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[en] A ground-based field campaign was conducted during the summer of 2011, 10 km east of the Israeli coast, aimed at studying small, warm convective clouds. During the campaign, clouds were detected on days that were predicted to be cloud-free by standard forecasting methods. Moreover, the clouds’ bases were often much lower than the estimated lifting condensation level. Detailed air parcel model simulations revealed that such small non-buoyant clouds can form only if the convective motion is driven by perturbations in the relative humidity in the middle of the boundary layer, rather than by temperature perturbations near the surface. Furthermore, cloud base height exhibited weak sensitivity to the initial elevation of the parcel, suggesting that it serves as an accumulation point for many relative-humidity-perturbed thermodynamic trajectories. Such a mechanism is likely to be common under atmospheric conditions of a hot and humid boundary layer capped by a strong inversion layer. (letter)
[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] 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] Silica nanoparticles with different sizes (ranging from 10 nm to 104 nm) and size distributions were synthesized by semi-batch and semi-batch/batch methods of the Stöber process. Then the amorphous silica with different surface areas (ranging from 30m"2/g to 400m"2/g) and pores (ranging from 3 nm to 33 nm) were obtained by various aging treatments and drying methods of the synthesized colloidal silica sol. The aging treatment resulted in the monodispersed pore distribution and decreased BET surface area of silica. The high-humidity drying method led to the mesoporous silica with uniform pores and decreased small pores. As the silica was obtained by the arrangement of silica nanoparticles, the pore diameter and pore distribution of mesoporous silica were directly related to the size and distribution of nanoparticles. Furthermore, this study offered a new thought for the synthesis of other mesoporous materials with uniform pore distributions
[en] Highlights: • Impact of environmental relative humidity on NCA based cell performance is investigated. • Higher environmental relative humidity impacts first discharge capacity and coulombic efficiency. • Higher environmental relative humidity has negligible impact on cycling stability of NCA cathode.
[en] A theoretic model is developed to describe the moisture desorption-and-adsorption cycle of silica gel dehumidification system with or without ultrasonic-assisted regeneration. The model has been validated by a series of experiments. The AMRC (additional moisture removal capacity) and the DCOP (dehumidification coefficient of performance) are suggested to illustrate the performance of silica gel dehumidification system with ultrasonic radiation. The effects of ultrasonic-assisted regeneration on the performance of the dehumidification system are investigated with the model under different conditions. Some crucial conclusions have been drawn from the simulation results, e.g., the higher regeneration temperature is conducive to increasing the AMRC; the higher ambient air temperature is conducive to increasing the AMRC and DCOP of the system; the higher ambient air humidity level will result in the bigger AMRC and the lower DCOP of the system; the higher initial moisture ratio of silica gel is in its favor for improving the DCOP, but unfavorable for increasing the AMRC; the optimal regeneration time aiming at the maximum AMRC or DCOP decreases as the regeneration temperature or the air velocity increases. And it increases as the ambient air temperature or humidity or the initial moisture content of silica gel increases. - Highlights: • A model is developed for silica gel dehumidification system with ultrasonic-assisted regeneration. • The model has been validated by a series of experiments. • The AMRC and DCOP are suggested to study the performance of silica gel dehumidification system. • The effects of ultrasonic-assisted regeneration on the system performance are studied under different conditions. • The optimal regeneration for achieving the best effect by the ultrasonic-assisted regeneration is discussed
[en] In this article authors investigated physical and chemical and physicotechnical properties of stalks of the cotton. These investigations letdetermine physical and chemical bases of structure forming of materials,articles and constructions with its application
[en] The extrapolation method, which is one of the two methods currently employed by standardizing laboratories for the weighing of drops of radioactive solutions, easily leads to errors. However, it is very convenient to store active solutions in rubber-capped vials and to use disposable syringes for extractions and depositions; it is then also convenient to use the extrapolation technique for weighing. Studies have been made with the aim of attaining accuracies for the extrapolation method of not less than the ± 10 μg attainable with the pycnometer method. The following procedures were adopted: (a) The standard method, but with weighings started sufficiently early to account as much as possible for non-equilibrium effects; (b) The high humidity method; it was expected that the non-equilibrium effects would be reduced by operating as close as practicable to a relative humidity (rh) of 100%; and (c) The sleeve method where the non-equilibrium effects are reduced by cooling the active solution prior to the depositions. Within the range rh 50% - 75%, weighings with method (c) yield radioactive concentrations identical (within ± 0.1%) to the results obtained with the pycnometer method. Method (a) is somewhat less reliable than method (c), method (b) offers no advantages over measurements within the readily attainable range of rh 50% - 75%. (author)
[en] A study is made regarding the nature and the amount of condensed tannin which can extract of bark from 11 tree species present in Costa Rica: guanacaste (Enterolobium cyclocarpum), cork oak (Licania arborea), jobo (Spondias mombin), pochote (Pachira quinata), loquat (Manilkara chicle), almond (Andira inermis), oak (Tabebuia rosea), cedar (Cedrela odorata), cenizaro (Samanea saman), pine (Pinus caribaea) and cypress (Cupressus lusitanica). The cortex samples were prepared, dried and extracted with ethanol. The ethanolic extracts were analyzed for condensed tannin content through the number of Stiasny, and characterized by infrared spectroscopy (FT-IR). The species with the highest proportion of extracted material were: guanacaste (9.5841% w/w), pochote (15.0066% w/w), pine (19.3400% w/w) and cypress (10.5300% w/w). The extracts with a higher proportion of condensed tannins have been: cork oak (61.9% w/w), jobo (66.1% w/w), pochote (72.8% w/w), loquat (50.5% w/w), cedar (72.7% w/w) and pine (70.7% w/w). (author)
[es]Un estudio es realizado sobre la naturaleza y la cantidad del tanino condensado que se puede extraer de la corteza de 11 especies arboreas presentes en Costa Rica: guanacaste (Enterolobium cyclocarpum), alcornoque (Licania arborea), jobo (Spondias mombin), pochote (Pachira quinata), nispero (Manilkara chicle), almendro (Andira inermis), roble (Tabebuia rosea), cedro (Cedrela odorata), cenizaro (Samanea saman), pino (Pinus caribaea) y cipres (Cupressus lusitanica). Las muestras de corteza han sido preparadas, secadas y extraidas con etanol. Los extractos etanolicos se han analizado para determinar el contenido de taninos condensados a traves del numero de Stiasny, y se han caracterizado mediante espectroscopia infrarroja (FT-IR). Las especies con mayor proporcion de material extraido han sido: guanacaste (9.5841% m/m), pochote (15.0066% m/m), pino (19.3400% m/m) y cipres (10.5300% m/m). Los extractos con una mayor proporcion de taninos condensados han sido: alcornoque (61.9% m/m), jobo (66.1% m/m), pochote (72.8% m/m), nispero (50.5% m/m), cedro (72.7% m/m) y pino(70.7% m/m). (autor)