Convergence–confinement analysis of a bolt-supported tunnel using the homogenization method

2006 ◽  
Vol 43 (5) ◽  
pp. 462-483 ◽  
Author(s):  
Henry Wong ◽  
Didier Subrin ◽  
Daniel Dias
Keyword(s):  
Input Parameter ◽  
Uniaxial Stress ◽  
Homogenization Method ◽  
External Input ◽  
Proposed Model ◽  
Homogenization Approach ◽  
Parametric Studies ◽  
Perfect Bonding ◽  
The Moment ◽  
Grouted Bolts

The behaviour of tunnels reinforced with radially disposed fully grouted bolts is investigated in this paper. Perfect bonding and ideal diffusion of bolt tension are assumed, so that the bolt tension can be assimilated to an equivalent uniaxial stress tensor. An analytical model of the convergence–confinement type is proposed that accounts for the delayed action of bolts due to ground decompression prior to bolt installation. This factor leads to nonsimultaneous yielding, and more generally, a different stress history for each constituent, requiring special treatments in the incremental elastoplasticity calculations. Nonetheless, the resulting model remains sufficiently simple, and an analytical solution is still accessible. Charts are provided to allow for parametric studies and quick preliminary designs. Comparisons with 3D numerical calculations show that the model gives precise results if the correct convergence at the moment of bolt installation is used as an "external" input parameter, validating the homogenization approach. An approximate methodology based on previous works is proposed to determine this parameter to render the proposed model "self-sufficient." Its predictions are again compared to 3D numerical computations, and the results are found to be sufficiently accurate for practical applications.Key words: reinforcement, anisotropy, analytical, lining, yield, elastoplasticity.

MULTISTAGE ROCKET FLIGHT SIMULATION

2019 ◽  
pp. 105-107
Author(s):  
A. S. Busygin ◽  
А. V. Shumov
Keyword(s):  
State Vector ◽  
Center Of Mass ◽  
Flight Simulation ◽  
Continuous Change ◽  
Information Tools ◽  
The Earth ◽  
Proposed Model ◽  
Piecewise Continuous ◽  
The Moment ◽  
Simulated Object

The paper considers a method for simulating the flight of a multistage rocket in Matlab using Simulink software for control and guidance. The model takes into account the anisotropy of the gravity of the Earth, changes in the pressure and density of the atmosphere, piecewise continuous change of the center of mass and the moment of inertia of the rocket during the flight. Also, the proposed model allows you to work out various targeting options using both onboard and ground‑based information tools, to load information from the ground‑based radar, with imitation of «non‑ideality» of incoming target designations as a result of changes in the accuracy of determining coordinates and speeds, as well as signal fluctuations. It is stipulated that the design is variable not only by the number of steps, but also by their types. The calculations are implemented in a matrix form, which allows parallel operations in each step of processing a multidimensional state vector of the simulated object.

AN ELECTROMAGNETIC CATAPULT FOR LAUNCHING HEAVY UAVs (DRONES) FROM SMALL VESSELS

2021 ◽  
pp. 25-34
Author(s):  
A.P. Baganov ◽  
◽  
V.G. Butov ◽  
G.V. Nosov ◽  
M.G. Nosova ◽  
...  
Keyword(s):  
Maximum Acceleration ◽  
Idle Mode ◽  
Small Vessels ◽  
Mhd Generator ◽  
Electromechanical Energy Conversion ◽  
Proposed Model ◽  
Rail Accelerator ◽  
Electromechanical Energy ◽  
The Moment ◽  
The Mathematical Model

The paper presents the results of mathematical modeling of the operation of a novel electromagnetic catapult design. The main elements of the latter are a single-section multi-rail accelerator with a metal armature and a pulsed energy source based on the powerful pulsed MHD generator and current-increasing transformer. The possibilities of such a scheme for accelerating bodies weighing 7 tons to speeds of about 150 km/h at a maximum permissible acceleration of 15 g are investigated. The mathematical model describes the coordinated operation of the device, starting with connecting of the pulsed MHD generator in idle mode to the primary winding of the transformer and up to the moment when the drone accelerates to a given takeoff speed. Using the proposed model, the efficiency of the electromechanical energy conversion in the developed catapult scheme is tested. The parameters of the main elements of the device, namely the length of the acceleration section of the catapult and the maximum acceleration of the drone, are determined.

scholarly journals NEW WAYS OF PACKAGE PROJECTS FOR SMALL AND MEDIUM-SIZED ENTERPRISES (SME) IN GERMANY/NEUE WEGE IM SCHLÜSSELFERTIGBAU FÜR KLEINE UND MITTELSTÄNDISCHE UNTERNEHMEN

2001 ◽  
Vol 7 (4) ◽  
pp. 294-303
Author(s):  
Bernd Reichelt
Keyword(s):  
Public Relations ◽  
Integrated System ◽  
Software Test ◽  
Software Support ◽  
Business Units ◽  
Proposed Model ◽  
New Ideas ◽  
Good Potential ◽  
The Moment ◽  
Support Software

In Germany the building industry is in recession at the moment. Especially the SMEs have to adapt to different situation in order to survive. One possible strategy could be taken on orders as main contractors. This has until now been donne dominantely by large building enterprises. The author describes problems and chances which arise if the SMEs take on package projects. He develops a strategic idea that is based on intensive use of computers in all processes and on new forms of cooperation (partnering) that is less known in Germany. The author is convinced that in future the collaboration of partners will play a significant role in the construction of structures that are completely finished and ready for sale. After the improvement of the prototype and optimisation of the information system, the proposed model has a good potential in the field of small and medium business units. After the methodological knowledge and software blend into one product, a new solution will be received, viz the franchise. The integrated system of working with an interested contractor general, his subcontractors and, if necessary, the construction master, that includes training, software support, software test runs, elimination of conflicts and faults, etc. In the first projects the franchiser must provide the intermediator. The Institute of Collaboration of Construction Partners that earns its income from the sale of franchises may perform scientific improvement of methods and software; the Institute is also engaged in dealing with atypical problems, support of subcontractors and contractors in their search for new ideas, as well as in the promotion of its methods using public relations.

Valuation of machinery and equipment subject to the Wiener degradation process

2021 ◽  
Vol 57 (3) ◽  
pp. 97
Author(s):  
Sergey Smolyak
Keyword(s):  
Service Life ◽  
Wiener Process ◽  
Market Value ◽  
Degradation Process ◽  
Average Value ◽  
Boundary State ◽  
Proposed Model ◽  
Negative Drift ◽  
The Mean ◽  
The Moment

We propose a model describing the decrease in the market value of machines (depreciation) with age. Usually it is characterized by the percent good factor, i.e. the ratio of machine’s value to the value of similar new machinery item. Often, appraisers know about a used machinery item only by its age, but not its performance. Therefore, for the valuation of the machinery item of a known age, they have to use the mean (for machines of this age) of percent good factor. In the proposed model, the state of the machine is characterized by the intensity of the benefits it brings. In this case, the benefits from using the machine in a certain period are defined as the market value of the work performed by it minus operating costs. We describe the change in the intensity of benefits over time by the Wiener process with negative drift. This allows us to take into account the tendency for the performance of machine to deteriorate during operation. The market value of a machine is defined as the maximum mathematical expectation of the sum of discounted benefits from its use. It is shown that it corresponds to the moment the machine reaches a certain boundary state. The parameters of the Wiener process (drift and volatility) are expressed through the known characteristics of the machine's durability, namely the average value and the coefficient of variation of the service life. The dependences of the mean percent good factor of machines on the relative age (the ratio of age to the average service life) are found. It turned out that these dependencies are almost independent of the discount rate and average service life.

Study on Constitutive Model of Weibull Distribution of Cement-Soil Uniaxial Stress Conditions

2012 ◽  
Vol 184-185 ◽  
pp. 810-817
Author(s):  
Zhi Nang Yu ◽  
Xin Jiang Song
Keyword(s):  
Constitutive Model ◽  
Weibull Distribution ◽  
Random Variable ◽  
Uniaxial Stress ◽  
Distribution Model ◽  
Proposed Model ◽  
Soil Stress ◽  
Uniaxial Compressive Test ◽  
Cement Soil ◽  
Nonlinear Elastic

According to the results of cement-soil uniaxial compressive test, consider cement-soil stress-strain relations as a continuous random process, the function of random variable obeys Weibull distribution, and introduce generalized hooke′s law in order to establish Weibull distribution of cement-soil constitutive model, solve the softening problem that a variety of incremental nonlinear elastic models cannot reflect the cement-soil. This paper discussed the parameter character of Weibull distribution model of cement-soil, presented the solving method of parameters of cement-soil Weibull distribution constitutive model, verified by results of test, revealed the rationality of the model and shows that the proposed model is more convenient than other model, have widely application value.

scholarly journals An Analytical Model for the Effect of Vertical Wind Veer on Wind Turbine Wakes

Energies ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1838 ◽  
Author(s):  
Mahdi Abkar ◽  
Jens Sørensen ◽  
Fernando Porté-Agel
Keyword(s):  
Wind Turbine ◽  
Input Parameter ◽  
Mass Conservation ◽  
Wake Flow ◽  
Mean Velocity ◽  
Gaussian Shape ◽  
Velocity Deficit ◽  
Proposed Model ◽  
The Mean ◽  
Wake Model

In this study, an analytical wake model for predicting the mean velocity field downstream of a wind turbine under veering incoming wind is systematically derived and validated. The new model, which is an extended version of the one introduced by Bastankhah and Porté-Agel, is based upon the application of mass conservation and momentum theorem and considering a skewed Gaussian distribution for the wake velocity deficit. Particularly, using a skewed (instead of axisymmetric) Gaussian shape allows accounting for the lateral shear in the incoming wind induced by the Coriolis force. This analytical wake model requires only the wake expansion rate as an input parameter to predict the mean wake flow downstream. The performance of the proposed model is assessed using the large-eddy simulation (LES) data of a full-scale wind turbine wake under the stably stratified condition. The results show that the proposed model is capable of predicting the skewed structure of the wake downwind of the turbine, and its prediction for the wake velocity deficit is in good agreement with the high-fidelity simulation data.

scholarly journals On the Prediction of Biogas Production from Vegetables, Fruits, and Food Wastes by ANFIS- and LSSVM-Based Models

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Yong Yang ◽  
Shuaishuai Zheng ◽  
Zhilu Ai ◽  
Mohammad Mahdi Molla Jafari
Keyword(s):  
Mean Squared Error ◽  
Fuzzy Inference ◽  
Biogas Production ◽  
Input Parameter ◽  
Machine Learning Algorithms ◽  
Least Square ◽  
Support Vector ◽  
Robust Algorithms ◽  
Inference System ◽  
Proposed Model

This study is aimed at modeling biodigestion systems as a function of the most influencing parameters to generate two robust algorithms on the basis of the machine learning algorithms, including adaptive network-based fuzzy inference system (ANFIS) and least square support vector machine (LSSVM). The models are assessed utilizing multiple statistical analyses for the actual values and model outcomes. Results from the suggested models indicate their great capability of predicting biogas production from vegetable food, fruits, and wastes for a variety of ranges of input parameters. The values that are calculated for the mean relative error (MRE %) and mean squared error (MSE) were 29.318 and 0.0039 for ANFIS, and 2.951 and 0.0001 for LSSVM which shows that the latter model has a better ability to predict the target data. Finally, in order to have additional certainty, two analyses of outlier identification and sensitivity were performed on the input parameter data that proved the proposed model in this paper has higher reliability in assessing output values compared with the previous model.

scholarly journals A New Generalized Transmuted Inverse Exponential Distribution: Properties and Application

2018 ◽  
pp. 1-13
Author(s):  
Uchenna U. Uwadi ◽  
Elebe E. Nwaezza
Keyword(s):  
Exponential Distribution ◽  
Real Life ◽  
Quantile Function ◽  
Moment Generating Function ◽  
Maximum Likelihood Estimates ◽  
Data Set ◽  
Real Life Data ◽  
Proposed Model ◽  
Inverse Exponential Distribution ◽  
The Moment

In this study, we proposed a new generalised transmuted inverse exponential distribution with three parameters and have transmuted inverse exponential and inverse exponential distributions as sub models. The hazard function of the distribution is nonmonotonic, unimodal and inverted bathtub shaped making it suitable for modelling lifetime data. We derived the moment, moment generating function, quantile function, maximum likelihood estimates of the parameters, Renyi entropy and order statistics of the distribution. A real life data set is used to illustrate the usefulness of the proposed model.     

scholarly journals Synchronization of Mechanical Oscillators: An Experimental Study

2011 ◽  
Author(s):  
Roozbeh Daneshvar ◽  
Tama´s Kalma´r-Nagy
Keyword(s):  
Feedback Loop ◽  
External Input ◽  
Degree Of Freedom ◽  
Proposed Model ◽  
Moving Base ◽  
Mechanical Basis ◽  
Mechanical Oscillators ◽  
Changes Over Time ◽  
Coupling Medium ◽  
Over Time

In this paper we investigate synchronization of oscillators. We use mechanical metronomes that are coupled through a mechanical medium. In passive coupling of two oscillators, the coupling medium is a one degree of freedom passive mechanical basis. The analysis of the system is shown and supported by simulations of the proposed model and experimental results. We show how the oscillators synchronize and discuss the affecting parameters in synchronization. In another case, the oscillators are forced by an external input while that input is also affected by the oscillators. This feedback loop introduces dynamics to the whole system. For this case, we place the mechanical metronomes on a one degree of freedom moving base. The movements of the base are a function of a feedback from the phases of the metronomes. We study the space of possibilities for the movements of the base and consider impacts of the base movement on the synchronization of metronomes. We also show how such a system evolves in time when we introduce an adjusting parameter that changes over time and updates based on feedbacks from the system.

scholarly journals Modeling the spread of fake news on Twitter

PLoS ONE ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. e0250419
Author(s):  
Taichi Murayama ◽  
Shoko Wakamiya ◽  
Eiji Aramaki ◽  
Ryota Kobayashi
Keyword(s):  
Process Model ◽  
Negative Impact ◽  
News Item ◽  
Compact Representation ◽  
News Story ◽  
Fake News ◽  
Proposed Model ◽  
Significant Negative Impact ◽  
Twitter Users ◽  
The Moment

Fake news can have a significant negative impact on society because of the growing use of mobile devices and the worldwide increase in Internet access. It is therefore essential to develop a simple mathematical model to understand the online dissemination of fake news. In this study, we propose a point process model of the spread of fake news on Twitter. The proposed model describes the spread of a fake news item as a two-stage process: initially, fake news spreads as a piece of ordinary news; then, when most users start recognizing the falsity of the news item, that itself spreads as another news story. We validate this model using two datasets of fake news items spread on Twitter. We show that the proposed model is superior to the current state-of-the-art methods in accurately predicting the evolution of the spread of a fake news item. Moreover, a text analysis suggests that our model appropriately infers the correction time, i.e., the moment when Twitter users start realizing the falsity of the news item. The proposed model contributes to understanding the dynamics of the spread of fake news on social media. Its ability to extract a compact representation of the spreading pattern could be useful in the detection and mitigation of fake news.

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