Color opponencies in the system of the uniform color scales of the Optical Society of America

Many problems regarding color opponency are still unsolved. In this study the system of the uniform color scales of the Optical Society of America (OSA-UCS) is analyzed with the aim of obtaining answers to very general questions on color opponency. The perceptual color opponencies in the OSA-UCS system, represented by its coordinates (j, g), appear to work in a mutually interacting way. On the hypothesis that such an interaction is due to a linear mixing of a pair of independent opponent mechanisms with scales satisfying a proper Weber fraction, three chromatic opponency functions are derived, whose sum is equal to zero. These functions are the logarithms of the ratios of two tristimulus values in a proper reference frame (called the "main reference frame") and therefore are antisymmetric and zero-degree homogeneous functions of these tristimulus values. Any pair of these three functions is a set of two independent functions. A new formula for color opponency in the OSA-UCS system is derived in which the perceptual color opponencies (j, g) are written as products of the lightness by a proper linear mixing of any pair of the three chromatic opponency functions. All this is possible because the lattice of the OSA-UCS system is composed of geodesic lines.     

Method of including the anisotropy of the optical properties of the surface and the nonunidimensionality of the system in determining the effective radiation

Based on the method of successive substitutions, an integral equation is derived in which multiple reflections are explicitly identified. This equation is used provide simple methods of estimating the local effective radiation of two-dimensional and three-dimensional systems of surfaces, with due regard for the anisotropy of their optical properties. A cylindrical cavity confined by the surface of a right circular cylinder with a side pyrometric hole is treated as an example. The results obtained by the suggested method are compared with the data of direct solution of an integral equation for the two-dimensional problem.     

Investigation of the influence of polymer admixtures on the magnitude of the local drag coefficient

Experimental data are presented on the influence of polyox-admixtures in an aqueous solution on the magnitude of the local drag coefficients. Theoretical and experimental results on determining the pressure drop in a pump during the flow of polymer solutions in a real hydraulic apparatus are compared.     

Traceability of measurement results in the nanometric range to the units of the international system of units of physical quantities

Questions involved in the assurance of the traceability of results of measurements in the nanometric range to standards included in the BIPM CMC base of measurements of geometric quantities are considered for which a set of calibrated (verified) gauges along with a chain of traceability to the standard, i.e., the metrological atomic-force microscope, are proposed. Two methods of calibration of scanning probe microscopes are also proposed, a direct method and a method that employs the Fourier transform of the measure topogram. A technique of calibration of scanning electron microscopes; the uncertainty budget and formulas for use in calculating its components in calibration relative to a relief measure in the TGQ1 nanometric range are also given.     

Stability of the unfolding of the predator-prey model

We prove a conjecture of Zeeman that any generic unfolding of the Volterra's original predator-prey model is stable. This well-known two-dimensional model has co-dimension one in the planar Lotka- Volterra system and all its orbits are closed in the region of physical interest. Any generic unfolding of the model locally induces a degenerate Hopf bifurcation, but the presence of a cycle of saddles makes the global stability analysis quite involved. We solve the problem by working in the equivalent replicator system. Our proof of stability uses a family of Lyapunov functions for the unfolding. There are two other co-dimension one bifurcations in the planar replicator (equivalently Lotka- Volterra) system, which involve cycles of saddles and are therefore non-trivial. In one case we prove the stability of the bifurcation and in the other we determine a topologically versa! unfolding of the co-dimension one flow. This then, together with previous work on the subject, completes the study of co-dimension one bifurcations of the system     

On the effect of the backup plate stiffness on the brittle failure of a ceramic armor

The present investigation enquires the role of the backup plate mechanical properties in the brittle failure of a ceramic tile. It provides a full-field solution for the elastostatic problem of an infinite Kirchhoff plate containing a semi-infinite rectilinear crack (the tile) resting on a two-parameter elastic foundation (the backup plate) and subjected to general transverse loading condition. The backup plate is modeled as a weakly non-local (Pasternak type) foundation, which reduces to the familiar local (Winkler) model once the Pasternak modulus is set to zero. The same governing equations are obtained for a curved plate (shell) subjected to in-plane equi-biaxial loading. Fourier transforms and the Wiener–Hopf technique are employed. The solution is obtained for the case when the Pasternak modulus is greater than the Winkler modulus. Superposition and a two-step procedure are employed: First, an infinite uncracked plate subjected to general loading is considered; then, the bending moment and shearing force distribution acting along the crack line are adopted as the (continuous) loading condition to be fed in the solution for the cracked plate. Results are obtained as a function of the ratio of the Pasternak over the Winkler foundation stiffness times the tile flexural rigidity. It is established that the elastic foundation significantly affects the mechanical behavior of the elastic plate. In particular, the Winkler model substantially underestimates the stress state near the crack tip. Stress-intensity factors are determined, and they are employed as a guideline for increasing the composite toughness. The analytical solution presented in this paper may serve as a benchmark for a more refined numerical analysis.     

On a closure of the governing equations of defect dynamics and the resulting theory of the plastic state

The equations of defect dynamics are derived from the single system of relations that specifies the time rate of change of the dislocation densities. The resulting source equations are shown to admit a 12-fold gauge group and the resulting kinematic equations are shown to admit a 15-fold gauge group. The generators of the two gauge groups are determined by the requirements that the Burgers and Frank vectors have their classical representations. This determination results in a unique decomposition of all quantities in terms of sums of internal variables and external geometric variables, and represents the first and second closures of the field equations. The presence of a unique external system of geometric variables permits derivation of the forms of the equations of balance of mass, momentum, moment of momentum and energy. The third closure is obtained through use of the practices of nonequilibrium thermodynamics. This results in a system of equations that determines the dislocation currents in terms of the distortion, the dislocation density and the geometric strain measures. A class of models is exhibited wherein most of the properties of plasticity theories are obtained.     

Dependence of the dose estimate on the time pattern of intake by the example of tritiated water intakes

The uncertainties related to activity measurement and time pattern of intake in routine monitoring of internal exposure are considered through the example of tritiated water intakes. For this purpose, a combination of intake-to-bioassay and bioassay-to-intake calculations with Monte Carlo integration technique is introduced as a method of investigation. The time pattern of intake and the measured activity are defined as random input quantities. The probability density functions (PDFs) of the input quantities are defined and a Monte Carlo integration is performed to obtain the PDF of the output quantity which is either the value of intake estimated from a measured value of activity or the estimated activity from a given value of intake. Different possible estimates of the intake are considered: some represent the parameters of the PDF of the output quantity, others are derived from the commonly used constant chronic, I(CC), and mid-point, I(1/2), methods. The combinations of activity and intake estimates that would provide a stable estimate of the initial intake in intake-to-bioassay and bioassay-to-intake calculations were studied. Several intake estimates satisfying this requirement can be chosen depending on the task to be solved by adjusting the proper activity estimate.     

Application of the Cosserat continua to numerical studies on the properties of the materials

The finite element models of Cosserat continuum in two- and three-dimensions are presented. The size effects of a cantilever beam and a micro-rod, the well-posedness, the mesh-independent solutions of the boundary value problems with non-associated elastoplastic and strain softening constitutive behavior, and the progressive failure of the two- and three-dimensional vertical excavations are studied. Numerical results illustrate that the proposed Cosserat continuum models are capable of reflecting the size effects of micro-structures, preserving the well-posedness of the boundary value problem characterized by the strain localization, ensuring mesh-independent solutions, and simulating the entire progressive failure process occurring in engineering structures.     

Investigation of the mechanisms of heat conduction in dielectrics and metals on the basis of the molecular-radiation theory of transfer

The activation mechanisms of transfer of a substance in condensed media are described. Analytical expressions defining the dependences of the electron, photon, and diffusion heat conductivity on the temperature, density, and microscopic characteristics of these media are presented. The temperature dependence of the density of free electrons in conductors was obtained. The results of a comparison of theoretical and experimental data are presented.     

Increasing the Accuracy of Reproduction of Pressure by Means of the Ukrainian Secondary Standard of the Unit of Pressure

The estimated components of the error in the determination of the effective area of a measuring piston-cylinder assembly of a piston manometer with a non-sealed piston are reported. Such manometers are incorporated into the secondary standard of the unit of pressure.     

High-Order Approximation Equations for the Primitive Equations of the Atmosphere

In this article, a family of models approximating the primitive equations of the atmosphere, which are known to be the fundamental equations of the atmosphere, is presented. The primitive equations of the atmosphere are used as a starting point and asymptotic expansions with respect to the Rossby number are considered to derive the nth-order approximate equations of the primitive equations of the atmosphere. Simple global models of the atmosphere are obtained. These higher-order models are linear and of the same form (with different right-hand sides, depending on the lower-order approximations) as the (first-order) global quasi-geostrophic equations derived in an earlier article. From a computational point of view, there are two advantages. Firstly, all the models are linear, so that they are easy to implement. Secondly, all order models are of the same form, so that, with slight modifications, the numerical code for the (first-order) global quasi-geostrophic model can be employed for all higher-order models. From a physical point of view, higher-order models capture more physical phenomena, such as the meridional flows, even though they are small in magnitude. Of course, there are still many subtle issues involved in this project, such as the convergence of the asymptotics; they will be addressed elsewhere. The article is concluded by a presentation of numerical simulations based on these models.     

In-situ optical analysis of the gas phase during the formation of carbon nanotubes

A reactor has been developed at ONERA to investigate the gas phase during carbon nanotube formation by laser-induced fluorescence (LIF), Laser-induced incandescence (LII), coherent anti-Stokes Raman Scattering (CARS), and emission spectroscopy. Continuous vaporization is achieved with a continuous wave CO2 laser. Optimized conditions are used for single-walled nanotube growth, that is, a graphite target doped with 2 atom % Ni and 2 atom % Co, helium as buffer gas at a flow rate of 50 ml/s, and a pressure of 300 hPa. Temperature profiles are measured by CARS on H2, and soot images are obtained by LII in the hot carbonaceous flow. LIF and spontaneous emission of the C2 radical and Ni and Co atoms are presented. Spectral investigations are conducted at 3100 and 3200 K to have an optimized pair of excitation/detection wavelengths. Spatial investigations of the relative concentrations in the hot carbonaceous flow are performed up to 3500 K. The concentrations are measured as a function of target temperature. Two regimes of vaporization are observed. Vaporization is slow up to 3350 K and becomes much faster above this temperature. The fast regime in the 3350-3500 K range corresponds to the observed spatial extent of the metal vapors region. At 3500 K, the C2 profiles obtained with and without catalysts are very different as a result of carbon coalescence as well as carbon dissolution into the metal nanoparticles when these are present in the gas phase. The shape of the C2 profile can be related to nanotube formation and growth at a target temperature of 3500 K.     

The Problem of Estimating the Uncertainty of the Fixed Point Temperature Due to the Presence of Impurities

The main problems in estimating the uncertainty due to the presence of impurities in the material: the absence in the documents of a unique definition of the quantity being measured – the fixed point temperature, the lack of agreed methods of realizing the fixed points and the insufficient justification of the equations used for the estimate, are analyzed. The results of a measurement of the melting point of gallium are presented, which differ in the conditions in which they were realized – with one and two liquid-solid interfaces and different solidification conditions, are presented. The reasons for the considerable difference between the values of the temperatures obtained in these experiments are discussed.     

Modeling of the impact dynamics of large meteoric bodies on the surface of the planet

We present a procedure for numerical modeling and the results predicted for dynamics of crater formation in asteroid impact on the ground in the approximation of two-dimensional gas dynamics in an axisymmetric formulation. Gas-dynamic equations are solved using a fully conservative difference scheme in Eulerian variables. Predictions are performed with both an analytic representation of the equation of state (according to Tillotson) and wide-range semiempirical equations of state with a phase transition into vapor and a more exact specification of cold compression. Consideration is given to impact at a velocity of 50 km/sec with body dimensions of the order of 1 km.     

Simulating the behavior of the material in the vicinity of wedge-shaped zones of engine components

A method is proposed of evaluating the endurance of the material and its thermal and stress states in the vicinity of wedge-shaped zones of engine components on the basis of the results of testing wedge-shaped models whose faces are subjected to the effect of a gas flow in the direction normal to the axis of the wedge and the edges are insulated. The results are presented of an accurate analytical solution of temperature and stress fields in the cross section of the wedge-shaped model during the cyclic variation of the temperature of the medium and arbitrary duration of half cycles of heating and cooling. The calculation results are compared with the results obtained in thermometric examination. It is shown that it is possible to specify accurately and unambiguously and determine the temperature and stresses in the vicinity of wedge-shaped zones of models in a wide range of variation of the parameters of thermal-stress state of the material corresponding to the range of states of the material during service of engine components. The proposed test method reduces the consumption of gas and increases the temperature and stresses on the faces with a relatively large radius of curvature and a short length of the wedge. The gas has almost no effect on the components of the testing chamber.Translated from Problemy Prochnosti, No. 1, pp. 9–13, January, 1990.     

The role of hemodynamics in the development of the outflow tract of the heart

The question whether, and if so to what extent, hemodynamic forces and mechanical stimuli do modulate the morphogenesis of the vascular system is a century-old problem. It is important especially in the outflow tract where a spiraling septum develops in and after a strong bend in the tube. Spiraling patterns of the flow in bends are well known. Of the mechanical stimuli that can potentially exert an effect on morphogenesis, wall shear stress is the most likely candidate; a number of genes that are expressed in the cardiovascular system have shear-stress responsive elements in their regulatory units. Recent investigations have clearly shown that the disturbance of normal hemodynamic conditions results in maldevelopment of the heart. However, an experimental model alone is necessary, but not sufficient to identify the intermediate steps of the interaction between blood flow and tissue remodeling in the developing cardiovascular system, certainly at Reynolds numbers and Dean numbers that are very small. Therefore, a model with a simple geometry has been created, using the ComFlo software: a fully 3D computational fluid-dynamics code that solves the Navier-Stokes equations on a Cartesian grid. A first assessment of the possible influence of a strong curvature, with biological realistic dimensions, was made using steady-flow conditions. Since both the Reynolds number and the Womersley number (indicating the influence of the pulsatility on the velocity profile of the flow) are extremely low, it is likely that these flow patterns do not differ significantly from those under pulsatile conditions. A first assessment of the effects of the strong curvature on the flow under the given circumstances showed only very small secondary velocities and negligible heterogeneity of the wall shear stress, even in the presence of a strong secondary flow pattern in the inlet of the tube.     

Track-etched detectors for the dosimetry of the radiation of cosmic origin

Cosmic rays contribute to the exposure on the Earth's surface as well as in its surroundings. At the surface and/or at aviation altitudes, there are mostly secondary particles created through the cosmic rays interaction in the atmosphere, which contribute to this type of exposure. Onboard a spacecraft, the exposure comes mostly from primary cosmic rays. Track-etched detectors (TED) are able to characterise both these types of exposure. The contribution of neutrons, of cosmic origin, on the Earth's surface was studied at altitudes from few hundreds to 3000 m using TED in a moderator sphere. The results obtained are compared with other data on this type of natural radiation background. The results of studies performed onboard aircraft and/or spacecraft are presented afterwards. We used TED-based neutron dosemeter, as well as a spectrometer of linear energy transfer based on a chemically etched TED. The results of studies performed onboard aircraft, as well as spacecraft, are presented and discussed, including an attempt to estimate a neutron component onboard the spacecraft. It was found that they correlate with the results of other independent investigations.     

Estimates of the errors when determining the direction and localization of the magnetic-field source of a dipole model

Stationary methods for the direction finding and localization of a magnetic-field source of a dipole model in real time are considered. For each method, an analytical estimate is made of the root mean square deviation of the measurement errors. The estimates are made using computer modeling of the errors. The limiting ranges when the equipment contains flux-gate magnetometers and gradiometers are determined. The methods are compared with respect to stability, range, and accuracy and the best method is chosen. __________ Translated from Izmeritel’naya Tekhnika, No. 5, pp. 30–35, May, 2008.     

Limitations on the use of the mixed-mode delaminating beam test specimen: Effects of the size of the region of K-dominance

The mixed-mode delaminating beam (MMDB) is a widely used test geometry designed to measure the fracture resistance of bimaterial interfaces under mixed-mode loading conditions. In the present work, linear-elastic finite element analyses are employed to determine the complex stress intensity factor, K, for an interfacial crack in this sample; results are found to confirm those of previous studies of the bilayer specimen. However, the numerical results further reveal that the region of K-dominance near the crack tip is very limited, extending merely 1/100 to 1/1000 of the sample height, about an order of magnitude smaller than for other common fracture-mechanics test samples. Analyses performed for this specimen geometry modified to include a thin sandwiched interlayer also indicate a very limited region of K-dominance, for example, extending 1/10 of the height of the sandwiched layer from the crack tip for very thin sandwiched layers. For the sandwiched geometry, two situations leading to a useful small scale yielding condition are described. Examples of the use of this specimen in the evaluation of the fracture toughness of ceramic joints are cited from the literature and comparisons are made between the size of the K-dominant region and the extent of crack tip plasticity. Based on these comparisons, the geometry-independent predictive power of linear-elastic fracture mechanics for common bimaterial couples and specimen dimensions using this geometry is challenged.