Identifying objectives for a learning space management system with value-focused thinking.

A classroom with a blackboard and some rows of desks is obsolete in special education. Depending on the needs, some students may need more tactile and inspiring surroundings with various pedagogical accessories while others benefit from a simplified environment without unnecessary stimuli. This understanding is applied to a new Finnish special education school building with open and adaptable learning spaces. We have joined the initiative creation process by developing software support for these new spaces in the form of a learning space management system. Participatory design and value-focused thinking were implemented to elicit the actual values of all the stakeholders involved and transform them into software implementation objectives. This paper reports interesting insights about the elicitation process of the objectives

Improving the design of industrial microwave processing systems through prediction of the dielectric properties of complex multi-layered materials

Rigorous design of industrial microwave processing systems requires in-depth knowledge of the dielectric properties of the materials to be processed. These values are not easy to measure, particularly when a material is multi-layered containing multiple phases, when one phase has a much higher loss than the other and the application is based on selective heating. This paper demonstrates the ability of the Clausius-Mossotti (CM) model to predict the dielectric constant of multi-layered materials. Furthermore, mixing rules and graphical extrapolation techniques were used to further evidence our conclusions and to estimate the loss factor. The material used for this study was vermiculite, a layered alumina-silicate mineral containing up to 10 % of an interlayer hydrated phase. It was measured at different bulk densities at two distinct microwave frequencies, namely 934 and 2143 MHz. The CM model, based on the ionic polarisability of the bulk material, gives only a prediction of the dielectric constant for experimental data with a deviation of less than 5 % at microwave frequencies. The complex refractive index model (CRIM), Landau, Lifshitz and Loyenga (LLL), Goldschmidt, Böttcher and Bruggeman-Hanai model equations are then shown to give a strong estimation of both dielectric constant and loss factor of the solid material compared to that of the measured powder with a deviation of less than 1 %. Results obtained from this work provide a basis for the design of further electromagnetic processing systems for multi-layered materials consisting of both high loss and low loss components

Dielectric characterization of powdery substances using an indirectly coupled open-ended coaxial cavity resonator

Abstract The main objective of this thesis was to research and develop a sensitive characterization method for dielectric powdery substances which could be utilized in various industrial and research fields. With modern electromagnetic simulation tools and the presented experimental measurements, the characterization of dielectric powders using an indirectly coupled open-ended coaxial cavity resonator operating in TEM mode at 4.5 GHz was found to have potential. The modelling and the experimental measurement results of commonly used dielectric powders revealed that, from the nine classical mixing rules, it was possible to derive reliable inclusion permittivity values when using the properties of the perturbed resonator and the Bruggeman symmetric and the Looyenga mixing theories. In addition, the determination accuracy of the inclusion permittivity was found to be greatly improved with the correction factor included into the previously presented permittivity equation of the quarter wave coaxial resonator. Determination of the dielectric losses was found to be reliable when using the differences between the perturbed and unperturbed resonator and the general mixing model equation. The sensitivity of the characterization method was researched with both humidity exposed and surfactant treated modified SiO2, Al2O3 and ZrO2 powders. Experimental results showed that the effect of adsorbed water on the particles was most pronounced when measuring the dielectric losses of the inclusions. Furthermore, a clear correlation with the theory of the general mixing model was found. Thus, in addition to the changed dielectric properties between dry and humidity exposed powders, it was also possible to determine the moisture content with reasonable accuracy. This correlated well with the traditional, mass based, determination. Stearic acid coating of the particles induced only a small change in inclusion permittivity but a notable change in dielectric losses. Unlike the cases with the larger particle sized SiO2 and Al2O3, the dielectric loss of ZrO2 inclusions, with stearic acid coating, was decreased significantly from 6.2 × 10-3 to 3.8 × 10-3. When characterizing magnesium and calcium titanate composite powders, with CaTiO3 molar ratios of 0.0, 0.02, 0.05 and 0.1, the method was found to have good sensitivity and accuracy. Additions of CaTiO3 exhibited a clear increase in net inclusion permittivities from 13.4 up to 14.9 and in dielectric loss tangents from 7.1 × 10-3 up to 8.5 × 10-3. In addition, a good correlation was found in the theoretical determination of the CaTiO3 molar ratios using the resonator measurement results and the general mixing model. The characterization method was proved to be capable of measuring the dielectric properties and detecting even very slight changes in the powders. Thus, the method could be utilized in various types of powdery material characterization, for example, in the analysis and quality control of different composite powders.Tiivistelmä Väitöstyön päätavoitteena oli tutkia ja kehittää herkkä jauhemaisten eristemateriaalien karakterisointimenetelmä, jota voitaisiin hyödyntää usealla teollisuuden ja tutkimuksen alueella. Hyödyntäen nykyaikaisia sähkömagnetiikan simulointityökaluja sekä kokeellisia mittauksia, havaittiin TEM -moodissa 4,5 GHz taajuudella toimivan avoimen epäsuorasti kytketyn koaksiaalionteloresonaattorin soveltuvan karakterisoimaan eristejauheita. Sähkömagneettinenmallinnus yhdessä yleisesti käytettyjen eristejauheiden kokeellisten mittausten kanssa osoitti, että partikkelin permittiivisyysarvot voitiin johtaa luotettavasti. Tällöin käytettiin näytemateriaalilla täytetyn resonaattorin ominaisuuksia, sekä yhdeksästä vertaillusta klassisesta sekoitusyhtälöstä Bruggeman symmetristä ja Looyengan sekoitusteorioita. Tämän lisäksi tarkkuutta voitiin parantaa huomattavasti lisäämällä korjauskerroin aikaisemmin julkaistuun neljännesaalto-koaksiaaliresonaattorin permittiivisyyden määrittävään yhtälöön. Eristehäviöiden määrittäminen havaittiin luotettavaksi, kun käytettiin mitattavalla materiaalilla muutetun ja tyhjän resonaattorin ominaisuuksien eroja, sekä general mixing model -yhtälöä. Karakterisointimenetelmän herkkyys tutkittiin ilmankosteudelle altistetuilla, sekä pintakäsittelyllä muutetuilla SiO2, Al2O3 ja ZrO2 -jauheilla. Mittaustulokset osoittivat, että partikkelin pinnalle adsorpoituneen veden vaikutus oli kaikkein korostunein, kun mitattiin partikkelien eristehäviöitä. Tämän lisäksi havaittiin myös selkeä korrelaatio general mixing model -teorian kanssa. Näin ollen muuttuneiden eristeominaisuuksien määritysten lisäksi voitiin määrittää jauheen kosteussisältö riittävällä tarkkuudella. Tulokset korreloivat hyvin perinteisen massaeroihin perustuvan määrittämisen kanssa. Partikkelien pinnoitus steariinihapolla aiheutti ainoastaan pienen muutoksen permittiivisyyteen mutta merkittävän muutoksen eristehäviöihin. Toisin kuin suuremman partikkelikoon SiO2:lla ja Al2O3:lla ZrO2 -partikkelin eristehäviö laski huomattavasti steariinihappopinnoituksen jälkeen, 6,2 × 10-3:sta 3,8 × 10-3:een. Karakterisoitaessa magnesium- ja kalsiumtitanaattikomposiittijauheita käyttämällä CaTiO3 -moolisuhteita 0,0, 0,02, 0,05 ja 0,1 menetelmällä havaittiin olevan hyvä herkkyys ja tarkkuus mitattavan materiaalin muutoksille. CaTiO3 -määrän lisäykset aiheuttivat selkeän nousun partikkelien kokonaispermittiivisyyksissä, joka kasvoi 13,4:sta 14,9:ään, sekä häviötangentissa, joka kasvoi 7,1 × 10-3:sta aina 8,5 × 10-3:een. Tämän lisäksi resonaattorin mitattuihin ominaisuuksiin sekä general mixing model -yhtälöön perustuvan teoreettisen määrityksen havaittin korreloivan hyvin CaTiO3 -moolisuhteisiin. Karakterisointimenetelmän osoitettiin soveltuvan eristeominaisuuksien mittaukseen sekä havaitsemaan jopa erittäin pienet muutokset jauheiden eristeominaisuuksissa. Menetelmää voitaisiin hyödyntää usean tyyppisissä jauhemateriaalien ominaisuuksien määrityksissä, kuten esimerkiksi erilaisten komposiittijauheiden analysoinnissa ja laaduntarkkailussa

Sinusoidally modulated reactance surface loaded leaky coaxial cable

Abstract In this paper, the theory of sinusoidally modulated reactance surface (SMRS) is employed to enhance the radiation efficiency of leaky coaxial cable (LCX). The LCX’s slots are loaded by a periodically etched dielectric stripe, partially converting the bounded monofilar mode into a radiating mode. The simulated results are discussed and it is shown that the coupling loss can be significantly decreased by SMRS loading, which increases the indoor coverage capability of the LCX

Periodically slotted coupled mode leaky coaxial cable with enhanced radiation performance

Abstract A novel technique to periodically modulate the aperture of a coupled mode leaky coaxial cable (LCX) is presented in this communication. The surface wave (monofilar mode) over the cable is modulated by periodically slotted aperture, converting it to a leaky wave. This leaky wave due to periodic modulation complements the leaked bifilar mode, thus enhancing the radiation efficiency of the LCX. The numerical results obtained through CST simulation are presented to prove the coexistence of a complex surface wave and a leaky wave over the surface of periodically modulated cable. As a proof of concept, a periodically slotted LCX operating at 4.5 GHz is designed and fabricated. Parametric studies are performed to observe the influence of the key parameters on the radiation performance. The measured results reasonably agree with the simulations

Leaky coaxial cable with enhanced radiation performance for indoor communication systems

Abstract In this paper, a novel method to selectively enhance the radiation performance of coupled mode leaky coaxial cable (LCX) is proposed. The LCX’s jacket is printed by periodically spaced metallic stripes, which partially converts the bounded monofilar mode into a radiating mode. This adds to the leaked bifilar mode, enhancing the radiation performance of the leaky cable. It is shown that the coupling loss can be significantly decreased by the addition of periodic metallic stripes over the jacket. The radio coverage, at the desired locations of an indoor environment can be enhanced by adding the metallic stripes over the installed leaky coaxial cable

Leaky coaxial cable with continuous scanning directive beam

Abstract Leaky Coaxial Cable (LCX) is an antenna array used for many applications such as train communication, highway information broadcasting and object detection sensors. We propose leaky Coaxial cable which it can continuously scan a directive beam over a wide range of angles by just varying the frequency with improved radiation efficiency. Furthermore, we can obtain a continuous directive beams over the top and the bottom face of the LCX by adding slots array at both sides

A leaky coaxial cable antenna based on sinusoidally-modulated reactance surface

Abstract This paper presents the simulated results of a leaky coaxial cable antenna (LCXA) based on sinusoidally modulated reactance surface (SMRS). The theory of SMRS is employed to transform the leaky coaxial cable (LCX), a uniformly radiating structure into a directional antenna, LCXA. It is shown that high gain and arbitrary direction of radiation could be achieved by LCXA

The effect of BaTiO₃ particle shape on complex permittivity of 0.98MgTiO₃–0.02BaTiO₃ composite powders at GHz frequencies

Abstract The effect of BaTiO₃ particle shape on the properties of 0.98MgTiO₃–0.02BaTiO₃ composite powders was characterized and analyzed using an indirectly coupled open-ended coaxial cavity resonator at gigahertz frequencies. Elongated micrometre sized BaTiO₃ particles were found to have a significantly stronger effect on permittivity when compared to composite powders having micro and nano sized spherical BaTiO₃ particles. Inclusion permittivities and dielectric loss tangents of composite powders increased from that of pure MgTiO₃ powder, 13.3 and 4.6 × 10⁻³, up to 15.7 and 1.7 × 10⁻² with needle shaped BaTiO₃ particles, respectively. The presented results give valuable information for tailoring the properties of dielectrics which can be utilized in the vast field of electronic component manufacturing

Identifying Objectives for a Learning Space Management System with Value-focused Thinking

A classroom with a blackboard and some rows of desks is obsolete in special education. Depending on the needs, some students may need more tactile and inspiring surroundings with various pedagogical accessories while others benefit from a simplified environment without unnecessary stimuli. This understanding is applied to a new Finnish special education school building with open and adaptable learning spaces. We have joined the initiative creation process by developing software support for these new spaces in the form of a learning space management system. Participatory design and value-focused thinking were implemented to elicit the actual values of all the stakeholders involved and transform them into software implementation objectives. This paper reports interesting insights about the elicitation process of the objectives