排序方式： 共有63条查询结果，搜索用时 125 毫秒
31.
S. Baruah A. Devi K. G. Bhattacharyya A. Sarma 《International Journal of Environmental Science and Technology》2017,14(2):341-352
Dried, mature leaves of Aegle Marmelos tree were converted to a powder, which was used as a biosorbent for dyes in water with methylene blue as a case study. The biosorbent had a surface area of 52.63 mg/g, and FTIR spectra showed the presence of –COOH, –NH2, –R–SC=O (thioester) and R1–S(=O, =O)-N(–R2, –R3) groups on the surface. The particles were found to be porous in nature from scanning electron micrographs, and EDX measurements showed the elements C, O, Na, Mg, K, Ca and Fe on the surface. Batch adsorption experiments showed that the adsorption of the dye was preferred at near-neutral conditions. Adsorption equilibrium was achieved in ~120 min with maximum dye uptake of 19.9 mg/g. Investigation into the kinetics of adsorption indicated that second-order kinetics gave the best fit to the experimental data, and a rate coefficient of 8.0 × 10?2 to 32.3 × 10?2 g mg?1 min?1 was obtained. 相似文献
32.
Prabhu Saurabh Javanbarg Mohammad Lehmann Marc Atamturktur Sez 《Natural Hazards》2019,99(3):1327-1343
The chemical industry is one of the most important industry sectors in terms of energy consumption and CO2 emissions in China. However, few studies have undertaken accounting of the CO2 emissions in the chemical industry. In addition, there are some shortcomings in the traditional accounting method as a result of poor data availability, such as the incomplete consideration of emission sources and overestimation of actual emissions. Based on the traditional accounting method and the actual situation of the chemical industry, this study proposes a method called the Emission Accounting Model in the Chemical Industry, which covers fossil energy-related emission, indirect emission generated by electricity and heat, carbonate-related process emission and the reuse of CO2. In particular, fossil energy used as feedstock is included. By applying the Emission Accounting Model in the Chemical Industry in China, the calculated CO2 emissions would be 19–30% less than the result from the traditional method. In addition, it is found that the indirect CO2 emissions generated by electricity and heat account for 67% of the total amount, the fossil energy-related emissions account for approximately 37%, the process-related emissions accounted for 2%, and reuse of CO2 accounts for ??6% in 2016. The production of ammonia, ethylene and calcium carbide generated approximately half of the total CO2 emissions in 2016. In addition, in view of emission sources and carbon source flow, two other bottom-up accounting methods are proposed that can take effect when the chemical plant-level data are available.
相似文献33.
Saurabh Jha Guillermo Torres Robert P. Stefanik David W. Latham Tsevi Mazeh 《Monthly notices of the Royal Astronomical Society》2000,317(2):375-384
The triple-lined spectroscopic triple system HD 109648 has one of the shortest periods known for the outer orbit in a late-type triple, 120.5 d, and the ratio between the periods of the outer and the inner orbits is small, 22:1. With such extreme values, this system should show orbital element variations over a time-scale of about a decade. We have monitored the radial velocities of HD 109648 with the CfA Digital Speedometers for 8 yr, and have found evidence for modulation of some orbital elements. While we see no definite evidence for modulation of the inner binary eccentricity, we clearly observe variations in the inner and the outer longitudes of periastron, and in the radial velocity amplitudes of the three components. The observational results, combined with numerical simulations, allow us to put constraints on the orientation of the orbits. 相似文献
34.
Sowrav Saikia Santanu Baruah Sumer Chopra Upendra K. Singh Bibhuti Gogoi Himanata B. Gohain 《Journal of Seismology》2018,22(1):229-249
It is noticed that few geophysical studies have been carried out to decipher the crustal structure of southwestern part of the Northeast India comprising of Tripura fold belt and Bengal basin as compared to the Shillong plateau and the Brahmaputra basin. This region has a long history of seismicity that is still continuing. We have determined first-order crustal features in terms of Moho depths (H) and average VP/VS ratios (κ) using H-κ stacking technique. The inversion of receiver functions data yields near surface thick sedimentary layer in the Bengal basin, which is nearly absent in the Shillong plateau and Tripura fold belt. Our result suggests that the crust is thicker (38–45 km) in the Tripura fold belt region with higher shear-wave velocity in the lower crust than the Shillong plateau. The distribution of VP/VS ratio indicates heterogeneity throughout the whole region. While low to medium value of Poisson’s ratio (1.69–1.75) indicates the presence of felsic crust in the Shillong plateau of the extended Indian Archean crust. The medium to high values of VP/VS ratio (> 1.780) in the Bengal basin and the Tripura fold belt region represent mafic crust during the formation of the Bengal delta and the Tripura fold belt creation in the Precambrian to the Permian age. The depth of the sediments in the Bengal basin is up to 8 km on its eastern margin, which get shallower toward its northeastern and southeastern margins. 相似文献
35.
Saurabh Singh Ravi Subrahmanyan N. Udaya Shankar Mayuri Sathyanarayana Rao B. S. Girish A. Raghunathan R. Somashekar K. S. Srivani 《Experimental Astronomy》2018,45(2):269-314
The global 21-cm signal from Cosmic Dawn (CD) and the Epoch of Reionization (EoR), at redshifts \(z \sim 6-30\), probes the nature of first sources of radiation as well as physics of the Inter-Galactic Medium (IGM). Given that the signal is predicted to be extremely weak, of wide fractional bandwidth, and lies in a frequency range that is dominated by Galactic and Extragalactic foregrounds as well as Radio Frequency Interference, detection of the signal is a daunting task. Critical to the experiment is the manner in which the sky signal is represented through the instrument. It is of utmost importance to design a system whose spectral bandpass and additive spurious signals can be well calibrated and any calibration residual does not mimic the signal. Shaped Antenna measurement of the background RAdio Spectrum (SARAS) is an ongoing experiment that aims to detect the global 21-cm signal. Here we present the design philosophy of the SARAS 2 system and discuss its performance and limitations based on laboratory and field measurements. Laboratory tests with the antenna replaced with a variety of terminations, including a network model for the antenna impedance, show that the gain calibration and modeling of internal additive signals leave no residuals with Fourier amplitudes exceeding 2 mK, or residual Gaussians of 25 MHz width with amplitudes exceeding 2 mK. Thus, even accounting for reflection and radiation efficiency losses in the antenna, the SARAS 2 system is capable of detection of complex 21-cm profiles at the level predicted by currently favoured models for thermal baryon evolution. 相似文献
36.
The daily variations in the atmospheric pollutants like suspended particulate matter (SPM), respirable suspended particulate matter (RSPM), sulphur dioxide (SO2) and nitrogen dioxide (NO2) depend on both local meteorological processes and various natural as well as anthropogenic sources and sinks. It was shown in an earlier work (Goswami and Baruah in Mon Wea Rev 136(9):3597?C3607, 2008) that the daily variations in SPM over a location could be simulated quite well by considering daily meteorological fields from NCEP Reanalysis in combination with a model for natural and anthropogenic sources over Delhi. In the present work, we extend the scope of the model to include three other pollutants: RSPM, SO2 and NO2. While the basic conservation equations and the meteorological fields are common to all the three (and SPM) pollutants, the sources and sinks for each is modeled in a species-specific manner to obtain maximum skill. As we do not consider active chemistry, the present model provides the minimal dynamics of pollution over an urban location in terms of annual load; the model error is about 10% on the average, with no significant bias for any of the species. 相似文献
37.
Saurabh Baruah Dipok K. Bora Rajib Biswas 《International Journal of Earth Sciences》2011,100(6):1283-1292
In this study, an attempt is made to determine seismic velocity structure of the crust and upper mantle beneath the Shillong-Mikir
Hills Plateau in northeast India region. The principle of the technique is to relate seismic travel times with crustal thickness
above the Conrad and Moho discontinuities. Broadband digital waveforms of the local earthquakes make a precise detection of
the seismic phases possible that are reflected at these discontinuities. The results show that the Conrad discontinuity is
at 18–20 (±0.5) km beneath the Shillong-Mikir Hills Plateau and the Moho discontinuity is at 30 ± 1.0 km beneath the Shillong
Plateau and at 35 ± 1.0 km beneath the Mikir Hills. 相似文献
38.
R. Gopalakrishnan A. K. Chaurasia I. Baruah V. Veer 《International Journal of Environmental Science and Technology》2014,11(7):1855-1860
The loss of permethrin from impregnated uniforms due to repeated washings was studied by chromatographic estimation of the residues. The mean (± SEmean) percentage losses of permethrin after one to five washings were 16.7 ± 2.3, 22.5 ± 3, 29.6 ± 2.9, 40.2 ± 2 and 52.2 ± 2.4, respectively. The reduction in contact toxicity against mosquitoes after each washing was studied by World Health Organization tube and cone bioassays against Aedes albopictus mosquitoes. The median knockdown time for 5-min exposure to the treated uniforms increased from 5.9 to 71.8 min after five washings. Mosquito mortality 24 h post-exposure in cone bioassays was <80 % after the fifth washing, indicating the loss of efficacy. The uniforms need to be retreated after five washings so as to ensure adequate protection against disease vectors. The washing water should be properly disposed off to prevent environmental contamination and toxicity to aquatic organisms. Methods for treatment of military uniforms, which ensure high resistance to washing, need to be adopted so as to avoid frequent re-impregnations with permethrin. 相似文献
39.
In many parts of the world sedimentary horizons with potential for hydrocarbon are located below flood basalt provinces. However,
the presence of high velocity basaltic overburden makes delineation of sediments difficult due to the low velocity layer problem.
Electrical and electromagnetic methods have been used in such scenarios because of the good electrical conductivity contrast
between basalts and underlying sediments. However, mapping of the target sediments becomes difficult when the layer is thin
as the data errors due to inherent noise lead to equivalent solutions. To tackle such difficult situations, a joint inversion
scheme incorporating seismic reflection and refraction, magnetotelluric and deep electrical resistivity datasets is presented.
Efficacy of the scheme is tested for a model comprising a thin sedimentary layer sandwiched between a thick basalt cover and
a granitic basement. The results indicate that the parameters of the target sedimentary layer are either poorly resolved or
equivalent solutions are obtained by the inversion of individual datasets. Joint inversions of seismic reflection (RFLS) and
refraction (RFRS), or DC and MT dataset pairs provide improved results and the range of equivalent solutions is narrowed down.
Combination of any three of the above datasets leads to further narrowing of this range and improvements in mean model estimates.
Joint inversion incorporating all the datasets is found to yield good estimates of the structure. Resolution analysis is carried
out to appraise estimates of various model parameters obtained by jointly inverting different combinations of datasets. 相似文献
40.
Rulee Baruah Kalpana Duorah H. L. Duorah 《Journal of Astrophysics and Astronomy》2009,30(3-4):165-175
The rapid neutron capture process (r-process) is one of the major nucleosynthesis processes responsible for the synthesis of heavy nuclei beyond iron. Isotopes beyond Fe are most exclusively formed in neutron capture processes and more heavier ones are produced by the r-process. Approximately half of the heavy elements with mass number A > 70 and all of the actinides in the solar system are believed to have been produced in the r-process. We have studied the r-process in supernovae for the production of heavy elements beyond A = 40 with the newest mass values available. The supernova envelopes at a temperature >109 K and neutron density of 1024 cm?3 are considered to be one of the most potential sites for the r-process. The primary goal of the r-process calculations is to fit the global abundance curve for solar system r-process isotopes by varying time dependent parameters such as temperature and neutron density. This method aims at comparing the calculated abundances of the stable isotopes with observation. We have studied the r-process path corresponding to temperatures ranging from 1.0 × 109 K to 3.0 × 109 K and neutron density ranging from 1020 cm?3 to 1030 cm?3. With temperature and density conditions of 3.0 × 109 K and 1020 cm?3 a nucleus of mass 273 was theoretically found corresponding to atomic number 115. The elements obtained along the r-process path are compared with the observed data at all the above temperature and density range. 相似文献