Consecutive Bins Research Articles

Rao test of polarimetric detection for targets with energy spillover in non-Gaussian clutter

In this paper, we address the problem of polarimetric detection for targets with energy spillover in non-Gaussian clutter. The polarization diversity and spillover of target energy to consecutive range bins are jointly exploited to enhance the performance of target detection. Two adaptive detectors are designed according to the Rao test, as well as its two-step implementation, i.e., 2S-Rao test. It is shown that the 2S-Rao test detector coincides with the existing generalized likelihood ratio test (GLRT) detector, whereas the Rao test detector is new, and outperforms the existing detectors in probability of detection. Experiments based on both simulated and real data illustrate the superiority of the proposed detector.

DOA Estimation for Multiple Speech Sources Based on Flexible Single-Source Zones and Concentration Weighting

Direction of arrival (DOA) estimation is the key to many audio applications. Recently, sparse component analysis (SCA)-based methods have attracted much attention, in which single-source points (SSPs) and single-source zones (SSZs) where one source is dominant over the others in time-frequency domain are usually detected to construct the pooled histogram containing multi-source DOA information. Nonetheless, the SSZ size in existing methods is fixed and empirically predetermined, which cannot accommodate to the varying spectro-temporal property of speech sources. Furthermore, higher SSP concentration in a SSZ implies a locally stronger dominant source as well as more reliable DOA information extracted therein, which however is also not taken into account yet. To address these problems, a DOA estimation algorithm for multiple speech sources based on flexible SSZs and concentration weighting is presented in this paper. First, in each frame, correlation coefficients of time delay vectors across adjacent frequency bins are calculated to identify SSPs, followed by flexible SSZs construction using varying number of SSPs located at consecutive frequency bins. Next, the number of SSPs in each flexible SSZ is considered as a proxy of corresponding concentration degree, and employed as weighting factor to form the pooled histogram. Finally, a matching pursuit (MP)-based approach is utilized to obtain multi-source DOA estimates. Simulation results reveal that the proposed method significantly outperforms existing approaches in terms of noise floor in pooled histogram, angular resolution, and performance under various signal-to-noise ratio and reverberant conditions. Real-world experiments also verify its effectiveness, and meanwhile demonstrate considerably reduced computational complexity.

Arcflow Formulations and Constraint Generation Frameworks for the Two Bar Charts Packing Problem

We consider the two bar charts packing problem (2-BCPP), a recent combinatorial optimization problem whose aim is to pack a set of one-dimensional items into the minimum number of bins. As opposed to the well-known bin packing problem, pairs of items are grouped to form bar charts, and a solution is only feasible if the first and second items of every bar chart are packed in consecutive bins. After providing a complete picture of the connections between the 2-BCPP and other relevant packing problems, we show how we can use these connections to derive valid lower and upper bounds for the problem. We then introduce two new integer linear programming (ILP) models to solve the 2-BCPP based on a nontrivial extension of the arcflow formulation. Even though both models involve an exponential number of constraints, we show that they can be solved within a constraint generation framework. We then empirically evaluate the performance of our bounds and exact approaches against an ILP model from the literature and demonstrate the effectiveness of our techniques on both benchmarks inspired by the literature and new classes of instances that are specifically designed to be hard to solve. The outcomes of our experiments are important for the packing community because they indicate that arcflow formulations can be used to solve targeted packing problems with precedence constraints and also that some of these formulations can be solved with constraint generation. History: Accepted by Andrea Lodi, Area Editor for Design & Analysis of Algorithms–Discrete. Supplemental Material: The online supplement is available at https://doi.org/10.1287/ijoc.2022.1256 .

Harmonization of indirect reference intervals calculation by the Bhattacharya method.

The aim of this study was to harmonize the criteria for the Bhattacharya indirect method Microsoft Excel Spreadsheet for reference intervals calculation to reduce between-user variability and use these criteria to calculate and evaluate reference intervals for eight analytes in two different years. Anonymized laboratory test results from outpatients were extracted from January 1st 2018 to December 31st 2019. To assure data quality, we examined the monthly results from an external quality control program. Reference intervals were determined by the Bhattacharya method with the St Vincent's hospital Spreadsheet firstly using original criteria and then using additional harmonized criteria defined in this study. Consensus reference intervals using the additional harmonized criteria were calculated as the mean of four users' lower and upper reference interval results. To further test the operation criteria and robustness of the obtained reference intervals, an external user validated the Spreadsheet procedure. The extracted test results for all selected laboratory tests fulfilled the quality criteria and were included in the present study. Differences between users in calculated reference intervals were frequent when using the Spreadsheet. Therefore, additional criteria for the Spreadsheet were proposed and applied by independent users, such as: to set central bin as the mean of all the data, bin size as small as possible, at least three consecutive bins and a high proportion of bins within the curve. The proposed criteria contributed to the harmonization of reference interval calculation between users of the Bhattacharya indirect method Spreadsheet.

Single Nucleotide Polymorphism Effects on Lamb Fecal Egg Count Estimated Breeding Values in Progeny-Tested Katahdin Sires.

Estimated breeding values (EBV) for fecal egg counts (FEC) at 42–90 days of age (WFEC) and 91–150 days of age (PFEC) for 84 progeny-tested Katahdin sires were used to identify associations of deregressed EBV with single-nucleotide polymorphisms (SNP) using 388,000 SNP with minor-allele frequencies ≥0.10 on an Illumina high-density ovine array. Associations between markers and FEC EBV were initially quantified by single-SNP linear regression. Effects of linkage disequilibrium (LD) were minimized by assigning SNP to 2,535 consecutive 1-Mb bins and focusing on the effect of the most significant SNP in each bin. Bonferroni correction was used to define bin-based (BB) genome- and chromosome-wide significance. Six bins on chromosome 5 achieved BB genome-wide significance for PFEC EBV, and three of those SNP achieved chromosome-wide significance after Bonferroni correction based on the 14,530 total SNP on chromosome 5. These bins were nested within 12 consecutive bins between 59 and 71 Mb on chromosome 5 that reached BB chromosome-wide significance. The largest SNP effects were at 63, 67, and 70 Mb, with LD among these SNP of r 2 ≤ 0.2. Regional heritability mapping (RHM) was then used to evaluate the ability of different genomic regions to account for additive variance in FEC EBV. Chromosome-level RHM indicated that one 500-SNP window between 65.9 and 69.9 Mb accounted for significant variation in PFEC EBV. Five additional 500-SNP windows between 59.3 and 71.6 Mb reached suggestive (p < 0.10) significance for PFEC EBV. Although previous studies rarely identified markers for parasite resistance on chromosome 5, the IL12B gene at 68.5 Mb codes for the p40 subunit of both interleukins 12 and 23. Other immunoregulatory genes are also located in this region of chromosome 5, providing opportunity for additive or associative effects.

Strides to Achieve a Stable Symmetry Index During Running.

The quality of running mechanics is often characterized by limb pattern symmetry and used to support clinical decisions throughout the rehabilitation of lower-extremity injuries. It is valuable to ensure that gait analyses provide stable measures while not asking an individual to complete an excessive number of running strides. The present study aimed to determine the minimum number of strides required to establish a stable mean symmetry index (SMSI) of discrete-level measures of spatiotemporal parameters, joint kinematics, and joint kinetics. Further, the study aimed to determine if differences occurred between random and consecutive strides for directional and absolute symmetry indices. Descriptive laboratory study. A sequential average was used to determine how many strides were required to achieve a SMSI within a 60-second trial. Multiple 2-factor repeated-measure analysis of variances were used to determine if differences between bins of strides and symmetry calculations were significantly different. A median SMSI was achieved in 15 strides for all biomechanical variables. There were no significant differences (P > .05) found between consecutive and random bins of 15 strides within a 60-second trial. Although there were significant differences between symmetry calculation values for most variables (P < .05), there appeared to be no systematic difference between the numbers of strides required for stable symmetry for either index. As 15 strides were sufficient to achieve a SMSI during running, a continued emphasis should be placed on the number of strides collected when examining interlimb symmetry.

High biogeographic and latitudinal variability in gastropod drilling predation on molluscs along the eastern Indian coast: Implications on the history of fossil record of drillholes.

Studies on the large-scale latitudinal patterns of gastropod drilling predation reveal that predation pressure may decrease or increase with increasing latitude, or even show no trend, questioning the generality of any large-scale latitudinal or biogeographic pattern. Here, we analyze the nature of spatio-environmental and latitudinal variation in gastropod drilling along the Indian eastern coast by using 76 samples collected from 39 locations, covering ~2500 km, incorporating several ecoregions, and ~15° latitudinal extents. We find no environmental or latitudinal gradient. In fact, drilling intensity varies highly within the same latitudinal bin, or oceanic sub-basins, or even the same ecoregions. Moreover, different ecoregions with their distinctive biotic and abiotic environmental variables show similar predation intensities. However, one pattern is prevalent: some small infaunal prey taxa, living in the sandy-muddy substrate—which are preferred by the naticid gastropods—are always attacked more frequently over others, indicating taxon and size selectivity by the predators. The result suggests that the biotic and abiotic factors, known to influence drilling predation, determine only the local predation pattern. In the present case, the nature of substrate and prey composition determines the local predation intensity: soft substrate habitats host dominantly small, infaunal prey. Since the degree of spatial variability in drilling intensity within any time bin can be extremely high, sometimes greater than the variability across consecutive time bins, temporal patterns in drilling predation can never be interpreted without having detailed knowledge of the nature of this spatial variability within a time bin.

Magnetotail Dipolarizations and Ion Flux Variations During the Main Phase of Magnetic Storms

AbstractNear‐Earth tail dipolarizations are usually associated with fast plasma flows and an increase in energetic particle fluxes. Yet, the role of these dipolarizations in energetic ion flux transport toward the inner magnetosphere and in ring current (including partial ring current) development during the main phase of a geomagnetic storm is not fully understood. We investigated observations from Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes A, D, and E with apogees at X ≈ −13 RE and Los Alamos National Laboratory (LANL) geosynchronous spacecraft in the midnight magnetic local time (MLT) sector (21.5–1.5 h MLT) during the main phases of storms with integrated Dst exceeding 600 nT*hr from the 2010 to 2016 THEMIS tail seasons. We selected 10 storms during which at least one of the THEMIS probes was in the midnight sector during a storm’s main phase and identified 39 dipolarization events with a Bz increase exceeding 10 nT within 500 s during these storms’ main phases. In 21 of the 39 events, an increase in the magnetic field elevation angle Θ estimated from LANL magnetospheric plasma analyzer (MPA) data was detected at geosynchronous orbit (GEO) within ±15‐min‐long time window around dipolarization onset detected by THEMIS. In only 10 of those 21 events, however, did ion fluxes at energies from 50 to 500 keV increase in three or more consecutive energy bins at LANL. Comparisons of ion spectra collected by THEMIS and LANL in these 10 events revealed a similar increase in fluxes at energies E &gt; 20 keV. Our results indicate that a dipolarization that occupies a large portion of the nightside magnetosphere from GEO to ∼12 RE is a necessary but not sufficient condition for energetic ion flux enhancements at GEO. As suggested in previous studies, an increase in the azimuthal electric field (i.e., enhanced earthward magnetic flux transport) is most likely required for an ∼100 keV ion flux increase at GEO.

Neuronal Avalanches to Study the Coordination of Large-Scale Brain Activity: Application to Rett Syndrome.

Many complex systems, such as the brain, display large-scale coordinated interactions that create ordered patterns. Classically, such patterns have been studied using the framework of criticality, i.e., at a transition point between two qualitatively distinct patterns. This kind of system is generally characterized by a scale-invariant organization, in space and time, optimally described by a power-law distribution whose slope is quantified by an exponent α. The dynamics of these systems is characterized by alternating periods of activations, called avalanches, with quiescent periods. To maximize its efficiency, the system must find a trade-off between its stability and ease of propagation of activation, which is achieved by a branching process. It is quantified by a branching parameter σ defined as the average ratio between the number of activations in consecutive time bins. The brain is itself a complex system and its activity can be described as a series of neuronal avalanches. It is known that critical aspects of brain dynamics are modeled with a branching parameter σ = , and the neuronal avalanches distribution fits well with a power law distribution exponent α = -3/2. The aim of our work was to study a self-organized criticality system in which there was a change in neuronal circuits due to genetic causes. To this end, we have compared the characteristics of neuronal avalanches in a group of 10 patients affected by Rett syndrome, during an open-eye resting-state condition estimated using magnetoencephalography, with respect to 10 healthy subjects. The analysis was performed both in broadband and in the five canonical frequency bands. We found, for both groups, a branching parameter close to 1. In this critical condition, Rett patients show a lower distribution parameter α in the delta and broadband. These results suggest that the large-scale coordination of activity occurs to a lesser extent in RTT patients.

Shot noise in multitracer constraints on fNL and relativistic projections: Power spectrum

ABSTRACT Multiple tracers of the same surveyed volume can enhance the signal-to-noise on a measurement of local primordial non-Gaussianity and the relativistic projections. Increasing the number of tracers comparably increases the number of shot noise terms required to describe the stochasticity of the data. Although the shot noise is white on large scales, it is desirable to investigate the extent to which it can degrade constraints on the parameters of interest. In a multitracer analysis of the power spectrum, a marginalization over shot noise does not degrade the constraints on fNL by more than ∼30 per cent so long as haloes of mass $M\lesssim 10^{12}\, \mathrm{M}_\odot$ are resolved. However, ignoring cross shot noise terms induces large systematics on a measurement of fNL at redshift z &amp;lt; 1 when small mass haloes are resolved. These effects are less severe for the relativistic projections, especially for the dipole term. In the case of a low and high mass tracer, the optimal sample division maximizes the signal-to-noise on fNL and the projection effects simultaneously, reducing the errors to the level of ∼10 consecutive mass bins of equal number density. We also emphasize that the non-Poissonian noise corrections that arise from small-scale clustering effects cannot be measured with random dilutions of the data. Therefore, they must either be properly modelled or marginalized over.

Lithospheric layering beneath northern Central Africa by S-to-P receiver functions

Using a total of 4520 S-to-P receiver functions (SRFs) recorded by 19 broadband seismic stations belonging to the Libyan Center for Remote Sensing and Space Science and the Incorporated Research Institutions for Seismology Data Management Center, we imaged the depth of the lithosphere–asthenosphere boundary (LAB) beneath northern Central Africa. This boundary occurs over the depth range of 57–124 km which we imaged in consecutive circular bins (radius of 2°) using a high number of receiver functions. The mean depth of the discontinuity is 80 ± 17 km, which is significantly shallower than the global average of ~250 km, commonly found beneath ancient cratons. The SRFs in the study area produced 156 bins with observable arrivals from the LAB. All the stacked traces were plotted along eight latitudinal profiles from 20°N to 35°N. The observed depth of the LAB increases systematically toward the northern central part of the study area from approximately 67 km–120 km. The apparent depth of the LAB increases from 70 to 90 km from 21°N to 28°N and then further increases to 120 km from 28°N to 34°N. These depth variations are extreme beneath the northern central part of Libya. The LAB depth beneath the Hoggar volcanic province area is relatively low (~57 km) compared to other areas. This study provides new constraints on regional-scale tectonic processes such as lithospheric stretching or thinning, due to partial melting beneath the study region that may be an effect of the LAB topography in this part of northern Central Africa.

Fluorescence Lifetime Spectroscopy of the Cornea using a Multichannel Scaler

An interface based on Multichannel scaler (MCS; SR430; Stanford Research Systems, USA) has been tested for enabling fluorescence lifetime measurements of pO2-sensitive fluorophores with a custom-made confocal scanning microfluorometer (CSMF) for transcorneal pO2 measurements. SR430 served as a transient photon counter. A trigger pulse, coincident with the rising edge of an excitation pulse for fluorescence, was coupled to accumulate emission pulses detected by a photomultiplier tube (PMT; R928 HA, Hamamatsu, Inc). The pulse started the photon counting and segmented the photon count data into consecutive time bins (ranging from 1 up to 32k), the width of which could be varied from 5 ns to 10.486 ms. With no dead time between bins, photon counting with the fluorescence decay is seamless. Silica-bound Ruthenium phenanthroline, dispersed in silicone rubber, was employed as a fluorophore sensitive to pO2. The test interface for CSMF-MCS system showed sensitive pO2 measurements and hence is suitable to measure local pO2 at any depth across the cornea.

A Large Capacity Histogram-Based Watermarking Algorithm for Three Consecutive Bins

The histogram watermark, which performs watermark embedding by slightly modifying the histogram of the original image, has been a hot research topic in information hiding technology due to the superiority of its pixel modification during the watermark embedding process, which is independent of the pixel position. This property makes the histogram-based watermark strong resistant to geometric attacks, such as cropping attack, crossed attack, rotation attack, etc. In this paper, we propose a large capacity histogram-based robust watermarking algorithm based on three consecutive bins for the first time. In our scheme, we divide the shape of three consecutive bins into eight cases. According to these cases, we embed Information Number 0, 1, 2, 3, 4, 5, 6, or 7, respectively. The embedded information capacity reaches one bit per bin (bpb), and the amount of embedded information is equal to 200% of the previous existing algorithms. Experimental results show that the new algorithm not only has a large capacity of embedding information, but also has strong robustness to geometric attacks, as well as common image processing operations.

Absence of thermal influence from the African Superswell and cratonic keels on the mantle transition zone beneath southern Africa: Evidence from receiver function imaging

The depths of the 410 km (d410) and 660 km (d660) discontinuities beneath southern Africa, which is presumably underlain by the lower-mantle African Superswell, are imaged in 1∘ radius consecutive circular bins using over 6400 P-to-S receiver functions (RFs) recorded by 130 seismic stations over a 27 yr period. When the IASP91 standard Earth model is utilized for moveout correction and time-depth conversion, a normal mantle transition zone (MTZ) thickness of 246 ± 7 km is observed, suggesting that the Superswell has no discernible effect on mantle transition zone temperature. Based on the negligible disparity of the mean MTZ thicknesses between on (246 ± 6 km) and off (246 ± 8 km) cratonic regions, we conclude that the deep Archean cratonic keels possess limited influence on MTZ thermal structure. The apparently shallower-than-normal MTZ discontinuities and the parallelism between the d410 and d660 are mostly the results of upper mantle high wave speed anomalies probably corresponding to a thick lithosphere with a mean thickness of about 245 km beneath the Kaapvaal and 215 km beneath the Zimbabwe cratons. In contradiction to conclusions from some of the previous studies, the resulting spatial distribution of the stacking amplitudes of the P-to-S converted phases at the discontinuities is inconsistent with the presence of an excessive amount of water in the MTZ and atop the d410.

Distributed Target Detection With Partial Observation

This paper considers the detection of a distributed target in a partial observation scenario. A distributed target model is usually adopted when the target size is larger than the range bin, for example, in some high-resolution radars. Based on the distributed target model, joint processing of several consecutive range bins can be adopted to achieve performance improvement with respect to processing just one range bin. In applications in complex electromagnetic environments, the radars may miss some of their observations, a phenomenon that usually caused by interference, spectrum sharing, and so on. This partial observation problem leads to degradation of the estimation accuracy for the disturbance (clutter plus noise) covariance matrix and target amplitude vector, which results in decline of the target detection performance. In this paper, a scheme is proposed by using the low-rank priori knowledge of clutter covariance matrix to estimate the detector's unknown parameters. Specifically, the target amplitude vector is obtained by maximizing the likelihood function, and the disturbance covariance matrix is reconstructed by solving an optimization that considers both the likelihood maximization and low-rank property of the clutter covariance matrix. The simulation results indicate that this algorithm improves the estimation accuracy, and achieves a better detection performance in the partial observation scenarios.

Geometrically Invariant Image Watermarking Using Histogram Adjustment

In this article, a blind image watermarking scheme, which is a robust against common image processing and geometric attacks is proposed by adopting the concept of histogram-based embedding. The average filter is employed to low-pass pre-filter the host image. The watermark bits are embedded into the histogram of the low-frequency component and the template bits are embedded in the high-frequency residual. The embedding is performed by adjusting the value of two consecutive histogram bins. Furthermore, a post-quantization is employed after the embedding round to improve robustness. All pixel modifications incurred are based on the human visual system (HVS) characteristics. As a result, a good tradeoff between robustness and imperceptibility is achieved. Experimental results reported the satisfactory performance of the proposed scheme with respect to both common image processing and geometric attacks.

Abstract 5371: Effect of DNA methyltransferase inhibitor 5-azacitidine on 3D chromatin structure measured by Hi-C

Abstract Therapies targeting epigenetic modifiers such as the DNA methyltransferase (DNMT) inhibitor, 5-azacytidine (Aza), are used in treating hematologic malignancies and also show promising results in subsets of solid tumors. The molecular mechanisms for these results, however, are not fully understood. Nonetheless, a number of clinical studies using combinations of epigenetic therapies plus chemo or immunotherapy to enhance the tumor response are ongoing. HCT-116, a colon cancer cell line genetically defined by microsatellite instability (MSI), resulting in a highly mutated, yet primarily diploid genome, has been routinely used to study epigenetic mechanisms and response to DNMT inhibition. In a previous study, we integrated a combination of data types including DNA methylation, DNA accessibility, histone modifications and transcriptomic data that revealed strong correlations between epigenomic changes and gene expression following Aza treatment. However, for some genes, we could not predict expression changes using these unidimensional, region-specific analysis methods. As others have demonstrated, genes do not work as single, isolated units, but rather interact with distal regulatory elements. These regulatory elements, often several Mb away can control gene expression through physical interactions such as bending and looping. We reason that in addition to direct demethylation of the immediate regulatory elements within the gene, Aza treatment can affect long-range chromosomal communications. In order to further understand the chromatin remodeling effect of Aza treatment, we performed high resolution genome-wide chromosome conformation capture (Hi-C) followed by NGS. HCT-116 cells were treated with DMSO or 1 μM Aza for 42 and 96 hours. Hi-C and RNA-Seq data was analyzed and integrated with other datatypes. The results showed that AZA treatment alters topologically associating domains (TAD), with the formation of new TAD boundaries and disappearance of others. The genome was then separated into 25K base pair consecutive bins, with each bin marked as type A (active) or type B (inactive). We observed bin switching following AZA treatment and differential loop formations (e.g. promoter-enhancer). Bins that switched from B to A at both time points were found enriched in genes that are related to acute phase response, interferon pathway, and cancer including PI3KCB, DDX58, CD274 and CDKN2A. Our findings using Hi-C were found to be in agreement with previous results using alternative experimental methods, which identified Aza and CTCF as the top upstream regulators of these genes. Our data also suggests that overall changes in 3D chromatin activities measured by Hi-C could be a better predictor of transcriptional regulation compared to H2K27me3 and H3K4me3 alone, particularly in situations where there are no significant changes in those marks but where changes in gene expression exist. Citation Format: Yuchen Vincent Bai, John Whitaker, Emanuele Palescandolo, Vinod Krishna, Vipul Bhargava, Satya Saxena, Xiang Yao, David Pocalyko, Kurt Bachman. Effect of DNA methyltransferase inhibitor 5-azacitidine on 3D chromatin structure measured by Hi-C [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5371. doi:10.1158/1538-7445.AM2017-5371

Fitting the generalized lambda distribution to pre-binned data

Density estimation for pre-binned data is challenging due to the loss of exact position information of the original observations. Traditional kernel density estimation methods cannot be applied when data are pre-binned in unequally spaced bins or when one or more bins are semi-infinite intervals. We propose a novel density estimation approach using the generalized lambda distribution (GLD) for data that have been pre-binned over a sequence of consecutive bins. This method enjoys the high power of the parametric model and the great shape flexibility of the GLD. The performances of the proposed estimators are benchmarked via simulation studies. Both simulation results and a real data application show that the proposed density estimators work well for data of moderate or large sizes.

Constraining the epoch of reionization with the variance statistic: simulations of the LOFAR case

Several experiments are underway to detect the cosmic redshifted 21-cm signal from neutral hydrogen from the Epoch of Reionization (EoR). Due to their very low signal-to-noise ratio, these observations aim for a statistical detection of the signal by measuring its power spectrum. We investigate the extraction of the variance of the signal as a first step towards detecting and constraining the global history of the EoR. Signal variance is the integral of the signal's power spectrum, and it is expected to be measured with a high significance. We demonstrate this through results from a simulation and parameter estimation pipeline developed for the Low Frequency Array (LOFAR)-EoR experiment. We show that LOFAR should be able to detect the EoR in 600 hours of integration using the variance statistic. Additionally, the redshift ($z_r$) and duration ($\Delta z$) of reionization can be constrained assuming a parametrization. We use an EoR simulation of $z_r = 7.68$ and $\Delta z = 0.43$ to test the pipeline. We are able to detect the simulated signal with a significance of 4 standard deviations and extract the EoR parameters as $z_r = 7.72^{+0.37}_{-0.18}$ and $\Delta z = 0.53^{+0.12}_{-0.23}$ in 600 hours, assuming that systematic errors can be adequately controlled. We further show that the significance of detection and constraints on EoR parameters can be improved by measuring the cross-variance of the signal by cross-correlating consecutive redshift bins.

A geometrical attack resistant image watermarking algorithm based on histogram modification

In order to avoid geometric distortions in watermark embedding, a geometrical attack resistant image watermarking algorithm is proposed based on histogram modification. The watermark information is embedded into the host image by modifying the number of the gray samples of the image histogram. In a fixed gray range, every three consecutive bins are divided into a group for embedding one-bit watermark, through modifying the sample value of a bin to another of the adjacent bin to realize the watermark insertion. Moreover, to avoid duplicate modification and improve the transparency, only one bin is modified every two neighbor bins, the modified histogram is mapped into the watermarked image. For watermark detection, it is in fact an inverse process of watermark embedding. Watermark is extracted through calculating and judging the relationship of the number of samples of the three successive bins. The experimental results show that the algorithm is robust to both geometrical attacks and those conventional signal processing attacks.