Basic Concept of Ophthalmology and Visual Disorder

The eye is a complex sensory organ that is responsible for vision. Within the protective sheath, each eye has receptors, a lens system for focusing light on receptors, and a nervous system for transmitting impulses from the receptors to the brain. Visual dysfunction can be caused by abnormal eye movements or changes in visual acuity, refraction, color vision, or accommodation. Visual dysfunction may also be a secondary effect of other neurological disorders. This narrative review aims to describe the structure of the eye in general and visual disturbances caused by the aging process and disorders of the protective structure of the eye.

Impact action of a projectiles on special protective structures and ways to increase their protective capacity

A method for studying the reaction of elastic elements of protective structures to a series of impact actions of shells has been developed. In the work, the elastic elements of the protective structure are modeled by homogeneous beams, and the dynamic action of the shells is simulated by instantaneous point-applied forces. A mathematical model of this dynamic process is constructed, which is a boundary value problem for a hyperbolic equation with an irregular right-hand side. The latter is described using Dirac delta functions. Cases of both fixed and free ends of protective elements are considered. The main ideas of perturbation methods are used for the researches carried out in the work. Analytical dependences for the description of elastic deformations of a protective element which are basic for definition of its strength characteristics are received. They and the graphical dependences built on their basis for specific cases show that the dynamic deformations of the protective element for the fixed ends are greater in the case of the projectile closer to its middle, at the same time for the free ends – closer to the end. With regard to the modernization of protective structures, the dynamic effect on their elements can be reduced by using elastic reinforcement or changing the method of fixing the ends of the protective element: elastic or with a certain angle of inclination of the bearing surfaces. It is proposed to use special plastics, soil layer, flexible wood flooring, etc. as elastic reinforcement. The technique used in the work is the basis for determining the strength characteristics of protective elements, and from so – to check the reliability of the protective structure; study of the dynamics of protective and similar types of structures, taking into account the nonlinear characteristics of the elastic elements of protective structures; study of more complex oscillations of elements of protective structures. In the case of a series of impacts, it is obvious that the amplitude of deflection of the protective element after each impact will increase over time, because the model does not take into account the force of viscoelastic friction. These tasks will be the subject of further research.

RESULTS OF STATIC TESTS OF PROTECTIVE STRUCTURES OF AGRICULTURAL TRACTORS CABINS

The purpose of research is determination of cabin deformation indicators using standardized methods and developed technical means. Research methods. The tests were performed according to the methods described in [DSTU ISO 5700, 2019] using a loading bench, pressure and displacement sensors, digital measuring amplifier Spider 8 and laptop Panasonic CF-19 Touchbook, model: CF-19KHR88PE. Research results. The protective structure AI.209.45.011.00 of the cab of tractors type C25 "Slobozhanets" was provided for testing. Before the tests, the dimensions of the cab structure were measured and recorded. During the first longitudinal loading from front to right, the load was applied to the upper transverse element of the protective structure. The point of application of the load was at a distance of 260 mm from the outer corner of the edge of the protective structure. An even load distribution in the direction perpendicular to the direction of action and along the loading beam was ensured using a sealing element. The value of the energy absorbed by the protective structure was 13100 J (required energy - 12586 J) with a maximum applied force of 82 kN and a displacement of 340 mm. During the first and second compression tests, the structure was loaded vertically with a force of 180 kN along the front and rear upper transverse elements of the protective structure with a holding of the specified force for 5 s. The side load was applied horizontally to the upper right longitudinal element of the protective structure at a distance of 85 mm forward from the control point of the driver's seat. The length of the loading beam was 600 mm. The value of the energy absorbed by the protective structure of 17000 J (required energy - 15732 J) at a maximum applied force of 80 kN and a displacement of 290 mm was achieved. After all test stages, the frontmost point of the protective structure was 70 mm and the front left point was 35 mm. The rear end points were also shifted backwards by 45 mm - right and 30 mm - left. In the lateral direction, the front right extreme point moved forward by 15 mm. After the tests, the free space area was not violated. Conclusions. The methods and technical means used during the tests allow determine the magnitude of the applied forces and deformation with the necessary accuracy and reliability. During the compression tests, the values of the test force (180 kN) were achieved, and during the application of horizontal loads - the energy absorbed by the protective structure (13100 J - longitudinal load and 17000 J - lateral load). The greatest final deformation was suffered by the protective structure at the front extreme point - 70 mm, while the violation of the zone of free space of the driver by the elements of the protective structure is not observed. Therefore, the protective structure AI.209.45.011.00 cab of tractors type C25 "Slobozhanets" withstood static tests for compliance with DSTU ISO 5700.

Comparative Study for Evaluation of Blast Load Parameters using IS 4991-1968 and UFC 3-340-02

The essence of the blast load relies on the factors such as explosive weight, standoff distance of the structure from the explosive, the location of the explosion concerning the structure, shape of the protective structure, and orientation of the structure relative to the explosion. The study provides an approach for calculating blast wave parameters according to IS 4991-1968 and UFC 3-340-02 and demonstrated by examples. It concludes that, in Indian Standard, only positive blast wave is considered but in UFC, both the positive as well as negative blast wave is taken into consideration. Also, there are significant differences in evaluating the parameters as per both standards.

Development of pneumatic test rig protection for elements of underwater oil & gas production system

Object and purpose of research. This paper discusses protective structure for a pneumatic test rig intended for experiments with the elements of underwater mining system at KSRC Open Test Tank. The purpose of this study was to justify the design parameters ensuring the safety in case of an emergency leakage from the tested equipment. Materials and methods. The study followed the methods of computer-based simulation to analyse gas dynamics of leakage escalation and its effect upon the protective structure. Main results. This paper presents development results of a floating submersible protective structure, with analytical estimates of hazardous factors and protection robustness in case of a hypothetical emergency during pneumatic tests of equipment. Conclusion. Protective structure design suggested in this paper for given conditions of submerging into an open tank and given conditions of pneumatic tests (pressure 69 MPa, nitrogen volume 1 m3) prevents hazardous leakage to the environment. Accordingly, these tests will be safe for both personnel and test facilities.

Problems of medical and biological support of the process of developing advanced bulletproof vests

Currently, as part of combat equipment, body armor is the main tool designed for individual protection of a persons torso from bullets, shrapnel and steel arms. Since March 1, 2019, GOST 34286-2017 has been introduced as a national standard of the Russian Federation, in which one of the assessed indicators of the resistance of armored clothing to the effects of means of destruction is the indicator of the reserve effect of the striking element when the protective structure is not penetrated, which should not exceed the value taken as the maximum permissible in the prescribed manner. In this case, the pre-armor effect of a striking element in case of non-penetration of the protective structure is assessed only after the completion of the development of a sample of armored clothing by the corresponding accredited organization. The existing methods for determining the permissibility of the reserve impact indicator when the protective structure is not penetrated can in principle be divided into medical, biological and technical, and technical. In the Russian Federation, the method using large laboratory animals, pigs weighing 8090 kg, is mainly used to determine the level of the reserve impact in terms of the severity of the reserve contusion injury. While in NATO countries, human corpses, individual tissues and organs, as well as parts of carcasses of large animals are used to determine the same parameter. However, at present, both in our country and abroad, there is no single methodological approach to assessing the impact of armor when testing protective products. As a result of targeted research, it is necessary to scientifically substantiate the principles of modeling this effect when the body armor is not penetrated with the subsequent processing of standard methods of state testing of body armor. The tests must be based on a method that allows obtaining parameters expressed in digital values and correlated with the results of experiments on biological objects. It is this numerical parameter that should be taken as a criterion for assessing the permissibility of the level of shock impact when testing promising personal body armor (bibliography: 21 refs).

Finite element modeling of the joint action of flow slide and protective structure

Introduction. In the context of the problem of plane deformation, a finite-element model of a natural landslide slope is developed. It allows for the joint work of a flow slide and a protective engineering structure. The Drucker-Prager model is used to take into account the physical nonlinearity of the slope layer material. To activate the kinematic instability, a viscoelastic interlayer is introduced into the design scheme, along which the landslide layer slides.Materials and Methods. Numerical experiments were performed using the ANSYS Mechanical software package, which implements the finite element method in the form of the displacement method. Slope discretization is performed on the basis of PLANE42 flat four-node finite elements. To simulate the displacement of the landslide layer relative to the fixed base, the combined viscoelastic elements COMBIN14 were used.Results. A physically nonlinear model of a natural landslide slope consisting of a base, a landslide layer, and a viscoelastic interlayer, is formalized. An engineering technique for analyzing the stress-strain state of the “slopeprotective structure” system has been developed, taking into account the kinematic instability of the landslide layer. A series of computational experiments was carried out.Discussion and Conclusion. Based on the calculations performed, it is shown that the proposed method enables to specify the force action of the landslide layer on the protective structure and, thereby, to increase the reliability of the risk assessment when activating the landslide process.