An Online Approach to Dynamic Channel Access and Transmission Scheduling

Making judicious channel access and transmission scheduling decisions is essential for improving performance as well as energy and spectral efficiency in multichannel wireless systems. This problem has been a subject of extensive study in the past decade, and the resulting dynamic and opportunistic channel access schemes can bring potentially significant improvement over traditional schemes. However, a common and severe limitation of these dynamic schemes is that they almost always require some form of a priori knowledge of the channel statistics. A natural remedy is a learning framework, which has also been extensively studied in the same context, but a typical learning algorithm in this literature seeks only the best static policy, with performance measured by weak regret, rather than learning a good dynamic channel access policy. There is thus a clear disconnect between what an optimal channel access policy can achieve with known channel statistics that actively exploits temporal, spatial and spectral diversity, and what a typical existing learning algorithm aims for, which is the static use of a single channel devoid of diversity gain. In this paper we bridge this gap by designing learning algorithms that track known optimal or sub-optimal dynamic channel access and transmission scheduling policies, thereby yielding performance measured by a form of strong regret, the accumulated difference between the reward returned by an optimal solution when a priori information is available and that by our online algorithm. We do so in the context of two specific algorithms that appeared in [1] and [2], respectively, the former for a multiuser single-channel setting and the latter for a single-user multichannel setting. In both cases we show that our algorithms achieve sub-linear regret uniform in time and outperforms the standard weak-regret learning algorithms.Comment: 10 pages, to appear in MobiHoc 201

Forecasting land-use change and its impact on the groundwater system of the Kleine Nete catchment, Belgium

International audienceLand-use change and climate change, along with groundwater pumping are frequently indicated to be the main human-induced factors influencing the groundwater system. Up till now, research has mainly been focusing on the effect of the water quality of these human-induced changes on the groundwater system, often neglecting changes in quantity. The focus in this study is on the impact of land-use changes in the near future, from 2000 until 2020, on the groundwater quantity and the general hydrologic balance of a sub-catchment of the Kleine Nete, Belgium. This study tests a new methodology which involves coupling a land-use change model with a water balance model and a groundwater model. The future land-use is modelled with the CLUE-S model. Four scenarios (A1, A2, B1 and B2) based on the Special Report on Emission Scenarios (SRES) are used for the land-use modelling. Water balance components, groundwater level and baseflow are simulated using the WetSpass model in conjunction with a MODFLOW groundwater model. Results show that the average recharge slowly decreases for all scenarios, the decreases are 2.9, 1.6, 1.8 and 0.8% for respectively scenario A1, A2, B1 and B2. The predicted reduction in recharge results in a small decrease of the average groundwater level, ranging from 2.5 cm for scenario A1 to 0.9 cm for scenario B2, and a reduction of the total baseflow with maximum 2.3% and minimum 0.7% respectively for scenario A1 and B2. Although these average values do not indicate significant changes for the groundwater system, spatial analysis of the changes shows the changes are concentrated in the neighbourhood of the major cities in the study areas. It is therefore important for spatial managers to take the groundwater system into account for reducing the negative impacts of land-use and climate change as much as possible

Predicting land-use change and its impact on the groundwater system of the Kleine Nete catchment, Belgium

Land-use changes are frequently indicated to be one of the main human-induced factors influencing the groundwater system. For land-use change, groundwater research has mainly focused on the change in water quality thereby neglecting changes in quantity. The objective of this paper is to assess the impact of land-use changes, from 2000 until 2020, on the hydrological balance and in particular on groundwater quantity, as results from a case study in the Kleine Nete basin, Belgium. New is that this study tests a methodology, which couples a land-use change model with a water balance and a steady-state groundwater model. Although the averages found appear to indicate small changes in the groundwater system, spatial analysis shows that much larger changes are located near the major cities in the study area. Hence, spatial planning should take better account of effects of land-use change on the groundwater system and define mitigating actions for reducing the negative impacts of land-use change

Slibbalans-Zeeschelde: deelrapport 3.Literatuurstudie

This literature review is a deliverable within the study "slibbalans Zeeschelde" (WL Project 00_029), and gives an overview of available knowledge on mud transport and stock in the Scheldt estuary. It is meant to be used as a reference and an inventarisation of available knowledge on the mud balance of the Scheldt estuary. Sometimes a claim by an author may have come at odds with more recent insights in system behaviour. The authors have tried to indicate that in the text. Because insights are constantly evolving, this document should be a living document.First, available methodologies to estimate mud transport are presented. Anthropogenic activities in the Scheldt estuary that had a possible impact on the mud dynamics are listed. The main part of this literature review consists of a summary of the most important conclusions of literature describing the mud stock in the Scheldt estuary since 1964 and an overview of historic estimations of mud transport and sedimentation over time in different parts of the estuary.For the sake of consistency, mud quantities are converted to Ton Dry Matter whenever possible (TDM in English, Ton Droge Stof or TDS in Dutch), which correspond to the mass of the grains of sediment in the water-sediment mixture

"Machtergreifung?" - Kontinuitäten und Brüche bei Institutionen und Persönlichkeiten der Agrar-, Siedlungs- und Raumordnungspolitik

In diesem Beitrag werden anhand des Schicksals der mit Raumplanung und Raumforschung befassten Institutionen und ihrer jeweiligen Führungspersonen Verbindungslinien und Brüche vor, innerhalb und nach Ende des "Dritten Reiches" nachgezeichnet. Bereits im Kaiserreich und in der Weimarer Republik wurden Konzepte und Planungen entwickelt, die zwar nicht den Namen Raumforschung und Raumordnung trugen, aber mit dem Auftrag der Inneren Kolonisation regionale Entwicklungen auslösten. Die Gründung von Institutionen (z. B. Deutsches Institut für Agrar- und Siedlungswesen 1921; Verein für Socialpolitik 1872) und das wissenschaftliche Engagement von herausragenden Persönlichkeiten (vor allem von Max Sering) prägen diese Phase. Der NS-Staat reagierte durch den Aufbau eigener Trägerstrukturen für Raumforschung und Raumordnung, insbesondere durch die Aufstellung des Generalplans Ost. Hier spielt der Obmann des "Forschungsdienstes", Konrad Meyer, die dominierende Rolle. Das Institut für Agrar- und Siedlungswesen wurde im Dritten Reich aufgelöst und nach 1945 im Zeichen der Pflege und Fortentwicklung ihres früheren Gründers Max Sering durch Constantin von Dietze (Freiburg) in der Forschungsgesellschaft für Agrarpolitik und Agrarsoziologie e.V. (FAA) wieder aufgebaut. Unter der Bundesministerin Künast wurde ihre Finanzierung eingestellt und die Forschungsstelle nach Braunschweig in die Bundesinstitution Institut für Ländliche Räume der Forschungsanstalt für Landwirtschaft (FAL) eingegliedert. 1946 wurde die Akademie für Raumforschung und Landesplanung (ARL) gegründet. Altbekannte Personen der NS-Zeit standen dabei Pate. Manche von ihnen betonten die Kontinuität zur Reichsarbeitsgemeinschaft für Raumforschung (1936) mit ihrer Zeitschrift "Raumforschung und Raumordnung". Andere leugneten die Kontinuität der ARL zu Institutionen des Nationalsozialismus.By considering the fate of institutions dedicated to spatial planning and research, and the individuals who headed them, this article traces continuities and ruptures before, under and after the end on the Third Reich. As early as in Imperial Germany and during the Weimar Republic, concepts and plans were developed which, though not actually thought of in terms of spatial research or spatial planning, served nonetheless as a trigger for regional development under the watchword of "internal colonisation". This period is marked particularly by the foundation of various institutions (e.g. the German Institute for Agriculture and Settlement in 1921; the Society for Social Policy in 1872) and by the commitment of a number of leading scholars (particularly Max Sering). The Nazi state reacted by setting up various structures with responsibilities in spatial research and planning, and more specifically by framing the Generalplan Ost. Here the key role fell to Konrad Meyer, the representative of the “research service”. The Institute for Agriculture and Settlement was closed down during the Third Reich, but subsequently revived after 1945 by Constantin von Dietze (Freiburg) as part of the Research Association for Agricultural Policy and Sociology e. V. (FAA) in recognition of, and to further advance, the work of its original founder Max Sering. Under federal minister Künast funding was discontinued, and its research division was integrated within a federal authority located in Brunswick, the Institute for Rural Areas at the FAL (the Forschungsanstalt für Landwirtschaft - a centre for agricultural research). In 1946 the Academy for Spatial Research and Planning (ARL) was founded, inspired by a number of individuals eminent during the National Socialist era. With the journal Raumforschung und Raumordnung, some stressed the continuation of the work of the Reichsarbeitsgemeinschaft für Raumforschung (a working group on spatial research founded in 1936); others denied any continuity between the work of the ARL and that of institutions created under Nazi rule

Short-term effects of 448 kilohertz radiofrequency stimulation on supraspinatus tendon elasticity measured by quantitative ultrasound elastography in professional badminton players: a double-blinded randomized clinical trial

Objective: To study changes in supraspinatus tendon elasticity after a 448 kHz capacitive resistive monopolar radiofrequency (CRMR) intervention in professional badminton players. Design: Double-blinded randomized clinical trial. Setting: All participants were recruited in a private care practice. Participants were randomized to receive either a CRMR treatment (n ¼ 19) or placebo (n ¼ 19). Subjects: Professional badminton players (n ¼ 38). Intervention: A total of nine intervention (three per week) with CRMR at 448 kHz were carried out in the experimental group. The same intervention without an active CRMR current was carried out in the control group. Main measures: Mean values of three different regions of the supraspinatus tendon were reported at baseline (T1), immediately after the intervention (T2) and one week after the end of the whole intervention program (T3) using quantitative ultrasound strain elastography (SEL). Results: There were statistically significant differences in the supraspinatus tendon elasticity immediately after the intervention (p¼ <.001) and one week after the end of the whole intervention program (p¼.001). Conclusion: CRMR at 448 kHz produces significant changes in supraspinatus tendon elasticity after an intervention program of three weeks and those changes last for a week when compared to control group

Spatio-temporal impact of climate change on the groundwater system

Given the importance of groundwater for food production and drinking water supply, but also for the survival of groundwater dependent terrestrial ecosystems (GWDTEs) it is essential to assess the impact of climate change on this freshwater resource. In this paper we study with high temporal and spatial resolution the impact of 28 climate change scenarios on the groundwater system of a lowland catchment in Belgium. Our results show for the scenario period 2070–2101 compared with the reference period 1960– 1991, a change in annual groundwater recharge between −20% and +7%. On average annual groundwater recharge decreases 7%. In most scenarios the recharge increases during winter but decreases during summer. The altered recharge patterns cause the groundwater level to decrease significantly from September to January. On average the groundwater level decreases about 7 cm with a standard deviation between the scenarios of 5 cm. Groundwater levels in interfluves and upstream areas are more sensitive to climate change than groundwater levels in the river valley. Groundwater discharge to GWDTEs is expected to decrease during late summer and autumn as much as 10%, though the discharge remains at reference-period level during winter and early spring. As GWDTEs are strongly influenced by temporal dynamics of the groundwater system, close monitoring of groundwater and implementation of adaptive management measures are required to prevent ecological loss

A Stochastic Fluid Model Approach to the Stationary Distribution of the Maximum Priority Process

In traditional priority queues, we assume that every customer upon arrival has a fixed, class-dependent priority, and that a customer may not commence service if a customer with a higher priority is present in the queue. However, in situations where a performance target in terms of the tails of the class-dependent waiting time distributions has to be met, such models of priority queueing may not be satisfactory. In fact, there could be situations where high priority classes easily meet their performance target for the maximum waiting time, while lower classes do not. Here, we are interested in the stationary distribution at the times of commencement of service of this maximum priority process. Until now, there has been no explicit expression for this distribution. We construct a mapping of the maximum priority process to a tandem fluid queue, which enables us to find expressions for this stationary distribution. We derive the results for the stationary distribution of the maximum priority process at the times of the commencement of service.Comment: The Eleventh International Conference on Matrix-Analytic Methods in Stochastic Models (MAM11), 2022, Seoul, Republic of Kore

Predicting land-use change and its impact on the groundwater system of the Kleine Nete catchment, Belgium

Land-use changes are frequently indicated to be one of the main human-induced factors influencing the groundwater system. For land-use change, groundwater research has mainly focused on the change in water quality thereby neglecting changes in quantity. The objective of this paper is to assess the impact of land-use changes, from 2000 until 2020, on the hydrological balance and in particular on groundwater quantity, as results from a case study in the Kleine Nete basin, Belgium. New is that this study tests a methodology, which couples a land-use change model with a water balance and a steady-state groundwater model. Four future land-use scenarios (A1, A2, B1 and B2) based on the Special Report on Emission Scenarios (SRES) are modelled with the CLUE-S model. Water balance components, groundwater level and baseflow are simulated using the WetSpass model in conjunction with a steady-state MODFLOW groundwater flow model. Results show that the average recharge decreases with 2.9, 1.6, 1.8 and 0.8% for scenario A1, A2, B1 and B2, respectively, over the 20 covered years. The predicted reduction in recharge results in a small decrease of the average groundwater level in the basin, ranging from 2.5 cm for scenario A1 to 0.9 cm for scenario B2, and a reduction of the baseflow with maximum 2.3% and minimum 0.7% for scenario A1 and B2, respectively. Although these averages appear to indicate small changes in the groundwater system, spatial analysis shows that much larger changes are located near the major cities in the study area. Hence, spatial planning should take better account of effects of land-use change on the groundwater system and define mitigating actions for reducing the negative impacts of land-use change