Modeling in the OMNET ++ environment of connection processes in Wi-Fi networks

Предложен подход к разработке в среде OMNeT++ INET простейшей имитационной модели инфраструктурного режима функционирования Wi-Fi сети, который позволяет проводить подробный анализ функционирования таких сетей, а также строить и анализировать временные диаграммы взаимодействия всех элементов сети. Разработанную модель можно использовать как базовую для формирования более сложных моделей с произвольным числом мобильных клиентов, позволяя определять необходимое количество точек доступа и мест их размещения для обеспечения полноценного покрытия зоны мониторинга лесной территории. An approach to the development in the OMNeT ++ INET environment of the simplest simulation model of the infrastructure mode of Wi-Fi network operation is proposed, which allows a detailed analysis of the functioning of such networks, as well as to build and analyze the time diagram of the interaction of all network elements. The developed model can be used as a base for the formation of more complex models with an arbitrary number of mobile clients, allowing you to determine the required number of access points and their locations to ensure full coverage of the monitoring area of the forest area.

Magnetic flux transport in the photosphere of the Sun

<p>On the basis of the synoptic maps of the photospheric magnetic field obtained by the National Solar Observatory Kitt Peak for 1978-2016, a latitude-time diagram of the magnetic field was built. When averaging intensity values over the heliolongitude, the magnetic field sign was taken into account. In order to consider the characteristics of the distribution of weak magnetic fields an upper limit of 5 G was set.</p><p>The latitude-time diagram clearly shows inclined bands corresponding to positive and negative polarity magnetic flows drifting towards the poles of the Sun. Two groups of flows are observed: 1. Relatively narrow bands, with alternating polarity, beginning near the equator and reaching almost the poles of the Sun. Along the time axis, the flow length of one polarity is on the order of 1-2 years; 2. short powerful flows, 3-4.5 years wide, propagating from the spot zone to the poles. These flows reach the poles simultaneously with the begin of the polar field reversal, apparently representing  the so-called “Rush to the Poles” phenomenon.</p><p>The pattern of magnetic field transport is significantly different for the northern and southern hemispheres. Alternating flows of positive and negative polarities most clearly appear in the southern hemisphere during periods of positive polarity of the southern polar field. For the northern hemisphere the picture is much less clear but for individual time intervals alternating flows of opposite polarities can be traced. The slopes of magnetic flux bands allow us to estimate the rate of meridional drift of magnetic fields, which was slightly different for the two hemispheres: V = (16±2) m/s for the southern hemisphere and V = (21±4) m/s for the northern hemisphere. The results obtained indicate that the distribution of weak magnetic fields over the surface of the Sun has a complex structure that is different for the two hemispheres and varies from cycle to cycle.</p>

Simulations and Modeling of Intermediate Luminosity Optical Transients and Supernova Impostors

Intermediate-luminosity-optical-transients (ILOTs) are stellar outbursts with luminosity between those of classical novae and supernovae. They are divided into a number of sub-groups depending on the erupting progenitor and the properties of the eruption. Many of the ILOTs sit on the slanted Optical Transient Stripe (OTS) in the Energy-Time Diagram (ETD) that shows their total energy vs. duration of their eruption. We describe the different kinds of ILOTs that populate the OTS and other parts of the ETD. We also stand on similarities between Planetary Nebulae (PN) to ILOTs, and suggest that some PNe were formed in an ILOT event. The high energy part of the OTS is reserved to the supernova impostors -- giant eruption of very massive stars. We show results of 3D hydrodynamical simulations of supernova impostors that expose the mechanism behind these giant eruptions, and present new models for recent ILOTs. We stand on the connection between different kinds of ILOTs, and suggest that they are powered by a similar source of energy -- gravitational energy released by mass transfer.

Identification and quantification of human microcirculatory leukocytes using handheld video microscopes at the bedside

Leukocyte recruitment and adhesion to the endothelium are hallmarks of systemic inflammation that manifest in a wide range of diseases. At present, no method is available to directly measure leukocyte kinetics at the bedside. In this study, we validate a new method to identify and quantify microcirculatory leukocytes observed by handheld vital microscopy (HVM) using space-time diagram (STD) analysis. Video clips ( n = 59) containing one capillary-postcapillary venule unit where leukocytes could be observed emanating from a capillary into a venule in cardiac surgery patients ( n = 20) were included. STD analysis and manual counting were used to quantify the number of leukocytes (total, rolling, and nonrolling). Pearson’s correlation and Bland-Altman analysis were used to determine agreement between the STDs and manual counting. For reproducibility, intra- and interobserver coefficients of variation (CVs) were assessed. Leukocyte (rolling and nonrolling) and red blood cell velocities were assessed. The STDs and manual counting procedures for the quantification of rolling leukocytes showed good agreement ( r = 0.8197, P < 0.0001), with a Bland-Altman analysis mean difference of −0.0 (−6.56; 6.56). The overall intraobserver CV for the STD method was 1.5%. The overall interobserver CVs for the STD and the manual method were 5.6% and 9.4%, respectively. The nonrolling velocity was significantly higher than the rolling velocity (812 ± 519 µm/s vs. 201 ± 149 µm/s, P = 0.001). STD results agreed with the manual counting procedure results, had a better reproducibility, and could assess the leukocyte velocity. STD analysis using bedside HVM imaging presented a new methodology for quantifying leukocyte kinetics and functions in the microcirculation. NEW & NOTEWORTHY In this study, we introduce space-time diagram analysis of sublingual microcirculation imaging using handheld vital microscopy to identify and quantify the presence and kinetics of human microcirculatory leukocytes. We validated the methodology by choosing anatomical units consisting of a capillary connected to a venule, which allowed precise identification of leukocytes.

The Story of the Hovmöller Diagram: An (Almost) Eyewitness Account

The Hovmöller diagram or the trough–ridge diagram, a simple longitude–time diagram, was designed in 1948 by Ernest Hovmöller (1912–2008) to help understand certain features in the dynamics of the atmosphere, in particular the “downstream development” phenomenon. Originally depicting the 500-hPa geopotential, today many other parameters are used, and Hovmöller diagrams have during the last 25 years found a rapidly increasing use in a wide range of atmospheric research.

Occurrence of synchronized flow due to overtaking strategy in the Nagel–Schreckenberg model

The Nagel–Schreckenberg model with overtaking strategy (NSOS) is proposed, and numerical simulations are performed for both closed and open boundary conditions. The fundamental diagram, space-time diagram and spatial-temporal distribution of speed are investigated. In order to identify the synchronized flow state, both the correlation functions (autocorrelation and cross-correlation) and the one-minute average flow rate versus density diagram are studied. All the results verify that synchronized flow does occur in our model.

A two-lane cellular automaton traffic flow model with the influence of driver, vehicle and road

On the basis of one-lane comfortable driving model, this paper established a two-lane traffic cellular automata model, which improves the slow randomization effected by brake light. Considering the driver psychological characteristics and mixed traffic, we studied the lateral influence between vehicles on adjacent lanes. Through computer simulation, the space-time diagram and the fundamental figure under different conditions are obtained. The study found that aggressive driver makes a slight congestion in low-density traffic and improves the capacity of high-density traffic, when the density exceeds 20[Formula: see text]pcu/km the more aggressive drivers the greater the flow, when the density below 40[Formula: see text]pcu/km driver character makes an effect, the more cautious driver, the lower the flow. The ratio of big cars has the same effect as the ratio of aggressive drivers. Brake lights have the greatest impact on traffic flow and when the density exceeds 10[Formula: see text]pcu/km the traffic flow fluctuates. Under periodic boundary conditions, the disturbance of road length on traffic is minimal. The lateral influence only play a limited role in the medium-density conditions, and only affect the average speed of traffic at low density.