Influences of load pattern selection and higher modes on pushover analysis for R.C. structures

Load pattern selection is one of the critical issues in pushover analysis (POA) when the influence of higher modes is evident. In terms of interstory drift, comparisons between the nonlinear time history analysis (NL-THA) and the pushover analysis (POA) were conducted for three typical RC frame buildings under a variety of ground motion levels. Eight typical earthquake inputs, including four earthquake records and four artificial earthquake waves, were employed as the input of NL-THA; five typical lateral load patterns were considered in POA. By means of modal participation factor, the higher mode effect in POA was quantified considering floor numbers and the ground motion intensity. Suggestions about load pattern selection in POA were provided when higher mode influence was found evident.

Control system design for a pressure-tube-type supercritical water-cooled nuclear reactor via a higher order sliding mode method

Nuclear power plants exhibit non-linear and time-variable dynamics.Therefore,designing a control system that sets the reactor power and forces it to follow the desired load is complicated.A supercritical water reactor(SCWR)is a fourth-generation conceptual reactor.In an SCWR,the non-linear dynamics of the reactor require a controller capable of control-ling the nonlinearities.In this study,a pressure-tube-type SCWR was controlled during reactor power maneuvering with a higher order sliding mode,and the reactor outgoing steam temperature and pressure were controlled simultaneously.In an SCWR,the temperature,pressure,and power must be maintained at a setpoint(desired value)during power maneuvering.Reactor point kinetics equations with three groups of delayed neutrons were used in the simulation.Higher-order and classic sliding mode controllers were separately manufactured to control the plant and were compared with the PI controllers speci-fied in previous studies.The controlled parameters were reactor power,steam temperature,and pressure.Notably,for these parameters,the PI controller had certain instabilities in the presence of disturbances.The classic sliding mode controller had a higher accuracy and stability;however its main drawback was the chattering phenomenon.HOSMC was highly accurate and stable and had a small computational cost.In reality,it followed the desired values without oscillations and chattering.

Record-Breaking Frequency of 44 GHz Based on the Higher Order Mode of Surface Acoustic Waves with LiNbO_(3)/SiO_(2)/SiC Heterostructures

Surface acoustic wave (SAW) technology has been extensively explored for wireless communication, sensors, microfluidics, photonics, and quantum information processing. However, due to fabrication issues, the frequencies of SAW devices are typically limited to within a few gigahertz, which severely restricts their applications in 5G communication, precision sensing, photonics, and quantum control. To solve this critical problem, we propose a hybrid strategy that integrates a nanomanufacturing process (i.e., nanolithography) with a LiNbO_(3)/SiO_(2)/SiC heterostructure and successfully achieve a record-breaking frequency of about 44 GHz for SAW devices, in addition to large electromechanical coupling coefficients of up to 15.7%. We perform a theoretical analysis and identify the guided higher order wave modes generated on these slow-on-fast SAW platforms. To demonstrate the superior sensing performance of the proposed ultra-high-frequency SAW platforms, we perform micro-mass sensing and obtain an extremely high sensitivity of approximately 33151.9 MHz·mm2·μg−1, which is about 1011 times higher than that of a conventional quartz crystal microbalance (QCM) and about 4000 times higher than that of a conventional SAW device with a frequency of 978 MHz.

Robust Adaptive Gain Higher Order Sliding Mode Observer Based Control-constrained Nonlinear Model Predictive Control for Spacecraft Formation Flying

This work deals with the development of a decentralized optimal control algorithm, along with a robust observer,for the relative motion control of spacecraft in leader-follower based formation. An adaptive gain higher order sliding mode observer has been proposed to estimate the velocity as well as unmeasured disturbances from the noisy position measurements.A differentiator structure containing the Lipschitz constant and Lebesgue measurable control input, is utilized for obtaining the estimates. Adaptive tuning algorithms are derived based on Lyapunov stability theory, for updating the observer gains,which will give enough flexibility in the choice of initial estimates.Moreover, it may help to cope with unexpected state jerks. The trajectory tracking problem is formulated as a finite horizon optimal control problem, which is solved online. The control constraints are incorporated by using a nonquadratic performance functional. An adaptive update law has been derived for tuning the step size in the optimization algorithm, which may help to improve the convergence speed. Moreover, it is an attractive alternative to the heuristic choice of step size for diverse operating conditions. The disturbance as well as state estimates from the higher order sliding mode observer are utilized by the plant output prediction model, which will improve the overall performance of the controller. The nonlinear dynamics defined in leader fixed Euler-Hill frame has been considered for the present work and the reference trajectories are generated using Hill-Clohessy-Wiltshire equations of unperturbed motion. The simulation results based on rigorous perturbation analysis are presented to confirm the robustness of the proposed approach.

Higher-mode effect on the seismic responses of buildings with viscoelastic dampers

In conventional modal analysis procedures,usually only a few dominant modes are required to describe the dynamic behavior of multi-degrees-of-freedom buildings.The number of modes needed in the dynamic analysis depends on the higher-mode contribution to the structural response,which is called the higher-mode effect.The modal analysis approach, however,may not be directly applied to the dynamic analysis of viscoelastically damped buildings.This is because the dynamic properties of the viscoelastic dampers depend on their vibration frequency.Therefore,the structural stiffness and damping contributed from those dampers would be different for each mode.In this study,the higher-mode effect is referred to as the response difference induced by the frequency-dependent property of viscoelastic dampers at higher modes.Modal analysis procedures for buildings with viscoelastic dampers distributed proportionally and non-proportionally to the stiffness of the buildings are developed to consider the higher-mode effect.Numerical studies on shear-type viscoelastically damped building models are conducted to examine the accuracy of the proposed procedures and to investigate the significance of the higher-mode effect on their seismic response.Two damper models are used to estimate the peak damper forces in the proposed procedures. Study results reveal that the higher-mode effect is significant for long-period viscoelastically damped buildings.The higher-mode effect on base shear is less significant than on story acceleration response.Maximum difference of the seismic response usually occurs at the top story.Also,the higher-mode effect may not be reduced by decreasing the damping ratio provided by the viscoelastic dampers.For practical application,it is realized that the linear viscous damping model without considering the higher-mode effect may predict larger damper forces and hence,is on the conservative side.

Study of the Mode of Cost-sharing by Indi-viduals for Higher Education in China

In recent years, financial crises of higher education have become universal. The policy of cost-sharing by in- dividuals was tried out in many countries. However, empirical studies have shown that the policy has, to a certain de- gree, negative effects for the poor in accepting higher education costs. This paper points out it is the mismatch between tuition fees and the ability to pay that causes the problem. Using two dimensions of group and time to pay, a mode sys- tem, including seven modes for the individual to share the cost of higher education, was constructed. It is suggested that only three modes of pay-immediately have been carried out in China and they all have same shortcomings. To try new modes and exercise different modes synthetically will be meaningful for solving the questions that exist in the current policy.

Speech-stream detection in short-wave channel based on empirical mode decomposition and higher-order statistics

To capture the presence of speech embedded in nonspeech events and background noise in short-wave non-cooperative communication,an algorithm for speech-stream detection in noisy environments is presented based on Empirical Mode Decomposition (EMD) and statistical properties of higher-order cumulants of speech signals.With the EMD,the noise signals can be decomposed into different numbers of IMFs.Then,the fourth-order cumulant (FOC) can be used to extract the desired feature of statistical properties for IMF components.Since the higher-order cumulants are blind for Gaussian signals,the proposed method is especially effective regarding the problem of speech-stream detection,where the speech signal is distorted by Gaussian noise.With the self-adaptive decomposition by EMD,the proposed method can also work well for non-Gaussian noise.The experiments show that the proposed algorithm can suppress different noise types with different SNRs,and the algorithm is robust in real signal tests.

Theory of higher harmonics imaging in tapping-mode atomic force microscopy

The periodic impact force induced by tip-sample contact in a tapping mode atomic force microscope （AFM） gives rise to the non-harmonic response of a micro-cantilever. These non-harmonic signals contain the full characteristics of tip-sample interaction. A complete theoretical model describing the dynamical behaviour of tip-sample system was developed in this paper. An analytic formula was introduced to describe the relationship between time-varying tip-sample impact force and tip motion. The theoretical analysis and numerical results both show that the timevarying tip-sample impact force can be reconstructed by recording tip motion. This allows for the reconstruction of the characteristics of the tip-sample force, like contact time and maximum contact force. It can also explain the ability of AFM higher harmonics imaging in mapping stiffness and surface energy variations.

Contrastive Study of Differences between Chinese and American Higher Education Teaching Modes

This paper,based on the classroom teaching in University of Bridgeport and Anhui Polytechnic University,explores some differences in education notions,course design,teacher-student relationship,teaching methods,assessment and evaluation system between Chinese and American higher education.And some reflections and suggestions on Chinese higher education are given to promote Chinese higher education effect.

An Exploration of a New Running Mode of Equipment Management for Institutions of Higher Learning

With the great changes in China's economic mechanism, the present running modes of equipment management at most institutions of higher learning are becoming less and less effective and efficient. Being fully aware of the common problems and their characteristics, this paper proposes a new running mode which aims at these problems' permanent resolution. It involves (1) Systems such as renting, competition and paid services are to be introduced to the campus, in order to effectively associate duty with interest. (2) The present managerial pattern is to be replaced by a new running network, in which all the links cooperate with as well as restrain each other. Such a mode focuses on the “two mechanisms and four patterns,”that is, to rely on the stimulative mechanism and restraint mechanism, and to enforce such patterns as centralized management and application centralized management and common application, opening to public use, and renting and borrowing. Through persistent exploration of the inner potential of the institutions, the ratio of investment and economic efficiency will accordingly be elevated.

新工科背景下智能制造工程专业教学探索与实践

为应对“中国制造2025”国家战略,顺应新工科背景下高等工程教育改革发展,国家提出建设智能制造新工科专业。智能制造工程专业在强数理基础上,基于机械学科主干知识体系,融入控制、计算机、人工智能等信息学科知识,探索“数字化+网络化+智能化”时代背景下,新技术特色的智能制造理论课程体系;同时,为有利于学生系统掌握交叉学科知识,实践教学体系通过打通专业交叉知识之间的边界,破除知识孤岛,以工程项目为导向构建实践教学内容,探讨适应智能制造工程专业人才培养的实践教学体系。智能制造工程专业教学探索与实践将促进新工科专业知识之间的交叉融合,逐步适应未来制造领域发展的新需要,有效提升高等教育机械工程专业复合型高端人才的培养质量。

基于POA理论的农业高职英语教学模式研究

以“高等职业教育专科英语课程标准(2021年版)”为准则,以POA理论为指导,构建农业高职英语“二场域三阶段四素养”教学模式,以任务驱动、教学促成和综合评价的课堂教学为路径,课程思政融入其中,实现对学生语言输出能力和职场综合能力的培养。

智能制造视域下电子制造类专业创新应用型人才的培养模式思考

针对当前传统电子产品制造类(SMT)专业人才的生存空间不断受到挤压甚至专业被取消的现象,将以实际案例分析传统SMT专业人才培养模式的现状、不足与生存困境。立足于大数据、工业互联网以及人机协作的新型智能制造背景下,通过多学科交叉、产教融合、科教协同以及数字化转型等途径,以创新应用为导向,坚持将创新意识、创新思维、创新品格、创新能力以及创新惯性等“五创”融入专业人才培养的各个环节;重构SMT专业课程体系,以合伙人身份融入智能制造各相关专业,突破原来的“点对点”模式;多元协同育人,线上线下融合,打破课堂45分钟的边界;改变师资搭配、充分利用校企合作育人平台,将学生、学徒以及工人三种身份融为一体,探究一套新的创新应用型人才培养路径,为高职院校培养符合智能化时代新岗位、新职业特征的创新应用型人才提供参考借鉴。

广东省高等教育国际化的政策演变与发展模式创新

“十一五”以来,广东省高等教育国际化的政策经历了以技术过程为核心层次、增加组织管理核心层次以及开始关注外部关系为核心层次的国际化活动阶段。单一维度发展模式在一定程度上限制了其国际化的发展,广东高等教育国际化应构建技术过程层次的质量体系、完善组织管理层次的支持机制以及搭建外部关系层次的枢纽门户的三维动态交互发展模式。

高职英语混合式教学模式构建及应用策略探究

近几年,以现代信息网络技术为支撑的混合式教学模式,因融合线上与线下教学的双重优势,为高职英语教学改革带来新机遇。通过构建高职英语混合式教学模式,能够在一定程度上弥补传统英语课堂教学单一性的弊端,以丰富多样的教学资源,多维度着手的教学模式,提升高职英语教学实效性。

信息化背景下高等学历继续教育远程化教学模式改革的深化研究

高校高等学历继续教育远程化教学模式改革已经开展较长时间,取得显著成效,但某些方面如规章制度、课程内容与教学方式、教学评价与质量监控等方面暴露出新的问题。在新时期,需要在信息化背景下科学确立人才培养目标、优化课程体系、创新教学方式和教学手段、推进学分制改革、实现学籍档案的数字化和强化教学评价与质量监控等6个方面,深入构建高等学历继续教育远程化教学及人才培养新模式,从而推进继续教育全面协调可持续发展。