The variation of joint groove size during tungsten inert gas （TIG） welding will result in the non-uniform fill of deposited metal. To solve this problem, an adaptive fill control system was developed based on laser ...The variation of joint groove size during tungsten inert gas （TIG） welding will result in the non-uniform fill of deposited metal. To solve this problem, an adaptive fill control system was developed based on laser vision sensing. The system hardware consists of a modular development kit （MDK） as the real-time image capturing system, a computer as the controller, a D/A conversion card as the interface of controlled variable output, and a DC TIG welding system as the controlled device. The system software is developed and the developed feature extraction algorithm and control strategy are of good accuracy and robustness. Experimental results show that the system can implement adaptive fill of melting metal with high stability, reliability and accuracy. The groove is filled well and the quality of the weld formation satisfies the relevant industry criteria.展开更多
The Tahiti-Darwin Southern Oscillation index provided by Climate Analysis Center of USA has been used in numerous studies. But, it has some deficiency. It contains noise mainly due to high month-to-month variability. ...The Tahiti-Darwin Southern Oscillation index provided by Climate Analysis Center of USA has been used in numerous studies. But, it has some deficiency. It contains noise mainly due to high month-to-month variability. In order to reduce the level of noise in the SO index, this paper introduces a fully data-adaptive filter based on singular spectrum analysis. Another interesting aspect of the filter is that it can be used to fill data gaps of the SO index by an iterative process. Eventually, a noiseless long-period data series without any gaps is obtained.展开更多
This paper is mainly focused on the attitude dynamics and control of a fuel-filled flexible spacecraft sub- jected to the thermal payload during eclipse transitions. The flexible appendages are considered as Euler-Ber...This paper is mainly focused on the attitude dynamics and control of a fuel-filled flexible spacecraft sub- jected to the thermal payload during eclipse transitions. The flexible appendages are considered as Euler-Bernoulli beams, and the sloshing liquid is modeled as in two modes multi-spring-mass models; the governing equations of this coupled system are developed by using Hamilton＇s prin- ciple. Numerical results show that the spacecraft attitude responses consist of a quasi-static displacement and superim- posed vibration. Then, we design an adaptive sliding mode and use the Lyapunov approach control law to control the attitude disturbance and suppress the thermal jitter and liq- uid sloshing for the fuel filled flexible spacecraft subject to the thermal payload. Numerical results are presented to verify the efficiency of the hybrid control methods. The results show that the adaptive sliding mode method might be effective to handle the steady-state errors and the Lyapunov control algo- rithm would suppress the residual vibration.展开更多
Efficient and reliable subcarrier power joint allocation is served as a promising problem in cognitive OFDM-based Cognitive Radio Networks (CRN). This paper focuses on optimal subcarrier allocation for OFDM-based CRN....Efficient and reliable subcarrier power joint allocation is served as a promising problem in cognitive OFDM-based Cognitive Radio Networks (CRN). This paper focuses on optimal subcarrier allocation for OFDM-based CRN. We mainly propose subcarrier allocation scheme denoted as Worst Subcarrier Avoiding Water-filling (WSAW), which is based on Rate Adaptive (RA) criterion and three constraints are considered in CRN. The algorithm divides the assignment procedure into two phases. The first phase is an initial subcarrier allocation based on the idea of avoiding selecting the worst subcarrier in order to maximize the transmission rate; while the second phase is an iterative adjustment process which is realized by swapping pairs of subcarriers between arbitrary users. The proposed scheme could assign subcarriers in accordance with channel coherence time. Hence, real time subcarrier allocation could be implemented. Simulation results show that, comparing with the similar existing algorithms, the proposed scheme could achieve larger capacity and a near-optimal BER performance.展开更多
Orthogonal frequency division multiple access (OFDMA) is a promising access technology based on multiple carrier transmission. In this paper, we develop a power and bits allocation scheme for multiuser OFDMA to minimi...Orthogonal frequency division multiple access (OFDMA) is a promising access technology based on multiple carrier transmission. In this paper, we develop a power and bits allocation scheme for multiuser OFDMA to minimize the system margin according to channel state information (CSI). Compared with other OFDM methods, our scheme has higher system capacity and better BER performance.展开更多
针对底水能量充足、裂缝高度发育的礁灰岩油藏,在使用水平井开发的过程中出现含水上升快、开发效果差的问题。在现有控水工艺适应性和应用效果分析基础上,研究形成了包括采用配套研发的充填管柱实现裂缝过饱和充填、优选选择性控水颗粒...针对底水能量充足、裂缝高度发育的礁灰岩油藏,在使用水平井开发的过程中出现含水上升快、开发效果差的问题。在现有控水工艺适应性和应用效果分析基础上,研究形成了包括采用配套研发的充填管柱实现裂缝过饱和充填、优选选择性控水颗粒对水平井筒与井眼之间环空进行封隔和使用电动流入控制装置(Automatic Inflow Control Device,AICD)控水工具实现水平井分段自适应控水的水平井过饱和充填自适应控水技术。通过数值模拟软件形成控水工具优化设计方案并进行现场试验,现场试验表明该技术控水效果明显。该控水技术对裂缝型底水油藏的高效开发具有借鉴意义。展开更多
文摘The variation of joint groove size during tungsten inert gas （TIG） welding will result in the non-uniform fill of deposited metal. To solve this problem, an adaptive fill control system was developed based on laser vision sensing. The system hardware consists of a modular development kit （MDK） as the real-time image capturing system, a computer as the controller, a D/A conversion card as the interface of controlled variable output, and a DC TIG welding system as the controlled device. The system software is developed and the developed feature extraction algorithm and control strategy are of good accuracy and robustness. Experimental results show that the system can implement adaptive fill of melting metal with high stability, reliability and accuracy. The groove is filled well and the quality of the weld formation satisfies the relevant industry criteria.
文摘The Tahiti-Darwin Southern Oscillation index provided by Climate Analysis Center of USA has been used in numerous studies. But, it has some deficiency. It contains noise mainly due to high month-to-month variability. In order to reduce the level of noise in the SO index, this paper introduces a fully data-adaptive filter based on singular spectrum analysis. Another interesting aspect of the filter is that it can be used to fill data gaps of the SO index by an iterative process. Eventually, a noiseless long-period data series without any gaps is obtained.
基金supported by the National Natural Science Foundation of China(NNSFC)(Grant 11472041)the Research Fund for the Doctoral Program of Higher Education of China(Grant 20131101110002)
文摘This paper is mainly focused on the attitude dynamics and control of a fuel-filled flexible spacecraft sub- jected to the thermal payload during eclipse transitions. The flexible appendages are considered as Euler-Bernoulli beams, and the sloshing liquid is modeled as in two modes multi-spring-mass models; the governing equations of this coupled system are developed by using Hamilton＇s prin- ciple. Numerical results show that the spacecraft attitude responses consist of a quasi-static displacement and superim- posed vibration. Then, we design an adaptive sliding mode and use the Lyapunov approach control law to control the attitude disturbance and suppress the thermal jitter and liq- uid sloshing for the fuel filled flexible spacecraft subject to the thermal payload. Numerical results are presented to verify the efficiency of the hybrid control methods. The results show that the adaptive sliding mode method might be effective to handle the steady-state errors and the Lyapunov control algo- rithm would suppress the residual vibration.
基金Supported by the National Natural Science Foundation of China (NSFC) (No. 61102066)the China Postdoctoral Science Foundation (Grant No. 2012M511365)the Scientific Research Project of Zhejiang Provincial Education Department (No. Y201119890)
文摘Efficient and reliable subcarrier power joint allocation is served as a promising problem in cognitive OFDM-based Cognitive Radio Networks (CRN). This paper focuses on optimal subcarrier allocation for OFDM-based CRN. We mainly propose subcarrier allocation scheme denoted as Worst Subcarrier Avoiding Water-filling (WSAW), which is based on Rate Adaptive (RA) criterion and three constraints are considered in CRN. The algorithm divides the assignment procedure into two phases. The first phase is an initial subcarrier allocation based on the idea of avoiding selecting the worst subcarrier in order to maximize the transmission rate; while the second phase is an iterative adjustment process which is realized by swapping pairs of subcarriers between arbitrary users. The proposed scheme could assign subcarriers in accordance with channel coherence time. Hence, real time subcarrier allocation could be implemented. Simulation results show that, comparing with the similar existing algorithms, the proposed scheme could achieve larger capacity and a near-optimal BER performance.
基金Supported by the National Natural Science Foundation of China (No.60372013)
文摘Orthogonal frequency division multiple access (OFDMA) is a promising access technology based on multiple carrier transmission. In this paper, we develop a power and bits allocation scheme for multiuser OFDMA to minimize the system margin according to channel state information (CSI). Compared with other OFDM methods, our scheme has higher system capacity and better BER performance.
文摘针对底水能量充足、裂缝高度发育的礁灰岩油藏,在使用水平井开发的过程中出现含水上升快、开发效果差的问题。在现有控水工艺适应性和应用效果分析基础上,研究形成了包括采用配套研发的充填管柱实现裂缝过饱和充填、优选选择性控水颗粒对水平井筒与井眼之间环空进行封隔和使用电动流入控制装置(Automatic Inflow Control Device,AICD)控水工具实现水平井分段自适应控水的水平井过饱和充填自适应控水技术。通过数值模拟软件形成控水工具优化设计方案并进行现场试验,现场试验表明该技术控水效果明显。该控水技术对裂缝型底水油藏的高效开发具有借鉴意义。
