Small Ropes Research Articles

Testing Device for Hydraulic Rope System Tensile Force Equalizing Unit

Abstract Rope elevators, also referred to as traction elevators, have a cabin suspended from a system of ropes. The system of ropes consists of at least two load-bearing steel ropes with six strands or, from the point of view of easier bending, and currently more widespread, ropes with eight strands. Lifting or lowering of the car, run between the guides, is ensured by the frictional force of the steel ropes in the grooves of the traction disk of the elevator machinery. As the load-bearing capacity of the elevator increases, the required number of load-bearing ropes also increases, especially in the case where small diameter ropes are used in traction elevators. The actual weight of the car and the weight of the load must be evenly distributed among all supporting ropes that are used in the given layout of the elevator. Currently, several principles are known by which it is possible to detect and also change the values of the instantaneous magnitudes of the tensile forces acting in a system of ropes. The paper describes the principle of operation of hydraulic balancing of tensile forces in the system of supporting ropes, which uses the laws of hydromechanics and knowledge of pressure transfer to any place in the fluid, known as Pascal's law. Balancing of differently set values of tensile forces in three supporting ropes, to values of the same size, can be simulated on a test device. This presents the correct operation of the hydraulic system and the possibility of balancing tensile forces in the system of supporting ropes described by the principle of hydraulic device.

Magnetic Disconnections at the Boundary of a Small Interplanetary Magnetic Flux Rope Associated with a Reconnection Exhaust

A local current sheet and a subsequent small interplanetary magnetic-flux rope were observed on 1 April 2003 by Wind and the Advanced Composition Explorer (ACE). A Petschek reconnection-like exhaust crossing of the local current sheet was identified using the Walen test. The Wind spacecraft re-entered the reconnection exhaust after the main exhaust encounter, and the reentry may be due to a spatial fold of the current-sheet surface itself. The absence of parallel strahls and the presence of antiparallel strahls on either side of the current sheet suggest that the magnetic-field lines before the exhaust and in the subsequent small flux rope are all open. The $180^{\circ}$ pitch-angle strahls were clearly absent, and halo-suprathermal electron pitch-angle distributions were observed in the exhaust. This finding means that the open field lines of the magnetic-flux rope were reconnecting to the adjacent open field lines to produce U-shaped field lines disconnected from the Sun. These observations provide direct evidence that the magnetic fields of the interplanetary small magnetic-flux rope were disconnecting from the Sun through magnetic reconnection. This type of disconnected event potentially has important implications for the magnetic-flux budget of the heliosphere.

Tension fatigue failure prediction for HMPE fibre ropes

In order to predict the lifetime of fibre rope mooring lines it is essential to be able to predict their behaviour under tension fatigue. Creep failure is known to be a major contributor to fatigue in synthetic fibres and models to predict creep failure are well-established. We show that expansion of such models to varying loading conditions allows the prediction of the fatigue performance. However, it is difficult to design tests to quantify the fatigue performance for HMPE ropes since often premature failure occurs due to external abrasion and viscous heating due to too high testing frequencies or amplitudes. This paper presents a testing methodology which allows tensile fatigue lifetime to be evaluated by testing at higher temperature to avoid premature abrasion failure. We also show that when the temperature evolution due to viscous heating is properly accounted for the modelling framework presented can be effectively used to describe the premature failure occurring due to this heating effect. Results from tests on yarns and small ropes are presented, and a predictive model for rope fatigue lifetime has been validated.

Seat Optimization for Single Handed Paralympic Sailing Boat

PURPOSEThe aim of this study was to optimize the seat for the skipper of a 2.4mR, a Paralympic sailing boat (single-hander). Primarily, the seat was designed for a man with diastrophic dysplasia, a disorder of cartilage and bone development. This 39 year old man has a short stature with very short arms and legs and joint deformities which restrict movement. The skipper's main tasks are handling the rudder and the mainsheet using small ropes with his hands and pedals with his feet. He is sitting on a seat attached to the floor of the boat, while his body is positioned facing the bow of the boat. The combination of movements of the boat and tasks during sailing resulted in a constantly changing instability of the body. This might declare some of the injuries (pain in hips, knees and shoulders) that were called. The design goal for the seat was to find an optimum in body stability and range of motion during sailing. METHODSAn analysis of the possible movements in the frontal and sagittal plane of the skipper in the boat was made using a mock-up. A movement analysis of sailing was made in three boat conditions: 1. Boat heeling 32° (sailing close hauled), bodyweight as much windward as possible in the hull; 2. No boat heeling (reaching), bodyweight in front of the seat; 3. No boat heeling (reaching), bodyweight at the back of the seat. A biomechanical analysis was made in order to estimate the forces on the body in the three boat conditions where the boat heeling and the position of the bodyweight of the sailor are varied. An iterative design process was followed which resulted in different prototypes and finally in a new seat. RESULTSThe main requirement on the seat is that it should prevent sliding on the seat in the frontal plane, especially in condition 1. Then, a friction coefficient of 0,63 is needed. Three prototypes have been build and tested. The final design consists of an aluminium seat with three sloping surfaces and a backrest that stabilizes the body. The seat can slide 19cm forwards and backwards. CONCLUSIONThe third prototype has been tested in the lab and on the water. Freedom of movement and stability were enhanced. The prototype is further developed and applied for different Paralympic sailors and sailboats.

Investigation of the Damage-Dependent Response of Mooring Ropes

The focus of this paper is on the development of an analytical damage model for predicting the deterioration of the mechanical properties of polyester (PET) ropes subjected to static tension loading. Experimental data on small PET ropes are used to estimate the evolution of damage using the effective stress concept and the principle of strain equivalence. The proposed damage model relies on an empirically based cumulative scalar damage function, which is founded on the assumption that the strain range experienced by rope elements is the main source of damage under static tension loading conditions. In this particular study, the evolution of the damage function is represented by both power law and polynomial forms. Based on experimental observations, softening behavior is developed by rope elements after reaching their maximum load-carrying capacities. This softening behavior is captured by the damage function through an asymptotic expansion technique (perturbation method). Comparisons between predicted rope responses and experimental data are provided to illustrate the use of the proposed damage model to estimate PET rope response.

Role of structure and morphology in the elastic modulus of carbon nanotube composites

The nature of nanoscale reinforcements in the carbon nanotube composites indicates nanocomposite properties are heavily dependent on the micro/nano-structure and morphology. Macroscopic parameter-based properties estimation may lead to deviation as large as 30%. In this paper, a modified shear-lag model, combined with probability statistical theory and composites morphology, is established to investigate the elastic properties of single wall carbon nanotubes (SWNTs)-reinforced polymer composites. The computational results indicated that elastic modulus of nanocomposite was remarkably dependent on the micro/nano-structure, including diameter, length, and orientation of the dispersed SWNTs. Microstructure-dependent shape factor and orientation effect factor played a key role on achieving high-performance nanocomposites. Elastic modulus of nanocomposite with well-dispersed carbon nanotubes was more susceptible to the orientation. Similarly, nanocomposite modulus was more subject to the dispersion influence when SWNTs were well-aligned. The maximal modulus was located in the zone of small rope diameters and small orientation angles when adequate interfacial bonding was provided. The computational results were also compared with experimental outcome and demonstrated good consistence.

Comparative analysis of electric, magnetic, and mechanical properties of epoxy matrix composites with different contents of multiple walled carbon nanotubes

AbstractEpoxy composites based on aligned chemical vapor deposition–grown multiwall carbon nanotubes (MWCNTs), containing trapped iron nanoparticles, with weight fractions ranging from 0.03 to 1 wt%, were produced following a well‐known processing way. Electrical and mechanical properties as well as their densities were measured. The results are compared with previous studies investigating the magnetic percolation behavior in the same samples of composites. A percolation threshold at 0.4 wt% of MWCNTs was determined by the electrical property and it agrees with the threshold observed in the magnetic properties. A hop in the porosity and a depression of the bulk mechanical properties were also found at the threshold value. These results point out that there is an efficiency threshold related to the sonication stage of the fabrication process and the weight fraction of MWCNTs, and after this threshold, the initial nanotubes pans were not separated into individual MWCNTs or into small ropes. An optimized sonication stage is proposed and the improvement in the dispersion of the filler is shown. POLYM. COMPOS., 28:612–617, 2007. © 2007 Society of Plastics Engineers

Quantum Yield Heterogeneities of Aqueous Single-Wall Carbon Nanotube Suspensions

Aqueous suspensions of single-wall carbon nanotubes (SWNTs) prepared by traditional methods from the supernatant of ultracentrifuged micellar SWNT mixtures are shown to be strongly heterogeneous with respect to the quantum yield of their constituents. The heterogeneities are isolated using preparative ultracentrifugation in iodixanol density gradients and are optically characterized by photoluminescence and linear absorption spectroscopy. We find that the most buoyant fractions with a density of 1.055 ± 0.005 g·cm-3 have the highest photoluminescence quantum yield η of 1.1%, a factor of 5 higher than that of the supernatant. Denser fractions with lower η make up for about 2/3 of these samples and contain mostly small ropes in which the quantum yield is reduced by nonradiative decay through coupling to metallic tubes.

Adsorption of Streptavidin onto Single-Walled Carbon Nanotubes: Application in Fluorescent Supramolecular Nanoassemblies

We report the solubilization of full-length single-walled carbon nanotubes into a physiological buffer by sonication in presence of streptavidin. Transmission electron microscopy showed that the resultant dispersion was enriched of individual/small ropes of nanotubes. By the analysis of the crystal structure of tetrameric streptavidin and of the tryptophan emission of adsorbed proteins we hypothesized that proteins adsorbed onto SWNT sidewalls through their amine functionalities. Our results suggested using streptavidin as an interlinker between carbon nanotubes and semiconducting nanocrystals. We fabricated a supramolecular luminescent nanoassembly composed of individual or small ropes of full-length single-walled carbon nanotubes decorated with streptavidin-conjugated quantum dots. The luminescent nanoassembly was stably dispersed under physiological conditions and was readily visible by optical fluorescent microscopies.

Full-Length Single-Walled Carbon Nanotubes Decorated with Streptavidin-Conjugated Quantum Dots as Multivalent Intracellular Fluorescent Nanoprobes

We report the formation of a supramolecular luminescent nanoassembly composed of individual or small ropes of full-length, single-walled carbon nanotubes decorated with streptavidin-conjugated quantum dots. The supramolecular luminescent nanoassembly was stably dispersed under physiological conditions and was readily visible by both optical and confocal fluorescent microscopies. Jurkat T leukemia cells were able to internalize the nanoassembly by multivalent CD3 receptor-mediated endocytosis (adsorption by cell). Once internalized by cells, the nanoassembly was found to be transported to lysosomes. These properties should make this supramolecular luminescent nanoassembly an excellent building block for the construction of intracellular polyvalent nanoprobes, mimicking natural viral delivery entities with enhanced loading capacity compared to small molecules.

Water-soluble single-walled carbon nanotubes via noncovalent functionalization by a rigid, planar and conjugated diazo dye

A new noncovalent approach for the dissolution and exfoliation of SWNTs in water by a rigid, planar and conjugated diazo dye, Congo red (CR), is reported. Using a simple physical grinding treatment, the mixture of SWNTs and CR can be dissolved in water with a solubility as high as 3.5 mg/ml for SWNTs. The complete elimination of free CR from the mixture hardly changed this excellent solubility. High-resolution transmission electron microscope images showed that the SWNTs bundles were efficiently exfoliated into individual SWNTs or small ropes, which was further demonstrated by the increased π-plasmon UV–vis absorption and the upshift of the radical breathing mode in Raman scatterings. The π-stacking interaction between adsorbed CR and SWNTs was considered responsible for the high solubility. The uninterrupted structure of SWNTs with CR functionalization was ascertained by the unchanged disorder-induced Raman scattering.

Hierarchical morphology of carbon single-walled nanotubes during sonication in an aliphatic diamine

Dispersion of single-walled carbon nanotubes (SWNTs) by sonication into diamine curing agents is studied as a means to improve the dispersion of SWNTs in cured epoxy. Cured and uncured specimens are analyzed by light microscopy, electron microscopy, light scattering (LS), ultra small-angle X-ray scattering (USAXS), electrical conductivity and Raman spectroscopy. A flexible diamine (D2000) forms a stable SWNT suspension leading to good homogeneity in both the diamine and the cured epoxy. High resolution transmission electron microscopy (TEM) shows that small ropes of SWNTs (mostly under 15 nm) are present despite the sample's visual homogeneity. Further morphological investigation of cured and uncured D2000 resins using light and small-angle X-ray scattering indicates that the SWNTs are networked into fractal clusters that electrically percolate at low SWNTs loadings (0.05 wt%).

Coating single-walled carbon nanotubes with cadmium chalcogenides

Non-covalently functionalized single walled carbon nanotubes (SWNTs) have been coated with CdE (E = S, Se) by liquid phase deposition (LPD) from aqueous and hydrocarbon solution. The coating of individual SWNTs versus small ropes or composite structures is controlled by the use of SDS surfactant SWNTs and the relative concentration of the SWNTs and the cadmium source. Coating reactions in non-aqueous systems result in either composite formation or incomplete coatings. The CdE-SWNTs have been characterized by SEM, TEM, EDX, and Raman spectroscopy. The Raman fluoresence of the SWNTs is maintained at 90% with coatings of CdS > 5 nm.

LPD silica coating of individual single walled carbon nanotubes

Single walled carbon nanotubes (SWNTs) have been coated with fluorine-doped silica by liquid phase deposition (LPD) using a silica–H2SiF6 solution and a surfactant stabilized solution of SWNTs. The coating of individual SWNTs versus small ropes is controlled by the choice of surfactant. Since the LPD reaction is performed close to the isoelectric point of the silica, some of the SiO2–SWNTs are fused together but the SWNTs remain individual in these composite structures. The SiO2–SWNTs have been characterized by SEM, TEM, Raman and IR spectroscopy, and XPS. Raman fluoresence is maintained even with coatings >50 nm. Using the relative intensity of the Raman G peak and the 8,3 SWNT fluorescence as a convenient measure of bundling, it may be shown that any decrease of fluoresence during growth is not due to changes in ionic strength or pH, as a consequence of addition of the LPD solution or the presence of HF as a side product in the deposition. The Raman D and G modes show no change in intensity, while the Fano line increases, both suggesting that no sidewall functionalization or proton adsorption of the SWNTs occurs during coating. The UV-visible-near infrared spectra shows a red shift in the first Van Hove transitions of the coated SWNTs inferring that the SWNTs in SiO2–SWNTs are in a more polarizable and inhomogeneous environment than that of surfactant solutions. Mats of SiO2–SWNT may be deposited onto silicon and gold substrates and through lithography may be patterned by etching off selected areas of the silica coating.

Molecular selectivity due to adsorption properties in nanotubes

The adsorption of small molecules $({\mathrm{N}}_{2},$ ${\mathrm{O}}_{2},$ CO, ${\mathrm{CO}}_{2},$ ${\mathrm{H}}_{2}\mathrm{O},$ and HF) in model ropes of carbon nanotubes has been studied to determine the main parameters (stable adsorption sites, potential barriers, $\dots{})$ which define the ability of carbon nanotubes to select small molecules through their different behavior in the diffusion mechanism. When the polarization of the nanotubes is taken into account in the semiempirical potentials, it has a significant influence on the adsorption of polar species. Examination of the potential maps along the ropes shows that the nature and the stability of the adsorption sites are strongly dependent on the molecular species and on the diameter of the tubes. For a small rope formed with (10,10) single-wall nanotubes, different trapping sites are favored by the molecules considered. Furthermore the corresponding trapping well depths are sufficiently selective to discriminate the species. Improving the size homogeneity of the ropes and judiciously calibrating their diameter would provide an efficient mean of selecting molecular species.

Silica Coated Single Walled Carbon Nanotubes

Single walled carbon nanotubes (SWNTs) have been coated with silica by the addition of a silica/H2SiF6 solution to a surfactant-stabilized solution of SWNTs. The thickness of the coating is controlled by reaction time, while the coating of individual SWNTs versus small ropes is controlled by the choice of surfactant. Individual nanotubes encased by a silica coating show retention of the characteristic Raman fluorescence. Selective etching of the silica coating allows for the exposure of either one end of the tubes or the central section. Exposure of the ends results in the formation of spontaneous interconnects between isolated SWNTs.

Production and measurements of individual single-wall nanotubes and small ropes of carbon

This work focuses on the size and spatial dependence of single-wall carbon nanotubes produced by the pulsed-laser vaporization technique. The study indicates that very long (tens of microns) individual nanotubes form in the vicinity of the target, and subsequently coalesce into bundles. The role of the inner flow tube is confirmed to restrict plume expansion and improve interactions between carbon atoms resulting in nanotube and rope formation. The effect of the flowing buffer gas seems to influence the dispersion of particulate contaminant material in the nanotube product. More particulate matter is produced at lower oven temperatures.

Dissolution of Full-Length Single-Walled Carbon Nanotubes

Full-length single-walled carbon nanotubes (SWNTs) were rendered soluble in common organic solvents by noncovalent (ionic) functionalization of the carboxylic acid groups present in the purified SWNTs. Atomic force microscopy (AFM) showed that the majority of the SWNTs ropes were exfoliated into small ropes (2−5 nm in diameter) and individual nanotubes with lengths of several micrometers during the dissolution process. The combination of multiwavelength laser excitation Raman scattering spectroscopy and solution-phase visible and near-infrared spectroscopies was used to characterize the library of SWNTs that is produced in current preparations. The average diameter of metallic nanotubes was found by Raman spectroscopy to be smaller than that of semiconducting nanotubes in the various types of full-length SWNT preparations. This observation sheds new light on the mechanism of SWNT formation.

Experimental observation of individual single-wall nanotube species by Raman microscopy

Abstract Individual single-wall carbon nanotubes (SWNT) or small ropes of SWNTs with the same diameter have been characterised by Raman spectroscopy. Highly pure, length-selected SWNTs adsorbed onto substrates designed for surface-enhanced Raman spectroscopy were investigated with a Raman microscope. Various spectra, each with a distinct sharp peak in the radial breathing mode area and four C–C stretching modes could be observed. The modes also showed a strong variation in the relative intensities. In correlation with theoretical predictions this should establish Raman microscopy as a non-destructive nano-technological tool, capable of determining the diameter, symmetry and position of individual SWNTs.

A Simple, Quantifiable, and Accurate Method for Applying a Noxious Mechanical Stimulus

A Simple, Quantifiable, and Accurate Method for Applying a Noxious Mechanical Stimulus