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41.
A sample of 1,411 older adults (age 55+) who had been interviewed both prior to and after bereavement was studied, allowing for pre-event controls. Those who had lost a parent, spouse, or child had the strongest depressive reactions, as predicted by an attachment-bonding hypothesis; however, material losses were also related to depression. Although bereavement/loss events were clearly related to subsequent depression even after pre-event depression, resources, and events were controlled, certain pre-event characteristics were predictive of the bereavement/loss events, including prior undesirable events, age, and urban/rural residency. A further analysis of 1,007 persons with two post-event interviews (at 6-month to 1-year follow-up) revealed an initial depressive reaction to a bereavement/loss event, which then dissipated completely within 1 year's time. Generally, bereavement appeared to have limited etiologic importance. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
42.
43.
The data obtained on inclusion types and concentrations has been analysed in the present part in terms of their effect on
filtration time and fluidity (measured by the length of solidified metal in quartz tubes). The dross, i.e., the oxide layer
that formed on the surface of the molten metal, was carefully collected and its mass determined; then it was examined in a
scanning electron microscope equipped with an energy-dispersive X-ray system. The results show that inclusions are not the
only parameter to be considered. More importantly, it is Al2O3 (films or particles), which seems to be the deciding factor.
It is found, however, that it is quite difficult to separate the individual role of each parameter using the porous disc filtration
apparatus (PoDFA) technique, i.e., sampling, without disturbing the molten metal. Sampling would introduce undesirable oxides
into the PoDFA crucible, resulting in an artificial increase in the filtration time. Increasing the holding periods of the
molten metal increases the quantity of dross. In all cases, the skimmed dross is wet, i.e., it contains an appreciable amount
of molten metal. The main types of oxides in the dross are MgO, MgAl2O4, Al4C3 and Al2O3.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
44.
GN Clarke 《Canadian Metallurgical Quarterly》1993,60(1):198-199
45.
This paper describes a new IM/DD optical transmission system simulation which incorporates the impact of laser diode stochastic turn-on effects on system performance. Using this simulation, experimentally observed error rate floors, due to inappropriate laser diode biasing, can be theoretically modelled and predicted, for the first time 相似文献
46.
The solidification behavior of two composites based on Al-Si alloy has been investigated as a function of cooling rate. Thermal
analysis techniques have been used to establish the relationship between solidification history and the microstructure developed.
The results of thermal analysis show that the characteristic parameters are influenced by the cooling rate. A marked difference
in these parameters is observed between the reinforced and the unreinforced materials at all cooling rates studied. The cooling
rates used in the present study range from 0.3 to 20 K/s. Increasing the cooling rate is shown to affect the undercooling
parameters both in the liquidus and eutectic solidification region. The eutectic growth temperature of the composites is observed
to be higher than that of the base alloy at all cooling rates. The depression in eutectic temperature ΔT is found to decrease
by 27 K for the unreinforced alloy (A356) and by 17 K for the composites (A356 + 10, 20 vol pct SiC) at a higher cooling rate
of ≃16 K/s. The presence of SiC reinforcement is observed to suppress the Mg2Si precipitate formation and decrease the amount of heat liberated during both primary and eutectic phase formation. Dendrite
arm spacing (DAS) is correlated to the cooling rate by a relationship of the form DAS =AT
-n, wheren is found to be of the order of 0.33. 相似文献
47.
John Drennan David R. Clarke Richard H. J. Hannink Thomas M. Shaw 《Journal of the American Ceramic Society》1994,77(8):2001-2008
The microstructure, average grain size, and density of Mg-PSZ sintered with SrO and SiO2 additions are found to depend on the partial pressure of oxygen in the sintering atmosphere. Over the range of 10−1 to 10° atm, both the average grain size and the density increase with oxygen partial pressure, for a constant SrO/SiO2 ratio. The partial pressure of oxygen also affects the microstructural distribution of the remnant liquid phase. At high partial pressures the liquid phase is uniformly distributed, whereas at lower oxygen pressures it is preferentially located near the surface. It is proposed that the microstructure produced by sintering is the result of a competition between liquid-phase-enhanced densification and the migration of the liquid phase to the free surface. The migration is attributed to vaporization of MgO from the liquid phase which increases with decreasing partial pressure of oxygen. 相似文献
48.
Yaping Liu James D. Livingston Samuel M. Allen 《Metallurgical and Materials Transactions A》1992,23(12):3303-3308
The microstructure within particles of the Laves phase Fe2Zr in a two-phase Fe-10 at. pct Zr alloy after compression was investigated using X-ray diffraction and electron microscopy.
Stressinduced phase transformation between C36 and C15 structures was found to be a major deformation mode for the Laves phase.
Twinning and stacking faults were also found within C15 regions. Phase transformation models based on partial dislocations
are discussed. 相似文献
49.
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
50.
S.‐C. Lo G.J. Richards J.P.J. Markham E.B. Namdas S. Sharma P.L. Burn I.D.W. Samuel 《Advanced functional materials》2005,15(9):1451-1458
We describe the preparation of a dendrimer that is solution‐processible and contains 2‐ethylhexyloxy surface groups, biphenyl‐based dendrons, and a fac‐tris[2‐(2,4‐difluorophenyl)pyridyl]iridium(III ) core. The homoleptic complex is highly luminescent and the color of emission is similar to the heteroleptic iridium(III ) complex, bis[2‐(2,4‐difluorophenyl)pyridyl]picolinate iridium(III ) (FIrpic). To avoid the change in emission color that would arise from attaching a conjugated dendron to the ligand, the conjugation between the dendron and the ligand is decoupled by separating them with an ethane linkage. Bilayer devices containing a light‐emitting layer comprised of a 30 wt.‐% blend of the dendrimer in 1,3‐bis(N‐carbazolyl)benzene (mCP) and a 1,3,5‐tris(2‐N‐phenylbenzimidazolyl)benzene electron‐transport layer have external quantum and power efficiencies, respectively, of 10.4 % and 11 lm W–1 at 100 cd m–2 and 6.4 V. These efficiencies are higher than those reported for more complex device structures prepared via evaporation that contain FIrpic blended with mCP as the emitting layer, showing the advantage of using a dendritic structure to control processing and intermolecular interactions. The external quantum efficiency of 10.4 % corresponds to the maximum achievable efficiency based on the photoluminescence quantum yield of the emissive film and the standard out‐coupling of light from the device. 相似文献