摘要 :
At present, there is no common model or approach that can comprehensively cover all stages and influence factors of the general fatigue and crack growth behavior. Classical fatigue models cannot be directly applied to service life...
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At present, there is no common model or approach that can comprehensively cover all stages and influence factors of the general fatigue and crack growth behavior. Classical fatigue models cannot be directly applied to service life prediction under variable amplitude (VA) load spectra without calibration and validation by fatigue tests data. In this research, a generalized correction methodology is proposed, which is divided into life correction rule and crack growth rate (CGR) correction rule, the former is limited to crack initiation models, and the latter is limited to effective block approach (EBA) model, based on the assumption that the uncalibrated classical fatigue models can provide a reasonable prediction for the relative severity of two VA load spectra. The application procedure of generalized correction methodology is detailed, and the way how to select the durability and damage tolerance (DADT) optimal models is provided. Furthermore, sensitivity analyses of model parameters largely affecting the accuracy of life predictions in crack initiation models and EBA models are presented and suggestions on their derivation are given. Finally, case study of some bulkhead representative coupon data under three test spectra at different stress levels is reviewed where the implementation of generalized correction methodology has been comprehensively examined and validated, which is anticipated to provide highly accurate and reliable structural service life assessment for agile fighter aircraft under operational load spectrum.
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摘要 :
Scatter of structural fatigue life is mainly caused by the variability in structures and load-time histories. To study the scatter of structural load-time history of aircrafts in a fleet, this research is focused on analysis of op...
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Scatter of structural fatigue life is mainly caused by the variability in structures and load-time histories. To study the scatter of structural load-time history of aircrafts in a fleet, this research is focused on analysis of operational load spectra at four typical structure details, of which representative coupon fatigue tests have been carried out. First, operational load-time histories at critical locations in question of each aircraft are obtained according to the flight-data based load equation and transfer function relating the monitored load to the critical location stresses. Then, the fatigue notch coefficient in local stress-strain method is calibrated and validated by representative coupon test data and then used to calculate fatigue damage under different structural load-time histories of each aircraft. Finally, statistical analysis of the fatigue damages is conducted on the assumption of log-normal distribution and scatter factor are obtained. It has indicated that there are significant differences in the scatter factor of different structural load-time histories. It may be advisable to fully consider the differences of scatter factor among different structures in structure fatigue life assessment.
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Saikosaponin D is a saponin extract derived from several species of Bupleurum (Umbelliferae), which is used for the treatment of various liver diseases in traditional Chinese medicine. In this study, we report that Saikosaponin D ...
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Saikosaponin D is a saponin extract derived from several species of Bupleurum (Umbelliferae), which is used for the treatment of various liver diseases in traditional Chinese medicine. In this study, we report that Saikosaponin D inhibits the cell growth of human lung cancer cell line A549 and provide a molecular understanding of this effect. The results showed that Saikosaponin D inhibited the proliferation of A549 by inducing apoptosis and blocking cell cycle progression in the G1 phase. ELISA assay showed that Saikosaponin D significantly increased the expression of p53 and p21/WAF1 protein, contributing to cell cycle arrest. An enhancement in Fas/APO-1 and its two form ligands, membrane-bound Fas ligand (mFasL) and soluble Fas ligand (sFasL), as well as Bax protein, was responsible for the apoptotic effect induced by Saikosaponin D. Taken together,our study suggests that the induction of p53 and activity of the Fas/FasL apoptotic system may participate in the antiproliferative activity of Saikosaponin D in A549 cells.
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摘要 :
Saikosaponin D is a saponin extract derived from several species of Bupleurum (Umbelliferae), which is used for the treatment of various liver diseases in traditional Chinese medicine. In this study, we report that Saikosaponin D ...
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Saikosaponin D is a saponin extract derived from several species of Bupleurum (Umbelliferae), which is used for the treatment of various liver diseases in traditional Chinese medicine. In this study, we report that Saikosaponin D inhibits the cell growth of human lung cancer cell line A549 and provide a molecular understanding of this effect. The results showed that Saikosaponin D inhibited the proliferation of A549 by inducing apoptosis and blocking cell cycle progression in the G1 phase. ELISA assay showed that Saikosaponin D significantly increased the expression of p53 and p21/WAFl protein, contributing to cell cycle arrest. An enhancement in Fas/APO-1 and its two form ligands, membrane-bound Fas ligand (mFasL) and soluble Fas ligand (sFasL), as well as Bax protein, was responsible for the apoptotic effect induced by Saikosaponin D. Taken together, our study suggests that the induction of p53 and activity of the Fas/FasL apoptotic system may participate in the antiproliferative activity of Saikosaponin D in A549 cells.
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摘要 :
Saikosaponin D is a saponin extract derived from several species of Bupleurum (Umbelliferae), which is used for the treatment of various liver diseases in traditional Chinese medicine. In this study, we report that Saikosaponin D ...
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Saikosaponin D is a saponin extract derived from several species of Bupleurum (Umbelliferae), which is used for the treatment of various liver diseases in traditional Chinese medicine. In this study, we report that Saikosaponin D inhibits the cell growth of human lung cancer cell line A549 and provide a molecular understanding of this effect. The results showed that Saikosaponin D inhibited the proliferation of A549 by inducing apoptosis and blocking cell cycle progression in the G1 phase. ELISA assay showed that Saikosaponin D significantly increased the expression of p53 and p21/WAF1 protein, contributing to cell cycle arrest. An enhancement in Fas/APO-1 and its two form ligands, membrane-bound Fas ligand (mFasL) and soluble Fas ligand (sFasL), as well as Bax protein, was responsible for the apoptotic effect induced by Saikosaponin D. Taken together, our study suggests that the induction of p53 and activity of the Fas/FasL apoptotic system may participate in the antiproliferative activity of Saikosaponin D in A549 cells.
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A set of GDI system for ethanol injection is installed on a F188 diesel engine, and the diesel supply system of the original diesel engine is used for diesel injection. The computational fluid dynamics software FIRE is adopted to ...
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A set of GDI system for ethanol injection is installed on a F188 diesel engine, and the diesel supply system of the original diesel engine is used for diesel injection. The computational fluid dynamics software FIRE is adopted to establish a 3D combustion model of the ethanol - diesel direct injection engine. The total heat energy of the fuel is equivalent to that of the original diesel engine under the same condition. As the diesel injection starting point is 344℃A and there is simultaneous diesel and ethanol injection, the ethanol injection starting points at 344℃A, 338℃A, 332℃A, 326℃A and 320℃A are subject to 3D simulation for fuel injection, mixed gas formation and combustion and pollutant formation process. The results show that, the earlier the ethanol injection is, the steeper the heat release rate curve during the initial combustion period, the higher the peak value, and the shorter the heat release duration are, and the higher the maximum combustion pressure, the headmost phase of the maximum combustion pressure and the more obvious the premixed combustion are. Earlier ethanol injection starting point and quicker rise of the temperature curve of the cylinder bring the headmost phase of the highest average temperature in the cylinder, and higher average temperature in the cylinder brings higher NO concentration. The ethanol injection starting point shall be earlier than the diesel injection starting point injection, for it is the most favorable for reducing soot generation.
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摘要 :
Aircraft structural load analysis has great significance for individual aircraft life monitoring and structural health management. Multiple linear regression method is commonly used for flight data based in-service structural load...
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Aircraft structural load analysis has great significance for individual aircraft life monitoring and structural health management. Multiple linear regression method is commonly used for flight data based in-service structural load monitoring at critical locations. Based on multi-collinearity diagnosis, residual analysis and stepwise regression, an approach for synthetically building an optimal multiple linear regression load model is proposed in this paper. First of all, the multi-collinearity between independent variables should be diagnosed and attenuated; then, residual analysis is carried out to remove abnormal observations; finally, stepwise regression is used to find the optimal combination of independent variables. Furthermore, it's pointed out that traditional multi-collinearity diagnosis methods have some defects and two more feasible methods for reducing the multi-collinearity are put forward and compared. As a case study, load and stress samples of a critical wing attachment bulkhead location are used to illustrate the procedures of establishing an optimal regression equation. It is proved that the approach can not only ensure the accuracy of aircraft structural load analysis, but also select the parameters of great statistical influence, which has significant engineering practical value.
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The frequency, current, and phase of the transmission of high-voltage power lines are important measures of the quality of the power transmission. Therefore, it is very important to monitor the power transmission quality in real t...
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The frequency, current, and phase of the transmission of high-voltage power lines are important measures of the quality of the power transmission. Therefore, it is very important to monitor the power transmission quality in real time. This thesis designs a portable non-contact online monitoring system for power quality of tramsmission lines. Using electromagnetic inductionprinciple to collect the induced current of AC high-voltage trasmission lines. The signal processing circuit converts the collected current signal into a stable voltage signal and displays the output. The current waverforms in the transmission lines can be monitored in real time. Experimental result show that the system can obtain current amplitude of instantaneous high-voltage transmission line, waveform quality, frequency fluctuations and other information.
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摘要 :
The frequency, current, and phase of the transmission of high-voltage power lines are important measures of the quality of the power transmission. Therefore, it is very important to monitor the power transmission quality in real t...
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The frequency, current, and phase of the transmission of high-voltage power lines are important measures of the quality of the power transmission. Therefore, it is very important to monitor the power transmission quality in real time. This thesis designs a portable non-contact online monitoring system for power quality of tramsmission lines. Using electromagnetic inductionprinciple to collect the induced current of AC high-voltage trasmission lines. The signal processing circuit converts the collected current signal into a stable voltage signal and displays the output. The current waverforms in the transmission lines can be monitored in real time. Experimental result show that the system can obtain current amplitude of instantaneous high-voltage transmission line, waveform quality, frequency fluctuations and other information.
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摘要 :
The frequency, current, and phase of the transmission of high-voltage power lines are important measures of the quality of the power transmission. Therefore, it is very important to monitor the power transmission quality in real t...
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The frequency, current, and phase of the transmission of high-voltage power lines are important measures of the quality of the power transmission. Therefore, it is very important to monitor the power transmission quality in real time. This thesis designs a portable non-contact online monitoring system for power quality of tramsmission lines. Using electromagnetic inductionprinciple to collect the induced current of AC high-voltage trasmission lines. The signal processing circuit converts the collected current signal into a stable voltage signal and displays the output. The current waverforms in the transmission lines can be monitored in real time. Experimental result show that the system can obtain current amplitude of instantaneous high-voltage transmission line, waveform quality, frequency fluctuations and other information.
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