Home – Home – Jornals – Advanced Search

This paper presents the results of experiments to study the shock compression of samples of vanadium deuterides and hydrides of the following compositions: VX_0.51, VX_0.7-0.9 and VX _≥1.6, wher X is H or D. The experiments were carried out in a pressure range of 20-140 GPa. The technology of synthesizing samples using electrolytic vanadium containing not less than 99.7% of the basic substance. The shock adiabats of vanadium deuterides and hydrides were determined using the well-known reflection method. The samples were compressed using shock-wave generators based on the use of explosive charges of different power. The obtained experimental data are described by the equation of state developed using a model in which the specific heat and Gruneisen ratios of ions and electrons are functions of density and temperature. At low temperature, the specific heat changes in accordance with the Debye theory. The removal of the degeneracy of the electron gas at higher temperatures is considered. The influence of ionization processes on the thermodynamic functions is effectively taken into account.

Coal particles when subjected to shock waves can undergo rapid fragmentation, pyrolysis, and combustion, causing enhanced process intensity and efficiency. Particle fragmentation plays a crucial role in this process. Exposure of coal particles to a shock wave is modelled in the present work as combined convection and radiation at the surface and conduction in the interior. Local temperatures within a coal particle and the corresponding thermal stresses are computed to study particle failure. Particle fracture is modelled by a three-parameter Weibull probability to predict the failure location and time. Simulations indicate that pulverized coal of size up to 250 μm subjected to a shock wave for varying operational, thermal, and physical parameters can experience initial failure within 150 μs. Particles of size d ≥50 μm or higher wave strengths (with Mach numbers M ≥5) mostly trigger exfoliation, while interior fragmentation dominates at smaller sizes (d ≤ 25 μm). An initial fracture study reveals that pulverized coal with predominant sizes d ≤ 100 μm and the coal rank from lignite to bituminous coal is potentially suitable for detonation combustion in waves at Mach numbers M = 3-6. Coal particles under continuous exposure to post-shock conditions undergo recursive exfoliation until the core is 20-40 μm, after which an interior fragmentation phase is seen until the core is about 1-3 μm. Much finer coal particles, of the order of internal fragmenting cores, are hardly fractured due to low thermal stresses caused by rapid uniform heating. The fracture model approach for studying shock-induced combustion is validated by a reasonable match of the computed ignition delay with experiments. The fragmentation history indicates a substantial increase in the particle surface area and temperature under shock exposure, as against conventional combustion, leading to an increased order of the burning rates at the onset of ignition, which can sustain through the entire burning phase.

In this paper, the commercial finite element code LS-DYNA is employed to simulate the process of a certain kind of a linear shaped charge jet penetrating into a TC4 (Ti-6Al-4V) titanium alloy plate of moderate thickness. The fracture profiles agree well with experimental observations, which confirms the validity of the code and the Johnson-Cook material model applied to describe the TC4 plate. The fracture pattern of the plate is drawn based on this comparison.

This paper deals with the management of Mediterranean Planted Conifer Forests (MPCF), dominated by the aleppo pine Pinus halepensis and the potential for using natural regeneration as a basis for transformation of simply structured even-aged and mono crops plantations into mixed forest. We studied the variation along a rainfall gradient, in the natural regeneration of tree species. The study was conducted in four forests located within the Mediterranean zone of Israel, which extends from the semiarid northern Negev desert (rainfall ca. 300 mm per year) in the south to the humid central region close the coast line (ca 550 mm per year). Standing trees measurements including mean tree height, diameter at breast height, crown width, canopy cover, stand density of the mature strata and the number of saplings and their species composition along with the landscape characteristics (slope, aspect, percentage of rock cover and forest floor light regime) have been performed at randomly established 200 m² area circular plots. Although a water supply is the main limiting resource for forest growth and productivity, so far no significant relationship between the quantity of regeneration and precipitation could be found. Strong linear correlation between the number of the mature trees and pine’s regeneration have been revealed and the detailed management plan of how to support a natural regeneration using a principal of Continues Cover Forestry was suggested for MPCF, including a recommendation for intensity and time of thinning.

The forests of Northern Kyrgyzstan are distinguished by poor species composition. Severe forest growing conditions, dry climate, vertical zoning, exposition of forests to the northern slopes, while the opposite slopes are treeless created a more or less tolerable conditions for the existence of only one species - Tien Shan spruce Picea schrenkiana Fisch. et Mey . Increase of productivity and stability, as well as strengthening protective properties of the spruce forests of Northern Kyrgyzstan is possible by the introduction of a tree species growing in other areas. For more than 80-year period in the region have been introduced about 120 different species of coniferous and deciduous trees. Many of them have second stage of introduction, noted by good growth, fruiting, and in some cases regeneration. The article summarizes the introduction of 83 years old Scots pine forest plantations in Northern Kyrgyzstan, growing in a variety of forest conditions. Forest inventory characteristic and an analysis of the growth in stem diameter is done. There is an estimation of the viability and prospects for the species in local conditions. Phenological observations completed. Regeneration of Scots pine and Tien Shan spruce in forest crops and out of its boundaries have been studied, which can lead to a species’ change in future. Pine in local conditions starts to occupy areas with severe forest growing conditions, and this confirms that the specie is acclimatized well and able to occupy areas, where Tien-Shan spruce can’t grow due to its bio-ecological features.

The microevolution theory can serve as the theoretical foundation of forest seed zoning and of the population introduction, the subdivision of Pinus sylvestris range in Russia into 10 phylogenogeographical regions - as their genetic-geographical base and climatologic-geographical regularities of the acclimatization of the introduced crops - as the ecological base. As a result of regressive analysis of Pinus sylvestris provenance crops parameters in Russian Plain forest-steppe is was determined the authentic decrease of the parameters of their survival and stands production, according to the increase of gradients of climate limiting factors - duration of vegetative period and photoperiod - between sites of origin and introduction of populations both along of the submeridional transect and of the longitudinal ones. Thus, the hypothesis about the greater adaptivity of the local plant populations by comparison with introduced ones and the correctness of the principle of «climatic topoanalogues» in the acclimatization were confirmed on the quantitative factorial-climatological level. The total net of geographical coordinates and of corresponding elementary forest seed regions measuring 1° in latitude and 5° in longitude formed by it was suggested as the ordination matrix of forest seed zoning within the P. sylvestris areal. The parameters of seed transfer reglamentation in latitude, longtitude and altitude were suggested on the connections base of survival and stands production of introduced Scots pine crops with climatic gradients. These principles can serve as a genetic-climatologic-geographical base for the development of the theory of plants acclimatization and of regional and federal seeds zoning of Scots pine forests for their crops, selection and hybridization.

Differentiation of 83 Scots pine climatypes by height growth at the age of 37 years in the provenance trial was done. Three groups of climatypes were distinguished as: fast-growing, moderate-growing and slow-growing. The research at the age of 20-25 revealed 13 climatypes of 27 from the fast-growing group as candidates to breed-populations. These climatypes are from Krasnoyarsk Krai, Irkutsk Oblast, Kemerovo Oblast, Murmansk Oblast, Karelia, and the Republic of Komi. At the age of 37 years they confirm the status of perspective climatypes in height growth, survival, and resistance to fungal pathogens as it was noted earlier (Kuzmina, Kuzmin, 2007, 2008). The average height of trees of these climatypes exceeds control height by 32 %. The moderate-growing group consists of 18 climatypes, five of them are candidates to breed-populations. The intensity of their growth was reduced but average height is at the level of control average value. The third group has the largest number of climatypes. After the inventory in 2013 two climatypes previously marked as perspective were added into the third group. Last years the intensity of their growth was significantly reduced because of disease caused by cenangium dieback at the 22-24 years old. So the rank status of studied climatypes in different age periods is significantly changeable because of different reaction to ecological factors. The analysis of annual height increments growth confirms that objective conclusions about selection of perspective climatypes could be possible only after 25 years old of pine.

The structure of pine forests in various natural areas of European Russia depends on environmental conditions, specifics of soil and underlying parent rock. Types of pine forests are distinguished by such features as their species composition of the lower layers, structure of grass-shrub layer and the nature of its mosaic. The purpose of the study are regional features of the composite pine forests, distributed on ancient terraces of left bank of the Volga River in north-western Tatarstan, considering specifics of their position in the contact zone of coniferous-deciduous forests with steppes. The structure of the communities of the pine forests on such indicators as species richness, quantitative participation of species, their occurrence and horizontal structure of grass cover were analyzed, and detailed description of the stand and of its renewal was given. In addition, ecological and coenotic structure of communities of pine forests was investigated. It was found that group of types of composite pine forests on the slopes and flat sections of high Volga terraces in northwest of Tatarstan are distinguished by age and completeness of the stand, but is characterized by similar composition of dominant species of lower layer and microgroups in grass layer composition. These communities are characterized by high participation of meadow-steppe plants. This feature distinguishes them from composite pine forests that are found in the central part of the European Russia. This is due to the fact that the area of our study takes position of a buffer, with broad invasion of meadow and meadow-steppe species in the communities of pine forests, especially when anthropogenic disturbances take place. The probability of further transformation of pine stands in the direction of their xerophytization has been identified.

Wildland fires distribute unevenly in time and over area under the influence of weather and other factors. It is unfeasible to air patrol the whole forest area daily during a fire season as well as to keep all fire suppression forces constantly alert. Daily work and preparedness of forest fire protection services is regulated by the level of fire danger according to weather conditions (Nesterov’s index. PV-1 index), fire hazard class (Melekhov’s scale), regional scales (earlier called local scales). Unfortunately, there is still no unified comparable technique of making regional scales. As a result, it is difficult to maneuver forest fire protection resources, since the techniques currently used are not approved and not tested for their performance. They give fire danger rating incomparable even for neighboring regions. The paper analyzes the state-of-the-art in Russia and abroad. It is stated the irony is that with factors of fire danger measured quantitatively, the fire danger itself as a function has no quantitative expression. Thus, selection of an absolute criteria is of high importance for improvement of daily fire danger rating. On the example of the Chunsky forest ranger station (Krasnoyarsk Krai), an improved technique is suggested of making comparable local scales of forest fire danger rating based on an absolute criterion of fire danger rating - a probable density of active fires per million ha. A method and an algorithm are described of automatized local scales of fire danger that should facilitate effective creation of similar scales for any forest ranger station or aviation regional office using a database on forest fires and weather conditions. The information system of distant monitoring by Federal Forestry Agency of Russia is analyzed for its application in making local scales. To supplement the existing weather station net it is suggested that automatic compact weather stations or, if the latter is not possible, simple weather observation points should be organized in forest ranger stations and aviation bases for obtaining up-to-date weather information.

The study of tree-ring cell structure changes as the result of tree adaptation to varying environmental conditions becomes increasingly important to predict future vegetation shifts under projected climate changes. The estimate of intrapopulation annual variability of wood anatomy characteristics is particularly informative. It helps to divide the contribution of different ecological factors to total features dispersion. In this work, a comparative analysis of individual and climatic variability of tree ring structure characteristics of Gmelin’s larch Larix gmelinii (Rupr.) growth within northernmost forest was carried out. The trees from forest-tundra boundary has greater radial growth intensity, forms the bigger conductive zone in rings with wider mean lumen area in comparison with trees from closed forest. This result can be explained by adaptive features and height ecological xylem plasticity of larch. The tree rings structure of larch from boundary with tundra is determined by largely current weather conditions. Is because these ones evince high adaptive plasticity on the level of xylem structure. The xylem reflects joint changes of climate factors and local ecological conditions. The trees from closed forest are characterized by larger individual variability. The local conditions in oldest forest (for example, bad hydrothermal soil conditions) inhibit the radial growth and sensitivity to environmental factors. In this case, the trees on individual level are tended to save the normal functioning of water-transport system. The significant differences in ratio individual to climate variability of tree ring structure characteristics can be caused by the different in the level of ecological habitat heterogeneity or the different in the level genetic within-population heterogeneity.