Effect of thickness of wall of polypropylene raschig rings and method of their manufacture on materials consumption of dumped mass-exchange packings

For external beam in vivo measurements, the dosimeter is normally placed on the patient's skin, and the dose to a point of interest inside the patient is derived from surface measurements. In order to obtain accurate and reliable measurements, which correlate with the dose values predicted by a treatment planning system, a dosimeter needs to be at a point of electronic equilibrium. This equilibrium is accomplished by adding material (buildup) above the detector. This paper examines the use of buildup caps in a clinical setting for two common detector types: OSLDs and diodes. Clinically built buildup-caps and commercially available hemispherical caps are investigated. The effects of buildup cap thickness and fabrication material on field-size correction factors, C(FS), are reported, and differences between the effects of thickness and fabrication material are explained based on physical parameters. Measurements are made on solid water phantoms for 6 and 15 MV x-ray beams. Two types of dosimeters are used: OSLDs, InLight∕OSL Nanodot dosimeters (Landauer, Inc., Glenwood, IL) and a P-type surface diode (Standard Imaging, Madison, WI). Buildup caps for these detectors were fabricated out of M3, a water-equivalent material, and sheet-metal stock of Al, Cu, and Pb. Also, commercially available hemispherical buildup caps made of plastic water and brass (Landauer, Inc., Glenwood, IL) were used with Nanodots. OSLDs were read with an InLight microStar reader (Landauer, Inc., Glenwood, IL). Dose calculations were carried out with the XiO treatment planning system (CMS∕Elekta, Stockholm) with tissue heterogeneity corrections. For OSLDs and diodes, when measurements are made with no buildup cap a change in C(FS) of 200% occurs for a field-size change from 3 cm × 3 cm to 30 cm × 30 cm. The change in C(FS) is reduced to about 4% when a buildup cap with wall thickness equal to the depth of maximum dose is used. Buildup caps with larger wall thickness do not cause further reduction in C(FS). The buildup cap fabrication material has little or no effect on C(FS). The perturbation to the delivered dose caused by placing a detector with a buildup cap on the surface of a patient is measured to be 4%-7%. A comparison between calculated dose and dose measured with a Nanodot and a diode for 6 and 15 MV x-rays is made. When C(FS) factors are carefully determined and applied to measurements made on a phantom, the differences between measured and calculated doses were found to be between ±1.3%. OSLDs and diodes with appropriate buildup caps can be used to measure dose on the surface of a patient and predict the delivered dose to depth dmax in a range of ±1.3% for 100 cGy. The buildup cap: can be fabricated from any material examined in this work, is best with wall thickness dmax, and causes a perturbation to the delivered dose of 4%-7% when the wall thickness is dmax. OSLDs and diodes with buildup caps can both give accurate measurements of delivered dose.

ABSTRACTThis paper is devoted to a further investigation on a range of externally pressurised egg-shaped pressure hulls. Hulls are 2.561 m long, 1.767 m wide, and have uniform wall thickness varying from 10 to 80 mm with 5 mm increment. Series of numerical simulations and laboratory scale experiments are performed to systematically study the buckling of egg-shaped pressure hulls, along with the effect of wall thickness on the buckling. Volume and mass equivalent spherical pressure hulls are also proposed to make a like-for-like comparison with egg-shaped pressure hulls. The results show that egg-shaped pressure hulls seem to be applicable to deep sea manned/unmanned submersibles, especially to full ocean depth ones (11,000 m). Also, deep pressure hulls tend to buckle in an elastic–plastic regime, which is strongly affected by the wall thickness.

Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): FWO-Flanders, KU Leuven internal starting grant Introduction and Purpose Cardiac electrograms (EGMs) are one of the most important recordings obtained during electroanatomical voltage mapping and lie at the basis for planning most clinical electrophysiological interventions. Despite its widespread use, the relation of EGM shape and amplitude to the underlying excitation patterns and properties of cardiac tissue is not completely understood. Recent clinical studies [1] have provided important new guidelines on the relation between EGM amplitudes and the thickness of myocardial walls. The aim of this study is to quantify the effect of the wall thickness on EGM amplitudes and duration using analytical and in-silico approaches. Methods We study bipolar EGMs both in-silico and analytically in a homogeneous slab of cardiac tissue (70 x 70 x L mm), where L = 2, 5, or 10 mm, with parallel fiber direction. Simulations were performed using the cardiac electrophysiology simulator openCARP [2]. Cardiac cells were described by the ten Tusscher-Panfilov 2006 model (TP06) [4] with epicardial tissue parameters. A plane wave propagating along the fiber direction was initiated. The extracellular voltage at 147 points arranged in a hemisphere around a point was measured to study the effect of bipolar electrode orientation (see Fig. 1A [3]). In addition, we developed an analytical approach to obtain an EGM, using an equivalent dipole representation of the depolarization wavefront and analytical evaluation of the corresponding integrals. Results Fig. 1B and 1C show the dependency of the EGM properties on the electrode orientation, as represented by the angles α (incidence angle) and β (angle between electrode and propagation direction) [3]. Solid lines represent data from a state-of-the-art numerical methodology, the dashed lines show our analytical estimations. Both the peak-to-peak amplitude and EGM width are well approximated by our theory for all orientations of the electrodes. Fig. 2 shows how the EGM is influenced by the myocardial wall thickness L. Both the amplitude and the duration are in good agreement with our theory. We observe that the amplitude as well as the width increase with the slab thickness, confirming the result in [1] but also delivering an accurate analytical expression for this change. It may thus allow to discriminate effects of thickness and other factors affecting the EGMs, such as substrate abnormalities, for example. Conclusion We developed an analytical approach which can correctly describe the amplitude, duration, and shape of the depolarization part of the EGM. Our theory agrees with the previous in-silico and clinical studies on the influence of catheter orientation [3,5], and wall thickness [1,3]. Subsequent work in this direction is expected to provide better guidelines for clinical interpretation of EGMs, accounting for the effects of the thickness of myocardial wall in the characterization of the substrate of cardiac arrhythmias.

In this work, a particle‐resolved computational fluid dynamics model of the acetylene hydrogenation process is developed to investigate the effects of catalyst particle structures on the reaction–diffusion behaviors aiming to improve selectivity toward target ethylene. The effects of packing structures on mass and heat transfer are explored by employing particles with varying shapes, wall thicknesses, and external diameters. The simulation results reveal that decreasing diffusion paths and elevating reactor bed temperature will enhance ethylene selectivity, and cylinder and Raschig ring packing structures exhibit the lowest and highest ethylene selectivity of 35.6% and 48.9% at 70% of acetylene conversion, respectively. Reducing wall thicknesses of Raschig ring particles facilitates the diffusion of generated ethylene from the interior zone of catalysts but concurrently inhibits the conversion of acetylene to ethylene. The Raschig ring catalyst particle with 1.9 mm of wall thickness and 3.5 mm of external diameter is finally revealed to exhibit the highest ethylene selectivity.

In this study, we analyzed the coupling effect of laser scanning speed and wall thickness on the phase transformation behavior and tensile properties of selective laser melted NiTi thin-wall structures. It is demonstrated that either scanning speed or wall thickness has their respective influence rule, whereas this influence could be changed when coupling them together; that is, under different scanning speeds, the effect of wall thickness could be different. It is found that the deviation of phase transformation temperature among different wall thicknesses is ~3.7 °C at 400 mm/s, while this deviation increases to ~23.5 °C at 600 mm/s. However, the deviation of phase transformation peak width among different wall thicknesses shows little change under different scanning speeds. At low scanning speed, the samples with thicker wall thickness exhibit better tensile ductility than thinner, whereas they all show poor tensile properties and brittle behavior at high scanning speed. This uncertain influence rule is mainly due to the interaction effect between different thermal histories generated by wall thickness and scanning speed.

Characteristics of microjet hydrogen diffusion flames stabilized near extinction are investigated numerically. Two-dimensional simulations are carried out using a detailed reaction mechanism. The effect of burner wall material, thickness, and thermal radiation on flame characteristics such as flame height and maximum flame temperature are studied. Results show that the flame stabilizes at lower fuel jet velocities for quartz burner than steel or aluminum. Higher flame temperatures are observed for low conductive burners, whereas the flame length increases with an increase in thermal conductivity of the burner. Even though thermal radiation has a minor effect on flame characteristics like flame temperature and flame height, it significantly influences the flame structure for low conductive burner materials. The burner tip and its vicinity are substantially heated for low conductive burners. The effect of burner wall thickness on flame height is significant, whereas it has a more negligible effect on maximum flame temperature. Variation in wall thickness also affects the distribution of H and HO2 radicals in the flame region. Although the variation in wall thickness has the least effect on the overall flame shape and temperature distribution, the structure near the burner port differs.

In order to analyze the effect of vascular wall structures on static and dynamic mechanical properties of vascular grafts, small calibre PHBHHx (Poly(3-hydroxybutyrate-co-3-hydroxhexanoate)) vascular grafts (inner diameter 6 mm) with various wall shapes and thicknesses were fabricated by changing electrospinning time and receiving molds. As spinning time increased, wall thickness of the vascular grafts increased and both circumferential tensile strength and suture retention strength improved significantly. When the wall thicknesses of straight grafts were about 120 μm, the great radial dynamic compliance was exhibited, however, the tensile strength and suture retention strength of the straight tubes can’t reach the requirements of normal blood vessel grafting. With the wall thicknesses increasing above 250 μm, although the circumferential tensile strength and suture retention strength gradually achieved the transplanting requirements, the dynamic compliance of the straight tubes declined too sharply to adapt the blood radial shock. For corrugated grafts, the effect of wall thickness on radial dynamic compliance was little, and the radial dynamic compliance was close to that of the commercial vascular grafts. The circumferential tensile strength and suture retention strength of the corrugated grafts were also improved to approach the commercial vessels’ performances with the wall thickness improving to about 425 μm. Elastic recovery rates of all the prepared vascular grafts were superior to that of the commercial sample. Along with the wall thickness exceeding 250 μm, the water permeabilities of both the straight and the corrugated grafts were less than 300 ml/(cm2·min).

Effect of build orientation and layer thickness on manufacturing accuracy, printing time, and material consumption of 3D printed complete denture bases

In physiology, blood vessel function is maintained mainly through nitric oxide (NO)-mediated cross-talk between endothelial cells (ECs) and smooth muscle cells (SMCs), which is compromised in pathology. Lack of an appropriate in vitro model hampers the study of vascular disease progression mechanisms. This study attempted to use tissue engineered blood vessel (TEBV) as a model system to understand the effect of wall thickness and shear stress on EC to SMC communication. Differentiated ECs and SMCs obtained by in vitro culture of sheep peripheral blood mononuclear cells (PBMNCs) were seeded on biodegradable €-polycaprolactone (PCL) conduits of different wall thicknesses and exposed to shear stress in a two-channel bioreactor to construct functional TEBV. Phenotypes of ECs and SMCs were studied in terms of nitric oxide synthase (eNOS) and basic calponin expressions respectively, using real time polymerase chain reaction. Endothelial to SMC cross-talk under the influence of wall thickness and shear stress was interrelated to NO and cyclic GMP (cGMP) production. Shear stress accelerates, but wall thickness has no influence on endothelial NO production. Increased release of NO in response to shear stress resulted in augmented cGMP production, but only when the wall thickness was lower. Both wall thickness and shear stress affect cGMP production and smooth muscle contractile phenotype. From this study, it is also suggested that TEBV may be a suitable model to study various risk factors on vessel integrity. Keywords: Blood vessel wall thickness, cGMP synthesis in SMC, endothelial nitric oxide synthetase, functional tissue engineering, nitric oxide synthesis, shear stress, tissue engineered blood vessel.

Effects of fiber orientation and wall thickness on energy absorption characteristics of carbon-reinforced composite tubes under different loading conditions

Combined effect of secondary dendrite orientation and wall thickness on creep behavior of a Ni-base single crystal superalloy

Additively manufactured IN718 in thin wall and narrow flow channel geometries: Effects of post-processing and wall thickness on tensile and fatigue behaviors

Effects of wall's insulation thickness and position on time lag and decrement factor

The reflection and transmission coefficients of waves due to perforated wall are mainly determined by both the porosity and wall thickness of the perforated wall and the period and nonlinearity of incident waves. Among them the wall thickness is very important because it affects the head loss coefficient and the inertia length of the wall. However, by employing the head loss coefficient derived for sharp crested orifice, the previous researches have neglected, or incorrectly considered the effect of wall thickness on the head loss coefficient. Even though it is considered, the effect of the inertia length is neglected in some empirical formulae. Thus, the effect of wall thickness on the reflection and transmission coefficients of waves is not properly considered. In this study comprehensive experiments are conducted for the perforated walls with various thicknesses, and the results are compared with those predicted by the empirical formulae. As a result it is found that the existing formulae can not properly consider the effect of wall thickness, and it is confirmed that a new formula which can correctly consider the effect of wall thickness on the head loss coefficient is necessary.

Conjugate heat transfer is a coupled, fluid-structure, heat transfer problem where heat conduction in a solid wall interacts with heat convection in adjacent fluid flow. This paper examines numerically the conjugate conduction-free convection heat transfer in an annulus between two concentric cylinders. The annulus contains Newtonian fluid and is heated isothermally from its inner wall. The full governing equations of momentum and energy have been solved by using Fourier spectral method to give the details of flow and thermal fields. The effect of Rayleigh number, thermal conductivity ratio between solid inner wall and adjacent fluid and thickness of inner wall on heat transfer rate (in terms of Nusselt number) within the annulus has been examined through numerical experimentation. The heat transfer through concentric annulus increases as the thermal conductivity ratio increases. The study has also shown that the effect of inner wall thickness on heat transfer through concentric annulus depends upon the thermal conductivity ratio and Rayleigh number. For thermal conductivity ratio less than one the increase of inner wall thickness decreases the rate of heat transfer. While for thermal conductivity ratio bigger than one the increase in inner wall thickness will increase or decrease the heat transfer through concentric annulus depending upon Rayleigh number and radius ratio of the annulus.