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41.
Determination of Coefficient of Radial Consolidation Using Steepest Tangent Fitting Method 总被引：1，自引：1，他引：0
J. S. Vinod A. Sridharan Buddhima Indraratna 《Geotechnical and Geological Engineering》2010,28(4):533-536
Barron (Trans ASCE 113:718–724, 1948) theoretical relationship between degree of consolidation (U
r
) and time factor (T
r
) is generally used to determine the coefficient of radial consolidation c
r
. Several researchers have proposed different laboratory techniques for obtaining the value of c
r
. However, the usual approach is to compare some salient features of the theoretical U
r
–T
r
relationship with the compression, δ and time, t based on the laboratory data. In this paper, rapid consolidation test procedure originally proposed by Su (J Soil Mech Found
Div Am Soc Civ Eng No. 95: Proc. Pap. 1729 (1–9), 1958) to determine the coefficient of vertical consolidation (c
v
) is extended to evaluate Barron’s coefficient of radial consolidation c
r
for the case of equal strain. The characteristic feature of the proposed method is the identification of the steepest tangent
from the δ–log t plot. The slope of steepest tangent is independent of the drain spacing ratio (n) with a value of 0.847. This approach is rapid, and it predicts more reliable values of c
r
as it is less influenced by the secondary compression. In addition, this method is more versatile and can be applied for
consolidation trends which do not always exhibit the typical S-shape. 相似文献
42.
Asuri Sridharan Ahmed El-Shafei Norihiko Miura 《Marine Georesources & Geotechnology》2013,31(1):21-50
The soft clay of Ariake Bay, in western Kyushu, Japan covers several hundred square kilometers. Ariake clay consists of the principal clay minerals namely smectite, illite, kaolinite and vermiculite, and other minerals in lesser quantity. The percentage of the principal clay mineral can vary significantly. The percent clay size fraction and the salt concentration can also vary significantly. In view of the importance of undrained shear strength in geotechnical engineering practice, its behavior has been studied with respect to variation in salt concentration. Basically two mechanisms control the undrained strength in clays, namely (a) cohesion or undrained strength is due to the net interparticle attractive forces, or (b) cohesion is due to the viscous nature of the double layer water. Concept (a) operates primarily for kaolinitic soil, and concept (b) dominates primarily for montmorillonitic soils. In Ariake clay, different clay minerals with different exchangeable cations and varying ion concentration in the pore water and varying nonclay size fraction are present. In view of this while both concepts (a) and (b) can coexist and operate simultaneously, one of the mechanisms dominates. For Isahaya clay, concept (a), factors responsible for an increase in level of flocculation and attractive forces result in higher undrained strength. Increase in salt concentration increases the remolded undrained strength at any moisture content. For Kubota and Kawazoe clays, concept (b) factors responsible for an expansion of diffuse double layer thickness, resulting in higher viscous resistance, increase the undrained shear strength, that is, as concentration decreases, the undrained strength increases at any moisture content. The liquid limit of Isahaya clay increases with increase in ion concentration and a marginal decrease is seen for both Kubota and Kawazoe clays, and their behavior has been explained satisfactorily. 相似文献
43.
Geocentric orbits of large eccentricity (e=0.9 to 0.95) are significantly perturbed in cislunar space by the Sun and Moon. The time-history of the height of perigee, subsequent to launch, is particularly critical. The determination of ‘launch windows’ is mostly concerned with preventing the height of perigee from falling below its low initial value before the mission lifetime has elapsed. Between the extremes of high accuracy digital integration of the equations of motion and of using an approximate, but very fast, stability criteria method, this paper is concerned with the development of a method of intermediate complexity using non-numeric computation. The computer is used as the theory generator to generalize Lidov's theory using six osculating elements. Symbolic integration is completely automatized and the output is a set of condensed formulae well suited for repeated applications in launch window analysis. Examples of applications are given. 相似文献
44.
Girija Rajaram A. N. Hanchinal R. Kalra K. Unnikrishnan K. Jeeva M. Sridharan A. Dhar 《Journal of Earth System Science》2002,111(1):51-62
The Indian Antarctic station Maitri (geog. 70‡45’S, 11‡45’E, geom. 66‡.03S, 53‡.21E) occupies a sub-auroral location during
magnetically quiet conditions(Σκρ < 10), but attains an auroral position when the auroral oval shifts equatorwards with increasing strength of magnetic disturbance.
At the latter times, triangulation with 3 fluxgate magnetometers located at the vertices of a suitable triangle provides a
means of monitoring mobile auroral ionospheric current systems over Maitri. The spacing between the magnetometers is typically
kept at 75–200 km, keeping in mind the scale-sizes of ∼ 100 km for these mobile current systems. This work reports the results
of two triangulation experiments carried out around Maitri in January 1992 and January 1995, both during Antarctic summer.
The velocities estimated for pulsations of the Pc4 and Pc5 type were about 0.59 km/sec in the direction 102‡.7 east of due
north, in the first case, and about 1–3 km/sec in the second case in the east-west direction.
While several magnetometer arrays exist in the northern auroral regions (e.g., the Alberta array in Canada, the Alaskan array
in the U.S. and the IMS Scandinavian array), there is no report in literature of triangulation through arrays in Antarctica,
except for a one-day study by Neudegget al 1995 for ULF pulsations of the Pc1 and Pc2 type. The velocities obtained for the Pi3 type of irregular pulsations over Antarctica
in the present study tally well with those obtained for northern auroral locations. 相似文献
45.
The zonally averaged UK Meteorological Office (UKMO) zonal mean temperature and zonal winds for the latitudes 8.75°N and 60°N are used to investigate the low-latitude dynamical response to the high latitude sudden stratospheric warming (SSW) events that occurred during winter of the years 1998–1999, 2003–2004 and 2005–2006. The UKMO zonal mean zonal winds at 60°N show a short-term reversal to westward winds in the entire upper stratosphere and lower mesosphere and the low-latitude winds (8.75°N) show enhanced eastward flow in the upper stratosphere and strong westward flow in the lower mesosphere during the major SSW events at high latitudes. The mesosphere and lower thermosphere (MLT) zonal winds acquired by medium frequency (MF) radar at Tirunelveli (8.7°N, 77.8°E) show a change of wind direction from eastward to westward several days before the onset of SSW events and these winds decelerate and weak positive (eastward) winds prevail during the SSW events. The time variation of zonal winds over Tirunelveli is nearly similar to the one reported from high latitudes, except that the latter shows intense eastward winds during the SSW events. Besides, the comparison of daily mean meridional winds over Tirunelveli with those over Collm (52°N, 15°E) show that large equatorial winds are observed over Tirunelveli during the 2005–2006 event and over Collm during the 1998–1999 events. The variable response of MLT dynamics to different SSW events may be explained by the variability of gravity waves. 相似文献
46.
G.J. Bhagavathiammal S. Sathishkumar S. Sridharan Manohar Lal S. Gurubaran K.U. Nair 《Journal of Atmospheric and Solar》2010,72(16):1204-1211
Spectral analysis of Tirunelveli (8.7°N, 77.8°E) MF radar winds for the year 2007 indicate the presence of long-period Kelvin waves with periods ～23 and ～16 days in the low-latitude mesosphere during Indian summer monsoon months. The dominant presence of these slow-phase speed waves at mesospheric altitudes motivated us to investigate their origin and vertical propagation characteristics. Space-time Fourier analysis of NCEP winds and OLR show the presence of these periodicities with zonal wavenumber 1 indicating that tropical convection is the potential source for these waves and westward phase of stratospheric QBO winds might have favoured these waves to reach the mesosphere. 相似文献
47.
This paper describes the pattern of geomagnetic solar quiet day, Sq, variations recorded at the Indian geomagnetic observatories. The extent to which the high and low latitude ionosphere is
interlinked electromagnetically during periods of quiet geomagnetic conditions is a point of debate. The concept of Gabriel
graph is applied to derive the boundaries for the variations of horizontal, vertical, and declination components of the earth’s
magnetic field during geomagnetically quiet periods. Data of the six Indian geomagnetic observatories (Alibag, Hyderabad,
Nagpur, Pondicherry, Visakapatnam, and Trivandrum) are considered for this analysis. This graph theoretical model is complementary
to the classical data analysis techniques. Analytical method and the results of the analysis are presented in the paper. 相似文献
48.
T. K. Sridharan 《Journal of Astrophysics and Astronomy》1992,13(3):217-239
We report a study of the kinematics of the cometary globules in the Gum Nebula using theJ= 1 → 0 transition line of12 CO. A morphological center for the system with which 60% of the globules are associated is identified. It is shown that the
observed radial velocities of the heads of the globules are consistent with an expansion of the system. Systematic velocity
gradients are present along some of the tails. The estimatedexpansion age and thetail stretching age are both ∼ a few million years, suggesting a common origin for the expansion and the formation of the tails. The presence
of young stars of similar ages in some of the globules points to star formation triggered by the same cause. Possible scenarios
are briefly discussed.
In partial fulfillment of the requirements for the Degree of Doctor of Philosophy of the Indian Institute of Science. 相似文献
49.
Anil Bhardwaj Stas Barabash Yoshifumi Futaana Yoichi Kazama Kazushi Asamura David McCann R. Sridharan Mats Holmstrom Peter Wurz Rickard Lundin 《Journal of Earth System Science》2005,114(6):749-760
This paper reports on the Sub-keV Atom Reflecting Analyzer (SARA) experiment that will be flown on the first Indian lunar
mission Chandrayaan-1. The SARA is a low energy neutral atom (LENA) imaging mass spectrometer, which will perform remote sensing
of the lunar surface via detection of neutral atoms in the energy range from 10 eV to 3 keV from a 100km polar orbit. In this
report we present the basic design of the SARA experiment and discuss various scientific issues that will be addressed. The
SARA instrument consists of three major subsystems: a LENA sensor (CENA), a solar wind monitor (SWIM), and a digital processing
unit (DPU). SARA will be used to image the solar wind-surface interaction to study primarily the surface composition and surface
magnetic anomalies and associated mini-magnetospheres. Studies of lunar exosphere sources and space weathering on the Moon
will also be attempted. SARA is the first LENA imaging mass spectrometer of its kind to be flown on a space mission. A replica
of SARA is planned to fly to Mercury onboard the BepiColombo mission. 相似文献
50.
Global surface temperature in relation to northeast monsoon rainfall over Tamil Nadu 总被引：3，自引：0，他引：3
The local and teleconnective association between Northeast Monsoon Rainfall (NEMR) over Tamil Nadu and global Surface Temperature
Anomalies (STA) is examined using the monthly gridded STA data for the period 1901–2004. Various geographical regions which
have significant teleconnective signals associated with NEMR are identified. During excess (deficient) NEMR years, it is observed
that the meridional gradient in surface air temperature anomalies between Europe and north Africa, in the month of September
is directed from the subtropics (higher latitudes) to higher latitudes (subtropics). It is also observed that North Atlantic
Oscillation (NAO) during September influences the surface air temperature distribution over north Africa and Europe. Also,
the NAO index in January shows significant inverse relationship with NEMR since recent times. The central and eastern equatorial
Pacific oceanic regions have significant and consistent positive correlation with NEMR while the western equatorial region
has significant negative correlation with NEMR. A zonal temperature anomaly gradient index (ZTAGI) defined between eastern
equatorial Pacific and western equatorial Pacific shows stable significant inverse relationship with NEMR 相似文献