Computer-aided analysis and design of the shape rolling process for producing turbine engine airfoils

Mild steel (AISI 1018) was selected as model cold-rolling material and Ti-6Al-4V and INCONEL 718 were selected as typical hot-rolling and cold-rolling alloys, respectively. The flow stress and workability of these alloys were characterized and friction factor at the roll/workpiece interface was determined at their respective working conditions by conducting ring tests. Computer-aided mathematical models for predicting metal flow and stresses, and for simulating the shape-rolling process were developed. These models utilize the upper-bound and the slab methods of analysis, and are capable of predicting the lateral spread, roll-separating force, roll torque and local stresses, strains and strain rates. This computer-aided design (CAD) system is also capable of simulating the actual rolling process and thereby designing roll-pass schedule in rolling of an airfoil or similar shape. The predictions from the CAD system were verified with respect to cold rolling of mild steel plates. The system is being applied to cold and hot isothermal rolling of an airfoil shape, and will be verified with respect to laboratory experiments under controlled conditions

Computer-aided analysis and design of the shape rolling process for producing turbine engine airfoils

Mild steel (AISI 1018) was selected as model cold rolling material and Ti-6A1-4V and Inconel 718 were selected as typical hot rolling and cold rolling alloys, respectively. The flow stress and workability of these alloys were characterized and friction factor at the roll/workpiece interface was determined at their respective working conditions by conducting ring tests. Computer-aided mathematical models for predicting metal flow and stresses, and for simulating the shape rolling process were developed. These models utilized the upper bound and the slab methods of analysis, and were capable of predicting the lateral spread, roll separating force, roll torque, and local stresses, strains and strain rates. This computer-aided design system was also capable of simulating the actual rolling process, and thereby designing the roll pass schedule in rolling of an airfoil or a similar shape

Management and Prognostic Factors for Delayed Reconstruction of Neglected Posterior Shoulder Fracture-Dislocation

Introduction: Posterior fracture-dislocations of the shoulder are rare conditions. Misdiagnosis can occur in 50% - 80% of the patients. Due to the size of the lesion, stability of the joint could not be achieved with transfer of subscapular tendon or tuberosity. Case Presentation: A 54-year-old male patient was referred to our hospital with a neglected posterior shoulder fracture-dislocation. Functional results of the patient, and technical informations were explained in this case report. The reverse Hill-Sachs lesion involved 40% of the articular surface. Depressed and malunited fragment was elevated, and fixated to the humeral head. Conclusions: Glenohumeral joint reduction with reconstruction of the humeral head seems to be possible even in a neglected locked posterior shoulder fracture-dislocation. If the depressed osteochondral fragment is still spheric, signs of the avascular necrosis are absent on CT, and malunion of the fragment has occurred, it is quite possible to reconstruct the head. Although results of the case are good, it is worthwhile to follow these patients for long-term complications

Monitoring and analysis of landuse changes in historical periods for the city of Istanbul by means of aerial photography and satellite imagery

Arazi kullanımının belirlenmesi için günümüze değin farklı teknikler kullanılmış, bu teknikler dahilinde değişik veri tipleri değerlendirilmiştir. Yapılan çalışmalar farklı ölçekte olup farklı amaca hizmet etmektedirler. Bu çalışmada, İstanbul kenti için sadece tek bir döneme ait değil, farklı dönemleri içeren arazi kullanımının tesbit edilmesi amaçlanmıştır. Bu şekilde, dönemler arasındaki değişimler tesbit edilerek bu değişimlerin analizleri yapılabilecektir. Adı geçen dönemlerin belirlenmesinde, verinin varlığı ve bu verinin ulaşılabilir olması dikkate alınmıştır. Bu şekilde 2000, 1987/88, 1968 ve 1940’lı yıllar dikkate alınmıştır. 2000 ve 1987/88 yılları için uydu görüntüleri, 1968 ve 1940’lı yıllar için hava fotoğrafları kullanılması planlanmıştır. Temel topoğrafik veri olarak farklı ölçekte basılı ve sayısal haritalar kullanılmıştır. Çalışmanın doğruluğunun araştırması sadece geometrik olarak yapılmayacak, çalışmanın sonucunda oluşturulacak coğrafi bilgi sistemi için tematik doğruluk araştırması da gerçekleştirilmiştir. Anahtar Kelimeler: Arazi kullanımı, coğrafi bilgi sistemi, konumsal doğruluk, tematik doğruluk.In order to monitor landuse types, several techniques have been used, by which several types of data have been evaluated. These studies are in different scale and have different aims. In this study, it is aimed that to monitor the landuse types for Istanbul not only for one period but also for different periods. This allows making an analysis on landuse changes between these periods. By selecting these periods, existence of data was the defining parameter. So, the years 2000, 1987/88, 1968 and 1940?ies have been taken as evaluation years. It is planned to use satellite imagery for the years 2000 and 1987/88, aerial photographs for the years 1968 and 1940?ies. For the year 2000, IKONOS and IRS-1C/D images and for 1987/88, KVR-1000 and KFA-1000 satellite images are used. As basic topographic data, hardcopy and softcopy maps from different scale are dealt with. In order to define the landuse changes between evaluation years, a unique coordinate system has been used within the whole study. It would be suitable that having this coordinate system the same datum as the conventional maps in order to make an accuracy assessment at the end of the study. This accuracy assessment would not be only about the geometry but also a thematic accuracy investigation would take place for the geographical information system, which was produced at the end of the study.Keywords: Landuse, geographical information system, geometric accuracy, thematic accurac

Bubble dynamics in DNA

The formation of local denaturation zones (bubbles) in double-stranded DNA is an important example for conformational changes of biological macromolecules. We study the dynamics of bubble formation in terms of a Fokker-Planck equation for the probability density to find a bubble of size n base pairs at time t, on the basis of the free energy in the Poland-Scheraga model. Characteristic bubble closing and opening times can be determined from the corresponding first passage time problem, and are sensitive to the specific parameters entering the model. A multistate unzipping model with constant rates recently applied to DNA breathing dynamics [G. Altan-Bonnet et al, Phys. Rev. Lett. 90, 138101 (2003)] emerges as a limiting case.Comment: 9 pages, 2 figure

Bubbles and denaturation in DNA

The local opening of DNA is an intriguing phenomenon from a statistical physics point of view, but is also essential for its biological function. For instance, the transcription and replication of our genetic code can not take place without the unwinding of the DNA double helix. Although these biological processes are driven by proteins, there might well be a relation between these biological openings and the spontaneous bubble formation due to thermal fluctuations. Mesoscopic models, like the Peyrard-Bishop-Dauxois model, have fairly accurately reproduced some experimental denaturation curves and the sharp phase transition in the thermodynamic limit. It is, hence, tempting to see whether these models could be used to predict the biological activity of DNA. In a previous study, we introduced a method that allows to obtain very accurate results on this subject, which showed that some previous claims in this direction, based on molecular dynamics studies, were premature. This could either imply that the present PBD should be improved or that biological activity can only be predicted in a more complex frame work that involves interactions with proteins and super helical stresses. In this article, we give detailed description of the statistical method introduced before. Moreover, for several DNA sequences, we give a thorough analysis of the bubble-statistics as function of position and bubble size and the so-called $l$-denaturation curves that can be measured experimentally. These show that some important experimental observations are missing in the present model. We discuss how the present model could be improved.Comment: 15 pages, 5 figures, published as Eur. Phys. J. E 20 : 421-434 AUG 200

Compressive sensing imaging with a graphene modulator at THz frequency in transmission mode

In this study we demonstrate compressive sensing imaging with a unique graphene based optoelectronic device which allows us to modulate the THz field through an array of columns or rows distributed throughout its face. © 2016 IEEE

Virtual Reality Simulator for Medical Auscultation Training

© Springer Nature Switzerland AG 2019. According to the Oxford English dictionary, auscultation is “the action of listening to sounds from the heart, lungs, or other organs, typically with a stethoscope, as a part of medical diagnosis.” In this work, we describe a medical simulator that includes audio, visual, pseudo-haptic, and spatial elements for training medical students in auscultation. In our training simulator, the user is fully immersed in a virtual reality (VR) environment. A typical hospital bedside scenario was recreated, and the users can see their own body and the patient increase immersion. External tracking devices are used to acquire the user’s movements and map them into the VR environment. The main idea behind this work is for the user to associate the heart and lung sounds, as heard through the stethoscope with the corresponding health-related problems. Several sound parameters including the volume, give information about the type and severity of the disease. Our simulator can reproduce sounds belonging to the heart and lungs. Through the proposed VR-based training, the medical student ideally will learn to relate sounds to illnesses in a realistic setting, accelerating the learning process

A stalagmite test of North Atlantic SST and Iberian hydroclimate linkages over the last two glacial cycles

Close coupling of Iberian hydroclimate and North Atlantic sea surface temperature (SST) during recent glacial periods has been identified through the analysis of marine sediment and pollen grains co-deposited on the Portuguese continental margin. While offering precisely correlatable records, these time series have lacked a directly dated, site-specific record of continental Iberian climate spanning multiple glacial cycles as a point of comparison. Here we present a high-resolution, multi-proxy (growth dynamics and delta C-13, delta O-18, and delta U-234 values) composite stalagmite record of hydroclimate from two caves in western Portugal across the majority of the last two glacial cycles (similar to 220 ka). At orbital and millennial scales, stalagmite-based proxies for hydroclimate proxies covaried with SST, with elevated delta C-13, delta O-18, and delta U-234 values and/or growth hiatuses indicating re-duced effective moisture coincident with periods of lowered SST during major ice-rafted debris events, in agreement with changes in palynological reconstructions of continental climate. While in many cases the Portuguese stalagmite record can be scaled to SST, in some intervals the magnitudes of stalagmite isotopic shifts, and possibly hydroclimate, appear to have been somewhat decoupled from SST.Agência financiadora / Número do subsídio Center for Global and Regional Environmental Research, Cornell College US National Science Foundation BCS-1118155 BCS-1118183 AGS-1804132 IGESPAR Associacao de Estudos Subterraneos e Defesa do Ambienteinfo:eu-repo/semantics/publishedVersio

Observation of Gate-Tunable Coherent Perfect Absorption of Terahertz Radiation in Graphene

We report experimental observation of electrically tunable coherent perfect absorption (CPA) of terahertz (THz) radiation in graphene. We develop a reflection-type tunable THz cavity formed by a large-area graphene layer, a metallic reflective electrode, and an electrolytic medium in between. Ionic gating in the THz cavity allows us to tune the Fermi energy of graphene up to 1 eV and to achieve a critical coupling condition at 2.8 THz with absorption of 99%. With the enhanced THz absorption, we were able to measure the Fermi energy dependence of the transport scattering time of highly doped graphene. Furthermore, we demonstrate flexible active THz surfaces that yield large modulation in the THz reflectivity with low insertion losses. We anticipate that the gate-tunable CPA will lead to efficient active THz optoelectronics applications. © 2016 American Chemical Society