Performance and emission characteristics of biofuel in a small-scale gas turbine engine

Performance and emissions characteristics of a 30 kW gas turbine engine burning Jet A, soy methyl ester, canola methyl ester, recycled rapeseed methyl ester, hog-fat biofuel, and their 50% (volume) blends in Jet A were studied over a range of throttle settings. The addition of biofuel resulted in a reduction in static thrust and thrust-specific fuel consumption, and increased thermal efficiency. The CO and NO emissions from the turbine were reduced with the biofuel blends. The results suggest that an optimum mixture may be found that reduces pollutant emissions while producing the desired thrust. This study demonstrates that biofuels may serve as viable supplements to petroleum-based fuels.     

Partially compressed-encrypted domain robust JPEG image watermarking

Digital media is often handled in a compressed and encrypted form in Digital Asset Management Systems. And watermarking of the compressed encrypted media items in the compressed-encrypted domain itself is required sometimes for copyright violation detection or other purposes. In this paper, we propose a robust image watermarking technique for partially compressed-encrypted JPEG images. However, arbitrary embedding of a watermark in a partially compressed encrypted image can cause drastic degradation of the quality as the underlying change may result in random decrypted values. In addition, due to the encryption the compression efficiency may become very low. Thus the challenge is to design a watermarking technique that provides good watermarked image quality and at the same time gives good compression efficiency. While the proposed technique embeds watermark in the partially compressed-encrypted domain, the extraction of watermark can be done in the encrypted or decrypted domains. The experiments show that the watermarked image quality is good and the reduction in compression efficiency is low. The proposed watermarking technique is robust to common signal processing attacks. The watermark detection performance of the proposed scheme is better than the existing encrypted domain watermarking techniques.     

Upper critical field of Bi1·5-Pb0·5-Ca2-Sr2-Cu3-O x superconductor

The highT _c superconductor of nominal composition Bi_1·5-Pb_0·5-Ca₂-Sr₂-Cu₃-O _x was prepared by solid-state reaction method. The upper critical fieldH _c2 of the material with a zero-resistance transition at 110K was investigated by observing variations in resistance with temperature down to 90 K and with a magnetic field up to7T. The slope ofH _c2 with temperature was about −0·41T/K for zero resistance transition and −6·86T/K for onset of superconductivity.H _c2 values at 0K were estimated to be 31·3T and 563T for zero-resistance transition and onset of superconductivity respectively.     

Electrical switching in benzidine-DDQ under pressure

The effect of pressure on non-ohmic conduction and electrical switching in the charge transfer complex benzidine-DDQ has been studied up to a pressure of 7·66 GPa at a temperature of 300K. Pulsed I-V measurements reveal heating contribution to non-ohmicity and switching. At high electric fields (∼ 3 × 10³ V/cm), the sample switches from high resistance OFF state of several kiloohms to low resistance ON state of several ohms. Temperature dependence of conductivity of ON state show semiconducting behaviour with very low activation energy.     

Influence of space-charge on hysteresis loop characteristics of ferroelectric thin films

Hysteresis loops of Pb(Zr, Ti)O3 (PZT) thin films obtained by using a Sawyer-Tower (ST) circuit are affected by many factors. This paper investigated the influence of space charge on the hysteresis loop of thin-film ferroelectrics, based on the model that polarization consists of two parts: linear and switching polarization. It is found that the space charge affects both the shape and offset of the ideal hysteresis loop. Further investigation shows that the practical hysteresis loop has a close relationship with the equivalent ST circuit parameters: the leakage resistance of the FE film, the equivalent input impedance of the measurement equipment, the signal source, and other similar parameters. The normally assumed symmetric hysteresis loop without any offset is obtained with an ST circuit when the output becomes stable. The hysteresis loop obtained at the initial stage of applied signal depends on the initial status of the FE film, and remnant polarization causes an initial offset that gradually disappears.     

Structural morphology of amorphous conducting carbon film

Amorphous conducting carbon films deposited over quartz substrates were analysed using X-ray diffraction and AFM technique. X-ray diffraction data reveal disorder and roughness in the plane of graphene sheet as compared to that of graphite. This roughness increases with decrease in preparation temperature. The AFM data shows surface roughness of carbon films depending on preparation temperatures. The surface roughness increases with decrease in preparation temperature. Also some nucleating islands were seen on the samples prepared at 900°C, which are not present on the films prepared at 700°C. Detailed analysis of these islands reveals distorted graphitic lattice arrangement. So we believe these islands to be nucleating graphitic. Power spectrum density (PSD) analysis of the carbon surface indicates a transition from the nonlinear growth mode to linear surface-diffusion dominated growth mode resulting in a relatively smoother surface as one moves from low preparation temperature to high preparation temperature. The amorphous carbon films deposited over a rough quartz substrate reveal nucleating diamond like structures. The density of these nucleating diamond like structures was found to be independent of substrate temperature (700–900° C).     

Solid phase extraction method for the determination of lead, nickel, copper and manganese by flame atomic absorption spectrometry using sodium bispiperdine-1,1'-carbotetrathioate (Na-BPCTT) in water samples

A novel column solid phase extraction procedure was developed for the determination of lead, nickel, copper and manganese in various water samples by flame atomic absorption spectrometry (FAAS) after preconcentration on sodium bispiperdine-1,1'-carbotetrathioate (Na-BPCTT) supported by Amberlite XAD-7. The sorbed element was subsequently eluted with 1M nitric acid and the acid eluates are analysed by Flame atomic absorption spectrometry (FAAS). Various parameters such as pH, amount of adsorbent, eluent type and volume, flow-rate of the sample solution, volume of the sample solution and matrix interference effect on the retention of the metal ions have been studied. The optimum pH for the sorption of above mentioned metal ions was about 6.0+/-0.2. The loading capacity of adsorbent for Pb, Cu, Ni and Mn were found to 28, 26, 22 and 20x10(-6) g/mL, respectively. The recoveries of lead, copper, nickel and manganese under optimum conditions were found to be 96.7-99.2 at the 95% confident level. The limit of detection was 3.0, 3.2, 2.8 and 3.6x10(-6) g/mL for lead, copper, nickel and manganese, respectively by applying a preconcentration factor 50. The proposed enrichment method was applied for metal ions in various water samples. The results were obtained are good agreement with reported method.     

Redox polymerisation—kinetics of polymerisation of acrylamide initiated by the Mn3+-citric acid redox system

The kinetics and mechanism of polymerisation of acrylamide initiated by manganese(III) acetate-citric acid (CA) redox system in aqueous acetic acid and sulphuric acid medium were studied over the temperature range 30-50° C. The overall rates of polymerisation (R_p), disappearance of manganic ion (—R_m), and degree of polymerisation (X?_n) were measured with variation in [monomer], [Mn³⁺], [CA], [H⁺], μ and temperature. The polymerisation is initiated by the organic free radical arising from the Mn³⁺-CA reaction and the termination is by metal ions. The various rate parameters were evaluated and discussed.