检索结果-南通市图书馆

Investigation on nonlinear lateral-torsional coupled vibration of a rotor system with substantial unbalance

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2020年第6期33卷 1642-1660页

作者： Jie HONG Pingchao YU Yanhong MA dayi ZHANG school of Energy and Power Engineering Beihang UniversityBeijing 100083China Collaborative Innovation Center of Advanced Aero-Engine Beihang UniversityBeijing 100083China Beijing Key Laboratory of Aero-Engine structure and strength Beijing 100083China

substantial unbalance may be caused by fan blade off during the operation period of gas turbine engines,and related dynamic problems are very critical to the safety design of rotor system in *** article aims to understand lateral-torsional coupled vibration of the rotor system with substantial *** governing equation of a modified unbalanced rotor system is established based on Lagrangian ***,a mathematical analytical method is proposed in which a linear approximation is derived and the Floquet theory and Hill’s method are incorporated,from which the modal characteristics of the unbalanced rotor are *** modal characteristics of the unbalanced rotor system are revealed comprehensively for the first ***,the relation between the modes and responses of the unbalanced rotor is discussed in *** results show that the lateral vibration and torsional vibration of the unbalanced rotor are coupled through the inertial terms in the governing *** to the coupling,veering and lock-in phenomena occur between the frequencies of the forward whirl mode and the torsional ***,lock-in can lead to a kind of principal *** regard to the response of the unbalanced rotor,both natural vibration components and enforced vibration components appear in the lateral response,while only natural vibration components appear during torsional ***,natural vibration components play a crucial role in the response within the principal instability region and cause divergence of the vibration amplitudes in the lateral and torsional directions.

关键词： Instability Lateral-torsional coupled vibration Lock-in phenomenon Modes Unbalanced rotor

Bending and vibration of a discontinuous beam with a curvic coupling under different axial forces

在线全文

学校读者我要写书评

暂无评论

Frontiers of Mechanical Engineering 2020年第3期15卷 417-429页

作者： Heng LIU Jie HONG dayi ZHANG school of Energy and Power Engineering Beihang UniversityBeijing 100191China state Key Laboratory of Laser Propulsion and Application Beijing Power Machinery InstituteBeijing 100074China

The transverse stiffness and vibration characteristics of discontinuous beams can significantly differ from those of continuous beams given that an abrupt change in stiffness may occur at the interface of the *** this study,the equations for the deflection curve and vibration frequencies of a simply supported discontinuous beam under axial loads are derived analytically on the basis of boundary,continuity,and deformation compatibility conditions by using equivalent spring *** equation for the deflection curve is solved using undetermined coefficient *** normal function of the transverse vibration equation is obtained by separating *** differential equations for the beam that consider moments of inertia,shearing effects,and gyroscopic moments are investigated using the transfer matrix *** deflection and vibration frequencies of the discontinuous beam are studied under different axial loads and connection spring *** show that deflection decreases and vibration frequencies increase exponentially with increasing connection spring ***,both variables remain steady when connection spring stiffness reaches a considerable ***,an experimental study is conducted to investigate the vibration characteristics of a discontinuous beam with a curvic coupling,and the results exhibit a good match with the proposed model.

关键词： discontinuous beam bending stiffness transverse vibration axial loads gyroscopic moments

Application of statistical analysis of sample size:How many occupant responses are required for an indoor environmental quality(IEQ)field study

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

Building simulation 2023年第4期16卷 577-588页

作者： Heng Du Zhiwei Lian Li Lan dayi Lai Department of Architecture School of DesignShanghai Jiao Tong UniversityShanghai 200240China

Determining required sample size is one of the critical pathways to reproducible,reliable and robust results in human-related *** paper aims to answer a fundamental but often overlooked question:what sample size is required in surveys of occupant responses to indoor environmental quality(IEQ).The statistical models are introduced in order to promote determining required sample size for various types of data analysis methods commonly used in IEQ field *** Monte Carlo simulations are performed to verify the statistical methods and to illustrate the impact of sample size on the study accuracy and *** examples are presented to illustrate how to determine the value of the parameters in the statistical models based on previous similar research or existing *** required sample size including“worst”and“optimal”cases in each condition is obtained by this method and *** is indicated that 385 is a“worst case”sample size to be adequate for a subgroup analysis,while if the researcher has an estimate of the study design and outcome,the“optimal case”sample size can potentially be *** the required sample size is not achievable,the uncertainty in the result can properly interpret via a confidence *** is hoped that this paper would fill in the gap between statistical analysis of sample size and IEQ field research,and it can provide a useful reference for researchers when planning their own studies.

关键词： indoor environmental quality built environment field study sample size thermal comfort

Autonomous relative optical navigation based on unified modeling of external systematic errors

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

Chinese Journal of Aeronautics 2024年第3期37卷 282-289页

作者： dayi WANG Bowen sUN Maodeng LI Jiaxing LI Haiyin ZHOU Beijing Institute of spacecraft system Engineering Beijing 100191China College of sciences National University of Defense TechnologyChangsha 410073China National Key Laboratory of space Intelligent Control Beijing Institute of Control EngineeringBeijing 100191China

To solve the problem that external systematic errors of the optical camera cannot be fully estimated due to limited computing resources,a unified dimensionality reduction representation method for the external systematic errors of the optical camera is proposed,and autonomous relative optical navigation is *** camera translational and misalignment errors are converted into a three-dimensional rotation error,whose differential model can be established through specific attitude control and appropriate ***,the rotation error and the relative motion state are jointly estimated in an augmented Kalman filter *** with the traditional method that estimates the camera translational and misalignment errors,the proposed method reduces the computational complexity in that the estimated state dimension is ***,as demonstrated by numerical simulation,the estimation accuracy is improved significantly.

关键词： Unified model systematic errors Optical navigation Observability analysis Calibration

Modal characteristics analysis for a flexible rotor with non-smooth constraint due to intermittent rub-impact

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2018年第3期31卷 498-513页

作者： Jie HONG Pingchao YU dayi ZHANG Zhichao LIANG school of Energy and Power Engineering Beihang University Collaborative Innovation Center of Advanced Aero-Engine Beihang University

Intermittent rub-impact, during which the contact between rotor and stator is characterized by a ‘‘bouncing＂ or intermittent type of behavior, is one of the most common rubbing forms in rotating machinery. When the intermittent rub-impact occurs, the non-smooth constraint, which is the phenomenon that the system stiffness changes with respect to the state of contact and noncontact, will appear. The paper aims at discovering the possible effects of the non-smooth constraint on the flexible rotor＇s modal characteristics by theoretical and experimental methods. The qualitative description for non-smooth constraint is given for the intermittent rub-impact process, and the dynamic modeling for a rotor system with non-smooth constraint is carried out. Meanwhile, the analysis method is developed by Floquet theory and Hill＇s method to obtain the rotor＇s modal characteristics. The results reveal that the non-smooth constraint produced by the intermittent rubimpact will increase the modal frequencies and critical speeds of the rotor system *** to the time-varying features of the constraint stiffness, the modal frequencies for the intermittent rub-impact rotor present fluctuant changes with the increase of rotation speed, which is different from the general linear rotor system. The non-smooth constraint is possible to lead the rotor＇s instability, and the rotor＇s instable regions can be expanded significantly for the increase of average constraint stiffness, constraint amplitude and contact time ratio. Non-smooth constraint could also expand the resonance speed and resonance sideband of the rotor system, which sometimes results in amplitude jump phenomenon.

关键词： Flexible rotor Intermittent rub-impact Instabifity Modal characteristics Non-smooth constraint

A semi-analytical multi-harmonic balance method on full-3D contact model for dynamic analysis of dry friction systems

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第2期37卷 309-329页

作者： He sUN dayi ZHANG Yaguang WU Qingyang sHEN Dianyin HU Research Institute of Aero-Engine Beihang UniversityBeijing 100191China school of Energy and Power Engineering Beihang UniversityBeijing 100191China Beijing Key Laboratory of Aero-Engine structure and strength Beijing 100191China sino-French Engineering school Beihang UniversityBeijing 100191China AECC sichuan Gas Turbine Research Establishment Chengdu 610500China

Dry friction damping structures are widely-used in aero-engines to mitigate *** nonlinear nature of friction and the two-dimensional in-plane motion on the contact interface bring challenges to accurately and efficiently predict the forced response of frictionally damped *** state-of-the-art Multi-Harmonic Balance Method(MHBM)on quasi-3D contact model in engineering cannot precisely capture the kinematics on the friction interface although the efficiency is *** full-3D contact model can describe the constitutive relationship of the interface in a more accurate manner;however,the efficiency and convergence are not guaranteed for large-scale *** this paper,a semi-analytical MHBM on full-3D contact model is *** original Trajectory Tracking Method(TTM)for evaluating the contact force is reformulated to make the calculation more concise and the derivation of the Analytical Jacobian Matrix(AJM)*** on the chain rule of derivation,the AJM which is the core to upgrade the performance is *** a shrouded blade finite element model,the accuracy and efficiency of the proposed method are compared with both the MHBM on full-3D contact model with numerical Jacobian matrix and the MHBM on quasi-3D contact model with *** results show that the AJM improves significantly the efficiency of the MHBM on full-3D contact *** time cost of the proposed method is in the same order of magnitude as that of the MHBM on quasi-3D contact *** also confirm that the full-3D contact model is necessary for the dynamic analyses of shrouded *** one uses the quasi-3D model,the estimation relative error of damping can even reach 31.8%in some *** addition,the AJM also brings benefits for stability *** is highly recommended that engineers use the MHBM on full-3D contact model for the dynamic analysis and design of shrouded blades.

关键词： Dry friction damping Multi-harmonic balance method Trajectory tracking method Jacobian matrix shrouded blade

Thermal comfort models and their developments:A review

在线全文

学校读者我要写书评

暂无评论

Energy and Built Environment 2021年第1期2卷 21-33页

作者： Qiantao Zhao Zhiwei Lian dayi Lai Department of Architecture School of DesignShanghai Jiao Tong UniversityChina

In the past several years,thermal comfort,especially development and application of thermal comfort model,has been a research focus of building *** the 1970s,a series of thermal comfort models based on people’s thermal sensation to environment have been established,and gradually became an important part of the field of thermal comfort *** this review,the existing thermal comfort models are summarized from various perspectives,such as models applied in different environments like sleeping environment and outdoor ***,models used for different groups people,such as elderly and different races are *** the part,adaptive models are *** additions,data-driven models were *** paper introduced the advantages and disadvantages of each *** on the above review,future research work of thermal comfort model is proposed.

关键词： Thermal comfort Model Human thermoregulation Built environment Development

Optimal maneuvering strategy of spacecraft evasion based on angles-only measurement and observability analysis

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

Journal of systems Engineering and Electronics 2023年第1期34卷 172-184页

作者： ZHANG Yijie WANG Jiongqi HOU Bowen WANG dayi CHEN Yuyun College of Liberal Arts and sciences National University of Defense TechnologyChangsha 410073China Beijing Institute of spacecraft system Engineering Beijing 100190China school of Mathematics and Big Data Foshan UniversityFoshan 528000China

spacecraft orbit evasion is an effective method to ensure space safety. In the spacecraft’s orbital plane, the space non-cooperate target with autonomous approaching to the spacecraft may have a dangerous rendezvous. To deal with this problem, an optimal maneuvering strategy based on the relative navigation observability degree is proposed with angles-only measurements. A maneuver evasion relative navigation model in the spacecraft’s orbital plane is constructed and the observability measurement criteria with process noise and measurement noise are defined based on the posterior Cramer-Rao lower bound. Further, the optimal maneuver evasion strategy in spacecraft’s orbital plane based on the observability is proposed. The strategy provides a new idea for spacecraft to evade safety threats autonomously. Compared with the spacecraft evasion problem based on the absolute navigation, more accurate evasion results can be obtained. The simulation indicates that this optimal strategy can weaken the system’s observability and reduce the state estimation accuracy of the non-cooperative target, making it impossible for the non-cooperative target to accurately approach the spacecraft.

关键词： rendezvous evasion orbit maneuver angles-only measurement observability degree posterior Cramer-Rao lower bound

Characterization of recuperating talent of white-rot fungi cells to dye-contaminated soil/water

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2019年第3期27卷 634-638页

作者： Bugra dayi Aidai Duishemambet Kyzy Hatice Ardag Akdogan Pamukkale University Faculty of Science and Arts Department of Chemistry

This study was purposed to explore the decolorization of dyes by fungi on either a soil or in a liquid medium and to determine the application through batch shaking system. Two commercial dyes were decolorized and studied with four fungal strains in three media. Fungal growth is the best in malt extract/glucose medium for all organisms. Decolorization of reactive blue 220 and methyl red was investigated in soil medium by Trametes versicolor. These dyes were removed 91% and 80% for methyl red and reactive blue 220 respectively(dye concentration; 100 mg·L^(-1)) by both organisms. Enzymatic activities were monitored. Laccase(Lac) and manganese peroxidase(Mn P) were detected. MnP enzyme had important role for the dye decolorization. This study demonstrates that it is possible to decolorize some synthetic dyes, which would be highly advanced for dye containing wastewater and soil. These applications could be used for dye bioremediation.

关键词： Trametes versicolor Bioremediation Dye Contamination soil Waste water