Segmented Cylinders Research Articles

Determination of 3D pore network structure of freeze-dried maltodextrin

This article describes and discusses the determination of the pore network structure from X-ray microcomputed tomography images of freeze-dried maltodextrin based on image processing. Maltodextrin is used because of its relevance for research and pharmaceutical applications. Image processing is based on conventional methods for image filtering and binarization, which are specifically the Gaussian filter, anisotropic diffusion filter, and Otsu thresholding as well as adaptive thresholding. It is shown, that the combination of the different image processing methods has only a minor impact on the final results of the estimated porosity. More critical is the segmentation of the overall void space into individual pores using the watershed algorithm, especially if the markers of the Euclidean distance map are not accurately defined. Oversegmentation of the void space into too many small pores was obviated by the use of a Gaussian smoothing filter on the Euclidean distance map. The approximation of the structure by spherical or cylindrical geometrical objects was addressed in further discussions as an essential step for the determination of the mathematical pore network model. It was found that the choice of the specific geometrical object has a major impact on the final pore size distribution of the generated pore networks. For the case of maltodextrin, with long and narrow pores, the approximation by segmented cylinders, replacing the individual pore subvolumes, yields the best agreement. The computed pore network structures are further investigated in regard of the correlation of vapor transport regimes and structure variation. It is shown that the small differences obtained from the various combinations of image processing and network reconstruction methods have a negligible impact if temperature and pressure are low (T = −18 °C, P = 10 Pa) and constant.

Simple phantom fabrication for MRI‐based HDR brachytherapy applicator commissioning

A new high dose rate (HDR) brachytherapy program was initiated in a community hospital setting, with the goal of using magnetic resonance (MR) images with the implant in place during the planning process. Physics acceptance testing and commissioning was completed for key program components, including multiple applicators. To image new applicators for MRI‐based planning prior to use with patients, agar gel doped with copper sulfate was created using simple, MR‐safe household materials as a practical and inexpensive alternative to custom‐machined precision phantoms. Applicators in‐phantom were scanned in a 1.5 T MRI scanner using the same sequences developed for the brachytherapy program, then rigidly registered to high‐resolution computed tomography (CT) images to assess distortion, artifact, and geometric displacement. To date, Varian tandem and ring sets, segmented cylinders, cervical probes, endometrial applicators; and third‐party plastic needles, tandems, and vaginal guides have been imaged in phantom and are available for use clinically.

Evaluating transducer bandwidth and effectiveness on overall acoustic system performance

Piezoelectric ceramic cylindrical transducers are used extensively for underwater acoustic communication applications on mobile platforms (UUVs). Employing piezoelectric single crystals, used in either fully-active or active-passive segmented cylinders, in the transducer design has the potential to increase the usable bandwidth while reducing the overall size and weight of the device. In some instances, one single crystal transducer may replace several ceramic transducers and reduce the number of hardware channels. The impact on acoustic system design (power amplifier, matching transformer, and tuning network) for several piezoelectric ceramic and single crystal cylindrical transducer technologies is modeled and supported with measured transducer data.

Two‐ and Three‐Dimensional Liquid‐Crystal Phases from Axial Bundles of Rodlike Polyphiles: Segmented Cylinders, Crossed Columns, and Ribbons between Sheets

Two‐ and Three‐Dimensional Liquid‐Crystal Phases from Axial Bundles of Rodlike Polyphiles: Segmented Cylinders, Crossed Columns, and Ribbons between Sheets

Two‐ and Three‐Dimensional Liquid‐Crystal Phases from Axial Bundles of Rodlike Polyphiles: Segmented Cylinders, Crossed Columns, and Ribbons between Sheets

Stabförmige Mesogene (siehe Schema) mit Schwalbenschwanz-artigen Seitenketten ordnen sich axial zu bänderförmigen Bündeln an. Bei hoher Temperatur rotieren die Bänder unter Bildung einer neuartigen hexagonalen 3D-Flüssigkristallphase (siehe Bild, links). Bei niedrigerer Temperatur stoppt die Rotation, und man erhält eine Struktur aus gekreuzten aromatischen und fluorierten Säulen (rechts). Bei weiterer Abkühlung fusionieren die Bänder zu Flächen mit interkalierten fluorierten Säulen. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Analysis of the piezoelectric properties of tangentially polarized, stripe-electroded cylinders

The electromechanical properties of thin tangentially polarized, stripe-electroded piezoceramic elements are considered. Theoretical analysis is made based on a piecewise linear approximation of the actual nonuniform electric field in the volume of the stripe-electroded cylinder design. Analytical expressions are derived for the electromechanical properties (including the effective coupling coefficient) of the tangentially polarized elements as a function of the geometry and electrode configuration (i.e., electrode width and spacing). The properties of stripe-electroded cylinders are calculated and compared with the ideal case of a uniform circumferential electric field, which may be realized in practice with segmented cylinders comprised of 33-polarized bar elements. The reasons for the reduction in the effective coupling coefficient of tangentially polarized stripe-electroded cylinders compared to the ideal coupling coefficient k(33) achievable with the segmented cylinder designs are discussed. The results of calculations of the electromechanical properties are in good agreement with experimentally obtained data on a variety of samples.

ABC triblock copolymer hamburger-like micelles, segmented cylinders, and Janus particles

An ABC linear triblock copolymer with a carboxyl-containing terminal C block and a photocrosslinkable middle B block was synthesized and characterized. In a poor solvent for the B block and in the presence of a diamine, (−)-sparteine, which complexed with the C block and made it insoluble, the triblock copolymer self-assembled into hamburger-like micellar aggregates and segmented cylinders. In a “hamburger”, the “buns” were made of the B block, the filling was made of the complexed C block, and the soluble A chains stretched out from the bun surface into the solvent phase. The main body of the segmented cylinders was made of stacking alternating B and C stubs. The cylinders were dispersed in solvent by the A chains stretching out from the surfaces of the B stubs. After the photocrosslinking of the buns of the hamburgers and the removal of (−)-sparteine by dialysis, we were able to separate the buns of the hamburgers to yield presumably Janus particles.

Three-dimensional vibrations of cylindrical elastic solids with V-notches and sharp radial cracks

This paper provides free vibration data for cylindrical elastic solids, specifically thick circular plates and cylinders with V-notches and sharp radial cracks, for which no extensive previously published database is known to exist. Bending moment and shear force singularities are known to exist at the sharp reentrant corner of a thick V-notched plate under transverse vibratory motion, and three-dimensional (3-D) normal and transverse shear stresses are known to exist at the sharp reentrant terminus edge of a V-notched cylindrical elastic solid under 3-D free vibration. A theoretical analysis is done in this work utilizing a variational Ritz procedure including these essential singularity effects. The procedure incorporates a complete set of admissible algebraic–trigonometric polynomials in conjunction with an admissible set of “ edge functions” that explicitly model the 3-D stress singularities which exist along a reentrant terminus edge (i.e., α>180°) of the V-notch. The first set of polynomials guarantees convergence to exact frequencies, as sufficient terms are retained. The second set of edge functions—in addition to representing the corner stress singularities—substantially accelerates the convergence of frequency solutions. This is demonstrated through extensive convergence studies that have been carried out by the investigators. Numerical analysis has been carried out and the results have been given for cylindrical elastic solids with various V-notch angles and depths. The relative depth of the V-notch is defined as (1− c/ a), and the notch angle is defined as (360°− α). For a very small notch angle (1° or less), the notch may be regarded as a “sharp radial crack.” Accurate (four significant figure) frequencies are presented for a wide spectrum of notch angles (360°− α), depths (1− c/ a), and thickness ratios ( a/ h for plates and h/ a for cylinders). An extended database of frequencies for completely free thick sectorial, semi-circular, and segmented plates and cylinders are also reported herein as interesting special cases. A generalization of the elasticity-based Ritz analysis and findings applicable here is an arbitrarily shaped V-notched cylindrical solid, being a surface traced out by a family of generatrix, which pass through the circumference of an arbitrarily shaped V-notched directrix curve, r( θ), several of which are described for future investigations and close extensions of this work.

Resonant electromechanical vibrations of piezoelectric shells of revolution (review)

Scientific results from studies on the resonant electromechanical vibrations of piezoceramic thin-walled shells of revolution, their fragments, and segmented cylinders are analyzed, systematized, and generalized. Considerable attention is focused on experimental studies of resonant vibrations. It is shown that the modes in which deformation occurs inphase throughout the volume are of the highest intensity in all piezoceramic shell structures

Analysis of segmented cylinder ceramic transducers using multiport interconnection techniques

For many years transducer analysis using multiport interconnection techniques has been successfully applied to tonpilz designs and other transducer types in which the vibratory motion is entirely one-dimensional. The analysis of radially vibrating cylindrical ceramic elements has generally used either empirically derived equivalent circuit methods or has started directly from the differential equations of motion. For segmented cylinders it is possible to perform an approximate analysis using linear network analysis methods. This allows the use of standard multiport analysis computer codes such as SEADUCER to perform much of the calculation. Furthermore these methods eliminate the need for empiricism. Calculated radiation impedance and finite mounting surface impedance effects can be directly included. A description of the method and comparison of the results with previous methods will be provided.