488 research outputs found
Axion electrodynamics in topological matter
Get PDFIn this thesis we search for the topological magnetoelectric effect. We first review the theoretical aspects of axion electrodynamics in topological matter. It was found that for such materials, an additional term can be added to the Lagrangian density, which leads to the modification of Maxwell's equations. These modifications arise due to spatial or temporal changes in the axion angle, which is non-zero in topological materials. Several experiments have been proposed to measure the resulting topological magnetoelectric effects, of which we consider three experiments which are related to electronic properties. Two experiments, the search for the magnetic monopole and the interference experiment for fractional charge, are related to a spatial gradient in the axion angle, while the chiral magnetic effect relates to temporal changes in the axion angle of Weyl semimetals. In the rest of this thesis, we use thin films, deposited by molecular beam epitaxy (MBE), and exfoliated flakes of topological materials to study the experiments that were proposed above. For the magnetic monopole experiment, we fabricate top gate samples of magnetically doped topological insulator films. We measure the magnetic response as a function of applied gate voltage via a SQUID sensor in a dilution refrigerator. We find that heat dissipation in the sample plays a major role at ultra low temperatures. The signature of fractional charges is measured in an interference experiment where we make use of a Josephson junction array that is fabricated on both topological and reference samples. While no topological signature was observed in the measurements, we find a good agreement between the experimental results and numerical simulations. For the chiral magnetic effect, we used exfoliated flakes of a Dirac semimetal, of which we fabricated non-local nanostructures to measure the diffusion length of the chiral charge polarization. We find that the relaxation rate of the chiral charge is slower than the Ohmic relaxation rate.</p
Dialectal position of Daan Tibetan spoken in the Naxi cultural area
Get PDFチベット語が分布する地域の南東端を占める中国雲南省迪慶藏族自治州のさ
らに南に位置する麗江市において，いくつかチベット族の村落が点在する。永
勝県大安納西族彝族郷はその1 つであり，今なお同地のチベット族はチベット
語を話していることが筆者の調査によって判明した。しかしながら長期にわた
るナシ語や漢語の影響を受け，現在では漢語への移行が進み，すでにその話者
数は激減している。
本稿の目的は大安郷のチベット語Daan 方言のカムチベット語における方言所
属を明らかにすることである。この議論は主に方言間の比較によって成立する。
地理的環境や民間伝承を考慮して，比較対象として最も近くに分布する迪慶州
の諸方言を射程に収める。具体的に比較する言語現象は2 点あり，1 つはチベッ
ト文語形式と口語形式との対応関係の分析で，もう1 つは語形式の分析である。
これらの作業を通して，Daan 方言の方言所属を考察する。
本稿の具体的な構成は，まずDaan 方言のチベット文語形式と口語形式との対
応関係を明らかにし，それによって得られた特徴と迪慶州のチベット語方言の
特徴を比較する。そしてDaan 方言に見られる特徴的な語形式を迪慶州のチベッ
ト語方言の例と比較し，考察を加える。考察の結果，Daan 方言はSems-kyi-nyila
方言群全般の特徴と近似し，特に破擦音/摩擦音の発展過程において同方言群の
Melung 下位方言群の特徴と一致することが判明した。There are several villages populated by Tibetans in Lijiang Municipal Region,
the southeastern neighbourhood of Diqing Tibetan Autonomous Prefecture,
where the Tibetan language is mainly spoken. The author has found that
the Tibetan inhabitants still use Tibetan in Daan village, Yongsheng County in
Lijiang, but this dialect is close to extinction because of the strong influence of
Naxi and Chinese.
This paper aims to clarify the dialectal position of the Daan dialect of Khams
Tibetan using a comparative method involving both comparison of using a
sound correspondences between spoken forms and Written Tibetan (WrT) in
multiple Tibetan dialects, and also word forms. In consideration of the geographical
situation and the folklore of the Daan Tibetans, the scope of the
dialectal comparison covers the dialects spoken in Diqing Prefecture, which
can be divided into three main groups: Sems-kyi-nyila, nJol and gTorwa. Of
those, the dialects of the Sems-kyi-nyila and nJol groups are compared with the
Daan dialect.
The main matter consists of three parts: sound correspondences between
WrT and the Daan dialect, comparison of the latter with multiple dialects of
Diqing, and comparison of several characteristic word forms. The paper concludes
that the Daan dialect is genetically close to the Sems-kyi-nyila dialect
group, especially to its Melung subgroup, based on the sound development of
the affricate / fricative series.Articledepartmental bulletin pape
Doplor Sleep: Monitoring Hospital Soundscapes for Better Sleep Hygiene
Get PDFGood sleep is conducive to the recovery process of hospital patients - and yet, in many wards, sleep duration and quality can often be suboptimal, in part due to modifiable hospital-related sounds and noises. At the neurological ward of the Reinier de Graaf hospital in Delft, the Netherlands, we developed and evaluated a prototype information exchange system to raise awareness of specific sounds as disturbing patients' sleep. The system both classifies different relevant sound events and tracks sleep quality (using a Fitbit device). This information is then visualized for patients and staff to present the influence of the soundscape on patients' sleep hygiene in a friendly and comprehensive way. We discuss the design process, including a context study and various evaluations of the technology, interface, and created affordances. Our initial findings indicate that visualizing hospital soundscapes may, indeed, support both patients and staff in their efforts towards better sleep hygiene. Design AestheticsInternet of Thing
SQUID measurements on gate tunable magnetic topological insulator thin films in a dilution refrigerator
No full textThickness-Dependent Sign Change of the Magnetoresistance in VTe2 Thin Films
Get PDFTransition metal dichalcogenides of type VX2 (X = S, Se, Te) have recently attracted great interest as it has been predicted that they host ferromagnetism at room temperature. Whether ferromagnetism is indeed present is an open experimental question. An in-depth study of the structural and magnetoelectric properties of VTe2 thin films is presented in this work. The VTe2 thin films were grown through molecular beam epitaxy, which allows for precise control of thicknesses, ranging from several nanometers down to monolayers. The low-temperature magnetoelectric transport studies reveal no sign of intrinsic ferromagnetism. However, a transition from positive to negative magnetoresistance is present upon decreasing film thickness
Revisiting the van der Waals Epitaxy in the Case of (Bi(0.4)Sb(0.6))(2)Te(3) Thin Films on Dissimilar Substrates
Get PDFUltrathin films of the ternary topological insulator (Bi [Formula: see text] Sb [Formula: see text]) [Formula: see text] Te [Formula: see text] are fabricated by molecular beam epitaxy. Although it is generally assumed that the ternary topological insulator tellurides grow by van der Waals epitaxy, our results show that the influence of the substrate is substantial and governs the formation of defects, mosaicity, and twin domains. For this comparative study, InP (111)A, Al [Formula: see text] O [Formula: see text] (001), and SrTiO [Formula: see text] (111) substrates were selected. While the films deposited on lattice-matched InP (111)A show van der Waals epitaxial relations, our results point to a quasi-van der Waals epitaxy for the films grown on substrates with a larger lattice mismatch
Manual Control Adaptation to Variations in Short-Period Natural Frequency and Damping
No full textThis paper presents the results of a human-in-the-loop experiment performed to investigate the effects of variations in aircraft short-period mode characteristics on human operators’ manual control behavior. In the experiment, 15 participants performed a tracking task for a factorial variation in both short-period mode natural frequency (five settings) and damping ratio (three settings). The baseline aircraft dynamics were those of a Cessna Citation aircraft, as used in a number of previous experiments, and the variations in short-period dynamics were chosen to span a range of interest with respect to available handling qualities criteria and Maximum Unnoticed Added Dynamics (MUAD) envelopes. To objectively quantify the induced adaptation of manual control behavior, human operator models were fitted to the collected tracking data. In addition to these control behavior measures also subjective ratings of the noticeability of differences with respect to the baseline aircraft were collected. Overall, the results show consistent adaptation of manual control behavior to variations in both short-period parameters and a worsening of task performance with decreased short-period natural frequency and decreased damping ratio settings. In spite of inconsistencies in the subjective rating data, the overall objective adaptation of manual control dynamics correlates with the subjective noticeability ratings, as well as correspondence of the tested configurations with available MUAD envelopes
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