Analysis Apparatus Research Articles

High-sensitive metal oxide gas sensor for BTEX gases based on ternary composite of Ce x Mn1−x O2/SnO2

A sensitive gas sensor based on a ternary composite of Ce x Mn1−x O2/SnO2 was used for BTEX detection. The ternary Ce x Mn1−x O2/SnO2 was synthesized via hydrothermal and immersion method and characterized by high resolution transmission electron microscopy and x-ray photoelectron spectroscopy. The gas sensor performances were measured on a designed flow-through microsystem consisted of a dynamic multiple gas handling unit, a test gas preheater, an olive-like test chamber and a data analysis apparatus. The developed gas sensor shows a high sensitivity towards BTEX (benzene, toluene, ethylbenzene and xylene) gases with a linear ranging from 100 to 600 ppb at optimal temperature. The sensor exhibited relative selectivity to BTEX gases compared to other VOC components. The sensing mechanism can be concluded as the ‘spillover effects’ of Ce x Mn1−x O2 and heterogeneous effect at the interphase of the Ce x Mn1−x O2–SnO2. The gas sensor developed in this paper provide a possible further application in BTEX gases, especially in ppb-level detection.

METHODS OF COMPARATIVE STATICS AND DYNAMICS IN THE THEORY OF ECONOMIC CYCLES

The subject of this work is the problem of describing the dynamic behavior of the price in the market of one product. The typical balance of interaction of supply and demand functions depending on the price is considered. The dynamic model of price evolution is based on the assumption that the demand function at a given time depends on the supply function at all previous points in time, i.e. there is a process with an aftereffect. The core of the integral transformation is a characteristic of the second order, which can initiate periodic regimes in price variables. The aim of the work is to synthesize a mathematical model of price changes in the market of one product and study the stability of its equilibrium states with the manifestation of the structure of marginal cycles. The task of the study is to demonstrate the degree of connection between the problem of stability of equilibrium and the problem of obtaining fruitful results in comparative statics. This duality is the principle of conformity of P. Samuelson. The basic mathematical model of the studied process of price dynamics is a system of two nonlinear differential equations of the first order. The research methods are the nonlinear theory of analysis of dynamical systems, the mathematical theory of stability of systems of differential equations, the conceptual apparatus of analysis of typical bifurcations of birth (death) of the boundary cycle, known as the Andronov-Hopf bifurcation. As a result of a detailed analysis of the properties and parameters of self-oscillating modes, a double cycle is revealed, i.e. there is a fact of coexistence around the equilibrium state of stable and unstable limit cycles. Subsequent mathematical transformations prove that the line of demarcation of these two cycles is completely determined by the static parameters of the studied system, which illustrates the mechanism of action of the principle of conformity of P. Samuelson. Conclusions: on the example of the functioning of the labor market, a comprehensive analysis of the stability of two positive equilibrium states, which characterize the effects of substitution and income. Computer simulations are used to perform computational experiments that demonstrate self-oscillating modes of price changes. As a result of the analysis of the obtained numerical results, it is possible to draw a conclusion about the stability of the limit cycle in the vicinity of the equilibrium state, which corresponds to the substitution effect.

Modeling acidizing of carbonate formations with different reservoir properties

Introduction. The efficiency of matrix acidizing of the bottom-hole formation zone depends on many factors, the chief being the reservoir properties. The research aim is to assess the effect produced by the formation reservoir properties on the result of hydrochloric acid treatment. Experiments simulating carbonate formation acid treatment were carried out. Methods. The experiments were carried out using the UIK-1 core analysis apparatus. Carbonate cores with different porosity and permeability were selected. Some of the experiments modeled permeability reduction as a result of bottom-hole formation zone contamination with drilling mud. Results. The research has shown that during low permeability reservoirs acidizing, permeability increases to a greater extent than during high permeability cores acidizing. In low permeability cores, the acid solution mainly forms new channels, while in high permeability cores the expansion of existing ones mainly occurs. In the present paper, the equivalent surface area of the acid-formed channels was estimated. When acidizing low permeability cores, the equivalent area of the channels is larger than when acidizing high permeability cores. The outcome of acidizing of the core samples with impaired porosity and permeability and contaminated with model drilling mud is comparable to acidizing of low permeability samples not contaminated with drilling mud. Conclusions. Acidizing of low permeability reservoirs leads to a greater increase in permeability. The equivalent area of acid-formed channels is larger than that of high permeability cores treatment. This reveals that the impact of acid on low permeability reservoirs is more effective.

APPLICATION OF THE CORRELATION ANALYSIS MATHEMATICAL APPARATUS FOR DETERMINATION THE LEAD–ACID BATTERIES MANAGEMENT AND STATUS CONTROL MINIMUM DIAGNOSIS

The subject matter of the article is the lead–acid batteries carrier and management. The goal of the study is the development of a methodology for assessing the lead–acid batteries’ parameters and to provide recommendations for their long–term management and carrier in the army operation. The tasks to be solved are: on the basis of the lead–acid batteries operation experience to define a set of diagnostic parameters on which it is possible to draw a conclusion about the technical state of a battery and change of its electric, operational and design properties; to determine the correlations between the properties of the battery and make their assessment based on the established criteria; to build a diagnostic graph–model of causal relationships of a battery’s parameters in the form of a correlation galaxy; to justify the lead–acid batteries carrier and management minimum diagnosis which can be carried out during their life cycle management та status control under the lack of time. General scientific and special methods of scientific knowledge are used. The following results were obtained: The set of diagnostic parameters to assess the battery technical state was determinated. Statistical data processing using the mathematical apparatus of correlation analysis was done. The diagnostic graph model of a lead–acid battery in the form of a correlation galaxy was constructed. The lead–acid batteries carrier and management minimum diagnosis during the life cycle was determined. Conclusions. Analysis of the experience of the lead–acid batteries operation determines a set of diagnostic parameters, which can be used to draw a conclusion about the technical state of a battery and change of its electric, operational and design properties. As generalized diagnostic parameters of the battery technical state can be considered the State of Health and the State of charge. Statistical data processing using the mathematical apparatus of correlation analysis allows to determine the causal and dependencies between the battery’s parameters and make their assessment based on the established criteria. Presentation of generalized results in the form of a correlation galaxy makes it possible to build a diagnostic graph–model of battery in the form of a correlation galaxy. Control of the SoC and SoH of the lead–acid battery will ensure the monitoring of the remaining charge, as well as the issuance of a warning about the need to replace the battery. A promising direction in the development of battery operation can be considered the development of battery–powered trackers – software and hardware devices capable of caring for battery care and battery management.

Latest theoretical approaches to uncertainty modelling in enterprise management: historical, conceptual and instrumental aspects

The article is devoted to fuzzy-set and interval approaches to modelling uncertainty within the issues of enterprise management. The nodal events of origin and development of fuzzy set theory, the main stages of formation and development of fuzzy-set approach as an applied methodology are considered. Particular attention is paid to the economic application of fuzzy set theory, including in relation to applied problems of enterprise management. The historical, conceptual and instrumental aspects of interval methodology, which is based on the apparatus of interval mathematics or analysis, as another significant approach to modelling uncertainty in economics and business, are highlighted. It is concluded that fuzzy set theory and interval analysis form a mathematical basis for powerful approaches to modelling uncertainty, which cannot be described using traditional probabilistic-statistical methods. Methods and models based on these theories are successfully used for a wide range of enterprise management tasks. It is proved that in the field of investment analysis and business planning one of the most important achievements of the theory of fuzzy sets should be considered the introduction of fuzzy numbers and the development of fuzzy arithmetic. Their use allows to carry out the entire volume of analytical work and financial and economic calculations for specific tasks in these areas at the level of fuzzy-multiple descriptions, starting from the assessment of initial parameters and ending with the finding and analysis of the resulting indicators. In general, the significance of both fuzzy set theory and interval analysis goes far beyond purely economic issues. The information presented in the publication convincingly proves that both the theory of fuzzy sets and interval analysis now determine the high degree of development of their theoretical and conceptual basis and instrumentalapplied component. At the same time, the issue of further formation and development of these methodologies remains relevant.

UNCERTAINTY ESTIMATION OF THE STRAIN GAUGES CONFIGURATION

The trend of improving the quality of products in the field of energy is aimed, in particular, at improving the quality of validation and verification of the declared parameters (strength of industry and research nuclear reactors and other pressure vessels, etc.). For verification of the parameters of the integrity and strength within the plant and operational tests and control the operating parameters using high-quality measurement and control equipment, which is part of the measuring channel. Improving the quality of the information is obtained, in particular, during full-scale tests using strain gauges, leads to an increase in the quality of products in general. The measurement result depends on many factors, which are not always possible to control due to technical and economic reasons. Using the apparatus of mathematical analysis and the theory of elasticity, it is shown that one of the parameters – the configuration of the strain gauge can reduce the uncertainty of the results of measurements by tensometric methods.

Security basic model for applied tasks of the distributed information system

The tasks of modelling and the components of the basic model of applied task protection of a distributed information system have been considered. The measurement and relationship of security parameters, protection, new and reference attacks, anomalies, and threat environments have been proposed. The conditions of threats, attacks and, consequently, inconsistencies in the results of applied tasks are proved. At the beginning of the article the concept of a distributed information system, system of applied tasks, modern trends of zero-trust architecture in building information security systems are discussed. Further, it gives an overview of existing methods of detection and counteraction to attacks based on reference knowledge bases. To improve the level of security it is proposed to analyze the causes of attacks, namely hazards and threats to the system. Attacks, hazards and threats are considered as structured processes that affect the internal and external environment of the system of the applied tasks with a further impact on the output of these tasks. The concepts of security level and security level of a distributed information system are introduced, as well as the concepts of applied task, environment, and user contradictions. As the logical metrics of discrepancy detection the apparatus of semantic analysis is proposed, which (based on the reference knowledge base, the apparatus of text transformations) should be applied at the stage of loading of applied task and describe the input and output data, requirements to the environment of the task solution. The result of the research is the proposed method for identifying additional data about hazards, threats, attacks, countermeasures to attacks, applied task-solving. This data is generated from the reference and augmented textual descriptions derived from the proposed contradictions. By building additional reference images of threats, attacks, countermeasures, it becomes possible to prevent the activation of new attacks on the distributed information system.

Processing of expert information for anti-pollution systems research

The introduction in Russia of the Euro-5 standard and the tightening of rules on emissions of harmful substances has resulted in an overdue improvement in the methods and algorithms of calculation and design of toxicity decreasing systems to enhance the functioning of devices of these systems. Despite widespread methods of simulation and computer modelling for the study and testing of the proposed organizational and technical measures, it is relevant to assess the increase of exhaust recirculation motor units with the help of experimental studies. The purpose of the study is to evaluate emissions of harmful substances of the car exhaust and suggest an experimental device based on the apparatus and methodology for analysis of carbonyl compounds and volatile organic compounds. In assessing of the effectiveness of reducing the toxicity, significant attention is paid to methods of experimental studies. As an indicator of the effectiveness in reducing the toxicity of motor units, the volume of emissions of harmful substances was selected. The choice of the components of the experimental system for the automated processing of the environmental inspection results of motor vehicles was substantiated. These components are: software tools that implement the conduction of the test by a cold start of the engine and chassis dynamometer settings, as well as monitoring the progress of the experiment; interactive systems to transmit information between the posts of ecological police, private persons and legal entities, companies for the maintenance of vehicles.

About the B-spline wavelet discrete-continual finite element method of the local plate analysis

Introduction. This distinctive paper addresses the local semi-analytical solution to the problem of plate analysis. Isotropic plates featuring the regularity (constancy) of physical and geometric parameters (modulus of elasticity of the plate material, Poisson’s ratio of the plate material, dimensions of the cross section of the plate) along one direction (dimension) are under consideration. This direction is conventionally called the basic direction.
 Materials and methods. The B-spline wavelet discrete-continual finite element method (DCFEM) is used. The initial operational formulation of the problem was constructed using the theory of distribution and the so-called method of extended domain, proposed by Prof. Alexander B. Zolotov.
 Results. Some relevant issues of construction of normalized basis functions of the B-spline are considered; the technique of approximation of corresponding vector functions and operators within DCFEM is described. The problem remains continual if analyzed along the basic direction, and its exact analytical solution can be obtained, whereas the finite element approximation is used in combination with a wavelet analysis apparatus in respect of the non-basic direction. As a result, we can obtain a discrete-continual formulation of the problem. Thus, we have a multi-point (in particular, two-point) boundary problem for the first-order system of ordinary differential equations with constant coefficients. A special correct analytical method of solving such problems was developed, described and verified in the numerous papers of the co-authors. In particular, we consider the simplest sample analysis of a plate (rectangular in plan) fixed along the side faces exposed to the influence of the load concentrated in the center of the plate.
 Conclusions. The solution to the verification problem obtained using the proposed version of wavelet-based DCFEM was in good agreement with the solution obtained using the conventional finite element method (the corresponding solutions were constructed with and without localization; these solutions almost completely coincided, while the advantages of the numerical-analytical approach were quite obvious). It is shown that the use of B-splines of various degrees within wavelet-based DCFEM leads to a significant reduction in the number of unknowns.

Iterative algorithms for minimizing the Hausdorff distance between convex polyhedrons

The problem of finding the optimal location of moving bodies in three-dimensional Euclidean space is considered. We study the problem of finding such a position for two given polytopes A and B at which the Hausdorff distance between them would be minimal. To solve it, the apparatus of convex and nonsmooth analysis is used, as well as methods of computational geometry. Iterative algorithms have been developed and justification has been made for the correctness of their work. A software package has been created, its work is illustrated with specific examples.

Structure of adaptive resonant model of managing the quality of city public passenger transportation

Problem. The need to develop and implement city passenger transport management systems is explained by the current trend to account the integrated efficiency of technological processes implementation within enterprises, transport infrastructure and socio-ecological environment. Also, the assessment of management efficiency should reflect the list of requirements to social significance of public transportation quality. The introduction of city passenger transport management system is a complex task that requires development and formalization of the apparatus for identification and structural multilevel analysis of the quality of public transportation as a fundamental tool for assessing its effectiveness. Methodology. By adapting the principles of identification and structural analysis to syntactic structural models of describing the quality of transportation and establishing the basic production connection of its change, a set of instrumental directions for city public passenger transport management is stressed through formalization of processes within the basic levels of their evaluation. Identification and structural analysis of city passenger transport means establishing a general algorithm for forming a hierarchy of problematic tasks of ensuring the quality of transportation and find effective measures to solve them in a multivariate management. The formed structure of the complex adaptive resonant model of passenger transport management is based on establishing the classification signs of public transportation quality and contains the basic layers of comparison and recognition of conditions for its maintenance. Originality. The situational and structural approach is offered as an invariant basis for the system analysis of difficult objects when implementing the principles of complex management of city passenger transport. It is proposed to approach the choice of the structural modeling apparatus that satisfies the selected requirements of the strategic management of city passenger transport from the standpoint of the possibilities of syntactic formalization of descriptions of its levels and the tasks of identification and structural analysis. Practical value. Based on the principles of adaptive resonance theory, the structure of the model of multilevel coordination of local control parameters is developed and a sequence of their quantitative comparative evaluation is formed according to the basic units corresponding to strategic types of city passenger transport management: improving mobility and quality of transportation, economic incentives, resource efficiency of transport infrastructure, road safety, environmental impact. The developed general structure of the contour of integrated city public transport management allows in prospect to form a model of multilevel coordination of local parameters and is a methodological basis for implementation of automated decision support systems.

Taste Masking Study Based on an Electronic Tongue: the Formulation Design of 3D Printed Levetiracetam Instant-Dissolving Tablets

PurposeProper taste-masking formulation design is a critical issue for instant-dissolving tablets (IDTs). The purpose of this study is to use the electronic tongue to design the additives of the 3D printed IDTs to improve palatability.MethodsA binder jet 3D printer was used to prepare IDTs of levetiracetam. A texture analyzer and dissolution apparatus were used to predict the oral dispersion time and in vitro drug release of IDTs, respectively. The palatability of different formulations was investigated using the ASTREE electronic tongue in combination with the design of experiment and a model for masking bitter taste. Human gustatory sensation tests were conducted to further evaluate the credibility of the results.ResultsThe 3D printed tablets exhibited rapid dispersion (<30 s) and drug release (2.5 min > 90%). The electronic tongue had an excellent ability of taste discrimination, and levetiracetam had a good linear sensing performance based on a partial least square regression analysis. The principal component analysis was used to analyze the signal intensities of different formulations and showed that 2% sucralose and 0.5% spearmint flavoring masked the bitterness well and resembled the taste of corresponding placebo. The results of human gustatory sensation test were consistent with the trend of the electronic tongue evaluation.ConclusionsOwing to its objectivity and reproducibility, this technique is suitable for the design and evaluation of palatability in 3D printed IDT development.

Curing kinetics of a siloxane pre-ceramic prepreg resin

Ceramic matrix composites are being investigated as new material of choice for aeronautic and aerospace applications, because of their higher thermal resistance. Among the different ways to manufacture these materials, the polymer infiltration pyrolysis (PIP) is the most versatile. This route uses preceramic resins that present the benefit to be processed like thermosets. However, there is a lack of information available regarding the curing kinetics of preceramic resins and their detailed chemical composition. This limits the possibility for the end user to freely operate the resin, with sufficient accuracy to manufacture components. Dynamic Differential Scanning Calorimetry (DSC) were carried out at 1, 3, 5, 10, 15 and 20°C/min, to plot a Time-Temperature-Transformation (TTT) diagram for a commercial polysiloxane resin, the SPR-688. The activation energy and kinetic parameters were estimated using Kinetics Neo. The glass transition temperature of SPR-688 was modelled using the Di Benedetto's equation. The gelation point was investigated by chemorheology using a Dynamic Mechanical Analysis (DMA) apparatus, by plotting tan δ vs time. The degree of cure was thereafter estimated. The curing mechanism was shown to be a single step reaction (A→B). The cure kinetic was successfully described by numerical optimization, which is based on the analytical Friedman method. The proposed model showed a good agreement between predicted and experimental data. This suggests that the curing kinetics of preceramic resins can be approximated using models that are well accepted for thermosetting polymers. This general strategy is key to manufacturing prepregs made of preceramic resins.

A designed flow-through microsystem for accurate and fast measurement of gas sensors at the ppb level

The characteristic parameters of gas sensors depend highly on the method used to evaluate them. This paper presents a flow-through microsystem for accurate and fast measurement of gas sensors, especially for the sensor with a fast response and high sensitivity at the ppb level. The microsystem consists of four parts, i.e. a dynamic multiple gas handling unit, a test gas preheater, an olive-like test chamber with an inner volume of 4.98 ml and data analysis apparatus. Thereinto, the multiple gas handling unit was constructed to meet the needs of dynamical sensor response tests, and the olive-like test chamber was designed based on the principles of low background interference and fast replacement of ambient conditions, which was optimized by computational fluid dynamics simulation and verified by its airtightness and applicable flow rate range. For a flow rate of 300 ml min−1, it can discern that the replacement time for the chamber ambient gas test was about 1 s. Finally, performance tests for two commercial sensors and one home-made sensor were carried out on this microsystem. The results showed that this system can serve as a means of highly sensitive (ppb level) and fast gas sensor evaluation, and the measured values obtained by this system can be considered to be closer to a sensor’s true values.

About Using Composite Materials when Restoring High-Resource Details with Application of Additive Technologies are Given

The process of restoration of high-resource parts of equipment for various purposes using AM technologies is considered. This method can save significantly the material of the formed coating, while providing the necessary efficiency in increasing the wear resistance of the restored parts. The causes of the leakage from the resulting coatings are residual stresses. Using a regression analysis apparatus, recommendations for the selection of technological modes from coatings are determined. The kinematic features of the recovery process are taken into account, dynamic relationships for determining stresses in the formed coating are determined. To find the volume of work, a worn surface is scanned. Further creation of the composite coating is carried out, taking into account the degree of wear from each section, separately. The influence of technological parameters on the micro-hardness and thickness of the applied composite coatings is investigated. Recommendations are given on the development of production technology, using 3-D printing of composite metal coatings, that can increase the wear resistance of high-resource parts.

Effect of magnetic field on elements segregation in electroslag ingot

In order to improve the production efficiency of electroslag remelting process and the solidification quality of electroslag ingot, a novel electroslag furnace with electromagnetic stirring was designed and the effects of external magnetic field and different electrical parameters on electroslag remelting process were studied. The distribution of carbon, chromium, phosphorus and compactness in electroslag ingot was analyzed through original position analysis apparatus. Results show that the external magnetic field accelerates the remelting of consumable electrode. Under the condition of remelting voltage of 34 V and current of 1500 A, the remelting rate of metal consumable electrode increases from 20 to 27 mm min−1 when the magnetic induction intensity of 62 × 10−4 and 108 × 10−4 T is applied. However, the remelting current decreases from 1500 to 1100 A under the condition of constant remelting rate and remelting voltage, thereby reducing the energy consumption. The effect of external magnetic field on the segregation of different elements in electroslag ingot is different. Under the experimental conditions, the carbon segregation is unremarkable, but the phosphorus segregation is improved when the electromagnetic force generated by the interaction between the external magnetic field and the remelting current is small. However, the excessive electromagnetic force aggravates the segregation of carbon and phosphorus. With the increase in electromagnetic force, the chromium segregation gradually increases.

Testing of the developed methodology of comparative analysis on the example of foreign and domestic documents of strategic planning in the sphere of energy security

Energy security is currently one of the key components of national security of any country. The object of this research is the basic documents of strategic planning of the European Union in sphere of ensuring energy security (Roadmap of the European Union &amp;ldquo;Final 10-year ETIP SNET R&amp;amp;I roadmap covering 2017-26&amp;rdquo;) in the context of comparative analysis of the existing approaches towards ensuring energy security of the Russian Federation (Energy Security Doctrine of the Russian Federation). The analysis is conducted from the perspective of comparison of two documents of strategic planning for the purpose of identification of threats and risks to the economic security. The subject of this research is the threats and risks to energy security of the countries, and thus, their national security. The scientific novelty consists in examination of the documents of strategic planning in the sphere of energy security using methodology of comparative analysis developed by the authors, which is based on the dynamic semantic network. In accordance with the aforementioned methodology, analysis is carried out on the structure of documents that encompasses the processes, the manifestation of which can be observed through objective and subjective methods of monitoring. The authors developed the expert analytical apparatus of comparative analysis, as well as the methodology for assessing the objectivity of comparative analysis. The developed methodology of comparative analysis is tested on the example of strategic planning documents in the sphere of energy security of the European Union and the Russian Federation. The conclusion is made on the need for further research of the methodological foundations of comparative analysis in order to detect the risks and threats to the economic security of the Russian Federation.

Modeling and forecasting the dynamics of wastewater contaminant pollution by manganese (II) ions

Modeling and forecasting of the dynamics of wastewater contaminant pollution by manganese (II) ions is carried out. The informational basis of the technique is statistical indicators of changing in the chemical composition of raw materials and change in the mass concentration of manganese (II) ions in river water used for washing the process gas obtained by calcining limestone. The purpose of the modeling is to detect the relationship between the independent values (change in the compounds of bivalent manganese in limestones as well as change in the mass concentration of manganese (II) ions in river water) and the dependent factor (change in the volume of wastewater contaminant pollution by manganese (II) ions. For modeling, it is proposed to use the mathematical apparatus of correlation and regression analysis, in particular multiple regression. According to calculations, there is a relationship between the change in the volume of environmental pollution and the parameters of the model, that is between the change in the amount of bivalent manganese compounds in the raw material and the change in the content of manganese (II) ions in river water.

Development of an auto compensation system in cyclic triaxial apparatus for liquefaction analysis

When performing cyclic triaxial tests, the connection process between loading piston and specimen could have significant effect on the test results. Tensile pre-shearing effect occurs during saturation and consolidation stages in screw-based configurations and compressive pre-shearing stress is induced while making the connection between loading piston and specimen in vacuum-based configurations. In order to overcome these technical problems, a special auto compensation system was incorporated into an existing cyclic triaxial apparatus, allowing: (1) no physical contact between loading piston and specimen to achieve an isotropic consolidation state, (2) the later connection between these two components to be easily accomplished with almost insignificant disturbance on the specimen (maximum 100 N in axial force). To assess the performance of this auto compensation system, two experiments of same dense reference sand specimens were respectively conducted, and the results were found to be similar, showing the good repeatability. Moreover, as compared with screw-based configuration, the test specimen did not undergo an adverse tensile pre-shearing. As a result, the test specimen became more resistant to cyclic mobility. On the contrary, as compared with another vacuum-based configuration (without auto compensation) well-documented in the literature, the obtained result was less stable since the employment of auto compensation system ensured that there was no beneficial compressive pre-shearing during the connection stage. The results obtained in this study showed the good performance of the developed auto compensation system in the triaxial test apparatus for liquefaction analysis.

Association of vitamin D nutritional status with body muscle mass in school-age children adolescents

Objective: To investigate the association between vitamin D nutritional status and the body muscle mass in children. Methods: Data were obtained from School-based Cardiovascular and Bone Health Promotion Program. In 2017, a total of 15 391 children aged 6-16 years in Beijing were selected through stratified cluster sampling in baseline survey. A follow-up investigation was conducted in 2019. The questionnaire survey and the detection of serum 25-hydroxyvitamin D [25(OH)D] level were conducted. The bioelectrical impedance analysis (BIA) apparatus was used to measure body muscle mass, and muscle mass index (MMI) was calculated. Multivariable linear models were used to analyze the association of vitamin D nutritional status with the baseline and follow-up MMI measures. Results: A total of 10 890 children aged (11.5±3.3) years(boys accounting for 49.6%) were included in the analysis. The average 25(OH)D level was (35.4±12.0) nmol/L, with an adequacy ratio of 11.1%. After multivariate linear regression adjustment for age, sex, body fat mass, smoking status, alcohol use status, dairy supplement, calcium supplement, physical activity, and pubertal development, no statistically significant association between vitamin D nutritional status and baseline MMI level was observed (P>0.05). For the follow-up MMI, the Z-score increased by 0.008 (P=0.058) for per 10 nmol/L increase in 25(OH)D, which were 0.002 (P=0.815) and 0.037 (P=0.031) higher in children with insufficient and adequate vitamin D than those with vitamin D deficiency, respectively (P for trend =0.089). Subgroup analysis showed that in the normal BMI group, for per 10 nmol/L increase in 25 (OH) D, the MMI at baseline survey and MMI Z-score at follow-up of children with adequate vitamin D and increased by 0.019 and 0.014, respectively (both P<0.05). Conclusions: Vitamin D nutritional status was related to muscle mass in children, and children with adequate vitamin D tended to obtain higher MMI. Children and adolescents are encouraged to maintain sufficient vitamin D levels, strengthen nutrition and exercise to promote body health.