Analysis Of Dynamic Characteristics Research Articles

Study on vibration characteristics of hydraulic planetary transmission considering engine and torque converter excitation

Large-size vehicle loaders are mainly used in various construction projects with complex working environment, which has a serious impact on the internal vibration of the whole system. In this study, the vibration characteristics of hydraulic planetary transmission of vehicle loader considering the influence of the external excitation are evaluated theoretically and experimentally. The output torque of the four-stroke six-cylinder diesel engine is obtained by force calculation of crank and connecting rod mechanism. The equivalent stiffness and damping of the torque converter are solved according to the torsional dynamic equation of the torque converter. The trapped oil area, oil pressure, and flow rate of gear meshing part are extracted to obtain the trapped oil pressure of variable-speed pump. Then, the multi-degree-of-freedom gear system dynamic model is established to calculate the meshing force, which is applied to vibration response analysis model by using mode superposition method. Lastly, the vibration response test is performed on the experimental prototype to verify the calculation method. The conclusion shows that the generation principle of external excitation and its calculation method in this paper are feasible in the analysis of dynamic characteristics of hydraulic planetary torque converter.

Theoretical and Experimental Analysis of Dynamic Characteristics for a Valve Train System.

The valve train is one of the main sources of engine vibration, and its dynamic performance is crucial for output power and fuel consumption. The flexibilities of slender bars and beams should be emphasised in the design of valve trains to develop high-power and high-speed engines with industrial applications. A flexible dynamic model of a valve train system is proposed. In the proposed model, the components, except the cam and gear bodies, are modelled as flexible bodies with multidirectional deformations. The gyroscopic effects of the camshaft, cams and gear discs are also considered to predict dynamic responses at high speeds accurately. Gear meshing, the friction of the cam–tappet pair, the centrifugal force of the cams and valve clearance are also considered. Experiments on housing vibration and pushrod stress are conducted to validate the proposed model. Results show that the proposed model can predict the dynamic stress of the flexible components well and predict the trend shown by the housing vibration. The proposed model shows that excessive cam rotation speed and valve clearance will cause intense bounce and jump phenomena. The proposed model can be an important reference for designing engine work speed, adjusting valve clearance and improving component durability.

Performance analysis of an adiabatic compressed air energy storage system with a pressure regulation inverter-driven compressor

Adiabatic compressed air energy storage provides an efficient and emission free approach for large-scale energy storage. In adiabatic compressed air energy storage system with isochoric air storage tank, the throttle valves cause large exergy losses. To reduce throttling loss, a novel system is proposed by regulating the discharging pressure with an inverter-driven air compressor. Variable- and constant-output power operation modes of the novel system are proposed and studied from the aspects of exergy, economic and dynamic characteristic analysis. Furthermore, parametric analysis of the novel system is conducted from the perspective of the system discharge total output power, inverter-driven compressor efficiency and equipment purchase cost. The results indicate that for the novel system, the round-trip efficiency is improved by 1.8–2.7%, and the levelized cost of electricity decreases by 0.57–0.85 ¢/kWh. Hence, the proposed novel system is verified an effective way for adiabatic compressed air energy storage system optimization.

Modeling the temporal dynamics of gut microbiota from a local community perspective

Given gut microbiota's important role in human health, a clear understanding of the microbial ecosystem dynamics is vital. Mathematical models for analyzing time-series data of gut microbiotas would, therefore, be highly beneficial. Although a generalized Lotka–Volterra (gLV) model for identifying the interactions between gut microbiota members and quantifying the effects of external factors already exists, it is limited in its practical applications. Therefore, we established a stochastic gLV model for analyzing temporal data about the gut microbiota from a local community perspective and provided a reliable parameter estimation method for our model. Our model has abilities similar to those of the existing gLV model but can also capture emigration/immigration effects and avoid the existing model's inadequacies. To test our model's applicability, we fitted our model on a previously published data set. We found the interactions between the gut microbiota of different individuals and between different periods for the same individual were different in the data sets. Analysis of the random dynamic characteristics of the gut microbiota revealed that the number of microorganisms in the local community tended to decrease as a result of random factors, but the numbers were restored by the immigration of external microbes .

CONFLICTS IN THE NEW UKRAINIAN SCHOOL: FROM THE FIGHT AGAINST BULLYING TO RESOLVING DEVELOPMENT CONTRADICTIONS

This paper is about socio-psychological features of conflicts in the new Ukrainian school. Based on the study, systematization of existing scientific definitions of «conflict(s)» and the possibility of their use in the new Ukrainian school. Paper proposes the author's understanding of conflict as contradictions actualized in the minds and interactions of participants of the educational process those change the system of attitudes and do not allow participants to coexist unchanged, but encourage the transformation of conflicting positions, goals, interests, attitudes, etc. Constructive forces, possibilities of dialectical and causal conflicts to be resolved in the new Ukrainian school have been identified. Based on the results of a systematic analysis of structural and dynamic characteristics, a model of the conflict in an educational institution (school) has been developed, which assumes the subjectivity of human perception of existing objective contradictions, the use of human cognitive activity determined by conflict. The psychological content of the concept of «conflict situation» is clarified as a subjective interpretation of reality by any of the parties to the conflict, or the objectification of interaction by the parties to the conflict, or someone else. Members of the bullying commission are asked to use the definition of «conflict situation» as a structural unit in which all the attributes of the conflict (temporal and spatial boundaries are determined by the period of time for which there are no qualitative changes in the conflict) are presented. According to the results of an empirical study using the methodology available in psychological science, a description of the conflicts in the new Ukrainian school is given.

Analysis of Dynamic Channel Characteristics Based on a Body Area Network

Analysis of Dynamic Channel Characteristics Based on a Body Area Network

Dynamic energy efficiency characteristics analysis of a distributed solar photovoltaic direct-drive solar cold storage

A novel method for constructing a distributed solar photovoltaic (PV) direct-drive cold storage system is proposed. In this system, the vapour compression refrigeration cycle (VCRC) is directly driven by a PV array, and ice thermal energy storage is used as the energy storage unit instead of a battery. The dynamic energy efficiency model of the system was established at an extremely small resolution. On this basis, the key factors affecting system performance were studied. Moreover, experiments conducted under different weather conditions verified the accuracy of the model. The results show that, the solar-cold energy conversion efficiency of the system is negatively correlated with the solar radiation intensity at the same evaporation temperature. When the solar radiation intensity reaches the minimum value required to drive the VCRC, the average solar-cold energy conversion efficiency of the system decreases by 2.28%–2.62% as the solar radiation increases by 100 W/m2. The changing trend of the solar-cold energy conversion efficiency of the system with time during sunny weather is similar to that of an upper opening parabola. Under lower radiation conditions, the effect of the evaporation temperature on the solar-cold conversion efficiency weakens. Compared with the experimental results, the average daily deviation of the simulation results is approximately 2.8%–3.2% on clear days and 4.4%–5.1% on cloudy days. The experimental results show that the cold energies during sunny and partly cloudy weather are 128.83 and 122.00 MJ and the average solar-cold energy conversion efficiencies are 0.30 and 0.31, respectively.

Modeling and dynamic characteristic analysis of dual rotor-casing coupling system with rubbing fault

With the rapid development of aero-engine manufacturing technology, the dual-rotor system has been employed in part of turbofan engine in order to improve the working performance of aircraft more efficiently. In this study, taking the counter-rotation dual-rotor as the research object, the dynamic model of dual rotor-casing coupling system is established by the aid of MATLAB. The dynamic frequency curves are in good agreement with the results in references and calculated by FEM method, that shows the validity and feasibility of the model. The local rub-impact dynamic model of dual rotor-casing coupling system is established, and rubbing analysis is carried out using Newmark- β method. The effects of rotating speed and speed ratio on local rub-impact response are deeply discussed. The results show that with the increase of rotating speed, combined frequencies and frequency multiplication components are more significant. In addition, speed ratio has a great influence on the periodic motion of the system. With the increase of the absolute value of the speed ratio, the whirl radius of the outer rotor and the normal rubbing force increase dramatically.

Dynamic Characteristics Analysis and Chaotic Synchronization of Fractional Order Financial Dynamic System

The equations of time-delay fractional order financial dynamic system are studied. Fractional calculus, as the expansion of the corresponding integer parts, has more complex definition and update laws. It is found that modeling by fractional-order differential equation in some nature phenomenon and engineering field can be consistent with essentiality of the phenomenon and matters, such as in mathematical modeling of viscoelastic materials, electromagnetic wave and other fields. Moreover, there exist more complex dynamical behaviors in fractional-order dynamical system than in integral-order one, and it has more preferable history memory ability. Therefore, it is of theoretical value and practical significance researching the fractional-order nonlinear dynamical systems on the base of the researches on the traditional integral-order nonlinear dynamical 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.

Dynamic Characteristics Analysis of Cover System

Up to now, although a lot of research has been done on the control algorithm of cover motion, no systematic analysis has been carried out on the trajectory planning of cover opening yet. In order to improve the dynamic characteristics of the cover in the process of cover opening, a velocity planning algorithm based on trigonometric function is proposed in this paper, which improves the poor smoothness of the acceleration curve of the traditional S-shaped feedrate planning algorithm. The simulation model of the cover system is established to verify the effectiveness of the algorithm, and the results show that the algorithm is effective.

Dynamic characteristics analysis for energy release process of liquid air energy storage system

In order to further research the dynamic characteristics of liquid air energy storage (LAES) system under typical operating conditions, a dynamic simulation model of energy release process of the 10 MW LAES system is established in this paper. The characteristic curves of expander are considered during modeling and simulation process. The dynamic changes of key parameters, such as temperature, pressure, mass flow rate, and so on, of energy storage system over time under the startup and grid connection are simulated. The sensitivity analyses of rotor speed rising rate and frequency disturbance on the key parameters are carried out. The results show that the outlet temperature and outlet pressure of 1st expander stabilized at 395.96K and 5.37 MPa, respectively, at 602s when the rotor starts up with a rising rate of 360 rpm/min. The actual rotor speed reaches the maximum value of 3010r/min at 504s, the overspeed ratio is 100.3%. During the grid connection, the outlet temperature and outlet pressure of 1st expander stabilized at 345.6K and 3.0 MPa, respectively, at 910s, and the mass flow rate of air rises from 11.25 kg/s of the no-load operation to 23.60 kg/s. In addition, the rotor speed rising rate and frequency disturbance have great influence on the key parameters of expander. The new startup scheme of changing rotor speed rising rate have been put forward to balance the relationship between maximum rotor speed and startup time. The fluctuation amplitudes of outlet temperature, outlet pressure, power and rotor speed increase with the frequency disturbance amplitude increasing. The analysis results of dynamic simulation can provide data reference for learning the dynamic characteristics of LAES system.

Dynamic Characteristic Analysis of a Gas–Liquid Swirl Injector Using Planar Laser Imaging

The oscillation of the mass flow rate of the input propellant in liquid rocket engines may induce a periodic heat energy release within the combustion chamber, resulting in operational instability. Since propellant components are discharged from the injector head, the injectors can play a role as a source of oscillation in the dynamic system of a liquid rocket engine. Prior studies confirmed that if the liquid spray and gas flow intersect by using gas-centered dual-swirl injector with tangential inlet in the gas flow path, droplets are generated with periodicity (fracture frequency). In this study, the characteristics and mechanisms of this periodicity were analyzed using longitudinal cross-section spray images. Since the multiple scattering signal that inhibits clarity is non-modulated components, it can be removed by using two modulated images with a phase difference of 180 deg (two-phase structured laser illumination planar imaging technique). And the dynamic characteristics of the gas–liquid spray were analyzed by applying the fast Fourier transform method. It was confirmed by this method that the fracture frequency was related to the impinging velocity of gas and hydrodynamic feature of liquid film. That is, it can be said that fracture frequency of the liquid film is dependent on the liquid Weber number and gas Weber number as the entrainment effect and impact force by gas flow are applied to the liquid film.

Dynamic Characteristics Analysis of a Circumferential Short Spring Dual Mass Flywheel with the Influence of Centrifugal Force and Friction

Multiple sets of spring, spring seat structures are uniformly arranged in circumferential short spring dual mass flywheel (DMF), which generally have a symmetrical structure. The internal springs and spring seats are constrained by the shape of the primary flywheel and the secondary flywheel. At different rotational speeds, the springs and spring seats have different centrifugal forces. To study the dynamic characteristics of the DMF including torque and stiffness with considering the influence of centrifugal force and friction, the discrete method is used to analyze the mechanical actions of the transmission parts in DMF. The torque action between the spring seat and the secondary flywheel is deduced. The dynamic characteristics of the DMF are obtained through analyzing and calculating. Due to the symmetry of the structure, the torque transmitted and the stiffness of the DMF also have specific symmetrical characteristics. Namely, at two relative rotational angles of the same magnitude and opposite direction, the magnitude of the transmitted torque is the same, the direction is opposite. The magnitude and direction of stiffness are the same. The influence of speed, friction coefficient, spring mass, and spring seat mass on the torque and stiffness characteristics are analyzed. Finally, the theoretical analysis is proved to be valid by the torque characteristics test of DMF.

Temperature–Humidity Coupled Analysis in Battery Pack Based on Airflow Characteristics of Waterproof Breathable Valve

Abstract Waterproof breathable valves (WBV) are applied to the battery packs in electric vehicles due to their advantages of high efficiency waterproof and air pressure balance. With the continuity of mass transfer of WBV and uncertain thermal conditions, the dynamic thermal characteristic of the moisture inside the battery pack is difficult to obtain by experiments, especially the phase change of the moisture. To analyze WBV mass transfers to the temperature–humidity characteristic in the battery pack, this study presents a temperature–humidity coupling model of the battery pack based on the mass transfer characteristic of WBV. A mass transfer model of WBV is developed with the airflow mass transfer characteristic in air pressure difference. The proposed models verified the feasibility of dynamic thermal characteristic analysis with experiments. Finally, a practical case study on a battery pack is used to analyze dynamic characteristics of the temperature–humidity during idle and working. Using the coupling model and the WBV model, temperature–humidity distribution and the location and time attributes of moisture condensation in the battery pack are effectively obtained. The inner walls of the pack casing and the battery surface near WBV are condensation areas during environmental conditions changing.

Analysis of Dynamic Characteristics and Power Losses of High Speed on/off Valve with Pre-Existing Control Algorithm

A high-speed on/off valve (HSV) is generally the core component of a digital hydraulic transmission system. Therefore, its dynamic characteristics often restrict the overall performance of the digital hydraulic system. Most of the current studies focus on the optimization on the dynamic characteristics or the energy characteristics, few studies have comprehensively considered the two characteristics of the valve together. In this paper, a pre-existing control algorithm (PECA) is proposed to improve the dynamic characteristics of the HSV, and simultaneously optimize the power losses of the HSV to improve its energy conversion efficiency. The results show that, compared with the traditional single-voltage driven strategy, the opening time of the PECA decreases by 29.4%, the closing time decreases by 59.6%, and the energy conversion rate increases by 7.9%.

Analysis of static and dynamic characteristics of aerostatic bearing with reflux orifices

Purpose The purpose of this paper is to provide a solution for Reynolds equation with both throttling term and reverse throttling term and provides a reference for changing damping of hydrostatic bearing. Design/methodology/approach The reverse throttling term is introduced into the Reynolds equation, and the adaptive damping factor is used in the Newton iteration method to improve convergence of numerical calculations. The static and dynamic performances of this bearing are numerically investigated by the finite-element method. Findings The results indicate that the reflux orifices lead to a decrease in load capacity at a high eccentricity ratio. Additionally, the mass inflow rate is increased; however, the additional inflow increase can be controlled by enhanced backpressure of the reflux orifice. Nevertheless, the bearing with the reflux orifice shows superiority in resisting high-frequency disturbances and enhances direct damping by 20% under a high backpressure. Originality/value This work presents an adaptive Newton damping iterative method for solving Reynolds equation with both throttling term and reverse throttling term. This work also provides a new idea for bearing structure design in improving damping.

Selection of New Type Radial Steel Gate and Analysis of Static and Dynamic Characteristics

Selection of New Type Radial Steel Gate and Analysis of Static and Dynamic Characteristics

Model order reduction and dynamic characteristic analysis of the bolted flange structure with free-free boundaries

The problem of model order reduction and dynamic characteristic analysis of the bolted flange structure with free-free boundary conditions is studied by proposing a novel simplified modeling method. The proposed simplified modeling method is able to reduce the finite element model of the linear components through free-interface mode synthesis method and condense the number of degree-of-freedom of the joint interface through coordinate condensation, which can fix the model size not to increase with the number of bolts and greatly reduce the computational cost. Rigid-body mode elimination is also considered to further reduce the order of the integrated dynamic equation and avoid the problem of computational instability in the proposed simplified modeling method. An experimental bolted flange structure with free-free boundary conditions is built and the corresponding modal testing is carried out to verify the accuracy of the proposed simplified modeling method. Comparative results of modal testing and simulation indicate that gravity leads to unequal bending frequencies of the same order in X and Y directions, which also proves that the proposed simplified modeling method is able to analyze the dynamic characteristic of the bolted flange structure with free-free boundary conditions.

Comparative Analysis of Structural and Dynamical Features of Ribosome Upon Association With mRNA Reveals Potential Role of Ribosomal Proteins.

Ribosomes play a critical role in maintaining cellular proteostasis. The binding of messenger RNA (mRNA) to the ribosome regulates kinetics of protein synthesis. To generate an understanding of the structural, mechanistic, and dynamical features of mRNA recognition in the ribosome, we have analysed mRNA-protein interactions through a structural comparison of the ribosomal complex in the presence and absence of mRNA. To do so, we compared the 3-Dimensional (3D) structures of components of the two assembly structures and analysed their structural differences because of mRNA binding, using elastic network models and structural network-based analysis. We observe that the head region of 30S ribosomal subunit undergoes structural displacement and subunit rearrangement to accommodate incoming mRNA. We find that these changes are observed in proteins that lie far from the mRNA-protein interface, implying allostery. Further, through perturbation response scanning, we show that the proteins S13, S19, and S20 act as universal sensors that are sensitive to changes in the inter protein network, upon binding of 30S complex with mRNA and other initiation factors. Our study highlights the significance of mRNA binding in the ribosome complex and identifies putative allosteric sites corresponding to alterations in structure and/or dynamics, in regions away from mRNA binding sites in the complex. Overall, our work provides fresh insights into mRNA association with the ribosome, highlighting changes in the interactions and dynamics of the ribosome assembly because of the binding.