simulation procedure
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Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 263
Author(s):  
Sergei Ivanov ◽  
Antoni Artinov ◽  
Evgenii Zemlyakov ◽  
Ivan Karpov ◽  
Sergei Rylov ◽  
...  

The present work seeks to extend the level of understanding of the stress field evolution during direct laser deposition (DLD) of a 3.2 mm thick multilayer wall of Ti-6Al-4V alloy by theoretical and experimental studies. The process conditions were close to the conditions used to produce large-sized structures by the DLD method, resulting in specimens having the same thermal history. A simulation procedure based on the implicit finite element method was developed for the theoretical study of the stress field evolution. The accuracy of the simulation was significantly improved by using experimentally obtained temperature-dependent mechanical properties of the DLD-processed Ti-6Al-4V alloy. The residual stress field in the buildup was experimentally measured by neutron diffraction. The stress-free lattice parameter, which is decisive for the measured stresses, was determined using both a plane stress approach and a force-momentum balance. The influence of the inhomogeneity of the residual stress field on the accuracy of the experimental measurement and the validation of the simulation procedure are analyzed and discussed. Based on the numerical results it was found that the non-uniformity of the through-thickness stress distribution reaches a maximum in the central cross-section, while at the buildup ends the stresses are distributed almost uniformly. The components of the principal stresses are tensile at the buildup ends near the substrate. Furthermore, the calculated equivalent plastic strain reaches 5.9% near the buildup end, where the deposited layers are completed, while the plastic strain is practically equal to the experimentally measured ductility of the DLD-processed alloy, which is 6.2%. The experimentally measured residual stresses obtained by the force-momentum balance and the plane stress approach differ slightly from each other.


2021 ◽  
Vol 7 (1) ◽  
pp. 1
Author(s):  
Veronica De Leo ◽  
Alessandro Scordo ◽  
Catalina Curceanu ◽  
Marco Miliucci ◽  
Florin Sirghi

The VOXES collaboration at INFN National Laboratories of Frascati developed a prototype of a high resolution Von Hamos X-ray spectrometer using HAPG (Highly Annealed Pyrolytic Graphite) mosaic crystals. This technology allows the employment of extended isotropic sources and could find application in several physics fields. The capability of the spectrometer to reach energy precision and resolution below 1 and 10 eV, respectively, when used with wide sources, has been already demonstrated. Recently, the response of this device, for a ρ = 206.7 mm cylindrically bent HAPG crystal using CuKα1,2 and FeKα1,2 XRF lines, has been investigated in terms of reflection efficiency by a dedicated ray-tracing simulation. Details of the simulation procedure and the comparison with the experimental results are presented. This study is crucial in order to retrieve information on the spectrometer signal collection efficiency, especially in the energy range in which the standard calibration procedures cannot be applied.


Author(s):  
A.Yu. Melnikov ◽  
S.N. Ilukhin

The article considers a technique for constructing an optimal guidance procedure for an aerospace aircraft. The technique is based on the adaptation of the Pontryagin maximum principle for the considered class of problems. At the same time the guidance accuracy is ensured by solving a boundary value problem, which is periodically performed during the flight. The developed procedure for predicting the final parameters of the optimal flight according to a simplified motion model is presented, which also makes it possible to determine the value of the actual miss. A detailed mathematical description of the proposed technique is given. The feasibility of the proposed technique is ensured by minimizing the amount of computational operations. The guidance algorithm efficiency is illustrated by a numerical example with a flight simulation procedure taking into account all significant factors. The paper also provides examples of solving boundary value problems and the results of modeling the optimal guidance.


2021 ◽  
pp. 135-146
Author(s):  
Kris Ferguson ◽  
Alaa Abd-Elsayed

This chapter will detail the surgical recommendations and step-by-step approaches for both trial stimulation and permanent implantation of peripheral nerve stimulation to treat sacroiliac joint pain. It also provides a brief history of this procedure, which has evolved from being a procedure that required careful, open dissection of the target nerve to a sleek treatment requiring only image guidance and a minimally invasive percutaneous approach. A trial stimulation period typically ranges from 7 to 14 days; steps for the trial simulation procedure include preparation, target point identification, and lead insertion. Additional topics for the permanent implantation procedure include tunneling and pocket dissection.


2021 ◽  
Vol 11 (16) ◽  
pp. 7764
Author(s):  
Kewei Ji ◽  
Linguo Chai ◽  
Sihui Li ◽  
Xiangyan Liu ◽  
Xiu Pan

To meet the demand for middle and low-density railway lines, a Global Navigation Satellite System (GNSS) based on a train integrity monitoring system (TIMS) is used for train integrity detection. Each system has to be analyzed before it is applied in practice. To evaluate the safety of the train integrity detection, a collision risk evaluation method is proposed based on the positioning errors and protection level, in which the Probability of dangerous Failure per Hour (PFH) is computed to quantify the the criteria of Safety Integrity Level (SIL). Then, an experiment-based simulation procedure is presented for safety verification. Statistics results have been obtained from field test data, and simulations are carried out using CPN and MATLAB to verify the collision risk of GNSS-based train integrity detection. The result showed that the GNSS-based train integrity detection satisfies the safety requirements in the system design phase for railway applications.


Author(s):  
Guilerme A. C. Caldeira ◽  
JoaquimAP Braga ◽  
António R. Andrade

Abstract The present paper provides a method to predict maintenance needs for the railway wheelsets by modeling the wear out affecting the wheelsets during its life cycle using survival analysis. Wear variations of wheel profiles are discretized and modelled through a censored survival approach, which is appropriate for modeling wheel profile degradation using real operation data from the condition monitoring systems that currently exist in railway companies. Several parametric distributions for the wear variations are modeled and the behavior of the selected ones is analyzed and compared with wear trajectories computed by a Monte Carlo simulation procedure. This procedure aims to test the independence of events by adding small fractions of wear to reach larger wear values. The results show that the independence of wear events is not true for all the established events, but it is confirmed for small wear values. Overall, the proposed framework is developed in such a way that the outputs can be used to support predictions in condition-based maintenance models and to optimize the maintenance of wheelsets.


2021 ◽  
Vol 41 (I) ◽  
pp. 61-67
Author(s):  
S. SAVCHUK ◽  
◽  
A. KHOPTAR ◽  

The content and distribution of water vapor in the Earth’s atmosphere are related to various weather conditions and climatic processes, and are therefore important for understanding many meteorological phenomena. At the current stage of development and formation of Global Navigation Satellite Systems (GNSS), the distribution of water vapor content can be established using such observations from GNSS tomography, which, in turn, allows to study changes in the vertical profile of water vapor content in the Earth’s troposphere. In troposphere GNSS tomography, accurate information on the distribution of water vapor is obtained using integrated measurements, such as the water vapor content value in the slant direction (Slant Water Vapor, SWV). The essence of the problem of troposphere GNSS tomography is the solution of equations system, the number of which is limited by the number of satellites involved in observations. In this case, the functional relationship between observations and unknowns, in the pathways of GNSS signals through the troposphere, must be known in sufficient numbers. However, today there is a problem of lack of such information, which leads to the main problem of the troposphere GNSS-tomography method – overcoming the deficit of rank in the inversion of the original equation. This problem can be solved by increasing the number of satellite signals in a wide range of positions. The purpose of this work is to maximize the use ofGNSS signals inmodeling tomographic solutions based on data simulation. Method. Based on the developed method of multi-GNSS observations data processing by the PPP method, an algorithm of the procedure of simulation of additional satellites in tomographic modeling in order to overcome the problems of rank deficit is proposed. Results. The results of application of the data simulation procedure for the vertical profile of water vapor content in the Earth’s troposphere are presented based on the results of processingGNSS observations at the GANP station (Poprad, Slovakia) in the period from 31.05.2019 to 1.06.2019. Scientific novelty and practical significance. For the first time, an algorithm for the procedure of additional satellites simulation was proposed in order to overcome the problems of rank deficit in the tomographic modeling.


2021 ◽  
Author(s):  
Yasuo Murai ◽  
Shun Sato ◽  
Atsushi Tsukiyama ◽  
Asami Kubota ◽  
Fumihiro Matano ◽  
...  

Abstract Objective: The increase in minimally invasive surgery and endovascular procedures has led to a decrease in surgical experience. This may adversely affect both surgical training and postoperative management. Since it poses no risk to a patient, simulation training may be a solution these problems. COVID-19 requires social distancing which has created a negative impact on the simulation educational environment. To date, there is only limited research examining whether skills are evaluated objectively and equally in simulation training, especially in microsurgery. The purpose of this study was to analyze the objectivity and equality of simulation evaluation results conducted in a contest format.Methods: A nationwide recruitment process was conducted to select study participants. Participants were recruited from a pool of qualified physicians with less than 10 years’ experience. In this study, the simulation procedure consisted of incising a 1 mm thick artificial blood vessel and suturing it with a 10-0 thread using a surgical microscope. To evaluate the simulation procedures, a scoring chart was developed with a maximum of 5 points each for eight different evaluation criteria. Five neurosurgical supervisors from different hospitals were asked to use this scoring chart to grade the simulation proceduresResults: Initially, we planned to have the neurosurgical supervisors score the simulation procedure by direct observation. However, due to COVID-19 some study participants were unable to attend. Thus requiring some simulation procedures to be scored by video review. A total of 14 trainees participated in the study. The Cronbach's alpha coefficient among the scorers was 0.99, indicating a strong correlation. There was no statistically significant difference between the scores from the video review and direct observation judgments. There was a statistically significant difference (p < 0.001) between the scores for some criteria. For the eight criteria, individual scorers assigned scores in a consistent pattern. However, this pattern differed between scorers indicating that some scorers were more lenient than others.Conclusions: The results of this study indicate that both video review and direct observation methods are useful and highly objective techniques evaluate simulation procedures. Despite differences in score assignment patterns between individual scorers.


2021 ◽  
pp. 13-28
Author(s):  
Eduardo P Falcetti ◽  
Álvaro Gardenghi ◽  
Alvaro B Dietrich ◽  
Luben Cabezas-Gómez

It is presented a hermetic compressor startup simulation procedure considering a simplified approach to obtain the transient data of different compressor parameters. The main numerical technique is a four order Runge-Kutta procedure to numerically integrate the systems of ordinary differential equations, which describe the variables’ variation with time in each part of the compressor. The simulations were performed in the Windali software. The results show how the oil viscosity influences the electrical motor torque, the compressor load and crankshaft angular velocity with time for two electric motor input voltage values. The increase of oil viscosity by a factor of 2, retards the compressor startup for more than one second. The presented simple model could be valuable for studying the geometrical and operational influence on compressor startup.


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