The influence of loading on the heat of transformation in shape memory alloys

Standard caloric measurements on Shape Memory Alloys (SMAs) are usually carried out with the specimen in a state free of stress, by means of standard calorimeters. However, in its every application, the material is subjected to some load, being therefore necessary to investigate the influence of loading on the caloric behavior of SMAs, in order to take this into account when modeling their thermodynamic behavior. The present work investigates the influence of loading on the heat of transformation in SMAs. Experimental measurements were carried out on Ni Ti samples and a mathematical description of the observed behavior was developed. The theoretical results are in agreement with the experimental ones

Risks and benefits of colonoscopy in patients aged 80 and older: a prospective study

OBJECTIVE: this study aims to compare colonoscopy results in patients aged 50-79 and those aged 80 and older. PATIENTS AND METHODS: a total of 533 diagnostic colonoscopies performed from August 2011 to January 2012 were evaluated in a prospective study analyzing age, ASA classification, comorbidities, endoscopic findings, time to reach the cecum, number of complete examinations, difficulties and complications. Chi-square test was used to compare categorical data whereas Student's t test to compare means. A p value < 0.05 was considered significant. RESULTS: 479 patients were in Group A - age 50 to 79, whereas 54 were in Group B, 80 versus older. The following results are shown for Group A and B, respectively: age 63 &#177; 8 versus 84 &#177; 4 years. ASA 1 difficult examination: 58 (21 %) versus 12 (27%) p > 0.05, ASA > 2 difficult examination: 41 (20%) versus 6 (60%) p < 0,05. Comorbidities 255 (53%) versus 36 (66%) p > 0.05. Complete colonoscopy in 450 (94%) versus 45 (83%), p < 0.01. Difficulties in 99 (20%) versus 32 (40%), p < 0.01. Complications in 1 (0.2%) versus 3 (5%) p < 0.01. Diverticulitis/ sequelae in 3 (0.6%) versus 3 (5%) p < 0.01. CRC in 42 (8.7%) and 10 (18.5%), p < 0.05. Adenoma in 130 (27 %) versus 15 (27%), p > 0.05 Time to reach the cecum was 39 &#177; 10 minutes for difficult procedures and 13 &#177; 9 for the easy ones. CONCLUSION: age 80 and older is associated with more adverse events during colonoscopy

Comparative study of vibration measuring techniques applied to Aluminum beams with localized damage

Mestrado de dupla diplomação com a UTFPR - Universidade Tecnológica Federal do ParanáWhen a structural damage changes the characteristics of stiffness and mass of a mechanical system, the dynamic behavior of this beam will also change. Only a few studies about the correlation between damage and the effect caused in dynamic behavior can be found. Based on this, this study will analyze the behavior of the natural frequencies and damping ratios of four aluminum beams, with and without damages. This work aims to determine the error between the two methods of data acquisition and the effects of the damage inflicted on the shape modes, natural frequencies and damping ratios for each beam. To achieve the purposes, initially, a numerical FEM simulation will be performed, followed by experimental impact tests, aiming to obtain the estimated natural frequencies and damping ratios. After this, damages will be made on these beams and the impact tests will be repeated for each beam. The FEM analysis will be performed using Ansys. For the impact tests, two data acquirement methods will be used during the impact testing, the first, using accelerometers to obtain the vibration response, the second using a Brüel & Kjær’s sound level meter. The obtained data will be compared and will be possible to determinate the error between the natural frequencies measured using both methods. The results obtained will be used to correlates the dynamic behavior with the damages inflicted on the beams. This paper allowed analyzing the usage viability of the sound level meter to measure the output of a vibrating system, considering certain limitations. In addition, the damage effects on the natural frequencies of the beams.Quando um dano altera as características de massa e rigidez de um sistema (uma viga, por exemplo), seu comportamento dinâmico também é afetado. O estudo dos efeitos do dano infligido no comportamento modal é relativamente recente, tendo poucos estudos correlacionando o dano com seus efeitos em vigas. Baseado nisso, este estudo visa analisar o comportamento e variação do valor das frequências naturais e dos fatores de amortecimento de quatro vigas de alumínio com e sem danos. Este trabalho tem por objetivo determinar: o erro entre as medições efetuadas utilizando ambos os métodos de obtenção da resposta de vibração das vigas e os efeitos dos danos causados no comportamento modal do sistema analisado (modos de vibração, frequências naturais e fatores de amortecimento). Para tal, incialmente, uma simulação numérica utilizando elementos finitos será efetuada, seguida por testes de impacto, com o objetivo de obter as frequências naturais e os fatores de amortecimento para cada caso. A simulação numérica será efetuada utilizando o software Ansys e os testes de impacto utilizarão dois métodos de aquisição da resposta do sistema: utilizando acelerômetros e um medidor de pressão sonora. Os dados obtidos serão comparados e será possível determinar o erro entre os métodos de medição utilizados. Os resultados obtidos também serão utilizados para analisar os efeitos dos danos no comportamento dinâmico das vigas utilizadas. A elaboração deste trabalho possibilitou averiguar a viabilidade do uso de um medidor de pressão sonora para medição de vibrações, dentro de seus limites de utilização e suas limitações. Também foi possível analisar os efeitos dos danos nos valores de frequências naturais das vigas analisadas

Experimental Demonstration of Dual Polarization Nonlinear Frequency Division Multiplexed Optical Transmission System

Multi-eigenvalues transmission with information encoded simultaneously in both orthogonal polarizations is experimentally demonstrated. Performance below the HD-FEC limit is demonstrated for 8-bits/symbol 1-GBd signals after transmission up to 207 km of SSMF

Dual polarization nonlinear Fourier transform-based optical communication system

New services and applications are causing an exponential increase in internet traffic. In a few years, current fiber optic communication system infrastructure will not be able to meet this demand because fiber nonlinearity dramatically limits the information transmission rate. Eigenvalue communication could potentially overcome these limitations. It relies on a mathematical technique called "nonlinear Fourier transform (NFT)" to exploit the "hidden" linearity of the nonlinear Schr\"odinger equation as the master model for signal propagation in an optical fiber. We present here the theoretical tools describing the NFT for the Manakov system and report on experimental transmission results for dual polarization in fiber optic eigenvalue communications. A transmission of up to 373.5 km with bit error rate less than the hard-decision forward error correction threshold has been achieved. Our results demonstrate that dual-polarization NFT can work in practice and enable an increased spectral efficiency in NFT-based communication systems, which are currently based on single polarization channels

Steady‐State Modeling of Equilibrium Distillation

In this chapter, an algorithm for the solution of the mathematical model featuring steady‐state multicomponent distillation columns is analyzed and applied in the case study of the separation of hydrocarbon mixture. The development of the model has assumed each stage outlet streams in thermodynamic equilibrium in the phases liquid and vapor. The modeling of liquid was considerate and the non‐ideality behavior was described by activity. The non‐ideality of gas phase was calculated by Peng‐Robinson equation of state. The model consists of a set of nonlinear algebraic equations. The algorithm and numerical procedure to solve a set of equations are presented in a sequential, general and very simple form. A methodology to produce the good initial guess was defined based on rude simplifications of the system. In the study case, the initial estimates generated by the method are very good, being only about 20% far from the simulation results and considering a tolerance of 10−10, the convergence was obtained with 28 iterations

Time Response of Shape Memory Alloy Actuators

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Force/displacement actuators with the high output power and time response can be fabricated from shape memory wires or ribbons. Typically Ni-Ti shape memory alloys are used as an active material in such actuators. They are driven by Joule heating and air convection cooling. In the present work, the time response of various types of Ni-Ti actuators having different transformation temperatures and geometrical sizes, is studied systematically under conditions of free and forced air convection. The simple analytical model for calculating the time response is developed which accounts for the latent heat and thermal hysteresis of transformation. For all the types of considered actuators, the calculated time response is in a good agreement with that observed experimentally. Finally, on the base of the suggested model, we present the time response of Ni-Ti actuators calculated as a function of their transformation temperature and cross section dimensions