Determination of forces in a shallow shell loaded on a circular area

1988 ◽  
Vol 20 (6) ◽  
pp. 790-794
Author(s):  
V. P. Ol'shanskii
Keyword(s):  
1999 ◽  
Vol 77 (8) ◽  
pp. 1175-1184 ◽  
Author(s):  
W James Rettie ◽  
Philip D McLoughlin

For many species, determination of habitat selection is based on habitat-use data obtained through radiotelemetry. Recent papers pertaining to study techniques have largely ignored the effect of habitat-dependent bias in the performance of radiotelemetry systems. Such biases cannot be overcome by increasing radiotelemetry precision, excluding data, or increasing sample sizes, as the biases are centred around data that are missing or that contain habitat-dependent errors in location. The problem is best addressed at the data-analysis stage through the use of geographic information systems. We used Monte Carlo simulations to assess the effect of habitat-dependent bias in radiotelemetry studies on the assessment of habitat selection. We looked at the effects of habitat-patch size, level of telemetry signal inhibition, level of habitat co-occurrence, and selection pattern. We demonstrated that regarding use as the composition of habitat types within a circular area around each telemetry location can help to overcome the inaccurate assessment of habitat-selection patterns that biased data produce. The size of the circular area best able to overcome the bias is related to habitat patch size and to the level of association between two or more habitat types. Furthermore, we argue that the characteristics of habitat mosaics selected by animals can and should be studied in this way.


1978 ◽  
Vol 45 (4) ◽  
pp. 845-851
Author(s):  
H. Ainso

A general method is presented for solving shallow shell problems with finite boundaries and with an arbitrarily placed load that is uniformly distributed over a circular area of radius r0. A known solution for the distributed load on an unbounded shell is used to describe the load effects, and this particular solution is combined with Reissner’s general solution of the shallow shell equations in such a manner that all the boundary conditions are satisfied. Numerical results have been obtained for a shallow shell, clamped at the outer boundary and having a circular polar aperture free of tractions and support.


1989 ◽  
Vol 29 (6) ◽  
pp. 915-919
Author(s):  
B. V. Nerubailo ◽  
I. F. Obraztsov ◽  
V. P. Ol'shanskii

Development ◽  
1994 ◽  
Vol 120 (1) ◽  
pp. 71-81 ◽  
Author(s):  
A. Fjose ◽  
J.C. Izpisua-Belmonte ◽  
C. Fromental-Ramain ◽  
D. Duboule

The zebrafish hlx-1 gene belongs to the H2.0 subfamily of homeobox genes and is closely related to the mouse Dbx gene with respect to both homeodomain homology (96.7%) and neural expression during embryogenesis. Analysis of hlx-1 expression by in situ hybridization reveals several particularly interesting features. In late gastrula embryos, hlx-1 transcripts are detected within a circular area in the region of the presumptive rostral brain. Subsequently, the expression domain becomes restricted to the hypoblast and undergoes dynamic changes involving conversion into a longitudinal stripe which elongates and retracts following a temporal sequence. The site of transient hlx-1 expression along the ventral midline of the rostral neurectoderm, which in part corresponds to the prechordal plate, suggests a role in the determination of head mesoderm as well as in patterning of the rostral brain. As the midline stripe gradually disappears, the hlx-1 gene becomes regionally expressed within the diencephalon and at a specific dorsoventral level along the hindbrain and spinal cord. In the hindbrain, expression is initiated in dorsoventrally restricted transversal stripes which correlate with the segmental pattern of rhombomeres. The stripes fuse into bilateral columns that are later converted to two series of paired transversal stripes at the rhombomere borders. This pattern is consistent with the proposed subdivision of hindbrain segments into rhombomere centers separated by border regions.


1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.


1999 ◽  
Vol 190 ◽  
pp. 549-554
Author(s):  
Nino Panagia

Using the new reductions of the IUE light curves by Sonneborn et al. (1997) and an extensive set of HST images of SN 1987A we have repeated and improved Panagia et al. (1991) analysis to obtain a better determination of the distance to the supernova. In this way we have derived an absolute size of the ringRabs= (6.23 ± 0.08) x 1017cm and an angular sizeR″ = 808 ± 17 mas, which give a distance to the supernovad(SN1987A) = 51.4 ± 1.2 kpc and a distance modulusm–M(SN1987A) = 18.55 ± 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to bed(LMC) = 52.0±1.3 kpc, which corresponds to a distance modulus ofm–M(LMC) = 18.58±0.05.


1961 ◽  
Vol 13 ◽  
pp. 29-41
Author(s):  
Wm. Markowitz
Keyword(s):  

A symposium on the future of the International Latitude Service (I. L. S.) is to be held in Helsinki in July 1960. My report for the symposium consists of two parts. Part I, denoded (Mk I) was published [1] earlier in 1960 under the title “Latitude and Longitude, and the Secular Motion of the Pole”. Part II is the present paper, denoded (Mk II).


1972 ◽  
Vol 1 ◽  
pp. 27-38
Author(s):  
J. Hers

In South Africa the modern outlook towards time may be said to have started in 1948. Both the two major observatories, The Royal Observatory in Cape Town and the Union Observatory (now known as the Republic Observatory) in Johannesburg had, of course, been involved in the astronomical determination of time almost from their inception, and the Johannesburg Observatory has been responsible for the official time of South Africa since 1908. However the pendulum clocks then in use could not be relied on to provide an accuracy better than about 1/10 second, which was of the same order as that of the astronomical observations. It is doubtful if much use was made of even this limited accuracy outside the two observatories, and although there may – occasionally have been a demand for more accurate time, it was certainly not voiced.


2000 ◽  
Vol 179 ◽  
pp. 205-208
Author(s):  
Pavel Ambrož ◽  
Alfred Schroll

AbstractPrecise measurements of heliographic position of solar filaments were used for determination of the proper motion of solar filaments on the time-scale of days. The filaments have a tendency to make a shaking or waving of the external structure and to make a general movement of whole filament body, coinciding with the transport of the magnetic flux in the photosphere. The velocity scatter of individual measured points is about one order higher than the accuracy of measurements.


1975 ◽  
Vol 26 ◽  
pp. 341-380 ◽  
Author(s):  
R. J. Anderle ◽  
M. C. Tanenbaum

AbstractObservations of artificial earth satellites provide a means of establishing an.origin, orientation, scale and control points for a coordinate system. Neither existing data nor future data are likely to provide significant information on the .001 angle between the axis of angular momentum and axis of rotation. Existing data have provided data to about .01 accuracy on the pole position and to possibly a meter on the origin of the system and for control points. The longitude origin is essentially arbitrary. While these accuracies permit acquisition of useful data on tides and polar motion through dynamio analyses, they are inadequate for determination of crustal motion or significant improvement in polar motion. The limitations arise from gravity, drag and radiation forces on the satellites as well as from instrument errors. Improvements in laser equipment and the launch of the dense LAGEOS satellite in an orbit high enough to suppress significant gravity and drag errors will permit determination of crustal motion and more accurate, higher frequency, polar motion. However, the reference frame for the results is likely to be an average reference frame defined by the observing stations, resulting in significant corrections to be determined for effects of changes in station configuration and data losses.


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