44,859 research outputs found
The use of reed canary-grass (Phalaris arundinacea) as a short fibre raw material for the pulp and paper industry
No full textThis thesis describes the use of delayed harvested reed canary-grass (Phalaris arundinacea) as a short fibre raw material for the pulp and paper industry. This study examines the following aspects of reed canary-grass: quality, transportation, storage, refining of the raw material by dry fractionation, chemical pulping, bleaching and paper production. The delayed harvesting method of reed canary-grass produces an economically and environmentally sustainable short fibre raw material for the pulp and paper industry. The ash content and fibre properties of reed canary-grass depend on soil type and growing location. The yearly variation in fibre yield and fibre properties is also considerable. There is, however, a potential for minimising quality variations by choosing reed canary-grass varieties suitable to a specific growing location. The leaf and leaf sheath content of reed canary-grass also affects the quality of the pulp. These quality variations can be eliminated by dry fractionation, a method that removes the unwanted parts of the grass. These unwanted parts can be used as a valuable bio-fuel raw material. Transport of reed canary grass after fractionation can be improved by briquetting, a method that doubles the transport capacity of reed canary-grass compared to that of birch logs on a fibre basis. High quality short fibre chemical pulp can be produced from reed canary-grass. The whole process from grass production to pulp production has been demonstrated successfully in full scale. Bleached reed canary-grass pulp can be used in products such as fine paper and white-top liner paper
Desenvolvimento em linguagem de descrição de hardware de codificador e decodificador Reed-Solomon
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Elétrica, Florianópolis, 2014.Atualmente, diversos sistemas de comunicação demandam grandes volumes de tráfego de dados para consumo quase instantâneo. Estes dados devem ser entregues aos usuários tal qual foram gerados: sem erros. Por isso, técnicas de controle e correção de erros estão intrinsecamente ligadas aos sistemas que realizam trocas de dados, sejam sistemas de armazenamento, os quais estão sujeitos a falhas durante a leitura, ou sistemas de comunicação, que estão sujeitos às adversidades do meio (radiação, interferência eletromagnética, desvanecimento, entre outros). Neste cenário, os códigos Reed-Solomon representam uma solução viável para inúmeras aplicações, bem como pesquisas acadêmicas, mesmo tanto tempo após sua invenção. Este trabalho realiza um estudo da teoria que embasa os códigos Reed-Solomon, assim como implementa as técnicas do estado-da-arte dos módulos que compõem tanto o codificador quanto o decodificador, as quais são prototipadas em hardware reconfigurável.<br
Assessment of tertiary reed beds in chemically-dosed wastewater treatment plants for phosphorus removal
No full textEutrophication is one of the problems affecting the environmental quality standards of fresh waters. Phosphorus (P) is considered a main nutrient contributing to this. In the UK, the Water Industry is responsible for c. 50% of the total phosphorus load to freshwater ecosystems. Within this, small wastewater treatment plants (WwTPs) (<2,000 population equivalent) have a significant role since they represent 75% of all WwTPs in the UK.
The current option for P removal from wastewater is chemical precipitation through the dosing of iron (Fe) salts in combination with a tertiary filtration treatment step. This study aims to determine the transformation processes whereby tertiary reed beds permanently store or release iron and phosphorus in chemically-dosed sites to provide recommendations regarding the conditions where reed beds can be used as such final filtration treatment in small WwTPs. This was carried out through sampling campaigns in 14 full-scale tertiary reed beds.
Chemically-dosed WwTPs with tertiary reed beds can perform satisfactorily achieving phosphorus removals above 85% and average P and Fe final effluent concentrations of 0.7 mg P/L and 0.2 mg Fe/L, respectively, both well below consents (2 mg TP/L and 4 mg Fe/L). The majority of the total phosphorus in the reed bed influents was associated to either suspended solids or dissolved fractions, whereas 60¬90% of the effluent TP is in the dissolved form. Occasional episodes of phosphorus release from the reed bed can occur, as evidenced in an increase in soluble reactive phosphorus in the effluent. The main mechanism for trapping of Fe and P in mature beds was settlement of suspended particles, with phosphorus and iron concentrations in the accumulated sludge being up to 55.9 g P/kg dry matter and 246.6 g Fe/kg DM. The removal of particulate pollutants was successful in the reed beds studied, but colloidal and dissolved particles passing through the beds untreated. This could compromise the use of reed beds with future tightening P consents if the current chemical dosing practices are unchanged
Dual Grating Assisted Optical Coupler
No full textAn optical coupler comprises an input waveguide, an intermediate waveguide, an output waveguide, a first grating situated between the input and intermediate waveguides, and a second grating situated between the intermediate and output waveguides such that, in use, light propagating in the input waveguide is coupled into the intermediate waveguide with the assistance of the first grating, and thence is coupled into the output waveguide with the assistance of the second grating. The coupler is a directional coupler, in particular a dual grating-assisted directional coupler, and may be used to couple light between an optical fibre and an integrated semiconductor device, or between dissimilar waveguides
Dual grating-assisted directional coupling between fibers and thin semiconductor waveguides
No full textA novel dual grating-assisted directional coupler (DGADC) for coupling an optical fiber with a thin semiconductor waveguide is proposed. As an example, a DGADC in silicon-on-insulator is discussed. Maximum coupling efficiency in excess of 90% can be obtained using this coupler, while the highest coupling efficiency previously reported was only 40%
Konstruksi Kode Reed-Solomon sebagai Kode Siklik dengan Polinomial Generator
No full textSuatu kode pengoreksi kesalahan adalah himpunan vektor kode yang dirancang untuk mendeteksi dan mengoreksi kesalahan bit di dalam untaian yang diterima atau diakses. Kode siklik adalah salah satu kelas dari kode pengoreksi kesalahan. Kode siklik mempunyai subkelas yang disebut sebagai kode BCH yang mempunyai bentuk khusus yang disebut Kode Reed-Solomon. Kode Reed-Solomon mempunyai kemampuan mengoreksi kesalahan yang tinggi. Pada tulisan ini kode Reed-Solomon dibatasi bekerja pada lapangan hingga (Galois Field) GF(2^m), untuk m bilangan bulat.. Lebih tepatnya, kode Reed-Solomon yang merupakan ideal prima dari GF(2^m)/???x^n-1??? dalam tulisan ini dikonstruksi dengan menggunakan sebuah polinom generator g(x)???GF(2^m)/???x^n-1???. Agar bisa mengoreksi t kesalahan bit dan merentang kode Reed-Solomon dengan panjang n=2^m-1, dimensi k=n-2t, jarak minimum d_min=n-k+1 dan memuat q^k vektor kode, polinom generator harus memiliki derajat 2t
A Procedure to Optimize Reed Type Valves Considering Efficiency and Bending Fatigue
No full textReed valves are the most common type of valves used in small compressors due to their simplicity and low cost. Such valves greatly affect the compressor volumetric and isentropic efficiencies and their suitable design is also crucial for reliability, since they may be subjected to severe bending and impact stresses. This paper reports an optimization procedure for reed type valves considering efficiency and bending fatigue, which is attained by coupling a thermodynamic model for the compression cycle and a finite element model for the valve dynamics. Then, a genetic algorithm is adopted to find different valve geometries that give the best compromise between efficiency and reliability. As an example, the method is applied to optimize the suction valve of a small reciprocating compressor
The numerical modelling of rockbolts in geomechanics by finite element methods
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University, 15/03/1999.In tunnel excavation, the use of rockbolts has long been a popular means of reinforcement in rock masses to prevent the rock opening from caving in. The idea has evolved from the earliest form of rockbolt made of wood to the more up-to-date form of pre-tensioned or grouted steel rockbolts.
A major breakthrough in the design of rockbolt models was made by Aydan (1989). This rockbolt element was modelled in coupled form, with one sub-element representing the steel bolt, and the other sub-element the grout. This representation was necessary to model the complex action in the continuous rock mass near the joint.
In elasticity problems, the large displacement formulation of a beam element is derived from the fundamental theory, and the bending phenomenon of a thin rod is analysed by the finite element discretizations of the bar elements and the beam elements. Experiments show that the deformation characteristics of the latter representation resemble a more realistic life behaviour. Based on this finding, this thesis proposes a modification to Aydan's two-dimensional rockbolt element, with the beam elements discretising the steel bolt.
The different mechanical responses of a perfectly elastic rockbolt are considered, and the large displacement formulation of the new rockbolt element is derived by combining those of Aydan's rockbolt element and the beam element.
The mechanics of the Aydan element and the new rockbolt element are described, and their performances are compared in an identical situation. It is found that in the two two-dimensional examples used in this thesis, the modified element ensures the continuity of curvature of the rockbolt, and in general, can act as support across a discontinuity or joint between rock masses well.
In conjunction with the displacement method in the finite element procedures, a conventional iteration solution procedure is first described to solve the nonlinear incremental stiffness equation. However, it is found that this procedure is cumbersome, and requires a large amount of comptutations. Some limited storage quasi-Newton minimization algorithms are considered as an alternative
Negotiating the semantics of agent communication languages
No full textThis paper presents a formal framework and outlines a method that autonomous agents can use to negotiate the semantics of their communication language at run-time. Such an ability is needed in open multi-agent systems so that agents can ensure they understand the implications of the utterances that are being made and so that they can tailor the meaning of the primitives to best fit their prevailing circumstances. To this end, the semantic space framework provides a systematic means of classifying the primitives along multiple relevant dimensions. This classification can then be used by the agents to structure their negotiation (or semantic fixing) process so that they converge to the mutually agreeable semantics that are necessary for coherent social interactions
Coupling to nanophotonic waveguides using a dual grating-assisted directional coupler
No full textAn analysis of a device we have called a dual grating-assisted directional coupler (DGADC) in silicon-on-insulator technology is presented. The device enables efficient coupling from optical fibres to small waveguides, typically <1 µm in cross-sectional dimensions. Coupling efficiency and device length are determined as functions of layer thicknesses and refractive indices, grating periods, depths and duty ratios, and finally wavelength. For our example calculation of coupling to a 250 nm silicon waveguide, this efficient and robust coupler can have coupling efficiency as high as 90%, while the wavelength range can have an FWHM of ~1.6 nm at resonance. Fabrication tolerances have also been analysed and they are up to two orders of magnitude larger than those of a GADC with only one grating
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