Dynamic Transmission Characteristics Research Articles

Reliability Analysis for RV Reducer by Combining PCE and Saddlepoint Approximation Considering Multi-Failure Modes

Abstract RV (Rotate Vector) reducer is an essential mechanical transmission device extensively used in industrial machinery, robotics, aerospace and other fields. The dynamic transmission characteristics and strength of the cycloidal pin gear, turning arm bearing of RV reducer significantly affect the motion accuracy and reliability of the whole equipment. Uncertainties from manufacturing and assembly error, working loads add complexity to these effects. Developing effective methods for uncertainty propagation and reliability analysis for the RV reducer is crucial. In this work, the mail failure modes of RV reducer are studied, and an effective reliability analysis method for RV reducer considering the correlation between multi-failure modes by combining polynomial chaos expansions (PCE) and saddlepoint approximation method (SPA) is proposed. This paper develops an uncertainty propagation strategy for RV reducer based on dynamic simulation and PCE method with high accuracy. On this basis, a surrogated cumulant generating function (CGF) and SPA are combined to analyze the stochastic characteristic for the failure behavior. Based on the probability density function (PDF) and cumulative distribution function (CDF) calculated by SPA, copula function is employed to quantify the correlations between the multi-failure modes. Then, the system reliability with multi-failure modes is estimated by SPA and optimal copula function. The proposed method provides an effective reliability assessment technology with high-accuracy for complex system under unknown physical model and distribution characteristics. The validity of the proposed approach is illustrated RV-320E reducer reliability estimation, offering a basis to improve the performance of complex dynamic system. .

Spatial–temporal transmission dynamics of HIV-1 CRF01_AE in Indonesia

Human immunodeficiency virus type 1 (HIV-1) remains a serious health threat in Indonesia. In particular, the CRF01_AE viruses were the predominant HIV-1 strains in various cities in Indonesia. However, information on the dynamic transmission characteristics and spatial–temporal transmission of HIV-1 CRF01_AE in Indonesia is limited. Therefore, the present study examined the spatial–temporal transmission networks and evolutionary characteristics of HIV-1 CRF01_AE in Indonesia. To clarify the epidemiological connection between CRF01_AE outbreaks in Indonesia and the rest of the world, we performed phylogenetic studies on nearly full genomes of CRF01_AE viruses isolated in Indonesia. Our results showed that five epidemic clades, namely, IDN clades 1–5, of CRF01_AE were found in Indonesia. To determine the potential source and mode of transmission of CRF01_AE, we performed Bayesian analysis and built maximum clade credibility trees for each clade. Our study revealed that CRF01_AE viruses were commonly introduced into Indonesia from Southeast Asia, particularly Thailand. The CRF01_AE viruses might have spread through major pandemics in Asian countries, such as China, Vietnam, and Laos, rather than being introduced directly from Africa in the early 1980s. This study has major implications for public health practice and policy development in Indonesia. The contributions of this study include understanding the dynamics of HIV-1 transmission that is important for the implementation of HIV disease control and prevention strategies in Indonesia.

A Coupling Model for Tribodynamic Behavior of the Hydroviscous Flexible Drive With Consideration of Saucer-Warping Deformation

An improved coupling model, including the dynamic transmission characteristics and thermal deformation behavior of the disks, is developed for predicting the tribodynamic behavior of the hydroviscous flexible drive under realistic driving conditions. The present work overcomes previous limitations by incorporating transient saucer-warping deformation due to friction heat. Dynamic parameters because of the saucer-warping angle effects, including the film thickness and total torque, are analyzed based on an iterative method. Axial deformation, radial deformation, and saucer-warping angle are simultaneously obtained by finite-element analysis. Based on the comparison with the experimental data, the performance of the coupling model is found satisfactory. The results show that the increase of the saucer-warping angle is favorable for the improvement of flexible transmission characteristics. As a result of the saucer-warping angle effects, significant reduction of the inlet flow rate will lead to the reduction of maximum total torque. Neither radial displacements nor axial displacements are good enough to predict the evolution rule about friction heat during the engagement process. Based on the combined effects of equivalent film thickness and real frictional area, the torque results for the deformed disks are larger than those when the disks are parallel. The saucer-warping angle effect begins to dominate the total torque especially when the film thickness reaches its minimum. The model developed in this research may become an efficient alternative model for the prediction of flexible transmission behavior of the real driving system.

Vibration energy leakage analysis and diagnosis of vibration-isolation thrust bearing

Objectives The vibration-isolation thrust bearing is a new device for the longitudinal vibration control of propulsion shafts. Experimental results show that the dynamic transmission properties of the propulsion shaft are quite different from those of theoretical calculation predictions. Analysis shows that there is serious vibration energy leakage from the vibration-isolation thrust bearing. For better understanding the cause of poor acoustical property of the system, a study is conducted with the focus upon the flexible assemblies of the thrust bearing to determine directions for optimization improvement design Methods The dynamic characteristic analysis is conducted concentrated on the coil spring and coil spring cylinder which are key vibration isolation components of the thrust bearing to research the vibration energy leakage. Then, the dynamic model of the coil spring cylinder is established base on both vibration isolation theory and experiment analysis. Moreover, the dynamic property experiment platform in vertical state is also built up. Results The experimental analysis results show that the vibration resonance peak of the coil spring is sharp and smooth, while that of the coil spring cylinder is flat with more harmonic components induced by contact friction. When there is contact friction, there will be additional stiffness and damping, which significantly change the dynamic properties of the coil spring cylinder. Conclusion The dynamic model of the coil spring cylinder is verified by experiments. The dynamic transmission characteristics of the coil spring can be used as an evaluation standard for design improvement. The results of this study can provide theoretical support for the design optimization and improvement of the vibration-isolation thrust bearing, which can have great significance for practical engineering.

A 6-DOF micro-vibration isolation platform based on the quasi-zero-stiffness isolator

Micro-vibrations generated by rotating machinery could influence the working performance of the precise instruments equipped in industrial facilities, aircraft, ships, etc. Isolation systems are thus essential for preventing the high-sensitive instruments from being disturbed. In this work, a 6 degrees-of-freedom (DOF) micro-vibration isolation platform is proposed based on the quasi-zero-stiffness (QZS) isolator. The structure of the isolation platform is a conventional Stewart mechanism equipped with the QZS isolators in each leg. To analyze the stiffness of the leg, the static analysis is carried out. Afterwards, the stiffness of the platform in six directions are also discussed. Moreover, the dynamical equations of the isolation platform are formulated by the Lagrange Equation. Finally, the dynamic response of the proposed model is investigated and compared with the linear case whose stiffness of the leg is linear. The results show that the newly designed QZS platform in this work has a good isolation performance, which can attenuate the external vibrations significantly within a broad frequency band. Parametric analysis shows that the structure parameters, damping and excitation amplitude have a great influence on the isolation performance of the QZS platform. Delightfully, the result of indicates that, (a) the newly designed QZS platform is able to provide an excellent isolation performance in all the six DOFs, which advances the dynamic study of multi-dimensional QZS vibration isolation; (b) The multi-dimensional vibration isolation platform is innovatively designed using geometric nonlinear technology, there is no influence of the magnetic sources to the precision instruments when compared with the previous designs; (c) the regulation mechanism of the structure parameters of the QZS isolation platform on the dynamic transmission characteristics of the system is revealed, which indicates that the platform is particularly suitable for micro-vibration isolation whose vibration magnitude and frequency are quite low.

Effect of superior mesenteric artery branch structure-based flow field on PEMFC performance

The flow field structure of a proton exchange membrane fuel cell (PEMFC) is a key factor that affects its performance. In this study, based on the structural characteristics of the superior mesenteric artery and branches of the human body, a new type of bionic flow field was designed for a PEMFC. The effects of the conventional serpentine flow field (CSFF) and new bionic flow field (NBFF) on fuel cell performance were studied via simulation and experiment. Compared with the CSFF, the NBFF significantly improves droplet dynamic transmission characteristics, reduces droplet aggregation at bends, shortens the retention time of droplets in the flow field, and increases the droplet removal rate by 36.3%. The output performance of the NBFF-based fuel cell is the best under an air flow rate of 4 L/min and a hydrogen flow rate of 2.5 L/min. The NBFF exhibits better heat dissipation than the CSFF does. When the current density is high and the operating temperature exceeds 50 °C, the performance of the NBFF fuel cell is improved by 30.03% compared with that of the CSFF-best fuel cell. Moreover, the actual working temperature of PEMFC is 60–80 °C. Therefore, the NBFF can enhance the practicability of fuel cells.

Study on transmission error of double circular arc spiral bevel gears for nutation drive based on assembly errors and different loads

As a new type of gear transmission, nutation gear drive is extensively applied in aviation, ship, medical equipment and other fields. In this paper, a two-stage nutation drive mechanism of double circular arc (DCA) bevel gears is presented and its dynamic characteristics are studied. First, according to the principle of meshing transmission, a mathematical model of dynamic transmission error (DTE) based on assembly errors is established. Through the analysis of dynamic transmission characteristics, the DTE curves with assembly errors and varying load are obtained, and the simulation results are analyzed reasonably by using RMS evaluating indicator. Finally, through the test verification under different loads, it is concluded that in a reasonable loading range, the decrease of load will reduce the fluctuation range of transmission error. The reduction of transmission error fluctuation indicates that the nutation drive of DCA spiral bevel gears is more stable and the noise is reduced under low load conditions. The study of the dynamic characteristics will provide theoretical basis and practical reference for the design of DCA spiral bevel gears.

Dynamic Transmission of Correlation between Investor Attention and Stock Price: Evidence from China’s Energy Industry Typical Stocks

The relationship between investor attention and stock prices has been a topic of interest in economics. Previous studies have shown that the correlation relationship between the two changes with time. However, there are few studies to explore the time‐varying evolution of the relationship, as well as the transmission characteristics under important cycles. Thus, this paper is dedicated to discover the dynamic transmission characteristics of the correlation between investor attention and stock price. We selected the typical stocks of China’s energy industry, PetroChina and Sinopec, as the research objects, as they occupy a large market share and are representative. And the transaction data and attention data are used to build investor attention indicator. In order to reproduce the dynamic transmission process of correlation at different cycles, sliding time window and complex network are applied. The results show that PetroChina and Sinopec stocks have a weakly negative correlation between investor attention and stock price from 2017 to 2018. However, from the perspective of different cycles, the correlation has time‐varying characteristics. As the cycle grows, the types of transmission patterns of the five consecutive days of correlation between the two become less, but the transmission intensity between the modes increases and the transition becomes more regular and inclined. In addition, by mining the important transmission modes and main transmission paths under important periods, we find that the series modes of uncorrelated or weakly positive correlation for five consecutive days dominate the transition of modes in the networks. Also, the closed loop formed by these two important modes and related modes is the main transmission path. These findings can reveal the rules of the typical stock market in China’s energy industry and help investors with different investment cycle preferences make sound decisions.

Molecular Communication over Gas Stream Channels using Portable Mass Spectrometry.

The synthetic generation/coding and transmission of olfactory information over a gas stream or an odor network is a new and unexplored field. Application areas vary from the entertainment or advertisement industry to security and telemedicine. However, current technological limitations frustrate the accurate reproduction of decoded and transmitted olfactory data. This study describes the development, testing, and characterization of a novel odor emitter (OE) that is used to investigate the generation-encoding of gaseous standards with odorous characteristics with a regulatable way, for scent transmission purposes. The calibration and the responses of a developed OE were examined using a portable quadrupole mass spectrometer (MS). Experiments were undertaken for a range of volatile organic compounds (VOCs) at different temperatures and flow rates. Individual compounds and mixtures were tested to investigate periodic and dynamic transmission characteristics within two different size tubular containers for distances up to 3 m. Olfactory information transmission is demonstrated using MS as the main molecular sensor for odor detection and monitoring and for the first time spatial encryption of olfactory information is shown. Graphical Abstract ᅟ.

Theoretical Description of Dynamic Transmission Characteristics in MDM Waveguide Aperture-Side-Coupled with Ring Cavity

We investigate the dynamic transmission characteristics in metal-dielectric-metal (MDM) waveguide aperture-side-coupled with ring cavity. Assuming the aperture as a resonator, a theoretical model was established to describe the formation and evolution mechanisms of the spectral responses in circular ring structure, and the theoretical results are in good agreement with the finite-difference time-domain (FDTD) simulations. In particular, combining Maxwell’s equations and field distributions, the analytical theory is also applicable to other aperture-side-coupled ring nanostructures, which highlights the utility of the theoretical description. The results may pave the way towards controlling light in highly integrated optical circuits.

Dynamic Transmission Characteristics during Soft-Start of Hydro-Viscous Drive Considering Fluid-Inertia Item

Dynamic Transmission Characteristics during Soft-Start of Hydro-Viscous Drive Considering Fluid-Inertia Item

A model for the determination of VECP latencies.

The time between stimulus event and onset of the visually evoked cortical potential (VECP) reflects the dynamic transmission characteristics of the precortical part of the visual system. A simple mathematical model describing this sub-system with regard to the triggering of luminance VECP is presented. The four functional parameters of the model can be calculated from the measured latency versus stimulus intensity curve of luminance VECP and can provide a quantitative evaluation of the functional state of the precortical visual system for clinical use. Some experiments and first clinical results show the applicability of the model.