Research on the Mechanical Behavior of Buried Double-Wall Corrugated Pipes.

The mechanical behavior of buried HDPE double-wall corrugated pipes is mainly affected by the material and the structure of the pipe wall. Here we studied a peculiar material that added fly ash (FA) in high density polyethylene (HDPE) to develop composites. We have conducted research on FA/HDPE composites with different mix proportions. When 5% compatibilizer was added to the 10% FA masterbatch/HDPE composite, the Young's Modulus of FA/HDPE composite was higher. This paper mainly studies the mechanical behavior of the structure of pipe walls for materials with this proportion of the ingredients. The mechanical behavior of double-wall corrugated pipes with different ratios of interior and exterior wall thicknesses is studied by keeping the sum of the interior and exterior wall thicknesses unchanged. Pipes with six different ratios of interior and exterior wall thicknesses are simulated; the results show that the strain of crest and liner gradually decreased and the valley strain gradually increased with the increase of the exterior wall thickness. By comparing inner and outer wall thickness ratios from 0.67 to 2.33, it is found that the structural performance and economic advantage for the double-wall corrugated pipes is best when the thickness ratio of the interior wall and the exterior wall is controlled to be from 1.3 to 1.8. This paper expounds the deformation mechanism of double-wall corrugated pipes from the perspective of mechanical behavior and structural characteristics, and provides a reference for material selection and structural design of double-wall corrugated pipes.

Methodical approaches to determine the rate of radial muscle displacement using tensiomyography: A scoping review and new reporting guideline.

Tensiomyography is a non-invasive method to assess skeletal muscle contractile properties from the stimulated radial displacement. Many studies have used the rate of displacement (Vc) as an indirect measure of muscle contraction velocity. However, no standardised methodical approach exists to measure displacement and determine Vc. This review aimed to provide an overview of concepts to determine Vc and measurement protocols to foster the development of a standardised methodical approach. This review followed the Preferred Reporting Items for Systematic Reviews and meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guideline. Systematic searches were performed within five electronic databases and additional sources. The included 62 studies reported 10 different concepts to determine Vc, which we summarised in three groups. The determination concepts differed mainly regarding time intervals during the contraction phase considered and criteria used to define these intervals. Essential information on the equipment and raters, measurement setup, electrical stimulation procedure, and data analysis were frequently not reported. In conclusion, no consensus on how to determine Vc existed. Incomplete reporting of measurement protocols hindered study comparison, which obstructs developing a standardised approach. Therefore, we propose a new guideline for reporting measurement protocols, which covers the 1) equipment and rater, 2) measurement setup, including positioning of the subject, sensor and electrodes, 3) electrical stimulation, including initial stimulation amplitude, increment, and endpoint, and 4) data analysis, including selection criteria and number of analysed signals and a definition of derived parameters.

Distribution Law of Corrosion Products in a Marine Chloride Environment.

Steel corrosion is the main cause of reinforced concrete cracking. Conventionally, concrete is considered to crack when the circumferential tensile stress reaches the tensile strength of the concrete. However, few analyses have considered the fracture criteria of the internal cross-section of concrete. Based on the von Mises distribution of angle probabilities, this paper proposes a new probability distribution function for investigating the distribution law of corrosion products. The cracking process of experimental samples was numerically analyzed, and the results were consistent with those of the theoretical model. The effect of the dry-wet cycle ratio on the corrosion products was preliminarily investigated by microscopic observation of the reinforced concrete under different dry-wet cycle corrosion environments.

Method for Tunnel Displacements Calculation Based on Mobile Tunnel Monitoring System.

Efficient, high-precision, and automatic measurement of tunnel structural changes is the key to ensuring the safe operation of subways. Conventional manual, static, and discrete measurements cannot meet the requirements of rapid and full-section detection in subway construction and operation. Mobile laser scanning technology is the primary method for tunnel detection. Herein, we propose a method to calculate shield tunnel displacements of a full cross-section tunnel. The point cloud data, obtained via a mobile tunnel deformation detection system, were fitted, projected, and interpolated to generate an orthophoto image. Combined with the cumulative characteristics of the tunnel gray gradient, the longitudinal ring seam of the tunnel was identified, while the Canny algorithm and Hough line detection algorithm identified the transverse seam. The symmetrical vertical foot method and cross-section superposition analysis were used to calculate the circumferential and radial displacements, respectively. The proposed displacement calculation method achieves automatic recognition of a ring seam, reduces human-computer interaction, and is fast, intelligent, and accurate. Furthermore, the description of the tunnel deformation location and deformation amount is more quantitative and specific. These results confirm the significance of shield tunnel displacement monitoring based on mobile monitoring systems in tunnel disease monitoring.

Rotor radial displacement sensorless control of bearingless permanent magnet synchronous motor based on MRAS and suspension force compensation.

Limitations exist on the displacement sensors employed in a bearingless permanent magnet synchronous motor (BPMSM). They lead to the increase in cost, size and complexity of the motor. Apart from that, the measurement errors are sensitive to the temperature and the electromagnetic noise. In order to resolve these problems, a novel rotor radial displacement sensorless control method of the BPMSM is proposed. In this paper, the operation principle and mathematical model of the BPMSM are introduced firstly. Secondly, the rotor radial displacement self-sensing method using the model reference adaptive system is designed. Thirdly, a direct control strategy of rotor eccentric displacement with suspension force compensation is proposed to promote the property of the displacement sensorless control system. Finally, a torque control subsystem based on the id=0 control scheme and a displacement control subsystem based on the proposed displacement self-sensing method and the suspension force control method are constructed. The related simulations and experiments are carried out. According to the research results, the rotor radial displacements of the BPMSM are effectively estimated and the stable suspension of the BPMSM rotor without displacement sensors is achieved.

Concrete Protective Layer Cracking Caused by Non-Uniform Corrosion of Reinforcements.

The volume expansion of reinforcement corrosion products resulting from the corrosion of steel reinforcement embedded into concrete causes the concrete's protective layer to crack or spall, reducing the durability of the concrete structure. Thus, it is necessary to analyze concrete cracking caused by reinforcement corrosion. This study focused on the occurrence of non-uniform reinforcement corrosion in a natural environment. The characteristics of the rust layer were used to deduce the unequal radial displacement distribution function of concrete around both angular and non-angular bars. Additionally, the relationship between the corrosion ratio and the radial displacement of the concrete around the bar was established quantitatively. Concrete cracking due to the non-uniform corrosion of reinforcements was simulated using steel bars embedded in concrete that were of uneven displacement because of rust expansion. The distribution of the principal tensile stress around the bar was examined. A formula for calculating the critical radial displacement at the point when cracking began was obtained and used to predict the corrosion ratio of the concrete cover. The determined analytical corrosion ratio agreed well with the test result. The effect factor analysis based on the finite element method indicated that increasing the concrete strength and concrete cover thickness delays concrete cracking and that the adjacent rebar causes the stress superposition phenomenon.

Rupture of posterior cruciate ligament leads to radial displacement of the medial meniscus.

BACKGROUND: To explore the association between the rupture of posterior cruciate ligament (PCL) and the radial displacement of medial meniscus under the conditions of different flexion and various axial loads. METHODS: The radial displacement value of medial meniscus was measured for the specimens of normal adult knee joints, including 12 intact PCLs, 6 ruptures of the anterolateral bundle (ALB), 6 ruptures of the postmedial bundle (PMB), and 12 complete ruptures. The measurement was conducted at 0°, 30°, 60°, and 90° of knee flexion angles under 200 N, 400 N, 600 N, 800 N and 1000 N of axial loads respectively. RESULTS: The displacement values of medial meniscus of the ALB rupture group increased at 0° flexion under 800 N and 1000 N, and at 30°, 60° and 90° flexion under all loads in comparison with the PCL intact group. The displacement values of the PMB rupture group was higher at 0° and 90° flexion under all loads, and at 30° and 60° flexion under 800 N and 1000 N loads. The displacement of the PCL complete rupture group increased at all flexion angles under all loads. CONCLUSIONS: Either partial or complete rupture of the PCL can increase in the radial displacement of the medial meniscus, which may explain the degenerative changes that occuring in the medial meniscus due to PCL injury. Therefore, early reestablishment of the PCL is necessarily required in order to maintain stability of the knee joint after PCL injury.

Evaluation of the size and position of the insertion of the anterior medial meniscus root in varus osteoarthritic knees.

PURPOSE: Recent studies have suggested radial displacement of the medial meniscus as a cause of varus knee osteoarthritis (OA). Two anatomical studies reported that such displacement may be associated with anterior insertion of the medial meniscus anterior horn. It was aimed to evaluate the location and area of this insertion in patients with advanced knee OA. METHODS: Medial meniscus anterior horn insertions were classified into four types, as described in a previously reported classification during 225 total knee arthroplasty (TKA) in 184 patients. The incidence rates of insertion type were compared with previously reported rates in nearly normal or non-arthritic knees. The insertion surface area was also measured during 158 TKAs. RESULTS: Of the 225 knees, 82 (36.4 %), 93 (41.3 %), 35 (15.6 %), and 15 (6.7 %) were classified as I, II, III, and IV, respectively. An anteriorly inserted anterior horn was not more frequent in advanced varus OA knees than in previously reported nearly normal or non-arthritic knees. The insertion surface areas were 57.5 ± 18.9, 56.1 ± 16.0, and 56.4 ± 14.4 mm2 for types I, II, and III, respectively; these areas did not differ significantly. CONCLUSION: Since the incidence of an anteriorly inserted medial meniscus anterior horn was not higher in advanced varus OA knees than in normal or non-arthritic knees, an anteriorly inserted anterior horn may have little or no effect on the aetiology of varus OA knees. This study provides some information for clarifying the aetiology of knee OA. LEVEL OF EVIDENCE: IV.

Effect of posterior cruciate ligament rupture on the radial displacement of lateral meniscus.

BACKGROUND: The relationship between lateral meniscus tear and posterior cruciate ligament injury is not well understood. The present study aims to investigate and assess the effect of posterior cruciate ligament rupture on lateral meniscus radial displacement at different flexion angles under static loading conditions. METHODS: Twelve fresh human cadaveric knee specimens were divided into four groups such as posterior cruciate ligament intact, anterolateral band rupture, posteromedial band rupture and posterior cruciate ligament complete rupture groups, according to the purpose and order of testing. Radial displacement of lateral meniscus was measured under different loads (200-1000N) at 0°, 30°, 60°, and 90° of knee flexion. FINDINGS: Compared with posterior cruciate ligament intact group, the displacement values of lateral meniscus in anterolateral band rupture group increased at 0° flexion with 600N, 800N, and 1000N and at 30°, 60° and 90° flexion under all loading conditions. Posteromedial band rupture group exhibited higher displacement at 0° flexion under all loading conditions, at 30° and 60° flexion with 600, 800N and 1000N, and at 90° flexion with 400N, 600N, 800N, and 1000N than the posterior cruciate ligament intact group. The posterior cruciate ligament complete rupture group had a higher displacement value of lateral medial meniscus at 0°, 30°, 60° and 90° flexion under all loading conditions, as compared to the posterior cruciate ligament intact group. INTERPRETATION: The study concludes that partial and complete rupture of the posterior cruciate ligament can trigger the increase of radial displacement on lateral meniscus.

Ventricular septal dysfunction after surgical closure of multiple ventricular septal defects.

BACKGROUND: We assessed the global and regional ventricular septal functions using conventional echocardiography and two-dimensional speckle tracking imaging in children with postoperative multiple ventricular septal defects. METHODS: Thirty-six children were studied: 16 with postoperative multiple ventricular septal defects and 20 normal control subjects. In children with multiple ventricular septal defects, 60 ventricular septal defects were closed using one of three different techniques (patch closure, the sandwich technique, direct closure). Speckle tracking imaging was applied to three short-axis echocardiographic images. RESULTS: The total patch area used in the multiple ventricular septal defects group was correlated with the postoperative ejection fraction (r=0.703) and Tei index (r=0.778). The global septal peak systolic radial displacement and global septal peak systolic radial strain in the multiple ventricular septal defects group were significantly lower than those observed in the control subjects. The peak systolic radial strain in the segments closed with patches and the peak systolic radial displacement in the segments closed with the felt sandwich technique were significantly lower than those observed in the intact septal segments. No significant regional functional depressions were identified in the segments that were closed directly. CONCLUSIONS: The postoperative ventricular global and septal functions were significantly reduced in children with multiple ventricular septal defects, especially in the cases with complex congenital heart disease and that were closed with large prosthetic materials. These results suggest that an effort to minimize the use of patch materials may lead to preserved postoperative ventricular function.

Effects of age on left ventricular twist-displacement loop assessed by velocity vector imaging / 中南大学学报(医学版)

Objective:To assess effect of age on the characteristic of letf ventricular (LV) twist-displacement loop in health volunteers by velocity vector imaging (VVI) and to provide a new method for LV function evaluation in clinic. Methods:Atfer obtaining basal and apical LV short-axis images in 98 healthy volunteers (18-75 years old) by 2-dimensional echocardiography, we use VVI sotfware to analysis LV twist motion and radial displacement at each plane off-line. hTe peak LV twist (Ptw), the peak untwist velocity (PutwV), the proportion of untwist in isovolumetric relaxation period (Iutw%) and LV radial displacement (Dis) were measured and calculated. Then we constructed LV twist-displacement loop and compared the characteristic of them among different groups. Results:Ptw increased gradually with the increase in age. The biggest PutwV was in the group of 30-60 years old. Iutw%increased gradually before 60 years old, then decreased atfer that. Dis was not obviously different among the three groups. hTe characteristic of LV twist-displacement loop was like the configuration of 8. There was a linear relation between twist and displacement during systole, and the slope increased gradually with the increase in age. During early diastole, the relatively small radial expanding displacement displayed with untwisting, resulting in a much steeper twist-displacement relationship curve occurred in each group, which was getting smooth gradually when the radial expanding displacement increased during mid to late diastole. Conclusions:VVI can be used to effectively and noninvasively assess LV twist-displacement loop with change in age and provide important information for LV function. hTe effect of age must take into account when evaluate the LV function by the twist-displacement loop.