Form Of Hollow Cylinder Research Articles

Twisted Nanotubes of Transition Metal Dichalcogenides with Split Optical Modes for Tunable Radiated Light Resonators

AbstractSynthesized micro‐ and nanotubes composed of transition metal dichalcogenides (TMDCs) such as MoS2 are promising for many applications in nanophotonics because they combine the abilities to emit strong exciton luminescence and to act as whispering gallery microcavities even at room temperature. In addition to tubes in the form of hollow cylinders, there is an insufficiently studied class of twisted tubes, the flattened cross‐section of which rotates along the tube axis. As shown by theoretical analysis, in such nanotubes the interaction of electromagnetic waves excited at the opposite sides of the cross‐section can cause splitting of the whispering gallery modes. By studying micro‐photoluminescence spectra measured along individual MoS2 tubes, it has been established that the splitting value, which controls the energies of the split modes, depends exponentially on the aspect ratio of the cross‐section, which varies in “breathing” tubes, while the relative intensity of the modes in a pair is determined by the angle of rotation of the cross‐section. These results open up the possibility of creating multifunctional tubular TMDC nanodevices that provide resonant amplification of self‐emitting light at adjustable frequencies.

Investigation of an Electrical System for Induction Heating of Cylindrical Parts with Different Sizes

The article is devoted to the study of an electrical complex, including a high-frequency power source (2400 Hz), a heating inductor and cylindrical parts in the form of hollow cylinders (pipes). An autonomous electric machine power supply based on a high-speed magnetoelectric generator, which provides an output voltage of 950 V with a frequency of 2400 Hz, is considered. The features of inductors during heating of parts made of ferromagnetic steel and non-magnetic steel for low-temperature and high-temperature heating are presented. The results of inductor calculations are shown with a change in the diameters of processed pipes heated from a given inductor, which makes it possible to determine the areas of rational geometric parameters of parts that can be applied for a given inductor.

Water Softening and Disinfection Using an Electrolysis Unit with a Filtering Cartridge

The removal of a set of contaminations consisting of hardness salts, iron, humic substances, and microorganisms by using a unit combining electrochemical treatment and filtration is investigated. Constructively, the electrochemical unit is based on the flask of a standard domestic water filter equipped with a filtering cartridge, in the form of hollow cylinder, filled with sintered activated carbon. A graphite anode is placed on the inside of the cartridge, and a steel mesh cathode is placed coaxially outside the cartridge. In experiments, we use tap water from the Kiev’s water supply network characterized by a total hardness of 4.5 mg-eq/L (the concentrations of calcium and magnesium ions are 70 and 12 mg/L, respectively) and a carbonate alkalinity of 3.6 mg-eq/L. Model solutions are prepared by adding either iron(II) (as FeCl2) or humic acid to water to a concentration of 7 and 20 mg/L, respectively; Bacillus subtilis is also added to a concentration of 104 CFU/L. To evaluate the effectiveness of using the filtering cartridge, water electrolysis is carried out in two configurations: in the presence and absence of the filtering cartridge, without separating the electrode compartments. In experiments without the cartridge, the current slightly decreases from 0.5 to 0.45 A (i.e., by only 10%), while the hardness falls by only 12%. In experiments with the cartridge, the current falls to a steady value amounting to 40% of its initial value, while the hardness falls from 4.6 to 0.28 mg-eq/L (i.e., by 93%) and the concentrations of iron, humic substances, and bacteria decrease from 7 mg/L, 20 mg/L, and 5 × 104 CFU/mL to 0.01 mg/L, 1 mg/L, and 0 CFU/mL, respectively. The energy consumption of the unit is up to 2 kWh/m3.

EFFECTIVE KEYED CONNECTIONS OF HOLLOW-CORE FLOOR SLABS WITH WALLS IN MODERN LARGE-PANEL HOUSE BUILDING

The paper considers large-panel constructive system of multi-storey buildings and its industrial basis creates conditions for intensive volume growth in house construction. Application of hollow-core panels are recommended as floor slabs that allows to increase a distance between bearing walls, to improve planning solutions, and also significantly to increase thermal and sound protection properties of floor discs (coatings). Keyed joints having the highest resistance to shearing forces are used to ensure joint action of the slabs with wall panels. A supporting unit of floor elements in the precast-monolithic constructive system ARKOS by means of concrete keys is considered as a prototype of the considered joint. In order to increase a bearing capacity and improve reliability of joints it is envisaged to reinforce keys with space frames. Improvement of joint units is possible to carry out with due account of total number of the factors influencing on strength. Poltava National Technical University named after Yuri Kondratyuk has developed a general methodology for assessment of bearing capacity in keyed joints which is based on the variational method in the theory of concrete plasticity and reflects specificity of stress-strain state of the failure zone. For experimental verification of this methodology investigations have been carried out with the purpose to test operation of keys when they are reinforced in mid-height and reinforcement is distributed in two tiers. The observed experimental fracture pattern in the specimens has confirmed kinematic schemes accepted for calculations and comparative analysis of experimental and theoretical values points to their closeness. Two-level reinforcement significantly improves plastic properties of concrete keys and excludes brittle failure. The proposed design of the joint unit for floor slabs with wall panels is characterized by the ratio of key dimensions and shape of reinforcing cages in the form of hollow cylinders which ensure higher strength and seismic resistance of a joint.

Making Hollow Cylindrical Products of High-Porosity Silicon Nitride by the Centrifugal Forming of Granules of a Thixotropic Thermoplastic Slip

This article describes features of the manufacture of high-porosity silicon semifinished products in the form of hollow cylinders by the warm centrifugal casting of elements obtained from cutting up castings of a silicon-based thermoplastic slip. Silicon nitride obtained by plasmochemical synthesis is added to the slip to impart the necessary rheological properties. Products in the form of hollow cylinders with walls made of a highly porous silicon nitride material are obtained from the semifinished products by removing the binder through sublimation and then subjecting the semifinished products to reaction sintering in nitrogen. The areas of application proposed for the material and the hollow products obtained from it: porous partitions for the filtration and combustion of natural fuels in power plants; porous inserts for the local reinforcement of die-cast products made of light metals.

Development of High Precision Test Masses for the MICROSCOPE Space Project

The MICROSCOPE (MicroSatellite à traînée Compensée pour l'Observation du Principe d'Equivalence) project is an orbit-based mission to verify the Weak Equivalent Principle with an uncertainty of 10-15. To achieve this goal two differential accelerometer, each equipped with two high precision test masses (made of PtRh10 and TiAl6V4 in the form of hollow cylinders with four flats at the outer shell and six precision countersinks at each face), are to be launched in Spring 2016 and shall orbit the earth for approx. one and a half year.

A hybrid waveguide cell for the dielectric properties of reservoir rocks

A hybrid waveguide cell is described for broad-band measurements of the dielectric properties of hydrocarbon reservoir rocks. The cell is designed to operate in the radio frequency range of 1 MHz to 1 GHz. The waveguide consists of 50 Ω coaxial lines feeding into a central cylindrical section which contains the sample under test. The central portion of the waveguide acts as a circular waveguide and can accept solid core plugs of 38 mm diameter and lengths from 2 to 150 mm. The central section can also be used as a conventional coaxial waveguide when a central electrode with spring-loaded end collets is installed. In the latter mode the test samples are required to be in the form of hollow cylinders. An additional feature of the cell is that the central section is designed to telescope over a limited range of 1–2 mm with the application of an axial load. Effective pressures up to 35 MPa can be applied to the sample under the condition of uniaxial strain. The theoretical basis of the hybrid waveguide cell is discussed together with calibration results. Two reservoir rocks, a Donnybrook sandstone and a kaolin rich clay, are then tested in the cell, both as hollow cylinders in coaxial mode and in the form of solid core plugs. The complex dielectric properties of the two materials over the bandwidth of 1 MHz to 1 GHz are compared with the results of the two testing methods.

Treatment of Goat Femur Segmental Defects with Silica-Coated Hydroxyapatite—One-Year Follow-Up

Segmental bone defects caused by tumor resections, trauma, and skeletal abnormalities such as osteomyelitis remain a major problem in orthopedics because of the lack of predictability in attaining functional bone after the treatment. The objective of this study was to propose an indigenous porous biodegradable triphasic ceramic (calcium silicate, tricalcium phosphate, and hydroxyapatite [HA])-coated HA (core) (HASi) for the repair of such segmental defects. With respect to the synthesis of HASi, HA blocks were prepared by wet precipitation, dipped in silica sol (sol gel method), sintered at 1200 degrees C, polished in the form of hollow cylinder (2 cm long with an outer and inner diameter of 2 cm and 7 mm, respectively), and implanted into a 2-cm segmental defect created in the goat femur diaphysis. This study prolonged for 12 uneventful months and thereafter neo-osteogenesis in par with material degradation was analyzed through radiography, histology, histomorphometry, scanning electron microscope (SEM)-energy dispersive spectrum, micro-computed tomography, and inductively coupled plasma spectrometry. HASi proved to be osteoconductive, osteointegrative, and degradative in nature, without the intervention of fibrous tissue formation at the defect site. Histologically, the newly formed bone reorganized, mineralized, and attained the appearance and contour of the original femoral diaphysis in 1 year. The interconnected porous structure with silica composition aided progressive bone regeneration and repair in par with degradation of the material. Thus the study proposed the possibility of using HASi as a suitable material in clinical orthopedic reconstructive surgery, which remains a formidable challenge.

Synthesis, characterizations and applications of some nanomaterials (TiO2 and SiC nanostructured films, organized CNT structures, ZnO structures and CNT-blood platelet clusters)

TiO2 nanostructured films have been synthesized by the hydrolysis of Ti[OCH(CH3)2]4 as the precursor. These films have been utilized for the dissociation of phenol contaminant in water. Free-standing nanostructured film of silicon carbide (SiC) has been synthesized, employing a simple and new route of spray pyrolysis technique utilizing a slurry of Si in hexane. Another study is done on organized carbon nanotube (CNT) structures. These are made in the form of hollow cylinders (50 mm length, 4 mm diameter and 1.5 mm wall thickness). These CNT-based cylinders are made of conventional CNT and bamboo-shaped CNT. The filtrations of heavy hydrocarbons andE. coli bacteria from water have been carried out. In addition to this, ZnO nanostructures have also been studied. Another study concerns CNT-blood platelet clusters.

Utilising the Hoek triaxial cell for multiaxial testing of hollow rock cylinders

Specimens in the form of hollow cylinders are versatile tools which can be used in many applications ranging from simulating stress conditions around underground openings to studying the behaviour of geomaterials under a wide variety of stress paths. Nevertheless, they remain little utilised in experimental studies due to the lack of suitable testing facilities and the difficulties involved in developing such facilities. This work presents a simple and practical solution for hollow cylinder test apparatus devised by combining a widely used and readily available conventional triaxial cell, developed by Hoek and Franklin (Trans. Inst. Min. Metall. 77 (1968) A22 (Section A)), and specially designed internal pressure loading configuration. In order to verify the performance of the new apparatus and demonstrate its versatility, various tests have been carried out on specimens of Springwell sandstone under uniaxial, biaxial, triaxial and polyaxial compression as well as indirect tension. The results obtained confirm the effect of the intermediate principal stress on rock failure and show that the apparent strength of rock is markedly influenced by the stress conditions imposed. It is aimed that the introduction of such simple apparatus would contribute to establishing common multiaxial testing systems that can provide more realistic predictions of the actual behaviour of rock and guide the formulation of more adequate numerical models.

Effect of processing conditions on the yield and failure response of an aliphatic polyketone terpolymer

AbstractThe effect of processing conditions on the yield and failure behavior of an aliphatic polyketone terpolymer was studied. Testing and characterization were performed on samples that were extruded in the form of hollow cylinders. We performed the extrusion process at different shear rates and at different cooling rates to assess the effect that process conditions had on the polymer properties. We performed biaxial testing on the samples to characterize the failure envelopes, including the ductile–brittle transition condition for each process condition. The effect of shear rate was negligible, whereas the cooling rate significantly affected the failure behavior. To explain these differences in behavior, we performed characterization via differential scanning calorimetry, wide‐angle X‐ray diffraction, attenuated total reflection IR spectroscopy, dynamic mechanical thermal analysis, scanning electron microscopy, and residual stress measurements. A broad glass transition was found for all samples at temperatures higher than previously reported for this material. Alteration of the processing conditions did not influence the crystalline phase (percentage crystallinity, crystalline orientation, crystallite size, etc.). A change in spherulitic structure was also observed with altered cooling rate and is suggested to have contributed to the change in failure behavior. Residual stresses also affected the behavior of all samples. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 318–334, 2002; DOI 10.1002/app.10334

Electromagnetic coupling in small grain YBa 2Cu 3O 7–δ superconducting ceramics: full and hollow cylinders

This paper describes a method to assess the electromagnetic characteristics of a superconducting ceramic material. YBa 2Cu 3O 7– δ ceramic samples have been made in the form of hollow cylinders with the standard 4 terminal configuration for measurement of the critical current ( I c) attached to the outer surface. An additional wire carries a second internal current ( I int) along the central axis. I c can thus be modulated by I int. In particular, an increase in I c can be achieved by directing I int in the opposite direction to the cylinder current in order to compensate the self-generated magnetic field. The I c– I int characteristic can be described by a critical state model where we assume a linear dependence between the local critical current density ( j c) and the local magnetic field ( H) for the superconducting polycrystalline material. Based on this linear model the experimental data for a given sample can be analysed to extract two parameters: the maximum local critical current density ( j 0) and the local magnetic field ( H 0) for which j c should vanish. The best sample yielded j 0=1023 A cm –2 and H 0=4450 A m –1.

Transient analysis of HTS inductive fault current limiter

High temperature superconductors (HTS) have been considered for current limiting devices based on the fast transition from the superconducting state to the resistive one when the current overcomes the critical current. Recent developments have shown the feasibility of the inductive fault current limiters using HTS in the form of hollow cylinders or stacked rings. In the present work, an inductive fault current limiter consisting of a primary copper winding, a HTS cylinder or ring as the secondary winding and an iron core is analysed. A mathematical model, taking into account the real current-voltage characteristics of HTS as well as the nonlinearity of B(H) (magnetic flux density as a function of field) curve of the iron core, is proposed and solved. Some typical results are presented and compared with experimental ones.

Mechanical properties of sisal fibre at elevated temperatures

Sisal fibres extracted from the leaves of Agava sisalana plants 3, 5, 7 and 9 years old were tested at different temperatures for tensile strength, elongation, toughness and modulus. The tensile strength, modulus and toughness values of sisal fibre decreased with increase in temperature. The effect of plant age on tensile strength, tensile modulus and toughness of sisal fibre became very much less at 100 °C as compared to 30 °C. Fractured fibres were observed by using a scanning electron microscope. The ends of fibres fractured at elevated temperature showed a failure similar to that of inorganic fibres. Elongation values at all temperatures increased with age. Elongated capillaries were observed in fibres fractured at 80 and 100 °C, due to the removal of moisture and volatiles originally present in the fibres. The fibrils are clearly observed in the form of hollow cylinders. Fractured surfaces are composed of brittle as well as ductile phases. The ductile portion increased with the increase of temperature.

Shielding characteristics of the hight-Tc ceramic hollow cylinders

Abstract The results of shielding characteristics measurements of superconducting shields in the form of hollow cylinders based on YBa2Cu3O7 high-Tc superconducting ceramics are reported. Shields provided ac shielding coefficinet up to 72 dB at 89 K. It was shown that spectrum analysis of magnetic flux insided cylindrical shield can be a tool to distinguish a mechanisms of field penetration into shielded volume.

Determination of the amplitudes of mechanical stresses and displacements in short cylindrical piezoelectric transducers with passive layers

The distribution of dynamic mechanical stresses and displacements in piezoelectrical transducers with a transition layer, made in the form of hollow cylinders whose length is commensurable with the radius, is considered. Expressions for the mechanical stresses and displacements in relation to the voltage are obtained by solving the boundary-value problem of forced transducer vibrations. This axisymmetric problem is stated under the assumption that the hypothesis of plane sections holds. It is found that the greatest dynamic tensile stress acts on the transition layer and that the strength of cylindrical transducers with a transition layer is primarily determined by the strength characteristics of the material of which the transition layer is made. The theoretical results are supported by experiments performed according to the laser interferometry method.

Spatial and angular characteristics of the radiation from high-power lasers utilizing solutions of organic compounds with active elements in the form of hollow cylinders

A study was made of the characteristic features of the output radiation pattern of a rhodamine laser with cells in the form of hollow cylinders excited from outside and from inside by linear flashlamps. Different methods of suppressing nonaxial rays were proposed and tested. It was found that when a cell in the form of a hollow cylinder was excited from the inside, the active medium acquired the properties of a negative lens and the paths of the rays in the resonator became similar to those in an unstable resonator. This made it possible to increase the radiation brightness by more than an order of magnitude and also to demonstrate the advantages of using internally excited active elements in the form of hollow cylinders in high-power low-divergence dye solution lasers.

Applicability of a hollow cathode emission source for determining trace elements in electrically non-conducting powders

The applicability of the hollow cathode emission source for the determination of trace elements in mineral residues from ashing of biological materials is investigated. The method uses samples previously diluted with a 1:4 graphite-copper powder mixture to render them electrically conductive and subsequently pressed into the form of hollow cylinders. The procedure was tested with synthetic specimens; the latter contain Ag, Al, B, Cr, Mn, Ni, Pb, Sn, Ti and Zn, and a matrix similar to that of organic materials after mineralization. The use of Ga as an internal standard greatly improved the linearity of log I x vs log c x relationship. The precision of the measurements and the detection limits were also found to be entirely satisfactory.

Magnetostriction in some amorphous Fe-Co-Ni-P alloys

Amorphous bulk samples of Fe-Co-Ni-P were prepared by continuous electroless deposition in the form of hollow cylinders 6mm diameter, 20mm length and with a uniform thickness of the order 0.2mm. The specimens had a general formula Ni <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">w</inf> Co <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</inf> P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</inf> , with a range of compositions given by 0< w< 0.81; 0 < x < 0.92; 0 < y < 0.10; 0.06 < z < 0.25. The room temperature magnetostriction and the temperature dependence of the saturation magnetisation of the amorphous samples were measured. A number of the samples were heat treated to obtain a single phase crystalline material, the heat treatment conditions being determined by differential scanning calorimetry. The magnetisation values showed a composition dependence similar to that of crystalline alloys of Ni-Co and Ni-Fe. The magnetostriction coefficients, however, were all negative in sign, unlike the behaviour observed in polycrystalline alloys of Ni-Co and Ni-Fe. The magnetostriction values for the amorphous samples were found to be roughly twice the magnitude of those for the crystallised samples. A qualitative explanation of this phenomenon is given based on the lower value of Young's modulus which has been observed in amorphous materials.

Selective Absorption of Slow Neutrons

IN our letter of April 121, we mentioned that the absorption of slow neutrons by iodine was apparently greater when the induced (-ray activity of an iodine detector was used as a measure of the number of neutrons transmitted than when detectors of silver or rhodium were employed. We have now confirmed this selective absorption and have extended the measurements to absorbers of silver and of copper, where analogous though somewhat less marked selectivity is found. The accompanying table shows the activity (expressed as a fraction of that obtained in the absence of the absorber) when hollow cylinders of silver (1.0 gm. cm.2), copper (4.5 gm. cm.2) and iodine (2 gm. cm.2) were placed in turn around various detectors, themselves in the form of hollow cylinders. A layer of cadmium, sufficiently thick to absorb nearly all slow neutrons striking it, was always placed inside each detector during irradiation, so that when the absorber was in place, neutrons reaching the detector must have passed once, and only once, through the absorber. The irradiation was performed within a 4 cm. cavity in a large block of wax, the source being at 9 cm. from the centre of the cavity. It seems clear that different nuclei prefer neutrons of different velocities.