Log in

Relevant bibliographies by topics / Correlations / Journal articles

To see the other types of publications on this topic, follow the link: Correlations.

Journal articles on the topic 'Correlations'

Author: Grafiati

Published: 4 June 2021

Last updated: 7 July 2024

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Consult the top 50 journal articles for your research on the topic 'Correlations.'

Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.

You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.

Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.

1

Prevost, A. Toby, Dan Mason, Simon Griffin, Ann-Louise Kinmonth, Stephen Sutton, and David Spiegelhalter. "Allowing for correlations between correlations in random-effects meta-analysis of correlation matrices." Psychological Methods 12, no. 4 (December 2007): 434–50. http://dx.doi.org/10.1037/1082-989x.12.4.434.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Szapudi, I., A. S. Szalay, and P. Boschan. "Cluster correlations from N-point correlation amplitudes." Astrophysical Journal 390 (May 1992): 350. http://dx.doi.org/10.1086/171286.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Anand, Vijayakumar, Tomas Katkus, Soon Hock Ng, and Saulius Juodkazis. "Review of Fresnel incoherent correlation holography with linear and non-linear correlations [Invited]." Chinese Optics Letters 19, no. 2 (2021): 020501. http://dx.doi.org/10.3788/col202119.020501.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Auletta, Gennaro. "Correlations and Hyper-Correlations." Journal of Modern Physics 02, no. 09 (2011): 958–61. http://dx.doi.org/10.4236/jmp.2011.29114.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Hu, Zheng-Da, Jicheng Wang, Yixin Zhang, and Ye-Qi Zhang. "Dynamics of Nonclassical Correlations with an Initial Correlation." Journal of the Physical Society of Japan 83, no. 11 (November 15, 2014): 114004. http://dx.doi.org/10.7566/jpsj.83.114004.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Walther, Andreas, and Christof Faller. "Interaural correlation discrimination from diffuse field reference correlations." Journal of the Acoustical Society of America 133, no. 3 (March 2013): 1496–502. http://dx.doi.org/10.1121/1.4790473.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Joe, Harry. "Generating random correlation matrices based on partial correlations." Journal of Multivariate Analysis 97, no. 10 (November 2006): 2177–89. http://dx.doi.org/10.1016/j.jmva.2005.05.010.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Cope, Leslie, Daniel Q. Naiman, and Giovanni Parmigiani. "Integrative correlation: Properties and relation to canonical correlations." Journal of Multivariate Analysis 123 (January 2014): 270–80. http://dx.doi.org/10.1016/j.jmva.2013.09.011.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Neff, T., and H. Feldmeier. "Tensor correlations in the unitary correlation operator method." Nuclear Physics A 713, no. 3-4 (January 2003): 311–71. http://dx.doi.org/10.1016/s0375-9474(02)01307-6.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Kermarrec, Gaël, and Steffen Schön. "Taking correlations into account: a diagonal correlation model." GPS Solutions 21, no. 4 (September 6, 2017): 1895–906. http://dx.doi.org/10.1007/s10291-017-0665-y.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Andreev, I. "Correlation length versus radius in Bose-Einstein correlations." Nuclear Physics A 525 (April 1991): 527–30. http://dx.doi.org/10.1016/0375-9474(91)90377-i.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Lipa, P., P. Carruthers, H. C. Eggers, and B. Buschbeck. "The correlation integral as probe of multiparticle correlations." Physics Letters B 285, no. 3 (July 1992): 300–308. http://dx.doi.org/10.1016/0370-2693(92)91468-o.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Ehling, Paul, and Christian Heyerdahl-Larsen. "Correlations." Management Science 63, no. 6 (June 2017): 1919–37. http://dx.doi.org/10.1287/mnsc.2015.2413.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Guo, Zhihua, Huaixin Cao, and Zhengli Chen. "Distinguishing classical correlations from quantum correlations." Journal of Physics A: Mathematical and Theoretical 45, no. 14 (March 23, 2012): 145301. http://dx.doi.org/10.1088/1751-8113/45/14/145301.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Khrennikov, Andrei. "Quantum correlations from classical Gaussian correlations." Journal of Russian Laser Research 30, no. 5 (September 2009): 472–79. http://dx.doi.org/10.1007/s10946-009-9095-9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Eliazar, Iddo. "From micro-correlations to macro-correlations." Annals of Physics 374 (November 2016): 138–61. http://dx.doi.org/10.1016/j.aop.2016.07.027.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Hamilton, A. J. S., and J. R. ,. III Gott. "Cluster-cluster correlations and constraints on the correlation hierarchy." Astrophysical Journal 331 (August 1988): 641. http://dx.doi.org/10.1086/166587.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Arias de Saavedra, F., and E. Buendía. "σz-dependent correlations with other correlation mechanisms in liquidHe3." Physical Review B 46, no. 21 (December 1, 1992): 13934–41. http://dx.doi.org/10.1103/physrevb.46.13934.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Høstmark, Arne Torbjørn. "DISTRIBUTION DEPENDENT CORRELATIONS: A MATHEMATICAL PRINCIPLE UTILIZED IN PHYSIOLOGY, OR CORRELATION BIAS?" International Journal of Research -GRANTHAALAYAH 8, no. 11 (November 27, 2020): 63–75. http://dx.doi.org/10.29121/granthaalayah.v8.i11.2020.1470.

Full text

Abstract:

In many studies, we may raise the question of whether relative amounts of particular variables are positively or negatively associated, but investigations specifically focusing upon this issue seem hard to find. Previously, we reported some general rules for associations between relative amounts of positive scale variables. The main research question of the present work was: How are correlations between percentages of the same sum brought about? One particular feature of such correlations seemed to be that distributions (ranges) of the variables were crucial for obtaining either positive or negative correlations, and for their strength, suggesting the name Distribution Dependent Correlations (DDC). Certainly, such correlations might cause bias. However, previous findings raise the question of whether DDC might have a physiological relevance as well. In the current work, we extend and systematize theoretical considerations, and show results of computer experiments to test the hypotheses. Finally, we briefly mention a couple of examples from physiology. The results seem to support the idea that true, within-person distributions of the variables are crucial for obtaining positive or negative correlations between their relative amounts, raising the question of whether evolution might utilize DDC to regulate metabolism.

APA, Harvard, Vancouver, ISO, and other styles

20

Keating, J. P., and D. J. Smith. "Twin prime correlations from the pair correlation of Riemann zeros." Journal of Physics A: Mathematical and Theoretical 52, no. 36 (August 13, 2019): 365201. http://dx.doi.org/10.1088/1751-8121/ab3521.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Ariunbold, Gombojav O., Yuri V. Rostovtsev, Vladimir A. Sautenkov, and Marlan O. Scully. "Intensity correlation and anti-correlations in coherently driven atomic vapor." Journal of Modern Optics 57, no. 14-15 (April 15, 2010): 1417–27. http://dx.doi.org/10.1080/09500341003777905.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

Iskhakov, R. S., V. A. Ignatchenko, S. V. Komogortsev, and A. D. Balaev. "Study of magnetic correlations in nanostructured ferromagnets by correlation magnetometry." Journal of Experimental and Theoretical Physics Letters 78, no. 10 (November 2003): 646–50. http://dx.doi.org/10.1134/1.1644310.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Fataftah, Hiba, and Wael Karain. "Detecting protein atom correlations using correlation of probability of recurrence." Proteins: Structure, Function, and Bioinformatics 82, no. 9 (April 18, 2014): 2180–89. http://dx.doi.org/10.1002/prot.24574.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Ryu, J., Y. i. Jo, and S. H. Lee. "Correlation between Signal Correlations and Noise Correlations among Local Cortical Populations Reveals the Functional Architecture of Early Visual Cortex." Journal of Vision 12, no. 9 (August 10, 2012): 1306. http://dx.doi.org/10.1167/12.9.1306.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Nuzum, C. Thomas. "Morphological Correlations." Science 229, no. 4712 (August 2, 1985): 428. http://dx.doi.org/10.1126/science.229.4712.428.b.

Full text

APA, Harvard, Vancouver, ISO, and other styles

26

Nicolae, Moroianu, and Moroianu Daniela. "Inflations Correlations." Annales Universitatis Apulensis Series Oeconomica 3, no. 8 (July 31, 2006): 109–12. http://dx.doi.org/10.29302/oeconomica.2006.8.3.19.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Latham, Peter E. "Correlations demystified." Nature Neuroscience 20, no. 1 (December 27, 2016): 6–8. http://dx.doi.org/10.1038/nn.4455.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Li, Wentian, and Kunihiko Kaneko. "DNA correlations." Nature 360, no. 6405 (December 1992): 635–36. http://dx.doi.org/10.1038/360635b0.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

Munson, Peter J., Ronald C. Taylor, and George S. Michaels. "DNA correlations." Nature 360, no. 6405 (December 1992): 636. http://dx.doi.org/10.1038/360636a0.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Olkin, Ingram, and Jeremy D. Finn. "Correlations redux." Psychological Bulletin 118, no. 1 (July 1995): 155–64. http://dx.doi.org/10.1037/0033-2909.118.1.155.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Wesson, John. "Tricky correlations." Physics World 29, no. 5 (May 2016): 22. http://dx.doi.org/10.1088/2058-7058/29/5/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Aspden, H. "Constant correlations." American Journal of Physics 54, no. 11 (November 1986): 967. http://dx.doi.org/10.1119/1.14829.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Zahn, Rainer. "Core correlations." Nature 371, no. 6495 (September 1994): 289–90. http://dx.doi.org/10.1038/371289a0.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Balucani, Umberto, M. Howard Lee, and Valerio Tognetti. "Dynamical correlations." Physics Reports 373, no. 6 (January 2003): 409–92. http://dx.doi.org/10.1016/s0370-1573(02)00430-1.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

NUZUM, C. T. "Morphological Correlations." Science 229, no. 4712 (August 2, 1985): 428. http://dx.doi.org/10.1126/science.229.4712.428-a.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Baba, Kunihiro, and Ritei Shibata. "Multiplicative Correlations." Annals of the Institute of Statistical Mathematics 58, no. 2 (March 15, 2006): 311–26. http://dx.doi.org/10.1007/s10463-006-0036-x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

37

Luo, Shun-Long, and Nan Li. "Quantum Correlations Reduce Classical Correlations with Ancillary Systems." Chinese Physics Letters 27, no. 12 (December 2010): 120304. http://dx.doi.org/10.1088/0256-307x/27/12/120304.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

Wang, Min, Fang Chen, Tao Lu, and Jianping Dong. "Bayesian t-tests for correlations and partial correlations." Journal of Applied Statistics 47, no. 10 (November 21, 2019): 1820–32. http://dx.doi.org/10.1080/02664763.2019.1695760.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Copi, Craig J., James Gurian, Arthur Kosowsky, Glenn D. Starkman, and Hezi Zhang. "Exploring suppressed long-distance correlations as the cause of suppressed large-angle correlations." Monthly Notices of the Royal Astronomical Society 490, no. 4 (October 24, 2019): 5174–81. http://dx.doi.org/10.1093/mnras/stz2962.

Full text

Abstract:

ABSTRACT The absence of large-angle correlations in the map of cosmic microwave background temperature fluctuations is among the well-established anomalies identified in full-sky and cut-sky maps over the past three decades. Suppressed large-angle correlations are rare statistical flukes in standard inflationary cosmological models. One natural explanation could be that the underlying primordial density perturbations lack correlations on large distance scales. To test this idea, we replace Fourier modes by a wavelet basis with compact spatial support. While the angular correlation function of perturbations can readily be suppressed, the observed monopole- and dipole-subtracted correlation function is not generally suppressed. This suggests that suppression of large-angle temperature correlations requires a mechanism that has both real-space and harmonic-space effects.

APA, Harvard, Vancouver, ISO, and other styles

40

Rosnow, Ralph L., Robert Rosenthal, and Donald B. Rubin. "Contrasts and Correlations in Effect-Size Estimation." Psychological Science 11, no. 6 (November 2000): 446–53. http://dx.doi.org/10.1111/1467-9280.00287.

Full text

Abstract:

This article describes procedures for presenting standardized measures of effect size when contrasts are used to ask focused questions of data. The simplest contrasts consist of comparisons of two samples (e.g., based on the independent t statistic). Useful effect-size indices in this situation are members of the g family (e.g., Hedges's g and Cohen's d) and the Pearson r. We review expressions for calculating these measures and for transforming them back and forth, and describe how to adjust formulas for obtaining g or d from t, or r from g, when the sample sizes are unequal. The real-life implications of d or g calculated from t become problematic when there are more than two groups, but the correlational approach is adaptable and interpretable, although more complex than in the case of two groups. We describe a family of four conceptually related correlation indices: the alerting correlation, the contrast correlation, the effect-size correlation, and the BESD (binomial effect-size display) correlation. These last three correlations are identical in the simple setting of only two groups, but differ when there are more than two groups.

APA, Harvard, Vancouver, ISO, and other styles

41

Visscher, Peter M. "On the Sampling Variance of Intraclass Correlations and Genetic Correlations." Genetics 149, no. 3 (July 1, 1998): 1605–14. http://dx.doi.org/10.1093/genetics/149.3.1605.

Full text

Abstract:

Abstract Widely used standard expressions for the sampling variance of intraclass correlations and genetic correlation coefficients were reviewed for small and large sample sizes. For the sampling variance of the intraclass correlation, it was shown by simulation that the commonly used expression, derived using a first-order Taylor series performs better than alternative expressions found in the literature, when the between-sire degrees of freedom were small. The expressions for the sampling variance of the genetic correlation are significantly biased for small sample sizes, in particular when the population values, or their estimates, are close to zero. It was shown, both analytically and by simulation, that this is because the estimate of the sampling variance becomes very large in these cases due to very small values of the denominator of the expressions. It was concluded, therefore, that for small samples, estimates of the heritabilities and genetic correlations should not be used in the expressions for the sampling variance of the genetic correlation. It was shown analytically that in cases where the population values of the heritabilities are known, using the estimated heritabilities rather than their true values to estimate the genetic correlation results in a lower sampling variance for the genetic correlation. Therefore, for large samples, estimates of heritabilities, and not their true values, should be used.

APA, Harvard, Vancouver, ISO, and other styles

42

He, Yan, Chao Tang, and Dongsheng Chen. "Evaluation of heat transfer correlations for two-phase flow boiling in twisted tapes inserted tubes." Journal of Physics: Conference Series 2758, no. 1 (April 1, 2024): 012016. http://dx.doi.org/10.1088/1742-6596/2758/1/012016.

Full text

Abstract:

Abstract Many experimental researches were conducted in the twisted tapes inserted tubes, and many correlations were proposed and evaluated. However, most of the evaluations were based on specific experimental data, and the number of correlations evaluated was limited in each paper. This paper conducted a review of correlations and experimental investigations of the two-phase flow boiling heat transfer coefficient for twisted tapes inserted tubes, the key forms of the 5 correlations were reviewed, and the prediction accuracy of the 5 correlations was evaluated against the 508 published experimental data. This paper proposed a new correlation which has a MAD of 17.2%, 10.2% lower than the best existing correlation.

APA, Harvard, Vancouver, ISO, and other styles

43

Joe, George W., and Jorge L. Mendoza. "The Internal Correlation: Its Applications in Statistics and Psychometrics." Journal of Educational Statistics 14, no. 3 (September 1989): 211–26. http://dx.doi.org/10.3102/10769986014003211.

Full text

Abstract:

The internal correlation, a measure of dependency in a set of variables, is discussed and generalized. This coefficient is an upper bound to the product moment correlations, multiple correlations, and canonical correlations that can be defined in a set of variables. Applications of the internal correlation coefficient and its generalizations are given for a number of data-analytic situations. Where appropriate, we discuss tests of significance. We illustrate the internal correlation and expand the concept to a series of additional indices: local internal, up-internal, and down-internal correlations. Uses of these indices are illustrated in several areas: multicollinearity, ridge regression, factor analysis, principal components analysis, and test reliability.

APA, Harvard, Vancouver, ISO, and other styles

44

Liang, Ke, Sihang Zhou, Meng Liu, Yue Liu, Wenxuan Tu, Yi Zhang, Liming Fang, Zhe Liu, and Xinwang Liu. "Hawkes-Enhanced Spatial-Temporal Hypergraph Contrastive Learning Based on Criminal Correlations." Proceedings of the AAAI Conference on Artificial Intelligence 38, no. 8 (March 24, 2024): 8733–41. http://dx.doi.org/10.1609/aaai.v38i8.28719.

Full text

Abstract:

Crime prediction is a crucial yet challenging task within urban computing, which benefits public safety and resource optimization. Over the years, various models have been proposed, and spatial-temporal hypergraph learning models have recently shown outstanding performances. However, three correlations underlying crime are ignored, thus hindering the performance of previous models. Specifically, there are two spatial correlations and one temporal correlation, i.e., (1) co-occurrence of different types of crimes (type spatial correlation), (2) the closer to the crime center, the more dangerous it is around the neighborhood area (neighbor spatial correlation), and (3) the closer between two timestamps, the more relevant events are (hawkes temporal correlation). To this end, we propose Hawkes-enhanced Spatial-Temporal Hypergraph Contrastive Learning framework (HCL), which mines the aforementioned correlations via two specific strategies. Concretely, contrastive learning strategies are designed for two spatial correlations, and hawkes process modeling is adopted for temporal correlations. Extensive experiments demonstrate the promising capacities of HCL from four aspects, i.e., superiority, transferability, effectiveness, and sensitivity.

APA, Harvard, Vancouver, ISO, and other styles

45

Nyberg, Nils T., Jens Ø. Duus, and Ole W. Sørensen. "Heteronuclear Two-Bond Correlation: Suppressing Heteronuclear Three-Bond or Higher NMR Correlations while Enhancing Two-Bond Correlations Even for Vanishing2JCH." Journal of the American Chemical Society 127, no. 17 (May 2005): 6154–55. http://dx.doi.org/10.1021/ja050878w.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Shah, Mirza M. "Further Study and Development of Correlations for Heat Transfer during Subcooled Boiling in Plain Channels." Fluids 8, no. 9 (August 31, 2023): 245. http://dx.doi.org/10.3390/fluids8090245.

Full text

Abstract:

The author’s published correlations for subcooled boiling in channels are further studied and developed in this work. The areas explored include choice of equivalent diameters for annuli and partially heated channels, effects of flow direction, micro-gravity, and orientation of heated surface. A new correlation is developed, which is a modification of the author’s earlier correlation. The author’s previous correlations and the new correlation are compared with a very wide range of test data for round tubes, rectangular channels, and annuli. Several other correlations are also compared with the same data. The authors’ correlations provide good agreement with data, the new correlation giving the least deviation. The data included hydraulic diameters from 0.176 to 22.8 mm, reduced pressure from 0.0046 to 0.922, subcooling from 0 to 165 K, mass flux from 59 to 31,500 kgm−2s−1, all flow directions, and terrestial to micro gravity. The new correlation has mean absolute deviation (MAD) of 13.3% with 2270 data points from 49 sources. Correlations by others had MAD of 18% to 116%. The results are presented and discussed.

APA, Harvard, Vancouver, ISO, and other styles

47

Elghannay, Husam A., and Yousef M. F. El Hasadi. "DEVELOPMENT OF DRAG COEFFICIENT CORRELATIONS FOR CIRCULAR CYLINDER USING SYMBOLIC REGRESSION." Al-Mukhtar Journal of Engineering Research 7, no. 1 (May 10, 2024): 20–28. http://dx.doi.org/10.54172/wadd2q70.

Full text

Abstract:

The current paper provides a symbolic regression-based correlation for the drag coefficient for circular cylinder. The correlation is intended to be applicable over a wide range of flow regimes namely that range from the creeping flow regime up to the turbulent flow regime. Demo version of TuringBot symbolic regression software was used to develop different correlations using different sets of data. Experimental set of data was used in one run whereas steady numerical results for Reynolds number up to ~ 25 were used in generating a second set of formulas. In a different run data generated using Sucker and Brauwer (Wärme-und Stoffübertragung, 1975. 8: p. 149-158) correlation with uniform distribution in each order of magnitude was used to obtain a different set of correlations. The data was generated across five orders of magnitude of change of Re. Among all suggested formulas in the three cases, four correlations are considered for their simplicity and accuracy. The predictions of the correlations ranged from reasonably good to very good as compared to existing data and correlations. The relative error of the four developed correlations ranged between 9% and 16% when compared to experimental data for Reynolds numbers ranging from 1-105. In particular, one correlations was able to capture all the qualitative and quantitative changes in the drag coefficient over the different flow regimes for 0.15 < Re < 105. The relative error of this correlation was comparable to Sucker and Brauwer correlation.

APA, Harvard, Vancouver, ISO, and other styles

48

von Frese, Ralph R. B., Michael B. Jones, Jeong Woo Kim, and Jeong‐Hee Kim. "Analysis of anomaly correlations." GEOPHYSICS 62, no. 1 (January 1997): 342–51. http://dx.doi.org/10.1190/1.1444136.

Full text

Abstract:

Recognizing correlations between data sets is the basis for rationalizing geophysical interpretation and theory. Procedures are presented that constitute an effective process for identifying correlative features between two or more digital data sets. The procedures include the development of normalization factors from the mean and variance properties of the data sets. Using these factors, the data sets may be transformed so that they have common amplitude ranges, means, and variances, thereby allowing a common graphical representation of the data sets that facilitates the visualization of feature correlations. Anomaly features that show direct, inverse, or no correlations between data sets may be separated by the application of correlation filters in the frequency domains of the data sets. The correlation filter passes or rejects wavenumbers between coregistered data sets based on the correlation coefficient between common wavenumbers as given by the cosine of their phase difference. Standardizing and summing the filtered outputs where directly correlative features have been enhanced yields local favorability indices that optimize the perception of these features. Differencing the standardized outputs where inversely correlative features have been enhanced, on the other hand, provides favorability indices that improve the perception of the inverse correlations. This study includes a generic example, as well as magnetic and gravity anomaly profile examples that illustrate the usefulness of these procedures for extracting correlative features between digital data sets.

APA, Harvard, Vancouver, ISO, and other styles

49

Singh, Narendra, and Thomas E. Schwartzentruber. "Aerothermodynamic correlations for high-speed flow." Journal of Fluid Mechanics 821 (May 25, 2017): 421–39. http://dx.doi.org/10.1017/jfm.2017.195.

Full text

Abstract:

Heat flux and drag correlations are developed for high-speed flow over spherical geometries that are accurate for any Knudsen number ranging from continuum to free-molecular conditions. A stagnation point heat flux correlation is derived as a correction to the continuum (Fourier model) heat flux and also reproduces the correct heat flux in the free-molecular limit by use of a bridging function. In this manner, the correlation can be combined with existing continuum correlations based on computational fluid dynamics simulations, yet it can now be used accurately in the transitional and free-molecular regimes. The functional form of the stagnation point heat flux correlation is physics based, and was derived via the Burnett and super-Burnett equations in a recent article, Singh & Schwartzentruber (J. Fluid Mech., vol. 792, 2016, pp. 981–996). In addition, correlation parameters from the literature are used to construct simple expressions for the local heat flux around the sphere as well as the integrated drag coefficient. A large number of direct simulation Monte Carlo calculations are performed over a wide range of conditions. The computed heat flux and drag data are used to validate the correlations and also to fit the correlation parameters. Compared to existing continuum-based correlations, the new correlations will enable engineering analysis of flight conditions at higher altitudes and/or smaller geometry radii, useful for a variety of applications including blunt body planetary entry, sharp leading edges, low orbiting satellites, meteorites and space debris.

APA, Harvard, Vancouver, ISO, and other styles

50

Al-Shammasi, A. A. "A Review of Bubblepoint Pressure and Oil Formation Volume Factor Correlations." SPE Reservoir Evaluation & Engineering 4, no. 02 (April 1, 2001): 146–60. http://dx.doi.org/10.2118/71302-pa.

Full text

Abstract:

Summary This paper evaluates published correlations and neural-network models for bubblepoint pressure (pb) and oil formation volume factor (Bo) for their accuracy and flexibility in representing hydrocarbon mixtures from different locations worldwide. The study presents a new, improved correlation for pb based on global data. It also presents new neural-network models and compares their performances to numerical correlations. The evaluation examines the performance of correlations with their original published coefficients and with new coefficients calculated based on global data, data from specific geographical locations, and data for a limited oil-gravity range. The evaluation of each coefficient class includes geographical and oil-gravity grouping analysis. The results show that the classification of correlation models as most accurate for a specific geographical area is not valid for use with these two fluid properties. Statistical and trend performance analysis shows that some published correlations violate the physical behavior of hydrocarbon fluid properties. Published neural-network models need more details to be reproduced. New developed models perform better but suffer from stability and trend problems. Introduction Solutions to reservoir performance problems at various stages of reservoir life require knowledge of the physical properties of reservoir fluids at elevated pressures and temperatures. The pressure/volume/temperature (PVT) properties for reservoir hydrocarbon mixtures are usually obtained from laboratory analysis of preserved or recombined reservoir fluid samples. Because experimental facilities are not always available, other means for estimating PVT properties have been developed; during the last 50 years, many correlations have been developed for this purpose. PVT properties are a function of temperature, pressure, composition of the hydrocarbon mixture, and the presence of paraffins and impurities. The performance of an empirical model depends mainly on how accurately a correlation model represents this mixture under specific conditions. The purpose of this paper is to study the performance of models available in the literature, based on published experimental data. The study was carried out to model the pb and the Bo at and below the pb. Both empirical correlations and neural-network models were considered to reach a clearer understanding about what model to use and what to expect. A large global database gathered for this study was used to develop correlation models that predict oil properties better than existing models. Literature Review Since the 1940's, engineers in the United States have realized the importance of developing empirical correlations for PVT properties. Studies carried out in this field resulted in the development of new correlations. Several studies of this kind were published by Katz,1 Standing,2 Lasater,3 and Cronquist.4 For several years, these correlations were the only source available for estimating PVT properties when experimental data were unavailable. In the last 20 years there has been an increasing interest in developing new correlations for crude oils obtained from various regions in the world. Vazquez and Beggs,5 Glaso,6 Al-Marhoun,7,8 and Abdul-Majeed and Salman9 carried out some of the recent studies. The following presents a review of the best-known correlation models published in the literature. A summary of these published correlation models is provided in the Appendix (Tables 1 and 2), including the forms of correlation used, errors reported by each author, and details of the data used for each development. Empirical Correlations. In 1942, Katz1 published a graphical correlation for predicting Bo. Katz1 used U.S. midcontinent crude to develop his correlations. The graphical correlation uses reservoir temperature, pressure, solution gas/oil ratio (GOR), oil gravity, and gas gravity. The correlations were presented only in graphical form and were hard to use because they required the use of graphs and calculations in combination. In 1947, Standing2,10,11 published his correlations for pb and for Bo. The correlations were based on laboratory experiments carried out on 105 samples from 22 different crude oils in California, U.S.A. The correlations treated the pb and the Bo as a function of the reservoir temperature, GOR, oil gravity, and gas gravity. Standing's2,10,11 correlations were the first to use these four parameters, which now are commonly used to develop correlations. In fact, these correlations are the most widely used in the oil industry. Lasater3 in 1958 presented a new correlation model based on 158 samples from 137 reservoirs in Canada, the U.S., and South America. His correlation was only for pb. It is based on standard physical chemical equations of solutions. It uses Henry's law constant and the observation that the bubblepoint ratio at different temperatures is equal to the absolute temperatures ratio for hydrocarbon systems not close to the critical point. The correlation was presented in graphical form and was used as a lookup chart. An advantage of Lasater's3 correlation is the wide variety of data sources used to develop the correlation. In 1972, Cronquist4 presented a ratio correlation based on 80 data points from 30 Gulf Coast reservoirs. The correlation is useful for the analysis of depletion-drive reservoirs when PVT analysis is not available. The method was presented in graphical form and requires an estimation of average reservoir properties. In 1976, Vazquez and Beggs5 published correlations for GOR and Bo. They started categorizing oil mixtures into two categories, above 30°API gravity and below 30°API gravity. They also pointed out the strong dependence on gas gravity and developed a correlation to normalize the gas-gravity measurement to a reference separation pressure of 100 psi. This eliminated its dependence on separation conditions. More than 6,000 data points from 600 laboratory measurements were used in developing the correlations. Glaso6 in 1978 developed correlations for pb, formation volume factor, GOR, and oil viscosity for North Sea hydrocarbon mixtures. The main feature of Glaso's6 correlations is that they account for paraffinicity by correcting the flash stock-tank-oil gravity to an equivalent corrected value with reservoir temperature and oil viscosity. They also account for the presence of nonhydrocarbons on saturation pressure by using correction factors for the presence of CO2, N2, and H2S in the total surface gases. A total of 45 oil samples, most of which came from the North Sea region, were used in the development of these correlations. In 1988, Al-Marhoun8 published new correlations for estimating pb and Bo for Middle East oils. A total of 160 data sets from 69 Middle Eastern reservoirs were available for the correlation development. Al-Marhoun's7,8 correlations were the first to be developed for Middle East reservoirs.

APA, Harvard, Vancouver, ISO, and other styles

We offer discounts on all premium plans for authors whose works are included in thematic literature selections. Contact us to get a unique promo code!