Journal of the Persian Gulf (Marine Science)
Volume:4 Issue: 12, Summer 2013

Tubular KT-joints are quite common in offshore structural design and despite the crucial role of stress concentration factors (SCFs) in evaluating the fatigue performance of tubular joints. However, the SCF distribution in internally ring-stiffened KT-joints have not been investigated and no design equation is currently available to determine the SCFs for this type of joint. In the present paper, results of experimental and numerical investigations of the SCF distribution in internally ring-stiffened tubular KT-joints are presented. In this research, experimental study has been followed by a set of parametric stress analyses for 118 steel ring-stiffened KT-joints subjected to balanced axial loads. The analysis results are used to present the general remarks on the effect of geometrical parameters on the SCF distribution along the weld toe and to establish a new set of SCF parametric equations for the fatigue design of internally ring-stiffened KT-joints.

A study was conducted to determine the effects of water temperature and rations size on growth performance, feed utilization and carcass biochemical composition of juvenile Benni. Six treatments representing a combination of two water temperature (24 and 28 °C) and three feeding rations (1%, 3% and 5%) were tested with three replicates. Each replicate was stocked with 12 fish (30.66±0.81 g average weight). Growth performances were significantly affected (P<0.05) between water temperature and ration size. Mean weight gain and percentage of weight gain significantly increased with increasing water temperature from 24 to 28 °C and higher (P<0.05) at 3% ration size. Average daily growth and specific growth rate were significantly (P<0.05) affected only by ration size at 3% level. Increasing water temperature (24 to 28 °C) resulted in increasing feed conversion efficiency (FCE). Whereas, FCE significantly decreased with increasing rations size from 1 to 5% at each water temperatures. Protein efficiency ratio (PER) followed a trend similar to that in FCE. The highest protein content of carcass (41.17%) was observed at 3% feeding ration at 28 °C. Lipid content was significantly highest in group fed 5% at 24 °C (13.58%). Hepatosomatic index was not significantly (P>0.05) affected by water temperatures and feeding rations. Viscerosomatic index (VSI) was significantly affected (P<0.05) by with increasing water temperatures and ration size. Results showed the 3% BW/day ration was optimal for growth of M. sharpeyi juvenile at water temperature 28 °C. (P<0.05).

This paper reports on the karyotyping of mullet fish species, Liza klunzingeri, endemic of the Persian Gulf. The metaphase chromosome spreads, obtained from kidney cells of 13 specimens were examined. The diploid chromosome number was found to be 2n=48. The karyotype was discovered to be consisted of 48 acrocentric chromosome pairs. The arm number was determined to be NF=48. The chromosome number observed in this fish is the same as the majority of Mugil fish, thus confirming the commonality of this feature in the family.

This study was conducted to determine Pb (Pb) and Cd (Cd) concentrations in the liver and muscle of Platycephalus indicus (flathead) in Minab, Qeshm Island and Khamir Port in the Northeastern Persian Gulf. Moreover, the influences of season (winter and summer) and target tissue (liver and muscle) on the Pb and Cd concentrations in flathead were investigated and compared with FAO/WHO standards for human consumptions. Sampling was done in three stations (Minab, Qeshm Island and Khamir Port) and within two seasons (winter and summer). Thirty samples were prepared per season per station. The concentration of metals (Pb and Cd) was measured using Atomic Absorption Spectrometry (AAS). The results showed that metal levels differred significantly (P<0.05) between stations, seasons and organs. The concentrations of Pb and Cd in the muscle of flathead fish were below the FAO/ WHO standard values indicating flathed fishes in Minab, Qeshm Island and Khamir port were safe for human consumptions.

A study was conducted to investigate the effects of dietary essential amino acid (EAA) concentrations on the spawning performance of Acanthopagrus latus. Broodstocks were fed with three replicates of isonitrogenous and isolipid formulated diets (diet 1, diet 2 and diet 3) with different concentrations of EAA (15.40, 16.88 and 18.14%, respectively) for 138 days. Results showed relative fecundity and percentage of buoyant eggs did not display any significant differences among the three dietary EAA concentrations. Fertilizability and hatchability were significantly higher (P<0.05) in broodfish fed with diet 3. However, lowest percentage of abnormal larvae and highest survival rate in 3 day post-hatching (DPH) larvae were observed in broodstock fed with diet 2. Results showed that the EAA concentration in broodstock diet had considerable effects on reproductive performance of A. latus.

In vitro antioxidant activity of Ulva lactuca (Chlorophyta) and three brown seaweeds belonging to the division Phaeophyta were evaluated. The species Padina pavonica, Colpomenia sinuosa, Cystoseira myrica and U. lactuca were collected during low tide between March and June 2012 from the coastline of the Persian Gulf (Hormozgan and Bushehr provinces), Iran.Ethyl acetate, n-Hexane and methanol extracts were prepared. The ethyl acetateextract of Ulva lactuca showed the highest radical scavenging activity (IC50 62.13 µg/ml) in comparison with brown seaweeds, when tested by the DPPH (1-diphenyl-2-picrylhydrazyl). Butylated hydroxytoluene (BHT) was used as a reference. This study indicated that the ethyl acetate extract of seaweeds had better antioxidant effect in comparison with methanol and n-Hexane extracts. Additionally, the antioxidant activities of ethyl acetate extracts of all the four seaweeds exhibited dose dependency and increased with increasing concentration of the extract. Since, these algal species are easily available in coastal waters of the Persian Gulf, their antioxidant potential make them suitable candidate as ingredients in food and pharmaceutical industries.

During their service life, marine pipelines continually accumulate damage as a result of the action of various environmental forces. Clearly, the development of robust techniques for early damage detection is very important to avoid the possible occurrence of a disastrous structural failure. Most of vibration-based damage detection methods require the modal properties that are obtained from measured signals through the system identification techniques. However, the modal properties, such as natural frequencies and mode shapes are not adequate sensitive indicators of structural damage. In this paper, structural damage was identified based on a new method called Detail Signal Energy Rate Index (DSERI). Damage localization of offshore pipeline was then based on Continuous Wavelet Transform (CWT) and Discrete Wavelet Transform (DWT). For modeling the damage, the stiffness of 1 and 2 elements were reduced in three models and the dynamic signals were measured by finite element analysis. The dynamic signals were analyzedby applying discrete and continuous wavelet transforms. Then, by using Daubechies wavelet, a peak was clearly evident and the exact damage location was identified by the peak with the maximum absolute value in the plots of the detail signal calculated with the DWT and CWT. To eliminate the effects of the boundary conditions on the wavelet-based damage, the authors proposed a new DSERI. Component energies were then calculated and used for damage assessment. The results showed that the DSERI were good candidate indices sensitive to structural damage. These component energies could be used for damage assessment including identifying damage occurrence and location of damage. Wavelet coefficient was a good candidate for structural damage identification when damage occured at the middle of pipeline but not sensitive for damaged elements near to supports.