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31.
Iron ore concentrates that are used in the iron production are usually agglomerated into sinter or pellets in order to improve their properties in the blast furnace. The main minerals in the magnetite base sinters are hematite, magnetite and Si and Al containing calcium ferrites of which the latter can exist as either monocalcium ferrite, dicalcium ferrite or hemicalcium ferrite depending on the conditions and on the material's iron/calcium‐ratio. In order to study the reduction behaviour of the sinter in the iron production, samples of monocalcium ferrite, dicalcium ferrite and hemicalcium ferrite were prepared by melting different proportions of pure calcium and iron oxides. After melting the samples were cast and cooled. Samples of hemicalcium ferrite were also heated at a certain temperature before the actual reduction experiments in order to ensure the wanted phase composition of the samples. The mineral compositions of the samples were verified using scanning electron microscopy (SEM‐EDS) as well as X‐ray diffraction (XRD). The verification showed that it was possible to produce the samples of calcium ferrites via melting. The conditions needed to reduce the calcium ferrites were estimated with thermodynamic calculations. 相似文献
32.
Current advances in multi-dimensional channel sounding techniques make it possible to evaluate performances of signal processing
algorithms in realistic conditions. By using channel impulse response measurement data collected in the real fields, link-level
performances of signal transmission techniques in the fields such as bit error rate (BER) and frame error rate (FER) performances
can be evaluated. This technique is called link-level simulation. Through statistical analysis of link-level simulation results,
system-level performances of the techniques such as geographical distribution of BER and FER in the area of interest can also
be evaluated. This technique is called system-level simulation. This paper focuses on link- and system-level performances
of a multiple-input multiple-output (MIMO) Turbo Equalizer in real fields. Methodologies for the link- and system-level simulations
using field measurement data are first presented. Results of link- and system-level simulations using two-dimensional channel
sounding field measurement data collected in Tokyo are then presented.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
33.
Lauri Kettunen Kimmo Forsman 《International journal for numerical methods in engineering》1995,38(1):99-117
This paper presents a method for generating tetrahedral meshes in three-dimensional primitives. Given a set of closed and convex polyhedra having non-zero volume and some mesh controlling parameters, the polyhedra are automatically split to tetrahedra satisfying the criteria of standard finite element meshes. The algorithm tries to generate elements close to regular tetrahedra by maximizing locally the minimum solid angles associated to a set of a few neighbouring tetrahedra. The input parameters define the size of the tetrahedra and they can be used to increase or decrease the discretization locally. All the new nodes, which are not needed to describe the geometry, are generated automatically. 相似文献
34.
Heena Inani Dong Hoon Shin Jacob Madsen HyunJeong Jeong Min Hee Kwon Niall McEvoy Toma Susi Clemens Mangler Sang Wook Lee Kimmo Mustonen Jani Kotakoski 《Advanced functional materials》2021,31(13):2008395
Vertically stacked low-dimensional heterostructures are outstanding systems both for exploring fundamental physics and creating new devices. Due to nanometer-scale building blocks, atomic scale phenomena become for them of fundamental importance, including during device operation. These can be accessed in situ in aberration-corrected scanning transmission electron microscopy (STEM) experiments. Here, the dynamics of a graphene-MoS2 heterostructure are studied under Joule heating, where the graphene serves as a high temperature atomically thin and electron transparent “hot plate” for the MoS2. Structural dynamics and evolution of the system are shown at the atomic scale, demonstrating that at the highest temperatures (estimated to exceed 2000 K), the continuous 2D MoS2 transforms into separated 3D nanocrystals, initiated by sulfur vacancy creation and migration followed by formation of voids and clustering at their edges. The resulting nanocrystals exhibit predominantly hexagonal shapes with the 2H and hybrid (2H/3R, 3R/TZ) polytypes. The observed morphology of the crystals is further discussed during and after the transformation, as well as their different edge configurations and stability under electron irradiation. These observations of MoS2 at extreme temperatures provide insights into the operation of devices based on graphene/MoS2 heterostructures and ultimately may help device fabrication techniques to create MoS2-based nanostructures, for example, in hydrogen evolution reaction applications. 相似文献
35.
Summary
Thirteen differently substituted long-chain amide- and amine-functional alkenes were synthesised and used as comonomers in
zirconocene/methylaluminoxane-catalysed copolymerizations with ethylene and propylene. Characterization of the prepared copolymers
showed the formation of functionalized copolymers with isolated comonomer units. The incorporation level of the comonomers
ranged from 0.24 to 1.3 mol % with ethylene and from 0.04 to 0.96 mol % with propylene. The molar masses of the copolymers
were lower than those of the corresponding homopolymers. End group analysis of the copolymers by NMR suggested that the dominant
chain termination mechanism was chain transfer to aluminium.
Received: 8 December 2000/Accepted: 12 February 2001 相似文献
36.
Kimmo Kaija Ville Pekkanen Santtu Koskinen Eerik Halonen 《Microelectronic Engineering》2010,87(10):1984-1991
Printed electronics is expected to increase its market share significantly in near future. The emerging applications include e.g. display applications, RFID tags, and photovoltaic applications. A benefit of printing is the additive character of the process, which means that material is deposited only the amount that is needed. Digital printing increases flexibility of the process, because circuits are manufactured directly from a digital file, which removes need of fixed masks or patterned screens for each layout. Formation of a multilayer circuitry requires printing of conductive and insulative layers. This paper focuses on printing of a dielectric layer with an inkjet printer. Six sigma DMAIC approach was applied during the process characterization and analysis. The study began by defining the process parameters and evaluating their importance to the outputs. Highest rated parameters were taken into consideration and a design of experiments was established. Measured values were analyzed and it was observed which parameters had the highest effect on the outputs. The results were further verified and it was observed that electrically the printed structures were successful. 相似文献
37.
Electrical Resistance Tomography imaging of concrete 总被引:2,自引:0,他引:2
We apply Electrical Resistance Tomography (ERT) for three dimensional imaging of concrete. In ERT, alternating currents are injected into the target using an array of electrodes attached to the target surface, and the resulting voltages are measured using the same electrodes. These boundary measurements are used for reconstructing the internal (3D) conductivity distribution of the target. In reinforced concrete, the metallic phases (reinforcing bars and fibers), cracks and air voids, moisture gradients, and the chloride distribution in the matrix carry contrast with respect to conductivity. While electrical measurements have been widely used to characterize the properties of concrete, only preliminary results of applying ERT to concrete imaging have been published so far. The aim of this paper is to carry out a feasibility evaluation with specifically cast samples. The results indicate that ERT may be a feasible modality for non-destructive evaluation of concrete. 相似文献
38.
Kimmo Wihervaara 《Journal of the Institute of Brewing》1967,73(2):167-171
The biosynthesis of nicotinic acid by baker's yeast was investigated in laboratory-scale aerobic batch cultivation in nitrogen-rich and nitrogen-poor nutrient solutions. Biosynthesis, which occurred parallel with yeast growth, was vigorous during the exponential growth phase and almost ceased during the retardation phase. The amount of nicotinic acid synthesized per batch was dependent on the nitrogen content of the solution. When a small inoculation of seed yeast was used, the amount of nicotinic acid synthesized per unit weight of yeast formed and the nicotinic acid content of the yeast did not depend on the nitrogen concentration of the nutrient solution. With a large inoculum, both the amount of nicotinic acid synthesized per unit weight of yeast produced and the nicotinic acid concentration of the yeast decreased with the nitrogen concentration of the nutrient solution. Calculated as μg. per g. of protein formed, the amount of nicotinic acid synthesized and the nicotinic acid concentration in the yeast were higher in the nitrogen-poor medium than in the nitrogen-rich medium when a small inoculum was used, but lower when large amounts of seed yeast were used. 相似文献
39.
Davide Barreca Giorgio Carraro Alberto Gasparotto Chiara Maccato Michael E. A. Warwick Kimmo Kaunisto Cinzia Sada Stuart Turner Yakup Gnüllü Tero‐Petri Ruoko Laura Borgese Elza Bontempi Gustaaf Van Tendeloo Helge Lemmetyinen Sanjay Mathur 《Advanced Materials Interfaces》2015,2(17)
Harnessing solar energy for the production of clean hydrogen by photoelectrochemical water splitting represents a very attractive, but challenging approach for sustainable energy generation. In this regard, the fabrication of Fe2O3–TiO2 photoanodes is reported, showing attractive performances [≈2.0 mA cm−2 at 1.23 V vs. the reversible hydrogen electrode in 1 M NaOH] under simulated one‐sun illumination. This goal, corresponding to a tenfold photoactivity enhancement with respect to bare Fe2O3, is achieved by atomic layer deposition of TiO2 over hematite (α‐Fe2O3) nanostructures fabricated by plasma enhanced‐chemical vapor deposition and final annealing at 650 °C. The adopted approach enables an intimate Fe2O3–TiO2 coupling, resulting in an electronic interplay at the Fe2O3/TiO2 interface. The reasons for the photocurrent enhancement determined by TiO2 overlayers with increasing thickness are unraveled by a detailed chemico‐physical investigation, as well as by the study of photogenerated charge carrier dynamics. Transient absorption spectroscopy shows that the increased photoelectrochemical response of heterostructured photoanodes compared to bare hematite is due to an enhanced separation of photogenerated charge carriers and more favorable hole dynamics for water oxidation. The stable responses obtained even in simulated seawater provides a feasible route in view of the eventual large‐scale generation of renewable energy. 相似文献
40.
Rackauskas S Mustonen K Järvinen T Mattila M Klimova O Jiang H Tolochko O Lipsanen H Kauppinen EI Nasibulin AG 《Nanotechnology》2012,23(9):095502
ZnO tetrapods (ZnO-Ts) were synthesized in a vertical flow reactor by gas phase oxidation of Zn vapor in an air atmosphere. The morphology of the product was varied from nearly spherical nanoparticles to ZnO-Ts, together with the partial pressure of Zn and reaction temperature. MgO introduced during synthesis, increased the band gap, the optical transparency in the visible range, and also changed the ZnO-T structure. Fabricated flexible transparent UV sensors showed a 45-fold current increase under UV irradiation with an intensity of 30 μW cm(-2) at a wavelength of 365 nm and response time of 0.9 s. 相似文献