Browsing by Issue Date, starting with "2015-01-14"

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Enhanced Thermoelectric Performance of PEDOT:PSS Flexible Bulky Papers by Treatment with Secondary Dopants
(2015-01-14)
Mengistie, Desalegn A.
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Chen, Chang-Hsiao
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Boopathi, Karunakara M.
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Pranoto, Ferry W.
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Li, Lain-Jong
For inorganic thermoelectric materials, Seebeck coefficient and electrical conductivity are interdependent, and hence optimization of thermoelectric performance is challenging. In this work we show that thermoelectric performance of PEDOT:PSS can be enhanced by greatly improving its electrical conductivity in contrast to inorganic thermoelectric materials. Free-standing flexible and smooth PEDOT:PSS bulky papers were prepared using vacuum-assisted filtration. The electrical conductivity was enhanced to 640, 800, 1300, and 1900 S cm(-1) by treating PEDOT:PSS with ethylene glycol, polyethylene glycol, methanol, and formic acid, respectively. The Seebeck coefficient did not show significant variation with the tremendous conductivity enhancement being 21.4 and 20.6 mu V K-1 for ethylene glycol- and formic acid-treated papers, respectively. This is because secondary dopants, which increase electrical conductivity, do not change oxidation level of PEDOT. A maximum power factor of 80.6 mu W m(-1) K-2 was shown for formic acid-treated samples, while it was only 29.3 mu W m(-1) K-2 for ethylene glycol treatment. Coupled with intrinsically low thermal conductivity of PEDOT:PSS, ZT approximate to 0.32 was measured at room temperature using Harman method. We investigated the reasons behind the greatly enhanced thermoelectric performance.
Highly Thermal Stable and Efficient Organic Photovoltaic Cells with Crosslinked Networks Appending Open-Cage Fullerenes as Additives
(2015-01-14)
Chen, Chih-Ping
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Huang, Chien-Yu
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Chuang, Shih-Ching
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應用化學系
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Department of Applied Chemistry
Highly thermal stable organic bulk heterojunction (OBHJ) photovoltaic cells are demonstrated with crosslinkable open-cage fullerenes (COF) as additives in the active layer. Partial incorporation of COF, approximate to 10-15 wt% with weight ratio of P3HT:PC61BM = 1:0.9, builds up three-dimensional local borders upon heating treatment at 150 degrees C for 10 min. This process induces crosslinking chemical reaction through activating the styryl moiety in COF and reduces phase aggregation rates of fullerenes materials. Supported by statistics of devices degradation data analysis and optical microscopy study, the devices with COF show longer lifetime with keeping their efficiency (t = 144 h) under accelerated heating test at 150 degrees C, while PCE of normal devices without COF drop dramatically. These results demonstrate that the thermally crosslinkable COF is an excellent additive for highly thermal stable and durable OPVs applications.
Zinc Oxide Nanowire-Poly(Methyl Methacrylate) Dielectric Layers for Polymer Capacitive Pressure Sensors
(2015-01-14)
Chen, Yan-Sheng
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Hsieh, Gen-Wen
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Chen, Shih-Ping
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Tseng, Pin-Yen
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Wang, Cheng-Wei
Polymer capacitive pressure sensors based on a dielectric composite layer of zinc oxide nanowire and poly(methyl methacrylate) show pressure sensitivity in the range of 2.63 x 10(-3) to 9.95 x 10(-3) cm(2) gf(-1). This represents an increase of capacitance change by as much as a factor of 23 over pristine polymer devices. An ultralight load of only 10 mg (corresponding to an applied pressure of similar to 0.01 gf cm(-2)) can be clearly recognized, demonstrating remarkable characteristics of these nanowire-polymer capacitive pressure sensors. In addition, optical transmittance of the dielectric composite layer is approximately 90% in the visible wavelength region. Their low processing temperature, transparency, and flexible dielectric film makes them a highly promising means for flexible touching and pressure-sensing applications.
Novel Reddish-Orange-Emitting BaLa2Si2S8:Eu2+ Thiosilicate Phosphor for LED Lighting
(2015-01-14)
Lee, Szu-Ping
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Chan, Ting-Shan
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Chen, Teng-Ming
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應用化學系
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應用化學系分子科學碩博班
A novel reddish-orange-emitting BaLa2Si2S8:Eu2+ thiosilicate was prepared in a sealed fused silica ampule and its crystal structure was refined using Rietveld methods. The BaLa2Si2S8:Eu2+ phosphor is excitable over a broad range from UV to blue (350-450 nm) and generated a reddish-orange broadband emission peaking at 645 nm with a quantum efficiency of similar to 24%. The thermal luminescence quenching of BaLa2Si2S8:Eu2+ was investigated over the range 25 to 150 degrees C. This phosphor was utilized to incorporate with two commercially available phosphors, blue BaMgAl10O17:Eu2+ and green (Ba,Sr)(2)SiO4:Eu2+, and a near-UV LED chip (405 nm), a white light with Ra of similar to 94 was obtained.
D-s -> eta,eta ' semileptonic decay form factors with disconnected quark loop contributions
(2015-01-14)
Bali, Gunnar S.
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Collins, Sara
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Duerr, Stephan
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Kanamori, Issaku
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物理研究所
We calculate for the first time the form factors of the semileptonic decays of the D-s meson to eta and eta ' using lattice techniques. As a by-product of the calculation we obtain the masses and leading distribution amplitudes of the eta and eta' mesons. We use N-f = 2 + 1 nonperturbatively improved clover fermions on configurations with a lattice spacing a similar to 0.075 fm. We are able to obtain clear signals for relevant matrix elements, using several noise reduction techniques, for both the connected and the disconnected contributions. This includes a new method for reducing the variance of pseudoscalar disconnected two-point functions. At zero momentum transfer, we obtain for the scalar form factors, vertical bar f(0)(Ds ->eta)vertical bar = 0.564(11) and vertical bar f(0)(Ds ->eta')vertical bar = 0.437(18) at M-pi approximate to 470 MeV, as well as vertical bar f(0)(Ds ->eta)vertical bar = 0.542(13) and vertical bar f(0)(Ds ->eta')vertical bar = 0.404(25) at M-pi approximate to 370 MeV, w here the errors are statistical only.
Significantly Improved Luminescence Properties of Nitrogen-Polar (000(1over bar>)over-bar) InGaN Multiple Quantum Wells Grown by Pulsed Metalorganic Chemical Vapor Deposition
(2015-01-14)
Song, Jie
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Chang, Shih-Pang
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Zhang, Cheng
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Hsu, Ta-Cheng
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Han, Jung
We have demonstrated nitrogen-polar (000 (1) over bar) (N-polar) InGaN multiple quantum wells (MQWs) with significantly improved luminescence properties prepared by pulsed metalorganic chemical vapor deposition. During the growth of InGaN quantum wells, Ga and N sources are alternately injected into the reactor to alter the surface stoichiometry. The influence of flow duration in pulsed growth mode on the luminescence properties has been studied. We find that use of pulsed-mode creates a high density of hexagonal mounds with an increased InGaN growth rate and enhanced In composition around screw-type dislocations, resulting in remarkably improved luminescence properties. The mechanism of enhanced luminescence caused by the hexagonal mounds is discussed. Luminescence properties of N-polar InGaN MQWs grown with short pulse durations have been significantly improved in comparison with a sample grown by a conventional continuous growth method.
Chiral Hall effect and chiral electric waves
(2015-01-14)
Pu, Shi
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Wu, Shang-Yu
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Yang, Di-Lun
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物理研究所
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丘成桐中心
We investigate the vector and axial currents induced by external electromagnetic fields and chemical potentials in chiral systems at finite temperature. Similar to the normal Hall effect, we find that an axial Hall current is generated in the presence of the electromagnetic fields along with an axial chemical potential, which may be dubbed as the "chiral Hall effect" (CHE). The CHE is related to the interactions of chiral fermions and exists with a nonzero axial chemical potential. We argue that the CHE could lead to nontrivial charge distributions at different rapidity in asymmetric heavy ion collisions. Moreover, we study the chiral electric waves led by the fluctuations of the vector and axial chemical potentials along with the chiral electric separation effect, where a density wave propagates along the applied electric field. Combining with the normal/chiral Hall effects, the fluctuations of chemical potentials thus result in Hall density waves. The Hall density waves may survive even at zero chemical potentials and become nondissipative. We further study the transport coefficients including the Hall conductivities, damping times, wave velocities, and diffusion constants of chiral electric waves in a strongly coupled plasma via the AdS/CFT correspondence.
Highly Effective Field-Effect Mobility Amorphous InGaZnO TFT Mediated by Directional Silver Nanowire Arrays
(2015-01-14)
Liu, Hung-Chuan
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Lai, Yi-Chun
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Lai, Chih-Chung
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Wu, Bing-Shu
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Zan, Hsiao-Wen
In this work, we demonstrate sputtered amorphous indium-gallium-zinc oxide thin-film transistors (a-IGZO TFTs) with a record high effective field-effect mobility of 174 cm(2)/V s by incorporating silver nanowire (AgNW) arrays to channel electron transport. Compared to the reference counterpart without nanowires, the over 5-fold enhancement in the effective field-effect mobility exhibits clear dependence on the orientation as well as the surface coverage ratio of silver nanowires. Detailed material and device analyses reveal that during the room-temperature IGZO sputtering indium and oxygen diffuse into the nanowire matrix while the nanowire morphology and good contact between IGZO and nanowires are maintained. The unchanged morphology and good interfacial contact lead to high mobility and air-ambient-stable characteristics up to 3 months. Neither hysteresis nor degraded bias stress reliability is observed. The proposed AgNW-mediated a-IGZO TFTs are promising for development of large-scale, flexible, transparent electronics.
20150115第三期目錄
(2015-01-15)
編輯室
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Shing-Tung Yau Center
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丘成桐中心
編輯曲線數理簡訊 [專題] 數學教育與十二年國教教改的矛盾 [數] 「克萊恩瓶」主題變奏曲 [理] 數學在分子生物學中的有效性 [人] 漫步在馮諾曼花園　天才的花朵 [文] 數學家，出來吧！　誤入歧途的數學師資培育 CCSS餘波蕩漾　近年美國媒體的數學教育論戰別聽威爾森胡扯 [書評] 推薦《一個數學家的嘆息》白臉：嘆息之後黑臉：數學教育的兩難
漫步在馮諾曼的花園天才的花朵
(2015-01-15)
戴森 Freeman Dyson、趙學信
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Shing-Tung Yau Center
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丘成桐中心
約翰．馮諾曼（Johnny von Neumann）身後留下大量著作，這些作品由陶伯（Abraham Taub）編纂成六卷的文集 [1]。這套文集是他的花園，裡面收藏著他種下的各式各樣的繁茂植栽，每一株都是從一粒種籽、亦即他腦海裡的一個想法或問題所長成。他發展想法或是解決問題，然後寫下並發表。他寫作速度快，發表也快，所以園中繁花仍鮮麗。今天這場演講，我決定要去他的花園走一趟，看看能發現什麼。很幸運的是，文集裡只有兩篇論文是以匈牙利文寫成。他在三十歲來到美國定居之前，大多是用德文寫作，此後則是用英文。
Gold nanoparticles: BSA (Bovine Serum Albumin) coating and X-ray irradiation produce variable-spectrum photoluminescence
(2015-01-15)
Lee, Kuo-Hao
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Lai, Sheng-Feng
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Lin, Yan-Cheng
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Chou, Wu-Ching
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Ong, Edwin B. L.
We show that by using different x-ray irradiation times of BSA-coated Au nanoparticles (NPs) we can change their ultraviolet-stimulated photoluminescence and shift the spectral weight over the visible spectral range. This is due to the interplay of two emission bands, one due to BSA and the other related to gold. The emission properties did not change with time over a period of several months. (C) 2014 Published by Elsevier B.V.
數學在分子生物學中不合理的有效性
(2015-01-15)
雷斯克 Arthur M. Lesk、周樹靜
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Shing-Tung Yau Center
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丘成桐中心
.基因是生物的基本藍圖，存於 DNA 的鹼基序列中，再靠著「遺傳密碼」直接轉譯成蛋白質的胺基酸序列，蛋白質於是自發折疊成天然的三維結構。序列和空間結構都可用數學的語言描述。 .分子生物學運用序列比對和結構疊合這兩項數學工具，試圖描述並分類序列或結構。希望以演化做為指導原則，描述並預測蛋白質的序列、結構、功能彼此之間的內在關係。 .從胺基酸序列決定蛋白質的三維結構是大自然的演算法，但受制於生物學的特性，從物化原理預測蛋白質結構並不容易。這個熱門又重要的問題，應該從基本原理做起，或採用實用而有效的預測，考驗數學的應用能耐。
教改的矛盾一個數學家的觀點
(2015-01-15)
林長壽
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Shing-Tung Yau Center
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丘成桐中心
關於十二年國教，我想從社會快速變遷的角度談起。臺灣整體社會的變化非常大，傳統教育部分難免跟社會現有的價值觀脫節。當然這在許多國家都一樣，解決這個問題的方式，也多少反映這個國家本身的特性，其中之一就是深刻反映政治體系的本質，但因為這需要更通盤的討論，必須先省略。面對社會的快速變化，跟所有人都有關的國民教育體制應該做怎麼樣的調整或改變，是國家政策制訂或發展中的一個很重要的參考重點。從國家體制來講，教育體制的調整或改革的重要目標，是要同時達到國家的目的與個人教育的目的。在臺灣，這點不僅從事政治的人、甚至從事教育的學者或相關人士似乎從未深刻體認、探討或反省，這是非常不幸的一點。
Hierarchical scheme for detecting the rotating MIMO transmission of the in-door RGB-LED visible light wireless communications using mobile-phone camera
(2015-01-15)
Chen, Shih-Hao
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Chow, Chi-Wai
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光電工程學系
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Department of Photonics
Multiple-input and multiple-output (MIMO) scheme can extend the transmission capacity for the lightemitting-diode (LED) based visible light communication (VLC) systems. The MIMO VLC system that uses the mobile-phone camera as the optical receiver (Rx) to receive MIMO signal from the n x n Red-GreenBlue (RGB) LED array is desirable. The key step of decoding this signal is to detect the signal direction. If the LED transmitter (Tx) is rotated, the Rx may not realize the rotation and transmission error can occur. In this work, we propose and demonstrate a novel hierarchical transmission scheme which can reduce the computation complexity of rotation detection in LED array VLC system. We use the n x n RGB LED array as the MIMO Tx. In our study, a novel two dimensional Hadamard coding scheme is proposed. Using the different LED color layers to indicate the rotation, a low complexity rotation detection method can be used for improving the quality of received signal. The detection correction rate is above 95% in the indoor usage distance. Experimental results confirm the feasibility of the proposed scheme. (C) 2014 Elsevier B.V. All rights reserved
REAL-TIME MULTI-CHANNEL AUTOMATIC EYE BLINK ARTIFACT ELIMINATOR
(2015-01-15)
Fang Wai-Chi
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Liao Jui-Chieh
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Shih Wei-Yeh
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Huang Kuan-Ju
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Chen Chiu-Kuo
A real-time multi-channel automatic eye blink artifact eliminator includes a receiving unit for receiving independent component data; a temporary storage unit for saving pieces of the independent component data to form a data segment; a detection unit for detecting an eye blink artifact in the data segment through a sample entropy algorithm to generate a sample entropy value corresponding to the data segment; and a processing unit for determining whether the data segment contains the eye blink artifact according to the sample entropy value to generate an output result, eliminating the eye blink artifact according to the output result and outputting processed independent component data. The receiving unit continuously receives a next piece of the independent component data and the temporary storage unit discards the oldest one and adds a new one to form a new data segment, thereby continuously performing the eye blink artifact elimination to each data segment.
白臉：嘆息之後
(2015-01-15)
張海潮
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Shing-Tung Yau Center
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丘成桐中心
本文是筆者讀《一個數學家的嘆息》之後的回應，文中 L 代表原作者 Paul Lockhart 教授，H 代表本人。頁數是指自 L 書中引文的出處。圖形告訴我們連續奇數的和總是一個完全平方數，圖形所呈現的是平方數的一種分解，這是平方數的「真」，而圖形的呈現方式正是數學（藝術）的美。這和我小時候的經驗是吻合的，28 這個數有各種各樣的分解，這是美，但都是代表 28，這是真。很難想像，當我們離開了真與美，我們要怎樣尷尬的學習數學。
推薦《一個數學家的嘆息》
(2015-01-15)
洪萬生
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Shing-Tung Yau Center
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丘成桐中心
本書應該是我所見過的數學教育宣言中最基進的（radical）一篇了。作者拉克哈特（Paul Lockhart）是一位成功的專業數學家，公元 2000 年，他毅然轉入紐約市一所小學任教，身體力行他認為有意義的數學教學活動。本書即是他的現身說法，因此，他對於美國目前中小學數學教育的現實之沈重但真誠的嘆息，似乎沒有幾個有識之士敢視而不見。
Palladium based cermet composite for hydrogen separation at elevated temperature
(2015-01-15)
Tsai, Yen-Chang
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Lin, Chien-Cheng
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Lin, Wei-Lin
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Wang, Jeng-Han
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Chen, San-Yuan
A cermet composite consisting of palladium and BaCe0.4Zr0.4Gd0.1DY0.1O3-x (BCZGD) is fabricated by mixing palladium and BCZGD powders in a ball mill, followed by pressing and sintering at 1450 degrees C for 24 h in air. The Pd-BCZGD cermet demonstrates impressive hydrogen permeation flux in a mixture of hydrogen and carbon dioxide at elevated temperature, in which the palladium plays the predominant role of facile transport in the hydrogen atoms whereas the BCZGD provides channels for proton conduction. Material characterization including scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermo-gravimetric analysis (TGA) are performed. XRD patterns indicate pure phases of fcc palladium and perovskite BCZGD. SEM images and element mapping suggest a homogeneous mixture of cermet without noticeable defect and phase segregation. TGA results confirm stability of the cermet against carbon dioxide without chemical decomposition. The hydrogen permeation flux is determined via a gas chromatography from 400 to 700 degrees C at various hydrogen concentration gradients. We record a hydrogen flux of 1.25 cm(3) min(-1) cm(-2) in 50% hydrogen and 50% carbon dioxide at 700 degrees C, with a selectivity of H-2/CO2 approaching infinity. (C) 2014 Elsevier B.V. All rights reserved.
數學教育與十二年國教 or 十二年國教的數學教育
(2015-01-15)
張鎮華、單維彰、張海潮、翁秉仁
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Shing-Tung Yau Center
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丘成桐中心
十二年國教數學課程綱要之我見小學數學學習相關事宜，個人意見認為，由訂定課程綱要、寫書、審書、選書、教書、讀書、到考試、入學，歷年來前半段的問題少，後半段的問題多。數學教育面臨的大議題高中數學可以如何因應自從92 年版的九年一貫數學領域數學課綱指出「數學是一種語言」以來，這個觀念一直傳延至今。沿著這個思路，當我們將數學教育類比於語言的習得，則國小的數學教育就像母語教育，而高中的數學教育就變成外語教育了。雖然外語能力（就像所有能力一樣）總是多多益善，但我們總該認清：外語是為某種目的而刻意地學，其本身即是一種專業。進入高中數學教室的中學生，想必都潛意識地認知這一點。所以我邀請讀者批判以下兩個基本假設：沒有一套適合所有中學生的高中數學，而且高中數學本身並非目的。會考啟示錄年是十二年國教第一次舉辦全國性的會考和特招。特招考試後，我寫了一篇〈103 學年度高中特招的幾何考題──兼談12 年國教國中的幾何教學〉（《高中數學學科中心電子報》第89 期）。寫完不久，就發生了各明星高中停辦特招，準備以會考來作為升學的部分根據。這個變化讓我重新思考應該回頭來看看會考的考題，原因是「考試領導教學」。此外，會考既然傳承了過去從90 年到102 年13 次基測的經驗，應該穩定性極高。國小數學很簡單嗎課程綱要必須先談課程的目標。不論是就個人發展或國家發展，小學數學教育有兩個固有的目的，因此也是課程綱要制訂的基本條件。首先，小學數學就是國民數學基本素養的養成階段，一般人是否能解決日常生活碰到的數學問題，一個現代公民是否能具備終身會用到的數量能力，絕大部分都是是以小學數學為基礎，這是小學數學的根本使命。
CCSS餘波蕩漾　近年美國媒體的數學教育論戰
(2015-01-15)
蘇惠玉
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Shing-Tung Yau Center
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丘成桐中心
美國近三十年來，所謂的數學戰爭（mathwars）一直時強時弱地在進行著，這些論戰起因於1960 年代「新數學」（New Math）後的課程改革。雖然在新數學運動之後，美國數學教育以「回歸基礎」（back to basic）為口號，回到強調基礎演練，熟練基本運算的老路，不過美國在國際數學競試的評比卻一直處於落後的地位。