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Complex Permittivity Characterization of Low-loss Slabs Using Time-gating Technique
No full textPublisher Copyright: © 2011-2012 IEEE.This letter presents an innovative method for assessing the complex dielectric constants of low-loss dielectric slabs at sub-terahertz (THz) frequencies. Differing from conventional free-space techniques, the proposed approach removes the need for precise thickness knowledge of the material under test (MUT) and reference plane calibration. Even when the MUT thickness varies in a single sample, the proposed method effectively reduces the relevant estimate uncertainty. When applying it to estimate the permittivity of thick plexiglass and nylon plates across the 140–210-GHz frequency range, it demonstrates good agreement with published articles and lower uncertainty of the estimates. The proposed method is well-suited for permittivity characterizations at THz frequencies, particularly in scenarios where precise rulers are lacking or MUT thickness varies in a single sample.Peer reviewe
Implementing Zero-Trust Architecture for Edge Computing
No full textIoT (Internet of Things) devices are everywhere nowadays. Such devices, for example IP cameras or smart thermostats, send and receive data using the Internet. Some IoT devices utilize what are called edge servers, which permit information processing closer to the user. Compared to a single central cloud server, edge servers are often distributed globally, or are otherwise located near the end device. Edge computing introduces new difficulties to system security. Edge networks may be distributed, heterogeneous, physically vulnerable, and the devices may be constrained in their processing power. A traditional approach to information security is the use of an external firewall. This method is difficult to implement in distributed networks, and a single breach may give the intruder access to every device on the network. A better approach is using the principles of zero-trust. This thesis introduces one partial implementation for zero-trust in an edge computing network. This implementation strives to be computationally light, and includes only authentication and authorization of services. The work was performed on three devices, one of which is a constrained Raspberry Pi 3B+, which represents an end device. This device sends data to an edge server, which sends data further to a cloud server. We implemented zero-trust on this system. Validation tests were run to ensure the system was secure. We tested the end device's throughput with multiple configurations and packet sizes. Overall, the results are positive, although the authentication stack was more computationally taxing than expected. The implementation fulfills the requirements of authentication and authorization for zero-trust as expected, inducing only a moderate load on the system. This proof-of-concept demonstrates that SPIRE, Envoy, and OPA are a practical technology stack for securing edge systems, although we stress that its maintenance suffers compared to similar alternatives employing containers or even Kubernetes.IoT (Internet of Things) -laitteet ovat nykyään kaikkialla. Nämä laitteet, esimerkiksi valvontakamerat tai älykodin termostaatit, lähettävät ja vastaanottavat tietoa Internetin kautta. Jotkut IoT-laitteet hyödyntävät ns. reunapalvelimia, jotka sallivat tiedon prosessoinnin lähempänä käyttäjää. Verrattuna yksittäiseen keskeiseen pilvipalvelimeen, reunapalvelimet ovat usein hajautettuja ympäri maapalloa tai ovat muuten laitteelle paikallisia.
Reunapalvelimien käyttö hankaloittaa järjestelmän tietoturvan ylläpitoa. Reunaverkot ovat hajautettuja ja heterogeenisiä, fyysisesti haavoittuvia, ja reunalaitteet ovat usein laskennallisesti rajoitettuja. Perinteinen tapa lähestyä tietoturvaa on ulkoisen palomuurin käyttäminen. Tämä tapa on kuitenkin vaikea toteuttaa hajautetuissa verkoissa, ja yksittäinen tietomurto saattaa antaa tunkeutujalle reitin kaikkiin verkon laitteisiin. Parempi menetelmä on käyttää niin sanottuja nollaluottamuksen (zero-trust) periaatteita. Tämä työ esittelee yhden osittaisen nollaluottamuksen toteutuksen reunaverkkojärjestelmään. Tämä toteutus pyrkii olemaan päätelaitteelle laskennallisesti kevyt, ja sisältää vain palveluiden todentamisen ja valtuutuksen.
Työ toteutettiin kolmella tietokoneella, joista yksi oli pienitehoinen Raspberry Pi 3+, joka kuvaa järjestelmän päätelaitetta. Tämä laite lähettää dataa reunapalvelimelle, joka jälleen lähettää dataa pilvipalvelimelle. Tähän järjestelmään asennettiin edellä mainittu toteutus.
Testasimme päätelaitteen kykyä lähettää ja vastaanottaa dataa usealla eri konfiguraatiolla ja paketinkoolla. Yleisesti tulokset ovat positiiviset, vaikka järjestelmän resurssijano oli odotettua suurempi. Tämä käytännön todiste osoitti, että SPIRE, Envoy, ja OPA ovat käyttökelpoinen teknologiapaketti reunalaskentajärjestelmien suojaamiseksi, tosin huomauttaa järjestelmän ylläpidon kärsivän verrattuna vastaaviin vaihtoehtoihin, jotka käyttävät kontteja tai jopa Kubernetestä
Esivalmistettujen hissien käyttöönoton dynamiikka
No full textPrefabrication has been proposed as a method to modernize the fragmented, low-productivity construction industry by shifting parts of the on-site works to controlled factory conditions. While prefabrication has shown promise in some contexts, widespread adoption remains slow due to various barriers. This thesis examines the development of prefabricated elevator concepts within an incumbent manufacturer’s innovation projects. Despite early interest, these projects have struggled to gain traction.
The thesis takes an exploratory grounded theory approach to analyze the advantages of prefabricated elevators, identifies barriers preventing adoption, and uncovers additional factors shaping development out-comes. The qualitative insights were derived from stakeholder inter-views, structured into a data framework, and synthesized into an emergent, phased model that contextualizes prefabrication adoption dynamics. The findings identify five aggregate dimensions affecting adoption: Perceived advantages of prefabricated elevators, Organizational barriers, Technical, logistical, and industry hindrances, Commercialization barriers, and Key enablers of prefabricated elevator success. The model illustrates how challenges emerge in phases, how organizational barriers and enablers moderate the process, and how interdependencies shape the un-certain future outcomes of prefabricated elevators, contextualizing the findings and providing a structured perspective on their development.
This thesis contributes to the literature by refining existing prefabrication concepts, introducing new perspectives on adoption barriers and enablers, and offering insights into the influence of organizational dynamics and decision-making uncertainty. It also informs industry practitioners by outlining key considerations for overcoming adoption challenges and integrating prefabrication into broader innovation efforts. Finally, future research directions are proposed to explore these dynamics further.Esivalmistus on esitetty keinona modernisoida pirstaloitunutta ja matalan tuottavuuden rakennusalaa siirtämällä osa työmaalla tehtävistä töistä hallittuihin tehdasolosuhteisiin. Vaikka esivalmistus on osoittanut potentiaalia tietyissä sovelluksissa, sen laajamittainen käyttöönotto on edennyt hitaasti erilaisten esteiden vuoksi. Tämä diplomityö tarkastelee esivalmistettujen hissikonseptien kehitystä vakiintuneen hissivalmistajan innovaatiohankkeissa, joissa alkuvaiheen kiinnostuksesta huolimatta hankkeiden laajempi käyttöönotto on kohdannut haasteita.
Tässä diplomityössä hyödynnetään eksploratiivista grounded theory -lähestymistapaa esivalmistettujen hissien etujen analysoimiseen, käyttöönottoa estävien tekijöiden tunnistamiseen ja muiden kehitykseen vaikuttavien tekijöiden selvittämiseen. Laadulliset löydökset johdettiin sidosryhmähaastatteluista, jäsennettiin tietorakenteeseen ja lopulta prosessimalliin, joka kontekstualisoi esivalmistuksen käyttöönoton dynamiikkaa. Tulokset tunnistavat viisi keskeistä käyttöönottoon vaikuttavaa kokonaisulottuvuutta: esivalmistettujen hissien koetut edut, organisatoriset esteet, tekniset, logistiset ja toimialakohtaiset haasteet, kaupallistamisen esteet sekä esivalmistuksen keskeiset mahdollistajat. Malli kuvaa haasteiden vaiheittaista ilmenemistä, organisatorisien esteiden ja mahdollistajat vaikutusta prosessiin, sekä tulevaisuuden kehityspolkujen muotoutumista, kontekstualisoiden tulokset ja tarjoten strukturoidun näkökulman kehitykseen.
Tämä diplomityö täydentää esivalmistusta koskevaa kirjallisuutta tarkentamalla aiempia käsitteitä, tuomalla esiin uusia näkökulmia käyttöönoton esteisiin ja mahdollistajiin sekä tarjoamalla oivalluksia organisaatiodynamiikan ja päätöksenteon epävarmuuden vaikutuksista. Lisäksi diplomityö tarjoaa alan toimijoille keskeisiä näkökulmia käyttöönoton haasteiden voittamiseen ja esivalmistuksen integroimiseen laajempiin innovaatiohankkeisiin. Lopuksi työssä esitetään useita ideoita aihealueen jatkotutkimukselle
Non-destructive evaluation of early strength of concrete with slag thermally activated using electrical cable
No full textPublisher Copyright: © 2025High levels of clinker substitution by supplementary cementitious materials, such as slag, are necessary to decrease the CO2 emissions of concrete manufacturing. However, this leads to low early concrete strength, delaying construction schedules. In cold regions, heating is an essential part of accelerating the early hydration, thus, the strength of concrete. Therefore, this study analysed the effect of thermal activation of the concrete with 45% and 70% slag in the binder using internal electrical cable heating utilised in construction by evaluating compressive strength and heat development. In addition, non-destructive test methods, such as rebound hammer and ultrasound pulse velocity meter, were introduced to widen their application in estimating early strength development using the SonReb approach. The heating with the power of 20 W and 30 W during the first 10–15 h (11.1–16.7 kWh/m3) effectively improved the early strength of concrete with 45% and 70% slag up to 14% and 60%, respectively during the first 24 h without any strength losses at the later ages. However, considering the initially low strength values (2.5–10 MPa) of concrete with 70% slag, the heat curing resulted in about a 1 – 4 MPa increase, with a maximum rise of 7 MPa, requiring additional strategies for slag activation, for example, alkali activation, to fulfil construction requirements.Peer reviewe
Long-term optimization of district heating networks using thermal energy storage
No full textDistrict heating is used to transfer heat from power plants that produce com-bined heat and power or from heat pumps. This thesis addresses the problem of modeling a district heating network and investigates alternative scenarios for the network to aid in planning. This thesis proposes an energy optimization model for a specific case of a district heating system which has access to thermal storage. The model is built using SpineOpt modelling framework and the study discovers that significant operational and investment costs in heat pumps are incurred in a scenario where combined heat and power plants are decommissioned
Probing fast quantum circuit refrigeration in the quantum regime
No full textPublisher Copyright: © 2025 American Physical Society.Recent advancements in circuit quantum electrodynamics have enabled precise manipulation and detection of a single energy quantum in quantum systems. A quantum circuit refrigerator (QCR) is capable of electrically cooling an excited population of quantum systems, such as superconducting resonators and qubits, through photon-assisted tunneling of quasiparticles within a superconductor-insulator-normal-metal junction. In this study, we demonstrate fast QCR in the quantum regime. We perform time-resolved measurement of the QCR-induced cooling of photon number inside a superconducting resonator by harnessing a qubit as a photon detector. From the enhanced photon loss rate of the resonator estimated from the ac Stark shift, the QCR was shown to have a cooling power of approximately 300 aW. Furthermore, even below the single energy quantum, a 100-ns pulse on the QCR can reduce the number of photons inside the resonator below thermal equilibrium. Numerical calculations based on the Lindblad master equation successfully reproduce these experimental results.Peer reviewe
Sustainable business model innovation for redefining value within planetary boundaries
No full textThis thesis examines sustainable business model innovation (SBMI) as a pathway for companies to operate within planetary boundaries. It explores the theoretical underpinnings of sustainability and SBMI, supported by empirical insights from five case studies of Finnish small and medium-sized enterprises and multinational enterprises. The research investigates how SBMI enables companies to align their operations with environmental, social and economic constraints, identifying enablers, challenges, and strategies for sustainable transformation. The study combines a literature review with qualitative data collected through eight semi-structured inter-views. Key findings highlight the importance of iterative experimentation, stakeholder collaboration, as well as embedding sustainability and impact into core business strategies
Multi-task neural networks for the estimation of cardiorespiratory biomarkers from raw photoplethysmogram signals
No full textPhotoplethysmography (PPG) is a non-invasive optical measurement technique commonly integrated into wearable devices. Critical cardiorespiratory biomarkers such as heart rate (HR), heart rate variability (HRV) and respiratory rate (RR) can be derived from PPG signals. As PPG signals are susceptible to noise and motion artifacts, conventional algorithms integrate complex signal pre-processing and error handling procedures to accurately estimate these biomarkers. End-to-end deep learning models, which automate feature extraction and learn robust representations of the PPG signal, have shown excellent performance for PPG-based HR estimation, although they are under-explored for HRV and RR. Multi-task learning (MTL) combines multiple tasks into a single neural network, thereby leveraging shared representations of the input signal. Compared to training separate models for each task, MTL can often reduce memory and runtime costs without compromising accuracy. However, in MTL, the key challenge lies in balancing task-specific gradients during training, as unbalanced contributions can lead to task interference or dominance. This thesis presents an end-to-end multi-task neural network for the estimation of HR, HRV and RR from raw PPG. The network architecture integrates a convolutional neural network (CNN) and a long-short term memory (LSTM) module, combined with task-specific multi-layer perceptron (MLP) heads. Single-task baseline models and multi-task models are trained, validated and tested on 30-second PPG segments with ground-truth labels from medical-grade reference devices, using data from a single-night sleep study with 908 participants. To address the challenge of balancing task-specific gradients, several MTL methods are implemented and compared, and the final multi-task model is chosen by best validation performance from a total of 36 training runs. It achieves state-of-the-art accuracy across the 230-participant test set, with coefficients of determination of 0.999 (HR), 0.983 (HRV), and 0.906 (RR) for overnight averages and 0.992 (HR), 0.905 (HRV), and 0.675 (RR) across 30-second segments. These results are on par with single-task baselines and improve upon the accuracy of conventional methods in comparable studies
The effect of feedstock concentration on the crystal phase, morphology, and optical properties of WO3 nanostructures
No full textPublisher Copyright: © 2025 The Author(s)In this study, the effect of feedstock concentration on the synthesis of WO3 nanostructures in a one-step hydrothermal process was investigated. According to our experiments, when titrating aqueous Na2WO4$2H2O with HCl solutions of different concentrations to a constant pH of 1.5, after identical hydrothermal treatments at 180 °C, the morphology, crystal size and phase composition as well as the optical properties of the products could be tuned. Furthermore, by applying Na2SO4 in the precursor solution, we get a further degree of freedom to alter the structural and optical properties of the products. The precursor concentration dependent optical band gap energy values (that vary from ∼2.5 eV to ∼2.9 eV) are in good agreement with the associated hexagonal (from 32.7% to 65.5%) and orthorhombic (from 67.3% to 34.5%) phases of nanostructured tungsten oxide products. The calculated Urbach energies can be well explained by the oxygen deficient crystals. The latter is also coherent with measured photoluminescence (multiple peaks between 400 and 580 nm) that indicate abundant defect states in the tungsten oxide products.Peer reviewe
Shift in activated sludge microbiomes associated with nitrite accumulation and high nitrous oxide emissions
No full textPublisher Copyright: © 2025 The AuthorsNitrous oxide (N2O) emissions can constitute over half of the carbon footprint of a wastewater treatment plant (WWTP), and emission peaks frequently correlate with nitrite (NO2−) concentrations. However, connections between the microbiome and high N2O and NO2− levels are not well-documented. Here, we characterize the microbiomes in several parallel lines of a WWTP during massive N2O emissions (20 % of influent nitrogen load) with prolonged NO2− accumulation in most lines, aiming to identify key differences between communities in lines with high and low NO2− concentrations. The abundance of nitrite-oxidizing bacteria (NOB) was extremely low in the lines with NO2− accumulation, which also had slightly lower abundances of ammonia-oxidizing bacteria (AOB). Some incomplete denitrifiers were more abundant in the lines with NO2− accumulation. Lines without NO2− had a higher relative abundance of filamentous bacteria and better floc formation. These findings confirmed our hypothesis that loss of NOB caused NO2− accumulation, inducing increased N2O emissions. AOB are suspected to be the main source of N2O during the studied period, with a likely contribution from heterotrophic denitrifiers. A few species were identified as interesting candidates for further study regarding their potential role in increased N2O emission from WWTPs. Long-term microbiome monitoring is necessary to understand the changes in the microbiome that might initiate NO2− accumulation and high N2O emissions.Peer reviewe