Different failure modes assessment to improve the sandwich composite panel stiffness with honeycomb core for marine structures application

This research paper focuses on the prediction of different failure modes to improve the sandwich composite panel with honeycomb core for application in marine structures. Marine, automotive and aerospace industries are continually trying to optimize material performance in terms of strength and weight. Success has been achieved through the growth of high performance materials, including fibrous composites such as ceramics, new alloys, and carbon fiber composites and through the use of structural concepts such as sandwich composite panel construction. Sandwich composite panel construction with honeycomb core consists of three components: two facing sheets, the core that fill the space between the facing sheet and the core-to-facing bonding adhesives. The facing sheets of a sandwich panel can be compared to the flanges of an I-beam element, as they carry the bending stresses to which the beam is subjected. With one facing sheet in compression, the other is in tension. Similarly the honeycomb core corresponds to the web of the I-beam that resists the shear loads and vertical compressive load to the face sheet. This paper presents a model for prediction of different failure mode of face sheet and core material. The obtained results of this model were compared with experimental results and presents that it is a simple and good model

Numerical estimation of shallow water effect on multipurpose amphibious vehicle resistance

This research paper numerically investigated the hydrodynamic resistance of Multipurpose Amphibious Vehicles (MAV) navigating in shallow water. This type of vehicle and other coastal floating vehicles encounter the problem of a small under keel clearance with river bed. The proper estimation of ship resistance and squat is influenced largely on the power calculation in the design stage. The present work describes the effect of shallow water on the Multipurpose Amphibious Vehicles (MAV) resistance at different speeds using Computational Fluid Dynamics (CFD) techniques. A comparison in the drag on the hull is illustrated between depth restriction and infinite depth water. This paper provides a wide introduction into the problems of modeling the restricted water depth effects on the ship behaviour, specifically hydrodynamic resistance and squat using CFD as implemented by ANSYS-CFX14.0

Computational fluid dynamics (CFD) mesh independency technique for a propeller characteristics in open water condition

This paper numerically investigated mesh refinement method in order to obtain a mesh independent solution for a marine propeller working in open water condition.Marine propeller blade geometries, especially of LNG carriers, are very complicated and determining the hydrodynamic performance of these propellers using experimental work is very expensive, time consuming and has many difficulties in calibration of marine laboratory facilities. The present research workhas focused on the hydrodynamic propeller coefficients of a LNG carrier Tanaga class such as Kt, Kq and η, with respect to the different advance coefficient (j). Finally, the results of numerical simulation in different mesh density that have been calculated based on RANS (Reynolds Averaged Navier Stocks) equations, were compared with existing experimental results, followed by analysis and discussion sections. As a result the maximum hydrodynamic propeller efficiency occurred when j=0.84

Passive noise control strategies for jets exhausting over flat surfaces : an LES study

Unconventional aircraft propulsion configurations have to be considered in the future to address environmental issues, including air traffic noise that is know to affect communities surrounding airports. One approach involves rectangular jets in the vicinity of flat surfaces that are parallel to the jet axis in an attempt to shield the noise, but previous experimental work indicated that there is an increase in the noise generated by these configurations, mainly associated with the effect that the plate trailing edge exerts on the flow. In this work, we use large eddy simulations to investigate the potential of wall deformations at the plate trailing edge to reduce jet noise. We consider a high aspect ratio rectangular nozzle exhausting a jet over a flat surface in different configurations, and estimate the farfield noise using the Ffowcs Williams and Hawkins acoustic analogy. Because of the high aspect ratio of the rectangular nozzle, we approximate the jet as being two-dimensional, and use periodic boundary conditions in the spanwise direction. For the configurations that we considered here, the trailing edge deformations did not seem to affect the noise significantly; an overall sound pressure level in the order of 1-2 dB was observed for some selected cases

Hydrodynamic resistance analysis of new hull design for multipurpose amphibious vehicle applying with finite volume method

This paper numerically investigated the hydrodynamic resistance of Multipurpose Amphibious Vehicles (MAV) in three bow shapes to approach the better hull bow shape design. This type of vehicle and other blunt-shaped floating vehicles encounter the problem of a large bow wave forming at high speeds. This wave formation is accompanied by higher resistance and at a critical speed results in bow submergence or swamping. Three new shapes of hull bow design for the multipurpose amphibious vehicle were conducted at several speeds to investigate the hydrodynamic phenomena using Computational Fluid Dynamics (CFD, RANS code) which is applied by Ansys-CFX14.0 and Maxsurf. The vehicle’s hydrodynamic bow shapes were able to break up induced waves and avoid swamping. Comparative results with the vehicle fitted with U-shape, V-shape and Flat-shape of hull bow, showed that the U-shape of the hull bow has reduced the total resistance to 20.3% and 13.6% compared with the V-shape and flat shape respectively. Though, the U-shape of hull bow is capable to increase the amphibious operating life and speed of vehicle in calm water. Also it has ability to reduce the vehicle’s required power, fossil fuel consumption and wetted hull surfac

The role of viral and bacterial infections in the pathogenesis of IPF: a systematic review and meta-analysis

Background: Idiopathic pulmonary fibrosis (IPF) is a chronic progressive lung disease. Several risk factors such as smoking, air pollution, inhaled toxins, high body mass index and infectious agents are involved in the pathogenesis of IPF. In the present study, this meta-analysis study investigates the prevalence of viral and bacterial infections in the IPF patients and any possible association between these infections with pathogenesis of IPF. Methods: The authors carried out this systematic literature review from different reliable databases such as PubMed, ISI Web of Science, Scopus and Google Scholar to December 2020.Keywords used were the following �Idiopathic pulmonary fibrosis�, �Infection�, �Bacterial Infection� and �Viral Infection�, alone or combined together with the Boolean operators "OR�, �AND� and �NOT� in the Title/Abstract/Keywords field. Pooled proportion and its 95 CI were used to assess the prevalence of viral and bacterial infections in the IPF patients. Results: In this systematic review and meta-analyses, 32 studies were selected based on the exclusion/inclusion criteria. Geographical distribution of included studies was: eight studies in American people, 8; in European people, 15 in Asians, and one in Africans. The pooled prevalence for viral and bacterial infections w ere 53.72 (95 CI 38.1�69.1) and 31.21 (95 CI 19.9�43.7), respectively. The highest and lowest prevalence of viral infections was HSV (77.7 95 CI 38.48�99.32), EBV (72.02, 95 CI 44.65�90.79) and Influenza A (7.3, 95 CI 2.66�42.45), respectively. Whereas the highest and lowest prevalence in bacterial infections were related to Streptococcus sp. (99.49, 95 CI 96.44�99.9) and Raoultella (1.2, 95 CI 0.2�3.08), respectively. Conclusions: The results of this review were confirmed that the presence of viral and bacterial infections are the risk factors in the pathogenesis of IPF. In further analyses, which have never been shown in the previous studies, we revealed the geographic variations in the association strengths and emphasized other methodological parameters (e.g., detection method). Also, our study supports the hypothesis that respiratory infection could play a key role in the pathogenesis of IP. © 2021, The Author(s)

Evaluation of quantitative and qualitative of microbial indicator the lake behind Shahid Rajaee dam of Mazandaran province (Sari)

One of the country's dams is dam Shahid Rajaee Sari. In this study it was evaluated some bacterial indices. Some bacterial parameters including total bacteria, total coliform, fecal coliform, fecal streptococci , Sulphitereducing Bacteria (SRB) in the water behind the dam Shahid Rjaee for one year at five stations (the entrance Shireenrood branches, input branch of the Sefidrood, cross the river and sweet Sefidrood in the tank, close to the Taj (zero, 15 and 30) and the output reservoir) and seven samples collected during six periods (June, July, August, September, November and February) were tested in 1391. Analysis of water samples for bacterial plate count agar medium (total bacteria count) ECC were inoculated (total coliforms and fecal), SPS (sulfite reducing bacteria) and KF (bacteria Inserts fecal streptococci) was performed using the culture surface culture method. ECC in both 37 and 44 ° C medium temperature Tc, KF and SPS at 37 ° C for 72-24 hours were incubated. The results showed that the mean log of bacteria in different months of CFU / 100ml12 / 0 ± 85/6 1n September months to CFU100ml15 / 0 ± 65/4 is variable in February, the mean total coliform Log in of the CFU / 100ml15 / 0 ± 63/4 in September to CFU / 100ml44 / 0 ± 27/3 in February are variable, the mean log Clostridium Clostridium CFU / 100ml89 / 0 ± 17 / 4 in September to CFU / 100ml13 / 0 ± 07/3 in February is variable, ranging from the mean log reduction in fecal streptococci in different months CFU / 100ml19 / 0 ± 59/3 in September CFU / 100ml17 / 0 ± 10 / 3 in February is variable. The results showed that bacterial indicator pollution load of the dam in more stations in August and September months. . Compare the results of the surface water standards indicate that indicator bacteria have been studied in the standard range. If the water behind the dam is intended to be used for drinking, it has need for more treatments during the final purification for drinking purposes

The percentage determination of Rutilus frisii kutum (200, 500 and 1000 mg) resistance to salinity, turbidity and decrease of oxygen by usage of the river water at the releasing meantime

The survey effect of salinity, turbidity and dissolved oxygen performed on Rutilus frisii Kutum juveniles with aim, which was determined about survival rate and histological changes in gill and kidney tissues. Juveniles provided from the Rajai's fish propagation center and then examined in Caspian Sea Ecology Research Center laboratory. The juveniles were investigated on three weight group (200-75%) had shown in 400-<600mg weight group with dissolve oxygen: 3.8±0.15SE mg/l. In addition, the lowest survival rates under turbidity stress (95.83%) had shown that in weight group less than 400 mg with turbidity 15600 FTU. Therefore, survival of juveniles was high. However, gill tissue of juveniles under turbidity and salinity stress became short (necrosis) and thick (edema and hyperplasia) in the end of experiments. The juveniles gill tissues were not changes in the river clear freshwater. Therefore, the factors of gill tissue deformation were salinity and suspended particles in the water. However, the structures of kidney in the different groups of juveniles were similar. Nevertheless, juveniles glomerular diameter increased with increasing weight (p<0.05, Duncan test). Furthermore, there was a increasing the internal cavity of the proximal and distal tubules and decreasing of glomeruli in diameter in the transfer of juveniles from freshwater to brackish water. Although the survival rate of juveniles is acceptable in this study, but there was abnormal changes in the structure of them gills. It appears that this change will cause a disruption in trend of juvenile's growth

Quantitative evaluation and identification of fungi in Shahid Rajaeii Dam Lake, Mazandaran Province (Sari)

The present study is carried out to investigate the fungal species present in water of Shahid Rajaeii damlake in Sari, (Mazandaran province). Samples were taken from five stations including, Station 1: Input of Shirinrud river, station 2: Input of Sefidrud river, Station 3: The confluence of the two branches, Station 4: dam crest and stations 5: Output dam from June to February 2012. Every sample was diluted by sterile saline (10-1 and 10-2) and 0.5 mL from each dilution was cultured on SD and incubated at 27-30°C for 3-5 days. Finally, the number of colonies wasrecorded as (colony forming unit = CFU) per 100 mL. Identification of fungal agents were conducted by slide culture preparation and stained in lacto-phenol blue. The results showed that in August and February were significantly highest and lowest rates of fungal colonies were isolated from water in different stations respectively. Moreover, the number of fungal colonies in the crown and the output was significantly higher than other stations. The frequency of identified fungi were: Aspergillus species (31.4%), various types of yeast (mainly Candida) (24.2%), Penicillium sp. (19.3%), Cladosporium sp.(10.3%), Mucor sp. (5.4%), Fusarium sp. (2.9%), sterile hype (2.8%), Alternaria sp. (2.3%) and Paecilomyces sp. (1.4%)

Evaluation of stocking density vannamei shrimp Litopenaeus vannamei (Boone, 1931) in culturing with brackish water of Caspian Sea

Recently, the development of aquaculture has focused on the use of seawater, because of freshwater crisis in the world. Whiteleg shrimp (Litopenaeus vannamei) is one of the most important species for aquaculture development, because of tolerance and adaptation to different ecological conditions. One of the advantages of species in aquaculture, compatibility status is dense in the rearing period. In this study, the effect of different densities (45/m^2 , 50/m^2 , 55/m^2 and 60/m^2 ), of primary stock whiteleg shrimp postlarvae (PL12) on the growth and survival rate were evaluated. Brackish water (10.52±0.43 ppt) was providing from Caspian Sea. The experiments were performed in 12 circular concrete pond with a sandy bed (area: 78m^2 ) in four treatments and three replications for each treatment. The experiments performed in a 75-day period. In this study, the water temperature was 27.4±1.79°C. The results showed statistically difference in growth parameters and survival rate among experimental treatments (Duncan test, P<0.05). Therefore, with high levels of density, has decreased the amount of weight gain and survival rate (SR), specific growth rate (SGR) and average daily growth (ADG). In addition, the treatments were different variations of FCR (P<0.05) and not depend on the primary stock density of postlarvae. In low density (45/m^2 ) were observed the highest growth (SGR=11±0.04 and ADG=0.25±0.01 gr/day/ind.), survival rate and calculate the amount of production per 78m2 equal 43.6±3.3kg (5596±433kg/ha). Therefore, It is possibility that there is commonly increasing primary stocking of density about L. vannamei postlarvae culture in Iran