A BiCMOS Differential Amplifier and Timing Discriminator for the Receiver of a Laser Radar

A differential BiCMOS amplifier channel with gain control circuitry and a timing discriminator has been designed for a pulsed time-of-flight laser radar. The measured bandwidth of the amplifier channel is 160 MHz and its gain can be controlled with a variable R-2R ladder attenuator in 7 discrete steps from 0.44 to 23. A peak detector, used for gain control, can detect the peak of a single 10 ns pulse, the amplitude of which varies from 50 mV to 3.5 V. The timing discriminator produces accurately timed logic level pulses from noisy analog output pulses of the amplifier channel. The distance measurement result of the designed timing discriminator varies +/– 4 mm with an input amplitude range of 55 mV – 3.3 V. The single shot resolution with SNR = 250 is better than 6 mm. Measurement results suggest that a cm-level distance measurement accuracy can be realized using integrated ASICs.     

On the design of a hierarchical BTC-VQ compression system

In the present paper we study the use of vector quantization in the BTC-VQ image compression system. We propose an inverted order of proceeding in the BTC-VQ algorithm, so that the interaction of coding the bit-plane and the quantization data will be taken into consideration. The quality of the image depends radically on the codebook used in VQ. The use of frequencies in the selection of the initial codebook turns out to be superior to random selection.     

Isomerisation of α-Pinene Oxide to Campholenic Aldehyde Over Supported Ionic Liquid Catalysts (SILCAs)

The isomerisation of α-pinene oxide to campholenic aldehyde, an expensive ingredient utilized by e.g. flavor industry, was studied over Supported Ionic Liquid Catalysts (SILCAs) consisting of catalytically active species residing in ionic liquid. The ionic liquid, in turn, was immobilized on a solid support material. SILCAs were demonstrated as efficient catalysts for the transformation of α-pinene oxide into campholenic aldehyde, with the product distribution and activity being dependent on the nature of the ionic liquid.

     

Contribution à une meilleure approche dans la détection et l’estimation de la fréquence laryngienne

Combined use of different laryngeal frequency information furnished simultaneously by short-time Fourier transform and by instantaneous frequency distribution function leads to a higher precision of the frequency estimation. Two parameters are defined : the spectral dissymmetry coefficient and the “inter-correlation function. These parameters give a clear insight into the nature of the analysed speech windows, leading to an exact detection of the voicing feature. The exploitation of the sensibility with respect to the nature of the speech windows enables the extraction of voiced/mixed/unvoiced decision and also the specification of the mixed source.     

Similarity classifier using similarities based on modified probabilistic equivalence relations

This paper examines a classifier based on similarity measures originating from probabilistic equivalence relations with a generalized mean. Equivalences are weighted and weight optimization is carried out with differential evolution algorithms. In the classifier, a similarity measure based on the ?ukasiewicz structure has previously been used, but this paper concentrates on measures which can be considered to be weighted similarity measures defined in a probabilistic framework, applied variable by variable and aggregated along the features using a generalized mean. The weights for these measures are determined using a differential evolution process. The classification accuracy with these measures are tested on different data sets. Classification results are obtained with medical data sets, and the results are compared to other classifiers, which gives quite good results. The result presented in this paper are promising, and in several cases better results were achieved.     

A pilot-scale fireside deposit study of co-firing Cynara with two coals in a fluidised bed

Costs of biofuel production from energy crops can be reduced by applying the crop residues in heat and power production. Perennial herbaceous crops like Cynara cardunculus L. are challenging fuels because they tend to have high ash and chlorine contents. Coals, however, are often rich in aluminium silicates and sulphur, and co-firing of these biofuels with coal could be expected to reduce operational problems. In addition, CO₂ emissions are lower than during coal firing alone. Blends of Cynara and two coals, South African bituminous and Spanish sub-bituminous coal, were combusted in a 20 kW bubbling bed pilot reactor to ascertain the ability of the coals to reduce operational problems by alkali capture. The Cynara fuel sample contained almost 2 wt% chlorine. The South African coal was rich in kaolinite capable of capturing alkalies from chlorides to produce alkali aluminium silicate and HCl. The Spanish coal was rich in sulphur (mostly present as FeS₂), and produced high concentrations of SO₂ that partially oxidised to SO₃. The SO₃ can capture alkalies from chlorides by sulphation. Up to 30% Cynara, on energy basis, could be co-fired with Spanish coal without operational problems, whereas the same percentage of Cynara with South African coal led to strong Cl deposition. Co-firing of Cynara with both coals resulted in high HCl emissions (up to 1500 mg/Nm³ in 6% O₂). In addition, co-firing of the Spanish coal led to very high SO₂ emissions (up to about 16,000 mg/N m³ in 6% O₂). Thus, a power plant capable of firing such blends must be equipped with flue gas cleaning equipment for effective SO₂ and HCl capture in the flue gas channel after the superheaters, or else the quality of the Cynara must be markedly improved by changing the harvesting technology and fertilisers, which could be major sources of high ash and chlorine content in the fuel.     

White LED light coupling into light guides with diffraction gratings

Radial diffractive gratings are used to couple light of a white LED into a light guide. Theoretical coupling efficiencies are evaluated with rigorous diffraction theory in a pure conical mounting. It is shown that when the refractive index of the grating increases from 1.46 to 2.05 the incoupling efficiency increases from 42% to 63%. Also, with the increasing refractive index the incoupling efficiency is shown to become more nearly uniform over the visible spectrum. Experimental results for the incoupled efficiencies and the color coordinates of the incoupled spectra are introduced for refractive indices n=1.46 and n=1.56.     

Colloidal properties and gelation of aqueous dispersions of conductive poly(benzimidazobenzophenanthroline) derivatives

Poly(benzimidazobenzophenanthroline), BBL, is a practically insoluble conductive polymer. It can be gradually dispersed in water, however by dialysis and sonication, i.e. during the purification and dilution right after synthesis. Dispersions with higher solids content and colloidal stability were prepared by first turning the polymer amphiphilic adding poly(ethylene oxide), PEO, into BBL chain ends (BBL–PEO). Dynamic light scattering and zeta potential measurements showed that the dispersions consist of negatively-charged particles with a broad size distribution. These dispersions were found to be sensitive to ionic strength. Salting out occurred within a NaCl concentration range of 0.5–4 mM and some samples showed re-entrant behavior with redispersion upon further salt addition. Addition of a non-ionic surfactant was found to enhance the stability of BBL–PEO dispersions against salting-out. Upon increasing the polymer concentration the dispersions form gels upon resting. The strength of the gels depends on the total polymer concentration as well as the proportions of BBL and PEO in the BBL–PEOs. The gel formation was attributed to a formation of a network of nano-wire-type aggregates, which was verified with electron cryo-microscopy.     

Analysis of stirred tanks with two‐zone models

Stirred tank turbulence and fluid flow characteristics are analyzed based on a two‐zone model. Instead of using the zonal model for stirred tank performance prediction as often proposed in the literature, the zoning is used here as a tool for mixing analysis. A systematic zoning approach is proposed, where the tank is divided into two nested regions. By gradually increasing the inner zone volume, continuous curves can be obtained for turbulent energy dissipation distribution and pumping numbers between the zones as functions of the zone sizes. It is shown here that these curves can be used as a powerful tool for visualizing stirred tank performance. They can be used, e.g., in impeller performance comparisons and analysis of mixing characteristics with changing rheology, or to examine various numerical aspects related to stirred tank CFD modeling. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Integration of microfluidic sample delivery system on silicon nanowire-based biosensor

Silicon nanowire-based (SiNW) biosensors have gained a lot of attention during recent years. However, studies often totally neglect, or only briefly describe, the incorporation of microfluidic channel into the sensor architecture, although it is a crucial step towards a real lab-on-chip device. This paper proposes a process that can be applied to integration of microfluidic sample delivery system onto different SiNW biosensors. The sample delivery system includes a hydrophilic channel that enables the use of capillary action in delivering sample directly onto the sensor array, which leads to reduced sample loss, faster detection process, and frees from the use of external pumps. In addition, the microfluidic channel system protects the fragile SiNWs from mechanical shocks, chemical spatters, and dust. The sample delivery system was fabricated of surface treated polydimethylsiloxane (PDMS), using a four-step approach, as follows: (1) master molds for soft lithography were etched onto Si. (2) PDMS replicas of the molds were fabricated and (3) bonded onto example sensor chips using oxygen plasma. (4) Oxygen plasma treatment also enabled the attachment of polyvinylpyrrolidone (PVP) to the sample channel surfaces to synthesize hydrophilic polymer coating. A contact angle for the PVP treated PDMS was 21 after 17 days, indicating the formation of a long-term hydrophilic PDMS surface. Finally, the example SiNW sensor is modified to allow direct real-time detection of thyroid-stimulating hormone (TSH). The sensor was able to detect as low TSH concentration values as 0.5 mIU/l, which indicates a successfully integrated sample delivery system.