Direct Density Ratio Estimation for Large-scale Covariate Shift Adaptation

Experiments were conducted to investigate the effect of compressibility on turbulent reacting mixing layers with moderate heat release. Side- and plan-view visualizations of the reacting mixing layers, which were formed between a high-speed high-temperature vitiated-air stream and a low-speed ambient-temperature hydrogen stream, were obtained using a combined OH/acetone planar laser-induced fluorescence imaging technique. The instantaneous images of OH provide two-dimensional maps of the regions of combustion, and similar images of acetone, which was seeded into the fuel stream, provide maps of the regions of unburned fuel. Two low-compressibility (Mc=0.32, 0.35) reacting mixing layers with differing density ratios and one high-compressibility (Mc=0.70) reacting mixing layer were studied. Higher average acetone signals were measured in the compressible mixing layer than in its low-compressibility counterpart (i.e. same density ratio), indicating a lower entrainment ratio. Additionally, the compressible mixing layer had slightly wider regions of OH and 50% higher OH signals, which was an unexpected result since lowering the entrainment ratio had the opposite effect at low compressibilities. The large-scale structural changes induced by compressibility are believed to be primarily responsible for the difference in the behaviour of the high- and low-compressibility reacting mixing layers. It is proposed that the coexistence of broad regions of OH and high acetone signals is a manifestation of a more biased distribution of mixture compositions in the compressible mixing layer. Other mechanisms through which compressibility can affect the combustion are discussed.

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Inlier-Based Outlier Detection via Direct Density Ratio Estimation

2008 Eighth IEEE International Conference on Data Mining ◽

10.1109/icdm.2008.49 ◽

2008 ◽

Cited By ~ 32

Author(s):

Shohei Hido ◽

Yuta Tsuboi ◽

Hisashi Kashima ◽

Masashi Sugiyama ◽

Takafumi Kanamori

Keyword(s):

Outlier Detection ◽

Density Ratio ◽

Ratio Estimation

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Interactions of Film Cooling Rows: Effects of Hole Geometry and Row Spacing on the Cooling Performance Downstream of the Second Row of Holes

Volume 5: Turbo Expo 2003, Parts A and B ◽

10.1115/gt2003-38195 ◽

2003 ◽

Cited By ~ 5

Author(s):

Christian Saumweber ◽

Achmed Schulz

Keyword(s):

Boundary Layer ◽

Film Cooling ◽

Large Scale ◽

Density Ratio ◽

Operating Conditions ◽

Transfer Coefficients ◽

Film Cooling Effectiveness ◽

Heat Transfer Coefficients ◽

Staggered Arrangement ◽

Film Cooling Holes

A comprehensive set of generic experiments is conducted to investigate the interaction of film cooling rows. Five different film cooling configurations are considered on a large scale basis each consisting of two rows of film cooling holes in staggered arrangement. The hole pitch to diameter ratio within each row is kept constant at P/D = 4. The spacing between the rows is either x/D = 10, 20, or 30. Fanshaped holes or simple cylindrical holes with an inclination angle of 30 deg. and a hole length of 6 hole diameters are used. With a hot gas Mach number of Mam = 0.3, an engine like density ratio of ρc/ρm = 1.75, and a freestream turbulence intensity of Tu = 5.1% are established. Operating conditions are varied in terms of blowing ratio for the upstream and, independently, the downstream row in the range 0.5<M<2.0. The results illustrate the importance of considering ejection into an already film cooled boundary layer. Adiabatic film cooling effectiveness and heat transfer coefficients are significantly increased. The decay of effectiveness with streamwise distance is much less pronounced downstream of the second row primarily due to pre-cooling of the boundary layer by the first row of holes. Additionally, a comparison of measured effectiveness data with predictions according to the widely used superposition model of Sellers [11] is given for two rows of fanshaped holes.

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Condition assessment of electro-mechanical actuators for aerospace using relative density-ratio estimation

IFAC-PapersOnLine ◽

10.1016/j.ifacol.2018.09.070 ◽

2018 ◽

Vol 51 (15) ◽

pp. 957-962 ◽

Cited By ~ 1

Author(s):

M. Mazzoleni ◽

M. Scandella ◽

Y. Maccarana ◽

F. Previdi ◽

G. Pispola ◽

...

Keyword(s):

Relative Density ◽

Density Ratio ◽

Condition Assessment ◽

Ratio Estimation

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Online Direct Density-Ratio Estimation Applied to Inlier-Based Outlier Detection

Neural Computation ◽

10.1162/neco_a_00761 ◽

2015 ◽

Vol 27 (9) ◽

pp. 1899-1914

Author(s):

Marthinus Christoffel du Plessis ◽

Hiroaki Shiino ◽

Masashi Sugiyama

Keyword(s):

Outlier Detection ◽

Density Estimation ◽

Density Ratio ◽

Learning Problems ◽

Conditional Density ◽

Ratio Estimation ◽

Data Set ◽

Step Procedure ◽

Training Samples ◽

Probability Densities

Many machine learning problems, such as nonstationarity adaptation, outlier detection, dimensionality reduction, and conditional density estimation, can be effectively solved by using the ratio of probability densities. Since the naive two-step procedure of first estimating the probability densities and then taking their ratio performs poorly, methods to directly estimate the density ratio from two sets of samples without density estimation have been extensively studied recently. However, these methods are batch algorithms that use the whole data set to estimate the density ratio, and they are inefficient in the online setup, where training samples are provided sequentially and solutions are updated incrementally without storing previous samples. In this letter, we propose two online density-ratio estimators based on the adaptive regularization of weight vectors. Through experiments on inlier-based outlier detection, we demonstrate the usefulness of the proposed methods.

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Unsteady RANS Simulation of Turbulent Flow and Heat Transfer in Ribbed Coolant Passages of Different Aspect Ratios

Volume 3: Turbo Expo 2004 ◽

10.1115/gt2004-53986 ◽

2004 ◽

Author(s):

A. K. Saha ◽

Sumanta Acharya

Keyword(s):

Heat Transfer ◽

Secondary Flow ◽

Rotation Number ◽

Large Scale ◽

Density Ratio ◽

Navier Stokes ◽

Flow Structures ◽

Flow And Heat Transfer ◽

Aspect Ratios ◽

Unsteady Rans

The flow and heat transfer in ribbed coolant passages of aspect ratios (AR) of 1:1, 4:1, and 1:4 are numerically studied through the solution of the Unsteady Reynolds Averaged Navier-Stokes (URANS) equations. The ribs are oriented normal to the flow and arranged in a staggered configuration on the leading and trailing surfaces. The URANS procedure can resolve large-scale bulk unsteadiness, and utilizes a two equation k-ε model for the turbulent stresses. Both Coriolis and centrifugal buoyancy effects are included in the simulations. The computations are carried out for a fixed Reynolds number of 25000 and density ratio of 0.13 while the Rotation number has been varied between 0.12–0.50. The average duct heat transfer is the highest for the 4:1 AR case. For this case, the secondary flow structures consist of multiple roll cells that direct flow both to the trailing and leading surfaces. The 1:4 AR duct shows flow reversal along the leading surface at high rotation numbers with multiple rolls in the secondary flow structures near the leading wall. For this AR, the potential for conduction-limited heat transfer along the leading surface is identified. At high rotation number, both the 1:1 and 4:1 AR cases exhibit loss of axial periodicity over one inter-rib module. The friction factor reveals an increase with the rotation number for all aspect ratio ducts, and shows a sudden jump in its value at a critical rotation number because of either loss of spatial periodicity or the onset of backflow.

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Effects of Concrete on Propagation Characteristics of Guided Wave in Steel Bar Embedded in Concrete

Shock and Vibration ◽

10.1155/2014/910750 ◽

2014 ◽

Vol 2014 ◽

pp. 1-14 ◽

Cited By ~ 3

Author(s):

Zhupeng Zheng ◽

Ying Lei

Keyword(s):

Large Scale ◽

Guided Waves ◽

Density Ratio ◽

Guided Wave ◽

Wave Number ◽

Propagation Characteristics ◽

Civil Infrastructures ◽

Steel Bar ◽

Reinforced Concrete Member ◽

Steel Bars

Techniques based on ultrasonic guided waves (UGWs) play important roles in the structural health monitoring (SHM) of large-scale civil infrastructures. In this paper, dispersion equations of longitudinal wave propagation in reinforced concrete member are investigated for the purpose of monitoring steels embedded in concrete. For a steel bar embedded in concrete, not the velocity but the attenuation dispersion curves will be affected by the concrete. The effects of steel-to-concrete shear modulus ratio, density ratio, and Poisson’s ratio on propagation characteristics of guided wave in steel bar embedded in concrete were studied by the analysis of the real and imaginary parts of the wave number. The attenuation characteristics of guided waves of steel bar in different conditions including different bar concrete constraint and different diameter of steel bar are also analyzed. Studies of the influence of concrete on propagation characteristics of guided wave in steel bars embedded in concrete will increase the accuracy in judging the structure integrity and promote the level of defect detection for the steel bars embedded in concrete.

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