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COLD SPRAY TANTALUM COATING Researchers at the University of Wisconsin-Madison are using a new coating technology to produce a hardworking material that can withstand the harsh conditions inside a fusion [...]

The spectral analysis of surface waves (SASW) method is a nondestructive testing method of pavements based on the dispersive characteristic of seismic surface waves. The method can provide the thickness and stiffness of pavement layers. One of the more complex aspects of the SASW method is an iterative process to estimate the pavement parameters, called the inversion procedure. In this paper, the feasibility of completely automating the inversion process and substituting it with artificial neural network (ANN) models was explored. A number of different ANN models were developed using various ANN training strategies. To improve the performance of some ANN models, a sequential modeling technique was implemented. In the sequential modeling, some pavement parameters are estimated first from an initial set of ANN models, which is then the input to subsequent ANN models to estimate other parameters of interest. Furthermore, the performance of the ANN models was evaluated using a number of well-characterized pavement sections. The results illustrated that ANN models could estimate the upper layers' parameters so well that they could replace the inversion process. The ANN models for other layers were capable of generating robust initial estimates for a well-constrained formal inversion that can be readily automated. DOI: 10.1061/(ASCE)0899-1561(2009)21:12(722) CE Database subject headings: Neural networks; Pavements; Surface waves; Automation.

To investigate the complex hydrological, morphodynamic, and environmental processes in watersheds, a physically-based integrated two-dimensional (2D) surface and three-dimensional (3D) subsurface model for flow, soil erosion and transport, and contaminant transport in the surface-subsurface system is presented in this paper. The model simulates the rainfall-induced surface flow by solving the depth-averaged 2D diffusion wave equation and the variably-saturated subsurface flow by solving the 3D mixed-form Richards equation. The surface and subsurface flow equations are coupled using the continuity conditions of pressure and exchange flux at the ground surface. The model uses the concept of nonequilibrium in the depth-averaged 2D simulation of nonuniform total-load sediment transport in upland fields, considering detachments by rainsplash and hydraulic erosion driven by surface flow. The integrated 2D surface and 3D subsurface contaminant transport model takes into account the contaminant changes due to sediment sorption and desorption, as well as exchanges between surface and subsurface domains due to infiltration, diffusion, and bed change. The model applies the same set of surface equations of flow, sediment, and contaminant transport for describing both upland areas and streams, so that no special treatments are required at their interface. The established model has been evaluated by comparisons with published experimental, numerical, and analytical data and then applied in an agricultural watershed. The model is suitable for wetland areas and agricultural watersheds in which streams are not very narrow and deep, and meanwhile a relatively fine mesh that can distinguish the streams is preferred. DOI: 10.1061/(ASCE)HY. 1943-7900.0000116 CE Database subject headings: Numerical models; Integrated systems; Rainfall; Infiltration; Overland flow; Subsurface flow; Erosion; Pollution; Sorption; Watersheds.

Through experiments using two-dimensional particle-image velocimetry (PIV), this paper examines the nature of transition in a separation bubble and manipulations of the resultant breakdown to turbulence through passive means of control. An airfoil was used that provides minimal variation in the separation location over a wide operating range, with various two-dimensional modifications made to the surface for the purpose of manipulating the transition process. The study was conducted under low-freestream-turbulence conditions over a flow Reynolds number range of 28,000-101,000 based on airfoil chord. The spatial nature of the measurements has allowed identification of the dominant flow structures associated with transition in the separated shear layer and the manipulations introduced by the surface modifications. The Kelvin--Helmholtz (K-H) instability is identified as the dominant transition mechanism in the separated shear layer, leading to the roll-up of spanwise vorticity and subsequent breakdown into small-scale turbulence. Similarities with planar free-shear layers are noted, including the frequency of maximum amplification rate for the K-H instability and the vortex-pairing phenomenon initiated by a subharmonic instability. In some cases, secondary pairing events are observed and result in a laminar intervortex region consisting of freestream fluid entrained toward the surface due to the strong circulation of the large-scale vortices. Results of the surface-modification study show that different physical mechanisms can be manipulated to affect the separation, transition, and reattachment processes over the airfoil. These manipulations are also shown to affect the boundary-layer losses observed downstream of reattachment, with all surface-indentation configurations providing decreased losses at the three lowest Reynolds numbers and three of the five configurations providing decreased losses at the highest Reynolds number. The primary mechanisms that provide these manipulations include: suppression of the vortex-pairing phenomenon, which reduces both the shear-layer thickness and the levels of small-scale turbulence; the promotion of smaller-scale turbulence, resulting from the disturbances generated upstream of separation, which provides quicker transition and shorter separation bubbles; the elimination of the separation bubble with transition occurring in an attached boundary layer; and physical disturbance, downstream of separation, of the growing instability waves to manipulate the vortical structures and cause quicker reattachment. [DOI: 10.1115/1.2978997]

Biofilms represent the predominant form of microbial life on Earth. They are aggregates of microorganisms embedded in a matrix formed by extracellular polymeric substances (EPS). Detailed information about chemical composition and structure of the EPS matrix is relevant e.g. for the optimization of biocides, of antifouling strategies and for biological wastewater treatment. Raman microscopy (RM) is a capable tool that can provide detailed chemical information about biofilm constituents with spatial resolution of optical microscope. However, the sensitivity of RM is limited. Surface-enhanced Raman scattering (SERS), which enables investigations of biomolecules at very low concentration levels, allows overcoming this drawback. To our knowledge, this paper is the first report on reproducible SERS spectra from different constituents of a multispecies biofilm. We believe that the reproducibility is partly owed to the in situ measurement of the biofilm, while up to now SERS measurements of microbiological samples by RM were carried out after sample drying. We employed colloidal silver nanoparticles for in situ SERS measurements by RM. The achieved enhancement factor of up to 2 orders of magnitude illustrates a high potential of SERS for ultrasensitive chemical analysis of biofilms, including the detection of different components and the determination of their relative abundance in the complex biofilm matrix.

In this paper we present two approaches for extracting the surface profile as well as obtaining 3D imaging of near field objects by usage of partial coherence and digital holography. In the first approach a light source with given temporal partial coherence is used to illuminate a near field object. The reflected light is interfered with the reference source. By computing the local contrast of the generated fringes one may estimate the 3D topography and the profile of the object. This approach extracts the 3D information from a single image, and its accuracy does not depend on triangulation angle like in fringe projection methods. The second approach is tomography based. There we illuminate the object from several slightly different angles, and for each we compute the wrapped phase using digital holography techniques. Combining the wrapped phase estimation from several points of projection allows calculating the unwrapped phase and therefore the true profile of even a phase-only object. Increasing the number of points of view decreases the relative error of the estimated profile. OCIS codes: 090.1995, 150.6910, 030.1640, 110.5086.

We report methods for the acquisition and analysis of optical images formed by thin films of twisted nematic liquid crystals (LCs) placed into contact with surfaces patterned with bio/chemical functionality relevant to surface-based assays. The methods are simple to implement and are shown to provide easily interpreted maps of chemical transformations on surfaces that are widely exploited in the preparation of analytic devices. The methods involve acquisition of multiple images of the LC as a function of the orientation of a polarizer; data analysis condenses the information present in the stack of images into a spatial map of the twist angle of the LC on the analytic surface. The potential utility of the methods is illustrated by mapping (i) the displacement of a monolayer formed from one alkanethiol on a gold film by a second thiol in solution, (ii) coadsorption of mixtures of amine-terminated and ethylene glycol-terminated alkanethiols on gold films, which leads to a type of mixed monolayer that is widely exploited for immobilization of proteins on analytic surfaces, and (iii) patterns of antibodies printed onto surfaces. These results show that maps of the twist angle of the LC constructed from families of optical images can be used to reveal surface features that are not apparent in a single image of the LC film. Furthermore, the twist angles of the LC can be used to quantify the energy of interaction of the LC with the surface with a spatial resolution of < 10 [micro]m. When combined, the results described in this paper suggest nondestructive methods to monitor and validate chemical transformations on surfaces of the type that are routinely employed in the preparation of surface-based analytic technologies.

Approximate closed-form equations are derived for normal and tangential contact forces of rough surfaces in dry friction. Using an extension of the Greenwood and Tripp (1970, Proc, Inst. Mech. Eng., 185, pp. 625-633) model, in which the derivations permit asperity shoulder-to-shoulder contact and viscoelastic asperity behavior, mathematical formulae are derived for normal and tangential components of the contact force that depend not only on the proximity of the two surfaces but also the rate of approach and relative sliding. A statistical approach is forwarded in which dependence of the asperity tangential contact force on relative tangential velocity of two asperities can be cast as corrective factors in the mathematical description of tangential force. In this regard two corrective coefficients are derived: force directionality corrective coefficient and force-velocity directionality corrective coefficient. The results show that for a moderate to high load ranges the contact force can be analytically described to within 20% accuracy of that from a numerical integration of the contact equations, well below the uncertainties due to surface profile measurement. [DOI: 10.1115/1.2736730] Keywords: kinetic friction, viscoelastic contact model, rough surfaces

Non-Sustained Disruptive Discharge (NSDD) sometimes occurs when the voltage is applied for a certain time between vacuum gaps after the current is interrupted. However the mechanism of NSDD has not yet been clarified. We conducted a study to clarify this phenomenon using the contact materials CuCr, CuW, and AgWC. We applied a voltage (20[kV]-30[kV]) of ac 50[Hz] after current interruption (1[kArms]-8[kArms]), and checked the generating frequency of NSDD. After the current interruption test, we measured the contact surface roughness and field emission current. The result showed that surface roughness and field emission current are not related to this phenomenon and also that CuCr (melt) showed the best performance in all tests. Index Terms--Non-sustained disruptive discharge (NSDD), metallic particle.

This paper demonstrates a chemical surface modification method for covalent attachment of various polymers by using silane-based 'click' chemistry on silica surfaces and within glass microchannels suitable for CE systems. Modified surfaces are characterized by contact angle measurements, X-ray photoelectron spectroscopy, and Fourier transform infrared-attenuated total reflection spectroscopy. Electroosmotic flow (EOF) measurements in modified and unmodified channels are provided. Spectroscopic and transport data show that various polymers can be covalently attached to glass surfaces with a measurable change in EOF.

Glow discharge optical emission spectrometry has cemented itself as an important surface elemental analysis technique in part because of its superb depth resolution (on the order of single nanometers). However, very few studies have explored the ability of the glow discharge to provide laterally resolved elemental information. In the present study, an end-on-viewed pulsed radio frequency glow discharge is coupled to a monochromatic imaging spectrometer to provide lateral surface imaging. The performance of the technique is demonstrated with etched copper circuits on fiber-glass substrates, and it is shown how several operating parameters including pressure, pulsed mode operation, and time-resolved detection affect the lateral surface resolution. In addition, because a pulsed radio frequency glow discharge offers elemental information on nonconducting samples, the technique is applied to the three-dimensional elemental analysis of proteins on blotting substrates. Several alternative sample types are also examined, including photographic film and glass.

This paper proves that a generalized Hertz pressure (the product of Hertz square root and an even polynomial of degree 2n with respect to coordinates) applied over elastic half-space boundary generates a polynomial normal displacement of degree 2n + 2. Polynomial surface coefficients are combinations of elliptical integrals. The equation of rigid punch surface generating this pressure is derived, as well as the conditions in which an elliptical contact occurs. For second order surfaces, n = 0, these results yield all Hertz formulas, whereas new formulas are derived for contact parameters between fourth, sixth, and eight order surfaces. [DOI: 10.1115/1.2345420] Keywords: elliptic contact, generalized Hertz pressure, high order surfaces, polynomial normal displacement

Instead of a general consideration of the fractal dimension (D) and the topothesy (G *) as two invariants in the fractal analysis of surface asperities, these two roughness parameters in the present study are varied by changing the mean separation (d *) of two contact surfaces. The relationship between the fractal dimension and the mean separation is found first. By equating the structure functions developed in two different ways, the relationship among the scaling coefficient in the power spectrum function, the fractal dimension, and topothesy of asperity heights can be established. The variation of topothesy can be determined when the fractal dimension and the scaling coefficient have been obtained from the experimental results of the number of contact spots and the power spectrum function at different mean separations. A numerical scheme is developed in this study to determine the convergent values of fractal dimension and topothesy corresponding to a given mean separation. The theoretical results of the contact spot number predicted by the present model show good agreement with the reported experimental results. Both the fractal dimension and the topothesy are elevated by increasing the mean separation. Significant differences in the contact load or the total contact area are shown between the models of constant D and G * and variable D and G * as the mean separation is reduced to smaller values. [DOI: 10.1115/1.2197839] Keywords: roughness, fractal dimension, topothesy

For several decades, asperities of nominally flat rough surfaces were considered to be points higher than their immediate neighbors. Recently, it has been recognized that this model is incorrect. To address the issue, a new multiple-point asperity model, called the n-point asperity model, is introduced in this paper In the new model asperities are composed of n neighboring sampled points with n-2 middle points being above a certain level. When the separation between two surfaces decreases, new asperities with higher number of sample points, n, will come into existence. Based on the above model the height and curvature of n-point asperities are defined and their distributions are found. The model is developed for Gaussian surfaces and for the general case of an autocorrelation function (ACF). As a case study, the exponential ACF is applied to the new model, which is shown to produce remarkably good agreement with measurements from real and simulated surfaces. [DOI: 10.1115/1.2194915]

For ductile solids with periodic microstructures (e.g., honeycombs, fiber-reinforced composites, cellular solids) which are loaded primarily in compression, their ultimate failure is related to the onset of a buckling mode. Consequently, for periodic solids of infinite extent, one can define as the onset of failure the first occurrence of a bifurcation in the fundamental solution, for which all cells deform identically. By following all possible loading paths in strain or stress space, one can construct onset-of-failure surfaces for finitely strained, rate-independent solids with arbitrary microstructures. The calculations required are based on a Bloch wave analysis on the deformed unit cell. The presentation of the general theory is followed by the description of a numerical algorithm which reduces the size of stability matrices by an order of magnitude, thus improving the computational efficiency for the case of continuum unit cells. The theory is subsequently applied to porous and particle-reinforced hyperelastic solids with circular inclusions of variable stiffness. The corresponding failure surfaces in strain-space, the wavelength of the instabilities, and their dependence on micro-geometry and macroscopic loading conditions are presented and discussed. [DOI: 10.1115/1.2126695]

An efficient algorithm for isometry-invariant matching of surfaces is presented. The key idea is computing the minimum-distortion mapping between two surfaces. For this purpose, we introduce the generalized multidimensional scaling, a computationally efficient continuous optimization algorithm for finding the least distortion embedding of one surface into another. The generalized multidimensional scaling algorithm allows for both full and partial surface matching. As an example, it is applied to the problem of expression-invariant three-dimensional face recognition. Gromov-Hausdorff distance | isometric embedding | iterative-closest-point | partial embedding

Imaging of a coimmobilized diaphorase and albumin surface was investigated by scanning electrochemical microscopy (SECM) with shear force based tip-substrate distance control. A microelectrode tip was attached to a commercially available tuning fork to detect the shear force between the microelectrode tip and the surface. We used the standing approach mode, which repeats an approach and retraction at each data point of the surface to obtain simultaneous current and topographic images. To check the performance of our SECM system, we imaged a platinum-patterned array electrode and a diaphorase/albumin coimmobilized glass surface. Since the system acquires current when the tip is retracted to a desired distance, this mode is useful for a relatively large microelectrode (~10 [micro]m) and for scanning a large area (few hundreds of micrometers). Furthermore, by retracting the tip when the tip moves laterally to the next data point to avoid contact between the tip and sample surface, we successfully imaged the surface without destroying its morphology.

Turbulent boundary-layer measurements have been carried out on flat surfaces coated with two different new generation marine antifoulings. The coatings were applied on 2.1-m-long test sections that were fitted in a 2.1-m-long flat plate setup. The measurements were carried out in two different recirculating water tunnels by means of two-component laser Doppler velocimetry and were compared with measurements of a smooth steel reference surface and a surface covered with sand grit. Both coatings exhibited an increase in frictional resistance compared to the reference surface, but the increase was significantly smaller for the Foul(ing) Release coatings than for the Tin-free SPC coating. The coatings did not significantly affect the boundary-layer thickness. When expressed in inner variables, the coatings did not have an effect on the turbulence intensity profiles, but when expressed in outer variables, the coatings affected the near-wall turbulence intensities. [DOI: 10.1115/1.1891148]

The meshing clearance of the helical surfaces under the condition of conjugation is studied in depth in this paper, which is significant to industrial practice as well as scholastic field. A general conjugation criterion for making clearance of the meshed helical surfaces is clearly defined for the first time, which states that the rotation angle of return stroke caused by clearance for all the points in the tooth surface must be identical. Based on this criterion, it is shown that the commonly adopted uniform clearance is not reasonable for all the meshed helical surfaces. For traditional involute helical surfaces, it is intrinsically correct to adopt the uniform clearance. However, for the helical surfaces with complex transverse tooth profiles, such as those applied to the twin screw compressors, it is unreasonable and harmful to do so due to violation of the conjugation criterion, leading to a severe local contact in the tooth surfaces and higher noise level and, hence, damaging the performance of the helical surfaces in application. As a general principle, the 'uniform rotation angle' clearance distribution is a unique one, satisfying the conjugation criterion.

The stiction forces that exist in microelectromechanical systems (MEMS) are characterized by surface energy and surface roughness. To simulate this contact condition, a three-dimensional fractal surface geometry and an adhesive contact model for a single asperity are used together to create a numerical adhesive rough surface solution methodology. This novel method of solution determines the characteristic adhesive contact type for each individual asperity uniquely at the time of load and area integration. Such a simulation more accurately represents the physics of the asperity-based contact. Numerical results for the adherence force are presented as a function of surface topography, interface compliance, and the work of adhesion for a MEMS interface. The magnitude of the force required to separate an adhesive rough surface interface is given in relation to a polysilicon system.

The focus in this paper is to automatically design the air-bearing surface (ABS) considering the randomness of its geometry as an uncertainty of design variables. Designs determined by the conventional optimization could only provide a low level of confidence in practical products due to the existence of uncertainties in either engineering simulations or manufacturing processes. This calls for a reliability-based approach to the design optimization, which increases product or process quality by addressing randomness or stochastic properties of design problems. In this study, a probabilistic design problem is formulated considering the reliability analysis which is employed to estimate how the fabrication tolerances of individual slider parameters affect the final flying attitude tolerances. The proposed approach first solves the deterministic optimization problem. Beginning with this solution, the reliability-based design optimization (RBDO) is continued with the probabilistic constraints affected by the random variables. Probabilistic constraints overriding the constraints of the deterministic optimization attempt to drive the design to a reliability solution with a minimum increase in the objective. The simulation results of the probabilistic design are directly compared with the values of the initial design and the results of the deterministic optimum design, respectively. In order to show the effectiveness of the proposed approach, the reliability analyses by the Monte Carlo simulation are carried out. And the results demonstrate how efficient the proposed approach is, considering the enormous computation time of the reliability analysis.

The Greenwood and Williamson (1966) model is an elegant and often-cited paradigm for predicting the load-displacement behavior of contacting rough surfaces given the height distribution of the contacting asperities. By use of an inverse technique and available load-displacement data, this work provides an alternative method to determine the asperity distribution directly from topographic measurement and subsequent data reduction. This method produces distributions that are consistent with the Greenwood and Williamson representation of the load-displacement data and demonstrates how the asperity height distribution can evolve with loading. Keywords: Rough Surface, Asperity, Contact, Inverse Methods

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.apergo.2004.07.001 Byline: Gary R Jones, Robin H Hooper Keywords: Interface pressure; Military load carriage; Clothing layers Abstract: Experiments were aimed at determining whether interface pressure measurements are a true reflection of skin contact pressure when made over different layers of clothing. Interface pressures were recorded at the skin interface and above clothing layers, with 11 participants wearing 10 different clothing combinations. The clothing used was standard issue British military clothing, including body armour (without ballistic plate). Participants wore both single and multiple clothing layers whilst walking on a treadmill carrying a loaded backpack (23.5kg, British military issue). Results showed no significant differences (p=>0.05) in pressure between different clothing layers either singly, or worn in multiple. In conclusion, the soldier (or leisure user) will gain no or very little relief from applied pressure by wearing garments, even in layers, when carrying a backpack. Also, the findings suggest that interface pressure may adequately be assessed using a sensor placed above the clothing layer(s) rather than at skin surface. Author Affiliation: Department of Human Sciences, Loughborough University, Leicestershire, LE11 3TU. UK. Article History: Received 5 August 2002; Revised 1 June 2004; Accepted 26 July 2004

Investigating the preparation and microwave properties of Tl-2212 and Tl-1223 thin films on a CeO2, buffered sapphire substrate is discussed. It shows the surface resistance of Tl-1223 film slightly higher than the Tl-2212 film due to an inferior surface morphology.

Discussing the TMQF technique applied to measurements of Q (sub o) of a dielectric resonator system investigated the effect of the impedance mismatch on its accuracy is presented. The results confirm that high accuracy in the unloaded Q (sub o) factor is needed to provide errors smaller than 1% in the surface resistance.

The bifurcation structure of viscous flow in curved square ducts is studied numerically and the stability of solutions on various solution branches is examined extensively. The solution structure of the flow is determined using the Euler-Newton continuation, the arc-length continuation, and the local parameterization continuation scheme. Test function and branch switch technique are used to monitor the bifurcation points in each continuation step and to switch branches. Up to 6 solution branches are found for the case of a flow in the curved square channel within the parameter range under consideration. Among them, three are new. The flow patterns on various bifurcation branches are also examined. A direct transient calculation is made to determine the stability of various solution branches. The results indicate that, within the scope of the present work, at given set of parameter values, the arbitrary initial disturbances lead all solutions to the same state. In addition to stable steady two-vortex solutions and temporally periodic solutions, intermittent and chaotic oscillations are discovered within a certain region of the parameter space. Temporal intermittency that is periodic for certain time intervals manifests itself by bursts of aperiodic oscillations of finite duration. After the burst, a new periodic phase starts, and so on. The intermittency serves as one of the routes for the onset of chaos. The results show that the chaotic flow in the curved channel develops through the intermittency. The chaotic oscillations appear when the number of bursts becomes large. The calculations also show that transient solutions on various bifurcation branches oscillate chaotically about the common equilibrium states at a high value of the dynamic parameter. [DOI: 10.1115/1.1412457]

Highly unsteady three-dimensional flows in curved pipes with significant variation of flow geometry and flow parameters are studied. Using improvements in computational efficiency, detailed knowledge concerning flow structures is obtained. The numerical solutions of the Navier-Stokes equations have been obtained with a variation of the projection method, and the numerical method was enhanced by new algorithms derived from the physics of the flow. These enhancements include a prediction of the flow unsteady pressure gradient based on fluid acceleration and global pressure field corrections based on mass flow. This new method yields an order of magnitude improvement in the calculation's efficiency, allowing the study of complex flow problems. Numerical flow simulations for oscillating flow cycles show that the curved pipe flows have a significant inviscid-like nature at high values of the frequency parameter. The shape of the velocity profiles is strongly influenced by the frequency parameter, whereas the influence of variations on the pipe cross-sectional area is shown to be rather weak. For large values of the frequency parameter the flow history strongly influences the low mass flow part of the cycle leading to highly unusual velocity profiles. The wall shear stress is studied for all the flows calculated. Our results show that wall shear stress is sensitive to area constrictions, the frequency parameter, as well as the shape of the entrance profile. [DOI: 10.1115/1.1400748]

Research is presented concerning the use of multimode scanning acoustic force microscopy and lateral force microscopy to investigate the influence of vertical and in-plane surface oscillation components on cantilevers.

Research is presented concerning the exposure of Ag-As-S chalcogenide glasses to focused laser beams in order to investigate the prominent surface deformations they cause. The relationship between deformation and beam composition is discussed.

Research is presented concerning the exposure of AgAsS2 chalcogenide films to 2.0 eV light spots which are linearly polarized and which have diameters of 5-200-micrometers in order to study the anisotropic surface deformations produced.

The author develops theorems applying Fermat's last theorem to topology. The proofs offered suggest Fermat's work is equally applicable to topology and number theory.

Issues concerning the effect of core charge and solvent refractive index on the surface plasmon absorbance of alkanethiolate monolayer-protected gold clusters are presented.

Research is presented demonstrating the importance of precise control of the average distances between large biomolecules on silicon surfaces to biochip, molecular electronic and sensor technologies of the future.

When one illuminates a computer-generated hologram by a plane wave, the obtained two-dimensional image is usually displayed on a planar plane. Other possibilities for reconstructing images on arbitrary curved surfaces are discussed herein. As an example, the reconstruction of an image on a virtual spherical surface is demonstrated.

An average monthly variable, called the Obstruction Illuminance Multiplier (OIM), defined as the ratio of the illuminance received on a vertical surface due to light received from the sky, ground and the obstruction to the illuminance on the same surface without the presence of the obstruction, is proposed as a simple tool to investigate the potential of perfectly diffuse vertical south-oriented facades to reflect daylight onto the opposing facades.

Mathematician John Conway's discovery of the Zero Irrelevancy Proof (ZIP proof) eliminates the irrelevancies associated with the proofs presented by Seifert and Threlfall regarding closed surfaces. The ZIP proof retains the constructive nature of Seifert and Threlfall's proofs while doing away with the artificial standard form required by Seifert and Threlfall. In addition, the ZIP proof remains faithful to classical elementary topology.

A study was conducted to analyze the location of the onset of rivulet formation in the surface-water flow over a wing supporting a NACA 4412 airfoil. The rivulet formation was examined using wind-tunnel studies. A framework was then developed to determine the formation of rivulets when the surface-tension shear stress correlates with the interface shear stress created by aerodynamic forces on the liquid. Results indicated that the location of rivulet onset correlated with the aerodynamic shear stress and surface-tension shear stress.

During the study of laser-scattering properties of machined surfaces, an interesting reflective characteristic has been observed. For a certain range of angles of incidence a stationary reflective pattern has been observed regardless of the angle of incidence. We explain the same by using geometric optics. The intensities calculated from the model are found to be in good agreement with the experimentally measured intensity of the scattered pattern.

A new method is presented for identifying and comparing closed, bounded, free-form curves that are defined by even implicit polynomial (IP) equations in the Cartesian coordinates x and y. The method provides a new expression for an IP involving a product of conic factors with unique conic factor centers. The critical points for an IP curve also are defined. The conic factor centers and the critical points are shown to be useful related points that directly map to one another under affine transformations. In particular, the explicit determination of such points implies both a canonical form for the curves and the transformation matrix which relates affine equivalent curves. Index Terms - Implicit polynomials, affine transformations, object recognition, pose estimation, canonical curves.

We compute the sign of Gaussian curvature using a purely geometric definition. Consider a point p on a smooth surface S and a closed curve y on S which encloses p. The image of [Gamma] on the unit normal Gaussian sphere is a new curve [Beta]. The Gaussian curvature at p is defined as the ratio of the area enclosed by [Gamma] over the area enclosed by [Beta] as [Gamma] contracts to p. The sign of Gaussian curvature at p is determined by the relative orientations of the closed curves [Gamma] and [Beta]. We directly compute the relative orientation of two such curves from intensity data. We employ three unknown illumination conditions to create a photometric scatter plot. This plot is in one-to-one correspondence with the subset of the unit Gaussian sphere containing the mutually illuminated surface normals. This permits direct computation of the sign of Gaussian curvature without the recovery of surface normals. Our method is albedo invariant. We assume diffuse reflectance, but the nature of the diffuse reflectance can be general and unknown. Error analysis on simulated images shows the accuracy of our technique. We also demonstrate the performance of this methodology on empirical data. Index Terms - Gaussian curvature, differential geometry, photometric invariant, photometric data, shape recovery, curve orientation.

As an extension of the knife-edge test, a noninterferometric method for inspecting circularly symmetric aspheres is proposed in which the test surface is illuminated by a spherical wave. When a small circular stop is placed around the curvature center of the best-fitting sphere, only rays characteristic for the deviation from a perfect sphere remain unobstructed. An image of the tested surface is thereby obtained, showing light and dark regions whose boundaries are correlated to the surface profile, the stop size, and the stop position along the symmetry axis. The experiment has been carried out with a paraboloid.

The possibility of magnetoelastic SH-waves in a semi-infinite perfectly conducting medium having a superficial layer was examined. Basic equations such as Maxwell's equations established the electromagnetic boundary conditions. Numerical solutions were presented for the propagation of magnetoelastic Love waves. Results indicated that the magnetic field may cause such waves, even when they are absent in the purely elastic case.