Influence of the temperature of a flow on the readings of a hot-wire anemometer

The error due to the flow temperature and sensor wire temperature in measuring the mean velocity of a flow using a hot-wire anemometer is studied.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 3, pp. 366–374, September, 1985.     

Forensic analysis of the failure of the foundations of a tunnel built to channel the course of a river

This paper presents the results of a forensic analysis of a tunnel above which an embankment was built that served as a roadbed. The joint tunnel–embankment structure is located on the outskirts of the town of Piedrafita in northwestern Spain. The tunnel channels the course of the River Vilela in its crossing of the aforementioned road.This article presents a detailed report of the problem, including the damage caused to the structure of the tunnel and the embankment, and it presents the measurements taken and the determination of the origin of the problem. For this determination, a numerical simulation of the joint tunnel–embankment–ground structure was conducted on the basis of the data obtained from tests carried out both in situ and in the laboratory. The study was complemented by an analysis performed using classical methods that confirmed that the movements detected in the overall structure were caused by the collapse of the foundations.The uniqueness of the study presented in this paper lies in the combination of very simple analytical calculations to evaluate the stresses transmitted by the foundations to the ground with a numerical model that enables us to evaluate the stress and deformational state of the study area in a highly detailed way.     

Analysis of the Transfer Processes in a Vapor Film during the Interaction of a Highly Heated Body with a Cold Liquid

The processes of heat and mass transfer in a vapor film formed during the interaction of a highly heated body with a cold liquid are investigated using a numerical solution of the kinetic Boltzmann equation and a one-dimensional unsteady-state formulation of the problem. The solution is derived for Knudsen numbers values exceeding 0.005. The results are in good agreement with the relations for steady-state heat transfer through the interface. The duration of the nonstationary process is shown to be short on a macroscopic time scale. Therefore, the heat transfer through a vapor film during the investigation of various applied problems may be considered steady-state.     

Interval Estimation of the Parameters of a Distribution from a Sample of a Random Quantity

A program is developed for solving the problem of making an interval estimation of the parameters of a distribution from a single sample of a random quantity, based on a statistical modeling method. The results of a solution of the problem for certain symmetric and asymmetric distributions are presented. The average error in estimating the confidence intervals and their limits is 4–15% in the range of values of the confidence level of 0.8 P 0.998 for a sample volume of N = 500–1000.     

Evaluation of the Field near a Cusp of a Caustic

The field in the neighbourhood of a cusp of a caustic can be expressed in terms of a function of two variables, P(X,Y), known as Pearcey's integral or the Pearcey function. In this paper we develop efficient algorithms for computing this function and its derivatives P/ X and P/ Y. They are based on a Taylor series expansion in a region close to the cusp at X = Y = 0, and on asymptotic approximations in regions far from the cusp. The asymptotic results are given in terms of contributions of isolated stationary points in regions far from the caustic, and in terms of the Airy integral function and its derivative in a region close to the caustic. Three terms in the asymptotic expansions are used, and they give an accuracy for P(X,Y) better than 0·006 in amplitude and 0·6° in phase at distances from the cusp greater than (X² +Y² )^1/2 = 4.     

Reconstruction of the area-moment-of-inertia of a rotor blade using a shifting point-load and the end-slope

The main focus of this study was to develop an inverse model that could be used to determine the changes in sectional area-moment-of-inertia of a helicopter rotor blade from the knowledge of a shifting point-load and the end-slope data. In this investigation, the cross-sectional area-moment-of-inertias of a rotor blade model with n segments are reconstructed using a shifting point-load and the corresponding end-slope data. The end-slope data used in this inverse problem were numerically generated using the finite element method. The end-slope data and the loading were then used in the inverse problem to reconstruct the cross-sectional area-moment-of-inertias for the model. To solve the inverse problem, the solution domain was discretized into finite number of segments, and a shifting point-load was applied to the mid-point of each segment. The beam equation was then integrated to create a set of linear equations in terms of loading and end-slopes. Next, the resulting set of equations was solved simultaneously to recover the area-moment-of-inertia for each segment. A series of numerical experiments were performed to check the validity and sensitivity of the inverse model. Comparison of the inverse solutions with the direct solutions confirms that the variations in the area-moment-of-inertia for a helicopter rotor blade can be reconstructed with good accuracy from the knowledge of the shifting point-load and end-slopes.     

Diffraction by a corner on the edge of a wedge

The spherical wave diffracted by a corner on the edge of a wedge is determined for a scalar field. A corner is a point at which the edge possesses a jump discontinuity in its $\text{J}$th derivative, $\text{j?2}$, or in its slope, $\text{j = 1}$, provided that the jump in slope is small. The boundary layer method is used to determine the diifraction coefficients for this corner. In this method, an asymptotic expansion of the field is constructed within a boundary layer surrounding the corner, and another expansion is found outside this layer. The matching of the two expansions yields the diffraction coefficients. Both the Dirichlet and Neumann boundary value problems are considered.     

Specific features of the flow of a two-phase stream in a grainy bed of a separator

The structure of a two-phase stream in a regular grainy bed of a separator was analyzed. A two-phase emulsion stream in a grainy bed transforms into a stream of two mutually permeable continuous phases with a highly developed and nondegenerate (i.e., not varying noticeably with time) phase boundary surface, which creates favorable conditions both for induced coalescence of emulsion contaminations and for mass exchange between the streams. High retaining power of a grainy bed toward minor stream and the corresponding differences in the flow velocities give rise to a braking effect for impurities adsorbed on the phase boundary, which allows the use of the separator for removing solid phase particles from the product stream. The possibility of removing carbon black particles from a stream simulating a spent nuclear fuel solution was demonstrated.     

Analysis of the fracture of a turbine blade on a turbojet engine

The fracture on a turbine blade of a turbojet engine has been investigated to see the cause of crack initiation. The fractured turbine blade did not seem to have suffered any damages by foreign objects. The turbine blade had initially cracked by a fatigue mechanism over a period of time and then fractured by the overload at the last moment.The crack initiated at the subsurface or close to the surface and showed the cleavage-like features. The segregated area of Ti and Mo, caused usually by improper manufacturing process, is found by the microstructure and EDX analysis of the blade. The crack initiated at this area and was due to the stress concentration at the segregation of Ti and Mo near the blade surface.     

Modeling a mechanism of decreasing the drug of a shell of revolution streamlined by a viscous fluid

The problem of determining the shape and parameters of a running wave on the surface of a body of revolution so as to minimize its drag in the streamlining flow of a viscous fluid is considered. The physical effects involved in this method of flow control are analyzed. The possibility of a numerical experiment on the streamlining of a shell of revolution within the framework of a complete set of hydroelasticity equations, including the Navier-Stokes equation and the equations of motion of a linearly elastic shell, is discussed.     

On the Stability of a Nonlinear Viscoelastic Rod Subjected to a Longitudinal Force in the Form of a Random Stationary Process

The stability and reliability of a nonlinear viscoelastic rod under a stochastic excitation is investigated. The loads are assumed to be in the form of random stationary processes. The solution is obtained with the help of a numerical method, which is based on the method of the statistical simulation of random input processes and on the numerical solution of the system of nonlinear and linearized integro-differential equations. These equations describe a nonperturbed and perturbed motion of the rod. The estimation of the stability is carried out with the help of top Lyapunov exponents.     

Switching the conformation of a DNA molecule with a chemical oscillator

pH oscillations generated by a nonequilibrium chemical reaction are used to switch a pH-sensitive DNA structure between two distinct conformations. The utilization of a chemical oscillator represents a novel method for achieving autonomous motion in molecular devices. The oscillatory reaction is a variant of the Landolt reaction and produces pH variations in the range between pH 5 and 7. In this range, a cytosine-rich DNA strand can be switched between a random coil conformation and the folded i-motif structure. The conformational changes are monitored simultaneously with the pH value in fluorescence-resonance energy-transfer experiments.     

Reconstruction of the area-moment-of-inertia of a beam using a shifting load and the end-slope data

In recent years, much concern has been reported about the condition of US infrastructure, particularly the bridges. These concerns have brought attention to the area of structural health monitoring and its significance in averting tragedies. The main focus of this study was to develop a mathematical model that could be used to determine the changes in the structural characteristics such as cross-sectional area-moment-of-inertia from the knowledge of a shifting load and the end-slope data. In this investigation, the cross-sectional area-moment-of-inertias of a scaled model of simply supported steel bridge are reconstructed using a shifting load scheme and the corresponding end-slope data. The end-slope data used in this inverse problem were numerically generated using the finite element method. The end-slope data and the loading were then used in the inverse problem to reconstruct the cross-sectional area-moment-of-inertias for the model. To solve the inverse problem, the solution domain was discretized into finite number of elements and nodes. A shifting uniformly distributed load was applied to each element, and the beam equation was integrated to create a set of linear equations in terms of loading and end-slope differences that could be solved simultaneously to recover the area-moment-of-inertia for each element. Comparison of the inverse solutions with the direct solutions confirms that the variations in the area-moment-of-inertia for a bridge cross section can be reconstructed, with a good accuracy, from the knowledge of the shifting load and end-point slopes.     

Stress Analysis and the Cause of the Fracture of a Clevis at the End of a Hydraulic Piston Rod

A hydraulic piston assembly fractured while in service. The fracture involved a clevis assembled to the end of the cylinder piston rod. In fact, there were two fractures: one where a threaded end on the clevis was assembled to the piston rod and a second involving a fracture through the wall of the clevis. Analysis by plant personnel suggested that the stresses involved were small and that fracture should not have been expected. As a more detailed stress analysis of the clevis ring demonstrated, the stresses associated with the clevis, treated as a closed ring, were more than sufficient to have resulted in the fracture through the clevis wall. The other fracture, the fracture at the point of assembly to the piston rod, was proved to be secondary. Stress analysis as well as fracture analysis proved the point and allowed appropriate recommendations to be made to avoid a reoccurrence.     

Determination of the Coordinates of the Center of a Gaussian Beam by Means of a Matrix Photodetector Using a Weighting Method

A weighting algorithm to determine the coordinates of the center of a Gaussian laser beam projected onto a matrix photodetector is considered. The influence of the internal noise of the photodetector, the maximum brightness of the signal at the beam maximum, and the beam radius on the precision of the algorithm is investigated. Recommendations on image processing are presented.     

聚醚砜四元制膜液体系的相图计算

以Ｆｌｏｒｙ－Ｈｕｇｇｉｎｓ理论为基础，对ＰＥＳ－ＰＧ－ＮＭＰ＿Ｈ２Ｏ＿）聚醚砜丙二醇－Ｎ－甲基－２－哟咯烷酮水）四元制液体系的相图进行了计算，利用三元相图考察Ｈ２Ｏ和ＰＧ对液－液相分离的影响，在三元的理论的基础上提出了低分子量添加剂的卤元改性Ｆｌｏｒｙ－Ｈｕｇｇｉｎｓ理论，并提出了一种获得四元相图的方法，利用四元相图能较争地描述四元体系，利用改性的四元理论，能了地理解该种体系的液－液相分离行为。     

On the flow of a stratified fluid over a barrier

Summary The flow of a stratified fluid over a barrier is considered. The initial-value problem is solved, and it is shown that there is no disturbance far upstream of the barrier whent . The stationary solution which is obtained by lettingt, is given in a simple closed form for a barrier of an arbitrary shape.     

On a Solution to the Equation of Filtration of a Liquid in a Permeable Medium

Journal of Engineering Physics and Thermophysics - The authors consider nonstationary flow of a gas from a screen vacuum thermal insulation into vacuum and discuss its coupling to the Boussinesq...     

Thermodynamics of the interaction of a group of nanoparticles with a macrophase

An expression describing the variation of the Gibbs potential for a system consisting of a group of nanoparticles and a macrophase has been derived. It has been shown that in this system there are diffusion flows of the substance from nanoparticles to the macrophase. The conditions have been defined, under which a nanoparticle or a group of nanoparticles can be in an equilibrium state and maintain the size and shape arbitrarily long.