scholarly journals On the Geometrical Properties of the Lightlike Rectifying Curves and the Centrodes

Mathematics ◽  
2021 ◽  
Vol 9 (23) ◽  
pp. 3103
Author(s):  
Jianguo Sun ◽  
Yanping Zhao ◽  
Xiaoyan Jiang
Keyword(s):  
Detailed Analysis ◽  
Geometrical Properties ◽  
Geometrical Characteristics

This paper mainly focuses on some notions of the lightlike rectifying curves and the centrodes in Minkowski 3-space. Some geometrical characteristics of the three types of lightlike curves are obtained. In addition, we obtain the conditions of the centrodes of the lightlike curves are the lightlike rectifying curves. Meanwhile, a detailed analysis between the N-type lightlike slant helices and the centrodes of lightlike curves is provided in this paper. We give the projections of the lightlike rectifying curves to the timelike planes.

Simultaneous Determination of Basic Geometrical Characteristics of Porous Media

1969 ◽  
Vol 9 (04) ◽  
pp. 413-416 ◽  
Author(s):  
Candelario Perez-Rosales
Keyword(s):  
Porous Media ◽  
Specific Surface ◽  
Porous Materials ◽  
Surface Area ◽  
Cross Section ◽  
Absolute Permeability ◽  
Geometrical Properties ◽  
Geometrical Characteristics ◽  
Internal Geometry ◽  
Long Line

Abstract A statistical method for determining simultaneously some of the basic geometrical characteristics of porous media such as porosity, specific surface, porous media such as porosity, specific surface, mean pore with, mean grain thickness and absolute permeability is presented. The proposed method is permeability is presented. The proposed method is characterized by its simplicity and the minimum amount of laboratory equipment that it requires. The experimental procedure used to evaluate the various geometrical characteristics is based upon the surface analysis of a sample. in view of this fact the applicability of the method is limited to homogeneous and isotropic materials. Introduction The behavior of a fluid flowing through a porous medium depends, among other things, upon the internal geometry of the medium; hence the importance of developing efficient methods to determine the geometrical properties of porous materials. This paper describes a statistical method to determine simultaneously some of the basic geometrical properties of porous materials such as porosity, specific surface, mean pore width, mean grain thickness and absolute permeability. The mathematical formulation has been developed that the data required to calculate the various geometrical characteristics of a sample can be easily measured by analyzing a section of the sample with an evenly spaced grid. THEORY A simple way of obtaining information about the internal geometry of a porous material is to throw a point at random over a cross-section of a sample. point at random over a cross-section of a sample. Through this procedure the porosity can be determined. By considering that the material is homogeneous and isotropic, and that the point is dropped many times, the porosity is given by ...........(1) where N is the total number of times the point is thrown and n is the number of times the point falls within pore areas. Another simple manner of analyzing the structural characteristics of a porous material is to superimpose an arbitrarily long line on a cross-section so that its length is evenly distributed over the surface area. Through this procedure the porosity can also be determined. If L is the total length of the line, and l is the sum of the lengths of the line segments within void spaces, the porosity is given by .............(2) The advantage of this type of analysis is that geometrical characteristics other than porosity can be obtained. Thus, if c represents the number of intersections between the line and the perimeter of pores, it can be shown that the specific surface, pores, it can be shown that the specific surface, defined as the surface area of pores per unit bulk volume, is given by ............(3) To give a proper description of the internal geometry of a porous medium, it is necessary to define quantities that characterize the notions of pore size and grain size. Unfortunately, because of pore size and grain size. Unfortunately, because of the complexity of porous materials, it is difficult to give exact geometrical definitions of what is meant by the concepts of "pores" and "grains", especially when dealing with consolidated materials. Nevertheless, one often talks about the "size of pores" and the "size of grains" without defining accurately the terms. In possible solution to this problem follows. Assume that an arbitrarily long line is placed on a section of a sample so that the line is evenly distributed over the surface area (see Fig. 1). In a system like this, each line segment within a void space will be, by definition, the pore width in a given location and direction. SPEJ P. 413

Wide-Angle Imaging Lidar Deployment at the ARM Southern Great Plains Site: Intercomparison of Cloud Property Retrievals

2005 ◽  
Vol 22 (6) ◽  
pp. 628-648 ◽  
Author(s):  
Igor N. Polonsky ◽  
Steven P. Love ◽  
Anthony B. Davis
Keyword(s):  
Great Plains ◽  
Wide Angle ◽  
Geometrical Properties ◽  
Southern Great Plains ◽  
Geometrical Characteristics ◽  
New Instrument ◽  
Atmospheric Radiation Measurement ◽  
Lidar Return ◽  
Beam Component ◽  
Observation Period

Abstract The Wide-Angle Imaging Lidar (WAIL), a new instrument that measures cloud optical and geometrical properties by means of off-beam lidar returns, was deployed as part of a multi-instrument campaign to probe a cloud field at the Atmospheric Radiation Measurement (ARM) Southern Great Plain (SGP) site on 25 March 2002. WAIL is designed to determine physical and geometrical characteristics using the off-beam component of the lidar return that can be adequately modeled within the diffusion approximation. Using WAIL data, the extinction coefficient and geometrical thickness of a dense cloud layer is estimated, from which optical thickness is inferred. Results from the new methodology agree well with counterparts obtained from other instruments located permanently at the SGP ARM site and from the WAIL-like airborne instrument that flew over the site during our observation period.

Collapse Strength of Stiffened Panels With Local Dent Damage

2008 ◽  
Author(s):  
Malgorzata Witkowska ◽  
C. Guedes Soares
Keyword(s):  
Finite Element ◽  
Ultimate Strength ◽  
Linear Analysis ◽  
Local Damage ◽  
Stiffened Panels ◽  
Geometrical Properties ◽  
Geometrical Characteristics ◽  
Collapse Strength ◽  
Non Linear ◽  
Local Dent

In this study the behaviour and ultimate strength of damaged stiffened panels is investigated. The damage is in a form of local imperfection and represents a dent that could be caused by a fall or strike of an object. The model used is a panel made of five plates joined transversally with four longitudinal flat-bar stiffeners. Finite element non-linear analysis of panels having different geometrical properties is carried out. The influence of several parameters has been studied in order to establish their interaction with the presence of the local dent. It has been found that stiffened panels present quite good performance while subjected to the local damage, however, depending on geometrical characteristics, a problem of stiffener deformations may occur, significantly lowering the ultimate strength.

scholarly journals Parametric surface and properties defined on parallelogrammic domain

2014 ◽  
Vol 1 (1) ◽  
pp. 27-36 ◽  
Author(s):  
Shuqian Fan ◽  
Jinsong Zou ◽  
Mingquan Shi
Keyword(s):  
Mathematical Model ◽  
Logarithmic Spiral ◽  
Tooth Surface ◽  
Parametric Surface ◽  
Surface Geometry ◽  
Spiral Bevel Gears ◽  
Geometrical Properties ◽  
Bevel Gears ◽  
Geometrical Characteristics ◽  
Spiral Bevel

Abstract Similar to the essential components of many mechanical systems, the geometrical properties of the teeth of spiral bevel gears greatly influence the kinematic and dynamic behaviors of mechanical systems. Logarithmic spiral bevel gears show a unique advantage in transmission due to their constant spiral angle property. However, a mathematical model suitable for accurate digital modeling, differential geometrical characteristics, and related contact analysis methods for tooth surfaces have not been deeply investigated, since such gears are not convenient in traditional cutting manufacturing in the gear industry. Accurate mathematical modeling of the tooth surface geometry for logarithmic spiral bevel gears is developed in this study, based on the basic gearing kinematics and spherical involute geometry along with the tangent planes geometry; actually, the tooth surface is a parametric surface defined on a parallelogrammic domain. Equivalence proof of the tooth surface geometry is then given in order to greatly simplify the mathematical model. As major factors affecting the lubrication, surface fatigue, contact stress, wear, and manufacturability of gear teeth, the differential geometrical characteristics of the tooth surface are summarized using classical fundamental forms. By using the geometrical properties mentioned, manufactura-bility (and its limitation in logarithmic spiral bevel gears) is analyzed using precision forging and multi-axis freeform milling, rather than classical cradle-type machine tool based milling or hobbing. Geometry and manufacturability analysis results show that logarithmic spiral gears have many application advantages, but many urgent issues such as contact tooth analysis for precision plastic forming and multi-axis freeform milling also need to be solved in a further study.

scholarly journals Geometrical characteristics of Gaussian sea waves

2005 ◽  
Vol 42 (2) ◽  
pp. 407-425 ◽  
Author(s):  
Jean-Marc Azaïs ◽  
José R. León ◽  
Joaquín Ortega
Keyword(s):  
Energy Spectrum ◽  
Level Sets ◽  
Limit Theorems ◽  
Sea Surface ◽  
Gaussian Field ◽  
Sea Waves ◽  
Geometrical Properties ◽  
Geometrical Characteristics ◽  
Field Modeling ◽  
The Mean

In this work, we study some geometrical properties of a stationary Gaussian field modeling the sea surface, using the energy spectrum. We consider the length of a crest and the mean speed of contours, which can be expressed as integrals over level sets. We also give central limit theorems for some of these quantities, using chaos expansions.

scholarly journals Geometrical characteristics of Gaussian sea waves

2005 ◽  
Vol 42 (02) ◽  
pp. 407-425 ◽  
Author(s):  
Jean-Marc Azaïs ◽  
José R. León ◽  
Joaquín Ortega
Keyword(s):  
Energy Spectrum ◽  
Level Sets ◽  
Limit Theorems ◽  
Sea Surface ◽  
Gaussian Field ◽  
Sea Waves ◽  
Geometrical Properties ◽  
Geometrical Characteristics ◽  
Field Modeling ◽  
The Mean

In this work, we study some geometrical properties of a stationary Gaussian field modeling the sea surface, using the energy spectrum. We consider the length of a crest and the mean speed of contours, which can be expressed as integrals over level sets. We also give central limit theorems for some of these quantities, using chaos expansions.

Some Geometrical Characteristics of the Long-Lived Solar Filaments

1994 ◽  
Vol 144 ◽  
pp. 387-389
Author(s):  
P. Duchlev ◽  
Z. Mouradian ◽  
V. N. Dermendjiev
Keyword(s):  
Filament Length ◽  
Geometrical Characteristics ◽  
Solar Filaments

AbstractTwo basic geometric quantities - the filament length and the height above the limb of the long-lived filaments are studied. Some statistical relations are obtained.

Prosodic Impairment Associated With Traumatic Brain Injury

2009 ◽  
Vol 19 (3) ◽  
pp. 97-102
Author(s):  
Billy Irwin
Keyword(s):  
Traumatic Brain Injury ◽  
Brain Injury ◽  
Detailed Analysis ◽  
Acoustic Characteristics ◽  
Individual Variations

Abstract Purpose: This article discusses impaired prosody production subsequent to traumatic brain injury (TBI). Prosody may affect naturalness and intelligibility of speech significantly, often for the long term, and TBI may result in a variety of impairments. Method: Intonation, rate, and stress production are discussed in terms of the perceptual, physiological, and acoustic characteristics associated with TBI. Results and Conclusions: All aspects of prosodic production are susceptible to the effects of damage resulting from TBI. There are commonly associated prosodic impairments; however, individual variations in specific aspects of prosody require detailed analysis.

Comparison of Cross-sectional Geometrical Properties and Bone Density between Saint-Bernard and other Giant Breed Dogs

2019 ◽  
Author(s):  
S. Mejia ◽  
A. Iodence ◽  
L. Griffin ◽  
S.J. Withrow ◽  
M. Salman ◽  
...  
Keyword(s):  
Bone Density ◽  
Cross Sectional ◽  
Geometrical Properties ◽  
Saint Bernard

Assessment of the state and level of development of public-private partnership projects in the subjects of the Russian Federation

2018 ◽  
pp. 131-141 ◽  
Author(s):  
A. N. Savrukov ◽  
N. T. Savrukov ◽  
E. A. Kozlovskaya
Keyword(s):  
Detailed Analysis ◽  
Russian Federation ◽  
Significant Proportion ◽  
Transport Sector ◽  
Private Partnership ◽  
Current State ◽  
Central Regions ◽  
The Russian Federation ◽  
Project Data ◽  
Municipal Level

The article analyzes the current state and level of development of publicprivate partnership (PPP) projects in the subjects of the Russian Federation. The authors conclude that a significant proportion of projects is implemented on a concession basis at the municipal level in the communal sphere. A detailed analysis of the project data showed that the structure of the projects is deformed in favor of the central regions of the Russian Federation, and a significant share in the total amount of financing falls on the transport sector. At the stage of assessing the level of development by the subjects of the Russian Federation, criteria were proposed, and index and integral indicators were used, which ensured comparability of the estimates obtained. At the end of the analysis, the regions were ranked and clustered according to the level of PPP development, which allowed to reveal the number and structure of leaders and outsiders.

Sign in / Sign up

Export Citation Format

Share Document