1,347 research outputs found
Plane Segmentation and Registration of Sparse and Heterogeneous Mobile Laser Scanning Point Clouds
This research discussed and analysed the limitations of different state of the art methods for point cloud processing tasks due to the sparseness and the heterogeneousness of the MLS point clouds. A novel plane detection and segmentation method for sparse MLS point clouds is proposed. Finally, the most suitable techniques for automatic registration of MLS sparse point clouds were determined based on a new error metric for evaluation
Solar variability over the Holocene period : disentangling geomagnetic and solar influences on a new continuous 10Be record from Little Dome C, Antarctica
Reliable information on solar activity over the Holocene period is important to predict the Sun in the future and to understand the mechanism behind the Sun-climate linkage. Presently, there are discrepancies in the proxy data of solar activity due to reasons that are not yet understood. This leads to major uncertainties in Holocene solar reconstructions. This PhD project aims to improve the Holocene solar reconstructions with a new dataset and a better reconstruction method. The results are be important for s lar and Sun-climate studies as well as for a better understanding of past changes in the carbon cycle.Cosmogenic radionuclides such as 10Be in ice cores and 14C in tree rings are the best-known proxies for solar activity far back in time. The radionuclide records reflect a combination of production, transportation and deposition processes (atmospheric circulation (10Be) and carbon cycle (14C)). Presently, the different radionuclide records show disagreements regarding their long-term (millennial-scales) changes for unknown reasons. Moreover, the radionuclide records are also influenced by long term changes in the geomagnetic field that are not well constrained. This leads to major uncertainties in reconstructions of past changes in solar activity.This thesis is based on new 10Be measurements from 759 ice chip samples drilled at the East Antarctic site called Little Dome C (LDC). The new 10Be record continuously covers the entire Holocene. A Bayesian model was also developed to disentangle solar activity and geomagnetic field influences on the radionuclide records. The model was applied on the new LDC 10Be data and also on the existing 10Be data from other ice cores and tree-ring 14C data. The reconstructions show consistent short-term variations (decadal- and centennial-scale) of solar activity while longterm variations (multi-millennial-scale) are still uncertain. Long-term discrepancies are present among the 10Be records and the 14C data, especially for the last 4 ka. We also found hints of a polar bias effect that dampens the geomagnetic field influence on Antarctic 10Be records but the effect is absent in a Greenland 10Be record. These results point to a difference in the transportation mode of 10Be toward the different ice core sites and an influence of the carbon cycle changes on the 14C data
Outage performance analysis of non-orthogonal multiple access with time-switching energy harvesting
In recent years, although non-orthogonal multiple access (NOMA) has shown its potentials thanks to its ability to enhance the performance of future wireless communication networks, a number of issues emerge related to the improvement of NOMA systems. In this work, we consider a half-duplex (HD) relaying cooperative NOMA network using decode-and-forward (DF) transmission mode with energy harvesting (Ell) capacity, where we assume the NOMA destination (D) is able to receive two data symbols in two continuous time slots which leads to the higher transmission rate than traditional relaying networks. To analyse EH, we deploy time-switching (TS) architecture to comprehensively study the optimal transmission time and outage performance at D. In particular, we are going to obtain closed-form expressions for outage probability (OP) with optimal TS ratio for both data symbols with both exact and approximate forms. The given simulation results show that the placement of the relay (R) plays an important role in the system performance.Web of Science253918
Real-time Optimal Resource Allocation for Embedded UAV Communication Systems
We consider device-to-device (D2D) wireless information and power transfer
systems using an unmanned aerial vehicle (UAV) as a relay-assisted node. As the
energy capacity and flight time of UAVs is limited, a significant issue in
deploying UAV is to manage energy consumption in real-time application, which
is proportional to the UAV transmit power. To tackle this important issue, we
develop a real-time resource allocation algorithm for maximizing the energy
efficiency by jointly optimizing the energy-harvesting time and power control
for the considered (D2D) communication embedded with UAV. We demonstrate the
effectiveness of the proposed algorithms as running time for solving them can
be conducted in milliseconds.Comment: 11 pages, 5 figures, 1 table. This paper is accepted for publication
on IEEE Wireless Communications Letter
Rapid Prototyping for Sheet Metal Products
The aim of this chapter is to evaluate and predict forming limit and then to improve and develop the incremental sheet metal forming (ISMF) processes for complex surface products of sheet metal. The theoretical study was first overviewed and synthesized in order to recognize the effect of geometry, technology parameters, and processing conditions on ISMF process. Finite element method (FEM) simulation study was then used to compare the accuracy of constitutive material models and fracture criteria and propose new equations in order to improve the prediction of FEM simulation for incremental sheet metal forming process. To develop a new technique for improving the formability of sheet metal using ISMF, FEM was also adopted to reduce the cost and time of research. The basic experimental studies were performed to determine the input data for FEM simulation such as tensile data, fracture parameters, and so on. To investigate and compare the simulation results, the incremental sheet metal forming processes for complex shapes were also conducted
Automatic limit and shakedown analysis of 3-D steel frames
This paper presents an efficient algorithm for both limit and shakedown analysis of 3-D steel frames by kinematical method using linear programming technique. Several features in the application of linear programming for rigid-plastic analysis of three-dimensional steel frames are discussed, as: change of the variables, automatic choice of the initial basic matrix for the simplex algorithm, direct calculation of the dual variables by primal-dual technique. Some numerical examples are presented to demonstrate the robustness, efficiency of the proposed technique and computer program
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