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341.
Several water and surface microlayer samples from Lake St. Clair, the Niagara River, and the North Shore of Lake Ontario collected during 1983–1986 have been assayed for a variety of radionuclides. In addition, the foam accumulating in the pool just below Niagara Falls was also analyzed and found to be the most efficient aqueous phase collector of137Cs,210Pb, and226Ra.The order of radioisotope specific activities from highest to lowest is: Lake Ontario sediment, Niagara River suspended solids, Niagara River foam, surface microlayer water, and subsurface water. Radiological dose rates to the sediments from137Cs,226Ra, and228Th total about 5 mGy/y. 相似文献
342.
With the aim of investigating the resonance system of NO, equivalent width calculations have been made for the 213.575 nm, Q
1(31.5) line of the 1–0 band of -system of NO for the photospheric HSRA model, and for the line 214.012 nm, Q
1(25.5) line of the same band system for Zwaan's (1974) sunspot model.Calculations show that -band system would not show up in the photospheric spectrum whereas a sunspot model yields an equivalent width of 72 mÅ suggesting that sunspots may provide relatively more favourable conditions for the detections of the resonance systems of some abundant molecules in the inaccessible ultraviolet region. 相似文献
343.
Displacement of the Sun from the Galactic plane 总被引:1,自引:0,他引:1
Y. C. Joshi 《Monthly notices of the Royal Astronomical Society》2007,378(2):768-776
344.
Surya K. Dutta Someshwar Das S. C. Kar U. C. Mohanty P. C. Joshi 《Journal of Earth System Science》2009,118(5):413-440
The change in the type of vegetation fraction can induce major changes in the local effects such as local evaporation, surface
radiation, etc., that in turn induces changes in the model simulated outputs. The present study deals with the effects of
vegetation in climate modeling over the Indian region using the MM5 mesoscale model. The main objective of the present study
is to investigate the impact of vegetation dataset derived from SPOT satellite by ISRO (Indian Space Research Organization)
versus that of USGS (United States Geological Survey) vegetation dataset on the simulation of the Indian summer monsoon. The present
study has been conducted for five monsoon seasons (1998–2002), giving emphasis over the two contrasting southwest monsoon
seasons of 1998 (normal) and 2002 (deficient).
The study reveals mixed results on the impact of vegetation datasets generated by ISRO and USGS on the simulations of the
monsoon. Results indicate that the ISRO data has a positive impact on the simulations of the monsoon over northeastern India
and along the western coast. The MM5-USGS has greater tendency of overestimation of rainfall. It has higher standard deviation
indicating that it induces a dispersive effect on the rainfall simulation. Among the five years of study, it is seen that
the RMSE of July and JJAS (June–July–August–September) for All India Rainfall is mostly lower for MM5-ISRO. Also, the bias
of July and JJAS rainfall is mostly closer to unity for MM5-ISRO. The wind fields at 850 hPa and 200 hPa are also better simulated
by MM5 using ISRO vegetation. The synoptic features like Somali jet and Tibetan anticyclone are simulated closer to the verification
analysis by ISRO vegetation. The 2 m air temperature is also better simulated by ISRO vegetation over the northeastern India,
showing greater spatial variability over the region. However, the JJAS total rainfall over north India and Deccan coast is
better simulated using the USGS vegetation. Sensible heat flux over north-west India is also better simulated by MM5-USGS. 相似文献
345.
A. Apparao G.S. Srinivas V. Subrahmanya Sarma P.J. Thomas M.S. Joshi P. Rajendra Prasad 《Geophysical Prospecting》2000,48(5):797-813
We define the apparent frequency effect in induced polarization (IP) as the relative difference between apparent resistivities measured using DC excitation on the one hand and high‐frequency excitation (when the IP effect vanishes) on the other. Assuming a given threshold for the minimum detectable anomaly in the apparent frequency effect, the depth of detection of a target by IP can be defined as that depth below which the target response is lower than the threshold for a given electrode array. Physical modelling shows that for the various arrays, the depth of detection of a highly conducting and volume polarizable target agrees closely with the depth of detection of an infinitely conducting and non‐polarized body of the same shape and size. The greatest depth of detection is obtained with a two‐electrode array, followed by a three‐electrode array, while the smallest depth of detection is obtained with a Wenner array when the array spread is in‐line (i.e. perpendicular to the strike direction). The depth of detection with a Wenner array improves considerably and is almost equal to that of a two‐electrode array when the array spread is broadside (i.e. along the strike direction). 相似文献
346.
2013年4月20日在我国四川省芦山(30.284o N, 102.955o E)发生MS7.0地震,计算该地区潮汐变化,地震时刻引潮力处于最低相位点,显示引潮力的诱震作用属于典型逆冲断层作用类型。以此潮汐周期为时间指示(4月12日~4月23日),利用NOAA卫星地面长波辐射(OLR)数据资料分析全国范围地震前后热辐射值连续变化,结果显示:伴随潮汐演化,在全国范围(17°N-55°N ~ 73°E-155°E)内,震前OLR仅震中及其相关联断裂附近发生了显著而连续异常变化过程:在时间上经历了起始增温→异常加强→高峰→衰减→发震→平静的演化过程;在空间上异常位置与震中基本吻合,发展过程表现出沿断裂带由分散→汇聚→分散的破裂过程,与岩石应力加载破裂演化经历:初始微动破裂→扩张破裂→应力闭锁→地震爆发→平静阶段的力学过程完全吻合,显示天体引潮力对处于临界状态的活动断层具有诱发作用,而长波辐射异常是地震构造应力应变过程辐射表征。将引潮力与OLR异常结合在地震前兆研究中有一定的实用价值。 相似文献
347.
Use of spectral acceleration data for determination of three-dimensional attenuation structure in the Pithoragarh region of Kumaon Himalaya 总被引:1,自引:0,他引:1
Three-dimensional attenuation structures are related to the subsurface heterogeneities present in the earth crust. An algorithm
for estimation of three-dimensional attenuation structure in the part of Garhwal Himalaya, India has been presented by Joshi
(Curr Sci 90:581–585, 2006b; Nat Hazards 43:129–146, 2007). In continuation of our earlier approach, we have presented a method in which strong motion data have been used to estimate
frequency-dependent three-dimensional attenuation structure of the region. The border district of Pithoragarh in the Higher
Himalaya, India, lies in the central seismic gap region of Himalaya. This region falls in the seismic zones IV and V of the
seismic zoning map of India. A dense network consisting of eight accelerographs has been installed in this region. This network
has recorded several local events. An algorithm based on inversion of strong motion digital data is developed in this paper
to estimate attenuation structure at different frequencies using the data recorded by this network. Twenty strong motion records
observed at five stations have been used to estimate the site amplification factors using inversion algorithm defined in this
paper. Site effects obtained from inversion has been compared with that obtained using Nakamura (1988) and Lermo et al. (Bull Seis Soc Am 83:1574–1594, 1993) approach. The obtained site amplification term has been used for correcting spectral acceleration data at different stations.
The corrected spectral acceleration data have been used as an input to the developed algorithm to avoid effect of near-site
soil amplification term. The attenuation structure is estimated by dividing the entire area in several three-dimensional block
of different frequency-dependent shear wave quality factor Q
β
(f). The input to this algorithm is the spectral acceleration of S phase of the corrected accelerogram. The outcome of the algorithm
is given in terms of attenuation coefficient and source acceleration spectra. In the present study, this region has been divided
into 25 rectangular blocks with thickness of 10 km and surface dimension of 12.5 × 12.1 km, respectively. Present study gives
three-dimensional attenuation model of the region which can be used for both hazard estimation and simulation of strong ground
motion. 相似文献
348.
349.
We present broad bandR and narrow band Hα emission line images of a sample of optically selected starburst galaxies from the Markarian lists. The
emission line morphology is studied and global properties like luminosities, equivalent widths and star formation rates are
derived. The radial distribution of Ha flux and the EW are determined using concentric aperture photometry on the emission
line and the continuum images. Ha flux is generally found to peak in the nuclear region and fall off outwards. The EW is found
to peak off-center in most of the cases implying that though the intensity of emission is maximum at the nucleus, the star
formation activity relative to the underlying continuum often peaks away from the center in Markarian starburst galaxies. 相似文献
350.
The effects of a Halo Coronal Mass Ejection (CME) erupted on 4 April 2000 are studied and reported here. The effect of such CME on the interplanetary medium (IPM) is sensed by the Interplanetary Scintillation (IPS) recorded at Rajkot. The Solar Observations of this CME and associated events, like Solar Energetic Particles (SEP) and flare, are presented. CME events with high speeds and negative magnetic field components have higher possibility of penetrating the earth's shield, viz. the magnetosphere. The 4 April 2000 CME with a high speed and southward component of IMF produced a big geomagnetic storm with Dst reaching . Simultaneous ionospheric effects in F layer heights and auroral observations are reported. Such events are important in Space Weather Studies as these pose hazards to space operations including satellite communications and surveillance systems. 相似文献