Distribution Law Research Articles

Study on the side friction resistance capacity of prefabricated pipe piles in coral reef strata

Coral reefs are widely distributed along the “Maritime Silk Road”, and their unique mechanical properties pose numerous challenges for marine engineering construction. The side friction resistance (SFR) capacity of traditional driven piles in coral reef strata remains unclear, and there is a lack of effective calculation methods. Furthermore, the complex marine environment imposes higher requirements on pile foundation construction and durability. In this study, a series of interfacial shear tests were carried out for coral sand and coral reef limestone (CRL) in the sea area near the Maldives islands and reefs, and the distribution law of the SFR of prefabricated pipe piles in coral sand was investigated by using a large-scale pile foundation model test apparatus. The interfacial shear behavior of the coral sand is similar to that of the crushed coral reef limestone, both of which experience ideal elastic-plastic changes, with an interfacial friction angle of approximately 35°. The ultimate SFR of the prefabricated pipe piles in coral sand increases gradually and then plateaus, and the distribution of the SFR along the depth direction can be simplified as a combination of triangular and rectangular patterns. Based on the distribution law of the pile SFR, this study establishes a modified formula for calculating SFR of the pile in coral sand, which is verified by comparing the calculated SFR capacity of driven piles of the China-Maldives Friendship Bridge with the results of the field test piles. This study provides an important theoretical basis and practical guidance for the design and construction of pile foundation engineering in coral reef sea areas such as Maldives.

Predictive Model for Deformation of Adjacent Pipelines Caused by Tunnel Boring in Twin-Lane Tunnels in Soft Ground Layers

To create a discretized prediction model for the deformation of an adjacent pipeline, the pipeline structure is discretized, the differential equations governing the longitudinal deformation of the pipeline are inferred, and the displacement expressions and the solution methods of the virtual nodes of each unit are provided after discretization. This approach is based on the Pasternak foundation beam theory. It aims to address the issue of the difficulty in predicting the deformation of the adjacent pipeline caused by shield tunneling in a saturated soft ground layer in the Yangtze River Delta. The deformation pattern of the surrounding soil is determined and confirmed through additional numerical simulation, and the discretized prediction model is contrasted with the conventional Winkler foundation beam model and the Pasternak foundation beam model. The findings demonstrate that the discrete prediction model is simpler to solve and more accurately describes the deformation characteristics of the adjacent pipeline as well as the deformation distribution law. The calculated deformation characteristics primarily appear as the adjacent pipeline’s deformation due to the double tunnel boring exhibiting a “mono-peak shape” with a large middle and small ends, which is consistent with the actual situation. The two main factors influencing the pipeline deformation are the shield tunneling distance and pipeline spacing; the former has a negative correlation with the pipeline deformation, while the latter has a positive correlation. This work can offer a straightforward deformation prediction technique for shield tunneling in the Yangtze River Delta’s saturated soft ground next to existing pipelines.

"Facilitate" or "Hinder"： Impact of Spatial Connectivity Networks in the Digital Economy on Carbon Performance

This study took 254 cities in China from 2011 to 2021 as samples to empirically test how the spatial correlation network characteristics and node centrality of the urban digital economy affect carbon emission performance. The research showed that ① China's urban digital economy showed an obvious network development mode, but from the perspective of network node centrality, there were still significant spatial differences, showing the hierarchical distribution law of "eastern region-central and western region" and "four core urban agglomerations-four non-core urban agglomerations." ② A significant positive correlation was observed between the digital economy spatial correlation network and carbon emission performance. This conclusion was still supported after the control of the endogeneity problem and the robustness test. ③ Human capital investment had a positive moderating effect on the spatial correlation network of the digital economy and carbon emission performance. ④ The impact mechanism showed that the spatial correlation network of the digital economy could promote the improvement of carbon emission performance through industrial regional linkages and innovation cooperation networks. ⑤ Upon further analysis, the empirical results showed heterogeneity in four dimensions： geographic region, core urban agglomeration, urban resource endowment, and city size.

Study on frequency spectrum characteristics and attenuation law of buried PE pipeline leakage infrasound signal

This article addresses the insufficient application of infrasound in the detection of nonmetallic pipeline leaks. Through a combination of numerical simulations and experimental verification, we analyze the sound field distribution, spectral characteristics, and attenuation laws of infrasound leakage signals under varying pressures and leakage apertures. The results indicate that the amplitude of the sound pressure level of the leakage infrasound signal consistently exceeds that of the non-leakage sound pressure level. Additionally, the sound pressure level exhibits rapid attenuation with increasing frequency, pressure, and leakage aperture, particularly in proximity to the leakage hole.

A Demonic Outcome Logic for Randomized Nondeterminism

Programs increasingly rely on randomization in applications such as cryptography and machine learning. Analyzing randomized programs has been a fruitful research direction, but there is a gap when programs also exploit nondeterminism (for concurrency, efficiency, or algorithmic design). In this paper, we introduce Demonic Outcome Logic for reasoning about programs that exploit both randomization and nondeterminism. The logic includes several novel features, such as reasoning about multiple executions in tandem and manipulating pre- and postconditions using familiar equational laws—including the distributive law of probabilistic choices over nondeterministic ones. We also give rules for loops that both establish termination and quantify the distribution of final outcomes from a single premise. We illustrate the reasoning capabilities of Demonic Outcome Logic through several case studies, including the Monty Hall problem, an adversarial protocol for simulating fair coins, and a heuristic based probabilistic SAT solver.

Contact force calculation and evolution analysis of granular systems based on micro-CT experiment

The calculation of inter-granule contact force in three-dimensional (3D) granular systems is a key and challenging aspect of granular mechanics research. Two elastic rubber balls are used as research objects for in-situ flat pressing Micro-CT experiments. Based on the Hertzian contact theory and Tatara large deformation contact theory, the contact model of elastic balls is verified, and the theoretical formula of the contact force of elastic balls based on the experiment is obtained. Taking the 3D granular systems as research object, in-situ probe loading experiment of micro-CT is carried out to obtain the 2D image sequence of the granules, after a series of digital transformations, the digital body images emerge, the contact force networks of the 3D granular systems under different loading conditions are obtained by constructing pore network models. The contact force distribution and evolution law of the granular systems are analyzed. The relation among the number of strong contacts, the distribution evolution, and the stability of the granular system is explored. The results show that the two elastic ball contact model conforms to the Hertzian contact theory and Tatara large deformation contact theory, and the contact force fitting formula based on experiment can characterize the contact force between two granules reasonably and effectively. The contact force of granules under probe loading is distributed in a net-like pattern starting from the contact point of the indenter and gradually transmitted to the lower and the surrounding area. The trend of average contact force is consistent with the trend of the contact times, showing a significant phase transition. With the increase of contact times, the frequency of particle compression increases, resulting in a greater contact force between granules, ultimately stabilizing at about 10.5 N. The number of strong contacts accounts for 45% to 50% of the total number of contacts, distributed throughout the whole granular system and supporting the network structure of the granular system. The larger values are concentrated below the indenter and exhibit a branching distribution. In the loading process, an equilibrium point is established at <i>z</i> = 14 mm, where the number of strong contacts reaches the peak. The network structure of strong contact force is spread throughout the entire 3D granular system, establishing the main skeleton that can withstand external loads. As the loading continues, the total value of strong contact forces increases, and their distribution within the granular system becomes more uniform.

Analysis of the main factors affecting the polar axis offset characteristics of intact spherical superconducting rotors

Superconducting rotor has great potential for application in the field of precision measurement by virtue of its unique physical properties. The superconducting rotor magnetic levitation device can make high-precision angular velocity sensors. Under the action of external interference torque, the pole-axis deviation from the initial position is the cause of the superconducting rotor pole-axis drift error, in which the spherical surface error and the earth's rotation belong to the main sources of error, and compensating the pole-axis drift speed caused by the spherical surface error of the superconducting rotor is a key step in realizing the high precision of the superconducting rotor magnetic levitation device. Based on this, the research on the influence factors of the spherical surface error of a complete spherical superconducting rotor and the rotation of the earth on the pole-axis offset characteristics of a superconducting rotor is carried out. First, this paper models the magnetic support structure of the superconducting rotor based on the vector magnetic potential equation, analyzes the magnetic field strength distribution on the surface of the superconducting rotor in the ideal state (i.e., suspended in the center of the spherical cavity), and investigates the magnetic support force characteristics. Then the magnetic support interference moment of the superconducting rotor caused by the spherical surface error is analyzed, and a superconducting rotor dynamics model is established based on the superconducting rotor dynamics equations, and the distribution law of the superconducting rotor pole-axis drift error under different rotor structural parameters is given. Finally, the influence of the earth's rotation on the superconducting rotor drift test is investigated. The results provide a reference for the subsequent improvement of rotor drift accuracy, optimization of rotor structure design and improvement of drift test methods.

Experimental study on the impact load characteristics of a single-row pile dam against debris flow

A single-row pile dam is a type of rigid debris flow barrier structure. In order to reveal the mutual interaction effects between debris flow and a single-row pile dam and the distribution law of debris flow impact forces, an analysis of the correlation between debris flow density, characteristic particle size, and relative pile spacing (the ratio of pile gap size to debris flow characteristic particle diameter) and debris flow impact forces was conducted to obtain dimensionless parameters related to debris flow impact force and climbing height. These parameters were verified through flume model experiments to provide theoretical support for the engineering design of single-row pile dams. The results show that the impact force of the debris flow on the pile dam is mainly affected by the flow velocity, debris flow density, and relative pile spacing. The dimensionless parameters are introduced, and the semi-empirical expression of the impact load coefficient is established. The impact pressure coefficient of debris flow is classified into two categories, and the calculation model of impact load of a single-row pile dam is constructed. The research results can provide a theoretical basis and technical parameters for designing a single-row pile dam.

Design and Detection Performance of Metal Contaminant Sensor with Triple Coil Structure

In marine engineering, the daily management of mechanical equipment needs to ensure that the oil is normal. Oil plays the role of sealing, cooling, lubrication, and other functions in the equipment, and can also be used as hydraulic fluid to transfer energy. By analyzing the state of the oil, it is possible to obtain information about the operation of the equipment, such as judging the wear or failure of the equipment by detecting impurities in the oil. This paper proposes and designs a wireless triple-coil structure oil detection sensor for detecting metal particles in the oil circuit. The sensor consists of three coils placed concentrically with the same parameters. When the sensor detects metal particles in the oil, the ferromagnetic and non-ferromagnetic particles flowing through the sensor produce magnetization and eddy current effects, resulting in variable inductive signals that complete the detection of metal particles. This paper firstly explains the sensing principle of this triple coil sensor detection by formula derivation. Secondly, the simulation model of the sensor was established by using COMSOL 6.0 simulation software according to the scale of 1:1, and the magnetic field strength distribution law inside the coil of the triple-coil sensor was simulated. The experimental results showed that the sensor was able to detect iron particles at 73 µm and copper particles at 220 µm, moreover the obtained signal characteristics are obvious, with high detection sensitivity. The sensor is wireless and performs contactless detection of metal particles. This is important for the detection of metal particle contaminants in oil.

Reliability assessment of mobile pumping units

An analytical formula for determining the mathematical expectation and variance is derived . functions reliability mobile pumping units, allowing evaluate residual development With taking into account their technical condition at the start of the next process. An analytical expression was determined For definitions mathematical expectations And differences V safe functions, which allows mobile pumping units to calculate the residual period at the beginning of the process taking into account its technical condition. The problem of trouble-free operation of mobile pumping units at any point in time taking into account their technical condition requires a new approach to assessing the level of reliability in order to ensure uninterrupted performance of the function as intended. Analysis of work in this area shows that to date their technical condition at the time of the start of operation is not taken into account. Therefore, when assessing the failure-free function, it is necessary to take into account that the mobile pumping unit at the time of its entry into operation has some random operating time “ η ” , preceding the moment of the start of the next operation. In other words, the mobile pumping unit begins to function with varying degrees of risk of failure. The above indicates the need to conduct a calculation assessment of the level of failure-free operation of mobile pumping units before its operation. The importance of assessing the random time of a mobile pumping unit , taking into account some developed random operating time, dictates the need to develop new calculation models for their definition. Below is a mathematical formulation and solution to this problem. According to the obtained results of the statistical study, the type of the considered probability function of failure-free operation of the mobile pumping unit obeys the Weibull distribution law. Then the probability of failure-free operation is expressed as a pump that has worked without failure for a time, according to the stated requirement, will still function for u time, i.e. until the moment of time , characterizing the moment of failure. Then, the probability of this event, according to the definition of the conditional distribution function /1/: the average time before failure, under the condition we denote by .

STATE OF MICROBIOCENOSY AND DEFENSIVE MECHANISMS OF THE ORAL CAVITY OF CHILDREN IN THE DYNAMICS OF OBSERVATION AFTER THE SURGERY OF TOOTH REMOVAL FOR ORTHODONTIC INDICATIONS

In children, tooth extraction is performed not only in the presence of odontogenic inflammatory processes, but also for orthodontic indications. One of the main conditions for the qualitative course of the process of epithelialization of the socket after tooth extraction is a sufficiently high level of hygiene, a certain species composition of the resident microflora and the state of the protective mechanisms of the oral cavity. The aim of the study was to identify changes in the microbiocenosis and protective reactions of the oral cavity of children after tooth extraction for orthodontic indications. Material and methods. To establish the effectiveness of prevention and treatment of complications, two observation groups were under observation: the main group (n=30), whose children were treated with the developed drug complex, and the comparison group (n=29), where the tooth extraction operation was performed without any additional actions. It should be noted that the patients involved in the study did not have concomitant somatic pathology. To prevent post-extraction complications, we proposed a method of pharmacological influence on the condition of the tissues of the maxillofacial area of orthodontic patients before the start of the surgical stage of treatment. The complex we developed is aimed at increasing the protective capabilities and normalizing the microbiocenosis of the oral cavity of children and involves the systemic use of a vitamin-mineral preparation, an immunomodulator and a probiotic at the local level. Statistical processing of the data was carried out using the methods of variation statistics using the Statistica statistical software package. The law of distribution of the studied traits was checked for normality using the Kolmogorov-Smirnov test. The hypothesis that the law of distribution of the sample population is normal was accepted at the significance level of α=0.05. Two samples were compared using the Student-Fisher test if the hypothesis of the normal distribution of both samples was accepted. The study was conducted in accordance with the main provisions of the Convention of the Council of Europe on Human Rights and Biomedicine (4 April 1997), the Declaration of Helsinki of the World Medical Association for the Ethical Principles of Scientific Medical Research Involving Human Subjects (1964-2013), ICH GCP (1996), Orders of the Ministry of Health of Ukraine No.690 dated 23.09.2009, No.944 dated 14.12.2009, No.616 dated 03.08.2012. The Biomedical Ethics Commission of the Bukovinian State Medical University (Protocol No. 3 of 17 September 2021) did not find any violations of moral and legal norms during the research work. The study was performed within the framework of the research work of the Department of Paediatric Dentistry of Bukovinian State Medical University on the topic ‘Development of methods for the prevention and treatment of major dental diseases in children, taking into account the risk factors for their development’ (SR No. 0121U110122). Results. The study of oral fluid of children who underwent tooth extraction for orthodontic indications against the background of pharmacological correction showed the restoration of its protective functions (an increase in lysozyme activity by 20.52 % (p<0.05), sIgA level by 6.26 % against the background of a decrease in total protein content by 21.34 % (p<0.05) and IL-4 concentration by 21.22 % (p<0.05)) and antioxidant protection (an increase in catalase activity by 46.4 2% (p<0.05), superoxide dismutase by 15.53 %, the level of HS groups by 24.58 % (p<0.05), G-SH by 60.87 % (p<0.05), inactivation of glutathione peroxidase by 14.08 % and restoration of glutathione reductase function by 15.21 %), which ensured the course of postoperative period without complications. Conclusions. The oral microbiocenosis of children who used the agents proposed by us during the surgical stage of orthodontic treatment demonstrated quantitative and qualitative changes (the total microbial count decreased by 20.75 % (p<0.05)), the number of pathogenic and opportunistic bacteria decreased by 2.09 times, Str. mutans – by 3.0 times against the background of an increase in the number of lactobacilli by 2.34 times and the complete absence of Candida species, which was a prerequisite for the normal course of the wound process.

Study on numerical simulation of groundwater flow field and slope stability in multi-aquifer open pit mine

Water is one of the most important influences on slope stability in open pit mines. In order to solve the problem of slope stability analysis in multi-aquifer open pit mines, the open pit mine in Block I of Thar Coalfield in Pakistan with multiple aquifers was taken as the research background. The groundwater flow field at different excavation phases was analyzed by numerical simulation method. Based on the seepage theory of groundwater, the distribution law of hydrostatic pressure in phreatic aquifer and confined aquifer was analyzed. Based on the rigid body limit equilibrium method, the slope stability analysis method under the action of hydrostatic pressure of multiple aquifers was proposed. Based on the water level distribution within the slope body obtained by numerical simulation, the slope stability at different excavation phases was calculated, and the influence of aquifers on slope stability was analysed. The research results show that: With the excavation and drainage of the mine pit, the groundwater flow field in the open pit mining area changes significantly, and a descending funnel was formed at the mine pit. When mining reached the pit bottom boundary, the water level dropped by about 155–163 m in the mining area. The hydrostatic pressure action of aquifer on slope is related to water level, quantity and location of aquifer. Under the condition of considering hydrostatic pressure of aquifer, the slope stability coefficients are all reduced. And the slope stability coefficients of the three different mining phases were reduced by 6.74%, 11.87%, and 5%, respectively. The more aquifers the sliding surface crosses, the greater the effect of hydrostatic pressure on slope stability. When mining to the boundary, the combined sliding surface passed through two aquifers, and the slope stability coefficient decreased by 5% under the hydrostatic pressure condition, and the arc sliding surface passed through three aquifers, and the slope stability coefficient decreased by 8.74% under the hydrostatic pressure condition. The stability of slope with arc sliding mode is more affected by aquifer hydrostatic pressure than that with combined sliding mode. When mining to the floor of the coal seam roof confined aquifer, the stability coefficient of slope with combined sliding surface decreased by 11.87%, while that with arc sliding mode decreased by 16.32%.

Expression of calibration and measurement capabilities of accredited calibration laboratories in a measurement range

The expression of calibration and measurement capabilities (CMCs) of accredited calibration laboratories in a range of values is analysed, and the insurance of appropriate linear interpolation to find the measurement uncertainty at average values is considered. To minimize the expanded measurement uncertainty, it is proposed to calculate the coverage factor using the kurtosis method so that it would correspond to the composition of the distribution laws of the input quantities. To approximate the laboratory calibration and measurement capabilities when expressing them as an explicit function of the measurand, it is proposed to apply the least squares method. For non-polynomial dependencies, the capabilities shall be first transformed by replacing the variables into linear ones, which shall be followed by using the least squares method. To facilitate the approximation of CMCs, the use of the “trend line” function of MS Excel is proposed. Four additional nonlinear functions are considered, which are approximated by hyperbolic and homographic functions of Types 1 and 2, as well as by quadrature addition, which can also be transformed into a linear function, and the estimates of their parameters can be obtained by using the least squares method. An example of performing the approximation by various functions of calibration and measuring capabilities of a laboratory when calibrating a digital caliper is considered.

Reliability assessment of the thyristor module of high-voltage hybrid switchgears in reservation conditions

In the article, the authors proposed a methodology for evaluating the main indicators of the operational reliability of a high-voltage thyristor module, which is an element of electric power equipment, using the example of the design of such electrical devices as hybrid switches and converters in the structure of traction substations, power supply systems of metallurgical complexes, etc. The proposed method makes it possible to estimate the prob-ability of failure-free operation of the real design of the thyristor module, taking into account its design and implementation scheme, as well as the level and depth of redundancy of the semiconductor devices included in it. As initial data, the proposed method involves the use of electrical load parameters in terms of voltage and current and their redistribution as the reserve resource is exhausted, taking into account the design features of both the electrical device itself and the power supply network where it is located. is established. The proposed method makes it possible to evaluate the effectiveness of the influence of design factors (the number of semiconductor devices, the principle and depth of redundancy, the economic component, etc.) on the main indicators of the operational reliability of the corresponding types of high-voltage equipment, taking into account the electrical load and its changes. The proposed method was tested on the example of a real scheme of the thyristor module of the on-load tap-changer switching device, which was in industrial operation for a long time in the most unfavourable conditions in the power supply structure of the metallurgical industry, where there is high switching frequency, load fluctuations, etc. The implementation of this technique in the conditions of designing high-voltage switching and converting electrical equipment, as well as its operation in the power supply structure, allows to evaluate the influence of the structural features of the semiconductor part, taking into account the load mode, as well as the influence of external and operational factors. A more accurate determination of the effectiveness of the proposed methodology for predicting operational reliability indicators depending on the mode and depth of the load and the type of backup system can be achieved by conducting an additional series of experimental tests on the choice of the type of theoretical system. distribution law and determination of its parameters for specific designs of electrical devices. Thus, a conclusion was made about the possibility of using the obtained results to evaluate the parameters of the operational reliability of the above-mentioned high-voltage equipment, which is used as part of switchgear and power supply systems in both high and low voltage conditions.

Применение параметрических критериев однородности дисперсий в условиях нарушения стандартных предположений

When analyzing measurement series in various applications, it becomes necessary to ensure that the scattering characteristics of the measured quantities have not changed over time, or that the accuracy of measurements carried out by different laboratories in similar tests meets the necessary requirements. For these purposes, it is advisable to use various k-sample parametric criteria for testing hypotheses about the homogeneity of variances (about the equality of variances). The prerequisite for the possibility of using parametric criteria is that the analyzed samples belong to normal distribution laws, which is not always the case. When the assumption of normal distribution of statistics is violated, parametric criteria usually change significantly, which excludes the possibility of using classical results when testing hypotheses. The best parametric tests have a significant advantage in power over nonparametric tests. This advantage is usually retained when the standard assumption of normality is violated. The paper shows how the distributions of parametric test statistics change under conditions of violation of the standard assumption. It is shown that using simulation modeling based on the Monte Carlo method and with appropriate software support, it is possible to find the distributions of the statistics of the applied criteria under non-standard conditions corresponding to specific applications. The use of the results of such modeling makes it possible to make correct statistical conclusions based on the criteria used. The methodology of applying parametric criteria of homogeneity of variances under conditions of violation of the standard assumption is considered. The method involves, at the first stage, testing the hypothesis about the belonging of the analyzed samples to normal laws using a set of special criteria. In case of a negative result, at the second stage a law is selected that describes the combined sample. At the third stage, using the results of the modeling under this law, a conclusion is formed based on the applied criteria. Examples of the implementation of the methodology within the framework of the developed software system are given.

Optimization Problem for Probabilistic Time Intervals of Quasi-Deterministic Output and Self-Similar Input Data Packet Flow in Telecommunication Networks

Introduction. When managing traffic at the packet level in modern telecommunication networks, it is proposed to use methods that transform a self-similar stochastic packet flow into a quasi-deterministic one. To do this, it is required to apply complex probabilistic laws of distribution of self-similar flows. From the literature, methods of balancing the network load are known, which, with the problem indicated above, contribute to increasing the efficiency of telecommunication systems. However, there is no strictly mathematical solution to find out the optimal probabilistic characteristics of the output flow, based on the input flow. The presented research is intended to fill this gap. Its objective is to create a method for determining the optimal probabilistic characteristics of the packet flow, using the minimum value of the proximity measure of the self-similar input and quasi-deterministic output flows.Materials and Methods. To solve the research problem, the parameters of the output flow distribution were selected so that the approximation function was close to 𝛿𝛿-function. The Kullback-Leibler divergence was used as a proximity measure of the input and output distributions of time intervals. Methods of set theory, metric spaces, multidimensional optimization, and teletraffic were used. The solution algorithm included minimization of the Kullback-Leibler divergence and the limit passage to 𝛿𝛿-function.Results. A probability distribution is shown — an approximation of 𝛿𝛿-function, which maintains the equality of time intervals of a quasi-deterministic output packet flow. A method for transforming a self-similar input flow into a quasideterministic output flow is presented. The Kullback–Leibler divergence was used as a measure of their proximity. The minimum of the Kullback-Leibler divergence between the input and output flows with a normal distribution was achieved in the case of equality of the mathematical expectations of these flows. Using the passage to the limit, it has been established that time interval T between packets of the quasi-deterministic output flow must be equal to the mathematical expectation of the time intervals between packets of the input self-similar flow. To obtain a quasi-deterministic flow, the passage to the limit is performed for the found value of the mathematical expectation at σ → 0.Discussion and Conclusion. The application of this method will reduce the negative impact of self-similarity of network traffic on the efficiency of the telecommunication network. The use of quasi-deterministic flows makes it possible to predict the load of network resources, which can be the basis for improving the quality of user service. Two difficulties associated with calculations and practical implementation of the solution are eliminated. Firstly, it is difficult to use the delta function as a function of the output flow distribution density. Secondly, there are no ideal deterministic flows in the operation of telecommunication networks. The proposed method has great potential in the design and optimization of communication networks.

Анализ технологических и энергетических параметров шаровых мельниц

The paper considers issues related to the analysis of the most important process parameters of ball mills, such as changes in productivity, power consumption, amount of water entering the mill, oil pressure in the mill hydraulic system, pulp density during mill unloading. It was found that the power consumed by the mills varies within 836–1260 kW. The energy characteristics of the mills, as well as specific power consumption, correlation coefficients and regression equations are presented. The values of the coefficients of variation, asymmetry and excess show good agreement with the normal distribution law of random variables. Specific power consumption for mills varies within 6.71–9.94 kWh/t. In the future, it is planned to carry out a verification calculation of the drive electric motors of the mills in order to establish that the actual power of the electric motor corresponds to the calculated one. Such a check allows to objectively assess whether the actual power consumption corresponds to the adopted technology of the grinding process in the autogenous grinding body of the mining and processing plant.

ALGORITHM FOR CALCULATING RELIABILITY OF ON-SITE POWER SUPPLY SCHEMES USING CONNECTION COEFFICIENTS

The article deals with the method of simplifying the forecasting of reliability parameters and assessing the technical condition of the most critical nodes of the power supply system by means of connection coefficients. The aim of the study is to develop a methodology to determine the probability of failure-free operation of the power supply scheme using connection coefficients. Materials and methods. The scheme of 10/0,4 kV power supply within the workshop is presented. Probabilistic methods of reliability determination and mathematical statistics were used. Research results. The probability of failure-free operation in time using the exponential distribution law has been calculated. Graphs of dependences of probability of system uptime on the number of load connections, as well as graphs of changes in the values of connection coefficients in time are presented. The formulas for the load connection factors depending on the number of connections are derived. The received analytical expressions allow to model values at possible additional load connections. The obtained dependences allow to determine the probability of failure-free operation time of low-voltage electrical equipment, as well as the schemes of the in-house power supply. Conclusions. The proposed methodology simplifies the forecasting of reliability parameters of the scheme of the internal shop power supply and the assessment of the technical condition of the most important and critical nodes. The modeled values of the load connection coefficients can be used in technical and economic calculations, namely for further increase of the number of outgoing lines from the switchboard and distribution point or increase of the load on the line taking into account the permissible probability of failure-free operation of the scheme. The results of the study are recommended to evaluate technical performance and determination of the main reliability parameters of the operating systems of in-plant power supply.

Development of a neural network approach for risk management in helicopter technical condition diagnostics

The object of the study is the quality of helicopter maintenance based on digital diagnostic tools. To ensure the required quality, quantitative risk assessment models for the in-depth and express diagnostics system of helicopter gas turbine engines in a neural network environment are proposed. The assessment of diagnostic efficiency is based on the analysis of probable control risks by standard deviations, which distinguishes the proposed approach from the traditional one. Two diagnostic modes are considered: rapid diagnostics exemplified by vibration diagnostics, and in-depth diagnostics, including both vibration diagnostics and pyrometric control. These diagnostic methods make it possible to implement a remote monitoring system at aircraft repair facilities, which significantly reduces maintenance labor intensity. As a result, it was found that control risks depend not only on the metrological level of measuring instruments but also on a combination of the statistical nature of control agents in their system composition according to the following characteristics: statistical parameters of the controlled indicator, distribution laws, and values of uncertainty of measuring instruments, as well as the uncertainty of control standards (tolerances). In the modeling process, risks were assessed as a function of the ratio of uncertainties of measuring instruments to the uncertainty of the controlled parameter, with varying values of the standard (tolerance). This approach will allow, in practice, the creation of a more effective system for monitoring and collecting statistical information on the operational reliability of the Mi-8 helicopter engine, where the quality of control is predicted to a greater extent based on the metrological indicators of the measuring instruments and methods

Study on the Full‐Cycle Stress Evolution Law and Reasonable Size of Isolated Coal Pillar

ABSTRACTTo study the stress distribution law under different mining times and spaces of the protected coal pillar in the isolated working face, this paper takes a coal mine in Shanxi as the engineering background and adopts numerical simulation and theoretical analysis to obtain the stress distribution law of protecting coal pillar in the isolated working face during the tunneling period and the mining period of the working face, and proves the reasonable size of protecting coal pillar. The results show that the vertical stress and maximum principal stress increase correspondingly with the decrease of the protective coal pillar size under both stages, and the minimum value of the minimum principal stress occurs on the 8 m protective coal pillar; The values of the principal stress ratio and the principal stress deflection angle do not differ greatly in the protection of the coal pillar, and the fluctuation of the values is mainly concentrated in the vicinity of the back‐mining roadway; The second invariant of bias stress (J2) is mainly concentrated in the protective coal pillar near the side of the extraction zone, when the size of the protective coal pillar is reduced to 10 m, the J2 on the side of the extraction zone and the J2 on the side of the roadway are connected, and the whole protective coal pillar is under the influence of J2, which is basically the same as the damage pattern of the plastic zone; Based on the formula of limit balance theory to calculate the elastic core width of different sizes of protective coal pillars, and combined with the results of numerical simulation analysis, it finally concluded that the reasonable size of the protective coal pillar of this isolated island working face is 15 m.