Detection for Operation Chain: Histogram Equalization and Dither-like Operation

( Zhipeng Chen ),( Yao Zhao ),( Rongrong Ni ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.9

Many sorts of image processing software facilitate image editing and also generate a great number of doctored images. Forensic technology emerges to detect the unintentional or malicious image operations. Most of forensic methods focus on the detection of single operations. However, a series of operations may be used to sequentially manipulate an image, which makes the operation detection problem complex. Forensic investigators always want to know as much exhaustive information about a suspicious image`s entire processing history as possible. The detection of the operation chain, consisting of a series of operations, is a significant and challenging problem in the research field of forensics. In this paper, based on the histogram distribution uniformity of a manipulated image, we propose an operation chain detection scheme to identify histogram equalization (HE) followed by the dither-like operation (DLO). Two histogram features and a local spatial feature are utilized to further determine which DLO may have been applied. Both theoretical analysis and experimental results verify the effectiveness of our proposed scheme for both global and local scenarios.

Effects of Hydrodynamic Disturbance on Vegetation Development in Coastal Salt Marshes: A Model Study in Jiangsu, China

Chen Zhipeng,Luo Feng,Zeng Jingwei,Dai Jiancheng,Zhou Guanghuai,Li Ruijie 한국해양과학기술원 2023 Ocean science journal Vol.58 No.1

Salt marshes are now known to improve coastal safety by attenuating waves and stabilizing the bed. Meanwhile, for salt marsh conservatin and restoration, a great deal of research has been done on the establishment mechanism of vegetation in salt marshes. However, research on the efects of hydrodynamic disturbance on the development of salt marsh vegetation is limited. The purpose of this paper is to investigate how the hydro-morphodynamic process afects the establishment and expansion of plants in salt marshes and to simulate the establishment process. First, we used a 2D fnite-element model to simulate hydro-morphodynamics in the selected tidal fat in Jiangsu, China. We then defned the variables describing the frequency and magnitude of hydrodynamic disturbance and quantifed the efects of disturbance on plant establishment using Spearman correlation coefcients. Finally, the vegetation development process was further analyzed using a logistic regression model, and the vegetation development in the study area was simulated from 2017 to 2021. The results show that salt marsh vegetation colonization has a relatively high correlation with fooding time and bed shear stress (ρ>0.6), and bed shear stress is the main hydrodynamic disturbance parameter limiting further expansion of salt marsh vegetation. The method combining hydrodynamic modeling and logistic regression has the potential to be used to identify hydrodynamic disturbances in future salt marsh restoration and management processes and to help design appropriate restoration measures.

A vacuum-sealed flat-panel X-ray source based on ZnO nanowire field emitters

Daokun CHEN,Zhipeng ZHANG,Guofu ZHANG,Juncong SHE,Shaozhi DENG,Ningsheng XU,Jun CHEN 한국진공학회 2016 한국진공학회 학술발표회초록집 Vol.2016 No.8

A Source Code Cross-site Scripting Vulnerability Detection Method

Mu Chen,Lu Chen,Zhipeng Shao,Zaojian Dai,Nige Li,Xingjie Huang,Qian Dang,Xinjian Zhao 한국인터넷정보학회 2023 KSII Transactions on Internet and Information Syst Vol.17 No.6

To deal with the potential XSS vulnerabilities in the source code of the power communication network, an XSS vulnerability detection method combining the static analysis method with the dynamic testing method is proposed. The static analysis method aims to analyze the structure and content of the source code. We construct a set of feature expressions to match malignant content and set a "variable conversion" method to analyze the data flow of the code that implements interactive functions. The static analysis method explores the vulnerabilities existing in the source code structure and code content. Dynamic testing aims to simulate network attacks to reflect whether there are vulnerabilities in web pages. We construct many attack vectors and implemented the test in the Selenium tool. Due to the combination of the two analysis methods, XSS vulnerability discovery research could be conducted from two aspects: “white-box testing” and “black-box testing”. Tests show that this method can effectively detect XSS vulnerabilities in the source code of the power communication network.

Experimental study on timing and pattern of gas injection in low permeability reservoir

Wei Huang,Shenglai Yang,Meng Chen,Zhipeng Qiu,Can Chen,Hao Chen 한국자원공학회 2014 Geosystem engineering Vol.17 No.3

Experiments were conducted to study the selection of development methods for low permeability reservoir exploitation after water drive, including the effects of different gas injection cycle times and different injection modes on oil displacement efficiency. Results showed that both gas injection cycle time and injection mode have significant effects on oil displacement efficiency. Based on the results of gas injection cycle time of the displacement with mode shifting to gas drive when water cut reaches 50% and 100%, it can be concluded that in the low permeability reservoir, which is exploited by water drive in the early time, the sooner the gas injection, the higher the oil displacement efficiency is. Because high water saturation can cause serious water-blocking effect, leading to a large amount of trapped oil and low displacement efficiency. Further, in view of the results of water drive, gas injection, and water alternating gas (WAG) flooding, it is obvious that WAG flooding is one of the best methods in enhanced oil recovery. Under the effect of gravity differentiation, WAG flooding can spread to the upper reservoir, which cannot be swept by water drive. Thus, the oil recovery factor can be improved effectively. However, it should be noted that gas injectivity should be considered in the field test.

Decoupled SVPWM for Five-Phase Permanent Magnet Machines with Trapezoidal Back-EMF

Zhipeng Lin,Guohai Liu,Wenxiang Zhao,Qian Chen 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.5

This paper presents a novel space vector pulse-width modulation (SVPWM) to synthesize an arbitrary non-sinusoidal phase voltage. The key of the proposed method is that the switching vectors used to comprise the reference vectors in the α₁-β₁ frame and the α₃-β₃ frame are decoupled. In the α₁-β₁ frame, the reference vector is comprised by near two large vectors. The corresponding vector comprised by the two vectors in the α₃-β₃ frame is considered as a disturbance, which is restrained by close-loop control. In the α₃-β₃ frame, there are two methods to comprise the reference vector. Method I is a near two middle vectors method. Method II uses near four vectors (two middle and two little vectors). The proposed SVPWM using decoupled switching vectors can guarantee a maximum modulation index in the α₁-β₁ frame. The effectiveness of the proposed method is verified by simulated and experimental results under various operation conditions.

A negative stiffness inerter system (NSIS) for earthquake protection purposes

Zhipeng Zhao,Qingjun Chen,Ruifu Zhang,Yiyao Jiang,Chao Pan 국제구조공학회 2020 Smart Structures and Systems, An International Jou Vol.26 No.4

The negative stiffness spring and inerter are both characterized by the negative stiffness effect in the force-displacement relationship, potentially yielding an amplifying mechanism for dashpot deformation by being incorporated with a series tuning spring. However, resisting forces of the two mechanical elements are dominant in different frequency domains, thus leading to necessary complementarity in terms of vibration control and the amplifying benefit. Inspired by this, this study proposes a Negative Stiffness Inerter System (NSIS) as an earthquake protection system and developed analytical design formulae by fully utilizing its advantageous features. The NSIS is composed of a sub-configuration of a negative stiffness spring and an inerter in parallel, connected to a tuning spring in series. First, closed-form displacement responses are derived for the NSIS structure, and a stability analysis is conducted to limit the feasible domains of NSIS parameters. Then, the dual advantageous features of displacement reduction and the dashpot deformation amplification effect are revealed and clarified in a parametric analysis, stimulating the establishment of a displacement-based optimal design framework, correspondingly yielding the design formulae in analytical form. Finally, a series of examples are illustrated to validate the derived formulae. In this study, it is confirmed that the synergistic incorporation of the negative stiffness spring and the inerter has significant energy dissipation efficiency in a wide frequency band and an enhanced control effect in terms of the displacement and shear force responses. The developed displacement-based design strategy is suitable to utilize the dual benefits of the NSIS, which can be accurately implemented by the analytical design formulae to satisfy the target vibration control with increased energy dissipation efficiency.

An investigation on the dynamics of domain switching of Bi0.5Na0.5TiO3-based ferroelectric ceramics

Zhipeng Gao,Hang Zhang,Yi Liu,Lingfeng Wu,Jia Yang,Tao Zhang,Haiyan Wang,Xuefeng Chen,Genshui Wang,Hongliang He 한국물리학회 2017 Current Applied Physics Vol.17 No.4

The dynamics of domain switching of Bi0.5Na0.5TiO3-based ferroelectric ceramic was investigated. With the electric field increasing, the domain switch experienced three sections of no domain switch region, creep region and flow region. In the creep region, the domain switch is dominated by the thermally activated domain wall movement. In flow region, the domain wall experience the viscous flow motion. For the BNT-BA-Zn ceramic, the activation energy of creep domain switch is much higher than it in flow region. With temperature increasing, the sensitivity of domain wall motion to the frequency is decreasing. This result demonstrated the domain switch of different ferroelectric materials could be quantitatively analyzed and compared based on the simple polarization - current - electric field data.

Decoupled SVPWM for Five-Phase Permanent Magnet Machines with Trapezoidal Back-EMF

Lin, Zhipeng,Liu, Guohai,Zhao, Wenxiang,Chen, Qian The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.5

This paper presents a novel space vector pulse-width modulation (SVPWM) to synthesize an arbitrary non-sinusoidal phase voltage. The key of the proposed method is that the switching vectors used to comprise the reference vectors in the ${\alpha}_1-{\beta}_1$ frame and the ${\alpha}_3-{\beta}_3$ frame are decoupled. In the ${\alpha}_1-{\beta}_1$ frame, the reference vector is comprised by near two large vectors. The corresponding vector comprised by the two vectors in the ${\alpha}_3-{\beta}_3$ frame is considered as a disturbance, which is restrained by close-loop control. In the ${\alpha}_3-{\beta}_3$ frame, there are two methods to comprise the reference vector. Method I is a near two middle vectors method. Method II uses near four vectors (two middle and two little vectors). The proposed SVPWM using decoupled switching vectors can guarantee a maximum modulation index in the ${\alpha}_1-{\beta}_1$ frame. The effectiveness of the proposed method is verified by simulated and experimental results under various operation conditions.

Numerical analysis of Poiseuille-Rayleigh-Bénard convection in supercritical carbon dioxide

Wang Zhipeng,Xu Hong,Chen Chong,Hong Gang,Song Zhenguo,Zhang Yaoli 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.9

The supercritical carbon dioxide (SeCO2) Brayton cycle is an important energy conversion technology for the fourth generation of nuclear energy. Since the printed circuit heat exchanger (PCHE) used in the SeCO2 Brayton cycle has narrow channels, Rayleigh-Benard (RB) convection is likely to exist in the tiny channels. However, there are very few studies on RB convection in supercritical fluids. Current research on RB convection mainly focuses on conventional fluids such as water and air that meet the Boussinesq assumption. It is necessary to study non-Boussinesq fluids. PRB convection refers to RB convection that is affected by horizontal incoming flow. In this paper, the computational fluid dynamics simulation method is used to study the PRB convection phenomenon of non-Boussinesq fluid-supercritical carbon dioxide. The result shows that the inlet Reynolds number (Re) of the horizontal incoming flow significantly affects the PRB convection. When the inlet Re remains unchanged, with the increase of Rayleigh number (Ra), the steady-state convective pattern of the fluid layer is shown in order: horizontal flow, local traveling wave, traveling wave convection. If Ra remains unchanged, as the inlet Re increases, three convection patterns of traveling wave convection, local traveling wave, and horizontal flow will appear in sequence. To characterize the relationship between traveling wave convection and horizontal incoming flow, this paper proposes the relationship between critical Reynolds number and relative Rayleigh number (r).