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[en] The aim of present research was to measure and analyze the dynamic changes of internal pressure in shrinking vs. non-shrinking materials during convective drying for the use as a possible process control method. Drying experiments were carried out on wet and fired clay at 50°C and 60°C. In addition, the shrinkage curve was investigated. Experimental measurements show the existence of 4 stages of the process. The comparison of the results for wet and fired clay shows differences in pressure trends. During drying the internal pressure changes from underpressure to overpressure at the level of 3÷5kPa, what correlates well with transition from the first to the second drying period. (Author)
[en] Electrostatic collection technique is widely used in various radon monitors. The mechanism of this kind of radon monitor is that the positive Po particles, produced by decay of radon, can be collected on the surface of detector in electric field. Collection efficiency, therefore, could be affected by air humidity. Calibration under different humidity conditions or test of humidity response is necessary consequently. In this study, a humidity control technique based on Nafion membrane tube (NMT) is developed. Under a consistent flowrate with a certain stable level of radon concentration and humidity of main-path inlet, the humidity of outlet sample gas from the main-path can be adjusted and stably controlled at a certain level by changing side-path's flowrates of NMT. By adjusting main and side-path flowrate, RH of outlet gas of the main-path can be controlled from 5.3 to 80.0%. Theoretical study were also performed. Based on this, humidity influence calibration of an electrostatic radon monitor was performed, and a relationship between the sensitivity of the radon monitor and relative humidity was obtained. (authors)
[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] This paper investigates monthly, seasonal, and annual trends in rainfall, streamflow, temperature, and humidity amounts at Urmia lake (UL) basin and analyzes the interaction between these variables and UL’s water level fluctuation during the 1971–2013 period. Two new methods including nonparametric hybrid wavelet Mann–Kendall test and Şen’s methodology have been used to determine potential trends in the variables and their dominant periods. The results showed significant decreasing trends in the water level and streamflow series, moderate decreasing trend in the rainfall and relative humidity series, and increasing trends in the observed temperature data. The 8- , 12-month, and 2-year periods were detected as the dominant periods of the variables in monthly, seasonal, and annual timescales, respectively. The results from the interaction analysis revealed that the main factor influencing the water level at UL is decreasing trend in the streamflow series. Both the monthly series of UL’s water level and the streamflow series of the stations indicated two start points of significant decreasing trend in 1973 and 1998. Furthermore, a comparative analysis among the applied methods indicated a good agreement between the results of hybrid wavelet Mann–Kendall test and Şen’s trend analyzing method.
[en] Abstract Background: Relative humidity (RH) is one of the key environmental parameters in many experimental processes, and RH control is particularly important for in-situ synchrotron radiation experiments. However, there is no suitable commercial RH control equipment available for such experiments. Purpose: Based on the dynamic control of microcontroller, this study aims to develop an integrated set of numerically controlled (NC) RH control device, which can be conveniently loaded on the synchrotron radiation end-stations. Methods: A moisture channel and another dry air channel are connected to the sample chamber for humidification and dehumidification respectively. The dynamic equilibrium of RH at various values is controlled by the microcontroller using a fuzzy algorithm. Results: This device can hold the RH with an error of ± 1.0% at any set value from 20% to 94%. It also can increase the RH from 20% to 90% and decrease the RH from 90% to 20% with an error of ± 1.5% at a constant speed. Conclusion: This device can provide RH controlling environment with three switchable operation modes including RH holding, increasing and decreasing. It can meet various requirements of humidity control in kinds of synchrotron radiation in-situ experiments. (authors)
[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] In this paper, the effect of humidity conditions on thermal buckling analysis of graphene system contained two layers under different boundary conditions is investigated. The two-variable shear deformation plate theory is employed with the nonlocal continuum theory to deduce the governing stability equations. These equations are solved analytically to obtain the thermal buckling of the nanoplate system with simply supported, clamped and free boundary conditions. The present system of double-layered graphene sheets is composed from two sheets of graphene joined together by an elastic medium and hedged by two-parameter foundations. The external foundations are modeled as Winkler–Pasternak model. Two characteristic types of thermal buckling are considered: synchronous and asynchronous modes of buckling. The temperature rise and moisture concentration are assumed as a fixed, linear or nonlinear function of z (along the thickness direction). For the validation of the formulations, the present results are compared with those published in the references. Furthermore, the influences of the nonlocal parameter, humidity and other parameters on thermal buckling of double-layered graphene system are all discussed. (paper)
[en] Convective drying is a common process for the treatment of particulate solids also operated in continuous mode. Continuous operation is characterised by operation in steady-state with constant product throughput and constant product quality. Due to external influences, i.e. seasonal or local variations in the properties of the initial wet material, deviations in the product quality can result, for example over- or under-drying, or on-set of unwanted reaction. In this contribution a new feedback control concept is developed that is robust with respect to variations and uncertainties in the drying kinetics of the material and can reject and attenuate process disturbances. (Author)
[en] A common coldrex, paracetamol, was used as humidity sensing material. The capacitance-type humidity sensor was fabricated by aerosol deposition method. The humidity sensitive properties were investigated through dielectric measurements. Our results reveal that the sensor has exciting performances in high relative humidity. Both −OH and −NH groups have contributions to water absorption. The −OH groups lead to a water-containing surface layer giving rise to pronounced Maxwell-Wagner response, which in turn, yields the humidity response that can be easily adjusted by an external electric field. This work indicates that the paracetamol is a promising humidity sensing material. (paper)
[en] Highlights: • Shrinkage of concrete is measured with various temperature and humidity conditions. • The fib MC2010 shrinkage model is accurate for low RH and high T conditions. • The fib MC2010 shrinkage model slightly underestimate for other conditions. • The fib MC2010 creep model conservatively predicts creep strains. - Abstract: Creep and shrinkage of concrete is influenced by many factors including relative humidity and temperature. The combined effect of low relative humidity (<20%) and high temperature (38 °C) on creep and shrinkage of concrete is uncertain as limited tests have been conducted in this domain. Also unknown is the ability of the fib MC2010 model code in predicting the shrinkage and creep at the environment. This paper presents the results of experiments conducted in which concrete was cast and exposed to the aforementioned environmental conditions. The shrinkage and creep behaviour of the concrete was observed for 110 days, and experimental results were compared with predicted values using fib MC2010 model code.