Browsing by Issue Date, starting with "2020-04-17"

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Widely Tunable Single/Dual RF Signal Generation by a Monolithic Three-Section DFB Laser
(2020-04-17)
Huang, Chung-Ping
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Huang, Yu-Ming
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Shih, Hsiang-Yun
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Hsiao, Fu-Chun
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Chen, Chun-Hong
A three-section distributed feedback laser with a 2.5 InP/air pair of distributed Bragg reflectors (DBRs) was fabricated and analyzed in terms of its microwave generation capability. A widely tunable single radio frequency (RF) signal can be detected using optical heterodyning, and the tuning range is from 2 to 45 GHz. The incorporation of the third section provides an opportunity to present the dual RF operation when three emission peaks are near to each other in the wavelength domain. The proposed design provides a 21.3% enhancement in the RF tuning range compared with the range of a two-section laser (35.29 GHz versus 42.81 GHz). The compactness of the proposed device can be useful for future radio-over-fiber applications.
Nonvolatile molecular memory with the multilevel states based on MoS2 nanochannel field effect transistor through tuning gate voltage to control molecular configurations
(2020-04-17)
Lan, Yann-Wen
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Hong, Chuan-Jie
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Chen, Po-Chun
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Lin, Yun-Yan
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Yang, Chih-Hao
A new flexible memory element is crucial for mobile and wearable electronics. A new concept for memory operation and innovative device structure with new materials is certainly required to address the bottleneck of memory applications now and in the future. We report a new nonvolatile molecular memory with a new operating mechanism based on two-dimensional (2D) material nanochannel field-effect transistors (FETs). The smallest channel length for our 2D material nanochannel FETs was approximately 30 nm. The modified molecular configuration for charge induced in the nanochannel of the MoS2 FET can be tuned by applying an up-gate voltage pulse, which can vary the channel conductance to exhibit memory states. Through controlling the amounts of triggered molecules through either different gate voltage pulses or gate duration time, multilevel states were obtained in the molecular memory. These new molecular memory transistors exhibited an erase/program ratio of more than three orders of current magnitude and high sensitivity, of a few picoamperes, at the current level. Reproducible operation and four-level states with stable retention and endurance were achieved. We believe this prototype device has potential for use in future memory devices.
天然對上化學　哪種防曬不傷身
(2020-04-19)
王冠云
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Department of Communication and Technology
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傳播與科技學系
防曬產品百百種，哪些對皮膚及身體不會造成傷害？化學及物理性防曬產品會有哪些風險？天然防曬又有哪些該注意的呢？
Astor的自信秘訣：做最自在的自己
(2020-04-19)
高儷玲
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Department of Communication and Technology
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傳播與科技學系
Astor，一位美妝YouTuber，同時也是位模特兒。現在充滿自信的她卻也曾自卑過；外表看似讓人難以親近，私底下的她卻非常幽默風趣，理性的個性卻在碰到家人時變得感性，藉由這篇報導帶你認識不一樣的Astor。
時代不同　下一代還看電視嗎？
(2020-04-19)
吳政陽
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Department of Communication and Technology
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傳播與科技學系
世代交替，從前我們坐在電視機前看卡通，現在他們拿著平板、手機在玩遊戲和看網路影片，難道以電視為主流的傳統媒體真的被淘汰了嗎？
總編輯的話
(2020-04-19)
梁子敬
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Department of Communication and Technology
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傳播與科技學系
本期為喀報334期，共有9篇文章，包含社會議題3篇、人物特寫3篇、藝文評論2篇以及科技新知1篇。本次頭題為黃順愉的《防疫不忘學習，「遠」來不易？》，探討使用遠距教學與否的疑慮，以及教授與學生們對此的看法。本期喀報也透過其他多元的題材，帶領讀者思考議題、欣賞藝文以及刻劃人物。
《最美的一天》，最美的音樂劇
(2020-04-19)
周容萱
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Department of Communication and Technology
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傳播與科技學系
台灣原創音樂劇《最美的一天》是「C MUSICAL製作」的作品之一，全劇對白趨近於零，僅由15首歌曲串連而成。2017年在國家戲劇院實驗劇場首演廣受好評，2019年在水源劇場演出了長達三週，共12場戲。並代表臺北市文化局至韓國大邱國際音樂劇節演出，更入圍了「最佳海外音樂劇」以及「最佳女配角」獎項。
防疫不忘學習，「遠」來不易？
(2020-04-19)
黃順愉
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Department of Communication and Technology
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傳播與科技學系
數位學習並不是空降在校園，早在疫情爆發之前，校園裡就已經有開設數位教學的課程。如今，面對需進行「全面遠距教學」的情況，對於校園推動數位教學到底是危機還是轉機？
與勞為伍──顧玉玲
(2020-04-19)
謝孟如
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Department of Communication and Technology
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傳播與科技學系
印象中，社會運動者不是看起來正經的冷漠，就是激動的剽悍，然而顧玉玲打破了我的認知，溫和，卻堅韌。
壓垮地球的衣服山
(2020-04-19)
李而
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Department of Communication and Technology
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傳播與科技學系
經過調查顯示，台灣高達五成的舊衣因不符合回收資格，直接被當成垃圾焚燒處理，為環境帶來了更多負擔。探尋問題根本，若民眾能認清需求且不隨波逐流，或許就能當一位環保的時尚達人。
華人世界的善意謊言　別告訴她
(2020-04-19)
何雨潮
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Department of Communication and Technology
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傳播與科技學系
在《別告訴她》電影中，從奶奶的死亡延伸了許多中、西方的文化差異。寫實生動的電影情節，彷彿日常瑣事上演，帶給觀眾更真實的感受。
林子竣　熱血追夢的冒險家
(2020-04-19)
王乃安
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Department of Communication and Technology
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傳播與科技學系
熱血不需要事先定義。一個「酷」就可以構成冒險的契機。「人生好難，但很好玩」，你準備好一起冒險了嗎？
Radial and tangential velocity effects of a probed scanning mirror on laser Doppler frequency shift
(2020-04-20)
Agusanto, Kusuma
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Lau, Gih-Keong
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Liu, Ting
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Zhu, Chuangui
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機械工程學系
A laser Doppler vibrometer (LDV) is precise and fast in measuring the translational velocity of a vibrating diffuse surface. However, it could fail to measure the tangential velocity of a rotating mirror. While the specular reflection away from the mirror can be recovered by a retroreflective collector, the recovered LDV reading is found to deviate from the true tangential velocity of the probed scanning mirror. This happens because the probed spot shifts radially along the rotating mirror surface and thus introduces extra Doppler shift, while the laser beam is aimed at a constant height on the scanning mirror. Here, we derive an analytical relationship between the laser Doppler shift and the tangential velocity of the measured spot. With the input of the prescribed scan profile, we recover the true reading of tangential velocity of the scanning mirror even at a large rotational angle. This corrected LDV reading is as precise as the measurement by a high-speed camera. (C) 2020 Optical Society of America
High-brightness and high-speed vertical cavity surface-emitting laser arrays
(2020-04-20)
Khan, Zuhaib
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Shih, Jie-Chen
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Chao, Rui-Lin
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Tsai, Tzong-Liang
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Wang, Hsin-Chuan
High-power vertical-cavity surface-emitting laser (VCSEL) arrays, which can serve as the light source in modem lidar and three-dimensional optical sensing systems, have recently attracted a lot of attention. In these types of systems, the time-of-flight (ToF) technique, based on the round-trip time of short optical pulses is usually adopted. Further enhancement of the ranging distance and depth resolution in these ToF driven systems by the incorporation of a VCSEL array with a high available power, high brightness (narrow divergence angle), and fast response time is highly deskable. However, a large number of light emission apertures (several hundreds) in the VCSEL array is usually necessary to raise the output power level to several watts. This leads to a large parasitic capacitance and the RC-limited bandwidth may become the dominant limiting factor of the speed of the high-power VCSEL array. In this work, Zn-diffusion and oxide-relief apertures are used to manipulate the optical modes and reduce the parasitic capacitance, respectively, in a unit device for a 940 nm VCSEL array. The demonstrated VCSEL array has a quasi-single-mode output, high available power (4 W; 1% duty cycle), narrow divergence angle (similar to 14 degrees at 1/e(2)) under maximum output power, and a fast rise time (<100 ps). These results open up new possibilities for further enhancing the performance of ToF sensing systems at the 940 nm wavelength. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Designing an anamorphic illumination system with an RTIR prism for a tilt-and-roll-pixel-type projector
(2020-04-20)
Chen, Yu-Jia
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Pan, Jui-wen
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光電系統研究所
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Institute of Photonic System
A relay lens system design for a mini-projector with telecentric illumination is described. The reverse total internal reflection (RTIR) prism for angular magnification and lateral magnification is discussed in detail, and magnifications under different digital micromirror devices (DMD) are compared. The tilt-and-roll pixel (TRP) DMD chip (tilt angle is +/- 17 degrees) is the latest spatial light modulator, and the f-number of the illumination system is 1.71. Using the TRP DMD, the lateral magnification and the angular magnification for the RTIR prism can be increased by 3.77% and 8.73% over that obtainable using the conventional DMD chip (tilt angle is +/- 12 degrees). In order to solve for the angular magnification of an RTIR prism, the baffle is set at the aperture stop of the relay lens system. There is a trade-off between the efficiency and the contrast ratio with the baffle. When B (the position of the baffle) is at 0.11, the contrast ratio of the illumination system is 7590:1 and the efficiency is 57%. The spot size at the edge and corner of the DMD active area is controlled to be less than 250 mu m, and the optical distortion is less than 1%. (C) 2020 Optical Society of America
Ultramicrostructural reductions in teeth: implications for dietary transition from non-avian dinosaurs to birds
(2020-04-21)
Li, Zhiheng
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Wang, Chun-Chieh
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Wang, Min
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Chiang, Cheng-Cheng
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Wang, Yan
Background Tooth morphology within theropod dinosaurs has been extensively investigated and shows high disparity throughout the Cretaceous. Changes or diversification in feeding ecology, i.e., adoption of an herbivorous diet (e.g., granivorous), is proposed as a major driver of tooth evolution in Paraves (e.g., Microraptor, troodontids and avialans). Here, we studied the microscopic features of paravian non-avian theropod and avialan teeth using high-spatial-resolution synchrotron transmission X-ray microscopy and scanning electron microscopy. Results We show that avialan teeth are characterized by the presence of simple enamel structures and a lack of porous mantle dentin between the enamel and orthodentin. Reduced internal structures of teeth took place independently in Early Cretaceous birds and a Microraptor specimen, implying that shifts in diet in avialans from that of closely related dinosaurs may correlate with a shift in feeding ecology during the transition from non-avian dinosaurs to birds. Conclusion Different lines of evidence all suggest a large reduction in biting force affecting the evolution of teeth in the dinosaur-bird transition. Changes in teeth microstructure and associated dietary shift may have contributed to the early evolutionary success of stemward birds in the shadow of other non-avian theropods.
Synthesis of side-chain regioregular and main-chain alternating poly(bichalcogenophene)s and an ABC-type periodic poly(terchalcogenophene)
(2020-04-21)
Liu, Huai-Hsuan
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Liang, Wei-Wei
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Lai, Yu-Ying
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Su, Yen-Chen
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Yang, Hau-Ren
Three unsymmetrical diiodobichalcogenophenes SSeI2, STeI2, and SeTeI2 and a diiodoterchalcogenophene SSeTeI2 were prepared. Grignard metathesis of SSeI2, STeI2, SeTeI2, and SSeTeI2 occurred regioselectively at the lighter chalcogenophene site because of its relatively lower electron density and less steric bulk. Nickel-catalyzed Kumada catalyst-transfer polycondensation of these Mg species provided a new class of side-chain regioregular and main-chain AB-type alternating poly(bichalcogenophene)s-PSSe, PSTe, and PSeTe-through a chain-growth mechanism. The ring-walking of the Ni catalyst from the lighter to the heavier chalcogenophene facilitated subsequent oxidative addition, thereby suppressing the possibility of chain-transfer or chain-termination. More significantly, the Ni catalyst could walk over the distance of three rings (ca. 1 nm)-from a thiophene unit via a selenophene unit to a tellurophene unit-to form PSSeTe, the first ABC-type regioregular and periodic poly(terchalcogenophene) comprising three different types of 3-hexylchalcogenophenes.
Pathogenic Variants in CEP85L Cause Sporadic and Familial Posterior Predominant Lissencephaly
(2020-04-22)
Tsai, Meng-Han
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Muir, Alison M.
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Wang, Won-Jing
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Kang, Yi-Ning
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Yang, Kun-Chuan
Lissencephaly (LIS), denoting a "smooth brain," is characterized by the absence of normal cerebral convolutions with abnormalities of cortical thickness. Pathogenic variants in over 20 genes are associated with LIS. The majority of posterior predominant LIS is caused by pathogenic variants in LIS1 (also known as PAFAH1B1), although a significant fraction remains without a known genetic etiology. We now implicate CEP85L as an important cause of posterior predominant LIS, identifying 13 individuals with rare, heterozygous CEP85L variants, including 2 families with autosomal dominant inheritance. We show that CEP85L is a centrosome protein localizing to the pericentriolar material, and knockdown of Cep85l causes a neuronal migration defect in mice. LIS1 also localizes to the centrosome, suggesting that this organelle is key to the mechanism of posterior predominant LIS.
Porous Self-Assembled Molecular Networks as Templates for Chiral-Position-Controlled Chemical Functionalization of Graphitic Surfaces
(2020-04-22)
Tahara, Kazukuni
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Kubo, Yuki
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Hashimoto, Shingo
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Ishikawa, Toru
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Kaneko, Hiromasa
Controlled covalent functionalization of graphitic surfaces with molecular scale precision is crucial for tailored modulation of the chemical and physical properties of carbon materials. We herein present that porous self-assembled molecular networks (SAMNs) act as nanometer scale template for the covalent electrochemical functionalization of graphite using an aryldiazonium salt. Hexagonally aligned achiral grafted species with lateral periodicity of 2.3, 2.7, and 3.0 nm were achieved utilizing SAMNs having different pore-to-pore distances. The unit cell vectors of the grafted pattern match those of the SAMN. After the covalent grafting, the template SAMNs can be removed by simple washing with a common organic solvent. We briefly discuss the mechanism of the observed pattern transfer. The unit cell vectors of the grafted pattern align along nonsymmetry axes of graphite, leading to mirror image grafted domains, in accordance with the domain-specific chirality of the template. In the case in which a homochiral building block is used for SAMN formation, one of the 2D mirror image grafted patterns is canceled. This is the first example of a nearly crystalline one-sided or supratopic covalent chemical functionalization. In addition, the positional control imposed by the SAMN renders the functionalized surface (homo)chiral reaching a novel level of control for the functionalization of carbon surfaces, including surface-supported graphene.
Ultralow Schottky Barriers in Hexagonal Boron Nitride-Encapsulated Monolayer WSe2 Tunnel Field-Effect Transistors
(2020-04-22)
Pande, Gaurav
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Siao, Jyun-Yan
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Chen, Wei-Liang
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Lee, Chien-Ju
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Sankar, Raman
To explore the potential of field-effect transistors (FETs) based on monolayers (MLs) of the two-dimensional semiconducting channel (SC) for spintronics, the two most important issues are to ensure the formation of variable low-resistive tunnel ferromagnetic contacts (FCs) and to preserve intrinsic properties of the SC during fabrication. Large Schottky barriers lead to the formation of high resistive contacts, and methods adopted to control the barriers often alter the intrinsic properties of the SC. This work aims at addressing both issues in fully encapsulated ML WSe2 FETs using bilayer hexagonal boron nitride (h-BN) as a tunnel barrier at the FC/SC interface. We investigate the electrical transport in ML WSe2 FETs with the current-in-plane geometry that yields hole mobilities of similar to 38.3 cm(2) V-1 s(-1) at 240 K and on/off ratios of the order of 10(7), limited by the contact regions. We have achieved an ultralow effective Schottky barrier (similar to 5.34 meV) with an encapsulated tunneling device as opposed to a nonencapsulated device in which the barrier heights are considerably higher. These observations provide an insight into the electrical behavior of the FC/h-BN/SC/h-BN heterostructures, and such control over the barrier heights opens up the possibilities for WSe2-based spintronic devices.