Pole placement method of controlling chaos in DC-DC buck converters

Based on the mechanism for the generation of chaos in a buck converter, a pole placement method is proposed and applied to controlling the chaos in a circuit. The control circuit is designed and tested. Numerical calculation and circuit implementation demonstrate the validity of this chaos control method.

Study on Component Synthesis Active Vibration Suppression Method Using Zero-placement Technique

The component synthesis active vibration suppression method （CSVS） can be applied to suppress the vibration of flexible systems. By this method, several same or similar time-varying components are arranged according to certain rules along the time axis. The synthesized command can suppress the arbitrary unwanted vibration harmonic while achieving the desired rigid body motion. The number of the components increases rapidly when the number of harmonic vibration is growing. In this article, the CSVS based on zero-placement technique is used to construct the synthesized command to suppress the multi-harmonics simultaneously in the discrete domain. The nature of zero-placement method is to put enough zeros to cancel system poles at necessary points. The designed synthesized command has equal time intervals between each component and which is much easier to be implemented. Using this method, the number of components increases linearly with the increasing of the number of being suppressed harmonics. For the spacecraft with flexible appendages, CSVS based on zero-placement is used to design the time optimal large angle maneuver control strategy. Simulations have verified the validity and superiority of the proposed approach.

Optimal sensor placement in hydropower house based on improved triaxial effective independence method

The capacity and size of hydro-generator units are increasing with the rapid development of hydroelectric enterprises, and the vibration of the powerhouse structure has increasingly become a major problem. Field testing is an important method for research on dynamic identification and vibration mechanisms. Research on optimal sensor placement has become a very important topic due to the need to obtain effective testing information from limited test resources. To overcome inadequacies of the present methods, this paper puts forward the triaxial effective independence driving-point residue （EfI3-DPR3） method for optimal sensor placement. The Efl3-DPR3 method can incorporate both the maximum triaxial modal kinetic energy and linear independence of the triaxial target modes at the selected nodes. It was applied to the optimal placement oftriaxial sensors for vibration testing in a hydropower house, and satisfactory results were obtained. This method can provide some guidance for optimal placement of triaxial sensors of underground powerhouses.

AN ALGEBRAIC METHOD FOR POLE PLACEMENT IN MULTIVARIABLE SYSTEMS

This paper considers the pole placement in multivariable systems involving known delays by using dynamic controllers subject to multirate sampling. The controller parameterizations are calculated from algebraic equations which are solved by using the Kronecker product of matrices. It is pointed out that the sampling periods can be selected in a convenient way for the solvability of such equations under rather weak conditions provided that the continuous plant is spectrally controllable. Some overview about the use of nonuniform sampling is also given in order to improve the system's performance.

Placement Effect on the Stability of Tetrapod Armor Unit on Breakwaters in Irregular Waves

Tetrapod, one of the well-known artificial concrete units, is frequently used as an armor unit on breakwaters. Two layers of tetrapod units are normmaly placed on the breakwaters with different placement methods. In this study, the stability of tetrapod units with two different regularly placement methods are investigated experimentally in irregular waves. Stability coefficients of tetrapod units for both placement methods are obtained. The important characteristic wave parameters of irregular waves causing the same damage ratio as those of the regular waves are also determined. It reveals that the average of one-tenth highest wave heights within the wave train （H1/lo） causes the similar damage as regular waves.

Adaptive Controller Placement in Software Defined Wireless Networks

Controller placement problem(CPP)is a critical issue in software defined wireless networks(SDWN).Due to the limited power of wireless devices,CPP is facing the challenge of energy efficiency in SDWN.Nevertheless,the related research on CPP in SDWN hasn’t modeled the energy consumption of controllers so far.To prolong the lifetime of SDWN and improve the practicability of research,we rebuilt a CPP model considering the minimal transmitted power of controllers.An adaptive controller placement algorithm(ACPA)is proposed with the following two stages.First,data field method is adopted to determine sub-networks for different network topologies.Second,for each sub-network we adopt an exhaustive method to find the optimal location which meets the minimal average transmitted power to place controller.Compared with the other algorithms,the effectiveness and efficiency of the proposed scheme are validated through simulation.

Effects of Fertilizer Placement and Nitrogen Forms on Soil Nitrogen Diffusion and Migration of Red-Yellow Soil in China

A better understanding of nitrogen (N) diffusion and transformation in soils could reveal the capacity of the biological inorganic N and improve the efficiency of N fertilizers. A field micro-plot experiment was carried out to study the effects of fertilization methods (mixed uniformly with 12 cm top soil, placed in holes at a 12-cm depth, or placed in furrows at a 12-cm depth) and forms of N fertilizers (urea and ammonium phosphate) on the dynamics of soil N’s vertical diffusion and horizontal migration in red-yellow soil. The soil inorganic N ( NH4+-N and NH3--N) content following point deep placement was greater than that from mixed or furrow applications. Under point placement, the migration of soil inorganic N in urea and ammonium phosphate treatments occurred in the 6 - 15 cm layer at a horizontal distance of 0 - 9 cm. However, the nutrient preservation capability of the soil receiving ammonium phosphate was greater than that receiving urea under point deep placement. Thus, point deep placement had a tendency to increase the inorganic N in the soil and reduce inorganic N loss, which probably occurred due to the reduced soil volume with which the N fertilizer was mixed. According to crop growth and fertilizer requirements, the optimized fertilizer placement and N species resulted in a continuously high nutrient supply to crops for 90 d. However, the effects of point deep placement on increasing the N-use efficiency and reducing N loss have to be evaluated under natural field conditions.

Simplified Methods for Eigenvalue Assignment

A state feedback method of reduced order for eigenvalue assignment is developed in this paper. It offers immediate assignment of m eigenvalues, with freedom to assign the remaining n-m eigenvalues. The method also enjoys a systematic one-step application in the case where the system has a square submatrix. Further simplification is also possible in certain cases. The method is shown to be applicable to uncontrollable systems, offering the simplest control law when having maximum uncontrollable eigenvalues.

Study on <i>in Vitro</i>Accurate Measurement Method of PICC Insertion Depth

Objective to study an in vitro accurate measurement method for the placement depth of PICC. Methods 270 patients undergoing PICC catheterization under ultrasound guidance in outpatient PICC catheterization from March to September 2019 were selected by convenient sampling. By using the random number table method, the subjects were divided into group A (horizontal L-type measurement method) and Group B (characteristic index measurement calculation) by 1:1, with 135 cases in each group. X-ray chest radiograph was taken after catheterization in both groups, and the indwelling position of the catheter was adjusted according to the X-ray chest radiograph. The correlation between PICC predicted length and ideal depth and patient satisfaction were compared between the two groups. Results The success rate of PICC catheter tip insertion in group B was 97.78%, while that in control group A was 82.22%, the difference was statistically significant (P < 0.05). The satisfaction degree of patients in group B was significantly higher than that in group A. The differences were statistically significant (P < 0.05). Conclusion Improving the success rate of the precise depth of PICC catheter placement can significantly reduce the incidence of complications, waste of human and material resources caused by adjusting the catheter position, and significantly improve patient satisfaction.

Real-Time Update of Sequence Placement Logic for High Arch Dams Based on Evidence Weight Discount

Sequence placement logic plays a significant role in construction simulation of high arch dams and directly affects the simulation process and results. To establish a sequence logic for dam block placement, the construction scheme, real-time construction process, and random factors of the site all need to be considered in detail. There are few studies available currently that take all these factors into consideration. To address this problem, a real-time update of sequence placement logic for high arch dams based on evidence weight discount is proposed in this study. First, the subjective weight of the dam block sequence priority criteria is built using a consistent matrix method based on the construction scheme. Second, using evidence theory, dynamic objective weight of the priority criteria and basic probability assignment is built. Finally, using a weight self-adaptive adjustment method and comprehensive evidence discounting, the placing probabilities of different dam blocks are obtained. A case study indicates that this method can realize real-time update of sequence placement logic. © 2017, Tianjin University and Springer-Verlag Berlin Heidelberg.

基于MF-EI法的水闸底板脱空参数反演

为了更好地解决水工结构以损伤诊断为目标的传感器布置问题,以软基水闸为研究对象、水闸底板脱空为损伤类型,针对传统有效独立法未考虑结构损伤信息的缺陷,将模态柔度作为结构损伤敏感特征量,并引入结构的模态柔度修正有效独立法,提出基于模态柔度-有效独立法(modal flexibility-effective independent method,简称MFEI)的水闸底板脱空参数反演方法。采用模态置信准则、Fisher信息阵、条件数准则和奇异值分解比准则4种评价指标,分别对距离系数-有效独立法(distance coefficient-effective independence method,简称DC-EI)、有效独立-总位移法(effective independence-total displacement method,简称EI-TD)和MF-EI法进行评价,并将3种方法得到的布置方案应用到不同工况下软基水闸底板脱空动力学反演中,对比分析3种方法各工况脱空参数的反演结果。结果表明:MF-EI法测得的模态矩阵具有更好的正交性、可观测性和模态扩阶性,同时保留了对软基水闸底板脱空敏感的损伤信息,3种工况下的脱空参数反演识别精度分别提高至97.5%,96.1%和75.9%,是一种较为有效的水闸底板脱空参数反演方法。

线圈放置方式对脉冲涡流检测的影响分析

[目的]核电厂汽水管线一般在管道外壁加装保温层,从而提高换热效率。目前对于铁磁性管道的检测手段主要为常规超声及超声导波,检测前需要将管道外壁保温层拆除,导致检测工期延长,人力成本增加,无法达到核电厂高质量发展的要求。核电厂脉冲涡流技术的应用可以省去保温层的拆装,实现不停机在线筛查。检测线圈的放置方式对缺陷的检出能力是脉冲涡流技术重要指标。[方法]文章利用ANSYS中的Maxwell模块进行管件建模及仿真,分别设计同轴式与垂直式检测线圈,保持提离距离、材料一致及其他条件一致下,模拟脉冲涡流对平底缺陷的检测能力。选取核电厂样管进行同轴式与垂直式脉冲涡流测试,将脉冲涡流(Pulsed Eddy Current Testing,PECT)测试结果与超声测厚进行复核,对比两种线圈放置方式对脉冲涡流检测的影响。[结果]研究表明:垂直式线圈相对于同轴式线圈对缺陷检出效果更佳。[结论]核电厂脉冲涡流技术的应用对脉冲涡流技术在核电领域实施具有重要意义。

经腹膜外三孔法机器人辅助前列腺癌根治术的初步经验

目的介绍一种经本中心改良的手术技术--经腹膜外三孔法机器人辅助前列腺癌根治术(RARP)通道建立,探讨其操作方法、安全性及效果。方法回顾性分析2022年8月-2023年6月南通大学附属医院泌尿外科采用经腹膜外三孔法RARP的21例早、中期前列腺癌患者的临床资料,分享其手术通道建立的方法及技巧,同时观察手术相关指标如手术时间、术中出血量、术后并发症、引流管留置时间、术后住院时间及随访结果。结果21例患者的手术均由同一位医生顺利完成,术中未出现腹膜破损、增加辅助孔。建立腹膜外间隙和安装机械臂的时间为20.2(16.0~28.0)min,手术时间为107.0(60.0~161.0)min,术中出血量为52.8(31.0~121.0)mL,手术后第2天均恢复饮食,术后引流管留置时间为3.9(2.0~6.0)d,术后住院时间为4.9(3.0~7.0)d,术后均未发生严重并发症,术后尿管常规留置10 d,术后1月尿控满意的患者有20例(95.2%)。术后病理均为前列腺腺癌,切缘均阴性。国际泌尿病理协会(ISUP)预后分组:1组2例、2组6例、3组10例、4组2例、5组1例。结论经腹膜外三孔法RARP是一种安全可行的手术方式,具有腹膜外空间建立确切、器械之间碰撞少、手术费用低,术后肠道恢复快、切口美观、尿控恢复满意等优点。

腰椎骨折患者螺旋CT设计钉道行腰椎椎弓根置钉的准确性及安全性分析

目的探讨基于螺旋CT影像中钉道位置判断腰椎骨折患者椎弓根置钉的参数变化、准确性及安全性。方法选取2020年1月—2022年1月120例采用螺旋CT设计钉道行腰椎椎弓根置钉的腰椎骨折患者作为观察组,另选取采用传统Weinstein法进行腰椎椎弓根置钉的腰椎骨折患者120例作为对照组。分析观察组螺旋CT测定腰椎椎弓根钉道参数,并对比2组腰椎椎弓根置钉准确率、安全率、完成钉道准备时间及置钉出血量。结果观察组L 1~5节段椎弓根轴线与棘突轴线成角、椎弓根宽度逐渐增大(P<0.05);L 1~4节段入钉点至椎体前缘距离无明显变化,到L 5节段明显减小(P<0.05)。同一椎体左右两侧椎弓根轴线与棘突轴线成角、椎弓根宽度、入钉点至椎体前缘距离比较差异无统计学意义(P>0.05)。男性L 1~5节段椎弓根轴线与棘突轴线成角、椎弓根宽度、入钉点至椎体前缘距离均大于女性(P<0.05,P<0.01)。双侧最小椎弓根宽度为(8.13±0.59)mm,为安全进钉区域,可安全容纳3.5 mm螺钉。术后3 d,复查螺旋CT了解腰椎椎弓根置钉情况,观察组共置入椎弓根螺钉235枚,对照组共置入椎弓根螺钉229枚。观察组置钉准确率为91.49%(215/235)、安全率为99.15%(233/235)均高于对照组置钉准确率72.05%(165/229)、安全率90.39%(207/229)(P<0.05);观察组完成钉道准备时间短于对照组,置钉出血量少于对照组(P<0.01)。结论基于螺旋CT影像中L 1~5节段椎弓根轴线与棘突轴线成角、椎弓根宽度、入钉点至椎体前缘距离各腰椎节段间及不同性别间存在差异,可为腰椎椎弓根置钉提供解剖依据,能缩短完成钉道准备时间,减少置钉出血量,提高置钉准确性及安全性。

动力学系统在亏损时的反馈控制设计

通过引入反馈控制,使亏损系统动态特性得到优化。基于广义模态理论,利用系统矩阵结构特征,讨论亏损系统增益向量的计算方法,简化计算过程。通过分析二自由度飞机机翼运动学模型数据,验证该方法的有效性。

月面手动插旗过程的离散元-有限元耦合分析

在月球表面插入旗帜对人类探索宇宙具有重要意义.本文采用离散元G有限元耦合算法对手动插旗过程进行数值分析,首先,建立月壤的离散元模型、旗杆的有限元模型以及月壤与旗杆相互作用的离散元G有限元耦合模型;然后,对旗杆的结构进行优化设计以提高其稳固性;最后,提出三种不同的插旗方式并讨论不同插旗方式下旗杆的动力特性.研究结果表明,离散元G有限元耦合算法对月面插旗过程的模拟是有效的;底部尖锐度及稳定支架开叉角度的合理设计有利于增大旗杆的入壤深度和旗杆的稳固性;增大直接插入法中轴向力、提高敲击插入法中敲击力和敲击频率均可以增加旗杆的入壤深度;旋转插入法中旋转速度和旋转频率对插入过程影响较小.以上研究可为月面手动插旗提供有效的方案和理论参考.

Micro CT检测小鼠骨微结构指标受标本通量影响的方案设计

在过去几十年中,Micro CT已成为评估小动物骨骼微结构的金标准。然而Micro CT得到的定量指标会受到很多因素影响,如成像参数、重建像素大小和图像分割阈值等。为了提高相关实验准确性和可重复性,以及在各个研究间进行更可靠的比较,结合小鼠离体股骨的Micro CT实验,设计不同通量的标本及组合方案来验证骨微结构测量结果是否受其影响。结果表明,标本通量及组合方式的不同对骨微结构指标测量没有产生显著性影响,但高通量扫描会降低输出图像的质量,可能会减弱组间差异的检测能力,仍需注意其产生的影响。因此在确定实验方案前需探讨标本通量对实验结果是否产生影响,或者在整个研究中保持标本通量和标本摆放方式的一致性。

冗余铺放机器人的自运动流形及逆解优化研究

针对用于复合材料铺放成型的八自由度冗余机器人系统的逆运动学问题,提出了一种求解其自运动流形及逆解优化的算法。首先,基于位姿分离思想定义了位置子流形和姿态子流形,采用几何求解法得到了基于自运动变量的参数化方程形式的位置子流形和姿态子流形;然后,根据机器人的关节约束和实际铺放工艺过程,对给定的铺放位姿进行了位置子流形和姿态子流形配对的仿真,并用流形中若干组逆解通过正向运动学得到了末端位姿矩阵(其结果均与给定位姿相符,从而验证了自运动流形求解过程的正确性);最后,在完成自运动流形求解的基础上,从机械臂运动的平滑性和关节运动变化量两个方面出发,提出了一种基于自运动变量参数化方程的全局优化目标函数;以飞机尾椎模型为实验研究对象,对其中一条铺放路径进行了逆解全局优化仿真,得到了自运动变量和机器人各关节角在铺放路径上的优化曲线,将仿真结果与一种多目标优化算法进行了比较。研究结果表明:针对相同的铺放路径,采用上述优化算法后关节角变化总量降低了11.25%;该算法能够有效地求解八自由度冗余铺放机器人系统的自运动流形,基于全局优化目标函数,其能够在自运动流形中寻找出自运动变量和机器人各关节的最优解。该算法同样也适用于其他位姿解耦的冗余机器人系统逆解问题的求解。

基于区域划分的多波束测线布设

研究了海底地形为坡面和不规则面的多波束测线布设,包括测线方向和测线间距.针对坡面海域,利用数学证明得出沿平行等深线走向进行测线布设是最优方向,并根据多波束测线布设的基本原则,建立了满足测线总长度最小、重叠率在规定范围内的递推公式,利用该公式求解测线间距;针对不规则海域,将海底地形划分为若干个近似为坡面的海域,用最小二乘法将各区域拟合为坡面海域,并对拟合效果不佳的区域进行进一步划分.按照坡面海域的求解公式分别得到各个海域的测线布设,最终汇总得到了该不规则海域的测线布设方案.

面向在轨组装结构的传感器优化布置方法

大型航天结构在进行在轨组装时其构型与动力学参数不断改变,针对某一中间构型的传感器优化布置难以适用于在轨组装阶段的其余构型。针对这一问题,提出了一种基于组装有效独立法(Assembled Effective Independence, AEFI)的传感器优化布置方法。该方法对在轨组装阶段各构型的有效独立系数进行加权求和,提出了基于各组装阶段结构目标模态数量的权重计算方法,最后采用倒序删除法获得面向在轨组装结构的最优传感器布局。针对某一典型在轨组装结构对该方法进行了验证,选取了“I”型、“T”型以及“H”型构型三种典型组装阶段。结果表明,AEFI方法实现了所有组装构型的传感器最优布置。