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This chapter describes a nonparametric Bayesian approach to the estimation of curves and surfaces that act as parameters in statistical models. The approach is based on mixing variable dimensional piecewise constant approximations, whose ‘smoothness’ is regulated by a Markov random field prior. Random partitions of the domain are defined by Voronoi tessellations of random generating point patterns. Variable dimension Markov chain Monte Carlo methods are proposed for the numerical estimation, and a detailed algorithm is specified for one special case. General applicability of the approach is discussed in the context of density estimation, regression and interpolation problems, and an application to the intensity estimation for a spatial Poisson point process is presented.

To study the poorly known fire history of Larix-dominated forest in central Siberia, we collected samples from 200 trees in 46 systematically located study plots. Our study area stretches ~90 km from north to south along the River Nizhnyaya Tunguska in northern Irkustk district. Cross-dated tree-ring chronology for all samples combined extended from the year 1360 AD to the present and included 76 fire years and 88 separate fire events. Average fire cycle gradually lengthened from 52 years in the 18th century to 164 years in the 20th century. During the same time, the number of recorded fires decreased even more steeply, i.e. by more than 85%. Fires were more numerous but smaller in the past. Contrary to expectations, climate change in the 20th century has not resulted in increased forest fires in this region. Fire suppression may have contributed to the scarcity of fires since the 1950s. However, a significant decline in fires was evident earlier; therefore an additional explanation is required, a reduction in human-caused ignitions being likely in the light of historical accounts.

A flexible Bayesian method is suggested for the pair potential estimation with a high-dimensional parameter space. The method is based on a Bayesian smoothing technique, commonly applied in statistical image analysis. For the calculation of the posterior mode estimator a new Monte Carlo algorithm is developed. The method is illustrated through examples with both real and simulated data, and its extension into truly nonparametric pair potential estimation is discussed.

Results from an experimental study of electric and/or ultrasonic field assisted filtration are presented. Both electric and ultrasonic fields can reduce fouling of the filtration medium and have significant influence on filtration capacity. The extent of filtration improvement is affected mostly by particle size, surface charge, acoustic frequency, and field strengths. Theoretical examinations of the use of electric field and/or ultrasonic field to enhance filtration efficiency were laid out. Some aspects regarding orthokinetic interaction in acoustic agglomeration were considered. Energy consumptions of the filtrations of different suspensions used in experiments were also determined. For pyrite suspension the best results with ultrasound were obtained when filtration was done as follows: 15‐s negative pressure filtration, 15‐s negative pressure filtration with 22‐kHz ultrasonic burst (0.5 s) and 20‐s drying with negative pressure. In this case the moisture content of cake was 7% while in the reference c...

SUMMARY A common method of studying biogeographical ranges is an atlas survey, in which the research area is divided into a square grid and the data consist of the squares where observations occur. Often the observations form only an incomplete map of the true range, and a method is required to decide whether the blank squares indicate true absence or merely a lack of study there. This is essentially an image restoration problem, but it has properties that make the common empirical Bayesian procedures inadequate. Most notably, the observed image is heavily degraded, causing difficulties in the estimation of spatial interaction, and the assessment of reliability of the restoration is emphasized. A fully Bayesian approach is suggested, its implementation and practical properties are discussed and the procedure is applied to data from an atlas survey of Finnish herpetofauna.

Tässä julkaisussa esitetään valtakunnan metsien yhdeksänteen inventointiin (VMI9) perustuvat Etelä-Pohjanmaan metsäkeskuksen alueen metsävaratiedot ja niiden muutokset 1968–97 sekä analysoidaan muutosten syitä. Lisäksi artikkelissa kuvataan VMI:n maastomittaus, tuloslaskenta ja luotettavuuden arviointimenetelmät.

I denna artikel presenteras resultaten för den nionde riksskogstaxeringen (RST9) på Åland. Förändringar i resultat från början av sextiotalet samt deras orsaker granskas och analyseras. Ytterligare presenteras metoderna för sampling, fältmätningar och resultatberäkning i stora drag. En mera detaljerad beskrivning av mätningar och resultatberäkning ingår i en tidigare utkommen artikel, med inventeringsresultaten från södra Österbotten (Metsätieteen aikakauskirja 2B/1998). Mätningar och placering av provytorna ändrades i syfte att effektivisera den nionde inventeringen. Ålands landskapsstyrelse finansierade delvis inventeringen, vilket möjliggjorde en uppmätning av dubbla tätheten provytor jämfört med till exempel Syd-Västra Finland.

I föreliggande publikation presenteras på den nionde riksskogstaxeringen (RST9) grundade uppgifter om skogstillgångarna inom Kustens skogscentral och förändringar inom dessa 1965–1998, samt ges en analys av orsakerna till förändringarna. Ytterligare ges en allmän beskrivning av samplingsmetoden i artikeln. Taxeringens samplingsdesign, fältmätningarna och uträkningen av resultaten utvecklades särskilt för den nionde taxeringen. En redogörelse för metoden har getts i samband med publiceringen av resultaten för Södra Österbotten (Metsätieteen aikakauskirja 2B/1998). Kustens skogscentral bildades av de svenskspråkiga tidigare skogsnämnderna Helsingfors och Österbotten. Dessa områden skiljer sig från varandra såväl ifråga om växtbetingelser som beståndsstruktur. Därför analyseras även resultaten för regionerna Sydkusten och Österbotten separat. Vardera regionen präglas av ett maritimt klimat. Ett för region Österbotten speciellt drag är dessutom den snabba landhöjningen.

Tässä julkaisussa esitetään valtakunnan metsien yhdeksänteen inventointiin (VMI9) perustuvat Keski-Suomen metsäkeskuksen alueen metsävaratiedot ja niiden muutokset 1967–1996 sekä analysoidaan muutosten syitä. Lisäksi artikkelissa kuvataan yleispiirteet otantamenetelmästä ja tuloslaskennasta sekä maastomittaukset niiltä osin kuin ne poikkeavat aiemmin julkaistuista Etelä-Pohjanmaan metsäkeskuksen alueen mittauksista. Inventoinnin otantamenetelmää, maastomittauksia ja tuloslaskentaa kehitettiin yhdeksättä inventointia varten. Menetelmä on kuvattu yksityiskohtaisesti Etelä-Pohjanmaan tulosjulkaisun yhteydessä.

Tässä julkaisussa esitetään valtakunnan metsien yhdeksänteen inventointiin (VMI9) perustuvat Pohjois-Savon metsäkeskuksen alueen metsävaratiedot ja niiden muutokset 1967–1996 sekä analysoidaan muutosten syitä. Lisäksi artikkelissa kuvataan yleispiirteet otantamenetelmästä ja tuloslaskennasta sekä maastomittaukset niiltä osin kuin ne poikkeavat aiemmin julkaistuista Etelä-Pohjanmaan metsäkeskuksen alueen mittauksista. Inventoinnin otantamenetelmää, maastomittauksia ja tuloslaskentaa kehitettiin yhdeksättä inventointia varten. Menetelmä on kuvattu yksityiskohtaisesti Etelä-Pohjanmaan tulosjulkaisun yhteydessä.

Most chemists regard sonochemistry as a relatively new branch of chemistry.However, applications of power ultrasound in polymer science date back to the 1930s when sonication of some natural polymers was discovered to reduct viscosity.After that ultrasonication has proved to be a very advantageous method for depolymerization of macromolocules because it simply reduces their molecular weight by splitting the most susceptible chemical bond without causing any changes in the chemical nature of the polymer.It is now well established that the prolonged exposure of solutions of macromolecules to high-energy ultrasonic waves produces a permanent reduction in the solution viscosity.The aim of the present work was to study the effect of ultrasonic input power, ultrasonic frequency and solution concentration on the degradation of polyvinyl alcohol in the aqueous solution.