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91.
In this communication, the stability of the double-diffusive solar ponds has been investigated in the linear approximation. The corresponding linearized system of equations of motion is reduced to a single integro-differential equation using the Green-function technique. In contrast to the conclusions of Veronis that, initially, the instability occurs as an oscillatory mode and at a value of RT (Rayleigh number for temperature) greater than RS the motion becomes steady, the present analysis shows that, initially, as RT increases from zero but remains considerably less than RS, exponentially growing and decaying modes (steady motion) occur first; for a value of RT more than a critical value RTc, the motion becomes oscillatory. This oscillatory motion may, due to the basic non-linear dynamics of the system, even become aperiodic. Further, for RS → ∞, the minimum value of RT for which steady motions can occur tends to , where where KS and KT are diffusivity coefficients for salt and temperature, respectively; as a contrast, according to Veronis, being the kinematic viscosity. 相似文献
92.
A. V. Kalinin V. P. Mal’tsev K. S. Shcheglov 《Journal of Communications Technology and Electronics》2007,52(5):510-526
The experimental characteristics of a 25-m reflector antenna used as part of a radiointerferometer with a base of 100 m are presented. The radiointerferometer operates in the 10-cm wave band on the basis of signals from natural extraterrestrial radio sources and artificial satellites. Measurement techniques and corresponding hardware are developed and investigated. 相似文献
93.
W. Jack Lackey John A. Hanigofsky Garth B. Freeman Regina D. Hardin Ajit Prasad 《Journal of the American Ceramic Society》1995,78(6):1564-1570
The feasibility of preparing small-diameter, high-strength, thermally stable silicon carbide fiber tows by the continuous chemical vapor deposition (CVD) of SiC onto carbon fiber tows was experimentally evaluated. Calculations of bending stresses and stresses caused by thermal expansion mismatch between the substrate and coating were used to evaluate the influence of coating thickness and substrate fiber diameter and type. Statistically designed and analyzed processing studies quantitatively showed the influence of key CVD process variables (temperature, pressure, and flow rates of CH3 SiCl3 and H2 ) on fiber attributes such as coating thickness and uniformity, surface roughness, percent agglomeration, and strength. Emphasis was given to conceiving and evaluating various fiber spreading devices in order to enhance coating uniformity and to minimize filament agglomeration within a tow. Uniform coatings and fiber tensile strengths as high as 4 GPa were achieved. 相似文献
94.
95.
Water quality management of a stretch of river Yamuna: An interactive fuzzy multi-objective approach 总被引:2,自引:2,他引:0
This paper presents an Interactive Fuzzy Multi-Objective Linear Programming (IFMOLP) model for water quality management in
a river basin. The IFMOLP model formulated will first evaluate dissolved oxygen (DO) concentrations or DO deficits at a point
in different reaches depending on the overall Biochemical Oxygen Demand (BOD) concentration present in the respective drain.
Subsequently, the model incorporates the aspirations and conflicting objectives of the decision maker (DM) by taking into
consideration the aspects relevant for pollution control boards as well as dischargers responsible for generating wastewater.
The uncertainty associated with specifying the water quality criteria (based on DO concentration or DO deficit) and treatment
cost to remove pollution level is incorporated by interacting the decision maker. In this process DM is asked to specify the
reference aspiration levels of achievement for the values of all membership functions generated with respect to each objective.
This provides flexibility for the pollution control authorities and dischargers to specify their aspirations. IFMOLP model
developed herein is then used in a case study for the evaluation of optimal BOD removal in different drains located across
the river Yamuna at New Delhi, India. The presented model will simulate the allocation of waste load efficiencies with satisfactory
results which will indicate usefulness of the model in managing more complex river basins along with better flexible policies
of water management. 相似文献
96.
Ajit R. Dhamdhere Ajay P. Malshe William F. Schmidt William D. Brown 《Microelectronics Reliability》2003,43(2):287-295
As applications continue to demand increasingly higher optical output power and longer lifetime, thermo-mechanical stresses on dissimilar materials interfaced for packaging pose an ever-growing challenge for the realization of a durable system. Particularly important for an epitaxy-down configuration is the die-attachment interface, which is desired to be defect free and stress managed for reliable optical alignment. A knowledge of the changes in the physical defect density and magnitude of the thermo-mechanical stress present in the active region as a function of the fabrication process and aging is crucial to an understanding of the influence of the process parameters and operating conditions on device performance and reliability. In this study, we investigated high power laser diode array packages aged under various conditions. Microscopic defect analyses of the die attachment interface and device stress were carried out using primarily metallography, scanning electron microscopy, scanning acoustic microscopy, microhardness, and micro-Raman spectroscopy. It was noted that the intermetallic compounds and microscopic physical defects at the die attach interface are detrimental to transient heat transfer, and thus, overall package reliability. Using micro-Raman spectroscopy, we found that tensile stress near the bar-package interface increases with aging for the first few hundred hours and then decreases with further aging. 相似文献
97.
In a recent paper a method is described for constructing certain approximations to a general element in the closure of the convex hull of a subset of an inner product space. This is of interest in connection with neural networks. Here we give an algorithm that generates simpler approximants with somewhat less computational cost. 相似文献
98.
Argues that the genetic and social variables were so confounded in S. Scarr and R. A. Weinberg's (see record 1977-07996-001) article on Black children adopted by White families that the results are consistent with virtually any theory of race differences in IQ. It is difficult to see any scientific or applied value in transracial adoption studies. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
99.
A sequential procedure is developed in order to construct a confidence interval of “fixed-width and preassigned coverage probability” for the inverse of the coefficient of variation of a normal population. The proposed sequential procedure is proved to be “asymptotically efficient and consistent” in the sense of Chow and Robbins ([1]: Ann. Math. Statist. 36, 457–462 (1965)). Asymptotic distribution of the stopping time is derived. 相似文献
100.
Cross-ply composite specimens of metal matrix (SCS-6/Ti-6-4 [90/0]
s
) and polymer matrix (graphite/epoxy AS4/3502 [0/90]
s
) were subjected to tensile fatigue tests to induce stiffness degradaton. Extensional plate wave velocities in the 0, 45,
and 90° directions, together with the quasi-shear wave velocity in the 90° direction, were used to characterize the degradation of the stiffness constants of each specimen during fatigue. The laminate
stiffness constants in the x - and y -directions (E
x
,E
y
) and the shear modulus (G
xy
) were determined. The laminate stiffness, E
x
, was also monitored through direct measurement by using an extensometer during fatigue loading. The trend in the stiffness
degradation of the titanium matrix composite was identical in both measurement techniques, but the stiffness values calculated
from the extensional velocity measurements were higher than those obtained from the extensometer. This discrepancy was shown
to be due to microcrack closure during wave velocity measurements when the tensile stress was removed from the specimen. The
graphite/epoxy specimens appeared to suffer only a small reduction in their stiffness. 相似文献