Support Columns Research Articles

The Vacuum Mires of the Transit Instrument at Nikolaev

At Nikolaev, in 1978, a system for the improvement in the stability of the light path between the transit instrument and the meridian mires was designed. Its purpose is to improve the accuracy of the azimuth determination and that of the collimation. This system consists of twelve sections of 8 mm thick steel tube with 160 mm diameter, each nine meters long. These tubes are lying in special steel cradles which rest on brick support columns spaced 8 meters apart, and these can be moved vertically and horizontally by 100 mm and 50 mm, respectively. Thus it is possible to align the axis of the tube exactly.

Homogenized model for fluid-structure interaction of the pressurized water reactor core internals during blowdown

A method for the numerical simulation of the pressurized water reactor core internal's behaviour during a blowdown accident is described, by which the motion of the reactor core and the interaction of the fuel elements with the core barrel and the coolant medium is calculated. Furthermore, some simple models for the support columns, lower and upper core support and the grid plate are provided. In order to investigate the global core motion during the blowdown accident, the core model describes the coupled fluid-rod motion with Homogenization methods. The heterogeneous fluid-rod mixture thus is treated as a special continuum with anisotropic material properties. Furthermore, the core model considers elastical rod forces against bending and axial straining and the direct interaction of neighbouring fuel elements, which is a highly nonlinear process due to the finite gaps. Because this effect is very important, two simulation models have been developed and are compared. All these models have been implemented into the blowdown code FLUX-4. With the new code version FLUX-5 the PWR-blowdown is parametrically investigated.

Influence of AC Source Parameters on Flashover Characteristics of Polluted Insulators

The paper comprises a systematic experimental investigation into the influence of AC test source parameters on the leakage current pulses, voltage fluctuations and flashover voltages of polluted insulators. The test techniques include both salt-and clean-fog methods, while the test insulators comprise long-rod and cap and pin strings of different lengths as well as support columns.

Fracture healing assessment with external fixation.

The increased use of external fracture fixation has brought a need for improved methods of assessing bone healing while the fixator is still in place. In this paper, a method using a strain gauge transducer clamped to the support column of the Oxford External Fixator is considered. Experimental strain gauge data are found to agree very closely with the theoretical analysis for a range of fracture stiffnesses, and to provide a useful measure of progressive bone healing. Bone pin loosening during the course of fracture healing is shown to have a significant effect on the assessment, typically decreasing the strain gauge data by 20 per cent for one loose pin and by 55 per cent for two loose pins. The effects are such that pin loosening could erroneously be interpreted as increased fracture stiffness. Methods are given for correcting the strain gauge data to account for loose pins.

In vitro Isolation of Plasmodium chabaudi Merozoites by Continuous Flow Ultrasound, Cell Sieving, Concanavalin A-Affinity Chromatography and Poly-L-Lysine Coated Bead Support Columns

Techniques of merozoite isolation based on continuous flow ultrasound, cell sieving, Concanavalin A-affinity chromatography and cationically charged bead support columns were compared using the rodent malaria parasite, Plasmodium chabaudi. While each technique proved useful in isolating merozoites in reasonable numbers, the use of Con A-Sepharose 4B columns consistently provided the greatest numbers which were free of host cell contaminating membrane material and which were invasive to cells both in vivo and in vitro. In addition, Con A-Sepharose columns could be regenerated using alpha methyl-D mannoside. These results, when considered in light of merozoite isolation procedures used for other malarial species, indicated that the host-parasite model system had a bearing on which merozoite isolation technique was most likely to be successful.

Grimsby bridge pier piles provide composite foundation and support columns : Ground EngngV17, N2, March 1984, P18–21

Grimsby bridge pier piles provide composite foundation and support columns : Ground EngngV17, N2, March 1984, P18–21

Discussion on ‘An analysis of secondary toppling rock failures—the stress distribution method’ by R. S. Evans

M. D unbavan writes: Evans used the assumption of two discrete basal support columns of different moduli in developing his stress distribution equations. An alternative assumption is that the Young's modulus varies continuously across the base of the column and the following equations were derived for a linear variation. The general form of the linear relationship for Young's modulus, E , is: where x is the distance from the inside edge of the column towards the free face along the base (see inset of Fig. 1) and E 0 is the value at the inside edge of the column. In comparing the variation of modulus with the two discrete values used by Evans, two interpretations for the value of m arise as shown in Fig. 1. One case assumes that the moduli for the two columns are the values at each end of the base, giving: The second case assumes that the moduli for the two columns are average values for the half base width, giving: The stress distribution across the base for linear variation in settlement then becomes: with the notation being the same as that used by Evans. Using integration methods with the independent variable x , vertical force and moment equations when solved yield: and For For Evans' data was used for calculations so that a comparison of results could be made: and the values are given in Table 1 The first interpretation for the linear variation of Young's modulus is more practical, indicating that any other functional would best be

Buckling and post-buckling behavior of the ACS support columns

Computer program development and modeling procedures for above-core structures (ACS) have recently focused on modeling the buckling and post-buckling behavior of the ACS support columns. These developments are directed toward two considerations: (1) the prediction of the forces exerted by the column in a hypothetical core-disruptive accident (HCDA) in order that the motion of the ACS can be predicted in a coupled fluid-structure analysis, (2) the calculation of the strains and deformations of the support columns so that situations which lead to complete failure can be identified. One of the aims of this study was to examine the effect of the change in cross section, previously not treated, on the behavior of the support columns. For this purpose, models have been developed in which the portions of the column which undergo significant changes in cross section are modeled by plate elements. Results are presented for two sets of studies. In the first set, results are presented for a series of Stanford Research International scale model tests. Comparison of the tests with the computed results shows reasonable agreement. In the second, the column was displaced with a constant velocity at one end to examine its resistance as a function of displacement. The behavior of support columns consisting of two concentric cylinders has also been studied. The interesting feature of this design is that when one of the cylinders buckles, it moves laterally against the other, which may not have buckled. An effective but simple model was developed for representing the interaction between the columns. Results are presented for an HCDA corresponding to a release of 1000 MJ.

Core support columns in the upper plenum of a pressurized water reactor under blowdown loading: I. Two-dimensional analysis, assessment of essential simplifications.

A sudden and complete break is assumed close to the outlet nozzle of a pressurized water reactor and the accelerating flow is calculated within a slice taken from the upper plenum. The slice includes sections of the core support columns. An advanced boundary integral method is used for solution. Some results are checked by shallow water experiments. Based on the calculated pressure field, the transient loadings and deflections are determined for the sections of the core support columns. As an essential result, the fluid compressibility is found to be unimportant for calculation of the maximum structural response of the core support columns. This finding provides the basis for a three-dimensional analysis in part II of this paper. In addition, also the influence of other important assumptions and simplifications has been studied by several parameter variations.

Core support columns in the upper plenum of a pressurized water reactor under blowdown loading: II. Three-dimensional analysis, calculation of deformations and stresses

A sudden and complete break is assumed close to the outlet nozzle of a pressurized water reactor and the accelerating flow is calculated within the three-dimensional space of the upper plenum. The closely spaced core support columns are treated as fluid boundaries. From the pressures acting on these boundaries the transient loadings, deflections and bending stresses in the columns are determined. Also the stresses in the complex feet constructions of the columns are investigated. Important assumptions have been checked in part I of this paper. The results show that in general the columns are able to withstand even severe blowdown loadings. Furthermore it may be concluded that under certain conditions a two-dimensional flow analysis is sufficient. However, consideration of only one depressurization wave propagating through the upper plenum may be insufficient.

Stacking of high-voltage resistance dividers

Stacking of high-voltage resistance dividers, especially if the support columns are made from different materials, can lead to errors in the division ratio. An expression for the error introduced by leakage currents is presented and some values are given for a typical case.

Observations on the Root Anatomy of Rice (Oryza sativa L.)

Rice plants were grown hydroponically and roots were prepared for light and electron microscopy using standard techniques. The roots are bounded by an epidermis, exodermis, and fibrous layer. The exodermis has a suberin lamella along its inner tangential wall. The fibrous layer is composed of thick-walled lignified cells with little pitting. The cortical parenchyma is compact when young, but expands and separates to form a zone of cell walls and air spaces in a spoked arrangement. Supporting columns of living parenchyma cells are occasionally present, particularly near lateral roots. The endodermis is typical for grasses with Casparian strips, suberin lamellae, and tertiary state walls with numerous pits. The pericycle and pith become sclerified. Protoxylem elements alternate with protophloem in the young root; later, early metaxylem, late metaxylem, and metaphloem proliferate. The exodermis, fibrous layer, lacunate cortex, and endodermis appear to present a formidable barrier to radial ion movement in the mature portions of the root.

OBSERVATIONS ON THE ROOT ANATOMY OF RICE (ORYZA SATIVA L.)

Rice plants were grown hydroponically and roots were prepared for light and electron microscopy using standard techniques. The roots are bounded by an epidermis, exodermis, and fibrous layer. The exodermis has a suberin lamella along its inner tangential wall. The fibrous layer is composed of thick‐walled lignified cells with little pitting. The cortical parenchyma is compact when young, but expands and separates to form a zone of cell walls and air spaces in a spoked arrangement. Supporting columns of living parenchyma cells are occasionally present, particularly near lateral roots. The endodermis is typical for grasses with Casparian strips, suberin lamellae, and tertiary state walls with numerous pits. The pericycle and pith become sclerified. Protoxylem elements alternate with protophloem in the young root; later, early metaxylem, late metaxylem, and metaphloem proliferate. The exodermis, fibrous layer, lacunate cortex, and endodermis appear to present a formidable barrier to radial ion movement in the mature portions of the root.

Strain Field Response of 0° Glass/Epoxy Composites Under Tension

As part of a general effort to study the development of damage in fiber-reinforced composite materials, the method of moiré interferometry is being applied to specimens under tensile load to examine the strain field on one face of the specimen and thereby reduce displacements in underlying plies. A 600-line/mm silicone rubber diffraction grating is bonded directly to the surface of the specimen. A virtual reference grating is formed in space parallel to this active grating and a pattern of interference fringes representing lines of constant displacement is observed. The required optical elements shown in Fig. 1 are attached to a rigid plate which is in turn attached to the support columns of an MTS testing machine.

Variables in the high-performance anion-exchange chromatography of proteins

The effect of mobile phase velocity, separation time, support pore diameter, column length, and temperature on resolution and loading capacity of a new commercially available high-performance anion-exchange support, SynChropak AX-300, has been examined. This material is a macroporous spherical silica of 10 μm particle size with a bonded polymeric amine layer. It was found that the heterogeneity of ovalbumin samples, combined with bovine serum albumin, make them useful probes in evaluation of anion-exchange supports. In the columns of 4.1 mm i.d., the highest resolutions of proteins were achieved at a flow rate of 0.25 ml/min. Up to 10 mg of protein per injection could be applied on a 4.1 × 250 mm AX-300 column with good resolution. Columns of 50 mm length had one-tenth the protein load capacity of a 250-mm column, retaining approximately 75% of the resolution.

Characterization of Some Commercial High Performance Size-Exclusion Chromatography Columns for Water-Soluble Polymers

Test procedures for characterizing size-exclusion chromatography (SEC) columns utilizing molecular probes of various sizes are described. Studies with several commercially available SEC columns showed that under certain conditions they exhibited ion exclusion, cation exchange, and hydrophobic partitioning. These nonpermeation effects were minimized by using mobile phases with ionic strengths between 0.10 and 0.60 M at pH 7.0$. Deuterium oxide was found to be the most suitable probe for the determination of total permeation volume (VT), while the UV absorbing nucleoside monophosphatee and glycyltyroslne were also acceptable on most columns. An equation was derived which allowed the determination of SEC resolution by using the elope (m) of the molecular weight calibration curve, pore volume (Vi), and theoretical plates (N) for a particular sample. Resolution was expressed in terms of the minimum molecular weight ratio (RM) necessary for two components to be resolved on the column. A series of commercial SEC columns was subjected to the described protocol which compared support characteristics and column efficiency. Column characteristics and performance data are reported that serve as a guide to their optimization for use In the strict SEC mode and as a reference for further column development.

Analysis of primary containment response with upper internal structure

In the fast reactor containment the upper internal structure is a massive structural component located in the region above the core. The main body of this structure consists of four support columns, an upper plate and a lower plate holding numerous coolant passageways for directing the core sodium to the outlet plenum. The aim of this paper is to provide hydrodynamic analysis of the fluid motion in the above core region and to study the effect of the upper internal structure on the slug impact as well as the primary system response. At ANL, two excursion containment codes, ICECO and ALICE, are chosen for such an analysis. These two codes, based on the ICE technique and ICED-ALE method, respectively, are ideal for analyzing flow through coolant passageways and flow blockage near the bottom plate. They also have other advantages, such as: (1) treating fluid motion around internal structure with geometrical discontinuities; (2) investigating excursions with large distortions; (3) handling two-dimensional sliding conditions; and (4) providing a stable solution throughout the entire excursion. In both ICECO and ALICE the upper internal structure can be modelled by rigid obstacles similar to the scheme used in the MAC method. The coolant passageways can be approximated by means of narrow cells. Another option is provided in the ICECO code in which the upper internal is considered as a perforated structure. In this model large cells can be used over the entire computational region. The analysis utilizes a control-volume technique to solve the conservation equations of mass, momentum, and energy. The basic idea is to use the actual fluid volume and the actual flow area in the mathematical formulation. Three modified Poisson equations are derived which govern the hydrodynamic pressures inside, above, and below the perforated structure. These three equations, in conjunction with the Poisson equation of the ICE technique as well as the relaxation equation at the moving boundary, are solved iteratively. Two sample problems are given. The first one deals with the ICECO analysis of primary containment response to an HCDA. The effect of the upper internal structure on the wave propagation and slug impact are investigated. The second example presents a simulation of SRI complex vessel experiments using the Alice code. The results are discussed in detail.

Formulation and application of a three-dimensional structural model for upper internal structures

A finite element structural model is developed for the upper internals which is capable of treating material nonlinearities and geometric nonlinearities arising from large displacements when subjected to dynamic loads. This structural model can be used either by itself or in an interactive mode with a hydrodynamics code. The upper internal structures which are located above the core and below the head cover may play a significant role in the hydrodynamics of an energy excursion by mitigating its response. The upper internal structure (UIS) is essentially a massive, perforated rigid body which is connected to the reactor head by support columns with a cylindrical cross section. The major response of interest is the buckling of these support columns which results from the compressive forces they sustain when the upper internals are loaded vertically upward by dynamic loads. In addition to buckling, these columns sustain plastic deformations and changes in cross section making geometric and material nonlinearities accountable. For the case of substantial change in the shape of the column cross section, it will be more convenient to treat the behaviour of the elements stiffness in terms of moment-curvature relations which account for the changes in flexural rigidity with change in cross section. Two factors considered of importance in developing the model are: (1) whether an imperfection is necessary in the initial mesh of the columns to trigger buckling and to what extent does the magnitude of the imperfection effect the results; (2) whether the buckling pattern is symmetric or asymmetric. It was established by these studies that elastic buckling is not affected by the magnitude of the imperfection; for plastic buckling, the results are more sensitive to the magnitude. The studies also showed that the UIS mass is sufficiently large so that it cannot be laterally displaced. By checking the deformed shape, it was observed that the column always attempts to reach the symmetric buckling mode. Even if the asymmetric shape is triggered, it is always at a load higher than that required to trigger a symmetric response. The behavior of the model has also been compared with the SRI tests simulating highly energetic CDAs. The model predicts the magnitude of the axial deflection quite well.

Die Vaskularisation der Kiemen von Myxine glutinosa L. (Cyclostomata)

The angioarchitecture of the gills in Myxine glutinosa L. was studied by scanning electron microscopy of vascular corrosion casts (methylmethacrylate). It was found that the afferent branchial artery may be connected to the sinus peribranchialis by a papilla. The sinus is connected to delicate vessels and sinuses, which are interposed between meridionally arranged radial arteries. These delicate vascular formations continue into the interior of the gill and form a plexus on both poles of the gill folds. Light and scanning electron microscopical studies on the vascular endothelium of the afferent vessels of the gill lamellae reveal rounded endothelial cells, which are characterized by a high content of granula, by long cellular processes and by bridge‐formations towards neighbouring cells. Supporting columns within the vascular system of the lamellae were found to be set up by several spirally arranged cells. SEM observations reveal goblet cells and numerous superficial epithelial cells with various numbers of microvilli and microridges forming the epithelial surface of the gill folds.

A method for gene enrichment based on the avidin-biotin interaction. Application to the Drosophila ribosomal RNA genes

A method of enriching, from the total DNA of an organism, for long DNA strands carrying a particular gene is described. The purified RNA corresponding to the gene is covalently attached to biotin via a cytochrome c bridge. This modified RNA is hybridized to the total DNA. Those DNA strands which hybridize are separated from all the other DNA, using the avidin-biotin interaction, by one of two methods. Avidin is covalently attached to submicroscopic polymer spheres; the complexes of avidin spheres with the DNA: RNA-biotin hybrids band in CsCl at a much lower buoyant density than does free DNA. Alternatively, the DNA:RNA-biotin hybrids are isolated by affinity chromatography on an avidin-solid support column. These methods have been used to prepare long single strands of Drosophila ribosomal DNA (rDNA) in high yield and 42 to 80% pure.