Electropolishing is the electrochemical process to remove the metallic material from the workpiece, in order to obtain a smoother metal surface. It has found vast engineering applications in many fields, such as food, medical, pharmaceutical and semiconductor industries. This review is aimed to provide the readership with insightful understanding of the electropolishing process, from the fundamental aspects as well as from the application aspects. The general aspects of electropolishing, including its definition, the classic setup, the fundamentals behind it and methods used to evaluate the electropolishing finishes are reviewed here. Various electropolishing theories, be them quantitative or qualitative are briefly discussed. Based on those theories, important parameters evolved in the electropolishing process are enumerated. Many microscopic technologies are used to evaluate the electropolishing surface finishes. This includes optical microscope, electron microscope and atomic force microscope. Some key features of electropolishing are briefly outlined in the end.

No abstract

No abstract

This research aims to determine soil vertical saturated hydraulic conductivity (K s ) in situ from the measured steady infiltration rate (I), initial soil properties and double-ring infiltrometer (DRI) test data. Characterizing the effects of these variables on the measured steady infiltration rate will enable more accurate prediction of K s . We measured the effects of the ring diameter, head of ponding, ring depth, initial effective saturation and soil macroscopic capillary length on measured steady infiltration rates. We did this by simulating 864 DRI tests with the finite element program HYDRUS-2D and by conducting 39 full-scale in situ DRI tests, 30 Mini-Disk infiltrometer experiments and four Guelph Permeameter tests. The M5 ′ model trees and genetic programming (GP) methods were applied to the data to establish formulae to predict the K s of sandy to sandy-clay soils. The nine field DRI tests were used to verify the computer models. We determined the accuracy of the methods with 30% of the simulated DRI data to compare I/K S values of the finite element models with estimates from the suggested formulae. We also used the suggested formulae to predict the K s values of 30 field DRI experiments and compared them with values measured by Guelph Permeameter tests. Compared with the GP method, the M5 ′ model was better at predicting K S , with a correlation coefficient of 0.862 and root mean square error (RMSE) of 0.282 cm s −1 . In addition, the latter method estimated K s values of the field experiments more accurately, with an RMSE of 0.00346 cm s −1 . Highlights• Effects of initial soil properties and DRI test data on steady infiltration rate are studied. • M5 ′ model algorithm and genetic programming method are applied on the data to formulate the equations.• Compared to the GP method, the M5 ′ model was better at predicting K s . • The equation from M5 ′ tree model is robust for estimating in situ K s with the DRI.

Microbial fuel cell (MFC) technology has been practised in the treatment of landfill leachate. However, it is a big challenge for the usage of MFCs to treat landfill leachate with high ammonium content. The purpose of this study was to design and test two MFC reactors, i.e. an ammonium oxidation/MFC reactor and an MFC/Anammox reactor for the treatment of landfill leachate with high ammonium content in terms of power generation and nitrogen removal. Using the ammonium oxidation/MFC reactor, the landfill leachate collected from Leon County Landfill of Northwest Florida generated a power density of 8 mW/m2 together with 92% of nitrogen removal. For the MFC/Anammox reactor, a power density of 12 mW/m2 was achieved with 94% of nitrogen removal. Compared with the ammonium oxidation/MFC reactor, 50% more energy was generated because in the MFC/Anammox Reactor, nitrite served as the electron acceptor; while in the Ammonium Oxidation/MFC reactor, nitrate served as the electron acceptor. In this research, power generation was also found to be directly linked to the microbial species that were involved in organic decomposition, i.e. the greater the microbial concentration, the more the power generated.

No abstract

No abstract

A field study was conducted to assess the ability of landfill covers to control percolation into the waste. Performance of one conventional cover was compared to that of two evapotranspiration (ET) tree covers, using large (7 x 14 m) lined lysimeters at the Leon County Solid Waste management facility in Tallahassee, Florida. Additional unlined test sections were also constructed and monitored in order to compare soil water storage, soil temperature, and tree growth inside lysimeters and in unlined test sections. The unlined test sections were in direct contact with landfill gas. Surface runoff on the ET covers was a small proportion of the water balance (1% of precipitation) as compared to 13% in the conventional cover. Percolation in the ET covers averaged 17% and 24% of precipitation as compared to 33% in the conventional cover. On average, soil water storage was higher in the lined lysimeters (429 mm) compared to unlined test sections (408 mm). The average soil temperature in the lysimeters was lower than in the unlined test sections. The average tree height inside the lysimeters was not significantly lower (8.04 mfor eucalyptus and 7.11 mfor cottonwood) than outside (8.82 m for eucalyptus and 8.01 m for cottonwood). ET tree covers vegetated with cottonwood or eucalyptus are feasible for North Florida climate as an alternative to GCL covers.