5,740 research outputs found

    Newly Discovered RR Lyrae Stars in the SDSSXPanXSTARRS1XCatalina Footprint

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    We present the detection of 6,371 RR Lyrae (RRL) stars distributed across ~14,000 deg^2 of the sky from the combined data of the Sloan Digital Sky Survey (SDSS), the Panoramic Survey Telescope and Rapid Response System 1 (PS1), and the second photometric catalogue from the Catalina Survey (CSDR2), out of these, ~2,021 RRL stars (~572 RRab and 1,449 RRc) are new discoveries. The RRL stars have heliocentric distances in the 4--28 kpc distance range. RRL-like color cuts from the SDSS and variability cuts from the PS1 are used to cull our candidate list. We then use the CSDR2 multi-epoch data to refine our sample. Periods were measured using the Analysis of Variance technique while the classification process is performed with the Template Fitting Method in addition to the visual inspection of the light curves. A cross-match of our RRL star discoveries with previous published catalogs of RRL stars yield completeness levels of ~50% for both RRab and RRc stars, and an efficiency of ~99% and ~87% for RRab and RRc stars, respectively. We show that our method for selecting RRL stars allows us to recover halo structures. The full lists of all the RRL stars are made publicly available.Comment: 14 pages, 11 figures. Accepted 2014 March 30. Received 2014 March 12; in original form 2013 November 2

    Design and simulation of a low voltage wide band RF MEMS switch

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    This paper presents design of an electrostatic wide band shunt capacitive coupling RF MEMS switch with low actuation voltage. The key factors of the RF MEMS switch design are the proper scattering parameters, low actuation voltage, and the cost of the fabrication process. An overview of the recent low actuation voltage RFMEMS switches has been presented. These designs still suffer from the complexity of process, lack of reliability, limitation of frequency band, and process cost. RF characteristics of a shunt RF MEMS switches are specified mostly by coupling capacitor in upstate position of the membrane Cu. This capacitor is in trade-off with actuation voltage. In this work, the capacitor is eliminated by using two short high impedance transmission lines, at the input and output of the switch. The simulation results demonstrate an improvement in the RF characteristic of the switch.<br /

    Physical Properties of Cu Doped ZnO Nanocrystiline Thin Films

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     تم تصنيع اغشية أكسيد الزنك البلورية النانوية المطعمة بالنحاس  (ZnO: Cu)بتراكيز مختلفة .. تم ترسيب (0 ، 6 ، 9 ، 12 ، 18) ٪ من النحاس على ركيزة زجاجية باستخدام تقنية ترسب الليزر النبضي (PLD) وبتراكيز مختلفة. وقد تم توصيف بلورات ZnO: Cu   النانوية بواسطة أطياف UV-VIS ، حيود الأشعة السينية (XRD) ومجهر القوة الذرية (AFM). تم استخدام التحليل الطيفي للأشعة المرئية وفوق البنفسجية لتحديد نوع وقيمة فجوة الطاقة الضوئية ، بينما تم استخدام حيود الأشعة السينية لفحص الهيكل وتحديد حجم البلورات. تم استخدام مجاهر القوة الذرية لدراسة تكوين سطح المواد المترسبة. تم استخدام التحليل الطيفي للأشعة المرئية وفوق البنفسجية لتحديد نوع وقيمة فجوة الطاقة الضوئية. Thin films of ZnO nano crystalline doped with different concentrations (0, 6, 9, 12, and 18 )wt. % of copper were deposited on a glass substrate via pulsed laser deposition method (PLD). The properties of ZnO: Cu thin-nanofilms have been studied by absorbing UV-VIS, X-ray diffraction (XRD) and atomic force microscopes (AFM). UV-VIS spectroscopy was used to determine the type and value of the optical energy gap, while X-ray diffraction was used to examine the structure and determine the size of the crystals.  Atomic force microscopes were used to study the surface formation of precipitated materials. The UV-VIS spectroscopy was used to determine the type and value of the optical energy gap

    Multifocus Images Fusion Based On Homogenity and Edges Measures

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    Image fusion is one of the most important techniques in digital image processing, includes the development of software to make the integration of multiple sets of data for the same location; It is one of the new fields adopted in solve the problems of the digital image, and produce high-quality images contains on more information for the purposes of interpretation, classification, segmentation and compression, etc. In this research, there is a solution of problems faced by different digital images such as multi focus images through a simulation process using the camera to the work of the fuse of various digital images based on previously adopted fusion techniques such as arithmetic techniques (BT, CNT and MLT), statistical techniques (LMM, RVS and WT) and spatial techniques (HPFA, HFA and HFM). As these techniques have been developed and build programs using the language MATLAB (b 2010). In this work homogeneity criteria have been suggested for evaluation fused digital image's quality, especially fine details. This criterion is correlation criteria to guess homogeneity in different regions within the image by taking a number of blocks of different regions in the image and different sizes and work shifted blocks per pixel. As dependence was on traditional statistical criteria such as (mean, standard deviation, and signal to noise ratio, mutual information and spatial frequency) and compared with the suggested criteria to the work. The results showed that the evaluation process was effective and well because it took into measure the quality of the homogenous regions

    An experimental study on the effect of gas injection configuration on flow characteristics in high viscosity oil columns

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    Gas-viscous liquid bubbly and slug flow are very common in petroleum, chemical, bioengineering, polymer, and food processing. However, there is a major knowledge gap in two-phase flow research in the design of gas injectors/distributers in very high viscosity oil systems. The present study investigates the effect of gas injection methods in columns containing very high viscosity oils (i.e., realistic liquids), and more specifically using 360 Pa · s viscosity oil in a 240-mm diameter column. The effects that the radial positioning, number of gas nozzles, and their distance from each other have on the structure of the flow in viscous liquids are presented in detail. Electrical capacitance tomography (ECT) is used to extract experimental data. Void fraction, bubble velocity, frequency, liquid film thickness, and bubble length were measured and analyzed at different radial gas injection positions. It has been observed that bubble length increases significantly by 0.3 m when the injection nozzle is located next to the wall of the pipe. Bubble velocity and length also increase by 0.217 m/s and 3.6 m, respectively, with increasing gas flowrate when multiple injection points are used. Increasing the distance between the gas injection points increased bubbles' length by 1.2 m. Bubbles' velocity and frequency (at higher gas flow rate) were also increased

    On-Line Monitoring for Temporal Logic Robustness

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    In this paper, we provide a Dynamic Programming algorithm for on-line monitoring of the state robustness of Metric Temporal Logic specifications with past time operators. We compute the robustness of MTL with unbounded past and bounded future temporal operators MTL over sampled traces of Cyber-Physical Systems. We implemented our tool in Matlab as a Simulink block that can be used in any Simulink model. We experimentally demonstrate that the overhead of the MTL robustness monitoring is acceptable for certain classes of practical specifications

    Small bubbles formation and contribution to the overall gas holdup in large diameter columns of very high viscosity oil

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    A limited number of studies are available in literature on the small bubbles which create from gas-very high viscosity oils interaction and its contribution to the gas holdup in the system. The rate of small bubble formation has an important impact on heat and mass transfer in many chemical and industrial processes. The work presented in the current paper provides unique information on the formation of bubbles of millimetre diameter in high viscosity oil. A column of 290 mm diameter and Silicon oil of 330 Pa.s viscosity, were employed besides Electrical Capacitance Tomography and a high-resolution camera to investigate the characteristics of the small bubbles. Mechanism of bubble generation, effect of gas injection time and flowrate were studied. The average void fraction, total gas-liquid height, overall Probability Density Function (PDF) profile, small bubbles volume fractions and diameter were measured. Small bubbles generate from the eruption of large bubbles, at gas injection nozzles, coalescence of large bubbles, and at liquid bridges at transition to churn flow regime. Properties and concentration of the small bubbles are controlled by the location of the bubble generation, gas flowrate, and gas injection time. Small bubbles contribute by 6.6- 30% to the total gas holdup. Bubble diameter increased from 0.68 mm to 0.75 mm and decreased from 1.1 mm to 0.75 mm at the top and the bottom sections of the column respectively after 60 minof gas injection

    The effect of placenta previa on fetal weight and feto-maternal blood flow: a prospective cohort study

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    Background: The current study aims to evaluate the effect of placenta previa on the fetal weight and to explore its effect on the uterine and umbilical arteries blood flow.Methods: The current study was a prospective cohort study conducted at Assiut Women’s Health Hospital, Egypt from 1st of October 2016 to 30th of September 2017 including placenta previa and non-placenta previa women. They were followed up by two-dimensional ultrasound and Doppler blood flow in the uterine and umbilical arteries. The main study outcome was the number of low birth weight (LBW) babies delivered at or beyond 37 weeks and blood flow changes in uterine and umbilical arteries.Results: Two hundred twelve women were divided into two groups; group I included 106 placenta previa women (PP group) and 106 non-placenta previa women (NPP group). The number of LBW babies were comparable in both groups without statistically significant difference (P value= 0.555). Neither; uterine artery nor umbilical artery blood flow had any significant differences between the groups.  Preterm delivery was significantly higher in the PP group (p value=0.000).Conclusions: Although there is no agreement, in the literature, on the association between placenta previa and LBW, authors suggest that placenta previa is not a reason for LBW babies. In addition, placenta previa shows no effect on uterine artery or umbilical artery blood flow
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