Despite their crucial roles in health and climate concerns, the gas-particle partitioning of carbonyl compounds is poorly characterized in the ambient atmosphere. In this study, we investigate their partitioning by simultaneously measuring six carbonyl compounds (formaldehyde, acetaldehyde, acetone, propionaldehyde, glyoxal, and methylglyoxal) in the gas and particle phase at an urban site in Beijing. The field-derived partitioning coefficients ( K) are in the range of 10-10 m μg, and the corresponding effective Henry's law coefficients ( K) should be 10-10 M atm. The Pankow's absorptive partitioning theory and Henry's law both significantly underestimate concentrations of particle-phase carbonyl compounds (10-10 times and >10 times, respectively). The observed "salting-in" effects only partially explain the enhanced partitioning to particles, which is approximately 1 order of magnitude. The measured K values are higher at low relative humidity, and the overall effective vapor pressure of these carbonyl species are lower than their hydrates, indicating that carbonyl oligomers potentially formed in highly concentrated particle phase. The reaction kinetics of oligomer formation should be included if applying Henry's law to low-to-moderate relative humidity, and the high partitioning coefficients observed need to be proved by further field and laboratory studies. These findings provide deeper insights into the formation of carbonyl secondary organic aerosols in the ambient atmosphere.

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Sliding mode control of semi-active suspensions possesses excellent performance as well as high robustness. However, it is difficult to obtain sufficient data concerning the various states of the suspension. A model reference sliding mode controller that is easy to implement has been designed. The proposed controller needs only two acceleration sensors and eliminates the necessity of measuring road signals in real-time. The controller uses an approximate ideal skyhook system as a reference model, and the control law is determined so that an asymptotically stable sliding mode will occur in the error dynamics between the plant and the reference model states. The effectiveness of this controller has been verified via experimental studies. A real-time control system has been constructed with a virtual instrument system. Experimental rapid control prototyping for the proposed controller has been conducted on a quarter-car suspension system. The experimental results indicate that, compared with a practical skyhook controller and a passive suspension, the sliding mode controller can effectively improve ride comfort and safety performance. The designed controller should be directly transferable to commercial implementations of semi-active vehicle suspensions.

Partially overlapped channels (POCs)-based design has been identified recently as an emerging technology to further eliminate interference and improve network capacity. However, there are only few studies of channel assignment algorithms for POCs. In this paper, we research on utilizing POCs to improve network capacity and propose a traffic-irrelevant channel assignment algorithm, which assigns channels for all links in the network while minimizing total network interference. Theoretical calculation approach is utilized to obtain the direct relationship between interference ranges and channel separations, which can be easily applied to mesh networks with various configurations without modification. As traffic between the Internet and clients is considered to be dominant, distance from the gateway, number of neighbors, and interference are used to determine the channel assignment order of links. Simulation results reveal that network throughput and end-to-end delay performance can be dramatically improved by fully exploiting POCs as well as orthogonal channels.

Smart structures such as damping adjustable dampers made of magnetorheological (MR) fluid can be used to attenuate vibration transmission in vehicle seat suspension. The main research content of this paper is the nonlinearity and hysteresis characteristics of the MR damper. A hysteretic model considering both excitation characteristics and input current is proposed to fit the damper force-velocity curve for the MR damper under different conditions. Multifactor sensitivity analysis based on the neural network method is used to obtain importance parameters of the hyperbolic tangent model. In order to demonstrate the fitting precision of the different models, the shuffled frog-leaping algorithm (SFLA) is employed to identify the parameters of MR damper models. The research results indicate that the modified model can not only describe the nonlinear hysteretic behavior of the MR damper more accurately in fixed conditions, compared with the original model, but also meet the fitting precision under a wide range of magnitudes of control current and excitation conditions (frequency and amplitude). The method of parameter sensitivity analysis and identification can also be used to modify other nonlinear dynamic models.

In this study, a random forest machine‐learning method is introduced on the basis of the analysis of measured constant amplitude stress fatigue data. This method aims to predict rubber fatigue life under constant amplitude stress. Strain mean value, strain amplitude, and strain ratio are used as independent variables, and the prediction model of rubber fatigue life under constant amplitude stress is established. A nonlinear cumulative fatigue damage model is proposed to calculate rubber fatigue life under the variable amplitude stress. Results show that the random forest method has high precision and generalization capability for rubber fatigue life prediction under constant amplitude stress and the nonlinear cumulative fatigue damage model could be employed to calculate the fatigue life of rubber under variable amplitude stress with enough accuracy according to the constant amplitude stress fatigue life data. This research can provide a reference for rubber fatigue life prediction. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48519.

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