试验用空气焓值法试验装置温湿度测量系统

从试验用空气焓值法试验装置的制冷量计算及不确定度分析入手,指出影响制冷量的关键因素。对各种温湿度测量系统进行分析研究,给出校准方法、注意事项和系统不确定度。     

湿度自动测量装置

本文阐述了采用可编程控制器(PLC)对湿度进行测量的原理，并对其硬件组成和软件结构作了详细的介绍。在软件编制中运用了一些新颖的算法，以提高运算的精度。     

Microresonator interference fiber-optic sensor of relative air humidity

A novel type of fiber-optic sensor of relative air humidity is developed on the basis of the micromechanical silicon microresonator and silica gel. The output signal of such a sensor in the frequency form has low sensitivity to variations in the laser-source power and to random attenuations in the fiber. In the case of purely optical excitation of oscillations of the resonator, the sensitive element of such a sensor is completely passive because it does not contain any electronic circuits and components. The sensor showed high sensitivity at a relative humidity less than 75%, possibility to operate at temperatures below freezing, and low dependence of readings on air temperature. The dependence of the humidity mass adsorbed by silica gel on the relative air humidity was found to be linear, which simplifies sensor calibration.     

The effect of relative humidity and evaporation rate on electrospinning: fiber diameter and measurement for control implications

This paper presents an experimental study of the influence that relative humidity and evaporation rate have on the electrospinning process in terms of fiber diameter, process measurements, and selection of operating regime (applied voltage and flow rate) for polyethylene oxide/water (aqueous) solutions and poly(vinylpyrrolidone)/alcohol (non-aqueous) solutions. Poly(vinylpyrrolidone) alcohol solutions are studied to understand the separate influence of relative humidity and evaporation rate. Correlations are developed that relate measurable process parameters (jet diameter, charge density) as well as relative humidity and evaporation rate to fiber diameter. In addition, the influence that relative humidity has on selection of operating regime to achieve desired fiber diameter and maximum production rate is presented.     

Hydration behaviour of synthetic saponite at variable relative humidity

Hydration behaviour of synthetic saponite was examined by X-ray powder diffraction simulation at various relative humidities (RH). The basal spacing of the Ca-saponite increased stepwise with increase in RH. The (00l) reflections observed reflect single or dual hydration states of smectite. Quasi-rational, intermediate, or asymmetrical reflections were observed for all XRD patterns and reflecting heterogeneity of the samples, especially along the transition between two hydration states.     

Relationship between critical relative humidity and solubility of drugs

Both the critical relative humidity (H(cr)) and the solubility are important physicochemical properties that affect the quality of drugs. However, the relationship between them is not noticed yet. By an analysis of interaction between molecules of drug and water, the conclusion logically obtained is: the higher the solubility is, the lower the H(cr) will be. To validate this idea, the H(cr) and the solubility of 33 drugs and chemicals were determined and a negative linear correlation was found between the two factors when the solubility was expressed as the mole fraction of water. This negative linear correlation was further confirmed by a computer simulation according to modified Debye-Hückel equation.     

Internal relative humidity and drying stress gradients in concrete

A moisture gradient develops as concrete dries, inducing a drying shrinkage stress gradient that can lead to early-age cracking in restrained concrete. A new internal relative humidity measurement system was used to quantify the moisture gradient in early-age concrete exposed to drying. A simple model was developed to estimate the stress gradient associated with drying in both free and fully restrained concrete specimens. The model predicts that the stresses in the surface layer of restrained concrete exceed the tensile strength of the material prior to complete specimen failure. Comparison of the model and experimental results indicate that the fully restrained specimens with the most severe drying stress gradients failed at the earliest ages.     

The measurement of humidity at high pressures

A humidity calibrator for measurements at pressures up to 15 MPa is designed. The effect of pressure on the characteristics of capacitive humidity sensors is demonstrated. A method of taking this effect into account is proposed. A procedure for calibrating humidity transducers with capacitive sensors at high pressure is described. __________ Translated from Izmeritel’naya Tekhnika, No. 2, pp. 61–64, February, 2008.     

一种新型文物展柜湿度控制系统

基于扩散吸收式制冷无噪音、寿命长和运行稳定的优点,研制出了一种新型湿度控制系统。利用该系统进行了初步实验并确定了控制策略,继而采用PID控制方法对文物展柜内的湿度进行了控制实验研究。结果表明:该湿度控制系统能使展柜内相对湿度(Relative Humidity,RH)在45%—65%之间连续可调,且在设定值附近几乎保持恒定;具体地,当展柜内的相对湿度设定值为45%、50%、60%和65%时控制偏差在±0.5%以内,设定值为55%时控制偏差在±1.25%以内,满足绝大多数文物保存对湿度的要求。该系统可为博物馆中独立文物展柜提供不同的恒湿环境。     

Possibilities for accurate control of the relative humidity of air

Studies considering the control of relative humidity are analyzed.     

Surface energies of hardenned cement paste depending on relative humidity

In the lower region of relative humidity, one assumption of the Munich Model regarding the volumetric changes in hardened cement paste (hep) is that adsorbed water molecules decrease surface energy. Recent work with inverse gas chromatography (IGC) on hep provides the first experimental evidence to support this assumption. Under conditions of varying relative humidity, the equipment used (iGC SMS— POROTEC) allowed a series of pulse experiments with non-polar (alkenes) and polar probe molecules at temperatures in the region of 30°C. From the retention times, specific interaction energies and a dispersive surface energy of the solid can be derived. The results are in agreement with the findings of many other experiments conducted under different relative humidities. Furthermore they may help to understand strongly nonliner moisture related phenomena like shrinkage, swelling, change in the pore size, strength, and diffusion in hardened cement paste.

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Résumé à faible humidité relative, l'une des hypothèses du modèle de Munich concernant les changements volumétriques des pates de ciment durcies (hcp), est que les molécules d'eau adsorbées diminuent les énergies de surface. De récents travaux de Chromatographie en Phase Gazeuse Inverse (CIG) sur les hcp ont fourni les premières preuves de vérification de cette hypothèse. L'appareil utilisé (CIG SMS— POROTEC) a permis, à différentes humidités relatives, des séries de mesures avec des sondes moléculaires non polaires (alcènes) et polaires, à des températures voisines de 30°C. à partir des temps de rétention, les énergies d'interaction spécifiques et l'énergie de surface dispersive du solide ont pu être dérivées. Les résultats sont en accord avec ceux obtenus par d'autres expériences réalisées dans des conditions d'humidité relative variables. Ils permettent en outre d'aider à comprendre les phénomènes fortement non-linéaires induits par l'humidité tels que le retrait, le gonflement, le changement de taille des pores, la résistance et la diffusion dans les pates durcies.

     

Thermal dilation and internal relative humidity of hardened cement paste

The coefficient of thermal dilation (CTD) of hardened cement paste and concrete is a function of the state of internal moisture in the pore system. It has been theorized that changes in the pore fluid pressure induced by temperature change causes additional dilation when the material is partially saturated. Drying shrinkage stresses in early-age concrete also evolve from changes in the pore fluid pressure. The Kelvin-Laplace equation relates changes in the pore fluid pressure to the measured internal relative humidity (RH). This research investigated the role of pore pressure changes on the CTD through internal RH measurements. A maximum change in humidity (ΔRH) due to temperature change (ΔT) was measured when the initial humidity was at an intermediate value. Likewise, the maximum CTD was also measured at an intermediate initial RH. Based on these findings, the additional thermal strain caused by changes in pore fluid pressure was modelled using internal RH measurements as a primary parameter.     

Associations between indoor relative humidity and global COVID-19 outcomes

Globally, the spread and severity of COVID-19 have been distinctly non-uniform. Seasonality was suggested as a contributor to regional variability, but the relationship between weather and COVID-19 remains unclear and the focus of attention has been on outdoor conditions. Because humans spend most of their time indoors and because most transmission occurs indoors, we here, instead, investigate the hypothesis that indoor climate—particularly indoor relative humidity (RH)—may be the more relevant modulator of outbreaks. To study this association, we combined population-based COVID-19 statistics and meteorological measurements from 121 countries. We rigorously processed epidemiological data to reduce bias, then developed and experimentally validated a computational workflow to estimate indoor conditions based on outdoor weather data and standard indoor comfort conditions. Our comprehensive analysis shows robust and systematic relationships between regional outbreaks and indoor RH. In particular, we found intermediate RH (40–60%) to be robustly associated with better COVID-19 outbreak outcomes (versus RH < 40% or >60%). Together, these results suggest that indoor conditions, particularly indoor RH, modulate the spread and severity of COVID-19 outbreaks.     

A fiberoptic pressure measurement system

Translated from Izmeritel'naya Tekhnika, No. 8, pp. 31–33, August, 1991.     

Capacitive sensor for relative angle measurement

Based on a capacitive angle and angular rate sensor, a sensor measuring the relative angle between two rotating shafts has been developed. Two rotatable electrodes are placed between two sensor plates. The relative angle between the two rotors and the absolute position of the rotor blades are calculated from measurements of the capacitive coupling between different transmitting stator segments and a single receiving electrode. A prototype of this sensor has been developed with a range of the relative angle of /spl plusmn/7.5/spl deg/ with a resolution of 0.1/spl deg/.