• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 2440
  • 985
  • 964
  • 3
  • 2
  • Tagged with
  • 4394
  • 4394
  • 4394
  • 2448
  • 2281
  • 2281
  • 2281
  • 2281
  • 2113
  • 2113
  • 1413
  • 1413
  • 1413
  • 1413
  • 223
  • 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.
61

Towards BIM implementation for Geotechnical projects

Alaei, Armin January 2023 (has links)
Despite significant changes in the construction industry due to the digital revolution, geotechnical engineering has been slower to adopt novel technologies such as Building Information Modeling (BIM). While the benefits of BIM in construction management and planning are recognized, its potential for geotechnical projects is less understood. This study seeks to develop a method for incorporating BIM into geotechnical projects, focusing in particular on the role of parametric design. A qualitative study was conducted based on a scoping review of various secondary data sources. Alongside a literature review, a case study was undertaken to provide practical insights and examine a real-world application of the method, integrating ArcGIS, Excel, Dynamo, and Revit with a Common Data Environment (CDE) to facilitate collaborative and efficient management and visualization of geotechnical data and assets. This research showcases the feasibility of merging parametric geotechnical modeling with BIM, laying the groundwork for future progress in geotechnical modeling and its digital transformation.
62

Enhance pilot's decision : Determination of balanced field length using neural network / Förbättra pilotbeslutet

Wan, Antony January 2020 (has links)
The data reliability is crucial in aeronautics because the least miscalculation can lead to crash. Among these data, the balanced field length (BFL) is defined as the shortest field length at which both the take-off and the acceleration-stop can be performed. As the BFL is a critical data, it is subject to certifications that add constraints for all its stages of calculation. An in-house software to calculate the BFL is developed at Dassault Aviation but it can not be embedded and its use requires an expert. Due to the nonlinear dependencies and because an available data set is available, neural networks are proposed to predict the BFL with a maximum relative error less than 2%. The data set of simulations has been set up from Falcon 7X in different configurations of take-off. However, different modelings were used for test- ing purposes and so, the data base is contaminated with points which do not respond to our issue. First of all, it was necessary to find a way to identify these points and a data cleaning algorithm is first implemented. A bagging consensus of neural network is then added to it to detect and filter the other mislabeled data points. Different neural networks are finally trained on the data set and are aggregated to propose the best model. The final model is tested on different database and in this instance, on a Falcon 8X one which has very closed characteristic. It turns out that the algorithm worked for both airplanes and reaches the expected results. / Datatillförlitligheten är avgörande inom luftfarten eftersom minsta felberäk- ning kan leda till krasch. Bland dessa data definieras den balanserade fältläng- den (BFL) som den kortaste fältlängden, vid vilken både start och accelera- tionsstopp kan utföras. Eftersom BFL är en kritisk data, är den föremål för certifieringar som lägger till begränsningar för alla dess beräkningssteg. En egen programvara för att beräkna BFL utvecklas hos Dassault Aviation men den kan inte inbäddas och dess användning kräver en expert. På grund av de olinjära beroenden och eftersom en tillgänglig datauppsättning är tillgänglig föreslås neurala nätverk att förutsäga BFL med ett maximalt relativa fel mindre än 2 %. Datauppsättningen av simuleringar har skapats från Falcon 7X i olika start- konfigurationer. Emellertid användes olika modeller för teständamål och så är databasen förorenad med punkter som inte svarar på vårt problem. Först och främst var det nödvändigt att hitta ett sätt att identifiera dessa punkter och en datalengöringsalgoritm implementerades först. Ett säckskonsensus om neura- la nätverk läggs sedan till det för att detektera och filtrera de andra felmärk- ta datapunkterna. Olika nervnätverk tränas slutligen i datauppsättningen och samlas för att föreslå den bästa modellen. Den slutliga modellen testas i olika databaser och i detta fall på en Falcon 8X som har mycket stängd egenskap. Det visar sig att algoritmen fungerade för båda flygplanen och når de förväntade resultaten.
63

Automatiserad laddning avlitiumjonbatterier i mobiltelefoner : En tillämpad studie av hållbarhet ochlivslängdsförlängning för mobiltelefonbatterier

Lindblad, Ludvig, Berntsson, Fredrik January 2020 (has links)
Sammanfattning Kapaciteten i litiumjonbatterier minskar över tid och användning. Faktorer såsom temperatur,laddningsnivå och djupet av laddningscykeln bidrar till en snabbare degradering. I vissa fall är detomöjligt att kontrollera dessa faktorer, till exempel om användaren lämnar sin telefon på laddningöver natten. Examensarbetets hypotes är att automatisk styrning av batteriladdningen kan reduceralånga perioder av hög laddning och därmed förlänga batteriets livslängd med en liten ansträngningför användaren. Efter en studie och analys om batteridegradering och dess miljöaspekter utformades ochkonstruerades en prototyplösning som proof-of-concept där laddningen styrs automatiskt. Enmobilapplikation skapades för att samla information om batterikonsumtion över dagen. Med hjälpav volontärer genomfördes en fältstudie som pågick under fyra veckor, där syftet var att presenterahur mobiltelefonägare laddar och laddar ur sina mobiltelefoner. Resultaten visade att prototypen skulle ge en försumbar till liten förlängning av batterilivslängden,starkt beroende på användarens tidigare laddningsmönster. Vidare arbete krävs för att uppskattapåverkan av batteridegradering vid alternativa prototyplösningar. Nyckelord Litiumjonbatteri, batteridegradering, mobiltelefon, simulering, automation, android, bluetooth,mikrokontroller
64

Röst som håller : Samband mellan efterklangstid och lärares röstbelastning / Loud and Clear : Sustainable voice for teachers in classrooms with different reverberation timeout

Sundström Lillberg, Karin, Rosén Månsson, Johan January 2017 (has links)
Läraryrket kräver mycket av rösten och sjukfrånvaro relaterad till röstbesvär är högre hos lärare än hos andra yrkesgrupper. Efterklangstid kan påverka risken för besvär. I Region Skåne anpassas efterklangstiden i klassrum där hörselskadade elever skall delta i undervisningen efter regionens Hörselenhets riktlinjer. Effekten på lärarnas röstbettende efter anpassning av efterklangstiden är inte utredd. Syftet med studien var att utvärdera om ljudmiljön i klassrum som anpassats efter Hörselenhetens riktlinjer påverkar lärarnas röstbeteende. Syftet var även att undersöka vilken av svensk standards SS25268:2007 ljudklasser klassrummen som användes under studien uppfyllde utifrån uppmätt efterklangstid. En kvantitativ studie med mätning av efterklangstid, fonationstid, fonationsfrekvens, röststyrka (röst-SPL) och omgivningsbuller (omgivnings-SPL) genomfördes på en skola där både klassrum som anpassats och ej anpassats fanns. Sju lärare deltog. Skattning av upplevelse av talbarhet, buller och röstansträngning utfördes. Statistiskt signifikanta skillnader visades vid jämförelse mellan registrerad röst-SPL och omgivnings-SPL i klassrum med efterklangstid som anpassats efter hörselenhetens riktlinjer och övriga klassrum. Signifikanta skillnader visades även vid jämförelse av upplevelsen av talbarhet och rösttrötthet. Resultaten av efterklangsmätningarna tyder på att det i flera klassrum finns risk för negativ påverkan på lärarnas hälsa. Resultaten gör att frågor kring huruvida skolan uppfyller kraven i föreskriften Belastningsergonomi (AFS 2012:2) väcks. Resultaten för röst-SPL och omgivnings-SPL indikerar att sänkning av efterklangstiden är positiv ur en belastningsergonomisk synvinkel. Slutsatsen av resultaten är att förändring av efterklangstiden i enlighet med Hörselenhetens riktlinjer verkar ha positiv påverkan på lärarnas röstbeteende på talbarheten och rösttröttheten. Studien visade vidare på ett behov av regelbunden undersökning och kontroll av ljudmiljön och övriga riskfaktorer för uppkomsten av röstrelaterade besvär i enlighet med föreskriften Systematiskt arbetsmiljöarbete (AFS 2001:1) i syfte att kartlägga och minska riskerna. För framtida studier rekommenderas ett ökat antal deltagare och ökad observation under mätningarna för att öka säkerheten i resultaten. / The teaching profession is stressful for the voice and the sick leaves related to voice disorders are higher for teachers than for other professions. The reverberation time for a room can increase the risk for voice related disorders. The reverberation time in classrooms in Region Skåne is adjusted according to guidelines from the regions´s Hearing Unit to make it possible for hearingimpaired students to participate in the teaching. The impact on the teacher’s voices has not been investigated after these adjustments. The aim of this study was to evaluate whether the sound environment in classrooms, which has been adjusted according to the guidelines from the Hearing Unit affects the teachers voice behavior. The aim was also to investigate reverberation time and which sound classification according to SS25268:2007 the classrooms that was used during the study fulfilled. A quantitative study with measurements of reverberation time, phonation time, phonation rate, voice strength and background noise was conducted at an uppersecondary school with both rooms adapted for shorter reverberation times and rooms with unknown reverberation time available. Seven teachers took part in the study. Estimations of speech ability, noise experience and voice effort were done. Statistically significant differences were shown by comparison of registered voice sound pressure level, SPL, and ambient-SPL in classrooms with reverberation time tailored to the guidelines from the Hearing Unit and other classrooms. Significant differences were also shown when comparing the perception of speech ability and voice fatigue. The results of the measurements of reverberation time indicate that in several classrooms there is a risk of negative impact on the teacher’s health. The results raise questions about whether the school fulfil the requirements of the regulation Ergonomic, for the prevention of musculoskeletal disorders (AFS 2012: 2). The difference in voice-SPL and ambient-SPL indicates that the decrease in reverberation time is positive from an ergonomic point of view. The conclusion of the results is that changes in reverberation time in accordance with the guidelines from the Hearing Unit have a positive impact on the teachers’ voice behaviour and on the speech ability and the voice fatigue. The study shows a need for regular investigations of the acoustic environment and other risk factors of voice-related disorders in order to find and reduce the risks. For future studies an increased number of participants and increased observation during the measurements are recommended to increase the reliability of the results.
65

Robustness simulation ofbus crew schedules : Case Study Frihamnen Depot (Stockholm)

LLORET CENDALES, KEVIN January 2019 (has links)
This thesis develops a model aimed at predicting the performance of bus crew schedules and study their operational capacity to face disruptions, that is, its robustness. It is based on the relation among schedule deviation, passengers and slack times, considered as non-productive times before trips.Optimization of Public Transport is a challenge that main cities are facing since this type of transport is the backbone of mobility. New powerful versions of transport planning software are providing more optimal schedules to operators, therefore decreasing their costs, but increasing the risk of delays due to more gathered schedules that can cause fines and passengers’ dissatisfaction.A trade-off between production and fines costs is needed to find the optimal slack times. To reach that goal, the Frihamnen bus depot in Stockholm (Sweden) was selected as case study, having historical data of all their lines for last year. A regression model for schedule deviation was calculated which served to create a computer tool in Microsoft Excel, giving the possibility to checking the performance of new schedules based on that historical data.The results showed an inverse relation between schedule deviation and slack times. Moreover, short non-productive times before trips also mean high delays on departures. A positive output is that adding a stop of at least 10% of the total trip time, the first departure would be on time or 2 minutes late as maximum. Several software developers are applying similar studies to their products to keep optimizing bus schedules while taking an economic and social approach.
66

Simulation-based evaluation of a new floating vehicle speeding detection method

Yang, Wentao January 2019 (has links)
Driving too fast is one of the major causes that lead to road crashes. A new speed enforcement management method based on autonomous vehicle technologies has the potential to enhance the speed limit compliance and improve traffic safety. This paper investigates the performance of this method in the detection stage under different scenarios. 27 scenarios are generated using microscopic simulation in VISSIM to collect performance data of this method. Analysis of variance (ANOVA) is used to examine the performance difference between scenarios, including the detectable distance, the number of lanes, the speed of the measuring vehicle, the flow of the traffic, the desired average speed of the traffic, and the desired speed variance of the traffic. As a result, the influences of the factors on the performance of the method are distinguished. The detectable distance, the speed of the measuring vehicle and the flow of traffic have non-linear effects on the number of detected speeding vehicles. The measuring vehicle can interact with more speeding vehicles when the average speed of the traffic is high and the speed variance is small.
67

Geographically Weighted Regression as a Predictive Tool for Station-Level Ridership : The Case of Stockholm

Ounsi, Karim January 2019 (has links)
This thesis studies a new regression method, Geographically Weighted Regression (GWR)to predict ridership at the station level for future stations. The case study of Stockholm’s blue lineis used as new stations will be built by 2030. This paper is written in English.Historically, linear regression methods, independent of the geographical location of theobservations, was and is still used as the Ordinary Least Square regression method. With the riseof GIS-softwares these last decades, geographically dependent regression can be used and previouspreliminary studies have shown a dependency between ridership and location of the station withinthe network.GWR equations for new stations are determined and used to predict their respectiveridership. GIS-data was collected using Geodata and Traffikverket (Traffic Authority) andridership as well as socio-economic related material for the base year of 2016 was used in order todetermine, first, significant variables from a group of candidate ones (Workers, number of buslines and type of change were chosen) and, second the OLS and GWR equations. Significances ofboth models were compared and the OLS equation was used in order to determine the hypotheticalridership of the new stations if they were present in 2016. GWR equations were then determinedusing these calculated ridership of these new stations. Having all GWR equations (each stationhaving its own equation), ridership was thus predicted for the new stations for 2030 usingassumptions and planned, programmed development around the stations (population, apartment tobe built…) and compared with the official predictions.The results show that the GWR method, generally, overpredicts ridership when comparedto the official predictions. Many reasons can explain this overprediction like the assumptions madewith regards to the number of buses as well as the method followed to calculate the number ofworkers around each station.Three main conclusions were drawn for this case study. One main conclusion, specific forthis study and two other, more general, conclusions were deduced from this study. First, GWR isa good predicting tool for future stations that are close to most currently available stations. Second,GWR is a good predicting method for stations where limited changes in the future environmentwill occur.
68

Har lärares psykosociala arbetsmiljö påverkats av karriärstegsreformen och lärarlönelyftet?

Fiedler, Lotta January 2019 (has links)
Under åren 2013 – 2018 har två statliga lönereformer genomförts, som huvudsakligen riktar sig till lärare i Sverige. Riksrevisionen gjorde 2017 en granskning av de två reformerna i vilken man fann att sammanhållningen mellan lärare påverkats negativt. Denna undersökning startar i Riksrevisionens granskning och mina erfarenheter som facklig representant. Undersökningen ger en bild av vad lärares uppfattning är i en kommun. Den visar att arbetsgivaren behöver utveckla arbetet med information och kommunikation vid förändringsarbete. Statens lärarlönesatsningar har medfört både positiva och negativa effekter på lärares arbetsmiljö. Det finns anledning att arbeta för ökad transparens i informationen om lönereformerna och att involvera lärarna i arbetet. För att förbättra arbetsklimatet på skolorna är en rekommendation att göra lärarna delaktiga i arbetet med framtida förändringar och arbeta för tydliga löneprocesser. Detta för att ge förutsättningar för goda och hållbara arbetsmiljöförhållanden. / Employers are responsible for the work environment of all employed and shall achieve a good work environment. The state has implemented two salary reforms for teachers in Sweden during the period 2013 - 2018. The Swedish national audit office has made an audit of the Teacher salary boost and the Teacher career reform. They found a deterioration of cohesion between teachers. This investigation starts in my experiences as a union representative and in the Swedish National Audit Office report of the Teacher salary boost and the Teacher career reform. It gives a picture of the teachers´ opinion about the reforms. The result shows that the employer needs to develop the work with information and communication at change work. The state salary reforms have given both positive and negative effects on teachers´ work environment. There is reason to work for increased transparency in information about the reforms and to involve the teachers in the work. To improve working climate at schools, the recommendation is to make the teachers participant in future work at change processes and to work for clearer processes. This will give the basis for good and sustainable working conditions.
69

Inlandsbanan – befintliga spår, ny trafik : Förutsättningar för regional spårtrafik i glesbebyggda områden

LIDSTRÖM OLSSON, DANIEL January 2019 (has links)
When the car dependency grew under many decades in Sweden parts of the rail network was shutdown or got reduced traffic due to the diminishing demand for rail travel. The railway lines affectedwere primarily those in rural areas with an already low number of travellers. One of these linesthreatened to be shut down was the line called Inlandsbanan (Inland line). Inlandsbanan was savedby the municipalities located along the line who now manage the railway by a co-owned company.Since the railway became managed by the co-owned company the railway has mostly been used fortourist-oriented traffic and freight traffic.Today the conditions are different, the demand for rail travel has increased due to a general highertransport demand and an increased environmental awareness. This study has been carried out tofind out if there is possibility to re-establish regional rail traffic for passengers on Inlandsbanan.The study has been carried out using statistics of current travel volumes and inhabitants in thepopulation centres along the line. This data has been analysed with support from earlier studiesregarding regional rail traffic and public transport in rural areas. As an extra tool in the study asimulation program has been used to estimate the travel demand for the line.The study found that the current low speed on Inlandsbanan is the biggest obstacle for implementingan attractive regional rail service on the line. The train is too slow in comparison to the car andtherefore it is not able to gain any considerable share of the total amount of travellers. It is possibleto replace regional bus service at some parts of the line since the train has some minor time gaincompared to the current bus service and the train could also offer a higher level of comfort.
70

Gångavstånd för resor med elsparkcykel : En studie baserat på elsparkcykelaktören Voi Technology i Stockholm

BERG WINCENT, BOEL January 2019 (has links)
Electric scooters, or e-scooters as they also are called, were launched in California in USA as a bike share system, in 2017. A year later, in September 2018, the Swedish company Voi Technology launched the first e-scooters in Stockholm, Sweden. Bike share systems has been around since the 1960s but has grown substantially in the past 15 years. New technical solutions have solved past problems with theft and payment in bike shares. Since e-scooters are new, there is a lack of research and knowledge about practical use. The study aims to examine how long users of e-scooters walk to utilize the service. Travel data from Voi Technology is used to determine walking distance. The distance from the location where the app was opened to the location where the e-scooter trip begun was measured. The result was also compared the walking distance of other bike share systems and travelers of public transportation. The majority of e-scooter users walk less than 100 meters and 38 per cent walk less than 50 meters. The users have the shortest walking distance in the morning and the longest in the afternoon. During the weekend's users walk further than in weekdays. The users who travel longer distances with the e-scooters don’t walk further than other users. About a third of the users walk in the opposite direction of travel, to some extent, to catch an e-scooter. That indicates that the aim of the user in general seems to be to always have the shortest possible walking distance to the e-scooter.

Page generated in 0.1663 seconds