Color Image Encryption Algorithm Based on Dynamic Block Zigzag Transformation and Six-Sided Star Model

As a result of the rise in network technology, information security has become particularly important. Digital images play an important role in network transmission. To improve their security and efficiency, a new color image encryption algorithm is proposed. The proposed algorithm adopts a classical scrambling–diffusion framework. In the scrambling stage, the dynamic block Zigzag transformation is designed by combining the chaotic sequence with the standard Zigzag transformation, which can dynamically select the transformation range and the number of times. It is used to scramble the pixel positions in the R, G, and B components. In the diffusion stage, the six-sided star model is established by combining the chaotic sequence and the six-sided star structure characteristics, which can store the 24 bits of the pixel in a defined order to realize bit-level diffusion operation. Experimental analyses indicate that our algorithm has the characteristics of high key sensitivity, large key space, high efficiency, and resistance to plaintext attacks, statistical attacks, etc

Receding Water Line and Interspecific Competition Determines Plant Community Composition and Diversity in Wetlands in Beijing

<div><p>Climate and human-induced wetland degradation has accelerated in recent years, not only resulting in reduced ecosystem services but also greatly affecting the composition and diversity of wetland plant communities. To date, the knowledge of the differences in community parameters and their successional trends in degraded wetlands remains scarce. Here based on remote sensing images, geographic information system technology, and statistical methods, we produced a successional gradient map of the Yeyahu Wetland Nature Reserve in Beijing, which has experienced a steady decline in water level in recent decades. In addition, we analyzed community composition and diversity along with each identified gradient. The results showed that community diversity decreases while dominance increases with the progress of succession, with the highest diversity occurring during the early stage of succession. Moreover, the community demonstrates greater similarity among subareas during later successional stages, and the similarity coefficients calculated from the important value (IV) of each species are more accurate. Correlation analysis showed that the impact of soil factors on diversity was not significant at a subarea scale, although these nutrients showed an increasing trend with the community succession. Furthermore, the IVs of the dominant species had a particularly significant impact on diversity, showing a significantly negative correlation with diversity indices and a significantly positive correlation with dominance indices. Further analysis showed that the retreat of water level resulted from sustained drought and local human activities was a major extrinsic driving force resulting in observed differences in the community successional stages, which resulted in differences in community composition and diversity. On the other hand, interspecific competition was the main intrinsic mechanism, which significantly influenced the IVs of the dominant species and community diversity. The results of this study could aid in improving the understanding of community composition, diversity, and its successional trends in degraded wetlands.</p></div

Comparisons of competitive ability between <i>Phragmites australis and Hemarthria altissima</i> at the in quadrat scale.

<p>Comparisons of competitive ability between <i>Phragmites australis and Hemarthria altissima</i> at the in quadrat scale.</p

Correlations between IVs of the dominant species and diversity indices in the three subareas.

<p>Note: ** Correlation is significant at p < 0.01 (two-tailed)</p><p>Correlations between IVs of the dominant species and diversity indices in the three subareas.</p

Comparisons of soil variables and elevations among three subareas.

<p>Note: the values are given as mean ± standard error. AN: available nitrogen; AP: available phosphorus; TN: total nitrogen; TP: total phosphorus; SOM: soil organic matter; SWC: soil water content. Per column, those values sharing a common superscript letter were not significantly different. Significance level is P < 0.05.</p><p>Comparisons of soil variables and elevations among three subareas.</p

Mean value for each parameter measured in each quadrat in the three subareas.

<p>Note: the values are given as mean ± standard error. IV: Important value of the dominant species. Per column, those values sharing a common superscript letter were not significantly different. Significance level is P < 0.05.</p><p>Mean value for each parameter measured in each quadrat in the three subareas.</p

Comparisons of competitive ability between <i>Phragmites australis and Hemarthria altissima</i> at the subarea scale.

<p>Comparisons of competitive ability between <i>Phragmites australis and Hemarthria altissima</i> at the subarea scale.</p

Variation in the cumulative IVs for each community in the three subareas.

<p>Variation in the cumulative IVs for each community in the three subareas.</p

Locations of the study area and the sampling points in the Beijing’s Yeyahu wetland nature reserve.

<p>Note: a and b show the location of the study area in the Beijing metropolitan area and the Yeyahu wetland nature reserve, respectively; c shows the successional gradient map and the locations of the sampling points in each subarea.</p