Optimal constant-stress ADDT plan with one main effect and one interaction effect

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Preeti Wanti Srivastava ◽  
Manisha Manisha ◽  
Manju Agarwal
Keyword(s):  
Interaction Effect ◽  
High Reliability ◽  
Stress Factor ◽  
Operating Conditions ◽  
Constant Stress ◽  
Stress Factors ◽  
Inspection Time ◽  
Model Parameters ◽  
Content Type ◽  
Main Effect

PurposeDegradation measurement of some products requires destructive inspection; that is, the degradation of each unit can be observed only once. For example, observation on the mechanical strength of interconnection bonds or on the dielectric strength of insulators requires destruction of the unit. Testing high-reliability items under normal operating conditions yields a small amount of degradation in a reasonable length of time. To overcome this problem, the items are tested at higher than normal stress level – an approach called an accelerated destructive degradation test (ADDT). The present paper deals with formulation of constant-stress ADDT (CSADDT) plan with the test specimens subject to stress induced by temperature and voltage.Design/methodology/approachThe stress–life relationship between temperature and voltage is described using Zhurkov–Arrhenius model. The fractional factorial experiment has been used to determine optimal number of stress combinations. The product's degradation path follows Wiener process. The model parameters are estimated using method of maximum likelihood. The optimum plan consists in finding out optimum allocations at each inspection time corresponding to each stress combination by using variance optimality criterion.FindingsThe method developed has been explained using a numerical example wherein point estimates and confidence intervals for the model parameters have been obtained and likelihood ratio test has been used to test for the presence of interaction effect. It has been found that both the temperature and the interaction between temperature and voltage influence the quantile lifetime of the product. Sensitivity analysis is also carried out.Originality/valueMost of the work in the literature on the design of ADDT plans focusses on only a single stress factor. An interaction exists among two or more stress factors if the effect of one factor on a response depends on the levels of other factors. In this paper, an optimal CSADDT plan is studied with one main effect and one interaction effect. The method developed can help engineers study the effect of elevated temperature and its interaction with another stress factor, say, voltage on quantile lifetime of a high-reliability unit likely to last for several years.

Developing the stress testing algorithms for companies: A metal industry case study

2020 ◽  
Vol 19 (8) ◽  
pp. 1458-1489
Author(s):  
V.G. Kogdenko
Keyword(s):  
Stress Testing ◽  
Production Capacity ◽  
Stress Factor ◽  
Stress Factors ◽  
Model Parameters ◽  
Real Economy ◽  
Predictive Values ◽  
Iron And Steel ◽  
Continuity Of Operations ◽  
Testing Algorithms

Subject. The article addresses the development of stress testing algorithms for companies operating in the real economy. Objectives. The study generalizes stress-testing algorithms and assesses the hypothesis about the resistance of steel companies to external shocks. Methods. I employ general scientific principles and methods of research, like abstraction, generalization of approaches of domestic and foreign authors to stress testing and industry analysis. Results. I developed methods of aggregated direct single-factor historical stress testing based on the top-down approach. The methodology includes three stages. First, I identify stress-testing parameters: stress factors, variables and constant model parameters. Revenue, which is influenced by market risk, is defined as a stress factor. At the second stage, I substantiate the algorithms for predicting stress-testing parameters, then I calculate the predictive values of variable and permanent parameters of the model, assess the volatility of the stress factor, calculate confidence intervals and justify stress-testing scenarios. At the final stage, the results of stress testing are analyzed. The methodology was tested on the investigation of data of 454 metallurgical enterprises. Conclusions. The companies assigned to the first group (20% of companies that account for 80% of revenue) have a high degree of resilience in the short term, owing to their operational efficiency, which ensures continuity of operations. In the long term, iron and steel companies have insufficient resilience due to the high loan debt burden offsetting the aggressive dividend policy, and inadequate investment in production capacity and safety.

The impact research of online reviews’ sentiment polarity presentation on consumer purchase decision

2017 ◽  
Vol 30 (3) ◽  
pp. 522-541 ◽  
Author(s):  
Qi Wang ◽  
Lin Wang ◽  
Xiaohang Zhang ◽  
Yunxia Mao ◽  
Peng Wang
Keyword(s):  
Decision Making ◽  
Interaction Effect ◽  
Perceived Risk ◽  
Purchase Intention ◽  
Online Reviews ◽  
Mediation Effect ◽  
Significant Interaction Effect ◽  
Content Type ◽  
Main Effect ◽  
The Impact

Purpose Because online shopping is risky, there is a strong need to develop better presentation of online reviews, which may reduce the perceived risk and create more pleasurable shopping experiences. To test the impact of online reviews’ sentiment polarity presentation, the purpose of this paper is to adopt a scenario experiment to study consumers’ decision-making process under the two scenarios of mixed presentation and classified presentation of online reviews collected from Jingdong.com in China: focusing on the comparative analysis on the differences of the consumers’ perceived risk, purchase intention and purchase delay, and further studying the interaction effect of involvement and online reviews’ sentiment polarity presentation. Design/methodology/approach This paper employed a 2×2 factorial experiment to test the hypothesis. The experimental design is divided into four groups: 2 (online reviews’ sentiment polarity presentation: mixed presentation vs classified presentation) × 2 (involvement: low vs high), each of which contains 90 samples. Through the data analysis, the main effect, mediation effect and moderating effect were examined. Findings The results show that compared with mixed presentation, classified presentation can reduce purchase intention and increase purchase delay due to the existence of loss aversion and availability heuristic. Furthermore, the paper also confirms that there is a significant interaction effect between involvement and online reviews’ sentiment polarity presentation. Originality/value The existing research pays less attention to the impact of online reviews presentation on consumers’ decision making, especially the lack of discussion on the interaction effect between involvement and online reviews presentation. For this reason, this paper proposes a problem, which concerns whether mixed presentation and classified presentation of online reviews will affect consumers’ decision making differently.

scholarly journals Constant-stress partially accelerated life tests for inverted Weibull distribution with multiple censored data

2015 ◽  
Vol 3 (1) ◽  
pp. 72 ◽  
Author(s):  
Amal S. Hassan ◽  
Salwa M. Assar ◽  
Ahmed N. Zaky
Keyword(s):  
Weibull Distribution ◽  
Censored Data ◽  
High Reliability ◽  
Asymptotic Variance ◽  
Constant Stress ◽  
Acceleration Factor ◽  
Accelerated Life Test ◽  
Maximum Likelihood Estimates ◽  
Model Parameters ◽  
Accelerated Life

<p>Testing the lifetime of items under normal use condition often requires a long period of time, especially for products having high reliability. To minimize the costs involved in testing without reducing the quality of the data obtained, the items run at higher than usual level of stresses to induce early failures in a short time. This article concerns with constant–stress partially accelerated life test with multiple censored data. The life time of test item is assumed to follow inverted Weibull distribution. Maximum likelihood estimates are obtained for the model parameters and acceleration factor. In addition, asymptotic variance and covariance matrix of the estimators is given. The confidence intervals of the unknown parameters and acceleration factor are constructed for large sample sizes. Simulation studies are performed to investigate the performance of the estimators.</p>

"Recent Patents on the Triboelectrostatic Separation of Fly Ash"

2019 ◽  
Vol 13 ◽  
Author(s):  
Haisheng Li ◽  
Wenping Wang ◽  
Yinghua Chen ◽  
Xinxi Zhang ◽  
Chaoyong Li
Keyword(s):  
Fly Ash ◽  
Power Plants ◽  
High Efficiency ◽  
Separation Efficiency ◽  
High Reliability ◽  
Operating Conditions ◽  
Security Requirements ◽  
Unburned Carbon ◽  
Efficient Operation ◽  
Triboelectrostatic Separation

Background: The fly ash produced by coal-fired power plants is an industrial waste. The environmental pollution problems caused by fly ash have been widely of public environmental concern. As a waste of recoverable resources, it can be used in the field of building materials, agricultural fertilizers, environmental materials, new materials, etc. Unburned carbon content in fly ash has an influence on the performance of resource reuse products. Therefore, it is the key to remove unburned carbon from fly ash. As a physical method, triboelectrostatic separation technology has been widely used because of obvious advantages, such as high-efficiency, simple process, high reliability, without water resources consumption and secondary pollution. Objective: The related patents of fly ash triboelectrostatic separation had been reviewed. The structural characteristics and working principle of these patents are analyzed in detail. The results can provide some meaningful references for the improvement of separation efficiency and optimal design. Methods: Based on the comparative analysis for the latest patents related to fly ash triboelectrostatic separation, the future development is presented. Results: The patents focused on the charging efficiency and separation efficiency. Studies show that remarkable improvements have been achieved for the fly ash triboelectrostatic separation. Some patents have been used in industrial production. Conclusion: According to the current technology status, the researches related to process optimization and anti-interference ability will be beneficial to overcome the influence of operating conditions and complex environment, and meet system security requirements. The intelligent control can not only ensure the process continuity and stability, but also realize the efficient operation and management automatically. Meanwhile, the researchers should pay more attention to the resource utilization of fly ash processed by triboelectrostatic separation.

scholarly journals Modeling Bacterial Regrowth and Trihalomethane Formation in Water Distribution Systems

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 463
Author(s):  
Gopinathan R. Abhijith ◽  
Leonid Kadinski ◽  
Avi Ostfeld
Keyword(s):  
Distribution Systems ◽  
Water Distribution ◽  
Mechanistic Model ◽  
Water Distribution Systems ◽  
Sensitivity Study ◽  
Operating Conditions ◽  
Growth Rate Constant ◽  
Model Parameters ◽  
Bacterial Regrowth ◽  
The Impact

The formation of bacterial regrowth and disinfection by-products is ubiquitous in chlorinated water distribution systems (WDSs) operated with organic loads. A generic, easy-to-use mechanistic model describing the fundamental processes governing the interrelationship between chlorine, total organic carbon (TOC), and bacteria to analyze the spatiotemporal water quality variations in WDSs was developed using EPANET-MSX. The representation of multispecies reactions was simplified to minimize the interdependent model parameters. The physicochemical/biological processes that cannot be experimentally determined were neglected. The effects of source water characteristics and water residence time on controlling bacterial regrowth and Trihalomethane (THM) formation in two well-tested systems under chlorinated and non-chlorinated conditions were analyzed by applying the model. The results established that a 100% increase in the free chlorine concentration and a 50% reduction in the TOC at the source effectuated a 5.87 log scale decrement in the bacteriological activity at the expense of a 60% increase in THM formation. The sensitivity study showed the impact of the operating conditions and the network characteristics in determining parameter sensitivities to model outputs. The maximum specific growth rate constant for bulk phase bacteria was found to be the most sensitive parameter to the predicted bacterial regrowth.

Reliability analysis and state transfer scheduling optimization of degrading load-sharing system equipped with warm standby components

2021 ◽  
pp. 1748006X2110017
Author(s):  
Sheng-Jia Ruan ◽  
Yan-Hui Lin
Keyword(s):  
Reliability Analysis ◽  
System Reliability ◽  
High Reliability ◽  
Quadrature Rule ◽  
Load Sharing ◽  
Measurement Information ◽  
Model Parameters ◽  
Scheduling Optimization ◽  
State Transfer ◽  
Warm Standby

Standby redundancy can meet system safety requirements in industries with high reliability standards. To evaluate reliability of standby systems, failure dependency among components has to be considered especially when systems have load-sharing characteristics. In this paper, a reliability analysis and state transfer scheduling optimization framework is proposed for the load-sharing 1-out-of- N: G system equipped with M warm standby components and subject to continuous degradation process. First, the system reliability function considering multiple dependent components is derived in a recursive way. Then, a Monte Carlo method is developed and the closed Newton-Cotes quadrature rule is invoked for the system reliability quantification. Besides, likelihood functions are constructed based on the measurement information to estimate the model parameters of both active and standby components, whose degradation paths are modeled by the step-wise drifted Wiener processes. Finally, the system state transfer scheduling is optimized by the genetic algorithm to maximize the system reliability at mission time. The proposed methodology and its effectiveness are illustrated through a case study referring to a simplified aircraft hydraulic system.

scholarly journals Determination of synchronous generator nonlinear model parameters based on power rejection tests using a gradient optimization algorithm

2017 ◽  
Vol 65 (4) ◽  
pp. 479-488 ◽  
Author(s):  
A. Boboń ◽  
A. Nocoń ◽  
S. Paszek ◽  
P. Pruski
Keyword(s):  
Parameter Estimation ◽  
Objective Function ◽  
Optimization Algorithm ◽  
Least Squares Method ◽  
Synchronous Generator ◽  
Operating Conditions ◽  
Model Parameters ◽  
State Variables ◽  
Starting Point ◽  
Gradient Optimization

AbstractThe paper presents a method for determining electromagnetic parameters of different synchronous generator models based on dynamic waveforms measured at power rejection. Such a test can be performed safely under normal operating conditions of a generator working in a power plant. A generator model was investigated, expressed by reactances and time constants of steady, transient, and subtransient state in the d and q axes, as well as the circuit models (type (3,3) and (2,2)) expressed by resistances and inductances of stator, excitation, and equivalent rotor damping circuits windings. All these models approximately take into account the influence of magnetic core saturation. The least squares method was used for parameter estimation. There was minimized the objective function defined as the mean square error between the measured waveforms and the waveforms calculated based on the mathematical models. A method of determining the initial values of those state variables which also depend on the searched parameters is presented. To minimize the objective function, a gradient optimization algorithm finding local minima for a selected starting point was used. To get closer to the global minimum, calculations were repeated many times, taking into account the inequality constraints for the searched parameters. The paper presents the parameter estimation results and a comparison of the waveforms measured and calculated based on the final parameters for 200 MW and 50 MW turbogenerators.

A dynamic simulator for the ergonomics evaluation of powered torque tools for human assembly

2017 ◽  
Vol 37 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Haluk Ay ◽  
Anthony Luscher ◽  
Carolyn Sommerich
Keyword(s):  
Risk Factors ◽  
Joint Torque ◽  
Human Hand ◽  
Model Parameters ◽  
Test Rig ◽  
Musculoskeletal Discomfort ◽  
Data Set ◽  
Content Type ◽  
Working Posture ◽  
Displacement Measurements

Purpose The purpose of this study is to design and develop a testing device to simulate interaction between human hand–arm dynamics, right-angle (RA) computer-controlled power torque tools and joint-tightening task-related variables. Design/methodology/approach The testing rig can simulate a variety of tools, tasks and operator conditions. The device includes custom data-acquisition electronics and graphical user interface-based software. The simulation of the human hand–arm dynamics is based on the rig’s four-bar mechanism-based design and mechanical components that provide adjustable stiffness (via pneumatic cylinder) and mass (via plates) and non-adjustable damping. The stiffness and mass values used are based on an experimentally validated hand–arm model that includes a database of model parameters. This database is with respect to gender and working posture, corresponding to experienced tool operators from a prior study. Findings The rig measures tool handle force and displacement responses simultaneously. Peak force and displacement coefficients of determination (R2) between rig estimations and human testing measurements were 0.98 and 0.85, respectively, for the same set of tools, tasks and operator conditions. The rig also provides predicted tool operator acceptability ratings, using a data set from a prior study of discomfort in experienced operators during torque tool use. Research limitations/implications Deviations from linearity may influence handle force and displacement measurements. Stiction (Coulomb friction) in the overall rig, as well as in the air cylinder piston, is neglected. The rig’s mechanical damping is not adjustable, despite the fact that human hand–arm damping varies with respect to gender and working posture. Deviations from these assumptions may affect the correlation of the handle force and displacement measurements with those of human testing for the same tool, task and operator conditions. Practical implications This test rig will allow the rapid assessment of the ergonomic performance of DC torque tools, saving considerable time in lineside applications and reducing the risk of worker injury. DC torque tools are an extremely effective way of increasing production rate and improving torque accuracy. Being a complex dynamic system, however, the performance of DC torque tools varies in each application. Changes in worker mass, damping and stiffness, as well as joint stiffness and tool program, make each application unique. This test rig models all of these factors and allows quick assessment. Social implications The use of this tool test rig will help to identify and understand risk factors that contribute to musculoskeletal disorders (MSDs) associated with the use of torque tools. Tool operators are subjected to large impulsive handle reaction forces, as joint torque builds up while tightening a fastener. Repeated exposure to such forces is associated with muscle soreness, fatigue and physical stress which are also risk factors for upper extremity injuries (MSDs; e.g. tendinosis, myofascial pain). Eccentric exercise exertions are known to cause damage to muscle tissue in untrained individuals and affect subsequent performance. Originality/value The rig provides a novel means for quantitative, repeatable dynamic evaluation of RA powered torque tools and objective selection of tightening programs. Compared to current static tool assessment methods, dynamic testing provides a more realistic tool assessment relative to the tool operator’s experience. This may lead to improvements in tool or controller design and reduction in associated musculoskeletal discomfort in operators.

scholarly journals The differential effects of related and unrelated emotions on judgments about media messages

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Rinaldo Kühne ◽  
Claudia Poggiolini ◽  
Werner Wirth
Keyword(s):  
Experimental Study ◽  
Interaction Effect ◽  
News Article ◽  
Differential Effects ◽  
Media Messages ◽  
Processing Depth ◽  
Main Effect ◽  
The Media ◽  
Media Message

AbstractThe present study investigated the influence of related and unrelated emotions on judgments about a news article. An experimental study was designed to manipulate both the relatedness of an elicited emotion (i. e., anger) to the news article and processing depth. Following mood and emotion effects theory, related anger was expected to have a stronger effect on judgments about the media message than unrelated anger. Processing depth was expected to moderate this effect. The results showed a main effect of relatedness and a main effect of processing depth, but the interaction effect was not found. Implications of the findings for understanding how emotions influence the processing of media stimuli are discussed.

When do job insecure employees adapt to change?

2019 ◽  
Vol 25 (3) ◽  
pp. 271-286 ◽  
Author(s):  
Kristi N. Lavigne ◽  
Victoria L. Whitaker ◽  
Dustin K. Jundt ◽  
Mindy K. Shoss
Keyword(s):  
Job Insecurity ◽  
Small Sample ◽  
Adaptive Performance ◽  
Work Behaviors ◽  
Content Type ◽  
Work Tasks ◽  
Main Effect ◽  
Low Levels ◽  
The Impact ◽  
The Relationship

Purpose The purpose of this paper is to examine the relationship between job insecurity and adaptive performance (AP), contingent on changes to core work tasks, which we position as a situational cue to employees regarding important work behaviors. Design/methodology/approach Employees and their supervisors were invited to participate in the study. Supervisors were asked to provide ratings of employees’ AP and changes to core tasks; employees reported on job insecurity. Findings As predicted, changes to core tasks moderated the relationship between job insecurity and AP. Job insecurity was negatively related to AP for those experiencing low levels of change, but was not related to AP for those experiencing high levels of change. Counter to expectations, no main effect of job insecurity was found. Research limitations/implications This study employed a fairly small sample of workers from two organizations, which could limit generalizability. Practical implications The study identifies changes to core tasks as a boundary condition for the job insecurity–AP relationship. Findings suggest that organizations may not observe deleterious consequences of job insecurity on AP when changes to core tasks are high. Originality/value Few researchers have examined boundary conditions of the impact of job insecurity on AP. Furthermore, inconsistent findings regarding the link between job insecurity and AP have emerged. This study fills the gap and expands upon previous research by examining changes to core tasks as a condition under which job insecurity does not pose an issue for AP.

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