Adaptive reversible image watermarking algorithm based on DE

( Zhengwei Zhang ),( Lifa Wu ),( Yunyang Yan ),( Shaozhang Xiao ),( Shangbinggao ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.3

In order to improve the embedding rate of reversible watermarking algorithm for digital image and enhance the imperceptibility of the watermarked image, an adaptive reversible image watermarking algorithm based on DE is proposed. By analyzing the traditional DE algorithm and the generalized DE algorithm, an improved difference expansion algorithm is proposed. Through the analysis of image texture features, the improved algorithm is used for embedding and extracting the watermark. At the same time, in order to improve the embedding capacity and visual quality, the improved algorithm is optimized in this paper. Simulation results show that the proposed algorithm can not only achieve the blind extraction, but also significantly heighten the embedded capacity and non-perception. Moreover, compared with similar algorithms, it is easy to implement, and the quality of the watermarked images is high.

Does the Launch of Shanghai Crude Oil Futures Stabilize the Spot Market? A Financial Cycle Perspective

Zhang Dan,Farnoosh Arash,Ma Zhengwei 한국국제경제학회 2022 International Economic Journal Vol.36 No.1

Based on the examination of price discovery between Shanghai crude oil futures and the spot market, this paper explores whether the introduction of Shanghai crude oil futures can play a stabilizing role in the spot market, alleviating the impact of the financial cycle risk on the crude oil market from March 2018 to December 2019. The results show that there is only a uni-directional relationship of the spot price to futures price, and spot plays a leading role in price discovery. The risk of the financial cycle will increase the volatility of spot price, and the introduction of crude oil futures market can increase the impact of the financial cycle on the spot market. The additional research on the microcosmic mechanism of Shanghai crude oil futures indicates that crude oil futures market mainly influences the spot market fluctuation through the behaviour of traders: speculation increases price volatility in the spot market, which is more pronounced in the high volatility of the financial cycle as oppose to hedging transaction.

Reversible Coordinative Chain Transfer Polymerization of Butadiene Using a Neodymium Phosphonate Catalyst

Zhengwei Tang,Aimin Liang,Handong Liang,Jiangwei Zhao,Lin Xu,Jie Zhang 한국고분자학회 2019 Macromolecular Research Vol.27 No.8

This study involves an investigation of the chain transfer reaction of butadiene (Bd) polymerization, under the neodymium tris[bis(2-ethylhexyl)phosphate] (Nd)/diisobutyl aluminum hydride (Al)/ethylaluminum sesquichloride (Cl)/Bd catalytic system. The results show that the chain transfer reaction itself is reversible. Only chain propagation and chain exchange reactions occurred during the later period of polymerization, and there was a linear relationship between the molecular weight and the conversion rate. All polymer chains showed sufficient reactivity to propagate by reacting with the monomer. The degree of the chain transfer reaction can be determined by the amount of Al, and the molecular weight in the synthetic polybutadiene can be accurately designed by the formula Mn=54·Bd/Nd/(0.67Al/Nd-7.17). The catalyst-polymerized butadiene afforded products featuring a relatively narrow molecular weight distribution and a high cis-1,4 stereospecificity. One of these products, polybutadiene rubber, showed narrow distribution in the sample, and exhibited good physical and mechanical properties, low abrasion, and low rolling resistance.

Tri-Axial Confining Numerical Test and Settlement Analysis of the Gravel Layer

Liang Zhang,Zhengwei Guo,Zheng Liang 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.9

The discrete element method (DEM) is used according to the discreteness of the gravel layer to analysis the gravel particle. This paper presents simulations of tri-axial experiment tests and settlement of gravel layer. The stress-strain curves of gravel layer were analysed with different confining pressure through tri-axial numerical test, and the effect with different particle parameters and confining pressures was analysed. The numerical model of gravel layer after the excavation was established by the DEM to statistically analyse the settlement of gravel layer. The analyses results show that confining pressure corresponds to axial pressure that be destroyed of gravel particle model. The static friction coefficient has little effect on the failure of the tri-axial confining experimental model. The experiment model with various particle sizes need higher axial stress that be destroyed than the same particle size. During the collapse of the gravel stratum, the gravels are closer to the top of the hole which have a larger shift of settlement and a faster sedimentation rate. If the gravel are further away from top of the hole which have a smaller shift of settlement and slower sedimentation rate. The settlement of gravel causes the forces variation in all directions.

False Data Injection Attack Detection and Improved WLS Power System State Estimation Based on Node Trust

Qu Zhengwei,Zhang Jianxuan,Wang Yunjing,Georgievitch Popov Maxim,Guo Kai 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.2

To solve the problem that the false data injection attack can evade the unfavorable data recognition mechanism and tamper with the state estimation, this paper proposes a detection and defense scheme for the fake data injecting attack based on the trust degree of the nodes. Considering the failure of the attacker’ s carefully constructed implicit data injection attack with residual threshold method, this paper proposes a node trust model and a trust update algorithm based on the characteristics of state estimation of power system nodes. Feasibility of detecting false data injection based on trustworthiness and using IEEE-14 and IEEEE-118 nodes to systematically analyze diff erent false information injection scenarios. Secondly, in order to eliminate the interference of the false data injected by the attacker to the normal operation of power network, this paper combines the process of trust updating algorithm with the classical weighted least square algorithm to improve the robustness of state estimation and to mitigate the infl uence of fake data injection attacks on power networks. In this paper, simulation experiments are carried out on 14 nodes and 118 nodes system to test the accuracy of the optimized state estimation algorithm

Hyper-heuristic algorithm for traffic flow-based vehicle routing problem with simultaneous delivery and pickup

Wang Zhengwei,Liu Jinlong,Zhang Jingling 한국CDE학회 2023 Journal of computational design and engineering Vol.10 No.6

To address the realistic problem of seriously reducing distribution efficiency and increasing distribution cost caused by road traffic congestion, this paper constructs a time-dependent speed describing vehicle travel speed and road traffic flow by simulating the change of urban traffic flow, to establish a vehicle route problem model considering traffic flow with distribution cost and customer satisfaction as optimization objectives. To solve this problem, a hyper-heuristic algorithm based on tabu search is designed in this paper, in which the underlying search operator is selected more efficiently by a high-level heuristic strategy. In addition, the correctness of the model and the effectiveness of the algorithm are verified by conducting simulation experiments on several benchmark sets. Experiment results are shown as the travel speed of the vehicle increases, the average customer satisfaction in lc1-type instances increases to 0.94. And the impact of urban traffic changes on logistics costs and customer satisfaction is further analyzed.

Optical Polarization Characteristics of Low-Earth-Orbit Space Targets

Zhenduo Zhang,Yuanhao Wu,Zhengwei Li 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.76 No.4

This study investigates the optical polarization characteristics of low-earth-orbit (LEO) space targets at different operating attitudes for different surface materials by analyzing these characteristics using a microfacet analysis model. Subsequently, the polarization image of a typical LEO space target was simulated, and several laboratory and outfield polarization detection experiments were conducted. Simulated and experimental results validate the effectiveness of polarization in analyzing and evaluating the operating attitudes of the LEO space targets and in identifying their material properties. Results show that the polarization images can effectively determine the constituent structure of the LEO space targets.

Novel Design and Research for a High-retaining-force, Bi-directional, Electromagnetic Valve Actuator with Double-layer Permanent Magnets

You Jiaxin,Zhang Kun,Zhu Zhengwei,Liang Huimin 한국자기학회 2016 Journal of Magnetics Vol.21 No.1

To increase the retaining force, a novel design for a concentric, bi-directional, electromagnetic valve actuator that contains double-layer permanent magnets is presented in this paper. To analyze the retaining-force change caused by the magnets, an equivalent magnetic circuit (EMC) model is established, while the EMC circuit of a double-layer permanent-magnet valve actuator (DLMVA) is also designed. Based on a 3D finite element method (FEM), the calculation model is built for the optimization of the key DLMVA parameters, and the valve-actuator optimization results are adopted for the improvement of the DLMVA design. A prototype actuator is manufactured, and the corresponding test results show that the actuator satisfies the requirements of a high retaining force under a volume limitation; furthermore, the design of the permanent magnets in the DLMVA allow for the attainment of both a high initial output force and a retaining force of more than 100 N.

Polycaprolactone Scaffold Modified with Galactosylated Chitosan for Hepatocyte Culture

Yuan Qiu,Changyou Gao,Zhengwei Mao,Yimu Zhao,Jichuan Zhang,Qi Guo,Zhongru Gou 한국고분자학회 2012 Macromolecular Research Vol.20 No.3

A suitable extracellular matrix that can maintain long-term proliferation and liver-specific functions of hepatocytes is essential for both extracorporeal bioartificial liver (BAL) assist systems and implantable cell-scaffold constructs. In this work, a polycaprolactone (PCL) scaffold was modified with galactosylated chitosan (GC) to achieve better bioactivity and mechanical stability. The PCL scaffold, prepared by a method of gelatin particle leaching,was hydrolyzed to produce carboxylic groups that were utilized to react with the amine groups of the GC, which was synthesized by grafting the galactose to chitosan. Results showed that the content of carboxylic groups was increased initially with the hydrolysis time until 10 min, at which a COOH density of 2.0×10-5 mol/mg scaffold was reached. The incorporated GC amount showed a positive relationship with the COOH density and finally reached a 100 μg/mg scaffold with a hydrolysis time of 15 min. The incorporated GC was rather stable against incubation in the medium, and could significantly enhance the compression strength of the PCL scaffold in a wet state. With the galactose ligands on the surface, the PCL scaffold could be better recognized by hepatocytes, and show better cell viability, spheroid formation and long-term maintenance of liver-specific functions such as albumin secretion.

Study on the size reduction factor of extreme wind pressure of facade cladding of high-rise buildings with square section

Xiang Wang,Yong Quan,Zhengwei Zhang,Ming Gu 한국풍공학회 2023 Wind and Structures, An International Journal (WAS Vol.36 No.1

The effect of cladding panel size on the size reduction factor (SRF) of extreme area-averaging wind pressure (EAWP) on the facades of a high-rise building is often ignored in previous studies. Based on wind tunnel tests, this study investigated the horizontal and vertical correlations of wind pressure on the facade claddings of square-section high-rise buildings. Then, the influencing parameters on the SRF of the EAWP on the cladding panels were analyzed, which were the panel area, panel width, panel length and building width. The results show clear regional distinctions in the correlation of wind pressures on the building facades and the rules of the horizontal and vertical correlations are remarkably different, which causes the cladding size ratio to impact the SRF significantly. Therefore, this study suggests the use of the non-dimensional comprehensive size parameter − / ( is the fitting parameter) determined by the cladding panel horizontal size b, cladding panel vertical size h and the building width B rather than the cladding panel area to describe the variation of the EAWP. Finally, some empirical formula for the SRF of the EAWP on the cladding of a high-rise building is proposed with the nondimensional comprehensive size parameter.