關於渦旋〈二〉
在做這實驗之前，我花了很長一段時間思考一個問題：我如何能得到同\r 樣大小（均勻）的水珠陣列？我在家中各個角落放置許多水瓶，看看哪\r 個地方能培養出顆粒相同的水珠？ 往往肉眼見到整齊排列的水珠，一經\r 顯微鏡觀察，可就大小不齊整了。\r 第一篇中的實驗，幾乎是「水珠日記」，記載冷凝過程；其中我特地比對\r 「穩定的水蒸氣氣流」與「擾動的水蒸氣氣流」、「水蒸氣氣流與凝結盤\r 間溫度差別」、「凝結盤密度差別」、「凝結因子的重量百分濃度差別」、「水\r 蒸氣氣流之流速差別」，並加以複合比對。希望能找到產生均勻排列的條\r 件–探討水分子的自我組裝機制（Self Mechanism of Water Droplets）。\r 這其中提出『均勻假說』： 當條件合宜時，冷凝下降的細微水珠會產生\r free vortex ring，形成整齊的渦環組合，進而產生均勻排列的細微水珠陣\r 列。\r 實驗是藉由溶液密度小於水的設計，讓水蒸氣冷凝於液面上，並且因密\r 度較大而下沉。設計的要點是：儘量減少細微水珠自冷凝後的堆疊\r （coalescence），以呈現水珠原貌。\r 在第二篇實驗中，將對渦旋比例尺修正。渦旋本身難測大小，在空氣中\r 也不易觀察，但是若由水中觀看，可藉由空氣蕊長短估算。這次更進一\r 步考慮到排水速率、水深、排水口形狀、與極值。\r \r I have tried to ask a famous math professor if he can create a formula\r describing the ordered array of water droplets。〝Then, I should study Physics\r first !〞He said。\r Condensation is the thing we live with , being found everywhere, passing\r without notice。But we never know0 when it does start？\r This experiment presented here is actually the diary of the growth of water\r droplets through condensation。Through convection and vortex ring, it\r discusses the self assembly mechanism of water droplets and peep into the\r uniformity of the size of water droplets。\r Here, vortex ring plays an important role in the self assembly mechanism of\r water droplets which is not triggered in the daily life。\r By coalescence, water droplets grow bigger, but are not round again。We used\r the polymer film as template and designed the solution lighter than water, so\r the minute droplets will sink to the bottom and layer by layer。After seconds\r we may have multilayers of ordered array。\r This is the first step in discovering the uniformity of water droplets, besides, I\r made some correction to the Vortex-Ruler。Vortex-Ruler will be useful in\r researching the flying mechanism of butterfly and dragonfly as to judge\r which one induces more vortices。
芯電感應
Based on Ampere，s Law, the magnetic field intensity of the solenoids is B=μ0μr?n?I, where μ0 is the magnetic permeability of free space, μr is the relative magnetic permeability, n is the number of coils per unit length and I is the solenoidal current. The end magnetic field of the solenoid must multiply by one half. According to the above result, it can be greatly strengthened by the addition of a ferromagnetic core. First, we observe three different inserted materials of coils (wood, iron and magnetite), whose magnetic induction in different solenoidial current. By experiment, when the iron and magnetite materials were inserted into the coil, it would produce larger magnetic induction. The calculated relative magnetic permeabilities of wood, iron and magnetite materials are 0.57, 18.37 and 18.32, which are close to the reported paper (1). When the driving field is removed, the fraction of the saturation magnetization of the magnetite is retained, which is called hysteresis and is related to the existence of magnetic domains in the material. In the second part, we change the frequency of circuit switch, which induced different current. Compared with the result of the first part, it would fit the result, which is the induced magnetic field is proportion to the solenoidal current. 根據安培定律，螺線管的磁場為B=μ0μr?n?I。其中μ0為真空中的導磁率，μr為相對的導磁率，n為單位長度的線圈匝數，I則為通入螺旋管的電流。至於螺旋管的端點磁場須再乘上1/2。所以根據上述的結果，當螺旋管插入鐵磁性物質，會增強螺旋管的磁場。首先，觀察三種不同的芯物質；非鐵磁性材料，軟磁材料，硬磁材料（木棒，低碳鋼棒，磁鐵棒）在不同的外加磁場下的感應磁場，得到芯物質的磁化曲線，而計算出來的相對導磁率分別為0.57, 18.37 和18.32與參考文獻(1)接近。而當外加磁場移走時，硬磁性物質的磁性仍然存在，稱為殘磁現象。在第二部分，我們改變線路開關的頻率。發現不同的開關頻率，會得到不同的螺旋管電流，而造成不同的感應磁場。再度驗證了感應磁場大小是正比於螺旋管電流的大小。
Elastomeric Grating for Wavelength Switching in Optical Communication Systems
A diffraction grating was fabricated from an elastic polymer. It was patterned after a plane reflection grating with a pitch of 1200 lines/mm. It was characterized using a HeNe laser to verify properties. Angular scanning as a function of applied strain was observed for two individual wavelengths. Intensity of fiber output was optimized as an application of angular scanning in fine alignment. Beam profiles showed consistency of first order diffraction intensities at different levels of strain. This showed that the elastomeric grating’s efficiency is independent from strain. The elastomeric grating’s variable pitch can be of immense utility in optical communication systems. A stretchable grating can be used to replace typical high-cost architectures of metal or glass gratings of different pitches that correspond to various spectral regions. By changing the pitch, the grating can be used for different wavelength ranges. The elastomeric grating’s variable pitch can be used to scan different wavelengths over a wide range of angles. Angular scanning is used for wavelength channel selection, and since an elastomeric grating diffracts different wavelengths differently, it can be used for wavelength switching and wavelength division multiplexing in optical communication systems. Laser beams of different wavelengths carrying different signals can be transmitted simultaneously through an optical fiber and diffracted to route the wavelengths onto separate wavelength-specific channels.
數位攝譜儀及其數位分析方法
Color is not a physical quantity, but it is a characteristic of spectra. Traditionally spectra of light sources are characterized by the wavelengths and intensities of the spectral lines. We propose an alternative way of charactering spectra using colors. Using digital cameras, convex lens, and a 600 Lines/mm grating, we design a “Digital Spectrophotometer” (Pic.1), which uses no light sensors and electrical circuits that are necessary for conventional spectrometers. To analyze a spectrum using the “Digital Spectrophotometer”, we take digital images of the diffracted light through the grating emitted by the light source and then analyze the intensity distribution of the color components of the spectral lines. The structure of the “Digital Spectrophotometer” is simple and is easy to operate. The Digital Spectrophotometer includes a computer software program we have developed called the “Digital Spectrological Method”. After enlarging the digital spectrographs to a mosaic scale and regards each mosaic as a basic color block, the Digital Spectrological Method will transform every color block into a four dimensional “color coordinates” (λ (wavelength), R(red), G(green), B(blue)), where the coordinateλ is translated from the spatial position of the spectral line and the R, G, and B coordinates specifies respectively the corresponding intensity of the red, green, and blue color components. Comparing the “color coordinates” of the unknown light sources to the known, we can easily identify the wavelengths of the lights emitted by the unknown illuminant precisely. We have accomplished the following experiments by using the “Digital Spectrophotometer”: 1. Measure the spectra of various gaseous atoms, and establish the “database of digital spectra in color coordinates” (DDSCC). 2. Compare the characters of color presentation between digital camera images and positive film of the optical camera. 3. Identify the absorption spectrum of the Solar spectrum (Fraunhofer Lines) using the DDSCC. 4. Analyze the Orion αandβ spectrum using the DDSCC. 5. Identify the 589.0 and 589.6 nm wavelength difference between the “Double Lines of sodium spectrum”. 6. Measure the range of wavelength of the colored LED and register the results into the (λ, R, G, B) coordinates. 7. Compare the range of wavelength of He-Ne Laser and commercial Laser pointer. 8. Measure the Zeeman splitting of the hydrogen atom spectrum at 0.5 Tesla.
顏色雖不是物理量，卻是光譜的特性，傳統上對光譜的分析只記錄波長及對應的強度，而非以顏色來區分。我們運用數位相機、凸透鏡及600 條/㎜光柵，設計一個以顏色成分為標準來分析各類光譜的「數位攝譜儀」(Pic.1)。這個新的設計無須使用傳統光譜儀所需之光感應器及電路設計，只需拍攝光源透過光柵的繞射影像即可分析對應之光譜。我們製作的「數位攝譜儀」包含了一個自行設計的電腦軟體程式「數位光譜分析法」；將拍攝到光譜數位影像放大成「馬賽克」，作為光譜的最小「色塊」，該程式可將每個色塊轉換為一組四維的「顏色座標」 (λ (波長)，R(紅)，G(綠)，B(藍))，其中的λ 座標係由光譜線的位置轉換而來，而紅、綠、藍座標則記錄對應的紅、綠、藍色成分強度。與已知光源譜線的「顏色座標」比較，「數位攝譜儀」可精確測量各種未知光源放射出的光波波長且操作方便。利用「數位攝譜儀」的數位分析方法，我們完成以下實驗：1. 測量不同種類的原子光譜，建立「數位光譜資料庫」，包括氫、汞及鈉原子。2. 比較數位相機影像與光學相機正片的色彩顯影。3. 利用「數位光譜資料庫」，鑑定太陽光譜中的吸收光譜(Fraunhofer Lines)。4. 利用「數位光譜資料庫」，分析獵戶座α、β的可見光光譜。5. 鑑別波長589.0、589.6 奈米的鈉雙線。6. 用顏色座標(λ,R,G,B)測量發光二極體的波長範圍。7. 比較He-Ne 雷射與雷射光筆放光的波長範圍，發現市售雷射光筆所放之光並非單頻。
從小玩意探討大問題－磁浮隔空旋轉器的轉動情形與磁場變化之研究
磁浮隔空旋轉器是由一個旋轉軸和底座構成，利用兩者間相互排斥的磁力， 產生隔空漂浮的效果。本研究首先對旋轉軸的結構加以分析，並設計啟動裝置， 探討啟動電壓、旋轉軸重量及底座磁力等因素對漂浮轉動的影響。 我們分析維持旋轉平衡的各種作用力，並探討旋轉軸重心位置與摩擦力的關 係，以驗證我們的分析結果。此外，我們也利用自行設計的啟動裝置，提供穩定 的初始轉速，探討旋轉軸重心位置不同時，持續轉動時間的變化，進一步驗證所 做的分析。 為了瞭解磁場在旋轉軸漂浮過程中發生的變化，我們設計了支架把空間座標 化，再以高斯計測量出各點的磁場，獲得各平面的磁場強度分佈圖。配合磁力線 分佈圖與所測得的磁場強度分佈圖，我們以一個嶄新的分析模式，將抽象的磁場 概念具體化，使我們對旋轉軸放置前後及磁力與重力平衡時的磁場變化，更深入 的了解，同時也發現磁場強度會隨距離的增加而減弱。 最後我們在旋轉器上裝置感應線圈，經由旋轉實驗測得感應電壓的存在，證 明旋轉器轉動時，磁場會產生變化。 經由對磁浮隔空旋轉器的探討，我們得以了解它的漂浮原理、磁力與摩擦力 間的平衡關係，以及旋轉前後磁場變化。The Magnetic Floating Spinner(MFS) is composed of one spinner with a magnetic base. The floating effect of the spinner is caused by the interaction between the two opposite magnetic fields. We first analyzed the detail structure of the MFS, and then designed a starter to rotate it. Later, we studied the effect of starting electric potential, the weight of the spinner and the magnetic force of the base on the floating movement. We presented an explanation for the forces that maintained the floating of the spinner and, to support that, we studied the friction force with the position change of the spinner gravity centre. We also used the starter designed by us to provide a stable initial rotating force and analyzed the relationship between the change of gravity centre position and the duration of rotation. In order to understand the magnetic field change during floating movement, we designed a spatial frame to coordinate the spinner that floated above the base. We measured the surrounding magnetic force with the Goth’s apparatus and conducted a magnetic force distribution diagram. According to this diagram and the line of magnetic force, we therefore provide a brand new analysis model , which bring the abstract concepts of the magnetic field into a concrete theory. This research not only brings us to understand the magnetic field change of the spinner before and after its placement over the base and the balance between the magnetic and the gravity force, but also reveals that the magnetic force will wane with the increase of distance. Finally, we placed an induction coil by the spinner to detect a voltage change during spinner movement. This is an evidence that the magnetic field will change during the spinner movement. Through the study of MFS, we can now understand why it floats, the balance between magnetic and friction force, and the change of the magnetic force before and after the spinner movement. MFS = Magnetic Floating Spinner