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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.
481

Maximum Strength, Rate of Force Development, Jump Height, and Peak Power Alterations in Weightlifters across Five Months of Training

Hornsby, W. Guy, Gentles, Jeremy A., MacDonald, Christopher J., Mizuguchi, Satoshi, Ramsey, Michael W., Stone, Michael H. 13 October 2017 (has links)
The purpose of this monitoring study was to investigate how alterations in training affect changes in force-related characteristics and weightlifting performance. Subjects: Seven competitive weightlifters participated in the study. Methods: The weightlifters performed a block style periodized plan across 20 weeks. Force plate data from the isometric mid-thigh pull and static jumps with 0 kg, 11 kg, and 20 kg were collected near the end of each training block (weeks 1, 6, 10, 13, 17, and 20). Weightlifting performance was measured at weeks 0, 7, 11, and 20. Results: Very strong correlations were noted between weightlifting performances and isometric rate of force development (RFD), isometric peak force (PF), peak power (PP), and jump height (JH). Men responded in a more predictable manner than the women. During periods of higher training volume, RFD was depressed to a greater extent than PF. JH at 20 kg responded in a manner reflecting the expected fatigue response more so than JH at 0 kg and 11 kg. Conclusions: PF appears to have been more resistant to volume alterations than RFD and JH at 20 kg. RFD and JH at 20 kg appear to be superior monitoring metrics due to their “sensitivity.”
482

Migrationsprozesse im Kontext der EU-Osterweiterung : Modellierung von Wanderungsszenarien für die Beitrittsländer Estland, Polen, Slowenien, Tschechische Republik und Ungarn mit Ziel Deutschland

Ströker, Kerstin 07 March 2006 (has links)
Im Rahmen der EU-Osterweiterung werden spätestens 2011 sämtliche Migrationsrestriktionen für die Beitrittsländer Polen, Ungarn, Tschechische Republik, Estland und Slowenien gegenüber den Alt-EU-Ländern dauerhaft abgeschafft. Veränderte Migrationsprozesse, die in der öffentlichen Diskussion häufig mit überzogenen Erwartungen in Bezug auf das Ausmaß möglicher Zuwanderung verbunden werden, gelten in diesem Kontext als wahrscheinlich. Für eine sachliche Diskussion und Bewertung potenzieller Auswirkungen, welche mit einem Ansteigen bzw. Sinken von Emigration und Imigration für Aufnahme- aber auch für die Herkunftsländer- einhergehen können, ist eine realistische Schätzung der Größenordnung des möglichen Migrationspotenzials nicht nur hilfreich, sondern mit Blick auf denkbare künftige EU-Erweiterungen unbedingt erforderlich. Die Entwicklung eines eigenständigen Modells zur Vorausschätzung der Zuwanderung aus den genannten EU-Beitrittsländern nach Deutschland steht im Mittelpunkt dieser Dissertation. Methodisch werden zunächst aus den thematisch relevanten empirischen Informationen und theoretischen Grundlagen Push- und Pull-Faktoren für Migrationsprozesse abgeleitet und Schritt für Schritt in einem Werkzeug integriert, welches dann in seiner Anwendung jeweils neun Migrationszenarien für jedes einzelne Beitrittsland liefert. Diese neun Szenarien bilden einen Korridor, in den mit hoher Wahrscheinlichkeit die tatsächliche Entwicklung fällt.
483

Optimisation of a pillow production line applying Lean principles

Fookes, William January 2010 (has links)
Manufacturing companies throughout the world are interested in reducing the time between a customer placing an order and them receiving the payment for that order. This premise is something that is a central characteristic for the Lean philosophy, and is one of the reasons to apply it. Today manufacturers around the world are embracing Lean techniques in order to reduce waste and increase productivity, and also increase the inventory turns, which reflects in an improvement of cash flow for the company. Nowadays, with all the financial turmoil, every company is looking forward to reduce the inventories, to work with Just in Time supply chains, to develop production systems that reduce the scrap and produce only what is needed, saving space, and freeing up time to work on new design and be at the edge of innovation in order to gain market share and keep improving. This master thesis is focused on implementing the Lean principles in a pillow production line, in order to achieve it, a series of techniques to assess the facility where implemented, which allowed to understand how the facility was working, where is the bottleneck, and to understand the function of it as a system, avoiding to focus on a single point but viewing it as a whole, where each part contributes in a specific and unique way, but where all of them are necessary. Applying Lean principles is a daunting task that takes a long time, a never ending trial and error process, because of this the goal of this study is to develop the bases for a Lean transformation, a schedule for the implementation will be developed and proposed to the company, after analyzing the facility. The study reveals that it is possible to reduce the lead-time of the facility in 60%, and avoid the backorders situation that is present in the company, improving also the service level.
484

A Comprehensive Model for Technology Push Product Development

Bishop, Gregory Loren 19 March 2004 (has links) (PDF)
Successful product development has been a fundamental part of many of today's companies and their continued prosperity depends on continuing to develop new products in the future. There are many models of product development. The two most common classes of development are market pull (MP) and technology push (TP). TP product development differs from MP in that the development begins with a specified technology rather than a specified customer. Because TP development is generally considered more difficult and challenging, most of the product development research has focused on MP development and many researchers and practitioners favor MP development over TP development. However, successful TP development has been shown to be a source of innovation that cannot be realized through MP development and is performed by many companies. The research in this thesis focuses on developing a comprehensive TP model to guide product developers on how to implement TP development successfully. This new TP model is developed by comparing recently published TP models to published best practices of TP development and known deficiencies of TP models. The comprehensive TP model makes improvements to the existing TP models through the addition of processes and tools that overcome deficiencies and incorporate best practices. The new comprehensive TP model includes elements of existing generic MP models, a "Technology Application Selection" (TAS) process and several new processes and tools associated with prototypes and network groups. Some of the new processes and tools are demonstrated through a case example. The comprehensive TP model provides product developers with the necessary step-by-step guide to TP product development. The model effectively deals with deficiencies of previous TP models, is sufficiently comprehensive and detailed to guide product developers, is complimentary and consistent to existing design processes and terms, is applicable to most TP product development projects, and is useful and repeatable in making product development decisions.
485

Growing Up Innovative : A Multiple Case Study of Digital Innovation in Digital Startups

Henriksson Shackter, Emilia, Andersson, Frida January 2022 (has links)
Digital startup firms are key actors in innovation landscapes and a viable part of the Swedish tech industry. They operate within hypercompetitive environments, which are dynamic and volatile due to the nature of digital technologies. However, startups often face challenges such as limited resources in terms of finances, skills, and knowledge that affect their preconditions for innovation. Previous research has failed to address the unique characteristics and required management competencies of startups engaged in digital innovation. We aim to contribute to the field of IS and digital innovation, but also provide deeper insights for new startups on how to manage digital innovation. Therefore, we explore the following research question: how do digital startups manage innovation? We have conducted a multiple case study and our findings included two different approaches for digital innovation management in startups - knowledge-push and need-pull. Our findings suggest that these different approaches to digital innovation management affect several activities within the startups. These are: strategic use of data, value creation, financial resources, knowledge-sharing/capabilities, and networking. Further, we suggest practical implications for startups and suggestions for future research.
486

Värt att vara värd? : En kvantitativ studie om Mega-sport events påverkan på destinationsbild och reseintention hos svenska sportintresserade personer.

Svensson, Daniel, Spetz, Olle January 2022 (has links)
This study aims to create a greater understanding of how mega-sports events can be used as a means of nation branding to influence the destination image and travel intention of the host nation. In this thesis, the authors, through a deductive approach and a quantitative research strategy, conducted a survey of Swedish people interested in sports. The Statistical Package for Social Sciences (SPSS) program was used to process the collected quantitative data from the questionnaire. The empirical results of the thesis were analyzed with previous research to strengthen the study. The result of the study shows that mega-sports events can be a pull-factor for tourist’s travel intentions and mega-sports events can also be used as a means for nation branding. Furthermore, the study shows that interest in sports functions as a push-factor when traveling, for Swedish people interested in sports. However, the effects of nation branding on the destination image and travel intentions vary, and largely depend on whether people have visited the event or not. Media surrounding a mega-sport event also has an impact, as do the host countries' geographical and cultural differences to the targeted market. Differences in the empirical result mean that it is not possible to draw conclusions about how mega-sports events affect the destination picture.
487

Bond Performance between Corroded Steel and Recycled Aggregate Concrete Incorporating Nano Silica

Alhawat, Musab M. January 2020 (has links)
The current research project mainly aims to investigate the corrosion resistance and bond performance of steel reinforced recycled aggregate concrete incorporating nano-silica under both normal and corrosive environmental conditions. The experimental part includes testing of 180 pull-out specimens prepared from 12 different mixtures. The main parameters studied were the amount of recycled aggregate (RCA) (i.e. 0%, 25%, 50% and 100%), nano silica (1.5% and 3%), steel embedment length as well as steel bar diameter (12 and 20mm). Different levels of corrosion were electrochemically induced by applying impressed voltage technique for 2, 5, 10 and 15 days. The experimental observations mainly focused on the corrosion level in addition to the ultimate bond, failure modes and slips occurred. Experimental results showed that the bond performance between un-corroded steel and recycled aggregate concrete slightly reduced, while a significant degradation was observed after being exposed to corrosive conditions, in comparison to normal concrete. On the other hand, the use of nano silica (NS) showed a reasonable bond enhancement with both normal and RCA concretes under normal conditions. However, much better influence in terms of bond and corrosion resistance was observed under advancing levels of corrosion exposure, reflecting the improvement in corrosion resistance. Therefore, NS was superbly effective in recovering the poor performance in bond for RCA concretes. More efficiency was reported with RCA concretes compared to the conventional concrete. The bond resistance slightly with a small amount of corrosion (almost 2% weight loss), then a significant bond degradation occurs with further corrosion. The influence of specific surface area and amount of nano silica on the performance of concrete with different water/binder (w/b) ratios has been also studied, using 63 different mixtures produced with three different types of colloidal NS having various surface areas and particle sizes. The results showed that the performance of concrete is heavily influenced by changing the surface area of nano silica. Amongst the three used types of nano silica, NS with SSA of 250 m2 /g achieved the highest enhancement rate in terms of compressive strength, water absorption and microstructure analysis, followed by NS with SSA of 500 m2/g, whilst NS with SSA of 51.4 m2 /g was less advantageous for all mixtures. The optimum nano silica ratio in concrete is affected by its particle size as well as water to binder ratio. The feasibility of the impact-echo method for identifying the corrosion was evaluated and compared to the corrosion obtained by mass loss method. The results showed that the impact echo testing can be effectively used to qualitatively detect the damage caused by corrosion in reinforced concrete structures. A significant difference in the dominant frequencies response was observed after exposure to the high and moderate levels of corrosion, whilst no clear trend was observed at the initial stage of corrosion. Artificial neural network models were also developed to predict bond strength for corroded/uncorroded steel bars in concrete using the main influencing parameters (i.e., concrete strength, concrete cover, bar diameter, embedment length and corrosion rate). The developed models were able to predict the bond strength with a high level of accuracy, which was confirmed by conducting a parametric study. / Higher Education Institute of the Libyan Government
488

Bond Performance between Corroded Steel and Recycled Aggregate Concrete Incorporating Nano Silica

Alhawat, Musab M. January 2020 (has links)
The current research project mainly aims to investigate the corrosion resistance and bond performance of steel reinforced recycled aggregate concrete incorporating nano-silica under both normal and corrosive environmental conditions. The experimental part includes testing of 180 pull-out specimens prepared from 12 different mixtures. The main parameters studied were the amount of recycled aggregate (RCA) (i.e. 0%, 25%, 50% and 100%), nano silica (1.5% and 3%), steel embedment length as well as steel bar diameter (12 and 20mm). Different levels of corrosion were electrochemically induced by applying impressed voltage technique for 2, 5, 10 and 15 days. The experimental observations mainly focused on the corrosion level in addition to the ultimate bond, failure modes and slips occurred. Experimental results showed that the bond performance between un-corroded steel and recycled aggregate concrete slightly reduced, while a significant degradation was observed after being exposed to corrosive conditions, in comparison to normal concrete. On the other hand, the use of nano silica (NS) showed a reasonable bond enhancement with both normal and RCA concretes under normal conditions. However, much better influence in terms of bond and corrosion resistance was observed under advancing levels of corrosion exposure, reflecting the improvement in corrosion resistance. Therefore, NS was superbly effective in recovering the poor performance in bond for RCA concretes. More efficiency was reported with RCA concretes compared to the conventional concrete. The bond resistance slightly with a small amount of corrosion (almost 2% weight loss), then a significant bond degradation occurs with further corrosion. The influence of specific surface area and amount of nano silica on the performance of concrete with different water/binder (w/b) ratios has been also studied, using 63 different mixtures produced with three different types of colloidal NS having various surface areas and particle sizes. The results showed that the performance of concrete is heavily influenced by changing the surface area of nano silica. Amongst the three used types of nano silica, NS with SSA of 250 m2 /g achieved the highest enhancement rate in terms of compressive strength, water absorption and microstructure analysis, followed by NS with SSA of 500 m2/g, whilst NS with SSA of 51.4 m2 /g was less advantageous for all mixtures. The optimum nano silica ratio in concrete is affected by its particle size as well as water to binder ratio. The feasibility of the impact-echo method for identifying the corrosion was evaluated and compared to the corrosion obtained by mass loss method. The results showed that the impact-echo testing can be effectively used to qualitatively detect the damage caused by corrosion in reinforced concrete structures. A significant difference in the dominant frequencies response was observed after exposure to the high and moderate levels of corrosion, whilst no clear trend was observed at the initial stage of corrosion. Artificial neural network models were also developed to predict bond strength for corroded/uncorroded steel bars in concrete using the main influencing parameters (i.e., concrete strength, concrete cover, bar diameter, embedment length and corrosion rate). The developed models were able to predict the bond strength with a high level of accuracy, which was confirmed by conducting a parametric study. / Higher Education Institute in the Libyan Government MONE BROS Company in Leeds (UK) for providing recycled aggregates BASF and Akzonobel Companies for providing nano silica NS, Hanson Ltd, UK, for suppling cement
489

Modeling and Simulation of Microelectromechanical Systems in Multi-Physics Fields

Younis, Mohammad Ibrahim 09 July 2004 (has links)
The first objective of this dissertation is to present hybrid numerical-analytical approaches and reduced-order models to simulate microelectromechanical systems (MEMS) in multi-physics fields. These include electric actuation (AC and DC), squeeze-film damping, thermoelastic damping, and structural forces. The second objective is to investigate MEMS phenomena, such as squeeze-film damping and dynamic pull-in, and use the latter to design a novel RF-MEMS switch. In the first part of the dissertation, we introduce a new approach to the modeling and simulation of flexible microstructures under the coupled effects of squeeze-film damping, electrostatic actuation, and mechanical forces. The new approach utilizes the compressible Reynolds equation coupled with the equation governing the plate deflection. The model accounts for the slip condition of the flow at very low pressures. Perturbation methods are used to derive an analytical expression for the pressure distribution in terms of the structural mode shapes. This expression is substituted into the plate equation, which is solved in turn using a finite-element method for the structural mode shapes, the pressure distributions, the natural frequencies, and the quality factors. We apply the new approach to a variety of rectangular and circular plates and present the final expressions for the pressure distributions and quality factors. We extend the approach to microplates actuated by large electrostatic forces. For this case, we present a low-order model, which reduces significantly the cost of simulation. The model utilizes the nonlinear Euler-Bernoulli beam equation, the von K´arm´an plate equations, and the compressible Reynolds equation. The second topic of the dissertation is thermoelastic damping. We present a model and analytical expressions for thermoelastic damping in microplates. We solve the heat equation for the thermal flux across the microplate, in terms of the structural mode shapes, and hence decouple the thermal equation from the plate equation. We utilize a perturbation method to derive an analytical expression for the quality factor of a microplate with general boundary conditions under electrostatic loading and residual stresses in terms of its structural mode shapes. We present results for microplates with various boundary conditions. In the final part of the dissertation, we present a dynamic analysis and simulation of MEMS resonators and novel RF MEMS switches employing resonant microbeams. We first study microbeams excited near their fundamental natural frequencies (primary-resonance excitation). We investigate the dynamic pull-in instability and formulate safety criteria for the design of MEMS sensors and RF filters. We also utilize this phenomenon to design a low-voltage RF MEMS switch actuated with a combined DC and AC loading. Then, we simulate the dynamics of microbeams excited near half their fundamental natural frequencies (superharmonic excitation) and twice their fundamental natural frequencies (subharmonic excitation). For the superharmonic case, we present results showing the effect of varying the DC bias, the damping, and the AC excitation amplitude on the frequency-response curves. For the subharmonic case, we show that if the magnitude of the AC forcing exceeds the threshold activating the subharmonic resonance, all frequency-response curves will reach pull-in. / Ph. D.
490

En studie på traceurers maximala styrka och explosiva styrka : att mäta hoppförmåga inom Parkour/Freerunning med Isometric Mid-Thigh Pull och Countermovement Jump

Piili, Don, Nilsson, Tobias January 2023 (has links)
Syfte: Syftet för studien var att undersöka om isometric mid-thigh pull (IMTP) tillsammans med (CMJ) kan anses som lämpliga testmetoder för att mäta prestation i hoppförmåga inom parkour/freerunning (PK/FR). Vi undersökte detta genom att mäta traceurers maximala styrka och explosiva styrka i de nedre extremiteterna, för att sedan jämföra resultaten med fysiskt aktiva idrottsstudenter på högskolenivå. Vi undersökte även om IMTP och CMJ korrelerar med varandra. Urval: 23 personer, 11 traceurer och 12 fysiskt aktiva idrottare rekryterades för denna studie. Metod: vi mätte maximal styrka: Peak force (PF) IMTP (N) på kraftplatta och maximal vertikal hopphöjd: CMJ (cm) på IR-matta. Statistisk analys: Shapiro Wilks användes för normalfördelningar, en oberoende tvåvägs Mann-Whitney U t-test användes för att undersöka skillnader mellan grupperna. Två Spearmans- och ett Pearsons korrelationskoefficienttest användes för att undersöka samband mellan IMTP och CMJ. Resultat: PK gruppen var normalfördelad i alla variabler IMTP (N) och CMJ (cm) men kontroll (KTRL) gruppen var ej normalfördelad i CMJ (cm) och gav utslag för IMTP (N). PK gruppen uppnådde ett IMTP (N) medianvärde på: 2269,9 ± 661.72N och CMJ medianvärde på 36.2 ± 7.48 cm. KTRL gruppen uppnådde ett IMTP (N) medianvärde på: 1626.9 ± 501.95N och ett CMJ medianvärde på: 31.8 ± 5.91cm. Ingen statistiskt signifikant skillnad hittades mellan grupperna, men traceurerna visar en trend för ett högre IMTP (N) värde. Ett statistiskt signifikant samband fanns mellan IMTP och CMJ för hela populationen. R-värde = 0.404. R² värde avrundades till 23%. P-värde = 0.031. Inget statistiskt signifikant samband fanns för PK eller KTRL grupperna individuellt. Slutsats: Traceurerna och de fysiskt aktiva högskolestudenterna visade snarlika resultat i maximal styrka och explosiv styrka i denna studie. Resultaten klassificerades som lågpresterande i förhållande till referensvärden från tidigare studier på traditionella idrotter för IMTP och på traceurer i CMJ. Den maximala styrkan från IMTP tycks förklara 23% av hoppförmågan i CMJ vilket kan vara en indikation av betydelse för traceurers prestation. Framtida forskare uppmuntras använda IMTP och CMJ på större populationer för att kartlägga traceurers force-velocity kurvor och/eller inrätta skadepreventiva program för PK/FR. Begrepp: Traceur (FRE) = tracer (ENG), spårare (SWE). Traceur = manlig Parkour utövare. Traceuse = kvinnlig Parkourutövare. PK/FR = Parkour/Freerunning. PK = Studiens Parkour grupp. KTRL = Studiens kontrollgrupp. Countermovement jump (CMJ), (N) = Newton. 1RM = en 100% maximal ansträngd repetition. / Purpose: The aim of the study was to investigate if IMTP together with CMJ can be considered as suitable methods to measure performance in jumping ability in PK/FR. We investigated this by measuring maximal strength and explosive strength of the lower extremities of traceurs and comparing the results with physically active college student athletes. We investigated also if IMTP and CMJ correlate with each other. Recruitment: 23 people, 11 traceurs and 12 psychical active collegial sport athletes were recruited for this study. Method: We measured maximal strength: PF IMTP (N) on force plate and maximal vertical jump height: CMJ (cm) on IR mat. Statistical analysis: Shapiro Wilks was used for normal distribution; an independent two-way Mann-Whitney U t-test was used to examine differences between groups. Linear regression tests with two Spearman's and one Pearson's correlation coefficient tests were used to examine relationships between IMTP and CMJ. R² values were calculated. Results: The PK group was normally distributed in IMTP (N) and CMJ (cm). The KTRL group was not normally distributed in CMJ (cm) and flagged an indication for IMTP (N). The PK group achieved a IMTP (N) median of 2269.9N SD ± 661.72N. And CMJ median of 36.2cm SD ± 7.48cm. The KTRL group achieved a IMTP (N) median of 1626.9N SD ± 501.95N. And a CMJ median of 31.8cm SD ± 5.91cm. No statistically significant differences were found between the groups. But the traceurs showed a trend for a higher IMTP (N) value. A statistically significant relationship was found between IMTP and CMJ for the entire population. R value = 0.404. R² value was rounded to 23%. P-value = 0.031. No statistically significant relationships were found for the PK- or the KTRL groups individually. Conclusion: The traceurs and the physically active college students were similar in maximal- and explosive strength in this study. The results were classified as low performance in comparison to previous studies of traditional sports on IMTP and on traceurs on CMJ. The maximal strength from the IMTP appears to account for 23% of the jumping ability in CMJ which may be an indication of importance for traceurs performance. Future researchers are encouraged to use IMTP and CMJ on larger populations to map force-velocity curves and/or establish injury prevention programs for PK/FR. Concepts: Traceur (FRE) = tracer (ENG), tracker (SWE). Traceur = male Parkour practitioner. Traceuse = female Parkour practitioner. PK/FR = Parkour/Freerunning. PK = The study's Parkour group. KTRL = Study control group. Countermovement jump (CMJ), Isometric mid-thigh pull (IMTP). 1 RM = a 100% maximum effort repetition. / <p>Ämneslärarprogrammet, Specialidrott</p>

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