Symmetric Waveform Research Articles

The Effect of Neuromuscular Electrical Stimulation of the Infraspinatus on Shoulder External Rotation Force Production after Rotator Cuff Repair Surgery

Background Muscle weakness, particularly of shoulder external rotation, is common after rotator cuff repair surgery. Neuromuscular electrical stimulation has been shown to be an effective adjunct in the enhancement of muscle recruitment. Hypothesis Shoulder external rotation peak force can be enhanced by neuromuscular electrical stimulation after rotator cuff repair surgery. Study Design Controlled laboratory study. Methods Thirty-nine patients (20 men, 19 women) who had undergone rotator cuff repair surgery were tested a mean of 10.5 days after surgery. Testing consisted of placing patients supine with the shoulder in 45° of abduction, neutral rotation, and 15° of horizontal adduction. Neuromuscular electrical stimulation was applied to the infraspinatus muscle belly and inferior to the spine of the scapula. Placement was confirmed by palpating the muscle during a resisted isometric contraction of the external rotators. Patients performed 3 isometric shoulder external rotation contractions with and without neuromuscular electrical stimulation, each with a 5-second hold against a handheld dynamometer. Neuromuscular electrical stimulation was applied at maximal intensity within comfort at 50 pulses per second, symmetrical waveform, and a 1-second ramp time. The 3 trials under each condition were recorded, and an average was taken. The order of testing was randomized for each patient tested. A paired samples t test was used to determine significant differences between conditions (P < .05). Each group was also divided based on age, rotator cuff tear size, number of days postoperative, and neuromuscular electrical stimulation intensity. Analysis of variance Models were used to determine the influence of these variables on external rotation force production (P < .05). Results Peak force production was significantly greater (P < .001) when tested with neuromuscular electrical stimulation (3.75 kg) as opposed to without neuromuscular electrical stimulation (3.08 kg) for all groups tested. There was no significant difference based on the size of the tear, age of the patient, number of days after surgery, or level of neuromuscular electrical stimulation intensity. Conclusion Peak shoulder external rotation force was significantly increased by 22% when tested with neuromuscular electrical stimulation after rotator cuff repair surgery. Neuromuscular electrical stimulation significantly increased force production regardless of the age of the patient, size of the tear, intensity of the current, or the number of days postoperative. Clinical Relevance Neuromuscular electrical stimulation may be used concomitantly with exercises to enhance the amount of force production and potentially minimize the inhibition of the rotator cuff after repair surgery.

Enhanced in vivo transgene expression and immunogenicity from plasmid vectors following electrostimulation in rodents and primates

Safe and efficient methods for in vivo delivery of transgenes of interest must be developed so that the promise of these therapies can be practically used in the clinic. In this work, we describe the use of electrostimulation to enhance the in vivo efficiency of plasmid DNA delivery. The method was optimized to work over a range of moderate frequencies, utilizing low field strengths and simple symmetrical waveforms. After studying several parameters of delivery in mice, we demonstrate how this methodology can be employed to significantly improve both gene expression (over 16-fold) and the immunogenicity of HIV-1 vaccines (over 28-fold) compared to naked DNA in non-human primates. Compared to an efficient viral Ad5 vector system, the gene expression levels of DNA + electrostimulation were surprisingly within a factor of four of the viral delivery system.

Asymptotic rejection of unmatched general periodic disturbances in a class of nonlinear systems

The study deals with asymptotic rejection of unmatched general periodic disturbances in nonlinear systems in the output feedback form. The class of disturbances covers asymmetric wave forms in the half period such as alternating sawtooth wave form, as well as disturbances with symmetric half-period wave forms such as sinusoidal disturbances and triangular disturbances etc. The amplitude and phase of the disturbances are unknown. An equivalent input disturbance is introduced based on the periodic steady-state solutions of the system state variables. Conditions are identified for the existence of such an equivalent input disturbance. The half-period alternating feature is ensured for the equivalent input disturbance based on the fact that the steady state solutions of stable linear systems are shown to be half-period alternating if the inputs are. As the half-period alternating property is persevered in the equivalent input disturbances, recently proposed asymptotic rejection, based on the half-period integration and delay operations, of general periodic disturbances with asymmetric half-period wave forms can be applied, with a careful consideration of the phase offsets in the equivalent input disturbances. The proposed control design with the disturbance estimation asymptotically rejects the unknown disturbance and ensures the overall stability of the system.

Current imbalance in superconducting strand-to-strand joint and its relaxation in multistage cable-in-conduit conductor

This paper presents non-uniformity or imbalance in the transport current of the superconducting toroidal-field coil (TFC) made of multistage cable-in-conductor (CICC) due to inductive current in a strand-to-strand (STS) soldered joint of cylindrical shape and also the relaxation of the inductive current in the conductor. Using an NbTi CICC consisting of 486 strands, a joint sample is fabricated and experimented. An external magnetic field of symmetric trapezoidal waveform is vertically applied to the sample joint. The field maximum and the ramp rate (d B/d t) maximum are 1 T and 0.25 T/s, respectively. Voltage taps and Hall probes are utilized to measure the inductive voltage and current. Experimental results are analyzed numerically using an infinite electrical transmission line model, which is found to explain our sample system well. The flattop induced current is proportional to the d B/d t. Being different from our expectation that the inductive current will distribute widely over the cross-sectional surface of the joint, it localizes to a narrow region; a triplet located in the outer-most side of the joint, for instance. The relaxation phenomenon in the induced current is observed experimentally. From numerical analysis, the relaxation length is found to increase logarithmically with decreasing d B/d t and saturate at a certain value of d B/d t.

INFLUENCE OF EVEN ORDER DISPERSION ON SOLITON TRANSMISSION QUALITY WITH COHERENT INTEREFERENCE

The transmission speed of optical networks strongly depends on the impact of higher order dispersion. In the presence of coherent interference which can’t be kept under control by optical filtering, the impact of higher order dispersion becomes more serious. In this paper we give general expressions that describe pulse deformation due to even higher order dispersion in a single-mode fiber. The impulsive responses for even order dispersion in the presence of coherent interference are characterized by symmetrical waveforms with long trailing skirts. Individual and joint influence of second and fourth order dispersion on the transmission quality is studied. Pulse shape and eye diagram are obtained.

The Comparison of Three High-Frequency Chest Compression Devices

High-frequency chest compression (HFCC) is shown to enhance clearance of pulmonary airway secretions. Several HFCC devices have been designed to provide this therapy. Standard equipment consists of an air pulse generator attached by lengths of tubing to an adjustable, inflatable vest/jacket (V/J) garment. In this study, the V/Js were fitted over a mannequin. The three device air pulse generators produced characteristic waveform patterns. The variations in the frequency and pressure setting of devices were consistent with specific device design features. These studies suggest that a better understanding of the effects of different waveform, frequency, and pressure combinations may improve HFCC therapeutic efficacy of three different HFCC machines. The V/J component of HFCC devices delivers the compressive pulses to the chest wall to produce both airflow through and oscillatory effects in the airways. The V/J pressures of three HFCC machines were measured and analyzed to characterize the frequency, pressure, and waveform patterns generated by each of three device models. The dimensions of all V/Js were adjusted to a circumference of approximately 110% of the chest circumference. The V/J pressures were measured, and maximum, minimum, and mean pressure, pulse pressure, and root mean square of three pulse generators were calculated. Jacket pressures ranged between 2 and 34 mmHg. The 103 and 104 models' pulse pressures increased with the increase in HFCC frequency at constant dial pressure. With the ICS the pulse pressure decreased when the frequency increased. The waveforms of models 103 and 104 were symmetric sine wave and asymmetric sine wave patterns, respectively. The ICS had a triangular waveform. At 20 Hz, both the 103 and 104 were symmetric sine waveform but the ICS remained triangular. Maximum crest factors emerged in low-frequency and high-pressure settings for the ICS and in the high-frequency and low-pressure settings for models 103 and 104. Recognizing the significant differences in frequency and pressure amplitude may help clinicians and patients optimize the efficacy of HFCC therapy. Evidence-based therapeutic guidelines are needed.

Solving The Optimal PWM Problem for Odd Symmetry Waveforms

Optimal pulse width modulation (PWM) problem is an established method of generating PWM waveforms with low baseband distortion. In this paper we focused on computation of optimal switching angles of a PWM waveform for generating general odd symmetric waveforms with applications in control. We introduce an exact and fast algorithm with the complexity of only O(n2) arithmetic operations. This algorithm is based on transformation of appropriate trigonometric equations for each harmonics to a polynomial system of equations that is transferred to a special system of power sums. The solution of this system is carried out by modification of Newton's identity via Padé approximation and orthogonal polynomials theory and property of symmetric polynomials. Finally, the optimal switching sequence is obtained by computing the zeros of two orthogonal polynomials in one variable.

Ultrafast cyclic voltammetry with asymmetrical potential scan

Based on the perfect ohmic drop compensation by online electronic positive feedback, ultrafast cyclic voltammetry with asymmetrical potential scan is achieved for the first time, with the reduction of anthracene acting as the test system. Compared with the traditional cyclic voltammetry utilizing symmetrical triangular waveform as the excitation one, the new method allows a simpler approach to mechanistic analysis of ultrafast chemical reactions coupled with a charge transfer. And perhaps more important, it also provides a way to eliminate the interference of the adsorbed product in dynamic monitoring.

Partial Discharge Pulse Propagation in Shielded Power Cable and Implications for Detection Sensitivity

Boggs and Stone (1982) defined the fundamental limits to the electrical detection of corona and partial discharge (PD), i.e., wideband detection of a PD-induced pulse in the presence of thermal noise. This paper treated the effect of frequency-dependent attenuation in shielded power cable in that context. However, most of the plots in that paper were the result of numerical computations. In the same year, Stone and Boggs set out a theory for high-frequency attenuation of shielded power cable. They showed good agreement between attenuation predicted from measured material properties and measured, high-frequency attenuation of shielded power cable. Since 1982, measurements of high-frequency cable attenuation have been reported by a number of authors for a variety of cables. In addition, software tools have become available that facilitate an analytic solution for the parameters of interest. This article summarizes the theory for PD propagation in shielded power cable for both symmetric (Gaussian) and asymmetric PD-pulse waveforms, based on the assumption that the attenuation constant (dB/m or Nepers/m) of the cable is proportional to frequency. This appears to be the most complete possible analytic exposition of PD attenuation in shielded-power cable, which has obvious applications to field PD measurements of such cable.

Analytic Solutions for Pulse Propagation in Shielded Power Cable for Symmetric and Asymmetric PD Pulses

Shielded power cable can be considered as a lossy transmission line, the high frequency attenuation of which causes the PD pulse amplitude, as well as the pulse energy, to decrease as a function of distance propagated. We develop analytical expressions which characterize PD pulse propagation in a shielded power cable for both symmetric and asymmetric PD pulse waveforms for an attenuation constant which increases linearly with frequency.

Design and optimization for variable rate selective excitation using an analytic RF scaling function

At higher B 0 fields, specific absorption rate (SAR) deposition increases. Due to maximum SAR limitation, slice coverage decreases and/or scan time increases. Conventional selective RF pulses are played out in conjunction with a time independent field gradient. Variable rate selective excitation (VERSE) is a technique that modifies the original RF and gradient waveforms such that slice profile is unchanged. The drawback is that the slice profile for off-resonance spins is distorted. A new VERSE algorithm based on modeling the scaled waveforms as a Fermi function is introduced. It ensures that system related constraints of maximum gradient amplitude and slew rate are not exceeded. The algorithm can be used to preserve the original RF pulse duration while minimizing SAR and peak b1 or to minimize the RF pulse duration. The design is general and can be applied to any symmetrical or asymmetrical RF waveform. The algorithm is demonstrated by using it to (a) minimize the SAR of a linear phase RF pulse, (b) minimize SAR of a hyperbolic secant RF pulse, and (c) minimize the duration of a linear phase RF pulse. Images with a T1-FLAIR (T1 FLuid Attenuated Inversion Recovery) sequence using a conventional and VERSE adiabatic inversion RF pulse are presented. Comparison of images and scan parameters for different anatomies and coils shows increased scan coverage and decreased SAR with the VERSE inversion RF pulse, while image quality is preserved.

SYMMETRIC INTERPOLATORY FRAMELETS AND THEIR ERASURE RECOVERY PROPERTIES

A new class of wavelet-type frames in signal space that uses (anti)symmetric waveforms is presented. The construction employs interpolatory filters with rational transfer functions. These filters have linear phase. They are amenable either to fast cascading or parallel recursive implementation. Robust error recovery algorithms are developed by utilizing the redundancy inherent in frame expansions. Experimental results recover images when (as much as) 60% of the expansion coefficients are either lost or corrupted. The proposed approach inflates the size of the image through framelet expansion and multilevel decomposition thus providing redundant representation of the image. Finally, the frame-based error recovery algorithm is compared with a classical coding approach.

Run-to-run variations, asymmetric pulses, and long time-scale transient phenomena in dielectric-barrier atmospheric pressure glow discharges

The dielectric-barrier (DB) discharge is an important approach to generate uniform non-equilibrium atmospheric-pressure glow discharges. We report run-to-run variations, asymmetric pulse formation and long time-scale transient phenomena in these discharges. For similar DB discharge geometric and operating conditions, we observe significant run-to-run variations as manifested in the different voltage–current waveforms at the start of each new run. These run-to-run variations are also accompanied by asymmetric pulses at the start of each run. The variations are observed to drift to a repeatable true steady-state condition on time scales of order tens of minutes to hours. Asymmetric pulse waveforms drift to a symmetric pulse waveform at the true steady state. We explore reasons for these phenomena and rule out thermal drift during a discharge run and gas-phase impurity buildup as potential causes. The most plausible explanation appears to be variations in the surface characteristics of the DBs between two consecutive runs owing to varying inter-run environmental exposure and the conditioning of the dielectric surface during a run owing to plasma–surface interactions. We speculate that the dielectric surface state affects the secondary electron emission coefficient of the surface which in turn is manifested in the discharge properties. A zero-dimensional model of the discharge is used to explore the effect of secondary electron emission.

Asymptotic rejection of a class of periodic disturbances in nonlinear output-feedback systems

Asymptotic rejection of periodic disturbances whose basic wave patterns can be described by odd functions is considered. This class of disturbances covers asymmetric waveforms in a half-period such as sawtooth waveforms, as well as disturbances with symmetric half-period waveforms such as sinusoidal and triangular disturbances. The systems considered can be transformed to a nonlinear output-feedback form. The amplitude and phase of the disturbances are unknown. The newly proposed half-period integration technique is used to estimate the unknown disturbances in the systems, together with observer design techniques to deal with nonlinearity. The proposed control design with disturbance estimation asymptotically rejects the unknown disturbance, and ensures the overall stability of the system.

Modified SVPWM Algorithm for Three Level VSI With Synchronized and Symmetrical Waveforms

The objective of the present work is to improve the output waveform of three level inverters used in high-power applications, where the switching frequency is very low. This is achieved by maintaining the synchronization, half-wave symmetry, quarter-wave symmetry, and three-phase symmetry in the pulsewidth modulation (PWM) waveforms. The principles of achieving synchronization and symmetries in terms of space vectors for three level inverters are presented. A novel synchronized space vector pulsewidth modulation (SVPWM) algorithms is proposed and verified experimentally. The experimental waveforms of the inverter output voltage and motor no load current for different operating conditions of the drive are presented. The performance measure in terms of the weighted total harmonic distortion (THD) of the line voltage is computed for the linear modulation region of the drive for the proposed algorithm and compared with that of synchronized SVPWM and synchronized sine-triangle pulsewidth modulation (SPWM) technique. The comparative results show that consideration of synchronization and symmetry results in improved THD. Another significant feature of the proposed algorithm is that the symmetry and synchronization leads to self-balancing of the direct current (dc) bus capacitor voltages over every one third cycle of the fundamental

Asymptotic rejection of asymmetric periodic disturbances in output-feedback nonlinear systems

This paper deals with asymptotic rejection of periodic disturbances which may have asymmetric basic wave patterns. This class of disturbances covers asymmetric wave forms in the half-period such as alternating sawtooth wave form, some disturbances which are generated from nonlinear oscillation such as Van de Pol oscillators, as well as disturbances with symmetric half-period wave forms such as sinusoidal disturbances and triangular disturbances etc. The systems considered in this paper can be transformed to the nonlinear output feedback form. The amplitude and phase of the disturbances are unknown. The novel concept of integral phase shift is introduced together with the newly introduced half-period integration operator to investigate the invariant properties of asymmetric periodic disturbances. They are used for the estimation of unknown disturbances in the systems, together with observer design techniques to deal with nonlinearity. The proposed control design with the disturbance estimation asymptotically rejects the unknown disturbance, and ensures the overall stability of the system.

Symmetrical waveform generation based on temporal pulse shaping using amplitude-only modulator

Symmetrical waveform generation based on temporal pulse shaping using only an amplitude modulator is proposed and investigated. The fundamental principle of this technique is that the Fourier transform of a real and symmetrical waveform is still real and symmetrical. Therefore, it is possible to use an electro-optic modulator that is biased at the minimum transmission point to perform temporal spectrum shaping with a real signal that has both positive and negative values. The proposed approach provides a simple and effective solution to ultrashort symmetrical waveform generation.

Differences in Waveform Characteristics Have No Effect on the Anti-Hyperalgesia Produced by Transcutaneous Electrical Nerve Stimulation (TENS) in Rats With Joint Inflammation

Transcutaneous electrical nerve stimulation (TENS) is a nonpharmacological method for pain management. Commercial TENS units differ in their waveform characteristics. However, effects of different waveforms on analgesia produced by TENS are unknown. Therefore, we compared effects of high-frequency TENS with different waveforms--asymmetric biphasic square and symmetric biphasic square--on inflammatory hyperalgesia. Paw withdrawal latency to heat (PWL) was assessed prior to inflaming the knee joint with 3% carrageenan/kaolin in rats. Four hours after induction of inflammation, PWL significantly decreased in all groups, indicating development of hyperalgesia. High-frequency TENS was then applied to the inflamed knee joint for 20 minutes while the rat was lightly anesthetized with halothane. TENS treatment with either the asymmetric or symmetric waveform significantly increased the PWL when compared with sham TENS. Thus, differences in waveform characteristics do not affect the anti-hyperalgesia produced by TENS. This study shows that different waveforms of TENS do not affect analgesic efficacy. This suggests that clinicians can select different waveforms to provide comfort during treatment but that reduction in pain is not a factor for waveform selection.

The immediate effects of heat and TENS on pressure pain threshold and pain intensity in patients with Stage I shoulder impingement syndrome

Abstract Aim: Our study was planned to compare the immediate effects of heat, transcutaneous electrical nerve stimulation (TENS) and heat plus TENS applications on the pain related to stage I shoulder impingement syndrome. Methods: 92 patients who had shoulder impingement syndrome were separated randomly in three groups. The heat was applied to 31 patients in the first group for 20 min, TENS (100 Hz 0.1 ms pulse duration, symmetric biphasic wave form, tolerable intensity) was used for 30 patients in the second group for 20 min and heat plus TENS was applied to the 31 patients in the third group for 40 min. Before and immediately after the applications, pressure pain threshold (PPT) was measured by a dolorimeter in the painful points on the anterobrachial area. Measurements were repeated three times and the mean value was recorded. The severity of subjective pain was recorded using a visual analogue scale (VAS) before and after the applications.One-way ANOVA was used to compare differences of PPT, VAS, and...

Solution trajectories of the harmonic-elimination problem

The paper considers the problem of finding the notch angles which are required for implementing programmed-harmonic-elimination switching in pulse-width-modulated (PWM) invertors. For a desired fundamental output voltage, the proposed methodology employs the Krawczyk–Moore test within a linear-programming-based search to determine, with mathematical certainty, a set of N-dimensional boxes enclosing all solutions of the harmonic-elimination problem. Each of these boxes contains a distinct and unique solution, and is a safe starting region for a Newton iterative method applied to solve the transcendental harmonic-elimination equations. Once all solutions for a given fundamental amplitude are determined, the solution trajectories for all feasible amplitudes are traced using a simple continuation method which is essentially a numerical adaptation of the implicit-function theorem. The proposed technique is used for optimising line-to-neutral quarter-wave symmetric PWM waveforms employed in three-phase applications. Switching-angle spreads from 0° to 60° and 0° to 90° are considered. Solution trajectories are computed for up to eight switching angles.