237 research outputs found
The study of pavements in transportation engineering with special reference to N.H.- 1
Rigid pavements are those which posses note worthy flexural strength or flexural rigidity. The stresses are not transferred from grain to grain to the lower layers as in the ease of flexible pavements layers the rigid pavements are made of Portland cement concrete-either plain, reinforced or prestressed concrete. The plain cement concrete slabs are expected to take up about 40 kg/cm2 flexural stress. As the rigid pavements slab has tensile strength, tensile stresses are developed due to the bending of the slab under wheel load and temperature variations thus the type of stress develop and their distribution within the cement concrete slab are quit different. The rigid pavement does not get deformed to the shape of the lower surface as it can bridge the minor variation of lower layer
The criteria for selection of sites for bridges
Bridge is a structure which provides a passage to people, vehicles, railways or pipelines to cross various obstacles to travel. Engineers build bridges over obstacles such as lakes, rivers, canyons, and dangerous roads and railway tracks. Without bridges, people would need boats to cross waterways and would have to travel around canyons and ravines. The first bridges were made by nature itself — as simple as a log fallen across a stream or stones in the river. The first bridges made by humans were probably spans of cut wooden logs or planks and eventually stones, using a simple support and crossbeam arrangement. Some early Americans used trees or bamboo poles to cross small caverns or wells to get from one place to another. A common form of lashing sticks, logs, and deciduous branches together involved the use of long reeds or other harvested fibers woven together to form a connective rope which was capable of binding and holding in place materials used in early bridges
A New Narrow-Line Seyfert 1 galaxy : RXJ1236.9+2656
We report identification of a narrow-line Seyfert 1 galaxy RXJ1236.9+2656.
X-ray emission from the NLS1 galaxy undergoes long-term variability with
0.1--2.0 keV flux changing by a factor of 2 within about 3 yr. The ROSAT PSPC
spectrum of RXJ1236.9+2656 is well represented by a power-law of Gamma = 3.7
absorbed by matter in our own Galaxy (N_H = 1.33X10^20 cm**-2). Intrinsic soft
X-ray luminosity of the NLS1 galaxy is estimated to be 1.5X10^43 erg/s in the
energy band of 0.1-2.0 keV. The optical spectrum of RXJ1236.9+2656 is typical
of NLS1 galaxies and shows narrow Balmer emission lines (1100 km/s < FWHM <
1700 km/s) of Hbeta, Halpha, and forbidden lines of [O III] and [N II]. Fe II
multiplets, usually present in optical spectra of NLS1 galaxies, are also
detected in RXJ1236.9+2656.Comment: 4 pages, A&A style Latex, To apear in A&A as a research not
Star formation around mid-infrared bubble N37: Evidence of cloud-cloud collision
We have performed a multi-wavelength analysis of a mid-infrared (MIR) bubble
N37 and its surrounding environment. The selected 1515 area around
the bubble contains two molecular clouds (N37 cloud; V37-43 km
s, and C25.29+0.31; V43-48 km s) along the line of
sight. A total of seven OB stars are identified towards the bubble N37 using
photometric criteria, and two of them are spectroscopically confirmed as O9V
and B0V stars. Spectro-photometric distances of these two sources confirm their
physical association with the bubble. The O9V star is appeared to be the
primary ionizing source of the region, which is also in agreement with the
desired Lyman continuum flux analysis estimated from the 20 cm data. The
presence of the expanding HII region is revealed in the N37 cloud which could
be responsible for the MIR bubble. Using the CO line data and
photometric data, several cold molecular condensations as well as clusters of
young stellar objects (YSOs) are identified in the N37 cloud, revealing ongoing
star formation (SF) activities. However, the analysis of ages of YSOs and the
dynamical age of the HII region do not support the origin of SF due to the
influence of OB stars. The position-velocity analysis of CO data reveals
that two molecular clouds are inter-connected by a bridge-like structure,
favoring the onset of a cloud-cloud collision process. The SF activities (i.e.
the formation of YSOs clusters and OB stars) in the N37 cloud are possibly
influenced by the cloud-cloud collision.Comment: 18 pages, 13 figures, 2 tables, Accepted for publication in the Ap
Multi-wavelength study of the star-formation in the S237 H II region
We present a detailed multi-wavelength study of observations from X-ray,
near-infrared to centimeter wavelengths to probe the star formation processes
in the S237 region. Multi-wavelength images trace an almost sphere-like shell
morphology of the region, which is filled with the 0.5--2 keV X-ray emission.
The region contains two distinct environments - a bell-shaped cavity-like
structure containing the peak of 1.4 GHz emission at center, and elongated
filamentary features without any radio detection at edges of the sphere-like
shell - where {\it Herschel} clumps are detected. Using the 1.4 GHz continuum
and CO line data, the S237 region is found to be excited by a radio
spectral type of B0.5V star and is associated with an expanding H{\sc ii}
region. The photoionized gas appears to be responsible for the origin of the
bell-shaped structure. The majority of molecular gas is distributed toward a
massive {\it Herschel} clump (M 260 M), which
contains the filamentary features and has a noticeable velocity gradient. The
photometric analysis traces the clusters of young stellar objects (YSOs) mainly
toward the bell-shaped structure and the filamentary features. Considering the
lower dynamical age of the H\,{\sc ii} region (i.e. 0.2-0.8 Myr), these
clusters are unlikely to be formed by the expansion of the H\,{\sc ii} region.
Our results also show the existence of a cluster of YSOs and a massive clump at
the intersection of filamentary features, indicating that the collisions of
these features may have triggered cluster formation, similar to those found in
Serpens South region.Comment: 21 pages, 14 figures, 1 table, Accepted for publication in The
Astrophysical Journa
The significance of Mivan technology
The technology has been used extensively in other countries such as Europe, Gulf Countries, Asia and all other parts of the world. MIVAN technology is suitable for constructing large number of houses within short time using room size forms to construct walls and slabs in one continuous pour on concrete. Early removal of forms can be achieved by hot air curing / curing compounds. This facilitates fast construction, say two flats per day. All the activities are planned in assembly line manner and hence result into more accurate, well – controlled and high quality production at optimum cost and in shortest possible time. This paper reveals about significance of Mivan
A multi-wavelength study of star formation activity in the S235 complex
We have carried out an extensive multi-wavelength study to investigate the
star formation process in the S235 complex. The S235 complex has a sphere-like
shell appearance at wavelengths longer than 2 m and harbors an O9.5V type
star approximately at its center. Near-infrared extinction map traces eight
subregions (having A 8 mag), and five of them appear to be
distributed in an almost regularly spaced manner along the sphere-like shell
surrounding the ionized emission. This picture is also supported by the
integrated CO and CO intensity maps and by Bolocam 1.1 mm
continuum emission. The position-velocity analysis of CO reveals an almost
semi-ring like structure, suggesting an expanding H\,{\sc ii} region. We find
that the Bolocam clump masses increase as we move away from the location of the
ionizing star. This correlation is seen only for those clumps which are
distributed near the edges of the shell. Photometric analysis reveals 435 young
stellar objects (YSOs), 59\% of which are found in clusters. Six subregions
(including five located near the edges of the shell) are very well correlated
with the dust clumps, CO gas, and YSOs. The average values of Mach numbers
derived using NH data for three (East~1, East~2, and Central~E) out of
these six subregions are 2.9, 2.3, and 2.9, indicating these subregions are
supersonic. The molecular outflows are detected in these three subregions,
further confirming the on-going star formation activity. Together, all these
results are interpreted as observational evidence of positive feedback of a
massive star.Comment: 28 pages, 15 figures, 3 tables, Accepted for publication in The
Astrophysical Journa
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