Vibration Mitigation of Railway Bridge Using Magnetorheological Damper

The purpose of this study is to analyze the railway bridge vibrations and control their negative effects through semi-active magnetorheological (MR) damper. Dynamic analysis of a railway bridge subjected to the moving load is performed. The real structural parameters are used, and the six-axle train is simulated as moving loads. The railway bridge is modeled as Euler-Bernoulli beam theory, and it is discretized through Galerkin method. To mitigate the bridge vibrations, MR damper with a fuzzy logic-based controller (FLC) is positioned at the ends of the bridge. The simulations of the system are performed by MatLab software. Finally, the results are examined both in the time and frequency domains

Effects of resins on mechanical performance of polymer concrete

Industrija cementa je danas odgovorna za najveće razine emisije ugljičnog dioksida (CO2) i potrošnje energije u građevinskoj industriji. Stoga je u današnje vrijeme primjena održivih vezivnih materijala kao zamjene za cement postalo pitanje od globalnog značenja. Iz prethodnih se radova vidi da su polimeri pouzdana i održiva alternativa cementu u graditeljstvu, a dugoročno gledano, polimerni betoni (PC) smatraju se najprikladnijom zamjenom tradicionalnih betona s cementom. U ovom se radu kao glavni cilj postavlja istraživanje utjecaja smola, koje se koriste kao vezivne komponente u polimernom betonu, na mehanička svojstva polimernih betona. U tom se smislu u radu analizira deset ortoftalnih nezasićenih poliesterskih smola (OUPR) koje se često koriste u građevinarstvu, te se provode ispitivanja svježeg i očvrsnulog betona u obliku ploča koje sadrže navedene smole. Nakon analize, svakom se tipu smole dodjeljuje indeks učinkovitosti. Eksperimentalni rezultati pokazuju da vrsta smole bitno utječe na mehanička svojstva polimernog betona.Cement manufacturing is currently responsible for one of the highest levels of carbon dioxide (CO2) emissions and energy consumption in construction industry. Thus, the use of sustainable binder materials instead of cement has become a worldwide issue. Previous studies have shown that polymers are a reliable and sustainable alternative to cement in construction, while polymer concretes (PCs) are seen as the biggest alternative to conventional cement concretes in the long term. In this study, the main objective is to investigate the effects of resins, which are used as binder components in polymer concrete, on the mechanical properties of the PCs. To achieve this, ten different orthophthalic unsaturated polyester resins (OUPR) that are commonly used in construction industry are considered, and fresh concrete tests and hardened concrete tests are performed on deck plates prepared with these resins. Based on the analysis results, each resin is given a performance index. The experimental results indicate that the type of resin has a significant impact on mechanical properties of polymer concrete

Cerh ve Ta’dil Kriteri Olarak Ehl-i Sünnet ve Ehl-i Bidat

İslam'ın ilk dönemlerinden itibaren hadis ravilerinin isnad zincirinin gerekliliğine dair pek çok yorum yapılmıştır. bu tespitlerden biri de Tabiun döneminin önde gelen alimlerinden olan İbn Sirin'e aittir. O, isnadın tarihi ve uygulama alanı ile ilgili de önemli bir  tespitte bulunmuştur. Onun bu tespiti ilk dönemlerden itibaren kaleme alınana bazı eserlerde bazı farklılıklarla yer almaktadır. onun şöyle dediği söylenebilir: "Önceleri isnaddan sormazlardı; ne zaman ki fitne ortaya çıktı, ravilerin kimler olduğu sorulmaya başlandı. Raviler ehl-i sünnet olurlarsa hadisleri alınıyor, ehl-i bidat olursa hadisleri alınmıyordu." İbn Sirin ve çağdaşı alimler, kendi döneminde ağırlıklı olarak fırkaların hadis uydurma faaliyeti içinde olduklarını bildiklerinden önlemlerini de buna göre almışlardır

Comparative Analysis of Two Different Light Rail Superstructures in Istanbul Traffic in Terms of Vibration

Railway-induced vibrations are one of the major problems that need to be suppressed for the passengers or peoplewho are living around the railway. It is essential that the vibrations are first tried to be suppressed on the source,railway. Thus, the railway superstructure components contain various elastic elements used in vibration insulation,such as rail pads. In this study, two different railway superstructures used in Istanbul railway traffic were testedwhile passing the railway vehicle at various speeds, and the vibrations generated by the wheel-rail interaction werecompared regarding passenger comfort and the environment in compliance with the relevant standards. Usedrailway superstructures to compare the propagated vibrations are constructions with single and double elastomericlayers installed on the same line, sequentially. In this experimental benchmarking study which contains someevaluations according to standards, the behaviour of these two railway superstructure types in terms of vibrationinsulation in light metro lines is revealed using measurement results. Consequently, when the double-layeredelastomer is used instead of a single-layered in the superstructure, the comfort level of the people living aroundthe line is improved as up to 64% and the comfort level of the passengers is improved as up to 54%. In addition,in terms of the safety investigations of the buildings around the line, a meaningful decrease in vibrations greaterthan 70 Hz is observed and it is concluded that residential buildings could be built up to 5 m distance

İstanbul Trafiğinde Bulunan İki Farklı Hafif Metro Üstyapısının Titreşim Bakımından Karşılaştırmalı Analizi

Railway-induced vibrations are one of the major problems that need to be suppressed for the passengers or peoplewho are living around the railway. It is essential that the vibrations are first tried to be suppressed on the source,railway. Thus, the railway superstructure components contain various elastic elements used in vibration insulation,such as rail pads. In this study, two different railway superstructures used in Istanbul railway traffic were testedwhile passing the railway vehicle at various speeds, and the vibrations generated by the wheel-rail interaction werecompared regarding passenger comfort and the environment in compliance with the relevant standards. Usedrailway superstructures to compare the propagated vibrations are constructions with single and double elastomericlayers installed on the same line, sequentially. In this experimental benchmarking study which contains someevaluations according to standards, the behaviour of these two railway superstructure types in terms of vibrationinsulation in light metro lines is revealed using measurement results. Consequently, when the double-layeredelastomer is used instead of a single-layered in the superstructure, the comfort level of the people living aroundthe line is improved as up to 64% and the comfort level of the passengers is improved as up to 54%. In addition,in terms of the safety investigations of the buildings around the line, a meaningful decrease in vibrations greaterthan 70 Hz is observed and it is concluded that residential buildings could be built up to 5 m distance

The perforating branches of the P1 segment of the posterior cerebral artery

The perforating branches of the P1 segment of the posterior cerebral artery are vulnerable to injury. Because of their close proximity to the basilar artery, the vulnerability occurs especially during surgical interventions for vascular pathologies such as basilar apex aneurysms. Therefore, extensive knowledge of the microsurgical anatomy of this area is mandatory to prevent poor post-operative outcomes. We microscopically examined 28 P1 segments obtained from 14 adult fresh cadaver brains (6 silicone injected, 8 freshly examined). The P1 segments ranged between 2.8 mm and 12.2 mm (mean 6.8 mm) in length with a mean outer diameter of 1.85 mm (range 0.8-4.5 mm). All 94 thalamoperforating branches identified in 27 P1 segments (mean 3.35 branches per segment) arose from the postero-superior aspect of P1 and were the most proximally originating branch in nearly all specimens (96.4%). In addition in 28 P1s, 12 short circumflex arteries (42.8%; mean 0.42 branches per segment), 16 long circumflex arteries (57.1%; mean 0.57 branches per segment) and 10 medial posterior choroidal arteries (35.7%; mean 0.35 branches per segment) were identified and all originated from the posterior or postero-inferior surface of the P1 segment. When the P1 segment had more than one type of branch, it was the short circumflex arteries that were always more proximal in origin than the others. The medial posterior choroidal arteries were always more distal in origin. All three branches were not observed together in any of the P1 segments. The findings in this, and future, anatomical Studies may help to reduce the post-surgical morbidity and mortality rates after surgery for posterior circulation aneurysms. (C) 2009 Elsevier Ltd. All rights reserved

Prognostic significance of serum galectin-3 levels in patients with hepatocellular cancer and chronic viral hepatitis

Background/Aim: Galectins affect diverse physiological and pathophysiological processes such as development, inflammation, and tumor growth. We aimed to compare serum galectin-3 levels in three patient groups with chronic hepatitis B and C virus (HBV, HCV), cirrhosis secondary to HBV or HCV, and hepatocellular carcinoma (HCC) secondary to HBV or HCV and evaluate the role of galectin-3 during HCC progression. Patients and Methods: Nineteen patients with hepatocellular cancer, 22 patients with cirrhosis, and 24 patients with chronic hepatitis B and C were included in this study. Serum galectin-3 levels in different liver diseases were assessed by enzyme-linked immunosorbent assay. Results: The mean galectin-3 levels were 4.61 ng/mL (±2.32) in HCC patients, 5.68 ng/mL (±2,2) in cirrhotic patients, 1.98 ng/mL (±1.50) in chronic viral hepatitis group. There were no statistical differences between HCC and cirrhotic patients (P = 0.5), but lower in chronic hepatitis group statistically compared with cirrhosis and HCC (P < 0.001, P = 0.002, respectively). In case of cirrhotic patients, galectin-3 levels were significantly higher in patients with cirrhosis secondary to HCV compared with HBV (P = 0.03). When we evaluated galectin-3 levels in HCC patients, it was found to be 3.92 ng/mL in HCC secondary to hepatitis B and 5.37 ng/mL in HCC secondary to hepatitis C. Conclusion: Serum galectin-3 levels in patients with chronic HBV or HCV may guide us about progression to cirrhosis or HCC and prognosis of the disease. Especially, galectin-3 levels may be more pronounced in case of HCV