ChemInform Abstract: Selectivity from a Kinetic Point of View: Nonlinear Behavior of Logarithmic Product Ratios as a Function of the Reciprocal Temperature

ChemInform ◽  
2010 ◽  
Vol 29 (38) ◽  
pp. no-no
Author(s):  
D. HELLER ◽  
H. BUSCHMANN
Keyword(s):  
Nonlinear Behavior ◽  
Point Of View ◽  
Reciprocal Temperature

Covert Underwater Acoustic Communication System Using Parametric Array

2019 ◽  
Vol 53 (1) ◽  
pp. 20-26 ◽  
Author(s):  
Anbang Zhao ◽  
Yue Cheng ◽  
Tiansi An ◽  
Juan Hui
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Low Frequency ◽  
Nonlinear Behavior ◽  
Beam Width ◽  
Point Of View ◽  
Underwater Acoustic Communication ◽  
Water Tank ◽  
Narrow Beam ◽  
Underwater Acoustic ◽  
Parametric Array

AbstractA novel and efficient covert underwater acoustic (UWA) communication scheme using an acoustic parametric array and orthogonal frequency division multiplexing (OFDM) system is presented. The proposed system is robust and can easily be implemented in the ocean environment. The system is also very useful in military applications where the secrecy of transmission signal and location of the transmitter are extremely important. The paper exploits the difference frequency generated by the acoustic parametric array due to the nonlinear behavior of an underwater medium. Besides the lightness and compactness, the parametric array also possesses the advantage of being low-frequency, broadband, highly directive, and narrow beam with no side lobes. The narrow beam width also helps to secure the data from a spatial point of view. Experiments have been performed in a water tank, and the results are presented to show the effectiveness of the proposed scheme.

Review on Combustion Control of Marine Engine by Fuzzy Logic Control Concerning the Air to Fuel Ratio

2014 ◽  
Vol 66 (2) ◽  
Author(s):  
Mohammad Javad Nekooei ◽  
Jaswar Jaswar ◽  
A. Priyanto
Keyword(s):  
Control Point ◽  
Nonlinear Behavior ◽  
Spark Ignition ◽  
Point Of View ◽  
Engine Operation ◽  
Marine Engine ◽  
Loop Control ◽  
Fuel Ratio ◽  
Highly Nonlinear ◽  
Close Loop Control

This research reviews a close loop control-oriented model, combined with air to fuel ratio, to regulate  combustion phasing in a spark- ignition marine engine operation. On the other hand ,Stoichiometric air-to-fuel ratio () control plays a significant role on the  three way catalysts in the reduction of exhaust pollutants of the SI marine engine. Air to fuel management for SI marine engines is a major challenge from the control point of view because of the highly nonlinear behavior of this system. For this reason, linear control techniques are unable to provide the required performance, and nonlinear controllers are used instead. Therefore, a fuzzy MIMO Control system is designed for robust control of  lambda. As an accurate and control oriented model, an  air to fuel ratio model of a Spark Ignition (SI) marine engine is developed to generate simulation data of the engine's subsystems. The Goal of this control is to maintain the A/F ratio at stoichiometry.

Mechanical Characterization of Linen Fibers: The Turin Shroud Dating

2017 ◽  
Vol 24 (02) ◽  
pp. 1750006
Author(s):  
Giulio Fanti ◽  
Roberto Basso
Keyword(s):  
Complex Structure ◽  
Nonlinear Behavior ◽  
Point Of View ◽  
First Century ◽  
Statistical Point ◽  
Flax Fibers ◽  
Special Support ◽  
Three Samples ◽  
Dating Methods

As the 1988 radiocarbon dating of the Turin Shroud (TS) was debatable also from a statistical point of view, new dating methods have been proposed. This paper presents the result of an improved mechanical dating. A recent cyclic-load machine has been improved to better fix fibers under test by using a special support designed for the purpose. The mechanical behavior of linen fibers of three different ages are measured and compared discussing these results in reference to the complex structure of aged linen fibers; the three samples are a linen fiber from an Egyptian mummy of 27[Formula: see text] Century B.C.; a linen fiber coming from the TS, and a recent linen fiber. This machine allowed to confirm the previous results regarding the TS mechanical dating, showing that these results are again compatible with the First Century A.D., the period in which Jesus Christ lived in Palestine. The improved machine also showed that the complex nonlinear behavior of the fibers is also due to the packing of the Secondary Cell Wall of the linen fibers, mostly composed of micro fibrils, that produces a memory-effect. The stiffening of the linen fibers with the loading increasing is a property detected for all the tested fibers that must not be forgotten also in the construction of flax fibers based composites.

Numerical Simulation of Geogrid Reinforced Adobe Walls

2019 ◽  
Vol 817 ◽  
pp. 73-79
Author(s):  
Stefano Invernizzi
Keyword(s):  
Numerical Simulation ◽  
Soil Stabilization ◽  
Model Simulation ◽  
Nonlinear Behavior ◽  
Experimental Tests ◽  
Element Model ◽  
Point Of View ◽  
Seismic Load ◽  
Increased Strength ◽  
Strengthening Technique

The paper describes the finite element model simulation of reinforced adobe walls to assess the feasibility of an innovative strengthening technique for earthen constructions, which improves the seismic performance. The retrofitting technique is based on the application of geogrids on both sides of the earthen wall. The geogrid is comprised in the mud plaster layer, which is applied to the wall surface in two steps. No additional connections are put in place, and the connection between the geogrid and the wall is granted exclusively by the mud plaster. The numerical simulation accounted for the presence of adobe blocks and clay joints, as well as for the presence of the reinforcing geogrid and of the mud plaster. The nonlinear behavior of the material was modeled with smeared cracking in tension and plasticity in compression, allowing to minimize the number of fitting material parameters. The numerical results are compared with the output from experimental tests [1] performed on almost twenty small walls without reinforcement, or with different types of geogrids available from the market. The laboratory tests included simple compression, diagonal shear, and three-point bending. The tests and the numerical simulation revealed that the retrofitting system is particularly effective from the mechanical point of view thanks to the optimal ratio between the wall and the geogrid stiffness and strength. The reinforced samples showed increased strength and greatly increased ductility, which is very promising in particular with respect to the seismic load behavior. The material compatibility between the geogrid and the mud plaster and the earthen wall is also very good, mainly due to the fact that geogrids were developed primarily for soil stabilization applications. The analyzed retrofitting system looks very promising for both the seismic improvement of existing vernacular heritage and for application in new bio-architecture building contexts.

scholarly journals NONLINEAR BEHAVIOR CALCULATION ALGORITHM FOR THIN-WALLED SYSTEMS

2019 ◽  
Vol 46 (2) ◽  
pp. 176-184
Author(s):  
G. M. Murtazaliev ◽  
M. M. Payzulaev
Keyword(s):  
Numerical Methods ◽  
Nonlinear Behavior ◽  
High Strength ◽  
Stability Loss ◽  
Point Of View ◽  
Calculation Algorithm ◽  
Postcritical Deformation ◽  
Initial Stage ◽  
Thin Walled ◽  
Bifurcation Behavior

Objectives The emergence of modern high-strength materials leads to the creation of thin-walled structures in various fields of technology. To obtain the necessary information about their behavior under load, one should analyze all the characteristic features encountered at all stages of their loading - at the initial (initial) stage of their operation, taking into account one or more types of nonlinearities, find possible critical states and, depending on the type of stability loss, study the nature of the initial stage of postcritical deformation. Based on an algorithm combining approximate analytical and numerical methods, the article solves the model problem — studying the behavior of a thin-walled spherical shell under load.Method. The study is based on solving the nonlinear problem of determining the stress-strain state at the initial - axisymmetric stage of work; critical (bifurcation) load values; analysis of the nature of post-bifurcation behavior. The work uses a variant of the general theory of stability and postcritical behavior of structures previously developed by V.T. Coiter.Result. The solution of such a general problem associated with discontinuous phenomena is carried out on the basis of mathematical ideas formulated in the theory of branching solutions of nonlinear equations. The values of the coefficients characterizing the initial stage of the post-bifurcation behavior of the shells and, from a practical point of view, the relations between the critical and limiting values of the loads are obtained. It is shown that depending on the area of the shell surface part loaded by the distributed load, the nature of the initial stage of postcritical deformation changes not only quantitatively, but also qualitatively.Conclusion. The most effective in solving problems associated with discontinuous phenomena are combinations of approximate analytical ones - catastrophe theory and numerical methods that do not require complex, timeconsuming and significant amounts of computation. Analysis of the initial stage of the postbifurcation behavior of structures allows us to assess the degree of danger of reaching a critical state, which is achieved by taking into account the values of the corresponding reliability coefficients in the calculations. 

A Nonlinear Viscoelastic Model of a Hydraulic Bushing for Multi-Body Vehicle Models

2005 ◽  
Author(s):  
Francesco Braghin ◽  
Elisabetta Leo ◽  
Edoardo Sabbioni
Keyword(s):  
Computational Cost ◽  
Viscoelastic Model ◽  
Nonlinear Behavior ◽  
Point Of View ◽  
Vehicle Model ◽  
Nonlinear Viscoelastic ◽  
Highly Nonlinear ◽  
Entire Vehicle ◽  
Nonlinear Viscoelastic Model ◽  
Multi Body

The present paper deals with the development and identification of a new dynamic model of an hydraulic bushing. The peculiarity and the difficulty of such a bushing is its highly nonlinear behavior. In fact, common linear rheological models are not able to realistically reproduce the relation between applied displacements and reaction forces. A nonlinear viscoelastic model presents significant difficulties in the identification of its parameters since no frequency based approach is feasible. Thus, special multi-step identification procedures have to be implemented. The adoption of such a nonlinear viscoelastic model inside a multi-body vehicle model significantly increases the computational cost of the entire vehicle model. It is therefore necessary to optimize the model not only from a reliability point of view but also from a computational cost point of view. The best compromise has therefore to be chosen.

The Geosciences Applied to Lunar Exploration

1962 ◽  
Vol 14 ◽  
pp. 169-257 ◽  
Author(s):  
J. Green
Keyword(s):  
Lunar Surface ◽  
Probable Mechanism ◽  
Point Of View ◽  
Lunar Exploration ◽  
Geological Model ◽  
Apply Geophysics ◽  
Surface Features ◽  
The Impact

The term geo-sciences has been used here to include the disciplines geology, geophysics and geochemistry. However, in order to apply geophysics and geochemistry effectively one must begin with a geological model. Therefore, the science of geology should be used as the basis for lunar exploration. From an astronomical point of view, a lunar terrain heavily impacted with meteors appears the more reasonable; although from a geological standpoint, volcanism seems the more probable mechanism. A surface liberally marked with volcanic features has been advocated by such geologists as Bülow, Dana, Suess, von Wolff, Shaler, Spurr, and Kuno. In this paper, both the impact and volcanic hypotheses are considered in the application of the geo-sciences to manned lunar exploration. However, more emphasis is placed on the volcanic, or more correctly the defluidization, hypothesis to account for lunar surface features.

How a sheperd guides a sheep herd?

1984 ◽  
Vol 75 ◽  
pp. 331-337
Author(s):  
Richard Greenberg
Keyword(s):  
Point Of View ◽  
Single Ring ◽  
Damping Effects ◽  
Ring Particle

ABSTRACTThe mechanism by which a shepherd satellite exerts a confining torque on a ring is considered from the point of view of a single ring particle. It is still not clear how one might most meaningfully include damping effects and other collisional processes into this type of approach to the problem.

The growth of mica polytypes as studied by conventional and high-resolution TEM

1983 ◽  
Vol 41 ◽  
pp. 174-177
Author(s):  
A. Baronnet ◽  
M. Amouric
Keyword(s):  
Water Pressure ◽  
Point Of View ◽  
Temperature Fields ◽  
Natural Occurrence ◽  
Growth Mechanisms ◽  
Long Period ◽  
High Resolution Tem ◽  
Layer Stacking ◽  
Experimental Works ◽  
Potential Use

The origin of mica polytypes has long been a challenging problem for crystal- lographers, mineralogists and petrologists. From the petrological point of view, interest in this field arose from the potential use of layer stacking data to furnish further informations about equilibrium and/or kinetic conditions prevailing during the crystallization of the widespread mica-bearing rocks. From the compilation of previous experimental works dealing with the occurrence domains of the various mica "polymorphs" (1Mr, 1M, 2M1, 2M2 and 3T) within water-pressure vs temperature fields, it became clear that most of these modifications should be considered as metastable for a fixed mica species. Furthermore, the natural occurrence of long-period (or complex) polytypes could not be accounted for by phase considerations. This highlighted the need of a more detailed kinetic approach of the problem and, in particular, of the role growth mechanisms of basal faces could play in this crystallographic phenomenon.

Radiation Damage in Ceramics

1982 ◽  
Vol 40 ◽  
pp. 600-603
Author(s):  
T. E. Mitchell ◽  
M. R. Pascucci ◽  
R. A. Youngman
Keyword(s):  
Radiation Damage ◽  
Outer Space ◽  
Point Of View ◽  
Nuclear Waste Storage ◽  
Waste Storage ◽  
Storage Media ◽  
Transmission Electron ◽  
Fundamental Point ◽  
Small Defect ◽  
Present Understanding

1. Introduction. Studies of radiation damage in ceramics are of interest not only from a fundamental point of view but also because it is important to understand the behavior of ceramics in various practical radiation enyironments- fission and fusion reactors, nuclear waste storage media, ion-implantation devices, outer space, etc. A great deal of work has been done on the spectroscopy of point defects and small defect clusters in ceramics, but relatively little has been performed on defect agglomeration using transmission electron microscopy (TEM) in the same kind of detail that has been so successful in metals. This article will assess our present understanding of radiation damage in ceramics with illustrations using results obtained from the authors' work.

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