Laboratory plant for evaluation of burnout rate of various materials

Описана методика исследования скорости выгорания различных материалов. Для реализации методики создана лабораторная установка. Экспериментально установлено, что процесс выгорания материалов зависит от температуры реактора и скорости воздушного потока. Кривая выгорания имеет S-образный вид и три характерных участка: индукционный период, линейный участок и участок реакции, где происходит выгорание углеродистого остатка. В табличной форме представлены результаты исследования некоторых широко распространенных материалов. The article describes a method for studying the burnout rate of various materials. There was created the laboratory plant for implementation of the method. It is experimentally established that the process of burnout of materials depends on the temperature of the reactor and the air flow rate. The burn-up curve has an S-shape and three characteristic sections: the induction period, the linear section, and the reaction section where the carbon residue burns out. The article presents the results of study of some widely distributed materials in tabular form. The mass burn rate of beech wood is 1.5 times higher than that one of pine. Perhaps this is due to the impregnation of beech with furniture varnish, since the sample was part of the furniture lining. It is noteworthy that significant discrepancy in the burn-up rates was obtained during combustion of samples of different brands of polyurethane foams. So, for hard polyurethane foam - “izolan 2”, which has a flame retardant in its composition, burnout curves with longer induction period are obtained (as a result of flame retardant action). However, the burnout rate is higher in comparison with soft polyurethane foam without flame retardant (foam rubber). The composition of the material “isolan-2”. Rubber also has a long induction period, but a high burnout rate.

Characteristics dependence of the silicon photoelectronic multipliers on temperature

The characteristics dependence on the ambient temperature for three types of silicon photoelectronic multipliers have been studied in this research. The prototypes of Si-photoelectronic multipliers with a p+–p–n+ structure produced by JSC Integral (Republic of Belarus), serially produced silicon photoelectronic multipliers KETEK РМ3325 and ON Semi FC 30035 have been used as objects of research. We present the setup diagram and research technique. Measurements of the photocurrent magnitude versus the illumination intensity, calculations of the critical and threshold intensities, and the dynamic range have been performed. We also present the photocurrent dependences on the illumination intensity at different ambient temperatures. As it was found, these dependences have a linear section, the length of which characterizes the critical intensity value, and the inclination angle of the linear section to the intensity axis characterizes the photodetector sensitivity to optical radiation. It has been determined that the temperature increase leads to an increase in the critical intensity value and to a decrease in the sensitivity value. We present the dependences of the threshold intensity on the overvoltage at different ambient temperatures. The dependence of the threshold intensity on overvoltage is most strongly pronounced when the supply voltage is below the breakdown voltage. It was found that the threshold intensity is increased with the temperature increase and the threshold intensity dependence on the temperature is the same for all investigated photodetectors. It was found that the dynamic range value is decreased with the temperature increase, which is caused by a more significant change in the threshold intensity as compared to the critical one. The results given in this article can be applied when developing and designing the tools and devices for recording optical radiation based on silicon photoelectronic multipliers.

Features of nonlinear in-plane shear deformation of a unidirectional and orthogonally reinforced polymer sheets of composite materials

A comparative analysis of typical stress-strain diagrams obtained for in-plain shear of the 25 unidirectional and cross-ply reinforced polymer matrix composites under quasi-static loading was carried out. Three of them were tested in the framework of this study, and the experimental data on other materials were taken from the literature. The analysis of the generalized shear-strength curves showed that most of the tested materials exhibit the similar deformation pattern depending on their initial shear modulus: a linear section is observed at the beginning of loading, whereas further increase of the load decreases the slope of the curve reaching the minimum in the failure point. For the three parameters (end point the linear part, maximum reduced deviation of the diagram, tangent shear modulus at the failure point) characterizing the individual features of the presented stress-strain diagrams, approximating their dependences on the value of the reduced initial shear modulus are obtained. At the characteristic points of the deformation diagrams, boundary conditions are determined that can be used to find the parameters of the approximating functions. A condition is proposed for determination of the end point of the linear section on the experimental stress-strain curve, according to which the maximum deviation between the experimental and calculated (according to Hooke’s law) values of the shear stress in this section is no more than 1%, thus ensuring rather high accuracy of approximation on the linear section of the diagram. The results of this study are recommended to use when developing universal and relatively simple in structure approximating functions that take into account the characteristic properties of the experimental curves of deformation of polymer composite materials under in-plane shear of the sheet. The minimum set of experimental data is required to determine the parameters of these functions.

Derived categories of quintic del Pezzo fibrations

We provide a semiorthogonal decomposition for the derived category of fibrations of quintic del Pezzo surfaces with rational Gorenstein singularities. There are three components, two of which are equivalent to the derived categories of the base and the remaining non-trivial component is equivalent to the derived category of a flat and finite of degree 5 scheme over the base. We introduce two methods for the construction of the decomposition. One is the moduli space approach following the work of Kuznetsov on the sextic del Pezzo fibrations and the components are given by the derived categories of fine relative moduli spaces. The other approach is that one can realize the fibration as a linear section of a Grassmannian bundle and apply homological projective duality.

Tilt angle and lifetime of sunspot groups

We use the Catalog of Solar Activity (CSA) to study the latitudinal variations of tilt of solar active regions. The tilt angles β are computed taking into account changes of the heliographic grid with latitude ϕ. We show that when sunspot groups of different sizes and lifetimes are included, a classical representation of the Joy’s law as a linear function of latitude (β∝ϕ) is only the first approximation valid within a limited range of latitudes (−25○ ≤ ϕ ≤ +25○). Outside this range, the functional dependence β = f(ϕ) becomes non-linear. Separating the dataset on large long-living groups (LLG) and small short-living groups (SSG) reveals two quite different dependencies in β = f(ϕ): non-linearity in tilt is only present in LLGs and the steepness of linear section of β = f(ϕ) fit is higher for LLGs. This suggests a difference in the physical properties of two populations of solar groups, which could be hypothesized as an indication of different localization of subsurface zones of their formation in the framework of a distributed dynamo. However, since CSA contains the coordinates of sunspots averaged over the lifetime (or disk passage) of each group, one cannot ruled out that the difference in tilts of SSG and LLG groups may be affected by the evolution of tilt angles during the lifetime/disk passage of the groups.

Research of the amplitude-frequency characteristics of magnetorheological hydromounts under the influence of broadband random vibration

The results of a study of the amplitude-frequency characteristics of magnetorheological hydromounts on a Star28 vibrating stand generating broadband random vibration are presented. A linear section was determined on the static characteristic of magnetorheological hydromounts, tested with different loads. Keywords: static load, linear section, operating point, random broadband vibration, amplitude-frequency characteristics, spectral density, white noise [email protected]; [email protected]

Wahl maps and extensions of canonical curves and K⁢3K3 surfaces

Let C be a smooth projective curve (resp. {(S,L)} a polarized {K3} surface) of genus {g\geqslant 11}, with Clifford index at least 3, considered in its canonical embedding in {\mathbb{P}^{g-1}} (resp. in its embedding in {|L|^{\vee}\cong\mathbb{P}^{g}}). We prove that C (resp. S) is a linear section of an arithmetically Gorenstein normal variety Y in {\mathbb{P}^{g+r}}, not a cone, with {\dim(Y)=r+2} and {\omega_{Y}=\mathcal{O}_{Y}(-r)}, if the cokernel of the Gauss–Wahl map of C (resp. {\operatorname{H}^{1}(T_{S}\otimes L^{\vee})}) has dimension larger than or equal to {r+1} (resp. r). This relies on previous work of Wahl and Arbarello–Bruno–Sernesi. We provide various applications.