Search results for "materiaalit"
showing 10 items of 102 documents
Lignin Inter-Diffusion Underlying Improved Mechanical Performance of Hot-Pressed Paper Webs
2021
Broader use of bio-based fibres in packaging becomes possible when the mechanical properties of fibre materials exceed those of conventional paperboard. Hot-pressing provides an efficient method to improve both the wet and dry strength of lignin-containing paper webs. Here we study varied pressing conditions for webs formed with thermomechanical pulp (TMP). The results are compared against similar data for a wide range of other fibre types. In addition to standard strength and structural measurements, we characterise the induced structural changes with X-ray microtomography and scanning electron microscopy. The wet strength generally increases monotonously up to a very high pressing tempera…
From Norway Spruce Bark to Carbon Foams : Characterization, and Applications
2020
Fresh bark from spruce Picea abies was milled and extracted with hot water. The extracts were purified in a number of steps in order to get tannin-extracts pure enough to prepare tannin-based carbon foams. The chemical composition of the extracts were analyzed. The foams were maturated and thermally treated to obtain desired properties, such as specific surface area, porosity, and compressive strength. It was possible to produce carbon foams even if they contained carbohydrate impurities. Differences in the properties of the carbon foams such as compressive strength, specific surface areas, and pore size distributions might be related to the compositions of the extracts. The foams were fina…
Spectroscopic analysis of hot-water- and dilute-acid-extracted hardwood and softwood chips
2017
Hot-water and dilute sulfuric acid pretreatments were performed prior to chemical pulping for silver/white birch (Betula pendula/B. pubescens) and Scots pine (Pinus sylvestris) chips to determine if varying pretreatment conditions on the original wood material were detectable via attenuated total reflectance (ATR) infrared spectroscopy. Pretreatment conditions varied with respect to temperature (130 °C and 150 °C) and treatment time (from 30 min to 120 min). The effects of the pretreatments on the composition of wood chips were determined by ATR infrared spectroscopy. The spectral data were compared to those determined by common wood chemistry analyses to evaluate the suitability of ATR spe…
Simultaneous production of furfural and levulinic acid from pine sawdust via acid-catalysed mechanical depolymerization and microwave irradiation
2019
In this work pine sawdust was converted into levulinic acid (LA) and furfural. Sawdust was first pre-treated with sulfuric acid-catalysed mechanical depolymerization. The conversion reactions were then performed with microwave heating at 180 °C. To enhance the furfural yield and the efficient separation of furfural and LA, a biphasic water-toluene reaction system was used. The effect of an additional catalyst, AlCl3, on the yield of LA and furfural was also studied. According to the results the pre-treatment method enhanced the yields of LA. In addition, due to the microwave heating the reaction times were short. Additional AlCl3 catalyst enhanced the LA yield, however excellent furfural yi…
Syntactic complexity in Finnish-background EFL learners’ writing at CEFR levels A1–B2
2022
Eurooppalaisen viitekehyksen (EVK) merkitys kielikoulutukselle on lisännyt tutkimusta sen taitotasojen kielellisistä piirteistä; tarkempi tieto näistä piirteistä auttaisi EVK:n soveltamista opetusmateriaalien, kurssien ja arviointin laatimiseen. Tutkimuksessa selvitettiin eroavatko EVK:n tasot toisistaan syntaksin kompleksisuuden perusteella. Suomalaiset 14- ja 17-vuotiaat englannin oppijat (N=379) kirjoittivat kolme kirjoitelmaa, jotka arvioitiin EVK:n taitotasoille. Arviointiaineisto tutkittiin monitahoisella Rasch-analyysillä ja tekstien piirteet selvitettiin automaattisilla analyysiohjelmilla. Tuloksien perusteella alimpia EVK-tasoja (A1–A2) erotti selvimmin toisistaan lauseiden ja T-yk…
Solvent-mediated assembly of atom-precise gold–silver nanoclusters to semiconducting one-dimensional materials
2020
Bottom-up design of functional device components based on nanometer-sized building blocks relies on accurate control of their self-assembly behavior. Atom-precise metal nanoclusters are well-characterizable building blocks for designing tunable nanomaterials, but it has been challenging to achieve directed assembly to macroscopic functional cluster-based materials with highly anisotropic properties. Here, we discover a solvent-mediated assembly of 34-atom intermetallic gold–silver clusters protected by 20 1-ethynyladamantanes into 1D polymers with Ag–Au–Ag bonds between neighboring clusters as shown directly by the atomic structure from single-crystal X-ray diffraction analysis. Density fun…
Contextualization of Open Educational Resources in Asia and Europe
2014
Open Educational Resources (OER) are a promising concept for international collaborations: sharing, utilizing, and collaborating around OER across borders might help educational institutions and their staff to internationalize their activities. However, several barriers exist keeping stakeholders away from engaging in international collaborations. In this paper, we discuss the main challenges of OER uptake in international settings. Three case studies show potential solutions for OER uptake and collaboration in the European-Asian context. The case studies identify good practices, success factors and challenges. This paper provides a starting point for systematic analytical as well as design…
Overcoming Cultural Distance in Social OER Environments
2014
Open educational resources (OERs) provide opportunities as enablers of societal development, but they also create new challenges. From the perspective of content providers and educational institutions, particularly, cultural and context-related challenges emerge. Even though barriers regarding large-scale adoption of OERs are widely discussed, empirical evidence for determining challenges in relation to particular contexts is still rare. Such context-specific barriers generally can jeopardize the acceptance of OERs and, in particular, social OER environments. We conducted a large-scale (N = 855) cross-European investigation in the school context to determine how teachers and learners percei…
Precipitation and Calcination of High-Capacity LiNiO2 Cathode Material for Lithium-Ion Batteries
2020
This article presents the electrochemical results that can be achieved for pure LiNiO2 cathode material prepared with a simple, low-cost, and efficient process. The results clarify the roles of the process parameters, precipitation temperature, and lithiation temperature in the performance of high-quality LiNiO2 cathode material. Ni(OH)2 with a spherical morphology was precipitated at different temperatures and mixed with LiOH to synthesize the LiNiO2 cathode material. The LiNiO2 calcination temperature was optimized to achieve a high initial discharge capacity of 231.7 mAh/g (0.1 C/2.6 V) with a first cycle efficiency of 91.3% and retaining a capacity of 135 mAh/g after 400 cycles. These a…
Korpuspohjaista oppijansanakirjaa tekemässä: esimerkkinä ConLexis
2013
Artikkelimme kasittelee korpuspohjaisia oppijansanakirjoja. Sahkoisiin aineistoihin ja kielenkaytosta hankittuun tutkimukselliseen tietoon perustuvat sanakirjat ovat edelleen harvinaisia, ja kielenoppijoille niita on tarjolla hyvin vahan. Suomesta tallaisia sanakirjoja ei ole ollut lainkaan. Esittelemme yleisesti oppijoille suunnattujen sahkoisten sanakirjojen vaatimuksia ja tarkemmin uuden tekeilla olevan ConLexis-verkkosanakirjan suunnittelutyota, tavoitteita ja sisaltoa. ConLexis on suunnattu B1-tason ja sita edistyneemmille kielenoppijoille, mutta sita voivat opettajat kayttaa opetuksensa tukena alemmillakin taitotasoilla. Sana-artikkeleissa esitetty tieto perustuu laajoihin korpusanaly…