Temperature is an important environmental factor affecting streamer discharge. However, the mechanism and regularity of the influence are still unclear. This paper analyzes the mechanism of how the ...parameters in the hydrodynamic model are affected by temperature and the finite element method is used to solve three particle continuity equations along with Poisson's equation simultaneously. The results show that the increase in temperature inhibits the ionization and the attachment process, and the reduction rate of the ionization coefficient is 40 times the attachment coefficient numerically, which means that the streamer is easier to initiate at low temperatures. The increase in temperature accelerates the diffusion and drift of electrons. This effect increases the average velocity of the streamer, and the average velocity increases by about 4.89m/(s∙K) with temperature, which means that the fast-moving charged particles at high temperature may affect the discharge signals. The essence of the influence of temperature on the physical quntities in the streamer discharge is its influence on ionization, attachment, diffusion, and drift effects. The results in this paper can comprehensively consider the effects and obtain the effect mechanism of temperature on the micro-process of the streamer, contributing to the research on the insulation design of power equipment and the influence of temperature on the discharge signals.
Skin temperature plays a certain role in the dermal absorption of substances, but the extent and mechanisms of skin temperatures-induced modulation in ranges caused by physiological thermoregulation ...or environmental conditions are largely unknown. The influence of dermal temperature on the absorption of the model lipophilic compound (anisole) and the model hydrophilic compounds (1,4-dioxane, ethanol) through human skin was investigated at three dermal temperatures (25, 32 and 39 °C) in an ex-vivo diffusion cell model. The substances were applied to the skin and transdermal penetration was monitored. All substances showed temperature dependent variations in their penetration behavior (3 h: 25–39 °C: 202–275% increase in cumulative, transdermally penetrated amounts). The relative differences in absorption in relation to temperature were greatest within 45 min after exposure (25–39 °C: 347–653% rise in cumulated penetration), although absolute amounts absorbed were small (45 min vs. 3 h: 4.5–14.5%). Regardless of blood circulation, skin temperature significantly influences the amount and kinetics of dermal absorption. Substance-dependent, temperature-related changes of the lipid layer order or the porous pathway may facilitate penetration. The early-stage modulation of transdermal penetration indicates transappendageal absorption, which may be relevant for short-term exposures. For both, toxicological evaluation and perfusion cell studies, it is important to consider the thermal influence on absorption or to perform the latter at a standardized temperature (32±1 °C).
•Regardless the effect on blood flow, skin temperature significantly influences absorption.•The impact of temperature on dermal absorption is substrate-specific.•The penetration pathways through skin are influenced differently by temperature.•The influence of the temperature varies over the time course of the absorption.
The opinion exists that water stability is provided by hydrophobic bonds between organic soil particles; however, there are works in which the main role in the occurrence of this property is assigned ...to the presence of hydrophilic organic substances in soils. The goal of this study is to clarify the nature of the bonds (hydrophilic or hydrophobic) that ensure the water stability of soils. We used samples of sod-podzolic and gray forest soils, as well as leached chernozem. Experiments to assess water stability were carried out using the method of “blades.” It is based on the dissection of linearly arranged aggregates, which were preliminarily moistened in vacuum to values close to saturation. The energy of hydrophobic bonds depends on the temperature; therefore, the influence of temperature on the value of the determined water stability was studied. Experiments showed that, as the temperature increases, the water stability of aggregates stored in the wet state increases from the moment of selection and decreases as the temperature increases. This indicates the leading role of hydrophobic bonds in the formation of water stability. As for the samples dried to an air-dry state, moistened again, and kept wet for more than two weeks, no temperature dependence of the water stability has been found. Taking into account that the strength of hydrophobic bonds increases with increasing temperature, while that of hydrophilic bonds decreases, the obtained data immutability of water stability can be explained if we assume the joint participation both hydrophobic and hydrophilic bonds in water stability of soil samples that have passed through the stage of drying to an air-dry state. In fact, these results indicate a strong change in the structural organization of soils during drying.
Nicht vorwiegend ruhend beanspruchte Konstruktionen werden im Stahlbau i. Allg. mit gleitfest vorgespannten Verbindungen ausgeführt, da diese aufgrund ihrer reibschlüssigen Kraftübertragung einen ...hohen Ermüdungswiderstand aufweisen. Die übertragbaren Kräfte in Schraubenverbindungen unter Scherbeanspruchung sind jedoch begrenzt. Wird zusätzlich Klebstoff auf die Reibflächen appliziert, entsteht die sog. vorgespannte Hybridverbindung. Die damit verbundene Traglaststeigerung unter Berücksichtigung verschiedener Fertigungseinflüsse und das Tragverhalten unter Dauerstandslast sowie unter Temperatureinfluss werden im folgenden Beitrag thematisiert.
Translation
Current insights of the use of adhesive in preloaded bolted connections considering manufacturing influences
Not predominantly static loaded structures in steel construction are preferably executed with slip‐resistant connections since they exhibit a high resistance against fatigue. Nevertheless, the transferable shear loads are limited. With additionally applied adhesive on the friction surfaces, the so‐called preloaded hybrid connection is formed. The related increase of load capacity considering various manufacturing influences and the load‐bearing behaviour under permanent load as well as under the influence of temperature is presented in the following article.
The accurate installation of long-span arch bridges’ arch ribs remains a challenge due to the complex calculations required for cable forces and arch rib displacements, as well as the significant ...influence of environmental and construction loads. In this study, we propose a practical approach to alignment and error feedback control for long-span arch bridges. Cable forces were optimized using multiple control objectives based on influence matrix principles. The impact of temperature on the next segment to be installed was analyzed using the metastatic GM(1, 1) model and fitting results. Several tunable parameters were employed to account for parameter errors and environmental interference. These parameters were adjusted based on the deviations between practical and theoretical alignments for different arch rib segments, achieving a model output of an offset-free-tracking arch rib structure. This technology was applied to monitor the construction of the Tian’e Longtan Grand Bridge. Compared to conventional alignment control approaches, the proposed method achieved excellent arch ring alignment after the closure of the high-accuracy arch rib and cable release, as well as effective control of cable force uniformity and tower deviation. Field measurement data indicate that the closing deviation of the arch ring is only 3 mm. This study provides a valuable reference for the construction control of long-span arch bridges.
To perform geodetic measurements of displacements of the ground and manmade constructions, stabilised reference points are needed from which control points on the object or its surroundings could be ...measured. Reference points are most commonly stabilised with reinforced concrete pillars; however, they are not always constructed in an appropriate manner. The influence of temperature variation within a pillar on the position of the fixed screw for forced centring is not negligible and should be considered when performing precise measurements. In this research paper, the displacement of a pillar was calculated as a result of the temperature changes in the pillar, and then an experiment was performed in which the pillar was heated from one side, and the horizontal displacement of the fixed screw for forced centring was measured. Both, calculations and measurements, show that at a temperature difference of 16.2 °C, the fixed screw on a 1.5 m high pillar moves by approximately 1 mm, which is a displacement that should be taken into account in precise measurements.
In this study, the rheological characteristic of shear thickening fluid (STF) with various mass ratios of zirconium dioxide (ZrO2) to silicon dioxide (SiO2) was investigated. The influence of the ...ZrO2 mass ratio on the sensitivity of nano-ZrO2/SiO2-STF to temperature was further discussed. Nano-ZrO2/SiO2-STF of different concentrations (9.0-20.0 wt%) were prepared via an ultrasonication and mechanical stirring technique. The presence of ZrO2 and their interaction with the SiO2 nanoparticles in the STF were analyzed using scanning electron microscope (SEM), Energy dispersive spectroscopy (EDS) and x-ray diffractometer (XRD). The rheological testing results showed that the ZrO2/SiO2-STF system produced a considerable shear thickening effect; when the nano-ZrO2 mass ratio was 12%, the critical shear rate of the system was relatively small and the peak value of apparent viscosity was relatively large. More importantly, as the nano-ZrO2 mass ratio increased, temperature exerted less influence on the viscosity of the ZrO2/SiO2-STF system diminished, but still had a significant influence on the shear thickening effect.
The applicability of chloridizing roasting for removal of copper from the sulphide copper smelting waste slag of the ”Karabashmed'” copper-smelting plant is investigated. Calcium chloride CaCl2 was ...used as chlorination agent. It is established that the chlorinating roasting of the initial slag presented by fayalite 2FeO∙SiO2, hasn't led to noticeable removal of copper. Considerable degree of removal of copper (more than 90 %) has been reached as a result of the chlorinating of preliminary oxidized slag in which fayalite was oxidized to form Fe2O3 and SiO2. Using a fractional factorial experiment 23–1, dependence of degree of copper removal from preliminary oxidized slag upon temperature of the chlorinating roasting, time of isothermal roasting period and content of CaCl2 was established. It is found that increase of temperature and of CaCl2 content leads to increase in degree of copper removal. The influence of time of isothermal roasting period in the studied interval (2–4 h) is statistically insignificant.
Two pedestrian bridges, which were equipped with tuned mass dampers almost two decades ago, have been evaluated for their long-term performance. The response due to pedestrian action is compared to ...the response at installation. Forced vibration tests are used to identify system parameters of the bridges and the tuned mass dampers. The assessment shows that both bridges and tuned mass dampers are still working well. Detuning has been observed in one of the two bridges, which is, however believed to have existed already at installation. Parameters of the tuned mass dampers are shown to depend significantly on seasonal temperatures, which gives some practical limits to exact optimal tuning.
Difficulties may arise in system identification when only the deck response can be measured. Since both inherent bridge damping and absorber effects reduce the overall response, it is difficult to separate the two effects. In some cases even a negative bridge damping together with a high absorber mass has been identified. For reliable results, one of these parameters has to be fixed to a reasonable value. The concept of effective damping is used to show the correlation between the two effects. This concept permits separating the effects of bridge damping, absorber mass, and detuning in an approximate manner.
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