Analog Fault Detection Comparison between Supply Current and Output Voltage

Chaojie Zhang,Guo He,Qiaobin Zhang 보안공학연구지원센터 2014 International Journal of Control and Automation Vol.7 No.11

In view of the difficulties caused by determining threshold for fault detection of analog circuits, a method based on principal component analysis (PCA) was proposed to overcome these difficulties. The basic model of the proposed method and the general rule for analog fault detection were described in detail. Power supply current test has the advantages that only one test point is needed and there is no need to propagate fault effects to the outputs. Fault detection of analog circuits using PCA of power supply current was evaluated by experiment. The signal filtering and amplifying circuit used in the ultrasonic liquid sensor was selected as the research object. And the detection results using power supply current are compared with those using the output voltage under the same stimulus. The results show that the PCA based method can use the information in both time and frequency domain simultaneously, and it can overcome the difficulty in determining threshold by the expert’s empirical knowledge. These make it a more suitable candidate for fault detection of analog circuits than pure time-domain or pure frequency-domain methods.

Mechanical Heterogeneity of Heat-Resistant EV31A Magnesium Alloy with Large Size Processed by Direct-Chill Casting

Deping Zhang,Boqiong Li,Chaojie Che,Baosheng Liu,Peng Cheng,Yali Zhao,Jinhui Zhang,Liren Cheng 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.10

High quality of large-sized EV31A benchmark alloy was fabricated by direct-chill casting, without significant composition segregation along its radial direction. As-cast samples show noticeable mechanical heterogeneity, such as strength decreasing but ductility increasing from the surface to the center positions of the ingot. After heat treatment, however, mechanical properties of the alloy are nearly the same in each position, indicating mechanical homogeneity, which is mainly attributed to the strengthening mechanism transition from grain-boundary hardening in as-cast samples to precipitation hardening in peak-aged samples. In addition, we found that solute hardening is the athermal strengthening which contributes more to high-temperature strength than precipitation hardening, as evidenced by lower strength loss from 25 to 250 °C in T4-treated sample than in peak-aged sample. Solute hardening effect is thermally stable and extends to high temperatures, which favors the retention of linear strain hardening by retarding dynamic recovery. This work thus provides new insight into designing heat-resistant Mg alloys and understanding mechanical heterogeneity of large-scale Mg alloy ingots.

Grid-friendly Characteristics Analysis and Implementation of a Single-phase Voltage-controlled Inverter

Zhang, Shuaitao,Zhao, Jinbin,Chen, Yang,He, Chaojie The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5

Inverters are widely used in distributed power generation and other applications. However, their lack of inertia and variable impedance may cause system instability and power transfer inaccuracy. This paper proposes a control scheme for a single phase voltage-controlled inverter with some grid-friendly characteristics. The proposed control algorithm enables the inverter to function as a voltage source with an inner output impedance in both the islanded and grid-connected modes. Virtual inertia and rotor equations are embedded in the PLL part. Thus, the frequency stability can remain. The inner output impedance can be adjusted freely, which helps to accurately decouple and transmit the output active and reactive power. The proposed inverter operates like a traditional synchronous generator. Simulations and experiments are designed and carried out to verify the proposed control strategy.

Molecular Dynamics Simulation of supercritical spray at micro & nano scale

( Zhang Yunxiao ),( Fu Qingfei ),( Mo Chaojie ),( Yang Lijun ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-

The supercritical jets have many applications in many fields ranging from aerospace propulsion to chemical engineering. However, there is still lack of relevant theoretical research on the characteristics of supercritical fluids, and also lack of deep understanding of the destabilization mechanism of supercritical jets. Molecular dynamics method, which has been quite mature, can simulate extreme harsh physical conditions and exceptionally complex geometric model. The simulation process spontaneously contains all the physical effects. Therefore, the purpose of this paper is to study the characteristics and destabilization mechanism of supercritical jets from the microcosmic perspective using molecular dynamics method. Firstly, the molecular dynamics simulation of EOS (Equation of State) of liquid nitrogen was carried out. The influence of different simulation parameters on the simulation results was analyzed and then compared with the theoretical results. Four conditions were selected to study the influences of different time step, total simulation steps and truncation distance on the simulation results. The results show that the truncation distance has a great influence on the simulation precision, the time step and the total simulation steps have no significant impact on the EOS of liquid nitrogen. The results are in good agreement with the SRK (Soave-Redlich-Kwong) equation, which show the correctness of the simulation of supercritical fluids using molecular dynamics method. Secondly, the molecular dynamics simulation of supercritical nitrogen jet was carried out at different conditions. The supercritical jets ejected into a supercritical environment and a subcritical environment, respectively. Through the analysis of the results, the distribution of jet velocity, density, temperature and other jet characteristics was obtained. The interface was determined where concentration of supercritical fluid component reached 50% because the supercritical jet has no obvious vapor-liquid interface. Stable analysis of the results was performed and the disturbance growth rate of the supercritical shear layer at different conditions was obtained. Finally, the growth rate achieved by processing the results of molecular simulation was compared to the results by the linear stability analysis.

Analysis of deliverability data in shale gas reservoirs: pseudo-pressure and pressure employed

Zhao, Chaojie,Li, Jun,Zhang, Hui 한국자원공학회 2019 Geosystem engineering Vol.22 No.4

Forecasting deliverability in shale gas reservoirs accurately has received much attention in the industry in recent years. Most wells in shale gas reservoirs are horizontal with multiple fractures, and it has been widely recognized that the dominant early flow regime is usually long-duration transient flow. The most popular method for analyzing linear flow is the plot of rate-normalized pressure versus square root of time, where the pseudo-pressure is employed for gas. However, the pseudo-pressure employed approach is difficult to handle by hand than the pressure employed approach. The purpose of this work is to evaluate the accuracy of pseudo-pressure employed method for analyzing gas rate in shale gas reservoirs, and establish which method is the most simple and accurate for reserve estimation. Based on a number of numerically simulated cases, comparisons between the pseudo-pressure and pressure employed methods for estimating gas rate are made. It is shown that the pressure employed method yields the gas rate that not quite accurately match the simulated values, however, as the same general parameters, the pseudo-pressure employed method really does not improve this inaccuracy. Accordingly, the pressure employed approach is a good and simple method for forecasting gas rate. In addition, depending on the simple hand method, a modification approach is proposed by incorporating constant factors to forecast the gas rate with more confidence. This work will provide an efficient guidance to assist analysts in evaluating hydrocarbon deliverability rapidly and efficiently in shale gas reservoirs.

A numerical method for evaluating fire performance of prestressed concrete T bridge girders

Gang Zhang,Venkatesh Kodur,Chaojie Song,Wei Hou,Shuanhai He 사단법인 한국계산역학회 2020 Computers and Concrete, An International Journal Vol.25 No.6

This paper presents a numerical method for evaluating fire performance of prestressed concrete (PC) T shaped bridge girders under combined effect of structural loading and hydrocarbon fire exposure conditions. A numerical model, developed using the computer program ANSYS, is employed to investigate fire response of PC T shaped bridge girders by taking into consideration structural inherent parameters, namely; arrangement of prestressing strands with in the girder section, thickness of concrete cover over prestressing strands, effective degree of prestress and content of prestressing strands. Then, a sequential thermo-mechanical analysis is performed to predict cross sectional temperature followed by mechanical response of T shaped bridge girders. The validity of the numerical model is established by comparing temperatures, deflections and failure time generated from fire tests. Through numerical studies, it is shown that thickness of concrete cover and arrangement of prestressing strands in girder section have significant influence on the fire resistance of PC T shaped bridge girders. Increase in effective degree of prestress in strands with triangular shaped layout and content in prestressing strands can slow down the progression of deflections in PC T shaped bridge girder towards the final stages of fire exposure, to thereby preventing sudden collapse of the girder. Rate of deflection based failure criterion governs failure in PC T shaped bridge girders under most hydrocarbon fire exposure conditions. Structural inherent parameters incorporated into sectional configuration can significantly enhance fire resistance of PC bridge girders; thus mitigating fire induced collapse of these bridge girders.

Grid-friendly Characteristics Analysis and Implementation of a Single-phase Voltage-controlled Inverter

Shuaitao Zhang,Jinbin Zhao,Yang Chen,Chaojie He 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5

Inverters are widely used in distributed power generation and other applications. However, their lack of inertia and variable impedance may cause system instability and power transfer inaccuracy. This paper proposes a control scheme for a single phase voltage-controlled inverter with some grid-friendly characteristics. The proposed control algorithm enables the inverter to function as a voltage source with an inner output impedance in both the islanded and grid-connected modes. Virtual inertia and rotor equations are embedded in the PLL part. Thus, the frequency stability can remain. The inner output impedance can be adjusted freely, which helps to accurately decouple and transmit the output active and reactive power. The proposed inverter operates like a traditional synchronous generator. Simulations and experiments are designed and carried out to verify the proposed control strategy.

Fire Performance of Continuous Steel-Concrete Composite Bridge Girders

Gang Zhang,Chaojie Song,Xuyang Li,Shuanhai He,Qiao Huang 대한토목학회 2021 KSCE Journal of Civil Engineering Vol.25 No.3

This paper presents a detailed investigation in to fire resistance along with failure mode in continuous steel-concrete composite twin I-shaped bridge girders under different localized fire through considering fire severity and fire exposure positions namely; mid-span zone in one of the two span, hogging moment zone and side-support zone. A 3-D finite element (FE) model, built utilizing the computer program ANSYS, is used to track structural fire performance in a typical two span of continuous composite twin I-shaped bridge girders (fabricated with twin I-shaped plates supporting a concrete slab) dependent on thermo-mechanical coupled analysis. The model validation is undertook through comparison of temperature and deflection response attained from a scaled composite single I-shaped girder tested exposed to ISO834 fire. The numerical analysis results show that the developed model can be favorably used to analyze the behavior and failure mode of continuous steel-concrete composite twin I-shaped bridge girders during entire range of fire exposure. Fire severity and fire exposure positions present critical influence in to the fire resistance of continuous composite bridge girders. Fire exposure prevention on hogging moment zone can significantly extend failure time of continuous girders, and further hold back progressive structural collapse. Web buckling based failure criterion can be applicable to calculate fire resistance of realistic continuous girders under simultaneous structural loading together with localized fire. Continuous composite bridge girders subjected to localized fire present highly significant local deformation response in the fire exposed bridge girder span.

Vibration control performance of particle tuned mass inerter system

Zheng Lu,Deyu Yan,Chaojie Zhou,Ruifu Zhang 국제구조공학회 2024 Structural Engineering and Mechanics, An Int'l Jou Vol.89 No.4

To improve the vibration control performance and applicability of traditional particle tuned mass damper (PTMD) and realize the significant characteristic of lightweight design, this study proposes a novel particle tuned mass inerter system (PTMIS) by introducing inerter system (IS) to the PTMD. In the study, the motion equation of single degree of freedom (SDOF) structure attached with PTMIS is established first, then the variation law of the system’s vibration reduction performance (VRP) is discussed through parameter analysis, and it is compared with the PTMD to analyze its VRP advantages. Finally, its vibration reduction (VR) mechanism from the perspective of core control force and energy analysis is explored, and its cavity relative displacement from the application perspective is analyzed. The results show that the PTMIS can remarkably improve the vibration control effectiveness of the PTMD. The reason is that the inerter can store energy and transfer the energy to the cavity and particles, which further stimulates the interaction between the two parts, thereby improving the nonlinear energy consumption effectiveness. Also, the IS can amplify the damping element’s energy dissipation efficiency. In addition, the PTMIS can effectively reduce the working stroke of the PTMD, and through the analysis of the lightweight characteristics of the PTMIS, it is found that its lightweight advantage can reach nearly 100%.

The establishment of a DNA fifi ngerprinting database for 73 varieties of Lactuca sativa capitate L. using SSR molecular markers

Huiyan Zhou,Penghang Zhang,Jiang Luo,Xueying Liu,Shuangxi Fan,Chaojie Liu,Yingyan Han 한국원예학회 2019 Horticulture, Environment, and Biotechnology Vol.60 No.1

Head lettuce originating near the Mediterranean coast was introduced to China in the fi fth century. It is diffi cult to identifydiff erent varieties of head lettuce due to their close genetic relationships. Simple sequence repeats (SSR) technology is apractical method that has been widely used in variety identifi cation, fi ngerprint construction and genetic diversity analysis. In this paper, 23 pairs of SSR primers were selected to identify and analyse 73 varieties of head lettuce. The results identified a total of 117 mutated alleles detected in 23 loci, with the number of each loci ranging from 2 to 11, with an averageof 5.1 mutated alleles per locus. Additionally, 152 genotypes were detected in 23 loci, with an average of 6.6 genotypes perlocus derived from a range of 2–13. The polymorphism information content ranged from 0.071 to 0.702, with an average of0.499. The selected primer pairs could clearly refl ect the genotypic diversity level of the 73 head lettuce varieties tested, andcan be used in the detection and analysis of the head lettuce varieties. The results of our sequence analysis also showed thatthese 73 varieties of head lettuce could be eff ectively identifi ed by a combination of 19 primer pairs even though the geneticsimilarity among the 73 varieties ranged from 0.647 to 0.991, with an average of 0.798. Based on a capillary electrophoresisplatform, a DNA fi ngerprinting database of 73 head lettuce varieties was established.