The temperature dependence of density d, electric permittivity ϵs and nonlinear high field dielectric variation Δϵ are reported for various benzonitrile-alkane solutions. For the benzonitrile-isooctane mixtures which exhibit a phase separation in the considered temperature range, the phase diagram has been obtained. In the “homogeneous” one phase region, significant deviations from the normal temperature dependence of d, ϵ0, Δϵ have been observed and characterize a precritical region of several degrees C above the consolute temperature. These results support the hypothesis of strong precritical orientational interactions or local ordering phenomena. The precritical dielectric behaviour of the benzonitrile-isooctane system is shown to be very different from those of nitrobenzene-alkane or aniline-alkane mixtures.

Dielectric behaviour of a molecular liquid mixture in the one-phase precritical region

The effect of the inclusion of silicon atoms in the network of diamond-like carbon (amorphous carbon and hydrogenated amorphous carbon) is studied. Samples of amorphous hydrogenated CSi are deposited by means of a sputter-assisted plasma chemical vapour deposition system in which a carbon target is sputtered in an atmosphere composed of silane-diluted argon, where the silane flow rate is varied. It is shown that initially the effect of silicon inclusion is to reduce the size of the graphitic-like islands. When the amount of silicon is increased over a critical value, the network assumes the characteristic of the semiconductor-type amorphous hydrogenated SiC, where the properties of silicon are predominant.

Influence of silicon on the physical properties of diamond-like films

Hydrogenated amorphous carbon films (a-C:H) were deposited on p-type silicon as well as silica substrates by pulsed laser deposition technique using a mixture of graphite and camphor powders. The Fourier transform infrared spectroscopy measurement revealed the presence of hydrogen in the a-C:H films. The optical properties and structure of the a-C:H film were investigated by UV–visible and Raman scattering spectroscopy. The formation of a heterojunction between the a-C:H film and silicon substrate was confirmed by the current–voltage ( I – V ) measurement. Furthermore, the structure of a-C:H/p-Si showed photovoltaic characteristics with an open-circuit voltage ( V oc ) of 0.4 V and short-circuit current density ( J sc ) of about 15 mA/cm 2 under AM1.5 (100 mW/cm 2 ) illumination. From the calculation, the energy conversion efficiency and fill factor were found to be 2.1% and 0.38, respectively. The carbon layer contributed to the energy conversion efficiency, which was proved by the measurement of quantum efficiency.

The a-C:H/p-Si solar cell deposited by pulsed laser deposition

The application of the Wiener-Hopf technique to the coupled linear integral equation ofX- andY-equations gives rise to the Fredholm equations with simpler kernels.X-equation is expressed in terms ofY-equation and vice-versa. These are unique in representation with respect to coupled linear constraints.

Application of the Wiener-Hopf Technique for a New Representation of X- and Y-Equations

Application of Wiener-Hopf technique to linear nonhomogeneous integral equations for a new representation of Chandrasekhar's H -function in radiative transfer, its existence and uniqueness

We obtain a new representation of Chandrasekhar'sH-functionsH(z) corresponding to the dispersion functionT(z) = |δ
 rs
 −f

 rs
 (z)|, [f

 rs
 (z)] is of rank one.H(z) is obtained in the form 
$$H\left( z \right) = \left( {A_0 + A_1 z} \right)/\left( {K + z} \right) - \sum\limits_1^n {\int\limits_{E_r } {P_r (x) dx/(x + z),} }$$

 WhereP

 r
 
x(=o

 r
 (x)/H(x)) is continuous onE

 r
 which are subsets of [0, 1].A

 o
 ,A

 1
 are determinable constants andK is the positive root ofT(z),o

 r
 (x) are known functions. From this formH(z) is then obtained in terms of a Fredholm type integral equation. This new form ofH(z) has proved to be very useful in solving coupled integral equations involvingX-,Y-functions of transport problems.P
r(x) can be replaced by approximating polynomials whose coefficients can be determined as functions of the moments of known functions; a closed form approximation ofH(z) to a sufficiently high degree of accuracy is then readily available by term integrations.

A new representation of the H -functions of radiative transfer

Some useful results and remodelled representations ofH-functions corresponding to the dispersion function

$$T\left( z \right) = 1 - 2z^2 \sum\limits_1^n {\int_0^{\lambda r} {Y_r } \left( x \right){\text{d}}x/\left( {z^2 - x^2 } \right)} $$

are derived, suitable to the case of a multiplying medium characterized by

$$\gamma _0 = \sum\limits_1^n {\int_0^{\lambda r} {Y_r } \left( x \right){\text{d}}x > \tfrac{1}{2} \Rightarrow \xi = 1 - 2\gamma _0< 0} $$

A note on theH-functions of transfer problems in multiplying media

The transfer equations for non-coherent scattering arising from interlocking of principal lines without redistribution is exactly solved in a very simple way by Laplace tranform and Wiener-Hopf technique which are easily applied by the use of the new representation ofH-functions obtained recently by the author (1977). The emergent intensity in therth line is expressed in terms of anH-function and a Cauchy type integral admitting of closed form evaluation.

An exact solution of transfer equations for interlocked multiplets

Films of amorphous carbon (a-C) and hydrogenated amorphous carbon (a-C:H) have been prepared by r.f. magnetron sputtering of a graphite target in atmospheres without and with hydrogen respectively. These films have been studied by optical, electrical and electron spin resonance measurements. The conductivity and the optical absorption coefficient values were found to be similar for the two materials. The only relevant difference was detected in the volume density of spins. It was found to be around 10 21 cm -3 for a-C and below 10 20 cm -3 for a-C:H samples. It is shown that diamond-like a-C, having similar properties to a-C:H, can be obtained by means of this technique. As a consequence, hydrogen plays only an indirect role in determining the relevant optical and electrical parameters. However, the hydrogenated material is less defective.

Diamond-like properties of amorphous carbon and hydrogenated amorphous carbon thin films

In this paper we develop a new method, combined with Laplace transformation and Wiener-Hopf technique, to obtain unique solutions of transport equations in finite media. For this purpose we consider the simple transfer equation for diffuse reflection by a plane-parallel finite atmosphere scattering radiation with moderate anisotropy. It is transformed, by Laplace transformation, into two coupled linear integral equations which are then reduced to two uncoupled Fredholm integral equations admitting of unique solutions by the method of iteration for values of the breadth of the atmosphere greater than that specified, depending on the scattering process.

Das Gupta

Papers

A new representation of the H -functions of radiative transfer

A note on theH-functions of transfer problems in multiplying media

An exact solution of transfer equations for interlocked multiplets

Diamond-like properties of amorphous carbon and hydrogenated amorphous carbon thin films

A new technique for exact and unique solution of transfer equations in finite media