Objectives A systematic review and network meta-analysis was conducted to evaluate the effectiveness of different childbirth positions in reducing the duration of the second stage of labor,providing evidence-based ins...Objectives A systematic review and network meta-analysis was conducted to evaluate the effectiveness of different childbirth positions in reducing the duration of the second stage of labor,providing evidence-based insights for obstetric institutions to guide interventions related to childbirth positions.Methods A comprehensive literature search was conducted in databases,including PubMed,Web of Science,the Cochrane Library,Embase,Wanfang Databases,China National Knowledge Infrastructure Databases(CNKI),China Science and Technology Journal Database(CSTJ),and China Biology Medicine disc(CBMdisc)to identify studies on the effectiveness of different childbirth positions in reducing the duration of the second stage of labor.The search included randomized controlled trials published from database inception to September 30,2024.The Cochrane risk-of-bias tool was used to assess the quality of the studies.Two independent reviewers screened the literature,extracted data,and evaluated study quality.Subsequently,a network meta-analysis was performed using STATA software.The study protocol has been registered in PROSPERO(CRD42023428217).Results This study analyzed data from 25 randomized controlled trials involving 9,844 women.The findings indicated that in comparison to lithotomy position,free position(MD=20.53,95%CI[11.38,29.68])and upright position(MD=−24.13,95%CI[−42.94,-5.32])were found to be superior in reducing the duration of the second stage of labor.Free position outperformed kneeling position(MD=21.48,95%CI[4.67,38.28])and squatting position(MD=23.43,95%CI[1.88,44.97]);upright position was superior to kneeling position(MD=−25.08,95%CI[−46.93,−3.22]);semirecumbent position surpassed squatting position(MD=19.71,95%CI[2.05,37.38]);and upright position was also superior to squatting position(MD=−27.03,95%CI[−51.48,−2.57]).According to the surface under the cumulative ranking curve(SUCRA),the upright position emerged as the most effective for reducing the duration of the second stage of labor(87.4%),followed by free position(81.1%),semirecumbent position(70.0%),and lateral position(62.3%).Conclusion These findings offer valuable insights for midwifery practice and help inform future research directions.Considering the limitations of this review,more larger-scale,multicenter randomized controlled trials are warranted to further evaluate the relative effectiveness of different childbirth positions in reducing the duration of the second stage of labor.展开更多
AIM: To study the effectiveness of second-linetreatments for advancer gastric cancer by application of Bayesian network meta-analysis.METHODS: Our search covered the literature up to February 2015. The following 6 tre...AIM: To study the effectiveness of second-linetreatments for advancer gastric cancer by application of Bayesian network meta-analysis.METHODS: Our search covered the literature up to February 2015. The following 6 treatments were evaluated:(1) irinotecan(camptothecins);(2) paclitaxel(taxanes class);(3) docetaxel(taxanes);(4) everolimus(mammalian target of rapamycin inhibitors);(5) ramucirumab(vascular endothelial growth factor receptor 2 inhibitors);(6) ramucirumab + paclitaxel. Our methodology was based on standard models of Bayesian network meta-analysis. The reference treatment was best supportive care(BSC). The endpoint was overall survival. Median survival was the outcome measure along with 95% credible intervals. RESULTS: Our search identified a total of 7 randomized controlled trials. These trials included 2298 patients(in 15 treatment arms) in whom a total of 6 active treatments were evaluated as well as BSC. There were 21 head-to-head comparisons(6 direct, 15 indirect). The difference in survival between each of two active treatments(paclitaxel and ramucirumab + paclitaxel) vs BSC was statistically significant, while the other 4 showed no statistical difference. In the 6 head-to-head comparisons between active treatments, no significant survival difference was demonstrated. CONCLUSION: Our results indicate that both paclitaxel monotherapy and ramucirumab + paclitaxel determine a significant prolongation in survival as compared with BSC.展开更多
Higher-order band topology not only enriches our understanding of topological phases but also unveils pioneering lower-dimensional boundary states,which harbors substantial potential for next-generation device applica...Higher-order band topology not only enriches our understanding of topological phases but also unveils pioneering lower-dimensional boundary states,which harbors substantial potential for next-generation device applications.The distinct electronic configurations and tunable attributes of two-dimensional materials position them as a quintessential platform for the realization of second-order topological insulators(SOTIs).This article provides an overview of the research progress in SOTIs within the field of two-dimensional electronic materials,focusing on the characterization of higher-order topological properties and the numerous candidate materials proposed in theoretical studies.These endeavors not only enhance our understanding of higher-order topological states but also highlight potential material systems that could be experimentally realized.展开更多
Literature review is an important component in any scientific research. In ecological and agricultural sciences, many studies have been conducted over years. With accumulation of scientific studies and published paper...Literature review is an important component in any scientific research. In ecological and agricultural sciences, many studies have been conducted over years. With accumulation of scientific studies and published papers, it is critical to summarize and evaluate these previous research findings. Different literature review methods have been applied, including traditional qualitative literature review, quantitative meta-analysis, and more recently, mega-analysis, or meta-meta-analysis. Here we briefly describe these different approaches and draw attention to the recent development of data synthesis. Several case studies were used to illustrate the application of these methods in the ecological and agricultural sciences.展开更多
The topic on the subspaces for the polynomially or exponentially bounded weak mild solutions of the following abstract Cauchy problem d^2/（dr^2）u（t,x）=Au（t,x）;u（0,x）=x,d/（dt）u（0,x）=0,x∈X is studied, wher...The topic on the subspaces for the polynomially or exponentially bounded weak mild solutions of the following abstract Cauchy problem d^2/（dr^2）u（t,x）=Au（t,x）;u（0,x）=x,d/（dt）u（0,x）=0,x∈X is studied, where A is a closed operator on Banach space X. The case that the problem is ill-posed is treated, and two subspaces Y（A, k） and H（A, ω） are introduced. Y（A, k） is the set of all x in X for which the second order abstract differential equation has a weak mild solution v（ t, x） such that ess sup{（1＋t）^-k｜d/（dt）〈v（t,x）,x^＊〉｜：t≥0,x^＊∈X^＊,｜x^＊‖≤1}〈＋∞. H（A, ω） is the set of all x in X for which the second order abstract differential equation has a weak mild solution v（t,x）such that ess sup{e^-ωl｜d/（dt）〈v（t,x）,x^＊）｜：t≥0,x^＊∈X^＊,‖x^＊‖≤1}〈＋∞. The following conclusions are proved that Y（A, k） and H（A, ω） are Banach spaces, and both are continuously embedded in X; the restriction operator A ｜ Y（A,k） generates a once-integrated cosine operator family { C（t） }t≥0 such that limh→0＋^-1/h‖C（t＋h）-C（t）‖Y（A,k）≤M（1＋t）^k,arbitary t≥0; the restriction operator A ｜H（A,ω） generates a once- integrated cosine operator family {C（t）}t≥0 such that limh→0＋^-1/h‖C（t＋h）-C（t）‖H（A,ω）≤≤Me^ωt,arbitary t≥0.展开更多
In this paper,the oscillation criteria for the solutions of the nonlinear differential equations of neutral type of the forms:[x(t)+p(t)x(σ(t))]″+q(t)f(x(τ(t)))g(x′(t))=0and[x(t)+p(t)x(σ(t))]″+q(t)f(x(t),x(τ(t)...In this paper,the oscillation criteria for the solutions of the nonlinear differential equations of neutral type of the forms:[x(t)+p(t)x(σ(t))]″+q(t)f(x(τ(t)))g(x′(t))=0and[x(t)+p(t)x(σ(t))]″+q(t)f(x(t),x(τ(t)))g(x′(t))=0are obtained.展开更多
By applying the second order Melnikov function, the chaos behaviors of a bistable piezoelectric cantilever power generation system are analyzed. Firstly, the conditions for emerging chaos of the system are derived by ...By applying the second order Melnikov function, the chaos behaviors of a bistable piezoelectric cantilever power generation system are analyzed. Firstly, the conditions for emerging chaos of the system are derived by the second order Melnikov function. Secondly, the effects of each item in chaos threshold expression are analyzed. The excitation frequency and resistance values, which have the most influence on chaos threshold value, are found. The result from the second order Melnikov function is more accurate compared with that from the first order Melnikov function. Finally, the attraction basins of large amplitude motions under different exciting frequency, exciting amplitude, and resistance parameters are given.展开更多
Suffcient conditions for the existence of at least one solution of two-point boundary value problems for second order nonlinear differential equations [φ(x(t))] + kx(t) + g(t,x(t)) = p(t),t ∈(0,π) x(0) = x(π) = 0 ...Suffcient conditions for the existence of at least one solution of two-point boundary value problems for second order nonlinear differential equations [φ(x(t))] + kx(t) + g(t,x(t)) = p(t),t ∈(0,π) x(0) = x(π) = 0 are established,where [φ(x)] =(|x |p-2x) with p > 1.Our result is new even when [φ(x)] = x in above problem,i.e.p = 2.Examples are presented to illustrate the effciency of the theorem in this paper.展开更多
This article is concerned with the oscillation of the forced second order differ- ential equation with mixed nonlinearities（a（t）（x＇（t））γ）＇＋po（t）xγ（go（t））＋n∑t=1pi（t）｜x（gi（t））｜αi sgn x（gi...This article is concerned with the oscillation of the forced second order differ- ential equation with mixed nonlinearities（a（t）（x＇（t））γ）＇＋po（t）xγ（go（t））＋n∑t=1pi（t）｜x（gi（t））｜αi sgn x（gi（t））=e（t）,where γ is a quotient of odd positive integers αi〉0,i=1,2 ……n,a,e,and pi ∈ C（[0,∞）R）,a（t）〉0,gi：R→R are positive continuous functions on R with lim gi （t）=∞,i=0,1,……,n. Our results generalize and improve the results in a recent article by Sun and Wong[29].展开更多
In this paper, a high accuracy finite volume element method is presented for two-point boundary value problem of second order ordinary differential equation, which differs from the high order generalized difference me...In this paper, a high accuracy finite volume element method is presented for two-point boundary value problem of second order ordinary differential equation, which differs from the high order generalized difference methods. It is proved that the method has optimal order error estimate O(h3) in H1 norm. Finally, two examples show that the method is effective.展开更多
Adaptive broadband beamforraing is a key issue in array applications. The adaptive broadband beamformer with tapped delay line （TDL） structure for nonuniform linear array （NLA） is designed according to the rule of...Adaptive broadband beamforraing is a key issue in array applications. The adaptive broadband beamformer with tapped delay line （TDL） structure for nonuniform linear array （NLA） is designed according to the rule of minimizing the beamformer＇s output power while keeping the distortionless response （DR） in the direction of desired signal and keeping the constant beamwidth （CB） with the prescribed sidelobe level over the whole operating band. This kind of beamforming problem can be solved with the interior-point method after being converted to the form of standard second order cone programming （SOCP）. The computer simulations are presented which illustrate the effectiveness of our beamformer.展开更多
Target tracking control for wheeled mobile robot(WMR)need resolve the problems of kinematics model and tracking algorithm.High-order sliding mode control is a valid method used in the nonlinear tracking control system...Target tracking control for wheeled mobile robot(WMR)need resolve the problems of kinematics model and tracking algorithm.High-order sliding mode control is a valid method used in the nonlinear tracking control system,which can eliminate the chattering of sliding mode control.Currently there lacks the research of robustness and uncertain factors for high-order sliding mode control.To address the fast convergence and robustness problems of tracking target,the tracking mathematical model of WMR and the target is derived.Based on the finite-time convergence theory and second order sliding mode method,a nonlinear tracking algorithm is designed which guarantees that WMR can catch the target in finite time.At the same time an observer is applied to substitute the uncertain acceleration of the target,then a smooth nonlinear tracking algorithm is proposed.Based on Lyapunov stability theory and finite-time convergence,a finite time convergent smooth second order sliding mode controller and a target tracking algorithm are designed by using second order sliding mode method.The simulation results verified that WMR can catch up the target quickly and reduce the control discontinuity of the velocity of WMR.展开更多
This paper discussses the random singular integral of random process with second order moment, establishes the concepts of the random singular integral and proves that it's a linear bounded operator of space Ha(L)...This paper discussses the random singular integral of random process with second order moment, establishes the concepts of the random singular integral and proves that it's a linear bounded operator of space Ha(L)(m, s). Then Plemelj formula and some other properties for random singular integral are proved.展开更多
A new criterion is established for the oscillation of second order superlinear ordinary differential equations of the formx″(t) + p(t)x′(t) + q(t)｜x(t)｜αsgnx(t) = 0, t ≥ t0,where α>1,p and q are continuous f...A new criterion is established for the oscillation of second order superlinear ordinary differential equations of the formx″(t) + p(t)x′(t) + q(t)｜x(t)｜αsgnx(t) = 0, t ≥ t0,where α>1,p and q are continuous functions on[t0,∞). This criterion extends and unifies some of the results obtained in [1]- [5].展开更多
In this paper eigenstructure assignment via proportional-plus-derivative feedback is investigated for a class of second-order descriptor linear systems.Under certain conditions,simple,general and complete parametric s...In this paper eigenstructure assignment via proportional-plus-derivative feedback is investigated for a class of second-order descriptor linear systems.Under certain conditions,simple,general and complete parametric solutions of both finite closed-loop eigenvector matrices and feedback gain matrices are derived.The parametric approach utilizes directly original system data,involves manipulations only on n-dimensional matrices,and reveals all the design degrees of freedom which can be further utilized to achieve certain additional system specifications.A numerical example shows the effect of the proposed approach.展开更多
The existence of homoclinic orbits is obtained by the variational approach for a class of second order Hamiltonian systems q（t） ＋ ↓△V（t, q（t）） = 0, where V（t, x） = -K（t, x） ＋ W（t, x）, K（t, x） is neit...The existence of homoclinic orbits is obtained by the variational approach for a class of second order Hamiltonian systems q（t） ＋ ↓△V（t, q（t）） = 0, where V（t, x） = -K（t, x） ＋ W（t, x）, K（t, x） is neither a quadratic form in x nor periodic in t and W（t, x） is superquadratic in x.展开更多
This paper presents a simple and systematic approach to design second order sliding mode controller for buck converters.The second order sliding mode control(SOSMC)based on twisting algorithm has been implemented to c...This paper presents a simple and systematic approach to design second order sliding mode controller for buck converters.The second order sliding mode control(SOSMC)based on twisting algorithm has been implemented to control buck switch mode converter.The idea behind this strategy is to suppress chattering and maintain robustness and finite time convergence properties of the output voltage error to the equilibrium point under the load variations and parametric uncertainties.In addition,the influence of the twisting algorithm on the performance of closed-loop system is investigated and compared with other algorithms of first order sliding mode control such as adaptive sliding mode control(ASMC),nonsingular terminal sliding mode control(NTSMC).In comparative evaluation,the transient response of the output voltage with the step change in the load and the start-up response of the output voltage with the step change in the input voltage of buck converter were compared.Experimental results were obtained from a hardware setup constructed in laboratory.Finally,for all of the surveyed control methods,the theoretical considerations,numerical simulations,and experimental measurements from a laboratory prototype are compared for different operating points.It is shown that the proposed twisting method presents an improvement in steady state error and settling time of output voltage during load changes.展开更多
In this paper we introduce the class of Hermite's matrix polynomials which appear as finite series solutions of second order matrix differential equations Y'-xAY'+BY=0.An explicit expression for the Hermit...In this paper we introduce the class of Hermite's matrix polynomials which appear as finite series solutions of second order matrix differential equations Y'-xAY'+BY=0.An explicit expression for the Hermite matrix polynomials,the orthogonality property and a Rodrigues' formula are given.展开更多
The problem of the chattering phenomenon is still the main drawback of the classical sliding mode control. To resolve this problem, a discrete second order sliding mode control via input-output model is proposed in th...The problem of the chattering phenomenon is still the main drawback of the classical sliding mode control. To resolve this problem, a discrete second order sliding mode control via input-output model is proposed in this paper. The proposed control law is synthesized for decouplable multivariable systems. A robustness analysis of the proposed discrete second order sliding mode control is carried out. Simulation results are presented to illustrate the effectiveness of the proposed strategy.展开更多
基金the Obstetrics and Gynecology Hospital of Fudan University for supporting this project。
文摘Objectives A systematic review and network meta-analysis was conducted to evaluate the effectiveness of different childbirth positions in reducing the duration of the second stage of labor,providing evidence-based insights for obstetric institutions to guide interventions related to childbirth positions.Methods A comprehensive literature search was conducted in databases,including PubMed,Web of Science,the Cochrane Library,Embase,Wanfang Databases,China National Knowledge Infrastructure Databases(CNKI),China Science and Technology Journal Database(CSTJ),and China Biology Medicine disc(CBMdisc)to identify studies on the effectiveness of different childbirth positions in reducing the duration of the second stage of labor.The search included randomized controlled trials published from database inception to September 30,2024.The Cochrane risk-of-bias tool was used to assess the quality of the studies.Two independent reviewers screened the literature,extracted data,and evaluated study quality.Subsequently,a network meta-analysis was performed using STATA software.The study protocol has been registered in PROSPERO(CRD42023428217).Results This study analyzed data from 25 randomized controlled trials involving 9,844 women.The findings indicated that in comparison to lithotomy position,free position(MD=20.53,95%CI[11.38,29.68])and upright position(MD=−24.13,95%CI[−42.94,-5.32])were found to be superior in reducing the duration of the second stage of labor.Free position outperformed kneeling position(MD=21.48,95%CI[4.67,38.28])and squatting position(MD=23.43,95%CI[1.88,44.97]);upright position was superior to kneeling position(MD=−25.08,95%CI[−46.93,−3.22]);semirecumbent position surpassed squatting position(MD=19.71,95%CI[2.05,37.38]);and upright position was also superior to squatting position(MD=−27.03,95%CI[−51.48,−2.57]).According to the surface under the cumulative ranking curve(SUCRA),the upright position emerged as the most effective for reducing the duration of the second stage of labor(87.4%),followed by free position(81.1%),semirecumbent position(70.0%),and lateral position(62.3%).Conclusion These findings offer valuable insights for midwifery practice and help inform future research directions.Considering the limitations of this review,more larger-scale,multicenter randomized controlled trials are warranted to further evaluate the relative effectiveness of different childbirth positions in reducing the duration of the second stage of labor.
文摘AIM: To study the effectiveness of second-linetreatments for advancer gastric cancer by application of Bayesian network meta-analysis.METHODS: Our search covered the literature up to February 2015. The following 6 treatments were evaluated:(1) irinotecan(camptothecins);(2) paclitaxel(taxanes class);(3) docetaxel(taxanes);(4) everolimus(mammalian target of rapamycin inhibitors);(5) ramucirumab(vascular endothelial growth factor receptor 2 inhibitors);(6) ramucirumab + paclitaxel. Our methodology was based on standard models of Bayesian network meta-analysis. The reference treatment was best supportive care(BSC). The endpoint was overall survival. Median survival was the outcome measure along with 95% credible intervals. RESULTS: Our search identified a total of 7 randomized controlled trials. These trials included 2298 patients(in 15 treatment arms) in whom a total of 6 active treatments were evaluated as well as BSC. There were 21 head-to-head comparisons(6 direct, 15 indirect). The difference in survival between each of two active treatments(paclitaxel and ramucirumab + paclitaxel) vs BSC was statistically significant, while the other 4 showed no statistical difference. In the 6 head-to-head comparisons between active treatments, no significant survival difference was demonstrated. CONCLUSION: Our results indicate that both paclitaxel monotherapy and ramucirumab + paclitaxel determine a significant prolongation in survival as compared with BSC.
基金supported by the National Natu-ral Science Foundation of China(Grants No.12174220 and No.12074217)the Shandong Provincial Science Foundation for Excellent Young Scholars(Grant No.ZR2023YQ001)+1 种基金the Taishan Young Scholar Program of Shandong Provincethe Qilu Young Scholar Pro-gram of Shandong University.
文摘Higher-order band topology not only enriches our understanding of topological phases but also unveils pioneering lower-dimensional boundary states,which harbors substantial potential for next-generation device applications.The distinct electronic configurations and tunable attributes of two-dimensional materials position them as a quintessential platform for the realization of second-order topological insulators(SOTIs).This article provides an overview of the research progress in SOTIs within the field of two-dimensional electronic materials,focusing on the characterization of higher-order topological properties and the numerous candidate materials proposed in theoretical studies.These endeavors not only enhance our understanding of higher-order topological states but also highlight potential material systems that could be experimentally realized.
文摘Literature review is an important component in any scientific research. In ecological and agricultural sciences, many studies have been conducted over years. With accumulation of scientific studies and published papers, it is critical to summarize and evaluate these previous research findings. Different literature review methods have been applied, including traditional qualitative literature review, quantitative meta-analysis, and more recently, mega-analysis, or meta-meta-analysis. Here we briefly describe these different approaches and draw attention to the recent development of data synthesis. Several case studies were used to illustrate the application of these methods in the ecological and agricultural sciences.
基金The Natural Science Foundation of Department ofEducation of Jiangsu Province (No06KJD110087)
文摘The topic on the subspaces for the polynomially or exponentially bounded weak mild solutions of the following abstract Cauchy problem d^2/（dr^2）u（t,x）=Au（t,x）;u（0,x）=x,d/（dt）u（0,x）=0,x∈X is studied, where A is a closed operator on Banach space X. The case that the problem is ill-posed is treated, and two subspaces Y（A, k） and H（A, ω） are introduced. Y（A, k） is the set of all x in X for which the second order abstract differential equation has a weak mild solution v（ t, x） such that ess sup{（1＋t）^-k｜d/（dt）〈v（t,x）,x^＊〉｜：t≥0,x^＊∈X^＊,｜x^＊‖≤1}〈＋∞. H（A, ω） is the set of all x in X for which the second order abstract differential equation has a weak mild solution v（t,x）such that ess sup{e^-ωl｜d/（dt）〈v（t,x）,x^＊）｜：t≥0,x^＊∈X^＊,‖x^＊‖≤1}〈＋∞. The following conclusions are proved that Y（A, k） and H（A, ω） are Banach spaces, and both are continuously embedded in X; the restriction operator A ｜ Y（A,k） generates a once-integrated cosine operator family { C（t） }t≥0 such that limh→0＋^-1/h‖C（t＋h）-C（t）‖Y（A,k）≤M（1＋t）^k,arbitary t≥0; the restriction operator A ｜H（A,ω） generates a once- integrated cosine operator family {C（t）}t≥0 such that limh→0＋^-1/h‖C（t＋h）-C（t）‖H（A,ω）≤≤Me^ωt,arbitary t≥0.
文摘In this paper,the oscillation criteria for the solutions of the nonlinear differential equations of neutral type of the forms:[x(t)+p(t)x(σ(t))]″+q(t)f(x(τ(t)))g(x′(t))=0and[x(t)+p(t)x(σ(t))]″+q(t)f(x(t),x(τ(t)))g(x′(t))=0are obtained.
基金supported by the National Natural Science Foundation of China (Grant 11172199)
文摘By applying the second order Melnikov function, the chaos behaviors of a bistable piezoelectric cantilever power generation system are analyzed. Firstly, the conditions for emerging chaos of the system are derived by the second order Melnikov function. Secondly, the effects of each item in chaos threshold expression are analyzed. The excitation frequency and resistance values, which have the most influence on chaos threshold value, are found. The result from the second order Melnikov function is more accurate compared with that from the first order Melnikov function. Finally, the attraction basins of large amplitude motions under different exciting frequency, exciting amplitude, and resistance parameters are given.
基金Supported by the Natural Science Foundation of Hunan Province（06JJ50008） Supported by the Natural Science Foundation of Guangdong Province（7004569）
文摘Suffcient conditions for the existence of at least one solution of two-point boundary value problems for second order nonlinear differential equations [φ(x(t))] + kx(t) + g(t,x(t)) = p(t),t ∈(0,π) x(0) = x(π) = 0 are established,where [φ(x)] =(|x |p-2x) with p > 1.Our result is new even when [φ(x)] = x in above problem,i.e.p = 2.Examples are presented to illustrate the effciency of the theorem in this paper.
文摘This article is concerned with the oscillation of the forced second order differ- ential equation with mixed nonlinearities（a（t）（x＇（t））γ）＇＋po（t）xγ（go（t））＋n∑t=1pi（t）｜x（gi（t））｜αi sgn x（gi（t））=e（t）,where γ is a quotient of odd positive integers αi〉0,i=1,2 ……n,a,e,and pi ∈ C（[0,∞）R）,a（t）〉0,gi：R→R are positive continuous functions on R with lim gi （t）=∞,i=0,1,……,n. Our results generalize and improve the results in a recent article by Sun and Wong[29].
基金heprojectissupportedbyNNSFofChina (No .1 9972 0 39) .
文摘In this paper, a high accuracy finite volume element method is presented for two-point boundary value problem of second order ordinary differential equation, which differs from the high order generalized difference methods. It is proved that the method has optimal order error estimate O(h3) in H1 norm. Finally, two examples show that the method is effective.
基金supported by the National Nature Science Foundation of China (60472101)President Award of ChineseAcademy of Sciences(O729031511).
文摘Adaptive broadband beamforraing is a key issue in array applications. The adaptive broadband beamformer with tapped delay line （TDL） structure for nonuniform linear array （NLA） is designed according to the rule of minimizing the beamformer＇s output power while keeping the distortionless response （DR） in the direction of desired signal and keeping the constant beamwidth （CB） with the prescribed sidelobe level over the whole operating band. This kind of beamforming problem can be solved with the interior-point method after being converted to the form of standard second order cone programming （SOCP）. The computer simulations are presented which illustrate the effectiveness of our beamformer.
基金supported by National Natural Science Foundation of China(Grant No.61075081)State Key Laboratory of Robotics Technique and System Foundation,Harbin Institute of Technology,China(Grant No.SKIRS200802A02)
文摘Target tracking control for wheeled mobile robot(WMR)need resolve the problems of kinematics model and tracking algorithm.High-order sliding mode control is a valid method used in the nonlinear tracking control system,which can eliminate the chattering of sliding mode control.Currently there lacks the research of robustness and uncertain factors for high-order sliding mode control.To address the fast convergence and robustness problems of tracking target,the tracking mathematical model of WMR and the target is derived.Based on the finite-time convergence theory and second order sliding mode method,a nonlinear tracking algorithm is designed which guarantees that WMR can catch the target in finite time.At the same time an observer is applied to substitute the uncertain acceleration of the target,then a smooth nonlinear tracking algorithm is proposed.Based on Lyapunov stability theory and finite-time convergence,a finite time convergent smooth second order sliding mode controller and a target tracking algorithm are designed by using second order sliding mode method.The simulation results verified that WMR can catch up the target quickly and reduce the control discontinuity of the velocity of WMR.
基金The project is supported by the NSF of China (10271098)Education Foundation of Fujian (JB02083) Science & Technical Development Foundation of Fuzhou University (2003xy-11).
文摘This paper discussses the random singular integral of random process with second order moment, establishes the concepts of the random singular integral and proves that it's a linear bounded operator of space Ha(L)(m, s). Then Plemelj formula and some other properties for random singular integral are proved.
文摘A new criterion is established for the oscillation of second order superlinear ordinary differential equations of the formx″(t) + p(t)x′(t) + q(t)｜x(t)｜αsgnx(t) = 0, t ≥ t0,where α>1,p and q are continuous functions on[t0,∞). This criterion extends and unifies some of the results obtained in [1]- [5].
文摘In this paper eigenstructure assignment via proportional-plus-derivative feedback is investigated for a class of second-order descriptor linear systems.Under certain conditions,simple,general and complete parametric solutions of both finite closed-loop eigenvector matrices and feedback gain matrices are derived.The parametric approach utilizes directly original system data,involves manipulations only on n-dimensional matrices,and reveals all the design degrees of freedom which can be further utilized to achieve certain additional system specifications.A numerical example shows the effect of the proposed approach.
基金Supported by National Natural Science Foundation of China (10771173)
文摘The existence of homoclinic orbits is obtained by the variational approach for a class of second order Hamiltonian systems q（t） ＋ ↓△V（t, q（t）） = 0, where V（t, x） = -K（t, x） ＋ W（t, x）, K（t, x） is neither a quadratic form in x nor periodic in t and W（t, x） is superquadratic in x.
文摘This paper presents a simple and systematic approach to design second order sliding mode controller for buck converters.The second order sliding mode control(SOSMC)based on twisting algorithm has been implemented to control buck switch mode converter.The idea behind this strategy is to suppress chattering and maintain robustness and finite time convergence properties of the output voltage error to the equilibrium point under the load variations and parametric uncertainties.In addition,the influence of the twisting algorithm on the performance of closed-loop system is investigated and compared with other algorithms of first order sliding mode control such as adaptive sliding mode control(ASMC),nonsingular terminal sliding mode control(NTSMC).In comparative evaluation,the transient response of the output voltage with the step change in the load and the start-up response of the output voltage with the step change in the input voltage of buck converter were compared.Experimental results were obtained from a hardware setup constructed in laboratory.Finally,for all of the surveyed control methods,the theoretical considerations,numerical simulations,and experimental measurements from a laboratory prototype are compared for different operating points.It is shown that the proposed twisting method presents an improvement in steady state error and settling time of output voltage during load changes.
文摘In this paper we introduce the class of Hermite's matrix polynomials which appear as finite series solutions of second order matrix differential equations Y'-xAY'+BY=0.An explicit expression for the Hermite matrix polynomials,the orthogonality property and a Rodrigues' formula are given.
基金supported by the Ministry of Higher Education and Scientific Research in Tunisia
文摘The problem of the chattering phenomenon is still the main drawback of the classical sliding mode control. To resolve this problem, a discrete second order sliding mode control via input-output model is proposed in this paper. The proposed control law is synthesized for decouplable multivariable systems. A robustness analysis of the proposed discrete second order sliding mode control is carried out. Simulation results are presented to illustrate the effectiveness of the proposed strategy.
