectory. This controller is shown to stabilize the T-S fuzzy model. In controller II, individual linear subsystems are locally stabilized. Fuzzy blending of individual control actions is shown to make the T-S fuzzy system Lyapunov stable. Although applicability of both control schemes depends on the norm bound of unmatched state disturbance, this constraint is relaxed further in controller II. The efficacy of controllers I and II has been tested on two nonlinear systems.     

A Novel Multi-agent Formation Control Law With Collision Avoidance

In this paper a stable formation control law that simultaneously ensures collision avoidance has been proposed. It is assumed that the communication graph is undirected and connected. The proposed formation control law is a combination of the consensus term and the collision avoidance term (CAT). The first order consensus term is derived for the proposed model, while ensuring the Lyapunov stability. The consensus term creates and maintains the desired formation shape, while the CAT avoids the collision. During the collision avoidance, the potential function based CAT makes the agents repel from each other. This unrestricted repelling magnitude cannot ensure the graph connectivity at the time of collision avoidance. Hence we have proposed a formation control law, which ensures this connectivity even during the collision avoidance. This is achieved by the proposed novel adaptive potential function. The potential function adapts itself, with the online tuning of the critical variable associated with it. The tuning has been done based on the lower bound of the critical variable, which is derived from the proposed connectivity property. The efficacy of the proposed scheme has been validated using simulations done based on formations of six and thirty-two agents respectively.