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131.
132.
Edina Rusen Bogdan Marculescu Ana‐Maria Albu Dumitru Mircea Vuluga Adrian Boborodea Dan Sorin Vasilescu 《Polymer International》2005,54(1):215-220
The present study describes the kinetic investigation of the complex binary copolymerization system maleic anhydride (MA)—dicyclopentadiene (DCPD). All syntheses were carried out in homogeneous solution; high conversions in soluble and linear copolymer are achievable when starting from an equimolecular monomer feed. Excess of DCPD would limit the attainable conversions, while surplus of MA would induce crosslinking of the copolymers. The findings of the thorough kinetic study were sustained by structural assessment from IR and NMR spectra recorded for various copolymers, both soluble and gels. Copyright © 2004 Society of Chemical Industry 相似文献
133.
A new diol with bistriazene groups, 1,1′[4,4′‐diphenylether]‐3,3′‐di(β‐hydroxyethyl methyl)‐bistriazene (BTD), was synthesized and characterized. BTD, along with N‐methyldiethanolamine as a chain extender, was used to prepare a segmented polyurethane based on poly(tetramethylene oxide) diol (weight‐average molecular weight = 2000) and 2,4‐tolylene diisocyanate (80:20 v/v 2,4‐/2,6‐isomer mixture). Subsequent quaternization of the amine with benzyl chloride formed the cationomer. The structure–property relationships, including the photochemical behavior of the triazene linkage in these polymers, were investigated with respect to another polyurethane prepared from 4,4′‐diphenylmethane diisocyanate and a bistriazene compound. Photolysis experiments were carried out in polymer solutions and in the film state, and the reduction of the π–π* absorption band, characteristic of the triazene chromophore in ultraviolet spectra, was followed. A kinetic evaluation revealed a first‐order photoprocess. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 385–391, 2005 相似文献
134.
Fiber to the Home Using a PON Infrastructure 总被引:3,自引:0,他引:3
Traffic patterns in access networks have evolved from voice- and text-oriented services to video- and image-based services. This change will require new access networks that support high-speed (> 100 Mb/s), symmetric, and guaranteed bandwidths for future video services with high-definition TV quality. To satisfy the required bandwidth over a 20-km transmission distance, single-mode optical fiber is currently the only practical choice. To minimize the cost of implementing an FTTP solution, a passive optical network (PON) that uses a point-to-multipoint architecture is generally considered to be the best approach. There are several multiple-access techniques to share a single PON architecture, and the authors addressed several of these approaches such as time-division multiple access, wavelength-division multiple access, subcarrier multiple access, and code-division multiple access. Among these multiple techniques, they focus on time-division multiplexing (TDM)-PON and wavelength-division multiplexing (WDM)-PON, which will be the most promising candidates for practical future systems. A TDM-PON shares a single-transmission channel with multiple subscribers in time domain. Then, there exists tight coupling between subscribers. A WDM-PON provides point-to-point optical connectivity using a dedicated pair of wavelengths per user. While a TDM-PON appears to be a satisfactory solution for current bandwidth demands, the combination of future data-rate projections and traffic patterns coupled with recent advances in WDM technology may result in WDM-PON becoming the preferred solution for a future proof fiber-based access network 相似文献
135.
The Internet in the Communication Infrastructure of Urban Residential Communities: Macro‐ or Mesolinkage? 总被引:2,自引:0,他引:2
The article refines the view that the Internet is increasingly incorporated in everyday life, concluding that the new medium has been partially integrated in the "communication infrastructure" of English-speaking Los Angeles neighborhoods. Here, Internet connectedness is associated with civic participation and indirectly contributes to "belonging" to a residential community. However, in predominantly Asian and Latino areas, the Internet is disengaged from communication environments that lead to belonging, being associated with mainstream media. In these communities its contribution is contradictory; although it probably contributes to the process of ethnic assimilation, it might also lead to disengagement of most educated and technologically savvy residents from their neighborhoods. A possible "magnifying glass effect" is proposed as explanation for the differential integration of new media in community life. 相似文献
136.
A special multi-step thermodynamic technique for the systematic synthesis of energy-efficient configurations of sorption processes acting between four temperatures for cold production has been proposed. In the first step, a special superstructure which embeds all the energy flows going through an ideal sorption system is postulated. The superstructure is represented on a dimensionless Carnot factor vs. heat diagram. In the second step, the minimization of special areas on the diagram, corresponding to the so called “unused” and “excess” exergies, combined with the maximization of desorption temperature to its upper level makes it possible to target the maximum energy performance and COP of the future ideal process ahead of design. In the third step, the process is systematically synthesized on the Clausius-Clapeyron diagram by using the thermodynamic correspondence with the Carnot factor vs. heat diagram. The final step is to conduct a traditional assessment of the thermodynamic performance of real sorption systems that have the same structures as the ideal systems defined in the previous step. A new energy-efficient configuration of a triple-effect thermochemical refrigerator using two salt materials has been designed as an example. 相似文献
137.
Alameldeen A.R. Martin M.M.K. Mauer C.J. Moore K.E. Min Xu Hill M.D. Wood D.A. Sorin D.J. 《Computer》2003,36(2):50-57
As dependence on database management systems and Web servers increases, so does the need for them to run reliably and efficiently-goals that rigorous simulations can help achieve. Execution-driven simulation models system hardware. These simulations capture actual program behavior and detailed system interactions. The authors have developed a simulation methodology that uses multiple simulations, pays careful attention to the effects of scaling on workload behavior, and extends Virtutech AB's Simics full system functional simulator with detailed timing models. The Wisconsin Commercial Workload Suite contains scaled and tuned benchmarks for multiprocessor servers, enabling full-system simulations to run on the PCs that are routinely available to researchers. 相似文献
138.
This article reports a comparison of the structural and textural properties of bioglass–hydroxyapatite (HA) composites obtained
in the SiO2–CaO–P2O5 system by sol–gel method, with different amounts of hydrogen peroxide (3% H2O2) or water (H2O). X-ray diffraction, Raman, and FT-IR spectroscopy reveal the presence of nanocrystalline HA. Scanning electron microscopy
images illustrate that the HA phase is mainly distributed on the glass surface. The results point out that the sintering at
550 °C of a sol–gel derived SiO2–CaO–P2O5 bioglass leads to a single crystalline phase of HA, and validate a new processing method for obtaining bioglass–HA composites.
Structural analyses of the investigated composites indicate the existence of a silicate network built up from Q3 and Q2 units. The replacement of water with hydrogen peroxide has as consequence the increase of depolymerization degree of silica
network. Textural properties were investigated with N2-adsorption technique. The composites prepared with hydrogen peroxide exhibit a more uniform and narrow mesoporous distribution
that recommends them for drug uptake and release applications. It was found that the specific surface area and pore volume
are clearly influenced by the H2O2(H2O):TEOS molar ratio. 相似文献
139.
G. Mazzone G. Sannazzaro T. Schioler V. Sorin 《Fusion Engineering and Design》2011,86(9-11):1984-1988
In order to assess the structural performance of the ITER Main Components it is important to take into account not only the mutual dynamic interaction among them during a seismic event but also their interactions with the Tokamak Buildings (TB) complex. The seismic behavior of the TB is affected by the large dimensions of the building, the concrete basemat thickness that has to be sufficiently rigid to support the weight of the Tokamak, the presence of anti-seismic bearing (ASB) under the basemat, and the distribution of heavy equipment at higher levels. These factors require that the soil–structural interaction must be studied in detail, taking into account the specific effects such as the excavation influence and the building rocking motion due to seismic wave propagation. The study of the seismic behavior has been carried out using two different linear dynamic methodologies: power spectral density (PSD) and spectral analyses. The paper illustrates the main results of the seismic analyses and gives the seismic design input for the Tokamak components in terms of support loads, accelerations and displacements. 相似文献
140.
Ki-Won KimSung-Dal Jung Dong-Seok KimKi-Sik Im Hee-Sung KangJung-Hee Lee Youngho BaeDae-Hyuk Kwon Sorin Cristoloveanu 《Microelectronic Engineering》2011,88(7):1225-1227
Normally-off GaN-MOSFETs with Al2O3 gate dielectric have been fabricated and characterized. The Al2O3 layer is deposited by ALD and annealed under various temperatures. The saturation drain current of 330 mA/mm and the maximum transconductance of 32 mS/mm in the saturation region are not significantly modified after annealing. The subthreshold slope and the low-field mobility value are improved from 642 to 347 mV/dec and from 50 to 55 cm2 V−1 s−1, respectively. The ID-VG curve shows hysteresis due to oxide trapped charge in the Al2O3 before annealing. The amount of hysteresis reduces with the increase of annealing temperature up to 750 °C. The Al2O3 layer starts to crystallize at a temperature of 850 °C and its insulating property deteriorates. 相似文献