The elastic properties of the Achilles tendon (AT) are altered in local injury or other diseases and in response to changes in mechanical load. Recently, elastography has been used to evaluate ...variations in tendon elastic properties, mainly among healthy individuals or athletes. Therefore, this study evaluated the biomechanical changes in ATs in individuals with and without plantar fasciitis (PF). The purposes were as follows: (1) to evaluate the passive stiffness of three regions of the AT which defined as 0 (AT0 cm), 3 (AT3 cm), and 6 cm (AT6 cm) above the calcaneal tuberosity in participants with and without PF, (2) to investigate the interplay between the passive stiffness in patients with PF and pain, (3) to detect optimal cut-off points of stiffness of the AT in assessing individuals with chronic PF, and (4) to determine the correlation between the plantar fascia thickness (PFT) and pain. This cross-sectional study included 40 participants (mean age = 51 ± 13 years). When the ankle was in a relaxed position, patients with PF experienced increased passive stiffness in AT0 cm (
p
= 0.006) and AT3 cm (
P
= 0.003), but not in the neutral position. Significant correlations were observed between pain and stiffness of AT (AT0 cm
r
= 0.489,
P
= 0.029; AT3 cm
r
= 487,
P
= 0.030; AT6 cm
r
= 0.471,
P
= 0.036), but not in the PFT (
P
= 0.557). Optimal cut-off stiffness was AT (452 kPa) in the relaxed ankle position. The plantar fascia of patients with PF was significantly thicker than that of the controls (
P
< 0.001). Findings from the present study demonstrate that tendon stiffness is a good indicator of the clinical situation of patients with PF. Monitoring passive tendon stiffness may provide additional information to assess severity of the condition and guide therapeutic. The treatment programs for PF should also be tailored to the distal AT, as conventional therapy might not be targeted to tight tendons.
The mechanical properties of the deep fascia, particularly their stiffness, strongly affect the development of muscle pathologies (such as compartment syndrome) and the action of the muscles. ...However, the mechanical characteristics of the deep muscular fascia are still not clearly understood. The present study focuses on examining the reliability of ultrasonic shear wave elastography (USWE) devices in quantifying the shear modulus of the gastrocnemius fascia in healthy individuals, particularly their ability to measure the shear modulus of the deep fascia of the gastrocnemius during ankle dorsiflexion. Twenty-one healthy males (age: 21.48 ± 1.17 years) participated in the study. Using USWE, the shear moduli of the medial gastrocnemius fascia (MGF) and lateral gastrocnemius fascia (LGF) were quantified at different angles during passive lengthening. The two operators took turns measuring each subject's MGF and LGF over a 1-h period, and operator B took an additional measurement 2 h later. For the intra-operator test, the same subjects were measured again at the same time of day 5 days later. Both the intrarater intraclass correlation coefficient (ICC) = 0.846-0.965) and interrater (ICC = 0.877-0.961) reliability values for measuring the shear moduli of the MGF and LGF were rated as excellent; the standard error of the mean (SEM) was 3.49 kPa, and the minimal detectable change (MDC) was 9.68 kPa. Regardless of the ankle angle, the shear moduli of the LGF were significantly greater than that of the MGF (p < 0.001). Significant increases in the shear moduli of both the MGF and the LGF were observed in the neutral position compared to the relaxed position. These results indicate that USWE is a reliable technique to assess the shear modulus of the gastrocnemius fascia and detect its dynamic changes during ankle dorsiflexion. USWE can be used for biomechanical studies and intervention experiments concerning the deep fascia.
The fault diagnosis of rolling element bearing is of great significance to avoid serious accidents and huge economic losses. However, the characteristics of the nonlinear, non-stationary vibration ...signals make the fault feature extraction of signal become a challenging work. This paper proposes an improved variational mode decomposition (IVMD) algorithm for the fault feature extraction of rolling bearing, which has the advantages of extracting the optimal fault feature from the decomposed mode and overcoming the noise interference. The Shuffled Frog Leap Algorithm (SFLA) is employed in the optimal adaptive selection of mode number K and bandwidth control parameter α. A multi-objective evaluation function, which is based on the envelope entropy, kurtosis and correlation coefficients, is constructed to select the optimal mode component. The efficiency coefficient method (ECM) is utilized to transform the multi-objective optimization problem into a single-objective optimization problem. The envelope spectrum technique is used to analyze the signals reconstructed by the optimal mode components. The proposed IVMD method is evaluated by simulation and practical bearing vibration signals under different conditions. The results show that the proposed method can improve the decomposition accuracy of the signal and the adaptability of the influence parameters and realize the effective extraction of the bearing vibration signal.
Infertility is an area of increasing in life science research. Although follicular maturation disorders and anovulation are the primary causations of infertility, its molecular mechanism is not well ...understood. Recent research has shown that microRNAs (miRNAs) might play an important role in the regulation of ovarian follicle development and maturation. In this study, the expression of miRNAs in metaphase I (MI) oocytes treated with or without insulin-like growth factor 1 (IGF-1) was observed by microRNA microarray analysis. Results show that 145 miRNAs were up-regulated and 200 miRNAs were down-regulated in MI oocytes after IGF-1 treatment. MiR-133b, which was up-regulated more than 30-fold, was chosen for further research. As a potential target of miR133b, transgelin 2 (TAGLN2) gene was down-regulated, at both transcription and translation levels, in miR-133b- over-expressed 293T cells, but TAGLN2 was up-regulated when the expression of miR-133b was inhibited. Furthermore, the expression level of TAGLN2 in the ovaries of 8-week- old mice was higher than that observed in 4-week-old mice. Immunofluorescence experiments showed that TAGLN2 was located in the cytoplasm. In general, our results indicate that miR-133b may play important roles in the growth and maturation of oocytes by regulating its potential target, TAGLN2, at both transcription and translation levels. Therefore, our research provides a potential new target for infertility therapy.
Natural gas, whose primary constituent is methane, has been considered a convincing alternative for the growth of the energy supply worldwide. Adsorbed natural gas （ANG）, the most promising methane ...storage method, has been an active field of study in the past two decades. ANG constitutes a safe and low-cost way to store methane for natural gas vehicles at an acceptable energy density while working at substantially low pressures （3.5- 4.0 MPa）, allowing for conformable store tank. This work serves to review the state-of-the-art development reported in the scientific literature on adsorbents, adsorption theories, ANG conformable tanks, and related technolo- gies on ANG vehicles. Patent literature has also been searched and discussed. The review aims at illustrating both achievements and problems of the ANG technologies-based vehicles, as well as forecasting the development trends and critical issues to be resolved of these technologies.
The faults of rolling element bearings can result in the deterioration of machine operating conditions; how to assess the working condition and identify the fault of the rolling element bearing has ...become a key issue for ensuring the safe operation of modern rotating machineries. This paper presents a novel hybrid approach that detects bearing faults and monitors the operating status of rolling element bearings in modern rotating machineries. Based on redundant second-generation wavelet packet transform and local characteristic-scale decomposition, this method is implemented to extract the fault features, the vibration signal is adaptively decomposed into a number of desired intrinsic scale components by two-step screening processes based on the energy ratio, and reduce random noises and eliminate the pseudofrequency components. The fault features are then used to implement the identification classification of faults using singular value decomposition and extreme learning machine. The approach is evaluated by simulation and practical bearing vibration signals under different conditions. The experiment results show that the proposed approach is feasible and effective for the fault diagnosis of rolling element bearing.
•This work reviews the theoretical background of pressure drop for open cell foams.•Pressure drop was investigated on aluminum foams of a broad range of properties.•This work compares simulation ...result with theoretical predictions and experiments.•The heat transfer coefficients and friction factors of foams were evaluated.
This work reviews the theoretical backgrounds of pressure drop prediction for open cell foams. The pressure drop of open cell foams was investigated on aluminum foam structures of pore densities 10–50ppi and porosities 70–95%, with the commercial CFD analysis package: ANSYS Fluent, and performed over flow velocities ranging from 0.5m/s to 20m/s. The 3D foam structures were created by Laguerre-Voronoi tessellations. The numerical results for pressure drop were compared with the theoretical predictions by Inayat et al. and experimental data in the literature. The results show that the pressure drop of foams increases with increasing pore density and decreasing porosity. The numerical results are consistent with theoretical predictions and experimental data. The computed interfacial heat transfer coefficient was investigated. The Nusselt number increases with increasing Reynolds number, and increases with increasing porosity at constant pore density. The friction factor of foams was also evaluated.
The fault diagnosis of rolling element bearings is very important for ensuring the safe operation of rotary machineries. Targeting the nonstationary characteristics of the vibration signals of ...rolling element bearings, a novel approach based on dual-tree complex wavelet packet transform, improved intrinsic time-scale decomposition, and the online sequential extreme learning machine is proposed in this article for the fault recognition of rolling element bearing. First, the feature extraction method of the measured signal is presented by combining improved intrinsic time-scale decomposition with dual-tree complex wavelet packet transform as preprocessor and two-step screening processes based on the energy ratio, the vibration signal is adaptively decomposed into a set of proper rotation components; second, the matrix formed by different proper rotation components and singular value decomposition is used to obtain singular value as eigenvector; finally, singular values are input to online sequential extreme learning machine to realize the fault diagnosis of rolling element bearings. The effectiveness of the proposed method of fault diagnosis is demonstrated. The experimental results show that the proposed method can effectively extract the fault characteristics and accurately identify the fault patterns.
•This work describes pore-scale two-phase simulations for open-cell metal foams.•The dispersed oil-phase was tracked using a Lagrangian approach: discrete phase model.•Foams of pore densities ...10–50 ppi and porosities 75, 85 and 95% were investigated.•The fractions of non-captured oil droplets of the investigated foams were evaluated.
Oil/air separation is a critical process in aero engines since a two-phase flow is created in bearing chambers with closed-loop oil systems. This work describes an application of a two-phase pore-scale modeling method to open-cell metal foams, which are used in secondary oil separation in aero-engine separators. The dispersed oil-phase flow through open-cell foams was studied using a Lagrangian approach: discrete phase model (DPM) and investigated on foam structures of pore densities 10–50 ppi and porosities 75, 85 and 95%. The simulations were performed over flow velocities ranging from 5 m/s to 50 m/s, and for separate uniform droplets of diameters ranging from 0.5 to 15 μm, with the commercial CFD analysis package Ansys Fluent. Results indicated that the fraction of non-captured droplets decreased when the flow velocity rose, and the higher the foam porosity, the higher the number of non-captured oil droplets. The flow velocity had a significant impact on the oil capture for intermediate droplet diameters of 1–3 μm. The fraction of non-captured oil droplets increased as the pore density of the open-cell foam increased at the normalized position of x/dp = 5. Foams with a larger pore size and smaller specific surface area showed an increased oil capture when compared with foams with smaller pore sizes and larger specific surface area. For Stokes numbers below 0.1, the oil capture efficiency was small and remained rather constant independent of the Stokes number. However, for 0.1 < Stokes numbers < 1.0, the oil capture efficiency increased substantially with increasing Stokes numbers. Stokes number values above 1.0 were associated with a high capture efficiency, which remained stable with increasing Stokes numbers.
The attitude parameters of the 3-D movement of an aircraft are indicators of an aircraft's operating state. A method of sequence screen-spot imaging based on the laser-aided cooperative target is ...presented to support the measurement of aircraft attitude parameters in ground test experiments. The laser-aided cooperative target is mounted on the aircraft surface and the laser spots are projected onto two fixed screen. High-speed cameras synchronously record the position of the laser spots on the screen. According to the position transformation relation between the coordinate systems, the aircraft attitude parameters can be calculated by analyzing the position of the sequence screen-spot image, which will change along with the aircraft attitude. A global calibration method based on the coplanar control points is proposed for the calibration of the measuring system. The experimental results show that the measurement accuracy of the attitude parameters for the proposed method is no more than 3' under the rotation angle from − 10° to + 10°. The proposed method can amplify the motion attitude of the aircraft by mounting the laser-aided cooperative target on the surface of the aircraft, which breaks the limitation of the geometric condition of the aircraft and improves the measurement accuracy.
PDF
