We have made the first detailed measurements of a diffusive supersonic radiation wave in the laboratory. A 10 mg/cm(3) SiO2 foam is radiatively heated by the x-ray flux from a laser-irradiated hohlraum. The resulting radiation wave propagates axially through the optically thick foam and is measured via time-resolved x-ray imaging as it breaks out the far end. The data show that the radiation wave breaks out at the center prior to breaking out at the edges, indicating a significant curvature in the radiation front. This curvature is primarily due to energy loss into the walls surrounding the foam.
Experiments have been conducted using laser-driven cylindrical hohlraums whose walls are machined from Ta2O5 foams of 100 mg/cc and 4 g/cc densities. Measurements of the radiation temperature demonstrate that the lower density walls produce higher radiation temperatures than the high density walls. This is the first experimental demonstration of the prediction that this would occur [M. D. Rosen and J. H. Hammer, Phys. Rev. E 72, 056403 (2005)10.1103/PhysRevE.72.056403]. For high density walls, the radiation front propagates subsonically, and part of the absorbed energy is wasted by the flow kinetic energy. For the lower wall density, the front velocity is supersonic and can devote almost all of the absorbed energy to heating the wall.
Polylactic acid (PLA) is a polymer that has good biocompatibility and excellent mechanical properties, and the modulus of elasticity and the thermoplastic ability can satisfy the need for the carrier material of cells to grow during bone tissue engineering, such as in regeneration and repair of bone and cartilage. Notably, PLA, which is a versatile material made from corn, sugar beet, or wheat, is an important material in the medical industry and has been used for over 30 years. PA is a biodegradable, bioresorbable polymer that can be assimilated by the body, and has important applications in sustained-release drug delivery systems. The mechanical properties and absorbability of PLA make it an ideal candidate for implants in bone and soft tissue, and for resorbable sutures [1][2][3][4][5]. The time required for resorbtion can range from a few weeks to a few years. In addition, the strength of surgical suture has to conform to certain diameters based on United States Pharmacopoeia (U.S.P.). The surgical suture must have good biocompatibility and be irritation free. As to the general thread, it is not necessary to consider the foregoing conditions, because it is it mainly used in dressing, industry and so on. 1 In early 1998, Lin et al. [6-9] fabricated a rotor-twister that twists multifilaments to increase yarn strength. Enormous advances have been made in recent years in the development of synthetic absorbable suture materials. In this study, PLA multifilament was twisted by a rotortwister to fabricate an absorbable surgical suture [10][11][12][13][14]. The PLA surgical suture composite with chitosan inhibits bacterial growth and promotes wound healing.Abstract Polylactic acid (PLA) is a polymer that has good biocompatibility, good biodegradability and excellent mechanical properties. The modulus of elasticity and the thermoplastic ability of PLA can satisfy the need for the carrier material of the cell to grow in bone tissue engineering, such as in regeneration and repair of bone and cartilage tissue. The PLA multifilament was twisted using different twisting parameters and a rotor-twister to fabricate United States Pharmacopoeia (U.S.P.) size 5-0 and 7-0 surgical sutures. The best tensile strengths were 3.1 and 12.3 N, and the coefficients of variation were 3.70% and 1.75%. The PLA suture was then scoured with 1 wt% sodium hydroxide to eliminate impurities, and the knot-pull strengths decreased to 1.66 and 6.84 N for 7-0 and 5-0 PLA sutures, respectively, but still conforming to the U.S.P. knot-pull strength standard. An in vitro hydrolysis test was performed at 37°C by immersing 5-0 PLA suture in physiological saline (0.9 wt% NaCl aqueous solution); the knot-pull strength decreased by 12% after 28 days.
Owing to growing demand for figure hugging and comfortable clothes made with stretchable fibers, spandex fibers are being used in underwear, diapers, hosiery, leisurewear, sportswear, jeans, and so on. In the present study a polyester core-spun yarn containing spandex fibers was made using a self-designed, multi-section drawing frame and a ring spinning frame. The mechanical properties of the core-spun elastic yarns were examined in various processing conditions. The analytical results show that when the main drawing ratio of the spandex fibers was either 2.2 or 2.7, the maximum breaking tenacity and elongation of the core-spun elastic yarns exceeded those in any other of the main drawing ratio conditions. Demand for elastic fibers is still growing. Consumption of elastic fibers reached 137,000 tons in Asia in 2001. Bayer in Germany was the first to develop polyurethane elastic fibers. US scientists began to develop the commercial applications of polyurethane from the 1940s. Soft and flexible elastomer or hard and abrasion-resistant materials can be fabricated with polyurethane. Spandex fibers are long-chain polymer fibers containing at least 85% segmented polyurethane [2]. Spandex fibers have been developed and produced by numerous companies, for example Spanzelle, Vyrene, Lycra, Glospan, etc.Various previous studies have reported the physical and chemical properties of spandex fibers. An elastic fiber has been characterized by high breaking elongation (exceeding 100% and generally 500 to 800%), a low modulus of elasticity (approximately 1/1000 that of a conventional "hard" fiber, such as nylon, cotton, and so on), and both a high degree and a high rate of recovery from 100% stretching (about 95%). Spandex fibers are resistant to hydrolysis (Lycra had power retention of 100% after boiling for 1 hour in water at pH 3 to 11). In addition the spandex fibers have good resistance to ultraviolet radiation, oxygen, heat, and oil [5]. Babaarslan described a method of producing a polyester/viscose core-spun yarn using spandex fibers. The spandex fibers (Lycra) were covered with polyester staple fibers of 38 mm and 1.3 dtex and viscose staple fibers of 38 mm and 2.4 dtex using a modified ring spinning frame with a positive feed roller system and a V-groove guide. The mechanical properties of the yarn and its uniformity were examined. The corespun yarns had lower tenacity than polyester/viscose staple yarns, but they had higher elongation [1]. Previously, several investigators have studied core-yarns containing a nylon or polyester filament [3,4,6,7].Nowadays, the textile industry is producing various core-spun yarns with spandex fibers of 22 to 156 dtex. The spandex fibers covered with staple fibers can be used for daily commodities and industrial products. This work made a polyester core-spun yarn from spandex fibers using a self-designed, multi-section drawing frame and a ring spinning frame. To keep their elas-
The next generation of large scale fusion devices--ITER/LMJ/NIF--will require diagnostic components to operate in environments far more severe than those encountered in present facilities. This harsh environment is the result of high fluxes of neutrons, gamma rays, energetic ions, electromagnetic radiation, and in some cases, debris and shrapnel, at levels several orders of magnitude higher than those experienced in today's devices. The similarities and dissimilarities between environmental effects on diagnostic components for the inertial confinement and magnetic confinement fusion fields have been assessed. Areas in which considerable overlap have been identified are optical transmission materials and optical fibers in particular, neutron detection systems and electronics needs. Although both fields extensively use cables in the hostile environment, there is little overlap because the environments and requirements are very different.
Elastic fibers are mostly used in elastic textiles. In this study, we develop a novel and original method to make highly elastic complex yarns using a self-designed, multi-section drawing frame and rotor twister. We examine the mechanical properties of these elastic complex yams. Their maximum breaking tenacity is high when the speed of the rotor is 4000 rpm and the wrapping count of the textured nylon filaments is either 2.5 or 3.0 turns/cm. These data are useful for the textile industry.
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