On the Effect and Analysis of Fluid-Structural Mode Coupling

2020 ◽  
Author(s):  
Mani Sadeghi ◽  
Ming-Ta Yang ◽  
Huan-Min Shang ◽  
Eric Grover
Keyword(s):  
Mode Coupling ◽  
Vital Role ◽  
Forced Response ◽  
Space Representation ◽  
Aerodynamic Forces ◽  
Analysis Techniques ◽  
State Space Representation ◽  
Linear Dynamic ◽  
The Impact ◽  
Structural Mode

Abstract The consideration of aeromechanics plays a vital role in the design of machines that operate under aerodynamic forces, such as turbomachinery, and aircraft. The structure of those machines is subject to aeromechanical dynamics, including forced response and flutter. The strength of aeromechanical interaction depends on the level of coupling between flow and structure. One effect that can lead to strong coupling is the interaction between eigenmodes of the structure and eigenmodes of the flow near coincidence. This paper examines the impact of modal coincidence on the linear dynamic stability of aeromechanical systems for two illustrative canonical examples, one governed by inviscid acoustics, and one by the eigenmode of a wake. Three commonly used analysis techniques are applied and ranked for various levels of coupling: The 1-way coupled work-per-cycle method, a 2-way coupled non-linear modal FSI analysis in time, and an eigenanalysis of the 2-way coupled linear system, based on a state-space representation. It is demonstrated that all three methods agree for low to moderate levels of 2-way coupling, typical in turbomachinery applications. At higher levels, the work-per-cycle assessment is insufficient, whereas the FSI and eigenvalue analysis agree well.

scholarly journals Maximum Likelihood Estimation for Identification of Aircraft Aerodynamic Derivatives

2013 ◽  
Vol 60 (2) ◽  
pp. 219-230 ◽  
Author(s):  
Piotr Lichota ◽  
Maciej Lasek
Keyword(s):  
Maximum Likelihood ◽  
Maximum Likelihood Estimation ◽  
Likelihood Estimation ◽  
Space Representation ◽  
Process Noise ◽  
State Space Representation ◽  
Aerodynamic Derivatives ◽  
Marquardt Algorithm ◽  
The Impact ◽  
Body Fixed Coordinate System

This article investigates identification of aircraft aerodynamic derivatives. The identification is performed on the basis of the parameters stored by Flight Data Recorder. The problem is solved in time domain by Quad-M Method. Aircraft dynamics is described by a parametric model that is defined in Body-Fixed-Coordinate System. Identification of the aerodynamic derivatives is obtained by Maximum Likelihood Estimation. For finding cost function minimum, Lavenberg-Marquardt Algorithm is used. Additional effects due to process noise are included in the state-space representation. The impact of initial values on the solution is discussed. The presented method was implemented in Matlab R2009b environment.

Regenerative Chatter in High-Speed Tandem Rolling Mills

2006 ◽  
Author(s):  
Huyue Zhao ◽  
Kornel F. Ehmann
Keyword(s):  
Mode Coupling ◽  
High Speed ◽  
Process Model ◽  
Structural Model ◽  
Rolling Process ◽  
Space Representation ◽  
Regenerative Chatter ◽  
State Space Representation ◽  
Negative Damping ◽  
Delay Differential

Third-octave-mode chatter, the most detrimental form of rolling chatter, is generated by means of negative damping, mode coupling, and regeneration. While mechanisms that include negative damping, and mode coupling have been thoroughly investigated, those associated with the regenerative effect remain elusive. In this paper, the mechanisms that may lead to regenerative chatter are studied through a state-space representation of a multi-stand mill that is constructed by coupling a homogenous dynamic rolling process model with a structural model for the mill stands in a high-speed tandem mill configuration. Stability analysis, by using the integral criterion for the stability of systems described by delay differential equations, is carried out for the regenerative mechanism in order to better understand the effects of rolling parameters on a single stand as well as the overall system. Preliminary simulation results, based on the proposed chatter model, are presented to demonstrate the feasibility and the accuracy of the chatter model, as well as to investigate chatter phenomena too complex to be studied analytically.

Leg-Seabed Interactions of Jack-Up Vessels due to Motions in Irregular Waves

2014 ◽  
Author(s):  
Edwin Kreuzer ◽  
Eugen Solowjow ◽  
Gang Qiu ◽  
Thorben Hamann ◽  
Jürgen Grabe
Keyword(s):  
Offshore Wind ◽  
Irregular Waves ◽  
Space Representation ◽  
Efficient Computation ◽  
Sea Floor ◽  
State Space Representation ◽  
Proposed Model ◽  
Reaction Forces ◽  
Jack Up ◽  
The Impact

This paper analyzes the leg-seabed interaction due to motions of a 3rd generation jack-up vessel in irregular waves. The proposed model considers hydrodynamic forces on the hull as well as on the legs. The sea floor reaction forces are analyzed with a Coupled Eulerian-Lagrangian (CEL) method. The results are used to develop a mechanical rheological model for the sea floor. With computational efficiency in mind a state-space representation in time domain is derived. The excitation of the system is caused by irregular waves, which are described by the JONSWAP spectrum. The proposed method allows the efficient computation of short term (2–15 min) scenarios and events through sampling of realizations. It is used to compute the impact forces on the legs from the seabed induced by irregular vessel motions. The presented framework is suitable for the planning of jack-up operations in the offshore wind industry. It can also be applied for the design of dynamic positioning and jacking systems.

scholarly journals An Electromechanical Simulation Method for Active Vibration Control of a Magnetic Bearing Supported Rotor

1993 ◽  
Author(s):  
Punan Tang ◽  
A. B. Palazzolo ◽  
Gerald Brown ◽  
Eliseo DiRusso ◽  
Albert Kascak
Keyword(s):  
State Space ◽  
Active Vibration Control ◽  
Simulation Method ◽  
Magnetic Bearing ◽  
Forced Response ◽  
Space Representation ◽  
Rotor Systems ◽  
State Space Representation ◽  
Measured Frequency Response ◽  
Active Vibration

A reliable electromechanical simulation model is essential for designing rotor systems supported by magnetic bearings. Accurate predictions of forced response, critical speeds and stability are required to assure machinery health and reliability. This paper presents a general methodology which couples a finite element based model of the rotor with state space models of the sensors, control system and actuators. A least squares based algorithm is presented for obtaining the state space representation of the digital (DSP) controller, actuator, and power amplifiers from their measured frequency response functions. This general simulation method is illustrated by application to a cryogenic magnetic bearing test rig at NASA Lewis.

Material analysis techniques using the ion mill

1996 ◽  
Vol 54 ◽  
pp. 1034-1035
Author(s):  
J. P. Benedict ◽  
R. M. Anderson ◽  
S. J. Klepeis
Keyword(s):  
Polished Surface ◽  
Surface Material ◽  
Analysis Techniques ◽  
Material Analysis ◽  
Optical Inspection ◽  
Electron Microscopy Analysis ◽  
Microscopy Analysis ◽  
Argon Ions ◽  
The Impact ◽  
Scanning Electron

Ion mills equipped with flood guns can perform two important functions in material analysis; they can either remove material or deposit material. The ion mill holder shown in Fig. 1 is used to remove material from the polished surface of a sample for further optical inspection or SEM ( Scanning Electron Microscopy ) analysis. The sample is attached to a pohshing stud type SEM mount and placed in the ion mill holder with the polished surface of the sample pointing straight up, as shown in Fig 2. As the holder is rotating in the ion mill, Argon ions from the flood gun are directed down at the top of the sample. The impact of Argon ions against the surface of the sample causes some of the surface material to leave the sample at a material dependent, nonuniform rate. As a result, the polished surface will begin to develop topography during milling as fast sputtering materials leave behind depressions in the polished surface.

INDONESIA LANGUAGE INTERFERENCE FORM IN BASIC PPL LEARNING THAILAND UNHASY COLLEGE SYUDENTS

2020 ◽  
Vol 8 (2) ◽  
pp. 38
Author(s):  
Siti Mariana Ulfa
Keyword(s):  
Qualitative Research ◽  
Data Analysis ◽  
Data Collection ◽  
Teaching Practice ◽  
Data Presentation ◽  
Analysis Techniques ◽  
Thai Students ◽  
The Impact ◽  
Collection Methods ◽  
Recording Techniques

AbstractHumans on earth need social interaction with others. Humans can use more than one language in communication. Thus, the impact that arises when the use of one or more languages is the contact between languages. One obvious form of contact between languages is interference. Interference can occur at all levels of life. As in this study, namely Indonesian Language Interference in Learning PPL Basic Thailand Unhasy Students. This study contains the form of interference that occurs in Thai students who are conducting teaching practices in the classroom. This type of research is descriptive qualitative research that seeks to describe any interference that occurs in the speech of Thai students when teaching practice. Data collection methods in this study are (1) observation techniques, (2) audio-visual recording techniques using CCTV and (3) recording techniques, by recording all data that has been obtained. Whereas the data wetness uses, (1) data triangulation, (2) improvement in perseverance and (3) peer review through discussion. Data analysis techniques in this study are (1) data collection, (2) data reduction, (3) data presentation and (4) conclusions. It can be seen that the interference that occurs includes (1) interference in phonological systems, (2) interference in morphological systems and (3) interference in syntactic systems. 

The Impact Of Emotional Intelligence On Leadership Excellence Of Executive Empoloyees In Public Sector Organizationin Ampara District Of Sri Lanka

2019 ◽  
Vol 118 (9) ◽  
pp. 52-60
Author(s):  
Dr.S. Gunapalan ◽  
Dr.K. Maran
Keyword(s):  
Emotional Intelligence ◽  
Public Sector ◽  
Vital Role ◽  
Public Organization ◽  
Self Awareness ◽  
Public Sector Organization ◽  
Expression Of Emotion ◽  
Asking Questions ◽  
Private Sector Organizations ◽  
The Impact

Emotional Intelligence is play a vital role to decide  leadership excellence. So this paper to study the  impact of emotional intelligence on leadership excellence of executive employee in public sector organization.Hence the objective of this  research   is to identify the  impact of emotional intelligence on leadership excellence of executive employee in Public Sector Organization in Ampara districtof Sri Lanka.emotional intelligence includes the verbal and non-verbal appraisal and expression of emotion, the regulation of emotion in the self and others, and the utilization of emotional content in problem solving. Cook (2006)[1]. Emotional intelligence is one of the  essential skill for leaders to manage their subordinate. Accordingly although there is some research done under “Emotional intelligence on leadership excellence of the executive employee in the public organization in Ampara district so this study full filed the gap. Based on the analysis, Self-awareness, Self-management, Social-awareness and Relationship management are the positively affect to the Leadership excellence. So, executive employees should consider about the Emotions of their subordinators when they completing their targets. leaders should pay the attention for recognize the situation, hove to impact their feelings for the performance & recognized their own feelings. Leaders should consider and see their own emotions when they work with others by listening carefully, understand the person by asking questions, identifying non-verbal expressions and solving problems without helming someone’s. Leadersshould consider their subordinators emotions when they find a common idea, government should give to moderate freedom to executive employees in public organization to take the decision with competing the private sector organizations.

Comparative crosstalk performance analysis of different configurations of heterogeneous multicore fiber

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Umar Farooque ◽  
Rakesh Ranjan
Keyword(s):  
Refractive Index ◽  
Mode Coupling ◽  
The Other ◽  
Heterogeneous Multicore ◽  
Coupled Mode ◽  
The Core ◽  
Bending Radius ◽  
Multicore Fiber ◽  
The Impact ◽  
Core Pitch

AbstractIn order to select the heterogeneous multicore fiber (MCF) configuration with ultra-low crosstalk and low peak bending radius, comparative crosstalk analysis have been done for the three possible core configurations, namely, Configuration 1 - different refractive index (R.I.) and different radius, Configuration 2 - different R.I., and Configuration 3 - different radius. Using the coupled mode equation and the simplified expressions of mode coupling coefficient (MCC) for different configurations of heterogeneous cores, the crosstalk performance of all the heterogeneous MCF configurations along with the homogeneous MCF have been investigated analytically with respect to core pitch (D) and fiber bending radius (${R}_{b}$). Further, these expressions of MCC have been extended to obtain the simplified expressions of MCC for the estimation of crosstalk levels in respective trench-assisted (TA) heterogeneous MCF configurations. It is observed from the analysis that in Configuration 1, crosstalk level is lowest and the rate of decrease in the crosstalk with respect to the core pitch is highest compared to the other configurations of heterogeneous MCF. The values of crosstalk obtained analytically have been validated by comparing it with the values obtained from finite element method (FEM) based numerical simulation results. Further, we have investigated the impact of a fixed percent change (5%) in the core parameters (radius and/or R.I.) of one of the core of a homogeneous MCF, to realize the different heterogeneous MCF configurations, on the variations in crosstalk levels, difference in the mode effective refractive index of the core 1 and core 2 ($\Delta {n}_{eff}={n}_{eff1}-{n}_{eff2}$), and the peak bending radius (${R}_{pk}$). For the same percent variations (5%) in the core parameters (radius and/or R.I.) of different configurations of cores (Config. 1-Config. 3), Config. 1 MCF has highest variation in $\Delta {n}_{eff}$ value compared to other configurations of MCF. Further, this highest variation in $\Delta {n}_{eff}$ value of Config. 1 MCF results in smallest peak bending radius. The smaller value of peak bending radius allows MCF to bend into smaller radius. Therefore, Configuration 1 is the potential choice for the design of MCF with smaller peak bending radius and ultra-low crosstalk level compared to the other configurations of SI-heterogeneous MCF.

scholarly journals High Expression of KLF10 Is Associated with Favorable Survival in Patients with Oral Squamous Cell Carcinoma

Medicina ◽  
2020 ◽  
Vol 57 (1) ◽  
pp. 17
Author(s):  
Chung-Min Yeh ◽  
Yi-Ju Lee ◽  
Po-Yun Ko ◽  
Yueh-Min Lin ◽  
Wen-Wei Sung
Keyword(s):  
Survival Rate ◽  
Oral Cancer ◽  
Cancer Patients ◽  
Protective Factor ◽  
Female Gender ◽  
Vital Role ◽  
Cancer Stage ◽  
Independent Prognostic Marker ◽  
Oral Cancer Patients ◽  
The Impact

Background and objectives: Krüppel-like transcription factor 10 (KLF10) plays a vital role in regulating cell proliferation, including the anti-proliferative process, activation of apoptosis, and differentiation control. KLF10 may also act as a protective factor against oral cancer. We studied the impact of KLF10 expression on the clinical outcomes of oral cancer patients to identify its role as a prognostic factor in oral cancer. Materials and Methods: KLF10 immunoreactivity was analyzed by immunohistochemical (IHC) stain analysis in 286 cancer specimens from primary oral cancer patients. The prognostic value of KLF10 on overall survival was determined by Kaplan–Meier analysis and the Cox proportional hazard model. Results: High KLF10 expression was significantly associated with male gender and betel quid chewing. The 5-year survival rate was greater for patients with high KLF10 expression than for those with low KLF10 expression (62.5% vs. 51.3%, respectively; p = 0.005), and multivariate analyses showed that high KLF10 expression was the only independent factor correlated with greater overall patient survival. The significant correlation between high KLF10 expression and a higher 5-year survival rate was observed in certain subgroups of clinical parameters, including female gender, non-smokers, cancer stage T1, and cancer stage N0. Conclusions: KLF10 expression, detected by IHC staining, could be an independent prognostic marker for oral cancer patients.

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