Energetic and exergetic parametric study of a SOFC-GT hybrid power plant

A parametric study is conducted on a hybrid SOFC-GT cycle as part of a national program aiming to improve the efficiency of the actual gas turbine power plants and to better undertake the future investigations. The proposed power plant is mainly constituted by a Gas Turbine cycle, a SOFC system, and an ammonia water absorption refrigerating system. An external pre-reformer is installed before the SOFC. Heat recovery systems are adopted to valorize the waste heat at the SOFC and GT exhausts. The gas from the SOFC exhaust is also used as additional supply for the combustion chamber. An extraction is performed on the gas Turbine in order to feed the SOFC cycle by thermal heat flux at medium pressure.The equations governing the electrochemical processes, the energy and the exergy balances of the power plant components are established. Numerical simulation using EES software is performed. The influences of key operating parameters, such as humidity, pre-reforming fraction, extraction fraction from the Gas Turbine and fuel utilization on the performances of the SOFC-GT hybrid system are analyzed. Obtained results show that the integration of the SOFC enhances significantly the hybrid overall cycle efficiency. The increase of the ambient temperature and humidity reduces the system efficiencies. The utilization factor has a negative effect on the SOFC temperature and voltage. That leads to a decrease in the power plant performances. While the pre-reforming fraction, has a positive effect on the indicated parameters.     

Salt effects on Origanum majorana fatty acid and essential oil composition

BACKGROUND: The effects of salt on the essential oil yield and fatty acid composition of aerial parts of two marjoram varieties were investigated. Plants with 6 leaves were treated with NaCl (75mM). RESULTS: Salt treatment led to a reduction in aerial part growth. Salinity increased the fatty acid content more significantly in Tunisian variety (TV) than in Canadian variety (CV). CV showed an increase in double‐bond index (DBI) and a decrease in malondialdehyde content under salt stress, while the opposite was observed in TV. The DBI was mainly affected by a strong reduction in oleic and linoleic acids in TV, whereas a strong stimulation of linoleic acid in CV was observed. Salt decreased and increased the essential oil yield in TV and CV respectively. The main constituents of the essential oil of TV were trans‐hydrate sabinene and terpinen‐4‐ol, which showed a significant decrease under salt stress. In contrast, the main constituents of the essential oil of CV were sabinene and trans‐hydrate sabinene, which showed a significant decrease and increase respectively under salt stress. CONCLUSION: Marjoram oil is a rich source of many compounds such as essential oils and fatty acids, but the distribution of these compounds differed significantly between the two varieties studied. Copyright © 2011 Society of Chemical Industry     

Intelligent and perceptual-based approach to musical instruments sound design

A novel, generic framework for musical instrument sound design is proposed. The framework uses an intelligent and perceptual based approach to address the two main problems in sound design - optimization of synthesis parameters and assessment of sound quality. A fuzzy model is used to capture and exploit knowledge of sound design from audio experts. A robust methodology, based on the ITU Perceptual Evaluation of Audio Quality (PEAQ) algorithm, is used for objective prediction of sound synthesis quality and sound quality assessment. The new framework makes it possible to automate the optimization of synthesis parameters. It also allows the designer to evaluate objectively, the perceptual impact of individual parameters on the final sound quality which is useful for benchmarking sound synthesis methods. The framework is generic and can be used for sound design for a wide range of musical instruments. We illustrate the use of the framework in pipe organ sound design. Results from this show that the new approach provides an important and useful alternative to existing methods.     

Magnetohydrodynamic co-rotating flow in a vertical cylindrical container

ABSTRACT

The effect of an external axial magnetic field on the liquid metal flow produced by co-rotation of the top and bottom disks in a vertical cylindrical container with a vertical temperature gradient is numerically analyzed. The governing Navier–Stokes, energy, and potential equations along with appropriate boundary conditions are solved using the finite-volume method. Comparisons with the previous results were performed and found to be in excellent agreement. It was observed that the Reynolds number is increased, and the axisymmetric basic state loses stability for circular patterns of axisymmetric vortices and spiral waves. In the mixed convection case the axisymmetric mode disappears, giving an asymmetric mode m = 1. It was also found that the primary thresholds, Re_cr corresponding to modes m = 1 and 2, increase with an increase in Hartmann number (Ha). We can therefore conclude that when the magnitude of the magnetic field exceeds a certain value, the instability becomes a steady bifurcation. Finally, stability diagrams were established according to the numerical results of this investigation. These diagrams show the evolution of primary thresholds as a function of Hartmann number for various values of Richardson number.     

Experimental analysis of the solidification of Sn–3 wt.%Pb alloy under natural convection

A quasi-two-dimensional solidification benchmark experiment with controlled thermal boundary conditions is proposed. The experiment consists in solidifying a rectangular ingot of Sn–3 wt.%Pb alloy using two lateral heat exchangers to extract the heat flux from one or two sides of the sample. The temperature difference between the two sides of the heat exchangers may vary from 0 to 40 K and the cooling rate from 0.02 to 0.04 K/s. This slow-cooling condition has been used to promote segregation formation. An array of fifty thermocouples placed on the corresponding sample walls is used to determine the instantaneous temperature distribution. During the solidification process, the temperature field is recorded versus time and analyzed. This makes it possible to estimate the change in temperature due to natural convection, the velocity field and the solidification macrostructure and segregation behavior. After each experiment, the segregation patterns are obtained by X-ray analysis and confirmed by eutectic fraction measurements. The local solute distribution is determined by means of induction coupled plasma analysis.     

Determination of ball mill residence time distributions form tracer data taken in closed-circuit operation

Based on a method which searches on the parameter values for models, the possible one- and two-detection system tracer methods for the determination of ball mill residence time distributions from data taken on closed-circuit recycle systems are treated. Mathematical relationships for the most promising approaches are developed for both methods. This includes deriving, demonstrating, and verifying (with existing simple analytical models of closed-circuit mills) analytical models of tracer input and output based on the use of tanks-in-series and finite stage models with the convolution integral principle. Simulated results for typical processes are given and non-linear search methods are described and demonstrated for determining mill residence time distribution model parameters.     

Essential oils and fatty acids composition of Tunisian and Indian cumin (Cuminum cyminum L.) seeds: a comparative study

BACKGROUND: Cumin (Cuminum cyminum L.) seeds of two geographic origins, Tunisia (TCS) and India (ICS), were studied regarding their fatty acid and essential oil composition. RESULTS: Oil yields were 17.77 and 15.40% for TCS and ICS respectively. Petroselinic acid (C18:1n‐12) was the major fatty acid in both varieties, with a higher proportion being found in TCS (55.90% of total fatty acids (TFA)) than in ICS (41.42% TFA). Moreover, the most predominant fatty acids were palmitic, petroselenic and linoleic acids, accounting for more than 91% TFA in both varieties. The unsaturated fatty acid content was high: 70.95% TFA in TCS and 62.17% TFA in ICS. Essential oil yields differed significantly (P < 0.05) between the two varieties: 1.21 and 1.62% for ICS and TCS respectively. A total of 40 compounds were identified, 34 of which were present in both essential oils. The two varieties displayed different chemotypes: γ‐terpinene/1‐phenyl‐1,2‐ethanediol for TCS and cuminaldheyde/γ‐terpinene for ICS. CONCLUSION: The study revealed that the biochemical composition of cumin seeds is origin‐dependent and that cumin seeds are rich in an unusual fatty acid, petroselinic acid. Besides, cumin essential oil is a rich source of many compounds, including cuminaldehyde and γ‐terpinene. The overall results suggest the exploitation of cumin seeds as a low‐cost renewable source for industrial processing in the fields of cosmetics, perfumes and pharmaceuticals. Copyright © 2011 Society of Chemical Industry     

Kinetic Investigation of Rosemary Essential Oil by Two Methods: Solvent-Free Microwave Extraction and Hydrodistillation

Depending on the use area of rosemary essential oil, pharmaceutical, cosmetic, or in food, the choice of both method and extraction time is fundamental, and the sample characterization is mainly based on comparing a few compounds that act as markers of a defined quality for a precise application. In the present work, the kinetic study of major components of Rosmarinus officinalis L. essential oils obtained by solvent-free microwave extraction (SMFE) and by hydrodistillation (HD) has been followed in order to determine the optimum extraction time of a defined bioactive molecule or its chemical family as well as its recommended extraction technique, either SFME or HD. The monoterpene hydrocarbons were nearly extracted completely in the first instants by SFME and progressively by HD. In contrast, the oxygenated monoterpenes were substantially extracted during the first minutes by HD and progressively by SFME. While the extraction of trans-caryophyllene was achieved at the beginning with SFME, it required more than 2 h with HD. A substantial gain in the extraction time has been obtained using SFME. Even though the essential oils extracted by SFME (30 min) and HD (3 h) are qualitatively similar, the oil fractions obtained during extraction time are very different.     

Effects of Processing on the Compositions and Physicochemical Properties of Fibre Concentrate from Cooked Fruit Pomaces

This study examined the influence of applied technologies namely desugaring, grinding, and bleaching on the compositions (cellulose, hemicelluloses, lignins, and pectins), physicochemical properties (water-holding capacity (WHC), swelling capacity (SWC), oil-holding capacity (OHC)) and the colour of dietary fibre (DF) during the production of fibre concentrates from unusual cooked apple and pear pomaces. Thermogravimetric analysis (TGA) and optical microscopy were also performed to monitor process-induced modification. All the processing conditions affected the compositions and physicochemical properties of DF. The bleaching treatment induced the greatest changes on DF producing yellow cellulose-rich fibre concentrates with improved WHC from 3.2 to 10.0 g/g and improved SWC from 4.0 to 8.8 ml/g. Otherwise, reduction of the particle size influenced hydration properties and colours of DF. WHC and SWC tended to increase with the particle size whereas smaller granulometric size increased the lightness of fibres. Desugaring increased the DF content in both pomaces by 1.2-fold with slight modification of apple insoluble dietary fibre ratio. Fibre concentrates had improved WHC and SWC up to 1.4-fold. All processes had no significant effect (p?<?0.05) on OHC of DF except with ultrafine apple fibre concentrates. Results showed that processing had overall positive effects on DF contents and hydration properties of pomaces from cooked fruits. Bleached fibre concentrates from apple pomace had the highest WHC (10.0 g/g) whereas that of pear had the highest fibre content (89.9 %). Fibres from cooked fruit pomaces may therefore be used as textural ingredients or functional foods.     

Context-based matching for Web service composition

In this paper, we propose a novel matching framework for Web service composition. The framework combines the concepts of Web service, context, and ontology. We adopt a broad definition of context for Web services, encompassing all information needed for enabling interactions between clients and providers. Context-based matching for Web services requires dealing with three major research thrusts: context categorization, modeling, and matching. We first propose an ontology-based categorization of contextual information in Web service environments. We then define a two-level mechanism for modeling Web service contexts. In the first level, service providers create context specifications using category-specific Web service languages and standards. In the second level, context specifications are enveloped by policies (called context policies) using WS-Policy standard. Finally, we present a peer-to-peer architecture for matching context policies. The architecture relies on a context matching engine, context policy assistants, and context community services. Community services implement rule-based techniques for comparing context policies. Recommended by: Zakaria Maamar