Return Migration Intentions Driven by Parental Concerns and the Value of Children

Using an integrated qualitative approach and semi-structured interviews with 32 second-generation Turkish parents in Germany, this study examines the parental concerns formed by assessing the value of children, which, in turn, influence return migration intentions. This study proposes that parents develop three main concerns in an attempt to maximize the value of their children: (1) socioeconomic, (2) assimilation, and (3) marriage concerns. Return migration intention itself turns into a parental investment by designating the home country as the final destination where these concerns can be resolved, and thus their children may reach their full potential for themselves and their families. This study suggests that in the context of migrant families, the value of children can be a potential predictor of return migration since it is subject to changes during the life course in response to the cultural, social, and economic contexts of the host and home countries

Many-server diffusion limits for G/Ph/n+GIG/Ph/n+GI queues

This paper studies many-server limits for multi-server queues that have a phase-type service time distribution and allow for customer abandonment. The first set of limit theorems is for critically loaded $G/Ph/n+GI$ queues, where the patience times are independent and identically distributed following a general distribution. The next limit theorem is for overloaded $G/ Ph/n+M$ queues, where the patience time distribution is restricted to be exponential. We prove that a pair of diffusion-scaled total-customer-count and server-allocation processes, properly centered, converges in distribution to a continuous Markov process as the number of servers $n$ goes to infinity. In the overloaded case, the limit is a multi-dimensional diffusion process, and in the critically loaded case, the limit is a simple transformation of a diffusion process. When the queues are critically loaded, our diffusion limit generalizes the result by Puhalskii and Reiman (2000) for $GI/Ph/n$ queues without customer abandonment. When the queues are overloaded, the diffusion limit provides a refinement to a fluid limit and it generalizes a result by Whitt (2004) for $M/M/n/+M$ queues with an exponential service time distribution. The proof techniques employed in this paper are innovative. First, a perturbed system is shown to be equivalent to the original system. Next, two maps are employed in both fluid and diffusion scalings. These maps allow one to prove the limit theorems by applying the standard continuous-mapping theorem and the standard random-time-change theorem.Comment: Published in at http://dx.doi.org/10.1214/09-AAP674 the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

Promoting Collaborative Care: Relative Performance-based Payment Models for Hospitals and Post-acute Care Providers

Diagnosis-Related Group (DRG) and bundled payment models are widely used in healthcare reimbursement by entities like the Centers for Medicare & Medicaid Services (CMS) and insurance companies. However, these models were primarily designed for conditions managed by a single healthcare provider in a centralized manner, often overlooking the complexities of cases requiring post-acute care (PAC) following an initial hospital stay. This can result in inadequate incentives for effective care coordination between hospitals and PAC providers, especially when treatment decisions are decentralized. Motivated by the Comprehensive Care for Joint Replacement (CJR) payment model recently introduced by CMS, which holds hospitals accountable for the quality and cost of the entire CJR episode, including the cost of PAC, we propose simple payment models that incentivize hospitals and PAC providers to collaboratively enhance the cost efficiency and quality of care for such conditions. Our approach extends traditional payment models by introducing performance targets for all providers, encompassing the entire care episode. Using a game-theoretical model, we demonstrate that the proposed payment model elicits socially optimal actions from all providers, under various assumptions. Importantly, our models do not require detailed knowledge of the hospital-PAC network structure but rely solely on observed cost and quality outcomes within the entire system. Furthermore, while the CJR payment model represents a positive step forward, our analysis reveals potential areas for improvement. Specifically, we suggest that holding both hospitals and PAC providers financially accountable, instead of solely focusing on hospitals, would yield further enhancements in the care delivery model

Türkiye ve Yakın Çevresinde Güneş Fotometreleri ile Elde Edilen Aerosol Optik Derinliği Verisinin Zamansal ve Mekansal Değişimi

Yer seviyesinde konumlandırılmış AERONET ağına bağlı güneş fotometreleri ile belirlenen Aerosol Optik Derinliği (AOD), atmosferik aerosollerin izlenmesinde kullanılan temel parametredir. Kısaca, belli bir dalga boyundaki elektromanyetik enerjinin atmosferdeki aerosoller nedeniyle azalması olarak tanımlanan bu parametrenin bir bölgede mekansal ve zamansal değişimlerinin belirlenmesi o bölge atmosferinde aerosol varlığına ve özelliklerine ilişkin önemli bilgiler vermektedir. Bu çalışma kapsamında, ülkemizin de içinde yer aldığı Doğu Akdeniz bölgesinde 2008-2018 yılları arasındaki toplam 10 AERONET istasyonunda AOD değişimleri incelenmiştir. Değerlendirmeler farklı zaman dönemleri (yıllık, mevsimlik ve aylık) için ayrı ayrı yapılmıştır. Buna göre, çalışma alanı içinde AOD verilerinin mevsimlere göre farklılık gösterdiği ortaya konmuştur. İlkbahar ve yaz aylarında büyük AOD değerleri elde edilirken sonbahar ve kış aylarında daha küçük değerler görülmüştür. Türkiye’de yer alan kırsal istasyonda, kentsel istasyona göre daha büyük AOD değerleri elde edilmiştir. Özellikle yaz, ilkbahar ve sonbahar mevsimleri kırsal istasyonun Afrika ve Asya kaynaklı toz taşınımından en çok etkilendiği mevsimler olup, bu durumun istasyonda büyük AOD değerlerinin ölçülmesine neden olduğu bilinmektedir. Çalışma kapsamında değerlendirilen Türkiye ve yakın çevresinde yer alan 8 AERONET istasyonunda aylık değişimlerin birbirine benzediği, en çok veri sayısına yaz aylarında (Temmuz ve Ağustos) ulaşıldığı görülmüştür. En az veri sayıları ise kış mevsiminde Aralık ve Ocak aylarında elde edilmiştir. Diğer istasyonlardan farklı olarak toz taşınımından etkilendiği bilinen Atina (ATHENS-NOA), Kıbrıs Limasol (CUT-TEPAK), Girit adası (FORTH_CRETE) ve İskeçe (Xanthi) gibi Akdeniz Bölgesi istasyonlarında ilkbahar aylarında, Türkiye’de yer alan kırsal istasyonda olduğu gibi büyük AOD değerleri elde edilmiştir. Çalışma kapsamında elde edilen AOD verisi yardımıyla, bölgede yer seviyesindeki partikül madde konsantrasyonlarının tahminine yönelik istatistiksel tahmin modellerinin hazırlanması mümkün olabilecektir

Electrical resistance welding

Bu çalışmada elektrik direnç kaynağı ile ilgili teorik ve pratik uygulamalar anlatılmış; kullanılan malzemeler, kaynak hataları, proses esasları ve ekipman boyutlandırmaları incelenmiştir. . Önce konu ile ilgili kaynak araştırması yapılmıştır. Metallerin kaynak edilebilirliği, elektrotlarda kullanılan bakır alaşımlar, kaynak prosesinin elektrik, mekanik ve termal etkileri incelenmiştir. Kaynak kalitesini etkileyen parametreler, proses tasarımı ve elektrod boyutlandırma çizelgeleri detaylı olarak ele alınmıştır. . Kaynak kalitesini muayene yöntemleri de modern yöntemlerle birlikte sunulmuştur.In this thesis, electrical resistance welding (ERW) theory and process is explained with theoretical and practical applications: the materials used for process and machinery, failures, process design parameters and fundamental designing are investigated. After having checked the literature about the issue, the weld ability of the metals, copper alloys the electrical, mechanical and thermal effects of the ERW process are analyzed. The parameters those which affect the welding quality, process design and electrode dimensioning & design are explained. Destructive and non-destructive test methods are also given with either conventional or modern methods

“Kurumsal ayrımcılık alanı” olarak kamu sektöründe çalışan engellilerin yaşadıkları ayrımcılık.

This study is an attempt to analyze the discriminatory practices in the public sector within institutionalized form disabled employees faced. The exclusion of disabled people from the private sector forces disabled people to prefer the public sector that allow analyzing the discrimination in the public sector. Their employment is an obligation to be fulfilled by law and therefore they are considered around “burden” paradigm than an employee constitutes the traces of discrimination. The combination of institutional discrimination and disability harassment constitute on the one hand “invisible barriers” to satisfactory employment in public sector, on the other hand make discrimination visible in it. State, its institutions and society have shaped disabled people’s life through modeling and defining them. In other words, the mainstream activities of disabled people are influenced by disability models and definitions. Medical model conceptualizes the “normality” and excludes people who do not fit to the conceptualization of “normal” that set a ground for marginalization of disabled people. In this context, employment conditions are greatly influenced by medical model adopted by the public sector.M.S. - Master of Scienc

State Space Collapse in Many-Server Diffusion Limits of Parallel Server Systems and Applications

We consider a class of queueing systems that consist of server pools in parallel and multiple customer classes. Customer service times are assumed to be exponentially distributed. We study the asymptotic behavior of these queueing systems in a heavy traffic regime that is known as the Halfin and Whitt many-server asymptotic regime. Our main contribution is a general framework for establishing state space collapse results in the Halfin and Whitt many-server asymptotic regime for parallel server systems having multiple customer classes. In our work, state space collapse refers to a decrease in the dimension of the processes tracking the number of customers in each class waiting for service and the number of customers in each class being served by various server pools. We define and introduce a state space collapse function, which governs the exact details of the state space collapse. Our methodology is similar in spirit to that in Bramson (1998); however, Bramson studies an asymptotic regime in which the number of servers is fixed and Bramson does not require a state space collapse function. We illustrate the applications of our results in three different parallel server systems. The first system is a distributed parallel server system under the minimum-expected-delay faster-server-first (MED-FSF) or minimumexpected- delay load-balancing (MED-LB) policies. We prove that the MED-FSF policy minimizes the stationary distribution of total number of customers in the system. However, under the MED-FSF policy all the servers in our distributed system except those with the lowest service rate experience 100% utilization but under the MED-LB policy, on the other hand, the utilizations of all the server pools are equal. The second system we consider is known as the N-model. We show that when the service times only depend on the server pool providing service a static priority rule is asymptotically optimal. Finally, we study two results conjectured in the literature for V-systems. We show for all of these systems that the conditions on the hydrodynamic limits can easily be checked using the standard tools that have been developed in the literature to analyze fluid models.Ph.D.Committee Co-Chair: Amy Ward; Committee Co-Chair: Jiangang Dai; Committee Member: Anton Kleywegt; Committee Member: Mor Armony; Committee Member: Ron Billing