Combinatorial optimization model and MIP formulation for the structural analysis of conditional differential-algebraic systems

In this paper we consider the structural analysis problem for differential-algebraic systems with conditional equations. This problem consists, given a conditional differential-algebraic system, in verifying if the system is structurally nonsingular for every state, and if not in finding a state in which the system is structurally singular. We give a formulation for this problem as an integer linear program. This is based on a transformation of the problem into a matching problem in an auxiliary graph. We also show that the linear relaxation of that formulation can be solved in polynomial time. Using this, we develop a Branch-and-Cut algorithm for solving the problem and present some experimental results.     

Phenolic composition, isolation, and structure of a new deoxyloganic acid derivative from Dhokar and Gemri-Dhokar olive cultivars

Two rare olive cultivars, Dhokar and Gemri-Dhokar, growing in the south of Tunisia were investigated to identify their phenolic profile and evaluate their sugar content and antioxidant activity. The highest value of phenolic content was detected in Gemri-Dhokar cultivar extract (6.97 g gallic acid equivalents/kg of fresh olive). In addition, sugar content was quantified; glucose (45.17 g/kg of fresh olive) was the predominant sugar in Dhokar cultivar, followed by fructose (40.83 g/kg of fresh olive). The identification of phenolic compounds was based on separation by high-performance liquid chromatography equipped with a diode array detector followed by liquid chromatography-mass spectrometry analysis. In both cultivars, Oleuropein aglycon derivatives and elenolic acid were the main phenolic components. Oleuropeins were the major compounds quantified in the Gemri-Dhokar drupes olives (61.04 mg/100 g of fresh olive), while 0.25 mg/100 g were found in fresh Dhokar. A new iridoid compound, isolated as pure compound, was not previously reported in the literature. Its structure was established by spectroscopic analyses (NMR, UV, MS, and IR). DPPH, ABTS, and FRAP assays showed that the most important antioxidant capacity of olive extracts was found in with Gemri-Dhokar cultivar.     

Traction–separation laws for progressive failure of bonded scarf repair of composite panel

Repair of composites has become of considerable importance recently as modern commercial airliners employ much more composites in their airframes then previously. Major maintenance, repair, and overhaul (MRO) centers must contend with issues of damage tolerance, efficiency, integrity and cost of repairs. Computational methods have been developed to sufficiently sophisticated levels to aid in the design, evaluation and optimization of proposed repair schemes before they are implemented, potentially saving time and cost. In this paper, parametric studies on progressive failure analysis of a bonded scarf repair of a composite panel was performed. The study finds that finite element models with an appropriate material property degradation scheme using the micromechanics of failure criterion are able to predict the failure load of undamaged and damaged specimen. Results of the parametric studies on adhesive properties suggest that the failure stress of a repaired composite panel is more sensitive to the strength of the cohesive elements than to its toughness when a linear or trapezoidal softening traction–separation law is used, but the influence of adhesive strength is not significant when exponential softening traction–separation law is used.     

Catalyse redox homogene de reduction des p-toluenesulfonamides. Determination des parametres cinetiques et thermodynamiques

The redox catalysis of the reduction of tertiary p-toluenesulfonamides and gem-N-di-p-toluenesulfonamides by electrogenerated organic anion radicals, on mercury cathode, was studied by cyclic voltammetry and controlled-potential electrolysis in aprotic DMF. Tertiary tosylamides, not directly reducible by electrochemical means in presence of LiClO₄ as a supporting electrolyte, were cleaved by electrogenerated pyren anion radical. The new theoretical treatments, recently developed by Savéant and coworkers and extended to a SET-type mechanism and cyclic voltammetry results, allowed us to determine the rate controlling step of the catalytic process and to calculate the standard rate constant of the homogeneous electron transfer reaction and the standard potential in respect to the tosylamide anion radical formation.     

TRACER RESPONSE IN PARTIALLY FRACTURED RESERVOIRS

There is considerable interest in the petroleum industry to characterize partially fractured reservoirs and to develop an increased understanding of the physics of fluid flow in these types of reservoirs. This is because fractured reservoirs have different behavior and there exist a large number of these reservoirs that are not fully developed. This paper presents a numerical simulation study that was performed to investigate the effect of rock properties on the tracer response in partially fractured reservoirs using a finite difference numerical simulator. These properties include fracture intensity, fracture porosity and matrix permeability. The functional relationships between these parameters and the calculated effective permeabilities are also investigated. Several images, each with different probability of fracture intensity, were generated randomly. Numerical simulations of single-phase tracer transport were then performed in each of the generated fractured models. Results show that the fracture intensity, fracture porosity and matrix permeability have a significant effect on the tracer response in naturally fractured reservoirs. Depending on the reservoir properties, the results also show that the flow in partially fractured reservoirs can be either matrix-dominated or fracture-dominated. The characteristics of each regime and the conditions for its occurrence are presented.     

The morphology of limestone-based pellets prepared with kaolin-based binders

Modifications and pelletization of limestone were investigated in order to improve the utilization of CaO-based materials for different catalytic reactions and environmental applications. Attempts to purify the limestone by ion-exchange with CaCl₂ solution did not result in significant removal of impurities. On the other hand, acetification with 10 vol.% acetic acid enhanced pore surface area and pore volume of the sorbent by 42% and 3-fold, respectively. The acetification was found to widen small pores, and thus create a beneficial pore size distribution with more pores in the range of 25–100 nm. In order to utilize such powdered materials in fluidized beds, pelletization is the next step. Unfortunately, pelletization results suggested that natural kaolin is an unsuitable binder for preparing CaO-based pellets due to its negative impact on pellet morphology. By contrast, Al(OH)₃ binder obtained from kaolin leaching had a strong positive effect on the porous texture of the pellets, demonstrated by pore surface area and volume of 22.48 m² g⁻¹ and 0.051 cm³ g⁻¹ for 1 mm pellets with CaO/binder ratio of 5.5, compared to 10.92 m² g⁻¹ and 0.039 cm³ g⁻¹ for natural materials. The enhancement in pellet morphology is mainly attributed to transformation of Al(OH)₃ to the highly porous Al₂O₃ at high temperatures. Pellets synthesized from limestone modified with 10 vol.% acetic acid with Al(OH)₃ binder (ratio of 5.5) exhibited high pore surface area and volume, represented by 1.3-fold and 44% increase over those for natural limestone. It was concluded that the combination of acetified limestone with Al(OH)₃ binder is a promising approach for synthesis of CaO-based pellets with enhanced morphology.     

An adaptive CFAR embedded system architecture for target detection

This paper presents field-programmable gate array (FPGA)-based novel forward and backward automatic censored cell algorithms using a Nios II core processor embedded on a Stratix II FPGA programmable device. These algorithms were recently presented for target detection in a nonhomogeneous environment, and they operate in a complementary manner to allow for high-resolution target detection with a time constraint fixed below 0.5 μs. The ACOSD-based constant false alarm rate detector does not require any prior information regarding the background environment and employs statistical analysis to dynamically calculate the threshold at which the ordered cells under investigation are accepted or rejected. The advantages of the proposed system lie in its simplicity and short processing time while maintaining a low development cost. For a reference window of 16 range cells, the experimental results obtained using the Stratix II development kit demonstrate that the proposed architecture works properly with a processing speed of 100 MHz and an overall detector execution time of 0.11 μs for each range cell. The designed hardware, which is an example of system-on-chip architecture, was physically realized in a Stratix II FPGA device, and the results are presented and discussed.     

A novel hardware/software embedded system based on automatic censored target detection for radar systems

This paper presents a practical design exploration for a new application related to real-time, high-resolution target detection for radar systems. In this paper, an embedded architecture that combines the hardware and software components in a single platform is experienced using a field programmable gate array FPGA-based PC-board. The detection process utilises three techniques: namely, automatic censored ordered statistics detection (ACOSD), cell averaging (CA) and ordered statistics (OS) CFAR techniques, all of which operate in parallel to increase the accuracy of the detection and to reduce the false-alarm rate for both homogeneous and non-homogeneous environments. A prototype of the embedded system detector has been implemented for homogeneous and non-homogeneous environments on Stratix IV FPGA Board. The prototype operates at 200 MHz and performs real-time target detection with an execution delay of 0.27 μs, which is less than the critical time (0.5 μs) for high-resolution detection.     

In situ-based assessment of soil liquefaction potential–Case study of an earth dam in Tunisia

The present paper examines the evaluation of liquefaction potential of an earth dam foundation in Tunisia. The assessment of soil liquefaction was made using deterministic and probabilistic simplified procedures developed from several case histories. The data collected from the field investigation performed before and after the vibrocompaction are analyzed and the results are reported. The obtained results show that after vibrocompaction, a significant improvement of the soil resistance reduces the liquefaction potential of the sandy foundation. Indeed, in the untreated layers, the factor of safety FS drops below 1 which means that the soil is susceptible for liquefaction. However, in the compacted horizons, the values of FS exceed the unit which justifies the absence of liquefaction hazard of the foundation.