物理

磁性流體（magnetic fluids）是一種含有磁性奈米粒子的液體，當磁場外加於磁性流體時，流體中各磁性奈米粒子的磁矩會沿外加磁場方向排列，而導致粒子間相互吸引，形成較大的磁性叢集，即所謂的磁鍊。當外加磁場增強，該磁鍊數會變多，並使磁性流體的折射率產生變化。磁性流體的折射率變化會隨外加磁場之變大而增大。本研究除探討磁性流體折射率受外加磁場控制的變化情形及其物理原由外，並進一步運用此特性研發可調性光纖「光調制器」 ，以探討磁性流體可調性折射率應用在光電元件上的可行性。A magnetic fluid is one kind of colloids which contain magnetic nano-particles. Under an external magnetic field, the magnetic moment of nano-particles is aligned along the direction of the external magnetic field. This leads to the agglomeration of magnetic particles and to form magnetic clusters under an external magnetic field. With the formation of the magnetic clusters, the refractive index of magnetic fluid is varied. The refractive index of magnetic fluid was found to increase under a higher magnetic field. In this work, In addition to investigating in detail the behavior of the field-dependent refractive index of the magnetic fluid, we also explore the relevant physical origins. Furthermore, the feasibility of developing fiber-optical modulators by utilizing the tunable refractive index of magnetic fluids is discussed.

一般人從小就知道如果要判斷西瓜有無成熟，只要用手輕拍瓜皮，利用聲音的特性就可以知道西瓜是否成熟，此技術看起來容易，卻需有多年經驗之西瓜商始可為之。本研究利用拍擊西瓜所造成之聲音進行非破壞性音波檢測，來探討西瓜之成熟度。換言之，本研究希望在依照西瓜商拍擊的習慣下，從客觀的科學角度，探討存在於西瓜商手上「聽音辨瓜」的奧秘。由研究結果得知，西瓜的拍聲在頻譜中可分為三個頻區，即西瓜殼所造成的高頻區，水及含水量高的果肉所形成的中頻區，及由空洞及含水量低的果肉所造成的低頻區，而西瓜商就是藉由這三種音頻所表現出的綜合效果進行判斷。The method, tapping the watermelon rind and listening to the sound, has been often used to judge whether the watermelon is mature or not. Although it is not difficult to tap the rind of a watermelon, it is not so easy to have a correct judgment of the maturity just from the sound you heard, unless you are an experienced watermelon farmer. In order to investigate the secret that the farmers have, this research detects and analyzes the sound of tapping watermelons in an objectively scientific way. According to the experimental results, the sound could be approximately partitioned into three regions in the frequency spectrum, denoted as high-frequency, mid-frequency, and low-frequency regions. The high-frequency region and mid-frequency region are resulted from the hard solid rind and the juicy flesh of a watermelon, respectively. As for the low-frequency region, it comes from the vacant holes or flesh with little amount of water. Based on the experiment, it can be concluded that the maturity of a watermelon can be correctly judged from the combination of these three frequency regions, just like the farmer’s method.

本研究主題是要探討以電解質作為電介質之電容器的放電情況及電容值。作者在電容器的兩極板中，灌入電解質溶液，作為電介質，發現確實能使電容值大增。作者再以不同電解質和外加磁場為變因，作出以下研究,以深入了解電容和電解質溶液的關係。The main idea of this topic is to explore the amount of capacitance with electrolyte as dielectrics. The authors poured electrolyte solutions into the polar plate of capacitor and found the amount of capacitance increased. Then the authors used the different kinds of electrolyte and added magnetic field as changing factors. Authors performed the following research to deeply find out the correlations between capacitance and electrolyte solutions.

The purpose of the research is to investigate the settling mode of the viscid micro-particle, such as the ones from the “Miso Soup”, in static liquid. We constructed the “constant temperature environment” by constant temperature trough and transparent glass trough. The data is gathered from pictures captured from DV and then analyzed by Media Player. We did a stability test prior to the start of the experiment and found the system with good stability. The results of the experiment are as followed: 1. The settling mode can be divided into four phases: (a) Initial accelerated phase (b) Maximum phase (c) Gradually decelerated phase (d) Stationary phase. 2. The lower the fluid concentration is in the fixed temperature: a. the faster its settling interfaces appears; and the deeper it becomes for the depth of its settling interface. b. the faster the maximum sedimentation rates of the settling interface becomes and the slower it appears. 3. At the fixed concentration, the higher temperature: a. has the bigger maximum sedimentation rates of the settling interface b. gets to the stationary phase sooner c. has shallower stationary settling interfaces d. the time when the settling interface appears is independent with the temperature 4. The shape of the container has no effect on the settling mode as the settling interface is always perpendicular to gravity field. 5. If we add salt into the liquid, the stationary settling interfaces of the result will be higher than non-added ones.本研究的目的在於探討味噌這樣的微小黏性顆粒，在靜止液體中的沈澱模式。運用恆溫槽與透明玻璃水槽所建構之恆溫環境透過數位攝影機，以電腦播放軟體於特定時間擷取畫面進行分析。在正式實驗前，進行了穩定性試驗，發現穩定性良好。實驗的結果發現：一、 沈降模式：可以分為四個時期，分別為（一）起始加速期（二）高峰期（三）逐漸穩定期（四）完全靜止期。二、 在固定溫度下，溶液濃度越低：(一) 出現沈降交界面的時間越短且穩定距離距液面越深。(二) 沈降面沈降速率最大值越大且出現的越晚。三、 在固定濃度下，溶液溫度越高：(一) 沈降面沈降速率最大值越大。(二) 沈降交界面完全靜止期出現的時間越短，也就是越快達到穩定。(三) 沈降交界面的穩定距離距液面越淺。(四) 沈降面沈降速率最大值出現的時間與溶液的溫度無關。四、 容器內部的形狀與沈降面的沈降行為並沒有影響，都是成與重力場垂直的水平線沈降。五、 添加食鹽之後最終穩定沈降面比同濃度同溫度的高了許多。表示添加了食鹽對於味噌溶液有阻止沈澱的效果。

本研究欲探討垂直水柱遇障礙物成節的形成機制。以數位照相機、光電計時器等進行觀測。 實驗結果如下： （一）因往返水柱波速不同，而且節無波腹大幅振動現象，故節不是駐波現象。 （二）細針插入水柱表面時，當針上方超過某長度後，針下方產生Ｖ字形震波。但不論針相對水柱的速度是否超過波速，針上方都有節，故不是震波所產生的現象。 （三）根據水波槽模擬實驗，不論木條是否超過波速，木條前方均產生波紋。木條前方的水受到木條推動，往前方加速，因此顯現出波紋了。 我們認為，在水柱中所看到的節，不是震波或駐波，而是相對於木條往前傳遞的波。波源是撞擊物，改變了水柱表面的壓力，而成為波源，水柱的水因受撞擊，某個範圍內流速會小於波速，使得撞擊物前方存在波紋。This experiment uses digital camera and photoelectric timer to discuss the mechanism of causing spouts to form nodes on its surface. Because the downward wave velocity of the spout is different from that upwardand there are no significant vibrations of antinodes, standing waves are not the mechanism of causing nodes. In the experiment of inserting a needle into the spout, we found out that while the needle was inserted above a certain length of the spout, v shaped bow waves emerged. However, no matter the velocity of the needle related to the spout is over the wave velocity, there are always nodes above the needle. Therefore, bow waves are not the mechanism of causing nodes. According to the ripple tank simulating experiment, no matter whether the speed of the wooden stick is faster than the wave velocity or not, there are always waves forming in front of the wooden stick. The wooden stick pushes water in front of it and causes the water to accelerate forward. Therefore, waves appear. We think that the nodes we see on spouts are neither standing waves nor bow waves. The nodes are rather caused by the relatively moving wooden stick. The object, which impacted the spout (wooden stick), changed the pressure of the spout’s surface and became the source of wave. Because of the impact, the velocity of the water current of a certain area became slower than the wave velocity and causes nodes forming on the surface of the spout.

交叉波（ cross wave ）為波峰和振源表面垂直的波，移動方向和振源表面平行，它是以表面張力為恢復力的表面張力波（ capillary wave）的一種。

A polysiloxane elastomeric lens was formed by mixing a silicone elastomeric base and silicone elastomer curing agent. It was molded from a +100 glass lens attached to a milled Plexiglas mold. The changing focal length as a result of the application of different degrees and ways of applying strain was observed with the help of a diverging laser beam and 28 and 30- diopter lenses. The shortening of the focal length as a function of applied strain using weights was observed for two treatments namely low weight and high weight. The focal lengths were measured using a vernier caliper and an adjustable white board on which the laser beam was reflected. Data for the experiment involving weights showed that there is a general decrease in the length of the foci of the elastomeric lenses as more weights were added to the set-up. This can be attributed to the increase in curvature of the lenses as more weights were added. Data for the experiment involving spring balances showed that there is a general increase in the length of the foci of the elastomeric lenses as the spring balances are pulled harder. This can be attributed to the flattening or decrease in curvature of the lenses as the spring balances are pulled harder. A stretchable lens can be used to replace intraocular lenses in cataract extraction. By changing the focal length, the lens can work for a wide range of distances, and therefore serve as the definite solution to the development of cataracts and other conditions that affect visual activity.

「風笛」是台灣原住民鄒族的信號用具及祈雨法器，由一條繩子綁一支竹片構成。轉動風笛時，竹片會繞繩子自轉並拍打空氣而發出聲音，並有上下飛舞的現象。 \r 風笛產生聲音的原因，為竹片拍打空氣而造成的渦流共振現象；又由於繩子扭力大小及方向改變，使風笛的音調忽高忽低、響度忽大忽小、且竹片會在兩個平面上公轉，而有週期性變化。 \r 施力使風笛公轉轉速加快時，竹片自轉速率也變快，使其音調愈高、響度愈大；而繩愈短、愈粗時，竹片的公轉週期將愈短。

本實驗使用磁流變流體(Magnetorheological fluid, MRF)來估查其磁場作用下的光學性質。本實驗採用Lord公司的MRF-132LD磁流變流體加以稀釋到不同的重量濃度，並以氫氟酸蝕刻玻片產生不同的厚度。吾人觀察到濃度參數以及厚度參數均對MRF薄膜的光繞射產生影響。膜厚越薄，產生的繞射較明顯，而重量濃度較小的容易亦有較大的繞射角度。吾人亦移動上下兩玻片相對位置，施加剪力的作用，繞射現象也產生明顯的改變。\r The Magnetorheological fluid (MRF) is used to observe the optical properties under the vertical magnetic field , The MRF-132LD from Lord Company is used, The MRF is diluted to different weight ratio of particulate and carrier fluid . The different thicknesses of the MR thin film are also made with the diluted MRF. The concentration of the MRF and the thickness of the thin film are both found to have significant effects on the optical diffraction phenomenon. The optical diffraction is also found to be affected by the applied shear force to the thin film.

This experiment mainly aims at three kinds of solution - Dextrose, Saccharose, and Fructose. By changing its temperature, density, length of tube, as well as different wave length factor of polarized light, we observe the influence of the direction of polarization by those factors. The experimental result showed as follow. The Dextrose and the Saccharose can cause the polarized light with the rotary direction of clockwise, so both are ‘dextrorotatory’. The Fructose can cause the polarized light with the direction of counterclockwise, so it is the ‘laevorotatory’. For the Dextrose, when the\r temperature is lower than 20℃, the direction of polarization has changed observably, but doesn’t have any rule. When the temperature is higher than 20℃, the direction of polarization increase slowly. For those three kinds of solution, when\r density increased, the polarization increased observably. When the polarized light passed through the solution with longer path, the direction of polarization has more change. When the wave length of the polarized light changed, the direction of polarization has been changed observably. When the wave length of the polarized light is shorter, the direction of polarization change increased.本實驗主要針對葡萄糖、蔗糖、及果糖等三種旋光性溶液，改變其溫度、濃度、容器管長、以及不同波長的偏振光等因子，觀察這些因素對偏振方向所造成的影響。實驗結果顯示：葡萄糖與蔗糖會使得偏振光的偏振方向以順時針旋轉，屬右旋性之光學異構物；果糖會使得偏振光的偏振方向以逆時針旋轉，屬左旋性之光學異構物。若溶液為葡萄糖，當溫度低於20℃時，偏振光的偏振方向會有明顯的改變，但無規則可尋；當溫度大於20℃時，偏振方向旋轉角位移則以非常緩慢的方式增加。當此三種溶液之濃度增加時，偏振光的偏振方向有明顯遞增的現象。此外，當容器長度越長（即偏振光在介質中的行程越長）時，偏振方向的改變亦越明顯。當偏振光的波長改變時，偏振光的偏振方向有明顯的變化，且當偏振光的波長越短，偏振方向的改變越大，似乎與波長呈反比，但此結果與理論值（即旋光度與波長平方成反比）仍有一些差距。