Modeling and Dynamic Characteristic Analysis of a Ball Screw Feed Drive System Based on Receptance Coupling

Modeling and modal analysis method based on receptance coupling are proposed for a vibration mode of a ball screw feed drive system, which cannot be determined by axial and torsional modal shape curves through a traditional method. In this study, the mathematical model for ball screw feed drive system is obtained by improved receptance coupling. The natural frequencies of different assembly states are calculated in the modeling process. The vibration modes of the feed drive system are determined by comparing the natural frequency distributions of different assembly states for a detailed analysis of the dynamic characteristics of the feed drive system. In the proposed method, a self-developed ball screw feed drive system is selected to study the influence of worktable position, worktable mass, and screw lead on the dynamic characteristics of the ball screw feed drive system. A change in the worktable position mainly affects the vibration of the ball screw itself. A change in the worktable mass mainly affects the coupling vibration between the ball screw and the rotor or bearing. The screw lead has an opposite influence on axial and torsional vibrations of the feed drive system, and the stability of the feed drive system improves with the screw lead. The validity of the proposed method is verified by the case study

Multi-Position Identification of Joint Parameters in Ball Screw Feed System Based on Response Coupling

Existing methods of parameters identification do not consider the torsion characteristics of a ball screw and the worktable position simultaneously. Therefore, this paper proposes a multi-position identification method based on receptance coupling. Firstly, the mathematical model of the feed drive system is established by the improved receptance coupling, and this model considers both axial and torsional vibration of the ball screw. Secondly, the identification equation is established by minimum error of the modal parameters of multiple worktable position, and differential evolution algorithm is used to calculate the stiffness and damping of the joint. Finally, the self-developed ball screw feed drive system is used for experimental study. The maximum error of the first four orders of natural frequencies predicted through multi-position identification results is 2.95%, and the multi-position method is more robust than the common method identification at one position. The experiment study showed that the proposed method is accuracy and necessity

Disruption of Smad7 Promotes ANG II-Mediated Renal Inflammation and Fibrosis via Sp1-TGF-β/Smad3-NF.κB-Dependent Mechanisms in Mice

Smad7 is an inhibitory Smad and plays a protective role in obstructive and diabetic kidney disease. However, the role and mechanisms of Smad7 in hypertensive nephropathy remains unexplored. Thus, the aim of this study was to investigate the role and regulatory mechanisms of Smad7 in ANG II-induced hypertensive nephropathy. Smad7 gene knockout (KO) and wild-type (WT) mice received a subcutaneous infusion of ANG II or control saline for 4 weeks via osmotic mini-pumps. ANG II infusion produced equivalent hypertension in Smad7 KO and WT mice; however, Smad7 KO mice exhibited more severe renal functional injury as shown by increased proteinuria and reduced renal function (both p<0.05) when compared with Smad7 WT mice. Enhanced renal injury in Smad7 KO mice was associated with more progressive renal fibrosis with elevated TGF-β/Smad3 signalling. Smad7 KO mice also showed more profound renal inflammation including increased macrophage infiltration, enhanced IL-1β and TNF-α expression, and a marked activation of NF-κB signaling (all p<0.01). Further studies revealed that enhanced ANG II-mediated renal inflammation and fibrosis in Smad7 KO mice were also associated with up-regulation of Sp1 but downregulation of miR-29b expression. Taken together, the present study revealed that enhanced Sp1-TGF-β1/Smad3-NF-κB signaling and loss of miR-29 may be mechanisms by which deletion of Smad7 promotes ANG II-mediated renal fibrosis and inflammation. Thus, Smad7 may play a protective role in ANG II-induced hypertensive kidney disease. © 2013 Liu et al.published_or_final_versio

A New Hybrid Method in Global Dynamic Path Planning of Mobile Robot

Path planning and real-time obstacle avoidance is the key technologies of mobile robot intelligence. But the efficiency of the global path planning is not very high. It is not easy to avoid obstacles in real time. Aiming at these shortcomings it is proposed that a global dynamic path planning method based on improved A* algorithm and dynamic window method. At first the improved A* algorithm is put forward based on the traditional A* algorithm in the paper. Its optimized heuristic search function is designed. They can be eliminated that the redundant path points and unnecessary turning points. Simulation experiment 1 results show that the planned path length is reduced greatly. And the path transition points are less, too. And then it is focused on the global dynamic path planning of fusion improved A* Algorithm and Dynamic Window Method. The evaluation function is constructed taking into account the global optimal path. The real time dynamic path is planning. On the basis of ensuring the optimal global optimization of the planning path, it is improved that the smoothness of the planning path and the local real-time obstacle avoidance ability. The simulation experiments results show that the fusion algorithm is not only the shorter length, but also the smoother path compared the traditional path planning algorithms with the fusion algorithm in the paper. It is more fit to the dynamics of the robot control. And when a dynamic obstacle is added, the new path can be gained. The barrier can be bypass and the robot is to reach the target point. It can be guaranteed the global optimality of the path. Finally the Turtlebot mobile robot was used to experiment. The experimental results show that the global optimality of the proposed path can be guaranteed by the fusion algorithm. And the planned global path is smoother. When the random dynamic obstacle occurs in the experiment, the robot can be real-time dynamic obstacle avoidance. It can re-plan the path. It can bypass the random obstacle to reach the original target point. The outputting control parameters are more conducive to the robot’s automatic control. The fusion method is used for global dynamic path planning of mobile robots in this paper. In summary the experimental results show that the method is good efficiency and real-time performance. It has great reference value for the dynamic path planning application of mobile robot

Deficiency of Smad7 Enhances Cardiac Remodeling Induced by Angiotensin II Infusion in a Mouse Model of Hypertension

Smad7 has been shown to negatively regulate fibrosis and inflammation, but its role in angiotensin II (Ang II)-induced hypertensive cardiac remodeling remains unknown. Therefore, the present study investigated the role of Smad7 in hypertensive cardiopathy induced by angiotensin II infusion. Hypertensive cardiac disease was induced in Smad7 gene knockout (KO) and wild-type (WT) mice by subcutaneous infusion of Ang II (1.46 mg/kg/day) for 28 days. Although equal levels of high blood pressure were developed in both Smad7 KO and WT mice, Smad7 KO mice developed more severe cardiac injury as demonstrated by impairing cardiac function including a significant increase in left ventricular (LV) mass (P<0.01),reduction of LV ejection fraction(P<0.001) and fractional shortening(P<0.001). Real-time PCR, Western blot and immunohistochemistry detected that deletion of Smad7 significantly enhanced Ang II-induced cardiac fibrosis and inflammation, including upregulation of collagen I, α-SMA, interleukin-1β, TNF-α, and infiltration of CD3+ T cells and F4/80+ macrophages. Further studies revealed that enhanced activation of the Sp1-TGFβ/Smad3-NF-κB pathways and downregulation of miR-29 were mechanisms though which deletion of Smad7 promoted Ang II-mediated cardiac remodeling. In conclusions, Smad7 plays a protective role in AngII-mediated cardiac remodeling via mechanisms involving the Sp1-TGF-β/Smad3-NF.κB-miR-29 regulatory network. © 2013 Wei et al.published_or_final_versio

Comparison of Oropharyngeal Microbiota in Healthy Piglets and Piglets With Respiratory Disease

Porcine respiratory disease (PRD) is responsible for severe economic losses in the swine industry worldwide. Our objective was to characterize the oropharyngeal microbiota of suckling piglets and compare the microbiota of healthy piglets and piglets with PRD. Oropharyngeal swabs were collected from healthy (Healthy_A, n = 6; Healthy_B, n = 4) and diseased (PRD_A, n = 18; PRD_B, n = 5) piglets at 2–3 weeks of age from two swine farms in Guangdong province, China. Total DNA was extracted from each sample and the V3-V4 hypervariable region of the 16S rRNA gene was amplified and sequenced using the Illumina MiSeq platform. No statistically significant differences were observed in bacterial diversity and richness between the healthy and PRD groups in the two farms except for Shannon index in farm A. Principal coordinates analysis (PCoA) showed structural segregation between diseased and healthy groups and between groups of different farms. Among all samples, the phyla Firmicutes, Proteobacteria, and Bacteroidetes were predominant. At the genus level, Streptococcus, Lactobacillus, and Actinobacillus were the core genera in the oropharynx of healthy piglets from the two farms. Significant differences in bacterial taxa were found when the microbiota was compared regarding the health status. In farm A, the percentages of Moraxella and Veillonella were higher in the PRD group, while only Porphyromonas was significantly increased in the PRD group in farm B (p &lt; 0.05). Compared to PRD groups, statistically significant predominance of Lactobacillus was observed in the healthy groups from both farms (p &lt; 0.05). Our findings revealed that Moraxella, Veillonella, and Porphyromonas may play a potential role in PRD and Lactobacillus may have a protective role against respiratory diseases

A high-throughput phenotyping assay for precisely determining stalk crushing strength in large-scale sugarcane germplasm

Sugarcane is a major industrial crop around the world. Lodging due to weak mechanical strength is one of the main problems leading to huge yield losses in sugarcane. However, due to the lack of high efficiency phenotyping methods for stalk mechanical strength characterization, genetic approaches for lodging-resistant improvement are severely restricted. This study attempted to apply near-infrared spectroscopy high-throughput assays for the first time to estimate the crushing strength of sugarcane stalks. A total of 335 sugarcane samples with huge variation in stalk crushing strength were collected for online NIRS modeling. A comprehensive analysis demonstrated that the calibration and validation sets were comparable. By applying a modified partial least squares method, we obtained high-performance equations that had large coefficients of determination (R2 &gt; 0.80) and high ratio performance deviations (RPD &gt; 2.4). Particularly, when the calibration and external validation sets combined for an integrative modeling, we obtained the final equation with a coefficient of determination (R2) and ratio performance deviation (RPD) above 0.9 and 3.0, respectively, demonstrating excellent prediction capacity. Additionally, the obtained model was applied for characterization of stalk crushing strength in large-scale sugarcane germplasm. In a three-year study, the genetic characteristics of stalk crushing strength were found to remain stable, and the optimal sugarcane genotypes were screened out consistently. In conclusion, this study offers a feasible option for a high-throughput analysis of sugarcane mechanical strength, which can be used for the breeding of lodging resistant sugarcane and beyond