FLEXURAL BEHAVIOR OF STRENGTHENED AND RPIARED SUSTAINABLE R.C. BEAMS USING REACTIVE POWDER CONCRETE JACKET

Thin fiber reinforcement and rehabilitation of reinforced concrete beams Concrete jackets have several benefits, including increased ultimate load and improved serviceability limit condition. The current paper was carried out to investigate the effect of the strengthening and repairing by using reactive powder concrete(RPC) jacket for reinforced concrete beams that’s casted with recycled coarse aggregate (RCA) in enhancement the mechanical properties such as load capacity and deflection . Nine reinforced concrete beams mm were casted by using RCA with constant details and jacketed with RPC with variable of steel fiber content and jacket thickness to estimate the optimum details. The result showed the effectiveness of the proposed technique in both deflection and ultimate load.

Reclamation Suitability Evaluation of Damaged Mined Land Based on the Limit Condition Method－Example of Pingdingshan Tianan Ten Coal Mine

Reclamation suitability evaluation is the basis for determining the reuse direction of damaged land. Limit condition method is the most widely used method in land reclamation suitability evaluation at present. In this paper, the limit condition method is used to evaluate the suitability of land reclamation of damaged land in Pingdingshan Tianan ten coal mine. The evaluation index of damaged area is determined as six main factors: field slope/land flatness, ponding, depth of collapse, soil texture, thickness of soil layer, irrigation and drainage conditions, and finally determine the reclamation direction of the land to be reclaimed in combination with the overall local land use planning and the overall wishes of local residents.

OPERATIONAL ASSESSMENT OF THE LIMIT STATE OF TRACTOR UNITS WITH THE USE OF INDICATOR COUNTERS

In accordance with GOST 20793-2009, the tractor and its components are subjected to resource diagnostics before maintenance. The technical condition of the components of the tractor or machine should be checked with the use of control and diagnostic equipment. Currently, the criteria for the limit state are significantly outdated and require revision from the point of view of tightening modern requirements for operational and economic characteristics and reliability indicators. (Research purpose) The research purpose is in analyzing the state of the issue and the current regulatory documentation and making proposals for remote monitoring of the criteria for the limit states of individual components and aggregates. (Materials and methods) The article presents an analysis of scientific and technical documentation, State standards of the Russian Federation and scientific papers on the problems of minimizing technological risks, diagnostics and control suitability for determining the maximum technical condition, and staged studies on the possibility of monitoring the operation of individual components and units online. The article notes the need to adjust the criteria for the maximum technical condition in accordance with the new designs of resource-determining units, aggregates and existing technical regulations. (Results and discussion). The article presents the justification of the diagnostic process and identified contradictions in the design of tractors and existing scientific and technical documentation and standards, and proposed option of using meters-identifiers when upgrading tractors as a system of built-in online diagnostic tools. (Conclusions) Timely, automated monitoring of the technical condition of tractors, which is based on comparing data with the criteria of the limit condition, serves as a justification for the effective operation of equipment with built-in devices for diagnostics, which allows minimizing agrotechnological risks.

EXPERIENCE IN THE APPLICATION OF ADAPTIVE STRATEGIES FOR MAINTENANCE AND REPAIR OF MILITARY PRODUCTS IN NATO MEMBER COUNTRIES

Maintenance of armaments and military equipment, implementation of a set of measures to maintain armaments and military equipment in working order are related to the need to solve the problem of ensuring the specified indicators of their efficiency, especially samples with long service life. Given the current state of the domestic armaments and military equipment park, it is important to study the experience of NATO member states in implementing adaptive maintenance and repair strategies, including maintenance and repair strategies. The aim of the article is to analyze the current state of use of adaptive strategies for maintenance and repair of weapons and military equipment in the world's leading countries with further substantiation based on its recommendations for their practical implementation during the organization of their operation in the Air Force of Ukraine. According to the results of research, a positive impact of the application of maintenance and repair strategy, including by solving the problem of minimizing the cost of operation of weapons and military equipment. As a result, substantiated and proposed the necessary conditions for the application of the strategy of their maintenance and repair, which are in service with the Armed Forces of Ukraine in technical condition, the implementation of which as an alternative to the use of service life (resource) of relevant samples control of the limit condition or the need for maintenance and repair of the product, which are accepted as a result of continuous (periodic) control of the parameters that determine the technical condition.

CFD Analysis of Transient Heat Conduction in the Electronic Control Circuitry of Steering Wheel Column Adjustment System

Automotive grade 3 electronic components are expected to meet their functional, performance and thermal safety requirements within the ambient temperature range from −40-degree C to +85-degree C. In this study, CFD and thermal analysis of electronic control circuitry of a power steering wheel column adjustment system is performed. It consists of 6 MOSFETs (Metal Oxide Semi-Conductor Field Effect Transistor) packaged in 3 Dual package MOSFET casings (Q6, Q7 and Q8) that are arranged in two H-bridge configurations for dependent control of the two motors. Two of these MOSFETs cause thermal power dissipation during the normal operation of the system. There are also other thermally significant devices such as a reverse polarity protection MOSFET (Q1), two inductors used in a low pass filter and one current sense resistor. Because of cost and packaging limitations, there are no external heat sinks to enhance heat transfer. The components will rely on the Printed Circuit Board (PCB) and plated-through-holes/thermal vias for heat transfer to maintain operation within the thermal safety limits. The inherent transient nature of operation of the power steering wheel column adjustment system causes the circuit to draw high current for a short duration of time. This necessitates temperature dependent heat source formulation. In this study, an initial CFD study was performed to assess the thermal safety of all the electronic components in the control circuitry. It was found that the electronic components such as MOSFETs and inductors were below the maximum operating junction temperature under the hot limit condition (+85degree C) for the entire duration of operation. However, under the cold limit condition (−40-degree C), both the MOSFETs and the inductors were significantly hotter than the maximum junction temperature. Based on CFD results, the sizing and placement of thermal vias may be optimized. Further, a comparative analysis was performed to assess the different levels of fidelity offered by lumped PCB model, multi-layer PCB model and explicit modeling of thermal vias in PCB.

Research on the Cooperative Detection of Stochastic Resonance and Chaos for Weak SNR Signals in Measurement While Drilling

In the process of drilling, severe downhole vibration causes attitude measurement sensors to be erroneous; the errors will accumulate gradually during the inclination calculation. As a result, the ultimate well path could deviate away from the planned trajectory. In order to solve this problem, this paper utilized the stochastic resonance (SR) and chaos phase transition (CPT) produced by the second-order Duffing system to identify the frequency and estimate the parameters of the signal during measurement while drilling. Firstly, the idea of a variable-scale is introduced in order to reconstruct the frequency of the attitude measurement signal, and an SR frequency detection model based on a scale transformation Duffing system is established in order to meet the frequency limit condition of the SR. Then, an attitude measurement signal with a known frequency value is input into the Duffing chaos system, and the scale transformation is used again to make the frequency value meet the parameter requirement of chaos detection. Finally, two Duffing oscillators with different initial phases of their driving signal are combined in order to estimate the amplitude and phase parameters of the measurement signal by using their CPT characteristics. The results of the laboratory test and the field-drilling data demonstrated that the proposed algorithm has good immunity to the interference noise in the attitude measurement sensor, improving the solution accuracy of the inclination in a severe noise environment and thus ensuring the dynamic stability of the well trajectory.

Optimal Plastic Analysis and Design of Pile Foundations Under Reliable Conditions

In this research, in order to evaluate the plastic limit load and also plastic design parameters of the long pile foundations subjected to horizontal loads, shakedown method is applied. In carrying out shakedown analysis and design methods, large plastic deformations and residual displacements could develop in the pile foundation which might lead to the failure of the structure. For this reason, complementary strain energy of residual forces proposed as a limit condition to control the plastic deformation of the pile structure. Furthermore, considering the uncertainties (strength, manufacturing, geometry) the limit conditions on the complementary strain energy of residual forces are assumed randomly and the reliability condition was formed by the use of the strict reliability index. The influence of the limit conditions on the plastic limit load and design parameters of the long pile in cohesionless soil subjected to lateral load were investigated and limit curves for shakedown load factors are presented. The numerical results show that the probabilistic given limit conditions on the complementary strain energy of residual forces have significant influence on the load bearing limit and the design parameters of pile foundations. The formulations of the reliability based problems lead to mathematical programming which were carried out by the use of non-linear algorithm.

Output process of the M|GI|1 is an asymptotical renewal process

Most of the studies on models with retrials are devoted to the research of the number of applications in the system or in the source of repeated calls using asymptotic and numerical approaches or simulation. Although one of the main characteristics that determines the quality of the communication system is the number of applications served by the system per unit of time. Information on the characteristics of the output processes is of great practical interest, since the output process of one system may be incoming to another. The results of the study of the outgoing flows of queuing networks are widely used in the modeling of computer systems, in the design of data transmission networks and in the analysis of complex multi-stage production processes. In this paper, we have considered a single server system with redial, the input of which receives a stationary Poisson process. The service time in considered system is a random value with an arbitrary distribution function B(x). If the customer enters the system and finds the server busy, it instantly joins the orbit and carries out a random delay there during an exponentially distributed time. The object of study is the output process of this system. The output is characterized by the probability distribution of the number of customers that have completed service for time t. We have provided the study using asymptotic analysis method under low rate of retrials limit condition. We have shown in the paper that the output of retrial queue M|GI|1 is an asymptotical renewal process. Moreover, the lengths of the intervals in output process are the sum of an exponential random value with the parameter lambda + kappa and a random variable with the distribution function B(x). The results of a numerical experiment show that the probability distributions of the number of served customers in the system are practically the same for significantly different distribution laws B(x) of service time if the service times have the same first two moments.

Soil Medium Electromagnetic Scattering Model for the Study of Wireless Underground Sensor Networks

In recent years, there has been keen interest in the area of Internet of Things connected underground, and with this is the need to fully understand and characterize their operating environment. In this paper, a model, based on the Peplinski principle, for the propagation of waves in soils that takes into account losses attributable to the presence of local inhomogeneity is proposed. In the work, it is assumed that the inhomogeneities are obstacles such as stones or pebbles, of moderate size, all identical and randomly distributed in space. A new wave number is obtained through a combination of the multiple scattering theory and the Peplinski principle. Since the latter principle considers the propagation in a homogeneous medium (without obstacles), the wave number it provides is inserted into the one resulting from the former, the multiple scattering theory. The effective wave number thus obtained is compared numerically with that of Peplinski alone on the one hand and with that of multiple scattering alone on the other hand. The phase velocity and the loss tangent are analyzed against the particle concentration at the low-frequency Rayleigh limit condition ( k a ≲ 0.1 ) and against the frequency at two particle concentrations ( c = 0.2 and c = 0.4 ), two particle radii ( a = 0.55 cm and a = 1.10 cm), and 5% and 50% volumetric water content of the soil. Path losses are also compared to each other to examine the effects on transmission of soil containing obstacles. The results obtained suggest that the proposed model has better accuracy in estimating the wave number than previously used schemes.