Hienopaperimassojen lujuusominaisuudet nopeassa vetokuormituksessa

Työssä verrattiin koivu-, akaasia- ja eucalyptussellujen käyttökelpoisuutta hienopapereiden kuituraaka-aineena. Kirjallisuusosassa todettiin radan hallinnan paperikoneiden avoimissa vienneissä riippuvan käytetyn geometrian lisäksi lujuus- ja relaksaatio-ominaisuuksista. Kuituverkoston käyttäytymiseen jännityksen alaisena vaikuttavat kuitudimensiot, kosteus ja lämpötila sekä kuituverkostoon kohdistetun jännityksen nopeus ja määrä. Relaksaationopeus ja vetolujuus kasvavat kuivilla papereilla vetonopeuden lisääntyessä. Kosteuspitoisuuden kasvattaminen alentaa puukuiduissa olevien polymeerien lasisiirtymälämpötilaa, jonka seurauksena vetolujuus ja relaksaatiokireys laskevat voimakkaasti. Kosteuspitoisuuden kasvaessa murtovenymä kasvaa lähes lineaarisesti ja repäisylujuus sekä murtotyö saavuttavat maksiminsa tietyssä kosteuspitoisuudessa. Kokeellisessa osassa keskityttiin hienopaperimassojen lujuus- ja relaksaatiokäyttäytymisen selvittämiseen nopeassa vetokuormituksessa. Lisäksi määritettiin laatu-, massa- ja rakenneominaisuuksia valituille koepisteille. Muuttujina kokeissa olivat massojen kuiva-ainepitoisuudet ja jauhatusolosuhteet sekä havusellun osuus hienopaperimassoissa.CSF-tasoon 350 ml jauhetuista näytteistä parhaat lujuus ja relaksaatio-ominaisuudet olivat koivulla ja heikoimmat akaasialla. Erot koepisteiden välillä korostuivat pienellä havusellun määrällä, mutta kaventuivat huomattavasti havusellun määrää lisättäessä. Samaan vetolujuuteen jauhettaessa massojen erot poistuvat kokonaan. Kuivilla näytteillä löydettiin erinomainen korrelaatio myötölujuuden ja relaksaatiokireyden välille. Puristinkuivien näytteiden relaksaatiokireyksiä voidaan kokeiden valossa ennustaa parhaiten kuivien näytteiden vetolujuuksista. Myös elastisten venymien osuuksille ja kuituseinämien paksuuksille löydettiin selvä yhteys.Eucalyptus- ja akaasiamassojen erinomaisuus hienopapereiden raaka-aineena korostui niiden optisissa ominaisuuksissa, erityisesti korkeana valonsirontana. Verrattaessa samassa vetolujuudessa ja relaksaatiokireydessä valonsirontakertoimien arvoja havaittiin akaasian olevan paras koivun jäädessä heikoimmaksi. Lisäksi akaasian ja eucalyptuksen kapeat kuitujakaumat ovat edullisia painokoneessa värin tasaisen imeytymisen kannalta. Akaasian pienet ja taipuisat kuidut antavat paperille tasaisen pinnan ja siten painatuksessa tasaisen painoalustan.

Mittaukset kostean höyryn turbiineille

Diplomityön tavoitteena oli selvittää Loviisan ydinvoimalaitoksen höyryturbiinin suoritus-kyvyn mittaamiseen käytettävissä olevia menetelmiä ja mittausjärjestelmiä. Tavoitteena oli selvittää mitkä tekijät aiheuttavat mittauksiin mittausvirheitä ja tutkia turbiineiden nykyisten mittalaitteiden epävarmuudet. Tässä diplomityössä selvitettiin millaisia standardinmukaisia testejä sekä muita varteenotettavia testejä turbiinin suorituskyvyn määrittämiseen on käytetty ja millaisia mittauksia ne vaativat. Lisäksi tutkittiin eri lähteistä millaisia mittalaitteita ja mittausjärjestelmiä voidaan käyttää turbiinin toiminnan mittauksiin. Soveltuvista mittausmenetelmistä esitettiin toimintaperiaatteet ja teoria. Kunnonvalvontaa varten esiteltiin värähtelyiden ja vääntö-momentin mittaamisen periaatteet. Epävarmuuksia arvioitiin mittalaitteiden teoreettisen epävarmuuden ja laitesijoittelun pohjalta. Työssä havaittiin, että suorituskyvyn arvioimiseksi on olemassa useita standardeja, mutta niiden mukaisiin mittauksiin tarvittaisiin nykyistä enemmän mittaustuloksia. Tarkkoja sekä luotettavia mittaustuloksia on haasteellista saada kaksifaasivirtauksesta. Mittalaitevalinnoilla ja mittalaitteiden määrää lisäämällä voidaan mittausten epävarmuutta pienentää. Loviisan ydinvoimalaitokselle ehdotettiin muutamia mittausjärjestelmiä turbiinin suoritus-kyvyn määrittämiseksi. Erityisesti turbiinin sisäiset olosuhteet tulisi määrittää nykyistä tarkemmin. Vääntömomentin mittaaminen olisi hyvä kunnonvalvonnan työkalu.

Siistausmassan saostuksessa kiekkosuodattimella käytettävän suodatinväliaineen testaus ja kehittäminen

Työn aiheena on siistausmassan saostuksessa käytettävä kiekkosuodatinväliaine ja tarkoituksena selvittää lankamateriaalien ja pinnoitusaineiden vaikutusta väliaineen likaantumisherkkyyteen ja suodatusteknisiin ominaisuuksiin. Siistauslaitosten ongelmana on suodatinväliaineen likaantuminen massassa olevien tahmo- ja painoväripartikkelien johdosta. Tällä hetkellä siistauslaitosten kiekkosuodatinpussien valmistuksessa käytetään pääasiassa polypropeeni- ja polyvinylideenifluoridimonofilamenttilankoja, joiden lianhylkivyys on osoittautunut huonoksi. Uusiksi lankamateriaaleiksi tutkimuksiin valittiin Easy Kleen I, Easy Kleen II, Hyflon, Halar ja Polyesteri. Tulosten perusteella Easy Kleen I ja II monofilamenttilangoista kudotun suodatinkankaan lianhylkivyys on polypropeeni- ja polyvinylideenifluoridimonofilamenttilangoista kudottua kangasta parempi. Suodatusteknisissä ominaisuuksissa ei materiaalien välillä havaittu merkittävää eroa. Easy Kleen monofilamenttilangat näyttävät soveltuvan myös keittokutistumiltaan ja mekaanisilta ominaisuuksiltaan kiekkosuodatinpussien materiaaleiksi. Polypropeeni- ja polyesterimonofilamenettilangoista kudottujen suodatinkankaiden pinnoittamisessa käytettiin hydrofiilisiä ja hydrofobisia pinnoitusaineita. Tulosten perusteella on mahdollista parantaa suodatinkankaan lianhylkivyyttä pinnoittamalla. Pinnoitettu kangas on myös suodatusteknisiltä ominaisuuksiltaan toimiva. Ongelmaksi suodatinkankaiden pinnoittamisessa saattaa kuitenkin muodostua pinnoituslämpötila, jossa kangas kutistuu asennuskelvottomaksi.

Simulation and optimization of IGCC technique for power generation and hydrogen production by using lignite Thar coal and cotton stalk

The purpose of this study was to simulate and to optimize integrated gasification for combine cycle (IGCC) for power generation and hydrogen (H2) production by using low grade Thar lignite coal and cotton stalk. Lignite coal is abundant of moisture and ash content, the idea of addition of cotton stalk is to increase the mass of combustible material per mass of feed use for the process, to reduce the consumption of coal and to increase the cotton stalk efficiently for IGCC process. Aspen plus software is used to simulate the process with different mass ratios of coal to cotton stalk and for optimization: process efficiencies, net power generation and H2 production etc. are considered while environmental hazard emissions are optimized to acceptance level. With the addition of cotton stalk in feed, process efficiencies started to decline along with the net power production. But for H2 production, it gave positive result at start but after 40% cotton stalk addition, H2 production also started to decline. It also affects negatively on environmental hazard emissions and mass of emissions/ net power production increases linearly with the addition of cotton stalk in feed mixture. In summation with the addition of cotton stalk, overall affects seemed to negative. But the effect is more negative after 40% cotton stalk addition so it is concluded that to get maximum process efficiencies and high production less amount of cotton stalk addition in feed is preferable and the maximum level of addition is estimated to 40%. Gasification temperature should keep lower around 1140 °C and prefer technique for studied feed in IGCC is fluidized bed (ash in dry form) rather than ash slagging gasifier

Development of filter media treatments for liquid filtration

Woven monofilament, multifilament, and spun yarn filter media have long been the standard media in liquid filtration equipment. While the energy for a solid-liquid separation process is determined by the engineering work, it is the interface between the slurry and the equipment - the filter media - that greatly affects the performance characteristics of the unit operation. Those skilled in the art are well aware that a poorly designed filter medium may endanger the whole operation, whereas well-performing filter media can make the operation smooth and economical. As the mineral and pulp producers seek to produce ever finer and more refined fractions of their products, it is becoming increasingly important to be able to dewater slurries with average particle sizes around 1 ¿m using conventional, high-capacity filtration equipment. Furthermore, the surface properties of the media must not allow sticky and adhesive particles to adhere to the media. The aim of this thesis was to test how the dirt-repellency, electrical resistance and highpressure filtration performance of selected woven filter media can be improved by modifying the fabric or yarn with coating, chemical treatment and calendering. The results achieved by chemical surface treatments clearly show that the woven media surface properties can be modified to achieve lower electrical resistance and improved dirt-repellency. The main challenge with the chemical treatments is the abrasion resistance and, while the experimental results indicate that the treatment is sufficiently permanent to resist standard weathering conditions, they may still prove to be inadequately strong in terms of actual use.From the pressure filtration studies in this work, it seems obvious that the conventional woven multifilament fabrics still perform surprisingly well against the coated media in terms of filtrate clarity and cake build-up. Especially in cases where the feed slurry concentration was low and the pressures moderate, the conventional media seemed to outperform the coated media. In the cases where thefeed slurry concentration was high, the tightly woven media performed well against the monofilament reference fabrics, but seemed to do worse than some of the coated media. This result is somewhat surprising in that the high initial specific resistance of the coated media would suggest that the media will blind more easily than the plain woven media. The results indicate, however, that it is actually the woven media that gradually clogs during the coarse of filtration. In conclusion, it seems obvious that there is a pressure limit above which the woven media looses its capacity to keep the solid particles from penetrating the structure. This finding suggests that for extreme pressures the only foreseeable solution is the coated fabrics supported by a strong enough woven fabric to hold thestructure together. Having said that, the high pressure filtration process seems to follow somewhat different laws than the more conventional processes. Based on the results, it may well be that the role of the cloth is most of all to support the cake, and the main performance-determining factor is a long life time. Measuring the pore size distribution with a commercially available porometer gives a fairly accurate picture of the pore size distribution of a fabric, but failsto give insight into which of the pore sizes is the most important in determining the flow through the fabric. Historically air, and sometimes water, permeability measures have been the standard in evaluating media filtration performance including particle retention. Permeability, however, is a function of a multitudeof variables and does not directly allow the estimation of the effective pore size. In this study a new method for estimating the effective pore size and open pore area in a densely woven multifilament fabric was developed. The method combines a simplified equation of the electrical resistance of fabric with the Hagen-Poiseuille flow equation to estimate the effective pore size of a fabric and the total open area of pores. The results are validated by comparison to the measured values of the largest pore size (Bubble point) and the average pore size. The results show good correlation with measured values. However, the measured and estimated values tend to diverge in high weft density fabrics. This phenomenon is thought to be a result of a more tortuous flow path of denser fabrics, and could most probably be cured by using another value for the tortuosity factor.

Factors affecting the usability of aspen (Populus tremula) wood dried at different temperature levels

In this dissertation the main aim was to study the usability of aspen wood in the mechanical wood processes, especially the factors that affect the usability of aspen wood, which is dried at different temperature levels. The problematic of varying temperatures from level to another seem to have significant effects on distortions. According to the studies conducted, many practical solutions for drying of aspen timber can be made. European aspen sawn timber should be dried in relatively narrow widths, short lengths, edged and sawn pith free. The results achieved give an interesting view for the distortions of aspen wood between HT drying and heat treatment. The most significant result is that cupping seems to decrease when increasing temperature level from HT drying to heat treatment phase. The difference is significant. Other very obvious result is that bow and crook are increasing between these two temperature levels, bow significantly. Also the modelling gives a good background for this result since cupping is reduced by higher temperatures. It can also be assumed that these distortions can be affected for example by sorting out the timber used to different moisture levels before drying. This could be a very simple solution for practical purposes. From practical point of view, it was also noted during the drying tests performed that the discoloration seem to be no problem for aspen boards dried in temperatures under 150 °C. Altogether, this dissertation covers many interesting points of view of factors affecting distortions of wood in different temperature stages. Aspen as species in use of mechanical wood industries seems to be a species suitable for component production. According to the results, the best yield from aspen timber can be achieved in industry that can utilize relatively short components of sawn wood. Results achieved give a significant indication about the factors affecting distortions of wood at different temperature stages of drying, especially considering European aspen.

Replacing Copper with New Carbon Nanomaterials in Electrical Machine Windings

Electrical machines have significant improvement potential. Nevertheless, the field is characterized by incremental innovations. Admittedly, steady improvement has been achieved, but no breakthrough development. Radical development in the field would require the introduction of new elements, such that may change the whole electrical machine industry system. Recent technological advancements in nanomaterials have opened up new horizons for the macroscopic application of carbon nanotube (CNT) fibres. With values of 100 MS/m measured on individual CNTs, CNT fibre materials hold promise for conductivities far beyond those of metals. Highly conductive, lightweight and strong CNT yarn is finally within reach; it could replace copper as a potentially better winding material. Although not yet providing low resistivity, the newest CNT yarn offers attractive perspectives for accelerated efficiency improvement of electrical machines. In this article, the potential for using new CNT materials to replace copper in machine windings is introduced. It does so, firstly, by describing the environment for a change that could revolutionize the industry and, secondly, by presenting the breakthrough results of a prototype construction. In the test motor, which is to our knowledge the first in its kind, the presently most electrically conductive carbon nanotube yarn replaces usual copper in the windings.

A Research of Resource Scheduling Algorithm Based on Hadoop

With the development of electronic devices, more and more mobile clients are connected to the Internet and they generate massive data every day. We live in an age of “Big Data”, and every day we generate hundreds of million magnitude data. By analyzing the data and making prediction, we can carry out better development plan. Unfortunately, traditional computation framework cannot meet the demand, so the Hadoop would be put forward. First the paper introduces the background and development status of Hadoop, compares the MapReduce in Hadoop 1.0 and YARN in Hadoop 2.0, and analyzes the advantages and disadvantages of them. Because the resource management module is the core role of YARN, so next the paper would research about the resource allocation module including the resource management, resource allocation algorithm, resource preemption model and the whole resource scheduling process from applying resource to finishing allocation. Also it would introduce the FIFO Scheduler, Capacity Scheduler, and Fair Scheduler and compare them. The main work has been done in this paper is researching and analyzing the Dominant Resource Fair algorithm of YARN, putting forward a maximum resource utilization algorithm based on Dominant Resource Fair algorithm. The paper also provides a suggestion to improve the unreasonable facts in resource preemption model. Emphasizing “fairness” during resource allocation is the core concept of Dominant Resource Fair algorithm of YARM. Because the cluster is multiple users and multiple resources, so the user’s resource request is multiple too. The DRF algorithm would divide the user’s resources into dominant resource and normal resource. For a user, the dominant resource is the one whose share is highest among all the request resources, others are normal resource. The DRF algorithm requires the dominant resource share of each user being equal. But for these cases where different users’ dominant resource amount differs greatly, emphasizing “fairness” is not suitable and can’t promote the resource utilization of the cluster. By analyzing these cases, this thesis puts forward a new allocation algorithm based on DRF. The new algorithm takes the “fairness” into consideration but not the main principle. Maximizing the resource utilization is the main principle and goal of the new algorithm. According to comparing the result of the DRF and new algorithm based on DRF, we found that the new algorithm has more high resource utilization than DRF. The last part of the thesis is to install the environment of YARN and use the Scheduler Load Simulator (SLS) to simulate the cluster environment.

Calibration of time domain reflectometry (DTR) for soil moisture measurements in cultivated peat soils

Tiivistelmä: TDR-mittausten kalibrointi viljeltyjen turvemaiden kosteuden mittaamiseen

Interaction of prechilling, temperature, osmotic stress, and light in Picea abies seed germination

Summary

Soil temperature regimes in Finland

Selostus: Maan lämpötila Suomessa