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1

One shot profilometry using iterative two-step temporal phase-unwrapping

Du G., Wang M., Zhou C., Si S., Li H., Lei Z., Li Y.

Optica Applicata

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2017

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Vol. 47, nr 1

97--110

EN

This paper reviews two techniques that have been recently published for three-dimensional profilometry and proposes one shot profilometry using iterative two-step temporal phase-unwrapping by combining the composite fringe projection and the iterative two-step temporal phase unwrapping algorithm. In temporal phase unwrapping, many images with different frequency fringe pattern are needed to project, which would take much time. In order to solve this problem, Ochoa proposed a phase unwrapping algorithm based on phase partitions using a composite fringe. However, we found that the fringe order determined through the construction of phase partitions tended to be imprecise. Recently, we proposed an iterative two-step temporal phase unwrapping algorithm, which can achieve high sensitivity and high precision shape measurement. But it needs multiple frames of fringe images which would take much time. In order to take into account both the speed and accuracy of three-dimensional shape measurement, we get a new, and more accurate unwrapping method based on a composite fringe pattern by combining these two techniques. This method not only retains the speed advantage of Ochoa’s algorithm, but also greatly improves its measurement accuracy. Finally, the experimental evaluation is conducted to prove the validity of the proposed method.

2

Improved method for phase wraps reduction in profilometry

Du G., Wang M., Zhou C., Si S., Li H., Lei Z., Li Y.

Optica Applicata

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2017

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Vol. 47, nr 2

295--306

EN

In order to completely eliminate, or greatly reduce the number of phase wraps in 2D wrapped phase map, Gdeisat and co-workers proposed an algorithm, which uses shifting the spectrum towards the origin. But the spectrum can be shifted only by an integer number, meaning that the phase wraps reduction is often not optimal. In addition, Gdeisat’s method will take much time to make the Fourier transform, inverse Fourier transform, select and shift the spectral components. In view of the above problems, we proposed an improved method for phase wraps elimination or reduction. First, the wrapped phase map is padded with zeros, the carrier frequency of the projected fringe is determined by high resolution, which can be used as the moving distance of the spectrum. And then realize frequency shift in spatial domain. So it not only can enable the spectrum to be shifted by a rational number when the carrier frequency is not an integer number, but also reduce the execution time. Finally, the experimental results demonstrated that the proposed method is feasible.

3

Steel soil composite bridge: an alternative design solution for short-span bridge towards sustainability

Du G., Petersson L., Karoumi R.

Archiwum Instytutu Inżynierii Lądowej

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2017

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Nr 23

91--101

EN

The construction sector is a major source of greenhouse gases. Under the increasing concern about climate change and growing construction activities, the whole sector is challenged to shift focus toward sustainable solutions. The traditional procurement often prioritizes technical and economic viability, while their environmental performance is overlooked. Today’s designers are urged to seek new design options to reduce environmental burdens. Sweden owns more than 24574 bridges, most of which are short spans. Among them, the slab frame bridge (CFB) is a common solution. Soil steel composite bridge (SSCB), alternatively, is a functional equivalent solution to CFB and shows advantages in low cost and easy construction. This paper compares the environmental performance between these two bridge types based on life cycle assessment (LCA). The analysis and its results show that the SSCB is preferable over CFB in most of the examined environmental indicators.

4

Ecological Adaptation of the Seed Microsculptures of Saussurea from Different Altitudes (Qinghai-Tibet Plateau)

Li Z., Du G.

Polish Journal of Ecology

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2015

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Vol. 63, nr 4

593--598

EN

The aim of this study was to explore ecological adaptation of seed microsculptures of Saussurea from different altitudes. Scanning electron microscopy was used to observe the cypselae surface of 10 taxa of Saussurea collected from the eastern edge of Qinghai-Tibet plateau, China. The results indicated that the microsculptures had clear and consistent variations in some samples collected from high (4200 m a.s.l.) and low-altitude sites (2200 m a.s.l.). The thickness of stripes and distance between stripes are increasing while sulcus depth is increasing from a low to a high altitude (P < 0.01). The seed-coat surface was becoming rougher from low to high altitude. The surviving rate of seeds was lower at high altitude than that at low altitude in all the species. The surviving rate of the seeds collected from the high altitudes was higher than that of the seeds collected from low altitudes when sown at the same altitude. All the results suggested that there is selection pressure of the altitude on the development of the microsculpture patterns, which increases absorbed sunlight, the residence time of soil water and nutrition. The changes can make the seeds survive better at extreme environments (cold and dry). The cypselae microsculpture patterns should be used as potential adaptation biomarkers for the species of Saussurea from low- to high-altitude.

5

Effects of seed mass and light on seedling success in Artemisia sieversiana Willd in the Tibetan Plateau

Wu G., Li W., Du G.

Polish Journal of Ecology

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2010

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Vol. 58, nr 3

469-474

EN

Seed mass and light availability are important factors which affect seedling recruitment in plant populations. Effects of seed mass and light availability on seed germination and seedling recruitment in Artemisia sieversiana Willd, which is a widely distributed herbs and a common component species in alpine meadows of the Tibetan Plateau, were tested in a manipulative field experiment. Our research indicated that seed mass and light significantly affected seed germination and seedling emergence and survival and there was a significant interaction effect between seed mass and light availability on these life traits within species. Our study showed that larger seeds presented significant advantages in germination, seedling emergence and survival than smaller seeds under different light availability, especially under deep shade. Our results suggested that seedling success of Artemisia sieversiana appears to be regulated by an interactive effect of seed mass and light availability in alpine meadow of the Qinghai-Tibetan Plateau. In addition, seedlings from larger seeds have more and more stronger advantages from germination, emergence to survival stage than seedlings from smaller seed within species.