547 research outputs found
Depth Image Processing for Obstacle Avoidance of an Autonomous VTOL UAV
We describe a new approach for stereo-based obstacle avoidance. This method analyzes the images of a stereo camera in realtime and searches for a safe target point that can be reached without collision.
The obstacle avoidance system is used by our unmanned helicopter ARTIS (Autonomous Rotorcraft Testbed for Intelligent Systems) and its simulation environment. It is optimized for this UAV, but not limited to aircraft systems
Command injection attacks, continuations, and the Lambek calculus
This paper shows connections between command injection attacks,
continuations, and the Lambek calculus: certain command injections, such as the
tautology attack on SQL, are shown to be a form of control effect that can be
typed using the Lambek calculus, generalizing the double-negation typing of
continuations. Lambek's syntactic calculus is a logic with two implicational
connectives taking their arguments from the left and right, respectively. These
connectives describe how strings interact with their left and right contexts
when building up syntactic structures. The calculus is a form of propositional
logic without structural rules, and so a forerunner of substructural logics
like Linear Logic and Separation Logic.Comment: In Proceedings WoC 2015, arXiv:1606.0583
Categorical structure of continuation passing style
Laboratory for Foundations of Computer ScienceThis thesis attempts to make precise the structure inherent in Continuation Passing Style (CPS).
We emphasize that CPS translates lambda-calculus into a very basic calculus that does not have functions as primitive.
We give an abstract categorical presentation of continuation semantics by taking the continuation type constructor (cont in Standard ML of New Jersey) as primitive. This constructor on types extends to a contravariant functor on terms which is adjoint to itself on the left; restricted to the subcategory of those programs that do not manipulate the current continuation, it is adjoint to itself on the right.
The motivating example of such a category is built from (equivalence classes of typing judgements for) continuation passing style (CPS) terms. The categorical approach suggests a notion of effect-free term as well as some operators for manipulating continuations. We use these for writing programs that illustrate our categorical approach and refute some conjectures about control effects.
A call-by-value lambda-calculus with the control operator callcc can be interpreted. Arrow types are broken down into continuation types for argument/result-continuations pairs, reflecting the fact that CPS compiles functions into a special case of continuations. Variant translations are possible, among them lazy call-by-name, which can be derived by way of argument thunking, and a genuinely call-by-name transform. Specialising the semantics to the CPS term model allows a rational reconstruction of various CPS transforms
A Proof-of-Principle Study in Rural Kenya
Tungiasis (sand flea disease) is a neglected tropical disease, prevalent in
resource-poor communities in South America and sub-Saharan Africa. It is
caused by an inflammatory response against penetrated female sand fleas (Tunga
penetrans) embedded in the skin of the host. Although associated with
debilitating acute and chronic morbidity, there is no proven effective drug
treatment. By consequence patients attempt to remove embedded sand fleas with
non-sterile sharp instruments, such as safety pins, a procedure that
represents a health threat by itself. In this proof-of-principle study we
compared the topical application of a mixture of two dimeticones of low
viscosity (NYDA) to the topical application of a 0.05% solution of KMnO4 in 47
school children in an endemic area in rural Kenya. The efficacy of the
treatment was assessed during a follow up period of seven days using viability
signs of the embedded parasites, alterations in the natural development of
lesion morphology and the degree of local inflammation as outcome measures.
Seven days after treatment, in the dimeticone group 78% (95% CI 67â86%) of the
parasites had lost all signs of viability as compared to 39% (95% CI 28â52%)
in the KMnO4 group (p<0.001). In the dimeticone group 90% (95% CI 80â95%) of
the penetrated sand fleas showed an abnormal development already after 5 days,
compared to 53% (95% CI 40â66%; p<0.001) in the KMnO4 group. Seven days after
treatment, signs of local skin inflammation had significantly decreased in the
dimeticone group (p<0.001). This study identified the topical application of
dimeticones of low viscosity (NYDA) as an effective means to kill embedded
sand fleas. In view of the efficacy and safety of the topical treatment with
dimeticone, the mechanical extraction of embedded sand fleas using hazardous
instruments is no longer warranted
LEGO Mindstorms Votingbot
Auch in diesem Jahr 2021 wurde das Legopraktikum trotz komplizierter Situation durchgefĂŒhrt. Dabei wurde einigen Studierenden der Fachschaft fĂŒr Elektro- und Informationstechnik die Möglichkeit geboten allein oder als Gruppe eine Idee fĂŒr einen Roboter zu entwickeln und diese umzusetzen. Dieser Roboter sollte aus LEGO gebaut werden und eine oder mehrere Aufgaben autonom ausfĂŒhren können. In diesem Paper wird auf die Konstruktion, Programmierung und Entwicklung einesRoboters eingegangen, welcher durch einen Ultraschallsensor Objekte erkennen, diese aufnehmen, in einen BehĂ€lter ablegenund anschlieĂend die Anzahl der Objekte, die er sortiert hat per Sprachausgabe ausgeben konnte
Active Fluid Borne Noise Reduction for Aviation Hydraulic Pumps
The aviation environment holds challenging application constraints for efficient hydraulic system noise reduction devices. Besides strong limits on component weight and size, high safety and reliability standards demand simple solutions. Hence, basic silencers like inline expansion chambers and Helmholtz-Resonators are state-of-the-art aboard commercial aircrafts. Unfortunately, they do not meet todayâs noise attenuation aims regarding passenger comfort and equipment durability. Significant attenuation performance is expected from active concepts that generate anti-phase noise. However, such concepts remain a long term approach unless related costs, e.g. due to additional power allocation and real-time control equipment can be avoided. In this paper an active fluid borne noise attenuation concept is discussed that accounts for the mentioned constraints. An aircraft hydraulic pump is considered as main noise source. The active attenuator is an in-house rotary valve design. The basic feature is a known direct shaft coupling principle of pump and rotary valve, so no speed/ frequency control of the valve and no separate power supply are required. The common-shaft principle is further simplified here and proposed as integral feature of future âsmart pumpsâ
Dependence of impedance of embedded single cells on cellular behaviour
Non-invasive single cell analyses are increasingly required for the medicaldiagnostics of test substances or the development of drugs and therapies on the single celllevel. For the non-invasive characterisation of cells, impedance spectroscopy whichprovides the frequency dependent electrical properties has been used. Recently,microfludic systems have been investigated to manipulate the single cells and tocharacterise the electrical properties of embedded cells. In this article, the impedance ofpartially embedded single cells dependent on the cellular behaviour was investigated byusing the microcapillary. An analytical equation was derived to relate the impedance ofembedded cells with respect to the morphological and physiological change ofextracellular interface. The capillary system with impedance measurement showed afeasibility to monitor the impedance change of embedded single cells caused bymorphological and physiological change of cell during the addition of DMSO. By fittingthe derived equation to the measured impedance of cell embedded at different negativepressure levels, it was able to extrapolate the equivalent gap and gap conductivity betweenthe cell and capillary wall representing the cellular behaviour
Learning Topometric Semantic Maps from Occupancy Grids
Today's mobile robots are expected to operate in complex environments they
share with humans. To allow intuitive human-robot collaboration, robots require
a human-like understanding of their surroundings in terms of semantically
classified instances. In this paper, we propose a new approach for deriving
such instance-based semantic maps purely from occupancy grids. We employ a
combination of deep learning techniques to detect, segment and extract door
hypotheses from a random-sized map. The extraction is followed by a
post-processing chain to further increase the accuracy of our approach, as well
as place categorization for the three classes room, door and corridor. All
detected and classified entities are described as instances specified in a
common coordinate system, while a topological map is derived to capture their
spatial links. To train our two neural networks used for detection and map
segmentation, we contribute a simulator that automatically creates and
annotates the required training data. We further provide insight into which
features are learned to detect doorways, and how the simulated training data
can be augmented to train networks for the direct application on real-world
grid maps. We evaluate our approach on several publicly available real-world
data sets. Even though the used networks are solely trained on simulated data,
our approach demonstrates high robustness and effectiveness in various
real-world indoor environments.Comment: Presented at the 2019 IEEE/RSJ International Conference on
Intelligent Robots and Systems (IROS
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