scholarly journals Tidal disturbances of small cohesionless bodies: limits on planetary close approach distances

2006 ◽  
Vol 2 (S236) ◽  
pp. 201-210
Author(s):  
Patrick Michel ◽  
K. A. Holsapple
Keyword(s):  
Bulk Density ◽  
Close Approach ◽  
General Concept ◽  
Material Strength ◽  
Small Bodies ◽  
Tidal Forces ◽  
Planetary Satellites ◽  
Real Objects ◽  
Definition Of ◽  
Asteroids And Comets

AbstractThe population of Near-Earth Objects contains small bodies that can make very close passages to the Earth and the other planets. Depending on the approach distance and the object's internal structure, some shape readjustment or disruption may occur as a result of tidal forces. A real example is the comet Shoemaker Levy 9 which disrupted into 21 fragments as a result of a close approach to Jupiter, before colliding with the planet during the next passage in July 1994. We have recently developed an exact analytical theory for the distortion and disruption limits of spinning ellipsoidal bodies subjected to tidal forces, using the Drucker-Prager strength model with zero cohesion. This model is the appropriate one for dry granular materials such as sands and rocks, for rubble-pile asteroids and comets, as well as for larger planetary satellites, asteroids and comets for which the cohesion can be ignored. Here, we recall the general concept of this theory for which details and major results are given in a recent publication. In particular, we focus on the definition of “material strength”: while it has great implications this concept is often misunderstood in the community of researchers working on small bodies. Then, we apply our theory to a few real objects, showing that it can provide some constraints on their unknown properties such as their bulk density. In particular it can be used to estimate the maximum bulk density that a particular object, such as 99942 Apophis, must have to undergo some tidal readjustments during a predicted planetary approach. The limits of this theory are also discussed. The cases where internal cohesion cannot be ignored will then be investigated in the near future.

scholarly journals Tidal distortion and disruption of rubble-pile bodies revisited

2020 ◽  
Vol 640 ◽  
pp. A102
Author(s):  
Yun Zhang ◽  
Patrick Michel
Keyword(s):  
Small Body ◽  
Influence Factors ◽  
Dynamical Evolution ◽  
Continuum Theory ◽  
Close Approach ◽  
Material Strength ◽  
Discrete Element Modeling ◽  
Small Bodies ◽  
Tidal Forces ◽  
Rubble Pile

Context. In the course of a close approach to planets or stars, the morphological and dynamical properties of rubble-pile small bodies can be dramatically modified, and some may catastrophically break up, as in the case of comet Shoemaker-Levy 9. This phenomenon is of particular interest for the understanding of the evolution and population of small bodies, and for making predictions regarding the outcomes of future encounters. Previous numerical explorations have typically used methods that do not adequately represent the nature of rubble piles. The encounter outcomes and influence factors are still poorly constrained. Aims. Based on recent advances in modeling rubble-pile physics, we aim to provide a better understanding of the tidal encounter processes of rubble piles through soft-sphere discrete element modeling (SSDEM) and to establish a database of encounter outcomes and their dependencies on encounter conditions and rubble-pile properties. Methods. We performed thousands of numerical simulations using the SSDEM implemented in the N-body code pkdgrav to study the dynamical evolution of rubble piles during close encounters with the Earth. The effects of encounter conditions, material strength, arrangement, and resolution of constituent particles are explored. Results. Three typical tidal encounter outcomes are classified, namely: deformation, mass shedding, and disruption, ranging from mild modifications to severe damages of the progenitor. The outcome is highly dependent on the encounter conditions and on the structure and strength of the involved rubble pile. The encounter speed and distance required for causing disruption events are much smaller than those predicted by previous studies, indicating a smaller creation rate of tidally disrupted small body populations. Extremely elongated fragments with axis ratios ~1:6 can be formed by moderate tidal encounters. Our analyses of the spin-shape evolution of the largest remnants reveal reshaping mechanisms of rubble piles in response to tidal forces, which is consistent with stable rubble-pile configurations derived by continuum theory. A case study for Shoemaker-Levy 9 suggests a low bulk density (0.2–0.3 g cc−1) for its progenitor.

Mean Diameters in Parallel-Flow and Counter-Flow Aerosol Systems

1976 ◽  
Vol 98 (2) ◽  
pp. 297-302 ◽  
Author(s):  
K. G. T. Hollands ◽  
K. C. Goel
Keyword(s):  
Mass Transfer ◽  
Continuous Phase ◽  
General Concept ◽  
Parallel Flow ◽  
General Definition ◽  
Single Pair ◽  
Counter Flow ◽  
Mean Diameter ◽  
The Mean ◽  
Definition Of

The general concept of the mean diameter of the disperse phase of an aerosol system, first introduced by Mugele and Evans in 1951, has proven to be a very useful one. In this concept, the proper mean diameter, xp,q, is characterized by a single pair of indices, p and q, which are dependent on the actual type of aerosol system under consideration. This paper re-examines the validity of this concept of mean diameter in heat and mass transfer aerosol systems. The concept is found to be applicable only under a very narrow range of conditions. Attention is then given to a more general definition of a mean diameter, applicable to aerosol heat or mass exchangers. Analyses of these devices shows that the more general mean diameter is a function of the capacity rate ratio, R, and effectiveness of the heat exchanger, ε. Solutions to the governing equations have permitted the mean diameter to be presented graphically as a function of these variables. These solutions are given for two types of particle size distributions, the Rosin-Rammler and the log-probability, and for both parallel-flow and counter-flow heat exchangers. The solutions are, however, restricted to cases where the resistance to heat or mass transfer lies exclusively in the continuous phase.

PROTECTION OF INTELLECTUAL PROPERTY RIGHTS IN UKRAINE: MODERN REALITIES AND PROSPECTS

2017 ◽  
Author(s):  
Yuliia Tovstohan ◽  
◽  
Serhii Ivanov ◽  
Keyword(s):  
Intellectual Property ◽  
Civil Rights ◽  
Property Rights ◽  
Intellectual Property Rights ◽  
Current System ◽  
General Procedure ◽  
Legal Protection ◽  
General Concept ◽  
Scientific Article ◽  
Definition Of

The scientific article examines the modern mechanism of protection of intellectual property rights in Ukraine. Attention is paid to the historically first using of the concept of intellectual property rights in international law and the shortcomings of this definition. The legal definition of this concept contained in the Civil Code of Ukraine is analyzed. It is concluded that the legislative enshrinement of intellectual property rights is evidence of its recognition by the state, and such a right applies to special objects, the list of which is enshrined at both national and international levels. The question of the relationship between the concepts of "protection" and "defense" of civil rights is covered. The main groups of approaches of scientists to the solution of this problem are indicated. An approach that defines "protection" as a general concept for "defense" is supported, where "protection" is a broader concept that covers the term "defense". Emphasis is placed on the fact that although these legal categories are related, they cannot be identified. The main features that distinguish these concepts are listed, and the features of "defense" as an independent concept are highlighted. There are given examples of definition of the concept of protection of intellectual property rights given by scientists. Based on these definitions, the main features of this term are summarized. The issue of forms of protection (jurisdictional and non-jurisdictional) has been studied. The general and special order within the jurisdictional form is distinguished. It is noted about the peculiarities of self-defense as a non-jurisdictional form. The focus is on the judicial (general) procedure for protection of intellectual property rights as the main one. Possible ways of protection (civil, administrative, criminal, and criminal) are analyzed. The problems and shortcomings of the current system of legal protection and protection of intellectual property rights in Ukraine are analyzed. Both reports from international partners and research by Ukrainian scientists were used. The authors outline ways to solve existing problems. The conclusions of the study are formulated and the possibility of further scientific research in this area is indicated.

scholarly journals (3200) Phaethon: Bulk density from Yarkovsky drift detection

2018 ◽  
Vol 620 ◽  
pp. L8 ◽  
Author(s):  
J. Hanuš ◽  
D. Vokrouhlický ◽  
M. Delbo’ ◽  
D. Farnocchia ◽  
D. Polishook ◽  
...  
Keyword(s):  
Bulk Density ◽  
Semimajor Axis ◽  
Close Approach ◽  
Numerical Approach ◽  
Radar Data ◽  
Characteristic Size ◽  
Parent Body ◽  
Accurate Analysis ◽  
Shape Model ◽  
Yarkovsky Effect

Context. The recent close approach of the near-Earth asteroid (3200) Phaethon offered a rare opportunity to obtain high-quality observational data of various types. Aims. We used the newly obtained optical light curves to improve the spin and shape model of Phaethon and to determine its surface physical properties derived by thermophysical modeling. We also used the available astrometric observations of Phaethon, including those obtained by the Arecibo radar and the Gaia spacecraft, to constrain the secular drift of the orbital semimajor axis. This constraint allowed us to estimate the bulk density by assuming that the drift is dominated by the Yarkovsky effect. Methods. We used the convex inversion model to derive the spin orientation and 3D shape model of Phaethon, and a detailed numerical approach for an accurate analysis of the Yarkovsky effect. Results. We obtained a unique solution for Phaethon’s pole orientation at (318 ° , − 47 ° ) ecliptic longitude and latitude (both with an uncertainty of 5°), and confirm the previously reported thermophysical properties (D = 5.1 ± 0.2 km, Γ = 600 ± 200J m−2 s−0.5 K−1). Phaethon has a top-like shape with possible north-south asymmetry. The characteristic size of the regolith grains is 1 − 2 cm. The orbit analysis reveals a secular drift of the semimajor axis of −(6.9 ± 1.9)×10−4 au Myr−1. With the derived volume-equivalent size of 5.1 km, the bulk density is 1.67 ± 0.47 g cm−3. If the size is slightly larger ∼5.7 − 5.8 km, as suggested by radar data, the bulk density would decrease to 1.48 ± 0.42 g cm−3. We further investigated the suggestion that Phaethon may be in a cluster with asteroids (155140) 2005 UD and (225416) 1999 YC that was formed by rotational fission of a critically spinning parent body. Conclusions. Phaethon’s bulk density is consistent with typical values for large (> 100 km) C-complex asteroids and supports its association with asteroid (2) Pallas, as first suggested by dynamical modeling. These findings render a cometary origin unlikely for Phaethon.

Introduction to “History and epistemology of psychopathology”

2015 ◽  
Author(s):  
Josef Parnas
Keyword(s):  
General Concept ◽  
Definition Of

Chapter 4 is an introduction to Chapter 2, which discusses the history and epistemology of psychopathology, and covers the definition of change as a feature or a general concept of psychiatry, and the definition’s relation to specific ontological regions (e.g., physics, biology, and sociology).

Spatial position and perceived color of objects

2003 ◽  
Vol 26 (1) ◽  
pp. 43-44
Author(s):  
Romi Nijhawan
Keyword(s):  
Spatial Position ◽  
Real Object ◽  
Real Objects ◽  
Definition Of ◽  
Perceived Color

AbstractVisual percepts are called veridical when a “real” object can be identified as their cause, and illusions otherwise. The perceived position and color of a flashed object may be called veridical or illusory depending on which viewpoint one adopts. Since “reality” is assumed to be fixed (independent of viewpoint) in the definition of veridicality (or illusion), this suggests that “perceived” position and color are not properties of “real” objects.

Mechanical Engineering Design-for-Reliability

2011 ◽  
Author(s):  
William R. Wessels
Keyword(s):  
Density Function ◽  
Failure Modes ◽  
Mechanical Design ◽  
Mass Density ◽  
Failure Mechanisms ◽  
Strength Properties ◽  
Material Strength ◽  
Design For Reliability ◽  
Mechanical Part ◽  
Definition Of

This paper presents a design-for-reliability approach for mechanical design. Reliability analysis in part design, indeed the very definition of reliability, has been focused towards the electronic and digital disciplines since the emergence of reliability engineering in the late 1940’s. That focus dictates that parts fail in time; that all parts have a constant failure rate, and that part failure is modeled by the exponential mass density function. This paper presents current research that proposes that reliability in mechanical design is not characterized by ‘best practices’ reliability analyses. One premise investigated is that time does not cause failure in mechanical design; only failure mechanisms do. Mechanical parts experience wear-out and fatigue, unlike electronic and digital parts. Mechanical design analysis for part design investigates material strength properties required to survive failure mechanisms induced by part operation and by part exposure to external failure mechanisms. Such failure mechanisms include physical loads, thermal loads, and reactivity/corrosion. Each failure mechanism acting on a mechanical part induces one or more part failure modes, and each part failure mode has one or more failure effects on the part and the upper design configurations in which the part is integrated. The second premise investigated is that mechanical part failure is modeled by the Weibull mass density function in terms of stress, not time. A reliability math model for tensile strength in composite materials is presented to illustrate the two premises.

MINIMAL AND STRANGE ATTRACTORS

1996 ◽  
Vol 06 (06) ◽  
pp. 1177-1183 ◽  
Author(s):  
A. GORODETSKI ◽  
Yu. ILYASHENKO
Keyword(s):  
Dynamical System ◽  
General Concept ◽  
Principal Result ◽  
Strange Attractors ◽  
Mild Form ◽  
Attracting Set ◽  
Probabilistic Character ◽  
A Chain ◽  
The One ◽  
Definition Of

A general concept going back to Kolmogorov claims that if a dynamical system has a complicated attracting set then its behavior has not a deterministic, but rather probabilistic character. This concept was not formalized up to now. Even the definition of attractor has a lot of different versions. This paper presents an attempt to give some definitions and results formalizing this heuristic ideas. It contains a definition of a minimal attractor, modifying the one given in Ilyashenko [1991]. The actual minimality of the attractor is discussed. The principal result is the Triple Choice Theorem. It claims that the existence of a strange minimal attractor implies some mild form of chaos for the map itself or for a nearby one. The program of further investigation is proposed as a chain of problems at the end of the paper.

scholarly journals CLASSIFICATION OF TEXTURES WITH AND WITHOUT ROTATION ANGLES: A DAUBECHIES WAVELET BASED APPROACH

2014 ◽  
pp. 49-54
Author(s):  
SHAIKHJI ZAID M ◽  
J B JADHAV ◽  
V N KAPADIA
Keyword(s):  
Image Processing ◽  
Texture Classification ◽  
Daubechies Wavelet ◽  
Statistical Features ◽  
Visual Texture ◽  
Multi Resolution Analysis ◽  
Real Objects ◽  
Resolution Analysis ◽  
Definition Of

Textures play important roles in many image processing applications, since images of real objects often do not exhibit regions of uniform and smooth intensities, but variations of intensities with certain repeated structures or patterns, referred to as visual texture. The textural patterns or structures mainly result from the physical surface properties, such as roughness or oriented structured of a tactile quality. It is widely recognized that a visual texture, which can easily perceive, is very difficult to define. The difficulty results mainly from the fact that different people can define textures in applications dependent ways or with different perceptual motivations, and they are not generally agreed upon single definition of texture [1]. The development in multi-resolution analysis such as Gabor and wavelet transform help to overcome this difficulty. In this paper it describes that, texture classification using Wavelet Statistical Features (WSF), Wavelet Co-occurrence Features (WCF) and a combination of wavelet statistical features and co-occurrence features of wavelet transformed images with different feature databases can results better [2]. Several Image degrading parameters are introduced in the image to be classified for verifying the features. Wavelet based decomposing is used to classify the image with code prepared in MATLAB.

scholarly journals Managerial innovations: Approach to definition and classification

2020 ◽  
Vol 19 (4) ◽  
pp. 493-519
Author(s):  
Yaroslav D. Sovetkin ◽  
Keyword(s):  
General Concept ◽  
Business Community ◽  
Scientific Publications ◽  
Bibliographic Analysis ◽  
New Approach ◽  
Citation Indexes ◽  
Definition Of ◽  
The Relationship ◽  
Managerial Innovation

Managerial innovations have become the topic of interest for many scholars, but this concept remains underdeveloped and poorly managed among the academy and business community in Russia. This paper offers the composition of approach to definition and classifi cation of managerial innovations, formed on the basis of exploration of the concept “managerial innovation” evolution, and estimation of the relationship with a more general concept “innovation”. The suggested composition of approach is based on the three-stage bibliographic analysis of scientific literature. In course of the bibliographic research, scientific articles were selected according to the key words, period of publication and citation index. 140 scientific publications were identified and collected for the period from 1975 to 2019 covering citation indexes from 0 to 12 476 by Web of Science citation database and from 4 to 2 185 by Scopus database. On the basis of the conducted bibliographic research, the author introduces his definition of innovation and managerial innovation and explains the connection between them. Within the conducted research different approaches to classification of managerial innovations were studied and on their basis a new approach to classification of managerial innovations was proposed. The findings can be useful for different avenues of further research regarding managerial innovations.

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