[article-cris] Palvelut / Services
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- A 0.9-Nyquist-Band Digital Timing Mismatch Correction for Time-Interleaved ADCs Achieving Delay Tuning Range of 0.12-Sample-Period
A4 Artikkeli konferenssijulkaisussa(2022) Kempi, Ilia; Jarvinen, Okko; Kosunen, Marko; Unnikrishnan, Vishnu; Stadius, Kari; Ryynanen, JussiTime-interleaved analog-to-digital converters (TIADC) require channel matching in terms of offset, gain, and sampling clock skew to achieve best data conversion performance. Conventionally, correction of skew mismatch is realized with analog delay lines, making it challenging for high-speed ADC designs to achieve fine delay resolution over wide tuning range while maintaining low clock jitter. Digital skew correction allows greater flexibility than analog solutions, but is hindered by a significant hardware footprint. This paper demonstrates digital filter-based timing skew correction approach suitable for on-chip implementation. In a 10-bit 8-channel TI-ADC the proposed structure corrects mismatch magnitudes up to 0.12 sample period across 0.9 Nyquist band while requiring only 65% hardware of similar architectures of equivalent performance. The presented digital circuit uses reduced combinational paths and operates at a clock rate of single ADC channel, making it applicable for digitally-assisted high-speed TI-ADCs. - 3d printing of a continuous carbon fiber reinforced bronze-matrix composite using material extrusion
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2025-01-15) Mousapour, Mehrdad; Kumar, S. Siddharth; Partanen, Jouni; Salmi, MikaThe main objective of this study is to investigate, for the first time, the feasibility of 3d printing a continuous carbon fiber (CCF) reinforced metal matrix composite using a cost-effective material extrusion (MEX) technology. Notably, this paper presents a detailed analysis of the microstructure and mechanical and physical properties of a bronze matrix composite reinforced with CCF. The results reveal that CCF significantly impedes the expected densification levels of the composite's structure, causing extensive gaps between the bronze particles. However, despite the high porosity level, the composite's electrical conductivity remains relatively high, demonstrating the limited negative impact of the CCF material on the composite's conductivity. Moreover, mechanical evaluations were performed through 3-point bending and tensile tests, highlighting the composite material's advantages and limitations. The results show that the composite material exhibits an improved yield stress of 76 %, increased ultimate tensile strength of 20 %, and an extended fracture strain of 30 %. However, the flexural strength decreases by 23 % due to the presence of massive gaps formed by CCF. - 3D Radio Map-based GPS spoofing Detection and Mitigation for Cellular-Connected UAVs
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2023) Dang, Yongchao; Karakoc, Alp; Saba, Norshahida; Jäntti, RikuWith the upcoming 5G and beyond wireless communication system, cellular-connected Unmanned Aerial Vehicles (UAVs) are emerging as a new pattern to give assistance for target searching, emergency rescue, and network recovery. Such cellular-connected UAV systems highly rely on accurate and secure navigation systems, e.g. the Globe Navigation System (GPS). However, civil GPS services are unencrypted and vulnerable to spoofing attacks that can manipulate UAVs’ location and abort the UAVs’ mission. This paper leverage 3D radio map and machine learning methods to detect and mitigate GPS spoofing attacks for cellular-connected UAVs. Precisely, the edge UAV flight controller uses ray tracing tools deterministic channel models, and Kriging methods to construct a theoretical 3D radio map. Then the machine learning methods, such as Multi-Layer Perceptrons (MLP), Convolutional Neural Networks (CNN), and Recurrent Neural Networks (RNN), are employed to detect GPS spoofing by analyzing the UAV/base station reported Received Signal Strength (RSS) values and the theoretical radio map RSS values. Once spoofing is detected, the particle filter is applied to relocate the UAV and mitigate GPS deviation. The experiment results indicate that the Universal Kriging (UK) with exponential covariance function has the lowest standard errors for radio map construction. Moreover, the MLP achieves the highest spoofing detection accuracy with different spoofing margins because of the statistic prepossessing relieving environmental impacts, while the CNN has a comparable detection accuracy with less training time than MLP since CNN inputs are raw RSS data. Furthermore, the particle filter-based GPS spoofing mitigation can relocate the UAV to the real position within an error of 10 meters using 100 particles. - 420 stainless steel-Cu parts fabricated using 3D Multi-Material Laser Powder Bed Fusion: a new solution for plastic injection moulds
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2022-08) Cunha, A.; Marques, A.; Silva, F. S.; Gasik, M.; Trindade, B.; Carvalho, O.; Bartolomeu, F.A novel multi-material design concept to be applied in plastic injection moulds is proposed combining the mechanical resistance of the 420 stainless steel alloy and the high thermal conductivity of copper, in a single component, fabricated in just one event by means of homemade 3D Multi-Material Laser Powder Bed Fusion equipment. The processing strategy and the interface region between both materials are analysed and discussed both from a metallurgical and mechanical point of view. The results show a good metallurgical bonding between the two materials, with a diffusion zone of about 10 µm, capable of providing mechanical interlocking, i.e. entrapment of one material in the other, creating a physical link between them. Both materials have low porosity and the pores detected present a sub-micrometre size distribution. A few pores and cracks on both the top and cross-section surfaces were detected with some tens of micrometres in size, at the interface zone. The hardness of the 420 stainless steel and copper varied from 482 to 532 HV and 99 and 116 HV, respectively. - 4D printing of electro-activated thermochromic composites for dynamic 3D displays
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2025-03) Kumar, S. Siddharth; Niyagama, Wudith W.; Akmal, Jan S.; Salmi, MikaThis paper introduces a novel 4D printing approach for dynamic displays, using thermochromic-PLA composites embedded with FeCrAl wires activated by Joule heating. Previous studies struggled with high energy consumption, heat bleed, and slow activation. By embedding continuous resistance wires directly within the thermochromic-plastic matrix, localized, efficient heating is achieved, improving response speed and energy efficiency. The study optimizes color change by focusing on specimen thickness, current intensity, and pulse duration. A customized G-code workflow allowed for precise wire integration into 3D-printed specimens fabricated using a composite dual-nozzle co-extrusion printer, enabling controlled color changes upon activation. Experiments identified 1.5 mm as the ideal specimen thickness, balancing rapid response time (∼78.5 s for 80 % color change) with effective wire concealment. A water medium significantly accelerated recovery time compared to air, emphasizing the benefits of faster heat dissipation. The color change was found to be linearly proportional to pulse-on time and the square of the current. Shorter pulses at higher currents resulted in more efficient and predictable color transformations than constant current inputs. A functional 7-segment display was fabricated, demonstrating the practical application of this technology for smart displays, sensors, and other 4D-printing applications. - 5G edge for power system applications
A4 Artikkeli konferenssijulkaisussa(2023-06-15) Kokkoniemi-Tarkkanen, H.; Raussi, P.; Horsmanheimo, S.; Hovila, P.; Kulmala, A.; Borenius, S.Constantly evolving wireless technologies accelerate the trend to move from application on hardware devices to the edge. 5G standalone (SA) and beyond networks enable large-scale virtualization, which could benefit smart grids. This paper investigates the potential of 5G SA and edge technology to provide a platform for smart grid applications. We study how operating on the edge could benefit applications and provide a concrete perspective based on measurements and the process of building an edge communication pilot for smart grids. Results of preliminary QoS measurements with a commercial 5G SA network are compared with prior 5G non-standalone (NSA). - 5G-Network-Based Connectivity and Data Platforms for Smart Cities– an Explorative Case Study of Drivers for Industry Transformation
A4 Artikkeli konferenssijulkaisussa(2022-01-04) Tukiainen, Taina; Paavola, LauriDigital platforms, more detailed connectivity and increased availability of data are re-shaping markets. This is an opportunity for telecom companies to partner with other industries and offerings. We conduct an explorative case study to understand the connectivity and data platforms in smart cities. The contribution of our study is that it provides insights on the business models, platform control and competitive strategy in smart cities. Specifically, we find that the understanding of business models together with political, economic, social, environmental, technological and legal aspects are prerequisites to successful cases. Finally, we highlight the importance of co-creation and collaboration, as a means to tackle the challenges of platform localisations. Based on our findings we indicate promising aspects for future research in these fields. - A 6–20 GHz 400-MHz Modulation-Bandwidth CMOS Transmitter IC
A4 Artikkeli konferenssijulkaisussa(2022-10-26) Saleem, Ali Raza; Naghavi, Saeed; Zahra, Mahwish; Stadius, Kari; Kosunen, Marko; Anttila, Lauri; Valkama, Mikko; Ryynänen, JussiThis paper presents a transmitter IC with two identical signal paths, including base-band amplifier, up-converting mixer, and power amplifier (PA) stages. The design is focused on wide modulation bandwidth, and the use of a resonatorless small die-area class-D power amplifier at cm-wave frequencies. This work also incorporates a local oscillator (LO) signal distribution network with phase tuning elements. The circuit is implemented in a 22-nm CMOS process, and the active die area is 0.8 mm2. Operation over the 6–20 GHz range of carrier frequencies through the transmission of both continuous wave (CW) and wideband quadrature phase shift keying (QPSK) modulated signals were verified with measurements. Results with 20/40/100, and 400 MHz modulation bandwidths are presented, and for instance for a 20-MHz QPSK modulated input signal the measured adjacent channel leakage ratio (ACLR) of the transmitter is 28 dBc and error vector magnitude (EVM) is 5%. - A 98.2% energy efficiency Li-O2 battery using a LaNi-0.5Co0.5O3 perovskite cathode with extremely fast oxygen reduction and evolution kinetics
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2023-01-15) Qiu, Qianyuan; Pan, Zheng-Ze; Yao, Penghui; Yuan, Jiashu; Xia, Chun; Zhao, Yicheng; Li, YongdanRechargeable lithium-oxygen (Li-O2) batteries have been regarded as a promising energy storage device, but its practical use is impeded by its low energy efficiency. Herein, a bi-functional catalytic perovskite LaNi0.5Co0.5O3 (LNCO) is employed as the cathode of an efficient Li-O2 battery with a molten nitrate salt electrolyte at 160 °C. It displays a stable low charge–discharge overpotential 50 mV with a high energy efficiency (EE) 98.2 % at 0.1 mA cm−2 for over 100 cycles. The excellent performance is attributed to the extremely fast oxygen reduction and evolution kinetics on the surface of LNCO. The discharge product is Li2O with a porous and fluffy morphology which facilitates the transfer of oxygen and other intermediate species. It is noted that Li2O as a discharge product enables a theoretical specific energy density of 5200 Wh kg−1, which is superior to the Li2O2 as product giving 3500 Wh kg−1 for those ambient temperature Li-O2 batteries. - A People's Green New Deal, de Max Ajl
Book/Film/Article review(2024-02-15) Pedregal Villodres, AlejandroReview of A People's Green New Deal, by Max Ajl - Aalto Gear Fault datasets for deep-learning based diagnosis
Data Article(2024-12) Dahl, Zacharias; Hämäläinen, Aleksanteri; Karhinen, Aku; Miettinen, Jesse; Böhme, Andre; Lillqvist, Samuel; Haikonen, Sampo; Viitala, RaineAccurate system health state prediction through deep learning requires extensive and varied data. However, real-world data scarcity poses a challenge for developing robust fault diagnosis models. This study introduces two extensive datasets, Aalto Shim Dataset and Aalto Gear Fault Dataset, collected under controlled laboratory conditions, aimed at advancing deep learning-based fault diagnosis. The datasets encompass a wide range of gear faults, including synthetic and realistic failure modes, replicated on a downsized azimuth thruster testbench equipped with multiple sensors. The data features various fault types and severities under different operating conditions. The comprehensive data collected, along with the methodologies for creating synthetic faults and replicating common gear failures, provide valuable resources for developing and testing intelligent fault diagnosis models, enhancing their generalization and robustness across diverse scenarios. - Aalto open access fund pilot
Poster(2017) Tiitinen, Kalle - Ab initio study of Ni2MnGa under shear deformation
A4 Artikkeli konferenssijulkaisussa(2015) Zelený, Martin; Straka, Ladislav; Sozinov, Alexei - Accelerating XR Innovation through a pan-European Lab Network: An overview of the EMIL project
A4 Artikkeli konferenssijulkaisussa(2024-06-12) Blönnigen, Justus; Clarke, Christopher; Dahn, Andreas; Forelli, Lisa; Gowrishankar, Ramyah; Heikura, Tuija; Helzle, Volker; Hine, Paul; Jicol, Crescent; Kreische, Alexander; Lutteroth, Christof; MacÍa, Francisco; Moesgen, Tim; Pares, Narcis; Plichta, Leszek; Potts, Dominic; Schäfer, Eduard; Sharma, Adwait; Spielmann, Simon; Tenhunen, Juhani; Trottnow, Jonas; Tseng, Yu Han; Vikberg, Esa; Xiao, YuEuropean Media and Immersion Lab, or EMIL, is a pan-European network of extended reality (XR) labs consisting of 4 European academic institutions, with a mission to accelerate development of virtual, augmented and mixed reality technologies, content, services and applications. The 30-month project, which started in September 2022, has been funded by the European Union and co-funded by Innovate UK. This paper gives an overview of the project's goals, its organization, and selected results that have been achieved. - The Acceptance of Digital Surveillance in an Age of Big Data
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2021-03) Westerlund, Mika; Isabelle, Diane A.; Leminen, SeppoNews media companies and human rights organizations have been increasingly warning about the rise of the surveillance state that builds on distrust and mass surveillance of its citizens. The COVID-19 pandemic is fostering digitalization and state-corporate collaboration, leading to the introduction of contact tracing apps and other digital surveillance technologies that bring about societal benefits, but also increase privacy invasion. This study examines citizens' concerns about their digital identity, the nation-state's intelligence activities, and the security of biodata, addressing their impacts on the trust in and acceptance of governmental use of personal data. Our analysis of survey data from 1,486 Canadians suggest that those concerns have negative impacts on citizens' acceptance of governmental use of personal data, but not necessarily on their trust in the nation-state being respectful of privacy. Government and corporations, it is concluded, should be more transparent about the collection and uses of data, and citizens should be more active in "watching the watchers" in the age of Big Data. - Accountability for sustainability – An institutional entrepreneur as the representative of future stakeholders
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2023-03) Chakhovich, Terhi; Virtanen, TuijaStakeholder views have often been presented as the source of sustainability while a lack of sustainability has been presented as a self-centered focus on the organization itself. The present paper reports a case in which a case organization, not present stakeholders, brings up sustainability and a concern for future stakeholders. We rely on interviews and archival data gathered in a case organization in the construction industry, and interview data from stakeholders. The study shows how the representatives of the case organization feel accountable to future (not present) stakeholders’ needs, as present stakeholders are considered to be short-term oriented. As it is organizational representatives, not stakeholders, who predominantly envision the future, the source of accountability for sustainability appears, surprisingly, to originate from the organization itself. The organization thus becomes an institutional entrepreneur in altering accountabilities in the industry. This is shown here particularly in the organization's “war against the gray economy”. It is suggested that the needs of certain stakeholders whose views cannot easily be expressed in existing accountability systems, such as future stakeholders, flora and fauna, can sometimes be legitimately represented by unexpected entities. The study also sheds light on an important paradox in sustainability: it requires dialogue with stakeholders while future stakeholders, considered important, cannot directly participate in a dialogue and it is uncertain who can speak for such stakeholders. In this study, the organizational representatives represent the future stakeholders, making true dialogue with outsiders demanding. Concerns for dialogue and the future can sometimes contradict each other. - Accounting in Identity Regulation
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2023) Vaivio, Juhani; Järvenpää, Marko; Rautiainen, AnttiIt is acknowledged that identity regulation in organizations relies on discursive resources. This study moves beyond discourse – illustrating how discourse and accounting measurements are mobilized together in revising identity. Measurement produces persistence, clarity, transparency and comparability, as well as direction: Accounting’s quantitative knowledge ‘amplifies’ discourse. We explain the Great Alliance between words and numbers in a case study addressing events in an organization’s transformation. This extends our understanding of what takes place on the interface between identity and accounting. - Accounting Reporting Complexity Measured Behaviorally
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2019-12) Beerbaum, Dirk; Piechocki, Maciej; Puaschunder, Julia M.We propose a new measure of accounting reporting complexity (ARC) based on customized extensions XBRL elements in relation to the number of reporting tags (NRT), expressed as the relative Extension Rate (ER) as a behavioral economics solution to improve markets. Behavioral insights have recently gained attention in different scientific and applied fields. Thereby behavioral economists set out to improve market conditions to aid practitioners and consumers make wiser and more informed decisions that have a positive impact over time. XBRL extensions reduce comparability of financial disclosures and complicate financial analysis and investor decision making. We find that ER is negatively associated with market capitalization and profitability. ER is on average higher in industries perceived as complex. The preparation and disclosure of more accounting items deviating from the base taxonomy is more complex for consumers of financial and non-financial information. Increasing ER imply comparability among peers is less enabled. In comparison to commonly used measures of operating and linguistic complexity, the associations between ARC and these outcomes are more consistent, exhibit greater explanatory power, and have stronger economic significance. The ER resulting from IFRS-filers, i.e. companies which prepare their financial statements under International Financial Reporting Standard (IFRS) are on average significantly higher than US GAAP filers, i.e. companies which prepare their financial statements under United States General Accepted Accounting Principles (US GAAP). This article is based on the “transparency technology XBRL (eXtensible Business Reporting Language)” (Sunstein, 2013), which should make data more accessible as well as usable for private investors. Overall, the findings contribute to the emerging behavioral economics trend with a novel application in data science and accounting. - Accurate RF-sensing of complex gestures using RFID with variable phase-profiles
A4 Artikkeli konferenssijulkaisussa(2023) Golipoor, Sahar; Sigg, StephanWe propose the use of clothing-integrated conductive textile-based Radio Frequency Identification (RFID) tags featuring variable-phase profiles for RF-based human sensing. This approach enables the distinction and interpretation of movements from various body parts independently. We propose a scheme based on varying phase profiles in order to isolate reflections from distinct tags. The feasibility of the approach is demonstrated analytically in this work. Our instrumentation in a laboratory environment involves tag-groups attached to a solid board. The next step is the evaluation of the system when tags are mounted to a moving person. - Acoustics and the well-being of children and personnel in early childhood education and care
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2023-12-07) Martikainen, Silja; Prawda, Karolina; Ståhlberg-Aalto, Freja; Lautanala, Ida; Kostilainen, Kaisamari; Välimäki, Vesa; Tervaniemi, MariStudies implementing a multimethod perspective in evaluating the acoustics of early childhood education and care (ECEC) spaces both quantitatively and qualitatively are still scarce. In this study the acoustic environments (noise levels and reverberation times) of seven Finnish ECEC group’s premises were examined in association with personnel’s (N = 22) and children’s (N = 71) well-being. Personnel’s well-being and vocal health and children’s well-being were assessed with questionnaires. The findings were further elaborated by documentation of the ECEC spaces and semi-structured interviews with the ECEC personnel detailing their views on the acoustic environment of the daycare buildings and how and if the acoustics should be improved. The results showed that noise exceeding 70 dB affected personnel’s vocal health negatively, whereas no associations were found regarding acoustics and children’s or personnel’s well-being. Based on the interviews, sound spreading, poor insulation, and hard surfaces add to negative experiences of noisiness. ECEC groups need spaces that can be closed and acoustically separated from each other and from other groups. The possibility to close a space supports the perceived well-being of the users and provides a more varied and individualized use of the spaces.