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

Fungal contaminants observed during micropropagation of Lilium candidum L. and the effect of chemotherapeutic substances applied after sterilization

Lilium candidum L. is a species which grows in the South West Anatolia region of Turkey. It is a bulbous plant with beautifully scented flowers and is used in the floral industry. The bulbs are produced by using traditional propagation and in vitro techniques. Micropropagation is a rapid propagation technique, but the greatest problem is contamination with fungi and bacteria. Antibiotic and fungicide treatments were done after sterilization for micropropagation of L. candidum. Fungal contaminants formed during the culture were determined. Bulb scales were used as explants (5 - 10 mm width) and were cultured in photoperiodic conditions (16 h light, 8 h dark) or complete darkness. Bulb scales rinsed in water were surface sterilized, then solutions containing chemotherapeutic substances (Benomyl, Nystatin, Streptomycin, Penicillin) in different combinations were applied for 30 min and subsequently were cultured in MS medium with supplement 0.1 mg dm-3 NAA + 0.01 mg dm-3 BA. During the experiment, fungal contaminants were observed in full treatments. Determined contaminants were identified according to their morphological and cultural characteristics by cultivation and were comprised of: Fusarium, Penicillium, Alternaria, Rhizopus, Cylindrocarpon and Aspergillus species. The most effective treatment against fungal contaminations was achieved by utilizing a Benomyl (100 mg dm-3) + Nystatin (100 mg dm-3) treatment combination

Design of a novel THz sensor for structural health monitoring applications

In this paper, we propose a study on the characterization, design and simulation of a THz sensor for applications in Structural Health Monitoring (SHM). The proposed sensor is assembled using two frequency selective surfaces (FSSs) based on metamaterial wire resonators. We present a theoretical model to describe its electromagnetics which is used not only to understand the physical principles underlying the functioning of the sensor but also to determine a set of optimized parameters for its operation in the THz window from 395 GHz to 455 GHz. We present our numerical simulations, involving both electromagnetic and mechanical simulation techniques, to determine the reflectance profile of the sensor as a function of applied force. In this study we considered the possibility of using two thermoplastic polymers as host materials: High-Density PolyEthylene (HDPE) and PolyTetraFluoroEthylene (PTFE). The two sensors have a good dynamic range and comparable characteristics. However, we found that with HDPE it is possible to construct a sensor with a more linear response, although not as sensitive as in the case of PTFE. With HDPE we are able to pass from a situation of full transparency to almost full opacity using only its linear operating zone.info:eu-repo/semantics/acceptedVersio

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

Broadband terahertz modulators using self-gated graphene capacitors

We demonstrate a terahertz intensity modulator using a graphene supercapacitor which consists of two large-area graphene electrodes and an electrolyte medium. The mutual electrolyte gating between the graphene electrodes provides very efficient electrostatic doping with Fermi energies of 1 eV and a charge density of 8 × 1013 cm-2. We show that the graphene supercapacitor yields more than 50% modulation between 0.1 and 1.4 THz with operation voltages less than 3 V. The low insertion losses, high modulation depth over a broad spectrum, and the simplicity of the device structure are the key attributes of graphene supercapacitors for THz applications. © 2015 Optical Society of America

Broadband THz modulators based on multilayer graphene on PVC

In this study we present the direct terahertz time-domain spectroscopic measurement of CVD-grown multilayer graphene (MLG) on PVC substrate with an electrically tunable Fermi level. In a configuration consisting MLG and injected organic dopant, the transmitted intensity loss of terahertz radiation was observed with an applied voltage between 0 and 3.5 V. We showed that MLG on PVC devices provided approximately 100 % modulation between 0.2 and 1.5 THz at preferentially low operation voltage of ca. 3V. The observed modulation bandwidth in terahertz frequencies appears to be instrument limited. © 2016 IEEE

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

Silver Nanoparticle-Coated Polyhydroxyalkanoate Based Electrospun Fibers for Wound Dressing Applications

Wound dressings are high performance and high value products which can improve the regeneration of damaged skin. In these products, bioresorption and biocompatibility play a key role. The aim of this study is to provide progress in this area via nanofabrication and antimicrobial natural materials. Polyhydroxyalkanoates (PHAs) are a bio-based family of polymers that possess high biocompatibility and skin regenerative properties. In this study, a blend of poly(3-hydroxybutyrate) (P(3HB)) and poly(3-hydroxyoctanoate-co-3-hydroxy decanoate) (P(3HO-co-3HD)) was electrospun into P(3HB))/P(3HO-co-3HD) nanofibers to obtain materials with a high surface area and good handling performance. The nanofibers were then modified with silver nanoparticles (AgNPs) via the dip-coating method. The silver-containing nanofiber meshes showed good cytocompatibility and interesting immunomodulatory properties in vitro, together with the capability of stimulating the human beta defensin 2 and cytokeratin expression in human keratinocytes (HaCaT cells), which makes them promising materials for wound dressing applications

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