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Статті в журналах з теми "K luminosity"
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Wagner, S. J., and M. W. Kümmel. "The K-Band Luminosity Function." Symposium - International Astronomical Union 171 (1996): 465. http://dx.doi.org/10.1017/s0074180900233834.
Повний текст джерелаАнотація:
Investigations of broad band energy distributions of specific classes of sources requires homogeneous samples of a sufficiently large number of objects. Deep and homogeneous surveys in those energy ranges which are accessible to satellites only are rare. One such a field in the north ecliptic pole (NEP). The ROSAT and IRAS whole sky surveys and deep additional observations by other satellites make the NEP the region of the deepest mid-IR and X-ray observations. We performed complete surveys in three optical/IR colors at 460nm, 700nm, and 2.1 μm (B, R, and K′) within a one square degree field around the NEP. Limiting magnitudes in the three bands are 23, 24, and 19, respectively. The optical bands are observed with sufficient spatial sampling to classify extended and point sources. Down to levels which still correspond to high completeness limits we detect 80.000, 240.000 and 25.000 sources in B, R, and K′, respectively.
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Gardner, J. P., R. M. Sharples, C. S. Frenk, and B. E. Carrasco. "The K-Band Luminosity Function of Galaxies." Symposium - International Astronomical Union 179 (1998): 278–80. http://dx.doi.org/10.1017/s0074180900128773.
Повний текст джерелаАнотація:
The luminosity function of galaxies is central to many problems in cosmology, including the interpretation of faint number counts. The near-infrared provides several advantages over the optical for statistical studies of galaxies, including smooth and well-understood K-corrections and expected luminosity evolution. The K–band is dominated by near-solar mass stars which make up the bulk of the galaxy. The absolute K magnitude is a measure of the visible mass in a galaxy, and thus the K–band luminosity function is an observational counterpart of the mass function of galaxies.
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Baker, A. C., and P. C. Hewett. "K-Correction Biases and the Quasar Luminosity Function." Symposium - International Astronomical Union 159 (1994): 498. http://dx.doi.org/10.1017/s0074180900176715.
Повний текст джерелаАнотація:
By characterising the range of quasar UV-optical spectral indices and any correlation with it e.g. luminosity or line parameters, we hope to remove one more bias from the quasar luminosity function (QLF).
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Deng, Xin-Fa, Xiao-Qing Wen, Yong Xin, Xiao-Ping Qi, and Ying-Ping Ding. "K-band luminosity–density relation at fixed parameters or for different galaxy families." Open Physics 18, no. 1 (July 9, 2020): 290–301. http://dx.doi.org/10.1515/phys-2020-0016.
Повний текст джерелаАнотація:
AbstractUsing the apparent magnitude-limited Main galaxy sample of the Sloan Digital Sky Survey Data Release 10, we examine the K-band luminosity–density relation at fixed parameters or for different galaxy families. It is found that the limiting or fixing galaxy properties, such as galaxy morphology, stellar mass, and color, exert substantial influence on the environmental dependence of the K-band luminosity of galaxies, which suggests that the K-band luminosity–density relation is likely attributable to the relation between these galaxy properties and density.
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Gyulbudaghian, A. L., N. Baloian, and I. A. Sanchez. "Color-color diagrams in near infrared: (J-H)/(H-K). II." Communications of the Byurakan Astrophysical Observatory 2, no. 1 (2018): 21–26. http://dx.doi.org/10.52526/25792776-2018.2.1-21.
Повний текст джерелаАнотація:
In the paper the color-color diagrams (J-H)/(H-K) for all stars with visible magnitudes B<11m (for which in the existing catalogs the magnitudes of J, H, K, and also their spectral types and luminosity classes are given) are presented. In the preceding paper the data for luminosity classes I, Ia, Ib, II and III were given. In this paper the data on luminosity classes IV (sub giants) and V (main sequence stars) are given. Among the diagrams of luminosity classes the most interesting are the diagrams for GII and GIV stars, each of these diagrams have two centers of concentrations. For stars of spectral class M the minimal amount of stars is at luminosity class IV, the maximal –at class III, which is not so for other spectral classes: for other classes the maximal amount is at class V. There is a tendency (seen in all diagrams)of increasing of the values of J-H and H-K along the sequence O-B-A-F-G-K-M.
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Loveday, Jon. "Optical and Near-IR Field Luminosity Functions." International Astronomical Union Colloquium 171 (1999): 68–75. http://dx.doi.org/10.1017/s0252921100054130.
Повний текст джерелаАнотація:
AbstractWe present preliminary measurements of the bJ and K-band luminosity functions (LFs) of field galaxies obtained from optical and K-band imaging of a sample of galaxies selected from the Stromlo-APM Redshift Survey. The bJ LF is consistent with that previously published from photographic data. The K-band LF has been estimated over a range of 12 magnitudes and is reasonably well fit by a Schechter function with faint-end slope α = −1.2.
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Brainerd, Tereasa G. "K-band Luminosity Functions of IllustrisTNG300-1 Galaxies." Research Notes of the AAS 5, no. 10 (October 8, 2021): 224. http://dx.doi.org/10.3847/2515-5172/ac2d36.
Повний текст джерела
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Alves, David R. "K‐Band Calibration of the Red Clump Luminosity." Astrophysical Journal 539, no. 2 (August 20, 2000): 732–41. http://dx.doi.org/10.1086/309278.
Повний текст джерела
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Brunello, A., P. Saracco, B. Garilli, D. Maccagni, and G. Chincarini. "Multicolor Luminosity Function of Field Galaxies." Symposium - International Astronomical Union 183 (1999): 156. http://dx.doi.org/10.1017/s007418090013236x.
Повний текст джерелаАнотація:
The aim of this programme is to determine the luminosity function of field galaxies in different bands for a unique sample. From the ESP [1] redshift survey of 3344 bj ≤ 19.4 galaxies, we have extracted a fair subsample and obtained multicolor photometry for 354 (11%) galaxies in the V, R (Johnson) and i (Gunn) filters and for 148 (4%) in the K′ band. Errors on the total magnitudes are smaller than 0.1 in all bands. In order to obtain absolute magnitudes, we applied k-corrections [2] after deriving a rough morphological classification based on color information. Here we present a by product of this programme: the determination of the color-luminosity relationship. The figure shows how the rest-frame Bj-K' color is strongly related to the absolute i magnitude while such correlation is not present using optical colors. If we assume Mi is a good mass tracer, the figure indicates that bluer galaxies are the less massive ones.
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Loveday, J. "The K-band luminosity function of nearby field galaxies." Monthly Notices of the Royal Astronomical Society 312, no. 3 (March 1, 2000): 557–66. http://dx.doi.org/10.1046/j.1365-8711.2000.03179.x.
Повний текст джерелаДисертації з теми "K luminosity"
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Nikodem, Thomas [Verfasser], and Stephanie [Akademischer Betreuer] Hansmann-Menzemer. "Angular analysis of B0→ K*0µ+µ- decays using 3fb-1 of integrated luminosity at LHCb / Thomas Nikodem ; Betreuer: Stephanie Hansmann-Menzemer." Heidelberg : Universitätsbibliothek Heidelberg, 2016. http://d-nb.info/1180614321/34.
Повний текст джерела
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Barai, Paramita. "Modeling the Power Evolution of Classical Double Radio Galaxies over Cosmological Scales." Digital Archive @ GSU, 2006. http://digitalarchive.gsu.edu/phy_astr_diss/9.
Повний текст джерелаАнотація:
During the quasar era (redshifts between 1 and 3) Radio Galaxies (RGs) have been claimed to have substantially influenced the growth and evolution of large scale structures in the universe. In this dissertation I test the robustness of these exciting claims. In order to probe the impacts in more detail, good theoretical models for such RG systems are required. With this motivation, I seek to develop an essentially analytical model for the evolution of Fanaroff-Riley Class II radio galaxies both as they age individually and as their numbers vary with cosmological epoch. To do so, I first compare three sophisticated semi-analytical models for the dynamical and radio lobe power evolution of FR II galaxies, those given by Kaiser, Dennett-Thorpe & Alexander (1997, KDA), Blundell, Rawlings, & Willott (1999, BRW) and Manolakou & Kirk (2002, MK). I perform multi-dimensional Monte Carlo simulations leading to virtual radio surveys. The predictions of each model for redshift, radio power (at 151 MHz), linear size and spectral index are then compared with data. The observational samples are the low frequency radio surveys, 3CRR, 6CE and 7CRS, which are flux-limited and redshift complete. I next perform extensive statistical tests to compare the distributions of model radio source parameters and those of the observational samples. The statistics used are the 1-Dimensional and 2-Dimensional Kolmogorov-Smirnov (K-S) tests and the 4-variable Spearman partial rank correlation coefficient. I search for and describe the "best" parameters for each model. I then produced modifications to each of the three original models, and extensively compare the original and the modified model performances in fitting the data. The key result of my dissertation is that using the Radio Luminosity Function of Willott et al. (2001) as the redshift birth function of radio sources, the KDA and MK models perform better than the BRW models in fitting the 3CRR, 6CE and 7CRS survey data when using K-S based statistical tests, and the KDA model provides the best fits to the correlation coefficients. However, no pre-existing or modified model can provide adequate fits for the spectral indices. I also calculate the volume fraction of the relevant universe filled by the generations of radio galaxies over the quasar era. This volume filling factor is not as large as estimated earlier. Nonetheless, the allowed ranges of various model parameters produce a rather wide range of astrophysically interesting relevant volume fraction values. I conclude that the expanding RGs born during the quasar era may still play significant roles in the cosmological history of the universe.
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Samuel, Angela E. "The nature of star formation in the Trapezium Cluster." Phd thesis, 1993. http://hdl.handle.net/1885/12624.
Повний текст джерелаАнотація:
The Trapezium Cluster stellar population is studied in detail using near-infrared and optical means in order to probe the clustered mode of low and high mass star formation. We determine fundamental stellar parameters such as the spectral types, ages, masses, extinctions and dust excesses for a significant number of cluster stars. Various techniques are applied to deredden the stars in the color-magnitude diagram and hence compare intrinsic positions with theoretical evolutionary tracks. Through these means, we estimate properties of the low mass stellar population to greater accuracy than has previously been achieved. Near-infrared photometry of Trapezium Cluster stars provides an initial evaluation of the nature of the cluster population. This evaluation is improved upon using optical spectroscopy to measure spectral types of a large number of Trapezium Cluster stars for the first time. We find our sample of Trapezium Cluster stars to have a mean spectral type of mid-K, in agreement with :findings for the low mass stars in the vicinity of, and external to, the central cluster. The stars are dereddened on the color-magnitude diagram using our acquired spectral types. Their intrinsic positions provide the most accurate determination for the cluster age obtained to date, -10/6 yr, confirming the pre-main sequence nature of the population. This age estimate is extended to the infrared cluster population of more than 550 stars revealed by infrared-array images. The K luminosity function for the infrared cluster is used in combination with the cluster age to derive the stellar mass distribution. The slope of the mass function obtained here is found to be comparable with the slopes of field initial mass functions. A mean stellar mass of, -0.9 Mo is estimated
for the low mass stars. Our determinations for the masses, ages, and spectral types
of Trapezium Cluster stars shows that they are a similar stellar population to the more extended Orion Nebula Cluster population, except in density of stars. The mass density of the Trapezium system of low mass and high mass (01 Ori) stars is found to be -4690 Mo pc-3 , approximately 1.5 times greater than previous estimates based on optical studies. The stellar mass derived for the low mass cluster is also used to calculate the star formation efficiency in the region to first order, -72%. This is similar to, but higher than, the star formation efficiencies determined in other regions of embedded cluster formation. The mean extinction estimated for the low mass cluster stars in our sample place the stars at approximately the same depth into the molecular cloud as the Trapezium OB stars, at the near-face of the cloud. Our sample is biased towards optical members of the cluster, suggesting that a significant number of the low mass stars may be embedded more deeply in the molecular cloud than the OB stars. However,
using the K luminosity function for the infrared cluster we determine that the
low mass cluster is most probably not spread through the whole cloud, but is pre-dominantly located close to the near-face of the cloud. Dust excess determinations show that the Trapezium Cluster stars sampled here contain a typical proportion of classical (dust-excess) T Tauri stars compared with naked (no dust-excess) T Tauri
stars for a young stellar population. Approximately one-third of our sample have
insignificant dust excesses. Calcium II IR triplet emission is observed in members of our Trapezium Cluster sample. We judge that the strengths of the triplet features imply a circumstellar disk origin for the emission. The frequency of calcium triplet emitting stars is estimated for our sample. We compare this estimate with the proportion of triplet emitters in a sample of Chamaeleon pre-main sequence stars. We find that 20-30 % of classical T Tauri stars in the two populations exhibit triplet emission; the frequency of triplet emission in the Trapezium Cluster sample is found to be comparable with that in Chamaeleon. We perform an approximate dynamical analysis of the Trapezium Cluster star-forming region using our estimates for stellar mass and age. The low mass cluster is found to be at an early stage in its dynamical evolution, and has not had time to completely relax as a system and lose its initial characteristics. It is too young, therefore, to exhibit mass segregation, and the observed isothermality of the stars is proposed here to arise from the distribution of the clumps from which the stars have formed. The high mass stars considered separately are determined to be old enough to have relaxed as a system. We find that, if the 01 Ori stars are located centrally with respect to the low mass cluster, then they are most likely to have formed in their present locations rather than have arrived there from larger radii through dynamical friction processes. In addition, the binding energies of the two high mass binary systems are found to be almost forty times the energy of the low mass cluster. It is suggested that the binary energies must have been acquired through their formation processes instead of through dynamical interactions with the low mass cluster. Thus, present characteristics of the stellar population of the Trapezium Cluster directly relate to the conditions under which the cluster formed, and are not due to dynamical processes among the stars themselves. The total stellar mass determined for the low mass cluster is estimated to be sufficient to bind the cluster at this time. This remains true even with future removal of gas from the region. However, continued dynamical interactions may lead to the eventual dissipation of the low mass cluster.
Книги з теми "K luminosity"
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Measurement of the nighttime infrared luminosity of Spacelab 1 in the H- and K-bands. Moffett Field, Calif: National Aeronautics and Space Administration, Ames Research Center, 1985.
Знайти повний текст джерелаЧастини книг з теми "K luminosity"
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Wagner, S. J., and M. W. Kümmel. "The K-Band Luminosity Function." In New Light on Galaxy Evolution, 465. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-009-0229-9_176.
Повний текст джерела
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Gardner, J. P., R. M. Sharples, C. S. Frenk, and B. E. Carrasco. "The K-Band Luminosity Function of Galaxies." In New Horizons from Multi-Wavelength Sky Surveys, 278–80. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-009-1485-8_63.
Повний текст джерела
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González-Serrano, J. I., C. Benn, R. Carballo, S. F. Sánchez, and M. Vigotti. "B-K Colours of Low-Luminosity Radio Quasars." In ESO Astrophysics Symposia, 260–65. Berlin, Heidelberg: Springer Berlin Heidelberg, 1997. http://dx.doi.org/10.1007/978-3-540-69648-3_48.
Повний текст джерела
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Baker, A. C., and P. C. Hewett. "K-Correction Biases and the Quasar Luminosity Function." In Multi-Wavelength Continuum Emission of AGN, 498. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-010-9537-2_196.
Повний текст джерела
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Nishiura, S., T. Murayama, Y. Taniguchi, Y. Sato, and D. B. Sanders. "A K-Band Luminosity Function of Hickson Compact Groups of Galaxies." In Galaxy Interactions at Low and High Redshift, 415. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-4665-4_117.
Повний текст джерела
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Hoyt, Douglas V., and Kenneth H. Shatten. "Gaia or Athena? The Early Faint-Sun Paradox." In The Role of the Sun in Climate Change. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195094138.003.0017.
Повний текст джерелаАнотація:
Stellar evolution theory predicts large, long-term solar large, long-term solar luminosity (L⊙) changes over the lifetime of the sun. The most certain prediction is a general monotonic increase (neglecting short-period variations) in L⊙ of about 30% over the past 4.7 billion years, an increase that will continue. This prediction is well founded theoretically (based on the conversion of hydrogen into heavier elements) and supported observationally by the famous Hertzsprung-Russell diagram showing stellar evolution. If the solar luminosity increases monotonically with time, one might expect to find evidence of increasing surface temperatures in the Earth’s paleoclimatic record. Instead, isotopic indicators show Earth’s mean surface temperature is now significantly lower than it was 3 billion years ago. In 1975, R. K. Ulrich termed this the “faint young sun” paradox. Simultaneous solar luminosity increase and terrestrial temperature decrease imply additional strong influences on climate evolution. To understand climate evolution (and, by inference, the present climate), we must first determine the nature of these “compensatory mechanisms.” The positively increasing line in Figure 12.1 shows the evolution of solar luminosity (in units of present luminosity, L). Since terrestrial surface temperatures have remained nearly constant during the last 2.3 billion years, this requires a very effective compensatory mechanism. Several theories attempt to explain why the Earth’s surface temperature has remained relatively constant even while the solar luminosity has increased by 30%. Also, various scenarios have been advanced to explain why the Earth remained ice-free even during periods when the sun was much dimmer than it is today. Some of these ideas are: • Since it had fewer continents and more oceans, the early Earth was much darker. This same darker surface absorbed enough additional incoming solar radiation to remain ice-free. • In the past, energy transport from the equator to polar regions was easier because the continents had lower elevations. This enhanced heat transport allowed the Earth to remain relatively warm. • The early atmosphere had more carbon dioxide and methane, creating an enhanced greenhouse effect sufficient to trap the incoming solar radiation and keep the Earth warm. The enormous amount of carbon trapped in limestone suggests that Earth’s former atmosphere contained much more carbon dioxide than it does today.
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Rosenkranz, Sven. "Two systems of epistemic logic." In Justification as Ignorance, 80–106. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198865636.003.0005.
Повний текст джерелаАнотація:
Drawing on the results of chapters 2 to 4, two non-normal, multimodal axiomatic systems for both knowledge (k) and being in a position to know (K) are introduced—an idealized system and a weaker, more realistic system. Both share important theorems governing the complex operators ‘¬K¬K’ and ‘¬K¬K’, whose availability will be of crucial importance in later chapters. Unlike the realistic system, the idealized system requires subjects to be logically omniscient and must therefore ultimately be rejected in favour of the realistic system. A semantic characterization of the idealized system is devised that shows it to be sound and allows us to invalidate principles we previously found unacceptable for independent reasons. Since the realistic system is weaker, this result implies that it too has these features. Both systems imply that each of ⌜¬K¬Kφ⌝, ⌜K¬Kφ⌝, and ⌜¬K¬Kφ⌝ encodes a luminous condition. The scenario of the unmarked clock presents a prima facie case against this implication. It is shown that the relevant anti-luminosity argument presupposes the principle that being in a position to know (K) distributes across provable conditionals—a principle that has been shown to be deeply problematic and that the realistic system is designed to flout.
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Hoyt, Douglas V., and Kenneth H. Shatten. "Observations of the Sun." In The Role of the Sun in Climate Change. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195094138.003.0005.
Повний текст джерелаАнотація:
Our sun is a typical “second generation,” or G2, star nearly 4.5 billion years old. The sun is composed of 92.1% hydrogen and 7.8% helium gas, as well as 0.1% of such all-important heavy elements as oxygen, carbon, nitrogen, silicon, magnesium, neon, iron, sulfur, and so forth in decreasing amounts (see Appendix 3). The heavy elements are generated from nucleosynthetic processes in stars, novae, and supernovae after the original formation of the Universe. This has led to the popular statement that we are, literally, the “children of the stars” because our bodies are composed of the elements formed inside stars. From astronomical studies of stellar structure, we know that, since its beginnings, the sun’s luminosity has gradually increased by about 30%. This startling conclusion has raised the so-called faint young sun climate problem: if the sun were even a few percent fainter in the past, then Earth could have been covered by ice. In this frozen state, it might not have warmed because the ice would reflect most of the incoming solar radiation back into space. Although volcanic aerosols covering the ice, early oceans moderating the climate, and other theories have been suggested to circumvent the “faint young sun” problem, how Earth escaped the ice catastrophe remains uncertain. How can the sun generate vast amounts of energy for billions of years and still keep shining? Before nuclear physics, scientists believed the sun generated energy by means of slow gravitational collapse. Still, this process would only let the sun shine about 30 million years before its energy was depleted. To shine longer, the sun requires another energy source. We now believe that a chain of nuclear reactions occurs inside the sun, with four hydrogen nuclei fusing into one helium nucleus at the sun’s center. Because the four hydrogen nuclei have more mass than the one helium nucleus, the resulting mass deficit is converted into energy according to Einstein’s famous formula E = mc2. The energy, produced near the sun’s center, creates a central temperature of about 15 million degrees Kelvin (°K).
Тези доповідей конференцій з теми "K luminosity"
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Gardner, J. P., R. M. Sharples, C. S. Frenk, and B. E. Carrasco. "The K-band luminosity function of galaxies." In The seventh astrophysical conference: Star formation, near and far. AIP, 1997. http://dx.doi.org/10.1063/1.52763.
Повний текст джерела
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Kim, T., and J. B. Ghandhi. "Investigation on the Ignition Conditions From a Comparison Between Reacting and Non-Reacting Diesel Spray Experiments." In ASME 2002 Internal Combustion Engine Division Spring Technical Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/ices2002-456.
Повний текст джерелаАнотація:
Natural luminosity images from reacting diesel sprays were acquired in a combustion-type constant-volume spray chamber. Using an ambient condition of 15 kg/m3 and 1000 K, the effects of peak injection pressures (60, 90 and 150 MPa) and nozzle hole sizes (140, 158 and 200 μm) were investigated. From high-speed natural luminosity cinematography, macroscopic reacting spray characteristics such as flame lift-off height and ignition delay time were obtained. For increasing injection pressures the ignition delay time decreased, and the flame lift off height increased. For increasing hole diameter the ignition time delay decreased, and the flame lift-off height decreased. The authors’ previous results of the fuel concentration measurement from non-reacting spray experiments were used to ascertain the local equivalence ratio for the reacting spray during the ignition and initial flame development period. The first detection of the luminosity (believed to be chemiluminescence) signal was found to occur in fuel-rich vapor regions near the boundary of the liquid core with an equivalence ratio near 2 and a temperature of approximately 800 K. These conditions were found to be independent of injection pressure and nozzle diameter for the condition tested (15 kg/m3 and 1000 K ambient), suggesting that this is a kinetically controlled process.
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Samimi Abianeh, O. "Study of Turbulent Spray Combustion of N-Dodecane Fuel." In ASME 2015 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/icef2015-1018.
Повний текст джерелаАнотація:
Turbulent spray combustion of n-dodecane fuel was studied numerically in current paper. The ignition delay, lift-off length, combustion chamber pressure rise, fuel penetration and vapor mass fraction were compared with experimental data. n-Dodecane kinetic model was studied by using a recently developed mechanism. The combustion chamber pressure rise was modeled and compared with experiments; the result was corrected for speed-of-sound to find the ignition delay timing in comparison with pressure-based ignition delay measurement. Species time histories and reaction paths at low and high temperature combustion are modeled and studied at two conditions, 900 K and 1200 K combustion chamber temperatures. The modeled species mass histories were discussed to define the first-stage and total ignition delay timings. Among all of the studied species in this work, including OH, Hydroperoxyalkyl mass history can be utilized to determine the exact timing of luminosity-based ignition delay. Moreover, n-dodecane vapor penetration can be used to determine the luminosity-based ignition delay.
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Wu, Yifeng, Ronghua Huang, and Chia-fon F. Lee. "Experimental Investigation of Spray and Combustion Characteristics of Soybean Biodiesel in a Constant-Volume Combustion Chamber: The Effects of Fuel and Ambient Gas Temperature." In ASME 2013 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/icef2013-19196.
Повний текст джерелаАнотація:
Effects of fuel and ambient gas temperature on the spray and combustion characteristics of soybean biodiesel were studied in a constant-volume combustion chamber. Four different fuels or fuel blends including B0, B20, B50 and B100 were investigated experimentally. The soot mass data were obtained via a new technique called forward illumination light extinction (FILE). The ambient gas temperature was varied from 700 K to 1200 K. To simulate the engine operating conditions, the ambient oxygen concentration and its density were kept at 21 % and 15 kg/m3, respectively. A higher peak pressure is found as the biodiesel content decreases. B20, B50 and B100 have a shorter ignition delay than B0 and the ignition delay decreases with increasing biodiesel content. The liquid penetration decreases with decreasing biodiesel content. Moreover, the integrated natural flame luminosity (INFL) increases with decreasing biodiesel content. Shorter flame (i.e., soot luminosity) duration and a longer delay between start of combustion (SOC) and the appearance of flame are found as the biodiesel content increases. The flame duration also increases with increasing ambient gas temperature for all fuels. Soot is lower and appears later at a lower ambient gas temperature, while it is burned out at around the same time. Near-zero soot mass was observed for all tested fuels at 700 K. A shorter soot formation process is observed for biodiesel fuels. The soot reduction using B20 and B50 is not obvious compared to B0 at a low temperature. But under the ordinary diesel engine operating condition at 1000 K, the soot reduction is significant. It is also found that the soot can be reduced by 60% and above when B100 is used in this study.
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Mosbach, Thomas, Victor Burger, and Barani Gunasekaran. "Fuel Influence on Targeted Gas Turbine Combustion Properties: Part I — Detailed Diagnostics." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25075.
Повний текст джерелаАнотація:
The threshold combustion performance of different fuel formulations under simulated altitude relight conditions were investigated in the altitude relight test facility located at the Rolls-Royce plc. Strategic Research Centre in Derby, UK. The combustor employed was a twin-sector representation of an RQL gas turbine combustor. Eight fuels including conventional crude-derived Jet A-1 kerosene, synthetic paraffinic kerosenes (SPKs), linear paraffinic solvents, aromatic solvents and pure compounds were tested. The combustor was operated at sub-atmospheric air pressure of 41 kPa and air temperature of 265 K. The temperature of all fuels was regulated to 288 K. The combustor operating conditions corresponded to a low stratospheric flight altitude near 9 kilometres. The experimental work at the Rolls-Royce (RR) test-rig consisted of classical relight envelope ignition and extinction tests, and ancillary optical measurements: Simultaneous high-speed imaging of the OH* chemiluminescence and of the soot luminosity was used to visualize both the transient combustion phenomena and the combustion behaviour of the steady burning flames. Flame luminosity spectra were also simultaneously recorded with a spectrometer to obtain information about the different combustion intermediates and about the thermal soot radiation curve. This paper presents first results from the analysis of the weak extinction measurements. Further detailed test fuel results are the subject of a separate complementary paper [1]. It was found in general that the determined weak extinction parameters were not strongly dependent on the fuels investigated, however at the leading edge of the OH* chemiluminescence intensity development in the pre-flame region fuel-related differences were observed.
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Kopylova, F., and A. Kopylov. "Study of groups/clusters of galaxies with the SDSS." In ASTRONOMY AT THE EPOCH OF MULTIMESSENGER STUDIES. Proceedings of the VAK-2021 conference, Aug 23–28, 2021. Crossref, 2022. http://dx.doi.org/10.51194/vak2021.2022.1.1.148.
Повний текст джерелаАнотація:
For a large sample of groups/clusters of galaxies (N =185), we obtained the scaling relations among of their photometricaland dynamical parameters. We find:0.77±0.011. that in the virialized regions of the galaxy systems the total luminosity increase with mass L K ∝ M 200(M K <−21. m 0);2. that the new halo boundary of the galaxy systems corresponds to the splashback radius R sp . These radius is definedby the observed intergrated distribution of the number of galaxies as a function of the angular distance from thegroup/cluster center squared;3. that the fraction of galaxies with quenched star formation is maximal in the central regions of the galaxy systems,and it decreases to the radius R sp , but remains higher than in the field on ∼ 27%.
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Samimi Abianeh, O., M. Levins, and C. P. Chen. "Pressure-Based Ignition Delay Times of Non-Premixed Turbulent Jet Flames Using Various Turbulence Models." In ASME 2016 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/icef2016-9307.
Повний текст джерелаАнотація:
Pressure-based ignition delay times of turbulent spray combustion of n-dodecane fuel were studied using two turbulence models: Large Eddy Simulations (LES) of turbulence and Reynolds Averaged Navier Stokes (RANS). Standard RNG k-ε and Dynamic Structure models were utilized for RANS and LES turbulence modeling respectively. The simulated combustion chamber pressure rise, lift-off length, liquid penetration, and vapor penetration were compared with experimental data. The combustion chamber initial gas temperatures ranged from 850 K to 1200 K at an initial gas density of 22.8 kg/m3. A recently developed skeletal mechanism of n-dodecane with 85 species was utilized in the current work. The pressure-based ignition delay times using the Dynamic Structure turbulence model were well matched with experimental data, but the simulated pressure-based ignition delay time was over-predicted using RNG k-ε model at initial combustion chamber temperature of 850 K. The flame lift-off length, spray structure and species production and consumption histories were also investigated using different models. Both turbulence models show similar spray lift-off length at time of luminosity-based ignition delay at various combustion chamber temperatures.
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Nguyen, Quang-Viet. "Measurements of Equivalence Ratio Fluctuations in a Lean Premixed Prevaporized (LPP) Combustor and Its Correlation to Combustion Instability." In ASME Turbo Expo 2002: Power for Land, Sea, and Air. ASMEDC, 2002. http://dx.doi.org/10.1115/gt2002-30060.
Повний текст джерелаАнотація:
Experimental evidence correlating equivalence ratio fluctuations with combustion instabilities and NOX emissions in a jet-A fueled lean premixed prevaporized (LPP) combustor utilizing a non-proprietary ‘generic’ fuel injector is presented. Real-time laser absorption measurements of equivalence ratio, together with dynamic combustor pressure, flame luminosity and fuel pressure were obtained at inlet air conditions up to 16.7 atm and 817 K. From this data, an extensive database of real-time variables was obtained for the purposes of providing validation data for future studies of LPP combustion modeling. In addition, time and frequency space analysis of the data revealed measurable levels of acoustic coupling between all variables. Equivalence ratio and dynamic pressure cross-correlations were found to predict the level of combustion instability. Furthermore, NOX production was found to follow the root-mean-square (RMS) flame luminosity and RMS combustor dynamic pressure. However, the unmixedness of the fuel-air mixture was not found to predict NOX production in this combustor. The generic LPP injector, although not optimized for low-emissions or combustion stability, provides some of the essential features of real injectors for the purposes of studying the relationship between fluctuations in equivalence ratios and combustion instability. In particular, the fuel premixer advection time was found to have a significant and direct impact on the level of combustion instability. The results of this work support the time-lag concept for avoiding combustion instability when designing injector/premixers in LPP combustors.
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Mosbach, T., R. Sadanandan, W. Meier, and R. Eggels. "Experimental Analysis of Altitude Relight Under Realistic Conditions Using Laser and High-Speed Video Techniques." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-22625.
Повний текст джерелаАнотація:
The altitude relight performance of a lean fuel injector and combustor was investigated at the altitude relight test rig at the Rolls-Royce Strategic Research Centre (SRC) in Derby. The studies were performed for different mass flow rates of air and kerosene, a combustor temperature and pressure of 278 K and 0.5 bar, respectively. Good optical access to the combustion chamber enabled the application of optical and laser measuring techniques. High-speed video imaging in the UV and visible wavelength range at a frame rate of 3.5 kHz was used to visualize the temporal development of the flame kernel. The observed differences between the UV and visible flame emissions demonstrate the different origins of the luminosity, i.e. OH* chemiluminescence and soot radiation. Further, laser-induced fluorescence of kerosene and OH radicals was applied at a frame rate of 5 Hz to visualize the fuel distribution and regions of hot and reacting mixtures. For two exemplary flames with different mass flow rates and fuel-to-air ratios, the steady burning flames after successful ignition are characterized in this paper by the distributions of kerosene, OH*, OH and soot luminosity. An example of the flame kernel development for a successful ignition is given by an image sequence from a high-speed video recording of the chemiluminescence. The importance of the upstream movement of the flame kernel as a condition preceding successful flame stabilization is identified.
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Shafiei, Somayeh B., and Khurshid A. Guru. "Use of Numerical-Clustering Framework for End-Effector Tracking During Robot-Assisted Surgery." In ASME 2017 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/detc2017-67616.
Повний текст джерелаАнотація:
Imaging plays an important role in all clinical processes. One challenge in medical image data processing is detection and tracking objects and instruments, which faces complications arising from the developed medical image acquisition systems and also the nature of in-vivo medical images. Special properties of the in-vivo bio images such as noise, specular highlights, inhomogeneity, heterogeneity, varying luminosity, and background change, in addition to the changes of camera, out of camera view tools, and multiple moving tools (instrument tools, surgical suture, cutting instrument, tissue movement) make object detection and tracking in the biomedical image processing complicated. In this study, the k-means clustering method in combination with the level set active curve model are used to develop a platform for low-cost tracking of surgical tools in robotic surgery videos. After removing the image background, the smoothed image is used as input to the numerical method. This model tracks the robot tools even when the camera view changes, the tool is lost, the tissue is bleeding and moving, and the luminosity of the images changes. The developed model is validated using video frames of real and simulated robotic surgeries. The accuracy of model in tracking da vinci robot end-effectors for a video with 12000 frames, recorded at Roswell Park Cancer Institute, is 93%. Accuracy of proposed framework is compared to those for existing numerical models, DRLSE and Chan-Vese. The results show that proposed surgical robot tool tracking model is more efficient than existing computational models.