Tubular Shell Research Articles

The classical version of Stokes' theorem revisited

Using only fairly simple and elementary considerations–essentially from first year undergraduate mathematics–we show how the classical Stokes' theorem for any given surface and vector field in ℝ3 follows from an application of Gauss' divergence theorem to a suitable modification of the vector field in a tubular shell around the given surface. The two stated classical theorems are (like the fundamental theorem of calculus) nothing but shadows of the general version of Stokes' theorem for differential forms on manifolds. However, the main point in the present article is first, that this latter fact usually does not get within reach for students in first year calculus courses and second, that calculus textbooks in general only just hint at the correspondence alluded to above. Our proof that Stokes' theorem follows from Gauss' divergence theorem goes via a well-known and often used exercise, which simply relates the concepts of divergence and curl on the local differential level. The rest of this article uses only integration in 1, 2 and 3 variables together with a ‘fattening’ technique for surfaces and the inverse function theorem.

Ultrastructural changes in the oviduct of the laying hen during the laying cycle

The ultrastructural changes occurring in the fully functional oviduct of Isa Brown laying hens were studied during various stages of the laying cycle. Hens were killed at different positions of the egg in the oviduct. The oviduct was lined by ciliated and non-ciliated cells (also referred to as granular cells). The granular cells in the infundibulum contributed to secretion during egg formation, whereas ciliated cells showed little evidence of secretion. Ultrastructural changes were recorded in the granular and glandular cells of the distal infundibulum. In the magnum, the surface ultrastructure revealed glandular openings associated with the ciliated and granular cells. Cyclic changes were recorded in the glandular cells of the magnum. With respect to the three observed types of glands, the structure of gland type A and C cells varied at different egg positions in the oviduct, whereas type B cells represented a different type of gland cell containing amorphous secretory granules. The surface epithelium of the isthmus was also lined by mitochondrial cells. Two types of glandular cell (types 1 and 2) were recorded in the isthmus during the laying cycle. Intracisternal granules were found in type 2 cells of the isthmus. A predominance of glycogen particles occurred in the tubular shell gland. The granular cells in the shell gland contain many vacuoles. During egg formation, these vacuoles regressed following the formation of extensive rough endoplasmic reticulum; the reverse also occurred. The disintegrated material found in the vacuoles may have been derived from the disintegrating granules.

Ultrastructural Observations on Effects of Infectious Bronchitis Virus in Eggshell-Forming Regions of the Oviduct of the Commercial Laying Hen

The pathogenesis of 2 strains of infectious bronchitis virus (T and N1/88 strains) was studied in the eggshell-forming regions of the oviduct of commercial laying hens. There were no external shell deformities, except for paler shells. There was no decline in egg production in either of the infected groups. One hen from the N1/88-infected group and 2 hens from the T-infected group were out of lay. The light, scanning, and transmission electron microscopic changes in infected shell-forming regions of the oviduct were compared with the control oviducts at different egg positions. The ultrastructural finding revealed that the extent of cytopathology in the isthmus was greater than in the tubular shell gland and shell gland pouch. The T strain of infectious bronchitis virus was more pathogenic compared with the N1/88 strain. Severe cytopathology was recorded in the shell-forming region of hens that were out of production, and virus particles were observed in hens that had stopped laying. Virus particles were recorded in the dilated rough endoplasmic reticulum and Golgi complex of the isthmus, tubular shell gland, and shell gland pouch of all 3 hens that had stopped laying. Although a decrease in egg production and deterioration in eggshell quality were not observed in this trial, cessation of egg production in a small number of hens could be due to severe cytopathology in the eggshell-forming regions of the oviduct.

Improving the manufacturing technology for thin-walled pipe and small-diameter shells

In arc welding, attention focuses on the electrode materials, based on powder wire. Benefits of powder wire include a high melting rate, its universal applicability for different welding and soldering systems, generation of specified properties of the metal, and high quality of the weld joints. In powder-wire production technology, continuous roller shaping of the packed tubular shell is followed by drawing to the specified size, with winding of the final product in coils. One of the main operations is shaping of the tubular shell. To evaluate the influence of the contact interaction on the shaping and motion of the billet through the working grooves, a method of determining the contact area of the roller with the pipe blank for two-radius grooving has been developed [1]. In determining the shaping energy and forces for the pipe blank, the total vertical force is the key factor. The shaping force ( in the i th cell for two-radius grooving of shaping-mill rollers is

Synthesis and characterization of polyethylene chains grafted onto the sidewalls of single-walled carbon nanotubes via copolymerization

Polyethylene (PE) chains grafted onto the sidewalls of SWCNTs (SWCNT-g-PE) were successfully synthesized via ethylene copolymerization with functionalized single-walled carbon nanotubes (f-SWCNTs) catalyzed by rac-(en)(THInd)(2)ZrCl2/ MAO. Here f-SWCNTs, in which alpha-alkene groups were chemically linked on the sidewalls of SWCNTs, were synthesized by Prato reaction. The composition and microstructure of SWCNT-g-PE were characterized by means of H-1 NMR, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetric analyses (TGA), field-emission scanning electron microscope (FESEM), and transmission electron microscope (TEM). Nanosized cable-like structure was formed in the SWCNT-g-PE, in which the PE formed a tubular shell and several SWCNTs bundles existed as core. The formation of the above morphology in the SWCNT-g-PE resulted from successfully grafting of PE chains onto the surface of SWCNTs via copolymerization. The grown PE chains grafted onto the sidewall of the f-SWCNTs promoted the exfoliation of the mass nanotubes. Comparing with pure PE, the physical mixture of PE/f-SWCNTs and in situ PE/SWCNTs mixture, thermal stability, and mechanical properties of SWCNT-g-PE were higher because of the chemical bonding between the f-SWCNTs and PE chains.

Evaluation of the Fracture Strength for Silicon Carbide Layers in the Tri‐Isotropic‐Coated Fuel Particle

A program to develop new methods to measure the fracture strength of the chemical vapor deposition SiC coatings in nuclear fuel particles has been carried out. Internal pressurization and crush test techniques were developed and applied to prototype‐sized tubular and hemispherical shell specimens. The fracture strength measured from each test method applying the Weibull two‐parameter distribution, and Weibull parameters were measured. It was shown that data generated with each test technique were independent of the test technique applied. This implies that the developed test methods are reliable and provide reasonable strength data. For the same material, fracture strength varied with the specimen geometry and loading configuration. These size and loading configuration effects on the fracture strength are explained with the concept of effective surface.

Histopathology of Two Serotypes of Infectious Bronchitis Virus in Laying Hens Vaccinated in the Rearing Phase

The comparative histopathology of 2 different strains of infectious bronchitis virus (T and N1/ 88) in vaccinated hens was studied at 110 wk of age. The Harderian gland showed similar histopathology in T- and N1/88-infected hens. The trachea and kidney of challenged vaccinated hens were protected to a moderate extent, but the oviduct was protected to only a small extent. The severity and persistence of lesions were greater in tubular shell gland, shell gland pouch, and kidney of the T-infected hens, whereas, for the magnum, N1/88 had a greater effect.

Comparative Histopathology of Two Serotypes of Infectious Bronchitis Virus (T and N1/88) in Laying Hens and Cockerels

The comparative and sequential histopathology of different tissues of unvaccinated laying hens and cockerels were studied in chickens exposed to T and N1/88 strain of infectious bronchitis virus (IBV). The Harderian gland and trachea of hens and cockerels in both T- and N1/88-infected groups were damaged to a similar extent. The cecum was unaffected for both strains of IBV in both hens and cockerels. The sequential histopathological changes in hens revealed that IBV multiplies initially in the Harderian gland, then in the tracheal mucosa and simultaneously in the kidney and regions of the oviduct such as the magnum, tubular shell gland, and shell gland pouch. In cockerels, IBV multiplies first in the Harderian gland, then simultaneously in the trachea and kidney. Overall, the severity and persistence of lesions were greater in the kidneys of T-infected hens as compared with N1/88-infected hens. However, pathological changes in the kidney were mild in T- and N1/88-infected cockerels.

SCAPHOPODIZATION IN PALAEOZOIC MOLLUSCS

Abstract: The relationship of a variety of problematic Early Palaeozoic fossils to the true scaphopods (Late Palaeozoic–Recent) is clarified by the recognition that a trend towards the development of a tubular shell is a recurrent theme within Palaeozoic benthic molluscs. This trend is here termed scaphopodization and can be recognized already in the Cambrian in helcionelloids such as Yochelcionella and Eotebenna. The problematic Early Palaeozoic tubular fossils Janospira, Jinonicella and Rhytiodentalium are interpreted as pseudo‐scaphopod derivatives of the apparently exogastric ribeirioid rostroconchs. The direction of coiling of the protoconch indicates that they are not closely related to the true scaphopods, which were derived from endogastric concocardioidean rostroconchs in the Devonian or Carboniferous. Scaphopods show a comparable underlying morphological blueprint to these conocardioideans, but they represent a distinct stream‐lining to the infaunal habitat.

A Vermetid Gastropod with Complex Intracapsular Cannibalism of Nurse Eggs and Sibling Larvae and a High Potential for Invasion

ABSTRACT A vermetid gastropod, previously unreported from the Pacific Ocean, was found at O‘ahu, Hawai‘i, in aquariums at the Kewalo Marine Laboratory, in fouling communities on docks, and on intertidal and shallow subtidal coral rubble. It also occurs on coral rubble in Florida. Eggs, or nurse eggs, and early embryos are about 100 μm in diameter. Young are brooded in 1–13 stalked capsules attached inside the tubular shell. Intracapsular development involves an unusual complex adelphophagy (sibling cannibalism). Most eggs are non-developing nurse eggs. Ten to 20 eggs develop into apparently normal small veligers. Of these most arrest as small veligers, but a few grow to hatch as large pediveligers or juveniles. The species has a high potential for invasion and establishment following maritime transport or natural rafting. Protected intracapsular development ends with the release of crawling hatchlings that also produce mucous threads on which they can drift. Juveniles settle readily on hard substrata. An ...

Mass transfer in liquid–liquid membrane-based extraction at small fiber packing fractions

Results are presented of carefully controlled mass transfer experiments, complemented by theoretical analysis. A simple test section is employed, comprised of five microporous nearly parallel fibers (fixed within a tubular glass shell), to study mass transfer when the shell-side resistance is controlling. The feed phase, flowing in the shell side, is an aqueous solution of either benzaldehyde or 2-hexanal, whereas n-hexane is used as the organic solvent (in the lumen); the respective partition coefficients at 25 °C are 10 and 57. Accurate data are obtained by using ‘once-through’ flow of both fluids. For the class of problems studied here (i.e. small fiber packing fraction Φ and high Sc number at shell side), a boundary layer solution is obtained for the mass transfer rate to the outer fiber surface. This expression, model variations thereof, as well as similar theoretical results recently reported in the literature, are assessed by comparison with the new data. By combining the analytical solution for the shell with a known expression for mass transfer at the lumen side, a closed-form expression is derived for the solute concentration variation in the organic solvent along the fiber/module. Very good agreement is obtained between experimental data and theoretical predictions, with no recourse to adjustable parameters. An important conclusion of this work, concerning shell-side mass transfer, is the dependence of Sh· Sc −1/3 on Reynolds number to the 1/3 power. Furthermore, the flow rate in the lumen (though not controlling) is shown to be a significant parameter affecting process efficiency.

Discrimination of B–C–N nanotubes through energy-filtering electron microscopy

Various multi-walled nanotubes in the B–C–N system are thoroughly investigated using a JEOL-3100FEF high-resolution field emission transmission electron microscope operating at 300 kV and equipped with an in-column built Omega filter. Spatially-resolved B, C and N elemental maps of the nanotubes are constructed. It is realized that a wide variety of tubular arrays composed of B, C and N atoms may exist in the system. Sandwich-like BN-rich and C-rich alternating tubular shells, graphitic C layers inside and outside of pure BN shells induced either by surface contamination, or electron beam irradiation, separation of C-rich and BN-rich tubes and/or BN particles within tubular bunches may take place. One should carefully take these effects into account while analyzing nanotube physical properties, e.g., electrical or optical, rather than simply rely on electron energy loss spectra typically collected from B, C and N containing nanostructures as a whole. Striking dependence of an individual nanotube electrical conductivity on tubular shell chemistry is demonstrated using I– V curve recording in an atomic force microscope.

Energetics of finite, clean and hydrogenated silicon nanotubes

Abstract The energetics and relative stability of infinite and finite, clean and hydrogenated open-ended Si nanotubes is investigated using the extended Brenner potential. The calculations show that the excess strain energy of infinite clean Si tubes is reduced when the tubes are hydrogenated on both sides of the tubular shell. For finite Si tubes the total energy exhibits a minimum which reflects a balance between the strain energy of the shell and the chemical energy of the open ends. If hydrogen atoms are chemisorbed on the outer surface of finite Si nanotubes, the tubes show a tendency to close their open ends. For very short, large-diameter tubes, topologically different structures are formed––hydrogenated silicon tori.

Iron fouling in membrane gas transfer applications

Iron fouling characteristics of gas permeable composite and wetted microporous hollow fiber membranes were studied. Membrane modules, operated in the sealed end configuration, were pressurized with oxygen and enclosed within a tubular shell. A solution consisting of tap water and ferrous sulfate was metered though the shell side of the module. The added mass-transfer resistance due to iron fouling was determined from the required increase in oxygen feed pressure to the membranes in order to maintain constant flux across the membranes, and was evaluated as a function of operating time and process parameters. Process parameters investigated include Reynolds number, ferric and ferrous iron concentrations, iron oxidation rate, and oxygen flux. It was found that iron oxidation rate, ferric iron concentration, and oxygen flux had no impact on the rate of membrane fouling, whereas the rate and maximum extent of membrane fouling increased with Reynolds number and ferrous iron concentration. The induction period was also found to increase with Reynolds number. A maximum fouling resistance of 2779 s/cm was measured at 17 h for a Reynolds number of 9000 and ferrous iron concentration of 14.0 mg/l. This is 7.2 times greater than the overall mass-transfer resistance for the clean membrane. For all conditions in this study, constant flux across the membrane was maintained, and the impacts of fouling compensated for by operating at higher driving forces. For membrane gas transfer systems where the driving forces can be controlled, such as membrane oxygenation, driving forces can be used to compensate for increases in mass-transfer resistance. However, for applications where driving forces cannot be as easily manipulated, such as VOC stripping, iron fouling is likely to have significant impact on transfer performance.

The oviduct in chaos

The unilateral avian oviduct is divisible into five functional regions which, moving distally, include the infundibulum, magnum, isthmus, tubular shell gland and shell gland pouch. Each region subserves a variety of functions, which through their interaction give rise to the multilayered albumen, shell membranes and the organic/inorganic complex, which comprises the shell. The sequential activity of these structurally diverse regions is a necessary prerequisite for “normal” egg formation. The reproductive effort can be influenced by a number of disease processes either directly by virtue of the fact that they alter the ability of the lining cells to synthesise their integral components or indirect by generally compromising bird health. Notable amongst the former are Infectious Bronchitis, Newcastle Disease and Egg Drop Syndrome. All change the quality of the final product in terms of the shape and texture of the shell. In recent years it has become evident that environmental stress has an equally, if not more, important role to play in oviduct disfunction. In the absence of large areas of functional surface epithelium, the eggs laid were structurally defective at all levels from the mammillary layer outwards. As the epithelial layers regenerated, shell quality approximated normality, but never returned to the pre-stress condition.The process of candling signals amongst other internal defects a variety of inclusions variously classified as blood and meat spots. They are quite specific in their locations; thus blood spots originating from the rupture of ovarian blood vessels at ovulation, are invariably confined to the periphery of the yolk mass, while meat spots now classified according to their composition are confined to albumen. Within the latter they are recognised as tissue rich deposits, the result of oviduct breakdown and/or calcium rich fragments. The latter implies a breach in the barrier provided by the soft shell membranes.

Buckling and collapse of open and closed cylindrical shells

The buckling of a finite section of a cylindrical shell resembling a two-dimensional contact lens, and the collapse of a tubular shell of infinite extent are considered. The deformation is due, respectively, to the application of an edge force or to a negative transmural pressure. In both cases, the shell develops elastic bending moments due to the deformation from a specified resting shape according to a linear constitutive equation, accompanied by in-plane and transverse shear tensions. In the case of a section of a shell with a flat resting shape, classical results due to Euler and Love show that, as the applied edge force is increased beyond a sequence of thresholds, an infinite family of deformed shapes becomes possible corresponding to buckled states that bifurcate from the zero-curvature resting configuration. It is shown here that a corresponding infinite family of shapes is also possible for a finite shell whose resting shape is a section of circle. These shapes, however, no longer arise from bifurcations, but rather constitute disconnected solution branches of a nonlinear boundary-value problem. A closed cylindrical shell whose cross-section has a circular resting shape exhibits similar bifurcations when the difference between the exterior and interior pressure exceeds a sequence of thresholds, but a shell with a non-circular resting shape deforms into a multitude of shapes described by isolated solution branches. The computed two-dimensional buckled shapes are used to reconstruct the three-dimensional shape of a slowly collapsing fluid-conveying vessel. The reconstruction procedure involves stacking together cross-sections at axial positions that are found by integrating the differential equation determining the axial pressure distribution in unidirectional pressure-driven flow, subject to a constant flow rate. The dimensionless coefficient relating the local pressure gradient to the flow rate is computed by solving the Poisson equation governing unidirectional viscous flow using a boundary-element method, and expressing the flow rate as a boundary integral involving the shear stress which is available from the solution of the boundary-integral equation. In an appendix, the energy of the bending state is discussed with reference to specific choices made by previous authors in various branches of science and engineering.

A prototype of a fast cycle adsorption refrigerator utilizing a novel carbon—aluminium laminate

A laboratory prototype of a fast cycle adsorption refrigerator is presented: it uses a monolithic carbon-aluminium laminate adsorbent and ammonia refrigerant. The system has a high effective thermal conductivity and density bed and is powered by heat and designed to provide a specific cooling power up to 1 kW/kg adsorbent. There are two generators and each one consists of a tubular stainless steel shell containing a laminate of activated carbon discs and aluminium fins formed in situ. The full unit is designed for a power input up to 10 kW and a cooling power up to 3 kW. Preliminary results of the performance are presented and allow assessment of the intensification of heat transfer within the bed. At specific working conditions (evaporating and condensing temperatures, 7.5 and 32°C respectively; generating temperature, 140°C; half-cycle time, 620 s), the results have demonstrated the intensification of heat transfer within the generator through temperature and pressure profiles during the cycles. With an intrinsic heating power input of about 1.130 kW, the refrigerator produces continuously about 0.500 kW of cooling that corresponds to a specific cooling power of 0.180 kW/kg. The cooling coefficient of performance (COP) is about 0.44.

Damage Tolerance and Assessment of Foam-Inflated Aerospace Structures

Design and operational issues with respect to the use of inflatable-deployable foam-rigidized components in aerospace structures are investigated in this paper. The sample structures used in this study are fabricated from flexible Kapton film formed into a cylindrical shell by bonding a flat sheet along a longitudinal seam. This tubular shell is injected with a hardening urethane foam to form a composite strut coupon. As with all structures touted for aerospace use, the survivability of foam-rigidized structures when subjected to a micrometeor flux is of interest. This issue is investigated in this paper by performing two controlled experiments: (1) Foam-rigidized test coupons were evaluated in their pristine state to determine structural properties, severely damaged in a controlled fashion, and then evaluated again to compare the undamaged to damaged behavior; and (2) a single specimen was repeatedly tested and then slightly damaged to examine how structural behavior evolves as damage accumulates. The results of these experiments are then used to draw conclusions about the utility of foam-rigidized structures in space applications, including an evaluation of appropriate structural health monitoring strategies.

Unconfined membranes: Transfer performance and module design

The transfer performance and power requirements of unconfined sealed end hollow fiber membranes were studied. Membrane modules, operated in the sealed end mode, were pressurized with oxygen and placed within a submerged rectangular jet discharge. This design is especially well suited for use in waters containing high solids concentrations. The membranes have a greater degree of freedom for movement and are, therefore, less likely to become fouled due to solids being lodged within the fiber bundle. Furthermore, because the membranes are not enclosed within a tubular shell, head losses across the membranes are reduced. In a related study, Johnson et al. [1] developed a mass-transfer correlation for unconfined membranes similarly situated within a circular jet discharge. In this study, the mass-transfer correlation developed for circular jets is verified experimentally for larger rectangular module designs better suited for use in large scale applications. The headlosses across the modules are characterized in detail as a function of water flowrate and membrane spacing. These data are used to estimate the power requirements for different designs under a variety of operating conditions. The mass-transfer rates and corresponding power requirements for the unconfined configuration are compared with other membrane configurations.

Diffusive transport across unconfined hollow fiber membranes

The mass transfer characteristics of gas permeable, hollow fiber membranes in a liquid jet mixed reactor are studied. A membrane module, operated in the sealed-end mode, was pressurized with oxygen at the base of the fibers and centered within a submerged jet discharge. Unlike conventional membrane module designs, this configuration did not have the hollow fibers enclosed within a tubular shell. The membranes were unconfined and free to move within the generated flow field. This design is especially well suited for use in waters containing high solid concentrations. The membranes have a greater degree of freedom for movement and are therefore less likely to become fouled due to solids being lodged within the fiber bundle. Mass transfer rates were measured over a practical range of physical and process parameters. A mass transfer correlation for the unconfined configuration is presented and the transfer performance of this configuration is compared with conventional membrane contactor designs.