The novel method to analyze metallic structure corrosion status was proposed in the presence of stray current in DC mass transit systems. Firstly, the characteristic parameter and the influence parameters for the corr...The novel method to analyze metallic structure corrosion status was proposed in the presence of stray current in DC mass transit systems. Firstly, the characteristic parameter and the influence parameters for the corrosion status were determined. Secondly, an experimental system was established for simulating the corrosion process within the stray current interference. Then, a predictive model for the corrosion status was built, using a support vector machine(SVM) method and experimental data. The data were divided into two sets, including training set and testing set. The training set was used to generate the SVM model and the testing set was used to evaluate the predictive performance of the SVM model. The results show that the relationship between the characteristic parameter and the influence parameters is nonlinear and the SVM model is suitable for predicting the corrosion status.展开更多
The influence of casting parameters on stray grain formation of a unidirectionally solidified superalloy IN738LC casting with three platforms was investigated by using a 3D cellular automaton-finite element （CAFE） m...The influence of casting parameters on stray grain formation of a unidirectionally solidified superalloy IN738LC casting with three platforms was investigated by using a 3D cellular automaton-finite element （CAFE） model in CALCOSOFT package. The model was first validated by comparison of the reported grain structure of AI-7%Si （mass fraction） alloy. Then, the influence of pouring temperature, heat flux of the lateral surface, convection heat coefficient of the cooled chill and mean undercooling of the bulk nucleation on the stray grain formation was studied during the unidirectional solidification. The predictions show that the stray grain formation is obviously sensitive to the pouring temperature, heat flux and mean undercooling of the bulk nucleation. However, increasing the heat convection coefficient has little influence on the stray grain formation.展开更多
The Allan variance analysis method is used to identify the stochastic noise in the stray current sensor. The stray current characteristic is firstly introduced. Then the optical configuration and the signal processing...The Allan variance analysis method is used to identify the stochastic noise in the stray current sensor. The stray current characteristic is firstly introduced. Then the optical configuration and the signal processing method of the stray current sensor are illustrated. Moreover, the cause of the stochastic noise in the stray current sensor is analyzed. The calculation method of the stochastic noise coefficient is presented in detail. And the feasibility of the stochastic noise identification with the Allan variance analysis method is evaluated. Furthermore, the zero-drift signal acquisition experiment is conducted to identify the stochastic noise in the stray current sensor. According to the experimental result, the bias instability noise, the quantization noise and the white noise are identified as the major stochastic noise. Finally, the experiment on the direct-current signal acquisitions is conducted, whose results indicate that the signal drift of the measured direct-current is mainly caused by the major stochastic noise. And the suppression methods of the major stochastic noise are proposed.展开更多
This article aims at throwing some light on the spiritual world of Holden Caulfield,the protagonist of J. D Salinger’s novel The Catcher in the Rye . Holden is a teenager who is considered "mad"in the eyes ...This article aims at throwing some light on the spiritual world of Holden Caulfield,the protagonist of J. D Salinger’s novel The Catcher in the Rye . Holden is a teenager who is considered "mad"in the eyes of many,but who sees the world as full of"madman stuff". He is like a stray dog whose wish of being a"catcher in the rye"is nothing but a strong wish to be caught or cared by the indifferent people around him.展开更多
To solve the problem of stray interference to star point target identification while a star sensor imaging to the sky, a study on space luminous environment adaptability of missile-borne star sensor was carried out. B...To solve the problem of stray interference to star point target identification while a star sensor imaging to the sky, a study on space luminous environment adaptability of missile-borne star sensor was carried out. By Plank blackbody radiation law and some astronomic knowledge, irradiancies of the stray at the star sensor working height were estimated. By relative astrophysical and mathematics knowledge, included angles between the star sensor optical axis point and the stray at any moment were calculated. The calculation correctness was verified with the star map software of Stellarium. By combining the upper analysis with the baffle suppression effect, a real-time model for space luminous environment of missile-borne star sensor was proposed. By signal-noise rate （SNR） criterion, the adaptability of missile-borne star sensor to space luminous environment was studied. As an example, a certain type of star sensor was considered when imaging to the starry sky on June 22, 2011 （the Summer Solstice） and September 20, 2011 （August 23 of the lunar year, last quarter moon） in Beijing. The space luminous environment and the adaptability to it were simulated and analyzed at the star sensor working height. In each period of time, the stray suppression of the baffle is analyzed by comparing the calculated included angle between the star sensor optical axis point and the stray with the shielded provided by system index. When the included angle is larger than the shielded angle and less than 90~, the stray is restrained by the baffle. The stray effect on star point target identification is analyzed by comparing the irradiancy of 6 magnitude star with that of the stray on star sensor sensitization surface. When the irradiancy of 6 magnitude star is 5 times more than that of the stray, there is no effect on the star point target identification. The simulation results are identicat with the actual situation. The space luminous environment of the missile-borne star sensor can be estimated real-timely by this model. The adaptability of the star sensor to space luminous environment can be analyzed conveniently. A basis for determining the relative star sensor indexes, the navigation star chosen strategy and the missile launch window can be provided.展开更多
基金Project(BE2010043) supported by the Technology Support Program of Jiangsu Province,ChinaProject(CXZZ13_0928) supported by the Graduate Education Innovation Project of Jiangsu Province,China
文摘The novel method to analyze metallic structure corrosion status was proposed in the presence of stray current in DC mass transit systems. Firstly, the characteristic parameter and the influence parameters for the corrosion status were determined. Secondly, an experimental system was established for simulating the corrosion process within the stray current interference. Then, a predictive model for the corrosion status was built, using a support vector machine(SVM) method and experimental data. The data were divided into two sets, including training set and testing set. The training set was used to generate the SVM model and the testing set was used to evaluate the predictive performance of the SVM model. The results show that the relationship between the characteristic parameter and the influence parameters is nonlinear and the SVM model is suitable for predicting the corrosion status.
基金Project(08BZ1130100) supported by the Science and Technology Committee of Shanghai,ChinaProject(SHUCX102251) supported by the Innovation Fund for Graduate Student of Shanghai University,China
文摘The influence of casting parameters on stray grain formation of a unidirectionally solidified superalloy IN738LC casting with three platforms was investigated by using a 3D cellular automaton-finite element （CAFE） model in CALCOSOFT package. The model was first validated by comparison of the reported grain structure of AI-7%Si （mass fraction） alloy. Then, the influence of pouring temperature, heat flux of the lateral surface, convection heat coefficient of the cooled chill and mean undercooling of the bulk nucleation on the stray grain formation was studied during the unidirectional solidification. The predictions show that the stray grain formation is obviously sensitive to the pouring temperature, heat flux and mean undercooling of the bulk nucleation. However, increasing the heat convection coefficient has little influence on the stray grain formation.
基金Project(2017QNA13)supported by Fundamental Research Funds for the Central Universities,ChinaProject(PAPD)supported by Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘The Allan variance analysis method is used to identify the stochastic noise in the stray current sensor. The stray current characteristic is firstly introduced. Then the optical configuration and the signal processing method of the stray current sensor are illustrated. Moreover, the cause of the stochastic noise in the stray current sensor is analyzed. The calculation method of the stochastic noise coefficient is presented in detail. And the feasibility of the stochastic noise identification with the Allan variance analysis method is evaluated. Furthermore, the zero-drift signal acquisition experiment is conducted to identify the stochastic noise in the stray current sensor. According to the experimental result, the bias instability noise, the quantization noise and the white noise are identified as the major stochastic noise. Finally, the experiment on the direct-current signal acquisitions is conducted, whose results indicate that the signal drift of the measured direct-current is mainly caused by the major stochastic noise. And the suppression methods of the major stochastic noise are proposed.
文摘This article aims at throwing some light on the spiritual world of Holden Caulfield,the protagonist of J. D Salinger’s novel The Catcher in the Rye . Holden is a teenager who is considered "mad"in the eyes of many,but who sees the world as full of"madman stuff". He is like a stray dog whose wish of being a"catcher in the rye"is nothing but a strong wish to be caught or cared by the indifferent people around him.
文摘To solve the problem of stray interference to star point target identification while a star sensor imaging to the sky, a study on space luminous environment adaptability of missile-borne star sensor was carried out. By Plank blackbody radiation law and some astronomic knowledge, irradiancies of the stray at the star sensor working height were estimated. By relative astrophysical and mathematics knowledge, included angles between the star sensor optical axis point and the stray at any moment were calculated. The calculation correctness was verified with the star map software of Stellarium. By combining the upper analysis with the baffle suppression effect, a real-time model for space luminous environment of missile-borne star sensor was proposed. By signal-noise rate （SNR） criterion, the adaptability of missile-borne star sensor to space luminous environment was studied. As an example, a certain type of star sensor was considered when imaging to the starry sky on June 22, 2011 （the Summer Solstice） and September 20, 2011 （August 23 of the lunar year, last quarter moon） in Beijing. The space luminous environment and the adaptability to it were simulated and analyzed at the star sensor working height. In each period of time, the stray suppression of the baffle is analyzed by comparing the calculated included angle between the star sensor optical axis point and the stray with the shielded provided by system index. When the included angle is larger than the shielded angle and less than 90~, the stray is restrained by the baffle. The stray effect on star point target identification is analyzed by comparing the irradiancy of 6 magnitude star with that of the stray on star sensor sensitization surface. When the irradiancy of 6 magnitude star is 5 times more than that of the stray, there is no effect on the star point target identification. The simulation results are identicat with the actual situation. The space luminous environment of the missile-borne star sensor can be estimated real-timely by this model. The adaptability of the star sensor to space luminous environment can be analyzed conveniently. A basis for determining the relative star sensor indexes, the navigation star chosen strategy and the missile launch window can be provided.
