The wash-out filter （WF） technique is used to control the flutter of a two dimensional airfoil with cubic non-linearity in incompressible flow. Firstly, Hopf bifurcation theory is used to determine the point at whic...The wash-out filter （WF） technique is used to control the flutter of a two dimensional airfoil with cubic non-linearity in incompressible flow. Firstly, Hopf bifurcation theory is used to determine the point at which the nonlinear controller is introduced. The system is then transformed into Jordan canonical form, based on analysis of linearized eigenvalues of the system. Secondly, for the introduced WF controller, the linear control gain is determined according to Hopf bifurcation condition. The sym- bolic computing program of normal form direct method （NFDM） is also used to obtain the normal form of the controlled system. The non-linear control gain can be determined based on the relation of the type of bifurcation and the parameters of the normal form, to transform sub-critical Hopf bifurcation to be su- per-critical one. Lastly, numerical simulations are used to certify the validity of theoretical analysis, in which the amplitude of flutter or limit cycle of the controlled system is reduced greatly, comparing to the original system.展开更多
目的探讨SonoVue实时超声造影在乳腺肿瘤诊断中的价值。方法选用SonoVue超声造影剂,对34例乳腺肿块(良性16例,恶性18例)进行彩色多普勒实时超声造影,应用随机配置的造影剂声学定量时间-强度曲线分析软件(Wash-in and Wash-out)观察曲线...目的探讨SonoVue实时超声造影在乳腺肿瘤诊断中的价值。方法选用SonoVue超声造影剂,对34例乳腺肿块(良性16例,恶性18例)进行彩色多普勒实时超声造影,应用随机配置的造影剂声学定量时间-强度曲线分析软件(Wash-in and Wash-out)观察曲线形态,测量声学定量参数,对比分析良、恶性肿瘤的变化和特征。结果乳腺良性肿瘤组的时间-强度曲线呈慢上快下型,恶性肿瘤组呈快上慢下型;声学定量参数峰值时间良性组与恶性组之间差异无显著性(P>0.05),60s时峰值强度和峰值平均强度恶性组大于良性组(P<0.05),斜率和峰值曲线下面积恶性组明显高于良性组(P<0.01)。结论实时超声造影能反映良、恶性肿瘤在时间-强度曲线上的差异,可帮助提高乳腺肿瘤诊断的准确性。展开更多
为了对红层软岩生态防护边坡的抗冲刷能力进行定量研究,采用现场模拟降雨的方法,测量不同雨强降雨时红层软岩生态防护坡面的径流量、坡体截留量和冲蚀量.试验结果表明,在雨强为20 mm/h持续降雨190 m in和雨强为50 mm/h持续降雨120 m in...为了对红层软岩生态防护边坡的抗冲刷能力进行定量研究,采用现场模拟降雨的方法,测量不同雨强降雨时红层软岩生态防护坡面的径流量、坡体截留量和冲蚀量.试验结果表明,在雨强为20 mm/h持续降雨190 m in和雨强为50 mm/h持续降雨120 m in的情况下,采用植被防护的红层软岩边坡基本未冲蚀;生态防护能有效阻碍红层软岩在水环境作用下进一步风化崩解,从而降低红层软岩坡体的冲蚀.展开更多
文摘The wash-out filter （WF） technique is used to control the flutter of a two dimensional airfoil with cubic non-linearity in incompressible flow. Firstly, Hopf bifurcation theory is used to determine the point at which the nonlinear controller is introduced. The system is then transformed into Jordan canonical form, based on analysis of linearized eigenvalues of the system. Secondly, for the introduced WF controller, the linear control gain is determined according to Hopf bifurcation condition. The sym- bolic computing program of normal form direct method （NFDM） is also used to obtain the normal form of the controlled system. The non-linear control gain can be determined based on the relation of the type of bifurcation and the parameters of the normal form, to transform sub-critical Hopf bifurcation to be su- per-critical one. Lastly, numerical simulations are used to certify the validity of theoretical analysis, in which the amplitude of flutter or limit cycle of the controlled system is reduced greatly, comparing to the original system.
文摘目的探讨SonoVue实时超声造影在乳腺肿瘤诊断中的价值。方法选用SonoVue超声造影剂,对34例乳腺肿块(良性16例,恶性18例)进行彩色多普勒实时超声造影,应用随机配置的造影剂声学定量时间-强度曲线分析软件(Wash-in and Wash-out)观察曲线形态,测量声学定量参数,对比分析良、恶性肿瘤的变化和特征。结果乳腺良性肿瘤组的时间-强度曲线呈慢上快下型,恶性肿瘤组呈快上慢下型;声学定量参数峰值时间良性组与恶性组之间差异无显著性(P>0.05),60s时峰值强度和峰值平均强度恶性组大于良性组(P<0.05),斜率和峰值曲线下面积恶性组明显高于良性组(P<0.01)。结论实时超声造影能反映良、恶性肿瘤在时间-强度曲线上的差异,可帮助提高乳腺肿瘤诊断的准确性。
文摘为了对红层软岩生态防护边坡的抗冲刷能力进行定量研究,采用现场模拟降雨的方法,测量不同雨强降雨时红层软岩生态防护坡面的径流量、坡体截留量和冲蚀量.试验结果表明,在雨强为20 mm/h持续降雨190 m in和雨强为50 mm/h持续降雨120 m in的情况下,采用植被防护的红层软岩边坡基本未冲蚀;生态防护能有效阻碍红层软岩在水环境作用下进一步风化崩解,从而降低红层软岩坡体的冲蚀.
