9,880 research outputs found
Three new species of Theridiidae Sundevall, 1833 (Araneae) from Xizang, China
No full textThree new species belonging to the spider family Theridiidae are described based on materials collected from Xizang Autonomous Region, Southwestern China: Moneta linzhi Gan, Mi & Wang, sp. nov. (♀♂), M. yinae Gan, Mi & Wang, sp. nov. (♀♂) and Phoroncidia cibagou Gan, Mi & Wang, sp. nov. (♀♂). Diagnostic photos of the habitus and copulatory organs, and a distribution map are provided
Tuning Electrical Properties in GaN Nanowires for Optimization of Artificial Photosynthesis
No full textTechnological advancements in a variety of renewables have given previously less prominent energy sources new potential. Hydrogen fuel cells have shown great overall potential, but limitations are primarily in the rate of hydrogen generation due to the sluggish speeds of the underlying reactions. Chemical reaction rates depend on a variety of factors, one of which being the activation barrier: the system must gain energy and exceed a certain energy to reach completion, and the barrier for the hydrogen-generation-reactions is particularly high. Catalysts are materials that when introduced to a system reduce this activation barrier and make certain reactions possible or faster without consuming the catalyst by creating an alternative reaction pathway that’s more efficient. The Mi Lab’s research focuses on utilizing certain materials to stimulate the hydrogen-generation-reactions, combining catalysts and nanomaterials to reduce the activation barrier and provide more energy to the system. This process, which the Mi group is calling Artificial Photosynthesis due to its utilization of the sun to increase the rate of hydrogen generation, has the overarching goal of acting as a renewable energy source to generate electricity for utilization in homes or buildings similar to the solar panels on North Campus. The underlying process takes energy from the sun to excite electrons in semiconductor nanotubes, and those electrons are funneled to a catalyst material to significantly increase the rate of the hydrogen redox reactions by increasing the concentration of reactants. The focus of this project is to observe the effect of temperature on the electron excitation and transport in semiconductor nanotubes. Temperature is one of the few parameters that can be controlled in these systems to optimize operating conditions. While we understand that temperature is a balancing act between excitation and lattice vibration, being able to specifically quantify these mechanisms is essential for application. We ran computer simulation using Materials Studio to predict the electrical material properties of GaN over a range of operating temperatures. By understanding and analyzing these results, we can identify the temperature conditions that are optimal for system operation.NAhttp://deepblue.lib.umich.edu/bitstream/2027.42/176753/1/Capstone_Report_caitaot_-_Tao_Cai.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/176753/2/Honors_Capstone_Poster_-_Tao_Cai.ppt
Gan Nanotubes
No full textWe perform parametrized density-functional calculations to predict the stability and formation mechanism of GaN nanotubes. Strain energies of GaN nanotubes are comparable to those of carbon nanotubes, suggesting the possibility for the formation of GaN nanotubes. We note that an intermediate phase with [4,6,10] polygons exist at armchair tube edge, which may play as a nucleation seed of further tube growth.</jats:p
Gan Nanotubes
No full textAbstractWe perform parametrized density-functional calculations to predict the stability and formation mechanism of GaN nanotubes. Strain energies of GaN nanotubes are comparable to those of carbon nanotubes, suggesting the possibility for the formation of GaN nanotubes. We note that an intermediate phase with [4,6,10] polygons exist at armchair tube edge, which may play as a nucleation seed of further tube growth.</jats:p
Revision of the orb-weaver spider genus Gea C.L. Koch, 1843 (Araneae, Araneidae) from China
No full textThe orb-weaver spider genus Gea C.L. Koch, 1843 from China is revised, and three species including one new species, are recognized: Gea jingdong Mi, Wang &amp; Gan, sp. nov. (♂♀) from Yunnan; Gea spinipes C.L. Koch, 1843 (♂♀) from Guangdong, Guangxi, Guizhou, Hainan, Taiwan, and Yunnan; and Gea subarmata Thorell, 1890 (♂♀) from Guangxi and Hainan. Gea subarmata is newly recorded in China
Ji yu ju ben e bao fu de jin na mi jie gou de biao mian deng li zi ti ji yuan kai guan yu chuan gan qi
No full textJiang, Nina = 基于聚苯胺包覆的金纳米结构的表面等離子體激元开关与传感器 / 蔣妮娜.Thesis Ph.D. Chinese University of Hong Kong 2014.Includes bibliographical references.Abstracts also in Chinese.Title from PDF title page (viewed on 27, September, 2016).Jiang, Nina = Ji yu ju ben e bao fu de jin na mi jie gou de biao mian deng li zi ti ji yuan kai guan yu chuan gan qi / Jiang Nina
The role of growth temperature on the indium incorporation process for the MOCVD growth of InGaN/GaN heterostructures
No full textInternational audiencePurpose – The purpose of this paper is to investigate the effect of growth temperature on the evolution of indium incorporation and growth process of InGaN/GaN heterostructures.Design/methodology/approach – To examine this effect, the InGaN/GaN heterostructures were grown using Taiyo Nippon Sanso Corporation (TNSC) metal organic chemical vapor deposition (MOCVD) SR4000-HT system. The InGaN/GaN heterostructures were epitaxially grown on 3.4 μm undoped-GaN (ud-GaN) and GaN nucleation layer respectively over a commercial 2” c-plane flat sapphire substrate (FSS). The InGaN layers were grown at different temperature setting ranging from 860°C to 820°C in a step of 20°C. The details structural, surface morphology and optical properties were investigated using X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), atomic force microscopy (AFM) and ultraviolet-visible (UV-Vis) spectrophotometer, respectively.Findings – InGaN/GaN heterostructure with indium composition up to 10.9% has been successfully grown using MOCVD technique without any phase separation detected within the sensitivity of the instrument. Indium compositions were estimated through simulation fitting of XRD curve and calculation of Vegard’s law from UV-Vis measurement. The thickness of the structures was determined using Swanepoel method and the FE-SEM cross-section image.Originality/value – This paper report on the effect of MOCVD growth temperature on the growth process of InGaN/GaN heterostructure which are of interest in solid state lighting technology especially in light emitting diodes (LEDs) and solar cells application
Marknadsföring av kurser inom fria bildningen : Utvecklande av en hemsida för sykurser i Pedersöre MI
No full textFöreliggande examensarbete omfattar utarbetande av en hemsida som marknadsföringskanal för sykurser i Pedersöre MI. Syftet var att denna kanal skulle ge flera kursdeltagare samt behålla de tidigare kursdeltagarna. Som uppdragsgivare fungerade Åsa Nyberg-Sundqvist, rektor på Pedersöre MI.
Som teoridelar i arbetet gjordes definition och beskrivning av marknadsföring och traditionella och digitala marknadsföringskanaler, samt av skillnaderna mellan dessa. Fria bildningen och medborgarinstitutens verksamhet generellt, samt skapande av en hemsida, beskrevs som teoridelar i detta arbete. Skapande av en hemsida beskrevs som bakgrund till det praktiska arbetet, utvecklandet av en hemsida.
Som metod användes intervju med intervjuguide för beskrivning av marknadsföring med betoning på marknadsföringskanaler inom Pedersöre MI 2002 – 2021. Som bakgrund och forskningsmetoder till teoridelarna samt utvecklande av hemsidan låg litteraturstudier, nätstudier via webbsökning samt egen fortbildning i digital kompetens för undervisning inom fria bildningen.
Vid utvecklandet av hemsidan testades och jämfördes två olika digitala verktyg för att erhålla den optimala hemsidans utseende och användning för sykurser i Pedersöre MI. Det praktiska skapandet av hemsidan beskrevs och resultatet diskuterades samt förslag gavs för uppdragsgivaren om hemsidan som en digital marknadsföringskanal för sykurser i Pedersöre MI.This thesis includes developing a website as a digital marketing channel for the sewing courses in Pedersöre Adult Education Centre. The aim was to get more participants to the sewing courses and encourage the current participants to continue participating. Åsa Nyberg–Sundqvist, principal of Pedersöre Adult Education Centre, was acting as the supervisor.
A description of marketing and traditional and digital marketing channels and the distinction between those were included in the theoretical part. A description of the liberal adult education and Adult Education Centre in general as well as developing of website were presented as theoretical parts in this thesis. The marketing of Pedersöre Adult Education Centre during 2002-2021 was described by two interviews. The theory on creating websites worked as a background to the practical part and the development of the website for the commissioner.
As research method on the marketing of Pedersöre Adult Education Centre an interview with interview guide were made. As background and research methods for the developing of the website were used different literature studies, web searches and the author´s continuing education in digital competences for teaching in liberal adult education. During the developing of the website two different digital website programs and tools were tested and compared, to get the most optimized look and use for sewing courses in Pedersöre Adult Education Centre.
The thesis resulted in a website for sewing courses in Pedersöre Adult Education Centre. The process of developing the website and the result were discussed and suggestions for future marketing were given to the commissioner
Selective area epitaxy of GaN-based nanowire heterostructures for applications in photonic and electronic devices
No full textThe development of optoelectronic devices and electronic devices made using conventional GaN-based planar heterostructures is ultimately restricted by the challenges in growing high-quality In-rich InGaN planar heterostructures, using mismatched substrates and/or device fabrications. Moreover, extensive demanding applications require the use of micro-scale and nano-scale GaN-based materials and devices for the integration of optoelectronic devices into a limited space, the integration of dense optoelectronic devices into larger scale systems, or the shrinkage of overall systems. Dislocation-free GaN-based nanowires have emerged as a promising candidate for applications in photonic and electronic devices. This dissertation focuses on the development of GaN-based nanowire heterostructures by using molecular beam epitaxy (MBE) as well as their device applications.Through the monolithic integration of spontaneously grown blue, green, red (RGB) and yellow/orange InGaN nanowire LEDs on Si substrates, controllable and tunable full-color light generations are demonstrated using a three-step selective-area growth process with SiOx mask created on Si substrates. The lateral-arranged monochromatic subpixels enable controlled light mixing at the chip level and exhibit color-tunable light emissions with correlated color temperature values in the range from 1900 K to 6800 K, while maintaining excellent color rendering capability. Selective area epitaxy (SAE) enables one to precisely control the size, position and morphology of nanowires, and hence enables one to precisely control and tune nanowire emission wavelength. Through SAE of RGB InGaN-based nanowire arrays on GaN/sapphire substrate with Ti mask defined by using high-resolution lithography, the overall RGB pixel size was 7×7 µm2 with monochromatic subpixel sizes of 2.8×2.8 µm2. By incorporating InGaN quantum dots in single GaN nanowires, diameter-dependent emissions tuning from blue to red were achieved from the single GaN-based nanowires on the same substrate and its mechanism was investigated. Based on this achievement, we have developed, for the first time, the world's smallest pixel size full-color InGaN/GaN single nanowire LED pixel optimized for ultra-fine projection displays using only one step epitaxial growth process.Spontaneously grown AlInGaN quaternary core-shell nanowire heterostructures are demonstrated on Si substrate, wherein an In-rich core and an Al-rich shell were spontaneously formed during the epitaxial growth process. Such core-shell structures can largely suppress nonradiative surface recombination, leading to a significant enhancement of carrier lifetime from ~ 0.2 ns to ~ 2 ns and output power. By varying the growth conditions, the emission wavelengths can be tuned from ~ 430 nm to ~ 630 nm. Electrical transport properties of vertical-aligned GaN single nanowires on Si substrate have been systematically studied by in-situ nanoprobing in a SEM chamber. A current density up to 4.65 MA/cm2 has been achieved from a single GaN nanowire selective-area grown on Si substrate, promising the realization of vertical GaN-based nanowire electronic devices on Si substrates.SAE of uniform AlInGaN quaternary nanowire array has also been demonstrated on Si substrates. Selective-area grown p-i-n AlInGaN nanowire devices can exhibit light-emitting properties and photovoltaic effect over the same chips. Under the AM 1.5G illuminations, AlInGaN nanowire devices exhibit higher photovoltaics efficiency than those ever reported for p-i-n InGaN-based nanowire solar cell, benefiting from suppressed nonradiative surface recombination.Le développement de dispositifs photoniques et électroniques réalisés en utilisant des hétérostructures planaires conventionnelles à base de GaN sont limités par des difficultés quant à la croissance d'hétérostructures planaires en InGaN riches en In de haute qualité, l'utilisation de substrats mésappariés, et la fabrication d'appareils à base d'hétérostructures planaires en GaN. Les nanofils à base de GaN sans dislocation ont émergé comme un candidat prometteur pour de futures applications pour les dispositifs photoniques et électroniques. Cette thèse se concentre sur le développement d'hétérostructures de nanofils à base de GaN en utilisant l'épitaxie par jets moléculaires (MBE), ainsi que leurs diverses applications pour écrans, illuminations, photovoltaïques et transistors.Grâce à l'intégration monolithique de diodes électroluminescentes (LED) à base de nanofils bleu, vert, rouge (RVB) et jaune/orange sur des substrats de Si, des générations de lumières colorées contrôlables et ajustables ont été démontrées en utilisant un processus de croissance sélective en trois étapes utilisant un masque en SiOx. Les sous-pixels monochromatiques disposés latéralement permettent un mélange contrôlé de la lumière au niveau de la puce électronique et émettent de la lumière de couleurs ajustables avec des valeurs de température de couleur corrélées comprises entre 1900 K et 6800 K, tout en conservant une excellente capacité de rendement des couleurs.L'épitaxie sélective (SAE) permet de contrôler avec précision la taille, la position et la morphologie des nanofils, et ainsi d'obtenir une longueur d'onde d'émission contrôlée et ajustable avec précision. Grâce à la SAE, des matrices de nanofils à base de GaN RVB sur des substrats de GaN/saphir avec un masque en Ti, une taille de pixel polychrome de 7 × 7 μm2 a été obtenue avec des tailles de sous-pixels monochromatiques de 2,8 × 2,8 μm2. En incorporant des points quantiques (QDs) en InGaN dans des nanofils individuels à base de GaN, des émissions de couleurs allant du bleu au rouge ont été obtenues en ajustant le diamètre des nanofils uniques sur le même substrat, et ce mécanisme a été étudié. En se basant sur cette réalisation, nous avons développé, pour la première fois, avec la plus petite taille de pixel au monde, des DELs avec des pixels de nanofils individuels en InGaN/GaN à haute performance en utilisant un seul processus de croissance épitaxiale.Des hétérostructures de nanofils quaternaires en AlInGaN à croissance épitaxiale spontanée ont été étudiées sur un substrat de Si, dans lesquelles un noyau riche en In et une coquille riche en Al ont été formés spontanément au cours du processus de croissance épitaxiale. De telles structures noyau-enveloppe peuvent largement supprimer la recombinaison de surface non radiante, menant à une augmentation significative de la durée de vie des porteurs de charge, de ~ 0,2 ns à ~ 2 ns, et de la puissance de sortie. En faisant varier les conditions de croissance, les longueurs d'onde d'émission peuvent être ajustées de ~ 430 nm à ~ 630 nm.Les propriétés de transport électrique de nanofils uniques en GaN alignés verticalement sur un substrat de Si ont été étudiées de manière systématique en utilisant une nanoprobation in situ à l'intérieur d'une chambre d'un microscope électronique à balayage (SEM). Une densité de courant allant jusqu'à 4,65 MA/cm2 a été atteinte par une seule zone sélective de nanofils en GaN sur un substrat de Si, promettant la réalisation de transistors à nanofils verticaux à base de GaN sur des substrats de Si.La SAE de réseaux de nanofils quaternaires AlInGaN uniformes a également été démontrée sur des substrats de Si. Sous une illuminations AM 1,5G, les nanofils en AlInGaN de type p-i-n démontrent une efficacité photovoltaïque supérieure aux cellules solaires à base de nanofils en InGaN de type p-i-n en raison de la suppression de la recombinaison de surface non radiante
Fabrication and optical properties of nano-structured semipolar InGaN/GaN quantum wells on c-plane GaN template
No full textHigh density self-assembled nanostructured semipolar (NSSP) GaN pyramids are fabricated based on c-plane GaN template by in situ silane treatment followed by high temperature treatment. Semipolar InGaN/GaN multiple quantum wells (MQWs) were subsequently grown on the NSSP GaN. Optical properties of the MQWs were studied by temperature- dependent and excitation density varied photoluminescence. It was found that the internal electric field in the NSSP MQWs were remarkably reduced in comparison with planar c-plane MQWs. The internal quantum efficiency of the NSSP MQWs was measured to be > 30% which showed potential applications in III-nitride light emitters. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/58655/1/1618_ftp.pd
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