Tube Electrode Research Articles

Geometric Accuracy Improvement by Using Electrochemical Reaming with a Helical Tube Electrode as Post-Processing for EDM.

Electrochemical reaming using a helical tube electrode together with lateral flushing is proposed as post-processing to improve the machining accuracy and surface quality of holes produced by electrical discharge machining (EDM). The velocity distributions of flushing in the machining gap for a cylindrical tube electrode and for a helical tube electrode were compared using flow field simulations. The role of the helical structure in promoting removal of machining products was illustrated by the results of the flow field simulations for different lateral flushing pressures. The performance of electrochemical reaming as post-processing in improving machining accuracy and surface quality was verified by comparative experiments examining the exit circularity error, taper, and surface morphology of machined holes. Finally, an optimum combination of machining parameters was obtained through a process parameter optimization experiment.

Study of electrohydrodynamic phenomena in high temperature high pressure nitrogen

The study of corona discharge current-voltage characteristics (CVCs) in high temperature high pressure (HTHP) gases is an important step in development of compact HTHP electrostatic equipment. The scope of the current work was the study of corona discharge CVCs in HTHP nitrogen. Corona discharge ionizer was installed inside of a HTHP casing. Ionizer included star-shaped high voltage electrodes installed inside of a grounded tube electrode. The grounded electrode could be heated. Tests were carried out at various gas pressure and grounded electrode temperatures. The CVC-direct and CVC-indirect characteristics were measured for positive and negative polarity of applied voltage. For the same values of applied voltage, current for negative corona was higher than for positive one. The increase of gas pressure stabilized corona discharge and increased corona onset voltage. Operation of the ionizer at CVC-indirect ensured stable corona discharge. Corona discharge CVCs have shown hysteresis loop which area depended on gas pressure and temperature.

Effects of Helical Tube Electrode Structure on Mixed Machining Product Transfer in Micro-Machining Channel during Tube Electrode High-Speed Electrochemical Discharge Machining.

In tube electrode high-speed electrochemical discharge machining (TSECDM), mixed products are constantly produced in the narrow machining gap by simultaneous discharge erosion and electrochemical dissolution. For the high-efficiency removal of these products from the machining gap, a tool electrode with an optimized helical structure was utilized in TSECDM in this study. Firstly, the concentration distributions of the processed products in the machining gap using tube electrode tools with three typical helical structures were studied through the simulation of solid–liquid coupling; this showed that a trapezoidal helical structure benefited the reduced accumulation of products in grooves and the effective removal of products from the machining gap. Secondly, the main geometric parameters of the trapezoidal helical structure, including the helical groove depth, pitch, and tooth angle, were optimized by gap flow-field simulation to enhance the removal effect on processed products. Finally, it was verified that the trapezoidal helical electrode showed a definitive and significant advantage over the ordinary cylindrical electrode in effectively removing processed products from the machining gap by the comparison of flow-field simulations and actual machining experiments.

Numerical analysis of a novel [formula omitted] antimony selenide solar cell

Sb2Se3 antimony selenide is a great potential for solar cell commercial application with good absorption coefficient and optimal band gap. In recent years the maximum power conversion efficiency (PCE) achieved from Sb2Se3 is about 6.5% with CNT/PbS /Sb2Se3/CdS/ITO structure. In this structure PbS works as hole transport material (HTM), CdS as buffer layer and Au as back contact. But the toxic nature of (Cd,Pb) and high cost of Au contact it cannot be considered for commercial application. Because of this reason for the first-time alternate solar cell structure with Cu2O as HTM layer, In2S3 as buffer layer and carbon nano tube (CNT) electrode used as a back contact is proposed in this work for Sb2Se3. Device modeling for solar cell with structure CNT/Cu2O /Sb2Se3/In2S3/ITO was performed in solar cell capacitance simulator (SCAPS). After optimization of physical parameters like absorber thickness, acceptor doping of absorber layer, donor doping of buffer and replacing CdS buffer layer with In2S3 efficiency of experimentally designed cell jumped from 6.5% to 13.20%.

Intraoperative Monitoring for Vagus Nerve Stimulation

Vagus nerve stimulation is a palliative treatment for patients with refractory epilepsy; however, the misplacement of electrodes may cause complications and thus needs to be avoided. We herein report an intraoperative monitoring technique to prevent the misplacement of electrodes. Endotracheal tube electrodes were inserted to record electromyographic activity from the vocal cords and identify the vagus nerve. Electromyography electrodes were placed on the sternomastoid muscle, sternohyoid muscle, geniohyoid muscle, and trapezius muscle to record muscle activities innervated by the ansa cervicalis. The vagus nerve and ansa cervicalis were electrically stimulated during surgery, and electromyography of the vocal cords and muscles innervated by the ansa cervicalis was recorded. The threshold of vagus nerve activation ranged between 0.05 and 0.75 mA. The vagus nerve was successfully identified and differentiated from the nerve root of the ansa cervicalis using this technique. Intraoperative monitoring of the vagus nerve and ansa cervicalis is useful for safe and effective vagus nerve stimulation.

Mechanically Active Transducing Element Based on Solid–Liquid Triboelectric Nanogenerator for Self-Powered Sensing

As power generation from the electronically active materials has been made remarkable progress to scavenge the ambient mechanical energy, harnessing energy from fluidics with liquid–solid contact electrification charging from the flow has become new capabilities to be applied as the sensory module. In this paper, a mechanical fluidic nanogenerator based on solid–liquid contact triboelectrification is demonstrated in which liquid electricity signal can be transferred into from the mechanical motion. This simply designed device is composed of Polytetrafluoroethylene (PTFE) tube and copper electrodes at both ends. To evaluate the effectiveness of the device, deionized water (DI) is poured into the tube and the movement is controlled by air flow from the internal volume difference of the rotating mechanism. The peak current value of the mechanical active transducing element based triboelectric nanogenerator (MAT-TENG) signal is used for analyzing movement speed. Speed gradient was applied for back and forth motion of the liquid column with a stable peak of short circuit current and open circuit voltage was about 0.23 µA and 2.31 V, respectively, at the length of the motion amplitude of 23 mm and frequency of 1 Hz. Finally, the flexible MAT-TENG has shown distinct response with the change of the motion length and speed of the liquid and the results have been achieved with better linearity ~ R2 = 0.99. Therefore, the velocity transducing can be very effective in the practical applications of the TENGs based for self-powered sensing.

Workpiece reciprocating movement aided wire electrochemical machining using a tube electrode with an array of holes

Parts with a ruled surface manufactured to high accuracy and good surface integrity are widely used in industry. Wire electrochemical machining (WECM) has great advantages and potential in the processing of these parts because there is no residual machining stress, the surface is free of burrs and has no recast layer, and there is no tool wear. In this paper, WECM using a tube electrode with an array of holes was introduced to further improve the machining efficiency and capability for thick workpiece. Additionally, the reciprocating movement of the workpiece was used to change the spraying position of the electrolyte on the machining surface. The simulation results indicate that this method can improve the velocity and uniformity of the electrolyte flow field in the machining gap. Experiments verified that when the amplitude of the reciprocating movement is greater than the spacing of holes, machining efficiency and accuracy are greatly improved. Finally, using optimized machining parameters, an array of slits with a width of 550 μm (standard deviation of 5.99 μm) was fabricated on 10-mm-thick stainless steel 304 at a cutting rate of 3 mm²/min.

Encapsulating segment-like antimony nanorod in hollow carbon tube as long-lifespan, high-rate anodes for rechargeable K-ion batteries

K-ion battery (KIB) is a new-type energy storage device that possesses potential advantages of low-cost and abundant resource of potassium. To develop advanced electrode materials for accommodating the large size and high activity of potassium ion is of great interests. Herein, a segment-like antimony (Sb) nanorod encapsulated in hollow carbon tube electrode material (Sb@HCT) was prepared. Beneficial from the virtue of abundant nitrogen doping in carbon tube, one-dimensional and hollow structure advantages, Sb@HCT exhibits excellent potassium storage properties: in the case of potassium bis(fluorosulfonyl)imide (KFSI) electrolyte, Sb@HCT displays a reversible capacity of up to 453.4 mAh·g−1 at a current density of 0.5 A·g−1 and good rate performance (a capacity of 211.5 mAh·g−1 could be achieved at an ultrahigh rate of 5 A·g−1). Additionally, Sb@HCT demonstrates excellent long-cycle stability at a current density of 2 A·g−1 over 120 cycles. Meanwhile, electrolyte optimization is an effective strategy for greatly improving electrochemical performance. Through ex-situ characterizations, we disclosed the potassiation of Sb anode is quite reversible and undergoes multistep processes, combining solid solution reaction and two-phase reaction.

Effect of heat-treatment on the pH sensitivity of stainless-steel electrodes as pH sensors

Effect of heat-treatment on the pH sensitivity of uncoated stainless-steel electrodes was investigated to comprehend the pH sensitivity of metal-oxide coated stainless-steel electrodes as novel pH sensors. The pH sensitivity of stainless-steel electrodes as-received and heat-treated at 500 °C, 600 °C and 700 °C for 24 h were 91 %, 94 %, 102 % and 91 %, respectively. The pH sensitivity tended to increase with increasing heat-treatment time at a given temperature. Thus, the most suitable heat-treatment condition for the stainless-steel electrodes was 600 °C for 24 h. The austenite phase (fcc) was the main phase on the surface of the heat-treated stainless-steel electrodes. Unexpectedly, the change in the martensite phase (bcc) as the second phase with heat-treatment temperature was similar to the pH sensitivity, with the martensite phase affecting the pH sensitivity. Therefore, it appeared that the pH sensitivity of the metal-oxide coated stainless-steel electrodes was affected by the underlying stainless-steel as well as the outer metal-oxide film coating. A prototype stainless-steel tube electrode was used as a working electrode for demonstrating the depth profiling of pH. The stainless-steel tube electrode showed good performance for measuring pH depth profiles compared to commercially available glass electrodes.

Direct-Current Rotary-Tubular Triboelectric Nanogenerators Based on Liquid-Dielectrics Contact for Sustainable Energy Harvesting and Chemical Composition Analysis

Ambient mechanical energy harvesting technology introduces a promising solution to alleviate expanding energy demands on a sustainable basis, of which the drawbacks should attract attention for further advances. In this work, a liquid-dielectrics interface based triboelectric nanogenerator (TENG) with direct-current output is reported as an energy harvester and a chemical sensor, with advantages of feasible fabrication, anti-wearing durability, and low energy consumption. The TENG consisting of an fluorinated ethylene propylene (FEP) tube and Cu electrodes is designed into a ring structure, with two electric brushes bilaterally anchored that converts an alternating-current output into direct-current output. The liquids and copper pellets as the fluid-state dielectrics are prefilled to generate triboelectric charges with an FEP tube. The relevant parameters of TENG are initially optimized, enabling a satisfactory output under rotating excitations. Furthermore, the inherent impacts of various liquids on the output performance of TENG are comprehensively studied, based on which chemical analysis system is developed. Meanwhile, the design for TENG with pellets is also modified for output-current enhancement. Finally, an assembled TENG has been demonstrated not only for energy harvesting without rectification but also for chemical detecting in liquid composition and moisture content analysis. The proposed TENG renders a more-efficient method for energy harvesting and greatly expands its application in direct-current self-powered systems.

Investigation on EMG Profiles of the Superior Laryngeal Nerve in a In Vivo Porcine Model

Background: The electromyographic (EMG) profiles of external branch of the superior laryngeal nerve (EBSLN) have been defined and the optimal intensity of the stimulation of EBSLN in an in vivo porcine model has been explored. Materials: EMG was simultaneously registered by the surface of endotracheal tube and needle electrodes by applying a monopolar stimulation probe in 12 piglets (22 EBSLNs). Vagal nerve (VN), RLN and EBSLN were excited to record the EMG tracings and cricothyroid muscle twitch (CTM). VN, RLN and EBSLN were stimulated from 0.1 to 1.0 mA. Cmin and Cmax have been defined as the minimum and maximal stimulation to evoke an EMG response. Results: The stimulation resulted in a dose-response curve. Cmin were 0.19 mA (0.04–0.4), 0.19 mA (0.08–0.3) and 0.21 mA (0.1-0.4) for EBSLN, RLN and VN (p > 0.05) respectively. Cmax were 0.6 mA along with an amplitude value of 396 ± 330 μV, 0.5 mA including 1058 ± 382 μV, 0.8 mA coupled with 870 ± 382 μV, equally for EBSLN, RLN and VN (p > 0.05) respectively. No asymmetry of amplitude responses each side for EBSLN, RLN and VN (p = 0.317, p = 0.203 and p = 0.468, respectively) was noted. The amplitudes of EBSLN were significantly lower than RLNs and VN (42% of RLN and 50% of VN amplitude rates). Also, CTM twitch was always detectable with the stimulation of EBSLN. Conclusions: Cmin and Cmax of EBSLN were comparable to RLN and VN standards. The amplitude stimulus-response curves of RLN, VN and EBSLN were highly variable. It has been suggested to apply a stimulation of 1.0 mA and a visual appreciation of CTM twitch for the identification of EBSLN.

Development of Laser and Electrochemical Machining Based on Internal Total Reflection

To address the issues of the existing laser and electrochemical machining (LECM) processes in controlling the machining precision, machining depth limit, and taper angle, a novel LECM based on internal total reflection (LECM-ITR) has been proposed. In LECM-ITR, both the electrolyte jet and laser beam were guided and transferred to the machining area, synchronously. Since the tube electrode could feed into the workpiece, the laser could act on the high depth machining area with less laser attenuation. The materials could be removed by using laser-materials interaction and electrochemical dissolution. Small holes with depth of 2 mm have been processed on aluminum alloy and stainless-steel workpiece successfully. Experimental results showed that LECM-ITR could decrease the side gap by 23.6%, reduce the taper angle by 60.8%, and improve materials removal rate by 118.8%. The mechanism of materials removal rate and precision enhancement by LECM-ITR were discussed, including (1) Laser induced temperature rise at the machining area could improve the machining efficiency of ECM with the increased electric current density; (2) The formed anodic oxide layer in larger thickness could enhance the machining precision of ECM with increasing time constant of the electric double layer at the machining area.

Development of radiofrequency ablation devices with neuromonitoring system to detect recurrent laryngeal nerve in thyroid nodule

Background Radiofrequency ablation (RFA) is an emerging minimally invasive treatment modality of benign thyroid nodule and limited small papillary thyroid cancer. Among the RFA related complications, the recurrent laryngeal nerve (RLN) damage is one of the most concerned complications. To reduce the RLN injury during RFA, we developed a RFA device with intraoperative neuromonitoring system (IONM) to detect recurrent laryngeal nerve. Furthermore, to avoid a use of EMG tube requiring general anesthesia, we developed an accelerometer sensor that can be attached on the anterior neck skin. In this study, we examined the feasibility of neuromonitoring system to detect RLN during RFA in thyroid gland. Methods Three beagles (six thyroid glands) underwent the RFA under general anesthesia. Tip of the RF electrode acted as a neurostimulator probe and its location was ultrasonographically monitored. Stimulation current was set based on NIM-Response 3.0 system. During the procedure, nervemonitoring was performed simultaneously using NIM® standard EMG reinforced tube, needle electrode and accelerometer. Results When the tip of the RF electrode was placed near the tracheoesophageal groove, RLN was successfully identified with EMG tube, needle electrode and accelerometer sensor. After RFA near the tracheoesophageal groove, nerve injury was detected in EMG tube, needle electrode and accelerometer sensor. Conclusion Neuromonitoring system to detect RLN using RF electrode was feasible in the animal study. Like both EMG tube and needle electrode, the accelerometer sensor can detect laryngeal muscle twitching during RLN stimulation. Accelerometer sensor for detecting RLN is expected to make the RFA procedure safer without any invasive monitoring system.

Multi Objective Optimization during Small Hole Electrical Discharge Machining (EDM) of Ti-6Al-4V using TOPSIS

Abstract The current study deals with electric discharge machining (EDM) of Ti-6Al-4V using brass tube electrode. The goal is to perform multi-objective optimization on the effect of process parameters namely current, capacitance, on-time and off-time to determine the response characteristics such as material removal rate, tool wear rate and overcut. The experiments layout was planned using RSM-CCD. The multi-objective optimization method, the “Technique for Order of Preference by Similarity to Ideal Solution” is pertained in the current study. The results authenticate that using a TOPSIS, the MRR of 3.6996 mm3/sec, TWR of 0.0625 mm/sec and OC of 0.33 mm have been achieved.

Taperness and Linear Wear Rate Analysis of High Aspect Ratio EDM Meso-Holes in Ti-6Al-4V

EDM using rotary tube electrode is best suited for machining high aspect ratio meso-holes in Ti-6Al-4V. In this paperwork, we have analyzed taperness and linear wear rate of the electrode for implementation of high aspect ratio EDM in drilling meso-holes. An experimental layout is prepared to use Taguchi’s L 27 orthogonal array. The 300 μm brass tube electrode was selected with high accuracy for the entire experiment. Using TOPSIS the optimized input parameters (current, gap voltage, on-time, and off-time) are selected for responses such as taperness and linear wear rate among the available. By the measurement minimum, taperness of 0.0029o and linear wear rate of 1.5131 mm/sec were observed in EDM using brass tube electrodes.

Observation and Investigation of “Reverse Breakdown” in a Discharge Tube

A discharge operating in a 80-cm-long discharge tube with an inner diameter of 15 mm, filled with a 3 : 1 neon–argon mixture at a pressure of 1 Torr, was investigated experimentally. Square voltage pulses with a period of 1 s were supplied to one of the tube electrodes, the second electrode being ungrounded. The initial stage of breakdown—the primary breakdown between the high-voltage (active) electrode and the tube wall, accompanied by the propagation of the prebreakdown ionization wave—was the same as in the conventional scheme with a grounded low-voltage electrode. Since the discharge gap was not closed, the discharge was not ignited. An essentially new effect was observed after the end of the voltage pulse. After a certain time interval, voltage spikes of opposite polarity, the amplitude and shape of which were close to those observed during the primary breakdown, appeared in the voltage and current waveforms of the active electrode. Simultaneously, a radiation pulse from the region adjacent to the active electrode was observed and an ionization wave began to propagate toward the second electrode. This work is dedicated to investigating this effect (which was named “reverse breakdown”) and analyzing its mechanism. A conclusion is made on the similarity of this phenomenon to the processes occurring in atmospheric-pressure dielectric barrier discharges.

Experimental study of needle recording electrodes placed on the thyroid cartilage for neuromonitoring during thyroid surgery.

Needle electrodes placed on the thyroid cartilage (TC) are an alternative to endotracheal tube (ET) electrodes for assessing recurrent laryngeal nerve (RLN) function during thyroid surgery. Needle electrodes placed on the TC were evaluated in an experimental porcine model. Continuous intraoperative neuromonitoring was used to record the electromyogram. Each TC side was delineated into nine areas to determine the optimal placement of the electrode, and needle electrode area, depth and orientation for optimal electromyographic (EMG) amplitudes were evaluated. RLN root locations were stimulated at four locations: vagus nerve distal to the neuromonitoring electrode, and most proximal, middle and laryngeal entry points of the nerve. A nerve retraction injury model was adapted to compare RLN monitoring by TC versus ET electrodes. An optimal site for placement of needle electrodes was identified, and electromyograms obtained from the various needle insertion depths and orientations were similar. Latencies recorded from the TC and ET electrodes were similar. The amplitude profile of TC electrodes responded earlier to RLN injury than that of ET electrodes. Amplitude and drop to loss of signal were also registered earlier. EMG amplitudes obtained using TC electrodes were higher, and identified RLN injury earlier than ET electrodes. Surgical relevance Needle electrodes placed on the thyroid cartilage (TC) are an alternative to endotracheal tube (ET) electrodes for assessing the function of the recurrent laryngeal nerve (RLN) in thyroid surgery. This study used an experimental porcine model to evaluate the use of needle electrodes inserted in the TC, compared with ET electrodes, for producing an electromyographic (EMG) profile of the RLN. Nine areas of the TC, with various needle insertion depths and orientations, were compared. Perichondral insertion into the avascular area of the TC was found to be safe. The EMG amplitude and latency features recorded via the TC and ET electrodes were compared, using both intermittent and continuous monitoring. Changes in EMG amplitudes in response to nerve traction injury were registered earlier with TC electrodes than with ET electrodes, and the amplitudes were higher and more stable. Latencies obtained via the TC and ET electrodes were similar. These results indicate that the development of a non-invasive monitoring electrode with improved function, easy placement and low cost is possible.

The evolution and progress of intraoperative monitoring of the external branch of the superior laryngeal nerve in thyroid surgery

Hypoparathyroidism and recurrent laryngeal nerve (RLN) damage are the most frequent reported morbidity in thyroid surgery whereas damage of the external branch of the superior laryngeal nerve (EBSLN) has been considered to be the most neglected sequel. EBSLN injury results in subtle changes in voice as a result of dysfunction of the cricothyroid muscle (CTM): changed basic voice frequency, deterioration of voice quality in the production of high frequency sounds and reduced voice projection. Symptoms of this dysfunction are usually more notable for professional voice users and can be difficult to diagnose. EBSLN injury can happen during dissection of the vessels of the upper thyroid pole due to proximity between the nerve and these vessels. Several maneuvers can minimize the risk of injury to the EBSLN including visual identification of the nerve before ligation of the upper thyroid pole vessels and use of either a nerve stimulator or intraoperative neuromonitoring (IONM) for neuromapping and evidence of the EBSLN identification. The EBSLN monitoring is relied on evaluation of CTM twitch (present in all patients) and electromyographic curve traced by the monitor using surface tube electrodes within the vocal folds which present in the majority but not all individuals (70–80% of patients using standard EMG tubes) or approaching to 100% of patients (using NIM TriVantage tubes). IONM has a potential to increase the rate of the EBSLNs identification, diminish prevalence of neural damage, and decrease prevalence of postoperative voice impairment which has been repeatedly supported by recently published data. It is advised that at the end of upper thyroid lobe dissection the EBSLN should be stimulated at the most cranial arc of dissection to confirm not only anatomical but what is even more important functional preservation of intact neural function.

Human laryngeal sensory receptor mapping illuminates the mechanisms of laryngeal adductor reflex control

The laryngeal adductor reflex (LAR) is an airway protective response triggered by sensory laryngeal receptors. It is unknown whether different glottic and supraglottic subsites vary in their reflex elicitation abilities. The recent discovery that a bilateral LAR is present in humans under general anesthesia upon laryngeal mucosal stimulation has enabled us to map the sensory receptor density for LAR elicitation at different laryngeal subsites. Our findings expose the likely mechanisms of LAR control. Prospective series of 10 patients undergoing laryngoscopy. Laryngeal subsites (epiglottic tip, membranous vocal fold, midventricular vocal fold, posterior supraglottis, epiglottic petiole) were stimulated via direct laryngoscopy with a bipolar probe. Vocal fold responses were recorded by endotracheal tube and hook wire electrodes, and visual observation. Posterior supraglottic stimulation elicited bilateral LARs in all patients at all intensities. Membranous vocal folds, epiglottic petiole, and subglottis elicited no LAR. Ventricular fold and epiglottic tip responses converted from ipsi- to bilateral at high intensities. There are likely three checkpoints for control of the LAR in humans. These checkpoints protect against inappropriate LAR activation during volitional tasks without compromising airway protection: 1) topographical differences in receptor density with the highest density in subsites most likely to contact foreign substances; 2) absence of receptors in membranous vocal folds; and 3) central summation threshold for crossed interneuron activation at brainstem level where only strong intensity stimuli will elicit bilateral responses. Checkpoint dysfunction provides a novel framework to diagnose and treat disease processes, including aspiration, laryngospasm, and sudden infant death. 4. Laryngoscope, E365-E370, 2018.

Noninvasive, tube-based, continuous vagal nerve monitoring using the laryngeal adductor reflex: Feasibility study of 134 nerves at risk.

Continuous vagal intraoperative neuromonitoring (IONM) currently requires placement of a vagal nerve electrode. Herein, we present data from 100 patients (134 nerves-at-risk) monitored continuously during neck endocrine surgeries using a noninvasive, new methodology that solely utilizes endotracheal tube electrodes to simultaneously stimulate laryngeal mucosa and record a laryngeal adductor reflex continuous IONM (LAR-C-IONM) response. The laryngeal adductor reflex (LAR) was elicited by electrical laryngeal mucosal stimulation on the side contralateral to the operative field using endotracheal tube electrodes. All patients completed preoperative and postoperative laryngeal and voice examinations. One hundred patients (134 nerves-at-risk) were included. Significantly more nerves-at-risk with an LAR opening to closing amplitude decrement >60% or with absolute closing amplitude <100 μV had postoperative vocal fold paralysis (P < .001). The LAR-C-IONM was highly sensitive to recurrent laryngeal nerve (RLN) stretch or compression. The LAR-C-IONM is a promising new way to perform continuous vagal monitoring that requires no equipment other than an electromyography (EMG) endotracheal tube and is undergoing further, large-scale evaluation.