Statistical Estimation of Resistance to Cyclic Deformation of Structural Steels and Aluminum Alloy

Resistance to cyclic loading is a key property of the material that determines the operational reliability of the structures. When selecting a material for structures operating under low-cycle loading conditions, it is essential to know the cyclic deformation characteristics of the material. Low-cycle strain diagrams are very sensitive to variations in chemical composition, thermal processing technologies, surface hardening, loading conditions, and other factors of the material. The application of probability methods enables the increase in the life characteristics of the structures and the confirmation of the cycle load values at the design phase. Most research papers dealing with statistical descriptions of low-cycle strain properties do not look into the distribution of low-cycle diagram characteristics. The purpose of our paper is to provide a probability assessment of the low-cycle properties of materials extensively used in the automotive and aviation industries, taking into account the statistical assessment of the cyclic elastoplastic strain diagrams or of the parameters of the diagrams. Materials with contrasting cyclic properties were investigated in the paper. The findings of the research allow for a review of durability and life of the structural elements of service facilities subjected to elastoplastic loading by assessing the distribution of low-cycle strain parameters, as well as the allowed distribution limits.

Drought Drives Growth and Mortality Rates in Three Pine Species under Mediterranean Conditions

Drought constrains tree growth in regions with seasonal water deficit where growth decline can lead to tree death. This has been observed in regions such as the western Mediterranean Basin, which is a climate-warming hotspot. However, we lack information on intra- and inter-specific comparisons of growth rates and responses to water shortage in these hotspots, considering tree species with different drought tolerance. We sampled several sites located in north-eastern Spain showing dieback and high mortality rates of three pine species (Pinus sylvestris, Pinus pinaster, Pinus halepensis). We dated death years and reconstructed the basal area increment of coexisting living and recently dead trees using tree ring data. Then, we calculated bootstrapped Pearson correlations between a drought index and growth. Finally, we used linear mixed-effects models to determine differences in growth trends and the response to drought of living and dead trees. Mortality in P. sylvestris and P. pinaster peaked in response to the 2012 and 2017 droughts, respectively, and in sites located near the species’ xeric distribution limits. In P. halepensis, tree deaths occurred most years. Dead trees showed lower growth rates than living trees in five out of six sites. There was a strong growth drop after the 1980s when climate shifted towards warmer and drier conditions. Tree growth responded positively to wet climate conditions, particularly in the case of living trees. Accordingly, growth divergence between living and dead trees during dry periods reflected cumulative drought impacts on trees. If aridification continues, tree drought mortality would increase, particularly in xeric distribution limits of tree species.

Compaction pressure distribution and pressure uniformity of segmented rollers for automated fiber placement

For automated fiber placement onto molds with complex surfaces, uneven compaction pressure distribution limits tows number in a single sequence and affects layup quality. Compaction roller has a direct influence on the pressure distribution, but the relationship between the two has not been widely explored. In this paper, the segmented compaction roller is used, and a theoretical model of compaction pressure distribution for layup onto general surfaces is established by analyzing the contact between the roller and prepreg layers, followed by experimental validation. Based on the model, single-point pressure uniformity and whole-path pressure uniformity are proposed to quantitatively evaluate the pressure distribution. Furthermore, pressure distribution and pressure uniformity of segmented roller and common roller are compared, as well as the influence of the two pressure distribution on layup quality. The results show that the established model can predict pressure distribution and provide a basis for analyzing layup defects, and segmented rollers apply evener compaction pressure and help to improve layup quality.

Northern distribution limits of Sphagnum wulfianum (Sphagnaceae, Bryophyta) in the Northern Palearctic – records from tundra: coincidence or rule?

Sphagnum wulfianum is a widespread circumboreal species in the Northern Hemisphere. The distribution of this species in the Northern Palearctic was studied by generalizing and combining data from open sources (GBIF, literature data) and herbarium samples from LE, MW, NSK, and MHA into a single database. Data from herbarium labels and annotated lists were put on the map of Eurasia as points in the ArcGis 10.0 software. Analysis of the data shows that out of 3061 points 15 samples only were found in the tundra zone, which is 0.49% of all samples. This demonstrates that tundra habitats are not typical for S. wulfianum. Spatial analysis of samples collected in the Arctic of Eurasia shows that S. wulfianum was found only in the tundra of Yamal, Taz, and Taimyr peninsulas and in the part of Bolshezemelskaya tundra, which is adjacent to the Polar Urals. Analysis of vegetation history shows that S. wulfianum is a relic of the Holocene climatic optimum, preserved in the present southern tundra since the existence of forest vegetation. It is unknown from the tundras of Yakutia and Chukotka and from the mountainous tundras of Scandinavia, where any forest vegetation is unknown in the Holocene.

Complex genetic patterns and distribution limits mediated by native congeners of the worldwide invasive red-eared slider turtle

Non-native (invasive) species offer a unique opportunity to study the geographic distribution and range limits of species, wherein the evolutionary change driven by interspecific interactions between native and non-native closely related species is a key component. The red-eared slider turtle, Trachemys scripta elegans (TSE), has been introduced and successfully established worldwide. It can coexist with its native congeners T. cataspila, T. venusta and T. taylori in Mexico. We performed comprehensive fieldwork, executed a battery of genetic analyses and applied a novel species distribution modeling approach to evaluate their historical lineage relationships and contemporary population genetic patterns. Our findings support the historical common ancestry between native TSE and non-native (TSEalien), while also highlighting the genetic differentiation of the exotic lineage. Genetic patterns are associated with their range size/endemism gradient, the microendemic T. taylori showed significant reduced genetic diversity and high differentiation, whereas TSEalien showed the highest diversity and signals of population size expansion. Counter to our expectations, lower naturally occurring distribution overlap and little admixture patterns were found between and its congeners, exhibiting reduced gene flow and clear genetic separation across neighboring species despite having zones of contact. We demonstrate that these native Trachemys species have distinct climatic niche suitability, likely preventing establishment of and displacement by the non-native TSE. Additionally, we found major niche overlap between TSEalien and native species worldwide, supporting our prediction that sites with closer ecological optima to the invasive species have higher establishment risk than those that are closer to the niche-center of the native species.

Shared Bicycle Distribution Connected to Subway Line Considering Citizens’ Morning Peak Social Characteristics for Urban Low-Carbon Development

The transport sector has produced numerous carbon emissions in China, and it is important to promote low carbon commuting. As an emerging mode of urban low-carbon transportation in China, shared bicycles have been used by more and more citizens on a daily basis, with advantages of green and low-carbon emissions to environment, flexibility for short trips, and convenience for covering the distance between the normal low-carbon transportation and destinations. However, the imbalanced distribution of shared bicycles along subway lines, especially during the morning peak hours, has directly restricted their performance in urban traffic. In this paper, an integer linear program model (ILPM) is proposed to obtain an optimal low-carbon distribution plan of shared bicycles connecting with the subway line (SBCSL) during the morning peak hours. First, an objective function is built to improve the carbon emission reduction of SBCSL. Second, constraint functions are extracted considering the quantity of bicycles to be distributed to the subway line as well as the distribution limits of each subway station. At last, a case study is conducted on the distribution of shared bicycles in Beijing Subway Line 13 of China during the morning peak hours. The results show that the ILPM is of significance to provide optimal distribution scheme of shared bicycles in subway line with different station types including office-oriented, residential-oriented, and hybrid-oriented stations.

A new locality record for the Syrian hamster, Mesocricetus auratus

A new occurrence record significantly expanded known distribution limits of the Syrian hamster further south into the Syrian Desert, about 150 km to the south from the known southern range border is reported. Updated distribution map for this species is given based on previous records from Syria and Turkey.

Emergent features of species: existence between populations and communities

The key block of tasks in defining species as a phenomenon, as a concept, and as a category — its emergent features, is considered. These include 5 systems of features, such as 1) diagnosis (primarily morphological, including unique apomorphies); 2) genotype in the broadest sense (including karyotype); 3) system of reproduction and protection of the gene pool from mixing with foreign forms (reproductive isolation); 4) geographical range (including type habitats and distribution limits); 5) system of variability (including the presence and features of age-related changes, sexual differences, and trends in geographical variation). There is evidence that species as a reality is characterized by the properties of "repeating structures". To the latter the author includes the following six: 1) limited volumes of species composition of communities; 2) limited body-size rows of guilds; 3) parallelisms and the phenomenon of isomorphism; 4) limited number of ecotypes and the phenomenon of vicariates; 5) homeomorphies and restrictions of morphological types; 6) synperates as overlaps of range boundaries. Areas of non-alternative application of the concept of "species", including red lists, checklists, descriptions of unique parts of communities (endemics, rarities, etc.), and objects of economic value are given.