检索结果-南通市图书馆

The Optimization Design of the Nozzle Section for theWater Jet Propulsion System Applied in Jet Skis

Computer Modeling in Engineering & Sciences 2024年第3期138卷 2277-2304页

作者： Cheng-Yeh li Jui-Hsiang Kao Department of Systems Engineering and Naval Architecture Taiwan Ocean UniversityKeelungTaiwanChina

The performance of a water jet propulsion system is related to the inlet duct,rotor,stator,and nozzle.Generally,the flow inlet design must fit the bottom line of the hull,and the design of the inlet duct is often limited by stern space.The entire section,from the rotor to the nozzle through the stator,must be designed based on system integration in that the individual performance of these three components will influence each other.Particularly,the section from the rotor to the nozzle significantly impacts the performance of a water jet propulsion system.This study focused on nozzle design and established referable analysis results to facilitate subsequent integrated studies on the design parameters regarding nozzle contour.Most existing studies concentrate on discussions on rotor design and the tip leakage flow of rotors or have replaced the existing complex computational domain with a simple flow field.However,research has yet to implement an integrated,optimal design of the section from the rotor to the nozzle.Given the above,our program conducted preliminary research on this system integration design issue,discussed the optimal nozzle for this section in-depth,and proposed design suggestions based on the findings.This program used an existing model as the design case.This study referred to the actual trial data as the design conditions for the proposed model.Unlike prior references’simple flow field form,this study added a jet ski geometry and free surface to the computational domain.After the linear hull shape was considered,the inflow in the inlet duct would be closer to the actual condition.Based on the numerical calculation result,this study recommends that the optimal nozzle outlet area should be 37%of the inlet area and that the nozzle contour should be linear.Furthermore,for the pump head,static pressure had a more significant impact than dynamic pressure.

关键词： Water jet propulsion system rotor nozzle outlet area nozzle contour

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Preparation of a biomimetic superomniphobic hierarchical structure and analysis of droplet wettability

引用

Biosurface and Biotribology 2022年第2期8卷 129-139页

作者： jing li Qunxiang feng Nan Guo Fei Wang Xin Du feng Du College of Mechanical and Electric Engineering Changchun University of Science and TechnologyChangchunChina School of Opto-Electronic Engineering Changchun University of Science and TechnologyChangchunChina Non-Commissioned Officer School of Army Academy of Armored Forces Changchun Economic and Technological Development Zone of Jilin ProvinceChangchunChina

In this study,a bioinspired hierarchical structure was formed with superomniphobicity on a 7075 aluminium alloy using laser ablation.The morphology and wetting characteristics of the biomimetic sample surface were characterised using scanning electron microscopy,laser confocal microscopy,and contact angle measurements.The effect of the liquid properties and surface structures on the rolling behaviour was investigated.The results suggest that the fabricated biomimetic sample surface was a hierarchical structure.The prepared sample had superomniphobicity and low adhesion properties,and the contact angles of six different liquid droplets on the sample surface reached or approached 150°.Specifically,the largest contact angle was 152°,and the average rolling angle was 7.7°.This multi-hydrophobic surface provides a valuable reference for the research study and use of a variety of solid–liquid contacts.

关键词： bioinspiration hierarchical structures low adhesion superomniphobicity

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Enriched Constant Elements in the Boundary Element Method for Solving 2D Acoustic Problems at Higher Frequencies

引用

Computer Modeling in Engineering & Sciences 2024年第3期138卷 2159-2175页

作者： Zonglin li Zhenyu Gao Yijun liu School of Astronautics Harbin Institute of TechnologyHarbin150001China Department of Mechanics and Aerospace Engineering Southern University of Science and TechnologyShenzhen518055China

The boundary element method(BEM)is a popular method for solving acoustic wave propagation problems,especially those in exterior domains,owing to its ease in handling radiation conditions at infinity.However,BEM models must meet the requirement of 6–10 elements per wavelength,using the conventional constant,linear,or quadratic elements.Therefore,a large storage size of memory and long solution time are often needed in solving higher-frequency problems.In this work,we propose two new types of enriched elements based on conventional constant boundary elements to improve the computational efficiency of the 2D acoustic BEM.The first one uses a plane wave expansion,which can be used to model scattering problems.The second one uses a special plane wave expansion,which can be used tomodel radiation problems.Five examples are investigated to showthe advantages of the enriched elements.Compared with the conventional constant elements,the new enriched elements can deliver results with the same accuracy and in less computational time.This improvement in the computational efficiency is more evident at higher frequencies(with the nondimensional wave numbers exceeding 100).The paper concludes with the potential of our proposed enriched elements and plans for their further improvement.

关键词： Enriched boundary elements constant elements 2D acoustic problems higher frequency

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Marangoni-flow-assisted assembly of single-walled carbon nanotube films for human motion sensing

引用

Fundamental Research 2024年第3期4卷 570-574页

作者： Yuguang Chen Yitan li Lu Han Hao Sun Min Lyu Zeyao Zhang Shigeo Maruyama Yan li Key Laboratory for the Physics and Chemistry of Nanodevices Beijing National Laboratory of Molecular SciencesState Key Laboratory of Rare Earth Materials Chemistry and ApplicationsCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China Academy for Advanced Interdisciplinary Studies Peking UniversityBeijing 100871China Bruker(Beijing)Scientific Technology Co.Ltd. Beijing 100192China Department of Mechanical Engineering The University of TokyoTokyo 113-8656Japan Peking University Shenzhen Institute Shenzhen 518057China PKU-HKUST ShenZhen-HongKong Institution Shenzhen 518057China

Single-walled carbon nanotubes(SWCNTs)present excellent electronic and mechanical properties desired in wearable and flexible devices.The preparation of SWCNT films is the first step for fabricating various devices.This work developed a scalable and feasible method to assemble SWCNT thin films on water surfaces based on Marangoni flow induced by surface tension gradient.The films possess a large area of 40 cm×30 cm(extensible),a tunable thickness of 15∼150 nm,a high transparency of up to 96%,and a decent conductivity.They are ready to be directly transferred to various substrates,including flexible ones.Flexible strain sensors were fabricated with the films on flexible substrates.These sensors worked with high sensitivity and repeatability.By realizing multi-functional human motion sensing,including responding to voices,monitoring artery pulses,and detecting knuckle and muscle actions,the assembled SWCNT films demonstrated the potential for application in smart devices.

关键词： Single-walled carbon nanotubes Marangoni flow Assembly Interfaces Sensors

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

外部干扰和随机DoS攻击下的网联车安全H∞队列控制

引用

自动化学报 2024年第2期50卷 348-355页

作者：宋秀兰李洋阳何德峰浙江工业大学信息工程学院杭州310023

针对网联车队列系统易受到干扰和拒绝服务(Denial of service, DoS)攻击问题,提出一种外部干扰和随机DoS攻击作用下的网联车安全H∞队列控制方法.首先,采用马尔科夫随机过程,将网联车随机DoS攻击特性建模为一个随机通信拓扑切换模型,据... 详细信息

针对网联车队列系统易受到干扰和拒绝服务(Denial of service, DoS)攻击问题,提出一种外部干扰和随机DoS攻击作用下的网联车安全H∞队列控制方法.首先,采用马尔科夫随机过程,将网联车随机DoS攻击特性建模为一个随机通信拓扑切换模型,据此设计网联车安全队列控制协议.然后,采用线性矩阵不等式(linear matrix inequality, LMI)技术计算安全队列控制器参数,并应用Lyapunov-Krasovskii稳定性理论,建立在外部扰动和随机DoS攻击下队列系统稳定性充分条件.在此基础上,分析得到该队列闭环系统的弦稳定性充分条件.最后,通过7辆车组成的队列系统对比仿真实验,验证该方法的优越性.

关键词：网联自主车辆队列控制安全控制随机DoS攻击稳定性

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

20~59岁山西籍个别正常(牙合)上前牙正面观美学指标分析

引用

口腔颌面修复学杂志 2024年第3期25卷 180-186页

作者：王景李风兰杨红霞李立美山西医科大学口腔医学院·口腔医院太原030001 山西医科大学第五临床医院口腔修复科太原030001

目的:分析山西籍个别正常(牙合)上前牙正面观美学指标,探讨性别、年龄、牙形、面形对牙齿美学指标的影响,为上前牙美学修复设计提供参考。方法:2022年10月~2023年6月于山西省人民医院体检中心选取20~59岁个别正常(牙合)受试者322例,以1... 详细信息

目的:分析山西籍个别正常(牙合)上前牙正面观美学指标,探讨性别、年龄、牙形、面形对牙齿美学指标的影响,为上前牙美学修复设计提供参考。方法:2022年10月~2023年6月于山西省人民医院体检中心选取20~59岁个别正常(牙合)受试者322例,以10岁为组距,按照年龄等距分为4个年龄组,拍摄其息止颌位正面像与前牙列正面咬合照,观测并记录面形分类与上中切牙形态分类,使用图像处理软件测量上前牙宽度、长度、上中切牙与侧切牙及尖牙间切缘台阶,并计算上中切牙宽长比、上前牙宽度比,分析各测量项目的性别差异与组间差异。结果:男性的W1/L1[0.83(0.10)]显著小于女性[0.86(0.10)](P0.05),不同形态天然上中切牙的宽长比不同[尖圆形、卵圆形、方圆形分别为0.78(0.07)、0.84(0.06)、0.90(0.08)](P<0.001)。40~49岁组的L1[(10.21±0.85) mm]显著大于20~29岁组[(9.84±0.76)mm]与30~39岁组[(9.87±1.01)mm](P<0.05)。女性的上中切牙与侧切牙间切缘台阶、上中切牙与尖牙间切缘台阶[分别为0.92(0.60)、1.32(1.00)mm]均显著大于男性[分别为0.80(0.60)、1.08(1.50)mm](P<0.05)。上中切牙与侧切牙间的切缘台阶从尖圆面形、卵圆面形到方圆面形逐渐减小[分别为1.33(0.38)、0.81(0.23)、0.43(0.95)mm](P<0.001)。关于上中切牙与尖牙间的切缘台阶,尖圆面形最大,其次是卵圆形和方圆形[分别为1.81(0.84)、1.17(0.87)、0.56(0.88)mm](P<0.001)。结论:前牙美学设计时需考虑性别差异的影响,但上中切牙宽长比的两性差异与牙齿形态无关;40~49岁个别正常上中切牙临床冠长度较20~29岁与30~39岁显著增加;前牙切缘台阶的设计应考虑性别差异及面形的影响。

关键词：牙齿美学美学比例切缘台阶牙齿形态牙修复体设计

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

基于Seed-PCG法的列车-轨道-地基土三维随机振动GPU并行计算方法

引用

Journal of Central South University 2024年第1期31卷 302-316页

作者：朱志辉冯杨杨啸李昊邹有 National Engineering Research Center of High-speed Railway Construction Technology Changsha 410075China School of Civil Engineering Central South UniversityChangsha 410075China School of Computer Science and Engineering Center South UniversityChangsha 410083China Information and Network Center Central South UniversityChangsha 410083China

为了解决列车-轨道-地基土三维有限元模型随机多样本计算效率低的问题,本文提出了一种基于Seed-PCG法的高效并行计算方法。基于有限元法和虚拟激励法建立轨道不平顺激励下的三维列车-轨道-地基土耦合随机振动分析模型;针对车致地基土随... 详细信息

为了解决列车-轨道-地基土三维有限元模型随机多样本计算效率低的问题,本文提出了一种基于Seed-PCG法的高效并行计算方法。基于有限元法和虚拟激励法建立轨道不平顺激励下的三维列车-轨道-地基土耦合随机振动分析模型;针对车致地基土随机振动分析产生的多右端项线性方程组求解问题,采用Seed-PCG方法进行求解。通过PCG方法求解种子系统得到的Krylov子空间进行投影,以改进其余线性方程组的初始解和对应的初始残量,有效提高了PCG法的收敛速度,最后,在MATLABCUDA混合平台上开发了并行计算程序。数值算例表明:相同计算平台下的该方法相比多点同步算法获得了104.2倍的加速;相比PCG法逐个求解方案减少了18%的迭代次数,获得了1.21倍的加速。

关键词： Seed-PCG法多右端项线性方程组随机振动 GPU并行计算列车-轨道-地基土耦合模型

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Dynamic motion of quadrupedal robots on challenging terrain:a kinodynamic optimization approach

引用

Frontiers of Mechanical Engineering 2024年第3期19卷 23-40页

作者： Qi li Lei DING Xin LUO Engineering Research Center of Hubei Province for Clothing Information Wuhan 430200China School of Computer Science and Artificial Intelligence Wuhan Textile UniversityWuhan 430200China State Key Laboratory of Digital Manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhan 430074China

The dynamic motion of quadrupedal robots on challenging terrain generally requires elaborate spatial–temporal kinodynamic motion planning and accurate control at higher refresh rate in comparison with regular terrain.However,conventional quadrupedal robots usually generate relatively coarse planning and employ motion replanning or reactive strategies to handle terrain irregularities.The resultant complex and computation-intensive controller may lead to nonoptimal motions or the breaking of locomotion rhythm.In this paper,a kinodynamic optimization approach is presented.To generate long-horizon optimal predictions of the kinematic and dynamic behavior of the quadruped robot on challenging terrain,we formulate motion planning as an optimization problem;jointly treat the foot’s locations,contact forces,and torso motions as decision variables;combine smooth motion and minimal energy consumption as the objective function;and explicitly represent feasible foothold region and friction constraints based on terrain information.To track the generated motions accurately and stably,we employ a whole-body controller to compute reference position and velocity commands,which are fed forward to joint controllers of the robot’s legs.We verify the effectiveness of the developed approach through simulation and on a physical quadruped robot testbed.Results show that the quadruped robot can successfully traverse a 30°slope and 43% of nominal leg length high step while maintaining the rhythm of dynamic trot gait.

关键词： quadrupedal robot kinodynamic planning nonlinear optimization challenging terrain whole-body control

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

PBX内部裂纹水浸超声全聚焦成像方法研究

引用

含能材料 2024年第4期32卷 353-359页

作者：甘仁杰禹利达李海宁张伟斌李卫彬杨占锋中国工程物理研究院化工材料研究所四川绵阳621999 厦门大学航空航天学院福建厦门361102 中南大学交通运输工程学院湖南长沙410075

高聚物粘结炸药(PBX)的内部裂纹检测对其使用安全性和结构完整性评价具有重要意义和工程应用价值。为了提高PBX内部裂纹缺陷的成像检测精度和图像质量,研究了曲面修正水浸超声全聚焦成像方法,并在此基础上进一步结合了延迟乘和波束形成(... 详细信息

高聚物粘结炸药(PBX)的内部裂纹检测对其使用安全性和结构完整性评价具有重要意义和工程应用价值。为了提高PBX内部裂纹缺陷的成像检测精度和图像质量,研究了曲面修正水浸超声全聚焦成像方法,并在此基础上进一步结合了延迟乘和波束形成(DMAS)技术,通过水浸法对Φ100.0 mm的半圆柱PBX的底部裂纹缺陷进行了超声成像检测研究,实现了对曲面构形PBX底部裂纹缺陷的高精度成像表征。实验结果表明,传统全聚焦成像算法的裂纹缺陷高度测量误差为12.0%,图像信噪比为1.37 dB;曲面修正后的裂纹缺陷高度测量误差为3.6%,图像信噪比为2.13 dB;而曲面修正结合DMAS算法成像的裂纹缺陷高度测量误差仅为0.4%,图像信噪比为5.32 dB。

关键词：高聚物粘结炸药(PBX) 曲面修正成像算法延迟乘和波束形成(DMAS)技术裂纹

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

A Formal Model for Analyzing Fair Exchange Protocols Based on Event Logic

引用

Computer Modeling in Engineering & Sciences 2024年第3期138卷 2641-2663页

作者： Ke Yang Meihua Xiao Zehuan li School of Electrical Engineering and Automation East China Jiaotong UniversityNanchang330013China School of Software East China Jiaotong UniversityNanchang330013China

Fair exchange protocols play a critical role in enabling two distrustful entities to conduct electronic data exchanges in a fair and secure manner.These protocols are widely used in electronic payment systems and electronic contract signing,ensuring the reliability and security of network transactions.In order to address the limitations of current research methods and enhance the analytical capabilities for fair exchange protocols,this paper proposes a formal model for analyzing such protocols.The proposed model begins with a thorough analysis of fair exchange protocols,followed by the formal definition of fairness.This definition accurately captures the inherent requirements of fair exchange protocols.Building upon event logic,the model incorporates the time factor into predicates and introduces knowledge set axioms.This enhancement empowers the improved logic to effectively describe the state and knowledge of protocol participants at different time points,facilitating reasoning about their acquired knowledge.To maximize the intruder’s capabilities,channel errors are translated into the behaviors of the intruder.The participants are further categorized into honest participants and malicious participants,enabling a comprehensive evaluation of the intruder’s potential impact.By employing a typical fair exchange protocol as an illustrative example,this paper demonstrates the detailed steps of utilizing the proposed model for protocol analysis.The entire process of protocol execution under attack scenarios is presented,shedding light on the underlying reasons for the attacks and proposing corresponding countermeasures.The developedmodel enhances the ability to reason about and evaluate the security properties of fair exchange protocols,thereby contributing to the advancement of secure network transactions.

关键词： Fair exchange protocols fairness formal analysis logic reasoning

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：