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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

On Modelling and Estimation of Curl and Twist in Multi-Ply Paperboard

Bortolin, Gianantonio January 2002 (has links)
<p>This thesis describes a grey-box model for the dimensionalstability properties (i.e. curl and twist) of the carton boardproduced at AssiDomän Frövi paper mill in Sweden.AssiDomän Frövi AB is one of Sweden major cartonboard manufacturer, and produces some 350000 ton of board peryear.</p><p>Curl is defined as the departure from a at form, and it mayseriously affect the processing of the paper. For this reason,customers impose quite restrictive limits on the allowedcurvatures of the board. So, it is becoming more and moreimportant to be able to produce a carton board with a curlwithin certain limits. Due to the economic significance of thecurl problem, much research has been performed to find sheetdesign and processing strategies to eliminate or reducecurl.</p><p>The approach we used to tackle this problem is based ongrey-box modelling. The reasons for such an approach is thatthe physical process is very complex and nonlinear. The inuenceof some inputs is not entirely understood, and besides itdepends on a number of unknown parameters andunmodelled/unmesurable disturbances.</p><p>One of the main part of the model is based on classicallaminate theory which is used to model the dimensionalstability of multi-ply board. The main assumption is that eachlayer is considered as an homogeneous elastic medium.</p><p>The model is then complemented with a sub-model forunmodelled/umeasurable disturbances which are described asstates of a dynamical system, and estimated by means of anextended Kalman filter.</p><p>The simulated curvatures show a general agreement with themeasurements. However, the prediction errors are too large forthe model to be used in an effective way, and a bigger efforthas to be carried out in order to improve the physicalsub-models.</p><p>A chapter of this thesis discusses the modelling of thewet-end part of the paper machine with Dymola, a modelling toolfor simulation of large systems based on Modelica language.</p>
2

Investigation of Wind, Current and Water level variations in the coastal waters of National Museum of Marine Biology and Aquarium

Yang, Wan-hua 13 September 2006 (has links)
Two bottom-mounted ADCPs were deployed in the coastal waters off the National Museum of Marine Biology and Aquarium at southwestern Taiwan coast from June 5, 2004 to December 20, 2005. The long-term observational dataset of wind, currents, water level and drifters were analyzed here to investigate the mechanism and seasonal variations of tidal and subtidal flows. Diurnal tidal constituent of K dominates the tidal energy in this area. The calculated form ratio is 1.53, indicating that the tide is of the diurnal type. Tidal current direction is consistent with the local coastal line, with the principal axis in the NNE-SSW orientation. The tidal waves of two major constituents¡]K an M ¡^are found to exist in the form of propagating waves in this region, rather than the form of standing waves as was found in the east coast of central Taiwan Strait. The subtidal currents flow toward the south with a speed of about 20-50 cm/s during the winter northeastern monsoon. On the other hand, subtidal flow speed is smaller but still toward the south during the summer southwestern monsoon. Current speed in the surface layer is larger than that in the mid and bottom layers. The persistent southward flow in this region is also found to correlate with the wind stress curl. When the wind stress curl reaches a maximum negative value in winter, an anticyclonic eddy develops and the flow in the study area is toward the south. Analysis of Argos drifter data reveal the existence of anticyclone off the southwestern Taiwan coast. Surface drifters were also deployed in this area, and the trajectories indicate that general flow patterns are toward the south. This finding is consistent with the progressive vector diagram from the moored ADCP current data. To summarize, a persistent southward flow exists in the study region all year round. However, the flow intensifies in winter and decays in summer. The southward flow is also associated with the anticyclonic eddy driven by the negative wind stress curl in winter. The intrusion of Kuroshio water from the Luzon Strait into the northern South China Sea is the possible source of water mass for this phenomenon.
3

On Modelling and Estimation of Curl and Twist in Multi-Ply Paperboard

Bortolin, Gianantonio January 2002 (has links)
This thesis describes a grey-box model for the dimensionalstability properties (i.e. curl and twist) of the carton boardproduced at AssiDomän Frövi paper mill in Sweden.AssiDomän Frövi AB is one of Sweden major cartonboard manufacturer, and produces some 350000 ton of board peryear. Curl is defined as the departure from a at form, and it mayseriously affect the processing of the paper. For this reason,customers impose quite restrictive limits on the allowedcurvatures of the board. So, it is becoming more and moreimportant to be able to produce a carton board with a curlwithin certain limits. Due to the economic significance of thecurl problem, much research has been performed to find sheetdesign and processing strategies to eliminate or reducecurl. The approach we used to tackle this problem is based ongrey-box modelling. The reasons for such an approach is thatthe physical process is very complex and nonlinear. The inuenceof some inputs is not entirely understood, and besides itdepends on a number of unknown parameters andunmodelled/unmesurable disturbances. One of the main part of the model is based on classicallaminate theory which is used to model the dimensionalstability of multi-ply board. The main assumption is that eachlayer is considered as an homogeneous elastic medium. The model is then complemented with a sub-model forunmodelled/umeasurable disturbances which are described asstates of a dynamical system, and estimated by means of anextended Kalman filter. The simulated curvatures show a general agreement with themeasurements. However, the prediction errors are too large forthe model to be used in an effective way, and a bigger efforthas to be carried out in order to improve the physicalsub-models. A chapter of this thesis discusses the modelling of thewet-end part of the paper machine with Dymola, a modelling toolfor simulation of large systems based on Modelica language. / NR 20140805
4

Residual stresses in paperboard and the influence of drying conditions

Östlund, Magnus January 2005 (has links)
The drying sequence in the manufacturing process for paperboard involves evaporation of water, primarily from within the fibres. The vapour is then transported out of the web by pressure or concentration gradients. As the moisture transport from the paper web to the ambient is quicker than the moisture transport within the fibre network to the surfaces of the web, moisture gradients develop through the thickness of the web. This work concerns effects on the mechanics of paper drying from the variation in moisture through the relatively thin structures of paper and paperboard. Distributions of inplane residual stresses through paper materials in the unloaded state after drying are believed to be caused by the varying moisture through the thickness during drying. The distributions in general exhibit compressive stress near the board surfaces and tensile stress in the interior of the board. This may be modified after drying and is also affected by structural variation in the material between different plies of multi-ply paperboards. The stress development during drying is important because it influences the resulting material properties of the paper and because it can lead to curl, which is a quality problem. The residual stresses themselves are an error source in simulation or evaluation of the mechanical behaviour of paper. In this work, residual stress distributions in paperboard were determined experimentally, to clarify the mechanisms of residual stress build-up. An experimental method for such tests was also developed. Based on the experimental findings, the mechanics of paper drying was modelled and the stress build-up simulated. Simulation offers a way of studying how the properties of paper develop during drying of wet paper webs.
5

Residual stresses in paperboard and the influence of drying conditions

Östlund, Magnus January 2005 (has links)
<p>The drying sequence in the manufacturing process for paperboard involves evaporation of water, primarily from within the fibres. The vapour is then transported out of the web by pressure or concentration gradients. As the moisture transport from the paper web to the ambient is quicker than the moisture transport within the fibre network to the surfaces of the web, moisture gradients develop through the thickness of the web. This work concerns effects on the mechanics of paper drying from the variation in moisture through the relatively thin structures of paper and paperboard.</p><p>Distributions of inplane residual stresses through paper materials in the unloaded state after drying are believed to be caused by the varying moisture through the thickness during drying. The distributions in general exhibit compressive stress near the board surfaces and tensile stress in the interior of the board. This may be modified after drying and is also affected by structural variation in the material between different plies of multi-ply paperboards.</p><p>The stress development during drying is important because it influences the resulting material properties of the paper and because it can lead to curl, which is a quality problem. The residual stresses themselves are an error source in simulation or evaluation of the mechanical behaviour of paper.</p><p>In this work, residual stress distributions in paperboard were determined experimentally, to clarify the mechanisms of residual stress build-up. An experimental method for such tests was also developed. Based on the experimental findings, the mechanics of paper drying was modelled and the stress build-up simulated. Simulation offers a way of studying how the properties of paper develop during drying of wet paper webs.</p>
6

Begomovirus disease complex: emerging threat to vegetable production systems of West and Central Africa

Leke, Walter N., Mignouna, Djana B., Brown, Judith K., Kvarnheden, Anders January 2015 (has links)
Vegetables play a major role in the livelihoods of the rural poor in Africa. Among major constraints to vegetable production worldwide are diseases caused by a group of viruses belonging to the genus Begomovirus, family Geminiviridae. Begomoviruses are plant-infecting viruses, which are transmitted by the whitefly vector Bemisia tabaci and have been known to cause extreme yield reduction in a number of economically important vegetables around the world. Several begomoviruses have been detected infecting vegetable crops in West and Central Africa (WCA). Small single stranded circular molecules, alphasatellites and betasatellites, which are about half the size of their helper begomovirus genome, have also been detected in plants infected by begomoviruses. In WCA, B. tabaci has been associated with suspected begomovirus infections in many vegetable crops and weed species. Sequencing of viral genomes from crops such as okra resulted in the identification of two previously known begomovirus species (Cotton leaf curl Gezira virus and Okra yellow crinkle virus) as well as a new recombinant begomovirus species (Okra leaf curl Cameroon virus), a betasatellite (Cotton leaf curl Gezira betasatellite) and new alphasatellites. Tomato and pepper plants with leaf curling were shown to contain isolates of new begomoviruses, collectively referred to as West African tomato-infecting begomoviruses (WATIBs), new alphasatellites and betasatellites. To study the potential of weeds serving as begomovirus reservoirs, begomoviruses and satellites in the weed Ageratum conyzoides were characterized. Sequence analyses showed that they were infected by isolates of a new begomovirus (Ageratum leaf curl Cameroon virus) that belong to the WATIBs group, a new betasatellite (Ageratum leaf curl Cameroon betasatellite), an alphasatellite and two types of defective recombinants between a begomovirus and an alphasatellite. Putative recombinations were detected in begomovirus genomes for all four plant species studied, indicating that recombination is an important mechanism for their evolution. A close relationship between the begomoviruses infecting pepper and tomato and A. conyzoides and the detection of the same alphasatellite in them support the idea that weeds are important reservoirs for begomoviruses and their satellites. With this high diversity, recombination potential and transmission by B. tabaci, begomoviruses and ssDNA satellites pose a serious threat to crop production in West and Central Africa.
7

Partnerių vieša API ir jos panaudojimas WHMCS modulyje / Partners' public API and its usage from WHMCS module

Valinskis, Mindaugas 16 July 2014 (has links)
Įmonė UAB „Duomenų Centras“ nuomoja serverius jau 13 metų. Atlikus tyrimus paaiškėjo, kad įmonė eksportuoja apie 75% savo paslaugų į daugiau nei 130 pasaulio šalių. Prie šio rezultato labai prisidėjo Duomenų Centro partneriai iš Lietuvos ir kitų šalių. Partneris – tai svarbiausias klientas, kuris pritraukia kitus naujus klientus. Per įmonės gyvavimo metus visas perpardavinėjimo ir partnerių klientų paslaugų valdymo procesas buvo per elektorinį paštą - tai užtrunka, tokios paslaugos nėra itin patrauklios šiuolaikinėje interneto rinkoje. Todėl dokumente atskleidžiama „partnerių programa“, bei API posistemė, kuri leidžia įmonės partneriams vykdyti su paslaugomis susijusias funkcijas. / The modern data center of Balticservers have been selling their services now for 13 years. The research revealed that the company exports 75% of its services to more than 130 countries worldwide. Moreover, the company has partners from Lithuania and many other countries. The product has been designed for partners that optimizes the process of reselling Balticservers services. It offers a WHMCS module which allows an easy creation and customization of services that are desired to be resold from Balticservers. Also, this includes an API communication between two separated systems that are WHMCS and Korys which Balticservers are currently developing and using in their daily work. API has been developed by using PHP scripting language, cURL and JSON technologies. The document exposes a few similar API systems’ comparison, product requirement specification, architecture’s specification, testing protocol and partners API documentation.
8

Molecular characterization of a naturally occurring intraspecific recombinant begomovirus with close relatives widespread in southern Arabia

Al-Saleh, Mohammed, Al-Shahwan, Ibrahim, Brown, Judith, Idris, Ali January 2014 (has links)
BACKGROUND:Tomato leaf curl Sudan virus (ToLCSDV) is a single-stranded DNA begomovirus of tomato that causes downward leaf curl, yellowing, and stunting. Leaf curl disease results in significant yield reduction in tomato crops in the Nile Basin. ToLCSDV symptoms resemble those caused by Tomato yellow leaf curl virus, a distinct and widespread begomovirus originating in the Middle East. In this study, tomato samples exhibiting leaf curl symptoms were collected from Gezira, Sudan. The associated viral genome was molecularly characterized, analyzed phylogenetically, and an infectious clone for one isolate was constructed.FINDINGS:The complete genomes for five newly discovered variants of ToLCSDV, ranging in size from 2765 to 2767-bp, were cloned and sequenced, and subjected to pairwise and phylogenetic analyses. Pairwise analysis indicated that the five Gezira isolates shared 97-100% nucleotide identity with each other. Further, these variants of ToLCSDV shared their highest nucleotide identity at 96-98%, 91-95%, 91-92%, and 91-92% with the Shambat, Gezira, Oman and Yemen strains of ToLCSDV, respectively. Based on the high maximum nucleotide identities shared between these ToLCSDV variants from Gezira and other previously recognized members of this taxonomic group, they are considered isolates of the Shambat strain of ToLCSDV. Analysis of the complete genome sequence for these new variants revealed that they were naturally occurring recombinants between two previously reported strains of ToLCSDV. Finally, a dimeric clone constructed from one representative ToLCSV genome from Gezira was shown to be infectious following inoculation to tomato and N. benthamiana plants.CONCLUSION:Five new, naturally occurring recombinant begomovirus variants (>96% shared nt identity) were identified in tomato plants from Gezira in Sudan, and shown to be isolates of the Shambat strain of ToLCSDV. The cloned viral genome was infectious in N. benthamiana and tomato plants, and symptoms in tomato closely resembled those observed in field infected tomato plants, indicating the virus is the causal agent of the leaf curl disease. The symptoms that developed in tomato seedlings closely resembled those observed in field infected tomato plants, indicating that ToLCSDV is the causal agent of the leaf curl disease in Gezira.
9

Nodal sets and contact structures

Komendarczyk, Rafal 22 June 2006 (has links)
In this thesis the author develops techniques to study contact structures via Riemannian geometry. The main observation is a relation between characteristic surfaces of contact structures and zero sets of solutions to certain subelliptic PDEs. This relation makes it possible to derive, under a symmetry assumption, necessary and sufficient conditions for tightness of contact structures arising from a certain class of invariant curl eigenfields. Further, it has implications in the energy relaxation of this special class of fluid flows. Specifically, the author shows existence of an energy minimizing curl eigenfield which is orthogonal to an overtwisted contact structure. It provides a counterexample to the conjecture of Etnyre and Ghrist posed in their work on hydrodynamics of contact structures.
10

Engineered Disease Resistance in Cotton Using RNA-Interference to Knock down Cotton leaf curl Kokhran virus-Burewala and Cotton leaf curl Multan betasatellite Expression

Ahmad, Aftab, Zia-Ur-Rehman, Muhammad, Hameed, Usman, Qayyum Rao, Abdul, Ahad, Ammara, Yasmeen, Aneela, Akram, Faheem, Bajwa, Kamran, Scheffler, Jodi, Nasir, Idrees, Shahid, Ahmad, Iqbal, Muhammad, Husnain, Tayyab, Haider, Muhammad, Brown, Judith 14 September 2017 (has links)
Cotton leaf curl virus disease (CLCuD) is caused by a suite of whitefly-transmitted begomovirus species and strains, resulting in extensive losses annually in India and Pakistan. RNA-interference (RNAi) is a proven technology used for knockdown of gene expression in higher organisms and viruses. In this study, a small interfering RNA (siRNA) construct was designed to target the AC1 gene of Cotton leaf curl Kokhran virus-Burewala (CLCuKoV-Bu) and the beta C1 gene and satellite conserved region of the Cotton leaf curl Multan betasatellite (CLCuMB). The AC1 gene and CLCuMB coding and non-coding regions function in replication initiation and suppression of the plant host defense pathway, respectively. The construct, V b, was transformed into cotton plants using the Agrobacterium-mediated embryo shoot apex cut method. Results from fluorescence in situ hybridization and karyotyping assays indicated that six of the 11 T-1 plants harbored a single copy of the V beta transgene. Transgenic cotton plants and non-transgenic (susceptible) test plants included as the positive control were challenge-inoculated using the viruliferous whitefly vector to transmit the CLCuKoV-Bu/ CLCuMB complex. Among the test plants, plant V beta-6 was asymptomatic, had the lowest amount of detectable virus, and harbored a single copy of the transgene on chromosome six. Absence of characteristic leaf curl symptom development in transgenic V beta-6 cotton plants, and significantly reduced begomoviral-betasatellite accumulation based on real-time polymerase chain reaction, indicated the successful knockdown of CLCuKoV-Bu and CLCuMB expression, resulting in leaf curl resistant plants.

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