• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 26
  • 6
  • 5
  • 3
  • 3
  • 3
  • 3
  • 3
  • 1
  • 1
  • Tagged with
  • 76
  • 17
  • 16
  • 15
  • 8
  • 7
  • 7
  • 7
  • 7
  • 6
  • 6
  • 6
  • 6
  • 6
  • 6
  • 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.
51

Passform på shorts : En studie om grensömmar och passformens utformning på träningsshorts för kvinnor.

Vuolle, Linda January 2020 (has links)
I den här kandidatuppsatsen inom Designteknik ska passform på shorts utforskas. I rapporten undersöks grensömmars passform i komfort, visuellt och under fysiska avprovningar. Olika faktorer som påverkar grensömmars passformsproblem analyseras. Arbetet baseras på ett samarbete mellan ett företag där en fältstudie utfördes, där företaget producerar träningskläder. Kärnan till ämnet uppkom när man sett brister i passform runt grensömmen på byxor och shorts i vävda material under avprovningar på marknaden. I tidigare forskning instämmer en stor majoritet av författarna att grensömmen är en kritisk punkt. Framställning av byxor med en god passform i grensömmen kan vara förhållandevis komplext men det beror inte bara på arbetslivserfarenheten. Under projektet granskas fyra befintliga shorts från marknaden. Det som dokumenteras är passformen, grensömmen på provpersoner och genomskärning av grensömmen för att utvärdera likheter och olikheter. Två shortsmodeller konstrueras utifrån litteratur och annan sekundära data. En tabell för kroppsmått för dam från företaget och mätningar på de tilldelade shortsen används som referens. Shortsens passform provas fram i form av 3D- simulering och på levande modeller. Resultatet av avprovningarna visar likheter av placering av veckbildning och dragningar i 3D- simuleringen respektive de fysiska avprovningarna. Shortsen provas även av i tränings positioner, det resulterade i att shortsen kändes annorlunda runt grensömmen vid hukande gentemot stående position och att grenkurvan ändrade form. Shortsen vidareutvecklades utifrån tidigare prövningar och studier, det resulterade i ett grundmönster. Grundmönstret ska kunna vara till hjälp för flera företag i deras framtagning av byxor och shorts till dam och minimera tillverkning av fysiska prototyper.
52

Genealogická sémantická wiki / Genealogic Semantic Wiki

Brychová, Jana Unknown Date (has links)
This thesis project is about possibilities of storing genealogic data in different formats and based on the results it suggests data format which can be used consequently as a source for the vizualization by semantic web. In the scope of the project there is a genealogic application implemented for KiWi platform. This application enable visualization of designed format using prefuse technology. There are basic and aslo some other usefull information about the basic technologies of the semantic web like RDF, XM, ontology, OWL language stated in the document.
53

Spectroscopy and Dynamics of Small Molecules with Large Amplitude Motion

Dawadi, Mahesh B. 11 September 2014 (has links)
No description available.
54

Ultrasonic Additive Manufacturing: Weld Optimization for Aluminum 6061, Development of Scarf Joints for Aluminum Sheet Metal, and Joining of High Strength Metals

Wolcott, Paul Joseph January 2015 (has links)
No description available.
55

Prediction of Lateral Restraint Forces in Sloped Z-section Supported Roof Systems Using the Component Stiffness Method

Seek, Michael Walter 04 September 2007 (has links)
Z-sections are widely used as secondary members in metal building roof systems. Lateral restraints are required to maintain the stability of a Z-section roof system and provide resistance to the lateral forces generated by the slope of the roof and the effects due to the rotation of the principal axes of the Z-section relative to the plane of the roof sheathing. The behavior of Z-sections in roof systems is complex as they act in conjunction with the roof sheathing as a system and as a light gage cold formed member, is subject to local cross section deformations. The goal of this research program was to provide a means of predicting lateral restraint forces in Z-section supported roof systems. The research program began with laboratory tests to measure lateral restraint forces in single and multiple span sloped roof systems. A description of the test apparatus and procedure as well as the results of the 40 tests performed is provided in Appendix II. To better understand the need for lateral restraints and to provide a means of testing different variables of the roof system, two types of finite element models were developed and are discussed in detail in appended Paper I. The first finite element model is simplified model that uses frame stiffness elements to represent the purlin and sheathing. This model has been used extensively by previous researchers and modifications were made to improve correlation with test results. The second model is more rigorous and uses shell finite elements to represent the Z-section and sheathing. The shell finite element model was used to develop a calculation procedure referred to as the Component Stiffness Method for predicting the lateral restraint forces in Z-section roof systems. The method uses flexural and torsional mechanics to describe the behavior of the Z-section subject to uniform gravity loads. The forces generated by the system of Z-sections are resisted by the "components" of the system: the lateral restraints, the sheathing and Z-section-to-rafter connection. The mechanics of purlin behavior providing the basis for this method are discussed in appended Paper II. The development of the method and the application of the method to supports restraints and interior restraints are provided in appended papers III, IV and V. / Ph. D.
56

Computational and Experimental Study on the Behavior of Diaphragms in Steel Buildings

Wei, Gengrui 03 February 2022 (has links)
The lateral force resisting system (LFRS) of a steel building consist of two parts, i.e., a vertical LFRS such as braced frames or shear walls, and a horizontal LFRS with diaphragms playing a crucial role. There are various types of floor and roof diaphragms in steel buildings, such as concrete-filled steel deck diaphragms for the floor system and bare steel deck diaphragms for the roof system of a typical steel braced frame building, and standing seam roof diaphragms for a typical metal building. Compared to vertical elements of a building's LFRS, our understanding of the horizontal elements, i.e., the diaphragms, is grossly lacking. The motivation for this work comes from the gaps identified in the research, including the lack of generally adopted acceptance criteria and modeling protocols for seismic performance-based design of bare steel deck and concrete-filled steel deck diaphragms through linear and nonlinear analysis, the need to better understand the complex behavior of concrete-filled steel deck diaphragms with irregular configurations such as reentrant corners and openings under lateral loading, the absence of appropriate Rs values for the alternative diaphragm seismic design approach in the current building code that considers diaphragm inelasticity, and the demand for understanding the in-plane behavior of a standing seam roof system and its use in lateral bracing of rafters in metal buildings. A series of computational and experimental studies were conducted to investigate the behavior of diaphragms in buildings systems, including: 1) development of acceptance criteria and modeling protocol for performance-based seismic design of bare and concrete-filled steel deck diaphragms using a database of existing cantilever diaphragm tests; 2) a computational study on the nonlinear behavior of diaphragms with irregular configurations under lateral loading using high-fidelity finite element models validated against experiment test results; 3) investigation of the seismic behavior and performance of steel buildings with buckling restrained braced frames that considers different diaphragm design approaches and diaphragm inelasticity using nonlinear three-dimensional (3D) computational models; and 4) an experimental study that investigated the in-plane behavior of full-scale standing seam roof assemblies and their use in lateral bracing of rafters in metal building systems. The results of these studies contribute to a better understanding of the behavior of diaphragms in steel buildings and lead to several recommendations for diaphragm design. Firstly, a series of m-factors (ductility measures) and nonlinear modeling parameters (multi-linear cyclic backbone curves) were determined for bare steel deck diaphragms and concrete-filled steel deck diaphragms. These new provisions are recommended for adoption in ASCE 41 / AISC 342, which allows the use of ductility in steel deck diaphragms for their design and retrofits. Secondly, results of the finite element analysis on concrete-filled steel deck diaphragms revealed a concentrated distribution of shear transfer through the shear connections on the collectors of the diaphragm near braced frames and a stress concentration in the composite slab near reentrant corners and openings. Thirdly, results of eigenvalue analyses with nonlinear 3D building models showed that the consideration of diaphragm flexibility led to an increase in first mode period between 13% and 48%. A comparison of results from pushover analyses and response history analyses indicated that even though the pushover analyses (based on a first mode load pattern) identified the BRBF as being weaker than the diaphragms and therefore dominating the inelastic pushover behavior, response history analyses demonstrated that the diaphragms can experience substantial inelasticity during a dynamic response. The response history results also suggest that there would be a significant difference in seismic behavior of buildings modeled as two-dimensional (2D) planar frames as compared to the 3D structures modeled herein. Furthermore, the observed final collapse mode involves an interaction between large BRBF story drifts combined with diaphragm deformations that are additive and exacerbate second order effects leading to collapse. The computed adjusted collapse margin ratios for all buildings satisfied the FEMA P695 criteria for acceptance. Therefore, it is concluded that the alternative diaphragm design procedure with the proposed Rs values (Rs = 2 for concrete-filled steel deck diaphragm and Rs = 2.5 for bare steel deck diaphragm) are reasonable for use in design of these types of structures. Lastly, the effects of different standing seam roof configurations (panel type, clip type, thermal insulation, and purlin spacing) on the in-plane stiffness and strength of the standing seam roof system were investigated through an experimental testing program, and a method was described to use these experimental results in the calculations of required bracing for metal building rafters. / Doctor of Philosophy / A diaphragm is a horizontal structural component (e.g. floors and roof) that transfers lateral forces induced by wind or earthquakes to the vertical portions (e.g. frames and walls) of the lateral force resisting system (LFRS) of the building. There are various types of floor and roof diaphragms in steel buildings, such as concrete-filled steel deck diaphragms for the floor system and bare steel deck diaphragms for the roof system of a typical steel braced frame building, and standing seam roof diaphragms for a typical metal building. Compared to vertical elements of a building's LFRS, our understanding of the horizontal elements, i.e., the diaphragms, is grossly lacking. To address the research gaps in understanding the behavior of diaphragms and utilizing them in building design, this work presents a series of computational and experimental studies. In the first study, past experimental test data were analyzed to develop acceptance criteria and modeling protocol for performance-based seismic design of steel deck diaphragms. In the second study, finite element analyses were conducted to understand the nonlinear behavior of concrete-filled steel deck diaphragms subjected to in-plane lateral loading. In the third study, nonlinear three-dimensional computational building models were developed to investigate the seismic behavior and performance of steel buildings with different diaphragm design approaches and diaphragm inelasticity. In the fourth study, experimental testing on full-scale standing seam roof assemblies was conducted to investigate their in-plane behavior and their use in lateral bracing of rafters in metal building systems. The results of these studies contribute to a better understanding of the behavior of diaphragms in steel buildings and lead to several recommendations for diaphragm design.
57

Real time evaluation of weld quality in narrow groove pipe welding

Marmelo, Patricia C. January 2012 (has links)
With the growth in pipeline installations all over the world, there is a great demand for highly productive and robust welding systems. Mechanised pipe welding has been developed over the last 50 years and the present focus is towards development of automated pipeline welding systems. Pipeline welding automation is aimed at reducing costs and improving the installation quality. To attain fully automated pipe welding systems there is a need to rely on sensors and controls systems to mimic human like capabilities, such as visual inspection, in real time. The key aim of this work is to develop and evaluate methods of automatic assessment of weld bead shape and quality during narrow gap GMAW of transmission pipelines. This implies that the measured bead profile will be assessed to determine whether the bead shape will cause defects when the subsequent pass is deposited. Different approaches have been used to conquer the challenge that is emulating human reasoning, all with different objectives in mind. In spite of extensive literature research performed, very little information was found concerning the real time determination and assessment of bead shape quality and none of it was reported to be applied successfully to the pipeline industry. Despite the continuous development of laboratory laser vision systems commercial ones have been on the market for decades, some specifically developed for the welding application. Laser vision sensor systems provide surface profile information, and are the only sensors which can satisfactorily measure bead profile on a narrow groove. In order to be able to use them to automatically assess weld bead shape and quality, a deep understanding of their characteristics and limitations needs to be achieved. Once that knowledge was attained it was then applied to determine the best sensor configuration for this purpose. After that the development of human like judgment algorithms were developed to accomplish the aim that was set. Empirical rules were obtained from an experienced welder regarding the acceptability of bead shapes and were then applied in the developed system with good results. To scientifically evaluate and determine the rules to use in this system, further experiments would be required. The output of the system developed showed very accurate, reliable and consistent results that were true to the external measurements and comparisons performed. The developed system has numerous applications in the pipeline industry and it could easily be implemented on commercial systems.
58

Investigating the regulation and functioning of RNT-1 and BRO-1 in C. elegans

Brabin, Charles Edward January 2012 (has links)
The stem cell-like seam cells of the nematode, Caenorhabditis elegans, represent a tractable and powerful model for studying stem cell biology. rnt-1, the worm homologue of the mammalian RUNX family of transcription factors, together with the CBFβ homologue bro-1, is essential for the proliferation of the seam cells. RUNX genes and CBFβ are important regulators of stem cell development in mammals, and are associated with a variety of cancers. The worm seam cell model offers an opportunity to examine how these genes function in stem cell biology. The aim of this work was to shed light on the genetic network in which bro-1 and rnt-1 function, and to reveal the identity of regulators of these genes as well the downstream targets of the bro-1/rnt-1 pathway. Here, a number of genes that interact with bro-1 and rnt-1 have been identified. ELT-1, a GATA transcription factor, is shown to be a direct regulator of bro-1. Findings which show that the MEIS gene unc-62 acts upstream of bro-1/rnt-1 and regulates the symmetry of seam cell divisions are also presented. The seam cell marker, scm::gfp, is widely used in studies of the seam cells; here the results of an investigation into its identity and functional links are described. In addition, the mechanism underlying spatial regulation of rnt-1 was examined; this led to the discovery of distinct tissue-specific enhancer modules within an intron of this gene. Finally, interactions between pal-1 and bro-1/rnt-1 are reported and described. Together, these findings provide a framework for furthering our understanding of the mechanisms and genes associated with the functioning of bro-1 and rnt-1 in the worm.
59

Intelligent 3D seam tracking and adaptable weld process control for robotic TIG welding

Manorathna, Prasad January 2015 (has links)
Tungsten Inert Gas (TIG) welding is extensively used in aerospace applications, due to its unique ability to produce higher quality welds compared to other shielded arc welding types. However, most TIG welding is performed manually and has not achieved the levels of automation that other welding techniques have. This is mostly attributed to the lack of process knowledge and adaptability to complexities, such as mismatches due to part fit-up. Recent advances in automation have enabled the use of industrial robots for complex tasks that require intelligent decision making, predominantly through sensors. Applications such as TIG welding of aerospace components require tight tolerances and need intelligent decision making capability to accommodate any unexpected variation and to carry out welding of complex geometries. Such decision making procedures must be based on the feedback about the weld profile geometry. In this thesis, a real-time position based closed loop system was developed with a six axis industrial robot (KUKA KR 16) and a laser triangulation based sensor (Micro-Epsilon Scan control 2900-25).
60

Ποιοτικός έλεγχος ραφής σε υπερ-εύκαμπτα υλικά με χρήση μεθόδων ψηφιακής επεξεργασίας σημάτων βίντεο / Seam quality control of non-rigid materials based on digital signal processing techniques of video data

Μαριόλης, Ιωάννης 07 July 2010 (has links)
Στα πλαίσια της διατριβής μελετήθηκε αρχικά το πρόβλημα της εύρεσης της θέσης του υφάσματος επάνω στην τράπεζα εργασίας με μεθόδους ψηφιακής ανάλυσης σημάτων βίντεο, παρουσία φαινομένων παραμόρφωσης και μερικής επικάλυψης του υφάσματος. Οι νέες μέθοδοι εντοπισμού που αναπτύχθηκαν αξιολογήθηκαν πειραματικά παρουσιάζοντας ικανοποιητική ακρίβεια εντοπισμού και ανοχή του συστήματος σε μερικές επικαλύψεις και παραμορφώσεις. Μετά την ολοκλήρωση της ραφής του υφάσματος πραγματοποιείται αυτόματος εντοπισμός της θέσης της ραφής από ψηφιακές φωτογραφίες. Αναπτύχθηκαν τρείς πρωτότυπες μέθοδοι εντοπισμού της θέσης της ραφής οι οποίες διαφοροποιούνται στο στάδιο της προεπεξεργασίας. Η πειραματική αξιολόγηση γίνεται σε βάση δεδομένων που περιέχει 118 εικόνες έτοιμων ενδυμάτων. Προτού πραγματοποιηθεί ποιοτικός έλεγχος ραφής, οι εικόνες κανονικοποιούνται ως προς τη θέση και τον προσανατολισμό της ραφής χρησιμοποιώντας τις παραπάνω μεθόδους αυτόματου εντοπισμού της θέσης της ραφής. Αναπτύχθηκαν και αξιολογήθηκαν τρείς διαφορετικές μέθοδοι αυτόματης αναγνώρισης της ποιότητας σε δείγματα ραφής οι οποίες εξάγουν τρία διαφορετικά σύνολα χαρακτηριστικών. Η πρώτη μέθοδος βασίζεται σε φασματικά χαρακτηριστικά, η δεύτερη στην επιβολή αυτό-σκίασης, ενώ η τρίτη βασίζεται στην εκτίμηση της ανομοιομορφίας της επιφάνειας των δειγμάτων ραφής. Η πειραματική αξιολόγηση γίνεται σε βάση δεδομένων δειγμάτων ραφής που περιλαμβάνει 325 ραφές. Η εκτίμηση της ποιότητας ραφής πραγματοποιείται με ταξινόμηση σε πέντε διατεταγμένους βαθμούς ποιότητας. Σε αυτήν την κατεύθυνση, προτείνονται και συγκρίνονται τέσσερις μέθοδοι αναγνώρισης προτύπων διατεταγμένων κατηγοριών. Η πρώτη μέθοδος χρησιμοποιεί για την ταξινόμηση μοντέλο σύμμετρων αναλογιών πιθανότητας. Η δεύτερη μέθοδος κάνει αναγνώριση με χρήση γραμμικού μοντέλου. Οι άλλες δύο μέθοδοι είναι πρωτότυπες και επίσης χρησιμοποιούν γραμμικό μοντέλο για την ταξινόμηση. Η διαφοροποίησή τους από τη δεύτερη μέθοδο είναι ότι η επιλογή των αριθμητικών τιμών των διατεταγμένων κατηγορίων δεν γίνεται αυθαίρετα., αλλά προκύπτει ως λύση προβλημάτων ελαχιστοποίησης.. Η πειραματική αξιολόγηση και σύγκριση των μεθόδων στο πρόβλημα του ποιοτικού ελέγχου ραφών οδηγεί στην επιλογή του μοντέλου σύμμετρων αναλογιών πιθανότητας σε περίπτωση που υπάρχει ικανός αριθμός παραδειγμάτων εκπαίδευσης, ενώ σε αντίθετη περίπτωση μπορεί να προτιμηθεί το γραμμικό μοντέλο αφού προηγηθεί βελτιστοποίηση με χρήση κάποιας εκ των δύο προτεινόμενων μεθόδων επιλογής αριθμητικών τιμών. / One of the problems studied in the present dissertation is that of the detection of the fabrics’ position on the working area. The proposed detection methods are based on image processing and analysis techniques and take into consideration both partial occlusion and fabric deformation. The methods have been experimentally evaluated and the results indicate sufficient detection accuracy and robustness regarding partial occlusion and fabric deformation. After sewing the fabric, the position and orientation of the seam is automatically detected. Three novel seam detection methods have been developed using different pre-processing techniques. The experimental evaluation of the three detection methods is made on a database containing 118 images of ready sewn garments. Before performing seam quality control the seam images are normalized with respect to the seam position and orientation, using the aforementioned seam detection methods. Feature selection has been studied next, extracting three different sets of features and assessing seam quality using three different methods. The first method uses spectral features; the second method is based on the detection of self-shadows onto the seam specimens, while the third method is based on the estimation of the surface roughness of the specimens. The experimental evaluation of the proposed methods is made on a database containing 325 images of seam specimens. Seam quality control is performed by classifying the seam specimens into five ordinal grades of quality. In this direction, four classification methods are proposed and evaluated, taking into account the ordered arrangement of the classes. The first method uses the proportional odds model; while the second method uses a linear model. The other two methods are novel and also employ a linear model. The difference between these two methods and the second method is that the numerical values they are assigning to the ordered categories are not arbitrary like in the case of the second method. The experimental evaluation of these four methods indicates that in case of a large number of training data, the first method which is based on the proportional odds model is more efficient, while in case of an insufficient number of training data the linear model optimized by one of the two novel methods should be selected.

Page generated in 0.0269 seconds