物理

It is extremely costly to care for elderly people who have suffered a serious fall. Thus, doctors welcome a device or method to identify people prone to falling, to reduce elderly health costs and enable those identified as “fallers” to take precautions. Recently, a Sound Wave Assessment (SWA) device was developed to determine if tested human subjects were prone to falling. It is based on the concept that all humans exhibit postural sway while standing stationarily. The device employs two sonar transducers, which emit and receive ultrasonic pulse signals. The first transducer is positioned on a tripod, while the second is attached to the lower back of the human subject. Each transducer emits ultrasonic modulation pulses, which are detected by the other transducer. The distance between the two transducers is calculated from the time taken for the pulses to travel from the sender to the receiver. Hence, we can measure the small displacement fluctuations of the standing human subject, both approaching and receding from a static transducer, as a function of time.

本研究探討不同的控制變因，對磁性流體薄膜在水平磁場下有序結構的影響。我們發現，外加水平磁場於磁流體薄膜時，會形成一維有序磁鍊排列，磁鍊間距除會隨著磁場增強而變小外，另外其條件值如磁場強度、流體濃度、磁增率、薄膜寬度及厚度等也影響磁鍊間距。其中磁增率及磁流體濃度增加會使磁鍊間距變小，而凹槽寬度及薄膜厚度增加會使磁鍊間距變大等現象。至於其形成磁鍊的物理作用，我們假設薄膜有三種能量交互作用，即(1)磁鍊與外加磁場間的磁能UdH。(2)兩條同方向磁化的磁鍊間相互排斥所造成的磁能Udd。(3)熱能Uther等。藉由系統能量Udh+Udd+Uther最小化，我們導出了磁鍊間距和外加磁場之間理論上的關係，並比較實驗結果確實具有相當的一致性。因這些有序結構會引發許多的光學性質，將來這些特殊的光學性質預料應可製成可調式光柵、光開關及顯示器等光電元件，使磁流體在奈米世界及光電領域裡扮演重要角色。We investigate experimentally the structure of the magnetic chains formed in the magnetic fluid thin film under the influence of the external magnetic field parallel to the film surface. A one-dimensional ordered structure forced by magnetic chains can be obtain in the magnetic fluid film. It is worth noting that the ordered structure can be manipulated by changing the control parameters such as the magnetic field, concentration of magnetic fluid, the thickness of the film, the width of the film, and the dH/dt. On the other hand, the physical mechanism of forming the ordered structure can be also studied theoretically. These magnetic chains are regarded as magnetic dipoles and three possible interactions are condisered for the energy of the system: the attracting potential energy between the magnetic chain and H(denoted by UdH),the repulsive potential energy between two magnetic chains with parallel magnetizations(denoted by Udd), and the thermal energy Uther. The relationship between the chain distance △x and the applied magnetic field H was derived by minimizing the total energy of the system with respect to the chain distance. The experimental data is consistent with the theoretical results.

My aim was to test the effectiveness of coolboxes under different\r conditions, to use this information to do comparisons using commercially\r available coolboxes and finally to build an effective and cheaper coolbox\r appropriate to Namibia\r The general method used to compare different coolboxes involved\r measuring the rate at which ice melted inside the cool boxes under\r different conditions.

某次於學校的科學表演中，見到黑白陀螺在旋轉後會產生顏色的\r 變化，使人印象深刻。文獻上記載此類陀螺稱為“Prevost”圓盤，\r 其色彩產生的原因一般被認為是人眼產生之錯覺。不過究竟為何會有\r 這種錯覺，總令人相當納悶。於是我們請教了老師，不僅做了實驗，\r 也用像機拍攝下來分析，不過令我們感到奇怪的是：如果是眼睛產生\r 的錯覺，又為何能拍出顏色？甚至，在研究的過程中我們意外的觀察到鏤空圓盤內的色塊裡，\r 尚有像水波「波紋」般的條紋出現。這個現象十分奇特，於是我們設\r 計了一系列的實驗去探討這些現象，開始了這次的研究。在研究過程中我們遇到相當大的困難，所幸同伴的程式設計技術\r 卓越。為了實驗也撰寫了許多套色彩分析程式，使得實驗更能得心應\r 手。而我是負責實驗儀器的架設及實驗操作，希望能以分工合作的方\r 式，來完成這次的研究。

這份報告的主題是藉由實驗，來探討雷射光的性質及它的應用，並實際製作利用雷射光原理的小器具。1.證明雷射光是否為單色光：先將雷射光射入不同顏色的玻璃紙，利用光無法穿透不同顏色玻璃紙的性質，以及將雷射光照射三稜鏡，觀察其反射的光線，藉此來證明雷射光是否為單色光。2.雷射光的直進性質：利用彎管或其他不透光物品將光線阻擋，觀察其是否能穿透物品，並且用不透光物質，使我們能夠看出雷射光的軌跡，來證明雷射光的直進性質。3.雷射光的折射與反射：將雷射光射入不同的物質中，觀察其折射角度，來得知雷射光在不同介質中的傳播速率不同，也觀察其是否有反射的現象。4.雷射光的應用：研究運用雷射光製成的物品，如雷射印表機、光碟機等等，並了解其製作原理。5.自行研製雷射小器具：利用雷射光的原理，來製作簡單而獨特、有效率的小器具。The topic of this report is to study the quality and applications of laser by experiments, and actually make a tool by using the principles of laser.1.Prove if laser is a one-color light: By lasing laser through a triangular prism, observe the light it reflected to prove that laser is a one-color light.2.The quality of in-line approach: By using tubes or other lightproof items to block out the light to observe if it can penetrate things, and also let us see the trace of laser to proof the quality of in-line approach.3.The refraction and reflection of laser: Study the differences of refracting angles by lasing laser into different items, to know the speed of laser in different mediums, and also observe if it will have any reflections.4.The applications of laser: Understand how laser products are made by studying them, like laser printers and CD players. 5.DIY laser tools: Make simple but unique and efficient tools by using the principles of laser.

本專題研究之目的，在於運用簡單的原理自製出準確、廉價、適用於低風速範圍的風速計；方法是藉由將一連接轉軸的玻璃片迎風，探討迎風時，玻璃片偏轉夾角和風速之間的關係。實驗過程中同時發展出可以用馬達旋臂的裝置與v=rω的原理，產生穩定可計算風速的環境。研究結果發現：在低風速的環境下，θ 範圍小時玻璃片與地夾角和風速大略成正比的關係，所以我們可以得到近似式” v≒aθ+b”，參數(a,b)依玻璃片而定。另外θ 範圍大時，我們可以使用二次逼近曲線的方程式與內插法來作角度與風速的對應。藉由控制玻璃片的厚度、質量與形狀，我們可以製造出相對應風速範圍的風速計。The purpose of our research is to use easy theorems to make accurate and inexpensive anemometer which is available in low wind velocity. To make such anemometers, we made a piece of glass, which was connected to a axle, to face wind; then, we could figure out the corresponding relation between wind speed and the angle created by the original and the resulting positions of the piece of glass. While we were experimenting, we found that we could make a steady-wind-speed environment by using motors, sticks, and the theorem ”v=rω”. The research showed that the angle created by the original and the resulting positions of the piece of glass and wind speed are in direct proportion in low wind velocity in small θ range. Consequently, we\r can derive the formula ” v≒aθ+b” , for each piece of glass (a,b) can be different. In addition, when in bigger θ range, we can use quadratic approximate equation and interpolation to describe the corresponding relation between the angle and wind speed. By adjusting the thickness, mass , and the shape of the glass, we can make anemometers corresponding to different wind velocity ranges.

這是一系列關於水蒸氣冷凝為極細微小水珠的長程實驗。其中可以分為下列三個階段：第一階段是基礎實驗。將水氣導入至潔淨的光滑表面上(蓋玻片)，觀察水珠冷凝的機制。第二階段是在外加磁場及電場作用下，將水氣導入至潔淨的光滑表面（蓋玻片），觀察水珠冷凝的機制。這部分的實驗推翻了一般「水分子是電中性，在電場或磁場中不受影響 」的刻板觀念！實驗所呈現出來的冷凝水珠，不但有明確的自我組成模式( Self assembly pattern)。並且發現：電場會增速凝結水珠的成長(Aggregation)，而磁場則會抑制凝結水珠的成長。第三階段是將水蒸氣導引至超聲波的環境中：我們先將超聲波訊號產生器(變頻、定頻)面向於載台旁，再讓水氣導入至潔淨的光滑表面上(蓋玻片)，觀察冷凝水珠的機制。當使用固定頻率超聲波波源，我們發現：在超聲波場中水珠的成長會受到抑制，且成長速率會隨著頻率的升高而逐漸減小。第一階段與第二階段的實驗結果與討論已分別發表於2004 年及2005 年的台灣國際科學展覽報告中，本作品將詳述第三階段。 This experiment explores the basic nature of the condensation of water vapor into droplets on the surfaces of cover glasses. This condensation occurs because of the difference in temperature between the water vapor and the cover glass. The condensation process is observed under a microscope. The growth of the droplets can be described as: nucleation, aggregation (piling up) and coalescence. The growth is irrelevant to surfaces or environments. It is found that the temperature difference of moist air over the cover glass do not affect the nucleation size of the droplets in simple plain surroundings; while the change of flow rate does. In general, the coalescence is speeded up at higher temperatures. Furthermore, the effects of electric fields 、magnetic fields and ultrasonic waves are also studied. It can be observed that the size of water droplets become smaller and grow more uniformly under magnetic fields or imposed ultrasonic waves; also, the aggregation rate is decreased by imposed magnetic fields or ultrasonic waves, and it is increased by imposed electric fields. These effects of magnetic fields 、electric fields and imposed ultrasonic waves might be related to the flow conditions and the vibration of surrounding air in the system. This experiment provides the first step in the understanding of the formation of water droplets and their self assembly mechanism in different environment.

One afternoon, a photography enthusiast, Mr. Cheung was holding some photos, completely absorbed in the fond (but ancient) memories of his honeymoon in Cairo. The badly-yellowed photo prints reminded him of every sweet and romantic moment of the “good old days”. He was soon rudely awakened when Mrs. Cheung shouted, “Honey dear! I was told that high-tech is ‘in’, and the single-lens reflex camera is totally out! So stop hugging the old out-dated pictures.” Mr. Cheung fired back, “Oh, you know nothing. This is something you cannot replace at all, and my camera is a classic.” Smiling at him, Mrs. Cheung took out a new gadget, “Right, right, now calm down. It never hurts to have both worlds. Look what I’ve got you. This is called ‘Stereoscopic Camera Lens’. Its little coloured spectacles can capture everything, say, the sensational Great Pyramid, in three dimensions!” As we are asking for and relying more on technological advances, the Stereoscopic Camera lens and the Stereoscopic Magic Box are surely innovations that promise to add a new dimension to our lives. Surprisingly, the working of these two gadgets involve only some simple scientific theories such as polarization, doping and anaglyph; and employs the special property of Liquid Crystal Layer (LCD) under electric current. Stereoscopic photos can now be easily available to us. Both of our designs, the Stereoscopic Camera Lens and the Stereoscopic Magic Box, can turn something ordinary into extraordinary by making plain, 2-dimensional things ‘stand out’ before your eyes. The Lens itself is crafted with such precision that it can capture any image both faithfully and flawlessly. The Magic Box uses electric current to catalyze and enhance the 3-dimensional transformation. So each picture is vibrant and true-to-life. The Lens and the Magic Box will certainly revolutionize our vision of things around us. To enable you to have a good understanding of the theories behind the making of the Stereoscopic Camera Lens and the Stereoscopic Magic Box, we have made simple models of them with prisms, and they are in display at our booth. Anyone who is interested in these fancy gadgets should definitely come to our booth to experience a new view of the world!

An orbital angular momentum (OAM) sorter concept was designed for high-speed data transfer. The OAM of a light beam known as an optical vortex can exist in one of an infinite number of states and may be used to carry information. The augmented alphabet of states carries the potential to increase date transfer speeds over conventional binary (0 and 1) methods. A vortex generator, or OAM encoder , was constructed from a slit cover slip functioning as an adjustable spiral phase plate, and a vortex analyzer, or OAM measurer, was created using a transparent print of a computer-generated hologram. The two components were then incorporated in an OAM sorter concept that that employs a novel combinatoric method for sorting data. The vortex generator and analyzer created were inexpensive simpli-fications of previous devices and have the potential to increase the alphabet of transmission states several thousand times over binary methods if implemented in the OAM sorter concept.

Our traditional bow is a kind of horn bow which appeared at the side wall in the sepulcher\r around A.D 600. A lot of traits of the horn bow have been handed down to us in an\r unwritten form. This is the reason why I would like to research and investigate the several\r potential capacities in the field of Physics, such as structures, materials and efficiency.