Anisotropic Chitosan Scaffolds Generated by Electrostatic Flocking Combined with Alginate Hydrogel Support Chondrogenic Differentiation

The replacement of damaged or degenerated articular cartilage tissue remains a challenge, as this non-vascularized tissue has a very limited self-healing capacity. Therefore, tissue engineering (TE) of cartilage is a promising treatment option. Although significant progress has been made in recent years, there is still a lack of scaffolds that ensure the formation of functional cartilage tissue while meeting the mechanical requirements for chondrogenic TE. In this article, we report the application of flock technology, a common process in the modern textile industry, to produce flock scaffolds made of chitosan (a biodegradable and biocompatible biopolymer) for chondrogenic TE. By combining an alginate hydrogel with a chitosan flock scaffold (CFS+ALG), a fiber-reinforced hydrogel with anisotropic properties was developed to support chondrogenic differentiation of embedded human chondrocytes. Pure alginate hydrogels (ALG) and pure chitosan flock scaffolds (CFS) were studied as controls. Morphology of primary human chondrocytes analyzed by cLSM and SEM showed a round, chondrogenic phenotype in CFS+ALG and ALG after 21 days of differentiation, whereas chondrocytes on CFS formed spheroids. The compressive strength of CFS+ALG was higher than the compressive strength of ALG and CFS alone. Chondrocytes embedded in CFS+ALG showed gene expression of chondrogenic markers (COL II, COMP, ACAN), the highest collagen II/I ratio, and production of the typical extracellular matrix such as sGAG and collagen II. The combination of alginate hydrogel with chitosan flock scaffolds resulted in a scaffold with anisotropic structure, good mechanical properties, elasticity, and porosity that supported chondrogenic differentiation of inserted human chondrocytes and expression of chondrogenic markers and typical extracellular matrix.     

Thermoplastic composite from innovative flat knitted 3D multi-layer spacer fabric using hybrid yarn and the study of 2D mechanical properties

Due to their improved mechanical properties, 3D multi-layer spacer fabrics could be used for lightweight applications such as textile-based sandwich preforms. Modern flat knitting machines using high performance yarns are able to knit complex 3D multi-layer spacer fabrics consisting of individual surface and connecting layers. This paper reports on the development of 3D flat knitted spacer fabric for 3D thermoplastic composites using hybrid yarns made of glass (GF) and polypropylene (PP) filaments. Moreover, mechanical properties of reinforcement yarns, 2D knit fabrics and 2D composites manufactured using various integration methods of reinforcement yarns were also studied. The integration of reinforcement yarns as biaxial inlays (warp and weft yarns) is found to be the best solution for knitting, whereas the tuck stitches show optimal results.     

Relation Between Mechanical Instabilities and Corrosion Sensitivity of Aluminum Body Cans Surfaces

Protection of Metals and Physical Chemistry of Surfaces - In this work we investigated the mechanical and corrosion behavior of aluminum can bodies. The results obtained show homogeneous...     

Comparative study and performance evaluation of central and distributed topologies of photovoltaic system

In this paper, we present a new alternative for improving both the performance of photovoltaic (PV) systems and the efficiency of the energy conversion by using different configuration of power converters. For this purpose, a comparative study between two configurations is carried out. The first configuration consists of a classical PV generator with a single centralized high power converter and the second one concerns a distributed topology. For this latter we use a certain number of PV strings with low power converters attached in series, in parallel or in a combination of series and parallel. Obviously the string topology has some advantages. Each power converter can control the power conversion of each module individually, which results in increased overall energy conversion of the entire system. The MPPT control system in this case can react effectively to atmospheric variations, to shading effect and to changes in the load. The PV system still operates even in case of failure on one of the power converters in a string. We simulated and compared the different conversion configurations in order to find the best one in terms of efficiency and produced energy. The obtained results are very interesting and can lead to optimal sizing and selection of best PV topology for a given application.     

Effect of the tank geometry on the storage and destocking of hydrogen on metal hydride (LaNi5H2)

The present numerical study aimed at studying the solid-statehydrogen storage and destocking in the LanthanumNickel (LaNi₅H₂) in a concentric triple-tube heat exchanger. Moreover, the influence of the thermal-reactor geometry for the storage and destocking hydrogen have been examined by changing the diameters of the heat exchanger. The performance of LanthanumNickel was compared with those of the hydride (MmNi₄.₆Fe₀.₄) and activated carbon. The flowing parameters: kinetics of hydrogen absorption/desorption, chemical reactions, enthalpy of fusion, equilibrium pressure, hydrogen concentration and the storage capacity were considered for calculating the terms of mass and energy equations. The hydride thermal and mass behaviour was integrated in the CFD Fluent with software (C++). A good agreement between the presented model and the literature experimental results was obtained. Additionally, the mentioned above parameters have shown a significant impact on the geometry of the reactor.     

Control and real time monitoring of less battery storage photovoltaic plants

Control, sizing and management of stand-alone or grid-connected photovoltaic (PV) plants are based on static methods, energy estimation and simulations of the PV systems in average conditions. Despite the fact that these approaches provide information about the expected performances, they do not perform an optimization of the PV plant; nor do they allow an optimal matching of PV-load association for the local climate conditions. Besides that, the problems of the PV cost, the maintenance and the battery replacements remain an obstacle for the development of PV plants.

To surmount these problems (storage, control, cost and efficiency), we have developed in our laboratory new prototypes of less battery storage systems (LBSS), which substitute the battery storage by a thermal storage for PV refrigeration or a hydraulic storage for PV pumping and water desalination (Cherif, A. (1994). Optimization and management of new PV refrigeration plant using latent storage. In Proceedings of the 12th E.P.S.E. Conference, Amsterdam, Vol. 1, HS Stephens & Associates, pp. 448–452). This approach will contribute to reduce the maintenance operations, the PV cost and the breakdowns of the battery and its regulator. We have introduced a new control strategy based on the performance of the DC/DC and DC/AC converters and the real time monitoring of the PV plant. This paper presents the technical and experimental aspects of these LBSS systems.     

Contrǒle hydrodynamique en convection mixte de l'épaisseur de dépǒts en phase gazeuse de semi-conducteurs sur des corps à symétrie de révolution

The authors solve using an finite difference method the equations of steady-state laminar boundary layer around a body of revolution (sphere, extended and flattened ellipsoids). Hydrogen gas at 25°C flows upward around the body. Its nose faces downward, the temperature of its surface is 500°C and it rotates about its vertical axe at a constant velocity. The variability of the physical properties of the fluid as a function of temperature is considered as well as the resulting natural convection. It is revealed that flow, heat and mass transfers depend of the physical properties of the gas. It is possible to control the development of thermal and diffusional boundary layers through the operational conditions, specially the contour of the body.     

纱罗织造——用新技术革新老工艺

纱罗组织由于织造复杂且产品收益率低,多年来一直未受重视,但近年来纺织工程的发展重振了纱罗组织的生产.报道了为揭示纱罗织物的潜力和织造设备对纱罗织物各参数的影响所做扎实的研究工作,这些工作是扩大纱罗织物生产的基础.     

On a Hybrid Preamble/Soft-Output Demapper Approach for Time Synchronization for IEEE 802.15.6 Narrowband WBAN

In this paper,we present a maximum likelihood(ML) based time synchronization algorithm for Wireless Body Area Networks(WBAN).The proposed technique takes advantage of soft information retrieved from the soft demapper for the time delay estimation.This algorithm has a low complexity and is adapted to the frame structure specified by the IEEE 802.15.6standard[1]for the narrowband systems.Simulation results have shown good performance which approach the theoretical mean square error limit bound represented by the Cramer Rao Bound(CRB).     

ITMA 2007: 针织技术的创新和发展趋势

概述了2007年世界纺机展中针织技术的创新及产品发展趋势,重点介绍全球几大著名针织设备生产商的最新产品.