612 research outputs found
Wear performance optimization of Silicon Nitride using Genetic and simulated annealing algorithm
Replacing damaged joint with the suitable alternative material is a prime requirement in a patient who has arthritis. Generation of wear particles in the artificial joint during action or movement is a serious issue and leads to aseptic loosening of joint. Research in the field of bio-tribology is trying to evaluate materials with minimum wear volume loss so as to extend joint life. Silicon nitride (Si3N4) is non-oxide ceramic suggested as a new alternative for hip/knee joint replacement. Hexagonal Boron Nitride (hBN) is recommended as a solid additive lubricant to improve the wear performance of Si3N4. In this paper, an attempt has been made to evaluate the optimum combination of load and % volume of hBN in Si3N4 to minimize wear volume loss (WVL). The experiments were conducted according to Design of Experiments (DoE)–Taguchi method and a mathematical model is developed. Further, this model is processed with Genetic Algorithm (GA) and Simulated Annealing (SA) to find out the optimum percentage of hBN in Si3N4 to minimize wear volume loss against Alumina (Al2O3) counterface. Taguchi method presents 15 N load and 8% volume of hBN to minimize WVL of Si3N4. While GA and SA optimization offer 11.08 N load, 12.115% volume of hBN and 11.0789 N load, 12.128% volume of hBN respectively to minimize WVL in Si3N4
Intracaesarean forceps application
Background: In a time when repeat caesarean deliveries are becoming more frequent, more elective LSCS are being performed and floating vertex are commonly encountered. Sometimes fundal pressure is not adequate, and the physician needs to use instrument (vaccum/forceps) to deliver the head. The objective of the present study is to evaluate maternal and neonatal complications of intracaesarean forceps applicationMethods: This was an interventional study which was conducted in OBGY department of Sassoon General Hospital, Pune for 1 year. 75 cases including both emergency and elective sections were included in the study, in which intracaesarean outlet forceps was applied.Results: Out of 75 cases, maternal complications were seen in 5 cases with uterine incision extensions being the commonest (4%). Neonatal complications were seen in 3 cases, with minor facial injuries due to pressure of forceps being commonest (2.6%).Conclusions: Intracaesarean forceps when applied skillfully can be effective, fast and safe technique of delivering fetal head in this rising trend of caesarean sections
Anisotropic flow from Lee-Yang zeroes: a practical guide
We present a new method to analyze anisotropic flow from the genuine
correlation among a large number of particles, focusing on the practical
implementation of the method.Comment: 4 pages; contribution to Quark Matter 2004, Oakland, January 11-17,
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Markov random field segmentation for industrial computed tomography with metal artefacts
X-ray Computed Tomography (XCT) has become an important tool for industrial measurement and quality control through its ability to measure internal structures and volumetric defects. Segmentation of constituent materials in the volume acquired through XCT is one of the most critical factors that influence its robustness and repeatability. Highly attenuating materials such as steel can introduce artefacts in CT images that adversely affect the segmentation process, and results in large errors during quantification. This paper presents a Markov Random Field (MRF) segmentation method as a suitable approach for industrial samples with metal artefacts. The advantages of employing the MRF segmentation method are shown in comparison with Otsu thresholding on CT data from two industrial objects
Multi-wavelength observations of IGR J17544-2619 from quiescence to outburst
In this paper we report on a long multi-wavelength observational campaign of
the supergiant fast X-ray transient prototype IGR J17544-2619. A 150 ks-long
observation was carried out simultaneously with XMM-Newton and NuSTAR, catching
the source in an initial faint X-ray state and then undergoing a bright X-ray
outburst lasting about 7 ks. We studied the spectral variability during
outburst and quiescence by using a thermal and bulk Comptonization model that
is typically adopted to describe the X-ray spectral energy distribution of
young pulsars in high mass X-ray binaries. Although the statistics of the
collected X-ray data were relatively high we could neither confirm the presence
of a cyclotron line in the broad-band spectrum of the source (0.5-40 keV), nor
detect any of the previously reported tentative detection of the source spin
period. The monitoring carried out with Swift/XRT during the same orbit of the
system observed by XMM-Newton and NuSTAR revealed that the source remained in a
low emission state for most of the time, in agreement with the known property
of all supergiant fast X-ray transients being significantly sub-luminous
compared to other supergiant X-ray binaries. Optical and infrared observations
were carried out for a total of a few thousands of seconds during the
quiescence state of the source detected by XMM-Newton and NuSTAR. The measured
optical and infrared magnitudes were slightly lower than previous values
reported in the literature, but compatible with the known micro-variability of
supergiant stars. UV observations obtained with the UVOT telescope on-board
Swift did not reveal significant changes in the magnitude of the source in this
energy domain compared to previously reported values.Comment: Accepted for publication on A&A. V2: few typos correcte
Tracing the Orphan Stream to 55 kpc with RR Lyrae Stars
We report positions, velocities and metallicities of 50 ab-type RR Lyrae
(RRab) stars observed in the vicinity of the Orphan stellar stream. Using about
30 RRab stars classified as being likely members of the Orphan stream, we study
the metallicity and the spatial extent of the stream. We find that RRab stars
in the Orphan stream have a wide range of metallicities, from -1.5 dex to -2.7
dex. The average metallicity of the stream is -2.1 dex, identical to the value
obtained by Newberg et al. (2010) using blue horizontal branch stars. We find
that the most distant parts of the stream (40-50 kpc from the Sun) are about
0.3 dex more metal-poor than the closer parts (within ~30 kpc), suggesting a
possible metallicity gradient along the stream's length. We have extended the
previous studies and have mapped the stream up to 55 kpc from the Sun. Even
after a careful search, we did not identify any more distant RRab stars that
could plausibly be members of the Orphan stream. If confirmed with other
tracers, this result would indicate a detection of the end of the leading arm
of the stream. We have compared the distances of Orphan stream RRab stars with
the best-fit orbits obtained by Newberg et al. (2010). We find that model 6 of
Newberg et al. (2010) cannot explain the distances of the most remote Orphan
stream RRab stars, and conclude that the best fit to distances of Orphan stream
RRab stars and to the local circular velocity is provided by potentials where
the total mass of the Galaxy within 60 kpc is M_{60}~2.7x10^{11} Msun, or about
60% of the mass found by previous studies. More extensive modelling that would
consider non-spherical potentials and the possibility of misalignment between
the stream and the orbit, is highly encouraged.Comment: Submitted to ApJ, 15 pages in emulateapj format, three tables in
machine-readable format (download "Source" from "Other formats"
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