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81.
A recently built experimental setup was employed for the estimation of the solid–liquid equilibria of alternative refrigerant systems. In this paper two binaries, i.e., carbon dioxide + trifluoromethane (CO2 + R23) and nitrous oxide + trifluoromethane (N2O + R23), were studied down to temperatures of 117 K. In order to check the reliability of the apparatus, the triple points of the pure fluids contained in the mixture were measured, revealing good consistency with the literature. The results obtained for the mixtures were interpreted by means of the Schröder equation.  相似文献   
82.
Coplanar Al/graphene/Al junctions fabricated on the same graphene sheet deposited on silicon carbide (SiC), show robust Josephson coupling at subKelvin temperature, when the separations between the electrodes is below 400 nm. Remarkably, a hysteretic Critical State sets in when ramping an orthogonal magnetic field, with a sudden collapse of the Josephson critical current I c when turning the field on, and a revival of I c when inverting the sweep. Similar hysteresis can be found in granular superconducting films which may undergo the Berezinskii-Kosterlitz-Thouless transition. Here, we give quantitative arguments to prove that this odd behavior of the magnetoconductance gives evidence for an incipient Berezinskii-Kosterlitz-Thouless transition with drift and pinning of fluctuating free vortices induced by the current bias.  相似文献   
83.
Magnetic resonance imaging findings of median nerve hamartoma are presented in three patients with palpable wrist masses and median neuropathy. Fat-suppressed T1-weighted images demonstrated adipose tissue separating the neural and fibrous tissue bundles in two of three patients, which results in the distinctive appearance of these tumors on magnetic resonance imaging. Fibrous tissue appeared as enhancing longitudinal bundles within the tumor on gadolinium enhanced fat-suppressed T1-weighted images.  相似文献   
84.
    
The electrical conductivity of ceria thin films (epitaxial as well as dense and porous nanocrystalline) is investigated in dry and wet atmosphere at temperatures below 500 °C. For the epitaxial and the fully dense nanocrystalline samples, no significant differences can be observed between dry and wet conditions. In marked contrast, the nanocrystalline porous films obtained via spin coating exhibit a considerable enhancement of the protonic conductivity below 300 °C in wet atmosphere. This outcome reveals that the residual open mesoporosity plays the key role for the enhancement of the proton transport at low temperatures and not the high density of grain boundaries. The quantitative analysis of the various pathways, along which the proton transport can take place, indicates that the observed proton conduction can arise not only from bulk water adsorbed in the open pores but also from the space charge zones on the water side of the water/oxide interface.  相似文献   
85.
    
This paper addresses both solid state power amplifiers (sspas) and travelling wave tube amplifiers (twtas), highlighting their capabilities, drawbacks and future developments, for space systems. These two technologies are complementary and will coexist in future pay loads.  相似文献   
86.
    
The unique capabilities of new cellular systems are expected to provide users with integrated multimedia services. Since the air interface still represents the system bottleneck, this paper proposes novel scheduling techniques to integrate efficiently the support of real‐time traffic (i.e. voice and video) and data bursty traffic under quality of service (QoS) guarantees. Prioritization among traffic classes is adopted and a polling service discipline is employed within a class, where the permission rights of each traffic source are determined on the basis of token bucket regulators. Two polling‐based approaches are compared to serve the sources of a class: (i) when a source is enabled to transmit, a burst of packets is sent at once; (ii) within the time interval destined to a traffic class, a cyclic service of the sources is allowed on a packet basis. With realistic assumptions on both radio channel conditions and protocol signaling overhead, this paper compares these two different approaches and the dynamic slot assignment++ (DSA++) scheme appeared in the literature. The obtained results highlight that our second scheme (case ii) allows increasing the number of supported video traffic sources of many units with respect to DSA++. Finally, an analytical approach has been proposed for our second polling scheme. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
87.
To describe the geographical patterns and trends of macronutrient intake in Japan for the recent 20 years, we analyzed the data sets of the National Nutrition Surveys (J-NNS). First, we calculated regression coefficients for survey year by prefecture for energy, protein, fat, and carbohydrate intake. These results, however, could be affected by the changes in age and sex distributions of the survey samples. Secondly, as the food consumption data were based on household as a unit, we used proportions of the subjects who belong to age-specific groups and female subjects in a sub-sample for each prefecture in a given year for adjustment by general lineal model. As a result, 1% increase in the subjects aged 1-4, 10-19 and 65- years and female subjects was equivalent to the changes in average energy intake by -5.88, +2.27, -1.45 and -1.62 kcal, respectively. After the adjustment for age and sex, number of significant negative coefficients among 47 prefectures decreased for energy and carbohydrate intake, and that of positive coefficients increased for fat intake. This suggested that unadjusted trend data might lead to an overestimation of decreasing trends of energy and carbohydrate intake, and an underestimation of increasing trend of fat intake in the recent 20 years.  相似文献   
88.
By reacting a stoichiometric amount of BPM or Me2BPM (BPM = bis(pyrazol-1-yl)methane, Me2BPM = bis(3,5-dimethylpyrazol-1-yl)methane) with Pd(OAc)2 (OAc = acetate) in CH2Cl2, the new neutral complexes [Pd(OAc)2(BPM)] (1) and [Pd(OAc)2(Me2BPM)] (1Me) were isolated and characterized by NMR and IR spectroscopy. Acidolysis of one Pd-OAc bond of compound 1 by using aqueous perchloric acid in methanol led to the formation of the stable cationic aqua-complex [Pd(OAc)(H2O)(BPM)](ClO4) (2-ClO4). The [Pd(OAc)(H2O)(BPM)]+ cation was obtained also by reacting 1 with trifluoromethanesulfonic acid. NMR studies on inter- and intra-molecular hydrogen bonding of the aqua-ligand have been carried out and the data obtained have been interpreted on the basis of the results of DFT calculations.  相似文献   
89.
Bernardino Ramazzini (1633-1714) systematically studied the relationship between work and diseases. He realized that it was not possible to ascribe all workers' diseases to chemicals or physical agents and foresaw that other factors were involved. He observed that common diseases could originate following the maintenance either of prolonged stationary postures or of unnatural postures (e.g. bakers, workers who stand, sedentary worker, scribes, weavers) or following activities requiring heavy muscular performance (e.g. porters and woodworkers). Furthermore, Ramazzini recognized the need to undertake measures to prevent disorders from repetitive motions and manual lifting and anticipated the now accepted advice of moderation and recommendations of reduction of work duration for a number of hard jobs requiring a standing position or severe muscular effort. From his early writings therefore it is evident that Ramazzini realized the importance of assessing the ergonomic factors associated with the occurrence of work-related musculoskeletal disorders.  相似文献   
90.
The energy market is undergoing major changes, the most notable of which is the transition from a hierarchical closed system toward a more open one highly based on a ??smart?? information-rich infrastructure. This transition calls for new information and communication technologies infrastructures and standards to support it. In this paper, we review the current state of affairs and the actual technologies with respect to such transition. Additionally, we highlight the contact points between the needs of the future grid and the advantages brought by service-oriented architectures.  相似文献   
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