DEVELOPMENT OF A µBRDF GONIOSPECTROPHOTOMETER FOR BRDF MEASUREMENT ON TINY SURFACES

A µBRDF goniospectrophotometer has been developed at LNE-CNAM. This device performs traceable BRDF measurement with a measurement surface of 30 µm of diameter. All angular configuration of measurement belonging to the hemisphere are possible. The spectral range is the visible. This device intends to help to progress in the effort to extent the BRDF metrological scale from the centimetre size to micrometre size. Traceable µBRDF measurement are requested today to validate physical based rendering models used in virtual prototyping and to progress in the comprehension of the appearance of natural material like wool, wood, or leather.

The Influence of Target Properties on the Accuracy of Reflectorless Distance Measurements

Recent years have brought dynamic developments in surveying equipment and techniques. These include reflectorless electromagnetic distance measurement (RL EDM), which is used in a range of devices, especially total stations. Studies concerning the influence of the reflecting surface on the accuracy of RL EDM tend to focus on the colour of the measurement surface, while the influence of the density and thickness of materials is usually neglected. Therefore, this study undertook to examine 53 samples representing various materials of dissimilar features: colour, type of surface and density. The results show that dark and mat surfaces cause higher RL EDM errors than bright, gloss materials. Nonetheless, 76% of the results were in compliance with equipment specifications. Moreover, it was found that the density of the samples had significant impact on the overall accuracy. RL EDM to EPS (expanded polystyrene sheets, low-density material, commonly called Styrofoam) involved a significantly higher error rate. It demonstrates that total station measurements and laser scanning should be performed cautiously, especially with regard to materials of low density (e.g., EPS) and on short distances, where the value of relative error is high.

Recovering the Free-Field Acoustic Characteristics of a Vibrating Structure from Bounded Noisy Underwater Environments

The vibrational behavior of an underwater structure in the free field is different from that in bounded noisy environments because the fluid–structure interaction is strong in the water and the vibration of the structure caused by disturbing fields (the reflections by boundaries and the fields radiated by sources of disturbances) cannot be ignored. The conventional free field recovery (FFR) technique can only be used to eliminate disturbing fields without considering the difference in the vibrational behavior of the structure in the free field and the complex environment. To recover the free-field acoustic characteristics of a structure from bounded noisy underwater environments, a method combining the boundary element method (BEM) with the vibro-acoustic coupling method is presented. First, the pressures on the measurement surface are obtained. Second, the outgoing sound field and the rigid body scattered sound field are calculated by BEM. Then, the vibro-acoustic coupling method is employed to calculate the elastically radiated scattered sound field. Finally, the sound field radiated by the structure in the free field is recovered by subtracting the rigid body scattered sound field and the elastically radiated scattered sound field from the outgoing sound field. The effectiveness of the proposed method is validated by simulation results.

Sound power and sound energy measurements using an ellipsoidal measurement surface

To support purchasing low noise products, sound power and sound energy measurements of sufficient quality need to be routinely made by consumers on a global scale. Sound power measurements using ISO 3744, 3745, and 3746 are conducted in a free field using an acoustic far-field approximation of the intensity integrated over an enveloping measurement surface. Sound power and sound energy measurements generally use a hemispherical, parallelepiped, or cylindrical measurement surface. Those measurement surfaces have limitations and assume that the measurement points lie on the measurement surface often in preferred positions. An alternative approach is to choose microphone positions that optimally satisfy the assumptions of the measurement. The measurement surface should then be fit to the chosen microphone positions. Regression methodologies are available for fitting ellipsoids. The number of microphone positions can be as few as three to fit an ellipsoid. An ellipsoidal measurement surfaces can abut zero, one, two, or three orthogonal reflecting planes. Correction equations for the microphone locations and the angle errors for the microphone orientation and wave propagation direction are shown. This paper will present simulations of sound power, sound energy, and corrections for environmental reflections for ISO 3745 and other measurement surfaces.

Sound field separation of multiple coherent sound sources with single measurement surface

Sound field separation based on near-field acoustical holography has been developed worldwide, but with the increase in the number of sound sources, traditional measurement methods and calculation methods will generate more workload. To reduce the number of measuring points and save calculation time, the sound field separation of multiple coherent sources with a single measurement surface is proposed. On the basis of separating two coherent sources with this method, the separation formula of more sources based on an equivalent source method is given. Through numerical simulation, the effects of the number of holographic surface measuring points, measuring distance, array shape, and equivalent source number on the calculation accuracy of the sound field separation were compared at different frequencies. The correctness and effectiveness of the sound field separation method with a single surface are verified by actual experiments.

Geometrical consideration for mechanical contact between rolling circle and surface roughness as an improvement to the surface profile

This paper describes measurement methods of surface profiles that improve contact-type displacement sensor outputs by focusing on the contact point between the sphere tip of the sensor and the rough surface. We examined the geometry of a surface profile model and compared measurements using various methods with the measurement using a roughness meter. The spherical tip of the contact type displacement sensor touches the measurement surface and detects the displacement. The sphere tip radius of a typical contact-type displacement sensor ranges from 1–3 mm, causing the roughness curve to be “filtered” by the radius of the sphere. Three methods for estimating the valley portion of the surface profile are evaluated in this study: a) linear approximation of the concave portion of the surface profile, b) function approximation of the concave portion, and c) using the known nose radius of the machining tool. The following sphere tip radii were used to measure actual surface profiles: 0.25 mm, 0.5 mm, 1.0 mm and 1.5 mm. Given the conditions of the experimental model, we found that surface profiles with a roughness that approximates a predictable curve can be measured with a high degree of accuracy.

Physical and Mechanical Characterization of Poly(methyl methacrylate) Based Cements for Bone Regeneration

This laboratory study set out to characterize Calcium Phosphate (CaP) based bone cements with added Zinc Oxide (ZnO) embedded in Poly (methyl methacrylate) (PMMA). Bone cements with varying percentages of CaP mixed with and without varying percentages of ZnO in PMMA were fabricated by one-step polymerization by reacting equimolar ratios of MMA powder and acrylic resin. Neat-PMMA was used as control throughout the experiment. Fabricated samples were tested for their contact angle measurement, surface roughness, nanohardness, elastic modulus, and also their chemical characterization using Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy. A one-way analysis of variance (ANOVA) was used as a statistical method, and a p-value of less than 0.05 was considered statistically significant. It was found that increasing CaP content elevated the hydrophobicity of the composites while mechanical properties increased with the increase of CaP. On the contrary, the addition of ZnO did not show any significant effect. The optimal concentration was observed to be at 20% CaP loading where the mechanical properties were balanced with the hydrophilic nature of CaP. It was also noted that different wt.% of ZnO and CaP did not affect the physicochemical characteristics of the composites. The PMMA-CaP composites demonstrated encouraging results and necessitate further studies to ascertain the implementation of these bone cements clinically.

Research and Design of Warehouse Environment and Personal Radiation Monitoring Experiment System

With reference to the technical standards of radiation monitoring professionals in the “National Post and Occupational Skills Appraisal and Evaluation System”, the idea of simulation system development and integration is adopted to build a warehouse environment and personal radiation monitoring experiment system for principle teaching and installation operations. Through the establishment of experiments such as environmental radiation dose measurement, surface pollution measurement and removal, personal dose measurement and alarm, radiation protection and emergency treatment, the students’ theoretical knowledge has been consolidated and practical ability has been improved.

On study of antenna-radome system near-field measurements with a spherical scanner

The paper presents a research technique for studying an antenna-radome system based on nearfield measurements with a most common «roll over azimuth» spherical scanner. It is based on the relationship between the components of the plane wave spectrum and the spherical wave coefficients, in terms of which the radiation fields of the tested antenna and the antenna-radome system are represented. Expressions for the plane wave spectrum components at the pole of the spherical measurement surface are given. To assess the effect of the radome on the antenna characteristics, it is proposed to use the spectral vector characteristic of the radome passage. Methods for estimating the dielectric constant of the radome by determining the transmission coefficient of its wall at various points on the surface are proposed. It is shown that the use of a weakly directional antenna in the study of the radome characteristics simplifies the task, since the transmission coefficient is determined using the components of the electric field strengths in spherical coordinates.

Using Acoustic Emission for Measuring Surface Roughness

This paper is focused on exploring and utilizing the acoustic emission and its behaviour during surface roughness measurement. Surface quality or coating properties significantly affect the reliability and durability of operations. Three samples were selected for an experiment to demonstrate the possibility of measuring the roughness of surface textures by means of acoustic emission method (AE). These samples were made of the following materials: sample A2 – EN 54SiCr6 steel formed in water, austenitized at 850 °C for 20 minutes, sample A3 – non-heat-treated spheroidal graphite cast iron, and sample B5 – abrasion resistant austenitic manganese steel. The surfaces were subjected to the same surface treatments (roughness Ra = 1.6–3.2 μm) and measured under the same conditions. All possible measurements were measured on both x- and y-axes. Final results are presented graphically. The measured AE values showed a visible effect in the AE signals due to the lack of surface roughness.