Spectral reflectance variations and mineral transformations during the formation of acid sulphate soil in an incubation experiment

Understanding the reflectance spectral variations associated with oxidation of iron sulphide materials is highly important to the detection of environmental changes affected by the detrimental acid mining drainage and acid sulphate soil (ASS) using hyperspectral sensing. An incubation experiment with iron-sulphide-rich sediments was set up to simulate the formation and evolution of ASS. The sediments were shaped into different micro-landforms. Spectral changes and mineral transformation were observed by comparing weekly measurements of the materials in the different landforms using an ASD (Analytical Spectral Devices) reflectance spectrometer, as well as comparing the measurements of the initial materials and the residual materials after oxidation. We found that the spectral changes usually occur at the spectral absorptions near 0.9 μm, which relate to ferric iron contents, near 1.17 μm, which relate to ferrous iron content, and near 2.265 μm, which relate to jarosite. Spectral variations are detected both in specific absorption position and depth. We also found that the causes of the spectral variations are mainly due to the variations in mineral transformation and consequent mineral composition, owing to lying in different oxidation stages and drainage conditions in the different landforms. This article shows not only oxidation of sulphides to different mineral phases spectrally but also the link of the phases with landforms and drainage conditions and the link between oxidation degree and oxidation progress, all of which have not been sufficiently studied before.     

A comparative study of the carbon dioxide and nitrogen minimum miscibility pressure determinations for an Iranian light oil sample

Miscible gas injection is an approved profitable process that could significantly enhance oil recovery from different types of reservoirs while the major factor affecting its efficiency would be the minimum miscibility pressure (MMP) value. A recent experimental technique, known as vanishing interfacial tension (VIT), can estimate the MMP for gas–oil mixtures by measuring interfacial tension values and extrapolating them to zero at a sequence of pressures. Compositional simulation models are also useful in MMP determination by tuning an equation of state to compute the realistic phase behavior of reservoir fluid. In this paper, the capability and quality of MMP prediction via different methods such as laboratory slim tube tests, VIT technique, compositional simulation, and various empirical correlations were examined using a light oil sample taken from an Iranian carbonate reservoir, employing two pure gases of CO₂ and N₂ as the injectants. The accuracy and validation of the mentioned methods were then confirmed successfully by obtaining negligible overall absolute deviation percentages (AD%) compared with the conducted slim tube tests results.     

The role of electrochemical migration and moisture adsorption on the reliability of metallized ceramic substrates

Data presented here have resulted from an extensive investigation into fundamental mechanisms involved in electrochemical migration and dendrite growth on metallized ceramic substrates. Significant new results are presented, and pertinent data from previous studies are outlined to provide a comprehensive, coherent analysis of the complex process of electrochemical migration. A number of critical issues are addressed including formation of an absorbed moisture layer and the effect of humidity on the thickness and conductivity of this layer. Migration has been quantified by examining dendrite morphology and dendrite growth rates. Morphology and growth rates are nearly identical for immersion tests in both bulk and thin layer electrolytes, but is quite different in absorbed layers of moisture. Immersion tests are still useful in determining the effects of solution variables that would be difficult or impossible to quantify in adsorbed moisture layers. In addition the maximum velocity theory for predicting dendrite growth rates can be used for predicting general trends, but requires further refinement for more precise predictions. Clearly the most important parameters affecting reliability are the adsorption of moisture combined with surface contamination.     

Microbially-influenced corrosion, victaulic couplings, water treatment, and DNA studies

The utilities at a major government office facility include both condenser and chilled water systems. Though they are similar, the water in the condenser system is regularly aerated, while the chilled water is a closed system. Piping in both is largely carbon steel, with a minor amount of cast iron. Both systems use Victaulic mechanical couplings (Victaulic Company) rather than welded joints. The joints in the condenser section of the system are deeply corroded, while the chilled water system is in good condition. The cause appears to be initial system pressure testing without biocide, followed by several months of no use at all. Microbially-influenced corrosion (MIC) started below the gaskets in the joints and could not be stopped. Polymerase chain reaction analysis allowed identification of the bacteria involved after the system was dismantled. The entire condenser water system had to be replaced.     

BURIAL HISTORY RECONSTRUCTION USING LATE DIAGENETIC PRODUCTS IN THE EARLY PERMIAN SILICICLASTICS OF THE FARAGHAN FORMATION, SOUTHERN ZAGROS, IRAN

In spite of the increasing importance to hydrocarbon exploration and production of the Palaeozoic succession in the Zagros area of SW Iran, few burial history and palaeothermal modelling studies of the interval have been carried out. This paper attempts to assess the burial and palaeotemperature history of the Lower Permian Faraghan Formation which is composed of stromatolitic dolomites overlain by mainly cross‐bedded sandstones. The formation grades up into the thick bedded carbonates of the Upper Permian Dalan Formation. The Faraghan and Dalan Formations are major hydrocarbon reservoir units in SW Iran and are time‐equivalents of the Unayzah and Khuff Formations in Saudi Arabia, respectively. The Faraghan Formation consists of shallow‐marine siliciclastics and foreshore deposits, including tidal‐flat and tidal‐channel, estuarine, sabkha, shoreface and offshore facies. In this study, diagenetic constituents are used to evaluate the formation's burial history in the Southern Zagros, an area for which only limited subsurface data is available. A burial history diagram for the formation was constructed for well Finu # 1 using WinBury^TM software. The diagram shows that the formation underwent progressive burial at variable rates between its deposition and the mid‐Tertiary, since when it has undergone rapid uplift. Burial diagenetic products in the Faraghan Formation comprise saddle, ferroan and zoned dolomites, together with dickite, illite/sericite and chlorite minerals. Additional burial‐related features include stylolites and dissolution seams. Isotopic signatures (δ¹⁸O versus δ¹³C) of the ferroan dolomites suggest a burial trend for the formation. Reconstruction of the paragenetic sequence together with the burial history diagram suggests a maximum burial depth of about 5000 m and a wide palaeotemperature range of 80‐160°C. However considering the saddle dolomites as a palaeothermometer, the temperature range narrows to 78 to 138 °C. The burial depth and temperature ranges closely correlate with the main stage of oil generation to the dry gas zone.     

Security Path: An Emerging Design Methodology to Protect the FPGA IPs Against Passive/Active Design Tampering

Modern FPGAs have a great market share in hardware prototyping, massive parallel systems and reconfigurable architectures. Although the field-programmability of FPGAs is an effective feature in the growth and diversity of their applications; it has caused security concerns for IPs/Designs on FPGAs. Recent researches show that a reliable mechanism is required to protect the IPs/applications on FPGAs against malicious manipulations during all stages of design lifecycle, especially when they are operating in the field. In this paper, we propose a new tamper-resistant design methodology (Security Path methodology) and a revised security-aware FPGA architecture. This methodology protects the configured design against tampering attacks in parallel with the normal operation of the circuit. When the attack is discovered, the normal data flow is obfuscated and the circuit is blocked. Experimental results show that this methodology provides near full coverage in tampering detection with overhead of 12.32 % in power, 12 % in delay and 38 % in area.     

Reflectance spectral characterization of acid sulphate soil in South Yunderup,Western Australia

Acid sulphate soils (ASS) are widely spread worldwide and are detrimental to the environment. South Yunderup is one of the coastal areas of Western Australia heavily affected by ASS. Conventional investigation is costly and time-consuming, and thus there is an urgent need to rapidly characterize and identify this type of soil. This paper aims to characterize these soils using reflectance spectra, which may be one of the most significant steps in effectively identifying them and mapping their extent by remote sensing. The ASS from the study area were divided into several groups and subtypes according to both pH measurements and mineral composition as identified by X-ray diffraction analysis. Each group and subtype was then characterized by its spectral reflectance features. We found that the spectral characteristics of ASS are governed by the spectral features of its compositional minerals. In particular, some secondary iron-bearing minerals produced by the formation of ASS, together with surrounding minerals such as carbonate, play vitally important roles in influencing the spectral characterization of ASS. These iron-bearing minerals, including iron oxides, hydroxides/oxyhydroxides (e.g. haematite, goethite, and ferrihydrite), and iron sulphates (e.g. jarosite and copiapite), have diagnostic spectral features and are therefore detectable in the reflectance range. Moreover, these secondary iron-bearing minerals could be indicators suggesting the pH conditions in which they formed. The results of this study include the overall mineral distribution of the study area, the spectral characterization of different groups and subtypes of ASS, and the linkages between spectral features and pH ranges.