scholarly journals Polystructural organization of a landscape: geophysical analysis of geosystems synergy

2020 ◽  
pp. 5-13
Author(s):  
В.В. СЫСУЕВ

Эмпирические концепции ландшафтоведения в рамках геофизической парадигмы позволяют ассимилировать физические законы для описания структуры и функционирования геосистем. Исследованы южно-таежные ландшафты конечно-моренной зоны Валдайского оледенения на территории Национального парка «Валдайский». Геоструктуры описываются с помощью параметров силовых геофизических полей – поля силы тяжести и поля инсоляции, которые можно получить на основе морфометрии цифровых моделей рельефа и цифровых данных космической съемки. Выбор небольшого числа главных параметров с ясным физическим смыслом проводится в соответствии с классическими определениями. Обоснование числа и значимости параметров состояния элементарных пикселей и геосистем осуществляется при анализе результатов численного моделирования структуры ландшафтов. Методом дихотомической группировки элементов поверхности рельефа по параметрам состояния (высота, уклон, горизонтальная и вертикальная кривизна, доза прямой солнечной радиации, NDVI) реализован типологический подход к классификации природно-территориальных комплексов (по принципу однородности) и получена структура ландшафтов на уровне урочищ. С другой стороны, функциональный подход позволил построить иерархию водосборных геосистем по морфометрическим параметрам, описывающим перераспределение воды в поле гравитации – уклонам, удельной площади водосбора, горизонтальной и вертикальной кривизне. Все классификации строятся на единой базе данных и могут использоваться для разных прикладных задач. Приводится пример расчета скоростей стока поверхностных вод и на их основе – зонирование водосборных геосистем по времени добегания до контрольных створов. Таким образом, формальный алгоритм выделения наименьших и иерархических единиц поверхности рельефа на основе параметров состояния приобретает фундаментальный геофизический смысл. Понятие полиструктурности ландшафта в этом случае является абсолютно логичным: выбирая те или иные физически содержательные структурообразующие процессы и их параметры, можно реализовать разные классификации ландшафтов, необходимые в прикладных задачах. Empirical concepts of physical geography enable us to apply the physical laws to describe the landscape structure and functioning. The finitely morainic landscapes of the Valdai Glaciation on the National Park “Valdaisky” territory were investigated. A development of geostructures identified by classical landscape analysis can be described by the parameters of power geophysical fields, mainly gravitation and insolation fields. Selection of a small number of main parameters with extremely clear physical meaning is carried out in accordance with the classical definitions of landscape science. Justification of the number and importance of parameters of elementary pixels and geosystems is carried out when analyzing the results of numerical simulation of the structure of landscapes. Using the method of dichotomic grouping of the relief surface elements by the state parameters (height, slope, horizontal and vertical curvature, dose of direct solar radiation, NDVI), the typological approach to the classification of the natural-territorial complexes (according to homogeneity principle) was realized and the structure of landscapes at a level of natural boundaries was obtained. On the other hand, the functional approach allowed to construct the hierarchy of the water-collecting geosystems by morphometic parameters describing the water redistribution in the gravitation field – slopes, drainage factor, horizontal and vertical curvature. All the classifications are constructed on the single base of data and can be used for different applied tasks. An example of calculating the surface water flow rate is presented and, on their basis, a zoning of the water-collecting geosystems, using the flow time to the control sections. If one uses these parameters the formal mathematical algorithm for identification of elementary and hierarchical units of landforms acquires fundamental geophysical interpretation. In this case the concept of landscape patterns multiplicity is quite relevant. By choosing these or other physical parameters and structure-forming processes we have the opportunity to perform various landscape classifications needed in the applied tasks.

Author(s):  
M. Azeredo ◽  
◽  
V. Priimenko ◽  

This work presents a mathematical algorithm for modeling the propagation of poroelastic waves. We have shown how the classical Biot equations can be put into Ursin’s form in a plane-layered 3D porous medium. Using this form, we have derived explicit for- mulas that can be used as the basis of an efficient computational algorithm. To validate the algorithm, numerical simulations were performed using both the poroelastic and equivalent elastic models. The results obtained confirmed the proposed algorithm’s reliability, identify- ing the main wave events in both low-frequency and high-frequency regimes in the reservoir and laboratory scales, respectively. We have also illustrated the influence of some physical parameters on the attenuation and dispersion of the slow wave.


Author(s):  
V. V. Sysuev

Potential of advance in landscape science is associated with the synthesis of physical-mathematical, geophysical and empirical scientific directions on the basis of GIS technology. This stage is characterized as a geophysical paradigm of landscape science, a feature of which is a new understanding of the physical fundamentals, the need to consider landscapes as dynamic systems. Empirical theoretical concepts of physical geography enable us to apply physical laws to describe landscape structure and functioning. Land structures are described using independent morphometric parameters of geophysical force fields (gravity and insolation), which can be viewed as state parameters of geosystems. The modeling of landscape functioning in terms of continuum mechanics is closely related to the structure of landscapes through boundary conditions and distributed parameters of transfer processes. Verification and development of models requires the use of a complex of geophysical methods. Creating models in accordance with the principles of the irreversible thermodynamics is complete representation of the genesis of natural processes. The dualism and strong non-linearity necessitates the stochastic analysis of geosystems, including using the fractal methods.


Phlebologie ◽  
2011 ◽  
Vol 40 (06) ◽  
pp. 344-355 ◽  
Author(s):  
H.A.M. Neumann

SummarySkin, veins and legs are the three ingredients which compose together the symptom complex know as chronic venous insufficiency (CVI). High ambulatory venous pressure is transferred by simple physical laws to the skin microcirculation. The capillaries are not resistant to this high pressure and will leak water, erythrocytes and plasma proteins into the in-terstitium. The result is oedema, pigmentation, sclerosis, inflammation and ulceration. Although many forms of intervention for incompetent veins are available, compression therapy is still the cornerstone in the treatment of CVI. Beside the interface pressure, the stiffness of the compression material is essential. By increasing the stiffness the difference in pressure during walking increases and with this the massage effect of the therapy.Thermo-ablation is the treatment for varicose veins today. Knowledge about the development and transfer of the intravascular heat is essential to understand this treatment. New experiments, specially about steam development from the heat source in the blood are of great importance for the success rate. Fine tuning in those physical parameters is needed to optimally this treatment.


Author(s):  
Lei Xing-lin ◽  
Huang Shan-fan ◽  
Guo Zhong-xiao ◽  
Guo Xiao-yu

As a safety device to alleviate the loss of reactor coolant, the siphon breaking system is widely used in nuclear power plant. Researchers are very interested in this technique for its “passive” characteristic. Vertical downward air-water two-phase flow is encountered in the siphon breaking process. Previous researches have been more focused on some physical parameters, such as water flow rate, air flow rate, pressure drop and the undershooting height. Void fraction, as a key parameter in multiphase flow, should be studied in the siphon breaking phenomenon. Therefore, a needle-contact capacitance probe is used for flow-phase identification and a single-wire capacitance for obtaining the average value of gas distribution along the straight line. Experimental results show that the flow pattern during the vertical downward air-water two-phase flow is mostly annular flow. With the gas entering the pipeline, void fraction profile against time can be divided into three stages. The slope in the first stage is similar to that in the third. However, the slope slows down in the middle stage. The experimental results also show that the real duration time to break the siphon flow is as short as about 6 s. The void fraction at the end of the siphon breaking process is about 0.38. During this stage, a large amount of gas is sucked into the downcomer and little water is inhaled. The gas phase results in a convergent effect, where the air intake is the direct and fundamental reason of siphon breaking.


Author(s):  
Mahdi Haghshenas-Jaryani ◽  
Alan Bowling

This paper presents a multiscale dynamic model for the simulation and analysis of flexibility in myosin V. A 3D finite segment model, a multirigid body model connected with torsional springs, is developed to mechanically model the biological structure of myosin V. The long simulation run time is one of the most important issues in the dynamic modeling of biomolecules and proteins due to the disproportionality between the physical parameters involved in their dynamics. In order to address this issue, the most-used models, based on the famous overdamped Langevin equation, omit the inertial terms in the equations of motion; that leads to a first order model that is inconsistent with Newton's second law. However, the proposed model uses the concept of the method of multiple scales (MMS) that brings all of the terms of the equations of motion into proportion with each other; that helps to retain the inertia terms. This keeps the consistency of the model with the physical laws and experimental observations. In addition, the numerical integration's step size can be increased from commonly used subfemtoseconds to submilliseconds. Therefore, the simulation run time is significantly reduced in comparison with other approaches. The simulation results obtained by the proposed multiscale model show a dynamic behavior of myosin V which is more consistent with experimental observations in comparison with other overdamped models.


2018 ◽  
Vol 36 (4) ◽  
pp. 1
Author(s):  
Igor Barbosa de Oliveira ◽  
Marcia Miranda Azeredo ◽  
Mariane Ribeiro Silva Tiradentes Miranda ◽  
Viatcheslav Ivanovich Priimenko

ABSTRACT. There is considered a layered heterogeneous poroelastic isotropic medium with physical parameters characterized by piecewise constant functions of the depth only. We derive a mathematical algorithm for calculating reflected/transmitted poroelastic waves across all temporal frequencies. To define the frequency effect we use the dynamic permeability expression proposed by Jonhson, Koplik and Dashen; in the time domain, this coefficient introduces order 1/2 shifted fractional time derivative involving a convolution product. The algorithm proposed is based on the formalism introduced by Ursin. The algorithm is tested numerically in a 1D-case. The numerical experiments confirm the effectiveness of the proposed algorithm in identifying the main wave events in both low frequency and high frequency regimes in the reservoir and laboratory scales.Keywords: stratified porous medium, Biot and Biot-JKD models, Ursin’s Formalism.RESUMO. Neste trabalho, consideramos um meio poroelástico estratificado, isotrópico e heterogêneo com parâmetros físicos caracterizados por funções constantes por partes em relação à profundidade. Nós derivamos um algoritmo matemático para calcular as ondas poroelásticas refletidas/transmitidas em todas as frequências temporais. Para definir o efeito da frequência, usamos a expressão de permeabilidade dinâmica proposta por Jonhson, Koplik e Dashen; no domínio do tempo, este coeficiente introduz a derivada do tempo fracionária de 1/2 de ordem de deslocamento envolvendo um produto de convolução. O algoritmo proposto é baseado no formalismo introduzido por Ursin e foi testado numericamente para o caso 1D. Os experimentos numéricos confirmaram a efetividade do algoritmo na identificação dos principais eventos de onda nos regimes de baixa frequência e alta frequência, nas escalas de reservatório e laboratórial, respectivamente.Palavras-chave: meio poroso estratificado; Modelos de Biot e Biot-JKD; Formalismo de Ursin.


Author(s):  
М.А. БЫХОВСКИЙ

Представлен новый подход к исследованию систем MISO в многолучевых каналах связи. Модели таких каналов, учитывающие физические законы распространения радиоволн, использованы при анализе помехоустойчивости приема сигналов в радиорелейной связи, а также в сетях сотовой связи и беспроводного доступа. Параметры этих моделей входят в полученные в статье формулы для расчета вероятности ошибки в системах MISO при демодуляции принимаемых сигналов с многопозиционной квадратурно-амплитудной модуляцией. Результаты работы дают возможность оценивать для конкретных многолучевых каналов связи один из важных параметров систем MISO с пространственно-временными кодами - величину пространственного разнесения передающих антенн, при которой устраняется интерференция приходящих к приемной антенне лучей. A new approach to the study of MISO systems in multipath communication channels is presented. Models of such channels, taking into account the physical laws of radio wave propagation, are used in the analysis of noise immunity of signal reception in radio relay communication, cellular and wireless access networks. The parameters of these models are included in the formulas obtained in the article for calculating the probability of demodulation error of received signals with multi-position quadrature amplitude modulation in MISO systems. The results of the article make it possible to evaluate one of the important parameters of MISO systems with space-time block codes for specific multipath communication channels - the spatial diversity of transmitting antennas, which eliminates the interference of the rays arriving at the receiving antenna.


2018 ◽  
Author(s):  
Tomer David Ullman

Humans acquire their most basic physical concepts early in development, and continue to enrich and expand their intuitive physics throughout life as they are exposed to more and varied dynamical environments. We introduce a hierarchical Bayesian framework to explain how people can learn physical parameters at multiple levels. In contrast to previous Bayesian models of theory acquisition (Tenenbaum et al., 2011), we work with more ex- pressive probabilistic program representations suitable for learning the forces and properties that govern how objects interact in dynamic scenes unfolding over time. We compare our model to human learners on a challenging task of estimating multiple physical parameters in novel microworlds given short movies. This task requires people to reason simultane- ously about multiple interacting physical laws and properties. People are generally able to learn in this setting and are consistent in their judgments. Yet they also make systematic errors indicative of the approximations people might make in solving this computationally demanding problem with limited computational resources. We propose two approximations that complement the top-down Bayesian approach. One approximation model relies on a more bottom-up feature-based inference scheme. The second approximation combines the strengths of the bottom-up and top-down approaches, by taking the feature-based inference as its point of departure for a search in physical-parameter space.


Author(s):  
Xiaoqing Wang ◽  
Zhengguo Tan ◽  
Nick Scholand ◽  
Volkert Roeloffs ◽  
Martin Uecker

Conventional magnetic resonance imaging (MRI) is hampered by long scan times and only qualitative image contrasts that prohibit a direct comparison between different systems. To address these limitations, model-based reconstructions explicitly model the physical laws that govern the MRI signal generation. By formulating image reconstruction as an inverse problem, quantitative maps of the underlying physical parameters can then be extracted directly from efficiently acquired k-space signals without intermediate image reconstruction—addressing both shortcomings of conventional MRI at the same time. This review will discuss basic concepts of model-based reconstructions and report on our experience in developing several model-based methods over the last decade using selected examples that are provided complete with data and code. This article is part of the theme issue ‘Synergistic tomographic image reconstruction: part 1’.


2015 ◽  
Vol 40 (1) ◽  
pp. 7-37 ◽  
Author(s):  
Camilo A. Correa Ayram ◽  
Manuel E. Mendoza ◽  
Andrés Etter ◽  
Diego R. Pérez Salicrup

The study of landscape connectivity in conservation has increased considerably since the early part of the 21st century. While the implications of landscape connectivity are self-evident for conservation, they are also important for physical geography since a proper understanding of landscape patterns and processes allows for better landscape management practices, which are at the core of geography. This paper presents a review of the literature based on 162 publications from 2000 to 2013, in which we evaluated the current state and recent advances in the integration of landscape connectivity in the identification and planning of conservation areas. The literature review and data analysis were based on a database organized into five categories: General information, study areas, research objectives, research methods in connectivity studies, and integration of connectivity with conservation. We found a substantial increase in the number of publications relating to connectivity and conservation from 2008 to 2013. Least cost analysis was the method most commonly applied. We found no implementation of landscape connectivity proposals generated by the studies (e.g. potential corridors) into real landscape elements to ensure the permanence and functionality of ecosystems. We identified four important niches for potential future research projects: a) connectivity and climate change, b) contribution of connectivity studies to restoration planning, c) connectivity and land cover/land use change modeling and planning, d) contribution of connectivity analysis in the provision of ecosystem services across landscapes.


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