Doklady Physics最新文献

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Synchronized Active Antenna Arrays for Studying the Passage of Ultra-Wideband Signals in the Atmosphere and Ionosphere 用于研究大气层和电离层中超宽带信号传递的同步有源天线阵列

IF 0.8 4区物理与天体物理 Q3 Engineering

Doklady Physics

Pub Date : 2024-01-29 DOI: 10.1134/s1028335823050117

E. F. Lebedev, V. E. Ostashev, A. V. Ulyanov, V. M. Fedorov, M. A. Shurupov

Abstract

Active synchronized antenna arrays generating ultra-wideband radiation with an electric field strength of about 1 V/m at a distance of several hundred kilometers have been studied. They are designed to study the passage of ultra-wideband signals in the surface layer of the atmosphere and through the ionosphere. Synchronous antenna arrays with four and nine radiating modules have been created. Their radiation has a symmetrical radiation pattern along the x and y axes with a pulse duration at half-height of about 100 ps. They have a pulse energy potential (E × R) of about 60 and 150 kV, with a gross weight of 50 and 100 kg, respectively. Such characteristics allow these arrays to be placed on air carriers. The option of using air balloons under irradiation in the surface layer of the atmosphere and the option of placing meteorological rockets under irradiation from a height of 300 km to the Earth’s surface is considered.

摘要研究了在几百公里距离上产生电场强度约为 1 V/m 的超宽带辐射的有源同步天线阵列。设计这些天线阵列的目的是研究超宽带信号在大气表层和穿过电离层的情况。已创建了具有四个和九个辐射模块的同步天线阵列。它们的辐射具有沿 x 和 y 轴对称的辐射模式，半高脉冲持续时间约为 100 ps。它们的脉冲能量势能（E × R）分别约为 60 千伏和 150 千伏，总重量分别为 50 千克和 100 千克。这些特点使这些阵列可以放置在航空母舰上。考虑了在大气表层照射下使用气球的方案，以及在从 300 千米高空向地球表面照射下放置气象火箭的方案。

引用次数: 0

Critical Conditions of Self-Ignition at Bifurcation Points 分岔点自燃的临界条件

IF 0.8 4区物理与天体物理 Q3 Engineering

Doklady Physics

Pub Date : 2024-01-29 DOI: 10.1134/s1028335823050063

A. A. Philippov, A. A. Berlin

Abstract

The results of the main research in the field of self-ignition theory are summarized. For symmetrical vessels, the following are presented: critical conditions of spontaneous ignition in dimensional coordinates, temperature distribution in the vessel, pre-explosive heating of fuel, and the critical size of the vessel at the time of explosion. It is noted that the self-ignition conditions for various vessels differ only by a digital multiplier, which indicates that the shape of the vessel does not affect the physicochemical processes going on in the fuel at the time of the explosion. Each singular point, being a bifurcation point, determines a number that allows finding a single critical condition of self-ignition from the set of solutions to the heat equation. This condition, in the coordinates of its variables, represents a multidimensional surface separating the zone of stationary existence of a combustible system from the zone of “no return,” where a combustible system cannot exist.

摘要总结了自燃理论领域的主要研究成果。对于对称容器，介绍了以下内容：尺寸坐标中的自燃临界条件、容器中的温度分布、爆炸前的燃料加热以及爆炸时容器的临界尺寸。值得注意的是，不同容器的自燃条件仅有一个数字乘数的差别，这表明容器的形状并不影响爆炸时燃料中发生的物理化学过程。每个奇异点都是一个分岔点，它决定了一个数字，可以从热方程的解集中找到一个单一的自燃临界条件。该条件在其变量坐标中代表了一个多维表面，将可燃系统的静止存在区与可燃系统无法存在的 "不归区 "区分开来。

引用次数: 0

Transition of a Supersonic Boundary Layer Over an Unswept Wing Due to Acoustic Noise 声学噪声导致未下垂机翼上超音速边界层的转变

IF 0.8 4区物理与天体物理 Q3 Engineering

Doklady Physics

Pub Date : 2023-12-26 DOI: 10.1134/s1028335823040031

P. V. Chuvakhov, I. V. Egorov

Abstract

In this paper, we present the results of direct numerical modeling of the process of susceptibility of a supersonic boundary layer over an unswept wing with a thin parabolic profile to acoustic noise of various intensities. It was demonstrated that acoustic noise can cause a laminar–turbulent transition over the unswept wing of a supersonic passenger aircraft.

摘要在本文中，我们介绍了对具有薄抛物线轮廓的非后掠翼上的超音速边界层易受不同强度声学噪声影响的过程进行直接数值建模的结果。结果表明，声学噪声可导致超音速客机无后掠面机翼上的层流-湍流过渡。

引用次数: 0

Features of Nitrogen Degassing of Dhajala Chondrite (3.8) 达贾拉软玉（3.8）的脱氮特征

IF 0.8 4区物理与天体物理 Q3 Engineering

Doklady Physics

Pub Date : 2023-12-26 DOI: 10.1134/s1028335823040067

S. A. Voropaev, N. V. Dushenko, V. S. Fedulov, V. G. Senin

Abstract

Samples of the Dhajala meteorite (ordinary chondrite, type H3.8) were kept isothermically in a specially designed device in the temperature range from 300 to 800°C for 90 minutes. The composition and content of the released gases were studied on a gas chromatograph. The following were detected: CO, CO₂, and H₂O in concentrations of 10–60 µg/g of the sample; in addition, H₂, CH₄, and H₂S in concentrations of 0.3–2 µg/g. The total nitrogen content during degassing increased quasi-linearly over time from 1–2 to 10–12 µg/g at each fixed temperature. Based on experimental observations of the change in the rate of nitrogen release depending on temperature, it was concluded that the effect of phase transitions depends on the permeability of the mineral matrix.

摘要 Dhajala 陨石（普通软玉，H3.8 型）的样本在一个特别设计的装置中，在 300 至 800°C 的温度范围内等温保存 90 分钟。用气相色谱仪研究了释放气体的成分和含量。检测到以下气体CO、CO2 和 H2O 的浓度为 10-60 µg/g 样品；此外，H2、CH4 和 H2S 的浓度为 0.3-2 µg/g。在每个固定温度下，脱气过程中的总氮含量随时间呈近似线性增长，从 1-2 微克/克增至 10-12 微克/克。根据对氮释放速率随温度变化的实验观察，得出的结论是相变的影响取决于矿物基质的渗透性。

引用次数: 0

Maintaining Microwave Discharge in Hollow Core Optical Fibers for Gas Fiber Lasers 维持气体光纤激光器空芯光纤中的微波放电

IF 0.8 4区物理与天体物理 Q3 Engineering

Doklady Physics

Pub Date : 2023-12-26 DOI: 10.1134/s102833582304002x

I. A. Bufetov, A. V. Gladyshev, S. M. Nefedov, A. F. Kosolapov, V. V. Velmiskin, P. A. Goncharov, A. P. Mineev

Abstract

The minimal values of the 2.45 GHz microwave electric field, which are necessary to maintain a discharge in a number of noble gases (argon, neon, and helium) in optical fibers with hollow cores of small diameter up to 100 μm, have been measured for the first time. The minimal electric field values for all three gases are (2.5–2.8) kV/cm at a pressure of argon ~50 Torr, neon ~300 Torr, and helium ~500 Torr.

摘要首次测量了 2.45 GHz 微波电场的最小值，该电场是在直径小至 100 μm 的空心光纤中维持一些惰性气体（氩气、氖气和氦）放电所必需的。在氩气 ~50 托、氖气 ~300 托和氦气 ~500 托的压力下，这三种气体的最小电场值为 (2.5-2.8) kV/cm。

引用次数: 0

Exact Solution of the Wiener–Hopf Equation on the Segment for Contact Problems of the Theory of Cracks in a Layered Medium 层状介质裂缝理论中接触问题分段上的维纳-霍普夫方程精确解法

IF 0.8 4区物理与天体物理 Q3 Engineering

Doklady Physics

Pub Date : 2023-12-26 DOI: 10.1134/s1028335823040018

V. A. Babeshko, O. V. Evdokimova, O. M. Babeshko, M. V. Zaretskaya, V. S. Evdokimov

Abstract

This paper presents an approach that allows us for the first time to construct an exact solution of the Wiener–Hopf integral equations on a finite segment for the case of meromorphic functions in Fourier transforms of the kernel. The Wiener–Hopf integral equation is traditionally considered set on a semi-infinite segment. However, in applications, there are often cases of their application specified on a finite segment. For these purposes, approximate methods of applying these integral equations have been developed. However, when considering the Wiener–Hopf integral equations generated by mixed problems of continuum mechanics and mathematical physics in a multilayer medium of finite thickness, it turned out that these integral equations are solved exactly both on semi-infinite and finite segments. The approach is based on a new modeling method in differential equations and in some types of integral equations. It allows the reduction of Wiener–Hopf integral equations to infinite systems of linear algebraic equations that are solved exactly. The obtained result opens up the possibility of constructing exact solutions to boundary value problems for deformable stamps and cracks of a new type in bounded bodies.

摘要本文介绍了一种方法，它使我们首次能够在有限段上构建维纳-霍普夫积分方程的精确解，用于内核的傅里叶变换中的微变函数情况。维纳-霍普夫积分方程传统上被认为是在半无限段上的集合。然而，在应用中，经常会出现在有限段上指定应用的情况。为此，人们开发了应用这些积分方程的近似方法。然而，当考虑有限厚度多层介质中连续介质力学和数学物理混合问题所产生的维纳-霍普夫积分方程时，发现这些积分方程在半无限段和有限段上都能精确求解。该方法基于微分方程和某些类型积分方程的一种新建模方法。它允许将维纳-霍普夫积分方程简化为可精确求解的无限线性代数方程组。所获得的结果为构建有界体中可变形印章和新型裂缝的边界值问题的精确解提供了可能性。

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引用次数: 0

The Moment-Membrane Theory of Elastic Flexible Plates as a Continual Geometrically Nonlinear Theory of a Graphene Sheet 弹性柔性板的动量-膜理论作为石墨烯薄片的连续几何非线性理论

IF 0.8 4区物理与天体物理 Q3 Engineering

Doklady Physics

Pub Date : 2023-12-26 DOI: 10.1134/s1028335823040055

S. H. Sargsyan

Abstract

A geometrically nonlinear moment-membrane theory of elastic plates has been built as a continual theory of deformations of flexible graphene under the assumption of smallness of deformations, bending-torsional characteristics, and angles of rotation (including a free one) of plate elements on the basis of the 3D geometrically nonlinear moment theory of elasticity with preservation of only the nonlinear terms that come from normal displacement (deflection) and its derivatives. For this nonlinear theory of elastic plates, the resolving equations are presented also in mixed form by introducing stress functions: this is a system of equilibrium equations for the transverse bending deformation compiled in the deformed state of the plate and the deformation continuity equations expressed by the stress and deflection functions. The Lagrangian-type variational principle for the geometrically nonlinear moment-membrane theory of elastic plates has been established.

摘要在三维几何非线性弹性力矩理论的基础上，建立了弹性板的几何非线性力矩-膜理论，作为柔性石墨烯变形的连续理论，该理论假定板元素的变形、弯曲-扭转特性和旋转角度（包括自由角度）都很小，只保留了来自法向位移（挠度）及其导数的非线性项。对于这种非线性弹性板理论，通过引入应力函数，解析方程也以混合形式呈现：这是一个在板变形状态下编制的横向弯曲变形平衡方程组，以及由应力和挠度函数表示的变形连续性方程组。为弹性板的几何非线性力矩-膜理论建立了拉格朗日型变分原理。

引用次数: 0

Elastic-Wave Scattering by a Plane Crack: Application of Flaw Detection 平面裂缝的弹性波散射：缺陷检测的应用

IF 0.8 4区物理与天体物理 Q3 Engineering

Doklady Physics

Pub Date : 2023-12-25 DOI: 10.1134/s1028335823030011

N. P. Aleshin, L. Yu. Mogilner

Abstract

The 3D problem of elastic wave scattering by a crack in the form of a half-plane in an elastic medium is considered. It is noted that the previously published solutions do not fully cover the issues relevant to ultrasonic flaw detection, for example, detecting transverse cracks in welds. The proposed solution is made by the Wiener–Hopf technique. It is shown that scattered longitudinal and transverse waves can be generally written in closed form. Some features of the identification of the tip of transverse cracks are noted, including scattering features during sonication of cracks along their surface and the influence of critical angles.

摘要研究了弹性介质中半平面形式裂纹对弹性波散射的三维问题。研究指出，以前公布的解决方案并没有完全涵盖超声波探伤的相关问题，例如检测焊缝中的横向裂纹。所提出的解决方案采用了 Wiener-Hopf 技术。结果表明，散射纵波和横波一般可以用封闭形式写出。还指出了识别横向裂纹尖端的一些特征，包括裂纹表面声波处理过程中的散射特征和临界角的影响。

引用次数: 0

Symmetry of the Lundgren–Monin–Novikov Equation for the Probability Distribution of the Vortex Field 涡流场概率分布的伦德格伦-莫宁-诺维科夫方程的对称性

IF 0.8 4区物理与天体物理 Q3 Engineering

Doklady Physics

Pub Date : 2023-12-25 DOI: 10.1134/s1028335823010044

V. N. Grebenev, A. N. Grishkov, M. Oberlack

Abstract

Polyakov [Nuclear Phys. B, 396, 1993] proposed a program for expanding the group of symmetries of hydrodynamic models to the conformal invariance of statistics in inverse cascades, where the conformal group is infinite-dimensional. This study presents group G of transformations of the equation for an (n)-point probability density function f_n (PDF) from an infinite chain of the Lundgren–Monin–Novikov equations (the statistical form of the Euler equations) for the field of a vortex of two-dimensional flow. The main result obtained is that the group G transforms conformally the characteristics of the zero-vorticity equation and, invariantly, the family of the f_n equations for the PDF along these lines. Along with other characteristics, the equation is not invariant. The action of G retains the PDF class. The results obtained can be used to study the invariance of the statistical properties in optical turbulence.

摘要波利亚科夫[核物理 B, 396, 1993]提出了一个方案，将流体力学模型的对称性群扩展到反级联中统计的保角不变性，其中保角群是无限维的。本研究提出了二维流涡旋场的 Lundgren-Monin-Novikov 方程（欧拉方程的统计形式）的无穷级联的（n）-点概率密度函数 fn (PDF) 方程的变换群 G。得到的主要结果是，G 组对零涡度方程的特征进行了保角变换，并且不变地对 PDF 的 fn 方程族进行了保角变换。与其他特征一起，该方程并不是不变的。G 的作用保留了 PDF 类。所得结果可用于研究光学湍流中统计特性的不变性。

引用次数: 0

Experimental Study of the Nonmodal Perturbation Growth Mechanism in a Laminar Submerged Jet 层流浸没式喷流中的非模态扰动增长机制实验研究

IF 0.8 4区物理与天体物理 Q3 Engineering

Doklady Physics

Pub Date : 2023-12-25 DOI: 10.1134/s1028335823020015

D. A. Ashurov, V. V. Vedeneev, L. R. Gareev, O. O. Ivanov

Abstract

It is known that, in wall-bounded flows, along with the growth of instability modes, an important role is played by the nonmodal (algebraic) mechanism of linear growth. In unbounded flows, including submerged jets, the nonmodal growth mechanism has been theoretically studied only in the last decade; this mechanism has not yet been identified in experiments. This paper describes experiments on excitation of the nonmodal “lift-up” growth mechanism. Special wavy structures (deflectors) are introduced into a laminar submerged jet of circular cross section, which excites a roller-like transverse motion. The data obtained make it possible to identify unambiguously the nonmodal lift-up growth of the introduced perturbations. The development of perturbations in the experiment qualitatively agrees with the theoretically calculated optimal perturbations. The specificities of the transition to turbulence caused by nonmodal growth are considered.

摘要众所周知，在有壁流动中，除了不稳定模式的增长之外，线性增长的非模式（代数）机制也起着重要作用。在包括浸没式喷流在内的无约束流动中，非模态增长机制直到最近十年才得到理论研究；这种机制尚未在实验中得到确认。本文介绍了激发非模态 "抬升 "增长机制的实验。在圆形截面的层流浸没射流中引入了特殊的波浪形结构（偏转器），从而激发了类似滚筒的横向运动。根据所获得的数据，可以明确地识别出所引入扰动的非模式抬升增长。实验中扰动的发展与理论计算的最佳扰动基本一致。研究还考虑了由非模式增长引起的向湍流过渡的特殊性。

引用次数: 0

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