다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

This chapter introduces the finite element method (FEM) as a tool for solution of classical electromagnetic problems. Although we discuss the main points in the application of the finite element method to electromagnetic design, including formulation and implementation, those who seek deeper understanding of the finite element method should consult some of the works listed in the bibliography section.

Introduction to the Finite Element Method

PREFACE. ACKNOWLEDGMENTS. PROLOGUE. 1 INTRODUCTION. 1.1 Historical Perspective. 1.2 Diagnostic and Prognostic System Requirements. 1.3 Designing in Fault Diagnostic and Prognostic Systems. 1.4 Diagnostic and Prognostic Functional Layers. 1.5 Preface to Book Chapters. 1.6 References. 2 SYSTEMS APPROACH TO CBM/PHM. 2.1 Introduction. 2.2 Trade Studies. 2.3 Failure Modes and Effects Criticality Analysis (FMECA). 2.4 System CBM Test-Plan Design. 2.5 Performance Assessment. 2.6 CBM/PHM Impact on Maintenance and Operations: Case Studies. 2.7 CBM/PHM in Control and Contingency Management. 2.8 References. 3 SENSORS AND SENSING STRATEGIES. 3.1 Introduction. 3.2 Sensors. 3.3 Sensor Placement. 3.4 Wireless Sensor Networks. 3.5 Smart Sensors. 3.6 References. 4 SIGNAL PROCESSING AND DATABASE MANAGEMENT SYSTEMS. 4.1 Introduction. 4.2 Signal Processing in CBM/PHM. 4.3 Signal Preprocessing. 4.4 Signal Processing. 4.5 Vibration Monitoring and Data Analysis. 4.6 Real-Time Image Feature Extraction and Defect/Fault Classification. 4.7 The Virtual Sensor. 4.8 Fusion or Integration Technologies. 4.9 Usage-Pattern Tracking. 4.10 Database Management Methods. 4.11 References. 5 FAULT DIAGNOSIS. 5.1 Introduction. 5.2 The Diagnostic Framework. 5.3 Historical Data Diagnostic Methods. 5.4 Data-Driven Fault Classification and Decision Making. 5.5 Dynamic Systems Modeling. 5.6 Physical Model-Based Methods. 5.7 Model-Based Reasoning. 5.8 Case-Based Reasoning (CBR). 5.9 Other Methods for Fault Diagnosis. 5.10 A Diagnostic Framework for Electrical/Electronic Systems. 5.11 Case Study: Vibration-Based Fault Detection and Diagnosis for Engine Bearings. 5.12 References. 6 FAULT PROGNOSIS. 6.1 Introduction. 6.2 Model-Based Prognosis Techniques. 6.3 Probability-Based Prognosis Techniques. 6.4 Data-Driven Prediction Techniques. 6.5 Case Studies. 6.6 References. 7 FAULT DIAGNOSIS AND PROGNOSIS PERFORMANCE METRICS. 7.1 Introduction. 7.2 CBM/PHM Requirements Definition. 7.3 Feature-Evaluation Metrics. 7.4 Fault Diagnosis Performance Metrics. 7.5 Prognosis Performance Metrics. 7.6 Diagnosis and Prognosis Effectiveness Metrics. 7.7 Complexity/Cost-Benefit Analysis of CBM/PHM Systems. 7.8 References. 8 LOGISTICS: SUPPORT OF THE SYSTEM IN OPERATION. 8.1 Introduction. 8.2 Product-Support Architecture, Knowledge Base, and Methods for CBM. 8.3 Product Support without CBM. 8.4 Product Support with CBM. 8.5 Maintenance Scheduling Strategies. 8.6 A Simple Example. 8.7 References. APPENDIX. INDEX.

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Intelligent Fault Diagnosis and Prognosis for Engineering Systems

Boundary Value Problems in Physics and Engineering By Frank Chorlton. Pp. 250. (Van Nostrand: London, July 1969.) 70s

Boundary value problems

random data analysis and measurement procedures is available in our digital library an online access to it is set as public so you can get it instantly. Our book servers spans in multiple countries, allowing you to get the most less latency time to download any of our books like this one. Merely said, the random data analysis and measurement procedures is universally compatible with any devices to read.

Random Data Analysis And Measurement Procedures

Noncontacting mechanical face seals are often described as unpredictable machine elements, gaining this moniker from numerous instances of premature and unexpected failure. Machine faults such as misalignment or imbalance exacerbate seal vibration, leading to undesirable and unforeseen contact between the seal faces. A hypothesis explaining the high probability of failure in noncontacting mechanical face seals is this undesired seal face contact. However, research supporting this hypothesis is heuristic and experiential and lacks the rigor provided by robust simulation incorporating contact into the seal dynamics. Here, recent developments in modeling rotor–stator rub using rough surface contact are employed to simulate impact phenomena in a flexibly mounted stator (FMS) mechanical face seal designed to operate in a noncontacting regime. Specifically, the elastoplastic Jackson–Green rough surface contact model is used to quantify the contact forces using real and measurable surface and material parameters. This method also ensures that the seal face clearance remains positive, thus allowing one to calculate fluid-film forces. The seal equations of motion are simulated to indicate several modes of contacting operation, where contact is identified using waveforms, frequency spectra, and contact force calculations. Interestingly, and for the first time, certain parameters generating contact are shown to induce aperiodic mechanical face seal vibration, which is a useful machine vibration monitoring symptom. Also for the first time, this work analytically shows a mechanism where severe contact precipitates seal failure, which was previously known only through intuition and/or experience. The utility of seal face contact diagnostics is discussed along with directions for future work. [DOI: 10.1115/1.4033366]

Impact Phenomena in a Noncontacting Mechanical Face Seal

A comprehensive numerical model is developed to investigate the behavior of a tilted thrust washer bearing. The goal of this work is to investigate the physical phenomena that distress the bearing system. This work includes thermoelastic deformations, which have been neglected in previous studies. The thrust washer bearing is subjected to non-axisymmetric loads within the planetary gear sets of automatic transmissions and consists of flat-faced washers placed between an idle helical gear and an adjacent carrier face. Various coupled numerical schemes model sliding friction, boundary lubrication, asperity contact, thermo-mechanical deformation, thermoviscous effects, and full-film lubrication. The model provides predictions of frictional torque, bearing temperature, hydrodynamic lift, and other indicators of bearing performance. The numerical model and theoretical predictions confirm the experimental results, showing that the bearing under consideration is very susceptible to the mechanisms of thermoelasti...

The Thermoelastic Behavior of Thrust Washer Bearings Considering Mixed Lubrication, Asperity Contact, and Thermoviscous Effects

The complete nonlinear equations of motion of a flexibly mounted stator in a noncontacting coned-face mechanical seal are solved numerically. The solution utilizes a transient dynamic analysis and takes into account rotor axial runout and assembly tolerances in the form of initial stator misalignment. Cavitation of the fluid film is also accounted for. A parametric investigation is performed and the effect of various design parameters and operation conditions on the seal dynamics is presented and discussed. A critical shaft speed is found above which the seal becomes dynamically unstable. A critical rotor runout is found which, if exceeded, will cause seal failure due to local face rubbing contact. A comparison is made between the numerical results and those of a simpler analytical solution. It is found that the analytical solution is valid for most practical applications of mechanical seals. Presented at the 40th Annual Meeting in Las Vegas, Nevada May 6–9, 1985

Nonlinear Dynamic Analysis of Noncontacting Coned-Face Mechanical Seals

In order to investigate experimentally the dynamic behavior of a noncontacting flexibly mounted rotor (FMR) mechanical face seal a test rig was designed and built. Test results showed that the FMR seal was vulnerable to higher harmonic oscillations with frequencies that are integer multiples of the shaft speed. Because system nonlinearities can cause higher harmonic oscillations, the dynamic moments acting on the rotor are derived to include the effects of imbalance and axial offset of the rotor. The analysis reveals that the nonlinear terms involved are of second order and generally can be neglected. Investigation is then directed to analyze the possibility of rubbing contact between the rotor and the stator. Rubbing contact can occur as a result of a high relative angular misalignment between the rotor and the stator. A contact kinematics model is proposed and a Fourier series analysis is performed on the resulting rotor response. The analysis shows that the proposed response contains higher harmonics. Fourier series expansion and numerical filtering of a sampled rotor response from the test rig yield resembling signals which contain higher harmonics. This suggests that rubbing contact is the source of higher harmonic oscillations. Design modification to the rotor flexible support system resulted in a virtual elimination of higher harmonic oscillations.

Higher harmonic oscillations in a noncontacting FMR mechanical face seal test rig

This study addresses the mechanisms that distress a flat-faced thrust washer bearing system. This washer bearing system separates a helical gear and its carrier within a gearset. It was found that the bearing can experience distress by the combination of rotational speed, axial load, and the sequence and rate of their application. Distress is defined as a sudden rise in the real-time frictional torque and temperature. The various tests suggest the presence of hydrodynamic effects at certain rotational speeds and axial load combinations marked by decreases in the calculated effective coefficient of friction with decreases in velocity. In the tested cases, a distinct increase in the coefficient of friction occurs at the instant of distress. Presented at the 56th Annual Meeting Orlando, Florida May 20–24, 2001

Itzhak Green

Papers

Impact Phenomena in a Noncontacting Mechanical Face Seal

The Thermoelastic Behavior of Thrust Washer Bearings Considering Mixed Lubrication, Asperity Contact, and Thermoviscous Effects

Nonlinear Dynamic Analysis of Noncontacting Coned-Face Mechanical Seals

Higher harmonic oscillations in a noncontacting FMR mechanical face seal test rig

Study of the Tribological Behavior of a Thrust Washer Bearing