Two-dimensional multifractal cross-correlation analysis

International Nuclear Information System (INIS)

Xi, Caiping; Zhang, Shuning; Xiong, Gang; Zhao, Huichang; Yang, Yonghong

2017-01-01

Highlights: • We study the mathematical models of 2D-MFXPF, 2D-MFXDFA and 2D-MFXDMA. • Present the definition of the two-dimensional N 2 -partitioned multiplicative cascading process. • Do the comparative analysis of 2D-MC by 2D-MFXPF, 2D-MFXDFA and 2D-MFXDMA. • Provide a reference on the choice and parameter settings of these methods in practice. - Abstract: There are a number of situations in which several signals are simultaneously recorded in complex systems, which exhibit long-term power-law cross-correlations. This paper presents two-dimensional multifractal cross-correlation analysis based on the partition function (2D-MFXPF), two-dimensional multifractal cross-correlation analysis based on the detrended fluctuation analysis (2D-MFXDFA) and two-dimensional multifractal cross-correlation analysis based on the detrended moving average analysis (2D-MFXDMA). We apply these methods to pairs of two-dimensional multiplicative cascades (2D-MC) to do a comparative study. Then, we apply the two-dimensional multifractal cross-correlation analysis based on the detrended fluctuation analysis (2D-MFXDFA) to real images and unveil intriguing multifractality in the cross correlations of the material structures. At last, we give the main conclusions and provide a valuable reference on how to choose the multifractal algorithms in the potential applications in the field of SAR image classification and detection.

Detrended cross-correlation analysis of electroencephalogram

International Nuclear Information System (INIS)

Wang Jun; Zhao Da-Qing

2012-01-01

In the paper we use detrended cross-correlation analysis (DCCA) to study the electroencephalograms of healthy young subjects and healthy old subjects. It is found that the cross-correlation between different leads of a healthy young subject is larger than that of a healthy old subject. It was shown that the cross-correlation relationship decreases with the aging process and the phenomenon can help to diagnose whether the subject's brain function is healthy or not. (interdisciplinary physics and related areas of science and technology)

Random matrix theory analysis of cross-correlations in the US stock market: Evidence from Pearson’s correlation coefficient and detrended cross-correlation coefficient

Science.gov (United States)

Wang, Gang-Jin; Xie, Chi; Chen, Shou; Yang, Jiao-Jiao; Yang, Ming-Yan

2013-09-01

In this study, we first build two empirical cross-correlation matrices in the US stock market by two different methods, namely the Pearson’s correlation coefficient and the detrended cross-correlation coefficient (DCCA coefficient). Then, combining the two matrices with the method of random matrix theory (RMT), we mainly investigate the statistical properties of cross-correlations in the US stock market. We choose the daily closing prices of 462 constituent stocks of S&P 500 index as the research objects and select the sample data from January 3, 2005 to August 31, 2012. In the empirical analysis, we examine the statistical properties of cross-correlation coefficients, the distribution of eigenvalues, the distribution of eigenvector components, and the inverse participation ratio. From the two methods, we find some new results of the cross-correlations in the US stock market in our study, which are different from the conclusions reached by previous studies. The empirical cross-correlation matrices constructed by the DCCA coefficient show several interesting properties at different time scales in the US stock market, which are useful to the risk management and optimal portfolio selection, especially to the diversity of the asset portfolio. It will be an interesting and meaningful work to find the theoretical eigenvalue distribution of a completely random matrix R for the DCCA coefficient because it does not obey the Marčenko-Pastur distribution.

Analyzing the Cross-Correlation Between Onshore and Offshore RMB Exchange Rates Based on Multifractal Detrended Cross-Correlation Analysis (MF-DCCA)

Science.gov (United States)

Xie, Chi; Zhou, Yingying; Wang, Gangjin; Yan, Xinguo

We use the multifractal detrended cross-correlation analysis (MF-DCCA) method to explore the multifractal behavior of the cross-correlation between exchange rates of onshore RMB (CNY) and offshore RMB (CNH) against US dollar (USD). The empirical data are daily prices of CNY/USD and CNH/USD from May 1, 2012 to February 29, 2016. The results demonstrate that: (i) the cross-correlation between CNY/USD and CNH/USD is persistent and its fluctuation is smaller when the order of fluctuation function is negative than that when the order is positive; (ii) the multifractal behavior of the cross-correlation between CNY/USD and CNH/USD is significant during the sample period; (iii) the dynamic Hurst exponents obtained by the rolling windows analysis show that the cross-correlation is stable when the global economic situation is good and volatile in bad situation; and (iv) the non-normal distribution of original data has a greater effect on the multifractality of the cross-correlation between CNY/USD and CNH/USD than the temporary correlation.

Flow velocity measurement by using zero-crossing polarity cross correlation method

International Nuclear Information System (INIS)

Xu Chengji; Lu Jinming; Xia Hong

1993-01-01

Using the designed correlation metering system and a high accurate hot-wire anemometer as a calibration device, the experimental study of correlation method in a tunnel was carried out. The velocity measurement of gas flow by using zero-crossing polarity cross correlation method was realized and the experimental results has been analysed

Multifractal detrended cross-correlation analysis in the MENA area

Science.gov (United States)

El Alaoui, Marwane; Benbachir, Saâd

2013-12-01

In this paper, we investigated multifractal cross-correlations qualitatively and quantitatively using a cross-correlation test and the Multifractal detrended cross-correlation analysis method (MF-DCCA) for markets in the MENA area. We used cross-correlation coefficients to measure the level of this correlation. The analysis concerns four stock market indices of Morocco, Tunisia, Egypt and Jordan. The countries chosen are signatory of the Agadir agreement concerning the establishment of a free trade area comprising Arab Mediterranean countries. We computed the bivariate generalized Hurst exponent, Rényi exponent and spectrum of singularity for each pair of indices to measure quantitatively the cross-correlations. By analyzing the results, we found the existence of multifractal cross-correlations between all of these markets. We compared the spectrum width of these indices; we also found which pair of indices has a strong multifractal cross-correlation.

Testing Cross-Sectional Correlation in Large Panel Data Models with Serial Correlation

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Badi H. Baltagi

2016-11-01

Full Text Available This paper considers the problem of testing cross-sectional correlation in large panel data models with serially-correlated errors. It finds that existing tests for cross-sectional correlation encounter size distortions with serial correlation in the errors. To control the size, this paper proposes a modification of Pesaran’s Cross-sectional Dependence (CD test to account for serial correlation of an unknown form in the error term. We derive the limiting distribution of this test as N , T → ∞ . The test is distribution free and allows for unknown forms of serial correlation in the errors. Monte Carlo simulations show that the test has good size and power for large panels when serial correlation in the errors is present.

Multifractal Detrended Cross-Correlation Analysis of agricultural futures markets

International Nuclear Information System (INIS)

He Lingyun; Chen Shupeng

2011-01-01

Highlights: → We investigated cross-correlations between China's and US agricultural futures markets. → Power-law cross-correlations are found between the geographically far but correlated markets. → Multifractal features are significant in all the markets. → Cross-correlation exponent is less than averaged GHE when q 0. - Abstract: We investigated geographically far but temporally correlated China's and US agricultural futures markets. We found that there exists a power-law cross-correlation between them, and that multifractal features are significant in all the markets. It is very interesting that the geographically far markets show strong cross-correlations and share much of their multifractal structure. Furthermore, we found that for all the agricultural futures markets in our studies, the cross-correlation exponent is less than the averaged generalized Hurst exponents (GHE) when q 0.

Minimum disturbance rewards with maximum possible classical correlations

Energy Technology Data Exchange (ETDEWEB)

Pande, Varad R., E-mail: varad_pande@yahoo.in [Department of Physics, Indian Institute of Science Education and Research Pune, 411008 (India); Shaji, Anil [School of Physics, Indian Institute of Science Education and Research Thiruvananthapuram, 695016 (India)

2017-07-12

Weak measurements done on a subsystem of a bipartite system having both classical and nonClassical correlations between its components can potentially reveal information about the other subsystem with minimal disturbance to the overall state. We use weak quantum discord and the fidelity between the initial bipartite state and the state after measurement to construct a cost function that accounts for both the amount of information revealed about the other system as well as the disturbance to the overall state. We investigate the behaviour of the cost function for families of two qubit states and show that there is an optimal choice that can be made for the strength of the weak measurement. - Highlights: • Weak measurements done on one part of a bipartite system with controlled strength. • Weak quantum discord & fidelity used to quantify all correlations and disturbance. • Cost function to probe the tradeoff between extracted correlations and disturbance. • Optimal measurement strength for maximum extraction of classical correlations.

Correlation between maximum isometric strength variables and specific performance of Brazilian military judokas

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Michel Moraes Gonçalves

2017-06-01

Full Text Available It was our objective to correlate specific performance in the Special Judo Fitness Test (SJFT and the maximum isometric handgrip (HGSMax, scapular traction (STSMax and lumbar traction (LTSMax strength tests in military judo athletes. Twenty-two military athletes from the judo team of the Brazilian Navy Almirante Alexandrino Instruction Centre, with average age of 26.14 ± 3.31 years old, and average body mass of 83.23 ± 14.14 kg participated in the study. Electronic dynamometry tests for HGSMax, STSMax and LTSMax were conducted. Then, after approximately 1 hour-interval, the SJFT protocol was applied. All variables were adjusted to the body mass of the athletes. Pearson correlation coefficient for statistical analysis was used. The results showed moderate negative correlation between the SJFT index and STSMax (r= -0.550, p= 0.008, strong negative correlations between the SJFT index and HGSMax (r= -0.706, p< 0.001, SJFT index and LTSMax (r= -0.721; p= 0.001, besides the correlation between the sum of the three maximum isometric strength tests and the SJFT index (r= -0.786, p< 0.001. This study concludes that negative correlations occur between the SJFT index and maximum isometric handgrip, shoulder and lumbar traction strength and the sum of the three maximum isometric strength tests in military judokas.

Statistical tests for power-law cross-correlated processes

Science.gov (United States)

Podobnik, Boris; Jiang, Zhi-Qiang; Zhou, Wei-Xing; Stanley, H. Eugene

2011-12-01

For stationary time series, the cross-covariance and the cross-correlation as functions of time lag n serve to quantify the similarity of two time series. The latter measure is also used to assess whether the cross-correlations are statistically significant. For nonstationary time series, the analogous measures are detrended cross-correlations analysis (DCCA) and the recently proposed detrended cross-correlation coefficient, ρDCCA(T,n), where T is the total length of the time series and n the window size. For ρDCCA(T,n), we numerically calculated the Cauchy inequality -1≤ρDCCA(T,n)≤1. Here we derive -1≤ρDCCA(T,n)≤1 for a standard variance-covariance approach and for a detrending approach. For overlapping windows, we find the range of ρDCCA within which the cross-correlations become statistically significant. For overlapping windows we numerically determine—and for nonoverlapping windows we derive—that the standard deviation of ρDCCA(T,n) tends with increasing T to 1/T. Using ρDCCA(T,n) we show that the Chinese financial market's tendency to follow the U.S. market is extremely weak. We also propose an additional statistical test that can be used to quantify the existence of cross-correlations between two power-law correlated time series.

Bunches of random cross-correlated sequences

International Nuclear Information System (INIS)

Maystrenko, A A; Melnik, S S; Pritula, G M; Usatenko, O V

2013-01-01

The statistical properties of random cross-correlated sequences constructed by the convolution method (likewise referred to as the Rice or the inverse Fourier transformation) are examined. We clarify the meaning of the filtering function—the kernel of the convolution operator—and show that it is the value of the cross-correlation function which describes correlations between the initial white noise and constructed correlated sequences. The matrix generalization of this method for constructing a bunch of N cross-correlated sequences is presented. Algorithms for their generation are reduced to solving the problem of decomposition of the Fourier transform of the correlation matrix into a product of two mutually conjugate matrices. Different decompositions are considered. The limits of weak and strong correlations for the one-point probability and pair correlation functions of sequences generated by the method under consideration are studied. Special cases of heavy-tailed distributions of the generated sequences are analyzed. We show that, if the filtering function is rather smooth, the distribution function of generated variables has the Gaussian or Lévy form depending on the analytical properties of the distribution (or characteristic) functions of the initial white noise. Anisotropic properties of statistically homogeneous random sequences related to the asymmetry of a filtering function are revealed and studied. These asymmetry properties are expressed in terms of the third- or fourth-order correlation functions. Several examples of the construction of correlated chains with a predefined correlation matrix are given. (paper)

Stochastic systems with cross-correlated Gaussian white noises

International Nuclear Information System (INIS)

Wang Cheng-Yu; Song Yu-Min; Zhou Peng; Yang Hai; Gao Yun

2010-01-01

This paper theoretically investigates three stochastic systems with cross-correlation Gaussian white noises. Both steady state properties of the stochastic nonlinear systems and the nonequilibrium transitions induced by the cross-correlated noises are studied. The stationary solutions of the Fokker—Planck equation for three specific examples are analysed. It is shown explicitly that the cross-correlation of white noises can induce nonequilibrium transitions

Cross-correlation of long-range correlated series

International Nuclear Information System (INIS)

Arianos, Sergio; Carbone, Anna

2009-01-01

A method for estimating the cross-correlation C xy (τ) of long-range correlated series x(t) and y(t), at varying lags τ and scales n, is proposed. For fractional Brownian motions with Hurst exponents H 1 and H 2 , the asymptotic expression for C xy (τ) depends only on the lag τ (wide-sense stationarity) and scales as a power of n with exponent H 1 +H 2 for τ→0. The method is illustrated on: (i) financial series, to show the leverage effect; (ii) genomic sequences, to estimate the correlations between structural parameters along the chromosomes

Signal Digitizer and Cross-Correlation Application Specific Integrated Circuit

Science.gov (United States)

Baranauskas, Dalius (Inventor); Baranauskas, Gytis (Inventor); Zelenin, Denis (Inventor); Kangaslahti, Pekka (Inventor); Tanner, Alan B. (Inventor); Lim, Boon H. (Inventor)

2017-01-01

According to one embodiment, a cross-correlator comprises a plurality of analog front ends (AFEs), a cross-correlation circuit and a data serializer. Each of the AFEs comprises a variable gain amplifier (VGA) and a corresponding analog-to-digital converter (ADC) in which the VGA receives and modifies a unique analog signal associates with a measured analog radio frequency (RF) signal and the ADC produces digital data associated with the modified analog signal. Communicatively coupled to the AFEs, the cross-correlation circuit performs a cross-correlation operation on the digital data produced from different measured analog RF signals. The data serializer is communicatively coupled to the summing and cross-correlating matrix and continuously outputs a prescribed amount of the correlated digital data.

Cross-correlation of instantaneous phase increments in pressure-flow fluctuations: Applications to cerebral autoregulation

Science.gov (United States)

Chen, Zhi; Hu, Kun; Stanley, H. Eugene; Novak, Vera; Ivanov, Plamen Ch.

2006-03-01

We investigate the relationship between the blood flow velocities (BFV) in the middle cerebral arteries and beat-to-beat blood pressure (BP) recorded from a finger in healthy and post-stroke subjects during the quasisteady state after perturbation for four different physiologic conditions: supine rest, head-up tilt, hyperventilation, and CO2 rebreathing in upright position. To evaluate whether instantaneous BP changes in the steady state are coupled with instantaneous changes in the BFV, we compare dynamical patterns in the instantaneous phases of these signals, obtained from the Hilbert transform, as a function of time. We find that in post-stroke subjects the instantaneous phase increments of BP and BFV exhibit well-pronounced patterns that remain stable in time for all four physiologic conditions, while in healthy subjects these patterns are different, less pronounced, and more variable. We propose an approach based on the cross-correlation of the instantaneous phase increments to quantify the coupling between BP and BFV signals. We find that the maximum correlation strength is different for the two groups and for the different conditions. For healthy subjects the amplitude of the cross-correlation between the instantaneous phase increments of BP and BFV is small and attenuates within 3-5 heartbeats. In contrast, for post-stroke subjects, this amplitude is significantly larger and cross-correlations persist up to 20 heartbeats. Further, we show that the instantaneous phase increments of BP and BFV are cross-correlated even within a single heartbeat cycle. We compare the results of our approach with three complementary methods: direct BP-BFV cross-correlation, transfer function analysis, and phase synchronization analysis. Our findings provide insight into the mechanism of cerebral vascular control in healthy subjects, suggesting that this control mechanism may involve rapid adjustments (within a heartbeat) of the cerebral vessels, so that BFV remains steady in

Results from transcranial Doppler examination on children and adolescents with sickle cell disease and correlation between the time-averaged maximum mean velocity and hematological characteristics: a cross-sectional analytical study

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Mary Hokazono

Full Text Available CONTEXT AND OBJECTIVE: Transcranial Doppler (TCD detects stroke risk among children with sickle cell anemia (SCA. Our aim was to evaluate TCD findings in patients with different sickle cell disease (SCD genotypes and correlate the time-averaged maximum mean (TAMM velocity with hematological characteristics. DESIGN AND SETTING: Cross-sectional analytical study in the Pediatric Hematology sector, Universidade Federal de São Paulo. METHODS: 85 SCD patients of both sexes, aged 2-18 years, were evaluated, divided into: group I (62 patients with SCA/Sß0 thalassemia; and group II (23 patients with SC hemoglobinopathy/Sß+ thalassemia. TCD was performed and reviewed by a single investigator using Doppler ultrasonography with a 2 MHz transducer, in accordance with the Stroke Prevention Trial in Sickle Cell Anemia (STOP protocol. The hematological parameters evaluated were: hematocrit, hemoglobin, reticulocytes, leukocytes, platelets and fetal hemoglobin. Univariate analysis was performed and Pearson's coefficient was calculated for hematological parameters and TAMM velocities (P < 0.05. RESULTS: TAMM velocities were 137 ± 28 and 103 ± 19 cm/s in groups I and II, respectively, and correlated negatively with hematocrit and hemoglobin in group I. There was one abnormal result (1.6% and five conditional results (8.1% in group I. All results were normal in group II. Middle cerebral arteries were the only vessels affected. CONCLUSION: There was a low prevalence of abnormal Doppler results in patients with sickle-cell disease. Time-average maximum mean velocity was significantly different between the genotypes and correlated with hematological characteristics.

Cross-correlation enhanced stability in a tumor cell growth model with immune surveillance driven by cross-correlated noises

International Nuclear Information System (INIS)

Zeng Chunhua; Zhou Xiaofeng; Tao Shufen

2009-01-01

The transient properties of a tumor cell growth model with immune surveillance driven by cross-correlated multiplicative and additive noises are investigated. The explicit expression of extinction rate from the state of a stable tumor to the state of extinction is obtained. Based on the numerical computations, we find the following: (i) the intensity of multiplicative noise D and the intensity of additive noise α enhance the extinction rate for the case of λ ≤ 0 (i.e. λ denotes cross-correlation intensity between two noises), but for the case of λ > 0, a critical noise intensity D or α exists at which the extinction rate is the smallest; D and α at first weaken the extinction rate and then enhance it. (ii) The immune rate β and the cross-correlation intensity λ play opposite roles on the extinction rate, i.e. β enhances the extinction rate of the tumor cell, while λ weakens the extinction rate of the tumor cell. Namely, the immune rate can enhance the extinction of the tumor cell and the cross-correlation between two noises can enhance stability of the cancer state.

Measuring time-of-flight in an ultrasonic LPS system using generalized cross-correlation.

Science.gov (United States)

Villladangos, José Manuel; Ureña, Jesús; García, Juan Jesús; Mazo, Manuel; Hernández, Alvaro; Jiménez, Ana; Ruíz, Daniel; De Marziani, Carlos

2011-01-01

In this article, a time-of-flight detection technique in the frequency domain is described for an ultrasonic local positioning system (LPS) based on encoded beacons. Beacon transmissions have been synchronized and become simultaneous by means of the DS-CDMA (direct-sequence code Division multiple access) technique. Every beacon has been associated to a 255-bit Kasami code. The detection of signal arrival instant at the receiver, from which the distance to each beacon can be obtained, is based on the application of the generalized cross-correlation (GCC), by using the cross-spectral density between the received signal and the sequence to be detected. Prior filtering to enhance the frequency components around the carrier frequency (40 kHz) has improved estimations when obtaining the correlation function maximum, which implies an improvement in distance measurement precision. Positioning has been achieved by using hyperbolic trilateration, based on the time differences of arrival (TDOA) between a reference beacon and the others.

Cross-correlation interference effects in multiaccess optical communications

Science.gov (United States)

Peterson, G. D.; Gardner, C. S.

1981-03-01

An analysis is presented of the cross correlation between user codes in an optical code-division multiple-access communication system. The system model is a multiaccess satellite repeater, where the uplink and downlink channels are direct-detection optical-polarization modulation links. The error probability is obtained in terms of the cross correlation between the intended and interfering user codes. It is demonstrated that the system error rate can be minimized by the use of code sequences in which the normalized second moment of the cross correlation between codes is small.

PyCCF: Python Cross Correlation Function for reverberation mapping studies

Science.gov (United States)

Sun, Mouyuan; Grier, C. J.; Peterson, B. M.

2018-05-01

PyCCF emulates a Fortran program written by B. Peterson for use with reverberation mapping. The code cross correlates two light curves that are unevenly sampled using linear interpolation and measures the peak and centroid of the cross-correlation function. In addition, it is possible to run Monto Carlo iterations using flux randomization and random subset selection (RSS) to produce cross-correlation centroid distributions to estimate the uncertainties in the cross correlation results.

Cross-correlations between RMB exchange rate and international commodity markets

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Lu, Xinsheng; Li, Jianfeng; Zhou, Ying; Qian, Yubo

2017-11-01

This paper employs multifractal detrended analysis (MF-DFA) and multifractal detrended cross-correlation analysis (MF-DCCA) to study cross-correlation behaviors between China's RMB exchange rate market and four international commodity markets, using a comprehensive set of data covering the period from 22 July 2005 to 15 March 2016. Our empirical results from MF-DFA indicate that the RMB exchange rate is the most inefficient among the 4 selected markets. The results from quantitative analysis have testified the existence of cross-correlations and the result from MF-DCCA have further confirmed a strong multifractal behavior between RMB exchange rate and international commodity markets. We also demonstrate that the recent financial crisis has significant impact on the cross-correlated behavior. Through the rolling window analysis, we find that the RMB exchange rates and international commodity prices are anti-persistent cross-correlated. The main sources of multifractality in the cross-correlations are long-range correlations between RMB exchange rate and the aggregate commodity, energy and metals index.

Two dimension MDW OCDMA code cross-correlation for reduction of phase induced intensity noise

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Sh. Ahmed Israa

2017-01-01

Full Text Available In this paper, we first review 2-D MDW code cross correlation equations and table to be improved significantly by using code correlation properties. These codes can be used in the synchronous optical CDMA systems for multi access interference cancellation and maximum suppress the phase induced intensity noise. Low Psr is due to the reduction of interference noise that is induced by the 2-D MDW code PIIN suppression. High data rate causes increases in BER, requires high effective power and severely deteriorates the system performance. The 2-D W/T MDW code has an excellent system performance where the value of PIIN is suppressed as low as possible at the optimum Psr with high data bit rate. The 2-D MDW code shows better tolerance to PIIN in comparison to others with enhanced system performance. We prove by numerical analysis that the PIIN maximally suppressed by MDW code through the minimizing property of cross correlation in comparison to 2-D PDC and 2-D MQC OCDMA code.scheme systems.

Two dimension MDW OCDMA code cross-correlation for reduction of phase induced intensity noise

Science.gov (United States)

Ahmed, Israa Sh.; Aljunid, Syed A.; Nordin, Junita M.; Dulaimi, Layth A. Khalil Al; Matem, Rima

2017-11-01

In this paper, we first review 2-D MDW code cross correlation equations and table to be improved significantly by using code correlation properties. These codes can be used in the synchronous optical CDMA systems for multi access interference cancellation and maximum suppress the phase induced intensity noise. Low Psr is due to the reduction of interference noise that is induced by the 2-D MDW code PIIN suppression. High data rate causes increases in BER, requires high effective power and severely deteriorates the system performance. The 2-D W/T MDW code has an excellent system performance where the value of PIIN is suppressed as low as possible at the optimum Psr with high data bit rate. The 2-D MDW code shows better tolerance to PIIN in comparison to others with enhanced system performance. We prove by numerical analysis that the PIIN maximally suppressed by MDW code through the minimizing property of cross correlation in comparison to 2-D PDC and 2-D MQC OCDMA code.scheme systems.

Strong anticipation and long-range cross-correlation: Application of detrended cross-correlation analysis to human behavioral data

Science.gov (United States)

Delignières, Didier; Marmelat, Vivien

2014-01-01

In this paper, we analyze empirical data, accounting for coordination processes between complex systems (bimanual coordination, interpersonal coordination, and synchronization with a fractal metronome), by using a recently proposed method: detrended cross-correlation analysis (DCCA). This work is motivated by the strong anticipation hypothesis, which supposes that coordination between complex systems is not achieved on the basis of local adaptations (i.e., correction, predictions), but results from a more global matching of complexity properties. Indeed, recent experiments have evidenced a very close correlation between the scaling properties of the series produced by two coordinated systems, despite a quite weak local synchronization. We hypothesized that strong anticipation should result in the presence of long-range cross-correlations between the series produced by the two systems. Results allow a detailed analysis of the effects of coordination on the fluctuations of the series produced by the two systems. In the long term, series tend to present similar scaling properties, with clear evidence of long-range cross-correlation. Short-term results strongly depend on the nature of the task. Simulation studies allow disentangling the respective effects of noise and short-term coupling processes on DCCA results, and suggest that the matching of long-term fluctuations could be the result of short-term coupling processes.

CROSS-CORRELATIONS AS A COSMOLOGICAL CARBON MONOXIDE DETECTOR

International Nuclear Information System (INIS)

Pullen, Anthony R.; Doré, Olivier; Chang, Tzu-Ching; Lidz, Adam

2013-01-01

We present a new procedure to measure the large-scale carbon monoxide (CO) emissions across cosmic history. As a tracer of large-scale structure (LSS), the CO gas content as a function of redshift can be quantified by its three-dimensional fluctuation power spectra. Furthermore, cross-correlating CO emission with other LSS tracers offers a way to measure the emission as a function of scale and redshift. Here we introduce the model relevant for such a cross-correlation measurement between CO and other LSS tracers, and between different CO rotational lines. We propose a novel use of cosmic microwave background (CMB) data and attempt to extract redshifted CO emissions embedded in the Wilkinson Microwave Anisotropy Probe (WMAP) data set. We cross-correlate the all-sky WMAP7 data with LSS data sets, namely, the photometric quasar sample and the luminous red galaxy sample from the Sloan Digital Sky Survey Data Releases 6 and 7, respectively. We are unable to detect a cross-correlation signal with either CO(1-0) or CO(2-1) lines, mainly due to the instrumental noise in the WMAP data. However, we are able to rule out models more than three times greater than our more optimistic model. We discuss the cross-correlation signal from the thermal Sunyaev-Zeldovich effect and dust as potential contaminants, and quantify their impact for our CO measurements. We discuss forecasts for current CMB experiments and a hypothetical future CO-focused experiment, and propose to cross-correlate CO temperature data with the Hobby-Eberly Telescope Dark Energy Experiment Lyα-emitter sample, for which a signal-to-noise ratio of 58 is possible.

Hidden crossing theory of charge exchange in H+ + He+(1 s) collisions in vicinity of maximum of cross section

Science.gov (United States)

Grozdanov, Tasko P.; Solov'ev, Evgeni A.

2018-04-01

Within the framework of dynamical adiabatic approach the hidden crossing theory of inelastic transitions is applied to charge exchange in H+ + He+(1 s) collisions in the wide range of center of mass collision energies E cm = (1.6 -70) keV. The good agreement with experiment and molecular close coupling calculations is obtained. At low energies our 4-state results are closest to the experiment and correctly reproduce the shoulder in energy dependence of the cross section around E cm = 6 keV. The 2-state results correctly predict the position of the maximum of the cross section at E cm ≈ 40 keV, whereas 4-state results fail to correctly describe the region around the maximum. The reason for this is the fact that adiabatic approximation for a given two-state hidden crossing is applicable for values of the Schtueckelberg parameter >1. But with increase of principal quantum number N the Schtueckelberg parameter decreases as N -3. That is why the 4-state approach involving higher excited states fails at smaller collision energies E cm ≈ 15 keV, while the 2-state approximation which involves low lying states can be extended to higher collision energies.

Cross-correlation time-of-flight analysis of molecular beam scattering

International Nuclear Information System (INIS)

Nowikow, C.V.; Grice, R.

1979-01-01

The theory of the cross-correlation method of time-of-flight analysis is presented in a form which highlights its formal similarity to the conventional method. A time-of-flight system for the analysis of crossed molecular beam scattering is described, which is based on a minicomputer interface and can operate in both the cross-correlation and conventional modes. The interface maintains the synchronisation of chopper disc rotation and channel advance indefinitely in the cross-correlation method and can acquire data in phase with the beam modulation in both methods. The shutter function of the cross-correlation method is determined and the deconvolution analysis of the data is discussed. (author)

Detecting PM2.5's Correlations between Neighboring Cities Using a Time-Lagged Cross-Correlation Coefficient.

Science.gov (United States)

Wang, Fang; Wang, Lin; Chen, Yuming

2017-08-31

In order to investigate the time-dependent cross-correlations of fine particulate (PM2.5) series among neighboring cities in Northern China, in this paper, we propose a new cross-correlation coefficient, the time-lagged q-L dependent height crosscorrelation coefficient (denoted by p q (τ, L)), which incorporates the time-lag factor and the fluctuation amplitude information into the analogous height cross-correlation analysis coefficient. Numerical tests are performed to illustrate that the newly proposed coefficient ρ q (τ, L) can be used to detect cross-correlations between two series with time lags and to identify different range of fluctuations at which two series possess cross-correlations. Applying the new coefficient to analyze the time-dependent cross-correlations of PM2.5 series between Beijing and the three neighboring cities of Tianjin, Zhangjiakou, and Baoding, we find that time lags between the PM2.5 series with larger fluctuations are longer than those between PM2.5 series withsmaller fluctuations. Our analysis also shows that cross-correlations between the PM2.5 series of two neighboring cities are significant and the time lags between two PM2.5 series of neighboring cities are significantly non-zero. These findings providenew scientific support on the view that air pollution in neighboring cities can affect one another not simultaneously but with a time lag.

Cross-correlations between agricultural commodity futures markets in the US and China

Science.gov (United States)

Li, Zhihui; Lu, Xinsheng

2012-08-01

This paper examines the cross-correlation properties of agricultural futures markets between the US and China using a cross-correlation statistic test and multifractal detrended cross-correlation analysis (MF-DCCA). The results show that the cross-correlations between the two geographically distant markets for four pairs of important agricultural commodities futures are significantly multifractal. By introducing the concept of a “crossover”, we find that the multifractality of cross-correlations between the two markets is not long lasting. The cross-correlations in the short term are more strongly multifractal, but they are weakly so in the long term. Moreover, cross-correlations of small fluctuations are persistent and those of large fluctuations are anti-persistent in the short term while cross-correlations of all kinds of fluctuations for soy bean and soy meal futures are persistent and for corn and wheat futures are anti-persistent in the long term. We also find that cross-correlation exponents are less than the averaged generalized Hurst exponent when q0 in the short term, while in the long term they are almost the same.

Speed Estimation in Geared Wind Turbines Using the Maximum Correlation Coefficient

DEFF Research Database (Denmark)

Skrimpas, Georgios Alexandros; Marhadi, Kun S.; Jensen, Bogi Bech

2015-01-01

to overcome the above mentioned issues. The high speed stage shaft angular velocity is calculated based on the maximum correlation coefficient between the 1 st gear mesh frequency of the last gearbox stage and a pure sinus tone of known frequency and phase. The proposed algorithm utilizes vibration signals...

Cross-correlations between Renminbi and four major currencies in the Renminbi currency basket

Science.gov (United States)

Wang, Gang-Jin; Xie, Chi

2013-03-01

We investigate the cross-correlations between Renminbi (CNY) and four major currencies (USD, EUR, JPY, and KRW) in the Renminbi currency basket, i.e., the cross-correlations of CNY-USD, CNY-EUR, CNY-JPY, and CNY-KRW. Qualitatively, using a statistical test in analogy to the Ljung-Box test, we find that cross-correlations significantly exist in CNY-USD, CNY-EUR, CNY-JPY, and CNY-KRW. Quantitatively, employing the detrended cross-correlation analysis (DCCA) method, we find that the cross-correlations of CNY-USD, CNY-EUR, CNY-JPY, and CNY-KRW are weakly persistent. We use the DCCA cross-correlation coefficient ρ to quantify the level of cross-correlations and find the currency weight in the Renminbi currency basket is arranged in the order of USD>EUR>JPY >KRW. Using the method of rolling windows, which can capture the time-varying cross-correlation scaling exponents, we find that: (i) CNY and USD are positively cross-correlated over time, but the cross-correlations of CNY-USD are anti-persistent during the US sub-prime crisis and the European debt crisis. (ii) The cross-correlation scaling exponents of CNY-EUR have the cyclical fluctuation with a nearly two-year cycle. (iii) CNY-JPY has long-term negative cross-correlations, during the European debt crisis, but CNY and KRW are positively cross-correlated.

Testing power-law cross-correlations: Rescaled covariance test

Czech Academy of Sciences Publication Activity Database

Krištoufek, Ladislav

2013-01-01

Roč. 86, č. 10 (2013), 418-1-418-15 ISSN 1434-6028 R&D Projects: GA ČR GA402/09/0965 Institutional support: RVO:67985556 Keywords : power-law cross-correlations * testing * long-term memory Subject RIV: AH - Economics Impact factor: 1.463, year: 2013 http://library.utia.cas.cz/separaty/2013/E/kristoufek-testing power-law cross-correlations rescaled covariance test.pdf

Evaluation of adaptation to visually induced motion sickness based on the maximum cross-correlation between pulse transmission time and heart rate

Directory of Open Access Journals (Sweden)

Chiba Shigeru

2007-09-01

Full Text Available Abstract Background Computer graphics and virtual reality techniques are useful to develop automatic and effective rehabilitation systems. However, a kind of virtual environment including unstable visual images presented to wide field screen or a head mounted display tends to induce motion sickness. The motion sickness induced in using a rehabilitation system not only inhibits effective training but also may harm patients' health. There are few studies that have objectively evaluated the effects of the repetitive exposures to these stimuli on humans. The purpose of this study is to investigate the adaptation to visually induced motion sickness by physiological data. Methods An experiment was carried out in which the same video image was presented to human subjects three times. We evaluated changes of the intensity of motion sickness they suffered from by a subjective score and the physiological index ρmax, which is defined as the maximum cross-correlation coefficient between heart rate and pulse wave transmission time and is considered to reflect the autonomic nervous activity. Results The results showed adaptation to visually-induced motion sickness by the repetitive presentation of the same image both in the subjective and the objective indices. However, there were some subjects whose intensity of sickness increased. Thus, it was possible to know the part in the video image which related to motion sickness by analyzing changes in ρmax with time. Conclusion The physiological index, ρmax, will be a good index for assessing the adaptation process to visually induced motion sickness and may be useful in checking the safety of rehabilitation systems with new image technologies.

Prevalence of mental illness among inmates at Mukobeko maximum security prison in Zambia: A cross-sectional study

Directory of Open Access Journals (Sweden)

Mweene T Mweene

2016-01-01

Full Text Available Objectives: The objective of this study is to determine the prevalence and sociodemographic correlates for mental illness among inmates at Mukobeko Maximum Security Prison, Zambia. Materials and Methods: A cross sectional study was conducted to assess psychiatric disturbance using a Self-Reported Questionnaire (SRQ20. A cut off point of 7/8 was used. The Chi-square test and Fishers′ exact test were used to determine associations at the 5% significance level, and magnitude of association was estimated using the odds ratio and its 95% confidence interval. Results: Of the 394 inmates in prison, 29.2% had a current mental illness. Gender status was significantly associated with mental illness. Male participants were 35% (odds ratio = 0.65, 95% confidence interval [0.51, 0.82] less likely to have mental illness compared to female participants. Conclusions: The prevalence of mental illness is high in Mukobeko Maximum Security Prison in Zambia. Gender-specific interventions should be designed to reduce the level of mental illness in this prison.

Cross-correlations between crude oil and exchange markets for selected oil rich economies

Science.gov (United States)

Li, Jianfeng; Lu, Xinsheng; Zhou, Ying

2016-07-01

Using multifractal detrended cross-correlation analysis (MF-DCCA), this paper studies the cross-correlation behavior between crude oil market and five selected exchange rate markets. The dataset covers the period of January 1,1996-December 31,2014, and contains 4,633 observations for each of the series, including daily closing prices of crude oil, Australian Dollars, Canadian Dollars, Mexican Pesos, Russian Rubles, and South African Rand. Our empirical results obtained from cross-correlation statistic and cross-correlation coefficient have confirmed the existence of cross-correlations, and the MF-DCCA results have demonstrated a strong multifractality between cross-correlated crude oil market and exchange rate markets in both short term and long term. Using rolling window analysis, we have also found the persistent cross-correlations between the exchange rates and crude oil returns, and the cross-correlation scaling exponents exhibit volatility during some time periods due to its sensitivity to sudden events.

General renormalized statistical approach with finite cross-field correlations

International Nuclear Information System (INIS)

Vakulenko, M.O.

1992-01-01

The renormalized statistical approach is proposed, accounting for finite correlations of potential and magnetic fluctuations. It may be used for analysis of a wide class of nonlinear model equations describing the cross-correlated plasma states. The influence of a cross spectrum on stationary potential and magnetic ones is investigated. 10 refs. (author)

Current cross-correlations in double quantum dot Cooper pair splitter

Energy Technology Data Exchange (ETDEWEB)

Wrzesniewski, Kacper; Trocha, Piotr; Weymann, Ireneusz [Faculty of Physics, Adam Mickiewicz University, 61-614 Poznan (Poland)

2016-07-01

We investigate theoretically transport properties of a quantum dot (QD) system working as a Cooper pair splitter. The device is coupled to one superconducting and two ferromagnetic leads. Presented results are calculated using real-time diagrammatic technique in the sequential tunneling approximation with respect to the coupling to ferromagnetic leads. The transport properties are evaluated within the superconductor subgap regime taking into account Andreev reflection processes solely. We focus on the analysis of current and current cross-correlations, both in linear and nonlinear responses. Current cross-correlations give additional information about dynamics of transport processes. We identify both positive and negative signs of current cross-correlations and discuss mechanisms leading to those results. Strong negative cross-correlations are found when the occupation number of QD system becomes degenerate and near the emergence of the triplet blockade, while positive ones occur in the most range where current flows due to crossed Andreev processes. Finally, we consider ferromagnetic leads polarization and temperature influences on aforementioned features.

The asymptotic behaviour of the maximum likelihood function of Kriging approximations using the Gaussian correlation function

CSIR Research Space (South Africa)

Kok, S

2012-07-01

Full Text Available continuously as the correlation function hyper-parameters approach zero. Since the global minimizer of the maximum likelihood function is an asymptote in this case, it is unclear if maximum likelihood estimation (MLE) remains valid. Numerical ill...

Stationary-phase integrals in the cross correlation of ambient noise

NARCIS (Netherlands)

Boschi, L.; Weemstra, C.

2015-01-01

The cross correlation of ambient signal allows seismologists to collect data even in the absence of seismic events. “Seismic interferometry” shows that the cross correlation of simultaneous recordings of a random wavefield made at two locations is formally related to the impulse response between

Image processing by use of the digital cross-correlator

International Nuclear Information System (INIS)

Katou, Yoshinori

1982-01-01

We manufactured for trial an instrument which achieved the image processing using digital correlators. A digital correlator perform 64-bit parallel correlation at 20 MH. The output of a digital correlator is a 7-bit word representing. An A-D converter is used to quantize it a precision of six bits. The resulting 6-bit word is fed to six correlators, wired in parallel. The image processing achieved in 12 bits, whose digital outputs converted an analog signal by a D-A converter. This instrument is named the digital cross-correlator. The method which was used in the image processing system calculated the convolution with the digital correlator. It makes various digital filters. In the experiment with the image processing video signals from TV camera were used. The digital image processing time was approximately 5 μs. The contrast was enhanced and smoothed. The digital cross-correlator has the image processing of 16 sorts, and was produced inexpensively. (author)

Detrended cross-correlation analysis on RMB exchange rate and Hang Seng China Enterprises Index

Science.gov (United States)

Ruan, Qingsong; Yang, Bingchan; Ma, Guofeng

2017-02-01

In this paper, we investigate the cross-correlations between the Hang Seng China Enterprises Index and RMB exchange markets on the basis of a cross-correlation statistic test and multifractal detrended cross-correlation analysis (MF-DCCA). MF-DCCA has, at best, serious limitations for most of the signals describing complex natural processes and often indicates multifractal cross-correlations when there are none. In order to prevent these false multifractal cross-correlations, we apply MFCCA to verify the cross-correlations. Qualitatively, we find that the return series of the Hang Seng China Enterprises Index and RMB exchange markets were, overall, significantly cross-correlated based on the statistical analysis. Quantitatively, we find that the cross-correlations between the stock index and RMB exchange markets were strongly multifractal, and the multifractal degree of the onshore RMB exchange markets was somewhat larger than the offshore RMB exchange markets. Moreover, we use the absolute return series to investigate and confirm the fact of multifractality. The results from the rolling windows show that the short-term cross-correlations between volatility series remain high.

Cross-correlation analysis of Ge/Li/ spectra

International Nuclear Information System (INIS)

MacDonald, R.; Robertson, A.; Kennett, T.J.; Prestwich, W.V.

1974-01-01

A sensitive technique is proposed for activation analysis using cross-correlation and improved spectral orthogonality achieved through use of a rectangular zero area digital filter. To test the accuracy and reliability of the cross-correlation procedure five spectra obtained with a Ge/Li detector were combined in different proportions. Gaussian distributed statistics were then added to the composite spectra by means of a pseudo-random number generator. The basis spectra used were 76 As, 82 Br, 72 Ga, 77 Ge, and room background. In general, when the basis spectra were combined in roughly comparable proportions the accuracy of the techique proved to be excelent (>1%). However, of primary importance was the ability of the correlation technique to identify low intensity components in the presence of high intensity components. It was found that the detection threshold for Ge, for example, was not reached until the Ge content in the unfiltered spectrum was <0.16%. (T.G.)

Quantifying the range of cross-correlated fluctuations using a q- L dependent AHXA coefficient

Science.gov (United States)

Wang, Fang; Wang, Lin; Chen, Yuming

2018-03-01

Recently, based on analogous height cross-correlation analysis (AHXA), a cross-correlation coefficient ρ×(L) has been proposed to quantify the levels of cross-correlation on different temporal scales for bivariate series. A limitation of this coefficient is that it cannot capture the full information of cross-correlations on amplitude of fluctuations. In fact, it only detects the cross-correlation at a specific order fluctuation, which might neglect some important information inherited from other order fluctuations. To overcome this disadvantage, in this work, based on the scaling of the qth order covariance and time delay L, we define a two-parameter dependent cross-correlation coefficient ρq(L) to detect and quantify the range and level of cross-correlations. This new version of ρq(L) coefficient leads to the formation of a ρq(L) surface, which not only is able to quantify the level of cross-correlations, but also allows us to identify the range of fluctuation amplitudes that are correlated in two given signals. Applications to the classical ARFIMA models and the binomial multifractal series illustrate the feasibility of this new coefficient ρq(L) . In addition, a statistical test is proposed to quantify the existence of cross-correlations between two given series. Applying our method to the real life empirical data from the 1999-2000 California electricity market, we find that the California power crisis in 2000 destroys the cross-correlation between the price and the load series but does not affect the correlation of the load series during and before the crisis.

Multifractal detrended Cross Correlation Analysis of Foreign Exchange and SENSEX fluctuation in Indian perspective

Science.gov (United States)

Dutta, Srimonti; Ghosh, Dipak; Chatterjee, Sucharita

2016-12-01

The manuscript studies autocorrelation and cross correlation of SENSEX fluctuations and Forex Exchange Rate in respect to Indian scenario. Multifractal detrended fluctuation analysis (MFDFA) and multifractal detrended cross correlation analysis (MFDXA) were employed to study the correlation between the two series. It was observed that the two series are strongly cross correlated. The change of degree of cross correlation with time was studied and the results are interpreted qualitatively.

Modeling CMB lensing cross correlations with CLEFT

Energy Technology Data Exchange (ETDEWEB)

Modi, Chirag; White, Martin [Department of Physics, University of California, Berkeley, CA 94720 (United States); Vlah, Zvonimir, E-mail: modichirag@berkeley.edu, E-mail: mwhite@berkeley.edu, E-mail: zvlah@stanford.edu [Stanford Institute for Theoretical Physics and Department of Physics, Stanford University, Stanford, CA 94306 (United States)

2017-08-01

A new generation of surveys will soon map large fractions of sky to ever greater depths and their science goals can be enhanced by exploiting cross correlations between them. In this paper we study cross correlations between the lensing of the CMB and biased tracers of large-scale structure at high z . We motivate the need for more sophisticated bias models for modeling increasingly biased tracers at these redshifts and propose the use of perturbation theories, specifically Convolution Lagrangian Effective Field Theory (CLEFT). Since such signals reside at large scales and redshifts, they can be well described by perturbative approaches. We compare our model with the current approach of using scale independent bias coupled with fitting functions for non-linear matter power spectra, showing that the latter will not be sufficient for upcoming surveys. We illustrate our ideas by estimating σ{sub 8} from the auto- and cross-spectra of mock surveys, finding that CLEFT returns accurate and unbiased results at high z . We discuss uncertainties due to the redshift distribution of the tracers, and several avenues for future development.

The effects of common risk factors on stock returns: A detrended cross-correlation analysis

Science.gov (United States)

Ruan, Qingsong; Yang, Bingchan

2017-10-01

In this paper, we investigate the cross-correlations between Fama and French three factors and the return of American industries on the basis of cross-correlation statistic test and multifractal detrended cross-correlation analysis (MF-DCCA). Qualitatively, we find that the return series of Fama and French three factors and American industries were overall significantly cross-correlated based on the analysis of a statistic. Quantitatively, we find that the cross-correlations between three factors and the return of American industries were strongly multifractal, and applying MF-DCCA we also investigate the cross-correlation of industry returns and residuals. We find that there exists multifractality of industry returns and residuals. The result of correlation coefficients we can verify that there exist other factors which influence the industry returns except Fama three factors.

Cross-Correlations between Energy and Emissions Markets: New Evidence from Fractal and Multifractal Analysis

Directory of Open Access Journals (Sweden)

Gang-Jin Wang

2014-01-01

Full Text Available We supply a new perspective to describe and understand the behavior of cross-correlations between energy and emissions markets. Namely, we investigate cross-correlations between oil and gas (Oil-Gas, oil and CO2 (Oil-CO2, and gas and CO2 (Gas-CO2 based on fractal and multifractal analysis. We focus our study on returns of the oil, gas, and CO2 during the period of April 22, 2005–April 30, 2013. In the empirical analysis, by using the detrended cross-correlation analysis (DCCA method, we find that cross-correlations for Oil-Gas, Oil-CO2, and Gas-CO2 obey a power-law and are weakly persistent. Then, we adopt the method of DCCA cross-correlation coefficient to quantify cross-correlations between energy and emissions markets. The results show that their cross-correlations are diverse at different time scales. Next, based on the multifractal DCCA method, we find that cross-correlated markets have the nonlinear and multifractal nature and that the multifractality strength for three cross-correlated markets is arranged in the order of Gas-CO2 > Oil-Gas > Oil-CO2. Finally, by employing the rolling windows method, which can be used to investigate time-varying cross-correlation scaling exponents, we analyze short-term and long-term market dynamics and find that the recent global financial crisis has a notable influence on short-term and long-term market dynamics.

Strong Solar Control of Infrared Aurora on Jupiter: Correlation Since the Last Solar Maximum

Science.gov (United States)

Kostiuk, T.; Livengood, T. A.; Hewagama, T.

2009-01-01

Polar aurorae in Jupiter's atmosphere radiate throughout the electromagnetic spectrum from X ray through mid-infrared (mid-IR, 5 - 20 micron wavelength). Voyager IRIS data and ground-based spectroscopic measurements of Jupiter's northern mid-IR aurora, acquired since 1982, reveal a correlation between auroral brightness and solar activity that has not been observed in Jovian aurora at other wavelengths. Over nearly three solar cycles, Jupiter auroral ethane emission brightness and solar 10.7 cm radio flux and sunspot number are positively correlated with high confidence. Ethane line emission intensity varies over tenfold between low and high solar activity periods. Detailed measurements have been made using the GSFC HIPWAC spectrometer at the NASA IRTF since the last solar maximum, following the mid-IR emission through the declining phase toward solar minimum. An even more convincing correlation with solar activity is evident in these data. Current analyses of these results will be described, including planned measurements on polar ethane line emission scheduled through the rise of the next solar maximum beginning in 2009, with a steep gradient to a maximum in 2012. This work is relevant to the Juno mission and to the development of the Europa Jupiter System Mission. Results of observations at the Infrared Telescope Facility (IRTF) operated by the University of Hawaii under Cooperative Agreement no. NCC5-538 with the National Aeronautics and Space Administration, Science Mission Directorate, Planetary Astronomy Program. This work was supported by the NASA Planetary Astronomy Program.

Stationary echo canceling in velocity estimation by time-domain cross-correlation

DEFF Research Database (Denmark)

Jensen, Jørgen Arendt

1993-01-01

The application of stationary echo canceling to ultrasonic estimation of blood velocities using time-domain cross-correlation is investigated. Expressions are derived that show the influence from the echo canceler on the signals that enter the cross-correlation estimator. It is demonstrated...

Volatility-constrained multifractal detrended cross-correlation analysis: Cross-correlation among Mainland China, US, and Hong Kong stock markets

Science.gov (United States)

Cao, Guangxi; Zhang, Minjia; Li, Qingchen

2017-04-01

This study focuses on multifractal detrended cross-correlation analysis of the different volatility intervals of Mainland China, US, and Hong Kong stock markets. A volatility-constrained multifractal detrended cross-correlation analysis (VC-MF-DCCA) method is proposed to study the volatility conductivity of Mainland China, US, and Hong Kong stock markets. Empirical results indicate that fluctuation may be related to important activities in real markets. The Hang Seng Index (HSI) stock market is more influential than the Shanghai Composite Index (SCI) stock market. Furthermore, the SCI stock market is more influential than the Dow Jones Industrial Average stock market. The conductivity between the HSI and SCI stock markets is the strongest. HSI was the most influential market in the large fluctuation interval of 1991 to 2014. The autoregressive fractionally integrated moving average method is used to verify the validity of VC-MF-DCCA. Results show that VC-MF-DCCA is effective.

Exploiting Cross Correlations and Joint Analyses

Energy Technology Data Exchange (ETDEWEB)

Rhodes, J. [Caltech; Allen, S. [SLAC; Benson, B. A. [Chicago U., Astron. Astrophys. Ctr.; Chang, T. [Taipei, Inst. Astron. Astrophys.; de Putter, R. [Caltech; Dodelson, S. [Chicago U., Astron. Astrophys. Ctr.; Doré, O. [Caltech; Honscheid, K. [Ohio State U., CCAPP; Linder, E. [UC, Berkeley; Ménard, B. [Tokyo U., IPMU; Newman, J. [Pittsburgh U.; Nord, B. [Fermilab; Rozo, E. [SLAC; Rykoff, E. [SLAC; Vallinotto, A. [LBL, Berkeley; Weinberg, D. [Ohio State U., CCAPP

2014-02-28

In this report, we present a wide variety of ways in which information from multiple probes of dark energy may be combined to obtain additional information not accessible when they are considered separately. Fundamentally, because all major probes are affected by the underlying distribution of matter in the regions studied, there exist covariances between them that can provide information on cosmology. Combining multiple probes allows for more accurate (less contaminated by systematics) and more precise (since there is cosmological information encoded in cross-correlation statistics) measurements of dark energy. The potential of cross-correlation methods is only beginning to be realized. By bringing in information from other wavelengths, the capabilities of the existing probes of dark energy can be enhanced and systematic effects can be mitigated further. We present a mixture of work in progress and suggestions for future scientific efforts. Given the scope of future dark energy experiments, the greatest gains may only be realized with more coordination and cooperation between multiple project teams; we recommend that this interchange should begin sooner, rather than later, to maximize scientific gains.

Pleasant/Unpleasant Filtering for Affective Image Retrieval Based on Cross-Correlation of EEG Features

Directory of Open Access Journals (Sweden)

Keranmu Xielifuguli

2014-01-01

Full Text Available People often make decisions based on sensitivity rather than rationality. In the field of biological information processing, methods are available for analyzing biological information directly based on electroencephalogram: EEG to determine the pleasant/unpleasant reactions of users. In this study, we propose a sensitivity filtering technique for discriminating preferences (pleasant/unpleasant for images using a sensitivity image filtering system based on EEG. Using a set of images retrieved by similarity retrieval, we perform the sensitivity-based pleasant/unpleasant classification of images based on the affective features extracted from images with the maximum entropy method: MEM. In the present study, the affective features comprised cross-correlation features obtained from EEGs produced when an individual observed an image. However, it is difficult to measure the EEG when a subject visualizes an unknown image. Thus, we propose a solution where a linear regression method based on canonical correlation is used to estimate the cross-correlation features from image features. Experiments were conducted to evaluate the validity of sensitivity filtering compared with image similarity retrieval methods based on image features. We found that sensitivity filtering using color correlograms was suitable for the classification of preferred images, while sensitivity filtering using local binary patterns was suitable for the classification of unpleasant images. Moreover, sensitivity filtering using local binary patterns for unpleasant images had a 90% success rate. Thus, we conclude that the proposed method is efficient for filtering unpleasant images.

Dynamic evolution of cross-correlations in the Chinese stock market.

Directory of Open Access Journals (Sweden)

Fei Ren

Full Text Available The analysis of cross-correlations is extensively applied for the understanding of interconnections in stock markets and the portfolio risk estimation. Current studies of correlations in Chinese market mainly focus on the static correlations between return series, and this calls for an urgent need to investigate their dynamic correlations. Our study aims to reveal the dynamic evolution of cross-correlations in the Chinese stock market, and offer an exact interpretation for the evolution behavior. The correlation matrices constructed from the return series of 367 A-share stocks traded on the Shanghai Stock Exchange from January 4, 1999 to December 30, 2011 are calculated over a moving window with a size of 400 days. The evolutions of the statistical properties of the correlation coefficients, eigenvalues, and eigenvectors of the correlation matrices are carefully analyzed. We find that the stock correlations are significantly increased in the periods of two market crashes in 2001 and 2008, during which only five eigenvalues significantly deviate from the random correlation matrix, and the systemic risk is higher in these volatile periods than calm periods. By investigating the significant contributors of the deviating eigenvectors in different time periods, we observe a dynamic evolution behavior in business sectors such as IT, electronics, and real estate, which lead the rise (drop before (after the crashes. Our results provide new perspectives for the understanding of the dynamic evolution of cross-correlations in the Chines stock markets, and the result of risk estimation is valuable for the application of risk management.

Dynamic evolution of cross-correlations in the Chinese stock market.

Science.gov (United States)

Ren, Fei; Zhou, Wei-Xing

2014-01-01

The analysis of cross-correlations is extensively applied for the understanding of interconnections in stock markets and the portfolio risk estimation. Current studies of correlations in Chinese market mainly focus on the static correlations between return series, and this calls for an urgent need to investigate their dynamic correlations. Our study aims to reveal the dynamic evolution of cross-correlations in the Chinese stock market, and offer an exact interpretation for the evolution behavior. The correlation matrices constructed from the return series of 367 A-share stocks traded on the Shanghai Stock Exchange from January 4, 1999 to December 30, 2011 are calculated over a moving window with a size of 400 days. The evolutions of the statistical properties of the correlation coefficients, eigenvalues, and eigenvectors of the correlation matrices are carefully analyzed. We find that the stock correlations are significantly increased in the periods of two market crashes in 2001 and 2008, during which only five eigenvalues significantly deviate from the random correlation matrix, and the systemic risk is higher in these volatile periods than calm periods. By investigating the significant contributors of the deviating eigenvectors in different time periods, we observe a dynamic evolution behavior in business sectors such as IT, electronics, and real estate, which lead the rise (drop) before (after) the crashes. Our results provide new perspectives for the understanding of the dynamic evolution of cross-correlations in the Chines stock markets, and the result of risk estimation is valuable for the application of risk management.

Cross-Correlation-Function-Based Multipath Mitigation Method for Sine-BOC Signals

Directory of Open Access Journals (Sweden)

H. H. Chen

2012-06-01

Full Text Available Global Navigation Satellite Systems (GNSS positioning accuracy indoor and urban canyons environments are greatly affected by multipath due to distortions in its autocorrelation function. In this paper, a cross-correlation function between the received sine phased Binary Offset Carrier (sine-BOC modulation signal and the local signal is studied firstly, and a new multipath mitigation method based on cross-correlation function for sine-BOC signal is proposed. This method is implemented to create a cross-correlation function by designing the modulated symbols of the local signal. The theoretical analysis and simulation results indicate that the proposed method exhibits better multipath mitigation performance compared with the traditional Double Delta Correlator (DDC techniques, especially the medium/long delay multipath signals, and it is also convenient and flexible to implement by using only one correlator, which is the case of low-cost mass-market receivers.

Cross Correlation versus Normalized Mutual Information on Image Registration

Science.gov (United States)

Tan, Bin; Tilton, James C.; Lin, Guoqing

2016-01-01

This is the first study to quantitatively assess and compare cross correlation and normalized mutual information methods used to register images in subpixel scale. The study shows that the normalized mutual information method is less sensitive to unaligned edges due to the spectral response differences than is cross correlation. This characteristic makes the normalized image resolution a better candidate for band to band registration. Improved band-to-band registration in the data from satellite-borne instruments will result in improved retrievals of key science measurements such as cloud properties, vegetation, snow and fire.

Detrended fluctuation analysis made flexible to detect range of cross-correlated fluctuations

Science.gov (United States)

Kwapień, Jarosław; Oświecimka, Paweł; DroŻdŻ, Stanisław

2015-11-01

The detrended cross-correlation coefficient ρDCCA has recently been proposed to quantify the strength of cross-correlations on different temporal scales in bivariate, nonstationary time series. It is based on the detrended cross-correlation and detrended fluctuation analyses (DCCA and DFA, respectively) and can be viewed as an analog of the Pearson coefficient in the case of the fluctuation analysis. The coefficient ρDCCA works well in many practical situations but by construction its applicability is limited to detection of whether two signals are generally cross-correlated, without the possibility to obtain information on the amplitude of fluctuations that are responsible for those cross-correlations. In order to introduce some related flexibility, here we propose an extension of ρDCCA that exploits the multifractal versions of DFA and DCCA: multifractal detrended fluctuation analysis and multifractal detrended cross-correlation analysis, respectively. The resulting new coefficient ρq not only is able to quantify the strength of correlations but also allows one to identify the range of detrended fluctuation amplitudes that are correlated in two signals under study. We show how the coefficient ρq works in practical situations by applying it to stochastic time series representing processes with long memory: autoregressive and multiplicative ones. Such processes are often used to model signals recorded from complex systems and complex physical phenomena like turbulence, so we are convinced that this new measure can successfully be applied in time-series analysis. In particular, we present an example of such application to highly complex empirical data from financial markets. The present formulation can straightforwardly be extended to multivariate data in terms of the q -dependent counterpart of the correlation matrices and then to the network representation.

Multifractal detrended cross-correlation analysis on gold, crude oil and foreign exchange rate time series

Science.gov (United States)

Pal, Mayukha; Madhusudana Rao, P.; Manimaran, P.

2014-12-01

We apply the recently developed multifractal detrended cross-correlation analysis method to investigate the cross-correlation behavior and fractal nature between two non-stationary time series. We analyze the daily return price of gold, West Texas Intermediate and Brent crude oil, foreign exchange rate data, over a period of 18 years. The cross correlation has been measured from the Hurst scaling exponents and the singularity spectrum quantitatively. From the results, the existence of multifractal cross-correlation between all of these time series is found. We also found that the cross correlation between gold and oil prices possess uncorrelated behavior and the remaining bivariate time series possess persistent behavior. It was observed for five bivariate series that the cross-correlation exponents are less than the calculated average generalized Hurst exponents (GHE) for q0 and for one bivariate series the cross-correlation exponent is greater than GHE for all q values.

Multiscale properties of DNA primary structure: cross-scale correlations

International Nuclear Information System (INIS)

Altajskij, M.V.; Ivanov, V.V.; Polozov, R.V.

2000-01-01

Cross-scale correlations of wavelet coefficients of the DNA coding sequences are calculated and compared to that of the generated random sequence of the same length. The coding sequences are shown to have strong correlation between large and small scale structures, while random sequences have not

DCCA cross-correlation coefficients reveals the change of both synchronization and oscillation in EEG of Alzheimer disease patients

Science.gov (United States)

Chen, Yingyuan; Cai, Lihui; Wang, Ruofan; Song, Zhenxi; Deng, Bin; Wang, Jiang; Yu, Haitao

2018-01-01

Alzheimer's disease (AD) is a degenerative disorder of neural system that affects mainly the older population. Recently, many researches show that the EEG of AD patients can be characterized by EEG slowing, enhanced complexity of the EEG signals, and EEG synchrony. In order to examine the neural synchrony at multi scales, and to find a biomarker that help detecting AD in diagnosis, detrended cross-correlation analysis (DCCA) of EEG signals is applied in this paper. Several parameters, namely DCCA coefficients in the whole brain, DCCA coefficients at a specific scale, maximum DCCA coefficient over the span of all time scales and the corresponding scale of such coefficients, were extracted to examine the synchronization, respectively. The results show that DCCA coefficients have a trend of increase as scale increases, and decreases as electrode distance increases. Comparing DCCA coefficients in AD patients with healthy controls, a decrease of synchronization in the whole brain, and a bigger scale corresponding to maximum correlation is discovered in AD patients. The change of max-correlation scale may relate to the slowing of oscillatory activities. Linear combination of max DCCA coefficient and max-correlation scale reaches a classification accuracy of 90%. From the above results, it is reasonable to conclude that DCCA coefficient reveals the change of both oscillation and synchrony in AD, and thus is a powerful tool to differentiate AD patients from healthy elderly individuals.

Hidden cross-correlation patterns in stock markets based on permutation cross-sample entropy and PCA

Science.gov (United States)

Lin, Aijing; Shang, Pengjian; Zhong, Bo

2014-12-01

In this article, we investigate the hidden cross-correlation structures in Chinese stock markets and US stock markets by performing PCSE combined with PCA approach. It is suggested that PCSE can provide a more faithful and more interpretable description of the dynamic mechanism between time series than cross-correlation matrix. We show that this new technique can be adapted to observe stock markets especially during financial crisis. In order to identify and compare the interactions and structures of stock markets during financial crisis, as well as in normal periods, all the samples are divided into four sub-periods. The results imply that the cross-correlations between Chinese group are stronger than the US group in the most sub-periods. In particular, it is likely that the US stock markets are more integrated with each other during global financial crisis than during Asian financial crisis. However, our results illustrate that Chinese stock markets are not immune from the global financial crisis, although less integrated with other markets if they are compared with US stock markets.

Cross-Correlation Asymmetries and Causal Relationships between Stock and Market Risk

Science.gov (United States)

Borysov, Stanislav S.; Balatsky, Alexander V.

2014-01-01

We study historical correlations and lead-lag relationships between individual stock risk (volatility of daily stock returns) and market risk (volatility of daily returns of a market-representative portfolio) in the US stock market. We consider the cross-correlation functions averaged over all stocks, using 71 stock prices from the Standard & Poor's 500 index for 1994–2013. We focus on the behavior of the cross-correlations at the times of financial crises with significant jumps of market volatility. The observed historical dynamics showed that the dependence between the risks was almost linear during the US stock market downturn of 2002 and after the US housing bubble in 2007, remaining at that level until 2013. Moreover, the averaged cross-correlation function often had an asymmetric shape with respect to zero lag in the periods of high correlation. We develop the analysis by the application of the linear response formalism to study underlying causal relations. The calculated response functions suggest the presence of characteristic regimes near financial crashes, when the volatility of an individual stock follows the market volatility and vice versa. PMID:25162697

Cross-correlation asymmetries and causal relationships between stock and market risk.

Science.gov (United States)

Borysov, Stanislav S; Balatsky, Alexander V

2014-01-01

We study historical correlations and lead-lag relationships between individual stock risk (volatility of daily stock returns) and market risk (volatility of daily returns of a market-representative portfolio) in the US stock market. We consider the cross-correlation functions averaged over all stocks, using 71 stock prices from the Standard & Poor's 500 index for 1994-2013. We focus on the behavior of the cross-correlations at the times of financial crises with significant jumps of market volatility. The observed historical dynamics showed that the dependence between the risks was almost linear during the US stock market downturn of 2002 and after the US housing bubble in 2007, remaining at that level until 2013. Moreover, the averaged cross-correlation function often had an asymmetric shape with respect to zero lag in the periods of high correlation. We develop the analysis by the application of the linear response formalism to study underlying causal relations. The calculated response functions suggest the presence of characteristic regimes near financial crashes, when the volatility of an individual stock follows the market volatility and vice versa.

Angle-correlated cross sections in the framework of the continuum shell model

International Nuclear Information System (INIS)

Moerschel, K.P.

1984-01-01

In the present thesis in the framework of the continuum shell modell a concept for the treatment of angle-correlated cross sections was developed by which coincidence experiments on electron scattering on nuclei are described. For this the existing Darmstadt continuum-shell-model code had to be extended to the calculation of the correlation coefficients in which nuclear dynamics enter and which determine completely the angle-correlated cross sections. Under inclusion of the kinematics a method for the integration over the scattered electron was presented and used for the comparison with corresponding experiments. As application correlation coefficients for the proton channel in 12 C with 1 - and 2 + excitations were studied. By means of these coefficients finally cross sections for the reaction 12 C (e,p) 11 B could be calculated and compared with the experiment whereby the developed methods were proved as suitable to predict correctly both the slope and the quantity of the experimental cross sections. (orig.) [de

The Dynamic Cross-Correlations between Mass Media News, New Media News, and Stock Returns

Directory of Open Access Journals (Sweden)

Zuochao Zhang

2018-01-01

Full Text Available We investigate the dynamic cross-correlations between mass media news, new media news, and stock returns for the SSE 50 Index in Chinese stock market by employing the MF-DCCA method. The empirical results show that (1 there exist power-law cross-correlations between two types of news as well as between news and its corresponding SSE 50 Index return; (2 the cross-correlations between mass media news and SSE 50 Index returns show larger multifractality and more complicated structures; (3 mass media news and new media news have both complementary and competitive relationships; (4 with the rolling window analysis, we further find that there is a general increasing trend for the cross-correlations between the two types of news as well as the cross-correlations between news and returns and this trend becomes more persistent over time.

Sodium boiling detection in LMFBRs by acoustic-neutronic cross correlation

International Nuclear Information System (INIS)

Wright, S.A.

1977-01-01

The acoustic and neutronic noise signals caused by boiling are the signals primarily considered likely to detect sodium boiling in an LMFBR. Unfortunately, these signals may have serious signal-to-noise problems due to strong background noise sources. Neutronic-acoustic cross correlation techniques are expected to provide a means of improving the signal-to-noise ratio. This technique can improve the signal-to-noise ratio because the neutronic and acoustic signals due to boiling are highly correlated near the bubble repetition frequency, while the background noise sources are expected to be uncorrelated (or at most weakly correlated). An experiment was designed to show that the neutronic and acoustic noise signals are indeed highly correlated. The experiment consisted of simulating the void and pressure effects of local sodium boiling in the core of a zero-power reactor (ARK). The analysis showed that the neutronic and acoustic noise signals caused by boiling are almost perfectly correlated in a wide frequency band about the bubble repetition frequency. The results of the experiments were generalized to full-scale reactors to compare the inherent effectiveness of the methods which use the neutronic or acoustic signals alone with a hybrid method, which cross correlates the neutronic and acoustic signals. It was concluded that over a zone of the reactor where the void coefficient is sufficiently large (approximately 85 percent the core volume), the cross correlation method can provide a more rapid detection system for a given signal-to-noise ratio. However, where the void coefficient is small, one must probably rely on the acoustic method alone

Needlet estimation of cross-correlation between CMB lensing maps and LSS

Energy Technology Data Exchange (ETDEWEB)

Bianchini, Federico [Astrophysics Sector, SISSA, Via Bonomea 265, I-34136 Trieste (Italy); Renzi, Alessandro; Marinucci, Domenico, E-mail: fbianchini@sissa.it, E-mail: renzi@mat.uniroma2.it, E-mail: marinucc@mat.uniroma2.it [Dipartimento di Matematica, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma (Italy)

2016-11-01

In this paper we develop a novel needlet-based estimator to investigate the cross-correlation between cosmic microwave background (CMB) lensing maps and large-scale structure (LSS) data. We compare this estimator with its harmonic counterpart and, in particular, we analyze the bias effects of different forms of masking. In order to address this bias, we also implement a MASTER-like technique in the needlet case. The resulting estimator turns out to have an extremely good signal-to-noise performance. Our analysis aims at expanding and optimizing the operating domains in CMB-LSS cross-correlation studies, similarly to CMB needlet data analysis. It is motivated especially by next generation experiments (such as Euclid) which will allow us to derive much tighter constraints on cosmological and astrophysical parameters through cross-correlation measurements between CMB and LSS.

Collapsing of multigroup cross sections in optimization problems solved by means of the maximum principle of Pontryagin

International Nuclear Information System (INIS)

Anton, V.

1979-05-01

A new formulation of multigroup cross section collapsing based on the conservation of point or zone value of hamiltonian is presented. This attempt is proper to optimization problems solved by means of maximum principle of Pontryagin. (author)

A comparison of maximum likelihood and other estimators of eigenvalues from several correlated Monte Carlo samples

International Nuclear Information System (INIS)

Beer, M.

1980-01-01

The maximum likelihood method for the multivariate normal distribution is applied to the case of several individual eigenvalues. Correlated Monte Carlo estimates of the eigenvalue are assumed to follow this prescription and aspects of the assumption are examined. Monte Carlo cell calculations using the SAM-CE and VIM codes for the TRX-1 and TRX-2 benchmark reactors, and SAM-CE full core results are analyzed with this method. Variance reductions of a few percent to a factor of 2 are obtained from maximum likelihood estimation as compared with the simple average and the minimum variance individual eigenvalue. The numerical results verify that the use of sample variances and correlation coefficients in place of the corresponding population statistics still leads to nearly minimum variance estimation for a sufficient number of histories and aggregates

The Atacama Cosmology Telescope: cross correlation with Planck maps

Energy Technology Data Exchange (ETDEWEB)

Louis, Thibaut; Calabrese, Erminia; Dunkley, Joanna; Næss, Sigurd [Department of Astrophysics, Oxford University, Oxford OX1 3RH (United Kingdom); Addison, Graeme E.; Hincks, Adam D. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z4 (Canada); Hasselfield, Matthew; Hlozek, Renée [Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544 (United States); Bond, J. Richard; Hajian, Amir [Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, ON M5S 3H8 (Canada); Das, Sudeep [Argonne National Laboratory, 9700 S. Cass Ave., Lemont, IL 60439 (United States); Devlin, Mark J. [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104, U.S.A (United States); Dünner, Rolando; Infante, Leopoldo [Departamento de Astronomía y Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22 (Chile); Gralla, Megan; Marriage, Tobias A. [Dept. of Physics and Astronomy, The Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218-2686 (United States); Huffenberger, Kevin [Department of Physics, Florida State University, Keen Physics Building, 77 Chieftan Way, Tallahassee, Florida (United States); Kosowsky, Arthur [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260 (United States); Moodley, Kavilan [Astrophysics and Cosmology Research Unit, School of Mathematical Sciences, University of KwaZulu-Natal, Durban, 4041 (South Africa); Niemack, Michael D., E-mail: Thibaut.Louis@astro.ox.ac.uk [Joseph Henry Laboratories of Physics, Jadwin Hall, Princeton University, Princeton, NJ 08544 (United States); and others

2014-07-01

We present the temperature power spectrum of the Cosmic Microwave Background obtained by cross-correlating maps from the Atacama Cosmology Telescope (ACT) at 148 and 218 GHz with maps from the Planck satellite at 143 and 217 GHz, in two overlapping regions covering 592 square degrees. We find excellent agreement between the two datasets at both frequencies, quantified using the variance of the residuals between the ACT power spectra and the ACT × Planck cross-spectra. We use these cross-correlations to measure the calibration of the ACT data at 148 and 218 GHz relative to Planck, to 0.7% and 2% precision respectively. We find no evidence for anisotropy in the calibration parameter. We compare the Planck 353 GHz power spectrum with the measured amplitudes of dust and cosmic infrared background (CIB) of ACT data at 148 and 218 GHz. We also compare planet and point source measurements from the two experiments.

Random matrix approach to cross correlations in financial data

Science.gov (United States)

Plerou, Vasiliki; Gopikrishnan, Parameswaran; Rosenow, Bernd; Amaral, Luís A.; Guhr, Thomas; Stanley, H. Eugene

2002-06-01

We analyze cross correlations between price fluctuations of different stocks using methods of random matrix theory (RMT). Using two large databases, we calculate cross-correlation matrices C of returns constructed from (i) 30-min returns of 1000 US stocks for the 2-yr period 1994-1995, (ii) 30-min returns of 881 US stocks for the 2-yr period 1996-1997, and (iii) 1-day returns of 422 US stocks for the 35-yr period 1962-1996. We test the statistics of the eigenvalues λi of C against a ``null hypothesis'' - a random correlation matrix constructed from mutually uncorrelated time series. We find that a majority of the eigenvalues of C fall within the RMT bounds [λ-,λ+] for the eigenvalues of random correlation matrices. We test the eigenvalues of C within the RMT bound for universal properties of random matrices and find good agreement with the results for the Gaussian orthogonal ensemble of random matrices-implying a large degree of randomness in the measured cross-correlation coefficients. Further, we find that the distribution of eigenvector components for the eigenvectors corresponding to the eigenvalues outside the RMT bound display systematic deviations from the RMT prediction. In addition, we find that these ``deviating eigenvectors'' are stable in time. We analyze the components of the deviating eigenvectors and find that the largest eigenvalue corresponds to an influence common to all stocks. Our analysis of the remaining deviating eigenvectors shows distinct groups, whose identities correspond to conventionally identified business sectors. Finally, we discuss applications to the construction of portfolios of stocks that have a stable ratio of risk to return.

The cross-correlation analysis of multi property of stock markets based on MM-DFA

Science.gov (United States)

Yang, Yujun; Li, Jianping; Yang, Yimei

2017-09-01

In this paper, we propose a new method called DH-MXA based on distribution histograms of Hurst surface and multiscale multifractal detrended fluctuation analysis. The method allows us to investigate the cross-correlation characteristics among multiple properties of different stock time series. It may provide a new way of measuring the nonlinearity of several signals. It also can provide a more stable and faithful description of cross-correlation of multiple properties of stocks. The DH-MXA helps us to present much richer information than multifractal detrented cross-correlation analysis and allows us to assess many universal and subtle cross-correlation characteristics of stock markets. We show DH-MXA by selecting four artificial data sets and five properties of four stock time series from different countries. The results show that our proposed method can be adapted to investigate the cross-correlation of stock markets. In general, the American stock markets are more mature and less volatile than the Chinese stock markets.

Detrended partial cross-correlation analysis of two nonstationary time series influenced by common external forces

Science.gov (United States)

Qian, Xi-Yuan; Liu, Ya-Min; Jiang, Zhi-Qiang; Podobnik, Boris; Zhou, Wei-Xing; Stanley, H. Eugene

2015-06-01

When common factors strongly influence two power-law cross-correlated time series recorded in complex natural or social systems, using detrended cross-correlation analysis (DCCA) without considering these common factors will bias the results. We use detrended partial cross-correlation analysis (DPXA) to uncover the intrinsic power-law cross correlations between two simultaneously recorded time series in the presence of nonstationarity after removing the effects of other time series acting as common forces. The DPXA method is a generalization of the detrended cross-correlation analysis that takes into account partial correlation analysis. We demonstrate the method by using bivariate fractional Brownian motions contaminated with a fractional Brownian motion. We find that the DPXA is able to recover the analytical cross Hurst indices, and thus the multiscale DPXA coefficients are a viable alternative to the conventional cross-correlation coefficient. We demonstrate the advantage of the DPXA coefficients over the DCCA coefficients by analyzing contaminated bivariate fractional Brownian motions. We calculate the DPXA coefficients and use them to extract the intrinsic cross correlation between crude oil and gold futures by taking into consideration the impact of the U.S. dollar index. We develop the multifractal DPXA (MF-DPXA) method in order to generalize the DPXA method and investigate multifractal time series. We analyze multifractal binomial measures masked with strong white noises and find that the MF-DPXA method quantifies the hidden multifractal nature while the multifractal DCCA method fails.

The q-dependent detrended cross-correlation analysis of stock market

Science.gov (United States)

Zhao, Longfeng; Li, Wei; Fenu, Andrea; Podobnik, Boris; Wang, Yougui; Stanley, H. Eugene

2018-02-01

Properties of the q-dependent cross-correlation matrices of the stock market have been analyzed by using random matrix theory and complex networks. The correlation structures of the fluctuations at different magnitudes have unique properties. The cross-correlations among small fluctuations are much stronger than those among large fluctuations. The large and small fluctuations are dominated by different groups of stocks. We use complex network representation to study these q-dependent matrices and discover some new identities. By utilizing those q-dependent correlation-based networks, we are able to construct some portfolios of those more independent stocks which consistently perform better. The optimal multifractal order for portfolio optimization is around q  =  2 under the mean-variance portfolio framework, and q\\in[2, 6] under the expected shortfall criterion. These results have deepened our understanding regarding the collective behavior of the complex financial system.

Structure of a financial cross-correlation matrix under attack

Science.gov (United States)

Lim, Gyuchang; Kim, SooYong; Kim, Junghwan; Kim, Pyungsoo; Kang, Yoonjong; Park, Sanghoon; Park, Inho; Park, Sang-Bum; Kim, Kyungsik

2009-09-01

We investigate the structure of a perturbed stock market in terms of correlation matrices. For the purpose of perturbing a stock market, two distinct methods are used, namely local and global perturbation. The former involves replacing a correlation coefficient of the cross-correlation matrix with one calculated from two Gaussian-distributed time series while the latter reconstructs the cross-correlation matrix just after replacing the original return series with Gaussian-distributed time series. Concerning the local case, it is a technical study only and there is no attempt to model reality. The term ‘global’ means the overall effect of the replacement on other untouched returns. Through statistical analyses such as random matrix theory (RMT), network theory, and the correlation coefficient distributions, we show that the global structure of a stock market is vulnerable to perturbation. However, apart from in the analysis of inverse participation ratios (IPRs), the vulnerability becomes dull under a small-scale perturbation. This means that these analysis tools are inappropriate for monitoring the whole stock market due to the low sensitivity of a stock market to a small-scale perturbation. In contrast, when going down to the structure of business sectors, we confirm that correlation-based business sectors are regrouped in terms of IPRs. This result gives a clue about monitoring the effect of hidden intentions, which are revealed via portfolios taken mostly by large investors.

CROSS-CORRELATION MODELLING OF SURFACE WATER – GROUNDWATER INTERACTION USING THE EXCEL SPREADSHEET APPLICATION

Directory of Open Access Journals (Sweden)

Kristijan Posavec

2017-01-01

Full Text Available Modelling responses of groundwater levels in aquifer systems, which occur as a reaction to changes in aquifer system boundary conditions such as river or stream stages, is commonly being studied using statistical methods, namely correlation, cross-correlation and regression methods. Although correlation and regression analysis tools are readily available in Microsoft Excel, a widely applied spreadsheet industry standard, the cross-correlation analysis tool is missing. As a part of research of groundwater pressure propagation into alluvial aquifer systems of the Sava and Drava/Danube River catchments following river stages rise, focused on estimating groundwater pressure travel times in aquifers, an Excel spreadsheet data analysis application for cross-correlation modelling has been designed and used in modelling surface water – groundwater interaction. Examples of fi eld data from the Zagreb aquifer system and the Kopački rit Nature Park aquifer system are used to illustrate the usefulness of the cross-correlation application.

A 32-channel photon counting module with embedded auto/cross-correlators for real-time parallel fluorescence correlation spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Gong, S.; Labanca, I.; Rech, I.; Ghioni, M. [Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy)

2014-10-15

Fluorescence correlation spectroscopy (FCS) is a well-established technique to study binding interactions or the diffusion of fluorescently labeled biomolecules in vitro and in vivo. Fast FCS experiments require parallel data acquisition and analysis which can be achieved by exploiting a multi-channel Single Photon Avalanche Diode (SPAD) array and a corresponding multi-input correlator. This paper reports a 32-channel FPGA based correlator able to perform 32 auto/cross-correlations simultaneously over a lag-time ranging from 10 ns up to 150 ms. The correlator is included in a 32 × 1 SPAD array module, providing a compact and flexible instrument for high throughput FCS experiments. However, some inherent features of SPAD arrays, namely afterpulsing and optical crosstalk effects, may introduce distortions in the measurement of auto- and cross-correlation functions. We investigated these limitations to assess their impact on the module and evaluate possible workarounds.

A 32-channel photon counting module with embedded auto/cross-correlators for real-time parallel fluorescence correlation spectroscopy

International Nuclear Information System (INIS)

Gong, S.; Labanca, I.; Rech, I.; Ghioni, M.

2014-01-01

Fluorescence correlation spectroscopy (FCS) is a well-established technique to study binding interactions or the diffusion of fluorescently labeled biomolecules in vitro and in vivo. Fast FCS experiments require parallel data acquisition and analysis which can be achieved by exploiting a multi-channel Single Photon Avalanche Diode (SPAD) array and a corresponding multi-input correlator. This paper reports a 32-channel FPGA based correlator able to perform 32 auto/cross-correlations simultaneously over a lag-time ranging from 10 ns up to 150 ms. The correlator is included in a 32 × 1 SPAD array module, providing a compact and flexible instrument for high throughput FCS experiments. However, some inherent features of SPAD arrays, namely afterpulsing and optical crosstalk effects, may introduce distortions in the measurement of auto- and cross-correlation functions. We investigated these limitations to assess their impact on the module and evaluate possible workarounds

Cross-correlations in volume space: Differences between buy and sell volumes

Science.gov (United States)

Lee, Sun Young; Hwang, Dong Il; Kim, Min Jae; Koh, In Gyu; Kim, Soo Yong

2011-03-01

We study the cross-correlations of buy and sell volumes on the Korean stock market in high frequency. We observe that the pulling effects of volumes are as small as that of returns. The properties of the correlations of buy and sell volumes differ. They are explained by the degree of synchronization of stock volumes. Further, the pulling effects on the minimal spanning tree are studied. In minimal spanning trees with directed links, the large pulling effects are clustered at the center, not uniformly distributed. The Epps effect of buy and sell volumes are observed. The reversal of the cross-correlations of buy and sell volumes is also detected.

Study of water flowrate using time transient and cross-correlation techniques with 82Br radiotracer

International Nuclear Information System (INIS)

Salgado, William L.; Brandao, Luiz E.B.

2013-01-01

This paper aims to determinate the water flowrate using Time Transient and Cross-Correlation techniques. The detection system uses two NaI (T1) detectors adequately positioned on the outside of pipe and a gamma-ray source ( 82 Br radiotracer). The water flowrate measurements using Time Transient and Cross-Correlation techniques were compared to invasive conventional measurements of the flowrate previously installed in pipeline. Discrepancies between Time Transient and Cross-Correlation techniques flowmeter previously installed in pipeline. Discrepancies between Time Transient and Cross-Correlation techniques flowrate values were found to be less than 3% in relation to conventional ones. (author)

Autocorrelation and cross-correlation in time series of homicide and attempted homicide

Science.gov (United States)

Machado Filho, A.; da Silva, M. F.; Zebende, G. F.

2014-04-01

We propose in this paper to establish the relationship between homicides and attempted homicides by a non-stationary time-series analysis. This analysis will be carried out by Detrended Fluctuation Analysis (DFA), Detrended Cross-Correlation Analysis (DCCA), and DCCA cross-correlation coefficient, ρ(n). Through this analysis we can identify a positive cross-correlation between homicides and attempted homicides. At the same time, looked at from the point of view of autocorrelation (DFA), this analysis can be more informative depending on time scale. For short scale (days), we cannot identify auto-correlations, on the scale of weeks DFA presents anti-persistent behavior, and for long time scales (n>90 days) DFA presents a persistent behavior. Finally, the application of this new type of statistical analysis proved to be efficient and, in this sense, this paper can contribute to a more accurate descriptive statistics of crime.

World currency exchange rate cross-correlations

Science.gov (United States)

Droå¼dż, S.; Górski, A. Z.; Kwapień, J.

2007-08-01

World currency network constitutes one of the most complex structures that is associated with the contemporary civilization. On a way towards quantifying its characteristics we study the cross correlations in changes of the daily foreign exchange rates within the basket of 60 currencies in the period December 1998 May 2005. Such a dynamics turns out to predominantly involve one outstanding eigenvalue of the correlation matrix. The magnitude of this eigenvalue depends however crucially on which currency is used as a base currency for the remaining ones. Most prominent it looks from the perspective of a peripheral currency. This largest eigenvalue is seen to systematically decrease and thus the structure of correlations becomes more heterogeneous, when more significant currencies are used as reference. An extreme case in this later respect is the USD in the period considered. Besides providing further insight into subtle nature of complexity, these observations point to a formal procedure that in general can be used for practical purposes of measuring the relative currencies significance on various time horizons.

Spectral density analysis of time correlation functions in lattice QCD using the maximum entropy method

International Nuclear Information System (INIS)

Fiebig, H. Rudolf

2002-01-01

We study various aspects of extracting spectral information from time correlation functions of lattice QCD by means of Bayesian inference with an entropic prior, the maximum entropy method (MEM). Correlator functions of a heavy-light meson-meson system serve as a repository for lattice data with diverse statistical quality. Attention is given to spectral mass density functions, inferred from the data, and their dependence on the parameters of the MEM. We propose to employ simulated annealing, or cooling, to solve the Bayesian inference problem, and discuss the practical issues of the approach

Audio Quality Assurance : An Application of Cross Correlation

DEFF Research Database (Denmark)

Jurik, Bolette Ammitzbøll; Nielsen, Jesper Asbjørn Sindahl

2012-01-01

We describe algorithms for automated quality assurance on content of audio files in context of preservation actions and access. The algorithms use cross correlation to compare the sound waves. They are used to do overlap analysis in an access scenario, where preserved radio broadcasts are used in...

Nonreciprocal Green’s function retrieval by cross correlation

NARCIS (Netherlands)

Wapenaar, C.P.A.

2006-01-01

The cross correlation of two recordings of a diffuse acoustic wave field at different receivers yields the Green’s function between these receivers. In nearly all cases considered so far the wave equation obeys time-reversal invariance and the Green’s function obeys source-receiver reciprocity. Here

CROSS-CORRELATION BETWEEN X-RAY AND OPTICAL/NEAR-INFRARED BACKGROUND INTENSITY FLUCTUATIONS

Energy Technology Data Exchange (ETDEWEB)

Mitchell-Wynne, Ketron; Cooray, Asantha [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Xue, Yongquan [CAS Key Laboratory for Researches in Galaxies and Cosmology, Center for Astrophysics, Department of Astronomy, University of Science and Technology of China, Chinese Academy of Sciences, Hefei, Anhui 230026 (China); Luo, Bin [School of Astronomy and Space Science, Nanjing University, Nanjing, 210093 (China); Brandt, William [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA, 16802 (United States); Koekemoer, Anton [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

2016-12-01

Angular power spectra of optical and infrared background anisotropies at wavelengths between 0.5 and 5 μ m are a useful probe of faint sources present during reionization, in addition to faint galaxies and diffuse signals at low redshift. The cross-correlation of these fluctuations with backgrounds at other wavelengths can be used to separate some of these signals. A previous study on the cross-correlation between X-ray and Spitzer fluctuations at 3.6 μ m and 4.5 μ m has been interpreted as evidence for direct collapse black holes present at z  > 12. Here we return to this cross-correlation and study its wavelength dependence from 0.5 to 4.5 μ m using Hubble and Spitzer data in combination with a subset of the 4 Ms Chandra observations in GOODS-S/ECDFS. Our study involves five Hubble bands at 0.6, 0.7, 0.85, 1.25, and 1.6 μ m, and two Spitzer -IRAC bands at 3.6 μ m and 4.5 μ m. We confirm the previously seen cross-correlation between 3.6 μ m (4.5 μ m) and X-rays with 3.7 σ (4.2 σ ) and 2.7 σ (3.7 σ ) detections in the soft [0.5–2] keV and hard [2–8] keV X-ray bands, respectively, at angular scales above 20 arcsec. The cross-correlation of X-rays with Hubble is largely anticorrelated, ranging between the levels of 1.4 σ –3.5 σ for all the Hubble and X-ray bands. This lack of correlation in the shorter optical/NIR bands implies the sources responsible for the cosmic infrared background at 3.6 and 4.5 μ m are at least partly dissimilar to those at 1.6 μ m and shorter.

Corrections for frequency domain transformations of Winfrith binary cross correlator responses

International Nuclear Information System (INIS)

Cummins, J.D.

1968-04-01

This report considers the corrections for frequency domain transformations of Winfrith binary cross correlator responses; (i) for the finite bandwidth of the equivalent input signal; (2) for the finite time required for the actuator to move between the two positions appropriate to the two levels of the periodic binary chain code input and (3) for the averaging of experimental determinations of the system frequency response and calculations of the standard deviations of the modulus and phase of the frequency responses determined from the cross correlator responses. (author)

Perspectives of Cross-Correlation in Seismic Monitoring at the International Data Centre

Science.gov (United States)

Bobrov, Dmitry; Kitov, Ivan; Zerbo, Lassina

2014-03-01

We demonstrate that several techniques based on waveform cross-correlation are able to significantly reduce the detection threshold of seismic sources worldwide and to improve the reliability of arrivals by a more accurate estimation of their defining parameters. A master event and the events it can find using waveform cross-correlation at array stations of the International Monitoring System (IMS) have to be close. For the purposes of the International Data Centre (IDC), one can use the spatial closeness of the master and slave events in order to construct a new automatic processing pipeline: all qualified arrivals detected using cross-correlation are associated with events matching the current IDC event definition criteria (EDC) in a local association procedure. Considering the repeating character of global seismicity, more than 90 % of events in the reviewed event bulletin (REB) can be built in this automatic processing. Due to the reduced detection threshold, waveform cross-correlation may increase the number of valid REB events by a factor of 1.5-2.0. Therefore, the new pipeline may produce a more comprehensive bulletin than the current pipeline—the goal of seismic monitoring. The analysts' experience with the cross correlation event list (XSEL) shows that the workload of interactive processing might be reduced by a factor of two or even more. Since cross-correlation produces a comprehensive list of detections for a given master event, no additional arrivals from primary stations are expected to be associated with the XSEL events. The number of false alarms, relative to the number of events rejected from the standard event list 3 (SEL3) in the current interactive processing—can also be reduced by the use of several powerful filters. The principal filter is the difference between the arrival times of the master and newly built events at three or more primary stations, which should lie in a narrow range of a few seconds. In this study, one event at a

Positive Noise Cross Correlation in a Copper Pair Splitter.

Science.gov (United States)

Das, Anindya; Ronen, Yuval; Heiblum, Moty; Shtrikman, Hadas; Mahalu, Diana

2012-02-01

Entanglement is in heart of the Einstein-Podolsky-Rosen (EPR) paradox, in which non-locality is a fundamental property. Up to date spin entanglement of electrons had not been demonstrated. Here, we provide direct evidence of such entanglement by measuring: non-local positive current correlation and positive cross correlation among current fluctuations, both of separated electrons born by a Cooper-pair-beam-splitter. The realization of the splitter is provided by injecting current from an Al superconductor contact into two, single channel, pure InAs nanowires - each intercepted by a Coulomb blockaded quantum dot (QD). The QDs impedes strongly the flow of Cooper pairs allowing easy single electron transport. The passage of electron in one wire enables the simultaneous passage of the other in the neighboring wire. The splitting efficiency of the Cooper pairs (relative to Cooper pairs actual current) was found to be ˜ 40%. The positive cross-correlations in the currents and their fluctuations (shot noise) are fully consistent with entangled electrons produced by the beam splitter.

A novel fast phase correlation algorithm for peak wavelength detection of Fiber Bragg Grating sensors.

Science.gov (United States)

Lamberti, A; Vanlanduit, S; De Pauw, B; Berghmans, F

2014-03-24

Fiber Bragg Gratings (FBGs) can be used as sensors for strain, temperature and pressure measurements. For this purpose, the ability to determine the Bragg peak wavelength with adequate wavelength resolution and accuracy is essential. However, conventional peak detection techniques, such as the maximum detection algorithm, can yield inaccurate and imprecise results, especially when the Signal to Noise Ratio (SNR) and the wavelength resolution are poor. Other techniques, such as the cross-correlation demodulation algorithm are more precise and accurate but require a considerable higher computational effort. To overcome these problems, we developed a novel fast phase correlation (FPC) peak detection algorithm, which computes the wavelength shift in the reflected spectrum of a FBG sensor. This paper analyzes the performance of the FPC algorithm for different values of the SNR and wavelength resolution. Using simulations and experiments, we compared the FPC with the maximum detection and cross-correlation algorithms. The FPC method demonstrated a detection precision and accuracy comparable with those of cross-correlation demodulation and considerably higher than those obtained with the maximum detection technique. Additionally, FPC showed to be about 50 times faster than the cross-correlation. It is therefore a promising tool for future implementation in real-time systems or in embedded hardware intended for FBG sensor interrogation.

Correlation between maximum phonetically balanced word recognition score and pure-tone auditory threshold in elder presbycusis patients over 80 years old.

Science.gov (United States)

Deng, Xin-Sheng; Ji, Fei; Yang, Shi-Ming

2014-02-01

The maximum phonetically balanced word recognition score (PBmax) showed poor correlation with pure-tone thresholds in presbycusis patients older than 80 years. To study the characteristics of monosyllable recognition in presbycusis patients older than 80 years of age. Thirty presbycusis patients older than 80 years were included as the test group (group 80+). Another 30 patients aged 60-80 years were selected as the control group (group 80-) . PBmax was tested by Mandarin monosyllable recognition test materials with the signal level at 30 dB above the averaged thresholds of 0.5, 1, 2, and 4 kHz (4FA) or the maximum comfortable level. The PBmax values of the test group and control group were compared with each other and the correlation between PBmax and predicted maximum speech recognition scores based on 4FA (PBmax-predict) were statistically analyzed. Under the optimal test conditions, the averaged PBmax was (77.3 ± 16.7) % for group 80- and (52.0 ± 25.4) % for group 80+ (p < 0.001). The PBmax of group 80- was significantly correlated with PBmax-predict (Spearman correlation = 0.715, p < 0.001). The score for group 80+ was less statistically correlated with PBmax-predict (Spearman correlation = 0.572, p = 0.001).

Nonlinear Analysis on Cross-Correlation of Financial Time Series by Continuum Percolation System

Science.gov (United States)

Niu, Hongli; Wang, Jun

We establish a financial price process by continuum percolation system, in which we attribute price fluctuations to the investors’ attitudes towards the financial market, and consider the clusters in continuum percolation as the investors share the same investment opinion. We investigate the cross-correlations in two return time series, and analyze the multifractal behaviors in this relationship. Further, we study the corresponding behaviors for the real stock indexes of SSE and HSI as well as the liquid stocks pair of SPD and PAB by comparison. To quantify the multifractality in cross-correlation relationship, we employ multifractal detrended cross-correlation analysis method to perform an empirical research for the simulation data and the real markets data.

Cross-correlation of weak lensing and gamma rays: implications for the nature of dark matter

Science.gov (United States)

Tröster, Tilman; Camera, Stefano; Fornasa, Mattia; Regis, Marco; van Waerbeke, Ludovic; Harnois-Déraps, Joachim; Ando, Shin'ichiro; Bilicki, Maciej; Erben, Thomas; Fornengo, Nicolao; Heymans, Catherine; Hildebrandt, Hendrik; Hoekstra, Henk; Kuijken, Konrad; Viola, Massimo

2017-05-01

We measure the cross-correlation between Fermi gamma-ray photons and over 1000 deg2 of weak lensing data from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS), the Red Cluster Sequence Lensing Survey (RCSLenS), and the Kilo Degree Survey (KiDS). We present the first measurement of tomographic weak lensing cross-correlations and the first application of spectral binning to cross-correlations between gamma rays and weak lensing. The measurements are performed using an angular power spectrum estimator while the covariance is estimated using an analytical prescription. We verify the accuracy of our covariance estimate by comparing it to two internal covariance estimators. Based on the non-detection of a cross-correlation signal, we derive constraints on weakly interacting massive particle (WIMP) dark matter. We compute exclusion limits on the dark matter annihilation cross-section , decay rate Γdec and particle mass mDM. We find that in the absence of a cross-correlation signal, tomography does not significantly improve the constraining power of the analysis. Assuming a strong contribution to the gamma-ray flux due to small-scale clustering of dark matter and accounting for known astrophysical sources of gamma rays, we exclude the thermal relic cross-section for particle masses of mDM ≲ 20 GeV.

Detecting Near-Earth Objects Using Cross-Correlation with a Point Spread Function

Science.gov (United States)

2009-03-01

impact in the Yucatan Peninsula caused the extinction of the dinosaurs in the Cretaceous Period [Fix, 1995]. Even the Moon is pot marked by many...the atmosphere that the light traverses. For this reason , it is typically better to be at higher elevations to decrease the amount of atmosphere the...detection on average for the Rayleigh sampling with cross-correlation of a PSF than the Rayleigh sampling without cross- correlation. For this reason

Linearized semiclassical initial value time correlation functions with maximum entropy analytic continuation.

Science.gov (United States)

Liu, Jian; Miller, William H

2008-09-28

The maximum entropy analytic continuation (MEAC) method is used to extend the range of accuracy of the linearized semiclassical initial value representation (LSC-IVR)/classical Wigner approximation for real time correlation functions. LSC-IVR provides a very effective "prior" for the MEAC procedure since it is very good for short times, exact for all time and temperature for harmonic potentials (even for correlation functions of nonlinear operators), and becomes exact in the classical high temperature limit. This combined MEAC+LSC/IVR approach is applied here to two highly nonlinear dynamical systems, a pure quartic potential in one dimensional and liquid para-hydrogen at two thermal state points (25 and 14 K under nearly zero external pressure). The former example shows the MEAC procedure to be a very significant enhancement of the LSC-IVR for correlation functions of both linear and nonlinear operators, and especially at low temperature where semiclassical approximations are least accurate. For liquid para-hydrogen, the LSC-IVR is seen already to be excellent at T=25 K, but the MEAC procedure produces a significant correction at the lower temperature (T=14 K). Comparisons are also made as to how the MEAC procedure is able to provide corrections for other trajectory-based dynamical approximations when used as priors.

Power-law cross-correlations estimation under heavy tails

Czech Academy of Sciences Publication Activity Database

Krištoufek, Ladislav

2016-01-01

Roč. 40, č. 1 (2016), s. 163-172 ISSN 1007-5704 R&D Projects: GA ČR(CZ) GP14-11402P Institutional support: RVO:67985556 Keywords : Power-law cross-correlations * Heavy tails * Monte Carlo study Subject RIV: AH - Economics Impact factor: 2.784, year: 2016 http://library.utia.cas.cz/separaty/2016/E/kristoufek-0472030.pdf

Statistical analysis of correlated experimental data and neutron cross section evaluation

International Nuclear Information System (INIS)

Badikov, S.A.

1998-01-01

The technique for evaluation of neutron cross sections on the basis of statistical analysis of correlated experimental data is presented. The most important stages of evaluation beginning from compilation of correlation matrix for measurement uncertainties till representation of the analysis results in the ENDF-6 format are described in details. Special attention is paid to restrictions (positive uncertainty) on covariation matrix of approximate parameters uncertainties generated within the method of least square fit which is derived from physical reasons. The requirements for source experimental data assuring satisfaction of the restrictions mentioned above are formulated. Correlation matrices of measurement uncertainties in particular should be also positively determined. Variants of modelling the positively determined correlation matrices of measurement uncertainties in a situation when their consequent calculation on the basis of experimental information is impossible are discussed. The technique described is used for creating the new generation of estimates of dosimetric reactions cross sections for the first version of the Russian dosimetric file (including nontrivial covariation information)

Minimizing the trend effect on detrended cross-correlation analysis with empirical mode decomposition

International Nuclear Information System (INIS)

Zhao Xiaojun; Shang Pengjian; Zhao Chuang; Wang Jing; Tao Rui

2012-01-01

Highlights: ► Investigate the effects of linear, exponential and periodic trends on DCCA. ► Apply empirical mode decomposition to extract trend term. ► Strong and monotonic trends are successfully eliminated. ► Get the cross-correlation exponent in a persistent behavior without crossover. - Abstract: Detrended cross-correlation analysis (DCCA) is a scaling method commonly used to estimate long-range power law cross-correlation in non-stationary signals. However, the susceptibility of DCCA to trends makes the scaling results difficult to analyze due to spurious crossovers. We artificially generate long-range cross-correlated signals and systematically investigate the effect of linear, exponential and periodic trends. Specifically to the crossovers raised by trends, we apply empirical mode decomposition method which decomposes underlying signals into several intrinsic mode functions (IMF) and a residual trend. After the removal of residual term, strong and monotonic trends such as linear and exponential trends are successfully eliminated. But periodic trend cannot be separated out according to the criterion of IMF, which can be eliminated by Fourier transform. As a special case of DCCA, detrended fluctuation analysis presents similar results.

Cross correlations of quantum key distribution based on single-photon sources

International Nuclear Information System (INIS)

Dong Shuangli; Wang Xiaobo; Zhang Guofeng; Sun Jianhu; Zhang Fang; Xiao Liantuan; Jia Suotang

2009-01-01

We theoretically analyze the second-order correlation function in a quantum key distribution system with real single-photon sources. Based on single-event photon statistics, the influence of the modification caused by an eavesdropper's intervention and the effects of background signals on the cross correlations between authorized partners are presented. On this basis, we have shown a secure range of correlation against the intercept-resend attacks.

Cosmic microwave and infrared backgrounds cross-correlation for ISW detection

International Nuclear Information System (INIS)

Ilić, S

2014-01-01

We have investigated the cross-correlation between the cosmic infrared and microwave backgrounds (CIB and CMB) anisotropies through the integrated Sachs-Wolfe effect. We have first described the CIB anisotropies using a linearly biased power spectrum, then derive the theoretical angular power spectrum of the CMB-CIB cross-correlation for different instruments and frequencies. We have discussed the detectability of the ISW signal by performing a signal-to-noise (SNR) analysis with our predicted spectra. The significances obtained range from 6σ to 7σ in an ideal case, depending on the frequency; in realistic cases which account for the presence of noise including astrophysical contaminants, the results span the range 2 – 5σ, depending strongly on the major contribution to the noise term

Measurement of correlated b quark cross sections at CDF

International Nuclear Information System (INIS)

Gerdes, D.

1994-09-01

Using data collected during the 1992--93 collider run at Fermilab, CDF has made measurements of correlated b quark cross section where one b is detected from a muon from semileptonic decay and the second b is detected with secondary vertex techniques. We report on measurements of the cross section as a function of the momentum of the second b and as a function of the azimuthal separation of the two b quarks, for transverse momentum of the initial b quark greater than 15 GeV. Results are compared to QCD predictions

Maximum Likelihood Blood Velocity Estimator Incorporating Properties of Flow Physics

DEFF Research Database (Denmark)

Schlaikjer, Malene; Jensen, Jørgen Arendt

2004-01-01

)-data under investigation. The flow physic properties are exploited in the second term, as the range of velocity values investigated in the cross-correlation analysis are compared to the velocity estimates in the temporal and spatial neighborhood of the signal segment under investigation. The new estimator...... has been compared to the cross-correlation (CC) estimator and the previously developed maximum likelihood estimator (MLE). The results show that the CMLE can handle a larger velocity search range and is capable of estimating even low velocity levels from tissue motion. The CC and the MLE produce...... for the CC and the MLE. When the velocity search range is set to twice the limit of the CC and the MLE, the number of incorrect velocity estimates are 0, 19.1, and 7.2% for the CMLE, CC, and MLE, respectively. The ability to handle a larger search range and estimating low velocity levels was confirmed...

A technique for plasma velocity-space cross-correlation

Science.gov (United States)

Mattingly, Sean; Skiff, Fred

2018-05-01

An advance in experimental plasma diagnostics is presented and used to make the first measurement of a plasma velocity-space cross-correlation matrix. The velocity space correlation function can detect collective fluctuations of plasmas through a localized measurement. An empirical decomposition, singular value decomposition, is applied to this Hermitian matrix in order to obtain the plasma fluctuation eigenmode structure on the ion distribution function. A basic theory is introduced and compared to the modes obtained by the experiment. A full characterization of these modes is left for future work, but an outline of this endeavor is provided. Finally, the requirements for this experimental technique in other plasma regimes are discussed.

Cross-correlation between EMG and center of gravity during quiet stance: theory and simulations.

Science.gov (United States)

Kohn, André Fabio

2005-11-01

Several signal processing tools have been employed in the experimental study of the postural control system in humans. Among them, the cross-correlation function has been used to analyze the time relationship between signals such as the electromyogram and the horizontal projection of the center of gravity. The common finding is that the electromyogram precedes the biomechanical signal, a result that has been interpreted in different ways, for example, the existence of feedforward control or the preponderance of a velocity feedback. It is shown here, analytically and by simulation, that the cross-correlation function is dependent in a complicated way on system parameters and on noise spectra. Results similar to those found experimentally, e.g., electromyogram preceding the biomechanical signal may be obtained in a postural control model without any feedforward control and without any velocity feedback. Therefore, correct interpretations of experimentally obtained cross-correlation functions may require additional information about the system. The results extend to other biomedical applications where two signals from a closed loop system are cross-correlated.

Multifractal detrended cross-correlation between the Chinese domestic and international gold markets based on DCCA and DMCA methods

Science.gov (United States)

Cao, Guangxi; Han, Yan; Chen, Yuemeng; Yang, Chunxia

2014-05-01

Based on the daily price data of Shanghai and London gold spot markets, we applied detrended cross-correlation analysis (DCCA) and detrended moving average cross-correlation analysis (DMCA) methods to quantify power-law cross-correlation between domestic and international gold markets. Results show that the cross-correlations between the Chinese domestic and international gold spot markets are multifractal. Furthermore, forward DMCA and backward DMCA seems to outperform DCCA and centered DMCA for short-range gold series, which confirms the comparison results of short-range artificial data in L. Y. He and S. P. Chen [Physica A 390 (2011) 3806-3814]. Finally, we analyzed the local multifractal characteristics of the cross-correlation between Chinese domestic and international gold markets. We show that multifractal characteristics of the cross-correlation between the Chinese domestic and international gold markets are time-varying and that multifractal characteristics were strengthened by the financial crisis in 2007-2008.

Cross-correlated imaging of distributed mode filtering rod fiber

DEFF Research Database (Denmark)

Laurila, Marko; Barankov, Roman; Jørgensen, Mette Marie

2013-01-01

We analyze the modal properties of an 85μm core distributed mode filtering rod fiber using cross-correlated (C2) imaging. We evaluate suppression of higher-order modes (HOMs) under severely misaligned mode excitation and identify a single-mode regime where HOMs are suppressed by more than 20dB....

Cross-correlation of motor activity signals from dc-magnetoencephalography, near-infrared spectroscopy, and electromyography.

Science.gov (United States)

Sander, Tilmann H; Leistner, Stefanie; Wabnitz, Heidrun; Mackert, Bruno-Marcel; Macdonald, Rainer; Trahms, Lutz

2010-01-01

Neuronal and vascular responses due to finger movements were synchronously measured using dc-magnetoencephalography (dcMEG) and time-resolved near-infrared spectroscopy (trNIRS). The finger movements were monitored with electromyography (EMG). Cortical responses related to the finger movement sequence were extracted by independent component analysis from both the dcMEG and the trNIRS data. The temporal relations between EMG rate, dcMEG, and trNIRS responses were assessed pairwise using the cross-correlation function (CCF), which does not require epoch averaging. A positive lag on a scale of seconds was found for the maximum of the CCF between dcMEG and trNIRS. A zero lag is observed for the CCF between dcMEG and EMG. Additionally this CCF exhibits oscillations at the frequency of individual finger movements. These findings show that the dcMEG with a bandwidth up to 8 Hz records both slow and faster neuronal responses, whereas the vascular response is confirmed to change on a scale of seconds.

MEASUREMENT OF 21 cm BRIGHTNESS FLUCTUATIONS AT z {approx} 0.8 IN CROSS-CORRELATION

Energy Technology Data Exchange (ETDEWEB)

Masui, K. W.; Switzer, E. R.; Calin, L.-M.; Pen, U.-L.; Shaw, J. R. [Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George St., Toronto, Ontario, M5S 3H8 (Canada); Banavar, N. [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George St., Toronto, Ontario, M5S 3H4 (Canada); Bandura, K. [Department of Physics, McGill University, 3600 Rue University, Montreal, Quebec, H3A 2T8 (Canada); Blake, C. [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218, Hawthorn, VIC 3122 (Australia); Chang, T.-C.; Liao, Y.-W. [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei, 10617, Taiwan (China); Chen, X.; Li, Y.-C. [National Astronomical Observatories, Chinese Academy of Science, 20A Datun Road, Beijing 100012 (China); Natarajan, A.; Peterson, J. B.; Voytek, T. C. [McWilliams Center for Cosmology, Carnegie Mellon University, Department of Physics, 5000 Forbes Ave., Pittsburgh, PA 15213 (United States)

2013-01-20

In this Letter, 21 cm intensity maps acquired at the Green Bank Telescope are cross-correlated with large-scale structure traced by galaxies in the WiggleZ Dark Energy Survey. The data span the redshift range 0.6 < z < 1 over two fields totaling {approx}41 deg. sq. and 190 hr of radio integration time. The cross-correlation constrains {Omega}{sub HI} b{sub HI} r = [0.43 {+-} 0.07(stat.) {+-} 0.04(sys.)] Multiplication-Sign 10{sup -3}, where {Omega}{sub HI} is the neutral hydrogen (H I) fraction, r is the galaxy-hydrogen correlation coefficient, and b{sub HI} is the H I bias parameter. This is the most precise constraint on neutral hydrogen density fluctuations in a challenging redshift range. Our measurement improves the previous 21 cm cross-correlation at z {approx} 0.8 both in its precision and in the range of scales probed.

Temporal cross-correlation asymmetry and departure from equilibrium in a bistable chemical system.

Science.gov (United States)

Bianca, C; Lemarchand, A

2014-06-14

This paper aims at determining sustained reaction fluxes in a nonlinear chemical system driven in a nonequilibrium steady state. The method relies on the computation of cross-correlation functions for the internal fluctuations of chemical species concentrations. By employing Langevin-type equations, we derive approximate analytical formulas for the cross-correlation functions associated with nonlinear dynamics. Kinetic Monte Carlo simulations of the chemical master equation are performed in order to check the validity of the Langevin equations for a bistable chemical system. The two approaches are found in excellent agreement, except for critical parameter values where the bifurcation between monostability and bistability occurs. From the theoretical point of view, the results imply that the behavior of cross-correlation functions cannot be exploited to measure sustained reaction fluxes in a specific nonlinear system without the prior knowledge of the associated chemical mechanism and the rate constants.

Finite sample properties of power-law cross-correlations estimators

Czech Academy of Sciences Publication Activity Database

Krištoufek, Ladislav

2015-01-01

Roč. 419, č. 1 (2015), s. 513-525 ISSN 0378-4371 R&D Projects: GA ČR(CZ) GP14-11402P Keywords : power-law cross-correlations * long - term memory * econophysics Subject RIV: AH - Economics Impact factor: 1.785, year: 2015 http://library.utia.cas.cz/separaty/2014/E/kristoufek-0433530.pdf

IMPROVING CORRELATION FUNCTION FITTING WITH RIDGE REGRESSION: APPLICATION TO CROSS-CORRELATION RECONSTRUCTION

International Nuclear Information System (INIS)

Matthews, Daniel J.; Newman, Jeffrey A.

2012-01-01

Cross-correlation techniques provide a promising avenue for calibrating photometric redshifts and determining redshift distributions using spectroscopy which is systematically incomplete (e.g., current deep spectroscopic surveys fail to obtain secure redshifts for 30%-50% or more of the galaxies targeted). In this paper, we improve on the redshift distribution reconstruction methods from our previous work by incorporating full covariance information into our correlation function fits. Correlation function measurements are strongly covariant between angular or spatial bins, and accounting for this in fitting can yield substantial reduction in errors. However, frequently the covariance matrices used in these calculations are determined from a relatively small set (dozens rather than hundreds) of subsamples or mock catalogs, resulting in noisy covariance matrices whose inversion is ill-conditioned and numerically unstable. We present here a method of conditioning the covariance matrix known as ridge regression which results in a more well behaved inversion than other techniques common in large-scale structure studies. We demonstrate that ridge regression significantly improves the determination of correlation function parameters. We then apply these improved techniques to the problem of reconstructing redshift distributions. By incorporating full covariance information, applying ridge regression, and changing the weighting of fields in obtaining average correlation functions, we obtain reductions in the mean redshift distribution reconstruction error of as much as ∼40% compared to previous methods. We provide a description of POWERFIT, an IDL code for performing power-law fits to correlation functions with ridge regression conditioning that we are making publicly available.

Groundwater travel time uncertainty analysis. Sensitivity of results to model geometry, and correlations and cross correlations among input parameters

International Nuclear Information System (INIS)

Clifton, P.M.

1985-03-01

This study examines the sensitivity of the travel time distribution predicted by a reference case model to (1) scale of representation of the model parameters, (2) size of the model domain, (3) correlation range of log-transmissivity, and (4) cross correlations between transmissivity and effective thickness. The basis for the reference model is the preliminary stochastic travel time model previously documented by the Basalt Waste Isolation Project. Results of this study show the following. The variability of the predicted travel times can be adequately represented when the ratio between the size of the zones used to represent the model parameters and the log-transmissivity correlation range is less than about one-fifth. The size of the model domain and the types of boundary conditions can have a strong impact on the distribution of travel times. Longer log-transmissivity correlation ranges cause larger variability in the predicted travel times. Positive cross correlation between transmissivity and effective thickness causes a decrease in the travel time variability. These results demonstrate the need for a sound conceptual model prior to conducting a stochastic travel time analysis

Cross-correlation analysis between Chinese TF contracts and treasury ETF based on high-frequency data

Science.gov (United States)

Zhou, Yu; Chen, Shi

2016-02-01

In this paper, we investigate the high-frequency cross-correlation relationship between Chinese treasury futures contracts and treasury ETF. We analyze the logarithmic return of these two price series, from which we can conclude that both return series are not normally distributed and the futures markets have greater volatility. We find significant cross-correlation between these two series. We further confirm the relationship using the DCCA coefficient and the DMCA coefficient. We quantify the long-range cross-correlation with DCCA method, and we further show that the relationship is multifractal. An arbitrage algorithm based on DFA regression with stable return is proposed in the last part.

Characteristics of angular cross correlations studied by light scattering from two-dimensional microsphere films

Science.gov (United States)

Schroer, M. A.; Gutt, C.; Grübel, G.

2014-07-01

Recently the analysis of scattering patterns by angular cross-correlation analysis (CCA) was introduced to reveal the orientational order in disordered samples with special focus to future applications on x-ray free-electron laser facilities. We apply this CCA approach to ultra-small-angle light-scattering data obtained from two-dimensional monolayers of microspheres. The films were studied in addition by optical microscopy. This combined approach allows to calculate the cross-correlations of the scattering patterns, characterized by the orientational correlation function Ψl(q), as well as to obtain the real-space structure of the monolayers. We show that CCA is sensitive to the orientational order of monolayers formed by the microspheres which are not directly visible from the scattering patterns. By mixing microspheres of different radii the sizes of ordered monolayer domains is reduced. For these samples it is shown that Ψl(q) quantitatively describes the degree of hexagonal order of the two-dimensional films. The experimental CCA results are compared with calculations based on the microscopy images. Both techniques show qualitatively similar features. Differences can be attributed to the wave-front distortion of the laser beam in the experiment. This effect is discussed by investigating the effect of different wave fronts on the cross-correlation analysis results. The so-determined characteristics of the cross-correlation analysis will be also relevant for future x-ray-based studies.

Simulation data for an estimation of the maximum theoretical value and confidence interval for the correlation coefficient.

Science.gov (United States)

Rocco, Paolo; Cilurzo, Francesco; Minghetti, Paola; Vistoli, Giulio; Pedretti, Alessandro

2017-10-01

The data presented in this article are related to the article titled "Molecular Dynamics as a tool for in silico screening of skin permeability" (Rocco et al., 2017) [1]. Knowledge of the confidence interval and maximum theoretical value of the correlation coefficient r can prove useful to estimate the reliability of developed predictive models, in particular when there is great variability in compiled experimental datasets. In this Data in Brief article, data from purposely designed numerical simulations are presented to show how much the maximum r value is worsened by increasing the data uncertainty. The corresponding confidence interval of r is determined by using the Fisher r → Z transform.

The large-scale quasar-Lyman α forest cross-correlation from BOSS

Energy Technology Data Exchange (ETDEWEB)

Font-Ribera, Andreu [Institute of Theoretical Physics, University of Zurich, Winterthurerstrasse 190, 8057 Zurich (Switzerland); Arnau, Eduard [Institut de Ciències del Cosmos (IEEC/UB), Martí i Franquès 1, 08028 Barcelona, Catalonia (Spain); Miralda-Escudé, Jordi, E-mail: font@physik.uzh.ch, E-mail: edu.arnau.lazaro@gmail.com, E-mail: miralda@icc.ub.edu [Institució Catalana de Recerca i Estudis Avançats, Passeig Lluís Companys 23, 08010 Barcelona, Catalonia (Spain); and others

2013-05-01

We measure the large-scale cross-correlation of quasars with the Lyα forest absorption in redshift space, using ∼ 60000 quasar spectra from Data Release 9 (DR9) of the Baryon Oscillation Spectroscopic Survey (BOSS). The cross-correlation is detected over a wide range of scales, up to comoving separations r of 80 h{sup −1}Mpc. For r > 15 h{sup −1}Mpc, we show that the cross-correlation is well fitted by the linear theory prediction for the mean overdensity around a quasar host halo in the standard ΛCDM model, with the redshift distortions indicative of gravitational evolution detected at high confidence. Using previous determinations of the Lyα forest bias factor obtained from the Lyα autocorrelation, we infer the quasar bias factor to be b{sub q} = 3.64{sup +0.13}{sub −0.15} at a mean redshift z = 2.38, in agreement with previous measurements from the quasar auto-correlation. We also obtain a new estimate of the Lyα forest redshift distortion factor, β{sub F} = 1.1±0.15, slightly larger than but consistent with the previous measurement from the Lyα forest autocorrelation. The simple linear model we use fails at separations r < 15h{sup −1}Mpc, and we show that this may reasonably be due to the enhanced ionization due to radiation from the quasars. We also provide the expected correction that the mass overdensity around the quasar implies for measurements of the ionizing radiation background from the line-of-sight proximity effect.

The large-scale quasar-Lyman α forest cross-correlation from BOSS

International Nuclear Information System (INIS)

Font-Ribera, Andreu; Arnau, Eduard; Miralda-Escudé, Jordi

2013-01-01

We measure the large-scale cross-correlation of quasars with the Lyα forest absorption in redshift space, using ∼ 60000 quasar spectra from Data Release 9 (DR9) of the Baryon Oscillation Spectroscopic Survey (BOSS). The cross-correlation is detected over a wide range of scales, up to comoving separations r of 80 h −1 Mpc. For r > 15 h −1 Mpc, we show that the cross-correlation is well fitted by the linear theory prediction for the mean overdensity around a quasar host halo in the standard ΛCDM model, with the redshift distortions indicative of gravitational evolution detected at high confidence. Using previous determinations of the Lyα forest bias factor obtained from the Lyα autocorrelation, we infer the quasar bias factor to be b q = 3.64 +0.13 −0.15 at a mean redshift z = 2.38, in agreement with previous measurements from the quasar auto-correlation. We also obtain a new estimate of the Lyα forest redshift distortion factor, β F = 1.1±0.15, slightly larger than but consistent with the previous measurement from the Lyα forest autocorrelation. The simple linear model we use fails at separations r −1 Mpc, and we show that this may reasonably be due to the enhanced ionization due to radiation from the quasars. We also provide the expected correction that the mass overdensity around the quasar implies for measurements of the ionizing radiation background from the line-of-sight proximity effect

Dynamical Analysis of Stock Market Instability by Cross-correlation Matrix

Science.gov (United States)

Takaishi, Tetsuya

2016-08-01

We study stock market instability by using cross-correlations constructed from the return time series of 366 stocks traded on the Tokyo Stock Exchange from January 5, 1998 to December 30, 2013. To investigate the dynamical evolution of the cross-correlations, crosscorrelation matrices are calculated with a rolling window of 400 days. To quantify the volatile market stages where the potential risk is high, we apply the principal components analysis and measure the cumulative risk fraction (CRF), which is the system variance associated with the first few principal components. From the CRF, we detected three volatile market stages corresponding to the bankruptcy of Lehman Brothers, the 2011 Tohoku Region Pacific Coast Earthquake, and the FRB QE3 reduction observation in the study period. We further apply the random matrix theory for the risk analysis and find that the first eigenvector is more equally de-localized when the market is volatile.

Dynamical Analysis of Stock Market Instability by Cross-correlation Matrix

International Nuclear Information System (INIS)

Takaishi, Tetsuya

2016-01-01

We study stock market instability by using cross-correlations constructed from the return time series of 366 stocks traded on the Tokyo Stock Exchange from January 5, 1998 to December 30, 2013. To investigate the dynamical evolution of the cross-correlations, crosscorrelation matrices are calculated with a rolling window of 400 days. To quantify the volatile market stages where the potential risk is high, we apply the principal components analysis and measure the cumulative risk fraction (CRF), which is the system variance associated with the first few principal components. From the CRF, we detected three volatile market stages corresponding to the bankruptcy of Lehman Brothers, the 2011 Tohoku Region Pacific Coast Earthquake, and the FRB QE3 reduction observation in the study period. We further apply the random matrix theory for the risk analysis and find that the first eigenvector is more equally de-localized when the market is volatile. (paper)

Financial liberalization and stock market cross-correlation: MF-DCCA analysis based on Shanghai-Hong Kong Stock Connect

Science.gov (United States)

Ruan, Qingsong; Zhang, Shuhua; Lv, Dayong; Lu, Xinsheng

2018-02-01

Based on the implementation of Shanghai-Hong Kong Stock Connect in China, this paper examines the effects of financial liberalization on stock market comovement using both multifractal detrended fluctuation analysis (MF-DFA) and multifractal detrended cross-correlation analysis (MF-DCCA) methods. Results based on MF-DFA confirm the multifractality of Shanghai and Hong Kong stock markets, and the market efficiency of Shanghai stock market increased after the implementation of this connect program. Besides, analysis based on MF-DCCA has verified the existence of persistent cross-correlation between Shanghai and Hong Kong stock markets, and the cross-correlation gets stronger after the launch of this liberalization program. Finally, we find that fat-tail distribution is the main source of multifractality in the cross-correlations before the stock connect program, while long-range correlation contributes to the multifractality after this program.

Multifractal cross-correlations between crude oil and tanker freight rate

Science.gov (United States)

Chen, Feier; Miao, Yuqi; Tian, Kang; Ding, Xiaoxu; Li, Tingyi

2017-05-01

Analysis of crude oil price and tanker freight rate volatility attract more attention as the mechanism is not only the basis of industrialization but also a vital role in economics, especially after the year 2008 when financial crisis notably blew the maritime transportation. In this paper, we studied the cross-correlations between the West Texas International crude oil (WTI) and Baltic Exchange Dirty Tanker Index (BDTI) employing the Multifractal Detrended Cross-Correlation Analysis (MF-DCCA). Empirical results show that the degree of short-term cross-correlation is higher than that in the long term and that the strength of multifractality after financial crisis is larger than that before. Moreover, the components of multifractal spectrum are quantified with the finite-size effect taken into consideration and an improved method in terms of constructing the surrogated time series provided. Numerical results show that the multifractality is generated mostly from the nonlinear and the fat-tailed probability distribution (PDF) part. Also, it is apparent that the PDF part changes a lot after the financial crisis. The research is contributory to risk management by providing various instructions for participants in shipping markets. Our main contribution is that we investigated both the multifractal features and the origin of multifractality and provided confirming evidence of multifractality through numerical results while applying quantitative analysis based on MF-DCCA; furthermore, the research is contributory to risk management since it provides instructions in both economic market and stock market simultaneously. However, constructing the surrogated series in order to obtain consistence seems less convincing which requires further discussion and attempts.

Atmospheric pollution measurement by optical cross correlation methods - A concept

Science.gov (United States)

Fisher, M. J.; Krause, F. R.

1971-01-01

Method combines standard spectroscopy with statistical cross correlation analysis of two narrow light beams for remote sensing to detect foreign matter of given particulate size and consistency. Method is applicable in studies of generation and motion of clouds, nuclear debris, ozone, and radiation belts.

The generalized correlation method for estimation of time delay in power plants

International Nuclear Information System (INIS)

Kostic, Lj.

1981-01-01

The generalized correlation estimation is developed for determining time delay between signals received at two spatially separated sensors in the presence of uncorrelated noise in a power plant. This estimator can be realized as a pair of receiver prefilters followed by a cross correlator. The time argument at which the correlator achieves a maximum is the delay estimate. (author)

Importance of Preserving Cross-correlation in developing Statistically Downscaled Climate Forcings and in estimating Land-surface Fluxes and States

Science.gov (United States)

Das Bhowmik, R.; Arumugam, S.

2015-12-01

Multivariate downscaling techniques exhibited superiority over univariate regression schemes in terms of preserving cross-correlations between multiple variables- precipitation and temperature - from GCMs. This study focuses on two aspects: (a) develop an analytical solutions on estimating biases in cross-correlations from univariate downscaling approaches and (b) quantify the uncertainty in land-surface states and fluxes due to biases in cross-correlations in downscaled climate forcings. Both these aspects are evaluated using climate forcings available from both historical climate simulations and CMIP5 hindcasts over the entire US. The analytical solution basically relates the univariate regression parameters, co-efficient of determination of regression and the co-variance ratio between GCM and downscaled values. The analytical solutions are compared with the downscaled univariate forcings by choosing the desired p-value (Type-1 error) in preserving the observed cross-correlation. . For quantifying the impacts of biases on cross-correlation on estimating streamflow and groundwater, we corrupt the downscaled climate forcings with different cross-correlation structure.

Multifractal detrended cross-correlation analysis for epileptic patient in seizure and seizure free status

International Nuclear Information System (INIS)

Ghosh, Dipak; Dutta, Srimonti; Chakraborty, Sayantan

2014-01-01

Highlights: • We analyze EEG of patients during seizure and in seizure free interval. • Data from different sections of the brain and seizure activity was analyzed. • Assessment of cross-correlation in seizure and seizure free interval using MF-DXA technique. - Abstract: This paper reports a study of EEG data of epileptic patients in terms of multifractal detrended cross-correlation analysis (MF-DXA). The EEG clinical data were obtained from the EEG Database available with the Clinic of Epileptology of the University Hospital of Bonn, Germany. The data sets (C, D, and E) were taken from five epileptic patients undergoing presurgical evaluations. The data sets consist of intracranial EEG recordings during seizure-free intervals (interictal periods) from within the epileptogenic zone (D) and from the hippocampal formation of the opposite hemisphere of the epileptic patients’ brain, respectively (C). The data set (E) was recorded during seizure activity (ictal periods). MF-DXA is a very rigorous and robust tool for assessment of cross-correlation among two nonlinear time series. The study reveals the degree of cross-correlation is more among seizure and seizure free interval in epileptogenic zone. These data are very significant for diagnosis, onset and prognosis of epileptic patients

A new detrended semipartial cross-correlation analysis: Assessing the important meteorological factors affecting API

International Nuclear Information System (INIS)

Shen, Chen-Hua

2015-01-01

To analyze the unique contribution of meteorological factors to the air pollution index (API), a new method, the detrended semipartial cross-correlation analysis (DSPCCA), is proposed. Based on both a detrended cross-correlation analysis and a DFA-based multivariate-linear-regression (DMLR), this method is improved by including a semipartial correlation technique, which is used to indicate the unique contribution of an explanatory variable to multiple correlation coefficients. The advantages of this method in handling nonstationary time series are illustrated by numerical tests. To further demonstrate the utility of this method in environmental systems, new evidence of the primary contribution of meteorological factors to API is provided through DMLR. Results show that the most important meteorological factors affecting API are wind speed and diurnal temperature range, and the explanatory ability of meteorological factors to API gradually strengthens with increasing time scales. The results suggest that DSPCCA is a useful method for addressing environmental systems. - Highlights: • A detrended multiple linear regression is shown. • A detrended semipartial cross correlation analysis is proposed. • The important meteorological factors affecting API are assessed. • The explanatory ability of meteorological factors to API gradually strengthens with increasing time scales.

A new detrended semipartial cross-correlation analysis: Assessing the important meteorological factors affecting API

Energy Technology Data Exchange (ETDEWEB)

Shen, Chen-Hua, E-mail: shenandchen01@163.com [College of Geographical Science, Nanjing Normal University, Nanjing 210046 (China); Jiangsu Center for Collaborative Innovation in Geographical Information Resource, Nanjing 210046 (China); Key Laboratory of Virtual Geographic Environment of Ministry of Education, Nanjing 210046 (China)

2015-12-04

To analyze the unique contribution of meteorological factors to the air pollution index (API), a new method, the detrended semipartial cross-correlation analysis (DSPCCA), is proposed. Based on both a detrended cross-correlation analysis and a DFA-based multivariate-linear-regression (DMLR), this method is improved by including a semipartial correlation technique, which is used to indicate the unique contribution of an explanatory variable to multiple correlation coefficients. The advantages of this method in handling nonstationary time series are illustrated by numerical tests. To further demonstrate the utility of this method in environmental systems, new evidence of the primary contribution of meteorological factors to API is provided through DMLR. Results show that the most important meteorological factors affecting API are wind speed and diurnal temperature range, and the explanatory ability of meteorological factors to API gradually strengthens with increasing time scales. The results suggest that DSPCCA is a useful method for addressing environmental systems. - Highlights: • A detrended multiple linear regression is shown. • A detrended semipartial cross correlation analysis is proposed. • The important meteorological factors affecting API are assessed. • The explanatory ability of meteorological factors to API gradually strengthens with increasing time scales.

Extended families of 2D arrays with near optimal auto and low cross-correlation

Science.gov (United States)

Svalbe, I. D.; Tirkel, A. Z.

2017-12-01

Families of 2D arrays can be constructed where each array has perfect autocorrelation, and the cross-correlation between any pair of family members is optimally low. We exploit equivalent Hadamard matrices to construct many families of p p × p arrays, where p is any 4k-1 prime. From these families, we assemble extended families of arrays with members that exhibit perfect autocorrelation and next-to-optimally low cross-correlation. Pseudo-Hadamard matrices are used to construct extended families using p = 4k + 1 primes. An optimal family of 31 31 × 31 perfect arrays can provide copyright protection to uniquely stamp a robust, low-visibility watermark within every frame of each second of high-definition, 30 fps video. The extended families permit the embedding of many more perfect watermarks that have next-to-minimal cross-correlations.

Relationship between occlusal force and falls among community-dwelling elderly in Japan: a cross-sectional correlative study.

Science.gov (United States)

Eto, Maki; Miyauchi, Shinji

2018-05-09

Falls may cause serious health conditions among older population. Fall-related physical factors are thought to be associated with occlusal conditions. However, few studies examined the relationship between occlusal force and falls. To identify the association between occlusal force and falls among community-dwelling elderly individuals in Japan, public health nurses conducted a cross-sectional descriptive study. We performed extensive physical assessments of five items: maximum occlusal force, handgrip strength, maximal knee extensor strength, one-leg standing time with eyes open and body sway. We also conducted a questionnaire survey concerning the participants' demographic characteristics, health status and fall experience during the past year. Mean scores and standard deviations were calculated for age and the total points of the index of activities of daily living. Associations were examined using Mann-Whitney tests and logistic regression. We examined 159 community-dwelling people aged ≥65 years, who were independent and active, including 38 participants (24.5%) with experience of falls in the past year. Maximum occlusal force had significant correlation with handgrip strength, maximal knee extensor strength, and one-leg standing time and body sway (P force (P = 0.004). This is the first study, led by public health nursing researchers, to examine the associations between maximum occlusal force and falls among community-dwelling elderly in Japan. The results showed that maximum occlusal force was significantly related to the other four extensive physical assessments, and might also suggest that maximum occlusal force assessment by public health nurses could contribute to more sophisticated and precise prediction of fall risks among the community-dwelling elderly. The latest occlusal force measurement device is non-invasive and easy to use. Public health nurses can introduce it at periodical community health checkup assembly events, which might

Lenses in the forest: cross correlation of the Lyman-alpha flux with cosmic microwave background lensing.

Science.gov (United States)

Vallinotto, Alberto; Das, Sudeep; Spergel, David N; Viel, Matteo

2009-08-28

We present a theoretical estimate for a new observable: the cross correlation between the Lyman-alpha flux fluctuations in quasar spectra and the convergence of the cosmic microwave background as measured along the same line of sight. As a first step toward the assessment of its detectability, we estimate the signal-to-noise ratio using linear theory. Although the signal-to-noise is small for a single line of sight and peaks at somewhat smaller redshifts than those probed by the Lyman-alpha forest, we estimate a total signal-to-noise of 9 for cross correlating quasar spectra of SDSS-III with Planck and 20 for cross correlating with a future polarization based cosmic microwave background experiment. The detection of this effect would be a direct measure of the neutral hydrogen-matter cross correlation and could provide important information on the growth of structures at large scales in a redshift range which is still poorly probed.

Measurement of the dipole in the cross-correlation function of galaxies

CERN Document Server

Gaztanaga, Enrique; Hui, Lam

2017-01-01

It is usually assumed that in the linear regime the two-point correlation function of galaxies contains only a monopole, quadrupole and hexadecapole. Looking at cross-correlations between different populations of galaxies, this turns out not to be the case. In particular, the cross-correlations between a bright and a faint population of galaxies contain also a dipole. In this paper we present the first attempt to measure this dipole. We discuss the four types of effects that contribute to the dipole: relativistic distortions, evolution effect, wide-angle effect and large-angle effect. We show that the first three contributions are intrinsic anti-symmetric contributions that do not depend on the choice of angle used to measure the dipole. On the other hand the large-angle effect appears only if the angle chosen to extract the dipole breaks the symmetry of the problem. We show that the relativistic distortions, the evolution effect and the wide-angle effect are too small to be detected in the LOWz and CMASS sam...

Robust Maximum Association Estimators

NARCIS (Netherlands)

A. Alfons (Andreas); C. Croux (Christophe); P. Filzmoser (Peter)

2017-01-01

textabstractThe maximum association between two multivariate variables X and Y is defined as the maximal value that a bivariate association measure between one-dimensional projections αX and αY can attain. Taking the Pearson correlation as projection index results in the first canonical correlation

Quantifying and modeling long-range cross correlations in multiple time series with applications to world stock indices.

Science.gov (United States)

Wang, Duan; Podobnik, Boris; Horvatić, Davor; Stanley, H Eugene

2011-04-01

We propose a modified time lag random matrix theory in order to study time-lag cross correlations in multiple time series. We apply the method to 48 world indices, one for each of 48 different countries. We find long-range power-law cross correlations in the absolute values of returns that quantify risk, and find that they decay much more slowly than cross correlations between the returns. The magnitude of the cross correlations constitutes "bad news" for international investment managers who may believe that risk is reduced by diversifying across countries. We find that when a market shock is transmitted around the world, the risk decays very slowly. We explain these time-lag cross correlations by introducing a global factor model (GFM) in which all index returns fluctuate in response to a single global factor. For each pair of individual time series of returns, the cross correlations between returns (or magnitudes) can be modeled with the autocorrelations of the global factor returns (or magnitudes). We estimate the global factor using principal component analysis, which minimizes the variance of the residuals after removing the global trend. Using random matrix theory, a significant fraction of the world index cross correlations can be explained by the global factor, which supports the utility of the GFM. We demonstrate applications of the GFM in forecasting risks at the world level, and in finding uncorrelated individual indices. We find ten indices that are practically uncorrelated with the global factor and with the remainder of the world indices, which is relevant information for world managers in reducing their portfolio risk. Finally, we argue that this general method can be applied to a wide range of phenomena in which time series are measured, ranging from seismology and physiology to atmospheric geophysics.

Quantifying and modeling long-range cross correlations in multiple time series with applications to world stock indices

Science.gov (United States)

Wang, Duan; Podobnik, Boris; Horvatić, Davor; Stanley, H. Eugene

2011-04-01

We propose a modified time lag random matrix theory in order to study time-lag cross correlations in multiple time series. We apply the method to 48 world indices, one for each of 48 different countries. We find long-range power-law cross correlations in the absolute values of returns that quantify risk, and find that they decay much more slowly than cross correlations between the returns. The magnitude of the cross correlations constitutes “bad news” for international investment managers who may believe that risk is reduced by diversifying across countries. We find that when a market shock is transmitted around the world, the risk decays very slowly. We explain these time-lag cross correlations by introducing a global factor model (GFM) in which all index returns fluctuate in response to a single global factor. For each pair of individual time series of returns, the cross correlations between returns (or magnitudes) can be modeled with the autocorrelations of the global factor returns (or magnitudes). We estimate the global factor using principal component analysis, which minimizes the variance of the residuals after removing the global trend. Using random matrix theory, a significant fraction of the world index cross correlations can be explained by the global factor, which supports the utility of the GFM. We demonstrate applications of the GFM in forecasting risks at the world level, and in finding uncorrelated individual indices. We find ten indices that are practically uncorrelated with the global factor and with the remainder of the world indices, which is relevant information for world managers in reducing their portfolio risk. Finally, we argue that this general method can be applied to a wide range of phenomena in which time series are measured, ranging from seismology and physiology to atmospheric geophysics.

Kinetic description of the total photoabsorption cross section: correlation effects

International Nuclear Information System (INIS)

Ferreira Filho, L.G.; Nemes, M.C.

1986-02-01

It is shown that the inclusion of correlation effects in describing the nuclear photoabsorption cross section leads to a Breit-Wigner type curve with energy dependent width. It is also shown that a very slow energy dependence is enough to reproduce the data up to ∼ 139 MeV. (Author) [pt

Computational nanometrology of line-edge roughness: noise effects, cross-line correlations and the role of etch transfer

Science.gov (United States)

Constantoudis, Vassilios; Papavieros, George; Lorusso, Gian; Rutigliani, Vito; Van Roey, Frieda; Gogolides, Evangelos

2018-03-01

The aim of this paper is to investigate the role of etch transfer in two challenges of LER metrology raised by recent evolutions in lithography: the effects of SEM noise and the cross-line and edge correlations. The first comes from the ongoing scaling down of linewidths, which dictates SEM imaging with less scanning frames to reduce specimen damage and hence with more noise. During the last decade, it has been shown that image noise can be an important budget of the measured LER while systematically affects and alter the PSD curve of LER at high frequencies. A recent method for unbiased LER measurement is based on the systematic Fourier or correlation analysis to decompose the effects of noise from true LER (Fourier-Correlation filtering method). The success of the method depends on the PSD and HHCF curve. Previous experimental and model works have revealed that etch transfer affects the PSD of LER reducing its high frequency values. In this work, we estimate the noise contribution to the biased LER through PSD flat floor at high frequencies and relate it with the differences between the PSDs of lithography and etched LER. Based on this comparison, we propose an improvement of the PSD/HHCF-based method for noise-free LER measurement to include the missed high frequency real LER. The second issue is related with the increased density of lithographic patterns and the special characteristics of DSA and MP lithography patterns exhibits. In a previous work, we presented an enlarged LER characterization methodology for such patterns, which includes updated versions of the old metrics along with new metrics defined and developed to capture cross-edge and cross-line correlations. The fundamental concept has been the Line Center Roughness (LCR), the edge c-factor and the line c-factor correlation function and length quantifying the line fluctuations and the extent of cross-edge and cross-line correlations. In this work, we focus on the role of etch steps on cross-edge and

Multifractal detrended cross correlation analysis of neuro-degenerative diseases-An in depth study

Science.gov (United States)

Dutta, Srimonti; Ghosh, Dipak; Chatterjee, Sucharita

2018-02-01

This work revisits our previous study on human gait diseases, (Dutta et al., 2013) where we have studied the autocorrelation of human gait pattern in normal and diseased set. Significant difference in results was observed for normal and diseased set. However we were not able to distinguish between sets of Parkinson's and Huntington's disease. In this paper we attempt to study whether cross correlations between two feet of human gait pattern can help to distinguish between different diseased set. The results reveal that study of cross correlations can help to distinguish between Parkinson's and Huntington's disease.

Performance of penalized maximum likelihood in estimation of genetic covariances matrices

Directory of Open Access Journals (Sweden)

Meyer Karin

2011-11-01

Full Text Available Abstract Background Estimation of genetic covariance matrices for multivariate problems comprising more than a few traits is inherently problematic, since sampling variation increases dramatically with the number of traits. This paper investigates the efficacy of regularized estimation of covariance components in a maximum likelihood framework, imposing a penalty on the likelihood designed to reduce sampling variation. In particular, penalties that "borrow strength" from the phenotypic covariance matrix are considered. Methods An extensive simulation study was carried out to investigate the reduction in average 'loss', i.e. the deviation in estimated matrices from the population values, and the accompanying bias for a range of parameter values and sample sizes. A number of penalties are examined, penalizing either the canonical eigenvalues or the genetic covariance or correlation matrices. In addition, several strategies to determine the amount of penalization to be applied, i.e. to estimate the appropriate tuning factor, are explored. Results It is shown that substantial reductions in loss for estimates of genetic covariance can be achieved for small to moderate sample sizes. While no penalty performed best overall, penalizing the variance among the estimated canonical eigenvalues on the logarithmic scale or shrinking the genetic towards the phenotypic correlation matrix appeared most advantageous. Estimating the tuning factor using cross-validation resulted in a loss reduction 10 to 15% less than that obtained if population values were known. Applying a mild penalty, chosen so that the deviation in likelihood from the maximum was non-significant, performed as well if not better than cross-validation and can be recommended as a pragmatic strategy. Conclusions Penalized maximum likelihood estimation provides the means to 'make the most' of limited and precious data and facilitates more stable estimation for multi-dimensional analyses. It should

Cross-correlation studies between CMB temperature anisotropies and 21 cm fluctuations

International Nuclear Information System (INIS)

Cooray, Asantha

2004-01-01

During the transition from a neutral to a fully reionized universe, scattering of cosmic microwave background (CMB) photons via free electrons leads to a new anisotropy contribution to the temperature distribution. If the reionization process is inhomogeneous and patchy, the era of reionization is also visible via brightness temperature fluctuations in the redshifted 21 cm line emission from neutral hydrogen. Since regions containing electrons and neutral hydrogen are expected to trace the same underlying density field, the two are (anti)correlated and this is expected to be reflected in the anisotropy maps via a correlation between arcminute-scale CMB temperature and the 21 cm background. In terms of the angular cross-power spectrum, unfortunately, this correlation is insignificant due to a geometric cancellation associated with second-order CMB anisotropies. The same cross correlation between ionized and neutral regions, however, can be studied using a bispectrum involving large-scale velocity field of ionized regions from the Doppler effect, arcminute-scale CMB anisotropies during reionization, and the 21 cm background. While the geometric cancellation is partly avoided, the signal-to-noise ratio related to this bispectrum is reduced due to the large cosmic variance related to velocity fluctuations traced by the Doppler effect. Unless the velocity field during reionization can be independently established, it is unlikely that the correlation information related to the relative distribution of ionized electrons and regions containing neutral hydrogen can be obtained with a combined study involving CMB and 21 cm fluctuations

Background Noise Reduction Using Adaptive Noise Cancellation Determined by the Cross-Correlation

Science.gov (United States)

Spalt, Taylor B.; Brooks, Thomas F.; Fuller, Christopher R.

2012-01-01

Background noise due to flow in wind tunnels contaminates desired data by decreasing the Signal-to-Noise Ratio. The use of Adaptive Noise Cancellation to remove background noise at measurement microphones is compromised when the reference sensor measures both background and desired noise. The technique proposed modifies the classical processing configuration based on the cross-correlation between the reference and primary microphone. Background noise attenuation is achieved using a cross-correlation sample width that encompasses only the background noise and a matched delay for the adaptive processing. A present limitation of the method is that a minimum time delay between the background noise and desired signal must exist in order for the correlated parts of the desired signal to be separated from the background noise in the crosscorrelation. A simulation yields primary signal recovery which can be predicted from the coherence of the background noise between the channels. Results are compared with two existing methods.

CCFpams: Atmospheric stellar parameters from cross-correlation functions

Science.gov (United States)

Malavolta, Luca; Lovis, Christophe; Pepe, Francesco; Sneden, Christopher; Udry, Stephane

2017-07-01

CCFpams allows the measurement of stellar temperature, metallicity and gravity within a few seconds and in a completely automated fashion. Rather than performing comparisons with spectral libraries, the technique is based on the determination of several cross-correlation functions (CCFs) obtained by including spectral features with different sensitivity to the photospheric parameters. Literature stellar parameters of high signal-to-noise (SNR) and high-resolution HARPS spectra of FGK Main Sequence stars are used to calibrate the stellar parameters as a function of CCF areas.

Multifractal detrended cross-correlations between crude oil market and Chinese ten sector stock markets

Science.gov (United States)

Yang, Liansheng; Zhu, Yingming; Wang, Yudong; Wang, Yiqi

2016-11-01

Based on the daily price data of spot prices of West Texas Intermediate (WTI) crude oil and ten CSI300 sector indices in China, we apply multifractal detrended cross-correlation analysis (MF-DCCA) method to investigate the cross-correlations between crude oil and Chinese sector stock markets. We find that the strength of multifractality between WTI crude oil and energy sector stock market is the highest, followed by the strength of multifractality between WTI crude oil and financial sector market, which reflects a close connection between energy and financial market. Then we do vector autoregression (VAR) analysis to capture the interdependencies among the multiple time series. By comparing the strength of multifractality for original data and residual errors of VAR model, we get a conclusion that vector auto-regression (VAR) model could not be used to describe the dynamics of the cross-correlations between WTI crude oil and the ten sector stock markets.

An overview of the report: Correlation between carcinogenic potency and the maximum tolerated dose: Implications for risk assessment

International Nuclear Information System (INIS)

Krewski, D.; Gaylor, D.W.; Soms, A.P.; Szyszkowicz, M.

1993-01-01

Current practice in carcinogen bioassay calls for exposure of experimental animals at doses up to and including the maximum tolerated dose (MTD). Such studies have been used to compute measures of carcinogenic potency such as the TD 50 as well as unit risk factors such as q 1 for predicting low-dose risks. Recent studies have indicated that these measures of carcinogenic potency are highly correlated with the MTD. Carcinogenic potency has also been shown to be correlated with indicators of mutagenicity and toxicity. Correlation of the MTDs for rats and mice implies a corresponding correlation in TD 50 values for these two species. The implications of these results for cancer risk assessment are examined in light of the large variation in potency among chemicals known to induce tumors in rodents. 119 refs., 2 figs., 4 tabs

Two-detector cross-correlation noise technique and its application in measuring reactor kinetic parameters

International Nuclear Information System (INIS)

Lu Guiping; Peng Feng; Yi Jieyi

1988-01-01

The two-detector cross-correlation noise technique is a new method of measuring reactor kinetic parameters developed in the sixties. It has the advantages of non-perturbation in core, high signal to noise ratio, low space dependent effect, and simple and reliable in measurement. A special set of cross-correlation analyzer has been prepared for measuring kinetic parameters of several reactor assemblies, such as the High Flux Engineering Test Reactor, its zero power mock up facility and a low enriched uranium light water lattice zero power facility

DARK MATTER SEARCHES IN THE GAMMA-RAY EXTRAGALACTIC BACKGROUND VIA CROSS-CORRELATIONS WITH GALAXY CATALOGS

International Nuclear Information System (INIS)

Cuoco, Alessandro; Regis, Marco; Fornengo, Nicolao; Xia, Jun-Qing; Branchini, Enzo; Viel, Matteo

2015-01-01

We compare the measured angular cross-correlation between the Fermi-Large Area Telescope γ-ray sky and catalogs of extragalactic objects with the expected signal induced by weakly interacting massive particle (WIMP) dark matter (DM). We include a detailed description of the contribution of astrophysical γ-ray emitters such as blazars, misaligned active galactic nucleus (AGN), and star-forming galaxies, and perform a global fit to the measured cross-correlation. Five catalogs are considered: Sloan Digital Sky Survey (SDSS)-DR6 quasars, Two Micron All Sky Survey galaxies, NRAO VLA Sky Survey radio galaxies, SDSS-DR8 Luminous Red Galaxies, and the SDSS-DR8 main galaxy sample. To model the cross-correlation signal, we use the halo occupation distribution formalism to estimate the number of galaxies of a given catalog in DM halos and their spatial correlation properties. We discuss uncertainties in the predicted cross-correlation signal arising from the DM clustering and WIMP microscopic properties, which set the DM γ-ray emission. The use of different catalogs probing objects at different redshifts significantly reduces, though not completely, the degeneracy among the different γ-ray components. We find that the presence of a significant WIMP DM signal is allowed by the data but not significantly preferred by the fit, although this is mainly due to a degeneracy with the misaligned AGN component. With modest substructure boost, the sensitivity of this method excludes thermal annihilation cross sections at 95% level for WIMP masses up to few tens of GeV. Constraining the low-redshift properties of astrophysical populations with future data will further improve the sensitivity to DM

Dark Matter Searches in the Gamma-ray Extragalactic Background via Cross-correlations with Galaxy Catalogs

Science.gov (United States)

Cuoco, Alessandro; Xia, Jun-Qing; Regis, Marco; Branchini, Enzo; Fornengo, Nicolao; Viel, Matteo

2015-12-01

We compare the measured angular cross-correlation between the Fermi-Large Area Telescope γ-ray sky and catalogs of extragalactic objects with the expected signal induced by weakly interacting massive particle (WIMP) dark matter (DM). We include a detailed description of the contribution of astrophysical γ-ray emitters such as blazars, misaligned active galactic nucleus (AGN), and star-forming galaxies, and perform a global fit to the measured cross-correlation. Five catalogs are considered: Sloan Digital Sky Survey (SDSS)-DR6 quasars, Two Micron All Sky Survey galaxies, NRAO VLA Sky Survey radio galaxies, SDSS-DR8 Luminous Red Galaxies, and the SDSS-DR8 main galaxy sample. To model the cross-correlation signal, we use the halo occupation distribution formalism to estimate the number of galaxies of a given catalog in DM halos and their spatial correlation properties. We discuss uncertainties in the predicted cross-correlation signal arising from the DM clustering and WIMP microscopic properties, which set the DM γ-ray emission. The use of different catalogs probing objects at different redshifts significantly reduces, though not completely, the degeneracy among the different γ-ray components. We find that the presence of a significant WIMP DM signal is allowed by the data but not significantly preferred by the fit, although this is mainly due to a degeneracy with the misaligned AGN component. With modest substructure boost, the sensitivity of this method excludes thermal annihilation cross sections at 95% level for WIMP masses up to few tens of GeV. Constraining the low-redshift properties of astrophysical populations with future data will further improve the sensitivity to DM.

DARK MATTER SEARCHES IN THE GAMMA-RAY EXTRAGALACTIC BACKGROUND VIA CROSS-CORRELATIONS WITH GALAXY CATALOGS

Energy Technology Data Exchange (ETDEWEB)

Cuoco, Alessandro; Regis, Marco; Fornengo, Nicolao [Dipartimento di Fisica, Università di Torino, via P. Giuria 1, I-10125 Torino (Italy); Xia, Jun-Qing [Department of Astronomy, Beijing Normal University, Beijing 100875 (China); Branchini, Enzo [Dipartimento di Matematica e Fisica, Università degli Studi “Roma Tre,” via della Vasca Navale 84, I-00146 Roma (Italy); Viel, Matteo, E-mail: cuoco@to.infn.it, E-mail: regis@to.infn.it, E-mail: fornengo@to.infn.it, E-mail: xiajq@bnu.edu.cn, E-mail: branchin@fis.uniroma3.it, E-mail: viel@oats.inaf.it [INAF Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, I-34141, Trieste (Italy)

2015-12-15

We compare the measured angular cross-correlation between the Fermi-Large Area Telescope γ-ray sky and catalogs of extragalactic objects with the expected signal induced by weakly interacting massive particle (WIMP) dark matter (DM). We include a detailed description of the contribution of astrophysical γ-ray emitters such as blazars, misaligned active galactic nucleus (AGN), and star-forming galaxies, and perform a global fit to the measured cross-correlation. Five catalogs are considered: Sloan Digital Sky Survey (SDSS)-DR6 quasars, Two Micron All Sky Survey galaxies, NRAO VLA Sky Survey radio galaxies, SDSS-DR8 Luminous Red Galaxies, and the SDSS-DR8 main galaxy sample. To model the cross-correlation signal, we use the halo occupation distribution formalism to estimate the number of galaxies of a given catalog in DM halos and their spatial correlation properties. We discuss uncertainties in the predicted cross-correlation signal arising from the DM clustering and WIMP microscopic properties, which set the DM γ-ray emission. The use of different catalogs probing objects at different redshifts significantly reduces, though not completely, the degeneracy among the different γ-ray components. We find that the presence of a significant WIMP DM signal is allowed by the data but not significantly preferred by the fit, although this is mainly due to a degeneracy with the misaligned AGN component. With modest substructure boost, the sensitivity of this method excludes thermal annihilation cross sections at 95% level for WIMP masses up to few tens of GeV. Constraining the low-redshift properties of astrophysical populations with future data will further improve the sensitivity to DM.

A novel coefficient for detecting and quantifying asymmetry of California electricity market based on asymmetric detrended cross-correlation analysis.

Science.gov (United States)

Wang, Fang

2016-06-01

In order to detect and quantify asymmetry of two time series, a novel cross-correlation coefficient is proposed based on recent asymmetric detrended cross-correlation analysis (A-DXA), which we called A-DXA coefficient. The A-DXA coefficient, as an important extension of DXA coefficient ρDXA, contains two directional asymmetric cross-correlated indexes, describing upwards and downwards asymmetric cross-correlations, respectively. By using the information of directional covariance function of two time series and directional variance function of each series itself instead of power-law between the covariance function and time scale, the proposed A-DXA coefficient can well detect asymmetry between the two series no matter whether the cross-correlation is significant or not. By means of the proposed A-DXA coefficient conducted over the asymmetry for California electricity market, we found that the asymmetry between the prices and loads is not significant for daily average data in 1999 yr market (before electricity crisis) but extremely significant for those in 2000 yr market (during the crisis). To further uncover the difference of asymmetry between the years 1999 and 2000, a modified H statistic (MH) and ΔMH statistic are proposed. One of the present contributions is that the high MH values calculated for hourly data exist in majority months in 2000 market. Another important conclusion is that the cross-correlation with downwards dominates over the whole 1999 yr in contrast to the cross-correlation with upwards dominates over the 2000 yr.

A novel coefficient for detecting and quantifying asymmetry of California electricity market based on asymmetric detrended cross-correlation analysis

Science.gov (United States)

Wang, Fang

2016-06-01

In order to detect and quantify asymmetry of two time series, a novel cross-correlation coefficient is proposed based on recent asymmetric detrended cross-correlation analysis (A-DXA), which we called A-DXA coefficient. The A-DXA coefficient, as an important extension of DXA coefficient ρ D X A , contains two directional asymmetric cross-correlated indexes, describing upwards and downwards asymmetric cross-correlations, respectively. By using the information of directional covariance function of two time series and directional variance function of each series itself instead of power-law between the covariance function and time scale, the proposed A-DXA coefficient can well detect asymmetry between the two series no matter whether the cross-correlation is significant or not. By means of the proposed A-DXA coefficient conducted over the asymmetry for California electricity market, we found that the asymmetry between the prices and loads is not significant for daily average data in 1999 yr market (before electricity crisis) but extremely significant for those in 2000 yr market (during the crisis). To further uncover the difference of asymmetry between the years 1999 and 2000, a modified H statistic (MH) and ΔMH statistic are proposed. One of the present contributions is that the high MH values calculated for hourly data exist in majority months in 2000 market. Another important conclusion is that the cross-correlation with downwards dominates over the whole 1999 yr in contrast to the cross-correlation with upwards dominates over the 2000 yr.

Correlation between maximum voluntary contraction and endurance measured by digital palpation and manometry: An observational study

Directory of Open Access Journals (Sweden)

Fátima Faní Fitz

Full Text Available Summary Introduction: Digital palpation and manometry are methods that can provide information regarding maximum voluntary contraction (MVC and endurance of the pelvic floor muscles (PFM, and a strong correlation between these variables can be expected. Objective: To investigate the correlation between MVC and endurance, measured by digital palpation and manometry. Method: Forty-two women, with mean age of 58.1 years (±10.2, and predominant symptoms of stress urinary incontinence (SUI, were included. Examination was firstly conducted by digital palpation and subsequently using a Peritron manometer. MVC was measured using a 0-5 score, based on the Oxford Grading Scale. Endurance was assessed based on the PERFECT scheme. Results: We found a significant positive correlation between the MVC measured by digital palpation and the peak manometric pressure (r=0.579, p<0.001, and between the measurements of the endurance by Peritron manometer and the PERFECT assessment scheme (r=0.559, P<0.001. Conclusion: Our results revealed a positive and significant correlation between the capacity and maintenance of PFM contraction using digital and manometer evaluations in women with predominant symptoms of SUI.

Uncertainty estimation of core safety parameters using cross-correlations of covariance matrix

International Nuclear Information System (INIS)

Yamamoto, Akio; Yasue, Yoshihiro; Endo, Tomohiro; Kodama, Yasuhiro; Ohoka, Yasunori; Tatsumi, Masahiro

2013-01-01

An uncertainty reduction method for core safety parameters, for which measurement values are not obtained, is proposed. We empirically recognize that there exist some correlations among the prediction errors of core safety parameters, e.g., a correlation between the control rod worth and the assembly relative power at corresponding position. Correlations of errors among core safety parameters are theoretically estimated using the covariance of cross sections and sensitivity coefficients of core parameters. The estimated correlations of errors among core safety parameters are verified through the direct Monte Carlo sampling method. Once the correlation of errors among core safety parameters is known, we can estimate the uncertainty of a safety parameter for which measurement value is not obtained. (author)

Cross-correlation Doppler global velocimetry (CC-DGV)

Science.gov (United States)

Cadel, Daniel R.; Lowe, K. Todd

2015-08-01

A flow velocimetry method, cross-correlation Doppler global velocimetry (CC-DGV), is presented as a robust, simplified, and high dynamic range implementation of the Doppler global/planar Doppler velocimetry technique. A sweep of several gigahertz of the vapor absorption spectrum is used for each velocity sample, with signals acquired from both Doppler-shifted scattered light within the flow and a non-Doppler shifted reference beam. Cross-correlation of these signals yields the Doppler shift between them, averaged over the duration of the scan. With presently available equipment, velocities from 0 ms-1 to over 3000 ms-1 can notionally be measured simultaneously, making the technique ideal for high speed flows. The processing routine is shown to be robust against large changes in the vapor pressure of the iodine cell, benefiting performance of the system in facilities where ambient conditions cannot be easily regulated. Validation of the system was performed with measurements of a model wind turbine blade boundary layer made in a 1.83 m by 1.83 m subsonic wind tunnel for which laser Doppler velocimetry (LDV) measurements were acquired alongside the CC-DGV results. CC-DGV uncertainties of ±1.30 ms-1, ±0.64 ms-1, and ±1.11 ms-1 were determined for the orthogonal stream-wise, transverse-horizontal, and transverse-vertical velocity components, and root-mean-square deviations of 2.77 ms-1 and 1.34 ms-1 from the LDV validation results were observed for Reynolds numbers of 1.5 million and 2 million, respectively. Volumetric mean velocity measurements are also presented for a supersonic jet, with velocity uncertainties of ±4.48 ms-1, ±16.93 ms-1, and ±0.50 ms-1 for the orthogonal components, and self-validation done by collapsing the data with a physical scaling.

Memory-induced sign reversals of the spatial cross-correlation for particles in viscoelastic shear flows

International Nuclear Information System (INIS)

Sauga, Ako; Laas, Katrin; Mankin, Romi

2015-01-01

Highlights: • Cross-correlation (CC) of coordinates of particles in viscoelastic shear flows is discussed. • Expressions for CC functions subjected to both internal and external noises are presented. • Impact of internal and external noises on CC functions are compared. • Memory-induced reentrant sign reversals of the spatial cross-moment are established. - Abstract: The behavior of shear-induced cross-correlation functions between particle fluctuations along orthogonal directions in the shear plane for harmonically trapped Brownian particles in a viscoelastic shear flow is studied. A generalized Langevin equation with a power-law-type memory kernel is used to model the complex structure of the viscoelastic media. Interaction with fluctuations of environmental parameters is modeled by a multiplicative white Gaussian noise, by an internal fractional Gaussian noise, and by an additive external white noise. It is shown that the presence of a memory has a profound effect on the behavior of the cross-correlation functions. Particularly, memory-induced reentrant sign reversals of the spatial cross-moment between orthogonal random displacements of a particle are established, i.e., an increase of the memory exponent can cause the sign reversal from positive to negative, but by a further increase of the memory exponent a reentrant transition from negative to positive values appears. Similarities and differences between the behavior of the models with additive internal and external noises are considered. It is shown that additive external and internal noises cause qualitatively different dependencies of the cross-correlation functions on the time lag. The occurrence of energetic instability due to the influence of multiplicative noise is also discussed.

Changes in Cross-Sectional Area and Transverse Diameter of the Heart on Inspiratory and Expiratory Chest CT: Correlation with Changes in Lung Size and Influence on Cardiothoracic Ratio Measurement.

Directory of Open Access Journals (Sweden)

Hayato Tomita

Full Text Available The aim of this study was to investigate physiological changes in cardiac area and diameters between inspiratory and expiratory chest computed tomography (CT, and to assess their correlation with lung size change and influence on cardiothoracic ratio (CTR measurements.The institutional review board of our institution approved this study, and informed consent was waived. Forty-three subjects underwent inspiratory and expiratory chest CT as part of routine clinical care. On both inspiratory and expiratory scans, lung volumes and maximum lung diameters (transverse and vertical directions were measured. The maximum cardiac cross-sectional area (CSA and the maximum transverse cardiac diameter were measured on both scans, and the CT-based CTR was calculated. Changes in the lung and cardiac measurements were expressed as the expiratory/inspiratory (E/I ratios. Comparisons between inspiratory and expiratory measurements were made by the Wilcoxon signed-rank test. Correlations between the E/I ratios of lung and heart measurements were evaluated by Spearman's rank correlation analysis.Cardiac CSA and transverse cardiac diameter was significantly larger on expiratory than on inspiratory CT (p < 0.0001. Significant negative correlations were found between the E/I ratios of these cardiac measurements and the E/I ratios of lung volume and vertical lung diameter (p < 0.01. CT-based CTR was significantly larger on expiration than on inspiration (p < 0.0001.Heart size on chest CT depends on the phase of ventilation, and is correlated with changes in lung volume and craniocaudal lung diameter. The CTR is also significantly influenced by ventilation.

On the linearity of cross-correlation delay times

Science.gov (United States)

Mercerat, E. D.; Nolet, G.

2012-12-01

We investigate the question whether a P-wave delay time Δ T estimated by locating the maximum of the cross-correlation function between data d(t) and a predicted test function s(t): γ (t) = ∫ t1t_2 s(τ ) d(τ -t) \\ {d}τ, provides an estimate of the Delta T that is (quasi-)linear with the relative velocity perturbation deltaln V_P}. Such linearity is intuitive if the data d(t) is an undeformed but delayed replica of the test signal, i.e. if d(t)=s(t-Delta T). Then the maximum of gamma (t) is shifted exactly by the delay Delta T, and linearity holds even for Delta T very large. In this case, we say that the body waves are in the ray theoretical regime and their delays, because of Fermat's Principle, depend quasi-linearly on the relative velocity (or slowness) perturbations deltaln V_P in the model. However, even if we correct for dispersion induced by the instrument response and by attenuation, body waves may show frequency dependent delay times that are caused by diffraction effects around lateral heterogeneities. It is not a-priori clear that linearity holds for Delta T, as is assumed in finite-frequency theory, if the waveforms of d(t) and s(t) differ substantially because of such dispersion. To test the linearity, we generate synthetic seismograms between two boreholes, and between the boreholes and the surface, in a 3D box of 200 × 120 × 120 m. The heterogeneity is a checkerboard with cubic anomalies of size 12 × 12 × 12 m. We test two different anomaly amplitudes: ± 2% and ± 5%, and measure Delta T using a test seismogram s(t) computed for an homogeneous medium. We also predict the delays for the 5% model from those in the 2% model by multiplying with 5/2. These predictions are in error by 10-20% of the delay, which is usually acceptable for tomography when compared with actual data errors. A slight bias in the prediction indicates that the Wielandt effect - the fact that negative delays suffer less wavefront healing than positive delays - is a

A quantitative correlation between the mobility and crystallinity of photo-cross-linkable P3HT

KAUST Repository

Woo, Claire; Piliego, Claudia; Holcombe, Thomas W.; Toney, Michael F.; Frechet, Jean

2012-01-01

The performance of polymer field effect transistors (FETs) can vary by orders of magnitude by applying different processing conditions. Although it is generally believed that a higher degree of crystallinity results in a higher mobility, the correlation is not straightforward. In addition, the effect of cross-linking on polymer thin film microstructural order is relatively unknown. This study investigates the effect of thermal annealing and UV-initiated photo-cross-linking on the FET performance and microstructural order of a photo-cross-linkable P3HT derivative. Our results demonstrate that while cross-linking did not disrupt the overall crystallinity of the polymer thin film, the photo-cross-linking process likely induced doping in the semiconductor layer, leading to the absence of saturation behavior in the FET. Annealing after cross-linking slightly improved the FET performance but only minimally affected the microstructural order of the polymer film since the 3D morphology had been "locked in" during the first cross-linking step. Importantly, annealing and cross-linking simultaneously was a successful method to preserve polymer crystallinity while also achieving effective cross-linking. Using newly developed quantitative X-ray analysis techniques, our study established a quantitative correlation between FET charge mobility and thin film crystallinity. © 2012 American Chemical Society.

A quantitative correlation between the mobility and crystallinity of photo-cross-linkable P3HT

KAUST Repository

Woo, Claire

2012-04-10

The performance of polymer field effect transistors (FETs) can vary by orders of magnitude by applying different processing conditions. Although it is generally believed that a higher degree of crystallinity results in a higher mobility, the correlation is not straightforward. In addition, the effect of cross-linking on polymer thin film microstructural order is relatively unknown. This study investigates the effect of thermal annealing and UV-initiated photo-cross-linking on the FET performance and microstructural order of a photo-cross-linkable P3HT derivative. Our results demonstrate that while cross-linking did not disrupt the overall crystallinity of the polymer thin film, the photo-cross-linking process likely induced doping in the semiconductor layer, leading to the absence of saturation behavior in the FET. Annealing after cross-linking slightly improved the FET performance but only minimally affected the microstructural order of the polymer film since the 3D morphology had been "locked in" during the first cross-linking step. Importantly, annealing and cross-linking simultaneously was a successful method to preserve polymer crystallinity while also achieving effective cross-linking. Using newly developed quantitative X-ray analysis techniques, our study established a quantitative correlation between FET charge mobility and thin film crystallinity. © 2012 American Chemical Society.

MEASUREMENT OF 21 cm BRIGHTNESS FLUCTUATIONS AT z ∼ 0.8 IN CROSS-CORRELATION

International Nuclear Information System (INIS)

Masui, K. W.; Switzer, E. R.; Calin, L.-M.; Pen, U.-L.; Shaw, J. R.; Banavar, N.; Bandura, K.; Blake, C.; Chang, T.-C.; Liao, Y.-W.; Chen, X.; Li, Y.-C.; Natarajan, A.; Peterson, J. B.; Voytek, T. C.

2013-01-01

In this Letter, 21 cm intensity maps acquired at the Green Bank Telescope are cross-correlated with large-scale structure traced by galaxies in the WiggleZ Dark Energy Survey. The data span the redshift range 0.6 HI b HI r = [0.43 ± 0.07(stat.) ± 0.04(sys.)] × 10 –3 , where Ω HI is the neutral hydrogen (H I) fraction, r is the galaxy-hydrogen correlation coefficient, and b HI is the H I bias parameter. This is the most precise constraint on neutral hydrogen density fluctuations in a challenging redshift range. Our measurement improves the previous 21 cm cross-correlation at z ∼ 0.8 both in its precision and in the range of scales probed.

A prototype of on-line digital flow rate meter based on cross-correlation principle

International Nuclear Information System (INIS)

Sun Xiaodong; Dai Zhenxi; Xu Jijun

1997-01-01

An on-line, digital prototype of flow rate measurement system based on cross-correlation principle is developed. Laboratory measurements using the prototype show that sufficiently large temperature fluctuations exist naturally and that measurements are possible. Temperature fluctuations are detected by two identical thermocouples spaced along the flow direction and are pre-processed by a thermocouple signal amplifier. The pre-processed temperature fluctuations are analyzed by a cross-correlator which measures the transit time of temperature fluctuations between two thermocouples directly. Thus, the so-called correlation velocity can be determined by a chip microprocessor 8031. Experimental results with single-phase under steady conditions also show that the distance between two thermocouples and the Reynolds number of fluid are the most important parameters to the measurement

The Cross-Correlation and Reshuffling Tests in Discerning Induced Seismicity

Science.gov (United States)

Schultz, Ryan; Telesca, Luciano

2018-05-01

In recent years, cases of newly emergent induced clusters have increased seismic hazard and risk in locations with social, environmental, and economic consequence. Thus, the need for a quantitative and robust means to discern induced seismicity has become a critical concern. This paper reviews a Matlab-based algorithm designed to quantify the statistical confidence between two time-series datasets. Similar to prior approaches, our method utilizes the cross-correlation to delineate the strength and lag of correlated signals. In addition, use of surrogate reshuffling tests allows for the dynamic testing against statistical confidence intervals of anticipated spurious correlations. We demonstrate the robust nature of our algorithm in a suite of synthetic tests to determine the limits of accurate signal detection in the presence of noise and sub-sampling. Overall, this routine has considerable merit in terms of delineating the strength of correlated signals, one of which includes the discernment of induced seismicity from natural.

The importance of parameter variances, correlations lengths, and cross-correlations in reactive transport models: key considerations for assessing the need for microscale information

Energy Technology Data Exchange (ETDEWEB)

Reimus, Paul W [Los Alamos National Laboratory

2010-12-08

A process-oriented modeling approach is implemented to examine the importance of parameter variances, correlation lengths, and especially cross-correlations in contaminant transport predictions over large scales. It is shown that the most important consideration is the correlation between flow rates and retardation processes (e.g., sorption, matrix diffusion) in the system. lf flow rates are negatively correlated with retardation factors in systems containing multiple flow pathways, then characterizing these negative correlation(s) may have more impact on reactive transport modeling than microscale information. Such negative correlations are expected in porous-media systems where permeability is negatively correlated with clay content and rock alteration (which are usually associated with increased sorption). Likewise, negative correlations are expected in fractured rocks where permeability is positively correlated with fracture apertures, which in turn are negatively correlated with sorption and matrix diffusion. Parameter variances and correlation lengths are also shown to have important effects on reactive transport predictions, but they are less important than parameter cross-correlations. Microscale information pertaining to contaminant transport has become more readily available as characterization methods and spectroscopic instrumentation have achieved lower detection limits, greater resolution, and better precision. Obtaining detailed mechanistic insights into contaminant-rock-water interactions is becoming a routine practice in characterizing reactive transport processes in groundwater systems (almost necessary for high-profile publications). Unfortunately, a quantitative link between microscale information and flow and transport parameter distributions or cross-correlations has not yet been established. One reason for this is that quantitative microscale information is difficult to obtain in complex, heterogeneous systems. So simple systems that lack the

Uncertainty estimation of core safety parameters using cross-correlations of covariance matrix

International Nuclear Information System (INIS)

Yamamoto, A.; Yasue, Y.; Endo, T.; Kodama, Y.; Ohoka, Y.; Tatsumi, M.

2012-01-01

An uncertainty estimation method for core safety parameters, for which measurement values are not obtained, is proposed. We empirically recognize the correlations among the prediction errors among core safety parameters, e.g., a correlation between the control rod worth and assembly relative power of corresponding position. Correlations of uncertainties among core safety parameters are theoretically estimated using the covariance of cross sections and sensitivity coefficients for core parameters. The estimated correlations among core safety parameters are verified through the direct Monte-Carlo sampling method. Once the correlation of uncertainties among core safety parameters is known, we can estimate the uncertainty of a safety parameter for which measurement value is not obtained. Furthermore, the correlations can be also used for the reduction of uncertainties of core safety parameters. (authors)

Relative azimuth inversion by way of damped maximum correlation estimates

Science.gov (United States)

Ringler, A.T.; Edwards, J.D.; Hutt, C.R.; Shelly, F.

2012-01-01

Horizontal seismic data are utilized in a large number of Earth studies. Such work depends on the published orientations of the sensitive axes of seismic sensors relative to true North. These orientations can be estimated using a number of different techniques: SensOrLoc (Sensitivity, Orientation and Location), comparison to synthetics (Ekstrom and Busby, 2008), or by way of magnetic compass. Current methods for finding relative station azimuths are unable to do so with arbitrary precision quickly because of limitations in the algorithms (e.g. grid search methods). Furthermore, in order to determine instrument orientations during station visits, it is critical that any analysis software be easily run on a large number of different computer platforms and the results be obtained quickly while on site. We developed a new technique for estimating relative sensor azimuths by inverting for the orientation with the maximum correlation to a reference instrument, using a non-linear parameter estimation routine. By making use of overlapping windows, we are able to make multiple azimuth estimates, which helps to identify the confidence of our azimuth estimate, even when the signal-to-noise ratio (SNR) is low. Finally, our algorithm has been written as a stand-alone, platform independent, Java software package with a graphical user interface for reading and selecting data segments to be analyzed.

Automated vessel segmentation using cross-correlation and pooled covariance matrix analysis.

Science.gov (United States)

Du, Jiang; Karimi, Afshin; Wu, Yijing; Korosec, Frank R; Grist, Thomas M; Mistretta, Charles A

2011-04-01

Time-resolved contrast-enhanced magnetic resonance angiography (CE-MRA) provides contrast dynamics in the vasculature and allows vessel segmentation based on temporal correlation analysis. Here we present an automated vessel segmentation algorithm including automated generation of regions of interest (ROIs), cross-correlation and pooled sample covariance matrix analysis. The dynamic images are divided into multiple equal-sized regions. In each region, ROIs for artery, vein and background are generated using an iterative thresholding algorithm based on the contrast arrival time map and contrast enhancement map. Region-specific multi-feature cross-correlation analysis and pooled covariance matrix analysis are performed to calculate the Mahalanobis distances (MDs), which are used to automatically separate arteries from veins. This segmentation algorithm is applied to a dual-phase dynamic imaging acquisition scheme where low-resolution time-resolved images are acquired during the dynamic phase followed by high-frequency data acquisition at the steady-state phase. The segmented low-resolution arterial and venous images are then combined with the high-frequency data in k-space and inverse Fourier transformed to form the final segmented arterial and venous images. Results from volunteer and patient studies demonstrate the advantages of this automated vessel segmentation and dual phase data acquisition technique. Copyright © 2011 Elsevier Inc. All rights reserved.

Whistler-mode signals: Group delay by cross correlation

International Nuclear Information System (INIS)

Thomson, N.R.

1975-01-01

Group travel times of 18.6 kHz whistler-mode signals from NLK, Seattle, to Wellington, New Zealand, are now being measured using the normal FSK transmissions. This is done using a mini-computer programmed to perform real-time cross correlations between two receivers: one receiver gets its signal from a whip aerial on which the ground wave (subionospheric mode) dominates, while the other gets its signal from a loop oriented for minimum ground wave. Group travel time can thus be measured continuously while there are whistler-mode signals present. Delays of 0.2--0.8 seconds have been found

Bottomside sinusoidal irregularities in the equatorial F region. II - Cross-correlation and spectral analysis

Science.gov (United States)

Cragin, B. L.; Hanson, W. B.; Mcclure, J. P.; Valladares, C. E.

1985-01-01

Equatorial bottomside sinusoidal (BSS) irregularities have been studied by applying techniques of cross-correlation and spectral analysis to the Atmosphere Explorer data set. The phase of the cross-correlations of the plasma number density is discussed and the two drift velocity components observed using the retarding potential analyzer and ion drift meter on the satellite are discussed. Morphology is addressed, presenting the geographical distributions of the occurrence of BSS events for the equinoxes and solstices. Physical processes including the ion Larmor flux, interhemispheric plasma flows, and variations in the lower F region Pedersen conductivity are invoked to explain the findings.

Determination of maximum physiologic thyroid uptake and correlation with 24-hour RAI uptake value

International Nuclear Information System (INIS)

Duldulao, M.; Obaldo, J.

2007-01-01

Full text: In hyperthyroid patients, thyroid uptake values are overestimated, sometimes approaching or exceeding 100%. This is physiologically and mathematically impossible. This study was undertaken to determine the maximum physiologic thyroid uptake value through a proposed simple method using a gamma camera. Methodology: Twenty-two patients (17 females and 5 males), with ages ranging from 19-61 y/o (mean age ± SD; 41 ± 12), with 24-hour uptake value of >50%, clinically hyperthyroid and referred for subsequent radioactive iodine therapy were studied. The computed maximum physiologic thyroid uptake was compared with the 24-hour uptake using the paired Student t-test and evaluated using linear regression analysis. Results: The computed physiologic uptake correlated poorly with the 24-hour uptake value. However, in the male subgroup, there was no statistically significant difference between the two (p=0.77). Linear regression analysis gives the following relationship: physiologic uptake (%) = 77.76 - 0.284 (24-hour RAI uptake value). Conclusion: Provided that proper regions of interest are applied with correct attenuation and background subtraction, determination of physiologic thyroid uptake may be obtained using the proposed method. This simple method may be useful prior to I-131 therapy for hyperthyroidism especially when a single uptake determination is performed. (author)

A method for the estimation of the significance of cross-correlations in unevenly sampled red-noise time series

Science.gov (United States)

Max-Moerbeck, W.; Richards, J. L.; Hovatta, T.; Pavlidou, V.; Pearson, T. J.; Readhead, A. C. S.

2014-11-01

We present a practical implementation of a Monte Carlo method to estimate the significance of cross-correlations in unevenly sampled time series of data, whose statistical properties are modelled with a simple power-law power spectral density. This implementation builds on published methods; we introduce a number of improvements in the normalization of the cross-correlation function estimate and a bootstrap method for estimating the significance of the cross-correlations. A closely related matter is the estimation of a model for the light curves, which is critical for the significance estimates. We present a graphical and quantitative demonstration that uses simulations to show how common it is to get high cross-correlations for unrelated light curves with steep power spectral densities. This demonstration highlights the dangers of interpreting them as signs of a physical connection. We show that by using interpolation and the Hanning sampling window function we are able to reduce the effects of red-noise leakage and to recover steep simple power-law power spectral densities. We also introduce the use of a Neyman construction for the estimation of the errors in the power-law index of the power spectral density. This method provides a consistent way to estimate the significance of cross-correlations in unevenly sampled time series of data.

Waveform correlation and coherence of short-period seismic noise within Gauribidanur array with implications for event detection

International Nuclear Information System (INIS)

Bhadauria, Y.S.; Arora, S.K.

1995-01-01

In continuation with our effort to model the short-period micro seismic noise at the seismic array at Gauribidanur (GBA), we have examined in detail time-correlation and spectral coherence of the noise field within the array space. This has implications of maximum possible improvement in signal-to-noise ratio (SNR) relevant to event detection. The basis of this study is about a hundred representative wide-band noise samples collected from GBA throughout the year 1992. Both time-structured correlation as well as coherence of the noise waveforms are found to be practically independent of the inter element distances within the array, and they exhibit strong temporal and spectral stability. It turns out that the noise is largely incoherent at frequencies ranging upwards from 2 Hz; the coherency coefficient tends to increase in the lower frequency range attaining a maximum of 0.6 close to 0.5 Hz. While the maximum absolute cross-correlation also diminishes with increasing frequency, the zero-lag cross-correlation is found to be insensitive to frequency filtering regardless of the pass band. An extremely small value of -0.01 of the zero-lag correlation and a comparatively higher year-round average estimate at 0.15 of the maximum absolute time-lagged correlation yields an SNR improvement varying between a probable high of 4.1 and a low of 2.3 for the full 20-element array. 19 refs., 6 figs

Fractal approach towards power-law coherency to measure cross-correlations between time series

Czech Academy of Sciences Publication Activity Database

Krištoufek, Ladislav

2017-01-01

Roč. 50, č. 1 (2017), s. 193-200 ISSN 1007-5704 R&D Projects: GA ČR(CZ) GP14-11402P Institutional support: RVO:67985556 Keywords : power- law coherency * power- law cross-correlations * correlations Subject RIV: AH - Economics OBOR OECD: Applied Economics, Econometrics Impact factor: 2.784, year: 2016 http://library.utia.cas.cz/separaty/2017/E/kristoufek-0473066.pdf

Long memory of abnormal investor attention and the cross-correlations between abnormal investor attention and trading volume, volatility respectively

Science.gov (United States)

Fan, Xiaoqian; Yuan, Ying; Zhuang, Xintian; Jin, Xiu

2017-03-01

Taking Baidu Index as a proxy for abnormal investor attention (AIA), the long memory property in the AIA of Shanghai Stock Exchange (SSE) 50 Index component stocks was empirically investigated using detrended fluctuation analysis (DFA) method. The results show that abnormal investor attention is power-law correlated with Hurst exponents between 0.64 and 0.98. Furthermore, the cross-correlations between abnormal investor attention and trading volume, volatility respectively are studied using detrended cross-correlation analysis (DCCA) and the DCCA cross-correlation coefficient (ρDCCA). The results suggest that there are positive correlations between AIA and trading volume, volatility respectively. In addition, the correlations for trading volume are in general higher than the ones for volatility. By carrying on rescaled range analysis (R/S) and rolling windows analysis, we find that the results mentioned above are effective and significant.

Calibration of the Dodewaard downcomer thermocouple cross-correlation flow-rate measurements

Energy Technology Data Exchange (ETDEWEB)

Stekelenburg, A J.C. [Technische Univ. Delft (Netherlands). Interfacultair Reactor Inst.; Hagen, T.H.J.J. van der [Technische Univ. Delft (Netherlands). Interfacultair Reactor Inst.; Akker, H.E.A. van den [Technische Univ. Delft (Netherlands). Lab. voor Fysische Technologie

1992-12-01

The cross-correlation flow measurement technique, applied for measuring the coolant flow rate in a nuclear reactor, was calibrated with the use of numerical simulations of turbulent flow. The three-dimensional domain was collapsed into two dimensions. With a two-dimensional calculation of steady-state flow with transient thermal characteristics the response of thermocouples to a temperature variation was calculated. By cross-correlating the calculated thermocouple responses, the link between total flow rate and measured transit times was made. Three calibration points were taken in the range of 579 kg/s to 1477 kg/s. In this range, the product of the calculated transit time and the mass flow-rate is constant up to +3.5% and -2.4%. The reliability of the calibration was estimated at {+-}4.6%. The influence of the inlet boundary conditions, and the modelling of the flow in the upper part of the downcomer channel on the calibration result is shown to be small. A measured velocity profile effect was successfully predicted. (orig.).

Cross-correlation measurement of quantum shot noise using homemade transimpedance amplifiers

International Nuclear Information System (INIS)

Hashisaka, Masayuki; Ota, Tomoaki; Yamagishi, Masakazu; Fujisawa, Toshimasa; Muraki, Koji

2014-01-01

We report a cross-correlation measurement system, based on a new approach, which can be used to measure shot noise in a mesoscopic conductor at milliKelvin temperatures. In contrast to other measurement systems in which high-speed low-noise voltage amplifiers are commonly used, our system employs homemade transimpedance amplifiers (TAs). The low input impedance of the TAs significantly reduces the crosstalk caused by unavoidable parasitic capacitance between wires. The TAs are designed to have a flat gain over a frequency band from 2 kHz to 1 MHz. Low-noise performance is attained by installing the TAs at a 4 K stage of a dilution refrigerator. Our system thus fulfills the technical requirements for cross-correlation measurements: low noise floor, high frequency band, and negligible crosstalk between two signal lines. Using our system, shot noise generated at a quantum point contact embedded in a quantum Hall system is measured. The good agreement between the obtained shot-noise data and theoretical predictions demonstrates the accuracy of the measurements

Time dependence of entropy flux and entropy production for a dynamical system driven by noises with coloured cross-correlation

Institute of Scientific and Technical Information of China (English)

Xie Wen-Xian; Xu Wei; Cai Li

2007-01-01

This paper shows the Fokker-Planck equation of a dynamical system driven by coloured cross-correlated white noises in the absence and presence of a small external force. Based on the Fokker-Planck equation and the definition of Shannon's information entropy, the time dependence of entropy flux and entropy production can be calculated. The present results can be used to explain the extremal behaviour of time dependence of entropy flux and entropy production in view of the dissipative parameter γ of the system, coloured cross-correlation time τ and coloured cross-correlation strength λ.

Cross-correlation of gravitational lensing from DES Science Verification data with SPT and Planck lensing

Energy Technology Data Exchange (ETDEWEB)

Kirk, D.; Omori, Y.; Benoit-Lévy, A.; Cawthon, R.; Chang, C.; Larsen, P.; Amara, A.; Bacon, D.; Crawford, T. M.; Dodelson, S.; Fosalba, P.; Giannantonio, T.; Holder, G.; Jain, B.; Kacprzak, T.; Lahav, O.; MacCrann, N.; Nicola, A.; Refregier, A.; Sheldon, E.; Story, K. T.; Troxel, M. A.; Vieira, J. D.; Vikram, V.; Zuntz, J.; Abbott, T. M. C.; Abdalla, F. B.; Becker, M. R.; Benson, B. A.; Bernstein, G. M.; Bernstein, R. A.; Bleem, L. E.; Bonnett, C.; Bridle, S. L.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Capozzi, D.; Carlstrom, J. E.; Rosell, A. Carnero; Kind, M. Carrasco; Carretero, J.; Crocce, M.; Cunha, C. E.; D' Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Eifler, T. F.; Evrard, A. E.; Flaugher, B.; Frieman, J.; Gerdes, D. W.; Goldstein, D. A.; Gruen, D.; Gruendl, R. A.; Honscheid, K.; James, D. J.; Jarvis, M.; Kent, S.; Kuehn, K.; Kuropatkin, N.; Lima, M.; March, M.; Martini, P.; Melchior, P.; Miller, C. J.; Miquel, R.; Nichol, R. C.; Ogando, R.; Plazas, A. A.; Reichardt, C. L.; Roodman, A.; Rozo, E.; Rykoff, E. S.; Sako, M.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Sevilla-Noarbe, I.; Simard, G.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Wechsler, R. H.; Weller, J.

2016-03-10

We measure the cross-correlation between weak lensing of galaxy images and of the cosmic microwave background (CMB). The effects of gravitational lensing on different sources will be correlated if the lensing is caused by the same mass fluctuations. We use galaxy shape measurements from 139 deg$^{2}$ of the Dark Energy Survey (DES) Science Verification data and overlapping CMB lensing from the South Pole Telescope (SPT) and Planck. The DES source galaxies have a median redshift of $z_{\\rm med} {\\sim} 0.7$, while the CMB lensing kernel is broad and peaks at $z{\\sim}2$. The resulting cross-correlation is maximally sensitive to mass fluctuations at $z{\\sim}0.44$. Assuming the Planck 2015 best-fit cosmology, the amplitude of the DES$\\times$SPT cross-power is found to be $A = 0.88 \\pm 0.30$ and that from DES$\\times$Planck to be $A = 0.86 \\pm 0.39$, where $A=1$ corresponds to the theoretical prediction. These are consistent with the expected signal and correspond to significances of $2.9 \\sigma$ and $2.2 \\sigma$ respectively. We demonstrate that our results are robust to a number of important systematic effects including the shear measurement method, estimator choice, photometric redshift uncertainty and CMB lensing systematics. Significant intrinsic alignment of galaxy shapes would increase the cross-correlation signal inferred from the data; we calculate a value of $A = 1.08 \\pm 0.36$ for DES$\\times$SPT when we correct the observations with a simple IA model. With three measurements of this cross-correlation now existing in the literature, there is not yet reliable evidence for any deviation from the expected LCDM level of cross-correlation, given the size of the statistical uncertainties and the significant impact of systematic errors, particularly IAs. We provide forecasts for the expected signal-to-noise of the combination of the five-year DES survey and SPT-3G.

DCCA cross-correlation in blue-chips companies: A view of the 2008 financial crisis in the Eurozone

Science.gov (United States)

Guedes, E.; Dionísio, A.; Ferreira, P. J.; Zebende, G. F.

2017-08-01

In this paper we analyze the blue-chips (up to 50% of the total index) companies in the Eurozone. Our motivation being analysis of the effect of the 2008 financial crisis. For this purpose, we apply the DCCA cross-correlation coefficient (ρDCCA) between the country stock market index and their respective blue-chips. Then, with the cross-correlation coefficient, we qualify and quantify how each blue-chip is adherent to its country index, evaluating the type of cross-correlation among them. Subsequently, for each blue-chip, we propose to study the 2008 financial crisis by measuring the adherence between post and pre-crisis. From this analysis, we can construct an adhesion map of each company with respect to the global index. Our database is formed of 12 Eurozone countries.

RECONSTRUCTING REDSHIFT DISTRIBUTIONS WITH CROSS-CORRELATIONS: TESTS AND AN OPTIMIZED RECIPE

International Nuclear Information System (INIS)

Matthews, Daniel J.; Newman, Jeffrey A.

2010-01-01

Many of the cosmological tests to be performed by planned dark energy experiments will require extremely well-characterized photometric redshift measurements. Current estimates for cosmic shear are that the true mean redshift of the objects in each photo-z bin must be known to better than 0.002(1 + z), and the width of the bin must be known to ∼0.003(1 + z) if errors in cosmological measurements are not to be degraded significantly. A conventional approach is to calibrate these photometric redshifts with large sets of spectroscopic redshifts. However, at the depths probed by Stage III surveys (such as DES), let alone Stage IV (LSST, JDEM, and Euclid), existing large redshift samples have all been highly (25%-60%) incomplete, with a strong dependence of success rate on both redshift and galaxy properties. A powerful alternative approach is to exploit the clustering of galaxies to perform photometric redshift calibrations. Measuring the two-point angular cross-correlation between objects in some photometric redshift bin and objects with known spectroscopic redshift, as a function of the spectroscopic z, allows the true redshift distribution of a photometric sample to be reconstructed in detail, even if it includes objects too faint for spectroscopy or if spectroscopic samples are highly incomplete. We test this technique using mock DEEP2 Galaxy Redshift survey light cones constructed from the Millennium Simulation semi-analytic galaxy catalogs. From this realistic test, which incorporates the effects of galaxy bias evolution and cosmic variance, we find that the true redshift distribution of a photometric sample can, in fact, be determined accurately with cross-correlation techniques. We also compare the empirical error in the reconstruction of redshift distributions to previous analytic predictions, finding that additional components must be included in error budgets to match the simulation results. This extra error contribution is small for surveys that sample

Optimal portfolio strategy with cross-correlation matrix composed by DCCA coefficients: Evidence from the Chinese stock market

Science.gov (United States)

Sun, Xuelian; Liu, Zixian

2016-02-01

In this paper, a new estimator of correlation matrix is proposed, which is composed of the detrended cross-correlation coefficients (DCCA coefficients), to improve portfolio optimization. In contrast to Pearson's correlation coefficients (PCC), DCCA coefficients acquired by the detrended cross-correlation analysis (DCCA) method can describe the nonlinear correlation between assets, and can be decomposed in different time scales. These properties of DCCA make it possible to improve the investment effect and more valuable to investigate the scale behaviors of portfolios. The minimum variance portfolio (MVP) model and the Mean-Variance (MV) model are used to evaluate the effectiveness of this improvement. Stability analysis shows the effect of two kinds of correlation matrices on the estimation error of portfolio weights. The observed scale behaviors are significant to risk management and could be used to optimize the portfolio selection.

Coordination analysis of players' distribution in football using cross-correlation and vector coding techniques.

Science.gov (United States)

Moura, Felipe Arruda; van Emmerik, Richard E A; Santana, Juliana Exel; Martins, Luiz Eduardo Barreto; Barros, Ricardo Machado Leite de; Cunha, Sergio Augusto

2016-12-01

The purpose of this study was to investigate the coordination between teams spread during football matches using cross-correlation and vector coding techniques. Using a video-based tracking system, we obtained the trajectories of 257 players during 10 matches. Team spread was calculated as functions of time. For a general coordination description, we calculated the cross-correlation between the signals. Vector coding was used to identify the coordination patterns between teams during offensive sequences that ended in shots on goal or defensive tackles. Cross-correlation showed that opponent teams have a tendency to present in-phase coordination, with a short time lag. During offensive sequences, vector coding results showed that, although in-phase coordination dominated, other patterns were observed. We verified that during the early stages, offensive sequences ending in shots on goal present greater anti-phase and attacking team phase periods, compared to sequences ending in tackles. Results suggest that the attacking team may seek to present a contrary behaviour of its opponent (or may lead the adversary behaviour) in the beginning of the attacking play, regarding to the distribution strategy, to increase the chances of a shot on goal. The techniques allowed detecting the coordination patterns between teams, providing additional information about football dynamics and players' interaction.

Cross-correlating the γ-ray Sky with Catalogs of Galaxy Clusters

Science.gov (United States)

Branchini, Enzo; Camera, Stefano; Cuoco, Alessandro; Fornengo, Nicolao; Regis, Marco; Viel, Matteo; Xia, Jun-Qing

2017-01-01

We report the detection of a cross-correlation signal between Fermi Large Area Telescope diffuse γ-ray maps and catalogs of clusters. In our analysis, we considered three different catalogs: WHL12, redMaPPer, and PlanckSZ. They all show a positive correlation with different amplitudes, related to the average mass of the objects in each catalog, which also sets the catalog bias. The signal detection is confirmed by the results of a stacking analysis. The cross-correlation signal extends to rather large angular scales, around 1°, that correspond, at the typical redshift of the clusters in these catalogs, to a few to tens of megaparsecs, I.e., the typical scale-length of the large-scale structures in the universe. Most likely this signal is contributed by the cumulative emission from active galactic nuclei (AGNs) associated with the filamentary structures that converge toward the high peaks of the matter density field in which galaxy clusters reside. In addition, our analysis reveals the presence of a second component, more compact in size and compatible with a point-like emission from within individual clusters. At present, we cannot distinguish between the two most likely interpretations for such a signal, I.e., whether it is produced by AGNs inside clusters or if it is a diffuse γ-ray emission from the intracluster medium. We argue that this latter, intriguing, hypothesis might be tested by applying this technique to a low-redshift large-mass cluster sample.

CROSS-CORRELATING THE γ -RAY SKY WITH CATALOGS OF GALAXY CLUSTERS

Energy Technology Data Exchange (ETDEWEB)

Branchini, Enzo [Dipartimento di Matematica e Fisica, Università degli Studi “Roma Tre,” via della Vasca Navale 84, I-00146 Roma (Italy); Camera, Stefano [Jodrell Bank Centre for Astrophysics, The University of Manchester, Alan Turing Building, Oxford Road, Manchester M13 9PL (United Kingdom); Cuoco, Alessandro [Institute for Theoretical Particle Physics and Cosmology, RWTH Aachen University, D-52056 Aachen (Germany); Fornengo, Nicolao; Regis, Marco [Dipartimento di Fisica, Università di Torino, via P. Giuria 1, I–10125 Torino (Italy); Viel, Matteo [INAF Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, I-34141, Trieste (Italy); Xia, Jun-Qing, E-mail: xiajq@bnu.edu.cn, E-mail: branchin@fis.uniroma3.it, E-mail: stefano.camera@manchester.ac.uk, E-mail: cuoco@physik.rwth-aachen.de, E-mail: fornengo@to.infn.it, E-mail: regis@to.infn.it, E-mail: viel@oats.inaf.it [Department of Astronomy, Beijing Normal University, Beijing 100875 (China)

2017-01-01

We report the detection of a cross-correlation signal between Fermi Large Area Telescope diffuse γ -ray maps and catalogs of clusters. In our analysis, we considered three different catalogs: WHL12, redMaPPer, and PlanckSZ. They all show a positive correlation with different amplitudes, related to the average mass of the objects in each catalog, which also sets the catalog bias. The signal detection is confirmed by the results of a stacking analysis. The cross-correlation signal extends to rather large angular scales, around 1°, that correspond, at the typical redshift of the clusters in these catalogs, to a few to tens of megaparsecs, i.e., the typical scale-length of the large-scale structures in the universe. Most likely this signal is contributed by the cumulative emission from active galactic nuclei (AGNs) associated with the filamentary structures that converge toward the high peaks of the matter density field in which galaxy clusters reside. In addition, our analysis reveals the presence of a second component, more compact in size and compatible with a point-like emission from within individual clusters. At present, we cannot distinguish between the two most likely interpretations for such a signal, i.e., whether it is produced by AGNs inside clusters or if it is a diffuse γ -ray emission from the intracluster medium. We argue that this latter, intriguing, hypothesis might be tested by applying this technique to a low-redshift large-mass cluster sample.

Cross correlation analysis of medium energy gamma rays for the northern hemisphere

International Nuclear Information System (INIS)

Long, J.; Zanrosso, E.; Zych, A.D.; White, R.S.

1982-01-01

Data obtained with the UCR gamma telescope have been analyzed using the cross-correlation method. The observations extended over 37.5 hr from 0930 UT, 30 Sept. to 2300 UT, 1 oct. 1978 at 32deg N. Lat. (Palestine, Texas). The Crab Nebula- Anticenter region was observed on consecutive days. The telescope's wide field-of-view permitted the search for a number of other medium energy (1-30 MeV) source candidates. As the telescope swept the sky, the count rates for fixed celestial directions were correlated with the expected response as a function of time and telescope geometry. Similar correlations were carried out for sources measured in the laboratory and computer-simulated sources. In the correlation method the time independence and azimuthal symmetry of the atmospheric and cosmic diffuse backgrounds provide zero correlation. In contrast, a celestial source produces an asymmetric response with respect to the azimuthal direction which varies predictably in time to give a positive correlation. Preliminary correlation skymaps of the Anticenter region are presented and their statistical significance discussed. An energy spectrum obtained from the ''correlated counts'' is compared with measurements by other methods

Improved dark energy detection through the polarization-assisted cross correlation of the cosmic microwave background with radio sources

International Nuclear Information System (INIS)

Liu, Guo-Chin; Ng, Kin-Wang; Pen, Ue-Li

2011-01-01

Integrated Sachs-Wolfe (ISW) effect can be estimated by cross-correlating the cosmic microwave background (CMB) sky with tracers of the local matter distribution. At late cosmic time, the dark energy-induced decay of gravitation potential generates a cross correlation signal on large angular scales. The dominant noise is the intrinsic CMB anisotropies from the inflationary epoch. In this paper we use CMB polarization to reduce this intrinsic noise. We cross-correlate the microwave sky observed by Wilkinson Microwave Anisotropy Probe (WMAP) with the radio source catalog compiled by NRAO VLA Sky Survey (NVSS) to study the efficiency of the noise suppression. We find that the error bars are reduced by about 4 to 14% and the statistical power in the signal is improved.

On the determination of neutrino masses and dark energy evolution from the cross-correlation of CMB and LSS

International Nuclear Information System (INIS)

Ichikawa, Kazuhide; Takahashi, Tomo

2008-01-01

We discuss the possibilities of the simultaneous determination of the neutrino masses and the evolution of dark energy from future cosmological observations such as cosmic microwave background (CMB), large scale structure (LSS) and the cross-correlation between them. Recently it has been discussed that there is a degeneracy between the neutrino masses and the equation of state for dark energy. It is also known that there are some degeneracies among the parameters describing the dark energy evolution. We discuss the implications of these for the cross-correlation of CMB with LSS in some detail. Then we consider to what extent we can determine the neutrino masses and the dark energy evolution using the expected data from CMB, LSS and their cross-correlation

Effect of cross-correlation on track-to-track fusion

Science.gov (United States)

Saha, Rajat K.

1994-07-01

Since the advent of target tracking systems employing a diverse mixture of sensors, there has been increasing recognition by air defense system planners and other military system analysts of the need to integrate these tracks so that a clear air picture can be obtained in a command center. A popular methodology to achieve this goal is to perform track-to-track fusion, which performs track-to-track association as well as kinematic state vector fusion. This paper seeks to answer analytically the extent of improvement achievable by means of kinetic state vector fusion when the tracks are obtained from dissimilar sensors (e.g., Radar/ESM/IRST/IFF). It is well known that evaluation of the performance of state vector fusion algorithms at steady state must take into account the effects of cross-correlation between eligible tracks introduced by the input noise which, unfortunately, is often neglected because of added computational complexity. In this paper, an expression for the steady-state cross-covariance matrix for a 2D state vector track-to-track fusion is obtained. This matrix is shown to be a function of the parameters of the Kalman filters associated with the candidate tracks being fused. Conditions for positive definiteness of the cross-covariance matrix have been derived and the effect of positive definiteness on performance of track-to-track fusion is also discussed.

Principles of femtosecond X-ray/optical cross-correlation with X-ray induced transient optical reflectivity in solids

Energy Technology Data Exchange (ETDEWEB)

Eckert, S., E-mail: sebastian.eckert@helmholtz-berlin.de, E-mail: martin.beye@helmholtz-berlin.de; Beye, M., E-mail: sebastian.eckert@helmholtz-berlin.de, E-mail: martin.beye@helmholtz-berlin.de; Pietzsch, A.; Quevedo, W.; Hantschmann, M. [Institute for Methods and Instrumentation in Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin (Germany); Ochmann, M.; Huse, N. [Institute for Nanostructure and Solid State Physics, University of Hamburg, Jungiusstr. 11, 20355 Hamburg, Germany and Max Planck Institute for the Structure and Dynamics of Matter, Center for Free-Electron Laser Science, Luruper Chaussee 149, 22761 Hamburg (Germany); Ross, M.; Khalil, M. [Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195 (United States); Minitti, M. P.; Turner, J. J.; Moeller, S. P.; Schlotter, W. F.; Dakovski, G. L. [LCLS, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Föhlisch, A. [Institute for Methods and Instrumentation in Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin (Germany); Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam (Germany)

2015-02-09

The discovery of ultrafast X-ray induced optical reflectivity changes enabled the development of X-ray/optical cross correlation techniques at X-ray free electron lasers worldwide. We have now linked through experiment and theory the fundamental excitation and relaxation steps with the transient optical properties in finite solid samples. Therefore, we gain a thorough interpretation and an optimized detection scheme of X-ray induced changes to the refractive index and the X-ray/optical cross correlation response.

Cross-Correlations in Quasar Radio Emission

Science.gov (United States)

Nefedyev, Yuri; Panischev, Oleg; Demin, Sergey

The main factors forming the complex evolution of the accretive astrophysical systems are nonlinearity, intermittency, nonstationarity and also collective phenomena. To discover the dynamic processes in these objects and to detain understanding their properties we need to use all the applicable analyzing methods. Here we use the Flicker-Noise Spectroscopy (FNS) as a phenomenological approach to analyzing and parameterizing the auto- and cross-correlations in time series of astrophysical objects dynamics. As an example we consider the quasar flux radio spectral density at frequencies 2.7 GHz and 8.1 GHz. Data have been observed by Dr. N. Tanizuka (Laboratory for Complex Systems Analysis, Osaka Prefecture University) in a period of 1979 to 1988 (3 309 days). According to mental habits quasar is a very energetic and distant active galactic nucleus containing a supermassive black hole by size 10-10,000 times the Schwarzschild radius. The quasar is powered by an accretion disc around the black hole. The accretion disc material layers, moving around the black hole, are under the influence of gravitational and frictional forces. It results in raising the high temperature and arising the resonant and collective phenomena reflected in quasar emission dynamics. Radio emission dynamics of the quasar 0215p015 is characterized by three quasi-periodic processes, which are prevalent in considering dynamics. By contrast the 1641p399's emission dynamics have not any distinguish processes. It means the presence of high intermittency in accretive modes. The second difference moment allows comparing the degree of manifesting of resonant and chaotic components in initial time series of the quasar radio emission. The comparative analysis shows the dominating of chaotic part of 1641p399's dynamics whereas the radio emission of 0215p015 has the predominance of resonant component. Analyzing the collective features of the quasar radio emission intensity demonstrates the significant

Cross-correlated relaxation rates between protein backbone H–X dipolar interactions

International Nuclear Information System (INIS)

Vögeli, Beat

2017-01-01

The relaxation interference between dipole–dipole interactions of two separate spin pairs carries structural and dynamics information. In particular, when compared to individual dynamic behavior of those spin pairs, such cross-correlated relaxation (CCR) rates report on the correlation between the spin pairs. We have recently mapped out correlated motion along the backbone of the protein GB3, using CCR rates among and between consecutive H N –N and H α –C α dipole–dipole interactions. Here, we provide a detailed account of the measurement of the four types of CCR rates. All rates were obtained from at least two different pulse sequences, of which the yet unpublished ones are presented. Detailed comparisons between the different methods and corrections for unwanted pathways demonstrate that the averaged CCR rates are highly accurate and precise with errors of 1.5–3% of the entire value ranges.

Cross-correlated relaxation rates between protein backbone H–X dipolar interactions

Energy Technology Data Exchange (ETDEWEB)

Vögeli, Beat, E-mail: beat.vogeli@ucdenver.edu [University of Colorado Denver, Department of Biochemistry and Molecular Genetics (United States)

2017-03-15

The relaxation interference between dipole–dipole interactions of two separate spin pairs carries structural and dynamics information. In particular, when compared to individual dynamic behavior of those spin pairs, such cross-correlated relaxation (CCR) rates report on the correlation between the spin pairs. We have recently mapped out correlated motion along the backbone of the protein GB3, using CCR rates among and between consecutive H{sup N}–N and H{sup α}–C{sup α} dipole–dipole interactions. Here, we provide a detailed account of the measurement of the four types of CCR rates. All rates were obtained from at least two different pulse sequences, of which the yet unpublished ones are presented. Detailed comparisons between the different methods and corrections for unwanted pathways demonstrate that the averaged CCR rates are highly accurate and precise with errors of 1.5–3% of the entire value ranges.

Determination of velocity vector angles using the directional cross-correlation method

DEFF Research Database (Denmark)

Kortbek, Jacob; Jensen, Jørgen Arendt

2005-01-01

and then select the angle with the highest normalized correlation between directional signals. The approach is investigated using Field II simulations and data from the experimental ultrasound scanner RASMUS and with a parabolic flow having a peak velocity of 0.3 m/s. A 7 MHz linear array transducer is used......A method for determining both velocity magnitude and angle in any direction is suggested. The method uses focusing along the velocity direction and cross-correlation for finding the correct velocity magnitude. The angle is found from beamforming directional signals in a number of directions......-time ) between signals to correlate, and a proper choice varies with flow angle and flow velocity. One performance example is given with a fixed value of k tprf for all flow angles. The angle estimation on measured data for flow at 60 ◦ to 90 ◦ , yields a probability of valid estimates between 68% and 98...

Cross-correlation redshift calibration without spectroscopic calibration samples in DES Science Verification Data

Science.gov (United States)

Davis, C.; Rozo, E.; Roodman, A.; Alarcon, A.; Cawthon, R.; Gatti, M.; Lin, H.; Miquel, R.; Rykoff, E. S.; Troxel, M. A.; Vielzeuf, P.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Annis, J.; Bechtol, K.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Castander, F. J.; Crocce, M.; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Doel, P.; Drlica-Wagner, A.; Fausti Neto, A.; Flaugher, B.; Fosalba, P.; Frieman, J.; García-Bellido, J.; Gaztanaga, E.; Gerdes, D. W.; Giannantonio, T.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; Jain, B.; James, D. J.; Jeltema, T.; Krause, E.; Kuehn, K.; Kuhlmann, S.; Kuropatkin, N.; Lahav, O.; Li, T. S.; Lima, M.; March, M.; Marshall, J. L.; Martini, P.; Melchior, P.; Ogando, R. L. C.; Plazas, A. A.; Romer, A. K.; Sanchez, E.; Scarpine, V.; Schindler, R.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, M.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Vikram, V.; Walker, A. R.; Wechsler, R. H.

2018-06-01

Galaxy cross-correlations with high-fidelity redshift samples hold the potential to precisely calibrate systematic photometric redshift uncertainties arising from the unavailability of complete and representative training and validation samples of galaxies. However, application of this technique in the Dark Energy Survey (DES) is hampered by the relatively low number density, small area, and modest redshift overlap between photometric and spectroscopic samples. We propose instead using photometric catalogues with reliable photometric redshifts for photo-z calibration via cross-correlations. We verify the viability of our proposal using redMaPPer clusters from the Sloan Digital Sky Survey (SDSS) to successfully recover the redshift distribution of SDSS spectroscopic galaxies. We demonstrate how to combine photo-z with cross-correlation data to calibrate photometric redshift biases while marginalizing over possible clustering bias evolution in either the calibration or unknown photometric samples. We apply our method to DES Science Verification (DES SV) data in order to constrain the photometric redshift distribution of a galaxy sample selected for weak lensing studies, constraining the mean of the tomographic redshift distributions to a statistical uncertainty of Δz ˜ ±0.01. We forecast that our proposal can, in principle, control photometric redshift uncertainties in DES weak lensing experiments at a level near the intrinsic statistical noise of the experiment over the range of redshifts where redMaPPer clusters are available. Our results provide strong motivation to launch a programme to fully characterize the systematic errors from bias evolution and photo-z shapes in our calibration procedure.

Isthmus Dependent Atrial Flutter Cycle Length Correlates with Right Atrial Cross-Sectional Area

Directory of Open Access Journals (Sweden)

Kousik Krishnan

2009-05-01

Full Text Available Background: Right atrial flutter cycle length can prolong in the presence of antiarrhythmic drug therapy. We hypothesized that the cycle length of right atrial isthmus dependent flutter would correlate with right atrial cross-sectional area measurements. Methods: 60 patients who underwent ablation for electrophysiologically proven isthmus dependent right atrial flutter, who were not on Class I or Class III antiarrhythmic drugs and had recent 2-dimensional echocardiographic data comprised the study group. Right atrial length and width were measured in the apical four chamber view. Cross-sectional area was estimated by multiplying the length and width. 35 patients had an atrial flutter rate ≥250 bpm (Normal Flutter Group and 25 patients had an atrial flutter rate < 250 bpm (Slow Flutter Group. Results: Mean atrial flutter rate was 283 bpm in the normal flutter group and 227 bpm in the slow flutter group. Mean atrial flutter cycle length was 213 ms in the Normal Flutter Group and 265 ms in the Slow Flutter Group (p<0.0001. Mean right atrial cross sectional area was 1845 mm2 in the Normal Flutter group and 2378 mm2 in the Slow Flutter Group, (p< 0.0001. Using linear regression, CSA was a significant predictor of cycle length (β =0.014 p = 0.0045. For every 1 mm2 increase in cross-sectional area, cycle length is 0.014 ms longer.Conclusion: In the absence of antiarrhythmic medications, right atrial cross sectional area enlargement correlates with atrial flutter cycle length. These findings provide further evidence that historical rate-related definitions of typical isthmus dependent right atrial are not mechanistically valid.

KiDS-450: tomographic cross-correlation of galaxy shear with Planck lensing

Science.gov (United States)

Harnois-Déraps, Joachim; Tröster, Tilman; Chisari, Nora Elisa; Heymans, Catherine; van Waerbeke, Ludovic; Asgari, Marika; Bilicki, Maciej; Choi, Ami; Erben, Thomas; Hildebrandt, Hendrik; Hoekstra, Henk; Joudaki, Shahab; Kuijken, Konrad; Merten, Julian; Miller, Lance; Robertson, Naomi; Schneider, Peter; Viola, Massimo

2017-10-01

We present the tomographic cross-correlation between galaxy lensing measured in the Kilo Degree Survey (KiDS-450) with overlapping lensing measurements of the cosmic microwave background (CMB), as detected by Planck 2015. We compare our joint probe measurement to the theoretical expectation for a flat Λ cold dark matter cosmology, assuming the best-fitting cosmological parameters from the KiDS-450 cosmic shear and Planck CMB analyses. We find that our results are consistent within 1σ with the KiDS-450 cosmology, with an amplitude re-scaling parameter AKiDS = 0.86 ± 0.19. Adopting a Planck cosmology, we find our results are consistent within 2σ, with APlanck = 0.68 ± 0.15. We show that the agreement is improved in both cases when the contamination to the signal by intrinsic galaxy alignments is accounted for, increasing A by ∼0.1. This is the first tomographic analysis of the galaxy lensing - CMB lensing cross-correlation signal, and is based on five photometric redshift bins. We use this measurement as an independent validation of the multiplicative shear calibration and of the calibrated source redshift distribution at high redshifts. We find that constraints on these two quantities are strongly correlated when obtained from this technique, which should therefore not be considered as a stand-alone competitive calibration tool.

Cross-correlation patterns in social opinion formation with sequential data

Science.gov (United States)

Chakrabarti, Anindya S.

2016-11-01

Recent research on large-scale internet data suggests existence of patterns in the collective behavior of billions of people even though each of them may pursue own activities. In this paper, we interpret online rating activity as a process of forming social opinion about individual items, where people sequentially choose a rating based on the current information set comprising all previous ratings and own preferences. We construct an opinion index from the sequence of ratings and we show that (1) movie-specific opinion converges much slower than an independent and identically distributed (i.i.d.) sequence of ratings, (2) rating sequence for individual movies shows lesser variation compared to an i.i.d. sequence of ratings, (3) the probability density function of the asymptotic opinions has more spread than that defined over opinion arising from i.i.d. sequence of ratings, (4) opinion sequences across movies are correlated with significantly higher and lower correlation compared to opinion constructed from i.i.d. sequence of ratings, creating a bimodal cross-correlation structure. By decomposing the temporal correlation structures from panel data of movie ratings, we show that the social effects are very prominent whereas group effects cannot be differentiated from those of surrogate data and individual effects are quite small. The former explains a large part of extreme positive or negative correlations between sequences of opinions. In general, this method can be applied to any rating data to extract social or group-specific effects in correlation structures. We conclude that in this particular case, social effects are important in opinion formation process.

Correlation between blister skin thickness, the maximum in the damage-energy distribution, and projected ranges of He+ ions in metals: V

International Nuclear Information System (INIS)

Kaminsky, M.; Das, S.K.; Fenske, G.

1976-01-01

In these experiments a systematic study of the correlation of the skin thickness measured directly by scanning electron microscopy with both the calculated projected-range values and the maximum in the damage-energy distribution has been conducted for a broad helium-ion energy range (100 keV-1000 keV in polycrystalline vanadium. (Auth.)

Correlation and path analysis of grain yield and morphological traits in test–cross populations of maize

NARCIS (Netherlands)

Sreckov, Z.; Nastasic, A.; Bocanski, J.; Djalovic, I.; Vukosavljev, M.; Jockovic, B.

2011-01-01

One of the goals of this paper was to determine correlation between grain yield, like the most important agronomic trait, and traits of the plant and ear that are influencing on the grain yield, in two test-cross populations, which are formed by crossing progenies of NSU(1) population after 17

Detectability of the 21-cm CMB cross-correlation from the epoch of reionization

NARCIS (Netherlands)

Tashiro, Hiroyuki; Aghanim, Nabila; Langer, Mathieu; Douspis, Marian; Zaroubi, Saleem; Jelic, Vibor

The 21-cm line fluctuations and the cosmic microwave background (CMB) are powerful probes of the epoch of reionization of the Universe. We study the potential of the cross-correlation between 21-cm line fluctuations and CMB anisotropy to obtain further constraints on the reionization history. We

Evidence for gravitational lensing of the cosmic microwave background polarization from cross-correlation with the cosmic infrared background.

Science.gov (United States)

Ade, P A R; Akiba, Y; Anthony, A E; Arnold, K; Atlas, M; Barron, D; Boettger, D; Borrill, J; Borys, C; Chapman, S; Chinone, Y; Dobbs, M; Elleflot, T; Errard, J; Fabbian, G; Feng, C; Flanigan, D; Gilbert, A; Grainger, W; Halverson, N W; Hasegawa, M; Hattori, K; Hazumi, M; Holzapfel, W L; Hori, Y; Howard, J; Hyland, P; Inoue, Y; Jaehnig, G C; Jaffe, A; Keating, B; Kermish, Z; Keskitalo, R; Kisner, T; Le Jeune, M; Lee, A T; Leitch, E M; Linder, E; Lungu, M; Matsuda, F; Matsumura, T; Meng, X; Miller, N J; Morii, H; Moyerman, S; Myers, M J; Navaroli, M; Nishino, H; Paar, H; Peloton, J; Poletti, D; Quealy, E; Rebeiz, G; Reichardt, C L; Richards, P L; Ross, C; Rotermund, K; Schanning, I; Schenck, D E; Sherwin, B D; Shimizu, A; Shimmin, C; Shimon, M; Siritanasak, P; Smecher, G; Spieler, H; Stebor, N; Steinbach, B; Stompor, R; Suzuki, A; Takakura, S; Tikhomirov, A; Tomaru, T; Wilson, B; Yadav, A; Zahn, O

2014-04-04

We reconstruct the gravitational lensing convergence signal from cosmic microwave background (CMB) polarization data taken by the Polarbear experiment and cross-correlate it with cosmic infrared background maps from the Herschel satellite. From the cross spectra, we obtain evidence for gravitational lensing of the CMB polarization at a statistical significance of 4.0σ and indication of the presence of a lensing B-mode signal at a significance of 2.3σ. We demonstrate that our results are not biased by instrumental and astrophysical systematic errors by performing null tests, checks with simulated and real data, and analytical calculations. This measurement of polarization lensing, made via the robust cross-correlation channel, not only reinforces POLARBEAR auto-correlation measurements, but also represents one of the early steps towards establishing CMB polarization lensing as a powerful new probe of cosmology and astrophysics.

Bias of damped Lyman-α systems from their cross-correlation with CMB lensing

Science.gov (United States)

Alonso, D.; Colosimo, J.; Font-Ribera, A.; Slosar, A.

2018-04-01

We cross-correlate the positions of damped Lyman-α systems (DLAs) and their parent quasar catalog with a convergence map derived from the Planck cosmic microwave background (CMB) temperature data. We make consistent measurements of the lensing signal of both samples in both Fourier and configuration space. By interpreting the excess signal present in the DLA catalog with respect to the parent quasar catalog as caused by the large scale structure traced by DLAs, we are able to infer the bias of these objects: bDLA=2.6±0.9. These results are consistent with previous measurements made in cross-correlation with the Lyman-α forest, although the current noise in the lensing data and the low number density of DLAs limits the constraining power of this measurement. We discuss the robustness of the analysis with respect to a number different systematic effects and forecast prospects of carrying out this measurement with data from future experiments.

Semi-Supervised Multi-View Ensemble Learning Based On Extracting Cross-View Correlation

Directory of Open Access Journals (Sweden)

ZALL, R.

2016-05-01

Full Text Available Correlated information between different views incorporate useful for learning in multi view data. Canonical correlation analysis (CCA plays important role to extract these information. However, CCA only extracts the correlated information between paired data and cannot preserve correlated information between within-class samples. In this paper, we propose a two-view semi-supervised learning method called semi-supervised random correlation ensemble base on spectral clustering (SS_RCE. SS_RCE uses a multi-view method based on spectral clustering which takes advantage of discriminative information in multiple views to estimate labeling information of unlabeled samples. In order to enhance discriminative power of CCA features, we incorporate the labeling information of both unlabeled and labeled samples into CCA. Then, we use random correlation between within-class samples from cross view to extract diverse correlated features for training component classifiers. Furthermore, we extend a general model namely SSMV_RCE to construct ensemble method to tackle semi-supervised learning in the presence of multiple views. Finally, we compare the proposed methods with existing multi-view feature extraction methods using multi-view semi-supervised ensembles. Experimental results on various multi-view data sets are presented to demonstrate the effectiveness of the proposed methods.

Retrieving the elastodynamic Green's function of an arbitrary inhomogeneous medium by cross correlation

International Nuclear Information System (INIS)

Wapenaar, Kees

2004-01-01

A correlation-type reciprocity theorem is used to show that the elastodynamic Green's function of any inhomogeneous medium (random or deterministic) can be retrieved from the cross correlation of two recordings of a wave field at different receiver locations at the free surface. Unlike in other derivations, which apply to diffuse wave fields in random media or irregular finite bodies, no assumptions are made about the diffusivity of the wave field. In a second version, it is assumed that the wave field is diffuse due to many uncorrelated sources inside the medium

Remote detection of weak aftershocks of the DPRK underground explosions using waveform cross correlation

Science.gov (United States)

Le Bras, R.; Rozhkov, M.; Bobrov, D.; Kitov, I. O.; Sanina, I.

2017-12-01

Association of weak seismic signals generated by low-magnitude aftershocks of the DPRK underground tests into event hypotheses represent a challenge for routine automatic and interactive processing at the International Data Centre (IDC) of the Comprehensive Nuclear-Test-Ban Treaty Organization, due to the relatively low station density of the International Monitoring System (IMS) seismic network. Since 2011, as an alternative, the IDC has been testing various prototype techniques of signal detection and event creation based on waveform cross correlation. Using signals measured by seismic stations of the IMS from DPRK explosions as waveform templates, the IDC detected several small (estimated mb between 2.2 and 3.6) seismic events after two DPRK tests conducted on September 9, 2016 and September 3, 2017. The obtained detections were associated with reliable event hypothesis and then used to locate these events relative to the epicenters of the DPRK explosions. We observe high similarity of the detected signals with the corresponding waveform templates. The newly found signals also correlate well between themselves. In addition, the values of the signal-to-noise ratios (SNR) estimated using the traces of cross correlation coefficients, increase with template length (from 5 s to 150 s), providing strong evidence in favour of their spatial closeness, which allows interpreting them as explosion aftershocks. We estimated the relative magnitudes of all aftershocks using the ratio of RMS amplitudes of the master and slave signal in the cross correlation windows characterized by the highest SNR. Additional waveform data from regional non-IMS stations MDJ and SEHB provide independent validation of these aftershock hypotheses. Since waveform templates from any single master event may be sub-efficient at some stations, we have also developed a method of joint usage of the DPRK and the biggest aftershocks templates to build more robust event hypotheses.

Endoanal MRI of the anal sphincter complex: correlation with cross-sectional anatomy and histology

NARCIS (Netherlands)

S.M. Hussain (Shahid); J. Stoker (Jacob); A.W. Zwamborn; J.C. den Hollander (Jan); J.-W. Kuiper (Jan-Willem); C.A. Entius; J.S. Lameris

1996-01-01

textabstractThe purpose of this study was to correlate the in vivo endoanal MRI findings of the anal sphincter with the cross-sectional anatomy and histology. Fourteen patients with rectal tumours were examined with a rigid endoanal MR coil before undergoing

The spectrum of R Cygni during its exceptionally low maximum of 1983

International Nuclear Information System (INIS)

Wallerstein, G.; Dominy, J.F.; Mattei, J.A.; Smith, V.V.

1985-01-01

In 1983 R Cygni experienced its faintest maximum ever recorded. A study of the light curve shows correlations between brightness at maximum and interval from the previous cycle, in the sense that fainter maxima occur later than normal and are followed by maxima that occur earlier than normal. Emission and absorption lines in the optical and near infrared (2.2 μm region) reveal two significant correlations. The amplitude of line doubling is independent of the magnitude at maximum for msub(v)(max)=7.1 to 9.8. The velocities of the emission lines, however, correlate with the magnitude at maximum, in that during bright maxima they are negatively displaced by 15 km s -1 with respect to the red component of absorption lines, while during the faintest maximum there is no displacement. (author)

Kinematic cross-correlation induces sensory integration across separate objects.

Science.gov (United States)

Debats, Nienke B; Ernst, Marc O; Heuer, Herbert

2017-12-01

In a basic cursor-control task, the perceived positions of the hand and the cursor are biased towards each other. We recently found that this phenomenon conforms to the reliability-based weighting mechanism of optimal multisensory integration. This indicates that optimal integration is not restricted to sensory signals originating from a single source, as is the prevailing view, but that it also applies to separate objects that are connected by a kinematic relation (i.e. hand and cursor). In the current study, we examined which aspects of the kinematic relation are crucial for eliciting the sensory integration: (i) the cross-correlation between kinematic variables of the hand and cursor trajectories, and/or (ii) an internal model of the hand-cursor kinematic transformation. Participants made out-and-back movements from the centre of a semicircular workspace to its boundary, after which they judged the position where either their hand or the cursor hit the boundary. We analysed the position biases and found that the integration was strong in a condition with high kinematic correlations (a straight hand trajectory was mapped to a straight cursor trajectory), that it was significantly reduced for reduced kinematic correlations (a straight hand trajectory was transformed into a curved cursor trajectory) and that it was not affected by the inability to acquire an internal model of the kinematic transformation (i.e. by the trial-to-trial variability of the cursor curvature). These findings support the idea that correlations play a crucial role in multisensory integration irrespective of the number of sensory sources involved. © 2017 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

The cross-correlation between 21 cm intensity mapping maps and the Lyα forest in the post-reionization era

Energy Technology Data Exchange (ETDEWEB)

Carucci, Isabella P. [SISSA—International School for Advanced Studies, Via Bonomea 265, 34136 Trieste (Italy); Villaescusa-Navarro, Francisco [Center for Computational Astrophysics, 160 5th Avenue, New York, NY, 10010 (United States); Viel, Matteo, E-mail: ipcarucci@sissa.it, E-mail: fvillaescusa@simonsfoundation.org, E-mail: viel@oats.inaf.it [INAF—Osservatorio Astronomico di Trieste, Via Tiepolo 11, 34143, Trieste (Italy)

2017-04-01

We investigate the cross-correlation signal between 21cm intensity mapping maps and the Lyα forest in the fully non-linear regime using state-of-the-art hydrodynamic simulations. The cross-correlation signal between the Lyα forest and 21cm maps can provide a coherent and comprehensive picture of the neutral hydrogen (HI) content of our Universe in the post-reionization era, probing both its mass content and volume distribution. We compute the auto-power spectra of both fields together with their cross-power spectrum at z = 2.4 and find that on large scales the fields are completely anti-correlated. This anti-correlation arises because regions with high (low) 21cm emission, such as those with a large (low) concentration of damped Lyα systems, will show up as regions with low (high) transmitted flux. We find that on scales smaller than k ≅ 0.2 h Mpc{sup −1} the cross-correlation coefficient departs from −1, at a scale where non-linearities show up. We use the anisotropy of the power spectra in redshift-space to determine the values of the bias and of the redshift-space distortion parameters of both fields. We find that the errors on the value of the cosmological and astrophysical parameters could decrease by 30% when adding data from the cross-power spectrum, in a conservative analysis. Our results point out that linear theory is capable of reproducing the shape and amplitude of the cross-power up to rather non-linear scales. Finally, we find that the 21cm-Lyα cross-power spectrum can be detected by combining data from a BOSS-like survey together with 21cm intensity mapping observations by SKA1-MID with a S/N ratio higher than 3 in k element of [0.06,1] h Mpc{sup −1}. We emphasize that while the shape and amplitude of the 21cm auto-power spectrum can be severely affected by residual foreground contamination, cross-power spectra will be less sensitive to that and therefore can be used to identify systematics in the 21cm maps.

Cross correlation measurement of low frequency conductivity noise

Science.gov (United States)

Jain, Aditya Kumar; Nigudkar, Himanshu; Chakraborti, Himadri; Udupa, Aditi; Gupta, Kantimay Das

2018-04-01

In order to study the low frequency noise(1/f noise)an experimental technique based on cross correlation of two channels is presented. In this method the device under test (DUT)is connected to the two independently powered preamplifiers in parallel. The amplified signals from the two preamplifiers are fed to two channels of a digitizer. Subsequent data processing largelyeliminates the uncorrelated noise of the two channels. This method is tested for various commercial carbon/metal film resistors by measuring equilibrium thermal noise (4kBTR). The method is then modified to study the non-equilibrium low frequency noise of heterostructure samples using fiveprobe configuration. Five contact probes allow two parts of the sample to become two arms of a balanced bridge. This configuration helps in suppressing the effect of power supply fluctuations, bath temperature fluctuations and contact resistances.

Liquid-metal pin-fin pressure drop by correlation in cross flow

International Nuclear Information System (INIS)

Wang, Zhibi; Kuzay, T.M.; Assoufid, L.

1994-01-01

The pin-fin configuration is widely used as a heat transfer enhancement method in high-heat-flux applications. Recently, the pin-fin design with liquid-metal coolant was also applied to synchrotron-radiation beamline devices. This paper investigates the pressure drop in a pin-post design beamline mirror with liquid gallium as the coolant. Because the pin-post configuration is a relatively new concept, information in literature about pin-post mirrors or crystals is rare, and information about the pressure drop in pin-post mirrors with liquid metal as the coolant is even more sparse. Due to this the authors considered the cross flow in cylinder-array geometry, which is very similar to that of the pin-post, to examine the pressure drop correlation with liquid metals over pin fins. The cross flow of fluid with various fluid characteristics or properties through a tube bank was studied so that the results can be scaled to the pin-fin geometry with liquid metal as the coolant. Study lead to two major variables to influence the pressure drop: fluid properties, viscosity and density, and the relative length of the posts. Correlation of the pressure drop between long and short posts and the prediction of the pressure drop of liquid metal in the pin-post mirror and comparison with an existing experiment are addressed

The correlations between natural elements (K, U, Th) concentrations and thermal neutron absorption cross-section value (Σa) for rock samples of Carpatia area

International Nuclear Information System (INIS)

Swakon, J.; Cywicka-Jakiel, T.; Drozdowicz, E.; Gabanska, B.; Loskiewicz, J.; Woznicka, U.

1991-01-01

The paper presents a study of correlations between concentrations of potassium, uranium and thorium and thermal neutron absorption cross section in rock samples. This knowledge of correlation should help in recognizing the expansion ways and accumulation places of the elements responsible of high thermal neutron absorption cross section in some geological environments. The correlations show the existence of connections between the thermal neutron absorption cross section value and natural radioactivity elements concentration in rocks. The results confirm the existence of correlations between natural radioactive elements concentrations (particularly thorium) and thermal neutron absorption cross - section value in some rocks. (author). 12 refs, 23 figs, 6 tabs

Evaluation of the performance of an ultrasonic cross-correlation flowmeter

International Nuclear Information System (INIS)

Bazerghi, H.; Serdula, K.J.

1977-09-01

An ultrasonic cross-correlation flowmeter, developed to assist in improving performance of heavy water plants, was evaluated. Overall performance of the flowmeter is satisfactory. The flowmeter is ideally suited to industrial applications and has an accuracy and repeatability comparable to many laboratory instruments. An accuracy of 3% is readily obtainable. This new 'clamp-on' portable flowmeter should prove useful in applications which provide flow measurements in systems where pipe penetration is too costly or not practical, verify or replace existing flowmeters, and measure flows in lines not previously instrumented to provide better control or to verify performance of systems

A cross-correlation objective function for least-squares migration and visco-acoustic imaging

KAUST Repository

Dutta, Gaurav

2014-08-05

Conventional acoustic least-squares migration inverts for a reflectivity image that best matches the amplitudes of the observed data. However, for field data applications, it is not easy to match the recorded amplitudes because of the visco-elastic nature of the earth and inaccuracies in the estimation of source signature and strength at different shot locations. To relax the requirement for strong amplitude matching of least-squares migration, we use a normalized cross-correlation objective function that is only sensitive to the similarity between the predicted and the observed data. Such a normalized cross-correlation objective function is also equivalent to a time-domain phase inversion method where the main emphasis is only on matching the phase of the data rather than the amplitude. Numerical tests on synthetic and field data show that such an objective function can be used as an alternative to visco-acoustic least-squares reverse time migration (Qp-LSRTM) when there is strong attenuation in the subsurface and the estimation of the attenuation parameter Qp is insufficiently accurate.

A cross-correlation objective function for least-squares migration and visco-acoustic imaging

KAUST Repository

Dutta, Gaurav; Sinha, Mrinal; Schuster, Gerard T.

2014-01-01

Conventional acoustic least-squares migration inverts for a reflectivity image that best matches the amplitudes of the observed data. However, for field data applications, it is not easy to match the recorded amplitudes because of the visco-elastic nature of the earth and inaccuracies in the estimation of source signature and strength at different shot locations. To relax the requirement for strong amplitude matching of least-squares migration, we use a normalized cross-correlation objective function that is only sensitive to the similarity between the predicted and the observed data. Such a normalized cross-correlation objective function is also equivalent to a time-domain phase inversion method where the main emphasis is only on matching the phase of the data rather than the amplitude. Numerical tests on synthetic and field data show that such an objective function can be used as an alternative to visco-acoustic least-squares reverse time migration (Qp-LSRTM) when there is strong attenuation in the subsurface and the estimation of the attenuation parameter Qp is insufficiently accurate.

Evidence of Cross-correlation between the CMB Lensing and the γ-Ray Sky

Science.gov (United States)

Fornengo, Nicolao; Perotto, Laurence; Regis, Marco; Camera, Stefano

2015-03-01

We report the measurement of the angular power spectrum of cross-correlation between the unresolved component of the Fermi-LAT γ-ray sky maps and the cosmic microwave background lensing potential map reconstructed by the Planck satellite. The matter distribution in the universe determines the bending of light coming from the last scattering surface. At the same time, the matter density drives the growth history of astrophysical objects, including their capability at generating non-thermal phenomena, which in turn give rise to γ-ray emissions. The Planck lensing map provides information on the integrated distribution of matter, while the integrated history of γ-ray emitters is imprinted in the Fermi-LAT sky maps. We report here the first evidence of their correlation. We find that the multipole dependence of the cross-correlation measurement is in agreement with current models of the γ-ray luminosity function for active galactic nuclei and star-forming galaxies, with a statistical evidence of 3.0σ. Moreover, its amplitude can in general be matched only assuming that these extragalactic emitters are also the bulk contribution of the measured isotopic γ-ray background (IGRB) intensity. This leaves little room for a big contribution from galactic sources to the IGRB measured by Fermi-LAT, pointing toward direct evidence of the extragalactic origin of the IGRB.

EVIDENCE OF CROSS-CORRELATION BETWEEN THE CMB LENSING AND THE γ-RAY SKY

Energy Technology Data Exchange (ETDEWEB)

Fornengo, Nicolao; Regis, Marco [Dipartimento di Fisica, Università di Torino, I-10125 Torino (Italy); Perotto, Laurence [LPSC, Université Grenoble-Alpes, CNRS/IN2P3, 53, rue des Martyrs, F-38026 Grenoble Cedex (France); Camera, Stefano, E-mail: regis@to.infn.it [Jodrell Bank Centre for Astrophysics, The University of Manchester, Manchester M13 9PL (United Kingdom)

2015-03-01

We report the measurement of the angular power spectrum of cross-correlation between the unresolved component of the Fermi-LAT γ-ray sky maps and the cosmic microwave background lensing potential map reconstructed by the Planck satellite. The matter distribution in the universe determines the bending of light coming from the last scattering surface. At the same time, the matter density drives the growth history of astrophysical objects, including their capability at generating non-thermal phenomena, which in turn give rise to γ-ray emissions. The Planck lensing map provides information on the integrated distribution of matter, while the integrated history of γ-ray emitters is imprinted in the Fermi-LAT sky maps. We report here the first evidence of their correlation. We find that the multipole dependence of the cross-correlation measurement is in agreement with current models of the γ-ray luminosity function for active galactic nuclei and star-forming galaxies, with a statistical evidence of 3.0σ. Moreover, its amplitude can in general be matched only assuming that these extragalactic emitters are also the bulk contribution of the measured isotopic γ-ray background (IGRB) intensity. This leaves little room for a big contribution from galactic sources to the IGRB measured by Fermi-LAT, pointing toward direct evidence of the extragalactic origin of the IGRB.

Maximum likelihood approach for several stochastic volatility models

International Nuclear Information System (INIS)

Camprodon, Jordi; Perelló, Josep

2012-01-01

Volatility measures the amplitude of price fluctuations. Despite it being one of the most important quantities in finance, volatility is not directly observable. Here we apply a maximum likelihood method which assumes that price and volatility follow a two-dimensional diffusion process where volatility is the stochastic diffusion coefficient of the log-price dynamics. We apply this method to the simplest versions of the expOU, the OU and the Heston stochastic volatility models and we study their performance in terms of the log-price probability, the volatility probability, and its Mean First-Passage Time. The approach has some predictive power on the future returns amplitude by only knowing the current volatility. The assumed models do not consider long-range volatility autocorrelation and the asymmetric return-volatility cross-correlation but the method still yields very naturally these two important stylized facts. We apply the method to different market indices and with a good performance in all cases. (paper)

Quadrature Errors and DC Offsets Calibration of Analog Complex Cross-Correlator for Interferometric Passive Millimeter-Wave Imaging Applications

Directory of Open Access Journals (Sweden)

Chao Wang

2018-02-01

Full Text Available The design and calibration of the cross-correlator are crucial issues for interferometric imaging systems. In this paper, an analog complex cross-correlator with output DC offsets and amplitudes calibration capability is proposed for interferometric passive millimeter-wave security sensing applications. By employing digital potentiometers in the low frequency amplification circuits of the correlator, the outputs characteristics of the correlator could be digitally controlled. A measurement system and a corresponding calibration scheme were developed in order to eliminate the output DC offsets and the quadrature amplitude error between the in-phase and the quadrature correlating subunits of the complex correlator. By using vector modulators to provide phase controllable correlated noise signals, the measurement system was capable of obtaining the output correlation circle of the correlator. When injected with −18 dBm correlated noise signals, the calibrated quadrature amplitude error was 0.041 dB and the calibrated DC offsets were under 26 mV, which was only 7.1% of the uncalibrated value. Furthermore, we also described a quadrature errors calibration algorithm in order to estimate the quadrature phase error and in order to improve the output phase accuracy of the correlator. After applying this calibration, we were able to reduce the output phase error of the correlator to 0.3°.

Improved efficiency of maximum likelihood analysis of time series with temporally correlated errors

Science.gov (United States)

Langbein, John

2017-08-01

Most time series of geophysical phenomena have temporally correlated errors. From these measurements, various parameters are estimated. For instance, from geodetic measurements of positions, the rates and changes in rates are often estimated and are used to model tectonic processes. Along with the estimates of the size of the parameters, the error in these parameters needs to be assessed. If temporal correlations are not taken into account, or each observation is assumed to be independent, it is likely that any estimate of the error of these parameters will be too low and the estimated value of the parameter will be biased. Inclusion of better estimates of uncertainties is limited by several factors, including selection of the correct model for the background noise and the computational requirements to estimate the parameters of the selected noise model for cases where there are numerous observations. Here, I address the second problem of computational efficiency using maximum likelihood estimates (MLE). Most geophysical time series have background noise processes that can be represented as a combination of white and power-law noise, 1/f^{α } with frequency, f. With missing data, standard spectral techniques involving FFTs are not appropriate. Instead, time domain techniques involving construction and inversion of large data covariance matrices are employed. Bos et al. (J Geod, 2013. doi: 10.1007/s00190-012-0605-0) demonstrate one technique that substantially increases the efficiency of the MLE methods, yet is only an approximate solution for power-law indices >1.0 since they require the data covariance matrix to be Toeplitz. That restriction can be removed by simply forming a data filter that adds noise processes rather than combining them in quadrature. Consequently, the inversion of the data covariance matrix is simplified yet provides robust results for a wider range of power-law indices.

An investigation of rugby scrimmaging posture and individual maximum pushing force.

Science.gov (United States)

Wu, Wen-Lan; Chang, Jyh-Jong; Wu, Jia-Hroung; Guo, Lan-Yuen

2007-02-01

Although rugby is a popular contact sport and the isokinetic muscle torque assessment has recently found widespread application in the field of sports medicine, little research has examined the factors associated with the performance of game-specific skills directly by using the isokinetic-type rugby scrimmaging machine. This study is designed to (a) measure and observe the differences in the maximum individual pushing forward force produced by scrimmaging in different body postures (3 body heights x 2 foot positions) with a self-developed rugby scrimmaging machine and (b) observe the variations in hip, knee, and ankle angles at different body postures and explore the relationship between these angle values and the individual maximum pushing force. Ten national rugby players were invited to participate in the examination. The experimental equipment included a self-developed rugby scrimmaging machine and a 3-dimensional motion analysis system. Our results showed that the foot positions (parallel and nonparallel foot positions) do not affect the maximum pushing force; however, the maximum pushing force was significantly lower in posture I (36% body height) than in posture II (38%) and posture III (40%). The maximum forward force in posture III (40% body height) was also slightly greater than for the scrum in posture II (38% body height). In addition, it was determined that hip, knee, and ankle angles under parallel feet positioning are factors that are closely negatively related in terms of affecting maximum pushing force in scrimmaging. In cross-feet postures, there was a positive correlation between individual forward force and hip angle of the rear leg. From our results, we can conclude that if the player stands in an appropriate starting position at the early stage of scrimmaging, it will benefit the forward force production.

Foreground mitigation strategy for measuring the 21 cm-LAE cross-correlation

Science.gov (United States)

Yoshiura, Shintaro; Line, Jack L. B.; Kubota, Kenji; Hasegawa, Kenji; Takahashi, Keitaro

2018-05-01

The cross power spectrum of the 21 cm signal and Lyman-α emitters (LAEs) is a probe of the Epoch of Reionization. Astrophysical foregrounds do not correlate with the LAE distribution, though the foregrounds contribute to the error. To study the impact of foregrounds on the measurement, we assume realistic observation by the Murchison Widefield Array using a catalogue of radio galaxies, a LAE survey by the Subaru Hyper Supreme-Cam and the redshift of LAEs is determined by the Prime Focus Spectrograph. The HI distribution is estimated from a radiative transfer simulation with models based on results of radiation hydrodynamics simulation. Using these models, we found that the error of cross power spectrum is dominated by foreground terms. Furthermore, we estimate the effects of foreground removal, and find 99% of the foreground removal is required to detect the 21 cm-LAE signal at k ~ 0.4 h Mpc-1.

Endoanal MRI of the anal sphincter complex: correlation with cross-sectional anatomy and histology

NARCIS (Netherlands)

Hussain, S. M.; Stoker, J.; Zwamborn, A. W.; den Hollander, J. C.; Kuiper, J. W.; Entius, C. A.; Laméris, J. S.

1996-01-01

The purpose of this study was to correlate the in vivo endoanal MRI findings of the anal sphincter with the cross-sectional anatomy and histology. Fourteen patients with rectal tumours were examined with a rigid endoanal MR coil before undergoing abdominoperineal resection. In addition, 12 cadavers

Burst Detection and Localization using Discrete Wavelet Transform and Cross-Correlation

Directory of Open Access Journals (Sweden)

Eduardo Trutié-Carrero

2018-03-01

Full Text Available Burst in water distribution systems causes great loss of this natural resource, interrupts the water supply, damages the streets, builds and increases the transmission of infectious diseases. In this paper we propose a new algorithm that allows the detection and automatic localization of burst in water distribution systems. As for detection, the novelty is to use the wavelet correlation criterion to compute the statistical decision and compare it with a detection threshold. The novelty in the localization is to use the statistical operator cross-correlation. The algorithm was implemented in Octave and was validated with 32 signals acquired in the laboratory in a 26.7 m long steel pipe. In 16 signals burst were triggered which were detected under a false positive probability of 2 %. No false positives were present on the 16 signals where only noise was present.

Decay of correlations between cross-polarized electromagnetic waves in a two-dimensional random medium.

Science.gov (United States)

Gorodnichev, E E

2018-04-01

The problem of multiple scattering of polarized light in a two-dimensional medium composed of fiberlike inhomogeneities is studied. The attenuation lengths for the density matrix elements are calculated. For a highly absorbing medium it is found that, as the sample thickness increases, the intensity of waves polarized along the fibers decays faster than the other density matrix elements. With further increase in the sample thickness, the off-diagonal elements which are responsible for correlations between the cross-polarized waves disappear. In the asymptotic limit of very thick samples the scattered light proves to be polarized perpendicular to the fibers. The difference in the attenuation lengths between the density matrix elements results in a nonmonotonic depth dependence of the degree of polarization. In the opposite case of a weakly absorbing medium, the off-diagonal element of the density matrix and, correspondingly, the correlations between the cross-polarized fields are shown to decay faster than the intensity of waves polarized along and perpendicular to the fibers.

Efficiency and cross-correlation in equity market during global financial crisis: Evidence from China

Science.gov (United States)

Ma, Pengcheng; Li, Daye; Li, Shuo

2016-02-01

Using one minute high-frequency data of the Shanghai Composite Index (SHCI) and the Shenzhen Composite Index (SZCI) (2007-2008), we employ the detrended fluctuation analysis (DFA) and the detrended cross correlation analysis (DCCA) with rolling window approach to observe the evolution of market efficiency and cross-correlation in pre-crisis and crisis period. Considering the fat-tail distribution of return time series, statistical test based on shuffling method is conducted to verify the null hypothesis of no long-term dependence. Our empirical research displays three main findings. First Shanghai equity market efficiency deteriorated while Shenzhen equity market efficiency improved with the advent of financial crisis. Second the highly positive dependence between SHCI and SZCI varies with time scale. Third financial crisis saw a significant increase of dependence between SHCI and SZCI at shorter time scales but a lack of significant change at longer time scales, providing evidence of contagion and absence of interdependence during crisis.

A Cross-Sectional Study Examining Youth Smoking Rates and Correlates in Tbilisi, Georgia

Directory of Open Access Journals (Sweden)

Carla J. Berg

2014-01-01

Full Text Available Georgia has high smoking rates; however, little is known about the prevalence and correlates of youth smoking. We conducted a secondary data analysis of a 2010 cross-sectional survey of 1,879 secondary and postsecondary school students aged 15 to 24 years in Tbilisi, Georgia, examining substance use, perceived risk, and recreational activities in relation to lifetime and current (past 30 days smoking. Lifetime and current smoking prevalence was 46.1% and 22.6%, respectively. In secondary schools, lifetime smoking correlates included being male, consuming alcohol, lifetime marijuana use, and lower perceived risk (P’s ≤ .001. Correlates of current smoking among lifetime smokers included being male, consuming alcohol, lifetime marijuana use, lower perceived risk, less frequently exercise, and more often going out (P’s < .05. In postsecondary schools, lifetime smoking correlates included being male, consuming alcohol, lifetime marijuana use, lower perceived risk, more often going out, and recreational internet use (P’s < .0. Correlates of current smoking among lifetime smokers included being male (P’s = .04, consuming alcohol, marijuana use, lower perceived risk, and more often going out (P’s < .05. Tobacco control interventions might target these correlates to reduce smoking prevalence in Georgian youth.

Dangers and uses of cross-correlation in analyzing time series in perception, performance, movement, and neuroscience: The importance of constructing transfer function autoregressive models.

Science.gov (United States)

Dean, Roger T; Dunsmuir, William T M

2016-06-01

Many articles on perception, performance, psychophysiology, and neuroscience seek to relate pairs of time series through assessments of their cross-correlations. Most such series are individually autocorrelated: they do not comprise independent values. Given this situation, an unfounded reliance is often placed on cross-correlation as an indicator of relationships (e.g., referent vs. response, leading vs. following). Such cross-correlations can indicate spurious relationships, because of autocorrelation. Given these dangers, we here simulated how and why such spurious conclusions can arise, to provide an approach to resolving them. We show that when multiple pairs of series are aggregated in several different ways for a cross-correlation analysis, problems remain. Finally, even a genuine cross-correlation function does not answer key motivating questions, such as whether there are likely causal relationships between the series. Thus, we illustrate how to obtain a transfer function describing such relationships, informed by any genuine cross-correlations. We illustrate the confounds and the meaningful transfer functions by two concrete examples, one each in perception and performance, together with key elements of the R software code needed. The approach involves autocorrelation functions, the establishment of stationarity, prewhitening, the determination of cross-correlation functions, the assessment of Granger causality, and autoregressive model development. Autocorrelation also limits the interpretability of other measures of possible relationships between pairs of time series, such as mutual information. We emphasize that further complexity may be required as the appropriate analysis is pursued fully, and that causal intervention experiments will likely also be needed.

Maximum likelihood window for time delay estimation

International Nuclear Information System (INIS)

Lee, Young Sup; Yoon, Dong Jin; Kim, Chi Yup

2004-01-01

Time delay estimation for the detection of leak location in underground pipelines is critically important. Because the exact leak location depends upon the precision of the time delay between sensor signals due to leak noise and the speed of elastic waves, the research on the estimation of time delay has been one of the key issues in leak lovating with the time arrival difference method. In this study, an optimal Maximum Likelihood window is considered to obtain a better estimation of the time delay. This method has been proved in experiments, which can provide much clearer and more precise peaks in cross-correlation functions of leak signals. The leak location error has been less than 1 % of the distance between sensors, for example the error was not greater than 3 m for 300 m long underground pipelines. Apart from the experiment, an intensive theoretical analysis in terms of signal processing has been described. The improved leak locating with the suggested method is due to the windowing effect in frequency domain, which offers a weighting in significant frequencies.

Big Data solution for CTBT monitoring: CEA-IDC joint global cross correlation project

Science.gov (United States)

Bobrov, Dmitry; Bell, Randy; Brachet, Nicolas; Gaillard, Pierre; Kitov, Ivan; Rozhkov, Mikhail

2014-05-01

Waveform cross-correlation when applied to historical datasets of seismic records provides dramatic improvements in detection, location, and magnitude estimation of natural and manmade seismic events. With correlation techniques, the amplitude threshold of signal detection can be reduced globally by a factor of 2 to 3 relative to currently standard beamforming and STA/LTA detector. The gain in sensitivity corresponds to a body wave magnitude reduction by 0.3 to 0.4 units and doubles the number of events meeting high quality requirements (e.g. detected by three and more seismic stations of the International Monitoring System (IMS). This gain is crucial for seismic monitoring under the Comprehensive Nuclear-Test-Ban Treaty. The International Data Centre (IDC) dataset includes more than 450,000 seismic events, tens of millions of raw detections and continuous seismic data from the primary IMS stations since 2000. This high-quality dataset is a natural candidate for an extensive cross correlation study and the basis of further enhancements in monitoring capabilities. Without this historical dataset recorded by the permanent IMS Seismic Network any improvements would not be feasible. However, due to the mismatch between the volume of data and the performance of the standard Information Technology infrastructure, it becomes impossible to process all the data within tolerable elapsed time. To tackle this problem known as "BigData", the CEA/DASE is part of the French project "DataScale". One objective is to reanalyze 10 years of waveform data from the IMS network with the cross-correlation technique thanks to a dedicated High Performance Computer (HPC) infrastructure operated by the Centre de Calcul Recherche et Technologie (CCRT) at the CEA of Bruyères-le-Châtel. Within 2 years we are planning to enhance detection and phase association algorithms (also using machine learning and automatic classification) and process about 30 terabytes of data provided by the IDC to

Robust alignment of chromatograms by statistically analyzing the shifts matrix generated by moving window fast Fourier transform cross-correlation.

Science.gov (United States)

Zhang, Mingjing; Wen, Ming; Zhang, Zhi-Min; Lu, Hongmei; Liang, Yizeng; Zhan, Dejian

2015-03-01

Retention time shift is one of the most challenging problems during the preprocessing of massive chromatographic datasets. Here, an improved version of the moving window fast Fourier transform cross-correlation algorithm is presented to perform nonlinear and robust alignment of chromatograms by analyzing the shifts matrix generated by moving window procedure. The shifts matrix in retention time can be estimated by fast Fourier transform cross-correlation with a moving window procedure. The refined shift of each scan point can be obtained by calculating the mode of corresponding column of the shifts matrix. This version is simple, but more effective and robust than the previously published moving window fast Fourier transform cross-correlation method. It can handle nonlinear retention time shift robustly if proper window size has been selected. The window size is the only one parameter needed to adjust and optimize. The properties of the proposed method are investigated by comparison with the previous moving window fast Fourier transform cross-correlation and recursive alignment by fast Fourier transform using chromatographic datasets. The pattern recognition results of a gas chromatography mass spectrometry dataset of metabolic syndrome can be improved significantly after preprocessing by this method. Furthermore, the proposed method is available as an open source package at https://github.com/zmzhang/MWFFT2. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solar wind structure suggested by bimodal correlations of solar wind speed and density between the spacecraft SOHO and Wind

Science.gov (United States)

Ogilvie, K. W.; Coplan, M. A.; Roberts, D. A.; Ipavich, F.

2007-08-01

We calculate the cross-spacecraft maximum lagged-cross-correlation coefficients for 2-hour intervals of solar wind speed and density measurements made by the plasma instruments on the Solar and Heliospheric Observatory (SOHO) and Wind spacecraft over the period from 1996, the minimum of solar cycle 23, through the end of 2005. During this period, SOHO was located at L1, about 200 R E upstream from the Earth, while Wind spent most of the time in the interplanetary medium at distances of more than 100 R E from the Earth. Yearly histograms of the maximum, time-lagged correlation coefficients for both the speed and density are bimodal in shape, suggesting the existence of two distinct solar wind regimes. The larger correlation coefficients we suggest are due to structured solar wind, including discontinuities and shocks, while the smaller are likely due to Alfvénic turbulence. While further work will be required to firmly establish the physical nature of the two populations, the results of the analysis are consistent with a solar wind that consists of turbulence from quiet regions of the Sun interspersed with highly filamentary structures largely convected from regions in the inner solar corona. The bimodal appearance of the distributions is less evident in the solar wind speed than in the density correlations, consistent with the observation that the filamentary structures are convected with nearly constant speed by the time they reach 1 AU. We also find that at solar minimum the fits for the density correlations have smaller high-correlation components than at solar maximum. We interpret this as due to the presence of more relatively uniform Alfvénic regions at solar minimum than at solar maximum.

An assessment of the precision and confidence of aquatic eddy correlation measurements

DEFF Research Database (Denmark)

Donis, Daphne; Holtappels, Moritz; Noss, Christian

2015-01-01

facility with well-constrained hydrodynamics. These observations are used to review data processing procedures and to recommend improved deployment methods, thus improving the precision, reliability, and confidence of EC measurements. Specifically, this study demonstrates that 1) the alignment of the time...... series based on maximum cross correlation improved the precision of EC flux estimations; 2) an oxygen sensor with a response time of

What is new about covered interest parity condition in the European Union? Evidence from fractal cross-correlation regressions

Science.gov (United States)

Ferreira, Paulo; Kristoufek, Ladislav

2017-11-01

We analyse the covered interest parity (CIP) using two novel regression frameworks based on cross-correlation analysis (detrended cross-correlation analysis and detrending moving-average cross-correlation analysis), which allow for studying the relationships at different scales and work well under non-stationarity and heavy tails. CIP is a measure of capital mobility commonly used to analyse financial integration, which remains an interesting feature of study in the context of the European Union. The importance of this features is related to the fact that the adoption of a common currency is associated with some benefits for countries, but also involves some risks such as the loss of economic instruments to face possible asymmetric shocks. While studying the Eurozone members could explain some problems in the common currency, studying the non-Euro countries is important to analyse if they are fit to take the possible benefits. Our results point to the CIP verification mainly in the Central European countries while in the remaining countries, the verification of the parity is only residual.

Effect of telescopic distal extension removable partial dentures on oral health related quality of life and maximum bite force: A preliminary cross over study.

Science.gov (United States)

Elsyad, Moustafa Abdou; Mostafa, Aisha Zakaria

2018-01-01

This cross over study aimed to evaluate the effect of telescopic distal extension removable partial dentures on oral health related quality of life and maximum bite force MATERIALS AND METHODS: Twenty patients with complete maxillary edentulism and partially edentulous mandibles with anterior teeth only remaining were selected for this cross over study. All patients received complete maxillary dentures and mandibular partial removable dental prosthesis (PRDP, control). After 3 months of adaptation, PRDP was replaced with conventional telescopic partial dentures (TPD) or telescopic partial dentures with cantilevered extensions (TCPD) in a quasi-random method. Oral health related quality of life (OHRQoL) was measured using OHIP-14 questionnaire and Maximum bite force (MBF) was measured using a bite force transducer. Measurements were performed 3 months after using each of the following prostheses; PRDP, TPD, and TCPD. TCPD showed the OHIP-14 lowest scores (i.e., the highest patient satisfaction with their OHRQoL), followed by TPD, and PRDP showed the highest OHIP-14 scores (i.e., the lowest patient satisfaction with OHRQoL). TCPD showed the highest MBF (70.7 ± 3.71), followed by TPD (57.4 ± 3.43) and the lowest MBF (40.2 ± 2.20) was noted with PRDP. WITHIN The Limitations of This Study, Mandibular Telescopic Distal Extension Removable Partial Dentures with Cantilevered Extensions Were Associated with Improved Oral Health Related Quality of Life and Maximum Bite Force Compared to Telescopic or Conventional PRDP. Telescopic distal extension removable prostheses is an esthetic restoration in partially edentulous patients with free end saddle. This article describes the addition of cantilevered extensions of this prosthesis. The results showed that telescopic distal extension removable prostheses with cantilevered extensions were associated with improved oral health related quality of life and maximum bite force compared to telescopic or conventional RPDs

Detrended cross-correlation coefficient: Application to predict apoptosis protein subcellular localization.

Science.gov (United States)

Liang, Yunyun; Liu, Sanyang; Zhang, Shengli

2016-12-01

Apoptosis, or programed cell death, plays a central role in the development and homeostasis of an organism. Obtaining information on subcellular location of apoptosis proteins is very helpful for understanding the apoptosis mechanism. The prediction of subcellular localization of an apoptosis protein is still a challenging task, and existing methods mainly based on protein primary sequences. In this paper, we introduce a new position-specific scoring matrix (PSSM)-based method by using detrended cross-correlation (DCCA) coefficient of non-overlapping windows. Then a 190-dimensional (190D) feature vector is constructed on two widely used datasets: CL317 and ZD98, and support vector machine is adopted as classifier. To evaluate the proposed method, objective and rigorous jackknife cross-validation tests are performed on the two datasets. The results show that our approach offers a novel and reliable PSSM-based tool for prediction of apoptosis protein subcellular localization. Copyright © 2016 Elsevier Inc. All rights reserved.

Estimation of velocity vector angles using the directional cross-correlation method

DEFF Research Database (Denmark)

Kortbek, Jacob; Jensen, Jørgen Arendt

2006-01-01

and then select the angle with the highest normalized correlation between directional signals. The approach is investigated using Field II simulations and data from the experimental ultrasound scanner RASMUS and a circulating flow rig with a parabolic flow having a peak velocity of 0.3 m/s. A 7 MHz linear array......A method for determining both velocity magnitude and angle in any direction is suggested. The method uses focusing along the velocity direction and cross-correlation for finding the correct velocity magnitude. The angle is found from beamforming directional signals in a number of directions...... transducer is used with a normal transmission of a focused ultrasound field. In the simulations the relative standard deviation of the velocity magnitude is between 0.7% and 7.7% for flow angles between 45 deg and 90 deg. The study showed that angle estimation by directional beamforming can be estimated...

Quasar-Lyman α forest cross-correlation from BOSS DR11: Baryon Acoustic Oscillations

Energy Technology Data Exchange (ETDEWEB)

Font-Ribera, Andreu [Institute of Theoretical Physics, University of Zurich, Winterthurerstrasse 190, 8057 Zurich (Switzerland); Kirkby, David; Blomqvist, Michael [Department of Physics and Astronomy, University of California, 4129 Frederick Reines Hall, Irvine, CA, 92697 (United States); Busca, Nicolas; Aubourg, Éric; Bautista, Julian [APC, Université Paris Diderot-Paris 7, CNRS/IN2P3, CEA, Observatoire de Paris, 10, rue A. Domon and L. Duquet, Paris (France); Miralda-Escudé, Jordi [Institut de Ciències del Cosmos (IEEC/UB), Martí i Franquès 1, Barcelona, 08028 Catalonia (Spain); Ross, Nicholas P.; Bailey, Stephen; Beutler, Florian; Carithers, Bill [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA (United States); Slosar, Anže [Brookhaven National Laboratory, Blgd 510, Upton, NY, 11375 (United States); Rich, James; Delubac, Timothée [CEA, Centre de Saclay, IRFU, Gif-sur-Yvette, 91191 France (France); Bhardwaj, Vaishali; Bizyaev, Dmitry [Department of Astronomy, University of Washington, Box 351580, Seattle, WA, 98195 (United States); Brewington, Howard; Brinkmann, Jon [Apache Point Observatory and New Mexico State University, P.O. Box 59, Sunspot, NM, 88349-0059 (United States); Brownstein, Joel R.; Dawson, Kyle S., E-mail: font@physik.uzh.ch [Department of Physics and Astronomy, University of Utah, 115 S 1400 E, Salt Lake City, UT, 84112 (United States); and others

2014-05-01

We measure the large-scale cross-correlation of quasars with the Lyα forest absorption, using over 164,000 quasars from Data Release 11 of the SDSS-III Baryon Oscillation Spectroscopic Survey. We extend the previous study of roughly 60,000 quasars from Data Release 9 to larger separations, allowing a measurement of the Baryonic Acoustic Oscillation (BAO) scale along the line of sight c/(H(z = 2.36)r{sub s}) = 9.0±0.3 and across the line of sight D{sub A}(z = 2.36)/r{sub s} = 10.8±0.4, consistent with CMB and other BAO data. Using the best fit value of the sound horizon from Planck data (r{sub s} = 147.49 Mpc), we can translate these results to a measurement of the Hubble parameter of H(z = 2.36) = 226±8 km s{sup −1} Mpc{sup −1} and of the angular diameter distance of D{sub A}(z = 2.36) = 1590±60 Mpc. The measured cross-correlation function and an update of the code to fit the BAO scale (baofit) are made publicly available.

Blind Cartography for Side Channel Attacks: Cross-Correlation Cartography

Directory of Open Access Journals (Sweden)

Laurent Sauvage

2012-01-01

Full Text Available Side channel and fault injection attacks are major threats to cryptographic applications of embedded systems. Best performances for these attacks are achieved by focusing sensors or injectors on the sensible parts of the application, by means of dedicated methods to localise them. Few methods have been proposed in the past, and all of them aim at pinpointing the cryptoprocessor. However it could be interesting to exploit the activity of other parts of the application, in order to increase the attack's efficiency or to bypass its countermeasures. In this paper, we present a localisation method based on cross-correlation, which issues a list of areas of interest within the attacked device. It realizes an exhaustive analysis, since it may localise any module of the device, and not only those which perform cryptographic operations. Moreover, it also does not require a preliminary knowledge about the implementation, whereas some previous cartography methods require that the attacker could choose the cryptoprocessor inputs, which is not always possible. The method is experimentally validated using observations of the electromagnetic near field distribution over a Xilinx Virtex 5 FPGA. The matching between areas of interest and the application layout in the FPGA floorplan is confirmed by correlation analysis.

Improving ambient noise cross-correlations in the noisy ocean bottom environment of the Juan de Fuca plate

Science.gov (United States)

Tian, Ye; Ritzwoller, Michael H.

2017-09-01

Ambient noise tomography exploits seismic ground motions that propagate coherently over long interstation distances. Such ground motions provide information about the medium of propagation that is recoverable from interstation cross-correlations. Local noise sources, which are particularly strong in ocean bottom environments, corrupt ambient noise cross-correlations and compromise the effectiveness of ambient noise tomography. Based on 62 ocean bottom seismometers (OBSs) located on Juan de Fuca (JdF) plate from the Cascadia Initiative experiment and 40 continental stations near the coast of the western United States obtained in 2011 and 2012, we attempt to reduce the effects of local noise on vertical component seismic records across the plate and onto US continent. The goal is to provide better interstation cross-correlations for use in ambient noise tomography and the study of ambient noise directionality. As shown in previous studies, tilt and compliance noise are major sources of noise that contaminate the vertical channels of the OBSs and such noise can be greatly reduced by exploiting information on the horizontal components and the differential pressure gauge records, respectively. We find that ambient noise cross-correlations involving OBSs are of significantly higher signal-to-noise ratio at periods greater than 10 s after reducing these types of noise, particularly in shallow water environments where tilt and compliance noise are especially strong. The reduction of tilt and compliance noise promises to improve the accuracy and spatial extent of ambient noise tomography, allowing measurements based on coherently propagating ambient noise to be made at stations in the shallower parts of the JdF plate and at longer periods than in previous studies. In addition such local noise reduction produces better estimates of the azimuthal content of ambient noise.

Dynamic Hebbian Cross-Correlation Learning Resolves the Spike Timing Dependent Plasticity Conundrum

Directory of Open Access Journals (Sweden)

Tjeerd V. olde Scheper

2018-01-01

Full Text Available Spike Timing-Dependent Plasticity has been found to assume many different forms. The classic STDP curve, with one potentiating and one depressing window, is only one of many possible curves that describe synaptic learning using the STDP mechanism. It has been shown experimentally that STDP curves may contain multiple LTP and LTD windows of variable width, and even inverted windows. The underlying STDP mechanism that is capable of producing such an extensive, and apparently incompatible, range of learning curves is still under investigation. In this paper, it is shown that STDP originates from a combination of two dynamic Hebbian cross-correlations of local activity at the synapse. The correlation of the presynaptic activity with the local postsynaptic activity is a robust and reliable indicator of the discrepancy between the presynaptic neuron and the postsynaptic neuron's activity. The second correlation is between the local postsynaptic activity with dendritic activity which is a good indicator of matching local synaptic and dendritic activity. We show that this simple time-independent learning rule can give rise to many forms of the STDP learning curve. The rule regulates synaptic strength without the need for spike matching or other supervisory learning mechanisms. Local differences in dendritic activity at the synapse greatly affect the cross-correlation difference which determines the relative contributions of different neural activity sources. Dendritic activity due to nearby synapses, action potentials, both forward and back-propagating, as well as inhibitory synapses will dynamically modify the local activity at the synapse, and the resulting STDP learning rule. The dynamic Hebbian learning rule ensures furthermore, that the resulting synaptic strength is dynamically stable, and that interactions between synapses do not result in local instabilities. The rule clearly demonstrates that synapses function as independent localized

CALIBRATING PHOTOMETRIC REDSHIFT DISTRIBUTIONS WITH CROSS-CORRELATIONS

International Nuclear Information System (INIS)

Schulz, A. E.

2010-01-01

The next generation of proposed galaxy surveys will increase the number of galaxies with photometric redshift identifications by two orders of magnitude, drastically expanding both the redshift range and detection threshold from the current state of the art. Obtaining spectra for a fair subsample of these new data could be cumbersome and expensive. However, adequate calibration of the true redshift distribution of galaxies is vital to tapping the potential of these surveys to illuminate the processes of galaxy evolution and to constrain the underlying cosmology and growth of structure. We examine here an alternative to direct spectroscopic follow-up: calibration of the redshift distribution of photometric galaxies via cross-correlation with an overlapping spectroscopic survey whose members trace the same density field. We review the theory, develop a pipeline to implement the method, apply it to mock data from N-body simulations, and examine the properties of this redshift distribution estimator. We demonstrate that the method is generally effective, but the estimator is weakened by two main factors. One is that the correlation function of the spectroscopic sample must be measured in many bins along the line of sight, which renders the measurement noisy and interferes with high-quality reconstruction of the photometric redshift distribution. Also, the method is not able to disentangle the photometric redshift distribution from redshift dependence in the bias of the photometric sample. We establish the impact of these factors using our mock catalogs. We conclude that it may still be necessary to spectroscopically follow up a fair subsample of the photometric survey data. Nonetheless, it is significant that the method has been successfully implemented on mock data, and with further refinement it may appreciably decrease the number of spectra that will be needed to calibrate future surveys.

Understanding volatility correlation behavior with a magnitude cross-correlation function

Science.gov (United States)

Jun, Woo Cheol; Oh, Gabjin; Kim, Seunghwan

2006-06-01

We propose an approach for analyzing the basic relation between correlation properties of the original signal and its magnitude fluctuations by decomposing the original signal into its positive and negative fluctuation components. We use this relation to understand the following phenomenon found in many naturally occurring time series: the magnitude of the signal exhibits long-range correlation, whereas the original signal is short-range correlated. The applications of our approach to heart rate variability signals and high-frequency foreign exchange rates reveal that the difference between the correlation properties of the original signal and its magnitude fluctuations is induced by the time organization structure of the correlation function between the magnitude fluctuations of positive and negative components. We show that this correlation function can be described well by a stretched-exponential function and is related to the nonlinearity and the multifractal structure of the signals.

Understanding volatility correlation behavior with a magnitude cross-correlation function.

Science.gov (United States)

Jun, Woo Cheol; Oh, Gabjin; Kim, Seunghwan

2006-06-01

We propose an approach for analyzing the basic relation between correlation properties of the original signal and its magnitude fluctuations by decomposing the original signal into its positive and negative fluctuation components. We use this relation to understand the following phenomenon found in many naturally occurring time series: the magnitude of the signal exhibits long-range correlation, whereas the original signal is short-range correlated. The applications of our approach to heart rate variability signals and high-frequency foreign exchange rates reveal that the difference between the correlation properties of the original signal and its magnitude fluctuations is induced by the time organization structure of the correlation function between the magnitude fluctuations of positive and negative components. We show that this correlation function can be described well by a stretched-exponential function and is related to the nonlinearity and the multifractal structure of the signals.

When can Empirical Green Functions be computed from Noise Cross-Correlations? Hints from different Geographical and Tectonic environments

Science.gov (United States)

Matos, Catarina; Silveira, Graça; Custódio, Susana; Domingues, Ana; Dias, Nuno; Fonseca, João F. B.; Matias, Luís; Krueger, Frank; Carrilho, Fernando

2014-05-01

Noise cross-correlations are now widely used to extract Green functions between station pairs. But, do all the cross-correlations routinely computed produce successful Green Functions? What is the relationship between noise recorded in a couple of stations and the cross-correlation between them? During the last decade, we have been involved in the deployment of several temporary dense broadband (BB) networks within the scope of both national projects and international collaborations. From 2000 to 2002, a pool of 8 BB stations continuously operated in the Azores in the scope of the Memorandum of Understanding COSEA (COordinated Seismic Experiment in the Azores). Thanks to the Project WILAS (West Iberia Lithosphere and Astenosphere Structure, PTDC/CTE-GIX/097946/2008) we temporarily increased the number of BB deployed in mainland Portugal to more than 50 (permanent + temporary) during the period 2010 - 2012. In 2011/12 a temporary pool of 12 seismometers continuously recorded BB data in the Madeira archipelago, as part of the DOCTAR (Deep Ocean Test Array Experiment) project. Project CV-PLUME (Investigation on the geometry and deep signature of the Cape Verde mantle plume, PTDC/CTE-GIN/64330/2006) covered the archipelago of Cape Verde, North Atlantic, with 40 temporary BB stations in 2007/08. Project MOZART (Mozambique African Rift Tomography, PTDC/CTE-GIX/103249/2008), covered Mozambique, East Africa, with 30 temporary BB stations in the period 2011 - 2013. These networks, located in very distinct geographical and tectonic environments, offer an interesting opportunity to study seasonal and spatial variations of noise sources and their impact on Empirical Green functions computed from noise cross-correlation. Seismic noise recorded at different seismic stations is evaluated by computation of the probability density functions of power spectral density (PSD) of continuous data. To assess seasonal variations of ambient noise sources in frequency content, time-series of

Correlation between ultrasound imaging, cross-sectional anatomy, and histology of the brachial plexus: a review.

Science.gov (United States)

van Geffen, Geert J; Moayeri, Nizar; Bruhn, Jörgen; Scheffer, Gert J; Chan, Vincent W; Groen, Gerbrand J

2009-01-01

The anatomy of the brachial plexus is complex. To facilitate the understanding of the ultrasound appearance of the brachial plexus, we present a review of important anatomic considerations. A detailed correlation of reconstructed, cross-sectional gross anatomy and histology with ultrasound sonoanatomy is provided.

Effect of in-medium nucleon-nucleon cross section on proton-proton momentum correlation in intermediate-energy heavy-ion collisions

Science.gov (United States)

Wang, Ting-Ting; Ma, Yu-Gang; Zhang, Chun-Jian; Zhang, Zheng-Qiao

2018-03-01

The proton-proton momentum correlation function from different rapidity regions is systematically investigated for the Au + Au collisions at different impact parameters and different energies from 400 A MeV to 1500 A MeV in the framework of the isospin-dependent quantum molecular dynamics model complemented by the Lednický-Lyuboshitz analytical method. In particular, the in-medium nucleon-nucleon cross-section dependence of the correlation function is brought into focus, while the impact parameter and energy dependence of the momentum correlation function are also explored. The sizes of the emission source are extracted by fitting the momentum correlation functions using the Gaussian source method. We find that the in-medium nucleon-nucleon cross section obviously influences the proton-proton momentum correlation function, which is from the whole-rapidity or projectile or target rapidity region at smaller impact parameters, but there is no effect on the mid-rapidity proton-proton momentum correlation function, which indicates that the emission mechanism differs between projectile or target rapidity and mid-rapidity protons.

Method for stationarity-segmentation of spike train data with application to the Pearson cross-correlation.

Science.gov (United States)

Quiroga-Lombard, Claudio S; Hass, Joachim; Durstewitz, Daniel

2013-07-01

Correlations among neurons are supposed to play an important role in computation and information coding in the nervous system. Empirically, functional interactions between neurons are most commonly assessed by cross-correlation functions. Recent studies have suggested that pairwise correlations may indeed be sufficient to capture most of the information present in neural interactions. Many applications of correlation functions, however, implicitly tend to assume that the underlying processes are stationary. This assumption will usually fail for real neurons recorded in vivo since their activity during behavioral tasks is heavily influenced by stimulus-, movement-, or cognition-related processes as well as by more general processes like slow oscillations or changes in state of alertness. To address the problem of nonstationarity, we introduce a method for assessing stationarity empirically and then "slicing" spike trains into stationary segments according to the statistical definition of weak-sense stationarity. We examine pairwise Pearson cross-correlations (PCCs) under both stationary and nonstationary conditions and identify another source of covariance that can be differentiated from the covariance of the spike times and emerges as a consequence of residual nonstationarities after the slicing process: the covariance of the firing rates defined on each segment. Based on this, a correction of the PCC is introduced that accounts for the effect of segmentation. We probe these methods both on simulated data sets and on in vivo recordings from the prefrontal cortex of behaving rats. Rather than for removing nonstationarities, the present method may also be used for detecting significant events in spike trains.

Inclusive D* Meson Cross Sections and D* Jet Correlations in Photoproduction at HERA

CERN Document Server

Aktas, A.; Anthonis, T.; Antunovic, B.; Aplin, S.; Asmone, A.; Astvatsatourov, A.; Babaev, A.; Backovic, S.; Baghdasaryan, A.; Baranov, P.; Barrelet, E.; Bartel, W.; Baudrand, S.; Baumgartner, S.; Beckingham, M.; Behnke, O.; Behrendt, O.; Belousov, A.; Berger, N.; Bizot, J.C.; Boenig, M.O.; Boudry, V.; Bracinik, J.; Brandt, G.; Brisson, V.; Bruncko, D.; Busser, F.W.; Bunyatyan, A.; Buschhorn, G.; Bystritskaya, L.; Campbell, A.J.; Caron, S.; Cassol-Brunner, F.; Cerny, K.; Cerny, V.; Chekelian, V.; Contreras, J.G.; Coughlan, J.A.; Cox, B.E.; Cozzika, G.; Cvach, J.; Dainton, J.B.; Dau, W.D.; Daum, K.; de Boer, Y.; Delcourt, B.; Del Degan, M.; De Roeck, A.; De Wolf, E.A.; Diaconu, C.; Dodonov, V.; Dubak, A.; Eckerlin, Guenter; Efremenko, V.; Egli, S.; Eichler, R.; Eisele, F.; Eliseev, A.; Elsen, E.; Essenov, S.; Falkewicz, A.; Faulkner, P.J.W.; Favart, L.; Fedotov, A.; Felst, R.; Feltesse, J.; Ferencei, J.; Finke, L.; Fleischer, M.; Flucke, G.; Fomenko, A.; Franke, G.; Frisson, T.; Gabathuler, E.; Garutti, E.; Gayler, J.; Gerlich, C.; Ghazaryan, Samvel; Ginzburgskaya, S.; Glazov, A.; Glushkov, I.; Goerlich, L.; Goettlich, M.; Gogitidze, N.; Gorbounov, S.; Grab, C.; Greenshaw, T.; Gregori, M.; Grell, B.R.; Grindhammer, G.; Gwilliam, C.; Habib, S.; Haidt, D.; Hansson, M.; Heinzelmann, G.; Henderson, R.C.W.; Henschel, H.; Herrera, G.; Hildebrandt, M.; Hiller, K.H.; Hoffmann, D.; Horisberger, R.; Hovhannisyan, A.; Hreus, T.; Hussain, S.; Ibbotson, M.; Ismail, M.; Jacquet, M.; Janssen, X.; Jemanov, V.; Jonsson, L.; Johnson, D.P.; Jung, Andreas Werner; Jung, H.; Kapichine, M.; Katzy, J.; Kenyon, I.R.; Kiesling, Christian M.; Klein, M.; Kleinwort, C.; Klimkovich, T.; Kluge, T.; Knies, G.; Knutsson, A.; Korbel, V.; Kostka, P.; Krastev, K.; Kretzschmar, J.; Kropivnitskaya, A.; Kruger, K.; Landon, M.P.J.; Lange, W.; Lastovicka-Medin, G.; Laycock, P.; Lebedev, A.; Leibenguth, G.; Lendermann, V.; Levonian, S.; Lindfeld, L.; Lipka, K.; Liptaj, A.; List, B.; List, J.; Lobodzinska, E.; Loktionova, N.; Lopez-Fernandez, R.; Lubimov, V.; Lucaci-Timoce, A.I.; Lueders, H.; Lux, T.; Lytkin, L.; Makankine, A.; Malden, N.; Malinovski, E.; Marage, P.; Marshall, R.; Marti, L.; Martisikova, M.; Martyn, H.U.; Maxfield, S.J.; Mehta, A.; Meier, K.; Meyer, A.B.; Meyer, H.; Meyer, J.; Michels, V.; Mikocki, S.; Milcewicz-Mika, I.; Milstead, D.; Mladenov, D.; Mohamed, A.; Moreau, F.; Morozov, A.; Morris, J.V.; Mozer, Matthias Ulrich; Muller, K.; Murin, P.; Nankov, K.; Naroska, B.; Naumann, T.; Newman, Paul R.; Niebuhr, C.; Nikiforov, A.; Nowak, G.; Nowak, K.; Nozicka, M.; Oganezov, R.; Olivier, B.; Olsson, J.E.; Osman, S.; Ozerov, D.; Palichik, V.; Panagoulias, I.; Papadopoulou, T.; Pascaud, C.; Patel, G.D.; Peng, H.; Perez, E.; Perez-Astudillo, D.; Perieanu, A.; Petrukhin, A.; Pitzl, D.; Placakyte, R.; Portheault, B.; Povh, B.; Prideaux, P.; Rahmat, A.J.; Raicevic, N.; Reimer, P.; Rimmer, A.; Risler, C.; Rizvi, E.; Robmann, P.; Roland, B.; Roosen, R.; Rostovtsev, A.; Rurikova, Z.; Rusakov, S.; Salvaire, F.; Sankey, D.P.C.; Sauter, M.; Sauvan, E.; Schmidt, S.; Schmitt, S.; Schmitz, C.; Schoeffel, L.; Schoning, A.; Schultz-Coulon, H.C.; Sefkow, F.; Shaw-West, R.N.; Sheviakov, I.; Shtarkov, L.N.; Sloan, T.; Smirnov, P.; Soloviev, Y.; South, D.; Spaskov, V.; Specka, Arnd E.; Steder, M.; Stella, B.; Stiewe, J.; Stoilov, A.; Straumann, U.; Sunar, D.; Tchoulakov, V.; Thompson, G.; Thompson, P.D.; Toll, T.; Tomasz, F.; Traynor, D.; Trinh, T.N.; Truoel, P.; Tsakov, I.; Tsipolitis, G.; Tsurin, I.; Turnau, J.; Tzamariudaki, E.; Urban, K.; Urban, Marcel; Usik, A.; Utkin, D.; Valkarova, A.; Vallee, C.; Van Mechelen, P.; Vargas Trevino, A.; Vazdik, Y.; Veelken, C.; Vinokurova, S.; Volchinski, V.; Wacker, K.; Weber, G.; Weber, R.; Wegener, D.; Werner, C.; Wessels, M.; Wessling, B.; Wissing, C.; Wolf, R.; Wunsch, E.; Xella, S.; Yan, W.; Yeganov, V.; Zacek, J.; Zalesak, J.; Zhang, Z.; Zhelezov, A.; Zhokin, A.; Zhu, Y.C.; Zimmermann, J.; Zimmermann, T.; Zohrabyan, H.; Zomer, F.

2007-01-01

Differential photoproduction cross sections are measured for events containing D* mesons. The data were taken with the H1 detector at the ep collider HERA and correspond to an integrated luminosity of 51.1 pb-1. The kinematic region covers small photon virtualities Q^2 < 0.01 GeV^2 and photon-proton centre-of-mass energies of 171 < W_gammap < 256 GeV. The details of the heavy quark production process are further investigated in events with one or two jets in addition to the D* meson. Differential cross sections for D* jet production are determined and the correlations between the D* meson and the jet(s) are studied. The results are compared with perturbative QCD predictions applying collinear- or kt -factorisation.

Effects of signal modulation and coloured cross-correlation of coloured noises on the diffusion of a harmonic oscillator

Institute of Scientific and Technical Information of China (English)

Liu Li; Zhang Liang-Ying; Cao Li

2009-01-01

The diffusion in a harmonic oscillator driven by coloured noises ζ(t) and η(t) with coloured cross-correlation in which one of the noises is modulated by a biased periodic signal is investigated. The exact expression of diffusion coefficient d as a function of noise parameter, signal parameter, and oscillator frequency is derived. The findings in this paper are as follows. 1) The curves of d versus noise intensity D and d versus noises cross-correlation time τ_3 exist as two different phases. The transition between the two phases arises from the change of the cross-correlation coefficient λ of the two Orustein-Uhlenbeck (O-U) noises. 2) Changing the value of τ3, the curves of d versus Q, the intensity of colored noise that is modulated by the signal, can transform from a phase having a minimum to a monotonic phase. 3)Changing the value of signal amplitude A, d versus Q curves can transform from a phase having a minimum to a monotonic phase. The above-mentioned results demonstrate that a like noise-induced transition appears in the model.

Effects of signal modulation and coloured cross-correlation of coloured noises on the diffusion of a harmonic oscillator

International Nuclear Information System (INIS)

Li, Liu; Li, Cao; Liang-Ying, Zhang

2009-01-01

The diffusion in a harmonic oscillator driven by coloured noises ζ(t) and η(t) with coloured cross-correlation in which one of the noises is modulated by a biased periodic signal is investigated. The exact expression of diffusion coefficient d as a function of noise parameter, signal parameter, and oscillator frequency is derived. The findings in this paper are as follows. 1) The curves of d versus noise intensity D and d versus noises cross-correlation time τ 3 exist as two different phases. The transition between the two phases arises from the change of the cross-correlation coefficient λ of the two Ornstein–Uhlenbeck (O-U) noises. 2) Changing the value of τ 3 , the curves of d versus Q, the intensity of colored noise that is modulated by the signal, can transform from a phase having a minimum to a monotonic phase. 3) Changing the value of signal amplitude A, d versus Q curves can transform from a phase having a minimum to a monotonic phase. The above-mentioned results demonstrate that a like noise-induced transition appears in the model. (general)

Seismic reflection response from cross-correlations of ambient vibrations on non-conventional hidrocarbon reservoir

Science.gov (United States)

Huerta, F. V.; Granados, I.; Aguirre, J.; Carrera, R. Á.

2017-12-01

Nowadays, in hydrocarbon industry, there is a need to optimize and reduce exploration costs in the different types of reservoirs, motivating the community specialized in the search and development of alternative exploration geophysical methods. This study show the reflection response obtained from a shale gas / oil deposit through the method of seismic interferometry of ambient vibrations in combination with Wavelet analysis and conventional seismic reflection techniques (CMP & NMO). The method is to generate seismic responses from virtual sources through the process of cross-correlation of records of Ambient Seismic Vibrations (ASV), collected in different receivers. The seismic response obtained is interpreted as the response that would be measured in one of the receivers considering a virtual source in the other. The acquisition of ASV records was performed in northern of Mexico through semi-rectangular arrays of multi-component geophones with instrumental response of 10 Hz. The in-line distance between geophones was 40 m while in cross-line was 280 m, the sampling used during the data collection was 2 ms and the total duration of the records was 6 hours. The results show the reflection response of two lines in the in-line direction and two in the cross-line direction for which the continuity of coherent events have been identified and interpreted as reflectors. There is certainty that the events identified correspond to reflections because the time-frequency analysis performed with the Wavelet Transform has allowed to identify the frequency band in which there are body waves. On the other hand, the CMP and NMO techniques have allowed to emphasize and correct the reflection response obtained during the correlation processes in the frequency band of interest. The results of the processing and analysis of ASV records through the seismic interferometry method have allowed us to see interesting results in light of the cross-correlation process in combination with

Intensive care antibiotic consumption and resistance patterns: a cross-correlation analysis

Directory of Open Access Journals (Sweden)

Luminita Baditoiu

2017-11-01

Full Text Available Abstract Background Over recent decades, a dramatic increase in infections caused by multidrug-resistant pathogens has been observed worldwide. The aim of the present study was to investigate the relationship between local resistance bacterial patterns and antibiotic consumption in an intensive care unit in a Romanian university hospital. Methods A prospective study was conducted between 1st January 2012 and 31st December 2013. Data covering the consumption of antibacterial drugs and the incidence density for the main resistance phenotypes was collected on a monthly basis, and this data was aggregated quarterly. The relationship between the antibiotic consumption and resistance was investigated using cross-correlation, and four regression models were constructed, using the SPSS version 20.0 (IBM, Chicago, IL and the R version 3.2.3 packages. Results During the period studied, the incidence of combined-resistant and carbapenem-resistant P. aeruginosa strains increased significantly [(gradient = 0.78, R2 = 0.707, p = 0.009 (gradient = 0.74, R2 = 0.666, p = 0.013 respectively], mirroring the increase in consumption of β-lactam antibiotics with β-lactamase inhibitors (piperacillin/tazobactam and carbapenems (meropenem [(gradient = 10.91, R2 = 0.698, p = 0.010 and (gradient = 14.63, R2 = 0.753, p = 0.005 respectively]. The highest cross-correlation coefficients for zero time lags were found between combined-resistant vs. penicillins consumption and carbapenem-resistant P. aeruginosa strains vs. carbapenems consumption (0.876 and 0.928, respectively. The best model describing the relation between combined-resistant P. aeruginosa strains and penicillins consumption during a given quarter incorporates both the consumption and the incidence of combined-resistant strains in the hospital department during the previous quarter (multiple R2 = 0.953, p = 0.017. The best model for explaining the carbapenem resistance of P

High precision Cross-correlated imaging in Few-mode fibers

DEFF Research Database (Denmark)

Muliar, Olena; Usuga Castaneda, Mario A.; Kristensen, Torben

2017-01-01

us to distinguishing differential time delays between HOMs in the picosecond timescale. Broad wavelength scanning in combination with spectral shaping, allows us to estimate the modal behavior of FMF without prior knowledge of the fiber parameters. We performed our demonstration at wavelengths from...... existing approaches for modal content analysis, several methods as S2, C2 in time and frequency domain are available. In this contribution we will present an improved time-domain cross-correlated (C2) imaging technique for the experimental evaluation of modal properties in HOM fibers over a broad range......) in a few-mode fiber (FMF) are used as multiple spatial communication channels, comes in this context as a viable approach to enable the optimization of high-capacity links. From this perspective, it becomes highly necessary to possess a diagnostic tool for the precise modal characterization of FMFs. Among...

Maximum a posteriori decoder for digital communications

Science.gov (United States)

Altes, Richard A. (Inventor)

1997-01-01

A system and method for decoding by identification of the most likely phase coded signal corresponding to received data. The present invention has particular application to communication with signals that experience spurious random phase perturbations. The generalized estimator-correlator uses a maximum a posteriori (MAP) estimator to generate phase estimates for correlation with incoming data samples and for correlation with mean phases indicative of unique hypothesized signals. The result is a MAP likelihood statistic for each hypothesized transmission, wherein the highest value statistic identifies the transmitted signal.

Multifractal Cross Wavelet Analysis

Science.gov (United States)

Jiang, Zhi-Qiang; Gao, Xing-Lu; Zhou, Wei-Xing; Stanley, H. Eugene

Complex systems are composed of mutually interacting components and the output values of these components usually exhibit long-range cross-correlations. Using wavelet analysis, we propose a method of characterizing the joint multifractal nature of these long-range cross correlations, a method we call multifractal cross wavelet analysis (MFXWT). We assess the performance of the MFXWT method by performing extensive numerical experiments on the dual binomial measures with multifractal cross correlations and the bivariate fractional Brownian motions (bFBMs) with monofractal cross correlations. For binomial multifractal measures, we find the empirical joint multifractality of MFXWT to be in approximate agreement with the theoretical formula. For bFBMs, MFXWT may provide spurious multifractality because of the wide spanning range of the multifractal spectrum. We also apply the MFXWT method to stock market indices, and in pairs of index returns and volatilities we find an intriguing joint multifractal behavior. The tests on surrogate series also reveal that the cross correlation behavior, particularly the cross correlation with zero lag, is the main origin of cross multifractality.

Probable maximum flood analysis, Richton Dome, Mississippi-Phase I: Technical report

International Nuclear Information System (INIS)

1987-03-01

This report presents results of a preliminary analysis of the extent of inundation that would result from a probable maximum flood (PMF) event in the overdome area of Richton Dome, Mississippi. Bogue Homo and Thompson Creek watersheds drain the overdome area. The US Army Corps of Engineers' HEC-1 Flood Hydrograph Package was used to calculate runoff hydrographs, route computed flood hydrographs, and determine maximum flood stages at cross sections along overdome tributaries. The area and configuration of stream cross sections were determined from US Geological Survey topographic maps. Using maximum flood stages calculated by the HEC-1 analysis, areas of inundation were delineated on 10-ft (3-m) contour interval topographic maps. Approximately 10% of the overdome area, or 0.9 mi 2 (2 km 2 ), would be inundated by a PMF event. 34 refs., 3 figs., 1 tab

Interdependence between crude oil and world food prices: A detrended cross correlation analysis

Science.gov (United States)

Pal, Debdatta; Mitra, Subrata K.

2018-02-01

This article explores the changing interdependence between crude oil and world food prices at varying time scales using detrended cross correlation analysis that would answer whether the interdependence (if any) differed significantly between pre and post-crisis period. Unlike the previous studies that exogenously imposed break dates for dividing the time series into sub-samples, we tested whether the mean of the crude oil price changed over time to find evidence for structural changes in the crude oil price series and endogenously determine three break dates with minimum Bayesian information criterion scores. Accordingly, we divided the entire study period in four sample periods - January 1990 to October 1999, November 1999 to February 2005, March 2005 to September 2010, and October 2010 to July 2016, where the third sample period coincided with the period of food crisis and enabled us to compare the fuel-food interdependence across pre-crisis, during the crisis, and post-crisis periods. The results of the detrended cross correlation analysis extended corroborative evidence for increasing positive interdependence between the crude oil price and world food price index along with its sub-categories, namely dairy, cereals, vegetable oil, and sugar. The article ends with the implications of these results in the domain of food policy and the financial sector.

Cross-correlation analysis of pulse wave propagation in arteries: in vitro validation and in vivo feasibility.

Science.gov (United States)

Nauleau, Pierre; Apostolakis, Iason; McGarry, Matthew; Konofagou, Elisa

2018-05-29

The stiffness of the arteries is known to be an indicator of the progression of various cardiovascular diseases. Clinically, the pulse wave velocity (PWV) is used as a surrogate for arterial stiffness. Pulse wave imaging (PWI) is a non-invasive, ultrasound-based imaging technique capable of mapping the motion of the vessel walls, allowing the local assessment of arterial properties. Conventionally, a distinctive feature of the displacement wave (e.g. the 50% upstroke) is tracked across the map to estimate the PWV. However, the presence of reflections, such as those generated at the carotid bifurcation, can bias the PWV estimation. In this paper, we propose a two-step cross-correlation based method to characterize arteries using the information available in the PWI spatio-temporal map. First, the area under the cross-correlation curve is proposed as an index for locating the regions of different properties. Second, a local peak of the cross-correlation function is tracked to obtain a less biased estimate of the PWV. Three series of experiments were conducted in phantoms to evaluate the capabilities of the proposed method compared with the conventional method. In the ideal case of a homogeneous phantom, the two methods performed similarly and correctly estimated the PWV. In the presence of reflections, the proposed method provided a more accurate estimate than conventional processing: e.g. for the soft phantom, biases of  -0.27 and -0.71 m · s -1 were observed. In a third series of experiments, the correlation-based method was able to locate two regions of different properties with an error smaller than 1 mm. It also provided more accurate PWV estimates than conventional processing (biases:  -0.12 versus -0.26 m · s -1 ). Finally, the in vivo feasibility of the proposed method was demonstrated in eleven healthy subjects. The results indicate that the correlation-based method might be less precise in vivo but more accurate than the conventional method.

Cross-correlating Cosmic IR and X-ray Background Fluctuations: Evidence of Significant Black Hole Populations Among the CIB Sources

Science.gov (United States)

Cappelluti, N.; Kashlinsky, A.; Arendt, R. G.; Comastri, A.; Fazio, G. G.; Finoguenov, A.; Hasinger, G.; Mather, J. C.; Miyaji, T; Moseley, S. H.

2013-01-01

In order to understand the nature of the sources producing the recently uncovered cosmic infrared background (CIB) fluctuations, we study cross-correlations between the fluctuations in the source-subtracted CIB from Spitzer/IRAC data and the unresolved cosmic X-ray background from deep Chandra observations. Our study uses data from the EGS/AEGIS field, where both data sets cover an approx = 8' x 45' region of the sky. Our measurement is the cross-power spectrum between the IR and X-ray data. The cross-power signal between the IRAC maps at 3.6 micron and 4.5 micron and the Chandra [0.5-2] keV data has been detected, at angular scales approx >20'', with an overall significance of approx = 3.8 sigma and approx. = 5.6 sigma, respectively. At the same time we find no evidence of significant cross-correlations at the harder Chandra bands. The cross-correlation signal is produced by individual IR sources with 3.6 micron and 4.5 micron magnitudes m(sub AB) approx. > 25-26 and [0.5-2] keV X-ray fluxes black holes than among the known populations. We discuss the various possible origins for the cross-power signal and show that neither local foregrounds nor the known remaining normal galaxies and active galactic nuclei can reproduce the measurements. These observational results are an important new constraint on theoretical modeling of the near-IR CIB fluctuations. local foregrounds, nor the known remaining normal galaxies and active galactic nuclei (AGN) can reproduce the measurements. These observational results are an important new constraint on theoretical modeling of the near-IR CIB fluctuations

Nonlinear stochastic exclusion financial dynamics modeling and time-dependent intrinsic detrended cross-correlation

Science.gov (United States)

Zhang, Wei; Wang, Jun

2017-09-01

In attempt to reproduce price dynamics of financial markets, a stochastic agent-based financial price model is proposed and investigated by stochastic exclusion process. The exclusion process, one of interacting particle systems, is usually thought of as modeling particle motion (with the conserved number of particles) in a continuous time Markov process. In this work, the process is utilized to imitate the trading interactions among the investing agents, in order to explain some stylized facts found in financial time series dynamics. To better understand the correlation behaviors of the proposed model, a new time-dependent intrinsic detrended cross-correlation (TDI-DCC) is introduced and performed, also, the autocorrelation analyses are applied in the empirical research. Furthermore, to verify the rationality of the financial price model, the actual return series are also considered to be comparatively studied with the simulation ones. The comparison results of return behaviors reveal that this financial price dynamics model can reproduce some correlation features of actual stock markets.

The Atacama Cosmology Telescope: Cross-Correlation of Cosmic Microwave Background Lensing and Quasars

Science.gov (United States)

Sherwin, Blake D; Das, Sudeep; Haijian, Amir; Addison, Graeme; Bond, Richard; Crichton, Devin; Devlin, Mark J.; Dunkley, Joanna; Gralla, Megan B.; Halpern, Mark;

Detection of non-stationary leak signals at NPP primary circuit by cross-correlation analysis

International Nuclear Information System (INIS)

Shimanskij, S.B.

2007-01-01

A leak-detection system employing high-temperature microphones has been developed for the RBMK and ATR (Japan) reactors. Further improvement of the system focused on using cross-correlation analysis of the spectral components of the signal to detect a small leak at an early stage of development. Since envelope processes are less affected by distortions than are wave processes, they give a higher-degree of correlation and can be used to detect leaks with lower signal-noise ratios. Many simulation tests performed at nuclear power plants have shown that the proposed methods can be used to detect and find the location of a small leak [ru

Step Test: a method for evaluating maximum oxygen consumption to determine the ability kind of work among students of medical emergencies.

Science.gov (United States)

Heydari, Payam; Varmazyar, Sakineh; Nikpey, Ahmad; Variani, Ali Safari; Jafarvand, Mojtaba

2017-03-01

Maximum oxygen consumption shows the maximum oxygen rate of muscle oxygenation that is acceptable in many cases, to measure the fitness between person and the desired job. Given that medical emergencies are important, and difficult jobs in emergency situations require people with high physical ability and readiness for the job, the aim of this study was to evaluate the maximum oxygen consumption, to determine the ability of work type among students of medical emergencies in Qazvin in 2016. This study was a descriptive - analytical, and in cross-sectional type conducted among 36 volunteer students of medical emergencies in Qazvin in 2016. After necessary coordination for the implementation of the study, participants completed health questionnaires and demographic characteristics and then the participants were evaluated with step tests of American College of Sport Medicine (ACSM). Data analysis was done by SPSS version 18 and U-Mann-Whitney tests, Kruskal-Wallis and Pearson correlation coefficient. Average of maximum oxygen consumption of the participants was estimated 3.15±0.50 liters per minute. 91.7% of medical emergencies students were selected as appropriate in terms of maximum oxygen consumption and thus had the ability to do heavy and too heavy work. Average of maximum oxygen consumption evaluated by the U-Mann-Whitney test and Kruskal-Wallis, had significant relationship with age (p<0.05) and weight groups (p<0.001). There was a significant positive correlation between maximum oxygen consumption with weight and body mass index (p<0.001). The results of this study showed that demographic variables of weight and body mass index are the factors influencing the determination of maximum oxygen consumption, as most of the students had the ability to do heavy, and too heavy work. Therefore, people with ability to do average work are not suitable for medical emergency tasks.

Multifractality, efficiency analysis of Chinese stock market and its cross-correlation with WTI crude oil price

Science.gov (United States)

Zhuang, Xiaoyang; Wei, Yu; Ma, Feng

2015-07-01

In this paper, the multifractality and efficiency degrees of ten important Chinese sectoral indices are evaluated using the methods of MF-DFA and generalized Hurst exponents. The study also scrutinizes the dynamics of the efficiency of Chinese sectoral stock market by the rolling window approach. The overall empirical findings revealed that all the sectoral indices of Chinese stock market exist different degrees of multifractality. The results of different efficiency measures have agreed on that the 300 Materials index is the least efficient index. However, they have a slight diffidence on the most efficient one. The 300 Information Technology, 300 Telecommunication Services and 300 Health Care indices are comparatively efficient. We also investigate the cross-correlations between the ten sectoral indices and WTI crude oil price based on Multifractal Detrended Cross-correlation Analysis. At last, some relevant discussions and implications of the empirical results are presented.

Signature of a possible relationship between the maximum CME speed index and the critical frequencies of the F1 and F2 ionospheric layers: Data analysis for a mid-latitude ionospheric station during the solar cycles 23 and 24

Science.gov (United States)

Kilcik, Ali; Ozguc, Atila; Yiǧit, Erdal; Yurchyshyn, Vasyl; Donmez, Burcin

2018-06-01

We analyze temporal variations of two solar indices, the monthly mean Maximum CME Speed Index (MCMESI) and the International Sunspot Number (ISSN) as well as the monthly median ionospheric critical frequencies (foF1, and foF2) for the time period of 1996-2013, which covers the entire solar cycle 23 and the ascending branch of the cycle 24. We found that the maximum of foF1 and foF2 occurred respectively during the first and second maximum of the ISSN solar activity index in the solar cycle 23. We compared these data sets by using the cross-correlation and hysteresis analysis and found that both foF1 and foF2 show higher correlation with ISSN than the MCMESI during the investigated time period, but when significance levels are considered correlation coefficients between the same indices become comparable. Cross-correlation analysis showed that the agreement between these data sets (solar indices and ionospheric critical frequencies) is better pronounced during the ascending phases of solar cycles, while they display significant deviations during the descending phase. We conclude that there exists a signature of a possible relationship between MCMESI and foF1 and foF2, which means that MCMESI could be used as a possible indicator of solar and geomagnetic activity, even though other investigations are needed.

Kalman/Map Filtering-Aided Fast Normalized Cross Correlation-Based Wi-Fi Fingerprinting Location Sensing

Directory of Open Access Journals (Sweden)

Yongliang Sun

2013-11-01

Full Text Available A Kalman/map filtering (KMF-aided fast normalized cross correlation (FNCC-based Wi-Fi fingerprinting location sensing system is proposed in this paper. Compared with conventional neighbor selection algorithms that calculate localization results with received signal strength (RSS mean samples, the proposed FNCC algorithm makes use of all the on-line RSS samples and reference point RSS variations to achieve higher fingerprinting accuracy. The FNCC computes efficiently while maintaining the same accuracy as the basic normalized cross correlation. Additionally, a KMF is also proposed to process fingerprinting localization results. It employs a new map matching algorithm to nonlinearize the linear location prediction process of Kalman filtering (KF that takes advantage of spatial proximities of consecutive localization results. With a calibration model integrated into an indoor map, the map matching algorithm corrects unreasonable prediction locations of the KF according to the building interior structure. Thus, more accurate prediction locations are obtained. Using these locations, the KMF considerably improves fingerprinting algorithm performance. Experimental results demonstrate that the FNCC algorithm with reduced computational complexity outperforms other neighbor selection algorithms and the KMF effectively improves location sensing accuracy by using indoor map information and spatial proximities of consecutive localization results.

Kalman/Map filtering-aided fast normalized cross correlation-based Wi-Fi fingerprinting location sensing.

Science.gov (United States)

Sun, Yongliang; Xu, Yubin; Li, Cheng; Ma, Lin

2013-11-13

A Kalman/map filtering (KMF)-aided fast normalized cross correlation (FNCC)-based Wi-Fi fingerprinting location sensing system is proposed in this paper. Compared with conventional neighbor selection algorithms that calculate localization results with received signal strength (RSS) mean samples, the proposed FNCC algorithm makes use of all the on-line RSS samples and reference point RSS variations to achieve higher fingerprinting accuracy. The FNCC computes efficiently while maintaining the same accuracy as the basic normalized cross correlation. Additionally, a KMF is also proposed to process fingerprinting localization results. It employs a new map matching algorithm to nonlinearize the linear location prediction process of Kalman filtering (KF) that takes advantage of spatial proximities of consecutive localization results. With a calibration model integrated into an indoor map, the map matching algorithm corrects unreasonable prediction locations of the KF according to the building interior structure. Thus, more accurate prediction locations are obtained. Using these locations, the KMF considerably improves fingerprinting algorithm performance. Experimental results demonstrate that the FNCC algorithm with reduced computational complexity outperforms other neighbor selection algorithms and the KMF effectively improves location sensing accuracy by using indoor map information and spatial proximities of consecutive localization results.

PROBING THE EPOCH OF PRE-REIONIZATION BY CROSS-CORRELATING COSMIC MICROWAVE AND INFRARED BACKGROUND ANISOTROPIES

International Nuclear Information System (INIS)

Atrio-Barandela, F.; Kashlinsky, A.

2014-01-01

The epoch of first star formation and the state of the intergalactic medium (IGM) at that time are not directly observable with current telescopes. The radiation from those early sources is now part of the cosmic infrared background (CIB) and, as these sources ionize the gas around them, the IGM plasma would produce faint temperature anisotropies in the cosmic microwave background (CMB) via the thermal Sunyaev-Zeldovich (TSZ) effect. While these TSZ anisotropies are too faint to be detected, we show that the cross-correlation of maps of source-subtracted CIB fluctuations from Euclid, with suitably constructed microwave maps at different frequencies, can probe the physical state of the gas during reionization and test/constrain models of the early CIB sources. We identify the frequency-combined, CMB-subtracted microwave maps from space- and ground-based instruments to show that they can be cross-correlated with the forthcoming all-sky Euclid CIB maps to detect the cross-power at scales ∼5'-60' with signal-to-noise ratios (S/Ns) of up to S/N ∼ 4-8 depending on the contribution to the Thomson optical depth during those pre-reionization epochs (Δτ ≅ 0.05) and the temperature of the IGM (up to ∼10 4 K). Such a measurement would offer a new window to explore the emergence and physical properties of these first light sources

Real time monitoring of induced seismicity in the Insheim and Landau deep geothermal reservoirs, Upper Rhine Graben, using the new SeisComP3 cross-correlation detector

Science.gov (United States)

Vasterling, Margarete; Wegler, Ulrich; Bruestle, Andrea; Becker, Jan

2016-04-01

Real time information on the locations and magnitudes of induced earthquakes is essential for response plans based on the magnitude frequency distribution. We developed and tested a real time cross-correlation detector focusing on induced microseismicity in deep geothermal reservoirs. The incoming seismological data are cross-correlated in real time with a set of known master events. We use the envelopes of the seismograms rather than the seismograms themselves to account for small changes in the source locations or in the focal mechanisms. Two different detection conditions are implemented: After first passing a single trace correlation condition, secondly a network correlation is calculated taking the amplitude information of the seismic network into account. The magnitude is estimated by using the respective ratio of the maximum amplitudes of the master event and the detected event. The detector is implemented as a real time tool and put into practice as a SeisComp3 module, an established open source software for seismological real time data handling and analysis. We validated the reliability and robustness of the detector by an offline playback test using four month of data from monitoring the power plant in Insheim (Upper Rhine Graben, SW Germany). Subsequently, in October 2013 the detector was installed as real time monitoring system within the project "MAGS2 - Microseismic Activity of Geothermal Systems". Master events from the two neighboring geothermal power plants in Insheim and Landau and two nearby quarries are defined. After detection, manual phase determination and event location are performed at the local seismological survey of the Geological Survey and Mining Authority of Rhineland-Palatinate. Until November 2015 the detector identified 454 events out of which 95% were assigned correctly to the respective source. 5% were misdetections caused by local tectonic events. To evaluate the completeness of the automatically obtained catalogue, it is

Investigating cluster astrophysics and cosmology with cross-correlation of the thermal Sunyaev-Zel'dovich effect and weak lensing

Science.gov (United States)

Osato, Ken; Flender, Samuel; Nagai, Daisuke; Shirasaki, Masato; Yoshida, Naoki

2018-03-01

Recent detections of the cross-correlation of the thermal Sunyaev-Zel'dovich (tSZ) effect and weak gravitational lensing (WL) enable unique studies of cluster astrophysics and cosmology. In this work, we present constraints on the amplitude of the non-thermal pressure fraction in galaxy clusters, α0, and the amplitude of the matter power spectrum, σ8, using measurements of the tSZ power spectrum from Planck, and the tSZ-WL cross-correlation from Planck and the Red Cluster Sequence Lensing Survey. We fit the data to a semi-analytic model with the covariance matrix using N-body simulations. We find that the tSZ power spectrum alone prefers σ8 ˜ 0.85 and a large fraction of non-thermal pressure (α0 ˜ 0.2-0.3). The tSZ-WL cross-correlation on the other hand prefers a significantly lower σ8 ˜ 0.6 and low α0 ˜ 0.05. We show that this tension can be mitigated by allowing for a steep slope in the stellar mass-halo mass relation, which would cause a reduction of the gas in low-mass haloes. In such a model, the combined data prefer σ8 ˜ 0.7 and α0 ˜ 0.2, consistent with predictions from hydrodynamical simulations.

Tomographic-spectral approach for dark matter detection in the cross-correlation between cosmic shear and diffuse γ-ray emission

International Nuclear Information System (INIS)

Camera, S.; Fornasa, M.; Fornengo, N.; Regis, M.

2015-01-01

We recently proposed to cross-correlate the diffuse extragalactic γ-ray background with the gravitational lensing signal of cosmic shear. This represents a novel and promising strategy to search for annihilating or decaying particle dark matter (DM) candidates. In the present work, we demonstrate the potential of a tomographic-spectral approach: measuring the cross-correlation in separate bins of redshift and energy significantly improves the sensitivity to a DM signal. Indeed, the technique proposed here takes advantage of the different scaling of the astrophysical and DM components with redshift and, simultaneously of their different energy spectra and different angular extensions. The sensitivity to a particle DM signal is extremely promising even when the DM-induced emission is quite faint. We first quantify the prospects of detecting DM by cross-correlating the Fermi Large Area Telescope (LAT) diffuse γ-ray background with the cosmic shear expected from the Dark Energy Survey. Under the hypothesis of a significant subhalo boost, such a measurement can deliver a 5σ detection of DM, if the DM particle is lighter than 300 GeV and has a thermal annihilation rate. We then forecast the capability of the European Space Agency Euclid satellite (whose launch is planned for 2020), in combination with an hypothetical future γ-ray detector with slightly improved specifications compared to current telescopes. We predict that the cross-correlation of their data will allow a measurement of the DM mass with an uncertainty of a factor of 1.5–2, even for moderate subhalo boosts, for DM masses up to few hundreds of GeV and thermal annihilation rates

Tomographic-spectral approach for dark matter detection in the cross-correlation between cosmic shear and diffuse γ-ray emission

Energy Technology Data Exchange (ETDEWEB)

Camera, S. [Jodrell Bank Centre for Astrophysics, The University of Manchester, Alan Turing Building, Oxford Road, Manchester M13 9PL (United Kingdom); Fornasa, M. [School of Physics and Astronomy, University of Nottingham, University Campus, Nottingham NG7 2RD (United Kingdom); Fornengo, N.; Regis, M., E-mail: stefano.camera@manchester.ac.uk, E-mail: fornasam@gmail.com, E-mail: fornengo@to.infn.it, E-mail: regis@to.infn.it [Dipartimento di Fisica, Università di Torino, Via P. Giuria 1, 10125 Torino (Italy)

2015-06-01

We recently proposed to cross-correlate the diffuse extragalactic γ-ray background with the gravitational lensing signal of cosmic shear. This represents a novel and promising strategy to search for annihilating or decaying particle dark matter (DM) candidates. In the present work, we demonstrate the potential of a tomographic-spectral approach: measuring the cross-correlation in separate bins of redshift and energy significantly improves the sensitivity to a DM signal. Indeed, the technique proposed here takes advantage of the different scaling of the astrophysical and DM components with redshift and, simultaneously of their different energy spectra and different angular extensions. The sensitivity to a particle DM signal is extremely promising even when the DM-induced emission is quite faint. We first quantify the prospects of detecting DM by cross-correlating the Fermi Large Area Telescope (LAT) diffuse γ-ray background with the cosmic shear expected from the Dark Energy Survey. Under the hypothesis of a significant subhalo boost, such a measurement can deliver a 5σ detection of DM, if the DM particle is lighter than 300 GeV and has a thermal annihilation rate. We then forecast the capability of the European Space Agency Euclid satellite (whose launch is planned for 2020), in combination with an hypothetical future γ-ray detector with slightly improved specifications compared to current telescopes. We predict that the cross-correlation of their data will allow a measurement of the DM mass with an uncertainty of a factor of 1.5–2, even for moderate subhalo boosts, for DM masses up to few hundreds of GeV and thermal annihilation rates.

Tomographic-spectral approach for dark matter detection in the cross-correlation between cosmic shear and diffuse γ-ray emission

Science.gov (United States)

Camera, S.; Fornasa, M.; Fornengo, N.; Regis, M.

2015-06-01

We recently proposed to cross-correlate the diffuse extragalactic γ-ray background with the gravitational lensing signal of cosmic shear. This represents a novel and promising strategy to search for annihilating or decaying particle dark matter (DM) candidates. In the present work, we demonstrate the potential of a tomographic-spectral approach: measuring the cross-correlation in separate bins of redshift and energy significantly improves the sensitivity to a DM signal. Indeed, the technique proposed here takes advantage of the different scaling of the astrophysical and DM components with redshift and, simultaneously of their different energy spectra and different angular extensions. The sensitivity to a particle DM signal is extremely promising even when the DM-induced emission is quite faint. We first quantify the prospects of detecting DM by cross-correlating the Fermi Large Area Telescope (LAT) diffuse γ-ray background with the cosmic shear expected from the Dark Energy Survey. Under the hypothesis of a significant subhalo boost, such a measurement can deliver a 5σ detection of DM, if the DM particle is lighter than 300 GeV and has a thermal annihilation rate. We then forecast the capability of the European Space Agency Euclid satellite (whose launch is planned for 2020), in combination with an hypothetical future γ-ray detector with slightly improved specifications compared to current telescopes. We predict that the cross-correlation of their data will allow a measurement of the DM mass with an uncertainty of a factor of 1.5-2, even for moderate subhalo boosts, for DM masses up to few hundreds of GeV and thermal annihilation rates.

The properties of cross-correlation and spectra of the low-mass X-ray binary 4U 1608-52

International Nuclear Information System (INIS)

Lei, Ya-Juan; Yuan, Hai-Long; Dong, Yi-Qiao; Zhang, Hao-Tong; Zhang, Cheng-Min; Zhao, Yong-Heng; Zhang, Shu; Qu, Jin-Lu; Wang, Ya-Nan; Li, Zhi-Bing

2014-01-01

With RXTE data, we analyzed the cross-correlation function between the soft and hard X-rays of the transient atoll source 4U 1608-52. We found anti-correlations in three outbursts occurred in 1998, 2002, and 2010, and we found significant time lags of several hundreds of seconds in the latter two outbursts. Our results show no correlation between the soft and hard X-rays in the extreme island state and a dominated positive correlation in the lower banana state. Anti-correlations are presented at the upper banana state for the outburst of 2010 and at the island and the lower left banana states for the other two outbursts. So far for atoll sources, the cross-correlation has been studied statistically only for 4U 1735-44, where anti-correlations showed up in the upper banana state. Here our investigation on 4U 1608-52 provides a similar result in its 2010 outburst. In addition, we notice that the luminosities in the upper banana of the 1998 and 2002 outbursts are about 1.5 times that of the 2010 outburst whose luminosity in the upper banana is close to that of 4U 1735-44. The results suggest that the states in the color-color diagram of a source could be correlated with the luminosity of the source. A further spectral analysis during the 2010 outburst is also shown, which suggests that the disk can be a little truncated in the upper banana. The feature on the upper banana is similar to the previous results of the flaring branch in Z sources.

Coherent correlation enhancement of outer shell photoionization cross sections of alkali-like ions

International Nuclear Information System (INIS)

Amusia, M.Y.; Avdonina, B.; Pratt, R.H.

1995-01-01

An alkali-like ion interaction with inner electrons of an alkali-like ion leads to a significant increase in the photoionization cross section of the outer s electron. This occurs not only for ground-state ions with one s electron in the outer shell, but also when the outer s electron is in an excited state. The reason for this amplification, in addition to coherent enhancement in summing of the correlation amplitudes, is that the zero in the direct amplitude occurs below threshold. This leads to a constructive interference with the correlation amplitude above the photoionization threshold, in contrast to a destructive interference in the case of a neutral atom with the same electronic configuration, for which the zero occurs above threshold. Results of this research were published

Correlations between the alpha angle and femoral head asphericity: Implications and recommendations for the diagnosis of cam femoroacetabular impingement

International Nuclear Information System (INIS)

Harris, Michael D.; Kapron, Ashley L.; Peters, Christopher L.; Anderson, Andrew E.

2014-01-01

Objective: To determine the strength of common radiographic and radial CT views for measuring true femoral head asphericity. Patients and methods: In 15 patients with cam femoroacetabular impingement (FAI) and 15 controls, alpha angles were measured by two observers using radial CT (0°, 30°, 60°, 90°) and digitally reconstructed radiographs (DRRs) for the: anterior–posterior (AP), standing frog-leg lateral, 45° Dunn with neutral rotation, 45° Dunn with 40° external rotation, and cross-table lateral views. A DRR validation study was performed. Alpha angles were compared between groups. Maximum deviation from a sphere of each subject was obtained from a previous study. Alpha angles from each view were correlated with maximum deviation. Results: There were no significant differences between alpha angles measured on radiographs and the corresponding DRRs (p = 0.72). Alpha angles were significantly greater in patients for all views (p ≤ 0.002). Alpha angles from the 45° Dunn with 40° external rotation, cross-table lateral, and 60° radial views had the strongest correlations with maximum deviation (r = 0.831; r = 0.823; r = 0.808, respectively). The AP view had the weakest correlation (r = 0.358). Conclusion: DRRs were a validated means to simulate hip radiographs. The 45° Dunn with 40° external rotation, cross-table lateral, and 60° radial views best visualized femoral asphericity. Although commonly used, the AP view did not visualize cam deformities well. Overall, the magnitude of the alpha angle may not be indicative of the size of the deformity. Thus, 3D reconstructions and measurements of asphericity could improve the diagnosis of cam FAI

The cross-correlation of the CMB polarization and the 21-cm line fluctuations from cosmic reionization

NARCIS (Netherlands)

Tashiro, Hiroyuki; Aghanim, Nabila; Langer, Mathieu; Douspis, Marian; Zaroubi, Saleem

2008-01-01

The cosmic microwave background (CMB) polarization and the 21-cm line fluctuations are powerful probes of cosmological reionization. We study how the cross-correlation between the CMB polarization (E modes) and the 21-cm line fluctuations can be used to gain further understanding of the reionization

Spatiotemporal Ultrafast-Plasmon Control Based on Response Functions of Nanostructures Measured by Interferometric Cross-Correlation Microscopy

Directory of Open Access Journals (Sweden)

Kusaba Miyuki

2013-03-01

Full Text Available We demonstrate an electrical-field cross-correlation imaging technique to obtain a response function of localized plasmon generated by femtosecond laser pulses on gold nanostructures. Based on the measured response functions, we spatiotemporally control the plasmon by shaping the femtosecond excitation laser pulses.

Development of the loss coefficient correlation for cross flow between graphite fuel blocks in the core of prismatic very high temperature reactor-PMR200

International Nuclear Information System (INIS)

Lee, Jeong-Hun; Cho, Hyoung-Kyu; Park, Goon-Cherl

2016-01-01

Highlights: • Cross flow experimental data are produced with wedge-shaped and parallel gaps. • The results of a CFD analysis and experimental data are in good agreement. • Pressure loss coefficient for the cross gap between fuel blocks in PMR200 is found. • A new correlation of the cross flow loss coefficient for PMR200 is proposed. - Abstract: The core of the very high temperature reactor (VHTR) PMR200 (a prismatic modular reactor rated at 200 MW of thermal power) consists of hexagonal prismatic fuel blocks and reflector blocks made of graphite. If the core bypass flow ratio increases, the coolant channel flow is decreased and can then lower the heat removal efficiency, resulting in a locally increased fuel block temperature. The coolant channels in the fuel blocks are connected to bypass gaps by the cross gap, complicating flow distribution in the VHTR core. Therefore, reliable estimation of the bypass flow is highly important for the design and safety analysis of the VHTR core. Because of the complexity of the core geometry and gap configuration, it is challenging to predict the flow distribution in the VHTR core. To analyze this flow distribution accurately, it is necessary to determine the cross flow phenomena, and the loss coefficient across the cross gap has to be evaluated to determine the flow distribution in the VHTR core when a lumped parameter code or a flow network analysis code that uses the correlation of the loss coefficient is employed. The purpose of this paper is to develop a loss coefficient correlation applicable to the cross gap in the PMR200 core. The cross flow was evaluated experimentally using the difference between the measured inlet and outlet mass flow rates. Next, the applicability of a commercial computational fluid dynamics (CFD) code, CFX 15, was confirmed by comparing the experimental data and CFD analysis results. To understand the cross flow phenomena, the loss coefficient was evaluated; in the high Reynolds number region

Development of the loss coefficient correlation for cross flow between graphite fuel blocks in the core of prismatic very high temperature reactor-PMR200

Energy Technology Data Exchange (ETDEWEB)

Lee, Jeong-Hun, E-mail: huny12@snu.ac.kr; Cho, Hyoung-Kyu, E-mail: chohk@snu.ac.kr; Park, Goon-Cherl, E-mail: parkgc@snu.ac.kr

2016-10-15

Highlights: • Cross flow experimental data are produced with wedge-shaped and parallel gaps. • The results of a CFD analysis and experimental data are in good agreement. • Pressure loss coefficient for the cross gap between fuel blocks in PMR200 is found. • A new correlation of the cross flow loss coefficient for PMR200 is proposed. - Abstract: The core of the very high temperature reactor (VHTR) PMR200 (a prismatic modular reactor rated at 200 MW of thermal power) consists of hexagonal prismatic fuel blocks and reflector blocks made of graphite. If the core bypass flow ratio increases, the coolant channel flow is decreased and can then lower the heat removal efficiency, resulting in a locally increased fuel block temperature. The coolant channels in the fuel blocks are connected to bypass gaps by the cross gap, complicating flow distribution in the VHTR core. Therefore, reliable estimation of the bypass flow is highly important for the design and safety analysis of the VHTR core. Because of the complexity of the core geometry and gap configuration, it is challenging to predict the flow distribution in the VHTR core. To analyze this flow distribution accurately, it is necessary to determine the cross flow phenomena, and the loss coefficient across the cross gap has to be evaluated to determine the flow distribution in the VHTR core when a lumped parameter code or a flow network analysis code that uses the correlation of the loss coefficient is employed. The purpose of this paper is to develop a loss coefficient correlation applicable to the cross gap in the PMR200 core. The cross flow was evaluated experimentally using the difference between the measured inlet and outlet mass flow rates. Next, the applicability of a commercial computational fluid dynamics (CFD) code, CFX 15, was confirmed by comparing the experimental data and CFD analysis results. To understand the cross flow phenomena, the loss coefficient was evaluated; in the high Reynolds number region

Impulse response measurements with an off-line cross correlator

International Nuclear Information System (INIS)

Corran, E.R.; Cummins, J.D.

1963-11-01

The impulse responses of simulated systems have been computed by off-line cross-correlation of the system input and output signals. The input test signal consisted of a discrete interval binary code whose autocorrelation was a triangular pulse at zero lag. The main object of the experiments was to study the inaccuracies introduced in ideal, noise free systems by determining the impulse response digitally from sampled versions of the system input and output signals. A second object was to determine the error introduced by adding controlled amounts of uncorrelated noise at the system outputs. The experimental results showed that for signal to noise ratios greater than 10:1 in the mean square sense, the impulse responses may be determined with reasonable accuracy using only one cycle of the binary code. The method lends itself to on-line computation of system impulse responses. The latter could be used to monitor the stability of the system or to determine control parameters in an adaptive control system. (author)

Impulse response measurements with an off-line cross correlator

Energy Technology Data Exchange (ETDEWEB)

Corran, E R; Cummins, J D [Dynamics Group, Control and Instrumentation Division, Atomic Energy Establishment, Winfrith, Dorchester, Dorset (United Kingdom)

1963-11-15

The impulse responses of simulated systems have been computed by off-line cross-correlation of the system input and output signals. The input test signal consisted of a discrete interval binary code whose autocorrelation was a triangular pulse at zero lag. The main object of the experiments was to study the inaccuracies introduced in ideal, noise free systems by determining the impulse response digitally from sampled versions of the system input and output signals. A second object was to determine the error introduced by adding controlled amounts of uncorrelated noise at the system outputs. The experimental results showed that for signal to noise ratios greater than 10:1 in the mean square sense, the impulse responses may be determined with reasonable accuracy using only one cycle of the binary code. The method lends itself to on-line computation of system impulse responses. The latter could be used to monitor the stability of the system or to determine control parameters in an adaptive control system. (author)

Cross-synergism in enzymatic hydrolysis of lignocellulosics: mathematical correlations according to a hyperbolic model

Energy Technology Data Exchange (ETDEWEB)

Tarantili, P.A.; Koullas, D.P.; Christakopoulos, P.; Kekos, D.; Koukios, E.G.; Macris, B.J. [National Technical Univ. of Athens (Greece). Dept. of Chemical Engineering

1996-10-01

The effect of cross-synergism in enzymatic hydrolysis of ball-milled Avicell, alkali-treated straw cellulose (ATSC), cotton and filter paper was investigated using mixtures of Fusarium oxysporum and Neurospora crassa enzymes. The experimental data were fitted according to an empirical hyperbolic model which utilized two parameters, the maximum conversion ({chi}{sub max}) and the enzymatic hydrolysis time corresponding to 50% of {chi}{sub max} (t{sub 1/2}). The model can predict conversion of polysaccharides as a function of hydrolysis time. Both model parameters were found to be strongly dependent on the crystallinity index as well as on the degree of delignification of the substrate. Up to 60% cellulose hydrolysis can be achieved when the crystallinity index of Avicell is reduced from 94.8% to 63.3%. The percentage increase of {chi}{sub max} due to delignification was higher than the corresponding increase of t{sub 1/2}. The extent of cross-synergism depends strongly on crystallinity index and degree of delignification. This type of synergism has been found to be significant in the case of substrates which are resistant to hydrolysis, such as Avicell (with high crystallinity index) or cotton. Cross-synergism phenomena caused by enzymatic mixtures can double cellulose hydrolysis yield with delignified straw as compared to the hydrolysis yields achieved by single-microorganism cellulases. (author)

Groundwater travel time uncertainty analysis: Sensitivity of results to model geometry, and correlations and cross correlations among input parameters

International Nuclear Information System (INIS)

Clifton, P.M.

1984-12-01

The deep basalt formations beneath the Hanford Site are being investigated for the Department of Energy (DOE) to assess their suitability as a host medium for a high level nuclear waste repository. Predicted performance of the proposed repository is an important part of the investigation. One of the performance measures being used to gauge the suitability of the host medium is pre-waste-emplacement groundwater travel times to the accessible environment. Many deterministic analyses of groundwater travel times have been completed by Rockwell and other independent organizations. Recently, Rockwell has completed a preliminary stochastic analysis of groundwater travel times. This document presents analyses that show the sensitivity of the results from the previous stochastic travel time study to: (1) scale of representation of model parameters, (2) size of the model domain, (3) correlation range of log-transmissivity, and (4) cross-correlation between transmissivity and effective thickness. 40 refs., 29 figs., 6 tabs

What is new about covered interest parity condition in the European Union? Evidence from fractal cross-correlation regressions

Czech Academy of Sciences Publication Activity Database

Krištoufek, Ladislav; Ferreira, P.

2017-01-01

Roč. 486, č. 1 (2017), s. 554-566 ISSN 0378-4371 R&D Projects: GA ČR(CZ) GA17-12408S Institutional support: RVO:67985556 Keywords : covered interest parity * detrended cross-correlation analysis * detrending moving cross-corrrelation analysis * financial integration Subject RIV: AH - Economics OBOR OECD: Applied Economics, Econometrics Impact factor: 2.243, year: 2016 http://library.utia.cas.cz/separaty/2017/E/kristoufek-0478811.pdf

Cross-correlating CMB temperature fluctuations with high-energy γ-ray from Dark-Matter annihilation

International Nuclear Information System (INIS)

Pieri, L.

2013-01-01

In this paper we compute the Integrated Sachs-Wolfe effect due to the presence of dark-matter structures on cosmological scale. We cross-correlate the CMB temperature fluctuations with the extragalactic high-energy γ-ray flux map obtained with FERMI-LAT. We find a null signal consistent with the theory and conclude that the presence of halos and subhalos at galactic and extragalactic scale, if not excluded, will be hardly discoverable.

Correlation of occupational stress with depression, anxiety, and sleep in Korean dentists: cross-sectional study.

Science.gov (United States)

Song, Kyung-Won; Choi, Won-Seok; Jee, Hee-Jung; Yuh, Chi-Sung; Kim, Yong-Ku; Kim, Leen; Lee, Heon-Jeong; Cho, Chul-Hyun

2017-12-12

This study aimed to investigate the degree of occupational stress and the clinical mental state of dentists. In addition, we investigated the correlation of occupational stress with depression, anxiety, and sleep among dentists in Korea. A cross-sectional survey on 231 dentists was conducted using the Doctor Job Stress Scale, Center for Epidemiologic Studies Depression Scale (CES-D), State-Trait Anxiety Index (STAI), and Pittsburgh Sleep Quality Index (PSQI). Correlation of occupational stress with mental health was investigated by adjusted multiple regression analysis. The scores of CES-D, STAI, and PSQI revealed a significant correlation with the Doctor Job Stress Scale (t = 3.93, P stress management focusing on interpersonal relationship with patients and responsibility as an expert rather than the intensity of work should be considered.

First results of cross-correlation analysis of ambient seismic noise from the Hellenic Unified Seismic Network

NARCIS (Netherlands)

Panou, Areti; Paulssen, Hanneke; Hatzidimitriou, Panagiotis

2015-01-01

In this study we present phase velocity maps that were obtained from the cross-correlation analysis of ambient seismic noise recorded in the region of Greece.We used one year (2013) of ambient seismic data obtained from the vertical component of 64 broadband permanent seismological stations that are

Personality correlates of Managerial talent: Cross cultural comparison

Directory of Open Access Journals (Sweden)

A. D. de Bod

1983-11-01

Full Text Available In spite of the worldwide use of the Managerial Assessment Centre, little, if any, cross-cultural research has been done on the method. Another neglected area of AC-research, is the study of personality. This study is aimed at making a contribution towards both these areas by investigating the relationship between the managerial dimensions and personality attributes for a group of Canadian (N = 1199 and a group of South African (N = 177 middle level managers. The first step was to compare the measuring instruments which were used to test the two groups, so as to ascertain any similarities and/or differences between the two instruments. The data which was generated by the application of the instruments was then subjected to a correlational and discriminant function analysis. The result of these analyses was used to (a define the personality correlates of managerial talent and (b to identify broad tendencies with regard to the relative influence of culture on the relationship between personality and managerial talent. Opsomming Ten spyte van die wêreldwye gebruik van die bestuursbeoordelingsentrum (AC is daar tot dusver weinig kruiskulturele navorsing hieroor gedoen. 'n Verdere verwaarloosde area van AC-navorsing, is die bestudering van persoonlikheid. Hierdie studie ondersoek die verwantskap tussen bestuursdimensies en persoonlikheidsattribute van 'n groep Kanadese (N = 1199 en 'n groep Suid-Afrikaanse (N = 177 middelvlakbestuurders. Die eerste stap was om die meetinstrumente wat gebruik is te toets en die twee groepe te vergelyk. Die ingesamelde data vir beide groepe is aan 'n korrelatiewe en diskriminant-funksie ontleding onderwerp. Die ontledings is gebruik om (a die persoonlikheidskorrelate van bestuurstalent te omlyn en (b breë tendense bloot te lê ten opsigte van die relatiewe invloed van kultuur op die verwantskap tussen persoonlikheid en bestuurstalent.

The large-scale cross-correlation of Damped Lyman alpha systems with the Lyman alpha forest: first measurements from BOSS

Energy Technology Data Exchange (ETDEWEB)

Font-Ribera, Andreu [Institute of Theoretical Physics, University of Zurich, 8057 Zurich (Switzerland); Miralda-Escudé, Jordi [Institució Catalana de Recerca i Estudis Avançats, Barcelona, Catalonia (Spain); Arnau, Eduard [Institut de Ciències del Cosmos (IEEC/UB), Barcelona, Catalonia (Spain); Carithers, Bill; Ross, Nicholas P.; White, Martin [Lawrence Berkeley National Laboratory, University of California Berkeley, Berkeley, California 94720 (United States); Lee, Khee-Gan [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany); Noterdaeme, Pasquier; Pâris, Isabelle; Petitjean, Patrick; Rollinde, Emmanuel [Institut d' Astrophysique de Paris, Université Paris 6 et CNRS, 98bis blvd. Arago, 75014 Paris (France); Rich, James [CEA, Centre de Saclay, IRFU, 91191 Gif-sur-Yvette (France); Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); York, Donald G., E-mail: font@physik.uzh.ch, E-mail: miralda@icc.ub.edu [Department of Astronomy and Astrophysics and The Fermi Institute, Chicago University, 5640 So. Ellis Ave., Chicago, IL 60637 (United States)

2012-11-01

We present the first measurement of the large-scale cross-correlation of Lyα forest absorption and Damped Lyman α systems (DLA), using the 9th Data Release of the Baryon Oscillation Spectroscopic Survey (BOSS). The cross-correlation is clearly detected on scales up to 40h{sup −1}Mpc and is well fitted by the linear theory prediction of the standard Cold Dark Matter model of structure formation with the expected redshift distortions, confirming its origin in the gravitational evolution of structure. The amplitude of the DLA-Lyα cross-correlation depends on only one free parameter, the bias factor of the DLA systems, once the Lyα forest bias factors are known from independent Lyα forest correlation measurements. We measure the DLA bias factor to be b{sub D} = (2.17±0.20)β{sub F}{sup 0.22}, where the Lyα forest redshift distortion parameter β{sub F} is expected to be above unity. This bias factor implies a typical host halo mass for DLAs that is much larger than expected in present DLA models, and is reproduced if the DLA cross section scales with halo mass as M{sub h}{sup α}, with α = 1.1±0.1 for β{sub F} = 1. Matching the observed DLA bias factor and rate of incidence requires that atomic gas remains extended in massive halos over larger areas than predicted in present simulations of galaxy formation, with typical DLA proper sizes larger than 20 kpc in host halos of masses ∼ 10{sup 12}M{sub ☉}. We infer that typical galaxies at z ≅ 2 to 3 are surrounded by systems of atomic clouds that are much more extended than the luminous parts of galaxies and contain ∼ 10% of the baryons in the host halo.

Estimation of uncertainty bounds for individual particle image velocimetry measurements from cross-correlation peak ratio

International Nuclear Information System (INIS)

Charonko, John J; Vlachos, Pavlos P

2013-01-01

Numerous studies have established firmly that particle image velocimetry (PIV) is a robust method for non-invasive, quantitative measurements of fluid velocity, and that when carefully conducted, typical measurements can accurately detect displacements in digital images with a resolution well below a single pixel (in some cases well below a hundredth of a pixel). However, to date, these estimates have only been able to provide guidance on the expected error for an average measurement under specific image quality and flow conditions. This paper demonstrates a new method for estimating the uncertainty bounds to within a given confidence interval for a specific, individual measurement. Here, cross-correlation peak ratio, the ratio of primary to secondary peak height, is shown to correlate strongly with the range of observed error values for a given measurement, regardless of flow condition or image quality. This relationship is significantly stronger for phase-only generalized cross-correlation PIV processing, while the standard correlation approach showed weaker performance. Using an analytical model of the relationship derived from synthetic data sets, the uncertainty bounds at a 95% confidence interval are then computed for several artificial and experimental flow fields, and the resulting errors are shown to match closely to the predicted uncertainties. While this method stops short of being able to predict the true error for a given measurement, knowledge of the uncertainty level for a PIV experiment should provide great benefits when applying the results of PIV analysis to engineering design studies and computational fluid dynamics validation efforts. Moreover, this approach is exceptionally simple to implement and requires negligible additional computational cost. (paper)

Cross-correlation matrix analysis of Chinese and American bank stocks in subprime crisis

International Nuclear Information System (INIS)

Zhu Shi-Zhao; Li Xin-Li; Zhang Wen-Qing; Wang Bing-Hong; Nie Sen; Yu Gao-Feng; Han Xiao-Pu

2015-01-01

In order to study the universality of the interactions among different markets, we analyze the cross-correlation matrix of the price of the Chinese and American bank stocks. We then find that the stock prices of the emerging market are more correlated than that of the developed market. Considering that the values of the components for the eigenvector may be positive or negative, we analyze the differences between two markets in combination with the endogenous and exogenous events which influence the financial markets. We find that the sparse pattern of components of eigenvectors out of the threshold value has no change in American bank stocks before and after the subprime crisis. However, it changes from sparse to dense for Chinese bank stocks. By using the threshold value to exclude the external factors, we simulate the interactions in financial markets. (paper)

Global correlation imaging of magnetic total field gradients

International Nuclear Information System (INIS)

Guo, Lianghui; Meng, Xiaohong; Shi, Lei

2012-01-01

Firstly we introduce the correlation imaging approach for the x-, y- and z-gradients of a magnetic total field anomaly for deriving the distribution of equivalent magnetic sources of the subsurface. In this approach, the subsurface space is divided into a regular grid, and then a correlation coefficient function is computed at each grid node, based on the cross-correlation between the x-gradient (or y-gradient or z-gradient) of the observed magnetic total field anomaly and the x-gradient (or y-gradient or z-gradient) of the theoretical magnetic total field anomaly due to a magnetic dipole. The resultant correlation coefficient is used to describe the probability of a magnetic dipole occurring at the node. We then define a global correlation coefficient function for comprehensively delineating the probability of an occurrence of a magnetic dipole, which takes, at each node, the maximum positive value of the corresponding correlation coefficient function of the three gradients. We finally test the approach both on synthetic data and real data from a metallic deposit area in the middle-lower reaches of the Yangtze River, China. (paper)

Dynamical maximum entropy approach to flocking.

Science.gov (United States)

Cavagna, Andrea; Giardina, Irene; Ginelli, Francesco; Mora, Thierry; Piovani, Duccio; Tavarone, Raffaele; Walczak, Aleksandra M

2014-04-01

We derive a new method to infer from data the out-of-equilibrium alignment dynamics of collectively moving animal groups, by considering the maximum entropy model distribution consistent with temporal and spatial correlations of flight direction. When bird neighborhoods evolve rapidly, this dynamical inference correctly learns the parameters of the model, while a static one relying only on the spatial correlations fails. When neighbors change slowly and the detailed balance is satisfied, we recover the static procedure. We demonstrate the validity of the method on simulated data. The approach is applicable to other systems of active matter.

Flaw characterization through nonlinear ultrasonics and wavelet cross-correlation algorithms

Science.gov (United States)

Bunget, Gheorghe; Yee, Andrew; Stewart, Dylan; Rogers, James; Henley, Stanley; Bugg, Chris; Cline, John; Webster, Matthew; Farinholt, Kevin; Friedersdorf, Fritz

2018-04-01

Ultrasonic measurements have become increasingly important non-destructive techniques to characterize flaws found within various in-service industrial components. The prediction of remaining useful life based on fracture analysis depends on the accurate estimation of flaw size and orientation. However, amplitude-based ultrasonic measurements are not able to estimate the plastic zones that exist ahead of crack tips. Estimating the size of the plastic zone is an advantage since some flaws may propagate faster than others. This paper presents a wavelet cross-correlation (WCC) algorithm that was applied to nonlinear analysis of ultrasonically guided waves (GW). By using this algorithm, harmonics present in the waveforms were extracted and nonlinearity parameters were used to indicate both the tip of the cracks and size of the plastic zone. B-scans performed with the quadratic nonlinearities were sensitive to micro-damage specific to plastic zones.

A study of the cross-correlation and time lag in black hole X-ray binary XTE J1859+226

Science.gov (United States)

Pei, Songpeng; Ding, Guoqiang; Li, Zhibing; Lei, Yajuan; Yuen, Rai; Qu, Jinlu

2017-07-01

With Rossi X-ray Timing Explorer (RXTE) data, we systematically study the cross-correlation and time lag in all spectral states of black hole X-ray binary (BHXB) XTE J1859+226 in detail during its entire 1999-2000 outburst that lasted for 166 days. Anti-correlations and positive correlations and their respective soft and hard X-ray lags are only detected in the first 100 days of the outburst when the luminosity is high. This suggests that the cross-correlations may be related to high luminosity. Positive correlations are detected in every state of XTE J1859+226, viz., hard state, hard-intermediate state (HIMS), soft-intermediate state (SIMS) and soft state. However, anti-correlations are only detected in HIMS and SIMS, anti-correlated hard lags are only detected in SIMS, while anti-correlated soft lags are detected in both HIMS and SIMS. Moreover, the ratio of the observations with anti-correlated soft lags to hard lags detected in XTE J1859+226 is significantly different from that in neutron star low-mass X-ray binaries (NS LMXBs). So far, anti-correlations are never detected in the soft state of BHXBs but detected in every branch or state of NS LMXBs. This may be due to the origin of soft seed photons in BHXBs is confined to the accretion disk and, for NS LMXBs, from both accretion disk and the surface of the NS. We notice that the timescale of anti-correlated time lags detected in XTE J1859+226 is similar with that of other BHXBs and NS LMXBs. We suggest that anti-correlated soft lag detected in BHXB may result from fluctuation in the accretion disk as well as NS LMXB.

Dynamical properties of a tumor growth system in the presence of immunization and colored cross-correlated noises

International Nuclear Information System (INIS)

Jia Zhenglin; Mei Dongcheng

2010-01-01

We investigate the effects of the noise parameters and immunization strength β on the dynamical properties of a tumor growth system with both immunization and colored cross-correlated noises. The analytical expressions for the associated relaxation time T C and the normalized correlation function C(s) are derived by means of the projection operator method. The results indicate that: (i) T C as a function of the multiplicative noise intensity α shows resonance-like behavior, i.e. the curves of T C versus α exhibit a single-peak structure and its peak position changes with increasing correlation strength between noises λ, the autocorrelation time of multiplicative noise τ 1 , the autocorrelation time of additive noise τ 2 and the cross-correlation time τ 3 . This behavior can be understood in terms of the noise-enhanced stability effect and the influence of the memory effects on it. (ii) The increasing λ, τ 1 , τ 2 and the additive noise intensity D slow down the fluctuation decay of the tumor population, whereas the increasing τ 3 and β speed it up. (iii) C(s) increases as λ, τ 1 , τ 2 and β increase, while it decreases with τ 3 increasing. Our study shows that the effects of some noise parameters on tumor growth can be modified due to the presence of the immunization effect.

Dynamical properties of a tumor growth system in the presence of immunization and colored cross-correlated noises

Science.gov (United States)

Jia, Zheng-Lin; Mei, Dong-Cheng

2010-05-01

We investigate the effects of the noise parameters and immunization strength β on the dynamical properties of a tumor growth system with both immunization and colored cross-correlated noises. The analytical expressions for the associated relaxation time TC and the normalized correlation function C(s) are derived by means of the projection operator method. The results indicate that: (i) TC as a function of the multiplicative noise intensity α shows resonance-like behavior, i.e. the curves of TC versus α exhibit a single-peak structure and its peak position changes with increasing correlation strength between noises λ, the autocorrelation time of multiplicative noise τ1, the autocorrelation time of additive noise τ2 and the cross-correlation time τ3. This behavior can be understood in terms of the noise-enhanced stability effect and the influence of the memory effects on it. (ii) The increasing λ, τ1, τ2 and the additive noise intensity D slow down the fluctuation decay of the tumor population, whereas the increasing τ3 and β speed it up. (iii) C(s) increases as λ, τ1, τ2 and β increase, while it decreases with τ3 increasing. Our study shows that the effects of some noise parameters on tumor growth can be modified due to the presence of the immunization effect.

Associated relaxation time and the correlation function for a tumor cell growth system subjected to color noises

Science.gov (United States)

Wang, Can-Jun; Wei, Qun; Mei, Dong-Cheng

2008-03-01

The associated relaxation time T and the normalized correlation function C(s) for a tumor cell growth system subjected to color noises are investigated. Using the Novikov theorem and Fox approach, the steady probability distribution is obtained. Based on them, the expressions of T and C(s) are derived by means of projection operator method, in which the effects of the memory kernels of the correlation function are taken into account. Performing the numerical computations, it is found: (1) With the cross-correlation intensity |λ|, the additive noise intensity α and the multiplicative noise self-correlation time τ increasing, the tumor cell numbers can be restrained; And the cross-correlation time τ, the multiplicative noise intensity D can induce the tumor cell numbers increasing; However, the additive noise self-correlation time τ cannot affect the tumor cell numbers; The relaxation time T is a stochastic resonant phenomenon, and the distribution curves exhibit a single-maximum structure with D increasing. (2) The cross-correlation strength λ weakens the related activity between two states of the tumor cell numbers at different time, and enhances the stability of the tumor cell growth system in the steady state; On the contrast, τ and τ enhance the related activity between two states at different time; However, τ has no effect on the related activity between two states at different time.

Microwave Correlation Measurement Crossed-pair Antennas ...

African Journals Online (AJOL)

We propose here new processes, an add and square correlation radiometer and the non-resonant perturbation, which thoroughly investigated for different muscle phantom materials to define the optimum penetration depth of the electromagnetic field at fixed distance between the antennas. Keywords: Microwave correlation ...

Resampling to accelerate cross-correlation searches for continuous gravitational waves from binary systems

Science.gov (United States)

Meadors, Grant David; Krishnan, Badri; Papa, Maria Alessandra; Whelan, John T.; Zhang, Yuanhao

2018-02-01

Continuous-wave (CW) gravitational waves (GWs) call for computationally-intensive methods. Low signal-to-noise ratio signals need templated searches with long coherent integration times and thus fine parameter-space resolution. Longer integration increases sensitivity. Low-mass x-ray binaries (LMXBs) such as Scorpius X-1 (Sco X-1) may emit accretion-driven CWs at strains reachable by current ground-based observatories. Binary orbital parameters induce phase modulation. This paper describes how resampling corrects binary and detector motion, yielding source-frame time series used for cross-correlation. Compared to the previous, detector-frame, templated cross-correlation method, used for Sco X-1 on data from the first Advanced LIGO observing run (O1), resampling is about 20 × faster in the costliest, most-sensitive frequency bands. Speed-up factors depend on integration time and search setup. The speed could be reinvested into longer integration with a forecast sensitivity gain, 20 to 125 Hz median, of approximately 51%, or from 20 to 250 Hz, 11%, given the same per-band cost and setup. This paper's timing model enables future setup optimization. Resampling scales well with longer integration, and at 10 × unoptimized cost could reach respectively 2.83 × and 2.75 × median sensitivities, limited by spin-wandering. Then an O1 search could yield a marginalized-polarization upper limit reaching torque-balance at 100 Hz. Frequencies from 40 to 140 Hz might be probed in equal observing time with 2 × improved detectors.

Application of an improved maximum correlated kurtosis deconvolution method for fault diagnosis of rolling element bearings

Science.gov (United States)

Miao, Yonghao; Zhao, Ming; Lin, Jing; Lei, Yaguo

2017-08-01

The extraction of periodic impulses, which are the important indicators of rolling bearing faults, from vibration signals is considerably significance for fault diagnosis. Maximum correlated kurtosis deconvolution (MCKD) developed from minimum entropy deconvolution (MED) has been proven as an efficient tool for enhancing the periodic impulses in the diagnosis of rolling element bearings and gearboxes. However, challenges still exist when MCKD is applied to the bearings operating under harsh working conditions. The difficulties mainly come from the rigorous requires for the multi-input parameters and the complicated resampling process. To overcome these limitations, an improved MCKD (IMCKD) is presented in this paper. The new method estimates the iterative period by calculating the autocorrelation of the envelope signal rather than relies on the provided prior period. Moreover, the iterative period will gradually approach to the true fault period through updating the iterative period after every iterative step. Since IMCKD is unaffected by the impulse signals with the high kurtosis value, the new method selects the maximum kurtosis filtered signal as the final choice from all candidates in the assigned iterative counts. Compared with MCKD, IMCKD has three advantages. First, without considering prior period and the choice of the order of shift, IMCKD is more efficient and has higher robustness. Second, the resampling process is not necessary for IMCKD, which is greatly convenient for the subsequent frequency spectrum analysis and envelope spectrum analysis without resetting the sampling rate. Third, IMCKD has a significant performance advantage in diagnosing the bearing compound-fault which expands the application range. Finally, the effectiveness and superiority of IMCKD are validated by a number of simulated bearing fault signals and applying to compound faults and single fault diagnosis of a locomotive bearing.

Power-law correlations in finance-related Google searches, and their cross-correlations with volatility and traded volume: Evidence from the Dow Jones Industrial components

Czech Academy of Sciences Publication Activity Database

Krištoufek, Ladislav

2015-01-01

Roč. 428, č. 1 (2015), s. 194-205 ISSN 0378-4371 R&D Projects: GA ČR(CZ) GP14-11402P Institutional support: RVO:67985556 Keywords : Online searches * Google Trends * Long-term memory * Cross-correlations * Volatility * Traded volume Subject RIV: AH - Economics Impact factor: 1.785, year: 2015 http://library.utia.cas.cz/separaty/2015/E/kristoufek-0452317.pdf

Parallel iterative decoding of transform domain Wyner-Ziv video using cross bitplane correlation

DEFF Research Database (Denmark)

Luong, Huynh Van; Huang, Xin; Forchhammer, Søren

2011-01-01

decoding scheme is proposed to improve the coding efficiency of TDWZ video codecs. The proposed parallel iterative LDPC decoding scheme is able to utilize cross bitplane correlation during decoding, by iteratively refining the soft-input, updating a modeled noise distribution and thereafter enhancing......In recent years, Transform Domain Wyner-Ziv (TDWZ) video coding has been proposed as an efficient Distributed Video Coding (DVC) solution, which fully or partly exploits the source statistics at the decoder to reduce the computational burden at the encoder. In this paper, a parallel iterative LDPC...

Trading Time with Space - Development of subduction zone parameter database for a maximum magnitude correlation assessment

Science.gov (United States)

Schaefer, Andreas; Wenzel, Friedemann

2017-04-01

Subduction zones are generally the sources of the earthquakes with the highest magnitudes. Not only in Japan or Chile, but also in Pakistan, the Solomon Islands or for the Lesser Antilles, subduction zones pose a significant hazard for the people. To understand the behavior of subduction zones, especially to identify their capabilities to produce maximum magnitude earthquakes, various physical models have been developed leading to a large number of various datasets, e.g. from geodesy, geomagnetics, structural geology, etc. There have been various studies to utilize this data for the compilation of a subduction zone parameters database, but mostly concentrating on only the major zones. Here, we compile the largest dataset of subduction zone parameters both in parameter diversity but also in the number of considered subduction zones. In total, more than 70 individual sources have been assessed and the aforementioned parametric data have been combined with seismological data and many more sources have been compiled leading to more than 60 individual parameters. Not all parameters have been resolved for each zone, since the data completeness depends on the data availability and quality for each source. In addition, the 3D down-dip geometry of a majority of the subduction zones has been resolved using historical earthquake hypocenter data and centroid moment tensors where available and additionally compared and verified with results from previous studies. With such a database, a statistical study has been undertaken to identify not only correlations between those parameters to estimate a parametric driven way to identify potentials for maximum possible magnitudes, but also to identify similarities between the sources themselves. This identification of similarities leads to a classification system for subduction zones. Here, it could be expected if two sources share enough common characteristics, other characteristics of interest may be similar as well. This concept

Brief communication: Landslide motion from cross correlation of UAV-derived morphological attributes

Science.gov (United States)

Peppa, Maria V.; Mills, Jon P.; Moore, Phil; Miller, Pauline E.; Chambers, Jonathan E.

2017-12-01

Unmanned aerial vehicles (UAVs) can provide observations of high spatio-temporal resolution to enable operational landslide monitoring. In this research, the construction of digital elevation models (DEMs) and orthomosaics from UAV imagery is achieved using structure-from-motion (SfM) photogrammetric procedures. The study examines the additional value that the morphological attribute of openness, amongst others, can provide to surface deformation analysis. Image-cross-correlation functions and DEM subtraction techniques are applied to the SfM outputs. Through the proposed integrated analysis, the automated quantification of a landslide's motion over time is demonstrated, with implications for the wider interpretation of landslide kinematics via UAV surveys.

On the interplay between short and long term memory in the power-law cross-correlations setting

Czech Academy of Sciences Publication Activity Database

Krištoufek, Ladislav

2015-01-01

Roč. 421, č. 1 (2015), s. 218-222 ISSN 0378-4371 R&D Projects: GA ČR(CZ) GP14-11402P Institutional support: RVO:67985556 Keywords : Power-law cross-correlations * Long term memory * Short term memory Subject RIV: AH - Economics Impact factor: 1.785, year: 2015 http://library.utia.cas.cz/separaty/2015/E/kristoufek-0452316.pdf

Inclusive D*± meson cross sections and D*±-jet correlations in photoproduction at HERA

Science.gov (United States)

Aktas, A.; Andreev, V.; Anthonis, T.; Antunovic, B.; Aplin, S.; Asmone, A.; Astvatsatourov, A.; Babaev, A.; Backovic, S.; Baghdasaryan, A.; Baranov, P.; Barrelet, E.; Bartel, W.; Baudrand, S.; Baumgartner, S.; Beckingham, M.; Behnke, O.; Behrendt, O.; Belousov, A.; Berger, N.; Bizot, J. C.; Boenig, M.-O.; Boudry, V.; Bracinik, J.; Brandt, G.; Brisson, V.; Bruncko, D.; Büsser, F. W.; Bunyatyan, A.; Buschhorn, G.; Bystritskaya, L.; Campbell, A. J.; Caron, S.; Cassol-Brunner, F.; Cerny, K.; Cerny, V.; Chekelian, V.; Contreras, J. G.; Coughlan, J. A.; Cox, B. E.; Cozzika, G.; Cvach, J.; Dainton, J. B.; Dau, W. D.; Daum, K.; de Boer, Y.; Delcourt, B.; Del Degan, M.; de Roeck, A.; de Wolf, E. A.; Diaconu, C.; Dodonov, V.; Dubak, A.; Eckerlin, G.; Efremenko, V.; Egli, S.; Eichler, R.; Eisele, F.; Eliseev, A.; Elsen, E.; Essenov, S.; Falkewicz, A.; Faulkner, P. J. W.; Favart, L.; Fedotov, A.; Felst, R.; Feltesse, J.; Ferencei, J.; Finke, L.; Fleischer, M.; Flucke, G.; Fomenko, A.; Franke, G.; Frisson, T.; Gabathuler, E.; Garutti, E.; Gayler, J.; Gerlich, C.; Ghazaryan, S.; Ginzburgskaya, S.; Glazov, A.; Glushkov, I.; Goerlich, L.; Goettlich, M.; Gogitidze, N.; Gorbounov, S.; Grab, C.; Greenshaw, T.; Gregori, M.; Grell, B. R.; Grindhammer, G.; Gwilliam, C.; Habib, S.; Haidt, D.; Hansson, M.; Heinzelmann, G.; Henderson, R. C. W.; Henschel, H.; Herrera, G.; Hildebrandt, M.; Hiller, K. H.; Hoffmann, D.; Horisberger, R.; Hovhannisyan, A.; Hreus, T.; Hussain, S.; Ibbotson, M.; Ismail, M.; Jacquet, M.; Janssen, X.; Jemanov, V.; Jönsson, L.; Johnson, D. P.; Jung, A. W.; Jung, H.; Kapichine, M.; Katzy, J.; Kenyon, I. R.; Kiesling, C.; Klein, M.; Kleinwort, C.; Klimkovich, T.; Kluge, T.; Knies, G.; Knutsson, A.; Korbel, V.; Kostka, P.; Krastev, K.; Kretzschmar, J.; Kropivnitskaya, A.; Krüger, K.; Landon, M. P. J.; Lange, W.; Laštovička-Medin, G.; Laycock, P.; Lebedev, A.; Leibenguth, G.; Lendermann, V.; Levonian, S.; Lindfeld, L.; Lipka, K.; Liptaj, A.; List, B.; List, J.; Lobodzinska, E.; Loktionova, N.; Lopez-Fernandez, R.; Lubimov, V.; Lucaci-Timoce, A.-I.; Lueders, H.; Lux, T.; Lytkin, L.; Makankine, A.; Malden, N.; Malinovski, E.; Marage, P.; Marshall, R.; Marti, L.; Martisikova, M.; Martyn, H.-U.; Maxfield, S. J.; Mehta, A.; Meier, K.; Meyer, A. B.; Meyer, H.; Meyer, J.; Michels, V.; Mikocki, S.; Milcewicz-Mika, I.; Milstead, D.; Mladenov, D.; Mohamed, A.; Moreau, F.; Morozov, A.; Morris, J. V.; Mozer, M. U.; Müller, K.; Murín, P.; Nankov, K.; Naroska, B.; Naumann, T.; Newman, P. R.; Niebuhr, C.; Nikiforov, A.; Nowak, G.; Nowak, K.; Nozicka, M.; Oganezov, R.; Olivier, B.; Olsson, J. E.; Osman, S.; Ozerov, D.; Palichik, V.; Panagoulias, I.; Papadopoulou, T.; Pascaud, C.; Patel, G. D.; Peng, H.; Perez, E.; Perez-Astudillo, D.; Perieanu, A.; Petrukhin, A.; Pitzl, D.; Plačakytė, R.; Portheault, B.; Povh, B.; Prideaux, P.; Rahmat, A. J.; Raicevic, N.; Reimer, P.; Rimmer, A.; Risler, C.; Rizvi, E.; Robmann, P.; Roland, B.; Roosen, R.; Rostovtsev, A.; Rurikova, Z.; Rusakov, S.; Salvaire, F.; Sankey, D. P. C.; Sauter, M.; Sauvan, E.; Schmidt, S.; Schmitt, S.; Schmitz, C.; Schoeffel, L.; Schöning, A.; Schultz-Coulon, H.-C.; Sefkow, F.; Shaw-West, R. N.; Sheviakov, I.; Shtarkov, L. N.; Sloan, T.; Smirnov, P.; Soloviev, Y.; South, D.; Spaskov, V.; Specka, A.; Steder, M.; Stella, B.; Stiewe, J.; Stoilov, A.; Straumann, U.; Sunar, D.; Tchoulakov, V.; Thompson, G.; Thompson, P. D.; Toll, T.; Tomasz, F.; Traynor, D.; Trinh, T. N.; Truöl, P.; Tsakov, I.; Tsipolitis, G.; Tsurin, I.; Turnau, J.; Tzamariudaki, E.; Urban, K.; Urban, M.; Usik, A.; Utkin, D.; Valkárová, A.; Vallée, C.; van Mechelen, P.; Vargas Trevino, A.; Vazdik, Y.; Veelken, C.; Vinokurova, S.; Volchinski, V.; Wacker, K.; Weber, G.; Weber, R.; Wegener, D.; Werner, C.; Wessels, M.; Wessling, B.; Wissing, C.; Wolf, R.; Wünsch, E.; Xella, S.; Yan, W.; Yeganov, V.; Žáček, J.; Zálešák, J.; Zhang, Z.; Zhelezov, A.; Zhokin, A.; Zhu, Y. C.; Zimmermann, J.; Zimmermann, T.; Zohrabyan, H.; Zomer, F.

2007-04-01

Differential photoproduction cross sections are measured for events containing D*± mesons. The data were taken with the H1 detector at the ep collider HERA and correspond to an integrated luminosity of 51.1 pb-1. The kinematic region covers small photon virtualities Q2 < 0.01 GeV2 and photon proton centre-of-mass energies of 171 < Wγ p < 256 GeV. The details of the heavy quark production process are further investigated in events with one or two jets in addition to the D*± meson. Differential cross sections for D*+jet production are determined and the correlations between the D*± meson and the jet(s) are studied. The results are compared with perturbative QCD predictions applying collinear- or kt-factorisation.

Detrending moving-average cross-correlation coefficient: Measuring cross-correlations between non-stationary series

Czech Academy of Sciences Publication Activity Database

Krištoufek, Ladislav

Roč. 406 , č. 1 (2014), s. 169-175 ISSN 0378-4371 R&D Projects: GA ČR(CZ) GP14-11402P Grant - others:GA ČR(CZ) GAP402/11/0948 Program:GA Institutional support: RVO:67985556 Keywords : correlations * econophysics * non-stationarity Subject RIV: AH - Economics Impact factor: 1.732, year: 2014 http://library.utia.cas.cz/separaty/2014/E/kristoufek-0433529.pdf

Development of OCDMA system based on Flexible Cross Correlation (FCC) code with OFDM modulation

Science.gov (United States)

Aldhaibani, A. O.; Aljunid, S. A.; Anuar, M. S.; Arief, A. R.; Rashidi, C. B. M.

2015-03-01

The performance of the OCDMA systems is governed by numerous quantitative parameters such as the data rate, simultaneous number of users, the powers of transmitter and receiver, and the type of codes. This paper analyzes the performance of the OCDMA system using OFDM technique to enhance the channel data rate, to save power and increase the number of user of OSCDMA systems compared with previous hybrid subcarrier multiplexing/optical spectrum code division multiplexing (SCM/OSCDM) system. The average received signal to noise ratio (SNR) with the nonlinearity of subcarriers is derived. The theoretical results have been evaluated based on BER and number of users as well as amount of power saved. The proposed system gave better performance and save around -6 dBm of the power as well as increase the number of users twice compare to SCM/OCDMA system. In addition it is robust against interference and much more spectrally efficient than SCM/OCDMA system. The system was designed based on Flexible Cross Correlation (FCC) code which is easier construction, less complexity of encoder/decoder design and flexible in-phase cross-correlation for uncomplicated to implement using Fiber Bragg Gratings (FBGs) for the OCDMA systems for any number of users and weights. The OCDMA-FCC_OFDM improves the number of users (cardinality) 108% compare to SCM/ODCMA-FCC system.

Retrieving the Green’s function in an open system by cross correlation : A comparison of approaches (L)

NARCIS (Netherlands)

Wapenaar, C.P.A.; Fokkema, J.; Snieder, R.

2005-01-01

We compare two approaches for deriving the fact that the Green’s function in an arbitrary inhomogeneous open system can be obtained by cross correlating recordings of the wave field at two positions. One approach is based on physical arguments, exploiting the principle of time-reversal invariance of

Analysis of cross-correlations in electroencephalogram signals as an approach to proactive diagnosis of schizophrenia

Science.gov (United States)

Timashev, Serge F.; Panischev, Oleg Yu.; Polyakov, Yuriy S.; Demin, Sergey A.; Kaplan, Alexander Ya.

2012-02-01

We apply flicker-noise spectroscopy (FNS), a time series analysis method operating on structure functions and power spectrum estimates, to study the clinical electroencephalogram (EEG) signals recorded in children/adolescents (11 to 14 years of age) with diagnosed schizophrenia-spectrum symptoms at the National Center for Psychiatric Health (NCPH) of the Russian Academy of Medical Sciences. The EEG signals for these subjects were compared with the signals for a control sample of chronically depressed children/adolescents. The purpose of the study is to look for diagnostic signs of subjects' susceptibility to schizophrenia in the FNS parameters for specific electrodes and cross-correlations between the signals simultaneously measured at different points on the scalp. Our analysis of EEG signals from scalp-mounted electrodes at locations F3 and F4, which are symmetrically positioned in the left and right frontal areas of cerebral cortex, respectively, demonstrates an essential role of frequency-phase synchronization, a phenomenon representing specific correlations between the characteristic frequencies and phases of excitations in the brain. We introduce quantitative measures of frequency-phase synchronization and systematize the values of FNS parameters for the EEG data. The comparison of our results with the medical diagnoses for 84 subjects performed at NCPH makes it possible to group the EEG signals into 4 categories corresponding to different risk levels of subjects' susceptibility to schizophrenia. We suggest that the introduced quantitative characteristics and classification of cross-correlations may be used for the diagnosis of schizophrenia at the early stages of its development.

Increasing the maximum daily operation time of MNSR reactor by modifying its cooling system

International Nuclear Information System (INIS)

Khamis, I.; Hainoun, A.; Al Halbi, W.; Al Isa, S.

2006-08-01

thermal-hydraulic natural convection correlations have been formulated based on a thorough analysis and modeling of the MNSR reactor. The model considers detailed description of the thermal and hydraulic aspects of cooling in the core and vessel. In addition, determination of pressure drop was made through an elaborate balancing of the overall pressure drop in the core against the sum of all individual channel pressure drops employing an iterative scheme. Using this model, an accurate estimation of various timely core-averaged hydraulic parameters such as generated power, hydraulic diameters, flow cross area, ... etc. for each one of the ten-fuel circles in the core can be made. Furthermore, distribution of coolant and fuel temperatures, including maximum fuel temperature and its location in the core, can now be determined. Correlation among core-coolant average temperature, reactor power, and core-coolant inlet temperature, during both steady and transient cases, have been established and verified against experimental data. Simulating various operating condition of MNSR, good agreement is obtained for at different power levels. Various schemes of cooling have been investigated for the purpose of assessing potential benefits on the operational characteristics of the syrian MNSR reactor. A detailed thermal hydraulic model for the analysis of MNSR has been developed. The analysis shows that an auxiliary cooling system, for the reactor vessel or installed in the pool which surrounds the lower section of the reactor vessel, will significantly offset the consumption of excess reactivity due to the negative reactivity temperature coefficient. Hence, the maximum operating time of the reactor is extended. The model considers detailed description of the thermal and hydraulic aspects of cooling the core and its surrounding vessel. Natural convection correlations have been formulated based on a thorough analysis and modeling of the MNSR reactor. The suggested 'micro model

Correlates of Unsupervised Bathing of Infants: A Cross-Sectional Study

Directory of Open Access Journals (Sweden)

Tinneke M. J. Beirens

2013-03-01

Full Text Available Drowning represents the third leading cause of fatal unintentional injury in infants (0–1 years. The aim of this study is to investigate correlates of unsupervised bathing. This cross-sectional study included 1,410 parents with an infant. Parents completed a questionnaire regarding supervision during bathing, socio-demographic factors, and Protection Motivation Theory-constructs. To determine correlates of parents who leave their infant unsupervised, logistic regression analyses were performed. Of the parents, 6.2% left their child unsupervised in the bathtub. Parents with older children (OR 1.24; 95%CI 1.00–1.54 were more likely to leave their child unsupervised in the bathtub. First-time parents (OR 0.59; 95%CI 0.36–0.97 and non-Western migrant fathers (OR 0.18; 95%CI 0.05–0.63 were less likely to leave their child unsupervised in the bathtub. Furthermore, parents who perceived higher self-efficacy (OR 0.57; 95%CI 0.47–0.69, higher response efficacy (OR 0.34; 95%CI 0.24–0.48, and higher severity (OR 0.74; 95%CI 0.58–0.93 were less likely to leave their child unsupervised. Since young children are at great risk of drowning if supervision is absent, effective strategies for drowning prevention should be developed and evaluated. In the meantime, health care professionals should inform parents with regard to the importance of supervision during bathing.

Encoding Strategy for Maximum Noise Tolerance Bidirectional Associative Memory

National Research Council Canada - National Science Library

Shen, Dan

2003-01-01

In this paper, the Basic Bidirectional Associative Memory (BAM) is extended by choosing weights in the correlation matrix, for a given set of training pairs, which result in a maximum noise tolerance set for BAM...

Neural correlates of cross-domain affective priming.

Science.gov (United States)

Zhang, Qin; Li, Xiaohua; Gold, Brian T; Jiang, Yang

2010-05-06

The affective priming effect has mostly been studied using reaction time (RT) measures; however, the neural bases of affective priming are not well established. To understand the neural correlates of cross-domain emotional stimuli presented rapidly, we obtained event-related potential (ERP) measures during an affective priming task using short SOA (stimulus onset asynchrony) conditions. Two sets of 480 picture-word pairs were presented at SOAs of either 150ms or 250ms between prime and target stimuli. Participants decided whether the valence of each target word was pleasant or unpleasant. Behavioral results from both SOA conditions were consistent with previous reports of affective priming, with longer RTs for incongruent than congruent pairs at SOAs of 150ms (771 vs. 738ms) and 250ms (765 vs. 720ms). ERP results revealed that the N400 effect (associated with incongruent pairs in affective processing) occurred at anterior scalp regions at an SOA of 150ms, and this effect was only observed for negative target words across the scalp at an SOA of 250ms. In contrast, late positive potentials (LPPs) (associated with attentional resource allocation) occurred across the scalp at an SOA of 250ms. LPPs were only observed for positive target words at posterior parts of the brain at an SOA of 150ms. Our finding of ERP signatures at very short SOAs provides the first neural evidence that affective pictures can exert an automatic influence on the evaluation of affective target words. Copyright 2010 Elsevier B.V. All rights reserved.

Atmospheric stellar parameters from cross-correlation functions

Science.gov (United States)

Malavolta, L.; Lovis, C.; Pepe, F.; Sneden, C.; Udry, S.

2017-08-01

The increasing number of spectra gathered by spectroscopic sky surveys and transiting exoplanet follow-up has pushed the community to develop automated tools for atmospheric stellar parameters determination. Here we present a novel approach that allows the measurement of temperature (Teff), metallicity ([Fe/H]) and gravity (log g) within a few seconds and in a completely automated fashion. Rather than performing comparisons with spectral libraries, our technique is based on the determination of several cross-correlation functions (CCFs) obtained by including spectral features with different sensitivity to the photospheric parameters. We use literature stellar parameters of high signal-to-noise (SNR), high-resolution HARPS spectra of FGK main-sequence stars to calibrate Teff, [Fe/H] and log g as a function of CCF parameters. Our technique is validated using low-SNR spectra obtained with the same instrument. For FGK stars we achieve a precision of σ _{{T_eff}} = 50 K, σlog g = 0.09 dex and σ _{{{[Fe/H]}}} =0.035 dex at SNR = 50, while the precision for observation with SNR ≳ 100 and the overall accuracy are constrained by the literature values used to calibrate the CCFs. Our approach can easily be extended to other instruments with similar spectral range and resolution or to other spectral range and stars other than FGK dwarfs if a large sample of reference stars is available for the calibration. Additionally, we provide the mathematical formulation to convert synthetic equivalent widths to CCF parameters as an alternative to direct calibration. We have made our tool publicly available.

Associated relaxation time and the correlation function for a tumor cell growth system subjected to color noises

International Nuclear Information System (INIS)

Wang Canjun; Wei Qun; Mei Dongcheng

2008-01-01

The associated relaxation time T c and the normalized correlation function C(s) for a tumor cell growth system subjected to color noises are investigated. Using the Novikov theorem and Fox approach, the steady probability distribution is obtained. Based on them, the expressions of T c and C(s) are derived by means of projection operator method, in which the effects of the memory kernels of the correlation function are taken into account. Performing the numerical computations, it is found: (1) With the cross-correlation intensity |λ|, the additive noise intensity α and the multiplicative noise self-correlation time τ 1 increasing, the tumor cell numbers can be restrained; And the cross-correlation time τ 3 , the multiplicative noise intensity D can induce the tumor cell numbers increasing; However, the additive noise self-correlation time τ 2 cannot affect the tumor cell numbers; The relaxation time T c is a stochastic resonant phenomenon, and the distribution curves exhibit a single-maximum structure with D increasing. (2) The cross-correlation strength λ weakens the related activity between two states of the tumor cell numbers at different time, and enhances the stability of the tumor cell growth system in the steady state; On the contrast, τ 1 and τ 3 enhance the related activity between two states at different time; However, τ 2 has no effect on the related activity between two states at different time

DOA Estimation Based on Real-Valued Cross Correlation Matrix of Coprime Arrays.

Science.gov (United States)

Li, Jianfeng; Wang, Feng; Jiang, Defu

2017-03-20

A fast direction of arrival (DOA) estimation method using a real-valued cross-correlation matrix (CCM) of coprime subarrays is proposed. Firstly, real-valued CCM with extended aperture is constructed to obtain the signal subspaces corresponding to the two subarrays. By analysing the relationship between the two subspaces, DOA estimations from the two subarrays are simultaneously obtained with automatic pairing. Finally, unique DOA is determined based on the common results from the two subarrays. Compared to partial spectral search (PSS) method and estimation of signal parameter via rotational invariance (ESPRIT) based method for coprime arrays, the proposed algorithm has lower complexity but achieves better DOA estimation performance and handles more sources. Simulation results verify the effectiveness of the approach.

Registration of synthetic tomographic projection data sets using cross-correlation

International Nuclear Information System (INIS)

Fitchard, E.E.; Aldridge, J.S.; Reckwerdt, P.J.; Mackie, T.R.

1998-01-01

Tomographic registration, a method that makes possible accurate patient registration directly from projection data, consists of three processing steps: (i) manual coarse positioning, (ii) tomographic projection set acquisition, and (iii) computer mediated refined positioning. In the coarse positioning stage, the degree of patient alignment is comparable with that achieved with the standard radiotherapy set-up. However, the accuracy requirements are somewhat more relaxed in that meticulous alignment of the patient using external laser indicators is not necessary. Instead, tomographic projection sets are compared with planning CTs in order to achieve improved patient set-up. The projection sets are cross-correlated to obtain the best-fit translation and rotation offsets. The algorithm has been tested on synthetic data with the incorporation of varying amounts of Gaussian pseudo-random noise. These tests demonstrate the algorithm's stability and also confirm that alignment can be achieved with an accuracy of less than one projection pixel. (author)

THE DiskMass SURVEY. III. STELLAR KINEMATICS VIA CROSS-CORRELATION

International Nuclear Information System (INIS)

Westfall, Kyle B.; Bershady, Matthew A.; Verheijen, Marc A. W.

2011-01-01

We describe a new cross-correlation (CC) approach used by our survey to derive stellar kinematics from galaxy-continuum spectroscopy. This approach adopts the formal error analysis derived by Statler, but properly handles spectral masks. Thus, we address the primary concerns regarding application of the CC method to censored data, while maintaining its primary advantage by consolidating kinematic and template-mismatch information toward different regions of the CC function. We identify a systematic error in the nominal CC method of approximately 10% in velocity dispersion incurred by a mistreatment of detector-censored data, which is eliminated by our new method. We derive our approach from first principles, and we use Monte Carlo simulations to demonstrate its efficacy. An identical set of Monte Carlo simulations performed using the well-established penalized-pixel-fitting code of Cappellari and Emsellem compares favorably with the results from our newly implemented software. Finally, we provide a practical demonstration of this software by extracting stellar kinematics from SparsePak spectra of UGC 6918.

Low-amplitude clustering in low-redshift 21-cm intensity maps cross-correlated with 2dF galaxy densities

Science.gov (United States)

Anderson, C. J.; Luciw, N. J.; Li, Y.-C.; Kuo, C. Y.; Yadav, J.; Masui, K. W.; Chang, T.-C.; Chen, X.; Oppermann, N.; Liao, Y.-W.; Pen, U.-L.; Price, D. C.; Staveley-Smith, L.; Switzer, E. R.; Timbie, P. T.; Wolz, L.

2018-05-01

We report results from 21-cm intensity maps acquired from the Parkes radio telescope and cross-correlated with galaxy maps from the 2dF galaxy survey. The data span the redshift range 0.057 clustering of neutral hydrogen (H I), a small correlation coefficient between optical galaxies and H I, or some combination of the two. Separating 2dF into red and blue galaxies, we find that red galaxies are much more weakly correlated with H I on k ˜ 1.5 h Mpc-1 scales, suggesting that H I is more associated with blue star-forming galaxies and tends to avoid red galaxies.

Application of fast Fourier transform cross-correlation and mass spectrometry data for accurate alignment of chromatograms.

Science.gov (United States)

Zheng, Yi-Bao; Zhang, Zhi-Min; Liang, Yi-Zeng; Zhan, De-Jian; Huang, Jian-Hua; Yun, Yong-Huan; Xie, Hua-Lin

2013-04-19

Chromatography has been established as one of the most important analytical methods in the modern analytical laboratory. However, preprocessing of the chromatograms, especially peak alignment, is usually a time-consuming task prior to extracting useful information from the datasets because of the small unavoidable differences in the experimental conditions caused by minor changes and drift. Most of the alignment algorithms are performed on reduced datasets using only the detected peaks in the chromatograms, which means a loss of data and introduces the problem of extraction of peak data from the chromatographic profiles. These disadvantages can be overcome by using the full chromatographic information that is generated from hyphenated chromatographic instruments. A new alignment algorithm called CAMS (Chromatogram Alignment via Mass Spectra) is present here to correct the retention time shifts among chromatograms accurately and rapidly. In this report, peaks of each chromatogram were detected based on Continuous Wavelet Transform (CWT) with Haar wavelet and were aligned against the reference chromatogram via the correlation of mass spectra. The aligning procedure was accelerated by Fast Fourier Transform cross correlation (FFT cross correlation). This approach has been compared with several well-known alignment methods on real chromatographic datasets, which demonstrates that CAMS can preserve the shape of peaks and achieve a high quality alignment result. Furthermore, the CAMS method was implemented in the Matlab language and available as an open source package at http://www.github.com/matchcoder/CAMS. Copyright © 2013. Published by Elsevier B.V.

Spatial clustering and halo occupation distribution modelling of local AGN via cross-correlation measurements with 2MASS galaxies

Science.gov (United States)

Krumpe, Mirko; Miyaji, Takamitsu; Coil, Alison L.; Aceves, Hector

2018-02-01

We present the clustering properties and halo occupation distribution (HOD) modelling of very low redshift, hard X-ray-detected active galactic nuclei (AGN) using cross-correlation function measurements with Two-Micron All Sky Survey galaxies. Spanning a redshift range of 0.007 2MASS galaxies.

Correlation between Macular Thickness and Visual Field in Early Open Angle Glaucoma: A Cross-Sectional Study.

Science.gov (United States)

Fallahi Motlagh, Behzad; Sadeghi, Ali

2017-01-01

The aim of this study was to correlate macular thickness and visual field parameters in early glaucoma. A total of 104 eyes affected with early glaucoma were examined in a cross-sectional, prospective study. Visual field testing using both standard automated perimetry (SAP) and shortwave automated perimetry (SWAP) was performed. Global visual field parameters, including mean deviation (MD) and pattern standard deviation (PSD), were recorded and correlated with spectral domain optical coherence tomography (SD-OCT)-measured macular thickness and asymmetry. Average macular thickness correlated significantly with all measures of visual field including MD-SWAP (r = 0.42), MD-SAP (r = 0.41), PSD-SWAP (r = -0.23), and PSD-SAP (r = -0.21), with P-values field parameters in early glaucoma. The results of this study should make macular thickness measurements even more meaningful to glaucoma specialists.

EVOLUTION OF THE CROSS-CORRELATION AND TIME LAG OF 4U 1735-44 ALONG THE BRANCHES

International Nuclear Information System (INIS)

Lei Yajuan; Zhang Haotong; Zhang Chengmin; Yuan Hailong; Dong Yiqiao; Zhao Yongheng; Zhang Yanxia; Qu Jinlu; Song Liming; Wang Dehua; Yin Hongxing

2013-01-01

We analyze the cross-correlation function between the soft and hard X-rays of atoll source 4U 1735-44 with RXTE data, and find anti-correlated soft and hard time lags of about a hecto-second. In the island state, the observations do not show any obvious correlations, and most observations of the banana branch show a positive correlation. However, anti-correlations are detected in the upper banana branch. These results are different from those of Z-sources (Cyg X-2, GX 5-1), where anti-correlations are detected in the horizontal branch and upper normal branch. In this case, the lag timescales of both this atoll and Z-sources are found to be similar, at a magnitude of several tens to hundreds of seconds. As a comparison, it is noted that anti-correlated lags lasting thousands of seconds have been reported from several black hole candidates in their intermediate states. In addition, for an observation containing four segments that show positive or anti-correlation, we analyze the spectral evolution with the hybrid model. In the observation, the anti-correlation is detected at the highest flux. The fitting results show that the Comptonized component is not the lowest at the highest flux, which suggests that the anti-correlation corresponds to the transition between the soft and hard states. Finally, we compare the corresponding results of atoll source 4U 1735-44 with those observed in Z-sources and black hole candidates, and the possible origins of the anti-correlated time lags are discussed

EVOLUTION OF THE CROSS-CORRELATION AND TIME LAG OF 4U 1735-44 ALONG THE BRANCHES

Energy Technology Data Exchange (ETDEWEB)

Lei Yajuan; Zhang Haotong; Zhang Chengmin; Yuan Hailong; Dong Yiqiao; Zhao Yongheng; Zhang Yanxia [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Qu Jinlu; Song Liming [Particle Astrophysics Center, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Wang Dehua [Astronomy Department, Beijing Normal University, Beijing 100875 (China); Yin Hongxing, E-mail: leiyjcwmy@163.com [School of Space Science and Physics, Shandong University, Weihai 264209 (China)

2013-09-15

We analyze the cross-correlation function between the soft and hard X-rays of atoll source 4U 1735-44 with RXTE data, and find anti-correlated soft and hard time lags of about a hecto-second. In the island state, the observations do not show any obvious correlations, and most observations of the banana branch show a positive correlation. However, anti-correlations are detected in the upper banana branch. These results are different from those of Z-sources (Cyg X-2, GX 5-1), where anti-correlations are detected in the horizontal branch and upper normal branch. In this case, the lag timescales of both this atoll and Z-sources are found to be similar, at a magnitude of several tens to hundreds of seconds. As a comparison, it is noted that anti-correlated lags lasting thousands of seconds have been reported from several black hole candidates in their intermediate states. In addition, for an observation containing four segments that show positive or anti-correlation, we analyze the spectral evolution with the hybrid model. In the observation, the anti-correlation is detected at the highest flux. The fitting results show that the Comptonized component is not the lowest at the highest flux, which suggests that the anti-correlation corresponds to the transition between the soft and hard states. Finally, we compare the corresponding results of atoll source 4U 1735-44 with those observed in Z-sources and black hole candidates, and the possible origins of the anti-correlated time lags are discussed.

Correction of clock errors in seismic data using noise cross-correlations

Science.gov (United States)

Hable, Sarah; Sigloch, Karin; Barruol, Guilhem; Hadziioannou, Céline

2017-04-01

Correct and verifiable timing of seismic records is crucial for most seismological applications. For seismic land stations, frequent synchronization of the internal station clock with a GPS signal should ensure accurate timing, but loss of GPS synchronization is a common occurrence, especially for remote, temporary stations. In such cases, retrieval of clock timing has been a long-standing problem. The same timing problem applies to Ocean Bottom Seismometers (OBS), where no GPS signal can be received during deployment and only two GPS synchronizations can be attempted upon deployment and recovery. If successful, a skew correction is usually applied, where the final timing deviation is interpolated linearly across the entire operation period. If GPS synchronization upon recovery fails, then even this simple and unverified, first-order correction is not possible. In recent years, the usage of cross-correlation functions (CCFs) of ambient seismic noise has been demonstrated as a clock-correction method for certain network geometries. We demonstrate the great potential of this technique for island stations and OBS that were installed in the course of the Réunion Hotspot and Upper Mantle - Réunions Unterer Mantel (RHUM-RUM) project in the western Indian Ocean. Four stations on the island La Réunion were affected by clock errors of up to several minutes due to a missing GPS signal. CCFs are calculated for each day and compared with a reference cross-correlation function (RCF), which is usually the average of all CCFs. The clock error of each day is then determined from the measured shift between the daily CCFs and the RCF. To improve the accuracy of the method, CCFs are computed for several land stations and all three seismic components. Averaging over these station pairs and their 9 component pairs reduces the standard deviation of the clock errors by a factor of 4 (from 80 ms to 20 ms). This procedure permits a continuous monitoring of clock errors where small clock

The cross wavelet analysis of dengue fever variability influenced by meteorological conditions

Science.gov (United States)

Lin, Yuan-Chien; Yu, Hwa-Lung; Lee, Chieh-Han

2015-04-01

The multiyear variation of meteorological conditions induced by climate change causes the changing diffusion pattern of infectious disease and serious epidemic situation. Among them, dengue fever is one of the most serious vector-borne diseases distributed in tropical and sub-tropical regions. Dengue virus is transmitted by several species of mosquito and causing lots amount of human deaths every year around the world. The objective of this study is to investigate the impact of meteorological variables to the temporal variation of dengue fever epidemic in southern Taiwan. Several extreme and average indices of meteorological variables, i.e. temperature and humidity, were used for this analysis, including averaged, maximum and minimum temperature, and average rainfall, maximum 1-hr rainfall, and maximum 24-hr rainfall. This study plans to identify and quantify the nonlinear relationship of meteorological variables and dengue fever epidemic, finding the non-stationary time-frequency relationship and phase lag effects of those time series from 1998-2011 by using cross wavelet method. Results show that meteorological variables all have a significant time-frequency correlation region to dengue fever epidemic in frequency about one year (52 weeks). The associated phases can range from 0 to 90 degrees (0-13 weeks lag from meteorological factors to dengue incidences). Keywords: dengue fever, cross wavelet analysis, meteorological factor

Measurement of angle-correlated differential (n,2n) reaction cross section with pencil-beam DV neutron source

International Nuclear Information System (INIS)

Takaki, S.; Kondo, K.; Shido, S.; Miyamaru, H.; Murata, I.; Ochiai, Kentaro; Nishitani, Takeo

2006-01-01

Angle-correlated differential cross-section for 9 Be(n,2n) reaction has been measured with the coincidence detection technique and a pencil-beam DT neutron source at FNS, JAEA. Energy spectra of two emitted neutrons were obtained for azimuthal and polar direction independently. It was made clear from the experiment that there are noise signals caused by inter-detector scattering. The ratio of the inter-detector scattering components in the detected signals was estimated by MCNP calculation to correct the measured result. By considering the inter-detector scattering components, the total 9 Be(n,2n) reaction cross-section agreed with the evaluated nuclear data within the experimental error. (author)

Measurement of zero power reactor dynamic response by cross correlation method; Merenje dinamickog odziva reaktora nulte snage kros korelacionom metodom

Energy Technology Data Exchange (ETDEWEB)

Kostic, Lj; Petrovic, M [Boris Kidric Institute of Nuclear Sciences Vinca, Beograd (Yugoslavia)

1969-07-15

Pulse response is comprehensive description of linear system dynamics. In this paper, cross correlation method was used for measuring the response of zero power reactor. Reactor system was perturbed by pseudo-random signal, which was cross correlated with the reactor signal responding to this perturbation on the digital ZUSE Z-23 computer. Cross-correlation functions were measured for different positions of stochastic oscillator and ionization chamber in the critical system. From numerical processing of performed experimental data, it was concluded that a more powerful faster computer would be needed for processing statistical experiments. In that case it would be possible to obtain information about spatial effects in the reactor and propagation of neutron waves in the multiplication medium. Impulsni odziv je potpuni opis dinamike linearnog sistema. Za merenje impulsnog odziva nultog reaktora, u ovom radu, koriscena je kros korelaciona metoda. Reaktorski sistem je perturbovan pseudoslucajnim signalom, koji je u digitalnom racunaru ZUSE Z-23 kroskorelisan sa signalom odziva reaktora na ove perturbacije. Merene su kroskorelacione funkcije za razlicite polozaje stohastickog oscilatora i jonizacione komore u kriticnom sistemu. Iz numericki obradjivanih eksperimenta namece se kao zakljucak da bi za obradu statistickih eksperimenata kod nultih reaktora bio potreban racunar veceg kapaciteta i brzine. U tom slucaju bi se iz ovako postavljenog eksperimenta moglo doci i do informacija o prostornim efektima u reaktoru i prostiranju neutronskih talasa kroz multiplikativnu sredinu. (author)

DOA Estimation Based on Real-Valued Cross Correlation Matrix of Coprime Arrays

Directory of Open Access Journals (Sweden)

Jianfeng Li

2017-03-01

Full Text Available A fast direction of arrival (DOA estimation method using a real-valued cross-correlation matrix (CCM of coprime subarrays is proposed. Firstly, real-valued CCM with extended aperture is constructed to obtain the signal subspaces corresponding to the two subarrays. By analysing the relationship between the two subspaces, DOA estimations from the two subarrays are simultaneously obtained with automatic pairing. Finally, unique DOA is determined based on the common results from the two subarrays. Compared to partial spectral search (PSS method and estimation of signal parameter via rotational invariance (ESPRIT based method for coprime arrays, the proposed algorithm has lower complexity but achieves better DOA estimation performance and handles more sources. Simulation results verify the effectiveness of the approach.

CROSS-CORRELATION WEAK LENSING OF SDSS GALAXY CLUSTERS. I. MEASUREMENTS

International Nuclear Information System (INIS)

Sheldon, Erin S.; Johnston, David E.; Scranton, Ryan; Koester, Benjamin P.; Oyaizu, Hiroaki; Cunha, Carlos; Lima, Marcos; Frieman, Joshua A.; McKay, Timothy A.; Lin Huan; Annis, James; Wechsler, Risa H.; Mandelbaum, Rachel; Bahcall, Neta A.; Fukugita, Masataka

2009-01-01

This is the first in a series of papers on the weak lensing effect caused by clusters of galaxies in Sloan Digital Sky Survey. The photometrically selected cluster sample, known as MaxBCG, includes ∼130,000 objects between redshift 0.1 and 0.3, ranging in size from small groups to massive clusters. We split the clusters into bins of richness and luminosity and stack the surface density contrast to produce mean radial profiles. The mean profiles are detected over a range of scales, from the inner halo (25 kpc h -1 ) well into the surrounding large-scale structure (30 Mpc h -1 ), with a significance of 15 to 20 in each bin. The signal over this large range of scales is best interpreted in terms of the cluster-mass cross-correlation function. We pay careful attention to sources of systematic error, correcting for them where possible. The resulting signals are calibrated to the ∼10% level, with the dominant remaining uncertainty being the redshift distribution of the background sources. We find that the profiles scale strongly with richness and luminosity. We find that the signal within a given richness bin depends upon luminosity, suggesting that luminosity is more closely correlated with mass than galaxy counts. We split the samples by redshift but detect no significant evolution. The profiles are not well described by power laws. In a subsequent series of papers, we invert the profiles to three-dimensional mass profiles, show that they are well fit by a halo model description, measure mass-to-light ratios, and provide a cosmological interpretation.

Cross-cultural differences in the neural correlates of specific and general recognition.

Science.gov (United States)

Paige, Laura E; Ksander, John C; Johndro, Hunter A; Gutchess, Angela H

2017-06-01

Research suggests that culture influences how people perceive the world, which extends to memory specificity, or how much perceptual detail is remembered. The present study investigated cross-cultural differences (Americans vs East Asians) at the time of encoding in the neural correlates of specific versus general memory formation. Participants encoded photos of everyday items in the scanner and 48 h later completed a surprise recognition test. The recognition test consisted of same (i.e., previously seen in scanner), similar (i.e., same name, different features), or new photos (i.e., items not previously seen in scanner). For Americans compared to East Asians, we predicted greater activation in the hippocampus and right fusiform for specific memory at recognition, as these regions were implicated previously in encoding perceptual details. Results revealed that East Asians activated the left fusiform and left hippocampus more than Americans for specific versus general memory. Follow-up analyses ruled out alternative explanations of retrieval difficulty and familiarity for this pattern of cross-cultural differences at encoding. Results overall suggest that culture should be considered as another individual difference that affects memory specificity and modulates neural regions underlying these processes. Copyright © 2017 Elsevier Ltd. All rights reserved.

Factors influencing parenting efficacy of Asian immigrant, first-time mothers: A cross-sectional, correlational survey.

Science.gov (United States)

Roh, Eun Ha; Ahn, Jeong-Ah; Park, Somi; Song, Ju-Eun

2017-12-01

In this study, we determined the factors influencing parenting efficacy of Asian immigrant, first-time mothers. The research design was a cross-sectional, correlational study. The study included 125 first-time mothers who immigrated and married Korean men, and were living in Korea. Data were collected using translated questionnaires, and analyzed for descriptive statistics, Pearson correlation, and multiple regression analysis. The major finding was that the parenting efficacy of immigrant women was influenced by childcare support from their husbands, maternal identity, and original nationality. The findings suggest that customized programs be developed and used to enhance parenting efficacy for Asian immigrant, first-time mothers. In developing such programs, the advantages of maternal identity, social support from the husband, and women's cultural context should be considered. © 2017 John Wiley & Sons Australia, Ltd.

Precipitation Interpolation by Multivariate Bayesian Maximum Entropy Based on Meteorological Data in Yun- Gui-Guang region, Mainland China

Science.gov (United States)

Wang, Chaolin; Zhong, Shaobo; Zhang, Fushen; Huang, Quanyi

2016-11-01

Precipitation interpolation has been a hot area of research for many years. It had close relation to meteorological factors. In this paper, precipitation from 91 meteorological stations located in and around Yunnan, Guizhou and Guangxi Zhuang provinces (or autonomous region), Mainland China was taken into consideration for spatial interpolation. Multivariate Bayesian maximum entropy (BME) method with auxiliary variables, including mean relative humidity, water vapour pressure, mean temperature, mean wind speed and terrain elevation, was used to get more accurate regional distribution of annual precipitation. The means, standard deviations, skewness and kurtosis of meteorological factors were calculated. Variogram and cross- variogram were fitted between precipitation and auxiliary variables. The results showed that the multivariate BME method was precise with hard and soft data, probability density function. Annual mean precipitation was positively correlated with mean relative humidity, mean water vapour pressure, mean temperature and mean wind speed, negatively correlated with terrain elevation. The results are supposed to provide substantial reference for research of drought and waterlog in the region.

Information Entropy Production of Maximum Entropy Markov Chains from Spike Trains

Science.gov (United States)

Cofré, Rodrigo; Maldonado, Cesar

2018-01-01

We consider the maximum entropy Markov chain inference approach to characterize the collective statistics of neuronal spike trains, focusing on the statistical properties of the inferred model. We review large deviations techniques useful in this context to describe properties of accuracy and convergence in terms of sampling size. We use these results to study the statistical fluctuation of correlations, distinguishability and irreversibility of maximum entropy Markov chains. We illustrate these applications using simple examples where the large deviation rate function is explicitly obtained for maximum entropy models of relevance in this field.

Autocorrelation and cross-correlation between hCGβ and PAPP-A in repeated sampling during first trimester of pregnancy

DEFF Research Database (Denmark)

Nørgaard, Pernille; Wright, Dave; Ball, Susan

2013-01-01

Theoretically, repeated sampling of free β-human chorionic gonadotropin (hCGβ) and pregnancy associated plasma protein-A (PAPP-A) in the first trimester of pregnancy might improve performance of risk assessment of trisomy 21 (T21). To assess the performance of a screening test involving repeated...... measures of biochemical markers, correlations between markers must be estimated. The aims of this study were to calculate the autocorrelation and cross-correlation between hCGβ and PAPP-A in the first trimester of pregnancy and to investigate the possible impact of gestational age at the first sample...

Severity of Acute Infectious Mononucleosis Correlates with Cross-Reactive Influenza CD8 T-Cell Receptor Repertoires.

Science.gov (United States)

Aslan, Nuray; Watkin, Levi B; Gil, Anna; Mishra, Rabinarayan; Clark, Fransenio G; Welsh, Raymond M; Ghersi, Dario; Luzuriaga, Katherine; Selin, Liisa K

2017-12-05

Fifty years after the discovery of Epstein-Barr virus (EBV), it remains unclear how primary infection with this virus leads to massive CD8 T-cell expansion and acute infectious mononucleosis (AIM) in young adults. AIM can vary greatly in severity, from a mild transient influenza-like illness to a prolonged severe syndrome. We questioned whether expansion of a unique HLA-A2.01-restricted, cross-reactive CD8 T-cell response between influenza virus A-M1 58 (IAV-M1) and EBV BMLF1 280 (EBV-BM) could modulate the immune response to EBV and play a role in determining the severity of AIM in 32 college students. Only ex vivo total IAV-M1 and IAV-M1+EBV-BM cross-reactive tetramer + frequencies directly correlated with AIM severity and were predictive of severe disease. Expansion of specific cross-reactive memory IAV-M1 T-cell receptor (TCR) Vβ repertoires correlated with levels of disease severity. There were unique profiles of qualitatively different functional responses in the cross-reactive and EBV-specific CD8 T-cell responses in each of the three groups studied, severe-AIM patients, mild-AIM patients, and seropositive persistently EBV-infected healthy donors, that may result from differences in TCR repertoire use. IAV-M1 tetramer + cells were functionally cross-reactive in short-term cultures, were associated with the highest disease severity in AIM, and displayed enhanced production of gamma interferon, a cytokine that greatly amplifies immune responses, thus frequently contributing to induction of immunopathology. Altogether, these data link heterologous immunity via CD8 T-cell cross-reactivity to CD8 T-cell repertoire selection, function, and resultant disease severity in a common and important human infection. In particular, it highlights for the first time a direct link between the TCR repertoire with pathogenesis and the diversity of outcomes upon pathogen encounter. IMPORTANCE The pathogenic impact of immune responses that by chance cross-react to unrelated

Imitating intrinsic alignments: a bias to the CMB lensing-galaxy shape cross-correlation power spectrum induced by the large-scale structure bispectrum

Science.gov (United States)

Merkel, Philipp M.; Schäfer, Björn Malte

2017-10-01

Cross-correlating the lensing signals of galaxies and comic microwave background (CMB) fluctuations is expected to provide valuable cosmological information. In particular, it may help tighten constraints on parameters describing the properties of intrinsically aligned galaxies at high redshift. To access the information conveyed by the cross-correlation signal, its accurate theoretical description is required. We compute the bias to CMB lensing-galaxy shape cross-correlation measurements induced by non-linear structure growth. Using tree-level perturbation theory for the large-scale structure bispectrum, we find that the bias is negative on most angular scales, therefore mimicking the signal of intrinsic alignments. Combining Euclid-like galaxy lensing data with a CMB experiment comparable to the Planck satellite mission, the bias becomes significant only on smallest scales (ℓ ≳ 2500). For improved CMB observations, however, the corrections amount to 10-15 per cent of the CMB lensing-intrinsic alignment signal over a wide multipole range (10 ≲ ℓ ≲ 2000). Accordingly, the power spectrum bias, if uncorrected, translates into 2σ and 3σ errors in the determination of the intrinsic alignment amplitude in the case of CMB stage III and stage IV experiments, respectively.

Performance correlations for high temperature potassium heat pipes

International Nuclear Information System (INIS)

Merrigan, M.A.; Keddy, E.S.; Sena, J.T.

1987-01-01

Potassium heat pipes designed for operation at a nominal temperature of 775K have been developed for use in a heat pipe cooled reactor design. The heat pipes operate in a gravity assist mode with a maximum required power throughput of approximately 16 kW per heat pipe. Based on a series of sub-scale experiments with 2.12 and 3.2 cm diameter heat pipes the prototypic heat pipe diameter was set at 5.7 cm with a simple knurled wall wick used in the interests of mechanical simplicity. The performance levels required for this design had been demonstrated in prior work with gutter assisted wicks and emphasis in the present work was on the attainment of similar performance with a simplified wick structure. The wick structure used in the experiment consisted of a pattern of knurled grooves in the internal wall of the heat pipe. The knurl depth required for the planned heat pipe performance was determined by scaling of wick characteristic data from the sub-scale tests. These tests indicated that the maximum performance limits of the test heat pipes did not follow normal entrainment limit predictions for textured wall gravity assist heat pipes. Test data was therefore scaled to the prototype design based on the assumption that the performance was controlled by an entrainment parameter based on the liquid flow depth in the groove structure. This correlation provided a reasonable fit to the sub-scale test data and was used in scale up of the design from the 8.0 cm 2 cross section of the largest sub-scale heat pipe to the 25.5 cm 2 cross section prototype. Correlation of the model predictions with test data from the prototype is discussed

Information Entropy Production of Maximum Entropy Markov Chains from Spike Trains

Directory of Open Access Journals (Sweden)

Rodrigo Cofré

2018-01-01

Full Text Available The spiking activity of neuronal networks follows laws that are not time-reversal symmetric; the notion of pre-synaptic and post-synaptic neurons, stimulus correlations and noise correlations have a clear time order. Therefore, a biologically realistic statistical model for the spiking activity should be able to capture some degree of time irreversibility. We use the thermodynamic formalism to build a framework in the context maximum entropy models to quantify the degree of time irreversibility, providing an explicit formula for the information entropy production of the inferred maximum entropy Markov chain. We provide examples to illustrate our results and discuss the importance of time irreversibility for modeling the spike train statistics.

A Review on Empirical Correlations for Jet/Spray Trajectory of Liquid Jet in Uniform Cross Flow

Directory of Open Access Journals (Sweden)

Soo-Young No

2015-12-01

Full Text Available The empirical correlations for the prediction of jet/spray penetration of liquid jet in subsonic uniform crossflow are reviewed in this study. Considerable number of empirical correlations had been proposed by many investigators. It has generally known that the jet/spray trajectory of a liquid jet in a cross-flow is a function of the liquid to air momentum flux ratio and the normalized distance in the airstream direction from the injector. However, several researchers incorporated the Weber number, liquid-to-water or air viscosity ratio, pressure ratio or Reynolds number, temperature ratio in the empirical correlations. Two different classification methods of correlations, i.e. classification based on mathematic functional form and classification based on flow regime, are introduced in this study. The one classification of existing correlations based on functional form includes correlations in a power-law, logarithmic, and exponential forms, respectively. The other classification of previous correlations based on flow regime includes one, two and three regime, correlations. Correlations in a power-law functional form can be further divided into three groups such as momentum flux ratio, Weber number and other parameters forms. Correlations in logarithmic functional form can be also grouped as momentum flux ratio and Weber number forms. Most of the evaluation studies reported the significant discrepancies of predicted values by the existing correlations. The possible reasons for discrepancies will be summarized as measurement technique, assumptions made in defining terms in the liquid to air momentum flux ratio, difficulties in defining the boundaries of the liquid jets, turbulence level in the core and boundary layer of incoming jet and gas flows, nozzle/injector geometry and its position in the crossflow. However, it can be found from the several evaluation studies that the power-law functional form with momentum flux ratio and two regimes

Methodological aspects of crossover and maximum fat-oxidation rate point determination.

Science.gov (United States)

Michallet, A-S; Tonini, J; Regnier, J; Guinot, M; Favre-Juvin, A; Bricout, V; Halimi, S; Wuyam, B; Flore, P

2008-11-01

Indirect calorimetry during exercise provides two metabolic indices of substrate oxidation balance: the crossover point (COP) and maximum fat oxidation rate (LIPOXmax). We aimed to study the effects of the analytical device, protocol type and ventilatory response on variability of these indices, and the relationship with lactate and ventilation thresholds. After maximum exercise testing, 14 relatively fit subjects (aged 32+/-10 years; nine men, five women) performed three submaximum graded tests: one was based on a theoretical maximum power (tMAP) reference; and two were based on the true maximum aerobic power (MAP). Gas exchange was measured concomitantly using a Douglas bag (D) and an ergospirometer (E). All metabolic indices were interpretable only when obtained by the D reference method and MAP protocol. Bland and Altman analysis showed overestimation of both indices with E versus D. Despite no mean differences between COP and LIPOXmax whether tMAP or MAP was used, the individual data clearly showed disagreement between the two protocols. Ventilation explained 10-16% of the metabolic index variations. COP was correlated with ventilation (r=0.96, P<0.01) and the rate of increase in blood lactate (r=0.79, P<0.01), and LIPOXmax correlated with the ventilation threshold (r=0.95, P<0.01). This study shows that, in fit healthy subjects, the analytical device, reference used to build the protocol and ventilation responses affect metabolic indices. In this population, and particularly to obtain interpretable metabolic indices, we recommend a protocol based on the true MAP or one adapted to include the transition from fat to carbohydrate. The correlation between metabolic indices and lactate/ventilation thresholds suggests that shorter, classical maximum progressive exercise testing may be an alternative means of estimating these indices in relatively fit subjects. However, this needs to be confirmed in patients who have metabolic defects.

Fractal Dimension and Maximum Sunspot Number in Solar Cycle

Directory of Open Access Journals (Sweden)

R.-S. Kim

2006-09-01

Full Text Available The fractal dimension is a quantitative parameter describing the characteristics of irregular time series. In this study, we use this parameter to analyze the irregular aspects of solar activity and to predict the maximum sunspot number in the following solar cycle by examining time series of the sunspot number. For this, we considered the daily sunspot number since 1850 from SIDC (Solar Influences Data analysis Center and then estimated cycle variation of the fractal dimension by using Higuchi's method. We examined the relationship between this fractal dimension and the maximum monthly sunspot number in each solar cycle. As a result, we found that there is a strong inverse relationship between the fractal dimension and the maximum monthly sunspot number. By using this relation we predicted the maximum sunspot number in the solar cycle from the fractal dimension of the sunspot numbers during the solar activity increasing phase. The successful prediction is proven by a good correlation (r=0.89 between the observed and predicted maximum sunspot numbers in the solar cycles.

Interference Cancellation Technique Based on Discovery of Spreading Codes of Interference Signals and Maximum Correlation Detection for DS-CDMA System

Science.gov (United States)

Hettiarachchi, Ranga; Yokoyama, Mitsuo; Uehara, Hideyuki

This paper presents a novel interference cancellation (IC) scheme for both synchronous and asynchronous direct-sequence code-division multiple-access (DS-CDMA) wireless channels. In the DS-CDMA system, the multiple access interference (MAI) and the near-far problem (NFP) are the two factors which reduce the capacity of the system. In this paper, we propose a new algorithm that is able to detect all interference signals as an individual MAI signal by maximum correlation detection. It is based on the discovery of all the unknowing spreading codes of the interference signals. Then, all possible MAI patterns so called replicas are generated as a summation of interference signals. And the true MAI pattern is found by taking correlation between the received signal and the replicas. Moreover, the receiver executes MAI cancellation in a successive manner, removing all interference signals by single-stage. Numerical results will show that the proposed IC strategy, which alleviates the detrimental effect of the MAI and the near-far problem, can significantly improve the system performance. Especially, we can obtain almost the same receiving characteristics as in the absense of interference for asynchrnous system when received powers are equal. Also, the same performances can be seen under any received power state for synchronous system.

Joint cross-correlation analysis reveals complex, time-dependent functional relationship between cortical neurons and arm electromyograms

Science.gov (United States)

Zhuang, Katie Z.; Lebedev, Mikhail A.

2014-01-01

Correlation between cortical activity and electromyographic (EMG) activity of limb muscles has long been a subject of neurophysiological studies, especially in terms of corticospinal connectivity. Interest in this issue has recently increased due to the development of brain-machine interfaces with output signals that mimic muscle force. For this study, three monkeys were implanted with multielectrode arrays in multiple cortical areas. One monkey performed self-timed touch pad presses, whereas the other two executed arm reaching movements. We analyzed the dynamic relationship between cortical neuronal activity and arm EMGs using a joint cross-correlation (JCC) analysis that evaluated trial-by-trial correlation as a function of time intervals within a trial. JCCs revealed transient correlations between the EMGs of multiple muscles and neural activity in motor, premotor and somatosensory cortical areas. Matching results were obtained using spike-triggered averages corrected by subtracting trial-shuffled data. Compared with spike-triggered averages, JCCs more readily revealed dynamic changes in cortico-EMG correlations. JCCs showed that correlation peaks often sharpened around movement times and broadened during delay intervals. Furthermore, JCC patterns were directionally selective for the arm-reaching task. We propose that such highly dynamic, task-dependent and distributed relationships between cortical activity and EMGs should be taken into consideration for future brain-machine interfaces that generate EMG-like signals. PMID:25210153

Phylogenetic patterns and correlation of key structures for jumping: bone crests and cross-sectional areas of muscles in Leptodactylus (Anura, Leptodactylidae).

Science.gov (United States)

Ponssa, María Laura; Fratani, Jéssica; Abdala, Virginia

2018-05-01

Anurans are characterized by their saltatory mode of locomotion, which is associated with a specific morphology. The coordinated action of the muscles and bones of the pelvic girdle is key to the transmission of the force of the hindlimbs to the axial skeleton during jumping. Two features are critical for optimal locomotory performance: the cross-sectional area of muscle and the bone crest attachment sites. The first character is a proxy of the force exerted by the muscle, whereas the crests are muscle attachments sites related to muscle force. The provisory relationship between these features has previously been identified and bone crest size can be used to infer the magnitude and, therefore, muscle force in fossils records. In this work, we explore the correlation between the cross-sectional area of essential muscles to the jumping mechanism (longissimus dorsi, extensor iliotibialis B, tenuissimus, puboischiofemoralis internus B, coccygeo-sacralis and coccygeo-iliacus) and the bone crests where these muscles are inserted (dorsal tubercle, dorsal crest and urostylar crest) in species of the genus Leptodactylus. This genus, along with other leptodactylids, exhibits a diversity of locomotor modes, including jumping, hopping, swimming and burrowing. We therefore analyzed the morphometric variation in the two features, cross-sectional area and bone crest area, expecting a correlation with different locomotor types. Our results showed: (i) a correlation between the urostylar crest and the cross-sectional area of the related muscles; (ii) that the bone crest surface area of urostyle and ilium and the cross-sectional area of the corresponding muscles can be utilized to infer locomotor faculties in leptodactylid frogs; and (iii) that the evolution of both characters demonstrates a general tendency from lower values in leptodactylid ancestors to higher values in the Leptodactylus genus. The results attest to the importance of the comparison of current ecological and

Polysomnographic Findings and Clinical Correlates in Huntington Disease: A Cross-Sectional Cohort Study

Science.gov (United States)

Piano, Carla; Losurdo, Anna; Della Marca, Giacomo; Solito, Marcella; Calandra-Buonaura, Giovanna; Provini, Federica; Bentivoglio, Anna Rita; Cortelli, Pietro

2015-01-01

Study Objectives: To evaluate the sleep pattern and the motor activity during sleep in a cohort of patients affected by Huntington disease (HD). Design: Cross-sectional cohort study. Setting: Sleep laboratory. Patients: Thirty HD patients, 16 women and 14 men (mean age 57.3 ± 12.2 y); 30 matched healthy controls (mean age 56.5 ± 11.8 y). Interventions: Subjective sleep evaluation: Epworth Sleepiness Scale (ESS); Berlin's Questionnaire, interview for restless legs syndrome (RLS), questionnaire for REM sleep behavior disorder (RBD). Clinical evaluation: disease duration, clinical severity (unified Huntington disease motor rating scale [UHDMRS]), genetic tests. Laboratory-based full-night attended video-polysomnography (V-PSG). Measurements and Results: The duration of the disease was 9.4 ± 4.4 y, UHMDRS score was 55.5 ± 23.4, CAG repeats were 44.3 ± 4.1. Body mass index was 21.9 ± 4.0 kg/m2. No patients or caregivers reported poor sleep quality. Two patients reported symptoms of RLS. Eight patients had an ESS score ≥ 9. Eight patients had high risk of obstructive sleep apnea. At the RBD questionnaire, two patients had a pathological score. HD patients, compared to controls, showed shorter sleep, reduced sleep efficiency index, and increased arousals and awakenings. Four patients presented with sleep disordered breathing (SDB). Periodic limb movements (PLMs) during wake and sleep were observed in all patients. No episode of RBD was observed in the V-PSG recordings, and no patients showed rapid eye movement (REM) sleep without atonia. The disease duration correlated with ESS score (P Marca G, Solito M, Calandra-Buonaura G, Provini F, Bentivoglio AR, Cortelli P. Polysomnographic findings and clinical correlates in Huntington disease: a cross-sectional cohort study. SLEEP 2015;38(9):1489–1495. PMID:25845698

Fluorescence correlation spectroscopy and fluorescence cross-correlation spectroscopy reveal the cytoplasmic origination of loaded nuclear RISC in vivo in human cells.

Science.gov (United States)

Ohrt, Thomas; Mütze, Jörg; Staroske, Wolfgang; Weinmann, Lasse; Höck, Julia; Crell, Karin; Meister, Gunter; Schwille, Petra

2008-11-01

Studies of RNA interference (RNAi) provide evidence that in addition to the well-characterized cytoplasmic mechanisms, nuclear mechanisms also exist. The mechanism by which the nuclear RNA-induced silencing complex (RISC) is formed in mammalian cells, as well as the relationship between the RNA silencing pathways in nuclear and cytoplasmic compartments is still unknown. Here we show by applying fluorescence correlation and cross-correlation spectroscopy (FCS/FCCS) in vivo that two distinct RISC exist: a large approximately 3 MDa complex in the cytoplasm and a 20-fold smaller complex of approximately 158 kDa in the nucleus. We further show that nuclear RISC, consisting only of Ago2 and a short RNA, is loaded in the cytoplasm and imported into the nucleus. The loaded RISC accumulates in the nucleus depending on the presence of a target, based on an miRNA-like interaction with impaired cleavage of the cognate RNA. Together, these results suggest a new RISC shuttling mechanism between nucleus and cytoplasm ensuring concomitant gene regulation by small RNAs in both compartments.

The Atacama Cosmology Telescope: Calibration with the Wilkinson Microwave Anisotropy Probe Using Cross-Correlations

Science.gov (United States)

Hajian, Amir; Acquaviva, Viviana; Ade, Peter A. R.; Aguirre, Paula; Amiri, Mandana; Appel, John William; Barrientos, L. Felipe; Battistelli, Elia S.; Bond, John R.; Brown, Ben;

Detecting particle dark matter signatures by cross-correlating γ-ray anisotropies with weak lensing

Science.gov (United States)

Camera, S.; Fornasa, M.; Fornengo, N.; Regis, M.

2016-05-01

The underlying nature of dark matter still represents one of the fundamental questions in contemporary cosmology. Although observations well agree with its description in terms of a new fundamental particle, neither direct nor indirect signatures of its particle nature have been detected so far, despite a strong experimental effort. Similarly, particle accelerators have hitherto failed at producing dark matter particles in collider physics experiments. Here, we illustrate how the cross-correlation between anisotropies in the diffuse γ-ray background and weak gravitational lensing effects represents a novel promising way in the quest of detecting particle dark matter signatures.

A Method for Vibration-Based Structural Interrogation and Health Monitoring Based on Signal Cross-Correlation

International Nuclear Information System (INIS)

Trendafilova, I

2011-01-01

Vibration-based structural interrogation and health monitoring is a field which is concerned with the estimation of the current state of a structure or a component from its vibration response with regards to its ability to perform its intended function appropriately. One way to approach this problem is through damage features extracted from the measured structural vibration response. This paper suggests to use a new concept for the purposes of vibration-based health monitoring. The correlation between two signals, an input and an output, measured on the structure is used to develop a damage indicator. The paper investigates the applicability of the signal cross-correlation and a nonlinear alternative, the average mutual information between the two signals, for the purposes of structural health monitoring and damage assessment. The suggested methodology is applied and demonstrated for delamination detection in a composite beam.

A damage detection method for instrumented civil structures using prerecorded Green’s functions and cross-correlation

OpenAIRE

Heckman, Vanessa; Kohler, Monica; Heaton, Thomas

2011-01-01

Automated damage detection methods have application to instrumented structures that are susceptible to types of damage that are difficult or costly to detect. The presented method has application to the detection of brittle fracture of welded beam-column connections in steel moment-resisting frames (MRFs), where locations of potential structural damage are known a priori. The method makes use of a prerecorded catalog of Green’s function templates and a cross-correlation method ...

Increasing the computational efficient of digital cross correlation by a vectorization method

Science.gov (United States)

Chang, Ching-Yuan; Ma, Chien-Ching

2017-08-01

This study presents a vectorization method for use in MATLAB programming aimed at increasing the computational efficiency of digital cross correlation in sound and images, resulting in a speedup of 6.387 and 36.044 times compared with performance values obtained from looped expression. This work bridges the gap between matrix operations and loop iteration, preserving flexibility and efficiency in program testing. This paper uses numerical simulation to verify the speedup of the proposed vectorization method as well as experiments to measure the quantitative transient displacement response subjected to dynamic impact loading. The experiment involved the use of a high speed camera as well as a fiber optic system to measure the transient displacement in a cantilever beam under impact from a steel ball. Experimental measurement data obtained from the two methods are in excellent agreement in both the time and frequency domain, with discrepancies of only 0.68%. Numerical and experiment results demonstrate the efficacy of the proposed vectorization method with regard to computational speed in signal processing and high precision in the correlation algorithm. We also present the source code with which to build MATLAB-executable functions on Windows as well as Linux platforms, and provide a series of examples to demonstrate the application of the proposed vectorization method.

Detailed Tremor Migration Styles in Guerrero, Mexico Imaged with Cross-station Cross-correlations

Science.gov (United States)

Peng, Y.; Rubin, A. M.

2015-12-01

Tremor occurred downdip of the area that slipped the most during the 2006 slow slip event (SSE) in Guerrero, Mexico, as opposed to Cascadia, where tremor locations and rupture zones of SSEs largely overlap. Here we obtain high resolution tremor locations by applying cross-station cross-correlations [Armbruster et al., 2014] to seismic data from the Meso-America Subduction Experiment deployment. A few 3-station detectors are adopted to capture detailed deformation styles in the tremor "transient zone" and the downdip "sweet spot" as defined in Frank et al., 2014. Similar to Cascadia, tremor activities in our study region were comprised mostly of short tremor bursts lasting minutes to hours. Many of these bursts show clear migration patterns with propagation velocities of hundreds of km/day, comparable to those in Cascadia. However, the propagation of the main tremor front was often not in a simple unilateral fashion. Before the 2006 SSE, we observe 4 large tremor episodes during which both the transient zone and the sweet spot participated, consistent with previous findings [Frank et al., 2014]. The transient zone usually became active a few days after the sweet spot. We find many along-dip migrations with recurrence intervals of about a half day within a region about 10 km along strike and 35 km along dip in the sweet spot, suggesting possible tidal modulation, after the main front moved beyond this region. These migrations appear not to originate at the main front, in contrast to tremor migrations from a few km to tens of km across observed in Cascadia [Rubin and Armbruster, 2013; Peng et al., 2015; Peng and Rubin, submitted], but possibly similar to Shikoku, Japan [Shelly et al., 2007]. We do not observe obvious half-day periodicity for the migrations farther downdip within the sweet spot. During the SSE, the recurrence interval of tremor episodes decreased significantly in both the transient zone and the sweet spot, with that of the former being much shorter

Photoionization of Xe inside C60: Atom-fullerene hybridization, giant cross-section enhancement, and correlation confinement resonances

International Nuclear Information System (INIS)

Madjet, Mohamed E.; Renger, Thomas; Hopper, Dale E.; McCune, Matthew A.; Chakraborty, Himadri S.; Rost, Jan-M.; Manson, Steven T.

2010-01-01

A theoretical study of the subshell photoionization of the Xe atom endohedrally confined in C 60 is presented. Powerful hybridization of the Xe 5s state with the bottom edge of C 60 π band is found that induces strong structures in the 5s ionization, causing the cross section to differ significantly from earlier results that omit this hybridization. The hybridization also affects the angular distribution asymmetry parameter of Xe 5p ionization near the Cooper minimum. The 5p cross section, on the other hand, is greatly enhanced by borrowing considerable oscillator strength from the C 60 giant plasmon resonance via the atom-fullerene dynamical interchannel coupling. Beyond the C 60 plasmon energy range the atomic subshell cross sections display confinement-induced oscillations in which, over the large 4d shape resonance region, the dominant 4d oscillations induce their ''clones'' in all degenerate weaker channels known as correlation confinement resonances.

Nuclear material enrichment identification method based on cross-correlation and high order spectra

International Nuclear Information System (INIS)

Yang Fan; Wei Biao; Feng Peng; Mi Deling; Ren Yong

2013-01-01

In order to enhance the sensitivity of nuclear material identification system (NMIS) against the change of nuclear material enrichment, the principle of high order statistic feature is introduced and applied to traditional NMIS. We present a new enrichment identification method based on cross-correlation and high order spectrum algorithm. By applying the identification method to NMIS, the 3D graphs with nuclear material character are presented and can be used as new signatures to identify the enrichment of nuclear materials. The simulation result shows that the identification method could suppress the background noises, electronic system noises, and improve the sensitivity against enrichment change to exponential order with no system structure modification. (authors)

Mechanical Dyssynchrony by Tissue Doppler Cross-Correlation is Associated with Risk for Complex Ventricular Arrhythmias after Cardiac Resynchronization Therapy

DEFF Research Database (Denmark)

Tayal, Bhupendar; Gorcsan, John; Delgado-Montero, Antonia

2015-01-01

BACKGROUND: Tissue Doppler cross-correlation analysis has been shown to be associated with long-term survival after cardiac resynchronization defibrillator therapy (CRT-D). Its association with ventricular arrhythmia (VA) is unknown. METHODS: From two centers 151 CRT-D patients (New York Heart...... Association functional classes II-IV, ejection fraction ≤ 35%, and QRS duration ≥ 120 msec) were prospectively included. Tissue Doppler cross-correlation analysis of myocardial acceleration curves from the basal segments in the apical views both at baseline and 6 months after CRT-D implantation was performed...... with a substantially increased risk for VA (hazard ratio [HR], 4.4; 95% CI, 1.2-16.3; P = .03) and VA or death (HR, 4.0; 95% CI, 1.7-9.6; P = .002) after adjusting for other covariates. Similarly, patients with new dyssynchrony had increased risk for VA (HR, 10.6; 95% CI, 2.8-40.4; P = .001) and VA or death (HR, 5...

Applications of the maximum entropy principle in nuclear physics

International Nuclear Information System (INIS)

Froehner, F.H.

1990-01-01

Soon after the advent of information theory the principle of maximum entropy was recognized as furnishing the missing rationale for the familiar rules of classical thermodynamics. More recently it has also been applied successfully in nuclear physics. As an elementary example we derive a physically meaningful macroscopic description of the spectrum of neutrons emitted in nuclear fission, and compare the well known result with accurate data on 252 Cf. A second example, derivation of an expression for resonance-averaged cross sections for nuclear reactions like scattering or fission, is less trivial. Entropy maximization, constrained by given transmission coefficients, yields probability distributions for the R- and S-matrix elements, from which average cross sections can be calculated. If constrained only by the range of the spectrum of compound-nuclear levels it produces the Gaussian Orthogonal Ensemble (GOE) of Hamiltonian matrices that again yields expressions for average cross sections. Both avenues give practically the same numbers in spite of the quite different cross section formulae. These results were employed in a new model-aided evaluation of the 238 U neutron cross sections in the unresolved resonance region. (orig.) [de

Effect on the mean first passage time in symmetrical bistable systems by cross-correlation between noises

International Nuclear Information System (INIS)

Wang, J.; Cao, L.; Wu, D.J.

2003-01-01

We present an analytic investigation of the mean first passage time in two opposite directions (from the left well to the right well and from right to left) by studying symmetrical bistable systems driven by correlated Gaussian white noises, and prove that the mean first passage time in two opposite directions is not symmetrical any more when noises are correlated. As examples, the mean first passage time in the quartic bistable model and the sawtooth bistable model are calculated, respectively. From the analytic results of the mean first passage time, we testify further the relation T(from x - to x + ,λ)≠T(from x + to x - ,λ) in the same area of the parameter plan. Moreover, it is found that the dependences of T + (i.e., T(from x - to x + ,λ)) and T - (i.e., T(from x + to x - ,λ)) upon the multiplicative noise intensity Q and the additive noise intensity D exhibit entirely different properties. For same areas of the parameter plan: in the quartic bistable system, when the T + vs. Q curve exhibits a maximum, while the T - vs. Q curve is monotonous; when the T + vs. D curve is monotonous, while the T - vs. D curve experiences a phase transition from decreasing monotonously to possessing one minimum. Increasing Q, when the T + vs. D curve experiences a phase transition from decreasing monotonously to possessing one maximum, while the T - vs. D curve only increases monotonously. Similar behaviours also exist in the sawtooth bistable model

Development of comprehensive image processing technique for differential diagnosis of liver disease by using multi-modality images. Pixel-based cross-correlation method using a profile

International Nuclear Information System (INIS)

Inoue, Akira; Okura, Yasuhiko; Akiyama, Mitoshi; Ishida, Takayuki; Kawashita, Ikuo; Ito, Katsuyoshi; Matsunaga, Naofumi; Sanada, Taizo

2009-01-01

Imaging techniques such as high magnetic field imaging and multidetector-row CT have been markedly improved recently. The final image-reading systems easily produce more than a thousand diagnostic images per patient. Therefore, we developed a comprehensive cross-correlation processing technique using multi-modality images, in order to decrease the considerable time and effort involved in the interpretation of a radiogram (multi-formatted display and/or stack display method, etc). In this scheme, the criteria of an attending radiologist for the differential diagnosis of liver cyst, hemangioma of liver, hepatocellular carcinoma, and metastatic liver cancer on magnetic resonance images with various sequences and CT images with and without contrast enhancement employ a cross-correlation coefficient. Using a one-dimensional cross-correlation method, comprehensive image processing could be also adapted for various artifacts (some depending on modality imaging, and some on patients), which may be encountered at the clinical scene. This comprehensive image-processing technique could assist radiologists in the differential diagnosis of liver diseases. (author)

ISW-galaxy cross correlation: a probe of dark energy clustering and distribution of dark matter tracers

Energy Technology Data Exchange (ETDEWEB)

Khosravi, Shahram; Mollazadeh, Amir [Department of Astronomy and High Energy Physics, Faculty of Physics, Kharazmi University, Mofateh Ave., Tehran (Iran, Islamic Republic of); Baghram, Shant, E-mail: khosravi_sh@khu.ac.ir, E-mail: amirmollazadeh@khu.ac.ir, E-mail: baghram@sharif.edu [Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of)

2016-09-01

Cross correlation of the Integrated Sachs-Wolfe signal (ISW) with the galaxy distribution in late time is a promising tool for constraining the dark energy properties. Here, we study the effect of dark energy clustering on the ISW-galaxy cross correlation and demonstrate the fact that the bias parameter between the distribution of the galaxies and the underlying dark matter introduces a degeneracy and complications. We argue that as the galaxy's host halo formation time is different from the observation time, we have to consider the evolution of the halo bias parameter. It will be shown that any deviation from ΛCDM model will change the evolution of the bias as well. Therefore, it is deduced that the halo bias depends strongly on the sub-sample of galaxies which is chosen for cross correlation and that the joint kernel of ISW effect and the galaxy distribution has a dominant effect on the observed signal. In this work, comparison is made specifically between the clustered dark energy models using two samples of galaxies. The first one is a sub-sample of galaxies from Sloan Digital Sky Survey, chosen with the r-band magnitude 18 < r < 21 and the dark matter halo host of mass M ∼10{sup 12} M {sub ⊙} and formation redshift of z {sub f} ∼ 2.5. The second one is the sub-sample of Luminous Red galaxies with the dark matter halo hosts of mass M ∼ 10{sup 13} M {sub ⊙} and formation redshift of z {sub f} ∼ 2.0. Using the evolved bias we improve the χ{sup 2} for the ΛCDM which reconciles the ∼1σ-2σ tension of the ISW-galaxy signal with ΛCDM prediction. Finally, we study the parameter estimation of a dark energy model with free parameters w {sub 0} and w {sub a} in the equation of state w {sub de} = w {sub 0} + w {sub az} /(1+ z ) with the constant bias parameter and also with an evolved bias model with free parameters of galaxy's host halo mass and the halo formation redshift.

A NOVEL APPROACH IN THE WEAKLY INTERACTING MASSIVE PARTICLE QUEST: CROSS-CORRELATION OF GAMMA-RAY ANISOTROPIES AND COSMIC SHEAR

International Nuclear Information System (INIS)

Camera, Stefano; Fornasa, Mattia; Fornengo, Nicolao; Regis, Marco

2013-01-01

Both cosmic shear and cosmological gamma-ray emission stem from the presence of dark matter (DM) in the universe: DM structures are responsible for the bending of light in the weak-lensing regime and those same objects can emit gamma rays, either because they host astrophysical sources (active galactic nuclei or star-forming galaxies) or directly by DM annihilations (or decays, depending on the properties of the DM particle). Such gamma rays should therefore exhibit strong correlation with the cosmic shear signal. In this Letter, we compute the cross-correlation angular power spectrum of cosmic shear and gamma rays produced by the annihilation/decay of weakly interacting massive particle DM, as well as by astrophysical sources. We show that this observable provides novel information on the composition of the extragalactic gamma-ray background (EGB), since the amplitude and shape of the cross-correlation signal strongly depend on which class of sources is responsible for the gamma-ray emission. If the DM contribution to the EGB is significant (at least in a definite energy range), although compatible with current observational bounds, its strong correlation with the cosmic shear makes such signal potentially detectable by combining Fermi Large Area Telescope data with forthcoming galaxy surveys, like the Dark Energy Survey and Euclid. At the same time, the same signal would demonstrate that the weak-lensing observables are indeed due to particle DM matter and not to possible modifications of general relativity.

A Novel Approach in the Weakly Interacting Massive Particle Quest: Cross-correlation of Gamma-Ray Anisotropies and Cosmic Shear

Science.gov (United States)

Camera, Stefano; Fornasa, Mattia; Fornengo, Nicolao; Regis, Marco

2013-07-01

Both cosmic shear and cosmological gamma-ray emission stem from the presence of dark matter (DM) in the universe: DM structures are responsible for the bending of light in the weak-lensing regime and those same objects can emit gamma rays, either because they host astrophysical sources (active galactic nuclei or star-forming galaxies) or directly by DM annihilations (or decays, depending on the properties of the DM particle). Such gamma rays should therefore exhibit strong correlation with the cosmic shear signal. In this Letter, we compute the cross-correlation angular power spectrum of cosmic shear and gamma rays produced by the annihilation/decay of weakly interacting massive particle DM, as well as by astrophysical sources. We show that this observable provides novel information on the composition of the extragalactic gamma-ray background (EGB), since the amplitude and shape of the cross-correlation signal strongly depend on which class of sources is responsible for the gamma-ray emission. If the DM contribution to the EGB is significant (at least in a definite energy range), although compatible with current observational bounds, its strong correlation with the cosmic shear makes such signal potentially detectable by combining Fermi Large Area Telescope data with forthcoming galaxy surveys, like the Dark Energy Survey and Euclid. At the same time, the same signal would demonstrate that the weak-lensing observables are indeed due to particle DM matter and not to possible modifications of general relativity.

A NOVEL APPROACH IN THE WEAKLY INTERACTING MASSIVE PARTICLE QUEST: CROSS-CORRELATION OF GAMMA-RAY ANISOTROPIES AND COSMIC SHEAR

Energy Technology Data Exchange (ETDEWEB)

Camera, Stefano [CENTRA, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Lisboa (Portugal); Fornasa, Mattia [School of Physics and Astronomy, University of Nottingham, Nottingham (United Kingdom); Fornengo, Nicolao; Regis, Marco [Dipartimento di Fisica, Universita di Torino and INFN, Torino (Italy)

2013-07-01

Both cosmic shear and cosmological gamma-ray emission stem from the presence of dark matter (DM) in the universe: DM structures are responsible for the bending of light in the weak-lensing regime and those same objects can emit gamma rays, either because they host astrophysical sources (active galactic nuclei or star-forming galaxies) or directly by DM annihilations (or decays, depending on the properties of the DM particle). Such gamma rays should therefore exhibit strong correlation with the cosmic shear signal. In this Letter, we compute the cross-correlation angular power spectrum of cosmic shear and gamma rays produced by the annihilation/decay of weakly interacting massive particle DM, as well as by astrophysical sources. We show that this observable provides novel information on the composition of the extragalactic gamma-ray background (EGB), since the amplitude and shape of the cross-correlation signal strongly depend on which class of sources is responsible for the gamma-ray emission. If the DM contribution to the EGB is significant (at least in a definite energy range), although compatible with current observational bounds, its strong correlation with the cosmic shear makes such signal potentially detectable by combining Fermi Large Area Telescope data with forthcoming galaxy surveys, like the Dark Energy Survey and Euclid. At the same time, the same signal would demonstrate that the weak-lensing observables are indeed due to particle DM matter and not to possible modifications of general relativity.

Correlation between maternal and umbilical cord blood in pregnant women of Pokhara Valley: a cross sectional study.

Science.gov (United States)

Timilsina, Sameer; Karki, Sirisa; Gautam, Aajeevan; Bhusal, Pujan; Paudel, Gita; Sharma, Deepak

2018-03-21

Complete blood count is one of the routinely advised blood investigation during pregnancy. It is also utilized as a diagnostic tool for neonatal anemia, sepsis and determining hemostatic status of the newborn. The present study aims at estimating the complete blood count of maternal and umbilical cord blood at the time of delivery and to establish its correlation. This cross sectional study included 114 mothers and their healthy neonates born through normal vaginal delivery. Complete blood count of umbilical cord blood and maternal blood was estimated using automatic hematology analyzer. The mean maternal and neonatal hemoglobin concentration was 11.14 ± 1.39 g/dL and 16.34 ± 2.01 g/dL respectively. A significant positive correlation was found between maternal and fetal hemoglobin concentration (p correlation between maternal and fetal WBC, RBC and Platelet count was not statistically significant. A significant positive correlation was found between maternal and fetal MCV and MCH while PCV showed a non-significant positive correlation. There was moderately positive correlation between maternal and fetal hemoglobin, MCV and MCH. The cord blood hemoglobin was lower in babies born to anemic mothers. The decrease in hemoglobin followed the severity of anemia, however, the correlation did not exist in anemic mothers. It suggested that fetal hematological parameters are not reflective of maternal hemogram.

Glycogen resynthesis rate following cross-country skiing is closely correlated to skeletal muscle glycogen content

DEFF Research Database (Denmark)

Ørtenblad, Niels; Nielsen, Joachim; Saltin, Bengt

on an optimal glycogen resynthesis rate before a subsequent exercise session. The purpose of present study was to evaluate the glycogen resynthesis rate in elite cross-country (cc) skiers, following exhaustive exercise, and to examine the role of muscular glycogen content on the resynthesis rate. METHOD: Ten...... as 4h and 22h after the race and analyzed for glycogen content. Figure 1. Correlation between muscle glycogen resynthesis rate and glycogen content after and in the rocery period after exercise. Line indicate best fit of all the data points (r2 = 0.41, p

Cross-correlation matrix analysis of Chinese and American bank stocks in subprime crisis

Science.gov (United States)

Zhu, Shi-Zhao; Li, Xin-Li; Nie, Sen; Zhang, Wen-Qing; Yu, Gao-Feng; Han, Xiao-Pu; Wang, Bing-Hong

2015-05-01

In order to study the universality of the interactions among different markets, we analyze the cross-correlation matrix of the price of the Chinese and American bank stocks. We then find that the stock prices of the emerging market are more correlated than that of the developed market. Considering that the values of the components for the eigenvector may be positive or negative, we analyze the differences between two markets in combination with the endogenous and exogenous events which influence the financial markets. We find that the sparse pattern of components of eigenvectors out of the threshold value has no change in American bank stocks before and after the subprime crisis. However, it changes from sparse to dense for Chinese bank stocks. By using the threshold value to exclude the external factors, we simulate the interactions in financial markets. Project supported by the National Natural Science Foundation of China (Grant Nos. 11275186, 91024026, and FOM2014OF001) and the University of Shanghai for Science and Technology (USST) of Humanities and Social Sciences, China (Grant Nos. USST13XSZ05 and 11YJA790231).

Reliability of one-repetition maximum performance in people with chronic heart failure.

Science.gov (United States)

Ellis, Rachel; Holland, Anne E; Dodd, Karen; Shields, Nora

2018-02-24

Evaluate intra-rater and inter-rater reliability of the one-repetition maximum strength test in people with chronic heart failure. Intra-rater and inter-rater reliability study. A public tertiary hospital in northern metropolitan Melbourne. Twenty-four participants (nine female, mean age 71.8 ± 13.1 years) with mild to moderate heart failure of any aetiology. Lower limb strength was assessed by determining the maximum weight that could be lifted using a leg press. Intra-rater reliability was tested by one assessor on two separate occasions . Inter-rater reliability was tested by two assessors in random order. Intra-class correlation coefficients and 95% confidence intervals were calculated. Bland and Altman analyses were also conducted, including calculation of mean differences between measures ([Formula: see text]) and limits of agreement . Ten intra-rater and 21 inter-rater assessments were completed. Excellent intra-rater (intra-class correlation coefficient 2,1 0.96) and inter-rater (intra-class correlation coefficient 2,1 0.93) reliability was found. Intra-rater assessment showed less variability (mean difference 4.5 kg, limits of agreement -8.11 to 17.11 kg) than inter-rater agreement (mean difference -3.81 kg, limits of agreement -23.39 to 15.77 kg). One-repetition maximum determined using a leg press is a reliable measure in people with heart failure. Given its smaller limits of agreement, intra-rater testing is recommended. Implications for Rehabilitation Using a leg press to determine a one-repetition maximum we were able to demonstrate excellent inter-rater and intra-rater reliability using an intra-class correlation coefficient. The Bland and Altman levels of agreement were wide for inter-rater reliability and so we recommend using one assessor if measuring change in strength within an individual over time.

Acoustic emission source location in plates using wavelet analysis and cross time frequency spectrum.

Science.gov (United States)

Mostafapour, A; Davoodi, S; Ghareaghaji, M

2014-12-01

In this study, the theories of wavelet transform and cross-time frequency spectrum (CTFS) are used to locate AE source with frequency-varying wave velocity in plate-type structures. A rectangular array of four sensors is installed on the plate. When an impact is generated by an artificial AE source such as Hsu-Nielsen method of pencil lead breaking (PLB) at any position of the plate, the AE signals will be detected by four sensors at different times. By wavelet packet decomposition, a packet of signals with frequency range of 0.125-0.25MHz is selected. The CTFS is calculated by the short-time Fourier transform of the cross-correlation between considered packets captured by AE sensors. The time delay is calculated when the CTFS reaches the maximum value and the corresponding frequency is extracted per this maximum value. The resulting frequency is used to calculate the group velocity of wave velocity in combination with dispersive curve. The resulted locating error shows the high precision of proposed algorithm. Copyright © 2014 Elsevier B.V. All rights reserved.

Side chain mobility as monitored by CH-CH cross correlation: The example of cytochrome b5

International Nuclear Information System (INIS)

Banci, Lucia; Bertini, Ivano; Felli, Isabella C.; Hajieva, Parvana; Viezzoli, Maria Silvia

2001-01-01

The mobility of βCH 2 moieties in oxidized and reduced cytochrome b 5 was studied by analyzing the 13 C relaxation of the J-split components, in terms of C-H dipole-C-H dipole cross correlation rates. A 2D 13 C- 1 H experiment is proposed to measure these rates that provide the internal effective reorientation correlation time for each CH 2 moiety. It is found that higher mobility is present in the α helices forming the heme pocket. On the contrary, the β strands, which form the hydrophobic core of the molecule, have the lowest mobility. The general pattern is the same for the oxidized and reduced species, indicating that any oxidation-dependent property detected for backbone NH moieties does not affect the CH 2 mobility

Probing reionization with the cross-power spectrum of 21 cm and near-infrared radiation backgrounds

Energy Technology Data Exchange (ETDEWEB)

Mao, Xiao-Chun, E-mail: xcmao@bao.ac.cn [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

2014-08-01

The cross-correlation between the 21 cm emission from the high-redshift intergalactic medium and the near-infrared (NIR) background light from high-redshift galaxies promises to be a powerful probe of cosmic reionization. In this paper, we investigate the cross-power spectrum during the epoch of reionization. We employ an improved halo approach to derive the distribution of the density field and consider two stellar populations in the star formation model: metal-free stars and metal-poor stars. The reionization history is further generated to be consistent with the electron-scattering optical depth from cosmic microwave background measurements. Then, the intensity of the NIR background is estimated by collecting emission from stars in first-light galaxies. On large scales, we find that the 21 cm and NIR radiation backgrounds are positively correlated during the very early stages of reionization. However, these two radiation backgrounds quickly become anti-correlated as reionization proceeds. The maximum absolute value of the cross-power spectrum is |Δ{sub 21,NIR}{sup 2}|∼10{sup −4} mK nW m{sup –2} sr{sup –1}, reached at ℓ ∼ 1000 when the mean fraction of ionized hydrogen is x-bar{sub i}∼0.9. We find that Square Kilometer Array can measure the 21 cm-NIR cross-power spectrum in conjunction with mild extensions to the existing CIBER survey, provided that the integration time independently adds up to 1000 and 1 hr for 21 cm and NIR observations, and that the sky coverage fraction of the CIBER survey is extended from 4 × 10{sup –4} to 0.1. Measuring the cross-correlation signal as a function of redshift provides valuable information on reionization and helps confirm the origin of the 'missing' NIR background.

Complex Correlation Kohn-T Method of Calculating Total and Elastic Cross Sections. Part 1; Electron-Hydrogen Elastic Scattering

Science.gov (United States)

Bhatia, A. K.; Temkin, A.; Fisher, Richard R. (Technical Monitor)

2001-01-01

We report on the first part of a study of electron-hydrogen scattering, using a method which allows for the ab initio calculation of total and elastic cross sections at higher energies. In its general form the method uses complex 'radial' correlation functions, in a (Kohn) T-matrix formalism. The titled method, abbreviated Complex Correlation Kohn T (CCKT) method, is reviewed, in the context of electron-hydrogen scattering, including the derivation of the equation for the (complex) scattering function, and the extraction of the scattering information from the latter. The calculation reported here is restricted to S-waves in the elastic region, where the correlation functions can be taken, without loss of generality, to be real. Phase shifts are calculated using Hylleraas-type correlation functions with up to 95 terms. Results are rigorous lower bounds; they are in general agreement with those of Schwartz, but they are more accurate and outside his error bounds at a couple of energies,

Spatial correlation between weed species densities and soil properties

DEFF Research Database (Denmark)

Walter, Mette; Christensen, Svend; Simmelsgaard, Svend Erik

2002-01-01

The spatial cross-correlation between weed species densities and six soil properties within fields was analysed using cross-semivariograms. The survey was carried out in three successive years in two fields. The most consistent relationship between weed species density (numbers m−2) and soil...... properties was negative cross-correlation between the density of Viola arvensis Murray and clay content. This correlation was found in both fields; however, the range of spatial dependence varied between fields. In one of the fields, the density of Lamium purpureum L. was positively cross......-correlated with the phosphorus content in the soil in all years. The density of Veronica spp. and Poa annua L. was negatively cross-correlated with pH in all three years. Other spatial cross-correlations that were found in this study were inconsistent over time or field site. The densities of some of the weed species were...

Maximum entropy analysis of liquid diffraction data

International Nuclear Information System (INIS)

Root, J.H.; Egelstaff, P.A.; Nickel, B.G.

1986-01-01

A maximum entropy method for reducing truncation effects in the inverse Fourier transform of structure factor, S(q), to pair correlation function, g(r), is described. The advantages and limitations of the method are explored with the PY hard sphere structure factor as model input data. An example using real data on liquid chlorine, is then presented. It is seen that spurious structure is greatly reduced in comparison to traditional Fourier transform methods. (author)

The Cross-Correlation Analysis of Indicators of the Scientific-Innovation and Educational Activity of the Regions of Ukraine

Directory of Open Access Journals (Sweden)

Zhuravka Andrey V.

2017-04-01

Full Text Available The article is aimed at exploring the cross-correlation dependency between the 11 selected indicators of the scientific-innovation and educational activity of the regions of Ukraine over the past years using the standard features of the MS Excel software. The calculated values of the pairwise coefficients of Pearson correlation changed from 0,66 to 1. The worst-case correlation coefficient, which changed from 0,7 to 0,8, was observed only with the number of students at the beginning of the academic year 2015/16. The article provides seven selected equations of linear regression and their graphs, with the latter equation corresponding to the worst correlation coefficient between the number of students and doctoral candidates (R = 0,6574. The first five equations of linear regression conform to correlations between financing the costs for completing scientific and scientific-technical works by the regions of Ukraine and various indicators of the scientific-educational potential of personnel. In all five cases, there was a high correlation dependency. As result of the study, fairly high correlation relationships among all indicators have been obtained. Prospect for further research is accounting for a larger number of indicators of the scientific-innovation and educational activity of the regions of Ukraine.

Linear intra-bone geometry dependencies of the radius: Radius length determination by maximum distal width

International Nuclear Information System (INIS)

Baumbach, S.F.; Krusche-Mandl, I.; Huf, W.; Mall, G.; Fialka, C.

2012-01-01

Purpose: The aim of the study was to investigate possible linear intra-bone geometry dependencies by determining the relation between the maximum radius length and maximum distal width in two independent populations and test for possible gender or age effects. A strong correlation can help develop more representative fracture models and osteosynthetic devices as well as aid gender and height estimation in anthropologic/forensic cases. Methods: First, maximum radius length and distal width of 100 consecutive patients, aged 20–70 years, were digitally measured on standard lower arm radiographs by two independent investigators. Second, the same measurements were performed ex vivo on a second cohort, 135 isolated, formalin fixed radii. Standard descriptive statistics as well as correlations were calculated and possible gender age influences tested for both populations separately. Results: The radiographic dataset resulted in a correlation of radius length and width of r = 0.753 (adj. R 2 = 0.563, p 2 = 0.592) and side no influence on the correlation. Radius length–width correlation for the isolated radii was r = 0.621 (adj. R 2 = 0.381, p 2 = 0.598). Conclusion: A relatively strong radius length–distal width correlation was found in two different populations, indicating that linear body proportions might not only apply to body height and axial length measurements of long bones but also to proportional dependency of bone shapes in general.

Noise Attenuation Estimation for Maximum Length Sequences in Deconvolution Process of Auditory Evoked Potentials

Directory of Open Access Journals (Sweden)

Xian Peng

2017-01-01

Full Text Available The use of maximum length sequence (m-sequence has been found beneficial for recovering both linear and nonlinear components at rapid stimulation. Since m-sequence is fully characterized by a primitive polynomial of different orders, the selection of polynomial order can be problematic in practice. Usually, the m-sequence is repetitively delivered in a looped fashion. Ensemble averaging is carried out as the first step and followed by the cross-correlation analysis to deconvolve linear/nonlinear responses. According to the classical noise reduction property based on additive noise model, theoretical equations have been derived in measuring noise attenuation ratios (NARs after the averaging and correlation processes in the present study. A computer simulation experiment was conducted to test the derived equations, and a nonlinear deconvolution experiment was also conducted using order 7 and 9 m-sequences to address this issue with real data. Both theoretical and experimental results show that the NAR is essentially independent of the m-sequence order and is decided by the total length of valid data, as well as stimulation rate. The present study offers a guideline for m-sequence selections, which can be used to estimate required recording time and signal-to-noise ratio in designing m-sequence experiments.

Maximum toe flexor muscle strength and quantitative analysis of human plantar intrinsic and extrinsic muscles by a magnetic resonance imaging technique.

Science.gov (United States)

Kurihara, Toshiyuki; Yamauchi, Junichiro; Otsuka, Mitsuo; Tottori, Nobuaki; Hashimoto, Takeshi; Isaka, Tadao

2014-01-01

The aims of this study were to investigate the relationships between the maximum isometric toe flexor muscle strength (TFS) and cross-sectional area (CSA) of the plantar intrinsic and extrinsic muscles and to identify the major determinant of maximum TFS among CSA of the plantar intrinsic and extrinsic muscles. Twenty six young healthy participants (14 men, 12 women; age, 20.4 ± 1.6 years) volunteered for the study. TFS was measured by a specific designed dynamometer, and CSA of plantar intrinsic and extrinsic muscles were measured using magnetic resonance imaging (MRI). To measure TFS, seated participants optimally gripped the bar with their toes and exerted maximum force on the dynamometer. For each participant, the highest force produced among three trials was used for further analysis. To measure CSA, serial T1-weighted images were acquired. TFS was significantly correlated with CSA of the plantar intrinsic and extrinsic muscles. Stepwise multiple linear regression analyses identified that the major determinant of TFS was CSA of medial parts of plantar intrinsic muscles (flexor hallucis brevis, flexor digitorum brevis, quadratus plantae, lumbricals and abductor hallucis). There was no significant difference between men and women in TFS/CSA. CSA of the plantar intrinsic and extrinsic muscles is one of important factors for determining the maximum TFS in humans.

Classification of THz pulse signals using two-dimensional cross-correlation feature extraction and non-linear classifiers.

Science.gov (United States)

Siuly; Yin, Xiaoxia; Hadjiloucas, Sillas; Zhang, Yanchun

2016-04-01

This work provides a performance comparison of four different machine learning classifiers: multinomial logistic regression with ridge estimators (MLR) classifier, k-nearest neighbours (KNN), support vector machine (SVM) and naïve Bayes (NB) as applied to terahertz (THz) transient time domain sequences associated with pixelated images of different powder samples. The six substances considered, although have similar optical properties, their complex insertion loss at the THz part of the spectrum is significantly different because of differences in both their frequency dependent THz extinction coefficient as well as differences in their refractive index and scattering properties. As scattering can be unquantifiable in many spectroscopic experiments, classification solely on differences in complex insertion loss can be inconclusive. The problem is addressed using two-dimensional (2-D) cross-correlations between background and sample interferograms, these ensure good noise suppression of the datasets and provide a range of statistical features that are subsequently used as inputs to the above classifiers. A cross-validation procedure is adopted to assess the performance of the classifiers. Firstly the measurements related to samples that had thicknesses of 2mm were classified, then samples at thicknesses of 4mm, and after that 3mm were classified and the success rate and consistency of each classifier was recorded. In addition, mixtures having thicknesses of 2 and 4mm as well as mixtures of 2, 3 and 4mm were presented simultaneously to all classifiers. This approach provided further cross-validation of the classification consistency of each algorithm. The results confirm the superiority in classification accuracy and robustness of the MLR (least accuracy 88.24%) and KNN (least accuracy 90.19%) algorithms which consistently outperformed the SVM (least accuracy 74.51%) and NB (least accuracy 56.86%) classifiers for the same number of feature vectors across all studies

Relationship between reflection ability and clinical performance: a cross-sectional and retrospective-longitudinal correlational cohort study in midwifery.

Science.gov (United States)

Embo, M; Driessen, E; Valcke, M; van der Vleuten, C P M

2015-01-01

increasingly, reflection is highlighted as integral to core practice competencies but empirical research into the relationship between reflection and performance in the clinical workplace is scarce. this study investigated the relationship between reflection ability and clinical performance. we designed a cross-sectional and a retrospective-longitudinal cohort study. Data from first, second and third year midwifery students were collected to study the variables 'clinical performance' and 'reflection ability'. Data were analysed with SPSS for Windows, Release 20.0. Descriptive statistics, Pearson׳s Product Moment Correlation Coefficients (r) and r² values were computed to investigate associations between the research variables. the results showed a moderate observed correlation between reflection ability and clinical performance scores. When adopting a cross-sectional perspective, all correlation values were significant (p0.6). The results based on the retrospective-longitudinal data set explained a moderate proportion of the variance after correction for attenuation. Finally, the results indicate that 'reflection ability' scores of earlier years are significant related with 'clinical performance' scores of subsequent years. These results suggest that (1) reflection ability is linked to clinical performance; (2) that written reflections are an important, but not the sole way to assess professional competence and that (3) reflection is a contributor to clinical performance improvement. the data showed a moderate but significant relationship between 'reflection ability' and 'clinical performance' scores in clinical practice of midwifery students. Reflection therefore seems an important component of professional competence. Copyright © 2014 Elsevier Ltd. All rights reserved.

Rapid and Robust Cross-Correlation-Based Seismic Phase Identification Using an Approximate Nearest Neighbor Method

Science.gov (United States)

Tibi, R.; Young, C. J.; Gonzales, A.; Ballard, S.; Encarnacao, A. V.

2016-12-01

The matched filtering technique involving the cross-correlation of a waveform of interest with archived signals from a template library has proven to be a powerful tool for detecting events in regions with repeating seismicity. However, waveform correlation is computationally expensive, and therefore impractical for large template sets unless dedicated distributed computing hardware and software are used. In this study, we introduce an Approximate Nearest Neighbor (ANN) approach that enables the use of very large template libraries for waveform correlation without requiring a complex distributed computing system. Our method begins with a projection into a reduced dimensionality space based on correlation with a randomized subset of the full template archive. Searching for a specified number of nearest neighbors is accomplished by using randomized K-dimensional trees. We used the approach to search for matches to each of 2700 analyst-reviewed signal detections reported for May 2010 for the IMS station MKAR. The template library in this case consists of a dataset of more than 200,000 analyst-reviewed signal detections for the same station from 2002-2014 (excluding May 2010). Of these signal detections, 60% are teleseismic first P, and 15% regional phases (Pn, Pg, Sn, and Lg). The analyses performed on a standard desktop computer shows that the proposed approach performs the search of the large template libraries about 20 times faster than the standard full linear search, while achieving recall rates greater than 80%, with the recall rate increasing for higher correlation values. To decide whether to confirm a match, we use a hybrid method involving a cluster approach for queries with two or more matches, and correlation score for single matches. Of the signal detections that passed our confirmation process, 52% were teleseismic first P, and 30% were regional phases.

Correlation of Streptococcus mutans count in Mother-child Pair of Working and Nonworking Mothers: A Cross-sectional Study.

Science.gov (United States)

Sharma, Priyanka; Goswami, Mousumi; Singh, Darrel; Massod, Shahid S; Nganba, Khundrakpam

2016-01-01

To determine the prevalence of Streptococcus mutans (MS) in mother-child pairs and to evaluate the correlation in the levels of salivary MS of working and nonworking mothers with that of their children and their associations with other related factors. A cross-sectional study was carried out among 100 mother-child pairs residing in New Multan Nagar Colony, New Delhi, India. A total of 50 children with their mothers were included in the working group and another 50 were included in the nonworking group. A questionnaire regarding the feeding habits, oral hygiene habits, daily intake of sugars of the children along with their weaning time was carried out. All mothers and children were clinically examined for recording decayed, extracted, and filled teeth (deft)/decayed, missing, and filled teeth (DMFT), and whole unstimulated saliva was collected and cultured for MS in the laboratory. The data were collected and subjected to statistical analysis using chi-square, Spearman's correlation, and logistic regression analysis. The prevalence of salivary MS in the children was 69%. A statistically significant correlation was found between the oral levels of MS in nonworking and working mother-child pairs. Regression analysis showed that those children who feed by bottle for more than 12 months, have daily sweet intake, have sugars in feeding bottle and have higher defts were more likely to have mutans score of 1 or 2. The mother, working or nonworking, being the primary care provider is the major source of transmission of MS to their child irrespective of the amount of time spent with them. Sharma P, Goswami M, Singh D, Massod SS, Nganba K. Correlation of Streptococcus mutans count in Mother-child Pair of Working and Nonworking Mothers: A Cross-sectional Study. Int J Clin Pediatr Dent 2016;9(4):342-348.

Cosmological constraints on dark matter annihilation and decay. Cross-correlation analysis of the extragalactic γ-ray background and cosmic shear

Energy Technology Data Exchange (ETDEWEB)

Shirasaki, Masato [National Astronomical Observatory of Japan, Mitaka, Tokyo (Japan); Macias, Oscar; Horiuchi, Shunsaku [Virginia Tech, Blacksburg, VA (United States). Center for Neutrino Physics; Shirai, Satoshi [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Yoshida, Naoki [Tokyo Univ. (Japan). Dept. of Physics; Tokyo Univ., Chiba (Japan). Kavli Inst. for the Physics and Mathematics of the Universe (WPI); Japan Science and Technology Agency, Saitama (Japan). CREST

2016-07-15

We derive constraints on dark matter (DM) annihilation cross section and decay lifetime from cross-correlation analyses of the data from Fermi-LAT and weak lensing surveys that cover a wide area of ∝660 squared degrees in total. We improve upon our previous analyses by using an updated extragalactic γ-ray background data reprocessed with the Fermi Pass 8 pipeline, and by using well-calibrated shape measurements of about twelve million galaxies in the Canada-France-Hawaii Lensing Survey (CFHTLenS) and Red-Cluster-Sequence Lensing Survey (RCSLenS). We generate a large set of full-sky mock catalogs from cosmological N-body simulations and use them to estimate statistical errors accurately. The measured cross correlation is consistent with null detection, which is then used to place strong cosmological constraints on annihilating and decaying DM. For leptophilic DM, the constraints are improved by a factor of ∝ 100 in the mass range of O(1) TeV when including contributions from secondary γ rays due to the inverse-Compton upscattering of background photons. Annihilation cross-sections of left angle σν right angle ∝ 10{sup -23} cm{sup 3}/s are excluded for TeV-scale DM depending on channel. Lifetimes of ∝10{sup 25} sec are also excluded for the decaying TeV-scale DM. Finally, we apply this analysis to wino DM and exclude the wino mass around 200 GeV. These constraints will be further tightened, and all the interesting wino DM parameter region can be tested, by using data from future wide-field cosmology surveys.

Cosmological constraints on dark matter annihilation and decay. Cross-correlation analysis of the extragalactic γ-ray background and cosmic shear

International Nuclear Information System (INIS)

Shirasaki, Masato; Macias, Oscar; Horiuchi, Shunsaku; Yoshida, Naoki; Tokyo Univ., Chiba; Japan Science and Technology Agency, Saitama

2016-07-01

We derive constraints on dark matter (DM) annihilation cross section and decay lifetime from cross-correlation analyses of the data from Fermi-LAT and weak lensing surveys that cover a wide area of ∝660 squared degrees in total. We improve upon our previous analyses by using an updated extragalactic γ-ray background data reprocessed with the Fermi Pass 8 pipeline, and by using well-calibrated shape measurements of about twelve million galaxies in the Canada-France-Hawaii Lensing Survey (CFHTLenS) and Red-Cluster-Sequence Lensing Survey (RCSLenS). We generate a large set of full-sky mock catalogs from cosmological N-body simulations and use them to estimate statistical errors accurately. The measured cross correlation is consistent with null detection, which is then used to place strong cosmological constraints on annihilating and decaying DM. For leptophilic DM, the constraints are improved by a factor of ∝ 100 in the mass range of O(1) TeV when including contributions from secondary γ rays due to the inverse-Compton upscattering of background photons. Annihilation cross-sections of left angle σν right angle ∝ 10"-"2"3 cm"3/s are excluded for TeV-scale DM depending on channel. Lifetimes of ∝10"2"5 sec are also excluded for the decaying TeV-scale DM. Finally, we apply this analysis to wino DM and exclude the wino mass around 200 GeV. These constraints will be further tightened, and all the interesting wino DM parameter region can be tested, by using data from future wide-field cosmology surveys.

Commercial counterboard for 10 ns software correlator for photon and fluorescence correlation spectroscopy

Science.gov (United States)

Molteni, Matteo; Ferri, Fabio

2016-11-01

A 10 ns time resolution, multi-tau software correlator, capable of computing simultaneous autocorrelation (A-A, B-B) and cross (A-B) correlation functions at count rates up to ˜10 MHz, with no data loss, has been developed in LabVIEW and C++ by using the National Instrument timer/counterboard (NI PCIe-6612) and a fast Personal Computer (PC) (Intel Core i7-4790 Processor 3.60 GHz ). The correlator works by using two algorithms: for large lag times (τ ≳ 1 μs), a classical time-mode scheme, based on the measure of the number of pulses per time interval, is used; differently, for τ ≲ 1 μs a photon-mode (PM) scheme is adopted and the correlation function is retrieved from the sequence of the photon arrival times. Single auto- and cross-correlation functions can be processed online in full real time up to count rates of ˜1.8 MHz and ˜1.2 MHz, respectively. Two autocorrelation (A-A, B-B) and a cross correlation (A-B) functions can be simultaneously processed in full real time only up to count rates of ˜750 kHz. At higher count rates, the online processing takes place in a delayed modality, but with no data loss. When tested with simulated correlation data and latex spheres solutions, the overall performances of the correlator appear to be comparable with those of commercial hardware correlators, but with several nontrivial advantages related to its flexibility, low cost, and easy adaptability to future developments of PC and data acquisition technology.

Internet addiction and its correlation with behavioral problems and functional impairments – A cross-sectional study

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Mayara de Rezende Machado

Full Text Available ABSTRACT Objective Evaluate the prevalence of internet addiction (IA among adolescents, as well as characterize behaviors that are considered to be a risk in this population regarding the use and addiction of the Internet. Methods In this cross-sectional study conducted in one public and one private school 91 adolescents, aged 12 to 16 years old, responded the Internet Addiction Test – Brazilian version (IAT and Child Behavior Checklist (CBCL. Results The prevalence of internet addiction found was 21%, with no difference between private and public schools. On the group dependent on the Internet, there was a statistically significant correlation with Anxiety/Depression, Withdrawn/Depression, Rule Breaking Behavior and Aggressive Behavior, as well as the syndrome scales Social Problems, Thought Problems and Attention Problems. Conclusion Our study provides evidence of a relationship between internet addiction and behavioral problems among adolescents. As this is a cross-sectional study, we consider that future research is necessary to corroborate our results.

DISSECTING THE HIGH- z INTERSTELLAR MEDIUM THROUGH INTENSITY MAPPING CROSS-CORRELATIONS

Energy Technology Data Exchange (ETDEWEB)

Serra, Paolo; Doré, Olivier [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Lagache, Guilaine, E-mail: Paolo.Serra@jpl.nasa.gov [Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, F-13388, Marseille (France)

2016-12-20

We explore the detection, with upcoming spectroscopic surveys, of three-dimensional power spectra of emission line fluctuations produced in different phases of the interstellar medium (ISM) by forbidden transitions of ionized carbon [C ii] (157.7 μ m), ionized nitrogen [N ii] (121.9 and 205.2 μ m), and neutral oxygen [O i] (145.5 μ m) at redshift z  > 4. These lines are important coolants of both the neutral and the ionized medium, and probe multiple phases of the ISM. In the framework of the halo model, we compute predictions of the three-dimensional power spectra for two different surveys, showing that they have the required sensitivity to detect cross-power spectra between the [C ii] line and both the [O i] line and the [N ii] lines with sufficient signal-to-noise ratio. The importance of cross-correlating multiple lines with the intensity mapping technique is twofold. On the one hand, we will have multiple probes of the different phases of the ISM, which is key to understanding the interplay between energetic sources, and the gas and dust at high redshift. This kind of study will be useful for a next-generation space observatory such as the NASA Far-IR Surveyor, which will probe the global star formation and the ISM of galaxies from the peak of star formation to the epoch of reionization. On the other hand, emission lines from external galaxies are an important foreground when measuring spectral distortions of the cosmic microwave background spectrum with future space-based experiments like PIXIE; measuring fluctuations in the intensity mapping regime will help constrain the mean amplitude of these lines, and will allow us to better handle this important foreground.

Correlation in photodetachment

International Nuclear Information System (INIS)

Pegg, D.J.

1992-01-01

Electron correlation plays a major role in all aspects of the photodetachment of an electron from a negative ion. Photodetachment measurements are well suited to investigate the relatively short range forces associated with correlation due to the absence of the long range Coulomb interaction. Measurements of electron affinities, asymmetry parameters and cross sections are described to illustrate the influence of correlation on photodetachment

Burden and correlates of non-communicable-diseases among rural residents: a cross-sectional study in Hebei, China.

Science.gov (United States)

Yang, Junjun; Yu, Wenya; Zhou, Qiang; Mahapatra, Tanmay; Li, Yiqiu; Zhang, Xiaoyan; Chen, Lei; Mahapatra, Sanchita; Yan, Yuying; Tang, Weiming

2015-06-20

Burden of non-communicable diseases (NCDs) is increasing rapidly in most of the developing countries including China, even in rural areas. Dearth of representative data called for an investigation to estimate the burden and identify the correlates of NCDs in rural China. A cross-sectional study was conducted involving a representative sample of 6003 consenting randomly selected rural residents aged 15 years or more, from 36 villages of Shijiazhuang in Hebei province of China between July 2010 and June 2011. Information on demographics and behavior were collected, body mass index (BMI) and blood pressure were measured and blood samples were tested to diagnose diabetes and hyperlipidemia. Majority participants were aged problems (12.1%) and gastrointestinal NCDs (7.8%) were identified among the participants, while proportion of subjects with one, two and three or more NCDs were 43%, 14.4% and 5.5% respectively. Higher odds of having more NCDs were associated with higher BMI (Kg/M(2)), family history of NCDs, daily and past history of smoking and drinking, passive smoking, lack of exercise, skipping breakfast and psychological disturbances. Despite limitations associated with cross-sectional design and self-reporting, observation in this large sample of rural residents could develop important insights regarding high burden of NCDs in this population. Based on the identified correlates, targeted intervention strategies seem to be required urgently to control NCDs in rural China.

Improved automatic estimation of winds at the cloud top of Venus using superposition of cross-correlation surfaces

Science.gov (United States)

Ikegawa, Shinichi; Horinouchi, Takeshi

2016-06-01

Accurate wind observation is a key to study atmospheric dynamics. A new automated cloud tracking method for the dayside of Venus is proposed and evaluated by using the ultraviolet images obtained by the Venus Monitoring Camera onboard the Venus Express orbiter. It uses multiple images obtained successively over a few hours. Cross-correlations are computed from the pair combinations of the images and are superposed to identify cloud advection. It is shown that the superposition improves the accuracy of velocity estimation and significantly reduces false pattern matches that cause large errors. Two methods to evaluate the accuracy of each of the obtained cloud motion vectors are proposed. One relies on the confidence bounds of cross-correlation with consideration of anisotropic cloud morphology. The other relies on the comparison of two independent estimations obtained by separating the successive images into two groups. The two evaluations can be combined to screen the results. It is shown that the accuracy of the screened vectors are very high to the equatorward of 30 degree, while it is relatively low at higher latitudes. Analysis of them supports the previously reported existence of day-to-day large-scale variability at the cloud deck of Venus, and it further suggests smaller-scale features. The product of this study is expected to advance the dynamics of venusian atmosphere.

Spatio-energetic cross talk in photon counting detectors: Detector model and correlated Poisson data generator.

Science.gov (United States)

Taguchi, Katsuyuki; Polster, Christoph; Lee, Okkyun; Stierstorfer, Karl; Kappler, Steffen

2016-12-01

An x-ray photon interacts with photon counting detectors (PCDs) and generates an electron charge cloud or multiple clouds. The clouds (thus, the photon energy) may be split between two adjacent PCD pixels when the interaction occurs near pixel boundaries, producing a count at both of the pixels. This is called double-counting with charge sharing. (A photoelectric effect with K-shell fluorescence x-ray emission would result in double-counting as well). As a result, PCD data are spatially and energetically correlated, although the output of individual PCD pixels is Poisson distributed. Major problems include the lack of a detector noise model for the spatio-energetic cross talk and lack of a computationally efficient simulation tool for generating correlated Poisson data. A Monte Carlo (MC) simulation can accurately simulate these phenomena and produce noisy data; however, it is not computationally efficient. In this study, the authors developed a new detector model and implemented it in an efficient software simulator that uses a Poisson random number generator to produce correlated noisy integer counts. The detector model takes the following effects into account: (1) detection efficiency; (2) incomplete charge collection and ballistic effect; (3) interaction with PCDs via photoelectric effect (with or without K-shell fluorescence x-ray emission, which may escape from the PCDs or be reabsorbed); and (4) electronic noise. The correlation was modeled by using these two simplifying assumptions: energy conservation and mutual exclusiveness. The mutual exclusiveness is that no more than two pixels measure energy from one photon. The effect of model parameters has been studied and results were compared with MC simulations. The agreement, with respect to the spectrum, was evaluated using the reduced χ 2 statistics or a weighted sum of squared errors, χ red 2 (≥1), where χ red 2 =1 indicates a perfect fit. The model produced spectra with flat field irradiation that

OPTICAL CROSS-CORRELATION FILTERS: AN ECONOMICAL APPROACH FOR IDENTIFYING SNe Ia AND ESTIMATING THEIR REDSHIFTS

International Nuclear Information System (INIS)

Scolnic, Daniel M.; Riess, Adam G.; Huber, Mark E.; Rest, Armin; Stubbs, Christoper W.; Tonry, John L.

2009-01-01

Large photometric surveys of transient phenomena, such as Panoramic Survey Telescope and Rapid Response System and Large Synoptic Survey Telescope, will locate thousands to millions of Type Ia supernova (SN Ia) candidates per year, a rate prohibitive for acquiring spectroscopy to determine each candidate's type and redshift. In response, we have developed an economical approach to identifying SNe Ia and their redshifts using an uncommon type of optical filter which has multiple, discontinuous passbands on a single substrate. Observation of a supernova through a specially designed pair of these 'cross-correlation filters' measures the approximate amplitude and phase of the cross-correlation between the spectrum and a SN Ia template, a quantity typically used to determine the redshift and type of a high-redshift SN Ia. Simulating the use of these filters, we obtain a sample of SNe Ia which is ∼98% pure with individual redshifts measured to σ z = 0.01 precision. The advantages of this approach over standard broadband photometric methods are that it is insensitive to reddening, independent of the color data used for subsequent distance determinations which reduce selection or interpretation bias, and because it makes use of the spectral features its reliability is greater. A great advantage over long-slit spectroscopy comes from increased throughput, enhanced multiplexing, and reduced setup time resulting in a net gain in speed of up to ∼30 times. This approach is also insensitive to host galaxy contamination. Prototype filters were built and successfully used on Magellan with LDSS-3 to characterize three SuperNova Legacy Survey candidates. We discuss how these filters can provide critical information for the upcoming photometric supernova surveys.

25(OHD3 Levels Relative to Muscle Strength and Maximum Oxygen Uptake in Athletes

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Książek Anna

2016-04-01

Full Text Available Vitamin D is mainly known for its effects on the bone and calcium metabolism. The discovery of Vitamin D receptors in many extraskeletal cells suggests that it may also play a significant role in other organs and systems. The aim of our study was to assess the relationship between 25(OHD3 levels, lower limb isokinetic strength and maximum oxygen uptake in well-trained professional football players. We enrolled 43 Polish premier league soccer players. The mean age was 22.7±5.3 years. Our study showed decreased serum 25(OHD3 levels in 74.4% of the professional players. The results also demonstrated a lack of statistically significant correlation between 25(OHD3 levels and lower limb muscle strength with the exception of peak torque of the left knee extensors at an angular velocity of 150°/s (r=0.41. No significant correlations were found between hand grip strength and maximum oxygen uptake. Based on our study we concluded that in well-trained professional soccer players, there was no correlation between serum levels of 25(OHD3 and muscle strength or maximum oxygen uptake.

Relationship between visual prostate score (VPSS and maximum flow rate (Qmax in men with urinary tract symptoms

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Mazhar A. Memon

2016-04-01

Full Text Available ABSTRACT Objective: To evaluate correlation between visual prostate score (VPSS and maximum flow rate (Qmax in men with lower urinary tract symptoms. Material and Methods: This is a cross sectional study conducted at a university Hospital. Sixty-seven adult male patients>50 years of age were enrolled in the study after signing an informed consent. Qmax and voided volume recorded at uroflowmetry graph and at the same time VPSS were assessed. The education level was assessed in various defined groups. Pearson correlation coefficient was computed for VPSS and Qmax. Results: Mean age was 66.1±10.1 years (median 68. The mean voided volume on uroflowmetry was 268±160mL (median 208 and the mean Qmax was 9.6±4.96mLs/sec (median 9.0. The mean VPSS score was 11.4±2.72 (11.0. In the univariate linear regression analysis there was strong negative (Pearson's correlation between VPSS and Qmax (r=848, p<0.001. In the multiple linear regression analyses there was a significant correlation between VPSS and Qmax (β-http://www.blogapaixonadosporviagens.com.br/p/caribe.html after adjusting the effect of age, voided volume (V.V and level of education. Multiple linear regression analysis done for independent variables and results showed that there was no significant correlation between the VPSS and independent factors including age (p=0.27, LOE (p=0.941 and V.V (p=0.082. Conclusion: There is a significant negative correlation between VPSS and Qmax. The VPSS can be used in lieu of IPSS score. Men even with limited educational background can complete VPSS without assistance.

Mechanical dyssynchrony evaluated by tissue Doppler cross-correlation analysis is associated with long-term survival in patients after cardiac resynchronization therapy

DEFF Research Database (Denmark)

Risum, Niels; Williams, Eric S; Khouri, Michel G

2013-01-01

Aims Pre-implant assessment of longitudinal mechanical dyssynchrony using cross-correlation analysis (XCA) was tested for association with long-term survival and compared with other tissue Doppler imaging (TDI)-derived indices. Methods and results In 131 patients referred for cardiac resynchroniz......Aims Pre-implant assessment of longitudinal mechanical dyssynchrony using cross-correlation analysis (XCA) was tested for association with long-term survival and compared with other tissue Doppler imaging (TDI)-derived indices. Methods and results In 131 patients referred for cardiac......-max was independently associated with improved survival when adjusted for QRS > 150 ms and aetiology {hazard ratio (HR) 0.35 [95% confidence interval (CI) 0.16-0.77], P = 0.01}. Maximal activation delay performed significantly better than Yu index, OWD, and the presence of left bundle branch block (P ..., for difference between parameters). In subgroup analysis, patients without dyssynchrony and QRS between 120 and 150 ms showed a particularly poor survival [HR 4.3 (95% CI 1.46-12.59), P

Experimental investigations on bubble turbulent diffusion in a vertical large diameter pipe by means of wire-mesh sensors and correlation techniques

International Nuclear Information System (INIS)

Annalisa Manera; Horst-Michael Prasser; Dirk Lucas

2005-01-01

Full text of publication follows: A large number of experiments for water-air vertical flows in a large-diameter pipe has been carried out at the TOPFLOW facility (Forschunszentrum Rossendorf). The experiments cover a wide range of liquid and superficial gas velocity. The test section consists of a vertical pipe of ∼194 mm and 8.5 m long. At a distance of 7.6 m from the air injection, two wire-mesh sensors are installed. The two sensors are mounted at a distance of 63.3 mm from each other. The wire-mesh sensors measure sequences of instantaneous two-dimensional gas-fraction distributions in the cross-section in which they are mounted with a spatial resolution of 3 mm and a frequency of 2500 Hz. The total dimension of the matrix of measuring points for each mesh sensor is 64 x 64. In a central region of the measuring plane, where the void-fraction gradients are small, points of the first wire-mesh sensor are individually cross-correlated in time domain with measuring points belonging to the second wire-mesh sensor. The cross-correlation functions were calculated for pairs of points that are located accurately above each other as well as for points with a lateral distance. The lateral distance was varied from 0 to 48 mm (16 points), which is still within 50% of the pipe radius, i.e. in the region of small void-fraction gradients. The maximum of each of the 17 correlations is selected in order to derive a spatial correlation in the radial direction. The obtained spatial cross-correlations shows a maximum at zero lateral distance and decrease with growing lateral shift. In a region without gradients, the lateral displacement of bubbles is dominated by turbulent diffusion. This gives the opportunity to derive bubble turbulent diffusion coefficients from the spreading of the spatial correlations. At this aim, the spatial correlations have been first corrected to take into account the finite spatial resolution of the sensor and the finite dimension of the bubbles. The

Correlation between thromboelastography and traditional coagulation test parameters in hospitalized dogs

Directory of Open Access Journals (Sweden)

Rubanick JV

2017-02-01

Full Text Available Jean V Rubanick, Medora B Pashmakova, Micah A Bishop, James W Barr Department of Veterinary Small Animal Clinical Sciences, Texas A&M University, College Station, TX, USA Abstract: A hospital-based, prospective cross-sectional study was used to compare kaolin-activated thromboelastography (TEG parameters with traditional coagulation tests in 29 hospitalized dogs. Cases were included if the attending clinician requested coagulation testing. Blood was obtained from each dog and coagulation (prothrombin time, partial thromboplastin time, antithrombin activity, d-dimer concentration, and fibrinogen concentration and TEG analyses were performed. Hematocrit (Hct was also measured. Traditional coagulation results were evaluated for correlation with those from kaolin-activated TEG. Spearman’s correlation was used to calculate correlation coefficients. Fibrinogen was positively correlated with maximum amplitude (Pearson r=0.72, P<0.001 and global clot strength (Pearson r=0.72, P<0.001. There was no correlation between any of the remaining coagulation variables, TEG parameters, or Hct. Results of kaolin-activated TEG and traditional coagulation tests are not interchangeable means of monitoring coagulation derangements in this intensive care unit patient population. Determination of a true outcome measure is necessary to establish TEG’s clinical relevance to veterinary medicine. Keywords: TEG, thromboelastography, coagulation, hemostasis

Correlation in photodetachment

International Nuclear Information System (INIS)

Pegg, D.J.; Tennessee Univ., Knoxville, TN

1991-01-01

Electron correlation plays a major role in all aspects of the photodetachment of an electron from a negative ion. Photodetachment measurements are well suited to investigate the relatively short range forces associated with correlation due to the absence of the long range Coulomb interaction. Measurements of electron affinities, asymmetry parameters and cross sections are described to illustrate the influence of correlation on photodetachment. 25 refs., 4 figs

Approximate maximum parsimony and ancestral maximum likelihood.

Science.gov (United States)

Alon, Noga; Chor, Benny; Pardi, Fabio; Rapoport, Anat

2010-01-01

We explore the maximum parsimony (MP) and ancestral maximum likelihood (AML) criteria in phylogenetic tree reconstruction. Both problems are NP-hard, so we seek approximate solutions. We formulate the two problems as Steiner tree problems under appropriate distances. The gist of our approach is the succinct characterization of Steiner trees for a small number of leaves for the two distances. This enables the use of known Steiner tree approximation algorithms. The approach leads to a 16/9 approximation ratio for AML and asymptotically to a 1.55 approximation ratio for MP.

Update of ENDF/B-V Mod 3 iron: neutron-producing reaction cross sections and energy-angle correlations

International Nuclear Information System (INIS)

Fu, C.Y.; Hetrick, D.M.

1986-07-01

An update of the ENDF/B-V Mod-3 evaluation for natural iron is described. The cross sections of (n,n') and (n,2n) reactions are revised. Energy-angle correlations in the secondary (n,n') neutrons are introduced in the ENDF/B-V formats. Anisotropic angular distributions are provided for the secondary neutrons in (n,2n), (n,np), and (n,nα) reactions. Revelant integral results, microscopic data, and nuclear model calculations that influence the revised results are summarized. 54 refs., 9 figs., 2 tabs

Cross-correlation of the cosmic microwave background with the 2MASS galaxy survey: Signatures of dark energy, hot gas, and point sources

International Nuclear Information System (INIS)

Afshordi, Niayesh; Loh, Yeong-Shang; Strauss, Michael A.

2004-01-01

We cross-correlate the cosmic microwave background temperature anisotropies observed by the Wilkinson Microwave Anisotropy Probe (WMAP) with the projected distribution of extended sources in the Two Micron All Sky Survey (2MASS). By modeling the theoretical expectation for this signal, we extract the signatures of dark energy [integrated Sachs-Wolfe effect (ISW)], hot gas [thermal Sunyaev-Zeldovich (SZ) effect], and microwave point sources in the cross-correlation. Our strongest signal is the thermal SZ, at the 3.1-3.7σ level, which is consistent with the theoretical prediction based on observations of x-ray clusters. We also see the ISW signal at the 2.5σ level, which is consistent with the expected value for the concordance ΛCDM cosmology, and is an independent signature of the presence of dark energy in the Universe. Finally, we see the signature of microwave point sources at the 2.7σ level

The roles of shear and cross-correlations on the fluctuation levels in simple stochastic models. Revision

International Nuclear Information System (INIS)

Krommes, J.A.

1999-01-01

Highly simplified models of random flows interacting with background microturbulence are analyzed. In the limit of very rapid velocity fluctuations, it is shown rigorously that the fluctuation level of a passively advected scalar is not controlled by the rms shear. In a model with random velocities dependent only on time, the level of cross-correlations between the flows and the background turbulence regulates the saturation level. This effect is illustrated by considering a simple stochastic-oscillator model, both exactly and with analysis and numerical solutions of the direct-interaction approximation. Implications for the understanding of self-consistent turbulence are discussed briefly

Brain neuroimaging of domestic cats: correlation between computed tomography and cross-sectional anatomy

International Nuclear Information System (INIS)

Nepomuceno, A.C.; Zanatta, R.; Chung, D.G.; Costa, P.F.; Feliciano, M.A.R.; Avante, M.L.; Canola, J.C.; Lopes, L.S.

2016-01-01

Computed tomography of the brain is necessary as part of the diagnosis of lesions of the central nervous system. In this study we used six domestic cats, male or female, aged between one and five years, evaluated by Computed Tomography (CT) examination without clinical signs of central nervous system disorders. Two euthanized animals stating a condition unrelated to the nervous system were incorporated into this study. The proposal consisted in establishing detailed anatomical description of tomographic images of normal brain of cats, using as reference anatomical images of cross sections of the stained brain and cranial part, with thicknesses similar to the planes of the CT images. CT examinations were performed with and without intravenous iodinated contrast media for live animals. With one euthanized animal, the brain was removed and immediately preserved in 10% formalin for later achievement in cross-sectional thickness of approximately 4mm and staining technique of Barnard, and Robert Brown. The head of another animal was disarticulated in the Atlanto-occipital region and frozen at -20 deg C then sliced to a thickness of about 5mm. The description of visualized anatomical structures using tomography is useful as a guide and allows transcribing with relative accuracy the brain region affected by an injury, and thus correlating it with the clinical symptoms of the patient, providing additional information and consequent improvement to veterinarians during the course of surgical clinic in this species. (author)

Brain neuroimaging of domestic cats: correlation between computed tomography and cross-sectional anatomy

Energy Technology Data Exchange (ETDEWEB)

Nepomuceno, A.C. [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil); Zanatta, R. [Universidade de Cuiaba, MT (Brazil); Chung, D.G.; Costa, P.F.; Feliciano, M.A.R.; Avante, M.L.; Canola, J.C., E-mail: marcusfeliciano@yahoo.com.br [Faculdade de Ciencias Agrarias e Veterinarias, Jaboticabal, SP (Brazil); Lopes, L.S. [Universidade de Sao Paulo (USP), Ribeirao Preto, SP (Brazil)

2016-09-15

Computed tomography of the brain is necessary as part of the diagnosis of lesions of the central nervous system. In this study we used six domestic cats, male or female, aged between one and five years, evaluated by Computed Tomography (CT) examination without clinical signs of central nervous system disorders. Two euthanized animals stating a condition unrelated to the nervous system were incorporated into this study. The proposal consisted in establishing detailed anatomical description of tomographic images of normal brain of cats, using as reference anatomical images of cross sections of the stained brain and cranial part, with thicknesses similar to the planes of the CT images. CT examinations were performed with and without intravenous iodinated contrast media for live animals. With one euthanized animal, the brain was removed and immediately preserved in 10% formalin for later achievement in cross-sectional thickness of approximately 4mm and staining technique of Barnard, and Robert Brown. The head of another animal was disarticulated in the Atlanto-occipital region and frozen at -20 deg C then sliced to a thickness of about 5mm. The description of visualized anatomical structures using tomography is useful as a guide and allows transcribing with relative accuracy the brain region affected by an injury, and thus correlating it with the clinical symptoms of the patient, providing additional information and consequent improvement to veterinarians during the course of surgical clinic in this species. (author)

Acumulación de hojarasca en un pastizal de Panicum maximum y en un sistema silvopastoril de Panicum maximum y Leucaena leucocephala Litter accumulation in a Panicum maximum grassland and in a silvopastoral system of Panicum maximum and Leucaena leucocephala

Directory of Open Access Journals (Sweden)

Saray Sánchez

2007-09-01

Full Text Available Se realizó un estudio en la Estación Experimental de Pastos y Forrajes "Indio Hatuey", Matanzas, Cuba, con el objetivo de determinar la acumulación de la hojarasca en un pastizal de Panicum maximum Jacq cv. Likoni y en un sistema silvopastoril de Panicum maximum y Leucaena leucocephala (Lam de Wit cv. Cunningham. En los pastizales de P. maximum de ambos sistemas se determinó la acumulación de la hojarasca según la técnica propuesta por Bruce y Ebershon (1982, mientras que la hojarasca de L. leucocephala acumulada en el sistema silvopastoril se determinó según Santa Regina et al. (1997. De forma general, los resultados demostraron que en ambos pastizales la guinea acumuló una menor cantidad de hojarasca durante el período junio-diciembre, etapa en la que se produce su mayor desarrollo vegetativo. En la leucaena la mayor producción de hojarasca ocurrió en el período de diciembre a enero, asociada con la caída natural de sus hojas que se produce por efecto de las temperaturas más bajas y la escasa humedad en el suelo. En el sistema silvopastoril la hojarasca de leucaena representó el mayor porcentaje de peso dentro de la producción total, con un contenido más alto de nitrógeno y de calcio que el de la hojarasca del estrato herbáceo. En la guinea la lluvia fue el factor climático que mayor correlación negativa presentó con la producción de hojarasca en ambos sistemas, y en la leucaena la mayor correlación negativa se encontró con la temperatura mínima.A study was carried out at the Experimental Station of Pastures and Forages "Indio Hatuey", Matanzas, Cuba, with the objective of determining the litter accumulation in a pastureland of Panicum maximum Jacq cv. Likoni and in a silvopastoral system of Panicum maximum and Leucaena leucocephala (Lam de Wit cv. Cunningham. In the P. maximum pasturelands of both systems the litter accumulation was determined by means of the technique proposed by Bruce and Ebershon (1982, while

Utilization of cross-linked carboxymethyl κ-carrageenan as adsorbent for hexavalent chromium (Cr+6) ion

International Nuclear Information System (INIS)

Antonio, Princess Joyce R.; Punzalan, Mark Emile H.; Saturno, Rochelle Anne B.; Bayquen, Aristea V.

2009-01-01

The sorption behavior of cross-linked carboxymethyl κ-carrageenan as an alternative adsorbent for hexavalent chromium was studies. The κ-carrageenan had been carboxymethylated three times with 40% NaOH and monochloroacetic acid (MCA) in 80% isopropyl alcohol at 40 0 C. Carboxymethylated κ-carrageenan was crosslinked using Co 60 irradiation facility at PNRI. Batch experiments were conducted using prepared stock solution of Cr 6+ (70 ppm) under different sorption parameters at room temperature. These parameters include effects of pH, initial metal ion concentration, and contact time. Carboxymethylation and cross-linking was successfully achieved under optimum parameters. It was observed that cross-linked carboxymethyl κ-carrageenan best adsorbs chromium (VI) ion at pH 6, removing 41.59% of the metal ions present in the solution. Freundlich isotherm gave the highest correlation, R 2 , which is equal to 0.9880. This suggests the existence of mutilayer adsorption of the hexavalent chromium ions. Maximum adsorption was found to be at contact time of 2.5 hours and the concentration of the solution remains almost constant after 5 hours. The adsorption kinetics could be approximated favorably by the Lagergren pseudo-second-order kinetic model giving a correlation, R 2 , of 0.9985 and adsorption capacity, qmax, equal to 27.88 mg g +1 . (author)

Current Correlations in a Majorana Beam Splitter

Science.gov (United States)

Haim, Arbel; Berg, Erez; von Oppen, Felix; Oreg, Yuval

We study current correlations in a T-junction composed of a grounded topological superconductor and of two normal-metal leads which are biased at a voltage V. We show that the existence of an isolated Majorana zero mode in the junction dictates a universal behavior for the cross correlation of the currents through the two normal-metal leads of the junction. The cross correlation is negative and approaches zero at high bias voltages as - 1 / V . This behavior is robust in the presence of disorder and multiple transverse channels, and persists at finite temperatures. In contrast, an accidental low-energy Andreev bound state gives rise to non-universal behavior of the cross correlation. We employ numerical transport simulations to corroborate our conclusions.

Prevalence, patterns, and correlates of equestrian injuries in Malaysia: A cross-sectional study.

Science.gov (United States)

Majeedkutty, Nizar A; Khairulanuar, Nor A B

2017-01-01

Equestrian sport carries with it an implicit risk of injury. Despite the frequency of injuries in equestrian sports, there is no published study on injuries of equestrian athletes in Malaysia. The objective of this study was to determine the prevalence of injuries and its correlates among horseback riders. A web-based standardized questionnaire was used to collect data for this cross-sectional survey. Horseback riders aged 18 years and above were included in the study. Out of 169 participants, 93 were females and 76 were males. The correlation of injuries to gender, age, level of experience, exercise habits, use of safety measures, and type of equestrian sport were determined. Chi-square test was performed to test for statistical significance. The prevalence was high with 85.8% of the participants reporting symptoms and characteristics of injuries in the past 12 months. The most frequently perceived symptoms reported were in the upper extremities (43.4%) followed by lower extremities (40.7%), head injury (8.3%) and injuries of upper and lower back (3.4%). There was a higher prevalence of injury among female participants (55.03%) than males (42.60%). A significant correlation was found between gender and prevalence of injuries. About 70% of the riders sustained soft tissue injuries. Fifty-five percent of the injured were involved in recreational riding. The most common mechanism of injury was a fall from a horse. Sixty percent of the injured riders did not seek medical attention after being injured, and physiotherapy consultation was even lower with 10.3%. The high prevalence of injuries and low rate of medical consultation emphasize the need for education programs on safety in Malaysia. Sessions should be held to improve coaching for riders and instructors, and their knowledge of the nature of the horse, mechanisms of injuries, horse handling, and riding skills to help them host safe equestrian activities.

Maximum Diameter Measurements of Aortic Aneurysms on Axial CT Images After Endovascular Aneurysm Repair: Sufficient for Follow-up?

International Nuclear Information System (INIS)

Baumueller, Stephan; Nguyen, Thi Dan Linh; Goetti, Robert Paul; Lachat, Mario; Seifert, Burkhardt; Pfammatter, Thomas; Frauenfelder, Thomas

2011-01-01

Purpose: To assess the accuracy of maximum diameter measurements of aortic aneurysms after endovascular aneurysm repair (EVAR) on axial computed tomographic (CT) images in comparison to maximum diameter measurements perpendicular to the intravascular centerline for follow-up by using three-dimensional (3D) volume measurements as the reference standard. Materials and Methods: Forty-nine consecutive patients (73 ± 7.5 years, range 51–88 years), who underwent EVAR of an infrarenal aortic aneurysm were retrospectively included. Two blinded readers twice independently measured the maximum aneurysm diameter on axial CT images performed at discharge, and at 1 and 2 years after intervention. The maximum diameter perpendicular to the centerline was automatically measured. Volumes of the aortic aneurysms were calculated by dedicated semiautomated 3D segmentation software (3surgery, 3mensio, the Netherlands). Changes in diameter of 0.5 cm and in volume of 10% were considered clinically significant. Intra- and interobserver agreements were calculated by intraclass correlations (ICC) in a random effects analysis of variance. The two unidimensional measurement methods were correlated to the reference standard. Results: Intra- and interobserver agreements for maximum aneurysm diameter measurements were excellent (ICC = 0.98 and ICC = 0.96, respectively). There was an excellent correlation between maximum aneurysm diameters measured on axial CT images and 3D volume measurements (r = 0.93, P < 0.001) as well as between maximum diameter measurements perpendicular to the centerline and 3D volume measurements (r = 0.93, P < 0.001). Conclusion: Measurements of maximum aneurysm diameters on axial CT images are an accurate, reliable, and robust method for follow-up after EVAR and can be used in daily routine.

Experimentation and correlates of electronic nicotine delivery system (electronic cigarettes) among university students – A cross sectional study

OpenAIRE

K.H. Awan

2016-01-01

Objective: E-cigarettes are becoming popular among youth as safe nicotine delivery systems. Many have expressed concern, however, that e-cigarettes may serve as a gateway to future smoking, given their low perceived risk, or that their use may prevent regular smokers from quitting by maintaining their nicotine addiction. The aim of this study was to assess experimentation with and correlates of e-cigarette use among university students. Material and methods: A cross-sectional study was car...

FDG-PET/CT and diffusion-weighted imaging for resected lung cancer: correlation of maximum standardized uptake value and apparent diffusion coefficient value with prognostic factors.

Science.gov (United States)

Usuda, Katsuo; Funasaki, Aika; Sekimura, Atsushi; Motono, Nozomu; Matoba, Munetaka; Doai, Mariko; Yamada, Sohsuke; Ueda, Yoshimichi; Uramoto, Hidetaka

2018-04-09

Diffusion-weighted magnetic resonance imaging (DWI) is useful for detecting malignant tumors and the assessment of lymph nodes, as FDG-PET/CT is. But it is not clear how DWI influences the prognosis of lung cancer patients. The focus of this study is to evaluate the correlations between maximum standardized uptake value (SUVmax) of FDG-PET/CT and apparent diffusion coefficient (ADC) value of DWI with known prognostic factors in resected lung cancer. A total of 227 patients with resected lung cancers were enrolled in this study. FEG-PET/CT and DWI were performed in each patient before surgery. There were 168 patients with adenocarcinoma, 44 patients with squamous cell carcinoma, and 15 patients with other cell types. SUVmax was a factor that was correlated to T factor, N factor, or cell differentiation. ADC of lung cancer was a factor that was not correlated to T factor, or N factor. There was a significantly weak inverse relationship between SUVmax and ADC (Correlation coefficient r = - 0.227). In analysis of survival, there were significant differences between the categories of sex, age, pT factor, pN factor, cell differentiation, cell type, and SUVmax. Univariate analysis revealed that SUVmax, pN factor, age, cell differentiation, cell type, sex, and pT factor were significant factors. Multivariate analysis revealed that SUVmax and pN factor were independent significant prognostic factors. SUVmax was a significant prognostic factor that is correlated to T factor, N factor, or cell differentiation, but ADC was not. SUVmax may be more useful for predicting the prognosis of lung cancer than ADC values.

Heterogeneous local order in self-assembled nanoparticle films revealed by X-ray cross-correlations

Directory of Open Access Journals (Sweden)

Felix Lehmkühler

2018-05-01

Full Text Available We report on the self-assembly of gold nanoparticles coated with a soft poly(ethylene glycol shell studied by X-ray cross-correlation analysis. Depending on the initial concentration of gold nanoparticles used, structurally heterogeneous films were formed. The films feature hot spots of dominating four- and sixfold local order with patch sizes of a few micrometres, containing 104–105 particles. The amplitude of the order parameters suggested that a minimum sample amount was necessary to form well ordered local structures. Furthermore, the increasing variation in order parameters with sample thickness demonstrated a high degree of structural heterogeneity. This wealth of information cannot be obtained by the conventional microscopy techniques that are commonly used to study nanocrystal superstructures, as illustrated by complementary scanning electron microscopy measurements.

Uncertainties and correlations for the 56Fe damage cross sections and spectra averaged quantities based on TENDL-TMC

International Nuclear Information System (INIS)

Simakov, S.P.; Konobeyev, A.Yu.; Koning, A.

2016-01-01

The goal of this work is a calculation of the covariance matrices for the physical quantities used to characterize the neutron induced radiation damage in the materials. Such quantities usually encompass: the charged particles kinetic energy deposition KERMA (locally deposited nuclear heating), damage energy (to calculate then the number of displaced atoms) and gas production cross sections [(n,xα), (n,xt), (n,xp) … to calculate then transmuting of target nuclei to gases]. The uncertainties and energy-energy or reaction-reaction correlations for such quantities were not assessed so far, whereas the covariances for many underlying cross sections are often presented in the evaluated data libraries. Due to the dependence of damage quantities on many reactions channels, on both total and differential cross sections, and in particular on the energy distribution of reaction recoils, the evaluation of uncertainty is not straightforward. To reach a goal, we used the method based on idea of Total Monte Carlo application to the Nuclear Data. This report summarises the current results for evaluation, validation and representation in the ENDF-6 format of the radiation damage covariances for n + 56 Fe from thermal energy up to 20 MeV. This study was motivated by the IAEA Coordinated Research Project ''Primary Radiation Damage Cross Sections'' and by present dedicated Technical Meeting “Nuclear Reaction Data and Uncertainties for Radiation Damage”

Orientational cross correlations between entangled branch polymers in primitive chain network simulations

Science.gov (United States)

Masubuchi, Yuichi; Pandey, Ankita; Amamoto, Yoshifumi; Uneyama, Takashi

2017-11-01

Although it has not been frequently discussed, contributions of the orientational cross-correlation (OCC) between entangled polymers are not negligible in the relaxation modulus. In the present study, OCC contributions were investigated for 4- and 6-arm star-branched and H-branched polymers by means of multi-chain slip-link simulations. Owing to the molecular-level description of the simulation, the segment orientation was traced separately for each molecule as well as each subchain composing the molecules. Then, the OCC was calculated between different molecules and different subchains. The results revealed that the amount of OCC between different molecules is virtually identical to that of linear polymers regardless of the branching structure. The OCC between constituent subchains of the same molecule is significantly smaller than the OCC between different molecules, although its intensity and time-dependent behavior depend on the branching structure as well as the molecular weight. These results lend support to the single-chain models given that the OCC effects are embedded into the stress-optical coefficient, which is independent of the branching structure.

Social networks, leisure activities and maximum tongue pressure: cross-sectional associations in the Nagasaki Islands Study.

Science.gov (United States)

Nagayoshi, Mako; Higashi, Miho; Takamura, Noboru; Tamai, Mami; Koyamatsu, Jun; Yamanashi, Hirotomo; Kadota, Koichiro; Sato, Shimpei; Kawashiri, Shin-Ya; Koyama, Zenya; Saito, Toshiyuki; Maeda, Takahiro

2017-12-06

Social environment is often associated with health outcomes, but epidemiological evidence for its effect on oral frailty, a potential risk factor for aspiration, is sparse. This study aimed to assess the association between social environment and tongue pressure, as an important measure of oral function. The study focused on family structure, social networks both with and beyond neighbours, and participation in leisure activities. A population-based cross-sectional study. Annual health check-ups in a rural community in Japan. A total of 1982 participants, all over 40 years old. Anyone with missing data for the main outcome (n=14) was excluded. Tongue pressure was measured three times, and the maximum tongue pressure was used for analysis. A multivariable adjusted regression model was used to calculate parameter estimates (B) for tongue pressure. Having a social network involving neighbours (B=2.43, P=0.0001) and taking part in leisure activities (B=1.58, P=0.005) were independently associated with higher tongue pressure, but there was no link with social networks beyond neighbours (B=0.23, P=0.77). Sex-specific analyses showed that for men, having a partner was associated with higher tongue pressure, independent of the number of people in the household (B=2.26, P=0.01), but there was no association among women (B=-0.24, P=0.72; P-interaction=0.059). Having a social network involving neighbours and taking part in leisure activities were independently associated with higher tongue pressure. Marital status may be an important factor in higher tongue pressure in men. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Cross-conjugation and quantum interference: a general correlation?

DEFF Research Database (Denmark)

Valkenier, Hennie; Guedon, Constant M.; Markussen, Troels

2014-01-01

We discuss the relationship between the pi-conjugation pattern, molecular length, and charge transport properties of molecular wires, both from an experimental and a theoretical viewpoint. Specifically, we focus on the role of quantum interference in the conductance properties of cross-conjugated...

Two-proton correlation functions in nuclear reactions

International Nuclear Information System (INIS)

Verde, G.

2001-01-01

Full text: Proton-proton correlation functions can be used to study the space-time characteristics of nuclear reactions. For very short-lived sources, the maximum value of the correlation at 20 MeV/c, due to the attractive nature of the S-wave phase shift, provides a unique measure of the size of the emitting source. For long-lived sources, the height of this maximum depends, in addition, on the life time of the source. In this talk, we investigate the common reaction scenario involving both fast dynamical as well as slower emissions from evaporation and/or secondary decays of heavy fragments. We show that the maximum at 20 MeV/c depends both on the source dimension and on the fraction of coincident proton pairs produced in the early stage of the reaction, dominated by fast dynamical preequilibrium emission. The width of the peak at 20 MeV/c, on the other hand, is uniquely correlated to the size of the source. Hence, the size of the emitting source must be extracted from the width or, even better, from the entire shape of the correlation peak, and not from the height. By numerically inverting the measured correlation function, we show that existing data determine only the shape of the fast dynamical source and that its size changes little with proton momenta, contrary to previous analyses with Gaussian sources of zero-lifetime. We further show that the well documented dramatic decrease in the correlation maximum with decreasing total proton momentum reflects directly a corresponding decrease in the fraction of contributing proton pairs from preequilibrium emissions. This provides a powerful method to decompose the proton spectrum into a fraction that originates from fast dynamical emission and a complimentary fraction that originates from slower evaporative emission or secondary decays. We discuss also the comparison of such correlations to transport theories and the generalizations of these techniques to correlations between composite particles. Such studies can

Multilevel parametrization of fissile nuclei resonance cross sections

International Nuclear Information System (INIS)

Lukyanov, A.A.; Kolesov, V.V.; Janeva, N.

1987-01-01

Because the resonance interference has an important influence on the resonance structure of neutron cross sections energy dependence at lowest energies, multilevel scheme of the cross section parametrization which take into account the resonance interference is used for the description with the same provisions in the regions of the interferential maximum and minimum of the resonance cross sections of the fissile nuclei

Dyslipidemia Pattern in Rheumatoid Arthritis Patients with Correlation of Disease Activity

Directory of Open Access Journals (Sweden)

Prakash Joshi

2017-06-01

Full Text Available Rheumatoid arthritis (RA is a multi-factorial disease which affects the immune system and ultimately various tissues in the body that typically affects middle-aged individuals. Our objectives were to evaluate prevalence of dyslipidemias and its pattern in RA patients in Central India and correlate dyslipidemia with disease activity. This cross-sectional study was conducted on RA patients at Sri Aurobindo Institute of Medical Sciences and Post Graduate Institute, Indore (M.P. between January 2014 and December 2015. Lipid profiles were determined following 12-hour overnight fasting, and the association of lipid profiles with and disease activity was determined. The maximum number of cases presented in the age group was 41-50(36%. Disease is more prevalent in female population. Maximum number of pateints (34 patients had duration of illness ranged between 1 to 10 years. Most of the patients presented with high disease activity (90%. Total cholesterol levels were significantly higher in female cases as compared to controls. Similar to total cholesterol, LDL cholesterol was significantly higher in female cases as compared to controls. There was no significant difference of HDL, VLDL and TG between cases and controls. Mean lipid profile values were similar in male cases and controls. Positive correlation of DAS-28 (ESR was observed with total cholesterol and LDL levels in female patients only. No correlation of HDL, LDL and triglyceride were observed with DAS- 28 (ESR in both male and female patients. Lipid profiles were similar in both treatment naive and on treatment patients. No significant difference in mean lipid profile values expect HDL was observed in two groups created on the basis of RA factor. A lipid profile value has no positive or negative correlation with duration of illness. [J Contemp Med 2017; 7(2.000: 132-137

Using cross correlations of turbulent flow-induced ambient vibrations to estimate the structural impulse response. Application to structural health monitoring.

Science.gov (United States)

Sabra, Karim G; Winkel, Eric S; Bourgoyne, Dwayne A; Elbing, Brian R; Ceccio, Steve L; Perlin, Marc; Dowling, David R

2007-04-01

It has been demonstrated theoretically and experimentally that an estimate of the impulse response (or Green's function) between two receivers can be obtained from the cross correlation of diffuse wave fields at these two receivers in various environments and frequency ranges: ultrasonics, civil engineering, underwater acoustics, and seismology. This result provides a means for structural monitoring using ambient structure-borne noise only, without the use of active sources. This paper presents experimental results obtained from flow-induced random vibration data recorded by pairs of accelerometers mounted within a flat plate or hydrofoil in the test section of the U.S. Navy's William B. Morgan Large Cavitation Channel. The experiments were conducted at high Reynolds number (Re > 50 million) with the primary excitation source being turbulent boundary layer pressure fluctuations on the upper and lower surfaces of the plate or foil. Identical deterministic time signatures emerge from the noise cross-correlation function computed via robust and simple processing of noise measured on different days by a pair of passive sensors. These time signatures are used to determine and/or monitor the structural response of the test models from a few hundred to a few thousand Hertz.

Intershell correlations in photoionization of outer shells

Energy Technology Data Exchange (ETDEWEB)

Amusia, M.Ya. [The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904 (Israel); A.F. Ioffe Physical-Technical Institute, St. Petersburg 194021 (Russian Federation); Chernysheva, L.V. [A.F. Ioffe Physical-Technical Institute, St. Petersburg 194021 (Russian Federation); Drukarev, E.G. [National Research Center “Kurchatov Institute”, Konstantinov Petersburg Nuclear Physics Institute, St. Petersburg 188300 (Russian Federation)

2016-02-15

We demonstrate that the cross sections for photoionization of the outer shells are noticeably modified at the photon energies close to the thresholds of ionization of the inner shells due to correlations with the latter. The correlations may lead to increase or to decrease of the cross sections just above the ionization thresholds.

Intershell correlations in photoionization of outer shells

International Nuclear Information System (INIS)

Amusia, M.Ya.; Chernysheva, L.V.; Drukarev, E.G.

2016-01-01

We demonstrate that the cross sections for photoionization of the outer shells are noticeably modified at the photon energies close to the thresholds of ionization of the inner shells due to correlations with the latter. The correlations may lead to increase or to decrease of the cross sections just above the ionization thresholds.

Cross correlation of chemical profiles in minerals: insights into the architecture of magmatic reservoirs

Science.gov (United States)

Probst, Line; Caricchi, Luca; Gander, Martin; Wallace, Glenn

2016-04-01

Analysis of chemical zoning in minerals offers the opportunity to reconstruct the pre-eruptive conditions and the temporal evolution of magmatic reservoirs. The chemical composition of minerals is a function of the thermodynamic conditions of the reservoir from which they grow and therefore minerals record the evolution and variation of residual melt chemistry and intensive parameters within the magmatic system. A quantitative approach is required to determine if similar crystals actually shared a portion of their crystallisation history. These analyses are in many cases extremely time consuming and rather expensive. Therefore, it is not always possible to analyse a statically significant number of crystals, especially within their textural context in thin sections and that is the main reason to build automated methods. We are presenting a numerical cross-correlation method that compares the zonation pattern of minerals to identify if they share the totality or part of their growth history. We modified the method first developed by Wallace and Bergantz (2004) to compare profiles in minerals also from samples collected in different outcrops and that can be used for any dataset (i.e. geochemical proxies in stratigraphic sections). The main purpose of this method is to objectively compare chemical profiles in minerals (collected by electron microprobe, LA-ICP-MS or cathodoluminescence images) and quantify their degree of similarity. For this purpose, we use a well-known mathematical tool: the cross correlation which is a way of quantifying the difference between two given signals at a given position. Once our program was built, we performed tests using a set of synthetic profiles, profiles acquired along different transects of the same mineral and also on different minerals. Finally we applied our program to about 100 zircons from Kilgore Tuff, Heise Volcanic Field (USA) collected at different stratigraphic levels in two different outcrops. The correlation shows that

Understanding the amplitudes of noise correlation measurements

Science.gov (United States)

Tsai, Victor C.

2011-01-01

Cross correlation of ambient seismic noise is known to result in time series from which station-station travel-time measurements can be made. Part of the reason that these cross-correlation travel-time measurements are reliable is that there exists a theoretical framework that quantifies how these travel times depend on the features of the ambient noise. However, corresponding theoretical results do not currently exist to describe how the amplitudes of the cross correlation depend on such features. For example, currently it is not possible to take a given distribution of noise sources and calculate the cross correlation amplitudes one would expect from such a distribution. Here, we provide a ray-theoretical framework for calculating cross correlations. This framework differs from previous work in that it explicitly accounts for attenuation as well as the spatial distribution of sources and therefore can address the issue of quantifying amplitudes in noise correlation measurements. After introducing the general framework, we apply it to two specific problems. First, we show that we can quantify the amplitudes of coherency measurements, and find that the decay of coherency with station-station spacing depends crucially on the distribution of noise sources. We suggest that researchers interested in performing attenuation measurements from noise coherency should first determine how the dominant sources of noise are distributed. Second, we show that we can quantify the signal-to-noise ratio of noise correlations more precisely than previous work, and that these signal-to-noise ratios can be estimated for given situations prior to the deployment of seismometers. It is expected that there are applications of the theoretical framework beyond the two specific cases considered, but these applications await future work.

Linearity of electrical impedance tomography during maximum effort breathing and forced expiration maneuvers.

Science.gov (United States)

Ngo, Chuong; Leonhardt, Steffen; Zhang, Tony; Lüken, Markus; Misgeld, Berno; Vollmer, Thomas; Tenbrock, Klaus; Lehmann, Sylvia

2017-01-01

Electrical impedance tomography (EIT) provides global and regional information about ventilation by means of relative changes in electrical impedance measured with electrodes placed around the thorax. In combination with lung function tests, e.g. spirometry and body plethysmography, regional information about lung ventilation can be achieved. Impedance changes strictly correlate with lung volume during tidal breathing and mechanical ventilation. Initial studies presumed a correlation also during forced expiration maneuvers. To quantify the validity of this correlation in extreme lung volume changes during forced breathing, a measurement system was set up and applied on seven lung-healthy volunteers. Simultaneous measurements of changes in lung volume using EIT imaging and pneumotachography were obtained with different breathing patterns. Data was divided into a synchronizing phase (spontaneous breathing) and a test phase (maximum effort breathing and forced maneuvers). The EIT impedance changes correlate strictly with spirometric data during slow breathing with increasing and maximum effort ([Formula: see text]) and during forced expiration maneuvers ([Formula: see text]). Strong correlations in spirometric volume parameters [Formula: see text] ([Formula: see text]), [Formula: see text]/FVC ([Formula: see text]), and flow parameters PEF, [Formula: see text], [Formula: see text], [Formula: see text] ([Formula: see text]) were observed. According to the linearity during forced expiration maneuvers, EIT can be used during pulmonary function testing in combination with spirometry for visualisation of regional lung ventilation.

Intracellular dynamics and fate of polystyrene nanoparticles in A549 Lung epithelial cells monitored by image (cross-) correlation spectroscopy and single particle tracking.

Science.gov (United States)

Deville, Sarah; Penjweini, Rozhin; Smisdom, Nick; Notelaers, Kristof; Nelissen, Inge; Hooyberghs, Jef; Ameloot, Marcel

2015-10-01

Novel insights in nanoparticle (NP) uptake routes of cells, their intracellular trafficking and subcellular targeting can be obtained through the investigation of their temporal and spatial behavior. In this work, we present the application of image (cross-) correlation spectroscopy (IC(C)S) and single particle tracking (SPT) to monitor the intracellular dynamics of polystyrene (PS) NPs in the human lung carcinoma A549 cell line. The ensemble kinetic behavior of NPs inside the cell was characterized by temporal and spatiotemporal image correlation spectroscopy (TICS and STICS). Moreover, a more direct interpretation of the diffusion and flow detected in the NP motion was obtained by SPT by monitoring individual NPs. Both techniques demonstrate that the PS NP transport in A549 cells is mainly dependent on microtubule-assisted transport. By applying spatiotemporal image cross-correlation spectroscopy (STICCS), the correlated motions of NPs with the early endosomes, late endosomes and lysosomes are identified. PS NPs were equally distributed among the endolysosomal compartment during the time interval of the experiments. The cotransport of the NPs with the lysosomes is significantly larger compared to the other cell organelles. In the present study we show that the complementarity of ICS-based techniques and SPT enables a consistent elaborate model of the complex behavior of NPs inside biological systems. Copyright © 2015 Elsevier B.V. All rights reserved.

Automated Processing of Two-Dimensional Correlation Spectra

Science.gov (United States)

Sengstschmid; Sterk; Freeman

1998-04-01

An automated scheme is described which locates the centers of cross peaks in two-dimensional correlation spectra, even under conditions of severe overlap. Double-quantum-filtered correlation (DQ-COSY) spectra have been investigated, but the method is also applicable to TOCSY and NOESY spectra. The search criterion is the intrinsic symmetry (or antisymmetry) of cross-peak multiplets. An initial global search provides the preliminary information to build up a two-dimensional "chemical shift grid." All genuine cross peaks must be centered at intersections of this grid, a fact that reduces the extent of the subsequent search program enormously. The program recognizes cross peaks by examining the symmetry of signals in a test zone centered at a grid intersection. This "symmetry filter" employs a "lowest value algorithm" to discriminate against overlapping responses from adjacent multiplets. A progressive multiplet subtraction scheme provides further suppression of overlap effects. The processed two-dimensional correlation spectrum represents cross peaks as points at the chemical shift coordinates, with some indication of their relative intensities. Alternatively, the information is presented in the form of a correlation table. The authenticity of a given cross peak is judged by a set of "confidence criteria" expressed as numerical parameters. Experimental results are presented for the 400-MHz double-quantum-filtered COSY spectrum of 4-androsten-3,17-dione, a case where there is severe overlap. Copyright 1998 Academic Press.

Big Data Solution for CTBT Monitoring Using Global Cross Correlation

Science.gov (United States)

Gaillard, P.; Bobrov, D.; Dupont, A.; Grenouille, A.; Kitov, I. O.; Rozhkov, M.

2014-12-01

Due to the mismatch between data volume and the performance of the Information Technology infrastructure used in seismic data centers, it becomes more and more difficult to process all the data with traditional applications in a reasonable elapsed time. To fulfill their missions, the International Data Centre of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO/IDC) and the Département Analyse Surveillance Environnement of Commissariat à l'Energie atomique et aux énergies alternatives (CEA/DASE) collect, process and produce complex data sets whose volume is growing exponentially. In the medium term, computer architectures, data management systems and application algorithms will require fundamental changes to meet the needs. This problem is well known and identified as a "Big Data" challenge. To tackle this major task, the CEA/DASE takes part during two years to the "DataScale" project. Started in September 2013, DataScale gathers a large set of partners (research laboratories, SMEs and big companies). The common objective is to design efficient solutions using the synergy between Big Data solutions and the High Performance Computing (HPC). The project will evaluate the relevance of these technological solutions by implementing a demonstrator for seismic event detections thanks to massive waveform correlations. The IDC has developed an expertise on such techniques leading to an algorithm called "Master Event" and provides a high-quality dataset for an extensive cross correlation study. The objective of the project is to enhance the Master Event algorithm and to reanalyze 10 years of waveform data from the International Monitoring System (IMS) network thanks to a dedicated HPC infrastructure operated by the "Centre de Calcul Recherche et Technologie" at the CEA of Bruyères-le-Châtel. The dataset used for the demonstrator includes more than 300,000 seismic events, tens of millions of raw detections and more than 30 terabytes of continuous seismic data

Photoplethysmogram signal quality estimation using repeated Gaussian filters and cross-correlation

International Nuclear Information System (INIS)

Karlen, W; Kobayashi, K; Dumont, G A; Ansermino, J M

2012-01-01

Pulse oximeters are monitors that noninvasively measure heart rate and blood oxygen saturation (SpO 2 ). Unfortunately, pulse oximetry is prone to artifacts which negatively impact the accuracy of the measurement and can cause a significant number of false alarms. We have developed an algorithm to segment pulse oximetry signals into pulses and estimate the signal quality in real time. The algorithm iteratively calculates a signal quality index (SQI) ranging from 0 to 100. In the presence of artifacts and irregular signal morphology, the algorithm outputs a low SQI number. The pulse segmentation algorithm uses the derivative of the signal to find pulse slopes and an adaptive set of repeated Gaussian filters to select the correct slopes. Cross-correlation of consecutive pulse segments is used to estimate signal quality. Experimental results using two different benchmark data sets showed a good pulse detection rate with a sensitivity of 96.21% and a positive predictive value of 99.22%, which was equivalent to the available reference algorithm. The novel SQI algorithm was effective and produced significantly lower SQI values in the presence of artifacts compared to SQI values during clean signals. The SQI algorithm may help to guide untrained pulse oximeter users and also help in the design of advanced algorithms for generating smart alarms. (paper)

Photoplethysmogram signal quality estimation using repeated Gaussian filters and cross-correlation.

Science.gov (United States)

Karlen, W; Kobayashi, K; Ansermino, J M; Dumont, G A

2012-10-01

Pulse oximeters are monitors that noninvasively measure heart rate and blood oxygen saturation (SpO2). Unfortunately, pulse oximetry is prone to artifacts which negatively impact the accuracy of the measurement and can cause a significant number of false alarms. We have developed an algorithm to segment pulse oximetry signals into pulses and estimate the signal quality in real time. The algorithm iteratively calculates a signal quality index (SQI) ranging from 0 to 100. In the presence of artifacts and irregular signal morphology, the algorithm outputs a low SQI number. The pulse segmentation algorithm uses the derivative of the signal to find pulse slopes and an adaptive set of repeated Gaussian filters to select the correct slopes. Cross-correlation of consecutive pulse segments is used to estimate signal quality. Experimental results using two different benchmark data sets showed a good pulse detection rate with a sensitivity of 96.21% and a positive predictive value of 99.22%, which was equivalent to the available reference algorithm. The novel SQI algorithm was effective and produced significantly lower SQI values in the presence of artifacts compared to SQI values during clean signals. The SQI algorithm may help to guide untrained pulse oximeter users and also help in the design of advanced algorithms for generating smart alarms.

Correlated uncertainties in integral data

International Nuclear Information System (INIS)

McCracken, A.K.

1978-01-01

The use of correlated uncertainties in calculational data is shown in cases investigated to lead to a reduction in the uncertainty of calculated quantities of importance to reactor design. It is stressed however that such reductions are likely to be important in a minority of cases of practical interest. The effect of uncertainties in detector cross-sections is considered and is seen to be, in some cases, of equal importance to that in the data used in calculations. Numerical investigations have been limited by the sparse information available on data correlations; some comparisons made of these data reveal quite large inconsistencies for both detector cross-sections and cross-section of interest for reactor calculations

Noise analysis of the measurement of group delay in Fourier white-light interferometric cross correlation

International Nuclear Information System (INIS)

Laude, Vincent

2002-01-01

The problem of noise analysis in measuring the group delay introduced by a dispersive optical element by use of white-light interferometric cross correlation is investigated. Two noise types, detection noise and position noise, are specifically analyzed. Detection noise is shown to be highly sensitive to the spectral content of the white-light source at the frequency considered and to the temporal acquisition window. Position noise, which arises from the finite accuracy of the measurement of the scanning mirror's position, can severely damage the estimation of the group delay. Such is shown to be the case for fast Fourier transform-based estimation algorithms. A new algorithm that is insensitive to scanning delay errors is proposed, and subfemtosecond accuracy is obtained without any postprocessing

Nuclear techniques and cross-correlation methods for spectral analysis in two-phase flow measurements in mineral pipelines

Energy Technology Data Exchange (ETDEWEB)

Brandao, Luis E.B.; Salgado, Cesar M., E-mail: brandaos@ien.gov.br, E-mail: otero@ien.gov.br [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Divisao de Radiofarmacos; Sicilliano, Umberto C.C.S., E-mail: umberto.cassara@poli.ufrj.br [Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ (Brazil). Dept. de Metalurgia

2013-07-01

In mineral industry is common to use water to transport pellets inside pipes. In these units, the correct measurement of flow (both solid and liquid phase) is important to guarantee a safe operation. Cross correlation flow meters are devices specially suited to be used in dual-phase flow and they are based on measure the transit time due the disturbances registered between two points, in our case gamma attenuation from radioactive sources. The emphasis of this work is the application of gamma transmission and scattering technique associated with spectral analysis methods to measure the flow of solid phase in a liquid fluid in side the pipe. The detectors and the sources are out side of the tube and are positioned 10.0 cm distant one from the other. The photons of transmission/scattering gamma radiation were registered, and across-correlation method was applied to measure the flow and spectral analysis was used to study the flow profile inside the pipe. (author)

25 ns software correlator for photon and fluorescence correlation spectroscopy

Science.gov (United States)

Magatti, Davide; Ferri, Fabio

2003-02-01

A 25 ns time resolution, multi-tau software correlator developed in LABVIEW based on the use of a standard photon counting unit, a fast timer/counter board (6602-PCI National Instrument) and a personal computer (PC) (1.5 GHz Pentium 4) is presented and quantitatively discussed. The correlator works by processing the stream of incoming data in parallel according to two different algorithms: For large lag times (τ⩾100 μs), a classical time-mode (TM) scheme, based on the measure of the number of pulses per time interval, is used; differently, for τ⩽100 μs a photon-mode (PM) scheme is adopted and the time sequence of the arrival times of the photon pulses is measured. By combining the two methods, we developed a system capable of working out correlation functions on line, in full real time for the TM correlator and partially in batch processing for the PM correlator. For the latter one, the duty cycle depends on the count rate of the incoming pulses, being ˜100% for count rates ⩽3×104 Hz, ˜15% at 105 Hz, and ˜1% at 106 Hz. For limitations imposed by the fairly small first-in, first-out (FIFO) buffer available on the counter board, the maximum count rate permissible for a proper functioning of the PM correlator is limited to ˜105 Hz. However, this limit can be removed by using a board with a deeper FIFO. Similarly, the 25 ns time resolution is only limited by maximum clock frequency available on the 6602-PCI and can be easily improved by using a faster clock. When tested on dilute solutions of calibrated latex spheres, the overall performances of the correlator appear to be comparable with those of commercial hardware correlators, but with several nontrivial advantages related to its flexibility, low cost, and easy adaptability to future developments of PC and data acquisition technology.

An asymptotic theory for cross-correlation between auto-correlated sequences and its application on neuroimaging data.

Science.gov (United States)

Zhou, Yunyi; Tao, Chenyang; Lu, Wenlian; Feng, Jianfeng

2018-04-20

Functional connectivity is among the most important tools to study brain. The correlation coefficient, between time series of different brain areas, is the most popular method to quantify functional connectivity. Correlation coefficient in practical use assumes the data to be temporally independent. However, the time series data of brain can manifest significant temporal auto-correlation. A widely applicable method is proposed for correcting temporal auto-correlation. We considered two types of time series models: (1) auto-regressive-moving-average model, (2) nonlinear dynamical system model with noisy fluctuations, and derived their respective asymptotic distributions of correlation coefficient. These two types of models are most commonly used in neuroscience studies. We show the respective asymptotic distributions share a unified expression. We have verified the validity of our method, and shown our method exhibited sufficient statistical power for detecting true correlation on numerical experiments. Employing our method on real dataset yields more robust functional network and higher classification accuracy than conventional methods. Our method robustly controls the type I error while maintaining sufficient statistical power for detecting true correlation in numerical experiments, where existing methods measuring association (linear and nonlinear) fail. In this work, we proposed a widely applicable approach for correcting the effect of temporal auto-correlation on functional connectivity. Empirical results favor the use of our method in functional network analysis. Copyright © 2018. Published by Elsevier B.V.

Correlates of sedentary time in different age groups: results from a large cross sectional Dutch survey.

Science.gov (United States)

Bernaards, Claire M; Hildebrandt, Vincent H; Hendriksen, Ingrid J M

2016-10-26

Evidence shows that prolonged sitting is associated with an increased risk of mortality, independent of physical activity (PA). The aim of the study was to identify correlates of sedentary time (ST) in different age groups and day types (i.e. school-/work day versus non-school-/non-work day). The study sample consisted of 1895 Dutch children (4-11 years), 1131 adolescents (12-17 years), 8003 adults (18-64 years) and 1569 elderly (65 years and older) who enrolled in the Dutch continuous national survey 'Injuries and Physical Activity in the Netherlands' between 2006 and 2011. Respondents estimated the number of sitting hours during a regular school-/workday and a regular non-school/non-work day. Multiple linear regression analyses on cross-sectional data were used to identify correlates of ST. Significant positive associations with ST were observed for: higher age (4-to-17-year-olds and elderly), male gender (adults), overweight (children), higher education (adults ≥ 30 years), urban environment (adults), chronic disease (adults ≥ 30 years), sedentary work (adults), not meeting the moderate to vigorous PA (MVPA) guideline (children and adults ≥ 30 years) and not meeting the vigorous PA (VPA) guideline (4-to-17-year-olds). Correlates of ST that significantly differed between day types were working hours and meeting the VPA guideline. More working hours were associated with more ST on school-/work days. In children and adolescents, meeting the VPA guideline was associated with less ST on non-school/non-working days only. This study provides new insights in the correlates of ST in different age groups and thus possibilities for interventions in these groups. Correlates of ST appear to differ between age groups and to a lesser degree between day types. This implies that interventions to reduce ST should be age specific. Longitudinal studies are needed to draw conclusions on causality of the relationship between identified correlates and ST.

Correlates of sedentary time in different age groups: results from a large cross sectional Dutch survey

Directory of Open Access Journals (Sweden)

Claire M. Bernaards

2016-10-01

Full Text Available Abstract Background Evidence shows that prolonged sitting is associated with an increased risk of mortality, independent of physical activity (PA. The aim of the study was to identify correlates of sedentary time (ST in different age groups and day types (i.e. school-/work day versus non-school-/non-work day. Methods The study sample consisted of 1895 Dutch children (4–11 years, 1131 adolescents (12–17 years, 8003 adults (18–64 years and 1569 elderly (65 years and older who enrolled in the Dutch continuous national survey ‘Injuries and Physical Activity in the Netherlands’ between 2006 and 2011. Respondents estimated the number of sitting hours during a regular school-/workday and a regular non-school/non-work day. Multiple linear regression analyses on cross-sectional data were used to identify correlates of ST. Results Significant positive associations with ST were observed for: higher age (4-to-17-year-olds and elderly, male gender (adults, overweight (children, higher education (adults ≥ 30 years, urban environment (adults, chronic disease (adults ≥ 30 years, sedentary work (adults, not meeting the moderate to vigorous PA (MVPA guideline (children and adults ≥ 30 years and not meeting the vigorous PA (VPA guideline (4-to-17-year-olds. Correlates of ST that significantly differed between day types were working hours and meeting the VPA guideline. More working hours were associated with more ST on school-/work days. In children and adolescents, meeting the VPA guideline was associated with less ST on non-school/non-working days only. Conclusions This study provides new insights in the correlates of ST in different age groups and thus possibilities for interventions in these groups. Correlates of ST appear to differ between age groups and to a lesser degree between day types. This implies that interventions to reduce ST should be age specific. Longitudinal studies are needed to draw conclusions on causality of

Fragmentation of the C60 molecule in collision with light ions studied by a multi-correlation technique. Cross-sections, electron spectroscopy

International Nuclear Information System (INIS)

Rentenier, A.

2004-04-01

A quantitative study of the C60 fullerenes fragmentation in collision with light ions (H n + with n=1,2,3, He q+ with q=1,2) in the velocity range 0,1 - 2,3 u.a.) is presented. The multi-correlation technique, developed between fragment ions and electrons with well defined energy, has enlightened some of the dependences and properties of fragmentation mechanisms (cross sections, electron spectroscopy, size distributions, kinetic energy of fragment ions, Campi's scatter plot, activation energies). The deposited energy hence appeared as an important parameter. Cross sections have been measured, for the first time, for all the collisional processes. Ionisation and capture only depends on the collision velocity. On the other hand, scaling laws with the deposited energy have been observed for the cross sections of multifragmentation, which depends on the collision energy and the nature of the projectile. The deposited energy has also been found as an essential parameter to understand the evolution of the charged fragment size distributions. The electron spectroscopy, achieved at an emission angle of 35 degrees, showed spectra peaked at important energies (from 5 to 20 eV). The spectra shape depends on the collision velocity. A first theoretical analysis points out the link between the observed energy distribution and the presence of a centrifugal potential barrier. Finally, correlation experiments between produced ions and electron energy reveal that electron energy increases with internal energy. (author)

Simultaneous Reduction in Noise and Cross-Contamination Artifacts for Dual-Energy X-Ray CT

Directory of Open Access Journals (Sweden)

Baojun Li

2013-01-01

Full Text Available Purpose. Dual-energy CT imaging tends to suffer from much lower signal-to-noise ratio than single-energy CT. In this paper, we propose an improved anticorrelated noise reduction (ACNR method without causing cross-contamination artifacts. Methods. The proposed algorithm diffuses both basis material density images (e.g., water and iodine at the same time using a novel correlated diffusion algorithm. The algorithm has been compared to the original ACNR algorithm in a contrast-enhanced, IRB-approved patient study. Material density accuracy and noise reduction are quantitatively evaluated by the percent density error and the percent noise reduction. Results. Both algorithms have significantly reduced the noises of basis material density images in all cases. The average percent noise reduction is 69.3% and 66.5% with the ACNR algorithm and the proposed algorithm, respectively. However, the ACNR algorithm alters the original material density by an average of 13% (or 2.18 mg/cc with a maximum of 58.7% (or 8.97 mg/cc in this study. This is evident in the water density images as massive cross-contaminations are seen in all five clinical cases. On the contrary, the proposed algorithm only changes the mean density by 2.4% (or 0.69 mg/cc with a maximum of 7.6% (or 1.31 mg/cc. The cross-contamination artifacts are significantly minimized or absent with the proposed algorithm. Conclusion. The proposed algorithm can significantly reduce image noise present in basis material density images from dual-energy CT imaging, with minimized cross-contaminations compared to the ACNR algorithm.

Maximum permissible dose

International Nuclear Information System (INIS)

Anon.

1979-01-01

This chapter presents a historic overview of the establishment of radiation guidelines by various national and international agencies. The use of maximum permissible dose and maximum permissible body burden limits to derive working standards is discussed

Long-range correlation and market segmentation in bond market

Science.gov (United States)

Wang, Zhongxing; Yan, Yan; Chen, Xiaosong

2017-09-01

This paper investigates the long-range auto-correlations and cross-correlations in bond market. Based on Detrended Moving Average (DMA) method, empirical results present a clear evidence of long-range persistence that exists in one year scale. The degree of long-range correlation related to maturities has an upward tendency with a peak in short term. These findings confirm the expectations of fractal market hypothesis (FMH). Furthermore, we have developed a method based on a complex network to study the long-range cross-correlation structure and applied it to our data, and found a clear pattern of market segmentation in the long run. We also detected the nature of long-range correlation in the sub-period 2007-2012 and 2011-2016. The result from our research shows that long-range auto-correlations are decreasing in the recent years while long-range cross-correlations are strengthening.

Maximum field capability of energy saver superconducting magnets

International Nuclear Information System (INIS)

Turkot, F.; Cooper, W.E.; Hanft, R.; McInturff, A.

1983-01-01

At an energy of 1 TeV the superconducting cable in the Energy Saver dipole magnets will be operating at ca. 96% of its nominal short sample limit; the corresponding number in the quadrupole magnets will be 81%. All magnets for the Saver are individually tested for maximum current capability under two modes of operation; some 900 dipoles and 275 quadrupoles have now been measured. The dipole winding is composed of four individually wound coils which in general come from four different reels of cable. As part of the magnet fabrication quality control a short piece of cable from both ends of each reel has its critical current measured at 5T and 4.3K. In this paper the authors describe and present the statistical results of the maximum field tests (including quench and cycle) on Saver dipole and quadrupole magnets and explore the correlation of these tests with cable critical current

Spatial correlations in compressible granular flows

OpenAIRE

Van Noije, T. P. C.; Ernst, M. H.; Brito López, Ricardo

1998-01-01

The clustering instability in freely evolving granular fluids manifests itself in the density-density correlation function and structure factor. These functions are calculated from fluctuating hydrodynamics. As time increases, the structure factor of density fluctuations develops a maximum, which shifts to smaller wave numbers (growing correlation length). Furthermore, the inclusion of longitudinal velocity fluctuations changes long-range correlations in the flow field qualitatively and exten...

Studying flow close to an interface by total internal reflection fluorescence cross-correlation spectroscopy: Quantitative data analysis

Science.gov (United States)

Schmitz, R.; Yordanov, S.; Butt, H. J.; Koynov, K.; Dünweg, B.

2011-12-01

Total internal reflection fluorescence cross-correlation spectroscopy (TIR-FCCS) has recently [S. Yordanov , Optics ExpressOPEXFF1094-408710.1364/OE.17.021149 17, 21149 (2009)] been established as an experimental method to probe hydrodynamic flows near surfaces, on length scales of tens of nanometers. Its main advantage is that fluorescence occurs only for tracer particles close to the surface, thus resulting in high sensitivity. However, the measured correlation functions provide only rather indirect information about the flow parameters of interest, such as the shear rate and the slip length. In the present paper, we show how to combine detailed and fairly realistic theoretical modeling of the phenomena by Brownian dynamics simulations with accurate measurements of the correlation functions, in order to establish a quantitative method to retrieve the flow properties from the experiments. First, Brownian dynamics is used to sample highly accurate correlation functions for a fixed set of model parameters. Second, these parameters are varied systematically by means of an importance-sampling Monte Carlo procedure in order to fit the experiments. This provides the optimum parameter values together with their statistical error bars. The approach is well suited for massively parallel computers, which allows us to do the data analysis within moderate computing times. The method is applied to flow near a hydrophilic surface, where the slip length is observed to be smaller than 10nm, and, within the limitations of the experiments and the model, indistinguishable from zero.

Efficient tracking of the cross-correlation coefficient

NARCIS (Netherlands)

Aarts, R.M.; Irwan, R.; Janssen, A.J.E.M.

2002-01-01

In many (audio) processing algorithms, involving manipulation of discrete-time signals, the performance can vary strongly over the repertoire that is used. This may be the case when the signals from the various channels are allowed to be strongly positively or negatively correlated. We propose and

The Hengill geothermal area, Iceland: Variation of temperature gradients deduced from the maximum depth of seismogenesis

Science.gov (United States)

Foulger, G. R.

1995-04-01

Given a uniform lithology and strain rate and a full seismic data set, the maximum depth of earthquakes may be viewed to a first order as an isotherm. These conditions are approached at the Hengill geothermal area S. Iceland, a dominantly basaltic area. The likely strain rate calculated from thermal and tectonic considerations is 10 -15 s -1, and temperature measurements from four drill sites within the area indicate average, near-surface geothermal gradients of up to 150 °C km -1 throughout the upper 2 km. The temperature at which seismic failure ceases for the strain rates likely at the Hengill geothermal area is determined by analogy with oceanic crust, and is about 650 ± 50 °C. The topographies of the top and bottom of the seismogenic layer were mapped using 617 earthquakes located highly accurately by performing a simultaneous inversion for three-dimensional structure and hypocentral parameters. The thickness of the seismogenic layer is roughly constant and about 3 km. A shallow, aseismic, low-velocity volume within the spreading plate boundary that crosses the area occurs above the top of the seismogenic layer and is interpreted as an isolated body of partial melt. The base of the seismogenic layer has a maximum depth of about 6.5 km beneath the spreading axis and deepens to about 7 km beneath a transform zone in the south of the area. Beneath the high-temperature part of the geothermal area, the maximum depth of earthquakes may be as shallow as 4 km. The geothermal gradient below drilling depths in various parts of the area ranges from 84 ± 9 °Ckm -1 within the low-temperature geothermal area of the transform zone to 138 ± 15 °Ckm -1 below the centre of the high-temperature geothermal area. Shallow maximum depths of earthquakes and therefore high average geothermal gradients tend to correlate with the intensity of the geothermal area and not with the location of the currently active spreading axis.

Gravitational wave chirp search: no-signal cumulative distribution of the maximum likelihood detection statistic

International Nuclear Information System (INIS)

Croce, R P; Demma, Th; Longo, M; Marano, S; Matta, V; Pierro, V; Pinto, I M

2003-01-01

The cumulative distribution of the supremum of a set (bank) of correlators is investigated in the context of maximum likelihood detection of gravitational wave chirps from coalescing binaries with unknown parameters. Accurate (lower-bound) approximants are introduced based on a suitable generalization of previous results by Mohanty. Asymptotic properties (in the limit where the number of correlators goes to infinity) are highlighted. The validity of numerical simulations made on small-size banks is extended to banks of any size, via a Gaussian correlation inequality

Sensitivity of neutron air transport to nitrogen cross section uncertainties

International Nuclear Information System (INIS)

Niiler, A.; Beverly, W.B.; Banks, N.E.

1975-01-01

The sensitivity of the transport of 14-MeV neutrons in sea level air to uncertainties in the ENDF/B-III values of the various Nitrogen cross sections has been calculated using the correlated sampling Monte Carlo neutron transport code SAMCEP. The source consisted of a 14.0- to 14.9-MeV band of isotropic neutrons and the fluences (0.5 to 15.0 MeV) were calculated at radii from 50 to 1500 metres. The maximum perturbations, assigned to the ENDF/B-III or base cross section set in the 6.0- to 14.5-MeV energy range were; (1) 2 percent to the total, (2) 10 percent to the total elastic, (3) 40 percent to the inelastic and absorption and (4) 20 percent to the first Legendre coefficient and 10 percent to the second Legendre coefficient of the elastic angular distribtuions. Transport calculations were carried out using various physically realistic sets of perturbed cross sections, bounded by evaluator-assigned uncertainties, as well as the base set. Results show that in some energy intervals at 1500 metres, the differential fluence level with a perturbed set differed by almost a factor of two from the differential fluence level with the base set. 5 figures