Implementation of quantum optical tristate CNOT gate using frequency encoding principle with a semiconductor optical amplifier

Controlled NOT (CNOT) gate is well known because of its several advantages in quantum computing and information processing. In the area of quantum computing, several methods of CNOT gates were established in last few years. In this paper, we propose a new approach of implementation of tristate CNOT operation with light as information carrying signal. To do this, the frequency encoding method has been exploited for successful realization of the CNOT gate with light.     

Thermistor controlled gunn oscillator at Ka-band

Frequency drift of Gunn oscillators is a major cause of concern in most of the Millimeter wave communication systems. This paper describes a simple and cost effective technique to arrest the frequency drift of a Ka band Gunn oscillator within 15 MHz for the operating temperature range of 0°C to 60°C as against a typical drift of about 50 to 100 MHz for free running Gunn oscillator for the same temperature range. At the ambient, the oscillator remains within ±1 MHz from switching on to stabilization. The temperature variation is sensed with a small thermistor bead placed close to the diode and a correction voltage is applied to the bias to compensate for the frequency drift. This compensation circuit also takes into account the non-linear behaviour of the thermistor and the Gunn oscillator with the temperature.     

Carbon-sulphur surface complexes on charcoal

Interaction of charcoal with sulphur, hydrogen sulphide, carbon disulphide and sulphur dioxide at 600°C results in appreciable fixation of sulphur. The amount fixed varies with the nature of the reagent used and, for a given reagent, it depends not so much on surface area as on oxygen and hydrogen contents, extent of surface unsaturation and pore structure of charcoal. There are indications that sulphur is fixed partly by addition at the unsaturated sites and partly by substitution through interaction with certain oxygen groups which come off as carbon monoxide on high temperature evacuation. The carbon-sulphur complex, resulting from fixation of sulphur on charcoal, is highly stable. The products, when heated in a current of nitrogen, evolve largely hydrogen sulphide and carbon disulphide but the entire amount cannot be recovered even at 1200°C. The amount of sulphur recovered as sulphate ion on prolonged treatment with excess of hot concentrated nitric acid varies with the nature of the reagent used in the fixation of sulphur. The results give some indication of the possible nature of sulphur-containing groups and structures formed. The products catalyse sodium azide-iodine reaction to varying extents. The adsorption isotherms of water, methanol and benzene indicate considerable narrowing down of capillary pores of charcoal, as a result of fixation of sulphur.     

Effect of Cold Rolling on as–ECAP Interstitial Free Steel

Ti-stabilized interstitial free steel subjected to eight passes, route B_C room temperature equal channel angular pressing (ECAP) additionally was cold rolled (CR) up to 95 pct thickness reduction. Electron back-scattering diffraction and transmission electron microscopy characterized microstructural refinement and microtexture evolution, whereas the mechanical properties were assessed by uniaxial tensile tests. After 95 pct CR, the average high-angle grain boundary spacing reduces to 0.14 μm, whereas the high-angle boundary fraction increases to ~81 pct. The ECAP negative simple shear texture components rotate by ~15 deg around the transverse direction toward the rolling direction for up to 50 pct CR, with typical rolling textures observed at 95 pct CR. The decrease in boundary spacing produces a ~500 MPa gain in 0.2 pct proof stress, a ~600 MPa increase in ultimate tensile strength (UTS), and a ~4 pct loss in total elongation after 95 pct CR. Similar rates of decrease in work hardening correspond to comparable rates of cross and/or multiple slip events irrespective of the processing regime and substructural refinement. The fracture mode of the tensile samples changes from ductile to brittle type between ECAP and 95 pct CR and is attributed to the reduced work hardening capacity of the latter. The modified Hall–Petch equation shows that the convergence of high-angle boundary spacing values with their low-angle counterparts results in an increased contribution via boundary strengthening to the 0.2 pct proof stress and UTS.     

Corrosion-Induced Fatigue Failure of a First-Stage Flow Straightener Vane of an Aeroengine

One of the first-stage vanes of double-row flow straightener vane assembly (at seventh stage in the compressor) of an aeroengine was found broken from its root, during strip examination of the aeroengine. A metal piece was also collected from inside the engine. The flow straightener vane was said to have broken prematurely with respect to its total as-specified technical life. The broken vane, collected metal piece and a serviceable first-stage flow straightener vane were received for failure analysis. The result of the failure analysis is presented in this article. The vane failed due to fatigue, which was initiated from a corrosion pit on the pressure side near the leading edge of the vane. Chloride-containing environment led to the development of pitting, followed by pitting-induced fatigue cracking and final overload fracture. Chemical composition, microstructure and hardness evaluations indicated that the material of construction for the vane was the usual 12% Cr martensitic stainless steel nearly conforming to SUS 410J1, used in the hardened and tempered condition. The recovered metal piece from inside the engine was also made of martensitic steel with similar composition and microstructure to that of the failed and serviceable flow straightener vanes. The piece was badly rubbed and damaged resulting in cold deformation, evident from strain marks and an increase in hardness. All these findings support that it could be the broken aerofoil of the failed flow straightener vane.     

Partially Sulfonated Poly(vinylidene fluoride) Induced Enhancements of Properties and DMFC Performance of Nafion Electrolyte Membrane

Partially sulfonated poly(vinylidene fluoride) (SPVdF) has been prepared by incorporation of sulfonic acid groups within poly(vinylidene fluoride), using chlorosulfonic acid as the sulfonating agent. The degree of sulfonation (DS) has been varied by modulating the duration of the sulfonation reaction. Blending of SPVdF (having DS = 36.78%) with Nafion at a constituent wt.% ratio of SPVdF:Nafion = 70:30 has resulted in the fabrication of polymer electrolyte membrane with superior properties compared to pristine Nafion‐117 membrane. This particular blend composition exhibited a proton conductivity value of 3.6 × 10⁻² S cm⁻¹ (i.e. ∼12.5% increase over Nafion‐117), a methanol permeability value of 6.81 × 10⁻⁷ cm² s⁻¹ at 6M methanol concentration (i.e. ∼99.31% decrease from Nafion‐117) and a corresponding membrane selectivity value of 5.29 × 10⁴ Ss cm⁻³ (i.e. an increase of approximately two‐orders of magnitude over Nafion‐117) at 20 °C. In addition, this blend composition has also exhibited (a) better heat stability at temperatures as high as 160 °C by virtue of it possessing higher glass transition temperature, (b) higher storage modulus, (c) higher stress relaxation at high angular frequency and (d) superior DMFC performance at high methanol feed concentration in presence of humidified, as well as, non‐humidified air as the catholyte, compared to Nafion‐117 membrane.     

Parallel computing

The author begins by discussing some basic terms and concepts used in parallel computing, and goes on to consider parallel software engineering principles and their implementation. The author concludes with a discussion of transputers and their future     

Effect of Coiling Temperature on the Microstructure and Mechanical Properties of Hot-Rolled Ti–Nb Microalloyed Ultra High Strength Steel

A novel low carbon Ti–Nb microalloyed hot rolled steel with minimum yield strength of 700 MPa and good balance of stretch-flangeability and impact toughness has been developed by controlled thermo-mechanical processing following thin slab direct rolling route. In the present work, the effects of two coiling temperatures on the resulting microstructure, micro-texture and mechanical properties on this Ti–Nb microalloyed steel have been studied. It is observed that increase in coiling temperature from 520 to 580 °C significantly affects the mechanical properties. Higher dislocation density and increased precipitation along with slightly smaller grain size is observed for 580 °C coiling temperature resulting in about 50 MPa increase in yield and tensile strengths as compared to 520 °C coiling temperature.     

Modified Cross-Correlation Method for the Blind Identification of Structures

Recently, blind source separation (BSS) methods have gained significant attention in the area of signal processing. Independent component analysis (ICA) and second-order blind identification (SOBI) are two popular BSS methods that have been applied to modal identification of mechanical and structural systems. Published results by several researchers have shown that ICA performs satisfactorily for systems with very low levels of structural damping, for example, for damping ratios of the order of 1% critical. For practical structural applications with higher levels of damping, methods based on SOBI have shown significant improvement over ICA methods. However, traditional SOBI methods suffer when nonstationary sources are present, such as those that occur during earthquakes and other transient excitations. In this paper, a new technique based on SOBI, called the modified cross-correlation method, is proposed to address these shortcomings. The conditions in which the problem of structural system identification can be posed as a BSS problem is also discussed. The results of simulation described in terms of identified natural frequencies, mode shapes, and damping ratios are presented for the cases of synthetic wind and recorded earthquake excitations. The results of identification show that the proposed method achieves better performance over traditional ICA and SOBI methods. Both experimental and large-scale structural simulation results are included to demonstrate the applicability of the newly proposed method to structural identification problems.