85 research outputs found
In Search of a Method for Measuring the Output Gap of the Swedish Economy
No full textThis paper describes and evaluates measures of trend (or potential) output in order to improve the measuring and understanding of the current state of the Swedish economy. The target group of the paper is primarily policy makers and analysts in Sweden and international organisations who study the Swedish economy and give recommendations concerning appropriate stabilization policies. The views expressed are those of the authors and do not necessarily represent the ones of neither the National Institute of Economic Research nor the Ministry of Finance.
Aerodynamic flow control for a generic truck cabin using synthetic jets
No full textThis experimental work presents the achievement in drag reduction with the use of active flow control (AFC) for a generic bluff body. Experiments were done in the Chalmers University closed loop wind-tunnel at Reynolds number . The is based on the undisturbed velocity m/s and the width of the model m. The model consists of a simplified truck cabin, characterized by sharp edge separation on top and bottom edges and pressure induced separation on the rounded vertical side edges. The pressure induced separation reproduces the flow detachment occurring at the front A-pillar of a real truck. The investigation of the unactuated and actuated flow was conducted by means of time-resolved particle image velocimetry (PIV). Loudspeakers were used as the actuation device. These were characterized before the actuation study, highlighting an interesting analogy between actuation frequency and jet vortex pair size. The effects of different actuations were evaluated with hot wire anemometry. The effect of the actuation was studied using phase averaging and modal analysis. A notable reduction of the side recirculation bubble was observed. The nature of the separation mechanism was investigated and related to different actuation frequencies spanning the range . As for the , the non-dimensional frequency is based on the undisturbed velocity and the width of the model W
Validation of PANS and active flow control for a generic truck cabin
No full textThis paper presents a drag reduction study using active flow control (AFC) on a generic bluff body. The model consists of a simplified truck cabin, characterized by sharp edge separation on top and bottom edges and pressure induced separation on the two other rounded vertical front corners. The pressure induced separation reproduces the flow detachment occurring at the front A-pillar of a real truck (Schuetz, 2015). The prediction of the flow field by partially averaged Navier-Stokes (PANS) simulations, conducted on a relatively coarse mesh, is validated against wind tunnel data (pressure measurements and particle image velocimetry (PIV)) and resolved large eddy simulations (LES) data. The Reynolds number for both simulations and experiments is Re=5×10^5 (which corresponds to 1/6 of a full scale truck Re) based on the inlet velocity Uinf and the width of the model W=0.4m. A validation of PANS results is followed by a CFD study on the actuation frequency that minimizes the aerodynamic drag and suppresses the side recirculation bubbles. PANS accurately predicts the flow field measured in experiments and predicted by a resolved LES. The side recirculation bubble of a simplified truck cabin model is suppressed almost completely and a notable drag reduction by means of AFC is observed
Predictive Capability Assesment of Finite Element Model using Digital Image Correlation (DIC)
No full textThe goal of this thesis is to improve the predictive capability of Finite element (FE) by gathering data from experimental test and implement the characteristics into the material model that is used. FE is a commonly used method to predict the mechanical behavior of materials and components during applied forces. Therefore, it’s an important part of product development since it gives an opportunity to lower the costs as well as saving resources since it reduces the number of experimental tests. The method for this thesis was to first simulate tensile tests in Abaqus and then to analyze its results. Once all the simulations were done, we replicated the simulation with experimental tests. This was done with DIC (Digital Image Correlation) to help gather data. Since the goal of this thesis is to see how the predictive capability of the FEM-simulation can be improved the results are compared and discussed to see what from the FEM-simulation matches the DIC results and what does not. This will help understand what in the material model that needs to be changed to better match the testing. DIC is a non-contact method that is used to measure deformations and strain locally over an area which results in a more detailed view of the mechanical behavior of the material. The idea of using DIC during this thesis is to sample enough valuable data and apply it to the original material model of the FE-simulations to increase the predictive capability. After the results from the experimental tests were analyzed it was clear that there were both resemblances and differences in the results, for example the Young’s modulus in the FEM-calculations was higher than it was for the experimental tests, Yield strength was lower in the FEM-calculations compared to the experimental tests, maximum load at fracture was lower in the FEM-calculations compared to the experimental tests and elongation was lower in the FEM-calculations compared to the experimental tests. The FEM-calculations were based of the assumptions that the material was homogenous but that wasn’t the case for the experimental tests. Due to the strain varying over the tests the material model could be improved by adding a statistical variation, to all the elements to give them varying mechanical properties simulate how the strain vary more correctly over the specimen.
Predictive Capability Assesment of Finite Element Model using Digital Image Correlation (DIC)
No full textThe goal of this thesis is to improve the predictive capability of Finite element (FE) by gathering data from experimental test and implement the characteristics into the material model that is used. FE is a commonly used method to predict the mechanical behavior of materials and components during applied forces. Therefore, it’s an important part of product development since it gives an opportunity to lower the costs as well as saving resources since it reduces the number of experimental tests. The method for this thesis was to first simulate tensile tests in Abaqus and then to analyze its results. Once all the simulations were done, we replicated the simulation with experimental tests. This was done with DIC (Digital Image Correlation) to help gather data. Since the goal of this thesis is to see how the predictive capability of the FEM-simulation can be improved the results are compared and discussed to see what from the FEM-simulation matches the DIC results and what does not. This will help understand what in the material model that needs to be changed to better match the testing. DIC is a non-contact method that is used to measure deformations and strain locally over an area which results in a more detailed view of the mechanical behavior of the material. The idea of using DIC during this thesis is to sample enough valuable data and apply it to the original material model of the FE-simulations to increase the predictive capability. After the results from the experimental tests were analyzed it was clear that there were both resemblances and differences in the results, for example the Young’s modulus in the FEM-calculations was higher than it was for the experimental tests, Yield strength was lower in the FEM-calculations compared to the experimental tests, maximum load at fracture was lower in the FEM-calculations compared to the experimental tests and elongation was lower in the FEM-calculations compared to the experimental tests. The FEM-calculations were based of the assumptions that the material was homogenous but that wasn’t the case for the experimental tests. Due to the strain varying over the tests the material model could be improved by adding a statistical variation, to all the elements to give them varying mechanical properties simulate how the strain vary more correctly over the specimen.
A study in the effectiveness of predicting default using the Merton model during financial distress
No full textBachelor thesis in financial economics
Applied financial pricing theory
Department of finance
School of Business, Economics and Law
Gothenburg University
9 June 2014.
Title: A study in the effectiveness of predicting default using the Merton model during financial distress
Author: Martin Gholami and Andreas Hjelm
Supervisor: Evert Carlsson, Ph.D.
Background: There are many approaches for calculating the default probability for a corporate bond, but none so important and widely used as the Merton model. The Merton model is a firm value model for pricing risky corporate bonds, from 1974 by Robert Merton.
Purpose: The purpose of this paper is to show how well the Merton model predicts corporate default during a period of financial distress.
Motivation: We intend to give the reader a step-by-step introduction to the Merton model and how to apply the model on real corporate data.
Methodology: First, we extract all the necessary data from the balance sheet and market quotes for equity. Second, a risk-free discount rate is constructed from two generic US government bonds. Then, we discount all future cash flows of the bond to be able to solve for the volatility. Finally, default probabilities are calculated.
Conclusion and Discussion: In our study we analyzed the outcome of the results and tried to find shortcomings and advantages in the Merton model. However in a period of financial distress it is hard to say if the model predicts default better or worse than more complex models.
Further research: There are many more developed and complex firm value models. An interesting approach would be to convey a comparative study of different models to conclude each model’s advantages and limitations
European Truck Aerodynamics – A Comparison Between Conventional and CoE Truck Aerodynamics and a Look into Future Trends and Possibilities
No full textIT solution for co-transporting of parcel goods
No full textFör varje år som går ökar E-handeln mer och mer, som leder till allt fler transporter. Som effekt av detta har effektivare logistiklösningar gällande transporter blivit ett ämne som intensivt diskuteras. Kommuner i gles- och landsbygden i Sverige har många problem med att de inte kan få sina paket levererade i samma mån som de södra delarna av landet. Sveriges paketombud har därför startat ett projekt för att undersöka skapandet av en nationell digital plattform för samdistribution. Syftet med rapporten är att undersöka vilken informationsdelning som krävs för att klara av att genomföra ett sådant projekt. Arbetet undersöker också hur Blockchain-teorin kan komma att användas i syfte att dela information. I denna rapporten har en fallstudie genomförts genom enkäter, intervjuer, interna dokument och deltagarobservationer, med aktörer verksamma inom distribution, paketombud eller myndigheter. I studien framkommer det att det finns ett intresse kring plattformen, där majoriteten vill att information ska delas per automatik. Det gäller dock att inte känslig information delas, samt att delningen anpassas så rätt mottagare får rätt information. Konkurrensdelen visas i studien vara ett stort hinder, och en anledning till att det i dagsläget inte finns en samverkan för paketdistribution. Detta kan vara något som Blockchain kan lösa med hjälp av smarta kontrakt som anpassas ut efter överenskomna villkor.Each year E-commerce continues to increase, which leads to more and more transports. As an effect of this, more effective logistics solutions regarding transports have become a topic that is frequently discussed. Municipalities in the rural and countryside in Sweden have big problems with not being able to receive packages as often as they do in the southern parts of the country. Sverigespaketombud (The Swedish package representative) has therefore started a project to investigate the creation of a national digital platform for joint distribution. The purpose with this research is to analyse what type of information sharing is needed to be able to implement such project. The study also investigates how the Blockchain theory can be used in order to share information. In this study, a case study has been conducted through surveys, interviews, internal documents and participatory with actors operating within distribution, package representative or authority. In the study it appears that there is an interest regarding the platform, where the majority want the information to be shared automatically. However, it must be done in a way where sensitive information is not shared, and that the sharing is customised, so the right receiver gets the right data. The competition part appears to be a big obstacle, and a reason why there is no collaboration for package distribution as of today. This can be something that the Blockchain technology may solve with smart contracts which is adapted according to agreed terms
Two-photon excited fluorescence depolarisation experiments: II. The proper response function for analysing TCSPC data
No full textThe instrumental response function (IRF) needed for the analyses of fluorescence time-correlated single-photon counting (TCSPC) experiments is usually determined by measuring the Rayleigh scattering (RS) of colloidal particles. Since RS is a one-photon process the response function obtained is referred to as a one-photon IRF (OP-IRF). Hence, in a two-photon excited (TPE) fluorescence experiment the hyper-Rayleigh scattering (HRS) might suit the determination of the two-photon IRF better [A. Habenicht, J. Hjelm, E. Mukhtar, F. Bergstrom, L.B.-angstrom. Johansson, Chem. Phys. Lett. 354 (2002) 3671.In the present study, we explore the importance of OP- and TP-IRF in fluorescence depolarisation studies. POPOP in ethanol and n-octanol is analysed when using OP- and TP-IRF. It is demonstrated that the TP-IRF yields significantly better statistics.</p
Experimental and Numerical Investigation of Wheel Housing Aerodynamics on Heavy Trucks
No full textWheel and underbody aerodynamics have become important topics in the search to reduce the aerodynamic drag of the heavy trucks. This study aims to investigate, experimentally as well as numerically, the local flow field around the wheels and in the wheel housing on a heavy truck; and how different approaches to modelling the wheel rotation in CFD influences the results. Emphasis is on effects due to ground simulation, and both moving ground and wheel rotation were requirements for this study.
A 1:4-scale model of part of a heavy truck geometry has been developed. During the model design numerical simulations were used to optimise the shape, in order to replicate the flow field near the wheel of a complete truck. This was done by changing the flow angles of the incoming and exiting flows, and by keeping the mass flow rates in to, and out of, the wheel housing at the same ratios as in a reference full size vehicle. To reduce blockage effects, the model was sectioned to reduce both height and width. In the experiments, pressure sensors and static pressure taps located in the wheel housing were utilised, and the simulations replicated the boundary conditions of the wind tunnel experiments, both in terms of the geometry of the model and wind tunnel as well as the
modelling of the ground simulation. It was found that the wheel wake structures changed significantly when ground simulation was utilised. The main outflow through the
wheel housing was influenced by the wheel rotation and took place further upstream, which resulted in large differences in the flow field downstream of the wheel. The influence of different strategies for modelling the wheel rotation in CFD was investigated and it was found that the Sliding Mesh approach was the most accurate method
- …
