Flexible Thread Research Articles

Attenuation of the tip vortex flow using a flexible thread

Tip vortex cavitation (TVC) is important in a number of practical engineering applications. The onset of TVC is a critical concern for navy surface ships and submarines that aim to increase their capability to evade detection. A flexible thread attachment at blade tips was recently suggested as a new method to delay the onset of TVC. Although the occurrence of TVC can be reduced using a flexible thread, no scientific investigation focusing on its mechanisms has been undertaken. Thus, herein, we experimentally investigated the use of the flexible thread to suppress TVC from an elliptical wing. These investigations were performed in a cavitation tunnel and involved an observation of TVC using high-speed cameras, motion tracking of the thread using image-processing techniques, and near-field flow measurements performed using stereoscopic particle image velocimetry. The experimental data suggested that the flexible thread affects the axial velocity field more than the circumferential velocity field around the TVC axis. Furthermore, we observed no clear dependence of the vortex core size, circulation, and flow unsteadiness on TVC suppression. However, the presence of the thread at the wing tip led to a notable reduction in the streamwise velocity field, thereby alleviating TVC.

Порівняльний аналіз одновимірної і просторової моделі для щогл мобільного зв'язку

In the article the questions of simulation of design schemes of mobile communication masts constructions are considered. On the basis of the existing calculation methods, numerical experiments were carried out to study the movement of the upper mast cut for the spatial rod and one-dimensional computational models. The spatial design model is described as a mast modeled by lattice structures with a triangular cross-section in plan on the braces. The design calculation in a one-dimensional setting is described as a rod with a reduced moment of inertia on the braces, which are modeled by a finite element of the flexible thread type for further non-linear calculation. The calculations were carried out in an environment PC SCAD Office software. A comparative analysis was carried out for the possibility of constructing simplified rod models for solving problems of sensitivity analysis and optimization.

Calculation of the problem on a rotating flexible thread

A solution to the problem of a flexible thread rotating around a horizontal axis is presented. Dependences calculated in elementary functions with graphic applications are obtained for determining the parameters of the rotating thread, such as the thread-shape outline, the largest deviation from the axis, the values of curvature angles, and the thread tension, among others.

Fabrication and Characterisation of Flexible Coaxial Thin Thread Supercapacitors

Flexible coaxial thin thread supercapacitors were fabricated semi-automatically using a dip coating method. A typical coaxial thin thread supercapacitor of a length of 70 cm demonstrated a specific length capacitance of 0.3 mF cm -1 (11.2 mF cm -2 and 2.18 F cm -3 ) at 5 mV s -1 , the device exhibited good electrochemical performance with a high volume energy density of 0.22 mWh cm -3 at a power density of 22 mW cm -3 . Thread supercapacitors were assembled in series and parallel combinations, the accepted models for series and parallel circuit combinations were obeyed for two coaxial thread supercapacitors. The thread shows high flexibility and uniformity of specific length capacitance, one integrated with a commercial solar cell could be charged and power a LED. The process is simple, robust and easy to scale up to make unlimited length thread supercapacitors for numerous miniaturized and flexible electronic applications.

Application of Evolutionary Method of Search Engine Optimization to Calculate Absolutely Flexible Inextensible Thread

The article describes a technique for solving the boundary value problem for an absolutely flexible inextensible thread suspended on two supports. As a solution, the method chosen method of differential evolution, allows to obtain xbcktyyjt solution. It describes the formulation of the problem for a perfectly flexible thread located in the gravity field.

Electronic Energy Transfer Modulation in a Dynamic Foldaxane: Proof‐of‐Principle of a Lifetime‐Based Conformation Probe

AbstractAbiotic aromatic oligoamide foldamers are shown to self‐assemble in solution to form a double helix, which can accommodate a bichromophoric thread in its central void. While in solution reversible electronic energy transfer is instilled between chromophoric termini of the free, flexible thread as evidenced through delayed luminescence, upon rigidification of the rod the chromophores are mutually distanced and effectively decoupled. Consequently, the chromophores display their individual photophysical characteristics. The observed conformation‐dependent changes of dynamic luminescence properties, which are particularly sensitive to distance, offers a new strategy for lifetime‐based detection of geometry on the molecular scale as demonstrated through real‐time luminescence detection of molecular complexation leading to foldaxane formation.

Electronic Energy Transfer Modulation in a Dynamic Foldaxane: Proof-of-Principle of a Lifetime-Based Conformation Probe.

Abiotic aromatic oligoamide foldamers are shown to self-assemble in solution to form a double helix, which can accommodate a bichromophoric thread in its central void. While in solution reversible electronic energy transfer is instilled between chromophoric termini of the free, flexible thread as evidenced through delayed luminescence, upon rigidification of the rod the chromophores are mutually distanced and effectively decoupled. Consequently, the chromophores display their individual photophysical characteristics. The observed conformation-dependent changes of dynamic luminescence properties, which are particularly sensitive to distance, offers a new strategy for lifetime-based detection of geometry on the molecular scale as demonstrated through real-time luminescence detection of molecular complexation leading to foldaxane formation.

Multilayer supercapacitor threads for woven flexible circuits

Purpose – Wearable electronic devices have emerged which require compact, flexible power storage devices such as batteries and supercapacitors. Recently, energy storage devices have been developed based on supercapacitor threads. However, current supercapacitor energy storage threads which use electrolytes based on aqueous gels have a 1 V potential window. This is much lower than the voltage required by most electronic devices. This current contribution presents an approach for fabricating a multilayer supercapacitor working as a circuit unit, in which series combinations of the multiple layer structures can achieve a higher potential window, which can better meet the needs of wearable electronic devices. Design/methodology/approach – Two-capacitive layer thread supercapacitors were fabricated using a semi-automatic dip coating method by coating two capacitive layers sequentially on a 50 μm stainless steel core wire, each capacitive layer includes ink, aqueous-based gel electrolyte and silver conductive paint layers. Findings – Two capacitive layers of the single thread supercapacitor can work independently, or as combination circuits – parallel and series. Cyclic voltammograms showed that all flexible circuits have high electrochemical stability. For the case of series circuit configuration, with H3PO-polyvinyl alcohol (PVA) gel electrolyte, a working potential window of 2 V was achieved. Originality/value – A flexible single thread supercapacitor of multilayer structure, with working voltage above 1 V in H3PO4-PVA gel electrolyte, has not been reported before. A semi-automatic dip coating setup used to process the thread supercapacitor has high potential for transfer to an industrial environment for mass production.

Flexible nanoscale thread of MnSn(OH)6 crystallite with liquid-like behavior and its application in nanocomposites.

We reported a solvent-free nanofluid based on MnSn(OH)6 crystallite with thread-like morphology through sulfuric-acid-terminated organosilanes as corona and polyether amine as canopy. The resultant is characterized by various analytical techniques and shows excellent solubility, good dispersity, improved processability and fluidity at room temperature in the absence of any solvents, which offer great potential in applications such as plasticizers with effects of toughening and reinforcement in nanocomposites. In addition, as a kind of plasticizer, it can also improve the Tg of its nanocomposites. These advantages of the flexible nanoscale thread of MnSn(OH)6 crystallite make it can be easily applied on the fabrication of high performance of nanocomposites.

The course of the posterior interosseous nerve in relation to the proximal radius: Is there a reliable landmark?

PurposeThe posterior interosseous nerve (PIN) is closely related to the proximal radius, and it is at risk when approaching the proximal forearm from the ventral and lateral side. This anatomic study analyzes the location of the PIN in relation to the proximal radius depending on forearm rotation by means of a novel investigation design. The purpose of this study is to define landmarks to locate the PIN intraoperatively in order to avoid neurological complications. MethodsWe dissected six upper extremities of fresh-frozen cadaveric specimens. The mean donor age at the time of death was 81.2 years. The PIN was dissected and marked on its course along the proximal forearm with a 0.3-mm flexible radiopaque thread. Three-dimensional (3D) X-ray scans were performed, and the location of the nerve was analyzed in neutral rotation, supination, and pronation. ResultsIn the coronal view, the PIN crosses the radial neck/shaft at a mean of 33.4 (±5.9)mm below the radial head surface (RHS) in pronation and 16.9 (±5.0)mm in supination. It crosses 4.9 (±2.2)mm distal of the most prominent point of the radial tuberosity (RT) in pronation and 9.6 (±5.2)mm proximal in supination.In the sagittal view, the PIN crosses the proximal radius 61.8 (±2.9)mm below the RHS in pronation and 41.1 (±3.6)mm in supination. The nerve crosses 29.2 (±6.2)mm distal of the RT in pronation and 11.0 (±2.8)mm in supination. ConclusionWith this novel design, the RT could be defined as a useful landmark for intraoperative orientation. On a ventral approach, the PIN courses 10mm proximal of it in supination and 5mm distal of it in pronation. Laterally, pronation increases the distance of the PIN to the RT to approximately 3cm.

Embroidered Wire Dipole Antennas Using Novel Copper Yarns

This letter presents a method of fabricating wearable antennas by embroidering novel fine copper yarn. In this work, fine copper wires are first twisted together to create a physically strong and yet flexible thread. A digital embroidery machine was used to create dipole antennas. The dc resistance of the antenna arms along with the return loss, radiation patterns, and efficiency of the antennas have been measured. The results are compared to embroidered dipoles using commercially available conductive threads and etched copper antennas.

One-piece bone flap osteotomy using thread wire saw for fronto-orbital advancement with distraction osteogenesis in craniosynostosis.

The objectives of this study are to describe our new technique of one-piece bone flap osteotomy for fronto-orbital advancement with distraction osteogenesis in craniosynostosis using a thin, flexible, and safe thread wire saw (the T-saw) and to compare the results with those of classic osteotomy using an osteotome. Initial osteotomy is performed between two pterion burr holes using a craniotome with a guarded footplate. The outer sphenoid wing and lateral orbital rim are separated using a reciprocating saw. Limited dura dissection from inner cortex between burr holes in the pterion and nasion is performed. The T-saw is inserted through the epidural space behind the superior orbital wall between the lateral orbital rim and nasion burr hole; the osteotomy is performed with gentle reciprocating strokes. Dura protection with a malleable retractor is not absolutely necessary. Five patients underwent one-piece fronto-orbital bone flap osteotomies using a T-saw in 2009-2014. The median age was 26 months (7-132 months), median operation time was 275 min (183-303 min), and median estimated blood loss was 65 mL (20-250 mL). These values did not differ from those of control cases. No complications, including incomplete osteotomy, occurred. The T-saw creates an osteotomy as a "one-stroke sketch," so incomplete osteotomy never occurs. The osteotomy can be performed safely without protecting the dura. Osteotomy with T-saw does not negate the advantages of fronto-orbital advancement with distraction osteogenesis, including shorter operative time, less intraoperative bleeding, and fewer complications.

An Experimental Study on Tip Vortex Cavitation Suppression in a Marine Propeller

Normally, tip vortex cavitation (TVC) is first observed at a certain location behind the tips of propeller blades. Therefore, TVC is important for naval ships and research vessels that require raising the cavitation inception speed to maximum possible values. The concepts for alleviating the tip vortex are summarized by Platzer and Souders (1979), who carried out a thorough literature survey. Active control of TVC involves the injection of a polymer or water from the blade tip. The main effect of such mass injection (both water and polymer solutions) into the vortex core is an increase in the core radius, consequently delaying TVC inception. However, the location of the injection port needs to be selected with great care to ensure that the mass injection is effective in delaying TVC inception. In the present study, we propose a semi-active control scheme that is achieved by attaching a thread at the propeller tip. The main idea of a semi-active control is that because of its flexibility, the attached thread can be sucked into the low-pressure region closer to the vortex core center. An experimental study using a scale model was carried out in the cavitation tunnel at the Seoul National University. It was found that a flexible thread can effectively suppress the occurrence of TVC under the design condition for a model propeller.

An Experimental Study on Tip Vortex Cavitation Suppression in a Marine Propeller

Normally, tip vortex cavitation (TVC) is first observed at a certain location behind the tips of propeller blades. Therefore, TVC is important for naval ships and research vessels that require raising the cavitation inception speed to maximum possible values. The concepts for alleviating the tip vortex are summarized by Platzer and Souders (1979), who carried out a thorough literature survey. Active control of TVC involves the injection of a polymer or water from the blade tip. The main effect of such mass injection (both water and polymer solutions) into the vortex core is an increase in the core radius, consequently delaying TVC inception. However, the location of the injection port needs to be selected with great care to ensure that the mass injection is effective in delaying TVC inception. In the present study, the authors propose a semiactive control scheme that is achieved by attaching a thread at the propeller tip. The main idea of a semiactive control is that because of its flexibility, the attached thread can be sucked into the low-pressure region closer to the vortex core center. An experimental study using a scale model was carried out in the cavitation tunnel at the Seoul National University. It was found that a flexible thread can effectively suppress the occurrence of TVC under the design condition for a model propeller.

Mathematical modeling of unloading a linear shock cord used in aircraft engineering

A mathematical model of accelerating a body along the inclined and horizontal rails under the tension force of the prestretched shock cord has been developed and numerically realized. The nonlinearity of load-strain dependence is taken into account. The shock cord is modeled as an absolutely flexible deformable thread. The results of numerical study are compared with the experiment data.

Fabrication and Characterisation of Flexible Coaxial Thin Thread Supercapacitors

Flexible coaxial thin thread supercapacitors were fabricated semi-automatically using a dip coating method. A typical coaxial thin thread supercapacitor of a length of 70 cm demonstrated a specific length capacitance of 0.3 mF cm−1 (11.2 mF cm−2 and 2.18 F cm−3) at 5 mV s−1, the device exhibited good electrochemical performance with a high volume energy density of 0.22 mWh cm−3 at a power density of 22 mW cm−3. Thread supercapacitors were assembled in series and parallel combinations, the accepted models for series and parallel circuit combinations were obeyed for two coaxial thread supercapacitors. The thread shows high flexibility and uniformity of specific length capacitance, one integrated with a commercial solar cell could be charged and power a LED. The process is simple, robust and easy to scale up to make unlimited length thread supercapacitors for numerous miniaturized and flexible electronic applications.

Геометрически нелинейный расчет висячих стержневых конструкций. Часть 1. Расчет гибких нитей

Is treated geometrically nonlinear matrix calculation core construction with the use of flexible threads. The first part is devoted to the study the major calculation dependencies of flexible threads. It is established that the geometric nonlinearity of flexible rods depends on the cube of the ratio of the calculation in a zero-offsets end stabilize relations to its current value. Also found that the constructive nonlinearity is a special case of geometrical nonlinearity and depends on the degree of impact on the VDS of flexible thread load on its own weight. It is found that the preliminary adjustment of the length of flexible rods leads to the increase of the share of the stresses of constant load and, accordingly, to the approximation of the nature of the work of these elements into a linear model.

Flexible Scheduling and Thread Allocation for Synchronous Parallel Tasks

We describe a task model and dynamic scheduling and resource allocation mechanism for synchronous parallel tasks to be executed on SPMD-programmed synchronous shared-memory MIMD parallel architectures with uniform, unit-time memory access and strict memory consistency, also known in the literature as PRAMs (Parallel Random Access Machines). Our task model provides a two-tier programming model for PRAMs that flexibly combines SPMD and fork-join parallelism within the same application. It offers flexibility by dynamic scheduling and late resource binding while preserving the PRAM execution properties within each task, the only limitation being that the maximum number of threads that can be assigned to a task is limited to what the underlying architecture provides. In particular, our approach opens for automatic performance tuning at run-time by controlling the thread allocation for tasks based on run-time predictions. By a prototype implementation of a synchronous parallel task API in the SPMD-based PRAM language Fork and experimental evaluation with example programs on the SBPRAM simulator, we show that a realization of the task model on a SPMD-programmable PRAM machine is feasible with moderate runtime overhead per task.

Statics and dynamics of a flexible elastic thread wound on a reel

The statics and dynamics of a flexible extensible elastic thread wound on a reel and interacting with the surface by the dry friction law are studied. Both the thread loading and unloading are analyzed. The depth of perturbation penetration is found.

Single Fiber Transport in a Fracture Slit: Influence of the Wall Roughness and of the Fiber Flexibility

The transport of fibers by a fluid flow is investigated in transparent channels modeling rock fractures: the experiments use flexible polyester thread (mean diameter 280 μm) and water or a water–polymer solution. For a channel with smooth parallel walls and a mean aperture ā = 0.65 mm, both fiber segments of length ℓ = 20–150 mm and “continuous” fibers longer than the channel length have been used: in both the cases, the velocity of the fibers and its variation with distance could be accounted for while neglecting friction with the walls. For rough self-affine walls and a continuous gradient of the local mean aperture transverse to the flow, transport of the fibers by a water flow is only possible in the region of larger aperture (ā ≲ 1.1 mm) and is of “stop and go” type at low velocities. With the polymer solution, the fibers move faster and more continuously in high aperture regions and their interaction with the walls is reduced; fiber transport becomes also possible in narrower regions where irreversible pinning occurred for water. In a third rough model with parallel walls and a low mean aperture ā = 0.65 mm, fiber transport is only possible with the water–polymer solution. The dynamics of fiber deformations and entanglement during pinning–depinning events and permanent pinning is analyzed.