Quantitative characterization of pore structure of several biochars with 3D imaging

Pore space characteristics of biochars may vary depending on the used raw material and processing technology. Pore structure has significant effects on the water retention properties of biochar amended soils. In this work, several biochars were characterized with three-dimensional imaging and image analysis. X-ray computed microtomography was used to image biochars at resolution of 1.14 $\mu$m and the obtained images were analysed for porosity, pore-size distribution, specific surface area and structural anisotropy. In addition, random walk simulations were used to relate structural anisotropy to diffusive transport. Image analysis showed that considerable part of the biochar volume consist of pores in size range relevant to hydrological processes and storage of plant available water. Porosity and pore-size distribution were found to depend on the biochar type and the structural anisotopy analysis showed that used raw material considerably affects the pore characteristics at micrometre scale. Therefore attention should be paid to raw material selection and quality in applications requiring optimized pore structure.Comment: 16 pages, 4 figures. The final publication is available at Springer via http://dx.doi.org/10.1007/s11356-017-8823-

Decision Support Tool for Tree Species Selection in Forest Regeneration Based on Harvester Data

Precision forestry—i.e., the division of a stand to smaller units and managing of the stand at a micro-stand level—provides new possibilities to increase forest growth, arrange forest stand structure and enhance forest health. In the regeneration phase by adjusting the tree species selection, soil preparation, intensity of regeneration measures (method, planting density, and material), and young stand management procedures according to precise information on soil properties (e.g., site fertility, wetness, and soil type) and microtopography will inevitably lead to an increase in growth of the whole stand. A new approach to utilizing harvester data to delineate micro-stands inside a large forest stand and to deciding the tree species to plant for each micro-stand was piloted in central Finland. The case stands were situated on Finsilva Oyj forest property. The calculation of the local growth (m3/ha/year) for each 16 × 16-m grid cell was based on the height of the dominant trees and the stand age of the previous tree generation. Tree heights and geoinformation were collected during cutting operation as the harvester data, and the dominant height was calculated as the mean of the three largest stems in each grid cell. The stand age was obtained from the forest management plan. The estimated local growth (average of nine neighboring grid cells) varied from 3 to 14 m3/ha/year in the case stands. When creating micro-stands, neighboring grid cells with approximately the same local growth were merged. The minimum size for an acceptable micro-stand was set to 0.23 ha. In this case study, tree species selection (Scots pine or Norway spruce) was based on the mean growth of each micro-stand. Different threshold values, varying from 6 to 8 m3/ha/year, were tested for tree species change, and they led to different solutions in the delineation of micro-stands. Further stand development was simulated with the Motti software and the net present values (NPVs (3%)) for the next rotation were estimated for different micro-stand solutions. The mixed Norway spruce–Scots pine stand structure never produced a clearly economically inferior solution compared to the single species stand, and in one case out of six, it provided a distinctly better solution in terms of NPV (3%) than the single species option did. Our case study showed that this kind of method could be used as a decision support tool at the regeneration phase

Decision Support Tool for Tree Species Selection in Forest Regeneration Based on Harvester Data

Precision forestry—i.e., the division of a stand to smaller units and managing of the stand at a micro-stand level—provides new possibilities to increase forest growth, arrange forest stand structure and enhance forest health. In the regeneration phase by adjusting the tree species selection, soil preparation, intensity of regeneration measures (method, planting density, and material), and young stand management procedures according to precise information on soil properties (e.g., site fertility, wetness, and soil type) and microtopography will inevitably lead to an increase in growth of the whole stand. A new approach to utilizing harvester data to delineate micro-stands inside a large forest stand and to deciding the tree species to plant for each micro-stand was piloted in central Finland. The case stands were situated on Finsilva Oyj forest property. The calculation of the local growth (m3/ha/year) for each 16 × 16-m grid cell was based on the height of the dominant trees and the stand age of the previous tree generation. Tree heights and geoinformation were collected during cutting operation as the harvester data, and the dominant height was calculated as the mean of the three largest stems in each grid cell. The stand age was obtained from the forest management plan. The estimated local growth (average of nine neighboring grid cells) varied from 3 to 14 m3/ha/year in the case stands. When creating micro-stands, neighboring grid cells with approximately the same local growth were merged. The minimum size for an acceptable micro-stand was set to 0.23 ha. In this case study, tree species selection (Scots pine or Norway spruce) was based on the mean growth of each micro-stand. Different threshold values, varying from 6 to 8 m3/ha/year, were tested for tree species change, and they led to different solutions in the delineation of micro-stands. Further stand development was simulated with the Motti software and the net present values (NPVs (3%)) for the next rotation were estimated for different micro-stand solutions. The mixed Norway spruce–Scots pine stand structure never produced a clearly economically inferior solution compared to the single species stand, and in one case out of six, it provided a distinctly better solution in terms of NPV (3%) than the single species option did. Our case study showed that this kind of method could be used as a decision support tool at the regeneration phase

Characterization of biochar pore structure with X-ray tomography

Biochar use as soil amendment can influence both physical and chemical properties of soil. The effects of biochar depend on the raw material from which biochar is derived as well as on the used processing technology and process conditions. One commonly highlighted benefit of biochar application is improved water retention properties of soil. Biochar may affect water retention in direct or direct way. In direct mechanism water is stored and held in the biochar pores while in indirect mechanisms biochar contributes to the soil structural development (aggregation). Please click on the file below for full content of the abstract

Electrical impedance and image analysis methods in detecting and measuring Scots pine heartwood from a log end during tree harvesting

Scots pine (Pinus sylvestris L.) heartwood is naturally durable wood material which has not been fully utilized in the wood industry. Currently, there are no practical measurement methods for detecting and measuring heartwood in a tree harvesting. The objective of this study was to evaluate the applicability of an electrical impedance spectroscopy and an image analysis of a log end face for pine heartwood measurements from the harvesting perspective. Both methods were tested with a fresh wood material which was collected during the harvesting operations. The results indicate that both methods have potential to measure the heartwood from processed stems with an average heartwood diameter error being less than two centimeters for each method. However, the image analysis of the log end face is only appropriate when visible contrast between the heartwood and a sapwood exists. Our findings indicate that the studied heartwood detection methods show great potential in measuring the heartwood of the stem in the harvesting phase which would ideally benefit later links in wood value chains.Peer reviewe

Atomic Structure of a Spinel-Like Transition Al2O3(100) Surface

We study a crystalline epitaxial alumina thin film with the characteristics of a spinel-type transition Al2O3(100)surface by using atom-resolved noncontact atomic force microscopy and density functional theory. It is shown that the films are terminated by an Al-O layer rich in Al vacancies, exhibiting a strong preference for surface hydroxyl group formation in two configurations. The transition alumina films are crystalline and perfectly stable in ambient atmospheres, a quality which is expected to open the door to new fundamental studies of the surfaces of transition aluminas.Peer reviewe

Assessing extraction trail trafficability using harvester CAN-bus data

Modern forest machines with a Controlled Area Network (CAN)-bus managed diesel engine and hydrostatic transmission can continuously measure power expended in traveling. At a constant speed on level ground, the power is expended in overcoming motion resistance, which is directly related to wheel sinkage and hence to site trafficability. In cut-to-length timber harvesting, the harvester precedes the forwarder on the site, making it feasible to utilize the harvester to collect data on site trafficability to produce a trafficability map for the forwarder. CAN-bus trafficability mapping was tested with an 8-wheeled Ponsse Scorpion King harvester and an 8-wheeled Ponsse Elk forwarder instrumented for collecting transmission power expenditure, in addition to appropriate available CAN-bus information. Trafficability was also mapped based solely on momentary engine power in order to eliminate the need for additional pressure transducers. The CAN-bus data showed good results for mapping site trafficability when compared to soil penetration resistance and harvesting machinery wheel rut depth measurements. Assessing harvester rolling resistance using CAN-bus data offers an interesting possibility to map harvesting site trafficability also in Big Data scale. Since modern harvesters are practically ready for indirect power recording, the additional cost of fully automated and comprehensive trafficability mapping as part of operative forestry is negligible.202

Dynamic forest trafficability prediction by fusion of open data, hydrologic forecasts and harvester-measured data

FOTETRAF project: www.luke.fi/projektit/fotetraf-sa-paatos-295337. Posteri esillä Marcus Wallenberg-palkintoseremonian yhteydessä pidettävässä nuorten tutkijoiden seminaarissa 26-27.10.2017 Tukholmassa (http://www.mwp.org/yr/).201

Fabrication and characterization of vacuum deposited fluorescein thin films

Simple vacuum evaporation technique for deposition of dyes on various solid surfaces has been developed. The method is compatible with conventional solvent-free nanofabrication processing enabling fabrication of nanoscale optoelectronic devices. Thin films of fluorescein were deposited on glass, fluorine-tin-oxide (FTO) coated glass with and without atomically layer deposited (ALD) nanocrystalline 20 nm thick anatase TiO2 coating. Surface topology, absorption and emission spectra of the films depends on their thickness and the material of supporting substrate. On a smooth glass surface the dye initially formes islands before merging into a uniform layer after 5 to 10 monolayers. On FTO covered glass the absorption spectra are similar to fluorescein solution in ethanol. Absorption spectra on ALD-TiO2 is red shifted compared to the film deposited on bare FTO. The corresponding emission spectra at {\lambda} = 458 nm excitation show various thickness and substrate dependent features, while the emission of films deposited on TiO2 is quenched due to the effective electron transfer to the semiconductor conduction band.Comment: 24 pages including 5 figure

Vapour phase deposition of dye sensitizer

Uusiutuvat energiamuodot ja aurinkosähkö ovat kuuma puheenaihe. Myös tutkimustyö tällä saralla on ollut kiivasta viime vuosikymmeninä ja tuloksena on syntynyt esimerkiksi väriaineherkistetyt aurinkokennot. Nämä aurinkokennot voivat olla halpa ratkaisu tulevaisuuden päästöttömään energiantuotantoon, mutta näissä aurinkokennoissa käytetyt valolle herkät väriaineet voivat antaa myös uusia mahdollisuuksia molekyylielektroniikan saralle ja tuleviin nanomittaluokan sovelluksiin. Väriaineiden laajempi käyttö vaatii kuitenkin uudenlaisten värjäysmetodien kehittämistä. Tässä työssä keskityttiinkin väriainehöyrystimen kehittämiseen ja testaamiseen. Työn alussa tehdään katsaus väriaineisiin ja käydään läpi höyrystämiseen liittyvää teoriaa, kuten filmin muodostumisnopeutta ja erilaisia kasvumoodeja. Tämän jälkeen tutustutaan väriaineherkistettyihin aurinkokennoihin, niiden toimintamekanismiin ja valmistukseen, jonka jälkeen tarkastellaan kiinteän väriaineen mahdollistamia ratkaisuja ja niiden toimintaperiaatetta. Seuraavassa luvussa käydään läpi värihöyrystimen kehityskaari sekä nykyinen laitteisto kaaviokuvineen. Samalla esitetään myös suoritetut kalibraatiotoimenpiteet sekä lämpö- että paksuusmittarille, ja kuvataan värin höyrystysprosessi. Näytteenvalmistus- ja tarvittavat litografiaprosessit käydään läpi eri näytetyypeille ja käytetyt mittausjärjestelyt kytkentäkaavioineen ja laitteistoineen kuvataan. Absorptiospektrien avulla varmistettiin, että väriaine höyrystyy näytteelle. Kiinteän värin spektriä myös verrattiin nesteeseen liuotettuun väriin. Emissiospektrien mittauksella todennettiin, että väri selviää höyrystysprosessista ja on täten vielä aktiivista. Näytteet osoittivat myös valosähköisiä ominaisuuksia. Värjättyjen näytteiden johtavuus parani, kun niitä valaistiin. Vaikutuksen voimakkuus korreloi näytteen absorptiospektrin kanssa. Myös hystereesisefekti oli huomattavissa: tasajännitepyyhkäisyn (negatiivisesta positiiviseen) tuloksena näytteen vastus kasvoi mikä huomattiin takaisin pyyhkäisyn aikana. Vaikutus kuitenkin pystyttiin tuhoamaan nopeasti tarpeeksi suurella negatiivisella jännitteellä. Höyrystysmetodi todettiin toimivaksi ratkaisuksi ja täten värjääminen voidaan ottaa osaksi litografiaprosessia. Tämä mahdollistaa väriherkistetyt mikro- ja nanorakenteet jotka omaavat edellä kuvatun kaltaisia valosähköisiä ominaisuuksia. Projekti tehtiin yhteistyössä Jyväskylän yliopiston professori Jouko Korppi-Tommolan fysikaalisen kemian ryhmän kanssa.Dye-sensitized solar cells (DSSC) have been investigated widely in last two decades and the research work has led to good results. Nowadays DSSCs are relatively efficient, but a problem is the long term stability and manufacturing. These dyes used in DSSCs would also give multiple possibilities to nanoapplications, but the typical sensitization method, soaking in solution, doesn’t work with nanofabrication. However increasing interest towards the molecular engineering has already developed different kind of molecule deposition methods. Anyway, these methods being relatively simple, don’t suit mass production and don’t allow to control the deposited layer thickness. The main objective of this thesis was the development a vacuum evaporation method for deposition of dye sensitizer molecules on PMMA-masked metal-oxide structures. This was done in high vacuum conditions where dye was sublimated in heated crucible at temperature range 145-160 C forming a gaseous jet of molecules from the evaporation chamber into the pumped target chamber. Thickness of the deposited dye layer was controlled by the crystal deposition controller that was calibrated with the AFM. Dye deposition were applied to TiO2 and FTO based components that showed spectral response according to the dye absorption spectra. Photo-electric properties of these components were also measured. Illumination affected the samples during the AC and DC measurements by reducing their resistance. The effect was found to be wavelength dependent and corresponding to the absorption spectrum of the samples. The method proved to be usable method for integration of dye sensitizers to conventional lithographical fabrication in order to develop dye based light sensitive micro and nano sized electronics. Research of these new possible structures can give us an information about dye-oxide interactions which could benefit the development of DSSCs. They could also provide knowledge of the spectra of the pure dye without any solvent, quantum effects in dye and maybe even serve as a single photon detector. This project was done in collaboration with Prof. Jouko Korppi-Tommola’s group from the department of Chemistry of the University of Jyväskylä. A confocal microscope was operated by Teemu Ihalainen from the department of Biological and Environmental Science of the University of Jyväskylä