27 research outputs found
Technology for carrying out hydraulic fracturing using a new material 'nitinol'
The paper examines the causes of proppant backflow from a fracture to a well, and presents the main technologies for proppant control. The consequences of the removal of the fracture filler into the wellbore are determined. It has been noted that proppant backflow is most damaging to wells operated by electric centrifugal pumps. Existing methods of hydraulic fracturing are investigated, their disadvantages are indicated. A method has been developed for hydraulic fracturing with injection of compressed springs made of metal with the effect of 'memory' and restoring their shape under reservoir temperature stress. In the first stage, the remote section of the crack is filled with a fine fraction of ceramic proppant, and at the final stage of crack attachment, compressed springs made of nitinol material are fed. Using of material with a shape memory will allow the proppant packing to be compacted and the proppant to be 'locked' in the fracture. © Published under licence by IOP Publishing Ltd
Theory of the propagation of coupled waves in arbitrarily-inhomogeneous stratified media
We generalize the invariant imbedding theory of the wave propagation and
derive new invariant imbedding equations for the propagation of arbitrary
number of coupled waves of any kind in arbitrarily-inhomogeneous stratified
media, where the wave equations are effectively one-dimensional. By doing this,
we transform the original boundary value problem of coupled second-order
differential equations to an initial value problem of coupled first-order
differential equations, which makes the numerical solution of the coupled wave
equations much easier. Using the invariant imbedding equations, we are able to
calculate the matrix reflection and transmission coefficients and the wave
amplitudes inside the inhomogeneous media exactly and efficiently. We establish
the validity and the usefulness of our results by applying them to the
propagation of circularly-polarized electromagnetic waves in one-dimensional
photonic crystals made of isotropic chiral media. We find that there are three
kinds of bandgaps in these structures and clarify the nature of these bandgaps
by exact calculations.Comment: 7 pages, 1 figure, to appear in Europhys. Let
Photonic Analogue of Two-dimensional Topological Insulators and Helical One-Way Edge Transport in Bi-Anisotropic Metamaterials
Recent progress in understanding the topological properties of condensed
matter has led to the discovery of time-reversal invariant topological
insulators. Because of limitations imposed by nature, topologically non-trivial
electronic order seems to be uncommon except in small-band-gap semiconductors
with strong spin-orbit interactions. In this Article we show that artificial
electromagnetic structures, known as metamaterials, provide an attractive
platform for designing photonic analogues of topological insulators. We
demonstrate that a judicious choice of the metamaterial parameters can create
photonic phases that support a pair of helical edge states, and that these edge
states enable one-way photonic transport that is robust against disorder.Comment: 13 pages, 3 figure
TRENDS OF INITIAL METABOLIC SYNDROME AND ITS RELATIONSHIP WITH SUBCLINICAL ATHEROSCLEROSIS AMONG YOUNG AND MIDDLE-AGED MEN
Atherosclerotic cardiovascular diseases substantially have contributing to mortality and structure of disability in developed countries. Metabolic syndrome is a cluster of clinico-biochemical changes with the most aterogenic potential.Objective: to determine trends of early stages of metabolic syndrome and its relationship with the initial atherosclerosis in young and middle-aged men. Have been examined 436 men with an assessment symptoms of metabolic syndrome, as well as signs of subclinical atherosclerosis. The young men with initial manifestations of metabolic syndrome were characterized by the classical cardiovascular risk factors. According to the results of the study have been already diagnosed dyslipidemia, violation of apolipoproteides fractions, postprandial hyperglycemia at the initial stage of metabolic syndrome in this category of patients. have been proposed assessment of waist circumference, degree of diastolic blood pressure and postprandial glycemia as the most sensitive diagnostic markers of cardiovascular lesions in primary manifestations of metabolic syndrome
Enantiospecific Detection of Chiral Nanosamples Using Photoinduced Force
We propose a novel high resolution microscopy technique for enantio-specific
detection of chiral samples down to sub-100 nm size, based on force
measurement. We delve into the differential photo-induced optical force exerted
on an achiral probe in the vicinity of a chiral sample, when left and right
circularly polarized beams separately excite the sample-probe interactive
system. We analytically prove that the differential force is entangled with the
enantiomer type of the sample enabling enantio-specific detection of chiral
inclusions. Moreover, we demonstrate that the differential force is linearly
dependent on both the chiral response of the sample and the electric response
of the tip and is inversely related to the quartic power of probe-sample
distance. We provide physical insight into the transfer of optical activity
from the chiral sample to the achiral tip based on a rigorous analytical
approach. We support our theoretical achievements by several numerical
examples, highlighting the potential application of the derived analytic
properties. Lastly, we demonstrate the sensitivity of our method to
enantio-specify nanoscale chiral samples with chirality parameter in the order
of 0.01, and discuss how this could be further improved