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Wang Z.,Zhejiang University | Wang Z.,Taizhou University | Chen M.,Maritime Safety Administration of Fuzhou | Wu J.,Zhejiang University | And 2 more authors.
Applied Mechanics and Materials | Year: 2010

Surface texture of tribological interfaces has the potential to improve friction and lubrication performance of various mechanical components. This review paper emphasizes on the current status of the research of surface texture, including the features, the effects on tribological performance, the forming techniques, and the modeling and simulation of surface texture. It is intended to help readers to gain a more comprehensive view on surface texture of tribological interfaces. © (2010) Trans Tech Publications.


Wu Z.,Hunan University | Yuan J.,Hunan University | Lv B.,Hunan University | Zheng X.,Ningbo Special Equipment Inspection Center
Proceedings - 2010 3rd International Congress on Image and Signal Processing, CISP 2010 | Year: 2010

Characteristics of the lesions in digital mammography images will be more clear after image enhancement, which can increase the detection rate of early breast cancer. This paper proposes a modified unsharp masking approach based on an improved high-pass filter. Experimental result of digital mammography image enhancement proves that the proposed method can effectively extrude the edges of lesions and at the same time can suppress the noises in uniform background areas. ©2010 IEEE.


Gao W.,Nanjing University of Technology | Jiang Y.,Nanjing University of Technology | Gong J.,Nanjing University of Technology | Chen H.,Ningbo Special Equipment Inspection Center | And 2 more authors.
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2012

T91/12Cr1MoV dissimilar welded joint is widely used in main steam pipelines of power plant, and because of the different material properties of weld-metal (WM) and base-metal (BM), high welding residual stress occurred in this joint. This high residual stress would induce failure in early life of joint. By using ABAQUS software and succession coupling thermal stress computation program, welding residual stress distribution on the outer surface and along the fusion line through the wall thickness direction of T91/12Cr1MoV dissimilar welded joint was analyzed. The influence of post weld heat treatment (PWHT) on welding residual stress was studied either. Numerical simulation results show both T91 and 12Cr1MoV BM heat affect zones (HAZ) have peak residual stresses and the stress amplitude in HAZ of T91 side is larger than that of 12Cr1MoV side. The PWHT could relieve residual stress in both HAZs, while the effect in 12Cr1MoV side is more remarkable than in T91 side. © 2012 Chinese Society for Electrical Engineering.


Qian J.-Y.,Zhejiang University | Wei L.,Zhejiang University | Zhu G.-R.,Ningbo Special Equipment Inspection Center | Chen F.-Q.,Zhejiang University | Jin Z.-J.,Zhejiang University
Energy Conversion and Management | Year: 2016

Valve contained pipelines have witnessed a great growth and there exists a lot of noise caused by valves. Thick perforated plates are especially used is valve contained pipelines for the noise control, but there are limited literatures about its noise control performances under different structural parameter of thick perforated plates, which limits its popularization and application. In this paper, transmission loss (TL) predictions of various thick perforated plates are carried out to analyze the noise control performances. Finite element method (FEM) is implemented to simulate the acoustic response, and TL is achieved by the sound pressure of four points on both sides of the thick perforated plates. Adopted numerical method shows good agreements with the existing research works and the results indicate that reducing the margin of the plates can enhance TL of some frequencies. Similar to chamber mufflers, the maximum TL depends on the area ratio and the frequency range with the best noise control performance is related to the plate thickness. Meanwhile, the low velocity flow does not affect the TL curve so much and in the situation of supersonic flow, and the TL curve turns into a periodic shape, which may weaken the effects of noise control. Besides, based on the analytical solution of TL for the chamber muffler, a linear correction formula of maximum TL is proposed for the thick perforated plate. This work can give several advices for similar perforated plates design works and someone who are dealing with decreasing the noise effects from the valves in pipelines. © 2015 Elsevier Ltd. All rights reserved.


Wei L.,Zhejiang University | Zhu G.,Ningbo Special Equipment Inspection Center | Qian J.,Zhejiang University | Fei Y.,Zhejiang University | Jin Z.,Zhejiang University
PLoS ONE | Year: 2015

The main objective of this paper is to study the characteristics of flow-induced noise in high pressure reducing valve (HPRV) and to provide some guidance for noise control. Based on computational fluid dynamics (CFD), numerical method was used to compute flow field. Ffowcs Williams and Hawkings Model was applied to obtain acoustic signals. The unsteady flow field shows that noise sources are located at the bottom of plug for valve without perforated plate, and noise sources are behind the plate for valve with perforated plate. Noise directivity analysis and spectrum characteristics indicate that the perforated plate could help to reduce noise effectively. Inlet pressure has great effects on sound pressure level (SPL). The higher inlet pressure will lead to larger SPL at high frequency. When the maximum Ma is close to 1, SPL at low frequency becomes very high. © 2015 Wei et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


Wei L.,Zhejiang University | Zhu G.,Ningbo Special Equipment Inspection Center | Jin Z.,Zhejiang University
Advances in Mechanical Engineering | Year: 2015

Heat recovery unit (HRU) is a heat exchange device in drying process. In HRU, room air is preheated by waste hot air and then transported to drying oven to remove moisture, which helps to save both energy and time. The main purpose of this paper is to build a heat transfer model of HRU and study its characteristics. A numerical method based on fluid-solid coupling was used to calculate the heat transfer between tube and fluids, and the actual structure was simplified to improve computation efficiency. The results were validated by theoretical calculation and experiments. Effects of Reynolds number (Re) on outlet temperature, Nusselt number, and pressure drop were investigated. It was found that the thermal resistance of shell side is large, by reducing which the total heat transfer coefficient can be improved. The difference between finned tube and smooth tube is in the shell side. Larger Re of shell side leads to good heat transfer performance but also larger pressure drop which increases the flow resistance. © Lin Wei et al.


PubMed | Ningbo Special Equipment Inspection Center and Zhejiang University
Type: Journal Article | Journal: PloS one | Year: 2015

The main objective of this paper is to study the characteristics of flow-induced noise in high pressure reducing valve (HPRV) and to provide some guidance for noise control. Based on computational fluid dynamics (CFD), numerical method was used to compute flow field. Ffowcs Williams and Hawkings Model was applied to obtain acoustic signals. The unsteady flow field shows that noise sources are located at the bottom of plug for valve without perforated plate, and noise sources are behind the plate for valve with perforated plate. Noise directivity analysis and spectrum characteristics indicate that the perforated plate could help to reduce noise effectively. Inlet pressure has great effects on sound pressure level (SPL). The higher inlet pressure will lead to larger SPL at high frequency. When the maximum Ma is close to 1, SPL at low frequency becomes very high.

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