Optimum Design of Resilient Sliding Isolation System for Seismic Protection of Equipments

Seismic isolation is one of the effective methods to protect equipments. It helps to keep seismic response accelerations in equipment below its allowable limits. Among different types of isolation systems, the combination of restoring spring and slider, also called as resilient sliding isolation (RSI) system, is the one which has been effectively used for protection of equipment. Principal design parameters for this type of isolation system are period of system (stiffness of spring) and friction coefficient of slider. There may be number of combinations of these design parameters which can enable the isolated equipment to remain functional during and after the predicted seismic event. The optimum design of RSI system can be considered as the one which maintains the response acceleration in the equipment below its allowable limit and at the same time keeps the relative displacement between floor and the equipment to the minimum. This study deals with optimum design of resilient sliding system. First the RSI system is modeled analytically by (i) precise and (ii) simplified SDOF models. The accuracy of the model is then validated by shaking table tests. The validated simplified SDOF model is then used to determine optimum design parameters for different levels of allowable accelerations. Results show that the optimum period decreases and the optimum friction coefficient increases with higher allowable acceleration.     

Balloon observations of fast intensity fluctuations and flare-like enhancements of X-ray emission from Cygnus X-1

The paper presents the results of the investigation on the short term X-ray emission characteristics of Cyg X-1 in the 20–150 keV range. The observations were made with balloon-borne oriented scintillation telescope and the flights were conducted from Hyderabad, India. The source was tracked over a duration of 1 hr that enabled detailed observations with time resolution of the order of 1 min. Fluctuations in the intensity of Cyg X-1 with time scales of the order of minutes have been detected besides short-term flare-like enhancements. The spectral characteristics of the flare emission features are discussed and their relationship to the phase of the binary is examined.Paper presented at the COSPAR Symposium on Fast Transients in X- and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975.     

p Modes in and Away from a Sunspot

A time series of GONG Dopplergrams for the period 10–14 May 1997 from Udaipur and Big Bear sites has been used to measure the velocity fluctuations in a sunspot (NOAA active region 8038) and quiet photosphere simultaneously. We observe that the power of pre-dominant p mode is reduced in the sunspot as compared to quiet photosphere by 39–52% depending on the location of the sunspot region on the solar disk. We also observe a relative peak frequency deviation of p modes in the sunspot, of the order of 80–310 Hz, which shows a linear dependence on the magnetic field gradient in the active region. The maximum frequency deviation of 310 Hz on 12 May appears to be an influence of a long-duration solar flare that occurred in this active region. We interpret this relative peak frequency deviation as either due to power re-distribution of p modes in the sunspot or a consequence of frequency modulation of these modes along the magnetic flux tubes due to rapidly varying magnetic field structure.     

Utility of Hyperspectral Data for Potato Late Blight Disease Detection

The study was carried out to investigate the utility of hyperspectral reflectance data for potato late blight disease detection. The hyperspectral data was collected for potato crop at different level of disease infestation using hand-held spectroradiometer over the spectral range of 325–1075 nm. The data was averaged into 10-nm wide wavebands, resulting in 75 narrowbands. The reflectance curve was partitioned into five regions, viz. 400–500 nm, 520–590 nm, 620–680 nm, 770–860 nm and 920–1050 nm. The notable differences in healthy and diseased potato plants were noticed in 770–860 nm and 920–1050 nm range. Vegetation indices, namely NDVI, SR, SAVI and red edge were calculated using reflectance values. The differences between the vegetation indices for plants at different levels of disease infestation were found highly significant. The optimal hyperspectral wavebands to discriminate the healthy plants from disease infested plants were 540, 610, 620, 700, 710, 730, 780 and 1040 nm whereas upto 25% infestation could be discriminated using reflectance at 710, 720 and 750 nm.     

Biological neutralization of chlor-alkali industry wastewater

The present work reports biological neutralization of chlor-alkali industrial effluent by an alkaliphilic bacterium, isolated from the Gujarat coast, which was identified as Enterococcus faecium strain R-5 on the basis of morphological, biochemical and partial 16S rRNA gene sequencing. The isolate was capable of bringing down the pH of waste water from 12.0 to 7.0 within 3 h in the presence of carbon and nitrogen sources, with simultaneous reduction in total dissolved solutes (TDS) up to 19-22%. This bacterium produced carboxylic acid, as revealed by FT-IR analysis, which facilitated neutralization of alkaline effluent. The presence of unconventional raw materials viz. Madhuca indica flowers or sugar cane bagasse as carbon and nitrogen sources could effectively neutralize alkaline effluent and thus making the bioremediation process economically viable. The time required for neutralization varied with size of inoculum. To the best of our knowledge, this is the first report on biological neutralization of a chlor-alkali industrial effluent.     

Winter fog over the Indo-Gangetic Plains: mapping and modelling using remote sensing and GIS

Almost every year in the winter months (December–February), the vast Indo-Gangetic Plain south of the Himalaya is affected by dense fog. This fog is considered as radiational fog, and sometime it becomes smog (when it mixes with smoke). The typical meteorological, topographic and increasing pollution conditions over the Indo-Gangetic Plain are perhaps the common contributing factors for fog formation. In the present study, the North Indian fog has been successfully mapped and analysed using NOAA-AVHRR satellite data. In the winter seasons of 2005–06, 2006–07 and 2007–08, the fog-affected area has been found to cover about 575,800 km², 594,100 km² and 478,000 km², respectively. Less fog in 2007–08 may be the consequence of high fluctuations in the meteorological parameters like temperature, relative humidity and wind speed as related to the prevailing synoptic regime for that season. The dissipation and migration pattern of fog in the study area has also been interpreted on the basis of the analysis of both meteorological and satellite data. Further analysis of the fog-affected area allowed identifying more fog-prone regions. Analysis of past fog-affected days and corresponding meteorological conditions enabled us to identify favourable conditions for fog formation viz. air temperature 3–13°C, relative humidity >87%, wind speed <2 m/s and elevation <300 m. Based on the observations of past fog formation and corresponding governing parameters, fog for few selected days could be predicted in hind-sight and later verified with NOAA images.     

A circular statistical method for extracting rotation measures

We propose a new method for the extraction of Rotation Measures from spectral polarization data. The method is based on maximum likelihood analysis and takes into account the circular nature of the polarization data. The method is unbiased and statistically more efficient than the standard χ² procedure.     

Variations in Oscillation Frequencies From Minimum to Maximum of Solar Activity

The temporal variation in intermediate-degree-mode frequencies is analysed using helioseismic data which cover the minimum to the maximum phase of the current solar cycle. To study the variation in detail, the measured frequency shifts of f and p modes are decomposed into two components, viz., oscillatory and non-oscillatory. The f-mode frequencies exhibit prominent oscillatory behavior in contrast to p modes where the oscillatory nature of the frequencies is not clearly seen. Also, the oscillatory part contributes significantly to the f-mode frequencies while p-mode frequencies have maximum contribution from the non-oscillatory part. The amplitude of both oscillatory and non-oscillatory parts is found to be a function of frequency. The non-oscillatory part is observed to have a strong correlation with solar activity.