物理與天文學

本研究提供一種低成本且高產率的奈米泡泡製備方法，我們以去離子水注入氮氣製程製備成溶液，再藉超音波震洗機(sonicator)高速振動來製備奈米泡泡。在實驗中我們藉由控制不同的震動時間及實驗參數，可製作出不同尺寸的奈米泡泡，藉此可找出奈米泡泡的臨界尺寸。藉由這種方法我們可成功製作出100nm以下的奈米泡泡。另外我們發現隨著振動時間增加，泡泡的尺寸會逐漸減少，呈現明顯且有趣的尺寸效應變化。實驗結果顯示以當離子水溶液以氮氣飽和20分鐘並以超音波振動30分鐘時，可製作出最小臨界尺寸為23nm的奈米泡泡，此一奈米泡泡尺寸為目前所觀察到最小尺寸的奈米泡泡。我們也對不同實驗條件下所觀察到的尺寸效應，提出分析及探討，以期未來能對奈米泡泡的尺寸現象有更多瞭解。而利用此一方法來製作奈米泡泡有別於傳統方法，除了可製作出高產率且高穩定性的奈米泡泡之外，更可進一步改善一般傳統方法製作泡泡因為表面張力造成的影響，其泡泡尺寸只能達到微米(10-6)等級。而我們的方法可將泡泡的尺寸縮小至數十奈米等級，將有助於未來奈米泡泡於生化領域以及醫學上的廣泛應用。

This project was inspired by a tournament call the International Young Physicist’ Tournament (IYPT). The problem could be broken into two aims: ‘Investigate the forces that cause a ball to levitate in a titled airstream’ and ‘optimize the system for the maximum angle of tilt that results in a supported ball’. The first stage of the investigation was research and learning. Two fluid mechanics courses online were used to build a basic of knowledge of the subject. Next a force diagram was created to model the forces acting on the ball. The diagram identified a force called the lift force that must be acting on the ball to be supported. There were three contending theories that could explain the lift force: The Bernoulli theory, the Coanda theory and the Magnus theory. A practical investigation was then instigated to differentiate between these three theories. Since the Magnus theory is only applicable if the ball is spinning in the airstream, this theory was isolated by changing the center of mass of the ball but keep everything else constant (this allowed control of how much the ball spun in the airstream). Changing the center of mass didn’t impact on the maximum angle of tilt at all, proving that the spinning of the ball isn’t producing a significant amount of lift, and therefore the Magnus theory couldn’t be a cause for lift. Because further testing couldn’t isolate the Coanda and Bernoulli theories, a solution was developed to explain why the two remaining theories might co-exist. Further testing methods have been designed to investigate this possibility in more depth. To meet the second aim of this project, an investigation was launched to see how parameters affected the maximum angle that the ball could be supported at. The parameters investigated were: Ball radius, ball mass, ball surface, air speed and airstream diameter. A lot of time was spent creating a reliable experimental method. The method could be used to support a ball in an air stream, slowly tilt the air stream, and then measure the angle of tilt the moment that the ball fell out. After experimentation, a table was created to describe how the listed parameters affect the maximum angle of tilt that a ball can be supported at. Explanations were proposed for why each parameter affected this angle. Future experiments have been devised to build a deeper understanding of the effects of a wider range of parameters.

本研究透過高速攝影機與流場可視化技術拍攝不同體型蝴蝶在自由飛行時之流場與飛行姿態，並分析不同蝴蝶體型、拍撲頻率與飛行姿態上之關係。相較於人類的發明的飛行器，蝴蝶的飛行更加的複雜、省力且優美，其主要原因為蝴蝶以拍擊翅膀產生渦漩來達到巧妙的飛行操控；由蝴蝶飛行流場發現，蝴蝶在飛行時會不斷的改變身體角度來控制渦漩環產生的方向，下拍時主要產生向下的渦漩環，蝴蝶此時主要產生向上升力；而上拍時蝴蝶產生往後的渦漩環，並藉此產生推力，透過此特殊的動力產生方式，蝴蝶飛行軌跡呈現類似Z字形。進一步透過研究不同種類的蝴蝶飛行發現，不論體型大小之蝴蝶，其翅膀單位面積之負重比皆落在0.01~0.02 g/cm2之間，且當蝴蝶體型被放大時，可以較低的拍撲頻率進行飛行，然而飛行軌跡變化則較劇烈，此研究之成果可做為未來拍撲微飛行器尺寸設計之依據。

本實驗乃研究超順磁性流體薄膜在通入垂直場後磁顆粒的動力學過程，以及排列的結構、磁鍊的幾何性質。我們使用了兩種創新的方法，分別是改良傳統磁性流體製造方法，避免磁性流體因凝聚而造成干擾；另一個是除了以往以電場或顯微鏡探討磁鍊的性質，使用Rayleigh scattering以及光遮蔽的方法，以CCD量測雷射透射光強度的時變率，改變不同變因(磁場大小、磁性流體樣本厚度、磁性流體濃度)，由於其結構性質影響了透射光強度，故分析透射光強度與諸變因間的關係，並與顯微鏡下的觀察結果比較，做出磁致散射動力學過程詮釋。

This science project is designed to answer a question of whether or not a chemical reaction is needed to produce industrial quantities of carbon nanostructures by exposing dry ice to a high temperature that is at least 3100°C. A small carbon arc furnace powered by an electric welder is used to produce the high temperature. During control runs, the carbon arc furnace is energized for a predetermined time, after which the carbon arc furnace is de-energized and any carbon particles within the furnace are collected. During carbon nanostructures synthesis runs, dry ice is placed within the carbon arc furnace. The carbon arc furnace is energized and the dry ice is consumed for the predetermined time. Carbon nanostructures synthesized during the synthesis runs are collected once the carbon arc furnace is de-energized and allowed to cool. The volume of the carbon particles collected during the control runs is compared to the volume of the carbon nanostructures produced by the synthesis runs. This science project has discovered that on average at least 16 times more carbon nanostructures are produced during synthesis runs consuming dry ice as opposed to the control runs. Moreover, the synthesis runs did not rely on chemical reactions. Further still, samples of the synthesized carbon nanostructures were imaged using a transmission electron microscope (TEM). The TEM images clearly show high-quality carbon nanostructures that include carbon nanotubes, faceted carbon nanospheres, and the super-material graphene.

將氮、氧、二氧化碳等三種氣體，分別注入水中成為飽和水溶液，將氣體水溶液分裝入塑膠試管中，用超音波洗淨儀以42kHz的頻率振動，可形成奈米氣泡水溶液。利用奈米粒徑及界面電位量測儀測量氣泡的尺寸以及界面電位後，作實驗探討不同尺寸的奈米氣泡對水溶液的磁性、表面張力、折射率、黏滯係數、以及擴散係數等物理性質的影響。 實驗得知:(1)氮和二氧化碳的奈米氣泡的尺寸愈小，水溶液受到的磁力愈大，氧氣則相反。(2)三種氣體水溶液的表面張力都是奈米氣泡尺寸愈小，表面張力愈小。(3)三種氣體水溶液的折射率都是奈米氣泡尺寸愈小，折射率愈大。(4)三種氣體水溶液的黏滯係數都是奈米氣泡尺寸愈小，黏滯係數愈小，110nm的二氧化碳奈米氣泡使水的黏滯係數降低38.8％。(5)三種氣體水溶液都會阻止甘油在水中的擴散，使其擴散係數變小。

本計畫採用數值模擬進行研究，撰寫一維電漿的物理程式來瞭解電漿孤立子在不均勻背景中的演化。我們於去年的計畫中，驗證了這個模型的準確性，這次進一步地在系統中，加入相對論的計算，用以觀察孤立子在相對論作用下的傳播及演化。我們可以觀察到不同參數的初始脈衝會影響到所生成的孤立子形狀，並藉由給予不均勻的背景環境，可以發現孤立子演化的準則。與期刊上發表的論文進行比較時，發現數值吻合，誤差約為1%。因此我們反向藉由論文中的運算式，解出一個孤立子，將其放入系統中，希望藉由這個方式更順利地了解孤立子在空間中的行為模式。未來，我們將利用這些結果來制定多維的電漿體數值模擬，其可以解釋現實宇宙中，蟹狀星雲能源運輸的問題。

We all do it – walk along with a cup in hand, and carelessly spill it. While it’s usually more annoying than anything else, it happens to affect almost all of us, and little is done to minimise the likelihood of it occurring. So my aim was to explain the physics behind why we spill drinks when we walk, and to investigate how we can minimise the likelihood of this occurring. I broke this investigation into two distinct parts, explaining the system of the cup, and explaining the effect of walking. From initial observations, it was clear that the cup was a resonating system. Like any resonating system, the cup has a natural frequency. When the cup is oscillated – moved back and forth – at near this frequency, the size of the liquid oscillations is very large. This is because the acceleration is in phase with the motion of the liquid, so in each cycle maximum energy is input into the system. In my investigation I experimentally measured this natural frequency, and created a mathematical model to explain this frequency. It was also found that as the size of liquid oscillations in the cup increases, so does distortion of the fluid surface, possibly enabling spilling. To systematically analyse the effect of walking, I had subjects walk on a treadmill, so walking surface and speed were controlled. However, I also needed an accurate way of measuring the motion of a carried cup. Firstly, I tried to use video analysis; however I found this far too imprecise for measuring small changes in velocity of a cup. In the end I used a smartphone to record the acceleration of a carried cup, as acceleration is what causes the movement of liquid in a cup. This allowed surprisingly accurate measurements to be made, and allowed both the size and frequency of the acceleration to be recorded. In order to relate the system of the cup and the oscillation provided whilst walking I conducted a qualitative experiment into the effect of stride frequency on the likelihood of spilling. When stride frequency was very close to the natural frequency of the cup, spilling occurred almost instantly, while it did not occur if stride frequency was much higher or lower. In the end, my research showed that to minimise the likelihood of spilling your drink walk slowly, use a narrow cup, focus on walking smoothly, and fill the cup well below the rim. Despite this, some people happen to be much smoother cup carriers than others, likely due to their individual biomechanics. And, if you really don’t want to spill your drink, you can always use a lid.

本研究主要探討傾角對面轉變的影響與面轉變的原因。當柱體由肥皂水中拉起時，泡膜圖形可分為中央膜平行與垂直底面的形式，兩種形式因高的變化而互相轉換的過程稱為面轉變。三到六角柱傾角越大，面轉變時的高越大，反之亦然；六角柱可以面轉變，且在40°到45°之間有臨界角度存在。本研究以力與能量的角度解釋面轉變．泡膜藉由改變面積以達到最低的能量、維持穩定狀態，因此本研究計算、比較不同形式的泡膜面積，以解釋面轉變。我們同時發現三角錐與四角錐都不會發生面轉換；三角錐的實驗值多大於理論值，四角錐的實驗值則多小於理論值。

本研究的風力發電裝置除了在轉子裝上旋翼外，再將定子裝上另外反轉旋翼，並分析單雙組旋翼在不同電阻、風速等變因下所受的影響，以及磁浮軸承的擺動軌跡。以QBLADE軟體設計旋翼，並以飛機木製作。利用送風機產生風能，以自耦變壓器控制風速、可變電阻改變電阻並進行單雙組旋翼測量；用不同水平力施於磁浮軸承，觀察其擺動。最後將測得數據製成Excel圖表，分析趨勢。