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Metro operations inevitably generate noise inside trains. For better understanding the characteristics of interior noise, we conducted interior noise measurements on 12 subway lines in a Chinese city, objectively explored the reasons for psychological annoyance. By conducting a survey on passengers, we investigated the noise-components that cause an increase in subjective annoyance and used ordinal logistic regression to explore the key factors. Finally, the noise time–frequency characteristics under different operating conditions were discussed. The results showed that loudness is the primary factor causing psychological annoyance. Rail corrugation, especially in the 63–125 Hz range, and broadcasts are the main noise sources that cause annoyance. There was a strong correlation between subjective annoyance and noise sensitivity, and track spatial position and alignment, while vehicle type and seating position had no significant effect. A new index has been proposed for quantifying subjective annoyance. During maintenance, attention should be paid to rail corrugation. [ABSTRACT FROM AUTHOR]

• The proposed method employs a notch filter (NF) to obtain the subsynchronous component. Then it generates the damping control signal of the oscillation frequency band. • The proposed damping control strategy tracks subsynchronous component changes and corrects corresponding output voltage to make MMC-STATCOM present positive resistance in subsynchronous frequency. • The studied strategy has some advantages of simple calculation, easy realization and is suitable for various complicated working conditions. The interaction between the DFIG-based wind farm and series compensation can easily cause subsynchronous control interaction (SSCI). The oscillation frequency of SSCI varies with the actual wind farm situation, which is different from the fixed subsynchronous oscillation frequency of the thermal power unit. Due to the time-variant of the SSCI's oscillation frequency, this paper proposes a supplementary wide-band damping control strategy for MMC-STATCOM to mitigate SSCI. The method adopts a notch filter (NF) to filter only the fundamental frequency component in the current and obtains the corresponding subsynchronous component to generate the damping control signal. Additional damping control signal tracking subsynchronous component changes correct corresponding output voltage, making MMC-STATCOM present positive resistance in subsynchronous frequency. This strategy does not require phase compensation and can always extract the corresponding subsynchronous component compared with the existing research. Finally, both the impedance analysis and time-domain simulation have been involved in verifying the feasibility of the proposed suppression strategy for SSCI under various operating conditions. [ABSTRACT FROM AUTHOR]

• The low-frequency multi-modal features of ABH rubber are applied to construct a novel phononic crystal vibration isolator. • The novel isolator increases the number of bandgaps and widens the bandgap. • A train–floating slab track–tunnel coupled dynamic model is established to investigate the vibration isolation capability. The problem of ambient vibration caused by urban rail transit continues to be serious, but it has not been satisfactorily resolved. This study investigates the structure of a novel phononic crystal vibration isolator (NPCVI) in which the low-frequency and multi-modal features of the acoustic black hole (ABH) structure are used to create coupling vibration between the ABH rubber and steel resonator. The bandgap is widened and the vibration isolation capability of the phononic crystal vibration isolator is optimized. By establishing a finite element model, the multi-bandgap behavior of the NPCVI is discussed, and its vibration isolation capability is demonstrated via studies of the force transmission spectrum. The energy distribution in the finite element model reveals the nature of multi-bandgap formation. Finally, a train–floating slab track–tunnel coupled dynamic model is established to investigate the vibration isolation capability of the NPCVI under the excitation of various track irregularities. The results demonstrate that, under various train speeds, the NPCVI exhibits a superior vibration isolation capability as compared to that of a steel-spring vibration isolator. [ABSTRACT FROM AUTHOR]

• A new floating slab track vibration isolator is developed using particle damping vibration absorption and bandgap vibration resistance. • Using the low-frequency vibration reduction effect of non-obstructive particle damping (NOPD), the attenuation of resonance peaks in the begin of bandgap frequency range is realized. • A coupled train-floating slab track-bridge dynamic model is established to investigate the vibration isolation capability. The environmental vibrations caused by rail transit continue to increase in importance. Even though there are a variety of efficient vibration reduction measures, there is still room for further improvement by trying new, effective vibration control mechanisms. In this paper, a new floating slab track vibration isolator is developed using particle damping vibration absorption and bandgap vibration resistance. Using the low-frequency vibration reduction effect of non-obstructive particle damping (NOPD), the particulate material is added to the outer ring vibrator to participate in vibrations, and the attenuation of resonance peaks in the begin of bandgap frequency range is realized. The energy loss factor and damping ratio of particle damping for different particle sizes are analyzed using a discrete element model. A finite element model with integrated particle damping effect is also formulated and the bandgap behavior of phononic crystal vibration isolator (PCVI) with additional particle damping is analyzed. The effect of particle damping is assessed by calculating the force transmission spectrum. In order to the investigate vibration isolation performance of the combined NOPD-PCVI when subjected to excitation from trains running at different speeds, a coupled train-floating slab track-bridge dynamic model is established. The results show that the NOPD-PCVI offers better vibration isolation than a steel-spring vibration isolator and the traditional PCVI (T-PCVI) in the frequency band of 50–150 Hz. The energy dissipation provided by particle damping and the bandgap damping of phononic crystals reduce the vertical accelerations of the bridge deck in the bandgap frequency band. Specifically, the total vertical accelerations of the bridge deck equipped with NOPD-PCVIs is reduced by 15.3 dB compared to steel springs, and 5.6 dB compared to T-PCVIs, respectively. [ABSTRACT FROM AUTHOR]

• A PSO and deep neural model based acoustic metamaterials Reverse design method is proposed. • A multi-gradient cavity acoustic metamaterial structure acoustic metamaterial with high ventilation and broadband sound insulation is designed. • Compared to existing upright railroad sound barriers, OMCAM sound barriers can increase the average noise reduction effect by 9.4 dB. A multi-gradient cavity acoustic metamaterial (MCAM) structure and a modular reverse design method (MRDM) that can realize high ventilation and broadband acoustic isolation are proposed. The method controls the deep neural network model of acoustic metamaterials through a particle swarm algorithm, and the optimized multi-gradient cavity acoustic metamaterial structure (OMCAM) can be reverse-designed by inputting only the constraints and the objective function such as the amount of noise reduction. Compared with the finite element method, the computational efficiency can be improved by about 500 times to achieve an optimized design. The acoustic simulation results show that the average noise reduction of the structure is 23.5 dB in the range of 0∼4000 Hz, and a broadband sound attenuation with 38 dB noise reduction is formed in the target frequency band of 500Hz∼2000 Hz. The acoustic experimental results of the 3D-printed structure are in agreement with the simulation results. Compared with the two existing ventilated acoustic metamaterials, the average noise reduction of OMCAM under equal ventilation capacity is improved by 10.6 dB and 17.4 dB, respectively. The sound barrier based on the proposed OMCAM design is implemented on an elevated rail transit line, showing an improvement of 9.4 dB of average noise reduction compared with existing upright railroad sound barriers. The noise reduction mechanism of the OMCAM structure was finally revealed by the sound field distribution in different modes. [ABSTRACT FROM AUTHOR]

Hypertriglyceridemia is an independent risk factor for acute pancreatitis, in which the pathological mechanisms are not fully illustrated. Intracellular inflammatory response is a key pathological response in acute pancreatitis and endoplasmic reticulum stress has been suggested to induce inflammation and CCAAT-enhancer-binding protein expression. Therefore, the current study aims to elucidate the possible relationship between endoplasmic reticulum stress and inflammation in hypertriglyceridemia associated pancreatitis and the possible involvement of CCAAT-enhancer-binding protein. In cholecystokinin-8 stimulated rat primary acinar cells, incubation with palmitic acid caused the activation of endoplasmic reticulum stress and inflammatory responses. Pre-incubation with the chemical chaperone 4-phenylbutyric acid inhibited inflammatory responses induced by palmitic acid, whereas stimulation with the endoplasmic reticulum stress inducer thapsigargin alone induced inflammatory responses. Meanwhile we found that the transcription factors CCAAT-enhancer-binding protein α and CCAAT-enhancer-binding protein β were also induced in the palmitic acid-stimulated pancreatic acinar cells, and were similarly inhibited by 4-phenylbutyric acid pre-incubation and induced by thapsigargin stimulation alone, indicating that endoplasmic reticulum stress was responsible for CCAAT-enhancer-binding protein α and CCAAT-enhancer-binding protein β induction in the pancreatic acinar cells. Knockdown of CCAAT-enhancer-binding protein β by siRNA transfection inhibited inflammatory responses and CCAAT-enhancer-binding protein α induction but did not affect endoplasmic reticulum stress. Our study provides strong evidence that in response to palmitic acid stimulation, endoplasmic reticulum stress induces inflammatory responses in pancreatic acinar cells through induction of the CCAAT-enhancer-binding protein family, wherein CCAAT-enhancer-binding protein β activation is responsible for CCAAT-enhancer-binding protein α activation. [ABSTRACT FROM AUTHOR]