Response-based method for determining the extreme behaviour of floating offshore platforms

The accurate prediction of extreme excursion and mooring force of floating offshore structures due to multi-variete environmental conditions which requires the joint probability analysis of environmental conditions for the worst case situation is still impractical as the processing of large amount of met-ocean data is required. On the other hand, the simplified multiple design criteria (e.g. the N-year wave with associated winds and currents) recommended by API known as traditional method does lead neither to the N-year platform response nor to the N-year mooring force. Therefore, in order to reduce the level of conservatism as well as uncertainties involved in the traditional method the response-based method can be used as a reliable alternative approach. In this paper this method is described. In order to perform the calculations faster using large databases of sea states, Artificial Neural Networks (ANN) is designed and employed. In the paper the response-based method is applied to a 200,000 tdw FPSO and the results are discussed.     

Ability of indigenous Bacillus licheniformis and Bacillus subtilis in microbial enhanced oil recovery

Microbially produced lipopeptide have been isolated and studied for microbial enhanced oil recovery. About 60 gram positive bacteria isolated from soil contaminated with crude oil, near the crude oil storage tank in Tehran Refinery, Tehran, Iran. However, most of these studies have produced lipopeptide by one of the pure-culture microbes isolated in a laboratory. Among the isolates, heamolytic tests revealed two biosurfactant producers. The isolated strains were designated as C2, E1. By using morphological, biochemical and molecular biology tests (16 SrRNA), the strains identified as Bacillus licheniformis and Bacillus subtitlis, respectively. Emulsification activity and measurement of surface tension indicated that, the isolates were high producers of biosurfactant. The product of C2 and E1 is mainly lipopeptide. This product reduce surface tension from 65 to 30 mN/m. Emulsified activity of crude oil was 92% for C2 and 90 % in case of E1. This is the first report of indigenous Bacillus licheniformis and Bacillus subtilis from a soil contaminated with oil in an Iranian refinery with ability to produce biosurfactant.     

Production of rhamnolipids by Pseudomonas aeruginosa growing on carbon sources

Arhamnolipid producing bacterium, Pseudomonas aeruginosa was previously isolated from Iranian oil over years. Isolated strain was identified by morphological, biochemical, physiological and 16 sr RNA (1). Glycolipid production by isolated bacterium using sugar beet molasses as a carbon and energy source was investigated. Biosurfactant production was quantified by surface tension reduction, Critical Micelle Dilution (CMD), Emulsification Capacity (EC), and Thin Layer Chromatogeraphy. biosurfactants during growth on waste Dates as the primary carbon and nitrogen sources, respectively. After 48 h of growth the culture supernatant fluid had a rhamnose concentration of 0.18 g/L and surface tension was reduced to 20 mN/m ( %).( reduced the interfacial tension against crude oil from 21 mN/m to 0,47 mN/m) Result from the study showed that the growth of the bacteria using molasses as carbon sources is growth-associated. The specific production rate of rhamnolipid with 2 %, 4 %, 6 %, 8 % and 10 % of molasses are 0.00065; 4.556; 8.94; 8.85; and 9.09. respectively The yield of rhamnolipid per biomass with 2%,4%,6%,8% and 10% molasses are 0.003;0.009;0.053;0.041 and 0.213 respectively. The production of rhamnolipid (0.0531 g rhamnolipid/g biomass) is higher compare to the culture grown in aerobic condition (0.04 g rhamnolipid/g biomass).The rhamnolipids were able to form stable emulsions with n-alkanes, aromatics, crude oil and olive oil. These studies indicate that renewable, relatively inexpensive and easily available resources can be used for important biotechnological processes.     

Study on infiltration rate based on primary particle size distribution data in arid and semiarid region soils

Soil particle size distribution (PSD) is used to estimate some soil processes, soil moisture characteristics, and infiltration rate (IR). Prediction of infiltration rate from soil texture data requires an accurate characterization of PSD. The objective of this study was to determine more important primary particle diameters that control IR. The experiments were conducted using double-ring method with constant head of 5 cm in 15 different soils and three replications. The range of measured IR for studied soils varied from 1.6 to 30.66 cm h^?1. The results indicated that the primary PSD had a significant influence on IR. In other words, most D _n fractions had significant positive effect on the final IR. Among different fractions, D ₃₀, D ₄₀, and D ₆₀ showed higher relationships with IR than the others. These diameters are attributed to particles with diameter of 0.05, 0.08, and 0.16 mm, respectively. The results also showed that increasing the percent of sand have intensified influence on increasing the final IR. Reversely, clay and silt contents showed negative effects on final IR. Furthermore, the CaCO₃ had a meaningful effect on the IR that showed the importance of lime in arid and semiarid regions. Finally, it is revealed that the role of texture was important, especially in behavior of infiltration, runoff, and production capability.     

Skarn development from limestone adjacent to the Glenrock Granodiorite,Marulan Batholith,New South Wales,Australia

Skarns are developed over two temperature‐time intervals in calcite limestone adjacent to the southern extension of the Glenrock Granodiorite, a pluton of the Marulan Batholith, Southern Highlands, New South Wales. The initial volumetrically‐dominant prograde phase of skarn formation produced a suite comprising bimetasomatic skarn, including pyroxene endoskarn, potassic endoskarn and wollastonite‐bearing exoskarn, together with mineralogically‐zoned vein skarn, massive garnet‐pyroxene skarn and calcite‐vesuvianite skarn. Retrograde replacement is manifested by the development of hydrous silicate minerals, carbonate and cross‐cutting sulphide veinlets.

A genetic model is proposed to account for the development of bimetasomatic skarn in the deposit. Exoskarn geochemistry indicates addition of many components relative to an essentially pure limestone precursor, including Si, Al, Fe, Zr, Zn, S, Mn and Cu, negligible transfer of K, Na and Rb and loss of CO₂. Strontium and Ca loss from the parent limestone is indicated by mass balance calculations at constant volume.

Garnet and pyroxene compositions in the massive garnet‐pyroxene skarn range from Gr₃₀ to Gr₆₆ and Hd₆₁ to Hd₈₇, respectively. Compositions from Gr₆₇ to Gr₉₅ are typical of the vein skarn garnets. Chemical zonation patterns in garnet, pyroxene and vesuvianite are generally characterized by rim Fe depletion relative to cores of grains.

Prograde skarn probably formed at T = 500–580°C; P < 220 MPa. The massive garnet‐pyroxene skarn evolved under conditions of log fO₂ = ‐18.9 to ‐22.9 (assuming a constant fCO₂ of 20 MPa) within the fS₂ stability field of pyrrhotite. Retrograde skarn formed at T < 400°C, possibly under conditions of X_H2O < 0.01.

Vesuvianite plus wollastonite assemblages, present in exoskarn, probably attest to very water‐rich conditions. The marble wall rocks, isolated from the source of skarn‐forming fluids, probably evolved under conditions of minimum X_co2 >0.2. Low temperature CO₂ ‐rich fluid inclusions and prehnite (stable at X_co2 <0.01), present in the marble and skarn, respectively, suggest that substantial differences in X_co2: X_H2O were maintained during cooling.

Observed mineralogical and chemical zonation within the skarn reflects the complex interaction of T, P, fO₂, Xco₂ and other chemical variables such as a_SiO2 and a_Al2O3 throughout the skarn system. No single variable can account adequately for the mineralogical diversity observed in the skarn deposit.     

Computer simulation of flow through a lattice flow-cell model

For single-phase flow through a network model of a porous medium, we report (1) solutions of the Navier–Stokes equation for the flow, (2) micro-particle imaging velocimetry (PIV) measurements of local flow velocity vectors in the “pores throats” and “pore bodies,” and (3) comparisons of the computed and measured velocity vectors. A “two-dimensional” network of cylindrical pores and parallelepiped connecting throats was constructed and used for the measurements. All pore bodies had the same dimensions, but three-different (square cross-section) pore-throat sizes were randomly distributed throughout the network. An unstructured computational grid for flow through an identical network was developed and used to compute the local pressure gradients and flow vectors for several different (macroscopic) flow rates. Numerical solution results were compared with the experimental data, and good agreement was found. Cross-over from Darcy flow to inertial flow was observed in the computational results, and the permeability and inertia coefficients of the network were estimated. The development of inertial flow was seen as a “two-step” process: (1) recirculation zones appeared in more and more pore bodies as the flow rate was increased, and (2) the strengths of individual recirculation zones increased with flow rate. Because each pore-throat and pore-body dimension is known, in this approach an experimental (and/or computed) local Reynolds number is known for every location in the porous medium at which the velocity has been measured (and/or computed).     

Evaluation and modification of JONSWAP spectral parameters in the Persian Gulf considering offshore wave characteristics under storm conditions

Ocean Dynamics - Some efforts have been done by previous researchers and scientists to represent the spectral behavior of wind waves in the Persian Gulf by analyzing real-time data, but in most of...     

Production of biosurfactant from Iranian oil fields by isolated Bacilli

Crude oil and water samples were collected from selected Iranian oil reservoirs. Experimental works were carried out in laboratory conditions. The samples have been grown on PYG medium and incubated at 30–80 °C. Thirty-six mesophile and thermophile bacterial strains have been isolated. All the isolates were able to grow at aerobic condition. Batch growth kinetic studies were carried out in a 500 ml. shake flask. Out of 36 isolated strains from 24 crude oil and water samples, 35 strains were gram positive rod. Shaped spore forming bacteria and one strain was coccid form. Eight out to 35 bacillus species were capable of producing surfactant. Production of biosurfactant was found to be cell growth associated. The ability of surfactant producing bacteria indicated by reduction of surface tension (ST) and interfacial tension (IFT) of the supernatant. Eight strains obtained the IFT reduction in crude oil, hexadecane, sucrose, glucose, fructose and mannose medium as a sole source of carbon and energy at 40 °C by 15–30 mN/m. Results showed that all the bacteria are producing more surfactant when glucose is the carbon source. Further screening of biosurfactant producer showed that three of the isolated strains resulted the maximum ST and IFT. Effect of temperature on these three isolates investigated at 30–80 °C, above 50 °C surfactant production was dramatically reduced. The isolated strains had the capacity to produce the surfactant at 3–5% NaCl a wide rang of pH (6.5–8.5).     

Environmental importance of rhamnolipid production from molasses as a carbon source

Rhamnolipid has been known as biosurfactant which is produced by Pseudomonas aeruginosa in fermentation process. Several carbon sources such as ethanol, glucose, vegetable oil and hydrocarbon have been used to produce rhamnolipid. In this study, we are trying to use molasses which is a waste product from sugar industry as carbon source to produce rhamnolipid. The bacterium which was previously isolated from Iranian oil over years Glycolipid production by isolated bacterium using sugar beet molasses as a carbon and energy source was investigated. Result from the study showed that the growth of the bacteria using molasses as carbon sources is growth-associated. The specific production rate of rhamnolipid with 2%, 4%, 6%, 8% and 10% of molasses are 0.00065, 4.556, 8.94, 8.85, and 9.09 respectively. The yield of rhamnolipid per biomass with 2%, 4%, 6%, 8% and 10% molasses are 0.003, 0.009, 0.053, 0.041 and 0.213 respectively. The production of rhamnolipid (0.0531 g. rhamnolipid/g biomass) is higher compare to the culture grown in aerobic condition (0.04 g. rhamnolipid/g biomass). These studies indicate that renewable, relatively inexpensive and easily available resources can be used for important biotechnological processes.     

Shoreline spatial and temporal response to natural and human effects in Boujagh National Park,Iran

Shoreline variation and river deltas are among the most dynamic systems in marine environments. The related different variations in spatial and temporal scales play significant roles in land planning and different management applications. Modeling the dynamics of seashore of Boujagh National Park (BNP) which is located on the southern coast of the Caspian Sea in the Sefidrud Delta (SD), considering natural and anthropogenic factors, was the main objective of the current study. To achieve this goal, a combination of remote sensing data, historical data, and numerical simulations was utilized. The BNP covers an area of 3,270 ha and includes two international wetlands, Boujagh and Kiashahr. In earlier periods, this area faced severe morphological changes whereas recently its shoreline has experienced gradual variations. Accordingly, at the first stage, the shoreline variation from 2006 to 2017 was extracted by processing and classifying Operational Land Imager (OLI) and Thematic Mapper (TM) images from Landsat satellites using the Maximum Likelihood approach. In the second stage, the two dimensional MIKE21 model was utilized to identify wave and coastal current patterns and parameters for the year 2015. Morphologically, the results showed that, the shoreline of the BNP is affected by several natural and anthropogenic factors. Seaward advancement of the shoreline occurred in zones A (east zone) and C (west zone) due to Caspian Sea Level drop and sedimentation while retreating occurred at Zone B (north zone) influenced by wave and current patterns and reduction of the Sefidrud River flows. Also, the results imply that maintaining the existing conditions results in the disappearance of a considerable part of the ecological area in the BNP. Hence, to manage and preserve the coastline of the BNP complying with the current anthropogenic and natural factors, it is vital to take necessary management measures.