• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 155
  • 28
  • 21
  • 20
  • 16
  • 14
  • 13
  • 8
  • 6
  • 5
  • 5
  • 3
  • 2
  • 2
  • 1
  • Tagged with
  • 332
  • 88
  • 36
  • 35
  • 35
  • 34
  • 32
  • 31
  • 29
  • 28
  • 27
  • 26
  • 23
  • 22
  • 20
  • 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.
141

New Technologies in Short Span Bridges: A Study of Three Innovative Systems

Lahovich, Andrew 01 January 2012 (has links) (PDF)
Short span bridges are commonly used throughout the United States to span small waterways and highway overpasses. New technologies in the civil engineering industry have aided in the creation of many unique designs of these short span highway bridges in efforts to decrease construction cost, decrease maintenance costs, increase efficiency, increase constructability, and increase safety. Three innovative systems, the Integral Abutment Bridge, “Bridge-in-a-Backpack”, and the Folded Plate Girder bridge will be analyzed to study how the bridges behave under various types of loading. Detailed finite element models were created for integral abutment bridges of varying geometry. These models are used to study how the live load distribution transversely across the bridge is effected by varying geometric properties and varying modeling techniques. These models will also be used to determine live load distribution factors for the integral abutment bridges and compare them to current American Association of State Highway and Transportation Officials specifications. The “Bridge-in-a-Backpack” and the Folded Plate Girder bridges were each constructed with a variety of instruments to measure the bridge movements. Readings from these instruments are used to determine the bridge response under various loading conditions. Bridges were analyzed during their construction process, during static live load testing, and during long term seasonal changes. The results from these studies will aid in the refinement of these innovative designs.
142

Exploring the Feasibility of Replicating SPAN-Model's Required Initial Margin Calculations using Machine Learning : A Master Thesis Project for Intraday Margin Call Investigation in the Commodities Market

Branestam, Clara, Sandgren, Amanda January 2023 (has links)
Machine learning is a rapidly growing field within artificial intelligence that an increasing number of individuals and corporations are beginning to utilize. In recent times, the financial sector has also started to recognize the potential of these techniques and methods. Nasdaq Clearing is responsible for managing the clearing business for the clearinghouse's members, and the objective of this thesis has been to explore the possibilities of using machine learning to replicate a subpart of the SPAN model's margin call calculations, known as initial margin, in the commodities market. The purpose of replicating SPAN's initial margin calculations is to open up for possibilities to create transparency and understanding in how the input variables affect the output. In the long run, we hope to broaden the insights on how one can use machine learning within the margin call processes. Various machine learning algorithms, primarily focused on regression tasks but also a few classification ones, have been employed to replicate the initial margin size. The primary objective of the methodology was to determine the algorithm that demonstrated the best performance in obtaining values that were as close as possible to the actual initial margin values. The findings revealed that a model composed of a combination of classification and regression, with non-parametric algorithms such as Random Forest and KNN, performed the best in both cases. Our conclusion is that the developed model possesses the ability to effectively compute the size of the initial margin and thus accomplishes its objective. / Maskininlärning är ett snabbt växande område inom artificiell intelligens som allt fler individer och företag börjar använda. Finanssektorn har nu också börjat undersöka hur dessa tekniker och metoder kan skapa värde. Nasdaq Clearing hanterar clearingverksamheten för clearinghusets medlemmar och syftet med denna uppsats har varit att undersöka möjligheterna att använda maskininlärning för att replikera en del av SPAN-modellens beräkningar av marginkravet som kallas Initial Marginal. Syftet med att replikera SPANs initiala marginberäkningar är att öppna upp för möjligheter att skapa transparens och förståelse för hur inputvariablernapåverkar outputen. På sikt hoppas vi kunna bredda insikterna hur maskininlärningslösningar skulle kunna användas inom "Margin Call"- processen. De metoder som användes för att replikera storleken på Initial Margin var olika maskininlärningsalgoritmer, främst fokuserade på regressionsuppgifter men några klassificeringsalgoritmer användes också. Fokus i metoden var att hitta vilken algoritm som presterade bäst, det vill säga den algoritm som predikterade närmst de faktiska värdena för Initial Margin. Resultatet visade sig vara en modell som kombinerade klassificering och regression, där icke-parametriska algoritmer såsom Random Forest och KNN var de som presterade bäst i båda fallen. Vår slutsats är att den utvecklade modellen har en god förmåga att beräkna storleken på Initial Margin och därmed uppfyller den sitt syfte.
143

How has social media affected future economists? : How has social media affected Swedish high school economic students' perception of their attention spans?

Phan, Francis January 2023 (has links)
This thesis explores how social media affects high school students' perception of their attention spans. This study examines how social media influences high school students' attention spans, both positively and negatively. The study was conducted using a qualitative deductive approach, and data was gathered through in-depth interviews with multiple participants, ensuring a comprehensive understanding of the topic. High school students with backgrounds in economic programs and social media habits were chosen.  Findings show that participants were concerned with the constant distractions and addiction yet saw the benefits of engaging content. Balancing social media and homework requires tailored techniques. Educators, parents, and children must create healthy behaviours and boundaries, according to the research. This study clarifies how social media affects high schoolers' attention spans. The study also emphasises how social media use and schooling are individual. Self-discipline, scheduling, and study spaces were some of the ways that helped participants focus. Some individuals struggled to prioritise education over social media, causing anxiety and lower productivity. The research illuminates social media's complex influence on high school pupils' attention spans. It emphasises the need for integrated initiatives involving educators, parents, and students to build healthy habits, set boundaries, and promote responsible social media use while prioritising academics. The findings further emphasise the significance of specific tactics and interventions to address the unique issues of controlling social media in high school.
144

Malingering Detection Measure Utility and Concordance in a University Accommodation-Seeking Student Population

Loser, Nichole M. 03 July 2012 (has links) (PDF)
According to the Americans with Disabilities Act, universities and colleges are required to provide accommodative services for students with disabilities. Many studies have examined the role of malingering mental health symptoms in order to obtain psychotropic medications, but very little research has been done on the role of accommodations as secondary gain in students who may malinger learning disabilities. This study sought to examine both the usefulness of implementing specific malingering detection measures in psychological evaluations with university students and the agreement of those measures within the population. Archival data was gathered from a university accommodation clinic that provided free psychological evaluations for consecutively presenting students (N=121). Four malingering detection measures were used: the Test of Memory and Malingering (TOMM), the Word Memory Test (WMT), the WAIS Digit Span (DS) and two cut scores for the MMPI-2 F Scale (F Scale 80 and F Scale 95). Scores for these four malingering detection measures were compared in terms of their agreement rates, their classification rates (at a 10% malingering base rate recommendation), and their sensitivity, specificity, positive and negative predictive powers using both the TOMM and WMT independently as diagnostic criterion. A qualitative examination of the data revealed that different combinations of measures did classify some of the same respondents as malingering. Results indicated that each of these four measures share the ability to detect malingering in its different forms and have similar classification rates. Although the TOMM and WMT likely provide overlapping information, the pragmatic implementation of one of these measures may assist in the evaluation of suspected malingering with accommodation-seeking students.
145

Review of codes of practice for the design of box culverts for recommendation for South African Bureau of Standards (SABS)

Mpeta-Phiri Namalima, Tina 04 April 2023 (has links) (PDF)
The study is a comparative desk study of the application of the vertical earth load, traffic live load and the nominal earth pressure in the design methodology of culverts as outlined in TMH7 – Code of Practice for the design of highways bridges and culverts in South Africa Part 2, AASHTO LRFD Bridge Design specification and the DMRB volume 2 section 2 part 12 - BD31/01. It involves the theoretical design and analysis of five single cell reinforced concrete box culverts ranging from 2.1m to 6.0m under different fill depths ranging from 0 to 8.0m by applying load obtained using the three design manuals. The objective of this study is to analyze the methodology involved in estimating vertical earth load on a culvert as outlined in the design manuals to ascertain relevance of the formulae and procedure in TMH7 or/and to recommend the most effective approach for evaluating the vertical earth load on box culverts specific and appropriate for South Africa. By comparing the load derivation methodology outlined in ASHTO LRFD and BD 31/01 and analyzing the load forces obtained from the analysis. Box culverts are designed as rigid monolithic structures to withstand the maximum bending moment and shear force. The design involves the analysis of the various loads acting on the culvert with the weight of the overhead earth embankment being the most significant. The vertical earth load, live load and the lateral earth pressure acting on the culverts at various fill depth are manually derived from equations as outlined in the three design manuals. The culverts are modelled and analyzed in Prokon as two-dimensional plane frame structures using the frame analysis module by applying this load to determine maximum positive hogging moments, maximum negative sagging moments and maximum positive shear forces for each span for the top slab. The load forces obtained for each span are then plotted against the soil cover depth to illustrate the discrete load effect of the vertical earth load and live load on the culverts at varying fill height and to determine the relationship between the culvert geometry, soil cover depth and the applied load. The result of the analysis shows that an increasing non-linear relationship exists between the load effects, the soil cover depth, and the span length. The dead load effect increases with increasing fill depth and culvert span while the live load effect diminishes with increasing fill height and culvert span i.e., for culverts buried at shallow depths, the traffic live load is the most critical load but as the height of the soil cover increases the dead load becomes more significant until a point is reached where the live load is totally insignificant. The vertical earth loads obtained from TMH7 and BD31/01 are constant at a particular fill depth for each culvert despite the different span length. The vertical earth load for these two manuals is estimated from the soil cover depth and density, the load tabulated clearly is independent of the culvert geometry. The load obtained from AASHTO LFRD is the lowest and less than 20% of the load obtained from the other two design manuals. Unlike TMH7 and BD31/01, AASHTO LFRD considers the effect of the soil-structure interaction to adjust the vertical earth load on the structure which automatically reduces the load value. The vertical earth load values obtained from TMH7 and BD31/01 are generally more conservative as compared to those obtained from AASHTO LFRD.
146

Using gaze aware regions in eye tracking calibration for users with low-attention span / Användning av regioner medvetna om blicken inom kalibrering av ögonstyrning för personer med låg fokuseringsförmåga

Larsson, Joakim January 2017 (has links)
Eye trackers have enabled users to interact with computers for a long time. Yet, there are still many challenges left to be solved to make the interaction easy for users with development disabilities. Especially, when it comes to setup eye tracking where calibration of the eye tracker is important to get accurate estimation of where users are looking. This paper presents a study in which three modified versions of a calibration interface for eye trackers has been designed and evaluated by nine participants with development disabilities. These calibration interfaces used regions that were aware of when a user gazed at them, gaze-aware regions, and varied in the speed of which a stimulus moved during the calibration and how quickly the regions around the stimulus grew. Data was collected for each interface about interaction with the gaze-aware regions, time to complete a calibration, how many calibration points that were completed and gaze offset from the stimulus. No statistically significance was found between the modified interfaces for its efficiency, effectiveness and accuracy. However, a stimulus moving quicker and a gaze-aware region growing faster indicated a more effective and efficient calibration method without loss in accuracy. Also, if only screen engagement is involved using smooth-pursuit calibration could improve the calibration process. / Ögonstyrning har under en längre tid möjliggjort interaktion för användare. Dock är det fortfarande många utmaningar för att göra interaktionen lätt för användare med intellektuella funktionsnedsättningar. Framförallt när det kommer till inställningar för ögonstyrning, där kalibrering har visat sig vara viktigt för att ge en noggrann uppskattning vart användarna fokuserar. Denna rapport presenterar en studie där tre modifierade versioner av ett kalibreringsgränsnitt för ögonstyrning har blivit designat och utvärderat av nio deltagare med låg fokuseringsförmåga. Dessa gränssnitt använde regioner som var medvetna när en användare tittade inom dom, så kallade blickmedvetna regioner, och varierade i vilken hastighet ett stimuli rörde sig och hur snabbt regionerna runt ett stimuli växte. Data samlades in för varje gränssnitt om interaktionen med de blickmedvetna regionerna, tiden för att genomföra kalibreringen, antal avklarade kalibreringspunkter och avståndet mellan användarnas blick och stimuli. Ingen statistisk signifikans hittades mellan de modifierade gränssnitten mellan tidseffektivitet, effektivitet och noggrannhet. Däremot indikerades en mer tidseffektiv och effektiv kalibreringsmetod, utan minskad noggrannhet, genom användningen av ett stimuli som rör sig snabbare med blickmedvetna regioner som växer. Dessutom skulle kalibreringsprocessen kunna förbättras om enbart engagemang med skärmen används genom smooth-pursuit kalibrering
147

The Impact Of Grade Configuration On Sixth Grade Academic Achievement In Florida Public Schools

Schafer, Karen 01 January 2010 (has links)
This study examined the impact of grade span configuration on the academic achievement of sixth grade students in Florida public schools. Grade configuration (PK-6, PK-8, and 6-8) was the independent variable. Academic achievement, the dependent variable, was measured using 2009 Florida Comprehensive Assessment Test (FCAT) Reading and Mathematics mean scale scores and the percentage of students making annual learning gains from 2008 to 2009. School socioeconomic status (SES) was used as a covariate to equalize the effect of poverty on achievement. Random samples of schools were drawn from the population of all Florida public schools with sixth grades in 2009, and from Florida's 2009 Academically High Performing School Districts. Findings showed that there was a statistically significant difference in achievement based on grade level configuration in reading and mathematics for all schools and for schools in Academically High Performing Districts. In all cases, the PK-6 configuration was statistically significantly higher than 6-8, with varied significance between PK-6 and PK-8, and PK-8 and 6-8. The strongest practical significance for all schools was found for learning gains in mathematics, with 26% of the variance in mean learning gain percentages accounted for by grade configuration when controlling for SES. Recommendations were made that future studies address differentiating grade configurations by instructional models and other factors that could impact achievement. The degree and the fidelity to which the middle school concept is implemented in 6-8 schools should be accounted for before making conclusions about the impact of configuration on academic achievement of students in that configuration.
148

Simplified dynamic analysis of railway bridges under high-speed trains

Johansson, Christoffer January 2013 (has links)
The world-wide development of new high-speed rail lines has led to more stringent design requirements for railway bridges. This is mainly due to the fact that a train at high speeds can cause resonance in the bridge superstructure.  In order to avoid problems of this kind, it has become essential to perform dynamic simulations, which are usually carried out in a time consuming finite element program. The main reason for not using an analytical solution is that this type of solution only exists for simple bridges, e.g., simply supported bridges. The aim of this thesis, is therefore the development of a simplified analytical model for preliminary dynamic analyses of railway bridges. The model is then used in several studies, both parametric and probabilistic ones, to determine the dynamic response of various railway bridges under moving loads. Special attention is paid to acceleration levels in the bridge superstructure, because previous studies have shown that these are often decisive. In the design, both the model and the numerical simulations can be used with considerable effectiveness to help engineers to define their structural systems. All bridges, throughout this thesis, have been modelled with elastically supported multi-span Bernoulli-Euler beams. The amount of dissipated energy is modelled using modal damping. The train load is modelled by concentrated loads, which implies that the vehicle-bridge interaction is not considered. A model with these characteristics can be used to analyse simply supported concrete bridges as well as multi-span steel bridges. Another advantage of the proposed method is that the solution is exact, because the equation of motion has been solved using a Laplace transform. A lot of effort has been made to have a model both as simple as possible and flexible enough to be able to study a wide variety of structures. The results of the case studies have shown that concrete bridges are more suitable than steel and composite bridges for use in the new high-speed lines. The simulations have also shown that short-span railway bridges have problems in meeting the design requirements. This confirms the high acceleration levels that were recorded in France, just after the inauguration of the new high-speed line between Lyon and Paris, on several short-span bridges. Furthermore, it was found that a multi-span bridge has a reduction in its dynamic response of up to 60 % compared to a similar simply supported bridge. / Utbyggnaden av nya höghastighetsbanor i världen har resulterat i striktare krav vid dimensionering av järnvägsbroar. Orsaken är främst att tåg vid höga hastigheter kan orsaka resonans i brons överbyggnad. För att kontrollera dessa effekter krävs omfattande dynamiska simuleringar, vilket ofta utförs med tidskrävande FE-analyser. Med analytiska metoder kan beräkningstiden minskas dramatiskt, dessa är dock ofta begränsade till enkla elementarfall, t.ex. fritt upplagda balkar. Syftet med föreliggande avhandling är att utveckla flexibla hjälpmedel för dynamiska kontroller av järnvägsbroar. Avhandlingen fokuserar på accelerationer i brons överbyggnad eftersom tidigare studier har visat att det är den som ofta är dimensionerande. Utöver detta görs det också ett flertal fallstudier och probabilistiska analyser. Ett stort fokus i arbetet har varit att modellen ska vara tillräckligt flexibel för att kunna analysera olika brotyper, samtidigt som mängden indata är begränsad. Följaktligen består modellen av en serie visköst dämpade Bernoulli-Euler balkar som vilar på elastiska upplag. Tåglasten beskrivs med rörliga punktlaster som appliceras direkt på brons överbyggnad utan att interaktion mellan tåg-spår-bro beaktas. Med dessa egenskaper kan modellen användas till att analysera alltifrån fritt upplagda betongbalkbroar till kontinuerliga samverkansbroar. En annan fördel med den föreslagna modellen är att lösningen är exakt eftersom rörelseekvationen har lösts med en Laplacetransform. Resultaten från fallstudierna visar att betongbroar har lägre dynamisk respons om man jämför med stål- och samverkansbroar. Simuleringarna bekräftar också resultat från tidigare studier som visar att broar med korta spann har svårt att uppfylla accelerationskravet. Detta är något som man också har erfarit i Frankrike, där man efter invigningen av höghastighetslinjen mellan Lyon och Paris uppmätte höga accelerationer hos ett flertal korta broar. Vidare visar också analyserna att en kontinuerlig balkbro har upp till 60 % lägre accelerationer jämfört med om samma bro hade utförts som fritt upplagd. / <p>QC 20130529</p>
149

Longitudinal Shear Capacity of the Slabs of Composite Beams

El-Ghazzi, Mohammed Nael 11 1900 (has links)
No abstract is provided. / Thesis / Master of Engineering (MEngr) / Scope and contents: In this report, a method for calculating the longitudinal shear capacity of the slab of simply-supported steel-concrete composite beams is presented. The method is based on analysing the stresses at failure of the concrete elements located at the slab shear surface. In this analysis, the slab width and the shear span are found to be two main parameters that have been neglected in the empirical solutions previously adopted.
150

Combination of calorie restriction mimetics improves health span in short-lived PEPCK bGH transgenic mice

Gautam, Anil 01 December 2023 (has links) (PDF)
Aging is the major risk factor for chronic age-related diseases characterized by loss of homeostasis, organ dysfunction, and inflammation. Calorie restriction (CR) has been shown to slow aging and delay the onset of chronic age-related diseases. Even though CR has many positive health effects, the degree and duration of the restriction needed would reduce the intervention's usefulness and make it challenging to start and maintain in humans. The difficulties brought on by CR have led to the development of CR mimetics that can mimic the effects of CR without reducing food intake (in an ad libitum state). We hypothesize that in PEPCK bovine Growth Hormone (bGH) overexpressing transgenic mice with accelerated metabolic and cognitive aging, the health span and phenotypes of aging can be improved by adding CR mimetics, a combination of lipoic acid, nicotinamide, thiamine, pyridoxine, and piperine to the diet. From 10 to 40 weeks of age, bGH-tg mice and their normal (N) littermates were fed CRM diet ad libitum. Normal littermates and bGH-tg mice fed a standard chow diet served as controls. Evaluation of the effects of CRM included insulin and glucose tolerance tests (ITT and GTT), indirect calorimetry as well as rotarod, working memory, grip strength testing. Body weight and percent fat mass were significantly lower, but percent lean mass was significantly higher in mice on a CRM diet at 40 weeks. At 19 weeks, insulin sensitivity was improved considerably in treated N and bGH-tg males. At 20 weeks of age, all mice on a CRM diet had significantly improved glucose tolerance and lower fasting glucose. At week 32, treated N female mice had significantly higher energy expenditure during the day and night per gram of body weight. In treated N males, this was true only during the day. Male bGH-tg mice on CRM diet had decreased energy expenditure during the night. Insulin sensitivity was significantly improved in treated male N and bGH-tg mice at week 37. Week 38 GTT showed enhanced glucose tolerance and lower fasting glucose in all mice on a CRM diet except Tg females. Week 39-40 Y-maze, rotarod and grip strength testing showed improved motor coordination and grip strength in all mice on CRM diet with no difference in working memory. Also, there was a significant improvement in metabolic and aging phenotype with lowered pro-inflammatory cytokines at the gene and protein levels in various tissues. Our study indicates the employed CRM produce the beneficial health effects in short-lived, insulin resistant bGH Tg mice but the effects are time-, sex-, genotype-, and diet-dependent. Most of the effects of this intervention resemble the effects of CR suggesting that employed compounds may act via similar mechanisms. This work was funded by the SIU-SOM Geriatrics Research Initiative (AB), NIA R01AG068288, and the Hillblom Foundation (PK).

Page generated in 0.0536 seconds