22 research outputs found
Behavior of Soil Reinforcements in Slopes
No full textAbstractIn geotechnical and transportation engineering, especially road constructions in cuts and deep excavation problems are solved by using different supporting excavation methods. Soil reinforcements are chosen due to easy and economic application. In this study, behavior of supported slopes with geotextiles and geogrids were analyzed by performing experiments on slope models in the laboratory. In the experiments, a static loading was applied to find failure surface and deformations for each case. Additionally, slopes were designed by using Plaxis program. At the end of the study, experimental and analytic models were compared and also behavior of models were presented
DC/DC Converters for Multiterminal HVDC Systems: Based on Modular Multilevel Converter
No full textThe increase in the energy demand has resulted in searching for new energy sources. Due to the increased prices of fossil fuels and the environmental issues, renewable energy sources has become popular in Europe. Renewable energy generation such as wind, solar and wave has point-to-point connections with the main grid. In order to minimize the disadvantages of renewable energy sources like energy fluctuations, multi-terminal systems are favoured interconnecting energy generation stations among them with the main grid. The long distance interconnection especially for offshore wind farms and intercontinental connections is not possible with traditional alternating current (AC) technology because of the limited power transfer. Therefore, high voltage direct current (HVDC) technology is considered as the main element for the future multi-terminal grid. The conversion between AC and DC is preferred via voltage source converters (VSC) as they offer more flexible power control compared to traditional current source converters in other words line commutated converters (LCC). HVDC power transmission schemes have been constructed depending on the technology of the time, which means that there is no standardization in voltage levels and configurations of the HVDC schemes. Therefore, the connection of such systems operating at different voltage levels and/or in different schemes such as monopole and bipolar systems for the future multi-terminal DC grids requires DC/DC converters. Although the voltage level and the configurations are the same for both DC systems, DC/DC converter may be required for the power flow control in multi-terminal DC grid. The modular multilevel converter (MMC) seems as the most suitable converter in this application due to its advantages such as low switching losses, high scalability and modularity. MMC control structures are introduced and front-to-front connection of two MMC forming a DC/AC/DC converter is modelled and simulated for different applications such as interconnecting systems with same voltage levels, different voltage levels or different configurations in this study. The passive element sizes of MMC submodules are also compared for different AC side frequency as the component sizes can be decreased thanks to the increase in the AC frequency which has a disadvantage of higher switching losses. Moreover, the designed converters are tested in multi-terminal DC grids to check their performance and functionality.Electrical Engineering, Mathematics and Computer ScienceElectrical Sustainable EnergyErasmus Mundus, European Wind Energy Master (EWEM), Electric Power System Trac
Underemployment : a skills utilisation perspective
No full textMore than half of all employees believe that the skills they possess are higher than those required to do their present jobs. This is one of several findings reported in a research paper on "under-employment" in the current edition of the University of Strathclyde's Fraser of Allander Review published today. According to the author of the paper, John Sutherland of the Scottish Centre for Employment Research at the university, this provides further evidence that "under-employment" is as important a policy problem as "unemployment"
Twitter reflections on Syrian conflict from Turkey
No full textThe Syrian conflict is a well-known regional conflict, where Turkey is among the most affected countries in political, social, and economic terms. This study explores the Turkish public reflections on the Syria conflict by analyzing 450,000 Tweets posted in the Turkish language between Feb 1, 2015, and Feb 27, 2016. This chapter contributes to the literature by providing a broader perspective with the main research questions of: (1) What are the widely discussed topics on Twitter about Syria by the Turkish users? (2) Were these topics attracting more users to Twitter or encouraging the further engagement of the already existing users? (3) How can the fading-out characteristics of the most popular topics be described? (4) Why-under which conditions and with which features-Tweets about Syria end up extensively re-Tweeted by Turkish users? The authors report a predictive model of 86.12% accuracy to classify high and low Tweets based on the number of re-Tweets received via seven features. The analysis reveals that armed fighting, religious, and political sensitivities within the Turkish public inflate the volume of posted Tweets
A Turkish Hate Speech Dataset and Detection System
No full textSocial media posts containing hate speech are reproduced and redistributed at an accelerated pace, reaching greater audiences at a higher speed. We present a machine learning system for automatic detection of hate speech in Turkish, along with a hate speech dataset consisting of tweets collected in two separate domains. We first adopted a definition for hate speech that is in line with our goals and amenable to easy annotation; then designed the annotation schema for annotating the collected tweets. The Istanbul Convention dataset consists of tweets posted following the withdrawal of Turkey from the Istanbul Convention. The Refugees dataset was created by collecting tweets about immigrants by filtering based on commonly used keywords related to immigrants. Finally, we have developed a hate speech detection system using the transformer architecture (BERTurk), to be used as a baseline for the collected dataset. The binary classification accuracy is 77% when the system is evaluated using 5-fold cross validation on the Istanbul Convention dataset and 71% for the Refugee dataset. We also tested a regression model with 0.66 and 0.83 RMSE on a scale of [0-4], for the Istanbul Convention and Refugees datasets
Intrinsic Spin Hall Edges
No full textThe prediction of intrinsic spin Hall currents by Murakami et al. and Sinova et al. raised many questions about methods of detection and the effect of disorder. We focus on a contact between a Rashba-type spin-orbit coupled region with a normal two-dimensional electron gas and show that the spin Hall currents, though vanishing in the bulk of the sample, can be recovered from the edges. We also show that the current-induced spin accumulation in the spin-orbit coupled system diffuses into the normal region and contributes to the spin current in the leads
Investigation of the effect of CNTs on the mechanical properties of LPET/glass fiber thermoplastic composites
No full textWithin this research, four kinds of multiwalled carbon nanotubes (MWCNTs; 0.0, 0.7, 0.9, and 1.1 wt%) integrated thermoplastic composites with commingled yarns (low melting point polyethylene terephthalate fiber/glass fiber) were fabricated using hot-press machine. The fabricated composites were tested against tensile and three-point flexural loadings. Specimens with 0.9-wt% MWCNTs in 90 degrees direction showed the highest values of tensile and flexural properties with an improvement of about 7% and 33% in tensile and flexural modulus and about 3% and 65% in tensile and flexural strength compared to specimens without MWCNTs in 90 degrees direction. This improvement can most likely be attributed to an increase in interfacial adhesion due to the presence of the carbon nanotubes.Ondokuz Mayis University [PYO.MUH.1901.16.001]The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: This work was supported by the research fund of Ondokuz Mayis University (Project No. PYO.MUH.1901.16.001)
VHDL-AMS based genetic optimisation of fuzzy logic controllers
No full textPurpose – This paper presents a VHDL-AMS based genetic optimisation methodology for fuzzy logic controllers (FLCs) used in complex automotive systems and modelled in mixed physical domains. A case study applying this novel method to an active suspension system has been investigated to obtain a new type of fuzzy logic membership function with irregular shapes optimised for best performance. Design/methodology/approach – The geometrical shapes of the fuzzy logic membership functions are irregular and optimised using a genetic algorithm (GA). In this optimisation technique, VHDL-AMS is used not only for the modelling and simulation of the FLC and its underlying active suspension system but also for the implementation of a parallel GA directly in the system testbench. Findings – Simulation results show that the proposed FLC has superior performance in all test cases to that of existing FLCs that use regular-shape, triangular or trapezoidal membership functions. Research limitations – The test of the FLC has only been done in the simulation stage, no physical prototype has been made. Originality/value – This paper proposes a novel way of improving the FLC’s performance and a new application area for VHDL-AMS
The role of HLA-DRB1 shared epitope alleles in predicting short-term response to leflunomide in rheumatoid arthritis
No full textPubMedID: 18032542Objectives: To investigate the role of shared epitope (SE) alleles in the short-term clinical response to leflunomide for the treatment of active RA. Methods: In an open-label, multi-centre study of 16-weeks duration, 93 patients (82% female) fulfilling ARA 1987 RA criteria were treated with leflunomide (100 mg loading dose for 3 days, then 20 mg/day as the maintenance dose). The primary efficacy criterion was the response status according to the European League Against Rheumatism (EULAR) response criteria using Disease Activity Score-28 (DAS28) activity measure. SE determinations have been undertaken by polymerase chain reaction and sequence-specific oligonucleotide genotyping methods. Results: The mean (s.d.) Disease Activity Score-28 (DAS28) was 5.1 (1.3) before the treatment, which was significantly decreased after 16 weeks [3.0 (1.1), P < 0.001]. According to the EULAR response criteria, 55 patients (59.1%) were classified as good responders. SE was positive in 51 (54.8%) of the patients, with 13 (13.9%) having SE homozygosity or carrying any two SE alleles. Among SE-positive patients, 68.6% (35/51) were good responders, compared with 47.6% (20/42) in SE negatives (P = 0.04). No difference was present according to SE hetero- or homozygosity (68.4 vs 69.2%). RF was also present significantly more frequently in the SE-positive group compared with negatives (78.4 vs 57.1%, P = 0.03). However, no significant difference was observed in the prevalence of RF positivity in patients with a good clinical response (72.7 vs 63.2%, P = 0.32). Conclusions: The results suggest that HLA-DRB1 SE presence may favourably affect the outcome of leflunomide monotherapy in an unselected group of RA patients with an active disease and naive to leflunomide. © The Author 2007. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved.Funding: This study was supported by an unrestricted research grant from Sanofi–Aventis
