Omnidirectional bearing-only see-and-avoid for small aerial robots:

Motivated by the growing interest in unmanned aerial system's applications in indoor and outdoor settings and the standardisation of visual sensors as vehicle payload. This work presents a collision avoidance approach based on omnidirectional cameras that does not require the estimation of range between two platforms to resolve a collision encounter. It will achieve a minimum separation between the two vehicles involved by maximising the view-angle given by the omnidirectional sensor. Only visual information is used to achieve avoidance under a bearing-only visual servoing approach. We provide theoretical problem formulation, as well as results from real flight using small quadrotors

Cross-entropy optimization for scaling factors of a fuzzy controller: a see-and-avoid approach for unmanned aerial systems

The Cross-Entropy (CE) is an efficient method for the estimation of rare-event probabilities and combinatorial optimization. This work presents a novel approach of the CE for optimization of a Soft-Computing controller. A Fuzzy controller was designed to command an unmanned aerial system (UAS) for avoiding collision task. The only sensor used to accomplish this task was a forward camera. The CE is used to reach a near-optimal controller by modifying the scaling factors of the controller inputs. The optimization was realized using the ROS-Gazebo simulation system. In order to evaluate the optimization a big amount of tests were carried out with a real quadcopter.

See-and-avoid quadcopter using fuzzy control optimized by cross-entropy

In this work we present an optimized fuzzy visual servoing system for obstacle avoidance using an unmanned aerial vehicle. The cross-entropy theory is used to optimise the gains of our controllers. The optimization process was made using the ROS-Gazebo 3D simulation with purposeful extensions developed for our experiments. Visual servoing is achieved through an image processing front-end that uses the Camshift algorithm to detect and track objects in the scene. Experimental flight trials using a small quadrotor were performed to validate the parameters estimated from simulation. The integration of crossentropy methods is a straightforward way to estimate optimal gains achieving excellent results when tested in real flights.

Quadcopter see and avoid using a fuzzy controller

Unmanned Aerial Vehicles (UAVs) industry is a fast growing sector. Nowadays, the market offers numerous possibilities for off-the-shelf UAVs such as quadrotors or fixed-wings. Until UAVs demonstrate advance capabilities such as autonomous collision avoidance they will be segregated and restricted to flight in controlled environments. This work presents a visual fuzzy servoing system for obstacle avoidance using UAVs. To accomplish this task we used the visual information from the front camera. Images are processed off-board and the result send to the Fuzzy Logic controller which then send commands to modify the orientation of the aircraft. Results from flight test are presented with a commercial off-the-shelf platform.

UAS See-and-Avoid Strategy using a Fuzzy Logic Controller Optimized by Cross-Entropy in Scaling Factors and Membership Functions

This work aims to develop a novel Cross-Entropy (CE) optimization-based fuzzy controller for Unmanned Aerial Monocular Vision-IMU System (UAMVIS) to solve the seeand- avoid problem using its accurate autonomous localization information. The function of this fuzzy controller is regulating the heading of this system to avoid the obstacle, e.g. wall. In the Matlab Simulink-based training stages, the Scaling Factor (SF) is adjusted according to the specified task firstly, and then the Membership Function (MF) is tuned based on the optimized Scaling Factor to further improve the collison avoidance performance. After obtained the optimal SF and MF, 64% of rules has been reduced (from 125 rules to 45 rules), and a large number of real flight tests with a quadcopter have been done. The experimental results show that this approach precisely navigates the system to avoid the obstacle. To our best knowledge, this is the first work to present the optimized fuzzy controller for UAMVIS using Cross-Entropy method in Scaling Factors and Membership Functions optimization.

UAS See-and-Avoid Strategy using a Fuzzy Logic Controller Optimized by Cross-Entropy in Scaling Factors and Membership Functions.

This work aims to develop a novel Cross-Entropy (CE) optimization-based fuzzy controller for Unmanned Aerial Monocular Vision-IMU System (UAMVIS) to solve the seeand-avoid problem using its accurate autonomous localization information. The function of this fuzzy controller is regulating the heading of this system to avoid the obstacle, e.g. wall. In the Matlab Simulink-based training stages, the Scaling Factor (SF) is adjusted according to the specified task firstly, and then the Membership Function (MF) is tuned based on the optimized Scaling Factor to further improve the collison avoidance performance. After obtained the optimal SF and MF, 64% of rules has been reduced (from 125 rules to 45 rules), and a large number of real flight tests with a quadcopter have been done. The experimental results show that this approach precisely navigates the system to avoid the obstacle. To our best knowledge, this is the first work to present the optimized fuzzy controller for UAMVIS using Cross-Entropy method in Scaling Factors and Membership Functions optimization.

Using the Cross-Entropy Method for Control Optimization: A Case Study of See-and-Avoid on Unmanned Aerial Vehicles

This paper presents an adaptation of the Cross-Entropy (CE) method to optimize fuzzy logic controllers. The CE is a recently developed optimization method based on a general Monte-Carlo approach to combinatorial and continuous multi-extremal optimization and importance sampling. This work shows the application of this optimization method to optimize the inputs gains, the location and size of the different membership functions' sets of each variable, as well as the weight of each rule from the rule's base of a fuzzy logic controller (FLC). The control system approach presented in this work was designed to command the orientation of an unmanned aerial vehicle (UAV) to modify its trajectory for avoiding collisions. An onboard looking forward camera was used to sense the environment of the UAV. The information extracted by the image processing algorithm is the only input of the fuzzy control approach to avoid the collision with a predefined object. Real tests with a quadrotor have been done to corroborate the improved behavior of the optimized controllers at different stages of the optimization process.

One thousand American Fungi : how to select and cook the edible : how to distinguish and avoid the poisonous : giving full botanic descriptions : made easy for reader and student /

Half title: American fungi.

Debt settlements : FmHA can do more to collect on loans and avoid losses : report to Congressional committees /

"B-257647"--P. 1.

Effectiveness of see-and-treat for approaching pre-invasive lesions of uterine cervix

OBJECTIVE: To compare the effectiveness between the see-and-treat (S&T) approach and the conventional one (with prior biopsy) for squamous intraepithelial lesions of uterine cervix. METHODS: A cross-sectional study was conducted with 900 nonpregnant women with cytology suggestive of high grade squamous intraepithelial lesions in the city of Rio de Janeiro, Southeastern Brazil, between 1998 and 2004. The S&T approach consists of a large loop excision of the transformation zone procedure and is recommended when cytology is suggestive of high grade squamous intraepithelial lesion, satisfactory colposcopy with abnormalities compatible with the suspected cytological results, and the lesion is limited to the ectocervix or extends up to one centimeter of the endocervical canal. A subgroup of 336 patients whose colposcopy was considered satisfactory was analyzed, and they were divided into two groups for comparison: patients treated without prior biopsy (n = 288) and patients treated after a biopsy showing high grade squamous intraepithelial lesions (n = 48). Patients who were not treated or only treated more than a year later after recruitment at the colposcopy unit were considered dropouts. RESULTS: Of patients recruited during the study period, 71 were not treated or were only treated for at least a year. The overall dropout rate was 7.9% (95% CI: 6.1;9.7). Mean time elapsed between patient recruitment and treatment was 17.5 days in the S&T group and 102.5 days in the prior biopsy group. Dropout rates were 1.4% (95% CI: 0.04;2.7) and 5.% (95% CI: 0;12.3), respectively (p=0.07). The proportion of overtreated cases (negative histology) in the S&T group was 2.0% (95% CI: 0.4;3.6). CONCLUSIONS: The difference in the mean time elapsed between patient recruitment and treatment indicates that S&T is a time-saving approach The proportion of negative cases from using the S&T approach can be regarded as low.

To see and to touch : God, honour, and irony in Shakespeare's English histories /

Failed and fragile states that result from intrastate war pose severe threats to the security of both the international system and individual states alike. In the post-Cold War era, the international community has come to recognize the reality of these threats and the difficulty involved in ending violence and building sustainable peace in failed and fragile states. This work focuses upon the development of a comprehensive strategy for sustainable peace-building by incorporating the tenets of the human security doctrine into the peace-building process. Through the use of case studies of The Former Yugoslav Republic of Macedonia and East Timor, the development and refinement of the doctrine of human security will occur, as well as, an understanding of how and where human security fits into the sustainable peace-building equation. The end result of the analysis is the development of a hierarchical pyramid formation that brings together human security and peace-building into one framework that ultimately creates the foundation and structure of sustainable peace-building. With the development of a sustainable peace-building structure based upon the human security doctrine, the role of Canada in the support of sustainable peace-building is analyzed in relation to the form and level of involvement that Canada undertakes and contributes to in the implementation and support of sustainable peace-building initiatives. Following from this, recommendations are provided regarding what role(s) Canada should undertake in the sustainable peace-building process that take into consideration the present and likely future capabilities of Canada to be involved in various aspects of the peace-building process. ii This paper outlines the need for a peace-building strategy that is designed to be sustainable in order that failed and fragile states resulting from intrastate conflict do not regress or collapse back into a condition of civil war, and subsequently designs such a strategy. The linking of peace-building and human security creates the required framework from which sustainable peace-building is derived. Creating sustainable peace is necessary in order to increase the likelihood that both present and future generations existing in failed and fragile states will be spared from the scourge of intrastate war.

Annual 10Be concentrations from Lakes Tiefer See and Czechowskie AD1983-2009

Beryllium 10 concentrations (10Becon) were measured at annual resolution from varved sediment cores of Lakes Tiefer See (TSK) and Czechowskie (JC) for the period 1983-2009 (~solar cycles 22 and 23). Calibrating the 10Becon time-series against complementing proxy records from the same archive as well as local precipitation and neutron monitor data, reflecting solar forced changes in atmospheric radionuclide production, allowed (i) identifying the main depositional processes and (ii) evaluating the potential for solar activity reconstruction. 10Becon in TSK and JC sediments are significantly correlated to varying neutron monitor counts (TSK: r=0.5, p=0.05, n=16; JC: r=0.46, p=0.03, n=22). However, the further correlations with changes in organic carbon contents in TSK as well as varying organic carbon and detrital matter contents in JC point to catchment specific biases in the 10Becon time-series. In an attempt to correct for these biases multiple regression analysis was applied to extract an atmospheric 10Be production signal (10Be atmosphere). To increase the signal to noise ratio a 10Be composite record (10Be composite) was calculated from the TSK and JC 10Be atmosphere time-series. 10Becomposite is significantly correlated to variations in the neutron monitor record (r=0.49, p=0.01, n=27) and matches the expected amplitude changes in 10Be production between solar cycle minima and maxima. This calibration study on 10Be from two sites indicates the large potential but also, partly site-specific, limitations of 10Be in varved lake sediments for solar activity reconstruction.

Pollen record from Muggesfelder See and Plussee in Germany

A basaltic tephra layer consisting of brownish-olive glass shards. and about 0.2 mm thick. was found in cores from four lakes in northwest Germany. According to pollen analysis it was deposited during the early Boreal period (corresponding to about 8700 BP). The petrographic properties. the geochemical composition and the age agree with those of the Saksunarvatn tephra. which was first found on the Faroe Islands. The position of the tephra layer in the pollen stratigraphy and in the absolute time-scale is discussed. Procedures for locating the tephra in other cores are suggested.

Global Linear Instability at the Dawn of its 4th Decade: A List of Challenges (A Practical Guide on how to Contain the Euphoria and Avoid the Oversell)

Global linear instability theory is concerned with the temporal or spatial development of small-amplitude perturbations superposed upon laminar steady or time-periodic threedimensional flows, which are inhomogeneous in two (and periodic in one) or all three spatial directions.1 The theory addresses flows developing in complex geometries, in which the parallel or weakly nonparallel basic flow approximation invoked by classic linear stability theory does not hold. As such, global linear theory is called to fill the gap in research into stability and transition in flows over or through complex geometries. Historically, global linear instability has been (and still is) concerned with solution of multi-dimensional eigenvalue problems; the maturing of non-modal linear instability ideas in simple parallel flows during the last decade of last century2–4 has given rise to investigation of transient growth scenarios in an ever increasing variety of complex flows. After a brief exposition of the theory, connections are sought with established approaches for structure identification in flows, such as the proper orthogonal decomposition and topology theory in the laminar regime and the open areas for future research, mainly concerning turbulent and three-dimensional flows, are highlighted. Recent results obtained in our group are reported in both the time-stepping and the matrix-forming approaches to global linear theory. In the first context, progress has been made in implementing a Jacobian-Free Newton Krylov method into a standard finite-volume aerodynamic code, such that global linear instability results may now be obtained in compressible flows of aeronautical interest. In the second context a new stable very high-order finite difference method is implemented for the spatial discretization of the operators describing the spatial BiGlobal EVP, PSE-3D and the TriGlobal EVP; combined with sparse matrix treatment, all these problems may now be solved on standard desktop computers.