When applying Grover＇s algorithm to an unordered database, the probabifity of obtaining correct results usually decreases as the quantity of target increases. A four-phase improvement of Grover＇s algorithm is propos...When applying Grover＇s algorithm to an unordered database, the probabifity of obtaining correct results usually decreases as the quantity of target increases. A four-phase improvement of Grover＇s algorithm is proposed to fix the deficiency, and the unitary and the phase-matching condition are also proposed. With this improved scheme, when the proportion of target is over 1/3, the probability of obtaining correct results is greater than 97.82% with only one iteration using two phases. When the computational complexity is O（ √M/N）, the algorithm can succeed with a probability no less than 99.63%.展开更多
Wave propagation in multi-phase porous media is a significant research topic. There are a series of studies about porous media saturated with a single fluid, a solid and a fluid, two fluids, and three fluids. Some gas...Wave propagation in multi-phase porous media is a significant research topic. There are a series of studies about porous media saturated with a single fluid, a solid and a fluid, two fluids, and three fluids. Some gas hydrate-bearing sediments are typical multiphase porous media saturated with a solid(gas hydrates) and two fluids(water and gas). Based on existing theories of porous media, we develop a theory and give a comprehensive analysis of wave propagation in a poroelastic medium saturated with two fluids and a solid. Initially, we establish the constitutive relations and equations of motion. Based on Biot's approach for describing the equations of motion in fluid-saturated porous media at the macroscale,the kinetic energy density, potential energy density, and dissipative energy density are derived. After deriving the equations of motion, a plane wave analysis predicts the existence of four compressional waves, denoted P1, P2, P3, and P4 waves,and two shear waves, denoted S1 and S2 waves. Numerical examples are presented to demonstrate how velocities and attenuations of various waves behave with gas saturation, gas hydrate saturation, and frequency. A model degradation to porous media saturated with a single fluid supports the validity of the theory, which enriches the theory of multiphase porous media and provides a foundation for the evaluation of gas hydrate-bearing sediments.展开更多
间接飞行时间(indirect time of flight,iTOF)相机在三维环境感知领域有着广泛的应用前景。根据iTOF相机成像原理,当曝光时间过大导致相机工作在非线性区时,解算的深度信息也会引入额外的偏差,从而影响测量准确度。为了进一步提高飞行...间接飞行时间(indirect time of flight,iTOF)相机在三维环境感知领域有着广泛的应用前景。根据iTOF相机成像原理,当曝光时间过大导致相机工作在非线性区时,解算的深度信息也会引入额外的偏差,从而影响测量准确度。为了进一步提高飞行时间相机的应用精度,根据飞行时间相机的光学成像机理,提出一种针对飞行时间相机的性能参数测量方法,通过实验和计算间接得到飞行时间深度相机的系统增益等性能参数,将其代入飞行时间相机的光学成像模型,即可得到距离与相机输出灰度值的对应曲线。建模与实验结果的相对误差可以达到20%以内,平均相对误差为0.16%。这些性能参数和仿真模型用于指导iTOF相机在不同场景使用时的积分时间选择,可以有效解决因使用不当引入非线性误差而降低距离测量精度的问题。展开更多
基金Supported by the National Basic Research Program of China under Grant No 2013CB338002the National Natural Science Foundation of China under Grant No 11504430
文摘When applying Grover＇s algorithm to an unordered database, the probabifity of obtaining correct results usually decreases as the quantity of target increases. A four-phase improvement of Grover＇s algorithm is proposed to fix the deficiency, and the unitary and the phase-matching condition are also proposed. With this improved scheme, when the proportion of target is over 1/3, the probability of obtaining correct results is greater than 97.82% with only one iteration using two phases. When the computational complexity is O（ √M/N）, the algorithm can succeed with a probability no less than 99.63%.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 12304496 and 12334019)。
文摘Wave propagation in multi-phase porous media is a significant research topic. There are a series of studies about porous media saturated with a single fluid, a solid and a fluid, two fluids, and three fluids. Some gas hydrate-bearing sediments are typical multiphase porous media saturated with a solid(gas hydrates) and two fluids(water and gas). Based on existing theories of porous media, we develop a theory and give a comprehensive analysis of wave propagation in a poroelastic medium saturated with two fluids and a solid. Initially, we establish the constitutive relations and equations of motion. Based on Biot's approach for describing the equations of motion in fluid-saturated porous media at the macroscale,the kinetic energy density, potential energy density, and dissipative energy density are derived. After deriving the equations of motion, a plane wave analysis predicts the existence of four compressional waves, denoted P1, P2, P3, and P4 waves,and two shear waves, denoted S1 and S2 waves. Numerical examples are presented to demonstrate how velocities and attenuations of various waves behave with gas saturation, gas hydrate saturation, and frequency. A model degradation to porous media saturated with a single fluid supports the validity of the theory, which enriches the theory of multiphase porous media and provides a foundation for the evaluation of gas hydrate-bearing sediments.
文摘间接飞行时间(indirect time of flight,iTOF)相机在三维环境感知领域有着广泛的应用前景。根据iTOF相机成像原理,当曝光时间过大导致相机工作在非线性区时,解算的深度信息也会引入额外的偏差,从而影响测量准确度。为了进一步提高飞行时间相机的应用精度,根据飞行时间相机的光学成像机理,提出一种针对飞行时间相机的性能参数测量方法,通过实验和计算间接得到飞行时间深度相机的系统增益等性能参数,将其代入飞行时间相机的光学成像模型,即可得到距离与相机输出灰度值的对应曲线。建模与实验结果的相对误差可以达到20%以内,平均相对误差为0.16%。这些性能参数和仿真模型用于指导iTOF相机在不同场景使用时的积分时间选择,可以有效解决因使用不当引入非线性误差而降低距离测量精度的问题。
文摘三相四桥臂换流器具备不平衡负载工作能力与三相解耦控制功能,已成为主动配电网领域的研究热点。结合三相四桥臂电压源转换器(voltage source converter,VSC)模型,提出一种分相准比例谐振控制(proportion resonant,PR)直接电流控制策略。针对台区首端电流不平衡问题,提出分相功率补偿思路。先设计补偿功率计算策略,再以功率为控制目标计算输入电流参考值,结合分相准比例谐振直接电流控制,对各相进行功率调节,以达到治理三相电流不平衡的目的。在某仿真软件搭建了基于嵌入式低压直流环节(embedded low voltage DC system,E-LVDC)的低压柔性台区模型。仿真结果表明,台区首端三相电流不平衡度降低,从而验证了所提控制策略的有效性。
