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Evaluation of a multi-layer microbraided polylactic acid fiber-reinforced conduit for peripheral nerve regeneration

JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE 2009年第5期20卷 1175-1180页

作者： Lu, Ming-Chin Huang, Yen-Ting Lin, Jia-Horng Yao, Chun-Hsu Lou, Ching-Wen Tsai, Chin-Chuan Chen, Yueh-Sheng China Med Univ Sch Post Baccalaureate Chinese Med Taichung Taiwan China Med Univ Grad Inst Chinese Med Sci Lab Biomat Taichung Taiwan Feng Chia Univ Grad Inst Text Engn Lab Fiber Applicat & Mfg Taichung 40724 Taiwan Cent Taiwan Univ Sci & Technol Inst Biomed Engn & Mat Sci Taichung Taiwan I Su Univ Dept Biol Sci & Technol Kaohsiung Taiwan

We evaluated peripheral nerve regeneration using a biodegradable multi-layer microbraided polylactic acid (PLA) fiber-reinforced conduit. Biodegradability of the PLA conduit and its effectiveness as a guidance channel were examined as it was used to repair a 10 mm gap in the rat sciatic nerve. As a result, tube fragmentation was not obvious and successful regeneration through the gap occurred in all the conduits at 8 weeks after operation. These results indicate the superiority of the PLA materials and suggest that the multi-layer microbraided PLA fiber-reinforced conduits provide a promising tool for neuro-regeneration.

关键词： programmable logic arrays Peripheral Nerves multilayers reinforcing fiber poly(lactic acid) Nerve Regeneration

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HEURISTIC MINIMIZATION OF BOOLEAN RELATIONS USING TESTING TECHNIQUES

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IEEE TRANSACTIONS ON COMPUTER-AIDED DESIGN OF INTEGRATED CIRCUITS AND SYSTEMS 1992年第9期11卷 1166-1172页

作者： GHOSH, A DEVADAS, S NEWTON, AR UNIV CALIF BERKELEY DEPT ELECT ENGN & COMP SCIBERKELEYCA 94720 MIT DEPT ELECT ENGN & COMP SCICAMBRIDGEMA 02139

A Boolean relation is a one-to-many multioutput Boolean mapping and is a generalization of incompletely specified logic functions. Boolean relations arise in several contexts, for instance, in a finite state machine with sets of equivalent states. Minimization of Boolean relations is important from the point of view of synthesis, especially synthesis for testability. In this paper we describe a fast heuristic procedure for finding an optimal sum-of-products representation for a function compatible with a Boolean relation. Starting with an initial function compatible with the relation, a process of iterative logic improvement based on test generation techniques is used to derive a minimal function.

关键词： programmable logic arrays Minimization methods logic testing logic functions Boolean functions Design automation

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Integration of graphene in poly(lactic) acid by 3D printing to develop creep and wear-resistant hierarchical nanocomposites

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POLYMER COMPOSITES 2018年第11期39卷 3877-3888页

作者： Bustillos, Jenniffer Montero, Daniela Nautiyal, Pranjal Loganathan, Archana Boesl, Benjamin Agarwal, Arvind Florida Int Univ Dept Mech & Mat Engn Plasma Forming Lab Miami FL 33174 USA

Polylactic acid (PLA) and graphene reinforced polylactic acid (PLA-graphene) composites have been fabricated by three-dimensional (3D) fused deposition modeling (FDM) printing. Indentation creep resistance was analyzed in terms of the strain-rate sensitivity index of PLA (0.11) and PLA-graphene (0.21). Enhanced creep resistance in PLA-graphene is attributed to the restriction of the polymeric chains by graphene, caused by low strain rates identified during secondary creep. The tribological properties of PLA and PLA-graphene composites were evaluated by ball-on-disk wear tests. Wear resistance was increased by a 14% in PLA-graphene as compared to PLA. A two-stage coefficient of friction (COF) behavior has been observed for PLA-graphene. Initially, PLA-graphene exhibits a 65% decrease in COF as compared to PLA. During the second stage, PLA-graphene approached similar COF behavior and value of PLA (approximate to 0.58). PLA-graphene composites have shown significant improvement in creep and wear resistance demonstrating 3D printing to be a novel manufacturing route. POLYM. COMPOS., 39:3877-3888, 2018. (c) 2017 Society of Plastics Engineers

关键词： Strain rate sensitivity programmable logic arrays Wear resistance wear testing Creep resistance graphene Printing, Three-Dimensional strain rate poly(lactic acid)

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RESTRUCTURING AND logic MINIMIZATION FOR TESTABLE PLA

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IEEE TRANSACTIONS ON COMPUTER-AIDED DESIGN OF INTEGRATED CIRCUITS AND SYSTEMS 1993年第4期12卷 488-496页

作者： HWANG, GH SHEN, WZ NATL CHIAO TUNG UNIV INST ELECTRHSINCHUTAIWAN

Based on the testable design techniques proposed in [12], [13], we first derive a testability measure named UCP (Untestability Cube-number Product) which can accurately indicate the extra logic needed in testable PLA. Using UCP as a cost function, we have developed two new algorithms. The first one is a restructuring algorithm named REST, and the other is a logic minimizer for testable PLA named LMTPLA. REST can not only restructure a minimized PLA and improve its UCP, but also preserve the same logic function and almost the same chip area simultaneously. Thus, we can make the restructured PLA testable by taking less extra hardware. In order to get a minimum UCP, two new techniques are proposed: 1) Cube-Reduction, and 2) Cube-Partition. Using Cube-Reduction, we can make cubes far from the primes and increases the testability. By Cube-Partition, we may find out those hard-to-test cubes and partition them into smaller but easier-to-test cubes. LMTPLA is principally based on ESPRESSO-II and REST. Different from other logic minimizers, it can consider the testability at the logic minimization process. In order to minimize UCP as well as the number of product terms, four strategies are developed: 1) deleting the cubes with poor testability and reserving the cubes with good testability, 2) giving up the primes, 3) if necessary, partitioning the more untestable cubes into smaller cubes, and 4) deleting the procedures which are useless in LMTPLA. REST and LMTPLA have been implemented on SUN4/260 in C language. For 40 benchmark circuits, the hardware overheads required are reduced by about 30-40%.

关键词： logic testing Minimization programmable logic arrays Circuit faults Hardware logic design logic arrays Circuit testing Shift registers Decoding

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Crystallization and morphology of a polymer blend based on linear PPDO and branched poly(p-dioxanone)-poly(lactic acid) block copolymer with immiscible blocks

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POLYMER CHEMISTRY 2012年第9期3卷 2537-2544页

作者： Zeng, Ling-Xi Liu, Ming-Jing Chen, Si-Chong Zeng, Jian-Bing Wang, Yu-Zhong Sichuan Univ State Key Lab Polymer Mat Engn Natl Engn Lab Ecofriendly Polymer Mat Sichuan Ctr Degradable & Flame Retardant Polymer Mat ERCE Chengdu 610064 Peoples R China

The crystallization behaviour and morphology of a polymer blend based on branched poly(p-dioxanone)-poly(lactic acid) block copolymer (PLA-b-LCB-PPDO) and linear PPDO with immiscible PPDO and PLA blocks has been investigated. Although the PPDO and PLA blocks are immiscible with each other, an interesting interpenetrating spherulite morphology, which always occurs in miscible blends, was observed. Since the chemical bonding and branching molecular structure of the copolymer may resulted in a relatively small phase separation, the crystals of PPDO can nucleate and grew confined inside the matrix of pre-crystallized PLA spherulites. The morphologies of both PLA and PPDO crystals were significantly affected by the crystallization condition and process. Both the growth rate and nucleation rate of PPDO segments were enhanced rather than depressed under the confinement crystallization imposed by pre-crystallized PLA when relatively small amounts of PLA were added. The nucleation density of PPDO increased obviously with a small change in the self-nucleation temperature of PLA suggesting that the pre-crystallized PLA may serve as a heterogeneous nucleation agent for the crystallization of PPDO segments.

关键词： Copolymers branches programmable logic arrays Crystallization NUCLEATION DENSITY block copolymers Polymer blends

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Studies on morphologies and thermal properties of poly(lactic acid)/polycaprolactone/organic-modified montmorillonite nanocomposites

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POLYMER COMPOSITES 2008年第10期29卷 1145-1151页

作者： Ren, Jie Yu, Tao Li, Hang Ren, Tianbin Yang, Shuang Tongji Univ Inst Nano & Bio Polymer Mat Sch Mat Sci & Engn Shanghai 200092 Peoples R China

Poly(lactic acid)/organic montmorillonite (PLA/OMMT) nanocomposites were prepared via twin-screw extrusion. Montmorillonite (MMT) was firstly organically modified to improve the compatibility between polyester and MMT. The effects of ratio between PLA and OMMT and the addition of polycaprolactone (PCL), as a compatilizer, on the properties of PLA/OMMT nanocomposites were studied. The morphology and the properties of the nanocomposites were characterized by XRD, DSC, and TEM. Using OMMT, the intercalated structure was formed during the extrusion process and the OMMT interlayers space was enlarged. More OMMT content was apt to form thicker structure with more stacked individual silicate layers, which led to lower degree of crystallinity of PLA. It showed that 1 phr OMMT could result in the largest interlayers space and the best crystallization state. PCL can effectively increase the binding force between two phases and improve the order of the nanocomposites. In addition, the annealing after treatment can form regular structure and enhance the thermal properties of nanocomposites.

关键词： Organo-modified montmorillonite binding force programmable logic arrays extrusion process Polyesters TWO-PHASE montmorillonite Nanocomposites Crystallinity Mezzanines Thermal properties

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Physical Layer Authentication in Backscatter Communication: A Review

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IEEE WIRELESS COMMUNICATIONS 2024年第3期31卷 264-270页

作者： Yang, Yishan Yan, Zheng Zeng, Kai Wang, Pu Li, Jiajun Xidian Univ Xian Peoples R China George Mason Univ Fairfax VA USA

Backscatter communication (BC) has been introduced as a cutting-edge technology due to low cost and ultra-low-power consumption. However, its openness and broadcast nature bring severe security threats and vulnerabilities to BC systems. Physical layer authentication (PLA) is viewed as a supplement to cryptography-based authentication on backscatter devices (BDs) to provide enhanced security for BC by ensuring the eligibility of communication parties. Through feature extraction from signals as the fingerprint of a BD for authentication, computation and energy consumption at the resource-limited BD can be greatly reduced due to the avoidance of complex cryptography calculations. Although many existing works are devoted to exploiting PLA on BDs in BC systems, a technical overview of PLA in BC is still missing. Based on a comprehensive analysis of the security threats in BC systems, this article gives a review on PLA schemes in BC by employing a set of proposed criteria to analyze their performance. Based on the review, open issues are pointed out, with valuable suggestions on future research directions.

关键词： Scattering Physical layer Authentication Low-power electronics programmable logic arrays Cryptography Fingerprint recognition Feature extraction Energy consumption Costs

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Using synchroton radiation-based micro-computer tomography (SR μ-CT) for the measurement of fibre orientations in cellulose fibre-reinforced polylactide (PLA) composites

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JOURNAL OF MATERIALS SCIENCE 2014年第1期49卷 450-460页

作者： Graupner, Nina Beckmann, Felix Wilde, Fabian Muessig, Joerg Univ Appl Sci Bremen Biol Mat Grp Fac Biomimet 5 D-28199 Bremen Germany Helmholtz Zentrum Geesthacht D-21502 Geesthacht Germany

The present work deals with the measurement of fibre orientation angles in composites. A study by Bax and Mussig [1] investigated the mechanical properties (tensile and impact characteristics) of injection-moulded flax and Cordenka-reinforced polylactide (PLA) composites with fibre mass fractions between 10 and 30 %. Raising the fibre content from 10 to 30 % resulted in an increase in tensile characteristics, but it was noted that a reinforcement with 10 % flax fibres led to poorer tensile strength as compared to the neat PLA matrix. This behaviour was not expected and needs clarification. Therefore, test specimens with a fibre content of 10 and 30 mass % were examined for their fibre orientations and void content. For the investigations, microcomputer tomography images were created by monochromatic synchrotron radiation. Fibre orientation angles of these micrographs were determined with an adapted measuring mask of the Fibre-shape software. It could be shown that the fibre orientation in the composite is dependent on the fibre mass fraction and the type of fibre. No voids were found in all the investigated composites. The average fibre orientation angle of 10 % flax/PLA showed a larger deviation from the longitudinal axis of the test specimen than the other samples, and is made primarily responsible for the lower tensile strength of this composite.

关键词： synchroton micro-computer composites Micro computer Fiber orientation mass-ratio programmable logic arrays Cellulose fibers ORIENTATION ANGLE Composites Tensile Strength Fiber tensile specimen fiber flax Tomography crude fibre TENSILE PROPERTIES Polylactides

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Mechanical Properties, Crystallization Characteristics, and Foaming Behavior of Polytetrafluoroethylene-Reinforced Poly(Lactic Acid) Composites

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POLYMER ENGINEERING AND SCIENCE 2017年第5期57卷 570-580页

作者： Huang, An Kharbas, Hrishikesh Ellingham, Thomas Mi, Haoyang Turng, Lih-Sheng Peng, Xiangfang South China Univ Technol Natl Engn Res Ctr Novel Equipment Polymer Proc Guangzhou 510640 Guangdong Peoples R China Univ Wisconsin Madison Ctr Polymer Engn Madison WI 53706 USA

In this study, poly(lactic acid) (PLA)/polytetrafluoroethylene (PTFE) composites containing different amounts of PTFE were prepared by melt blending. The mechanical, crystallization, and foaming properties of the prepared composites were investigated. Tensile test results indicated that the mechanical properties of the composite with PTFE showed significant reinforcement and toughening effects. The average elongation-at-break of the composite increased by 72% compared with pure PLA. Scanning electron microscopy (SEM) showed that the PTFE elongated into fibrils during blending and formed a physical network of entanglements in the melt. Differential scanning calorimetry (DSC) also showed that PTFE had a significant nucleation effect on polymer crystals and greatly increased the crystallinity of the PLA matrix. Moreover, PTFE dramatically enhanced the melt viscosity of PLA, which was investigated by rheological tests. The injection molding foaming experiments revealed that adding 1 wt% PTFE had the most notable heterogeneous nucleation effect on foamed cells, with the cell size decreasing from 81.5 mu m for neat PLA to 25.2 mu m, and the cell density increasing from 1.34 x 10(8) cells/cm(3) to 2.53 x 10(9) cells/cm(3). (C) 2016 Society of Plastics Engineers

关键词： Composites programmable logic arrays Injection molding Melt viscosity Scanning Electron Microscope foaming properties Polytetrafluoroethylene physical network poly(lactic acid) Mechanical properties Foaming

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Development of Plasticized PLA/NH₂-CNTs Nanocomposite: Potential of NH₂-CNTs to Improve Electroactive Shape Memory Properties

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POLYMER COMPOSITES 2014年第11期35卷 2129-2136页

作者： Alam, Javed Alam, Manawwer Dass, Lawrence Arockiasamy Shanmugharaj, A. M. Raja, Mohan King Saud Univ King Abdullah Inst Nanotechnol Riyadh 11451 Saudi Arabia King Saud Univ Coll Sci Res Ctr Riyadh 11451 Saudi Arabia Kyung Hee Univ Coll Environm & Appl Chem Yongin Kyunggido South Korea Amity Univ Amity Inst Nanotechnol Noida 201303 Uttar Pradesh India

A polymer nanocomposite system comprising epoxidized soya oil plasticized-polylactic acid (PLA) and amine functionalized carbon nanotubes (NH2 functionalized-CNTs) has been prepared with the aim of producing electrically conductive PLA products suitable for shape memory (SM) applications. An influence of the addition of NH2 functionalized-CNTs on thermal, mechanical properties, and morphology development of plasticized PLA/NH2 functionalized-CNTs nanocomposite was investigated by differential scanning calorimetry, tensile tests, scanning electron microscope, and atomic force microscopy, respectively. In addition, electroactive SM behavior in resulting nanocomposite was evaluated by a bending test, and the recovery process was recorded with video camera. The results showed that SM behavior in nanocomposite was influenced by NH2 functionalized-CNTs weight percent in matrix. Nanocomposite with 5 wt% NH2 functionalized-CNTs showed optimum values of shape recovery due to its relatively high electrical conductivity, and an adequate degree of crosslinking between NH2 functionalized-CNTs and plasticized PLA matrix. However, more than 5 wt% loading of NH2 functionalized-CNTs dropped down an elongation at break, while tensile at break increased with the increasing of CNTs weight percent in matrix. Interesting point in this study is that all improvements in the properties of resulting PLA/NH2 functionalized-CNTs nanocomposite sheet were observed at very low filler content, while other literature reports where large quantities of CNTs were used. (C) 2014 Society of Plastics Engineers

关键词： Soybean Oil Nanocomposites weight percent Amines high conductivity Samarium Shape memory programmable logic arrays center-notch tensile specimen Atomic Force Microscopy

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