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Avezov R.R.,LLC Solar Plus | Avezova N.R.,Academy of Sciences of Uzbekistan | Ruziev O.S.,Tashkent Institute of Irrigation and Melioration | Vakhidov A.,Karshi Engineering Economics Institute
Applied Solar Energy (English translation of Geliotekhnika) | Year: 2012

We study how heat losses through translucent coatings are affected by the partial absorption and heat transformation of the total solar radiation passing through the transluscent coatings of flat plate water-heating solar collectors; the radiation is incident on the frontal surfaces of the translucent coatings of their casings and is reflected from the antireflective surfaces of the heat-exchange panels of diffuse solar radiation collectors; the radiation is incident on the rear surfaces of the considered translucent walls. To allow for this factor in thermal engineering calculations for the "antireflective heat-exchange panel-translucent coating" system of the considered type of flat plate solar collectors, we introduce the effective coefficient of heat loss from the antireflective surface of a heat-exhange panel via the given translucent coating. We propose a calculation technique and the corresponding formula for determining the effective heat loss coefficient through the transluscent walls of flat plate water-heating solar collectors and present a practical calculation example for determining its value. © 2012 Allerton Press, Inc.


Isakov A.Z.,Tashkent Institute of Irrigation and Melioration | Bugakov A.G.,Academy of Sciences of Uzbekistan
Applied Solar Energy (English translation of Geliotekhnika) | Year: 2014

Problems and aspects of the service management of power engineering and its significance for the operation of photovoltaic power plants are considered. © 2014, Allerton Press, Inc.


Hamidov A.,Humboldt University of Berlin | Hamidov A.,Leibniz Center for Agricultural Landscape Research | Hamidov A.,Tashkent Institute of Irrigation and Melioration | Helming K.,Leibniz Center for Agricultural Landscape Research | And 2 more authors.
Agronomy for Sustainable Development | Year: 2016

Agriculture is major sector in the economy of Central Asia. The sustainable use of agricultural land is therefore essential to economic growth, human well-being, social equity, and ecosystem services. However, salinization, erosion, and desertification cause severe land degradation which, in turn, degrade human health and ecosystem services. Here, we review the impact of agricultural land use in the five countries of Central Asia, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan, during 2008–2013 in 362 articles. We use the Land Use Functions framework to analyze the type and relative shares of environmental, economic, and social topics related to agricultural land use. Our major findings are (1) research on land use in Central Asia received high levels of international attention and the trend in the number of publications exceeded the global average. (2) The impacts of land use on abiotic environmental resources were the most explored. (3) Little research is available about how agricultural land use affects biotic resources. (4) Relationships between land degradation, e.g., salinization and dust storms, and human health were the least explored. (5) The literature is dominated by indirect methods of data analysis, such as remote sensing and mathematical modeling, and in situ data collection makes up only a small proportion. © 2015, INRA and Springer-Verlag France.


Abdikarimov R.A.,Tashkent Financial Institute | Khodzhaev D.A.,Tashkent Institute of Irrigation and Melioration
Magazine of Civil Engineering | Year: 2014

The paper presents a numerical method and algorithm for solving tasks in dynamics of viscoelastic thin-walled elements in structures of variable thickness. The equations of motion concerning deflections are described by partial integro-differential equations (PIDE). Using Bubnov-Galerkin's method, based on the polynomial approximation of deflections, the task is limited to the study of the system of ordinary IDEs, where the independent variable is time. The solution to the system of IDEs is obtained by the offered numerical method, which results into the algorithm of the numerical solution and the program in the Delphi algorithmic language. The study of nonlinear vibrations of thin-walled elements in structures, allowing for variable thickness in the geometrical nonlinear statement, has enabled revealing a number of mechanical effects. Depending on physico-mechanical and geometrical parameters of the considered viscoelastic thinwalled elements in structures, the authors reccommend how to use the rigidity of the system.


Abdikarimov R.A.,Tashkent Financial Institute | Khudayarov B.A.,Tashkent Institute of Irrigation and Melioration
International Applied Mechanics | Year: 2014

The dynamic stability of viscoelastic plates of variable stiffness is analyzed. The deflections are described by partial integro-differential equations of motion. The Bubnov–Galerkin method based on monomial and polynomial approximation of deflections is used to reduce the problem to ordinary integro-differential equations with time as an independent variable. These equations are solved numerically using a singular kernel. A numerical problem-solving algorithm based on this method is described. A number of new mechanical effects are revealed. © 2014, Springer Science+Business Media New York.


Karimov A.,International Water Management Institute | Mavlonov A.,Institute of Hydrogeology and Engineering Geology | Miryusupov F.,Institute of Hydrogeology and Engineering Geology | Gracheva I.,Institute of Hydrogeology and Engineering Geology | And 2 more authors.
Water International | Year: 2012

Storing flow of the Syrdarya River in the aquifers of the upstream Fergana Valley in winter and recovery of this water in summer is examined as a solution for competing demands between upstream hydropower and downstream irrigation. Modelling of the Isfara and Sokh aquifers suggests the potential of reducing the Syrdarya River flow to the Fergana Valley downstream by 540 Mm 3 in winter and increasing it by 540 Mm 3 in summer. Implementing the proposed strategy in only these two aquifers would cover over 25% of the summer water deficit in the Syrdarya River downstream. © Copyright 2012 International Water Resources Association.


Rakhmatullaev S.,Tashkent Institute of Irrigation and Melioration | Rakhmatullaev S.,CNRS Georesources lab | Huneau F.,CNRS Georesources lab | Huneau F.,University of Bordeaux 1 | And 4 more authors.
Environmental Earth Sciences | Year: 2013

Water reservoirs play an important role in areas with limited and erratic precipitation where water is stored and re-distributed later for different purposes. Irrigation is primarily a major water consumer in arid countries of Central Asia for the economic development, employment and food security of the region. The major rivers of Central Asia (e. g., Amu Darya, Syr Darya, and Zerafshan) are turbid watercourses. Sedimentation reduces the main reservoir asset i. e., its volume capacity. In addition, vast territories of the region's countries have been transformed for agriculture to grow water intensive crops such as cotton, rice and wheat during the Soviet Union that dramatically accelerated soil erosion by water and wind. Thus, many man-made water reservoirs are affected by high sedimentation rates. Moreover, uneven spatial and temporal water resources and a Soviet-inherited unified hydraulic infrastructure have raised transboundary reservoir management issues over water resources allocation among the countries in the region such as Kyrgyzstan, Tajikistan, Kazakhstan, Uzbekistan and Turkmenistan. The rivers such as Syr Darya and Amu Darya are already regulated by more than 78 and 94 %, respectively and attempts for new reservoir projects upstream raises increased concerns of the downstream countries (e. g., the Rogun hydropower station in Tajikistan and the Toktogul reservoir in Kyrgyzstan). For instance, the uncoordinated use of reservoirs has caused the Arnasai lake problem in Uzbekistan with environmental, material damage and social unrest. The aim of this paper is first to review the present conditions and the role of man-made water reservoirs for irrigation in Central Asia with special focus on Uzbekistan, second to document past and current reservoir sedimentation conditions in Uzbekistan and third to discuss research carried out by Soviet and present-time local research community in the domain of erosion and sedimentation in the region. © 2012 Springer-Verlag.


Mirsaidov M.M.,Tashkent Institute of Irrigation and Melioration | Sultanov T.Z.,Tashkent Institute of Irrigation and Melioration
Magazine of Civil Engineering | Year: 2014

The paper presents results of studies on the dynamic behavior and stress-strain state of high earth dams with allowance for non-linearly viscoelastic properties of soil, large strains and heterogeneous features of a structure. The studies consider the effect of non-linearly viscoelastic properties of soil, large strains, heterogeneous character of a structure and geometrical parameters of a structure on the change of the stress-strain state of earth dams in pre-resonant, resonant and post-resonant modes of structure oscillations. As a result, some mechanical effects, occurring with allowance for the discussed factors in a dynamic mode of the structure operation, have been revealed. Consideration of large strains and heterogeneity of the structure leads to strengthening a stress jump between heterogeneous parts of the structure; consideration of non-linearly viscoelastic properties of the structure material in a resonant mode of oscillations decreases singnificantly the amplitude of displacements and amplitudes of stress intensity in dangerous (related to strength) points of a dam, comparing with a linearly elastic case.


Khudayarov B.A.,Tashkent Institute of Irrigation and Melioration
International Applied Mechanics | Year: 2010

The flutter of a viscoelastic plate in a supersonic gas flow is studied. A technique and algorithm for numerical solution of nonlinear integro-differential equations with weakly singular kernels are elaborated. The critical flutter speed of viscoelastic plates is determined © 2010 Springer Science+Business Media, Inc.


Mirsaidov M.M.,Tashkent Institute of Irrigation and Melioration | Sultanov T.Z.,Tashkent Institute of Irrigation and Melioration
Soil Mechanics and Foundation Engineering | Year: 2013

A linear-hereditary model of viscoelasticity is presented for description of the viscoelastic properties of soil for dynamic analyses of earthen structures. Parameters of the relaxation kernel are determined for several types of soils. Earthen dams in a resonance regime are analyzed dynamically. Certain mechanical effects manifested in a resonance regime, which are associated with viscoelastic properties of the soil, are exposed. © 2013 Springer Science+Business Media New York.

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