1,721,317 research outputs found
Measurement of antenna radiation efficiency using improved Wheeler cap algorithm
Full text linkRadiation efficiency measurement can inform the wireless design process by determining the total fraction of accepted power radiated by an antenna. The popular Wheeler cap method can be used to quickly and accurately determine the radiation efficiency of small antennas. However, due to cavity resonant modes and the use of a simplistic equivalent circuit model, the conventional Wheeler cap method yields poor results for electrically larger structures. When efficiency estimates can be obtained, they are often valid only over a narrow frequency band. Higher-order equivalent circuit models may be employed in a modified Wheeler cap algorithm to generate improved radiation efficiency measurements. Guided by advances in broadband modeling of antennas, we demonstrate a new Wheeler cap technique that makes use of parallel admittance subcircuits. We then illustrate the use of this technique to provide improved efficiency estimates at the operating frequencies of electrically larger structures.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2018-05-01The student, Elias Wilken-Resman, accepted the attached license on 2016-04-29 at 08:28.The student, Elias Wilken-Resman, submitted this Thesis for approval on 2016-04-29 at 08:29.This Thesis was approved for publication on 2016-04-29 at 09:09.DSpace SAF Submission Ingestion Package generated from Vireo submission #9575 on 2016-07-07 at 14:18:11Made available in DSpace on 2016-07-07T21:18:12Z (GMT). No. of bitstreams: 2
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Previous issue date: 2016-04-29Embargo set by: Seth Robbins for item 93330
Lift date: 2018-07-07T21:18:16Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemLimited Restriction Lifted for Item 93330 on 2018-07-08T09:15:20Z
Fractal analysis of hyperbolic saddles with applications
No full textIn this paper we express the Minkowski dimension of spiral trajectories near hyperbolic saddles and semi-hyperbolic singularities in terms of the dimension of intersections of such spirals with transversals near these singularities. We apply these results to hyperbolic saddle-loops and hyperbolic 2-cycles to obtain, using Minkowski dimension of a single spiral trajectory, some known upper bounds on the cyclicity of such limit periodic sets.This research was supported by Croatian Science Foundation (HRZZ) Grant PZS-2019-02-3055 from Research Cooperability program funded by the European Social Fund. The first two authors are supported by the Special Research Fund (BOF number:
BOF21BL01) of Hasselt University. The third author is supported by Croatian Science Foundation (HRZZ) Grant UIP-2017-05- 1020. The first and the third author are also supported by the bilateral Hubert-Curien Cogito grant 2023-24
Energy storage in reconfigurable antennas
Full text linkDespite their potential performance advantages, reconfigurable antennas have seen limited use in mobile devices. These complicated antennas can be challenging to design, especially when the structure is electrically small or mid-sized. With small elements, finite groundplanes, and switches or reactive tuning mechanisms, performance of these reconfigurable antennas is often strongly influenced by energy storage effects.
Many antenna types achieve their performance characteristics through a careful balance of electric and magnetic energy storage. The distinct effects of magnetic and electric energy storage convey important information about an antenna's characteristics. However, these quantities are not individually available from typical antenna measurements like impedance, or from conventional computational techniques such as the electric field integral equation. This work describes a parallel-computing optimized method of moments code that can be used to obtain the classic method of moments impedance matrix Z = R+jX as well as the Vandenbosch energy storage matrices Xe and Xm. The energy storage matrices can be used to provide a more complete picture of how an antenna's physical structure results in radiation and electric and magnetic energy storage.
Energy storage analysis techniques are applied to study familiar antennas, such as the dipole and monopole, as well as to investigate potential modifications to finite groundplanes. These techniques are then extended to develop design guidelines for reconfigurable structures, including a frequency-reconfigurable inverted-F antenna. The use of energy storage modes is found to simplify the task of designing effective electrically small and mid-sized reconfigurable antennas.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2022-12-01The student, Elias Wilken-Resman, accepted the attached license on 2020-08-11 at 21:52.The student, Elias Wilken-Resman, submitted this Dissertation for approval on 2020-08-12 at 17:47.This Dissertation was approved for publication on 2020-08-13 at 11:54.DSpace SAF Submission Ingestion Package generated from Vireo submission #15769 on 2021-03-04 at 16:29:54Made available in DSpace on 2021-03-05T21:45:04Z (GMT). No. of bitstreams: 2
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Previous issue date: 2020-08-13Embargo set by: Seth Robbins for item 117256
Lift date: 2023-03-05T21:45:47Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 117256
Lift date: 2023-03-05T21:47:41Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemAuthor requested closed access (OA after 2yrs) in Vireo ETD systemLimite
Influence of content and grain size distribution of recycled aggregate on concrete properties
Full text linkEnvironmental concerns are all around us. The influence of an increasing awareness and care for the environment is present also in construction sector, in the areas of material selection, construction technology and construction waste management. When using concrete we strive to avoid negative impacts on the environment. Legislation in the area of construction, environment and waste follows the decisions of authorities relatively fast. This year the government of the Republic of Slovenia adopted the Programme of waste management and waste prevention in the Republic of Slovenia in accordance\ud
with the legislation.\ud
The main aim of this diploma thesis is the assessment of the influence of content and grain size distribution of recycled aggregate on concrete properties. We tried to find out whether it is possible to exchange natural aggregate with a recycled one while maintaining the basic properties of fresh and hardened concrete.\ud
When preparing the concrete mixtures two types of aggregate were used. Natural aggregate was delivered from France within project "COST Action TU1404", while recycled aggregate from crushed waste concrete was acquired from a separation plant near Ljubljana. The preparation of samples and testing of recycled aggregate was carried out at the laboratory of UL FGG. With tests we first determined the physical properties of the recycled aggregate (grain size distribution, fines content, particle shape, density, water absorption, moisture content, presence of humus particles). On the basis of obtained results the suitability of the aggregate for use in concrete mixtures was assessed. Three mixtures of fresh concrete were prepared with the same amount of cement and the same water-to-cement ratio. The first mixture was prepared with fine natural aggregate and coarse recycled aggregate, the second one with recycled fine aggregate and natural coarse aggregate, while in the third mixture only recicled aggregate was used. The properties of fresh concrete (consistency, density, air content) and hardened concrete (compressive strength, splitting tensile strength, depth of water penetration under pressure) were determined according to SIST EN standard methods. On the basis of obtained results the tested concretes were classified into compressive strength classes, and analysis of the results was carried out. At the end, recommendations were given for the use of such concretes in the construction sector
Methodology for design and planning of smart factories based on digital models
No full textKoncepti pametnih tovarn v industriji postajajo vedno bolj pomembni in nujni, če podjetja želijo ohraniti konkurenčnost na globalnih trgih. Zaradi aktualnosti, pomembnosti, predvsem pa številnih nejasnosti v konceptih, pristopih in rešitvah v okviru pametnih tovarn, so raziskave na tem področju nujne in v zadnjih letih vse bolj številne tako v svetu, kot tudi v Sloveniji. Veliko število raziskav dokazuje, da to področje še ni dovolj raziskano. Za načrtovanje pametnih tovarn se razvijajo nove metodologije z vključenimi referenčnimi arhitekturnimi modeli in pristopi za definiranje potrebnih parametrov za načrtovanje digitalnih dvojčkov, s čimer postaja načrtovanje enostavnejše, jasnejše in hitrejše. Večina obstoječih metodologij in arhitekturnih modelov je zelo abstraktnih in zato za industrijsko uporabo manj primernih. Na podlagi predstavljenega problema smo se odločili razviti metodologijo za načrtovanje pametne tovarne, ki ima tri korake: (i) delavnice v podjetju, ki želi vpeljati koncept pametne tovarne, (ii) strukturni referenčni arhitekturni model ter (iii) univerzalni pristop za določevanje parametrov za razvoj digitalnih dvojčkov, ne glede na velikost in tip proizvodnje. Namen metodologije je predstaviti postopek načrtovanja pametne tovarne po korakih, od začetne ideje o pametni tovarni, do končne realizacije v realnem okolju. V doktorskem delu smo s študijo primera prikazali uporabo in postopek načrtovanja pametne tovarne po predstavljeni metodologiji. Osredotočili smo se predvsem na razvoj in uporabo arhitekturnega modela ter na definiranje podatkov, potrebnih za načrtovanje digitalnih dvojčkov. Za slednji korak smo prikazali celotni postopek načrtovanja digitalnega dvojčka z več fazami, od definiranja proizvodnega sistema, do končne uporabe digitalnih dvojčkov.The concepts of smart factories in industry are becoming increasingly important and necessary to remain competitive in global markets. Due to the timeliness, importance and especially the many ambiguities in the concepts, approaches and solutions in the field of smart factories, research in this area is necessary and has increased in number in recent years, both globally and in Slovenia. A large number of research papers prove that this area is not yet sufficiently researched. New methods for designing smart factories are being developed, including reference architecture models and approaches for defining the necessary parameters for the development of the digital twin, which make planning easier, clearer and faster. Most existing methods and architecture models are very abstract and therefore less suitable for industrial use. Based on the presented problem, we decided to develop a methodology for the design of a smart factory, which includes three steps: (i) workshops in the company that wants to introduce the smart factory concept, (ii) two-dimensional reference architecture model, and (iii) universal approach to determine the parameters for the development of digital twins, regardless of the size and type of production. The aim of the methodology is to present the process of planning a smart factory step by step, from the initial idea of a smart factory to its final realization in a real environment. In the dissertation, we used a case study to present the deployment and planning process of a smart factory according to the presented methodology. We focused mainly on the development and deployment of the architectural model and on the definition of the data needed for the development of digital twins. For the last step, we presented the whole design process for digital twins with several sub-steps, from the definition of the manufacturing system to the final use of the digital twins
Sexuality of adolescents with mild intellectual disability
Full text linkThe dissertation is about sexuality of adolescents with mild intellectual disability. Theoretical part focuses on sexuality of adolescents and who are adolescents with mild intellectual disability, and also the topics that involve their sexuality, such as sexual behavior, sexual information, social status, sexual disorders and integration in education. Empirical part describes the research and the results of it. Research instrument is a questionnaire, which was answered by pupils of eighth and ninth grade (aged from 13 to 16) of special adjusted classes on four special schools in Gorenjska region. Questionnaire had questions divided in three parts: information pupils have about sexuality, personal perspective on sexuality and sexual experience. Answers on each one of three parts answer on one of three research questions. We found out, that pupils with mild intellectual disability have correct information about contraception and sexual abuse, but do not know much about human anatomy (about their bodies) and sexual transmitted diseases. For pupils, sexuality in similar procentage has both, social (social influence) and individual (their own beliefs and wishes) meaning. According to answers, adolescents with mild intellectual disability have minor sexual experience than adolescents with average inteligence
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