Wind turbines are usually designed and operated with fixed startup speed. It could perform startup and shutdown operations repeatedly when the wind fluctuates around the startup speed. The excessive stress induced by ...Wind turbines are usually designed and operated with fixed startup speed. It could perform startup and shutdown operations repeatedly when the wind fluctuates around the startup speed. The excessive stress induced by frequent startup and shutdown could enhance the likelihood of component failure and hence negatively impact the availability of a wind turbine. Startup speed with dead band is proposed in this article to prevent the wind turbine from frequent startup. 22 years wind data from the Cheung Chau wind station in Hong Kong are analyzed to evaluate the reduction in the number of startup and potential loss of wind power production using the proposed approach. Numerical simulation suggests that the number of startup could be reduced by half with trivial reduction in potential wind power generation in most of investigated sites once an appropriate dead band is adopted.展开更多
The dynamic differences between a living human brain and a clinically dead (fixed) human brain were measured over international Quantitative Electroencephalographic (QEEG) sites for 1 Hz increments between 1 Hz and 50...The dynamic differences between a living human brain and a clinically dead (fixed) human brain were measured over international Quantitative Electroencephalographic (QEEG) sites for 1 Hz increments between 1 Hz and 50 Hz. Although the expected greater power (μV2•Hz<sup>–</sup><sup>1</sup>) for the living brain was apparent, the difference was particularly obvious for theta and low beta bands. The integrated square root values over the entire band indicated the difference in intrinsic charge-based energy between the living (higher) and dead brain was ~2•10<sup>–</sup><sup>23</sup> J. This quantity is remarkably proximal to the Cosmic Background Microwave value and would be consistent with the Hameroff-Penrose definition of consciousness that suggests a permeating presence derived from discrete physical events. A power value obtained by multiplying this increment of energy by the frequency of the universal hydrogen line resulted in ~10<sup>–</sup><sup>12</sup> W•m<sup>–</sup><sup>2</sup> when applied to the surface area of the human cerebrum. This value is the median flux density that has been measured from human brains during cognition and defines the ultra-weak photon emissions displayed by cells, tissue, and organisms. These results suggest that modern technology may now be sufficiently precise to discern the critical parameters that differentiate the living brain from the fixed “dead” brain. This information might be useful for future designs of virtual consciousness and simulations within cerebral space.展开更多
发电机组的一次调频控制回路中由于数字电液调节系统与机械液压调节系统的并存,使得本应发挥高灵敏度作用的 DEH 调节系统中设置了和机械液压机组相同的调频死区。考虑到调频死区这一非线性环节的存在使二次调频回路中控制器的受控对象...发电机组的一次调频控制回路中由于数字电液调节系统与机械液压调节系统的并存,使得本应发挥高灵敏度作用的 DEH 调节系统中设置了和机械液压机组相同的调频死区。考虑到调频死区这一非线性环节的存在使二次调频回路中控制器的受控对象发生了改变,因此需要用相应的非线性控制的方法来选择二次调频控制回路中的 PI 控制器的参数。该文研究了调频死区对二次调频回路中的 PI 控制器的受控对象特性的影响,用 Popov 稳定判据作为选择 PI 参数使系统稳定的数学工具,讨论了 PI 参数的变化对系统频率控制质量的影响。展开更多
文摘Wind turbines are usually designed and operated with fixed startup speed. It could perform startup and shutdown operations repeatedly when the wind fluctuates around the startup speed. The excessive stress induced by frequent startup and shutdown could enhance the likelihood of component failure and hence negatively impact the availability of a wind turbine. Startup speed with dead band is proposed in this article to prevent the wind turbine from frequent startup. 22 years wind data from the Cheung Chau wind station in Hong Kong are analyzed to evaluate the reduction in the number of startup and potential loss of wind power production using the proposed approach. Numerical simulation suggests that the number of startup could be reduced by half with trivial reduction in potential wind power generation in most of investigated sites once an appropriate dead band is adopted.
文摘The dynamic differences between a living human brain and a clinically dead (fixed) human brain were measured over international Quantitative Electroencephalographic (QEEG) sites for 1 Hz increments between 1 Hz and 50 Hz. Although the expected greater power (μV2•Hz<sup>–</sup><sup>1</sup>) for the living brain was apparent, the difference was particularly obvious for theta and low beta bands. The integrated square root values over the entire band indicated the difference in intrinsic charge-based energy between the living (higher) and dead brain was ~2•10<sup>–</sup><sup>23</sup> J. This quantity is remarkably proximal to the Cosmic Background Microwave value and would be consistent with the Hameroff-Penrose definition of consciousness that suggests a permeating presence derived from discrete physical events. A power value obtained by multiplying this increment of energy by the frequency of the universal hydrogen line resulted in ~10<sup>–</sup><sup>12</sup> W•m<sup>–</sup><sup>2</sup> when applied to the surface area of the human cerebrum. This value is the median flux density that has been measured from human brains during cognition and defines the ultra-weak photon emissions displayed by cells, tissue, and organisms. These results suggest that modern technology may now be sufficiently precise to discern the critical parameters that differentiate the living brain from the fixed “dead” brain. This information might be useful for future designs of virtual consciousness and simulations within cerebral space.
文摘发电机组的一次调频控制回路中由于数字电液调节系统与机械液压调节系统的并存,使得本应发挥高灵敏度作用的 DEH 调节系统中设置了和机械液压机组相同的调频死区。考虑到调频死区这一非线性环节的存在使二次调频回路中控制器的受控对象发生了改变,因此需要用相应的非线性控制的方法来选择二次调频控制回路中的 PI 控制器的参数。该文研究了调频死区对二次调频回路中的 PI 控制器的受控对象特性的影响,用 Popov 稳定判据作为选择 PI 参数使系统稳定的数学工具,讨论了 PI 参数的变化对系统频率控制质量的影响。
