Safe and Cost-Efficient Mobile Robot Navigation in Aware Environments

When designing autonomous mobile robotic systems, there usually is a trade-off between the three opposing goals of safety, low-cost and performance. If one of these design goals is approached further, it usually leads to a recession of one or even both of the other goals. If for example the performance of a mobile robot is increased by making use of higher vehicle speeds, then the safety of the system is usually decreased, as, under the same circumstances, faster robots are often also more dangerous robots. This decrease of safety can be mitigated by installing better sensors on the robot, which ensure the safety of the system, even at high speeds. However, this solution is accompanied by an increase of system cost. In parallel to mobile robotics, there is a growing amount of ambient and aware technology installations in today's environments - no matter whether in private homes, offices or factory environments. Part of this technology are sensors that are suitable to assess the state of an environment. For example, motion detectors that are used to automate lighting can be used to detect the presence of people. This work constitutes a meeting point between the two fields of robotics and aware environment research. It shows how data from aware environments can be used to approach the abovementioned goal of establishing safe, performant and additionally low-cost robotic systems. Sensor data from aware technology, which is often unreliable due to its low-cost nature, is fed to probabilistic methods for estimating the environment's state. Together with models, these methods cope with the uncertainty and unreliability associated with the sensor data, gathered from an aware environment. The estimated state includes positions of people in the environment and is used as an input to the local and global path planners of a mobile robot, enabling safe, cost-efficient and performant mobile robot navigation during local obstacle avoidance as well as on a global scale, when planning paths between different locations. The probabilistic algorithms enable graceful degradation of the whole system. Even if, in the extreme case, all aware technology fails, the robots will continue to operate, by sacrificing performance while maintaining safety. All the presented methods of this work have been validated using simulation experiments as well as using experiments with real hardware

Stratigraphy of offshore sediment of Lake Agassiz, North Dakota

Lake Agassiz occupied the Red River Valley between about 13,800 and 9,000 years ago. The Late Wisconsinan ice sheet that covered the Red River Valley retreated far enough to expose the drainage divide in northern South Dakota and south-central Minnesota sometime after 14,000 B.P. and meltwater ponded behind this divide in Richland County. Before 13,800 the ice readvanced over this area and then retreated again. As the ice margin retreated northward, deposition of the Argusville and Wylie Formations took place. Sometime before 12,800 the ice advanced again into the Red River Valley as far as Traill County; the terminus of this advance is marked by the clay rich pebble-loam of the Huot Formation, and the Falconer Formation was deposited behind the Huot. Deposition of the Argusville Formation continued in the southern part of the basin. Deposition of the Brenna Formation began when the ice margin began retreating out of the Red River Valley. About 11,000 B.P. an eastern outlet into the Lake Superior basin was opened, and Lake Agassiz dropped from the Campbell level to below the Ojata level. During the period between 11,000 B.P. and 9,900 B.P. the lake level fluctuated several times, but most of the time the lake floor was subject to erosion. A stream network similar to that of the present day developed, depositing the Poplar River Formadon. About 9,900 B.P. the eastern outlets were plugged by ice and Lake Agassiz rose back to the Campbell level. The lake stood at this level for about 900 years; during this time the Sherack Formation was deposited. The engineering properties of the Sherack Formation include low to moderate water content (17% to 56%), wide range of liquid limit (27% to 92%), and wide range of consistency index (22% to 86%). The northern part of the Brenna Formation has high water content (62% to 88%), a high liquid limit (63% to 104%), and very low penetration resistance (4 to 7 blows per foot). The southern part of the Brenna Formation and the Wylie and Argusville Formations have similar engineering properties. The range in water content (38% to 69%), liquid limit (39% to 93%), and penetration resistance (4 to 16 blows per foot) for these units are similar. The Poplar River Formation is under confined piezometric conditions, and pilings or footings in it are subject to failure. The Falconer and Huot Formations have engineering properties similar to the Sherack, Wylie, and Argusville Formations. The glacial sediments underlying the Lake Agassiz sediment provide a suitable foundation for nearly all types of construction

Experimental Reexamination of Transverse Tensile Strength for IM7/8552 Tape-Laminate Composites

Due to the observed dependence of transverse-tensile strength, YT, on test geometry and specimen size, there is no consensus regarding a test method that can uniquely measure YT. This study reexamines characterization of YT by comparing results from established flexure tests with results from a new tensile test that exhibits consistent failure in the gage region. Additionally, the effects of surface preparation and direction of transverse fracture are investigated. Results show that YT is inversely proportional to specimen volume and surface roughness, and is insensitive to direction of transverse fracture. The relationship between specimen volume and YT is adequately captured by Weibull strength-scaling theory, except at the tails of the YT distributions. However, specimens exhibited microcracking prior to failure, which violates the weak-link assumptions of the Weibull theory. These findings highlight the challenges of using deterministic YT values in progressive damage analysis

Nanoparticle detection in an open-access silicon microcavity

We report on the detection of free nanoparticles in a micromachined, open-access Fabry-P\'erot microcavity. With a mirror separation of $130\,\mu$m, a radius of curvature of $1.3\,$mm, and a beam waist of $12\,\mu$m, the mode volume of our symmetric infrared cavity is smaller than $15\,$pL. The small beam waist, together with a finesse exceeding 34,000, enables the detection of nano-scale dielectric particles in high vacuum. This device allows monitoring of the motion of individual $150\,$nm radius silica nanospheres in real time. We observe strong coupling between the particles and the cavity field, a precondition for optomechanical control. We discuss the prospects for optical cooling and detection of dielectric particles smaller than $10\,$nm in radius and $1\times10^7\,$amu in mass.Comment: 4 pages, 3 figure

Risk factor analysis for fast track protocol failure

Background: The introduction of fast-track treatment procedures following cardiac surgery has significantly shortened hospitalisation times in intensive care units (ICU). Readmission to intensive care units is generally considered a negative quality criterion. The aim of this retrospective study is to statistically analyse risk factors and predictors for re-admission to the ICU after a fast-track patient management program. Methods: 229 operated patients (67 ± 11 years, 75% male, BMI 27 ± 3, 6/2010-5/2011) with use of extracorporeal circulation (70 ± 31 min aortic crossclamping, CABG 62%) were selected for a preoperative fast-track procedure (transfer on the day of surgery to an intermediate care (IMC) unit, stable circulatory conditions, extubated). A uni- and multivariate analysis were performed to identify independent predictors for re-admission to the ICU. Results: Over the 11-month study period, 36% of all preoperatively declared fast-track patients could not be transferred to an IMC unit on the day of surgery (n = 77) or had to be readmitted to the ICU after the first postoperative day (n = 4). Readmission or ICU stay signifies a dramatic worsening of the patient outcome (mortality 0/10%, mean hospital stay 10.3 ± 2.5/16.5 ± 16.3, mean transfusion rate 1.4 ± 1,7/5.3 ± 9.1). Predicators for failure of the fast-track procedure are a preoperative ASA class > 3, NYHA class > III and an operation time >267 min ± 74. The significant risk factors for a major postoperative event (= low cardiac output and/or mortality and/or renal failure and/or re-thoracotomy and/or septic shock and/or wound healing disturbances and/or stroke) are a poor EF (OR 2.7 CI 95% 0.98-7.6) and the described ICU readmission (OR 0.14 CI95% 0.05-0.36). Conclusion: Re-admission to the ICU or failure to transfer patients to the IMC is associated with a high loss of patient outcome. The ASA > 3, NYHA class > 3 and operation time >267 minutes are independent predictors of fast track protocol failure

Emerging Data on Sorority/Fraternity-affiliated Student Government Presidents

Alongside sorority/fraternity governance structures, student government is another major form of campus involvement and student representation. At times, students share both student/leadership identities: as members of a sorority/fraternity and serving as a student government officer. In this study on student government presidents, descriptive statistics were used to tell the story of student government presidents who are also members of a sorority or fraternity and in comparison, to those who are not. Findings include present-day affiliation data, as well as campus contextual elements of their experience. There are subsequent recommendations for student affairs practice