On the relationship of aeolian relief, microrelief and wind direction with the concentration of dust aerosol in the near-surface layer

<p>Saltations, secondary knock-out of particles, and their rolling over the surface in the abrasion process are the main source of micron- and submicron-sized particles near the surface [1]. Zones with different aerosol generation rates and wiping dynamics emerge around growing aeolian structures [3,4]. On the leeward slope, larger particles remain in the embedding zone and abrasion is less active. On the windward slope, fractions of smaller size accumulate in the zone of cascade capture of layers by wind [2], and abrasion is predominant.</p><p> </p><p>The occurrence of aeolian forms varies in time depending on their height. Three areas are considered: 1-3 m, 1-3 cm, <1 cm. The effect of changes in wind direction at intervals of a few hours changes the length of zones near aeolian structures. Thus, the cascade trapping zone expands and the accumulation zone narrows. Aeolian microstructures on the surface of the windward slope decrease the length of the cascade capture zone, leaving structures with a height > 1 cm almost unchanged.</p><p> </p><p>We consider a sample of data from summer field measurements obtained in the evening with close values of air temperature (30-32°C) and wind speeds (6.1-6.5 m/s). Observations were made on a perennial patch of unfixed sands about 1.5 km long and 200-300 m wide at 5 km to the west of Naryn Khuduk settlement (Kalmykia, 2010-2020). The lines of dune ridges for this area extend approximately in the latitudinal direction.</p><p> </p><p>Based on the empirical functions of aerosol size and mass distribution, the classification related to the wind direction in relation to the line of windward and leeward slopes connection was obtained. When the wind direction changes from frontal to tangential along the slopes, mass concentrations of coarse aerosol fraction increase. This can be related to the processes of chipping for newly involved large particles from the layers of the leeward slope setting zone. The phenomenon is also illustrated by the observed emergence on the surface of a ripple with a ridge spacing of 10-30 cm during the next day of a micro-ridge with a period of 1-2 cm. For the windward slope line change model [5], it was obtained that the fraction of detached particles decreases with the growth of new structures. The presence of aeolian ripples [6] and larger particles generally reduces the fraction of particles moving in the wind flow.  There is weakening of wiping intensity at collision and reduction of concentration of submicron particles as a result, as compared to the case of absence of developed microrelief. The type of aerosol distribution function is influenced by the size of the embedding and cascade trapping zones and the composition of the layer of particles involved in collisions and displacements near the surface.</p><p>The study was supported by the Russian Science Foundation project 20-17-00214.</p><p> </p><p>1.Houser C.A., Nickling W.G. Sedimentology. 48(2). 255,. (2001)</p><p>2.Chepil W.S. Soil Science  60(4) 305.(1945)</p><p>3.Anderson R. Sedimentology 34, 943 (1987).</p><p>4.Hoyle R., Woods A. Phys. Rev. E 56, 6861 (1997).</p><p>5.Malinovskaya E.A. Izvestiya. Atmospheric and Oceanic Physics 55(2) 218 (2019)</p><p>6. Malinovskaya E. et al. EGU2019-3693-1 (2019)</p><p> </p>

External noise characteristics analysis of straddle-type monorail transit based on field tests

Compared with the traditional urban rail transit system, the running mechanism, line laying structure and operating environment condition of straddle-type monorail transit are unique. Therefore, external noise radiated by the train has its own characteristics when the train is running. In order to improve the acoustic quality and explore the methods of noise reduction, it is necessary to carry out field test and understand its radiation characteristics. In this study, typical running lines of straddle-type monorail transit are selected for multi-state and multi-site field tests of external noise of the running train. The test conditions include straight line running state, curve line running state, slope line running state, entry and exit station state. The obtained time data are post-processed in timefrequency domain, and then the radiation characteristics of external noise are analyzed in detail. The time domain characteristic is mainly discussed based on the overall level of external noise of the running train. In frequency domain, the contributions of the sound pressure energy (CSPE) of 1/3 octave bands under each running state of the train are analyzed, and the effects of straddle-type monorail traffic noise and urban road noise on urban transportation noise are evaluated using energy contribution analysis method. Finally, the main noise sources are briefly identified and analyzed. The research results will be helpful to provide meaningful reference for noise reduction and control.

Assessment of Climate Variability Trends in Nasarawa State, Nigeria

Changing global climate has emerged as one of the greatest environmental problems of mankind in the 21st century. However, there is still a dearth of information regarding the trends and patterns of climate variables at local and specific levels. It is against this background that this paper assessed climate variability trends in Nasarawa State, Nigeria over 21 years’ period (1997 – 2017). Daily data on climate variables for the State was obtained from the Nigerian Meteorological Agency and analysed using the linear trend function in Microsoft Excel. Pattern and course of the variables’ trend were determined using the trend/slope line and the trend equation. Out of the six investigated climatic parameters; maximum temperature, minimum temperature, total annual rainfall and dew points experienced the greatest fluctuation in Nasarawa State during the 21 years’ period (1997 – 2017). Also, while maximum and minimum temperature generally assumed an increasing trend, annual total rainfall and dew points alongside relative humidity and wind speed were generally decreasing. Policymakers in the various earth’s supporting systems such as agriculture, land and water, should employ the key findings of this study for advising some suitable adaptation and mitigation policies to cope with climate variability and change.

Mechanical model of muscle contraction. 6. Calculations of the tension exerted by a skeletal fiber during a shortening staircase

Accompanying Paper 1 tests a theoretical relationship between force and shortening velocity of a muscle fiber without justifying its validity. Paper 2 determines the kinematics and dynamics of a myosin II head during the working stroke (WS). Paper 3 imposes the Uniform law as a density representative of the orientation of the levers belonging to the WS heads. By support of these works, Papers 4 and 5 put into equation the evolution of the tension during the four phases of a length step. The present paper closes all six articles by imposing two tasks on itself. The first purpose is to apply the theoretical elements developed for a length step to a succession of identical length steps, otherwise known as shortening staircase. With the values of the geometric and temporal parameters assigned to a myosin head in Papers 1 to 5, a correct adjustment is established between the theoretical tension deduced from our model and the experimental tension published in 1997 by a team of Italian researchers relating to nine shortening staircases performed on the same fiber. In particular, we obtain the equation of the tension reached at the time end of the step (T*) which remains constant step by step as soon as the shortening of a half-sarcomere exceeds 17 nm. The second objective is to find and explain the equation of the Force-Velocity curve introduced ex abrupto into Paper 1: by decreasing the size and duration of the steps, the staircase tends towards a constant slope line corresponding to a continuous speed shortening. By applying the methods of infinitesimal calculus to the different formulations leading to T*, we deduce the Force-Velocity relationship (see Supplement S6.L). And the circle is complete.

Rampant Arch and Its Optimum Geometrical Generation

Gothic art was developed in western Europe from the second half of the 12th century to the end of the 15th century. The most characteristic Gothic building is the cathedral. Gothic architecture uses well-carved stone ashlars, and its essential elements include the arch. The thrust is transferred by means of external arches (flying buttresses) to external buttresses that end in pinnacles, which accentuates the verticality. The evolution of the flying buttresses should not only be considered as an aesthetic consideration, but also from a constructive point of view as an element of transmission of forces or loads. Thus, one evolves from a beam-type buttress to a simple arch, and finally to a rampant arch. In this work, we study the geometry of the rampant arch to determine which is the optimum from the constructive point of view. The optimum rampant arch obtained is the one with the common tangent to the two arches parallel to the slope line. A computer program was created to determine this optimal rampant arch by means of a numerical or graphical input. It was applied to several well-known and representative cases of Gothic art in France (church of Saint Urbain de Troyes) and Spain (Cathedral of Palma de Mallorca), establishing if they were designs of optimal rampant arches or not.

Dynamic Failure Mode and Dynamic Response of High Slope Using Shaking Table Test

A shaking table test was performed to study the dynamic response and failure modes of high slope. Test results show that PGA amplification coefficients increased with increasing elevation and the PGA amplification coefficient of the concave slope was slightly larger than that of the convex slope. The slope type affected the dynamic response of the slope. The elevation amplification effect of the concave slope under seismic load was more significant than that of the convex slope; thus, the concave slope was more unstable than the convex slope. Additionally, the PGA amplification coefficient measured on the slope surface was always larger than that inside the slope, and the data show an increasing trend with the broken line. The dynamic amplification effect of the high slope was closely related to the natural frequency of the slope. Within a certain range, the higher the frequency, the more significant the amplification effect. The dynamic failure process of concave and convex slopes was studied through tests. Findings indicate that the dynamic failure modes of the concave slope are characterized by shoulder collapse, formation of the sliding surface, and integral sliding above the slope line. Dynamic failure modes of the convex slope are mainly slips in the soil layer and collapse of the slope near the slope line.

Application of virtual glide path for calculation of aircraft deflection at the final stage of landing

Objective: The development of a calculation method of aircraft guidance parameters (linear and angular deflection from a synthetic glide path) by means of global satellite navigation system signals. As opposed to the existing methods, it is suggested to use an inclined plane, containing a glide slope line, as a base surface for vertical guidance. Methods: An experimental research was carried out, based on the suggested method of deflections’ calculation, as well as the comparison of results was fulfilled with identification of guidance parameters’ data by means of the existing methods. Results: It is shown that the results of calculating deflections from a glide path by means of the developed method and those methods, which are currently applied in transport planes landing, are practically the same. Practical importance: Application of the given method of calculating aircraft deflections from a glide path will make it possible to simplify significantly the deployment of the ground segment of landing system in airports, which in its turn will give the opportunity to equip regional airdromes of the third and the forth class, which are currently equipped with imprecise approach systems (compass locators or, the so-called, VOR) or have no radio-navigation aids, with satellite systems of precision approach. Satellite landing system implementation will allow aircraft crews, provided with proper airborne equipment, to pass, in case of need, from a contact fly to an instrumental fly conducted under flight rules. The above mentioned will reduce airdromes meteorological minimum, which in its turn will cause the decrease in the number of non-flying days and increase the efficiency of airdromes and fleet exploitation. One more advantage of satellite landing system application is the fact that it allows students to work out the procedure of approach on instrument landing system.