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

Design of Selective Laser Melting (SLM) Structures: Consideration of Different Material Properties in Multiple Surface Layers Resulting from the Manufacturing in a Topology Optimization

Topology optimization offers a possibility to derive load-compliant structures. These structures tend to be complex, and conventional manufacturing offers only limited possibilities for their production. Additive manufacturing provides a remedy due to its high design freedom. However, this type of manufacturing can cause areas of different material properties in the final part. For example, in selective laser melting, three areas of different porosity can occur depending on the process parameters, the geometry of the part and the print direction, resulting in a direct interrelation between manufacturing and design. In order to address this interrelation in design finding, this contribution presents an optimization method in which the three porous areas are identified and the associated material properties are considered iteratively in a topology optimization. For this purpose, the topology optimization is interrupted in each iteration. Afterwards, the three areas as well as the material properties are determined and transferred back to the topology optimization, whereby those properties are used for the calculation of the next iteration. By using the optimization method, a design with increased volume-specific stiffness compared to a design of a standard topology optimization can be created and will be used in the future as a basis for the extension by a global strength constraint to maintain the maximum permissible stress and the minimum wall thickness

Lightweight design in product development: a conceptual framework for continuous support in the development process

To get closer towards achieving the climate targets and the resulting reduction in CO2 emissions, one possible strategy is to consider lightweight activities across all industries. In product development, this means that lightweight design should be integrated at a very early stage, as this is the only way to achieve the highest lightweight potential. However, such an integration is very complex, since necessary lightweight activities cannot be applied sequentially or universally to all products. Even multiple usage of different lightweight design strategies is not sufficient to achieve a targeted lightweight design on the overall system level. Therefore, it is necessary to support the product developer in the application of lightweight design by providing a framework with necessary methods and processes as well as recommendations regarding their timing. The possibility to apply them individually to different systems and related problems has to be given. To develop such a framework, different projects with respect to lightweight design were analyzed and evaluated. The main focus was on the determination of lightweight design strategies that were applied in the projects and the subsequent derivation of requirements in order to raise further lightweight potential. Based on this analysis and evaluation, a conceptual framework was developed that focuses on the overall system to be optimized, which can be part of a previous generation, for example. Subsequently, the available lightweight activities and design strategies were linked with supporting tools and methods from knowledge management. Therefore, this conceptual framework provides continuous support for the product developer throughout the entire product development process in lightweight activities

The Programming and Assembly of a Transcriptional Silencing Complex

Argonautes and their small RNA guides form an ancient partnership with diverse roles in controlling gene expression and preserving genome stability. In the fission yeast Schizosaccharomyces pombe, the Argonaute Ago1 acts within the RITS complex to target the repetitive DNA elements that flank each centromere for heterochromatic silencing, which is necessary for faithful chromosome transmission. A separate Ago1-containing complex, termed ARC, is also required for pericentromeric silencing but its precise function, and the mechanisms that regulate the movement of Ago1 between ARC and RITS, have remained unclear. This dissertation investigates both of these questions. By combining distinct approaches, we have defined the role of ARC as that of enabling Ago1 to be programmed with small RNA guides. In an in vitro assay using immunopurified proteins, we found that loading of synthetic double-stranded small RNAs into Ago1 requires the ARC subunit Arb1 but not the RITS subunit Tas3. In parallel, we isolated cellular Ago1- associated small RNAs and, by high-throughput sequencing, observed that deletion of ARC components produced read features indicative of nonspecifically-interacting small RNAs. Together, these data indicate that the small-RNA-loading capability of Ago1 is conferred by ARC. We also discovered using co-immunoprecipitation that the ARC subunits Arb1 and Arb2 are required for the proper association between RITS subunits Ago1 and Tas3, suggesting that small-RNA loading by ARC might license Ago1 for assembly into RITS. Indeed, we went on to show that Ago1 mutants deficient for small-RNA loading universally fail to interact with Tas3, whereas other non-functional Ago1 variants maintain Tas3 association. We conclude that Tas3 distinguishes between loaded and unloaded Ago1, admitting only the former into RITS. Our studies have delineated the mechanisms that control the programming and assembly of the RITS complex. The results illuminate the role of ARC in heterochromatic silencing and identify this complex as the machinery required for loading small RNAs into Argonaute in S. pombe. Furthermore, we have uncovered small-RNA loading as a checkpoint for the entry of Argonaute into RITS, which may reflect a common discriminatory function of GW-repeat proteins such as Tas3 that precludes the formation of inactive and potentially deleterious complexes.Medical Science

A comparison between the LESA model and the marginal lands criteria of Senate Bill 237 : Linn County, Oregon

Marginal agricultural and forest lands are currently a focus of concern for public land use agencies in Oregon. Two alternatives for evaluating marginal agricultural lands are the Land Evaluation and Site Assessment (LESA) model of the U.S. Soil Conservation Service and the marginal lands criteria of the 1983 Oregon Legislature's Senate Bill 237. Each of these management tools have had limited application in Oregon, but have not been compared to each other to determine their relative effects. This study proposes to compare LESA and SB 237 by applying their criteria to the 23 case study tracts of the 1983-84 Linn County LESA study, and to a larger contiguous tract of agricultural land near Scio in northern Linn County. The study's determination of the comparative strengths and weaknesses of the two methods can be used by the Linn County Planning Department, by the Land Resource Management Program of the OSU Extension Service and by state agencies and legislators to help evaluate the 2-year performance of SB 237, and the feasibility of using LESA as an alternative to SB 237

Field evaluations of parcel-specific and area applications of Senate Bill 237 marginal lands criteria

Marginal agricultural land is currently a focus of concern for public land use agencies in Oregon. Two approaches for evaluating marginal agricultural lands are the Land Evaluation and Site Assessment (LESA) model of the U.S. Soil Conservation Service, and the marginal lands criteria of the 1983 Oregon Legislature's Senate Bill 237. Each of these land management tools have had limited application in Oregon, but have not undergone extensive field evaluation to determine their relative effects and requirements. This research paper examines the application of SB 237 criteria to 23 case study tax lots included in the 1983-84 Linn County LESA study. In addition, the SB 237 criteria are applied to a larger tract of agricultural land near Scio in northern Linn County. An analysis of the procedures and findings is presented. Other findings point out those spatial land characteristics which are associated with marginal land as defined by SB 237. The findings of this paper's SB 237 field evaluations are framed in the context of Oregon's land use planning program. Key Words: marginal agricultural land, parcelization

Micro-recanalization in a biodegradable graft for reconstruction of the vas deferens is enhanced by sildenafil citrate

This study investigated the effect of sildenafil citrate on micro-recanalization and neovascularization, which were previously demonstrated in a rat model using biodegradable grafts (BGs) for vas deferens reconstruction. A total of 24 male rats underwent bilateral vasectomy with removal of a 0.5-cm vasal segment and were randomly assigned to four groups. Groups 1 and 2 underwent immediate vasovasostomy. Groups 3 and 4 underwent interposition of a 0.5-cm BG in the vasal gap. Groups 1 and 3 were given 5 mg kg -1 day -1 oral sildenafil. Other groups were given placebo. Rats were housed with females 12 weeks postoperatively. Reconstructed vasal segments were harvested 16 weeks postoperatively and analyzed histologically. Fluid from the distal vasal stump was analyzed for motile sperm. Urine samples obtained 16 weeks postoperatively were analyzed for cGMP levels. cGMP levels in rats treated with sildenafil were significantly higher than in control rats. No pregnancies were sired by grafted groups. In all, 5/6 rats in group 1 and 3/6 rats in group 2 sired litters. No motile sperm were noted in the vasal fluid of the grafted groups. Motile sperm were noted in all rats in group 1 and in 5/6 rats in group 2. In addition, 29 and 4 microcanals were detected in the sildenafil and placebo groups, respectively (P = 0.023). No microcanal exceeded 3 mm in length. An average of 12 and 28 blood vessels per graft were noted in the placebo and sildenafil groups, respectively (P 0.0001). In conclusion, sildenafil enhances micro-recanalization and neovascularization in BG used for vas deferens reconstruction, but does not increase the microcanal length after 16 weeks