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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

The performance of syphonic rainwater outlets within gutters

Bramhall, Martyn A. January 2006 (has links)
Throughout Europe, roof areas are commonly drained using a conventional gutter and downspout system. These are usually large in volume and have the capacity to discharge rainwater at high rates of flow. There is now increased awareness of syphonic roof drainage systems. Historically, the definitive method for the design of gutters within the United Kingdom is BS6367: 1983 British Code of Practice for the Drainage of Roofs and Paved Areas. This publication clearly sets out the theoretical model to predict the hydraulic performance of a gutter. In 2000, this Code was superseded by BS EN 12056-3 which, shares a common theoretical basis and method of derivation as BS 6367:1983. These codes do not specifically address syphonic systems and currently there are no design criteria for such systems. Hence, there is an urgent need for a better understanding of the hydraulic performance of syphonic systems. This is particularly relevant to systems that are installed in gutters that drain large industrial and commercial buildings. The work reported in the thesis describes a series of experimental investigations that were carried out to improve knowledge and understanding of the way in which syphonic systems perform. Initially the study concentrated on the construction of a full-scale experimental system to test the hydraulic performance of syphonic system outlets located within a 600mm wide gutter. Tests were completed with single (primary) outlets and primary outlets in combination with independent overflow outlets (secondary outlets). The outlets were positioned at a number of different locations along the length of the gutter and combinations of both primary and secondary outlets were tested. The thesis has concluded that the performance of syphonic rainwater systems is much more complex than conventional roof drainage systems. Specific findings of the study are: • The application of existing theoretical models for the design of conventional rainwater drainage systems should not be transferred to syphonic systems. An additional factor of safety is required within the existing theoretical model. -11- • The position of the outlet in the gutter has a significant influence on the depth profile along the gutter length. Outlets located near to the gutter end resulted in an increase in the depth profile of the outlet. • When an independent overflow system (secondary system) was used in conjunction with a number of primary outlets within a common gutter, it was found that the overflow system, dominated the flow profile within the gutter. • A method, based on dispersion of solutes, was developed to determine the actual flow rate through each outlet of a syphonic system. It was shown that the flow rate through each outlet of the system was not the same and that the water level in the gutter was redistributed along the gutter length. This implies that the negative pressure created in syphonic systems is not a limiting factor. These findings have important design implications. • A methodology to calculate the influence on water depth in any gutter and for any outlet position has been established and is recommended as a basis for the improved design of a syphonic system.
2

Thatching in Cambridgeshire

Stanford, Christopher Paul January 2002 (has links)
A brief introduction defines the aims of the thesis in which thatching is analysed in Cambridgeshire as a living craft. The first chapter sets the historical context of thatching as a means of providing a waterproof roof in England and more particularly in Cambridgeshire, and how, over the years, this form of roof is now largely restricted to small houses in the countryside. Most of Cambridgeshire's thatched houses are small, were built for agricultural workers and small yeoman farmers, and have a form, though not necessarily a fabric, which is five centuries old. They are mostly thatched in wheat straw, but a significant minority is thatched in water reed. These houses are now increasingly owned by people employed in towns who, thanks to the motorcar, choose to live in villages and like the idea of living in a thatched cottage. Practically all of these houses are listed and protected by conservation laws and regulations. Chapter 2 examines the various materials used for thatching in Cambridgeshire, particularly wheat straw and water reed. How they are grown, harvested and prepared for use is explained, together with an analysis of their specific qualities and life expectancy. How the age of a thatched roof may be judged is set out in detail, and the method of doing so was applied to the thatched roofs of twenty-five parishes, and also to a number of old photographs of thatched roofs. Chapter 3 examines the characteristics of Cambridgeshire roofs, specifically those that were designed for a covering of thatch and what obstacles modern roofs present to the thatcher today. Chapter 4 then examines the training of the thatcher, most particularly the traditional form of apprenticeship still in use, why this continues and how it has been little affected by attempts to introduce government-sponsored training schemes. The methods of working are then analysed, and this again shows the continuing survival of traditional practices. Chapter 5 provides a detailed explanation of precisely how Cambridgeshire roofs are thatched in the three main ways using long wheat straw, combed wheat reed and water reed. This encompasses preparation on the ground and how such obstacles as dormers and chimneystacks are overcome, from eaves to ridge. Chapter 6 analyses the results of an extensive survey of about half of the 700 surviving thatched roofs in Cambridgeshire, and endeavours to explain the distribution of the various types of thatch. It accounts for the survival of a significant quantity of thatching material from the late Middle Ages, and examines the life-expectancy of a long-wheat-straw roofs, which is demonstrated to be on average between 35 and 40 years. This result is compared with the expectancy for water reed, and also for wheat straw in other parts of the United Kingdom, concluding that the quality of thatching in Cambridgeshire, as well as its climate, are particularly favourable to longevity. The Conclusion draws together these results and underlines the problems of a traditional building skill practised in what are more or less ancient ways in the current climate of conservation and economic prosperity based on the efficient use of material and human resources. The thesis is supported by a catalogue raisonne of all the thatched roofs in twenty-five Cambridgeshire parishes (and three in neighbouring parishes), and by appendices, one of them giving the responses to a questionnaire sent to all the thatchers known to be working in Cambridgeshire.
3

The development of an approach and decision support tool to inform sustainable roof selection

Hampshire, Philip January 2015 (has links)
Despite the importance of roofs, improved roof selection has not been explored in significant depth. Therefore this research explores the possibilities that roofs offer to improve the value and sustainability of buildings. It is concerned with the roof as a system, explicitly connected with the building and their impacts on wider society. This research, develops and tests techniques to better understand what constitutes value and sustainability for a building project’s context through action research. The sustainability and value themes output through the use of such techniques are then considered as a basis for the selection of roof attributes through Keeney’s value focused thinking approach. Once the roof performance attributes have been established, designers and clients then require quantitative data to decide which roof type represents the highest value / most sustainable option. Thus the research also collates and maps peer reviewed quantitative performance data on the performance of roofing systems in relation to climate type as well as providing information from leading modelling packages for different roof options. An approach for selecting the most appropriate data is then developed. This allows the practitioner to be able to access reliable peer reviewed information and utilise leading modelling techniques to quickly gain information regarding the performance of various roof systems for use in the project context. An approach is developed to bring this information together with the important sustainability considerations for the project to inform sustainable roof selection. This combines the different types of roof performance with the relevant decision attributes early in the design process, to provide insight into which roof option represents the best overall economic, environmental and social value and therefore the most sustainable roof option. The primary contribution to knowledge presented in this thesis is the development of a pragmatic realist approach to sustainable roof selection.
4

Development and integration of a green roof model within whole building energy simulation

Decruz, Aloysius January 2016 (has links)
Green roofs are increasingly being employed as a sustainability feature of buildings. The sustainability approach in building designs requires reducing energy consumption and adopting low carbon energy sources without compromising the increasing expectations of comfort and health levels. Given the wide range of building designs, climates and green roof types, it is desirable to evaluate at the design stage the energy saving impact and other potential benefits from the application of green roofs. Currently, the abilities of building simulation programs to simulate the influences of green roofs are limited. For example, they have limitations in representing dynamic inter-layer interactions and moisture infiltration mechanisms. This research aims to develop a new model for the simulation of green roofs based on the control volume approach and to integrate the model within a whole building energy simulation program. The green roof elements consist of special layers such as plants and soil for which the control volume approach is capable of capturing their special characteristics with regards to the thermal and moisture exchanges. The model has been integrated within the ESP-r whole building energy simulation program. Within the ESP-r, the new green roof model alters the boundary condition of a roof surface on which green roof is constructed. The model development is carried out by a series of steps which include a careful selection of governing equations that describe the thermal and moisture balances in various layers of green roof, the numerical implementation for a simultaneous solution of the governing equations for the whole green roof, algorithm and code development and finally developing the interface with ESP-r. After successful integration, the model results were validated on an experimental test cell, which consists of an approximately 2 m2 planted medium on an insulated box with facilities for thermal, moisture and drainage measurements. The results for the thermal validation were promising with the significant boundary temperature values within a root mean square deviation (RMSD) in the vicinity of 0.5 K, whereas the moisture validation results are found to depend on initial conditions, the lower layers showing an RMSD of approximately 0.05 m3/m3 and the top layer nearly 0.12 [m3/m3]. The model is also able to predict the slowing down of water run-off. A methodology for collecting soil and plant properties which are required to be used along with the program has also been described. Based on the current state of the model and also considering the new developments in green roofs, some suggestions are proposed at the end of the thesis as a continuation of this research.
5

Μελέτη του ρόλου του γονιδίου KLF10 στην αύξηση των επιπέδων της εμβρυικής αιμοσφαιρίνης ασθενών με β-μεσογειακή αναιμία και την ανταπόκρισή τους σε υδροξυουρία

Μπαρτσακούλια, Μαρίνα 11 October 2013 (has links)
Οι αιμοσφαιρινοπάθειες συγκαταλέγονται ανάμεσα στις πιο κοινές μονογονιδιακές διαταραχές παγκοσμίως, συμπεριλαμβανομένης της β-θαλασσαιμίας και της δρεπανοκυτταρικής αναιμίας. Η επανενεργοποίηση των γονιδίων της γ-σφαιρίνης φαίνεται να είναι μια ενδιαφέρουσα θεραπευτική προσέγγιση για τους ασθενείς που πάσχουν από β-τύπου αιμοσφαιρινοπάθειες. Ορισμένες φαρμακευτικές ουσίες έχουν τη δυνατότητα να επάγουν παροδικά την έκφραση των γονιδίων της γ-σφαιρίνης γεγονός που βελτιώνει το φαινότυπο των ασθενών λόγω των υψηλότερων επιπέδων HbF που παρατηρούνται. Η μόνη φαρμακευτική ουσία που έχει εγκριθεί από τον FDA και χρησιμοποιείται ευρύτατα σε ασθενείς που πάσχουν από β-τύπου αιμοσφαιρινοπάθειες και συγκεκριμένα από δρεπανοκυτταρική αναιμία είναι η HU. Παρά το γεγονός ότι στην πλειονότητα των ασθενών παρατηρείται αύξηση της παραγωγής HbF μετά από αγωγή με HU (Steinberg et al. 1997), τα επίπεδα αύξησης διαφέρουν αρκετά μεταξύ των ασθενών που πάσχουν από β-θαλασσαιμία και δρεπανοκυτταρική αναιμία(Patrinos and Grosveld 2008). Σύμφωνα με τους Borg και συνεργάτες, το γονίδιο KLF10 φαίνεται να σχετίζεται με την αύξηση των επιπέδων της HbF και την ανταπόκριση ασθενών με β-τύπου αιμοσφαιρινοπάθειες σε θεραπεία με HU(Borg et al. 2012). Στην παρούσα μελέτη διερευνήθηκε η πιθανή συσχέτιση των SNP rs319133 και rs11552577, που εδράζονται στο γονίδιο KLF10, με αυξημένα επίπεδα HbF και η αξιολόγηση αυτών ως φαρμακογονιδιωματικοί δείκτες, που σχετίζονται με τη μεταβλητότητα των επιπέδων της HbF ως απόκριση στη θεραπεία με HU. Χρησιμοποιήθηκαν ασθενείς που πάσχουν από βαριά β-θαλασσαιμία, ενδιάμεση β-θαλασσαιμία, μη-θαλασσαιμικοί ασθενείς και διπλά ετερόζυγοι ασθενείς για β-θαλασσαιμία και δρεπανοκυτταρική αναιμία. Η μέθοδος γονοτύπησης που χρησιμοποιήθηκε και για τους δύο πολυμορφισμούς ήταν η PCR-RFLP. Η απουσία του πολυμορφισμού rs319133 φαίνεται να σχετίζεται με αυξημένα επίπεδα HbF στους ασθενείς που χαρακτηρίζονται από ενδιάμεση β-θαλασσαιμία συγκριτικά με ασθενείς που πάσχουν από βαριά β-θαλασσαιμία (p=0.04). Επίσης παρατηρείται μια στατιστική τάση συσχέτισης χειρότερης ανταπόκρισης στην αγωγή με HU στους διπλά ετερόζυγους ασθενείς 96 για β-θαλασσαιμία και δρεπανοκυτταρική αναιμία. Για τον δεύτερο πολυμορφισμό που μελετήθηκε δεν παρατηρήθηκαν στατιστικά σημαντικές διαφορές. Τα δεδομένα της παρούσας μελέτης υποδεικνύουν συσχέτιση του γονιδίου KLF10 με αυξημένα επίπεδα HbF. Μελέτες σε πολυπληθέστερες ομάδες θα μπορούσαν να οδηγήσουν στον εντοπισμό και άλλων πολυμορφισμών που σχετίζονται με αυξημένη έκφραση των γονιδίων της γ-σφαιρίνης. / Hemoglobinopathies are amongst the most common single gene disorders worldwide, including the thalassemias and sickle cell disease (SCD). Reactivation of the human γ-globin genes would be a therapeutic intervention for β-type hemoglobinopathies patients. Some drugs and compounds can transiently induce γ-globin gene expression and improve the disease phenotype by augmenting HbF accumulation. Only HU (hydroxyurea) is approved from the FDA and is widely used to treat patients with β-type hemoglobinopathies, in particular sickle cell disease. Although the majority of patients show an increase of HbF production upon HU treatment(Steinberg et al. 1997), the level of HbF increase differs considerably among β-thalassemia and SCD patients(Patrinos and Grosveld 2008). According to Borg et al, KLF10 appears to be significantly associated with high HbF and it may act as an important pharmacogenetic biomarker for β-type hemoglobinopathies patients who are treated with HU(Borg et al. 2012). The aim of our study was to elucidate whether there is an association of the SNPs namely rs3191333 and rs11552577 in KLF10 gene with increased levels of HbF and with response to HU treatment in β-hemoglobinopathies patients. We analyzed samples of β-thalassemia major patients, of β-thalassemia intermedia patients, of healthy (non-thalassemic) donors and samples of SCD/β–thalassemia patients who have been treated with HU. Genotyping was carried out by using PCR-RFLP. The lack of rs3191333 is associated with increased HbF levels in β–thalassemia intermedia compared to β– thalassemia major patients (p=0.04). Also, it is shown a statistical trend of worse response to HU treatment in compound heterozygote β–thalassemia-SCD patients. As far as rs11552577 is concerned no statistically significant differences were observed. Our data show that KLF10 gene is strongly associated with HbF levels. Further analyses could possibly reveal novel variants which are associates with increased expression of γ-globin genes.
6

Comparison Of The 2d And 3d Analyses Methods For Cfrds

Ozel, Halil Firat 01 September 2012 (has links) (PDF)
The purpose is to compare the 2D and 3D analysis methodologies in investigating the performance of a Concrete Faced Rockfill Dam (CFRD) under static and dynamic loading conditions. &Ccedil / okal Dam is the case study which is a CFRD located in northwest Turkey at the Thracian Peninsula. Rockfill interface and faceplate were simulated as nonlinear modulus of elasticity, detailed nonlinear tractive behavior and total strain rotating crack model, respectively. These behaviors were calibrated to define the exact behavior by detailed material tests. The analyses that cannot be done by 2D analyses, such as stress, crack width distribution along the face slab are conducted by 3D analyses to determine the necessity of these outcomes. Since effect of valley ends cannot be produced by 2D analyses, it is necessary to check 3D analyses to ensure liability of the results. Another comparison between detailed analysis of 2D models and linear elastic 2D models were covered to get practical and industrial solutions for the guiding methods of CFRDs for preliminary designs in this study.
7

Flutter Analysis And Simulated Flutter Test Of Wings

Balevi, Birtan Taner 01 October 2012 (has links) (PDF)
Flutter is a dynamic instability which can result in catastrophic failures of an air vehicle. Preventing flutter can be an important factor in the aircraft design, affecting the structural design. Thus, the weight and performance of the aircraft is also being affected. Understanding the role of each design factor of a wing on the onset of flutter can help designers on the flutter clearance of the aircraft. Analysis to predict flutter, ground vibration tests and flight flutter tests, which are performed to verify that the dedicated flight envelope is clear from flutter, are the most important certification processes in modern aviation. Flight flutter testing is a very expensive process. In flight flutter tests the air vehicle is instrumentated with exciters, accelerometers and transmitters to send the test data simultaneously to the ground station to be analyzed. Since flutter is a very severe instability, which develops suddenly, the data should be followed carefully by the engineers at the ground station and feedback should be provided to the pilot urgently when needed. Low test step numbers per flight, increases the cost of flutter testing. Increasing efforts in pre-flight test processes in flutter prediction may narrow the flight flutter test steps and decrease the costs. In this study, flutter prediction methods are investigated to aid the flutter test process. For incompressible flight conditions, some sample problems are solved using typical section model. Flutter solutions of a simple 3D wing are also performed via a coupled finite element linear aerodynamics approach using the commercial tool Nastran. 3D flutter solutions of the wing are compared with the typical section solutions to see how close can the typical section method predict flutter compared to the flutter analyis using the three dimensional wing model. A simulated flutter test method is introduced utilizing the two dimensional typical section method. It is shown that with a simple two dimensional typical section method, flutter test simulation can be performed successfully as long as the typical section model approximates the dynamic properties of the wing closely.
8

Multidisciplinary Design And Optimization Of A Composite Wing Box

Hasan, Muvaffak 01 October 2003 (has links) (PDF)
In this study an automated multidisciplinary design optimization code is developed for the minimum weight design of a composite wing box. The multidisciplinary static strength, aeroelastic stability, and manufacturing requirements are simultaneously addressed in a global optimization environment through a genetic search algorithm. The static strength requirements include obtaining positive margins of safety for all the structural parts. The modified engineering bending theory together with the coarse finite element model methodology is utilized to determine the stress distribution. The nonlinear effects, stemming from load redistribution in the structure after buckling occurs, are also taken into account. The buckling analysis is based on the Rayleigh-Ritz method and the Gerard method is used for the crippling analysis. The aeroelastic stability requirements include obtaining a flutter/divergence free wing box with a prescribed damping level. The root locus method is used for aeroelastic stability analysis. The unsteady aerodynamic loads in the Laplace domain are obtained from their counterparts in the frequency domain by using Rogers rational function approximations. The outer geometry of the wing is assumed fixed and the design variables included physical properties like thicknesses, cross sectional dimensions, the number of plies and their corresponding orientation angles. The developed code, which utilizes MSC/NASTRAN&reg / as a finite element solver, is used to design a single cell, wing box with internal metallic substructure and composite skins.
9

A Methodology For Real-time Sensor-based Blockage Assessment Of Building Structures During Earthquakes

Ergin, Tuluhan 01 February 2013 (has links) (PDF)
During and after earthquakes, occupants inside a damaged building should be evacuated rapidly and safely whereas related units outside the buildings (e.g. first responders) should know the current condition of the building. Obviously, this information should be as accurate as possible and accessed timely in order to speed up the evacuation. Unfortunately, absence of such information during evacuation and emergency response operations results in increased number of casualties. Hence, there arises a need for an approach to make rapid damage and blockage assessment in buildings possible. This study focuses on sensor-based, real-time blockage assessment of buildings during earthquakes and it is based on the idea that / the blocked units of a building (e.g. corridors) can be assessed with the help of different types of sensors. The number and locations of these sensors are arranged in such a way that it becomes possible to picture the current condition of the building. Sensors utilized in this study can be listed as accelerometer, ultrasonic range finder, gyro sensor, closed cable circuit and video camera. The research steps of this thesis include (1) examination of the damage indicators which can cause blockage, (2) assessment of the monitoring devices, (3) expression of the conducted experimental studies in order to assess blokage condition of a corridor unit, (4) proposing an sensor fusion approach, and (5) presentation of the performed case study as an implementation of the blockage assessment. The findings of this research can be made use of in future studies on sensor-based blockage assessment.
10

A Practical Optimum Design Of Steel Structures With Scatter Search Method And Sap2000

Korkut, Ahmet Esat 01 February 2013 (has links) (PDF)
In the literature, a large number of metaheuristic search techniques have been proposed up to present time and some of those have been used in structural optimization. Scatter search is one of those techniques which has proved to be effective when solving combinatorial and nonlinear optimization problems such as scheduling, routing, financial product design and other problem areas. Scatter search is an evolutionary method that uses strategies based on a composite decision rules and search diversification and intensification for generating new trial points. Broodly speaking, this thesis is concerned with the use and application of scatter search technique in structural optimization. A newly developed optimization algorithm called modified scatter search is modified which is computerized in a software called SOP2012. The software SOP2012 is integrated with well-known structural analysis software SAP2000 using application programming interface for size optimum design of steel structures. Numerical studies are carried out using a test suite consisting of five real size design examples taken from the literature. In these examples, various steel truss and frame structures are designed for minimum weight according to design limitations imposed by AISC-ASD (Allowable Stress Design Code of American Institute of Steel Construction). The results reveal that the modified scatter search technique is very effective optimization technique for truss structures, yet its performance can be assessed ordinary for frame structures.

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