A study of dust structure nearby white dwarf WD1334-678

A low flux density region nearby white dwarf WD1334-678 in the 140 µm AKARI survey maps has been systematically searched and found a far-infrared cavity centered at R.A. (J2000) = 13h38m14.4s, Dec.(J2000) = −68◦40’42”, in which minimum flux is 19.5 MJy/sr at 90 µm wavelength. The physical properties (Size, dust color temperature, dust mass) and thermodynamic property (Planck function distribution) of the cavity using 140 µm and 90 µm AKARI survey data. The size of the cavity is found to be 0.17◦× 0.12◦ has been presented. The dust color temperature is found in the range 17.70 ± 0.01 K to 18.81 ± 0.01 K. The Plank function distribution along major and minor diameters shows a very good agreement with sinusoidal fitting. The period of oscillation of dust particles along major and minor diameters are 3.2 Wm-2Sr-1Hz-1arcmin-1and 1.6 Wm-2Sr-1Hz-1arcmin-1, respectively. BIBECHANA 18 (2) (2021) 130-137

Determining stresses in the metallic structure of an overhead crane when using running wheels of the new design

This paper proposes a method to experimentally study the stressed state of the metallic structure of an overhead crane when using running wheels of different designs. The study employed a functioning electric, supporting, double-girder overhead crane with a capacity of 5 tons and a run of 22.5 m. Strain gauges assembled in a semi-bridge circuit and connected to the analog-digital converter Zetlab210 (Russia) were used to determine the girder deformations at the time of hoisting and moving cargoes of different masses. The cargo was lifted and displaced under the same conditions, on the regular wheels of a cargo trolley and the wheels with an elastic rubber insert. The girder deformation diagrams were constructed. The subsequent recalculation produced the stressed state's dependences at each point of cargo movement when using both regular wheels and the wheels with an elastic rubber insert. Also established were the dependences and the duration of oscillations that occur over the cycle of cargo lifting and moving. The experimental study cycle included cargo lifting in the far-left position by a trolley, moving the cargo to the far-right position, and returning the trolley with the cargo to its original position. It should be noted that the application of a new, modernized design of the running wheels of a cargo trolley with an elastic rubber insert effectively dampen the oscillations in the metallic structure of the crane. The experimental study's results helped establish an 18 % reduction in stresses in the girder of the overhead crane, as well as a decrease in peak vibrations, by 20 seconds, at the same cycles of cargo hoisting and moving. In addition, using wheels with an elastic rubber insert reduces the period of oscillation damping at the end of the cycle of cargo movement, by at least 30 %.

Study of tunneling and oscillation in a GaAs/〖Al〗_(0.3) 〖Ga〗_(0.7) As superlattice: using transfer matrix method

The study of superlattice (SL) system in lower dimensions, which shows tunneling and oscillation of particles, is very interesting from the point of view of fundamental physics and is important for devices. Here, we present results of our calculations related to tunneling/oscillations in a general SL system using a Symmetrical Quadruple Well (SQW) potential. This class of problems is handled using a transfer matrix (T-matrix), which is obtained by taking the solution of Schroedinger equation with appropriate boundary conditions on either side of SQW and then repeatedly applying it for the SL system. The electron wave functions in the system are found to be either in a symmetric or an anti-symmetric state with a very small energy difference between the two, leading to oscillations between these states. In this study, probability density and period of oscillation of the particle in SQW is calculated. The result is useful for high frequency operations in devices using SL. BIBECHANA 18 (2021) 91-99

Systemic conditions of diabetic patients diagnosed with apical periodontitis

ABSTRACT Objective: This study aimed to evaluate the association between glycemic control status in type 2 diabetes mellitus (T2DM) patients and apical periodontitis. Methods: Twenty-seven patients were involved in this study. The survey was based on anamnesis, intra and extra oral examination and radiographic evaluation. Diabetes mellitus information involved type of diabetes and blood glucose analysis. Patients were divided according to their metabolic control status (glycemic controlled and poorly controlled T2DM patients). Results: A higher fasting blood glucose level (p = 0.004) and a higher percentage of HbA1c (p = 0.0001) were demonstrated in poorly controlled T2DM patients when compared to glycemic controlled T2DM. However, the frequency of apical periodontitis and the elapsed time since diabetes mellitus diagnosis were higher in controlled T2DM patients, reaching 64%. Nevertheless, controlled T2DM patients presented a higher number of apical periodontitis cases (p < 0.05). Findings support that controlled patients T2DM presented higher presence of apical periodontitis than poorly controlled T2DM ones. In these patients, the time elapsed since the diagnosis was higher, which may have provided a longer period of oscillation and/or uncontrolled metabolism. Conclusions: Therefore, it might contribute to the development and maintenance of apical periodontitis in glycemic controlled patients of this study.

Influence of gravity on torsional surface waves in a dissipative medium

The present paper deals with the possibilities of propagation of torsional surface waves in a viscoelastic medium under gravity field. During the study it will observe that the increase in gravity parameter will increase the velocity of the wave, the increase in viscoelastic parameter, decrease the velocity of the wave until the product of angular frequency and viscoelastic parameter is less than unity. It also notes that as the velocity increases, the curve becomes asymptotic in nature when the period of oscillation increases. In fact the maximum damping in velocity has been identified at this cut off point which may be considered as the point where a viscoelastic material becomes a viscous medium.The absorption coefficients have also been calculated for different values of the viscoelastic parameter and gravity field.

Propulsion Mechanism of Flexible Microbead Swimmers in the Low Reynolds Number Regime

A propulsion mechanism for a flexible microswimmer constructed from superparamagnetic microbeads with different diameters and subjected to an oscillating field was studied experimentally and theoretically herein. Various types of artificial swimmers with different bending patterns were fabricated to determine the flexibility and an effective waveform for a planar beating flagellum. Waveform evolutions for various swimmer configurations were studied to determine the flexible mechanism of the swimmers. A one-armed microswimmer can propel itself only if the friction of its wavelike body is anisotropic. A swimmer with a larger head and a stronger magnetic dipole moment with a flexible tail allows the bending wave to propagate from the head toward the tail to generate forward thrust. The oscillating head and tail do not simultaneously generate positive thrust all the time within a period of oscillation. To increase the propulsion for a bending swimmer, this study proposes a novel configuration for a microbead swimmer that ensures better swimming efficiency. The ratio of the oscillation amplitude of the head to the length of the swimmer (from 0.26 to 0.28) produces a faster swimmer. On the other hand, the swimmer is propelled more effectively if the ratio of the oscillation amplitude of the tail to the length of the swimmer is from 0.29 to 0.33. This study determined the optimal configuration for a flexible microbead swimmer that generates the greatest propulsion in a low Reynolds number environment.

Structural analysis of seasonal dynamics of daily growth of annual shoots of woolly-stemmed willow

Given the complex characteristics of woolly–stemmed willow. The necessity of studying the regularities of seasonal dynamics of daily growth of annual shoots is substantiated. The study used material from the model inbred-clone population. Empirical data were processed using structural–harmonic analysis methods. It was found that the seasonal dynamics of the daily growth of shoots is cyclic quasi–periodic. Empirical series of dynamics at the highest level of significance are approximated by sums of elementary harmonics with a period of oscillation of 9.2 to 92.0 days. Revealed high-amplitude harmonic with the oscillation period of 23.0 to 92.0 day and low amplitude with a period of oscillation of 9.2 to 18.4 days. On all the studied shoots only the fourth harmonics coincide with the oscillation period of 23.0 days. The main contribution to the seasonal dynamics of shoot growth is made by three high-amplitude harmonics, which form two main signals with oscillation periods of 23 and 36 days. Other harmonics have a modulating effect on the seasonal dynamics of shoot growth. The first harmonics with a period of oscillation 92.0 days determine the nonlinearity of the seasonal trend of growth of shoots. Higher harmonics with a period of oscillation of 9.2 to 15.3 days form the resulting quasi–cyclic oscillation. Significant interclonal and intraclonal differences in the rhythm of daily growth of annual shoots were not revealed. On this basis, the proposed recommendations for agroforestry–technical events in the plantings of woolly–stemmed willow.

Improving the efficiency of forest management based on the optimization of non-continuous felling of growing plantations

В результате анализа динамических таблиц роста высокопродуктивных сосновых, эвкалиптовых и акациевых насаждений с достаточно коротким оборотом рубок установлено, что в процессе роста древостоев общий объем уменьшения биомассы в результате естественного отпада деревьев равен (сосна) или превосходит (эвкалипт, акация) асимптотическое значение, соответствующее спелому состоянию. Поэтому равномерно-постепенные рубки древостоев по классам возрастов в сочетании со сплошными рубками спелых древостоев обеспечивают получение максимально возможного объема биомассы выращиваемых насаждений. Анализ динамического состояния системы «лес– заготовка» с позиции решения кинетических уравнений экологической модели «зайцы–лисы» (зайцы – лес, лисы – заготовка) указывает на возможность устойчивого осциллирующего состояния лесопользования при естественном возобновлении ресурсов. В результате решения кинетических уравнений становятся возможными определение частоты устойчивых осцилляций системы «лес–заготовка» (решение прямой задачи) и реализация принципа гармонии природных и техногенных систем. Здесь процесс заготовки осуществляется несплошными (равномерно-постепенными) рубками, роль класса возрастов выполняет период колебания, соответствующий определяемой частоте. Данный подход предполагает также решение обратной задачи: при выбранных частоте устойчивых осцилляций системы и динамике роста насаждений – определение соответствующих параметров заготовки. Analysis of the dynamic state of the system «forest–harvesting» from the standpoint of solving the kinetic equations of the ecological model «hares–foxes» (hares – forest, foxes – harvesting) indicates the possibility of a sustainable oscillating state of forest management with the natural renewal of resources. As a result of the kinetic equations solution it becomes possible to determine the frequency of stable oscillations of the forest- harvesting system (direct problem solution) and to realize the principle of natural and man- made systems harmony. Here the process of harvesting is carried out by non-flat (evenly- gradual) felling, the role of the age class performs the period of oscillation corresponding to the determined frequency. With this approach, it is possible to formulate the same inverse problem: the chosen frequency of stable oscillations of the system and the growth dynamics of plantings to determine the appropriate parameters of the work piece.

Vibrational World

Thinking that time and mass are correlated, like mass and energy are ( E =m*c^2 ). The period of oscillation of the simple oscillator, with a mass M andspring with coefficient k, is given by:T = 2*Pi*Sqrt(M/k); (1)orT ~ Sqrt(M); (2)

Simulations of coalescence of two colliding liquid drops using lattice Boltzmann method

In this paper, two-dimensional numerical simulations of the head-on and off-center binary collision of liquid drops are carried out using lattice Boltzmann method. The coalescence process of drops colliding is freely captured, regardless of tracking equations and drops model. Special attention is paid to investigate the effect of the Weber number, impact velocity, drop size ratio on the coalescence process. The research results demonstrate that numerical results of lattice Boltzmann method are in agreement with qualitatively experimental data in the same Weber number. It is also noted that the first oscillation period is invariably shorter than the second period, regardless of the Weber number. It is further found that variation of the first period of oscillation in off-center collision of two equal-size drops as function of Weber number are higher than the variation of the first period of oscillation in head-on collision of two equal-size drops in the same Weber number.