DC Katener hatlarının genelleştirilmiş matematiksel modeli .

Most of the subway systems are powered by electricity around the world. Although both AC and DC systems can be employed for energization, DC electrified systems are commonly preferred. The DC catenary line voltage can be calculated trivially for stationary systems at steady state. However, accurate modeling of the catenary voltage during the movement of the subway trains is cumbersome, as it requires solution of differential equation systems. This thesis proposes a generalized model for catenary voltage variation of DC powered systems. One of the challenges of modeling problem is calculation of the electrical parameters of the system, because of the non-regular shape of the rails, on which the electric current flows. The thesis firstly develops an analytical method for accurate computation of electrical parameters of the system, and validates it using finite elements analysis. After that, by using the electrical parameters the voltage and current variations through the catenary line are investigated analytically for different mode of operations of the subway trains, such as constant speed and accelerating/decelerating operations. Because of the dynamical behavior of the system, both time and position dependent differential equations are defined during the analytical derivations. The solution of the system based on differential equations is not trivial, and requires significant computational burden, Therefore, this work, proposes a linearized method in order to improve the computational performance of the derived model. The proposed linear method enables solution of the system with improved computational performance, while maintaining a high accuracy. Moreover, the effect of the regenerative braking and the effect of multiple substation and train are investigated. The results of the analytical solution of voltage variation are compared with the real life test results.M.S. - Master of Scienc

Voltage variation model for DC catenary line of a subway system

Considering the increasing number of electrified traction systems and changing technological advances in power electronics industry, it is required to successfully model electrified train systems. In this paper a DC catenary voltage model is proposed for a multi substation subway system. The proposed method is capable of simulating dynamic behavior of the train during different modes of operation. In this study, firstly, the electrical parameters of the system will be found to form distributed parameter model. In order to simplify analytic calculations, an approximate yet accurate solution method is proposed. Secondly, relations modeling voltage variation are linearized for improved computational performance. Finally, developed model is extended to multi substation case. Developed model is verified using real field data

DC Catenary Line Modeling of Subway Systems

Today's technology and trend for clean energy, made electrified traction systems more and more popular around the world. As number and capacities of those systems increase, electrical modeling of those systems became a must for power quality studies and dynamic distribution system analysis. However, those models have inaccuracies due to electrical parameters and high computational burden. This paper proposes a linearized DC catenary line model for real subway systems, which has a little computational burden. Moreover, the parameter approximations employed by the method provides more accurate results. The proposed method is validated using real measurement data

A Model Predictive Control for Microgrids Considering Battery Aging

The increasing number of distributed energy resources (DERs), advancing communication and computation technologies, and reliability concerns of the customers have caused an intense interest in the concept of microgrid. Although DERs are the biggest motivation of the microgrids due to their intermittent generation characteristics, they constitute a risk for system reliability. Battery storage systems (BSSs) stand as one of the most effective solutions for this reliability problem. However, the inappropriate use of BSS creates other operational problems in power systems. In order to deal with these concerns explicitly in microgrids, an optimized microgrid central controller (MGCC) is the key factor, which controls the realtime operation of a microgrid. This work proposes a model predictive control (MPC) based MGCC that will provide optimal control of the microgrid, considering economic and operational constraints. The proposed system will minimize the energy cost of the microgrid by utilizing mixed-integer linear programming (MILP) assuming the presence of DERs and BSS as well as the bi-directional grid connection. Moreover, the aging effect of BSS will be considered in the proposed optimization problem which will provide an up-to-date system model. The proposed method is evaluated using real load and photovoltaic (PV) generation data

Does glenoid bone loss accompany posterior shoulder instability with only labral tear? A magnetic resonance imaging–based study

The primary aim of this study was to investigate bone loss in the glenoid with magnetic resonance imaging in posterior shoulder instability with only a labral tear. Methods: A total of 76 patients operated on because of posterior and anteroposterior shoulder instability only with a labral tear between 2006 and 2019 (n = 40 and n = 36, respectively) were included in this study. The instability type, a presence of an additional superior labrum anteroposterior (SLAP) lesion, the number of dislocations, and the magnetic resonance imaging–based measurements (the glenoid diameter and the bone defect size in the glenoid, the Hill-Sachs lesion [HSL] and the reverse HSL [rHSL] length, the angle and the arc length of HSL and rHSL, and the humerus head diameter and its area) were analyzed. Results: The size of the anterior glenoid defect, the rHSL measurements (length, angle, and arc length), and the ratio of the anterior glenoid defect size to the glenoid diameter were significantly higher for anteroposterior instability (P < .01) cases. There was no significant difference (P = .49, .64, and .82, respectively) for the presence of an additional SLAP pathology, the glenoid diameter, the posterior glenoid defect, and the ratio of the posterior glenoid defect size to the glenoid diameter in posterior and anteroposterior instability groups. The increased number of dislocations was associated with increased rHSL length and total arc length (P = .04 and .03, respectively). An additional SLAP lesion in posterior shoulder instabilities was not associated with the bone defect size (P = .29). Conclusion: Although the posterior shoulder instability with only a labral tear is likely to cause a bone defect, we have shown that the instability is not expected to be caused by the bone defect. Therefore, this study points out that only soft tissue repair without considering the bone defect could be promising in this patient group

Novel radiographic hip fat thickness ratio correlates with early re-operation following total hip arthroplasty

*Sezgin, ‪Erdem Aras ( Aksaray, Yazar )Introduction: Obesity is thought to lead to increased failure rates following total hip arthroplasty (THA). Site-specific fat distribution has been suggested to be a better indicator of risk, compared to body mass index. Fat thickness measurement methods were developed for total knee arthroplasty, however, there is limited data on the methods for THA. The aim of this study was to assess the interobserver and intraobserver reliability of a newly defined radiographic subcutaneous fat thickness ratio and investigate the correlation of this ratio with early failure following THA. Methods: 321 patients who underwent primary THA at a single institution between 2014 and 2017, with at least 1-year of follow-up and a preoperative pelvis anteroposterior x-ray radiograph were included in this study. A high hip fat thickness ratio (HFTR) was arbitrarily defined as ⩾2. Early failure was defined as revision or re-operation for any reason and death related to operation first year following THA. Results: The HFTR was shown to have excellent intraobserver and interobserver reliability. High HFTR was associated with higher risk of early failure following THA (odds ratio 3.8, [95% confidence interval, 1.2–12.1], p < 0.05). The same association persisted when HFTR was analysed as a continuous variable (p < 0.01) and in multivariate analysis (p < 0.05). Conclusions: HFTR can be used to assess periarticular soft tissue distribution and may be regarded as a useful and reproducible tool for assessing risk of early failure following THA

Harmony Search Algorithm Based Management of Distributed Energy Resources and Storage Systems in Microgrids

Microgrids are composed of distributed energy resources (DERs), storage devices, electric vehicles, flexible loads and so on. They may either operate connected to the main electricity grid (on-grid operation) or separated from the grid (islanded operation). The outputs of the renewable energy sources may fluctuate and thus can cause deviations in the voltage magnitudes especially at islanded mode. This may affect the stability of the microgrids. This paper proposes an optimization model to efficiently manage controllable devices in microgrids aiming to minimize the voltage deviations both in on-grid and islanded operation modes. RSE Distributed Energy Resources Test Facility (DER-TF), which is a low voltage microgrid system in Italy, is used to verify the algorithm. The test system's data is taken through an online software system (REDIS) and a harmony search based optimization algorithm is applied to control the device parameters. The experimental results show that the harmony search based optimization approach successfully finds the control parameters, and can help the system to obtain a better voltage profile

Yüksek Çözünürlüklü Fosfor Ekran Temelli X-ışınları Radyografi Detektörünün Geliştirilmesi

TÜBİTAK EEEAG Proje01.07.2018TÜBITAK TARAL 1003 projesi kapsamında yapılan bu proje çalısmasında; fiber optikplakalar üzerinde özel mikro patern olusturulmus ve sintilatör filmlerin bu mikroyapı üzerindebüyütülmesi sureti ile yüksek çözünürlüklü fosfor ekranlar gelistirilmistir ki böylece herhangibir litografi yöntemine ihtiyaç duyulmadan mikro paternlenmis fosfor ekranların üretilmesihedefine ulasılmıstır. Bu proje kapsamında yürütülen çalısmalar farklı disiplinlerde çalısanüniversite, arastırma kurumları ve mikro-KOBI tarafından bir isbirligi çerçevesindeyürütülmüstür. Yürütülen deneysel çalısmalar kapsamında sadece malzeme sentezleme,ince film kaplama ve malzeme karakterizasyonu degil bir radyoloji detektörünün tasarımı vefosfor ekranların test edilmesine dair özgün yöntemler ortaya konulmustur.A phosphor screens is simply an optically transparent substrate coated with radioluminescentphosphor film. Visible light can be observed from the uncoated surface of the substrate whenX-ray or high-energy particles illuminate the phosphor film. Phosphor screens can beclassified as powder or vacuum coated screens. Phosphor screens are produced by coatingluminescent powder particles dispersed in highly optically transparent organic binder.Vacuum coated phosphor films are usually deposited by RF magnetron sputtering technique.Scintillators as CsI:Na, CsI:Tl and ceramic scintillators as Gd2O2S:Tb are the most commonmaterials used in conventional phosphor screens. Lateral resolution of a phosphor screen isrelated with morphology of radioluminescent film and microstructure of transparent substrate.Glass, single crystals and fused fibre optic plates are usually chosen as substrates forphosphor screens.Improvement of lateral resolution of phosphor screens by developing special micro patternon the surface of fused fibre optic plates is aimed in this work. Developing ceramic X-rayscintillators which represents high mass absorption coefficient, produce micro patternedphosphor screens using these phosphors and design a CCD field detector prototype which isequipped with improved phosphor screen are other studies involved by this project. Themicro-patterned phosphor screen concept was tested using an experimental X-ray imagingdetector construction and the concept was verified. The developed material and detectortechnology shown that it may primarily used for X-ray imaging applications. In addition tothat, developed device can be used as a small angle X-ray diffraction detector. This detectorhas potential to be used in medical and industrial X-ray imaging applications by optimizingscreen size used and optical coupling elements.Key Words: X-rays, Radiography, Phosphor Screen, Fused Fiberoptics, Spatial Resolution