Photoswitchable Superabsorbency Based on Nanocellulose Aerogels

Chemical vapor deposition of a thin titanium dioxide (TiO₂) film on lightweight native nanocellulose aerogels offers a novel type of functional material that shows photoswitching between water‐superabsorbent and water‐repellent states. Cellulose nanofibrils (diameters in the range of 5–20 nm) with native crystalline internal structures are topical due to their attractive mechanical properties, and they have become relevant for applications due to the recent progress in the methods of their preparation. Highly porous, nanocellulose aerogels are here first formed by freeze‐drying from the corresponding aqueous gels. Well‐defined, nearly conformal TiO₂ coatings with thicknesses of about 7 nm are prepared by chemical vapor deposition on the aerogel skeleton. Weighing shows that such TiO₂‐coated aerogel specimens essentially do not absorb water upon immersion, which is also evidenced by a high contact angle for water of 140° on the surface. Upon UV illumination, they absorb water 16 times their own weight and show a vanishing contact angle on the surface, allowing them to be denoted as superabsorbents. Recovery of the original absorption and wetting properties occurs upon storage in the dark. That the cellulose nanofibrils spontaneously aggregate into porous sheets of different length scales during freeze‐drying is relevant: in the water‐repellent state they may stabilize air pockets, as evidenced by a high contact angle, in the superabsorbent state they facilitate rapid water‐spreading into the aerogel cavities by capillary effects. The TiO₂‐coated nanocellulose aerogels also show photo‐oxidative decomposition, i.e., photocatalytic activity, which, in combination with the porous structure, is interesting for applications such as water purification. It is expected that the present dynamic, externally controlled, organic/inorganic aerogels will open technically relevant approaches for various applications.     

Quality inspection of metal surfaces by diffractive optical element-based glossmeter

Planar, convex and concave metal surfaces were produced by utilizing finishing processes that are exploited in the production of tools for plastics injection molding. A novel glossmeter, the so-called diffractive optical element-based glossmeter (DOG), was used for the inspection of the gloss of the surfaces. The Society of the Plastics Industry (SPI) A1 standard, which has the lowest surface roughness of such standards, served as a reference for the success of the finishing process. The results show that by using DOG we can gain local microscopic and macroscopic information on the gloss and its variation. The DOG is sufficiently sensitive to detect small gloss variation as well as the texture of the surface, e.g. anisotropy in surface marks. Some of the surfaces in this study have a higher surface quality than the A1 surface.     

Optimization of nuclear reactor strategies under uncertainty

Operations research is applied to analysing uncertainties in the selection of nuclear reactor types. Dynamic programming methods have been extended to account for uncertain decision factors by including in the objective function a variance-related uncertainty factor as well as expected cost values. A technique is also described for obtaining total cost probability distributions. A case study is presented which uses the method to analyze a long-term planning problem for a given electric utility system. This problem is also solved by using fuzzy programming methods.     

Risk-benefit evaluation of nuclear power plant siting

An assessment scheme is described for the risk-benefit analyses of nuclear power versus conventional alternatives. Given the siting parameters for the proposed nuclear plant an economic comparison is made with the most advantageous competitive conventional production scenario. The economic benefit is determined from the differential discounted annual energy procurement cost as a function of the real interest rate and amortization time. The risk analysis encompasses following factors: radiation risks in normal operation, reactor accident hazards and economic risks, atmospheric pollutants from the conventional power plants and fuel transportation. The hazards are first considered in terms of probabilistic dose distributions. In the second stage risk components are converted to a compatible form where excess mortality is used as the risk indicator. Practical calculations are performed for the power production alternatives of Helsinki where district heat would be extracted from the nuclear power plant. At the real interest rate of 10% and amortization time of 20 yr the 1000 MW(e) nuclear option is found to be $9.1 m per yr more economic than the optimal conventional scenario. Simultaneously the nuclear alternative is estimated to reduce excess mortality by 2–5 fatal injuries annually.     

Preventing chlorine deposition on heat transfer surfaces with aluminium-silicon rich biomass residue and additive

Biomass fuels often contain higher concentrations of easily vaporisable alkalis and chlorine than do coal and peat. The more vaporisable the alkalis or chlorine compounds the higher is the risk for ash-related problems. The presence of certain elements may reduce or remove these problems. This work shows how co-combusting of different biomass fuels in a fluidised bed boiler can result in useful interactions that decrease or totally inhibit Cl deposition and bed agglomeration. In a first set of experiments, fuel 1 contained easily vaporised chlorine that produces Cl-rich deposits on superheaters. Fuel 2 was enriched in aluminium silicate, but contained much ash, resulting in low heating value and high load of fly ash. In a second set of experiments, fuel 1 was enriched in Cl and alkalis, which lead to corrosive deposits, bed agglomeration and fouling. As a result of protecting reactions, the mixtures were free from the problems observed during their separate combustion.     

Supported iridium catalysts prepared by atomic layer deposition: effect of reduction and calcination on activity in toluene hydrogenation

Ligand removal from supported iridium catalysts prepared by atomic layer deposition from Ir(acac)₃ was studied by direct reduction in hydrogen flow and by calcination in oxygen flow followed by reduction in hydrogen flow, as well as by thermogravimetric analysis. Thermal decomposition of acac ligand residuals required high temperatures, and in samples containing no iridium the removal of carbonaceous species was not complete. Metallic iridium particles less than 2 nm in size were formed during direct reduction and larger particles upon calcination followed by reduction. The activity of the catalysts in toluene hydrogenation in most cases depended on particle size.     

Interest in energy wood and energy crop production among Finnish non-industrial private forest owners

EU targets and regulations regarding energy production and the reduction of greenhouse gas emissions have been tightening in the 2000s. In Finland the targets are planned to be achieved mainly by increasing the use of biomass. Wood already accounts for a marked proportion of Finnish energy production, but additional reserves are still available. Energy crop production also has considerable potential. Practically all Finnish farmers are also forest owners. Therefore, private forest owners are in a decisive position regarding the supply of energy wood and crops in Finland. In this paper the future supply of biomass is examined according to their past behaviour, intentions and attitudes. Finnish forest owners have a positive attitude towards the use of wood and crops in energy production. Price is becoming more critical as a motive for the supply of energy wood. Recreation and nature conservation play a smaller role than factors related to wood production and forest management as for motives for harvesting energy wood. However, almost a half of forest owners in this study were uncertain of their willingness to supply biomass. This is partly due to limited knowledge of the issues involved in energy wood and agricultural energy crop production and the underdeveloped markets for energy biomass. In order to achieve the targets, supply should be activated by further developing market practices, information, guidance and possibly other incentives for landowners. In general, there is interest among landowners in increasing the supply of energy biomass. However, the growth of supply presumes that production is an economically attractive and competitive alternative, that the markets are better organized than at present, and that more comprehensive information is available about bioenergy and biomass markets and production techniques.     

Energy conversion efficiency of the pumping kite wind generator

This paper is devoted to analytical modelling and numerical simulation of the so-called pumping kite wind generator whose operating principle is to mechanically drive a groundbased electric generator using tethered kites. On the basis of the refined crosswind motion law, the mathematical model of steady crosswind motion of the tethered kite is constructed. Necessary conditions for optimality of the mean mechanical power functional are derived. Optimal control of the tether length rate is studied for the cases of open-loop and closed-loop figure-of-eight trajectories. The performance coefficient of the pumping kite wind generator is introduced. Simple formulas for the mechanical power output are obtained.     

Optical analysis of adsorption sensitivity of titanium, Ti-6Al-4V, and Ti-35Nb-6Ta

Here we report the optical analysis of protein adsorption sensitivity of titanium (Ti), Ti(6)Al(4)V, and Ti(35)Nb(6)Ta. The optical sensor used was a diffractive optical element based sensor, which analyzes magnitude and coherence of probe beam reflected from the measured surfaces. Also, the roughness and other necessary parameters were taken into account on the final verdict. The material Ti(35)Nb(6)Ta showed positive initial reaction to the human plasma fibrinogen, which was the protein used. The Ti(35)Nb(6)Ta was observed to be more active than the grade 2 titanium.