[article-cris] Sähkötekniikan korkeakoulu / ELEC

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  • Eight-element polarisation independent transmission trap detector with high attenuation
    (2025-02-01) Vaigu, Aigar; Kubarsepp, Toomas; Ikonen, Erkki
    A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A polarisation-insensitive transmission trap detector was constructed from two identical polarisation-dependent transmission trap detectors, each containing four 10 mm × 10 mm silicon photodiodes. The performance of the 8-element polarisation-independent and coaxial input-output transmission trap detector has been characterised at laser wavelengths of 635 nm and 850 nm. The measured transmittances are lower than 10−4 and are in agreement with values calculated from the reflectances of single photodiodes. The measured relative transmittances and responsivities are independent of polarisation within 0.12%. The spectral responsivity is spatially uniform within 0.1% across an area of 4 mm × 4 mm , consistent with the expected variations due to the oxide layer thickness of the photodiodes.
  • Verifying Measures of Quantum Entropy
    (2022-06) Pastor, Giancarlo; Woo, Jae Oh
    A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This paper introduces a new measure of quantum entropy, called the effective quantum entropy (EQE). The EQE is an extension, to the quantum setting, of a recently derived classical generalized entropy. We present a thorough verification of its properties. As its predecessor, the EQE is a semi-strict quasi-concave function; it would be capable of generating many of the various measures of quantum entropy that are useful in practice. Thereafter, we construct a consistent estimator for our proposed measure and empirically test its estimation error, under different system dimensions and number of measurements. Overall, we build the grounds of the EQE, which will facilitate the analyses and verification of the next innovative quantum technologies.
  • Energy, environmental, and economic (3E) analysis of a dynamic ice storage system based on ice slurry for a super high-rise building in subtropical climates
    (2025-03-15) Hu, Xinyi; Yuan, Xiaolei; Jiang, Jingyao; Jiang, Yaoji; Liang, Yumin; Jia, Wenqi; Kosonen, Risto
    A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The building sector has overtaken industry and transportation as the largest global energy consumer, with Heating, Ventilation, Air-Conditioning, and Refrigeration (HVAC&R) systems accounting for the highest energy usage within buildings. Enhancing the energy efficiency of HVAC&R systems is therefore critical for achieving energy conservation and global carbon neutrality. This paper introduces an innovative dynamic ice storage system based on ice slurry designed to shift electricity demand and improve energy flexibility for consumers in subtropical climates, thereby reducing energy consumption and contributing to decarbonization. The proposed system was implemented in a high-rise office building in southern China and analyzed through energy, environmental, and economic perspective. On-site measurements demonstrate that the dynamic ice storage system is significantly more energy-efficient and has lower carbon emissions than traditional cooling systems. Specifically, the system achieved a 50 % reduction in operational energy costs, and its equivalent cooling coefficient of performance (COP) reached 9.07, nearly double that of standard cooling systems. Life cycle assessments indicate that the system could reduce equivalent CO2 emissions by 127 600 tCO2e, and carbon emissions by approximately 37 000 tons, equivalent to planting 75 421 trees over 20 years.
  • Analysis of Economic Benefits from Load Shifting Services in Energy Communities
    (2024) da Motta Pires, Sérgio; Maki, Kari; Baranauskas, Marius; Ollikainen, Ville
    A4 Artikkeli konferenssijulkaisussa
    Establishing energy communities provides a practical and effective approach to balance energy systems and support the green transition. Despite their recognized value, the widespread implementation of energy communities is yet to materialize, demanding a comprehensive understanding of technical, social, and economic aspects. This paper delves into the economic benefits of energy community operations, with a primary focus on load-shifting services. It accomplishes the objective by comparing different demand response strategies implemented in the Energy Community Smart Digital Node concept. Leveraging historical data from the electricity market, the study estimates economic benefits for stakeholders. Additionally, the paper further explores the translation of these economic benefits into sustainable business models for energy community operators while minimizing disruptions to end-users' energy consumption behavior caused by demand response actions.
  • The persistent shadow of the supermassive black hole of M87: II. Model comparisons and theoretical interpretations
    (2025-01-01) Ramakrishnan, Venkatessh; Savolainen, Tuomas; , Event Horizon Telescope Collaborat
    A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The Event Horizon Telescope (EHT) observation of M87∗ in 2018 has revealed a ring with a diameter that is consistent with the 2017 observation. The brightest part of the ring is shifted to the southwest from the southeast. In this paper, we provide theoretical interpretations for the multi-epoch EHT observations for M87∗ by comparing a new general relativistic magnetohydrodynamics model image library with the EHT observations for M87∗ in both 2017 and 2018. The model images include aligned and tilted accretion with parameterized thermal and nonthermal synchrotron emission properties. The 2018 observation again shows that the spin vector of the M87∗ supermassive black hole is pointed away from Earth. A shift of the brightest part of the ring during the multi-epoch observations can naturally be explained by the turbulent nature of black hole accretion, which is supported by the fact that the more turbulent retrograde models can explain the multi-epoch observations better than the prograde models. The EHT data are inconsistent with the tilted models in our model image library. Assuming that the black hole spin axis and its large-scale jet direction are roughly aligned, we expect the brightest part of the ring to be most commonly observed 90 deg clockwise from the forward jet. This prediction can be statistically tested through future observations.
  • MMIC Design for Radiometer Receiver at 240 GHz in 0.13 μm SiGe BiCMOS Technology
    (2024) Najmussadat, M.; Tawfik, Y.; Ahamed, R.; Varonen, M.; Parveg, D.; Lamminen, A.; Pursula, P.; Halonen, K. A.I.
    A4 Artikkeli konferenssijulkaisussa
    This paper introduces an MMIC radiometer receiver designed for integration into a 240 GHz radiometer receiver system using a 130-nm SiGe BiCMOS technology. The detector features an on-chip dipole antenna, an SPDT switch, a Low Noise Amplifier (LNA), a mixer, an IF amplifier, and a power detector. The resonator switch exhibits a measured minimum insertion loss of 4.2 dB, maximum isolation of 29 dB, and minimum input and output reflection coefficients of 16 dB and 20 dB, respectively. The LNA utilizes a 5 -stage cascode design, achieving a simulated gain of 28 dB at 240 GHz. The mixer, designed as a single-balanced second harmonic mixer, provides a simulated conversion gain of 0 dB. The IF amplifier, a 3 -stage differential cascode amplifier, can provide a simulated gain of 45 dB at its IF frequency. The power detector is designed using the Meyer topology for a high dynamic range contributing to the chip's ability to enhance radiometer resolution. Additionally, this paper also presents a free-space measurement conducted to verify the radiometer receiver's functionality. In the measurement, with a LO frequency set at 112 GHz, the detector provides an output voltage of 650 mV in response to an IF current of 43 mA, demonstrating its effective performance.
  • Simultaneous Planning of PV and DSTATCOM for Combined Mitigation of Voltage Deviation and Unbalance
    (2025-01-28) Mousa, Hossam H. H.; Mahmoud, Karar; Lehtonen, Matti
    A4 Artikkeli konferenssijulkaisussa
    The increased integration of photovoltaic systems (PVs) and unbalanced loads in low-voltage (LV) distribution systems has negative consequences on the overall performance of the utility grid (UG), resulting in voltage imbalance, power losses, line overheating, and various power quality issues. To enhance the hosting capacity (HC) of such distribution systems for accommodating increased capacities of PVs, the reactive power control (RPC) techniques, such as distribution static compensators (DSTATCOMs) are utilized to regulate voltage profiles and address voltage unbalances. In this regard, this study focuses on coordinating the sizing and placement of PVs and DSTATCOMs to mitigate voltage unbalances and maintain acceptable limits for other power quality metrics, particularly in unbalanced three-phase systems. By accounting for fluctuations in both load demand and solar irradiance, a multi-objective grey wolf optimization (MOGWO) algorithm verifies the planning method within the IEEE 123-bus unbalanced distribution system, employing the co-simulation between MATLAB and OpenDSS platforms. As a result of this proposed planning approach, voltage unbalances, power losses, and voltage deviations are reduced by 21%, 42%, and 23%, respectively, under 100% overloading conditions, alongside a 215% penetration level of PVs. Furthermore, the proposed planning strategy underscores that the combination of PVs and DSTATCOMs can alleviate voltage unbalances, consequently reducing power losses and thermal line overloading effectively.
  • Evaluating an Analog Main Memory Architecture for All-Analog In-Memory Computing Accelerators
    (2024) Adam, Kazybek; Monga, Dipesh; Numan, Omar; Singh, Gaurav; Halonen, Kari; Andraud, Martin
    A4 Artikkeli konferenssijulkaisussa
    Analog in memory Computing (IMC) has emerged as a promising method to accelerate deep neural networks (DNNs) on hardware efficiently. Yet, analog computation typically focuses on the multiply and accumulate operation, while other operations are still being computed digitally. Hence, these mixed-signal IMC cores require extensive use of data converters, which can take a third of the total energy and area consumption. Alternatively, all-analog DNN computation is possible but requires increasingly challenging analog storage solutions, due to noise and leakage of advanced technologies. To enable all-analog DNN acceleration, this work demonstrates a feasible IMC architecture using an efficient analog main memory (AMM) cell. The proposed AMM cell is 42x and 5x more power and area efficient than a baseline analog storage cell. An all-analog architecture using this cell achieves potential efficiency gains of 15x compared with a mixed-signal IMC core using data converters.
  • A Droop-Based Frequency Controller for Parallel Operation of VSCs and SG in Isolated Microgrids
    (2023-01-26) Hafez, Wessam Arafa; Mahmoud, Karar; Ali, Abdelfatah; Shaaban, Mostafa F.; Astero, Poria; Lehtonen, Matti
    A4 Artikkeli konferenssijulkaisussa
    Microgrids are a novel concept for modern power distribution networks that integrate renewable power sources and increase power control capabilities. This system's essential problem is controlling the frequency in island mode. Using the synchronous generator (SG) control approach, the microgrid frequency is more stable due to the inertial features of the SG. In this regard, this paper presents a control algorithm for voltage source converters (VSC)-based distributed generators (DGs), which emulates the principal behavior of synchronous machines and can support inertia to the grid and reduce frequency gradients considering the parallel operation of the SG. The controller is designed based on droop control theory, and a supervisory center controller is implemented to maintain system frequency close to a nominal value of the whole microgrid. The simulation results demonstrate that the system frequency is stabilized even in different and sudden load changes in the island mode where the microgrid is fed by multiple VSC units and a SG. The Simulink model of the system is designed using MATLAB Simulink Software.
  • Percolation-Based Metal−Insulator Transition in Black Phosphorus Field Effect Transistors
    (2023-03-15) Ali, Nasir; Lee, Myeongjin; Ali, Fida; Ngo, Tien Dat; Park, Hyokwang; Shin, Hoseong; YOO, Won Jong
    A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The existence of a novel phenomenon, such as the metal-insulator transition (MIT) in two-dimensional (2D) systems, affords emerging functional properties that provide new aspects for future electronics and optoelectronics. Here, we report the observation of the MIT in black phosphorus field effect transistors by tuning the carrier density (n) controlled by back-gate bias. We find that the conductivity follows an n dependence as σ(n) ∝ n α with α ∼ 1, which indicates the presence of screened Coulomb impurity scattering at high carrier densities in the temperature range of 10-300 K. As n decreases, the screened Coulomb impurity scattering breaks down, developing strong charge density inhomogeneity leading to a percolation-based transition at the critical carrier density (n C). At low carrier densities (n < n C), the system is in the insulating regime, which is expressed by Mott variable range hopping that demonstrates the role of disorder in the system. In addition, the extracted average values of critical exponent δ are ∼1.29 ± 0.01 and ∼1.14 ± 0.01 for devices A and B, respectively, consistent with the 2D percolation exponent of 4/ 3, confirming the 2D percolation-based MIT in BP devices. Our findings strongly suggest that the 2D MIT observed in BP is a classical percolation-based transition caused by charge inhomogeneity induced by screened Coulomb charge impurity scattering around a transition point controlled by n through back-gate bias.
  • Finite Element Modeling of Induction Machine Coupled with Three-Mass Mechanical System
    (2023) Far, Mehrnaz Farzam; Pippuri-Makelainen, Jenni; Keranen, Janne; Belahcen, Anouar; Laine, Sampo; Viitala, Raine
    A4 Artikkeli konferenssijulkaisussa
    Electrical drivetrains consist of an electrical machine drive connected to a mechanical system. Single-mass models are commonly used in electromechanical finite-element analyses to study various aspects of these drivetrains such as the output torque of the electrical machine or the transient performance. Nevertheless, single-mass models are inherently insufficient for the analysis of torsional vibrations. Higher degree-of-freedom mechanical models should be employed to inspect the behavior of the electric drives connected to flexible torsional systems. This paper presents a comprehensive finite element model of an induction machine coupled with a three-mass lumped-element model. The single-mass and three-mass models are compared in terms of stator current, produced torque, speed, and losses. It is shown that neglecting torsional oscillations results in underestimating the characteristics of electrical machines.
  • Direct DC-Bus Control for Grid-Forming Converters: Towards the Concept of Dual-Voltage-Forming Converters
    (2025) Mourouvin, Rayane; Nurminen, Tuure; Hinkkanen, Marko; Routimo, Mikko
    A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A control method for regulating both DC- and AC-side voltages, based on a disturbance observer, is presented. This method provides a voltage-source behavior from the AC-side perspective, a key functionality of grid-forming converters. A dynamic model is derived to develop the control law using feedback linearization. The control method is able to maintain the DC- and AC-side voltages without any cascaded loops. The method is therefore named the dual-voltage forming method to differentiate it from the recent definitions of grid-forming converters. The use of a disturbance observer provides integral action and also inherent synchronization. A transparent current controller is implemented to protect the converter from over-currents. Small-signal stability of the proposed method is studied analytically and design guidelines are drawn from the analysis. Furthermore, the asymmetric behavior of the converter in different operating modes is analytically assessed. The performance of the method is tested in experimental conditions using a 12.5-kVA test setup. The control method exhibits robust performance in both strong and weak grids in terms of DC- bus voltage reference tracking as well as the capacity to survive large external power variations with power-flow direction changes. Moreover, the effect of a grid voltage sag is studied.
  • MIP-Based Electrochemical Sensors in the Detection of Opioids, Benzodiazepines and Psychoactive Compounds
    (2024-10-25) Nekoueian, Khadijeh; Laurila, Tomi
    A3 Kirjan tai muun kokoomateoksen osa
    The introduction of modern molecular imprinting technology into electrochemical sensors has resulted in a new era of smart diagnostic sensors. Molecularly imprinted polymers (MIPs) are a specialized group of polymers engineered to contain precise “artificial receptors” or “artificial antibodies” capable of highly selective recognition of target analytes. Adding this unique molecular recognition property to the advantages of electrochemical sensors has paved the way for developing advanced sensing platforms to selectively interact with a diverse range of target analytes, spanning from small biomolecules to organic macromolecules, even within complicated environments. These electrochemical (bio)sensors have extraordinary sensitivity, allowing them to detect trace concentrations of target analytes, and establishing them as key players in advancing health assessment and ecological surveillance, among other applications. Furthermore, their potential for miniaturization paves the way for the design of lab-on-a-chip, biomedical assays, and wearable sensors. As the advancements in this field continue to progress, the potential for these smart diagnostic assays to revolutionize various industrial sectors becomes increasingly evident. The MIP-based electrochemical sensors hold immense promise for the future, offering unprecedented opportunities for precise, rapid, and accessible diagnostics in diverse scientific domains. This chapter discusses the latest developments in the use of MIP-based electrochemical (bio)sensors for detecting and monitoring opioids and psychoactive compounds, with a focus on biofluids including saliva, urine, sweat and blood as well as synthetic samples and beyond.
  • Architecture of a Feedback System for Human-Machine Interaction in a Collaborative Environment
    (2023) Kolesnikov, Mikhail V.; Blech, Jan Olaf; Atmojo, Udayanto Dwi; Vyatkin, Valeriy; Afanasev, Maxim Ya
    A4 Artikkeli konferenssijulkaisussa
    We present a methodology for measuring and increasing labor productivity using data collection and its analysis for optimizing production task management. Presented socio-cyber-physical system architecture and its technical implementation comprises a decision-making system that is integrated with a collaborative automated manufacturing system. This novel approach enables the implementation of flexible planning of all processes of an employee's work time by dynamically adjusting the environment and applying individual methods of influencing an employee's physical and psychological condition, as well as maintaining the employee's productive and relaxation phases and ensuring smooth transitions between them, using the collected in real-time data. As a result of this work, a system architecture is designed, enabling real-time task scheduling according to the laborer's condition. A description of the structural elements, components, and protocols used is provided. Early work on a prototype system used in the 'Aalto Factory of the Future' laboratory is presented.
  • Evaluation of Printed Coplanar Capacitive Sensors for Reliable Quantification of Fluids in Adult Diaper
    (2024) Tanweer, Muhammad; Gillan, Liam; Sepponen, Raimo; Tanzer, Ihsan Oguz; Halonen, Kari A.
    A4 Artikkeli konferenssijulkaisussa
    Advancements in printed technology have led to the development of economical and sustainable electronic solutions for wearable medical devices in the healthcare sector. Printed capacitive sensors in planar geometry are widely used in the development of smart diapers for detecting urination events, quantifying detection, and quantifying voided volumes. However, factors such as the effect of sodium electrolyte variation, body weight effect on a wet diaper and gravitational effect on wet diapers impair the quantification of voided volume with capacitive sensors. In this study, a printed capacitive sensor for quantifying human body fluids in adult diaper was evaluated to analyze these effects. Silver and carbon inks were used to print the parallel-plate capacitive electrodes on a flexible substrate in a coplanar geometry. In-diaper quantification measurements were performed at various concentration levels in pseudo urine with small incremental levels at the adult human urination flow rate. The impact of human body weight on quantification measurements using a wet diaper was studied. The gravitational pull effect of wetness was evaluated for on-human-torso use in both standing and lying positions. It was observed that a printed coplanar capacitive sensor alone is insufficient to reliably quantify the voided volume in diapers.
  • A Review of Applications of Machine Learning for Emissions Estimation in Diesel Engines
    (2024) Nguyen Khac, Hoang; Linh Nguyen, Thuy
    A4 Artikkeli konferenssijulkaisussa
    There has been an increasing demand to reduce the emissions of diesel engines, especially in maritime applications. Moreover, emission regulations are becoming stricter every year. This has led to an urge for more complex engine control systems with more accurate emissions estimators included. Machine learning methods have been long adopted to create models with high complexity to estimate the engine’s emissions and to rely less on conventional physical measurement devices. This paper presents a brief review of the development of engine emissions estimation using machine learning methods over the last 20 years. The review will however mainly focus on emissions prediction from engine in-cylinder pressure and engine functional vibration signal.
  • Deformable Wire Media Resonators
    (2024) Khobzei, M.; Tkach, V.; Haliuk, S.; Samila, A.; Bobrovs, V.; Ginzburg, P.; Simovski, C.; Vovchuk, D.
    A4 Artikkeli konferenssijulkaisussa
    Temporal degree of freedom opens new capabilities to control electromagnetic interactions with structured media. While fast, comparable to the carrier oscillation period, changes in effective material susceptibilities suggest emerging new peculiar phenomena, experimental realizations of lag theoretical predictions. However, phenomena, inspired by slow practically realizable parametric changes in effective media, have both fundamental interest and immediate practical applications. Here we perform comprehensive studies of modal hierarchy in a deformable Fabry-Perot resonator, constructed from a wire array, hosted in a compressible dielectric host. The lattice parameter of the wire media can be controlled over a 5 -fold range (between 10 and 50 mm), leading to superior electromagnetic tunability. Furthermore, the resonator response demonstrates an extreme sensitivity to mechanical deformation as resonance hierarchy in metamaterial assembly strongly depends on the lattice constant. Specifically, a 0.3 mm change in the lattice constant, being as small as ∼ 0.002 λ, shifts the Fabry-Perot resonance frequency around 1.9 GHz. Owing to their extraordinary responsivity, deformable electromagnetic metamaterials can find use as elements in adaptive user-controlled devices.
  • Enhancing Renewable Energy Hosting Capacity in Unbalanced Microgrids via Empowering Smart Inverters
    (2025) Mousa, Hossam H. H.; Mahmoud, Karar; Lehtonen, Matti
    A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This article presents a coordinated planning strategy for renewable energy sources (RESs) and energy storage systems (ESSs) in unbalanced microgrids. The approach aims to mitigate voltage unbalance, reduce power losses, alleviate feeder congestion, and maximize the hosting capacity (HC) of RESs in grid-connected unbalanced microgrids. By employing smart inverter control for photovoltaic (PV) and ESS inverters, the strategy enhances the integration of additional RESs while minimizing power exchange between operational zones and the utility grid (UG). To achieve such an ambitious goal, smart inverter control functions are employed, including combined mode, volt-var (VV), volt-watt (VW) for Photovoltaic (PV) inverters, and VW for ESS inverters. The IEEE 123-bus test system, divided into six operational zones, is used as a case study, incorporating plug-in electric vehicle (PEV) demand and wind-based distributed generation (DG). A metaheuristic algorithm is developed for optimal DG and ESS deployment using MATLAB and OpenDSS. The results demonstrate significant improvements, including a 16% reduction in feeder congestion, a 150% increase in PV penetration, a 13% reduction in power losses, and decreased reliance on the UG, ensuring enhanced power quality and system reliability.
  • Harnessing HARQ Retransmissions for Fast Average Consensus Over Unreliable Communication Channels
    (2023) Makridis, Evagoras; Charalambous, Themistoklis; Hadjicostis, Christoforos N.
    A4 Artikkeli konferenssijulkaisussa
    In this work, we introduce a new consensus mechanism by incorporating a Hybrid Repeat reQuest (HARQ) error control protocol into the Ratio Consensus (RC) algorithm to achieve fast discrete-time asymptotic average consensus in the presence of packet retransmissions (information delays), and packet-dropping links (information loss) over directed networks. Using this consensus mechanism (hereinafter referred to as HARQ-RC), each transmitting node decides whether to retransmit packets (containing values of consensus variables) to its out-neighbors by utilizing their HARQ feedback signals. Under this protocol, each receiving node may detect the corrupted part of the received packet, and by combining successfully received information from previous retransmission trials, it may recover the information of the packet. This mechanism leads in a lower number of retransmission trials compared to standard ARQ mechanism, and hence the consensus iterations converge faster to the average consensus value. By introducing the weighted adjacency matrix that models the HARQ-based information exchange between nodes, we show that the nodes are guaranteed to reach asymptotic average consensus using the HARQ-RC mechanism despite the information delays and losses. The effectiveness of the HARQ-RC over bad communication links, with respect to achieving faster convergence to the average consensus value, is demonstrated under different simulation scenarios.
  • Interoperability in Software-Defined Process Automation Using the Open Process Automation Standard and IEC 61499: Adapter Connections of IEC 61499 and OPAS Enable Plug-and-Play Integration
    (2024) Jhunjhunwala, Pranay; Stephen Bitar, S.; Zhukovskii, Kirill; Atmojo, Udayanto Dwi; Vyatkin, Valeriy
    A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The increasing demand for flexibility in factory automation has led to the need for high interoperability between controllers, sensors, and actuators. This paper demonstrates how the interoperability provisions developed by the Open Process Automation Standard (OPAS) can be used to improve the interchangeability and interoperability of controller function blocks in cascade control. We also show how this development enables easier integration of IIoT devices into process automation applications. This article demonstrates how OPAS development improved interoperability between controllers and IIoT devices while reducing on-floor system integration efforts by bringing the required transparency between the OT and IT layers in the factory.