Electron escape time from single quantum wells

A theoretical model for electrons escaping a quantum well under the influence of an applied electric field is developed. Both the thermionic emission and tunneling components of the currents are calculated, taking into account the proper partitioning between the two currents. The group velocity for a nonuniform electron distribution within the quantum well, which is a function of position and energy, and the continuous energy dependence of the quantum well density of states is considered. A comparison between this model and previously reported experimental results are made which demonstrates excellent agreement     

ROLE OF COMPOSITION ON THE VISCOSITY AND SHEAR STRESS TEMPERATURE BEHAVIOUR OF SOME LUBE OIL BASE STOCKS

Lubricating oil base stocks differ greatly in their chemical composition and consequently in their physical properties and applications. Influence of waxes and various hydrocarbon type constituents viz saturates and aromatic components on the viscosity and shear stress as a function of temperature in different lube oil base stocks has been studied in the present paper.     

Bias dependence of high-frequency noise in heterojunction bipolar transistors

Hawkins' isothermal model developed to study noise in bipolar junction transistors (BJTs) is modified to investigate bias-dependent noise in heterojunction bipolar transistors (HBTs) by incorporating thermal effects. It is shown that the inclusion of thermal effects into the high-frequency noise model of HBTs is necessary as the temperature of the device may become very different from the ambient temperature, especially at high bias current. Calculation of the noise figure by including the thermal effect shows that the isothermal calculation may underestimate the noise figure at high bias current. It is observed that noise at low bias is ideality factor n dependent whereas high bias noise is insensitive to the variation of n. Moreover, the common base current gain plays a major role in the calculation of the minimum noise figure. The excellent fit obtained between the theoretical calculation and the measured data are attributed to the inclusion of the bias-dependent junction heating as well as C/sub De/ and C/sub bc/ into the present calculation.     

An asymmetric line-axis compound parabolic concentrating single basin solar still

An asymmetric line-axis compound parabolic concentrating single basin solar still of concentration 1.15, exit aperture 0.24 metres and length 0.48 metres, 30° inclination and 60° half acceptance angle has been designed fabricated and tested.     

FTIR-ATR studies of diffusion and perturbation of water in polyelectrolyte thin films. Part 4. Diffusion, perturbation and swelling processes for ionic solutions in SPEES/PES membranes

We report diffusion rates and equilibrium concentrations of water in a polyelectrolyte SPEES/PES film using ATR/FTIR spectroscopy. The data for water obtained by fitting spectral intensities to a dual mode diffusion model in the presence of different counter ions (at 0.2 mol dm⁻³) follow the order Li⁺>Cs⁺>Na⁺>Ca²⁺>K⁺. Diffusion is progressively slower for higher concentrations of NaCl (0.2-0.85 mol dm⁻³) and the NO₃⁻ counter anion leads to a faster diffusion rate than for Cl⁻ at the same concentration. Both water uptake and diffusion rates are broadly consistent with expectations based on the differential degrees of swelling, caused by changes in the SO₃⁻/SO₃⁻ interpolymer chain repulsive forces leading to a decrease in volume diffusion compared with the value for pure water. Direct spectral measurements of the degree of swelling confirm that the process does occur, although the order of the swelling amounts does not map directly onto that of the diffusion rates. This is probably because the interfacial dissociation processes are hydration dependent.     

A comparison between reliability analyses based primarily on disjointness or statistical independence: The case of the generalized indra network

A switching expression is readily convertible to a reliability expression if (a) all ORed terms are disjoint, and (b) all ANDed sums are statistically independent. The usual approach of system reliability analysis makes a primary use of (a) and a secondary use of (b). An alternative approach reverses the roles of (a) and (b). Symbolic reliability expressions for the source-to-terminal reliability of a generalized Indra network (GIN) with nonidentical components are derived by the two approaches. For this particular case, the second approach leads to a shorter, more elegant derivation and simpler novel results. Typical plots of the GIN reliability functions are presented and their properties are discussed.     

A hybrid model for spelling error detection and correction for Urdu language

Neural Computing and Applications - Detecting and correcting misspelled words in a written text are of great importance in many natural language processing applications. Errors can be broadly...     

Improving security of the Internet of Things via RF fingerprinting based device identification system

Neural Computing and Applications - Security is one of the primary concerns when designing wireless networks. Along detecting user identity, it is also important to detect the devices at the...     

RFID-based interactive multimedia system for the children

In this paper, we present an interactive edutainment system for the children that leverages multimedia and RFID technologies in a seamless manner. The proposed system allows children to learn about new objects/entities by tapping on physical objects through a specially designed RFID-Bluetooth based Tangible User Interface (TUI) tool. The output of the system is delivered as a set of appropriate multimedia representations related to the objects being tapped. The TUI uses RFID technology for object identification and Bluetooth communication to transmit data to the computer where the system??s software is running. We incorporated our system in three games that allow children of different ages to benefit from the system??s functionalities and encourage them to interact with it.