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[en] Highlights: • Triboelectric nanogenerator was prepared using force-assembled colloidal arrays. • The electrical performance was determined by the structures and colloidal size. • They displayed high electric output, stability, and humidity resistance. We introduce a novel, robust, cost-effective, and scalable approach for the preparation of a large-area force-assembled triboelectric nanogenerator (FTENG), which allows a stable and high electric output under a wide range of humidity conditions through its dual-sized morphology (i.e., microstructures and nanostructures). In this study, hexagonally packed colloidal arrays prepared by a force assembly approach rather than by conventional self-assembly were used as a mold for a triboelectric poly(dimethylsiloxane) (PDMS) replica with desired pattern shapes (intaglio and embossed structures) and sizes. The morphological size of the PDMS films was determined by the diameter of the force-assembled colloids. The electrical output performance of FTENGs composed of electrodes and a PDMS film increased substantially as the size of the micropores (for intaglio-structured PDMS) or embossed features (for embossed-structured PDMS) decreased. Furthermore, the triboelectric PDMS film with micro-/nanosized features (i.e., dual-embossed PDMS) displayed a remarkable electrical output of 207 V (open-circuit voltage under a compressive force of 90 N in relative humidity (RH) of 20%) and high hydrophobicity compared to that of PDMS films with flat, intaglio or embossed structures. This device maintained a high electric output even in a high-humidity environment (i.e., open-circuit output voltage ~175 V in RH 80%). Our approach using force-assembly and hierarchical surface morphology will provide a novel and effective framework for developing strong power sources in various self-powered electronics.
[en] To know the importance of different climate variables on reference crop evapotranspiration (ETo), a step-by-step sensitivity analysis of ETo to single, two, and multi-climate variables (C) was conducted. ETo in north, south, and entire Xinjiang Province, China, over 1961–2013 was estimated using the Penman-Monteith equation. Trends in the involved six Cs (i.e., minimum temperature—Tmin, average temperature—Tave, maximum temperature—Tmax, wind speed at 2 m—U2, sunshine hour—n, and relative humidity—RH) were detected by the modified Mann-Kendall test. Nineteen scenarios of changed Cs were preset to obtain recalculated ETo values considering the actual trend in each C and the Pearson’s correlation relationship between ETo and Cs. The results showed that ETo was mostly sensitive to Tmax, U2, and n. Sensitivity of ETo to the two overlapped changes of Tmin and Tmax caused larger increases in ETo than Tmax and Tave, Tave and Tmax, Tmax and (−n), Tmax and RH, Tmax and (−U2), and Tmin and Tave, but the overlapped changes (−U2) and (−n) caused larger decreases in ETo than the other two C scenarios. The simultaneously increased Tmax, Tmin, Tave, and RH plus decreased U2 and n had caused the actual decreases in ETo in Xinjiang. In general, the effects of decreased U2 and n on decreasing ETo compensated the effects of increased Tmax on decreasing ETo in Xinjiang.
[en] Reliable tools for monitoring heat and moisture exchanger (HME) performance are in high demand by physicians, in order to assess the proper air conditioning delivered to intensive care unit (ICU) patients undergoing mechanical ventilation. To date, there is no system that comprehends all the requirements for clinical applications, in terms of performance and design. In this paper, a compact measurement system is proposed for monitoring HME performance in vivo, comparing the results with in vitro testing outcomes. The portable system presented is connected to the ventilation circuit close to the HME and assures wide compatibility with the new generation of smart devices because of its embedded Bluetooth low-energy module. Low power consumption ensures long-term monitoring capability of more than 24 h. Laboratory tests performed both in static and dynamic conditions showed rise- and fall-times for humidity measurements between 1 s and 1.8 s, compatible with many common variations in working operative conditions during mechanical ventilation. Clinical tests performed in the ICU demonstrated the possibility to effectively and continuously monitor in vivo HME performance. Furthermore, the comparison of the in vivo performances with the in vitro standard procedure and the agreement of the parameter ranges monitored allowed us to confirm the reliability of the system, highlighting the usefulness of this approach for proper real time HME monitoring. (paper)
[en] An increase of the 2 m temperature over Europe is expected within the current century. In order to consider health impacts, it is important to evaluate the combined effect of temperature and humidity on the human body. To achieve this, projections of a basic index—the humidex—representative of the perceived temperature, under different scenarios and periods, have been investigated. The simultaneous occurrence of observed extreme temperature events and perceived extreme temperature events is seldom found within the present climate, reinforcing the importance of investigating the combination of the two fields. A set of 10 km resolution regional climate simulations, provided within the EURO-CORDEX multi-model effort, demonstrates an ability in representing moderate to extreme events of perceived temperature over the present climate, and to be useful as a tool for quantifying future changes in geographical patterns of exposed areas over Europe. Following the RCP8.5 emission scenario, an expansion of the area subject to dangerous conditions is suggested from the middle of the current century, reaching 60 °N. The most significant increase of perceived extreme temperature conditions is found comparing the 2066–2095 projections to the 1976–2005 period; bearing in mind that changes in relative humidity may either amplify or offset the health effects of temperature, a less pronounced projected reduction of relative humidity in the north-eastern part of Europe, associated with extreme humidex events, makes northern Europe the most prone region to an increase of moderate to extreme values of perceived temperature. This is in agreement with a pronounced projected specific humidity increase. (letter)
[en] This work presents the computational evaluation of a new model for relative humidity sensor based on the principle of intermodal interference using a square-section no-core tapered optical fiber compared to a classical cylindrical tapered optical fiber sensor. Attempting at a new application of this type of sensor, simulations were carried out in the range of up to 60% of relative humidity, the main interest range of the pharmaceutical industry. Several materials were used in its modeling and an analysis was developed in its constructive dimensions, in order to verify the influence of each of them on the sensor performance.
[en] The article deals with the nitrogen cycle in the system atmosphere-plant-soil. It is known that in nature the process of nitrogen cycle in this system is very difficult. We have taken as a basis a simplified scheme of nitrogen cycle in the system atmosphere-plant-soil. In this paper, a mathematical model of the nitrogen cycle is constructed in the form of a system of six ordinary differential equations, each of which describes the change in the amount of nitrogen in the sources specified in scheme. Also in this paper, an analytical study of the subsystem of this scheme, consisting of two ordinary differential equations and describing the change in the amount of nitrogen in the humus. From the point of view of modeling the production process of the plant, it is important to determine the amount of nitrogen in the form digestible for the plant. Depending on soil conditions (humidity, temperature, activity of microorganisms, etc.) it is possible to transfer nitrogen from the assimilable form to humus and back. In this paper, we study another subsystem of the above scheme, consisting of two ordinary nonlinear differential equations and describing the change in the amount of nitrogen absorbed for the plant form and the change in the amount of nitrogen in the humus. Some special case of the developed model are investigated. The conditions of equilibrium functioning of the system are revealed. The corresponding periodic solutions of the model are obtained. Computational experiments using Matlab software environment are carried out. (author)
[en] This study explores change of precipitation and temperature using the Mann–Kendall test and the spatiotemporal variation of dryness/wetness using the standardized precipitation evapotranspiration index and empirical orthogonal function (EOF) analysis on 1-month time scales in Zhejiang Province, China, over 1971–2015. The results show that monthly precipitation had significant decreasing trends during April, May, September, and October, and significant increasing trends during November and December. Monthly temperatures had significant increasing trends in each month. Increasing temperature significantly increased drought events and intensity. There were consistent spatial patterns of dryness/wetness in Zhejiang. There were dryness trends in April, May, and September, a wetness trend in August, and no dryness/wetness pattern change in other months. The second EOF modes showed that dryness/wetness patterns were anti-phase between northern and southern Zhejiang during April–October. The third EOF modes showed that patterns were anti-phase between eastern and western Zhejiang in August and September.
[en] LnFeO3 (Ln = Sm, Nd, La) nanofibers are synthesized via electrospinning and the humidity sensors based on LnFeO3 nanofibers are fabricated and measured at different relative humidity to investigate the humidity sensing properties. The optimal working frequency of LnFeO3 nanofibers humidity sensors are all 100 Hz at which the sensors are of good linearity and high response. Compared with other LnFeO3 nanofibers humidity sensors, SmFeO3 nanofibers humidity sensor shows the best sensitivity and the impedance variation is more than five orders of magnitude with the relative humidity changing from 11% to 95%. The response time is about 10 s and the impedance versus RH curve is of good linearity. (The linear correlation coefficient is 0.98.) The results indicate that the SmFeO3 nanofibers with low Ln–O binding energy exhibit the best humidity sensing properties compared with others. We expect that our work has a great significance for fabricating high-performance humidity sensors. (paper)
[en] A set of tests is proposed to contribute to the experimental identification of the failure surfaces of an elasto-plastic model for a rammed earth along different stress paths such as compression, extension and tensile stress paths. The constitutive model involves two failure surfaces reflecting two different modes of failure within the material, a shear mode of failure and a tensile mode of failure typical of quasi-brittle materials. Secondly, the influence of water content on these failure surfaces is addressed. Such an influence is important to understand when stability of walls against unexpected storage of humidity is modelled since such storage is the main cause of failure of rammed earth construction. Three different water contents were considered in this study. The results show that for the studied material, the dissymmetry of behaviour between compression and extension is far greater than another quasi-brittle material such as concrete, which is new. As a first attempt, the influence of the water content can be modelled by a mere shift of the shear and of the tensile failure surface along the hydrostatic axis. Particularly, in the range of the investigated water contents, the shape of the failure surface can be stated as independent of the water content where just the apex will shift towards smaller values.
[en] In spite of extensive investigation and applications, influence of oxygen (O), and humidity on polyaniline (PANI) behaviour is not well understood. For this reason we have performed semi-empirical quantum mechanics, and ab-initio calculations of the pernigraniline base (PNB) PANI oligomers, of various lengths, before and after approach of H2O, O2 , and hydroxyl (OH −) group, and attachment of OH − and O to various molecular positions. Structure, charge and electrostatic potential distribution, relevant energies and enthalpies, infrared and electronic spectra of the PNB tetramer equilibrium conformation, and their changes induced by specific OH − , and O attachments are determined. These results provide identification of the most probable positions for O2 and H2O approach to PNB_PANI, enthalpies of OH − and O attachments to them, changes of molecular properties induced by the attachments, and infrared and electronic modes that are most suitable for the attachments detection. The results are compared to the existing experimental data, and the results of similar calculations, and implications for the PNB_PANI applications are notified. © 2019 Elsevier B.V.