scholarly journals Dynamic Stress of Subgrade Bed Layers Subjected to Train Vehicles with Large Axle Loads

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Fang Xu ◽  
Qi Yang ◽  
Wenjie Liu ◽  
Wuming Leng ◽  
Rusong Nie ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Dynamic Stress ◽  
Random Variable ◽  
Dynamic Responses ◽  
Fe Model ◽  
Dynamic Stresses ◽  
Factors Affecting ◽  
Vertical Excitation ◽  
Heavy Haul ◽  
Abaqus Code

The dynamic responses of subgrade bed layers are the key factors affecting the service performance of a heavy-haul railway. A 3D train-track-subgrade interaction finite element (FE) model was constructed using the ABAQUS code, where different vertical irregular track spectra were simulated by modifying the vertical node coordinates of the FE mesh of the rail. Then, the dynamic stresses in the subgrade bed layers subjected to heavy-haul trains were studied in detail. The results showed the following: (1) the transverse distribution of the dynamic stress transformed from a bimodal pattern to a unimodal pattern with increasing depth; (2) the pass of adjacent bogies of adjacent carriages can be simplified once loaded on the subgrade since the dynamic stresses are maintained around the peak value during the pass of the adjacent bogies; (3) the dynamic stress at the bottom of the subgrade bed surface layer was more sensitive to the train axle load compared with that at the subgrade surface because the dynamic stresses induced by the two rails were gradually overlaid with increasing depth; (4) the maximum dynamic stress at the subgrade bed bottom was reduced by approximately 70% compared with that at the subgrade surface; (5) the vertical track irregularities intensified the vertical excitation between the train vehicle wheels and rails, and the maximum dynamic stress at the subgrade surface under the action of the irregular heavy-haul track spectrum increased by 23% compared with the smooth rail condition; and (6) the possible maximum dynamic stress (σdm) at the subgrade surface under the action of irregular track spectra can be predicted using the triple standard deviation principle of a normally distributed random variable, i.e., σdm = μ + 3σ (where μ and σ are the expectation and standard deviation of σdm, respectively).

A Finite Element Approach to Dynamic Stresses of Helical Gear Pairs Considering Tip Relief and Crowning Modifications

2013 ◽  
Vol 284-287 ◽  
pp. 577-581
Author(s):  
Kuo Jao Huang ◽  
Ching Ya Su
Keyword(s):  
Finite Element ◽  
Dynamic Stress ◽  
Helical Gear ◽  
Dynamic Responses ◽  
High Quality ◽  
Dynamic Stresses ◽  
Dynamic Finite Element ◽  
Bending Stresses ◽  
Element Approach ◽  
Maximum Stresses

A dynamic finite element (FE) approach to contact and fillet bending stresses of helical gear pairs (HGPs) is presented. Using derived tooth profiles, high quality elements of HGPs can be efficiently constructed. The resulted maximum stresses of elements on teeth are 3D illustrated. Design of relief and profile modifications is also condisered. The effect of tooth modifications on HGP dynamic responses including misalignment errors is discussed. It shows adequate modification of tip relief and crowning can reduce dynamic stress peaks of HGPs.

scholarly journals Estimation of Electricity Generation by an Electro-Technical Complex with Photoelectric Panels Using Statistical Methods

Symmetry ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1278
Author(s):  
Anna Turysheva ◽  
Irina Voytyuk ◽  
Daniel Guerra
Keyword(s):  
Random Distribution ◽  
Graphical Representation ◽  
Random Variable ◽  
Climatic Conditions ◽  
Characteristic Energy ◽  
Study Region ◽  
Factors Affecting ◽  
Solar Systems ◽  
The Republic ◽  
Technical Complex

This paper presents a computational tool for estimating energy generated by low-power photovoltaic systems based on the specific conditions of the study region since the characteristic energy equation can be obtained considering the main climatological factors affecting these systems in terms of the symmetry or skewness of the random distribution of the generated energy. Furthermore, this paper is aimed at determining any correlation that exists between meteorological variables with respect to the energy generated by 5-kW solar systems in the specific climatic conditions of the Republic of Cuba. The paper also presents the results of the influence of each climate factor on the distribution symmetry of the generated energy of the solar system. Studying symmetry in statistical models is important because they allow us to establish the degree of symmetry (or skewness), which is the probability distribution of a random variable, without having to make a graphical representation of it. Statistical skewness reports the degree to which observations are distributed evenly and proportionally above and below the center (highest) point of the distribution. In the case when the mentioned distribution is balanced, it is called symmetric.

scholarly journals Damage Diagnosis in 3D Structures Using a Novel Hybrid Multiobjective Optimization and FE Model Updating Framework

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Nizar Faisal Alkayem ◽  
Maosen Cao ◽  
Minvydas Ragulskis
Keyword(s):  
Structural Damage ◽  
Model Updating ◽  
Complex Problem ◽  
Dynamic Responses ◽  
Mode Shapes ◽  
Fe Model ◽  
Modal Strain Energy ◽  
3D Structures ◽  
Multiobjective Particle Swarm Optimization ◽  
Damage Tracking

Structural damage detection is a well-known engineering inverse problem in which the extracting of damage information from the dynamic responses of the structure is considered a complex problem. Within that area, the damage tracking in 3D structures is evaluated as a more complex and difficult task. Swarm intelligence and evolutionary algorithms (EAs) can be well adapted for solving the problem. For this purpose, a hybrid elitist-guided search combining a multiobjective particle swarm optimization (MOPSO), Lévy flights (LFs), and the technique for the order of preference by similarity to ideal solution (TOPSIS) is evolved in this work. Modal characteristics are employed to develop the objective function by considering two subobjectives, namely, modal strain energy (MSTE) and mode shape (MS) subobjectives. The proposed framework is tested using a well-known benchmark model. The overall strong performance of the suggested method is maintained even under noisy conditions and in the case of incomplete mode shapes.

‘Quit while you are ahead – and smell the roses!’ A survey of retired Fellows of the Australian and New Zealand College of Anaesthetists

2021 ◽  
pp. 0310057X2110057
Author(s):  
Diana Strange Khursandi ◽  
Victoria Eley
Keyword(s):  
Clinical Practice ◽  
New Zealand ◽  
Standard Deviation ◽  
Response Rate ◽  
Common Factors ◽  
Published Data ◽  
Factors Affecting ◽  
Retirement Decisions ◽  
Zealand College ◽  
The Mean

There are no published data on the age of retirement of anaesthetists in Australia and New Zealand. We surveyed 622 retired Fellows of the Australian and New Zealand College of Anaesthetists to determine their ages of complete retirement from clinical practice, demographics, and whether they had retired at the age they had intended to retire. We also aimed to explore factors affecting the decision to retire, the practice of ‘winding down’, common post-retirement activities, and the arrangement of personal and professional affairs. Responses were received from 371 specialists (response rate 60%). The mean (standard deviation) age of retirement was 65.2 (6.9) years. The mean (standard deviation) retirement ages ranged from 62.0 (7.1) years (those who retired earlier than planned) to 68.0 (4.3) years (those who retired later than they had intended). The mean (standard deviation) age of retirement of the male respondents was 66.0 (6.5) years, and for female respondents was 62.7 (7.7) years. Two hundred and thirty-three respondents (63%) reported winding down their practice prior to retirement, and 360 (97%) had made a will. Poor health and loss of confidence were the two most common factors in the retirement decisions of those who retired earlier than they had planned. Our results may assist current practitioners plan for retirement, and suggest strategies to help health services, departments and private groups accommodate individuals in winding down their practice.

A Continuous Spectrophotometric Method for Measuring the Activity of Serum Alkaline Phosphatase

1966 ◽  
Vol 12 (2) ◽  
pp. 70-89 ◽  
Author(s):  
George N Bowers ◽  
Robert B McComb
Keyword(s):  
Alkaline Phosphatase ◽  
Standard Deviation ◽  
Sample Size ◽  
Spectrophotometric Method ◽  
Serum Alkaline Phosphatase ◽  
Serum Alkaline Phosphatase Activity ◽  
Factors Affecting ◽  
Nitrophenyl Phosphate ◽  
Relative Standard ◽  
Hydrolysis Of

Abstract A continuous spectrophotometric method for measuring serum alkaline phosphatase activity is described. The effects of temperature, pH, substrate concentration, type and molarity of the buffer, sample size, cofactors, and inhibitors on the enzymatic hydrolysis of p-nitrophenyl phosphate were studied. The optimal conditions for assay of serum alkaline phosphatase at 30° were found to be 0.75 M 2-amino-2-methyl-1-propanol buffer, pH30° 10.15, 4 mmole substrate, and 100 µl. or less sample size. Studies of the factors affecting analytical precision-i.e., control of reaction temperature, of reagent manufacture, and of standardization-are discussed. The precision of this method was 2.3% (relative standard deviation) on 10 within day replicates and 5.0% on day-to-day replicates spread over a 5-week period. The range of activity for 258 apparently healthy adult blood donors was 6-110 mU./ml. (International milliunits per milliliter), with a mean of 49 and a standard deviation of 14.

The effect of clamping a tensioned wire: Implications for the Ilizarov external fixation system

2003 ◽  
Vol 217 (2) ◽  
pp. 91-98 ◽  
Author(s):  
M A Watson ◽  
K J Mathias ◽  
N Maffulli ◽  
D W L Hukins
Keyword(s):  
Finite Element ◽  
Standard Deviation ◽  
External Fixator ◽  
Clinical Situation ◽  
Engineering Problem ◽  
Fe Model ◽  
Ilizarov External Fixator ◽  
Wire Tension ◽  
The Wire ◽  
Fixation System

This study demonstrates that clamping a tensioned wire can cause a reduction in wire tension. Tension (about 1275 N) was applied to a wire that was subsequently clamped, using cannulated bolts, to the steel half-ring of an Ilizarov external fixator. The tension in the wire was monitored before, during and after clamping. The apparatus was disassembled and the deformations in the wire caused by the clamps were measured. This experiment was repeated 15 times. When the wire was clamped to the frame, the wire tension was reduced by 22 ± 7 per cent (mean ± standard deviation, SD). The drop in wire tension was linearly correlated ( r = 0.96; p < 0.001) with the deformation caused by the bolts. A finite element (FE) model of the wire was also constructed. The model was pre-stressed (tensioned), and the clamping effect replicated. This analysis showed that clamping the wire could be considered to squeeze the wire outwards (like toothpaste from a tube) and so reduce its tension during fixator assembly. To assess the magnitude of this effect in the clinical situation, the FE model analysis was repeated to replicate clamping a 1.8-mm-diameter wire to a 180-mm-diameter steel Ilizarov ring component. The analysis showed that for these conditions the tension reduced by 8–29 per cent. The results of this study highlight a general engineering problem: how can a tensioned wire be secured to a structure without an appreciable loss of tension? If the performance of the structure depends on the wire tension, this performance will change when the wire is secured.

scholarly journals Analysis of Basic Failure Scenarios of a Truss Tower in a Probabilistic Approach

2019 ◽  
Vol 9 (13) ◽  
pp. 2662 ◽  
Author(s):  
Wojciech Mochocki ◽  
Urszula Radoń
Keyword(s):  
Standard Deviation ◽  
Reliability Analysis ◽  
System Reliability ◽  
Probabilistic Approach ◽  
Random Variable ◽  
Structure Reliability ◽  
System Reliability Analysis ◽  
Steel Truss ◽  
Buckling Coefficient ◽  
The Impact

This paper concerns the system reliability analysis of steel truss towers. Due to failures of towers, the assessment of their reliability seems to be a very important problem. In the analysis, two cases are examined: when the buckling coefficient is a deterministic value and when it is a random variable. The impact of failures of single elements on the structure reliability was investigated. Calculations of the standard deviation of the capacity and reliability indexes were made using author-developed programs in the Mathematica environment.

scholarly journals Natural Test for Random Numbers Generator Based on Exponential Distribution

Mathematics ◽  
2019 ◽  
Vol 7 (10) ◽  
pp. 920 ◽  
Author(s):  
Tanackov ◽  
Sinani ◽  
Stanković ◽  
Bogdanović ◽  
Stević ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Mathematical Expectation ◽  
Random Number ◽  
Random Variable ◽  
Random Numbers ◽  
The Third ◽  
Atmospheric Noise ◽  
Constant E ◽  
Fourth Series ◽  
Natural Test

We will prove that when uniformly distributed random numbers are sorted by value, their successive differences are a exponentially distributed random variable Ex(λ). For a set of n random numbers, the parameters of mathematical expectation and standard deviation is λ =n−1. The theorem was verified on four series of 200 sets of 101 random numbers each. The first series was obtained on the basis of decimals of the constant e=2.718281…, the second on the decimals of the constant π =3.141592…, the third on a Pseudo Random Number generated from Excel function RAND, and the fourth series of True Random Number generated from atmospheric noise. The obtained results confirm the application of the derived theorem in practice.

Components of the evoked potential in the MES auditory cortex

1960 ◽  
Vol 199 (3) ◽  
pp. 529-534 ◽  
Author(s):  
Archie R. Tunturi
Keyword(s):  
Standard Deviation ◽  
Auditory Cortex ◽  
Electrical Activity ◽  
Evoked Potential ◽  
Random Variable ◽  
Positive Component ◽  
Negative Component ◽  
Spontaneous Electrical Activity ◽  
Covariance Term ◽  
The Mean

The electrical activity during the potential evoked by a p pulse was analyzed statistically by considering amplitude at each 3-msec. epoch a random variable. The rise in standard deviation during the evoked potential was abolished a) by local cocaine on the cortex, b) by a preceding evoked potential and c) by ischemia. The residual mean positive component, with zero standard deviation, was subtracted from the mean of the evoked potential. This yielded a positive-negative component, with which the spontaneous electrical activity is believed to interact. The evoked potential is thus described as the sum of the three random variables: a) spontaneous electrical activity, b) positive component, and c) positive-negative component, with a covariance term involving the spontaneous electrical activity and the positive-negative component.

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