Search

Flexible supercapacitors (FS) are ideal as power backups for upcoming stretchable electronics due to their high power density and good mechanical compliance. However, lacking technology for FS mass manufacturing is still a significant obstacle.

A ferrimagnetic hexagonal Ising nanotube with spin-1/2 core and spin-5/2 shell is investigated using the mean field approximation (MFA) and the Monte Carlo simulation (MCS). More exactly, we have examined the effects of the exchange interactions and crystal field on the magnetic properties of the system. Our phase diagrams show the appearance of critical and compensation behaviors, as well as first-order phase transitions terminating at isolated critical end-points in the ferrimagnetic phase region at low temperatures. Furthermore, we have made a comparison with other studies of similar nanosystems.

La maladie mentale touche 48,9 % de la population marocaine. Malgré ce chiffre significatif, la maladie mentale reste méconnue. Les sujets qui souffrent de troubles mentales sont alors sujets de stigmatisation et de rejet social. Nous avons mené une étude descriptive au niveau du service de consultations de l’hôpital Ibn Nafiss de psychiatrie, du CHU de Marrakech. L’échantillon de notre étude est fait de 100 patients, stables sur le plan psychiatrique. Notre étude s’intéresse aux trois pathologies suivantes : le trouble dépressif, le trouble bipolaire et la schizophrénie. Nous nous sommes aidés d’un questionnaire, avec trois grandes parties : (1) profil sociodémographique du patient, (2) connaissance de la maladie et (3) évaluation du vécu de la stigmatisation. Nous avons noté que les extrêmes d’âges chez tous les patients sont de 19 à 68 ans, avec une moyenne de 38,5 et une nette prédominance féminine. 60 % de nos patients étaient des célibataires. Le niveau scolaire des deux tiers des patients soit 59 % ne dépassaient pas le primaire. Pour Les antécédents personnels médicaux, les pathologies endocriniennes étaient les plus représentés soit 18 % des cas, tandis que la dépression était l’antécédent familial psychiatrique le plus fréquent dans notre étude. D’après l’analyse des résultats du sondage, il apparaît que notre population souffre plus de discrimination et de divulgation de la part de leurs entourages qu’il soit familial, social ou professionnel avec moins d’estimation des aspects positifs.

•A mixed-spin (1/2, 3/2) Ising nanotube with core-shell structure is studied by MFA.•The effects of the exchange interactions and crystal field are investigated.•Typical phase diagrams are plotted in three planes.•The critical and compensation behaviors are highlighted.•First-order phase transitions occurred at low temperatures.

•The mixed spin-1/2 and spin-2 Ising model is studied by the mean field approach.•The ground-state phase diagram is constructed.•Two topologies of the phase diagrams have been presented and discussed.•The tricritical behavior is examined.•The compensation points are found in the system.

By the use of Monte Carlo simulation, we have investigated the phase diagrams and magnetic properties of a ferrimagnetic Ising multilayer system with mixed spins (1, 1∕2). The ground-state phase diagrams are first constructed for T=0K. To examine the influences of certain physical parameters of the system, namely the exchange interactions, the number of layers and the crystal field, we have studied the thermal behavior of the system magnetizations and the corresponding phase diagrams. The results obtained in this work show the existence of second- and first-order phase transitions and compensation temperatures. Moreover, we have investigated the hysteresis behavior, where the multi-loop phenomena are observed.

Using Monte Carlo simulation and mean field approximation, we studied the magnetic properties of spin-3/2 chain with hexagonal spin-1/2 shell and negative core-shell exchange coupling. The obtained results show that the spins 3/2 in the core have an important influence on the magnetic behavior of the system such as the appearance of compensation temperatures as well as first- and second-order phase transitions. Moreover, we investigated the effects of exchange interactions and anisotropy on the phase diagrams of the system.

Modification of the Egyptian Bentonite (EB) was carried out using organo-modifier namely; octadecylamine ODA. Before the modification, the cation exchange capacity (CEC) of the EB was measured, also it was purified from different impurities using HCl and distilled water. The Organo-bentonite OB was characterized using IR, XRD, and TEM. PU/ODA-B nanocomposites were prepared by in situ polymerization then characterized by XRD and TEM. An amount of ODA-B ranging from 0.25% up to 5% by weight was added to the polyol component of the resin before mixing with toluene diisocynate TDI. TEM showed that the nanocomposites achieved good dispersion in the polyurethane matrix. The mechanical, swelling and electrical properties of the nanocomposites were measured. The results indicate that the tensile strength of all the nanocomposites enhanced with the addition of OB compared with the pure PU. The crosslink density of the nanocomposites increases with increasing the content of OB. The Pool–Frenckel conduction mechanism predominates for all the nanocomposite samples and the blank one.

La présente étude a pour but la détermination de la qualité biologique des eaux d’un tronçon de l’oued Boufekrane au cours de l’année 2012 par l’utilisation de l’indice biologique global des réseaux de contrôle et de surveillance (IBG-RCS) normalisé. Les résultats obtenus au niveau des trois stations d’échantillonnage choisies pour la détermination de l’impact des rejets agricoles et urbains de la ville de Boufekrane sur la qualité biologique des eaux de cette rivière montrent la dominance des groupes faunistiques qui présentent des niveaux moyens à très tolérants vis-à-vis de la pollution. La diminution de la note d’indice biologique, subséquente à la diminution de la diversité des taxons, de la source d’eau en amont vers la station située à l’aval de la ville de Boufekrane, reflète la dégradation de la qualité des eaux à la suite de l’augmentation des apports anthropiques de la région.

The objective of this work is the study of the mechanical stress influence on the structural evolution. In particular, we studied the initiation and the plasticity mechanisms propagation of a semicrystalline polymer at small scales. The material is polylactic acid (PLA) film with average molar mass of 199 kg/mole and a thickness of 200 μm. The lamellate morphology of this material is very heterogeneous: in given area and packages of different orientation plates, they are spherulites α and β which have a different mechanical behaviour on a lamellate scale.

Purpose – The purpose of this paper is to present the problem of three-dimensional flow of a fluid of constant density forced through the porous bottom of a circular porous slider moving laterally on a flat plate. Design/methodology/approach – The transformed nonlinear ordinary differential equations are solved via the homotopy perturbation method (HPM) for small as well as moderately large Reynolds numbers. The convergence of the obtained HPM solution is carefully analyzed. Finally, the validity of results is verified by comparing with numerical methods and existing numerical results. Findings – Close agreement of the two sets of results is observed, thus demonstrating the accuracy of the HPM approach for the particular problem considered. Originality/value – Interesting conclusions which can be drawn from this study are that HPM is very effective and simple compared to the existing solution method, able to solve problems without using Padé approximants and can therefore be considered as a clear advantage over the N.M. Bujurke and Phan-Thien techniques. [ABSTRACT FROM AUTHOR]

In this paper, we will consider the Laplace decomposition method (LDM) for finding series solutions of nonlinear oscillator differential equations. The equations are Laplace transformed and the nonlinear terms are represented by He’s polynomials. The solutions are compared with the numerical (fourth-order Runge-Kutta) solution and the solution obtained by the Adomian decomposition method. The suggested algorithm is more efficient and easier to handle as compared to the numerical method. The results illustrate that LDM is an appropriate method in solving the highly nonlinear equations.

Abstract: In this paper, simultaneous position/force control of a closed-chain planar manipulator with the last link flexible is studied when the manipulator is in contact with an environment. The proposed manipulator consists of a flexible link connected to three rigid linkages whichare optimized for kinematic and force manipulability in the region of interest. The flexible link is modeled as a series of rigid links connected by virtual torsion springs. A hybrid position/force control algorithm is developed and implemented on the manipulator. Experimental results are presented to verify the performance of the controller. [Copyright &y& Elsevier]

This article elaborates on the numerical simulation of forced convective incompressi-ble flow in a horizontal plane channel and heat transfer over two isothermal tandem square cylinders. Finite-volume method was applied to discretize the momentum and energy equations. This study details the effects of S/H(gap between two squares), Reynolds number, and blockage ratio on the characteristics of flow field and heat transfer. The blockage ratios and Reynolds numbers were chosen between 12.5 to 50 per cent and 100≤Re≤300, respectively. Results are presented in the form of time-averaged streamlines, instantaneous contours of temperature and vorticity, and some characteristics of fluid flow and heat transfer such as time-averaged of the local and total Nusselt number, drag coefficient, and Strouhal number. The present results show that the gap spacing between squares at high blockage ratios does not have an obvious effect on heat transfer. On the other hand, this parameter plays a main role on the drag coefficient at a high value (S/H=4), which is because of the formation of the vortex cores in gap spacing and downstream of the second square. The heat transfer rate of the second square increases with the increase of S/H. Increasing the blockage ratio has a negative effect on convective heat transfer of the second square. With the vortex shedding in the gap spacing, the drag coefficient and the Nusselt number both increase in the second square in comparison to the first square.

We investigate the application of porous silicon (PS) in the field of the photovoltaic. In first step we realise a double porous silicon layer by electrochemical anodisation using two different current densities. The low current leads to a low porosity and during annealing, the recrystallisation of this layer allows epitaxial growth. The second current leads to a high porosity which permits the transfer onto a low cost substrate. During high temperature onto hydrogenation treatments of to passivate the structure and epitaxy in liquid phase, porous silicon is recristallized partially. In this work, a characterization by scanning electron microscopy informs us about the morphology of these porous layers.

Hydrogenated nanocrystalline silicon carbide (nc-SiC:H) thin films were prepared by reactive magnetron sputtering. Deposition was achieved in a plasma of argon (Ar) and an hydrogen (H2) gas mixture with various H2dilution percentages (10–80% H2) at a fixed substrate temperature of 500 °C. In order to describe the local bonding and the relative proportion of the different complexes formed during growth, the films were investigated by means of Fourier Transform Infrared absorption and Raman spectroscopy. Other structural features were analyzed by AFM measurements, electron diffraction and high resolution transmission electron microscopy observations. Optical and electrical properties of the films were also characterized. This study shows that hydrogen dilution plays an important role on the microstructure of the films as well as on their properties. The highest refractive index was obtained for a 60% ratio of hydrogen in the plasma and the highest dark conductivity found was 2.03 × 10−4 Ω−1cm−1. A close relationship between the Si-H bond content and the conductivity is confirmed.

Doppler tissue imaging (DTI) of mitral annular velocity is useful in assessing diastolic function. Most centers record at the septal or lateral segments of the annulus. Cardiopulmonary bypass produces changes in the motion of the interventricular septum. We evaluated the use of DTI after operation with and without cardiopulmonary bypass. 18 patients scheduled for cardiac surgery were prospectively examined. Nine underwent cardiopulmonary bypass. Nine had operation without bypass. DTI was performed 4 +/- 3 days before operation and again 31+/- 7 days afterwards. Early diastolic velocities of the lateral and septal segments of the mitral annulus were measured. Ejection fraction and transmitral diastolic early-to-late filling (E/A) ratios were also assessed. Early diastolic septal mitral annular velocity decreased (7.9 +/- 1.2 to 5.9 +/- 1.1 cm/s [P= .001]) after on-pump operation whereas lateral segment velocity remained unchanged (8.5 +/- 2.9 to 8.2 +/- 3.7 cm/s [P = .30]). E/A ratio did not change after operation (1.28 +/- 0.25 to 1.21 +/- 0.47 [P = .45]). In contrast, septal segment velocity in the off-pump group trended higher after operation (5.3 +/- 1.9 to 6.0 +/- 1.5 cm/s [P = .20]). Lateral segment velocity and E/A ratio also increased somewhat, but changes were not significant (6.2 +/- 1.7 to 6.7 +/- 2.9 cm/s [P = .15] and 1.1 +/- 0.5 to 1.2 +/- 0.4 [P = .13], respectively). Ejection fraction increased in both groups. Early diastolic velocity of the septal mitral annulus decreases after operation with cardiopulmonary bypass, but does not change after off-pump operation. In contrast, early diastolic velocity of the lateral segment is not affected by either on-pump or off-pump operation. Measuring lateral segment velocity is recommended for diastolic DTI after cardiopulmonary bypass, as septal DTI may incorrectly suggest diastolic dysfunction.

The influence of both beam irradiation and step cross-linking on high abrasion furnace (HAF) carbon black loaded natural rubber (NR) vulcanizates are reported. With irradiation, a higher cross-link density, ν, thermal conductivity, λ, and glass transition temperature, Tg, have been observed for such materials, as compared with the un-irradiated ones. There is also a decreased specific heat capacity, Cp. Meanwhile, the step cross-linking process has a slight effect on the cross-link density, glass transition temperature and thermal properties of these composites. The results of such changes in thermal conductivity are explained with the help of a simple modified model.

Investigations have continued for economic utilization of lignocellulosic waste, which represents one of the environmental problems facing third world countries. In this work, we intended to use old newsprint paper (ONP) as a filler in radiation shielding rubber composite.In this respect, the treatment of ONP with magnetite was carried out. The effect of incorporating untreated and treated newsprint in the rubber matrix on the swelling, electrical and mechanical properties, as well as gamma and neutron-shielding power has been studied. The changes in physico-mechanical properties of such composites by γ-irradiation were also investigated. This study led to conclusion that composite samples containing 6% wax and 54% newspaper or 18% wax and 42% modified ONP has the higher behavior to γ-irradiation dose. The incorporation of modified waste paper into the rubber matrix increases the conductivity and enhances the mechanical properties of produced composites. At higher non modified and modified newspaper loadings a serious loss of rubber elasticity were noticed.Composite with good attenuation properties for both gamma rays and thermal neutrons was produced from incorporation of 54% modified newsprint with 6% paraffin wax.

The influence of γ-irradiation on the electrical, swelling and mechanical properties of cross- linked butyl (IIR) rubber and ethylene propylene diene monomer (EPDM) and their blends have been investigated. The modulus increased, while the elongation at break decreased with irradiation. The gap width between carbon-carbon particles is found to be highly affected by the irradiation dose, which in turns influenced the electrical conductivity of these blends. The swelling equilibrium data in different solvents were analyzed by the Flory-Rehner equation to obtain estimates of the average molecular weight and cross-link density.

The influence of gamma-irradiation on the electrical conductance (Y) of natural rubber (NR)-butyl rubber (IIR) blend filled with different concentrations of general purpose furnace (GPF) carbon black has been studied during swelling in kerosene. Moreover, the degree of swelling and the penetration rate in kerosene for these rubber blends are also studied as a function of γ-irradiation dose. An attempt was made to calculate the carbon-carbon interspacing distance and its dependence on solvent penetration rate for unirradiated as well as irradiated samples.

Polypropylene/poly(methyl acrylate)-grafted glass wool (PMA-g-GW) mixes were prepared. The polymerization process was carried out using potassium persulfate (PPS) and PPS/acetone sodium bisulfite (ASBS) as a redox-pair initiation system at 60 and 70°C. The effect of using PPS or PPS/ASBS on the grafting percent and conversion percent reveals that the conversion percent values on using PPS as an initiator are higher than those of PPS/ASBS, while in the case of grafting, the inverse is true, that is, using PPS as an initiator gives grafting percent values lower than those that can be obtained using PPS/ASBS. The dielectric properties, thermal diffusivity, specific heat capacity, and thermal conductivity of PP loaded with modified glass wool as a function of different types and concentrations of initiators—used in the grafting polymerization process, namely, PPS and the redox initiating system—were also studied. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 723–732, 2003

Different amounts of boric acid (H 3 BO 3 ) were mixed with a conductive natural rubber (loaded with 40 phr of HAF carbon black) to get thermal neutron radiation shielding composites. It was found that the total macroscopic cross-section reaches 0.29 cm at 30 phr of H 3 BO 3 . The dependence of thermal and electrical properties of such composites on the concentration of H 3 BO 3 was also studied. Thermal oxidative aging was found to markedly affect the above properties.

Abstract: Oxide films grown on silicon in dry oxygen ambient at room temperature by negative point-to-plane corona discharge are investigated. A significant oxidation rate is observed at room temperature using this technique. Electrical properties of these room termperature grown oxides are examined. The capacitance-voltage measurements on the MOS structures fabricated from these oxides indicate a negative flat-band voltage of −1.5 V. Interface state density distribution in the range of 1010−1013 cm−2(eV)−1 is observed with a value of 2×1010 cm−2(eV)−1 at 0.17 eV above the valence band edge. Electrical conduction through the oxide is greater for negative values of applied gate bias voltages and the magnitude of conduction through the oxide decreases with decreasing current density during the corona discharge. Oxides grown at room temperature by this technique may find selective application in low temperature device processing.

Abstract: Free volume cavity sizes and fractions of epoxy specimens were determined using positron annihilation lifetime spectroscopy (PALS). PALS data were obtained before and after specimen water equilibration. Specimens were bisphenol A epoxide (B) and/or glycol epoxide (G) cured with a polyamide. Free volume sites increased linearly and cavity sizes decreased linearly with epoxide B:G ratio. Glass transition temperature (Tg) increased with epoxide B:G ratio. Water molecules in wet epoxy B filled approximately six percent of the cavities. Epoxy G cavity size increased 11.4% after water equilibrium and was ascribed to cavity expansion. PALS results differed for commercial corrosion inhibitors in wet and dry mixtures of these epoxides.

Positron annihilation in tin has been studied as a function of temperature. The Doppler broadening of the 511keV line has been measured with a germanium photon detector system. For annealed white tin the positron parameters show only a small increase on approach to melting. For the tin sample plastically deformed at 77 K, the grey-white phase transitions are strikingly manifested at 240 and 300 K.

La protamine est une protéine de bas poids moléculaire largement utilisée en chirurgie cardiovasculaire pour antagoniser l’effet de l’héparine, au décours de la circulation extracorporelle (CEC). Efficace et relativement sûre, la protamine peut, occasionnellement, être source d’une réaction anaphylactique systémique, responsable d’une instabilité hémodynamique, parfois réfractaire, mortelle. Le mécanisme exact de l’allergie à la protamine est encore mal élucidé. Des théories immunologiques et non immunologiques tentent de l’expliquer. Certains facteurs de risque prédisposent à ces réactions à la protamine. Leur identification en préopératoire devrait inciter des mesures préventives particulières. L’anesthésiste réanimateur et le chirurgien cardiovasculaire doivent être vigilants au moment de l’administration de la protamine. La reprise de la CEC peut être vitale devant un état de choc hémodynamique réfractaire aux thérapeutiques pharmacologiques.