Root Mean Square Ratio Research Articles

Spinal muscle characteristics during three different types of locomotion activities among college students with idiopathic scoliosis

Background contextPhysical activities such as walking and climbing stairs are pervasive in human daily life. Individuals with scoliosis frequently encounter dysfunction in their muscle recruitment. Multiple studies have corroborated the presence of muscle dysfunction in individuals diagnosed with scoliosis. However, there is currently a noteworthy research gap regarding the exploration of changes in muscle characteristics and disparities from those observed in individuals without scoliosis during everyday activities, specifically stair climbing.PurposeThis study aims to examine the unique patterns of muscle activity during daily life in individuals with scoliosis and distinguish the specific differences between scoliosis patients and the healthy controls. The findings of this study are significantly important for the future accurate assessment of scoliosis and the development of rehabilitation treatment plans.Study designCase–control study.Sample sizeTwenty eight idiopathic scoliosis patients and twenty eight controls.Outcome measuresRoot Mean Square(RMS), Maximum Voluntary Isometric Contraction(MVIC)%, RMS ratio(RMS convex / RMS concave).MethodsThe surface electromyography (sEMG) device used in this study was the Delsys Trigno, with a sampling frequency of 1500 Hz. It recorded the activation level, peak contraction, and average activation level of the erector spinae (at T6, T10, and L3 levels), gluteus maximus, gluteus medius, external oblique, and rectus abdominis muscles during three different types of locomotion for both the 28 individuals with idiopathic scoliosis and the 28 control participants.ResultsThe movement patterns of the idiopathic scoliosis patients significantly differ from those of the normal population during level walking and ascending or descending stairs. In level walking, there is an asymmetry in the activation levels of the T6 and L3 erector spinae muscles, with lower activation on the convex side compared to the concave side. Similarly, during stair ascent, the activation of the T6 and T10 erector spinae muscles is asymmetric, with higher activation on the convex side than the concave side. Moreover, during stair descent, the activation of the T6 erector spinae muscle is asymmetric, with higher activation on the convex side than the concave side.ConclusionsDuring level walking and stair activities, idiopathic scoliosis patients exhibit pronounced abnormal movement patterns that significantly differ from those of the control group. Under different activity conditions such as level walking, ascending and descending stairs, idiopathic scoliosis patients demonstrate abnormal muscle activation in different segments of the spine. It is crucial for clinicians to prioritize the symmetry of muscle activation in the spinal region of idiopathic scoliosis patients and consider incorporating symmetry training for these muscles.

An intelligent threshold selection method to improve orbital angular momentum-encoded quantum key distribution under turbulence

High-dimensional quantum key distribution (HD-QKD) encoded by orbital angular momentum (OAM) presents significant advantages in terms of information capacity. However, perturbations caused by free-space atmospheric turbulence decrease the performance of the system by introducing random fluctuations in the transmittance of OAM photons. Currently, the theoretical performance analysis of OAM-encoded QKD systems exists a gap when concerning the statistical distribution under the free-space link. In this article, we analyzed the security of QKD systems by combining probability distribution of transmission coefficient (PDTC) of OAM with decoy-state BB84 method. To address the problem that the invalid key rate is calculated in the part transmittance interval of the post-processing process, an intelligent threshold method based on neural network is proposed to improve OAM-encoded QKD, which aims to conserve computing resources and enhance system efficiency. Our findings reveal that the ratio of root mean square (RMS) OAM-beam radius to Fried constant plays a crucial role in ensuring secure key generation. Meanwhile, the training error of neural network is at the magnitude around 10−3, indicating the ability to predict optimization parameters quickly and accurately. Our work contributes to the advancement of parameter optimization and prediction for free-space OAM-encoded HD-QKD systems. Furthermore, it provides valuable theoretical insights to support the development of free-space experimental setups.

Effectiveness study of surface electromyography combined with spine 3D data system to evaluate scoliosis.

To evaluate the clinical effectiveness of surface electromyography combined with a spine 3D data system. 10 idiopathic scoliosis patients (age: 12.90±3.67 years, height: 155.90±20.07 cm, weight: 48.00±12.86 kg, 6 major thoracic lateral bends and 4 lumbar bends) who were selected to attend the outpatient clinic of Ruijin Rehabilitation Hospital, First diagnosed as scoliosis by imaging examination (EOS system), evaluation by using the surface electromyography monitoring system, the radiation-free 3D spine data acquisition and analysis system, the surface electromyography of the paravertebral muscles (root mean square value (RMS) of the resting standing and action position of the spine) and the Cobb angle of scoliosis were recorded. The RMS of the convex side was larger than that of the concave side in the two postures (P<0.05), and The RMS value of bilateral action position was significantly higher than that of rest position (P<0.05). There was no correlation between RMS ratio and Cobb angle in two positions of thoracic scoliosis (P>0.05). There was a significant correlation between the RMS ratio at rest position of lumbar scoliosis and Cobb angle. At rest, the RMS value of convex side was significantly correlated with the Cobb angle measured by the EOS system and the 3D data system (P<0.05, of which P<0.01). The Cobb angle measured by 3D data system and the EOS system was significantly correlated (P<0.01). Surface EMG can be used to evaluate the motor function of paravertebral muscles on both sides of scoliosis patients. The new 3D data system has high accuracy in evaluating scoliosis. The combination of the two can dynamically evaluate scoliosis, which is more clinically effective.

Exercise‐induced bronchoconstriction assessed by a ratio of surface diaphragm EMG to tidal volume

AbstractExercise‐induced bronchoconstriction (EIB) is usually assessed by changes in forced expiratory volume in 1 s (FEV1) which is effort dependent. The purpose of this study was to determine whether the diaphragm electromyogram (EMGdi) recorded from chest wall surface electrodes could be used to reflect changes in airway resistance during an exercise challenge test and to distinguish patients with EIB from those without EIB. Ninety participants with or without asthma history were included in the study. FEV1 was recorded before and 5, 10, 15, and 20 min after exercise. EIB was defined as an FEV1 decline greater than 10% after exercise. A ratio of root mean square of EMGdi to tidal volume (EMGdi/VT) was used to assess changes in airway resistance. Based on changes in FEV1, 25 of 90 participants exhibited EIB; the remainder were defined as non‐EIB participants. EMGdi/VT in EIB increased by 124% (19%–478%) which was significantly higher than that of 21% (−39% to 134%) in non‐EIB participants (p &lt; 0.001). At the optimal cutoff point (54% in EMGdi/VT), the area under the ROC curve (AUC) for detection of a positive test was 0.92 (p &lt; 0.001) with sensitivity 92% and specificity 88%. EMGdi/VT can be used to assess changes in airway resistance after exercise and could be used to distinguish participants with EIB from those without EIB.

Analysis of abnormal muscle activities in patients with loss of cervical lordosis: a cross-sectional study

BackgroundThis study aimed to detect the differences in cervical muscle activation patterns in people with versus without cervical lordosis and explore the possible mechanism of cervical pain originating therein.MethodsThis cross-sectional design included 39 participants without and 18 with normal cervical lordosis. Muscular activation was measured for 5 s in both groups using surface electromyography. Subsequently, the root mean square (RMS) of muscle amplitude was obtained at the bilateral splenius capitis, upper and lower parts of the splenius cervicis, upper and lower parts of the semispinalis cervicis, sternocleidomastoid, upper trapezius, and rhomboid muscles in five cervical positions: 0° (resting), 30° of flexion, 30° of extension, 60° of extension, and upon a 1-kg load on the head in a resting posture.ResultsThe RMS values of the upper trapezius muscle at all postures and the rhomboid muscles at 60° of extension were significantly lower in the loss of lordosis than control group. Comparing the RMS ratio of each posture to the resting position, the ratio of the upper trapezius at flexion was significantly higher and that of the rhomboids at 60° of extension and upon loading was significantly lower in the loss of lordosis than control group. Moreover, the pattern changes in the RMS values according to posture showed a similar shape in these two muscles, and lower in the loss of lordosis than the normal group.ConclusionsThe loss of normal cervical alignment may correlate with predisposed conditions such as reduced muscle activation of the trapezius and rhomboid muscle, and may also provoke over-firing of the upper trapezius muscle, possibly increasing neck musculoskeletal pain.Trial registration.Clinicaltrials.gov, registration number: NCT03710785.

Effect of tibialis anterior muscle resistance training on ankle and foot dorsum extension function in hypertensive cerebral hemorrhage hemiplegia patients: A randomized controlled trial.

This study aimed to investigate the effect of tibialis anterior muscle resistance training on ankle and foot dorsum extension function in patients with hemiplegia caused by hypertensive cerebral hemorrhage. Fifty cases of hypertensive cerebral hemorrhage in patients with hemiplegia were selected according to the random number table method. The patients were divided into the treatment group and control group. Each group included 25 cases, and the treatment group was given routine rehabilitation treatment and passive and active foot back stretch training (300 times/d). The control group received conventional rehabilitation treatment. The conventional rehabilitation treatment included stretching, muscle strengthening and other conventional rehabilitation treatment techniques. Surface electromyography was used to evaluate the muscle strength and tension of the triceps and tibialis anterior muscles of the affected side of the patients before and after treatment. The root mean square value of the surface electromyography (RMS) of the passive triceps extension before and after treatment was used to evaluate the muscle strength and tension of the affected side. The ratio of passive traction and relaxation of the triceps before and after treatment and the ratio of active contraction and relaxation of the tibialis anterior muscle before and after treatment were recorded. There was no significant difference in surface electromyography between the 2 groups before treatment (P > .05). After 2 months of treatment, the results of patients in both groups improved compared with those before treatment. The RMS of triceps in the treatment group was significantly lower than that in the control group, and the ratio of RMS of triceps in the treatment group was significantly lower than that in the control group. The RMS during active contraction and the RMS ratio between active contraction and relaxation of the tibialis anterior muscle in the treatment group were significantly higher than those in the control group (P < .05). Tibialis anterior muscle resistance training can effectively improve the strength of the tibialis anterior muscle in patients with hemiplegia caused by hypertensive cerebral hemorrhage, reduce tension in the triceps calf muscle, and improve ankle joint function and foot dorsum extension.

Surface electromyographic characteristics of forearm muscles after ulnar and radius fracture inchildren.

To evaluate the characteristics of forearm muscle activity in children with ulnar and radius fractures during different follow-up periods by surface electromyography. A retrospective analysis was performed on 20 children with ulnar and radius fractures treated with an elastic intramedullary nail from October 2020 to December 2021. All children were treated with transcubital casts after surgery. At 2 months and before taking out the elastic intramedullary nail, surface electromyographic signals were collected on the flexor/extension of the wrist and the maximum arbitrary isometric contraction of the grip strength in the forearm flexor and extensor muscles of the forearm. The root-mean-square values and integrated EMG values of the superficial flexor and extensor digitalis of the healthy side and the affected side were collected at the last follow-up and 2 months after surgery, and the co-systolic ratio was calculated. The root-mean-square values and co-systolic ratio were compared and analyzed, and the Mayo wrist function score was evaluated. The mean follow-up time was (8.4 ± 2.85) months. Mayo scores were (87.42 ± 13.01) and (97.69 ± 4.50) points at the last follow-up and two months after surgery, respectively (p < 0.05). In the test of grip strength, 2 months after surgery, the grip strength of the affected side was lower than that of the healthy side (p < 0.05), and the maximum and mean values of the superficial flexor of the affected side were lower than those of the healthy side (p < 0.05). At the last follow-up, there was no difference in the grip strength between the affected side and the healthy side (p > 0.05), and no difference in the maximum RMS, mean RMS and cooperative contraction ratio of the superficial flexor and digital extensor muscles between the affected side and the healthy side (p > 0.05). Satisfactory results can be obtained after elastic intramedullary napping in children with ulnar and radius fractures. However, 2 months after surgery, the grip strength of the affected side is small, and the electrical activity of the forearm muscle is low during flexion and extension activities of the wrist joint, which has not returned to normal, suggesting that children orthopaedic clinicians should remind children to conduct timely and effective rehabilitation training after the removal of the cast.

Investigation of gait and balance function in cervical spondylotic myelopathy patients using wearable sensors

Background ContextCervical spondylotic myelopathy (CSM) is a degenerative disease caused by cervical cord compression and can lead to the significant impairment of motor function including gait and balance disturbances and changes in lower extremity muscle activity. PurposeThis study aimed to characterize gait, balance and lower extremity muscle activity in patients with CSM compared to age-matched healthy controls (HCs) using wearable sensors in the clinical setting. Study DesignNonrandomized, prospective cohort study. Patient SampleTen CSM patients and 10 age-matched HCs were recruited for this study. Outcome MeasuresGait and balance function parameters contained spatial temporal parameters, step regularity (SR1), stride regularity (SR2) and harmonic ratio (HR). EMG muscle activity parameters included time to peak and peak value during loading, stance, and swing phase. MethodsIn this study, parameters of gait and balance function were extracted using triaxial accelerometer attached to the spinous processes of Lumbar 5 while participants performed an overground walking at a self-preferred speed. Moreover, muscular activity was simultaneously recorded via sEMG sensors attached to tibialis anterior (TA), rectus femoris (RF), bicep femoris (BF), and gastrocnemius lateral (GL). Independent sample t test was used to find the differences between CSM patients and HCs. ResultsGait analysis showed cadence, step length and walking speed were statistically significantly lower in CSM patients than HCs. Stride time was significantly higher for CSM patients in comparison to HCs. Lower root mean square ratio (RMSR) of acceleration in the mediolateral (ML) direction, HR in the anteroposterior (AP) direction, SR1 in the AP direction and SR2 in all three directions were observed in CSM patients. For muscle activity analysis, EMG RMS for TA and RF during loading phase and RMS for GL during midstance phase was significantly lower for CSM patients, while significantly higher value was observed for RF RMS during midstance phase and GL RMS during swing phase in CSM patients. ConclusionOur pilot study shows that wearable sensors are able to detect the changes of gait, balance and lower extremity muscle activities of CSM patients in the clinical setting. This pilot study sets the stage for future researches on the diagnosis and monitor progression of CSM disease using wearable technology.

Facility for calibration of photometers for measurement of temporal light modulation

A facility for calibration of temporal light modulation (TLM) photometers has been developed. The facility is based on a laser-fed reference integrating sphere source, the optical input power of which can be modulated with an acousto-optic modulator. A system of photodiodes, amplifiers and an analogue-to-digital converter is used to sample the temporally modulated irradiance at one of the exit ports of the source. With the facility, a TLM photometer was calibrated for display contrast ratio root mean square with an absolute combined standard uncertainty of 0.037%. In addition, the facility has been characterised with the aim of measuring flicker and stroboscopic effect, considering the Ecodesign ‘Single Lighting Regulation’. The frequency response of the facility is shown to be sufficient to accommodate measurements of flicker and the stroboscopic effect.

Filtering GRACE temporal gravity field solutions using ensemble empirical mode decomposition approach

Due to the strong noise that exists in GRACE (Gravity Recovery and Climate Experiment) temporal gravity field solutions, geophysical signals are normally drowned which need many effective filtering approaches. Considering the advantage of the ensemble empirical mode decomposition (EEMD) approach, we used the EEMD to filter the noise in this study together with the empirical mode decomposition (EMD) for comparisons. EMD method is a spectrum analysis method, which is very effective for non-stationary signals. EMD process is essentially a means to process non-stationary signals. It has been applied in many fields in recent years. Considering the characteristics of the spherical harmonic coefficient model that the noise level higher with the increasing degree, we divided the gravity field solutions into two parts (degrees 2–28 and degrees 29–60) based on the ratios of the latitude-weighted root mean square (RMS) over the land and ocean signals when adopting different truncated degrees. For the real GRACE solution experiments, the results show that the fitting errors of EEMD approach are always smaller than those of EMD approach, and the mean RMS ratio of EEMD is 3.45, larger than 3.40 of EMD. The simulation results show that the latitude weighted root mean square errors for EEMD approach are smaller than those of EMD, indicating that EEMD can extract the geophysical signals more accurately. Therefore, it is reasonable to conclude that EEMD performs better than EMD for filtering GRACE solutions.

Neonatal rhinorrhea and elevated heart rate variability predict exercise-induced wheeze at age 4-11 years among females.

We demonstrated a link between infant rhinorrhea and school age exercise-induced wheeze (EIW) with evidence for a parasympathetic nervous system (PNS) pathway. A novel measure of heart rate variability influenced by PNS signaling, the ratio of root mean square of successive differences in heart beats measured in quiet versus active sleep (RMSSDQS:AS), was associated with infant rhinorrhea and predicted school age EIW, but only among females. We hypothesized that female infants with both higher RMSSDQS:AS and rhinorrhea would be at the greatest risk for school age EIW.

Interpolation of spectra from 3D model atmospheres

Context. The use of 3D hydrodynamical simulations of stellar surface convection for model atmospheres is computationally expensive. Although these models have been available for quite some time, their use is limited because of the lack of extensive grids of simulations and associated spectra. Aims. Our goal is to provide a method to interpolate spectra that can be applied to both 1D and 3D models, and implement it in a code available to the community. This tool will enable the routine use of 3D model atmospheres in the analysis of stellar spectra. Methods. We have developed a code that makes use of radial basis functions to interpolate the spectra included in the CIFIST grid of 84 three-dimensional model atmospheres. Spectral synthesis on the hydrodynamical simulations was previously performed with the code ASSϵT. Results. We make a tool for the interpolation of 3D spectra available to the community. The code provides interpolated spectra and interpolation errors for a given wavelength interval, and a combination of effective temperature, surface gravity, and metallicity. In addition, it optionally provides graphical representations of the RMS and mean ratio between 1D and 3D spectra, and maps of the errors in the interpolated spectra across the parameter space.

An Adaptive ECG Noise Removal Process Based on Empirical Mode Decomposition (EMD).

The electrocardiogram (ECG) is a generally used instrument for examining cardiac disorders. For proper interpretation of cardiac illnesses, a noise-free ECG is often preferred. ECG signals, on the other hand, are suffering from numerous noises throughout gathering and programme. This article suggests an empirical mode decomposition-based adaptive ECG noise removal technique (EMD). The benefits of the proposed methods are used to dip noise in ECG signals with the least amount of distortion. For decreasing high-frequency noises, traditional EMD-based approaches either cast off the preliminary fundamental functions or use a window-based methodology. The signal quality is then improved via an adaptive process. The simulation study uses ECG data from the universal MIT-BIH database as well as the Brno University of Technology ECG Quality Database (BUT QDB). The proposed method's efficiency is measured using three typical evaluation metrics: mean square error, output SNR change, and ratio root mean square alteration at various SNR levels (signal to noise ratio). The suggested noise removal approach is compatible with other commonly used ECG noise removal techniques. A detailed examination reveals that the proposed method could be served as an effective means of noise removal ECG signals, resulting in enhanced diagnostic functions in automated medical systems.

Study on rapid convergence strategy of nano-precision optical surface by ion beam figuring

Ion beam figuring (IBF) provides a deterministic figuring method for fabricating ultra-high precision optical components such as lithographic objective lenses. But in the previous IBF process, the convergence of surface accuracy is often uncertain. Therefore, the iterative processing methods are mostly adopted. In the iterative process, the convergence ratio (the ratio of root mean square before and after figuring) of single figuring is relatively low. With the improvement of machining accuracy, the convergence ratio continues to decrease. The study analyzes the factors that limit the convergence ratio of single processing and the influence form and degree of each element on the convergence ratio. Furthermore, we present an IBF strategy with a high convergence ratio based on an optimized removal function. Based on this strategy, we complete the figuring experiment. The convergence ratio is much higher than the previous level. Compared with the surface of iterative figuring, the surface is simple and more favorable to figuring to sub-nanometer precision. The experimental results show that we can optimize the removal function to achieve rapid optical surface fabrication with nanometer precision.

The Use of a Single Trunk-Mounted Accelerometer to Detect Changes in Center of Mass Motion Linked to Lower-Leg Overuse Injuries: A Prospective Study.

Movement dynamics during running was previously characterized using a trunk-mounted accelerometer, and were associated with a history of overuse injuries. However, it remains unknown if these measures are also linked to the development of overuse injuries. The aim of this study was therefore to determine how movement dynamics alter in response to fatigue, and the possible link with developing lower-leg overuse injuries during a six-month follow-up period. Two hundred and eight movement science university students completed a 12-min all-out run while wearing a trunk-mounted accelerometer. Dynamic stability, dynamic loading and spatiotemporal measures were extracted from the accelerometer. Participants sustaining an injury within the 6-month period demonstrated significantly higher RMS ratio values in the vertical direction and lower RMS ratio values in the anteroposterior direction, and lower impact acceleration values in the anteroposterior direction in an unfatigued state compared to the uninjured group. They also demonstrated an increase in dynamic loading in the horizontal plane during the run. In addition, with running fatigue both groups exhibited changes in dynamic stability and loading measures. These results show the potential of using a single trunk-mounted accelerometer to detect changes in movement dynamics that are linked to lower-leg overuse injuries.

Weighted multichannel singular spectrum analysis for post-processing GRACE monthly gravity field models by considering the formal errors

SUMMARY Gravity Recovery and Climate Experiment (GRACE) Spherical Harmonics (SH) solutions are usually provided together with the corresponding formal errors, however, all multichannel singular spectrum analysis (MSSA) approaches neglect the formal errors of SH coefficients in processing the GRACE time-series. In this contribution, we propose a weighted MSSA to directly process the incomplete time-series of GRACE monthly gravity models by taking the formal errors into account. A 14-yr time-series of Release 06 (RL06) monthly gravity field models from the Center for Space Research (CSR) truncated to degree and order 60 for the period April 2002 to August 2016 is analysed by weighted MSSA, the results are compared with those from the improved MSSA that directly processes the incomplete time-series without considering the formal errors. The first 10 principal components derived by using the weighted MSSA can capture the variance in total up to 82.05 per cent, higher than 80.19 per cent by the improved MSSA. All the fitting errors of GRACE SH coefficients by the weighted MSSA are smaller than those by the improved MSSA, which indicates that weighted MSSA can extract more geophysical signals than the improved MSSA approach. To evaluate the efficiency of the weighted MSSA to eliminate noise, the ratios of the latitude weighted RMS of signals over lands and oceans are computed. Based on all the available months of GRACE solutions, the mean RMS ratio of signals over lands relative to oceans derived by the weighted MSSA is 5.04, higher than 4.96 by the improved MSSA. Therefore, we can conclude that the proposed weighted MSSA can suppress noise more efficiently and extract more geophysical signals from the GRACE time-series, which highlights the necessity of considering formal errors and the effectiveness of the weighted MSSA in post-processing the GRACE monthly gravity field models.

Analyzing sensitivity and resolution of some electrical resistivity configurations for detecting subsurface cavities using inverted synthetic models by 2D electrical resistivity tomography technique

It is important to determine the location, depth and shape (dimensions) of cavities under subsurface in site investigation phase before construction. This study aims to make a study for properties, analysis and comparison of the results of different electrodes configurations that used in 2-D electrical resistivity Tomography surveys to detection subsurface cavities to determining the appropriate and suitable configurations type that must be conduct in the field to obtain best and accurate results. Two-dimensional synthetic models were created for Geoelectrical resistivity of five different geological features, which reflects the common cases of cavities in nature. These models are (narrow, broad, shallow and deep) cavities adding to one model for multiple cavities. RES2DMOD program was used to create these models, while RES2DINV program used in Inversion method to obtain the true 2-D inverted resistivity sections for six configuration types of electrode array for 2D electrical resistivity technique, after adding a Gaussian noise ratio of (5%). Generally, we are noticed the possibilities of most tested configuration types for determine electrical anomalies, because the high contrast between the cavities and the surrounding rocks resistivities values. In addition, RMS ratio overall does not exceed 5%, hence, this ratio is an acceptable and indicates to the quality of the inverse process. The Wenner array have high sensitivity to vertical resistivity variations, and Dipole-dipole array have high sensitivity to lateral resistivity variations. While the Schlumberger-wenner have high sensitivity in both lateral and vertical resistivity variations Also, it was noted that the efficiency of all types decreasing with increasing depth of cavities detecting, due to the low percentage of contrast between the cavities and the surrounding rocks. The Wenner beta (WB) configuration is the best choice in terms of inversing true resistivity values, Secondly the Pole-Dipole (PD). While in term of determining the location and shape (approximately dimensions) of cavities, Dipole-Dipole (DD), Wenner-Schlumberger (WS), Wenner Alpha (WA), Dipole-Pole (DP) respectively. However, in case of noisy areas, Wenner Alpha (WA) configuration gives the best result.

Improved multichannel singular spectrum analysis for post-processing GRACE monthly gravity field models

SUMMARY Multichannel singular spectrum analysis (MSSA) is a powerful tool to extract spatiotemporal signals and filter errors from the noisy time-series of monthly gravity field models from the satellite data of gravity recovery and climate experiment (GRACE). Since the GRACE monthly gravity models are missed about 17 months, we develop an improved MSSA approach, which can directly process the incomplete time-series without either data interpolation or iteration. The time-series of 14-yr (2002.04–2016.08) monthly gravity field models of CSR-RL06 up to degree and order 60 are analysed with improved MSSA compared to the MSSA with linear data interpolation and iteration MSSA. By using our improved MSSA approach, the first 11 principal components derived can capture 91.18 per cent of the total variance, higher than 85.80 and 86.44 per cent of the total variance, derived by linear interpolation MSSA and iteration MSSA, respectively. The ratios of the latitude weighted RMS over the land and ocean signals are used to evaluate the efficiency of eliminating noise by the MSSA approach. For improved MSSA, the mean RMS ratio of land and ocean signals of all available months is higher than linear interpolation and iteration MSSA, which indicates that improved MSSA can suppress noise more efficiently and extract more geophysical signals from real GRACE data. Furthermore, the 50 repeated experiments show that all the root mean squared errors and mean absolute errors derived by our improved MSSA are smaller than other MSSA approaches. Moreover, the improved MSSA performs still better than other MSSA based approaches for the cases of large data gaps.

Analysis of a Sound Signal for Quality Monitoring in Laser Microlap Welding

This study focused on correlation analysis between welding quality and sound-signal features collected during microlaser welding. The study provides promising features for developing a monitoring system that detects low joint strength caused by a gap between metal sheets after welding. To obtain sound signals for signal analysis and develop the monitoring system, experiments for laser microlap welding were conducted on a laser microwelding platform by installing a microelectromechanical system (MEMS) microphone away from the welding point, and an acoustic emission (AE) sensor on the fixture. The gap between two metal sheet layers was controlled using clamp force, a pressing bar, and the appropriate installation of a thin piece of paper between the metal sheets. After sound signals from the microphone were collected, the correlation between features of time-domain sound signals and of welding quality was analyzed by categorizing the referred signals into eight sections during welding. After appropriately generating the features after signal analysis and selecting the most promising features for low-joint-strength monitoring on the basis of scatter index J, a hidden Markov model (HMM)-based classifier was applied to evaluate the performance of the selected sound-signal features. Results revealed that three sound-signal features were closely related to joint-strength variation caused by the gap between two metal-sheet layers: (1) the root-mean-square (RMS) value of the first section of sound signals, (2) the standard deviation of the first section of sound signals, and (3) the standard deviation to the RMS ratio of the second section of sound signals. In system evaluation, a 100% classification rate was obtained for normal and low-bonding-strength monitoring when the HMM-based classifier was developed on the basis of the three selected features.

Accelerometer Measurement of Trunk Lateral Fluctuation During Walking Following Total Knee Arthroplasty in Patients With Osteoarthritis.

This study aimed to clarify the effect of total knee arthroplasty (TKA) on trunk fluctuation and regularity of gait in patients with knee osteoarthritis by an accelerometer. The participants included 18 patients with knee osteoarthritis undergoing TKA. The gait at a comfortable velocity was assessed pre- and post-TKA by a triaxial accelerometer attached to the neck and lumbar regions. Measurement post-TKA was performed 4 weeks after surgery. Trunk fluctuation was estimated by the root mean square (RMS) of acceleration and RMS ratio (the ratio of RMS in each direction to the total RMS). Regularity of gait was estimated using the autocorrelation function. The results showed that TKA significantly decreased the RMS ratio in mediolateral acceleration of the neck and lumbar regions and reduced gait regularity. TKA appears to reduce compensatory trunk motion through the improvement of knee function. An assessment of trunk fluctuation using an accelerometer is useful for the clinical assessment of patients with knee osteoarthritis pre- and post-TKA.