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Predictor-corrector algorithm for solving quasi-separated-flow and transient distributed-parameter model

Ping ZHANG, Guoliang DING

《能源前沿（英文）》 2010年第4卷第4期页码 535-541 doi: 10.1007/s11708-010-0113-y

摘要： The successive sub?stitution (SS) method is a suitable approach to solving the transient distributed-parameter model for heat exchangers. However, this method must be enhanced because its convergence heavily depends on the iterative initial pressure. When the iterative initial pressure is improperly assigned, the calculated flow rates become negative values, causing the state parameters to exhibit negative values as well. Therefore, a predictor-corrector algorithm (PCA) is proposed to improve the convergence of the SS method. A predictor is developed to determine an appropriate iterative initial pressure. Total fluid mass is adopted as the convergence criterion of pressure iteration instead of outlet flow rate as is done in the SS method. Convergence analysis and case study of the PCA and SS method are conducted, which show that the PCA has better convergence than the SS method under the same working conditions.

关键词： algorithm convergence heat exchanger modeling transient

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Stability and coupling dynamic behavior of nonlinear journal active electromagnetic bearing rotor system

LU Yanjun, HEI Di, WANG Yuan, DAI Rong, LU Yanjun, LIU Heng, YU Lie

《机械工程前沿（英文）》 2008年第3卷第2期页码 193-199 doi: 10.1007/s11465-008-0023-4

摘要： The stability and coupling dynamic behavior of a journal active electromagnetic bearing rotor system are analyzed. The gyroscopic effect is considered in the rotor model. The system equations are formulated by combining equations for rotor motion and decentralized proportional integral differential (PID) controllers. A method combining the predictor-corrector mechanism and the Netwon-Raphson method is presented to calculate the critical speed at the corresponding Hopf bifurcation point of the system. For periodic motions, a continuation method combining the predictor-corrector mechanism and shooting method is presented. Nonlinear unbalanced periodic motions and their stability margins are obtained using the shooting method and established continuation method for periodic motions. With the change of control parameters, the system local stability and bifurcation behaviors are obtained using the Floquet theory. The numerical examples show that the schemes not only significantly save computing cost, but also have high precision.

关键词： proportional integral bifurcation corresponding integral differential predictor-corrector mechanism

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Analysis of stability and nonlinear response of rotor system with elliptical sliding bearing supports

LU Yanjun, LIU Heng, YU Lie, LI Qi, JIANG Ming, ZHANG Zhiyu

《机械工程前沿（英文）》 2007年第2卷第1期页码 37-45 doi: 10.1007/s11465-007-0006-x

摘要： Based on the variational constraint approach, the variational form of Reynolds equation in hydrodynamic lubrication is revised continuously to satisfy certain constraints in the cavitation zone of oil film field. According to the physical characteristic of oil film, an eight-node isoparametric finite element method is used to convert the revised variational form of Reynolds equation to a discrete form of finite dimensional algebraic variational equation. By this approach, a perturbance equation can be obtained directly on the finite element equation. Consequently, nonlinear oil film forces and their Jacobian matrices are calculated simultaneously, and compatible accuracy is obtained without increasing the computational costs. A method, which is a combination of predictor corrector mechanism and Newton Raphson method, is presented to calculate equilibrium position and critical speed corresponding to Hopf bifurcation point of bearing-rotor system, as by-product dynamic coefficients of bearing are obtained. The timescale, i.e., the unknown whirling period of Hopf bifurcation solution of bearing-rotor system is drawn into the iterative process using Poincar?Newton Floquet method. The stability of the Hopf bifurcation solution can be detected when estimating Hopf bifurcation solution and its periods. The nonlinear unbalanced periodic responses of the system are obtained by using PNF method and path-following technique. The local stability and bifurcation behaviors of periodic motions are analyzed by Floquet theory. Chaotic motions are analyzed by Lyapunov exponents. The numerical results revealed the rich and complex nonlinear behavior of the system, such as periodic, quasiperiodic, jumped solution, chaos, and coexistence of multisolution, and so on.

关键词： computational corrector mechanism predictor corrector multisolution quasiperiodic

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Stevens–Johnson syndrome and toxic epidermal necrolysis in China: evaluation of risk models and new predictor

Yanhong Shou, Lu Yang, Yongsheng Yang, Xiaohua Zhu, Feng Li, Bo Yin, Yingyan Zheng, Jinhua Xu

《医学前沿（英文）》 2021年第15卷第4期页码 585-593 doi: 10.1007/s11684-020-0817-2

摘要： Stevens--Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are rare but severe diseases. This study aimed to validate the predictive ability of risk models in patients with SJS/TEN and propose possible refinement in China. Patients in the Department of Dermatology of Huashan Hospital from January 2008 to January 2019 were included. Results showed that the severity-of-illness score for TEN (SCORTEN) had a good discrimination (area under the receiver operating characteristic curve (AUC), 0.78), and it was superior to auxiliary score (AS) and ABCD-10, which indicates age, bicarbonate level, cancer, dialysis, and 10% involved body surface area (AUC, 0.69 and 0.68, respectively). The calibration of SCORTEN (Hosmer–Lemeshow goodness-of-fit test, = 0.69) was also better than that of AS ( = 0.25) and ABCD-10 ( = 0.55). SCORTEN and ABCD-10 were similar (Brier score (BS), 0.04 and 0.04) in terms of accuracy of predictions. In addition, the imaging appearance of pulmonary consolidation on computed tomography was associated with high mortality. Refined models were formed using the variables and this imaging appearance. The refined AS and ABCD-10 models were similar in discrimination compared with the original SCORTEN (0.74 vs. 0.78, = 0.23; 0.74 vs. 0.78, = 0.30, respectively). Therefore, SCORTEN showed good discrimination performance, calibration, and accuracy, and refined AS or ABCD-10 model may be an option when SCORTEN variables are not available.

关键词： Stevens–Johnson syndrome toxic epidermal necrolysis auxiliary score ABCD-10 pulmonary consolidation

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面向TCP/AQM网络系统基于史密斯预估器的比例积分控制器的设计与分析 Research Articles

Ouassim MENACER1, Abderraouf MESSAI1, Lazhar KASSA-BAGHDOUCHE2

《信息与电子工程前沿（英文）》 2022年第23卷第2期页码 291-303 doi: 10.1631/FITEE.2000245

摘要：主动式队列管理（AQM）对于预防具有往返时滞的TCP/AQM系统的服务质量退化至关重要。往返时滞主要由数据包传播时延引起，但也可由队列操作的处理时间和动态改变的网络情况引起。本文聚焦带有时延不确定性的主动式队列管理数字控制器的设计与分析。该控制器基于史密斯预估器算法，我们称其为SMITHPI控制器。本文同时证明了该控制器的稳定性和抵御网络参数变化的鲁棒性，如传输控制协议源的数量、时延、用户数据电报协议流。运用NS-2仿真评估所提SMITHPI控制器的性能、鲁棒性和有效性。最后，将SMITHPI控制器与著名的主动式队列管理（称为比例积分控制器）进行性能比较。

关键词：主动式队列管理；传输控制协议；往返时滞；史密斯预估器

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Theory and method of mechanism system design

Huijun ZOU, Qinghua LIANG, Qing ZHANG

《机械工程前沿（英文）》 2010年第5卷第4期页码 399-411 doi: 10.1007/s11465-010-0116-8

摘要： Conceptual design is the most critical and creative phase of design. Recently, increasing attention has been directed to supporting conceptual-level computer aided creative design and its theories and methodologies. Specifically, for conceptual design of mechanical products, this paper presents a novel function solving model for mechanical product design and highlights the importance of systematic synthesis to achieve creative design. Then it builds a framework as a function-effect-process-action- mechanisms (FEPAM) mapping process, which enables creative design on the basis of conceiving different action schemes. After that, several key points are elaborated including 1) representing and decomposition methods of functions and motion behaviors; 2) action scheme representing method based on network plan techniques; and 3) variation and creation methods based on action scheme transformations.

关键词： mechanism system creative design process model function solving model process action procedure mechanisms knowledge base principle of mechanism system composition

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Formation mechanism and modeling of surface waviness in incremental sheet forming

《机械工程前沿（英文）》 2022年第17卷第2期 doi: 10.1007/s11465-022-0679-1

摘要： Improving and controlling surface quality has always been a challenge for incremental sheet forming (ISF), whereas the generation mechanism of waviness surface is still unknown, which impedes the widely application of ISF in the industrial field. In this paper, the formation mechanism and the prediction of waviness are both investigated through experiments, numerical simulation, and theoretical analysis. Based on a verified finite element model, the waviness topography is predicted numerically for the first time, and its generation is attributed to the residual bending deformation through deformation history analysis. For more efficient engineering application, a theoretical model for waviness height is proposed based on the generation mechanism, using a modified strain function considering deformation modes. This work is favorable for the perfection of formation mechanism and control of surface quality in ISF.

关键词： surface waviness incremental sheet forming numerical simulation formation mechanism deformation history

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Autogenous healing mechanism of cement-based materials

《结构与土木工程前沿（英文）》页码 948-963 doi: 10.1007/s11709-023-0960-3

摘要： Autogenous self-healing is the innate and fundamental repair capability of cement-based materials for healing cracks. Many researchers have investigated factors that influence autogenous healing. However, systematic research on the autogenous healing mechanism of cement-based materials is lacking. The healing process mainly involves a chemical process, including further hydration of unhydrated cement and carbonation of calcium oxide and calcium hydroxide. Hence, the autogenous healing process is influenced by the material constituents of the cement composite and the ambient environment. In this study, different factors influencing the healing process of cement-based materials were investigated. Scanning electron microscopy and optical microscopy were used to examine the autogenous healing mechanism, and the maximum healing capacity was assessed. Furthermore, detailed theoretical analysis and quantitative detection of autogenous healing were conducted. This study provides a valuable reference for developing an improved healing technique for cement-based composites.

关键词： autogenous healing cement-based materials healing mechanism aggregation effect

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Optimal design of a linkage–cam mechanism-based redundantly actuated parallel manipulator

《机械工程前沿（英文）》 2021年第16卷第3期页码 451-467 doi: 10.1007/s11465-021-0634-6

摘要： A redundantly actuated parallel manipulator (RAPM) with mixed translational and rotational degrees of freedom (DOFs) is challenged for its dimensionally homogeneous Jacobian modeling and optimal design of architecture. In this paper, a means to achieve redundant actuation by adding kinematic constraints is introduced, which reduces the DOFs of the end-effector (EE). A generic dimensionally homogeneous Jacobian is developed for this type of RAPMs, which maps the generalized velocities of three points on the EE to the joint velocities. A new optimization algorithm derived from this dimensionally homogeneous Jacobian is proposed for the optimal design of this type of RAPMs. As an example, this paper presents a spatial RAPM involving linkages and cam mechanisms. This RAPM has 4 DOFs and 6 translational actuations. The linkage lengths and the position of the universal joints of the RAPM are optimized based on the dimensionally homogeneous Jacobian.

关键词： redundant actuation parallel manipulator linkage–cam mechanism Jacobian optimal design

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Cryogenic minimum quantity lubrication machining: from mechanism to application

《机械工程前沿（英文）》 2021年第16卷第4期页码 649-697 doi: 10.1007/s11465-021-0654-2

摘要： Cutting fluid plays a cooling–lubrication role in the cutting of metal materials. However, the substantial usage of cutting fluid in traditional flood machining seriously pollutes the environment and threatens the health of workers. Environmental machining technologies, such as dry cutting, minimum quantity lubrication (MQL), and cryogenic cooling technology, have been used as substitute for flood machining. However, the insufficient cooling capacity of MQL with normal-temperature compressed gas and the lack of lubricating performance of cryogenic cooling technology limit their industrial application. The technical bottleneck of mechanical–thermal damage of difficult-to-cut materials in aerospace and other fields can be solved by combining cryogenic medium and MQL. The latest progress of cryogenic minimum quantity lubrication (CMQL) technology is reviewed in this paper, and the key scientific issues in the research achievements of CMQL are clarified. First, the application forms and process characteristics of CMQL devices in turning, milling, and grinding are systematically summarized from traditional settings to innovative design. Second, the cooling–lubrication mechanism of CMQL and its influence mechanism on material hardness, cutting force, tool wear, and workpiece surface quality in cutting are extensively revealed. The effects of CMQL are systematically analyzed based on its mechanism and application form. Results show that the application effect of CMQL is better than that of cryogenic technology or MQL alone. Finally, the prospect, which provides basis and support for engineering application and development of CMQL technology, is introduced considering the limitations of CMQL.

关键词： cryogenic minimum quantity lubrication (CMQL) cryogenic medium processing mode device application mechanism application effect

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Review on mechanism and process of surface polishing using lasers

Arun KRISHNAN, Fengzhou FANG

《机械工程前沿（英文）》 2019年第14卷第3期页码 299-319 doi: 10.1007/s11465-019-0535-0

摘要： Laser polishing is a technology of smoothening the surface of various materials with highly intense laser beams. When these beams impact on the material surface to be polished, the surface starts to be melted due to the high temperature. The melted material is then relocated from the ‘peaks to valleys’ under the multidirectional action of surface tension. By varying the process parameters such as beam intensity, energy density, spot diameter, and feed rate, different rates of surface roughness can be achieved. High precision polishing of surfaces can be done using laser process. Currently, laser polishing has extended its applications from photonics to molds as well as bio-medical sectors. Conventional polishing techniques have many drawbacks such as less capability of polishing freeform surfaces, environmental pollution, long processing time, and health hazards for the operators. Laser polishing on the other hand eliminates all the mentioned drawbacks and comes as a promising technology that can be relied for smoothening of initial topography of the surfaces irrespective of the complexity of the surface. Majority of the researchers performed laser polishing on materials such as steel, titanium, and its alloys because of its low cost and reliability. This article gives a detailed overview of the laser polishing mechanism by explaining various process parameters briefly to get a better understanding about the entire polishing process. The advantages and applications are also explained clearly to have a good knowledge about the importance of laser polishing in the future.

关键词： laser polishing surface roughness process parameters mechanism

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Creation and integration mechanism of instrumentation flexible developing system

Xiaoli XU, Qiushuang LIU

《机械工程前沿（英文）》 2011年第6卷第2期页码 235-240 doi: 10.1007/s11465-011-0122-5

摘要：

To solve many key technical problems during the development of modern instrumentation system integration and provide a new mode and fundamental technical equipment for the research and development (R&D) of modern instrumentation products, based on the concept of an instrumentation flexible developing system (IFDS), this paper discusses the creation and open flexible integration mechanism, perfects the integrated supporting environment and integrated system of the flexible interconnection, and constructs the new flexible integrated system. Based on the operation mechanism of the modern instrumentation developing system and the research and optimization of the rapid integration design method, the paper emphasizes the dynamic integrating method of multiple types of knowledge in a modern instrument R&D system, to effectively utilize the rich integrated resource and achieve rapid integration of the system. Applications show that the new IFDS can improve the integration level and efficiency of R&D of the modern instrumentation system, enforce the reliability of the system, shorten the R&D period, and reduce the development costs.

关键词： modern instrumentation developing flexible interconnection flexible integration mechanism rapid integration system dynamic integrating method

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Mechanism and characterization of microplastic aging process: A review

《环境科学与工程前沿（英文）》 2023年第17卷第8期 doi: 10.1007/s11783-023-1700-6

摘要：

● Methods for estimating the aging of environmental micro-plastics were highlighted.

关键词： Microplastics Aging Degradation Characterization Mechanism

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Design of a novel side-mounted leg mechanism with high flexibility for a multi-mission quadruped earth

《机械工程前沿（英文）》 2023年第18卷第2期 doi: 10.1007/s11465-022-0740-0

摘要： Earth rover is a class of emerging wheeled-leg robots for nature exploration. At present, few methods for these robots’ leg design utilize a side-mounted spatial parallel mechanism. Thus, this paper presents a complete design process of a novel 5-degree-of-freedom (5-DOF) hybrid leg mechanism for our quadruped earth rover BJTUBOT. First, a general approach is proposed for constructing the novel leg mechanism. Subsequently, by evaluating the basic locomotion task (LT) of the rover based on screw theory, we determine the desired motion characteristic of the side-mounted leg and carry out its two feasible configurations. With regard to the synthesis method of the parallel mechanism, a family of concise hybrid leg mechanisms using the 6-DOF limbs and an L_1F1C limb (which can provide a constraint force and a couple) is designed. In verifying the motion characteristics of this kind of leg, we select a typical (3-UPRU&RRRR)&R mechanism and then analyze its kinematic model, singularities, velocity mapping, workspace, dexterity, statics, and kinetostatic performance. Furthermore, the virtual quadruped rover equipped with this innovative leg mechanism is built. Various basic and specific LTs of the rover are demonstrated by simulation, which indicates that the flexibility of the legs can help the rover achieve multitasking.

关键词： design synthesis parallel mechanism hybrid leg mechanism screw theory quadruped robot