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71.
Unconrolled agglomeration of particles and adhesion of the particulate mass to wall surfaces are common severe problems in many drying operations. This paper reviews the mechanisms of interparticle and particle-surface attraction as well as the theory and the existing tests for characterising powders in terms of internal strength, wall friction and adhesion. The usefulness of the information obtained from these tests in dryer design and operation is critically reviewed. The importance of powder stickiness in various types of dryers is discussed and established methods of combating the problem are presented Recommendations an made for further research in the area of powder cohesion and adhesion. 相似文献
72.
Dielectric relaxation measurements are reported over a frequency range from 10−1 to 109 Hz as a function of exposure time for an epoxy resin-carbon fibre composite, ageing at 60 °C in water. Investigation of the nature of the dipole relaxation of the water molecules, indicates the nature of their interaction with the polymer matrix. Analysis of the dielectric relaxation spectra allow identification of processes that can be attributed to ‘free’ and ‘bonded’ water, water in micro-cracking, located in carbon fibre disbonds and plasticizing the polymer matrix. Identification of the various types of location in which water exists was aided by use of the Ng factor from the Kirkwood-Frölich equation, which describes the constraints on free dipole ration nature imposed by the environment in which it is located. These data indicate the power of the dielectric technique for quantitative analysis of water ingress into epoxy composites. 相似文献
73.
74.
Outlines an approach to epidemiologic-type life-stress studies that involves the intensive study of smaller groups of well-defined disordered individuals across the course of the response. On the basis of their previous research, the authors suggest that cyclothymia may be characterized by poor regulation of biologic and behavioral variation and that this condition may be exaggerated by stress. To extend the evidence on poor regulation generated in laboratory studies of cortisol functioning, 31 cyclothyme patients and 24 normal controls (median age 19.3 yrs) were asked to provide daily ratings of moods and events over 28 consecutive days. Data show that Ss with cyclothymia showed prolonged duration of recovery of behavioral levels compared to controls. Findings support a notion of weak inhibitory modulation in certain CNS systems that control biologic and behavioral variables related to affective disorder. It is suggested that the prolonged duration of behavioral change in cyclothymia is unlikely to be the consequence of concurrent depression and that the nature of prolonged recovery to stress in cyclothymia reflects the operation of an endogenous regulatory process, as opposed to a cognitive appraisal bias. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
75.
Grant Igor; Olshen Richard A.; Atkinson J. Hampton; Heaton Robert K.; Nelson Julie; McCutchan J. Allen; Weinrich James D. 《Canadian Metallurgical Quarterly》1993,7(1):53
The relationship of depressed mood to cognitive disturbance in HIV infection was examined in a sample of 139 homosexual men. Ss were grouped according to the classification of the Centers for Disease Control: 39 were in Group IV, 62 were in Group II or Group III, and 38 were HIV-negative. Ss completed the Profile of Mood States and 10 neuropsychological tests. Analysis employing a classification approach indicated that, although symptoms of depression and neuropsychological impairment were more common in Ss who were HIV-positive, particularly those classified as Group IV, there were no systematic relationships between depression and neuropsychological impairment. Depressed mood and cognitive disturbance each seem to have unique associations to HIV illness status. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
76.
Fifteen to 20 wt % polyetherimide (PEI) solutions with 1-methyl-2-pyrrolidinone (NMP) were prepared. The electrical conductivity and surface tension of the solutions were determined. The fiber spinning technique of electrospinning was optimized in order to prepare unidirectionally aligned, structurally oriented nanofiber tows. The morphology of the PEI fibers was investigated using field emission scanning electron microscopy (FESEM). The well-aligned fibers with diameters between 0.58 and 0.90 μm (FESEM) were collected by electrospinning 20 wt % PEI solutions with NMP in the range of 8–10 kV onto a target rotating with a surface velocity 9.8 m/s. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
77.
The formation of a porous polymer monolith (PPM) is influenced by the physico-chemical properties of the wall surface of its container. This influence can have a dramatic effect on the resulting monolith morphology depending on the nature and composition of the wall. Indeed, a dense polymer layer or “sheath”, distinct from the bulk porous material, has been observed at the wall surface of capillaries, and thus a study was undertaken to explore the dependence of this layer on the hydrophobicity of the surface. A range of silanizing reagents were used to modify the surface of the fused silica capillary, including aminopropyl, trimethylsilyl, octadecyl and perfluorooctyl functionalities. Crosslinked butyl acrylate-based PPM was formed in the modified capillaries and extruded. SEM images of the monoliths were used to examine the sheath morphology and thickness, which are discussed with respect to surface hydrophobicity. 相似文献
78.
Investigation of the thermal, mechanical, and fracture properties of alumina-epoxy composites 总被引:1,自引:0,他引:1
A combination of dynamic shear rheology, thermomechanical analysis (TMA), scanning electron microscopy (SEM), Near-Edge X-ray Absorption Fine Structure (NEXAFS), and fracture toughness testing was utilized to characterize the thermal, mechanical, chemical, and fracture properties of alumina (α-Al2O3)-filled epoxy resins as a function of average filler size, size distribution, particle shape, loading, and epoxy crosslink density. In general the cured properties of the filled composites were robust. Small changes in particle size, shape, and size distribution had little impact on the final properties. Resin crosslink density and filler loading were the most critical variables, causing changes in all properties. However, most applications could likely tolerate small changes in these variables also. SEM and NEXAFS characterization of the fracture surfaces revealed that the fracture occurs at the filler interface and the interfacial epoxy composition is similar to the bulk resin, indicating a weak epoxy-alumina interaction. These results are critical for implementation of particulate-filled polymer composites in practical applications because relaxed material specifications and handling procedures can be incorporated in production environments to improve efficiency. 相似文献
79.
Liew Jeffrey; Eisenberg Nancy; Losoya Sandra H.; Fabes Richard A.; Guthrie Ivanna K.; Murphy Bridget C. 《Canadian Metallurgical Quarterly》2003,17(4):584
Relations of heart rate and skin conductance reactions to mildly evocative empathy-inducing slides with socioemotional functioning were examined for 154 children (mean age = 9 years, 5 months). In addition, maternal expressivity was tested as a moderator of these relations. Parents and teachers rated children's socioemotional functioning, and a behavioral measure of children's regulation was obtained. Boys who exhibited higher skin conductance and higher heart rate to slides depicting negative emotions were better regulated, less emotionally intense, and better adjusted than their peers. Furthermore, boys' regulation and adjustment were positively related to such physiological responding to negative slides if maternal negative expressivity was relatively low or moderate, but not high. Fewer findings were obtained for girls or for positive slides. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
80.
A 1-D transient model (RESHEAT), developed by the writers, was used to study the thermal performance of a highly reflective paint applied sequentially to the outer walls and roof of a simulated residence in a hot and arid region of the southwestern United States. The model uses climatological inputs from a file that includes hourly data on ambient temperatures, insolation, cloud cover, and so on, at the particular location. The model focuses particularly on the potential cooling load reduction due to the reduced heat pickup from the inside attic surfaces to the outer surfaces of the supply duct. This simulation showed that a reduction of 33.6% (cooling load) on the average is achieved over the base case where no reflective paint is used when the outer surface of the roof and walls are painted. Alternatively, only a 11% reduction would be achieved if the reflective paint is applied only to the roof. Savings of $42 per month are conservatively estimated from calculations made when applying this technology to a typical residence (roof and walls) equipped with a 4 ton refrigeration unit in the Southwest. 相似文献