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Richard A. Pethrick Elisabeth A. Hollins Lain McEwan A. Pollock David Hayward Peter Johncock 《Polymer International》1996,39(4):275-288
Dielectric and rheological measurements are reported on the effect of cure temperature on the water absorption of tris[(2,3-epoxypropoxy)phenyl] methane cured with a 1 : 1 stoichiometric ratio of 4,4′-diaminodiphenylsulphone. Analysis of the water absorption characteristics of these materials using a combination of dielectric and gravimetric measurements has indicated that water molecules can be found in two distinctly different types of environments. There are water molecules which are strongly interacting with polar groups and water molecules clustered together into sub-micro-scale cavities within the matrix structure. Changes in the final cure temperature have the effect of changing both the extent and distribution of the types of water molecules present in the matrix. Validation of the diffusion coefficients obtained from the dielectric analysis is based on a comparison with gravimetric data and the implications are discussed. Differences observed between these two different types of measurement are related to peculiarity in the dielectric method and its extreme sensitivity to interfacial phenomena. 相似文献
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Cerium (III) fluoride as an antiwear or extreme pressure additive has been used in grease and bonded solid film lubricant, but its action mechanism has not been clarified. In this paper, the tribological characteristics of lithium grease containing CeF3, CaF2, SbF3, CeO2 and graphite fluoride ((CF)n) were evaluated with an SRV tester. The results show that pastes containing CaF2 and (CF)n give good antiwear and anti-friction performance, but do not possess extreme pressure properties. Adding CeO2 to grease offers no benefit to the antiwear and anti-friction performance of the paste. Paste containing SbF3 has poor lubricating properties. XPS analysis shows that the good antiwear and extreme pressure properties of paste containing CeF3 can be attributable to the formation of a physically adherent film and a chemical reaction film on the rubbing surface. Thermogravimetry shows that CeF3 acts as an agent for the slow release of the fluorine element. 相似文献
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Radio spectrum is the most valuable resource for wireless communication, thus high spectrum utilization is mostly desired to increase system economy. With an efficient frequency allocation method and an effective handoff procedure, a personal communication system can be operated with minimal number of carriers while maintaining an acceptable level of system performance, and thereby leading to a better spectrum utilization. In this paper, we study the effect of different channel selection criteria for handoff procedure on carrier planning problem with Block Oriented Network Simulator (BONeS). The results show that the C/I-based channel selection criterion leads to the best performance, and the minimal numbers of carriers required by Personal Access Communications System (PACS) are 16, 13, 10 carriers for propagation environments with path-loss exponent 2.76, 3, 4, respectively. 相似文献
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C. Seassal J. L. Leclercq G. Fierling X. Letartre M. Gendry P. Viktorovitch Y. Bertic A. Trouillet A. Cachard P. Benech J. P. Lainé F. Sidoroff 《Microsystem Technologies》1997,3(3):139-144
In the field of III–V-based compounds, new functionalities can be reached by integrating micromechanical structures with
electro-optical functions, in order to fabricate Micro Opto Electro Mechanical Systems (MOEMS). A possible application is
an InP-based integrated optical stress sensor. Such a system is based on a partly suspended waveguide that can be strained
under the effect of an external stress. The photoelastic effect induces a phase shift that can be converted into an intensity
shift of the signal if the device is configurated as a Mach-Zehnder interferometer. This system can be integrated monolithically
with the optical source and the photodetector. The mechanical, photoelastic and optical properties of this structure has been
simulated in order to configurate the alloy composition of the epitaxial layers and the geometry of the device. Micromachining
processes have been developed in order to realize InP-based suspended microstructures by sacrificial layer etching and bulk
micromachining. Preliminary results showed that the optical behaviour of the waveguides is close to the theoretical analysis.
Characterisation of the complete interferometer is underway in our group.
Received: 13 December 1996/Accepted: 18 December 1996 相似文献
8.
N Douziech A Lajas Z Coulombe E Calvo J Lainé J Morisset 《Canadian Metallurgical Quarterly》1998,9(2):171-183
Spore germination is a defined developmental process that marks a critical point in the life cycle of Dictyostelium discoideum. Upon germination the environmental conditions must be conducive to cell growth to ensure survival of emerged amoebae. However, the signal transduction pathways controlling the various aspects of spore germination in large part remain to be elucidated. We have used degenerate PCR to identify dhkB, a two-component histidine kinase, from D. discoideum. DhkB is predicted to be a transmembrane hybrid sensor kinase. The dhkB-null cells develop with normal timing to give what seem to be mature fruiting bodies by 22 to 24 h. However, over the next several hours, the ellipsoidal and encapsulated spores proceed to swell and germinate in situ within the sorus and thus do not respond to the normal inhibitors of germination present within the sorus. The emerged amoebae dehydrate due to the high osmolarity within the sorus, and by 72 h 4% or less of the amoebae remain as spores, while most cells are now nonviable. Precocious germination is suppressed by ectopic activation of or expression of cAMP-dependent protein kinase A. Additionally, at 24 h the intracellular concentration of cAMP of dhkB- spores is 40% that of dhkB+ spores. The results indicate that DHKB regulates spore germination, and a functional DHKB sensor kinase is required for the maintenance of spore dormancy. DHKB probably acts by maintaining an active PKA that in turn is inhibitory to germination. 相似文献
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A Nanostructuring Method to Decouple Electrical and Thermal Transport through the Formation of Electrically Triggered Conductive Nanofilaments
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José Ramón Durán Retamal Chen‐Fang Kang Der‐Hsien Lien Wei‐Cheng Kuo Zhen‐Yu Juang Meng‐Lin Tsai Chih‐Hsiang Ho Jenh‐Yih Juang Vincent K. S. Hsiao Ying‐Hao Chu Lain‐Jong Li Yue Wu Jr‐Hau He 《Advanced materials (Deerfield Beach, Fla.)》2018,30(28)
Transforming thermal energy into electric energy and vice versa needs the decoupling of electrical transport from thermal transport. An innovative strategy is proposed by forming/disrupting electrically triggered conductive nanofilaments within semiconducting thin films to switch thermoelectric properties between two states without further material modification and manufacturing processes. It can also controllably adjust the degree of decoupling, providing a potential resolution and performance adjustability for heat/coldness control or power consumption reduction on demand. 相似文献
10.
Phase Inversion Strategy to Flexible Freestanding Electrode: Critical Coupling of Binders and Electrolytes for High Performance Li–S Battery
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Wandi Wahyudi Zhen Cao Pushpendra Kumar Mengliu Li Yingqiang Wu Mohammed N. Hedhili Thomas D. Anthopoulos Luigi Cavallo Lain‐Jong Li Jun Ming 《Advanced functional materials》2018,28(34)
Development of flexible and freestanding electrode is attracting great attention in lithium–sulfur (Li–S) batteries, but the severe capacity fading caused by the lithium polysulfides (PSs) shuttle effect remains challenging. Herein, a completely new polymeric binder of polyethersulfone is introduced. Not only it enables massive production of flexible/current‐free electrode by a novel concept of “phase‐inversion” approach but also the resultant polymeric networks can effectively trap the soluble polysulfides within the electrode, owing to the higher hydrophilicity and stronger affinity properties than the routine polyvinylidene fluoride. Coupling with polysulfide‐based electrolyte, the Li–S cell shows a higher capacity of 1141 mAh g?1, a lower polarization of 192 mV, and a more stable capacity retention with 100% Coulombic efficiency over 100 cycles at 0.25C. The advantages of favored binder and electrolyte are further demonstrated in lithium‐ion sulfur full battery with lithiated graphite anode, which demonstrates much improved performance than those previously reported. This work not only introduces a novel strategy for flexible freestanding electrodes but also enlightens the importance of coupling electrodes and electrolytes to higher performances for Li–S battery. 相似文献