Coil Length Research Articles

Helical shape linen artificial muscles responsive to water

Artificial muscles, as the name suggests, can generate contractile force and movement from another source of energy in response to an external stimulus. Moisture-responsive artificial muscles can be manufactured from commodity natural fibers for smart textile applications taking advantage of the anisotropy, low cost and skin comfort of these fibers. Here we prepared water-driven artificial muscles by twisting linen yarns into spring-like cylindrical coils. Structural evolution, including increase in diameter and decrease in length of coils, is identified as a key factor to the actuation performances of the as-fabricated muscles. Artificial muscles with a single helical configuration can generate a large, reversible contraction stroke of about 22.5% and a high gravimetric work capacity during contraction of about 110 J kg−1 work capacity, which is many times greater than animal skeletal muscles and many synthetic fiber muscles. A torque-balanced double-helix muscle was constructed from the single helical muscle. The double helix showed good reversibility and high retention of contraction stroke (∼16.5%) in cyclic actuation tests. Finally, the as-fabricated water-responsive artificial muscles were used as manipulator arm of a miniature excavator.

Experimental Study of Coil Compaction: Impact of Pulsatile Stress.

Coil compaction after aneurysm embolization is one of the major issues associated with aneurysm recurrence. On the presumption that pulsatile stress to the aneurysm is responsible for coil compaction, we developed an experimental model in vitro to visualize the mechanical stresses exerted by blood pressure and pulse and their relation to coil compaction. A closed-type non-circulation system was developed by installing a syringe that generated pressure at one end of a tube, along with a spherical aneurysm made of silicone and a pressure sensor in the bifurcated end. We installed a fixed-pressure model under a steady pressure of 300 mmHg while the pressure-fluctuation model simulated the pressure variations using a plunger (in a syringe) by using a motor that applied pulsatile stress in the range of 50 mmHg for a 10-ms cycle. We devised four types of aneurysms with different depths and the same coil length. After coil packing, the aneurysms were observed for 3 days (the observation period in the pressure-fluctuation model corresponded to approximately 300 days in real time). The distance from the datum point to the observable coil loops was determined as the initial position, and the temporal change in the distance from that position was measured. In the fixed-pressure model, the average distance of coil movement was very small (less than ±0.1 mm). In the pressure-fluctuation model, the movement of coils was observed to be significant for the two longest depths (0.11 and 0.14 mm). The maximal dynamic change in coil movement was observed on the second day. The range of movement was observed to decrease thereafter. Our experimental study enabled the observation of coil movement within a short duration. It examined coil compaction by applying pulsed pressure to the coils at high speeds. Consequently, a shift of the coil loops inside the incompletely occluded aneurysms was detected on applying a pulsed pressure.

A novel flow injection amperometric sensor based on carbon black and graphene oxide modified screen-printed carbon electrode for highly sensitive determination of uric acid

A simple, rapid, and cost-effective flow injection amperometric (FI-Amp) sensor for sensitive determination of uric acid (UA) was developed based on a new combination of carbon black (CB) and graphene oxide (GO) modified screen-printed carbon electrode (SPCE). The CB-GO nanocomposites were simply synthesized and modified on the working electrode surface to increase electrode conductivity and enhance the sensitivity of UA determination via the electrocatalytic activity toward UA oxidation. The morphologies and electrochemical properties of the synthesized nanomaterials were investigated through scanning electron microscopy (SEM), transmission electron microscopy (TEM), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The modified electrode was incorporated with FI-Amp to improve UA detection's sensitivity, stability, and automation. Some parameters affecting sensitivity were optimized, including pH of the electrolyte solution, applied potential, amount of CB-GO suspension, flow rate, injection volume, and reaction coil length. Using an applied potential of +0.35 V (vs Ag/AgCl), the anodic current was linearly proportional to UA concentration over the range of 0.05–2000 μM with a detection limit of 0.01 μM (3 S/N). Besides, the developed method provides a sample throughput of 25 injections h−1, excellent sensitivity (0.0191 μA/μM), selectivity, repeatability (RSD 3.1%, n = 7), and stability (RSD 1.08%, n = 50). The proposed system can tolerate potential interferences commonly found in human urine. Furthermore, a good correlation coefficient between the results obtained from the FI-Amp sensor and a hospital laboratory implies that the proposed system is accurate and can be utilized for UA detection in urine samples.

High-spatial-resolution nuclear-magnetic-resonance method for investigation of fluid distribution in whole cores

Low field Nuclear Magnetic Resonance (NMR) has been widely used in laboratories to investigate hydrocarbon and water in small core plugs to provide accurate petrophysical measurements and for calibration of downhole NMR logs. One fundamental limiting factor of current NMR technologies on large whole core is that the spatial resolution is limited by the length of the radio-frequency (r.f.) detection coil. In addition, the end effects of finite coil length can compromise the accuracy of NMR measurement when the core is longer than the coil. Herein a method is developed to overcome these problems to acquire high-spatial-resolution (HSR-) NMR data of the fluid in the long rock samples. The method is implemented by first conducting a series of NMR measurements in synchronization with a stepwise movement of the long sample through the NMR r.f. coil with the step increment equal to the desired spatial resolution. It then inverts the acquired data to obtain HSR-NMR results using a robust inversion algorithm. This new method provides a non-destructive measurement of fluid content with any desired spatial resolution and is especially useful for tight rock samples with short NMR relaxation times. The method is tested on 23 preserved whole cores from a source rock reservoir. The measured fluid distribution from the HSR-NMR method matches well with the fluid content from GRI method on the same sections of the preserved cores. In addition, the measured fluid distribution correlates well with the kerogen content along the cores with obvious lamination in the samples.

Optimization of a quadrature birdcage coil for functional imaging of squirrel monkey brain at 9.4T

A quadrature transmit/receive birdcage coil was optimized for squirrel monkey functional imaging at the high field of 9.4 T. The coil length was chosen to gain maximum coil efficiency/signal-to-noise ratio (SNR) and meanwhile provide enough homogenous RF field in the whole brain area. Based on the numerical simulation results, a 16-rung high-pass birdcage coil with the optimal length of 9 cm was constructed and evaluated on phantom and in vivo experiments. Compared to a general-purpose non-optimized coil, it exhibits approximately 25% in vivo SNR improvement. In addition to the volume coil, details about how to design and construct the associated animal preparation system were provided.

Improvement of Superconducting Linear Acceleration System for Pellet Injection: Optimization of Current Profile

The improvement of the acceleration performance of a superconducting linear acceleration (SLA) system for injecting the pellet container into the helical fusion reactor has been investigated numerically. To this end, a numerical code used in the finite element method and the non-dominated sorting genetic algorithms-II has been developed for analyzing both the shielding current density in an HTS film and the dynamic motion of the film. In addition, the current profile of the acceleration coil is optimized by the normalized Gaussian network (NGnet) method. The results of the computations show that when the current profile of the outer coil is optimized by using the NGnet method, the pellet velocity is greatly faster than that for the homogeneous current profile. Moreover, the speedup ratio decreases monotonously as the coil length increases. If the length of the outer coil is more than twice that of the inner coil, the number of the filaments outside the inner coil reduces extremely. This result means that the amount of the filament and the energy consumption can be reduced compared with the homogeneous current profile.

Vessel Occlusion using Hydrogel-Coated versus Nonhydrogel Embolization Coils in Peripheral Arterial Applications: A Prospective, Multicenter, Randomized Trial

PurposeTo evaluate the safety and effectiveness of hydrogel-coated coils for vessel occlusion in the body trunk. Materials and MethodsA total of 77 patients with various peripheral vascular lesions, treatable by embolization with coils, were randomized (hydrogel group, n = 38; nonhydrogel group, n = 39). In the hydrogel group, embolization of the target vessel was conducted using 0.018-inch hydrogel-coated coils (AZUR 18; Terumo Medical Corporation, Tokyo, Japan) with or without bare platinum coils. The nonhydrogel group received both bare platinum coils and fibered coils without the use of hydrogel-coated coils. ResultsComplete target vessel occlusion was accomplished in 36 patients in the hydrogel group and 37 patients in the nonhydrogel group. No major adverse events were observed in either group. The median number of coils/vessel diameter and the median total coil length/vessel diameter were significantly larger in the nonhydrogel group than in the hydrogel group (P = .005 and P = .004, respectively). The median embolization length was significantly longer in the nonhydrogel group (31.95 mm) than in the hydrogel group (23.43 mm) (P = .002). If no expansion was assumed, the median packing density in the hydrogel group was 44.9%, which was similar to that in the nonhydrogel group (46.5%) (P = .79). With full expansion assumed, the median packing density in the hydrogel group was 125.7%. ConclusionsHydrogel-coated coils can be safely used for peripheral vascular coil embolization, and hydrogel-coated and conventional coils in combination allow for a shorter embolization segment and shorter coil length.

Multi-objective optimization of laminar flow characteristics in helical coiled tubes based on NSGA-II

To meet the requirement of energy conservation and optimize the design of helical coils in laminar flow, the pitch, the coil radius and the average inlet velocity were selected as design parameters to obtain the tendency of the heat transfer and flow resistance characteristics of the helical coils. Heat transfer coefficient and pressure drop per unit length of helical coils were taken as the optimization objective functions. A multi-objective optimization model was established, three candidate points A, B and C were obtained based on Non-dominated Sorted Genetic Algorithm-II (NSGA-II). The results showed that heat transfer coefficient and pressure drop per unit length increase with the pitch and inlet velocity whilst them decrease with coil radius, among which the influence of inlet velocity is the most obvious and the pitch is the least. It was found that the coil radius of most points in Pareto front was relatively concentrated. The comprehensive performance of candidate points A, B, C had been improved significantly by 16.3%, 28.3% and 19.6% respectively.

A Simulation Magnetic Induction Tomography (MIT) for Agarwood using COMSOL Multiphysics

Magnetic induction tomography is an imaging technique used to image electromagnetic properties of an object by using the eddy current effect. (MIT) is a non-destructive method that greatly is used in the agriculture industry. This method provided an opportunity to improve the quality of agricultural products. MIT simulation was used for agarwood existence detection. This paper presented for the simulation system contains 7 channel coils receiver and a channel transmitter which is a sensing detector. This experiment aims to demonstrate the reaction of induced current density and magnetic field at 10 MHz frequency. Then, it also determines the optimal solenoid coil to be used for a better outcome for the magnetic induction system. The simulation result shows that coil diameter, coil length, and coil layer have a crucial role in the great performance of the induced current and magnetic field. The more coil turns, the greater the strength of the permanent magnetic field around the solenoid coil. The result of the simulation is important and needs to be considered to verify the effectiveness of the system for developing the magnetic induction circuit design.

The Reduction of Force Component Produced by Short Sides by Analyzing the Corner of Coil in Planar Motor with Halbach Magnet Array

The planar motor with moving-magnet is purely levitated by the stator coils. The forces produced by coils are calculated with the analytical model of magnet array and coil surface model for applying to the real time control. Take the coil and the Halbach magnet array which is at 45 degree with the long side of coil for analysis. The force component produced by short sides can be eliminated for conveniently controlling when the length of coil takes certain dimension. In practice, the force component produced by short sides is small but not zero. There are two reasons, one is the higher harmonics and the other is the corner segments of coil. The force integral expressions of coil corner segments are given by the Lorenz force law. Then the forces numerically calculated with harmonic model and coil full model are verified by comparing with the magnetic surface charge model and finite element model. In order to reduce the force component produced by short sides, the different corners of coil are analyzed. Comparing the forces of different corners of coil, the force component produced by short sides can be significantly reduced with slightly change of the other force components.

Application Research of HTS Linear Motor Based on Halbach Array in High Speed Maglev System

For the application of the high speed maglev system, a high temperature superconducting linear synchronous motor (HTSLSM) structure based on the Halbach array and high temperature superconducting tape is proposed. The 2D finite element model of the HTSLSM is established. The magnetic field distribution characteristics of HTSLSMs with Halbach structure magnets and those with alternative structure magnets are compared and analyzed respectively. Then, the thrust and normal force characteristics of the HTSLSM are studied. The influence of the mover coil length and air gaps on the performance of the HTSLSM with Halbach structure magnets is also elaborated.

High energy implementation of coil-target scheme for guided re-acceleration of laser-driven protons

Developing compact ion accelerators using intense lasers is a very active area of research, motivated by a strong applicative potential in science, industry and healthcare. However, proposed applications in medical therapy, as well as in nuclear and particle physics demand a strict control of ion energy, as well as of the angular and spectral distribution of ion beam, beyond the intrinsic limitations of the several acceleration mechanisms explored so far. Here we report on the production of highly collimated (sim 0.2^{circ } half angle divergence), high-charge (10s of pC) and quasi-monoenergetic proton beams up to sim 50 MeV, using a recently developed method based on helical coil targetry. In this concept, ions accelerated from a laser-irradiated foil are post-accelerated and conditioned in a helical structure positioned at the rear of the foil. The pencil beam of protons was produced by guided post-acceleration at a rate of sim 2 GeV/m, without sacrificing the excellent beam emittance of the laser-driven proton beams. 3D particle tracing simulations indicate the possibility of sustaining high acceleration gradients over extended helical coil lengths, thus maximising the gain from such miniature accelerating modules.

Investigations of batch fluctuation regarding tribological conditions in series production of car body parts

Fluctuations of material properties are one reason for the occurrence of cracks and waviness in series production of car body parts. Especially fluctuating tribological conditions have an effect on the friction behavior and thus on the material flow. So far fluctuating material properties are not considered in the standard FE-simulation and consequently not in the tool design. In order to enhance the accuracy of the simulation result and thus improve the tool design regarding a robust process, the appearance of batch fluctuations has to be consistently understood. Therefore, the impact of varying lubricant quantities and roughness have been investigated. Several batches have been analyzed to identify the main influencing parameter regarding the friction behavior. Flat strip-drawing tests have been performed to determine the friction coefficient. The investigations have been performed by using material from the series production, as delivered. Since the amount of lubricant turns out to be the main influencing factor, the characteristics and appearance of the lubricant distribution has been analyzed in a further step. The analysis has shown that the distribution of the lubricant changes within one coil over the coil width and length. In addition, the time of storage has been identified as one main influencing factor on the homogeneity of the lubricant distribution over the coil width. Based on these findings, a method has been developed to map the series production conditions regarding the friction conditions in the simulation. Hence, simulations were performed using a side frame blank with different friction conditions, to investigate the impact on the forming result. The results reveal that by considering realistically existing tribological conditions, more scrap is to be expected compared to the conventional simulation. This leads to the conclusion that previous simulation results are too optimistic. Consequently, the introduced method offers the potential to optimize the tool design by considering fluctuating tribological conditions already in the process of development. Thus, it is possible to reduce scrap and increase productivity.

LabVIEW virtual instrument for zone penetration studies in flow-based analytical systems

In the flow method development, zone penetration studies are usually conducted as a part of the initial screening phase. A lack of an appropriate tool can keep these studies on the level of rough estimations. The developed LabVIEW virtual instrument (VI) which processes peak signals and calculates the overlapping area and fundamental peak-related parameters was used for the calculations in experiments that are modelling sample and reagent plug interaction within liquid conduits. The reliability of the predictions was initially confirmed on the artificial data set based on thirty-six files covering all the different types of cases that can be foreseen. To continue, the volumes of model solutions, propelling flow rate, and the coil length in the sequential injection analysis system, were varied by following the Box?Behnken response surface design. In three examples, it is demonstrated how the VI can help the planning of further experiments in the range which ensures the efficient zone overlapping, the economic exploitation of reagent plug and the adequate dispersion. The application of the VI is not limited just to the flow-based chemistry, it can also be used in spectroscopy and chromatography. In order to use the graphical user interface, it is not necessary to have the LabVIEW program installed.

Coil Selection, Handling and Troubleshooting in Detachment Failure

The first coil should be as thick, long, and large as possible. A retrospective study at the Toranomon Hospital revealed that if the volume of the first coil is 1/3rd or more of the total coil volume, there are less chances of retreatment. Thus, a thick and long first coil contributes to stable long-term anatomical results. The length of the first coil should be approximately 8% of the volume of the aneurysm. After the placement of the first coil, a smaller and shorter coil should be placed sufficiently close to it to complete the procedure. The goal is to achieve prevention of acute re-rupture in ruptured acute aneurysms and life-long prevention of rupture in unruptured asymptomatic aneurysms. If the coil does not detach, check the position of the detachment point, and replace the power supply. In addition, refer to the direction for use of the device for prevention of coil disconnection failure and countermeasures. Although it is not a recommended method, a method of rotating the delivery wire at the detached position to thread the coil and a method of reconstructing the electric circuit with a crocodile clip has been reported.

Influence of neurovascular embolic coil primary wind diameter on aneurysm packing density and case costs

Aims Endovascular coiling is a common modality for treating intracranial aneurysms; however, recanalization occurs in approximately 1 in 5 cases, with downstream consequences of regrowth and rupture. Aneurysm packing density >24% reduces recanalization risk; packing density can be increased by inserting additional coils or by using coils with larger volumetric filling. Coil volume depends on length and primary wind diameter (PWD). This study evaluated the influence of PWD on packing density and total case costs. Materials and methods Two hypothetical scenarios and one case study were analyzed. In scenario one, the number of coils required to achieve packing density >24% in a hypothetical aneurysm was determined for 0.012″ vs. 0.010″ PWD coils. In scenario two, the total length of 0.010″ vs. 0.012″ PWD coils required to achieve a packing density >24% was analyzed relative to aneurysm volume. In the case study, packing densities with one 0.012″ PWD coil (actual scenario) and one 0.010″ PWD coil (theoretical scenario) were compared. Results In scenario one, cost savings would be realized by using four 0.012″ PWD coils vs. seven 0.010″ PWD coils to achieve packing density >24%. In scenario two, greater volumetric filling of 0.012″ vs. 0.010″ PWD coils was correlated with lower total length of coil required. In the case study, a 0.012″ PWD coil achieved packing density >24%, whereas an equivalent length 0.010″ PWD coil would not. Limitations Theoretical modeling was used to explore the impact of coil PWD on aneurysm packing density. In clinical practice, packing density depends not only on PWD but on its length, shape, distribution within an aneurysm, and other recanalization risk factors. Conclusions Coil PWD influences packing density, the number of coils required to achieve a specific packing density, and total case costs. Using 0.012″ PWD coils may provide cost and procedural efficiencies.

A Ferromagnetic Wear Particle Sensor Based on a Rotational Symmetry High-Gradient Magnetostatic Field

To improve the wear monitoring accuracy of steel tribo-pairs, a ferromagnetic particle sensor that consists of a magnetic loop with two cylindrical magnetic poles and one magnetic housing is proposed. The induction coil is placed inside the magnetic poles to shield against external electromagnetic interference. The air gap is designed to 1 mm between the two magnetic poles, where a rotational symmetric high-gradient static magnetic field will be generated under constant direct current (dc) drive. The sine-wave-like signal of one period will be induced when one ferromagnetic particle flows through the sensor. The working principle of the sensor and the internal magnetic field distribution is explained by establishing a mathematical model and finite element analysis (FEA). Furthermore, the results about the effects of coil length and position show that the output voltage is not sensitive to the axial mounting positions of the induction coil, and a shorter inductive coil produces a larger output voltage. By the oil dynamic monitoring experiment, the sensor can distinguish 13- $\mu \text{m}$ ferromagnetic particles in an oil tube of 10-mm inner diameter. With its high sensitivity to ferromagnetic particles, the sensor is suitable for online wear monitoring of steel tribo-pairs.

Helically coiled solar cavity receiver for micro-scale direct steam generation

Concentrated solar systems have a large potential for power generation and water pumping in rural off-grid settlements with a high solar irradiance resource. With the use of a solar dish concentrator, superheated steam can be directly generated in a solar cavity receiver. Volumetric expanders show promise for micro-scale power production (below 1 kW). However, naturalistic experimental investigations of micro-scale direct steam generation using a solar dish is limited. In this work, a low-cost helically coiled cavity receiver and a novel solar concentrator manufactured from off-the-shelf components are experimentally investigated for steam generation at water pressures of above 3 bar. Working fluid temperatures were measured throughout the coil length and pressures were measured at the inlet and outlet of the receiver coil. Using a concentrator with a total incident area of 2.70 m2 and a water flow rate of 0.294 g/s, the working fluid captured 861 W of heat with an outlet temperature of 343 °C at an average solar irradiance of 757 W/m2. The average thermal efficiencies of the collector and receiver were determined to be 42% and 50%, respectively, for the testing period. Furthermore, the average second-law efficiency was 12%. Flow patterns within the coil were investigated by considering the temperature differences between the coil surface and the working fluid. A heat loss model was developed that could predict the steady-state heat loss rate with an accuracy of 97%. The observations made during the study and the results obtained highlight important design aspects that need to be considered in future work.

Effect of Ureteral Stent Length and Position of Stent Coil in Bladder on Stent-Related Symptoms and Quality of Life of Patients.

Introduction: Various standardized questionnaires can evaluate ureteral stent-related symptoms. The present study utilized a validated instrument, Ureteral Stent Symptoms Questionnaire (USSQ), to know the impact of the length of double J stent (DJS) in comparison to ureter length on patients and their quality of living.Materials and Method: This study is a prospective clinical study conducted in the Department of Urology at a tertiary care center in South India. Patients who underwent DJS after endoscopic ureteral lithotripsy were included in the study. On a computerized tomography scan, the ureteral to stent length ratio (USR) was calculated. USSQ scores at the time of DJS removal and two weeks thereafter were recorded. The distal coil of the stent in the bladder was recorded as grade 1 - not crossing the midline and grade 2 - crossing the midline. Different symptom scores were compared between both grades of bladder coil and for USR of all the patients.Result: A total of 157 patients were included in the study. Over 46 (29.3%) patients had grade-1 and 111 (70.7%) had grade-2 bladder coil. Totally 93 (59.23%) patients reported pain, while 64 (40.77%) patients had no pain. Grade-2 coil patients had more pain than grade 1 (P=0.01). There was a weak inverse relationship between the USR and urinary symptom (P=0.004), pain symptom (P=0.04), and quality of work (P=0.005).Conclusion: Stent length or position of the intravesical stent coil does not appear to affect the quality of life except for the pain. Hence, choosing stent length according to ureteral length seems to have a minimal role in decreasing stent-related morbidity.

Analysis of End-Windings Influence on the Transient Voltage Distribution in Machine Stator Windings by a Three Phase Model

Transient voltage distribution due to steep-fronted surges must be taken into account during the machine's design as it can lead to main and turn insulation failure. In medium voltage machines, the end-windings region has a considerable percentage of the coil length and plays an important role during transient studies. This article has the purpose of verifying the influence of end-windings on the transient voltage distribution by using a three-phase simulation model in which transient magnetic fields and electric circuit elements are coupled. The transient simulation and the calculation of the electrical parameters used in the model are done employing the Finite Elements Method (FEM). To verify the influence on the results, simulations for different surge rise times are performed, considering and neglecting the end-windings model. As main results, the intercoil and interturn voltages are analyzed for all turns from the three phases of one winding group. The model is validated by measurement results. It is shown that the end-windings, indeed, affect the transient voltage distribution for both, interturn and intercoil voltages, regarding the rate of rising (slope), instant, and the amplitude of the peak voltages. Moreover, all three phases are affected by the end-windings, especially for the turn-to-turn voltages.