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Influence of equal channel angular pressing on the properties of polylactic acid

POLYMER ENGINEERING AND SCIENCE 2018年第5期58卷 665-672页

作者： Li, Hong Wu, Zhemin Xue, Feng Bai, Jing Chu, Chenglin Southeast Univ Sch Mat Sci & Engn Nanjing 211189 Jiangsu Peoples R China Jiangsu Key Lab Adv Metall Mat Nanjing 211189 Jiangsu Peoples R China

The effects of equal channel angular pressing (ECAP) on the microstructures, mechanical, and degradation properties of polylactic acid (PLA) were investigated. The controllable microstructures of PLA can be achieved by a 3D rotary-die through various combinations of passes and routes (A and C). For A route, sample was extruded sequentially through four channels in a plane with compressive or tensile stress alternatively imposed on the two major load bearing surfaces, while for C route, sample was extruded only in two vertical channels back and forth with constant compressive or tensile stress imposed on the two major load bearing surfaces. The strong preferential orientation of (200) plane parallelled to the axis direction was formed under the conditions of A route for two passes and C route for three passes. There was a more uniform distribution in the microhardness for the sample extruded by two passes under C route. Meanwhile the sample had higher bending strength after two passes under A route, and better facture toughness after three passes under C route. The reductions in mass and bending strength of PLA processed by ECAP were more obvious than those of original sample in phosphate-buffered solution at 37 degrees C for 16 weeks. POLYM. ENG. SCI., 2017. (c) 2017 Society of Plastics Engineers

关键词： Routes Extruded Weight-Bearing programmable logic arrays COMPACTION PROPERTIES Equal channel angular pressing electronic circuit analysis program bending strength Carbon gaps (geology) poly(lactic acid) Tensile stress

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Insight on the striking influence of the chain architecture on promoting the exfoliation of clay in a polylactide matrix during the annealing process

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SOFT MATTER 2013年第45期9卷 10891-10898页

作者： Yao, Kun Wen, Xin Tan, Haiying Gong, Jiang Zheng, Jun Zhao, Wei Wang, Yang Cui, Dongmei Na, Hui Tang, Tao Changchun Inst Appl Chem State Key Lab Polymer Phys & Chem Changchun 130022 Jilin Peoples R China Univ Chinese Acad Sci Beijing 100039 Peoples R China Jilin Univ Coll Chem Alan G MacDiarmid Inst Changchun 130012 Peoples R China

The influence of the topological structure of polylactide (PLA) chains on the microstructure of PLA-organically modified clay (OMC) nanocomposites was studied. Here, an OMC with a hydroxyl group-containing modifier (I.34TCN) was used as the nanofiller. According to the results from the XRD and TEM measurements, the change in the dispersed states of the OMC with star-shaped PLA (PLA3-x) was totally different from that with linear PLA (PLA1-1) during annealing at high temperature. A transition from the intercalated to the exfoliated structure appeared in the simple PLA3-x/OMC mixture during the annealing process, but the intercalated structure was retained in the PLA1-1/OMC system. The enhanced exfoliation of the OMC in the PLA3-x matrix was attributed to the spatial limitation of the star-shaped PLA3-x, which made the intercalated interlayer swell. As a result, the concentration of PLA3-x chains within the layers of the OMC was lower than that of the outside bulk, and so, more PLA3-x chains diffused into the interlayers of the clay until the clay sheets separated (exfoliation state). Furthermore, the exfoliation extent of the OMC in the star-shaped PLA3-x/OMC composites strongly influenced the glass transition temperature (T-g) of star-shaped PLA3-x.

关键词： Insight striking influence chain architecture programmable logic arrays annealing Insight clays Polylactides open method of coordination

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GAMMA-RAY IRRADIATION EFFECTS IN LIGHT-EMITTING-DIODES AND PHOTODIODES FOR FIBER OPTICS

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IEEE TRANSACTIONS ON NUCLEAR SCIENCE 1985年第6期32卷 4453-4460页

作者： TAKAGI, T NODA, J Ilarali Electrical Communication Laboratory Nippon Telegraph and Telephone Corporation Ibaraki Japan Ibaraki Electrical Communication Laboratory Hippon Telegraph and Telephone Corporation Tokai Ibaraki-ken 319-11 Japan

Permanent damage induced in AlGaAs LEDs, GaInAsP LEDs, Si PDs, and Ge PDs has been investigated for gamma-ray doses up to 108 rad(Si). Degradation in light output accompanied by a decrease in forward voltage and in increase in reverse current are induced above 107 rad(Si) for both AlGaAs and GaInAsP LEDs. Device recovery can be produced by applying a large forward current. Sensitivity remains constant up to 108 rad(Si) for both Si and Ge PDs. The dark current increment after irradiation is three orders of magnitude higher for Ge PDs than for Si PDs. Contribution of the DLTS-detected traps to the dark current is negligible.

关键词： Light emitting diodes Photodiodes Optical fibers Indium phosphide programmable logic arrays Linear discriminant analysis Instruction sets

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Crystallization and Biodegradation of Polylactide/Carbon Nanotube Composites

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POLYMER ENGINEERING AND SCIENCE 2010年第9期50卷 1721-1733页

作者： Wu, Defeng Wu, Liang Zhou, Weidong Zhang, Ming Yang, Tao Yangzhou Univ Sch Chem & Chem Engn Jiangsu 225002 Peoples R China Prov Key Labs Environm Mat & Engn Jiangsu 225002 Peoples R China Yangzhou Univ Testing Ctr Jiangsu 225002 Peoples R China

The crystallization behavior of polylactide/carbon nanotube composites was studied using differential scanning calorimeter and polarized optical microscope. The nucleation mechanisms and the crystallization kinetics were explored. The results show that the presence of nanotubes has nucleating effect on both the melt crystallization and the cold crystallization of PLA. However, the nanotubes also play the role of physical barrier, impeding the crystal growth dynamically. In the experimental range of temperatures, the presence of nanotubes accelerates the melt crystallization, while retards the overall kinetics of the cold crystallization. The biodegradability of the samples with various crystallization histories was then further examined. The results show that the presence of nanotubes reduces the biodegradation rate of PLA, and the amorphous sample shows the highest degradation levels. Moreover, a lower degradation level is observed both on the surface and inside the sample with melt crystallization history in contrast to the one with cold crystallization history. POLYM. ENG. SCI., 50:1721-1733, 2010. (C) 2010 Society of Plastics Engineers

关键词： Cold crystallization biodegradation Crystallization programmable logic arrays MELT CRYSTALLISATION Nanotubes

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Physical Layer Performance Modeling of Modern Multicarrier Modulation Techniques

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IEEE TRANSACTIONS ON COMMUNICATIONS 2022年第6期70卷 3725-3741页

作者： Anwar, Waqar Kumar, Atul Franchi, Norman Fettweis, Gerhard Tech Univ Dresden Dept Elect Engn Vodafone Chair Mobile Commun Syst D-01069 Dresden Germany IIT BHU Varanasi Dept Elect Engn Varanasi 221005 Uttar Pradesh India Friedrich Alexander Univ FAU Erlangen Nuremberg Inst Elect Smart City Syst D-91054 Erlangen Germany

The fifth-generation (5G) and beyond standards are being challenged by the diverse requirements of modern use cases. Multicarrier modulation techniques are one of the key components of the physical layer (PHY) design, which has immense potential to improve efficiency and reliability. In current state-of-the-art wireless technologies (i.e., NR and IEEE 802.11ax) orthogonal frequency division multiplexing (OFDM) is used which has many disadvantages such as peak-to-average power ratio (PAPR), out-of-band emission (OOBE), and sensitivity to carrier frequency offset (CFO). To overcome these drawbacks several alternate multicarrier modulation techniques are being considered, such as discrete Fourier transform-spread-OFDM (DFT-s-OFDM), generalized frequency division multiplexing (GFDM), and orthogonal time-frequency space (OTFS). In this paper, we develop the physical layer abstraction (PLA) of these candidate multicarrier techniques to evaluate their performance under various use cases and scenarios. The PLA is a commonly used technique to avoid time-consuming PHY simulations in system-level simulators. To improve the accuracy of PLA in different fading conditions, we derive a fitting parameter as a function of the received signal-to-interference-plus-noise ratio (SINR) variance. The validation results show that performance can be accurately estimated through the proposed multicarrier PLA. Moreover, PLA techniques are at least thousands of times faster compared to PHY simulations.

关键词： OFDM Interference Signal to noise ratio Symbols programmable logic arrays Fading channels Modulation Physical layer abstraction system-level simulation link adaptation multicarrier modulation techniques eEESM EESM RBIR OFDM DFT-s-OFDM GFDM OTFS

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High speed insertion of bone fracture fixation pins: a finite element penetration model with experimental comparisons

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JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE 2011年第12期22卷 2823-2832页

作者： Prygoski, Matthew P. Pasang, Timotius Schmid, Steven R. Lozier, Antony J. Univ Notre Dame Dept Aerosp & Mech Engn Notre Dame IN 46637 USA AUT Univ Dept Mech & Mfg Engn Auckland New Zealand Zimmer Inc Warsaw IN USA

A new method of bone fracture fixation is considered in which small pins/darts are dynamically inserted into bone to prevent translation and rotation at the fracture site. An ABAQUS model was developed to analyze dart penetration in cortical and cancellous bone for varying dart diameter, material, and velocity, and cortical thickness. The method is advocated for bioresorbable darts, so polylactide (PLA) and magnesium are the materials examined in this study. Numerical results showed that magnesium darts can achieve full penetration in bone while suffering little damage. The PLA darts penetrated thin bone well, but substantial deformation was seen as the cortical thickness increased, especially for small diameter darts. As partial validation, prototype PLA fixation darts were fired into cadaveric bone with a custom nailer. As in the model, the PLA darts could penetrate thin cortices but saw gross deformation when impacted against thicker bone.

关键词： Cortex of kidney programmable logic arrays darts Cancellous Bone

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LORES-2 - A logic REORGANIZATION SYSTEM

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IEEE DESIGN & TEST OF COMPUTERS 1985年第5期2卷 35-42页

作者： ENOMOTO, K NAKAMURA, S OGIHARA, T MURAI, S Mitsubishi Electric Corporation

LORES-2 is a logic reorganization system which greatly contributes to the effective automation of logic design. LORES-2 usesa macro-expansion technique to help designers transform printed-circuit assembly logic composed of SSI and MSI circuits intomaster-slice LSI logic circuits. The number of gates of the most reorganized LSI circuit falls within ? 20 percent of thenumber of gates of the original circuit. When ROMS and/or PLAs are not-allowed on the target LSI circuit, those elements areconverted into optimized, multilevel random logic using logic minimization, factoring and macro-expansion techniques.

关键词： logic design logic circuits programmable logic arrays Circuit synthesis Synthesizers Large scale integration Circuit simulation Databases Read only memory logic testing

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Preparation and physical properties of polylactide/cellulose nanowhisker/nanoclay composites

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POLYMER COMPOSITES 2013年第2期34卷 293-298页

作者： Hong, Jinwook Kim, Dae Su Chungbuk Natl Univ Dept Chem Engn Cheongju 361763 Chungbuk South Korea

Polylactide (PLA) has been getting lots of interests in step with global concerns on sustainable green technology because it is biodegradable with reasonable mechanical strength and can be processed quite easily. But, to compete with commodity polymers in the market PLA-based green composites need to have higher mechanical and thermal properties. Therefore, in this study, cellulose nanowhiskers (CNWs) as well as nanoclay were used as nanofillers to improve physical properties of PLA. CNWs were prepared from microcrystalline cellulose (MCC) powder by acid hydrolysis, and confirmed by TEM. To improve interfacial bonding between PLA and CNWs maleic anhydride-grafted PLA (MAPLA) was prepared and used as a compatibilizer. PLA-based composites were prepared by melt mixing followed by compression molding. Mechanical properties of the composites were measured by UTM and DMA. The melt mixing conditions were optimized first, and then composition was optimized step by step to obtain a PLA-based green composite with excellent physical properties. CNWs were much better than MCC powder as reinforcing natural fillers. MAPLA and nanoclay could improve considerably physical properties of the PLA-based composites. Compared to the PLA/MCC composite the tensile strength of the PLA/CNW/MAPLA/nanoclay composite was almost doubled and the glass transition temperature of the composite was 23 degrees C higher, making the composite possible for commercial applications. POLYM. COMPOS., 2013 (C) 2013 Society of Plastics Engineers

关键词： Cellulose NANOFILLER chemicophysical properties nanoclays programmable logic arrays INTERFACIAL BONDING physical properties Composites Polylactides MCC Genes green composites

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A stretched coordinate technique for numerical absorption of evanescent and propagating waves in planar waveguiding structures

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IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES 1995年第12期43卷 2883-2889页

作者： Gribbons, MA Pinello, WP Cangellaris, AC Electronic Packaging Research Department of Electrical and Computer Engineering University of Arizona Tucson Tucson AZ USA

Berenger's PML technique is modified to allow for the absorption of evanescent and propagating waves in FDTD modeling of wave propagation in planar waveguiding structures. Analytic results illustrate the validity and capability of the proposed modification. Numerical studies explain the numerical implementation of the modified PML in the FDTD and in the compact 2D-FDTD algorithms. Guidelines for the proper selection of the various parameters that govern the performance of the modified PML are presented. The results from simulations indicate that the proposed modified PML grid truncation can be used efficiently for highly accurate numerical analysis of planar waveguiding structures.

关键词： Absorption programmable logic arrays Finite difference methods Time domain analysis Optical scattering Electromagnetic scattering Maxwell equations Computational modeling Guidelines Analytical models

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Properties of linear poly(lactic acid)/polyethylene glycol blends

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POLYMER ENGINEERING AND SCIENCE 2012年第1期52卷 108-116页

作者： Sungsanit, K. Kao, N. Bhattacharya, S. N. RMIT Univ Rheol & Mat Proc Ctr Sch Civil Environm & Chem Engn Melbourne Vic 3001 Australia

Poly(lactic acid) (PLA) has great potentials to be processed into films for packaging applications. However, film production is difficult to carry out due to the brittleness and low melt strength of PLA. In this investigation, linear PLA (L-PLA) was plasticized with poly(ethylene glycol) (PEG) having MW of 1000 g mol-1 in various PEG concentrations (0, 5, 10, 15, and 20 wt%). In relation to plasticizer content, the impact resistance and crystallinity of L-PLA was increased, whereas a decrease in glass transition temperature and lower stiffness was observed. Nevertheless, the phase separation has been found in samples which contained PEG greater than 10 wt%. The dynamic and shear rheological studies showed that the plasticized PLA possessed lower viscosity and more pronounced elastic properties than that of pure PLA. Both storage and loss moduli decreased with PEG loading at all frequencies while storage modulus exhibited weak frequency dependence with increasing PEG content. POLYM. ENG. SCI., 2012. (C) 2011 Society of Plastics Engineers

关键词： LOW VISCOSITY Elastic properties impact resistance MELT STRENGTH Phase separation Frequency dependence LOSS MODULUS Polyethylene Glycols programmable logic arrays Storage modulus Glycols

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