The protective structure is designed to protect the live force against the impact of a shock wave and projectiles, it cannot be diagnosed by the destructive method which devalues the protective ...structure by sampling. The authors are looking for a combination of suitable non-destructive technology (NDT) methods that would be used in the future to prove the degree of damage to cement-based protective structures after an explosion. This article represents the first part of an experiment designed to verify the applicability of NDT methods, to evaluate the degree of damage of the protective structure in the field. The experiment consists of three parts. The first part is a laboratory verification of the initial material characteristics of the materials used. The first test set of structural elements is made of steel fiber-reinforced concrete. The elements are evaluated using NDT methods and for comparison by destructive laboratory methods. The second part is the impact of structures using explosion and evaluation of the condition of structures using NDT methods in the field. The last part is used to verify the results of the NDT method, which ensures the residual strength of the structure in the laboratory and try to find the relationship between changes in the results of NDT methods and the residual strength. Radiography was included in the introductory and concluding parts of the experiment to verify the results. Although this method is not suitable for using in-situ, it is the only standardized method of the NDT methods used.
Fortification structures, both military and civilian, are designed to resist a blast explosion to some extent. Their technical condition after a blast load must be assessed in a fast and reliable way ...to enable the users’ decision about the future use of the structure. Preferably, for the assessment of the protective structure, the non-destructive testing method should be used. To assess the suitability of ultrasound testing method for fortification structures built from steel fiber reinforced concrete, an investigation in a laboratory and in situ was conducted, together with numerical simulation and statistical evaluation. The numerical simulation of the blast load of a steel fiber reinforced concrete slab was conducted using multiphysics simulation software with the aim to verify basic parameters of the field experiment. During the field tests, several slabs were loaded by plastic explosive and changes in the structure of the slabs, before and after the blast load, were examined using the ultrasound pass-through method. After the field tests, the slabs were subjected to a destructive laboratory test to determine their residual strength. Subsequently, the data sets obtained from the measurements were tested using functional data analysis. The results from the ultrasound pulse method show that specimens after a dynamic blast load can in some cases increase the strength of their cement matrix.
This article presents the Ant Colony Optimization algorithm to solve the Travelling Salesman Problem. The proposed algorithm implements three novel techniques to enhance the overall performance, ...lower the execution time and reduce the negative effects particularly connected with ACO-based methods such as falling into a local optimum and issues with settings of control parameters for different instances. These techniques include (a) the node clustering concept where transition nodes are organised in a set of clusters, (b) adaptive pheromone evaporation controlled dynamically based on the information entropy and (c) the formulation of the new termination condition based on the diversity of solutions in population. To verify the effectiveness of the proposed principles, a number of experiments were conducted using 30 benchmark instances (ranging from 51 to 2,392 nodes with various nodes topologies) taken from the well-known TSPLIB benchmarks and the results are compared with several state-of-the-art ACO-based methods; the proposed algorithm outperforms these rival methods in most cases. The impact of the novel techniques on the behaviour of the algorithm is thoroughly analysed and discussed in respect to the overall performance, execution time and convergence.
The aim of this article is to systematically review articles and annual reports concerning young peoples' physical activity (PA) and linking this to considerations of the state and national defense.
...A systematic search of the literature included an analysis of publications accessible in global databases and other available books, student papers, and projects. The articles and reports were categorized based on year of publication, methods used, age of respondents, sample size, country, and digital object identifier (DOI).
The result of this search is an overview of the extent and manner in which the worldwide scientific community is addressing the current situation and the long-term development of the physical fitness of adolescents. This publication also maps to what extent professional publications and articles are addressing PA from the perspective of the needs of armies and armed forces of various countries around the world.
The article provides a systematic overview of methods used to measure PA, and an overview of articles dealing with assessing PA. The examined articles indicate that from the perspective of not only national defense, but also health and overall quality of life, in particular, we need initiatives to encourage and motivate young people to increase their everyday PA. The research therefore also includes an overview of factors that may considerably influence PA. The results ascertained in this publication will be used,
. for investigating a longitudinal defense research project of the Ministry of Defense of the Czech Republic in which the authors are participating.
This paper is focused on furniture firms in the Czech Republic during the period 2005–2012, which covers the year of the crisis. The aim was to assess the given economic situation of the ...manufacturing businesses comparing some of the economic indicators such as tangible fixed assets, revenue from own production and services, pre-tax profit and labor costs. The study was conducted in the Czech Republic using the data provided by the Czech Statistical Office. Results for the specified period and selected groups of micro furniture companies are shown; dependence of economic indicators within the given time period is also analyzed. The analysis has shown that the smallest of the firms were least affected by the economic crisis; moreover, the medium-sized of the companies exhibit tangible assets growth and certain degree of inertia in years 2008 and 2009. Finally, possibilities how the micro furniture companies could proceed when purchasing new technologies are outlined.
•Classification test results of the condition of tool blades on a multi-tool head were presented.•Signals of the mining power by sharp and blunt mining tools were recorded.•The observed data were ...transformed into the probability density functions for two groups of ripping tools.•The probability density functions differ in almost all tested power ranges.
In the article, the ripping tools wear in the process of concrete cutting is investigated. Data were observed as signals of mining power of sharp and blunt tools. Using nonparametric estimates combined with the recent approach of a functional data analysis, it is possible to statistically distinguish between the two knife states in terms of their wear.
•Laminate composites reinforced by natural fibers and their reliability measures.•Complex reliability assessment of real testing records data on laminate composites.•Novel approach combining weighted ...regression, diffusion process and kernel estimates.•Modeling the hazard function using cooperating parametric and non-parametric models.•Practical applicability of suggested results on composites dependability performance.
Numerous technical systems are modeled to identify dependability and safety measures. The modeling approach here is a real data driven approach. We work with the results obtained by assessing a progressive material—natural fibers reinforced laminate composites. The knowledge of certain properties, namely reliability performance, has not been sufficiently studied. Our approaches include the Wiener diffusion process, parametric and non-parametric estimations and mainly a hazard function which is estimated parametrically and non-parametrically by kernel estimators. We also demonstrate the significance between parametric and non-parametric estimations, the way they influence the selection of a resulting model and prospective practical applicability.
Means of transport are an important part of today’s cities. Bus transport in particular is considered to be a reliable mode of transport. In cooperation with a city’s transport company, we process in ...this article data collected from two fleets of buses. The data records are related to the failures of individual bus subsystems. We focus on the study of data from engine and brake subsystems, the consequences of failures of which are the most serious in relation to traffic safety. The data are seemingly austere, as the records only contain information such as “operating/fault” during a given month (no known causes, mechanisms, or other more precise time information about the failure). On the basis of such sparse data, however, it is still possible to estimate the trend or predict the development of certain measures over time. For the study and subsequent prediction, we used approaches based on state space models. Specifically, we worked with a linear trend model and a periodic component model. For both fleets of buses, we have also analyzed what the respective model and its prediction could look like if we knew selected and more detailed time information about the failures. This model therefore provides a general idea of the rate of occurrence of failure trend development, expected number of failures within single months, and respective bus subsystem failure occurrence forecasts. Based on this information, operators and entrepreneurs can rationalize the processes related to operations, maintenance, and repair planning.
Kernel density estimations of circular data are an effective type of nonparametric estimation. The performance of these estimations depends significantly on a smoothing parameter referred to as ...bandwidth. Selecting suitable bandwidths for these types of estimation pose fundamental challenges, therefore fixed bandwidth selectors are often the initial choice. The study investigates common bandwidth selection methods and proposes novel methods which adopt the idea from the linear case. The attention is also paid to variable bandwidth selection. Using simulations which incorporate a range of circular distributions that exhibit multimodality, peakedness and skewness, the proposed methods were evaluated and then compared with other bandwidth selectors to determine their potential advantages. Two real datasets, one containing animal movements and the other wind direction data, were applied to illustrate the utility of the proposed methods.
•Contribution to description and modelling of Li-ion battery (LIB) behaviour.•Improved numerical and stochastic model of the LIB discharge course.•Novel approach to estimating the first hitting time ...distribution of LIB.•Critical capacity threshold estimated using kernel density estimation.•Numerical quantiles of the guaranteed capability region of LIB are provided.
Requirements for stable and reliable power sources are almost inseparable part of technical specifications. In this article, we deal with monitoring the capability of Li-ion batteries. We want to determine the time period for which their function will be guaranteed in the course of operation in different operational conditions. These conditions are represented by distinct temperature levels and various discharge currents. Capability monitoring is performed experimentally and mathematically. Within the experiments a decrease in battery voltage is monitored at different ambient temperature levels and discharge currents. Then, discharge courses are modelled and simulated using Wiener processes to obtain a set of time points when the battery voltage drops below a critical value. The first hitting time, i.e., a guaranteed period of an up-state with respect both to given operating conditions and critical threshold, is assessed by non-parametric methods, namely by the kernel density estimation. The results of testing, modelling and simulation provide an interesting picture about Li-ion battery operational behaviour. The outcomes acquired here are applicable in all the technical areas where Li-ion batteries are used and where guaranteed time of the battery safe and reliable operation in various climatic conditions is required.
PDF
