scholarly journals Numerical Simulation of Bending Stiffness Analysis for Spring Linkage Applied to In-Pipe Robot

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Jinwei Qiao ◽  
Na Liu
Keyword(s):  
Numerical Simulation ◽  
Bending Stiffness ◽  
Mathematical Representation ◽  
Stiffness Analysis ◽  
Compressive Stiffness ◽  
Pass Through ◽  
The Relationship ◽  
Kirchhoff Theory

Spring linkage can be applied to in-pipe robots for connecting different modules together and can make it pass through elbows more easily. However, its stiffness cannot be set to be too hard or too soft. This paper tries to make a balance between the compressive stiffness and the bending stiffness of the spring. After a brief introduction to the construction mechanism and some assumptions, the mathematical representation of the spring bending stiffness was deduced based on the Kirchhoff theory which describes the spatial curve with displacement rather than time. Then, some simulations aiming at verifying the correctness of the deduced bending stiffness expression were carried out. Finally, the relationship between the two rigidities was found out, which helps to find a way to decrease the bending stiffness of spring while keeping its compressive stiffness strong enough.

A stiffness-based degradation model for lifetime monitoring of nano/micro motion systems

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Xin Wen ◽  
Guoliang Lu ◽  
Shaohua Yang ◽  
Jinyin Li ◽  
Peng Yan
Keyword(s):  
Numerical Simulation ◽  
Dynamic Model ◽  
Prognostic Model ◽  
Dynamic Stiffness ◽  
Experimental Setup ◽  
Remaining Life ◽  
Degradation Model ◽  
Stiffness Analysis ◽  
Micro Motion ◽  
The Relationship

The ability to achieve accurate and reliable lifetime prognostics is critical to predictive maintenance of nano/micro motion systems. However, techniques to accomplish this task have not been well studied. This paper presents a stiffness-based degradation model for lifetime monitoring of a considered nanopositioning stage. Based on the dynamic model of the stage, an analysis of the relationship between system stiffness, running time and failure lifetime is investigated. A failure lifetime prognostic model for the stage is formulated by means of a dynamic stiffness analysis. This methodology is evaluated with numerical simulation and verified based on our experimental setup. The results reveal that this model can be used to effectively predict the failure lifetime and the remaining life of the investigated stage, which suggests its promising potentials in real applications.

Radiation Damage, Contrast and Statistics in High Resolution Biological Electron Microscopy

1970 ◽  
Vol 28 ◽  
pp. 260-261
Author(s):  
Robert M. Glaeser
Keyword(s):  
High Resolution ◽  
Particle Flux ◽  
Unit Area ◽  
Signal To Noise ◽  
Resolution Image ◽  
High Resolution Image ◽  
Pass Through ◽  
Counting Statistics ◽  
The Relationship ◽  
Picture Element

It is well known that a large flux of electrons must pass through a specimen in order to obtain a high resolution image while a smaller particle flux is satisfactory for a low resolution image. The minimum particle flux that is required depends upon the contrast in the image and the signal-to-noise (S/N) ratio at which the data are considered acceptable. For a given S/N associated with statistical fluxtuations, the relationship between contrast and “counting statistics” is s131_eqn1, where C = contrast; r2 is the area of a picture element corresponding to the resolution, r; N is the number of electrons incident per unit area of the specimen; f is the fraction of electrons that contribute to formation of the image, relative to the total number of electrons incident upon the object.

Science or Art? How Aesthetic Standards Grease the Way Through the Publication Bottleneck but Undermine Science

2012 ◽  
Vol 7 (6) ◽  
pp. 562-571 ◽  
Author(s):  
Roger Giner-Sorolla
Keyword(s):  
Information Sharing ◽  
False Positive ◽  
Psychological Research ◽  
Current Crisis ◽  
Journal Publication ◽  
Root Cause ◽  
Methodological Rigor ◽  
Pass Through ◽  
The Relationship ◽  
Positive Results

The current crisis in psychological research involves issues of fraud, replication, publication bias, and false positive results. I argue that this crisis follows the failure of widely adopted solutions to psychology’s similar crisis of the 1970s. The untouched root cause is an information-economic one: Too many studies divided by too few publication outlets equals a bottleneck. Articles cannot pass through just by showing theoretical meaning and methodological rigor; their results must appear to support the hypothesis perfectly. Consequently, psychologists must master the art of presenting perfect-looking results just to survive in the profession. This favors aesthetic criteria of presentation in a way that harms science’s search for truth. Shallow standards of statistical perfection distort analyses and undermine the accuracy of cumulative data; narrative expectations encourage dishonesty about the relationship between results and hypotheses; criteria of novelty suppress replication attempts. Concerns about truth in research are emerging in other sciences and may eventually descend on our heads in the form of difficult and insensitive regulations. I suggest a more palatable solution: to open the bottleneck, putting structures in place to reward broader forms of information sharing beyond the exquisite art of present-day journal publication.

scholarly journals Retrospectives: The Introduction of the Cobb–Douglas Regression

2012 ◽  
Vol 26 (2) ◽  
pp. 223-236 ◽  
Author(s):  
Jeff Biddle
Keyword(s):  
Time Series Data ◽  
Series Data ◽  
Mathematical Representation ◽  
Least Squares Regression ◽  
Empirical Measures ◽  
Stable Relationship ◽  
Initial Application ◽  
Economic Association ◽  
The Relationship ◽  
Theory Of Production

At the 1927 meetings of the American Economic Association, Paul Douglas presented a paper entitled “A Theory of Production,” which he had coauthored with Charles Cobb. The paper proposed the now familiar Cobb–Douglas function as a mathematical representation of the relationship between capital, labor, and output. The paper's innovation, however, was not the function itself, which had originally been proposed by Knut Wicksell, but the use of the function as the basis of a statistical procedure for estimating the relationship between inputs and output. The paper's least squares regression of the log of the output-to-capital ratio in manufacturing on the log of the labor-to-capital ratio—the first Cobb–Douglas regression—was a realization of Douglas's innovative vision that a stable relationship between empirical measures of inputs and outputs could be discovered through statistical analysis, and that this stable relationship could cast light on important questions of economic theory and policy. This essay provides an account of the introduction of the Cobb–Douglas regression: its roots in Douglas's own work and in trends in economics in the 1920s, its initial application to time series data in the 1927 paper and Douglas's 1934 book The Theory of Wages, and the early reactions of economists to this new empirical tool.

Some Relationship between Safety Factor of Earthquake Slope and Related Parameters

2011 ◽  
Vol 422 ◽  
pp. 688-692
Author(s):  
Xiao Hei He ◽  
Geng You Han ◽  
Rui Hua Xiao
Keyword(s):  
Numerical Simulation ◽  
Rock Mechanics ◽  
Safety Factor ◽  
Limit Equilibrium ◽  
Static Method ◽  
Acceleration Coefficient ◽  
The Wenchuan Earthquake ◽  
Stability Of Slope ◽  
The Stability ◽  
The Relationship

Abstract:Since the Wenchuan earthquake happened, the slope stability had been paid much more attention. The safety factor is an important parameter that can be used to evaluate the stability of slope. The pseudo-static method that based on limit equilibrium and the method of numerical simulation can calculate the safety factor accurately, but the velocity that gets the result is slow. If we can establish the relationship between safety factor and some other parameters, then we can calculate the safety factor by using the relationship more quickly. This paper establishes much relationship, such as the relationship between the rock mechanics parameters and the average danymic safety factor, the relationship between the rock mechanics parameters and the ratio of average danymic safety factor to static safety factor, the relationship between the rock mechanics parameters and the average earthquake acceleration coefficient, the relationship between the average earthquake acceleration coefficient and the ratio of average danymic safety factor to static safety factor, and the relationship between the earthquake acceleration coefficient and the ratio of danymic safety factor to static safety factor on the condition of different rock mass.

On the Friction Coefficient in the Numerical Simulation of Tidal Wave Propagation

2010 ◽  
Author(s):  
Z. Y. Song ◽  
C. Cheng ◽  
F. M. Xu ◽  
J. Kong
Keyword(s):  
Numerical Simulation ◽  
Wave Propagation ◽  
Friction Factor ◽  
Tidal Wave ◽  
Computational Time ◽  
Numerical Dissipation ◽  
Courant Number ◽  
Time Step ◽  
Large Time Step ◽  
The Relationship

Based on the analytical solution of one-dimensional simplified equation of damping tidal wave and Heuristic stability analysis, the precision of numerical solution, computational time and the relationship between the numerical dissipation and the friction dissipation are discussed with different numerical schemes in this paper. The results show that (1) when Courant number is less than unity, the explicit solution of tidal wave propagation has higher precision and requires less computational time than the implicit one; (2) large time step is allowed in the implicit scheme in order to reduce the computational time, but the precision of the solution also reduce and the calculation precision should be guaranteed by reducing the friction factor: (3) the friction factor in the implicit solution is related to Courant number, presented as the determined friction factor is smaller than the natural value when Courant number is larger than unity, and their relationship formula is given from the theoretical analysis and the numerical experiments. These results have important application value for the numerical simulation of the tidal wave.

scholarly journals Viscoelasticity of the trachea and its effects on flow limitation

2006 ◽  
Vol 100 (2) ◽  
pp. 384-389 ◽  
Author(s):  
Nikolai Aljuri ◽  
Jose G. Venegas ◽  
Lutz Freitag
Keyword(s):  
Wave Speed ◽  
Mathematical Representation ◽  
Forced Expiration ◽  
Flow Limitation ◽  
Time Dependency ◽  
Cross Sectional ◽  
Elastic Tubes ◽  
Forced Expiratory Flow ◽  
Expiratory Flow ◽  
The Relationship

To test the hypothesis that peak expiratory flow is determined by the wave-speed-limiting mechanism, we studied the time dependency of the trachea and its effects on flow limitation. For this purpose, we assessed the relationship between transmural pressure and cross-sectional area [the tube law (TL)] of six excised human tracheae under controlled conditions of static (no flow) and forced expiratory flow. We found that TLs of isolated human tracheae followed quite well the mathematical representation proposed by Shapiro (Shapiro AH. J Biomech Eng 99: 126–147, 1977) for elastic tubes. Furthermore, we found that the TL measured at the onset of forced expiratory flow was significantly stiffer than the static TL. As a result, the stiffer TL measured at the onset of forced expiratory flow predicted theoretical maximal expiratory flows far greater than those predicted by the more compliant static TL, which in all cases studied failed to explain peak expiratory flows measured at the onset of forced expiration. We conclude that the observed viscoelasticity of the tracheal walls can account for the measured differences between maximal and “supramaximal” expiratory flows seen at the onset of forced expiration.

Research on the Effect of Head Type on the Hydrodynamics of Vertical Motion Vehicle Launched by Gas Curtain

2013 ◽  
Vol 310 ◽  
pp. 218-222 ◽  
Author(s):  
Wei Cao ◽  
Hai Jun Liu ◽  
Cong Wang
Keyword(s):  
Numerical Simulation ◽  
Drag Coefficient ◽  
Vertical Motion ◽  
The State ◽  
Pass Through ◽  
Head Type

The numerical simulation was used to research the effect of different head vehicles on gas curtain and hydrodynamics in the process of underwater exiting tube and movement in water and exiting water under gas curtain launch. The two different heads of the vehicles could both smoothly pass through the narrowest place of the gas curtain and enter into the gas curtain jointed with air. Head type has little influence on the state and shape of the gas curtain and on the hydrodynamics. The drag coefficient is smallest and changes stably in the process of exiting water.

scholarly journals AN INVESTIGATION ON THE EFFECTS OF MICRO-PARAMETERS ON THE STRENGTH PROPERTIES OF ROCK

2021 ◽  
Vol 36 (1) ◽  
pp. 111-119
Author(s):  
Behzad Jafari Mohammadabadi ◽  
Kourosh Shahriar ◽  
Hossein Jalalifar ◽  
Kaveh Ahangari
Keyword(s):  
Mechanical Properties ◽  
Numerical Simulation ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Friction Coefficient ◽  
Critical Stress ◽  
Friction Angle ◽  
Strength Properties ◽  
Brazilian Tensile Strength ◽  
The Relationship

Rocks are formed from particles and the interaction between those particles controls the behaviour of a rock’s mechanical properties. Since it is very important to conduct extensive studies about the relationship between the micro-parameters and macro-parameters of rock, this paper investigates the effects of some micro-parameters on strength properties and the behaviour of cracks in rock. This is carried out by using numerical simulation of an extensive series of Uniaxial Compressive Strength (UCS) and Brazilian Tensile Strength (BTS) tests. The micro-parameters included the particles’ contact modulus, the contact stiff ness ratio, bond cohesion, bond tensile strength, the friction coefficient and the friction angle, and the mechanical properties of chromite rock have been considered as base values of the investigation. Based on the obtained results, it was found that the most important micro-parameters on the behaviour of rock in the compressive state are bond cohesion, bond tensile strength, and the friction coefficient. Also, the bond tensile strength showed the largest effect under tensile conditions. The micro-parameter of bond tensile strength increased the rock tensile strength (up to 5 times), minimized destructive cracks and increased the corresponding strain (almost 2.5 times) during critical stress.

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