學術演講


<專題討論>2018/9/27(四)14:10綜合大樓2樓48218教室演講 : 林明發 教授(成功大學物理系)

張貼者:2018年9月21日 上午12:32Dabby Lu   [ 已更新 2018年9月21日 上午12:34 ]

講題:Single-particle and collective excitations in layered graphenes
摘要:The generalized .. tight-binding model and the random-phase approximation are developed and combined together to fully the many-particle Coulomb interactions in 2D graphene systems. The intralayer & interlayer hopping integrals, the intralayer & interlayer Coulomb interactions, electric field, and magnetic field are taken into account simultaneously. The electron-hole excitations and plasmon modes are very sensitive to the number of layers, stacking configurations, doping levels, and external fields. Apparently, the (momentum, frequency)-phase diagrams exhibit the diverse Coulomb excitation phenomena. Part of theoretical predictions are consistent with the EELS measurements, while most of them require the further examinations. The dimensionless energy loss functions, being clearly characterized in the current work, are very useful in the near-future studies on (i) the time-dependent plasmon propagation on the 2D planes and (ii) the layer-related Coulomb decay rates.

2018/7/17(二)14:10綜合大樓3樓48312教室演講 : 小山孝一郎教授(Asia Space Environment Research Consortium, Kanagawa, Japan)

張貼者:2018年7月16日 上午1:59Ann-Chen Jang   [ 已更新 2018年7月16日 上午2:15 ]

Road to Venus mission in Japan
- from curiosity to the realization-

K.-.I. Oyama
1.Institute of Space and Plasma Sciences, National Cheng Kung University, Tainan Taiwan.
2.International Center of Space Weather Study and Education Fukuoka, Japan
3.Asia Space Environment Research Consortium, Kanagawa, Japan

In 2015, One Japanese spacecraft was successfully injected into Venus Orbit after failure of orbit injection in 2010, and it became the first orbiter of other planet, which was named “Akatsuki” (暁、Dawn) after its successful injection. The history of Venus exploration are Venera 1-16 in 1961-1983 by USSR. Mariner 2, 5, and 10 by USA in 1962 -1973, Pioneer Venus by USA in 1987. Vega 1, 2 in 1984 by USSR, Magellan in 1989 by USA, and lastly Venus express in 2001 by ESA. We describe here a road to successful Venus mission. We start from the failure of orbit injection in 2010, and successful injection to Venus orbiter in 2015. Then we go back to the history before successful orbit injection. We had a dream to send a Venus probe in 1980’s. The questions we had are: Why Venus has super rotation, Does active volcano exist, Is there lightning ? Is there Aurora ? Why neutral density in the cryosphere suddenly disappears ? . To make our curiosity satisfy, we prepared for the mission, starting from analysis of data obtained  with Pioneer Venus, read thick summary book on Venus, and asked private company to start study in late 1980’s. We describe here phenomena which are still not understood. These include instruments to find the clues to solve the problems for Venus mission, and finally orbit selection the spacecraft which is constrained under the limited capability of launcher. Most important task was to find scientists who are keen to send a probe to Venus. Here is a story which we want to convey to young scientists.


<專題討論>2018/5/10(四)14:10綜合大樓2樓48218教室演講 : 龔慧貞 副教授(成功大學地科系)

張貼者:2018年5月6日 下午8:20Dabby Lu

講題:地球內部構造與地球磁場 Earth’s interior structure and geodynamo
摘要:眾所皆知地球因本身磁場所形成的磁層,保護地球生物免於太陽的高能帶電粒子襲擊。從地質資料顯示地球磁場每隔一段時間都會反轉的,也觀察到南北磁極已不同的速度「漫遊」。 近170年來觀測結果顯示,地球磁場強度已減弱~15%。在這報告中,將以地球內部構造來談地球磁場機制,即「地球發電機理論」。

<專題討論>2018/5/3(四)14:10綜合大樓2樓48218教室演講 : 江偉宏 副教授(臺灣科技大學化學工程學系)

張貼者:2018年4月29日 下午7:13Dabby Lu

講題:Nanostructure Engineering using Microplasmas: Synthesis and Applications
摘要:Microplasmas are a special class of electrical discharges formed in geometries where at least one dimension is less than 1 mm. As a result of their unique scaling, microplasmas operate stably at atmospheric pressure and contain large concentrations of energetic electrons (1-10 eV). These properties are attractive for a range of nanomaterials synthesis and nanostructure engineering such as metal nanostructures and carbon-based materials [1-3]. 
In this presentation, I will discuss these topics in detail, highlighting the advantages of microplasma-based systems for the synthesis of well-defined nanomaterials. These experiments will aid in the rational design and fabrication of nanomaterials and may also have significant impact in emerging applications. Recently, we found that the energetic species including radicals, ions and electrons generated in the microplasmas were capable of initiating electrochemical-assisted reactions for the nucleation and growth of graphene quantum dots [4]. Moreover we develop a simple synthesis of metal nanoparticles/graphene composites using a unique atmospheric-pressure microplasma-assisted electrochemical method. Systematic micro Raman study indicates that the as-produced AgNP/graphene composites show exceptional SERS performance [5].

Reference: 
[1] W-H. Chiang and R. M. Sankaran, Adv. Mater. 20, 4857 (2008) 
[2] W-H. Chiang and R. M. Sankaran, Nature Mater. 8, 882 (2009)
[3] W-H. Chiang et al., J. Mater. Chem. A 4, 7624 (2016)
[4] W-H. Chiang et al., MRS Fall Meeting (2016)
[5] W-H. Chiang et al., MRS Fall Meeting (2016).

<專題討論>2018/4/26(四)14:10綜合大樓2樓48218教室演講 : 林俊良 博士(國家太空中心主任)

張貼者:2018年4月23日 上午2:32Dabby Lu

講題:我國太空計畫發展-過去及未來
摘要:本簡報將簡介我國太空長程發展計畫第一期(1991-2004)和第二期(2004-2018)的源起及成果。另介紹即將開展的第三期長程計畫(2019-2028),其目標和執行內容。希望藉這個簡報讓大家知悉十年後台灣太空科技發展對國家、產業和人才培育的影響。

<專題討論>2018/3/29(四)14:10綜合大樓2樓48218教室演講 : 方惠寬 博士(成功大學電漿所)

張貼者:2018年3月25日 下午8:09Dabby Lu

講題: In-situ plasma measurements in the Earth’s ionosphere
摘要:Measurements of plasma are fundamental for space physics, especially for space weather. Recently, giant progress of the CubeSat technologies greatly lowers the barrier to insert a satellite into a lower earth orbit for space exploration. Satellite constellation missions consisting of tens of CubeSats is planned and launched. These missions provide multi-point measurements and make it possible to separate spatial and temporal effects regarding couplings between ionosphere, atmosphere and even lithosphere. And the altitude of these missions are rarely explored by conventional satellites because of large air drag and short mission lifetime. In addition to Cubesat missions, simultaneous multi-instrument measurements onboard sounding rockets aiming for the plasma characteristic investigations in the ionosphere D layers, which is the least-explored region in the ionosphere, is planned. In this presentation, the plasma diagnostic techniques onboard CubeSats and sounding rockets will be introduced. The design concepts and preliminary results of the solar EUV probe onboard the Phoenix CubeSat in QB50 mission and the “Mesosphere and Ionosphere Plasma Exploration complex (MIPEX)” instrument onboard the NCKU sounding rocket, which is planned to be launched in 2020, will be shown. These experiments can provide unique high-quality data of the plasma environment to explore the ion distribution and the electrodynamic processes in the Ionosphere.

<專題討論>2018/3/27(二)13:10綜合大樓2樓48218教室演講 : 周紹暐 博士(台灣積體電路製造股份有限公司)

張貼者:2018年3月20日 下午11:10Dabby Lu

講題:Laser and Plasma wakefield acceleration
摘要:Energetic particle beams are important tool in many application, from basic science to healthcare, also a crucial element to produce high quality X-ray radiation. Conventional accelerators are relative large, from  10 m to   several km, due to  material-breakdown-limited  acceleration gradient and energy loss via synchrotron  radiation.    Size and cost of maintenance of conventional accelerator  limit  the extent of application for daily life. Wakefield accelerator driven by either high energy or high energy particle is a promising way to build a table-top accelerator. For example, GeV-scale electron bunch driven by laser pulses has been demonstrated by  using  cm long gas targets . As a contrast, it needs almost 100 m of conventional accelerator to reach this energy. In this talk, I will first introduce fundamental physic  of wakefield accelerator and related experiment. In the end of discussion, a physical phenomenon called "collective deceleration"  associated to the  unique properties of laser-driven electron bunches will be studied by experiment and PIC simulation. 

<專題討論>2018/3/22(四)14:10綜合大樓2樓48218教室演講 : 李昆翰 博士(中央研究院地球科學研究所)

張貼者:2018年3月18日 下午9:37Dabby Lu

講題:Generation of hydrogen, helium and oxygen EMIC waves by fast magnetosonic shocks in the magnetosphere and in the solar wind
摘要:Electromagnetic ion cyclotron (EMIC) waves are often observed in the magnetosphere and in the solar wind. Here we propose a new generation mechanism for hydrogen, helium and oxygen EMIC waves associated with fast magnetosonic shocks in the magnetosphere and in the solar wind. In the magnetosphere, these shocks can be associated with either dynamic pressure enhancement or shocks in the solar wind and can lead to the formation of a “bunch” distribution of O+ ions in the perpendicular velocity phase space. The O+ bunch distribution can excite strong He+ EMIC waves and weak O+ and H+ waves. The dominant He+ EMIC waves are strong in quasi-perpendicular propagation and show harmonics in frequency spectrum of Fourier analysis. Further analysis by using Hilbert-Huang transform shows that these signals are similar to Duffing oscillations and exhibit frequency modulation in the instantaneous frequency spectrum. The proposed mechanism can explain the generation and some observed properties of He+ and O+ EMIC waves in the magnetosphere.
Strong fast magnetosonic shocks are often observed in the solar wind. In the shock downstream, the hydrogen and helium ions are strongly heated to achieve high ion beta and high temperature anisotropy. These conditions can lead to efficient generation of EMIC waves and mirror mode waves in the downstream, which are often identified in satellite observations in the solar wind. We find that the EMIC waves are generated both in the parallel and quasi-perpendicular directions. The parallel EMIC waves have been widely studied theoretically and observationally, while the excitation of quasi-perpendicular EMIC waves is usually overlooked. We also find coalescence of mirror waves as they drift with the plasma to further downstream.

<專題討論>2018/3/20(二)13:10綜合大樓2樓48218教室演講 : 丘政倫 博士(清華大學天文研究所)

張貼者:2018年3月14日 下午7:03Dabby Lu

講題:Exploring the extreme Universe with a new generation of telescopes
摘要:Experimental high energy astrophysics probes the most energetic and exotic objects and locations in our Universe by using a variety of X-ray, gamma-ray, and cosmic-ray instruments. These high-energy sources span many orders of magnitude in size and energetics, from cosmic gamma-ray bursts and supermassive black holes to supernovae and compact objects in our Galaxy. The underlying physical processes in these sources are often similar and usually inaccessible in a laboratory. But at the same time, many of the observations have important implications for fundamental physics. Therefore, a key to these studies is to develop and utilize novel instruments with excellent sensitivity and resolution. A current generation, NuSTAR, and a next generation telescope, COSI, which are and will be revolutionizing the observation of high-energy astrophysics phenomena, will be introduced here.   
(1) The Compton Spectrometer and Imager (COSI) is a balloon-borne soft gamma-ray (0.2-5 MeV) telescope designed to study astrophysical sources of nuclear-line emission and gamma-ray polarization. COSI employs a compact Compton telescope design, imaging gamma-rays through their scattering history in novel 3D-tracking Germanium detectors. As a balloon payload, this telescope performs sensitive observations of positron annihilation, nucleosynthesis, compact objects, GRBs, and AGN. (2) The Nuclear Spectroscopic Telescope Array (NuSTAR) is the first focusing high energy X-ray satellite in orbit (launched in June 2012), providing more than two orders of magnitude improvement in sensitivity compared to previous high energy missions. NuSTAR's primary science goals include conducting a survey of black holes, mapping young supernovae explosions, studying cosmic accelerators, and identifying high energy sources in our Galaxy.     
In this talk, I will present our current achievements with both instruments and future research plans based on these efforts.

<專題討論>2018/3/15(四)14:10綜合大樓2樓48218教室演講 : 藍永強 教授(成功大學光電系)

張貼者:2018年3月11日 下午6:10Dabby Lu

講題:Generation of light beams by electron beam excited surface plasmons
摘要:When the electron beam moves along or normally onto the plasmonic nanostructures (PNs), it can excite the surface plasmons (SPs) on PNs along with the transition radiation (TR). In the former case, the SPs have specific frequencies determined by the intersection of dispersion curves of electron beam and SPs. In the latter case, conversely, the SPs have a wide frequency band [1]. Furthermore, SPs can be transferred into light emission (SP emission) by the surface structures of PNs. In this work, we will consider three types of light beam generation by electron beam excited SPs. First, we will investigate SP-manipulated and localized SP (LSP)-manipulated Smith-Purcell radiation (SPR) on metallic periodic gratings and disk arrays, respectively [2]. The SPR can be enhanced by exciting SPs and LSPs if their frequencies are within the emission bands of SPRs. Second, the generation of convergent beam by electron-excited SPs is examined. Here the mechanism of SPR on metallic chirped gratings is proposed to generate the convergent light beam. Finally, the SP-manipulated TR and SP emission from the electron beam normally incident PNs with designed slit structures are studied [3]. This work offers potential applications in the fields of optical imaging, holography, cryptography and tunable visible light source, etc.

[1] S. Gong, M. Hu, R. Zhong, X. Chen, P. Zhang, T. Zhao and S. Liu, “Electron beam excitation of surface plasmon polaritons,” Opt. Express 22, 19252-19261 (2014).

[2] Y. C. Lai, T. C. Kuang, B. H. Cheng, Y. C. Lan and D. P. Tsai, “Generation of convergent light beams by using surface plasmon locked Smith-Purcell radiation,” Scientific Reports 7, 11096 (2017).

[3] T. Coenen, B. J. M. Brenny, E. J. Vesseur and A. Polman, “Cathodoluminescence microscopy: Optical imaging and spectroscopy with deep-subwavelength resolution,” MRS Bulletin 40(4), 359-365 (2015).

1-10 of 42