Cumulative Change Research Articles

Combining remote sensing and tracking data to quantify species' cumulative exposure to anthropogenic change.

Identifying when and where organisms are exposed to anthropogenic change is crucial for diagnosing the drivers of biodiversity declines and implementing effective conservation measures. Accurately measuring individual-scale exposure to anthropogenic impacts across the annual cycle as they move across continents requires an approach that is both spatially and temporally explicit-now achievable through recent parallel advances in remote-sensing and individual tracking technologies. We combined 10 years of tracking data for a long-distance migrant, (common cuckoo, Cuculus canorus), with multi-dimensional remote-sensed spatial datasets encompassing thirteen relevant anthropogenic impacts (including infrastructure, hunting, habitat change, and climate change), to quantify mean hourly and total accumulated exposure of tracked individuals to anthropogenic change across each stage of the annual cycle. Although mean hourly exposure to anthropogenic change was greatest in the breeding stage, accumulated exposure to changes associated with direct mortality risks (e.g., built infrastructure) and with climate were greatest during the wintering stage, which comprised 63% of the annual cycle on average for tracked individuals. Exposure to anthropogenic change varied considerably within and between migratory flyways, but there were no clear between-flyway differences in overall exposure during migration stages. However, more easterly autumn migratory routes were significantly associated with lower subsequent exposure to anthropogenic impacts in the winter stage. Cumulative change exposure was not significantly associated with recent local-scale population trends in the breeding range, possibly because cuckoos from shared breeding areas may follow divergent migration routes and therefore encounter very different risk landscapes. Our study highlights the potential for the integration of tracking data and high-resolution remote sensing to generate valuable and detailed new insights into the impacts of environmental change on wild species.

Changes in diaphyseal cross-sectional properties with age in macaques.

The present study seeks to quantify changes in long bone cross-sectional properties in a colony of semi-free-ranging rhesus macaques and compare observed aging patterns to those of other primates, including humans. Peripheral quantitative computed tomography was used to obtain midshaft cross sections of the femora, tibiae, humeri, and radii of 115 macaque specimens ranging from 7 to 31 years of age. Linear regressions of cross-sectional properties on age were analyzed. An analysis of covariance was conducted to quantify differences in rates of change between males and females. Results show that medullary area increases while cortical area decreases with age in both sexes. The polar section modulus and the polar strain-strength index, measuring torsional and bending strength, show no decline in most sections but decrease significantly with age in the hindlimb elements of female macaques. Volumetric bone mineral density (vBMD) also decreases with age in both male and female macaques; however, the cumulative change in vBMD over the adult lifespan is relatively small, equivalent to a less than 10% decrease in material strength. An analysis of covariance shows no differences between males and females in the rate of change of properties with age. Overall, this study shows that there are some similarities in the skeletal aging patterns of macaques and those of other primates, including humans, but also some differences, with greater losses of bone found in human females as a result of an extended post-reproductive period that is generally not found among wild or semi-wild macaques.

Ukraine at war: Baseline identity and social construction

AbstractUkrainians' resilience in the face of Russia's 2022 invasion can be explained by cumulative identity change through successive revolutions: the Orange Revolution in 2004, the Maidan Revolution or Revolution of Dignity in 2013–2014 and the current as yet unnamed war. The two phases of the war, from 2014 and 2022, have accelerated both the civic and the social construction of Ukrainian identity. Post‐post‐Soviet Ukraine is now a consolidated civic and political nation. But there is also an increased consensus on traditional nationalist mythology, defined by opposition to Russia's aggressive reimperialisation and autocratic political culture and by Ukraine's hyper‐Europeanisation.

Change in Alcohol Consumption in Adolescence and Emerging Adulthood: A Meta-Analysis.

Most young people start to drink alcohol in adolescence and increase their consumption until their early 20s. The present study meta-analyzed results of longitudinal studies across the age range of 10 to 25 years. A systematic search in the PsycINFO, PSYNDEX, and Web of Science databases resulted in 513 studies that were included in multilevel meta-analysis. On average, alcohol consumption increased by .21 standard deviation units per year, with the strongest increase at age 12 to 13 years. Regarding cumulative change, drinking peaked around 22 years. Drinking started to decline at age 24, with minor changes being observed in 24- and 25-year-olds. Female participants increased their consumption less than their male peers, but gender differences were very small. Weaker increases in drinking were found in countries with higher minimum legal age of buying alcohol. Passing the minimum legal age of 16 years was associated with a stronger immediate increase in drinking compared with countries with higher minimum legal age, whereas passing higher minimum legal ages had no effect on alcohol consumption. In U.S. samples, smaller increases in drinking were observed in more recent studies. Prevention must start before age 12. Passing a low minimum legal drinking age only seems to have a short-term effect on alcohol consumption.

Increased Incidence of Pediatric Uveitis Associated with the COVID-19 Pandemic Occurring Before COVID-19 Vaccine Implementation: A Time-Series Analysis

To examine whether the COVID-19 pandemic was associated with an increased incidence of uveitis in children. We performed a time-series analysis of patient records from a national, hospital-based, French surveillance system. All children hospitalized for uveitis in France between January 2012 and March 2022 were included. The incidence of newly diagnosed uveitis per 100 000 children per trimester in France was analyzed by a quasi-Poisson regression. A cohort of children diagnosed with uveitis at Robert-Debré Hospital was used to compare the characteristics of uveitis after and before the onset of the pandemic. During the study period, 2492 children were hospitalized for uveitis in France. The COVID-19 pandemic, which started in March 2020, was associated with a significant increase in the occurrence of uveitis (estimated cumulative change, 44.9%; 95% CI 11.4-78.4; P<.001). The increase in the incidence of pediatric uveitis started in October 2020, while the national immunization program targeting children aged less than 18years began in June 2021. This increase involved all forms of uveitis, regardless of location, and clincial characteristics were similar to those diagnosed before the pandemic. Our study evidenced a significant increase in the incidence of pediatric uveitis following the COVID-19 pandemic. This increase occurred 6months before the implementation of the national COVID-19 vaccination program for children, suggesting that the resurgence of this rare disease is independent of COVID-19 vaccination.

Ambient climatic factors and term birthweight: A study of critical windows of exposure in the Republic of Cyprus

BackgroundReduced birthweight is associated with adverse perinatal and long-term outcomes. A few studies examined the association between climatic factors and birthweight with inconsistent results probably due to differences in exposure assessment, statistical models, climatic parameters, and study populations. MethodsWe obtained data from the Republic of Cyprus birth registry from 2007 to 2020, and matched climatic exposures (i.e., temperature, relative humidity, temperature variability, humidity variability) by the hospital district at birth. We used distributed lag models to examine the association between term birthweight, temperature, humidity, and their variability to identify critical windows. Our models were adjusted for coarse particulate matter level (≤10 μm [PM10), and individual-level covariates. Subgroup analysis was conducted to examine effect modification by maternal age and education. ResultsWe identified two critical windows of exposure to ambient temperature at early and late pregnancy. The cumulative change of birthweight per 5 °C increases in mean weekly temperature was −57.27 (2%) (95% Confidence Interval [CI]: 99.62 (3.1%), −14.92 (0.5%)) and −79.2 (2.5%) (95%CI: 117.03 (3.5%), −41.52 (1.3%)) grams during weeks 1–8 and weeks 28–37, respectively. There was no significant effect of humidity, temperature variability, or humidity variability on birthweight. Based on subgroup analysis, mothers with post-secondary education were more sensitive to temperature, but the marginal significance of differences in effect estimates may be linked with differences in sample size. ConclusionOur study suggests that higher ambient temperature exposure during early and late pregnancy is associated with lower birthweight in main and subgroup analysis. The findings demonstrate in a country highly impacted by climate change like Cyprus that rising temperatures may be associated with perinatal outcomes in susceptible populations during sensitive windows of exposure.

Policy change in socially embedded local policy processes in São Paulo, 1988–2020

ABSTRACT Policy transformation is a classic theme in policy analysis. Policy models have emphasized the role of actors, coalitions, leadership, and ideas in agenda-setting, the circulation of policy frameworks and solutions, and different mechanisms of gradual institutional change that accumulate in policy trajectories. We sustain that oscillating and incremental policy trajectories also produce policy change during policy implementation, triggered by political competition and partisan politics, the embeddedness of policy communities, and multilevel effects. This theorizing is built from the recent trajectories of social assistance and housing policies in São Paulo. Both trajectories followed incremental processes of expansion and diversification, although with sectoral specificities. These cases show that cumulative positive public policy change may happen even in the face of institutional conditions that the literature considers far from ideal – an extremely fragmented party system, decentralized federalism, and weak bureaucracies and state capacities. Competitive partisan politics reinforced the creation and reanimation of policy innovations under multilevel regulation. Networks of bureaucrats and civil society activists within the relevant policy communities enabled policy replication and reanimation by entering and exiting local administrations depending on their ideological colors.

Yield shortfall of cereals in Ukraine caused by the change in air temperature and precipitation amount

Yield shortfall of cereals in Ukraine caused by the change in air temperature and precipitation amount

The Role of National Green Tribunal on mitigating the effects of Climate Change

Climate change is the worldwide problem facing by all the countries. The main cause behind the climate change is the disturbance of ecology and natural environment. We need an attention for saving our environment by balancing our needs. Climate is the long-term average of a region’s weather events. The earth’s climate is not static. Over the billions of years of earth’s existence, it has changed many times in response to natural causes like sun spot, ice age glaciations etc. Climate change is defined as a change in the climate that may be directly or indirectly linked to human activity that modifies the global atmosphere. This shift is distinct from the natural climate variability that has been documented throughout comparable time periods. The phrase climate change represents a change in the long-term weather patterns. Climate change is not a change of weather in particular day; it is the cumulative change of long-term weather pattern i.e. changes in climate. Climate change is the measurable effect of the continual warming trend. Climate change is usually measured in major shifts in temperature, rainfall, snow and wind patterns lasting decades or more. Humans are creating climate change by burning large amounts of fossil fuels (Coal, oil, natural gas), deforestation. (When forests are cut down or burned, they can no longer store carbon is released to the atmosphere). Gradual rise in sea level, Rise in global temperature, Ocean water getting warmer, Greenland and Atlantic ice sheath are shrinking, Arctic sea ice have also thinned out, Melting of glaciers, Severity in seasons along with the intensity and frequency of climate hazards has greatly increased (floods, heavy rainfall, dry spell, cyclones etc.), Acidification of oceans, Death of corals etc. are nothing but the pure evidences of climate change. These evidence shows two kinds of impacts, that is bifurcated broadly into environmental and agricultural aspect.

#4261 RELATIONSHIP BETWEEN FLUID OVERLOAD AND AVERAGE PLASMA REFILL RATE IN HEMODIALYSIS PATIENTS

Abstract Background and Aims Attaining the optimal balance between achieving adequate volume removal while preserving organ perfusion remains challenging in patients on maintenance hemodialysis (HD). Quantification of fluid status using bioimpedance spectroscopy (BIS) has become routine in many countries. Inadequate vascular space refill from the interstitial tissue (plasma refill rate, PRR) is the main contributing factor of hemodynamic instability during HD. We aimed to explore the association between fluid overload (FO) and plasma refill rate (PRR) in chronic HD patients. Method Pre-HD FO [l] was assessed once per subject by BIS (Body Composition Monitor; Fresenius Medical Care) in four urban HD dialysis clinics in the U.S. For each treatment within 30 days before and after the BIS measurement, we calculated the respective pre-HD FO by assuming that differences in pre-HD body weight were equivalent to differences in FO. We then used intradialytic hematocrit (measured with the Crit-Line® Monitor, Fresenius Medical Care) and ultrafiltration data to quantify the average PRR, normalized by body weight (Wang et al. Kidney360, 2023): To calculate the starting blood volume (BV), we first calculated the ending BV using the Nadler equation, followed by back-calculating the starting BV based on the cumulative change in relative BV. Plasma refill volume was calculated as the sum of the changes in blood volume and ultrafiltration volume; plasma refill volume was then divided by treatment time and estimated clinical dry weight to calculate the PRR [ml/kg/hr]. Results We analyzed 746 HD sessions from 79 patients (age 61 ± 15 years; 52 (66%) males; 41 (52%) black and 33 (42%) white). Across all HD sessions, PRR was positively associated with FO [slope estimate 0.92 (95% confidence interval 0.83 to 1.02) ml/kg/hr per 1 l of FO, P value &amp;lt; 0.0001] (Figure 1). This was also the case in subgroup analyses of fluid depleted (r = 0.94, P&amp;lt;0.001), normohydrated (r = 1.03, P&amp;lt;0.0001), and fluid overloaded subjects (r = 0.83, P&amp;lt;0.0001). Conclusion Across the entire fluid status spectrum, from fluid depletion to fluid overload, higher FO was associated with higher PRR on average (overall, an increase of 0.92 ml/kg/hr in PRR for each additional liter of FO). While patients with greater FO would be expected to better tolerate higher ultrafiltration rates, there is large inter-individual variability in PRR. Further investigation of the utility of PRR throughout HD may offer novel insights into fluid management and intradialytic symptom mitigation.

#6648 LONG TERM EFFECT OF MEDIUM CUT-OFF DIALYZER ON MIDDLE UREMIC TOXINS

Abstract Background and Aims Better removal capacities for middle and large middle molecules in hemodialysis was achieved in (HD) treatment with the new medium cut-off (MCO) membranes. The aim of this study was to evaluate the long term removal efficacy of Theranova® in standard HD in comparison with standard high-flux HD. Method 11 patients were assigned to high flux and 11 to MCO membranes in 12-months observational study. Each patient was assessed every three months from T0 with high-flux dialyzers, T1 to T5 with MCO at first, third, sixth, nineth and twelfth month by measuring pre- and post-HD samples of β2-microglobilin (β2M), myoglobin, albumin, free light chains kappa (FLC-k), and free light chains lambda (FLC-λ). The cumulative change from as RR from T0 to T5 was defined as long term outcome. Results The data showed a higher average removal rate (RR) for all the uremic toxins with Theranova® dialyzers for β2M, myoglobin, FLC-k, and FLC-λ (66.1, 53.2, 59.2.5, and 60.9%, respectively) compared to high flux (57.1, 10.8, 29.9 and 37.4%, respectively). The analyses on the cumulative RR from T0 to T5 found significant decrement of β2M, myoglobin, FLC-λ in MCO vs high flux group where those values significantly raised (14.9 vs −6.1, p = 0.043; 27.7 vs −7.8, p = 0.001; 21.9 vs −4.2, p = 0.017, respectively). The FLC-k showed borderline significantly better removal with MCO (17.8 vs 8.4. p = 0.067). The distribution of patients with 12 month middle molecules reduction was much better in the MCO group. Albumin retention was better in MCO group and did not change between T0 and T5 (p = 0.824). Conclusion Compared to high-flux membranes, MCO membranes show greater permeability for middle molecules and albumin stability in long-term report. Their use in HD standard setting is effective and safe.

Seismicity parameters of Nepal by cumulative slope point change method

Nepal is one of the most seismically active countries with several seismic sources that are capable of generating moderate to high magnitude earthquakes. In this study, earthquake catalogue was developed by considering six major source zones. The completeness time period was determined by performing sensitivity analysis for various magnitude bin widths and time intervals. The seismicity parameters were computed by the least square method (LSM) and maximum likelihood method (MLM). LSM was based on Gutenberg Richter’s scale relationship, whereas for the maximum likelihood method, it was performed by a new method called cumulative slope point change method (CSPCM). The CSPCM was introduced to account the drawbacks of maximum curvature method (MCM), especially for bulk number of data. Furthermore, paper compares the LSM and the MLM for the calculation of seismicity parameters. The comparison shows that the proposed CSPCM based on MLM is reliable in terms of theoretical and analytical way as compared to LSM and MCM.

Henslow’s Sparrow shows positive response to prescribed fire rotation

Abstract We examined Henslow’s Sparrow (Centronyx henslowii) response to prescribed fire at 32 grasslands at Big Oaks National Wildlife Refuge in southeastern Indiana from 1999 to 2009. We burned grasslands in the spring between 1999 and 2007 and monitored Henslow’s Sparrows for up to 4 yr after treatment. We used linear mixed models to analyze our data. Henslow’s Sparrow counts were correlated with time since prescribed fire and grassland size. The estimated changes in mean Henslow’s Sparrow density relative to pre-burn densities were −0.19, 1.15, 0.74, and −0.68 birds ha−1 for 1–4 breeding seasons after a spring burn, respectively. We found that Henslow’s Sparrows preferred larger grasslands both during the first breeding season after prescribed fire, when vegetation was presumed to possess less litter and structural density, and during the fourth breeding season after fire, when vegetation was presumed to be a more ideal composition, but preferred smaller grasslands in the interim. Thus, grassland size shapes the magnitude of Henslow’s Sparrow population response to fire, with populations in smaller grasslands experiencing greater amplitude changes. Larger grasslands might provide more habitat diversity following prescribed fire, attenuating population change. On average, Henslow’s Sparrows responded positively to prescribed fire in a network of grasslands and cumulative net change in densities were highest three breeding seasons after a burn suggesting that maintaining this burn frequency would be beneficial to Henslow’s Sparrow abundance.

Cumulative postoperative change in serum albumin levels and organ failure after living-donor liver transplantation: A retrospective cohort analysis.

Many studies have reported that hypoalbuminemia could be associated with organ failure after liver transplantation. However, most of them focused on serum albumin levels measured at specific time points and not on the trend of serum albumin change. We investigated whether a cumulative postoperative change in serum albumin level up to postoperative day (POD) 5 is related to organ failure in patients who underwent living-donor liver transplantation (LDLT). Data of adult recipients who underwent LDLT between January 2016 and December 2020 at a single tertiary hospital were reviewed (n = 399). After screening, three patients were excluded because of insufficient data. A cumulative change in serum albumin level was demonstrated using the area under the threshold (AUT, threshold = 3.0 g/dL) of the serum albumin curve up to POD 5. Based on the AUT, the patients were divided into a high-decrease group (n = 156) and a low-decrease group (n = 240). All analyses were conducted using 1:1 propensity score matching. The primary endpoint was the Sequential Organ Failure Assessment (SOFA) score on POD 5. The secondary endpoints were postoperative hospital stay and postoperative 90-day mortality. A total of 162 patients were included. The SOFA score on POD 5 was significantly higher in the High-decrease group compared with the Low-decrease group (5.2 ± 2.6 vs. 4.1 ± 2.3; mean difference: 1.1, 95% CI: 0.3 to 1.8; P = 0.005). However, the length of postoperative hospital stay (P = 0.661) and 90-day mortality (P = 0.497) did not differ between the groups. In conclusion, a cumulative postoperative change in serum albumin level up to POD 5 could help predict postoperative organ failure on POD 5 in patients who underwent LDLT.

DISEÑO DE LA COMPOSICIÓN Y PROPIEDADES MECÁNICAS DE ESCORIAS DE MAGNESIO COMPACTADAS PARA BASES DE PAVIMENTOS EN CARRETERAS

Gradation composition is crucial to the performance of pavement bases, and differently structured pavement bases vary greatly in pavement performance. However, the gradation range recommended in the relevant code is large without specific provision for the gradation range of low-strength aggregates, such as magnesium slags, which easily leads to a wide selection range of synthetic gradation and weak guiding significance to practical projects. To solve the optimization problem of magnesium slag aggregate gradation design, skeleton-dense type gradation was constructed using the Bailey and Stone asphalt concrete (SAC) gradation methods with magnesium slag materials as the base aggregate. Then, the design gradation was optimally adjusted through compaction tests in combination with the fragile nature of magnesium slag materials. On this basis, the applicable gradation range of magnesium slag aggregates in engineering was obtained, and the gradation optimization design method for this kind of material was formed. Finally, the compaction characteristics and California bearing ratio (CBR) of magnesium slag aggregates with design gradation and those with local specification recommended gradation were analyzed. The test results show that the compaction process significantly influences the target gradation of magnesium slag aggregates, and the cumulative change rate of aggregate gradation of the median design gradation is 37.12%. The bearing capacity of the design gradation is excellent, and the CBR values of the upper limit and the gradation's lower limit are greater than 60%, meeting the paving requirements of different traffic load grades and structural layers. The CBR value of the design gradation is better than that recommended by the specification, which verifies the reliability of the gradation algorithm proposed in this study. This study can provide a theoretical reference for the gradation calculation of low-strength aggregates applied to roads. Keywords: road engineering, magnesium slag, gradation design, skeleton-dense type gradation, CBR

A Temporal Analysis of the Cost of Aesthetic Surgical Procedures Over the Past Decade in Relation to Consumer Price Indices and the Stock Market

Abstract Goals/Purpose As inflation continues to rise, virtually all consumer markets are affected. However, the effect of these increases on aesthetic surgical procedures are not well defined. An important relational understanding of these effects can help aesthetic practices offer fair market prices to benefit both patients and practices alike. The purpose of this study was to quantify temporal changes in pricing for the most common aesthetic surgeries and to make comparisons to various indices of inflation and the stock market. Methods/Technique Annual surgical fees for 18 aesthetic plastic surgery procedures were collected from 2007 to 2020 using the ASAPs and ASPS yearly plastic surgery statistic reports. In addition, annual consumer price indices (CPI) for all items, physicians’ services, and hospital services were collected from the U.S Bureau of Labor Statistics. Finally yearly Dow Jones Industrial (DJI) Averages were collected during the same time frame. Correlation statistics, generalized additive models, and parametric tests were performed to understand the relationships of these surgical costs to other indices. Results/Complications A total of 322 annual measurements were collected for analysis. The cumulative percent change from 2007 to 2020 was highest for rhytidectomy, blepharoplasty, and otoplasty 38.1%, 33.4%, and 30.4%, respectively. Liposuction had the lowest overall cumulative percent change at -10.0%. Kendall correlation test revealed that out of all surgeries, male gynecomastia had the strongest correlation with time, Tau= 0.74, p=0.001. Breast augmentation, blepharoplasty, and abdominoplasty also correlated with time. When comparing the temporal change in prices to the various indices through nonparametric general additive modeling, breast augmentation, blepharoplasty, facelift, and liposuction costs changed at a statistically different rate than the overall CPI of all items, p=0.035, 0.018, 0.012, and &amp;lt;0.001, respectively. In contrast, rates of price changes in rhinoplasty, buttock lift, and breast lift surgery have not differed significantly from that of the CPI. The DJI has grown at rates far greater than the price of any aesthetic surgery procedure and models have been statistically different. Conclusion While over the past decade aesthetic surgery costs have changed, certain procedure costs such as the rhytidectomy have greatly increased, while others have modestly increased, and liposuction has even decreased. Interestingly, the cost for the majority of the most performed aesthetic procedures are not greatly impacted by inflation. This suggests that other forces such as supply and demand may have a greater impact on price changes over the years. Many surgical procedures however were found to have similar rates of price change as the CPI, suggesting that these surgeries and their costs are more vulnerable to inflationary adjustments. Furthermore the price changes of aesthetic surgeries seem to be independent of how the stock market fluctuates and therefore possibly independent of other markets as a whole. This study has several limitations, with the data source as its greatest. The ASPS and ASAPs statistic reports are based on surveys from national members and computational adjustments, which have inherent biases and can vary significantly in any given year. Furthermore the various modeling and statistical analyses performed herein were based on several assumptions and estimates. An understanding of the price trends in aesthetic surgery over time and in relation to consumer price indices and the DJI can help plastic surgery practices and patients better appreciate the economics surrounding aesthetic surgeries.

The Use of Historical Data and Global Climate Models to Assess Historical and Future Surface Water and Groundwater Availability in the Trinity River Basin in Texas

This paper describes the results of a study that was done by the USGS to assess recent (2017) water availability, forecast long-term trends in water availability, assess changes in water availability, and forecast future water availability in the Trinity River Basin in Texas. The Trinity River Basin surface water model and Trinity River alluvium aquifer (TRAA) groundwater model were created to evaluate future conditions under different global climate models (GCM). The results of this study show minimal overall changes in water availability for both surface water and groundwater. Trend analyses using historical data (1900–2017) indicated an increase of annual precipitation on the watersheds that drain into the reservoirs in Regional Water Planning Group C. However, the Trinity River Basin surface water model GCM ensemble mean annual precipitation indicates a downward trend, resulting in a downward trend in surface runoff. Additionally, the GCM ensemble mean for the Trinity River Basin surface water model and the TRAA groundwater model both indicate a downward trend in recharge while the TRAA model GCM ensemble mean indicates an upward trend in the amount of groundwater leaving the aquifer to rivers and streams resulting in an upward trend of cumulative storage change.

Investigation of the Microseismic Response Characteristics of a Bottom Structure’s Ground Pressure Activity under the Influence of Faults

To further understand the changing pattern of the bottom structure’s ground pressure activity under the influence of faults, predicting the potential occurrence of geological hazards and rock blast problems to reduce the loss of resources is important. A new microseismic monitoring system was established based on the original Pulang copper mine microseismic monitoring system. This paper analyzed the change law of the microseismic events on the fault in the first mining area of the Pulang copper mine, calculated the cumulative apparent volume and energy index changes of the microseismic events near the fault base, and quantitatively analyzed the microseismic event anomalies under the influence of the fault. The results show that rupture of the rock makes the cumulative apparent volume and energy index change significantly, while the timeliness of both makes the cumulative apparent volume predictive of the occurrence of rock fracture and rockburst, and the number of microseismic events corresponds to the intensity of the fault activation, which plays a predictive and guiding role in the subsequent study of fault activation, stability monitoring, and safe production in the mine area of Pulang copper mine.

Analysis of Low-Temperature Rheological and Mechanical Properties of Steel Slag Asphalt Mixture Based on Direct Tensile Test

Due to the high resource requirements for specimen preparation and testing equipment, the direct tensile test method is seldom used to study the cracking behavior of asphalt mixture at low temperatures. In this study, three asphalt mixtures were prepared in which all of the basalt or part of the basalt and basalt aggregate was replaced by steel slag. Through the direct tensile creep test and direct tensile relaxation tests including the measurement of creep rate, cumulative strain change rate, and relaxation time, the variation law of rheological properties of low-temperature steel slag asphalt mixture was analyzed and the variation law of viscoelastic properties was explored. Meanwhile, based on the traditional viscoelastic constitutive model, the creep compliance and relaxation modulus were fitted. The mechanical response of the transformation from creep compliance to relaxation modulus of steel slag asphalt mixture was analyzed by a numerical method. The results show that, with the decrease of temperature, the creep rate εs and cumulative strain change rate of the three asphalt mixtures gradually decline, and the relaxation time gradually increases. In particular, when the temperature was reduced from −20°C to −30°C, the cumulative strain change rate of all three asphalt mixtures reached the minimum, which was less than 10%. Moreover, none of them relax to 75% σ0 within 3,600 s at −30°C. The mixture specimens with steel slag replacing all basalt exhibited the best low-temperature deformation adaptation performance under different temperature conditions. Mixture specimens with basalt as aggregate have the worst low-temperature deformation adaptation performance. The relaxation modulus obtained by the measurement of creep compliance is similar to that obtained by testing, and the relaxation modulus calculated through the direct tensile test is more accurate.

Evaluation of High-Temperature and Antireflection Cracking Performance of Warm Mixed Recycled Asphalt Mixture

To study the influence of temperature and reclaimed asphalt pavement (RAP) content (0%, 30%, 50%, and 70%) on the high-temperature performance and anti-reflection cracking performance of warm-mix recycled asphalt mixture, triaxial repeated creep tests and overlay tests (OT) based on digital image correlation technology (DIC) were used to analyze the high temperature and anti-reflection cracking performance of recycled asphalt mixtures. Based on the improved Burgers model, a permanent deformation (PD) model was established to evaluate the high-temperature performance of recycled asphalt mixtures. The anti-reflection cracking performance of recycled asphalt was quantitatively analyzed from macro and meso perspectives by using a macro index (load loss rate) and a meso index (vertical strain density DE). In addition, a reflection cracking damage model was developed by cumulative load loss rate relative change rate, and the fractal characteristics of reflection cracks were studied according to the fractal theory. The results show that with an increase in RAP content, the anti-deformation ability of a recycled asphalt mixture is enhanced, and the anti-reflection cracking performance becomes worse. However, with an increase in temperature, the anti-deformation ability of recycled asphalt mixture is weakened, and the anti-reflection cracking performance is enhanced. A PD mechanical model can well describe the high-temperature deformation resistance of recycled asphalt mixtures. The established reflection cracking damage model has high fitting accuracy and accurately describes the reflection cracking damage evolution process of recycled asphalt mixture. In addition, the analysis of the fractal characteristics of reflection cracks shows that the reflection cracks of a recycled asphalt mixture have fractal characteristics of statistical significance. DIC technology can be used to evaluate the anti-reflection cracking performance of recycled asphalt mixtures qualitatively and quantitatively from the mesoscopic perspective, which makes up for the current deficiency in macroscopic evaluation.