Regular Relief Research Articles

Modeling of friction at different scale levels

We construct a model for studying the common influence of the imperfect elasticity of actual bodies, the microgeometry of their surfaces, and their adhesive interaction on the contact characteristics (the contact pressure distribution, the region of actual contact) and on the sliding friction force. The model is based on the solution of a plane contact problem of sliding of a rigid body with a regular relief on the boundary of a viscoelastic foundation with surface molecular attraction in the gap between the surfaces taken into account. We analyze the influence of the surface microgeometry parameters at different scale levels on the character of the surface interaction (the saturated or discrete contact) and the friction force for different sliding velocities of the contacting bodies.

Anisotropic Spreading of Liquid Crystals and Isotropic Fluids on Anisometric Surface of DVD Discs

The first experimental data on spreading of liquid crystal droplets over the surface with a regular submicron relief are presented. It is established that such relief produces a motion of a precursor film in the direction of grooves. The dynamics of motion of a precursor film and a contact line is investigated via polarizing microscopy. The possible influence of anisotropic near-surface viscosity on spreading of liquid crystal droplets is discussed.

Can deformation of a polymer film with a rigid coating model geophysical processes?

The structural and mechanical behavior of polymer films with a thin rigid coating is analyzed. The behavior of such systems under applied stress is accompanied by the formation of a regular wavy surface relief and by regular fragmentation of the coating. The above phenomena are shown to be universal. Both phenomena (stress-induced development of a regular wavy surface relief and regular fragmentation of the coating) are provided by the specific features of mechanical stress transfer from a compliant soft support to a rigid thin coating. The above phenomena are associated with a specific structure of the system, which is referred to as "a rigid coating on a soft substratum" system (RCSS). Surface microrelief in RCSS systems is similar to the ocean floor relief in the vicinity of mid-oceanic ridges. Thus, the complex system composed of a young oceanic crust and upper Earth's mantle may be considered as typically "a solid coating on a soft substratum" system. Specific features of the ocean floor relief are analyzed in terms of the approach advanced for the description of the structural mechanical behavior of polymer films with a rigid coating. This analysis allowed to estimate the strength of an ocean floor.

Application of regular decorative relief to long parts

Application of regular decorative relief to long parts

Combined TEM-AFM study of “transrotational” spherulites growing in thin amorphous films

“Transrotational” Se and α-Fe2O3 spherulites have been investigated by transmission electron microscopy and atomic force microscopy. Combination of these two microscopic methods made it possible to reveal structural peculiarities and the character of the spherulite surface, as well as to compare these data. It is established that, along with the regularly changing lattice orientation at the crystallization front, there is a regular relief of the crystal surface. Inheritance of the globular structure of the amorphous matrix by a growing crystal is revealed. In this case, the structure remains homogeneous, independent of the differences in the lattice orientation and imperfection of the regions crystallized.

Direct bonding of silicon carbide wafers with a regular relief at the interface

The direct bonding of two oxide-free 6H-SiC(0001) silicon carbide single crystal wafers, one smooth and another bearing an artificial microscopic relief, has been studied. According to the X-ray topography data, the bonded surface fraction reaches 85% of the total area. The pattern of stress distribution at the interface is aperiodic, which is indicative of an inhomogeneous microroughness of the surface of bonded wafers.

Formation of a regular relief during self-oscillating neck propagation

Formation of a regular relief during self-oscillating neck propagation

Poor relief, labourers’ households and living standards in rural England c.1770–1834: a Bedfordshire case study1

This article estimates the contribution of poor relief to the household economies of the labouring poor in the two case‐study communities of Campton and Shefford, east Bedfordshire, and thereby throws further light on the standard of living of workers during industrialization in the south and east. Utilizing the technique of nominal record linkage between poor law sources and family reconstitution for the period c.1770—c.1834, the article charts the growth in social welfare and estimates the proportion of inhabitants benefiting from regular relief payments, the changing family circumstances of recipients, and the proportion of total income made up by poor relief.

Raman scattering enhancement using crystallographic surface of a colloidal crystal

Deposition of coinage metals on a crystallographic surface of a colloidal crystal is proposed with the aim of fabricating metal surfaces with a regular relief on a scale of 200–300 nm to get strong surface-enhanced Raman scattering (SERS). The approach is implemented through thin gold-film deposition on a surface of a crystal consisting of silica globules. Mitoxantrone molecules, a DNA intercalator, were used to prove high SERS efficiency of the structures proposed. As compared to other SERS-active substrates, metal-dielectric colloidal crystal structures possess well-defined surface parameters (globule diameter and film thickness), high stability and reproducibility. These advantages are important for systematic analysis of SERS mechanisms in mesoscopic structures and its application in single-molecule detection.

Analysis of charges and surface states at the interfaces of semiconductor-insulator-semiconductor structures

A method for determining the energy spectrum of charges and surface-state densities at the interfaces of semiconductor-insulator-semiconductor structures was developed; the method is based on the analysis of capacitance-voltage characteristics. The method was experimentally tested with Si-SiO2-Si structures prepared by direct bonding of both mirror-polished smooth wafers and wafers with a regular mesoscopic relief pattern at the inner surface of the wafers to be bonded. The density of surface states is lower at the surfaces with a regular relief pattern than that at the surfaces without the surface relief.

Autooscillation instability of the free surface of a viscoelastic medium

Oscillation instability of a layer of viscoelastic liquid is revealed on the basis of the numerical analysis of the dispersion equation. The instability is observed in the case of time-independent uniform external force action on the free surface of the liquid and may lead to the formation of a regular wavelike relief of a finite amplitude.

Reduction of elastic strains in directly-bonded silicon structures

The elastically strained state of the interface in directly-bonded silicon structures has been studied by x-ray diffraction topography and IR spectrometry. The pattern of the contrast observed in the x-ray topographs and the intensity oscillations in the IR spectra indicate a periodic strain distribution caused by the long-period surface microroughness on the plates to be bonded. The local microroughness did not exceed 2 A, and it did not noticeably affect the interface structure. Two types of the structure were subjected to a comparative analysis, (i) with a smooth interface prepared by standard direct-bonding technology, and (ii) with an interface displaying a regular relief. The strain level in type-II structures was found to be lower by more than an order of magnitude. A model is proposed to account for the observed reduction of elastic strains at the bonded sections of the interface in terms of elastic relaxation of the free surfaces in the relief voids through their deflection and displacement.

Formation of antireflection microstructures on the surfaces of diamond plates by the laser patterning method

A method for producing diamond plates, antireflective in the IR range, was proposed and implemented experimentally. This method involves formation, on the plate surfaces, of a regular relief structure with a period less than the radiation wavelength. The diamond surfaces were microstructured either by patterning with a focused Nd : YAP laser beam (λ = 1078 nm) or by scanning the image of a pattern in a projection system with the aid of an excimer KrF laser (λ = 248 nm). The shortest period of the resultant structures, consisting of a system of grooves or craters, was 3 μm. A study was made of the influence of the depth of the resultant structures on the transmission coefficient of a diamond plate. An increase in the transmission at the 10.6 μm wavelength amounted to 10% for a plate treated on both sides and the antireflection effect was then observed in a wide spectral range (10 — 20 μm).

Regular relief on a silicon surface as a structural defect getter

An investigation was made to determine how a regular relief on the silicon surface influences gettering in silicon-silicon-dioxide structures. The regular relief was created by a photolithographic technique before oxidation and comprised an orthogonal network of overlapping bands. The gettering was determined from the isothermal relaxation of the capacitance of a silicon-silicon-dioxide structure after switching from strong inversion to even stronger inversion. It is shown that a regular relief at the silicon-silicon-dioxide interface is an effective getter at a depth of several hundred micron.

Self-Assembling Functionalizable Polydiacetylenes and their Optical Properties

AbstractThe alkoxycarbonylmethylurethanes of 9-(N-methyl-N-phenylamino)-5,7-nonadiyn-l-ol were synthesized and polymerized by 60Co gamma radiation. The resulting polydiacetylenes (PDA) are soluble, processable, and self-assemble into an acentric array. These PDAs are susceptible to postpolymerization functionalization via its dialkylaniline and ester groups, and hence comprise the most versatile PDA system for systematic chemical modification reported to date. Dialkylaniline functionalization via tetracyanoethylene and diazonium salt coupling led, respectively, to materials with interesting second order nonlinear optical properties and that exhibit directly photofabricated regular surface relief gratings. The latter materials provide the first example of a rigid rod polymer (lacking a detectable glass transition) to exhibit such phenomena. Moreover, these PDAs can form self-assembled multilayer structure in water by ester hydrolysis.

A study of the contribution of effective pressure care on elderly female patients attending Accident and Emergency who have a suspected fractured neck of femur

This study describes the benefit of pressure relief and the use of pressure reducing mattresses on elderly female patients with a suspected fractured neck of femur, attending an Accident and Emergency department. The main aim of the study was to determine if pressure care, appropriate to each individual patient, reduced red pressure areas and if so, in what way? The results demonstrated that pressure relief given at regular intervals was most effective at reducing red pressure areas. The pressure reducing mattresses also showed to be beneficial in reducing these areas. The study highlighted the importance of giving regular pressure relief in all patients at risk of development of pressure sores.

Reflection and retention of low energy light ions during bombardment of fusion materials

Experimental and computational data on light ions reflection and retention for energy below hundreds of eV are presented. Mass spectrometric method is used to measure particle reflection R N and particle retention coefficients for different angles of incidence of D ions on different targets. Strong influence of surface oxidation for Be is observed. Results are compared with the binary collision computer simulations. R N as a function of primary energy reveals the maximum with amplitude and energy depending on the angle of incidence, attractive potential E s and atomic number of target. Strong isotopic effect in hydrogen backscattering from Be is observed. The regular relief influence on hydrogen ions backscattering from Be and C target was computer simulated and it is shown that considerable increase in R N ( R N max R N (0) = 1.85 for proton normal incidence on Be target) is noticed.

Experimental study of vortex heat-transfer enhancement mechanisms

In this paper comparative analysis of various heat transfer enhancement method effects and the experimental study results of vortex heat transfer enhancement physical mechanisms are presented. Experimental investigations were made of friction and heat transfer on surfaces shaped by systems of spherical cavities streamlined by a turbulent flow. Also flow structure in single, two- and three -dimensional cavities is investigated. The experiments were run on a special aerodynamic test bed using a traditional procedure for diagnosing a turbulent boundary layer. Obtained results allow to conclude that such a shaping of a heating surface has no appreciable effect on the hydrodynamics of a flow with considerable (up to 30–40%) heat transfer enhancement. Experimental data on heat transfer are generalized, and a relationship suitable for engineering estimation of heat transfer on surfaces shaped by a regular relief of spherical cavities and valid for the investigated geometric parameters of shaping and flow regimes has been obtained. Also, obtained results allow to formulate the physical flow model in the single cavity dependent on the geometric parameters and flow regime. Besides, the vortex technology problems, practical application of heat transfer enhancement by vortex method and progress prospectives are elucidated.

Turbulent flow friction and heat transfer characteristics for spherical cavities on a flat plate

Experimental investigations were made on friction and heat transfer on surfaces shaped by systems of spherical cavities streamlined by a turbulent flow. The experiments were run on a special aerodynamic test bed using a traditional procedure for diagnosing a boundary layer in conditions of outer flow. Ten plates were used as prototypes, nine of which had surfaces shaped by staggered ordered systems of spherical cavities at various densities and geometries, and one smooth surface for test experiments. All measurements were made with a DISA-55M thermoanemometric set and direct-acting standard transducers with 2.5 μm diameter filaments. For direct measurement of heat flux on a smooth surface, DTP-05 transducers were used, which did not produce any significant changes in the temperature field of the specimen. From the results obtained we conclude that such a shaping of a heating surface has no appreciable effect on the hydrodynamics of a flow with considerable (up to 30–40%) heat transfer enhancement. Experimental data on heat transfer are generalized, and a relationship suitable for engineering estimation of heat transfer on surfaces shaped by a regular relief of spherical cavities and valid for the investigated geometric parameters of shaping and flow regimes has been obtained.

Why does regular relief care end?

In a retrospective survey, patients whose regular hospital relief care came to an end were found to be similar to those in whom it continued in their medical and social features, and in the frequency of admissions, although their rota care did not last so long. The most frequent factors in ending rota care were acute illness leading to death, increased disability, and refusal by carers, the last two of which were often associated. Alternative care, refusal by patients and illness of carers affected smaller numbers. Patients whose rota care ended had a high mortality (56%) and seldom needed long-stay care, though only a minority of deaths (4/28) occurred during or shortly after a relief admission.