RESEARCH THERMOTECHNIC ANALYSIS OF CRADLE-CONVEYOR DRYER

In the given work, results numerical modeling for research and an estimation of thermal productivity of drying chamber combined solar-fuel drying installation which is based with cradle-conveyor, heated up by direct receipt of sunlight and an additional source of heat are presented. All calculations have been spent in cases of an “empty” condition drying chamber and “non-working” mode of infrared lamps.Into a database of the given program are entered all thermophysical and physical properties of materials and the substances used in solar dry kiln. Absorbing ability and factor of radiation of a surface of a wall solar dry kiln make chambers (case) 0.90 and 1.0 accordingly where it is made of the processed stainless steel having following properties: the density of 7900 kg/m3 , a specific thermal capacity of 500 J/(kg∙ ̊С), factor of heat conductivity of 16.3 W/(m ̊С), and as the entry condition its temperature has been chosen, equal ambient temperature. In quality translucent coverings have been used polycarbonate sheets having following properties: density of 1200.00 kg/m3 , a specific thermal capacity of 1200 J/(kg∙ ̊С), it has been specified that in them heat conductivity is homogeneous also their factor of heat conductivity of 0.20 W/(m ̊С). For a thermal protection of a ground part drying chambers the polystyrene having following properties has been used: Density of 1075.0 kg/m , a thermal capacity of 350 J/(kg ̊С), factor of heat conductivity of 0.082 W/(m ̊С). The heat-carrier in given solar dry kiln is air having the following physical and thermophysical property: relations of specific thermal capacities (Cp/Cv) 1.399, and molar weight of 0.0290 kg/mol.In the given work, results numerical modeling for research and an estimation of thermal productivity of drying chamber combined solar-fuel drying installation which is based with cradle-conveyor, heated up by direct receipt of sunlight and an additional source of heat are presented. All calculations have been spent in cases of an “empty” condition drying chamber and “non-working” mode of infrared lamps.Into a database of the given program are entered all thermophysical and physical properties of materials and the substances used in solar dry kiln. Absorbing ability and factor of radiation of a surface of a wall solar dry kiln make chambers (case) 0.90 and 1.0 accordingly where it is made of the processed stainless steel having following properties: the density of 7900 kg/m3 , a specific thermal capacity of 500 J/(kg∙ ̊С), factor of heat conductivity of 16.3 W/(m ̊С), and as the entry condition its temperature has been chosen, equal ambient temperature. In quality translucent coverings have been used polycarbonate sheets having following properties: density of 1200.00 kg/m3 , a specific thermal capacity of 1200 J/(kg∙ ̊С), it has been specified that in them heat conductivity is homogeneous also their factor of heat conductivity of 0.20 W/(m ̊С). For a thermal protection of a ground part drying chambers the polystyrene having following properties has been used: Density of 1075.0 kg/m , a thermal capacity of 350 J/(kg ̊С), factor of heat conductivity of 0.082 W/(m ̊С). The heat-carrier in given solar dry kiln is air having the following physical and thermophysical property: relations of specific thermal capacities (Cp/Cv) 1.399, and molar weight of 0.0290 kg/mol

Observation of Periodic Orbits on Curved Two - dimensional Geometries

We measure elastomechanical spectra for a family of thin shells. We show that these spectra can be described by a "semiclassical" trace formula comprising periodic orbits on geodesics, with the periods of these orbits consistent with those extracted from experiment. The influence of periodic orbits on spectra in the case of two-dimensional curved geometries is thereby demonstrated, where the parameter corresponding to Planck's constant in quantum systems involves the wave number and the curvature radius. We use these findings to explain the marked clustering of levels when the shell is hemispherical

Spectral asymmetry of the massless Dirac operator on a 3-torus

Consider the massless Dirac operator on a 3-torus equipped with Euclidean metric and standard spin structure. It is known that the eigenvalues can be calculated explicitly: the spectrum is symmetric about zero and zero itself is a double eigenvalue. The aim of the paper is to develop a perturbation theory for the eigenvalue with smallest modulus with respect to perturbations of the metric. Here the application of perturbation techniques is hindered by the fact that eigenvalues of the massless Dirac operator have even multiplicity, which is a consequence of this operator commuting with the antilinear operator of charge conjugation (a peculiar feature of dimension 3). We derive an asymptotic formula for the eigenvalue with smallest modulus for arbitrary perturbations of the metric and present two particular families of Riemannian metrics for which the eigenvalue with smallest modulus can be evaluated explicitly. We also establish a relation between our asymptotic formula and the eta invariant

Разработка гелиоаккумуляционной сушильной установки на основе теоретических исследований аккумуляции солнечной энергии

The process of heating a dewatered object in an infrared solar drying plant (with paraffin on the bottom) with solar energy storage is considered. To solve this problem, it is assumed that the heat capacity of paraffin exceeds the heat capacity of the dehydrated object. Infrared rays fall on the upper layer, and heat exchange takes place due to heat and mass transfer with the surface air located between the metal plate and the object to be dehydrated. The equations of thermal conductivity for a dewatered object are given, its relationship at the phase interface is determined using the equality of temperature and heat flow. For an exposure of overheating with a period of 6.5 h, the time of passage of the phase boundary in accordance with the law of motion of the spreading (hardening), was determined according to the formula of  ξ = α √6,5 h ≅ 12 h.The optimal thickness of the accumulating paraffin layer was ascertained. On the basis of the theoretical studies, experiments were conducted to study the temperature field of various heataccumulating materials in the laboratory of Tashkent State Technical University. It was found that of all heat-accumulating materials, paraffin has the best heat retention ability when its thickness is of 2–4 cm. The optimal variant of a solar accumulator drying plant with a heat accumulator, viz. paraffin has been designed. In particular, 2–4 cm of paraffin layer with a mass of 50 kg with a corresponding flat surface in terms of specific heat of evaporation is 2400 kJ/kg. The specific melting value of paraffin (150 kJ/kg) allows additional evaporation of 5.8 l of moisture when drying objects. The proposed solar accumulator drying plant can be used for dehydration of medicinal herbs.Рассмотрен процесс нагрева обезвоживаемого объекта в инфракрасной гелиосушильной установке (с парафином на дне) с аккумуляцией солнечной энергии. Для решения этой задачи принято, что теплоемкость парафина превосходит теплоемкость обезвоживаемого объекта. На верхний слой падают ИК-лучи, а также происходит теплообмен за счет тепломассообмена с поверхностным воздухом, находящимся между металлической пластиной и обезвоживаемым объектом. Приведены уравнения теплопроводности для обезвоживаемого объекта, определена его связь на границе раздела фаз с помощью равенства температур и потока теплоты. Для экспозиции перегрева с периодом 6,5 ч время прохождения границы раздела фаз, согласно закону движения границы расплавления (затвердения),определяли по формуле ξ = α √6,5 ч ≅ 12 ч.Получена оптимальная толщина слоя аккумулирующего парафина. На основе теоретических исследований проводились опыты по изучению температурного поля различных теплоаккумулирующих материалов в лаборатории Ташкентского государственного технического университета. Выявлено, что из всех теплоаккумулирующих материалов парафин обладает лучшей способностью удерживания теплоты при его толщине 2–4 см. Сконструирован оптимальный вариант гелиоаккумуляционной сушильной установки с аккумулятором теплоты – парафином. В частности, 2–4 см слоя парафина массой 50 кг с соответствующей плоской поверхностью в пересчете на удельную теплоемкость испарения – это 2400 кДж/кг. Удельное значение плавления парафина (150 кДж/кг) позволяет дополнительно испарять 5,8 л влаги при сушке объектов. Предлагаемая гелиоаккумуляционная сушильная установка может использоваться для обезвоживания лекарственных трав

Spintronics: Fundamentals and applications

Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.Comment: invited review, 36 figures, 900+ references; minor stylistic changes from the published versio

Effects of boundary conditions on magnetization switching in kinetic Ising models of nanoscale ferromagnets

Magnetization switching in highly anisotropic single-domain ferromagnets has been previously shown to be qualitatively described by the droplet theory of metastable decay and simulations of two-dimensional kinetic Ising systems with periodic boundary conditions. In this article we consider the effects of boundary conditions on the switching phenomena. A rich range of behaviors is predicted by droplet theory: the specific mechanism by which switching occurs depends on the structure of the boundary, the particle size, the temperature, and the strength of the applied field. The theory predicts the existence of a peak in the switching field as a function of system size in both systems with periodic boundary conditions and in systems with boundaries. The size of the peak is strongly dependent on the boundary effects. It is generally reduced by open boundary conditions, and in some cases it disappears if the boundaries are too favorable towards nucleation. However, we also demonstrate conditions under which the peak remains discernible. This peak arises as a purely dynamic effect and is not related to the possible existence of multiple domains. We illustrate the predictions of droplet theory by Monte Carlo simulations of two-dimensional Ising systems with various system shapes and boundary conditions.Comment: RevTex, 48 pages, 13 figure

Analytic definition of spin structure

We work on a parallelizable time-orientable Lorentzian 4-manifold and prove that in this case the notion of spin structure can be equivalently defined in a purely analytic fashion. Our analytic definition relies on the use of the concept of a non-degenerate two-by-two formally self-adjoint first order linear differential operator and gauge transformations of such operators. We also give an analytic definition of spin structure for the 3-dimensional Riemannian case

Fungal root endophyte associations of plants endemic to the Pamir Alay Mountains of Central Asia

The fungal root endophyte associations of 16 species from 12 families of plants endemic to the Pamir Alay Mountains of Central Asia are presented. The plants and soil samples were collected in Zeravshan and Hissar ranges within the central Pamir Alay mountain system. Colonization by arbuscular mycorrhizal fungi (AMF) was found in 15 plant species; in 8 species it was of the Arum type and in 4 of the Paris type, while 3 taxa revealed intermediate arbuscular mycorrhiza (AM) morphology. AMF colonization was found to be absent only in Matthiola integrifolia, the representative of the Brassicaceae family. The AM status and morphology are reported for the first time for all the species analyzed and for the genera Asyneuma, Clementsia, and Eremostachys. Mycelia of dark septate endophytes (DSE) accompanied the AMF colonization in ten plant species. The frequency of DSE occurrence in the roots was low in all the plants, with the exception of Spiraea baldschuanica. However, in the case of both low and higher occurrence, the percentage of DSE root colonization was low. Moreover, the sporangia of Olpidium spp. were sporadically found inside the root epidermal cells of three plant species. Seven AMF species (Glomeromycota) found in the trap cultures established with soils surrounding roots of the plants being studied were reported for the first time from this region of Asia. Our results provide information that might well be of use to the conservation and restoration programmes of these valuable plant species. The potential application of beneficial root-inhabiting fungi in active plant protection projects of rare, endemic and endangered plants is discussed