Resource Fluctuations Research Articles

Toward Low-Latency and High-Quality Adaptive 360$^\circ$ Streaming

Advanced 360-degree video streaming is essential for high-quality communication and industrial video applications, supporting novel and interactive visual experiences that promote consumption. However, due to the inherent fluctuations in communication networks, hardware resources, and power costs, a trade-off needs to be achieved between occupying network bandwidth and guaranteeing 360-degree visual quality. To address this issue, this paper proposes a quality-aware global optimization solution that combines different types of sensory characteristics to further enhance the 360-degree streaming efficiency in cellular networks. First, considering the characteristics of 360-degree video, each frame is divided into three different regions based on a proposed field-of-view (FoV) prediction method. Second, a new region-based rate-distortion model reflecting the bitrate-quality relationship is proposed. The divided regions are represented by different rate-distortion models. In addition, a rate-distortion model parameter update strategy with robustness to region changes is proposed to further guarantee transmission performance. Finally, we propose a globally optimized adaptive bitrate allocation algorithm to optimize 360-degree mobile streaming, which uses both the rate-distortion models and viewpoint prediction results. Evaluation results indicate that the proposed method outperforms state-of-the-art approaches in terms of several quality of experience (QoE) objectives under various network conditions.

Long‐term fluctuations and mechanisms of seed production of riparian tree canopy species

AbstractAnnual seedfall was measured over a 24‐year period for three canopy species, Fraxinus platypoda, Pterocarya rhoifolia, and Cercidiphyllum japonicum, in a riparian forest in the Chichibu Mountains, central Japan. We collected seeds from 20 traps approximately every month, except in the winter. Fraxinus platypoda and P. rhoifolia seedfall fluctuated, with a 2‐year cycle. The seedfall of C. japonicum also fluctuated, but this species produced seeds every year, with an approximate 4‐year cycle. The simple moving average over 5 years for F. platypoda and P. rhoifolia was maintained at a constant level over the 24‐year period, but it gradually increased for C. japonicum. Each year's seedfall for the three species was influenced by the previous year's seedfall. The results for F. platypoda suggest that the fluctuations in the amount of seedfall were almost entirely dependent on fluctuations in stored resources, regardless of the previous year's weather. Conversely, the amount of seedfall for P. rhoifolia and C. japonicum was influenced by fluctuations in stored resources and the average temperature or precipitation in the summer of the year before flowering. These differences in seed production patterns were associated with differences in life history characteristics such as seed size and regeneration mechanisms.

The Alien Invader, Rhus typhina L., Outperforms Its Native Competitor in the Scenario of Nitrogen Deposition and Arbuscular Mycorrhizal Fungi (AMF) Inoculation

Nitrogen deposition has been proven to facilitate the establishment of alien plants. Previous studies have certified that nitrogen deposition enhances the resource availability of habitats and promotes the growth of alien invaders. Arbuscular mycorrhizal fungi (AMF) symbiose with vascular plants and assist plants in nutrient acquisition. AMF colonization has been proven to be another driving factor of plant invasion. However, few studies have integrated nitrogen deposition and AMF inoculation into the exploration on invasion mechanism. Based on a trait approach, the present study subjected the alien invader, Rhus typhina L., and its co-occurring native species, Acer truncatum Bunge, to nitrogen deposition and AMF inoculation and compared the phenotypic variation in aboveground and belowground traits in an inter-specific competition experiment. Through the effects of different nitrogen deposition and AMF infection on the functional traits of R. typhina and A. truncatum, the effects of mycorrhizal symbiosis between R. typhina and A. truncatum on abiotic factors and interspecific relationships were analyzed. We found that inter-specific competition stimulated the colonization of AMF in R. typhina, however, decreased the colonization rate of AMF in A. truncatum. Correspondingly, inter-specific competition significantly reduced the plant growth of A. truncatum as the aboveground morphological traits including plant height and crown area, and belowground traits including root length, root surface area, root volume, number of root tips, number of root tip branches and number of root cross decreased for A. truncatum. Nitrogen deposition promoted the shoot growth of R. typhina rather than that of A. truncatum. AMF inoculation significantly affected the belowground traits of A. truncatum as the root length and root surface area significantly decreased after AMF inoculation in the mixture planting of the two species. The chlorophyll content of A. truncatum decreased without AMF inoculation, while nitrogen deposition enhanced the net photosynthetic rate of R. typhina. The alien invader R. typhina outperforms its native competitor in the simulated scenario of resource fluctuation and facilitates its establishment. We speculate that AMF colonization promotes the extension of R. typhina rhizosphere and, thus, accelerates the growth and invasion of R. typhina.

Feast to famine: Sympatric predators respond differently to seasonal prey scarcity on the low Arctic tundra.

Resource fluctuation is a major driver of animal movement, influencing strategic choices such as residency vs nomadism, or social dynamics. The Arctic tundra is characterized by strong seasonality: Resources are abundant during the short summers but scarce in winters. Therefore, expansion of boreal-forest species onto the tundra raises questions on how they cope with winter-resource scarcity. We examined a recent incursion by red foxes (Vulpes vulpes) onto the coastal tundra of northern Manitoba, an area historically occupied by Arctic foxes (Vulpes lagopus) that lacks access to anthropogenic foods, and compared seasonal shifts in space use of the two species. We used 4 years of telemetry data following 8 red foxes and 11 Arctic foxes to test the hypothesis that the movement tactics of both species are primarily driven by temporal variability of resources. We also predicted that the harsh tundra conditions in winter would drive red foxes to disperse more often and maintain larger home ranges year-round than Arctic foxes, which are adapted to this environment. Dispersal was the most frequent winter movement tactic in both fox species, despite its association with high mortality (winter mortality was 9.4 times higher in dispersers than residents). Red foxes consistently dispersed toward the boreal forest, whereas Arctic foxes primarily used sea ice to disperse. Home range size of red and Arctic foxes did not differ in summer, but resident red foxes substantially increased their home range size in winter, whereas home range size of resident Arctic foxes did not change seasonally. As climate changes, abiotic constraints on some species may relax, but associated declines in prey communities may lead to local extirpation of many predators, notably by favoring dispersal during resource scarcity.

АНАЛИЗ ПРОБЛЕМ В ПЛАНИРОВАНИИ ИРАКСКОГО ТОПЛИВНО-ЭНЕРГЕТИЧЕСКОГО СЕКТОРА: ИССЛЕДОВАНИЕ В MIDLANDS OIL COMPANY (БАГДАД)

In this article, the authors try to analyze the problems of planning in the Iraqi fuel and energy sector, focusing on the example of one enterprise (company) of the Iraqi oil industry. The main problem lies in the weak planning of an effective oil policy in Iraq in the field of oil and gas production and export, weak development of oil infrastructure. This leads to fluctuations in Iraqi oil and gas resources under price pressure, despite the huge volume of these resources and the huge revenues generated from them. The problems of planning are considered on the example of the Midlands Oil Company. Based on the results of the analysis, measures are proposed to improve the efficiency of Midlands Oil Company.

Neophyte invasions in European heathlands and scrub

Human-assisted introduction of alien plants is causing ecosystem transformations worldwide and is considered an important threat to biodiversity. We provide a European assessment of habitat levels of invasion in heathlands and scrub and identify successful alien plants and invasion trends across biogeographical regions. We analysed a geographically stratified data set of 24,220 dwarf shrub and scrub vegetation plots sampled across Europe. Among the 6547 vascular plant taxa occurring in these plots, we identified 311 neophytes (4.8%, i.e. alien species introduced in Europe or its sub-regions after 1500 AD) and compared five metrics of the level of invasion in (i) EUNIS habitats, (ii) broad habitat groups and (iii) biogeographical regions of Europe. We related habitat-specific levels of invasion to elevation and climatic variables using generalized linear models. Among neophytes, phanerophytes of non-European origin prevailed. The most frequent neophytes in the plots were Prunus serotina, Robinia pseudoacacia and Quercus rubra among phanerophytes, Impatiens parviflora among therophytes, and Erigeron canadensis and Solidago gigantea among hemicryptophytes. Levels of invasion significantly differed among habitats and biogeographical regions. The most invaded habitat was Macaronesian lowland scrub, followed by riparian scrub, Rubus scrub and forest-clearing scrub of temperate Europe, and coastal dune scrub of the Atlantic region. The levels of invasion were low in the shrublands of the Arctic and Mediterranean regions and decreased with elevation within habitats. Results suggest that insularity, low elevation, frequent disturbances, and high availability or considerable fluctuation of resources promote neophyte invasions in European shrublands.

A feedforward-feedback control strategy based on artificial neural network for solar receivers

In a solar power tower plant, the stability of the receiver’s outlet temperature is required for high-efficiency and safe operation. However, the dramatic variation of solar energy caused by clouds is a severe challenge for keeping the temperature steady at the outlet. To solve this problem, a feedforward-feedback control strategy based on an artificial neural network is proposed herein to cope with the fluctuation of solar energy by regulating the receiver’s mass flow rate. The feedforward controller based on artificial neural network can quickly respond to the change of solar energy, while the feedback controller can make the receiver achieve an expected ultimate temperature. The performance of the proposed control strategy is comprehensively evaluated and compared with PID controller under different conditions. The results show that the proposed control strategy can significantly reduce the fluctuation of receiver’s outlet temperature. For the step variation of direct normal irradiance ranging from −15 % to 15 %, the proposed control strategy can confine the temperature deviation within ± 1 °C. For the real dramatical and continuous direct normal irradiance variation, the temperature deviation is limited to 5 °C under the proposed control strategy, while it exceeds 30 °C under the PID controller only. The results provide an alternative efficient strategy for the receiver’s mass flow control to keep a steady outlet temperature under the fluctuation of the solar resource.

Ecologically driven differences in individual diet specialization across three populations of Guiana dolphin.

Populations usually considered foraging generalists may include specialized individuals that feed on a restricted subset of the prey spectrum consumed by the population. By analyzing the time series of δ13C and δ15N values in sequential growth layer groups within tooth dentin, we measured population- and individual-level variation in resource use of three populations of Guiana dolphins (Sotalia guianensis)-Caravelas River, Babitonga Bay, and Norte Bay-along a latitudinal gradient in the southwestern Atlantic Ocean. We show that the Guiana dolphin at Caravelas River is a generalist population consisting of individual dietary specialists, likely due to the absence of other resident dolphin populations thus allowing individuals to target prey across a wide range of habitats. The Babitonga Bay population is also composed of individual specialists potentially due to the selective foraging behavior of some individuals on high-quality prey sources within and near the bay. In contrast, the Norte Bay population comprises individual generalists, which likely reflects its distinctive cohesive social organization, coexistence with two other dolphin species, and an opportunistic foraging strategy in response to resource fluctuations inherent to the southern limit of the species distribution. Although the Guiana dolphin is generally considered to be a dietary generalist at the population level, our findings reveal that the total niche width of populations and the degree of individual diet specialization are highly context dependent, suggesting dietary plasticity that may be related to a latitudinal gradient in resource availability and environmental conditions.

Optimal Scheduling of a Hydrogen-Based Energy Hub Considering a Stochastic Multi-Attribute Decision-Making Approach

Nowadays, the integration of multi-energy carriers is one of the most critical matters in smart energy systems with the aim of meeting sustainable energy development indicators. Hydrogen is referred to as one of the main energy carriers in the future energy industry, but its integration into the energy system faces different open challenges which have not yet been comprehensively studied. In this paper, a novel day-ahead scheduling is presented to reach the optimal operation of a hydrogen-based energy hub, based on a stochastic multi-attribute decision-making approach. In this way, the energy hub model is first developed by providing a detailed model of Power-to-Hydrogen (P2H) facilities. Then, a new multi-objective problem is given by considering the prosumer’s role in the proposed energy hub model as well as the integrated demand response program (IDRP). The proposed model introduces a comprehensive approach from the analysis of the historical data to the final decision-making with the aim of minimizing the system operation cost and carbon emission. Moreover, to deal with system uncertainty, the scenario-based method is applied to model the renewable energy resources fluctuation. The proposed problem is defined as mixed-integer non-linear programming (MINLP), and to solve this problem, a simple augmented e-constrained (SAUGMECON) method is employed. Finally, the simulation of the proposed model is performed on a case study and the obtained results show the effectiveness and benefits of the proposed scheme.

Stable seasonal migration patterns in giant pandas.

A critical function of animal movement is to maximize access to essential resources in temporally fluctuating and spatially heterogeneous environments. Seasonally mediated resource fluctuations may influence animal movements, enabling them to track changing resource distributions, resulting in annual migration patterns. The conservation-dependent giant panda ( Ailuropoda melanoleuca) displays seasonal movement patterns; however, the key factor driving these seasonal migration patterns remains poorly understood. Here, we used GPS tracking collars to monitor the movements of six giant pandas over a 12-year period across different elevations, and performed statistical analysis of seasonal migration directions, routes, habitat revisitation, home range overlap, first arrival events, and stability. Our results revealed a compelling pattern of seasonal migrations that facilitated the ability of the pandas to forage at the appropriate time and place to maximize nutritional intake. Our results indicated that pandas utilize spatial memory to locate reliable food resources, as evidenced by their annual return to the same or similar winter and summer home ranges and the consistently maintained percentage of home range overlap. These novel insights into giant panda foraging and movement ecology not only enhance our understanding of its ability to adapt to nutritionally poor dietary resources but also provide important information for the development of resource utilization-based protection and management strategies.

Applications of Biophysical Modeling to Pacific High-Latitude Ecosystems

The high-latitude Pacific is home to highly productive ecosystems, including vast populations of commercially and subsistence harvested fish. These regions can be challenging to sample directly. Over several decades at the NOAA Pacific Marine Environmental Laboratory, we have applied numerical models to infer past, present, and future states of these regional oceans and their biota. These estimates are provided to fisheries scientists to help identify the local biophysical dynamics that underlie marine resource fluctuations and to managers to help develop effective management strategies in the face of short- and long-term environmental changes.

Analysis of livelihood security of tribal farmers

Agriculture is the backbone of India and it has traditionally been viewed as a source of subsistence living and livelihood by growing food crops like rice, maize, wheat, millets and pulses etc. The livelihoods among tribal communities in India is complex, dynamic and multidimensional phenomenon, the perception of which varies with geographic location, type of community, age, gender, education, fluctuations in resources, services and infrastructures and social, economic, cultural, ecological and political determinants. The present investigation was carried out in six purposively selected talukas of Tapi district of Gujarat State. From each selected taluka, two villages were selected randomly and from each village, 10 tribal farmers were selected randomly, making the total sample of 120 respondents. An interview schedule was developed in accordance with the objectives of the study. The data were collected through personal interview and were classified, tabulated and analyzed. The study concluded that around half of the respondents were having low level of livelihood security. Except for the Livestock possession variable, respondents’ livelihood security was found to be significant.

Genetic variation of the small yellow croaker (Larimichthys polyactis) inferred from mitochondrial DNA provides novel insight into the fluctuation of resources

Genetic variation of the small yellow croaker (Larimichthys polyactis) inferred from mitochondrial DNA provides novel insight into the fluctuation of resources

Environmental-related variation of stoichiometric traits in body and organs of non-native sailfin catfishes Pterygoplichthys spp.

Intraspecific variation in stoichiometric traits was thought to be an adaptive response to reduce the elemental imbalance between organism and diet in the habitat. Studying the spatial variation of stoichiometric traits of non-native species and the factors contributing to the variation could help to better understand the invasion mechanism of non-native fish. In this study, stoichiometric traits (i.e. carbon [C], phosphorus [P], calcium [Ca] and their ratios) variation in the body and organs of non-native sailfin catfishes Pterygoplichthys spp. were investigated across 13 river sections in the main river basins of Guangdong province. The relationships between environmental factors and stoichiometric traits were analyzed using a general linear model and an information-theoretic approach. A manipulated feeding experiment was conducted to investigate the impact of food quality on the stoichiometry of sailfin catfishes in a greenhouse. Sailfin catfishes exhibited considerable variability in body and organ elemental composition. Site identity was the main factor contributing to the variation, which could be explained by a combination of environmental factors including climate, diet quality, fish species richness and trophic status in the invaded rivers. Water chemistry (i.e. total nitrogen and phosphorus, ammonia nitrogen and soluble reactive phosphorus) contributed to the most variation of stoichiometric traits. Imbalances of P and Ca between sailfin catfishes and food resources varied among sampling sites, reflecting the spatial heterogeneity of nutrients limitation. Juvenile sailfin catfishes exhibited stoichiometric homeostasis (0 < 1/H < 0.25) for all elemental contents and ratios in the feeding experiment. These findings suggested variation in stoichiometric traits of sailfin catfishes might be attributed to the changes in elemental metabolism to cope with context-specific environments. This study provided heuristic knowledge about environmental-related variation in stoichiometric traits, which could enhance the understanding of the non-native species' adaptation to resource fluctuation in the invaded ecosystems.

Genetics reveals shifts in reproductive behaviour of the invasive bird parasite Philornis downsi collected from Darwin’s finch nests

Due to novel or dynamic fluctuations in environmental conditions and resources, host and parasite relationships can be subject to diverse selection pressures that may lead to significant changes during and after invasion of a parasite. Genomic analyses are useful for elucidating evolutionary processes in invasive parasites following their arrival to a new area and host. Philornis downsi (Diptera: Muscidae), the avian vampire fly, was introduced to the Galápagos Islands circa 1964 and has since spread across the archipelago, feeding on the blood of developing nestlings of endemic land birds. Since its discovery, there have been significant changes to the dynamics of P. downsi and its novel hosts, such as shifting mortality rates and changing oviposition behaviour, however no temporal genetic studies have been conducted. We collected P. downsi from nests and traps from a single island population over a 14-year period, and genotyped flies at 469 single nucleotide polymorphisms (SNPs) using restriction-site associated DNA sequencing (RADSeq). Despite significant genetic differentiation (FST) between years, there was no evidence for genetic clustering within or across four sampling years between 2006 and 2020, suggesting a lack of population isolation. Sibship reconstructions from P. downsi collected from 10 Darwin’s finch nests sampled in 2020 showed evidence for shifts in reproductive behaviour compared to a similar genetic analysis conducted in 2004–2006. Compared with this previous study, females mated with fewer males, individual females oviposited fewer offspring per nest, but more unique females oviposited per nest. These findings are important to consider within reproductive control techniques, and have fitness implications for both parasite evolution and host fitness.

Plant dependency and risk management in the Andean Puna during the Mid to Late-Holocene

The archeology of the Puna, a high elevation desert in South America, gives us a long-term perspective on the role of wild plants in people’s diets during the Holocene. We explore the impact of aridification on the use of edible wild plants among desert people through the study of macrobotanical remains. Our goal is to examine the variation in plant dependency and risk management strategies used over time, in particular during the drought of the Middle Holocene (ca. 8700–4500 BP). The macrobotanical record suggests the use of risk-averse strategies in order to cope with unpredictable resource productivity. Hunter-gatherers relied on carbohydrate rich resources from the vega wetlands and tolar shrublands, such as roots and tubers, as well as low-ranked seeds, stems, leaves, and fruits. They also obtained non-local edible plants by strengthening ties and forming safety nets with groups living in different ecozones that were not subject to the same resource fluctuation. Social interaction with areas lying beyond the ecological boundaries of the Puna has a longstanding tradition in this area beginning in the Early Holocene, and was likely a means of providing food security to populations whose subsistence depended mainly on camelid hunting, and eventually camelid pastoralism. A notable increase in that interaction began during the Late-Holocene, which was a period of lesser aridity, with the introduction of corn and quinoa.

Effects of meteorological droughts on water resources in Northern Morocco: Case study of the Martil watershed

Recent droughts in the Northern Morocco have highlighted the increasing vulnerability of water resources to this natural hazard, with reduced potential for drinking water supply in the city of Tetouan and its coastal area. Therefore, the main objectives of this work are: the identification of dry events that affected the Martil watershed on the one hand, and the study of the effects of meteorological droughts on water resources on the other hand. For this purpose, a meteorological-hydrological modelling framework was adopted, using standardized precipitation index (SPI) values and the volume of surface water resources recorded at the Torreta station. The results obtained show that the last decade of the 20th century and the beginning of the 21st century have seen the heaviest and most critical droughts in the study area, namely the drought of 1994-95, 1998-99, 2004-05, 2006-07, 2011-12 and 2013-14. Also, water resources have been reduced by 62% to 82% during critical dry years compared to the long-term average for the period 1970-71/2014-15. Finally, this study showed that the rainfall variability is the determining factor in the fluctuations of surface water resources at the Martil watershed because it explains 84% of their total variance.

Stage Specific food consumption and utilization by the Mexican beetle, Zygogramma bicolorata Pallister (Coleoptera: Chysomelidae) on Parthenium hysterophorus Linnaeus

The food is the foremost need for the existence of all living organisms and the fluctuations in its availabilitystrongly affects the population dynamics of both the primary and secondary consumers. In the presentstudy we have investigated the effect of food (Parthenium weed) resource fluctuations, in terms of quality,on the feeding attributes of the Parthenium beetle, Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae).Quantitative food utilization indices were measured in different larval instars and physiological ages ofadult Zygogramma bicolorata Pallister. Among the larval and adult stages of the beetle, third instar larvaeand egg laying females ingested maximum food. Various growth parameters like relative consumptionrate (RCR), relative growth rate (RGR) and approximate digestibility (AD) were relatively higher in thefirst, third and fourth instar and egg laying females. Efficiency of conversion of ingested food (ECI) andefficiency of conversion of digested food (ECD) were maximum in first, third and fourth instar larvae anddecreasing trend was observed in second instar larvae. During pre-oviposition stage adult, these parametersincreased tremendously in contrast to senescent stage. However, the fourth instars had higher feedingattributes than the adult females, proving them to be the better bio-control agents of Parthenium weed thanthe adult females. However, field based studies are still needed to validate the present findings.

A surface water mapping framework combining optical and radar remote sensing and its application in China

Satellite remote sensing provides an efficient pathway to map inland surface water extent across different spatial and temporal scales. However, how to monitor the surface water distribution and its spatiotemporal variability via combining optical and radar remote sensing datasets still faces substantial challenges. In this study, we propose a Seamless Surface Water Mapping Framework (SSWMF) which synergizes both optical (MODIS, Landsat 8, Sentinel-2) and SAR (Sentinel-1) imageries. The validity of SSWMF was first proved over the middle and lower reaches of the Yangtze River of China with abundant lake resources, showing an overall accuracy of 90.72%, and the results indicate that SSWMF can provide surface water map with higher spatial and temporal continuity compared to the Joint Research Centre Global Surface Water dataset. Multi-source validation showed that the SSWMF-derived surface water maps can well capture the temporal fluctuation and spatial heterogeneity of water resources over China, with an overall accuracy of 92.39%. Overall, our results suggest that the proposed water mapping framework is promising and is readily applicable to large-scale water resource management and drought/flood monitoring.

Energetic consequences of resource use diversity in a marine carnivore.

Understanding how intraspecific variation in the use of prey resources impacts energy metabolism has strong implications for predicting long-term fitness and is critical for predicting population-to-community level responses to environmental change. Here, we examine the energetic consequences of variable prey resource use in a widely distributed marine carnivore, juvenile sand tiger sharks (Carcharias taurus). We used carbon and nitrogen isotope analysis to identify three primary prey resource pools-demersal omnivores, pelagic forage, and benthic detritivores and estimated the proportional assimilation of each resource using Bayesian mixing models. We then quantified how the utilization of these resource pools impacted the concentrations of six plasma lipids and how this varied by ontogeny. Sharks exhibited variable reliance on two of three predominant prey resource pools: demersal omnivores and pelagic forage. Resource use variation was a strong predictor of energetic condition, whereby individuals more reliant upon pelagic forage exhibited higher blood plasma concentrations of very low-density lipoproteins, cholesterol, and triglycerides. These findings underscore how intraspecific variation inresource use may impact the energy metabolism of animals, and more broadly, that natural and anthropogenically driven fluctuations in prey resources could have longer term energetic consequences.