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991.
Giovanni Polacco Jiri Stastna Peter Michalica Dario Biondi Matteo Cantù Ludovit Zanzotto 《应用聚合物科学杂志》2007,104(4):2330-2340
The viscoelastic nonlinear behavior of several base and polymer modified asphalts (PMA) has been studied in step‐strain experiments. The polymers were poly(styrene‐b‐butadiene‐b‐styrene), poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene), poly(ethylene‐r‐vinylacetate) copolymers, and a linear low density poly(ethylene), which were chosen as representatives of the main categories of asphalt modifiers. Because of the complexity of the morphological structure of these materials, the relaxation modulus has only partial and qualitative similarities with that of melt or high concentrated solutions of entangled polymeric liquids. No time strain separability can be applied, and the relaxation experiments are conveniently described by means of the memory functions. These have been calculated both via a parametric fitting procedure and by interpolation algorithms. Results are presented, and a correlation between the PMA structure and the corresponding memory function is proposed for the investigated materials. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2330–2340, 2007 相似文献
992.
Maksim Jenihhin Giovanni Squillero Thiago Santos Copetti Valentin Tihhomirov Sergei Kostin Marco Gaudesi Fabian Vargas Jaan Raik Matteo Sonza Reorda Leticia Bolzani Poehls Raimund Ubar Guilherme Cardoso Medeiros 《Journal of Electronic Testing》2016,32(3):273-289
The Negative Bias Temperature Instability (NBTI) phenomenon is agreed to be one of the main reliability concerns in nanoscale circuits. It increases the threshold voltage of pMOS transistors, thus, slows down signal propagation along logic paths between flip-flops. NBTI may cause intermittent faults and, ultimately, the circuit’s permanent functional failures. In this paper, we propose an innovative NBTI mitigation approach by rejuvenating the nanoscale logic along NBTI-critical paths. The method is based on hierarchical identification of NBTI-critical paths and the generation of rejuvenation stimuli using an Evolutionary Algorithm. A new, fast, yet accurate model for computation of NBTI-induced delays at gate-level is developed. This model is based on intensive SPICE simulations of individual gates. The generated rejuvenation stimuli are used to drive those pMOS transistors to the recovery phase, which are the most critical for the NBTI-induced path delay. It is intended to apply the rejuvenation procedure to the circuit, as an execution overhead, periodically. Experimental results performed on a set of designs demonstrate reduction of NBTI-induced delays by up to two times with an execution overhead of 0.1 % or less. The proposed approach is aimed at extending the reliable lifetime of nanoelectronics. 相似文献
993.
Baraa Werghi Liheng Wu Amani M. Ebrahim Miaofang Chi Haoyang Ni Matteo Cargnello Simon R. Bare 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(20):2207956
The Pt-Sn bimetallic system is a much studied and commercially used catalyst for propane dehydrogenation. The traditionally prepared catalyst, however, suffers from inhomogeneity and phase separation of the active Pt–Sn phase. Colloidal chemistry offers a route for the synthesis of Pt–Sn bimetallic nanoparticles (NPs) in a systematic, well-defined, tailored fashion over conventional methods. Here, the successful synthesis of well-defined ≈2 nm Pt, PtSn, and Pt3Sn nanocrystals with distinct crystallographic phases is reported; hexagonal close packing (hcp) PtSn and fcc Pt3Sn show different activity and stability depending on the hydrogen-rich or poor environment in the feed. Moreover, face centred cubic (fcc) Pt3Sn/Al2O3, which exhibited the highest stability compared to hcp PtSn, shows a unique phase transformation from an fcc phase to an L12-ordered superlattice. Contrary to PtSn, H2 cofeeding has no effect on the Pt3Sn deactivation rate. The results reveal structural dependency of the probe reaction, propane dehydrogenation, and provide a fundamental understanding of the structure−performance relationship on emerging bimetallic systems. 相似文献
994.
Lorenzo Iorio Lionel Fourment Stéphane Marie Matteo Strano 《International Journal of Material Forming》2017,10(4):515-526
The problem of multi-objective optimization (MOP) is approached from the theoretical background of the Game Theory, which consists in finding a compromise between two rational players of a bargaining problem. In particular, the Kalai and Smorodinsky (K-S) model offers a balanced and attractive solution resulting from cooperative players. This approach allows avoiding the computationally expensive and uncertain reconstruction of the full Pareto Frontier usually required by MOPs. The search for the K-S solution can be implemented into methodologies with useful applications in engineering MOPs where two or more functions must be minimized. This paper presents an optimization algorithm aimed at rapidly finding the K-S solution where the MOP is transformed into a succession of single objective problems (SOP). Each SOP is solved by meta-model assisted evolution strategies used in interaction with an FEM simulation software for metal forming applications. The proposed method is first tested and demonstrated with known mathematical multi-objective problems, showing its ability to find a solution lying on the Pareto Frontier, even with a largely incomplete knowledge of it. The algorithm is then applied to the FEM optimization problem of wire drawing process with one and two passes, in order to simultaneously minimize the pulling force and the material damage. The K-S solutions are compared to results previously suggested in literature using more conventional methodologies and engineering expertise. The paper shows that K-S solutions are very promising for finding quite satisfactory engineering compromises, in a very efficient manner, in metal forming applications. 相似文献
995.
A 3D Real‐Scale,Biomimetic, and Biohybrid Model of the Blood‐Brain Barrier Fabricated through Two‐Photon Lithography 下载免费PDF全文
Attilio Marino Omar Tricinci Matteo Battaglini Carlo Filippeschi Virgilio Mattoli Edoardo Sinibaldi Gianni Ciofani 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(6)
The investigation of the crossing of exogenous substances through the blood‐brain barrier (BBB) is object of intensive research in biomedicine, and one of the main obstacles for reliable in vitro evaluations is represented by the difficulties at the base of developing realistic models of the barrier, which could resemble as most accurately as possible the in vivo environment. Here, for the first time, a 1:1 scale, biomimetic, and biohybrid BBB model is proposed. Microtubes inspired to the brain capillaries were fabricated through two‐photon lithography and used as scaffolds for the co‐culturing of endothelial‐like bEnd.3 and U87 glioblastoma cells. The constructs show the maturation of tight junctions, good performances in terms of hindering dextran diffusion through the barrier, and a satisfactory trans‐endothelial electrical resistance. Moreover, a mathematical model is developed, which assists in both the design of the 3D microfluidic chip and its characterization. Overall, these results show the effective formation of a bioinspired cellular barrier based on microtubes reproducing brain microcapillaries to scale. This system will be exploited as a realistic in vitro model for the investigation of BBB crossing of nanomaterials and drugs, envisaging therapeutic and diagnostic applications for several brain pathologies, including brain cancer. 相似文献
996.
Nonlinear structural optimization is fairly expensive and difficult, because a large number of nonlinear analyses is required due to the large number of design variables involved in topology optimization. In element density based topology optimization, the low density elements create mesh distortion and the updating of finite element material with low density elements has a severe effect on the optimization results in the next cycles. In order to overcome these difficulties, the equivalent static loads method for nonlinear response structural optimization (ESLSO) primarily used for size and shape optimization has been applied to topology optimization. The nonlinear analysis is performed with the given loading conditions to calculate equivalent static loads (ESLs) and these ESLs are used to perform linear response optimization. In this paper, the authors have presented the results of five case studies with material, geometric and contact nonlinearities showing good agreement and providing justification of the proposed method. 相似文献
997.
Anastasia Anna Foppoli Matteo Cerea Lucia Zema Andrea Gazzaniga 《Drug development and industrial pharmacy》2017,43(12):1919-1931
Dry coating techniques enable manufacturing of coated solid dosage forms with no, or very limited, use of solvents. As a result, major drawbacks associated with both organic solvents and aqueous coating systems can be overcome, such as toxicological, environmental, and safety-related issues on the one hand as well as costly drying phases and impaired product stability on the other. The considerable advantages related to solventless coating has been prompting a strong research interest in this field of pharmaceutics. In the article, processes and applications relevant to techniques intended for dry coating are analyzed and reviewed. Based on the physical state of the coat-forming agents, liquid- and solid-based techniques are distinguished. The former include hot-melt coating and coating by photocuring, while the latter encompass press coating and powder coating. Moreover, solventless techniques, such as injection molding and three-dimensional printing by fused deposition modeling, which are not purposely conceived for coating, are also discussed in that they would open new perspectives in the manufacturing of coated-like dosage forms. 相似文献
998.
Carbon Nanotube‐Quantum Dot Nanohybrids: Coupling with Single‐Particle Control in Aqueous Solution 下载免费PDF全文
Antonio Attanzio Andrei Sapelkin Felice Gesuele Arend van der Zande William P. Gillin Ming Zheng Matteo Palma 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(16)
A strategy is reported for the controlled assembly of organic‐inorganic heterostructures consisting of individual single‐walled carbon nanotubes (SWCNTs) selectively coupled to single semiconductor quantum dots (QDs). The assembly in aqueous solution was controlled towards the formation of monofunctionalized SWCNT‐QD structures. Photoluminescence studies in solution, and on surfaces at the single nanohybrid level, showed evidence of electronic coupling between the two nanostructures. The ability to covalently couple heterostructures with single particle control is crucial for the design of novel QD‐based optoelectronic and light‐energy conversion devices. 相似文献
999.
Matteo Bianchi Fabrizio L. Scarpa Christopher W. Smith 《Journal of Materials Science》2008,43(17):5851-5860
Auxetic open cell polyurethane (PU) foams have been manufactured and mechanically characterised under cyclic tensile loading.
The classical manufacturing process for auxetic PU foams involves multiaxial compression of the conventional parent foam,
and heating of the compressed specimens above the Tm of the foam polymer. Eighty cylindrical specimens were fabricated using manufacturing routes modified from those in the open
literature, with different temperatures (135 °C, 150 °C), compression ratios and different cooling methods (water or room
temperature exposure). Compressive tensile cyclic loading has been applied to measure tangent modulus, Poisson’s ratios and
energy dissipated per unit volume. The results are used to obtain relations between manufacturing parameters, mechanical and
hysteresis properties of the foams. Compression, both radial and axial, was found to be the most significant manufacturing
parameter for the auxetic foams in this work. 相似文献
1000.
Nessim GD Hart AJ Kim JS Acquaviva D Oh J Morgan CD Seita M Leib JS Thompson CV 《Nano letters》2008,8(11):3587-3593
By controlling the timing and duration of hydrogen exposure in a fixed thermal process, we tuned the diameters of carbon nanotubes (CNTs) within a vertically aligned film by a factor of 2, and tuned the areal densities by an order of magnitude. The CNT structure is correlated with the catalyst morphology, suggesting that while chemical reduction of the catalyst layer is required for growth, prolonged H2 exposure not only reduces the iron oxide and enables agglomeration of the Fe film, but also leads to catalyst coarsening. Control of this coarsening process allows tuning of CNT characteristics. 相似文献