Balanced scorecard is a strategic information system and a performance measurement system. It integrates almost all the interests of stakeholders and mainly comprises four perspectives： management, operational, marke...Balanced scorecard is a strategic information system and a performance measurement system. It integrates almost all the interests of stakeholders and mainly comprises four perspectives： management, operational, marketing, and knowledge.展开更多
The aerodynamic performances of a passenger car and a box car with different heights of windbreak walls under strong wind were studied using the numerical simulations, and the changes of aerodynamic side force, lift f...The aerodynamic performances of a passenger car and a box car with different heights of windbreak walls under strong wind were studied using the numerical simulations, and the changes of aerodynamic side force, lift force and overturning moment with different wind speeds and wall heights were calculated. According to the principle of static moment balance of vehicles, the overturning coefficients of trains with different wind speeds and wall heights were obtained. Based on the influence of wind speed and wall height on the aerodynamic performance and the overturning stability of trains, a method of determination of the load balance ranges for the train operation safety was proposed, which made the overturning coefficient have nearly closed interval. A min(|A1|+|A2|), s.t. |A1|→|A2|(A1 refers to the downwind overturning coefficient and A2 refers to the upwind overturning coefficient)was found. This minimum value helps to lower the wall height as much as possible, and meanwhile, guarantees the operation safety of various types of trains under strong wind. This method has been used for the construction and improvement of the windbreak walls along the Lanzhou–Xinjiang railway(from Lanzhou to Urumqi, China).展开更多
Dispersive optical phased arrays(DOPAs)offer a method for fast 2D beam scanning for solid-state LiDAR with a pure passive operation,and therefore low control complexity and low power consumption.However,in terms of sc...Dispersive optical phased arrays(DOPAs)offer a method for fast 2D beam scanning for solid-state LiDAR with a pure passive operation,and therefore low control complexity and low power consumption.However,in terms of scalability,state-of-the-art DOPAs do not easily achieve a balanced performance over the specifications of longrange LiDAR,including the number of pixels(resolvable points)and beam quality.Here,we experimentally demonstrate the pixelated DOPA concept,which overcomes the scaling challenges of classical(continuous)DOPAs by introducing a new design degree of freedom:the discretization of the optical delay lines distribution network into blocks.We also present the first demonstration of the unbalanced splitter tree architecture for the DOPA distribution network,incorporated in both the continuous DOPA and the pixelated DOPA variations.The small-scale demonstration circuits can scan over a field of view of 15°×7.2°,where the continuous DOPA provides 16×25 pixels,while the pixelated DOPA provides 4×25 pixels,for a 1500 to 1600 nm wavelength sweep.The pixelated DOPA exhibits a side lobe suppression ratio with a median of 7.6 dB,which is higher than that of the continuous version,with a median of 3.6 dB.In addition,the ratio of the main beam to the background radiation pattern is 11 dB(median value)for the pixelated DOPA,while for the continuous DOPA,it is 9.5 dB.This is an indication of a higher beam quality and lower phase errors in the pixelated DOPA.The degree of discretization,combined with other design parameters,will potentially enable better control over the beam quality,while setting practical values for the number of pixels for large-scale DOPAs.展开更多
In order to improve performance and security of image encryption algorithm effectively based on chaotic sequences, an extended chaotic sequence generating method is presented based on logistic chaotic system using Ber...In order to improve performance and security of image encryption algorithm effectively based on chaotic sequences, an extended chaotic sequence generating method is presented based on logistic chaotic system using Bernstein form Bézier curve generating algorithm. In order to test the pseudorandom performance of the extended chaotic sequence, we also analyze random performance, autocorrelation performance, and balance performance of the extended chaotic sequence. Simulation results show that the extended chaotic sequence generated using our method is pseudorandom and its correlation performance and balance performance are good. As an application, we apply the extended chaotic sequence in image encryption algorithm, the simulation results show that the performance of the encrypted image using our method is better than that using logistic chaotic sequence.展开更多
基金This paper is supported by National Social Science Foundation of China （No.96AJB043） and the Fund for Young Faculty of Tianjin University （No.5110104）.
文摘Balanced scorecard is a strategic information system and a performance measurement system. It integrates almost all the interests of stakeholders and mainly comprises four perspectives： management, operational, marketing, and knowledge.
基金Project(U1334203) supported by the National Natural Science Foundation of China
文摘The aerodynamic performances of a passenger car and a box car with different heights of windbreak walls under strong wind were studied using the numerical simulations, and the changes of aerodynamic side force, lift force and overturning moment with different wind speeds and wall heights were calculated. According to the principle of static moment balance of vehicles, the overturning coefficients of trains with different wind speeds and wall heights were obtained. Based on the influence of wind speed and wall height on the aerodynamic performance and the overturning stability of trains, a method of determination of the load balance ranges for the train operation safety was proposed, which made the overturning coefficient have nearly closed interval. A min(|A1|+|A2|), s.t. |A1|→|A2|(A1 refers to the downwind overturning coefficient and A2 refers to the upwind overturning coefficient)was found. This minimum value helps to lower the wall height as much as possible, and meanwhile, guarantees the operation safety of various types of trains under strong wind. This method has been used for the construction and improvement of the windbreak walls along the Lanzhou–Xinjiang railway(from Lanzhou to Urumqi, China).
文摘Dispersive optical phased arrays(DOPAs)offer a method for fast 2D beam scanning for solid-state LiDAR with a pure passive operation,and therefore low control complexity and low power consumption.However,in terms of scalability,state-of-the-art DOPAs do not easily achieve a balanced performance over the specifications of longrange LiDAR,including the number of pixels(resolvable points)and beam quality.Here,we experimentally demonstrate the pixelated DOPA concept,which overcomes the scaling challenges of classical(continuous)DOPAs by introducing a new design degree of freedom:the discretization of the optical delay lines distribution network into blocks.We also present the first demonstration of the unbalanced splitter tree architecture for the DOPA distribution network,incorporated in both the continuous DOPA and the pixelated DOPA variations.The small-scale demonstration circuits can scan over a field of view of 15°×7.2°,where the continuous DOPA provides 16×25 pixels,while the pixelated DOPA provides 4×25 pixels,for a 1500 to 1600 nm wavelength sweep.The pixelated DOPA exhibits a side lobe suppression ratio with a median of 7.6 dB,which is higher than that of the continuous version,with a median of 3.6 dB.In addition,the ratio of the main beam to the background radiation pattern is 11 dB(median value)for the pixelated DOPA,while for the continuous DOPA,it is 9.5 dB.This is an indication of a higher beam quality and lower phase errors in the pixelated DOPA.The degree of discretization,combined with other design parameters,will potentially enable better control over the beam quality,while setting practical values for the number of pixels for large-scale DOPAs.
基金the National Natural Science Foundation of China (No. 60572133)the Scientific Research Fund of Education Department of Shaanxi Province (No.06JK193)
文摘In order to improve performance and security of image encryption algorithm effectively based on chaotic sequences, an extended chaotic sequence generating method is presented based on logistic chaotic system using Bernstein form Bézier curve generating algorithm. In order to test the pseudorandom performance of the extended chaotic sequence, we also analyze random performance, autocorrelation performance, and balance performance of the extended chaotic sequence. Simulation results show that the extended chaotic sequence generated using our method is pseudorandom and its correlation performance and balance performance are good. As an application, we apply the extended chaotic sequence in image encryption algorithm, the simulation results show that the performance of the encrypted image using our method is better than that using logistic chaotic sequence.
