Papers by Keyword: Potential Distribution

Abstract: To investigate the corrosion state of subsea pipeline under cathodic protection, the surface potential distribution of the pipeline has to be measured exactly, but it’s very difficult to measure directly in actually. On base of boundary element methods (BEM), a 2D model about pipe’s cathodic protection under sea water was established, and then software to calculate the electric field distribution on pipe surface in even media (seawater) was developed by way of Matlab. The developed software was verified through an experiment in lab. The result shows that numerical calculation based on BEM by Matlab is feasible for cathodic protection electric field of pipe in marine environment.

Abstract: Coplanar capacitive sensors have been widely applied in many fields with its characterstics of non-invasion, lowcost and fast response. A complex structure of coplanar capacitive sensor is designed to be used for the film thickness measurement. Firstly, three types of coplanar capacitive sensors with different shapes are designed, and according to the experimental reuslts, the parameters affecting the sensor signal strength and sensitivities are discussed, the electric field distributions of sensors are simulated by COMSOL.Then the fringe capacitance of a series of spiral-type sensors are measured and analyzed. The experimental results indicate the rational geometrical parameter design about the coplanar capacitive sensor can improve the sensor performance obviously.

Abstract: This paper firstly introduces the composition and mathematical description of the capacitance sensor, meanwhile, establishes the mathematical and finite element model of it. According to previous finite element model as mention above, this paper bases on FEM to compile the program and calculate the distribution of potential with shield and no shield. The program obtains result of the contour figuer of every node. Then comparing the potential value on nodes at the same place. In terms of previous analysis result, this essay amis to change electrode plate width and the length of radial shielding electrode by the order. In the meantime, it also research Potential value change in the same area and analyze the influence of potential distribution in those electrodes that were affected by the width of electrode and length of radial shielding electrode. In the end, this study obtains a lot of useful conclusions for the capacitance sensor design.

Abstract: The galvanic and potential distributions of carbon steel immersed in seawater were studied by wire beam electrode (WBE) technique. Results indicated that the corrosion of carbon steel in seawater tended to local corrosion. With immersion time increasing, local corrosion was more and more serious. During the initial immersion period, the top of the coupon near the water surface was main cathode. With the corrosion extended, corrosion products gradually gathered on the surface of the carbon steel. Potential differences between cathode and anode gradually became small. Cathode and anode redistributed on the surface of carbon steel. At last, the top and the bottom were cathode while the middle was anode. The areas of anode first increased and then decreased. The areas of cathode were in contrast.

Abstract: For the jack-up platforms' huge size and complex structure, as well as the variation and complexity of their ambient corrosion environment, problems often arise in cathodic protection (CP) systems. The rise of the computer and the numerical simulation technology provide a new technical method to the prediction, evaluation and optimization of CP system for jack-up platform. Numerical simulation method has the advantage of examining potential maps of the entire structure easily and then the designer can determine the number and placement of anodes required to provide protection from the under and over protection regions based on a generic polarization response. In this paper the 3-D boundary element method was used to calculate the mathematical model of sacrificial anode CP system for a jack-up platform. Introduced piecewise quasi linearized method to deal with nonlinear problem of boundary conditions. Adopt block boundary element method to solve electrolyte inconsistency problem and points regional modeling to solve electrolyte discontinuous. From the results we can conclude that the jack-up platform sacrificial anode CP system meets the protection targets.

Abstract: Two models with and without insulating clapboard were established. The electric potential distribution and the flow of electric current in electrolytic cell under the two models were simulated by Ansoft finite element software. The results show that the distribution of equipotential surface is the most intensive in the area close to the electric plate,and the current in the cell obviously skewed flows to the bottom of the strip under the insulating clapboard model , which is important to improve the current efficiency of the electrolytic cleaning. Finally, the influence of insulating clapboard on current efficiency and under different plate spacing were carried on by experiment and analysis, proved the correctness of the simulation results.

Abstract: The hazard of Semiothisa cinerearia was explosive in multiple regions of China in recent years. The potential geographic distribution of S. cinerearia in China was predicted by the GARP ecological niche model combining with terrain and climate informations. The results indicated that 8 environmental variables could improve the accuracy of prediction. The test by using 50% of all the samples showed good performance and all the known distribution points in China were all correctly predicted. The potential distribution areas of S. cinerearia included whole China except Tibet, Qinghai, Xizhang, Hainan, Taiwan and south of Guangdong and Guangxi. And the central, North, East and Northeast of China had high suitability (>90%). Measures inhibiting Sophora japonica should be taken protect early and rapidly in its suitable areas.

Abstract: With the rapid development of China's high-speed rail construction, accidents caused by lightning are more frequent. How to achieve a more effective lightning protection and grounding is the urgent problem to be solved currently. A two-parallel-connecting-ground-wire transmission line model with the distributed parameter of electromagnetic coupling would be built in this paper. In this model, the connecting ground wire would be defined as horizontal infinite length grounding body. The own distribution parameters of segmented conductor and the parameters of the electromagnetic coupling between the parallel segmented conductors are calculated, based on the theory of electromagnetic field to select the appropriate segment size. Based on this transmission line model, the electric potential distribution of the different positions on the two parallel connecting ground wires is calculated by using the electromagnetic transient calculation software ATP-EMTP. Comparing the calculation results in this paper and the simulation results in the simulation software CDGES, it would demonstrate that the electromagnetic coupling distributed parameter transmission line model in this paper is consistent with the actual situation and it could be used to analyze the electromagnetic coupling effect between the two buried parallel connecting ground wires.

Abstract: The potential distribution of carbon steel under epoxy coating exposed to natural seawater was investigated by the wire beam electrode (WBE) technique. The electrochemical impedance spectroscopy (EIS) of the WBE was characterized to analyze the behaviour of the coating degradation and metal corrosion at coating/metal interface. The mechanism of coating degradation was discussed from a point of electrochemical distribution. This research showed that the potential distribution had a close relationship with the characteristic of EIS in local area. The combined method can help us better understand the mechanism of the organic coating degradation and beneath substrate corrosion.

Abstract: In order to study “shielding effect” problems of sacrificial anode cathodic protection system in the ballast water tanks, two sets of experiments, the “block-type shielding effect” and the “absorbed-type shielding effect” are carried out by changing the clapboard height and the distance from the upper surface of sacrificial anode to the copper tube, and corresponding numerical simulations are carried out. Both of the experimental data and the numerical simulation results illustrate the two kinds of “shielding effect” as mentioned above, and according to which, both the two kinds of “shielding effect” should be surely taken into account in sacrificial anode cathodic protection system for a ballast water tank.