Spatial distribution and properties of organic micropollutants in surface sediments from Bohai sea

WenXin Liu,JiangLin Chen,Shu Tao 환경독성보건학회 2004 한국독성학회 심포지움 및 학술발표회 Vol.- No.-

A High Precision Time-frequency Analysis Method

Wenxin Zhang,Xiaojun Liu,Xiuwei Chen,Qing Liu,Guangyou Fang 보안공학연구지원센터 2015 International Journal of Signal Processing, Image Vol.8 No.7

To analysis the signal whose frequency changes as time, this article presents a new time-frequency analysis method based on short-time fractional Fourier transform (FRFT) and integration of midpoints. This method uses window functions to divide the signal to many pieces, then the FRFT is used to calculate the frequency modulation (FM) rate of each piece. A chirp signal can be built based on the FM rate and the intermediate frequency (IF) signal is obtained by mixing the chirp signal and the primary signal. The frequency of the midpoints can be estimated by the chirp-z transform (CZT), therefore the frequency of every piece can be calculated. This method avoids the impact that the quick change of frequency leads to the error of short-time Fourier transform. It also can reduce the error brought by the estimation of chirp rate. Therefore, the method can improve the accuracy of time-frequency analysis. This article also puts forward a method to search the order of fractional Fourier transform, and the computer simulation and measurement verifies the effectiveness of the proposed algorithm.

New degradation feature extraction method of planetary gearbox based on alpha stable distribution

Wenxin Qiao,Xianglong Ni,Lei Wang,Xin Lv,Liwei Chen,Fucheng Sun 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.1

The planetary transmission system has been widely used in industry because of its various advantages. And the study on degradation feature extraction method of planetary gearbox is of major significance for mechanical system prognostics and health management (PHM). In this paper, the alpha stable distribution characteristics of planetary gearbox vibration signals in performance degradation process are verified. By observing the change of alpha stable distribution for planetary gearbox degradation experiment data, a new degradation feature extraction method based on alpha stable distribution is proposed, which is called the height of probability distribution (HPD). Through comparative analysis, it is determined that HPD has better linearity and less fluctuation compared with conventional degradation features in planetary gearbox accelerated degradation stage. Moreover, in the accelerated degradation stage, the degradation trend prediction result based on HPD is closer to the actual data than conventional degradation features no matter using Wiener-based or LSSVM-based prediction method. These conclusions indicate that the newly proposed HPD works well and gives accurate estimates for condition monitoring and degradation trend prediction of planetary gearbox.

Improvement of Yield Asymmetry and Enhancement of Mechanical Properties of Extruded AZ110 Alloy with La-Rich Misch Metal Addition

Qiyu Liao,Wenxin Hu,Qichi Le,Xingrui Chen,Yanchao Jiang 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.5

In this paper, effects of the La-rich MM (Misch Metal) on the microstructure, texture and mechanical properties of extrudedAZ110 alloy during tension and compression deformation were investigated. High strength and low tension–compressionyield asymmetry of AZ110MM alloy (AZ110 alloy with La-rich MM addition) are developed by hot extrusion. The additionof La-rich MM brings Al-RE phases (Al2(La, Ce) and Al11(La, Ce)3) to the as-cast AZ110 alloy, which play an importantrole in the grain refinement and texture weakening during extrusion deformation. Such grain refinement and texture weakeningobviously inhibit the nucleation and growth of twins and make the deformation mechanism change from twinning tomultiple slip during cold compression deformation. Furthermore, the Al-RE phases also improve the tension–compressionyield asymmetry performance of the extruded AZ110 alloy via the combining effects of grain refinement, texture weakeningand the transformation from twinning to multiple slip. Moreover, the extruded AZ110MM alloy shows much higher strengthover AZ110 alloy, owning to texture effect, grain boundary strengthening and precipitation strengthening.

Reliability‐aware service chaining mapping in NFV‐enabled networks

Yicen Liu,Yu Lu,Wenxin Qiao,Xingkai Chen 한국전자통신연구원 2019 ETRI Journal Vol.41 No.2

Network function virtualization can significantly improve the flexibility and effectiveness of network appliances via a mapping process called service function chaining. However, the failure of any single virtualized network function causes the breakdown of the entire chain, which results in resource wastage, delays, and significant data loss. Redundancy can be used to protect network appliances; however, when failures occur, it may significantly degrade network efficiency. In addition, it is difficult to efficiently map the primary and backups to optimize the management cost and service reliability without violating the capacity, delay, and reliability constraints, which is referred to as the reliability‐aware service chaining mapping problem. In this paper, a mixed integer linear programming formulation is provided to address this problem along with a novel online algorithm that adopts the joint protection redundancy model and novel backup selection scheme. The results show that the proposed algorithm can significantly improve the request acceptance ratio and reduce the consumption of physical resources compared to existing backup algorithms.

Single-Point Grinding of Alumina and Zirconia Ceramics Under Two-Dimensional Compressive Prestress

Gaofeng Zhang,Zhigang Wang,Wenxin Chen,Jingtao Li,Hao Sun,Kui Zhang 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.1

In this study, single-point grinding experiments were performed on alumina and zirconia ceramics to investigate the grinding processes under two-dimensional compressive prestress (TCP). Grinding forces and grooves were measured under different values of TCP to evaluate the grinding defects. The material removal rate and actual grinding depth were exploited to investigate the grinding-induced damage and material

A Dynamic Placement Mechanism of Service Function Chaining Based on Software-defined Networking

( Yicen Liu ),( Yu Lu ),( Xingkai Chen ),( Xi Li ),( Wenxin Qiao ),( Liyun Chen ) 한국인터넷정보학회 2018 KSII Transactions on Internet and Information Syst Vol.12 No.10

To cope with the explosive growth of Internet services, Service Function Chaining (SFC) based on Software-defined Networking (SDN) is an emerging and promising technology that has been suggested to meet this challenge. Determining the placement of Virtual Network Functions (VNFs) and routing paths that optimize the network utilization and resource consumption is a challenging problem, particularly without violating service level agreements (SLAs). This problem is called the optimal SFC placement problem and an Integer Linear Programming (ILP) formulation is provided. A greedy heuristic solution is also provided based on an improved two-step mapping algorithm. The obtained experimental results show that the proposed algorithm can automatically place VNFs at the optimal locations and find the optimal routing paths for each online request. This algorithm can increase the average request acceptance rate by about 17.6% and provide more than 20-fold reduction of the computational complexity compared to the Greedy algorithm. The feasibility of this approach is demonstrated via NetFPGA-10G prototype implementation.

Nanosized Carbon Black Combined with Ni₂O₃ as “Universal” Catalysts for Synergistically Catalyzing Carbonization of Polyolefin Wastes to Synthesize Carbon Nanotubes and Application for Supercapacitors

Wen, Xin,Chen, Xuecheng,Tian, Nana,Gong, Jiang,Liu, Jie,Rü,mmeli, Mark H.,Chu, Paul K.,Mijiwska, Ewa,Tang, Tao American Chemical Society 2014 Environmental science & technology Vol.48 No.7

<P>The catalytic carbonization of polyolefin materials to synthesize carbon nanotubes (CNTs) is a promising strategy for the processing and recycling of plastic wastes, but this approach is generally limited due to the selectivity of catalysts and the difficulties in separating the polyolefin mixture. In this study, the influence of nanosized carbon black (CB) and Ni<SUB>2</SUB>O<SUB>3</SUB> as a novel combined catalyst system on catalyzing carbonization of polypropylene (PP), polyethylene (PE), polystyrene (PS) and their blends was investigated. We showed that this combination was efficient to promote the carbonization of these polymers to produce CNTs with high yields and of good quality. Catalytic pyrolysis and model carbonization experiments indicated that the carbonization mechanism was attributed to the synergistic effect of the combined catalysts rendered by CB and Ni<SUB>2</SUB>O<SUB>3</SUB>: CB catalyzed the degradation of PP, PE, and PS to selectively produce more aromatic compounds, which were subsequently dehydrogenated and reassembled into CNTs via the catalytic action of CB together with Ni particles. Moreover, the performance of the synthesized CNTs as the electrode of supercapacitor was investigated. The supercapacitor displayed a high specific capacitance as compared to supercapacitors using commercial CNTs and CB. This difference was attributed to the relatively larger specific surface areas of our synthetic CNTs and their more oxygen-containing groups.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/esthag/2014/esthag.2014.48.issue-7/es404646e/production/images/medium/es-2013-04646e_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/es404646e'>ACS Electronic Supporting Info</A></P>