Browsing by Department "VTT Technical Research Centre of Finland"

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  • 220-240-GHz High-Gain Phase Shifter Chain and Power Amplifier for Scalable Large Phased-Arrays
    (2023) Najmussadat, Md; Ahamed, Raju; Varonen, Mikko; Parveg, Dristy; Kantanen, Mikko; Halonen, Kari A.I.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This paper focuses on the design aspects of the key components for a scalable phased-array system over the 200 GHz frequency range. A high-gain phase shifter chain for 220 to 240 GHz frequency range and a high-gain power amplifier (PA) with a high output power are designed in a 0.13-μm SiGe BiCMOS technology. The phase shifter chain includes a low-noise amplifier (LNA), a vector modulator phase shifter (PS), and a gain-enhancing amplifier. The LNA is a five-stage cascode design. The vector modulator core is realized by two variable gain amplifiers based on the Gilbert cell architecture. A four-stage cascode design is used for the gain-enhancing amplifier. The phase shifter chain shows a measured gain of 18 dB at 230 GHz with a 360° phase tuning range and more than 10 dB of gain control. The chip achieves a minimum measured noise figure of 11.5 dB at 230 GHz and shows a wideband noise characteristic. The complete phase shifter chain chip consumes a dc power of 153 mW and occupies a 1.41 mm2 area.A high-power PA that is critical for a large phased-array system is designed. This paper presents a unique 4-way power combining technique utilizing a differential quadrature coupler. The realized balanced PA occupies an area of 0.67 mm2 and shows a measured peak gain of 21 dB at 244 GHz. The PA consumes 819 mW of dc power and delivers a maximum saturated output power (Psat) of 7.1 dBm at 244 GHz and more than 4.3 dBm of Psat from 230 to 255 GHz.
  • Aalto-1, multi-payload CubeSat: Design, integration and launch
    (2021-10) Praks, Jaan; Mughal, M. Rizwan; Vainio, R.; Janhunen, P.; Envall, J.; Oleynik, P.; Näsilä, A.; Leppinen, H.; Niemelä, P.; Slavinskis, A.; Gieseler, J.; Toivanen, P.; Tikka, T.; Peltola, T.; Bosser, A.; Schwarzkopf, G.; Jovanovic, N.; Riwanto, B.; Kestilä, A.; Punkkinen, A.; Turku, University; Hedman, H.-P.; Lill, J.-O.; Slotte, J.M.K.; Kettunen, H.; Virtanen, A.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The design, integration, testing and launch of the first Finnish satellite Aalto-1 is briefly presented in this paper. Aalto-1, a three-unit CubeSat, launched into Sun-synchronous polar orbit at an altitude of approximately 500 km, is operational since June 2017. It carries three experimental payloads: Aalto Spectral Imager(AaSI), Radiation Monitor (RADMON) and Electrostatic Plasma Brake (EPB). AaSI is a hyperspectral imager in visible and near-infrared (NIR) wavelength bands, RADMON is an energetic particle detector and EPB is a de-orbiting technology demonstration payload. The platform was designed to accommodate multiple payloads while ensuring sufficient data, power, radio, mechanical and electrical interfaces. The design strategy of platform and payload subsystems consists of in-house development and commercial subsystems. The CubeSat Assembly, Integration & Test (AIT) followed Flatsat-Engineering-Qualication Model (EQM)-Flight Model (FM) model philosophy for qualification and acceptance. The paper briefly describes the design approach of platform and payload subsystems, their integration and test campaigns and spacecraft launch. The paper also describes the ground segment & services that were developed by Aalto-1 team.
  • Acquisition of supply market intelligence – An information processing perspective
    (2020-12) Lorentz, Harri; Aminoff, Anna; Kaipia, Riikka; Pihlajamaa, Matti; Ehtamo, Jesse; Tanskanen, Kari
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The capability to develop and sustain superior knowledge of markets and supply chains, or supply market intelligence (SMI), is an important element in increasing the strategic relevance of purchasing and supply management (PSM). This study draws on information processing theory (IPT) to shed light on how firms acquire SMI. In particular, the study aims to identify the drivers and mechanisms of information processing in SMI acquisition and to explore how the two constructs are related. Our findings emerged from an abductive multiple case study including 22 SMI tasks in eight case companies operating in various manufacturing industries. We find that the drivers of information processing needs in SMI acquisition are related either to uncertainty or equivocality. Uncertainty describes a situation in which decision-makers may be ignorant of a variable's value while equivocality describes a situation in which they may be ignorant of the variable's existence. We identify four structural mechanisms and three information technology mechanisms for information processing in the SMI context. We also find that equivocality seems to trump uncertainty in determining the use of the identified SMI acquisition mechanisms. In addition to elaborating IPT in the SMI context and exploring the theoretical foundations of SMI, we offer practitioners a framework for supporting the design of SMI practices in procurement organisations.
  • Activation of softwood Kraft pulp at high solids content by endoglucanase and lytic polysaccharide monooxygenase
    (2021-08) Ceccherini, Sara; Rahikainen, Jenni; Marjamaa, Kaisa; Sawada, Daisuke; Grönqvist, Stina; Maloney, Thaddeus
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The manufacturing of man-made cellulose fibers starts with the dissolution of wood pulp fibers. Pulps can dissolve at different rates and leave different amounts of undissolved particles. Thus, their properties can be modified to achieve better dissolution. Enzymatic treatments are an effective means of enhancing pulp dissolution, and this study compares the effect of endoglucanase (TrCel45A) and lytic polysaccharide monooxygenase (LPMO, TrAA9A) on bleached softwood Kraft pulp at 20 % solids content. The enzymes were applied individually and in combination. Both enzymes increased fibrillation, fines content, porosity, water retention value, crystallinity index and crystallite size, but the largest changes were achieved with the enzyme mixture. For example, fiber saturation point and water retention value increased by 64 and 37 % with TrCel45A, by 27 and 25 % with TrAA9A, and by 73 and 52 % with both TrCel45A and TrAA9A. Pulp reactivity was indirectly assessed by measuring the dissolution time in cupriethylenediamine. The average dissolution time of the reference pulp measured 642 s, while those of the pulps treated with TrCel45A, TrAA9A and their mixture were 399, 473 and 298 s, respectively. The decrease in dissolution time correlated with the increase in fines, fibrillation, porosity, and water retention value.
  • Adhesion Properties of Freestanding Hydrophobin Bilayers
    (2018-07-24) Hähl, Hendrik; Vargas, Jose Nabor; Jung, Michael; Griffo, Alessandra; Laaksonen, Päivi; Lienemann, Michael; Jacobs, Karin; Seemann, Ralf; Fleury, Jean Baptiste
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Hydrophobins are a family of small-sized proteins featuring a distinct hydrophobic patch on the protein's surface, rendering them amphiphilic. This particularity allows hydrophobins to self-assemble into monolayers at any hydrophilic/hydrophobic interface. Moreover, stable pure protein bilayers can be created from two interfacial hydrophobin monolayers by contacting either their hydrophobic or their hydrophilic sides. In this study, this is achieved via a microfluidic approach, in which also the bilayers' adhesion energy can be determined. This enables us to study the origin of the adhesion of hydrophobic and hydrophilic core bilayers made from the class II hydrophobins HFBI and HFBII. Using different fluid media in this setup and introducing genetically modified variants of the HFBI molecule, the different force contributions to the adhesion of the bilayer sheets are studied. It was found that in the hydrophilic contact situation, the adhesive interaction was higher than that in the hydrophobic contact situation and could be even enhanced by reducing the contributions of electrostatic interactions. This effect indicates that the van der Waals interaction is the dominant contribution that explains the stability of the observed bilayers.
  • Affinity of Keratin Peptides for Cellulose and Lignin: A Fundamental Study toward Advanced Bio-Based Materials
    (2022-08-16) Nuutinen, Emmi-Maria; Valle-Delgado, Juan José; Kellock, Miriam; Farooq, Muhammad; Österberg, Monika
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Keratin is a potential raw material to meet the growing demand for bio-based materials with special properties. Keratin can be obtained from feathers, a by-product from the poultry industry. One approach for keratin valorization is to use the protein to improve the properties of already existing cellulose and lignin-based materials to meet the requirements for replacing fossil-based plastics. To ensure a successful combination of keratin with lignocellulosic building blocks, keratin must have an affinity to these substrates. Hence, we used quartz crystal microbalance with a dissipation monitoring (QCM-D) technique to get a detailed understanding of the adsorption of keratin peptides onto lignocellulosic substrates and how the morphology of the substrate, pH, ionic strength, and keratin properties affected the adsorption. Keratin was fractionated from feathers with a scalable and environmentally friendly deep eutectic solvent process. The keratin fraction used in the adsorption studies consisted of different sized keratin peptides (about 1-4 kDa), which had adopted a random coil conformation as observed by circular dichroism (CD). Measuring keratin adsorption to different lignocellulosic substrates by QCM-D revealed a significant affinity of keratin peptides for lignin, both as smooth films and in the form of nanoparticles but only a weak interaction between cellulose and keratin. Systematic evaluation of the effect of surface, media, and protein properties enabled us to obtain a deeper understanding of the driving force for adsorption. Both the structure and size of the keratin peptides appeared to play an important role in its adsorption. The keratin-lignin combination is an attractive option for advanced material applications. For improved adsorption on cellulose, modifications of either keratin or cellulose would be required.
  • Analysis of large sparse graphs using regular decomposition of graph distance matrices
    (2019-01-22) Reittu, Hannu; Leskelä, Lasse; Räty, Tomi; Fiorucci, Marco
     Conference article in proceedings
    Statistical analysis of large and sparse graphs is a challenging problem in data science due to the high dimensionality and nonlinearity of the problem. This paper presents a fast and scalable algorithm for partitioning such graphs into disjoint groups based on observed graph distances from a set of reference nodes. The resulting partition provides a low-dimensional approximation of the full distance matrix which helps to reveal global structural properties of the graph using only small samples of the distance matrix. The presented algorithm is inspired by the information-theoretic minimum description principle. We investigate the performance of this algorithm for selected real data sets and for synthetic graph data sets generated using stochastic block models and power-law random graphs, together with analytical considerations for sparse stochastic block models with bounded average degrees.
  • Axial dispersion and CFD models for the extraction of levulinic acid from dilute aqueous solution in a Kühni column with 2-methyltetrahydrofuran solvent
    (2019-06-01) Laitinen, Antero; Penttilä, Karri; Manninen, Mikko; Syrjänen, Jouni; Kaunisto, Juha; Murtomäki, Lasse
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    1D axial dispersion and 3D CFD models for the extraction of levulinic acid from dilute aqueous solution by applying 2-methyltetrahydrofuran as a solvent are presented. The models are validated by comparison with the measured levulinic acid concentration profile data obtained in a bench-scale Kühni column. The 1D model contains NRTL parameters for the system levulinic acid-water-2MTHF. Correlations for drop size and hold-up for Kühni columns were taken from literature. The values for overall mass transfer coefficient ranged from 1.4E-5 to 2.2E-5 ms −1 , and increased as a function of the rotor speed. The fitting of the column performance resulted in a very good prediction of the solute concentration profiles in the extraction column, and the average absolute value of relative error for the 1D model was 23%. CFD model visualized the column performance at the column height of 150.5–160 cm giving valuable information on back mixing, phase velocities, dispersed phase volume fraction, and mass transfer. Dispersed phase volume fraction and mass transfer contours revealed, that the mass transfer rate (app. 0.25 g L −1 s −1 )is at its highest just below the rotor, and that there are blind spots in the compartments close to the extractor and just above each down comer. Values for the dispersed phase volume fraction are highest in the same area where the mass transfer reaches the highest values. The highest slip velocity values (app. 0.03 m −1 )are located in the tip of each compartment partition plates. General correlations, such as hold-up and drop size correlations, can successfully be applied in levulinic acid-water-2MTHF system reported in this work. The 1D axial dispersion model proved to be valuable tool for scale-up purposes, and CFD model, despite the long time needed for each simulation, gave useful information for the design purposes.
  • Beam-Reconfigurable Antenna Based on Vector Modulator and Rotman Lens on LTCC
    (2021) Karki, Sabin Kumar; Varonen, Mikko; Kaunisto, Mikko; Rantala, Arto; Lahti, Markku; Lamminen, Antti; Holmberg, Jan; Kantanen, Mikko; Ala-Laurinaho, Juha; Viikari, Ville
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A beam-switching array is designed using a $4\times 6$ Rotman lens as a beam-forming network to switch the beam towards -30°, -10°, 10°, and 30°. Six substrate integrated waveguide fed $1\times 4$ microstrip patch arrays are used as the radiating elements. The beam-switching array is designed on the LTCC substrate to operate at 71-76 GHz. In this work, the feasibility of implementing a beam-switching network with a vector modulator (VM) integrated circuit as switching element is studied for the first time. The measured radiation pattern of the beam-switching array with the VM is in line with the simulated radiation pattern. The measured peak realized gain of the beam port 1, 2, 3, and 4 with 3-dB backoff gain of the VM are 17, 17, 17.8, 16.9 dBi at 75 GHz, respectively. In addition, the work demonstrates the possibility of beam-reconfigurability in beam-switching array by simultaneous excitation of the beam ports in optimum phase using the VM. The simultaneous excitation of the adjacent two ports, 1-2, 2-3, and 3-4, steer the beam towards -19°, 0°, and 19°, respectively, which improves the beam cross-over level. With various combinations of simultaneous excitation, the half power beam-width of the beam-switching array is varied from 17.8° to 75°.
  • Bioinspired Functionally Graded Composite Assembled Using Cellulose Nanocrystals and Genetically Engineered Proteins with Controlled Biomineralization
    (2021-10-21) Mohammadi, Pezhman; Gandier, Julie-Anne; Nonappa; Wagermaier, Wolfgang; Miserez, Ali; Penttilä, Merja
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Nature provides unique insights into design strategies evolved by living organisms to construct robust materials with a combination of mechanical properties that are challenging to replicate synthetically. Hereby, inspired by the impact-resistant dactyl club of the stomatopod, a mineralized biocomposite is rationally designed and produced in the complex shapes of dental implant crowns exhibiting high strength, stiffness, and fracture toughness. This material consists of an expanded helicoidal organization of cellulose nanocrystals (CNCs) mixed with genetically engineered proteins that regulate both binding to CNCs and in situ growth of reinforcing apatite crystals. Critically, the structural properties emerge from controlled self-assembly across multiple length scales regulated by rational engineering and phase separation of the protein components. This work replicates multiscale biomanufacturing of a model biological material and also offers an innovative platform to synthesize multifunctional biocomposites whose properties can be finely regulated by colloidal self-assembly and engineering of its constitutive protein building blocks.
  • Broadband Continuous-Variable Entanglement Generation Using a Kerr-Free Josephson Metamaterial
    (2022-08) Perelshtein, M. R.; Petrovnin, K. V.; Vesterinen, V.; Hamedani Raja, S.; Lilja, I.; Will, M.; Savin, A.; Simbierowicz, S.; Jabdaraghi, R. N.; Lehtinen, J. S.; Grönberg, L.; Hassel, J.; Prunnila, M. P.; Govenius, J.; Paraoanu, G. S.; Hakonen, P. J.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Entangled microwave photons form a fundamental resource for quantum information processing and sensing with continuous variables. We use a low-loss Josephson metamaterial comprising superconducting, nonlinear, asymmetric inductive elements to generate frequency-entangled photons from vacuum fluctuations at a rate of 2 giga entangled bits per second spanning over the 4-GHz bandwidth. The device is operated as a traveling-wave parametric amplifier under Kerr-relieving biasing conditions. Furthermore, we demonstrate single-mode squeezing in such devices - 3.1±0.7dB below the zero-point level at half of modulation frequency.
  • Broadband tunable phase shifter for microwaves
    (2020-06-01) Zhang, Jinli; Li, Tianyi; Kokkoniemi, Roope; Yan, Chengyu; Liu, Wei; Partanen, Matti; Tan, Kuan Yen; He, Ming; Ji, Lu; Grönberg, Leif; Möttönen, Mikko
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We implement a broadly tunable phase shifter for microwaves based on superconducting quantum interference devices (SQUIDs) and study it both experimentally and theoretically. At different frequencies, a unit transmission coefficient, |S21| = 1, can be theoretically achieved along a curve where the phase shift is controllable by the magnetic flux. The fabricated device consists of three equidistant SQUIDs interrupting a transmission line. We model each SQUID embedded at different positions along the transmission line with two parameters, capacitance and inductance, the values of which we extract from the experiments. In our experiments, the tunability of the phase shift varies from 0.07 × π to 0.14 × π radians along the full-transmission curve with the input frequency ranging from 6.00 GHz to 6.28 GHz. The reported measurements are in good agreement with simulations, which is promising for future design work of phase shifters for different applications.
  • Calibration of cryogenic amplification chains using normal-metal-insulator-superconductor junctions
    (2019-05-13) Hyyppä, E.; Jenei, M.; Masuda, S.; Sevriuk, V.; Tan, K. Y.; Silveri, M.; Goetz, J.; Partanen, M.; Lake, R. E.; Grönberg, L.; Möttönen, M.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Various applications of quantum devices call for an accurate calibration of cryogenic amplification chains. To this end, we present an experimentally feasible calibration scheme and use it to accurately measure the total gain and noise temperature of an amplification chain by employing normal-metal-insulator-superconductor (NIS) junctions. Our method is based on the radiation emitted by inelastic electron tunneling across voltage-biased NIS junctions. We derive an analytical expression that relates the generated power to the applied bias voltage which is the only control parameter of the device. After the setup has been characterized using a standard voltage reflection measurement, the total gain and the noise temperature are extracted by fitting the analytical expression to the microwave power measured at the output of the amplification chain. The 1σ uncertainty of the total gain of 51.84 dB appears to be of the order of 0.10 dB.
  • CF-LIBS quantification and depth profile analysis of Be coating mixed layers
    (2021-06) Dwivedi, V.; Marín-Roldán, A.; Karhunen, J.; Paris, P.; Jõgi, I.; Porosnicu, C.; Lungu, C. P.; van der Meiden, H.; Hakola, A.; Veis, P.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A remote LIBS system is being considered as an analysis tool in ITER for monitoring the erosion and fuel retention in the first wall. This necessitates further investigation of the performance of LIBS for thick co-deposited layers consisting of ITER-relevant materials. The main goal of this work is determining the fuel content of the samples and D depth profile by LIBS and to compare the results with those obtained by other methods. The studied samples were Be-based mixed coatings on W substrates, containing D and in some cases C, O, or both. These impurities are relevant not only for ITER, but also for other fusion devices, such as JET-ILW. The laser ablation was performed at 10 mbar Ar pressure using a 5 ns pulse Nd:YAG laser at 1064 nm. Suitable Be and Ar spectral lines were employed for the evaluation of the electron temperature of the plasma using multi-elemental Saha-Boltzmann (MESB) plots. The electron density was obtained from the Stark broadening of the Dα and Hα spectral lines following deconvolution. The average elemental content of each coating was then obtained by calibration-free LIBS (CF-LIBS) and are in agreement with other techniques (TOF–ERDA, IBA).
  • Conductive cellulose based foam formed 3D shapes-from innovation to designed prototype
    (2019-02-01) Siljander, Sanna; Keinänen, Pasi; Ivanova, Anastasia; Lehmonen, Jani; Tuukkanen, Sampo; Kanerva, Mikko; Björkqvist, Tomas
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    In this article, we introduce for the first time, a method to manufacture cellulose based electrically conductive non-woven three-dimensional (3D) structures using the foam forming technology. The manufacturing is carried out using a minimum amount of processing steps, materials, and hazardous chemicals. The optimized solution applies a single surfactant type and a single predefined portion for the two main processing steps: (1) the dispersing of nanocellulose (NC) and carbon nanotubes (CNT) and (2) the foam forming process. The final material system has a concentration of the used surfactant that is not only sufficient to form a stable and homogeneous nanoparticle dispersion, but it also results in stable foam in foam forming. In this way, the advantages of the foam forming process can be maximized for this application. The cellulose based composite material has a highly even distribution of CNTs over the NC network, resulting a conductivity level of 7.7 S/m, which increased to the value 8.0 S/m after surfactant removal by acetone washing. Also, the applicability and a design product case 'Salmiakki' were studied where the advantages of the material system were validated for a heating element application.
  • Development and piloting of sustainability assessment metrics for arctic process industry in Finland-The biorefinery investment and slag processing service cases
    (2017-09-22) Husgafvel, Roope; Poikela, Kari; Honkatukia, Juha; Dahl, Olli
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Regionally, there has been a lot of focus on the advancement of sustainable arctic industry and circular economy activities within process industry in the Finnish Lapland. In this study, collaboration between university and industry was established facilitated by regional development actors to develop and pilot test a sustainability assessment approach taking into account previous work in this field. The industry partners in this study were a biorefinery investment in the first case and a slag processing service in the second case. As a result of the joint efforts, novel sets of environmental and economic sustainability assessment indicators and associated sub-indicators were developed and the existing set of social indicators was updated. Moreover, environmental and social sustainability assessments were implemented in the biorefinery case accompanied by a separate evaluation of regional economic impacts. In the slag processing case, environmental, economic and social sustainability were assessed. The results of the sustainability assessments indicated very good level of overall performance in both cases. However, specific elements that contributed to lower level of performance included lack of specific sustainability management and reporting approaches and need for better performance in supply chain sustainability, monitoring of greenhouse gas emissions, life cycle thinking and circular economy training. The expected effects of the planned investment on the regional economy were very positive based on the results of the evaluation.
  • A dual approach for improving homogeneity of a human-type N-glycan structure in Saccharomyces cerevisiae
    (2016-04) Piirainen, Mari A.; Boer, Harry; de Ruijter, Jorg C.; Frey, Alexander D.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    N-glycosylation is an important feature of therapeutic and other industrially relevant proteins, and engineering of the N-glycosylation pathway provides opportunities for developing alternative, non-mammalian glycoprotein expression systems. Among yeasts, Saccharomyces cerevisiae is the most established host organism used in therapeutic protein production and therefore an interesting host for glycoengineering. In this work, we present further improvements in the humanization of the N-glycans in a recently developed S. cerevisiae strain. In this strain, a tailored trimannosyl lipid-linked oligosaccharide is formed and transferred to the protein, followed by complex-type glycan formation by Golgi apparatus-targeted human N-acetylglucosamine transferases. We improved the glycan pattern of the glycoengineered strain both in terms of glycoform homogeneity and the efficiency of complex-type glycosylation. Most of the interfering structures present in the glycoengineered strain were eliminated by deletion of the MNN1 gene. The relative abundance of the complex-type target glycan was increased by the expression of a UDP-N-acetylglucosamine transporter from Kluyveromyces lactis, indicating that the import of UDP-N-acetylglucosamine into the Golgi apparatus is a limiting factor for efficient complex-type N-glycosylation in S. cerevisiae. By a combination of the MNN1 deletion and the expression of a UDP-N-acetylglucosamine transporter, a strain forming complex-type glycans with a significantly improved homogeneity was obtained. Our results represent a further step towards obtaining humanized glycoproteins with a high homogeneity in S. cerevisiae.
  • Effect of atomic layer annealing in plasma-enhanced atomic layer deposition of aluminum nitride on silicon
    (2023-09) Seppanen, H; Prozheev, I; Kauppinen, C; Suihkonen, S; Mizohata, K; Lipsanen, H
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The effect of adding an atomic layer annealing step to a plasma-enhanced atomic layer deposition process of aluminum nitride was investigated with commonly available materials. The refractive index, crystallinity, stoichiometry, and impurity concentrations were studied from films grown from trimethylaluminum and ammonia precursors at 300∘ C on Si(111) substrates. Additional energy provided by the atomic layer annealing step during each deposition cycle was found to enhance the crystallinity and stoichiometry and increase the refractive index and film density. A polycrystalline hexagonal film with a weak c-axis orientation was obtained on substrates with and without native oxide, which is promising for applications that require high quality films at low temperatures.
  • Elements of installed base information value
    (2016-06-13) Mahlamäki, Katrine; Borgman, Jukka; Rämänen, Jussi; Tuovinen, Joona; Finne, Max; Perminova-Harikoski, Olga; Tiihonen, Juha; Öhman, Mikael
     A4 Artikkeli konferenssijulkaisussa
    Installed base information (IBI) is used in industrial service operations, but currently there are challenges with maintaining and utilizing this information to its full potential. The purpose of this paper is to aid in improving the realized value of IBI. We conducted two case studies of IBI collection and utilization with two industrial product-service system suppliers. From this material, we identified four elements contributing to the value of IBI and constructed a framework for managing this value. Furthermore, we identified the sources of the difference between the potential value and the realized value of IBI. The elements contributing to the value of IBI are its management, scope, utilization and quality. These elements form interconnected leaves in the proposed value clover framework. Each element potentially contributes to the difference between the theoretical maximum value and the realized value of IBI. Future research should look into the different elements and their relationships in more detail.Our framework helps managers in identifying and balancing the different elements of IBI value and in deciding on investments in this area. Previous literature has recognized the need for IBI, but not analyzed the different elements affecting its value. Our research offers industrial service operations a novel framework of IBI value.
  • Enhancing the stability of aqueous dispersions and foams comprising cellulose nanofibrils (CNF) with CaCo3 particles
    (2018-09-01) Tenhunen, Tiia Maria; Pöhler, Tiina; Kokko, Annaleena; Orelma, Hannes; Gane, Patrick; Schenker, Michel; Tammelin, Tekla
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    In this work, stability of dispersions and foams containing CaCO3-based pigments and cellulose nanofibrils (CNF) was evaluated with the aim to reveal the mechanisms contributing to the overall stability of the selected systems. The utmost interest lies in the recently developed hydrocolloid hybrid CaCO3 pigments and their potential to form bionanocomposite structures when incorporated with CNF. These pigments possess a polyelectrolyte layer deposited on the surface of the particle which is expected to enhance the compatibility between inorganic and organic components. Stability assessment of both dispersions and foams was conducted using turbidity profile scanning. In dispersions, CNF provides stability due to its ability to form a firm percolation network. If surface-modified pigments are introduced, the favourable surface interactions between the pigments and CNF positively influence the stability behaviour and even large macro-size pigments do not interfere with the stability of either dispersions or foams. In foams, the stability can be enhanced due to the synergistic actions brought by CNF and particles with suitable size, shape and wetting characteristics resulting in a condition where the stability mechanism is defined by the formation of a continuous plateau border incorporating a CNF network which is able to trap the inorganic particles uniformly.