Extreme Distance Research Articles

Particle Equilibrium Method for Crack Propagation Simulation

Crack propagation simulation is constantly of great significance. This study presents the particle equilibrium method (PEM) to achieve this goal. PEM is based on the idealization of the problem domain as an assemblage of distinct particles, which release interaction forces to their surrounding particles. Once the distance between two particles exceeds the extreme distance, a permanent crack will emerge between them. The function of interaction force describes the mechanical response of elastic and plastic materials. The calculated structure attains its final state to the external load when all the particles reach the equilibrium condition of force. A calculation program is developed based on the proposed method’s theory and is applied to three numerical examples with reliable calculation results.

Exotic Abies Species in Czech Provenance Trials: Assessment after Four Decades

Abstract The growth of seven exotic true fir (Abies) species and native Abies alba have been compared in three provenance trials in the Czech Republic, at the relatively advanced ages of 44, 38, and 35 years respectively. A clear differentiation is observable between the species. The closely related species group of A. alba and A. cephalonica appears rather heterogeneous in its phenotypic behavior. A. alba provenances show superiority, but also a high differentiation. Productivity of provenances of A. cephalonica fall behind A. alba; however A. cilicica and A. pinsapo provenances have shown total mortality. The high potential of A. grandis is confirmed by outstanding growth; provenances from the coastal plain in Washington State performed best. A. procera grows slower than A. grandis, but still faster than A. alba provenances. Health risks, extreme ecologic distances of transfer, trend shifts of growth rate, and rank change with age are uncertainties that require necessary caution when selecting provenances for importation. In recent years, public and institutional perceptions concerning the introduction of non-native tree species and provenances has shifted, and the practice is no longer seen as necessarily inappropriate.

RETRACTED ARTICLE: Optimal design of transportation distance in logistics supply chain model based on data mining algorithm

Supply chain management first needs to solve the location problem of distribution center of logistics. At present, the application of the centre-of-gravity method to calculate site selection is relative extensive. Based on the method of extreme distance calculation in the field of data mining technology, a new supply chain distribution center selection method combined with clustering algorithm and the centre-of-gravity selection method was proposed in this paper. In order to avoid the limitation of the traditional centre-of-gravity algorithm, the geographical location price was added to the optimization algorithm as the weight value, and the total cost of the model was calculated; then a “three-segment” data mining clustering algorithm was given to improve the efficiency of clustering calculation and avoid isolation finally, the K-means algorithm, the optimized three-segment algorithm and the hierarchical clustering algorithm and so on were compared, and the simulation calculation was carried out. It can be found that the algorithm of clustering center of gravity of the extreme distance data mining can reduce the cost and is advantageous to solve the problem of the location of the supply chain logistics center of gravity location.

Rare long‐distance dispersal of a marine angiosperm across the Pacific Ocean

AbstractAimLong‐distance dispersal (LDD) events occur rarely but play a fundamental role in shaping species biogeography. Lying at the heart of island biogeography theory, LDD relies on unusual events to facilitate colonization of new habitats and range expansion. Despite the importance of LDD, it is inherently difficult to quantify due to the rarity of such events. We estimate the probability of LDD of the seagrass Heterozostera nigricaulis, a common Australian species, across the Pacific Ocean to colonize South America.LocationCoastal Chile, Australia and the Pacific Ocean.MethodsGenetic analyses of H. nigricaulis collected from Chile and Australia were used to assess the relationship between the populations and levels of clonality. Ocean surface current models were used to predict the probability of propagules dispersing from south‐east Australia to central Chile and shipping data used to determine the likelihood of anthropogenic dispersal.ResultsOur study infers that the seagrass H. nigricaulis dispersed from Australia across the entire width of the Pacific (c. 14,000 km) to colonize South America on two occasions. Genetic analyses reveal that these events led to two large isolated clones, one of which covers a combined area of 3.47 km2. Oceanographic models estimate the arrival probability of a dispersal propagule within 3 years to be at most 0.00264%. Early shipping provides a potential alternative dispersal vector, yet few ships sailed from SE Australia to Chile prior to the first recording of H. nigricaulis and the lack of more recent and ongoing introductions demonstrate the rarity of such dispersal.Main conclusionsThese findings demonstrate LDD does occur over extreme distances despite very low probabilities. The large number of propagules (100s of millions) produced over 100s of years suggests that the arrival of propagules in Chile was inevitable and confirms the importance of LDD for species distributions and community ecology.

Corrections to: Matching biological motion at extreme distances

Corrections to: Matching biological motion at extreme distances

Using Extreme Value Theory for Vehicle Level Safety Validation and Implications for Autonomous Vehicles

Much effort is put right now into how to make autonomous vehicles as capable as possible in order to be able to replace humans as drivers. Less focus is put into how to ensure that this transition happens in a safe way that we can put trust in. The verification of the extreme dependability requirements connected to safety is expected to be one of the largest challenges to overcome in the commercialization of autonomous vehicles. Using traditional statistical methods to validate complete vehicle safety would require the vehicle to cover extreme distances to show that collisions occur rare enough. However, recent research has shown the possibility of using near-collisions in order to estimate the frequency of actual collisions using Extreme Value Theory. To use this method, there is a need for a measure related to the closeness of a collision. This paper shows that the choice of this threat measure has a significant impact on the inferences drawn from the data. With the right measure, this method can be used to validate the safety of a vehicle. This, while keeping the validity high and the data required lower than the state of the art statistical methods.

Fractural structure of thick hard roof stratum using long beam theory and numerical modeling

The thick hard rock (THR) roof of the long-wall mining face is prone to the large-sized cantilever roof, and its sudden fracture will cause serious rock dynamic disasters, such as coal and gas outburst and rockburst. In this study, based on the long beam theory, the initial fracture mechanical model for THR was established, and the first weighting characteristics and extreme fracture step distance were calculated. This study introduced a new technology called deep-hole pre-splitting blasting (DPB) which could break the THR by drilling holes with different depths and angles at different levels of roof rock and then blasting it. Field measurement analysis indicated that the immediate roof and lower thick hard strata were fully collapsed to fill the goaf, and the upper thick hard stratum was effectively cut off. The results showed that mechanical model and drilling holes method and DPB technique were so notably that would lead to a foundation for large-scale popularization and application in a Chinese Mine.

On the maximal and minimal distances of flying-around satellite formation

PurposeThe purpose of this paper is to present the obtained analytic solutions of maximal and minimal inter-satellite distances for flying-around satellite formation.Design/methodology/approachThe relative motion equation is used to express the inter-satellite distance as the function of the orbital elements of two participating satellites for the flying-around satellite formation. Then by taking the derivative of the distance function with respect to the true anomaly, some possible extreme value points are obtained. According to the detailed analysis, the maximal and minimal distance solutions are found. By a reverse process, the expected initial differential orbital elements that generate the required extreme inter-satellite distances are also obtained.FindingsThe maximal and minimal distances of the flying-around formation can be analytically written as the functions of three initial orbital elements differences, i.e. the differential orbital inclination, the differential eccentricity and the differential right ascension. For the given maximal and minimal distances, there are lots of solutions of the initial differential orbital elements, which can produce the expected relative motions.Research limitations/implicationsThe solutions of the maximal and minimal inter-satellite distances are only accurate for the circular or near circular reference orbit. For the elliptic reference orbit, there is a need to develop new methods to find the analytic solutions.Practical implicationsThe results here can be applied to design the factual flying-around formation with dimension requirements in mission analysis stage.Originality/valueBy using the solutions presented in this paper, the engineers can design the expected flying-around formation with required maximal and minimal inter-satellite distances in a very easy way.

Sustainable remote Australian transport for living on country and going out bush

Both the domestic and international academic literature’s analysis of links between transport and wellbeing focuses mainly on urban settings and vulnerable population groups including older people, people with health issues, socio-economically disadvantaged people, or people undergoing more frequent extreme climatic events. While the relationship between remote Australians wellbeing and travelling activities is evident, its complexity still remains an under-researched topic. This is paradoxical when considering that extreme distances, high supply chain costs, limited access to services and to economic participation are well recognised obstacles for sustaining vibrant remote Australian communities. The latest accessibility-driven technological innovations in both the digital and the sharing economies are highly topical in transport projects in urban agglomerations but still a distant reality for remote Australia. There is a need for researching an appropriateness framework of such technologies because of the strong relevance of the multiple outcomes in terms of wellbeing that some of these innovations provide. Furthermore what defines a good quality of life can sometimes be very similar and other times greatly differ between remote and urban contexts. In the light of some recent transport and mobility research this paper analyses the potential connections between more appropriate transport innovations and increasingly resilient remote communities.

Long-term implications of observing an expanding cosmological civilization

AbstractSuppose that advanced civilizations, separated by a cosmological distance and time, wish to maximize their access to cosmic resources by rapidly expanding into the universe. How does the presence of one limit the expansionistic ambitions of another, and what sort of boundary forms between their expanding domains? We describe a general scenario for any expansion speed, separation distance and time. We then specialize to a question of particular interest: What are the future prospects for a young and ambitious civilization if they can observe the presence of another at a cosmological distance? We treat cases involving the observation of one or two expanding domains. In the single-observation case, we find that almost any plausible detection will limit one's future cosmic expansion to some extent. Also, practical technological limits to expansion speed (well below the speed of light) play an interesting role. If a domain is visible at the time one embarks on cosmic expansion, higher practical limits to expansion speed are beneficial only up to a certain point. Beyond this point, a higher speed limit means that gains in the ability to expand are more than offset by the first-mover advantage of the observed domain. In the case of two visible domains, it is possible to be ‘trapped’ by them if the practical speed limit is high enough and their angular separation in the sky is large enough, i.e. one's expansion in any direction will terminate at a boundary with the two visible civilizations. Detection at an extreme cosmological distance has surprisingly little mitigating effect on our conclusions.

Differences in Energy Expenditure Between Genders in Ultra-Endurance Nordic Skiing

PURPOSE: Given the new reclassification options for women serving in the, the purpose of this study was to evaluate sex differences in energy expenditure and body composition data collected during the Alaska Mountain Wilderness Ski Classic. METHODS: Fifteen race participants (8 males and 7 females, aged 31-54) were recruited for the study. Participants completed pre- and post-race body composition scans via dual energy x-ray absorptiometry (DEXA). Participants wore ActiGraph activity monitors around their wrists for the entire duration of their participation in the race. Pack weights were measured prior to the race. RESULTS: There was no difference in time to completion between men and women (ie.,125±20.1 hours and 119.3±18.0 hours, respectively, p=0.6). Pack weights relative to body mass were significantly lower in men (20.7±2.0%) compared to women (25.9±5.4%). Pre- and post-percent fat mass was significantly lower in men (14.8±4.0 and 12.8±3.5) compared to women (19.8±2.7 and 18.0±2.5), respectively. Calculated total energy expenditure for the duration of the race was higher in men (42,679 and 30,861 kcal, men and women, respectively, p=0.002). Energy expended in order to complete the race was proportionate to total weight (body and pack) regardless of gender (R2=0.84). CONCLUSION: Despite the challenge of carrying a heavier pack weight relative to their body mass, the women were able to complete the race in the same amount of time as the men. Previous studies suggest that at extreme distances women may possess a metabolic advantage over men. Further research is warranted to better understand the unique physiological advantages women in the military may offer under similar conditions.

The effect of anthropogenic and biological noise on fish behavior and physiology: A meta-analysis

Aquatic noise has the potential to travel extreme distances and as such many marine species rely on the soundscape for auditory information regarding habitat selection, predator or prey locations, and communication. These species not only take advantage of the prevailing sounds but also contribute to the soundscape through their own vocalizations. Certain sounds have the potential to negatively effect marine species resulting in unbalanced predator-prey interactions and disrupted communication. In an attempt to determine the implications that changes to the soundscape may have on fishes, we conducted a meta-analysis focusing on how anthropogenic and biological noises may alter fish behavior and physiology. We reviewed 3,174 potentially relevant papers of which 44 met our criteria and were used in the analysis. Results indicated that anthropogenic noise has an adverse effect on marine and freshwater fish behavior and physiology. Alternatively biological and environmental noises did not significantly alter fish behavior and physiology. These findings suggest that although certain species may be more susceptible to anthropogenic noise than others, the vast majority of fish have the potential to be negatively affected by noise pollution, while biological noises may not have the same negative consequences for fish behavior and physiology.

Performance and Energy Balance during a 439 Mile Endurance Run

Running for extreme distances or time has become increasingly popular, however, energy balance and its effect on performance is of great concern. PURPOSE: This case study examined the physical performance and energy balance in a 51 year old firefighter completing an 11-day, 439 mile solo run across Texas. METHODS: All food and drink consumed during the 11 day run were recorded to assess energy intake during the run. Energy expenditure and exercise data were recorded via a heart rate/GPS monitor during each run. Nude body weight was recorded each morning. RESULTS: Daily, the subject completed 39.98±2.61 miles (range 33.26-42.98 mi) in 11.2±1.2 hrs (range 9.74-12.97 hrs) at a 16.8±1.3 min/mi pace (range 15.17-18.45 min/mi). Subject consumed 4398±811 kcals per day (range 3280-5617 kcals/day) and expended 3804±271 kcals per run (range 3280-5617 kcals/run). Over the 11 days, the subject lost 2.6 kg of body weight. Total energy expenditure (5397 ± 271 kcal) was greater than energy intake (4398 ± 812 kcal; p=0.005). Over the 11 days, there was a trend towards a slower mile pace (r=0.832, p=0.001). Heart rate was also lower across the 11 days (range: 95 - 137 bpm; p=0.045). There was no change in core body temperature throughout each run (p=0.125 Time x Day interaction) or across the 11 days (p=0.078). On average, capillary lactate levels increased from 2.3 ± 1.3 mmol/L to 6.5 ± 2.3 mmol/L pre to post run (p=0.005). CONCLUSION: Energy balance is important for sustaining the high training and performance levels required for ultra-endurance events. However, the athlete was not able to consume enough calories to remain in energy balance. Nutritional needs assessments during training and competition should be an integral part of the preparation for participation in an ultra-endurance event. Supported by Valdosta State University Faculty Research Seed Grant

Perceptual evaluation of synthetic gaze jitter

AbstractEye movements are an essential part of non‐verbal behavior. Non‐player characters, as they occur in many games, communicate with the player through dialogue and non‐verbal behavior and can have a strong influence on player experience or even on gameplay. In this paper, we evaluate a procedural model designed to synthesize the subtleties of eye motion. More specifically, our model adds microsaccadic jitter and pupil unrest both modeled by 1/fα or pink noise to the saccadic main sequence. In a series of perceptual two‐alternative forced‐choice experiments, we explore the perceived naturalness of different parameters of pink noise by comparing synthesized motions to rendered motion of recorded eye movements at extreme close shot and close shot distances. Our results show that, on average, animations based on a procedural model with pink noise were perceived and evaluated as highly natural, whereas data‐driven motion without any jitter or with unfiltered jitter were consistently selected as the least natural in appearance.

Extreme Mountain Ultra-Marathon Leads to Acute but Transient Increase in Cerebral Water Diffusivity and Plasma Biomarkers Levels Changes

Background: Pioneer studies demonstrate the impact of extreme sport load on the human brain, leading to threatening conditions for athlete's health such as cerebral edema. The investigation of brain water diffusivity, allowing the measurement of the intercellular water and the assessment of cerebral edema, can give a great contribution to the investigation of the effects of extreme sports on the brain. We therefore assessed the effect of supra-physiological effort (extreme distance and elevation changes) in mountain ultra-marathons (MUMs) athletes combining for the first time brain magnetic resonance imaging (MRI) and blood parameters.Methods:This longitudinal study included 19 volunteers (44.2 ± 9.5 years) finishing a MUM (330 km, elevation + 24000 m). Quantitative measurements of brain diffusion-weighted images (DWI) were performed at 3 time-points: Before the race, upon arrival and after 48 h. Multiple blood biomarkers were simultaneously investigated. Data analyses included brain apparent diffusion coefficient (ADC) and physiological data comparisons between three time-points.Results:The whole brain ADC significantly increased from baseline to arrival (p = 0.005) and then significantly decreased at recovery (p = 0.005) to lower values than at baseline (p = 0.005). While sodium, potassium, calcium, and chloride as well as hematocrit (HCT) changed over time, the serum osmolality remained constant. Significant correlations were found between whole brain ADC changes and osmolality (p = 0.01), cholesterol (p = 0.009), c-reactive protein (p = 0.04), sodium (p = 0.01), and chloride (p = 0.002) plasma level variations.Conclusions:These results suggest the relative increase of the inter-cellular volume upon arrival, and subsequently its reduction to lower values than at baseline, indicating that even after 48 h the brain has not fully recovered to its equilibrium state. Even though serum electrolytes may only indirectly indicate modifications at the brain level due to the blood brain barrier, the results concerning osmolality suggest that body water might directly influence the change in cerebral ADC. These findings establish therefore a direct link between general brain inter-cellular water content and physiological biomarkers modifications produced by extreme sport.

Reliability analysis of wake-induced collision of flexible risers

Collision between risers is an important design and operational concern, especially in deep water since the probability of collision tends to increase as the riser length increases. Riser collision is due to the joint effects of many processes, i.e. environmental loads, hydrodynamic interference and surface floater motions and the most of them are stochastic processes. This paper provides an approach for estimating the failure probability of riser collision by considering these joint effects and their stochastic nature. Firstly, a procedure for establishing the distribution function of the extreme minimum relative distance between two risers is introduced based on simulation tools and statistical data. Numerical simulation is performed to compute the minimum distance between risers for a given duration. Repeated simulations are applied so that the extreme value distribution can be established. Secondly, reliability analysis is performed by considering the uncertainties of input parameters related to environmental loads and riser system. The collision probability is calculated based on both the First/Second Order Reliability Method and the Monte Carlo simulation techniques.

A rapid method for calculating maximal and minimal inter-satellite distances

This paper proposes a method to rapidly and effectively calculate the maximal and minimal distances between a pair of satellites in which the leader is in an elliptic orbit. The principal idea of this method is simplifying the nonlinear squared distance function into a Taylor series with limited orders and further fitting the trigonometric functions in the derivative function of the simplified squared distance by piece-wise quadratic polynomials. By solving the zero-crossing points of the fitted quadratic curve, the critical points of the original nonlinear distance function are approximately determined. It turns out that the accuracy of the obtained solutions of the extreme distances depends on the number of intervals of the polynomial fitting. The bigger the number of intervals is, the better the accuracy. However, it is also noticed that the number of intervals is not necessary too big. For real applications a small value (e.g. 8) may be enough for the number of intervals. Besides, the method is apparently more effective for the small eccentricity cases. Finally, some simulations are further carried out to demonstrate the performances of this new method.

Shear-Wave Elastography Assessments of Quadriceps Stiffness Changes prior to, during and after Prolonged Exercise: A Longitudinal Study during an Extreme Mountain Ultra-Marathon.

In sports medicine, there is increasing interest in quantifying the elastic properties of skeletal muscle, especially during extreme muscular stimulation, to improve our understanding of the impact of alterations in skeletal muscle stiffness on resulting pain or injuries, as well as the mechanisms underlying the relationships between these parameters. Our main objective was to determine whether real-time shear-wave elastography (SWE) can monitor changes in quadriceps muscle elasticity during an extreme mountain ultra-marathon, a powerful mechanical stress model. Our study involved 50 volunteers participating in an extreme mountain marathon (distance: 330 km, elevation: +24,000 m). Quantitative SWE velocity and shear modulus measurements were performed in most superficial quadriceps muscle heads at the following 4 time points: before the race, halfway through the race, upon finishing the race and after recovery (+48 h). Blood biomarker levels were also measured. A significant decrease in the quadriceps shear modulus was observed upon finishing the race (3.31±0.61 kPa) (p<0.001) compared to baseline (3.56±0.63 kPa), followed by a partial recovery +48 h after the race (3.45±0.6 kPa) (p = 0.002) across all muscle heads, as well as for each of the following three muscle heads: the rectus femoris (p = 0.003), the vastus medialis (p = 0.033) and the vastus lateralis (p = 0.001). Our study is the first to assess changes in muscle stiffness during prolonged extreme physical endurance exercises based on shear modulus measurements using non-invasive SWE. We concluded that decreases in stiffness, which may have resulted from quadriceps overuse in the setting of supra-physiological stress caused by the extreme distance and unique elevation of the race, may have been responsible for the development of inflammation and muscle swelling. SWE may hence represent a promising tool for monitoring physiologic or pathological variations in muscle stiffness and may be useful for diagnosing and monitoring muscle changes.

Экспериментальное исследование закономерностей испарения капель воды, движущихся последовательно в области высокотемпературных продуктов сгорания

Introduction. The paper presents the results of experimental investigation of cross impact of water droplets in a flow while moving and evaporation in a medium of high-temperature gases, which cor¬respond in temperature to the typical combustion products due to a fire. We considered the sequential schemes of droplet movement and the schemes when the trajectories of droplet movement diverged relative to each other. Materials and methods. The area full of high-temperature (about 1000 K) combustion products was created using the model of fire source (hollow cylinder of height h = 1 m and diameter d = 0.15 m). Droplets moved in the opposite direction of the gas medium. In experiments we applied the tools of high-speed video recording (up to 106 frames per second) and also the optical diagnostic methods of two-phase gas flows (Particle Image Velocimetry, Particle Tracking Velocimetry, Stereoscopic Particle Image Velocimetry, Shadow Photography). Results. In experiments the decrease in typical radius R of water droplets and change in distance Ld between neighboring droplets was the main defining characteristics. From the experiments we deter-mined the velocity variation of droplets moving sequentially, distance, at which the subsequent droplet catches the next one in a flow, and there is a coalescence. The influence of initial distance between neighboring droplets in a flow on their approximation while movement in a channel with high-¬temperature gases at various values of initial speed of droplet was investigated. Also, we determined the impact scale of the vapor trace forming from evaporation of droplets moving ahead on the eva¬pora¬tion intensity of the next droplets. It was revealed that heating and evaporation of the next droplets in a vapor-gas trace of preceding ones are less intense. The influence of initial water temperature on the approach and the coalescence of droplets moving subsequently in a flow of high-temperature gases were determined. It was illustrated that the previous heat-up of water accelerates the droplet coales¬cence in a flow under conditions of relatively short initial distances between droplets. Also, the extreme distances between droplets were defined, in pro-viding which there is a coalescence of droplets when they pass the area of high-temperature combustion products. Conclusions. We illustrated the satisfactory correlation of experimental results with the data of nu¬me¬-rical simulation carried out previously. The theoretical hypothesis about the significant influence of water droplets moving ahead (through high-temperature gases) on the conditions of evaporation and movement of subsequent ones was proved experimentally.

Potentially Extreme Population Displacement and Concentration in the Tropics Under Non-Extreme Warming.

Evidence increasingly suggests that as climate warms, some plant, animal, and human populations may move to preserve their environmental temperature. The distances they must travel to do this depends on how much cooler nearby surfaces temperatures are. Because large-scale atmospheric dynamics constrain surface temperatures to be nearly uniform near the equator, these displacements can grow to extreme distances in the tropics, even under relatively mild warming scenarios. Here we show that in order to preserve their annual mean temperatures, tropical populations would have to travel distances greater than 1000 km over less than a century if global mean temperature rises by 2 °C over the same period. The disproportionately rapid evacuation of the tropics under such a scenario would cause migrants to concentrate in tropical margins and the subtropics, where population densities would increase 300% or more. These results may have critical consequences for ecosystem and human wellbeing in tropical contexts where alternatives to geographic displacement are limited.