scholarly journals Estimation of the parameters of barbell’ lifting law of motion

Author(s):  
Mečislovas Mariūnas ◽  
Julius Griškevičius ◽  
Gintaras Jonaitis

Characteristic points of the law of motion were determined based on the results of experimental study on the velocities and accelerations of the lifted barbell. Relationship between the height of the athlete, lifted weight, maximal velocity and acceleration was estimated analytically. It was shown, that at the initial time moment the athlete must apply approximately 1,5 times larger force than lifted weight. The values of the parameters of the barbell’ law of motion and lifting force approximate law of change were estimated.

Author(s):  
L. S. Klimenko ◽  
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B. S. Maryshev ◽  
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...  

The paper is devoted to study of the cleaning a microchannel contaminated by solute particles deposited on channel walls. The main and the most common cause of microchannel clogging is sorption of solute particles on channel walls or “physical sorption”. In this paper, we study the problem of the drift of solid non-interacting particles into a microchannel, which can stick to its walls due to Van der Waals interactions and break away from the wall due to viscous stress. A constant pressure drop is fixed between the inlet and the outlet of the channel. At the initial time moment, the channel walls are contaminated with adhering particles, i.e. the form of walls affects the formation of the flow structure through the channel. Over time, under the action of viscous stress the particles detach from the channel walls, thus cleaning occurs. The interaction of the detached particles with the flow is taken into account within the Stokes approximation. In addition, the model takes into account random walks caused by diffusion. The problem is solved numerically in the framework of the random walk model. The evolution of the fluid flow in the channel during its cleaning is obtained. The dependences of the concentration of settled particles on the flow rate and the strength of the Van der Waals interaction between particle and wall are determined. The dependence of the flow rate through the channel cross section on the concentration of settled particles was investigated. The channel cleaning time was estimated.


Author(s):  
Alexander I. Kozhanov ◽  

The goal of the article is the study of solvability in the Sobolev spaces of boundary value problems for some classes of Sobolev-type fourth-order linear equations. We will prove that an initial boundary value problems well problems with data both at the initial time moment and the final time moments can be well-posed for the equations under study


Author(s):  
Jaan Lellep ◽  
Ella Puman

The inelastic response of circular conical shells to the blast loading is studied. The impact loading is applied at the initial time moment and it is removed at a certain instant of time. The load intensity depends of the coordinate of the shell. The material of the shell is a perfect plastic one obeying the Johansen yield condition and the associated flow law. It is assumed that the frustum of the cone is furnished with ring stiffeners made of the same material. A theoretical method for the evaluation of the stress strain state of the shell and for determination of maximal residual deflections is developed.


Author(s):  
V. M. Yartseva ◽  
E. B. Bryuzgina ◽  
V. V. Klimov ◽  
E. V. Bryuzgin ◽  
A. V. Navrotskii

The article presents the results of a study of the properties of chitosan spongy materials (aerogels) surface modified with copolymers of glycidyl methacrylate. The surface of the obtained materials is characterized by a highly hydrophobic state with contact angles at the initial time moment more than 140 degrees, while a decrease in water absorption of aerogels and a slight decrease in oil absorption are also observed as a result of the modification.


2013 ◽  
Vol 561 ◽  
pp. 533-536
Author(s):  
Yong Yan Wang ◽  
Nan Qin ◽  
Xin Yan ◽  
Tian Tian Niu

The incremental digital PID technology and pressure regulating technology are adopted for this thermostat. The results show that it can be better stabilize the temperature and can control the residuals between ±1 degrees Celsius. The experiment in transformation between solid and liquid of ice is designed on this basis. By changing the temperature and specific area, the law about melting time and rate between temperature and specific area is discussed and the proper empirical equations are obtained by using the MATLAB. Finally the result is that temperature and specific area can influence the process with power function relationship.


2014 ◽  
Vol 1023 ◽  
pp. 116-124
Author(s):  
Li Ming Ren ◽  
Jing Xue An ◽  
Chun Yu Wang ◽  
Lei Wang

This paper presents the experimental investigation on the operational performances of a Boiler after a Low NOx burner retrofit. After the retrofit, several operational performances emerge a major change, including the unburned combustible in flying ash raise under higher load, the temperature of reheat steam drop greatly under lower load. As a result, the changes have an influence on the economy of boiler. As for it, a special experimental study was carried out to obtain the best operating mode, and the law of change on the several parameters. The research results are a significant reference to retrofit involved in Low NOx burner utilized to a boiler.


Author(s):  
A.S. Steshin ◽  
A.V. Babkin

The paper considers a separate issue of the shaped charge functioning, i.e., functioning of a rotating charge under preliminary thermal action on its liner. Estimates of two oppositely directed factors are provided: 1) increase in the shaped-charge jet dynamic plasticity (limit elongation coefficient); 2) increase in the jet susceptibility to centrifugal destruction. These factors are activated by preliminary thermal action on the shaped charge liner in the jet heated in excess of usual parameters. The so-called "thermal" increase in the limit elongation coefficient was estimated using empirical and theoretical dependences of this value on the shaped-charge jet parameters, and on the characteristics of its material. Strength dependence on temperature was accepted as linearly decreasing. Centrifugal factor was estimated based on the law of kinetic moment conservation taking into consideration the gradient nature of stretching and, up to a certain point, the radial thinning of jet elements. The moment of centrifugal and strength forces relationship reaching the critical value was accepted as the beginning of the jet element centrifugal destruction. From this time moment the jet radial extension started. The law of decompaction of its enlarging part was taken from studies previously conducted by the authors. It was demonstrated that the two considered factors acting in the opposite directions in a jet were in compliance with each other ensuring optimal preliminary heating of the liner and penetration effect with a local maximum.


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