The effect of microfibrillated cellulose addition on drying shrinkage and dimensional stability of wood-free paper

Microfibrillated cellulose (MFC) is known to enhance strength properties of paper. Improved strength usually means increased bonding which is strongly connected to dimensional instability of paper. Dimensional instability is due to changes in moisture content of paper; when paper is moistened it expands and when dried, it shrinks. Hygroexpansion is linked to end-use problems and excessive drying shrinkage consumes strength potential. Effective use of materials requires controlling of these phenomena. There isn’t yet data concerning dimensional stability of papers containing MFC which restricts wider use of MFC. Main objective of the work was to evaluate dimensional stability of wood-free paper containing different amounts of MFC. Sheets were dried with different methods to see how drying strains effected on drying shrinkage and hygroexpansion. Also tensile strength was measured to find out the effect of MFC. Results were compared to sheets containing kraft fines and in some test points cationic starch was used alongside with MFC. MFC increased the dimensional instability of freely dried sheets. As the amounts of MFC increased the effects on dimensional stability became more severe. However the fineness of MFC didn’t play any important role. Both hygroexpansion and drying shrinkage were decreased with cationic starch addition. Prevention of drying shrinkage over powered the effects of additives on hygroexpansion. Tensile strength improved up till 7 % addition amount which could be set as the upper limit of MFC addition when paper preparation and tensile strength are concerned.

Calorimetry of hydrogen desorption from ɑ-Si nanoparticles

The process of hydrogen desorption from amorphous silicon (ɑ-Si) nanoparticles grown by plasmaenhanced chemical vapor deposition (PECVD) has been analyzed by differential scanning calorimetry (DSC), mass spectrometry, and infrared spectroscopy, with the aim of quantifying the energy exchanged. Two exothermic peaks centered at 330 and 410 °C have been detected with energies per H atom of about 50 meV. This value has been compared with the results of theoretical calculations and is found to agree with the dissociation energy of Si-H groups of about 3.25 eV per H atom, provided that the formation energy per dangling bond in ɑ-Si is about 1.15 eV. It is shown that this result is valid for ɑ-Si:H films, too

Optical and microstructural properties of MgF2 UV coatings grown by ion beam sputtering process

The optical, mechanical, and microstructural properties of MgF2 single layers grown by ion beam sputtering have been investigated by spectrophotometric measurements, film stress characterization, x-ray photoelectron spectroscopy (XPS), x-ray diffraction, and transmission electron microscopy. The deposition conditions, using fluorine reactive gas or not, have been found to greatly influence the optical absorption and the stress of the films as well as their microstructure. The layers grown with fluorine compensation exhibit a regular columnar microstructure and an UV-optical absorption which can be very low, either as deposited or after thermal annealings at very low temperatures. On the contrary, layers grown without fluorine compensation exhibit a less regular microstructure and a high ultraviolet absorption which is particularly hard to cure. On the basis of calculations, it is shown that F centers are responsible for this absorption, whereas all the films were found to be stoichiometric, in the limit of the XPS sensitivity. On the basis of external data taken from literature, our experimental curves are analyzed, so we propose possible diffusion mechanisms which could explain the behaviors of the coatings.

Escacs, un sistema intel·ligent

Des dels inicis dels ordinadors com a màquines programables, l’home ha intentat dotar-los de certa intel•ligència per tal de pensar o raonar el més semblant possible als humans. Un d’aquests intents ha sigut fer que la màquina sigui capaç de pensar de tal manera que estudiï jugades i guanyi partides d’escacs. En l’actualitat amb els actuals sistemes multi tasca, orientat a objectes i accés a memòria i gràcies al potent hardware del que disposem, comptem amb una gran varietat de programes que es dediquen a jugar a escacs. Però no hi ha només programes petits, hi ha fins i tot màquines senceres dedicades a calcular i estudiar jugades per tal de guanyar als millors jugadors del món. L’objectiu del meu treball és dur a terme un estudi i implementació d’un d’aquests programes, per això es divideix en dues parts. La part teòrica o de l’estudi, consta d’un estudi dels sistemes d’intel•ligència artificial que es dediquen a jugar a escacs, estudi i cerca d’una funció d’avaluació vàlida i estudi dels algorismes de cerca. La part pràctica del treball es basa en la implementació d’un sistema intel•ligent capaç de jugar a escacs amb certa lògica. Aquesta implementació es porta a terme amb l’ajuda de les llibreries SDL, utilitzant l’algorisme minimax amb poda alfa-beta i codi c++. Com a conclusió del projecte m’agradaria remarcar que l’estudi realitzat m’ha deixat veure que crear un joc d’escacs no era tan fàcil com jo pensava però m’ha aportat la satisfacció d’aplicar tot el que he après durant la carrera i de descobrir moltes altres coses noves.

Amenzas a través de la telefonía móvil e internet: perfil psicológico y consecuencias emocionales

En los últimos años se ha producido un incremento del uso de la telefonía móvil e Internet con fines intimidatorios o simplemente para amenazar a los iguales en los centros escolares de nuestro país. Con la voluntad de aportar datos que puedan ayudar a su prevención, se ha realizado un estudio de encuesta en el que se ha obtenido información relativa a las amenazas recibidas a través de los nuevos medios de comunicación, es decir, Internet y la telefonía móvil. Los resultados indican que un 23.3% de los estudiantes de los centros públicos de Enseñanza Secundaria Obligatoria de la ciudad de Girona (Cataluña), durante el curso escolar, han recibido vía Internet o telefonía móvil algún mensaje que, por su contenido, ha supuesto una amenaza para su bienestar. Se analizan las consecuenciasemocionales y las estrategias de afrontamiento utilizadas por parte de estos adolescentes

Ortopodología sustitutiva

La evolución de la Ortopodología como ciencia aplicada a lo largo de los años ha sido muy amplia y variada. 3.000 años antes de J.C. se utilizaba el cuero para la confección de sandalias, posteriormente se introdujo el corcho, considerando éste como el único material natural que presenta a la vez una débil densidad, gran compresibilidad, fuerte elasticidad y gran duración. Tenemos constancia a través de la Enciclopedia de Diderot (S. XVIII) de la utilización del corcho tanto para fines terapéuticos como estéticos, así las...

Magnesiumhydroksidialkalin käytön vaikutukset päällystämättömän aikakauslehtipaperin valmistukseen

Magnesiumhydroksidin on havaittu soveltuvan natriumhydroksidin korvaajaksi mekaanisen massan peroksidivalkaisun alkalina. Työssä selvitettiin, miten magnesiumhydroksidi vaikuttaa paperin valmistukseen ja valmiin paperin ominaisuuksiin. Laboratoriokokeet osoittivat magnesiumhydroksidin soveltuvan mekaanisen massan peroksidivalkaisun alkaliksi, sillä vaaleustavoite saavutettiin sen avulla. Valkaistun massan varaustila, johtokyky sekä ζ -potentiaali laskivat magnesiumhydroksidin vaikutuksesta. Nämä johtivat huomattavasti korkeampaan paperin täyteaineretentioon. Massan vedenpidätyskyky kasvoi korvattaessa natriumhydroksidi magnesiumhydroksidilla. Arkkien ominaisuuksista vetoindeksi, valonsirontakerroin ja taivutusjäykkyys kasvoivat. Kaikki edellä mainitut ominaisuudet viittaavat siihen, että magnesiumhydroksidin käyttö parantaa hienoaineen sitoutumista paperiin.

Virkavastuu. Määräaikainen virantoimituksesta erottaminen rajavartiomiehen, ammattisotilaan ja poliisin erityisenä kurinpitorangaistuksena.

Tutkielman tavoitteena on oikeudellisten lähteiden systematisoinnilla tuottaa johdonmukainen kuvaus poliisin, rajavartiomiehen sekä ammattisotilaan virkavelvollisuuksista, oikeudellisesta vastuusta ja virkarikosten rangaistavuudesta. Päähuomio kohdistuu virkamiehen määräaikaiseen virantoimituksesta erottamiseen. Oikeudellisella argumentaatiolla pyritään esittämään lainmukainen ja hyväksyttävä tulkintakannanotto siihen, miten kyseistä säädöstä tulisi tulkita. Tutkimusmetodi työssä on oikeusdogmatiikka. Ensisijaisena aineistona tutkielmassa on voimassa oleva lainsäädäntö valmisteluaineistoineen. Toissijaisina lähteinä käytetään kirjallisuutta, viranomaisten kurinpitopäätöksiä ja haastatteluja. Määräaikainen erottaminen voidaan määrätä virkamiehelle, joka toimii vastoin virkavelvollisuuksiaan tai laiminlyö niitä. Säädös on tulkittavissa laajentavasti siten, että myös muut kuin selkeästi viranomaisen valvontavastuulle kuuluvat teot voidaan katsoa virkatehtävien vastaiseksi. Erityisen käyttäytymisvelvoitteen johdosta menettely on rangaistavaa myös vapaa-ajalla. Määräaikainen erottaminen sijoittuu rangaistusasteikossa varoituksen ja irtisanomisen väliin. Rangaistus ei edellytä erityisen painavia perusteita, joita vaaditaan virkamiehen irtisanomiseen. Uuden säädöksen myötä irtisanomisten määrä on vähentynyt Rajavartiolaitoksessa. Säädöksestä on muotoutunut kurinpidollinen lisärangaistus, joka on määrätty virkamiehelle hallinnollisella päätöksellä yleensä rikostuomion jälkeen. Säädös on kuitenkin tarkoitettu ja se mahdollistaa myös puuttumisen varsinaisten virkatehtävien laiminlyönteihin. Lainsäädännön selkeyttämiseksi määräaikaisen erottamisen säädös tulisi poistaa eri viranomaisten erityislainsäädännöstä ja liittää suoraan virkamieslakiin. Säädöksen soveltaminen tulisi ulottaa koskemaan myös muita virkamiehiä, jotka palvelevat kyseisissä viranomaisissa. Tutkimuksen kohteena oleva virkamiesryhmä alistuu virkamiesoikeudessa blankkorangaistusuhan alle. Virkamiehen on vaikea hahmottaa kaikkea rangaistavaa toimintaa, ja virantoimittamisvelvollisuus on usein täsmentymätön ja tulkinnanvarainen. Kokonaisharkinnassa korostuvat myös muut kuin oikeudelliset lähteet (esimerkiksi moraalikäsitykset, etiikka, ohjeet, virkamiehen elämäntilanne). Sotilaiden ja poliisin oikeudenhoito poikkeaa monilta osin muiden virkamiesten oikeudenhoitomenettelystä. Rajavartiolaitoksessa sotilasoikeudenhoidon määräykset ja ohjeet ovat selkeästi puutteelliset. Rajavartiolaitoksen tehtäväkentän ja toimivaltuudet huomioiden tulisi kurinpito- ja virkarikosten tutkinnoissa lähentyä poliisin mallia sekä hyödyntää rikostorjuntahenkilöstön ammattitaitoa oman henkilökunnan esitutkinnoissa. Erityisen turvallisuusviranomaisten virkarikoksiin erikoistuneen tutkintaorganisaation perustaminen voisi tehostaa ja parantaa esitutkintojen tasoa sekä lisätä oikeusvarmuutta.

Dewatering of hard-to-dewater pulps

Nanocellulose has much potential for enhancing the tensile strength of paper but it slows down significantly drainage, restricting its use in industrial scale. Main objective of the work was to find ways to improve the dewatering of nanocellulose-containing papers. The effects of cationic potato starch, microparticle system and filler addition on dewatering and such key properties as formation, tensile strength and air permeance of manufactured paper were studied. Test points had 0, 4 or 8 % CNF and 0, 15 or 30 % PCC content. Based on earlier studies, 25 mg/g starch dosage was added to some test points. Modern microparticle system, consisted of cationic polyacrylamide and amorphous silica, was used in few test points. Dosages for both components were 0.3 and 0.6 mg/g, following the recommendations of the supplier. Also, the influences of CNF and filler on drying behaviour after different stages (drainage, wet pressing and cylinder drying) were estimated. Following trends were observed. Starch does not have unambiguous influence on dewatering. In some cases, it improved drainage slightly but effects on the properties of end product were discovered small. Filler quickened dewatering but large proportions were noticed to be detrimental for the drainage, air permeance and tensile strength. Microparticle system improved drainage notably, especially if CNF dosage was high. In addition, microparticle system increased tensile strength and decreased air permeance. However, its effects on formation were detrimental. Dewatering of nanocellulose-containing furnishes is treatable up to a certain point. In the end, such drainage times that were measured from test points which consisted only of pure kraft pulps are awkward to reach.

The Effects of Some Furnish and Paper Structure Related Factors on Wet Web Tensile and Relaxation Characteristics

The objective of this thesis was to identify the effects of different factors on the tension and tension relaxation of wet paper web after high-speed straining. The study was motivated by the plausible connection between wet web mechanical properties and wet web runnability on paper machines shown by previous studies. The mechanical properties of wet paper were examined using a fast tensile test rig with a strain rate of 1000%/s. Most of the tests were carried out with laboratory handsheets, but samples from a pilot paper machine were also used. The tension relaxation of paper was evaluated as the tension remaining after 0.475 s of relaxation (residual tension). The tensile and relaxation properties of wet webs were found to be strongly dependent on the quality and amount of fines. With low fines content, the tensile strength and residual tension of wet paper was mainly determined by the mechanical interactions between fibres at their contact points. As the fines strengthen the mechanical interaction in the network, the fibre properties also become important. Fibre deformations caused by the mechanical treatment of pulp were shown to reduce the mechanical properties of both dry and wet paper. However, the effect was significantly higher for wet paper. An increase of filler content from 10% to 25% greatly reduced the tensile strength of dry paper, but did not significantly impair wet web tensile strength or residual tension. Increased filler content in wet web was shown to increase the dryness of the wet web after the press section, which partly compensates for the reduction of fibrous material in the web. It is also presumable that fillers increase entanglement friction between fibres, which is beneficial for wet web strength. Different contaminants present in white water during sheet formation resulted in lowered surface tension and increased dryness after wet pressing. The addition of different contaminants reduced the tensile strength of the dry paper. The reduction of dry paper tensile strength could not be explained by the reduced surface tension, but rather on the tendency of different contaminants to interfere with the inter-fibre bonding. Additionally, wet web strength was not affected by the changes in the surface tension of white water or possible changes in the hydrophilicity of fibres caused by the addition of different contaminants. The spraying of different polymers on wet paper before wet pressing had a significant effect on both dry and wet web tensile strength, whereas wet web elastic modulus and residual tension were basically not affected. We suggest that the increase of dry and wet paper strength could be affected by the molecular level interactions between these chemicals and fibres. The most significant increases in dry and wet paper strength were achieved with a dual application of anionic and cationic polymers. Furthermore, selectively adding papermaking chemicals to different fibre fractions (as opposed to adding chemicals to the whole pulp) improved the wet web mechanical properties and the drainage of the pulp suspension.