Influence humidity and heat on tensile shear strength of lap joints made of solid fir/spruce wood

Determination of tensile shear strength of lap joints is carried out according to three standards: BAS EN 205:2018 for adhesives used for non–load–bearing structures, and according to BAS EN 302-1:2014 for adhesives used for the manufacture of load-bearing structures and according to EN 14257:2019 for lap joints who are exposed to elevated temperatures. The paper presents the results of tensile shear strength of lap joints made of solid fir/spruce (Abies alba ssp./Picea abies spp). Tensile shear strength was tested in 4 groups of tests samples. The Group 1 consisted the samples were 7 days in standard atmosphere [20/65]. The Group 2 consisted the samples were previously soaked in water at (20 ± 5) °C, then recondition in standard atmosphere [20/65]. The Group 3 consisted the samples were previously 6 h soaked in boiling water 2 h, then soaked in water at (20 ± 5) °C; the samples tested in the wet state. The Group 4 consisted the samples were previously exposed to heat in a preheated fan oven, at (80 ± 2) °C, for (60 ± 2) min. The test results can be applied for gluing windows, doors, stairs, high-frequency gluing, veneering panels, etc.

Greenhouse Effect in the Standard Atmosphere

The “line-by-line” method is used for the evaluation of thermal emission of the standard atmosphere toward the Earth. Accounting for thermodynamic equilibrium of the radiation field with air molecules and considering the atmosphere as a weakly nonuniform layer, we reduce the emission at a given frequency for this layer containing molecules of various types to that of a uniform layer, which is characterized by a certain radiative temperature Tω, an optical thickness uω and an opaque factor g(uω). Radiative parameters of molecules are taken from the HITRAN database, and an altitude of cloud location is taken from the energetic balance of the Earth. Within the framework of this model, we calculate the parameters of the greenhouse effect, including the partial radiative fluxes due to different greenhouse components in the frequency range up to 2600 cm−1. In addition, the derivations are determined from the radiative flux from the atmosphere to the Earth over the concentration logarithm of greenhouse components. From this, it follows that the observed rate of growth of the amount of atmospheric carbon dioxide accounts for a contribution of approximately 30% to the observed increase in the global atmosphere during recent decades. If we assume that the basic part of the greenhouse effect is determined by an increase in the concentration c(H2O) of water atmospheric molecules, it is approximately dlnc(H2O/dt)=0.003 yr−1. This corresponds to an increase in the average moisture of the atmosphere of 0.2%/yr.

Minimally processed cassava leaves: effect of packaging on the microbiological and physical-chemical standards

The study presents itself as an alternative for the minimal processing of crushed cassava leaves, a product widely used in the Northern Brazilian cuisine. A Box-Behnken design was used to define the concentration of the sodium hypochlorite solution (NaClO) and the immersion time (t) capable of guaranteeing acceptable levels for thermotolerant coliforms and molds and yeasts in the leaves. The leaves sanitized in this condition were crushed, packed in polyethylene packaging under standard atmosphere (PE-WV) and under vacuum (PE-V); also packed in polyamide packaging under vacuum (PA-V), and stored at 7ºC for 30 days. The following properties were monitored: fresh weight loss, water activity, pH, titratable acidity, soluble solids, instrumental color, chlorophyll a and b, and total phenolic contents. In addition, there were assessed Salmonella spp, coliform at 45ºC, molds and yeasts and psychrotrophic bacteria. The 20 min immersion time and 250 mg/L NaClO solution were defined as the optimal conditions for the sanitization of the leaves and, after that, the leaves were rinsed with water. The behavior of the physical-chemical and microbiological properties indicated that the sanitized and crushed cassava leaves will be suitable for consumption for 24 h when packed in PE-WV; for 7 days when packed in PE-V and for 14 days when packed in PA-V, at 7°C storage.

Аэродинамический профиль в трансзвуковом потоке газа

The subject of investigation in this article is transonic flow. This is a condition in which local speeds of sound are appears on the wing surface, even at the subsonic speed of the nonturbulent flow. As a result, at a certain speed of the incoming flow, the flow regime around the aerodynamic surface will change sharply, which in turn changes the aerodynamic characteristics. Aerodynamic surfaces of the most transport category airplane experience transonic airflow during flight. The goal of the investigation is to study aerodynamic characteristics using numerical methods. The use of numerical methods in the design of aircraft structures is used more and more often to determine the optimal parameters for given operating conditions. This contributes to obtaining a more optimal and perfect design. In this article, we carried out a numerical analysis of the aerodynamic characteristics of airfoils in the transonic flow case using the CAE system CFD ANSYS. As a result of the research, the distributions of the pressure coefficients over the profile surface were obtained. The nature of the flow is obtained, which is similar to the picture of the pressure coefficients for transonic flow in the published sources of this topic. In the area of the middle of the profile, a shock-wave is observed. As a result, the flow around the airfoil changes, which contributes to a change in aerodynamic characteristics. The behavior of the aerodynamic drag and lift coefficients depending on the speed of the Mach number is considered. Also, the position of the center of pressure was analyzed at various velocities of the nonturbulent flow. The calculation was carried out at the cruising altitude of a medium-range aircraft of 11 km. For the calculations, we used the characteristics of the air temperature, the pressure of a given height from the table of the standard atmosphere.

Climatology of Estimated Altimeter Error Due to Nonstandard Temperatures

General-aviation (GA) controlled flight into terrain accidents often occur when a pilot is unaware their aircraft’s true altitude is lower than the altitude indicated by the pressure altimeter due to colder than standard temperatures. However, little guidance is available that quantifies the magnitude of these altimeter errors and their variation with season. In this study, the fifth generation European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis of the global climate (ERA5) data set is combined with the pressure-altitude equation to construct a 30-year monthly climatology covering much of the U.S. and Canada of D-value (i.e., true altitude minus pressure altitude) corrected for the standard atmosphere height separation between the altimeter setting and standard mean sea-level pressure. This “corrected” D-value therefore provides a useful estimate of the error between true and altimeter-indicated altitude. During winter, the mean corrected D-values reach values as low as −350 m (~ −1,200 feet) in northern, low-terrain regions for flights near a pressure altitude of 3,600 m, meaning the aircraft would be nearly 350 m lower than the altimeter indicates. Furthermore, the minimum (maximum negative) corrected D-values are nearly double their mean values for the same time period. In addition, the reanalysis-based corrected D-values are compared to estimated values calculated using a simple rule-of-thumb based solely on the air temperature at altitude and the surface elevation. The rule-of-thumb tends to under-predict the magnitude of the estimated error, in some cases by 70 m (~200 feet), and therefore gives a lower margin of safety.

Influence of Environmental Parameters on the Output Power of the Wind Power Plant of a Renewable Energy Complex

The wind speed has the greatest influence on the power flow, since it is included in the power equation in the third degree. It is impossible to ignore the presence in the equation of the air density, which is affected by its temperature, pressure and humidity. The air density is most often chosen according to the conditions of the standard atmosphere. The concept of a standard atmosphere varies from source to source and depends on the field of study. (Research purpose) The research purpose is in studying the influence of temperature, pressure and humidity on the power of the wind flow. (Materials and methods) The article presents existing works on the effect of air density on the operation of wind turbines. Authors selected sources that use the parameters available for measurement, for which there is statistical meteorological data. The study uses the temperature, pressure and relative humidity of the air as data with extensive meteorological observations. (Results and discussion) The article considers the influence of each of the factors depending on the levels of the other factors. The temperature change from -40 to +60 degrees Celsius at low pressure gives a deviation spread of 36.43 percent, while at high pressure this spread is 39.42 percent. A similar situation is observed with pressure, the influence of which varies in the range of 6.97-9.96 percent. The most unfavorable combination of factors (high pressure, low temperature and humidity versus low pressure, high temperature and humidity demonstrated an effect of up to 46.39 percent. (Conclusions) Temperature has the greatest impact on air density and power flow, and humidity has almost no effect on air density and power flow. With the most unfavorable combination of factors, the power flow through the wind wheel can decrease almost to one and a half times while maintaining its speed. The influence of air temperature cannot be ignored when calculating the power of the wind flow.

Use of the Speed of Sound for Heights Below the Troposphere in Colombia to Determine the Distance of Lightning Strikes

Objective: This paper aims to conduct a study of the speed of sound in Colombia for heights below the troposphere, taking into account the temperature as a function of altitude for a tropical zone, in order to determine the distance of lightning strike. Methodology: A speed of sound profile for Colombia was determined by analyzing data on altitude, temperature, and relative humidity in the country. The temperature equation as a function of altitude presented by NASA and the International Standard Atmosphere was taken into account to compare with the data obtained from meteorological stations located in different parts of the country (this stations measure information of temperature and other physical variables). Additionally, a sound profile map of Colombia was obtained using the interpolation in ArcGIS software. Results: A map of the speed of sound in Colombia was obtained, thus finding the speed range in the country. Likewise, the temperature was determined as function of the altitude for Colombia (a country in the tropical zone), with which it is possible to have data closer to the real speed of sound in the place and determinate the distance of impact of a lighting in land. Conclusions: The study of variables such as temperature, relative humidity, and altitude helped determine the speed of sound for Colombia. It was also possible to define a temperature equation as a function of altitude for a tropical country; with the speed of sound, the radius of impact of a lightning can be found.