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1.
J. M. Parpia W. P. Kirk P. S. Kobiela Z. Olejniczak 《Journal of Low Temperature Physics》1985,60(1-2):57-72
The ac susceptibility of lanthanum-diluted cerium magnesium nitrate has been compared to the temperature scales as derived
from the (P, T) relation determined by Halperin and that was measured recently by Greywall. It is found that the susceptibility does
not obey a simple Curie-Weiss law over the temperature range between 1 and 50 mK. The results of these calibrations are also
used to determine the temperatures for the second-order phase transitions into the superfluid phases of3He at several pressures. TheseT
c(P) values are compared to results of earlier experiments that used thermometry based on the susceptibility of platinum as well
as other thermometry techniques. 相似文献
2.
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4.
Liang-Min Wang Shung K.K. Camps O.L. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1996,43(3):473-481
Time delay estimation is a very important operation in ultrasound time-domain flow mapping and correction of phase aberration of an array transducer. As the interest increases in the application of one and a half-dimensional (1.5-D) and two-dimensional (2-D) array transducers to improving image quality and three-dimensional (3-D) imaging, the need of simple, fast, and sufficiently accurate algorithms for real-time time delay estimation becomes exceedingly crucial. In this paper, we present an adaptive time-delay estimation algorithm which minimizes the problem of noise sensitivity associated with the one bit correlation while retaining simplicity in implementation. This algorithm converts each sample datum into a two bit representation including the sign of the sample and an adaptively selected threshold. A bit pattern correlation operation is applied to find the time delay between two engaged signals. By using the criterion of misregistration as an indicator, we are able to show that the proposed algorithm is better than one bit correlation in susceptibility to noise level. Analytical results show that the improvement in reducing misregistration of the two bit correlation over its counterpart is consistent over a wide range of noise level. This is achieved by an adaptive adjustment of the threshold to accommodate signal corruption due to noise. The analytical results are corroborated by results from simulating the blood as a random distribution of red blood cells. Finally, we also present a memory-based architecture to implement the two bit correlation algorithm whose computation time does not depend upon the time delay of the signals to be correlated 相似文献
5.
Scale and sludge from Bulalo geothermal field, Philippines, have been characterized by whole rock analysis, radioactivity counting, size analysis, light microscopy, scanning electron microscopy, and X-ray diffraction. Their leachability was assessed by regulatory leaching procedures and by sequential extraction. Both scale and sludge consisted mostly of oxides of Si, Al, and Fe with no radionuclides detected. The scale had 10% S content. Sulfides and silicates were important phases in both samples having size ranges from submicron to 2 mm. Geothermal soils at Bulalo have higher than normal soil levels of As, S, Cu, Cr, Zn, and Pb but regulatory leaching tests indicated that these elements are not released. However, the sequential extraction showed that As, Cu, and Zn were leachable under extreme conditions. 相似文献
6.
The crystallization behaviour of three amorphous alloys, Co50Ni25Si15B10, Ni50Co25Si15B10 and Ni50Co25P15B10, was studied by means of differential thermal analysis in conjunction with scanning transmission electron microscopy. Isochronal annealing showed a strong dependence of crystallization on scan rate over the range of 1.99 to 20.70 K min–1. At high Co/Ni ratios, a sequential two-stage crystallization process involving primary MS-I phase followed by MS-II phase precipitation was observed. At low Co/Ni ratios MS-I and MS-II crystallization were concurrent and inseparable. Replacement of the metalloid Si with P as the glass-former dramatically reduced the activation energy for crystallization as well as the crystallization temperature. A mechanistic understanding of these findings was pursued in light of TEM/STEM microanalysis 相似文献
7.
Douglas H. Taylor Kirk E. Lagory Daniel J. Zaccaro Ronald J. Pfohl R.Dana Laurie 《The Science of the total environment》1985
Trichloroethylene (TCE) is a common contaminant of underground water supplies. To examine the effect of TCE on the developing central nervous system, rats were exposed to TCE throughout gestation until 21 days postpartum via their dams' drinking water. TCE concentrations of 312 mg/l, 625 mg/l and 1250 mg/l were tested. Exploratory behavior was higher in 60- and 90-day old male rats which were exposed to any level of TCE. The effect of TCE-exposure on locomotor activity (running wheel) was also examined in 60-day old males (625 and 1250 ppm exposure groups). Locomotor activity was significantly higher in rats exposed to 1250 ppm TCE. These data suggest that TCE has long-term effects on behaviour. 相似文献
8.
The formation of zinc ferrite (ZnFe2O4) during the roasting of iron-bearing zinc concentrates requires substantial additional processing to recover the zinc from
this compound by leaching and to eliminate the iron from the leachate. The phase changes that occur in the particles of a
typical industrial zinc sulfide concentrate during roasting in a fluidized bed at 1223 K were investigated by the use of light
microscopy, electron microprobe analysis, and SEM with EDS. The processes which the iron undergoes during its eventual transformation
into ferrite have been clarified by examination of the phases and the morphology of partially roasted marmatitic sphalerite
particles (Zn, Fe)S, and by reference to the known phase equilibria involved in the Zn-Fe-S-0 system. The oxidation of ironbearing
sphalerite occurs in three stages. The first involves the selective diffusion of most of the iron to the particle surface
resulting in the formation of an iron oxide shell enclosing a largely unreacted zinc sulfide kernel. In the second stage,
this kernel is oxidized to form a solid solution of zinc oxide and iron oxide. The iron is initially present in the ferrous
state but, with the disappearance of the sulfide kernel, is oxidized to ferric iron. In the final stage, this dissolved iron
oxide and the iron oxide shell react with the surrounding zinc oxide to form the refractory spinel zinc ferrite. 相似文献
9.
Kirk C. Valanis 《Canadian Metallurgical Quarterly》2003,129(9):1039-1047
In this paper we derive Newton’s 2nd Law of Motion from the constitutive equation of elasticity of a space-time continuum in four dimensions. This we do by introducing a four-dimensional material continuum with a Minkowskian metric, in analogy with Einstein’s general theory of relativity. The four-continuum is deformable in both space and time. The physics of the deformation is embedded in a variational principle, which is a form-invariant extension of its classical mechanical counterpart in three dimensions, but with the acceleration term absent. General dynamic equations of elasticity in four dimensions are thereby derived. When the constraint of temporal inextensibility (universal time) is introduced, these equations yield readily the dynamic equations of elasticity in three dimensions. The presence of the inertia term in these equations, is a direct consequence of the temporal curvature induced by the deformation of the four-continuum. Newton’s law of motion for rigid bodies follows when the additional constraint of spatial inextensibility is introduced. 相似文献
10.
Factors affecting the power of the ultrasonic Doppler signal within the flow cycle have been evaluated experimentally using a pulsatile flow loop model. Polystyrene microspheres and porcine red cells suspended in saline solution for hematocrits between 2 and 40% were used as scattering fluid in the flow model. Experiments were performed at mean flow velocities of 11, 64, and 76 cm/s. In laminar flow experiments performed at a mean velocity of 11 cm/s, no variation of the Doppler power was found for both polystyrene microspheres and red cell suspensions (40% hematocrit). When turbulence was induced in the flow model, the power increasing during systole, a maximum was observed early after peak systole, and a decrease was obtained in diastole during deceleration of flow 相似文献