Data-Efficient Decentralized Visual SLAM

Decentralized visual simultaneous localization and mapping (SLAM) is a powerful tool for multi-robot applications in environments where absolute positioning systems are not available. Being visual, it relies on cameras, cheap, lightweight and versatile sensors, and being decentralized, it does not rely on communication to a central ground station. In this work, we integrate state-of-the-art decentralized SLAM components into a new, complete decentralized visual SLAM system. To allow for data association and co-optimization, existing decentralized visual SLAM systems regularly exchange the full map data between all robots, incurring large data transfers at a complexity that scales quadratically with the robot count. In contrast, our method performs efficient data association in two stages: in the first stage a compact full-image descriptor is deterministically sent to only one robot. In the second stage, which is only executed if the first stage succeeded, the data required for relative pose estimation is sent, again to only one robot. Thus, data association scales linearly with the robot count and uses highly compact place representations. For optimization, a state-of-the-art decentralized pose-graph optimization method is used. It exchanges a minimum amount of data which is linear with trajectory overlap. We characterize the resulting system and identify bottlenecks in its components. The system is evaluated on publicly available data and we provide open access to the code.Comment: 8 pages, submitted to ICRA 201

Detecting Invalid Map Merges in Lifelong SLAM

For Lifelong SLAM, one has to deal with temporary localization failures, e.g., induced by kidnapping. We achieve this by starting a new map and merging it with the previous map as soon as relocalization succeeds. Since relocalization methods are fallible, it can happen that such a merge is invalid, e.g., due to perceptual aliasing. To address this issue, we propose methods to detect and undo invalid merges. These methods compare incoming scans with scans that were previously merged into the current map and consider how well they agree with each other. Evaluation of our methods takes place using a dataset that consists of multiple flat and office environments, as well as the public MIT Stata Center dataset. We show that methods based on a change detection algorithm and on comparison of gridmaps perform well in both environments and can be run in real-time with a reasonable computational cost.Comment: Accepted at IROS 202

FDZ annual report 2007

"Following the two evaluations by the German Council for Social and Economic Data in 2006 and by the German Council of Science and Humanities in 2007, the Research Data Centre (FDZ) of the Federal Employment Agency at the Institute for Employment Research plans to report on its activities regularly in future. We are beginning with this FDZ Annual Report 2007, which is intended to summarise the main events of the past 12 or 24 months in a few pages. The Annual Report also serves to provide transparency for our users, who after all justify the existence of the FDZ. This Report is divided into the following chapters: 'General Function', 'Basic Information', 'The Service-Oriented FDZ', 'The International FDZ' and, as an apt conclusion, 'Research at the FDZ'. Parts of the appendices (for Example Publications or Presentations in German) are not translated into English." (Text excerpt, IAB-Doku) ((en)) Additional Information Here you can find the German version of the report.Forschungsdatenzentrum - Bericht, Bundesagentur für Arbeit, IAB, amtliche Statistik, Datenzugang, Datenschutz, Arbeitsmarkt- und Berufsforschung, IAB-Beschäftigtenstichprobe, IAB-Betriebspanel, IAB-Betriebs-Historik-Panel, IAB-Linked-Employer-Employee-Datensatz, Integrierte Erwerbsbiografien, Datenaufbereitung, Datenausgabe

Fokus auf der Untersuchung des Einflusses biometrischer Faktoren auf das Ergebnis der nTMS Messung sprachrelevanter Areale neurochirurgischer Patienten

Objective: Navigated transcranial magnetic stimulation (nTMS) is a non-invasive mapping tool to locate functional areas of the brain, gaining importance as a preoperative diagnostic device. This is a summary of three studies, Schwarzer et al., Rosenstock et al. and Zdunczyk et al., whose aim it is to increase the accuracy and usability of nTMS in different neurosurgical patient groups. They intend to describe neurophysiological data gained through nTMS as a supportive measure for surgical planning to increase patient safety and improve outcome. Methods: All patients and healthy subjects were examined via bihemispheric nTMS. Schwarzer et al. ascertained a baseline picture naming performance and used repetitive nTMS (rnTMS) to induce speech disruptions to identify individual language areas in patients with language eloquent lesions. Nine biometric factors were analyzed for correlation with elevated error occurrence. Rosenstock et al. concentrated on the primary motor cortex of patients with motor-eloquent glioma and performed correlation analyses to test the association of nTMS-related variables and postoperative motor outcome. Zdunczyk et al. examined patients with degenerative cervical myelopathy (DCM) and healthy volunteers to see differences in neurophysiological nTMS data due to disease severity. Results: Schwarzer et al. showed a significant increase in error occurrence with increased severity of cognitive impairment (p8mm (p=0.014). New postoperative deficits could be seen in patients with pathological excitability of the motor cortex (resting motor threshold ratio 110%, p=0.031). Patients with DCM had a reduced corticospinal excitability estimated by the recruitment curve (p=0.022), and patients with mild symptoms showed an increased activation on non- primary motor areas (p<0.005). Patients with severe symptoms showed a higher cortical inhibition (p<0.05) and a reduced motor area (p<0.05). Conclusion: Most patients are eligible for rnTMS language mapping. A new protocol for language mapping is proposed for secure identification of patients eligible for reliable rnTMS in Schwarzer et al. Rosenstock et al. introduce a new risk stratification model, based on objective functional-anatomical and neurophysiological measures, which enables physicians to counsel patients about the risk of functional deterioration or the potential for recovery and supports surgical planning. Zdunczyk et al. propose a new concept for functional compensation for DCM on the cortical and spinal level: the corticospinal reserve capacity. nTMS is a viable diagnostic tool to characterize this and its parameters serve as valuable prognostic factors.Fragestellung: Navigierte transkranielle Magnetstimulation (nTMS) ist eine nicht-invasive Untersuchungsmethode, um kortikale Funktionsareale zu identifizieren, welche zunehmend an Bedeutung als präoperatives diagnostisches Mittel gewinnt. Dies ist eine Zusammenfassung dreier Studien, Schwarzer et al., Rosenstock et al. und Zdunczyk et al. Die Studien haben als Ziel, die Benutzerfreundlichkeit und Genauigkeit von nTMS für unterschiedliche neurochirurgische Patientengruppen zu verbessern. Neurophysiologische Parameter wurden mittels nTMS erhoben, um die operative Planung zu unterstützen und das individuelle Patientenrisiko korrekt einzuschätzen und zu verbessern. Methodik: Alle Patienten und Probanden wurden bihemisphärisch mittels nTMS untersucht. Schwarzer et al. erhoben vorher die individuelle Fähigkeit zur Objektbenennung (baseline) und nutzten repetitive nTMS (rnTMS), um Sprachunterbrechungen hervorzurufen und somit Kortexareale bei Patienten mit sprachrelevanten Hirnläsionen zu identifizieren. Neun biometrische Patienteneigenschaften wurden in ein Verhältnis mit der Fehleranfälligkeit gesetzt. Rosenstock et al. untersuchten den primär motorischen Kortex bei Gliompatienten und analysierten den Zusammenhang von nTMS-ermittelten Parametern mit dem postoperativen Patientenzustand. Zdunczyk et al. betrachteten Patienten mit degenerativer zervikaler Myelopathie (DCM), sowie gesunde Probanden und ermittelten die unterschiedlichen nTMS-Parameter in Abhängigkeit von der Symptomschwere. Ergebnisse: Die meisten biometrischen Faktoren zeigten keinen statistischen Zusammenhang mit dem Stimulationsergebnis bei Schwarzer et al. Je schwerer der Aphasiegrad und die kognitiven Einschränkungen waren, desto mehr Sprachfehler wurden in der rnTMS Untersuchung gemacht (je p8mm zwischen Tumor und kortikospinalem Trakt keine neuen permanenten postoperativen Defizite auftraten (p=0.014). Neue postoperative Defizite traten bei Patienten mit präoperativ pathologischer Kortexerregbarkeit (Ruhemotorschwellenverhältnis RMT 110%, p=0.031) auf. DCM Patienten wiesen eine reduzierte kortikospinale Erregbarkeit, gekennzeichnet durch ein Abflachen der recruitment curve, auf (p=0.022). Ein vergrößertes motorisch relevantes Kortexareal mit Aktivierung sekundärer Motorareale zeigte sich bei Patienten mit milder Symptomatik (p<0.005), während bei schwer betroffenen Patienten eine erhöhte kortikale Hemmung (CSP, p<0.05) und reduzierte motorische Kortexfläche auffiel (p<0.05). Schlussfolgerung: Schwarzer et al. stellen ein neues Prüfungsprotokoll für die Eignung von Patienten für ein reliables rnTMS Ergebnis vor, wobei die statistische Analyse ergab, dass die meisten Patienten für eine reliable rnTMS Sprachuntersuchung geeignet sind. Rosenstock et al. präsentieren ein neues Risikostratifikationsmodell für Patienten mit motorisch relevanten Gliomen, wodurch der Operateur anhand von funktionell-anatomischen und neurophysiologischen Parametern das individuelle Patientenrisiko für den postoperativen Verlauf einschätzen kann. Zdunczyk et al. beschreiben einen möglichen funktionellen Kompensationsmechanismus bei DCM Patienten auf kortikaler und spinaler Ebene: die kortikospinale Reservekapazität. Die durch nTMS ermittelten Parameter lassen damit objektivierbare prognostische Aussagen zu

Micro-Evidence on Rent Sharing from Different Perspectives

This article provides evidence of rent sharing from orthogonal directions by exploiting different dimensions in the same data. Taking advantage of a rich matched employer-employee dataset for France over the period 1984-2001, we consistently compare across-industry heterogeneity in rent-sharing parameters derived from three different approaches. The accounting approach and the standard labor economics approach are compatible with distinct labor bargaining settings (right-to-manage, efficient bargaining, labor hoarding) whereas the productivity approach hinges on the assumption of efficient bargaining. Across the different approaches, we evidently find differences in dispersion of the rent-sharing parameter estimates which could be attributable to differences in modeling assumptions and/or data requirements but these estimates lie within a comparable range. We interpret the latter finding as lending empirical support to efficient bargaining as the nature of the bargaining process in France over the considered period.rent sharing, wage equation, production function, matched employer-employee data

New Tools for Studying Network Industry Reforms in Developing Countries: The Telecommunications and Electricity Regulation Database

Infrastructure industries including telecommunications, electricity, water, and gas underwent massive structural changes during the 1990s. During that decade, hundreds of privatization transactions valued at billions of dollars were completed in these sectors in developing and transitional economies. While privatization has received the most attention, reforms also included market liberalization, structural changes like unbundling, and the introduction of new laws and regulations. To date, regulations have received far less attention than their potential economic effects warrant, largely due to lack of data. In order to address this problem, we set out to compile an extensive, comprehensive, and consistent dataset through an extensive survey of telecommunications and electricity regulators in developing countries. Our database of telecommunications regulations includes 178 variables on regulatory governance and content in 45 countries. Our database of electricity regulations includes 374 variables in 20 countries.

Regional Determinants of FDI Distribution in Poland

In this paper we examine the location determinants of the inflow of Foreign Direct Investment (FDI) into Poland, at a regional level. Using survey data from an online questionnaire in February 2005 and a multinomial logit model incorporating the investorís specific characteristics, we show that knowledge-seeking factors alongside market and agglomeration factors, act as the main drivers for the inflow of FDI to the Mazowieckie region (including Warsaw), while efficiency and geographical factors encourage FDI to the other areas of Poland. Some implications are drawn for FDI attraction policy in Poland.http://deepblue.lib.umich.edu/bitstream/2027.42/64429/1/wp943.pd

Robust estimates of exporter productivity premia in German business services enterprises

A large and growing number of micro-econometric studies show that exporting firms are more productive than firms that sell their products on the home market only. This so-called exporter productivity premium qualifies as a stylized fact. Only recently researchers started to look at the role of extreme observations, or outliers, in shaping these findings. These studies use micro-econometric methods that are robust against outliers to show that very small shares of firms with extreme values drive the result. The large exporter productivity premium found for samples of firms including outliers are dramatically smaller in samples without these extreme observations. Evidence on this, however, is limited so far to firms from manufacturing industries. This note adds comparable evidence for firms from the business services industries. We find that the estimated exporter productivity premium is statistically significant and relevant from an economic point of view when a standard fixed effects estimator is used to control for unobserved firm characteristics, but that it drops to zero when a robust estimator is applied.Exporter productivity premium, services firms, robust estimation, panel data