Study of the change of crystallinity of polyethylene on oxidation by inverse phase gas chromatography

Inverse-phase gas chromatography has been used for monitoring the oxidative degradation of low density polyethylene, which has great industrial importance. Polyethylene was oxidized in a gas chromatographic column at 145°C with an oxygen flow of 10 mL/min for different periods. After oxidation for a specified period, the crystallinity and solvent interaction parameters were monitored. For crystallinity studies, the solvent probe was n-decane, and for solvent interaction these were n-decane, o-xylene, n-butanol, and n-butyl acetate. With oxidation there was a gradual fall in crystallinity, and after 15 h the crystallinity was practically nil. Total loss of crystallinity also occurred at 175°C with 1 h passage of oxygen. This has also been confirmed by differential scanning calorimetry. The specific retention volumes of polar solvents showed a sharp increase with oxidation. The results, which are different from that reported in the literature, have been explained.     

Dielectric behaviour of dysprosium oxide films

The dielectric properties of vacuum-deposited dysprosium oxide films have been studied in the audio-frequency range (10²–10⁴ Hz) at various temperatures (78–373 K). The dielectric constant (6.7) was independent of film thickness for thicker films (d > 1000 Å). The capacitance was dependent both on temperature and frequency, but became constant for all frequencies at low temperature. Tan δ showed a frequency minimum and its variation with frequency and temperature was in agreement with the model proposed earlier by Goswami and Goswami. The breakdown field (≌10⁶ V cm^-1) followed the Forlani-Minnaja relation. The activation energy and the refractive index of these films were also measured.     

Thermal reliability of n-GaAs/Ti/Pt/Au Schottky contacts with thin Ti films for reduced gate resistance

The thermal stability of Ti/Pt/Au Schottky contacts on n-GaAs with Ti films 0–60 nm is investigated. The contacts with Ti films as small as 10 nm remain thermally stable with annealing up to 400°C. The changes induced by thermal treatment in the electrical characteristics of the contacts are correlated with the Rutherford backscattering and microscopic analysis of the annealed samples. It shows profuse interdiffusion and interfacial reaction with 300°C anneal for the GaAs/Pt/Au system. It has been found that introducing the Ti film between GaAs and Pt/Au, the interdiffusion of Pt and Au is also prevented. These results are useful for reducing the gate metallisation resistance of metal semiconductor field effect transistors.     

Studies on physico-mechanical properties of some new light weight engineering materials

Industrial, agricultural, and naturally occurring waste materials in conjunction with liquid epoxy resin, silica and asbestos were employed to make light weight engineering composite materials. To bring down the cost of the expensive resin, additives such as linseed oil and urea formaldehyde were added to replace the bulk of epoxy resin. Various physico-mechanical properties of these composites were studied. In comparison with ordinary cement concrete, properties such as water absorption and fire resistance improved substantially for the majority of mixes, whereas other physico-mechanical properties did not improve greatly in many cases. Such composites, which are similar to (and in some cases better than) ordinary cement concrete can be of use in building technology because of substantially lower prices.     

A note on universal matrices for triangular finite elements for the quasi-harmonic equation

An algorithm to generate universal matrices for plane triangular finite elements for the general ‘quasi-harmonic’ equation is presented. For every member of the triangle family three numerical universal matrices are obtained which are independent of the size, shape and ‘material’ properties of the element. Of these, two are basic and the third can be generated from one of these two. The element ‘stiffness’ matrix is conveniently generated by manipulating these two basic matrices taking into account the size, shape and material properties of the element in a simple manner.     

Segmentation of moving observer frame sequences

This note presents a technique for the segmentation of dynamic scenes obtained using a moving camera. Using the motion of the observer the frame sequence is transformed into a polar frame sequence. It is shown that segmentation and extraction of motion information becomes computationally simpler in the Ego-Motion Polar (EMP) frame sequence.     

Implementation of an interactive relational graphics database

The benefits that accrue from the use of design database include (i) reduced costs of preparing data for application programs and of producing the final specification, and (ii) possibility of later usage of data stored in the database for other applications related to Computer Aided Engineering (CAE). An INTEractive Relational GRAphics Database (INTERGRAD) based on relational models has been developed to create, store, retrieve and update the data related to two dimensional drawings. INTERGRAD provides two languages, Picture Definition Language (PDL) and Picture Manipulation Language (PML). The software package has been implemented on a PDP 11/35 system under the RSX-11M version 3.1 operating system and uses the graphics facility consisting of a VT-11 graphics terminal, the DECgraphic 11 software and an input device, a lightpen.