Photoacoustic generation is an attractive alternative to generate ultrasound due to its broad bandwidth and high frequency capabilities. However, the challenges in low generation efficiency need to be addressed. In order to address this issue, a one-pot synthesized polydimethylsiloxane-gold nanoparticle (PDMS/Auu NP) nanocomposite was utilized to generate ultrasonic pulses excited by a nanosecond laser. The enhanced efficiency of the photoacoustic signal was investigated by varying the concentration and the thickness of the nanocomposite film. The optimal peak-to-peak amplitude of the acoustic signal was observed to be 189.49 kPa under the laser energy density of 13 mJ/cm 2 at 1.8 mm away from the nanocomposite film, when the thickness and the concentration of the film were 450 mum and 1.79 wt. %, respectively. Furthermore, the efficiency of the photoacoustic generation was increased 3 orders of magnitude compared to the aluminum thin film. The results indicate that high photoacoustic generation efficiency could be achieved through the PDMS/Au NPs nanocomposite.

Vertex component analysis (VCA) has become a very popular and useful tool to linear unmix large hyperspectral datasets without the use of any a priori knowledge of the constituent spectra. Although VCA is fast method, many hyperspectral imagery applications require a response in real time or near-real time. This paper proposes two different optimizations for accelerating the computational performance of VCA: the first one focus a parallel implementation based on graphics computing units (GPUs) to alleviate the VCA computational burden; The second one is focused on the development of a strategy to remove a large proportion of mixed pixels that play no effect on the VCA functioning. Experiments are conducted using simulated and real hyperspectral datasets. These results reveal considerable acceleration factors, which satisfies the real-time constraints given by the data acquisition rate.

An ergodic simulation model for the generation of multiple time uncorrelated Rayleigh waveforms with correct ensemble averages is proposed. This model uses the inverse discrete Fourier transform to generate the transmission coefficients with only one random number generator. Two recent modified versions of the Jake's and Smith's models, with correct ensemble averages, are analysed and compared with the proposed model. Analytical and simulation results show that the proposed model is ergodic in mean and autocorrelation, as is the modified Smith's model. Simulation results also show that the modified Jake's model requires the highest computation effort among the three analysed models. As a result, this model become less efficient in simulation.

Magnitude modulation (MM) envelope control is an efficient way of reducing the peak-to-average power ratio (PAPR) of single-carrier (SC) signals and improves an SC system's overall power efficiency. However, MM techniques reduce the PAPR at the cost of introducing distortion, highlighting a need to characterise the symbol error rate (SER) performance loss due to MM. This reported work focuses on the M-PSK case. An exact probability density function (PDF) based on the generalised extreme value distribution is proposed to model the statistical distribution of MM factors generated by MM techniques applied to SC constant amplitude constellations. By considering MM distortion as a form of fading, it is shown that this PDF may be used to derive an accurate union bound of the SER of M-PSK transmission on the additive white Gaussian channel channel when using MM envelope control.

In this paper, we present a multilayer device based on a-Si:H/a-SiC:H that operates as photodetector and optical filter. The use of such device in protein detection applications is relevant in Fluorescence Resonance Energy Transfer (FRET) measurements. This method demands the detection of fluorescent signals located at specific wavelengths bands in the visible part of the electromagnetic spectrum. The device operates in the visible range with a selective sensitivity dependent on electrical and optical bias. Several nanosensors were tested with a commercial spectrophotometer to assess the performance of FRET signals using glucose solutions of different concentrations. The proposed device was used to demonstrate the possibility of FRET signals detection, using visible signals of similar wavelength and intensity. The device sensitivity was tuned to enhance the wavelength band of interest using steady state optical bias at 400 nm. Results show the ability of the device to detect signals in this range. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim