Spatial Desynchronization Research Articles

Spatiotemporal desynchronization in the propagation from meteorological to soil moisture drought in the Loess Plateau, China

Study RegionThe Loess Plateau (LP) of China Study FocusMeteorological drought (MD) would propagate to soil moisture drought (SMD) with spatiotemporal desynchronization. The spatial desynchronization between them has frequently been ignored in previous studies due to limitation of identified droughts, which did not consider their 3-dimensional (3D, i.e. longitude, latitude and time) properties. This study presents a 3D perspective on the spatiotemporal desynchronization in the propagation from meteorological to soil moisture drought in the the Loess Plateau (LP) of China, using an improved drought matching method. Event Synchronization (ES) is extended to determine temporal linkage of the two types of droughts and spatial connection is tested using overlapping area. New Hydrological Insights for the RegionThe results showed that: (1) the improved method is reasonable for identifying MDs that trigger SMDs, down to specific clusters; (2) 8 SMDs preceded MDs 1 month, while approximately 79 % of SMDs did not recover after the determination of MDs; (3) severity of MD is an impact factor on recovery lag, while antecedent soil moisture dominates onset lag with the relative importance of approximately 50 %; and (4) incompletely overlap in migration trajectory between the two types of droughts was mainly caused by temperature, followed by antecedent soil moisture and potential evapotranspiration, with relative importance of 55 %, 14 % and 12 %, respectively.

The structure of beta-diversity explains why the relevance of phytoindication increases under the influence of park reconstruction

Urbanization causes the highest local extinction rates and often leads to the loss of the vast majority of native species. Plant communities are sensitive to urban expansion and are therefore indicators of human land use. A city park, part of which has undergone reconstruction, was studied. The study found that the changes in ecological conditions caused by the reconstruction of a city park can be detected using phytoindication. The informativeness of phytoindication scales was shown to increase under conditions of anthropogenic load. The phytoindication scales are a reliable source of information for assessing the state of the vegetation cover of park plantations. The ecological regimes were assessed based on descriptions of the vegetation cover using Didukh's phytoindication scales. The phytoindication approach allows one to identify changes in ecological regimes that occur as a result of park reconstruction and to separate them from ecological regimes of natural origin. The study showed that the reconstruction of the park significantly affects the conditions of the park and the diversity of vegetation. The ratio of useful phytoindicative information compared to information noise in the structure of beta-diversity of the park's plantations increases significantly as a result of the park's reconstruction. The reconstruction of the park has led to changes in the spatial organization of the vegetation cover. The results obtained indicate a decrease in soil moisture as a result of the park's reconstruction. The park’s reconstruction leads to a significant change in the light regime of the park’s plantings, which leads to changes in the park’s vegetation and soils. Reducing the density of plantations as a result of their pruning during the reconstruction process also decreases the amount of fallen leaves that form leaf litter. A significant increase in the variability of the moisture regime under the influence of the park reconstruction was found. The phytoindication revealed a decrease in the acidity of the soil solution as a result of the reconstruction. The changes in soil acidity are accompanied by an increase in phytoindication estimates of carbonate content in the soil. The observed increase in carbonate content estimates may be an artifact when representatives of another ecological group also have related ecological properties that can be misinterpreted as indicators of certain regimes. The phytoindication also revealed trends in the variability of microclimatic conditions in the park as a result of reconstruction. The reconstruction of the park leads not only to a change in the modal levels of ecological regimes, but also to the formation of specific patterns of their spatial distribution. The heterogenization of the ecological space under the influence of reconstruction has been established. This heterogenization is evident in the fact that areas with homogeneous vegetation cover are decreasing. The accuracy of the description of the spatial process was found to have decreased after the park reconstruction procedures. Smooth spatial structures of the park’s vegetation cover without reconstruction are changing into rough spatial structures of the park after reconstruction. The park’s reconstruction obviously disrupts the course of long-term processes that structure the vegetation cover, which leads to temporal and spatial desynchronization of the dynamics of ecological processes. The spatial variation of variables that indicate soil processes can best be described. In contrast, the phytoindication scales that indicate climatic factors are much less spatially structured. The best variogram model to describe the spatial process is also changing under the influence of reconstruction. The significant consequences of the park reconstruction are time variability and spatial heterogeneity of ecological processes.

A JPEG Forensic Detector for Color Bitmap Images

Identification of decompressed JPEG images, especially those compressed with high JPEG quality factors, is a challenging issue in image forensics. Furthermore, the applicability of the existing JPEG forensic detectors in forgery localization is limited by their inability to cope with spatial misalignment in the $8\times 8$ JPEG grid. This paper proposes a novel forensic detector for decompressed JPEG color images stored in the bitmap format. The basic idea is to exploit the chroma upsampling traces introduced during the JPEG decompression of color images. We first show that the chroma upsampling alters the wide-sense stationary nature of the chroma planes and introduces wide-sense cyclostationarity in the upsampled chroma planes of decompressed JPEG images. As a result, unlike in the case of never-compressed images, the distributions of the odd-even and even-odd pixel pair differences are different for the chroma planes of never-compressed and decompressed JPEG images. We use the two-sample Kolmogorov-Smirnov (KS) test to find the similarity between these distributions and thereby to differentiate between never-compressed and decompressed JPEG images. The experimental results on a large set of images, including realistically-forged images, show the efficacy of the proposed detector even in the presence of spatial desynchronization due to image cropping.

Towards a Video Passive Content Fingerprinting Method for Partial-Copy Detection Robust against Non-Simulated Attacks.

Passive content fingerprinting is widely used for video content identification and monitoring. However, many challenges remain unsolved especially for partial-copies detection. The main challenge is to find the right balance between the computational cost of fingerprint extraction and fingerprint dimension, without compromising detection performance against various attacks (robustness). Fast video detection performance is desirable in several modern applications, for instance, in those where video detection involves the use of large video databases or in applications requiring real-time video detection of partial copies, a process whose difficulty increases when videos suffer severe transformations. In this context, conventional fingerprinting methods are not fully suitable to cope with the attacks and transformations mentioned before, either because the robustness of these methods is not enough or because their execution time is very high, where the time bottleneck is commonly found in the fingerprint extraction and matching operations. Motivated by these issues, in this work we propose a content fingerprinting method based on the extraction of a set of independent binary global and local fingerprints. Although these features are robust against common video transformations, their combination is more discriminant against severe video transformations such as signal processing attacks, geometric transformations and temporal and spatial desynchronization. Additionally, we use an efficient multilevel filtering system accelerating the processes of fingerprint extraction and matching. This multilevel filtering system helps to rapidly identify potential similar video copies upon which the fingerprint process is carried out only, thus saving computational time. We tested with datasets of real copied videos, and the results show how our method outperforms state-of-the-art methods regarding detection scores. Furthermore, the granularity of our method makes it suitable for partial-copy detection; that is, by processing only short segments of 1 second length.

An image steganographic algorithm based on spatial desynchronization

Calibration based attack is one of the most important steganalytic attacks in recent past specifically for JPEG domain steganography. In calibration attack, the attacker generally predicts the cover image statistics from the stego image. Preventing attackers from such prediction is used to resist these attacks. Domain separation (or randomization) is such a technique which is used for hiding the embedding domain from the attacker. It is observed that existing domain randomization techniques cannot provide enough randomization such that they are easily be detected by recent steganalysis techniques. In this paper, we have extended our previous work based on spatial desynchronization using statistical analysis. It is also experimentally shown that proposed algorithm is less detectable against the calibration based blind as well as targeted steganalytic attacks than the existing JPEG domain steganographic schemes.

Video watermarking based on multi-dimensional scaling and singular value decomposition

Concerning the intellectual property rights of video on Internet,a new digital video watermarking method based on Multi-Dimensional Scaling (MDS) and Singular Value Decomposition (SVD) was proposed.First,the frames were mapped to points in the 2D space using MDS,and then the watermarks were embedded into the differences between the frames of video and their images under the mapping through SVD.The experimental results show that the proposed method has very strong robustness against spatial desynchronization attacks such as rotating,scaling and clipping.Furthermore,it also achieves high robustness against noise and median filtering.In addition,the method can resist temporal desynchronization such as frame dropping and insertion to some extent.

Spatial Desynchronization of Glycolytic Waves as Revealed by Karhunen−Loève Analysis

The dynamics of glycolytic waves in a yeast extract have been investigated in an open spatial reactor. At low protein contents in the extract, we find a transition from inwardly moving target patterns at the beginning of the experiment to outwardly moving spiral- or circular-shaped waves at later stages. These two phases are separated by a transition phase of more complex spatiotemporal dynamics. We have analyzed the pattern dynamics in these three intervals at different spatial scales by means of a Karhunen-Loeve (KL) decomposition. During the initial phase of the experiment, the observed patterns are sufficiently described by the two dominant KL modes independently of the spatial scale. However, during the last stage of the experiment, at least 6 KL modes are needed to account for the observed patterns at spatial scales larger than 3 mm, while for smaller scales, 2 KL modes are still sufficient. This indicates that in the course of the experiment, the local glycolytic oscillators become desynchronized at spatial scales larger than 3 mm. Possible reasons for the desynchronization of the glycolytic waves are discussed.

The extended Moran effect and large‐scale synchronous fluctuations in the size of great tit and blue tit populations

1. Synchronous fluctuations of geographically separated populations are in general explained by the Moran effect, i.e. a common influence on the local population dynamics of environmental variables that are correlated in space. Empirical support for such a Moran effect has been difficult to provide, mainly due to problems separating out effects of local population dynamics, demographic stochasticity and dispersal that also influence the spatial scaling of population processes. Here we generalize the Moran effect by decomposing the spatial autocorrelation function for fluctuations in the size of great tit Parus major and blue tit Cyanistes caeruleus populations into components due to spatial correlations in the environmental noise, local differences in the strength of density regulation and the effects of demographic stochasticity. 2. Differences between localities in the strength of density dependence and nonlinearity in the density regulation had a small effect on population synchrony, whereas demographic stochasticity reduced the effects of the spatial correlation in environmental noise on the spatial correlations in population size by 21.7% and 23.3% in the great tit and blue tit, respectively. 3. Different environmental variables, such as beech mast and climate, induce a common environmental forcing on the dynamics of central European great and blue tit populations. This generates synchronous fluctuations in the size of populations located several hundred kilometres apart. 4. Although these environmental variables were autocorrelated over large areas, their contribution to the spatial synchrony in the population fluctuations differed, dependent on the spatial scaling of their effects on the local population dynamics. We also demonstrate that this effect can lead to the paradoxical result that a common environmental variable can induce spatial desynchronization of the population fluctuations. 5. This demonstrates that a proper understanding of the ecological consequences of environmental changes, especially those that occur simultaneously over large areas, will require information about the spatial scaling of their effects on local population dynamics.

An Adaptive Video Watermarking Scheme Based on the Middle-Frequency Energy Relationship Between Adjacent Frames

The approximate invariance of the middle frequencies energy relationship between video adjacent frames under photometric distortion and spatial desynchronization is discovered by analysis.Based on this approximate invariance,a new robust video watermarking scheme is proposed.It can adjust embedding strength adaptively according to human visual system features.Experimental results show that the proposed scheme is resilient to photometric distortion,spatial desynchronization and combined distortion effectively.

Spatiotemporal temperature patterns during hydrogen oxidation on a nickel disk

AbstractSpatiotemporal temperature patterns on a polycrystalline nickel disk were recorded using infrared video imaging during atmospheric hydrogen oxidation and characterized by the proper orthogonal decomposition pattern analysis technique. The system was studied at two different residence times, 3.2 s and 6.4 s. At moderate feed temperatures, steady‐state multiplicity and rate oscillations were found. Oscillations at a residence time of 6.4 s were periodic and essentially spatially uniform. At a residence time of 3.2 s, however, the surface temperature became nonuniform, and rate oscillations occurred via traveling temperature waves which emanated from “pacemakers” (locally active regions) on the edge of the catalyst. During periodic oscillations, the waves were emitted synchronously from the pacemakers, while during chaotic oscillations, the pacemakers were desynchronized and emitted waves independently of each other. Nonlocal gas‐phase coupling between distance surface elements caused spatial desynchronization during rate oscillations.