Lihua Gong, Qing Xing and Huihuang Wang
The purpose of this paper is to investigate the effect of welding procedure on the corrosion behaviors of weathering steel 09CuPCrNi in marine atmospheric environment. The…
Abstract
Purpose
The purpose of this paper is to investigate the effect of welding procedure on the corrosion behaviors of weathering steel 09CuPCrNi in marine atmospheric environment. The corrosion processes of weathering steel 09CuPCrNi and its welded joints in marine atmospheric environment were simulated by a salt spray dry-wet test.
Design/methodology/approach
The corrosion behaviors of the base metal and the welded joints at corrosion times of 2, 4, 8, 12, 24 weeks were investigated by weight loss test, electrochemical techniques, scanning electron microscope (SEM) and electron probe micro-analyzer (EPMA). The corrosion rates, as well as the morphologies and electrochemical characteristics of corrosion products, the distribution of major alloying elements in rust layer were obtained. The influence of welding on the atmospheric corrosion of 09CuPCrNi was studied.
Findings
The results indicate that the corrosion rate of the 09CuPCrNi welded joints decreases gradually with the corrosion time, and the major alloying elements are enriched in the inner rust layer, which are similar to that of the base metal. In the early stage during the corrosion process, the welded joints with inhomogeneous structure show the poorer corrosion resistance than that of the base metal. However, it looks the opposite way around in the late corrosion stage, when the uniform corrosion products with even thickness of the base metal tend to detach from the substrate easier and earlier and resulting in cracks, which increase the corrosion rate comparatively with that of the welded joints.
Originality/value
09CuPCrNi low alloy steel is a kind of typical weathering steel developed in China which is similar to Corten A developed by USA. Nowadays, 09CuPCrNi low alloy steel is widely adopted in many fields which require welding processes. In the past years, the research of weathering steel welded joints was mainly concentrated on the strength, toughness and weldability. Less work has been done to investigate the difference of corrosion evolution and characteristics between the base metal and its welded joints. Thus, the main objective of the present work was to analyze the influence of welding on the atmospheric corrosion.
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Huihuang Zhao, Yaonan Wang, Zhijun Qiao and Bin Fu
The purpose of this paper is to develop an improved compressive sensing algorithm for solder joint imagery compressing and recovery. The improved algorithm can improve the…
Abstract
Purpose
The purpose of this paper is to develop an improved compressive sensing algorithm for solder joint imagery compressing and recovery. The improved algorithm can improve the performance in terms of peak signal to noise ratio (PSNR) of solder joint imagery recovery.
Design/methodology/approach
Unlike the traditional method, at first, the image was transformed into a sparse signal by discrete cosine transform; then the solder joint image was divided into blocks, and each image block was transformed into a one-dimensional data vector. At last, a block compressive sampling matching pursuit was proposed, and the proposed algorithm with different block sizes was used in recovering the solder joint imagery.
Findings
The experiments showed that the proposed algorithm could achieve the best results on PSNR when compared to other methods such as the orthogonal matching pursuit algorithm, greedy basis pursuit algorithm, subspace pursuit algorithm and compressive sampling matching pursuit algorithm. When the block size was 16 × 16, the proposed algorithm could obtain better results than when the block size was 8 × 8 and 4 × 4.
Practical implications
The paper provides a methodology for solder joint imagery compressing and recovery, and the proposed algorithm can also be used in other image compressing and recovery applications.
Originality/value
According to the compressed sensing (CS) theory, a sparse or compressible signal can be represented by a fewer number of bases than those required by the Nyquist theorem. The findings provide fundamental guidelines to improve performance in image compressing and recovery based on compressive sensing.
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Huihuang Zhao, Jianzhen Chen, Shibiao Xu, Ying Wang and Zhijun Qiao
The purpose of this paper is to develop a compressive sensing (CS) algorithm for noisy solder joint imagery compression and recovery. A fast gradient-based compressive sensing…
Abstract
Purpose
The purpose of this paper is to develop a compressive sensing (CS) algorithm for noisy solder joint imagery compression and recovery. A fast gradient-based compressive sensing (FGbCS) approach is proposed based on the convex optimization. The proposed algorithm is able to improve performance in terms of peak signal noise ratio (PSNR) and computational cost.
Design/methodology/approach
Unlike traditional CS methods, the authors first transformed a noise solder joint image to a sparse signal by a discrete cosine transform (DCT), so that the reconstruction of noisy solder joint imagery is changed to a convex optimization problem. Then, a so-called gradient-based method is utilized for solving the problem. To improve the method efficiency, the authors assume the problem to be convex with the Lipschitz gradient through the replacement of an iteration parameter by the Lipschitz constant. Moreover, a FGbCS algorithm is proposed to recover the noisy solder joint imagery under different parameters.
Findings
Experiments reveal that the proposed algorithm can achieve better results on PNSR with fewer computational costs than classical algorithms like Orthogonal Matching Pursuit (OMP), Greedy Basis Pursuit (GBP), Subspace Pursuit (SP), Compressive Sampling Matching Pursuit (CoSaMP) and Iterative Re-weighted Least Squares (IRLS). Convergence of the proposed algorithm is with a faster rate O(k*k) instead of O(1/k).
Practical implications
This paper provides a novel methodology for the CS of noisy solder joint imagery, and the proposed algorithm can also be used in other imagery compression and recovery.
Originality/value
According to the CS theory, a sparse or compressible signal can be represented by a fewer number of bases than those required by the Nyquist theorem. The new development might provide some fundamental guidelines for noisy imagery compression and recovering.
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Sai (Jane) Jing, Ping Li, Chris Ryan, Cora Un In Wong and Mary Anne Ramos Tumanan
This study aims to identify the attitudes of Chinese residents towards tourists and tourism development. Based on periods of observation, temporary residency and several visits…
Abstract
Purpose
This study aims to identify the attitudes of Chinese residents towards tourists and tourism development. Based on periods of observation, temporary residency and several visits for more than a decade, and supplemented by data collected from 478 residents, the study examines to what extent the rural villagers identify the tourism induced changes as being an outcome of official Chinese policies. The villages, Xidi, Hongcun and Nanping, are three heritage villages in Anhui Province and represent appropriate case studies for such an examination due to their differing histories of tourism administrative procedures. Findings contribute to scholarly knowledge by putting pro-poor tourism and community participation under scrutiny in Chinese context. A change of residents’ perceptions towards tourism could potentially be consequential for tourists’ experience and the sustainability of tourism development, particularly in emerging rural destinations.
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Drawing upon new institutional economics and contracting theory, this chapter extends the concept of headquarter (HQ)–subsidiary relationships to capture unconventional types of…
Abstract
Drawing upon new institutional economics and contracting theory, this chapter extends the concept of headquarter (HQ)–subsidiary relationships to capture unconventional types of subsidiary organizations in transition economies. A conceptual framework is first developed to examine how the interplay between institutions and subsidiaries shapes HQ–subsidiary relations in rapidly changing institutional environments. It is then applied to study contractual joint ventures in China, an important, yet often misunderstood, form of multinational subsidiary operation. The research sheds new light on how parent firms design contract provisions, credible commitments, and contract renegotiation mechanisms for the effective management of joint venture subsidiaries. These findings have important implications for future inquiry into the interplay between institutions and organizations in safeguarding subsidiary operations in transition economies.