Compensation for Joule–Thomson effect in flowrate measurements by GMDH polynomial

The international standard for flowrate measurements ISO-5167 recommends the temperature sensor to be located downstream of the differential device what may cause a significant error in the measurement of the flowrate of natural gas, especially at high differential pressure, low temperature and low diameter ratio. The flowrate generally needs to be compensated for the temperature change due to the Joule–Thomson effect caused by the constriction of the metering device. The accurate compensation involves double calculation of both the natural gas properties and the flowrate. To decrease the computational load, an automatic correction of the flowrate by the GMDH polynomial surrogate is proposed. By using the compound measure of the approximation error and the execution time for model selection, the modified GMDH algorithm searches for the satisfactory model fulfilling the constraints of real-time application. The automatic correction of the flowrate measurements of a natural gas is simulated and the corresponding results are discussed. The derived model can be equally used for a natural gas specified by composition or by physical properties.     

Amyloid beta-protein impairs astrocyte-mediated differentiation of hippocampal neurons

Embryonic rat hippocampal neurons were cultured on poly-D-lysine (PDL) or on cortical astrocytes, some of which had been pretreated for 24 h with amyloid beta-protein (beta-AP). Amino acid-induced currents were quantified. Membrane capacitance (Cm), as well as the amplitude and density of amino acid-evoked currents recorded in neurons cultured on untreated astrocytes were all statistically greater than those recorded in neurons grown on PDL. However, compared to untreated astrocytes, those treated with beta-AP led to significantly lower values in neurons for Cm and GABA, kainate- and NMDA-induced currents, while glycine-activated current values were not significantly different. Furthermore, beta-AP treatment abolished spontaneous Cac2+ fluctuations in astrocytes, which may account for their impaired ability to promote the expression of functional transmitter receptors in neurons.     

Mobility of queued call requests of a new call-queueing techniquefor cellular systems

A queueing algorithm for new call requests has been proposed to increase the system capacity of traditional fixed channel allocation (FCA) handoff channel reservation schemes. However, mobility of queued call requests was ignored in previous literature. In this paper, a detailed analysis on the effects of the mobility of queued call requests is included in the analytic model. This is important because we found that the mobiles with queued call requests are very likely to leave the cell before granted a free channel. Computer simulation is performed and the results are compared with the numerical ones. It is found that the mobility of the queued new call requests reduces the average queueing delay, but increases blocking probability generally     

Multimedia transmission in fiber-optic LANs using optical CDMA

In this paper, we address the problem of multimedia transmission in fiber-optic networks. We apply the code-division multiple-access (CDMA) technique for such a network. The necessary conditions for successful operation of the network are given. It is shown that for successful operation, new families of optical orthogonal codes (OOCs) are needed which will have not only good correlation properties within one code family, but also between families of different code lengths. Some possible constructions of multimedia OOCs and the corresponding basic structure of the receiver for the multimedia network are given. Specific examples of OOCs for the case of users with two different data rates are given, and the probability of error (using the Gaussian approximation) as a function of the number of low and high rate users is calculated     

Variable rate adaptive modulation for DS-CDMA

An adaptive coding scheme is introduced for a discrete sequence code-division multiple-access system. The system uses noncoherent M-ary orthogonal modulation with RAKE receiver and power control. Both a fast fading channel and a combined fast fading, shadowing and power control channel are considered. Analytical bounds and simulations are done to evaluate the performance of the system. It is found that there is significant improvement in the average throughput and the bit-error-rate performance in the adaptive coding scheme. The amount of improvement drops with the increase of diversity branches used. More importantly, it is found that adaptive coding scheme is relatively robust to shadowing, while fix-rate codes are ineffective in the shadowing environment. Finally, adaptive coding scheme is found to be robust to mobile speed, feedback delay, and finite interleaving depth     

Dynamic evaluation of low-temperature metal-supported solid oxide fuel cell oriented to auxiliary power units

A metal-supported solid oxide fuel cell (SOFC) composed of a Ni–Ce_0.8Sm_0.2O_2−δ (Ni–SDC) cermet anode and an SDC electrolyte was fabricated by suspension plasma spraying on a Hastelloy X substrate. The cathode, an Sm_0.5Sr_0.5CoO₃ (SSCo)–SDC composite, was screen-printed and fired in situ. The dynamic behaviour of the cell was measured while subjected to complete fuel shutoff and rapid start-up cycles, as typically encountered in auxiliary power units (APU) applications. A promising performance – with a maximum power density (MPD) of 0.176 W cm⁻² at 600 °C – was achieved using humidified hydrogen as fuel and air as the oxidant. The cell also showed excellent resistance to oxidation at 600 °C during fuel shutoff, with only a slight drop in performance after reintroduction of the fuel. The Cr and Mn species in the Hastelloy X alloy appeared to be preferentially oxidized while the oxidation of nickel in the metallic substrate was temporarily alleviated. In rapid start-up cycles with a heating rate of 60 °C min⁻¹, noticeable performance deterioration took place in the first two thermal cycles, and then continued at a much slower rate in subsequent cycles. A postmortem analysis of the cell suggested that the degradation was mainly due to the mismatch of the thermal expansion coefficient across the cathode/electrolyte interface.     

Rheology,spontaneous whey separation,microstructure and sensorial characteristics of probiotic yoghurts enriched with passion fruit fiber

Beyond demonstrated beneficial health attributes, passion fruit rinds are a by-product of the fruit pulp industry, rich in total dietary fiber, particularly pectin. The aim of this study was to evaluate the influence of the addition of passion fruit fiber on the whey formation, rheological parameters, microstructure and sensorial characteristics of probiotic yoghurts. Skim milk bases enriched with 1% of passion fruit fiber or not were heat treated and inoculated with Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, and divided into four groups according to the probiotic strain added — Lactobacillus acidophilus strains L10 and NCFM and Bifidobacterium animalis subsp. lactis strains Bl04 and B94. Fermentations were performed until the pH reached 4.5. Rheological characteristics of yoghurts were determined by a rotational rheometer in two cycles of shear rate ranging from 0 to 15 s^? 1 in both upward and downward curves. Sensorial analysis of passion fruit fiber yoghurts, either without any probiotic or co-fermented by L. acidophilus L10 or B. animalis subsp. lactis Bl04, was evaluated against a control yoghurt without fiber. Photomicrographs of freeze-dried yoghurts were made by field-emission scanning electron microscope (SEM). Thixotropy of enriched yoghurts was higher than that of their respective controls in the two cycles of shear rate. Apparent viscosity was significantly higher in fiber yoghurts co-fermented by the lactobacilli than in their controls at the end of cold storage. Photomicrographs demonstrated that in passion fruit fiber yoghurts the casein gel was more compact and overlaid the fiber, while filaments of exopolysaccharides were more frequent in control yoghurts. Appearance, odor and color of the passion fruit fiber yoghurts received scores as ‘good’, and the intensity of the passion fruit flavor was considered weak by the sensory assessors. Results indicate that the passion fruit fiber is an almost neutral ingredient for the design of new high value-added yoghurt.     

Açai pulp addition improves fatty acid profile and probiotic viability in yoghurt

The effects of açai pulp addition and different probiotic bacteria on the fatty acid profile of stirred yoghurt were examined. Skim milk was divided into two groups: one containing açai pulp and another without the fruit. Batches were inoculated with yoghurt starter culture and divided into five groups according to probiotic addition. Counts of viable microorganisms were measured at days 1, 14 and 28 of cold storage. Fatty acid profile was determined by gas chromatography at day 1. Açai pulp favoured an increase in Lactobacillus acidophilus L10, Bifidobacterium animalis ssp. lactis Bl04 and Bifidobacterium longum Bl05 counts at the end of 4 weeks of cold storage. This study demonstrated that açai pulp addition increased monounsaturated and polyunsaturated fatty acid contents in probiotic yoghurt and enhanced the production of α-linolenic and conjugated linoleic acids during fermentation of skim milk prepared with B. animalis ssp. lactis Bl04 and B94 strains.     

Optimization of self-organizing polynomial neural networks

The main disadvantage of self-organizing polynomial neural networks (SOPNN) automatically structured and trained by the group method of data handling (GMDH) algorithm is a partial optimization of model weights as the GMDH algorithm optimizes only the weights of the topmost (output) node. In order to estimate to what extent the approximation accuracy of the obtained model can be improved the particle swarm optimization (PSO) has been used for the optimization of weights of all node-polynomials. Since the PSO is generally computationally expensive and time consuming a more efficient Levenberg–Marquardt (LM) algorithm is adapted for the optimization of the SOPNN. After it has been optimized by the LM algorithm the SOPNN outperformed the corresponding models based on artificial neural networks (ANN) and support vector method (SVM). The research is based on the meta-modeling of the thermodynamic effects in fluid flow measurements with time-constraints. The outstanding characteristics of the optimized SOPNN models are also demonstrated in learning the recurrence relations of multiple superimposed oscillations (MSO).