High-latitude Areas Research Articles

Coordinate conversion and switching correction to reduce vessel heading related errors in high-latitude navigation

Considering the distortion errors of projected coordinates and the switching property of vessel heading, coordinate conversion and switching correction methods are proposed to modify a kinematic motion model and the Unscented Kalman Filter (UKF). The coordinate conversion method utilizes the grid convergence from a Universal Transverse Mercator (UTM) projection to correct the vessel heading. The switching correction is embedded in the UKF so that the innovations of vessel heading can be calculated correctly. The simulation results demonstrate that the proposed modifications in both model and algorithm can generate more accurate estimated vessel states from two simulated maneuvers. Since a reliable estimation of vessel maneuvers is the prerequisite in many intelligent systems that support various decision-making processes in maritime transportation, the proposed modifications can be therefore implemented into these systems to support navigation safety in high latitude areas.

FedBIP: A Federated Learning-Based Model for Wind Turbine Blade Icing Prediction

Prediction of icing on wind turbine blades is crucial, particularly in high-latitude areas where ice accumulation is a frequent occurrence. Traditional centralized data-driven approaches for predicting blade icing have demonstrated promising performance, but they require a large amount of storage and computational resources and may also raise concerns about data privacy. Federated Learning (FL) presents a potential solution to address these issues. These challenges include redundant features in the collected data, a highly imbalanced data distribution between normal and icing samples, and slow model convergence during FL training. To tackle these challenges, we proposed a novel FL model called FedBIP. FedBIP employs a feature selection approach enhanced with human knowledge to select relevant features, a segmentation-based oversampling method to alleviate class imbalance, and a new aggregation method that takes into account data size, timestamps, and offsets of each participating client. In addition, knowledge distillation is employed in the local model training to accelerate model convergence and speed up the overall training process. The results of comprehensive experiments demonstrate that FedBIP outperforms state-of-the-art FL methods, aggregation methods, and feature extractors. Ablation and sensitivity analysis were also conducted to validate the importance of each component and key parameters in FedBIP.

Frost heave mitigation of silt clay using nonionic polyacrylamide

Frost heave occurs frequently in high-latitude or high-altitude areas in many parts of the world, and it is a common challenge for geotechnical engineers in road construction. In order to solve the excessive frost heave induced frost damage to geotechnical engineering in cold regions, frost heave susceptible soil from the Tibetan Plateau (the seasonal frozen area) is modified by nonionic polyacrylamide (NPAM) and then used for frost heave testing. Moreover, cohesion test, permeability test, scanning electron microscopy (SEM) test, and Fourier transform infrared spectroscopy (FTIR) analysis are carried out on the NPAM modified soil to gain more insight into the frost heave mitigation mechanism. The impact of NPAM on soil frost heave and its physicochemical mechanism for frost heave mitigation are subsequently investigated. Our results demonstrate that NPAM is physically adsorbed on the surface of soil particles through hydrogen bonding. The increase of NPAM content does not only increase the viscosity of the solution, but it also enhances the aggregation of fine soil particles. In addition, the permeability of the modified soil decreases with increasing NPAM content, thus implying an increase in the water migration resistance. NPAM can be effectively used to reduce the frost heave susceptibility of soil. Our results show that 0.3 wt% of NPAM can significantly convert a strong frost heave soil to a weak frost heave soil. Our results reveal the mechanism of frost heave mitigation using NPAM and provides engineers and researchers with a new physicochemical method for the treatment of frost heave susceptible soil in railway and road construction in cold regions.

Monitoring the little fire ant, Wasmannia auropunctata (Roger 1863), in the early stage of its invasion in China: Predicting its geographical distribution pattern under climate change

Invasive alien ants (IAAs) are among the most aggressive, competitive, and widespread invasive alien species (IAS) worldwide. Wasmannia auropunctata, the greatest IAAs threat in the Pacific region and listed in “100 of the world’s worst IAS”, has established itself in many countries and on islands worldwide. Wild populations of W. auropunctata were recently reported in southeastern China, representing a tremendous potential threat to China’s agricultural, economic, environmental, public health, and social well-being. Estimating the potential geographical distribution (PGD) of W. auropunctata in China can illustrate areas that may potentially face invasion risk. Therefore, based on the global distribution records of W. auropunctata and bioclimatic variables, we predicted the geographical distribution pattern of W. auropunctata in China under the effects of climate change using an ensemble model (EM). Our findings showed that artificial neural network (ANN), flexible discriminant analysis (FDA), gradient boosting model (GBM), Random Forest (RF) were more accurate than categorical regression tree analysis (CTA), generalized linear model (GLM), maximum entropy model (MaxEnt) and surface distance envelope (SRE). The mean TSS values of ANN, FDA, GBM, and RF were 0.820, 0.810, 0.843, and 0.857, respectively, and the mean AUC values were 0.946, 0.954, 0.968, and 0.979, respectively. The mean TSS and AUC values of EM were 0.882 and 0.972, respectively, indicating that the prediction results with EM were more reliable than those with the single model. The PGD of W. auropunctata in China is mainly located in southern China under current and future climate change. Under climate change, the PGD of W. auropunctata in China will expand to higher-latitude areas. The annual temperature range (bio7) and mean temperature of the warmest quarter (bio10) were the most significant variables affecting the PGD of W. auropunctata in China. The PGD of W. auropunctata in China was mainly attributed to temperature variables, such as the annual temperature range (bio7) and the mean temperature of the warmest quarter (bio10). The populations of W. auropunctata in southern China have broad potential invasion areas. Developing strategies for the early warning, monitoring, prevention, and control of W. auropunctata in southern China requires more attention.

BSA-Seq Approach Identified Candidate Region and Diagnostic Marker for Chilling Tolerance of High Oleic Acid Peanut at Germination Stage

High oleic acid peanut (HOAP) is extensively embraced in China because of its high nutritional value and enhanced oxidative stability. However, its dissemination has been severely constrained in high altitude and high latitude areas due to chilling stress during sowing, resulting in significant yield loss in these regions. Despite the lack of understanding of the molecular mechanisms underlying low temperature germination (LTG) in HOAP, discovering the quantitative trait loci (QTL) that confer this trait will undoubtedly benefit breeding efforts. In the present study, we identified putative genomic regions and single nucleotide polymorphisms (SNPs) that govern LTG tolerance of HOAP in an F2 population derived from the cross of chilling-tolerant YH65 and chilling-sensitive FL14 using bulk segregant analysis (BSA). Analysis of ΔSNP-index and Euclidean distance (ED) value association pinpointed the overlapped region to a 2.29 Mb interval on chromosome A05. The candidate interval showed that 122 genes were significantly related to response to abiotic stress and plant–pathogen interaction. Furthermore, an SNP site associated with LTG tolerance was discovered. The SNP site was employed as a Kompetitive Allele Specific PCR (KASP) marker and validated in a universal peanut panel. These findings may provide valuable insight into the molecular mechanism underpinning LTG tolerance and facilitate marker-assisted selective breeding in HOAP.

Vegetation succession, climate change and cold events during 9.2–8.0 cal kyr BP in eastern China: High-resolution pollen evidence from the Yangtze delta plain area

High resolution pollen records in the northern edge of subtropical China are crucial to understand the pattern of postglacial vegetation change and climate transition. Here we present vegetation succession and climate change during 9.2–8.0 cal kyr BP based on sub-decennial scale pollen data. Pollen spectra show that Quercus (evergreen) &Cyclobalanopsis were relatively stable during the whole period, while Quercus (deciduous) were gradually decreased. Pollen-based climate change shows gradual warming during this period, and noticeably, the rapid warming during 8610–8545 cal yr BP can be detected according to the sharp decrease of Quercus (deciduous). Our results show two cold and dry events at 8.5 ka and 8.2 ka. The 8.5 ka event is rarely reported in the East Asian Monsoon area, while the 8.2 ka event is frequently mentioned. In this study, the 8.2 ka event has two peaks, similar to the previous reports from the Yangtze delta area and Dongge Dong Cave. In the Yangtze delta area, the vegetation and climate change show a strong relationship with the high latitude area, indicating that they are not only related to solar activity, but also impacted by the high latitude climate events. However, the impacts of these events on the Asian monsoon area still need further studies to verify.

Splitting an Impacting Droplet by a Superhydrophobic Wire

Splitting a droplet into several segments is of great significance in many applications such as the detection of tiny liquid samples, whereas the surface tension tends to hold liquid to remain as one drop, causing difficulty in separating the droplet into pieces. In this work, a method is proposed to split an impacting droplet with a relatively high velocity or Weber number into two halves by a superhydrophobic wire. The effects of the wire wettability and the impact velocity of the droplet on the splitting phenomena and the efficacy to an anti-icing application are investigated. Compared to a hydrophilic wire, a superhydrophobic wire splits an impacting droplet at a relatively high speed of the Weber number greater than 3.1 and inhibits ice accretion at the temperature as low as −20 °C. The results suggest that a superhydrophobic wire can be utilized in the droplet manipulation and anti-icing applications such as power lines in high latitude areas.

Hybrid purity identification using EST-SSR markers and heterosis analysis of quantitative traits of Russian wildrye.

Russian wildrye, Psathyrostachys junceus (Fisch.) Nevski, is widely distributed in the high latitude areas of Eurasia. It plays an important role in grassland ecosystem maintenance, as well as being a valuable palatable forage species for livestock and wildlife. Russian wildrye germplasm has rich phenotypic and genetic diversity and has potential for improvement through crossbreeding. In this study, fifteen Russian wildrye hybrid combinations were produced and one F1 population with 123 putative hybrids was obtained by crossing two individual plants with significant differences in nutritional characteristics and reproductive tiller number. Twelve phenotypic traits of the F1 population were measured for three consecutive years, and ten of the twelve traits were in line with the genetic characteristics of quantitative traits. Hybrid superiority was revealed among F1 hybrids in both nutritional and reproductive traits. One non-recurrent parent plant with the highest PCA-synthesis score was selected and used to make a backcross with the 'BOZOISKY SELECT' male parent, and 143 putative BC1 hybrids were obtained. Sixteen pairs of EST-SSR primers were randomly selected from polymorphic primers derived from different expressed tiller trait related genes. Three primer pairs that amplified both the paternal and maternal characteristic band were used to assess the purity of the F1 population, and three primer pairs (with one shared primer pair) were used to identify the BC1 population. The hybrid purity was 96.75% for the F1 population and 95.80% for the BC1 population, and the results were confirmed by self-fertility test through bagging isolation. The genetic similarity coefficients between the F1 progeny and the male parent ranged from 0.500 to 0.895, and those between the BC1 progeny and the male parent ranged from 0.667 to 0.939. A subset of individuals in the BC1 population had closer genetic distance to the recurrent parent, and genetic variation within the BC1 population decreased compared to the F1 population.

Cryptic taxonomic diversity and high-latitude melanism in the glossiphoniid leech assemblage from the Eurasian Arctic

The family Glossiphoniidae is a diverse and widespread clade of freshwater leeches, playing a significant role in functioning of aquatic ecosystems. The taxonomy and biogeography of leeches from temperate, subtropical, and tropical regions attracted much attention of zoologists, while their taxonomic richness and distribution in the Arctic are poorly understood. Here, we present an overview of the Eurasian Arctic Glossiphoniidae based on the most comprehensive occurrence and DNA sequence datasets sampled to date. This fauna contains 14 species, belonging to five genera and three subfamilies. One genus and five species are new to science and described here. The world’s northernmost occurrences of glossiphoniids are situated on the Taymyr Peninsula at 72° N, although further records at higher latitudes are expected. Most Arctic leeches are characterized by broad ranges crossing several climatic zones (e.g., Glossiphonia balcanica and G. nebulosa), although the distribution of two new species may be confined to the high-latitude areas. The Taymyr Peninsula with the nearby Putorana Plateau represents the most species-rich area (totally 9 species), while the European Arctic, Iceland, Kolyma Highland, and Chukotka Peninsula house depleted faunas (2–4 species per subregion). Finally, we show that the high-latitude melanism is a common phenomenon in glossiphoniid leeches.

Relict permafrost preserves megafauna, insects, pollen, soils and pore-ice isotopes of the mammoth steppe and its collapse in central Yukon

In eastern Beringia (unglaciated Alaska and western Yukon), the Pleistocene-Holocene transition was characterised by rapid changes in plant, insect and mammal communities as the mammoth steppe ecosystem was replaced, first by shrub tundra and later boreal forest. These changes indicate a transition from well drained terrain with deep active layers to wetter, cooler soils, to which steppe-tundra vegetation was poorly adapted. The nature and precise timing of these events is not well resolved, particularly in central Yukon where regional climate may have been strongly affected by the retreating Cordilleran-Laurentide ice sheet complex. Resolving this uncertainty is not only important for understanding past ecosystems, but also provides a long-term perspective for contemporary environmental change and shrub expansion that affects large areas of northern high-latitudes today. Here, we report chronology (41 radiocarbon dates), stratigraphy, pore-ice δ2H/δ18O measurements, pollen data, megafauna remains and fossil insect assemblages from a permafrost-preserved loessal sequence in central Yukon, named Lucky Lady. The site spans the interval from ca. 17,000 to 8000 cal yr BP (calibrated years before C.E. 1950) and records the Pleistocene-Holocene transition in exceptional resolution. Full glacial environments (ca. 16,500 cal yr BP) supported elements of steppe-tundra vegetation and an insect fauna dominated by Connatichela artemisiae - an endemic weevil indicating warm soil temperatures. The collapse of the mammoth steppe ecosystem began with slowing of loess accumulation and development of paleosol ca. 13,480 cal yr BP. At this time, C. artemisiae remains become infrequent and Artemisia pollen decline to be replaced by Cyperaceae (ca. 13,220), before mesic, shrub taxa (likely dwarf Betula and Salix) becomes dominant ca. 13,210 cal yr BP. The establishment of shrub tundra is associated with rapid changes in δ2H/δ18O measurements, suggesting that ecological turnover coincided with a shift in atmospheric conditions and moisture availability. Finally, boreal vegetation communities became established ca. 10,680 cal yr BP. The replacement of steppe-tundra vegetation in central Yukon lagged other areas of eastern Beringia by as much as 1000 years and coincided with rapid deglaciation during the Bølling–Allerød time-period (14,600–12,900 cal yr BP). Turnover in insect and vegetation communities took place in ca. 40 years as shrub tundra became dominant. This rapid turnover has parallels with contemporary Arctic greening and re-emphasises the sensitivity of high-latitude environments to climate change.

Evaluating the External Effect of Wind Power Development on Grassland Quality

<h3>Abstract</h3> This study employs a difference-in-differences approach to investigate the effect of county wind power development on grassland quality in China. We find robust evidence that increasing wind power capacity density by 0.02 MW/km² leads to a 0.5% reduction in the normalized difference vegetation index from its mean value. Excluding economic activities as a transmission channel, heterogeneous effects suggest that higher latitude areas with shorter nighttime hours in the growing season are less affected by the negative externality, supporting microclimate effects as the main mechanism. In addition, scarce wind resources and abundant precipitation may help weaken the negative effect.

Ground surface temperature monitoring data analysis and applications to geothermal exploration in volcanic areas, Mount Meager, western Canada

The southern Mount Meager area has been studied for its geothermal resource potential for a half century. Although attempts to commercialize the resource were unsuccessful in the past, a large volume of surface and subsurface geoscience data have been collected and made publicly available, making the Mount Meager area a unique natural laboratory for testing new ideas or tools for geothermal exploration. This study investigates the potential of using a ground surface temperature (GST) monitoring network as a tool in geothermal resource exploration. Twenty-two temperature data loggers were deployed in, and surrounding, the core area of the geothermal prospect for nearly one year. The collected temperature time series were analyzed statistically, and machine learning methods such as hierarchical clustering and k-means classification, were applied to data interpretation. The temporal variation of measured temperature can be divided into four segments: 1) snow free, 2) snow affected, 3) snow curtain, and 4) snow melt seasons. The intensity of daily ground temperature variation in the snow free season shows clear environmental and topographic footprints and is complicated by soil properties. The sites with a short period of near zero GST during the snow curtain period is spatially coincident with high heat flow areas. The measured mean GST shows a close affinity with subsurface heat flow and shallow ground water circulation, suggesting that GST time series contain information indicative of subsurface geothermal anomalies and that a GST monitoring network could be an effective tool for geothermal resource exploration in high latitude and/or elevation areas with seasonal snow cover.

CPUE retrieval from spaceborne lidar data: A case study in the Atlantic bigeye tuna fishing area and Antarctica fishing area

The measurement of Catch Per Unit Effort (CPUE) supports the assessment of status and trends by managers. This proportion of total catch to the harvesting effort estimates the abundance of fishery resources. Marine environmental data obtained by satellite remote sensing are essential in fishing efficiency estimation or CPUE standardization. Currently, remote sensing chlorophyll data used for fisheries resource assessment are mainly from passive ocean color remote sensing. However, high-resolution data are not available at night or in high-latitude areas such as polar regions due to insufficient solar light, clouds, and other factors. In this paper, a CPUE inversion method based on spaceborne lidar data is proposed, which is still feasible for polar regions and at nighttime. First, Atlantic bigeye tuna CPUE was modeled using Cloud aerosol lidar and infrared pathfinder satellite observations (CALIPSO) lidar-retrieved chlorophyll data in combination with sea surface temperature data. The Generalized Linear Model (GLM), Artificial Neural Network (ANN) and Support Vector Machine Methods (SVM) were used for modeling, and the three methods were compared and validated. The results showed that the correlation between predicted CPUE and nominal CPUE was higher for the ANN method, with an R2of 0.34, while the R2was 0.08 and 0.22 for GLM and SVM, respectively. Then, chlorophyll data in the polar regions were derived using CALIPSO diurnal data, and an ANN was used for Antarctic krill. The inversion result performed well, and it showed that the R2of the predicted CPUE to nominal CPUE was 0.92. Preliminary results suggest that (1) nighttime measurements can increase the understanding of the diurnal variability of the upper ocean; (2) CALIPSO measurements in polar regions fill the gap of passive measurements; and (3) comparison with field data shows that ANN-based lidar products perform well, and a neural network approach based on CALIPSO lidar data can be used to simulate CPUE inversions in polar regions.

The Evolution of Cold Adaptation Technology within Ancient Buildings in Amur River Basin Viewed from Archaeology.

The Amur River Basin is located in China's high-latitude and cold border areas. While inheriting the characteristics of Chinese traditional building, combined with its unique geographical and climatic environmental conditions, the local residential buildings have unique architectural features of cold climate adaptability. Outstanding insulation technology has become the main feature of the area, and has greatly affected the development of modern vernacular architecture. According to the archaeological reports and documents, this article selects ancient architectural sites from different historical periods as the research objects. Based on building restoration, AIRPAK software is used to simulate and analyze the indoor temperature of the building site, and to explore the effects of active heating measures, such as different forms of fire hypocaust system, and passive cold protection measures, such as different types of wall structures. According to archaeological information and simulation data, this paper summarizes the characteristics of the cold climate adaptability technology of ancient buildings in China's cold border areas over different historical periods. Because of the relatively lagging development background of the Amur River Basin in modern times, the construction of its vernacular buildings continued to use the traditional low-tech insulation technology of ancient buildings to adapt to the cold environment. Therefore, attention and research on insulation technology of ancient buildings can provide a new perspective of architectural heritage protection in cold regions. Establishing a development model that combines archaeology and cultural heritage protection is an effective way to achieve the goals of architectural cultural heritage research and protection.

Hotspots, co-occurrence, and shifts of compound and cascading extreme climate events in Eurasian drylands.

Eurasian drylands are the regions that are most vulnerable to climate change. Climate extremes have caused enormous or even devastating impacts on ecosystems and the social economy in this region, and the compound climate extremes (com_CEs, two or more extreme events occurring simultaneously) and cascading climate extremes (cas_CEs, two or more extreme events occurring successively) have exacerbated these problems. However, little is known about the occurrence patterns of com_CEs and cas_CEs in the Eurasian drylands. Based on the ERA5 reanalysis data range from 1979 to 2020, we improved the methodology for the extraction of co-occurrence events and identified high-frequency types, their hotspots, and occurrence rhythms (seasonally and annually) in Eurasian drylands. Our results showed that com_CEs and cas_CEs have high similarities in the types and spatial hotspots of extreme events; however, the former has a wider geographical and spatial distribution, and the latter has a longer duration. Specifically, co-occurring drought and heatwave events (DH) frequently appear in South Asia and western mid-latitude regions during summer, while in the winter, high latitude regions should be alert to the co-occurrence of drought and low-temperature events (DT). Central Asia and the Mongolian Plateau regions are prone to frequent drought and wind events (DW), and wind and high precipitation events (WP) in the spring and autumn. We have noticed that mid-latitude may suffer from extreme events that have never occurred before, such as com_DH being scattered sporadically in the first two decades and suddenly surging in West Asia and East Asia after the year 2000, and com_DT migrating from high-latitude areas such as the Arctic Ocean coast to mid-latitudes. Our results contribute to understanding hotspots of co-occurring CEs in Eurasian drylands, where more efforts will be needed in the future, especially in mid-latitudes which may suffer extreme climate events that have never occurred before.

PM10 aerosol enhancement in the anticyclonic anomalies caused by the East Asian spring warming of 2021

This study analyzed the PM10 aerosol enhancement caused by East Asian atmospheric warming during transboundary transport in March of 2021. It was found to be cooled near the north polar area and to have shifted the polar vortices northward over the East Asian region in the mid-troposphere. The Siberian high was weakened and the East Asian region was characterized by a positive air temperature anomaly and negative zonal wind speeds. The increasing rate of air temperature anomalies at 2 m was higher in the high latitude areas over 40°N in Mongolia and northeastern China, causing a decrease in zonal wind speeds at 10 m over eastern China and Korea. The anomalous variations of the MODIS-induced aerosol optical depth (AOD) were found to be positive with the highest value of +0.93 in the area ranging from northeastern China to Korea, despite the recent decreasing trends. The positive anomalous region of the MODIS-induced AOD was correlated with positive air temperatures and negative zonal wind speeds, causing enhanced formations of secondary aerosols in the atmosphere. As cold northerly winds were suppressed in the East Asian region, anomalous high pressures (anticyclonic anomalies) developed frequently in eastern China and moved to Korea. The Weather Research and Forecasting model to which meteorological and climate data were applied coupled with Chemistry (WRF-Chem) simulations on increases in the PM10 enhancement ratio, indicating enhanced formation amounts, during transboundary transport for the period of March 13–15, 2021. An air mass near the high terrain surface over eastern China under the backward side of an anticyclone warmed and moved toward the relatively low terrain of the Yellow Sea and Korea in keeping with the height. Air temperature inversion developed in the anomalous warmer center in the mid-troposphere, reaching the surface of the Yellow Sea and Korea. High PM10 concentrations were constrained near the shallow inversion layer. Furthermore, the PM10 enhancement ratio showed a positive level over the Yellow Sea with nearly zero anthropogenic emissions on the surface, gradually increasing at a rate of approximately 60% in Korea. The hourly contribution by the warming-induced PM10 enhancement (PM10 CbWIE) was calculated and found to be at the highest level of 70% in Seoul, Korea. Among PM10 secondary inorganic aerosols, nitrate formations were enhanced during transboundary transport in the warming-induced anticyclone with reactions rich in ammonium. While the sulfate enhancement ratio reached a positive level over the Yellow Sea, the gradual decrease during transboundary transport may be reflected by the decreased emissions of sulfur dioxide in eastern China.

Variability in the minimum temperature over two centuries in the overlap region between the fringe of the Asian westerly region and the temperate continental-monsoon climate transition zone.

The overlap region between the eastern fringe of the Asian westerly region and the temperate continental-monsoon climate transition zone is sensitive to climate changes and is characterized by fragile ecosystems. Uncovering the long-term historical climate variability patterns in this region is necessary. A standardized tree-ring width chronology was constructed based on the tree-ring samples collected from four representative tree species in four typical areas in the overlap region, and the 203- to 343-year annual mean minimum temperature series in the overlap region were reconstructed. The reconstructed series overlapped well with extreme climate events and low-temperature periods recorded in historical data. Therefore, the reconstructed model is stable and reliable. As suggested by the reconstructed series, the annual average minimum temperature in the overlap region changes sharply from east to west, and the periodicity change in the overlap region shows a trend of gradually weakening from the east and west ends to the middle. In the nineteenth century, the high-latitude area was in the high-temperature period, and the entire overlap region experienced significant low-temperature periods lasting 20-45years until the 1950s. The western part had an earlier low-temperature period start time, a longer cooling duration, and a slower cooling rate than the central part. The overlap region experienced a significant warming period in approximately the last half-century, with temperatures increasing faster in the western and eastern parts than in the central part. The temperature variability in the overlap region was more intense in the last two centuries, with shorter periodicities and a larger proportion of cold periods. The central and western parts of the Asian westerly region, the mid- to high-latitude regions of the transition zone, and the overlap region experienced significant low-temperature periods or drastic cooling trends (the Little Ice Age) in the first half of the nineteenth century and significant warming trends afterwards due to global warming. The influences of these changes may have been exacerbated by the westerly circulation. The results of this study provide new insights into the use of dendroclimatology to extract temperature series in the Asian westerly region and the transition zone and a reference for research on global climate change.

Effects of Fiber and Surface Treatment on Airport Pavement Concrete against Freeze-Thawing and Salt Freezing.

Airport pavement concrete often suffers from freeze-thawing damage in high latitude and cold areas. In addition, the use of aircraft deicer makes the airport pavement concrete suffer from salt-freezing damage. To improve the durability of airport pavement concrete, modified polyester synthetic fiber (FC), cellulose fiber (CF), and basalt fiber (BF) reinforced concrete were prepared in this paper. The mechanical strength, pore structure, and frost resistance (freeze-thawing and salt freezing) of fiber-reinforced concrete were investigated. The effects of the combined action of fiber (fiber type and content) and surface treatment methods (spraying silane and impregnating silane) on the frost resistance of concrete were investigated. The results show that the flexural strength of concrete is positively correlated with the elastic modulus of fiber, but has little effect on the compressive strength. Fiber can reduce mass loss and dynamic modulus loss of concrete subjected to frost damage. FC more effectively improved the frost resistance of concrete than CF. After 30 cycles of salt freezing, the spalling amount of concrete sprayed or soaked with silane was decreased by 65.5% and 55.5%, respectively. Adding fiber and impregnating silane reduced the spalled concrete by up to 70.5%. Spraying silane treatment is better than impregnating silane treatment in enhancing the frost resistance of concrete because a better silane condensation reaction is achieved with spraying silane.

Automatic Cardiopulmonary Endurance Assessment: A Machine Learning Approach Based on GA-XGBOOST.

Objective: Among various assessment paradigms, the cardiopulmonary exercise test (CPET) provides rich evidence as part of the cardiopulmonary endurance (CPE) assessment. However, methods and strategies for interpreting CPET results are not in agreement. The purpose of this study is to validate the possibility of using machine learning to evaluate CPET data for automatically classifying the CPE level of workers in high-latitude areas. Methods: A total of 120 eligible workers were selected for this cardiopulmonary exercise experiment, and the physiological data and completion of the experiment were recorded in the simulated high-latitude workplace, within which 84 sets of data were used for XGBOOST model training and36 were used for the model validation. The model performance was compared with Support Vector Machine and Random Forest. Furthermore, hyperparameter optimization was applied to the XGBOOST model by using a genetic algorithm. Results: The model was verified by the method of tenfold cross validation; the correct rate was 0.861, with a Micro-F1 Score of 0.864. Compared with RF and SVM, all data achieved a better performance. Conclusion: With a relatively small number of training samples, the GA-XGBOOST model fits well with the training set data, which can effectively evaluate the CPE level of subjects, and is expected to provide automatic CPE evaluation for selecting, training, and protecting the working population in plateau areas.

Freeze-thaw cycles lead to enhanced colloid-facilitated Pb transport in a Chernozem soil

Freeze-thaw cycles in soils lead to break up of soil aggregates and the formation of dispersible soil colloids. Leaching events following freeze-thaw cycles can therefore mobilize and transport colloids through the soil profile. Here, we investigated the effect of freeze-thaw cycles on the subsequent mobilization of colloids in a Pb contaminated soil, and we quantified the amount of colloid-facilitated Pb transport. Soil contaminated with Pb (250 mg/kg or 1000 mg/kg) was packed into 15 cm tall columns, and the soil water content adjusted to field capacity (0.306 kg/kg). Columns were subjected to freeze-thaw cycles of 12 h freezing at −20 °C followed by 12 h of thawing at 25 °C. Then, the soil columns were leached with distilled water, and the effluent was analyzed for colloids, soluble Pb, and colloidal-bound Pb. Freeze-thaw cycles were found to generate dispersible soil colloids and lead to colloid-facilitated Pb transport. Colloid and Pb mobilization increased with increasing number of freeze-thaw cycles. The majority (83–97%) of the Pb that leached out of the columns was colloid-bound. Our findings suggest that freeze-thaw cycles in high latitude areas can mobilize heavy metals, which are otherwise immobile, through colloid-facilitated transport. More frequent freeze-thaw cycles in high-latitude regions, as predicted by climate change models, thus increases the risk of metal leaching from contaminated soils and can lead to subsequent ground water pollution.