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Improving Particle Classification In Wimp Dark Matter Detection Using Neural Networks
In all experiments for detection of WIMP dark matter, it is essential to develop a classifier that can distinguish potential WIMP events from background radiation. Most often, clas- sifiers are developed manually, via physical modeling and empirical optimization. This is problematic for two reasons: it takes a great deal of time and effort away from developing the experiment, and the resulting classifiers often perform suboptimally (which means that a greater amount of expensive run time is required to obtain a confident experimental result). Machine learning has the potential to automate this and accelerate experimentation, and also to detect patterns that humans cannot. However, two major challenges, which are shared among several dark matter experiments, stand in the way: impure calibration data, which hinders training of models, and unpredictable physical dynamics within the detector itself. My objective was to develop a set of machine learning techniques that address these two problems, and thus more efficiently generate highly accurate classifiers. I was able to obtain raw data for two dark matter experiments which exhibit these challenges: the PICO-60 bubble chamber [2], and the DEAP-3600 liquid argon scintillator [1]. For each experiment, I developed and compared three general-purpose algorithms intended to resolve its inherent challenge (impurity and unpredictable dynamics, respectively). In PICO-60, background alpha and WIMP-like neutron calibration datasets are used for training; however, there is an impurity of 10% alphas in the neutron set. While a conventional classifier was developed (and is believed to be 100% accurate), machine learning in the form of a supervised neural network (NN) has also been previously explored, because of the benefits of automation. Unfortunately, it achieved a mean accuracy of only 80.2% – not usable as a practical replacement for conventional methods in future iterations of the experiment. In DEAP-3600, photons are absorbed by a wavelength shifting medium and re-emitted in an unpredictable direction, before being detected by one of 255 photomultiplier tubes (PMTs) around the spherical detector. The randomness severely limits the accuracy of conventional classifiers; in a simulation, the best so far removes 99.6% of alpha background, while also (undesirably) removing 91.0% of WIMP events. Because of physical limitations, simulated data is used for calibration, with 30 real-world experimental events available for testing. I have written a research paper [11] about my work on PICO-60, which has been approved by the PICO collaboration and pre-published at https://arxiv.org/abs/1811.11308. It is currently undergoing peer review for publication in Computer Physics Communications. All PICO researchers are listed on my paper for their work on the original PICO-60 experi- ment. They did not contribute to this study; I completed and documented it independently.
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「三」不轉「六」轉,「六」不轉機器人轉---從正多邊形翻轉問題到機器人掃樓梯
為了可以設計能打掃樓梯的掃地機,我們需探討正n邊形在階梯上的翻轉,因此我們從試作小正三角形在大正四邊形外圍的翻轉,畫出質心之翻轉軌跡並算出弧長與面積;接著我們擴展到小正n邊形在大正k邊形的翻轉,在千變萬化的軌跡中,找到弧長、面積的通式。同時,我們也探討:當由大正k邊形翻轉小正n邊形的弧長軌跡,並計算出回到原出發點的最小圈數,並發現其規律。最後在應用方面,我們依此發展到小正n邊形及圓形在階梯上的翻轉,並改變階梯之夾角推導出其通式,可應用在機器人掃地機打掃樓梯。
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福壽螺今天想吃什麼呢?-探究不同的餌料誘捕福壽螺,減少秧苗被啃食的機會
福壽螺,原產於中南美洲,商人認為有利可圖,便將其走私進入台灣,希望取代田螺,供民眾食用。但是,福壽螺的肉質不符合台灣民眾的口味,因此商人紛紛將福壽螺棄養。福壽螺具有耐污染、抗乾旱的特性,再加上它在台灣沒有天敵,因而建立起自己的族群,啃食農作物,造成鉅額的農業損失。為誘捕福壽螺,減少其對稻苗的啃食,本研究全程使用美濃當地盛產之農作物作為誘餌,一方面可物盡其用的消耗NG農作物,另一方面可誘捕福壽螺減少對稻苗的損害,促進台灣農業及防治福壽螺的雙重效益研究指出,選擇的誘餌具有顯著誘引福壽螺之效果,進一步發現擺放位置也會影響捕捉到的福壽螺數量,於是設計陷阱器來捕捉,希望能為台灣的有機農業盡一份力。
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