Generating Compact Tree Ensembles via Annealing

Tree ensembles are flexible predictive models that can capture relevant variables and to some extent their interactions in a compact and interpretable manner. Most algorithms for obtaining tree ensembles are based on versions of boosting or Random Forest. Previous work showed that boosting algorithms exhibit a cyclic behavior of selecting the same tree again and again due to the way the loss is optimized. At the same time, Random Forest is not based on loss optimization and obtains a more complex and less interpretable model. In this paper we present a novel method for obtaining compact tree ensembles by growing a large pool of trees in parallel with many independent boosting threads and then selecting a small subset and updating their leaf weights by loss optimization. We allow for the trees in the initial pool to have different depths which further helps with generalization. Experiments on real datasets show that the obtained model has usually a smaller loss than boosting, which is also reflected in a lower misclassification error on the test set.Comment: Comparison with Random Forest included in the results sectio

A review of autonomous docking technologies for an unmanned aircraft carrier

Aerial carrier is becoming a hotspot in Remote Piloted Aircraft System (RPAS) research area recently. As a variant of the general RPAS swarm, this technology is believed to be promising in both military and civilian applications. For example, it could enhance the safety of a military surveillance mission, it could enlarge the surveillance region coverage and it could extend the communication range of any single RPAS. One essential problem for the realisation of the aerial carrier is the autonomous docking in the air. This paper presents a review of autonomous docking techniques ranging from active LED recognition to passive laser scanning and three-dimensional (3D) remodelling. It is aimed at providing a broad perspective on the statues of the recognition and position estimation problems

Environmental impact assessments of the Three Gorges Project in China: issues and interventions

The paper takes China's authoritative Environmental Impact Statement for the Yangzi (Yangtze) Three Gorges Project (TGP) in 1992 as a benchmark against which to evaluate emerging major environmental outcomes since the initial impoundment of the Three Gorges reservoir in 2003. The paper particularly examines five crucial environmental aspects and associated causal factors. The five domains include human resettlement and the carrying capacity of local environments (especially land), water quality, reservoir sedimentation and downstream riverbed erosion, soil erosion, and seismic activity and geological hazards. Lessons from the environmental impact assessments of the TGP are: (1) hydro project planning needs to take place at a broader scale, and a strategic environmental assessment at a broader scale is necessary in advance of individual environmental impact assessments; (2) national policy and planning adjustments need to react quickly to the impact changes of large projects; (3) long-term environmental monitoring systems and joint operations with other large projects in the upstream areas of a river basin should be established, and the cross-impacts of climate change on projects and possible impacts of projects on regional or local climate considered. © 2013 Elsevier B.V.Xibao Xu, Yan Tan, Guishan Yan

The Development of a Conceptual Design Algorithm of Multicopters and the Study of its Applications

Multicopters is a large branch of unmanned aerial vehicles (UAVs). Due to the high agility and simple structure of multicopters, they are popularly used in many commercial and civilian applications. However, for a long time, there have existed few systematic algorithms to design multicopters. Most manufacturers and amateurs tend to design multicopters based on experiencerather than engineering principles.In this thesis, a conceptual design algorithm of multicopters is developed which has a better confidence of estimation than in previous works. The main part of this algorithm is a process which determines the minimum gross take-off mass (퐺푇푂푀) of a certain combination of design parameters. This process calls the layer_2 function; it begins with a guessed 퐺푇푂푀, considersthe given mission requirements, and then calculates the required power for different flight conditions. Next, the required performances of each component are calculated based on the power and are used for estimating the components’ mass and price. At the end, the total mass is summed as the estimated 퐺푇푂푀. If the error between the initial 퐺푇푂푀 and the estimated 퐺푇푂푀is close to zero, the initial 퐺푇푂푀 can be considered the minimum valid 퐺푇푂푀. Outside of this process, an external loop proceeds through all the design parameter combinations and develops a pool of valid designs (can converge to the minimum 퐺푇푂푀). Optimised designs can be filtered out with given targets (e.g. 푀푇푂푀, total price, endurance and the maximum speed, among others).Compared with the previous methods of multicopter conceptual design, this algorithm offers thefollowing innovations:• This algorithm considers the entire aircraft rather than focussing on a single separated system.• The forest-tree-bagging technique is applied on the regression process of components, achieving better accuracy of component selection.• The methods used in previous works are normally valid for only a narrow range of products, while this algorithm is valid for small (approximately 100 g) to relatively large (approximately 30 kg) multicopters.• The algorithm can optimise not only the maximum take-off mass (푀푇푂푀) but also the price, endurance, total energy consumed and maximum speed.This algorithm is validated for four aspects: the components estimation, total mass estimation, function output and optimisation process. Sensitivity analyses are then conducted for some selected parameters.With the aforementioned advantages, this validated algorithm can be used as a tool for studying some specific flight mission problems. The algorithm can not only determine the most suitable design for a specific mission but can also be used to evaluate the extent to which a design is matched to a mission, compare several designs for a mission or even help to improve the mission. This is one of the primary contributions of this thesis, since such a tool for multicopters has not yet been seen.An example scenario is provided at the end of this thesis. For a long-range mission involving several multicopters, the signal should remain connected throughout the mission. One multicopter would serve as the leader to complete the mission, while the others will remain at each waypoint to function as repeaters. For such a mission, the multicopters can be organised into different configurations, similar to how a mother carries several children. Three configurations are proposed and compared based on several aspects

Development of active directional antennae for use in small UAVs

Five different light-weight, medium and high gain directional antennas have been developed, which can be operated together with a gimbals system on the UAV or an antenna tracker system on the ground or with both to extend the range of communication and improve the quality of video signals. The antennas are based on PCB to reduce the mass. There are two types of antennas developed for different transmission frequency: Patch Antenna and Yagi-Uda Antenna. The gimbals system are under developing, which will be based on Arduino Micro Development Board, also quite light, and the board will drive a pan and tilt structure constructed with two small but powerful servos to ensure the antenna to point at the ground station

Development of an active gimbal system for a directional antenna on a small RPA

Remotely piloted aircraft are still not yet a feature of everyday life, however the numbers in use is growing rapidly and the range of operations that they support increasing. This conference, organised by the Royal Aeronautical Society’s Unmanned Aircraft Systems Specialist Group, will provide delegates with essential information on the factors that are supporting the proliferation of civil use as well as providing clear insights into the regulatory and other constraints in place to ensure public safety and privacy. The capabilities, opportunities and technologies are developing at a rapid pace and will be outlined by various experts from UK, Europe and America. In addition speakers from UK Government organisations will present a vision of the support available, the requirements to be adhered to and the way in which regulations are developing. - See more at: http://aerosociety.com/Events/Event-List/1402/RPAS-Today-Opportunities-and-Challenges#sthash.CHtG2mPW.dpu