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A numerical study of viscous dissipation effect on non-Newtonian fluid flow inside elliptical duct
No full textLaminar heat transfer inside duct with elliptical cross section, subjected to uniform wall temperature is studied by taking into account the viscous dissipation. The temperatures distributions are evaluated numerically by using a dynamic Alternating Direction Implicit method (dADI). Nusselt number (Nu) is presented graphically for various Brinkman number (Br) and aspect ratio for a non-Newtonian fluid described by the power law model. The results obtained showed a good agreement with those found in the literature for fluid flow in circular cross section ducts and in elliptical cross section without viscous dissipation effects. It is shown that in the fully developed region and for Br – 0, Nusselt number has a fixed asymptotic value independent of Brinkman number (Br). In the thermally developing region, it is observed a single fixed point independent of heating or cooling condition which the numerical value is equal to the asymptotic Nusselt number. Another relevant feature is that in the fully developed region, the Nusselt number increases with the aspect rati
Production of biosurfactant on crude date syrup under saline conditions by entrapped cells of Natrialba sp. strain E21, an extremely halophilic bacterium isolated from a solar saltern (Ain Salah, Algeria)
No full textA bacterial strain E21 was isolated from a sample of water collected in the salt lake located close to Ain Salah, Algeria. The analysis of 16S rRNA gene sequence had indicated that the strain had 93 % sequence similarity with the genus Natrialba sp. strain E21 (Gen- Bank, FR750525.1) and was considered extremely halo- philic. Production of biosurfactant by the strain E21 with free and entrapped cells was investigated using soluble starch in the saline conditions. Biosurfactant synthesis was followed by measuring the surface tension and emulsifying index 9 days under optimal conditions (40 C, pH 7). Some diffusional limitations in alginate and agar beads affected the kinetics of biosurfactant production when compared to that obtained with free cells culture. The minimum values of surface tension were 27 and 30 mN m - 1 achieved after 9 days with free and immobilized cells, respectively, while the corresponding maximum E24 values were 65.3 and 62.3 %, respectively. The re-use of bacterial cells along with the limited cell losses provided by the immobilized system might lead to significant reduction of the biosur- factant production cos
A statistical-based approach for fault detection in a three tank system
No full textFault detection in stochastic dynamical systems is usually carried out by the generation of residuals directly reflecting the magnitude of the faults. For this purpose, faults indicator is used to evaluate possible deviations from the normal operating conditions and the measurements of the system. This evaluation is often very difficult to implement in the multi-faults case. This article aims to demonstrate the efficiency of the coefficient of variation (CV) in detecting single and multi-faults in a multivariable laboratory three tank system DTS-200. The performance of the detection algorithm is based on the computation of the confidence intervals (CIs) which provide an estimate of the amount of error in the considered data and characterise the precision of the computed statistical estimates. The data variability may result from random measurement errors caused by the system parameters uncertainties, internal and external noises, and measuring instrument, which are not usually accurate. The CIs make the CV less sensitive to parameter uncertainties and to measure noises. The robustness and accuracy of the CV are shown in a healthy mode and various faulty situations in an entirely uncertain environmen
Effect of the heat curing on strength development of self-compacting mortars containing calcined silt of dams and ground brick waste
No full textThe strength development of self-compacting mortars (SCM) containing calcined silt (CS) and ground brick waste (GWB) was investigated. The variables are the nature of addition (CS and GWB) in the binder and the heat curing at different temperatures (20 ºC and 60 ºC) at 7 and 14 days of curing. Two temperatures 20 and 60 ºC were applied to samples with intermediate levels (depending on the drying method applied to precast) for 18 hours in total. In this study, a Portland cement (CEMII), Calcined silt (750 ºC for 5 hours), ground waste brick, were used in the binders of SCM. The results show that the compressive strength to 14 days of mortars, increases with annealing (60 ºC) compared to that measured at 20 ºC. Also, values of compressive strength of mortars at 14 days that are close to those obtained without 28 days curing treatment. Indeed, a strength gain of about 20.5% and 27.3% was obtained respectively for the SCM with GWB and the SCM with CS. However, a small change in mass recorded for both types of mortar
Experimental study of boiling heat transfer on multiple and single nucleation sites using a boiling-meter
No full textThe general objective of this study is to contribute to a better understanding of heat transfer in a nucleate boiling regime. The aim is to determine the heat transfer characteristics under controlled operating conditions (thermodynamics of the fluid, noncondensable gas, surface state). Experimental investigations have been carried out in natural convection and nucleate boiling regimes. An experimental device was realized to perform boiling experiments using a boiling-meter, allowing investigations for different orientations of the wall. The boiling-meter is designed to investigate boiling for single and multiple nucleation sites. The purpose of this paper is to detail the experimental setup as well as the boiling-meter. This device allows the determination of the temporal heat transfer characteristics evolutions. In particular, this new device allows bringing to light the phenomenon of nucleation, growth, and detachment of generated vapor bubbles on a single artificial nucleate site, as well as for multiple natural nucleation sites. First results of the influence of the orientation of the heating wall for multiple and single nucleation sites on heat transfer are presented and analyze
Using a DFIG-based wind farm for grid node reactive power compensation
No full textGrid nodes voltages are not allowed to deviate excessively from nominal value. Appropriate measures should be taken to prevent such a deviation. The voltage difference between two nodes is strongly affected by reactive power flow. In contrast to frequency control, node voltage control must be achieved locally. This article investigates the use of a wind farm based on a doubly fed induction generators (DFIG) for reactive power compensation of a grid node. A wind speed variation sample is applied to the model of a wind power unit. The power flow between the stator of the DFIG-based wind power unit and the grid is controlled by using the decoupled active and reactive power vector control method. The limits or capacity of the stator and power converters to consume or provide reactive power are discussed. SIMULINK software has been used for the simulation of the syste
دور القضـاء فـي قضـايا التحكيـم التجاري الدولي
No full textص. : إيض. ؛ 30 سم 131ويعتبر التحكيم التجاري الدولي عنصرا أساسيا في عقود الاستثمار الأجنبية، فجميع هذه العقود لا تكاد تخلو من شرط إحالة جميع منازعاتها إلى التحكيم التجاري، فالمستثمر الأجنبي يصر دائما على إضافة شرط التحكيم نظرا للمزايا التي يوفرها التحكيم إليه، والدولة المضيفة للاستثمارات تجد نفسها دائما ملزمة بقبول شرط التحكيم، فبدون إضافة هذا الشرط، لا تتمكن من جذب عقود الاستثمارات الأجنبية. ومهما يكن، فإنه تبقى الرقابة القضائية لضمان حسن سير التحكيم في تسوية المنازعات الناشئة عن عقود الاستثمارات قائمة بحيث يمنح الصيغة التنفيذية على الحكم التحكيمي بعد التأكد من سلامة العملية التحكيمية واحترامها للمقتضيات القانونية, لأن عملية منح الصيغة التنفيذية لأحكام التحكيم الدولية تكتسب طابعا خاصا بالنظر إلى كونها تمس بمبدأ السيادة الوطنية وتتأثر بنظرة القاضي الوطني إليها، في حين أن منطق التجارة الدولية الحديث هو نتاج غربي بلوره نظام عالمي جديد يطمح إلى تفادي منطق الحواجز والحدود الاقتصادية بين الدول، كما يسعى إلى أن ترقى فيه مؤسسة التحكيم التجاري الدولي كأداة فاعلة، علما أن سبب الإقبال على الوسائل البديلة لحل المنازعات ذات الارتباط بالاستثمار هو تعقيد الأنظمة القانونية المختلفة لاسيما في ميدان تنازع القوانين، الأمر الذي لم يسمح للقانون الدولي الخاص بالرد على حاجيات التجارة الدولية ويزيد من حدة هذا القصور ثقل وطأة قانون القاضي سواء فيما يتعلق بالإجراءات وتحديد التكييف أو التعسف في استخدام الدفوع المتعلقة بالنظام العام. إلا أن هذا لا يعني مطلقا استقلال القضاء عن التحكيم أو عدم خضوع هذا الأخير لرقابة القضاء، ولكن المشكلة تكمن في مدى استقلال التحكيم أو خضوعه للرقابة من جانب القضاء العادي، وهذا ما تمت معالجته في هذا البحث. وقد ساير المشرع الجزائري هذا الاتجاه في توسيع رقابة القضاء على عملية التحكيم في القانون رقم 08- 09 المؤرخ في 25 فبراير2008 المتضمن قانون الإجراءات المدنية والتجارية، كما سايره المشرع المصري كذلك في القانون رقم 27 لسنة 1994 في شأن التحكيم المواد المدنية والتجارية. والرقابة التي نهدف إليها، هي الرقابة القضائية وحدها والتي تضفي بظلالها على عملية التحكيم كلها منذ اتفاق التحكيم إلى صدور الحكم وتنفيذه، وإن كان الغالب الأهم أن الرقابة لا تثار إلا في نهاية الإجراءات عندما يطلب أحد أطراف خصومة التحكيم الحصول على أمر بتنفيذ حكم المحكمين، أو عند طلب إبطال هذا الحكم، مع العلم أنه قد لا تثار هذه الرقابة مطلقا إذا لم يطلب أحد الخصوم أو هيئة التحكيم طلب المساعدة من القضاء أثناء سير الخصومة أو إذا لم يطعن أحد الخصوم في حكم المحكمين بالبطلان أو لم يمانع في تنفيذه في المرحلة اللاحقة لصدوره. المتفق عليه أنه إذا كان الاتفاق على التحكيم يمنع قضاء الدولة من نظر النزاع موضوع التحكيم، فإنه لا يمنع هذا القضاء من ممارسة سلطته في الرقابة على أعمال المحكمين من خلال مجالين: أولهما: أن حكم المحكمين لا ينفذ إلا بأمر يصدر بتنفيذه من قضاء الدولة بعد إيداعه وثانيهما: أن قضاء الدولة هو المختص بنظر الطعون المقدمة على أحكام المحكمين. وعلى ضوء ما تقدم، وإذا كانت رقابة قضاء الدولة على أعمال المحكمين الهدف منها تدعيم دور التحكيم والتأكد من عدم انحرافه عن أدائه لوظيفته باعتباره منهجا في أداء العدالة كقضاء الدولة, فقد رأيت أن يكون موضوع بحثي هذا, هو الكشف عن حقيقة دور قضاء الدولة فـي قضايا التحكيم التجاري الدولي, وذلك من خلال تحديد مدى سلطة ورقابة قضاء الدولة على أعمال المحكمين، ومن تأهيل لمدى ملاءمتها كما وكيفا، بصفة خاصة على ضوء الهدف من التحكيم باعتباره قضاء خاصا موازيا لقضاء الدولة وعلى ضوء ما تقتضيه حسن السياسة التشريعية من أن تكون طرق الطعن في حكم المحكمين تتلاءم مع الطبيعة الخاصة لهذا الحكم، كما يجب أن تكون محدودة بالقياس إلى أحكام قضاء الدولة، باعتبار أن التحكيم وسيلة لحل النزاعات تتصف بالسرعة والبعد عن الإسراف في الشكليا
Diversity of microbial communities in production and injection waters of algerian oilfields revealed by 16S rRNA gene amplicon 454 pyrosequencing
No full textThe microorganisms inhabiting many petroleum reservoirs are multi-extremophiles capable of surviving in environments with high temperature, pressure and salinity. Their activity influences oil quality and they are an important reservoir of enzymes of industrial interest. To study these microbial assemblages and to assess any modifications that may be caused by industrial practices, the bacterial and archaeal communities in waters from four Algerian oilfields were described and compared. Three different types of samples were analyzed: production waters from flooded wells, production waters from non-flooded wells and injection waters used for flooding (water - bearing formations). Microbial communities of production and injection waters appeared to be significantly different. From a quantitative point of view, injection waters harbored roughly ten times more microbial cells than production waters. Bacteria dominated in injection waters, while Archaea dominated in production waters. Statistical analysis based on the relative abundance and bacterial community composition (BCC) revealed significant differences between production and injection waters at both OTUs 0.03 and phylum level. However, no significant difference was found between production waters from flooded and non-flooded wells, suggesting that most of the microorganisms introduced by the injection waters were unable to survive in the production waters. Furthermore, a Venn diagram generated to compare the BCC of production and injection waters of one flooded well revealed only 4% of shared bacterial OTUs. Phylogenetic analysis of bacterial sequences indicated that Alpha- , Beta- and Gammaproteobacteria were the main classes in most of the water samples. Archaeal sequences were only obtained from production wells and each well had a unique archaeal community composition, mainly belonging to Methanobacteria , Methanomicrobia , Thermoprotei and Halobacteria classes. Many of the bacterial genera retrieved had already been reported as degraders of complex organic molecules and pollutants. Nevertheless, a large number of unclassified bacterial and archaeal sequences were found in the analyzed samples, indicating that subsurface waters in oilfields could harbor new and still-non-described microbial specie
Fractal analysis based on the continuous wavelet transform and lithofacies classification from well-logs data using the self-organizing map neural network
No full textThe main goal of this paper is to show that the fractal analysis based on the continuous wavelet transform is not able to improve lithofacies classification using the self-organizing map (SOM) neural network model from well-logs data. The proposed idea consists to inject many inputs in SOM neural network machines and to choose the best map. These inputs are: data set 1: the five raw well-logs data which are: the gamma ray, density, neutron porosity, photoelectric absorption coefficient and sonic well-log; data set 2: the estimated Hölder exponents using the continuous wavelet transform of the data set 1; data set 3: data set 1 and the three radioactive elements concentrations; data set 4: the estimated Hölder exponents of the data set 1 and the Hölder exponents of the radioactive elements concentrations; data set 5: the estimated Hölder exponents of the data set 1 and the three radioactive elements concentrations logs. Application of the proposed idea at two boreholes located in the Algerian Sahara shows that the Hölder exponents estimated with the continuous wavelet transform as an input of the SOM neural network are not able to give geological details. However, the raw well-logs as an input give more details and precision especially when they are enhanced with the natural gamma ray spectrometry dat
Particleboards production from date palm biomass
Get PDFDate palm biomass is a renewable natural resource that has not widely been utilized in industry. The objective of this study was to examine some chemical properties of date palm trunk and rachis (holocellulose, cellulose, lignin and extractives) and to evaluate their suitability to produce composite panels. Particleboards were produced using trunk and rachis as an alternative raw material for forest products industry in the presence of two types of polycondensation resins (phenol–formaldehyde and melamine urea–formaldehyde) which were selected as binding agents. The panels were tested for their physical (water absorption and thickness swelling) and mechanical (modulus of rupture, modulus of elasticity and internal bond strength) properties. The internal bond strength of date palm trunk and date palm rachis based boards met the requirements of the general purpose product standards (EN 312) at 0.70 g/cm3 density. The panels made with phenol–formaldehyde resin showed better performance with respect to the panels made with melamine urea–formaldehyde. In addition, the particleboard made with date palm trunk particles had better quality compared to the particleboard made from date palm rachis particles. Based on preliminary results of this work, raw materials from date palm trunks and rachis can have a promising potential in the manufacture of particleboards and as a substitute for wood in board productio