Hollow Plug Research Articles

Microstructure and Hardness of Hollow Tube Shells at Piercing in Two-High Screw Rolling Mill with Different Plugs.

AA6060 ingots were pierced in a two-high screw rolling mill (MISIS-130D) with guiding shoes (Mannesmann mill type). Three different plugs, i.e., a conventional entire plug, a plug with a cavity, and a hollow plug, were used for piercing. We established that the grain size decreases after piercing, by order of magnitude, compared to the initial non-pierced annealed bill, with a grain size of 100–400 μm, and the hollow shell grains are elongated along the piercing direction. The produced hollow shells had 30% higher hardness than the initial billet. The highest hardness values were obtained after piercing the conventional entire plug. The most uniform hardness distribution through the hollow shell’s volume was obtained after piercing the hollow plug. The cross and longitudinal section hardness measurements demonstrate that the hardness decreases from the outer surface to the inner surface of the hollow shells.

Computer Simulation of Mannesmann Piercing of Aluminium Alloy Ingots

The piercing of aluminium ingots (made by permanent mold gravity casting) is done in a Mannesmann rolling mill with supporting shoe using plugs of various shapes with a spherical working part: an entire plug, a plug with cavity, and a hollow plug. The calibrating segments of the plugs have identical diameters. The piercing is carried out at an ingot temperature of 400°C. The influence of the plug shape on the variation in the outer hollow shell diameter and wall thickness along the shell length, as well as shell density over the length, is investigated. Hollow shells were cut into 15 equal rings to measure density using hydrostatic weighing. Experimental investigations are simulated with the help of the finite-element method (FEM) computer software. Ingot fabrication by permanent mold gravity casting is simulated using the ProCAST software and piercing—using the QForm software. The variation in the hollow shell diameter, wall thickness, and shell density along the length is also evaluated by computer simulation. Experimental and simulation data are compared to verify the adequacy of acquired models in the QForm. The difference in density does not exceed 2% and, for hollow shell dimensions, 20%. These results make it possible to establish the influence of the piercing plug shape on the accuracy of the shells and their density. It is most preferable to use a hollow plug or a plug with a cavity from the viewpoint of dimension accuracy of fabricated shells. Each of these piercing schematics makes it possible to densify the entire hollow shell volume to the true density, except for the near-edge domains, where the density is lower by 1%.

FEM SIMULATION OF MANNESMANN PIERCING OF ALUMINUM ALLOY INGOTS

Mannesmann piercing of ingots, which were made of aluminum alloy by casting, was done using plugs of different shape: entire plug, plug with cavity and hollow plug. Plugs had same diameter of calibrating segment. Piercing was carried out at 400 °C ofbillets. Influence of plugs’ shape on variation of hollow shells’ diameter, wall thickness and density along their length was estimated. Hollow shells were cut into 15 equal rings to measure density using hydrostatic (Archimedean) weighing. Experimental operations were simulated using FEM computer software. Casting was simulated using ProCAST, piercing — using QForm. Variation of hollow shells’ diameter, wall thickness and density along their length was estimated after simulation had been done. Experimental and simulation data were compared to check FEM simulation accuracy. Difference between experiment and simulation for density was not more than 2 %, for hollow shells’ dimensions — 20 %. Conducted investigation allowed estimation of how plug’s shape affects hollow shells’ dimensions accuracy and density. It was established that hollow plug or plug with cavity, in terms of dimensions accuracy and density variation, are preferable for piercing. Each of plugs being used, provides manufacturing of hollow shells with maximum density for all volume except close to hollow shell’s edges domains, where density is 1 % less than maximum value.

Encapsulation of Homogeneous Catalysts in Mesoporous Materials Using Diffusion-Limited Atomic Layer Deposition.

The heterogenization of homogeneous metal complex catalysts has attracted great attention. The encapsulation of metal complexes into nanochannels of mesoporous materials is achieved by coating metal oxides at/near the pore entrance by diffusion-limited atomic layer deposition (ALD) to produce a hollow plug. The pore size of the hollow plug is precisely controlled on the sub-nanometer scale by the number of ALD cycles to fit various metal complexes with different molecular sizes. Typically, Co or Ti complexes are successfully encapsulated into the nanochannels of SBA-15, SBA-16, and MCM-41. The encapsulated Co and Ti catalysts show excellent catalytic activity and reusability in the hydrolytic kinetic resolution of epoxides and asymmetric cyanosilylation of carbonyl compounds, respectively. This ALD-assisted encapsulation method can be extended to the encapsulation of other homogeneous catalysts into different mesoporous materials for various heterogeneous reactions.

Encapsulation of Homogeneous Catalysts in Mesoporous Materials Using Diffusion‐Limited Atomic Layer Deposition

AbstractThe heterogenization of homogeneous metal complex catalysts has attracted great attention. The encapsulation of metal complexes into nanochannels of mesoporous materials is achieved by coating metal oxides at/near the pore entrance by diffusion‐limited atomic layer deposition (ALD) to produce a hollow plug. The pore size of the hollow plug is precisely controlled on the sub‐nanometer scale by the number of ALD cycles to fit various metal complexes with different molecular sizes. Typically, Co or Ti complexes are successfully encapsulated into the nanochannels of SBA‐15, SBA‐16, and MCM‐41. The encapsulated Co and Ti catalysts show excellent catalytic activity and reusability in the hydrolytic kinetic resolution of epoxides and asymmetric cyanosilylation of carbonyl compounds, respectively. This ALD‐assisted encapsulation method can be extended to the encapsulation of other homogeneous catalysts into different mesoporous materials for various heterogeneous reactions.

Mannesmann piercing of ingots by plugs of different shapes

The purpose of the research reported here was to establish how plug shape influences the size and porosity of hollow shells produced by Mannesmann piercing of an ingot. Ingots were cast from 6060 aluminium alloy and then pierced with a solid plug, a plug with a cavity or a hollow plug. Computer simulation of these processes was carried out using ProCast and QForm software and showed that a hollow plug should produce hollow shells with minimal porosity. However, the results of the experimental piercing revealed that the hollow plug in fact produced hollow shells with higher porosity than that of shells produced using either of the other two plugs. This appears to be consequence of the hollow plug losing stability.

FIXING DEVICE FOR CLOSING AND COUPLING AN INTRAVENOUS CATHETER

skin fixing devices in peripheral, central or arterial catheters have several important drawbacks: site infection, stacking of material in the anatomical area which is very annoying for the patient and medical staff risk when fixating stitches are used. to develop a fixing device that simplifies presently used systems, favoring asepsis and motility. the device herein described is composed by a mechanical fixation, a closing system and coupling for intravenous catheters. The system has a thin circular piece with at least two holes for subcutaneous fixation, one or several conducts for lumina and a hollow cylindrical part in one side, screwed exteriorly and flat inside, with an oriented protuberance. A watertight plug with one or several thin tubes that adapt to the lumina, a positional slot, a handle and a solid screwed tap for perfect closure are available for at home use. An intermediate plug with one or several lumina and a screwed hollow plug are provided for in hospital use. the above described device is intended to be used in two settings: in hospital and at home. It is supposed to reduce the risk of infection and stacking of the anatomical site where cutaneo us puncture with fixation of peripheral, central or arterial catheters is performed.

Compact modular in-the-ear hearing aid

A modular hearing aid for arrangement in a user's ear comprises a hollow plug (1) adapted to the ear canal and having a generally irregular conical shape and an exterior opening which is covered by a faceplate (2), in which a recess (8) is formed for removable arrangement of a battery (23) as well as an electronic module (4) comprising a microphone part (5), a signal processing part (6) and a sound reproducer (7). The recess (8) comprises a first region (9) for insertion of the battery (23) and a second region (10) coherent with the first region for placing of a socket part (11) of the electronic module (4), and at the edge of the recess (8) the faceplate (2) is formed with engaging means (12-16) for the socket part (11), whereas further parts of the electronic module (4) are placed below the faceplate (2). The recess (8) is formed such that at removal of the battery (23) the first and second regions (9, 10) together allow passage also of said further parts (6, 7) for removal of the complete electronic module.

Endothelium-dependent vasodilation in well-developed coronary collateral vessels.

We examined endothelium-dependent vasodilator responses in well-developed coronary collateral vessels. Collateral vessels and size-matched normal epicardial coronary arteries were isolated from canine hearts 6 months after a hollow plug had been introduced into the left anterior descending coronary artery (LAD) to stimulate collateral vessel growth. Vessel segments were isolated and studied in organ chambers. After preconstriction with prostaglandin F2 alpha, (PGF2 alpha) responses to the endothelium-dependent vasodilators, acetylcholine (ACh), substance P, and bradykinin (BK), as well as the endothelium-independent vasodilator nitroglycerin (NTG), were measured. The maximum relaxation to ACh was greater in collateral vessels (129 +/- 3.6% of the preconstricted tension) than in normal vessels (110 +/- 6.2%, p < 0.001), although the EC50 value for ACh was not significantly different between collateral and normal vessels. Collateral vessels demonstrated sensitivity to BK similar to that of normal vessels, but the maximal vasodilation achieved was greater in collaterals (138 +/- 4.6% of preconstricted tension) than in normal vessels (108 +/- 5.0%, p < 0.05). Both substance P and NTG produced dose-related relaxation that was similar in collateral vessels and normal arteries. These findings demonstrate that endothelium-dependent relaxation is intact in well-developed coronary collateral vessels.

Dose-Dependent Effect of Endothelin-1 on Blood Flow to Normal and Collateral-Dependent Myocardium

Plasma levels of endothelin-1 (ET-1) increase during ischemia and could potentially contribute to impairment of myocardial blood flow (MBF). Because collateral vessels demonstrate enhanced responsiveness to certain vasoconstrictors, blood flow to collateral-dependent myocardium could be particularly sensitive to increases in ET-1 levels. Studies were performed in 13 dogs in which collateral vessel development was produced by fluoroscopic embolization of the midleft anterior descending coronary artery with a hollow plug 4 to 6 weeks before the study. MBF was measured with radioactive microspheres at baseline and during 30-minute infusions of ET-1 (1, 10, and 100 ng/min) into the left main coronary artery. Because ET-1 stimulates endothelial prostacyclin release, aortic and coronary sinus levels of ET-1 and 6-keto-prostaglandin F1 alpha were measured at the end of each infusion. ET-1 increased MBF from 0.82 mL.min-1.g-1 at baseline to 0.92 mL.min-1.g-1 at 10 ng/min (P < .05), which corresponded to a coronary plasma concentration of 73 +/- 16 pg/mL. Blood flow in the collateral zone was less (0.74 mL.min-1.g-1) than in the normal zone (P < .05) and did not increase at an ET-1 dose of 10 ng/min. MBF in the normal and collateral zones significantly decreased when ET-1 was increased to 100 ng/min, corresponding to a coronary sinus concentration of 175 +/- 45 pg/mL (P < .05). ET-1 produced dose-related increases in aortic and coronary sinus 6-keto-prostaglandin F1 alpha and the transcoronary difference (P < .05). To assess the importance of prostacyclin in opposing the vasoconstriction produced by ET-1, additional studies were performed after cyclooxygenase blockade with indomethacin. After indomethacin administration, ET-1 (10 ng/min) caused a 120 +/- 23% increase in collateral vascular resistance (P < .05) and abolished the vasodilation that this dose produced in the normal zone. Blood flow to normal myocardium is increased at moderate plasma elevations of ET-1, whereas collateral blood flow is unchanged. Only at significantly elevated plasma concentrations of ET-1 is blood flow to normal and collateral-dependent myocardium impaired. Coronary endothelial production of prostacyclin in response to increasing concentrations of ET-1 represents an important means of blunting the vasoconstrictor properties of ET-1 in the canine coronary circulation. Coronary collateral vessels demonstrate a much greater dependence on prostacyclin production in blunting the vasoconstrictor properties of ET-1.

Effect of Calcitonin Gene-Related Peptide on Well-Developed Canine Coronary Collateral Vasculature

This study was performed to examine the effect calcitonin gene-related peptide (CGRP) on blood flow through well-developed coronary collateral vessels. Studies were performed in 9 adult mongrel dogs 4-6 months after embolic occlusion of the left anterior descending coronary artery (LAD) with a hollow intravascular plug to stimulate collateral vessel growth. At the time of study, the LAD was cannulated to determine inter-arterial collateral flow from measurement of retrograde blood flow. Radioactive microspheres were injected during retrograde flow collection to determine continuing tissue flow in the collateral dependent region. CGRP was infused into the left main coronary artery in a dose of 0.2 microgram/kg/min to reach collateral vessels originating from the left coronary system. Retrograde blood flow was 40 +/- 9 ml/min during basal conditions and increased 22 +/- 9% in response to infusion of CGRP (n = 9, p < 0.05). Tissue flow to the collateral-dependent myocardial region did not change in response to CGRP infusion. Isolated rings of epicardial collateral vessels contracted with prostaglandin F2 alpha (PGF2 alpha) underwent relaxation in response to CGRP which was similar in magnitude to that of normal coronary arteries of comparable size. These data demonstrate that CGRP causes vasodilation of well-developed epicardial coronary collateral vessels, resulting in an increase in collateral blood flow.

Vasomotor activity of moderately well-developed canine coronary collateral circulation

This study examined the ability of moderately well-developed coronary collateral vasculature to undergo vasoconstriction in response to alpha-adrenergic agonists, vasopressin and angiotensin, and vasodilation in response to nitroglycerin. Studies were performed in 20 dogs 4-16 wk after left anterior descending coronary artery occlusion had been produced by an Ameroid constrictor or hollow intravascular plug. Collateral flow was estimated from retrograde flow from the cannulated left anterior descending artery. Tissue flow was measured with microspheres. Agonists were introduced into the left main coronary artery to reach collaterals arising from the left circumflex and septal arteries. Vasopressin and angiotensin II decreased retrograde flow from 22.7 +/- 5.5 to 15.5 +/- 2.7 and from 19.2 +/- 2.8 to 14.3 +/- 1.9 ml/min, respectively (each P less than 0.05). Both agents also significantly decreased tissue flow to normally perfused and collateral dependent myocardium. Neither the selective alpha 1-adrenergic agonist phenylephrine nor the alpha 2-agonist B-HT 933 decreased retrograde flow. Nitroglycerin increased retrograde flow by 63 +/- 27% (P less than 0.01). Thus, although the moderately well-developed coronary collateral circulation is capable of vasoconstriction in response to vasopressin and angiotensin II, these data fail to support a role for alpha-adrenergic mechanisms in modulating collateral flow.

プレスロールピアサーせん孔におけるプラグ形状と素管の関係

プレスロールピアサーせん孔におけるプラグ形状と素管の関係

Contact pressure distribution in circular tube expansion using a conical plug

The technique of evaluating contact pressure distributions along a plug metal interface by measuring the deformations in terms of plug surface strains using electrical resistance strain gauges has been explored. To relate the unknown pressure distributions to the strain gauge readings, a finite element model of a plug was used assuming that the normal and shear pressures can be represented as a linear combination of generalized distributions, which have the form of polynomials up to the fourth order. This technique has been suitably applied to a thin brass tube expanding process for a single expansion ratio, and a single conical hollow plug with and without lubricant. To ensure good accuracy in the results, particular care was given to technological plug design and the choice of a number of appropriate strain gauged points on the inside surface of the plug. The more adequate polynomial representations of the normal and shear contact pressures were found by analyzing the degree of randomness in the distribution of the residuals. A comparison was made between experimental pressure distributions and those predicted by the slab method. Results obtained were compared with those derived from the use of a polynomial curve fitting method, besides assuming an average coefficient of friction at the interface.

Effect of geometry on pressure losses across models of arterial stenoses

The influence of geometric characteristics such as shape, length, and percent lumen area reduction on the pressure drop across an arterial stenosis is studied by means of an extensive series of in vitro steady-flow tests utilizing model constrictions in the form of blunt-ended hollow plugs. Results show that the pressure drop can be accurately predicted by a relatively simple equation. Extension of the results to shapes other than blunt plugs is also considered and shown to be possible. The pressure drop across multiple stenoses is investigated by considering two blunt plugs in series. Experimental data indicate that in general the pressure drop cannot be obtained by a symmation of pressure drops for single stenoses since the proximal and distal stenoses “interfere” with each other unless the spacing between them exceeds some critical distance which depends on the Reynolds number.

Experimental myocardial infarction in the closed-chest dog: Controlled production of large or small areas of necrosis

In order to embolize the coronary arteries a closed-chest technique was employed using fluoroscopically-positioned catheters introduced selectively into the coronary arteries. Plugs made of catheter material were extruded directly into the coronary lumen. Small alterations in the coaxial catheter system permitted the use of either hollow or solid plugs, with production of delayed or immediate coronary artery occlusions, respectively. With hollow plugs the mortality rate was 11 per cent. An average of 4 ± 2 per cent of the left ventricular cross-sectional area was infarcted. Solid plugs were associated with a mortality rate of 15 per cent and infarction of 20 ± 2 per cent of the left ventricle. Using this method it is therefore possible to create reproducible, controlled infarct sizes in dogs enabling a careful study of collaterals, ischemic myocardium, and therapeutic interventions.

Stability of α‐amylase in model brewery mashes

AbstractExperiments with model mashes, of partly purified malt α‐amylase added to a grist of ethanol‐extracted pale‐ale malt confirmed that decreasing the concentration of the mash or increasing mash temperature caused an acceleration in the rate of α‐amylase destruction. the experimental mashes were devoid of proteolytic activity and contained high levels of calcium ions. the mash temperature was below that needed to inactivate the enzyme in solution, so that the instability of the enzyme was unexpected. α‐Amylase was estimated by a convenient reducing power method using a reduced starch substrate, and ‘hollow plug’ accelerated ion exchange for the removal of interfering substances.

A “hollow plug” for the rapid removal of ions from small volumes of liquid

A “hollow plug” for the rapid removal of ions from small volumes of liquid