Large size mechanical seals are one of the most important components used in reactor coolant pumps.However,the hydrodynamic seal rings with wavy face are difficult to machine due to their high hardness and high form a...Large size mechanical seals are one of the most important components used in reactor coolant pumps.However,the hydrodynamic seal rings with wavy face are difficult to machine due to their high hardness and high form accuracy demand.In order to solve this difficult problem,a novel four-axis linkage grinding method using a cup wheel to process the hydrodynamic seal rings by line contact was proposed.A preliminary study indicates that the form error of the ground seal ring surface is extremely sensitive to different linkage relations of the four axes.By taking the center height of the cup wheel and the laws of motion along the X-axis,Z-axis,B-axis and C-axis as control variables,their effects on the principle form error of the ground surface are evaluated.Six implementation strategies are proposed to reach lower principle form errors.It is found that the minimal principle form error is only 9.64 nm and hence its influence on the ground seal ring shape can be neglected in designing an ultra-precision grinding machine.In addition,the results indicate that the position accuracy of the X-axis at the microscale is acceptable no matter which implementation strategy is selected.This study is expected to serve as a theoretical basis for design and development of the four-axis ultra-precision grinding machine.展开更多
This paper proposes a general systems theory for fractals visualising the emergence of successively larger scale fluctuations resulting from the space-time integration of enclosed smaller scale fluctuations. Global gr...This paper proposes a general systems theory for fractals visualising the emergence of successively larger scale fluctuations resulting from the space-time integration of enclosed smaller scale fluctuations. Global gridded time series data sets of monthly mean temperatures for the period 1880- 2007/2008 are analysed to show that data sets and corresponding power spectra exhibit distributions close to the model predicted inverse power law distribution. The model predicted and observed universal spectrum for interannual variability rules out linear secular trends in global monthly mean temperatures. Global warming results in intensification of fluctuations of all scales and manifested immediately in high frequency fluctuations.展开更多
The rectangular optical filter is one of the most important optical switching components in the dense wavelength divi- sion multiplexing （DWDM） fiber-optic communication system and the intelligent optical network. T...The rectangular optical filter is one of the most important optical switching components in the dense wavelength divi- sion multiplexing （DWDM） fiber-optic communication system and the intelligent optical network. The integrated high- order silicon microring resonator （MRR） is one of the best candidates to achieve rectangular filtering spectrum re- sponse. In general, the spectrum response rectangular degree of the single MRR is very low, so it cannot be used in the DWDM system. Using the high-order MRRs, the bandwidth of flat-top pass band, the out-of-band rejection degree and the roll-off coefficient of the edge will be improved obviously. In this paper, a rectangular optical filter based on high- order MRRs with uniform couplers is presented and demonstrated. Using 15 coupled race-track MRRs with 10 pm in radius, the 3 dB flat-top pass band of 2 nm, the out-of-band rejection ratio of 30 dB and the rising and falling edges of 48 dB/nm can be realized successfully.展开更多
In this paper, a technique based on laser self-mixing effect for acquiring pulse wave profile is proposed and demonstrated. For the characteristics of extremely weak vibration in human pulse waves, a method of multipl...In this paper, a technique based on laser self-mixing effect for acquiring pulse wave profile is proposed and demonstrated. For the characteristics of extremely weak vibration in human pulse waves, a method of multiple reflections with external cavity is designed to improve the measurement accuracy to λ/4. Based on the fringe counting algorithm, one period of pulse wave is successfully reconstructed. The measurement results show that the root mean square error(RMSE) of the reconstructed pulse wave is 0.912 μm at sampling rate of 8 k Hz. Besides, the correlation coefficients and heart beats of this method and the traditional photoplethysmography(PPG) measurement are analyzed.展开更多
基金supported by the National Basic Research and Development Program(Grant No.2009CB724306)
文摘Large size mechanical seals are one of the most important components used in reactor coolant pumps.However,the hydrodynamic seal rings with wavy face are difficult to machine due to their high hardness and high form accuracy demand.In order to solve this difficult problem,a novel four-axis linkage grinding method using a cup wheel to process the hydrodynamic seal rings by line contact was proposed.A preliminary study indicates that the form error of the ground seal ring surface is extremely sensitive to different linkage relations of the four axes.By taking the center height of the cup wheel and the laws of motion along the X-axis,Z-axis,B-axis and C-axis as control variables,their effects on the principle form error of the ground surface are evaluated.Six implementation strategies are proposed to reach lower principle form errors.It is found that the minimal principle form error is only 9.64 nm and hence its influence on the ground seal ring shape can be neglected in designing an ultra-precision grinding machine.In addition,the results indicate that the position accuracy of the X-axis at the microscale is acceptable no matter which implementation strategy is selected.This study is expected to serve as a theoretical basis for design and development of the four-axis ultra-precision grinding machine.
文摘This paper proposes a general systems theory for fractals visualising the emergence of successively larger scale fluctuations resulting from the space-time integration of enclosed smaller scale fluctuations. Global gridded time series data sets of monthly mean temperatures for the period 1880- 2007/2008 are analysed to show that data sets and corresponding power spectra exhibit distributions close to the model predicted inverse power law distribution. The model predicted and observed universal spectrum for interannual variability rules out linear secular trends in global monthly mean temperatures. Global warming results in intensification of fluctuations of all scales and manifested immediately in high frequency fluctuations.
基金supported by the National Natural Science Foundation of China(No.61205062)the Scientific Research Project of Hubei Education Department(No.B2015191)the Project of Hubei Province Universities Outstanding Youth Scientific Innovation Team(Nos.T201431 and T201633)
文摘The rectangular optical filter is one of the most important optical switching components in the dense wavelength divi- sion multiplexing （DWDM） fiber-optic communication system and the intelligent optical network. The integrated high- order silicon microring resonator （MRR） is one of the best candidates to achieve rectangular filtering spectrum re- sponse. In general, the spectrum response rectangular degree of the single MRR is very low, so it cannot be used in the DWDM system. Using the high-order MRRs, the bandwidth of flat-top pass band, the out-of-band rejection degree and the roll-off coefficient of the edge will be improved obviously. In this paper, a rectangular optical filter based on high- order MRRs with uniform couplers is presented and demonstrated. Using 15 coupled race-track MRRs with 10 pm in radius, the 3 dB flat-top pass band of 2 nm, the out-of-band rejection ratio of 30 dB and the rising and falling edges of 48 dB/nm can be realized successfully.
基金supported by the National Natural Science Foundation of China(Nos.61675174 and 61308048)
文摘In this paper, a technique based on laser self-mixing effect for acquiring pulse wave profile is proposed and demonstrated. For the characteristics of extremely weak vibration in human pulse waves, a method of multiple reflections with external cavity is designed to improve the measurement accuracy to λ/4. Based on the fringe counting algorithm, one period of pulse wave is successfully reconstructed. The measurement results show that the root mean square error(RMSE) of the reconstructed pulse wave is 0.912 μm at sampling rate of 8 k Hz. Besides, the correlation coefficients and heart beats of this method and the traditional photoplethysmography(PPG) measurement are analyzed.
