Adsorptive Removal of Acid Blue 15: Equilibrium and Kinetic Study     

N. Thinakaran  P. Baskaralingam  K. V. Thiruvengada Ravi  P. Panneerselvam  Subramanian Sivanesan 《洁净——土壤、空气、水》2008,36(9):798-804

Activated carbons prepared from sunflower seed hull have been used as adsorbents for the removal of acid blue 15 (AB‐15) from aqueous solution. Batch adsorption techniques were performed to evaluate the influences of various experimental parameters, e. g., temperature, adsorbent dosage, pH, initial dye concentration and contact time on the adsorption process. The optimum conditions for AB‐15 removal were found to be pH = 3, adsorbent dosage = 3 g/L and equilibrium time = 4 h at 30°C. The adsorption of AB‐15 onto the adsorbent was found to increase with increasing dosage. It was found from experimental results that the Langmuir isotherm fits the data better than the Freundlich and Temkin isotherms. The maximum adsorption capacity, Q_m (at 30°C) was calculated for SF1, SF2, and SF3 as 75, 125 and 110 mg g^–1 of adsorbent, respectively. It was found that the adsorption follows pseudo‐second order kinetics. The thermodynamic parameters such as ΔG°, ΔH°, and ΔS° were also evaluated. The activated carbons prepared were characterized by FT‐IR, SEM and BET analysis.  相似文献   

Flux monitoring at 327 MHz during SL9-Jupiter collision     

Rakesh K. Malik  Pradeep Gothoskar  P. K. Manohran  G. Swarup  K. Subramanian  V. Balasubramanian 《Journal of Astrophysics and Astronomy》1995,16(3-4):393-398

Jupiter flux at 327 MHz was monitored using the Ooty radio telescope from July 12th to July 29th during the collision of comet Shoemaker-Levi 9 with Jupiter. Flux was found to increase steadily from July 17th to July 26th by ∼ 2–5 Jy, after which it declined to its pre-event value. The comparison of 327 MHz observations with those at 840 MHz and 2240 MHz indicates that the enhancement was mainly due to the increased synchrotron emission and the contribution of thermal emission was very small at metric-decimetric frequencies. The enhancement in radio emission was found to be more at 840 MHz than at 327 or 2240 MHz. The steepening of the spectrum between 327 and 840 MHz as well as between 2240 and 840 MHz was also noted.  相似文献   

Heavy metal distribution in sediments of Krishna River basin,India   总被引：1，自引：0，他引：1  

R. Ramesh  V. Subramanian  R. van Grieken 《Environmental Geology》1990,15(3):207-216

Suspended and bed sediments collected from the entire region of the Krishna River and its major tributaries were analyzed for heavy metals (V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Pb) by the thin-film energy dispersive x-ray fluorescence technique. There is considerable variation in the concentration of elements towards downstream, which may be due to the variation in the subbasin geology and various degrees of human impact. Suspended particles are enriched in heavy metals throughout the basin relative to bed sediments. The heavy metals are enriched in coarse size fractions (10–90 µm) throughout the Krishna River except its tributary Bhima, where finer fractions (2 µm) dominate. Transition elements correlate very well with each other. There is a striking similarity between the bed sediments of Krishna River and the Indian average. When the annual heavy metal flux carried by the Krishna River was estimated, and viewed in relation to the other major riverine transport, the Krishna is seen to be a minor contributor of heavy metals to the Bay of Bengal.  相似文献   

User comments on climate stories: impacts of anecdotal vs. scientific evidence     

Amanda Hinnant  Roma Subramanian  Rachel Young 《Climatic change》2016,137(3-4):411-426

Both statistical and dynamical downscaling methods are well established techniques to bridge the gap between the coarse information produced by global circulation models and the regional-to-local scales required by the climate change Impacts, Adaptation, and Vulnerability (IAV) communities. A number of studies have analyzed the relative merits of each technique by inter-comparing their performance in reproducing the observed climate, as given by a number of climatic indices (e.g. mean values, percentiles, spells). However, in this paper we stress that fair comparisons should be based on indices that are not affected by the calibration towards the observed climate used for some of the methods. We focus on precipitation (over continental Spain) and consider the output of eight Regional Climate Models (RCMs) from the EURO-CORDEX initiative at 0.44^° resolution and five Statistical Downscaling Methods (SDMs) —analog resampling, weather typing and generalized linear models— trained using the Spain044 observational gridded dataset on exactly the same RCM grid. The performance of these models is inter-compared in terms of several standard indices —mean precipitation, 90th percentile on wet days, maximum precipitation amount and maximum number of consecutive dry days— taking into account the parameters involved in the SDM training phase. It is shown, that not only the directly affected indices should be carefully analyzed, but also those indirectly influenced (e.g. percentile-based indices for precipitation) which are more difficult to identify. We also analyze how simple transformations (e.g. linear scaling) could be applied to the outputs of the uncalibrated methods in order to put SDMs and RCMs on equal footing, and thus perform a fairer comparison.  相似文献   

An efficient algorithm for strapdown accelerometer-based motion measurement     

V. Anantha Subramanian  C. P. Vendhan 《Ocean Engineering》1993,20(4)

The paper is concerned with the measurement of motion of free floating bodies using accelerometers strapped to a cross-arm mounted on the body. The measurement system has been studied with the help of a formulation involving a set of coupled nonlinear initial-value equations involving the angular acceleration components. A PC-based software using the Bulirsch-Stoer technique has been developed to solve the initial-value problem so as to deduce the body motions from the measured accelerations. Suitable filtering strategy has been employed at every stage of numerical integration. The reliability of the strapdown accelerometer system together with software developed has been validated using a “dry” test. Typical motion measurements have been done in all the six degrees of freedom of a tug model in a wave flume. The method is deemed to be an efficient and cost-effective technique suitable for free floating bodies and for large motions.  相似文献   

Parametric studies on seaworthiness of SWATH ships     

V.I. BeenaV.Anantha Subramanian 《Ocean Engineering》2003,30(9):1077-1106

This paper reports seakeeping studies performed on a parametrically varied set of SWATH hull forms. The SWATH form, because of its de-linked nature of design affords many variations of the underwater hull geometry without affecting overall deck length and beam. For a given displacement, the hull form can be varied in terms of length, basic section shape, maximum area of cross section of under water hull and strut water plane shape. Using these variants, a parametric family of hull forms has been generated employing Chebychev polynomial scheme for representing sectional area distribution and using a bi-quintic B-spline based surface definition scheme. Not all designs offer optimal performance in a given sea state. A twin-hull motion analysis program SEDOS has been used to study the motions and other dynamic effects. Setting criteria for operability, these dynamic effects have been quantified into a single value namely, operability index. The approach here fulfils an investigation at the design stage in order to tap the full advantage of the SWATH form. The study brings out a methodology for assessment of the SWATH at the design stage highlighting interesting results related to section shapes and sectional area distribution. Thus, combining a newly developed interactive surface generation scheme with an analysis package, a rapid assessment tool is offered for new design.  相似文献   

A FEM-MPM hybrid coupled framework based on local shear strength method for simulating rainfall/runoff-induced landslide runout     

Zhu  Yulong  Ishikawa  Tatsuya  Zhang  Yafen  Nguyen  Binh T.  Subramanian  Srikrishnan Siva 《Landslides》2022,19(8):2021-2032

Landslides - Limited by the independence and its defects of each general software package, simultaneous analysis of runoff, seepage, and large-deformation analysis is still an inevitable challenge....  相似文献   

Understanding the redshift evolution of the luminosity functions of Lyman α emitters     

Saumyadip Samui  Raghunathan Srianand  Kandaswamy Subramanian 《Monthly notices of the Royal Astronomical Society》2009,398(4):2061-2068

We present a semi-analytical model of star formation which explains simultaneously the observed ultraviolet (UV) luminosity function (LF) of high-redshift Lyman break galaxies (LBGs) and LFs of Lyman α emitters. We consider both models that use the Press–Schechter (PS) and Sheth–Tormen (ST) halo mass functions to calculate the abundances of dark matter haloes. The Lyman α LFs at   z ≲ 4  are well reproduced with only ≲10 per cent of the LBGs emitting Lyman α lines with rest equivalent width greater than the limiting equivalent width of the narrow band surveys. However, the observed LF at   z > 5  can be reproduced only when we assume that nearly all LBGs are Lyman α emitters. Thus, it appears that  4 < z < 5  marks the epoch when a clear change occurs in the physical properties of the high-redshift galaxies. As Lyman α escape depends on dust and gas kinematics of the interstellar medium (ISM), this could mean that on an average the ISM at   z > 5  could be less dusty, more clumpy and having more complex velocity field. All of these will enable easier escape of the Lyman α photons. At   z > 5  , the observed Lyman α LF are well reproduced with the evolution in the halo mass function along with very minor evolution in the physical properties of high-redshift galaxies. In particular, up to   z = 6.5  , we do not see the effect of evolving intergalactic medium opacity on the Lyman α escape from these galaxies.  相似文献   

Models of high redshift luminosity functions and galactic outflows: The dependence on halo mass function     

Saumyadip Samui  Kandaswamy Subramanian  Raghunathan Srianand 《New Astronomy》2009,14(7):591-603

  相似文献   

Magnetic fields in the early Universe     

K. Subramanian 《Astronomische Nachrichten》2010,331(1):110-120

We give a pedagogical introduction to two aspects of magnetic fields in the early Universe. We first focus on how to formulate electrodynamics in curved space time, defining appropriate magnetic and electric fields and writing Maxwell equations in terms of these fields. We then specialize to the case of magnetohydrodynamics in the expanding Universe. We emphasize the usefulness of tetrads in this context. We then review the generation of magnetic fields during the inflationary era, deriving in detail the predicted magnetic and electric spectra for some models. We discuss potential problems arising from back reaction effects and from the large variation of the coupling constants required for such field generation (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献