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Anantha Chanumolu Sivarani Thirupathi Damien Jones Sunetra Giridhar Deon Grobler Robert Jakobsson 《Experimental Astronomy》2017,43(1):39-58
As a continuation to the published work on model based calibration technique with HESP(Hanle Echelle Spectrograph) as a case study, in this paper we present the performance results of the technique. We also describe how the open parameters were chosen in the model for optimization, the glass data accuracy and handling the discrepancies. It is observed through simulations that the discrepancies in glass data can be identified but not quantifiable. So having an accurate glass data is important which is possible to obtain from the glass manufacturers. The model’s performance in various aspects is presented using the ThAr calibration frames from HESP during its pre-shipment tests. Accuracy of model predictions and its wave length calibration comparison with conventional empirical fitting, the behaviour of open parameters in optimization, model’s ability to track instrumental drifts in the spectrum and the double fibres performance were discussed. It is observed that the optimized model is able to predict to a high accuracy the drifts in the spectrum from environmental fluctuations. It is also observed that the pattern in the spectral drifts across the 2D spectrum which vary from image to image is predictable with the optimized model. We will also discuss the possible science cases where the model can contribute. 相似文献
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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
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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
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Knowledge of wake characteristics in the stern region is important for ensuring good propeller design and performance. This work examines the utility of CFD in the analysis of flow in the case of full aft beam vessels having characteristic cut stern shape to facilitate propeller aperture. The underwater stern shape may be more complex due to the occurrence of stern appendages such as bossings, strut supports and local shape variations. To this extent, CFD offers an effective tool for both qualitative as well as quantitative assessment of the local geometry. Wake estimate is required for choice of the most favorable propeller geometry. In the present method, the analysis quantifies the effects of small changes in stern rake angles and offers an inverse design approach towards finalising the stern shape. The method consists of solving the standard k-ε turbulent model of RANS equations in cell centered finite volume multi zone grid in the flow domain. This approach has been used in estimating the velocity at the propeller plane. The results have been compared with experimentally obtained values of nominal wake. The approach suggests that CFD can provide a cost effective and quick assessment of flow. It is also an attractive means of pre-empting heterogeneous flow related problems such as vibration and noise due to unfavorable wake in the stern region. 相似文献
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Journal of Earth System Science - The fuchsites described here occur in the lower portions of a precambrian quartzite bed, which typically encloses small bands and lenses of barytes. Of the two... 相似文献
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Louis R. Iverson Stephen N. Matthews Anantha M. Prasad Matthew P. Peters Gary Yohe 《Climatic change》2012,114(2):231-243
We present an approach to assess and compare risk from climate change among multiple species through a risk matrix, in which managers can quickly prioritize for species that need to have strategies developed, evaluated further, or watched. We base the matrix upon earlier work towards the National Climate Assessment for potential damage to infrastructures from climate change. Risk is defined here as the product of the likelihood of an event occurring and the consequences or impact of that event. In the context of species habitats, the likelihood component is related to the potential changes in suitable habitat modeled at various times during this century. Consequences are related to the adaptability of the species to cope with the changes, especially the increasing intensity and/or frequency of disturbance events that are projected. We derived consequence scores from nine biological and 12 disturbance characteristics that were pulled from literature for each species. All data were generated from an atlas of climate change for 134 trees of the eastern United States (www.nrs.fs.fed.us/atlas). We show examples which depict a wide range of risk for tree species of northern Wisconsin, including species that may gain substantial habitat as well as lose substantial habitat, both of which will require the development of strategies to help the ecosystems adapt to such changes. 相似文献
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T. R. N. Kutty G. N. Subbanna G. V. Anantha Iyer 《Journal of Earth System Science》1983,92(3):283-295
Electron microscopy (SEM and TEM) of unusual olivine (Fo = 88) crystals, with perfect (010) cleavages, from Chalk Hills, Salem,
Tamil Nadu has been carried out. SEM studies reveal the effect of compressive stress. Microstructures by TEM showed the abundance
of curved dislocations with jogs, kinks and dipoles, indicative of the dominant climb, characteristic of high temperature
deformation. The stacking fault fringes observed in olivine are due to mechanical weakening caused by nonstructural chemical
constituents. The evidences for this come from fiuid-microinclusions observed and higher amount of K, Na, Rb and Sr in the
olivine. Hydrolytic weakening through dislocation glide motion, assisted by H2O containing incompatible elements, may break the metal-oxygen bonds. This leads to perfect parting of crystallographic planes
under deformational stress, during solid emplacement of the dunite. The easily cleavable planes are those with the largest
interplanar spacings. 相似文献
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Virtual instrumentation represents a PC based control system which incorporates manipulation of data acquired from physical transducers in specific ways using a very high level graphical environment. The deployment of this non-traditional approach is demonstrated in this paper by application to design of a fin control system for a yacht. One of the disadvantages of the traditional stabilizer system is the enormous hardware involved in the controllers and instrumentation panels, which make maintenance and troubleshooting difficult. With the help of virtual instrumentation, design of the stabilization controller and instrumentation panels can be carried out much more effectively, in comparison with the traditional hardware approach. A multi-disciplinary approach is adopted here and it consists of the assessment of the hydrodynamic coefficients of the yacht using a numerical package, representation of the hydrodynamic coefficients by suitable polynomial functions, identification of the time dependent fundamental frequency in the roll disturbance signal sample, generation of control signal for an appropriate fin angle based on the fin lift characteristics of the chosen fin and employment of feedback control to maintain the fin at the appropriate angle for maximum control. Once the ship based hydrodynamic coefficients are generated, the entire control algorithm is developed in the virtual instrumentation mode using LabVIEW environment. The effectiveness of the system is verified through laboratory tests on a yacht hull form. The control algorithm permits choice of frequency dependent hydrodynamic coefficients by use of a harmonic distortion analyzer in the virtual instrumentation environment. 相似文献
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Y. J. Bhaskar Rao Anil Kumar A. B. Vrevsky R. Srinivasan G. V. Anantha Iyer 《Journal of Earth System Science》2000,109(1):57-65
Whole-rock Sm-Nd isochron ages are reported for two stratiform meta-anorthosite complexes emplaced into the Archean supracrustal-gneiss
association in the amphibolite facies terrain around Holenarsipur, in the Dharwar craton, South India. While these metaperidotite-pyroxenite-gabbro-anorthosite
complexes are petrologically and geochemically similar, they differ in the intensity of tectonic fabric developed during the
late Archean (c. 2.5 Ga) deformation. They also differ in their whole-rock Sm-Nd isochron ages and initial Nd isotopic compositions:
3.285 ± 0.17 Ga,ɛNd0.82 ± 0.78 for the Honnavalli metaanorthosite complex from a supracrustal enclave in the low-strain zone, and 2.495 ± 0.033
Ga, ɛNd = -2.2 ± 0.3 for the Dodkadnur meta-anorthosites from the high-strain southern arm of the Holenarsipur Supracrustal
Belt (HSB). We interpret these results as indicating that the magmatic protoliths of both meta-anorthosite complexes were
derived from a marginally depleted mantle at c. 3.29 Ga but only the Dodkadnur rocks were isotopically reequilibrated on a
cm-scale about 800 Ma later presumably due to the development of strong penetrative fabrics in them during Late Archean thermotectonic
event around 2.5 Ga. Our results set a younger age limit at c. 3.29 Ga for the supracrustal rocks of the HSB in the Dharwar
craton. 相似文献