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Wang X.C.,Shanghai JiaoTong University | Wang X.C.,DNV GL | Lu F.G.,Shanghai JiaoTong University | Andersen I.,DNV GL | Yu L.S.,Hudong Zhonghua Shipbuilding Group Co.
Advanced Materials Research | Year: 2014

Longitudinal hot tearing, popularly called as end cracking, frequently takes place in the end portions of large steel panels' butt joints, using one-sided, submerged-arc welding with flux copper backing welding process (FCB welding). The study was to look for the possibility to improve and/or prevent the end cracking issue during FCB welding, center blind-hole drilling technique was used to measure the welding residual stress for five different cases, considering hot tearing mechanism, its influence factors and the relevant reported prevention measures. Unpredictable result was observed subsequently that transverse compressive stress is found on the shallow surface of weld seams, which could give supplementary information to the common assumption for conventional low heat input welding method that cracks initiation is caused by tensile stresses across the welded joints. The study concluded that FCB welding end cracking issue is caused by the comprehensive function of different stresses, and also properly use tack welding practice, suitable elastic run-off plate and relatively low heat input energy which will reduce the end cracking susceptibility for the tested materials. © (2014) Trans Tech Publications, Switzerland.

Hu Y.,Huazhong University of Science and Technology | Hu Y.,Wuhan Naval University of Engineering | Liu H.,Huazhong University of Science and Technology | Rao Q.,Wuhan Naval University of Engineering | And 3 more authors.
Journal of Nanoscience and Nanotechnology | Year: 2011

N-doped TiO2 nanocrystalline powders were prepared by the sol-gel method using various N precursors, including triethylamine, hydrazine hydrate, ethylenediamine, ammonium hydroxide, and urea. The samples were characterized by X-ray diffraction, N2 adsorption isotherms, transmission electron microscopy, ultraviolet-visible diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The photocatalytic activities of as-prepared samples under irradiation of visible light (λ > 405 nm) were evaluated by photodecomposition of methyl orange. The alkalinity of N precursor was found to play a key role in the gel process. The N precursor with moderate alkalinity causes TiO2 nanoparticles to be sol-transformed into a loosely agglomerated gel. This transformation facilitates the preparation of an N-doped TiO2 powder with small nanocrystal size, large specific surface area, and high N doping level and results in high visible light photocatalytic activity. The N in TiO2 with N 1s binding energy at 399-400 eV may be assigned to the N-H species located in interstitial sites of TiO2 lattice which is the active N species responsible for the visible light photocatalytic activity. The N species of N 1s peak at ~402 and ~405 eV are ineffective to the visible light photocatalytic activity and may inhibit the photocatalytic activity. Moreover, a TiO2 nanoparticle powder with large specific area can be achieved by using urea as a template and then by using ammonium hydroxide to transform the sol into gel. Copyright © 2011 American Scientific Publishers.

Liu J.,Huazhong University of Science and Technology | Liu J.,Collaborative Innovation Center for Advanced Ship and Deep Sea Exploration | Liu J.,Hudong Zhonghua Shipbuilding Group Co. | Xiang L.,Huazhong University of Science and Technology | And 3 more authors.
Composites Part A: Applied Science and Manufacturing | Year: 2015

The effects of temperature on the bending properties and failure mechanism of carbon fiber reinforced polymer composite sandwich structure with pyramidal truss cores were investigated and presented in this paper. The three-point bending tests of composite sandwich structures were performed at seven different temperatures, and the scanning electron microscope was used to examine the fiber-matrix interface properties in order to understand the deformation and failure mechanism. Then the effects of temperature on deformation modes, failure mechanism and bending failure load were studied and analyzed. The results showed that the temperature has visible impact on the deformation modes, failure mechanism, and bending failure load. The bending failure load decreased as temperature increased, which was caused by the degradation of the matrix properties and fiber-matrix interface properties at high temperature. The analytical formulae were also presented to predict the bending stiffness and failure load of composite sandwich structures at different temperatures. © 2015 Elsevier Ltd.All rights reserved.

Chen X.,Shanghai JiaoTong University | Pang L.,Shanghai JiaoTong University | Tang Y.,Beijing University of Posts and Telecommunications | Yang H.,Hudong Zhonghua Shipbuilding Group Co. | Xue Z.,Shanghai JiaoTong University
2015 International Conference on Cyber Security of Smart Cities, Industrial Control System and Communications, SSIC 2015 - Proceedings | Year: 2015

Security is an important issue in the field of wireless channel. In this paper, the security problem of Gaussian MIMO wireless hybrid channel is considered where a transmitter with multiple antennas sends information to an intended receiver with one antenna in the presence of an eavesdropper with multiple antennas. Through utilizing some of the power to produce 'artificial noise', the transmitter can only degrade the eavesdropper's channel to ensure the security of the communication. But there is an inherent weakness in this scheme. Then a Hybrid Blind Space Elimination (HBSE) scheme is proposed and proved to fix the design flaw in order to strengthen the original scheme. © 2015 IEEE.

Huang J.-L.,Jimei University | Xiang Y.-B.,Jimei University | Qiao Y.-Z.,Hudong Zhonghua Shipbuilding Group Co. | Yin Z.-B.,Jimei University
Dalian Haishi Daxue Xuebao/Journal of Dalian Maritime University | Year: 2015

A nonlinear simulation model of 4190 type turbocharged 4-stroke marine diesel engine was built based on MATLAB/Simulink platform, and the simulation calculation of air intake and exhaust system was carried out. Taking 4190ZLC-2 type marine diesel engine as example, the correctness of the simulation model of diesel engine was verified by comparing the simulation results with the test ones. Finally, the proposed simulation model was used to study the effects of the intake and exhaust system on the performances of 4190ZLC-2 type diesel engine power, torque, fuel consumption rate as well as charging efficiency. Simulation results indicate that the fuel economy and emission of 4190 type diesel engine achieve the optimal value when the inlet manifold diameter offset +20 mm and exhaust manifold diameter of 65 mm, which provides the basis of performance optimization for the 190 series medium-speed marine diesel engine design. ©, 2015, Editorial Office of Journal of Dalian Maritime University. All right reserved.

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