Émile Meyerson and mass conservation in chemical reactions: a priori expectations versus experimental tests

2019 ◽  
Vol 21 (1) ◽  
pp. 109-124
Author(s):  
Roberto de Andrade Martins
Keyword(s):  
Chemical Reactions ◽  
A Priori ◽  
Mass Conservation ◽  
Experimental Tests ◽  
Émile Meyerson

Approximate Closed-Form Solutions for the Shift Mechanics of Rubber Belt Variators

2009 ◽  
Author(s):  
Marco Cammalleri ◽  
Francesco Sorge
Keyword(s):  
Closed Form ◽  
Mass Conservation ◽  
Experimental Tests ◽  
Speed Ratio ◽  
Equilibrium Equations ◽  
Closed Form Solutions ◽  
Rubber Belt ◽  
Linear Differential ◽  
The Mathematical Model ◽  
Transport Theorem

The mechanical behavior of V-belt variators during the speed ratio shift is different from the steady operation as a gross radial motion of the belt is superimposed to the circumferential motion. The theoretical analysis involves equilibrium equations similar to the steady case, but requires a re-formulation of the mass conservation condition making use of the Reynolds transport theorem. The mathematical model of the belt-pulley coupling implies the repeated numerical solution of a strongly non-linear differential system. Nevertheless, an attentive observation of the numerical diagrams suggests simple and useful closed-form approximations for the four possible working modes of any pulley, opening/closing, driver/driven, whose validity ranges over most practical cases. The present analysis focuses on the development of such simplified solutions, succeeding in an excellent matching with the numerical plots, and on the comparison of the theory with some experimental tests on a motorcycle variator, revealing a very good agreement.

Specificity of Aircraft Crash Compared to Other Missile Impacts

2008 ◽  
Author(s):  
Pierre Kœchlin ◽  
Serguei¨ Potapov
Keyword(s):  
A Priori ◽  
Structural Response ◽  
Bending Moment ◽  
Experimental Tests ◽  
Research Field ◽  
Quantitative Classification ◽  
Stress Resultant ◽  
Physical Phenomena ◽  
Aircraft Crash

Before modeling an aircraft crash on a shield building, it is very important to understand the physical phenomena and the structural behavior associated with this kind of impact. In the scientific literature, aircraft crash is classified as a soft impact, or as an impact of deformable missile. Nevertheless the existing classifications are not precise enough to be able to predict the structural response mode. In this paper, the author proposes a quantitative classification of soft and hard impacts, based on structural considerations, and in accordance with existing definitions and moreover with intuition. The experimental tests carried out during the last thirty years in the research field of aircraft crash are reviewed in the light of the new classification. It shows that this characterization has a real physical meaning: it gives the limit between two kinds of failure. Furthermore, since it is on one hand an a priori classification and on the other hand expressed in terms of non-dimension variables, it is very helpful to calibrate new experimental tests for aircraft crash. Finally, using this classification, the paper explains that during an aircraft crash, the perforation process of a concrete shield building is the result of structural waves (bending and shear waves). It opens the way to a prediction of aircraft crash perforation based on a criterion expressed in terms of stress resultant variables (combined bending moment, shear force and membrane force).

A Priori Motion Profile Control and Dynamic Performance of the Multi-Axis Ride Simulator (MARS) Facility

2007 ◽  
Author(s):  
Valeta Carol Chancey ◽  
Bradley A. Bumgardner ◽  
David D. Turner ◽  
Arlene M. Breaux-Sims ◽  
George T. Flowers ◽  
...  
Keyword(s):  
Dynamic Performance ◽  
A Priori ◽  
Experimental Tests ◽  
Performance Limits ◽  
Actuation System ◽  
Testing Facility ◽  
Profile Control ◽  
Vehicle Motion ◽  
And Performance ◽  
Motion Profile

The Multi-Axis Ride Simulator (MARS) facility is a versatile testing facility for the evaluation of vehicle motion effects on personnel and devices. It consists of a 6-DOF Stewart platform driven by a computer-controlled actuation system. An off-line strategy is used to correct the amplifier input and drive the table dynamic response to the desired trajectory. The capabilities and performance limits of the facility are described in detail. The off-line control strategy is also described and its performance evaluated with a series of experimental tests. The results are presented and discussed in detail.

An Enhanced Multi-GNSS Navigation Algorithm by Utilising a Priori Inter-System Biases

2017 ◽  
Vol 71 (2) ◽  
pp. 339-351 ◽  
Author(s):  
Zhounan Dong ◽  
Changsheng Cai ◽  
Rock Santerre ◽  
Cuilin Kuang
Keyword(s):  
Moving Average ◽  
A Priori ◽  
Three Dimensional ◽  
Main Idea ◽  
Experimental Tests ◽  
Satellite Observation ◽  
Satellite System ◽  
Estimation Algorithms ◽  
Navigation Algorithm ◽  
Sky Conditions

The integration of multi-constellation Global Navigation Satellite System (GNSS) measurements can effectively improve the accuracy and reliability of navigation and positioning solutions, while the Inter-System Bias (ISB) is a key issue for compatibility. The ISB is traditionally estimated as an unknown parameter along with three-dimensional position coordinates and a receiver clock offset with respect to Global Positioning System (GPS) time. ISB estimation of this sort will sacrifice a satellite observation for each integrated GNSS system. These sacrificed observations could be vital in situations of limited satellite visibility. In this study, an enhanced multi-GNSS navigation algorithm is developed to avoid sacrificing observations under poor visibility conditions. The main idea of this algorithm is to employ a moving average filter to smooth the ISBs estimated at previous epochs. The filtered value is utilised as a priori information at the current epoch. Experimental tests were conducted to evaluate the enhanced algorithm under open and blocked sky conditions. The results show that the enhanced algorithm effectively improves the accuracy and availability of navigation solutions under the blocked sky condition, with performance being comparable to traditional ISB estimation algorithms in open sky conditions. The improvement rates of the three-dimensional position accuracy and availability reach up to 63% and 21% in the blocked sky environment. Even in the case of only four different GNSS satellites, a position solution can still be obtained using the enhanced algorithm.

A PRIORI PRESSURE FIELD CONSTRUCTION ITERATIVE METHOD FOR THE SOLUTION OF THE STEADY-STATE NAVIER–STOKES EQUATIONS USING GENERAL FINITE-VOLUME CO-LOCATED GRIDS

2007 ◽  
Vol 04 (04) ◽  
pp. 567-601
Author(s):  
JOSE A. LAMAS
Keyword(s):  
Iterative Method ◽  
Pressure Field ◽  
Stokes Equations ◽  
A Priori ◽  
Mass Conservation ◽  
Momentum Conservation ◽  
Navier Stokes ◽  
Pressure Equation ◽  
Navier Stokes Equations ◽  
Correction Equations

An iterative method has been developed for the solution of the Navier–Stokes equations and implemented using finite volumes with co-located variable arrangement. A pressure equation is obtained combining algebraic momentum and mass conservation equations resulting in a self-consistent set of equations. An iterative procedure solves the pressure equation consistently with mass conservation and then updates velocities based on momentum equations without introducing velocity or pressure correction equations. The process is repeated until velocities satisfy both mass and momentum conservation. Tests demonstrate a priori pressure field solution consistent with mass conservation, and solution of hydrostatic problems in one iteration.

Sensorless In-Hand Manipulation by An Underactuated Robot Hand

2020 ◽  
Vol 12 (5) ◽  
Author(s):  
Diego Ospina ◽  
Alejandro Ramirez-Serrano
Keyword(s):  
State Of The Art ◽  
A Priori ◽  
Experimental Tests ◽  
Robot Hand ◽  
A Priori Information ◽  
Robot Hands ◽  
Priori Information ◽  
Underactuated Robot ◽  
Theoretical Results ◽  
Manipulation Strategy

Abstract The limited dexterity that existing hand prostheses provide to users contrasts with the manipulation abilities exhibited by state-of-the-art robot hands. This paper presents an underactuated robot hand with in-hand manipulation capabilities to demonstrate the use of underactuation in the development of effective hand replacements. This paper describes a specific underactuated hand architecture, representative of many existing underactuated hand prototypes. First, the hand is modeled and its ability to manipulate objects of different geometries is analyzed. Second, a manipulation strategy suitable for prosthetic applications is proposed. The strategy enables the hand to manipulate objects in-hand without any a priori information of their geometry or physical properties. Finally, experimental tests conducted to validate the theoretical results are presented.

CALIBRATION OF A CFD METHODOLOGY FOR THE SIMULATION OF ROUGHNESS EFFECTS ON FRICTION AND HEAT TRANSFER IN ADDITIVE MANUFACTURED COMPONENTS

2022 ◽  
pp. 1-18
Author(s):  
Lorenzo Mazzei ◽  
Riccardo Da Soghe ◽  
Cosimo Bianchini
Keyword(s):  
Heat Transfer ◽  
A Priori ◽  
Experimental Tests ◽  
Test Case ◽  
Test Cases ◽  
Roughness Effects ◽  
Cfd Models ◽  
High Roughness ◽  
Wavy Channels ◽  
Ks Values

Abstract It is well-known from the literature that surface roughness significantly affects friction and heat transfer. This is even more evident for additive manufactured (AM) components, which are taking an increasingly important role in the gas turbine field. However, the exploitation of numerical approaches to improve their design is hindered by the lack of dedicated correlations and CFD models developed for such high roughness conditions. Usually the additive manufactured components are simulated considering the surfaces as smooth or applying an equivalent sand-grain roughness (ks) that results in a velocity shift in the boundary layer. However, determining a priori the most appropriate value of ks is challenging, as dozens of correlations are available, returning scattered and uncertain results. A previous work proved how the CFD prediction of friction and heat transfer returns significant deviations, even exploiting the ks values obtained from experimental tests on the very same test case. That work also allowed identification of a promising CFD methodology based on friction and thermal corrections proposed by Aupoix from ONERA. The aim of this work is to further the assessment and calibration activity of the model, by analyzing additional experimental data of friction factor and Nusselt number from new test cases considering different geometries and flow conditions. The new coupons consisted of straight circular channels and wavy channels. This work represents a further step in the generation of a more validated and general methodology for the high-fidelity CFD analysis of additive-manufactured components.

A Novel Approach to Evaluation of Vibration Source Separation Based on Spatial Distribution of Sensors and Fourier Transforms

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Ali Mahvash ◽  
Aouni A. Lakis
Keyword(s):  
Spatial Distribution ◽  
Fourier Transforms ◽  
A Priori ◽  
Source Separation ◽  
Experimental Tests ◽  
Spatial Distance ◽  
Vibration Source ◽  
Mathematical Methods ◽  
Frequency Spectra ◽  
Multiple Sensors

An obstacle in diagnosis of multicomponent machinery using multiple sensors to acquire vibration data is firstly found in the data acquisition itself. This is due to the fact that vibration signals collected by each sensor are a mixture of vibration produced by different components and noise; it is not evident what signals are produced by each component. A number of research studies have been carried out in which this problem was considered a blind source separation (BSS) problem and different mathematical methods were used to separate the signals. One complexity with applying such mathematical methods to separate vibration sources is that no metric or standard measure exists to evaluate the quality of the separation. In this study, a method based on statistical energy analysis (SEA) is proposed using Fourier transforms and the spatial distance between sensors and components. The principle of this method is based on the fact that each sensor, with respect to its location in the system, collects a different version of the vibration produced in the system. By applying a short time Fourier transform to the signals collected by multiple sensors and making use of a priori knowledge of the spatial distribution of sensor locations with respect to the components, the source of the peaks on the frequency spectra of the signals can be identified and attributed to the components. The performance of the method was verified using a series of experimental tests on synthetic signals and real laboratory signals collected from different bearings and the results confirmed the efficacy of the method.

Designed Solution to Coat Titanium Sheets with Octacalcium Phosphate

2007 ◽  
Vol 361-363 ◽  
pp. 665-668 ◽  
Author(s):  
Christiane Xavier Resende ◽  
Gustavo Mendes Platt ◽  
Jean Dille ◽  
Ivan Napoleão Bastos ◽  
Gloria Dulce de Almeida Soares
Keyword(s):  
Calcium Phosphate ◽  
Thermodynamic Analysis ◽  
Chemical Reactions ◽  
Experimental Tests ◽  
Octacalcium Phosphate ◽  
Characterization Techniques

In this work, a solution able to precipitate calcium phosphate in titanium samples was studied. At first, a thermodynamic analysis of the proposed solution was conducted using a computational simulator that considers most of chemical reactions and evaluates parameters such as activity of species. After this procedure, experimental tests were performed in order to confirm this precipitation. With the use of TRIS at concentration of 50mM, the deposits were basically composed of octacalcium phosphate, as confirmed in some characterization techniques. The deposit presents a thickness of approximately 15μm after a 7-day exposure in the designed solution.

Sign in / Sign up

Export Citation Format

Share Document