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91.
Partial-thickness rotator cuff tears are now acknowledged to be an important entity in the spectrum of the impingement syndrome. The pathogenesis of partial-thickness tears is often age- and activity-related. Surgical decision making is influenced by the extent of the tear and the associated bony and soft-tissue pathology.  相似文献   
92.
The influence of the initial grain morphology on the anomalous grain growth in donor-doped barium titanate has been studied. The results show that powders with aspherically shaped grains exhibit a much lower critical donor-dopant concentration, inhibiting anomalous grain growth during sintering, than powders with equisized spherically shaped grains and a similar, or even a lower, initial specific surface area.  相似文献   
93.
We have studied suspensions of hard-magnetic BaFe12O19 particles in water, ethanol and 1-butanol. The surfaces of these particles were previously modified with the surfactant dodecylbenzylsulphonic acid. The stabilities of the suspensions were estimated from their saturation concentrations and zeta potentials. We found that the 1-butanol suspensions were more stable than the ethanol-based suspensions and much more stable than the water-based suspensions. We analyzed the suspensions and the dispersed particles using gravimetry, conductometry and transmission electron microscopy, measured their zeta potentials, and calculated the interparticle-attraction interaction energies due to the van der Waals and magnetic dipole–dipole forces. The magnitudes of the attraction energies varied significantly with the particles’ sizes and the separation distances between the particles, and we found that the contribution of the van der Waals attraction energy can be neglected with respect to the magnetic dipole–dipole attraction. The observed differences in the stability of the suspensions were explained on the basis of the calculated electrostatic and steric repulsion energies. Electrosteric stabilization was possible in the 1-butanol and the ethanol for particles with radii and thicknesses up to 15 nm, while a too small electrostatic repulsion and the absence of steric repulsion in the water resulted in rapid agglomeration.  相似文献   
94.

The present work introduces the main results of a detailed experimental program aimed at investigating the influence of the design parameters and of the working conditions on the global characteristics of squeeze film dampers (SFD) for serial aircraft engines. The SFD is sealed at both ends and is executing circular centered orbits. The results are presented for the tangential and the radial global force in the SFD and the leakage flow rate. The pressure field inside the SFD could also be measured and shows the influence of the inertia force, of the cavitation, and probably of the turbulence regime, as well as the interaction of these effects with the feeding groove. The limits of the existing theoretical models are also demonstrated.

  相似文献   
95.
In order to reduce the embarked mass, the new designs of turbojet engines use softened rotors working with higher speeds. Following this trend, the use of intershaft bearings in dual-spool turbojets is then recommended for reducing weight. However, due to residual unbalances present in both rotors, the intershaft bearing is submitted to hard working conditions. A supplementary damping might then be necessary in order to enable working to rotation speeds higher than the critical ones. The adopted solution consists of introducing a thin fluid film between the intershaft bearing and one of the two rotors in order to provide the necessary damping. However, due to the rotation of the inner and of the outer rings, fluid film instabilities similar to those met in classical hydrodynamic bearings can appear. This paper is focused on the experimental investigation of several designs of the intershaft bearing damper and of their influence on the dynamic behavior of a double spool rotor. First, a double spool rotor test rig integrating an intershaft bearing is presented.

Subsequently, the experimental results are discussed for two dynamic configurations of the double spool rotor and for three intershaft bearing damper designs. For co- and counterrotating shafts, the tests show that the integration of a fluid film on the intershaft bearing makes it possible to attenuate the vibrations on both rotors. Furthermore, the tests confirm that instabilities appear under certain conditions depending on the type of the crossed mode and on the design of the intershaft bearing damper.  相似文献   
96.
Assessment of brown rot decay is one of the most important issues within remedial treatment of attacked wood constructions. Pilodyn is a well-established tool for the assessment of density of several commercially important plantation species, therefore the authors were interested in its suitability to evaluate rate of decay as well. The Pilodyn measurements performed on Norway spruce wood exposed to several brown rot fungi clearly indicate correlations between needle penetration and mass loss.  相似文献   
97.
Waxes are used for treatment of wood surfaces for several decades predominately as surface treatments because they weakly penetrate into the wood. In order to overcome this issue, water emulsions were applied in the present experiment. Five water emulsions of various concentrations were used, namely montan wax, polyethylene, ethylene copolymer and oxidized polyethylene wax. Performance of wax treated beech (Fagus sylvatica) and Norway spruce (Picea abies) against white rot, brown rot and blue stain fungi was tested. In parallel, sorption properties of wax treated wood were determined. The treated specimens were more resistant to wood decay fungi. Polyethylene and oxidized polyethylene wax were found to be particularly efficient. Although this treatment does not improve resistance to blue stain fungi, it reduces the sorption of water.  相似文献   
98.
A dialkylsubstituted imidazolium iodide ionic liquid (1-methyl-3-[3-(trimethoxy-lambda4-silyl)propyl]imida-zolium iodide, MTMSPIm+I-) was prepared with the intention of using it as a quasi-solid-state electrolyte for dye-sensitized photoelectrochemical (DSPEC) cells of Gr?tzel design, while the analogous electrolyte in a gel state was made by the addition of tetramethoxysilane (TMOS) in the molar ratio MTMSPIm+I-:TMOS = 1:1. The structure of the MTMSPIm+I- in its non-hydrolyzed and hydrolyzed states and in its fully condensed form, obtained after ageing the sols for various times (from a few hours to a few weeks) and heating them at 200 degrees C (fully condensed form), was studied employing time-dependent infrared attenuated total reflection (ATR) and 29Si NMR spectroscopic measurements. The structure of the condensed species was correlated with the viscosity and the specific conductivity measurements of MTMSPIm+I- sols and TMOS/MTMSPIm+I- gels during their ageing. The final product of the condensation of MTMSPIm+I- sols was described as a positively-charged ladder-like polysilsesquioxane with Tn end groups exhibiting a single T3 signal in 29Si NMR spectra and characteristic doublet bands at 1138 and 1049 cm(-1) in IR. This structure was retained to a large extent in TMOS/MTMSPIm+I- gels, confirming their nanocomposite structure. The results of the ATR infrared time-dependent spectroscopic studies showed that in the course of condensation of sols, the refractive index of the modes attributed to the polysilsesquioxane species exhibited strong dispersion, which led to shifts in the vibrational band positions in the experimental ATR spectra. This effect accompanies the sol-to-gel transformations and has not yet been considered as a possible error in analysis of the ATR spectra of sols and gels. The calculation procedure for obtaining the corresponding transmission spectra is briefly outlined and the results applied in this work.  相似文献   
99.
BACKGROUND: Recent data suggest that winter depression (seasonal affective disorder [SAD]) may be a subtype of affective disorder that is closely related to alcoholism. Dawn simulation has been shown in controlled trials to be effective in SAD. The present study examined the effectiveness of dawn simulation in abstinent alcoholics who met DSM-III-R criteria for major depression, or bipolar disorder, depressed with seasonal pattern. METHOD: All 12 subjects with winter depression had a history of either alcohol dependence or alcohol abuse according to DSM-III-R and had been abstinent from alcohol for at least 6 months. They also fulfilled criteria for SAD according to Rosenthal and were hypersomnic and drug free. After a 1-week baseline period, the subjects were randomly assigned to a 1-week treatment period at home with either a white 1.5-hour dawn from 4:30 a.m. to 6:00 a.m. peaking at 250 lux or a red 1.5-hour dawn from 4:30 a.m. to 6:00 a.m. peaking at 2 lux. The subjects were told that they would receive daily either a red or a white dawn reaching the same illuminance, an illuminance that would be much dimmer than standard bright light treatment. At the end of each week, the subjects were blindly assessed by a psychiatrist using the Structured Interview Guide for the Hamilton Depression Rating Scale-Seasonal Affective Disorder version (SIGH-SAD). RESULTS: For the 6 subjects completing the white dawn treatment, the mean SIGH-SAD score decreased from 33.0 at baseline to 15.8 after treatment. For the 6 subjects completing the dim red dawn treatment, the mean SIGH-SAD score decreased from 34.3 to 32.7. The mean post-dawn SIGH-SAD score was significantly lower after the white dawn treatment than after the dim red dawn treatment (ANCOVA with baseline SIGH-SAD as the covariate, F = 12.95, p < .01). Superiority of the white dawn was also found by analogous analyses for the Hamilton Rating Scale for Depression (HAM-D) (p < .01) and the SAD Subscale (p < .05). CONCLUSION: The present study suggest that dawn simulation may be helpful in decreasing depression in abstinent alcoholics with SAD. Further study is necessary to confirm these preliminary findings and to determine whether dawn simulation might be helpful in preventing relapse in abstinent alcoholics who have SAD.  相似文献   
100.
Grain growth and semiconductivity of donor-doped BaTiO3ceramics with an excess of BaO and additions of SiO2or B2O3were studied. The microstructures and electrical measurements on sintered samples revealed that their electrical properties are related to the microstructure development of the sintered samples. Samples heated with an excess of BaO developed a normal microstructure during sintering, as a consequence of normal grain growth (NGG), and were yellow and insulating. In contrast, samples with an excess of BaO and an addition of SiO2or B2O3exhibited anomalous grain growth (AGG) and were dark blue and semiconducting after sintering. When some BaTiO3seed grains were embedded in a sample of donor-doped BaTiO3with an excess of BaO (without SiO2or B2O3), AGG was observed, i.e., some seed grains grew into large grains and were blue and semiconducting. An explanation is given for why AGG is responsible for the oxygen release and the formation of semiconducting grains in donor-doped BaTiO3and not NGG.  相似文献   
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