scholarly journals An Improved Sensitivity Method for the Simultaneous Identification of Unknown Parameters and External Loads of Nonlinear Structures

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
Chongwen Wang ◽  
Chengbin Du
Keyword(s):  
Regularization Parameter ◽  
Parameter Distribution ◽  
Nonlinear Structures ◽  
Noise Levels ◽  
Unknown Parameters ◽  
Key Issues ◽  
The Difference ◽  
Sensitivity Method ◽  
Simultaneous Identification ◽  
External Loads

Because structures may be subject to unknown loads and may simultaneously involve unknown parameters and because simple load identification or parameter identification algorithms cannot be applied under such conditions, it is necessary to seek algorithms that can simultaneously identify unknown parameters and external loads of structures. The sensitivity method is one of them, and this paper extends this method to nonlinear structures. In addition, the key issues associated with the sensitivity method are systematically studied, and suggestions for improvement are put forward, including the use of the difference method instead of the derivative method to calculate the sensitivity, the use of a fixed regularization parameter instead of the traditional regularization parameter calculation methods, and measures for guarantee of iterative convergence. The improved sensitivity method is applied to two types of nonlinear structures, and the effects of the regularization parameter, distribution of measured points, response types, noise levels, and the magnitude of the perturbation on the identified results are discussed.

Noise reduction of enhanced acoustic balconies on a high-rise building block

2021 ◽  
Vol 263 (1) ◽  
pp. 5327-5334
Author(s):  
SK Tang ◽  
Rudolf YC Lee
Keyword(s):  
Noise Reduction ◽  
Natural Ventilation ◽  
Traffic Noise ◽  
Elevation Angle ◽  
Noise Levels ◽  
Indoor Space ◽  
New Device ◽  
Air Inlet ◽  
The Difference ◽  
The Impact

A new device called 'enhanced acoustic balcony' is installed in a new housing estate in Hong Kong. It is intended to help reduce the impact of traffic noise on the residents. This balcony is basically an enlarged form of a plenum window and with three openings. Apart from the outdoor air inlet, there is the balcony door and a side-hung window on the interior balcony wall for natural ventilation of the indoor space. Sound absorption of NRC 0.7 is installed on the balcony ceiling and its sidewall facing the incoming traffic noise and an inclined panel is installed outside the balcony to provide noise screening. A site measurement of its noise reduction is carried out in the present study in a newly completed housing block. A 28 m long loudspeaker array is used as the sound source. The indoor noise levels are measured according to ISO standard. The results show that the difference between indoor and outdoor noise levels in the presence of this balcony form varies over a relatively narrow range between 10 to 13 dBA for an elevation angle from 25 to 60 deg. There is a weak increase of the noise level difference with elevation angle.

scholarly journals Impact of Damping Models in Damage Identification

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Michael Souza ◽  
Daniel Castello ◽  
Ney Roitman ◽  
Thiago Ritto
Keyword(s):  
Computational Models ◽  
Damage Identification ◽  
Model Parameters ◽  
Posterior Density ◽  
Unknown Parameters ◽  
Key Issues ◽  
Delayed Rejection ◽  
Lumped Masses ◽  
Aluminum Beam ◽  
The Impact

Several damage identification approaches are based on computational models, and their diagnostics depend on the set of modelling hypotheses adopted when building the model itself. Among these hypotheses, the choice of appropriate damping models seems to be one of the key issues. The goal of this paper is to analyze the impact of a set of damping models on the damage identification diagnostics. The damage identification is built on a Bayesian framework, and the measured data are the modal data associated with the first modes of the structure. The exploration of the posterior density of unknown model parameters is performed by means of the Markov chain Monte Carlo method (MCMC) with Delayed Rejection Adaptive Metropolis (DRAM) algorithm. The analyses are based on experimental dynamic response obtained from an aluminum beam instrumented with a set of accelerometers. The presence of damage/anomaly within the system is physically simulated by placing lumped masses over the beam, considering three different masses and two different placing positions. For the set of cases analyzed, it is shown that the proposed approach was able to identify both the position and magnitude of the lumped masses and that the damping models may not provide an increase of knowledge of some unknown parameters when damping rates are lower than 1%.

scholarly journals A New Extended Two-Parameter Distribution: Properties, Estimation Methods, and Applications in Medicine and Geology

Mathematics ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1578 ◽  
Author(s):  
Hazem Al-Mofleh ◽  
Ahmed Z. Afify ◽  
Noor Akma Ibrahim
Keyword(s):  
Estimation Method ◽  
Estimation Methods ◽  
Parameter Distribution ◽  
Model Parameters ◽  
Unknown Parameters ◽  
Proposed Model ◽  
Rate Functions ◽  
The Mean ◽  
Modeling Data ◽  
Two Parameter

In this paper, a new two-parameter generalized Ramos–Louzada distribution is proposed. The proposed model provides more flexibility in modeling data with increasing, decreasing, J-shaped, and reversed-J shaped hazard rate functions. Several statistical properties of the model were derived. The unknown parameters of the new distribution were explored using eight frequentist estimation approaches. These approaches are important for developing guidelines to choose the best method of estimation for the model parameters, which would be of great interest to practitioners and applied statisticians. Detailed numerical simulations are presented to examine the bias and the mean square error of the proposed estimators. The best estimation method and ordering performance of the estimators were determined using the partial and overall ranks of all estimation methods for various parameter combinations. The performance of the proposed distribution is illustrated using two real datasets from the fields of medicine and geology, and both datasets show that the new model is more appropriate as compared to the Marshall–Olkin exponential, exponentiated exponential, beta exponential, gamma, Poisson–Lomax, Lindley geometric, generalized Lindley, and Lindley distributions, among others.

scholarly journals Understanding the Legendary Sound Environment in the Lobby of Hotel Okura Tokyo

2020 ◽  
Vol 10 (13) ◽  
pp. 4552
Author(s):  
Ryoko Nojima ◽  
Natsuko Sugie ◽  
Akira Taguchi ◽  
Jun Kokubo
Keyword(s):  
Speech Intelligibility ◽  
Comprehensive Evaluation ◽  
The Other ◽  
Noise Levels ◽  
Sound Environment ◽  
Good Reputation ◽  
The Difference ◽  
Hotel Lobbies

The main lobby of Hotel Okura Tokyo has a good reputation for its sound environment, which affects the conversations of its users. We assumed that the lobby’s reputation was related to its speech intelligibility. In this study, first, the sound during hotel operations was measured to see if there was a difference in the sound environment between the lobby and the entrance hall. As a result, we clarified that the difference in noise levels affected by the degree of crowdedness of the room was smaller in the lobby than in the other rooms. Subsequently, the indoor noise and speech intelligibility were measured to clarify the correspondence of intelligibility with the lobby’s reputation. As a result, the indoor noise was found to be at a level suitable for hotel lobbies and the intelligibility was good. A comprehensive evaluation that included the results of other acoustical surveys revealed that the lobby of Okura is a space that is suitable for conversations, corresponding to the opinions of users.

CEPC and FCCee parameters from the viewpoint of the beam–beam and electron cloud effects

2019 ◽  
Vol 34 (13n14) ◽  
pp. 1940001 ◽  
Author(s):  
Kazuhito Ohmi
Keyword(s):  
Electron Cloud ◽  
Key Issues ◽  
The Difference

The parameters of CEPC and FCC-ee are being fixed. Despite the same circumference and energy of the two colliders, their strategies of the target luminosity are different. The key issues for the target luminosity are the beam–beam and electron cloud effects. We present studies on the beam–beam and electron cloud effects for the two colliders and discuss the difference of the strategies of the two colliders.

Application of Signal Analysis to Cavitation

1984 ◽  
Vol 106 (3) ◽  
pp. 342-346 ◽  
Author(s):  
C. Samuel Martin ◽  
P. Veerabhadra Rao
Keyword(s):  
Signal Analysis ◽  
Coherence Function ◽  
Noise Levels ◽  
Cavitation Noise ◽  
Cavitation Inception ◽  
Pressure Transducers ◽  
The Difference ◽  
Spool Valve ◽  
Regular Character ◽  
High Coherence

The diagnostic facilities of the cross power spectrum and the coherence function have been employed to enhance the identification of not only the inception of cavitation, but also its level. Two piezoelectric pressure transducers placed in the downstream chamber of a model spool valve undergoing various levels of cavitation allowed for the use of both functions—the phase angle of the complex cross spectrum and the dimensionless coherence function—to sense clearly the difference between noise levels associated with a noncavitating jet from those once cavitation inception is attained. The cavitation noise within the chamber exhibited quite a regular character in terms of the phase difference between instruments for limited cavitation. Varying cavitation levels clearly illustrated the effect of bubble size on the attendant frequency range for which there was an extremely high coherence or nearly perfect causality.

scholarly journals Factors confronting quantity surveying practice: the case of Nigeria

2018 ◽  
Vol 16 (5) ◽  
pp. 767-782 ◽  
Author(s):  
Olusola Ogunsina ◽  
Micah Ekwus Obiegbu ◽  
Onaopepo Adeniyi
Keyword(s):  
Design Methodology ◽  
Rank Correlation ◽  
Severity Index ◽  
Content Type ◽  
Five Factors ◽  
Port Harcourt ◽  
Key Issues ◽  
Quantity Surveying ◽  
The Difference ◽  
Probabilistic Sample

Purpose As the challenges confronting a system are better addressed when known and understood, this paper aims to report the findings of a study that investigated the factors confronting professional quantity surveying using Nigeria as a case. Design/methodology/approach A questionnaire was developed and pre-tested as the instrument for collecting data. A total of 64 quantity surveyors practicing in Lagos, Port Harcourt and Enugu completed the questionnaire out of a non-probabilistic sample of 100. Severity Index and Spearman rank correlation coefficient were used in data analysis. Findings The outcome revealed that the top five factors perceived to be confronting the profession include poor marketing of the profession, opposition from engineers, the dominance of multinational companies that do not have quantity surveying as a distinct profession in their country of origin, widespread corruption in Nigeria and professional incompetence of some quantity surveyors. Furthermore, the two categories of respondents – professional quantity surveyors and probationers – agree in their ranking of the factors confronting the profession. The ranking of the 17 factors between the two categories of respondents was tested using Spearman’s rho. The result showed that the difference in perception of professional members of the Nigerian Institute of Quantity Surveyors and the probationers with regard to factors confronting the quantity surveying profession is not significant at p < 0.01. These findings are then discussed in the light of previous works, and implications for both academics and professionals within the quantity surveying profession were highlighted. Originality/value This study has highlighted the key issues to consider as stakeholders attempt to advance the course of quantity surveying and construction cost management profession.

A nonlinear Wiener degradation model integrating degradation data under accelerated stresses and real operating environment

2020 ◽  
pp. 1748006X2097809
Author(s):  
Li Sun ◽  
Fangchao Zhao ◽  
Narayanaswamy Balakrishnan ◽  
Honggen Zhou ◽  
Xiaohui Gu
Keyword(s):  
Remaining Useful Life ◽  
Normal Stresses ◽  
Operating Environment ◽  
Unknown Parameters ◽  
Step Method ◽  
Degradation Model ◽  
Accelerated Degradation ◽  
Degradation Data ◽  
Proposed Model ◽  
The Difference

Remaining useful life (RUL) prediction in real operating environment (ROE) plays an important role in condition-based maintenance. However, the life information in ROE is limited, especially for some long-life products. In such cases, accelerated degradation test (ADT) is an effective method to collect data and then the accelerated degradation data are converted to normal level of accelerated stresses through acceleration factors. However, the stresses in ROE are different from normal stresses since there are some other stresses except normal stresses, which cannot be accelerated, but still have impact on the degradation. To predict the RUL in ROE, a nonlinear Wiener degradation model is proposed based on failure mechanism invariant principle which is the precondition and requirement of an ADT and a calibration factor is introduced to calibrate the difference between ROE and normal stresses. Moreover, the unit-to-unit variability is considered in the concern model. Based upon the proposed approach, the RUL distribution is derived in closed form. The unknown parameters in the model are obtained by a new two-step method through fuzing converted degradation data in normal stresses and degradation data in ROE. Finally, the validity of the proposed model is demonstrated through several simulation data and a case study.

Most Comfortable Listening Levels, Background Noise Levels, and Acceptable Noise Levels for Children and Adults with Normal Hearing

2011 ◽  
Vol 22 (05) ◽  
pp. 286-293 ◽  
Author(s):  
Robert Moore ◽  
Susan Gordon-Hickey ◽  
Alisha Jones
Keyword(s):  
Young Adults ◽  
Noise Level ◽  
Background Noise ◽  
Developmental Change ◽  
Pediatric Population ◽  
Strong Predictor ◽  
Normal Hearing ◽  
Noise Levels ◽  
Cross Sectional ◽  
The Difference

Background: For adults the acceptable noise level (ANL) has been shown to be a strong predictor of hearing aid success. ANL is calculated as the difference between most comfortable listening level (MCL) and background noise level (BNL). No studies have made direct comparisons of these measures between adults and children. Purpose: To evaluate and compare MCLs, BNLs, and ANLs in children and young adults. Research Design: A cross-sectional design was used in this study. Two groups (children and adults) were tested for each dependent variable. MCLs and BNLs were measured for each participant, and ANLs were computed from these two measurements. Study Sample: The participants were 34 children (8–10 yr) and 34 young adults (19–29 yr) with normal hearing. Results: Significant main effects were found for MCLs and BNLs. There was no main effect for ANLs. MCLs and BNLs were significantly lower for the children than for the adults. Conclusions: These results suggest that while ANLs are unchanged from childhood to adulthood, there appears to be a developmental change in MCLs and BNLs. These findings have implications for the use of ANLs in the pediatric population.

Best Practice Recommendations for Situational Judgment Tests

2015 ◽  
Vol 8 ◽  
Author(s):  
Stefanie Pollard ◽  
Helena D. Cooper-Thomas
Keyword(s):  
Best Practice ◽  
Ethical Issues ◽  
Situational Judgment Tests ◽  
Selection Procedures ◽  
Practice Recommendations ◽  
Situational Judgement Tests ◽  
Key Issues ◽  
The Difference ◽  
Best Practice Process ◽  
Situational Judgement

Situational judgement tests (SJTs) are increasingly popular as part of selection procedures because of their strong psychometric properties. SJTs present test takers with job-related situations and a series of potential responses. The aim of this review article is to provide evidence-based recommendations for practitioners who are considering implementing SJTs for their clients, as well as offering an analysis of some key issues for academics. This research provides a review of the literature on SJTs to answer three questions: (1) What is the difference between framing questions either as what should you do versus what would you do? (2) What is the difference between multimedia-based and text-based SJTs? (3) What is the best process for SJT creation? Following this, recommendations are provided as follows: That responses are optimally framed in terms of what a respondent thinks s/he should do, not what s/he would do; that multimedia-based SJTs are used in preference to text-based SJTs; and a ‘best practice’ process for creating an SJT is outlined. Finally, the review includes a discussion of implications for creating tests that are inclusive of different ethnic groups, as well as ethical issues relating to the use of SJTs in selection.

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