Kinetics and reaction mechanism of template polymerization investigated by conductimetric measurements. Part 1. Radical polymerization of sodium acrylate

The radical homopolymerization of sodium acrylate in water in the presence of potassium peroxodisulphate as initiator was investigator through the use of conductimetry and dilatometry. The kinetics were monitored while varying either the monomer concentration or temperature. Initial rate and order of reaction were determined with good accuracy in a comparative way. The conductimetric method proved superior in monitoring the reaction progress at temperatures higher than 50°C, allowing the activation energy of the reaction to be determined. © 1999 Society of Chemical Industry     

Kinetics and reaction mechanism of template polymerization investigated by conductimetric measurements. 2. Radical polymerization of sodium methacrylate in the presence of poly(allylamine) hydrochloride

The polymerization of sodium methacrylate in water was investigated using conductimetry and dilatometry. Conductimetry was shown to be a reliable tool for the determination of the kinetic parameters of the blank polymerization (order of reaction with respect to monomer and initiator, activation energy). The conductimetric investigation of template polymerization of the acrylic monomer onto poly(allylamine) hydrochloride at low monomer concentration indicates that the reaction proceeds by a ‘zip’ mechanism. © 1999 Society of Chemical Industry     

Output feedback control for attitude tracking

In this paper the problem of attitude tracking control for a rigid spacecraft is addressed. It is assumed that only attitude measurements are available, and thus spacecraft's angular velocity has to be properly estimated. Two alternative schemes are proposed in which the unit quaternion is adopted to represent the orientation. In the first scheme, a second-order model-based observer is adopted to estimate the angular velocity used in the control law. In the second scheme, an estimate of the angular velocity error is obtained through a lead filter. Sufficient conditions ensuring local exponential stability of the two controllers are derived via Lyapunov analysis.     

A survey of robot interaction control schemes with experimentalcomparison

A great many control schemes for a robot manipulator interacting with the environment have been developed in the literature. This paper is aimed at presenting a survey of robot interaction control schemes for a manipulator, the end effector of which comes in contact with a compliant surface. A salient feature of the work is the implementation of the schemes on an industrial robot with open control architecture equipped with a wrist force sensor. Two classes of control strategies are considered, namely, those based on static model-based compensation and those based on dynamic model-based compensation. The former provide a good steady-state behavior, while the latter enhance the behavior during the transient. The performance of the various schemes is compared in the light of disturbance rejection, and a thorough analysis is developed by means of a number of case studies     

THE ROLE OF EULER PARAMETERS IN ROBOT CONTROL

Euler parameters constitute a well-known nonminimal singularity-free representation of rigid body orientation. This paper is aimed at illustrating the role of Euler parameters in robot control; namely, the kinematic control, dynamic control and impedance control problems are surveyed in a unifying perspective, where robot's end-effector orientation displacements are described in terms of Euler parameters. The advantages over the Euler angles typically used in the operational space framework are demonstrated.     

A torsion–effusion study on the sublimation of Cu2Te

The sublimation of Cu₂Te was studied and its vapor pressure was measured by the torsion method. In the covered temperature range, the temperature dependence of the total vapor pressure can be expressed by the following equation: log p (kPa)=(6.17±0.20)−(11 680±300)(K/T) (1084–1234 K). The sublimation process of Cu₂Te is incongruent, and Te(g) and Te₂(g) being the only gaseous species present in the vapor, the partial sublimation reactions were studied: Cu₂Te(s)→2Cu(s)+Te(g), 2Cu₂Te(s)→4Cu(s)+Te₂(g). The standard sublimation enthalpies of these reactions, Δ_rH⁰(298)=254±10 and 248±8 kJ, respectively, were derived by the second- and third-law treatment of the pressure data. The heat of formation of Cu₂Te, Δ_fH⁰(298)=−43±6 kJmol⁻¹, was also derived.     

A square ring on square ring (SoS) ceramic strength testing technique for VLSI packaging

This paper describes a square ring on square ring (SoS) strength testing technique for reliability evaluation of ceramic pin grid array (PGA) packages. The unique features of this new technique are that the residual stresses are included in the strength results and that the package does not have to be cut, ground, or modified in any way to test the strength. The testing procedure is simple: after the fixture is calibrated for coplanarity, the package is placed in the SoS apparatus and force is applied until the ceramic fails. The ultimate force to failure is then converted into ceramic strength by using Finite Element Modeling (FEM). This paper also discusses failure analysis of ceramic packages that have been tested to failure with the SoS technique, ceramic strength and statistics, and verification of FEM models. The SoS apparatus consists of cantilevered beams and the free end of the beams come into contact with the edge of the package; therefore, the fixture conforms to the contour of the package during testing. This strength testing technique is currently being used to monitor the changes in strength and Weibull slope of PGAs. It is also being used for reliability evaluation of the heat sink side and cavity side of PGAs as received from suppliers and during the various stages of assembly/environmental processes.     

An X.25-compatible protocol for packet voice communications

Developments in packet-switched networks have generated interest in how to integrate voice and data traffic in such networks. The paper deals with a proposed communications protocol for voice transmission within X.25 packet-switched networks. Basic protocol procedures for handling voice communications are examined, and possible formats for the identified types of voice frame and packet fitting for current CCITT standards governing packet data communications are presented.     

Selection and Use of Phytate-Degrading LAB to Improve Cereal-Based Products by Mineral Solubilization During Dough Fermentation

ABSTRACT:  New producers of phytate-degrading enzymes, especially lactic acid bacteria (LAB), were used to improve mineral solubilization during dough fermentation. In all, among strains from different sources by microorganisms (150 lactic acid bacteria, 36 yeasts), 38 (24%) exhibited a clear zone around the colonies by hydrolyzing hexacalcium phytate contained in solid medium. When phytase-positive strains from plate assay were tested for phytase activity in liquid medium, 6 of the strains (37%) exhibited phytate-degrading activity in at least one of the 3 different media used. Of the LAB, the highest phytase values were found for  Enterococcus faecium  A86 (0.74 U/mL) and  Lactobacillus plantarum  H5 (0.71 U/mL). Two different starter cultures obtained by combinations of phytase-positive (phy+:  L. plantarum  H5 and L3,  Leuconostoc gelidum  A16, and  E. faecium  A86) or phytase-negative (phy−:  L. gelidum  LM249,  L. plantarum  H19, and  L. plantarum  L8) selected LAB strains, were used to measure mineral concentrations of iron, zinc, and manganese during dough fermentation. Although the 2 kinds of starter showed similar acidic values, the presence of phytate-degrading LAB strains increased mineral solubilization in comparison to the starter phy−.     

Multi-fingered grasp synthesis based on the object dynamic properties

The grasping and manipulation of objects, especially when they are heavy with respect to the hand power capability, requires the synthesis of grasp configurations that explicitly take into account the dynamic properties of the object. Specifically, suitable grasp configurations reducing gravitational and inertial effects during object manipulation, and minimizing and equally distributing the grasping forces among all the available fingers, must be computed. A new method for fast synthesis of multi-fingered grasp configurations is proposed in this paper. In particular, to reduce the computational complexity, all the regions of the object surface favoring the synthesis of minimal inertia grasps are evaluated first. Then, a reduced number of discrete grasping regions are selected on the basis of the fingertip size, model uncertainty, and surface curvature. Finally, an exhaustive search of the optimal grasp configurations with respect to the grasp quality is performed. Several case studies and comparisons with other methods are proposed to demonstrate the effectiveness of the proposed approach.