A Compound fault signal usually contains multiple characteristic signals and strong confusion noise, which makes it difficult to separate week fault signals from them through conventional ways, such as FFT-based envel...A Compound fault signal usually contains multiple characteristic signals and strong confusion noise, which makes it difficult to separate week fault signals from them through conventional ways, such as FFT-based envelope detection, wavelet transform or empirical mode decomposition individually. In order to realize single channel compound fault diagnosis of bearings and improve the diagnosis accuracy, an improved CICA algorithm named constrained independent component analysis based on the energy method(E-CICA) is proposed. With the approach, the single channel vibration signal is firstly decomposed into several wavelet coefficients by discrete wavelet transform(DWT) method for the purpose of obtaining multichannel signals. Then the envelope signals of the reconstructed wavelet coefficients are selected as the input of E-CICA algorithm, which fulfills the requirements that the number of sensors is greater than or equal to that of the source signals and makes it more suitable to be processed by CICA strategy. The frequency energy ratio(ER) of each wavelet reconstructed signal to the total energy of the given synchronous signal is calculated, and then the synchronous signal with maximum ER value is set as the reference signal accordingly. By this way, the reference signal contains a priori knowledge of fault source signal and the influence on fault signal extraction accuracy which is caused by the initial phase angle and the duty ratio of the reference signal in the traditional CICA algorithm is avoided. Experimental results show that E-CICA algorithm can effectively separate out the outer-race defect and the rollers defect from the single channel compound fault and fulfill the needs of compound fault diagnosis of rolling bearings, and the running time is 0.12% of that of the traditional CICA algorithm and the extraction accuracy is 1.4 times of that of CICA as well. The proposed research provides a new method to separate single channel compound fault signals.展开更多
The mechanism of mine water inrushes in coal mines in China differs considerably from that in other countries.In China, most water inrushes occur from floor strata, where the water-inrush sources are karstic limestone...The mechanism of mine water inrushes in coal mines in China differs considerably from that in other countries.In China, most water inrushes occur from floor strata, where the water-inrush sources are karstic limestone aquifers.Our study describes the mechanism of mine water inrushes through a fault in the mine floor using principles of strata mechanics and the path of water inrush from an aquifer to the working face.A criterion to judge whether a ground water inrush will occur through a fault or not is also described, together with a case history of water inflow in the Feicheng coalfield, China.展开更多
Background:We evaluated whether the serum procalcitonin(PCT)level could predict death in severe and critical coronavirus disease 2019(COVID-19)patients.Methods:This study included 129 COVID-19 patients.PCT levels on a...Background:We evaluated whether the serum procalcitonin(PCT)level could predict death in severe and critical coronavirus disease 2019(COVID-19)patients.Methods:This study included 129 COVID-19 patients.PCT levels on admission,treatment,and death were collected.The outcomes were compared.Results:The optimum cutoff value of the PCT level determined by receiver operator characteristic curve analysis to predict all-cause death was 0.085 ng/mL,with sensitivity of 95.7%and specifi city of 72.6%.Overall,78 patients had a PCT level below 0.085 ng/mL and 51 patients had a PCT level of 0.085 ng/mL or greater.High-PCT-level patients had lower levels of lymphocytes(P=0.001)and albumin(P=0.002)and higher levels of creatinine(P=0.024),D-dimer(P=0.002),and white blood cells,neutrocytes(P<0.001),high-sensitivity C-reactive protein(P<0.001),interleukin-6(P<0.001),interleukin-8(P=0.001),interleukin-10(P=0.001),tumor necrosis factor(P<0.001),erythrocyte sedimentation rate(P=0.001),and ferritin(P=0.001).During the 30-day observation period,23 patients died.Mortality was significantly higher in high-PCT-level patients than in patients with low PCT levels(43.1%vs.1.3%;P<0.001).The risks of death(P<0.0001)and ventilator use(P<0.0001)were increased in patients with PCT levels of 0.085 ng/mL or greater.Conclusions:A PCT level of 0.085 ng/mL or greater on admission could effectively predict death and ventilator use in severe and critical COVID-19 patients.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.51475034)
文摘A Compound fault signal usually contains multiple characteristic signals and strong confusion noise, which makes it difficult to separate week fault signals from them through conventional ways, such as FFT-based envelope detection, wavelet transform or empirical mode decomposition individually. In order to realize single channel compound fault diagnosis of bearings and improve the diagnosis accuracy, an improved CICA algorithm named constrained independent component analysis based on the energy method(E-CICA) is proposed. With the approach, the single channel vibration signal is firstly decomposed into several wavelet coefficients by discrete wavelet transform(DWT) method for the purpose of obtaining multichannel signals. Then the envelope signals of the reconstructed wavelet coefficients are selected as the input of E-CICA algorithm, which fulfills the requirements that the number of sensors is greater than or equal to that of the source signals and makes it more suitable to be processed by CICA strategy. The frequency energy ratio(ER) of each wavelet reconstructed signal to the total energy of the given synchronous signal is calculated, and then the synchronous signal with maximum ER value is set as the reference signal accordingly. By this way, the reference signal contains a priori knowledge of fault source signal and the influence on fault signal extraction accuracy which is caused by the initial phase angle and the duty ratio of the reference signal in the traditional CICA algorithm is avoided. Experimental results show that E-CICA algorithm can effectively separate out the outer-race defect and the rollers defect from the single channel compound fault and fulfill the needs of compound fault diagnosis of rolling bearings, and the running time is 0.12% of that of the traditional CICA algorithm and the extraction accuracy is 1.4 times of that of CICA as well. The proposed research provides a new method to separate single channel compound fault signals.
基金Projects Y2007F46 supported by the Natural Science Foundation of Shandong Province20070424005 by the Doctor Disciplines Special Scientific Researc Foundation of the Ministry of Education+1 种基金108158 by the Key Project of the Ministry of Education of China50539080 by the National Natural Scienc Foundation of China
文摘The mechanism of mine water inrushes in coal mines in China differs considerably from that in other countries.In China, most water inrushes occur from floor strata, where the water-inrush sources are karstic limestone aquifers.Our study describes the mechanism of mine water inrushes through a fault in the mine floor using principles of strata mechanics and the path of water inrush from an aquifer to the working face.A criterion to judge whether a ground water inrush will occur through a fault or not is also described, together with a case history of water inflow in the Feicheng coalfield, China.
文摘Background:We evaluated whether the serum procalcitonin(PCT)level could predict death in severe and critical coronavirus disease 2019(COVID-19)patients.Methods:This study included 129 COVID-19 patients.PCT levels on admission,treatment,and death were collected.The outcomes were compared.Results:The optimum cutoff value of the PCT level determined by receiver operator characteristic curve analysis to predict all-cause death was 0.085 ng/mL,with sensitivity of 95.7%and specifi city of 72.6%.Overall,78 patients had a PCT level below 0.085 ng/mL and 51 patients had a PCT level of 0.085 ng/mL or greater.High-PCT-level patients had lower levels of lymphocytes(P=0.001)and albumin(P=0.002)and higher levels of creatinine(P=0.024),D-dimer(P=0.002),and white blood cells,neutrocytes(P<0.001),high-sensitivity C-reactive protein(P<0.001),interleukin-6(P<0.001),interleukin-8(P=0.001),interleukin-10(P=0.001),tumor necrosis factor(P<0.001),erythrocyte sedimentation rate(P=0.001),and ferritin(P=0.001).During the 30-day observation period,23 patients died.Mortality was significantly higher in high-PCT-level patients than in patients with low PCT levels(43.1%vs.1.3%;P<0.001).The risks of death(P<0.0001)and ventilator use(P<0.0001)were increased in patients with PCT levels of 0.085 ng/mL or greater.Conclusions:A PCT level of 0.085 ng/mL or greater on admission could effectively predict death and ventilator use in severe and critical COVID-19 patients.
