Dynamic analysis of axle box bearings on the high-speed train caused by wheel-rail excitation

To explore the impact of wheel-rail excitation on the dynamic performance of axle box bearings,a dynamic model of the high-speed train including axle box bearings is developed.Subsequently,the dynamic response characteristics of the axle box bearing are examined.The investigation focuses on the acceleration characteristics of bearing vibration under excitation of track irregularities and wheel flats.In addition,experiments on both normal and faulty bearings are conducted separately,and the correctness of the model and some conclusions are verified.According to the research,track irregularity is unfavorable for bearing fault detection based on resonance demodulation.Under the same speed conditions,the acceleration peak of bearing is inversely proportional to the length of the wheel flat and directly proportional to its depth.The paper will contribute to a deeper understanding of the dynamic performance of axle box bearings.

水稻分蘖氮响应调控机理研究进展

氮肥是作物产量增加最主要的驱动因素,然而氮肥滥用会造成生态环境的严重破坏。因此,提高作物氮素利用效率(nitrogen use efficiency,NUE)对未来农业可持续发展至关重要。产量性状对氮素的敏感性是衡量作物氮素利用效率的重要指标。禾本科作物的分蘖数、穗粒数和粒重是产量的直接决定因子,虽然影响三者本身的分子机制已有大量研究,但氮素对这些性状的调控机理仍知之甚少。分蘖数是对氮素响应最为敏感的性状之一,也是氮肥促进作物增产的关键要素。因此,研究氮素如何调控水稻的分蘖发育对于提高作物产量尤为重要。本文总结了水稻氮素利用效率的影响因素和分蘖发育的调控机理,聚焦氮素如何调控水稻分蘖发育的机制,并对该领域未来研究工作进行了展望,以期为作物氮高效精准改良提供参考。

Research on hunting stability and bifurcation characteristics of nonlinear stochastic wheelset system

A stochastic wheelset model with a nonlinear wheel-rail contact relationship is established to investigate the stochastic stability and stochastic bifurcation of the wheelset system with the consideration of the stochastic parametric excitations of equivalent conicity and suspension stiffness.The wheelset is systematized into a onedimensional(1D)diffusion process by using the stochastic average method,the behavior of the singular boundary is analyzed to determine the hunting stability condition of the wheelset system,and the critical speed of stochastic bifurcation is obtained.The stationary probability density and joint probability density are derived theoretically.Based on the topological structure change of the probability density function,the stochastic Hopf bifurcation form and bifurcation condition of the wheelset system are determined.The effects of stochastic factors on the hunting stability and bifurcation characteristics are analyzed,and the simulation results verify the correctness of the theoretical analysis.The results reveal that the boundary behavior of the diffusion process determines the hunting stability of the stochastic wheelset system,and the left boundary characteristic value cL=1 is the critical state of hunting stability.Besides,stochastic D-bifurcation and P-bifurcation will appear in the wheelset system,and the critical speeds of the two kinds of stochastic bifurcation decrease with the increase in the stochastic parametric excitation intensity.

Analysis of the Temperature Characteristics of High-speed Train Bearings Based on a Dynamics Model and Thermal Network Method

High-speed trains often use temperature sensors to monitor the motion state of bearings.However,the temperature of bearings can be affected by factors such as weather and faults.Therefore,it is necessary to analyze in detail the relationship between the bearing temperature and influencing factors.In this study,a dynamics model of the axle box bearing of high-speed trains is established.The model can obtain the contact force between the rollers and raceway and its change law when the bearing contains outer-ring,inner-ring,and rolling-element faults.Based on the model,a thermal network method is introduced to study the temperature field distribution of the axle box bearings of high-speed trains.In this model,the heat generation,conduction,and dispersion of the isothermal nodes can be solved.The results show that the temperature of the contact point between the outer-ring raceway and rolling-elements is the highest.The relationships between the node temperature and the speed,fault type,and fault size are analyzed,finding that the higher the speed,the higher the node temperature.Under different fault types,the node temperature first increases and then decreases as the fault size increases.The effectiveness of the model is demonstrated using the actual temperature data of a high-speed train.This study proposes a thermal network model that can predict the temperature of each component of the bearings on a high-speed train under various speed and fault conditions.

Establishment of Dynamic Model for Axle Box Bearing of High-Speed Trains Under Variable Speed Conditions

In this study,a dynamic model for the bearing rotor system of a high-speed train under variable speed conditions is established.In contrast to previous studies,the contact stress is simplifed in the proposed model and the compensation balance excitation caused by the rotor mass eccentricity considered.The angle iteration method is used to overcome the challenge posed by the inability to determine the roller space position during bearing rotation.The simulation results show that the model accurately describes the dynamics of bearings under varying speed profles that contain acceleration,deceleration,and speed oscillation stages.The order ratio spectrum of the bearing vibration signal indicates that both the single and multiple frequencies in the simulation results are consistent with the theoretical results.Experiments on bearings with outer and inner ring faults under various operating conditions are performed to verify the developed model.

Characteristic analysis of mechanical thermal coupling model for bearing rotor system of high-speed train

Based on Newton’s second law and the thermal network method,a mechanical thermal coupling model of the bearing rotor system of high-speed trains is established to study the interaction between the bearing vibration and temperature.The influence of lubrication on the vibration and temperature characteristics of the system is considered in the model,and the real-time relationship between them is built up by using the transient temperature field model.After considering the lubrication,the bearing outer ring vibration acceleration and node temperature considering grease are lower,which shows the necessity of adding the lubrication model.The corresponding experiments for characteristics of vibration and temperature of the model are respectively conducted.In the envelope spectrum obtained from the simulation signal and the experimental signal,the frequency values corresponding to the peaks are close to the theoretical calculation results,and the error is very small.In the three stages of the temperature characteristic experiment,the node temperature change of the simulation model is consistent with the experiment.The good agreement between simulation and experiments proves the effectiveness of the model.By studying the influence of the bearing angular and fault size on the system node temperature,as well as the change law of bearing lubrication characteristics and temperature,it is found that the worse the working condition is,the higher the temperature is.When the ambient temperature is low,the viscosity of grease increases,and the oil film becomes thicker,which increases the sliding probability of the rolling element,thus affecting the normal operation of the bearing,which explains the phenomenon of frequent bearing faults of high-speed trains in the low-temperature area of Northeast China.Further analysis shows that faults often occur in the early stage of train operation in the low-temperature environment.

Land Breeze and Thermals: A Scale Threshold to Distinguish Their Effects

Land breeze is a type of mesoscale circulation developed due to thermal forcing over a heterogeneous landscape. It can contribute to atmospheric dynamic and hydrologic processes through affecting heat and water fluxes on the land-atmosphere interface and generating shallow convective precipitation. If the scale of the landscape heterogeneity is smaller than a certain size, however, the resulting land breeze becomes weak and becomes mixed up with other thermal convections like thermals. This study seeks to identify a scale threshold to distinguish the effects between land breeze and thermals. Two-dimensional simulations were performed with the Regional Atmospheric Modeling System （RAMS） to simulate thermals and land breeze. Their horizontal scale features were analyzed using the wavelet transform. The thermals developed over a homogeneous landscape under dry or wet conditions have an initial scale of 2-5 km during their early stage of development. The scale jumps to 10-15 km when condensation occurs. The solution of an analytical model indicates that the reduced degree of atmospheric instability due to the release of condensation potential heat could be one of the contributing factors for the increase in scale. The land breeze, on the other hand, has a major scale identical to the size of the landscape heterogeneity throughout various stages of development. The results suggest that the effects of land breeze can be clearly distinguished from those of thermals only if the size of the landscape heterogeneity is larger than the scale threshold of about 5 km for dry atmospheric processes or about 15 km for moist ones.

Genetic improvement toward nitrogen-use efficiency in rice: Lessons and perspectives

The indispensable role of nitrogen fertilizer in ensuring world food security together with the severe threats it poses to the ecosystem makes the usage of nitrogen fertilizer a major challenge for sustainable agriculture.Genetic improvement of crops with high nitrogen-use efficiency(NUE)is one of the most feasible solutions for tackling this challenge.In the last two decades,extensive efforts toward dissecting the variation of NUE-related traits and the underlying genetic basis in different germplasms have been made,and a series of achievements have been obtained in crops,especially in rice.Here,we summarize the approaches used for genetic dissection of NUE and the functions of the causal genes in modulating NUE as well as their applications in NUE improvement in rice.Strategies for exploring the variants controlling NUE and breeding future crops with“less-input-more-output”for sustainable agriculture are also proposed.

Crosstalk between brassinosteroid signaling and variable nutrient environments

Brassinosteroid(BR)represents a group of steroid hormones that regulate plant growth and development as well as environmental adaptation.The fluctuation of external nutrient elements is a situation that plants frequently face in the natural environment,in which nitrogen(N)and phosphorus(P)are two of the most critical nutrients restraint of the early growth of plants.As the macronutrients,N and P are highly required by plants,but their availability or solubility in the soil is relatively low.Since iron(Fe)and P always modulate each other’s content and function in plants mutually antagonistically,the regulatory mechanisms of Fe and P are inextricably linked.Recently,BR has emerged as a critical regulator in nutrient acquisition and phenotypic plasticity in response to the variable nutrient levels in Arabidopsis and rice.Here,we review the current understanding of the crosstalk between BR and the three major nutrients(N,P,and Fe),highlighting how nutrient signaling regulates BR synthesis and signaling to accommodate plant growth and development in Arabidopsis and rice.

Improving maize seed protein content and nitrogen-use efficiency by a teosinte asparagine synthetase

From the earliest farming civilization,artificial selection continuously improves the critical agronomic traits for easier cultivation,higher yield,and better nutrient quality during crop domestication.During this process,genetic diversity of modern crops might be largely lost due to bottleneck effect with relative relaxed selection pressure(Doebley et al.,2006).To this end,the wild ancestors of modern crops,with their abundant genetic diversity,act as valuable pools for modern crop improvement.

Ketogenic diet alleviates colitis by reduction of colonic group 3 innate lymphoid cells through altering gut microbiome

Accumulating evidence suggests that ketogenic diets(KDs)mediate the rise of circulating ketone bodies and exert a potential antiinflammatory effect;however,the consequences of this unique diet on colitis remain unknown.We performed a series of systematic studies using a dextran sulfate sodium(DSS)animal model of inflammatory colitis.Animals were fed with a KD,low-carbohydrate diet(LCD),or normal diet(ND).Germ-free mice were utilized in validation experiments.Colon tissues were analyzed by transcriptome sequencing,RT2 profiler PCR array,histopathology,and immunofluorescence.Serum samples were analyzed by metabolic assay kit.Fecal samples were analyzed by 16S rRNA gene sequencing,liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry.We observed that KD alleviated colitis by altering the gut microbiota and metabolites in a manner distinct from LCD.Quantitative diet experiments confirmed the unique impact of KD relative to LCD with a reproducible increase in Akkermansia,whereas the opposite was observed for Escherichia/Shigella.After colitis induction,the KD protected intestinal barrier function,and reduced the production of R0Ryt+CD3_group 3 innate lymphoid cells(ILC3s)and related inflammatory cytokines(IL-17a,IL-18,IL-22,Ccl4).Finally,fecal microbiota transplantation into germ-free mice revealed that the KD-mediated colitis inhibition and ILC3 regulation were dependent on the modification of gut microbiota.Taken together,our study presents a global view of microbiome-metabolomics changes that occur during KD colitis treatment,and identifies the regulation of gut microbiome and ILC3s as novel targets involving in IBD dietary therapy.

Modulation of nitrate-induced phosphate response by the MYB transcription factor RLI1/HINGE1 in the nucleus

The coordinated utilization of nitrogen(N)and phosphorus(P)is vital for plants to maintain nutrient balance and achieve optimal growth.Previously,we revealed a mechanism by which nitrate induces genes for phosphate utilization;this mechanism depends on NRT1.1B-facilitated degradation of cytoplasmic SPX4,which in turn promotes cytoplasmic-nuclear shuttling of PHR2,the central transcription factor of phosphate signaling,and triggers the nitrate-induced phosphate response(NIPR)and N-P coordinated utilization in rice.In this study,we unveiled a fine-tuning mechanism of NIPR in the nucleus regulated by Highly Induced by Nitrate Gene 1(HINGE1,also known as RLI1),a MYB-transcription factor closely related to PHR2.RLI1/HINGE1,which is transcriptionally activated by PHR2 under nitrate induction,can directly activate the expression of phosphate starvation-induced genes.More importantly,RLI1/HINGE1 competes with PHR2 for binding to its repressor proteins in the nucleus(SPX proteins),and consequently releases PHR2 to further enhance phosphate response.Therefore,RLI1/HINGE1 amplifies the phosphate response in the nucleus downstream of the cytoplasmic SPX4-PHR2 cascade,thereby enabling fine-tuning of N-P balance when nitrate supply is sufficient.

Identification of microRNAs in rice root in response to nitrate and ammonium

Nitrate and ammonium are two major nitrogen （N） sources for higher plants, but they differ in utilization and signaling. MicroRNAs （miRNAs） play an essential role in N signal transduction; however, knowledge remains limited about the regulatory role of miRNAs responsive to different N sources, especially in crop plants. To get global overview on miRNAs involved in N response in rice, we performed high-throughput small RNA-sequencing under different nitrate and ammonium treatments. The results demonstrated that only 16 and 11 miRNAs were significantly induced by nitrate and ammonium under short-term treat-ment, respectively. However, 60 differentially expressed miRNAs were found between nitrate and ammonium under long-term cultivation. These results suggested that miRNA response greatly differentiates between nitrate and ammonium treatments. Furthermore, 44 miRNAs were found to be differentially expressed between high- and low-N conditions. Our study reveals comprehensive expression profiling of miRNAs responsive to different N sources and different N treatments, which advances our understanding on the regulation of different N signaling and homeostasis mediated by miRNAs.

Traditional Chinese medicines and their active ingredients sensitize cancer cells to TRAIL-induced apoptosis

The rapidly developing resistance of cancers to chemotherapy agents and the severe cytotoxicity of such agents to normal cells are major stumbling blocks in current cancer treatments.Most current chemotherapy agents have significant cytotoxicity,which leads to devastating adverse effects and results in a substandard quality of life,including increased daily morbidity and premature mortality.The death receptor of tumor necrosis factor-related apoptosis-inducing ligand(TRAIL)can sidestep p53-dependent pathways to induce tumor cell apoptosis without damaging most normal cells.However,various cancer cells can develop resistance to TRAIL-induced apoptosis via different pathways.Therefore,it is critical to find an efficient TRAIL sensitizer to reverse the resistance of tumor cells to TRAIL,and to reinforce TRAIL’s ability to induce tumor cell apoptosis.In recent years,traditional Chinese medicines and their active ingredients have shown great potential to trigger apoptotic cell death in TRAIL-resistant cancer cell lines.This review aims to collate information about Chinese medicines that can effectively reverse the resistance of tumor cells to TRAIL and enhance TRAIL’s ability to induce apoptosis.We explore the therapeutic potential of TRAIL and provide new ideas for the development of TRAIL therapy and the generation of new anticancer drugs for human cancer treatment.This study involved an extensive review of studies obtained from literature searches of electronic databases such as Google Scholar and PubMed."TRAIL sensitize"and"Chinese medicine"were the search keywords.We then isolated newly published studies on the mechanisms of TRAIL-induced apoptosis.The name of each plant was validated using certified databases such as The Plant List.This study indicates that TRAIL can be combined with different Chinese medicine components through intrinsic or extrinsic pathways to promote cancer cell apoptosis.It also demonstrates that the active ingredients of traditional Chinese medicines enhance the sensitivity of cancer cells to TRAIL-mediated apoptosis.This provides useful information regarding traditional Chinese medicine treatment,the development of TRAIL-based therapies,and the treatment of cancer.

The divergence of brassinosteroid sensitivity between rice subspecies involves natural variation conferring altered internal auto-binding of OsBSK2

Japonica/geng and indica/xian are two major rice(Oryza sativa)subspecies with multiple divergent traits,but how these traits are related and interact within each subspecies remains elusive.Brassinosteroids(BRs)are a class of steroid phytohormones that modulate many important agronomic traits in rice.Here,using different physiological assays,we revealed that japonica rice exhibits an overall lower BR sensitivity than indica.Extensive screening of BR signaling genes led to the identification of a set of genes distributed throughout the primary BR signaling pathway with divergent polymorphisms.Among these,we demonstrate that the C38/T variant in BR Signaling Kinase2(OsBSK2),causing the amino acid change P13L,plays a central role in mediating differential BR signaling in japonica and indica rice.OsBSK2in indica plays a greater role in BR signaling than OsB SK2in japonica by affecting the auto-binding and protein accumulation of OsBSK2.Finally,we determined that OsBSK2 is involved in a number of divergent traits in japonica relative to indica rice,including grain shape,tiller number,cold adaptation,and nitrogen-use efficiency.Our study suggests that the natural variation in OsB SK2 plays a key role in the divergence of BR signaling,which underlies multiple divergent traits between japonica and indica.

OsCPL3 is involved in brassinosteroid signaling by regulating OsGSK2 stability

Glycogen synthase kinase 3(GSK3)proteins play key roles in brassinosteroid(BR)signaling during plant growth and development by phosphorylating various substrates.However,how GSK3 protein stability and activity are themselves modulated is not well understood.Here,we demonstrate in vitro and in vivo that C-TERMINAL DOMAIN PHOSPHATASELIKE 3(Os CPL3),a member of the RNA Pol II CTD phosphatase-like family,physically interacts with Os GSK2 in rice(Oryza sativa).Os CPL3 expression was widely detected in various tissues and organs including roots,leaves and lamina joints,and was induced by exogenous BR treatment.Os CPL3 localized to the nucleus,where it dephosphorylated Os GSK2 at the Ser-222 and Thr-284 residues to modulate its protein turnover and kinase activity,in turn affecting the degradation of BRASSINAZOLERESISTANT 1(BZR1)and BR signaling.Loss of Os CPL3 function resulted in higher Os GSK2 abundance and lower Os BZR1 levels,leading to decreased BR responsiveness and alterations in plant morphology including semi-dwarfism,leaf erectness and grain size,which are of fundamental importance to crop productivity.These results reveal a previously unrecognized role for Os CPL3 and add another layer of complexity to the tightly controlled BR signaling pathway in plants.

Atomic-scale tuned interface of nickel-rich cathode for enhanced electrochemical performance in lithium-ion batteries

The Ni-rich layered LiNi_(0.6)Mn_(0.2)Co_(0.2)O_(2)(NMC622)is one promising cathode for lithium-ion batteries(LIBs),but suffers from poor cycling stability under high cutoff potentials.The performance degradation was reflected as capacity fading and voltage drop,having their roots in instable interface of NMC622.Aimed at improving interfacial stability,in this study,we deposited nanoscale ZrO_(2) coatings conformally over NMC622 cathodes using atomic layer deposition(ALD).We found that,under a high cutoff voltage(4.5 V),the ALD ZrO_(2) coatings evidently improved the performance of NMC622 cathode,showing better cyclability and higher sustainable capacity.In addition,the ALD coatings dramatically boosted the rate capability of NMC622.All these compelling performance results are ascribed to the atomic-scale tunable ZrO_(2) coatings via ALD,which create stable interface and thereby inhibit unfavorable evolutions.In the study,we utilize a suite of characterization tools and various analyses to clarify the effects of ALD ZrO_(2) coatings.This study will be helpful for improving the performance of nickel-rich cathodes via interfacial engineering using ALD.

Development and stability analysis of a high-speed train bearing system under variable speed conditions

During a high-speed train operation,the train speed changes frequently,resulting in motion change as a function of time.A dynamic model of a double‐row tapered roller bearing system of a high-speed train under variable speed conditions is developed.The model takes into consideration the structural characteristics of one outer ring and two inner rings of the train bearing.The angle iteration method is used to determine the rotation angle of the roller within any time period,solving the difficult problem of determining the location of the roller.The outer ring and inner ring faults are captured by the model,and the model response is obtained under variable speed conditions.Experiments are carried out under two fault conditions to validate the model results.The simulation results are found to be in good agreement with the results of the formula,and the errors between the simulation results and the experimental results when the bearing has outer and inner ring faults are found to be,respectively,5.97% and 2.59%,which demonstrates the effectiveness of the model.The influence of outer ring and inner ring faults on system stability is analyzed quantitatively using the Lempel–Ziv complexity.The results show that for low train acceleration,the inner ring fault has a more significant effect on the system stability,while for high acceleration,the outer ring fault has a more significant effect.However,when the train acceleration changes,the outer ring has a greater influence.In practice,train acceleration is usually small and does not frequently change in one operation cycle.Therefore,the inner ring fault of the bearing deserves more attention.

Mesh stiffness calculation and vibration analysis of the spur gear pair with tooth crack,considering the misalignment between the base and root circles

An improved variable cross‐section cantilever beam model for evaluating the time‐varying mesh stiffness(TVMS)of the perfect gear tooth is developed in which the tooth number of driving gear is less than 42 and that of driven is more than 42.The TVMS obtained by the proposed method is compared with the result without considering the misalignment between the base circle and gear root.Four types of root crack models and changes inTVMS of 13‐crack levels are presented.The fault vibration characteristic of a single‐stage spur gear reducer with root crack is ana-lyzed and the correctness is qualitatively verified by the vibration signals of an experimental gearbox with crack or missing failure.The results presented in this paper are of great significance for a deep understanding of the possible causes of vibration and noise of gears and provide a theoretical foundation for the fault diagnosis of the gearbox.

Dimension reduction graph-based sparse subspace clustering for intelligent fault identification of rolling element bearings

Sparse subspace clustering(SSC)is a spectral clustering methodology.Since high-dimensional data are often dispersed over the union of many low-dimensional subspaces,their representation in a suitable dictionary is sparse.Therefore,SSC is an effective technology for diagnosing mechanical system faults.Its main purpose is to create a representation model that can reveal the real subspace structure of high-dimensional data,construct a similarity matrix by using the sparse representation coefficients of high-dimensional data,and then cluster the obtained representation coefficients and similarity matrix in subspace.However,the design of SSC algorithm is based on global expression in which each data point is represented by all possible cluster data points.This leads to nonzero terms in nondiagonal blocks of similar matrices,which reduces the recognition performance of matrices.To improve the clustering ability of SSC for rolling bearing and the robustness of the algorithm in the presence of a large number of background noise,a simultaneous dimensionality reduction subspace clustering technology is provided in this work.Through the feature extraction of envelope signal,the dimension of the feature matrix is reduced by singular value decomposition,and the Euclidean distance between samples is replaced by correlation distance.A dimension reduction graph-based SSC technology is established.Simulation and bearing data of Western Reserve University show that the proposed algorithm can improve the accuracy and compactness of clustering.