Load capacity of the board grillage with two stringers under ice loading

Снизить повреждаемость бортовых перекрытий при ледовых нагрузках можно за счет совершенствования расчетных зависимостей по оценке их несущей способности. Далеко не всегда такие зависимости, приводимые в справочных изданиях, дают верные рекомендации из-за не вполне ясного характера распределения нагрузок в сложных статически неопределимых системах. В справочнике по СМК приводится расчетная зависимость, позволяющая определить несущую способность регулярного перекрытия с двумя стрингерами при действиии локально распределенной нагрузки в пределах прямоугольника. Цель данной работы заключалась в оценке несущей способности реального бортового перекрытия ледокола типа Wind с помощью МКЭ при параметрах ледовой нагрузки, определяемой рекомендациями Морского Регистра РФ, и последующем сравнении полученных результатов с расчетами по теоретической зависимости, приведенной в справочнике. Полученные данные показали, что зависимость в справочнике для оценки несущей способности перекрытия дает удовлетворительно согласующиеся с МКЭ результаты после соответствующего уменьшения числового коэффициента в ней. При анализе несущей способности перекрытия варьировались шпация, толщина обшивки, высота стенок стрингеров и площадь приложения нагрузки. Установлено, что текучесть наблюдается в опорных сечениях шпангоутов и посредине их пролета, а из-за большой ширины присоединенного пояска обшивка у контура перекрытия практически никогда не течет. Полученные МКЭ результаты показали наличие обратно пропорциональной зависимости между предельной нагрузкой и шпацией при фиксированной площади нагружения. Отмечено, что увеличение толщины обшивки несущественно влияет на величину предельной нагрузки при остальных неизменных параметрах перекрытия. Выполненные расчеты позволяют кроме предельной нагрузки оценить также и величины прогибов при упругопластическом деформировании перекрытий, которые затруднительно подсчитать аналитически. To low damage of the board grillages under ice loading is possible by improving analytical relations on estimation of their load capacity. Not always such relations, bringing in manuals, give true recommendations because of complex character of the loads distribution in static indeterminate systems. Im manual on ship structural mechanics is giving analytical relation for determination of load capacity of regular grillage with two stringers under action of localy distributed load in rectangular area. Purpose of this study is to estimate load capacity of real board grillage of icebreaker of type Wind with help of FEM under parameters of ice load recommended in Maritime Register of RF, and following comparison of obtained results with calculation on analytical relation, given in manual. Obtained results show that relation in manual for estimation of load capacity of grillage give satisfactory results corresponding to FEM only after corresponding reducing of numerical coefficient in it. Under analysis of load capacity of grillage, it was changing frame space, thickness of plating, depth of stringers and area of application of load. It was estimated that most loaded zones of frames are their sections near supports and in the mid-span. Because of big width of associated plate the plating near contour of grillage is never yielding practically. Results obtained by FEM show existence of inversely proportional relation between the limit load and space framing under fixed area of loading. It was noticed that increasing of the plating thickness influent not essentially on value of the limit load under all other parameters of grillage unchangeable. Performed calculations allow to estimate limit load and value of deflections under elasto-plastic deformation of grillage, which is difficult to calculate analytically,

Extracting bigravity from string theory

The origin of the graviton from string theory is well understood: it corresponds to a massless state in closed string spectra, whose low-energy effective action, as extracted from string scattering amplitudes, is that of Einstein-Hilbert. In this work, we explore the possibility of such a string-theoretic emergence of ghost-free bimetric theory, a recently proposed theory that involves two dynamical metrics, that around particular backgrounds propagates the graviton and a massive spin-2 field, which has been argued to be a viable dark matter candidate. By choosing to identify the latter with a massive spin-2 state of open string spectra, we compute tree-level three-point string scattering amplitudes that describe interactions of the massive spin-2 with itself and with the graviton. With the mass of the external legs depending on the string scale, we discover that extracting the corresponding low-energy effective actions in four spacetime dimensions is a subtle but consistent process and proceed to appropriately compare them with bimetric theory. Our findings consist in establishing that string and bimetric theory provide to lowest order the same set of two-derivative terms describing the interactions of the massive spin-2 with itself and with the graviton, albeit up to numerical coefficient discrepancies, a fact that we analyze and interpret. We conclude with a mention of future investigations.

Applying the scalability apparatus to estimate the thermal efficiency of a single finned tube

The paper explores the possibility of scaling the integral parameters of the cooling system operation using the working elements with the length from 0.01 to 0.5 m. Numerical solution of the conjugate problem of external aeromechanics, internal hydrodynamics and heat exchange is carried out. Parametric studies of the cooling process and aerodynamic resistance of finned tubular elements of various lengths are performed. As a result of generalization and unification of the computational experimental data, a numerical coefficient has been obtained to calculate the necessary integral characteristics for a cooling element of the assigned length.

A pursuit-evasion differential game with slow pursuers on the edge graph of simplexes. I

We consider the differential game between several pursuing points and one evading point moving along the graph of edges of a simplex when maximal quantities of velocities are given. The normalization of the game in the sense of J. von Neumann including the description of classes of admissible strategies is exposed. In the present part of the paper the qualitative problem for the full graph of three dimensional simplex is solved using the strategy of parallel pursuit for a slower pursuer and some numerical coefficient of a simplex characterizing its proximity to the regular one. Next part will be devoted to higher dimensional cases.

NUMERICAL COEFFICIENT FOR ENDOMETRIAL CANCER INDIVIDUAL RISK EVALUATION IN POSTMENOPAUSAL WOMEN

Increased frequency of endometrial cancer (EC) since the beginning of this century exceeds that of breast cancer and to a large extent can be attributed to dynamics of parameters, which characterize hormonal and metabolic status of ill women and molecular genetic landscape of transforming endometrium. During the past few years there are suggested several options for a personalized assessment of the risk of EC. The aim of this article is to propose and justify own version of this score with the idea of its further not only retrospective but also prospective testing both in relation to the risk of developing endometrial cancer as well as an additional marker helping to predict tumor response to treatment.

Utilization of Anodized Aluminum Oxide Substrate for the Growth of ZnO Microcrystals on Polygonized Spirals

Anodized Aluminum Oxide (AAO) has been utilized as a substrate for the screw dislocation assisted growth of polygonize spirals (PS) of ZnO with diameter of the order of ~230 μm by Chemical Vapour Deposition (CVD) process. Stoichiometric ZnO microcrystals nucleated on the terraces and tops of these polygonized spirals. Stress inherent in the ZnO polygonized spiral morphology (~ 3.57 GPa) was deciphered from the values of the magnitude of shift in observed 2θ values of Glancing Incidence angle XRD (GIXRD) peaks from the standard values (JCPDS 36-1451) for hexagonal Zincite. The growth mechanism of these PS was explained albeit to a limited extent on the basis of the Burton, Cabrera and Frank (BCF) theory and its later modification, wherein data obtained from exsitu SEM measurements concomitant with numerical analysis was utilized to decipher values of the critical radius and supersaturation ratios. Nucleation of ZnO microcrystals on the PS was explained on the basis of the supersaturation ratio and the plausible values of diffusion lengths, existent on the summits of these PS. Retardation of the step rotation of the PS, due to elastic stress around the dislocation source and the Gibbs–Thomson effect, was explained on the basis of numerical coefficient ω0, the dimensionless frequency of spiral rotation. Role of stress in inhibition of ZnO nucleation on PS of smaller heights and with larger supersaturation ratio, has been discussed albeit qualitatively. The optical characteristics of a single ZnO microcrystal has been analyzed by room temperature CL measurements in the wavelength range 350 nm to 650 nm, revealing a single high intensity peak at 382 nm corresponding to a excitonic bandgap of 3.25 eV.

The elastocapillary Landau–Levich problem

We study the classical Landau–Levich dip-coating problem for the case in which the interface possesses both elasticity and surface tension. The aim of the study is to develop a complete asymptotic theory of the elastocapillary Landau–Levich problem in the limit of small flow speeds. As such, the paper also extends our previous study on purely elastic Landau–Levich flow (Dixit & Homsy J. Fluid Mech., vol. 732, 2013, pp. 5–28) to include the effect of surface tension. The elasticity of the interface is described by the Helfrich model and surface tension is modelled in the usual way. We define an elastocapillary number, $\epsilon $, which represents the relative strength of elasticity to surface tension. Based on the size of $\epsilon $, we can define three different regimes of interest. In each of these regimes, we carry out asymptotic expansions in the small capillary (or elasticity) numbers, which represents the balance of viscous forces to surface tension (or elasticity).In the weak elasticity regime, the film thickness is a small correction to the classical Landau–Levich law and can be written as $$\begin{eqnarray*}{\tilde {h} }_{\infty , c} = (0. 9458- 0. 0839~\mathscr{E}){l}_{c} C{a}^{2/ 3} , \quad \epsilon \ll 1,\end{eqnarray*}$$ where ${l}_{c} $ is the capillary length, $Ca$ is the capillary number and $\mathscr{E}= \epsilon / C{a}^{2/ 3} $. In the elastocapillary regime, the film thickness is a function of $\epsilon $ through the power-law relationship $$\begin{eqnarray*}{\tilde {h} }_{\infty , ec} = {\bar {h} }_{\infty , e} L\hspace{0.167em} f(\epsilon )C{a}^{4/ 7} , \quad \epsilon \sim O(1),\end{eqnarray*}$$ where ${\bar {h} }_{\infty , e} $ is a numerical coefficient obtained in our previous study, $L$ is the elastocapillary length, and $f(\epsilon )$ represents the functional dependence of film thickness on the elastocapillary parameter.

An extension of a norm inequality for a semi-discrete g*λ function

A norm inequality for a semi-discrete g*?(f) function is obtained for functions, f, that can be written as a sum whose terms consist of a numerical coefficient multiplying a member of a family of functions that have properties of geometric decay, minimal smoothness and almost orthogonality condition. The theorem is applied to the rate of change of u, a solution to Lu = div?f in a bounded, nonsmooth domain ? Rd, d?3, u = 0 on ??.

Role of neutral-particle bombardment in dust–dust interactions in plasmas

It is shown that the interaction of dust with neutral plasma particles can lead to attractive forces between dust particles, both in the case where the distance between dust particles is less than the mean free path of neutral particles and in the case where it is greater. The expressions for attractive forces differs in the two limits only by a numerical coefficient. The additional force of dust interaction is found to be due to the neutrals created by recombination of charged plasma particles on the surface of dust particles. The influence of radiative dust cooling on dust–dust interaction is considered.