Algorithm of axial compressor stall warning based on BP neural network and fuzzy logic

Stall warning of axial compressor is very challenging and the existing warning margin is not enough. A algorithm based on BP neural network fusion fuzzy logic is proposed. Firstly, BP neural network is used for training recognition, next the identification results are fused with fuzzy logic reasoning to form the result judgment of time sequence, finally the stall early warning of axial compressor is realized. The simulation results of the experimental data show that the stall data at all speeds are at least 0.1s in advance of the early warning. Compared with other methods, this method has a better surge early warning margin performance and engineering practicability.

VestAid: A Tablet-Based Technology for Objective Exercise Monitoring in Vestibular Rehabilitation

(1) Background: Current vestibular rehabilitation therapy is an exercise-based approach aimed at promoting gaze stability, habituating symptoms, and improving balance and walking in patients with mild traumatic brain injury (mTBI). A major component of these exercises is the adaptation of the vestibulo-ocular reflex (VOR) and habituation training. Due to acute injury, the gain of the VOR is usually reduced, resulting in eye movement velocity that is less than head movement velocity. There is a higher chance for the success of the therapy program if the patient (a) understands the exercise procedure, (b) performs the exercises according to the prescribed regimen, (c) reports pre- and post-exercise symptoms and perceived difficulty, and (d) gets feedback on performance. (2) Methods: The development and laboratory evaluation of VestAid, an innovative, low-cost, tablet-based system that helps patients perform vestibulo-ocular reflex (VORx1) exercises correctly at home without therapist guidance, is presented. VestAid uses the tablet camera to automatically assess patient performance and compliance with exercise parameters. The system provides physical therapists (PTs) with near real-time, objective (head speed and gaze fixation compliance), and subjective (perceived difficulty and pre- and post- exercise symptoms) metrics through a web-based provider portal. The accuracy of the head-angle and eye-gaze compliance metrics was evaluated. The accuracy of estimated head angles calculated via VestAid’s low-complexity algorithms was compared to the state-of-the-art deep-learning method on a public dataset. The accuracy of VestAid’s metric evaluation during the VORx1 exercises was assessed in comparison to the output of an inertial measurement unit (IMU)-based system. (3) Results: There are low mean interpeak time errors (consistently below 0.1 s) across all speeds of the VORx1 exercise, as well as consistently matching numbers of identified peaks. The spatial comparison (after adjusting for the lag measured with the cross-correlation) between the VestAid and IMU-based systems also shows good matching, as shown by the low mean absolute head angle error, in which for all speeds, the mean is less than 10 degrees. (4) Conclusions: The accuracy of the system is sufficient to provide therapists with a good assessment of patient performance. While the VestAid system’s head pose evaluation model may not be perfectly accurate as a result of the occluded facial features when the head moves further towards an extreme in pitch and yaw, the head speed measurements and associated compliance measures are sufficiently accurate for monitoring patients’ VORx1 exercise compliance and general performance.

Demonstrating the first postulate of relativity in a lift

The first of the two postulates of relativity states that the laws of physics are the same in all inertial reference frames. Often it is assumed that the postulates are mainly concerned with objects moving at a significant fraction of the speed of light. However, the postulates are applicable at all speeds from a snail to a photon. To practically demonstrate the first postulate, the time for a ball to drop a known distance was measured in a stationary and moving lift. An accelerometer app on an iPhone 7 was used to measure the vertical acceleration while the lift travelled between floors and verified that the lift ascended and descended at a constant speed when the ball was dropped. The slow-motion feature of the iPhone 7 (240 fps) was used to capture videos of the falling ball. The number of frames for the ball to fall in a stationary, descending, and ascending lift was respectively 102.4 ± 0.55 , 102.3 ± 1.64 , 99.8 ± 4.21. A t-test revealed no significant difference between these values, confirming the validity of the first postulate. The accelerometer signal was integrated to estimate the average speed of the lift between the bottom and top floor, which was then used to estimate the height difference. An electronic balance placed on the floor of the lift was used to demonstrate the first postulate and the equivalence principle of General Relativity that states that gravitational and inertial mass are equivalent.

Does Gait with an Ankle Foot Orthosis Improve or Compromise Minimum Foot Clearance?

The purpose of this study was to investigate if the use of an ankle foot orthosis in passive mode (without actuation) could modify minimum foot clearance, and if there are any compensatory mechanisms to enable these changes during treadmill gait at a constant speed. Eight participants walked on an instrumented treadmill without and with an ankle foot orthosis on the dominant limb at speeds of 0.8, 1.2, and 1.6 km/h. For each gait cycle, the minimum foot clearance and some gait linear kinematic parameters were calculated by an inertial motion capture system. Additionally, maximum hip and knee flexion and maximum ankle plantar flexion were calculated. There were no significant differences in the minimum foot clearance between gait conditions and lower limbs. However, differences were found in the swing, stance and step times between gait conditions, as well as between limbs during gait with orthosis (p < 0.05). An increase in hip flexion during gait with orthosis was observed for all speeds, and different ankle ranges of motion were observed according to speed (p < 0.05). Thus, the use of an ankle foot orthosis in passive mode does not significantly hinder minimum foot clearance, but can change gait linear and angular parameters in non-pathological individuals.

Optimal Speed Control Humps Design Based on Driver Comfort

The purpose of this study is to optimise the different speed control humps by considering the vertical and horizontal acceleration of the driver’s head. In previous researches, the main focus was only on vertical acceleration, but in this study, horizontal acceleration of the head is also considered. Here, the root mean square (RMS) of acceleration of head is considered as a measure of occupant comfort. The modelling is performed by a non-linear half-car suspension system (4-DOF) with a linear model of a driver (10-DOF) and a seat. The hamps under study are circular, sinusoidal, half-sinusoidal, and trapezoidal. Finally, by analysing the results, the optimal design of each type of hump is performed. The objective function used is a combination of horizontal and vertical acceleration which is performed using MATLAB genetic algorithm. The results show a significant reduction in horizontal and vertical acceleration at all speeds. From this modelling, it is possible to extract a suitable range for passing the speed of cars over different types of humps. In this study, it is shown that the acceleration values for the circular and half-sinusoidal humps at all speeds are quite close to each other.

Mechanical energy and propulsion mechanics in roller-skiing double-poling at increasing speeds

Objectives The aim of this study was to examine the effect of speed on mechanical energy fluctuations and propulsion mechanics in the double-poling (DP) technique of cross-country skiing. Methods Kinematics and dynamics were acquired while fourteen male skiers performed roller-skiing DP on a treadmill at increasing speeds (15, 21 and 27 km∙h-1). Kinetic (Ekin), potential (Epot), and total (Ebody) body mechanical energy and pole power (Ppole) were calculated. Inverse dynamics was used to calculate arm power (Parm). Trunk+leg power (PT+L) was estimated, as was the power associated with body movements perpendicular to goal-direction (E.body⊥). Results Ekin and Epot fluctuated out-of-phase throughout the cycle, at first sight indicating that pendulum-like behaviour occurs partly in DP. However, during the swing phase, the increase in Epot (body heightening) was mainly driven by positive PT+L, while the decrease in Ekin was lost to rolling friction, and during the poling phase, considerable positive Parm generation occurs. Thus, possible exchange between Ekin and Epot seem not to occur as directly and passively as in classic pendulum locomotion (walking). During the poling phase, E.body⊥fluctuated out-of-phase with Ppole, indicating a transfer of body energy to Ppole. In this way, power generated by trunk+leg mainly during the swing phase (body heightening) can be used in the poling phase as pole power. At all speeds, negative PT+L occurred during the poling phase, suggesting energy absorption of body energy not transferred to pole power. Thus, DP seem to resemble bouncing ball-like behaviour more than pendulum at faster speeds. Over the cycle, Parm contribution to Ppole (external power) was 63% at 15 km∙h-1 and 66% at 21 and 27 km∙h-1, with the remainder being PT+L contribution. Conclusions When speed increases in level DP, both power production and absorption by trunk+leg actions increase considerably. This enhanced involvement of the legs at faster speeds is likely a prerequisite for effective generation of pole power at high speeds with very short poling times. However, the relative trunk+leg power contribution did not increase at the speeds studied here.

Fuel Economy Results From Diesel Engine Tuning for Steady Speed and Drive Cycle Operation

As part of efforts to mitigate climate change by reducing fuel consumption in the transport sector in the Philippines, this paper presents the initial results of an investigation on the effects of engine tuning on fuel economy for different drive cycles using a commercially available piggyback tuning “chip” to modify fuel rail pressure from stock settings of a CRDI diesel passenger van. The drive cycles used in this study were the Japanese 10-15 Mode, US highway fuel economy test (HWFET), and one labeled “SMN” based on a Metro Manila local route. An initial steady state vehicle fuel economy performance map at five speeds per gear position and stock tuning was obtained from chassis dynamometer tests. The same series of tests were done with the tuning chip’s settings of progressively lower rail pressure to identify the setting giving lowest fuel consumption at each gear. Fuel consumption reduction of up to 47% was observed although not all speeds at a given gear and tuning setting gave reduced values. These lowest fuel settings were applied to corresponding gear positions in each of the selected drive cycles resulting to “specific tuning maps” per drive cycle. The test vehicle was then driven with these drive cycle-specific tuning maps and the fuel economy measured. It was found that overall fuel economy decreased with drive cycle-specific tuning settings. It was then decided to try using a constant tuning setting throughout a drive cycle to see if fuel economy improved. Trials with the Japanese 10-15 Mode cycle at different constant lower rail pressure settings likewise gave overall lower fuel economy. However, a more detailed look showed that in the constant-speed portions of the cycle, fuel consumption savings of up to 35% were realized while it worsened in the accelerating and decelerating sections. The drive cycle test results indicate that the engine ECU compensated for the lowered rail pressure, maybe with increased injection duration, to increase the amount of fuel injected to meet the road-load requirements imposed by the drive cycle. Control response instabilities may have also contributed to higher fuel consumption. Engine tuning by rail pressure reduction only was most effective in reducing fuel consumption for steady state driving and ineffective for transient driving under the conditions and methodology of this study.

Repurposing an EMG Biofeedback Device for Gait Rehabilitation: Development, Validity and Reliability

Gait impairment often limits physical activity and negatively impacts quality of life. EMG-Biofeedback (EMG-BFB), one of the more effective interventions for improving gait impairment, has been limited to laboratory use due to system costs and technical requirements, and has therefore not been tested on a larger scale. In our research, we aimed to develop and validate a cost-effective, commercially available EMG-BFB device for home- and community-based use. We began by repurposing mTrigger® (TJM Electronics, Warminster, PA, USA), a cost-effective, portable EMG-BFB device, for gait application. This included developing features in the cellphone app such as step feedback, success rate, muscle activity calibration, and cloud integration. Next, we tested the validity and reliability of the mTrigger device in healthy adults by comparing it to a laboratory-grade EMG system. While wearing both devices, 32 adults walked overground and on a treadmill at four speeds (0.3, 0.6, 0.9, and 1.2 m/s). Statistical analysis revealed good to excellent test–retest reliability (r > 0.89) and good to excellent agreement in the detection of steps (ICC > 0.85) at all speeds between two systems for treadmill walking. Our results indicated that mTrigger compared favorably to a laboratory-grade EMG system in the ability to assess muscular activity and to provide biofeedback during walking in healthy adults.

The Effect of Contextual Variables on Match Performance across Different Playing Positions in Professional Portuguese Soccer Players

This study investigated the position-specific physical demands of professional Portuguese players. The effects of situational variables on the physical performance demands were also analysed (match location, match half and match result). Match performance observations were collected using Global Navigation Satellite System devices across 11 matches during a competitive season (2019–2020). Data were analysed according to five playing positions: goalkeepers (n = 11), central defenders (n = 42), wide defenders (n = 31), central midfielders (n = 34), open attackers (n = 28), and centre forwards (n = 14). Central midfield players completed the greatest total distance (10,787 ± 1536 m), while central defenders covered the least distance (9272 ± 455; p < 0.001). Open attackers covered the greatest high and very-high-speed distance (1504 ± 363 m), number of high-speed decelerations per match (11 ± 4) and were the fastest players (30.6 ± 1.5 km/h), along with center forwards (30.6 ± 2.0 km/h), versus all other positions (p < 0.05). Greater distances were performed in teams that were winning (9978 ± 1963 m) or drawing (10,395 ± 875 m) versus losing (9415 ± 2050) p = 0.036 and p = 0.006, respectively. Increases in distance covered at walking speeds were observed during the 2nd half (1574 ± 179 m) compared with the 1st half (1483 ± 176; (p < 0.003). A higher number of decelerations across all speeds were performed in the 1st half (144 ± 39) versus the 2nd half (135 ± 37). The distance covered in home matches (10,206 ± 1926 m) far exceeded away matches (9471 ± 1932 m; p < 0.001). The number of faster accelerations were higher in away (7 ± 5) versus home matches (6 ± 4; p < 0.049). The data demonstrate the different physical demands of each playing position and suggest that situational variables influence physical performance. These findings suggest position-specific physical training is required to condition players for the bespoke demands of each playing position.

Are trunk muscles weaker in adolescents females with adolescent idiopathic scoliosis compared with their healthy counterparts?

BACKGROUND: Adolescent Idiopathic Scoliosis (AIS) requires complex medical care because of multiple consequences especially on daily activities. Muscular involvement is part of the problem and may be treatable. OBJECTIVE: To analyze trunk muscle strength using an isokinetic dynamometer in female adolescents with AIS one year after orthopedic treatment by brace and compare the findings to a matched group of an asymptomatic cohort. METHODS: The trunk flexors and extensors strength was measured using an isokinetic dynamometer at 60, 90 and 120∘/s. Peak Moment (PM), Mean Power (MP) and the flexor/extensor ratio in 100 patients aged 14 to 18 years old were compared to a control group (N= 32) of asymptomatic age-matched females. In the AIS group, correlation analyses were computed to search for contributing factors to isokinetic performances, including morphological characteristics of patients, as well as clinical and radiological characteristics of the scoliosis. RESULTS: The trunk flexors in the AIS group were significantly but moderately (15%) weaker across speeds compared to their control counterparts at all speeds. No parallel weakness was noted for the extensors. While the MP of AIS patients was significantly weaker than that of the controls, 33% for flexors and by 31% for extensors, no significant differences were observed for the F/E ratios. The correlational analyses has indicated that weight and BMI were contributing factors at all speeds. CONCLUSION: Adolescents with AIS had weaker trunk extensors and mostly flexors compared to healthy females. Within this AIS population, weight and BMI seem to have a negative impact on muscular performances, whereas clinical and radiological characteristics of the scoliosis do not seem to contribute.