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The effect of aging time on mechanical and microstructure properties of aa6061 joints welded by gas tungsten arc welding
This research examines the influence of heat treatment on mechanical properties and microstructure of AA6061 aluminium alloy welded with butt groove method, by using Gas Tungsten Arc Welding (GTAW) method. Welded samples were divided into two; heat treated (PWHT) and as-welded (AW) joints samples. For PWHT welded samples, the heat treatment applied were solution heat treatment at a temperature of 5300C for 1 h, followed by cooling water and artificial aging process at a temperature of 1600C for 18, 20 and 22 hours. Tensile test was performed based on standard ASTM E8 04, while the hardness test was taken at 3 different locations along the cross section of the weld zone of upper, middle and lower sections. Fracture surface at AW and PWHT welded samples were investigated by using Scanning Electron Microscopy (SEM) and the microstructure of the samples was analyzed by using Optical Microscopy (OM). From the results, the PWHT welded samples increased the tensile strength, hardness, and micro structural characteristics of welded joints aluminium AA6061 alloy
Blending of Cepheids in M33
A precise and accurate determination of the Hubble constant based on Cepheid
variables requires proper characterization of many sources of systematic error.
One of these is stellar blending, which biases the measured fluxes of Cepheids
and the resulting distance estimates. We study the blending of 149 Cepheid
variables in M33 by matching archival Hubble Space Telescope data with images
obtained at the WIYN 3.5-m telescope, which differ by a factor of 10 in angular
resolution.
We find that 55+-4% of the Cepheids have no detectable nearby companions that
could bias the WIYN V-band photometry, while the fraction of Cepheids affected
below the 10% level is 73+-4%. The corresponding values for the I band are
60+-4% and 72+-4%, respectively. We find no statistically significant
difference in blending statistics as a function of period or surface
brightness. Additionally, we report all the detected companions within 2
arcseconds of the Cepheids (equivalent to 9 pc at the distance of M33) which
may be used to derive empirical blending corrections for Cepheids at larger
distances.Comment: v2: Fixed incorrect description of Figure 2 in text. Accepted for
publication in AJ. Full data tables can be found in ASCII format as part of
the source distribution. A version of the paper with higher-resolution
figures can be found at
http://faculty.physics.tamu.edu/lmacri/papers/chavez12.pd
Aerodynamic performance sensitivity analysis of blade design for a 100 kW HAWT
Wind energy is gaining ever increasing popularity among renewable energy sources. In some European countries installed wind turbine capacity has reached over 20 % of the total power generation capacity. This paper examines aerodynamic performance sensitivity of wind turbine blades for main design variables. The sensitivity analysis has been conducted on a sample 100 kW three-bladed horizontal axis wind turbine (HAWT). Taguchi robust design techniques and orthogonal arrays have been used to perform experimental optimization using five main parameters: airfoil NACA profile, root chord length, tip chord length, root radius and chord profile distribution along the blade’s length. The airfoil profiles and their aerodynamic data are taken from the NACA airfoil database for which experimental lift and drag coefficient data are available. The airfoils for the studied blades have the same profile from root to tip. Three sets of analyses have been performed according to three different base load wind speeds. The sensitivity results have been presented for the optimal tip speed ratio values
HST Observations of the QSO pair Q1026-0045A,B
The spatial distribution of the Ly forest is studied using new HST
data for the quasar pair Q~1026--0045 A and B at = 1.438 and 1.520
respectively. The angular separation is 36 arcsec and corresponds to transverse
linear separations between lines of sight of kpc (
= 0.5) over the redshift range 0.833 < z < 1.438. From the observed numbers of
coincident and anti-coincident Ly absorption lines, we conclude that,
at this redshift, the Ly structures have typical dimensions of
kpc, larger than the mean separation of the two lines of
sight. The velocity difference, , between coincident lines is
surprisingly small (4 and 8 pairs with z_{abs}z_{abs}z_{abs}z_{abs}z_{abs}z_{abs}\alphah^{-1}_{50}$ kpc surrounding quasar A.Comment: 4 pages, 2 figures, A&A Letter acccepte
Gas Monitor: Developments in the Wholesale Gas Market in the Netherlands in 2006
The present situation in the wholesale gas market calls for measures aimed at enhancing competition. Our annual monitoring report into the functioning of the gas market identifies a number of serious problems that impede competition in the wholesale market. Market parties have indicated a lack of available import capacity, storage capacity and quality conversion capacity, though facilities are not always optimally utilised. The report’s findings confirm the necessity of the action plan which was presented by the NMa/ DTe to the Minister of Economic Affairs in early October this year. Improvement is required for the rules of play and the level of transparency in the gas market. It is also necessary to pursue further integration into North-West Europe.Monitoring,gas, competition, infrastructure
Identification and analysis of the young population in the starburst galaxy NGC 253
We present a study of the young population in the starburst galaxy NGC 253. In particular, we focused our attention on searching young star groups, obtaining their main properties and studying their hierarchical organization. For this task, we used multiband images and their corresponding photometric data obtained with the Advanced Camera for Surveys of the Hubble Space Telescope (ACS/HST).We have first derived the absorption affecting the different regions of the galaxy. Then, we applied an automatic and objective searching method over the corrected data in order to detect young star groups. We complemented this result with the construction of the stellar density map for the blue young population. A statistical procedure to decontaminate the photometric diagrams from field stars was applied over the detected groups and we estimated their fundamental parameters.As a result, we built a catalog of 875 new identified young groups with their main characteristics, including coordinates, sizes, estimated number of members, stellar densities, luminosity function (LF) slopes and galactocentric distances. We observed these groups delineate different structures of the galaxy, and they are the last step in the hierarchical way in which the young population is organized. From their size distribution, we found they have typical radius of ∼ 40 − 50 pc. These values are consistent with those ones found in others nearby galaxies. We estimated a mean value of the LF slope of 0.21 and an average density of 0.0006 stars/pc³ for the identified young groups taking into account stars earlier than B6.Fil: Rodriguez, Maria Jimena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Baume, Gustavo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Feinstein Baigorri, Carlos. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentin
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