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Journal articles on the topic 'Directional dependence'

Author: Grafiati

Published: 25 May 2024

Last updated: 22 June 2025

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1

Noh, Hohsuk, Hyuna Jang, Kun Ho Kim, and Jong-Min Kim. "Nonparametric Directional Dependence Estimation and Its Application to Cryptocurrency." Axioms 12, no. 3 (2023): 293. http://dx.doi.org/10.3390/axioms12030293.

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This paper proposes a nonparametric directional dependence by using the local polynomial regression technique. With data generated from a bivariate copula having a nonmonotone regression structure, we show that our nonparametric directional dependence is superior to the copula directional dependence method in terms of the root-mean-square error. To validate the directional dependence with real data, we use the log returns of daily prices of Bitcoin, Ethereum, Ripple, and Stellar. We conclude that our nonparametric directional dependence, by using the local polynomial regression technique with asymmetric-threshold GARCH models for marginal distributions, detects the directional dependence better than the copula directional dependence method by an asymmetric GARCH model.

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2

von Eye, Alexander, and Richard P. DeShon. "Decisions concerning directional dependence." International Journal of Behavioral Development 36, no. 4 (2012): 323–26. http://dx.doi.org/10.1177/0165025412450111.

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3

Aslanov, T. G., and S. A. Ibragimov. "STUDY OF THE TOPOLOGY OF THE VIVALDI ANTENNA WITH A MIRROR ARRANGEMENT OF THE PETALS." Herald of Dagestan State Technical University. Technical Sciences 45, no. 3 (2019): 76–84. http://dx.doi.org/10.21822/2073-6185-2018-45-3-76-84.

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Objectives. In work questions of a research of topology of the antenna of Vivaldi with a mirror arrangement of petals are considered.Method. By modeling in the program CST MicroWave Studio environment collecting necessary data, in particular dependence of width of the directional pattern on curvature and a distance from the middle of the top part of the antenna to the petal antenna petals is carried out.Result. Graphic dependences of curvature of petals and size of a distance from the middle of the top part of the antenna to the petal on directional pattern width in two planes for various frequencies are constructed. Approximation of the received dependences for two planes θ = 900 (the antenna plane) and φ = 00 is carried out (the plane perpendicular the antenna planes). The equations of the approximating curves for various frequencies are received. The analysis of change of curve dependences of curvature of petals and width of a distance from the middle of the top part of the antenna to the petal from directional pattern width upon transition from one frequency is carried out to another. The dependence of the standing wave ratio (VSWR) of the antenna on teflon thickness is investigated. The dependence of a strip of working frequencies on the sizes of the antenna is investigated.Conclusion. Dependences of topology of the antenna on directional pattern width on the range of frequencies of the antenna are revealed. Problems of construction and optimization of model of the set characteristics are solved. The mathematical model allowing depending on the set frequency and width of the directional pattern is received to receive necessary topology of petals of the antenna.

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4

Thoemmes, Felix. "Empirical evaluation of directional-dependence tests." International Journal of Behavioral Development 39, no. 6 (2015): 560–69. http://dx.doi.org/10.1177/0165025415582055.

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Testing of directional dependence is a method to infer causal direction that recently has attracted some attention. Previous examples by e.g. von Eye and DeShon (2012a) and extensive simulation studies by Pornprasertmanit and Little (2012) have demonstrated that under specific assumptions, directional-dependence tests can recover the true causal direction between two variables. Simulation results are important in the evaluation of any statistical method, but they are necessarily less complex than real data that come with potential irregularities (e.g. departures from linearity, presence of confounders, etc.). In this article, we evaluate the performance of directional-dependence tests using benchmark data consisting of 65 variable pairs with known causal order. We find that between 21% and 43% of all cases are correctly classified using different directional-dependence tests that rely on differences in skew, kurtosis, or a combined measure. We then examine some of the assumptions of the directional-dependence test and find that for virtually all variable pairs, some assumptions are violated. When only pairs in which assumptions are fulfilled are selected, performance of all directional-dependence tests improves. We probe whether particular features of the variable pairs impact whether a test yields a correct or incorrect result, but find no strong predictors. Our findings provide a complimentary picture to previously conducted simulation studies, and highlight the fact that directional-dependence tests are prone to causal classification errors when key assumptions are violated. Such violations are potentially common in real data.

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5

von Eye, Alexander, and Richard P. DeShon. "Directional dependence in developmental research." International Journal of Behavioral Development 36, no. 4 (2012): 303–12. http://dx.doi.org/10.1177/0165025412439968.

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In this article, we discuss and propose methods that may be of use to determine direction of dependence in non-normally distributed variables. First, it is shown that standard regression analysis is unable to distinguish between explanatory and response variables. Then, skewness and kurtosis are discussed as tools to assess deviation from normality. Deviation from normality can be used to assess direction of dependence. This proposition is based on the fact that the response variable will always have less skew than the independent variable (Dodge & Rousson, 2000). It has been shown that the cube of the Pearson correlation coefficient can be calculated as the ratio of the skewness measures of the correlated variables. Because correlations cannot exceed the interval (−1.0; +1.0), directional dependence of the two correlated variables can be determined by the ratio that results in a correlation that stays within this interval. It is also proposed that other measures of deviation from normality can be used to determine directional dependence; for example, kurtosis. Recommendations are given for making decisions concerning directional dependence. Empirical data examples from developmental research on violence against women and on attention deficit hyperactivity disorder (ADHD) illustrate the use of the methodology. Cross-sectional and temporal directional dependence are discussed, and the effects of onset of a causal agent and termination of a causal agent are illustrated.

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6

Quesada-Molina, José Juan, and Manuel Úbeda-Flores. "Directional dependence of random vectors." Information Sciences 215 (December 2012): 67–74. http://dx.doi.org/10.1016/j.ins.2012.05.019.

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7

Nelsen, Roger B., and Manuel Úbeda-Flores. "Directional dependence in multivariate distributions." Annals of the Institute of Statistical Mathematics 64, no. 3 (2011): 677–85. http://dx.doi.org/10.1007/s10463-011-0329-6.

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8

Hyun, Steve, Jimin Lee, Jong-Min Kim, and Chulhee Jun. "What Coins Lead in the Cryptocurrency Market: Using Copula and Neural Networks Models." Journal of Risk and Financial Management 12, no. 3 (2019): 132. http://dx.doi.org/10.3390/jrfm12030132.

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Exploring dependence structures between financial time series has been important within a wide range of applications. The main aim of this paper is to examine dependence relationships among five well-known cryptocurrencies—Bitcoin, Ethereum, Litecoin, Ripple, and Stella—by a copula directional dependence (CDD). By employing a neural network autoregression model to avoid the serial dependence in each individual cryptocurrency, we generate residuals of the fitted models with time series of daily log-returns in percentage of the five cryptocurrencies and then we apply a Gaussian copula marginal beta regression model to the residuals to explore the CDD. The results show that the CDD from Bitcoin to Litecoin is highest among all ordered directional dependencies and the CDDs from Ethereum to the other four cryptocurrencies are relatively higher than the CDDs to Ethereum from those cryptocurrencies. This finding implies that the return shocks of Bitcoin have the most effect on Litecoin and the return shocks of Ethereum relatively influence the shocks on the other four cryptocurrencies instead of being affected by them. This allows investors to build the market-timing strategies by observing the directional flow of return shocks among cryptocurrencies.

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9

Middlebrooks, John C., and David M. Green. "Directional dependence of interaural envelope delays." Journal of the Acoustical Society of America 87, no. 5 (1990): 2149–62. http://dx.doi.org/10.1121/1.399183.

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10

Sungur, Engin A., and Jessica M. Orth. "Understanding Directional Dependence Through Angular Correlation." Communications in Statistics - Theory and Methods 43, no. 19 (2014): 4143–55. http://dx.doi.org/10.1080/03610926.2012.707735.

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11

Axelsson, M., Y. Fantaye, F. K. Hansen, A. J. Banday, H. K. Eriksen та K. M. Gorski. "DIRECTIONAL DEPENDENCE OF ΛCDM COSMOLOGICAL PARAMETERS". Astrophysical Journal 773, № 1 (2013): L3. http://dx.doi.org/10.1088/2041-8205/773/1/l3.

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12

de Amo, Enrique, María del Rosario Rodríguez-Griñolo, and Manuel Úbeda-Flores. "Directional Dependence Orders of Random Vectors." Mathematics 12, no. 3 (2024): 419. http://dx.doi.org/10.3390/math12030419.

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In this paper, we define a multivariate order based on the concept of orthant directional dependence and study some of its properties. The relationships with other dependence orders given in the literature are also studied. We analyze the order between two random vectors in terms of their associated copulas and illustrate our results with several examples.

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13

Chino, Yasumasa, Katsuya Kimura, and Mamoru Mabuchi. "Direction Dependence of Compressive Properties of Mg Processed by Directional Solidification." MATERIALS TRANSACTIONS 49, no. 3 (2008): 393–97. http://dx.doi.org/10.2320/matertrans.ml200701.

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14

Amthor, Franklin R., and Norberto M. Grzywacz. "Nonlinearity of the inhibition underlying retinal directional selectivity." Visual Neuroscience 6, no. 3 (1991): 197–206. http://dx.doi.org/10.1017/s0952523800006210.

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AbstractAn important mechanism for the discrimination of direction of motion in the retina is a spatially asymmetric inhibition. This inhibition has been postulated to operate either as a subtraction, like in difference-of-Gaussians' models, or as a division, like in shunting-inhibition models of directional selectivity. The latter, but not the former, is nonlinear. This raises the question of whether the inhibitory mechanism involved in directional selectivity is nonlinear. To investigate this issue, we studied the linearity of the contrast dependence of the extracellularly recorded responses to apparent motions in ON-OFF directionally selective ganglion cells of the rabbit retina. The results show that the inhibition underlying directional selectivity is nonlinear and fits shunting-inhibition models well. Other biophysical mechanisms that might account for the type of nonlinearity observed in the data are also considered.

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15

Quesada-Molina, José Juan, and Manuel Úbeda-Flores. "Modeling Directional Monotonicity in Sequence with Copulas." Axioms 13, no. 11 (2024): 785. http://dx.doi.org/10.3390/axioms13110785.

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In this paper, we present the concept of being monotonic in sequence according to a specific direction for a collection of random variables. This concept broadens the existing notions of multivariate dependence, such as sequential left-tail and right-tail dependence. Furthermore, we explore connections with other multivariate dependence concepts, highlight key properties, and analyze the new concept within the framework of copulas. Several examples are provided to demonstrate our findings.

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16

MERWINE, DAVID K., NORBERTO M. GRZYWACZ, DARREL S. TJEPKES, and FRANKLIN R. AMTHOR. "Non-monotonic contrast behavior in directionally selective ganglion cells and evidence for its dependence on their GABAergic input." Visual Neuroscience 15, no. 6 (1998): 1129–36. http://dx.doi.org/10.1017/s0952523898156122.

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We serendipitously discovered that the preferred-direction responses of ON–OFF directionally selective (DS) ganglion cells in the rabbit retina fall as a function of contrast when the contrast of a moving bar exceeds about 100%. Null-direction responses did not fall for contrasts up to 400%. Because the non-monotonic (rise-then-fall) behavior as a function of contrast occurred only for preferred-direction responses, it must depend on the mechanism of directional selectivity. It became thus of interest to investigate how this non-monotonicity depends on the major synapses involved in directional selectivity. Blockades of nicotinic acetylcholine (ACh) and NMDA glutamate receptors reduced responses without eliminating preferred-response non-monotonicity. Blocking GABAergic inhibition, however, did eliminate non-monotonicity. These results pose a difficult puzzle, since in the accompanying paper (Grzywacz et al., 1998), we showed that residual responses under combined nicotinic and NMDA blockades are not statistically significantly directionally selective. How is it possible that null-direction GABAergic inhibition affects non-nicotinic-non-NMDA residual responses without generating directional selectivity? This may happen if there exists an asymmetric GABAergic input to distal dendrites of the DS cell while the excitatory, non-nicotinic-non-NMDA input is to proximal dendrites. In support of this hypothesis, bath-applied GABA reduces responses to exogenous ACh under synaptic block, providing for the first time in the rabbit's retina, direct evidence of GABA receptors on DS cells.

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17

Denney, Dennis. "Imparting Directional Dependence on Log-Derived Permeability." Journal of Petroleum Technology 54, no. 06 (2002): 50. http://dx.doi.org/10.2118/0602-0050-jpt.

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18

Schön, J. H., D. T. Georgi, and O. Fanini. "Imparting Directional Dependence on Log-Derived Permeability." SPE Reservoir Evaluation & Engineering 6, no. 01 (2003): 48–86. http://dx.doi.org/10.2118/82058-pa.

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19

Sungur, Engin A., and Jessica M. Orth. "On modeling directional dependence by using copulas." Model Assisted Statistics and Applications 7, no. 4 (2012): 305–13. http://dx.doi.org/10.3233/mas-2012-0242.

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20

Schwab, Russell, Marcus Rang, and Moritz Kassmann. "Integro-Differential equations with nonlinear directional dependence." Indiana University Mathematics Journal 63, no. 5 (2014): 1467–98. http://dx.doi.org/10.1512/iumj.2014.63.5394.

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21

Puccini, Gabriel D., Albert Compte, and Miguel Maravall. "Stimulus Dependence of Barrel Cortex Directional Selectivity." PLoS ONE 1, no. 1 (2006): e137. http://dx.doi.org/10.1371/journal.pone.0000137.

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22

Mauger, Scott A., Lilian Chang, Christopher W. Rochester, and Adam J. Moulé. "Directional dependence of electron blocking in PEDOT:PSS." Organic Electronics 13, no. 11 (2012): 2747–56. http://dx.doi.org/10.1016/j.orgel.2012.08.004.

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23

Bedenbecker, Matthias, Zbigniew Celinski, and H. H. Gatzen. "Directional Permeability Dependence in Electroplated Permalloy Layers." ECS Transactions 3, no. 25 (2019): 123–35. http://dx.doi.org/10.1149/1.2753247.

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24

Muddapur, M. V. "On Directional Dependence in a Regression Line." Communications in Statistics - Theory and Methods 32, no. 10 (2003): 2053–57. http://dx.doi.org/10.1081/sta-120023266.

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25

Sin Yip Cheng, Kin Seng Chiang, and Hau Ping Chan. "Polarization dependence in polymer waveguide directional couplers." IEEE Photonics Technology Letters 17, no. 7 (2005): 1465–67. http://dx.doi.org/10.1109/lpt.2005.848285.

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26

Brown, Michael G. "A directional spectrum evolution model for ship noise." Journal of the Acoustical Society of America 153, no. 6 (2023): 3469. http://dx.doi.org/10.1121/10.0019851.

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A radiation transport equation that describes the spatiotemporal evolution of the directional spectrum of underwater acoustic noise is presented and applied to ship noise. A ray-based algorithm is used to solve the transport equation and numerically simulate the evolution of the directional noise spectrum produced by a passing ship. The model described accounts for the transient and highly episodic nature of shipping noise, the strong anisotropy of the radiated shipping noise, the directional dependence of the resulting acoustic field, and the critical angle dependence of bottom-reflected energy. The model predicts time histories of sound pressure level and directional spectral energy density at distant locations if the ship track and the ship's radiated noise power are known. Simulations are shown to be in qualitatively good agreement with observations.

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27

Vakulenko, I. O., M. A. Hryshchenko, and O. M. Perkov. "THE DEPENDENCE OF THE FORMATION PROCESSES OF DEFORMATION BANDS FROM THE STRUCTURAL PARAMETERS OF LOW-CARBON STEELS AFTER THE ANNEALING." Science and Transport Progress, no. 19 (December 25, 2007): 241–42. http://dx.doi.org/10.15802/stp2007/17569.

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The causes of directionaty of the yield point, stress of microyielding, and Chernov–Luders deformation in lowcarbon steel have been investigated. The observed of Chernov–Luders deformation be haviour is considered to be the result of a directional variation in the grain size of berrite to cause formation dislocation cell structure.

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28

Pressel, Kyle G., and William D. Collins. "First-Order Structure Function Analysis of Statistical Scale Invariance in the AIRS-Observed Water Vapor Field." Journal of Climate 25, no. 16 (2012): 5538–55. http://dx.doi.org/10.1175/jcli-d-11-00374.1.

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Abstract The power-law scale dependence, or scaling, of first-order structure functions of the tropospheric water vapor field between 58°S and 58°N is investigated using observations from the Atmospheric Infrared Sounder (AIRS). Power-law scale dependence of the first-order structure function would indicate that the water vapor field exhibits statistical scale invariance. Directional and directionally independent first-order structure functions are computed to assess the directional dependence of derived first-order structure function scaling exponents (H) for a range of scales from 50 to 500 km. In comparison to other methods of assessing statistical scale invariance, the methodology used here requires minimal assumptions regarding the homogeneity of the spatial distribution of data within regions of analysis. Additionally, the methodology facilitates the evaluation of anisotropy and quantifies the extent to which the structure functions exhibit scale invariance. The spatial and seasonal dependence of the computed scaling exponents are explored. Minimum scaling exponents at all levels are shown to occur proximate to the equator, while the global maximum is shown to occur in the middle troposphere near the tropical–subtropical margin of the winter hemisphere. From a detailed analysis of AIRS maritime scaling exponents, it is concluded that the AIRS observations suggest the existence of two scaling regimes in the extratropics. One of these regimes characterizes the statistical scale invariance the free troposphere with H approximately = 0.55 and a second that characterizes the statistical scale invariance of the boundary layer with H approximately = ⅓.

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29

DECK, R. T., and C. MAPALAGAMA. "IMPROVED THEORY OF NONLINEAR DIRECTIONAL COUPLER." Journal of Nonlinear Optical Physics & Materials 02, no. 01 (1993): 43–70. http://dx.doi.org/10.1142/s0218199193000036.

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We present an improved coupled mode theory of the nonlinear directional coupler based on the supermodes of the coupler and show that the predicted value of the switching intensity agrees well with recent experimental data. The theory relates to couplers constructed from semi-conductor materials and makes use of the plasma theory to express the dependence of the dielectric function on the field intensity. The analysis accounts for both the time dependence of the incident laser pulse and the spacial variation of the laser field in the direction transverse to the propagation direction.

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30

Ribeiro, Dyogo Lesniewski, Tamara Cantú Maltauro, Luciana Pagliosa Carvalho Guedes, Miguel Angel Uribe-Opazo, and Gustavo Henrique Dalposso. "Directional Differences in Thematic Maps of Soil Chemical Attributes with Geometric Anisotropy." Stats 7, no. 1 (2024): 65–78. http://dx.doi.org/10.3390/stats7010005.

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In the study of the spatial variability of soil chemical attributes, the process is considered anisotropic when the spatial dependence structure differs in relation to the direction. Anisotropy is a characteristic that influences the accuracy of the thematic maps that represent the spatial variability of the phenomenon. Therefore, the linear anisotropic Gaussian spatial model is important for spatial data that present anisotropy, and incorporating this as an intrinsic characteristic of the process that describes the spatial dependence structure improves the accuracy of the spatial estimation of the values of a georeferenced variable in unsampled locations. This work aimed at quantifying the directional differences existing in the thematic map of georeferenced variables when incorporating or not incorporating anisotropy into the spatial dependence structure through directional spatial autocorrelation. For simulated data and soil chemical properties (carbon, calcium and potassium), the Moran directional index was calculated, considering the predicted values at unsampled locations, and taking into account estimated isotropic and anisotropic geostatistical models. The directional spatial autocorrelation was effective in evidencing the directional difference between thematic maps elaborated with estimated isotropic and anisotropic geostatistical models. This measure evidenced the existence of an elliptical format of the subregions presented by thematic maps in the direction of anisotropy that indicated a greater spatial continuity for greater distances between pairs of points.

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31

Xuan, Weihao, Feng Zhang, Hongye Zhou, Zhenhong Du, and Renyi Liu. "Improving Geographically Weighted Regression Considering Directional Nonstationary for Ground-Level PM2.5 Estimation." ISPRS International Journal of Geo-Information 10, no. 6 (2021): 413. http://dx.doi.org/10.3390/ijgi10060413.

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The increase in atmospheric pollution dominated by particles with an aerodynamic diameter smaller than 2.5 μm (PM2.5) has become one of the most serious environmental hazards worldwide. The geographically weighted regression (GWR) model is a vital method to estimate the spatial distribution of the ground-level PM2.5 concentration. Wind information reflects the directional dependence of the spatial distribution, which can be abstracted as a combination of spatial and directional non-stationarity components. In this paper, a GWR model considering directional non-stationarity (GDWR) is proposed. To assess the efficacy of our method, monthly PM2.5 concentration estimation was carried out as a case study from March 2015 to February 2016 in the Yangtze River Delta region. The results indicate that the GDWR model attained the best fitting effect (0.79) and the smallest error fluctuation, the ordinary least squares (OLS) (0.589) fitting effect was the worst, and the GWR (0.72) and directionally weighted regression (DWR) (0.74) fitting effects were moderate. A non-stationarity hypothesis test was performed to confirm directional non-stationarity. The distribution of the PM2.5 concentration in the Yangtze River Delta is also discussed here.

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32

Wiedermann, Wolfgang, and Alexander von Eye. "Directional Dependence in the Analysis of Single Subjects." Journal for Person-Oriented Research 2, no. 1-2 (2016): 20–33. http://dx.doi.org/10.17505/jpor.2016.04.

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33

Sungur, Engin A. "A Note on Directional Dependence in Regression Setting." Communications in Statistics - Theory and Methods 34, no. 9-10 (2005): 1957–65. http://dx.doi.org/10.1080/03610920500201228.

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34

Sommer, Martin W., Tim Schrabback, and Sebastian Grandis. "Directional miscentring dependence in weak lensing mass bias." Monthly Notices of the Royal Astronomical Society: Letters 538, no. 1 (2025): L50—L55. https://doi.org/10.1093/mnrasl/slaf007.

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ABSTRACT Galaxy cluster masses estimated from parametric modelling of weak lensing shear observations are known to be biased by inaccuracies in observationally determined centres. It has recently been shown that such systematic effects can be non-isotropic when centres are derived from X-ray or Compton-Y (Sunyaev–Zeldovich effect) observations, which is often the case in practice. This fact challenges current methods of accurately correcting for weak lensing mass biases using simulations paired with isotropic empirical miscentring distributions, in particular as the effect on determined masses is currently a dominant source of systematic uncertainty. We use hydrodynamical cosmological simulations taken from the Magneticum Pathfinder simulations to show that the non-isotropic component of the mass bias can be reduced to within one per cent of the mass when considering the centre of mass, rather than the bottom of the gravitational potential, as the reference centre of a galaxy cluster.

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35

Hirsekorn, Sigrun. "Directional dependence of ultrasonic propagation in textured polycrystals." Journal of the Acoustical Society of America 79, no. 5 (1986): 1269–79. http://dx.doi.org/10.1121/1.393706.

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36

Kvatadze, R. A., R. Møller, and B. Lörstad. "On the directional dependence of Bose-Einstein correlations." Zeitschrift für Physik C Particles and Fields 38, no. 4 (1988): 551–55. http://dx.doi.org/10.1007/bf01624359.

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37

Ding, Dong, Dongdong Xiang, and Jian Li. "Directional monitoring of categorical processes with serial dependence." Computers & Industrial Engineering 113 (November 2017): 502–11. http://dx.doi.org/10.1016/j.cie.2017.09.035.

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38

van Zoest, J. M., C. E. van der Mey, J. M. Fluit, and A. Niehaus. "Directional dependence of ion neutralization at a surface." Surface Science Letters 152-153 (April 1985): A111. http://dx.doi.org/10.1016/0167-2584(85)90077-5.

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39

Kysar, Jeffrey W. "Directional dependence of fracture in copper/sapphire bicrystal." Acta Materialia 48, no. 13 (2000): 3509–24. http://dx.doi.org/10.1016/s1359-6454(00)00127-0.

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40

Van Zoest, J. M., C. E. Van Der Mey, J. M. Fluit, and A. Niehaus. "Directional dependence of ion neutralization at a surface." Surface Science 152-153 (April 1985): 106–13. http://dx.doi.org/10.1016/0039-6028(85)90132-3.

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41

Gu, Donghua, Ohannes Eknoyan, and Henry F. Taylor. "Polarization dependence in Ti-diffused LiNbO_3 directional couplers." Applied Optics 41, no. 1 (2002): 74. http://dx.doi.org/10.1364/ao.41.000074.

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42

Kim, Jong-Min, and S. Y. Hwang. "The copula directional dependence by stochastic volatility models." Communications in Statistics - Simulation and Computation 48, no. 4 (2018): 1153–75. http://dx.doi.org/10.1080/03610918.2017.1406512.

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43

Tilstra, Lieuwe G., Martin de Graaf, Victor J. H. Trees, Pavel Litvinov, Oleg Dubovik, and Piet Stammes. "A directional surface reflectance climatology determined from TROPOMI observations." Atmospheric Measurement Techniques 17, no. 7 (2024): 2235–56. http://dx.doi.org/10.5194/amt-17-2235-2024.

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Abstract. In this paper, we introduce a spectral surface reflectivity climatology based on observations made by TROPOMI on board the Sentinel-5P satellite. The database contains the directionally dependent Lambertian-equivalent reflectivity (DLER) of the Earth's surface for 21 wavelength bands ranging from 328 to 2314 nm and for each calendar month. The spatial resolution of the database grid is 0.125° × 0.125°. A recently developed cloud shadow detection technique is implemented to avoid dark scenes due to cloud shadow. In the database, the anisotropy of the surface reflection is described using a third-order parameterisation of the viewing angle dependence. The viewing angle dependence of the DLER is analysed globally and for a selection of surface type regions. The dependence is found to agree with the viewing angle dependence found in the GOME-2 surface DLER database. Differences exist, related to the actual solar position. On average, the viewing angle dependence in TROPOMI DLER is weaker than for GOME-2 DLER, but still important. Validation of the new database was first performed by comparison of the non-directional TROPOMI surface LER with heritage LER databases based on GOME-1, OMI, SCIAMACHY, and GOME-2 data. Agreement was found within 0.002–0.02 in the UV-VIS (below 500 nm), up to 0.003 in the NIR (670–772 nm), and below 0.001 in the short-wave infrared (SWIR) (2314 nm). These performance numbers are dominated by the performance over ocean, but they are in most cases also representative for land surfaces. For the validation of the directional TROPOMI surface DLER, we made use of comparison with the MODIS surface bi-directional reflectance distribution function (BRDF) for a selection of surface type regions. In all cases the DLER performed significantly better than the traditional LER, and we found good agreement with the MODIS surface BRDF. The TROPOMI surface DLER database is a clear improvement on previous surface albedo databases and can be used as input not only for satellite retrievals from TROPOMI observations, but also for retrievals from observations from other polar-orbiting satellite instruments provided that their equator crossing time is close to that of TROPOMI. The algorithm that is introduced in this paper can be used for the retrieval of surface reflectivity climatologies from other polar satellite missions as well, including Ocean and Land Colour Instrument (OLCI) on the Sentinel-3 satellites, Sentinel-5, and Multi-viewing Multi-channel Multi-polarisation imager (3MI) on the MetOp-SG-A1 satellite to be launched in 2025, as well as the future CO2M mission.

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Mori, Nobuhito, Miguel Onorato, and Peter A. E. M. Janssen. "On the Estimation of the Kurtosis in Directional Sea States for Freak Wave Forecasting." Journal of Physical Oceanography 41, no. 8 (2011): 1484–97. http://dx.doi.org/10.1175/2011jpo4542.1.

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Abstract Based on Monte Carlo simulations of the nonlinear Schrödinger equation in two horizontal dimensions, the dependence of the kurtosis on the directional energy distribution of the initial conditions is examined. The parametric survey is carried out to obtain the behavior of the kurtosis as function of the Benjamin–Feir index and directional spread in directional sea states. As directional dispersion effect becomes significant, the kurtosis monotonically decreases in comparison with the unidirectional waves. A parameterization of the kurtosis estimated from directional spectra is proposed here; the error of the parameterization is at most 10%. The parameterization is verified against laboratory data, and good agreement is obtained.

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Hartansky, Rene. "Analysis of Omni-directivity Error of Electromagnetic Field Probe using Isotropic Antenna." Measurement Science Review 16, no. 6 (2016): 287–93. http://dx.doi.org/10.1515/msr-2016-0036.

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Abstract This manuscript analyzes the omni-directivity error of an electromagnetic field (EM) probe and its dependence on frequency. The global directional characteristic of a whole EM probe consists of three independent directional characteristics of EM sensors - one for each coordinate. The shape of particular directional characteristics is frequency dependent and so is the shape of the whole EM probe’s global directional characteristic. This results in systematic error induced in the measurement of EM fields. This manuscript also contains quantitative formulation of such errors caused by the shape change of directional characteristics for different types of sensors depending on frequency and their mutual arrangement.

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Wiedermann, Wolfgang, and Alexander von Eye. "Direction-dependence analysis." International Journal of Behavioral Development 39, no. 6 (2015): 570–80. http://dx.doi.org/10.1177/0165025415582056.

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The concept of direction dependence has attracted growing attention due to its potential to help decide which of two competing linear regression models ( X → Y or Y → X) is more likely to reflect the correct causal flow. Several tests have been proposed to evaluate hypotheses compatible with direction dependence. In this issue, Thoemmes (2015) reports results of an empirical evaluation of direction-dependence tests using real-world data sets with known causal ordering and concludes that the tests (known to perform excellent in simulation studies) perform poorly in the real-world setting. The present article aims at answering the question how this is possible. First, we review potential conceptual issues associated with Thoemmes’ (2015) approach. We argue that direction dependence is best conceptualized as a confirmatory approach to test focused directional theories. Thoemmes’ (2015) evaluation is based on an exploratory use of direction dependence. It implicitly follows the tradition of causal search algorithms. Second, we discuss potential statistical issues associated with Thoemmes’ (2015) selection schemes used to decide whether a variable pair is suitable for direction-dependence analysis. Based on these issues, new tests of direction dependence as well as new guidelines for confirmatory direction-dependence analysis are proposed. An empirical example is given to illustrate the application of these guidelines.

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Fanchi, John R. "Directional Permeability." SPE Reservoir Evaluation & Engineering 11, no. 03 (2008): 565–68. http://dx.doi.org/10.2118/102343-pa.

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Summary A relationship between permeability tensor and coordinate orientation is used to estimate the error that occurs when some of the terms in the permeability tensor are neglected. The formula for calculating the errors that appear in the magnitude and direction of flow rate are presented. The results are applicable to any reservoir system that is influenced by directional permeability. Introduction Reservoir management experience has demonstrated that anisotropic permeability is needed to correctly solve fluid-flow problems in a variety of realistic settings. Permeability anisotropy in a plane is usually represented using two directions: the direction of maximum permeability, and the direction that is transverse to the direction of maximum permeability. This procedure establishes a natural coordinate system for describing directional permeability. The coordinate system is considered the diagonalized coordinate system. If flow-rate calculations are not aligned with the diagonalized coordinate system, then additional terms should be included in the form of Darcy's law, which is used in flow calculations. All of the permeability terms are considered the elements of the permeability tensor. Most commercial reservoir simulators solve fluid-flow equations that have been formulated on the basis of the assumption that the permeability tensor has been diagonalized (Fanchi 2006b; Ertekin et al. 2001). As a rule, the off-diagonal permeability terms are not included in flow calculations, and an error occurs. Engineers usually assume without justification that the error can be neglected. Research in naturally fractured reservoir modeling (Gupta et al. 2001), geomechanics (Settari et al. 2001), and upscaling (Young 1999) has demonstrated that the full permeability tensor is needed to correctly solve fluid-flow problems in a variety of realistic settings. The purpose of this paper is to show how to assess the magnitude of the error that occurs when the off-diagonal terms are not included in reservoir flow calculations. The directional dependence of permeability and the permeability tensor are introduced in the section titled "Directional Dependence of Permeability." A relationship between the diagonalized-permeability-tensor assumption and coordinate orientation is discussed in the section titled "Permeability Tensor and Coordinate Orientation." This relationship is used in the section titled "Error Analysis" to estimate the error that occurs when some of the terms in the permeability tensor are neglected. We show that the error depends on orientation of the coordinate system, the permeability aspect ratio, and the pressure gradient. The formulas for calculating the errors that appear in the magnitude and direction of the flow rate are presented. Concluding remarks are then presented.

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Dautriat, Jeremie, Nicolas F. Gland, Souhail Youssef, Elisabeth Rosenberg, Samir Bekri, and Olga Vizika-kavvadias. "Stress-Dependent Directional Permeabilities of Two Analog Reservoir Rocks: A Prospective Study on Contribution of µ-Tomography and Pore Network Models." SPE Reservoir Evaluation & Engineering 12, no. 02 (2009): 297–310. http://dx.doi.org/10.2118/110455-pa.

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Summary To predict the effects of stress on rock permeability, the authors propose an integrated approach based on an extended rock characterization, an experimental investigation of pressure dependency of directional rock permeabilities and finally a pore-scale simulation of this dependency using equivalent pore network extracted from microtomography analysis. This study has been conducted on two analog reservoir rock types: the high-permeability Bentheimer Sandstone and a dual-porosity bioclastic carbonate, the Estaillades Limestone, having an intermediate permeability. Compression tests have been conducted using a new triaxial cell specially designed to measure directional permeabilities along and transverse to direction of maximum stress application. We measured the pressure dependency of porosity, directional permeabilities, compressibilities, and elastic moduli of the tested samples. We also performed computed microtomography (CMT) imaging of the rock samples, from which we extracted the poral skeletons and the associated characteristics lengths. Then, we calculated the macroscopic transport properties using Pore Network Modeling (PNM) based on the real pore geometry. We included a model of pressure dependence of pore and throat sizes based on pressurized cavity models derived from elasticity theory to simulate the evolution of porosity and permeability with pressure. First, we show that the experimental determination of the evolution of directional permeabilities under hydrostatic and deviatoric loading is feasible. Finally, we show that the PNM coupled with µ tomography can be a promising tool to forecast the evolution of transport properties under stresses representative of reservoir conditions, at the condition of integrating more advanced pore-scale compaction models.

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MRÓZ, S. "DIRECTIONAL AUGER ELECTRON SPECTROSCOPY — PHYSICAL FOUNDATIONS AND APPLICATIONS." Surface Review and Letters 04, no. 01 (1997): 117–39. http://dx.doi.org/10.1142/s0218625x97000158.

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Experimental data about the dependence of the Auger signal from crystalline samples on the primary beam direction are presented and discussed. It is shown that, for Auger electrons and elastically and inelastically backscattered electrons, maxima of the signal in its dependence on the polar and azimuth angles of the primary beam (in polar and azimuth profiles, respectively) appear when the primary beam is parallel either to one of the close-packed rows of atoms or to one of the densely packed atomic planes in the sample. This indicates that the diffraction of the primary electron beam is responsible for the dependence mentioned above. Mechanisms proposed for simple explanation of this dependence (channeling and forward focusing of primary electrons) are presented and results of their application are discussed. It is shown that both those mechanisms play an important role in the creation of the Auger signal contrast. The possibilities and limitations of the application of polar and azimuth Auger emission profiles in the determination of the surface layer crystalline structure (directional Auger electron spectroscopy — DAES) are presented and discussed. It is shown that the thickness of the investigated surface layer can be decreased up to a few monolayers. Results obtained with DAES are similar to those provided by X-ray photoelectron diffraction (XPD) and Auger electron diffraction (AED), but the DAES experimental equipment is simple and inexpensive and measurements are fast. Finally, experimental systems for DAES are described and examples of DAES applications are presented.

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Mori, Nobuhito, Hajime Mase, and Tomohiro Yasuda. "FREAK WAVE AND WEATHER CONDITION." Coastal Engineering Proceedings 1, no. 32 (2011): 70. http://dx.doi.org/10.9753/icce.v32.waves.70.

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The kurtosis of the surface elevation, Benjamin-Feir Index (BFI) and directional spread are measures of nonlinear four-wave interactions and freak waves. The dependence of kurtosis, BFI and directional spread under typhoon conditions are examined by numerical simulations. The BFI is significantly large in the fourth quadrant of the typhoon while the directional spread is small in the fourth quadrant. It was found that the potentially possible area of freak wave occurrence is the fourth quadrant of the typhoon rather than the other quadrants.

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