scholarly journals Research of reliability and efficiency of technological processes of mechanical assembly production on the basis of the common semi-Markov model

2018 ◽  
Vol 224 ◽  
pp. 01138
Author(s):  
Yuri Rapatskiy ◽  
Mikhail Zamorenov ◽  
Vadim Kopp ◽  
Yuri Obzherin ◽  
Vladimir Gusev ◽  
...  
Keyword(s):  
Distribution Functions ◽  
Mechanical Assembly ◽  
Renewal Equations ◽  
Technological Processes ◽  
Threaded Connections ◽  
Proposed Model ◽  
The Common ◽  
Semi Markov Processes ◽  
Simulation Parameters ◽  
Assembly Production

In the article a common semi-Markov mathematical model is considered that allows one to investigate the productivity and reliability of various technological processes of mechanical assembly production. The proposed model allows to study, inter alia, technological processes of manufacturing parts with screw and assemblies of threaded connections. Mathematical apparatus of the research is the theory of semi-Markov processes with a common phase space, which operates with a common kind of random variables distribution functions. If the considering process in the system is a subsystem located on a higher level of hierarchy, the hierarchical model for compatibility with each other levels as output simulation parameters required distribution functions. In the proposed model, based on the decision of the Markov renewal equations depend not only on the torque characteristics, but also the distribution function of time per unit of output service according to different kinds of undervalued failures.

Gas Phase Cluster Formation of Sodium Chloride and Water: Monte Carlo Simulations

1991 ◽  
Vol 46 (4) ◽  
pp. 351-356
Author(s):  
Bernd M. Rode
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Cluster Formation ◽  
Ion Pairs ◽  
Particle Interaction ◽  
Distribution Functions ◽  
Prebiotic Atmosphere ◽  
Low Concentrations ◽  
Phase Cluster ◽  
Simulation Parameters

Abstract Monte Carlo simulations of a system of 200 water and 24 NaCl molecules at 6 different densities in the range from 0.003 g/cm3 to 0.999 g,/cm3 and T = 125 °C and 225 CC were performed to obtain some insight into cluster formation which should precede and determine the formation of aerosol structures and has possibly played some role in prebiotic atmosphere chemistry. Solute hydration occurs already at very low concentrations mainly in the form of hydrated molecules ("contact ion pairs"). At higher densities larger cluster structures are observed, leading rather continuously to the structure of the supersaturated 7.1 M NaCl solution at the same temperature. Radial distribution functions, coordination numbers and particle interaction energies are discussed with respect to the simulation parameters density and temperature

scholarly journals Measurements and Computations of Internal Temperatures of the IGBT and the Diode Situated in the Common Case

Electronics ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 210
Author(s):  
Paweł Górecki ◽  
Krzysztof Górecki
Keyword(s):  
Thermal Properties ◽  
Measurement Error ◽  
Thermal Model ◽  
Bipolar Transistor ◽  
Internal Temperature ◽  
Self Heating ◽  
Factors Influencing ◽  
Proposed Model ◽  
The Common ◽  
Transient Thermal

This article proposes effective methods of measurements and computations of internal temperature of the dies of the Insulted Gate Bipolar Transistor (IGBT) and the diode mounted in the common case. The nonlinear compact thermal model of the considered device is proposed. This model takes into account both self-heating phenomena in both dies and mutual thermal couplings between them. In the proposed model, the influence of the device internal temperature on self and transfer thermal resistances is taken into account. Methods of measurements of each self and transfer transient thermal impedances occurring in this model are described and factors influencing the measurement error of these methods are analysed. Some results illustrating thermal properties of the investigated devices including the IGBT and the antiparallel diode in the common case are shown and discussed. Computations illustrating the usefulness of the proposed compact thermal model are presented and compared to the results of measurements. It is proved that differences between internal temperature of both dies included in the TO-247 case can exceed even 15 K.

Fuzzy Analysis of Geometric Tolerances Using Interval Method

2006 ◽  
Vol 220 (4) ◽  
pp. 489-497 ◽  
Author(s):  
W Wu ◽  
S S Rao
Keyword(s):  
Mechanical System ◽  
Current Approach ◽  
Distribution Functions ◽  
Manufacturing Cost ◽  
Mechanical Assembly ◽  
Geometric Dimensioning And Tolerancing ◽  
Analysis And Synthesis ◽  
Linear Interval ◽  
Linear Interval Equations ◽  
And Performance

The quality and performance of any mechanical system are greatly influenced by the GD&T (geometric dimensioning and tolerancing) used in its design. A proper consideration of the various types of tolerances associated with different components could not only satisfy the assembly requirements, but also minimize the manufacturing cost. To satisfy the design and functional specifications, one has to know how various tolerance patterns affect the manufacturability and assemblability of the designed parts. Therefore, a thorough understanding of how different forms of mechanical tolerances interact with each other becomes a must for designers and manufacturers. The effects of form, orientation, and position tolerances on the kinematic features and dimensions of mechanical systems are analysed using a new approach, based on fuzzy logic, in this article. In this approach, the α-cut method is used with the mechanical tolerances concerned as intervals. The proposed approach represents a more natural and realistic way of dealing with uncertain properties like geometric dimensions. A typical mechanical assembly system involving form, orientation, and position tolerances is used as an illustrative example. As the fuzzy approach leads to systems of non-linear interval equations, a modified Newton-Raphson method is developed for the solution of these equations. The current approach is found to be effective, simple, and accurate and can be extended to the analysis and synthesis of any uncertain mechanical system where the probability distribution functions of the uncertain parameters are unknown.

scholarly journals Stochastic Single Footfall Trace Model for Pedestrian Walking Load

2019 ◽  
Vol 19 (03) ◽  
pp. 1950029 ◽  
Author(s):  
Jun Chen ◽  
Guo Ding ◽  
Stana Živanović
Keyword(s):  
Random Variables ◽  
Distribution Functions ◽  
Dynamic Force ◽  
Gait Parameters ◽  
Proposed Model ◽  
Vibration Serviceability ◽  
Reliable Model ◽  
Time Histories ◽  
Trace Model ◽  
Force Time

Developing a model for the dynamic force generated by a pedestrian’s foot on a supporting structure (single footfall trace model) is crucial to advanced numerical analysis and vibration serviceability assessment of the structure. A reliable model needs to reflect the inter-subject and intra-subject randomness of human walking. This paper introduces a stochastic single footfall trace model in the form of a Fourier series in which body weight, walking frequency, and the first eight harmonics are treated as random variables. An experiment used 73 test subjects, walking at a range of pacing frequencies, to record force time histories and the corresponding gait parameters. Two variability descriptors were used to indicate inter-subject and intra-subject randomness. Further statistical analysis identified the relationships between key parameters as well as the probability distribution functions of random variables. In the final step, an application of the proposed single footfall trace model was developed and tested. The proposed model represented the experimental data well in both time and frequency domains.

Reliability of nonrepairable phased-mission systems with common bus performance sharing

2018 ◽  
Vol 232 (6) ◽  
pp. 647-660 ◽  
Author(s):  
Huan Yu ◽  
Jun Yang ◽  
Yu Zhao
Keyword(s):  
Genetic Algorithm ◽  
Reliability Analysis ◽  
Evaluation Method ◽  
Optimal Allocation ◽  
Recursive Algorithm ◽  
Entire System ◽  
Allocation Algorithm ◽  
Proposed Model ◽  
The Common ◽  
Multi Phase

This article considers the reliability analysis of phased-mission systems with common bus performance sharing. The whole system consists of client nodes, service elements, and a common bus redistribution system and it undertakes a multi-phase mission. In each phase, the service elements must satisfy the demands of the prespecified client nodes set. The service elements can share their surplus performance with other client nodes through the common bus. In any phase, the system fails if the demands of the prespecified client nodes set are not satisfied. In other words, the entire system succeeds if the demands of the prespecified client nodes set are satisfied in all phases. The reliability of the proposed model is analyzed by the backward recursive algorithm. The optimal allocation problem is solved by the genetic algorithm. Two examples are presented to demonstrate the proposed reliability evaluation method and optimal allocation algorithm.

A Model of Metabolic Supply-Demand Mismatch Leading to Secondary Brain Injury

2021 ◽  
Author(s):  
Jiangling Song ◽  
Jennifer A. Kim ◽  
Aaron Frank Struck ◽  
Rui Zhang ◽  
M. Brandon Westover
Keyword(s):  
Brain Injury ◽  
Mechanistic Model ◽  
Acute Brain Injury ◽  
Extracellular Potassium ◽  
Secondary Brain Injury ◽  
Proposed Model ◽  
The Common ◽  
High Level ◽  
The Brain ◽  
Common Association

Secondary brain injury (SBI) is defined as new or worsening injury to the brain after an initial neurologic insult, such as hemorrhage, trauma, ischemic stroke, or infection. It is a common and potentially preventable complication following many types of primary brain injury (PBI). However, mechanistic details about how PBI leads to additional brain injury and evolves into SBI are poorly characterized. In this work, we propose a mechanistic model for the metabolic supply demand mismatch hypothesis (MSDMH) of SBI. Our model, based on the Hodgkin-Huxley model, supplemented with additional dynamics for extracellular potassium, oxygen concentration and excitotoxity, provides a high-level unified explanation for why patients with acute brain injury frequently develop SBI. We investigate how decreased oxygen, increased extracellular potassium, excitotoxicity, and seizures can induce SBI, and suggest three underlying paths for how events following PBI may lead to SBI. The proposed model also helps explain several important empirical observations, including the common association of acute brain injury with seizures, the association of seizures with tissue hypoxia and so on. In contrast to current practices which assume that ischemia plays the predominant role in SBI, our model suggests that metabolic crisis involved in SBI can also be non-ischemic. Our findings offer a more comprehensive understanding of the complex interrelationship among potassium, oxygen, excitotoxicity, seizures and SBI.

scholarly journals A Study on Trend Analysis of Applicants Based on Patent Classification Systems

Information ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 364 ◽  
Author(s):  
Soohyeon Chae ◽  
Jangwon Gim
Keyword(s):  
Intellectual Property Rights ◽  
New Technologies ◽  
Classification Systems ◽  
International Patent Classification ◽  
Ripple Effects ◽  
Patent Classification ◽  
Proposed Model ◽  
International Patent ◽  
The Social ◽  
The Common

In recent times, with the development of science and technology, new technologies have been rapidly emerging, and innovators are making efforts to acquire intellectual property rights to preserve their competitive advantage as well as to enhance innovative competitiveness. As a result, the number of patents being acquired increases exponentially every year, and the social and economic ripple effects of developed technologies are also increasing. Now, innovators are focusing on evaluating existing technologies to develop more valuable ones. However, existing patent analysis studies mainly focus on discovering core technologies amongst the technologies derived from patents or analyzing trend changes for specific techniques; the analysis of innovators who develop such core technologies is insufficient. In this paper, we propose a model for analyzing the technical inventions of applicants based on patent classification systems such as international patent classification (IPC) and cooperative patent classification (CPC). Through the proposed model, the common invention patterns of applicants are extracted and used to analyze their technical inventions. The proposed model shows that patent classification systems can be used to extract the trends in applicants’ technological inventions and to track changes in their innovative patterns.

Application of Continuous Thermodynamics Method to Fuel Droplet Evaporation

2012 ◽  
Author(s):  
Way Lee Cheng ◽  
Cai Shen ◽  
Chia-fon F. Lee
Keyword(s):  
Liquid Phase ◽  
Effective Properties ◽  
Liquid Mixtures ◽  
Droplet Evaporation ◽  
Distribution Functions ◽  
Homogeneous Groups ◽  
Novel Approach ◽  
Proposed Model ◽  
Complex Liquid

A finite diffusion droplet evaporation model for complex liquid mixture composed of different homogeneous groups is presented in this paper. Separate distribution functions are used to describe the composition of each homogeneous group in the mixture. Only a few parameters are required to describe the mixture. Quasi-steady assumption is applied in the determination of evaporation rates and heat flux to the droplet, and the effects of surface regression, finite diffusion and preferential vaporization of the mixture are included in the liquid phase equations using an effective properties approach. A novel approach was used to reduce the transport equations for the liquid phase to a set of ordinary differential equations. The proposed model is capable in capturing the vaporization characteristics of complex liquid mixtures.

Automatic Determination of Tolerance Chains in Unidirectional Tolerancing

2000 ◽  
Author(s):  
Charles Forster ◽  
Jean-Paul Boufflet ◽  
Fabien Lecouvreur
Keyword(s):  
Graph Theory ◽  
Functional Constraint ◽  
Second Step ◽  
Automatic Method ◽  
Functional Constraints ◽  
Mechanical Assembly ◽  
Automatic Determination ◽  
Cad System ◽  
Proposed Model

Abstract Herein is proposed an automatic method by which the all-tolerance chains of a mechanical assembly may be constructed. The method, implementable in a CAD system, is divided into two main steps. In the first step, we model the mechanical assembly with a graph, of which the vertices represent the parts and the edges, the contact between the parts. By « sliding » the parts, we may determine all the configurations of the mechanical assembly. The proposed model, which uses classical algorithms of the graph theory, allows control of the coherence of the mechanical assembly. In the second step, we introduce an extended syntax by which the functional constraints may be decoded without ambiguity. Then, using the syntax and the model, we show how to construct the tolerance chain for each functional constraint.

scholarly journals Nash Equilibrium Investment-Reinsurance Strategies for an Insurer and a Reinsurer with Intertemporal Restrictions and Common Interests

Mathematics ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 139
Author(s):  
Yanfei Bai ◽  
Zhongbao Zhou ◽  
Rui Gao ◽  
Helu Xiao
Keyword(s):  
Nash Equilibrium ◽  
Value Premium ◽  
Insurance Company ◽  
Common Goal ◽  
General Insurance ◽  
Proposed Model ◽  
Common Interests ◽  
The Common ◽  
Mean Variance ◽  
Theoretical Results

This paper investigates the generalized multi-period mean-variance investment-reinsurance optimization model in a discrete-time framework for a general insurance company that contains a reinsurer and an insurer. The intertemporal restrictions and the common interests of the reinsurer and the insurer are considered. The common goal of the reinsurer and the insurer is to maximize the expectation of the weighted sum of their wealth processes and minimize the corresponding variance. Based on the game method, we obtain the Nash equilibrium investment-reinsurance strategies for the above-proposed model and find out the equilibrium strategies when unilateral interest is considered. In addition, the Nash equilibrium investment-reinsurance strategies are deduced under two special premium calculated principles (i.e., the expected value premium principle and the variance value premium principle). We theoretically study the effect of the intertemporal restrictions on Nash equilibrium investment-reinsurance strategies and find the effect depends on the value of some parameters, which differs from the previous researches that generally believed that intertemporal restrictions would make investors avoid risks. Finally, we perform corresponding numerical analyses to verify our theoretical results.

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