Monitoring the contact state of seal end faces would help the early warning of the seal failure. In the acoustic emission (AE) detection for mechanical seal, the main difficulty is to reduce the background noise and to classify the dispersed features. To solve these problems and achieve higher detection rates, a new approach based on genetic particle filter with autoregression (AR-GPF) and hypersphere support vector machine (HSSVM) is presented. First, AR model is used to build the dynamic state space (DSS) of the AE signal, and GPF is used for signal filtering. Then, multiple features are extracted, and a classification model based on HSSVM is constructed for state recognition. In this approach, AR-GPF is an excellent time-domain method for noise reduction, and HSSVM has advantage on those dispersed features. Finally experimental data shows that the proposed method can effectively detect the contact state of the seal end faces and has higher accuracy rates than some other existing methods.
Active control of the sound radiated from a piston set in a rigid sphere with a set of control point sources around is considered in this paper, where the scattering sound field of the control sound from the rigid sphere has been taken into account to minimize the total radiated sound power. Analytic results of the sound power are obtained and numerical simulations show that it is possible to reduce the radiation from a small piston set in a rigid sphere similar to the size of a human head up to a certain frequency. It is found that the introduction of the scattering object makes significant differences from the active control without scattering objects. This being the case, the scattering object makes the active noise control easier. To increase the global reduction of sound-power output, the optimal number and locations of the control sources and the optimal number and locations of error sensors are discussed. Finally, experiments with one control source and one error sensor around a head simulator have been carried out to verify the simulation results.
China is a top world producer of coal resources with numerous coal‐rich basins country‐wide that also contain coalbed methane (CBM), an unconventional natural gas resource. Recent exploration of coal and CBM resources has also led to the discovery of rare, precious, and scattered metal minerals, including sandstone‐type U and Ga–Ge–Li. High‐grade and industrial‐value deposits have been discovered in the Ordos, Junggar, and other basins across China during exploration for coal resources. Application of coordinated exploration theories and techniques in multiple energy and coal‐associated ore deposits, such as coal and unconventional natural gas in coal, achieves efficient and practical exploration of natural resources. Based on the systematic study of accumulation and occurrence of coal and coal‐associated mineral resources in coal basins, the basic idea of coordinated exploration for coal and coal‐associated deposits is proposed, and multi‐targets and multi‐methods based on a coordinated exploration model of coal‐associated deposits is developed. Coordinated exploration expands the main exploration objective from coal seams to coal‐associated series, extending the exploration target from targeting coal only to coal‐associated deposits. Entrance times for exploration are decreased to realize coordinated exploration for coal, unconventional natural gas and syngenetic/associated mineral resources in coal by implementing a ‘one‐time approach’ —one time in and out of a coal seam to minimize disturbance and time needed for extraction. According to the differences of geological background in China's coal basins, four coordinated exploration model types, including co‐exploration of coal and coal‐associated unconventional natural gas, coal and solid minerals, coal and metal minerals, and coal with water resources are established. Other models discussed include a multi‐target coordinated exploration model for the combination of coal, coal‐associated gas, solid minerals, and metal minerals accordingly. The exploration techniques of coal and coal‐associated resources include regional geological investigation and research and synthetic application of other techniques including seismic surveys, drilling, logging, and geochemical exploration. Particularly, applying the ‘multi‐purpose drill hole’ or reworking coalfield drill holes into parameter wells, adding sample testing and logging wells, determining gas‐bearing layers by logging and gas content measurement, jointly measuring multiple logging parameters, sampling, and testing of coal‐strata help in the exploration and evaluation of coal resources, coal‐associated unconventional natural gas resources, and coal‐associated element minerals. Accordingly, a system of integrated Space–Air–Ground exploration techniques for coordinated exploration of coal and coal‐associated minerals is established. This includes high‐resolution, hyperspectral remote‐sensing technique, high‐precision geophysical exploration and fast, precise drilling, testing of experimental samples, as wel...
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