A network approach for power grid robustness against cascading failures

Cascading failures are one of the main reasons for blackouts in electrical power grids. Stable power supply requires a robust design of the power grid topology. Currently, the impact of the grid structure on the grid robustness is mainly assessed by purely topological metrics, that fail to capture the fundamental properties of the electrical power grids such as power flow allocation according to Kirchhoff's laws. This paper deploys the effective graph resistance as a metric to relate the topology of a grid to its robustness against cascading failures. Specifically, the effective graph resistance is deployed as a metric for network expansions (by means of transmission line additions) of an existing power grid. Four strategies based on network properties are investigated to optimize the effective graph resistance, accordingly to improve the robustness, of a given power grid at a low computational complexity. Experimental results suggest the existence of Braess's paradox in power grids: bringing an additional line into the system occasionally results in decrease of the grid robustness. This paper further investigates the impact of the topology on the Braess's paradox, and identifies specific sub-structures whose existence results in Braess's paradox. Careful assessment of the design and expansion choices of grid topologies incorporating the insights provided by this paper optimizes the robustness of a power grid, while avoiding the Braess's paradox in the system.Comment: 7 pages, 13 figures conferenc

MATCASC: A tool to analyse cascading line outages in power grids

Blackouts in power grids typically result from cascading failures. The key importance of the electric power grid to society encourages further research into sustaining power system reliability and developing new methods to manage the risks of cascading blackouts. Adequate software tools are required to better analyze, understand, and assess the consequences of the cascading failures. This paper presents MATCASC, an open source MATLAB based tool to analyse cascading failures in power grids. Cascading effects due to line overload outages are considered. The applicability of the MATCASC tool is demonstrated by assessing the robustness of IEEE test systems and real-world power grids with respect to cascading failures

A Topological Investigation of Phase Transitions of Cascading Failures in Power Grids

Cascading failures are one of the main reasons for blackouts in electric power transmission grids. The economic cost of such failures is in the order of tens of billion dollars annually. The loading level of power system is a key aspect to determine the amount of the damage caused by cascading failures. Existing studies show that the blackout size exhibits phase transitions as the loading level increases. This paper investigates the impact of the topology of a power grid on phase transitions in its robustness. Three spectral graph metrics are considered: spectral radius, effective graph resistance and algebraic connectivity. Experimental results from a model of cascading failures in power grids on the IEEE power systems demonstrate the applicability of these metrics to design/optimize a power grid topology for an enhanced phase transition behavior of the system

An Investigation of the Relationship between Sportsmanship Behavior of Students in Physical Education Course and Their Respect Level

The aim of this study is to examine relationship between the physical education course sportspersonship behaviors and respect levels for high school students. The sample of study consists of randomly selected 505 high school students (215 female and 290 male) attending state schools in the province of İstanbul in 2016-2017 academic year. “Physical Education Course Sportspersonship Behavior Scale”, “Respect Scale” and personal information form created by the researcher were used in the study. It was found that the scales was valid and reliable and could be used for high school students. Sportsmanship behaviors significantly differed according to the gender of the students (in favor of the girls), the grade (in favor of 10th grade), school success (in favor of good level) and the type of sports most interested (in favor of physically noncontact sports). It was understood that the scale scores of the students are not significantly different according to the family economic conditions. It was found that physical education course sportspersonship behaviors (Realization of Positive Behavior, Avoidance from Negative Behavior) are significantly related to respect levels (Cosmopolitanism, Communitarianism) positively. And it was seen that the level of respect was a significant predictor of the sportsmanship of the students. It is believed that the implementation of activities aimed at improving the level of respect in schools will be helpful in improving sportsmanship behaviors

Pediatric Tracheotomy: A Relatively Rare Indication Limited to Pediatric Intensive Care Subjects?

Objective:To evaluate indications, underlying conditions and outcome in pediatric tracheotomy subjects.Methods:Between January 2004 and September 2013, pediatric subjects who underwent a tracheotomy operation were included for study. All subjects were under the age of 14. Subjects’ primary diseases, indication of tracheotomy, age, gender and type of complications were recorded.Results:Forty five subjects were identified. The mean age of subjects was 26.3 months (range between 2 to 140 months). Twenty one (46.6%) subjects were under the age of 1 year. In 34 (75.5%) out of 45 subjects, tracheotomy indication was prolonged intubation. In the remaining 11 (24.4%) subjects, tracheotomy indication was upper respiratory tract obstruction. Thirteen (n=13- 28.8%) out of 45 experienced early complications and 2 (n=2-4.5%) out of 45 subjects experienced late complications. One tracheotomy related death occurred in the immediate period. Eight (18.1%) of subjects died during the study period from underlying conditions. Decannulation was successfully performed in 13 (36.1%) subjects. In the remaining 23 (63.8%) subjects, decannulation could not be done.Conclusion:All tracheotomies in this report were performed on pediatric intensive care subjects on an elective basis. No tracheotomy was performed for acute upper airway obstruction. Even when planned and elective tracheotomy is performed it still has significant mortality and morbidity

Türkiye'de hal yönetimi ve belediyelerin rolü : İstanbul sebze ve meyve hali örneği

ÖZET TÜRKİYE’DE HAL YÖNETİMİ VE BELEDİYELERİN ROLÜ: İSTANBUL SEBZE VE MEYVE HALİ ÖRNEĞİ Toptancı halleri, üreticinin ürününü tüketiciye ulaştırması konusunda aracılık eden pazarlama kanallarından birini oluşturmaktadır. Üreticinin ve tüketicinin garantörü ve teminatı olan toptancı hallerinin önemi gün geçtikçe daha da artmaktadır. Çünkü toptancı halleri serbest piyasa şartları altında fiyatların oluşmasını sağlayarak üretici ve tüketici arasında denge rolü görmekte ve tekelcilik faaliyetlerinin oluşmasına engel olmaktadır. Bu tezde “Türkiye’de Hal Yönetimi ve Belediyelerin Rolü” konusu ele alınmış ve Türkiye’de Hal Yönetimi konusunda detaylı bir inceleme yapabilmek amacıyla İstanbul Sebze ve Meyve Hali Örneği seçilmiştir. Bu kapsamda, İstanbul Sebze ve Meyve Hali üzerinden yapılacak araştırma ile sebze ve meyve piyasasının işleyişinde hangi aktörlerin rol aldığı, fiyatların nasıl belirlendiği, sebze ve meyve piyasasının işleyişinde ne tür aksaklıklar yaşandığı, mevcut yasalar kapsamında toptancı hallerinin ve belediyelerin sebze ve meyve piyasasının işleyişinde nasıl bir role sahip oldukları sorularına cevap aranması amaçlanmıştır. Tez üç bölümden oluşmaktadır. Tezin birinci bölümünde sebze ve meyve ticareti ve hal yönetimi konusunda genel bilgilere yer verilmektedir. İkinci bölümde ise Türkiye’de Cumhuriyet öncesi ve sonrası dönemde sebze ve meyve hallerinin yönetimi konusu ele alınmaktadır. Birinci ve ikinci bölüme ilişkin veriler literatür, mevzuat ve ilgili raporların taranması yoluyla elde edilmiştir. Üçüncü bölümde yer alan ve İstanbul Sebze ve Meyve iii Hali Örneği üzerinden gerçekleştirilen araştırmada ise mülakat yöntemi ve bu yöntemi destekleyici bir yöntem olarak katılımcı gözlem yöntemleri kullanılmıştır. Yapılan araştırma sonucunda Türkiye’de meyve ve sebze sektörünün tamamen kendi haline bırakıldığı ve denetim ve kontrol mekanizmalarının yeterince işlemediği görülmüştür. Piyasada birçok pazarlama kanalları ve aracılar bulunmakta, fiyatların arz ve talebe göre belirlendiği toptancı hallerinin etkisi ise giderek azaltılmaktadır. Bu ise, hem üreticinin hem de tüketicinin aleyhine bir durum yaratmıştır. Toptancı halleri ile ilgili tüm sorunların giderilmesi, meyve-sebze piyasasının ve fiyatların istikrara kavuşması konusunda gerekli değişimlerin yapılması günümüzde zorunluluk haline gelmiştir. Bu noktada, toptancı hallerinin ve yerel halka en yakın hizmet birimleri olan belediyelerin rolünün artırılması gerektiği düşünülmektedir. -------------------- ABSTRACT WHOLESALE MARKET MANAGEMENT IN TURKEY AND THE ROLE OF THE MUNICIPALITIES: THE CASE OF ISTANBUL VEGETABLE AND FRUIT WHOLESALE FOOD MARKET Wholesale food markets are one of the marketing channels that mediate the manufacturer's delivery of the product to the consumer. The importance of wholesale food markets which are the guarantor and guarantee of the producer and the consumer is increasing day by day. This is because wholesale food markets state create prices under free market conditions and see a balance between producer and consumer and prevent monopoly activities. In this thesis " Wholesale Market Management in Turkey and the Role of the Municipalities" discussed and Istanbul Wholesale Food Market selected in order to make a detailed examination on Wholesale Market Management in Turkey were selected. In this context, the research to be conducted on the Istanbul Vegetable and Fruit Market, which actors play a role in the operation of the vegetable and fruit market, how the prices are determined, what kinds of problems occur in the functioning of the vegetable and fruit market, what kind of problems are observed in the functioning of the wholesale and the aim is to search for answers to the questions they have role. The thesis consists of three chapters. In the first part of the thesis, general information about vegetable and fruit trade and wholesale food market management is given. In the second part of the management issues before and after the Republic of Turkey in vegetables and fruits cases are discussed. Data for the first and second chapters were obtained by review literature, legislation and related reports. Interview method and v participatory observation methods were used as a supportive method in the study which was carried out on Istanbul Vegetable and Fruit Wholesale Market sample in the third part. Made of the fruit and vegetable sector in Turkey as a result of his research completely left to its own audit and control mechanisms has been shown to adequately processed. There are many marketing channels and intermediaries in the market and the effect of wholesaler situations where prices are determined according to supply and demand is gradually diminished. This has created a situation against both the producer and the consumer. It has become a necessity to eliminate all problems related to wholesalers and to make the necessary changes in order to stabilize the fruit and vegetable market and prices. At this point, it is considered that the role of wholesalers and municipalities which are the closest service units to the local people should be increased