Shell Bottom Research Articles

Numerical investigation of PCM melting using different tube configurations in a shell and tube latent heat thermal storage unit

Thermal energy storage plays an essential role in energy systems to reduce the mismatch between the energy supply and demand. Phase change materials are widely used in different technologies but suffer from low heat transfer performance. This numerical study aims to investigate the enhancement in the melting thermal characteristics of lauric acid as a phase change material by using Ansys-Fluent. Three inner tubes of heat transfer fluid were employed with four different arrangements: inline-central array (normal case, Case A), downward and upward triangle arrays (Case B and C) and an arc array at the shell bottom (Case D). Results revealed that the arc array and downward triangle configurations reduced the melting time by about 76% and 72%, respectively. However, the upward triangle tube arrangements increased the melting time by about 10% compared with the normal case.

Fatigue Evaluation of API 12F Shop-Welded Tanks With a New Roof-to-Shell Junction Detail

Abstract The American Petroleum Institute (API) provides a series of standards and specifications on storage tanks, in which the API 12F specification provides 12 tank designs that can be fabricated in the shop and transported to the field. The nominal capacity of the 12 API 12F tank designs ranges from 90 bbl (14.3 m3) to 1000 bbl (158.99 m3). The minimum required thickness and operational pressure levels that each tank case can sustain are given in Table 1 of the current 13th edition of API 12F (API, 2019, “API 12F Specification for Shop-Welded Tanks for Storage of Production Liquids,” 13th ed., API Publishing Services, Washington, DC, Standard No. API 12F). The objective of this study is to estimate the fatigue life of API 12F tanks under normal operation pressure cycles following the procedure presented in ASME VIII-2. The stored liquid product specific gravity is assumed to be 1.2 when the liquid height is half of the tank height, while the specific gravity is assumed to be 0.7 when the stored liquid height is 18 in. (460 mm). Meanwhile, a new roof–shell attachment detail is proposed in this study, the new rectangular cleanout junction detail presented in the 13th edition of API 12F is modeled, and various component thickness combinations are considered to investigate the effect of component thickness on fatigue life. The roof–shell joint (top junction) and shell–bottom plate (bottom junction) are studied by axisymmetric models under axisymmetric idealization as they are away from the cleanout junction, while the cleanout junction is studied by applying a submodeling technique. Stress classification is performed at each location of interest to obtain the stress components to calculate the stress range within each loading cycle that is needed to perform fatigue evaluation. The results and discussion about fatigue evaluation of API 12F tanks are presented in this report.

Macrofaunal Assemblages on Oyster Aquaculture and Rock Reef Habitat in Long Island Sound

AbstractTrap sampling was used to survey the relative abundance of juvenile fish and invertebrates near three habitats including an off‐bottom oyster cage farm (cage farm), a traditional on‐bottom oyster culture area (shell bottom), and a natural cobble and boulder reef (rock reef) in a coastal embayment in Long Island Sound near Milford, Connecticut. Ten traps, deployed on two subsites within each habitat (20/habitat), were allowed to soak for ~24 hours, two to three times per week, from June through September 2016. The assemblages of juvenile finfish appeared to be similar on the cage farm and rock reef, while the composition of the invertebrate community was more variable among the three habitats. These preliminary observations suggest that oyster cage farms may provide functional habitat that is populated by structure‐oriented finfish communities similar to those that are found on natural rock reefs in Long Island Sound.

Insight into Breakout Shell of a Bloom Casting by Its Dendritic Morphology and a New Mathematical Model

The steel solidification behavior in the mold during normal and breakout process is investigated on basis of microstructure observation from a bloom breakout shell about 500 mm in length. A total of three layers is observed in the breakout shell from the outer surface to the inner, namely, steady state layer, extra solidified layer, and adhesive layer. The steady state layer with equiaxed and columnar crystals is the true solidified shell under the normal casting condition. For the present bloom, the thickness of the steady state layer is about 10.96 mm at the location 500 mm below meniscus. The extra solidified layer forms in the breakout process where the liquid steel can solidify consecutively, and its thickness is about 1.59 mm on the breakout shell bottom. The boundary between extra solidified layer and steady state layer is a white band about 0.4 mm in thickness, where the solute elements C, Cr, and Mn are negative segregation. The adhesive layer is the attachment of the unsolidified steel in the inner face of the shell, in which the dendritic is quite smaller and the thickness is around 1.56 mm on the bottom of the breakout shell. Further insights are provided by a new mathematical model according to mass and energy conservation. The predicted thicknesses of steady state layer, extra solidified layer, and adhesive layer on the breakout bottom are 10.94, 1.69, and 1.57 mm, respectively. Favorable agreements are observed between the modeling results and the measurements.

On demand manufacturing of patient-specific liquid capsules via co-ordinated 3D printing and liquid dispensing

A method for the production of liquid capsules with the potential of modifying drug dose and release is presented. For the first time, the co-ordinated use of fused deposition modelling (FDM), 3D printing and liquid dispensing to fabricate individualised dosage form on demand in a fully automated fashion has been demonstrated. Polymethacrylate shells (Eudragit EPO and RL) for immediate and extended release were fabricated using FDM 3D printing and simultaneously filled using a computer-controlled liquid dispenser loaded with model drug solution (theophylline) or suspension (dipyridamole). The impact of printing modes: simultaneous shell printing and filling (single-phase) or sequential 3D printing of shell bottom, filling and shell cap (multi-phase), nozzle size, syringe volume, and shell structure has been reported. The use of shell thickness of 1.6 mm, and concentric architecture allowed successful containment of liquid core whilst maintaining the release properties of the 3D printed liquid capsule. The linear relationship between the theoretical and the actual volumes from the dispenser reflected its potential for accurate dosing (R2 = 0.9985). Modifying the shell thickness of Eudragit RL capsule allowed a controlled extended drug release without the need for formulation change. Owing to its low cost and versatility, this approach can be adapted to wide spectrum of liquid formulations such as small and large molecule solutions and obviate the need for compatibility with the high temperature of FDM 3D printing process. In a clinical setting, health care staff will be able to instantly manufacture in small volumes liquid capsules with individualised dose contents and release pattern in response to specific patient's needs.

The decapod community from the Early Pliocene (Zanclean) of “La Serra” quarry (San Miniato, Pisa, Toscana, central Italy): sedimentology, systematics, and palaeoenvironmental implications

We report an unusual and rich decapod crustacean assemblage from the early Pliocene (Zanclean), recently collected during the excavations of the “La Serra” quarry, located in La Serra, near San Miniato, Pisa (Toscana, central Italy). The studied specimens have been assigned, as follows: Axius sp., Callianassa chalmasiiBrocchi, 1883, and Calliaxina cf. C. punica (de Saint Laurent and Manning, 1982) (infraorder Axiidea de Saint Laurent, 1979); Gebiacantha tuscia Garassino, Pasini, De Angeli and Charbonnier sp. nov. (infraorder Gebiidea de Saint Laurent, 1979); Pagurus alatusFabricius, 1775, and Pagurus sp. (infraorder Anomura MacLeay, 1838); Dromia neogenicaMüller, 1978, Dromia sp., Medorippe cf. M. ampla Garassino, De Angeli, Gallo and Pasini, 2004, Ilia nucleus (Linnaeus, 1758), Ristoria pliocaenica (Ristori, 1891), Pisa armata (Latreille, 1803), Macropodia sp., Maja squinado (Herbst, 1788), Derilambrus angulifrons (Latreille, 1825), Atelecyclus undecimdentatus (Herbst, 1783), Liocarcinus sp., Thalamita italica Garassino, Pasini, De Angeli and Charbonnier sp. nov., Pilumnus cf. P. hirtellus (Linnaeus, 1761), Eriphia cocchiiRistori, 1886, Goneplax rhomboides (Linnaeus, 1758), Goneplax sacciCrema, 1895, (infraorder Brachyura Linnaeus, 1758). Moreover, two specimens have been assigned to callianassideans sensu lato and 13 specimens to indeterminate axiideans. CalliaxinaNgoc-Ho, 2003, GebiacanthaNgoc-Ho, 1989, Ristoria Garassino, Pasini, De Angeli and Charbonnier gen. nov., and Macropodia Leach, 1814, are reported for the first time in the fossil record and the extant Pagurus alatus, Ilia nucleus, Pisa armata, Derilambrus angulifrons, and Pilumnus cf. P. hirtellus, are reported in the fossil record from the Pliocene. Everywhere “La Serra” quarry bio-community is very important, representing one of the richest and most diversified crustacean faunas from the Pliocene reported to date in the Mediterranean basin and worldwide, increasing notably the knowledge on the decapod populations and distribution during the early Pliocene. This community is indicative of a palaeoenvironment of shallow sublittoral water, with sandy-muddy and alternate hard shell bottom, partially covered or in proximity of seagrass, similar to the extant Mediterranean Posidonia beds, mainly inhabited by fossorial and benthonic decapods.

Modeling of Piezoelectric Barrel Unimorph at the Flexural Vibration Mode

Barrel unimorph is composed of the metal barrel shell and piezoelectric ceramic disc affixed on the shell bottom, its flexural vibration is investigated with modeling and experiment. The barrel unimorph was modeled with finite-element method to analyze the vibration mode and calculate the relationship between the structure dimension and vibration frequency. The factors influencing resonance frequency were also discussed. According to the simulation, the structure of the barrel unimorph was optimized and the samples were fabricated in practice. The vibration mode of the sample was measured. The results show that the frist step resonance vibration frequency of the sample agrees well with the calculation by finite-element method.

Study on a fuel layering sequence of the foam target for the FIREX project

To develop the fuel layering sequence for the FIREX cryogenic target, redistribution of surrogate fuel, solid H2 in a shell with cooling duration has been studied. Two kinds of dummy targets with a foam and a polystyrene shells (∼800 μm and 2 mm in diameter, respectively) were tested. The solid H2 layer in the polystyrene shell was accumulated on the shell bottom as time elapsed. On the other hand, the foam shell had less elapsed time dependence than the polystyrene shell. Furthermore, elapsed time appeared to make the solid H2 layer uniform.

Presence of larger flatfish modifies habitat preference by Age-0 northern rock sole Lepidopsetta polyxystra

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 342:227-238 (2007) - doi:10.3354/meps342227 Presence of larger flatfish modifies habitat preference by Age-0 northern rock sole Lepidopsetta polyxystra Clifford H. Ryer1,*, Allan W. Stoner1, Mara L. Spencer1, Alisa A. Abookire2 1Fisheries Behavioral Ecology Program, Alaska Fisheries Science Center, NOAA Fisheries, Hatfield Marine Science Center, Newport, Oregon 97365, USA 2Alaska Fisheries Science Center, NOAA Fisheries, Kodiak Laboratory, 301 Research Court, Kodiak, Alaska 99615, USA *Email: cliff.ryer@noaa.gov ABSTRACT: Essential fish habitat (EFH) is poorly defined for the early stages of most commercially important species. Age-0 flatfish making summer use of shallow coastal embayments around Kodiak Alaska distribute themselves according to a variety of bottom features. Both field and laboratory studies indicate that the numerically dominant species, northern rock sole Lepidopsetta polyxystra and Pacific halibut Hippoglossus stenolepis, demonstrate an affinity for seafloor with emergent structure: algae, shell, worm-tubes, etc. We conducted field manipulations, in which bivalve shell was scattered on the seafloor along 100 m transects, with the goal of examining movements of juvenile flatfish in response to these habitat alterations. In the first manipulation, contrary to expectations, Age-0 flatfish emigrated from the shell-enhanced seafloor, producing fish densities that were lower than on adjacent un-enhanced bottom. In comparison, larger flatfish, predominantly Age-1+ rock sole Lepidopsetta spp., increased in abundance on shell-enhanced bottom. Small flatfish may have moved to avoid larger flatfish. The manipulation was repeated at another site with similar physical features, but where large flatfish abundances are generally lower. This time, Age-0 flatfish densities were greater on the shell-enhanced bottom than on adjacent un-enhanced bottom. Again, large flatfish were more abundant on the shell bottom, but they were nearly an order of magnitude less abundant than in the first manipulation. In a subsequent laboratory experiment, Age-1 northern rock sole demonstrated stronger affinity for shell bottom than did Age-0 northern rock sole. In another experiment, Age-0 northern rock sole moved to avoid aggregations of larger conspecifics as well as other species of large flatfish. We conclude that these Age-0 flatfish, predominantly northern rock sole, perceive larger fish as predators and/or competitors, with habitat quality degraded by their presence. These results demonstrate that habitat quality for juvenile fish is influenced by biotic factors as well as by physical characteristics of habitat. KEY WORDS: Habitat complexity · Habitat quality · Rock sole · Pacific halibut · Predator-prey interactions · Competitive interactions · Essential fish habitat · Indirect predation effects Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 342. Online publication date: July 24, 2007 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2007 Inter-Research.

Nekton use of subtidal oyster shell habitat in a Southeastern U.S. estuary

Subtidal accumulations of oyster shell have been largely overlooked as essential habitat for estuarine nekton. In southeastern U.S. estuaries, where oyster reef development is mostly confined to the intertidal zone, eastern oyster (Crassostrea virginica) shell covered bottoms are often the only significant source of hard subtidal structure. We characterized and quantified nekton use of submerged shell rubble bottoms, and compared it to use of intertidal reefs and other subtidal bottoms in the North Inlet estuary, South Carolina. Replicate trays (0.8 m2) filled with shell rubble were deployed in shallow salt marsh creeks, and were retrieved after soak times of 1 to 25 days from May 1998 to March 2000. Thirty six species of fishes, representing 21 families, were identified from the 455 tray collections. Water temperature, salinity, soak time and the presence of a shell substrate all affected the catch of fishes in the trays. Catches during the warmer months were two to five times greater than those during the winter. Fishes were present in 98% of the trays with an overall average of 5.7 fish m−2. The assemblage was numerically dominated by small resident species including naked goby (Gobiosoma bose), oyster toadfish (Opsanus tau), and crested blenny (Hypleurochilus geminatus). Transient species accounted for 23% of all individuals and 62% of the total biomass due to the presence of relatively large sheepshead (Archosargus probatocephalus) and black sea bass (Centropristis striata). Both the transient and resident species displayed distinct periods of recruitment and rapid growth from April to October. Lower abundances of juvenile gobies and blennies during 1998 were attributed to long periods of depressed salinity caused by high rainfall associated with El Nino conditions in spring. Crabs and shrimps, which were often more abundant than the fishes, accounted for comparable biomass in the tray collections. In comparisons of subtidal tray and trawl catches, trays yielded 10 to 1,000 fold higher densities of some demersal fish groups. Comparisons of intertidal and subtidal gear catches indicated that many species remain in the subtidal shell bottom at all stages of the tide. This study suggests that subtidal shell bottom may be essential fish habitat for juvenile seabass, groupers, and snappers and that it may be the primary habitat for a diverse assemblage of ecologically important resident fishes and crustaceans. Given the high levels of nekton use and the areal extent of oyster shell bottoms in eastern U.S. and Gulf estuaries, increased attention to protection and restoration of these areas appears justified.

Investigation of the Stress State of Pressure Vessels of Inhomogeneous Structure Made of Composite Materials

The problem on the stress-strain state of layered cylindrical shells with bottoms of intricate shape under the action of internal pressure is considered. The elastic system examined is formed by spiral-circular winding. Two variants of the shell bottom structure are investigated. In the first variant, one spiral layer is installed, which leads to great variations in the bottom thickness along the meridian. In the second one, the bottoms are formed according to the zone-winding scheme. The stress state of the shell constructions of the classes considered is determined by solving boundary-value problems for systems of ordinary differential equations. The solution results for cylindrical shells with elliptic bottoms for the two types of winding are given. It is shown that the zone winding leads to smaller deflections and stresses than the conventional ways of reinforcing shell bottoms.

NONLETHAL EFFECTS OF PREDATORS ON PREY POPULATIONS: PREDATOR-MEDIATED CHANGE IN BIVALVE GROWTH

Predators affect dynamics of prey populations not only by decreasing their survivorship, but also by changing other vital rates such as growth and reproduction. However, such nonlethal effects have rarely been examined experimentally in the field. In North Carolina estuaries, the hard clam Mercenaria mercenaria generally shows lower growth rates in habitats where predation rates are higher. Predator avoidance behavior of the clams (feeding inhibition) might be one of the factors responsible for this correlation. To examine possible effects of predators on clam growth, I first compared variation in clam growth rate among habitats with different predation pressure, and between predator-exclusion cages and uncaged controls. I then carried out a predator-enclosure experiment using the clam and the whelk Busycon carica, a major predator on adult clams. Among-habitat variation in survivorship, predation rate, and growth rate was generally small or not detected in winter, while large variation was found for adult clams in spring, their major growing season. Growth rate of adults was highest in a mud bottom where survivorship was highest (>60%) due to low predation rates, and it was lowest in an oyster shell bottom where survivorship was lowest (<10%). For juveniles, on the other hand, growth rate did not differ significantly among habitats, nor did survivorship. Clams in the predator-exclusion cages showed nearly twice the growth rate of uncaged controls in spring but not in winter. Clam growth rates were thus lower in habitats with lower survivorship and higher predation rates, suggesting that the predators can affect growth rates. In the whelk-enclosure experiment, the clams were enclosed in cages with three different treatments: (1) with whelks capable of attacking clams, (2) with whelks isolated from the prey, and (3) without whelks (control). The shell and somatic growth rates of the clam were at least twice as high in the control than in the two experimental treatments. However, the growth rates did not differ significantly between the two experimental treatments. The clam growth rates were therefore reduced in the presence of whelks even with no direct contact between whelks and clams, suggesting that the decrease in growth rates is due to a behavioral response of the prey to indirect cues, such as water-borne chemical signals produced by whelks. These findings show that predatory whelks can affect clam population dynamics not only by decreasing survivorship directly, but also by decreasing future reproduction and survivorship indirectly by suppressing growth rates, and that the predator-avoidance behavior observed in previous studies has significant demographic consequences. The nonlethal effects of predation on clam growth rate may also be responsible for observed variation in growth rates among habitats.

Predation on mud crab megalopae, Panopeus herbstii H. Milne Edwards: effect of habitat complexity, predator species and postlarval densities

Laboratory experiments were conducted to evaluate the magnitude of predation on megalopae of the Atlantic mud crab, Panopeus herbstii H. Milne Edwards, in four simulated habitats (salt marsh bottom, shell bottom, seaweed patch and sand bottom). Predators included juvenile blue crabs ( Callinectes sapidus Rathbun), common killifish ( Fundulus heteroclitus (L.)) and grass shrimp ( Paleomonetes pugio Holthius). Experiments were run at two different densities of megalopae. Two-way analysis of variance revealed significant effects of predator type and substratum. Proportional mortality was lowest on shell bottom, and blue crabs were the least effective predators, regardless of habitat. Additionally, proportional mortality was lower at low megalopal densities than at high megalopal densities. Decreased predation at low megalopal abundance may afford density-dependent modulation of mud crab populations.

Container structures on a Vlasov foundation with variable soil characteristics

In this study container structures such as cylindrical vessels which have a flat or shallow spherical shell bottom on a Vlasov foundation with variable soil characteristics, are investigated. The variation of the soil's elastic modulus is assumed exponential along the depth of soil layer. Interaction between superstructure, foundation and soil is taken into account. The loading is considered as axisymmetric relative to the center of the bottom. The solution is achieved using the flexibility method, in which the wall is represented by distributed loads and moments along the circumference of the bottom. Some parametrical results are obtained for various soil layer depth-to-bottom radius ratios and comparisons are made between exponential and the other variations of the soil's elastic modulus.

Sublittoral, Benthic Marine Algae of Southern Cape Cod and Adjacent Island: Seasonal Periodicity, Associations, Diversity, and Floristic Composition

The periodicity, associations, species diversity, and composition of the sublittoral, attached algal vegetation were studied at four ecologically distinct stations in southern Cape Cod and adjacent islands. In situ collections and observations of 142 species of attached sublittoral algae (Chlorophyta, Phaeophyta, and Rhodophyta) were made with the aid of diving equipment. These were categorized into four groups with respect to seasonal periodicity (seasonal annuals, aseasonal annuals, pseudoperennials, and perennials) based on thallus longevity, plant form during their adverse season, and the period in which each species population was present in the community. Using these criteria we recognize the influence of environmental change on algal development, and the plants' temporal influence on the community. Based on qualitative and quantitative sampling, 10 sublittoral alga associations have been recognized from 2 bottom substrata types. The distribution of sublittoral attached algae at our four stations was more complex than can be accounted for by the three sublittoral algal associations as described in studies of other geographic areas. This may be due to the different levels at which associations have been recognized, to the type and degree of substratum stability, and to whether consideration is given to algal seasonal periodicity. The concept of a universal tripartite zonation of sublittoral algae is unacceptable when these factors are considered in vegetational analyses. An in—habitat, seasonal comparison of species diversity and composition was based on adjacent quantitative collections from a uniform shell bottom at 6 and 12 m. Species diversity remained seasonally stable at these depths; species composition, however, changed dramatically throughout the year. At 6 m, brown algae dominated in winter and were replaced by red algae during summer. At 12 m, the seasonal floristic changes were less pronounced, and red algae dominated year—round. A between—habitat comparison of species numbers and composition was based on year—round qualitative collections and observations made at four regularly visited stations (5—22 m depth). Species numbers decreased with increased station depth from 5 to 22 m except for one heavily silted station. The seasonal change of floristic composition was most striking at West Chop (5—8 m) where short— and long—lived species were about equally represented. Seasonal differences in species composition between summer and winter were striking at a 5—8 m station but were less pronounced with increased station depth where long—lived species made up an increasingly larger percentage of the total vegetation. Floristic composition also differed among stations. About equal numbers of red and brown species occurred at 5—8 m in contrast to the occurrence of about 4 times more red than brown algal species at 22 m. The crust vegetation also made up an increasingly larger percentage of the deep vegetation when compared with the vegetation of shallower areas sampled. Species diversity at 20—22 m was much higher in southern Cape Cod than reported for similar depths to the north (Cape Ann, Massachusetts, New Hampshire; Halifax, Nova Scotia); this may be due in part to the intensive collecting of crustose forms during the present study.