Reflected and refracted waves from a linear transition layer     

Miss Wadhwa  Santosh Kumari 《Pure and Applied Geophysics》1971,89(1):45-66

Summary The problem of a transition layer lying between two homogeneous liquid media is discussed. After obtaining the formal solution for a periodic point source lying in the upper layer, the integrand in the expression for the displacement potential of the upper layer is expanded into series of negative powers of exponentials. Some of the terms in the Bromwich expansion are then evaluated along the Sommerfeld loops which give various reflected and refracted waves. The results for the refracted waves are discussed for the two extreme cases, when frequency is extremely low and extremely high. In both the cases it is found that the frequency dependence for refraction arrivals is the same as expected from a sharp boundary, viz., ^–1. And that for high frequency the travel-time of refraction arrivals is the same as expected from geometric ray theory. Both first- order and second-order discontinuities in density and bulk modulus are considered at the boundaries of the transition layer.  相似文献   

The disturbance due to a point source in a homogeneous liquid layer over a heterogeneous liquid half-space     

Miss Santosh Kumari Wadhwa 《Pure and Applied Geophysics》1971,89(1):67-83

Summary The problem of a periodic point source in a homogeneous liquid layer overlying a heterogeneous liquid half-space is discussed. After obtaining the formal solution, the path of integration for the displacement potential of the layer is transformed from the positive real axis to the positive imaginary axis and the Sommerfeld contour and the latter is further distorted to the modified Sommerfeld contour. The residues of the integrand at the poles contained within the Sommerfeld loop constitute the normal mode solution to the problem. The integrands in the expressions for the integrals along the imaginary axis are expanded in a series of negative powers of exponentials and then some of the terms in these expansions are evaluated approximately. This gives various waves reflected from the interface and the integral along the Sommerfeld loop vanishes. The frequency equation is obtained, also by the principle of constructive interference. An expression for the reflection coefficient at an interface of two liquid media, the upper medium being homogeneous and the lower one inhomogeneous, is obtained.  相似文献   

Comparison of high performance liquid chromatography and fluorometric ocean colour pigments     

Beena Kumari 《Journal of the Indian Society of Remote Sensing》2005,33(4):541-546

The accuracy of satellite derived chlorophylla (chla) using empirical algorithms (OC2 and OC4) is about ± 30–35%, which is attributed mainly to the sensor and atmospheric constraints and also the bio-optical algorithms. However errors inin situ measurement of chla may also contribute to the retrieval accuracy. The fluorometric method of chla measurement can significantly under or overestimate chla concentrations. This is mainly because of the overlap of the absorption and fluorescence bands of co-occurring chlorophyllsb andc, chlorophyll degradation products, and accessory pigment. Accurate chla measurements are important for validating satellite derived chla accuracy and algorithm development. The focus of this study was to understand the discrepancy between fluorometric and HPLC (High Performance Liquid Chromatography) derived chla using unialgal cultures, natural field samples from Bedford Basin and samples from MinOx cruise to analyse divinyl chla. Approximately 50% underestimation of chla both in the natural samples as well as cultured samples has been observed by fiuorometer. The results of MinOx cruise data indicated shifting of the blue absorption maxima towards longer wavelengths (~450nm), which is consistent with high concentration of divinyl chla (chla ₂) associated with prochlorophytes.  相似文献   

Biosorption studies on shelled Moringa oleifera Lamarck seed powder: Removal and recovery of arsenic from aqueous system     

Pushpa Kumari  Parul SharmaShalini Srivastava  M.M. Srivastava 《International Journal of Mineral Processing》2006

The present study explores the unexploited sorption property of the shelled Moringa oleifera seeds (SMOS) for decontamination of arsenic from water bodies. Sorption studies (batch experiments) result into the standardization of optimum conditions for removal of 60.21% As(III) and 85.60% As(V) as follows: biomass dosage (2.0 g), metal concentration (25 mg/L), contact time (60 min) and volume of the test solution (200 ml) at pH 7.5 and 2.5, respectively. The adsorption data are fitted with Langmuir isotherm. Surface area has been measured using BET surface area analyzer. Morphological changes observed in scanning electron micrograph of native and treated SMOS indicates the existence of biosorption process. Fourier transform infrared spectrometry of exhausted seed biomass highlights protein/amino acid–arsenic interactions responsible for sorption phenomenon. Regeneration has also been attempted for several cycles with a view to restore the sorbent to its original state. The sorption capacity of the regenerated biomass remained almost constant after three cycles of sorption process, suggesting that the lifetime cycle was sufficient for continuous application. The findings open up new avenues in the decontamination of arsenic using SMOS from arsenic contaminated water, as domestic and environment-friendly safe technology.  相似文献   

Do increasing horizontal resolution and downscaling approaches produce a skillful thunderstorm forecast?     

Priya  Kumari  Nadimpalli  Raghu  Osuri  Krishna K. 《Natural Hazards》2021,109(2):1655-1674

The timely prediction of thunderstorms (TS) is always a challenging task for operational and research community. The present study is aimed to address the credibility of the high grid-spacing and downscaling approach for improved simulation of TS. Fourteen TS are simulated with different domain configurations using weather research and forecasting (WRF) model. Two nested domains with 9–3 km (known as DD3), and 6–2 km (DD2), and 3 km single domain (SD3) are considered for simulations. Results indicate that the high-resolution DD2 has improved 2-m temperature (T2), 2-m relative humidity (RH2), and 10-m wind speed (WS10) at different stages of TS. The average mean error of T2 and RH2 in the DD2 experiment is 0.7 °C, ??6% during the mature stage, and 0.2 °C, ??4% at dissipating stage. The error in SD3 and DD3 is relatively higher (9–17% for T2 and 20–60% for RH2). Better horizontal and vertical representation of thermodynamic variables in DD2 run reinforces the atmosphere to initiate and intensify the convection in the right place. The DD2 could show slightly higher instability (convective available potential energy, CAPE, 3188 J kg^?1) as compared with DD3 (3164 J kg^?1) and SD3 (3020 J kg^?1). The model is biased to simulate early TS activity. DD2 run could simulate the formation, mature and dissipation stages with fewer timing errors (??1.35 h, ??1.5 h, and ??2.6 h, respectively) than other experiments. The critical success index of the DD2 run is higher for all the rainfall thresholds; however, it is more than 0.2 up to 2.5 mm h^?1. The results highlight that high resolution nested configuration yields better simulation skills than the single domain configuration.

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DEM-based delineation for improving geostatistical interpolation of rainfall in mountainous region of Central Himalayas,India     

Madhuri?Kumari  Chander?Kumar?SinghEmail author  Oinam?Bakimchandra  Ashoke?Basistha 《Theoretical and Applied Climatology》2017,130(1-2):51-58

In mountainous region with heterogeneous topography, the geostatistical modeling of the rainfall using global data set may not confirm to the intrinsic hypothesis of stationarity. This study was focused on improving the precision of the interpolated rainfall maps by spatial stratification in complex terrain. Predictions of the normal annual rainfall data were carried out by ordinary kriging, universal kriging, and co-kriging, using 80-point observations in the Indian Himalayas extending over an area of 53,484 km². A two-step spatial clustering approach is proposed. In the first step, the study area was delineated into two regions namely lowland and upland based on the elevation derived from the digital elevation model. The delineation was based on the natural break classification method. In the next step, the rainfall data was clustered into two groups based on its spatial location in lowland or upland. The terrain ruggedness index (TRI) was incorporated as a co-variable in co-kriging interpolation algorithm. The precision of the kriged and co-kriged maps was assessed by two accuracy measures, root mean square error and Chatfield’s percent better. It was observed that the stratification of rainfall data resulted in 5–20 % of increase in the performance efficiency of interpolation methods. Co-kriging outperformed the kriging models at annual and seasonal scale. The result illustrates that the stratification of the study area improves the stationarity characteristic of the point data, thus enhancing the precision of the interpolated rainfall maps derived using geostatistical methods.  相似文献   

IPv4与IPv6比较及IPv4向IPv6过渡方法   总被引：1，自引：0，他引：1  

吕迪波  乌日娜  杨丽萍 《内蒙古气象》2009,(2):27-28

文章介绍了Internet TCP/IP协议中主要协议IP协议的IPv4和IPv6,通过对目前IPv4存在的问题进行分析,从协议的地址空间、地址管理、地址表示方面对IPv4与IPv6进行比较,并分析和总结IPv6的优点。介绍了从IPv4过渡到IPv6的方法,对于了解下一代互联网主要的协议及如何逐渐平滑过渡到IPv6有着重要的意义。  相似文献   

鄂尔多斯近51a温度变化特征分析   总被引：1，自引：0，他引：1  

孙玉  苏日娜 《内蒙古气象》2012,(5):16-18

利用鄂尔多斯地区8个旗县中心站点1961—2011年的逐月平均气温序列资料,采用趋势变化、滑动t检验等方法,分析了鄂尔多斯气温的空间分布特点和时间特征,并且检验了51a来鄂尔多斯年平均气温的突变情况。结果表明:鄂尔多斯地区气温空间分布呈现西中部偏低,其余地区偏高的格局,气温51a增暖特征显著,并且在51a的时间尺度上,年平均气温经历了两次突变。  相似文献   

Hydrogeochemical processes in the groundwater environment of Muktsar,Punjab: conventional graphical and multivariate statistical approach   总被引：4，自引：0，他引：4  

Manish Kumar  Kalpana Kumari  Umesh Kumar Singh  AL. Ramanathan 《Environmental Geology》2009,57(4):873-884

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Impacts of paleohydrological changes on n-alkane biomarker compositions of a Holocene peat sequence in the eastern European Russian Arctic     

Rina A. Andersson  Peter Kuhry  Philip Meyers  Yngve Zebühr  Patrick Crill  Magnus Mörth 《Organic Geochemistry》2011,42(9):1065-1075

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