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Parallel on-axis two-step phase-shifting reflective point-diffraction interferometry for holographic phase microscopy based on Michelson architecture is proposed. A cube beamsplitter splits the object wave into two copies within the two arms. The reference wave is rebuilt by low-pass filtering with a pinhole-masked mirror. Both object and reference waves are split into two beams by a grating in a 4f imaging system; thus, two interferograms with quadrature phase-shift can be acquired simultaneously with the aid of polarization elements. The approach has the merit of nanometers-scale phase stability over hours due to its quasi-common-path geometry. It can make full use of camera spatial bandwidth while its temporal resolution is as fast as the camera frame rate. Phase imaging on microscale specimen is implemented, and the experimental results demonstrate that the proposed approach is suitable for investigating dynamic processes.

A reflection mode digital holographic microscope with light emitting diode (LED) illumination and off-axis interferometry is proposed. The setup is comprised of a Linnik interferometer and a grating-based 4f imaging unit. Both object and reference waves travel coaxially and are split into multiple diffraction orders in the Fourier plane by the grating. The zeroth and first orders are filtered by a polarizing array to select orthogonally polarized object waves and reference waves. Subsequently, the object and reference waves are combined again in the output plane of the 4f system, and then the hologram with uniform contrast over the entire field of view can be acquired with the aid of a polarizer. The one-shot nature in the off-axis configuration enables an interferometric recording time on a millisecond scale. The validity of the proposed setup is illustrated by imaging nanostructured substrates, and the experimental results demonstrate that the phase noise is reduced drastically by an order of 68% when compared to a He-Ne laser-based result.

Carbonate sands are widely used in coastal engineering for foundation and embankment. Impact loading could be encountered during driving piles or compacting foundations, which could lead to large grain crushing and changes in grain size distribution. Fractal grading and crushing of carbonate sands were investigated through impact loading tests. The fractal grading uplifted as grains crushed. The fractal dimension and mean diameter decreased with decreasing the specimen height or increasing the input work, while the grain crushing increased with decreasing the specimen height or increasing the input work. It was observed from the test results that the fractal grading of carbonate sand under impact loadings could be intrinsically pertaining to the grain crushing.ICE Publishing: all rights reserved NOTATION B p and B t breakage potential and total breakage, respectively B r relative breakage index (%) D 50 mean diameter (mm) d grain diameter (mm) d M maximum grain diameter (mm) d m minimum grain diameter (mm) e 0 initial void ratio F percentage finer (%) h 0 initial specimen height (mm) W input work (kJ) W v input work per volume (J/mm 3 ) α and β fractal dimensions β B 0 , χ B and α B material constants β D 0 , χ D and α D material constants β W 0 , χ W and α W material constants INTRODUCTIONCarbonate sands are widely used in the construction of coastal foundations. This sand is more crushable than quartz sand. Grain crushing could greatly influence the mechanical behaviours of granular soils. The basic way to investigate the grain crushing behaviours of sands is through laboratory tests -for example, one-dimensional compression tests (

A continuous fuel level sensor using a side-emitting optical fiber is introduced in this paper. This sensor operates on the modulation of the light intensity in fiber, which is caused by the cladding’s acceptance angle change when it is immersed in fuel. The fiber is bent as a spiral shape to increase the sensor’s sensitivity by increasing the attenuation coefficient and fiber’s submerged length compared to liquid level. The attenuation coefficients of fiber with different bent radiuses in the air and water are acquired through experiments. The fiber is designed as a spiral shape with a steadily changing slope, and its response to water level is simulated. The experimental results taken in water and aviation kerosene demonstrate a performance of 0.9 m range and 10 mm resolution.

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