Gait strategies for individuals with knee osteoarthritis when transitioning between floor and stair walking.

Objective: Individuals with knee osteoarthritis are at higher risk for falls during transitions between floor and stair walking due to their reduced lower extremity function. However, the adjust gait characteristics of knee osteoarthritis subjects for dealing with stair transitions have not been explored. We aimed to investigate gait strategies in individuals with knee osteoarthritis compared to age-matched individuals without knee OA during the transition between walking on floor and stairs. Method: Gait of 30 individuals with knee osteoarthritis and 30 individuals without knee osteoarthritis during floor-to-stair and stair-to-floor walking transitions were accessed using a 3D motion capture system. Foot-tread clearance, and angles of lower extremity joints and trunk at Foot-tread clearance timepoint were analyzed by using biomechanical software (Visual 3D). Results: Compared with asymptomatic control group, the knee osteoarthritis group demonstrated no difference in vertical Foot-tread clearance and horizontal Foot-tread clearance during stair transitions. However, ankle dorsiflexion (p = 0.01) decreased, hip flexion (p = 0.02) and trunk lateral tilt (p = 0.02) increased in knee osteoarthritis group during the stair ascent transition. Moreover, trunk lateral tilt to the support side (p = 0.003) and pelvic rotation (p = 0.03) increased, while hip abduction of the swing leg (p = 0.03) decreased during the stair descent transition in individuals with knee osteoarthritis. Conclusion: Increased trunk lateral tilt and altered angle of hip may be a strategy utilized by individuals with knee OA to increase the foot clearance ability and compensate for the disease-related loss of lower extremity strength, range of motion, and balance. However, compensatory manifestations, such as the increased lateral tilt of the trunk and movement of the gravity center may enhance the risk of falls and result in more abnormal knee joint loading.

Experiment on compaction of air-dried soil under drop shocks.

For the requirement in container nursery culture that growing media should be achieved the appropriate degree compaction, this paper presents an experiment on the compaction dynamics of air-dried soil under repetitive drop shocks, as a preliminary step toward the mechanization of this compaction method. The drop height used to adjust the shock intensity included 2 mm, 4 mm, 5 mm and 6 mm. And the overall packing density of soil in a vertically stratified cylinder vessel and the local packing density in each layer were taken as indicators of soil compaction states. The stretched exponential function derived from KWW law than the empirical inverse-logarithmic function has been found to be more suitable for expressing the temporal evolution of soil compaction, according to the results of curve-fitting to test values of the overall and local density. It is inherent in this experimental configuration that the drop shock intensity even at a constant drop height varies with drop times, owing to the interaction between the soil packing itself and drop shocks caused by the combination of the packing and the container. But the function t/τf(t,H) is manifested as a straight line on the drop times t with the line slope related to the drop height H, so the soil compaction dynamics caused by its drop shocks and that under the condition with actively controlled intensity actually share the common relaxation law. In addition, the soil's one-dimensional distribution of local packing density showed a slight positive gradient as similar as monodisperse particles did.

Influence of Toothed Rail Parameters on Impact Vibration Meshing of Mountainous Self-Propelled Electric Monorail Transporter.

In order to reduce the vibration of mountain self-propelled electric monorail transporters (MSEMT) caused by the impact of the meshing of roller gear with toothed rail (MRGTR), and to improve the stability and safety of monorail transporters, this paper theoretically analyzed the MRGTR mechanism of toothed monorail transporters as well as established the MSEMT displacement model and its instantaneous velocity model. The vibration signals of MSEMT with four different parameters of toothed rail were collected by the acceleration sensor and signal acquisition system. The signals were analyzed by the Hilbert envelope demodulation method to investigate the influence of toothed rail parameters on meshing impact vibration. Moreover, taking the vibration acceleration amplitude of MSEMT and the vibration attenuation time of meshing impact as evaluation indexes, a test based on the three-factor and two-level orthogonal test was engaged with factors of toothed rail pressure angle, the ratio of L-the chord length of two adjacent roller centers of a roller gear-and rack pitch p (wheel-tooth ratio) and the load mass of the MSEMT. It showed that the impact of MRGTR was the main excitation source of the vibration of MSEMT. The pressure angle and wheel-tooth ratio both have a significant impact on the smooth operation of MSEMT, the latter to a greater extent. So did the interaction between wheel-tooth ratio and load mass. The amplitude of the characteristic frequency of the MSEMT decreased with the growth of the pressure angle. When the wheel-tooth ratio was cosα, the number of the characteristic frequency was less than that when it was 1, and the amplitude became smaller too. When the pressure angle was 15, the amplitude of vibration acceleration characteristic frequency decreased as a consequence of load mass increasing. At the pressure angle of 25, the amplitude of characteristic frequency decreased with the increase of load mass if the wheel-tooth ratio was 1, and the opposite result occurs in the case when the wheel-tooth ratio was cosα. This paper provides a theoretical basis and reference for improving the impact vibration of MRGTR and optimizing the design of the toothed rail.

[Application of Wavelet Transform and Successive Projections Algorithm in the Non-Destructive Measurement of Total Acid Content of Pitaya].

The objective of present study was to find out an accurate, rapid and nondestructive method to detect total acid content (TA) of pitaya with visible/near-infrared spectrometry, wavelet transform (WT) and successive projections algorithm (SPA), which will provide scientific basis for non- destructive measurement of pitaya. Maya2000 fiber-optic spectrumeter was used to collect spectral data of pitaya on the wavelength in the range of 380~1 099 nm; and then with the methods of WT denosing pretreatment, SPA and partial least squares regression (PLSR) quantitative forecasting model of TA of pitaya was established. The result showed that the precision of WT-SPA-PLSR model, which combine the WT with SPA, was better than that of PLSR model based on the whole wave variables. The relation coefficient of the PLSR model (Rp) that predicted TA based on the original spectrum of all samples as the input variables was 0.851 394 and RMSEP was 0.086 848. The original spectrum variable of the all samples were processed by using wavelet function dbN(N=2, 3, …, 10) for wavelet decomposition and de-noising. The optimal results of noise reduction were decomposed in level 2 using wavelet function db4 (db4-2). The Rp of WT-PLSR model was 0.915 635 and RMSEP was 0.066 752. The prediction of model using wavelet transform de-noising was improved significantly. After the original spectrum processed by db10-3 and SPA, 12 preferred variables were selected from 570 spectrum variables, such as 530, 545, 604, 626, 648, 676, 685, 695, 730, 897, 972, 1 016 nm spectrum variables. The WT-SPA-PLSR model based on these 12 variables as input variables was established. Rp of the WT-SPA-PLSR prediction model was 0.882 83 and RMSEP was 0.077 39. SPA algorithm was suitable for the selection of spectrum variables which could effectively obtain the spectrum variables which were strong correlation with TA and increase the accuracy and stability of the prediction model. The results indicated that the nondestructive detection for TA of pitaya based on the diffuse reflectance visible/near-infrared spectrometry, WT and SPA was feasible.

[Rapid identification of potato cultivars using NIR-excited fluorescence and Raman spectroscopy].

Potato is one of the most important food in the world. Rapid and noninvasive identification of potato cultivars plays a important role in the better use of varieties. In this study, The identification ability of optical spectroscopy techniques, including near-infrared (NIR) Raman spectroscopy and NIR fluorescence spectroscopy, for invasive detection of potato cultivars was evaluated. A rapid NIR Raman spectroscopy system was applied to measure the composite Raman and NIR fluorescence spectroscopy of 3 different species of potatoes (98 samples in total) under 785 nm laser light excitation. Then pure Raman and NIR fluorescence spectroscopy were abstracted from the composite spectroscopy, respectively. At last, the partial least squares-discriminant analysis (PLS-DA) was utilized to analyze and classify Raman spectra of 3 different types of potatoes. All the samples were divided into two sets at random: the calibration set (74samples) and prediction set (24 samples), the model was validated using a leave-one-out, cross-validation method. The results showed that both the NIR-excited fluorescence spectra and pure Raman spectra could be used to identify three cultivars of potatoes. The fluorescence spectrum could distinguish the Favorita variety well (sensitivity: 1, specificity: 0.86 and accuracy: 0.92), but the result for Diamant (sensitivity: 0.75, specificity: 0.75 and accuracy: 0. 75) and Granola (sensitivity: 0.16, specificity: 0.89 and accuracy: 0.71) cultivars identification were a bit poorer. We demonstrated that Raman spectroscopy uncovered the main biochemical compositions contained in potato species, and provided a better classification sensitivity, specificity and accuracy (sensitivity: 1, specificity: 1 and accuracy: 1 for all 3 potato cultivars identification) among the three types of potatoes as compared to fluorescence spectroscopy.

Novel liquid flow sensor based on differential pressure method.

In this article, a novel liquid flow sensor which is composed of a special structure conduit main body and a differential pressure sensor was designed, fabricated, and calibrated. The conduit main body includes an inlet channel section with a branch conduit connecting one end of the pressure sensor, a throat channel section, and an outlet channel section with a branch conduit connecting another end of the pressure sensor. The basic principle is to employ a differential pressure sensor to measure the pressure difference between the inlet channel and outlet channel of the conduit main body when fluid passes through it. The pressure difference between the two ends of the differential pressure sensor (i.e., the two branch conduits located in the inlet and outlet channel sections) is of either forward or backward flow and directly interrelates with the volume flow rate (mass flow rate or flow velocity) via the conduit main body, so the volume flow rate or mass flow rate or flow velocity can be calculated and the flow direction can be determined from the detected pressure difference. This liquid flow sensor is characterized by using only one differential pressure sensor of a simple structure, the error of which is less than 1%.