2,418 research outputs found
Spectroscopic Observations and Modelling of Impulsive Alfv\'en Waves Along a Polar Coronal Jet
Using the Hinode/EIS 2 spectroscopic observations, we study the intensity,
velocity, and FWHM variations of the strongest Fe XII 195.12 \AA\ line along
the jet to find the signature of Alfv\'en waves. We simulate numerically the
impulsively generated Alfv\'en waves within the vertical Harris current-sheet,
forming the jet plasma flows, and mimicking their observational signatures.
Using the FLASH code and the atmospheric model with embedded weakly expanding
magnetic field configuration within a vertical Harris current-sheet, we solve
the two and half-dimensional (2.5-D) ideal magnetohydrodynamic (MHD) equations
to study the evolution of Alfv\'en waves and vertical flows forming the plasma
jet. At a height of from the base of the jet, the
red-shifted velocity component of Fe XII 195.12 \AA\ line attains its maximum
() which converts into a blue-shifted one between the
altitude of . The spectral intensity continously increases up
to , while FWHM still exhibits the low values with almost
constant trend. This indicates that the reconnection point within the jet's
magnetic field topology lies in the corona from its
footpoint anchored in the Sun's surface. Beyond this height, FWHM shows a
growing trend. This may be the signature of Alfv\'en waves that impulsively
evolve due to reconnection and propagate along the jet. From our numerical
data, we evaluate space- and time- averaged Alfv\'en waves velocity amplitudes
at different heights in the jet's current-sheet, which contribute to the
non-thermal motions and spectral line broadening. The synthetic width of Fe XII
line exhibits similar trend of increment as in the
observational data, possibly proving the existence of impulsively generated (by
reconnection) Alfv\'en waves which propagate along the jet
On Thermal-Pulse-Driven Plasma Flows in Coronal Funnels as Observed by Hinode/EUV Imaging Spectrometer (EIS)
Using one-arcsecond-slit scan observations from the Hinode/EUV Imaging
Spectrometer (EIS) on 05 February 2007, we find the plasma outflows in the open
and expanding coronal funnels at the eastern boundary of AR 10940. The Doppler
velocity map of Fe XII 195.120 A shows that the diffuse close-loop system to be
mostly red-shifted. The open arches (funnels) at the eastern boundary of AR
exhibit blue-shifts with a maximum speed of about 10-15 km/s. This implies
outflowing plasma through these magnetic structures. In support of these
observations, we perform a 2D numerical simulation of the expanding coronal
funnels by solving the set of ideal MHD equations in appropriate VAL-III C
initial temperature conditions using the FLASH code. We implement a rarefied
and hotter region at the footpoint of the model funnel, which results in the
evolution of slow plasma perturbations propagating outward in the form of
plasma flows. We conclude that the heating, which may result from magnetic
reconnection, can trigger the observed plasma outflows in such coronal funnels.
This can transport mass into the higher corona, giving rise to the formation of
the nascent solar wind.Comment: 17 Pages; 7 Figure
Photon redshift and the appearance of a naked singularity
In this paper we analyze the redshift as observed by an external observer
receiving photons which terminate in the past at the naked singularity formed
in a Tolman-Bondi dust collapse. Within the context of models considered here
it is shown that photons emitted from a weak curvature naked singularity are
always finitely redshifted to an external observer. Certain cases of strong
curvature naked singularities, including the self-similar one, where the
photons are infinitely redshifted are also pointed out.Comment: Latex file, 14 pages, no figures, one change in the reference.
Accepted for publication in Phys. Rev.
Assessment of roof water harvesting potential of Navsari city of Gujarat State, India by Remote sensing and Geographic information system (GIS)
Due to the water scarcity scenario in many parts of the Navsari city, Gujarat State in India, it is imperative to adopt cost-effective technologies that could harvest rainwater for satisfying drinking water requirements. The study was conducted with the aim of assessing the rainwater harvesting potential of Navsari city using remote sensing and Geographic Information System (GIS). The built-up areas of Navsari that could harness rainwater were identified by remote sensing and GIS. The effective built-up area contributing to rainwater harvesting was found to be 3.37 km2. The classification was carried out using “Remap” to assess the extent of the built-up area. The city was divided into equal grids and classification of each grid was implemented. The ground truth data was used for the evaluation of the built-up area. The roof water harvesting potential was estimated considering the average annual rainfall of 1621 mm and adopting suitable runoff coefficients. The rainwater harvesting potential of roofs for rainfall of different probabilities was estimated. For return periods of 10 years, 25 years, 50 years and 100 years, the roof water harvesting potentials were estimated to be 0.226, 0.261, 0.287 and 0.312 Million Cubic Metres (MCM), respectively. The estimated average roof water harvesting potential of Navsari city was 164 million litres per year, capable of satisfying the drinking water demand of approximately 1.12 lakh people annually. The rainwater harnessed from the rooftop could augment the current water supply and immensely help in fulfilling the drinking water demand of Navsari
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Techno-Economic Analysis of Hybrid Layered Manufacturing
Subtractive manufacturing (CNC machining) has high quality of geometric and
material properties but is slow, costly and infeasible in some cases; additive
manufacturing (RP) is just the opposite. Total automation and hence speed is
achieved in RP by compromising on quality. Hybrid Layered Manufacturing
(HLM) developed at IIT Bombay combines the best features of both these
approaches. It uses arc welding for building near-net shapes which are finish
machined to final dimensions. High speed of HLM surpasses all other processes
for tool making by eliminating NC programming and rough machining. The
techno-economic viability of HLM process has been proved through a real life
case study. Time and cost of tool making using HLM promises to be substantially
lower than that of CNC machining and other RP methods. Interestingly, the
material cost in HLM was also found to be lower. HLM is a cheaper retrofitment
to any 3 or 5 axis CNC milling machine or machining center.Mechanical Engineerin
Polyherbal Formulation used in the Treatment of Jaundice
Plants have traditionally served as man\u27s most important weapon against pathogens. Herbal medicines are widely used by all sections of the community, either as folk remedies or as medicaments in the indigenous as well as modern system of medicine. The present work was performed to enumerate the medicinal herbs that tribes and rural people uses for the treatment of jaundice. Data were collected by interviewing local traditional therapists and tribes of the region. Details of 10 herbs and 03 formulations were gathered along with their doses, duration and formulations during the course of present investigation in the study area. Our study revealed that all above herbs and their formulations have been used since quite a long time by the tribes and rural people and no side/ adverse effects were reported
Formulation and Evaluation of Polyherbal Anthelmintic Preparation
The present study was done with the aim to formulate an anthelmintic preparation and to evaluate anthelmintic activity of formulation containing traditionally user herbs viz., Plumbago zeylanica (leaves), Hyoscyamus niger (roots) and Abultion indicum (leaves) using adult earthworm Pheritima posthuma. The aqueous and ethanolic extract of the crude drug of different concentration were tested which involve determination of paralysis time and time to kill the worms. Piperazine citrate was used as standard and it was found that the PHFEE activity is higher than PHFAE
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Simplified Production of Large Prototypes using Visible Slicing
Rapid Prototyping (RP) is a totally automatic generative manufacturing
technique based on a “divide-and-conquer” strategy called ‘slicing’. Simple
slicing used on 2.5-axis kinematics of the existing RP machines is responsible for
the staircase error. Although thinner slices will have less error, the slice thickness
has practical limits. Visible Slicing overcomes these limitations. A few visible
slices exactly represent the object. Each visible slice can be realized using a 3- axis kinematics machine from two opposite directions. Visible slicing is
implemented on Segmented Object Manufacturing (SOM) machine under
development. SOM can produce soft large prototypes faster and cheaper with
accuracy comparable to that of CNC machining.Mechanical Engineerin
Evaluation of Grass Bales Stored under Cover and Plinth System of Storage
The feed and fodder requirement for dairy animals is primarily met by roughages, green fodder and homemade concentrate mixtures. Roughages are high in crude fibrous material which essentially consists of cellulose, hemi-cellulose and to some extent lignin. Livestock production is backbone of Indian Agriculture and source of employment in rural areas for centuries. To meet the demand of feeding these huge livestock population an adequate supply of feed throughout the year is the prerequisite for successful animal production programmes.
A huge gap between demand and supply of feed and fodder exists in our country. This huge gap between requirement and availability of livestock feeds like dry fodders, green fodders could however be bridged by proper post harvest management of all kind of forage resources and search for alternate source of protein rich forage supplement. The most common livestock feed resources are crop reduces (straw, stover, haulms etc). All of these fodder resources are highly voluminous and having lower density varying from 40-70 kg/m3 due to which there transportation, storage and handling are very cumbersome and expensive and therefore cannot be utilized up to a maximum extent. Storage is a repeated phase during transit of agricultural produce and the product needs to be stored from one harvest to next thus, demanding additional carry over as safe guard, against speculation in price and market demand or against shortage and famine
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