Separation of Damping and Velocity Strain Dependencies using an Ultrasonic Monochromatic Excitation

International audiencePrecise knowledge of the dependence of elastic modulus and Q factor on the amplitude of excitation is a prerequisite for the development and validation of models to explain the hysteresis observed in qua-sistatic experiments for various media, i.e., the different deformations at the same applied stress observed when stress change rate is positive or negative. Separation of different contributions to dynamic nonlin-earity (e.g., those due to nonequilibrium effects, often termed conditioning) and independent estimation of nonlinearities originated by the strain dependence of velocity and the damping factor are required, which is often not possible with standard approaches. Here we propose and validate a method that, measuring the response of a sample to a monochromatic excitation at different amplitudes, allows fast, continuous, and quasi-real-time monitoring of the dependence of the material elastic properties on amplitude: dynamic elastic modulus (related with velocity through density) and Q factor of the mechanical resonances (related with wave-amplitude attenuation parameters)

Separation of Damping and Velocity Strain Dependencies using an Ultrasonic Monochromatic Excitation

Precise knowledge of the dependence of elastic modulus and Q-factor on amplitude of excitation is a prerequisite for the development and validation of models to explain the hysteresis observed in quasi-static experiments for various media, i.e. the different deformations at the same applied stress observed when stress change rate is positive or negative. Separation of different contributions to dynamic nonlinearity (e.g those due to non equilibrium effects, often termed conditioning) and independent estimation of nonlinearities originated by the strain dependence of velocity and damping factor are required, which is often not possible with standard approaches. Here we propose and validate a method which, measuring the response of a sample to a monochromatic excitation at different amplitudes, allows fast, continuous and quasi real-time monitoring of the dependence of the material elastic properties on amplitude: dynamic elastic modulus (related with velocity through density) and Q-factor of the mechanical resonances (related with wave amplitude attenuation parameter

FAKTOR–FAKTOR PENYEBAB ALIH FUNGSI LAHAN PERTANIAN DI KECAMATAN TOMOHON SELATAN KOTA TOMOHON

This study aims to determine the factors that affect the conversion of agricultural land in South Tomohon Subdistrict Tomohon City. In particular, this study looks at internal factors that affect the conversion of agricultural land in South Tomohon Sub-District, Tomohon City. This study was conducted by using secondary data obtained from BPS (Statistics Bureau) office Tomohon City, Subdistrict office and Village Offices in South Tomohon Sub-district. And for the primary data obtained from the direct interview with the farmers. The data is then analyzed by using qualitative data analysis techniques using tables and described descriptively. The results of research showed that land function change happened in this area, allot of land that is as housing (70%). Furthermore, for the main cause of landowners sell or alter the function of agricultural land that is due to the cost of child education and high selling prices.*jnkd*

Changes in volatiles of olive tree Olea europaea according to season and foliar fertilization

In the present study, four foliar fertilizers (FF1, FF2, FF3 and FF4) were separately sprayed on Chemlali olive trees at different moments of the vegetative cycle. FF1 (rich in nitrogen) was applied during the vegetation stage (Last January-February) at a dose of 5 L/ha per spray (three sprays per season). FF2 (rich in boron, magnesium and sulphur), FF3 (rich in phosphorus and potassium) and FF4 (rich in phosphorus and calcium) were applied respectively during the stages of flowering (Last March-April), fruit growth (July-August) and ripening (October-November), at a dose of 3 L/ha per spray (three sprays per season for each fertilizer).The volatile fraction was analysed by GC-MS, 46 volatile compounds were identified and their amount were expressed as relative abundance (%). In a general view, the most abundant volatiles in Chemlali olive leaves across the vegetative cycle were (E)-2-hexenal, nonanal, (E)-β-damascenone, 3-ethenyl pyridine and β-caryophyllene. The levels of these main compounds and the general composition of the volatile fraction varied significantly through season.The volatile levels were mainly affected by the two foliar fertilizers enriched with nitrogen and Boron respectively. The most affected volatiles were (E)-2-hexenal, nonanal, 3-ethenyl pyridine, (E,E)-α-farnesene, and (E)-nerolidol. Less impact was noticed after the use of the other foliar fertilizers.Our study is the first investigation bringing data about the variation of leaf volatile profile of Chemlali cultivar across a vegetative cycle and showing the impact of nutrient foliar sprays on olive leaf volatile

Exploiting Slow Dynamics Effects for Damage Detection in Concrete

Nonlinear ultrasonic techniques have been developed over the last decades to detect the presence of damage in materials of interest in the field of civil engineering, such as concrete or mortar. The dependence on the strain amplitude of measurable quantities, such as wave velocity, damping factor, resonance frequency, etc. is normally considered a qualitative indicator of the presence of defects at the microstructural level. The experimental approaches proposed have the advantage of being sensitive to small variations in the sample microstructure and are therefore more adapted to detect the presence of small cracks or damaged areas with respect to traditional linear ultrasonic techniques. However, nonlinear methods are difficult to implement, since they usually require a calibrated experimental set-up which also behaves linearly at high amplitudes of excitation. The slow dynamics features, typical of the hysteresis generated by damage, have been given much less attention as a tool for damage detection even though their quantification is often less demanding in terms of an experimental set-up. Here, we provide the first evidence of how recovery, which is part of the slow dynamics process, is sensitive to the presence of damage in concrete samples and thus could be considered as an easy-to-measure nonlinear indicator for Structural Health Monitoring purposes

"Experimental evidence of correlations between conditioning and relaxation in hysteretic elastic media"

Consolidated granular materials and materials with damage at the microstructural level exhibit anomalous elastic behavior even when excited by low-amplitude elastic waves. Their response is given by a combination of slow- and fast-dynamics effects which, as their definition implies, act on very different time scales. In particular, conditioning (a transition to an elastic state dependent on the strain amplitude) and relaxation (full recovery of the elastic properties when the strain is removed) have been observed in different materials and under different dynamic excitations. An experimental parametric analysis of the phenomenon, aiming to establish correlations between the effects on different elastic physical properties (wave velocity and attenuation coefficient) and between the evolution of conditioning and relaxation is proposed here, with the goal of better characterizing slow dynamics and allowing one to go beyond the phenomenological description of elastic hysteresis currently available. At the same time, by studying different materials, we wish to highlight the possibility of using slow dynamics as an additional tool for materials characterization

Oil quality and aroma composition of 'Chemlali' olive trees (Olea europaea L.) under three irrigation regimes

The present work focused on the chemical composition of monovarietal virgin olive oil from the cultivar Chemlali cultivated in the South of Tunisia: sub-arid zone under three different irrigation regimes: stressed, moderate and well irrigation treatment with the restitution of 50, 75 and 100% of crop evapotranspiration (ETc), respectively. Quality characteristics (acidity and peroxide value) and chemical data (antioxidant compound, fatty acids volatile compounds and oxidative stability) were studied in addition to the pomological characteristic of olive fruit. Results show that there were significant differences observed in oil composition according to the irrigation regime applied. Total phenols, bitterness intensity and LOX products content showed the highest values for low irrigation regime, whereas polyunsaturated fatty acid and oxidative susceptibility values had highest values for olive oil from well irrigated trees. Analytic characteristic of fruits showed the highest values of pulp/stone ratios from olive trees irrigated by the highest amount of wate

Suicidal Behavior and Psychological Distress in University Students: A 12-Nation Study. Archives of Suicide Research

This study investigated the prevalence of suicidal behavior and psychological distress in university students across 12 nations. A total of 5572 university students from 12 countries were surveyed about suicide ideation, suicide attempts and psychological distress by means of a self-administered questionnaire. Almost 29% of the samples reported having contemplated suicide and 7% reported attempting suicide. Of the total sample, 51.1% scored above the General Health Questionnaire-12 ≥ 3 cut-off point, 41.6% above the GHQ-12 ≥ 4 cut-off point, and 33.8% scored above the GHQ-12 ≥ 5 cut-off point. While odds of suicide ideation were elevated in Austria and the UK, reduced ORs were detected for China, Italy, Saudi Arabia, Tunisia, and Turkey. Similarly, while odds of suicide attempt were high in Jordan, Palestine, Saudi Arabia, and to some extent in Turkey, reduced ORs were observed for Austria, China, Italy, Japan and the USA. Elevated ORs for psychological distress were seen in Japan, Jordan, Palestine, Saudi Arabia, Tunisia and Turkey but reduced ORs were noted in Austria, China, Iran, Italy and the USA. Psychological distress was strongly associated with reports of suicide ideation and attempts. Suicide ideation, suicide attempt and psychological distress are common in university students but their rates vary depending on the sociocultural context. Due attention should be devoted to the mental health needs of young adults enrolled in higher educational institutions and more cross-cultural research is warranted to better understand the etiology of the observed intersocietal variations in suicidal behavior and psychological distress