Local Exchange Research Articles

A Federated Reinforcement Learning Framework via a Committee Mechanism for Resource Management in 5G Networks.

This paper proposes a novel decentralized federated reinforcement learning (DFRL) framework that integrates deep reinforcement learning (DRL) with decentralized federated learning (DFL). The DFRL framework boosts efficient virtual instance scaling in Mobile Edge Computing (MEC) environments for 5G core network automation. It enables multiple MECs to collaboratively optimize resource allocation without centralized data sharing. In this framework, DRL agents in each MEC make local scaling decisions and exchange model parameters with other MECs, rather than sharing raw data. To enhance robustness against malicious server attacks, we employ a committee mechanism that monitors the DFL process and ensures reliable aggregation of local gradients. Extensive simulations were conducted to evaluate the proposed framework, demonstrating its ability to maintain cost-effective resource usage while significantly reducing blocking rates across diverse traffic conditions. Furthermore, the framework demonstrated strong resilience against adversarial MEC nodes, ensuring reliable operation and efficient resource management. These results validate the framework's effectiveness in adaptive and efficient resource management, particularly in dynamic and varied network scenarios.

Universality of ecological memory for local and global net ecosystem exchange, atmospheric CO2, and sea surface temperature

Modeling global net ecosystem exchange is essential to understanding and quantifying the complex interactions between the Earth’s terrestrial ecosystems and the atmosphere. Emphasizing the inter-relatedness between the global net ecosystem exchange, global sea surface temperature, and atmospheric CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext {CO}}_{2}$$\\end{document} levels, intuitively suggests that all three systems may exhibit collective environmental memory. Motivated by this, we explicitly identified a collective memory function and showed a similar non-Markovian stochastic behavior for these systems exhibiting superdiffusive behavior in short time intervals. We obtained the values of the memory parameter, μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu$$\\end{document}, and the characteristic frequencies, ν\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ u$$\\end{document}, for global net ecosystem exchange (GNEE) (μ=0.94±0.03,ν=0.67±0.08/mo.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu = 0.94\\pm 0.03, \ u = 0.67\\pm 0.08/mo.$$\\end{document}), global sea surface temperature (GSST) (μ=0.68±0.11,ν=0.30±0.18/mo.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu = 0.68\\pm 0.11, \ u = 0.30\\pm 0.18/mo.$$\\end{document}), and atmospheric CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext {CO}}_{2}$$\\end{document} (μ=0.78±0.08,ν=0.66±0.13/wk.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu = 0.78\\pm 0.08, \ u =0.66\\pm 0.13/wk.$$\\end{document}). The values of the memory parameter are within the range, 0<μ<1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$0< \\mu < 1$$\\end{document}, and thus all three systems are in the superdiffusive regime. We emphasize, further, that these results were consistent with our previous analyses at the ecosystem level (i.e. Great Barrier Reef) suggesting scale invariance for these phenomena. Thus, the observed superdiffusive behavior operating at different scales suggests universality of the collective memory function for these systems.

Forecasting Using the Markov Chain Transition Matrix for Exchange Rate Fluctuations

The current research is preparing an economic statistical study on exchange rate fluctuations for the period from ( 1996 to mid-2005 ) according to the well-known phrase: (The present is the past and the future is the present ). It is a modest attempt to crystallize this type of price in a scientific-statistic method by adopting the matrix of transitional probabilities in Markov chains, as these chains are among the models that are relied upon in the process of forecasting when the data are in the present time and in three cases: - High - Low - Stability. Between the past, the present and the future, the researcher was able to reach in his research to the analysis by applying the method of the greatest places, and to achieve the main purpose of this research, the researcher dealt with four chapters as follows: The first chapter dealt with the problem of research, its importance, need, purpose and determination of its terms. The second chapter reviewed the previous studies published on the subject, as well as the theoretical aspect, in which the matrix of transitional and stable possibilities, the state of stability and independence of the Markov chains, and the estimation of transitional possibilities in the greatest possible way were presented. As for the third chapter, it included the practical aspect and the field application. The data related to the research procedures were collected from the date of (17/10/2003 to 30/6/2005), in which the Iraqi currency was exchanged from the old to the currency currently in circulation, and in which the situation of the Iraqi market suggested great relative stability at the time. Finally, the fourth chapter of this research included the conclusions reached by the researcher from which it came: The market was characterized by a state of stability after the rise in the exchange rate against the dollar, which confirmed the accuracy of the results of the matrix of transitional possibilities, which was reflected on the local stock exchange, as well as the development of recommendations that can be used by the relevant parties.

Urban Sustainability in the Age of Digital Nomads - Diverse Group Impacts

Digital nomads are a whole new group of people empowered by digital information technology, and although they have a subtle impact on urban change, little attention has been paid to the impact on different urban groups with the influx of digital nomads. The aim of this paper is to examine how the increase in the number of digital nomads in recent years has affected different urban groups in the context of the broader goal of sustainable urban development. The case study comes from the Digital Nomad Commune in Anji, China, and through the literature research method, the urban groups are divided into: digital nomads, profit-driven locals and negatively affected locals, analyzing the various phenomena presented by different groups of people, such as the promotion of local economic development, cultural exchange and cultural diversity by the emergence of digital nomads, the pressure on the price of goods in the neighbouring towns and the irreversible negative impacts on the ecological environment, as well as proposing the strategies for the future construction of the city. It suggests how to build digital nomad-friendly cities from the economic, ecological and social perspectives.

The Role of Pre-Colonial Agikuyu Women’s Local Trade on Indigenous Food Crops and Food Security in Nyeri County Before 1902

The purpose of this paper was to establish the role of pre-colonial Agikuyu women’s local trade on indigenous food Crops in enhancing food security in Nyeri County before 1902. The research was guided by two theories Marxist feminist theory and articulation theory. This study was conducted in three sub-counties: Kieni East, Mathira East, and Nyeri Central. Data was collected from both primary and secondary sources such as key informants, archival data and document analysis. A sample size threshold of 54 respondents was interviewed. The main research instruments were the interview guide and focus group discussion. Data for this study was analyzed qualitatively using documentary content analysis, description and narration of the historical events. Data was also corroborated and both context and content analysis were done to ensure reliability and validity of the information. The study established that in pre-colonial period women formed the backbone of Nyeri County's food security through their local exchange system leveraging their deep understanding on well-established trade networks of indigenous food crops that helped to mitigate food shortage. The established that the indigenous food crops that women exchanged in the local markets were well adapted to local conditions, sustainably available and provided essential nutrients necessary for the health and well-being of the community. The findings of this study illustrate the pivotal role of Agikuyu women in local trade systems and its substantial contribution to food security in Nyeri County. The study concludes that the ministry of trade should come up with deliberate measures that will integrate women’s local trade into the country’s economic policies and practices and also consider the valuable contribution of women local trade in mitigating food shortage and ensuring eradication of extreme poverty and hunger

Imaging Strain-Controlled Magnetic Reversal in Thin CrSBr.

Two-dimensional materials are extraordinarily sensitive to external stimuli, making them ideal for studying fundamental properties and for engineering devices with new functionalities. One such stimulus, strain, affects the magnetic properties of the layered magnetic semiconductor CrSBr to such a degree that it can induce a reversible antiferromagnetic-to-ferromagnetic phase transition. Using scanning SQUID-on-lever microscopy, we directly image the effects of spatially inhomogeneous strain on the magnetization of layered CrSBr, as it is polarized by a field applied along its easy axis. The evolution of this magnetization and the formation of domains is reproduced by a micromagnetic model, which incorporates the spatially varying strain and the corresponding changes in the local interlayer exchange stiffness. The observed sensitivity to small strain gradients along with similar images of a nominally unstrained CrSBr sample suggest that unintentional strain inhomogeneity influences the magnetic behavior of exfoliated samples.

Preface

Peruvian Workshop on Solar Energy 2023 (JOPES 2023) These proceedings contain a selection of papers presented at the Peruvian Workshop on Solar Energy 2023 (Jornadas Peruanas de Energía Solar - JOPES), held for the sixth consecutive year. The motivation for these events dates back to 1981, when Prof. Manfred Horn began exploring the potential of renewable energies, particularly solar energy. He founded the Peruvian Association for Solar Energy and Environment (APES). A significant milestone occurred in 1986 when APES organized the first Peruvian Symposium on Solar Energy (SPES). Since 2003, SPES has been held annually without interruption, rotating among various cities in Peru with active university programs related to renewable energies. As an extension of these efforts, JOPES was established in 2008 to promote both local and international dissemination and exchange of ideas in the field of renewable energy research. We invite renowned keynote speakers, local researchers, and students to present their latest works. During the pandemic years of 2020-2022, the event continued virtually. JOPES 2023 was held in presential mode from July 20th to 22nd at the main auditorium of the Faculty of Sciences of the National University of Engineering (Universidad Nacional de Ingeniería, UNI). Keynote speakers from diverse countries, including Argentina, Brazil, Chile, France, Sweden, and the United Kingdom, participated. Numerous local researchers also contributed, covering topics such as bioremediation of polluted waters, FMEA risk evaluation in the design of solar cookers, properties of stable faces of SnO2 for improving solar cell production, Peltier cells for evaluating the thermal conductivity of insulating materials, calibration of a built spectrometer, and determination of cloud optical depths during over-irradiance. We would like to express our gratitude to the authorities of UNI for their support in making this event possible, especially the Faculty of Sciences for providing the venue and the Vice-Rectorate of Investigation (VRI) for covering some of the finances. Special thanks also go to the Peruvian Association of Solar Energy and the Environment (APES), the Renewable Energy Center of the National University of Engineering (CER-UNI), and the Peruvian government’s National Council of Science, Technology, and Technological Innovation (CONCYTEC). List of Organizing Committee is available in this Pdf.

A Theoretical Discussion on the Flow of Tourist Population and the Development of Tourism Market in Heilongjiang Province

This paper deeply discusses the basic law of tourist population flow and its influence on the development of tourism market in Heilongjiang Province. Under the background of the vigorous development of global tourism, the flow of tourist population, as the core element of tourism activities, has an important impact on the prosperity and sustainable development of regional tourism market, such as seasonal, spatial distribution and interactive effects. Through the detailed analysis of Heilongjiang tourism market, this paper reveals the market size, resource characteristics, challenges and problems of this market under the action of tourist population flow. Further, this paper analyzes the dual impact of tourist population flow on Heilongjiang tourism market, including the positive effect of promoting local economy, cultural exchange and industrial development, and the negative effect of environmental pressure, over-exploitation of resources and decline of service quality. At the same time, this paper puts forward some strategic suggestions to promote the sustainable development of Heilongjiang tourism market, including rational planning of tourist population flow, strengthening the protection and development of tourism resources, promoting the development of smart tourism, and strengthening regional cooperation and linkage. These suggestions are intended to provide theoretical basis and practical guidance for the scientific planning and management of Heilongjiang's tourism market, and help it achieve long-term prosperity and sustainable development.

A decision-making model for joint energy and reserve scheduling of wind power producers with local intraday demand response exchange market

In this paper, a three-stage stochastic bi-level optimization framework is presented for optimal participation of wind power producers (WPPs) in day-ahead (DA), intraday, and balancing markets. In this framework, to leverage demand response (DR) services, a peer-to-peer (P2P) energy trading platform is implemented that allows local load aggregators (LAs) to contribute to the intraday markets improving both LAs’ and WPP’s benefits. Participating in the intraday DR exchange (IDRX) market enables WPP to purchase DR services from LAs, to reduce the penalty cost on the deviation between the day-head bidding and the real-time dispatch. A Stackelberg game for the bi-level decision-making model captures the conflict of interests between the WPP and LAs, in which, the upper level seeks to maximize WPP profit, while the lower level aims to maximize LAs’ economic surplus. The bi-level model is converted into its equivalent single-level mixed-integer quadratic problem (MIQP) employing the Karush-Kuhn-Tucker (KKT) conditions and strong duality theorem. Simulation results show that participation of the WPP in the IDRX market and employing spinning reserve and DR services for compensating the uncertainties are greatly dependent on its risk preferences and increase its expected profit in all conditions, significantly.

Lifetime evaluation and material failure analysis of a PEMFC prepared using commercial materials

ABSTRACT Hydrogen fuel cells are vital for green energy to replace traditional energy. However, their lifetime is an important factor limiting their development. In this study, commercial materials were used to prepare proton exchange membrane fuel cells (PEMFCs), and pure oxygen was used as the cathode gas to accelerate their lifetime evaluation. The components of the membrane electrode assembly were characterized, and significant thinning was observed in the local proton exchange membrane (PEM). Therefore, the uniformity of the internal conditions of the fuel cell is the key to ensure a long lifetime. The hydrophilicity of the gas diffusion layers increased as the carbon disorder increased via the adsorption of hydrophilic chain segments produced by PEM degradation. The growth of platinum particles in the catalyst layer reduced the electrochemical active area of the catalyst, but the reduction rate slowed and then stabilized. This study of the lifetime of PEMFCs and changing properties of commercial materials clarifies the existing problems of fuel cells and contributes to the development of long-life fuel cells.

Unveiling nitrate contamination and health risks: Insights from groundwater quality assessment and Monte Carlo simulation along the Southern Caspian Sea Coasts

Groundwater resources are at great risk of contamination due to increased industrial and agricultural activities, population growth and urban expansion. This study investigated factors controlling spatio-temporal variability in groundwater quality and nitrate concentration at the southern coast of Caspian Sea, Iran to provide public health risk assessment. Na-Cl (44.8%) and Ca-HCO3 (58.6%) types water were the dominant hydrogeochemical facies in dry and wet seasons, respectively. Most of the examined groundwater samples were found unfit for drinking but appropriate for agricultural irrigation. The chemistry of groundwater predominantly influenced by combination of local lithology and ion exchange in aquifer as well as seawater intrsuin. Nitrate concentration varied from 0.05 to 200 mg/L with a mean value of 33.1 mg/L in which 13.7% and 27.5% of samples showed concentration higher than WHO's recommended value in dry and wet seasons, respectively. The highest nitrate concentrations were observed at locations in proximity to human settlements including cities, villages as well as agricultural lands. The identified pollution hotspots confirm nitrate contributions from un-treated wastewater effluents and agricultural practices with minimum contribution from industrial activities. The result of Monte Carlo simulation revealed that children were at highest risk from drinking of groundwater containing nitrate. This study highlights the urgent need for action to address the growing threat to groundwater quality and public health posed by contamination from various sources in the southern coasts of Caspian Sea.

Combining earth observations with ground data to assess river topography and morphologic change: Case study of the lower Jamuna River

The Jamuna is a major braided river of Bangladesh and poses enormous challenges related to flooding, erosion, and sedimentation. Effective river management requires an understanding of the Jamuna’s sediment transport dynamics and channel morphology. Yet, developing that understanding is hindered by a lack of topographic data for the river corridor. In this study, the waterline method was applied to a 65 km reach of the Jamuna to derive river channel and floodplain topography above the low water level. The analysis relies on surface water detection from Sentinel-1 and Sentinel-2 data, along with in-situ water level observations, to generate river-floodplain DEMs for the years 2016–2019. Morphologic change was assessed through DEMs of difference for sequential years and for the overall study period. A quantitative uncertainty analysis was conducted to characterize errors in the waterline DEMs, vertical change detection, and gross and net volumetric changes. The results indicate that gross annual erosion and accretion volumes have a similar order of magnitude to contemporary estimates of the river’s sediment influx. The study highlights that localized and reach-scale lateral exchange is a key component of the overall sediment budget. Finally, the uncertainty analysis framework provides insight and recommendations for how errors can be assessed and reduced in future waterline applications.

Sustained acoustic medicine treatment of discogenic chronic low back pain: A randomized, multisite, double-blind, placebo-controlled trial.

Sustained acoustic medicine (SAM) is a noninvasive long-term treatment that provides essential mechanical and thermal stimulus to accelerate soft tissue healing, alleviate pain, and improve physical activity. SAM increases localized deep tissue temperature, blood flow, cellular proliferation, migration, and nutrition exchange, resulting in reduced inflammation and an increased rate of tissue regeneration. To assess the efficacy of SAM treatment of discogenic back pain in the lower spinal column to reduce pain, improve quality of life, and lower pharmacotherapy use. Sixty-five subjects with chronic low back pain were randomly assigned to SAM (N= 33) or placebo (N= 32) groups. Subjects self-applied SAM device bilaterality on the lower lumbar region for 4 hours daily for 8 weeks and completed daily pain diaries before, during, and after treatment. Subjects recorded pain reduction using a numeric rating scale (NRS), medication use, and physical activity using the Global Rating of Change (GROC) and Oswestry Disability Index (ODI). SAM treatment significantly reduced chronic lower back pain from baseline relative to placebo treatment (p< 0.0001). SAM treated subjects reported significantly lower back pain at 4 weeks, with the highest pain reduction (-2.58 points NRS, p< 0.0001) reported at 8 weeks. Similar trends were observed in improved physical activity (3.48 GROC, p< 0.0001, 69-88% ODI, p< 0.0001) and 22.5% (15.2 morphine milligram equivalent) reduction in the use of opioid medication from baseline to 8 weeks. Daily, home-use SAM treatment significantly improves the clinical symptoms of chronic lower back pain, improves physical mobility, and reduces daily medication use. SAM treatment is well-tolerated by patients and may be considered a safe, non-invasive treatment option for chronic discogenic, lower back pain.

Warming of mid-latitude North Atlantic Sea surface temperature strengthens the daily variability of winter PM2.5 in eastern China

Abstract Climate factors, in addition to human activities, are acknowledged to exert a notable influence on the synoptic PM2.5 variations over eastern China in extensive case studies. Based on observed daily PM2.5 concentrations data, this study reveals the enhanced daily variability (DV) of PM2.5 concentrations over eastern China and identifies its association with mid-latitude sea surface temperature anomalies over the North Atlantic. The dominant daily mode of PM2.5 concentrations identified through empirical orthogonal function analysis accounts for 43.75% of the total variance, with its DV experienced a significant enhancement from 1979 to 2019. The identified enhancement is attributed to the intensified wave train propagation along the mid-latitudes on a time scale of 10–30 d. The eastward propagation of the identified wave train can expose eastern China to recurrent influences of cyclonic and anticyclonic anomalies, resulting in an initial increase and subsequent decrease in PM2.5 concentrations. Statistical analysis and dynamic diagnostics show that the warming of the mid-latitude North Atlantic Ocean enhances the wave train at its source through the local energy exchange, and ultimately leads to an increased DV of PM2.5 concentrations.

Beyond “buzz”: knowledge interactions, innovation, and neighborhood characteristics

Abstract We examine the link between neighborhood characteristics, the importance of knowledge exchange, and firm innovation in Montreal. To this end we combine two sources of data: place-of-residence census data from Statistics Canada and the results of an original firm survey. Through principal component analysis and subsequent clustering, we define five types of neighborhoods. The results revealed that firms assign higher importance to local knowledge exchange when located in dense, walkable neighborhoods with higher educated residents. Knowledge exchange, both local and global, correlates with incremental and radical innovation. Moreover, firms are innovative in any neighborhood, provided they engage in knowledge exchange.

Online LiDAR-camera extrinsic parameters self-checking and recalibration

Abstract During production, smart cars are equipped with calibrated LiDARs and cameras. However, due to the vibrations that inevitably occur during driving, the sensors’ extrinsic parameters may change slightly over time. It is a significant challenge to ensure the ongoing security of these systems throughout the car’s lifetime. To address this issue, we propose a self-checking and recalibration algorithm that can continuously detect the sensor data of intelligent vehicles. If the sensor’s miscalibration is detected, the data can be repaired promptly to ensure the vehicle’s reliability. Our self-checking algorithm extracts features from the point cloud and image and performs pixel-wise comparisons. To improve feature quality, we utilize the patch-wise transformer to enhance local information exchange, which also benefits the subsequent extrinsic recalibration. To facilitate the study, we generate two customized datasets from the KITTI dataset and the Waymo Open Dataset. The experiments conducted on these datasets demonstrate the effectiveness of our proposed method in accurately calibrating the LiDAR and camera systems throughout the car’s lifetime. This study is the first to highlight the importance of continually checking the calibrated extrinsic parameters for autonomous driving. Our findings contribute to the broader goal of improving safety and reliability in autonomous driving systems. The dataset and code are available at https://github.com/OpenCalib/LiDAR2camera_self-check.

European screen locations in the Indian film industry: evolutionary, spatial, and collaborative perspectives

India has long been known for its film industry and remains by far the largest film producer in the world, surpassing other film-producing superpowers like the US and China. A major factor in India’s dominance in the global media landscape is the outsourcing of film production, especially within Europe. Although there are studies trying to explain the context and mechanisms of foreign settings being incorporated into Indian filmmaking, this knowledge remains scattered and unsystematic. The objective of this paper is to comprehensively examine the evolutionary, spatial, and collaborative dynamics of Indian filmmaking in Europe by analysing statistical data from IMDb as the world’s largest film database. Our findings show that Indian filmmakers appeared relatively infrequently in Europe until the mid-1990s. The British Isles and Western Europe, with London and the Swiss Alps as the main centres, became the first and most popular destinations for outsourcing Indian films. However, this trend has changed in the last two decades, with the focus shifting to other areas in Southern, Central, Eastern, and Northern Europe as well in recent decades. The initial wave of Bollywood productions has gradually been followed by other regional cinematographies. The increasing presence of Indian film shooting in Europe has also led to growing co-production between filmmakers on both (sub)continents. The paper provides a solid basis for further exploration of socio-economic linkages between India and Europe, especially in terms of job creation, local economic development, tourism, and cultural exchange.

Consensus control and vibration suppression for multiple flexible nonlinear Timoshenko manipulators under undirected communication topology

In this paper, consensus control and vibration suppression problems are considered for the flexible nonlinear Timoshenko manipulator multi-agent system. The multi-agent system comprises multiple identical flexible Timoshenko manipulators, which can realize cooperation utilizing local information exchange between various agents. The bending deformation and shear deformation generated by the practical robotic manipulators during motion both affect the control effect, so the flexible Timoshenko manipulator is used to describe the dynamic characteristics. The flexible Timoshenko manipulator is a typical distributed parameter system, the deformation states are not only related to time but also to position, and the partial differential equations (PDEs) models are studied in this paper. Based on the PDEs models, the consensus control scheme is developed under the undirected communication topology structure, which can realize joint angle consensus tracking and vibration suppression of all the flexible Timoshenko manipulator agents simultaneously. Finally, the control effect is verified by the numerical simulations.

Ostrich eggshell beads from Little Muck Shelter, southern Africa: First impressions and regional perspectives

Hunting and gathering communities in southern Africa produced ostrich eggshell (OES) beads for personal ornamentation, trade and exchange, and various forms of symbolism. OES beads convey information related to not only technological processes, but also social histories, making them useful tools for investigating these processes in the archaeological record. In the middle Limpopo Valley, hunter-gatherers produced beads from periods that predated the arrival of farmer societies, before ca. AD 150, until the decline of the Mapungubwe capital, AD 1300. Their analysis may therefore lead to insights into local economies, craft activities, trade and exchange, and social roles. However, no study in the middle Limpopo Valley has sufficiently investigated these beads and their status within forager society. In this paper we study the manufacture of OES beads from one of the excavated forager-occupied shelters in the valley, Little Muck. This study is the first of its kind from a hunter-gatherer context in the region. It shows that Little Muck’s beads were standardised but produced in varying frequencies across temporal periods, and made following different production strategies. Use-wear analysis hints that some of the beads were pigmented and possibly altered using heat treatment. As an initial foray into a forager bead assemblage of the region, this study demonstrates the value such an approach may yield, and it aids in guiding future attempts. It also compares Little Muck’s bead assemblage with those from other sites across a much wider region where such studies have taken place. The findings demonstrate similar patterns to other parts of southern and eastern Africa, but also illustrate local shifts in bead production that follow changes in local socio-political dynamics.

Expediting battery investment returns for residential customers utilising spot price-aware local energy exchanges

This paper presents a local energy exchange mechanism to benefit residential customers and retailers under variable wholesale market spot prices. To do so, a peer-to-peer (P2P) trading-enabled local energy market (LEM) is proposed to facilitate frequent energy transactions among participants. The proposed LEM mechanism considers market operational constraints and maximises electricity cost reductions. Further, the proposed LEM optimises the customers' investment return for battery energy storage systems (BESSs) and minimises retailers’ financial losses during higher spot prices in the wholesale market. Finally, a case study is demonstrated using real-world Australian data in which P2P trading is performed between interested buyers and sellers. Two scenarios with high and low wholesale market spot prices are analysed comprehensively considering five metrics such as solar-to-spot (STS); solar-to-load (STL); forward buy contract (FBC)-to-load (FBC-L); spot-to-load (Short); and FBC-to-spot (Long). The simulation results reveal that the customers reap substantial benefits from the proposed LEM in contrast with business-as-usual (BAU), allowing them to expedite BESS investment returns. Also, the proposed LEM helps a retailer decrease the effect of higher spot prices by reducing its unexpected financial losses while improving self-consumption and self-sufficiency in the local energy network.