We define data analyses to monitor a change in R, the average number of secondary cases caused by a typical infected individual. The input dataset consists of incident cases partitioned into ...outbreaks, each initiated from a single index case. We split the input dataset into two successive subsets, to evaluate two successive R values, according to the Bayesian paradigm. We used the Bayes factor between the model with two different R values and that with a single R value to justify that the change in R is statistically significant. We validated our approach using simulated data, generated using known R. In particular, we found that claiming two distinct R values may depend significantly on the number of outbreaks. We then reanalyzed data previously studied by Jansen et al. Jansen et al. Science 301 (5634), 804, concerning the effective reproduction number for measles in the UK, during 1995-2002. Our analyses showed that the 1995-2002 dataset should be divided into two separate subsets for the periods 1995-1998 and 1999-2002. In contrast, Jansen et al. take this splitting point as input of their analysis. Our estimated effective reproduction numbers R are in good agreement with those found by Jansen et al. In conclusion, our methodology for detecting temporal changes in R using outbreak-size data worked satisfactorily with both simulated and real-world data. The methodology may be used for updating R in real time, as surveillance outbreak data become available.
Modelling the extraneous heat exchange of spacecraft using solar radiation simulation facility and simulators of the planetary radiation field in several cases is an intractable problem not only in ...technical but also in methodological terms. For some technical reasons, solar radiation simulator is stationary. Consequently, to reproduce a possible change in the orientation of the test object relative to the solar radiation flux, it is necessary to equip the thermal vacuum unit with devices that allow the test object to be rotated at least about two axes. In this paper, a mathematical model and a method for solving the problem of heat transfer in a multilayer structure of screen-vacuum thermal insulation under the influence of solar radiation is proposed. A method is proposed for the numerical solution of a normal system of nonlinear differential equations using the linearisation of nonlinear terms. Various results of numerical modelling were obtained, which indicate the adequacy of the proposed mathematical model. It has been revealed that high-inertia thermal insulation of sufficient thickness is required to stabilise the thermal state inside the spacecraft.
The boundary layer of the air flow blowing the surfaces of the brake mechanism prevents heat transfer from heated surfaces. The obtained analytical dependences of the velocities` and temperatures` ...distribution in the boundary layer represent the field of the boundary layer as a multilayer structural model, the laws of change in the velocities and temperatures of the air flow blowing depend on various sub layers of the boundary layer. According to these analytical dependencies, a thermal model “ventilated brake disc - external condition” was developed. The thicknesses of the boundary layers of the air flow blowing on the various surfaces of the brake disc are determined by various processes. For the working surfaces of the brake disc, the determining criterion is the thickness of the diffusion layer, while for the surfaces of the ventilation apparatus, the criterion for estimating the thickness of the boundary layer is thermal processes. In future, the developed thermal model “ventilated brake disc – external condition” should be the basis for thermal calculations in designing disc-shoe type brake mechanisms.
The study aims to compare the characteristics of the moment-inertial schemes of two aircrafts – a mainline aircraft of a normal aerodynamic scheme and an aircraft made according to the flying wing ...scheme, to improve their flight performance. The study uses the method of successive approximations using relative masses (when determining m0), the formula of A. Mozhaisky, an artificial method consisting of the layout of the aircraft oriented to the virtual center of mass. Design studies at the modern level of scientific and technical development have confirmed the relevance of using the proposed methods of forming a moment-inertial appearance for promising long-haul aircraft of large passenger capacity.
Friction Stir Welding (FSW) was utilized to butt−join 2024–T4 aluminum alloy plates of 1.9 mm thickness, using tools with conical and tapered hexagonal probe profiles. The characteristic effects of ...FSW using tools with tapered hexagonal probe profiles include an increase in the heat input and a significant modification of material flow, which have a positive effect on the metallurgical characteristics and mechanical performance of the weld. The differences in mechanical properties were interpreted through macrostructural changes and mechanical properties of the welded joints, which were supported by numerical simulation results on temperature distribution and material flow. The material flow resulting from the tapered hexagonal probe was more complicated than that of the conical probe. If in the first case, the dynamic viscosity and strain rate are homogeneously distributed around the probe, but in the case of the tapered hexagonal probe tool, the zones with maximum values of strain rates and minimum values of dynamic viscosity are located along the six tapered edges of the probe.
Atomic force microscopy (AFM) has now become a powerful technique for investigating on a molecular level, surface forces, nanomechanical properties of deformable particles, biomolecular interactions, ...kinetics, and dynamic processes. This paper specifically focuses on the analysis of AFM force curves collected on biological systems, in particular, bacteria. The goal is to provide fully automated tools to achieve theoretical interpretation of force curves on the basis of adequate, available physical models. In this respect, we propose two algorithms, one for the processing of approach force curves and another for the quantitative analysis of retraction force curves. In the former, electrostatic interactions prior to contact between AFM probe and bacterium are accounted for and mechanical interactions operating after contact are described in terms of Hertz-Hooke formalism. Retraction force curves are analyzed on the basis of the Freely Jointed Chain model. For both algorithms, the quantitative reconstruction of force curves is based on the robust detection of critical points (jumps, changes of slope or changes of curvature) which mark the transitions between the various relevant interactions taking place between the AFM tip and the studied sample during approach and retraction. Once the key regions of separation distance and indentation are detected, the physical parameters describing the relevant interactions operating in these regions are extracted making use of regression procedure for fitting experiments to theory. The flexibility, accuracy and strength of the algorithms are illustrated with the processing of two force-volume images, which collect a large set of approach and retraction curves measured on a single biological surface. For each force-volume image, several maps are generated, representing the spatial distribution of the searched physical parameters as estimated for each pixel of the force-volume image.
Risk management is a core of Safety Management System (SMS) of airline. It works in high level of uncertainty and is dealing with variety of information which is fuzzy in nature. So the fuzzy set ...theory (FST) is natural instrument that should be applied for solving problems that SMS faced with. The article provides a brief overview of examples of the use of FST elements in safety risk management, presents the results of processing expert surveys using fuzzy methods, and describes the developed practical method for assessing the index of probability of an aviation event based on the fuzzy inference technology.
The objective of this study was to develop the technology of butt friction stir welding (FSW) for Al–Cu–Li alloy sheets of 1.4 mm thick after hot rolling and subsequent quenching. This initial state ...of the alloy was chosen in order to provide heat treatment of the received joints after FSW. The TEM observation was performed for the base material and different zones of the joints in order to determine the precipitates and dislocations density and distributions. The grain size in the stir zone (SZ) was increased; the width of the softened region was narrowed down with the decreasing of linear energy. The differences in mechanical properties of the FSWed joints were explained by analysis of microstructural changes and tensile fracture surfaces, supported by the results of the numerical simulation of the temperature distribution and material flow. The fracture of the high linear energy FSW joints occurred in the SZ along the remnant oxide line (ROL), while the low linear energy FSW joint raptured in the transition between HAZ and TMAZ on the AS, where lower hardness value was detected.
Methods for the discovery of hidden structures of high-dimensional binary data are one of the most important challenges facing the community of machine learning researchers. There are many approaches ...in the literature that try to solve this hitherto rather ill-defined task. In the present study, we propose a general generative model of binary data for Boolean Factor Analysis and introduce two new Expectation-Maximization Boolean Factor Analysis algorithms which maximize the likelihood of a Boolean Factor Analysis solution. To show the maturity of our solutions we propose an informational measure of Boolean Factor Analysis efficiency. Using the so-called bars problem benchmark, we compare the efficiencies of the proposed algorithms to that of Dendritic Inhibition Neural Network, Maximal Causes Analysis, and Boolean Matrix Factorization. Last mentioned methods were taken as related methods as they are supposed to be the most efficient in bars problem benchmark. Then we discuss the peculiarities of the two methods we proposed and the three related methods in performing Boolean Factor Analysis.
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