A mathematical model of the error of the navigational accelerometer caused by the nonlinearity of its metrological model, taking into account the influence of vibration, was developed. The method of experimental estimation of the vibration error based on the developed model was proposed. The main idea of the method is to evaluate parameters of the developed model during static tests in the terrestrial gravitational field and to calculate error according to the specific vibration characteristics – the amplitude in the case of harmonic vibration profile or the frequency band and the power spectral density in the case of random vibration. The effectiveness of the proposed method has been tested using three types of navigation accelerometers in comparison with the results of classical dynamic testing in various vibration conditions (harmonic, white noise, etc.).
In traditional air taxi model, flight route and timing are assigned to every order individually, resulting in minimum utilization of seats, maximum number of empty legs and elevated price levels. Sharing flights, when possible, allow decreasing number of empty seats and distributing cost of flight among customers. Challenges to overcome are varying timing needs of customers and volatility of demand. This article investigates possibilities of synchronizing passenger orders. The proposed passenger pooling model replaces specific flight timing on order with constraints: latest arrival and earliest departure to provide room for coordination of orders, backed by web-based ICT. Theoretical test cases calculations verify the concept and compare it with traditional full on-demand and scheduled operations.
This work is about the effect of fine aggregate properties on the physicomechanical characteristics of hardened mortars. The results indicated that the increase in grain-size of fine aggregate increases the bulk density of hardened mortars. The strength of mortars including limestone fine aggregate is higher than that of the silica-sand. Regardless of the aggregate origin, the strength of the mortars with well-graded fine aggregate for all grain-size is greater than of with uniform fine aggregate. This indicates that grading of fine aggregate increases the strength, while uniformity decreases it.
The strength of mortars with well-graded fine aggregate increases as the grain-size increases. Regardless of the aggregate origin, the strength of mortars with uniform fine aggregate increases with increasing grain-size until the grain-size range of 425-1000 µm, but after this range it decreases with increasing grain-size. The thermal conductivity increases with the increase in the grain-size. Notedly, the relationship between thermal conductivity and maximum grain-size of well-graded fine aggregate has a very strong positive correlation. Further, the thermal conductivity value for mortars formed with uniform fine limestone aggregate is minimum at the grain-size range of 425-1000 µm, while it has greatest values close together from this grain-size range
The multitude of concepts and methods of management and control related to the word “visual” in the area of production and quality management may cause difficulties with their perception, proper understanding and use of these terms by researchers from various backgrounds (not necessarily related to production) and countries, including Poland. In particular, the noticed inaccuracies in the use of terms with the word “visual” concern such terms as visual: management, control, inspection, and testing, where, for example, in the Polish language the first three different terms in English are named with the same phrase, which sometimes causes some confusion. The aim of the article was an attempt to distinguish, sometimes “troublesome” definitions, to indicate the area of their application, to define possible relations between them, which is a peculiar novelty. The article is an analysis of the literature related to these concepts, systematizes the types of visual concepts and methods in the area of production and quality. It defines in what context the indicated terms should be used by researchers and what is the relationship between them, and under what conditions they can be used separately or jointly. The article is an attempt to indicating and analysis of the interrelation between concepts in which the word “visual” appears concerning production practice. Concepts visual: management, control, inspection, and testing, as the author proves in the article, they should be translated into English with due diligence, due to the differences between them. It has been shown that there is a strong relationship between type definition pairs as visual management & visual control and visual inspection & visual testing, where it is not a mistake to use them interchangeably, and cases, where all these concepts can intertwine, are also given.
The parameters of high-grade steel are influenced by a combination of factors, including chemical composition and production technology. The impurity content is also a key determinant of the quality of high-grade steel. Inclusions may also play an important role, subject to their type and shape. Inclusions may increase the strength of steel by inhibiting the development of micro-cracks. The analyzed material was one grade of medium-carbon structural steel. The study was performed on 6 heats produced in an industrial plant in 140 ton electric furnaces. The experimental variants were compared in view of the five heat treatment options. The results were presented to account for the correlations between the fatigue strength coefficient during rotary bending, the diameter of and spacing between impurities. The relationship between the fatigue strength and hardness of high-grade steel vs. the quotient of the diameter of impurities and the spacing between impurities was determined. The proposed equations contribute to the existing knowledge base of practices impact of impurities with various diameters and spacing between non-metallic inclusion on fatigue strength.
In the recent years, additive manufacturing became an interesting topic in many fields due to the ease of manufacturing complex objects. However, it is impossible to determine the mechanical properties of any additive manufacturing parts without testing them. In this work, the mechanical properties with focus on ultimate tensile strength and modulus of elasticity of 3D printed acrylonitrile butadi-ene styrene (ABS) specimens were investigated. The tensile tests were carried using Zwick Z005 loading machine with a capacity of 5KN according to the American Society for Testing and Materials (ASTM) D638 standard test methods for tensile properties of plastics. The aim of this study is to investigate the influence of printing direction on the mechanical properties of the printed specimens. Thus, for each printing direction ( and ), five specimens were printed. Tensile testing of the 3D printed ABS specimens showed that the printing direction made the strongest specimen at an ultimate tensile strength of 22 MPa while at printing direction it showed 12 MPa. No influence on the modulus of elasticity was noticed. The experimental results are presented in the manuscript.
Numerical studies on detonation wave propagation in rotating detonation engine and its propulsive performance with one- and multi-step chemistries of a hydrogen-based mixture are presented. The computational codes were developed based on the three-dimensional Euler equations coupled with source terms that incorporate high-temperature chemical reactions. The governing equations were discretized using Roe scheme-based finite volume method for spatial terms and second-order Runge-Kutta method for temporal terms. One-dimensional detonation simulations with one- and multi-step chemistries of a hydrogen-air mixture were performed to verify the computational codes and chemical mechanisms. In two-dimensional simulations, detonation waves rotating in a rectangular chamber were investigated to understand its flowfield characteristics, where the detailed flowfield structure observed in the experiments was successfully captured. Three-dimensional simulations of two-waved rotating detonation engine with an annular chamber were performed to evaluate its propulsive performance in the form of thrust and specific impulse. It was shown that rotating detonation engine produced constant thrust after the flowfield in the chamber was stabilized, which is a major difference from pulse detonation engine that generates repetitive and intermittent thrust.
Hard machining is a process which has become highly recommended in manufacturing industry to replace grinding and perform production. The important technological parameters that determine this process are tool wear, machined surface roughness, cutting force and morphology of the removed chip. In this work, an attempt has been made to analyse the morphology and form of chip removed during turning of hardened steel AISI 1045 (40HRC) with mixed ceramic tool type CC650. Using a Taguchi plan L9, whose factors are cutting speed and feed rate with three levels for each. Macroscopic and microscopic results of chip morphology were correlated with these two cutting parameters additional to surface roughness. Sufficient experimental results were obtained using the mixed ceramic tool when turning of hardened steel AISI 1045 (40HRC) at high cutting speeds. Roughness of machined surface confirmed that it is influenced by feed rate. Chips show a sawtooth shape for all combinations of the experimental plan used. The chip form changed with cutting parameters variation and given an important indicator of suraface quality for industriel. Having the indicators on the surface quality from simple control of chip without stopping machining give an important advantage in order to maximize production and reduce costs.
In the past, it was enough for the airport to have a runway and a modest terminal. The development of air traffic has also increased customer requirements (passengers, airlines, etc.), which has affected the need for airport infrastructure development. Throughout the world, passenger terminals have been built, many of which, according to architectural solutions, represent works of art. The design and functionality are tailored in such a way as to enable longer stay and meet the requirements of passengers and other users. Content and concept offer solutions that airport operators provide for additional revenue. One part of the content and service is offered in passenger terminal buildings, while the other part is provided outside them, whether in or outside the airport. Part of this content is offered by Airport City (AC). AC phenomenon represents the integration of infrastructure, superstructures, information and operations. It represents a part of the Supply Chain (SC) and usually includes facilities such as: passenger terminals, runways and other airport activities such as: ground handling, logistics, office space, shops, hotels, etc. In this paper, authors use a method of systems theory, a modeling method and a comparative method as a general and some specific scientific methods of cognition, to researching the problem to which different AC models and their structure can contribute to the optimal SC flow as its essential part and bring the results of the AC phenomenon as a part of the SC.