Forced laminar-to-turbulent transition of pipe flows

This paper presents the results of investigations into particular features of laminar-to-turbulent transition of pipe flows. The first part considers transitional flows that occur ‘naturally’, i.e. without any forcing, when a critical Reynolds number is reached. Measurements are reported that were carried out to study the intermittent nature of pipe flows before they become fully turbulent. The second part of the paper concentrates on forced laminar-to-turbulent transition where the forcing was achieved by ring-type obstacles introduced into the flow close to the pipe inlet. The influence of the ring height was investigated and the results showed a dependence of the critical Reynolds number on the normalized height of the disturbances. The laminar-to-turbulent transition was also investigated when caused by partially closing an iris diaphragm that permitted the flow to be forced to turbulence over short time intervals. Investigations of controlled intermittency became possible in this way and corresponding results are presented

Laminar-to-turbulent transition of pipe flows through puffs and slugs

Laminar-to-turbulent transition of pipe flows occurs, for sufficiently high Reynolds numbers, in the form of slugs. These are initiated by disturbances in the entrance region of a pipe flow, and grow in length in the axial direction as they move downstream. Sequences of slugs merge at some distance from the pipe inlet to finally form the state of fully developed turbulent pipe flow. This formation process is generally known, but the randomness in time of naturally occurring slug formation does not permit detailed study of slug flows. For this reason, a special test facility was developed and built for detailed investigation of deterministically generated slugs in pipe flows. It is also employed to generate the puff flows at lower Reynolds numbers. The results reveal a high degree of reproducibility with which the triggering device is able to produce puffs. With increasing Reynolds number, ‘puff splitting’ is observed and the split puffs develop into slugs. Thereafter, the laminar-to-turbulent transition occurs in the same way as found for slug flows. The ring-type obstacle height, h, required to trigger fully developed laminar flows to form first slugs or puffs is determined to show its dependence on the Reynolds number, Re = DU/ν (where D is the pipe diameter, U is the mean velocity in the axial direction and ν is the kinematic viscosity of the fluid). When correctly normalized, h+ turns out to be independent of Reτ (where h+ = hUτ/ν, Reτ = DUτ/ν and $U_{\tau}\,{=}\,\sqrt{\tau_{w}/ \rho}$; τw is the wall shear stress and ρ is the density of the fluid)

Effects of Bevacizumab, an Anti Vascular Endothelial Growth Factor Monoclonal Antibody, on Kidney Function and Morphology

AimTo constitute an experimental rat model by using human VEGF monoclonal antibody bevacizumab, for observation of renal side effects of this treatment.Materials and MethodsThirtysix adult female Wistar albino rats has been divided as two main groups: “3 days” and “21 days” . Each group has been divided in three; bevacizumab 10 mg/kg and 20 mg/kg were administered intravenously from the tail veins of the two subgroups and 1 mg/kg saline was administered to the third subgroup as control. Urine for 24 hours for detection of proteinuria and blood samples for detection of renal funtions were collected before, third day and 21st day of the drug administration and rats were sacrified at third and 21st days for pathological examination of kidneys.ResultsTwenty four hours urine protein excretion, creatinin excretion and urine protein/creatinin ratio were demonstrated as significantly increased on the third day of the rats administered 10 mg/kg bevacizumab; however, any significant increase of proteinuria couldn’t be shown on the 21 days group rats administered neither 10 mg/kg or 20 mg/kg. Pathological examination of rats sacrified on third day demonstrate the significant increase of bowman capsule gap and interstitial inflamation as correlated with the dosage of the drug. The thickness of vessel wall was observed on the pathological examination of rats sacrified on 21st day.ConclusionIt has been shown that bevacizumab administration of 10 mg/kg for three days is proper for constitution of an experimental rat model

P Wave and QT Dispersion in Patients with Generalized Anxiety Disorder

Giriş: Çalışmamızın amacı; yaygın anksiyete bozukluğu (YAB) olan hastalarda, ventriküler aritmi ve ani kardiyak ölümün noninvaziv belirleyicisi olan QT dispersiyonu ile atriyal aritminin noninvaziv belirleyicisi olan P dispersiyonunu araştırmaktır. Hastalar ve Metod: Ayaktan 40 YAB olan hasta ve 29 sağlıklı kontrol çalışmaya dahil edildi, Beck Anksiyete Envanteri (BAE) ve Beck Depresyon Envanteri (BDE) uygulandı ve 12 derivasyonlu EKG ölçümleri elde edildi. Pd ve QTd ölçümleri tek kör kardiyolog tarafından yapıldı. Bulgular: BAE puanları (26.6 ± 11.8 vs. 3.4 ± 3.3, p< 0.001) ve BDE puanları (12.6 ± 4 vs 3.7 ± 4.5, p< 0.001) kontrol grubuna göre hasta grubunda anlamlı olarak daha yüksekti. P dispersiyonu (Pd) [50.0 ± 17.5 milisaniye (ms) vs. 23.4 ± 7.7 ms, p< 0.001] ve ortalama QT dispersiyonu (QTd) (50.5 ± 18.1 msn vs. 28.3 ± 11.4 msn, p< 0.001)'nda kontrol grubuna göre hasta grubunda anlamlı olarak daha yüksekti. Sonuç: Pd ve QTd belirgin olarak YAB hastalarında artmıştır. Bu sonuçlar, YAB olan hastalarda artmış Pd'nin atriyal aritmi riskini artırabileceğini, artmış QTd'nin ise ventriküler aritminin artmış riskini düşündürmektedir.Introduction: The aim of this study is to investigate P wave dispersion (Pd) and QT dispersion (QTd), non-invasive predictors of atrial fi brillation and ventricular arrhythmia or sudden cardiac death, respectively, in patients with generalized anxiety disorder (GAD).Patients and Methods: A total of 40 outpatients diagnosed as GAD and 29 healthy control subjects were included in the study. Beck Anxiety Inventory (BAI) and Beck Depression Inventory (BDI) were administered and 12-lead ECG measurements were obtained. Pd and QTd measurements were performed by blinded cardiologists.Results: BAI scores (26.6 &plusmn; 11.8 vs. 3.4 &plusmn; 3.3, p&lt; 0.001) and BDI scores (12.6 &plusmn; 4 vs. 3.7 &plusmn; 4.5, p&lt; 0.001) were signifi cantly higher in the patient group compared to the controls. P wave dispersion (Pd) [50.0 &plusmn; 17.5 miliseconds (ms) vs. 23.4 &plusmn; 7.7 ms, p&lt; 0.001] and mean QT dispersion (QTd) (50.5 &plusmn; 18.1 ms vs. 28.3 &plusmn; 11.4 ms, p&lt; 0.001) signifi cantly increased in the GAD patient group compared to the controls. Conclusion: Increase in Pd may suggest that GAD patients have increased risk of atrial fi brillation. Similarly, increased QTd may show that these patients have a higher risk of ventricular arrhythmia

A Case of Primary Gastric Malign Melanoma with Multiple Hepatic Metastasis

Malign melanoma is an agressive tumor that can involve the gastrointestinal tract as metastasis or primary gastrointestinal lesions. Discrimination of primary lesions from metastatic ones may be difficult, especially when the tumor in the skin regresses. We aimed to present a case of primary gastric MM with liver metastasis

Zeitabhängige Laminare, transitionale und turbulente Rohrströmungen

This thesis summarises the author's research work carried out at the Institute of Fluid Mechanics of the Friedrich-Alexander Universiät Erlangen-Nüernberg (LSTM-Erlangen) during his time there as a researcher. The work deals with time dependent laminar, transitional, and turbulent pipe flows. Most investigations of pipe flows, available these days in the literature, are of steady state flow cases. The reason for this was found to lie in the fact that no suitable experimental equipment is available to reliably set up laminar, transitional, and turbulent flows that are time dependent. For this reason, a flow rate control system was set up, based on available developments at LSTM-Erlangen. The instrument provided the basis for all the experimental investigations described in this thesis. It was employed to study laminar pulsating flows where its features could be fully utilised to provide a mass flow rate in accordance with the input of an electronic signal. Hence, pulsations of different shapes with time could be set up and investigated. Numerous studies were carried out by the author and the results are summarised in this thesis.Diese Doktorarbeit umfasst die Forschungsarbeiten des Autors, die er während seiner Zeit als wissenschaftlicher Mitarbeiter am Lehrstuhl für Strömungsmechanik an der Friedrich-Alexander-Universität Erlangen-Nürnberg (LSTM-Erlangen) durchgeführt hat. Die Arbeit befasst sich mit zeitabhängigen laminaren, transitionalen und turbulenten Rohrströmungen. Die meisten Untersuchungen von Rohrströmungen, die in der Literatur zu finden sind, wurden in stationären Strömungen durchgeführt. Ein Grund hierfür liegt in der Tatsache, dass kein geeigneter Versuchsstand zur Verfügung stand, um verlässlich zeitabhängige laminare, transitionale und turbulente Durchflüsse zu erzeugen. Aus diesem Grunde wurde ein Durchflusskontrollsystem aufgebaut, das auf bereits vorhandenen Entwicklungen am LSTM-Erlangen basiert. Die Anlage bildete die Basis für all die experimentellen Untersuchungen, die in dieser Doktorarbeit beschrieben sind. Sie wurde eingesetzt, um laminare pulsierende Strömungen zu untersuchen, wobei ihre Eigenschaften genutzt werden konnten, um einen Massendurchfluss zu liefern, der dem Eingang eines elektronischen Signals entsprach. Folglich konnten Pulsationen verschiedener Zeitausprägung erzeugt und untersucht werden. Zahlreiche Studien an solchen Strömungen wurden vom Autor durchgeführt, und die Ergebnisse sind in dieser Doktorarbeit zusammengefasst

THE EVALUATION ON SOME FACTORS THAT HAVE AFFECTED IN PRIMARY SECOND-CLASS STUDENTS EATING HABITS

Bu arastırma 2005-2006 Egitim-Ögretim yılında, Bilecik ili sınırlarında yer alan Atatürk lkögretim Okulu'nda okuyan ilkögretim ikinci kademe ögrencilerinin yeme davranıslarını etkileyen bazı faktörlerin degerlendirilmesi amacıyla yürütülmüstür. Arastırma rastgele örnekleme yöntemi ile seçilen 125 kız ve 175 erkek olmak üzere toplam 300 ögrenci üzerinde yürütülmüstür. Arastırma sonucunda; lkögretim ikinci kademe ögrencilerinin % 79.7'si üç ögün, % 13.3'ü dört ögün, % 7.0'si ise iki ögün yemek yemektedir. En çok atlanan ögün sabah kahvaltısı, ögün atlama nedenleri ise daha çok istahsızlık ve zaman olmamasıdır. Ögrencilerin beslenme bilgi düzeyleri yaslarındaki artısa paralel olarak yükselmektedir. Anne ve babası üniversite ya da yüksekokul mezunu olan ögrencilerin beslenme bilgi düzeyleri diger ögrencilerden daha yüksektir.This research has been carried out in 2005 and 2006 School Year with the aim of some factors which affect in primary second-class students' eating habits in Atatürk lkögretim Okulu which is in Bilecik. This research carried out on total of 300 students; 175 sons and 125 girls that were chosen by random sampling method. At the result of research : 79.7 % of second-class students have only three, 13.3 % have only four, 7.0 % have only two meals. The most missed meal was breakfast and the reasons of missing meals are mostly lack of appetite and lack of time. The rank of nourishment knowledge of students are inreased by their ages simultaneously. Ranks of nourishment knowledge the students whose parents graduated from universities and high school are higher than the other ones

Social integration of Syrian refuges: Reyhanlı example

Suriye'de iç savaşın uzamasıyla beraber ilk önce misafir statüsünde olan Suriyeli mülteciler, daha sonra kalıcı bir hale gelmişlerdir. Türkiye'de yaklaşık olarak 4 milyon kadar Suriyeli mülteci bulunmaktadır. Bu mültecilerin özellikle de barınma alanları dışında kalanları ciddi manada ekonomik ve sosyal problemlerle karşı karşıyadırlar. Bununla birlikte uyum ve entegrasyon açısından son derece sıkıntı yaşamaktadırlar. Bu çalışmanın amacı Reyhanlı ilçesi baz alınarak ilçede yaşamını sürdürmekte olan Suriyeli mültecilerin sorunları göç teorilerine ilişkin yaklaşımların yardımı ile analiz edilmeye çalışılmıştır. Burada karşı karşıya kalınan uyum problemi, yalnızca mülteciler için değil aynı zamanda ilçede yaşayan yerel halk için de büyük bir problemdir. Araştırma kapsamında, Suriyelileri zorunlu göç etmeye sürükleyen siyasal, sosyal, ekonomik, kültürel ve tarihsel faktörler ele alınmış ve Suriyeli göçmenlerin göç deneyimlerine ve göç sonrası Türkiye'deki toplumsal ve ekonomik hayattaki yaşam deneyimlerine de araştırma bulgularında yer verilmiştir. Araştırma için nitel araştırma deseni uygun görülmüştür. Bu yöntemin tercih edilmesinde etkili olan unsur ise nitel araştırmanın özünden kaynaklı olan zengin metodolojik özelliklerdir. Mülakat tekniği, bu araştırmada verilerin toplanması amacıyla kullanılmıştır. Bu araştırmada, araştırma konusu hakkında daha derinlemesine bilgi alınabilmesi, araştırma konusuna odaklanabilmesi, mülakat sürecini bağlamdan kopmasını güçleştirerek mülakat sürecine daha fazla esneklik kazandırabilmesi nedeniyle yarı yapılandırılmış görüşmelere başvurulmuştur. Bu tekniğin uygulanması sürecinde etik normlara, araştırmacı tarafından sahada üstlenilmesi gereken sorumluluklara, görüşmeye ilişkin süreçte dikkat edilmesi gerekli olan ana konulara ve hassasiyetlere bağlı kalınmıştır. Araştırma neticesinde tematik analiz kullanılmıştır. Burada problem cümlesi dikkate alınmıştır. Katılımcı adaylarla alakalı olarak bilgiler ise mülakat öncesinde informal nitelikte yapılan görüşmeler neticesinde toplanmıştır. Pilot çalışmadan sonra saha ve katılımcı hakkında daha fazla bilgi edinmek için sahada zaman harcanmıştır. Bu amaçla araştırmacı Reyhanlı'nın merkezini incelemiştir. Bu bağlamda yaşanan uyum sorunu ve entegrasyon çalışma kapsamında, Reyhanlı ilçesinde yaşayan 150 Suriyeli mülteci ve yerel halk denekle, mülakat (görüşme) yapılmış ve bunların uyum tecrübelerine odaklanılmıştır. Mülakat aşamasında sağlanmış olan bulgular için nitel veri analizi kullanılmıştır. Buradan hareketle misafirlik süresinin uzamasıyla beraber problemlerin de artığını görebiliriz. Buradaki uyum süreci ve entegrasyon büyük bir çabayı gerektiren kompleks yapıda bir yol haritası niteliğindedir. Ayrıca mültecilere ilçede karşılaşılan güncel sorunlara ve entegrasyon ile ilişkili olarak katılımcıların savaş sonrası ülkelerine geri dönme ve Türk vatandaşlığına kabul edilme düşüncelerine ilişkin özgün bulgulara da ulaşılmıştır. Anahtar Kelimeler: Suriye, Entegrasyon, Uyum, Reyhanlı, Göç, MülteciWith the prolongation of the civil war in Syria, Syrian refugees, who were in the status of guests, first became permanent. There are approximately 4 million Syrian refugees in Turkey. These refugees, especially those outside the shelter, face serious economic and social problems. However, they have a great difficulty in terms of compliance and integration. The aim of this study is to analyze the problems of Syrian refugees who live in the district based on Reyhanlı district with the help of approaches to migration theories. The problem of adaptation faced here is a major problem not only for refugees but also for the local people living in the district. Within this study, Syrians forced migration to drag the political, social, economic, are permitted cultural and historical factors have been dealt and the Syrians after the migrants' immigration experience and migration in the social and economic life experience of living in Turkey research findings. Qualitative research design was found appropriate for the research. The factor that is effective in choosing this method is the rich methodological features that stem from the essence of qualitative research. Interview technique was used in this research to collect data. In this study, semi-structured interviews were used because of the fact that it could get more in-depth information about the research subject, focus on the research subject and make it more difficult for the interview process to break from the context. During the application of this technique, it was adhered to ethical norms, the responsibilities that should be assumed by the researcher in the field, the main issues and sensitivities that should be considered in the process related to the interview. As a result of the research, thematic analysis was used. Here the problem statement is taken into account. Information on the candidate participants was collected as a result of informal interviews before the interview. After the pilot study, time was spent on the field to learn more about the field and the participant. For this purpose, the researcher examined the center of Reyhanlı. Within the scope of the adaptation problem and integration study in this context, 150 Syrian refugees and local people living in Reyhanlı district were interviewed with the subjects and their adaptation experiences were focused on. Qualitative data analysis was used for the findings provided during the interview phase. From this point of view, we can see that the problems increase with the length of the stay. The harmonization process and integration here is a complex road map that requires great effort. In addition, current findings about refugees in the district and original findings related to the participants' return to their post-war countries and admission to Turkish citizenship were also reached. Keywords: Syria, Integration, Harmony, Reyhanlı, Migration, Refuge

Instantaneous mass flowrate measurements through fuel injection nozzles

A method of measuring the instantaneous mass flowrates of fuels passing through fast operating injection nozzles is described. The flowrate information is deduced from instantaneous pressure gradient measurements. Through a Fourier transformation, the Fourier coefficients of the pressure gradient are determined, which are used for the calculation of the transient mass flowrate of fuel through injection nozzles, utilizing a special reconstruction algorithm. The theoretical background of the measurement method is provided and the development work to yield a practically applicable measuring system is summarized. The latter is used for verification experiments, providing time-resolved flowrates for a magnetically driven injection valve operating at a pressure of approximately 6 bar. Online measurement of the injection mass flowrates can be recorded with this measuring system and information can be obtained for individual injection events. Cycle-to-cycle variations can be detected in this way

Laminar-to-turbulent transition of pipe flows through puffs and slugs

Laminar-to-turbulent transition of pipe flows occurs, for sufficiently high Reynolds numbers, in the form of slugs. These are initiated by disturbances in the entrance region of a pipe flow, and grow in length in the axial direction as they move downstream. Sequences of slugs merge at some distance from the pipe inlet to finally form the state of fully developed turbulent pipe flow. This formation process is generally known, but the randomness in time of naturally occurring slug formation does not permit detailed study of slug flows. For this reason, a special test facility was developed and built for detailed investigation of deterministically generated slugs in pipe flows. It is also employed to generate the puff flows at lower Reynolds numbers. The results reveal a high degree of reproducibility with which the triggering device is able to produce puffs. With increasing Reynolds number, 'puff splitting' is observed and the split puffs develop into slugs. Thereafter, the laminar-to-turbulent transition occurs in the same way as found for slug flows. The ring-type obstacle height, h, required to trigger fully developed laminar flows to form first slugs or puffs is determined to show its dependence on the Reynolds number, Re=DU/ν (where D is the pipe diameter, U is the mean velocity in the axial direction and ν is the kinematic viscosity of the fluid). When correctly normalized, h+ turns out to be independent of Reτ (where h+=hUτ/ν, Reτ=DUτ/ν and Uτ=√τw/ρ τw is the wall shear stress and ρ is the density of the fluid)