Gearbox fault diagnosis of rolling mills using multiwavelet sliding window neighboring coefficient denoising and optimal blind deconvolution

Fault diagnosis of rolling mills, especially the main drive gearbox, is of great importance to the high quality products and long-term safe operation. However, the useful fault information is usually submerged in heavy background noise under the severe condition. Thereby, a novel method based on multiwavelet sliding window neighboring coefficient denoising and optimal blind deconvolution is proposed for gearbox fault diagnosis in rolling mills. The emerging multiwavelets can seize the important signal proce...     

The Properties of the Rectangular Arc Ion Plating with Magnetic Filtering Shutter

A major obstacle to the broad application of cathodic arc plasma deposition is the presence of macroparticles. In this paper, the properties of the large rectangular arc ion plating with a magnetic filtering shutter system to filter macroparticles are studied. It is proposed that the macroparticles in the plasma beam are effectively removed with the magnetic filtering shutter system, and the quality of the deposited films is improved.     

Hydrogen-induced cracking and service safety evaluation for precipitation strengthened austenitic stainless steel as hydrogen storage tank

The safety of precipitation strengthened austenitic stainless steels used for hydrogen storage tanks is of great interest. However, their application may face hydrogen damage resulting in hydrogen-induced delayed failure. Results show that over-loading and hydrogen-induced failure always occur at the weld part of the alloy. Hydrogen damage such as microcracks could be observed on the surface of the matrix and the weld during charging even without any applied stress. Hydrogen-induced failure occurred during charging under constant load and the normalized threshold stress decreased exponentially with increasing defined time t_c. It is shown that the threshold stress with no hydrogen-induced failure occurring for expected service life, i.e. forty years, was 713 MPa. Therefore under the service stress, which is less than the threshold stress, 713 MPa, the safety factor of the hydrogen storage tank for hydrogen-induced fracture is great enough to indicate the tank to last for the entire designed service time.     

A novel vibration modeling method for a rotating blade with breathing cracks

This paper proposes a vibration modeling method for a rotating blade with breathing cracks, considering the coupling of the centrifugal effects, the breathing effects and the crack effects. Firstly, considering the combined effects of the centrifugal stress and the bending stress, a crack breathing model for the rotating blade is proposed. Since the crack surface cannot provide the spanwise centrifugal tensile stress, an additional bending moment will be generated at the crack surface in the rotating state.Therefore, an additional bending moment caused by the centrifugal stress is then constructed. In addition, due to the discontinuity of the crack cross section, the additional stiffness caused by the centrifugal effects of the cracked blade will be smaller than that of the normal blade. Therefore, a correction coefficient of the centrifugal stiffness is built. Furthermore, based on the Lagrange equation and the assumed modal method, the vibration equation of the rotating blade with a breathing crack is established(RBC model), and a strategy is constructed for solving this vibration equation. Finally, taking the finite element model(FEM) as a reference, the vibration responses of the RBC model, the open crack model(OC) and the bilinear crack model(BC) are compared. The necessity of the RBC model is illustrated, and the accuracy of the RBC model is verified. The RBC model is a computationally efficient alternative to the finite element analysis for the rotating cracked blade. It can provide an important tool for the vibration modeling and the vibration analysis of the rotating shaft-disk-blade system with cracked blades.     

价值链视角下哈萨克斯坦农业发展影响因素组态与路径研究——基于QCA方法的组态分析

自“一带一路”倡议提出以来，中国与哈萨克斯坦农业合作更加密切，但这种合作能否在激烈的国际市场竞争环境中进一步发展，农业投资领域的合理选择意义重大。论文从价值链视角出发，将农业价值链细分为生产链、物流链、信息链、营销链、创新链5条具有代表性的链条，以2019年哈萨克斯坦17个地州市的数据为研究样本，运用模糊集定性比较分析法（fsQCA）对哈萨克斯坦农业发展的影响因素组态与路径进行分析，研究发现：1）产销互链是形成哈萨克斯坦高水平农业价值链的主要驱动因素，该国高水平农业价值链下存在的两种条件组态分别是“生产链*营销链*（～信息链）*（～创新链）”和“生产链*物流链*营销链*（～创新链）”；2）导致哈萨克斯坦低水平农业价值链的路径则分为落后产能制约型和非农产业导向型，其中落后产能制约型的条件组态包括“（～生产链）*（～物流链）*（～信息链）”和“（～生产链）*物流链*信息链*（～营销链）*创新链”两种条件组态，非农产业导向型的条件组态则是“生产链*物流链*信息链*营销链*创新链”。结果表明：生产链和营销链是哈萨克斯坦目前农业发展的主要驱动因素，而创新链是制约该国农业高质量发展的主要瓶颈，物流链和信息链则具有发展潜力。针对以上结论提出应重点依托哈萨克斯坦部分地州市农业生产和营销方面的优势，积极发挥我国农业技术、信息技术和物流基础设施建设方面的优势，持续深化中哈双方在农业全产业链上的互补性合作，在帮助哈方摆脱“农业转型困境”的同时实现合作共赢。     

材料类专业化学系列课程体系改革的思考与实践

针对传统化学课程设置的弊病,结合材料类专业的特点,建立了符合材料类专业特点的化学系列课程新体系,较好地解决了"少学时"与"宽基础"的矛盾.     

A data-driven threshold for wavelet sliding window denoising in mechanical fault detection

Wavelet denoising is an effective approach to extract fault features from strong background noise.It has been widely used in mechanical fault detection and shown excellent performance.However,traditional thresholds are not suitable for nonstationary signal denoising because they set universal thresholds for different wavelet coefficients.Therefore,a data-driven threshold strategy is proposed in this paper.First,the signal is decomposed into different subbands by wavelet transformation.Then a data-driven threshold is derived by estimating the noise power spectral density in different subbands.Since the data-driven threshold is dependent on the noise estimation and adapted to data,it is more robust and accurate for denoising than traditional thresholds.Meanwhile,sliding window method is adopted to set a flexible local threshold.When this method was applied to simulation signal and an inner race fault diagnostic case of dedusting fan bearing,the proposed method has good result and provides valuable advantages over traditional methods in the fault detection of rotating machines.     

The principle of second generation wavelet for milling cutter breakage detection

Performance degradation or failure of manufacturing equipment will badly influence machining quality.Because of discontinuousness of the milling process,dynamic signals produced in the milling process become non-stationary.This paper indicates that the essence of SGW(second generation wavelet) transform in non-stationary signal processing is the mathematics principle of inner product transform of a dynamic signal with basis functions.Namely,by means of the inner product operation of a signal with basis func...     

220 kV变电站母线失压事故处理与分析

介绍了南郊变电站6.23母线失压事故的处理过程及发生原因,对送电方案的选择、事故处理中遇到的问题进行了详细分析,总结了应吸取的经验和教训,并对在新形势下如何提高电网安全水平提出了建议。     

Maximal-overlap adaptive multiwavelet for detecting transient vibration responses from dynastic signal of rotating machineries

Vibration signal is an important prerequisite for mechanical fault detection.However,early stage defect of rotating machineries is difficult to identify because their incipient energy is interfered with background noises.Multiwavelet is a powerful tool used to conduct non-stationary fault feature extraction.However,the existing predetermined multiwavelet bases are independent of the dynamic response signals.In this paper,a constructing technique of vibration data-driven maximal-overlap adaptive multiwavelet(MOAMW)is proposed for enhancing the extracting performance of fault symptom.It is able to derive an optimal multiwavelet basis that best matches the critical non-stationary and transient fault signatures via genetic algorithm.In this technique,two-scale similarity transform(TST)and symmetric lifting(SymLift)scheme are combined to gain high designing freedom for matching the critical faulty vibration contents in vibration signals based on the maximal fitness objective.TST and SymLift can add modifications to the initial multiwavelet by changing the approximation order and vanishing moment of multiwavelet,respectively.Moreover,the beneficial feature of the MOAWM lies in that the maximal-overlap filterbank structure can enhance the periodic and transient characteristics of the sensor signals and preserve the time and frequency analyzing resolution during the decomposition process.The effectiveness of the proposed technique is validated via a numerical simulation as well as a rolling element bearing with an outer race scrape and a gearbox with rub fault.