物理與天文學

The growth of the internet is propelling an ever-increasing need for faster communication. Modern telecommunication data is mainly carried through fibre-optic cables, with pulses of light representing bits of data; the main factor limiting data transfer speed is the rate at which the optical receiver at the opposite end of the cable can detect light pulses. Graphene-silicon Schottky photodiodes are a promising alternative to traditionally-used germanium photodiodes, promising higher detection frequency and better contrast between light and dark. To make it less susceptible to erroneous measurements due to graphene having a low band gap, hydrogen functionalisation was used to increase the barrier potential of the Schottky diode so that a higher voltage would be required to allow current to pass through in forward voltage bias and trigger the sensor. This study seeks to determine the optimal conditions — of physical proximity, duration of exposure, and plasma power — for hydrogen functionalisation using radio frequency plasma. Graphene was synthesised using low pressure chemical vapour deposition, then transferred onto P-type silicon to create a photodiode. The graphene-silicon photodiode was then doped with hydrogen plasma to introduce defects in the graphene layer to increase the barrier potential of the photodiode. To assess the effectiveness of hydrogen functionalisation, photocurrent measurements were conducted while light was shone onto the photodiode in pulses of increasing frequency to find the magnitude and spontaneity of the response. Light was shone in pulses of 100ms, and was successfully detected by the photodiode. The pulse spacings were gradually decreased and it was found that the diode was able to detect pulse spacings as low as 1µs, significantly better than germanium photodetectors. The sample demonstrated clear optoelectronic response and was sensitive to changes in frequency. Results show that the intensity of the optoelectronic response in graphene-silicon diodes is inversely related to its physical proximity to the plasma source during hydrogen functionalization; and directly related to the power of the plasma and to the duration of exposure up to a point, after which it will deteriorate. Thus, it can be concluded that graphene-silicon Schottky diodes offer much promise in electronic communication.

球體在旋轉平台上的運動分三階段：進動階段、螺線振盪階段、打滑階段。進動階段、螺線振盪階段為兩個運動模式的疊加：迴旋半徑漸增的螺旋線運動、向平台中心靠近的平移運動。當迴旋半徑漸增至滑動摩擦力的上限值，球進入打滑階段並向外甩出平台。 研究紀錄球體質心運動參數，並以接觸點準靜態理論計算及滑動-滾動摩擦模型進行數值分析，找出各種變因與運動參數間的關係。 結果發現滾動階段中鋼球作迴旋運動的頻率f球和平台旋轉頻率f盤和有正比關係，且比例值和球標準化轉動慣量δ正相關。由滾動階段過渡到滑動階段的最大迴旋半徑Rmax和f球2成反比、和δ呈負相關、和滑動摩擦係數μk成正比。滾動摩擦使球向平台中心靠近，也使迴旋半徑漸增。平台傾斜或呈錐狀時，球體的運動會向水平方向偏移。

方形盒盛透明液體，置放在冷源上方，液體發生熱擴散時，溫度由上往下逐漸下降，形成溫度梯度以及折射率梯度。雷射光照射和鉛直線成一定角度的玻棒透鏡，再穿過方形盒的透明液體時，在屏上形成斜直線，經一段時間的熱擴散後，變成曲線；曲線和斜直線的距離(h)，隨著時間(t)以及光線照射的位置(y)改變，作不同y的h-t圖可得知液體的熱擴散率狀況。 冷源的溫度0℃，分別用甘油和乙醇作待測液，得到的h-t圖，符合熱擴散推導出的h隨t改變的方程式；改用水當待測液，得到的h-t圖，就不符合熱擴散推導出的h隨t改變的方程式。改用-5℃的冷源，分別用水和氯化鈉水溶液作待測液，得到的h-t圖，不符合熱擴散推導出的h隨t改變的方程式。 用簡易的設備可以了解折射率梯度，溫度梯度，熱擴散率，以及液體的非線性熱擴散。

本專題利用混沌電路本身的不可預測性及混亂程度，製造出作為硬體安全實現的密鑰生成器。從實現基本的蔡氏電路，並探討蔡氏電路作為硬體安全的相關應用為基礎，進而實現進階的研究改造。透過電阻、電感、電容、運算放大器等電子元件，焊接在電路板上，實現一個「四渦漩狀」的混沌電路。 本研究的最大特點，就是會製作兩個具備相同電子元件及構型的多吸引子混沌電路，但天生的元件變異性會產生「類蝴蝶效應」，再利用數位乘法器，將兩個電路之類比訊號相乘，而這個操作會形成一個密鑰生成器的混沌系統。 最後會透過軟體MATLAB 確認電路操作和分析電路輸出信號，及所提出密鑰生成器的安全程度，將會驗證隨機性和獨特性這兩組特徵，分別計算平均及交叉相關函數來做為驗證的依據。最後從實驗中證明了「四渦漩狀」的混沌電路所產生的密鑰具有快速產生及高安全性。

Wireless transmission products are widely used in our daily life. In this research, we focus on knowing how solid-state tesla coil works in different conditions and finding the best parameters through an easy way. In our work, a commercial electroscope was used as detector for measuring the strength of radio wave created by our simplified tesla coils. In fact, many factors would lead to experimental erorrs such as detectors, selected types of NPN BJT components, applied voltage and measuring position of height. Therefore, all of the factors were under control to make sure of accuracy and precision for our designed measuring method. In our experiment, graphics of radio wave distribution around tesla coils were drew by mathemetic software of GeoGebra. It shows the BJT types of 2n2222 had good performance for wireless transmisstion efficiency. To our surprised, we found the extended wires (called antenna) from the top of tesla coil also had an ability to transfer electromagnetic energy, and had good retention if the extended wires were within the length of main coil’s height. Finally, the shape’s and size’s effect was determined by our testing work. The result shows that pipe’s length, pipe’s diameter and turns ratio of two coils had great influence on tesla coil’s transmission efficiency. It was found that the tesla’s performance would be more efficient if wire was used to make the length twice rather than make the diameter twice. However, the turns ratio of secondary coil to primary coil would change while making the length twice. To avoid that, we fixed the length and decrease the turns of primary coil. At last, we found tesla coil must work at the turns of primary coil higher than two. Furthermore, the frequency of radio wave not only had less relationship with their length or diameter but also had less relationship with types of BJT In our study, our handmade tesla coil was succesfully applied for wireless charging and we find that the induced voltage decrease in propotion to cube root of distance between tesla coil and induced coil.

將液滴置於鋪上介電層的電極板，接上電壓時，液滴因表面張力及接觸角產生變化而移動，此現象被稱為介電潤濕，其裝置能讓生醫等產業進行精準的微量藥物配置。為了探討此現象原理及改善裝置，本研究測量液滴位於不同電壓之電極板上方時，液滴接觸角及介電層厚度；透過數值模擬計算系統總能量、視覺化系統的電位空間分布，並計算電容，以能量角度模擬液滴移動模式；對於平面式裝置在長時間移動水珠後，產生水珠移動速率趨緩，甚至朝反方向移動的現象給予解釋；改良文獻中平面式和雙層式的電潤濕裝置，將雙層式上板改為導線。因為形狀酷似電車，因此我們稱其為「水電車」，此裝置保留高電容特性的同時，降低阻力。實驗證實其水珠移動能力優於平面式裝置，除了使液滴更好移動外，相較於封閉的雙層式裝置，開放式系統的特點能讓生醫研究人員更方便置換樣品。

Harmful microorganisms in food can cause deterioration of human health, poisoning and in some cases even death. Especially fresh meat and chicken products create a suitable environment for the growth of microorganisms in terms of the nutrients it contains, water activity and pH level. For this reason, detection of microorganisms in meat products is an important issue in terms of food safety and human health. In this project, it is aimed to detect live microorganisms in meat products, especially chicken meat, in a simple, non-destructive, non-contact and fast way using laser speckle method. Laser speckle images of healthy and stale chicken meat were taken, contrast parameter and correlation analysis of the obtained patterns were made. It was observed that the contrast parameter for staled chicken meat increased by approximately 3 times compared to fresh chicken. This increase provides an understanding of the difference between contaminated chicken and fresh chicken. Speckle density changes over time in relation to the movements of living microorganisms. Thus, the correlation in laser speckle density patterns taken from contaminated tissues is disrupted. In the measurements taken with photodiode, by analyzing the change of light intensity of the speckle patterns on fresh and contaminated tissues over time, the detection of microorganisms was made easier and more precisely without the need for image processing. The proposed measurement system is a new method that detects meat contamination with laser speckle imaging. It can be developed and made portable and can be used easily in homes. Since it is a simple, non-destructive and fast method, it can be used to determine the shelf life of meat in food distribution places and markets. In addition, it has the potential to be calibrated and used for other food products other than meat products. The system developed with this study is cheap and easy to use, and the laser speckle imaging method is used in a different field other than biomedical, contributing to the literature.

本研究探討滴簇的性質與行為，高溫穩定水溶液表面上會有一層水霧般的霧滴層，像是平貼飄浮在水面上，此水滴群為「滴簇」。本研究拍攝下熱水表面的滴簇，並使用ImageJ、Python分析滴簇粒徑等性質以建構物理模型。 藉雷射光凸顯滴簇，觀察滴簇的形成與消失過程。利用被雷射打亮的滴簇在水面的倒影，測量滴簇距水高度。滴簇由5~15μm厚蒸氣層撐起漂浮在水面上，水溫越高，蒸氣層越厚。華（繞射光像）半徑取決於水滴粒徑，本研究分析陽光經水面反射通過滴簇形成的華，測量滴簇粒徑10~20μm。由以上實驗推測：滴簇是高溫蒸氣層接觸低溫的室溫空氣凝結成，溫差愈大凝結量越多，粒徑、數量隨之上升。滴簇會因對流、氣流擾動集體離開水面，留下一道滴簇少的空隙，此現象為「絲狀剝離」。滴簇剛形成時粒徑小，吸收水氣後變大，因此絲狀剝離帶上少許滴簇皆是粒徑較小的滴簇。

星系的碰撞機制屬星系演化中非常重要的過程，目前研究多以星系質量比、速度等變因如何影響碰撞後星系性質為主。而本研究認為星系旋轉軸角也是影響星系碰撞的重要因素之一，故以SPH模擬螺旋星系旋轉軸角度對星系碰撞結果的影響。分別模擬以角度單變因，以及搭配其他參數之多變因情形。 根據模擬結果，發現兩初始星系在直接碰撞（撞擊參數等於零）時，若以碰撞角、初始角差異近似於0度以及180度時搭配高速低值量比進行碰撞，較能形成低核盤比的橢圓星系。間接碰撞時，若旋轉軸貼近速度軸、兩初始旋轉軸夾角小，以及初始盤面平行等情形下，較能形成低核盤比的螺旋星系。 本研究也發現碰撞後星系長軸分佈聚集於0與180度區域，可用來探討橢圓星系軸向問題。最後，本研究以核盤比作為新式星系碰撞分類標準，建立螺旋星系演化機制的參考。

45 度線偏振光入射銅化合物所得散射光為線偏振，銅片直立或橫置，在同一光源下，相對位置亮暗趨勢相似，故銅片上顏色變化非薄膜干涉。圓偏振光入射晶體，不同照相角度所得散射光強度、偏光軸偏轉及偏極化等變化，可推知為雙折射晶體。控溫定量供氧的均質銅化合物晶體，其散射光偏振態偏向圓偏振，因細紋、粒徑等因素，造成偏極化變化。 溫度梯度變化造成銅化合物晶體折射率及介電係數改變，為散射光強度、偏光軸偏轉及偏極化變化的主要因素，經由理論模擬更可得知散射光偏振態的細微變化；不同波長入射相同銅化合物晶體，所得偏光軸偏轉有極大差異，且變化不同波長的光強度所造成偏極化現象及晶體吸收率各有不同。 故不同波長的光進入銅化合物雙折射晶體時，因散射光強度變化、偏光軸偏轉差異、偏極化、取值角度及吸收率不同，晶體會有顏色差異及色彩變化。