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51.
In this paper, we address the problem of state observation for sensorless control of switched reluctance motors (SRMs), that is, the regulation of the motor measuring only the voltage and the current of the electrical supply. Instrumental for the construction of the observer is the derivation of algebraic relations, which define regression models, between the unknown rotor flux and the measured quantities. With the knowledge of the flux, it is shown that the mechanical coordinates can be estimated with suitably tailored adaptive nonlinear observers. Replacing the observed states, in a certainty equivalent manner, with a full information stabilizing law completes the sensorless controller design. In contrast with other motors, there is no universally accepted mathematical model to describe the dynamics of SRMs. To widen our target audience, we present the results for four different mathematical models reported in the literature. Simulation results with a precise (finite element) model of the SRM are used to illustrate the performance of the proposed observer and sensorless control. 相似文献
52.
In the present paper, we consider and summarize applications of the continuous wavelet transform to 2C and 3C polarization analysis and filtering, modeling the dispersed and attenuated wave propagation in the time–frequency domain, and estimation of the phase and group velocity and the attenuation from a seismogram. Along with a mathematical overview of each of the presented methods, we show that all these algorithms are logically combined into one software package “Geophysical Wavelet Library” developed by the authors. The novelty of this package is that we incorporate the continuous wavelet transform into the library, where the kernel is the time–frequency polarization and dispersion analysis. This library has a wide range of potential applications in the field of signal analysis and may be particularly suitable in geophysical problems that we illustrate by analyzing synthetic, geomagnetic and real seismic data. 相似文献
53.
Rhys E. A. Goodall Bonan Zhu Judith L. MacManus-Driscoll Alpha A. Lee 《Advanced functional materials》2021,31(52):2104696
High-temperature superconducting cuprates have the potential to be transformative in a wide range of energy applications. In this work, the corpus of historical data about cuprates is analyzed using materials informatics, re-examining how their structures are related to their critical temperatures (Tc). The available data is highly clustered and no single database contains all the features of interest to properly examine trends. To work around these issues a linear calibration approach that allows the utilization of multiple data sources is employed, combining fine resolution data for which the Tc is unknown with coarse resolution data where it is known. The hybrid data set constructed enables the exploration of the trends in Tc with the apical and in-plane copper–oxygen distances. It is shown that large regions of the materials space have yet to be explored. Novel experiments relying on the nano-engineering of the crystal structure may enable the exploration of such new regions. Based on the trends identified it is proposed that single layer Bi-based cuprates are good candidate systems for such experiments. 相似文献
54.
Ping Kwan Johnny Wong Wen Zhang Fabio Bussolotti Xinmao Yin Tun Seng Herng Lei Zhang Yu Li Huang Giovanni Vinai Sridevi Krishnamurthi Danil W. Bukhvalov Yu Jie Zheng Rebekah Chua Alpha T. N'Diaye Simon A. Morton Chao‐Yao Yang Kui‐Hon Ou Yang Piero Torelli Wei Chen Kuan Eng Johnson Goh Jun Ding Minn‐Tsong Lin Geert Brocks Michel P. de Jong Antonio H. Castro Neto Andrew Thye Shen Wee 《Advanced materials (Deerfield Beach, Fla.)》2019,31(23)
Monolayer VSe2, featuring both charge density wave and magnetism phenomena, represents a unique van der Waals magnet in the family of metallic 2D transition‐metal dichalcogenides (2D‐TMDs). Herein, by means of in situ microscopy and spectroscopic techniques, including scanning tunneling microscopy/spectroscopy, synchrotron X‐ray and angle‐resolved photoemission, and X‐ray absorption, direct spectroscopic signatures are established, that identify the metallic 1T‐phase and vanadium 3d1 electronic configuration in monolayer VSe2 grown on graphite by molecular‐beam epitaxy. Element‐specific X‐ray magnetic circular dichroism, complemented with magnetic susceptibility measurements, further reveals monolayer VSe2 as a frustrated magnet, with its spins exhibiting subtle correlations, albeit in the absence of a long‐range magnetic order down to 2 K and up to a 7 T magnetic field. This observation is attributed to the relative stability of the ferromagnetic and antiferromagnetic ground states, arising from its atomic‐scale structural features, such as rotational disorders and edges. The results of this study extend the current understanding of metallic 2D‐TMDs in the search for exotic low‐dimensional quantum phenomena, and stimulate further theoretical and experimental studies on van der Waals monolayer magnets. 相似文献
55.
56.
Rachel Alpha Johnston Hurst 《History of Photography》2016,40(4):413-431
From 1937 to 1939, Lorene Squire was commissioned by The Beaver (the company magazine of the Hudson’s Bay Company) and Canadian Airways to produce photographs of the Canadian North suitable for their publications, focused on her specialisation in wildfowl photography, as well as landscapes, planes, and people. This article focuses on her 1938 commissions, and in particular two photographs of Indigenous women and two self-portraits. When these photographs are considered alongside photographs of white settler women, her correspondence, and her book Wildfowling With A Camera (1938), I argue that they offer insights into gender as a colonial concept (what María Lugones calls the ‘colonial/modern gender system’). I contend that the setting of the ‘North’ as a psychical landscape makes Squire’s contestations possible. Squire’s photographs resist common ways of depicting white and Indigenous women in the 1930s, but they do so in a way that is paradoxical and leaves intact the colonial/modern gender system. In addition to providing biographical information about Squire, this article contributes to theoretical and historical scholarship on the meaning of photographs of Indigenous people in Canada for projects of nation-building and northern economic development, as well as on how the North functions as a reference point for Canadian identity. 相似文献
57.
Three-phase short-circuits of the induction machine yields to high levels of stress in an induction traction drive. To study these operations, the authors propose to model the machine by a multiple cage equivalent circuit. This enables us to take into account the deep bar effect with accuracy. The identification of the equivalent circuit and its validation are carried out experimentally for a 30-kW double-cage induction motor. 相似文献
58.
Alpha Amadou Diallo Hubert Brugère Monique Kérourédan Véronique Dupouy Pierre-Louis Toutain Alain Bousquet-Mélou Eric Oswald Delphine Bibbal 《Water research》2013,47(13):4719-4729
We compared the prevalence of pathogenic and extended-spectrum beta-lactamase (ESBL) – producing Escherichia coli in effluents of a municipal wastewater treatment plant (WWTP) receiving wastewater from a slaughterhouse. A total of 1248 isolates were screened for the presence of virulence genes associated with enterohemorrhagic E. coli (EHEC) (stx1, stx2, and eae) and extraintestinal pathogenic E. coli (ExPEC) (sfa/focDE, kpsMT K1, hlyA, papEF, afa/draBC, clbN, f17A and cnf). The prevalence of atypical enteropathogenic E. coli (EPEC) was 0.7%, 0.2% and 0.5% in city wastewater, slaughterhouse wastewater and in the treated effluent, respectively. One stx1a and stx2b-positive E. coli isolate was detected in city wastewater. The prevalence of ExPEC was significantly higher in city wastewater (8.4%), compared to slaughterhouse wastewater (1.2%). Treatment in the WWTP did not significantly impact the prevalence of ExPEC in the outlet effluent (5.0%) compared to city wastewater. Moreover, the most potentially pathogenic ExPEC were isolated from city wastewater and from the treated effluent. ESBL-producing E. coli was also mainly detected in city wastewater (1.7%), compared to slaughterhouse wastewater (0.2%), and treated effluent (0.2%). One ESBL-producing E. coli, isolated from city wastewater, was eae-β1 positive. These results showed that pathogenic and/or ESBL-producing E. coli were mainly detected in human wastewater, and at a lesser extend in animal wastewater. Treatment failed to eliminate these strains which were discharged into the river, and then these strains could be transmitted to animals and humans via the environment. 相似文献
59.
Model-based data engineering for Web services 总被引:1,自引:0,他引:1
Although XML offers heterogeneous IT systems a new level of interoperability, it doesn't ensure that the various systems correctly interpret the data they receive. To address this, data engineering supports clear definitions for exchanged data elements. With model-based data engineering, organizations use a common reference model, which offers further clarity and performance improvements. Organizations can use the resulting data to configure mediation services, translating dialects of new or legacy services into a common language for use in a service-oriented architecture. 相似文献
60.
K Ishikawa K Fransen K Ariyoshi JN Nkengasong W Janssens L Heyndrickx H Whittle MO Diallo PD Ghys IM Coulibaly AE Greenberg J Piedade W Canas-Ferreira G van der Groen 《Canadian Metallurgical Quarterly》1998,12(12):1419-1425
OBJECTIVE: To improve the detection rate of HIV-2 proviral DNA in primary uncultured peripheral blood mononuclear cells (PBMC) of HIV-2-seroreactive and HIV-1-HIV-2 dually seroreactive individuals. MATERIALS AND METHODS: Two newly designed HIV-2 PCR primer pairs in the long terminal repeat (LTR) gag and gag-pol regions and a previously described env and LTR HIV-2 PCR primer pairs were tested on samples from 66 confirmed HIV-2-seropositive individuals (The Gambia, 40; C?te d'Ivoire, 17; Guinea-Bissau, nine), 209 dually seroreactive individuals (The Gambia, 82; C?te d'Ivoire, 127), 24 genetically characterized isolated HIV-1 strains (group M subtypes A-H and group O), one simian immunodeficiency virus (SIV) strain cpz, 10 HIV-2 isolates (subtype A, B and unidentified), two SIVsm isolates, and 10 seronegative samples. RESULTS: All HIV-2 primers evaluated showed 100% specificity since there was no amplification observed with 24 HIV-1, one SIVcpz and 10 seronegative samples. One single copy of the HIV-2 genome could be detected with all outer primer pairs as well as all inner primer pairs on one PCR round used. Sensitivity of primers (at least one of the four primer pairs was positive) to HIV-2-seropositive samples was 100% (all nine) in Guinea-Bissau, 71% (12/17) in C?te d'Ivoire, 100% (all 20) in Gambian AIDS patients, and 85% (17/20) in Gambian pregnant women. Doubling the PBMC of dually seroreactive individuals from 7.5 x 10(4) to 1.5 x 10(5) in the PCR revealed the presence of both HIV-1 and 2 proviral DNA in 72% (92/127) in C?te d'Ivoire and 72% (59/82) in The Gambia. By doubling the number of PBMC, HIV-2 detection in dually seroreactive individuals by PCR was increased from 65 to 77% in C?te d'Ivoire and from 67 to 83% in The Gambia. CONCLUSIONS: The use of 1.5 x 10(5) primary uncultured PBMC and the newly designed HIV-2 primer pairs allowed us to document the highest percentage (72%) ever reported of HIV-1-HIV-2 dual infections amongst HIV-1-HIV-2 dually seroreactive individuals in C?te d'Ivoire and The Gambia. Improved detection of HIV-2 proviral DNA, rather than exposure to both viruses, infection with only one virus, or infection with a unique third virus containing epitopes common to both HIV-1 and HIV-2, contributes to a more accurate monitoring of the prevalence of HIV-1-HIV-2 dual infections. 相似文献