Maximum Allowable Value Research Articles

Evaluación in vitro de bloqueadores solares en el contexto de índices UV extremos en Lima - Perú

Currently in Peru, UV index levels exceed the maximum allowable value (11+ Extreme). For this reason, it is important to evaluate the effectiveness of sunscreens with different Sun Protection Factor (SPF) ratings, which is a laboratory measure of the sunscreen's efficacy against UV-B radiation on our skin. In this study, the in vitro technique will be used following COLIPA recommendations, which involves measuring the transmission of UV radiation through the cream. The results obtained for the different SPFs are consistent with the values indicated on the product packaging: Bahía-SPF 45, Avon-SPF 50, and Bahía-SPF 70. However, they deviate by 30% from the indicated values for the higher SPFs, specifically Bahía-SPF 90, Bahía-SPF 100, and Unique-SPF 100

Importance of Changes in the Copper Production Process through Mining and Metallurgical Activities on the Surface Water Quality in the Bor Area, Serbia

This paper considers the impact of copper mining-influenced water and metallurgical wastewater on the surface water in the Bor area, Serbia. Sampling, realized through the four campaigns (2020–2021), confirmed that both types of water, discharged without appropriate treatment in the Bor River, had a signific impact on the concentration of metal ions, pH and electrical conductivity on the watercourse in the Bor area. The highest concentrations of the following metal ions, Cu—271 mg/L, As—25,991 μg/L, Ni—13,856 μg/L, Cd—2627 μg/L, and Pb—2855 μg/L, were registered in the metallurgical wastewater samples. After changes occurred in the copper production process by stopping the discharge of untreated wastewater into the Bor River, the concentrations of monitored elements were drastically decreased. In the period 2022–2024, the concentration values for Cu, As and Pb ions were below the maximum allowable value, and the concentration values of Ni and Cd ions were also decreased. The values for pH and electrical conductivity were in the maximum allowable range. The return of wastewater to the copper production process would lead to both a reduction in the primary water consumption and reduction in the negative impact on the environment.

District heating utilizing waste heat of a data center: High-temperature heat pumps

Data centers are energy-intensive facilities with substantial low-grade waste heat. High-temperature heat pumps can be critical in boosting the data center’s waste heat for district heating, improving the system-level energy efficiency of data centers, and reducing CO2 emissions in district heating. This study built thermodynamic models to assess high-temperature heat pumps with six configurations using low global warming potential refrigerants to supply heat up to 120 °C. The heat pump configurations include single-stage or two-stage cycles with advanced components, such as internal heat exchanger, economizer, flash tank, or parallel compressor. The refrigerants include R1234ze(Z), R1233ed(E), R1224yd(Z), R600, and R600a, and R245fa is used as a reference. A case study was carried out to recover the waste heat from the Frontier high-performance computing data center and provide hot water for district heating at the US Department of Energy’s Oak Ridge National Laboratory campus. The optimized performance of high-temperature heat pumps is characterized with various effectiveness of internal heat exchangers, and the operating parameters of economizer or flash tank, as well as their combination. The results show that the configurations of two-stage cycles with internal heat exchanger + flash tank and internal heat exchanger + economizer/parallel-compressor provide the highest coefficient of performance under scenarios of the maximum allowable value and a fixed value (0.3) of the internal heat exchangers’ effectiveness, respectively. R1234ze(Z) and R600a are the most promising refrigerants, considering trade-offs between the coefficient of performance and the volumetric heating capacity. The single-stage cycle with internal heat exchanger + economizer/parallel-compressor using R1234ze(Z) is recommended for utilizing Fronter’s waste heat in district heating. A one mega-watt high-temperature heat pump will reduce 33,100–33,200 metric tons of CO2 emission annually, corresponding to 85.4 %–85.6 % of equivalent CO2 emissions from natural gas boilers. This study provides good guidelines for designing and deploying high-temperature heat pumps to support sustainable data centers and decarbonize district heating in the US.

ANALIZE NUMERICE DE CÂMP TERMIC ÎN MOTOARE ELECTRICE REDUNDANTE

In this paper, we propose to analyze the heat transfer of a torque motor with a limited angle under special space conditions. Three-dimensional models will be used, and two current values will be considered in numerical analysis. Variants in which the boundary conditions will consider different values of the emissivity of engine surfaces will also be considered. Inside the stator and rotor subassemblies of the motor, heat transfer will be carried out by conduction and radiation between the motor and the ambient environment. Using numerical analysis, it will be possible to determine the time during which the temperature in the winding reaches the maximum allowable value for the limited angle torque motor under the mentioned conditions.

Burst pressure prediction of carbon/natural fiber and hybrid composite pressure vessels by theoretical and numerical analysis

This study utilized finite element modeling to assess the stress and burst strength of a composite pressure vessel (CPV). The fiber type and its sequences were considered while developing the best CPV. The stress produced inside the CPV may cause damage to the vessel as well as loss of life and property. Therefore, it is critical to guarantee that the CPV's stress output does not surpass the vessel material's maximum allowable stress value. The primary goal of this research is to investigate the stresses induced in composite pressure vessels and then examine the stress using three different solutions: von Mises, Tresca, and ASSY. The theoretical burst strength is first established, and then a numerical solution is developed using ABAQUS. To confirm the correctness of FEA, the outcomes of the theoretical technique and the finite element method are compared. The six-layer carbon fiber-reinforced CPV shows twelve times higher burst strength than four layers but an equal thickness of jute fiber-based CPV. On the other hand, the hybrid combination of CPV (jute and carbon) shows a strength improvement over jute fiber based CPV by almost four times. Other jute fiber-based hybrid CPVs with glass, banana, and aluminum foil show very comparable strength relative to only jute CPV. This study's primary goal is to examine the failure phenomena and burst strength of thin, cylindrical pressure vessels.

INVBSTIGATION OF SINGLE FILLET WELD FOR BUILT-UPMEMBERS

The main purpose of this study is to investigated the single fillet weld design for built-up membersby using ftision welding and find the effects of welding power input on that design for member. Inthis work, investigation of welding metal for Low carbon steel plate type St.52-3, thickness 6-8rnm, which is to ensure good mechanical properties under high stresses for ( Welding metal , heataffected Zone (HAZ) and base metal ). Also it can be explain, that the effects of welding processeson the deformation and changes in mechanical and metallurgical properties due to high thermalenergy, results from welding process. This study involved: weld design, selection of suitableelectrode, evaluation of mechanical and metallurgical properties, the maximum allowable value ofsweep of welded mamber after ( fabrication and erection ) has been calculated, also leg and throughlength have been calculated for the welded Zone. The main results of this study are :- The value of sweep which occur before the erection and tightening is ( 29 mm. ).- The leg and through length of welding metal which welded by electrode type( E 7018 = OKUS ), its found equal to ( 4 mm. ).The study results can ensure good mechanical and metallurgical properties for signal filled weld( Built-up members ).' i

GenX caused liver injury and potential hepatocellular carcinoma of mice via drinking water even at environmental concentration

Hexafluoropropylene oxide dimer acid (GenX) is an alternative to perfluorooctanoic acid (PFOA), whose environmental concentration is close to its maximum allowable value established by the US Environmental Protection Agency, so its effects on human health are of great concern. The liver is one of the most crucial target organ for GenX, but whether GenX exposure induces liver cancer still unclear. In this research project, male C57 mice were disposed to GenX in drinking water at environmental concentrations (0.1 and 10 μg/L) and higher concentrations (1 and 100 mg/L) for 14 weeks to explore its effects on liver injury and potential carcinogenicity in mice. GenX was found to cause a dose-dependent increase in the serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), total cholesterol (TC), and triglyceride (TG). As the content of GenX in drinking water increased, so did the concentrations of Glypican-3 (GPC-3) and detachment gamma-carboxyprothrombin (DCP), indicators of early hepatocellular cancer. GenX destroyed the boundaries and arrangements of hepatocytes, in which monocyte infiltration, balloon-like transformation, and obvious lipid vacuoles were observed between cells. Following exposure to GenX, Masson sections revealed a significant quantity of collagen deposition in the liver. Alpha-feto protein (AFP), vascular endothelial growth factor (VEGF), Ki67, matrix metalloproteinase 2 (MMP-2) and matrix metalloproteinase 9 (MMP-9) gene expression increased in a dose-dependent manner in the treatment group relative to the control group. In general, drinking water GenX exposure induced liver function impairment, elevated blood lipid level, caused liver pathological structure damage and liver fibrosis lesions, changed the liver inflammatory microenvironment, and increased the concentration of liver-related tumor indicator even in the environmental concentration, suggesting GenX is a potential carcinogen.

Assessment of refining efficiency during the refining cycle in a foundry degassing unit in industrial conditions.

The article focuses on the issue of improving the efficiency of a Foundry Degassing Unit (FDU) via operational testing of aluminium alloys during casting at MOTOR JIKOV Slévárna a.s.. As part of the research, the efficiency of the refining process in the FDU was assessed. The main emphasis was placed on determining the moment of the greatest decrease in the hydrogen content in the melt and whether it is possible to shorten the refining cycle. The values of the Dichte Index were determined, on the basis of which the degassing curve was plotted and the progress of the melt degassing was assessed. To ensure the required quality of castings, the maximum allowable value of the Dichte Index ranged from 3 to 4%. During the process, the temperature drop during the refining cycle was also determined. The total temperature drop from pouring the melt into the ladle to the end of refining ranged from 26 to 32°C, which is within the acceptable limits of the foundry. Based on the knowledge resulting from the operational experiments, recommendations were formulated to optimize the refining technology at the FDU for the MOTOR JIKOV Slévárna a.s. foundry.

Estimation of Daily Maize Gross Primary Productivity by Considering Specific Leaf Nitrogen and Phenology via Machine Learning Methods

Maize gross primary productivity (GPP) contributes the most to the global cropland GPP, making it crucial to accurately estimate maize GPP for the global carbon cycle. Previous research validated machine learning (ML) methods using remote sensing and meteorological data to estimate plant GPP, yet they disregard vegetation physiological dynamics driven by phenology. Leaf nitrogen content per unit leaf area (i.e., specific leaf nitrogen (SLN)) greatly affects photosynthesis. Its maximum allowable value correlates with a phenological factor conceptualized as normalized maize phenology (NMP). This study aims to validate SLN and NMP for maize GPP estimation using four ML methods (random forest (RF), support vector machine (SVM), convolutional neutral network (CNN), and extreme learning machine (ELM)). Inputs consist of vegetation index (NDVI), air temperature, solar radiation (SSR), NMP, and SLN. Data from four American maize flux sites (NE1, NE2, and NE3 sites in Nebraska and RO1 site in Minnesota) were gathered. Using data from three NE sites to validate the effect of SLN and MMP shows that the accuracy of four ML methods notably increased after adding SLN and MMP. Among these methods, RF and SVM achieved the best performance of Nash–Sutcliffe efficiency coefficient (NSE) = 0.9703 and 0.9706, root mean square error (RMSE) = 1.5596 and 1.5509 gC·m−2·d−1, and coefficient of variance (CV) = 0.1508 and 0.1470, respectively. When evaluating the best ML models from three NE sites at the RO1 site, only RF and CNN could effectively incorporate the impact of SLN and NMP. But, in terms of unbiased estimation results, the four ML models were comprehensively enhanced by adding SLN and NMP. Due to their fixed relationship, introducing SLN or NMP alone might be more effective than introducing both simultaneously, considering the data redundancy for methods like CNN and ELM. This study supports the integration of phenology and leaf-level photosynthetic factors in plant GPP estimation via ML methods and provides a reference for similar research.

Observer Design for a Class of Uncertain Nonlinear Systems With Sampled-Delayed Output Using High-Gain Observer and Low-Pass Filter: Application for a Quadrotor UAV

In this paper, a novel structure of a Filtered High-Gain Observer (FHGO) is proposed for a class of nonlinear systems subject to sampled and delayed measurements, bounded disturbances and noise measurements effects. Using an LMI design approach, the novel structure of the continuous-discrete FHGO allows a larger bound of the Maximum Allowable Value of Time Delay (MAVTD). To prove the effectiveness of the proposed observer, a comparison with Kalman-like observer and standard high gain observer is provided and the corresponding experimental results are presented for a quadrotor UAV.

Statistical Process Control and Capability Six-pack for Conductivity Measurement in Medicinal Chemical Industry

Statistical Process Control (SPC) is indispensable in the medicinal chemical industry for maintaining pharmaceutical product quality and consistency. Background: With complex chemical processes and stringent regulatory standards, robust quality control measures are essential. SPC enables monitoring and control of key process parameters, identification and correction of process variations, and ensuring final product compliance with specifications. This study evaluates the quality and capability of a process measuring medicinal raw material quality from an international chemical manufacturing company. Methods: Data collected from the conductivity measurement process were analyzed using Minitab software. The process specification was fixed at 30 µS·cm-1 as a maximum permissible limit, with 33 subgroups of size one. The computation of the capability six-pack and analysis generated six plots providing insights into process stability, recent behavior, and capability against specifications, distribution verification and capability indices. Minitab® version 17.1.0 software was used to perform a process capability six-pack analysis, including various charts and statistics to assess process stability and capability. Results: The results indicate that while the process is stable, it lacks capability, with variations exceeding acceptable limit. The process does not meet the maximum allowable specification value, with deviations from normal distribution and following logistic dispersion pattern. Conclusion: The study's novelty lies in its comprehensive yet concise presentation of key metrics essential for evaluating process capability and performance, providing insights for process improvement and quality control. Further investigation and improvement actions are needed to address sources of variation and enhance process capability and performance.

Experimental verification of seismic vibration control of high-rise buildings with friction-type multiple tuned mass dampers

In recent decades, tuned mass damper (TMD) devices have been implemented in numerous high-rise buildings in the world. The vibration of tall buildings caused by natural or man-made dynamic loading poses a challenge. In this study, to ensure structural safety and resident comfort, a friction-type multiple TMD (FT-MTMD) system was investigated and its ability to reduce the seismic response of high-rise buildings was evaluated. The proposed FT-MTMD system comprises multiple TMD units in a parallel arrangement and has a greater frequency bandwidth than a conventional TMD system. To address practical issues, a prototype FT-MTMD system was designed and fabricated to control a scale-down test model which has similar fundamental modal properties to a real 36-story building. Because of the nonlinearity of friction, the parameters of the FT-MTMD system were determined using a proposed optimal design method. First, a component test was conducted to ensure that the parameters of the FT-MTMD agreed with the designed values. Then, the FT-MTMD was installed on the long-period test model and its control performance was experimentally evaluated. Shaking table test results indicated that the FT-MTMD system favorably reduced the seismic response in the test model, indicating that the proposed optimal design method is reliable. A theoretical structure–MTMD model was also developed to simulate the system response with unsynchronized stick-slip motion of the FT-MTMD system. The predicted system response agreed well with the measured response. In addition, to avoid damage to the FT-MTMD system during a severe earthquake, a fail-safe device was employed to lock the TMD when its stroke reached the maximum allowable value.

STUDY OF PHASE VOLTAGE AND LOAD SYMMETRATION IN ACTIVE-ADAPTIVE DISTRIBUTION ELECTRIC NETWORKS

Networks of 0.4 kV are characterized by a large unbalance of loads in phases. Current unbalance leads to voltage unbalance and additional losses of electrical energy. As a result, the voltage at the consumer may not meet the quality standards of electrical energy. In addition, due to unbalance, the service life of electrical equipment is reduced. Since the effect of stress balancing significantly depends on the place of balancing loads on the line, the paper proposes to determine the places of balancing loads by solving a multicriteria optimization problem. The paper proposes an objective function that minimizes active power losses and contains the total index of active power losses and indices of voltage unbalance coefficients in the negative and zero sequence.
 
 The purpose of the study is to obtain an effective objective function for determining the places of balancing loads and voltages in the network, which ensures a minimum of active power losses and the values of the voltage unbalance factors within the required limits; conduct a study of balancing loads and voltages depending on the places of balancing.
 
 Materials and methods. In the work, methods for calculating electrical networks were used, taking into account voltage losses and active power. To study the places of balancing loads and voltages, the method of multicriteria optimization with restrictions was used. The study of the objective function was carried out on a mathematical model of a low voltage overhead line. All calculations were carried out in MATLAB.
 
 Research results. A review and analysis of modern tools and methods for balancing loads and voltages in low voltage networks has been carried out. As a result of the analysis, it was concluded that there is no algorithm for determining the places of load balancing in low-voltage networks that provide minimal active power losses and the values of the voltage unbalance factors within the required limits. The task of finding places for balancing loads and voltages is a multiobjective optimization problem with constraints. Therefore, an objective function was proposed that minimizes active power losses in the network and contains the total index of active power losses and indices of voltage unbalance coefficients for the reverse and zero sequence. To study the proposed objective function, a model overhead line of a 0.4 kV network with specified phase loads and voltages was used. For the model line, the calculation of active power losses and the values of the voltage unbalance coefficients in the initial mode before balancing was carried out. All calculations were carried out for each phase separately. At the first stage, the calculation of the sensitivity coefficients of active power losses and the sensitivity coefficients for the voltage unbalance coefficients was carried out. To study the balancing of loads, nodes were selected that have the maximum values of the sensitivity coefficients. It follows from the calculation results that the best effect from balancing is observed when balancing loads simultaneously in two nodes: in the node with the highest value of the total sensitivity factor of active power losses, and in the node with the maximum value of the phase sensitivity factor of active power losses. When balancing loads in only one of the nodes, the most optimal of the selected ones will be the node most remote from the TS. We also obtained weight coefficients that provide a minimum of the objective function.
 
 Conclusions. The proposed objective function is effective for determining the places of load and voltage balancing in low voltage networks. In this case, the best effect is observed when balancing loads in nodes that have the highest values of the sensitivity coefficients of total active power losses and by phases. The node most remote from the TP will be more optimal. When balancing loads in places determined using the proposed objective function, it is possible to reduce power losses and ensure the values of the unbalance coefficients in the nodes on the line less than the maximum allowable value.

Analysis of the results of preventive testing of bushings using elements of the theory of statistical hypothesis testing

The article presents the results of a study of the dependence of insulation indicators on the duration of operation for serviceable and faulty high-voltage oil-filled bushings, both of hermetic and non-hermetic construction. The results of periodic tests of oil-filled bushings, with a voltage of 110 kV of hermetic design with paper-oil insulation of the capacitor type, as well as non-hermetic construction, were used as initial data. Three statistical criteria were used to form statistically homogeneous data sets: the Wilcoxon rank test, the Z-test, and the Fisher-Snedecor test. The values of the sample mean, sample variance, as well as coefficients of asymmetry and excess of insulation indicators of high-voltage bushings were obtained for the array of initial data and arrays obtained during statistical processing. The values of the sample averages for the arrays obtained as a result of the statistical processing procedure differ significantly. There is a significant decrease in the sample variance values for tgd1 compared to the original arrays. To check the homogeneity of the data in the obtained arrays, the one-factor variance analysis model is used. The practical use of this algorithm made it possible to significantly reduce the heterogeneity of the results of periodic tests of the state of insulation of high-voltage bushings. The analysis of the composition of the arrays with homogeneous values of the indicators made it possible to establish that the values of the indicators of bushings from different regions of Ukraine, of different types and made with different numbers of factory drawings, got into the homogeneous data arrays. It is noted that for high-voltage bushings that do not have insulation defects, the values of the mathematical expectation of the same indicator for different arrays of preventive tests of capacitor-type insulation have a shift relative to each other. From this it follows that the load factor and the operating time of the transformer significantly affect the determination of the maximum allowable value of the insulation index of the high-voltage bushing.

ASSESSMENT OF THE ACTUAL TEMPERATURE CONDITIONS IN THE CHAMBERS FOR PLACING FANS

Purpose. Assessment of the actual temperature conditions in the chambers of gas suction installations in the mining and geological conditions of the “Pokrovske” Mine Administration. Method. Analysis and generalisation of the results of observations of the actual temperature regime in the fan chambers of the component installations. Results. An analytical comparison of the actual temperature regime in the chambers of gas suction units with the permissible one according to sanitary and hygienic standards was carried out. The rational parameters of the temperature regime are determined, which can be considered “conditionally” acceptable in the chambers of gas suction units, are determined in the mining and geological conditions of the “Pokrovske” Mine Administration. Scientific novelty The substantiation of the necessary physical parameters of the air entering the chambers of gas suction installations, for their ventilation, to ensure sanitary and hygienic standards for temperature has been carried out. The dependence of the air flow rate entering the chambers of ventilation gas suction units on its maximum allowable value , according to sanitary and hygienic standards, has been established.. Practical significance. It has been established that in order to ensure the standard temperature regime in the chambers of gas suction units in the mining and geological conditions of the “Pokrovske” Mine Administration, it is not advisable to use refrigeration units. This will reduce the economic costs of ensuring the standard temperature regime. Key words: recommendations, methane, goaf, temperature, ventilation.

Home-produced eggs: An important pathway of methylmercury exposure for residents in mercury mining areas, southwest China

In light of the documented elevated concentrations of total mercury (Hg) and methylmercury (MeHg) in poultry originating from Hg-contaminated sites, a knowledge gap persists regarding the levels of Hg found in home-produced eggs (HPEs) and the associated dietary exposure risks in regions affected by Hg mining. To address this knowledge gap, a comprehensive investigation was undertaken with the primary objectives of ascertaining the concentrations of THg and MeHg in HPEs and evaluating the potential hazards associated with the consumption of eggs from the Wanshan Hg mining area in Southwest China. The results showed that THg concentrations in HPEs varied within a range of 10.5–809 ng/g (with a geometric mean (GM) of 64.1 ± 2.7 ng/g), whereas MeHg levels spanned from 1.3 to 291 ng/g (GM, 23.1 ± 3.4 ng/g). Remarkably, in half of all eggs, as well as those collected from regions significantly impacted by mining activities, THg concentrations exceeded the permissible maximum allowable value for fresh eggs (50 ng/g). Consumption of these eggs resulted in increased exposure risks associated with THg and MeHg, with GM values ranging from 0.024 to 0.17 µg/kg BW/day and 0.0089–0.066 µg/kg BW/day, respectively. Notably, the most substantial daily dosage was observed among children aged 2–3 years. The study found that consuming HPEs could result in a significant IQ reduction of 34.0 points for the whole mining area in a year. These findings highlight the potential exposure risk, particularly concerning MeHg, stemming from the consumption of local HPEs by residents in mining areas, thereby warranting serious consideration within the framework of Hg exposure risk assessment in mining locales.

Research on Optimization of Total Nitrogen Peak Suppression in Wastewater Treatment Based on the Data Driven Method

In order to solve the problems of water eutrophication, algae anoxic decay, and death by biological poisoning, which are caused by the excessive emission of total nitrogen in wastewater treatment process, this paper proposes a method of total nitrogen peak suppression which is based on neural network decision optimization. First, the SSORBF neural network is established according to the wastewater treatment process, and total nitrogen, inflow flow, current total nitrogen, dissolved oxygen concentration, and nitrate nitrogen concentration are selected to predict the total nitrogen concentration. Second, the density- and memory-based NSGA2 multiobjective optimization method is used to set the optimal solution to meet the requirement of energy consumption. If the prediction of total nitrogen exceeded the set value, the optimal control strategy is adopted to control the peak value of total nitrogen in advance, and it cannot exceed the national maximum allowable emission value. If the prediction of total nitrogen is lower than the set value, it continues to track the parameter set value. Finally, compared with other methods, the proposed method can effectively suppress the peak value of total nitrogen under 18 mg/L and reduce the energy consumption in wastewater treatment by 7.6%. It can provide decisions and advice for wastewater treatment plants.

CO Diffusion Study and Spatial and Temporal Variation Modeling during the Construction Period of the Plateau Railroad Tunnel.

In order to investigate the diffusion law of CO gas in the vicinity of the tunnel boring face of the plateau long tunnel, to improve the efficiency of tunnel smoke exhaust, and to derive the spatial-temporal variation model of CO concentration for predicting the concentration of CO at different times and in different cross sections under specific environments, a CO diffusion model of a tunnel in Yunnan was established by using Ansys Fluent Fluid Simulation Software, and the CO transport characteristics under different conditions were simulated by taking the ventilation time, wind speed, and location of the air ducts as the influencing factors. The results show that the wind flows from the mouth of the wind pipe after the wind speed decreases, the diffusion area increases and arrives at the face of the direction of the rebound in the jet stream of new wind, and the return wind under the joint action of the vortex produced obviously, to reach the wind pipe mouth after the tunnel wind flow field, basically tends to stabilize. When the wind pipe mouth was arranged in the arch waist, 20 m away from the boring face, the inlet wind speed was 9 m/s and the ventilation time was 30 min; the CO concentration in the tunnel was reduced to below the maximum allowable concentration value. Moreover, the concentration of CO in the tunnel at the moment of 15 min of ventilation has a nonlinear positive correlation with the change of distance L from the boring face, while at the cross section of the air outlet of the wind pipe L = 20 m, the ventilation time is from 1 to 30 min and the concentration of CO at the cross section has a nonlinear decreasing trend with the ventilation time, which can be deduced according to the different space-time change models.

Effect of dihydroquercetin on oxidative metabolism in young athletes engaged in winter sports in a northern region

AIM: To study the effect of dihydroquercetin on the indicators of oxidative metabolism in young athletes engaged in the winter sports in the Khanty-Mansiysk Autonomous Okrug (KhMAO).
 MATERIAL AND METHODS: The indicators of oxidative metabolism were studied in a group of 56 male students (mean age 19.300.51 years) from the Khanty-Mansiysk boarding school of the Olympic reserve. These students were actively involved in winter sports such as cross-country skiing and biathlon. To assess the impact of the plant-derived antioxidant bioflavonoid Baikal dihydroquercetin (DHQ), the participants were administered a daily dose of 120 mg of DHQ for a period of 60 days. Measurements were taken before and after the exposure. Blood lipid peroxidation (LPO) products were studied, namely, lipid hydroperoxides (LHP) and products that react with 2-thiobarbituric acid products (PR-TBA). Additionally, we examined the indicators of the body's antioxidant defense system (ADS) through the assessment of total antioxidant activity (TAA) and thiol status (TS). To quantify the overall oxidative stress experienced by the participants, we calculated the oxidative stress coefficient (OSC) using the formula: OSC = LHP PR-TBA / TAA TS.
 RESULTS: The average levels of LPO values (HPL and PR-TBA) among KhMAO athletes have surpassed the upper limit of optimal values. On the other hand, the ADS parameters (TAA and TS) fall within the range of physiologically optimal values, albeit closer to the lower limit. Notably, athletes have exhibited an OSC increase that is nearly 3.5 times higher than the maximum allowable value. A quarter of the individuals examined displayed elevated HPL values, while more than 30% showed increased PR-TBA levels. A third of male athletes exhibited reduced ADS values compared to the physiologically optimal range. In total, 70.4% of skiers and biathletes in KhMAO have exceeded the OSC parameters. After two months of daily intake of 120 mg DHQ, the normalization of indicators of oxidative metabolism was observed. All parameters aligned with physiologically optimal values, except for OSC. We found a decrease in primary (LHP, 1.15 times) and secondary (PR-TBA, p=0.046) LPO indicators parallel to a significant increase in ADS indicators, specifically TAA (p=0.022) and TS (p=0.049). Conversely, there was a significant increase in ADS indicators, specifically TAA (p=0.022) and TS (p=0.049).
 Despite these positive changes, the OSC value, although significantly reduced (p 0.001) by 2.3 times compared to the initial value, remained above the upper limit of the physiological norm.
 CONCLUSION: The study demonstrated that young athletes engaged in winter sports experienced improved indicators of oxidative metabolism after a consistent two-month intake of the potent antioxidant DHQ. This led to the restoration of a balanced prooxidant-antioxidant state, enhanced overall well-being, and expedited recovery following intense physical exertion. Furthermore, our results may suggest that DHQ may contribute to prevention of non-communicable diseases in the future.

Tracking Control Method of Multi Motor Actuator Saturation Based on Total Amount Consistency

In collaborative control of multi motors for heavy-duty locomotives, the output value of the motor frequently exceeds its maximum allowable value during power redistribution. This results in a saturated motor owing to the power redundancy of each wheel set of the train. In this study, an algorithm for the tracking control of a consistent total amount of the extended observer through anti-saturation is proposed. First, mathematical models of multi-motor traction systems are developed. The system includes uncertain parameter perturbations and external perturbations. Second, a new type of extended sliding mode observer (ESMO) is designed to reduce the influence of the tracking effect on the input saturation of the system. Subsequently, for collaborative control of multi motors in heavy-duty locomotives, a new scheme for dynamic and auxiliary anti-saturation compensation (anti-windup) is established. The perturbation observation results and the systems’ auxiliary status are respectively input into the sliding mode controller (SMC). A traction total-amount coordinated tracking control (TACTC) of multi motors is achieved to ensure consistency of the system’s total output torque and the given traction characteristic curve. Finally, simulations and tests are performed on the motor actuators to demonstrate a good control effect.