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1

Sharp and laterally constrained multitrace impedance inversion based on blocky coordinate descent

Wang Y., Lin W., Cheng S., She B., Hu G., Liu W.

Acta Geophysica

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2018

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Vol. 66, no. 4

623--631

EN

Seismic impedance inversion is a well-known method used to obtain the image of subsurface geological structures. Utilizing the spatial coherence among seismic traces, the laterally constrained multitrace impedance inversion (LCI) is superior to trace-by-trace inversion and can produce a more realistic image of the subsurface structures. However, when the traces are numerous, it will take great computational cost and a lot of memory to solve the large-scale matrix in the multitrace inversion, which restricts the efficiency and applicability of the existing multitrace inversion algorithm. In addition, the multitrace inversion methods are not only needed to consider the lateral correlation but also should take the constraints in temporal dimension into account. As usual, these vertical constraints represent the stratigraphic characteristics of the reservoir. For instance, total-variation regularization is adopted to obtain the blocky structure. However, it still limits the magnitude of model parameter variation and therefore somewhat distorts the real image. In this paper, we propose two schemes to solve these issues. Firstly, we introduce a fast algorithm called blocky coordinate descent (BCD) to derive a new framework of laterally constrained multitrace impedance inversion. This new BCD-based inversion approach is fast and spends fewer memories. Next, we introduce a minimum gradient support regularization into the BCD-based laterally constrained inversion. This new approach can adapt to sharp layer boundaries and keep the spatial coherence. The feasibility of the proposed method is illustrated by numerical tests for both synthetic data and field seismic data.

2

Muck problems in subway shield tunneling in sandy cobble stratum

Cui K., Lin W.

Polish Maritime Research

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2016

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S 1

175--179

EN

Experiments aiming at the muck improvement for Chengdu’s subway shield tunneling in water-rich sandy cobble ground initially finds out the kinds and ratio of muck improver suitable for the this strata, and through the field application determines the reasonable ratio of muck improver for shield tunneling in sandy cobble ground, providing a reference to other muck improvement for shied tunneling in similar ground. And the earth pressure balanced shield is widely used in tunnel engineering, with its characteristics as wide adaptability, safe operation, fast driving speed, low environmental noise and low cost. Taking Chengdu Metro Line as the background, aiming at the difficulty faced by EPB shield tunneling in water-rich sandy cobble ground, and based on the explorations and researches of the predecessors and scholars, engineering and technical personnel, the present paper combines with engineering examples to make a systematic summary and research on key construction technology of EPB shield tunneling through sandy cobble ground from the aspects of EPB shield adaptability, , structure and transformation of cutter and helical unearthed wares, settlement control method, and muck improvement measures. It has certain reference value and guiding significance to the selection of shield machine and the reconstruction of shield machine in complex geological condition.

3

Relationship Between Bake Hardening, Snoek-Köster and Dislocation-Enhanced Snoek Peaks in Coarse Grained Low Carbon Steel

Lin W., Zhao S., Zhang H., Jin X.

Archives of Metallurgy and Materials

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2016

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Vol. 61, iss. 3

1723--1732

EN

In the present work, specimens prepared from coarse grained low carbon steel with different prestrains were baked and then, their bake hardening (BH) property and internal friction were determined. TEM was used to characterize the dislocation structure in BH treated samples. The measurements of internal friction in prestrained samples and baked samples were carried out using a multifunctional internal friction apparatus. The results indicate that, in coarse grained low carbon steel, the bake hardening properties (BH values) were negative, which were increased by increasing the prestrain from 2 to 5%, and then were decreased by increasing the prestrain from 5 to 10%. In the specimen with prestrain 5%, the BH value reached the maximum value and the height of Snoek-Köster peak was observed to be the maximum alike. With increasing the prestrain, both of the BH value and Snoek-Köster peak heights are similarly varied. It is concluded that Snoek-Köster and dislocation-enhanced Snoek peaks, caused by the interactions between interstitial solute carbon atoms and dislocations, can be used in further development of the bake hardening steels.

4

The reliability analysis of cutting tools in the HSM processes

Lin W.

Archives of Materials Science and Engineering

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2008

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Vol. 30, nr 2

97-100

EN

Purpose: This article mainly describe the reliability of the cutting tools in the high speed turning by normal distribution model. Design/methodology/approach: A series of experimental tests have been done to evaluate the reliability variation of the cutting tools. From experimental results, the tool wear distribution and the tool life are determined, and the tool life distribution and the reliability function of cutting tools are derived. Further, the reliability of cutting tools at anytime for high speed machining (HSM) is easily calculated from cutting parameters and tool wear limit from the derived reliability function. Findings: The higher the cutting speed, the sooner the tool flank wear, and the faster the degrade speed of the reliability curve. It means that the sooner the tool flank wear rate, the shorter the tool life, and it is the time to change the cutting tool. Practical implications: This paper shows that the tool flank wear rate can be described by the reliability degrade rate, the higher the flank wear rate, the steeper the tool reliability degrade rate. Originality/value: This article is discussing about the tool wear variation of the cutting tool from the point of reliability. From the reliability variation of the cutting tool, we can further predict the tool life, in order to decide the tool replacement time.

5

The iterative approximation of solutions to system of multi-valued nonlinear operator equations

Lin W.

Journal of Applied Analysis

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2004

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Vol. 10, nr 2

303-309

EN

The purpose of this paper is to study the Ishikawa iterative approximation of solutions to system of multi-valued Φ-accretive operator equations in real uniformly smooth Banach spaces. The results presented in this paper improve and extend the recent corresponding results.