Dynamic positioning systems(DPS)on marine vessels exhibit actuator redundancy,with more actuators than degrees of freedom.A control allocation unit is employed to address this redundancy.Practical systems often featur...Dynamic positioning systems(DPS)on marine vessels exhibit actuator redundancy,with more actuators than degrees of freedom.A control allocation unit is employed to address this redundancy.Practical systems often feature time-varying elements in the effectiveness matrix due to factors such as changing operating conditions,nonlinearity,and disturbances.Additionally,not all thrusters require engagement at each step to counteract disturbances and maintain position.Control efforts can be generated by selecting some thrusters based on their instant effectiveness,while others can remain on standby.Therefore,introducing a control allocation method that calculates the effectiveness matrix online and selects the most efficient thrusters could be effective.This paper introduces a fault-tolerant control allocation strategy for DPS with a varying effectiveness matrix.Specifically,the investigation focuses on a case study featuring eight azimuth thrusters used on a drilling rig.At each time step,the effective matrix is calculated online,followed by the selection of the four most effective thrusters based on the actuator effectiveness index,with the four serving as backups in case of a fault.The proposed strategy has been validated through simulation results,demonstrating advantages such as robustness against changes in the effectiveness matrix and reduced energy usage by the thrusters.展开更多
The consequences of ship collisions with an oil rig, offshore installation or platform can be far more expensive in relation to safety, environment and costs of damage. The damage due to a single incident of an Oil Ri...The consequences of ship collisions with an oil rig, offshore installation or platform can be far more expensive in relation to safety, environment and costs of damage. The damage due to a single incident of an Oil Rig Collision can be catastrophic due to the number of people on board and the added risk of explosion. However, the existing rules and regulations of collisions prevention are insufficient. The purpose of this article is to critically evaluate the risk of ships collisions with offshore platforms and installations and therefore propose an international regulation for the preventions of this type of collisions.展开更多
2The joint opening degree is a critical index for assessing the stability of jointed rock masses,which directly impacts the rock mass quality.It is also a key factor influencing the design of tunnel support structures...2The joint opening degree is a critical index for assessing the stability of jointed rock masses,which directly impacts the rock mass quality.It is also a key factor influencing the design of tunnel support structures.Hammer and rotary drilling rigs,commonly employed as rock-breaking equipment in tunneling,inevitably encounter joints with varying opening degrees during construction.This research aims to enhance the sampling frequency of hammer and rotary drilling rigs and optimize the joint detection algorithm,thereby equipping these rigs with the capability to detect joint opening degrees.This paper develops high-frequency acquisition equipment for drilling parameters to realize millimeter-level data acquisition.Drilling experiments on jointed rock mass are conducted under conditions corresponding to joint opening degrees of 1 mm,3 mm,and 5 mm.The relationships among joint opening degree,drilling parameters,and width of rock failure region are investigated.A joint opening degree detection algorithm is proposed based on the drilling parameters and moving average filter.The results indicate that the curves of penetration velocity and rotary pressure along the drilling direction exhibit a three-segment distribution,i.e."stable segment-adjustment segment-stable segment".The variation curves of drilling parameters display a“velocity mountain”and a“pressure valley”in the failure region.The relative errors in joint opening degree estimation based on penetration velocity and rotary pressure range from 3.4%to 32%and from 6%to 35%,with average relative errors of 12.95%and 16.24%,respectively.展开更多
RIG-I样受体(RIG-I like receptors,RLRs)是天然免疫系统中一类重要模式识别受体,在细胞天然免疫应答中发挥重要的作用,LGP2是RLRs家族成员之一,对RLRs信号转导有正向和负向调控的双重作用。LGP2依据感染病毒种类的不同发挥着不同的调...RIG-I样受体(RIG-I like receptors,RLRs)是天然免疫系统中一类重要模式识别受体,在细胞天然免疫应答中发挥重要的作用,LGP2是RLRs家族成员之一,对RLRs信号转导有正向和负向调控的双重作用。LGP2依据感染病毒种类的不同发挥着不同的调控作用,但详细作用机制不明确。随着研究的深入,LGP2在天然免疫应答中的作用愈发重要。本文就近年来对LGP2参与RLRs介导的抗病毒天然免疫应答的调控及在不同病毒感染宿主中所起的作用作一综述,以期为LGP2深入研究提供参考。展开更多
As a high quality seismic imaging method, full waveform inversion （FWI） can accurately reconstruct the physical parameter model for the subsurface medium. However, application of the FWI in seismic data processing i...As a high quality seismic imaging method, full waveform inversion （FWI） can accurately reconstruct the physical parameter model for the subsurface medium. However, application of the FWI in seismic data processing is computationally expensive, especially for the three-dimension complex medium inversion. Introducing blended source technology into the frequency-domain FWI can greatly reduce the computational burden and improve the efficiency of the inversion. However, this method has two issues： first, crosstalk noise is caused by interference between the sources involved in the encoding, resulting in an inversion result with some artifacts; second, it is more sensitive to ambient noise compared to conventional FWI, therefore noisy data results in a poor inversion. This paper introduces a frequency-group encoding method to suppress crosstalk noise, and presents a frequency- domain auto-adapting FWI based on source-encoding technology. The conventional FWI method and source-encoding based FWI method are combined using an auto-adapting mechanism. This improvement can both guarantee the quality of the inversion result and maximize the inversion efficiency.展开更多
文摘Dynamic positioning systems(DPS)on marine vessels exhibit actuator redundancy,with more actuators than degrees of freedom.A control allocation unit is employed to address this redundancy.Practical systems often feature time-varying elements in the effectiveness matrix due to factors such as changing operating conditions,nonlinearity,and disturbances.Additionally,not all thrusters require engagement at each step to counteract disturbances and maintain position.Control efforts can be generated by selecting some thrusters based on their instant effectiveness,while others can remain on standby.Therefore,introducing a control allocation method that calculates the effectiveness matrix online and selects the most efficient thrusters could be effective.This paper introduces a fault-tolerant control allocation strategy for DPS with a varying effectiveness matrix.Specifically,the investigation focuses on a case study featuring eight azimuth thrusters used on a drilling rig.At each time step,the effective matrix is calculated online,followed by the selection of the four most effective thrusters based on the actuator effectiveness index,with the four serving as backups in case of a fault.The proposed strategy has been validated through simulation results,demonstrating advantages such as robustness against changes in the effectiveness matrix and reduced energy usage by the thrusters.
文摘The consequences of ship collisions with an oil rig, offshore installation or platform can be far more expensive in relation to safety, environment and costs of damage. The damage due to a single incident of an Oil Rig Collision can be catastrophic due to the number of people on board and the added risk of explosion. However, the existing rules and regulations of collisions prevention are insufficient. The purpose of this article is to critically evaluate the risk of ships collisions with offshore platforms and installations and therefore propose an international regulation for the preventions of this type of collisions.
基金the National Natural Science Foundation of China(No.52378411)for the support in this research.
文摘2The joint opening degree is a critical index for assessing the stability of jointed rock masses,which directly impacts the rock mass quality.It is also a key factor influencing the design of tunnel support structures.Hammer and rotary drilling rigs,commonly employed as rock-breaking equipment in tunneling,inevitably encounter joints with varying opening degrees during construction.This research aims to enhance the sampling frequency of hammer and rotary drilling rigs and optimize the joint detection algorithm,thereby equipping these rigs with the capability to detect joint opening degrees.This paper develops high-frequency acquisition equipment for drilling parameters to realize millimeter-level data acquisition.Drilling experiments on jointed rock mass are conducted under conditions corresponding to joint opening degrees of 1 mm,3 mm,and 5 mm.The relationships among joint opening degree,drilling parameters,and width of rock failure region are investigated.A joint opening degree detection algorithm is proposed based on the drilling parameters and moving average filter.The results indicate that the curves of penetration velocity and rotary pressure along the drilling direction exhibit a three-segment distribution,i.e."stable segment-adjustment segment-stable segment".The variation curves of drilling parameters display a“velocity mountain”and a“pressure valley”in the failure region.The relative errors in joint opening degree estimation based on penetration velocity and rotary pressure range from 3.4%to 32%and from 6%to 35%,with average relative errors of 12.95%and 16.24%,respectively.
文摘RIG-I样受体(RIG-I like receptors,RLRs)是天然免疫系统中一类重要模式识别受体,在细胞天然免疫应答中发挥重要的作用,LGP2是RLRs家族成员之一,对RLRs信号转导有正向和负向调控的双重作用。LGP2依据感染病毒种类的不同发挥着不同的调控作用,但详细作用机制不明确。随着研究的深入,LGP2在天然免疫应答中的作用愈发重要。本文就近年来对LGP2参与RLRs介导的抗病毒天然免疫应答的调控及在不同病毒感染宿主中所起的作用作一综述,以期为LGP2深入研究提供参考。
基金financially supported by the National Natural Science Foundation of China(No.41074075/D0409)the National Science and Technology Major Project(No.2011ZX05025-001-04)
文摘As a high quality seismic imaging method, full waveform inversion （FWI） can accurately reconstruct the physical parameter model for the subsurface medium. However, application of the FWI in seismic data processing is computationally expensive, especially for the three-dimension complex medium inversion. Introducing blended source technology into the frequency-domain FWI can greatly reduce the computational burden and improve the efficiency of the inversion. However, this method has two issues： first, crosstalk noise is caused by interference between the sources involved in the encoding, resulting in an inversion result with some artifacts; second, it is more sensitive to ambient noise compared to conventional FWI, therefore noisy data results in a poor inversion. This paper introduces a frequency-group encoding method to suppress crosstalk noise, and presents a frequency- domain auto-adapting FWI based on source-encoding technology. The conventional FWI method and source-encoding based FWI method are combined using an auto-adapting mechanism. This improvement can both guarantee the quality of the inversion result and maximize the inversion efficiency.
