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Aiming at reducing the effect of time delay on the control performance of magnetorheological (MR) damper semi-active suspension, a control strategy with strong robustness to time delay is investigated in this study, including the force controller of MR damper, the robust controller and the predictive compensator. The force controller of MR damper is built based on the hyperbolic tangent function; the robust controller is built based on the simplified model of car body lateral vibration and is designed by μ-synthesis method considering the effect of time delay; then the Smith predictive model and the lateral velocity predictor are designed, which form the predictive compensator of semi-active controller to reduce the effect of time delay. To validate the effectiveness of the proposed control strategy, several conventional semi-active controllers are designed as comparative objects. The simulation results show that the proposed semi-active control strategy can maintain good performance when time delay is in the range of 0–100 ms and has better robustness to time delay compared with the conventional control strategy. [ABSTRACT FROM AUTHOR]

The hunting motion of the vehicle increases the wear of the wheel tracks and affects the lateral stability of the vehicle system and safety, so the hunting motion of the vehicle needs to be recognized. However, the existing recognition methods ignore the small-amplitude hunting motion that precedes the onset of the running motion. In addition, due to the scarcity of real hunting data of high-speed trains, there is a problem of underfitting when training with traditional deep learning methods. In this paper, first, the dynamics model of a high-speed train is established, and the normal, small-amplitude hunting and hunting motions of high-speed trains in the process are simulated. Second, this paper proposes a transfer learning-based method for high-speed train hunting motion recognition. The method uses easily collected normal data samples in the training process, does not use real data samples of small-amplitude hunting and hunting motions, and completes the high-speed train running motions recognition task by transferring from simulation data (source domain) to real data (target domain). Finally, the validation is carried out using the real data, which proves that the method-related approach has some engineering application value in the intelligent monitoring of high-speed trains. [ABSTRACT FROM AUTHOR]

Amorphous nano-metal catalysts often exhibit appealing catalytic properties, because the intrinsic linear scaling relationship can be broken. However, accurate control synthesis of amorphous nano-metal catalysts with desired size and morphology is a challenge. In this work, we discover that Cu(0) could be oxidized to amorphous CuxO species by supercritical CO2. The formation process of the amorphous CuxO is elucidated with the aid of machine learning. Based on this finding, a method to prepare Cu nanoparticles with an amorphous shell is proposed by supercritical CO2 treatment followed by electroreduction. The unique feature of this method is that the size of the particles with amorphous shell can be easily controlled because their size depends on that of the original crystal Cu nanoparticles. Moreover, the thickness of the amorphous shell can be easily controlled by CO2 pressure and/or treatment time. The obtained amorphous Cu shell exhibits high selectivity for C2+ products with the Faradaic efficiency of 84% and current density of 320 mA cm−2. Especially, the FE of C2+ oxygenates can reach up to 65.3 %, which is different obviously from the crystalline Cu catalysts. Amorphous metal catalysts often exhibit appealing catalytic properties, however, accurate control synthesis of amorphous nano-metal catalysts is a challenge. Here, the authors report a feasible strategy to prepare the amorphous Cu catalysts by supercritical CO2 treatment followed by electroreduction. The resulted catalyst shows high selectivity towards multi-carbon products for CO2 electroreduction. [ABSTRACT FROM AUTHOR]

Methanol is a highly desirable product of CO2 electroreduction due to its wide array of industrial applications. However, the development of CO2-to-methanol electrocatalysts with high performance is still challenging. Here we report an operationally simple in situ dual doping strategy to construct efficient CO2-to-methanol electrocatalysts. In particular, when using Ag,S-Cu2O/Cu as electrocatalyst, the methanol Faradaic efficiency (FE) could reach 67.4% with a current density as high as 122.7 mA cm−2 in an H-type cell using 1-butyl-3-methylimidazolium tetrafluoroborate/H2O as the electrolyte, while the current density was below 50 mA cm−2 when the FE was greater than 50% over the reported catalysts. Experimental and theoretical studies suggest that the anion S can effectively adjust the electronic structure and morphology of the catalysts in favor of the methanol pathway, whereas the cation Ag suppresses the hydrogen evolution reaction. Their synergistic interactions with host material enhance the selectivity and current density for methanol formation. This work opens a way for designing efficient catalysts for CO2 electroreduction to methanol. Production of methanol from CO2 electroreduction is attractive but achieving high selectivity, current density and stability simultaneously remains a grand challenge. Here, the authors present an in situ dual doping strategy to construct efficient CO2-to-methanol electrocatalysts. [ABSTRACT FROM AUTHOR]

Novel durian-like TiO2@CdS core-shell particles were synthesized through a solvothermal method in ethylenediamine solution and the obtained nanocomposites were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and transmission electron microscopic (TEM) techniques. It can be seen from the characterization that the synthesized core-shell structured particles show uniform size. The possible formation mechanism of TiO2@CdS core-shell particles is also presented schematically. CdS grows on the TiO2 surface in the form of nanorods, turning the TiO2@CdS composite particles into durian-like structures. The durian-like TiO2@CdS core-shell particles prepared in the experiment can overcome the disadvantages of TiO2 and CdS, respectively. They not only produce a higher yield of H2 than pure TiO2; the durian-like TiO2@CdS nanostructures formed at 180 °C for 16 h produced 2.5 times as much H2 as did TiO2, also showing enhanced stability as compared with pure CdS. [ABSTRACT FROM AUTHOR]

The gear transmission system is a vital component of the locomotive bogie. During locomotive operation, the damage to the gear transmission system spreads rapidly and affects the locomotive’s operational safety. In this paper, a method is proposed to detect the degree of tooth root crack damage. First, a dynamic locomotive model with a gear transmission is built, and the vertical acceleration of the locomotive subsystem (car body, bogie frame, wheelset, and motor) vibrations is obtained under various degrees of tooth root crack damage on the gear transmission system. By comparing the characteristics of those signals, the subsystem that is more sensitive to the effect of the tooth root crack is found. The characteristic parameters of the sensitive subsystem are calculated, and a multidimensional characteristic parameter matrix is established. The multidimensional characteristic parameter matrix is optimized and reduced by principal component analysis (PCA). Using the Grey relational analysis method, the degree of tooth root crack damage is detected. The proposed method demonstrates the ability to recognize the degree of tooth root crack damage. [ABSTRACT FROM AUTHOR]

Hunting monitoring is very important for high-speed trains to achieve safe operation. But all the monitoring systems are designed to detect hunting only after hunting has developed sufficiently. Under these circumstances, some damage may be caused to the railway track and train wheels. The work reported in this paper aims to solve the detection problem of small amplitude hunting before the lateral instability of high-speed trains occurs. But the information from a single sensor can only reflect the local operation state of a train. So, to improve the accuracy and robustness of the monitoring system, a multi-sensor fusion framework for detecting small amplitude hunting of high-speed trains based on an improved Dempster–Shafer (DS) theory is proposed. The framework consists of a series of steps. Firstly, the method of combining empirical mode decomposition and sample entropy is used to extract features of each operation condition. Secondly, the posterior probability support vector machine is used to get the basic probability assignment. Finally, the DS theory improved by the authors is proposed to get a more accurate detection result. This framework developed by the authors is used on high-speed trains with success and experimental findings are provided. This multi-sensor fusion framework can also be used in other condition monitoring systems on high-speed trains, such as the gearbox monitoring system, from which nonstationary signals are acquired too. [ABSTRACT FROM AUTHOR]

Joint Approximate Diagonalization of Eigen-matrices (JADE) cannot deal with non-stationary data. Therefore, in this paper, a method called Non-stationary Kernel JADE (NKJADE) is proposed, which can extract non-stationary features and fuse multi-sensor features precisely and rapidly. In this method, the non-stationarity of the data is considered and the data from multi-sensor are used to fuse the features efficiently. The method is compared with EEMD-SVD-LTSA and EEMD-JADE using the bearing fault data of CWRU, and the validity of the method is verified. Considering that the vibration signals of high-speed trains are typically non-stationary, it is necessary to utilize a rapid feature fusion method to identify the evolutionary trends of hunting motions quickly before the phenomenon is fully manifested. In this paper, the proposed method is applied to identify the evolutionary trend of hunting motions quickly and accurately. Results verify that the accuracy of this method is much higher than that of the EEMD-JADE and EEMD-SVD-LTSA methods. This method can also be used to fuse multi-sensor features of non-stationary data rapidly. [ABSTRACT FROM AUTHOR]

Electrochemical CO 2 reduction reaction (CO 2 RR) to multicarbon (C 2+ ) products faces challenges of unsatisfactory selectivity and stability. Guided by finite element method (FEM) simulation, a nanoreactor with cavity structure can facilitate C-C coupling by enriching *CO intermediates, thus enhancing the selectivity of C 2+ products. We designed a stable carbon-based nanoreactor with cavity structure and Cu active sites. The unique geometric structure endows the carbon-based nanoreactor with a remarkable C 2+ product faradaic efficiency (80.5%) and C 2+ -to-C 1 selectivity (8.1) during the CO 2 electroreduction. Furthermore, it shows that the carbon shell could efficiently stabilize and highly disperse the Cu active sites for above 20 hours of testing. A remarkable C 2+ partial current density of-323 mA cm -2 was also achieved in a flow cell device. In situ Raman spectra and density functional theory (DFT) calculation studies validated that the *CO atop intermediates are concentrated in the nanoreactor, which reduces the free energy of C-C coupling. This work unveiled a simple catalyst design strategy that would be applied to improve C 2+ product selectivity and stability by rationalizing the geometric structures and components of catalysts., Competing Interests: The authors declare no competing interests., (This journal is © The Royal Society of Chemistry.)

The electrochemical reduction of carbon dioxide (CO 2 RR) holds great promise for sustainable energy utilization and combating global warming. However, progress has been impeded by challenges in developing stable electrocatalysts that can steer the reaction toward specific products. This study proposes a carbon shell coating protection strategy by an efficient and straightforward approach to prevent electrocatalyst reconstruction during the CO 2 RR. Utilizing a copper-based metal-organic framework as the precursor for the carbon shell, we synthesized carbon shell-coated electrocatalysts, denoted as Cu- x-y , through calcination in an N 2 atmosphere (where x and y represent different calcination temperatures and atmospheres: N 2 , H 2 , and NH 3 ). It was found that the faradaic efficiency of ethanol over the catalysts with a carbon shell could reach ∼67.8%. In addition, the catalyst could be stably used for more than 16 h, surpassing the performance of Cu-600-H 2 and Cu-600-NH 3 . Control experiments and theoretical calculations revealed that the carbon shell and Cu-C bonds played a pivotal role in stabilizing the catalyst, tuning the electron environment around Cu atoms, and promoting the formation and coupling process of CO*, ultimately favoring the reaction pathway leading to ethanol formation. This carbon shell coating strategy is valuable for developing highly efficient and selective electrocatalysts for the CO 2 RR., Competing Interests: The authors declare no competing interests., (This journal is © The Royal Society of Chemistry.)

To realize commercial CO 2 electrochemical reduction to C 2+ alcohols, the selectivity and production rate should be further improved. Establishing controllable surface sites with a favorable local environment is an interesting route to guide the C 2+ pathway. Herein, we report a room-temperature one-step synthetic strategy to fabricate a highly stable Cu aerogel as an efficient CO 2 reduction electrocatalyst. Controlling crystal growth kinetics using different reductants is an efficient strategy to modulate the nucleation and growth rate of Cu aerogels, enabling the creation of efficient surface sites for the C 2+ pathway. Over the Cu aerogel obtained by reducing Cu 2+ using a weak reductant (NH 3 ·BH 3 ), the faradaic efficiency of C 2+ products could reach 85.8% with the current density of 800 mA cm -2 at the potential of -0.91 V vs. reversible hydrogen electrode, and the C 2+ alcohol selectivity was 49.7% with a partial current density of 397.6 mA cm -2 , while the Cu aerogel prepared using a strong reductant (NaBH 4 ) was favorable to generating CO. Experimental and theoretical studies showed that the selectivity of the reaction depended strongly on the desorption and dimerization of *CO intermediates on the catalysts. The strong reductant induced a defective Cu surface that could facilitate the desorption of the *CO intermediate, subsequently producing CO, whereas the low defect Cu produced using a weak reductant could significantly enhance the selectivity for the C 2+ product by improving *CO adsorption and the C-C coupling on the catalyst. This work opens a new way for constructing efficient electrocatalysts for CO 2 electroreduction to C 2+ alcohols., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Current techno-economic evaluation manifests that the electrochemical CO 2 reduction reaction (eCO 2 RR) to CO is very promising considering its simple two-electron transfer process, minimum cost of electricity, and low separation cost. Herein, we report a Sn-modification strategy that can tune the local electronic structure of Cu with an appropriate valence. The as-prepared catalysts can alter the broad product distribution of Cu-based eCO 2 RR to predominantly generate CO. CO faradaic efficiency (FE) remained above 96% in the wide potential range of -0.5 to -0.9 V vs. the reversible hydrogen electrode (RHE) with CO partial current density up to 265 mA cm -2 . The catalyst also had remarkable stability. Operando experiments and density functional theory calculations demonstrated that the surface Cu δ + sites could be modulated and stabilized after introducing Sn. The Cu δ + sites with low positive valence were conducive to regulating the binding energy of intermediates and resulted in high CO selectivity and maintained the stability of the catalyst. Additionally, scaling up the catalyst into a membrane electrode assemble system (MEA) could achieve a high overall current of 1.3 A with exclusive and stable CO generation., Competing Interests: The authors declare no competing financial interests., (This journal is © The Royal Society of Chemistry.)

The electroreduction of CO 2 to CH 4 has attracted extensive attention. However, it is still a challenge to achieve high current density and faradaic efficiency (FE) for producing CH 4 because the reaction involves eight electrons and four protons. In this work, we designed Cu nanoparticles supported on N-doped carbon (Cu-np/NC). It was found that the catalyst exhibited outstanding performance for the electroreduction of CO 2 to CH 4 . The FE toward CH 4 could be as high as 73.4% with a high current density of 320 mA cm -2 . In addition, the mass activity could reach up to 6.4 A mg Cu -1 . Both experimental and theoretical calculations illustrated that the pyrrolic N in NC could accelerate the hydrogenation of *CO to the *CHO intermediate, resulting in high current density and excellent selectivity for CH 4 . This work conducted the first exploration of the effect of N-doped species in composites on the electrocatalytic performance of CO 2 reduction., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Powered by a renewable electricity source, electrochemical CO 2 reduction reaction is a promising solution to facilitate the carbon balance. However, it is still a challenge to achieve a desired product with commercial current density and high efficiency. Herein we designed quasi-square-shaped cadmium hydroxide nanocatalysts for CO 2 electroreduction to CO. It was discovered that the catalyst is very active and selective for the reaction. The current density could be as high as 200 mA cm -2 with a nearly 100% selectivity in a commonly used H-type cell using the ionic liquid-based electrolyte. In addition, the faradaic efficiency of CO could reach 90% at a very low overpotential of 100 mV. Density functional theory studies and control experiments reveal that the outstanding performance of the catalyst was attributed to its unique structure. It not only provides low Cd-O coordination, but also exposes high activity (002) facet, which requires lower energy for the formation of CO. Besides, the high concentration of CO can be achieved from the low concentration CO 2 via an adsorption-electrolysis device., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Electrocatalytic reduction of CO 2 into multicarbon (C 2+ ) products powered by renewable electricity offers one promising method for CO 2 utilization and promotes the storage of renewable energy under an ambient environment. However, there is still a dilemma in the manufacture of valuable C 2+ products between balancing selectivity and activity. In this work, cerium oxides were combined with CuO (CeO 2 /CuO) and showed an outstanding catalytic performance for C 2+ products. The faradaic efficiency of the C 2+ products could reach 75.2% with a current density of 1.21 A cm -2 . In situ experiments and density functional theory (DFT) calculations demonstrated that the interface between CeO 2 and Cu and the subsurface Cu 2 O coexisted in CeO 2 /CuO during CO 2 RR and two competing pathways for C-C coupling were promoted separately, of which hydrogenation of *CO to *CHO is energetically favoured. In addition, the introduction of CeO 2 also enhanced water activation, which could accelerate the formation rate of *CHO. Thus, the selectivity and activity for C 2+ products over CeO 2 /CuO can be improved simultaneously., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Oxide-derived copper (OD-Cu) has been discovered to be an effective catalyst for the electroreduction of CO 2 to C2+ products. The structure of OD-Cu and its surface species during the reaction process are interesting topics, which have not yet been clearly discussed. Herein, in situ surface-enhanced Raman spectroscopy (SERS), operando X-ray absorption spectroscopy (XAS), and 18 O isotope labeling experiments were employed to investigate the surface species and structures of OD-Cu catalysts during CO 2 electroreduction. It was found that the OD-Cu catalysts were reduced to metallic Cu(0) in the reaction. CuO x species existed on the catalyst surfaces during the CO 2 RR, which resulted from the adsorption of preliminary intermediates (such as *CO 2 and *OCO - ) on Cu instead of on the active sites of the catalyst. It was also found that abundant interfaces can be produced on OD-Cu, which can provide heterogeneous CO adsorption sites (strong binding sites and weak binding sites), leading to outstanding performance for obtaining C2+ products. The Faradaic efficiency (FE) for C2+ products reached as high as 83.8% with a current density of 341.5 mA cm -2 at -0.9 V vs. RHE., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Arenes are widely used chemicals and essential components in liquid fuels, which are currently produced from fossil feedstocks. Here, we proposed the self-supported hydrogenolysis (SSH) of aromatic ethers to produce arenes using the hydrogen source within the reactants, and it was found that RuW alloy nanoparticles were very efficient catalyst for the reactions. This route is very attractive and distinguished from the reported studies on the cleavage of the C Ar ─O bonds. The unique feature of this methodology is that exogenous hydrogen or other reductant is not required, and hydrogenation of aromatic rings could be avoided completely. The selectivities to arenes could reach >99.9% at complete conversion of the ethers. Moreover, lignin could also be transformed into arenes efficiently over the RuW alloy catalyst. The mechanism studies showed that the neighboring Ru and W species in the RuW alloy nanoparticles worked synergistically to accelerate the SSH reaction., (Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).)

The efficient electrochemical reduction of CO 2 to CO in aqueous electrolyte is very interesting. Due to the critical electron-transfer step during the activation of CO 2 , it is important to design efficient strategies to engineer the electronic properties of catalysts to improve the electrochemical performance. Herein cobalt phthalocyanine (CoPc) supported on ZnIn 2 S 4 (ZIS) nanosheets was synthesized. It was found that the hybrids showed excellent performance for CO 2 electroreduction to CO in aqueous solution. The faradaic efficiency, current density and mass activity could reach 93%, 8 mA cm -2 and 266 mA mg (CoPc) -1 , respectively. Introduction of Zn-defects resulted in dangling S bonds in the ZIS support, which interacted with Co active sites of CoPc via strong Co-S interaction. Mechanistic studies revealed that the enhancement of CO production over CoPc by Co-S interaction originated from the eased CO 2 activation.

We propose a strategy to synthesize ternary CdS/UiO-bpy/Co composites by integration of CdS and molecular redox catalysts through metal-organic framework (MOF) UiO-bpy. The CdS/UiO-bpy/Co composites were very effective for photocatalytic conversion of CO 2 to CO under visible light irradiation. The evolution rate of CO could reach 235 μmol g -1 h -1 , which was a 10.2-fold improvement compared to that for the parent CdS, and selectivity for CO was 85%. The outstanding performance of the CdS/UiO-bpy/Co composites resulted from promoting the separation and migration of photo-induced charge carriers, enhancing the adsorption of CO 2 molecules, and offering abundant active sites for CO 2 reduction. As far as we know, this is the first study to integrate inorganic semiconductors and molecular redox catalysts through MOFs.