110 research outputs found
Study of growing incongruent antiferromagnetic single crystals and characterization
No full textAntiferromagnets are gaining increased attention as potential spintronic materials with faster switching rates compared to conventional ferromagnets. Recently reported studies have demonstrated partial switching of the Néel vector of antiferromagnetic CuMnAs and Mn2Au with current-induced spin-orbit torques. More intermetallic antiferromagnets share the structure types of CuMnAs and Mn2Au, or at least contain degenerated in-plane magnetic configurations, are proposed as candidates for current-induced magnetic switching. Single crystals of such materials are needed to study the orientation dependence of their magnetic dynamics, but the growth of single crystals of intermetallics is challenging, especially for incongruent candidates that cannot be obtained by conventional solid-state synthesis. Here, multiple synthesis methods for single crystals of the metallic antiferromagnets Fe2As, FeSn, and Cr2Al were investigated.
The chemical vapor transport (CVT) has been used to assemble large crystalline grains below their melting/decomposition temperatures. In this thesis, the thermodynamics of these CVT reactions are investigated and presented alongside experimental efforts for single crystals of Fe2As and FeSn. Reasonably reliable predictions and analysis can be attained, but numerous approximations must be main due to unknown entropy and enthalpy for many of the phases involved in a given CVT reaction. Compared to the previously reported models of the intermetallic CVT systems, the proposed reactions provide a more comprehensive means to consider the effective parameters (including the transport agents, the possible intermetallic phases to deposit, and the partial pressures of each individual transport species) for predicting the outcomes of a CVT system.
The flux method was used to grow single crystals of Cr2Al, with crystallinity and purity confirmed by X-ray diffraction. The neutron diffraction of a Cr2Al powder sample revealed the magnetic ordering of Cr2Al. The Rietveld refinement, together with thermal analysis and resistivity, indicates a likely in-plane magnetic ordering instead of a canted angle to the c-axis as published in a previous study. The magnetometry measurements carried out on an aligned crystal sample provide the first high-temperature susceptibility confirmation of the Néel temperature in Cr2Al. According to magnetometry, resistivity, and differential scanning calorimetry measurements, the Néel transition is observed at 360±2 °C. This thesis reports the first experimental characterization of a single crystal of an antiferromagnetic material with the MoSi2 structure type. It provides detailed experimental supporting information that enables further studies of magnetic dynamics of Cr2Al closely-related antiferromagnetic spintronic candidates.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2023-05-01The student, Chengxi Zhao, accepted the attached license on 2021-04-18 at 20:34.The student, Chengxi Zhao, submitted this Dissertation for approval on 2021-04-18 at 20:43.This Dissertation was approved for publication on 2021-04-21 at 16:23.DSpace SAF Submission Ingestion Package generated from Vireo submission #16395 on 2021-09-16 at 17:03:38Made available in DSpace on 2021-09-17T02:34:34Z (GMT). No. of bitstreams: 3
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Previous issue date: 2021-04-21Embargo set by: Seth Robbins for item 118533
Lift date: 2023-09-17T02:34:57Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Onl
A Time-Series Analysis of the Shanghai and New York Stock Price Indices
No full textA time series analysis of the Shanghai and New York Stock Exchange composite price indices is provided to compare the weekly rates of return and volatilities of these two markets and to study their co-movement in 1992-2002. The rate of return and volatility of the Shanghai market were higher. The rates of returns in the two markets were approximately serially uncorrelated and mutually uncorrelated. Volatility, as measured by the absolute change in the rate of return, has positive serially correlations in both markets as expected, but the autoregressions are temporarily unstable. Most surprisingly the volatility measures of the two markets are significantly negatively correlated. Volatility in each market was found to Granger cause volatility in the other market negatively. This spurious correlation is explained by the negative correlations of macroeconomic fundamentals in the United States and China as indicated by a negative correlation between the rates of change in their GDP while their capital markets are not integrated. The analysis has implications for the use of autoregressions and Granger causality tests, and the interpretation of spurious correlation.Time series analysis; Rate of return; Volatility; Autogressions; Granger causality; Spurious correlation; Shanghai stock price; New York stock price
Rethinking Algerian Visibility and Invisibility in Ali au Pays des Merveilles
No full textThis article examines Djouhra Abouda and Alain Bonnamy’s experimental documentary Ali au pays des merveilles (1975) and discusses how the filmmakers expose Algerian workers’ living conditions in the 1970s France, a promised land where racism and exclusion persist. This study analyses the visibility and invisibility of the Algerian labour by first discussing the exclusion of Algerian migrants on the basis of their racial identity and their social status, in light of thinking related to French republican identification. The author then examines the interrelations between the Algerian labour and the commodities produced by their labour, as well as the glamorous spectacle associated with the commodities. Finally, the article reflects on the reflexive archaeology of the image that questions the power and limits of archives, interrogating the entanglements of French colonial history in Algeria. The article argues that Abouda and Bonnamy’s stylistic devices are in line with those of the Third Cinema, providing an alternative that allows post-colonial sensibilities to challenge the official discourse and the self-claiming “universal” but indeed Eurocentric aesthetics
Deep Learning in Maritime Autonomous Surface Ships: Current Development and Challenges
No full textAutonomous surface ships have become increasingly interesting for commercial maritime sectors. Before deep learning (DL) was proposed, surface ship autonomy was mostly model-based. The development of artificial intelligence (AI) has prompted new challenges in the maritime industry. A detailed literature study and examination of DL applications in autonomous surface ships are still missing. Thus, this article reviews the current progress and applications of DL in the field of ship autonomy. The history of different DL methods and their application in autonomous surface ships is briefly outlined. Then, the previously published works studying DL methods in ship autonomy have been categorized into four groups, i.e., control systems, ship navigation, monitoring system, and transportation and logistics. The state-of-the-art of this review paper majorly lies in presenting the existing limitations and innovations of different applications. Subsequently, the current issues and challenges for DL application in autonomous surface ships are discussed. In addition, we have proposed a comparative study of traditional and DL algorithms in ship autonomy and also provided the future research scope as well.Transport Engineering and Logistic
X-ray diffraction second derivative spectrum of Tibetan medicine based on the spline interpolation method
No full textPositioning Technology Without Ground Control Points for Spaceborne Synthetic Aperture Radar Images Using Rational Polynomial Coefficient Model Considering Atmospheric Delay
No full textThis study addresses the issue of atmospheric delay correction for the rational polynomial coefficient (RPC) model associated with spaceborne synthetic aperture radar (SAR) imagery under conditions lacking ephemeris data, proposing a novel approach to enhance the geometric positioning accuracy of RPC models. A satellite position inversion method based on the vector-autonomous intersection technique was developed, incorporating ionospheric delay and neutral atmospheric delay models to derive atmospheric delay errors. Additionally, an RPC model reconstruction approach, which integrates atmospheric correction, is proposed. Validation experiments using GF-3 satellite imagery demonstrated that the atmospheric delay values obtained by this method differed by only 0.0001 m from those derived using the traditional ephemeris-based approach, a negligible difference. The method also exhibited high robustness in long-strip imagery. The reconstructed RPC parameters improved image-space accuracy by 18–44% and object-space accuracy by 19–32%. The results indicate that this approach can fully replace traditional ephemeris-based methods for atmospheric delay extraction under ephemeris-free conditions, significantly enhancing the geometric positioning accuracy of SAR imagery RPC models, with substantial application value and development potential
The Effects of Short-term Meditation on the Creativity of Novice Designers: A Pilot Design Task Study using TTCT-Figural Assessment
No full textCreativity is long regarded as one of the fundamental traits that indicates design capability. The concept of creativity encompasses the capacity to produce innovative and novel concepts or ideas, to devise or articulate imagination and intellect, and to stimulate the potential of imagination and ingenuity embodying their capacity to conceive, craft, and develop innovative ideas for products. Previous studies have revealed the connection and functionality between meditation and creativity. However, general creativity measurements, which studies to date have mainly focused on, might not be able to demonstrate the performance of designers in a creative process adequately.Therefore, this study applied a design task-based evaluation with traditional TTCT assessment, which might be more suitable to describe the creative performance of novice designers. The study aims to explore: (1) the relationship between short-term meditation and creativity; (2) the effects of short-term meditation on the design qualities in design tasks of novice designers.42 first-year design students were recruited and were divided into meditation group (n=24) and control group (n=18). Participants conducted a demographic survey and the Torrance Tests of Creative Thinking (TTCT, in its figural variant) firstly. The meditation group was then given a 110-minute audio tape-based meditation intervention, and the control group was given a 110-minute audio tape intervention, which is a recording of scientific articles. Both interventions were performed twice a week on the weekends. After that, TTCT was given to the participants again. Then each participant received an interview on the changes in mood state and creativity. After the TTCT on the second day, the participants completed the Design with Morphological Table Task (DwMT) to assess their design qualities in a product design task. Through data analysis, TTCT results indicate that short-term meditation can significantly improve the creativity of novice designers and the meditation group outperformed the control group significantly in fluency and elaboration. DwMT results show that the meditation group significantly provided better design qualities than the control group
Database Design and Development of 3D Cadastral Registration based on LADM
No full textIn this paper, the database design and development of a prototype 3D cadastral registration will be presented. The key aspects of this prototype are the model is based on Land Administration Domain Model (LADM). The LADM provides a conceptual description for land administration system, including a 3D cadastral registration. LADM defines 3D parcel as a spatial unit against which (one or more) unique and homogeneous rights (e.g. ownership right or land use right), responsibilities or restrictions are associated to the whole entity based on ISO 19152. Spatial units have two specializations: legal spaces buildings and legal spaces networks. Here, we only focus on the 3D space of spatial unit based on strata objects representation. Other spatial units are out of the scope. In case of strata objects representation, it has parcel, accessory unit, common property, limited common property and land parcel. The prototype development begins with the data modelling based on LADM (i.e. selecting relevant model classes and extending the model with attributes and classes where needed). The LADM supports various options for representing spatial units; e.g. a 2D parcel or a 3D volume. 2D parcel is recognized, however, how to create and maintain 3D valid parcels is still a challenge in practice. There have been several research and development activities in the past on the LADM. However, these investigations mainly remain at the conceptual level and yet to be implemented in the real context. Therefore, the motivation of this paper is to discuss the practical pathway towards realising an LADM-based 3D cadastral registration in alignment with jurisdictional settings in Malaysia. This paper extends the model in LADM to create a prototype and confirm its feasibility in implementation. It focuses on data migration from existing database (i.e. .xml format) to open source database (i.e. Postgres) based on LADM standard. The visualization and application for the implementation are using open source platform (i.e. QGIS). This research not only important for Malaysia, but also useful for many other countries, that also have the strata title system. Further investigation is on the full potential of LADM for the Malaysia Information Infrastructure (i.e. SDI) development
What is the role of weather, built-environment and accessibility geographical characteristics in influencing travelers’ experience?
No full textWe examine the effect of weather, accessibility and built-environment characteristics on overall travel experience as well as the experience with the latest trips. These are factors that are often disregarded in the travel satisfaction literature even though they are believed to largely influence the first mile of the door-to-door trip. This study fills a research gap in investigating all these factors by using, amongst other, a relatively large travel satisfaction survey from years 2009 to 2015 and by focusing on urban and peri-urban geographical contexts, the city and county of Stockholm (Sweden), respectively. The ordered logit model results show that county dwellers living close to a metro station and in well linked-to-all areas report higher overall travel satisfaction evaluations. In addition, precipitation and ground covered with snow have a negative influence on travel satisfaction. Our findings indicate that built-environment characteristics exert a rather weak influence on the travel experience, especially in the peri-urban context. However, some aspects such as living in areas with medium densities, low income and with high safety perceptions around public transport stations are associated with higher satisfaction levels. In turn, areas with single land uses are found to have lower travel satisfactions. These results are important for public transport planners and designers in devising measures to prevent and mitigate the negative outcome of some weather conditions and to conceive better designed transit oriented developments.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Transport and Plannin
Single-Chip Isolated DC-DC Converter with Self-Tuned Maximum Power Transfer Frequency
No full textabstract: There is an increasing demand for fully integrated point-of-load (POL) isolated DC-DC converters that can provide an isolation barrier between the primary and the secondary side, while delivering a low ripple, low noise regulated voltage at their isolated sides to a high dynamic range, sensitive mixed signal devices, such as sensors, current-shunt-monitors and ADCs. For these applications, smaller system size and integration level is important because the whole system may need to fit to limited space. Traditional methods for providing isolated power are discrete solutions using bulky transformers. Miniaturization of isolated POL regulators is becoming highly desirable for low power applications.
A fully integrated, low noise isolated point-of-load DC-DC converter for supply regulation of high dynamic range analog and mixed signal sensor signal-chains is presented. The isolated DC-DC converter utilizes an integrated planar air-core micro-transformer as a coupled resonator and isolation barrier and enables direct connection of low-voltage mixed signal circuits to higher supply rails. The air core transformer is driven at its primary resonant frequency of 100 MHz to achieve maximum power transfer. A mixed-signal perturb-and-observe based frequency search algorithm is developed to improve maximum power transfer efficiency by 60% across the isolation barrier compared to fixed driving frequency method. The isolated converter’s output ripple is reduced by utilizing spread spectrum clocking in the driver. An isolated PMOS LDO in the secondary side is used to suppress switching noise and ripple by 21dB. Conducted and radiated EMI distribution on the IC is measured by a set of integrated ring oscillator based noise sensors with -68dBm noise sensitivity. The proposed isolated converter achieves highest level of integration with respect to earlier reported integrated isolated converters, while providing 50V on-chip junction isolation without the need for extra silicon post-processing steps.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201
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