DEVELOPMENT OF A MATHEMATICAL MODEL OF LIVER FILTRATION

Клетки печени занимают центральное место в реакциях промежуточного метаболизма. Печень принимает участие в метаболизме почти всех классов веществ. Основной структурной единицей печени является печеночная долька, которая представляет собой призму размером 1,5-2 мм с плоскими основанием и вершиной. По всей дольке также распределены лимфатические сосуды, которые активно поглощают интерстициальную жидкость и выводят ее с регулируемой скоростью, однако зависимость скорости поглощения от интерстициального давления и других параметров известна не полностью. В работе представлена математическая модель для оценки кровотока в печеночной дольке. Рассмотренная клеточная модель включает в себя производство и прохождение лимфы по двум основным путям: поглощение лимфатическими сосудами и выход из печени через поверхность дольки в интерстициальное пространство. Приведены геометрические и механические допущения модели и ее недостатки. В биологической модели исследовано влияние изменений кровяного давления в печени на выработку лимфы и оценивается скорость поглощения лимфы и поток жидкости (как лимфы, так и крови) по всей поверхности печени. В математической модели показана классификация: статическая (не зависящая от времени), пространственная, детерминированная, нелинейная, непрерывная. Результаты исследования показали, что предлагаемая клеточная модель микроциркуляции печени включает в себя производство и прохождение лимфы по двум основным путям: поглощение лимфатическими сосудами и выход из печени через поверхность дольки в интерстициальное пространство. Выявлены основные недостатки разрабатываемой модели Liver cells are central to intermediate metabolic reactions. The liver is involved in the metabolism of almost all classes of substances. The main structural unit of the liver is the hepatic lobule, which is a prism 1.5-2 mm in size with a flat base and apex. Lymphatic vessels are also distributed throughout the lobule, which actively absorb interstitial fluid and remove it at a controlled rate, however, the dependence of the rate of absorption on interstitial pressure and other parameters is not fully known. The paper presents a mathematical model for assessing blood flow in the hepatic lobule. The considered cellular model includes the production and passage of lymph through two main pathways: absorption by the lymphatic vessels and exit from the liver through the surface of the lobule into the interstitial space. Geometric and mechanical assumptions of the model and its disadvantages are presented. A biological model investigates the effect of changes in liver blood pressure on lymph production and estimates the rate of lymph absorption and fluid flow (both lymph and blood) over the entire surface of the liver. The mathematical model shows the classification: static (independent of time), spatial, deterministic, nonlinear, continuous. The results of the study showed that the proposed cellular model of liver microcirculation includes the production and passage of lymph through two main pathways: absorption by the lymphatic vessels and exit from the liver through the surface of the lobule into the interstitial space. The main shortcomings of the developed model are revealed

Prescription and Effect of Orthokeratology Lenses

Orthokeratology (OK) is the way to correct the myopia or astigmatism by flattening or the central cornea with specialty lenses. The range of correction is from -2.50 to -4.00 diopters after 10 days of fitting. The designs are constructed with flat base curve radius, steep reverse curve, flat alignment curve, and peripheral curve. This multi-curve design enabled the OK lenses to stay on the cornea stably and effectively. Recently, the application of OK is extending to hyperopia and presbyopia. In the future, the amount of correction and the application of OK will increase more and more.

A Novel High Concentration Fresnel Lens as a Solar Concentrator

This paper describes the design methodology for a novel Fresnel lens. The original Fresnel lens is obtained from a plano-convex lens, whose spherical surface is split into a number of divisions (called facets), collapsed onto the flat base. Thus, all the facets of the original Fresnel lens have the same radius as that of the plano-convex lens. The proposed design aims to achieve better ray concentration and reduced spherical aberration than the original Fresnel lens by constructing spherical facets with unequal radii. The centers and radii of facets are constrained so that the ray refracted from the bottom vertex of each facet on one side of the optical axis and the ray refracted from the outer vertex of the corresponding facet on the other side of the optical axis must intersect at the focal plane. The proposed lens design has resulted in a 275% gain in the concentration ratio and a 72.5% reduction in the spherical aberration compared to the original lens of the same aperture diameter and number of facets. The performance of both novel and original Fresnel lenses when used as solar concentrators with a conical coil receiver is evaluated. The novel Fresnel lens led to increased heat gain and resulted in a compact solar collector design.

Application of mathematical modeling methods to determine the effect of soil on natural vibration frequencies of pipelines

When a pipeline is subjected to an external influence that can affect the frequency of its natural vibrations, the parameters of its natural vibrations change, which increases the measurement error, and often simply distorts the results of vibration control. For pipelines, such an impact may be the influence of the soil when pipelines are laid without a channel. Different types of soil affect the change in the natural vibration frequency of the pipeline in different ways.The purpose of the article is to analyze the influence of various types of soils on the parameters of natural vibrations of the pipeline. The aim of the study was to theoretically confirm the dependence of the change in the frequency of vibration of the pipeline under the influence of soil.A modal analysis of natural oscillations of 5 polyethylene pipelines was performed. As initial data, it is assumed that the design pipeline is laid in a trench with inclined walls, with the slope laid on a flat base at a depth of 2.5 m. The calculations were performed in the ANSYS finite element analysis software package. In order to build a mathematical model, the degree of soil impact on pipelines is determined by studying the vertical and lateral pressure of the soil on the above pipelines, and the natural vibrations of pipelines are analyzed.The results of the modal analysis for polyethylene pipes with a laying scheme with inclined walls and different soils (gravel sands, coarse and medium-sized; heavy clays) are presented. The soils were chosen that are the most common on the territory of Russia.Thus, the obtained dependence of the degree of influence of different soil on the natural frequencies of pipelines significantly increases the reliability of vibration diagnostics of buried communications, can facilitate the work on its organization and allow determining long-term forecasts of pipeline operation.

REDUCTION OF LOCAL HEATING IN TANKS OF POWERFUL TRANSFORMERS BY HEAT-REMOVING LOCAL RADIATORS WITH RIBBED

The main approaches, the results of numerical modeling, and examples of the practical application of heat-dissipating radiators made of aluminum, with a flat base, and with ribbing to reduce local heating in ferromagnetic covers and walls of transformer tanks, which arise in cases of concentration of magnetic fluxes from multi-ampere taps or magnetic shunts are presented. The case of thermal coupling of a non-magnetic flange of a yoke beam with a flat base of a radiator (copper plate) is considered, which shows the possibility of reducing local heating of the beam using conductive heat transfer between the shelf and the plate and convection heat transfer from their surfaces to cooling oil. References 4, figures 7.

Three-dimensional geometry and growth of salt-detached strike-slip faults, Outer Kwanza Basin, offshore Angola

<p>Strike slip faults are a prominent tectonic feature in Earth to accommodate horizontal and/or oblique slip that trend parallel to fault strike. These faults are commonly formed on plate boundaries setting, where they are basement-involved and driven by elastic crustal loading at seismogenic depths. Still, we also observe the strike slip faults on salt-bearing slopes, where the faults are typically thin-skinned and accommodate spatial variability in the rate of seaward flow of salt and its overburden. In both cases, relatively little is still known of their three-dimensional geometry and growth in comparison to both normal and reverse fault, that have been extensively studied.</p><p>We use a high-quality, depth-migrated 3D seismic dataset to investigate salt-detached strike-slip faults in the mid-slope translational domain of the Outer Kwanza Basin, offshore Angola. We show that NE-SW-striking faults are presently located above elongate, margin-parallel, NE-trending ramps, more amorphous, dome-like structural highs, and areas of relatively subdued relief. The faults are broadly planar, display normal and/or reverse offsets, and may locally bound negative flower structures. These faults offset a range of salt and overburden structures, including salt walls and anticlines, and salt -detached thrusts and normal faults, defining six major structural compartments. Our displacement-distance (Tx) analysis of several faults reveal they are characterized by complex throw distributions that define 3-to-10, now hard-linked segments. In vertical profiles, these segments are characterized by symmetric-to-asymmetric throw distributions (Tz) that record throw maxima at the top of the Albian, Eocene and/or Early Miocene. Expansion indices (EI) and isopach maps demonstrate the presence of fault-related growth strata, with complex thickness patterns also reflecting the combined effect of vertical (i.e. diapirism) and horizontal (i.e. translation) salt tectonics.  Taken together, our observations suggest the salt detached strike-slip faults evolved during three key phases: (i) Albian – nucleation and local linkage of individual segments; (ii) Eocene-to-Oligocene – reactivation, propagation, and death of many now-linked segments; and (iii) Miocene – local fault reactivation due to salt diapirism.  </p><p>We show that salt detached strike-slip faults in the translational domain of the Outer Kwanza Basin grew above either rugose or relatively flat base-salt surface. More specifically, salt detached strike-slip faults, like normal and reverse faults documented elsewhere, grew in response to the propagation and eventual linkage of initially isolated segments. We also highlight that the coeval growth of salt walls can play a role in controlling the three-dimensional geometry and kinematics of salt detached strike-slip faults.</p>

Effects of Running Surface Stiffness on Three-Segment Foot Kinematics Responses with Different Shod Conditions

Objective. The aim of this study was to investigate the effects of surface stiffness on multisegment foot kinematics and temporal parameters during running. Methods. Eighteen male subjects ran on three different surfaces (i.e., concrete, artificial grass, and rubber) in both heeled running shoes (HS) and minimal running shoes (MS). Both these shoes had dissimilar sole profiles. The heeled shoes had a higher sole at the heel, a thick base, and arch support, whereas the minimal shoes had a flat base sole. Indeed, the studied biomechanical parameters responded differently in the different footwear during running. Subjects ran in recreational mode speed while 3D foot kinematics (i.e., joint rotation and peak medial longitudinal arch (MLA) angle) were determined using a motion capture system (Qualysis, Gothenburg, Sweden). Information on stance time and plantar fascia strain (PFS) was also collected. Results. Running on different surface stiffness was found to significantly affect the peak MLA angles and stance times for both HS and MS conditions. However, the results showed that the joint rotation angles were not sensitive to surface stiffness. Also, PFS showed no relationship with surface stiffness, as the results were varied as the surface stiffness was changed. Conclusion. The surface stiffness significantly contributed towards the effects of peak MLA angle and stance time. These findings may enhance the understanding of biomechanical responses on various running surfaces stiffness in different shoe conditions.

Computational Analysis of Base Drag Reduction for a Subsonic Missile Projectile at Different Flow Velocity Conditions

Base drag is arising from flow separation at blunt base of a body. It can be a sizeable fraction of total drag in context of projectiles, missiles and after bodies of fighter aircrafts. The base drag is the major contribution of total drag for low speed regimes, flight tests have shown that the base drag may account for up to 50% of total drag. In this paper an experimental investigation for simple semi-circular flight vehicle body of length 500mm and diameter 50mm was conducted for the purpose of investigating base drag. The base drags for three configurations are calculated and the results are compared with CFD data. The three configurations used for testing are flat base configuration, closed nozzle configuration and boat tail configuration. The evaluation of base drag for three different flow velocities such as (i) 20m/s, (ii) 35m/s and (iii) 50m/s at different angle of attack such as -2, 0 and 2 are experimented and compared.

Investigation of Reduction in Base Drag using Experiment and CFD at Subsonic Speed Regimes

Base drag, arising from flow separation at the blunt base of a body can be a sizeable fraction of total drag in the context of projectiles, missiles and after bodies of fighter aircrafts. The base drag is the major contribution of total drag for low speed regimes, flight tests have shown that the base drag may account for up to 50% of the total drag. Computational and experimental investigation for a hemispherical flight vehicle body of length 500mm and diameter 50mm was conducted for the purpose of investigating the base drag. Three case studies were conducted to investigate the properties of the flow field around the flight vehicle at different flow velocities of 20m/s, 30m/s and 50m/s at zero angle of attack (AoA). The three cases were (i) a flight vehicle with flat base configuration, (ii) a flight vehicle with a nozzle at the base and (iii) a flight vehicle configuration with a boat tail, Fig 1. Also, the three configurations were investigated at different AoA of -2, 0 and +2. The base drags for three configurations are calculated and the experimental results are compared with the CFD results.