The nonlinear branching process with immigration is constructed as the pathwise unique solution of a stochastic integral equation driven by Poisson random measures. Some criteria for the regularity, recurrence, ergodi...The nonlinear branching process with immigration is constructed as the pathwise unique solution of a stochastic integral equation driven by Poisson random measures. Some criteria for the regularity, recurrence, ergodicity and strong ergodicity of the process are then established.展开更多
Korean larch(Larix olgensis)is one of the main tree species for aff orestation and timber production in northeast China.However,its timber quality and growth ability are largely infl uenced by crown size,structure and...Korean larch(Larix olgensis)is one of the main tree species for aff orestation and timber production in northeast China.However,its timber quality and growth ability are largely infl uenced by crown size,structure and shape.The majority of crown models are static models based on tree size and stand characteristics from temporary sample plots,but crown dynamic models has seldom been constructed.Therefore,this study aimed to develop height to crown base(HCB)and crown length(CL)dynamic models using the branch mortality technique for a Korean larch plantation.The nonlinear mixed-eff ects model with random eff ects,variance functions and correlation structures,was used to build HCB and CL dynamic models.The data were obtained from 95 sample trees of 19 plots in Meng JiaGang forest farm in Northeast China.The results showed that HCB progressively increases as tree age,tree height growth(HT growth)and diameter at breast height growth(DBH growth).The CL was increased with tree age in 20 years ago,and subsequently stabilized.HT growth,DBH growth stand basal area(BAS)and crown competition factor(CCF)signifi cantly infl uenced HCB and CL.The HCB was positively correlated with BAS,HT growth and DBH growth,but negatively correlated with CCF.The CL was positively correlated with BAS and CCF,but negatively correlated with DBH growth.Model fi tting and validation confi rmed that the mixed-eff ects model considering the stand and tree level random eff ects was accurate and reliable for predicting the HCB and CL dynamics.However,the models involving adding variance functions and time series correlation structure could not completely remove heterogeneity and autocorrelation,and the fi tting precision of the models was reduced.Therefore,from the point of view of application,we should take care to avoid setting up over-complex models.The HCB and CL dynamic models in our study may also be incorporated into stand growth and yield model systems in China.展开更多
具备纯立方刚度的非线性能量阱(nonlinear energy sink,NES)具有轻质、宽频减振等优点,但在激励较大的情况下,会引起系统的稳定高分支响应。为扩大纯立方刚度NES的有效激励范围,提出一种磁力双稳态NES。在简谐激励下,通过基于龙格-库塔...具备纯立方刚度的非线性能量阱(nonlinear energy sink,NES)具有轻质、宽频减振等优点,但在激励较大的情况下,会引起系统的稳定高分支响应。为扩大纯立方刚度NES的有效激励范围,提出一种磁力双稳态NES。在简谐激励下,通过基于龙格-库塔法的程序分析了安装磁力双稳态NES系统的动态行为,研究了永磁铁的吸力对系统高分支响应的影响。结果表明:磁力双稳态NES在激励幅值较小时,拥有优于纯立方刚度NES的吸振效果;在激励幅值较大时,可抑制系统稳定的高分支响应,从而扩大有效激励范围。因此,磁力双稳态NES具有更广阔的应用前景和更好的吸振效果,可在某些较大激励环境下为结构的振动控制提供更有效的解决方案。展开更多
This paper presents a dual-nonlinear branch linearizer for reducing the corrected amplitude overshoot of conventional single nonlinear branch linearizer. Theoretical analysis is carried out, the analysis is verified b...This paper presents a dual-nonlinear branch linearizer for reducing the corrected amplitude overshoot of conventional single nonlinear branch linearizer. Theoretical analysis is carried out, the analysis is verified by simulation, and a prototype of Ka band 25.28~26.08 GHz dual nonlinear branch linearizer is achieved. It indicates that the corrected amplitude overshoot is less than 0.5 dB, the C/I3 improvement is more than 10 dB related to a single carrier IBO 9 dB, when it is linked and tested for 50 W spacebrone Travelling Wave Tube Amplifier(TWTA).展开更多
基金Supported by NSFC(Grant Nos.1131003,11626245 and 11571043)
文摘The nonlinear branching process with immigration is constructed as the pathwise unique solution of a stochastic integral equation driven by Poisson random measures. Some criteria for the regularity, recurrence, ergodicity and strong ergodicity of the process are then established.
基金supported by the National Key Research and Development Program of China(2017YFD0600401)the Fundamental Research Funds for the Central Universities(2572019CP08)
文摘Korean larch(Larix olgensis)is one of the main tree species for aff orestation and timber production in northeast China.However,its timber quality and growth ability are largely infl uenced by crown size,structure and shape.The majority of crown models are static models based on tree size and stand characteristics from temporary sample plots,but crown dynamic models has seldom been constructed.Therefore,this study aimed to develop height to crown base(HCB)and crown length(CL)dynamic models using the branch mortality technique for a Korean larch plantation.The nonlinear mixed-eff ects model with random eff ects,variance functions and correlation structures,was used to build HCB and CL dynamic models.The data were obtained from 95 sample trees of 19 plots in Meng JiaGang forest farm in Northeast China.The results showed that HCB progressively increases as tree age,tree height growth(HT growth)and diameter at breast height growth(DBH growth).The CL was increased with tree age in 20 years ago,and subsequently stabilized.HT growth,DBH growth stand basal area(BAS)and crown competition factor(CCF)signifi cantly infl uenced HCB and CL.The HCB was positively correlated with BAS,HT growth and DBH growth,but negatively correlated with CCF.The CL was positively correlated with BAS and CCF,but negatively correlated with DBH growth.Model fi tting and validation confi rmed that the mixed-eff ects model considering the stand and tree level random eff ects was accurate and reliable for predicting the HCB and CL dynamics.However,the models involving adding variance functions and time series correlation structure could not completely remove heterogeneity and autocorrelation,and the fi tting precision of the models was reduced.Therefore,from the point of view of application,we should take care to avoid setting up over-complex models.The HCB and CL dynamic models in our study may also be incorporated into stand growth and yield model systems in China.
文摘具备纯立方刚度的非线性能量阱(nonlinear energy sink,NES)具有轻质、宽频减振等优点,但在激励较大的情况下,会引起系统的稳定高分支响应。为扩大纯立方刚度NES的有效激励范围,提出一种磁力双稳态NES。在简谐激励下,通过基于龙格-库塔法的程序分析了安装磁力双稳态NES系统的动态行为,研究了永磁铁的吸力对系统高分支响应的影响。结果表明:磁力双稳态NES在激励幅值较小时,拥有优于纯立方刚度NES的吸振效果;在激励幅值较大时,可抑制系统稳定的高分支响应,从而扩大有效激励范围。因此,磁力双稳态NES具有更广阔的应用前景和更好的吸振效果,可在某些较大激励环境下为结构的振动控制提供更有效的解决方案。
文摘This paper presents a dual-nonlinear branch linearizer for reducing the corrected amplitude overshoot of conventional single nonlinear branch linearizer. Theoretical analysis is carried out, the analysis is verified by simulation, and a prototype of Ka band 25.28~26.08 GHz dual nonlinear branch linearizer is achieved. It indicates that the corrected amplitude overshoot is less than 0.5 dB, the C/I3 improvement is more than 10 dB related to a single carrier IBO 9 dB, when it is linked and tested for 50 W spacebrone Travelling Wave Tube Amplifier(TWTA).
