Heterosis is an important biological phenomenon, and it has been used to increase grain yield, quality and resistance to abiotic and biotic stresses in many crops. However, the genetic mechanism of heterosis remains u...Heterosis is an important biological phenomenon, and it has been used to increase grain yield, quality and resistance to abiotic and biotic stresses in many crops. However, the genetic mechanism of heterosis remains unclear up to now. In this study, a set of 184 chromosome segment substitution lines （CSSLs） population, which derived from two inbred lines Ix9801 （the recurrent parent） and Chang 72 （the donor parent）, were used as basal material to construct two test populations with the inbred lines Zheng 58 and Xun 9058. The two test populations were evaluated in two locations over two years, and the heterotic loci for plant height and ear height were identified by comparing the performance of each test hybrid with the corresponding CK at P〈0.05 significant level using one-way ANOVA analysis and Duncan＇s multiple comparisons. There were 24 and 29 different heterotic loci （HL） identified for plant height and ear height in the two populations at two locations over two years. Three HL （hlPH4a, hlPH7c, hlPHlb） for plant height and three （hlEHld, hlEH6b, hlEHlb） for ear height were identified in the CSSLs×Zheng 58 and CSSLs×Xun 9058 populations as contributing highly to heterosis performance of plant height and ear height across four environments. Among the 29 HL identified for ear height, 12 HL （41.4%） shared the same chromosomal region associated with the HL （50.0%） identified for plant height in the same test population and environment.展开更多
This paper presents a refined method for estimating the annual extreme wave heights at a coastal or offshore project site on the basis of the data acquired at some nearby routine hydrographic stations. This method is ...This paper presents a refined method for estimating the annual extreme wave heights at a coastal or offshore project site on the basis of the data acquired at some nearby routine hydrographic stations. This method is based on the orthogonality principle in linear mean square estimation of stochastic processes. The error of the method is analyzed and compared with that of the conventional method. It is found that the method is able to effectively reduce the error so long as some feasible measures are adopted. A simulated test of the method has been conducted in a large scale wind wave flume. The test results are in good agreement with those given by theoretical error analysis. A scheme to implement the method is proposed on the basis of error analysis. The scheme is so designed as to reduce the estimation error as far as possible. This method is also suitable to utilizing satellite wave data for the estimation.展开更多
The accurate control for the vehicle height and leveling adjustment system of an electronic air suspension(EAS) still is a challenging problem that has not been effectively solved in prior researches. This paper propo...The accurate control for the vehicle height and leveling adjustment system of an electronic air suspension(EAS) still is a challenging problem that has not been effectively solved in prior researches. This paper proposes a new adaptive controller to control the vehicle height and to adjust the roll and pitch angles of the vehicle body(leveling control) during the vehicle height adjustment procedures by an EAS system. A nonlinear mechanism model of the full?car vehicle height adjustment system is established to reflect the system dynamic behaviors and to derive the system optimal control law. To deal with the nonlinear characters in the vehicle height and leveling adjustment processes, the nonlinear system model is globally linearized through the state feedback method. On this basis, a fuzzy sliding mode controller(FSMC) is designed to improve the control accuracy of the vehicle height adjustment and to reduce the peak values of the roll and pitch angles of the vehicle body. To verify the effectiveness of the proposed control method more accurately, the full?car EAS system model programmed using AMESim is also given. Then, the co?simulation study of the FSMC performance can be conducted. Finally, actual vehicle tests are performed with a city bus, and the test results illustrate that the vehicle height adjustment performance is effectively guaranteed by the FSMC, and the peak values of the roll and pitch angles of the vehicle body during the vehicle height adjustment procedures are also reduced significantly. This research proposes an effective control methodology for the vehicle height and leveling adjustment system of an EAS, which provides a favorable control performance for the system.展开更多
针对传统郁闭果园空间狭小、枝干遮挡严重,现有割草机株间除草效率低,转场困难等问题,该研究设计了一种适用于丘陵山地的纯电驱动行间与株间避障除草机器人。基于果园作业环境与割草农艺需求,提出机器人总体结构方案,包括底盘驱动系统...针对传统郁闭果园空间狭小、枝干遮挡严重,现有割草机株间除草效率低,转场困难等问题,该研究设计了一种适用于丘陵山地的纯电驱动行间与株间避障除草机器人。基于果园作业环境与割草农艺需求,提出机器人总体结构方案,包括底盘驱动系统、电动推杆割草高度调节系统、转轴弹簧株间被动避障系统以及隔离型DCDC(direct current to direct current converter)高低压系统。为提高运动控制性能,设计了底盘驱动系统模糊PID控制器,并提出一种改进的麻雀搜索算法,融合混沌种群初始化、自适应动态步长及反向学习策略,优化模糊PID的量化因子与比例因子。仿真结果表明,ISSA-FuzzyPID(improved sparrow search algorithm-FuzzyPID)在阶跃信号下的稳态误差较SSA-FuzzyPID(sparrow search algorithm-FuzzyPID)和PID分别降低0.25、1.88 r/min,超调量分别减少6.19%和13.42%,表现出更高的鲁棒性。田间试验显示,机器人在满载除草作业下的平均速度为0.7811 m/s,平均转弯圆直径为984 mm,爬坡角度不低于16.8°,航向角偏差在±3°以内,行间平均除草率达91.97%,平均避障成功率为95.58%,割茬稳定性系数大于85%,割幅利用系数大于90%,各项作业指标均满足设计要求,能够有效实现果园行间与株间除草作业。研究结果可为丘陵山地郁闭果园除草机器人的设计与运动控制提供理论依据。展开更多
基金supported by the National Basic Research Program of China (2014CB138203)the National Natural Science Foundation of China (31271732)
文摘Heterosis is an important biological phenomenon, and it has been used to increase grain yield, quality and resistance to abiotic and biotic stresses in many crops. However, the genetic mechanism of heterosis remains unclear up to now. In this study, a set of 184 chromosome segment substitution lines （CSSLs） population, which derived from two inbred lines Ix9801 （the recurrent parent） and Chang 72 （the donor parent）, were used as basal material to construct two test populations with the inbred lines Zheng 58 and Xun 9058. The two test populations were evaluated in two locations over two years, and the heterotic loci for plant height and ear height were identified by comparing the performance of each test hybrid with the corresponding CK at P〈0.05 significant level using one-way ANOVA analysis and Duncan＇s multiple comparisons. There were 24 and 29 different heterotic loci （HL） identified for plant height and ear height in the two populations at two locations over two years. Three HL （hlPH4a, hlPH7c, hlPHlb） for plant height and three （hlEHld, hlEH6b, hlEHlb） for ear height were identified in the CSSLs×Zheng 58 and CSSLs×Xun 9058 populations as contributing highly to heterosis performance of plant height and ear height across four environments. Among the 29 HL identified for ear height, 12 HL （41.4%） shared the same chromosomal region associated with the HL （50.0%） identified for plant height in the same test population and environment.
文摘This paper presents a refined method for estimating the annual extreme wave heights at a coastal or offshore project site on the basis of the data acquired at some nearby routine hydrographic stations. This method is based on the orthogonality principle in linear mean square estimation of stochastic processes. The error of the method is analyzed and compared with that of the conventional method. It is found that the method is able to effectively reduce the error so long as some feasible measures are adopted. A simulated test of the method has been conducted in a large scale wind wave flume. The test results are in good agreement with those given by theoretical error analysis. A scheme to implement the method is proposed on the basis of error analysis. The scheme is so designed as to reduce the estimation error as far as possible. This method is also suitable to utilizing satellite wave data for the estimation.
基金Supported by National Natural Science Foundation of China(Grant Nos.51375212,61601203)Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions of China+1 种基金Key Research and Development Program of Jiangsu Province(BE2016149)Jiangsu Provincial Natural Science Foundation of China(BK20140555)
文摘The accurate control for the vehicle height and leveling adjustment system of an electronic air suspension(EAS) still is a challenging problem that has not been effectively solved in prior researches. This paper proposes a new adaptive controller to control the vehicle height and to adjust the roll and pitch angles of the vehicle body(leveling control) during the vehicle height adjustment procedures by an EAS system. A nonlinear mechanism model of the full?car vehicle height adjustment system is established to reflect the system dynamic behaviors and to derive the system optimal control law. To deal with the nonlinear characters in the vehicle height and leveling adjustment processes, the nonlinear system model is globally linearized through the state feedback method. On this basis, a fuzzy sliding mode controller(FSMC) is designed to improve the control accuracy of the vehicle height adjustment and to reduce the peak values of the roll and pitch angles of the vehicle body. To verify the effectiveness of the proposed control method more accurately, the full?car EAS system model programmed using AMESim is also given. Then, the co?simulation study of the FSMC performance can be conducted. Finally, actual vehicle tests are performed with a city bus, and the test results illustrate that the vehicle height adjustment performance is effectively guaranteed by the FSMC, and the peak values of the roll and pitch angles of the vehicle body during the vehicle height adjustment procedures are also reduced significantly. This research proposes an effective control methodology for the vehicle height and leveling adjustment system of an EAS, which provides a favorable control performance for the system.
文摘针对传统郁闭果园空间狭小、枝干遮挡严重,现有割草机株间除草效率低,转场困难等问题,该研究设计了一种适用于丘陵山地的纯电驱动行间与株间避障除草机器人。基于果园作业环境与割草农艺需求,提出机器人总体结构方案,包括底盘驱动系统、电动推杆割草高度调节系统、转轴弹簧株间被动避障系统以及隔离型DCDC(direct current to direct current converter)高低压系统。为提高运动控制性能,设计了底盘驱动系统模糊PID控制器,并提出一种改进的麻雀搜索算法,融合混沌种群初始化、自适应动态步长及反向学习策略,优化模糊PID的量化因子与比例因子。仿真结果表明,ISSA-FuzzyPID(improved sparrow search algorithm-FuzzyPID)在阶跃信号下的稳态误差较SSA-FuzzyPID(sparrow search algorithm-FuzzyPID)和PID分别降低0.25、1.88 r/min,超调量分别减少6.19%和13.42%,表现出更高的鲁棒性。田间试验显示,机器人在满载除草作业下的平均速度为0.7811 m/s,平均转弯圆直径为984 mm,爬坡角度不低于16.8°,航向角偏差在±3°以内,行间平均除草率达91.97%,平均避障成功率为95.58%,割茬稳定性系数大于85%,割幅利用系数大于90%,各项作业指标均满足设计要求,能够有效实现果园行间与株间除草作业。研究结果可为丘陵山地郁闭果园除草机器人的设计与运动控制提供理论依据。
