Effects of body size on orthostatic tolerance

Although physiological mechanisms have been considered to be associated with gender difference in orthostatic tolerance, physical factors could affect orthostatic tolerance potentially. This study is designed to explore effects of body size on orthostatic tolerance with and without consideration of gender. Methods: Forty-six (22 men and 24 women) healthy subjects participated in this study. After a 12 min baseline, subjects were exposed a graded lower body negative pressure (LBNP) from 0 [Difference symbol] -100 mmHg (or presyncope), with a reduction of 10 mmHg every 4 mins. Some physical factors and cardiovascular measurements were determined in the test. Least square linear regression analysis was used to assess the relationship between LBNP tolerance index (LTI) and physical and cardiovascular measurements. Results: No physical factors enter the final predict model with and without accounting for gender. The resting total peripheral conductance (TPC), pulse pressure (PP) and maximal change in heart rate (cHR) are positively related to LTI while the early change in HR (cHRe) has a negative coefficient. Two regression equations are LTI = 137.40 +36.13 gender + 746.90 TPC - 2.87 cHRe + 2.67 cHR and LTI = 82.68 + 1.35PP + 697.74 TPC -3.10 cHRe + 2.78cHR. The variety explained by gender in first model was replaced partly by variety explained by PP in second model. Conclusion: Physical factors have no effect on LBNP tolerance. Besides gender, LBNP tolerance is also associated with individual HR reserve and the releasing rate of HR reserve as well as resting vascular resistance. The gender difference in LBNP tolerance may be due to lower PP and other physiological factors rather than physical factors in women

Versatile Propylene-Based Polyolefins with Tunable Molecular Structure through Tailor-Made Catalysts and Polymerization Process

Since the discovery of Ziegler-Natta catalysts for olefin polymerization in the 1950s, the production of polyolefins with a variety of properties has continuously grown with rapid development of catalyst technology combined with polymerization process innovation. For propylene-based polyolefin, various polyolefins with distinctive characteristic of mechanical and optical properties were made with specific catalysts in commercial industries owned especially by those large worldwide companies. In this chapter, Ziegler-Natta catalysts, metallocene catalysts, and post-metallocene catalysts for PP polymerization are discussed in detail. Gas phase, bulk, slurry, and solution polymerization processes, such as Spheripol (Basell), Hypol (Mitsui Chemicals), Unipol (Dow Chemical), Innovene (INEOS), Novelen (BASF), Spherizone (Basell), and Borstar (Borealis), developed by the industrial tycoons were reviewed. The molecular architecture of the PP-based polyolefins could be tailored precisely using specific high-performance catalyst in an appropriate polymerization process, and different types of PPs, including homopolypropylene (HPP), random copolypropylene (RPP), impact PP, PP-based block copolymer, functionalized PP, etc., are produced. The relationship between molecular structure and performance of the PP-based polyolefins is also discussed thereof

A Novel Space-Time-Speed Method for Increasing the Passing Capacity with Safety Guaranteed of Railway Station

A method for improving the passing capacity of a station without adding any track and equipment is proposed in this paper. In the process of handling train routes, by transforming the existing fixed train-approaching locking section into a variable mode, the route locking time is shortened and in-station resource consumption is reduced. This approach improves the capacity of the station. At the same time, delay of the train can be quickly returned to normal. A method of variable train-approaching locking section is discussed; a mathematical model for increasing station passing capacity is shown. Comparison between the impact of a variable train-approaching locking section and a fixed mode on the station passing capacity is shown

Stereo Vision Based Hybrid Manufacturing of Ti-6Al-4V in Component Repair Process

Parts or products from high performance metal are very expensive, partly due to the processing complexities during manufacturing. Recent studies have indicated that hybrid processes of additive manufacturing and machining process can be used to repair titanium parts, thus extending the service life. In order to implement these methods automatically, it is necessary to obtain the spatial geometry information of component with defects to generate the tool path. The purpose of this paper is to summarize the research on hybrid manufacturing with stereo vision function which can be applied to the component repair process. Stereo vision is adopted to detect the location and the size of the defect area which is marked by color marker. And then laser displacement sensor is applied to scan the defect area. Therefore, automated alignment, reconstruction of the defect area and tool path planning could be implemented based on the spatial geometry information. Finally, a Ti64 part repair experiment is done to verify the method. This work provides an automatic method for repairing damaged parts by hybrid manufacturing.Mechanical Engineerin

Quasistatic deflection analysis of slender ball-end milling cutter

This work was supported by the National Natural Science Foundation of China (Grant No. 51975333), Jinan University and Institute Innovation Team Program (Grant No. 2020GXRC025), and Taishan Scholars Project of Shandong Province (ts201712002).Peer reviewedPostprin

A novel algorithm of posture best fit based on key characteristics for large components assembly

Measurement and variation control of geometrical Key Characteristics (KCs), such as flatness and gap of joint faces, coaxiality of cabin sections, is the crucial issue in large components assembly from the aerospace industry. Aiming to control geometrical KCs and to attain the best fit of posture, an optimization algorithm based on KCs for large components assembly is proposed. This approach regards the posture best fit, which is a key activity in Measurement Aided Assembly (MAA), as a two-phase optimal problem. In the first phase, the global measurement coordinate system of digital model and shop floor is unified with minimum error based on singular value decomposition, and the current posture of components being assembly is optimally solved in terms of minimum variation of all reference points. In the second phase, the best posture of the movable component is optimally determined by minimizing multiple KCs' variation with the constraints that every KC respectively conforms to its product specification. The optimal models and the process procedures for these two-phase optimal problems based on Particle Swarm Optimization (PSO) are proposed. In each model, every posture to be calculated is modeled as a 6 dimensional particle (three movement and three rotation parameters). Finally, an example that two cabin sections of satellite mainframe structure are being assembled is selected to verify the effectiveness of the proposed approach, models and algorithms. The experiment result shows the approach is promising and will provide a foundation for further study and application. © 2013 The Authors

Assessing the risk of reoperation for mild pulmonary vein obstruction post-TAPVC repair: a retrospective cohort study

ObjectiveThis study investigates the impact of mild pulmonary vein obstruction, detected via echocardiography before hospital discharge, on the likelihood of reoperation in patients who have undergone repair for Total Anomalous Pulmonary Venous Connection (TAPVC).MethodUtilizing a single-center, retrospective cohort approach, we analyzed 38 cases from October 2017 to December 2023, excluding patients with functionally univentricular circulations or atrial isomerism. Our primary outcome was the necessity for reoperation within one year due to anatomical issues related to the initial TAPVC repair. Mild obstruction was defined as a pulmonary vein flow velocity ≥1.2 m/s.ResultOur findings revealed that 31.6% of patients exhibited pre-discharge mild obstruction. During the median follow-up of 10 months, reoperations were notably higher in the mild obstruction group compared to the normal group, with a significant association between pre-discharge mild obstruction and increased risk of reoperation. Specifically, in the fully adjusted model, mild obstruction was linked to a 13.9-fold increased risk of reoperation.ConclusionOur results suggest that a pre-discharge echocardiography Doppler velocity threshold of 1.2 m/s could serve as a critical predictor for reoperation, emphasizing the need for targeted follow-up strategies for at-risk patients

Industrial Robot Trajectory Accuracy Evaluation Maps for Hybrid Manufacturing Process based on Joint Angle Error Analysis

Industrial robots have been widely used in various fields. The joint angle error is the main factor that affects the accuracy performance of the robot. It is important to notice that these kinematic parameters error cannot be eliminated from the robot system completely. Even after calibration, these errors still exist and will be fluctuated during the robot system running. This paper proposed a new method of finding the best position and orientation to perform a specific working path based on the current accuracy capacity of the robot system. By analyzing the robot forward/inverse kinematic and the angle error sensitivity of different joint in the serial manipulator system, a new evaluation formulation is established for mapping the trajectory accuracy within the robot’s working volume. The influence of different position and orientation on the movement accuracy of the end effector has been verified by experiments and discussed thoroughly. Finally, a visualized evaluation map can be obtained to describe the accuracy difference of a robotic laser deposition working path at different positions and orientations. This method is helpful for making the maximum usage of the robot’s current accuracy ability rather than blindly pursuing the higher accuracy of the robot system

Comparison Study on the Performances of Finite Volume Method and Finite Difference Method

Vorticity-stream function method and MAC algorithm are adopted to systemically compare the finite volume method (FVM) and finite difference method (FDM) in this paper. Two typical problems—lid-driven flow and natural convection flow in a square cavity—are taken as examples to compare and analyze the calculation performances of FVM and FDM with variant mesh densities, discrete forms, and treatments of boundary condition. It is indicated that FVM is superior to FDM from the perspective of accuracy, stability of convection term, robustness, and calculation efficiency. Particularly ,when the mesh is coarse and taken as 20×20, the results of FDM suffer severe oscillation and even lose physical meaning

Physicochemical properties of superfine grinding-microwave modified artichoke soluble dietary fiber and their alleviation of alcoholic fatty liver in mice

The effects of superfine grinding (SG) and microwave treatment (MT) on the structure and physicochemical properties of artichoke soluble dietary fiber (ASDF) and its protective effects on mice with alcoholic fatty liver (AFL) were studied. We compared the changes in structural characteristics and physicochemical properties of ASDF, SG-ASDF (ASDF treated by SG), MT-ASDF (ASDF treated by MT), and CM-ASDF (ASDF treated by SG and MT). Moreover, we evaluated the effects of the obtained ASDF on the growth characteristics, blood lipid levels, and liver of mice with AFL. Our results of the study showed that CM-ASDF had a more concentrated and uniform particle size, a higher extraction rate of ASDF and significantly improved water-holding capacity (WHC), oil-holding capacity (OHC) and water swelling capacity (WSC) of ASDF (p < 0.05). After the ASDF intervention, mice with AFL exhibited a significant improvement in body lipid levels and reduce liver inflammation. Specifically, aspartate aminotransferase (AST), alanine aminotransferase (ALT), malonaldehyde (MDA), Tumor necrosis factor-α (TNF-α) and Interleukin-6 (IL-6) were significantly decreased, while superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) were significantly increased (p < 0.05). And the hematoxylin–eosin (HE) staining results showed significant improvement of hepatic steatosis in mice with AFL. In summary, our study found that both SG and MT could improve the structure and physicochemical properties of ASDF, with CM-ASDF being the most effective. Additionally, CM-ASDF was selected to continue the investigation and demonstrated an excellent protective effect on mice with AFL, with the high dose group (H-ASDF) showing the greatest benefit. These findings provided some new insights for future comprehensive utilization of ASDF and drug development for the treatment of AFL