115 research outputs found
NON LINEAR FINITE ELEMENT ANALYSIS OF THE CONTACT, STRAIN AND STRESS STATES OF A BOLT - NUT - WASHER - COMPRESSED SHEET JOINT SYSTEM
A non-linear finite element model with contact elements was developed to evaluate the contact state of a bolt - nut - washer - compressed sheet joint system.
Applying the proper material law the non-linear behaviour of the members of the joint was studied in term of the clamping force. Based on the FE results the load distribution among the threads in contact and the real preload diagram of the system were evaluated.
To produce the required clamping force at medium strength bolts it is advisable to use heat-treated washers instead of lower strength ones
APPROXIMATE CALCULATION OF PRESSURE DROP IN BENDS BUILT IN PNEUMATIC CONVEYING PIPES IN THE CASE OF HIGH DENSITY CONVEYING
In this paper a computing method is described for the approximate determination of
pressure drop in bends of different plain built into pneumatic pipes in the case of high
density conveying.
Particles moving in the bend decelerate because of the force acting on them. The
conveying gas flow accelerates the decelerated particles in the connecting straight pipe
section following the bend to a limit velocity belonging to the straight section if it is long
enough. Pressure drop in the bend is approximately equal to the pressure drop necessary
for accelerating the material again.
Maximum velocity change occurs in a bend of vertical plane starting from vertical
position, therefore this bend has the greatest pressure drop, too
THE MATHEMATICAL MODEL OF PLUG FLOW CONVEYING
In the paper the movement characteristics of a special plug moving in the pneumatic pipe
are described considering forces influencing the plug that acceleration, velocity, and the
path made by the plug.
The state of motion in horizontal and vertical pipe sections, respectively, in a bend
built into the pipe section will be determined. The bend examined in this paper is laying
in the vertical plane and is connecting a horizontal pipe section with a vertical one.
Equations describing the movement characteristics are approximative because authors simplify the physical process, neglect different things. In the knowledge of the movement characteristics the data of the delivering machine can be determined
Search for high-amplitude Delta Scuti and RR Lyrae stars in Sloan Digital Sky Survey Stripe 82 using principal component analysis
We propose a robust principal component analysis (PCA) framework for the
exploitation of multi-band photometric measurements in large surveys. Period
search results are improved using the time series of the first principal
component due to its optimized signal-to-noise ratio.The presence of correlated
excess variations in the multivariate time series enables the detection of
weaker variability. Furthermore, the direction of the largest variance differs
for certain types of variable stars. This can be used as an efficient attribute
for classification. The application of the method to a subsample of Sloan
Digital Sky Survey Stripe 82 data yielded 132 high-amplitude Delta Scuti
variables. We found also 129 new RR Lyrae variables, complementary to the
catalogue of Sesar et al., 2010, extending the halo area mapped by Stripe 82 RR
Lyrae stars towards the Galactic bulge. The sample comprises also 25
multiperiodic or Blazhko RR Lyrae stars.Comment: 23 pages, 17 figure
The first CCD photometric study of the open cluster NGC 2126
We present the first CCD photometric observations of the northern open
cluster NGC 2126. Data were taken on eight nights in February and December 2002
with a total time span of ~57 hours. Almost 1000 individual V-band frames were
examined to find short-period variable stars. We discovered six new variable
stars, of which one is a promising candidate for an eclipsing binary with a
pulsating component. Two stars were classified as delta Scuti stars and one as
Algol-type eclipsing binary. Two stars are slow variables with ambiguous
classification. From absolute VRI photometry we have estimated the main
characteristics of the cluster: m-M=11.0+/-0.5, E(V-I)=0.4+/-0.1,
E(V-R)=0.08+/-0.06 (E(B-V)=0.2+/-0.15) and d=1.3+/-0.6 kpc. Cluster membership
is suggested for three variable stars from their positions on the
colour-magnitude diagram.Comment: 7 pages, 10 figures, accepted for publication in A&
Search for high-amplitude ÎŽ Scuti and RR Lyrae stars in Sloan Digital Sky Survey Stripe 82 using principal component analysis
We propose a robust principal component analysis framework for the exploitation of multiband photometric measurements in large surveys. Period search results are improved using the time-series of the first principal component due to its optimized signal-to-noise ratio. The presence of correlated excess variations in the multivariate time-series enables the detection of weaker variability. Furthermore, the direction of the largest variance differs for certain types of variable stars. This can be used as an efficient attribute for classification. The application of the method to a subsample of Sloan Digital Sky Survey Stripe 82 data yielded 132 high-amplitude ÎŽ Scuti variables. We also found 129 new RR Lyrae variables, complementary to the catalogue of Sesar et al., extending the halo area mapped by Stripe 82 RR Lyrae stars towards the Galactic bulge. The sample also comprises 25 multiperiodic or Blazhko RR Lyrae star
A photometric monitoring of bright high-amplitude delta Scuti stars. II. Period updates for seven stars
We present new photometric data for seven high-amplitude delta Scuti stars.
The observations were acquired between 1996 and 2002, mostly in the Johnson
photometric system. For one star (GW UMa), our observations are the first since
the discovery of its pulsational nature from the Hipparcos data.The primary
goal of this project was to update our knowledge on the period variations of
the target stars. For this, we have collected all available photometric
observations from the literature and constructed decades-long O-C diagrams of
the stars. This traditional method is useful because of the single-periodic
nature of the light variations. Text-book examples of slow period evolution (XX
Cyg, DY Her, DY Peg) and cyclic period changes due to light-time effect (LITE)
in a binary system (SZ Lyn) are updated with the new observations. For YZ Boo,
we find a period decrease instead of increase. The previously suggested
LITE-solution of BE Lyn (Kiss & Szatmary 1995) is not supported with the new
O-C diagram. Instead of that, we suspect the presence of transient light curve
shape variations mimicking small period changes.Comment: 11 pages, 15 figures, accepted for publication in A&
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