Density and Distribution Evaluation for Convolution of Independent Gamma Variables

Several numerical evaluations of the density and distribution of convolution of independent gamma variables are compared in their accuracy and speed. In application to renewal processes, an efficient formula is derived for the probability mass function of the event count

Ultra-Low-Frequency Radio Astronomy Observations from a Selenocentric Orbit: first results of the Longjiang-2 experiment

This paper introduces the first results of observations with the Ultra-Long-Wavelength (ULW) -- Low Frequency Interferometer and Spectrometer (LFIS) on board the selenocentric satellite Longjiang-2. We present a brief description of the satellite and focus on the LFIS payload. The in-orbit commissioning confirmed a reliable operational status of the instrumentation. We also present results of a transition observation, which offers unique measurements on several novel aspects. We estimate the RFI suppression required for such a radio astronomy instrumentation at the Moon distances from Earth to be of the order of 80 dB. We analyse a method of separating Earth- and satellite-originated radio frequency interference (RFI). It is found that the RFI level at frequencies lower than a few MHz is smaller than the receiver noise floor.Comment: Accepted for publication in Experimental Astronomy; 22 pages, 11 figure

Mobile product recognition and recommendation

With the rapid development of mobile phone and image processing technology, Mobile Visual Search has become a popular topic in recent years. Several innovative Mobile Visual Search applications have been released. However, some applications and algorithms still have the potential to be improved in accuracy and speed performance. For example, as a typical image recognition system, Vocabulary Tree (VT) Based Image Recognition has fine recognition accuracy but it takes a long time to query one image. The third process, Geometric Verification (GV) is time-consuming and therefore results in a slow recognition speed. In this Final Year Project, Fast Geometric Re-Ranking (FGRR) is developed and incorporated into the current VT Based Image Recognition system. It aims to speed up the overall image recognition and maintain or even improve the recognition accuracy. Experiments results show that FGRR achieves these objectives. FGRR alone improves VT recognition accuracy by around 1% and incorporated FGRR has maximum 0.8% accuracy improvement on VT Based Image Recognition. Besides, FGRR only takes a small portion of overall time consumption. When FGRR is incorporated to maintain same accuracy level, overall time consumption is reduced by 33%. To sum up, objectives of FGRR are achieved in this project.Bachelor of Engineerin

On Brownian Motion Governed by Telegraph Process

Statistical modeling of animal movement is of critical importance in addressing fundamental questions about space use, movement, resource selection, and behavior in animal ecology. The explosion of telemetry data on animal movement from the recent advancements in tracking and observation technologies presents a storm of opportunities and challenges. A moving-resting-handling (MRH) process is introduced to allow predators to have two different motionless states, resting, and handling. In essence, it is a Brownian motion whose infinitesimal variance changes according to a three-state continuous-time Markov Chain. The Markov Chain can be viewed as a telegraph process with one on state and two off states. We derive the distribution of the occupation times of this Markov Chain and develop a maximum likelihood estimation procedure when the stochastic process at hand is observed at discrete, possibly irregularly spaced time points. The likelihood function is evaluated with forward algorithm in the general framework of hidden Markov models. The second objective of this thesis is to introduce measurement errors to a recently proposed moving-resting (MR) process. MR process is a Brownian motion governed by a telegraph process, which allows periods of inactivity in one state of the telegraph process. It is promising in modeling the movements of predators with long inactive periods such as mountain lions, but the lack of accommodation of measurement errors seriously prohibits its applications in practice. Here we incorporate measurement errors in the MR model and derive basic properties of the model. Finally, convolutions of independent gamma variables are encountered in many applications, including animal movement modeling. Accurate and fast evaluations of their density and distribution functions are critical for such applications. We review several numerical evaluations of convolution of independent gamma variables and compare them with respect to their accuracy and speed. We also derive a new computationally efficient formula for the probability mass function of the number of renewals by a given time. Two R packages smam, coga provide efficient C++ based implementations of the discussed methods and are available in CRAN

AQUACULTURE IN MYANMAR: FISH FARM TECHNOLOGY, PRODUCTION ECONOMICS AND MANAGEMENT

Fish farming (aquaculture) has grown rapidly in Myanmar over the last two decades and plays an increasingly important role in national fish supply, but its technical and economic characteristics have been poorly studied. This report addresses this knowledge gap by presenting data from the first statistically representative survey of fish farms conducted in Myanmar - the Myanmar Aquaculture-Agriculture Survey (MAAS)