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11.
Marta Burgay Nanda Rea GianLuca Israel Andrea Possenti Luciano Burderi Tiziana Di Salvo Nichi D’Amico Luigi Stella Elisa Nichelli 《Astrophysics and Space Science》2007,308(1-4):531-534
We have performed deep searches for radio pulsations from four southern anomalous X-ray pulsars (AXPs) to investigate their
physical nature in comparison with the rotation powered pulsars. The data were acquired using the Parkes radio telescope with
the 1.4 GHz multibeam receiver. No pulsed emission with periodicity matching the X-ray ephemeris have been found in the observed
targets down to a limit of ∼0.1 mJy. A blind search has also been performed on all the 13 beams of the multibeam receiver
(the central beam being pointed on the target AXP), leading to the serendipitous discovery of two new radio pulsars and to
the further detection of 18 pulsars. Also a search for single dispersed pulses has been performed in the aim to detect signals
similar to those of the recently discovered rotating radio transients.
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12.
Bryan M. Gaensler Maura McLaughlin Stephen Reynolds Kazik Borkowski Nanda Rea Andrea Possenti Gianluca Israel Marta Burgay Fernando Camilo Shami Chatterjee Michael Kramer Andrew Lyne Ingrid Stairs 《Astrophysics and Space Science》2007,308(1-4):95-99
“Rotating RAdio Transients” (RRATs) are a newly discovered astronomical phenomenon, characterised by occasional brief radio
bursts, with average intervals between bursts ranging from minutes to hours. The burst spacings allow identification of periodicities,
which fall in the range 0.4 to 7 seconds. The RRATs thus seem to be rotating neutron stars, albeit with properties very different
from the rest of the population. We here present the serendipitous detection with the Chandra X-ray Observatory of a bright point-like X-ray source coincident with one of the RRATs. We discuss the temporal and spectral properties of
this X-ray emission, consider counterparts in other wavebands, and interpret these results in the context of possible explanations
for the RRAT population.
B.M.G. acknowledges the support of NASA through LTSA grant NAG5-13023 and of an Alfred P. Sloan Fellowship. 相似文献
13.
GeoJournal - This study is an attempt to carry landslide susceptibility assessment along national highway 1D a lifeline to the Ladakh region using Frequency Ratio Method in GIS environment. The... 相似文献
14.
R. L. Nanda 《Journal of the Indian Society of Remote Sensing》1978,6(2):67-74
In advanced countries, the survey of gravel deposits and soil for road construction is being increasingly conducted through aerial photographs as the process is expeditious and economical. However, no Air photo Interpretation technique had been developed to locate hiddenKankar deposits and other low grade aggregates met with in India. In view of this, research was undertaken at the Central Road Research Institute for the establishment of new Air Photo Patterns which enable the location of sources of these construction materials in the country. Since shortage of road aggregates both in the alluvial plains as well as desert areas is very acute andkankar is known to occur under an overburden of 2 to 4 ft. of soil, attempt were made for the formulation of Air Photo Patterns for the identification of such deposite. The investigation covered an area of about 4,500 sq. miles. (12,000 sq. kms.) in U.P. and 5,000 sq miles (13,000 sq kms.) in western Rajasthan and comprised a study of aerial photographs of the area in conjunction with ground survey. As a result of this study, well defined and distinct Air Photo Patterns for the location ofKankar deposits in both the above mentioned regions have been established. The accuracy of interpretation has been experienced to be of the order of about 75 to 80 per cent. Recently Air Photo Patterns for the indentification of hidden gravel deposits have also been confirmed by carrying out interpretation and survey in an area of about 300 sq miles (800 sq kms.) around Chandigarh. Since the country is embarking on big projects of road construction in the Five Year Plans, the utilisation of this technique for rapid survey of highway materials and the timely information about the location of such deposits, will go a long way in economising the cost of road construction. The Paper discusses the techniques of Air Photo Interpretation developed for hidden aggregate deposits and soils which would enable the indentification and location of potential natural resources, for future programme of the road construction. 相似文献
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S. N. Mahapatro A. K. Tripathy J. K. Nanda S. C. Rath 《Journal of the Geological Society of India》2013,82(4):319-329
The Eastern Ghats Belt (EGB), characterised by pervasive Grenvillian granulite facies metamorphism, is the host to several 950–1000 Ma old massif-type anorthosite complexes. The present work describes one such complex near Udayagiri from the northern margin of the EGB, reported for the first time as “Udayagiri anorthosite complex” (UAC). The ‘massif type’ UAC comprises mainly of anorthosite, leuconorite-olivine leuconorite and norite in the decreasing order of areal extent. Mineralogically, these rocks dominantly consist of cumulates of moderately calcic plagioclase (～An50–60), moderately magnesian intercumulus olivine (XMg: ～0.6) and orthopyroxene (XMg: 0.47 to 0.70). Metamorphic garnet (Alm: ～50 mol%) is also common in these rocks. Anorthosite and leuconorite of the UAC exhibit a moderate ‘+ve’ Eu anomaly. Norite occurs locally as schlierens and is relatively rich in Fe, P, Rb, Sr, Th, Nb, Ta, Y and REE which could be a residual melt product. These rocks exhibit both relict magmatic mineralogy and textures with a metamorphic impress manifested by the development of multilayered corona involving olivine, orthopyroxene, garnet, phlogopite, ilmenite and plagioclase during cooling of the pluton. The corona development is a result of combination of significant magmatic and metamorphic reactions which have the potential to provide important clues for deciphering the magmatic and metamorphic evolution of such plutons in ambient granulite facies conditions. 相似文献
18.
Marco P Maneta Purnendu N Singh Marcelo Torres Wesley W Wallender Stephen A Vosti Lineu N Rodrigues Luis H Bassoi Julie A Young 《Area》2009,41(1):94-106
Reducing poverty in rural areas of developing countries requires sustained and sustainable increases in agricultural water productivity. However, aside from traditional measures of precipitation, little is known about water available to farmers or how productively they use it. We present a crop-water productivity index (a ratio of the value of annual crop production to a dimensionless potential water availability index) for large water basins using readily available low-resolution data. The index is transferable, permits direct inter-basin comparisons, and is simple to calculate. We calculate the index for each municipality in the São Francisco river basin in Brazil. No clear patterns linking water availability and value of agricultural output are evident, even though clusters of municípios with high- and low-crop-water productivity emerge, and the former may be useful in guiding policies aimed at increasing water productivity. Finally, analyses of the effects of information uncertainty on the crop-water productivity index suggest that the returns to agricultural investments in certain places in the São Francisco river basin are more risky than others. Improvements in data quality and quantity can help refine estimates of the index and reduce their uncertainty. 相似文献
19.
In recent years, offshore reservoirs have been developed in deeper and deeper water environments. Steel catenary risers (SCRs) are being considered in deepwater development such as Northern North Sea. SCRs used in conjunction with a semi-submersible or floating production, storage and offloading (FPSO) in deepwater harsh environments present significant design challenges. The large vertical motions at the semi or FPSO induce severe riser response, which results in difficulty meeting strength and fatigue criteria at the hang off and touch down point locations. To improve the understanding of SCR behaviour and increase the confidence in the design of such systems in deepwater harsh environments, a parametric study on a SCR connected to a semi-submersible was carried out in this paper to deal with the factors that mainly influence the loading condition and fatigue life of the riser. Weight-optimized configurations were applied during the course of riser design. Riflex combined with DeepC was the primary analysis tool used for the long-term response of the nonlinear SCR structure simulations, which requires a large amount of computer time. Hence, the parameters affecting the efficiency and accuracy of the simulations have also been studied during the analysis process. 相似文献
20.
Nanda R. Shrestha 《The Professional geographer》1988,40(2):202-214
A preliminary analysis of the primary health care delivery component of a small rural development project in Deurali, Nepal, suggests that personal relations between project personnel and their target population (e.g., implementors'sincerity and commitment to service) can overcome many cultural, geographical, and class-related social barriers to achieving project objectives. The Deurali medical staff's ability to combine their technical skills with sincerity, hard work, and commitment has made the Deurali project reasonably successful in meeting villagers'primary health care needs. 相似文献