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Number of results: 8
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Abstract

Studies on the thermics, humidity and refreezing rate of two types of periglacial soils of the marine lowlands of the Hornsund area (SW Spitsbergen) were carried out during spring ablation of the snow cover (1.06.—30.06.1987). Structural soil and peat soil (moss community) were chosen. The soils were studied in places almost completely devoid of the snow cover. A considerable differentiation of temperature in vertical profile and of humidity of surface layer in both soils were found. The dynamics of ground water table and the course and depth of spring refreezing of both soils were also different. The differences reflect the different origin of soils and consequently, their different grain-size distribution, physical properties and morphology of both types of soils as well as their water balance.
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Abstract

Spatial differentiation of temperature and relative humidity of air on western coast of Spitsbergen in 1979—1983 is presented. Applying the author's classification of types of atmospheric circulation in the studied area, its influence on distribution of these elements is shown. Air temperature in the area is related more to the degree of climate continentality than to its latitude. The lowest mean 5—year temperatures were calculated for stations with highest degrees of thermic continentality (Svea Gruber and Svalbard Lufthavn). The highest thermic differentiation occurs from November to March (1 —4°C) and the lowest in May—June and August—October (0.0— 1.5°C). It is opposite if relative humidity is concerned: the highest differences occur in summer (10—15%) and the lowest in winter (0—9%). Influence of atmospheric circulation on air temperature is larger during a polar night than a polar day. Again, it is opposite in the case of relative humidity. In both analyzed seasons the highest thermic differentiation occurred at the circulation type Ca. However, it was the lowest during a polar night at advection of air from northern and southern sectors, and during a polar day at advection from a northern sector and at the type Cc.
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Abstract

Humidity is probably the most important abiotic factor influencing life cycles, distribution, survival, and population dynamics of stored product pests. Although most of these pests can complete their life cycles in any given relative humidity, their prolonged development time, as well as decreased emergence rate and fecundity, have been well documented in several previous studies. In the present study, we evaluated the changes in energetic substances (lipids, soluble carbohydrates, glycogen, and proteins) accumulated in different life stages of larvae and adults of Tribolium castaneum in response to different relative humidity levels (5, 12, 22, 30, 45, and 65%). The results showed that young larvae were more susceptible to low relative humidity levels and desiccation stress. Larvae tended to accumulate higher proportions of lipids during earlier stages while their energy content shifted towards proteins with an increase in their age. Adult beetles experienced a significant decrease in their protein content immediately after they initiated reproduction. The importance of these fluctuations in the biology of the red flour beetles was discussed in detail.
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Abstract

A concept of a highly sensitive and fast-response airborne optoelectronic hygrometer, based on the absorption spectroscopy with laser light tuned to an intense ro-vibronic absorption line of H2O in the 1391– 1393 nm range is presented. The target application of this study is airborne atmospheric measurements, in particular at the top of troposphere and in stratosphere. The cavity ring-down spectroscopy was used to achieve high sensitivity. In order to avoid interference of the results by water desorbed from the instrument walls, the open-path solution was applied. Tests of the instrument, performed in a climatic chamber, have shown some advantages of this concept over typical hygrometers designed for similar applications.
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Abstract

Polymer-based capacitive humidity sensors emerged around 40 years ago; nevertheless, they currently constitute large part of sensors’ market within a range of medium (climatic and industrial) humidity 20−80%RH due to their linearity, stability and cost-effectiveness. However, for low humidity values (0−20%RH) that type of sensor exhibits increasingly nonlinear characteristics with decreasing of humidity values. This paper presents the results of some experimental trials of CMOS polymer-based capacitive humidity sensors, as well as of modelling the behaviour of that type of sensor. A logarithmic functional relationship between the relative humidity and the change of sensor output value at low humidity is suggested.
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Abstract

Moulding sands containing sodium silicate (water-glass) belong to the group of porous mixture with low resistance to increased humidity. Thanks to hydrophilic properties of hardened or even overheated binder, possible is application of effective methods of hydrous reclamation consisting in its secondary hydration. For the same reason (hydrophilia of the binder), moulds and foundry cores made of high-silica moulding sands with sodium silicate are susceptible to the action of components of atmospheric air, including the contained steam. This paper presents results of a research on the effect of (relative) humidity on mechanical and technological properties of microwave-hardened moulding mixtures. Specimens of the moulding sand containing 1.5 wt% of sodium water-glass with module 2.5 were subjected, in a laboratory climatic chamber, to long-term action of steam contained in the chamber atmosphere. Concentration of water in atmospheric air was stabilized for 28 days (672 h) according to the relative humidity parameter that was ca. 40%, 60% and 80% at constant temperature 20 °C. In three cycles of the examinations, the specimens were taken out from the chamber every 7 days (168 h) and their mechanical and technological parameters were determined. It was found on the grounds of laboratory measurements that moulds and cores hardened with microwaves are susceptible to action of atmospheric air and presence of water (as steam) intensifies action of the air components on glassy film of sodium silicate. Microwave-hardened moulding sands containing sodium silicate may be stored on a longterm basis in strictly determined atmospheric conditions only, at reduced humidity. In spite of a negative effect of steam contained in the air, the examined moulding mixtures maintain a part of their mechanical and technological properties, so the moulds and foundry cores stored in specified, controlled conditions could be still used in manufacture.
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Abstract

A large number of defects of castings made in sand moulds is caused by gases. There are several sources of gases: gases emitted from moulds, cores or protective coatings during pouring and casting solidification; water in moulding sands; moisture adsorbed from surroundings due to atmospheric conditions changes. In investigations of gas volumetric emissions of moulding sands amounts of gases emitted from moulding sand were determined - up to now - in dependence of the applied binders, sand grains, protective coatings or alloys used for moulds pouring. The results of investigating gas volumetric emissions of thin-walled sand cores poured with liquid metal are presented in the hereby paper. They correspond to the surface layer in the mould work part, which is decisive for the surface quality of the obtained castings. In addition, cores were stored under conditions of a high air humidity, where due to large differences in humidity, the moisture - from surroundings - was adsorbed into the surface layer of the sand mould. Due to that, it was possible to asses the influence of the adsorbed moisture on the gas volumetric emission from moulds and cores surface layers by means of the new method of investigating the gas emission kinetics from thin moulding sand layers heated by liquid metal. The results of investigations of kinetics of the gas emission from moulding sands with furan and alkyd resins as well as with hydrated sodium silicate (water glass) are presented. Kinetics of gases emissions from these kinds of moulding sands poured with Al-Si alloy were compared.
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