物理與天文學

藉由結合液晶與奈米線，本研究設計出新型的光電元件，我們發現這些新設計具有先前元件很難達到的新穎特性。首先，我們研究液晶分子與一維磁性奈米線之結合，很有趣的是磁性奈米線在液晶元件內，會沿著液晶方向作整齊排列，更重要的是經由一外加電場，即可調控磁性奈米線之磁場方向。藉由電場調控磁場，是很久以來許多科學家追求的目標，然而成效不彰，本研究提供了一個簡便的方法，克服了長久以來的障礙。第二個例子，我們研究液晶分子與一維半導體奈米線結合之元件，我們證實了半導體奈米線所發射瑩光之電場偏極方向，可以經由外加電場來調控，這個特性對於資訊科技的應用，將很有用處。本研究所觀測到之結果，皆可利用下列事實來理解，奈米線具有很大的表面積，因而增加了與液晶分子之交互作用，經由此增大的交互作用力，奈米線會沿著液晶分子方向排列。值得強調的是，本研究利用了已成熟的液晶顯示器技術，其未來應用性將有很大潛力。New devices based on the composites of liquid crystals and one dimensional nanowires have been designed, fabricated, and characterized. It is discovered that these novel devices own interesting properties that are very difficult to be obtained by conventional ones. As the first example, the liquid crystal device with built-in one dimensional magnetic nanowires has been studied. It is found that the magnetic nanowires can be well aligned along the orientation of liquid crystal molecules. Quite interestingly, the direction of the magnetization of magnetic nanowires can be easily manipulated by an external electric field at room temperature. The phenomenon of electric manipulation of magnetization has been studied since nineteen century, but the achievement is rather limited. Here, we provide a convenient alternative to overcome the long quest search. For the second example, the liquid crystal device with built-in semiconductor nanowires has been investigated. We demonstrate that the polarization of the emission arising from semiconductor nanowires can be easily controlled by an external electric field, which is one of the basic requirements for information technology. All of our observed results can be well understood in terms of the inherent nature of a large surface to volume ratio of one dimensional nanowires, which induces a strong interaction between embedded nanowires and liquid crystal molecules. Therefore, the nanowires can be driven along the orientation of liquid crystal molecules. It is stressed here that our newly designed devices are based on the well established liquid crystal display technology and therefore their practical application can be realized in the near future.

The study aimed to compare the electricity generated from the fruit extracts of calamansi, camias and starfruit. Unripe fruits were extracted and varied percentage compositions of each extract were prepared.Wires wereconnected to a multi-tester (voltmeter or ammeter) to measure voltage or current that passes through. Results revealed, that amount of voltage and electric current generated are its lowest reading at 25% and are its highest reading at 100%. Nonetheless, of the three fruit extracts, it’s the calamansi that has the highest amount of voltage generated of0.97 volt while camias has the highest amount of electric current generated of 13.98 mA. Using ANOVA at 0.05 level of significance on the amount of voltage generated among varied percentage compositions of three extracts. However, there’s a significant difference on the amount of electric generated among varied percentage compositions. Results of ANOVA statistically signify that the three different extracts could either be used as a source of voltage and that camias extract should be preferably used over the other two fruit extracts in generating electric current. In all compositions, produced voltage is between 0.88 and 0.97 volts and current is between 3.28 and 13.98 mA. These currents produced are not enough to turn on a small light bulb having a smallest voltage capacity of 1.2 volt, but can be able to turn on a light-emitting diode (LED) that require such amount of current.

本實驗將小型塑膠圓片置於水中釋放模擬落葉的運動模式，發現圓片與水平之夾角呈現週期性變化，變化範圍會隨著時間改變。在運動幾個週期後，變化範圍會被限制，此時為穩定狀態。在水中加入鋁粉以觀察圓片運動時流場的變化，提出分流模型與最短時間原理，發現此模型可以解釋圓片的轉動機制。

本實驗主要是透過及程式模擬分析，探討變形之阿特午機 在一般狀況下及過渡期 的運動過 程。透實驗，我們找出不同的初始條件對於運動結果影響 ，如質量比、繩長 等。我們透過實驗和數值分析建構變形之阿特午機的模型 。因為 摩擦力和空氣阻對於運動 的影響皆不可忽略，因此 我們 也設計阿特午機和鉛直圓周運動的 實驗以求出兩個影響因素參數， 並將其結果統整於理論分析中。這份研究有助我們了解力學的過程目前我們 也正在進行更詳細的數值分析， 我們也希望能在之 後將變形之阿特午機的理論與實驗結 果合，預測不同變因的實驗結果。

It’s very important to control and monitor gases that are produced by industrial applications in different values and kinds because they can cause environmental pollution and health problems. Photonic Crystal Fiber (PCF), which is a different kind of optical fiber, is a new alternative for gas sensors due to their small sample volumes, low transmission losses and high flexibility properties. PCF’s are silica-glass fibers, made by periodic sequence of hollows along the fiber. By filling these hollows with optical liquids or gases very sensitive sensors can be made. In this project, we aimed to design a sensitive sensor by filling the hollows with proper gases and liquids in the solid core PCF. For these applications ethanol, methanol, toluene vapors and carbon dioxide was used. And to observe carbon dioxide’s effects ionic liquid (EMIMBF4), which carbon dioxide can dissolve in, was filled then the experiments were repeated. It was observed that the transmission of light in PCF changed depending on the refractive index of the gas that was filled. With this change, it was understood that there were another gas besides the usual containments of air. Our system could measure the absorbtion peak of toluen so it can be used as a toluen dedector and when ionic liquid filled the fiber, two steps that occur in the spectra of corbon dioxide so it can also be used as a carbon dioxide dedector. The system was customized as a carbon doxide sensor in a cost-efficient and portable way. Our system can be specialized and easiliy used with right light source, which is efficient to see the absorbtion peaks, and proper liquids to dedect intended gas. Making a carbon dioxide sensor by filling PCF with ionic liquid was never attempted before. Also the lack of carbon dioxide sensor studies supports the originality of our project. That’s why we think our project will contribute very importancies to the existing literature.

Dye-sensitized solar cells (DSSCs) have cheaper and easier means of fabrication compared to the currently used solar cells, which are mostly silicon-based, so DSSCs are developed for a prospect of solar energy accounting for a higher percentage in the world’s total energy production, which is currently 0.1%. However, compared to their inorganic counterparts, their efficiencies are low, and the search for a dye that will maximize the potential of DSSCs is still ongoing. The aim of this study is to be able to evaluate the absorption range in the solar spectrum of dyes extracted from Basella alba leaves and Bixin orellana seeds, and of dyes resulting from the mixture of both extracts, using UV-Vis Spectrophotometer, with the objective of increasing the absorption; to be able to fabricate functional DSSCs from the individual and mixed dyes; and to be able to evaluate the different conversion efficiencies of the DSSCs of the individual and mixed dyes using Linear Sweep Voltammetry, with the aim of increasing the conversion efficiency due to a wider absorption range. B. alba leaves and B. orellana seeds were extracted using soxhlet extraction. The clean extracts were mixed in different proportions, and were characterized using UV-Vis Spectrophotometer. The two individual dyes together with two proportions of the mixed B. alba:B. orellana dyes, 1:1 and 2:1, were then incorporated into DSSCs. In the fabrication of DSSCs, twelve plates of Fluorine doped tin oxide were coated with titanium dioxide (TiO2) using spray pyrolysis. They were sintered and scraped, and were afterwards immersed in the four dyes for four days. Platinum plates were placed on top, and iodine-triiodide couple electrolyte was introduced via capillary action. The sealed DSSCs were subjected to Linear Sweep Voltammetry under dark and illuminated conditions, using a sun simulator. Results from the UV-Vis spectrophotometry showed that mixing the dyes had increased the absorption range of the individual dyes, although not superpositionally, and that the 2:1 mixed dye has the most potential. Being incorporated into DSSCs, the dyes, including the mixed ones, have successfully converted solar energy into electrical energy, as shown by the significance in conversion efficiencies under dark and illuminated conditions. However, despite the increase in the absorption range, neither of the mixed dyes have shown a higher conversion efficiency than the individual ones, which can be accounted for a possible weaker interaction between the two dyes and the TiO2, resulting to lower efficiencies. The study has been able to obtain and characterize dyes from B. orellana seeds and B. alba leaves and has been able to incorporate the dyes into DSSCs. With the wider absorption range of the mixed dyes, the study has been able to confirm the possibility of the dyes to maximize the potential of DSSCs, as shown by the successful conversion of solar energy into electrical energy of all fabricated DSSCs, including those of mixed dyes. If the possible problem with the dye-dye as well as the dye-TiO2 interactions could be solved, the possibility of much higher conversion efficiencies could be expected.

Characterization of telescope lenses using physical optics and selection of the optimal physical parameters of a reflecting telescope’s optical units were done to improve the design, cost-efficiency, and quality of the 64-cm telescope (named Oof) housed at the National Institute of Physics. Characterization has been done through numerical modeling of the point spread function (PSF) in Python. The PSF code was based on the method of getting wave vectors by Richards and Wolf. The optimal PSF was established to be the PSF of a large monolithic mirror. The PSF of a single optical lens was compared to its counterpart segmented lenses. Through the comparison of maximum intensity, the normalized mean square error (NMSE) and the Linfoot’s criteria of correlation quality, fidelity, and relative structural content, the study has produced results which proved that highly segmented optical components produce results with less quality compared to less-segmented optical components. It was found that as the segmentation increases, the maximum intensity decreases. Higher values of maximum intensity denote higher light gathering power. The normalized mean square error of the set-ups having one to seven layers had values greater than zero but less than one. This denotes that the PSF of those set-ups are near the PSF of the optimal set-up. Higher values of correlation quality, fidelity, and relative structural content denote higher correlation, higher signal to noise ratio, higher closeness of correspondence between the optimal set-up and the segmented set-up. The number and the size of the optical components of the segmented mirror were manipulated in order to achieve a negligible difference between that of the optimal PSF and the PSF of a segmented mirror. The equivalent single lens radius in terms of maximum intensity of the current set-up of the telescope was determined to be 234.25 mm. If the optimal PSF is achieved, the physical parameters of the optical components generated may be applied to the optical components of the 64-cm telescope. The design that resulted from the study could be used in the future construction of a wide-aperture telescope, which could aid in the acquisition of knowledge about heavenly bodies.

靈光乍現：弦的震盪由直到彎，從單懸到雙懸迴盪不已，共振駐波顯現半波長的微妙變化。故佈疑陣：曲弦振盪、共振頻率、弦上張力、半駐波長，玄機重重。 高潮迭起：推翻同一弦上所受張力相同，得知曲弦曲度不同所受張力亦不等的真相。 明天過後：重現曲弦程度，知彈性係數迴旋，將曲弦駐波性質變化摸透透。 ;Inspirations: Vibrating the string of thing bar from longittudinal to transverse; from both arm to single arm; from the waves of the string to the mystery ofλ/4. Battle: Resonance frequency, string tension force, half stationary wave, questions flying everywhere. Revolution: Overturn the theory that the tension force on the same string equalizes everywhere by measuring the length of eachλ/2 ; proof that the tension force enlarges from the top of the string to the end because of the gravity of the string ; Calculate the constant of the difference between the length of the incomplete wave on the end andλ/4 / the last completeλ/2. Proof that the constant is decided by the thickness of the string rather than the length of the string ; Finding the fact that the number of completeλ/2 on the same string equals no matter where the vibrating spot is.

The aim was to determine whether there is an amount of gyroscopic force that keeps a bicycle wheel upright and stable. Two hypotheses were used, the first being as the mass of a wheel increases so does the force required to tilt the wheel by thirty degrees and the second that as the speed at which the wheel is spun increases so does the force required to tilt the wheel.