An efficient physical-based method for predicting the long-term evolution of vertical railway track geometries

The dynamic wheel-rail contact forces resulting from the interaction between vehicle and track are responsible for the local track settlement. If these local settlements vary along the track, geometric irregularities develop further amplifying the dynamic loading of the track caused by the interaction between the vehicle and track. In this work, an efficient vehicle-track interaction (VTI) model is presented for predicting the long-term evolution of vertical track settlement during operation. The VTI model has two interacting components – vehicle and track. The vehicle model describes the vertical dynamics of an 8th of a car. The track model considers an elastic rail on discrete (sleeper) supports. Each sleeper location can have its own stiffness, relative height and settlement characteristics. Dependent on the distribution of stiffness and settlement behaviour along the track together with the initial track geometry, each sleeper settles dependent on the number of load cycles (vehicle passes). The track model is initialized with measured vertical track geometry data and static track deflection data at the beginning (day 0) for two types of track sections in the field, a track section where concrete sleepers with Under Sleeper Pads (USP) are used and a track section where only concrete sleepers are used. Using the same settlement model parameters (constant along the track) for the two tracks, the physical-based VTI model can predict the different track geometry quality evolution for both tracks over 350 days. Finally, the VTI model is used to assess the track geometry deterioration when the track/vehicle properties are changed. The prediction strength of the fast VTI model based on the physical understanding can assist in designing and optimizing tracks and in supporting of maintenance activities.

Modeling structure of Scots pine stems volume by grade categories using stochastic process

The study highlights methodological aspects of predicting stem volume of merchantable Scots pine trees by grade categories using distribution models of different quality zones along stems. The study is based on empirical data collected in the mature stand during clear-cut harvesting. In total it includes measurements of 245 tree stems for which sequence and lengths of different quality categories were evaluated. A semi-Markov model was applied to characterize a random process of height-relevant co-occurrence and length of merchantable wood, firewood, and residues. The model was determined by the following parameters: 1) input occurrence probabilities of specific grade category in the butt section of tree stems (initial state of the system); 2) distribution matrix of grade categories by lengths; 3) matrix with transition probabilities between grade classes on different stem heights. In this study, we considered the process in which the initial state of the system was associated with merchantable wood which was true for most pine stems. We used beta-function to model lengths of grade categories which parameters were fitted using relative stems height. We also used empirical data to calculate probabilities of transition between merchantable wood, firewood, and residuals along pine stems. The analysis indicates that the length distribution of merchantable wood and firewood depends on the relative height where the grade is observed, and total tree stem height. Thus, we identified four zones where the function of beta-distribution was used to model lengths of each grade category with customized parameters depending on the relative height of their location on tree stem. As a result, we developed a methodology that can be used to simulate datasets with tree stem characteristics, and further to predict the distribution of volume by grade categories depending on their diameters, heights, and merchantability. It is worth noting that our study is focused merely on merchantable pine stems, and one should expect another relationship for stems of different tree species as well as for merchantable pulpwood trees. Given the new standard for merchantable wood classification adopted in Ukraine, the developed methodology is suitable for updating existing tables of distribution of tree stem volumes by wood grade categories.

Prediction of Transmission Coefficients of Regular Wave Attenuation by Emergent Vegetation

Transmission coefficient (Kt) for wave attenuation by vegetation is essential parameter for predicting the wave height. In this paper, based on the experimental data of three kind of artificial vegetation model, genetic programming (GP), artificial neural networks (ANNs) and multivariate non-linear regression (MNLR) were used to analyze the dimensionless factors including Ursell number (Ur), relative width (RB) relative height (α) and volume fraction (φ). The proposed GP formulae were compared with MNLR and ANNs. The predictions of GP models were in good agreement with measured data, and outperformed MNLR equations. Otherwise, GP and ANNs were used to obtain the weight of each factor. The results can provide a reference for the artificial planting of the three plants.

Structure of young growth of pine in various ecotopes of the Trans-Urals region

Рассмотрены результаты исследования пространственной и возрастной структуры подроста сосны на гарях-вырубках и вырубках сосняка брусничникового Среднего Урала. Показано, что подрост сосны на гарях-вырубках, по сравнению с вырубками, отличается значительно меньшей величиной диаметра на середине высоты ствола, но отличается существенно более высокими темпами роста в высоту. Относительная высота у подроста на гарях-вырубках на 31,5–37,3% выше, чем у подроста на вырубках. Связано это со значительно более высокой густотой подроста на гарях-вырубках, по сравнению с вырубками. Установлено, что большая часть возобновления сосны как на гарях-вырубках, так и на вырубках, была сосредоточена в районах примыкания трех сторон леса. С уменьшением источников обсеменения (примыкание двух сторон леса) густота подроста заметно снижалась. В свою очередь, на открытых участках на гарях-вырубках и вырубках численность подроста была наименьшей. Подрост сосны отличается регулярным (случайным) с переходом к рассеянному (равномерному) типом размещения на гарях-вырубках. На вырубках основной тип размещения – групповой. На гарях-вырубках основная часть деревьев относилась к возобновлению, появившемуся на 2–3-й год после пожаров и последующей вырубки. Возобновление, появившееся как на следующий год, так и на 4–5-й год после удаления древостоя, было незначительным. На 6-й год после пожара и вырубки возобновление полностью прекратилось. На вырубках основная часть деревьев относилась к возобновлению, появившемуся на 4–5-й год после вырубки. Однако, хотя и в значительно меньшей степени, возобновление сосны на вырубках имело место и в последующие годы. Закономерность изменения возрастной структуры подроста для гарей-вырубок хорошо аппроксимируется полиномиальным уравнением 4-го порядка, а на вырубках – 5-го порядка. The results of study of spatial and age structure of pine on slash-cutover and cutover of young growth of pine of cowberry-shrub pine forest of the Trans-Urals region are considered. It has been shown that the undergrowth of pine on slash-cutover in comparison with cutting differs by a significantly smaller diameter at the middle of the trunk height, but differs by a significantly higher growth rate in height. The relative height of the undergrowth on the slash-cutover was 31.5–37.3% higher than that of the undergrowth on the cutover. This is due to the significantly higher density of undergrowth on slash-cutover compared to cutover. It has been established that most of the resumption as pine on both slash-cutover and cutover was concentrated in the areas adjacent to three sides of the forest. With a decrease in sources of insemination (adjoining two sides of the forest), the density of undergrowth decreased markedly. In turn, in open areas on slash-cutover and cutover, the number of undergrowth was the smallest. The young growth of pine is characterized by a regular (random) with a transition to a scattered (uniform) type of placement on the slash-cutovers. In cutovers, the main placement type is group. On slash-cutovers, the main part of the trees belonged to the resumption, which appeared for 2–3 years after fires and subsequent felling. The resumption, which appeared both for the next year and for 4–5 years after the removal of the woodland, was insignificant. For 6-year after the fire and felling, the resumption completely ceased. On cutovers, the main part of the trees belonged to the resumption, which appeared for 4–5 years after felling. However, although to a much lesser extent, the resumption of pine on the cutovers, took place in subsequent years. The pattern of change in the age structure of undergrowth for cut-offs is well approximated by the polynomial equation of the 4th order, and on the cut-offs of the 5th order.

Optimal Design of Diversion Piers of Lateral Intake Pumping Station Based on Orthogonal Test

To explore the rectification parameters of the diversion piers optimized for the forebay of the pump station with a lateral angle of 45°, the orthogonal experiment and computational fluid dynamics methods are used to analyze the flow characteristics of the diversion piers under different parameter combinations. The flow pattern in the forebay of the side water inlet is improved. The rectification effect of the diversion piers under 16 schemes is analyzed, considering the length, width, radian, and relative height of the diversion piers. Combined with numerical simulation, a better rectification scheme is provided, and finally, a reasonable range of values for the rectification parameters of the forebay diversion pier of the side 45° bend angle pump station is obtained.

Experimental Analysis of Hydraulic Jump at High Froude Numbers

The hydraulic jump is a rapid transition state from supercritical to subcritical flow that occurs commonly in rivers, prismatic channels and downstream of spillways. In this study, the characteristics of the hydraulic jump in a stilling basin downstream of the spillway chute channel with the slopes of α = 12o and 30o were investigated experimentally for different Froude numbers of incoming flow, Fr1 = 7, 7.5, 8, 9, 10 and 12, and relative heights of sill in the range of 4 < hs/h1 (S) < 13 (S relative height). In the experiments, in which velocity field measured by laser Doppler Anemometry, it was particularly focused on the effects of both different structural configuration and flow conditions on the hydraulic jump and energy dissipation ratio. Experimental measurements showed that the length of hydraulic jump and the roller zone increases with the decrease of the sill height for α = 12o and 30o. In addition, the length of the hydraulic jump and roller zone increased with decreasing Froude numbers. The turbulence intensity in the jump region was determined to be greater than the turbulence intensity in the region near the bottom of stilling basin. The turbulence intensity, in general, tended to decrease with decreasing Froude number.

Large-scale variations in the dynamics of Amazon forest canopy gaps from airborne lidar data and opportunities for tree mortality estimates

We report large-scale estimates of Amazonian gap dynamics using a novel approach with large datasets of airborne light detection and ranging (lidar), including five multi-temporal and 610 single-date lidar datasets. Specifically, we (1) compared the fixed height and relative height methods for gap delineation and established a relationship between static and dynamic gaps (newly created gaps); (2) explored potential environmental/climate drivers explaining gap occurrence using generalized linear models; and (3) cross-related our findings to mortality estimates from 181 field plots. Our findings suggest that static gaps are significantly correlated to dynamic gaps and can inform about structural changes in the forest canopy. Moreover, the relative height outperformed the fixed height method for gap delineation. Well-defined and consistent spatial patterns of dynamic gaps were found over the Amazon, while also revealing the dynamics of areas never sampled in the field. The predominant pattern indicates 20–35% higher gap dynamics at the west and southeast than at the central-east and north. These estimates were notably consistent with field mortality patterns, but they showed 60% lower magnitude likely due to the predominant detection of the broken/uprooted mode of death. While topographic predictors did not explain gap occurrence, the water deficit, soil fertility, forest flooding and degradation were key drivers of gap variability at the regional scale. These findings highlight the importance of lidar in providing opportunities for large-scale gap dynamics and tree mortality monitoring over the Amazon.

Features for calculating beams with a thin transverse corrugated web plate considering bending-twisting forces

The article describes the features of the work of beams with a thin transverse corrugated web plate. Exponential fractional regression is presented, which allows one to estimate the relative height of web plate sections working together with flanges, obtained by the authors based on an analysis of numerical experiments. Based on the features of the work, a method is proposed for describing the stress state of an arbitrary cross-section of an I-beam with a thin transverse corrugated web plate (the profile of the corrugations is triangular, trapezoidal, sinusoidal) bent in the plane of the web plate and compressed in the longitudinal direction, using the theory of thin-web platted elastic rods by Professor V.Z. Vlasov. The calculations are given for determining the bending-twisting forces (local bending moments and bimoments arising from the action of the main forces) in an arbitrary cross section.

Effects of jet angle on harmonic structure of sound radiating from the flute

For an isolated flute head joint, the effects of jet angle on harmonic structure of a single note are investigated within the practical range for human players. The mechanisms of these effects are discussed on the basis of both the radiated sound and the flow field measured with a hot-wire anemometer. The blowing parameters, viz., jet angle (angle between jet direction and window), jet offset (relative height of jet direction from the edge), lip-to-edge distance, and flow rate, were varied independently by using an artificial blowing device based on measured conditions for a human player, where the jet direction is defined as that measured without the head joint. The radiated sound revealed that jet angle varied the differential sound pressure level of the second to third harmonic (ΔSPL) less than jet offset, however, as much as flow rate and more than lip-to-edge distance. The spatial distribution of jet fluctuation center showed that, with increasing jet angle (the jet direction approaches vertical to the window), the jet deflected more inside, so that the actual jet offset was estimated to be further inside. The variation of ∆SPL with jet angle seems to be caused mainly by this shift in the actual jet offset.