UCLA Loneliness Scale (Version 3): reliability, validity, and factor structure.
Russell, D W
1996-02-01
In this article I evaluated the psychometric properties of the UCLA Loneliness Scale (Version 3). Using data from prior studies of college students, nurses, teachers, and the elderly, analyses of the reliability, validity, and factor structure of this new version of the UCLA Loneliness Scale were conducted. Results indicated that the measure was highly reliable, both in terms of internal consistency (coefficient alpha ranging from .89 to .94) and test-retest reliability over a 1-year period (r = .73). Convergent validity for the scale was indicated by significant correlations with other measures of loneliness. Construct validity was supported by significant relations with measures of the adequacy of the individual's interpersonal relationships, and by correlations between loneliness and measures of health and well-being. Confirmatory factor analyses indicated that a model incorporating a global bipolar loneliness factor along with two method factor reflecting direction of item wording provided a very good fit to the data across samples. Implications of these results for future measurement research on loneliness are discussed.
Feelings about culture scales: development, factor structure, reliability, and validity.
Maffini, Cara S; Wong, Y Joel
2015-04-01
Although measures of cultural identity, values, and behavior exist in the multicultural psychological literature, there is currently no measure that explicitly assesses ethnic minority individuals' positive and negative affect toward culture. Therefore, we developed 2 new measures called the Feelings About Culture Scale--Ethnic Culture and Feelings About Culture Scale--Mainstream American Culture and tested their psychometric properties. In 6 studies, we piloted the measures, conducted factor analyses to clarify their factor structure, and examined reliability and validity. The factor structure revealed 2 dimensions reflecting positive and negative affect for each measure. Results provided evidence for convergent, discriminant, criterion-related, and incremental validity as well as the reliability of the scales. The Feelings About Culture Scales are the first known measures to examine both positive and negative affect toward an individual's ethnic culture and mainstream American culture. The focus on affect captures dimensions of psychological experiences that differ from cognitive and behavioral constructs often used to measure cultural orientation. These measures can serve as a valuable contribution to both research and counseling by providing insight into the nuanced affective experiences ethnic minority individuals have toward culture.
Investigating the Reliability and Factor Structure of Kalichman's "Survey 2
DEFF Research Database (Denmark)
Holm, Søren; Hofmann, Bjørn
2017-01-01
A precondition for reducing scientific misconduct is evidence about scientists' attitudes. We need reliable survey instruments, and this study investigates the reliability of Kalichman's "Survey 2: research misconduct" questionnaire. The study is a post hoc analysis of data from three surveys among...... biomedical doctoral students in Scandinavia (2010-2015). We perform reliability analysis, and exploratory and confirmatory factor analysis using a split-sample design as a partial validation. The results indicate that a reliable 13-item scale can be formed (Cronbach's α = .705), and factor analysis indicates...... that there are four reliable subscales each tapping a different construct: (a) general attitude to misconduct (α = .768), (b) attitude to personal misconduct (α = .784), (c) attitude to whistleblowing (α = .841), and (d) attitude to blameworthiness/punishment (α = .877). A full validation of the questionnaire...
The Eysenck Personality Questionnaire Brief Version: factor structure and reliability.
Sato, Toru
2005-11-01
The short scale of the Eysenck Personality Questionnaire-Revised (EPQR-S; H. J. Eysenck & S. B. G. Eysenck, 1992) is a 48-item personality questionnaire primarily designed to measure an individual's level of extraversion (vs. introversion) and neuroticism. Although L. J. Francis, L. B. Brown, and R. Philipchalk (1992) created the Eysenck Personality Questionnaire Revised-Abbreviated (EPQR-A), an even briefer version of the EPQR-S, the reliability coefficients of some of the measures have been less than satisfactory (S. Forrest, C. A. Lewis, & M. Shevlin, 2000). Because brevity and reliability are both extremely important, the author of the present study created a briefer version of the EPQR-S, more reliable than the EPQR-A, by making slight alterations in the item content as well as the response format of the EPQR-S. Two hundred and sixty eight participants completed the original EPQR-S and the 24-item newly revised briefer version of the EPQR-S (EPQ-BV) twice. The findings revealed that the EPQ-BV has good internal consistency, test-retest reliability, and concurrent validity. A principal component analysis revealed a solution with factor loadings that accurately reflected the primary measures of the EPQR-S. These findings are discussed in relation to the psychometric properties of the EPQR-A and the original version of the EPQR-S.
Partial Safety Factors and Target Reliability Level in Danish Structural Codes
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Hansen, J. O.; Nielsen, T. A.
2001-01-01
The partial safety factors in the newly revised Danish structural codes have been derived using a reliability-based calibration. The calibrated partial safety factors result in the same average reliability level as in the previous codes, but a much more uniform reliability level has been obtained...
Morales, Alexandra; Reis, Sibília; Espada, José P; Orgilés, Mireia
2016-09-01
The Short Health Anxiety Inventory is a brief instrument to assess health anxiety widely used across countries; however, no validated version is available for Portuguese-speaking population. Factorial structure, reliability, and equivalency factor with the Spanish version were analyzed with Portuguese adolescents aged 14-18 years. A Portuguese adolescent cohort ( N = 629) and a comparative Spanish adolescent cohort ( N = 1502) were evaluated. The original two-factor version was the best fitting model for the Portuguese version. The reliability was excellent. Complete measurement invariance across both countries was supported. The Portuguese version of the Short Health Anxiety Inventory is a valid screening inventory to assess health anxiety in adolescents.
Structural Reliability Methods
DEFF Research Database (Denmark)
Ditlevsen, Ove Dalager; Madsen, H. O.
of structural reliability, including the theoretical basis for these methods. Partial safety factor codes under current practice are briefly introduced and discussed. A probabilistic code format for obtaining a formal reliability evaluation system that catches the most essential features of the nature......The structural reliability methods quantitatively treat the uncertainty of predicting the behaviour and properties of a structure given the uncertain properties of its geometry, materials, and the actions it is supposed to withstand. This book addresses the probabilistic methods for evaluation...
Reliability-Based Calibration of Load Duration Factors for Timber Structures
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Svensson, Staffan; Stang, Birgitte Friis Dela
2005-01-01
states and stochastic models for timber structures, load duration factors are calibrated using probabilistic methods. Load duration e.ects are estimated on basis of simulation of realizations of wind, snow and imposed loads in accordance with the load models in the Danish structural codes. Three damage...... is evaluated using representative short- and long-term limit states, and the load duration factor k mod is estimated using the probabilistic model such that equivalent reliability levels are obtained using short- and long-term design equations. Time variant reliability aspect is considered using a simple...
The Obsessive Compulsive Cocaine Scale: assessment of factor structure, reliability, and validity.
Jardin, Bianca F; Larowe, Steven D; Hall, Brian J; Malcolm, Robert J
2011-12-01
The present study assessed the factor structure, reliability, test retest, convergent validity, and predictive validity of the Obsessive Compulsive Cocaine Scale (OCCS), a newly developed questionnaire adapted from the Obsessive Compulsive Drinking Scale (OCDS). The questionnaire was administered to 189 cocaine-dependent individuals participating in two medication treatment trials for cocaine dependence. Confirmatory factor analysis of this measure revealed that it primarily assesses two factors, obsessions and compulsions. In addition, the data provided strong support for the internal consistency, test-retest reliability, predictive validity, and convergent validity of this two-factor measure. Overall, the data provide support for the psychometric strength of a modified version of the OCDS specifically designed to assess obsessive and compulsive cocaine use among those with cocaine dependence. Copyright © 2011 Elsevier Ltd. All rights reserved.
Qu, Xueyong
Uncertainties exist practically everywhere from structural design to manufacturing, product lifetime service, and maintenance. Uncertainties can be introduced by errors in modeling and simulation; by manufacturing imperfections (such as variability in material properties and structural geometric dimensions); and by variability in loading. Structural design by safety factors using nominal values without considering uncertainties may lead to designs that are either unsafe, or too conservative and thus not efficient. The focus of this dissertation is reliability-based design optimization (RBDO) of composite structures. Uncertainties are modeled by the probabilistic distributions of random variables. Structural reliability is evaluated in term of the probability of failure. RBDO minimizes cost such as structural weight subject to reliability constraints. Since engineering structures usually have multiple failure modes, Monte Carlo simulation (MCS) was used employed to calculate the system probability of failure. Response surface (RS) approximation techniques were used to solve the difficulties associated with MCS. The high computational cost of a large number of MCS samples was alleviated by analysis RS, and numerical noise in the results of MCS was filtered out by design RS. RBDO of composite laminates is investigated for use in hydrogen tanks in cryogenic environments. The major challenge is to reduce the large residual strains developed due to thermal mismatch between matrix and fibers while maintaining the load carrying capacity. RBDO is performed to provide laminate designs, quantify the effects of uncertainties on the optimum weight, and identify those parameters that have the largest influence on optimum design. Studies of weight and reliability tradeoffs indicate that the most cost-effective measure for reducing weight and increasing reliability is quality control. A probabilistic sufficiency factor (PSF) approach was developed to improve the computational
Reliability Analysis of a Composite Blade Structure Using the Model Correction Factor Method
DEFF Research Database (Denmark)
Dimitrov, Nikolay Krasimiroy; Friis-Hansen, Peter; Berggreen, Christian
2010-01-01
This paper presents a reliability analysis of a composite blade profile. The so-called Model Correction Factor technique is applied as an effective alternate approach to the response surface technique. The structural reliability is determined by use of a simplified idealised analytical model which...... in a probabilistic sense is model corrected so that it, close to the design point, represents the same structural behaviour as a realistic FE model. This approach leads to considerable improvement of computational efficiency over classical response surface methods, because the numerically “cheap” idealistic model...... is used as the response surface, while the time-consuming detailed model is called only a few times until the simplified model is calibrated to the detailed model....
An Evaluation of the Reliability, Construct Validity, and Factor Structure of the Static-2002R.
Jung, Sandy; Ennis, Liam; Hermann, Chantal A; Pham, Anna T; Choy, Alberto L; Corabian, Gabriela; Hook, Tarah
2017-03-01
The fundamental psychometric properties of the subscales found in the Static-2002R, an actuarial measure of sexual recidivism risk, were evaluated in the current study. Namely, the reliability, concurrent and construct validity, and factor structure of the Static-2002R subscales were examined with a sample of 372 adult male sex offenders. In addition to using validated measures of sexual violence risk to examine concurrent validity, construct-related measures taken from extant risk measures and psychometric tests were correlated with three of the subscales to assess overall construct validity. Moderate support was found for the reliability of the Static-2002R. The concurrent and construct validity of the General Criminality, Persistence of Sexual Offending, and Deviant Sexual Interest subscales were supported. Generally, these findings further support the Static-2002R as a valid sex offender risk appraisal instrument that encompasses multiple distinct, clinically relevant, risk domains.
Factor Structure, Validity and Reliability of the Revised Version of Skin Picking Scale
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Mehdi Rabiei
2014-09-01
Full Text Available Background: The purpose of this study was to examine the factor structure, validity and reliability of the Skin Picking Scale-Revised Version. Materials and Methods: In this descriptive and validation study, participants were 550 (250 male and 300 female of the University of Isfahan were selected randomly from 15000 students. In order to examine the factor structure of the SPS-R we conducted both exploratory and confirmatory factor analyses and Cronbach's alpha. Results: Convergent validity of SPS-R with YBOCS-BDD, OCI-R and DASS 21-item were r=0.45, r=0.51 and r=0.70 (p<0.001. Exploratory and confirmatory factor analyses revealed two factors, one assessing impairment and the other symptom severity (4 items each. These factors could determine 58.1% of the variance. The Cronbach's alpha for the two factors were above 0.88. Also, results were shown to possess good psychometric properties, as well as discriminant validity and classification accuracy, in both clinical and community populations. Conclusion: It can be concluded that this instrument is a useful measure for assess skin-picking disorder symptoms in clinical assessment.
Factor structure and reliability of the 12-item Sinhala version of General Health Questionnaire
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Chrishantha Abeysena
2012-08-01
Full Text Available Introduction: The General Health Questionnaire (GHQ is widely used to detect common psychiatric disorders. Even though the GHQ 12 has been validated for many countries, psychometric properties in relation to the Sinhala speaking Sri Lankan population lack conclusive evidence. Objective: To determine the factor structure and the reliability of the Sinhala version of GHQ 12. Methods: This was a descriptive study including 385 patients with in the age range of 18 to 75 years, attending the Out Patient Department of Colombo North Teaching Hospital, Ragama, Sri Lanka, between June 2009 to September 2010. Sinhala version of GHQ-12 was completed by the participants. Each item of the GHQ was rated on a four-point scale (0-1-2-3. Factor analyses were performed by applying Generalized Least Squares method using oblimin rotation. The internal consistency was assessed by calculating Cronbach’s α coefficient.Results: Median age of the study population was 32.5 years (IQR= 21years and the median GHQ score was 9 (IQR=7. The GHQ 12 yielded two factor solutions. Factor I (Depression and Anxiety accounted for 88% of the total explained variance and Factor II (Social dysfunction 12%. Forty five percent (45% of the total variance could be explained by the two extracted factors. There was a clear distinction between the items that loaded on the two factors. The correlation coefficient between the factors I and II was 0.65. The Cronbach's alpha of GHQ 12 was 0.88, which indicated satisfactory internal consistency. Conclusions: GHQ 12 displays adequate reliability and validity for use in the Sinhala speaking primary care attendees of Colombo North Teaching Hospital for assessing psychiatric disorders.
Yun, Sung Hyun
2011-01-01
The present study investigated the factor structure and reliability of the revised Conflict Tactics Scales' (CTS2) 10-factor model in a community-based female sample (N = 261). The underlying factor structure of the 10-factor model was tested by the confirmatory multiple group factor analysis, which demonstrated complex factor cross-loadings…
DEFF Research Database (Denmark)
Dimitrov, Nikolay Krasimiroy; Friis-Hansen, Peter; Berggreen, Christian
2009-01-01
This paper presents a reliability analysis of a composite blade profile. The so-called Model Correction Factor technique is applied as an effective alternate approach to the response surface technique. The structural reliability is determined by use of a simplified idealised analytical model which...
Villar, Oscar Armando Esparza-Del; Montañez-Alvarado, Priscila; Gutiérrez-Vega, Marisela; Carrillo-Saucedo, Irene Concepción; Gurrola-Peña, Gloria Margarita; Ruvalcaba-Romero, Norma Alicia; García-Sánchez, María Dolores; Ochoa-Alcaraz, Sergio Gabriel
2017-03-01
Mexico is one of the countries with the highest rates of overweight and obesity around the world, with 68.8% of men and 73% of women reporting both. This is a public health problem since there are several health related consequences of not exercising, like having cardiovascular diseases or some types of cancers. All of these problems can be prevented by promoting exercise, so it is important to evaluate models of health behaviors to achieve this goal. Among several models the Health Belief Model is one of the most studied models to promote health related behaviors. This study validates the first exercise scale based on the Health Belief Model (HBM) in Mexicans with the objective of studying and analyzing this model in Mexico. Items for the scale called the Exercise Health Belief Model Scale (EHBMS) were developed by a health research team, then the items were applied to a sample of 746 participants, male and female, from five cities in Mexico. The factor structure of the items was analyzed with an exploratory factor analysis and the internal reliability with Cronbach's alpha. The exploratory factor analysis reported the expected factor structure based in the HBM. The KMO index (0.92) and the Barlett's sphericity test (p factor loadings, ranging from 0.31 to 0.92, and the internal consistencies of the factors were also acceptable, with alpha values ranging from 0.67 to 0.91. The EHBMS is a validated scale that can be used to measure exercise based on the HBM in Mexican populations.
Wei, Meifen; Alvarez, Alvin N.; Ku, Tsun-Yao; Russell, Daniel W.; Bonett, Douglas G.
2010-01-01
Four studies were conducted to develop and validate the Coping With Discrimination Scale (CDS). In Study 1, an exploratory factor analysis (N = 328) identified 5 factors: Education/Advocacy, Internalization, Drug and Alcohol Use, Resistance, and Detachment, with internal consistency reliability estimates ranging from 0.72 to 0.90. In Study 2, a…
Al-Dubai, Sami Abdo Radman; Alshagga, Mustafa Ahmed; Rampal, Krishna Gopal; Sulaiman, Nik Aziz
2012-01-01
Background: The Perceived Stress Scale 10 (PSS-10) is a validated and reliable instrument to measure global levels of perceived stress. This study aims to assess the internal consistency, reliability, and factor structure of the Malay version of the PSS-10 for use among medical students. Methods: The original English version of the PSS-10 was translated and back-translated into Malay language. The Malay version was distributed to 242 Bachelor of Medical Science students in a private university in Malaysia. Test–retest reliability was assessed in 70 students. An exploratory principal component factor analysis with varimax rotation was performed. Reliability was tested using the intraclass correlation coefficient (ICC). Results: All 242 students participated in the initial questionnaire study (validity and factor structure), and 70 students participated in the test–retest reliability of the study. Exploratory factor analysis yielded 2 factors that accounted for 57.8% of the variance. Cronbach’s alpha coefficients for the 2 factors were 0.85 and 0.70, respectively. The reliability test showed an ICC of 0.82 (95% CI: 0.70, 0.89). Conclusion: The Malay version of the PSS-10 showed adequate psychometric properties. It is a useful instrument for measuring stress among medical students in Malaysia. PMID:23785249
Vasconcelos-Raposo, José; Fernandes, Helder Miguel; Teixeira, Carla M
2013-01-01
The purpose of the present study was to assess the factor structure and reliability of the Depression, Anxiety and Stress Scales (DASS-21) in a large Portuguese community sample. Participants were 1020 adults (585 women and 435 men), with a mean age of 36.74 (SD = 11.90) years. All scales revealed good reliability, with Cronbach's alpha values between .80 (anxiety) and .84 (depression). The internal consistency of the total score was .92. Confirmatory factor analysis revealed that the best-fitting model (*CFI = .940, *RMSEA = .038) consisted of a latent component of general psychological distress (or negative affectivity) plus orthogonal depression, anxiety and stress factors. The Portuguese version of the DASS-21 showed good psychometric properties (factorial validity and reliability) and thus can be used as a reliable and valid instrument for measuring depression, anxiety and stress symptoms.
Reliability Based Ship Structural Design
DEFF Research Database (Denmark)
Dogliani, M.; Østergaard, C.; Parmentier, G.;
1996-01-01
with developments of models of load effects and of structural collapse adopted in reliability formulations which aim at calibrating partial safety factors for ship structural design. New probabilistic models of still-water load effects are developed both for tankers and for containerships. New results are presented......This paper deals with the development of different methods that allow the reliability-based design of ship structures to be transferred from the area of research to the systematic application in current design. It summarises the achievements of a three-year collaborative research project dealing...... structure of several tankers and containerships. The results of the reliability analysis were the basis for the definition of a target safety level which was used to asses the partial safety factors suitable for in a new design rules format to be adopted in modern ship structural design. Finally...
The Dysfunctional Attitudes Scale: factor structure, reliability, and validity with older adults.
Floyd, M; Scogin, F; Chaplin, W F
2004-03-01
The Dysfunctional Attitudes Scale Form A (DAS-A), a self-report measure of depression-related attitudes, has been used in numerous depression studies. The DAS-A has a two-factor structure that has been found consistently with college student samples and clinically depressed samples of middle-aged adults, but it has not been validated with older adults. The present study examined the factor structure with a sample of 100 depressed older adults (average age = 68.19; average initial Hamilton Rating Scale for Depression [HRSD] score = 16.72) who participated in a depression treatment study. Results indicated the factor structure established with younger adults was not replicated with older adults. Furthermore, the factor structure with older adults was uncertain: a single factor structure, two-factor structure, and three-factor structure were essentially of equal validity. The uncertainty of the latent structure of the DAS-A suggests that it should be interpreted with caution whenever used with older adults.
Jacobs, Karen; Struyf, Elke
2013-01-01
Socioemotional guidance of students has recently become an integral part of education, however no instrument exists to measure integrated socioemotional guidance. This study therefore examines the factor structure and reliability of the Socioemotional Guidance Questionnaire. Psychometric properties of the Socioemotional Guidance Questionnaire and…
Thombs, Brett D.; Bernstein, David P.; Lobbestael, Jill; Arntz, Arnoud
2009-01-01
Objective: The 28-item Childhood Trauma Questionnaire-Short Form (CTQ-SF) has been translated into at least 10 different languages. The validity of translated versions of the CTQ-SF, however, has generally not been examined. The objective of this study was to investigate the factor structure, internal consistency reliability, and known-groups…
Reliability based structural design
Vrouwenvelder, A.C.W.M.
2014-01-01
According to ISO 2394, structures shall be designed, constructed and maintained in such a way that they are suited for their use during the design working life in an economic way. To fulfil this requirement one needs insight into the risk and reliability under expected and non-expected actions. A ke
Reliability based structural design
Vrouwenvelder, A.C.W.M.
2013-01-01
According to ISO 2394, structures shall be designed, constructed and maintained in such a way that they are suited for their use during the design working life in an economic way. To fulfil this requirement one needs insight into the risk and reliability under expected and non-expected actions. A ke
Directory of Open Access Journals (Sweden)
Maryam Taleb Doaee
2017-07-01
Full Text Available The present study aimed to investigate the reliability and factor structure of the self-regulating capacity in vocabulary learning strategies scale (SRCvoc in the Iranian EFL context. To this end, the original (SRCvoc questionnaire (Tseng, Dornyei, & Schmitt, 2006 was translated into Persian, using a translation/back-translation procedure. Then, the Persian version of the SRCVOC was piloted to 43 high school students and showed acceptable internal consistency reliability (α = .81. In the main phase of the study, a sample of 1167 high school students (grades 9-12 from fifteen high schools in three Iranian cities completed the Persian SRCvoc. Based on the results, the Persian version of the scale demonstrated acceptable internal consistency reliability (α = 0.81. The factor structure of the translated version of the measure was investigated through a series of factor analyses. The results showed that the translated SVLSQ is composed of one dimension with five subcomponents, with a different factor structure as compared to the original questionnaire. The findings of the study suggest that the Persian version of the SVLSQ is a reliable and valid instrument for measuring self-regulatory vocabulary learning strategies in Iran.
Pham, Yen K; McWhirter, Ellen Hawley; Murray, Christopher
2014-04-01
Existing measures of help-seeking focus on assessing attitudes and beliefs, rather than specific behaviors, toward help-seeking. This study described the development of a self-report measure of informal help-seeking behaviors (HSB). Participants were 228 high school students (148 males, 80 females) with disabilities from four states. Factor analyses revealed three underlying factors, each addressing a different source of help: parent, peer, and teacher. The HSB had good internal reliability and moderate validity. Results from regression analyses suggested that help-seeking behaviors toward parents and teachers contributed uniquely to students' self-ratings of school bonding, life satisfaction, and career outcome expectations. Help-seeking behaviors toward peers was a negative predictor of career outcome expectations. The value of the HSB as a research instrument was discussed. Copyright © 2014 The Foundation for Professionals in Services for Adolescents. Published by Elsevier Ltd. All rights reserved.
Grygiel, Paweł; Humenny, Grzegorz; Rębisz, Sławomir
2016-12-08
The present investigation is the first examination of the factor structures, reliability, external validity, longitudinal invariance, and stability of the De Jong Gierveld Loneliness Scale (DJGLS), as used with early adolescents. It is based on a two-wave, large, representative sample of Polish primary school pupils. The results demonstrate that the model most reflective of the factor structure of the DJGLS is the bifactor model, which assumes the occurrence of one, highly reliable, general factor (overall sense of loneliness) and two, relatively irrelevant, subfactors. Essential unidimensionality (the general factor accounting for three fourth of the common variance) suggest that the interpretation of the subfactors over and above the general factor is inappropriate. The longitudinal confirmatory factor analysis indicated that the bifactor structure of the DJGLS is invariant over time. Correlations with self-rated loneliness, sociometric acceptance/rejection, social self-efficacy, identification with class group, family structure, and gender provide support for the validity of the DJGLS. This implies that it could be used as a measure of loneliness in adolescence, which does not involve references to the school context, making it possible to conduct studies that go beyond school period and compare the intensity of the feeling of loneliness in that group with other age groups.
Aarons, Gregory A; McDonald, Elizabeth J; Connelly, Cynthia D; Newton, Rae R
2007-12-01
The purpose of this study was to examine the factor structure, reliability, and validity of the Family Assessment Device (FAD) among a national sample of Caucasian and Hispanic American families receiving public sector mental health services. A confirmatory factor analysis conducted to test model fit yielded equivocal findings. With few exceptions, indices of model fit, reliability, and validity were poorer for Hispanic Americans compared with Caucasian Americans. Contrary to our expectation, an exploratory factor analysis did not result in a better fitting model of family functioning. Without stronger evidence supporting a reformulation of the FAD, we recommend against such a course of action. Findings highlight the need for additional research on the role of culture in measurement of family functioning.
Reliability of the factor structure of the Multidimensional Scale of Interpersonal Reactivity (EMRI
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Nilton S. Formiga
2013-10-01
Full Text Available This study aims to check the internal consistency and factor structure evaluative of the empathy scale in a high school and college sample in the state of Minas Gerais. The instruments that measure empathy can be easily found, however, of the existing, just multidimensional scale of interpersonal reactivity (Emri is the theoretical framework that has far more and better organized, and the scale that is most commonly used to assess this construct. Participated 488 subjects, male and female, with ages from 14-54 years old, distributed in primary and college levels in Patrocínio-MG composed this study sample. The subjects answered the Multidimensional Scale of Interpersonal Reactivity and socio-demographic data. From an equation analysis and structural modeling were observed psychometric indicators that assured the structural consistency of the scale, promoting in the security of the measure theoretical construct of empathy.
Decision theory in structural reliability
Thomas, J. M.; Hanagud, S.; Hawk, J. D.
1975-01-01
Some fundamentals of reliability analysis as applicable to aerospace structures are reviewed, and the concept of a test option is introduced. A decision methodology, based on statistical decision theory, is developed for determining the most cost-effective design factor and method of testing for a given structural assembly. The method is applied to several Saturn V and Space Shuttle structural assemblies as examples. It is observed that the cost and weight features of the design have a significant effect on the optimum decision.
Semerari, Antonio; Cucchi, Michele; Dimaggio, Giancarlo; Cavadini, Daniele; Carcione, Antonino; Battelli, Vittoria; Nicolò, Giuseppe; Pedone, Roberto; Siccardi, Tomaso; D'Angerio, Stefania; Ronchi, Paolo; Maffei, Cesare; Smeraldi, Enrico
2012-12-30
Metacognition is a multi-facet psychological construct; deficits in metacognitive abilities are associated to low social functioning, low quality of life, psychopathology, and symptoms. The aim of this study was to describe and develop a valid and reliable interview for assessing metacognition. The semi-structured interview, based on the author's theory model of the metacognition construct, is described. The Metacognition Assessment Interview (MAI) is an adaptation of the Metacognition Assessment Scale (MAS) and evaluates how the subject is interviewed used metacognition during his own real life experiences elicited by the interviewer. A user manual was developed to assist the interview and scoring procedure. Exploratory factor analysis and confirmatory factor analysis revealed preliminary evidence of a two factor-hierarchical structure, with two lower-order scales, representing the two main theoretical domains of the metacognitive function, "the Self" and "the Other", and one single higher-order scale that we labelled metacognition. Contrary to the authors' prediction the existence of the four distinct dimensions under the two domains was not confirmed. The MAI and its two domains demonstrated acceptable levels of inter-rater reliability and internal consistency. The MAI appears to be a promising instrument for assessing metacognition. Future psychometric validation steps and clinical directions are discussed. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.
Paivio, Sandra, C.; Cramer, Kenneth, M.
2004-01-01
Objective: The aims of this study were to examine (1) the psychometric properties of the Childhood Trauma Questionnaire [CTQ; Bernstein, D., Fink, L., Handelsman, L., Foote, J., Lovejoy, M., Wenzel, K., Sapareto, E., & Ruggiero, J. (1994). Initial reliability and validity of a new retrospective measure of child abuse and neglect. American…
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Dagmara Budnik-Przybylska
2014-12-01
Full Text Available Background An important component of mental training in sport is the utilization of positive imagery. The “human brain cannot distinguish between an imagined experience and a real experience. The same areas of the brain light up in an imagined experience or imagined performance as in a real experience or performance. For that reason, positive performance imagery has enormous potential” (Orlick, 2008, p. 101. Imagery “has been described as a centre pillar of applied sport psychology” research (Morris, Spittle, & Perry, 2004, p. 344. The aim of the present study was to examine reliability and validity characteristics of the Polish language version of the Sport Imagery Ability Measure (SIAM. Participants and procedure Polish athletes (N = 316 from a range of sports and competitive levels completed the 48 item SIAM. The participants (163 male, 153 female were aged between 12 and 57 years (M = 22.15, SD = 8.25. Results Results indicated that the SIAM had sound internal consistency and maintained good stability over a 3-week period. Confirmatory factor analysis demonstrated that the a priori 3-factor structure of the SIAM resulted in a set of acceptable and poor fit indices (CFI = .91, NFI = .90, RMSEA = .12. Finally, differences in athletes’ imagery abilities were examined in relation to competitive level, gender, and age. Conclusions Overall, results generally supported the reliability and construct validity of the Polish version of the SIAM.
Stokes, Julie E.; And Others
1994-01-01
This paper investigates the psychometric properties of the African Self-Consciousness (ASC) Scale in a noncollege heterogeneous population of 147 African Americans to determine the reliability and validity of the ASC Scale. Based on analysis of the scale's reliability, factor structure, and construct validity, the study shows the ASC Scale to be a…
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Friis-Hansen, P.; Nielsen, J.S.
2007-01-01
Traditionally, deterministic pushover analyses are performed for steel-jacket offshore platforms in order to calculate RSR (Reserve Strength Ratio) values as the representative reliability measure for the total collapse of the structure. In this paper, reliability analyses are performed for total...
DEFF Research Database (Denmark)
2006-01-01
Traditionally deterministic push-over analyses are performed for steel-jacket offshore platforms in order to calculate RSR (Reserve Strength Ratio) values as the representative reliability measure for total collapse of the structure. In this paper reliability analyses are performed for total...
Zheng, Lijun; Goldberg, Lewis R.; Zheng, Yong; Zhao, Yufang; Tang, Yonglong; Liu, Li
2010-01-01
Previous studies have suggested the cross-cultural generalizability of a 5-factor structure for personality traits. In this article, we analyzed the utility of 2 versions (100-item and 50-item) of the IPIP Big-Five factor markers in both heterosexual (N = 633) and homosexual (N = 437) samples in China. Factor analysis within versions showed that both versions of these IPIP measures showed clear 5-factor orthogonal structures that were nearly identical to the American structure in both subject samples. The reliabilities of the five factors were quite high except for the 50-item measure of Agreeableness. The part-whole correlations between the 100-item and 50-item factors were high, as were the factor congruence coefficients between the heterosexual and the homosexual samples. Both versions of the IPIP Big-Five factor markers were strongly correlated with the scales from the Big Five Inventory (BFI: John, Donahue & Kentle, 1991), thus providing some concurrent validation in a Chinese context. PMID:20383283
Energy Technology Data Exchange (ETDEWEB)
Dalsgaard Soerensen, J. [Aalborg Univ., Aalborg (Denmark); Friis-Hansen, P. [Technical Univ. Denmark, Lyngby (Denmark); Bloch, A.; Svejgaard Nielsen, J. [Ramboell, Esbjerg (Denmark)
2004-08-01
Different simple stochastic models for failure related to pushover collapse are investigated. Next, a method is proposed to estimate the reliability of real offshore jacket structures. The method is based on the Model Correction Factor Method and can be used to very efficiently to estimate the reliability for total failure/collapse of jacket type platforms with wave in deck loads. A realistic example is evaluated and it is seen that it is possible to perform probabilistic reliability analysis for collapse of a jacket type platform using the model correction factor method. The total number of deterministic, complicated, non-linear (RONJA) analysis is typically as low as 10. Such reliability analyses are recommended to be used in practical applications, especially for cases with wave in deck load, where the traditional RSR analyses give poor measures of the structural reliability. (au)
Structural Optimization with Reliability Constraints
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Thoft-Christensen, Palle
1986-01-01
During the last 25 years considerable progress has been made in the fields of structural optimization and structural reliability theory. In classical deterministic structural optimization all variables are assumed to be deterministic. Due to the unpredictability of loads and strengths of actual...... structures it is now widely accepted that structural problems are non-deterministic. Therefore, some of the variables have to be modelled as random variables/processes and a reliability-based design philosophy should be used, Comell [1], Moses [2], Ditlevsen [3] and Thoft-Christensen & Baker [ 4......]. In this paper we consider only structures which can be modelled as systems of elasto-plastic elements, e.g. frame and truss structures. In section 2 a method to evaluate the reliability of such structural systems is presented. Based on a probabilistic point of view a modern structural optimization problem...
Directory of Open Access Journals (Sweden)
Manon Marquet
2016-03-01
Full Text Available Introduction: The Attitudes to Aging Questionnaire (AAQ was developed to measure attitudes toward the aging process as a personal experience from the perspective of older people. The present study aimed to validate the French version of the AAQ. Participants and methods: This study examined factor structure, acceptability, reliability and validity of the AAQ’s French version in 238 Belgian adults aged 60 years or older. In addition, participants provided information on demographics, self-perception of their mental and physical health (single items, quality of life (WHOQOL-OLD and social desirability (DS-36. Results: Exploratory Factor Analysis produced a three-factor solution accounting for 36.9% of the variance. No floor or ceiling effects were found. The internal consistency, measured by Cronbach’s alpha coefficients for the AAQ subscales were 0.62 (Physical Change, 0.74 (Psychological Growth, and 0.75 (Psychosocial Loss. A priori expected associations were found between AAQ subscales, self-reported health and quality of life, indicating good convergent validity. The scale also showed a good ability to discriminate between people with lower and higher education levels, supporting adequate known-groups validity. Finally, we confirmed the need to control for social desirability biases when assessing self-reported attitudes toward one’s own aging. Conclusion: The data support the usefulness of the French version of the AAQ for the assessment of attitudes toward their own aging in older people.
Structural Reliability of Wind Turbine Blades
DEFF Research Database (Denmark)
Dimitrov, Nikolay Krasimirov
by developing new models and standards or carrying out tests The following aspects are covered in detail: ⋅ The probabilistic aspects of ultimate strength of composite laminates are addressed. Laminated plates are considered as a general structural reliability system where each layer in a laminate is a separate...... system component. Methods for solving the system reliability are discussed in an example problem. ⋅ Probabilistic models for fatigue life of laminates and sandwich core are developed and calibrated against measurement data. A modified, nonlinear S-N relationship is formulated where the static strength...... the reliability against several modes of failure in two different structures. This includes reliability against blade-tower collision, and the reliability against ultimate and fatigue failure of a sandwich panel. The results from the reliability analyses are then used for calibrating partial safety factors...
Forde, David R.; Baron, Stephen W.; Scher, Christine D.; Stein, Murray B.
2012-01-01
This study examines the psychometric properties of the Childhood Trauma Questionnaire short form (CTQ-SF) with street youth who have run away or been expelled from their homes (N = 397). Internal reliability coefficients for the five clinical scales ranged from 0.65 to 0.95. Confirmatory Factor Analysis (CFA) was used to test the five-factor…
System Reliability of Timber Structures
DEFF Research Database (Denmark)
Kirkegaard, Poul Henning; Sørensen, John Dalsgaard
2010-01-01
For reduction of the risk of collapse in the event of loss of structural element(s), a structural engineer may take necessary steps to design a collapse-resistant structure that is insensitive to accidental circumstances e.g. by incorporating characteristics like redundancy, ties, ductility, key ...... elements, alternate load path(s) etc. in the structural design. In general these characteristics can have a positive influence on system reliability of a structure however, in Eurocodes ductility is only awarded for concrete and steel structures but not for timber structures. It is well......-know that structural systems can redistribute internal forces due to ductility of a connection, i.e. some additional loads can be carried by the structure. The same effect is also possible for reinforced concrete structures and structures of steel. However, for timber structures codes do not award that ductility...
Structural reliability codes for probabilistic design
DEFF Research Database (Denmark)
Ditlevsen, Ove Dalager
1997-01-01
difficulties of ambiguity and definition show up when attempting to make the transition from a given authorized partial safety factor code to a superior probabilistic code. For any chosen probabilistic code format there is a considerable variation of the reliability level over the set of structures defined...... considerable variation of the reliability measure as defined by a specific probabilistic code format. Decision theoretical principles are applied to get guidance about which of these different reliability levels of existing practice to choose as target reliability level. Moreover, it is shown that the chosen...... probabilistic code format has not only strong influence on the formal reliability measure, but also on the formal cost of failure to be associated if a design made to the target reliability level is considered to be optimal. In fact, the formal cost of failure can be different by several orders of size for two...
Murray, Christopher; Zvoch, Keith
2011-01-01
This study investigates the factor structure, reliability, and validity of the Inventory of Teacher-Student Relationships (IT-SR), a measure that was developed by adapting the widely used Inventory of Parent and Peer Attachments (Armsden & Greenberg, 1987) for use in the context of teacher-student relationships. The instrument was field tested…
Reliability-based optimization of engineering structures
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard
2008-01-01
The theoretical basis for reliability-based structural optimization within the framework of Bayesian statistical decision theory is briefly described. Reliability-based cost benefit problems are formulated and exemplitied with structural optimization. The basic reliability-based optimization prob...
Hoben, Matthias; Estabrooks, Carole A.; Squires, Janet E.; Behrens, Johann
2016-01-01
We translated the Canadian residential long term care versions of the Alberta Context Tool (ACT) and the Conceptual Research Utilization (CRU) Scale into German, to study the association between organizational context factors and research utilization in German nursing homes. The rigorous translation process was based on best practice guidelines for tool translation, and we previously published methods and results of this process in two papers. Both instruments are self-report questionnaires used with care providers working in nursing homes. The aim of this study was to assess the factor structure, reliability, and measurement invariance (MI) between care provider groups responding to these instruments. In a stratified random sample of 38 nursing homes in one German region (Metropolregion Rhein-Neckar), we collected questionnaires from 273 care aides, 196 regulated nurses, 152 allied health providers, 6 quality improvement specialists, 129 clinical leaders, and 65 nursing students. The factor structure was assessed using confirmatory factor models. The first model included all 10 ACT concepts. We also decided a priori to run two separate models for the scale-based and the count-based ACT concepts as suggested by the instrument developers. The fourth model included the five CRU Scale items. Reliability scores were calculated based on the parameters of the best-fitting factor models. Multiple-group confirmatory factor models were used to assess MI between provider groups. Rather than the hypothesized ten-factor structure of the ACT, confirmatory factor models suggested 13 factors. The one-factor solution of the CRU Scale was confirmed. The reliability was acceptable (>0.7 in the entire sample and in all provider groups) for 10 of 13 ACT concepts, and high (0.90–0.96) for the CRU Scale. We could demonstrate partial strong MI for both ACT models and partial strict MI for the CRU Scale. Our results suggest that the scores of the German ACT and the CRU Scale for nursing
The stability safety factor calibration based on the reliability index
Institute of Scientific and Technical Information of China (English)
Tong Xiaolong; Fang Zhi
2014-01-01
When the bridge structure stability safety factor of the first type is 4,the research that whether the structure reliability index will reach target reliability index under the more-likely-to-happen collapse situation of the second type is necessary. The stability calculations of the first and the second type are made respectively for single layer and single span rigid frame bridge. Based on the critical load obtained from the stability calculation of the first type,the stability safety factor of the first type is taken as 4,and the first order reliability method is used to program and calculate the reliability index. Then,the load effect under the stability reliability index cal-culation of the first type and the critical load of the second type are employed to calculate the reliability index of the second type. The evaluation of structure stability safety factor is discussed according to reliability index. Based on the discussion above,parameter analysis of the stable critical loads of two types is made,and the in-fluence of critical load change on reliability index is researched. The result shows that stability analysis should identify collapse state;when the stability safety factor of the first type is 4,but the structure has the collapse of the second type,the reliability index cannot be ensured to reach the target reliability index under certain condi-tions.
The stability safety factor calibration pased on the reliability index
Institute of Scientific and Technical Information of China (English)
Tong Xiaolong; Fang Zhi
2014-01-01
When the bridge structure stability safety factor of the first type is 4, the research that whether the structure reliability index will reach target reliability index under the more-likely-to-happen collapse situation of the second type is necessary. The stability calculations of the first and the second type are made respectively for single layer and single span rigid frame bridge. Based on the critical load obtained from the stability calculation of the first type, the stability safety factor of the first type is taken as 4, and the first order reliability method is used to program and calculate the reliability index. Then, the load effect under the stability reliability index cal- culation of the first type and the critical load of the second type are employed to calculate the reliability index of the second type. The evaluation of structure stability safety factor is discussed according to reliability index. Based on the discussion above, parameter analysis of the stable critical loads of two types is made, and the in- fluence of critical load change on reliability index is researched. The result shows that stability analysis should identify collapse state; when the stability safety factor of the first type is 4, but the structure has the collapse of the second type, the reliability index cannot be ensured to reach the target reliability index under certain condi- tions.
Directory of Open Access Journals (Sweden)
Yukiko Ohashi
2016-08-01
Full Text Available Negative attitudes of mothers towards their infant is conceptualized as postpartum bonding disorder, which leads to serious health problems in perinatal health care. However, its measurement still remains to be standardized. Our aim was to examine and confirm the psychometric properties of the Postnatal Bonding Questionnaire (PBQ in Japanese mothers. We distributed a set of questionnaires to community mothers and studied 392 mothers who returned the questionnaires at 1 month after childbirth. Our model was compared with three other models derived from previous studies. In a randomly halved sample, an exploratory factor analysis yielded a three-factor structure: Anger and Restrictedness, Lack of Affection, and Rejection and Fear. This factor structure was cross-validated by a confirmatory factor analysis using the other halved sample. The three subscales showed satisfactory internal consistency. The three PBQ subscale scores were correlated with depression and psychological abuse scores. Their test–retest reliability between day 5 and 1 month after childbirth was measured by intraclass correlation coefficients between 0.76 and 0.83. The Akaike Information Criteria of our model was better than the original four-factor model of Brockington. The present study indicates that the PBQ is a reliable and valid measure of bonding difficulties of Japanese mothers with neonates.
Ohashi, Yukiko; Kitamura, Toshinori; Sakanashi, Kyoko; Tanaka, Tomoko
2016-08-02
Negative attitudes of mothers towards their infant is conceptualized as postpartum bonding disorder, which leads to serious health problems in perinatal health care. However, its measurement still remains to be standardized. Our aim was to examine and confirm the psychometric properties of the Postnatal Bonding Questionnaire (PBQ) in Japanese mothers. We distributed a set of questionnaires to community mothers and studied 392 mothers who returned the questionnaires at 1 month after childbirth. Our model was compared with three other models derived from previous studies. In a randomly halved sample, an exploratory factor analysis yielded a three-factor structure: Anger and Restrictedness, Lack of Affection, and Rejection and Fear. This factor structure was cross-validated by a confirmatory factor analysis using the other halved sample. The three subscales showed satisfactory internal consistency. The three PBQ subscale scores were correlated with depression and psychological abuse scores. Their test-retest reliability between day 5 and 1 month after childbirth was measured by intraclass correlation coefficients between 0.76 and 0.83. The Akaike Information Criteria of our model was better than the original four-factor model of Brockington. The present study indicates that the PBQ is a reliable and valid measure of bonding difficulties of Japanese mothers with neonates.
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Víctor Company Martínez
2015-07-01
Full Text Available The purpose of this study was to translate and validate the Criminal Sentiment Scale Modified (CSS-M, which measures the criminal attitudes into Spanish. Despite the large body of research proving their importance as one of the best predictors of criminal conduct, only a few measures have been psychometrically developed and validated, and none of them are available in the Spanish language. A sample of 153 male inmates from Penitentiary Brians I of the Catalan Prison Service (Spain participated voluntarily in the study (73.9% of Spanish nationality, mean age = 37.3 completed the final version of the Spanish adaptation. An exploratory factor analysis (EFA and a confirmatory factor analysis (CFA were conducted with all the scales simultaneously, showing that the underlying structure of the CSS-M was best explained by a two-factor solution: Sentiments toward the establishment and Criminality self-benefits. Moreover, a set of analyses of variance (ANOVA was also performed, validating the scale well. According to the results of the study, it was concluded that the Spanish version of the CSS-M has satisfactory psychometric properties, enabling its potential usefulness within the legal field of Spanish-speaking countries as a key element in crime prevention.
Directory of Open Access Journals (Sweden)
Simone Matulis
2015-10-01
Full Text Available Background: The Trauma Symptom Checklist for Children (TSC-C is the most widely used self-report scale to assess trauma-related symptoms in children and adolescents on six clinical scales. The purpose of the present study was to develop a German version of the TSC-C and to investigate its psychometric properties, such as factor structure, reliability, and validity, in a sample of German adolescents. Method: A normative sample of N=583 and a clinical sample of N=41 adolescents with a history of physical or sexual abuse aged between 13 and 21 years participated in the study. Results: The Confirmatory Factor Analysis on the six-factor model (anger, anxiety, depression, dissociation, posttraumatic stress, and sexual concerns with the subdimensions preoccupation and distress revealed acceptable to good fit statistics in the normative sample. One item had to be excluded from the German version of the TSC-C because the factor loading was too low. All clinical scales presented acceptable to good reliability, with Cronbach's α's ranging from .80 to .86 in the normative sample and from .72 to .87 in the clinical sample. Concurrent validity was also demonstrated by the high correlations between the TSC-C scales and instruments measuring similar psychopathology. TSC-C scores reliably differentiated between adolescents with trauma history and those without trauma history, indicating discriminative validity. Conclusions: In conclusion, the German version of the TSC-C is a reliable and valid instrument for assessing trauma-related symptoms on six different scales in adolescents aged between 13 and 21 years.
Directory of Open Access Journals (Sweden)
Weng Yee Chin
Full Text Available The Center for Epidemiologic Studies Depression Scale (CES-D is a commonly used instrument to measure depressive symptomatology. Despite this, the evidence for its psychometric properties remains poorly established in Chinese populations. The aim of this study was to validate the use of the CES-D in Chinese primary care patients by examining factor structure, construct validity, reliability, sensitivity and responsiveness.The psychometric properties were assessed amongst a sample of 3686 Chinese adult primary care patients in Hong Kong. Three competing factor structure models were examined using confirmatory factor analysis. The original CES-D four-structure model had adequate fit, however the data was better fit into a bi-factor model. For the internal construct validity, corrected item-total correlations were 0.4 for most items. The convergent validity was assessed by examining the correlations between the CES-D, the Patient Health Questionnaire 9 (PHQ-9 and the Short Form-12 Health Survey (version 2 Mental Component Summary (SF-12 v2 MCS. The CES-D had a strong correlation with the PHQ-9 (coefficient: 0.78 and SF-12 v2 MCS (coefficient: -0.75. Internal consistency was assessed by McDonald's omega hierarchical (ωH. The ωH value for the general depression factor was 0.855. The ωH values for "somatic", "depressed affect", "positive affect" and "interpersonal problems" were 0.434, 0.038, 0.738 and 0.730, respectively. For the two-week test-retest reliability, the intraclass correlation coefficient was 0.91. The CES-D was sensitive in detecting differences between known groups, with the AUC >0.7. Internal responsiveness of the CES-D to detect positive and negative changes was satisfactory (with p value 0.2. The CES-D was externally responsive, with the AUC>0.7.The CES-D appears to be a valid, reliable, sensitive and responsive instrument for screening and monitoring depressive symptoms in adult Chinese primary care patients. In its original
Fatigue reliability of cracked engineering structures
Lanning, David Bruce, Jr.
1997-12-01
This study investigates the reliability of engineering structures containing fatigue cracks. Stress concentrations and welded joints are probable locations for the initiation and propagation of fatigue cracks. Due to the many unknowns of loading, materials properties, crack sizes and crack shapes present at these locations, a statistics-based reliability analysis is valuable in the careful consideration of these many different random factors involved in a fatigue life analysis, several of which are expanded upon in this study. The basic problem of a crack near a stress concentration is first considered. A formulation for the aspect ratio (a/c) of a propagating semi-elliptical fatigue crack located at the toe of a welded T-joint is developed using Newman and Raju's stress intensity factor for a cracked flat plate with a weld magnification factor and compared to that of a cracked flat plate, and the reliability in terms of fatigue lifetime is calculated with the aid of Paris' crack propagation equation for membrane and bending loadings. Crack closure effects are then introduced in the consideration of short crack effects, where crack growth rates typically may exceed those found using traditional linear elastic fracture mechanics solutions for long cracks. The probability of a very small, microstructurally influenced crack growing to a size influenced by local plastic conditions is calculated utilizing the probability of a crack continuing to grow past an obstacle, such as a grain boundary. The result is then combined with the probability for failure defined using the crack closure-modified Paris equation to find an overall reliability for the structure. Last, the probability of fracture is determined when a crack front encounters regions of non-uniform toughness, such as typical in the heat affected zone of a welded joint. An expression for the effective crack lengths of the dissimilar regions is derived, and used in a weakest-link fracture model in the evaluation
Structural reliability of existing city bridges
Hellebrandt, L.; Steenbergen, R.; Vrouwenvelder, T.; Blom, K.
2015-01-01
Full probabilistic reliability analysis may be valuable for assessing existing structures. Measures for increasing the safety level are quite costly for existing structures and may be unnecessary when such a decision is grounded on a conservative analysis for determining the structural reliability.
Reliability Based Optimization of Structural Systems
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard
1987-01-01
The optimization problem to design structural systems such that the reliability is satisfactory during the whole lifetime of the structure is considered in this paper. Some of the quantities modelling the loads and the strength of the structure are modelled as random variables. The reliability...
Reliability-Based Optimization in Structural Engineering
DEFF Research Database (Denmark)
Enevoldsen, I.; Sørensen, John Dalsgaard
1994-01-01
-based optimal inspection planning and reliability-based experiment planning. It is explained how these optimization problems can be solved by application of similar techniques. The reliability estimation is limited to first order reliability methods (FORM) for both component and systems reliability evaluation......, inclusion of the finite element method as the response evaluation tool and how the size of the problem can be made practicable. Finally, the important task of model evaluation and sensitivity analysis of the optimal solution is treated including a strategy for model-making with both pre and post-analysis.......In this paper reliability-based optimization problems in structural engineering are formulated on the basis of the classical decision theory. Several formulations are presented: Reliability-based optimal design of structural systems with component or systems reliability constraints, reliability...
MULTIDIMENSIONAL RELIABILITY OF INSTRUMENT STUDENTS’ SATISFACTION USING CONFIRMATORY FACTOR ANALYSIS
Directory of Open Access Journals (Sweden)
Gaguk Margono
2014-11-01
Full Text Available The purpose of this paper is to compare unidimensional reliability and multidimensional reliability of instrument students’ satisfaction as an internal costumer. Multidimensional reliability measurement is rarely used in the field of research. Multidimensional reliability is estimated by using Confirmatory Factor Analysis (CFA on the Structural Equation Model (SEM. Measurements and calculations are described in this article using instrument students’ satisfaction as an internal costumer. Survey method used in this study and sampling used simple random sampling. This instrument has been tried out to 173 students. The result is concluded that the measuringinstrument of students’ satisfaction as an internal costumer by using multidimensional reliability coefficient has higher accuracy when compared with a unidimensional reliability coefficient. Expected in advanced research used another formula multidimensional reliability, including when using SEM.
Hardy, Precious; Aruguete, Mara
2014-01-01
Retention is a major problem in most colleges and universities. High dropout rates, especially in the STEM disciplines (science, technology, engineering and mathematics), have proved intractable despite the offering of supplemental instruction. A broad model of support systems that includes psychological factors is needed to address retention in…
De Almeida Vieira Monteiro, Ana Paula Teixeira
2011-02-01
The General Health Questionnaire (GHQ, Goldberg & Hillier, 1979 , Psychological Medicine, 9, 139-145) is a self-administered questionnaire used to measure non-psychotic psychiatric disorders. There is a study using a Portuguese version of this questionnaire (n = 60) including a group of inpatients with infectious diseases (Ribeiro & Antunes, 2003 , Revista Portuguesa de Psicossomática, 5(1), 37-45), but there are no larger studies in non-clinical Portuguese population. The primary aim of the study was to confirm the psychometric properties of the Portuguese version of the GHQ-28 among 171 Portuguese adults in non-clinical settings. The Portuguese version of the GHQ-28 was administered to 171 adult subjects of Portuguese general population. The Portuguese version of the GHQ-28 has an internally consistent measure Cronbach's α 0.922 for the GHQ-28 total scale. For the subscale somatic symptoms Cronbach's α was 0.825; for the subscale Anxiety/ Insomnia, Cronbach's α was 0.873; for the subscale Social dysfunction Cronbach's α was 0.873 and for the subscale Severe Depression was 0.838. Four factors were extracted using factor analysis: somatic symptoms (items 1-7); anxiety/insomnia (items 8-14); psychosocial dysfunction (items 15-21); and severe depression (items 22-28). The findings suggest that the GHQ-28 is a suitable screening instrument for adult Portuguese population in non-clinical settings.
On industrial application of structural reliability theory
Energy Technology Data Exchange (ETDEWEB)
Thoft-Christensen, P
1998-06-01
In this paper it is shown that modern structural reliability theory is being successfully applied to a number of different industries. This review of papers is in no way complete. In the literature there is a large number of similar applications and also application not touched on in this presentation. There has been some concern among scientists from this area that structural reliability theory is not being used by industry. It is probably correct that structural reliability theory is not being used by industry as much as it should be used. However, the work by the ESReDA Working Group clearly shows the vary wide application of structural reliability theory by many different industries. One must also have in mind that industry often is reluctant to publish data related to safety and reliability. (au) 32 refs.
Zimmermann, Gregoire; Mahaim, Elodie Biermann; Mantzouranis, Gregory; Genoud, Philippe A.; Crocetti, Elisabetta
2012-01-01
The purpose of this study was to evaluate the factor structure and the reliability of the French versions of the Identity Style Inventory (ISI-3) and the Utrecht-Management of Identity Commitments Scale (U-MICS) in a sample of college students (N = 457, 18-25 years old). Confirmatory factor analyses confirmed the hypothesized three-factor solution…
Nguyen, Trang Quynh; Poteat, Tonia; Bandeen-Roche, Karen; German, Danielle; Nguyen, Yen Hai; Vu, Loan Kieu-Chau; Nguyen, Nam Thi-Thu; Knowlton, Amy R
2016-08-01
We developed the first Vietnamese Internalized Homophobia (IH) scale for use with Vietnamese sexual minority women (SMW). Drawing from existing IH scales in the international literature and based on prior qualitative research about SMW in the Viet Nam context, the scale covers two domains: self-stigma (negative attitudes toward oneself as a sexual minority person) and sexual prejudice (negative attitudes toward homosexuality/same-sex relations in general). Scale items, including items borrowed from existing scales and items based on local expressions, were reviewed and confirmed by members of the target population. Quantitative evaluation used data from an anonymous web-based survey of Vietnamese SMW, including those who identified as lesbian (n = 1187), or as bisexual (n = 641) and those who were unsure about their sexual identity (n = 353). The scale was found to consist of two highly correlated factors reflecting self-stigma (not normal/wholesome and self-reproach and wishing away same-sex sexuality) and one factor reflecting sexual prejudice, and to have excellent internal consistency. Construct validity was evidenced by subscale associations with a wide range of hypothesized correlates, including perceived sexual stigma, outness, social support, connection to other SMW, relationship quality, psychological well-being, anticipation of heterosexual marriage, and endorsement of same-sex marriage legalization. Self-stigma was more strongly associated with psychosocial correlates, and sexual prejudice was more associated with endorsement of legal same-sex marriage. The variations in these associations across the hypothesized correlates and across sexual identity groups were consistent with the minority stress model and the IH literature, and exhibited context-specific features, which are discussed.
Combination of structural reliability and interval analysis
Institute of Scientific and Technical Information of China (English)
Zhiping Qiu; Di Yang; saac Elishakoff
2008-01-01
In engineering applications,probabilistic reliability theory appears to be presently the most important method,however,in many cases precise probabilistic reliability theory cannot be considered as adequate and credible model of the real state of actual affairs.In this paper,we developed a hybrid of probabilistic and non-probabilistic reliability theory,which describes the structural uncertain parameters as interval variables when statistical data are found insufficient.By using the interval analysis,a new method for calculating the interval of the structural reliability as well as the reliability index is introduced in this paper,and the traditional probabilistic theory is incorporated with the interval analysis.Moreover,the new method preserves the useful part of the traditional probabilistic reliability theory,but removes the restriction of its strict requirement on data acquisition.Example is presented to demonstrate the feasibility and validity of the proposed theory.
Tsuchiyagaito, Aki; Horiuchi, Satoshi; Igarashi, Toko; Kawanori, Yoshiya; Hirano, Yoshiyuki; Yabe, Hirooki; Nakagawa, Akiko
2017-01-01
The Hoarding Rating Scale-Self-Report (HRS-SR) is a five-item scale that assesses the symptoms of hoarding. These symptoms include excessive acquisition, difficulty in discarding, and excessive clutter that causes distress. We conducted three studies to examine the factor structure, reliability, and validity of the Japanese version of the HRS-SR (HRS-SR-J). Study 1 examined its reliability; 193 college students and 320 adolescents and adults completed the HRS-SR-J and, of the college students, 32 took it again 2 weeks later. Study 2 aimed to confirm that its scores in a sample of 210 adolescents and adults are independent of social desirability. Study 3 aimed to validate the HRS-SR-J in the aspects of convergent and discriminant validity in a sample of 550 adults. The HRS-SR-J showed good internal consistency and 2-week test-retest reliability. Based on the nonsignificant correlations between the HRS-SR-J and social desirability, the HRS-SR-J was not strongly affected by social desirability. In addition, it also had a good convergent validity with the Japanese version of the Saving Inventory-Revised (SI-R-J) and the hoarding subscale of the Obsessive-Compulsive Inventory, while having a significantly weaker correlation with the five subscales of the Obsessive-Compulsive Inventory, except for the hoarding subscale. In addition, the strength of the correlation between the HRS-SR-J and the Japanese version of the Patient Health Questionnaire-9 and that between the HRS-SR-J and the Generalized Anxiety Disorder-7 were significantly weaker than the correlation between the HRS-SR-J and the SI-R-J. These results demonstrate that the HRS-SR-J has good convergent and discriminant validity. The HRS-SR-J is a notable self-report scale for examining the severity of hoarding symptoms.
System Reliability of Timber Structures
DEFF Research Database (Denmark)
Kirkegaard, Poul Henning; Sørensen, John Dalsgaard
2010-01-01
will result in a semirigid behavior plus higher level of safety due to a lower probability that premature brittle failures occur and possible redistribution of forces for statically undetermined structures either internally in the joint or to other structural elements. A redistribution of forces, a so...
Cristofaro, Sarah L; Cleary, Sean D; Ramsay Wan, Claire; Broussard, Beth; Chapman, Colby; Haggard, Patrick J; Jananeh, Sara; Myers, Neely L; Compton, Michael T
2013-12-15
Past trauma and stressful events, especially in childhood and adolescence, are common among individuals with serious mental illnesses like schizophrenia. Traumatic experiences are thought to be a socio-environmental risk factor not only for poorer outcomes, but also potentially for the onset of these disorders. Because improved measurement tools are needed, we developed and studied, among 205 first-episode psychosis patients, the factor structure, internal consistency reliability, and initial validity of the Trauma Experiences Checklist (TEC), our measure of trauma and stressful events during childhood/adolescence. We assessed validity of subscales using correlations with Childhood Trauma Questionnaire-Short Form, Parental Harsh Discipline, Violence Exposure, and TEC-Informant Version scores. Exploratory factor analysis resulted in two internally consistent subscales (Cronbach's α=0.79 and 0.80, respectively), interpersonal abuse and family stress, and violence, death, and legal involvement. Scores from the former subscale were substantially associated with CTQ-SF physical, emotional, and sexual abuse (r=0.42-0.57, all p<0.001) and Violence Exposure (r=0.49, p<0.001). On the other hand, violence, death, and legal involvement scores were most highly correlated with Violence Exposure (r=0.49, p<0.001), and not with most CTQ-SF subscales. The TEC is a potentially useful tool in assessing diverse traumatic life events across various social contexts during childhood and adolescence.
Directory of Open Access Journals (Sweden)
Tsuchiyagaito A
2017-05-01
Full Text Available Aki Tsuchiyagaito,1–3 Satoshi Horiuchi,4 Toko Igarashi,5 Yoshiya Kawanori,4 Yoshiyuki Hirano,1,3 Hirooki Yabe,2 Akiko Nakagawa1,3 1Research Center for Child Mental Development, Chiba University, Chiba, 2Department of Neuropsychiatry, Fukushima Medical University, Fukushima, 3United Graduate School of Child Development, Osaka University, Kanazawa University, Hamamatsu University School of Medicine, Chiba University and University of Fukui, Osaka, 4Faculty of Social Welfare, Iwate Prefectural University, Iwate, 5Graduate School of Education, Joetsu University of Education, Niigata, Japan Background: The Hoarding Rating Scale-Self-Report (HRS-SR is a five-item scale that assesses the symptoms of hoarding. These symptoms include excessive acquisition, difficulty in discarding, and excessive clutter that causes distress. We conducted three studies to examine the factor structure, reliability, and validity of the Japanese version of the HRS-SR (HRS-SR-J. Methods: Study 1 examined its reliability; 193 college students and 320 adolescents and adults completed the HRS-SR-J and, of the college students, 32 took it again 2 weeks later. Study 2 aimed to confirm that its scores in a sample of 210 adolescents and adults are independent of social desirability. Study 3 aimed to validate the HRS-SR-J in the aspects of convergent and discriminant validity in a sample of 550 adults. Results: The HRS-SR-J showed good internal consistency and 2-week test–retest reliability. Based on the nonsignificant correlations between the HRS-SR-J and social desirability, the HRS-SR-J was not strongly affected by social desirability. In addition, it also had a good convergent validity with the Japanese version of the Saving Inventory-Revised (SI-R-J and the hoarding subscale of the Obsessive-Compulsive Inventory, while having a significantly weaker correlation with the five subscales of the Obsessive-Compulsive Inventory, except for the hoarding subscale. In addition, the
Recent advances in computational structural reliability analysis methods
Thacker, Ben H.; Wu, Y.-T.; Millwater, Harry R.; Torng, Tony Y.; Riha, David S.
1993-01-01
The goal of structural reliability analysis is to determine the probability that the structure will adequately perform its intended function when operating under the given environmental conditions. Thus, the notion of reliability admits the possibility of failure. Given the fact that many different modes of failure are usually possible, achievement of this goal is a formidable task, especially for large, complex structural systems. The traditional (deterministic) design methodology attempts to assure reliability by the application of safety factors and conservative assumptions. However, the safety factor approach lacks a quantitative basis in that the level of reliability is never known and usually results in overly conservative designs because of compounding conservatisms. Furthermore, problem parameters that control the reliability are not identified, nor their importance evaluated. A summary of recent advances in computational structural reliability assessment is presented. A significant level of activity in the research and development community was seen recently, much of which was directed towards the prediction of failure probabilities for single mode failures. The focus is to present some early results and demonstrations of advanced reliability methods applied to structural system problems. This includes structures that can fail as a result of multiple component failures (e.g., a redundant truss), or structural components that may fail due to multiple interacting failure modes (e.g., excessive deflection, resonate vibration, or creep rupture). From these results, some observations and recommendations are made with regard to future research needs.
Reliability-Based Optimization of Structural Elements
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard
In this paper structural elements from an optimization point of view are considered, i.e. only the geometry of a structural element is optimized. Reliability modelling of the structural element is discussed both from an element point of view and from a system point of view. The optimization...
Some Aspects of Reliability of Offshore Structures
DEFF Research Database (Denmark)
Sigurdsson, Gudfinnur
The use of modem structural reliability theory for modelling uncertainties in offshore engineering has gained widespread support. The uncertainties may relate to both physical quantities, e.g. material quantities and loads, and uncertainties in the mathematical modelling of the structural system....
Reliability-Based Design of Coastal Structures
DEFF Research Database (Denmark)
Burcharth, H. F.
1997-01-01
The objective of this paper is to introduce the application of reliability theory for conceptual design and evaluation of coastal structures. It is without the scope to discuss the validity and quality of the various design formulae available for coastal structures. The contents of the paper...... Engineering. Burcharth, H.F. (1993) Design of Breakwaters. Aalborg University. Department of Civil Engineering. Aalborg, Denmark. (Note). Burcbarth, H.F., Dalsgaard S9lrensen, J ., Cbristiani, E. (1995} Application for reliability analysis for optimal design of monolithic vertical wall breakwaters....... Proceedings Conference of Port and Coastal Engineering in developing countries. Rio de Janeiro, Brazil, 1995....
Structural reliability analysis and reliability-based design optimization: Recent advances
Qiu, ZhiPing; Huang, Ren; Wang, XiaoJun; Qi, WuChao
2013-09-01
We review recent research activities on structural reliability analysis, reliability-based design optimization (RBDO) and applications in complex engineering structural design. Several novel uncertainty propagation methods and reliability models, which are the basis of the reliability assessment, are given. In addition, recent developments on reliability evaluation and sensitivity analysis are highlighted as well as implementation strategies for RBDO.
Madewell, A N; Ponce-Garcia, E; Martin, S E
2016-09-01
The data presented in this article are related to the article entitled "Assessing Resilience in Emerging Adulthood: The Resilience Scale (RS), Connor Davidson Resilience Scale (CD-RISC), and Scale of Protective Factors (SPF)" (Madewell and Ponce-Garcia, 2016) [1]. The data were collected from a sample of 451 college students from three universities located in the Southwestern region of the United States: 374 from a large public university and 67 from two smaller regional universities. The data from the three universities did not significantly differ in terms of demographics. The data represent participant responses on six measurements to include the Resilience Scale-25 (RS-25), Resilience Scale-14 (RS-14), Connor Davidson Resilience Scale-25 (CD-RISC-25), Connor Davidson Resilience Scale-10 (CD-RISC-10), Scale of Protective Factors-24 (SPF-24), and the Life Stressor Checklist Revised (LSC-R).
On Industrial Application of Structural Reliability Theory
DEFF Research Database (Denmark)
Thoft-Christensen, Palle
For the last two decades we have seen an increasing interest in applying structural reliability theory to many different industries. However, the number of real applications is much smaller than what one would expect. At the beginning most applications were in the design/analyses area especially...
Lower confidence limits for structure reliability
Institute of Scientific and Technical Information of China (English)
CHEN Jiading; LI Ji
2006-01-01
For a class of data often arising in engineering,we have developed an approach to compute the lower confidence limit for structure reliability with a given confidence level.Especially,in a case with no failure and a case with only one failure,the concrete computational methods are presented.
Reliability Analysis of an Offshore Structure
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Thoft-Christensen, Palle; Rackwitz, R.
1992-01-01
A jacket type offshore structure from the North Sea is considered. The time variant reliability is estimated for failure defined as brittie fradure and crack through the tubular roerober walls. The stochastic modeiling is described. The hot spot stress speetral moments as fundion of the stochastic...
Lower bounds to the reliabilities of factor score estimators
Hessen, D.J.|info:eu-repo/dai/nl/256041717
2017-01-01
Under the general common factor model, the reliabilities of factor score estimators might be of more interest than the reliability of the total score (the unweighted sum of item scores). In this paper, lower bounds to the reliabilities of Thurstone’s factor score estimators, Bartlett’s factor score
Structural Reliability Sensitivities under Nonstationary Random Vibrations
Directory of Open Access Journals (Sweden)
Rita Greco
2013-01-01
Full Text Available Response sensitivity evaluation is an important element in reliability evaluation and design optimization of structural systems. It has been widely studied under static and dynamic forcing conditions with deterministic input data. In this paper, structural response and reliability sensitivities are determined by means of the time domain covariance analysis in both classically and nonclassically damped linear structural systems. A time integration scheme is proposed for covariance sensitivity. A modulated, filtered, white noise input process is adopted to model the stochastic nonstationary loads. The method allows for the evaluation of sensitivity statistics of different quantities of dynamic response with respect to structural parameters. Finally, numerical examples are presented regarding a multistorey shear frame building.
Arnau, Randolph C.; Broman-Fulks, Joshua J.; Green, Bradley A.; Berman, Mitchell E.
2009-01-01
The most commonly used measure of anxiety sensitivity is the 36-item Anxiety Sensitivity Index--Revised (ASI-R). Exploratory factor analyses have produced several different factors structures for the ASI-R, but an acceptable fit using confirmatory factor analytic approaches has only been found for a 21-item version of the instrument. We evaluated…
Arnau, Randolph C.; Broman-Fulks, Joshua J.; Green, Bradley A.; Berman, Mitchell E.
2009-01-01
The most commonly used measure of anxiety sensitivity is the 36-item Anxiety Sensitivity Index--Revised (ASI-R). Exploratory factor analyses have produced several different factors structures for the ASI-R, but an acceptable fit using confirmatory factor analytic approaches has only been found for a 21-item version of the instrument. We evaluated…
Reliability and Robustness Evaluation of Timber Structures
DEFF Research Database (Denmark)
Cizmar, Dean; Sørensen, John Dalsgaard; Kirkegaard, Poul Henning
In the last few decades there have been intensely research concerning reliability of timber structures. This is primarily because there is an increased focus on society on sustainability and environmental aspects. Modern timber as a building material is also being competitive compared to concrete...... parameters is given. System models (series and parallel) are discused and methods for reliability calculation are given. Special attention is drawn upon brittle/ductile modelling of timber and connections. In chapter 2 robustness requirements implemended in codes are presented. State of the art definitions...
Optimal Structural Reliability of Offshore Wind Turbines
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Tarp-Johansen, N.J.
2005-01-01
The main failure modes of modern large wind turbines are fatigue failure of wings, hub, shaft and main tower, local buckling of main tower, and failure of the foundation. This paper considers reliability-based optimal design of wind turbines. Compared to onshore wind turbines and building...... can be lower than for onshore wind turbines and other civil engineering structures and can be assessed by reliability-based cost-optimization. Specifically this paper considers the main tower and foundation. Both fatigue and ultimate strength failure modes are included. Different formulations...
SUPPORT VECTOR MACHINE FOR STRUCTURAL RELIABILITY ANALYSIS
Institute of Scientific and Technical Information of China (English)
LI Hong-shuang; L(U) Zhen-zhou; YUE Zhu-feng
2006-01-01
Support vector machine (SVM) was introduced to analyze the reliability of the implicit performance function, which is difficult to implement by the classical methods such as the first order reliability method (FORM) and the Monte Carlo simulation (MCS). As a classification method where the underlying structural risk minimization inference rule is employed, SVM possesses excellent learning capacity with a small amount of information and good capability of generalization over the complete data. Hence,two approaches, i.e., SVM-based FORM and SVM-based MCS, were presented for the structural reliability analysis of the implicit limit state function. Compared to the conventional response surface method (RSM) and the artificial neural network (ANN), which are widely used to replace the implicit state function for alleviating the computation cost,the more important advantages of SVM are that it can approximate the implicit function with higher precision and better generalization under the small amount of information and avoid the "curse of dimensionality". The SVM-based reliability approaches can approximate the actual performance function over the complete sampling data with the decreased number of the implicit performance function analysis (usually finite element analysis), and the computational precision can satisfy the engineering requirement, which are demonstrated by illustrations.
Fatigue Reliability of Deck Structures Subjected to Correlated Crack Growth
Institute of Scientific and Technical Information of China (English)
G.Q. Feng; Y. Garbatov; C. Guedes Soares
2013-01-01
The objective of this work is to analyse fatigue reliability of deck structures subjected to correlated crack growth. The stress intensity factors of the correlated cracks are obtained by finite element analysis and based on which the geometry correction functions are derived. The Monte Carlo simulations are applied to predict the statistical descriptors of correlated cracks based on the Paris-Erdogan equation. A probabilistic model of crack growth as a function of time is used to analyse the fatigue reliability of deck structures accounting for the crack propagation correlation. A deck structure is modelled as a series system of stiffened panels, where a stiffened panel is regarded as a parallel system composed of plates and are longitudinal. It has been proven that the method developed here can be conveniently applied to perform the fatigue reliability assessment of structures subjected to correlated crack growth.
Reliability Analysis of Elasto-Plastic Structures
DEFF Research Database (Denmark)
1984-01-01
. Failure of this type of system is defined either as formation of a mechanism or by failure of a prescribed number of elements. In the first case failure is independent of the order in which the elements fail, but this is not so by the second definition. The reliability analysis consists of two parts...... are described and the two definitions of failure can be used by the first formulation, but only the failure definition based on formation of a mechanism by the second formulation. The second part of the reliability analysis is an estimate of the failure probability for the structure on the basis...... are obtained if the failure mechanisms are used. Lower bounds can be calculated on the basis of series systems where the elements are the non-failed elements in a non-failed structure (see Augusti & Baratta [3])....
Reliability of redundant ductile structures with uncertain system failure criteria
Indian Academy of Sciences (India)
Baidurya Bhattacharya; Qiang Lu; Jinquan Zhong
2009-12-01
Current reliability based approaches to structural design are typically element based: they commonly include uncertainties in the structural resistance, applied loads and geometric parameters, and in some cases in the idealized structural model. Nevertheless, the true measure of safety is the structural systems reliability which must consider multiple failure paths, load sharing and load redistribution after member failures, and is beyond the domain of element reliability analysis. Identiﬁcation of system failure is often subjective, and a crisp deﬁnition of system failure arises naturally only in a few idealized instances equally important. We analyse the multi-girder steel highway bridge as a out of active parallel system. System failure is deﬁned as gross inelastic deformation of the bridge deck; the subjectivity in the failure criterion is accounted for by generalizing as a random variable. Randomness in arises from a non-unique relation between number of failed girders and maximum deﬂection and from randomness in the deﬁnition of the failure deﬂection. We show how uncertain failure criteria and structural systems analyses can be decoupled. Randomness in the transverse location of trucks is considered and elastic perfectly plastic material response is assumed. The role of the system factor modifying the element-reliability based design equation to achieve a target system reliability is also demonstrated.
Fatigue Reliability of Gas Turbine Engine Structures
Cruse, Thomas A.; Mahadevan, Sankaran; Tryon, Robert G.
1997-01-01
The results of an investigation are described for fatigue reliability in engine structures. The description consists of two parts. Part 1 is for method development. Part 2 is a specific case study. In Part 1, the essential concepts and practical approaches to damage tolerance design in the gas turbine industry are summarized. These have evolved over the years in response to flight safety certification requirements. The effect of Non-Destructive Evaluation (NDE) methods on these methods is also reviewed. Assessment methods based on probabilistic fracture mechanics, with regard to both crack initiation and crack growth, are outlined. Limit state modeling techniques from structural reliability theory are shown to be appropriate for application to this problem, for both individual failure mode and system-level assessment. In Part 2, the results of a case study for the high pressure turbine of a turboprop engine are described. The response surface approach is used to construct a fatigue performance function. This performance function is used with the First Order Reliability Method (FORM) to determine the probability of failure and the sensitivity of the fatigue life to the engine parameters for the first stage disk rim of the two stage turbine. A hybrid combination of regression and Monte Carlo simulation is to use incorporate time dependent random variables. System reliability is used to determine the system probability of failure, and the sensitivity of the system fatigue life to the engine parameters of the high pressure turbine. 'ne variation in the primary hot gas and secondary cooling air, the uncertainty of the complex mission loading, and the scatter in the material data are considered.
Calibrating ensemble reliability whilst preserving spatial structure
Directory of Open Access Journals (Sweden)
Jonathan Flowerdew
2014-03-01
Full Text Available Ensemble forecasts aim to improve decision-making by predicting a set of possible outcomes. Ideally, these would provide probabilities which are both sharp and reliable. In practice, the models, data assimilation and ensemble perturbation systems are all imperfect, leading to deficiencies in the predicted probabilities. This paper presents an ensemble post-processing scheme which directly targets local reliability, calibrating both climatology and ensemble dispersion in one coherent operation. It makes minimal assumptions about the underlying statistical distributions, aiming to extract as much information as possible from the original dynamic forecasts and support statistically awkward variables such as precipitation. The output is a set of ensemble members preserving the spatial, temporal and inter-variable structure from the raw forecasts, which should be beneficial to downstream applications such as hydrological models. The calibration is tested on three leading 15-d ensemble systems, and their aggregation into a simple multimodel ensemble. Results are presented for 12 h, 1° scale over Europe for a range of surface variables, including precipitation. The scheme is very effective at removing unreliability from the raw forecasts, whilst generally preserving or improving statistical resolution. In most cases, these benefits extend to the rarest events at each location within the 2-yr verification period. The reliability and resolution are generally equivalent or superior to those achieved using a Local Quantile-Quantile Transform, an established calibration method which generalises bias correction. The value of preserving spatial structure is demonstrated by the fact that 3×3 averages derived from grid-scale precipitation calibration perform almost as well as direct calibration at 3×3 scale, and much better than a similar test neglecting the spatial relationships. Some remaining issues are discussed regarding the finite size of the output
Neurology objective structured clinical examination reliability using generalizability theory.
Blood, Angela D; Park, Yoon Soo; Lukas, Rimas V; Brorson, James R
2015-11-03
This study examines factors affecting reliability, or consistency of assessment scores, from an objective structured clinical examination (OSCE) in neurology through generalizability theory (G theory). Data include assessments from a multistation OSCE taken by 194 medical students at the completion of a neurology clerkship. Facets evaluated in this study include cases, domains, and items. Domains refer to areas of skill (or constructs) that the OSCE measures. G theory is used to estimate variance components associated with each facet, derive reliability, and project the number of cases required to obtain a reliable (consistent, precise) score. Reliability using G theory is moderate (Φ coefficient = 0.61, G coefficient = 0.64). Performance is similar across cases but differs by the particular domain, such that the majority of variance is attributed to the domain. Projections in reliability estimates reveal that students need to participate in 3 OSCE cases in order to increase reliability beyond the 0.70 threshold. This novel use of G theory in evaluating an OSCE in neurology provides meaningful measurement characteristics of the assessment. Differing from prior work in other medical specialties, the cases students were randomly assigned did not influence their OSCE score; rather, scores varied in expected fashion by domain assessed. © 2015 American Academy of Neurology.
DEFF Research Database (Denmark)
Franchin, P.; Ditlevsen, Ove Dalager; Kiureghian, Armen Der
2002-01-01
The model correction factor method (MCFM) is used in conjunction with the first-order reliability method (FORM) to solve structural reliability problems involving integrals of non-Gaussian random fields. The approach replaces the limit-state function with an idealized one, in which the integrals...... are considered to be Gaussian. Conventional FORM analysis yields the linearization point of the idealized limit-state surface. A model correction factor is then introduced to push the idealized limit-state surface onto the actual limit-state surface. A few iterations yield a good approximation of the reliability...... reliability method; Model correction factor method; Nataf field integration; Non-Gaussion random field; Random field integration; Structural reliability; Pile foundation reliability...
Human Reliability Analysis for Design: Using Reliability Methods for Human Factors Issues
Energy Technology Data Exchange (ETDEWEB)
Ronald Laurids Boring
2010-11-01
This paper reviews the application of human reliability analysis methods to human factors design issues. An application framework is sketched in which aspects of modeling typically found in human reliability analysis are used in a complementary fashion to the existing human factors phases of design and testing. The paper provides best achievable practices for design, testing, and modeling. Such best achievable practices may be used to evaluate and human system interface in the context of design safety certifications.
Reliability of journal impact factor rankings
Directory of Open Access Journals (Sweden)
Greenwood Darren C
2007-11-01
Full Text Available Abstract Background Journal impact factors and their ranks are used widely by journals, researchers, and research assessment exercises. Methods Based on citations to journals in research and experimental medicine in 2005, Bayesian Markov chain Monte Carlo methods were used to estimate the uncertainty associated with these journal performance indicators. Results Intervals representing plausible ranges of values for journal impact factor ranks indicated that most journals cannot be ranked with great precision. Only the top and bottom few journals could place any confidence in their rank position. Intervals were wider and overlapping for most journals. Conclusion Decisions placed on journal impact factors are potentially misleading where the uncertainty associated with the measure is ignored. This article proposes that caution should be exercised in the interpretation of journal impact factors and their ranks, and specifically that a measure of uncertainty should be routinely presented alongside the point estimate.
System reliability in design and maintenance of fixed offshore structures
Energy Technology Data Exchange (ETDEWEB)
Dalane, J.I.
1993-05-01
Offshore structures are usually redundant, and several components must fail before structural collapse occurs. This work deals with system reliability for fatigue and overload of typical steel truss and frame structure such as jackets and jack-ups. The application of system reliability in design and maintenance is addressed. A formulation for a failure sequence of fatigue and overload is presented. The basic failure event for fatigue, is defined in terms of time to section failure. For overload, realistic failure criteria are applied. After an overload failure, the member replacement technique is used to account for the post collapse behavior. The branch and bound algorithm is used to identify important failure sequences, and system failure occur if any of these collapse sequences occur. The first order reliability methods are efficiently used to calculate the failure probabilities. In this work the importance of uncertainties in load and ultimate strength for a jacket and a jack-up structure is discussed. A joint environmental model for wave and current loading is applied. Ultimate capacity is calculated by nonlinear pushover analysis, and the uncertainties identified by Monte Carlo simulation. Fatigue may be an important failure mode for offshore structure, and in-service inspections are frequently performed. Underwater inspections are, however, very expensive and it is therefore important that the inspections are performed in such a way that they significantly increase our knowledge about the safety of the structure. In this work an inspection importance factor is defined. This importance factor can be used to identify the most important members in the system from an inspection point of view. Inspection for unexpected damages are also discussed. 122 refs., 72 figs., 50 tabs.
Structural Reliability Methods for Wind Power Converter System Component Reliability Assessment
DEFF Research Database (Denmark)
Kostandyan, Erik; Sørensen, John Dalsgaard
2012-01-01
is defined by the threshold model. The attention is focused on crack propagation in solder joints of electrical components due to the temperature loadings. Structural Reliability approaches are used to incorporate model, physical and statistical uncertainties. Reliability estimation by means of structural...
Reliability-Analysis of Offshore Structures using Directional Loads
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Bloch, Allan; Sterndorff, M. J.
2000-01-01
Reliability analyses of offshore structures such as steel jacket platforms are usually performed using stochastic models for the wave loads based on the omnidirectional wave height. However, reliability analyses with respect to structural failure modes such as total collapse of a structure...... heights from the central part of the North Sea. It is described how the stochastic model for the directional wave heights can be used in a reliability analysis where total collapse of offshore steel jacket platforms is considered....
Reliability estimation in a multilevel confirmatory factor analysis framework.
Geldhof, G John; Preacher, Kristopher J; Zyphur, Michael J
2014-03-01
Scales with varying degrees of measurement reliability are often used in the context of multistage sampling, where variance exists at multiple levels of analysis (e.g., individual and group). Because methodological guidance on assessing and reporting reliability at multiple levels of analysis is currently lacking, we discuss the importance of examining level-specific reliability. We present a simulation study and an applied example showing different methods for estimating multilevel reliability using multilevel confirmatory factor analysis and provide supporting Mplus program code. We conclude that (a) single-level estimates will not reflect a scale's actual reliability unless reliability is identical at each level of analysis, (b) 2-level alpha and composite reliability (omega) perform relatively well in most settings, (c) estimates of maximal reliability (H) were more biased when estimated using multilevel data than either alpha or omega, and (d) small cluster size can lead to overestimates of reliability at the between level of analysis. We also show that Monte Carlo confidence intervals and Bayesian credible intervals closely reflect the sampling distribution of reliability estimates under most conditions. We discuss the estimation of credible intervals using Mplus and provide R code for computing Monte Carlo confidence intervals.
Zimmermann, Grégoire; Mahaim, Elodie Biermann; Mantzouranis, Gregory; Genoud, Philippe A; Crocetti, Elisabetta
2012-04-01
The purpose of this study was to evaluate the factor structure and the reliability of the French versions of the Identity Style Inventory (ISI-3) and the Utrecht-Management of Identity Commitments Scale (U-MICS) in a sample of college students (N = 457, 18-25 years old). Confirmatory factor analyses confirmed the hypothesized three-factor solution of the ISI-3 identity styles (i.e. informational, normative, and diffuse-avoidant styles), the one-factor solution of the ISI-3 identity commitment, and the three-factor structure of the U-MICS (i.e. commitment, in-depth exploration, and reconsideration of commitment). Additionally, theoretically consistent and meaningful associations among the ISI-3, U-MICS, and Ego Identity Process Questionnaire (EIPQ) confirmed convergent validity. Overall, the results of the present study indicate that the French versions of the ISI-3 and UMICS are useful instruments for assessing identity styles and processes, and provide additional support to the cross-cultural validity of these tools.
Bayesian Network Enhanced with Structural Reliability Methods: Methodology
Straub, Daniel; Der Kiureghian, Armen
2012-01-01
We combine Bayesian networks (BNs) and structural reliability methods (SRMs) to create a new computational framework, termed enhanced Bayesian network (eBN), for reliability and risk analysis of engineering structures and infrastructure. BNs are efficient in representing and evaluating complex probabilistic dependence structures, as present in infrastructure and structural systems, and they facilitate Bayesian updating of the model when new information becomes available. On the other hand, SR...
[Factorial structure and reliability of Zimbardo Time Perspective Inventory].
Díaz-Morales, Juan Francisco
2006-08-01
Time orientation is a fundamental psychological variable, what it flows all aspects of human behaviour. Past, present, and future orientation decomposed of allocated into different temporal frames the continual flow of behaviour, providing meaning and coherence. It has been proposed the Zimbardo Time Perspective Inventory (ZTPI) so multidimensional measure of time orientation, which include positive and negative evaluation of past and present, as well as future evaluation. The factorial structure and reliability of ZTPI was analysed on Spanish adult population. The participants were 756 adults with age range 19-67 years old ( M = 40.1, SD = 15.45). The principal components analyses showed five factors, very similar to obtain on nort-american undergraduate samples, even thought a little difference in composition of the present-fatalist factor. The reliability of each factor was suitable. Age and gender differences analysis showed that older groups were more future oriented and less present hedonist, female were high orientation to past negative, past positive and present fatalist, while young females were more future oriented than older females.
Directory of Open Access Journals (Sweden)
Joan Boada-Grau
2013-03-01
Full Text Available En el presente artículo se estudian las propiedades psicométricas de la escala ELBus-21 que permite evaluar los estresores laborales que son propios de los conductores de autobuses españoles. Los participantes de la presente investigación son 287 conductores de autobuses (80.1% hombres y 19.9% mujeres de tres radios de acción: urbano, interurbano y discrecional. Los resultados obtenidos constatan, después de realizar un análisis factorial exploratorio de la escala, una estructura constituida por tres factores quehacen referencia a las condiciones del tráfico, a la sobrecarga y la fatiga, y a la falta de confort personal. Además, los tres factores obtenidos tienen una fiabilidad adecuada. Igualmente, se constatan indicios de validez de los tres factores si se toman como referencia el estrés, los trastornos psicofisiológicos, las conductas de seguridad en el vehículo, la autonomía en el puesto de trabajo y algunos correlatos empíricos. En suma, la presente escala puede resultar idónea para identificar de manera apropiada los estresores laborales en los conductores de autobuses españoles. La escala ELBus-21 puede ser utilizada como un inventario de screening en combinación con otros instrumentos.
Controllability and reliability issues related to electrorheological material adaptive structures
Energy Technology Data Exchange (ETDEWEB)
Shiang, A.; Coulter, J. [Lehigh Univ., Bethlehem, PA (United States). Mechanical Engineering and Mechanics--Packard Lab.
1994-12-31
The present investigation focused on the controllability and reliability of an electrorheological (ER) material filled adaptive beam. An AC ER material-filled composite beam was constructed and tested over a period of 500 hours. Attention was focused on changes in fundamental vibration frequencies and modal loss factor over the test period. Controllability in terms of beam vibration response time to both increasing and decreasing field strengths was also studied. Response times at the first two fundamental frequencies of 15 and 35 Hertz were focused on. The results indicated that at 35 Hertz, the structural response time was faster for both switching on and switching off of the electric field. In switching off the electric field, the structure returned to zero-field behavior within three seconds on all occasions. The duration of the electric field application did not affect beam response time.
Reliability Design in Structural Optimization - Literature Survey
Tapankov, Martin
2013-01-01
This survey focuses primarily on the historical development of RBDO and the various classes of methods which emerged through the years. While reviews on contemporary RBDO methods have been done previously, they haven’t incorporated the basis on which such developments were possible in the first place — risk-based design and limit-state design. This study attempts to link the RBDO field with these methodologies for a more complete picture of the field of reliability and safety. ProOpt
2004-01-01
Quisimos evaluar tanto la estructura factorial como la confiabilidad de la versión de 28 ítem del Cuestionario de Salud General (GHQ-28) en una muestra noclínica en El Salvador. Aplicamos el GHQ-28 a una muestra de 714 de alumnos universitarios en El Salvador. Utilizamos un análisis de componentes principales y seleccionamos una solución de 4 factores. Reaplicamos la prueba a un grupo de los participantes después de un promedio de 3 meses, para evaluar la confiabilidad de retes...
Theory of Economic Life Prediction and Reliability Assessment of Aircraft Structures
Institute of Scientific and Technical Information of China (English)
YAN Chuliang; LIU Kege
2011-01-01
The theory of economic life prediction and reliability assessment of aircraft structures has a significant effect on safety of aircraft structures.It is based on the two-stage theory of fatigue process and can guarantee the safety and reliability of structures.According to the fatigue damage process, the fatigue scatter factors of crack initiation stage and crack propagation stage are given respectively.At the same time, mathematical models of fatigue life prediction are presented by utilizing the fatigue scatter factors and full scale test results of aircraft structures.Furthermore, the economic life model is put forward.The model is of significant scientific value for products to provide longer economic life, higher reliability and lower cost.The theory of economic life prediction and reliability assessment of aircraft structures has been successfully applied to determining and extending the structural life for thousands of airplanes.
Nguyen, Trang Quynh; Poteat, Tonia; Bandeen-Roche, Karen; German, Danielle; Nguyen, Yen Hai; Vu, Loan Kieu-Chau; Nguyen, Nam Thi-Thu; Knowlton, Amy R.
2016-01-01
We developed the first Vietnamese internalized homophobia (IH) scale, for use with Vietnamese sexual minority women (SMW). Drawing from existing IH scales in the international literature and based on prior qualitative research about SMW in the Viet Nam context, the scale covers two domains: self-stigma (negative attitudes toward oneself as a sexual minority person) and sexual prejudice (negative attitudes toward homosexuality/same-sex relations in general). Scale items, including items borrowed from existing scales and items based on local expressions, were reviewed and confirmed by members of the target population. Quantitative evaluation used data from an anonymous web-based survey of Vietnamese SMW, including those who identified as lesbian (n=1187), or as bisexual (n=641) and those who were unsure about their sexual identity (n=353). The scale was found to consist of two highly correlated factors reflecting self-stigma (not normal/wholesome and self-reproach and wishing away same-sex sexuality) and one factor reflecting sexual prejudice, and to have excellent internal consistency. Construct validity was evidenced by subscales’ associations with a wide range of hypothesized correlates including perceived sexual stigma, outness, social support, connection to other SMW, relationship quality, psychological well-being, anticipation of heterosexual marriage and endorsement of same-sex marriage legalization. Self-stigma was more strongly associated with psychosocial correlates and sexual prejudice was more associated with endorsement of legal same-sex marriage. The variations in these associations across the hypothesized correlates and across sexual identity groups were consistent with the Minority Stress Model and the IH literature, and exhibited context-specific features, which are discussed. PMID:27007469
Reliability of Elasto-Plastic Structural Systems
DEFF Research Database (Denmark)
Delmar, M. V.; Sørensen, John Dalsgaard
1990-01-01
This paper proposes a method for generating safety margins and failure mode equations for elasto-plastic structures where interaction of load effects is taken into account. Structural failure is defined by large nodal displacements or plastic collapse. A branch-and-bound technique is used...
Reliability of stiffened structural panels: Two examples
Stroud, W. Jefferson; Davis, D. Dale, Jr.; Maring, Lise D.; Krishnamurthy, Thiagaraja; Elishakoff, Isaac
1992-12-01
The reliability of two graphite-epoxy stiffened panels that contain uncertainties is examined. For one panel, the effect of an overall bow-type initial imperfection is studied. The size of the bow is assumed to be a random variable. The failure mode is buckling. The benefits of quality control are explored by using truncated distributions. For the other panel, the effect of uncertainties in a strain-based failure criterion is studied. The allowable strains are assumed to be random variables. A geometrically nonlinear analysis is used to calculate a detailed strain distribution near an elliptical access hole in a wing panel that was tested to failure. Calculated strains are used to predict failure. Results are compared with the experimental failure load of the panel.
Green, Samuel B.; Yang, Yanyun
2009-01-01
A method is presented for estimating reliability using structural equation modeling (SEM) that allows for nonlinearity between factors and item scores. Assuming the focus is on consistency of summed item scores, this method for estimating reliability is preferred to those based on linear SEM models and to the most commonly reported estimate of…
Online cognition: factors facilitating reliable online neuropsychological test results.
Feenstra, Heleen E M; Vermeulen, Ivar E; Murre, Jaap M J; Schagen, Sanne B
2017-01-01
Online neuropsychological test batteries could allow for large-scale cognitive data collection in clinical studies. However, the few online neuropsychological test batteries that are currently available often still require supervision or lack proper psychometric evaluation. In this paper, we have outlined prerequisites for proper development and use of online neuropsychological tests, with the focus on reliable measurement of cognitive function in an unmonitored setting. First, we identified several technical, contextual, and psychological factors that should be taken into account in order to facilitate reliable test results of online tests in the unmonitored setting. Second, we outlined a methodology of quality assurance needed in order to obtain reliable cognitive data in the long run. Based on factors that distinguish the online unmonitored test setting from the traditional face-to-face setting, we provide a set of basic requirements and suggestions for optimal development and use of unmonitored online neuropsychological tests, including suggestions on acquiring reliability, validity, and norm scores. When properly addressing factors that could hamper reliable test results during development and use, online neuropsychological tests could aid large-scale data collection for clinical studies in the future. Investment in both proper development of online neuropsychological test platforms and the performance of accompanying psychometric studies is currently required.
Directory of Open Access Journals (Sweden)
Pat Gibbons
2004-01-01
Full Text Available Quisimos evaluar tanto la estructura factorial como la confiabilidad de la versión de 28 ítem del Cuestionario de Salud General (GHQ-28 en una muestra noclínica en El Salvador. Aplicamos el GHQ-28 a una muestra de 714 de alumnos universitarios en El Salvador. Utilizamos un análisis de componentes principales y seleccionamos una solución de 4 factores. Reaplicamos la prueba a un grupo de los participantes después de un promedio de 3 meses, para evaluar la confiabilidad de retest del instrumento y calculamos la confiabilidad interna del GHQ-28 a través de la prueba alfa de Cronbach. Los resultados del análisis factorial correspondieron estrechamente con la estructura factorial antes identificada, aunque encontramos una correlación más alta entre las escalas, sobre todo entre Ansiedad e insomnio y Somatización. La fiabilidad test-retest y la consistencia interna alcanzaron valores de 0,70 o superiores. Los resultados del análisis factorial indican una gran coincidencia con las conclusiones de otros entornos culturales, lo que apoya la hipótesis de Goldberg de que hay una manera común de comunicar angustia psicológica en culturas distintas. Las escalas de Depresión severa y de Disfunción social parecen ser relativamente estables e independientes, mientras que las de Ansiedad e insomnio y de Somatización se correlacionan más. La fiabilidad del instrumento es satisfactoria.
Reliability prediction for structures under cyclic loads and recurring inspections
Directory of Open Access Journals (Sweden)
Alberto W. S. Mello Jr
2009-06-01
Full Text Available This work presents a methodology for determining the reliability of fracture control plans for structures subjected to cyclic loads. It considers the variability of the parameters involved in the problem, such as initial flaw and crack growth curve. The probability of detection (POD curve of the field non-destructive inspection method and the condition/environment are used as important factors for structural confidence. According to classical damage tolerance analysis (DTA, inspection intervals are based on detectable crack size and crack growth rate. However, all variables have uncertainties, which makes the final result totally stochastic. The material properties, flight loads, engineering tools and even the reliability of inspection methods are subject to uncertainties which can affect significantly the final maintenance schedule. The present methodology incorporates all the uncertainties in a simulation process, such as Monte Carlo, and establishes a relationship between the reliability of the overall maintenance program and the proposed inspection interval, forming a “cascade” chart. Due to the scatter, it also defines the confidence level of the “acceptable” risk. As an example, the damage tolerance analysis (DTA results are presented for the upper cockpit longeron splice bolt of the BAF upgraded F-5EM. In this case, two possibilities of inspection intervals were found: one that can be characterized as remote risk, with a probability of failure (integrity nonsuccess of 1 in 10 million, per flight hour; and other as extremely improbable, with a probability of nonsuccess of 1 in 1 billion, per flight hour, according to aviation standards. These two results are compared with the classical military airplane damage tolerance requirements.
A Note on Structural Equation Modeling Estimates of Reliability
Yang, Yanyun; Green, Samuel B.
2010-01-01
Reliability can be estimated using structural equation modeling (SEM). Two potential problems with this approach are that estimates may be unstable with small sample sizes and biased with misspecified models. A Monte Carlo study was conducted to investigate the quality of SEM estimates of reliability by themselves and relative to coefficient…
Reliability Analysis of Structural Timber Systems
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Hoffmeyer, P.
2000-01-01
characteristics of the load-bearing capacity is estimated in the form of a characteristic value and a coefficient of variation. These two values are of primary importance for codes of practice based on the partial safety factor format since the partial safety factor is closely related to the coefficient...... the above stochastic models, statistical characteristics (distribution function, 5% quantile and coefficient of variation) are determined. Generally, the results show that taking the system effects into account the characteristic load bearing capacity can be increased and the partial safety factor decreased...... of variation. In the paper a stochastic model is described for the strength of a single piece of timber taking into account the stochastic variation of the strength and stiffness with length. Also stochastic models for different types of loads are formulated. First, simple representative systems with different...
Reliability analysis of ship structure system with multi-defects
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
This paper analyzes the influence of multi-defects including the initial distortions,welding residual stresses,cracks and local dents on the ultimate strength of the plate element,and has worked out expressions of reliability calculation and sensitivity analysis of the plate element.Reliability analysis is made for the system with multi-defects plate elements.Failure mechanism,failure paths and the calculating approach to global reliability index are also worked out.After plate elements with multi-defects fail,the formula of reverse node forces which affect the residual structure is deduced,so are the sensitivity expressions of the system reliability index.This ensures calculating accuracy and rationality for reliability analysis,and makes it convenient to find weakness plate elements which affect the reliability of the structure system.Finally,for the validity of the approach proposed,we take the numerical example of a ship cabin to compare and contrast the reliability and the sensitivity analysis of the structure system with multi-defects with those of the structure system with no defects.The approach has implications for the structure design,rational maintenance and renewing strategy.
Reliability based Design of Coastal Structures
DEFF Research Database (Denmark)
Burcharth, H. F.
2003-01-01
, for example the expectation (mean) value of the 100-year return period event. However, this selection is often made without consideration of the involved uncertainties. In most cases the resistance is defined in terms of the load that causes a certain design impact or damage to the structure...
Nonlinear system identification in offshore structural reliability
Energy Technology Data Exchange (ETDEWEB)
Spanos, P.D. [Rice Univ., Houston, TX (United States); Lu, R. [Hudson Engineering Corporation, Houston, TX (United States)
1995-08-01
Nonlinear forces acting on offshore structures are examined from a system identification perspective. The nonlinearities are induced by ocean waves and may become significant in many situations. They are not necessarily in the form of Morison`s equation. Various wave force models are examined. The force function is either decomposed into a set of base functions or it is expanded in terms of the wave and structural kinematics. The resulting nonlinear system is decomposed into a number of parallel no-memory nonlinear systems, each followed by a finite-memory linear system. A conditioning procedure is applied to decouple these linear sub-systems; a frequency domain technique involving autospectra and cross-spectra is employed to identify the linear transfer functions. The structural properties and those force transfer parameters are determine with the aid of the coherence functions. The method is verified using simulated data. It provides a versatile and noniterative approach for dealing with nonlinear interaction problems encountered in offshore structural analysis and design.
Quantifiable and Reliable Structural Health Management Systems Project
National Aeronautics and Space Administration — Major concerns for implementing a practical built-in structural health monitoring system are prediction accuracy and data reliability. It is proposed to develop...
Reliability sensitivity-based correlation coefficient calculation in structural reliability analysis
Yang, Zhou; Zhang, Yimin; Zhang, Xufang; Huang, Xianzhen
2012-05-01
The correlation coefficients of random variables of mechanical structures are generally chosen with experience or even ignored, which cannot actually reflect the effects of parameter uncertainties on reliability. To discuss the selection problem of the correlation coefficients from the reliability-based sensitivity point of view, the theory principle of the problem is established based on the results of the reliability sensitivity, and the criterion of correlation among random variables is shown. The values of the correlation coefficients are obtained according to the proposed principle and the reliability sensitivity problem is discussed. Numerical studies have shown the following results: (1) If the sensitivity value of correlation coefficient ρ is less than (at what magnitude 0.000 01), then the correlation could be ignored, which could simplify the procedure without introducing additional error. (2) However, as the difference between ρ s, that is the most sensitive to the reliability, and ρ R , that is with the smallest reliability, is less than 0.001, ρ s is suggested to model the dependency of random variables. This could ensure the robust quality of system without the loss of safety requirement. (3) In the case of | E abs|>0.001 and also | E rel|>0.001, ρ R should be employed to quantify the correlation among random variables in order to ensure the accuracy of reliability analysis. Application of the proposed approach could provide a practical routine for mechanical design and manufactory to study the reliability and reliability-based sensitivity of basic design variables in mechanical reliability analysis and design.
Review of Industrial Applications of Structural Reliability Theory
DEFF Research Database (Denmark)
Thoft-Christensen, Palle
For the last two decades we have seen an increasing interest in applying structural reliability theory to many different industries. However, the number of real practical applications is much smaller than what one would expect.......For the last two decades we have seen an increasing interest in applying structural reliability theory to many different industries. However, the number of real practical applications is much smaller than what one would expect....
Reliability Evaluation of Structure at Sea
DEFF Research Database (Denmark)
Burcharth, H. F.
1994-01-01
formulae are semi-empirical being based mainly on central fitting to model test results. The often considerable scatter in test results is not considered in general because the formulae normally express only the mean values. Consequently, the applied characteristic value of the resistance is then the mean...... force or deformation. This is because most of the available design formulae only give the relationship between wave characteristics and structural response, e.g. in terms of run-up, overtopping, armour layer damage etc. An example is the Hudson formula for armour layer stability. Almost all such design...
Reliability Evaluation of a Structure at Sea
DEFF Research Database (Denmark)
Burcharth, H. F.
1992-01-01
formulae are semi-empirical being based mainly on central fitting to model test results. The often considerable scatter in test results is not considered in general because the formulae normally express only the mean values. Consequently, the applied characteristic value of the resistance is then the mean...... force or deformation. This is because most of the available design formulae only give the relationship between wave characteristics and structural response, e.g. in terms of run-up, overtopping, armour layer damage etc. An example is the Hudson formula for armour layer stability. Almost all such design...
Reliability Evaluation of a Structure at Sea
DEFF Research Database (Denmark)
Burcharth, H. F.
1994-01-01
formulae are semi-empirical being based mainly on central fitting to model test results. The often considerable scatter in test results is not considered in general because the formulae normally express only the mean values. Consequently, the applied characteristic value of the resistance is then the mean...... force or deformation. This is because most of the available design formulae only give the relationship between wave characteristics and structural response, e.g. in terms of run-up, overtopping, armour layer damage etc. An example is the Hudson formula for armour layer stability. Almost all such design...
[Aging and spirituality: Factorial structure and reliability of 2 scales].
Galiana, Laura; Sancho, Patricia; Oliver, Amparo; Tomás, José Manuel; Calatayud, Pablo
2016-01-01
In the field of gerontology, the study of the improvement of health and quality of life, and «successfully aging», spirituality plays a key role and, is one of the current research approaches. However, its incorporation into scientific literature is arduous and slow, a fact that is in part due to the absence of developed and validated measurement tools, particularly, in the Spanish speaking area. This work aims to present evidence of the psychometric properties of two tools for the measurement of spirituality: the Functional Assessment of Chronic Illness Therapy Spiritual Well-Being (FACIT-Sp) and the GES Questionnaire. A sample of 224 elderly persons from Valencia (Spain) was recruited, on which two confirmatory factor analyses were estimated, with the proposed a priori structures for each tool, together with several reliability coefficients. Both models presented an good fit to the data: χ(2)51=104.97 (P.05); CFI=.996; RMSEA=.050 for the GES Questionnaire. Reliability indices also supported the use of the scales in elderly population, with alphas of .85 and .86, respectively. These results may be useful as a starting point to include spirituality in works that aim to discover the mechanisms involved in successful aging. Copyright © 2016 SEGG. Publicado por Elsevier España, S.L.U. All rights reserved.
Stochastic Finite Elements in Reliability-Based Structural Optimization
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Engelund, S.
1995-01-01
Application of stochastic finite elements in structural optimization is considered. It is shown how stochastic fields modelling e.g. the modulus of elasticity can be discretized in stochastic variables and how a sensitivity analysis of the reliability of a structural system with respect to optimi......Application of stochastic finite elements in structural optimization is considered. It is shown how stochastic fields modelling e.g. the modulus of elasticity can be discretized in stochastic variables and how a sensitivity analysis of the reliability of a structural system with respect...
Stochastic Finite Elements in Reliability-Based Structural Optimization
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Engelund, S.
Application of stochastic finite elements in structural optimization is considered. It is shown how stochastic fields modelling e.g. the modulus of elasticity can be discretized in stochastic variables and how a sensitivity analysis of the reliability of a structural system with respect to optimi......Application of stochastic finite elements in structural optimization is considered. It is shown how stochastic fields modelling e.g. the modulus of elasticity can be discretized in stochastic variables and how a sensitivity analysis of the reliability of a structural system with respect...
Integrated Reliability-Based Optimal Design of Structures
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Thoft-Christensen, Palle
1987-01-01
the reliability decreases with time it is often necessary to design an inspection and repair programme. For example the reliability of offshore steel structures decreases with time due to corrosion and development of fatigue cracks. Until now most inspection and repair strategies are based on experience rather......In conventional optimal design of structural systems the weight or the initial cost of the structure is usually used as objective function. Further, the constraints require that the stresses and/or strains at some critical points have to be less than some given values. Finally, all variables...... and parameters are assumed to be deterministic quantities. In this paper a probabilistic formulation is used. Some of the quantities specifying the load and the strength of the structure are modelled as random variables, and the constraints specify that the reliability of the structure has to exceed some given...
structural reliability of the nigerian grown abura timber bridge beam ...
African Journals Online (AJOL)
ENGR. J. I. AGUWA
2013-07-02
Jul 2, 2013 ... Structural reliability analysis was carried out on the Nigerian grown Abura timber, to ascertain its structural ... wall sheeting, formwork and furniture. The ... reinforced concrete members. ... fulfill certain performance criteria related to safety and ..... Plastic Structures” First Edition, Mir Publishers. Moscow ...
Methods for reliability based design optimization of structural components
Dersjö, Tomas
2012-01-01
Cost and quality are key properties of a product, possibly even the two most important. Onedefinition of quality is fitness for purpose. Load-bearing products, i.e. structural components,loose their fitness for purpose if they fail. Thus, the ability to withstand failure is a fundamentalmeasure of quality for structural components. Reliability based design optimization(RBDO) is an approach for development of structural components which aims to minimizethe cost while constraining the probabili...
Requalification of offshore structures. Reliability analysis of platform
Energy Technology Data Exchange (ETDEWEB)
Bloch, A.; Dalsgaard Soerensen, J. [Aalborg Univ. (Denmark)
1999-03-01
A preliminary reliability analysis has been performed for an example platform. In order to model the structural response such that it is possible to calculate reliability indices, approximate quadratic response surfaces have been determined for cross-sectional forces. Based on a deterministic, code-based analysis the elements and joints which can be expected to be the most critical are selected and response surfaces are established for the cross-sectional forces in those. A stochastic model is established for the uncertain variables. The reliability analysis shows that with this stochastic model the smallest reliability indices for elements are about 3.9. The reliability index for collapse (pushover) is estimated to 6.7 and the reliability index for fatigue failure using a crude model is for the expected most critical detail estimated to 3.2, corresponding to the accumulated damage during the design lifetime of the platform. These reliability indices are considered to be reasonable compared with values recommended by e.g. ISO. The most important stochastic variables are found to be the wave height and the drag coefficient (including the model uncertainty related to estimation of wave forces on the platform). (au)
Structural Reliability of Plain Bearings for Wave Energy Converter Applications
DEFF Research Database (Denmark)
Ambühl, Simon; Kramer, Morten Mejlhede; Sørensen, John Dalsgaard
2016-01-01
The levelized cost of energy (LCOE) from wave energy converters (WECs) needs to be decreased in order to be able to become competitive with other renewable electricity sources. Probabilistic reliability methods can be used to optimize the structure of WECs. Optimization is often performed...... the hydraulic cycle when waves are passing. The new PTO system leads to different load characteristics at the floater itself compared to the actual setup where the turbine/generator is directly coupled to the fluctuating hydraulic pressure within the PTO system. This paper calculates the structural reliability...
Structural Reliability Aspects in Design of Wind Turbines
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard
2007-01-01
Reliability assessment, optimal design and optimal operation and maintenance of wind turbines are an area of significant interest for the fast growing wind turbine industry for sustainable production of energy. Offshore wind turbines in wind farms give special problems due to wake effects inside...... turbines are described. Further, aspects are presented related to reliability-based optimization of wind turbines, assessment of optimal reliability level and operation and maintenance....... the farm. Reliability analysis and optimization of wind turbines require that the special conditions for wind turbine operation are taken into account. Control of the blades implies load reductions for large wind speeds and parking for high wind speeds. In this paper basic structural failure modes for wind...
Fatigue reliability and calibration of fatigue design factors of wave energy converters
DEFF Research Database (Denmark)
Ambühl, Simon; Ferri, Francesco; Kofoed, Jens Peter
2015-01-01
Target reliability levels, which are chosen dependent on the consequences in case of structural collapse, are used in this paper to calibrate partial safety factors for structural details of wave energy converters (WECs). The consequences in case of structural failure are similar for WECs...... and offshore wind turbines (no fatalities, low environmental pollution). Therefore, it can be assumed that the target reliability levels for WEC applications can be overtaken from offshore wind turbine studies. The partial safety factors cannot be directly overtaken from offshore wind turbines because the load...... is considered in order to extend and maintain a certain target safety level. This paper uses the Wavestar prototype located at Hanstholm (DK) as case study in order to calibrate FDFs for welded and bolted details in steel structures of an offshore bottom-fixed WEC with hydraulic floaters....
Risk-based Optimization and Reliability Levels of Coastal Structures
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Burcharth, Hans F.
2005-01-01
Identification of optimum reliability levels for coastal structures is considered. A class of breakwaters is considered where no human injuries can be expected in cases of failure. The optimum reliability level is identified by minimizing the total costs over the service life of the structure......, including building costs, maintenance and repair costs, downtime costs and decommission costs. Different formulations are considered. Stochastic models are presented for the main failure modes for rubble mound breakwaters without superstructures, typically used for outer protection of basins. The influence...... on the minimumcost reliability levels is investigated for different values of the real rate of interest, the service lifetime, the downtime costs due to malfunction and the decommission costs....
Risk-based Optimization and Reliability Levels of Coastal Structures
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Burcharth, H. F.
Identification of optimum reliability levels for coastal structures is considered. A class of breakwaters is considered where no human injuries can be expected in cases of failure. The optimum reliability level is identified by minimizing the total costs over the service life of the structure......, including building costs, maintenance and repair costs, downtime costs and decommission costs. Different formulations are considered. Stochastic models are presented for the main failure modes for rubble mound breakwaters without superstructures, typically used for outer protection of basins. The influence...... on the minimumcost reliability levels is investigated for different values of the real rate of interest, the service lifetime, the downtime costs due to malfunction and the decommission costs....
Human reliability, error, and human factors in power generation
Dhillon, B S
2014-01-01
Human reliability, error, and human factors in the area of power generation have been receiving increasing attention in recent years. Each year billions of dollars are spent in the area of power generation to design, construct/manufacture, operate, and maintain various types of power systems around the globe, and such systems often fail due to human error. This book compiles various recent results and data into one volume, and eliminates the need to consult many diverse sources to obtain vital information. It enables potential readers to delve deeper into a specific area, providing the source of most of the material presented in references at the end of each chapter. Examples along with solutions are also provided at appropriate places, and there are numerous problems for testing the reader’s comprehension. Chapters cover a broad range of topics, including general methods for performing human reliability and error analysis in power plants, specific human reliability analysis methods for nuclear power pl...
Interactive Reliability-Based Optimization of Structural Systems
DEFF Research Database (Denmark)
Pedersen, Claus
In order to introduce the basic concepts within the field of reliability-based structural optimization problems, this chapter is devoted to a brief outline of the basic theories. Therefore, this chapter is of a more formal nature and used as a basis for the remaining parts of the thesis. In secti...
Design of a Human Reliability Assessment model for structural engineering
De Haan, J.; Terwel, K.C.; Al-Jibouri, S.H.S.
2013-01-01
It is generally accepted that humans are the “weakest link” in structural design and construction processes. Despite this, few models are available to quantify human error within engineering processes. This paper demonstrates the use of a quantitative Human Reliability Assessment model within struct
Generating function approach to reliability analysis of structural systems
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
The generating function approach is an important tool for performance assessment in multi-state systems. Aiming at strength reliability analysis of structural systems, generating function approach is introduced and developed. Static reliability models of statically determinate, indeterminate systems and fatigue reliability models are built by constructing special generating functions, which are used to describe probability distributions of strength (resistance), stress (load) and fatigue life, by defining composite operators of generating functions and performance structure functions thereof. When composition operators are executed, computational costs can be reduced by a big margin by means of collecting like terms. The results of theoretical analysis and numerical simulation show that the generating function approach can be widely used for probability modeling of large complex systems with hierarchical structures due to the unified form, compact expression, computer program realizability and high universality. Because the new method considers twin loads giving rise to component failure dependency, it can provide a theoretical reference and act as a powerful tool for static, dynamic reliability analysis in civil engineering structures and mechanical equipment systems with multi-mode damage coupling.
Reliability-Based Inspection Planning for Structural Systems
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard
1993-01-01
A general model for reliability-based optimal inspection and repair strategies for structural systems is described. The total expected costs in the design lifetime is minimized with the number of inspections, the inspection times and efforts as decision variables. The equivalence of this model wi...
The reliability of the Structured Interview for Schizotypy-Revised
Vollema, MG; Ormel, J
2000-01-01
We investigated the reliability of the Structured Interview for Schizotypy-Revised (SIS-R). The original interview (SIS) was developed by Kendler, We revised the SIS, primarily by standardizing the rating procedures. Operational definitions and explicit criteria for rating were given. We introduced
The Seismic Reliability of Offshore Structures Based on Nonlinear Time History Analyses
Hosseini, Mahmood; Karimiyani, Somayyeh; Ghafooripour, Amin; Jabbarzadeh, Mohammad Javad
2008-07-01
Regarding the past earthquakes damages to offshore structures, as vital structures in the oil and gas industries, it is important that their seismic design is performed by very high reliability. Accepting the Nonlinear Time History Analyses (NLTHA) as the most reliable seismic analysis method, in this paper an offshore platform of jacket type with the height of 304 feet, having a deck of 96 feet by 94 feet, and weighing 290 million pounds has been studied. At first, some Push-Over Analyses (POA) have been preformed to recognize the more critical members of the jacket, based on the range of their plastic deformations. Then NLTHA have been performed by using the 3-components accelerograms of 100 earthquakes, covering a wide range of frequency content, and normalized to three Peak Ground Acceleration (PGA) levels of 0.3 g, 0.65 g, and 1.0 g. By using the results of NLTHA the damage and rupture probabilities of critical member have been studied to assess the reliability of the jacket structure. Regarding that different structural members of the jacket have different effects on the stability of the platform, an "importance factor" has been considered for each critical member based on its location and orientation in the structure, and then the reliability of the whole structure has been obtained by combining the reliability of the critical members, each having its specific importance factor.
OPTIMUM DESIGN BASED ON RELIABILITY IN STOCHASTIC STRUCTURE SYSTEMS
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
The optimum design method based on the reliability is presented to the stochastic structure systems (i. e., the sectional area, length, elastic module and strength of the structural member are random variables) under the random loads. The sensitivity expression of system reliability index and the safety margins were presented in the stochastic structure systems. The optimum vector method was given. First, the expressions of the reliability index of the safety margins with the improved first-order second-moment and the stochastic finite element method were deduced, and then the expressions of the systemic failure probability by probabilistic network evaluation technique(PNET) method were obtained. After derivation calculus, the expressions of the sensitivity analysis for the system reliability were obtained. Moreover, the optimum design with the optimum vector algorithm was undertaken. In the optimum iterative procedure, the gradient step and the optimum vector step were adopted to calculate. At the last, a numerical example was provided to illustrate that the method is efficient in the calculation, stably converges and fits the application in engineering.
MEMS Reliability: Infrastructure, Test Structures, Experiments, and Failure Modes
Energy Technology Data Exchange (ETDEWEB)
TANNER,DANELLE M.; SMITH,NORMAN F.; IRWIN,LLOYD W.; EATON,WILLIAM P.; HELGESEN,KAREN SUE; CLEMENT,J. JOSEPH; MILLER,WILLIAM M.; MILLER,SAMUEL L.; DUGGER,MICHAEL T.; WALRAVEN,JEREMY A.; PETERSON,KENNETH A.
2000-01-01
The burgeoning new technology of Micro-Electro-Mechanical Systems (MEMS) shows great promise in the weapons arena. We can now conceive of micro-gyros, micro-surety systems, and micro-navigators that are extremely small and inexpensive. Do we want to use this new technology in critical applications such as nuclear weapons? This question drove us to understand the reliability and failure mechanisms of silicon surface-micromachined MEMS. Development of a testing infrastructure was a crucial step to perform reliability experiments on MEMS devices and will be reported here. In addition, reliability test structures have been designed and characterized. Many experiments were performed to investigate failure modes and specifically those in different environments (humidity, temperature, shock, vibration, and storage). A predictive reliability model for wear of rubbing surfaces in microengines was developed. The root causes of failure for operating and non-operating MEMS are discussed. The major failure mechanism for operating MEMS was wear of the polysilicon rubbing surfaces. Reliability design rules for future MEMS devices are established.
Reliability and Hierarchical Structure of DSM-5 Pathological Traits in a Danish Mixed Sample
DEFF Research Database (Denmark)
Bo, Sune; Bach, Bo; Mortensen, Erik Lykke
2016-01-01
In this study we assessed the DSM-5 trait model in a large Danish sample (n = 1,119) with respect to reliability of the applied Danish version of the Personality Inventory for DSM-5 (PID-5) self-report form by means of internal consistency and item discrimination. In addition, we tested whether...... the five-factor structure of the DSM-5 trait model can be replicated in a Danish independent sample using the PID-5 self-report form. Finally, we examined the hierarchical structure of DSM-5 traits. In terms of internal consistency and item discrimination, the applied PID-5 scales were generally found...... reliable and functional; our data resembled the five-factor structure of previous findings, and we identified a hierarchical structure from one to five factors that was conceptually reasonable and corresponded with existing findings. These results support the new DSM-5 trait model and suggest that it can...
Reliability and factor validity of a Farsi version of The Positive and Negative Perfectionism Scale.
Besharat, Mohammad Ali
2009-08-01
This study investigated reliability and factor validity of a Farsi version of the Positive and Negative Perfectionism Scale in 606 undergraduate students (257 men, 349 women) from the University of Tehran. All participants were asked to complete the scale, along with the General Health Questionnaire (Goldberg, 1972) and the Coopersmith Self-Esteem Inventory (Coopersmith, 1967). Findings indicated good internal consistency, test-retest reliability, and construct validity of the two-factor structure of the Farsi version of the Positive and Negative Perfectionism Scale. These factors were similar to the factors found in previous studies and were accordingly labeled Positive Perfectionism and Negative Perfectionism. The results provide evidence for applicability of the scale and its cross-cultural validity.
Institute of Scientific and Technical Information of China (English)
JIN Wei-liang; HU Qi-zhong; SHEN Zhao-wei; SHI Zhong-min
2009-01-01
For the fulfillment of the probability-based structural design for the offshore jacket platforms in the Bohai Bay, the design factors of loads, resistance and load combinations are much necessary to be calibrated according to the proposed target reliability index. Firstly, the limit states function for the offshore jacket platforms is introduced. Then, four ap-proaches to calibrate the factors of load and resistance are presented and compared. Afterwards, the methods to calibrate the load combination factors are developed. Finally, the factors of load, resistance and load combination for the offshore jacket platforms in the Bohai Bay are calibrated and the corresponding design formulae are recommended. The results are proved to be rational in practice, and also illustrate that the proposed target reliability index for offshore jacket platforms in the Bohai Bay is also appropriate.
Structural Reliability of Plain Bearings for Wave Energy Converter Applications
Directory of Open Access Journals (Sweden)
Simon Ambühl
2016-02-01
Full Text Available The levelized cost of energy (LCOE from wave energy converters (WECs needs to be decreased in order to be able to become competitive with other renewable electricity sources. Probabilistic reliability methods can be used to optimize the structure of WECs. Optimization is often performed for critical structural components, like welded details, bolts or bearings. This paper considers reliability studies with a focus on plain bearings available from stock for the Wavestar device, which exists at the prototype level. The Wavestar device is a point absorber WEC. The plan is to mount a new power take-off (PTO system consisting of a discrete displacement cylinder (DDC, which will allow different hydraulic cycles to operate at constant pressure levels. This setup increases the conversion efficiency, as well as decouples the electricity production from the pressure variations within the hydraulic cycle when waves are passing. The new PTO system leads to different load characteristics at the floater itself compared to the actual setup where the turbine/generator is directly coupled to the fluctuating hydraulic pressure within the PTO system. This paper calculates the structural reliability of the different available plain bearings planned to be mounted at the new PTO system based on a probabilistic approach, and the paper gives suggestions for fulfilling the minimal target reliability levels. The considered failure mode in this paper is the brittle fatigue failure of plain bearings. The performed sensitivity analysis shows that parameters defining the initial crack size have a big impact on the resulting reliability of the plain bearing.
Barbaranelli, Claudio; Lee, Christopher S; Vellone, Ercole; Riegel, Barbara
2014-12-01
The Self-Care of Heart Failure Index (SCHFI) is used widely, but issues with reliability have been evident. Cronbach alpha coefficient is usually used to assess reliability, but this approach assumes a unidimensional scale. The purpose of this article is to address the dimensionality and internal consistency reliability of the SCHFI. This was a secondary analysis of data from 629 adults with heart failure enrolled in three separate studies conducted in the northeastern and northwestern United States. Following testing for scale dimensionality using confirmatory factor analysis, reliability was tested using coefficient alpha and alternative options. Confirmatory factor analysis demonstrated that: (a) the Self-Care Maintenance Scale has a multidimensional four-factor structure; (b) the Self-Care Management Scale has a two-factor structure, but the primary factors loaded on a common higher-order factor; and (c) the Self-Care Confidence Scale is unidimensional. Reliability estimates for the three scales, obtained with methods compatible with each scale's dimensionality, were adequate or high. The results of the analysis demonstrate that issues of dimensionality and reliability cannot be separated. Appropriate estimates of reliability that are consistent with the dimensionality of the scale must be used. In the case of the SCHFI, coefficient alpha should not be used to assess reliability of the self-care maintenance and the self-care management scales, due to their multidimensionality. When performing psychometric evaluations, we recommend testing dimensionality before assessing reliability, as well using multiple indices of reliability, such as model-based internal consistency, composite reliability, and omega and maximal reliability coefficients. © 2014 Wiley Periodicals, Inc.
Position Mooring Control Based on a Structural Reliability Criterion
DEFF Research Database (Denmark)
Fang, Shaoji; Leira, Bernt J.; Blanke, Mogens
2013-01-01
is achieved using structural reliability indices in a cost function, where both the mean mooring-line tension and dynamic effects are considered. An optimal set-point is automatically produced without need for manual interaction. The parameters of the extreme value distribution are calculated on-line thereby...... adapting the set-point calculations to the prevailing environment. In contrast to earlier approaches, several mooring line are simultaneously accounted for by the algorithm, not only the most critical one. Detailed simulations illustrate the features of the new method and it is shown that the structural...... reliability criterion based algorithm ensures the safety of mooring lines in a variety of external environmental conditions and also in situations of failure of a single line....
Reliability and optimization, application to safety of aircraft structures
Chu, Liu
2016-01-01
Tremendous struggles of researchers in the field of aerodynamic design and aircraft production were made to improve wing airfoil by optimization techniques. The development of computational fluid dynamic (CFD) in computer simulation cuts the expense of aerodynamic experiment while provides convincing results to simulate complicated situation of aircraft. In our work, we chose a special and important part of aircraft, namely, the structure of wing.Reliability based optimization is one of the m...
Reliability Analysis of Jacket Platforms in Malaysia-Environmental Load Factors
Directory of Open Access Journals (Sweden)
Nelson J. Cossa
2012-09-01
Full Text Available In recent years, there has been a significant trend for adoption of the ISO-19902 standards for design of fixed steel offshore structures. The implementation of this standard aims to provide a harmonized international framework of design. Unlike, the traditional and currently used, WSD-method, the ISO-19902, follows the LRFD-method, that consists of both partial load and resistance factors. These partial factors are usually calibrated through reliability analysis. In these analyses, the performance of a structure is defined by the limit state function for the critical mode of failure. This paper, focuses mainly on the ultimate (strength limit state which is directly related to the (highest environmental loading. The partial environmental load factors contained in the ISO 19902, were calibrated for the Gulf of Mexico and UK's North Sea conditions, which are relatively harsh than those in Malaysia. The study presents the steps taken for the determination of the environmental load factor for tubular members of jacket platforms in Malaysia. The factor was determined such that the reliability of tubular members of jacket designed as per the LRFD-method is at the level of target reliability obtained by the WSD-method.
Yu, Bo; Ning, Chao-lie; Li, Bing
2017-03-01
A probabilistic framework for durability assessment of concrete structures in marine environments was proposed in terms of reliability and sensitivity analysis, which takes into account the uncertainties under the environmental, material, structural and executional conditions. A time-dependent probabilistic model of chloride ingress was established first to consider the variations in various governing parameters, such as the chloride concentration, chloride diffusion coefficient, and age factor. Then the Nataf transformation was adopted to transform the non-normal random variables from the original physical space into the independent standard Normal space. After that the durability limit state function and its gradient vector with respect to the original physical parameters were derived analytically, based on which the first-order reliability method was adopted to analyze the time-dependent reliability and parametric sensitivity of concrete structures in marine environments. The accuracy of the proposed method was verified by comparing with the second-order reliability method and the Monte Carlo simulation. Finally, the influences of environmental conditions, material properties, structural parameters and execution conditions on the time-dependent reliability of concrete structures in marine environments were also investigated. The proposed probabilistic framework can be implemented in the decision-making algorithm for the maintenance and repair of deteriorating concrete structures in marine environments.
Structural Optimization for Reliability Using Nonlinear Goal Programming
El-Sayed, Mohamed E.
1999-01-01
This report details the development of a reliability based multi-objective design tool for solving structural optimization problems. Based on two different optimization techniques, namely sequential unconstrained minimization and nonlinear goal programming, the developed design method has the capability to take into account the effects of variability on the proposed design through a user specified reliability design criterion. In its sequential unconstrained minimization mode, the developed design tool uses a composite objective function, in conjunction with weight ordered design objectives, in order to take into account conflicting and multiple design criteria. Multiple design criteria of interest including structural weight, load induced stress and deflection, and mechanical reliability. The nonlinear goal programming mode, on the other hand, provides for a design method that eliminates the difficulty of having to define an objective function and constraints, while at the same time has the capability of handling rank ordered design objectives or goals. For simulation purposes the design of a pressure vessel cover plate was undertaken as a test bed for the newly developed design tool. The formulation of this structural optimization problem into sequential unconstrained minimization and goal programming form is presented. The resulting optimization problem was solved using: (i) the linear extended interior penalty function method algorithm; and (ii) Powell's conjugate directions method. Both single and multi-objective numerical test cases are included demonstrating the design tool's capabilities as it applies to this design problem.
Time-dependent reliability analysis and condition assessment of structures
Energy Technology Data Exchange (ETDEWEB)
Ellingwood, B.R. [Johns Hopkins Univ., Baltimore, MD (United States)
1997-01-01
Structures generally play a passive role in assurance of safety in nuclear plant operation, but are important if the plant is to withstand the effect of extreme environmental or abnormal events. Relative to mechanical and electrical components, structural systems and components would be difficult and costly to replace. While the performance of steel or reinforced concrete structures in service generally has been very good, their strengths may deteriorate during an extended service life as a result of changes brought on by an aggressive environment, excessive loading, or accidental loading. Quantitative tools for condition assessment of aging structures can be developed using time-dependent structural reliability analysis methods. Such methods provide a framework for addressing the uncertainties attendant to aging in the decision process.
Reliability-Based Structural Optimization of Wave Energy Converters
DEFF Research Database (Denmark)
Ambühl, Simon; Kramer, Morten; Sørensen, John Dalsgaard
2014-01-01
More and more wave energy converter (WEC) concepts are reaching prototype level. Once the prototype level is reached, the next step in order to further decrease the levelized cost of energy (LCOE) is optimizing the overall system with a focus on structural and maintenance (inspection) costs......, as well as on the harvested power from the waves. The target of a fully-developed WEC technology is not maximizing its power output, but minimizing the resulting LCOE. This paper presents a methodology to optimize the structural design of WECs based on a reliability-based optimization problem...
How Reliable is the Durability of RC Structures?
Directory of Open Access Journals (Sweden)
B. Teplý
2004-01-01
Full Text Available The goal of this paper is to show some trends and time profiles of the reliability index relevant to the Serviceability Limit State considering the design service life of RC structures. The interactive web page “RC_LifeTime” – originated by the authors – is used (see http://www.stm.fce.vutbr.cz/. The depassivation of reinforcing steel due to carbonation is considered conservatively as a limiting condition. It is based on model concrete carbonation with 12 random input variables; the Latin Hypercube Sampling simulation method is used. RC_LifeTime offers the following options: Service Life Assessment – a statistical evaluation of service life, where optionally the target value of reliability index ß may be an additional input value and then the corresponding service life is the output value; Concrete Cover Assessment – a statistical evaluation of concrete cover value for the target service life, where optionally the required concrete cover value may be input in this case and the relevant reliability index ß describes the reliability of reinforcement depassivation.
Spinal appearance questionnaire: factor analysis, scoring, reliability, and validity testing.
Carreon, Leah Y; Sanders, James O; Polly, David W; Sucato, Daniel J; Parent, Stefan; Roy-Beaudry, Marjolaine; Hopkins, Jeffrey; McClung, Anna; Bratcher, Kelly R; Diamond, Beverly E
2011-08-15
Cross sectional. This study presents the factor analysis of the Spinal Appearance Questionnaire (SAQ) and its psychometric properties. Although the SAQ has been administered to a large sample of patients with adolescent idiopathic scoliosis (AIS) treated surgically, its psychometric properties have not been fully evaluated. This study presents the factor analysis and scoring of the SAQ and evaluates its psychometric properties. The SAQ and the Scoliosis Research Society-22 (SRS-22) were administered to AIS patients who were being observed, braced or scheduled for surgery. Standard demographic data and radiographic measures including Lenke type and curve magnitude were also collected. Of the 1802 patients, 83% were female; with a mean age of 14.8 years and mean initial Cobb angle of 55.8° (range, 0°-123°). From the 32 items of the SAQ, 15 loaded on two factors with consistent and significant correlations across all Lenke types. There is an Appearance (items 1-10) and an Expectations factor (items 12-15). Responses are summed giving a range of 5 to 50 for the Appearance domain and 5 to 20 for the Expectations domain. The Cronbach's α was 0.88 for both domains and Total score with a test-retest reliability of 0.81 for Appearance and 0.91 for Expectations. Correlations with major curve magnitude were higher for the SAQ Appearance and SAQ Total scores compared to correlations between the SRS Appearance and SRS Total scores. The SAQ and SRS-22 Scores were statistically significantly different in patients who were scheduled for surgery compared to those who were observed or braced. The SAQ is a valid measure of self-image in patients with AIS with greater correlation to curve magnitude than SRS Appearance and Total score. It also discriminates between patients who require surgery from those who do not.
Reliability of a jacket structure in a tropical cyclone environment
Energy Technology Data Exchange (ETDEWEB)
Vanderschuren, L.; Efthymiou, M.; Tromans, P.S.; Graaf, J.W. van de
1996-12-31
The annual probability of failure due to extreme storm loading is calculated for a manned production platform installed about ten years ago in a tropical cyclone environment. Statistics of extreme loads are generated from a hindcast study using a random storm method. This method was originally developed for winter storms and has been extended, here, to treat tropical cyclones. Non-linear pushover analysis is used to evaluate the ultimate strength of the structure. The likelihood of structural failure is determined as the probability that the load vector will extend beyond the failure surface of the structure. The results indicate adequate reliability. The study highlights some features of this tropical cyclone environment and compares and contrasts them with the North Sea which is dominated by winter storms. An important element of the conventional practice outside US waters has been to use as a design condition separate extrapolations of 100 year wind, 100 year wave and 100 year current. It is demonstrated that conventional practice has resulted in significantly overdesigned structures in winter storm environments such as the North Sea. However, for tropical cyclone environments, it has produced structures of sufficient reliability but with relatively little overdesign.
Temporal reliability of cytokines and growth factors in EDTA plasma
Directory of Open Access Journals (Sweden)
Marrangoni Adele M
2010-11-01
Full Text Available Abstract Background Cytokines are involved in the development of chronic diseases, including cancer. It is important to evaluate the temporal reproducibility of cytokines in plasma prior to conducting epidemiologic studies utilizing these markers. Findings We assessed the temporal reliability of CRP, 22 cytokines and their soluble receptors (IL-1α, IL-1β, IL-1RA, IL-2, sIL-2R, IL-4, IL-5, IL-6, sIL-6R, IL-7, IL-8, IL-10, IL-12p40, IL-12p70, IL-13, IL-15, IL-17, TNFα, sTNF-R1, sTNF-R2, IFNα, IFNγ and eight growth factors (GM-CSF, EGF, bFGF, G-CSF, HGF, VEGF, EGFR, ErbB2 in repeated EDTA plasma samples collected an average of two years apart from 18 healthy women (age range: 42-62 enrolled in a prospective cohort study. We also estimated the correlation between serum and plasma biomarker levels using 18 paired clinical samples from postmenopausal women (age range: 75-86. Twenty-six assays were able to detect their analytes in at least 70% of samples. Of those 26 assays, we observed moderate to high intra-class correlation coefficients (ICCs(ranging from 0.53-0.89 for 22 assays, and low ICCs (0-0.47 for four assays. Serum and plasma levels were highly correlated (r > 0.6 for most markers, except for seven assays (r Conclusions For 22 of the 31 biomarkers, a single plasma measurement is a reliable estimate of a woman's average level over a two-year period.
Extreme value distribution and reliability of nonlinear stochastic structures
Institute of Scientific and Technical Information of China (English)
Chen Jianbing; Li Jie
2005-01-01
A new approach to evaluate the extreme value distribution (EVD) of the response and reliability of general multi-DOF nonlinear stochastic structures is proposed. The approach is based on the recently developed probability density evolution method, which enables the instantaneous probability density functions of the stochastic responses to be captured.In the proposed method, a virtual stochastic process is first constructed to satisfy the condition that the extreme value of the response equals the value of the constructed process at a certain instant of time. The probability density evolution method is then applied to evaluate the instantaneous probability density function of the response, yielding the EVD. The reliability is therefore available through a simple integration over the safe domain. A numerical algorithm is developed using the Number Theoretical Method to select the discretized representative points. Further, a hyper-ball is imposed to sieve the points from the preceding point set in the hypercube. In the numerical examples, the EVD of random variables is evaluated and compared with the analytical solution. A frame structure is analyzed to capture the EVD of the response and the dynamic reliability. The investigations indicate that the proposed approach provides reasonable accuracy and efficiency.
Directory of Open Access Journals (Sweden)
Hai An
2016-08-01
Full Text Available Aiming to resolve the problems of a variety of uncertainty variables that coexist in the engineering structure reliability analysis, a new hybrid reliability index to evaluate structural hybrid reliability, based on the random–fuzzy–interval model, is proposed in this article. The convergent solving method is also presented. First, the truncated probability reliability model, the fuzzy random reliability model, and the non-probabilistic interval reliability model are introduced. Then, the new hybrid reliability index definition is presented based on the random–fuzzy–interval model. Furthermore, the calculation flowchart of the hybrid reliability index is presented and it is solved using the modified limit-step length iterative algorithm, which ensures convergence. And the validity of convergent algorithm for the hybrid reliability model is verified through the calculation examples in literature. In the end, a numerical example is demonstrated to show that the hybrid reliability index is applicable for the wear reliability assessment of mechanisms, where truncated random variables, fuzzy random variables, and interval variables coexist. The demonstration also shows the good convergence of the iterative algorithm proposed in this article.
Reliability-Based Structural Optimization of Wave Energy Converters
Directory of Open Access Journals (Sweden)
Simon Ambühl
2014-12-01
Full Text Available More and more wave energy converter (WEC concepts are reaching prototypelevel. Once the prototype level is reached, the next step in order to further decrease thelevelized cost of energy (LCOE is optimizing the overall system with a focus on structuraland maintenance (inspection costs, as well as on the harvested power from the waves.The target of a fully-developed WEC technology is not maximizing its power output,but minimizing the resulting LCOE. This paper presents a methodology to optimize thestructural design of WECs based on a reliability-based optimization problem and the intentto maximize the investor’s benefits by maximizing the difference between income (e.g., fromselling electricity and the expected expenses (e.g., structural building costs or failure costs.Furthermore, different development levels, like prototype or commercial devices, may havedifferent main objectives and will be located at different locations, as well as receive varioussubsidies. These points should be accounted for when performing structural optimizationsof WECs. An illustrative example on the gravity-based foundation of the Wavestar deviceis performed showing how structural design can be optimized taking target reliability levelsand different structural failure modes due to extreme loads into account.
Reliability-Based Inspection Planning for Structural Systems
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard
1993-01-01
A general model for reliability-based optimal inspection and repair strategies for structural systems is described. The total expected costs in the design lifetime is minimized with the number of inspections, the inspection times and efforts as decision variables. The equivalence of this model...... with a preposterior analysis from statistical decision theory is discussed. It is described how information obtained by an inspection can be used in a repair decision. Stochastic models for inspection, measurement and repair actions are presented. The general model is applied for inspection and repair planning...
Directory of Open Access Journals (Sweden)
NARGES VASEGHI
2013-07-01
Full Text Available Introduction: Objective Structured Clinical Examination (OSCE is one of the most appropriate methods for assessment of clinical skills.Validity and reliability assurance is a mandatory factor for any assessment tool. In Shiraz University of Medical Sciences, medical students’ clinical competences are evaluated by a pre-internship OSCE. This study is designed to examine the validity and reliability of this exam. Validity is the extent to which the test measures what it intends to measure. Reliability refers to the accuracy of measurement and the consistency of test results. Methods: Content validity was evaluated by expert opinion about blueprinting and station checklists. To determine the construct validity, station scores correlation with the total OSCE score and inter station correlations were calculated. The inter examiner reliability was assessed by coefficient of correlation. Results: Content validity was established by alignment between the curriculum and the blueprint using expert opinion. Correlation of the station scores with the total OSCE score were positive and statistically significant in all stations except the 16th station (suturing. Inter examiner reliability coefficients of correlations ranged 0.33 – 0.99, with an average of 0.83. Conclusions: Our findings support the assumption that the pre-internship OSCE is valid, reliable and suitable to assess students’ clinical competence. Validity and reliability studies should be performed for all new assessment tools, particularly in high-stakes assessments.
Structural vulnerability assessment using reliability of slabs in avalanche area
Favier, Philomène; Bertrand, David; Eckert, Nicolas; Naaim, Mohamed
2013-04-01
Improvement of risk assessment or hazard zoning requires a better understanding of the physical vulnerability of structures. To consider natural hazard issue such as snow avalanches, once the flow is characterized, highlight on the mechanical behaviour of the structure is a decisive step. A challenging approach is to quantify the physical vulnerability of impacted structures according to various avalanche loadings. The main objective of this presentation is to introduce methodology and outcomes regarding the assessment of vulnerability of reinforced concrete buildings using reliability methods. Reinforced concrete has been chosen as it is one of the usual material used to build structures exposed to potential avalanche loadings. In avalanche blue zones, structures have to resist to a pressure up to 30kPa. Thus, by providing systematic fragility relations linked to the global failure of the structure, this method may serve the avalanche risk assessment. To do so, a slab was numerically designed. It represented the avalanche facing wall of a house. Different configuration cases of the element in stake have been treated to quantify numerical aspects of the problem, such as the boundary conditions or the mechanical behaviour of the structure. The structure is analysed according to four different limit states, semi-local and global failures are considered to describe the slab behaviour. The first state is attained when cracks appear in the tensile zone, then the two next states are described consistent with the Eurocode, the final state is the total collapse of the structure characterized by the yield line theory. Failure probability is estimated in accordance to the reliability framework. Monte Carlo simulations were conducted to quantify the fragility to different loadings. Sensitivity of models in terms of input distributions were defined with statistical tools such as confidence intervals and Sobol's indexes. Conclusion and discussion of this work are established to
Time-domain seismic reliability of nonlinear structures
Indian Academy of Sciences (India)
Achintya Haldar; Jungwon Huh; Ali Mehrabian
2006-08-01
A novel reliability analysis technique is presented to estimate the reliability of real structural systems. Its unique feature is that the dynamic loadings can be applied in time domain. It is a nonlinear stochastic ﬁnite element logarithm combined with the response surface method (RSM). It generates the response surface around the most probable failure point and incorporates information of the distribution of the random variables in the RSM formulation. It is veriﬁed using the Monte Carlo simulation technique, and is found to be very efﬁcient and accurate. Most sources of nonlinearlity and uncertainty can be explicitly incorporated in the formulation. The ﬂexibility of connections, represented by moment-relative rotation $(M–\\theta )$ curves, is addressed. After the Northridge earthquake of 1994, several improved steel connections were proposed. Structural Sesimic Design Associates (SSDA) tested several full-scale proprietory slotted web beam–column connections. The authors suggested $(M–\\theta )$ curves for this connection using actual test data. Behaviours of steel frames, assuming the connections are fully restrained, partially restrained, consisting of pre- and post-Northridge connections are evaluated and compared. Desirable features of the post-Northridge connections observed during testing are analytically conﬁrmed. Laterally weak steel frame is then strengthened with concrete shear walls. Capabilities and the advanced nature of the method are demonstrated with the help of realistic examples.
Reliability Analysis of Tubular Joints in Offshore Structures
DEFF Research Database (Denmark)
Thoft-Christensen, Palle; Sørensen, John Dalsgaard
1987-01-01
Reliability analysis of single tubular joints and offshore platforms with tubular joints is" presented. The failure modes considered are yielding, punching, buckling and fatigue failure. Element reliability as well as systems reliability approaches are used and illustrated by several examples....... Finally, optimal design of tubular.joints with reliability constraints is discussed and illustrated by an example....
Fracture-Safe and Fatigue-Reliable Structures
Directory of Open Access Journals (Sweden)
M. N. James
2014-10-01
Full Text Available Learning from history is, by popular account, something at which human beings are not particularly good; George Bernard Shaw having stated that “we learn from history that we learn nothing from history”, while the Spanish philosopher George Santayana apparently claimed that “those who cannot learn from history are doomed to repeat it”.1 This is certainly true in the field of structural integrity where, some 150 years after the first full-scale structural fatigue tests were carried out, fracture-safe and fatigue-reliable design can be achieved to a statistical probability in complex and sophisticated structures, such as aircraft. Alongside this, however, failures of large, and expensive, welded structures can still occur from such simple causes as inadequate communication, and lack of awareness of the importance of the design of structural details to the overall fatigue life and failure. This paper considers several examples of such difficulties in the context of the development of fatigue design philosophies and the success or otherwise of learning from the history of failures.
Reliability-Based Optimal Design for Very Large Floating Structure
Institute of Scientific and Technical Information of China (English)
ZHANG Shu-hua(张淑华); FUJIKUBO Masahiko
2003-01-01
Costs and losses induced by possible future extreme environmental conditions and difficulties in repairing post-yielding damage strongly suggest the need for proper consideration in design rather than just life loss prevention. This can be addressed through the development of design methodology that balances the initial cost of the very large floating structure (VLFS) against the expected potential losses resulting from future extreme wave-induced structural damage. Here, the development of a methodology for determining optimal, cost-effective design will be presented and applied to a VLFS located in the Tokyo bay. Optimal design criteria are determined based on the total expected life-cycle cost and acceptable damage probability and curvature of the structure, and a set of sizes of the structure are obtained. The methodology and applications require expressions of the initial cost and the expected life-cycle damage cost as functions of the optimal design variables. This study includes the methodology, total life-cycle cost function, structural damage modeling, and reliability analysis.
DEFF Research Database (Denmark)
Dimitrov, Nikolay Krasimirov; Friis-Hansen, Peter; Berggreen, Christian
2013-01-01
Reliability analysis of fiber-reinforced composite structures is a relatively unexplored field, and it is therefore expected that engineers and researchers trying to apply such an approach will meet certain challenges until more knowledge is accumulated. While doing the analyses included...... in the present paper, the authors have experienced some of the possible pitfalls on the way to complete a precise and robust reliability analysis for layered composites. Results showed that in order to obtain accurate reliability estimates it is necessary to account for the various failure modes described...... by the composite failure criteria. Each failure mode has been considered in a separate component reliability analysis, followed by a system analysis which gives the total probability of failure of the structure. The Model Correction Factor method used in connection with FORM (First-Order Reliability Method) proved...
Reliability of Mechanical Structures with Considering Seismic Loading
Directory of Open Access Journals (Sweden)
Drahomír RYCHECKÝ
2013-06-01
Full Text Available The paper deals with summarization of methods used in seismic response evaluation of mechanical structures. The seismic evaluation of structures is inseparable condition in the design of hazardous facilities such as nuclear power plants. Based on demanded results, different methods can be used. For instance, when the anchorage of the structure is determinative, the equivalent static method (ESM can be advantageously used. To evaluate complex seismic response of a large mechanical structure the ESM is un-sufficient and e.g. for steady-state response of the structure the response spectrum method (RSM can be employed [3]. The RSM combines the response based on known mode shapes. Applying direct time-history (accelerogram is also possibility but time consuming. The paper contains definition of seismic safety factor for determining safety reserve of structures. All methods are applied on a sample example. Obtained results of each method are compared and discussed.
Fasce H, Eduardo; Pérez V, Cristhian; Ortiz M, Liliana; Parra P, Paula; Matus B, Olga
2011-11-01
Continuous education is crucial among physicians. Therefore, medical schools must teach self-directed learning skills to their students. To evaluate the factorial structure and reliability of the Spanish version of the Self-Directed Learning Readiness Scale of Fisher, King & Tague, applied to medical students. The survey was answered by 330 students aged between 17 and 26years (58% men, with 10 missing cases). Factorial structure, internal reliability and temporary stability of scale was evaluated. The Exploratory Factorial Analysis, conducted using a principal factor method, identified five factors in the structure of the survey. Internal consistency was adequate with a Cronbach's alpha between 0.66 and 0.88. Test retest reliability, comparing the results of the survey applied six months after the first application, showed Pearson correlation coefficients that fluctuated between 0.399 and 0.68. These results show a defined factorial structure with adequate reliability of the survey.
A damage mechanics based approach to structural deterioration and reliability
Energy Technology Data Exchange (ETDEWEB)
Bhattcharya, B.; Ellingwood, B. [Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Civil Engineering
1998-02-01
Structural deterioration often occurs without perceptible manifestation. Continuum damage mechanics defines structural damage in terms of the material microstructure, and relates the damage variable to the macroscopic strength or stiffness of the structure. This enables one to predict the state of damage prior to the initiation of a macroscopic flaw, and allows one to estimate residual strength/service life of an existing structure. The accumulation of damage is a dissipative process that is governed by the laws of thermodynamics. Partial differential equations for damage growth in terms of the Helmholtz free energy are derived from fundamental thermodynamical conditions. Closed-form solutions to the equations are obtained under uniaxial loading for ductile deformation damage as a function of plastic strain, for creep damage as a function of time, and for fatigue damage as function of number of cycles. The proposed damage growth model is extended into the stochastic domain by considering fluctuations in the free energy, and closed-form solutions of the resulting stochastic differential equation are obtained in each of the three cases mentioned above. A reliability analysis of a ring-stiffened cylindrical steel shell subjected to corrosion, accidental pressure, and temperature is performed.
Fatigue Reliability and Calibration of Fatigue Design Factors for Offshore Wind Turbines
DEFF Research Database (Denmark)
Dominguez, Sergio Marquez; Sørensen, John Dalsgaard
2012-01-01
Consequences of failure of offshore wind turbines (OWTs) are in general lower than consequences of failure of, e.g., oil & gas platforms. It is reasonable that lower fatigue design factors can be applied for fatigue design of OWTs when compared to other fixed offshore structures. Calibration...... is discussed and results are presented for calibrated optimal fatigue design factors. Further, the influence of inspections is considered in order to extend and maintain a given target safety level....... of appropriate partial safety factors/Fatigue Design Factors (FDF) for steel substructures for OWTs is the scope of this paper. A reliability-based approach is used and a probabilistic model has been developed, where design and limit state equations are established for fatigue failure. The strength and load...
Reliability prediction of large fuel cell stack based on structure stress analysis
Liu, L. F.; Liu, B.; Wu, C. W.
2017-09-01
The aim of this paper is to improve the reliability of Proton Electrolyte Membrane Fuel Cell (PEMFC) stack by designing the clamping force and the thickness difference between the membrane electrode assembly (MEA) and the gasket. The stack reliability is directly determined by the component reliability, which is affected by the material property and contact stress. The component contact stress is a random variable because it is usually affected by many uncertain factors in the production and clamping process. We have investigated the influences of parameter variation coefficient on the probability distribution of contact stress using the equivalent stiffness model and the first-order second moment method. The optimal contact stress to make the component stay in the highest level reliability is obtained by the stress-strength interference model. To obtain the optimal contact stress between the contact components, the optimal thickness of the component and the stack clamping force are optimally designed. Finally, a detailed description is given how to design the MEA and gasket dimensions to obtain the highest stack reliability. This work can provide a valuable guidance in the design of stack structure for a high reliability of fuel cell stack.
Fan, Xiao-Ning; Zhi, Bo
2017-07-01
Uncertainties in parameters such as materials, loading, and geometry are inevitable in designing metallic structures for cranes. When considering these uncertainty factors, reliability-based design optimization (RBDO) offers a more reasonable design approach. However, existing RBDO methods for crane metallic structures are prone to low convergence speed and high computational cost. A unilevel RBDO method, combining a discrete imperialist competitive algorithm with an inverse reliability strategy based on the performance measure approach, is developed. Application of the imperialist competitive algorithm at the optimization level significantly improves the convergence speed of this RBDO method. At the reliability analysis level, the inverse reliability strategy is used to determine the feasibility of each probabilistic constraint at each design point by calculating its α-percentile performance, thereby avoiding convergence failure, calculation error, and disproportionate computational effort encountered using conventional moment and simulation methods. Application of the RBDO method to an actual crane structure shows that the developed RBDO realizes a design with the best tradeoff between economy and safety together with about one-third of the convergence speed and the computational cost of the existing method. This paper provides a scientific and effective design approach for the design of metallic structures of cranes.
ADJUSTMENT FACTORS AND ADJUSTMENT STRUCTURE
Institute of Scientific and Technical Information of China (English)
Tao Benzao
2003-01-01
In this paper, adjustment factors J and R put forward by professor Zhou Jiangwen are introduced and the nature of the adjustment factors and their role in evaluating adjustment structure is discussed and proved.
Mindock, Jennifer
The ability of crewmembers to perform various critical functions during spacecraft operations is widely recognized as being essential to mission success. This necessity motivates the desire to better characterize factors that can influence crewmember performance so that those with positive effects can be enhanced, while those with negative impacts can be minimized. Established Human Reliability Analysis methods exist for analyzing performance within the context of myriad terrestrial scenarios. Many of the existing methods have their roots in nuclear power plant operations. While perhaps similar, the factors influencing performance traditionally used in these methods do not take into account the unique conditions encountered during spaceflight. Therefore, this research has identified a tailored set of factors that influence human task performance during space missions. This thesis describes an organizational scheme developed to aid in classifying and communicating the factors across disciplines and organizations. Definitions of identified factors are given for the spaceflight-specific context. A visual display of the factors, called the Contributing Factor Map, is presented and its use as a risk communication tool is discussed. The Bayesian Network is discussed as a quantification approach allowing relationships between factors, in addition to the factor relationships to performance outcomes, to be modeled. A method for determining a network structure was developed for domains such as human spaceflight, in which a global set of data for analysis is not available. This method applied the Analytic Hierarchy Process, and causal latency concepts from the Human Factors Analysis and Classification System in a novel way to guide choices for modeling the dominant set of factors and relationships in a simplified Bayesian Network structure. In addition, an approach for modeling the factors as statistical variables in a Bayesian Network making use of existing design
Institute of Scientific and Technical Information of China (English)
AN WeiGuang; ZHAO WeiTao; AN Hai
2007-01-01
Multi-failures are possible to appear in the process of using the structural system,such as dead load failure, fatigue failure and stiffness failure. The expression of residual resistance is given based on the impact of random crack propagation induced by the fatigue load on the critical limit stress and section modulus in this paper. The failure modes of every element of the structural system are analyzed under dead and fatigue loads, and the influence of the correlation of failure modes on reliability of the element is considered. Failure mechanism and the correlation of failure modes under dead and fatigue loads are discussed, and the method of reliability analysis considering static strength, fatigue and stiffness is given. A numerical example is analyzed, which indicates that the failure probability is different for different use life and the influence of dead and fatigue loads on reliability of the structural system is different as well. This method of reliability analysis, in the paper, is better than the method only considering a single factor (or static strength, or fatigue, or stiffness, etc.) in the case of practical engineering.
Fatigue Reliability and Calibration of Fatigue Design Factors for Offshore Wind Turbines
Directory of Open Access Journals (Sweden)
Sergio Márquez-Domínguez
2012-06-01
Full Text Available Consequences of failure of offshore wind turbines (OWTs is in general lower than consequences of failure of, e.g., oil & gas platforms. It is reasonable that lower fatigue design factors can be applied for fatigue design of OWTs when compared to other fixed offshore structures. Calibration of appropriate partial safety factors/Fatigue Design Factors (FDF for steel substructures for OWTs is the scope of this paper. A reliability-based approach is used and a probabilistic model has been developed, where design and limit state equations are established for fatigue failure. The strength and load uncertainties are described by stochastic variables. SN and fracture mechanics approaches are considered for to model the fatigue life. Further, both linear and bi-linear SN-curves are formulated and various approximations are investigated. The acceptable reliability level for fatigue failure of OWTs is discussed and results are presented for calibrated optimal fatigue design factors. Further, the influence of inspections is considered in order to extend and maintain a given target safety level.
Directory of Open Access Journals (Sweden)
Marco Innamorati
2014-01-01
Full Text Available Objectives and Methods. The aim of the study was to investigate the construct validity of the ARSQ. Methods. The ARSQ and self-report measures of depression, anxiety, and hopelessness were administered to 774 Italian adults, aged 18 to 64 years. Results. Structural equation modeling indicated that the factor structure of the ARSQ can be represented by a bifactor model: a general rejection sensitivity factor and two group factors, expectancy of rejection and rejection anxiety. Reliability of observed scores was not satisfactory: only 44% of variance in observed total scores was due to the common factors. The analyses also indicated different correlates for the general factor and the group factors. Limitations. We administered an Italian version of the ARSQ to a nonclinical sample of adults, so that studies which use clinical populations or the original version of the ARSQ could obtain different results from those presented here. Conclusion. Our results suggest that the construct validity of the ARSQ is disputable and that rejection anxiety and expectancy could bias individuals to readily perceive and strongly react to cues of rejection in different ways.
Bast, Callie C.; Jurena, Mark T.; Godines, Cody R.; Chamis, Christos C. (Technical Monitor)
2001-01-01
This project included both research and education objectives. The goal of this project was to advance innovative research and education objectives in theoretical and computational probabilistic structural analysis, reliability, and life prediction for improved reliability and safety of structural components of aerospace and aircraft propulsion systems. Research and education partners included Glenn Research Center (GRC) and Southwest Research Institute (SwRI) along with the University of Texas at San Antonio (UTSA). SwRI enhanced the NESSUS (Numerical Evaluation of Stochastic Structures Under Stress) code and provided consulting support for NESSUS-related activities at UTSA. NASA funding supported three undergraduate students, two graduate students, a summer course instructor and the Principal Investigator. Matching funds from UTSA provided for the purchase of additional equipment for the enhancement of the Advanced Interactive Computational SGI Lab established during the first year of this Partnership Award to conduct the probabilistic finite element summer courses. The research portion of this report presents the cumulation of work performed through the use of the probabilistic finite element program, NESSUS, Numerical Evaluation and Structures Under Stress, and an embedded Material Strength Degradation (MSD) model. Probabilistic structural analysis provided for quantification of uncertainties associated with the design, thus enabling increased system performance and reliability. The structure examined was a Space Shuttle Main Engine (SSME) fuel turbopump blade. The blade material analyzed was Inconel 718, since the MSD model was previously calibrated for this material. Reliability analysis encompassing the effects of high temperature and high cycle fatigue, yielded a reliability value of 0.99978 using a fully correlated random field for the blade thickness. The reliability did not change significantly for a change in distribution type except for a change in
Improving Predictions with Reliable Extrapolation Schemes and Better Understanding of Factorization
More, Sushant N
2016-01-01
We investigate two distinct sources of uncertainty in low-energy nuclear physics calculations and develop ways to account for them. Harmonic oscillator basis expansions are widely used in ab-initio nuclear structure calculations. Finite computational resources usually require that the basis be truncated before observables are fully converged, necessitating reliable extrapolation schemes. We show that a finite oscillator basis effectively imposes a hard-wall boundary condition. We accurately determine the position of the hard-wall as a function of oscillator space parameters, derive extrapolation formulas for the energy and other observables, and discuss the extension of this approach to higher angular momentum. Nucleon knockout reactions have been widely used to study and understand nuclear properties. Such an analysis implicitly assumes that the effects of the probe can be separated from the physics of the target nucleus. This factorization between nuclear structure and reaction components depends on the ren...
Noteborn, M.G.C.; Hildebrand, M.
2015-01-01
Background: The use of brief, reliable, valid, and practical measures of substance use is critical for conducting individual (risk and need) assessments in probation practice. In this exploratory study, the basic psychometric properties of the Alcohol Use Disorders Identification Test (AUDIT) and
Institute of Scientific and Technical Information of China (English)
2007-01-01
Multi-failures are possible to appear in the process of using the structural system, such as dead load failure, fatigue failure and stiffness failure. The expression of residual resistance is given based on the impact of random crack propagation in- duced by the fatigue load on the critical limit stress and section modulus in this paper. The failure modes of every element of the structural system are analyzed under dead and fatigue loads, and the influence of the correlation of failure modes on reliability of the element is considered. Failure mechanism and the correlation of failure modes under dead and fatigue loads are discussed, and the method of reli- ability analysis considering static strength, fatigue and stiffness is given. A nu- merical example is analyzed, which indicates that the failure probability is different for different use life and the influence of dead and fatigue loads on reliability of the structural system is different as well. This method of reliability analysis, in the pa- per, is better than the method only considering a single factor (or static strength, or fatigue, or stiffness, etc.) in the case of practical engineering.
Optimization and Reliability Problems in Structural Design of Wind Turbines
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard
2007-01-01
reliability index equal to 3. An example with fatigue failure indicates that the reliability level is almost the same for single wind turbines and for wind turbines in wind farms if the wake effects are modeled equivalently in the design equation and the limit state equation.......Reliability-based cost-benefit optimization formulations for wind turbines are presented. Some of the improtant aspects for stochastic modeling of loads, strengths and models uncertainties for wind turbines are described. Single wind turbines and wind turbines in wind farms with wake effects...... are discussed. Limit state equations are presented for fatigue limit states and for ultimate limit states with extreme wind load, and illustrated by bending failure. Illustrative examples are presented, and as a part of the results optimal reliability levels are obtained which corresponds to an annual...
Reliability Factors for Electronic Components in a Storage Environment
1977-09-01
Dump storage is usually necessary when an Army must operate under mobile circumstances or in a new location outside the United States. In addition, the...Uthe, "Variables Affecting Weld Quality in Ultrasonic Aluminum Wire Bonding", Solid State Technoilogy , 12, 72 (1969). 45. C. W. Wirsing, Solid State...is related to the ionic mobility . Factors which are important to the build-up of surface-ion induced inversion layers are the moisture levels 4n the
Stachura, Zbigniew; Giżejowski, Marian
2015-03-01
Problems associated with the estimation of partial factors for structural systems, subsystems and buckling of individual elements are dealt with in this paper. Aspects related to resistance factors for the section resistance and member resistance are in particular referred to. The Eurocode's approach of resistance partial factor calibration assisted by experimental data for subframe systems is also summarized. Stan graniczny nośności konstrukcji, projektowanej w tradycyjnym podejściu na podstawie efektów oddziaływań jest oceniany z niezawodnościowego modelu szeregowego. Kalibrację współczynników częściowych do nośności przeprowadza się wówczas na podstawie analizy niezawodności pojedynczego elementu konstrukcji (pręta lub węzła). Eurokod stalowy [4] wprowadził zasady projektowania bazujące na bardziej złożonych modelach nośności niż w [8], gdyż stan graniczny można ocenić na podstawie warunku stateczności technicznej podukładu konstrukcji lub w ogólności, jak przedstawia to warunek (2.1) - na podstawie punktu granicznego na ścieżce równowagi wyznaczonej dla nieidealnego modelu całej konstrukcji. Pojawia się pytanie, czy stosowanie do nośności wyznaczonej na podstawie bardziej złożonych modeli mechaniki konstrukcji współczynników częściowych wyspecyfikowanych do oceny nośności pojedynczych elementów prowadzi do bezpiecznych oszacowań. Kalibracja współczynników częściowych w metodzie stanów granicznych może być dokonana przy różnych założeniach wyjściowych. Model niezawodności i ogólne zasady przyjętego w eurokodach rozdziału docelowego wskaźnika niezawodności na składowe odnoszące się do ustalenia obliczeniowych oddziaływań i ich kombinacji oraz do ustalania nośności obliczeniowej zostały podane w eurokodzie [1]. W artykule przedstawiono zagadnienia dotyczące przyjęcia współczynników częściowych do nośności układu lub podukładu konstrukcyjnego. Opisano eurokodową procedur
Institute of Scientific and Technical Information of China (English)
Lirong Sha; Tongyu Wang
2016-01-01
In order to evaluate the failure probability of a complicated structure, the structural responses usually need to be estimated by some numerical analysis methods such as finite element method ( FEM) . The response surface method ( RSM) can be used to reduce the computational effort required for reliability analysis when the performance functions are implicit. However, the conventional RSM is time⁃consuming or cumbersome if the number of random variables is large. This paper proposes a Legendre orthogonal neural network ( LONN)⁃based RSM to estimate the structural reliability. In this method, the relationship between the random variables and structural responses is established by a LONN model. Then the LONN model is connected to a reliability analysis method, i.e. first⁃order reliability methods (FORM) to calculate the failure probability of the structure. Numerical examples show that the proposed approach is applicable to structural reliability analysis, as well as the structure with implicit performance functions.
Directory of Open Access Journals (Sweden)
Brunham Robert C
2004-07-01
Full Text Available Abstract Background We establish that the occurrence of protein folds among genomes can be accurately described with a Weibull function. Systems which exhibit Weibull character can be interpreted with reliability theory commonly used in engineering analysis. For instance, Weibull distributions are widely used in reliability, maintainability and safety work to model time-to-failure of mechanical devices, mechanisms, building constructions and equipment. Results We have found that the Weibull function describes protein fold distribution within and among genomes more accurately than conventional power functions which have been used in a number of structural genomic studies reported to date. It has also been found that the Weibull reliability parameter β for protein fold distributions varies between genomes and may reflect differences in rates of gene duplication in evolutionary history of organisms. Conclusions The results of this work demonstrate that reliability analysis can provide useful insights and testable predictions in the fields of comparative and structural genomics.
Analysis of time-dependent reliability of degenerated reinforced concrete structure
Directory of Open Access Journals (Sweden)
Zhang Hongping
2016-07-01
Full Text Available Durability deterioration of structure is a highly random process. The maintenance of degenerated structure involves the calculation of the reliability of time-dependent structure. This study introduced reinforced concrete structure resistance decrease model and related statistical parameters of uncertainty, analyzed resistance decrease rules of corroded bending element of reinforced concrete structure, and finally calculated timedependent reliability of the corroded bending element of reinforced concrete structure, aiming to provide a specific theoretical basis for the application of time-dependent reliability theory.
Improving the Factor Structure of Psychological Scales
Zhang, Xijuan; Savalei, Victoria
2015-01-01
Many psychological scales written in the Likert format include reverse worded (RW) items in order to control acquiescence bias. However, studies have shown that RW items often contaminate the factor structure of the scale by creating one or more method factors. The present study examines an alternative scale format, called the Expanded format, which replaces each response option in the Likert scale with a full sentence. We hypothesized that this format would result in a cleaner factor structure as compared with the Likert format. We tested this hypothesis on three popular psychological scales: the Rosenberg Self-Esteem scale, the Conscientiousness subscale of the Big Five Inventory, and the Beck Depression Inventory II. Scales in both formats showed comparable reliabilities. However, scales in the Expanded format had better (i.e., lower and more theoretically defensible) dimensionalities than scales in the Likert format, as assessed by both exploratory factor analyses and confirmatory factor analyses. We encourage further study and wider use of the Expanded format, particularly when a scale’s dimensionality is of theoretical interest. PMID:27182074
Recent Advances in Optimal Design of Structures from a Reliability Point of View
DEFF Research Database (Denmark)
Thoft-Christensen, Palle; Sørensen, John Dalsgaard
1987-01-01
Structural optimisation and structural reliability theory are considered. Both of these areas have developed during the last two decades from being of purely theoretical interest to areas useful in practical design. The main elements of structural reliability theory are described in the second......-Christensen and Baker[4] and Madsen et al.[5]. Next a heuristic method, the so-called ß-unzipping method[6] is mentioned. This method can be used to estimate the reliability of a structural system if some modelling assumptions are fulfilled. In the third section some elements of structural optimisation theory...
DEFF Research Database (Denmark)
Iwankiewicz, R.; Nielsen, Søren R. K.; Skjærbæk, P. S.
The subject of the paper is the investigation of the sensitivity of structural reliability estimation by a reduced hysteretic model for a reinforced concrete frame under an earthquake excitation.......The subject of the paper is the investigation of the sensitivity of structural reliability estimation by a reduced hysteretic model for a reinforced concrete frame under an earthquake excitation....
Schweckendiek, T.; Courage, W.M.G.; Van Gelder, P.H.A.J.M.
2007-01-01
The Finite Element Method is well accepted in design practice nowadays. It can be used for modeling complex structures and systems. The constitutive models are improving, which enables us to make more accurate predictions of the real world behavior. On the other hand, especially in the field of geot
Schweckendiek, T.; Courage, W.M.G.; Gelder, A.J.M. van
2007-01-01
The Finite Element Method is well accepted in design practice nowadays. It can be used for modeling complex structures and systems. The constitutive models are improving, which enables us to make more accurate predictions ofthe real world behavior. On the other hand, especially in the field ofgeotec
Reliability Equivalence Factors of a System with 2 Non-identical Mixed Lifetimes and Delayed Time
Directory of Open Access Journals (Sweden)
Abdelfattah Mustafa
2011-01-01
Full Text Available Problem statement: In reliability theory and operations research, there are many methods and techniques to improve the performance of a system. The aim of this study is to generalize reliability equivalence technique to apply it to a mixed failure lifetimes system f1 (t, f2 (t with delayed time. Approach: We shall improve the system by using some reliability techniques: (i reducing the failure for some lifetimes; (ii add hot duplication components; (iii add cold duplication components; (iv add cold duplication components with imperfect switches. We start by establishing two different types of reliability equivalence factors, the Survival Reliability Equivalence (SRE and Mean Reliability Equivalence (MRE factors. Also, we introduced some numerical results. Results: The system reliability function and mean time to failure will be used as reference of the system performances. For this reason, we obtain the reliability functions and mean time to failures of the original and improved systems using each improving methods. Conclusion: The results can be used to distinguish between the original and improved systems performances and calculate the equivalent between different cases of improving methods.
Directory of Open Access Journals (Sweden)
Behrouz Asgarian
2009-01-01
Full Text Available There are plenty of uncertainties in environmental condition of ocean and also in platform element capacities. Reliability-based method could consider these uncertainties. A reliability-based earthquake design method was used to determine the earthquake LRFD parameters for two conventional, steel, pile-supported (template-type offshore platforms located in the Persian Gulf. The pile-soil-structure interaction, the buckling and postbuckling behavior of the braces were considered. Two steel platforms were simulated accurately by the finite element program Opensees. Field data were assumed based on past studies. Sensitiveness of reliability-based method was studied. It was found that the geometry of jacket and different types of braces was important in the capacity and the behavior of offshore platforms. Finally the calculated LRFD elements resistance factors for these two platforms were compared with API recommended factors and it was observed that API recommended element resistance factors were more appropriate for SSL 3.
Reliability Analysis of Timber Structures through NDT Data Upgrading
DEFF Research Database (Denmark)
Sousa, Hélder; Sørensen, John Dalsgaard; Kirkegaard, Poul Henning
for reliability calculation. In chapter 4, updating methods are conceptualized and defined. Special attention is drawn upon Bayesian methods and its implementation. Also a topic for updating based in inspection of deterioration is provided. State of the art definitions and proposed measurement indices......The first part of this document presents, in chapter 2, a description of timber characteristics and common used NDT and MDT for timber elements. Stochastic models for timber properties and damage accumulation models are also referred. According to timber’s properties a framework is proposed...
Reliability Evaluation considering Structures of a Large Scale Wind Farm
DEFF Research Database (Denmark)
Shin, Je-Seok; Cha, Seung-Tae; Wu, Qiuwei
2012-01-01
evaluation on wind farm is necessarily required. Also, because large scale offshore wind farm has a long repair time and a high repair cost as well as a high investment cost, it is essential to take into account the economic aspect. One of methods to efficiently build and to operate wind farm is to construct......Wind energy is one of the most widely used renewable energy resources. Wind power has been connected to the grid as large scale wind farm which is made up of dozens of wind turbines, and the scale of wind farm is more increased recently. Due to intermittent and variable wind source, reliability...
Reliability-based Calibration of Fatigue Safety Factors for Offshore Wind Turbines
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard
2011-01-01
This paper describes reliability-based investigations on the required safety factors / Fatigue Design Factors (FDF) values to be used for fatigue design of steel substructures for offshore wind turbines. Design and limit state equations are formulated and stochastic models for the uncertain...
Reliability and structural integrity management of PETROBRAS UN-Rio
Energy Technology Data Exchange (ETDEWEB)
Silva, Wallace B. e; Bessa, Guilherme de S. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil); Alves, Helio; Oliveira, Luiz F.; Alvarenga, Tobias V. [Det Norske Veritas (DNV), Rio de Janeiro, RJ (Brazil)
2009-12-19
This paper aims to present the Integrity and Reliability Management Program developed by UN-Rio, Rio de Janeiro E and P business unit of PETROBRAS. The program was developed with the support of DNV and has been implemented on all subsea assets of this business unit, which includes flexible and carbon steel pipelines and their components, umbilicals as well as subsea equipment (manifolds, valves, etc.). Optimizing resources and systematizing inspection and maintenance activities according to a combined probability and consequence of failure matrix were the goals to be achieved. A specific risk analysis tool was conceived as a part of the scope of the program. In addition to the risk analysis, availability studies were also carried out so as to assess the present condition of this subsea system. The main results and benefits as well as the challenges faced along the implementation of the program will be part of this work. (author)
Cost-Optimal Structural Reliability of Offshore Wind Turbines
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Tarp-Johansen, N. J.
2004-01-01
Wind turbines for electricity production are increasing drastically these years both in production capability and in size. Offshore wind turbines with an electricity production more than 5 MW are now being produced. The main failure modes are fatigue failure of wings, hub, shaft and main tower......, and failure costs. Different reconstruction policies in case of failure are considered, including systematic reconstruction in case of failure, no reconstruction and inspection and maintenance strategies. Illustrative examples for offshore wind turbines are presented, and as a part of the results optimal......, local buckling of main tower, and failure of the foundation. This paper considers reliability-based optimization of the tower and foundation. Different formulations are considered of the objective function including benefits, building costs of the wind turbine, inspection and maintenance costs...
Cost-Optimal Structural Reliability of Offshore Wind Turbines
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Tarp-Johansen, N. J.
2004-01-01
Wind turbines for electricity production are increasing drastically these years both in production capability and in size. Offshore wind turbines with an electricity production more than 5 MW are now being produced. The main failure modes are fatigue failure of wings, hub, shaft and main tower......, local buckling of main tower, and failure of the foundation. This paper considers reliability-based optimization of the tower and foundation. Different formulations are considered of the objective function including benefits, building costs of the wind turbine, inspection and maintenance costs......, and failure costs. Different reconstruction policies in case of failure are considered, including systematic reconstruction in case of failure, no reconstruction and inspection and maintenance strategies. Illustrative examples for offshore wind turbines are presented, and as a part of the results optimal...
Further HTGR core support structure reliability studies. Interim report No. 1
Energy Technology Data Exchange (ETDEWEB)
Platus, D.L.
1976-01-13
Results of a continuing effort to investigate high temperature gas cooled reactor (HTGR) core support structure reliability are described. Graphite material and core support structure component physical, mechanical and strength properties required for the reliability analysis are identified. Also described are experimental and associated analytical techniques for determining the required properties, a procedure for determining number of tests required, properties that might be monitored by special surveillance of the core support structure to improve reliability predictions, and recommendations for further studies. Emphasis in the study is directed towards developing a basic understanding of graphite failure and strength degradation mechanisms; and validating analytical methods for predicting strength and strength degradation from basic material properties.
Quantifiable and Reliable Structural Health Management Systems Project
National Aeronautics and Space Administration — Under Project Constellation, NASA is developing a new generation of spacecraft for human spaceflight. A significant percentage of the structures used in these...
Meeting Human Reliability Requirements through Human Factors Design, Testing, and Modeling
Energy Technology Data Exchange (ETDEWEB)
R. L. Boring
2007-06-01
In the design of novel systems, it is important for the human factors engineer to work in parallel with the human reliability analyst to arrive at the safest achievable design that meets design team safety goals and certification or regulatory requirements. This paper introduces the System Development Safety Triptych, a checklist of considerations for the interplay of human factors and human reliability through design, testing, and modeling in product development. This paper also explores three phases of safe system development, corresponding to the conception, design, and implementation of a system.
Carvalho, Teresa; Cunha, Marina; Pinto-Gouveia, José; Duarte, Joana
2015-03-30
The PTSD Checklist-Military Version (PCL-M) is a brief self-report instrument widely used to assess Post-traumatic Stress Disorder (PTSD) symptomatology in war Veterans, according to DSM-IV. This study sought out to explore the factor structure and reliability of the Portuguese version of the PCL-M. A sample of 660 Portuguese Colonial War Veterans completed the PCL-M. Several Confirmatory Factor Analyses were conducted to test different structures for PCL-M PTSD symptoms. Although the respecified first-order four-factor model based on King et al.'s model showed the best fit to the data, the respecified first and second-order models based on the DSM-IV symptom clusters also presented an acceptable fit. In addition, the PCL-M showed adequate reliability. The Portuguese version of the PCL-M is thus a valid and reliable measure to assess the severity of PTSD symptoms as described in DSM-IV. Its use with Portuguese Colonial War Veterans may ease screening of possible PTSD cases, promote more suitable treatment planning, and enable monitoring of therapeutic outcomes. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.
Reliability of structural systems subjected to extreme forcing events
Joo, Han-Kyul; Sapsis, Themistoklis P
2016-01-01
We characterize the complex, heavy-tailed probability distribution functions (pdf) describing the response and its local extrema for structural systems subjected to random forcing that includes extreme events. Our approach is based on the recent probabilistic decomposition-synthesis technique in, where we decouple rare events regimes from the background fluctuations. The result of the analysis has the form of a semi-analytical approximation formula for the pdf of the response (displacement, velocity, and acceleration) and the pdf of the local extrema. For special limiting cases (lightly damped or heavily damped systems) our analysis provides fully analytical approximations. We also demonstrate how the method can be applied to high dimensional structural systems through a two-degrees-of-freedom structural system undergoing rare events due to intermittent forcing. The derived formulas can be evaluated with very small computational cost and are shown to accurately capture the complicated heavy-tailed and asymmet...
Tissue Factor Structure and Function
Directory of Open Access Journals (Sweden)
Saulius Butenas
2012-01-01
Full Text Available Tissue factor (TF is an integral membrane protein that is essential to life. It is a component of the factor VIIa-TF complex enzyme and plays a primary role in both normal hemostasis and thrombosis. With a vascular injury, TF becomes exposed to blood and binds plasma factor VIIa, and the resulting complex initiates a series of enzymatic reactions leading to clot formation and vascular sealing. Many cells, both healthy, and tumor cells, produce detectable amounts of TF, especially when they are stimulated by various agents. Despite the relative simplicity and small size of TF, there are numerous contradictory reports about the synthesis and presentation of TF on blood cells and circulation in normal blood either on microparticles or as a soluble protein. Another subject of controversy is related to the structure/function of TF. It has been almost commonly accepted that cell-surface-associated TF has low (if any activity, that is, is “encrypted” and requires specific conditions/reagents to become active, that is, “decrypted.” However there is a lack of agreement related to the mechanism and processes leading to alterations in TF function. In this paper TF structure, presentation, and function, and controversies concerning these features are discussed.
The use of directional sampling in structural reliability
Waarts, P.H.; Vrouwenvelder, A.C.W.M.
1998-01-01
In cooperation with TNO, Delft University of Technology has written a computer code to calculate the failure probability of structures. Probabilistic methods have been implemented in the existing TNO Finite Element code DIANA which includes physically and geometrically non-linear behaviour of the
Stochastic Response and Reliability Analysis of Hysteretic Structures
DEFF Research Database (Denmark)
Mørk, Kim Jørgensen
During the last 30 years response analysis of structures under random excitation has been studied in detail. These studies are motivated by the fact that most of natures excitations, such as earthquakes, wind and wave loads exhibit randomly fluctuating characters. For safety reasons this randomness...
Improving Predictions with Reliable Extrapolation Schemes and Better Understanding of Factorization
More, Sushant N.
New insights into the inter-nucleon interactions, developments in many-body technology, and the surge in computational capabilities has led to phenomenal progress in low-energy nuclear physics in the past few years. Nonetheless, many calculations still lack a robust uncertainty quantification which is essential for making reliable predictions. In this work we investigate two distinct sources of uncertainty and develop ways to account for them. Harmonic oscillator basis expansions are widely used in ab-initio nuclear structure calculations. Finite computational resources usually require that the basis be truncated before observables are fully converged, necessitating reliable extrapolation schemes. It has been demonstrated recently that errors introduced from basis truncation can be taken into account by focusing on the infrared and ultraviolet cutoffs induced by a truncated basis. We show that a finite oscillator basis effectively imposes a hard-wall boundary condition in coordinate space. We accurately determine the position of the hard-wall as a function of oscillator space parameters, derive infrared extrapolation formulas for the energy and other observables, and discuss the extension of this approach to higher angular momentum and to other localized bases. We exploit the duality of the harmonic oscillator to account for the errors introduced by a finite ultraviolet cutoff. Nucleon knockout reactions have been widely used to study and understand nuclear properties. Such an analysis implicitly assumes that the effects of the probe can be separated from the physics of the target nucleus. This factorization between nuclear structure and reaction components depends on the renormalization scale and scheme, and has not been well understood. But it is potentially critical for interpreting experiments and for extracting process-independent nuclear properties. We use a class of unitary transformations called the similarity renormalization group (SRG) transformations to
An Imprecise Probability Model for Structural Reliability Based on Evidence and Gray Theory
Directory of Open Access Journals (Sweden)
Bin Suo
2013-01-01
Full Text Available To avoid the shortages and limitations of probabilistic and non-probabilistic reliability model for structural reliability analysis in the case of limited samples for basic variables, a new imprecise probability model is proposed. Confidence interval with a given confidence is calculated on the basis of small samples by gray theory, which is not depending on the distribution pattern of variable. Then basic probability assignments and focal elements are constructed and approximation methods of structural reliability based on belief and plausibility functions are proposed in the situation that structure limit state function is monotonic and non-monotonic, respectively. The numerical examples show that the new reliability model utilizes all the information included in small samples and considers both aleatory and epistemic uncertainties in them, thus it can rationally measure the safety of the structure and the measurement can be more and more accurate with the increasing of sample size.
Hedlund, Ann; Ateg, Mattias; Andersson, Ing-Marie; Rosén, Gunnar
2010-04-01
Workers' motivation to actively take part in improvements to the work environment is assumed to be important for the efficiency of investments for that purpose. That gives rise to the need for a tool to measure this motivation. A questionnaire to measure motivation for improvements to the work environment has been designed. Internal consistency and test-retest reliability of the domains of the questionnaire have been measured, and the factorial structure has been explored, from the answers of 113 employees. The internal consistency is high (0.94), as well as the correlation for the total score (0.84). Three factors are identified accounting for 61.6% of the total variance. The questionnaire can be a useful tool in improving intervention methods. The expectation is that the tool can be useful, particularly with the aim of improving efficiency of companies' investments for work environment improvements. Copyright 2010 Elsevier Ltd. All rights reserved.
On the use of NDT Data for Reliability-Based Assessment of Existing Timber Structures
DEFF Research Database (Denmark)
Sousa, Hélder S.; Sørensen, John Dalsgaard; Kirkegaard, Poul Henning
2013-01-01
is performed using First Order Reliability Methods (FORM). The results show that different degrees of belief in the updating data may significantly influence the reliability level. The updating data to be used are NDT results obtained with ultrasound, resistance drilling and pin penetration equipments......The objective of this paper is to address the possibilities of using non-destructive testing (NDT) data for updating information and obtaining adequate characterization of the reliability level of existing timber structures and, also, for assessing the evolution in time of performance...... of these structures when exposed to deterioration. By improving the knowledge upon the mechanical properties of timber, better and more substantiated decisions after a reliability safety assessment are aimed at. Bayesian methods are used to update the mechanical properties of timber and reliability assessment...
Institute of Scientific and Technical Information of China (English)
HE Xu-hui; CHEN Zheng-qing; YU Zhi-wu; HUANG Fang-lin
2006-01-01
To evaluate the fatigue damage reliability of critical members of the Nanjing Yangtze river bridge, according to the stress-number curve and Miner's rule, the corresponding expressions for calculating the structural fatigue damage reliability were derived. Fatigue damage reliability analysis of some critical members of the Nanjing Yangtze river bridge was carried out by using the strain-time histories measured by the structural health monitoring system of the bridge. The corresponding stress spectra were obtained by the real-time rain-flow counting method.Results of fatigue damage were calculated respectively by the reliability method at different reliability and compared with Miner's rule. The results show that the fatigue damage of critical members of the Nanjing Yangtze river bridge is very small due to its low live-load stress level.
A Structural Reliability Business Process Modelling with System Dynamics Simulation
Lam, C. Y.; S.L. Chan; Ip, W.H.
2010-01-01
Business activity flow analysis enables organizations to manage structured business processes, and can thus help them to improve performance. The six types of business activities identified here (i.e., SOA, SEA, MEA, SPA, MSA and FIA) are correlated and interact with one another, and the decisions from any business activity form feedback loops with previous and succeeding activities, thus allowing the business process to be modelled and simulated. For instance, for any company that is eager t...
Integrated Life-Cycle Framework for Maintenance, Monitoring and Reliability of Naval Ship Structures
2012-08-15
9, 106-109. Ayala-Uraga, E. and Moan, T. (2007). Time-Variant Reliability Assessment of FPSO Hull Girder With Long Cracks. Journal of Offshore...Sun, H-H and Guedes Soares, C. (2003). Reliability-Based Structural Design of Ship-Type FPSO Units. Transactions of the ASME, Vol. 125, May, 108...entire hull module (Chen et al. 1983, Kutt et al. 1985), but the computational requirements both in modeling the structure and computing time are
Analysis of whisker-toughened CMC structural components using an interactive reliability model
Duffy, Stephen F.; Palko, Joseph L.
1992-01-01
Realizing wider utilization of ceramic matrix composites (CMC) requires the development of advanced structural analysis technologies. This article focuses on the use of interactive reliability models to predict component probability of failure. The deterministic William-Warnke failure criterion serves as theoretical basis for the reliability model presented here. The model has been implemented into a test-bed software program. This computer program has been coupled to a general-purpose finite element program. A simple structural problem is presented to illustrate the reliability model and the computer algorithm.
Fatigue reliability analysis of fixed offshore structures:A first passage problem approach
Institute of Scientific and Technical Information of China (English)
MADHAVAN PILLAI T.M.; VEENA G.
2006-01-01
This paper describes a methodology for computation of reliability of members of fixed offshore platform structures,with respect to fatigue. Failure criteria were formulated using fracture mechanics principle. The problem is coined as a "first passage problem". The method was illustrated through application to a typical plane frame structure. The fatigue reliability degradation curve established can be used for planning in-service inspection of offshore platforms. A very limited parametric study was carried out to obtain insight into the effect of important variables on the fatigue reliability.
Reliability Evaluation and Probabilistic Design of Coastal Structures
DEFF Research Database (Denmark)
Burcharth, H. F.
1993-01-01
, e.g. the expectation (mean) value of the lOO-year return period event, however, often without consideration of the involved uncertainties. The resistance is in most cases defined in terms of the load which causes a certain design impact or damage to the structure and is not given as an ultimate...... formulae are semi-empirical being based mainly on central fitting to model test results. The often considerable scatter in test results is not considered in general because the formulae normally express only the mean values. Consequently, the applied characteristic value of the resistance is then the mean...
Reliability of Structural Systems with regard to Permanent Displacements
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Thoft-Christensen, Palle
1991-01-01
methods/experience related to permanent deformations are described in Grinda et al. [1] and Papadrakakis & Loukakis [2]. For general dynamic systems modelled by one-degree-of-freedom (and two-degrees-of freedom) systems a number of methods exist, see e.g. Nielsen et al. [3] and Toro & Cornell [4]. However...... approach - a differential equation approach - a superposition approach - the simple method These three approaches are described in Sørensen & Thoft-Christensen [5], Sørensen et al. [6] and Sørensen & Thoft-Christensen [7]. It is assumed that the structural system can be modelled by a multi-linear elastic...
Boermans, M.A.; Kattenberg, M.A.C.
2011-01-01
We show how to estimate a Cronbach's alpha reliability coefficient in Stata after running a principal component or factor analysis. Alpha evaluates to what extent items measure the same underlying content when the items are combined into a scale or used for latent variable. Stata allows for testing
Classifying Open-Ended Reports: Factors Affecting the Reliability of Occupation Codes
Directory of Open Access Journals (Sweden)
Conrad Frederick G.
2016-03-01
Full Text Available A source of survey processing error that has received insufficient study to date is the misclassification of open-ended responses. We report on efforts to understand the misclassification of open occupation descriptions in the Current Population Survey (CPS. We analyzed double-coded CPS descriptions to identify which features vary with intercoder reliability. One factor strongly related to reliability was the length of the occupation description: longer descriptions were less reliably coded than shorter ones. This effect was stronger for particular occupation terms. We then carried out an experiment to examine the joint effects of description length and classification “difficulty” of particular occupation terms. For easy occupation terms longer descriptions were less reliably coded, but for difficult occupation terms longer descriptions were slightly more reliably coded than short descriptions. Finally, we observed as coders provided verbal reports on their decision making. One practice, evident in coders’ verbal reports, is their use of informal coding rules based on superficial features of the description. Such rules are likely to promote reliability, though not necessarily validity, of coding. To the extent that coders use informal rules for long descriptions involving difficult terms, this could help explain the observed relationship between description length and difficulty of coding particular terms.
STUDY OF FACTORS AFFECTING PROFESSIONAL RELIABILITY SPECIALISTS OF SEARCH-AND-RESCUE SERVICES
Лещенко Геннадій Анатолійович
2015-01-01
The article deals with the issues of the professional activity of future specialists of aviation emergency service and safety. It’s being proved that the subject’s ability to resist the negative factors of professional activity and to perform effectively the professional functions characterize the resistance of the action, provided by the professional reliability. The factors that positively influence the quality of the specialist’s functioning are defined.
Analysis methods for structure reliability of piping components
Energy Technology Data Exchange (ETDEWEB)
Schimpfke, T.; Grebner, H.; Sievers, J. [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, Koeln (Germany)
2004-07-01
In the frame of the German reactor safety research program of the Federal Ministry of Economics and Labour (BMWA) GRS has started to develop an analysis code named PROST (PRObabilistic STructure analysis) for estimating the leak and break probabilities of piping systems in nuclear power plants. The long-term objective of this development is to provide failure probabilities of passive components for probabilistic safety analysis of nuclear power plants. Up to now the code can be used for calculating fatigue problems. The paper mentions the main capabilities and theoretical background of the present PROST development and presents some of the results of a benchmark analysis in the frame of the European project NURBIM (Nuclear Risk Based Inspection Methodologies for Passive Components). (orig.)
Directory of Open Access Journals (Sweden)
Bruce Weaver
2014-09-01
Full Text Available Missing data is a frequent problem for researchers conducting exploratory factor analysis (EFA or reliability analysis. The SPSS FACTOR procedure allows users to select listwise deletion, pairwise deletion or mean substitution as a method for dealing with missing data. The shortcomings of these methods are well-known. Graham (2009 argues that a much better way to deal with missing data in this context is to use a matrix of expectation maximization (EM covariances(or correlations as input for the analysis. SPSS users who have the Missing Values Analysis add-on module can obtain vectors ofEM means and standard deviations plus EM correlation and covariance matrices via the MVA procedure. But unfortunately, MVA has no /MATRIX subcommand, and therefore cannot write the EM correlations directly to a matrix dataset of the type needed as input to the FACTOR and RELIABILITY procedures. We describe two macros that (in conjunction with an intervening MVA command carry out the data management steps needed to create two matrix datasets, one containing EM correlations and the other EM covariances. Either of those matrix datasets can then be used asinput to the FACTOR procedure, and the EM correlations can also be used as input to RELIABILITY. We provide an example that illustrates the use of the two macros to generate the matrix datasets and how to use those datasets as input to the FACTOR and RELIABILITY procedures. We hope that this simple method for handling missing data will prove useful to both students andresearchers who are conducting EFA or reliability analysis.
Institute of Scientific and Technical Information of China (English)
YANG Duo-he; AN Wei-guang; ZHU Rong-rong; MIAO Han
2006-01-01
Based on the finite element method(FEM) for the dynamical analysis of piezoelectric truss structures, the expressions of safety margins of strength fracture and damage electric field in the structure element are given considering electromechanical coupling effect under the joint action of electric and mechanical load. By importing the stochastic FEM,reliability of piezoelectric truss structures is analyzed by solving for partial derivative in the process of solving dynamical response of structure system with mode-superposition method. The influence of electromechanical coupling effect to reliability index is then analyzed through an example.
Structure buckling and non-probabilistic reliability analysis of supercavitating vehicles
Institute of Scientific and Technical Information of China (English)
AN Wei-guang; ZHOU Ling; AN Hai
2009-01-01
To perform structure buckling and reliability analysis on supercavitating vehicles with high velocity in the submarine, supercavitating vehicles were simplified as variable cross section beam firstly. Then structural buckling analysis of supercavitating vehicles with or without engine thrust was conducted, and the structural buckling safety margin equation of supercavitating vehicles was established. The indefinite information was de-scribed by interval set and the structure reliability analysis was performed by using non-probabilistic reliability method. Considering interval variables as random variables which satisfy uniform distribution, the Monte-Carlo method was used to calculate the non-probabilistic failure degree. Numerical examples of supercavitating vehi-cles were presented. Under different ratios of base diameter to cavitator diameter, the change tendency of non-probabilistic failure degree of structural buckling of supereavitating vehicles with or without engine thrust was studied along with the variety of speed.
Suen, Yi-Nam; Cerin, Ester; Barnett, Anthony; Huang, Wendy Y J; Mellecker, Robin R
2017-09-01
Valid instruments of parenting practices related to children's physical activity (PA) are essential to understand how parents affect preschoolers' PA. This study developed and validated a questionnaire of PA-related parenting practices for Chinese-speaking parents of preschoolers in Hong Kong. Parents (n = 394) completed a questionnaire developed using findings from formative qualitative research and literature searches. Test-retest reliability was determined on a subsample (n = 61). Factorial validity was assessed using confirmatory factor analysis. Subscale internal consistency was determined. The scale of parenting practices encouraging PA comprised 2 latent factors: Modeling, structure and participatory engagement in PA (23 items), and Provision of appropriate places for child's PA (4 items). The scale of parenting practices discouraging PA scale encompassed 4 latent factors: Safety concern/overprotection (6 items), Psychological/behavioral control (5 items), Promoting inactivity (4 items), and Promoting screen time (2 items). Test-retest reliabilities were moderate to excellent (0.58 to 0.82), and internal subscale reliabilities were acceptable (0.63 to 0.89). We developed a theory-based questionnaire for assessing PA-related parenting practices among Chinese-speaking parents of Hong Kong preschoolers. While some items were context and culture specific, many were similar to those previously found in other populations, indicating a degree of construct generalizability across cultures.
Directory of Open Access Journals (Sweden)
Hao Zhang
2016-01-01
Full Text Available Under the increasingly uncertain economic environment, the research on the reliability of urban distribution system has great practical significance for the integration of logistics and supply chain resources. This paper summarizes the factors that affect the city logistics distribution system. Starting from the research of factors that influence the reliability of city distribution system, further construction of city distribution system reliability influence model is built based on Bayesian networks. The complex problem is simplified by using the sub-Bayesian network, and an example is analyzed. In the calculation process, we combined the traditional Bayesian algorithm and the Expectation Maximization (EM algorithm, which made the Bayesian model able to lay a more accurate foundation. The results show that the Bayesian network can accurately reflect the dynamic relationship among the factors affecting the reliability of urban distribution system. Moreover, by changing the prior probability of the node of the cause, the correlation degree between the variables that affect the successful distribution can be calculated. The results have significant practical significance on improving the quality of distribution, the level of distribution, and the efficiency of enterprises.
Fabrication of reliable semiconductor nanowires by controlling crystalline structure.
Kim, Sangdan; Lim, Taekyung; Ju, Sanghyun
2011-07-29
One-dimensional SnO(2) nanomaterials with wide bandgap characteristics are attractive for flexible and/or transparent displays and high-performance nano-electronics. In this study, the crystallinity of SnO(2) nanowires was regulated by controlling their growth temperatures. Moreover, the correlation of the crystallinity of nanowires with optical and electrical characteristics was analyzed. When SnO(2) nanowires were grown at temperatures below 900 °C, they showed various growth directions and abnormal discontinuity in their crystal structures. On the other hand, most nanowires grown at 950 °C exhibited a regular growth trend in the direction of [100]. In addition, the low temperature photoluminescence measurement revealed that the higher growth temperatures of nanowires gradually decreased the 500 nm peak rather than the 620 nm peak. The former peak is derived from the surface defect related to the shallow energy level and affects nanowire surface states. Owing to crystallinity and defects, the threshold voltage range (maximum-minimum) of SnO(2) nanowire transistors was 1.5 V at 850 °C, 1.1 V at 900 °C, and 0.5 V at 950 °C, with dispersion characteristics dramatically decreased. This study successfully demonstrated the effects of nanowire crystallinity on optical and electrical characteristics. It also suggested that the optical and electrical characteristics of nanowire transistors could be regulated by controlling their growth temperatures in the course of producing SnO(2) nanowires.
Ono, Yoshiro
1996-01-01
Evaluation of the factor validity and reliability of the Aberrant Behavior Checklist (Japanese version) with 322 subjects (mean age 30) with moderate to profound mental retardation found most items loading on the same factors as in the original factor solution, high coefficient alphas across 5 subscales, high test-retest reliability, and…
Efficient Structural System Reliability Updating with Subspace-Based Damage Detection Information
DEFF Research Database (Denmark)
Döhler, Michael; Thöns, Sebastian
modelling is introduced building upon the non-destructive testing reliability which applies to structural systems and DDS containing a strategy to overcome the high computational efforts for the pre-determination of the DDS reliability. This approach takes basis in the subspace-based damage detection method......Damage detection systems and algorithms (DDS and DDA) provide information of the structural system integrity in contrast to e.g. local information by inspections or non-destructive testing techniques. However, the potential of utilizing DDS information for the structural integrity assessment...... and prognosis is hardly exploited nor treated in scientific literature up to now. In order to utilize the information provided by DDS for the structural performance, usually high computational efforts for the pre-determination of DDS reliability are required. In this paper, an approach for the DDS performance...
Safety management of pipelines based on structural reliability: historical perspective and progress
Energy Technology Data Exchange (ETDEWEB)
Beck, Andre Teofilo; Bazan, Felipe Alexander Vargas [Universidade de Sao Paulo (USP), SP (Brazil); Mendes, Renato [Petroleo Brasileiro S.A. (PETROBRAS), Rio de Janeiro, RJ (Brazil); Donato, Guilherme [Petroleo Brasileiro S.A. (PETROBRAS/CENPES), Rio de Janeiro, RJ (Brazil). Centro de Pesquisas e Desenvolvimento; Gardiner, Michael [GL Noble Denton, Loughborough (United Kingdom)
2012-07-01
Since the early beginnings in the sixties and seventies, Structural Reliability theory has reached a mature stage encompassing solid theoretical developments and increasing practical applications. Structural reliability methods have permeated the engineering profession, finding applications in code calibration, structural optimization, life extension of existing structures, life-cycle management of infrastructure risks and costs, and so on. This review paper shows that the ground work for Reliability Based Design and Assessment (RBDA) of onshore pipeline systems is already developed. Hence, this allows the economic management of the risks involved in operation of pipeline systems. It is shown that RBDA is a rational tool to safely manage the operational life of pipeline systems, optimizing initial design and the expenditures in inspection and maintenance operations. (author)
Reduced Expanding Load Method for Simulation-Based Structural System Reliability Analysis
Institute of Scientific and Technical Information of China (English)
远方; 宋丽娜; 方江生
2004-01-01
The current situation and difficulties of the structural system reliability analysis are mentioned. Then on the basis of Monte Carlo method and computer simulation, a new analysis method reduced expanding load method ( RELM ) is presented, which can be used to solve structural reliability problems effectively and conveniently. In this method, the uncertainties of loads, structural material properties and dimensions can be fully considered. If the statistic parameters of stochastic variables are known, by using this method, the probability of failure can be estimated rather accurately. In contrast with traditional approaches, RELM method gives a much better understanding of structural failure frequency and its reliability indexβ is more meaningful. To illustrate this new idea, a specific example is given.
Reviewing progress in PJM's capacity market structure via the new reliability pricing model
Energy Technology Data Exchange (ETDEWEB)
Sener, Adil Caner; Kimball, Stefan
2007-12-15
The Reliability Pricing Model introduces significant changes to the capacity market structure of PJM. The main feature of the RPM design is a downward-sloping demand curve, which replaces the highly volatile vertical demand curve. The authors review the latest RPM structure, results of the auctions, and the future course of the implementation process. (author)
DEFF Research Database (Denmark)
Hovgaard, Mads Knude; Hansen, Jannick Balleby; Brincker, Rune
2013-01-01
A scenario- and vibration based structural damage detection method is demonstrated though simulation. The method is Finite Element (FE) based. The value of the monitoring is calculated using structural reliability theory. A high cycle fatigue crack propagation model is assumed as the damage mecha...
Energy Technology Data Exchange (ETDEWEB)
Reinhold H. Dauskardt
2005-08-01
Final report of our DOE funded research program. Aim of the research program was to provide a fundamental basis from which the mechanical reliability of layered structures may be understood, and to provide guidelines for the development of technologically relevant layered material structures with optimum resistance to fracture and subcritical debonding. Progress in the program to achieve these goals is described.
Directory of Open Access Journals (Sweden)
Marco Aurelio Lumertz Saffi
2013-10-01
Full Text Available Using a sample of patients with coronary artery disease, this methodological study aimed to conduct a cross-cultural adaptation and validation of a questionnaire on knowledge of cardiovascular risk factors (Q-FARCS, lifestyle changes, and treatment adherence for use in Brazil. The questionnaire has three scales: general knowledge of risk factors (RFs; specific knowledge of these RFs; and lifestyle changes achieved. Cross-cultural adaptation included translation, synthesis, back-translation, expert committee review, and pretesting. Face and content validity, reliability, and construct validity were measured. Cronbach’s alpha for the total sample (n = 240 was 0.75. Assessment of psychometric properties revealed adequate face and content validity, and the construct revealed seven components. It was concluded that the Brazilian version of Q-FARCS had adequate reliability and validity for the assessment of knowledge of cardiovascular RFs.
Morin, Amanda Leigh; Miller, Stacy Jo; Smith, Johan R; Johnson, Karen E
2017-04-01
Use of valid, affordable, accessible, and brief measures facilitates the assessment of mental health outcomes. The Child and Adolescent Behavior Assessment Scale, a brief, structured scale, assesses problem behavior through patient and/or informant report. The purpose of this paper is to illustrate the scale's psychometric properties. In the cross-sectional study presented, a large national sample of youth (aged 5-18) admitted for psychiatric treatment (N = 32,689) was examined. The two major domains of problem behavior assessed were Internalizing and Externalizing. Reliability was good to excellent with alpha levels ranging from 0.874 to 0.917. Additional items measured Risk Behavior (α = 0.648). Subscale total scores correlated well with the Brief Psychiatric Rating Scale for Children, 9-item version (BPRS-C-9). Exploratory and confirmatory factor analyses supported the three-factor, multidimensional model of problem behavior as satisfactory for child and adolescent use, although further research is required to refine some items for clarity and improved model fit.
Jin, Cheng Chuang; Li, Feng; Wang, Mo Nan; Bao, Ze Ping
2016-12-01
The structural form of prefabricated holes is one of the important factors to determine the quality and reliability of cold-pressing joining between dissimilar sheets. Different numbers of holes with the same area will lead to different wall thickness distributions and joining strengths. This paper takes the cold-pressing joining between AA1100 pure aluminum sheet and SS304 stainless steel sheet as an example, the further study results show that the end of aluminum sheet has an increasing tendency along the directions of length and width in the process of cold-pressing joining. The wall thickness of joints shows a symmetrical distribution on both sides and the joining thickness decreases from the center to both sides sequentially. With the continuous increase of the punch loading pressure, the average thinning ratio of the joints becomes larger. By contrast, when the other parameters are all the same, the joining strength is the most ideal when the punch loading pressure is 250 kN. The loading pressure which is too small or large is easy to cause an insufficient joining strength or defects. This paper provides a scientific basis in this aspect for optimizing the cold-pressing joining plan and designing a reasonable joint structure. It can also promote the existing cold-pressing joining technologies to be mature, and enrich the existing solid-state joining technology.
Teachers’ attitude regarding the use of ICT. A factor reliability and validity study
Juan Pablo HERNÁNDEZ RAMOS; Fernando MARTÍNEZ ABAD; Francisco José GARCÍA-PEÑALVO; María Esperanza HERRERA GARCÍA; Rodríguez-Conde, María José
2014-01-01
[EN] Current research examines the need for design and validation of a unifactorial scale to measure attitudes of university teachers with regard to ICT. The main goal of this study is to achieve a simple scale, composed of a single factor contributing a clearly reliable measure with acceptable content and factorial validity. A case study is presented, which has been developed with the teaching staff of the University of Salamanca (Spain). In this case study, an expert content validation was ...
On New Cautious Structural Reliability Models in the Framework of imprecise Probabilities
DEFF Research Database (Denmark)
Utkin, Lev V.; Kozine, Igor
2010-01-01
both aleatory (stochas-tic) and epistemic uncertainty and the flexibility with which information can be represented. The previous research of the authors related to generalizing structural reliability models to impre-cise statistical measures is summarized in Utkin & Kozine (2002) and Utkin (2004...... the above mentioned inputs do not exist and the analyst has on-ly some judgments or measurements (observations) of values of stress and strength. How to utilize this available information for computing the structural reliability and what to do if the number of judgments or measurements is very small...
Finite Element Reliability Analysis of Chloride Ingress into Reinforced Concrete Structures
DEFF Research Database (Denmark)
Frier, Christian; Sørensen, John Dalsgaard
2007-01-01
For many reinforced concrete structures corrosion of the reinforcement is an important problem since it can result in maintenance and repair actions. Further, a reduction of the load-bearing capacity can occur. In the present paper the Finite Element Reliability Method (FERM) is employed for obta......For many reinforced concrete structures corrosion of the reinforcement is an important problem since it can result in maintenance and repair actions. Further, a reduction of the load-bearing capacity can occur. In the present paper the Finite Element Reliability Method (FERM) is employed...
RELIABILITY ASSESSMENT OF STRUCTURAL SYSTEMS BASED ON DIRECTIONAL VECTOR SIMULATION TECHNIQUE
Institute of Scientific and Technical Information of China (English)
Zhang Liangxin; Hu Yunchang
2000-01-01
The new improved directional vector simulation method for analyzing the reliability of struc tural systems failure probability is researched. This paper also points out the defects of general directional vector simulation, and gives rise to a new higher accuracy approximate integral formula of structural systems failure probability. A new geometric meaning of characteristic function is obtained. A new simple method of generating uniformly distributed random vector samples in n-dimensional unit hyper-spherical surface is put forward and strictly proved. This method is easy to put into practice. Numerical examples are given to show the applicability and effectiveness of the suggested approach to structural systems reliability problems.
On new cautious structural reliability models in the framework of imprecise probabilities
DEFF Research Database (Denmark)
Utkin, Lev; Kozine, Igor
2010-01-01
New imprecise structural reliability models are described in this paper. They are developed based on the imprecise Bayesian inference and are imprecise Dirichlet, imprecise negative binomial, gamma-exponential and normal models. The models are applied to computing cautious structural reliability...... measures when the number of events of interest or observations is very small. The main feature of the models is that prior ignorance is not modelled by a fixed single prior distribution, but by a class of priors which is defined by upper and lower probabilities that can converge as statistical data...
Thomas, J. M.; Hanagud, S.
1974-01-01
The design criteria and test options for aerospace structural reliability were investigated. A decision methodology was developed for selecting a combination of structural tests and structural design factors. The decision method involves the use of Bayesian statistics and statistical decision theory. Procedures are discussed for obtaining and updating data-based probabilistic strength distributions for aerospace structures when test information is available and for obtaining subjective distributions when data are not available. The techniques used in developing the distributions are explained.
Hanish Nithin, Anu; Omenzetter, Piotr
2017-04-01
Optimization of the life-cycle costs and reliability of offshore wind turbines (OWTs) is an area of immense interest due to the widespread increase in wind power generation across the world. Most of the existing studies have used structural reliability and the Bayesian pre-posterior analysis for optimization. This paper proposes an extension to the previous approaches in a framework for probabilistic optimization of the total life-cycle costs and reliability of OWTs by combining the elements of structural reliability/risk analysis (SRA), the Bayesian pre-posterior analysis with optimization through a genetic algorithm (GA). The SRA techniques are adopted to compute the probabilities of damage occurrence and failure associated with the deterioration model. The probabilities are used in the decision tree and are updated using the Bayesian analysis. The output of this framework would determine the optimal structural health monitoring and maintenance schedules to be implemented during the life span of OWTs while maintaining a trade-off between the life-cycle costs and risk of the structural failure. Numerical illustrations with a generic deterioration model for one monitoring exercise in the life cycle of a system are demonstrated. Two case scenarios, namely to build initially an expensive and robust or a cheaper but more quickly deteriorating structures and to adopt expensive monitoring system, are presented to aid in the decision-making process.
Directory of Open Access Journals (Sweden)
McGinn Aileen P
2005-06-01
Full Text Available Abstract Background Despite the documented benefits of physical activity, many adults do not obtain the recommended amounts. Barriers to physical activity occur at multiple levels, including at the individual, interpersonal, and environmental levels. Only until more recently has there been a concerted focus on how the physical environment might affect physical activity behavior. With this new area of study, self-report measures should be psychometrically tested before use in research studies. Therefore the objective of this study was to document the test-retest reliability of a questionnaire designed to assess physical environmental factors that might be associated with physical activity in a diverse adult population. Methods Test and retest surveys were conducted over the telephone with 106 African American and White women and men living in either Forsyth County, North Carolina or Jackson, Mississippi. Reliability of self-reported environmental factors across four domains (e.g., access to facilities and destinations, functionality and safety, aesthetics, natural environment was determined using intraclass correlation coefficients (ICC overall and separately by gender and race. Results Generally items displayed moderate and sometimes substantial reliability (ICC between 0.4 to 0.8, with a few differences by gender or race, across each of the domains. Conclusion This study provides some psychometric evidence for the use of many of these questions in studies examining the effect of self-reported physical environmental measures on physical activity behaviors, among African American and White women and men.
Validity, reliability and factor analysis of Persian version of schizophrenia quality of life scale.
Masaeli, Nasrin; Omranifard, Victoria; Maracy, Mohammad Reza; Kheirabadi, Gholam Reza; Khedri, Anahita
2016-01-01
Exact measurement of quality of life (QOL) in schizophrenia patients for evaluation of the patient's deterioration and also to assess the efficacy of therapeutic Interventions has become a daily task, which requires accurate assessment tools. This study was aimed to assess the psychometric properties of a Persian version of schizophrenia QOL scale (SQLS) as a common transcultural instrument. One hundred and fifty schizophrenia patients who referred to Psychiatric Clinic in Noor Hospital (Isfahan, Iran) have been selected using simple sampling method. Aside with SQLS, short form-36 general health (SF-36) and World Health Organization QOL-brief-26 (WHOQOL-BREF-26). Questionnaires were completed by the cases for determination of correlation coefficients. The data were analyzed using descriptive statistics, factor analysis, Cronbach's coefficient alpha, Pearson correlation coefficient by Statistical Package for Social Sciences software, version 18 (SPSS-18). Total reliability of the questionnaire was reported by using Cronbach's coefficient alpha 0.84, reliability of individual relationships subscales was 0.91, signs 0/87, symptoms 0/72 and motivation/energy 0/61. Correlation coefficients of SF-36 with a total scale of SQLS and correlation coefficient of WHOQOL-BREF-26 with a total scale of SQLS were acceptable. Exploratory factor analysis using varimax rotation identified four principle components (interpersonal relationship, symptoms, signs, motivation, and energy), which will determine QOL at 52.7% variance. Persian version of the SQLS can be used as a simple, reliable and valid tool in Iranian population.
Comparing Factor Structures of Adolescent Psychopathology
Verona, Edelyn; Javdani, Shabnam; Sprague, Jenessa
2011-01-01
Research on the structure of adolescent psychopathology can provide information on broad factors that underlie different forms of maladjustment in youths. Multiple studies from the literature on adult populations suggest that 2 factors, Internalizing and Externalizing, meaningfully comprise the factor structure of adult psychopathology (e.g.,…
Comparing Factor Structures of Adolescent Psychopathology
Verona, Edelyn; Javdani, Shabnam; Sprague, Jenessa
2011-01-01
Research on the structure of adolescent psychopathology can provide information on broad factors that underlie different forms of maladjustment in youths. Multiple studies from the literature on adult populations suggest that 2 factors, Internalizing and Externalizing, meaningfully comprise the factor structure of adult psychopathology (e.g.,…
van Rijsoort, S; Emmelkamp, P; Vervaeke, G
1999-01-01
In this study the psychometric properties of the PSWQ and the WDQ were investigated in a community sample. The PSWQ proved to be unidimensional although the results indicated that the negatively keyed items contributed less to the general factor. Internal reliability of the PSWQ was satisfactory. Co
Energy Technology Data Exchange (ETDEWEB)
Kim, Ar Ryum; Jang, Inseok Jang; Seong, Poong Hyun [Korea Advanced Institute of Science and Technology, Daejon (Korea, Republic of); Park, Jinkyun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Kim, Jong Hyun [KEPCO, Ulsan (Korea, Republic of)
2015-05-15
The purpose of HRA implementation is 1) to achieve the human factor engineering (HFE) design goal of providing operator interfaces that will minimize personnel errors and 2) to conduct an integrated activity to support probabilistic risk assessment (PRA). For these purposes, various HRA methods have been developed such as technique for human error rate prediction (THERP), simplified plant analysis risk human reliability assessment (SPAR-H), cognitive reliability and error analysis method (CREAM) and so on. In performing HRA, such conditions that influence human performances have been represented via several context factors called performance shaping factors (PSFs). PSFs are aspects of the human's individual characteristics, environment, organization, or task that specifically decrements or improves human performance, thus respectively increasing or decreasing the likelihood of human errors. Most HRA methods evaluate the weightings of PSFs by expert judgment and explicit guidance for evaluating the weighting is not provided. It has been widely known that the performance of the human operator is one of the critical factors to determine the safe operation of NPPs. HRA methods have been developed to identify the possibility and mechanism of human errors. In performing HRA methods, the effect of PSFs which may increase or decrease human error should be investigated. However, the effect of PSFs were estimated by expert judgment so far. Accordingly, in order to estimate the effect of PSFs objectively, the quantitative framework to estimate PSFs by using PSF profiles is introduced in this paper.
Yang, Hongfei; Chang, Edward C
2014-01-01
We examined the factor structure, reliability, and validity of the Chinese version of the Personal Growth Initiative Scale-II (CPGIS-II) using data from a sample of 927 Chinese university students. Consistent with previous findings, confirmatory factor analyses supported a 4-factor model of the CPGIS-II. Reliability analyses indicated that the 4 CPGIS-II subscales, namely Readiness for Change, Planfulness, Using Resources, and Intentional Behavior, demonstrated good internal consistency reliability and adequate test-retest reliability across a 4-week period. In addition, evidence for convergent and incremental validity was found in relation to measures of positive and negative psychological adjustment. Finally, results of hierarchical regression analyses indicated that the 4 personal growth initiative dimensions, especially planfulness, accounted for additional unique variance in psychological adjustment beyond resilience. Some implications for using the CPGIS-II in Chinese are discussed.
Directory of Open Access Journals (Sweden)
Ebrahim Khodadady
2013-06-01
Full Text Available Home Journal Archive V1N3A8Reliability and construct validity of factors underlying the emotional intelligence of Iranian EFL teachers Ebrahim Khodadady Ferdowsi University of Mashhad Saaber Andargani TabrizFerdowsi University of MashhadInternational Branch, Mashhad, Iran ABSTRACT The 133-item Emotional Quotient Inventory (EQ-i designed by Bar-On (1997 and translated by Dehshiry (2003 was revised and modified by removing the response validity items, changing reverse indicators into positively worded statements and revising the remaining 117 Persian indicators on the basis of schema theory. It was administered to 669 instructors most of whom were teaching English as a foreign language (EFL in national branches of Iran Language Institute in 15 cities. The application of the Principal Axis Factoring to the data and rotating the extracted factors via Varimax with Kaiser Normalization yielded 15 latent variables (LVs called Humanistic, Self-Satisfying, Self-Confident, Self-Aware, Self-Controlled, Research-Oriented, Content, Sociable, Empathetic, Tolerant, Flexible, Realistic, Independent, Emotional and Happy in this study. Not only did the modified Persian EQ-I proved to be more reliable than its original version, but also its thirteen LVs reached very high and acceptable levels of reliability. With the exception of the last, all the LVs also correlated significantly with each other and thus established the EI as a multifactorial construct whose constituting LVs are closely related to each other. The findings question correlating the so-called competences of EI and offer employing the factorially valid LVs as the best factors to explore the relationship between EI and variables involved in teaching and learning EFL.
Kingston, Greer B.; Rajabalinejad, Mohammadreza; Gouldby, Ben P.; Gelder, van Pieter H.A.J.M.
2011-01-01
With the continual rise of sea levels and deterioration of flood defence structures over time, it is no longer appropriate to define a design level of flood protection, but rather, it is necessary to estimate the reliability of flood defences under varying and uncertain conditions. For complex geote
Guidelines for Interactive Reliability-Based Structural Optimization using Quasi-Newton Algorithms
DEFF Research Database (Denmark)
Pedersen, C.; Thoft-Christensen, Palle
Guidelines for interactive reliability-based structural optimization problems are outlined in terms of modifications of standard quasi-Newton algorithms. The proposed modifications minimize the condition number of the approximate Hessian matrix in each iteration, restrict the relative and absolute...
Design of a System for Monitoring Reliability of Structures and Constructions in Civil Engineering
Directory of Open Access Journals (Sweden)
Tomislav S. Igić
2011-07-01
Full Text Available Monitoring of civil engineering structures and constructions requires techniques which can produce high precision and accuracy, reliable measurements and fast processing speed. The development of information and communication systems as well as of microprocessor controllers has enabled a creation of monitoring systems that can be used for tracking reliability of structures and constructions in civil engineering, with described key features. This paper describes in detail the architecture of the Civil Engineering Structures Reliability Monitoring (CERM system. The system has been designed for the purposes of the Technical Mechanics and Theory of Constructions Department at the Faculty of Civil Engineering and Architecture, University of Nis. Unlike general commercial monitoring systems, the CERM system has been specially designed for the purpose of reliability monitoring, and its potential will be further exploited in this paper. It is based on usage of universal microprocessor controllers Integraf of series 10X, along with specially designed software package. This system provides real time acquisition of measurements for observed civil engineering structures and analysis of received values based on developed mathematical models.
Graham, Roseanna
2010-01-01
This study evaluated the reliability, validity, and educational usefulness of a comprehensive, multidisciplinary Objective Structured Clinical Examination (OSCE) in dental education. The OSCE was administered to dental students at the Columbia University College of Dental Medicine (CDM) before they entered clinical training. Participants in this…
Woodburn, Jim; Sutcliffe, Nick
1996-01-01
The Objective Structured Clinical Examination (OSCE), initially developed for undergraduate medical education, has been adapted for assessment of clinical skills in podiatry students. A 12-month pilot study found the test had relatively low levels of reliability, high construct and criterion validity, and good stability of performance over time.…
Mann, Karen V.; And Others
1990-01-01
Four years of experience with an objective structured clinical examination (OSCE) following an eight-week surgical clerkship (n=356 students) are reported, including data on mean student performance across years, reliability coefficients, and generalizability. Implications for improvement and development of OSCE are discussed. (Author/MSE)
RESEARCH OF SYNERGETIC RELIABILITY OF PEARLITE-REDUCED STRUCTURAL STEEL 09G2FB
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Gustov Yuriy Ivanovich
2012-10-01
Full Text Available The primary objective of the research is the synergetic reliability of perlite-reduced structural steel 09G2FB exposed to various thermal and mechanical treatments. In the aftermath of the above exposure, the steel in question has proved to assume a set of strength-related and plastic mechanical properties (σσδ and ψ.
2011-11-01
location. Keywords: Model-assisted POD evaluation, probability of detection (POD), reliability, structural health monitoring 1. Introduction The...damage detection method. An ETrema brand Terfenol-D magnetostrictive actuator was used for band- limited pseudo-random excitation up to 1200 Hz, and
The Reliability and Structure of the Classroom Assessment Scoring System in German Pre-Schools
Stuck, Andrea; Kammermeyer, Gisela; Roux, Susanna
2016-01-01
This study examined the reliability and structure of the Classroom Assessment Scoring System (CLASS; Pianta, R. C., K. M. La Paro, and B. K. Hamre. 2008. "Classroom Assessment Scoring System. Manual Pre-K." Baltimore, MD: Brookes) and the quality of interactional processes in a German pre-school setting, drawing on a sample of 390…
Kingston, Greer B.; Rajabali Nejad, Mohammadreza; Gouldby, Ben P.; van Gelder, Pieter H.A.J.M.
2011-01-01
With the continual rise of sea levels and deterioration of flood defence structures over time, it is no longer appropriate to define a design level of flood protection, but rather, it is necessary to estimate the reliability of flood defences under varying and uncertain conditions. For complex
Structural and Fractal Dimensions are Reliable Determinants of Grain Yield in Soybean
Reliable models are needed to describe plants with complex geometric structures, quantify the impact of management strategies on the plant’s geometric distribution in space and time, and predict yield as a function of fractal dimension. We measured growth and development variables on single soybean ...
Monte Carlo simulation - a powerful tool to support experimental activities in structure reliability
Energy Technology Data Exchange (ETDEWEB)
Yuritzinn, T. [CEA Saclay, Dept. de Mecanique et de Technologie (DRN/DMT/SEMT/LISN), 91 - Gif-sur-Yvette (France); Chapuliot, S. [CEA Saclay, Dept. Modelisation de Systemes et Structures (DM2S/SEMT), 91 - Gif sur Yvette (France); Eid, M. [CEA Saclay, Dept. de Mecanique et de Technologie (DRN/DMT/SERMA/LCA), 91 - Gif-sur-Yvette (France); Masson, R.; Dahl, A.; Moinereau, D. [Electricite de France (EDF), 75 - Paris (France)
2003-07-01
Monte-Carlo Simulation (MCS) can have different uses in supporting structure reliability investigations and assessments. In this paper we focus our interest on the use of MCS as a numerical tool to support the fitting of the experimental data related to toughness experiments. (authors)
Predictions of Crystal Structure Based on Radius Ratio: How Reliable Are They?
Nathan, Lawrence C.
1985-01-01
Discussion of crystalline solids in undergraduate curricula often includes the use of radius ratio rules as a method for predicting which type of crystal structure is likely to be adopted by a given ionic compound. Examines this topic, establishing more definitive guidelines for the use and reliability of the rules. (JN)
Reliability Analysis of Ice-Induced Fatigue and Damage in Offshore Engineering Structures
Institute of Scientific and Technical Information of China (English)
2000-01-01
－ In Bohai Gulf, offshore and other installations have collapsed by sea ice due to the fatigue and fracture of the main supporting components in the ice environments. In this paper presented are some results on fatigue reliability of these structures in the Gulf by investigating the distributions of ice parameters such as its floating direction and speed, sheet thickness, compressive strength, ice forces on the structures, and hot spot stress in the structure. The low temperature, ice breaking modes and component fatigue failure modes are also taken into account in the analysis of the fatigue reliability of the offshore structures experiencing both random ice loading and low temperatures. The results could be applied to the design and operation of offshore platforms in the Bohai Gulf.
A practical engineering method for fuzzy reliability analysis of mechanical structures
Energy Technology Data Exchange (ETDEWEB)
Li Bing; Zhu Meilin; Xu Kai
2000-03-01
The fuzzy sets theory in reliability analyses is studied. The structure stress is related to several other variables, such as structure sizes, material properties, external loads; in most cases, it is difficult to be expressed in a mathematical formula, and the related variables are not random variables, but fuzzy variables or other uncertain variables which have not only randomness but also fuzziness. In this paper, a novel approach is presented to use the finite element analysis as a 'numerical experiment' tool, and to find directly, by fuzzy linear regression method, the statistical property of the structure stress. Based on the fuzzy stress-random strength interference model proposed in this paper, the fuzzy reliability of the mechanical structure can be evaluated. The compressor blade of a given turbocharger is then introduced as a realistic example to illustrate the approach.
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
An efficient importance sampling algorithm is presented to analyze reliability of complex structural system with multiple failure modes and fuzzy-random uncertainties in basic variables and failure modes. In order to improve the sampling efficiency, the simulated annealing algorithm is adopted to optimize the density center of the importance sampling for each failure mode, and results that the more significant contribution the points make to fuzzy failure probability, the higher occurrence possibility the points are sampled. For the system with multiple fuzzy failure modes, a weighted and mixed importance sampling function is constructed. The contribution of each fuzzy failure mode to the system failure probability is represented by the appropriate factors, and the efficiency of sampling is improved furthermore. The variances and the coefficients of variation are derived for the failure probability estimations. Two examples are introduced to illustrate the rationality of the present method. Comparing with the direct Monte-Carlo method, the improved efficiency and the precision of the method are verified by the examples.
Directory of Open Access Journals (Sweden)
Hudson W. de Carvalho
2013-06-01
Full Text Available Objective: Positive and negative affect are the two psychobiological-dispositional dimensions reflecting proneness to positive and negative activation that influence the extent to which individuals experience life events as joyful or as distressful. The Positive and Negative Affect Schedule (PANAS is a structured questionnaire that provides independent indexes of positive and negative affect. This study aimed to validate a Brazilian interview-version of the PANAS by means of factor and internal consistency analysis. Methods: A representative community sample of 3,728 individuals residing in the cities of São Paulo and Rio de Janeiro, Brazil, voluntarily completed the PANAS. Exploratory structural equation model analysis was based on maximum likelihood estimation and reliability was calculated via Cronbach's alpha coefficient. Results: Our results provide support for the hypothesis that the PANAS reliably measures two distinct dimensions of positive and negative affect. Conclusion: The structure and reliability of the Brazilian version of the PANAS are consistent with those of its original version. Taken together, these results attest the validity of the Brazilian adaptation of the instrument.
Institute of Scientific and Technical Information of China (English)
JIN Wei-liang; HU Qi-zhong; SHEN Zhao-wei; SHI Zhong-min
2009-01-01
The target reliability index has been effectively used as the best solution to deal with the relationship between the structural safety and the optimal economy in any structural design.However,the target reliability index for offshore jacket platforms based on different sea areas in China has never been calibrated.This paper presents an approach for its calibration,and suggests many kinds of associated load cases.The uncertainties of loads and structural resistance are mainly investigated.The target reliability index for structural components,tubular joints and piles of offshore jacket platforms are discussed respectively in detail.Finally,through the calibrated results from the offshore jacket platforms of QK18-1,JZ20-2,SZ36-1 and BZ28-1 in the Bohai Bay,it is proposed to adopt 2.8 as the target reliability index of offshore jacket platforms in the Bohai Bay for a 25-year design period.The results provide significant reference for the design of offshore jacket platforms.
An Intelligent Method for Structural Reliability Analysis Based on Response Surface
Institute of Scientific and Technical Information of China (English)
桂劲松; 刘红; 康海贵
2004-01-01
As water depth increases, the structural safety and reliability of a system become more and more important and challenging. Therefore, the structural reliability method must be applied in ocean engineering design such as offshore platform design. If the performance function is known in structural reliability analysis, the first-order second-moment method is often used. If the performance function could not be definitely expressed, the response surface method is always used because it has a very clear train of thought and simple programming. However, the traditional response surface method fits the response surface of quadratic polynomials where the problem of accuracy could not be solved, because the true limit state surface can be fitted well only in the area near the checking point. In this paper, an intelligent computing method based on the whole response surface is proposed, which can be used for the situation where the performance function could not be definitely expressed in structural reliability analysis. In this method, a response surface of the fuzzy neural network for the whole area should be constructed first, and then the structural reliability can be calculated by the genetic algorithm. In the proposed method, all the sample points for the training network come from the whole area, so the true limit state surface in the whole area can be fitted. Through calculational examples and comparative analysis, it can be known that the proposed method is much better than the traditional response surface method of quadratic polynomials, because, the amount of calculation of finite element analysis is largely reduced, the accuracy of calculation is improved,and the true limit state surface can be fitted very well in the whole area. So, the method proposed in this paper is suitable for engineering application.
Directory of Open Access Journals (Sweden)
Ebrahim Khodadady
2013-06-01
The 133-item Emotional Quotient Inventory (EQ-i designed by Bar-On (1997 and translated by Dehshiry (2003 was revised and modified by removing the response validity items, changing reverse indicators into positively worded statements and revising the remaining 117 Persian indicators on the basis of schema theory. It was administered to 669 instructors most of whom were teaching English as a foreign language (EFL in national branches of Iran Language Institute in 15 cities. The application of the Principal Axis Factoring to the data and rotating the extracted factors via Varimax with Kaiser Normalization yielded 15 latent variables (LVs called Humanistic, Self-Satisfying, Self-Confident, Self-Aware, Self-Controlled, Research-Oriented, Content, Sociable, Empathetic, Tolerant, Flexible, Realistic, Independent, Emotional and Happy in this study. Not only did the modified Persian EQ-I proved to be more reliable than its original version, but also its thirteen LVs reached very high and acceptable levels of reliability. With the exception of the last, all the LVs also correlated significantly with each other and thus established the EI as a multifactorial construct whose constituting LVs are closely related to each other. The findings question correlating the so-called competences of EI and offer employing the factorially valid LVs as the best factors to explore the relationship between EI and variables involved in teaching and learning EFL.
Probabilistic Calibration of Fatigue Design Factors for Offshore Wind Turbine Support Structures
DEFF Research Database (Denmark)
Ramirez, José Rangel; Sørensen, John Dalsgaard
2010-01-01
This paper describes a reliability-based approach to determine fatigue design factors (FDF) for offshore wind turbine support structures made of steel. The FDF values are calibrated to a specific reliability level and linked to a specific inspection and maintenance (I&M) strategy used for the con...
Reliability design optimization of composite structures based on PSO together with FEA
Institute of Scientific and Technical Information of China (English)
Chen Jianqiao; Tang Yuanfu; Ge Rui; An Qunli; Guo Xiwei
2013-01-01
The present work aims to develop a method for reliability-based optimum design of composite structures.A procedure combining particle swarm optimization (PSO) and finite element analysis (FEA) has been proposed.Numerical examples for the reliability design optimization (RDO) of a laminate and a composite cylindrical shell are worked out to demonstrate the effectiveness of the method.Then a design for composite pressure vessels is studied.The advantages and necessity of RDO over the conventional equi-strength design are addressed.Examples show that the proposed method has good stability and is efficient in dealing with the probabilistic optimal design of composite structures.It may serve as an effective tool to optimize other complicated structures with uncertainties.
DEFF Research Database (Denmark)
Ingwersen, Kim Gordon; Hjarbæk, John; Eshøj, Henrik;
2016-01-01
changes on captured US images and movie sequences of relevance for patients with supraspinatus tendinopathy. Future studies should test intra-rater and inter-rater reliability of the method in vivo for use in clinical practice, in addition to validation against a gold standard, such as MRI.......Aim To evaluate the inter-rater reliability of measuring structural changes in the tendon of patients, clinically diagnosed with supraspinatus tendinopathy (cases) and healthy participants (controls), on ultrasound (US) images captured by standardised procedures. Methods A total of 40 participants...... (24 patients) were included for assessing inter-rater reliability of measurements of fibrillar disruption, neovascularity, as well as the number and total length of calcifications and tendon thickness. Linear weighted κ, intraclass correlation (ICC), SEM, limits of agreement (LOA) and minimal...
DEFF Research Database (Denmark)
Ingwersen, Kim Gordon; Hjarbæk, John; Eshøj, Henrik
2016-01-01
Aim To evaluate the inter-rater reliability of measuring structural changes in the tendon of patients, clinically diagnosed with supraspinatus tendinopathy (cases) and healthy participants (controls), on ultrasound (US) images captured by standardised procedures. Methods A total of 40 participants...... (24 patients) were included for assessing inter-rater reliability of measurements of fibrillar disruption, neovascularity, as well as the number and total length of calcifications and tendon thickness. Linear weighted κ, intraclass correlation (ICC), SEM, limits of agreement (LOA) and minimal...... detectable change (MDC) were used to evaluate reliability. Results ‘Moderate—almost perfect’ κ was found for grading fibrillar disruption, neovascularity and number of calcifications (k 0.60–0.96). For total length of calcifications and tendon thickness, ICC was ‘excellent’ (0.85–0.90), with SEM...
Predicting Reliability of Tactical Network Using RBFNN
Institute of Scientific and Technical Information of China (English)
WANG Xiao-kai; HOU Chao-zhen
2005-01-01
A description of the reliability evaluation of tactical network is given, which reflects not only the non-reliable factors of nodes and links but also the factors of network topological structure. On the basis of this description, a reliability prediction model and its algorithms are put forward based on the radial basis function neural network (RBFNN) for the tactical network. This model can carry out the non-linear mapping relationship between the network topological structure, the nodes reliabilities, the links reliabilities and the reliability of network. The results of simulation prove the effectiveness of this method in the reliability and the connectivity prediction for tactical network.
New reliability charge incentives and structure in the Colombian electrical sector
Directory of Open Access Journals (Sweden)
Julio E. Villareal Navarro
2010-07-01
Full Text Available Ensuring sector reliability has always been an important issue in electrical sector policy. However, the challenge could be even greater for hydro-dependent systems (as in the Colombian system operating in the South-American equatorial zone, since clima-tic shocks such as the “el niño” phenomenon usually have a very strong impact on supply, thereby leading to market disequili-brium. Such systems thus require a very specific regulatory structure to assure generation units as “backup units” which may gene-rate electrical energy during critical moments. This paper examines the new reliability charge developed by the Colombian Commission for Regulating Energy and Gas (CREG, its characteristics and incentive mechanisms to ensure Colombian electrical system reliability under extreme weather condition. The new system promotes sector reliability during periods of scarcity and provi-des a clear incentive for new investment in backup generation. However, the instrument’s design could be improved if it included an explicit penalty for those units which do not honor their firm energy commitment. The instrument could thus encourage the non-entry of units which have either low reliability levels or speculative purposes.
Network Reliability: The effect of local network structure on diffusive processes
Youssef, Mina; Eubank, Stephen
2013-01-01
This paper re-introduces the network reliability polynomial - introduced by Moore and Shannon in 1956 -- for studying the effect of network structure on the spread of diseases. We exhibit a representation of the polynomial that is well-suited for estimation by distributed simulation. We describe a collection of graphs derived from Erd\\H{o}s-R\\'enyi and scale-free-like random graphs in which we have manipulated assortativity-by-degree and the number of triangles. We evaluate the network reliability for all these graphs under a reliability rule that is related to the expected size of a connected component. Through these extensive simulations, we show that for positively or neutrally assortative graphs, swapping edges to increase the number of triangles does not increase the network reliability. Also, positively assortative graphs are more reliable than neutral or disassortative graphs with the same number of edges. Moreover, we show the combined effect of both assortativity-by-degree and the presence of triangl...
How Many Performance Shaping Factors are Necessary for Human Reliability Analysis?
Energy Technology Data Exchange (ETDEWEB)
Ronald L. Boring
2010-06-01
It has been argued that human reliability analysis (HRA) has expended considerable energy on creating detailed representations of human performance through an increasingly long list of performance shaping factors (PSFs). It is not clear, however, to what extent this refinement and expansion of PSFs has enhanced the quality of HRA. Indeed, there is considerable range in the number of PSFs provided by individual HRA methods, ranging from single factor models such as time-reliability curves, up to 50 or more PSFs in some current HRA models. The US Nuclear Regulatory Commission advocates 15 PSFs in its HRA Good Practices (NUREG-1792), while its SPAR-H method (NUREG/CR-6883) espouses the use of eight PSFs and its ATHEANA method (NUREG-1624) features an open-ended number of PSFs. The apparent differences in the optimal number of PSFs can be explained in terms of the diverse functions of PSFs in HRA. The purpose of this paper is to explore the role of PSFs across different stages of HRA, including identification of potential human errors, modeling of these errors into an overall probabilistic risk assessment, quantifying errors, and preventing errors.
Strategic planning decision making using fuzzy SWOT-TOPSIS with reliability factor
Mohamad, Daud; Afandi, Nur Syamimi; Kamis, Nor Hanimah
2015-10-01
Strategic planning is a process of decision making and action for long-term activities in an organization. The Strengths, Weaknesses, Opportunities and Threats (SWOT) analysis has been commonly used to help organizations in strategizing their future direction by analyzing internal and external environment. However, SWOT analysis has some limitations as it is unable to prioritize appropriately the multiple alternative strategic decisions. Some efforts have been made to solve this problem by incorporating Multi Criteria Decision Making (MCDM) methods. Nevertheless, another important aspect has raised concerns on obtaining the decision that is the reliability of the information. Decision makers evaluate differently depending on their level of confidence or sureness in the evaluation. This study proposes a decision making procedure for strategic planning using SWOT-TOPSIS method by incorporating the reliability factor of the evaluation based on Z-number. An example using a local authority in the east coast of Malaysia is illustrated to determine the strategic options ranking and to prioritize factors in each SWOT category.
Factor structure of emotional intelligence in schizophrenia.
Lin, Yu-Chung; Wynn, Jonathan K; Hellemann, Gerhard; Green, Michael F
2012-08-01
Social cognition, which includes emotional intelligence, is impaired in schizophrenia. The Mayer-Salovey-Caruso Emotional Intelligence Test (MSCEIT) is a widely-used assessment of emotional intelligence, with a four-factor structure in healthy individual. However, a recent factor analysis in schizophrenia patients revealed a two-factor structure of the MSCEIT. The current study aimed to replicate this finding in a larger, more diverse, schizophrenia sample (n=194). Our findings revealed an identical two-factor structure as in the previously-reported study, indicating that emotional intelligence is organized in a different manner in schizophrenia than it is in healthy controls.
Test-retest reliability of white matter structural brain networks: A multiband diffusion MRI study
Directory of Open Access Journals (Sweden)
Tengda eZhao
2015-02-01
Full Text Available The multiband EPI sequence has been developed for the human connectome project to accelerate MRI data acquisition. However, no study has yet investigated the test-retest (TRT reliability of the graph metrics of white matter (WM structural brain networks constructed from this new sequence. Here, we employed a multiband diffusion MRI (dMRI dataset with repeated scanning sessions and constructed both low- and high-resolution WM networks by volume- and surface-based parcellation methods. The reproducibility of network metrics and its dependence on type of construction procedures was assessed by the intra-class correlation coefficient (ICC. We observed conserved topological architecture of WM structural networks constructed from the multiband dMRI data as previous findings from conventional dMRI. For the global network properties, the first order metrics were more reliable than second order metrics. Between two parcellation methods, networks with volume-based parcellation showed better reliability than surface-based parcellation, especially for the global metrics. Between different resolutions, the high-resolution network exhibited higher TRT performance than the low-resolution in terms of the global metrics with a large effect size, whereas the low-resolution performs better in terms of local (region and connection properties with a relatively low effect size. Moreover, we identified that the association and primary cortices showed higher reproducibility than the paralimbic/limbic regions. The important hub regions and rich-club connections are more reliable than the non-hub regions and connections. Finally, we found WM networks from the multiband dMRI showed higher reproducibility compared with those from the conventional dMRI. Together, our results demonstrated the fair to good reliability of the WM structural brain networks from the multiband EPI sequence, suggesting its potential utility for exploring individual differences and for clinical
Test-retest reliability of white matter structural brain networks: a multiband diffusion MRI study.
Zhao, Tengda; Duan, Fei; Liao, Xuhong; Dai, Zhengjia; Cao, Miao; He, Yong; Shu, Ni
2015-01-01
The multiband EPI sequence has been developed for the human connectome project to accelerate MRI data acquisition. However, no study has yet investigated the test-retest (TRT) reliability of the graph metrics of white matter (WM) structural brain networks constructed from this new sequence. Here, we employed a multiband diffusion MRI (dMRI) dataset with repeated scanning sessions and constructed both low- and high-resolution WM networks by volume- and surface-based parcellation methods. The reproducibility of network metrics and its dependence on type of construction procedures was assessed by the intra-class correlation coefficient (ICC). We observed conserved topological architecture of WM structural networks constructed from the multiband dMRI data as previous findings from conventional dMRI. For the global network properties, the first order metrics were more reliable than second order metrics. Between two parcellation methods, networks with volume-based parcellation showed better reliability than surface-based parcellation, especially for the global metrics. Between different resolutions, the high-resolution network exhibited higher TRT performance than the low-resolution in terms of the global metrics with a large effect size, whereas the low-resolution performs better in terms of local (region and connection) properties with a relatively low effect size. Moreover, we identified that the association and primary cortices showed higher reproducibility than the paralimbic/limbic regions. The important hub regions and rich-club connections are more reliable than the non-hub regions and connections. Finally, we found WM networks from the multiband dMRI showed higher reproducibility compared with those from the conventional dMRI. Together, our results demonstrated the fair to good reliability of the WM structural brain networks from the multiband EPI sequence, suggesting its potential utility for exploring individual differences and for clinical applications.
CARES/LIFE Ceramics Analysis and Reliability Evaluation of Structures Life Prediction Program
Nemeth, Noel N.; Powers, Lynn M.; Janosik, Lesley A.; Gyekenyesi, John P.
2003-01-01
This manual describes the Ceramics Analysis and Reliability Evaluation of Structures Life Prediction (CARES/LIFE) computer program. The program calculates the time-dependent reliability of monolithic ceramic components subjected to thermomechanical and/or proof test loading. CARES/LIFE is an extension of the CARES (Ceramic Analysis and Reliability Evaluation of Structures) computer program. The program uses results from MSC/NASTRAN, ABAQUS, and ANSYS finite element analysis programs to evaluate component reliability due to inherent surface and/or volume type flaws. CARES/LIFE accounts for the phenomenon of subcritical crack growth (SCG) by utilizing the power law, Paris law, or Walker law. The two-parameter Weibull cumulative distribution function is used to characterize the variation in component strength. The effects of multiaxial stresses are modeled by using either the principle of independent action (PIA), the Weibull normal stress averaging method (NSA), or the Batdorf theory. Inert strength and fatigue parameters are estimated from rupture strength data of naturally flawed specimens loaded in static, dynamic, or cyclic fatigue. The probabilistic time-dependent theories used in CARES/LIFE, along with the input and output for CARES/LIFE, are described. Example problems to demonstrate various features of the program are also included.
Directory of Open Access Journals (Sweden)
Jarnlo Gun-Britt
2005-07-01
Full Text Available Abstract Background In most clubfoot studies, the outcome instruments used are designed to evaluate classification or long-term cross-sectional results. Variables deal mainly with factors on body function/structure level. Wide scorings intervals and total sum scores increase the risk that important changes and information are not detected. Studies of the reliability, validity and responsiveness of these instruments are sparse. The lack of an instrument for longitudinal follow-up led the investigators to develop the Clubfoot Assessment Protocol (CAP. The aim of this article is to introduce and describe the CAP and evaluate the items inter- and intra reliability in relation to patient age. Methods The CAP was created from 22 items divided between body function/structure (three subgroups and activity (one subgroup levels according to the International Classification of Function, Disability and Health (ICF. The focus is on item and subgroup development. Two experienced examiners assessed 69 clubfeet in 48 children who had a median age of 2.1 years (range, 0 to 6.7 years. Both treated and untreated feet with different grades of severity were included. Three age groups were constructed for studying the influence of age on reliability. The intra- rater study included 32 feet in 20 children who had a median age of 2.5 years (range, 4 months to 6.8 years. The Unweighted Kappa statistics, percentage observer agreement, and amount of categories defined how reliability was to be interpreted. Results The inter-rater reliability was assessed as moderate to good for all but one item. Eighteen items had kappa values > 0.40. Three items varied from 0.35 to 0.38. The mean percentage observed agreement was 82% (range, 62 to 95%. Different age groups showed sufficient agreement. Intra- rater; all items had kappa values > 0.40 [range, 0.54 to 1.00] and a mean percentage agreement of 89.5%. Categories varied from 3 to 5. Conclusion The CAP contains more detailed
Eysenck Personality Inventory Item Factor Structure.
Comrey, Andrew L.; And Others
1988-01-01
Three methods were used to test the factor structure of the Eysenck Personality Inventory administered to 583 Australians. The preferred method was to extract factors by the minimum residual method, use the Tandem Criteria Method, and then rotate that number of factors by the Tandem Criteria I method. (SLD)
Reliability based multiobjective optimization for design of structures subject to random vibrations
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
Based on a multiobjective approach whose objective function (OF) vector collects stochastic reliability performance and structural cost indices, a structural optimization criterion for mechanical systems subject to random vibrations is presented for supporting engineer's design. This criterion differs from the most commonly used conventional optimum design criterion for random vibrating structure, which is based on minimizing displacement or acceleration variance of main structure responses,without considering explicitly required performances against failure. The proposed criterion can properly take into account the design-reliability required performances, and it becomes a more efficient support for structural engineering decision making. The multiobjective optimum (MOO) design of a tuned mass damper (TMD) has been developed in a typical seismic design problem, to control structural vibration induced on a multi-storey building structure excited by nonstationary base acceleration random process.A numerical example for a three-storey building is developed and a sensitivity analysis is carried out. The results are shown in a useful manner for TMD design decision support.
Maaroufi, S.; Parrain, F.; Lefeuvre, E.; Boutaud, B.; Dal Molin, R.
2015-12-01
In this paper we propose an approach to study the reliability of piezoelectric structures and more precisely energy harvesting micro-devices dedicated to autonomous active medical implants (new generation pacemakers). The structure under test is designed as a bimorph piezoelectric cantilever with a seismic mass at its tip. Good understanding of material aging and mechanical failure is critical for this kind of system. To study the reliability and durability of the piezoelectric part we propose to establish a new accelerated methodology and an associated test bench where the environment and stimuli can be precisely controlled over a wide period of time. This will allow the identification of potential failure modes and the study of their impacts by the way of direct mechanical investigation based on stiffness and blocking force measurements performed periodically.
DEFF Research Database (Denmark)
Luo, Yangjun; Wu, Xiaoxiang; Zhou, Mingdong
2015-01-01
on a probability-interval mixed reliability model, the imprecision of design parameters is modeled as interval uncertainties fluctuating within allowable tolerance bounds. The optimization model is defined as to minimize the total manufacturing cost under mixed reliability index constraints, which are further...... transformed into their equivalent formulations by using the performance measure approach. The optimization problem is then solved with the sequential approximate programming. Meanwhile, a numerically stable algorithm based on the trust region method is proposed to efficiently update the target performance......Both structural sizes and dimensional tolerances strongly influence the manufacturing cost and the functional performance of a practical product. This paper presents an optimization method to simultaneously find the optimal combination of structural sizes and dimensional tolerances. Based...
Celorrio Barragué, Luis
2015-01-01
Congreso celebrado en la Escuela de Arquitectura de la Universidad de Sevilla desde el 24 hasta el 26 de junio de 2015. Uncertainties are inherent in material properties, geometry parameters and loading in structural design problems. In a realistic design, it is necessary to consider these types of uncertainties to ensure safety and quality. Design constraints are formulated in probabilistic terms such as probability of failure or reliability index. The process of design optimization enhan...
Reliability assessment of fatigue critical welded details in wind turbine jacket support structures
DEFF Research Database (Denmark)
Branner, Kim; Stensgaard Toft, Henrik; Haselbach, Philipp Ulrich;
2013-01-01
This paper describes a probabilistic approach to reliability assessment of fatigue critical welded details in jacket support structures for offshore wind turbines. The analysis of the jacket response to the operational loads is performed using Finite Element Method (FEM) simulations in SIMULIA...... Abaqus. Fatigue stress cycles are computed on the jacket members by applying tower top loads from an aeroelastic simulation with superimposed marine loads and in accordance to the IEC-61400-3 guidelines for operational conditions. The combined effect of the hydrodynamic loads and the rotor loads...... on the jacket structure is analyzed in a de-coupled scheme, but including the structural dynamics of the support structure. The failure prediction of the welded joints, connecting the individual members of the support structure is based on SN-curves and Miners rule according to ISO 19902 and DNV-RP-C203/DNV...
Institute of Scientific and Technical Information of China (English)
Xiaoyan Bai; Hong Shen
2007-01-01
OBJECTIVE To compare the expression of the thyroid transcription factor-1 (TTF-1) in human normal adult type Ⅱ alveolar epithelial cells,embryonic pneumocytes and cancer cells of lung carcinoma and metastatic lymph nodes using a tissue microarray (TMA) along with paired conventional full sections.and to jnvestigate the reliability of tissue microarrays in detecting protein expression in lung carcinoma.METHODS A lung carcinoma TMA including 765 cores was constructed.TTF-1 protein expression in both TMA and paired conventional full sections were detected by yhe immunohistochemical SP method using a monoclonal antibody to TTF-1.A PU (Positive Unit) of TTF-1 protein was assessed quantitatively by the Leica Q500MC image analysis system with results from the paired conventional full sections as controls.RESULTS There was no signifcance between TMA and paired conven tional full sections in TTF-1 expression in difierent nuclei of the lung tissue.CONCLUSION TTF-1 protein expression in lung carcinoma detected by TMA was highly concordanl with that of paired full sections.TMA is a reliable method in detecting protein expression.
Reliability analysis of the objective structured clinical examination using generalizability theory
Trejo-Mejía, Juan Andrés; Sánchez-Mendiola, Melchor; Méndez-Ramírez, Ignacio; Martínez-González, Adrián
2016-01-01
Background The objective structured clinical examination (OSCE) is a widely used method for assessing clinical competence in health sciences education. Studies using this method have shown evidence of validity and reliability. There are no published studies of OSCE reliability measurement with generalizability theory (G-theory) in Latin America. The aims of this study were to assess the reliability of an OSCE in medical students using G-theory and explore its usefulness for quality improvement. Methods An observational cross-sectional study was conducted at National Autonomous University of Mexico (UNAM) Faculty of Medicine in Mexico City. A total of 278 fifth-year medical students were assessed with an 18-station OSCE in a summative end-of-career final examination. There were four exam versions. G-theory with a crossover random effects design was used to identify the main sources of variance. Examiners, standardized patients, and cases were considered as a single facet of analysis. Results The exam was applied to 278 medical students. The OSCE had a generalizability coefficient of 0.93. The major components of variance were stations, students, and residual error. The sites and the versions of the tests had minimum variance. Conclusions Our study achieved a G coefficient similar to that found in other reports, which is acceptable for summative tests. G-theory allows the estimation of the magnitude of multiple sources of error and helps decision makers to determine the number of stations, test versions, and examiners needed to obtain reliable measurements. PMID:27543188
Reliability analysis of the objective structured clinical examination using generalizability theory
Directory of Open Access Journals (Sweden)
Juan Andrés Trejo-Mejía
2016-08-01
Full Text Available Background: The objective structured clinical examination (OSCE is a widely used method for assessing clinical competence in health sciences education. Studies using this method have shown evidence of validity and reliability. There are no published studies of OSCE reliability measurement with generalizability theory (G-theory in Latin America. The aims of this study were to assess the reliability of an OSCE in medical students using G-theory and explore its usefulness for quality improvement. Methods: An observational cross-sectional study was conducted at National Autonomous University of Mexico (UNAM Faculty of Medicine in Mexico City. A total of 278 fifth-year medical students were assessed with an 18-station OSCE in a summative end-of-career final examination. There were four exam versions. G-theory with a crossover random effects design was used to identify the main sources of variance. Examiners, standardized patients, and cases were considered as a single facet of analysis. Results: The exam was applied to 278 medical students. The OSCE had a generalizability coefficient of 0.93. The major components of variance were stations, students, and residual error. The sites and the versions of the tests had minimum variance. Conclusions: Our study achieved a G coefficient similar to that found in other reports, which is acceptable for summative tests. G-theory allows the estimation of the magnitude of multiple sources of error and helps decision makers to determine the number of stations, test versions, and examiners needed to obtain reliable measurements.
Moment Method Based on Fuzzy Reliability Sensitivity Analysis for a Degradable Structural System
Institute of Scientific and Technical Information of China (English)
Song Jun; Lu Zhenzhou
2008-01-01
For a degradable structural system with fuzzy failure region, a moment method based on fuzzy reliability sensitivity algorithm is presented. According to the value assignment of porformance function, the integral region for calculating the fuzzy failure probability is first split into a series of subregions in which the membership function values of the performance function within the fuzzy failure region can be approximated by a set of constants. The fuzzy failure probability is then transformed into a sum of products oftbe random failure probabilities and the approximate constants of the membership function in the subregions. Furthermore, the fuzzy reliability sensitivity analysis is transformed into a series of random reliability sensitivity analysis, and the random reliability sensitivity can be obtained by the constructed moment method. The primary advantages of the presented method include higher efficiency for implicit performance function with low and medium dimensionality and wide applicability to multiple failure modes and nonnormal basic random variables. The limitation is that the required computation effort grows exponentially with the increase of dimensionality of the basic random vari-able; hence, it is not suitable for high dimensionality problem. Compared with the available methods, the presented one is pretty com-petitive in the case that the dimensionality is lower than 10. The presented examples are used to verify the advantages and indicate the limitations.
Stroud, W. Jefferson; Krishnamurthy, Thiagaraja; Sykes, Nancy P.; Elishakoff, Isaac
1993-01-01
Computations were performed to determine the effect of an overall bow-type imperfection on the reliability of structural panels under combined compression and shear loadings. A panel's reliability is the probability that it will perform the intended function - in this case, carry a given load without buckling or exceeding in-plane strain allowables. For a panel loaded in compression, a small initial bow can cause large bending stresses that reduce both the buckling load and the load at which strain allowables are exceeded; hence, the bow reduces the reliability of the panel. In this report, analytical studies on two stiffened panels quantified that effect. The bow is in the shape of a half-sine wave along the length of the panel. The size e of the bow at panel midlength is taken to be the single random variable. Several probability density distributions for e are examined to determine the sensitivity of the reliability to details of the bow statistics. In addition, the effects of quality control are explored with truncated distributions.
Event-triggered H∞ reliable control for offshore structures in network environments
Zhang, Bao-Lin; Han, Qing-Long; Zhang, Xian-Ming
2016-04-01
This paper investigates the network-based modeling and event-triggered H∞ reliable control for an offshore structure. First, a network-based model of the offshore structure subject to external wave force and actuator faults is presented. Second, an event-triggering mechanism is proposed such that during the control implementation, only requisite sampled-data is transmitted over networks. Third, an event-triggered H∞ reliable control problem for the offshore structure is solved by employing the Lyapunov-Krasovskii functional approach, and the desired controller can be derived. It is shown through simulation results that for possible actuator failures, the networked controller is capable of guaranteeing the stability of the offshore structure. In addition, compared with the H∞ control scheme without network settings, the proposed controller can suppress the vibration of the offshore structure to almost the same level as the H∞ controller, while the former requires less control cost. Furthermore, under the network-based controller, the communication resources can be saved significantly.
Improved reliability, accuracy and quality in automated NMR structure calculation with ARIA
Energy Technology Data Exchange (ETDEWEB)
Mareuil, Fabien [Institut Pasteur, Cellule d' Informatique pour la Biologie (France); Malliavin, Thérèse E.; Nilges, Michael; Bardiaux, Benjamin, E-mail: bardiaux@pasteur.fr [Institut Pasteur, Unité de Bioinformatique Structurale, CNRS UMR 3528 (France)
2015-08-15
In biological NMR, assignment of NOE cross-peaks and calculation of atomic conformations are critical steps in the determination of reliable high-resolution structures. ARIA is an automated approach that performs NOE assignment and structure calculation in a concomitant manner in an iterative procedure. The log-harmonic shape for distance restraint potential and the Bayesian weighting of distance restraints, recently introduced in ARIA, were shown to significantly improve the quality and the accuracy of determined structures. In this paper, we propose two modifications of the ARIA protocol: (1) the softening of the force field together with adapted hydrogen radii, which is meaningful in the context of the log-harmonic potential with Bayesian weighting, (2) a procedure that automatically adjusts the violation tolerance used in the selection of active restraints, based on the fitting of the structure to the input data sets. The new ARIA protocols were fine-tuned on a set of eight protein targets from the CASD–NMR initiative. As a result, the convergence problems previously observed for some targets was resolved and the obtained structures exhibited better quality. In addition, the new ARIA protocols were applied for the structure calculation of ten new CASD–NMR targets in a blind fashion, i.e. without knowing the actual solution. Even though optimisation of parameters and pre-filtering of unrefined NOE peak lists were necessary for half of the targets, ARIA consistently and reliably determined very precise and highly accurate structures for all cases. In the context of integrative structural biology, an increasing number of experimental methods are used that produce distance data for the determination of 3D structures of macromolecules, stressing the importance of methods that successfully make use of ambiguous and noisy distance data.
The Factor Structure in Equity Options
DEFF Research Database (Denmark)
Christoffersen, Peter; Fournier, Mathieu; Jacobs, Kris
Principal component analysis of equity options on Dow-Jones firms reveals a strong factor structure. The first principal component explains 77% of the variation in the equity volatility level, 77% of the variation in the equity option skew, and 60% of the implied volatility term structure across...... equities. Furthermore, the first principal component has a 92% correlation with S&P500 index option volatility, a 64% correlation with the index option skew, and a 80% correlation with the index option term structure. We develop an equity option valuation model that captures this factor structure...
Reliability Analysis-Based Numerical Calculation of Metal Structure of Bridge Crane
Directory of Open Access Journals (Sweden)
Wenjun Meng
2013-01-01
Full Text Available The study introduced a finite element model of DQ75t-28m bridge crane metal structure and made finite element static analysis to obtain the stress response of the dangerous point of metal structure in the most extreme condition. The simulated samples of the random variable and the stress of the dangerous point were successfully obtained through the orthogonal design. Then, we utilized BP neural network nonlinear mapping function trains to get the explicit expression of stress in response to the random variable. Combined with random perturbation theory and first-order second-moment (FOSM method, the study analyzed the reliability and its sensitivity of metal structure. In conclusion, we established a novel method for accurately quantitative analysis and design of bridge crane metal structure.
Institute of Scientific and Technical Information of China (English)
ZHAO Yongxiang; PENG Jiachun; YANG Bing
2007-01-01
A state-of-art review is given to the new advances on fatigue reliability design and analysis methods of Chinese railway vehicle's structures. First, the structures are subject to a complicated random fatigue stressing history and this history should be determined by combining dynamic Simulation and on-line inspection. Second, the random fatigue constitutions belong to an intrinsic fatigue phenomenon and a probabilistic model is developed to well describe them with two measurements of survival probability and confidence, similar model is also presented for the random stress-life relations and extrapolated appropriately into long fatigue life regime. Third, concept of the fatigue limit should be understood as the fatigue strength at a given fatigue life and a so-called local Basquin model method is proposed for measuring the random strengths. In addition, drawing and application methods of the Goodman-Smith diagram for integrally characterizing the random fatigue strengths are established in terms of ten kilometers. Fourth, a reliability stress-based method is constructed with a consideration of the random constitutive relations. These new advances form a new frame work for railway fatigue reliability design and analysis.
Reliability of fixed and jack-up structures: a comparative study
Energy Technology Data Exchange (ETDEWEB)
Morandi, A.C.; Frieze, P.A. [MSL Engineering, Sunninghill, Ascot (United Kingdom); Birkinshaw, M. [Health and Safety Executive, London (United Kingdom); Smith, D.; Dixon, A.T. [Health and Safety Executive, Bootle (United Kingdom)
1997-12-31
This paper presents results of a comparison between the structural reliability of a jacket designed to the limit of API RP 2A-LRFD and of a jack-up designed to the limit of the SNAME T and R Bulletin 5-5A. Both platforms were assumed as operating in the same location and at the same water depth when evaluating metocean and geotechnical data. Component strength was evaluated on the basis of the latest ISO formulations and system strength was evaluated by pushover analysis using CAP/SeaStar. Reliability was evaluated using the Response Surface method. It was found that, for both platforms, failure probability at system level was about an order of magnitude smaller than at component level. The jack-up critical failure probabilities tended to be about an order of magnitude greater than the corresponding jacket results. (Author)
Favier, P.; Bertrand, D.; Eckert, N.; Naaim, M.
2012-04-01
To protect elements at risk (humans, roads, houses, etc.) against snow avalanches, civil engineering structures, such as dams or mounds, are used. The design of such defence structures is done following a deterministic approach which considers European regulation. The minimization of expected total losses is an interesting alternative that generalizes cost-benefit approach to a continuous decision variable. For this purpose, not only the hazard magnitude but also the buildings vulnerability must be evaluated carefully. The aim of this work is therefore to combine state of the art sub-models for the probabilistic description of avalanche flows and the numerical evaluation of damages to buildings. We defined the risk as the expectation of the cost consequences of avalanches activity. Disposal consequences are quantified thanks to reliability methods. In this formulation, the accuracy of both the hazard estimation and the vulnerability calculation has to be consistent according to precision and computational costs. To do so, a numerical approach has been developed to evaluate the physical vulnerability of concrete buildings submitted to avalanche loadings. The ensuing application illustrates our approach. A reinforced concrete slab is considered to model the building with a finite element method. Reliability approach enables to produce a response spectrum of the structure against avalanche impact. Finally, vulnerability curves are built. Outcomes of the risk calculation are examined to find sensitivity on the optimal design of snow defence structures.
Energy Technology Data Exchange (ETDEWEB)
Bouyssy, V.
1996-12-31
For tubular joints of offshore jacket structures, large discrepancies are observed between predicted and measured fatigue damages. The match between predictions and measurements is improved when one performs stochastic fatigue analyses. For a platform in the North Sea, however, it is found that stochastic fatigue life estimates still are inaccurate. The inaccuracy is due to uncertainties in the loading and local resistance and also in the calculation results - e.g. in the structural response and mean damage rate. By means of extensive numerical studies, it is shown how numerical uncertainties can be avoided in the calculation results. Further, it is explained that random fluctuations intrinsic in nature exist in the loading, local resistance and system properties. These random fluctuations can be accounted for in a probabilistic reliability analysis only. Then one computes the probability of a fatigue failure after a given service time instead of predicting a deterministic fatigue life. In the reliability analysis of offshore jacket structures usually only uncertainties in the loading and local resistance are taken into account. For dynamically excited jacket structures, however, stochastic analyses indicate that the influence of uncertainties in structural properties can be significant both with respect to extreme value failure and with respect to fatigue in some cases. A new numerical method is developed to estimate the reliability of offshore structures against both extreme and fatigue failures. The method allows to account for the random fluctuations in the loading, local resistance and structural properties. The suitability of the method to provide accurate estimates of failure probabilities in as few structural analyses as possible is investigated in two case studies representative for a number of offshore structures. (orig.) [Deutsch] Rohrverbindungen bei Meeresplattformen der Nordsee koennen durch Ermuedung versagen. Fuer bestehende Plattformen werden
Bellumori, Maria; Jaric, Slobodan; Knight, Christopher A
2011-07-01
Performing a set of isometric muscular contractions to varied amplitudes with instructions to generate force most rapidly reveals a strong linear relationship between peak forces (PF) achieved and corresponding peak rates of force development (RFD). The slope of this relationship, termed the RFD scaling factor (RFD-SF), quantifies the extent to which RFD scales with contraction amplitude. Such scaling allows relative invariance in the time required to reach PF regardless of contraction size. Considering the increasing use of this relationship to study quickness and consequences of slowness in older adults and movement disorders, our purpose was to further develop the protocol to measure RFD-SF. Fifteen adults (19-28 years) performed 125 rapid isometric contractions to a variety of force levels in elbow extensors, index finger abductors, and knee extensors, on 2 days. Data were used to determine (1) how the number of pulses affects computation of the RFD-SF, (2) day-to-day reliability of the RFD-SF, and (3) the nature of RFD-SF differences between diverse muscle groups. While sensitive to the number of pulses used in its computation (P50 pulses (ICC>.7) and more so with 100-125 pulses (ICC=.8-.92). Despite differences in size and function across muscles, RFD-SF was generally similar (i.e., only 8.5% greater in elbow extensors than in index finger abductors and knee extensors; P=.049). Results support this protocol as a reliable means to assess how RFD scales with PF in rapid isometric contractions as well as a simple, non-invasive probe into neuromuscular health.
Halo Models of Large Scale Structure and Reliability of Cosmological N-Body Simulations
Gaite, Jose
2013-01-01
Halo models of the large scale structure of the Universe are critically examined, focusing on the definition of halos as smooth distributions of cold dark matter. This definition is essentially based on the results of cosmological N-body simulations. By a careful analysis of the standard assumptions of halo models and N-body simulations and by taking into account previous studies of self-similarity of the cosmic web structure, we conclude that N-body cosmological simulations are not fully reliable in the range of scales where halos appear. Therefore, to have a consistent definition of halos, it is necessary either to define them as entities of arbitrary size with a grainy rather than smooth structure or to define their size in terms of small-scale baryonic physics.
Halo Models of Large Scale Structure and Reliability of Cosmological N-Body Simulations
Directory of Open Access Journals (Sweden)
José Gaite
2013-05-01
Full Text Available Halo models of the large scale structure of the Universe are critically examined, focusing on the definition of halos as smooth distributions of cold dark matter. This definition is essentially based on the results of cosmological N-body simulations. By a careful analysis of the standard assumptions of halo models and N-body simulations and by taking into account previous studies of self-similarity of the cosmic web structure, we conclude that N-body cosmological simulations are not fully reliable in the range of scales where halos appear. Therefore, to have a consistent definition of halos is necessary either to define them as entities of arbitrary size with a grainy rather than smooth structure or to define their size in terms of small-scale baryonic physics.
DEFF Research Database (Denmark)
Köyluoglu, H.U.; Nielsen, Søren R.K.; Cakmak, A.S.;
1997-01-01
The paper deals with the prediction of global and localized damage and the future reliability estimation of partly damaged reinforced concrete (RC) structures under seismic excitation. Initially, a global maximum softening damage indicator is considered based on the variation of the eigenfrequency...... of the first mode due to the stiffness and strength deterioration of the structure. The hysteresis of the first mode is modelled by a Clough and Johnston hysteretic oscillator with a degrading elastic fraction of the restoring force. The linear parameters of the model are assumed to be known, measured before....... The proposed model is next generalized for the MDOF system. Using the adapted models for the structure and the global damage state, the global damage in a future earthquake can then be estimated when a suitable earthquake model is applied. The performance of the model is illustrated on RC frames which were...
DEFF Research Database (Denmark)
Köyluoglu, H.U.; Nielsen, Søren R.K.; Cakmak, A.S.;
1994-01-01
The paper deals with the prediction of global and localized damage and the future reliability estimation of partly damaged reinforced concrete (RC) structures under seismic excitation. Initially, a global maximum softening damage indicator is considered based on the variation of the eigenfrequency...... of the first mode due to the stiffness and strength deterioration of the structure. The hysteresis of the first mode is modelled by a Clough and Johnston hysteretic oscillator with a degrading elastic fraction of the restoring force. The linear parameters of the model are assumed to be known, measured before....... The proposed model is next generalized for the MDOF system. Using the adapted models for the structure and the global damage state, the global damage in a future earthquake can then be estimated when a suitable earthquake model is applied. The performance of the model is illustrated on RC frames which were...
Regression analysis of the structure function for reliability evaluation of continuous-state system
Energy Technology Data Exchange (ETDEWEB)
Gamiz, M.L., E-mail: mgamiz@ugr.e [Departamento de Estadistica e I.O., Facultad de Ciencias, Universidad de Granada, Granada 18071 (Spain); Martinez Miranda, M.D. [Departamento de Estadistica e I.O., Facultad de Ciencias, Universidad de Granada, Granada 18071 (Spain)
2010-02-15
Technical systems are designed to perform an intended task with an admissible range of efficiency. According to this idea, it is permissible that the system runs among different levels of performance, in addition to complete failure and the perfect functioning one. As a consequence, reliability theory has evolved from binary-state systems to the most general case of continuous-state system, in which the state of the system changes over time through some interval on the real number line. In this context, obtaining an expression for the structure function becomes difficult, compared to the discrete case, with difficulty increasing as the number of components of the system increases. In this work, we propose a method to build a structure function for a continuum system by using multivariate nonparametric regression techniques, in which certain analytical restrictions on the variable of interest must be taken into account. Once the structure function is obtained, some reliability indices of the system are estimated. We illustrate our method via several numerical examples.
Directory of Open Access Journals (Sweden)
Jalal alsarraf
2014-06-01
Full Text Available Life-time cost minimization is considered as the optimal criterion for planning of inspection, repair and maintenance of structures. However, most of the probabilities and the cost items related to the cost analysis generally contain inevitable uncertainties in actual cases. The appropriateness of inspection planning may be lost by several errors induced by such uncertainties. In this study, a cost minimization method with the constraint of reliability is developed in order to obtain stable inspection planning against the estimation errors of the parameters. In the analysis, the life-time cost optimization is carried out under the constraint that the failure probabilities of the members are controlled below the respective target values allowed for the members. First, initial target failure probabilities are assumed for each member. Then, the robustness of the inspection planning is investigated by adjusting the parameters within the range of uncertainties. The initial values of the target failure probabilities are altered until an acceptable result is obtained. The applicability of the proposed method is examined for a structure with several uncertain parameters. A sequential cost minimization method is employed to optimize the life-time cost. It is made clear that by using this approach, the stability of the life-time cost is maintained without losing the benefit of the cost minimization method. Keywords: Crack, Fatigue, Inspection, Numerical Model, Reliability, Structure.
Nemeth, Noel N.
2002-01-01
Brittle materials are being used, or considered, for a wide variety of high tech applications that operate in harsh environments, including static and rotating turbine parts. thermal protection systems, dental prosthetics, fuel cells, oxygen transport membranes, radomes, and MEMS. Designing components to sustain repeated load without fracturing while using the minimum amount of material requires the use of a probabilistic design methodology. The CARES/Life code provides a general-purpose analysis tool that predicts the probability of failure of a ceramic component as a function of its time in service. For this presentation an interview of the CARES/Life program will be provided. Emphasis will be placed on describing the latest enhancements to the code for reliability analysis with time varying loads and temperatures (fully transient reliability analysis). Also, early efforts in investigating the validity of using Weibull statistics, the basis of the CARES/Life program, to characterize the strength of MEMS structures will be described as as well as the version of CARES/Life for MEMS (CARES/MEMS) being prepared which incorporates single crystal and edge flaw reliability analysis capability. It is hoped this talk will open a dialog for potential collaboration in the area of MEMS testing and life prediction.
Grant, Jon E; Kim, Suck Won; McCabe, James S
2006-06-01
Kleptomania presents difficulties in diagnosis for clinicians. This study aimed to develop and test a DSM-IV-based diagnostic instrument for kleptomania. To assess for current kleptomania the Structured Clinical Interview for Kleptomania (SCI-K) was administered to 112 consecutive subjects requesting psychiatric outpatient treatment for a variety of disorders. Reliability and validity were determined. Classification accuracy was examined using the longitudinal course of illness. The SCI-K demonstrated excellent test-retest (Phi coefficient = 0.956 (95% CI = 0.937, 0.970)) and inter-rater reliability (phi coefficient = 0.718 (95% CI = 0.506, 0.848)) in the diagnosis of kleptomania. Concurrent validity was observed with a self-report measure using DSM-IV kleptomania criteria (phi coefficient = 0.769 (95% CI = 0.653, 0.850)). Discriminant validity was observed with a measure of depression (point biserial coefficient = -0.020 (95% CI = -0.205, 0.166)). The SCI-K demonstrated both high sensitivity and specificity based on longitudinal assessment. The SCI-K demonstrated excellent reliability and validity in diagnosing kleptomania in subjects presenting with various psychiatric problems. These findings require replication in larger groups, including non-psychiatric populations, to examine their generalizability. Copyright (c) 2006 John Wiley & Sons, Ltd.
DEFF Research Database (Denmark)
Bech, B.; Lönn, L.; Falkenberg, M.
2011-01-01
Objectives To study the construct validity and reliability of a novel endovascular global rating scale, Structured Assessment of endoVascular Expertise (SAVE). Design A Clinical, experimental study. Materials Twenty physicians with endovascular experiences ranging from complete novices to highly...... experienced operators performed a video-recorded simulated contra-lateral iliac-artery-stenting procedure. The virtual-patient case was a novel technically challenging procedure presenting the distal arteries below the knee. Methods Three experts assessed the performances blinded to operator identity...
Martowicz, Adam; Uhl, Tadeusz
2012-10-01
The paper discusses the applicability of a reliability- and performance-based multi-criteria robust design optimization technique for micro-electromechanical systems, considering their technological uncertainties. Nowadays, micro-devices are commonly applied systems, especially in the automotive industry, taking advantage of utilizing both the mechanical structure and electronic control circuit on one board. Their frequent use motivates the elaboration of virtual prototyping tools that can be applied in design optimization with the introduction of technological uncertainties and reliability. The authors present a procedure for the optimization of micro-devices, which is based on the theory of reliability-based robust design optimization. This takes into consideration the performance of a micro-device and its reliability assessed by means of uncertainty analysis. The procedure assumes that, for each checked design configuration, the assessment of uncertainty propagation is performed with the meta-modeling technique. The described procedure is illustrated with an example of the optimization carried out for a finite element model of a micro-mirror. The multi-physics approach allowed the introduction of several physical phenomena to correctly model the electrostatic actuation and the squeezing effect present between electrodes. The optimization was preceded by sensitivity analysis to establish the design and uncertain domains. The genetic algorithms fulfilled the defined optimization task effectively. The best discovered individuals are characterized by a minimized value of the multi-criteria objective function, simultaneously satisfying the constraint on material strength. The restriction of the maximum equivalent stresses was introduced with the conditionally formulated objective function with a penalty component. The yielded results were successfully verified with a global uniform search through the input design domain.
Dalton, Michelle; Hollingworth, Sophie; Blundell, John; Finlayson, Graham
2015-01-01
Some individuals exhibit a weak satiety response to food and may be susceptible to overconsumption. The current study identified women showing consistently low or high satiety responses to standardised servings of food across four separate days and compared them on behavioural, psychological and physiological risk factors for overeating and future weight gain. In a crossover design, 30 female participants (age: 28.0 ± 10.6; body mass index (BMI): 23.1 ± 3.0) recorded sensations of hunger in the post-prandial period following four graded energy level breakfasts. Satiety quotients were calculated to compare individuals on satiety responsiveness across conditions. Body composition, resting metabolic rate (RMR), energy intake, food reward and craving, and eating behaviour traits were assessed under controlled laboratory conditions. A distinct low satiety phenotype (LSP) was identified with good consistency across separate study days. These individuals had a higher RMR, greater levels of disinhibition and reported feeling lower control over food cravings. Further, they consumed more energy and exhibited greater wanting for high-fat food. The inverse pattern of characteristics was observed in those exhibiting a consistently high satiety phenotype (HSP). Weak satiety responsiveness is a reliable trait identifiable using the satiety quotient. The LSP was characterised by distinct behavioural and psychological characteristics indicating a risk for overeating, compared to HSP. PMID:26404367
Directory of Open Access Journals (Sweden)
Michelle Dalton
2015-09-01
Full Text Available Some individuals exhibit a weak satiety response to food and may be susceptible to overconsumption. The current study identified women showing consistently low or high satiety responses to standardised servings of food across four separate days and compared them on behavioural, psychological and physiological risk factors for overeating and future weight gain. In a crossover design, 30 female participants (age: 28.0 ± 10.6; body mass index (BMI: 23.1 ± 3.0 recorded sensations of hunger in the post-prandial period following four graded energy level breakfasts. Satiety quotients were calculated to compare individuals on satiety responsiveness across conditions. Body composition, resting metabolic rate (RMR, energy intake, food reward and craving, and eating behaviour traits were assessed under controlled laboratory conditions. A distinct low satiety phenotype (LSP was identified with good consistency across separate study days. These individuals had a higher RMR, greater levels of disinhibition and reported feeling lower control over food cravings. Further, they consumed more energy and exhibited greater wanting for high-fat food. The inverse pattern of characteristics was observed in those exhibiting a consistently high satiety phenotype (HSP. Weak satiety responsiveness is a reliable trait identifiable using the satiety quotient. The LSP was characterised by distinct behavioural and psychological characteristics indicating a risk for overeating, compared to HSP.
Dalton, Michelle; Hollingworth, Sophie; Blundell, John; Finlayson, Graham
2015-09-04
Some individuals exhibit a weak satiety response to food and may be susceptible to overconsumption. The current study identified women showing consistently low or high satiety responses to standardised servings of food across four separate days and compared them on behavioural, psychological and physiological risk factors for overeating and future weight gain. In a crossover design, 30 female participants (age: 28.0 ± 10.6; body mass index (BMI): 23.1 ± 3.0) recorded sensations of hunger in the post-prandial period following four graded energy level breakfasts. Satiety quotients were calculated to compare individuals on satiety responsiveness across conditions. Body composition, resting metabolic rate (RMR), energy intake, food reward and craving, and eating behaviour traits were assessed under controlled laboratory conditions. A distinct low satiety phenotype (LSP) was identified with good consistency across separate study days. These individuals had a higher RMR, greater levels of disinhibition and reported feeling lower control over food cravings. Further, they consumed more energy and exhibited greater wanting for high-fat food. The inverse pattern of characteristics was observed in those exhibiting a consistently high satiety phenotype (HSP). Weak satiety responsiveness is a reliable trait identifiable using the satiety quotient. The LSP was characterised by distinct behavioural and psychological characteristics indicating a risk for overeating, compared to HSP.
Directory of Open Access Journals (Sweden)
Marco Mula
2008-08-01
Full Text Available Marco Mula, Stefano Pini, Simona Calugi, Matteo Preve, Matteo Masini, Ilaria Giovannini, Ciro Conversano, Paola Rucci, Giovanni B CassanoDepartment of Psychiatry, Neurobiology, Pharmacology and Biotechnologies, University of Pisa, ItalyAbstract: This study evaluates the validity and reliability of a new instrument developed to assess symptoms of depersonalization: the Structured Clinical Interview for the Depersonalization-Derealization Spectrum (SCI-DER. The instrument is based on a spectrum model that emphasizes soft-signs, sub-threshold syndromes as well as clinical and subsyndromal manifestations. Items of the interview include, in addition to DSM-IV criteria for depersonalization, a number of features derived from clinical experience and from a review of phenomenological descriptions. Study participants included 258 consecutive patients with mood and anxiety disorders, 16.7% bipolar I disorder, 18.6% bipolar II disorder, 32.9% major depression, 22.1% panic disorder, 4.7% obsessive compulsive disorder, and 1.5% generalized anxiety disorder; 2.7% patients were also diagnosed with depersonalization disorder. A comparison group of 42 unselected controls was enrolled at the same site. The SCI-DER showed excellent reliability and good concurrent validity with the Dissociative Experiences Scale. It significantly discriminated subjects with any diagnosis of mood and anxiety disorders from controls and subjects with depersonalization disorder from controls. The hypothesized structure of the instrument was confirmed empirically.Keywords: depersonalization, derealization, mood disorders, anxiety disorders
Toward More Reliable Lithium-Sulfur Batteries: An All-Graphene Cathode Structure.
Fang, Ruopian; Zhao, Shiyong; Pei, Songfeng; Qian, Xitang; Hou, Peng-Xiang; Cheng, Hui-Ming; Liu, Chang; Li, Feng
2016-09-27
Lithium-sulfur (Li-S) batteries are attracting increasing interest due to their high theoretical specific energy density, low cost, and eco-friendliness. However, most reports of the high gravimetric specific capacity and long cyclic life are not practically reliable because of their low areal specific capacity derived from the low areal sulfur loading and low sulfur content. Here, we fabricated a highly porous graphene with high pore volume of 3.51 cm(3) g(-1) as the sulfur host, enabling a high sulfur content of 80 wt %, and based on this, we further proposed an all-graphene structure for the sulfur cathode with highly conductive graphene as the current collector and partially oxygenated graphene as a polysulfide-adsorption layer. This cathode structural design enables a 5 mg cm(-2) sulfur-loaded cathode showing both high initial gravimetric specific capacity (1500 mAh g(-1)) and areal specific capacity (7.5 mAh cm(-2)), together with excellent cycling stability for 400 cycles, indicating great promise for more reliable lithium-sulfur batteries.
DEFF Research Database (Denmark)
Hougs Kjær, Birgitte; Ellegaard, Karen; Wieland, Ina
2017-01-01
BACKGROUND: US-examinations related to shoulder impingement (SI) often vary due to methodological differences, examiner positions, transducers, and recording parameters. Reliable US protocols for examination of different structures related to shoulder impingement are therefore needed. OBJECTIVES:...
On R factors for dynamic structure crystallography
DEFF Research Database (Denmark)
Coppens, Philip; Kaminski, Radoslaw; Schmøkel, Mette Stokkebro
2010-01-01
In studies of dynamic changes in crystals in which induced metastable species may have lifetimes of microseconds or less, refinements are most sensitive if based on the changes induced in the measured intensities. Agreement factors appropriate for such refinements, based on the ratios of the inte...... of the intensities before and after the external perturbation is applied, are discussed and compared with R factors commonly applied in static structure crystallography....
Predicting structure in nonsymmetric sparse matrix factorizations
Energy Technology Data Exchange (ETDEWEB)
Gilbert, J.R. (Xerox Palo Alto Research Center, CA (United States)); Ng, E.G. (Oak Ridge National Lab., TN (United States))
1992-10-01
Many computations on sparse matrices have a phase that predicts the nonzero structure of the output, followed by a phase that actually performs the numerical computation. We study structure prediction for computations that involve nonsymmetric row and column permutations and nonsymmetric or non-square matrices. Our tools are bipartite graphs, matchings, and alternating paths. Our main new result concerns LU factorization with partial pivoting. We show that if a square matrix A has the strong Hall property (i.e., is fully indecomposable) then an upper bound due to George and Ng on the nonzero structure of L + U is as tight as possible. To show this, we prove a crucial result about alternating paths in strong Hall graphs. The alternating-paths theorem seems to be of independent interest: it can also be used to prove related results about structure prediction for QR factorization that are due to Coleman, Edenbrandt, Gilbert, Hare, Johnson, Olesky, Pothen, and van den Driessche.
Factor structure of Raven's Coloured Progressive Matrices
Muniz, Monalisa; Gomes, Cristiano Mauro Assis; Pasian, Sonia Regina
2016-01-01
Abstract This study's objective was to verify the factor structure of Raven's Coloured Progressive Matrices (CPM). The database used included the responses of 1,279 children, 50.2% of which were males with an average age of 8.48 years old and a standard deviation of 1.49 yrs. Confirmatory factor analyses were run to test seven models based on CPM theory and on a Brazilian study addressing the test's structure. The results did not confirm the CPM theoretical proposition concerning the scales b...
Structural studies on leukaemia inhibitory factor
Energy Technology Data Exchange (ETDEWEB)
Norton, R.S.; Maurer, T.; Smith, D.K. [Biomolecular Research Institute, Parville (Australia); Nicola, N.A. [Institute of Medical Research, Melbourne (Australia)
1994-12-01
Leukaemia Inhibitory Factor (LIF) is a pleiotropic cytokine that acts on a wide range of target cells, including mega-karyocytes, osteoblasts, hepatocytes, adipocytes, neurons, embryonic stem cells, and primordial germ cells. Many of its activities are shared with other cytokines, particularly interleukin-6, oncostatin-M, ciliary neurotrophic factor, and granulocyte colony-stimulating factor (G-CSF). Although secreted in vivo as a glycoprotein, nonglycosylated recombinant protein expressed in E. coli is fully active and has been used in our nuclear magnetic resonance (NMR) studies of the three-dimensional structure and structure-function relationships of LIF. With 180 amino acids and a molecular mass of about 20 kDa, OF is too large for direct structure determination by two-dimensional and three-dimensional {sup 1}HNMR. It is necessary to label the protein with the stable isotopes {sup 15}N and {sup 13}C and employ heteronuclear three-dimensional NMR in order to resolve and interpret the spectral information required for three-dimensional structure determination. This work has been undertaken with both human LIF and a mouse-human chimaera that binds to the human LIF receptor with the same affinity as the human protein and yet expresses in E. coli at much higher levels. Sequence-specific resonance assignments and secondary structure elements for these proteins will be presented and progress towards determination of their three-dimensional structures described.
Reliability-based Calibration of Partial Safety Factors for Wave Energy Converters
DEFF Research Database (Denmark)
Ambühl, Simon; Kramer, Morten Mejlhede; Sørensen, John Dalsgaard
2015-01-01
of partial safety factors for design of welded details for wave energy converter applications is presented in this paper using probabilistic methods. The paper presents an example with focus on the Wavestar device. SN curves and Rainflow counting are used to model fatigue without considering inspections......Wave energy converters (WECs), which harvest energy from the waves and transfer them to electricity, are a new technology, where structural standards need to be developed. An important step towards standardization is the calibration of partial safety factors. A methodology for calibration....... The influence of inspections is modelled using a fracture mechanics approach, which is calibrated by the SN curve approach. Furthermore, the paper assesses the influence of the inspection quality. The results show that with multiple inspections during the lifetime of the device and by applying a good inspection...
Saddlepoint approximation based structural reliability analysis with non-normal random variables
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
The saddlepoint approximation (SA) can directly estimate the probability distribution of linear performance function in non-normal variables space. Based on the property of SA, three SA based methods are developed for the structural system reliability analysis. The first method is SA based reliability bounds theory (RBT), in which SA is employed to estimate failure probability and equivalent normal reliability index for each failure mode firstly, and then RBT is employed to obtain the upper and the lower bounds of system failure probability. The second method is SA based Nataf approximation, in which SA is used to estimate the probability density function (PDF) and cumulative distribution function (CDF) for the approximately linearized performance function of each failure mode. After the PDF of each failure mode and the correlation coefficients among approximately linearized performance functions are estimated, Nataf distribution is employed to approximate the joint PDF of multiple structural system performance functions, and then the system failure probability can be estimated directly by numerical simulation using the joint PDF. The third method is SA based line sampling (LS). The standardization transformation is needed to eliminate the dimensions of variables firstly in this case. Then LS method can express the system failure probability as an arithmetic average of a set of failure probabilities of the linear performance functions, and the probabilities of the linear performance functions can be estimated by the SA in the non-normal variables space. By comparing basic concepts, implementations and results of illustrations, the following conclusions can be drawn: (1) The first method can only obtain the bounds of system failure probability and it is only acceptable for the linear limit state function; (2) the second method can give the estimation of system failure probability, and its error mostly results from the approximation of Nataf distribution for the
Reliability-based service life prediction of existing concrete structures under marine environment
Institute of Scientific and Technical Information of China (English)
吴灵杰; 周拥军; 寇新建; 蒋萌
2015-01-01
Chloride-induced corrosion of the reinforcement is considered as one of the major mechanisms resulting in the reduction of structural resistance of reinforced concrete structural elements located in marine and other aggressive environments. A study of reinforced concrete structures located at the Fangcheng dock in the Beibu Gulf port, China, was present. The result from field survey indicates that the concrete cover depth and chloride diffusion coefficient fit best normal distribution and lognormal distribution, respectively. The service life of structure is about 55 a, while initiation time is 45 a. Sensitivity analysis indicates that the most influential factor of the structure service life prediction is concrete cover, followed by diffusion coefficient, diffusion decay index, critical chloride concentration, surface chloride concentration, current density and localized pitting corrosion. Finally, the effects of diffusion decay index and critical chloride concentration on structure service life prediction are discussed.
On the reliability design of hydraulic structures%论水工建筑物的可靠性设计
Institute of Scientific and Technical Information of China (English)
陈厚群
2013-01-01
So far the application of the method of limit state method with partial factors to substitute the conventional single safety factor method has been disputed especially in the design circles of hydraulic structures,mainly because the former to be confused with reliability analysis.The single safety factor method involves both the non-random factor of engineering experience and all random uncertainties but without regard to their degree of uncertainty.The reliability analysis method can evaluate the combined failure probability of random uncertainties with different degrees but is unable to consider the factor of engineering experience which is now still important for design of hydraulic structures.In this paper some confused concepts inducing the debate are clarified.In the limit state method not only the different degrees of all random uncertainties can be distinguished by the partial factors,but also a structural factor γd is introduced to reflect the engineering experience.Obviously,it should be more logical than the conventional single safety factor method.At present,all the partial factors have still to be determined in accordance with the traditional safety factor in order to keep the continuous of the design codes.So,the concerned method is actually a multi-safety factor method having no essential difference with the conventional single safety factor method concerning the setting of safety level as a whole.However,it is entirely different from the reliability analysis method,as a structural factor γd is introduced and all partial factors both of action effects and resistances are determined independently from the reliability index.So,neither complex theory and unfamiliar terms nor insufficient statistical data must be worried about by the designers.Finally,as an example the successful application of the method of limit state method with partial factors in the《Seismic Design Code of Hydraulic Structures》is briefly described.%主要由于替代惯用的
Directory of Open Access Journals (Sweden)
Rejas Javier
2011-06-01
Full Text Available Abstract Background Fibromyalgia (FM is a complex syndrome that affects many aspects of the patients life and it is very difficult to evaluate in clinical practice. A recent study has developed the Combined Index of Severity of Fibromyalgia (ICAF, an instrument that evaluates diverse aspects of FM and offers five indices: emotional, physical, active coping, passive coping and total. The objective of this study is to confirm the structure of the ICAF, check its test-retest reliability, assess its sensitivity to change, and compare the results obtained in a sample of patients with fibromyalgia with another sample of healthy controls. Methods A total of 232 patients took part in the study, 228 women and 4 men, with a mean age of 47.73 years of age (SD = 8.61 and a time of disease evolution since diagnosis of 4.28 years (SD = 4.03. The patients from the FM group completed the ICAF. Between one and two weeks later, they again attended the clinic and complete the 59 items on the ICAF (retest and immediately afterwards they began treatment (according to daily clinical practice criteria. A sample of healthy subjects was also studied as a control group: 110 people were included (106 women and 4 men with a mean age of 46.01 years of age (SD = 9.35. The study was conducted in Spain. Results The results obtained suggest that the four-factor model obtained in the previous study adequately fits the data obtained in this study. The test-retest reliability and internal consistency were all significant and show a high degree of correlation for all the factors as well as in overall score. With the exception of the passive coping factor, all the other scores, including the overall score, were sensitive to change after the therapeutic intervention. The ICAF scores of the patients with fibromyalgia compared with those of the control group were markedly different. Conclusions The findings suggest that the ICAF is a valid, reliable, sensitive to change instrument with
Graham, Roseanna
This study evaluated the reliability, validity, and educational usefulness of a comprehensive, multidisciplinary Objective Structured Clinical Examination (OSCE) in dental education. The OSCE was administered to dental students at the Columbia University College of Dental Medicine (CDM) before they entered clinical training. Participants in this study included CDM's class of 2010 which consisted of 78 students. The overall reliability of the examination was measured via calculation of Cronbach's alpha. Content validity was examined through evaluation of the OSCE by three experienced clinical faculty members. Predictive validity was evaluated by correlating student grades on the OSCE to future clinical performance as measured by number of clinical points achieved during the third year of training. Student perceptions regarding the educational usefulness of the examination were evaluated through a 12-question Liken-type survey and focus group interviews analyzed using a phenomenological approach. Findings of the study indicated the OSCE was a highly reliable examination (alpha=0.86) with high content validity and a moderately high correlation to future clinical performance (r=.614, p<.0001). Overall, student perceptions of the educational usefulness of the OSCE were positive as based on their responses to a 5-point Likert scale (1=strongly disagree and 5=strongly agree). They reported that the exam required the ability to think critically and problem-solve (4.0 +/- 0.85), assessed clinically relevant skills (4.59 +/- 0.69), helped identify clinical weaknesses (4.16 +/- 0.90), and was a learning experience (4.58 +/- 0.84). Findings from the qualitative portion of the study identified four main themes including the student perception that the OSCE is a unique assessment experience that required integration and application of knowledge. Recommendations for the use of the OSCE to improve clinical teaching and the implications of this study relating to the expanded use of
Venkatraman, Vijay K; Gonzalez, Christopher E.; Landman, Bennett; Goh, Joshua; Reiter, David A.; An, Yang; Resnick, Susan M.
2017-01-01
Diffusion tensor imaging (DTI) measures are commonly used as imaging markers to investigate individual differences in relation to behavioral and health-related characteristics. However, the ability to detect reliable associations in cross-sectional or longitudinal studies is limited by the reliability of the diffusion measures. Several studies have examined reliability of diffusion measures within (i.e. intra-site) and across (i.e. inter-site) scanners with mixed results. Our study compares the test-retest reliability of diffusion measures within and across scanners and field strengths in cognitively normal older adults with a follow-up interval less than 2.25 years. Intra-class correlation (ICC) and coefficient of variation (CoV) of fractional anisotropy (FA) and mean diffusivity (MD) were evaluated in sixteen white matter and twenty-six gray matter bilateral regions. The ICC for intra-site reliability (0.32 to 0.96 for FA and 0.18 to 0.95 for MD in white matter regions; 0.27 to 0.89 for MD and 0.03 to 0.79 for FA in gray matter regions) and inter-site reliability (0.28 to 0.95 for FA in white matter regions, 0.02 to 0.86 for MD in gray matter regions) with longer follow-up intervals were similar to earlier studies using shorter follow-up intervals. The reliability of across field strengths comparisons was lower than intra- and inter-site reliability. Within and across scanner comparisons showed that diffusion measures were more stable in larger white matter regions (> 1500 mm3). For gray matter regions, the MD measure showed stability in specific regions and was not dependent on region size. Linear correction factor estimated from cross-sectional or longitudinal data improved the reliability across field strengths. Our findings indicate that investigations relating diffusion measures to external variables must consider variable reliability across the distinct regions of interest and that correction factors can be used to improve consistency of measurement across
Structural reliability of alumina-, feldspar-, leucite-, mica- and zirconia-based ceramics.
Tinschert, J; Zwez, D; Marx, R; Anusavice, K J
2000-09-01
The objective of this study was to test the hypothesis that industrially manufactured ceramic materials, such as Cerec Mark II and Zirconia-TZP, have a smaller range of fracture strength variation and therefore greater structural reliability than laboratory-processed dental ceramic materials. Thirty bar specimens per material were prepared and tested. The four-point bend test was used to determine the flexure strength of all ceramic materials. The fracture stress values were analyzed by Weibull analysis to determine the Weibull modulus values (m) and the 1 and 5% probabilities of failure. The mean strength and standard deviation values for these ceramics are as follows: (MPa+/-SD) were: Cerec Mark II, 86.3+/-4.3; Dicor, 70.3+/-12.2; In-Ceram Alumina, 429. 3+/-87.2; IPS Empress, 83.9+/-11.3; Vitadur Alpha Core, 131.0+/-9.5; Vitadur Alpha Dentin, 60.7+/-6.8; Vita VMK 68, 82.7+/-10.0; and Zirconia-TZP, 913.0+/-50.2. There was no statistically significant difference among the flexure strength of Cerec Mark II, Dicor, IPS Empress, Vitadur Alpha Dentin, and Vita VMK 68 ceramics (p>0.05). The highest Weibull moduli were associated with Cerec Mark II and Zirconia-TZP ceramics (23.6 and 18.4). Dicor glass-ceramic and In-Ceram Alumina had the lowest m values (5.5 and 5.7), whereas intermediate values were observed for IPS-Empress, Vita VMK 68, Vitadur Alpha Dentin and Vitadur Alpha Core ceramics (8.6, 8.9, 10.0 and 13.0, respectively). Except for In-Ceram Alumina, Vitadur Alpha and Zirconia-TZP core ceramics, most of the investigated ceramic materials fabricated under the condition of a dental laboratory were not stronger or more structurally reliable than Vita VMK 68 veneering porcelain. Only Cerec Mark II and Zirconia-TZP specimens, which were prepared from an industrially optimized ceramic material, exhibited m values greater than 18. Hence, we conclude that industrially prepared ceramics are more structurally reliable materials for dental applications although CAD
Energy Technology Data Exchange (ETDEWEB)
Emery, John M; Coffin, Peter; Robbins, Brian A; Carroll, Jay; Field, Richard V.,; Yung Suk Jeremy Yoo; Josh Kacher
2017-09-01
Microstructural variabilities are among the predominant sources of uncertainty in structural performance and reliability. We seek to develop efficient algorithms for multiscale calcu- lations for polycrystalline alloys such as aluminum alloy 6061-T6 in environments where ductile fracture is the dominant failure mode. Our approach employs concurrent multiscale methods, but does not focus on their development. They are a necessary but not sufficient ingredient to multiscale reliability predictions. We have focused on how to efficiently use concurrent models for forward propagation because practical applications cannot include fine-scale details throughout the problem domain due to exorbitant computational demand. Our approach begins with a low-fidelity prediction at the engineering scale that is sub- sequently refined with multiscale simulation. The results presented in this report focus on plasticity and damage at the meso-scale, efforts to expedite Monte Carlo simulation with mi- crostructural considerations, modeling aspects regarding geometric representation of grains and second-phase particles, and contrasting algorithms for scale coupling.
Ugulu, Ilker
2013-01-01
This study focuses on the confirmatory factor analysis for testing validity and reliability of Traditional Knowledge Attitude Scale (TKAS) to measure university students' attitudes. The items in the TKAS were developed initially from the responses to two open-ended items by 30 university students and literature review on traditional…
Reliability Assessment Of Wind Turbines
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard
2014-01-01
Reduction of cost of energy for wind turbines are very important in order to make wind energy competitive compared to other energy sources. Therefore the turbine components should be designed to have sufficient reliability but also not be too costly (and safe). This paper presents models...... for uncertainty modeling and reliability assessment of especially the structural components such as tower, blades, substructure and foundation. But since the function of a wind turbine is highly dependent on many electrical and mechanical components as well as a control system also reliability aspects...... of these components are discussed and it is described how there reliability influences the reliability of the structural components. Two illustrative examples are presented considering uncertainty modeling, reliability assessment and calibration of partial safety factors for structural wind turbine components exposed...
Correlation Relationship of Performance Shaping Factors (PSFs) for Human Reliability Analysis
Energy Technology Data Exchange (ETDEWEB)
Bheka, M. Khumalo; Kim, Jonghyun [KEPCO International Nuclear Graduate School, Ulsan (Korea, Republic of)
2014-10-15
At TMI-2, operators permitted thousands of gallons of water to escape from the reactor plant before realizing that the coolant pumps were behaving abnormally. The coolant pumps were then turned off, which in turn led to the destruction of the reactor itself as cooling was completely lost within the core. Human also plays a role in many aspects of complex systems e.g. in design and manufacture of hardware, interface between human and system and also in maintaining such systems as well as for coping with unusual events that place the NPP system at a risk. This is why human reliability analysis (HRA) - an aspect of risk assessments which systematically identifies and analyzes the causes and consequences of human decisions and actions - is important in nuclear power plant operations. It either upgrades or degrades human performance; therefore it has an impact on the possibility of error. These PSFs can be used in various HRA methods to estimate Human Error Probabilities (HEPs). There are many current HRA methods who propose sets of PSFs for normal operation mode of NPP. Some of these PSFs in the sets have some degree of dependency and overlap. Overlapping PSFs introduce error in HEP evaluations due to the fact that some elements are counted more than once in data; this skews the relationship amongst PSF and masks the way that the elements interact to affect performance. This study uses a causal model that represents dependencies and relationships amongst PSFs for HEP evaluation during normal NPP operational states. The model is built taking into consideration the dependencies among PSFs and thus eliminating overlap. The use of an interdependent model of PSFs is expected to produce more accurate HEPs compared to other current methods. PSF sets produced in this study can be further used as nodes (variables) and directed arcs (causal influence between nodes) in HEP evaluation methods such as Bayesian belief (BN) networks. This study was done to estimate the relationships
Reliability-Based Calibration of Partial Safety Factors for Wind Turbine Blades
DEFF Research Database (Denmark)
Toft, Henrik Stensgaard; Branner, Kim; Sørensen, John Dalsgaard
2011-01-01
The reliability of a wind turbine blade can be estimated using a response surface technique, the First Order Reliability Method (FORM) and Monte Carlo simulation. The response surface is here estimated based on nonlinear finite element analysis by which nonlinear failure modes due to e.g. buckling...... of the unidirectional laminas. For this failure mode the reliability is estimated along the centreline of the main spar cap. The results show significant variations in the reliability along the blade length....... can be taken into account. Stochastic models for the material properties and the load-effect are formulated in order to take physical, model and statistical uncertainties into account. The blade fails due to buckling of the main spar cap which results in high stresses in the transverse direction...
Reliability-Based Calibration of Partial Safety Factors for Wind Turbine Blades
DEFF Research Database (Denmark)
Toft, Henrik Stensgaard; Branner, Kim; Sørensen, John Dalsgaard
2011-01-01
The reliability of a wind turbine blade can be estimated using a response surface technique, the First Order Reliability Method (FORM) and Monte Carlo simulation. The response surface is here estimated based on nonlinear finite element analysis by which nonlinear failure modes due to e.g. buckling...... can be taken into account. Stochastic models for the material properties and the load-effect are formulated in order to take physical, model and statistical uncertainties into account. The blade fails due to buckling of the main spar cap which results in high stresses in the transverse direction...... of the unidirectional laminas. For this failure mode the reliability is estimated along the centreline of the main spar cap. The results show significant variations in the reliability along the blade length....
Reliability-Based Calibration of Partial Safety Factors for Wind Turbine Blades
DEFF Research Database (Denmark)
Toft, Henrik Stensgaard; Branner, Kim; Sørensen, John Dalsgaard;
2011-01-01
The reliability of a wind turbine blade can be estimated using a response surface technique, the First Order Reliability Method (FORM) and Monte Carlo simulation. The response surface is here estimated based on nonlinear finite element analysis by which nonlinear failure modes due to e.g. buckling...... of the unidirectional laminas. For this failure mode the reliability is estimated along the centreline of the main spar cap. The results show significant variations in the reliability along the blade length....... can be taken into account. Stochastic models for the material properties and the load-effect are formulated in order to take physical, model and statistical uncertainties into account. The blade fails due to buckling of the main spar cap which results in high stresses in the transverse direction...
Influence Factors on the Value of Reliability Estimators in Marketing Research
2011-01-01
This paper is a literature review, with a conclusion that leaves open many doors for future research. In the first part are reviewed a series of qualitative and quantitative research characteristics. The second part explains briefly the reliability and validity of instruments used in qualitative and quantitative marketing research. The third part of the paper review a series of articles on the estimators of reliability, on their power, on their strengths and weaknesses. The conclusions of the...
DEFF Research Database (Denmark)
Nielsen, Søren R. K.; Peng, Yongbo; Sichani, Mahdi Teimouri
2016-01-01
The paper deals with the response and reliability analysis of hysteretic or geometric nonlinear uncertain dynamical systems of arbitrary dimensionality driven by stochastic processes. The approach is based on the probability density evolution method proposed by Li and Chen (Stochastic dynamics...... of structures, 1st edn. Wiley, London, 2009; Probab Eng Mech 20(1):33–44, 2005), which circumvents the dimensional curse of traditional methods for the determination of non-stationary probability densities based on Markov process assumptions and the numerical solution of the related Fokker–Planck and Kolmogorov......–Feller equations. The main obstacle of the method is that a multi-dimensional convolution integral needs to be carried out over the sample space of a set of basic random variables, for which reason the number of these need to be relatively low. In order to handle this problem an approach is suggested, which...
DEFF Research Database (Denmark)
Nielsen, Søren R.K.; Sørensen, John Dalsgaard; Thoft-Christensen, Palle
1983-01-01
A method is presented for life-time reliability' estimates of randomly excited yielding systems, assuming the structure to be safe, when the plastic deformations are confined below certain limits. The accumulated plastic deformations during any single significant loading history are considered...... to be the outcome of identically distributed, independent stochastic variables,for which a model is suggested. Further assuming the interarrival times of the elementary loading histories to be specified by a Poisson process, and the duration of these to be small compared to the designed life-time, the accumulated...... plastic deformation during several loadings can be modelled as a filtered Poisson process. Using the Markov property of this quantity the considered first-passage problem as well as the related extreme distribution problems are then solved numerically, and the results are compared to simulation studies....
Reliable LIF/Mie droplet sizing in sprays using structured laser illumination planar imaging.
Mishra, Yogeshwar Nath; Kristensson, Elias; Berrocal, Edouard
2014-02-24
In this article, Structured Laser Illumination Planar Imaging (SLIPI) is used in combination with the LIF/Mie ratio technique for extracting a reliable two-dimensional mapping of the droplets Sauter Mean Diameter (SMD). We show that even for the case of a fairly dilute spray, where single scattering events are in majority, the conventional LIF/Mie technique still remains largely affected by errors introduced by multiple light scattering. To remove this unwanted light intensity on both the LIF and Mie images SLIPI is used prior to apply the image ratio. For the first time, the SLIPI LIF/Mie results are calibrated and compared with measurement data from Phase Doppler Interferometry (PDI).
Computing the SKT Reliability of Acyclic Directed Networks Using Factoring Method
Institute of Scientific and Technical Information of China (English)
KONG Fanjia; WANG Guangxing
1999-01-01
This paper presents a factoringalgorithm for computing source-to-K terminal (SKT) reliability, the probability that a source s can send message to a specified set of terminals K, in acyclic directed networks (AD-networks) in which bothnodes and edges can fail. Based on Pivotal decomposition theorem, a newformula is derived for computing the SKT reliability of AD-networks. By establishing a topological property of AD-networks, it is shown that the SKT reliability of AD-networks can be computed by recursively applying this formula. Two new Reliability-Preserving Reductions are alsointroduced. The recursion tree generated by the presented algorithm hasat most 2(|V| - |K|- |C|) leaf nodes, where |V| and |K| are the numbers of nodes and terminals, respectively, while |C| is the number of the nodes satisfying some specified conditions. The computation complexity of the new algorithm is O (|E||V|2(|V| -|K| -|C|)) in the worst case, where |E| is the number of edges. Forsource-to-all-terminal (SAT) reliability, its computation complexity is O (|E|). Comparison of the new algorithm with the existing ones indicates that the new algorithm is more efficient for computing the SKT reliability of AD-networks.
Optimal Reliability-Based Code Calibration
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Kroon, I. B.; Faber, M. H.
1994-01-01
Calibration of partial safety factors is considered in general, including classes of structures where no code exists beforehand. The partial safety factors are determined such that the difference between the reliability for the different structures in the class considered and a target reliability...... level is minimized. Code calibration on a decision theoretical basis is also considered and it is shown how target reliability indices can be calibrated. Results from code calibration for rubble mound breakwater designs are shown....
Energy Technology Data Exchange (ETDEWEB)
Jung, Won Dea; Kim, Jae Whan; Park, Jin Kyun; Ha, Jae Joo [Korea Atomic Energy Research Institute, Taejeon (Korea)
2000-02-01
More than twenty HRA (Human Reliability Analysis) methodologies have been developed and used for the safety analysis in nuclear field during the past two decades. However, no methodology appears to have universally been accepted, as various limitations have been raised for more widely used ones. One of the most important limitations of conventional HRA is insufficient analysis of the task structure and problem space. To resolve this problem, we suggest SIA (Structured Information Analysis) for HRA. The proposed SIA consists of three parts. The first part is the scenario analysis that investigates the contextual information related to the given task on the basis of selected scenarios. The second is the goals-means analysis to define the relations between the cognitive goal and task steps. The third is the cognitive function analysis module that identifies the cognitive patterns and information flows involved in the task. Through the three-part analysis, systematic investigation is made possible from the macroscopic information on the tasks to the microscopic information on the specific cognitive processes. It is expected that analysts can attain a structured set of information that helps to predict the types and possibility of human error in the given task. 48 refs., 12 figs., 11 tabs. (Author)
Energy Technology Data Exchange (ETDEWEB)
Jung, Won Dea; Kim, Jae Whan; Park, Jin Kyun; Ha, Jae Joo [Korea Atomic Energy Research Institute, Taejeon (Korea)
2000-02-01
More than twenty HRA (Human Reliability Analysis) methodologies have been developed and used for the safety analysis in nuclear field during the past two decades. However, no methodology appears to have universally been accepted, as various limitations have been raised for more widely used ones. One of the most important limitations of conventional HRA is insufficient analysis of the task structure and problem space. To resolve this problem, we suggest SIA (Structured Information Analysis) for HRA. The proposed SIA consists of three parts. The first part is the scenario analysis that investigates the contextual information related to the given task on the basis of selected scenarios. The second is the goals-means analysis to define the relations between the cognitive goal and task steps. The third is the cognitive function analysis module that identifies the cognitive patterns and information flows involved in the task. Through the three-part analysis, systematic investigation is made possible from the macroscopic information on the tasks to the microscopic information on the specific cognitive processes. It is expected that analysts can attain a structured set of information that helps to predict the types and possibility of human error in the given task. 48 refs., 12 figs., 11 tabs. (Author)
Directory of Open Access Journals (Sweden)
Acar S
2016-06-01
Full Text Available Serap Acar,1 Sema Savci,1 Pembe Keskinoğlu,2 Bahri Akdeniz,3 Ebru Özpelit,3 Buse Özcan Kahraman,1 Didem Karadibak,1 Can Sevinc4 1School of Physical Therapy and Rehabilitation, 2Department of Biostatistics, Faculty of Medicine, 3Department of Cardiology, Faculty of Medicine, 4Department of Chest Disease, Faculty of Medicine, Dokuz Eylul University, İzmir, Turkey Purpose: Individuals with cardiac problems avoid physical activity and exercise because they expect to feel shortness of breath, dizziness, or chest pain. Assessing kinesiophobia related to heart problems is important in terms of cardiac rehabilitation. The Tampa Scale of Kinesiophobia Swedish Version for the Heart (TSK-SV Heart is reliable and has been validated for cardiac diseases in the Swedish population. The aim of this study was to investigate the reliability, parallel-form validity, and exploratory factor analysis of the TSK for the Heart Turkish Version (TSK Heart Turkish Version for evaluating kinesiophobia in patients with heart failure and pulmonary arterial hypertension.Methods: This cross-sectional study involved translation, back translation, and cross-cultural adaptation (localization. Forty-three pulmonary arterial hypertension and 32 heart failure patients were evaluated using the TSK Heart Turkish Version. The 17-item scale, originally composed for the Swedish population, has four factors: perceived danger for heart problem, avoidance of exercise, fear of injury, and dysfunctional self. Cronbach’s alpha (internal consistency and exploratory factor analysis were used to assess the questionnaire’s reliability. Results of the patients in the 6-minute walk test, International Physical Activity Questionnaire, and Nottingham Health Profile were analyzed by Pearson’s correlation analysis with the TSK Heart Turkish Version to indicate the convergent validity.Results: Cronbach’s alpha for the TSK Heart Turkish Version was 0.75, indicating acceptable internal
DEFF Research Database (Denmark)
Mohanty, Sankhya; Hattel, Jesper Henri
2016-01-01
modelling has been adopted towards improving the predictability of the outputs from the selective laser melting process. Establishing the reliability of the process, however, is still a challenge, especially in components having overhanging structures.In this paper, a systematic approach towards...... powder bed without support structures, by determining cumulative probability distribution functions for average layer thickness, sample density and thermal homogeneity....... establishing reliability of overhanging structure production by selective laser melting has been adopted. A calibrated, fast, multiscale thermal model is used to simulate the single track formation on a thick powder bed. Single tracks are manufactured on a thick powder bed using same processing parameters...
Directory of Open Access Journals (Sweden)
Targum Steven D
2013-01-01
Full Text Available Abstract Background The clinical global impression of severity (CGI-S scale is a frequently used rating instrument for the assessment of global severity of illness in Central Nervous System (CNS trials. Although scoring guidelines have been proposed to anchor these scores, the collection of sufficient documentation to support the derived score is not part of any standardized interview procedure. It is self evident that the absence of a standardized, documentary format can affect inter-rater reliability and may adversely affect the accuracy of the resulting data. Method We developed a structured interview guide for global impressions (SIGGI and evaluated the instrument in a 2-visit study of ambulatory patients with Major Depressive Disorder (MDD or schizophrenia. Blinded, site-independent raters listened to audio recorded SIGGI interviews administered by site-based CGI raters. We compared SIGGI-derived CGI-S scores between the two separate site-based raters and the site-independent raters. Results We found significant intraclass correlations (p = 0.001 on all SIGGI-derived CGI-S scores between two separate site-based CGI raters with each other (r = 0.768 and with a blinded, site-independent rater (r = 0.748 and r = 0.706 respectively and significant Pearson’s correlations between CGI-S scores with all MADRS validity comparisons for MDD and PANSS comparisons for schizophrenia (p- 0.001 in all cases. Compared to site-based raters, the site-independent raters gave identical “dual” CGI-S scores to 67.6% and 68.2% of subjects at visit 1 and 77.1% at visit 2. Conclusion We suggest that the SIGGI may improve the inter-rater reliability and scoring precision of the CGI-S and have broad applicability in CNS clinical trials.
McKay, Michael T.; Percy, Andrew; Goudie, Andrew J.; Sumnall, Harry R.; Cole, Jon C.
2012-01-01
The Temporal Focus Scale (TFS) is a 12-item self-report measure of cognitive engagement with the temporal domains of past, present and future. Developed in college student samples, a three-factor structure with adequate reliability and validity was documented in a series of independent studies. We tested the factor structure of the scale in a…
A structure-based software reliability allocation using fuzzy analytic hierarchy process
Chatterjee, Subhashis; Singh, Jeetendra B.; Roy, Arunava
2015-02-01
During the design phase of a software, it is often required to evaluate the reliability of the software system. At this stage of development, one crucial question arises 'how to achieve a target reliability of the software?' Reliability allocation methods can be used to set reliability goals for individual components. In this paper, a software reliability allocation model has been proposed incorporating the user view point about various functions of a software. Proposed reliability allocation method attempts to answer the question 'how reliable should the system components be?' The proposed model will be useful for determining the reliability goal at the planning and design phase of a software project, hence making reliability a singular measure for performance evaluation. Proposed model requires a systematic formulation of user requirements and preference into the technical design and reliability of the software. To accomplish this task, a system hierarchy has been established, which combines the user's view of the system with that of the software manager and the programmer. Fuzzy analytic hierarchy process (FAHP) has been used to derive the required model parameters from the hierarchy. Sensitivity analysis has also been carried out in this paper. Finally, an example has been given to illustrate the effectiveness and feasibility of the proposed method.
Structural Factors Affecting Health Examination Behavioral Intention.
Huang, Hui-Ting; Kuo, Yu-Ming; Wang, Shiang-Ru; Wang, Chia-Fen; Tsai, Chung-Hung
2016-04-01
Disease screening instruments used for secondary prevention can facilitate early determination and treatment of pathogenic factors, effectively reducing disease incidence, mortality rates, and health complications. Therefore, people should be encouraged to receive health examinations for discovering potential pathogenic factors before symptoms occur. Here, we used the health belief model as a foundation and integrated social psychological factors and investigated the factors influencing health examination behavioral intention among the public in Taiwan. In total, 388 effective questionnaires were analyzed through structural model analysis. Consequently, this study yielded four crucial findings: (1) The established extended health belief model could effectively predict health examination behavioral intention; (2) Self-efficacy was the factor that most strongly influenced health examination behavioral intention, followed by health knowledge; (3) Self-efficacy substantially influenced perceived benefits and perceived barriers; (4) Health knowledge and social support indirectly influenced health examination behavioral intention. The preceding results can effectively increase the acceptance and use of health examination services among the public, thereby facilitating early diagnosis and treatment and ultimately reducing disease and mortality rates.
Factors in reliable treatment plant operation for the production of safe water.
Hendry, Bruce A
2010-08-01
This contribution to the International Congress on Production of Safe Water, Izmir, Turkey, 20-24 January, 2009, relates to general aspects of a water supply undertaking rather than to particular technologies or chemistries for water treatment. The paper offers a "creative problem solving" approach following Fogler and LeBlanc (Strategies for creative problem solving. Prentice Hall, NJ, 1995) as a model for generating sustainable solutions when water quality and safety problems arise. Such a structured approach presents a systematic methodology that can promote communication and goal-sharing across the inter-related, but often isolated and dispersed, functions of water scientists and researchers, engineers, operations managers, government departments and communities. A problem-solving strategy, or "heuristic", invokes five main steps (define; generate; decide; implement; evaluate). Associated with each step are various creative and enabling techniques, many of which are quite familiar to us in one form or another, but which we can use more effectively in combination and through our increased awareness and practice. For example, taking a fresh view of a problem can be promoted by a variety of "lateral thinking" tools. First-hand investigation of a problem can trigger new thinking about the real problem and its origins. A good strategy implementation will always address each and every step (though not necessarily every possible technique) and will use them at various stages in the search for and implementation of solutions. The creative nature of our experience with a problem-solving heuristic develops our facility to cope better with complex formal situations, as well as with less formal or everyday problem situations. A few anecdotes are presented that illustrate some of the author's experiences relating to factors involved in safe water supply. Here, the term "factors" may signify people and organisations as agents, as well as meaning those aspects of a problem
Zhang, Huiping; Yip, Paul S. F.; Chi, Peilian; Chan, Kinsun; Cheung, Yee Tak; Zhang, Xiulan
2012-01-01
The purpose of this study was to explore the factor structure of the Work-Family Balance Scale (WFBS) and examine its reliability and validity in use in the urban Chinese population. The scale was validated using a sample of 605 urban Chinese residents from 7 cities. Exploratory factor analysis identified two factors: work-family conflict and…
Chortos, Alex; Zhu, Chenxin; Oh, Jin Young; Yan, Xuzhou; Pochorovski, Igor; To, John W-F; Liu, Nan; Kraft, Ulrike; Murmann, Boris; Bao, Zhenan
2017-08-22
Stretchable form factors enable electronic devices to conform to irregular 3D structures, including soft and moving entities. Intrinsically stretchable devices have potential advantages of high surface coverage of active devices, improved durability, and reduced processing costs. This work describes intrinsically stretchable transistors composed of single-walled carbon nanotube (SWNT) electrodes and semiconductors and a dielectric that consists of a nonpolar elastomer. The use of a nonpolar elastomer dielectric enabled hysteresis-free device characteristics. Compared to devices on SiO2 dielectrics, stretchable devices with nonpolar dielectrics showed lower mobility in ambient conditions because of the absence of doping from water. The effect of a SWNT band gap on device characteristics was investigated by using different SWNT sources as the semiconductor. Large-band-gap SWNTs exhibited trap-limited behavior caused by the low capacitance of the dielectric. In contrast, high-current devices based on SWNTs with smaller band gaps were more limited by contact resistance. Of the tested SWNT sources, SWNTs with a maximum diameter of 1.5 nm performed the best, with a mobility of 15.4 cm(2)/Vs and an on/off ratio >10(3) for stretchable transistors. Large-band-gap devices showed increased sensitivity to strain because of a pronounced dependence on the dielectric thickness, whereas contact-limited devices showed substantially less strain dependence.
Metacognition Assessment Interview: Instrument description and factor structure
Directory of Open Access Journals (Sweden)
Giovanni Pellecchia
2015-12-01
Full Text Available Objective: Metacognition is a multi-component psychological construct, characterised by the ability to identify and describe one’s own mental states and those of others. Evidence has been found for an association between deficits in metacognitive abilities and poor social functioning, low quality of life, psychopathology, and symptoms in Personality Disorders (PDs. However, to date, there are few psychometrically validated instruments available for assessing the different components of metacognition. A semi-structured interview, the Metacognition Assessment Interview (MAI, has been developed to evaluate different domains of metacognition. In the present study, we investigated the psychometric properties of the MAI in an outpatient clinical sample. Method: The MAI was administered to a clinical population of 306 outpatients attending a private clinical centre. Exploratory factor analysis, confirmatory factor analysis and correlation with instruments assessing alexithymia and interpersonal problems were carried out to examine the dimensionality and validity of the MAI. Result: Explorative and confirmatory factor analyses revealed a good fit for both a two-factor model and a four-factor model of metacognition. The two-factor model yielded two main dimensions, which we named: Self domain, defined as self-reflection, and Other domain, defined as critical distancing from one’s own mental state and that of others. The four-factor solution is composed of four sub-domains: monitoring, integration, differentiation and decentration. Moreover, the MAI showed good convergent validity, with significant correlations with both alexithymia and interpersonal problems. Conclusions: These results confirm that the MAI is a reliable instrument for measuring metacognition and its different sub-domains. In particular, the MAI represents a useful and flexible instrument for the assessment of metacognition impairments in different psychopathologies and it can provide
Yang, Soo In; Liu, Shuanghui; Brooks, Geoffrey J; Lanctot, Yves; Gruber, James V
2017-08-23
Current in vitro SPF screening method for plant oil body (oleosome)-based SPF products possesses significant inconsistency and low reliability in the SPF rating. The primary objective of this study was to evaluate the reliability and reproducibility of spectrophotometrically determined sun protection factor (SPF) from oleosome-based SPF products. The secondary objective was the data comparison of the spectrophotometric measurements against in vivo SPF testing to establish a reliable in vitro test method as a screening assay. Octyl methoxycinnamate (UVB filter) and avobenzone (UVA filter) were loaded into safflower oil bodies and formulated into oil-in-water emulsion-based finished products. To evaluate the reliability between in vivo and spectrophotometric test methods, samples were dispatched to a clinical laboratory, and the reported SPF values were compared with spectrophotometric test results. The observed SPF from the in vivo and spectrophotometric test results demonstrated a high correlation for SPF 30 products. Proportional correlation between the two evaluation methods was observed for SPF 15 and 50 products with slightly lesser accuracy with a smaller number of population tested in the clinical studies. A reliable spectrophotometric screening method for oil body-based SPF formulas has been developed using two broadly used organic UV sunscreen actives as a case study. The results demonstrated a high level of reproducibility and reliability compared to the US FDA-guided in vivo SPF testing method. © 2017 The Authors. Journal of Cosmetic Dermatology Published by Wiley Periodicals, Inc.
Directory of Open Access Journals (Sweden)
Saeideh Nasiri
2015-09-01
Full Text Available This study was conducted to determine the validity and reliability of OSCE in evaluating the clinical skills of midwifery students at Kashan University of Medical Sciences in 2014. This descriptive-correlational study was carried out on 23 senior midwifery students. The OSCE scores were calculated according to the structured objective checklists. Content and criterion validity and reliability were also assessed. The obtained data were analyzed by SPSS-16 using ANOVA and Spearman correlation coefficients. There was a significant relationship between the clinical scores and the OSCE score (P=0.03. The reliability results of the evaluation of stations by two observers showed that the lowest and highest correlation coefficients between observers were 0.58 and 1.00, respectively. Owing to good reliability and validity of this test in the first period of its implementation in Kashan, it can be recommended for subsequent periods as part of the final exam for midwifery students.
Khatibinia, M.; Salajegheh, E.; Salajegheh, J.; Fadaee, M. J.
2013-10-01
A new discrete gravitational search algorithm (DGSA) and a metamodelling framework are introduced for reliability-based design optimization (RBDO) of reinforced concrete structures. The RBDO of structures with soil-structure interaction (SSI) effects is investigated in accordance with performance-based design. The proposed DGSA is based on the standard gravitational search algorithm (GSA) to optimize the structural cost under deterministic and probabilistic constraints. The Monte-Carlo simulation (MCS) method is considered as the most reliable method for estimating the probabilities of reliability. In order to reduce the computational time of MCS, the proposed metamodelling framework is employed to predict the responses of the SSI system in the RBDO procedure. The metamodel consists of a weighted least squares support vector machine (WLS-SVM) and a wavelet kernel function, which is called WWLS-SVM. Numerical results demonstrate the efficiency and computational advantages of DGSA and the proposed metamodel for RBDO of reinforced concrete structures.
STRUCTURAL FLUCTUATIONS, ELECTRICAL RESPONSE AND THE RELIABILITY OF NANOSTRUCTURES (FINAL REPORT)
Energy Technology Data Exchange (ETDEWEB)
Philip J. Rous; Ellen D. Williams; Michael S. Fuhrer
2006-07-31
The goal of the research supported by DOE-FG02-01ER45939 was to synthesize a number of experimental and theoretical approaches to understand the relationship between morphological fluctuations, the electrical response and the reliability (failure) of metallic nanostructures. The primary focus of our work was the study of metallic nanowires which we regard as prototypical of nanoscale interconnects. Our research plan has been to link together these materials properties and behaviors by understanding the phenomenon of, and the effects of electromigration at nanometer length scales. The thrust of our research has been founded on the concept that, for nanostructures where the surface-to-volume ratio is necessarily high, surface diffusion is the dominant mass transport mechanism that governs the fluctuations, electrical properties and failure modes of nanostructures. Our approach has been to develop experimental methods that permit the direct imaging of the electromagnetic distributions within nanostructures, their structural fluctuations and their electrical response. This experimental research is complemented by a parallel theoretical and computational program that describes the temporal evolution of nanostructures in response to current flow.
The factor structure of six salutogenic constructs
Directory of Open Access Journals (Sweden)
Marita Breed
2006-01-01
Full Text Available The aim of this research was to investigate the factor structure of six salutogenic constructs, namely sense of coherence, hardiness, learned resourcefulness, potency, internal locus of control and self-efficacy. Measurement with a sample of 935 part-time students did not fit the conceptualisation of salutogenesis. A different factor structure for Whites versus Others occurred. For Whites, all six constructs more or less contributed towards the general salutogenic factor and for Others all but learned resourcefulness contributed. For Whites, salutogenesis consisted of two clear dimensions (a global positive orientation; specific behavioural skills and for Others one dimension (an optimistic life view. Confirmatory factor analysis performed on the data for both groups, indicated a weak fit. It was recommended that salutogenesis be further explored within an overall personality theory. Opsomming Die doel van hierdie navorsing was om die faktorstruktuur van ses salutogeniese konstrukte te ondersoek, naamlik sin vir koherensie, gehardheid, aangeleerde vindingrykheid, potensie, interne lokus van beheer en selfgenoegsaamheid. Meting met ‘n steekproef van 935 deeltydse studente het nie ‘n passing getoon met die konseptualisering van salutogenese nie. ‘n Eiesoortige faktorstruktuur vir Wit studente versus Ander studente het voorgekom. Vir Wittes, het al ses die konstrukte meer of minder bygedra tot die algemene salutugeniese faktor en vir Andere het almal behalwe aangeleerde vindingrykheid bygedra. Vir Wittes bestaan salutogenese uit twee duidelike dimensies (‘n globale positiewe lewensorientasie; spesifieke gedrags vaardighede en vir Andere uit een dimensie (‘n optimistiese lewensbeskouing. Bevestigende faktor ontleding uitgevoer op die data van beide groepe, het ‘n swak passing getoon. Daar is aanbeveel dat salutogenese verder ondersoek word binne ‘n oorkoepelende persoonlikheidsteorie.
Smith, Jack E.; Hakel, Milton D.
1979-01-01
Examined are questions pertinent to the use of the Position Analysis Questionnaire: Who can use the PAQ reliably and validly? Must one rely on trained job analysts? Can people having no direct contact with the job use the PAQ reliably and validly? Do response biases influence PAQ responses? (Author/KC)
Nikbay, M.; Fakkusoglu, N.; Kuru, M. N.
2010-06-01
We consider reliability based aeroelastic optimization of a AGARD 445.6 composite aircraft wing with stochastic parameters. Both commercial engineering software and an in-house reliability analysis code are employed in this high-fidelity computational framework. Finite volume based flow solver Fluent is used to solve 3D Euler equations, while Gambit is the fluid domain mesh generator and Catia-V5-R16 is used as a parametric 3D solid modeler. Abaqus, a structural finite element solver, is used to compute the structural response of the aeroelastic system. Mesh based parallel code coupling interface MPCCI-3.0.6 is used to exchange the pressure and displacement information between Fluent and Abaqus to perform a loosely coupled fluid-structure interaction by employing a staggered algorithm. To compute the probability of failure for the probabilistic constraints, one of the well known MPP (Most Probable Point) based reliability analysis methods, FORM (First Order Reliability Method) is implemented in Matlab. This in-house developed Matlab code is embedded in the multidisciplinary optimization workflow which is driven by Modefrontier. Modefrontier 4.1, is used for its gradient based optimization algorithm called NBI-NLPQLP which is based on sequential quadratic programming method. A pareto optimal solution for the stochastic aeroelastic optimization is obtained for a specified reliability index and results are compared with the results of deterministic aeroelastic optimization.
Corruble, E; Purper, D; Payan, C; Guelfi, J
1998-08-01
The inter-rater reliability of the French versions of the MADRS and the DRRS was studied on the basis of 58 videotape records of structured standardised interviews of depressed inpatients under antidepressant treatment. Each patient was assessed by two trained raters, from the same videotape recording. The inter-rater reliability of total scores was high with both scales (intra-class correlation coefficients: 0.86 for MADRS and 0.77 for DRRS). However, the inter-rater reliability for individual items was higher and more homogeneous for the MADRS than for the DRRS. Finally, the structured interview in French appears to be relevant for the MADRS, but it should be improved for the DRRS.
Probabilistic Calibration of Fatigue Design Factors for Offshore Wind Turbine Support Structures
DEFF Research Database (Denmark)
Ramirez, José Rangel; Sørensen, John Dalsgaard
2010-01-01
This paper describes a reliability-based approach to determine fatigue design factors (FDF) for offshore wind turbine support structures made of steel. The FDF values are calibrated to a specific reliability level and linked to a specific inspection and maintenance (I&M) strategy used for the con......This paper describes a reliability-based approach to determine fatigue design factors (FDF) for offshore wind turbine support structures made of steel. The FDF values are calibrated to a specific reliability level and linked to a specific inspection and maintenance (I&M) strategy used...... for the considered offshore wind turbines in such a way that the specific uncertainties for the fatigue life are accounted in a rational manner. Similar approaches have been used for offshore oil & gas sub-structures, but the required reliability level for offshore wind turbines is generally lower and the fatigue...... if inspections are planned during the design life, and thereby the basis is available for selecting a cost-effective fatigue design. Further, the results can be used as basis for recommendations in standardization....
Huang, Yan; Dessel, Jeroen Van; Nicolielo, Laura; Van de Casteele, Elke; Slagmolen, Pieter; Jacobs, Reinhilde
2015-01-01
Huang Y., Van Dessel J., Nicolielo L., Van de Casteele E., Slagmolen P., Jacobs R., ''The reliability of cone-beam computed tomography to analyze trabecular and cortical bone structures: an in-vitro study'', 24th annual congress of the European Association for Osseointegration - EAO 2015, September 24-26, 2015, Stockholm, Sweden.
Directory of Open Access Journals (Sweden)
Lyubimova Lyudmila
2016-01-01
Full Text Available This paper presents new approaches to solving problems of forecasting the life of heating surface of boilers, based on an analysis of internal structural stresses of the first and second kind that could affect the intragranular and intergranular strength and reliability of the pipeline in continuous operation by making it work without damage by preventing the disclosure of zone cracks.
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard
2011-01-01
Reliability-based cost-optimal planning of inspection, maintenance and operation has many applications. In this paper applications for planning of inspections for oil & gas jacket structures and of operation and maintenance of offshore wind turbines are described and illustrated by examples....
DEFF Research Database (Denmark)
Bruyn, George Aw; Naredo, Esperanza; Damjanov, Nemanja;
2016-01-01
OBJECTIVE: To assess whether ultrasonography (US) is reliable for the evaluation of inflammatory and structural abnormalities in patients with knee osteoarthritis (OA). METHODS: Thirteen patients with early knee OA were examined by 11 experienced sonographers during 2 days. Dichotomous and semiqu...
Seismic force modification factor for ductile structures
Institute of Scientific and Technical Information of China (English)
TONG Gen-shu; HUANG Jin-qiao
2005-01-01
The earthquake forces used in design codes of buildings should be theoretically determinable. This work examines the seismic force modification factor R based on elastic-plastic time-history earthquake analysis of SDOF systems, wherein the hysteresis models are elastic-perfectly-plastic (EPP), elastic-linearly-hardening (ELH), shear-slipped and bilinear-elastic. The latter two models are analysed for separating the effect of the ductility and the energy-dissipating capacity. Three-hundred eighty-eight earthquake records from different site conditions are used in analysis. The ductility is taken to be 2, 3, 4, 5 and 6, with the damping ratio being 0.02, 0.035 and 0.05 respectively. The post-yield stiffness ratios 0.0, 0.1 and 0.2 are used in the analysis. The R spectra are standardized by the characteristic period of the earthquake records, which leads to a much smaller scatter in averaged numerical results. It was found that the most important factor determining R is the ductility. R increases more than linearly with ductility. The energy-dissipating capacity, damping and the post-yield stiffness are the less important factors. The energy dissipating capacity is important only for structures with short period and moderate period (0.3≤T/Tg＜5.0). For EPP and ELH models, R for 0.05 damping is 10% to 15% smaller than for 0.02 damping. For EPP and ELH models, greater post-yield stiffness leads to greater R, but the influence of post-yield stiffness is obvious only when the post-yield stiffness is less than 10% of the initial stiffness. By means of statistical regression analysis the relation of the seismic force modification factor R with the natural period of the system and ductility for EPP and ELH models were established for each site and soil condition.
Bao, Han P.
1995-01-01
Fabricating primary aircraft and spacecraft structures using advanced composite materials entail both benefits and risks. The benefits come from much improved strength-to-weight ratios and stiffness-to-weight ratios, potential for less part count, ability to tailor properties, chemical and solvent resistance, and superior thermal properties. On the other hand, the risks involved include high material costs, lack of processing experience, expensive labor, poor reproducibility, high toxicity for some composites, and a variety of space induced risks. The purpose of this project is to generate a manufacturing database for a selected number of materials with potential for space applications, and to rely on this database to develop quantitative approaches to screen candidate materials and processes for space applications on the basis of their manufacturing risks including costs. So far, the following materials have been included in the database: epoxies, polycyanates, bismalemides, PMR-15, polyphenylene sulfides, polyetherimides, polyetheretherketone, and aluminum lithium. The first four materials are thermoset composites; the next three are thermoplastic composites, and the last one is is a metal. The emphasis of this database is on factors affecting manufacturing such as cost of raw material, handling aspects which include working life and shelf life of resins, process temperature, chemical/solvent resistance, moisture resistance, damage tolerance, toxicity, outgassing, thermal cycling, and void content, nature or type of process, associate tooling, and in-process quality assurance. Based on industry experience and published literature, a relative ranking was established for each of the factors affecting manufacturing as listed above. Potential applications of this database include the determination of a delta cost factor for specific structures with a given process plan and a general methodology to screen materials and processes for incorporation into the current
Reliability computation from reliability block diagrams
Chelson, P. O.; Eckstein, E. Y.
1975-01-01
Computer program computes system reliability for very general class of reliability block diagrams. Four factors are considered in calculating probability of system success: active block redundancy, standby block redundancy, partial redundancy, and presence of equivalent blocks in the diagram.
DEFF Research Database (Denmark)
Isaksen, Jesper; Hertel, Niels Thomas; Kjær, Niels Kristian
2013-01-01
In order to optimise the selection process for admission to specialist training in family medicine, we developed a new design for structured applications and selection interviews. The design contains semi-structured interviews, which combine individualised elements from the applications with stan...... with standardised behaviour-based questions. This paper describes the design of the tool, and offers reflections concerning its acceptability, reliability and feasibility....
NEW STRUCTURAL PROBABILISTIC AND NON-PROBABILISTIC HYBRID RELIABILITY MODEL%一种新的结构概率—非概率混合可靠性模型
Institute of Scientific and Technical Information of China (English)
乔心州; 吕震宙
2012-01-01
The problem of hybrid reliability analysis of structures with random and interval variables is investigated. On the basis of the probabilistic reliability model, a new probabilistic and non-probabilistic hybrid reliability model of structures is proposed. The ratio of the strength to the stress is defined as the random-interval safety factor. The probabilistic reliability for random-interval safety factors exceeding unity is suggested as the measure of structural hybrid reliability. To demonstrate the compatibility among the hybrid reliability model, the piobabilistic reliability model and the non-probabilistic reliability model, two specific cases of the hybrid reliability model are discussed. Two examples are utilized to illustrate the effectiveness and feasibility of the hybrid reliability model.%研究包含随机变量和区间变量的结构混合可靠性问题.基于概率一靠性模型,提出一种新的结构概率—非概率混合可靠性模型.将结构强度与结构应力的比值定义为随机区间安全系数,以随机区间安全系数大于1的概率可靠度来度量结构可靠性.探讨混合可靠性模型的两种特例,证明混合可靠性模型与已有概率和非概率可靠性模型的相容性.最后通过实例分析表明混合可靠性模型有效可行.
DEFF Research Database (Denmark)
Ramirez, José Rangel; Sørensen, John Dalsgaard
2011-01-01
This work illustrates the updating and incorporation of information in the assessment of fatigue reliability for offshore wind turbine. The new information, coming from external and condition monitoring can be used to direct updating of the stochastic variables through a non-parametric Bayesian...... updating approach and be integrated in the reliability analysis by a third-order polynomial chaos expansion approximation. Although Classical Bayesian updating approaches are often used because of its parametric formulation, non-parametric approaches are better alternatives for multi-parametric updating...... with a non-conjugating formulation. The results in this paper show the influence on the time dependent updated reliability when non-parametric and classical Bayesian approaches are used. Further, the influence on the reliability of the number of updated parameters is illustrated....
Energy Technology Data Exchange (ETDEWEB)
Oxstrand, J. (Vattenfall Ringhals AB, Stockholm (Sweden))
2010-12-15
The main goal of this Nordic Nuclear Safety Research Council (NKS) project is to produce guidance for how to use human reliability analysis (HRA) to strengthen overall safety. The project consists of two substudies: The Nordic Point of View - A User Needs Analysis, and The American Point of View - Insights of How the US Nuclear Industry Works with HRA. The purpose of the Nordic Point of View study was a user needs analysis that aimed to survey current HRA practices in the Nordic nuclear industry, with the main focus being to connect HRA to system design. In this study, 26 Nordic (Swedish and Finnish) nuclear power plant specialists with research, practitioner, and regulatory expertise in HRA, PRA, HSI, and human performance were interviewed. This study was completed in 2009. This study concludes that HRA is an important tool when dealing with human factors in control room design or modernizations. The Nordic Point of View study showed areas where the use of HRA in the Nordic nuclear industry could be improved. To gain more knowledge about how these improvements could be made, and what improvements to focus on, the second study was conducted. The second study is focused on the American nuclear industry, which has many more years of experience with risk assessment and human reliability than the Nordic nuclear industry. Interviews were conducted to collect information to help the author understand the similarities and differences between the American and the Nordic nuclear industries, and to find data regarding the findings from the first study. The main focus of this report is to identify potential HRA improvements based on the data collected in the American Point of View survey. (Author)
Passerieux, Christine; Bulot, Virginie; Hardy-Baylé, Marie-Christine; Roux, Paul
2017-04-11
We have developed a new scale that assesses disability caused by cognitive impairments in schizophrenia, in order to evaluate the functional impact of schizophrenia and help the prescription of rehabilitation interventions. The aim of the study was to assess its psychometrical properties. Mental healthcare professionals and relatives of individuals with schizophrenia developed and rated the evaluation of cognitive processes involved in disability in schizophrenia scale, which included 13 items. Its construct validity was assessed through a factorial analysis; its concurrent validity was evaluated based on ecological outcomes, its convergent validity was tested against the World Health Organization Disability Assessment Schedule (WHODAS II), and its reliability was estimated based on internal consistency and inter-rater reliability. Overall, 215 patients were included. Our findings supported a two-factor structure which accounted for 46% of the variance. The internal consistency and inter-rater reliability were good. The convergent validity showed a strong correlation with the WHODAS II. The concurrent validity showed strong relationships with work status, independent living, level and adequacy of institutional care. The good psychometric properties of the scale suggest a role for this tool in assessing schizophrenia-related disability and evaluating the need for cognitive remediation. Implication for Rehabilitation Schizophrenia is a chronic disorder leading to a severe psychiatric handicap. The scale showed good psychometric properties in individuals with schizophrenia and severe psychiatric disability. The scale is easy and quick to administer (about 15 min). The scale may help to identify targets for rehabilitation interventions in individuals with schizophrenia.
Barreira, João C M; Alves, Rita C; Casal, Susana; Ferreira, Isabel C F R; Oliveira, M Beatriz P P; Pereira, José Alberto
2009-06-24
In this study, the profile of tocopherols and tocotrienols in chestnut ( Castanea sativa Mill.) kernel oil was evaluated. Four Portuguese chestnut varieties were selected: Aveleira, Boaventura, Judia, and Longal. The vitamin E determination had already been applied to similar matrices, but, to the authors' knowledge, it is the first time that chestnut kernel oil has been evaluated. The prevalent vitamer was gamma-tocopherol, often present in trace amounts in other natural products. Due to the high commercial value of chestnut, a statistical analysis of the obtained results was also conducted to define the tocopherol and tocotrienol profile as a reliable indicator of a specific chestnut variety. To achieve this objective, an analysis of variance was performed to evaluate the accuracy of the method as well as the uniformity of results for each variety. A discriminant analysis was also carried out revealing quite satisfactory results. Four varieties were clustered in four individual groups through the definition of two discriminant analysis dimensions.
Reliability-Based Code Calibration
DEFF Research Database (Denmark)
Faber, M.H.; Sørensen, John Dalsgaard
2003-01-01
The present paper addresses fundamental concepts of reliability based code calibration. First basic principles of structural reliability theory are introduced and it is shown how the results of FORM based reliability analysis may be related to partial safety factors and characteristic values....... Thereafter the code calibration problem is presented in its principal decision theoretical form and it is discussed how acceptable levels of failure probability (or target reliabilities) may be established. Furthermore suggested values for acceptable annual failure probabilities are given for ultimate...... and serviceability limit states. Finally the paper describes the Joint Committee on Structural Safety (JCSS) recommended procedure - CodeCal - for the practical implementation of reliability based code calibration of LRFD based design codes....
Mohanty, Sankhya; Hattel, Jesper H.
2016-04-01
Repeatability and reproducibility of parts produced by selective laser melting is a standing issue, and coupled with a lack of standardized quality control presents a major hindrance towards maturing of selective laser melting as an industrial scale process. Consequently, numerical process modelling has been adopted towards improving the predictability of the outputs from the selective laser melting process. Establishing the reliability of the process, however, is still a challenge, especially in components having overhanging structures. In this paper, a systematic approach towards establishing reliability of overhanging structure production by selective laser melting has been adopted. A calibrated, fast, multiscale thermal model is used to simulate the single track formation on a thick powder bed. Single tracks are manufactured on a thick powder bed using same processing parameters, but at different locations in a powder bed and in different laser scanning directions. The difference in melt track widths and depths captures the effect of changes in incident beam power distribution due to location and processing direction. The experimental results are used in combination with numerical model, and subjected to uncertainty and reliability analysis. Cumulative probability distribution functions obtained for melt track widths and depths are found to be coherent with observed experimental values. The technique is subsequently extended for reliability characterization of single layers produced on a thick powder bed without support structures, by determining cumulative probability distribution functions for average layer thickness, sample density and thermal homogeneity.
2016-01-01
Objective The Injustice Experience Questionnaire (IEQ) assesses injury-related perceived injustice. This study aimed to (1) develop a Japanese version (IEQ-J), (2) examine its factor structure, validity, and reliability, and (3) discover which demographic variable(s) positively contributed to prediction of IEQ-J scores. Methods Data from 71 patients (33 male, 38 female; age = 20+) with injury pain were employed to investigate factor structure by exploratory and confirmatory factor analyses. C...
Beyond the Factor of Safety: Developing Fragility Curves to Characterize System Reliability
2010-07-01
hysteretic devices. Computers and Structures 86: 1769–1781. Celik, O. C., and B. R. Ellingwood. 2008. Modeling beam- column joints in fragility...fragility curves for reinforced concrete frame structures using an empirical model of the shear and bond- slip behavior of beam column joints exposed...southeastern United States. Fragility curves were developed for five components of each bridge type ( columns , steel bearings, expansion bearings, fixed
Energy Technology Data Exchange (ETDEWEB)
Kotte, K.L.; Eulitz, K.G. [TU Dresden, Institut fuer Festkoerpermechanik, Mommsenstr. 13, 01069 Dresden (Germany)
2003-09-01
After the german reunification Professor Harald Zenner initiated and promoted several research projects which were aimed to mantain the bulk of available experimental results and to preserve the know-how grown in both german countries. So it could be saved for future use. Here the IMAB (Institute of Plant Engineering and Fatigue Analysis) of Clausthal Technical University (TUC) and the Institute of Solid State Mechanics of TU Dresden (TUD) cooperated in two investigations -''Lifetime-prediction I and II''. This resulted in the ''Data Pool Operational Strength DABEF'' and in a profound statistical analysis on reliability of service life estimations. Herein the influence of the counting method could be separated from that of the damage accumulation hypothesis. Deriving subgroups from the sample it became possible to define modulation factors for allowable stress. Besides this the data collection serves as a basis of further investigations which resulted in a postdoctoral qualification and several graduation works. Last but not least the findings of the statistical analysis expanded into the design code ''Computational proof of strength'' of the german Research Comittee Engineering (FKM). (Abstract Copyright [2003], Wiley Periodicals, Inc.) [German] Nach der Wiedervereinigung Deutschlands initiierte Prof. Harald Zenner mehrere Forschungsvorhaben, die das Ziel verfolgten, das gesamtdeutsche Know-How der Betriebsfestigkeit und den existierenden Fundus an Versuchsergebnissen aufzuarbeiten und damit fuer die weitere Nutzung zu sichern. In diesem Zusammenhang bearbeiteten das IMAB der TU Clausthal und das IFKM der TU Dresden gemeinsam zwei Vorhaben ''Lebensdauervorhersage I und II'', die ihr Ergebnis zum einen in der Datensammlung Betriebsfestigkeit ''DABEF'', zum anderen in einer sauberen statistischen Analyse zur Treffsicherheit der Lebensdauerabschaetzungsverfahren hatten
Factor structure of the STAXI-2-AX and its relationship to burnout in housewives.
Moral de la Rubia, José; González Ramírez, Mónica Teresa; Landero Hernández, René
2010-05-01
This study was conducted in order to determine factor structure and reliability of STAXI-2-AX/EX (Spielberger, 1999) and to calculate the correlation between STAXI-2-AX/EX and the Housewives Burnout Questionnaire (CUBAC). The study sample included 226 housewives. Dimensional structure was estimated using exploratory and confirmatory factor analysis. Factor analysis results of STAXI-2-AX/EX showed that a four related factors model had an adequate goodness of fit, eliminating three items. Regarding the CUBAC, a two related factors structure presented the best goodness of fit, which improve if five items were eliminated. Finally, as we expected, the correlation between the two scales was positive (r = .38). We suggest that this study should be replicated in other countries.
Halfens, R J; Van Achterberg, T; Bal, R M
2000-08-01
The Braden scale is one of the most intensively studied risk assessment scales used in identifying the risk of developing pressure sores. However, not all studies show that the sensitivity and specificity of this scale is sufficient. This study, therefore, investigated whether adding new risk factors can enhance the sensitivity and specificity of the Braden scale. The Braden scale was tested in a prospective multi-centre design. The nurses of 11 wards filled in the Braden scale every 5 days for each patient who was admitted without pressure sores and who had a probable stay of at least 10 days. Based on a literature study and in-depth interviews with experts, the Braden scale was extended by the risk factor blood circulation. In addition, other risk factors, which are more or less stable patient characteristics, were measured during the admission of the patient. Independent research assistants measured the presence of pressure sores twice a week. As the external criterion for the risk of developing pressure sores, the presence of pressure sores and/or the use of preventive activities was used. Results showed that the original Braden scale was a reliable instrument and that the sensitivity and specificity was sufficient. However, reformulating the factors moisture and nutrition, and adding the risk factor age could enhance the sensitivity and specificity. Furthermore, results showed that the factors sensory perception, and friction and shear were especially important risk factors for the Braden scale. In fact, using only the factors sensory perception, friction and shear, moisture (a reformulated factor) and age give the highest explained variance of the risk of developing pressure sores. The added risk factor blood circulation, did not enhance the sensitivity and specificity of the original Braden scale. Suggestions are given on how to use risk assessment scales in practice.
Posttraumatic growth inventory: factor structure in Spanish-speaking people living with HIV.
Garrido-Hernansaiz, Helena; Rodríguez-Rey, Rocío; Alonso-Tapia, Jesús
2017-10-01
This cross-sectional study analyzed the factorial structure of the Posttraumatic Growth Inventory (PTGI) in a sample of 304 Spanish-speaking HIV-positive adults. Participants completed the PTGI and a socio-demographic questionnaire. Exploratory factor analysis (EFA) was carried out through structural equations modeling, with a Varimax rotation. Factors with eigenvalues greater than 1 were extracted, and items with loadings higher than .5 on a factor and lower than .4 on the rest were retained. Two confirmatory factor analyses (CFA) were performed to test a hierarchical model and a bifactor model. Reliability analyses were conducted. EFA suggested a three-factor model keeping 11 of the original 21 items. The three factors that emerged were changes in philosophy of life, in the self and in interpersonal relationships. CFAs suggested that only the bifactor model fitted the data. The three factors as well as the global scale showed good reliability. The factor structure of PTGI's scores in our data is consistent with the three dimensions theorized by Tedeschi and Calhoun, which speaks in favor of the construct validity of this measure.
Energy Technology Data Exchange (ETDEWEB)
Lathrop, J.W.; Hartman, R.A.; Saylor, C.R.
1981-01-01
The third year of the accelerated reliability testing program concentrated on electrical measurement instrumentation and in modeling cell behavior in the second quadrant. In addition, some preliminary work was done on correlating cell color changes with electrical degradation. Not reported are results of continuing accelerated stress tests on state of the art cells. A number of new cells were added to the program, but not in time for sufficient data to be obtained, while the older cells are undergoing extended test periods and new data are not yet available on them. The all-digital, microprocessor controlled, short interval tester, which was designed and fabricated, has replaced the manual measurement procedure formerly used. This has improved measurement accuracy and repeatability, reduced measurement time, and through coordinated data management procedures, eliminated data errors. A complete description of the tester including schematics and software is given and its operating procedures described. A computer model, based on the thermal and electrical properties of the cells and encapsulating materials, was developed to relate cell temperature to electrical characteristics in the second quadrant. This model adequately predicted the behavior of both encapsulated and unencapsulated cells, although accurate temperature measurements on encapsulated cells were difficult to obtain. In addition, only cells of one type were used for comparison and other cell types may require different parameter values for fitting. Use of the model should permit the prediction of a cell's sensitivity to degradation in the second quadrant. The computer program is listed together with a description of its operation.
Energy Technology Data Exchange (ETDEWEB)
Prince, J.L.; Lathrop, J.W.
1979-05-01
The results of accelerated stress testing of four different types of silicon terrestrial solar cells are discussed. The accelerated stress tests used included bias-temperature tests, bias-temperature-humidity tests, thermal cycle and thermal shock tests, and power cycle tests. Characterization of the cells was performed before stress testing and at periodic down-times, using electrical measurement, visual inspection, and metal adherence pull tests. Electrical parameters measured included short-circuit current, I/sub sc/, open circuit voltage, V/sub oc/, and output power, voltage, and current at the maximum power point, P/sub m/, V/sub m/, and I/sub m/ respectively. Incorporated in the report are the distributions of the prestress electrical data for all cell types. Data was also obtained on cell series and shunt resistance. Significant differences in the response to the various stress tests was observed between cell types. On the basis of the experience gained in this research work, a suggested Reliability Qualification Test Schedule was developed.
Energy Technology Data Exchange (ETDEWEB)
None
2015-08-01
Since 1990, the National Renewable Energy Laboratory’s (NREL's) National Wind Technology Center (NWTC) has tested more than 150 wind turbine blades. NWTC researchers can test full-scale and subcomponent articles, conduct data analyses, and provide engineering expertise on best design practices. Structural testing of wind turbine blades enables designers, manufacturers, and owners to validate designs and assess structural performance to specific load conditions. Rigorous structural testing can reveal design and manufacturing problems at an early stage of development that can lead to overall improvements in design and increase system reliability.
Yang, Hongfei; Hong, Chaoqin; Tao, Xiaodan; Zhu, Lingyi
2015-01-01
This study examined the structure, reliability, and validity of the revised Chinese version of the Child and Adolescent Perfectionism Scale (N = 933). The results confirmed the four-factor structure of the Chinese version of the Child and Adolescent Perfectionism Scale. Implications, limitations, and suggestions for future research are provided.
Directory of Open Access Journals (Sweden)
Tamrazyan Ashot Georgievich
2012-10-01
Full Text Available Accurate and adequate description of external influences and of the bearing capacity of the structural material requires the employment of the probability theory methods. In this regard, the characteristic that describes the probability of failure-free operation is required. The characteristic of reliability means that the maximum stress caused by the action of the load will not exceed the bearing capacity. In this paper, the author presents a solution to the problem of calculation of structures, namely, the identification of reliability of pre-set design parameters, in particular, cross-sectional dimensions. If the load distribution pattern is available, employment of the regularities of distributed functions make it possible to find the pattern of distribution of maximum stresses over the structure. Similarly, we can proceed to the design of structures of pre-set rigidity, reliability and stability in the case of regular load distribution. We consider the element of design (a monolithic concrete slab, maximum stress S which depends linearly on load q. Within a pre-set period of time, the probability will not exceed the values according to the Poisson law. The analysis demonstrates that the variability of the bearing capacity produces a stronger effect on relative sizes of cross sections of a slab than the variability of loads. It is therefore particularly important to reduce the coefficient of variation of the load capacity. One of the methods contemplates the truncation of the bearing capacity distribution by pre-culling the construction material.
Directory of Open Access Journals (Sweden)
Dal Grande Eleonora
2012-07-01
Full Text Available Abstract Background Accurate monitoring of health conditions and behaviours, and health service usage in the population, using an effective and economical method is important for planning and evaluation. This study examines the reliability of questions asked in a telephone survey by conducting a test/retest analysis of a range of questions covering demographic variables, health risk factors and self-reported chronic conditions among people aged 16 years and over. Methods A Computer Assisted Telephone Interviewing (CATI survey on health issues of South Australians was re-administered to a random sub-sample of 154 respondents between 13-35 days (mean 17 after the original survey. Reliability between questions was assessed using Cohen’s kappa and intraclass correlation coefficients. Results Demographic questions (age, gender, number of adults and children in the household, country of birth showed extremely high reliability (0.97 to 1.00. Health service use (ICC = 0.90 95% CI 0.86-0.93 and overall health status (Kappa = 0.60 95% CI 0.46-0.75 displayed moderate agreement. Questions relating to self-reported risk factors such as smoking (Kappa = 0.81 95% CI 0.72-0.89 and alcohol drinking (ICC 0.75 = 95% CI 0.63-0.83 behaviour showed good to excellent agreement, while questions relating to self-reported risk factors such as time spent walking for physical activity (ICC 0.47 = 95% CI 0.27-0.61, fruit (Kappaw = 0.60 95% CI 0.45-0.76 and vegetable consumption (Kappaw = 0.50 95% CI 0.32-0.69 showed only moderate agreement. Self-reported chronic conditions displayed substantial to almost perfect agreement (0.72 to 1.00 with the exception of moderate agreement for heart disease (Kappa = 0.82 95% CI 0.57-0.99. Conclusion These results show the questions assessed to be reliable in South Australia for estimating health conditions and monitoring health related behaviours using a CATI survey.
Reliability Analysis and Test Planning using CAPO-Test for Existing Structures
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Engelund, S.; Faber, M. H.
2000-01-01
of uncertainty related to this method are described. It is shown how the uncertainty in the transformation from the CAPO-test results to estimates of the concrete strength can be modeled. Further, the statistical uncertainty is modeled using Bayesian statistics. Finally, it is shown how reliability-based optimal...
Inter-rater reliability in disability assessment based on a semi-structured interview report
Spanjer, J.; Krol, B.; Brouwer, Silvia; Groothoff, J.W.
2008-01-01
Purpose. To investigate whether physicians are able to perform a disability assessment based on a written report and to assess the inter-rater reliability between physicians in the assessment of work limitations. Method. In total, 12 insurance physicians used written reports to assess work limitatio
DEFF Research Database (Denmark)
Ramirez, José Rangel; Sørensen, John Dalsgaard
2011-01-01
This work illustrates the updating and incorporation of information in the assessment of fatigue reliability for offshore wind turbine. The new information, coming from external and condition monitoring can be used to direct updating of the stochastic variables through a non-parametric Bayesian u...
1989-09-01
adjacent cells that are filled with soil or rock fragments (Lacroix, Esrig, and Luscher 1970). In analyzing cofferdams, one needs to consider not only the...reliability as a function of time, t, using Lacroix’s assumption that 0.0025 in./yr (Lacroix, Esrig, and Luscher 1970). t Shear Rupture in Cross Wall
Gravitational form factors and nucleon spin structure
Teryaev, O. V.
2016-10-01
Nucleon scattering by the classical gravitational field is described by the gravitational (energy-momentum tensor) form factors (GFFs), which also control the partition of nucleon spin between the total angular momenta of quarks and gluons. The equivalence principle (EP) for spin dynamics results in the identically zero anomalous gravitomagnetic moment, which is the straightforward analog of its electromagnetic counterpart. The extended EP (ExEP) describes its (approximate) validity separately for quarks and gluons and, in turn, results in equal partition of the momentum and total angular momentum. It is violated in quantum electrodynamics and perturbative quantum chromodynamics (QCD), but may be restored in nonperturbative QCD because of confinement and spontaneous chiral symmetry breaking, which is supported by models and lattice QCD calculations. It may, in principle, be checked by extracting the generalized parton distributions from hard exclusive processes. The EP for spin-1 hadrons is also manifested in inclusive processes (deep inelastic scattering and the Drell-Yan process) in sum rules for tensor structure functions and parton distributions. The ExEP may originate in either gravity-proof confinement or in the closeness of the GFF to its asymptotic values in relation to the mediocrity principle. The GFFs in time-like regions reveal some similarity between inflation and annihilation.
Structural integration in hypoxia-inducible factors
Energy Technology Data Exchange (ETDEWEB)
Wu, Dalei; Potluri, Nalini; Lu, Jingping; Kim, Youngchang; Rastinejad, Fraydoon
2015-08-20
The hypoxia-inducible factors (HIFs) coordinate cellular adaptations to low oxygen stress by regulating transcriptional programs in erythropoiesis, angiogenesis and metabolism. These programs promote the growth and progression of many tumours, making HIFs attractive anticancer targets. Transcriptionally active HIFs consist of HIF-alpha and ARNT (also called HIF-1 beta) subunits. Here we describe crystal structures for each of mouse HIF-2 alpha-ARNT and HIF-1 alpha-ARNT heterodimers in states that include bound small molecules and their hypoxia response element. A highly integrated quaternary architecture is shared by HIF-2 alpha-ARNT and HIF-1 alpha-ARNT, wherein ARNT spirals around the outside of each HIF-alpha subunit. Five distinct pockets are observed that permit small-molecule binding, including PAS domain encapsulated sites and an interfacial cavity formed through subunit heterodimerization. The DNA-reading head rotates, extends and cooperates with a distal PAS domain to bind hypoxia response elements. HIF-alpha mutations linked to human cancers map to sensitive sites that establish DNA binding and the stability of PAS domains and pockets.
DEFF Research Database (Denmark)
Mohanty, Sankhya; Hattel, Jesper Henri
2016-01-01
Repeatability and reproducibility of parts produced by selective laser melting is a standing issue, and coupled with a lack of standardized quality control presents a major hindrance towards maturing of selective laser melting as an industrial scale process. Consequently, numerical process...... modelling has been adopted towards improving the predictability of the outputs from the selective laser melting process. Establishing the reliability of the process, however, is still a challenge, especially in components having overhanging structures.In this paper, a systematic approach towards...... establishing reliability of overhanging structure production by selective laser melting has been adopted. A calibrated, fast, multiscale thermal model is used to simulate the single track formation on a thick powder bed. Single tracks are manufactured on a thick powder bed using same processing parameters...
DEFF Research Database (Denmark)
Nielsen, Søren R.K.; Skjærbæk, P. S.; Köylüoglu, H. U.;
The paper deals with the prediction of global damage and future structural reliability with special emphasis on sensitivity, bias and uncertainty of these predictions dependent on the statistically equivalent realizations of the future earthquake. The predictions are based on a modified Clough......-Johnston single-degree-of-freedom (SDOF) oscillator with three parameters which are calibrated to fit the displacement response and the damage development in the past earthquake....
Energy Technology Data Exchange (ETDEWEB)
Şirli, Roxana, E-mail: roxanasirli@gmail.com; Sporea, Ioan, E-mail: isporea@umft.ro; Bota, Simona, E-mail: bota_simona1982@yahoo.com; Jurchiş, Ana, E-mail: ana.jurchis@yahoo.com
2013-08-15
Aim: To retrospectively assess the feasibility of transient elastography (TE) and the factors associated with failed and unreliable liver stiffness measurements (LSMs), in patients with chronic liver diseases. Material and methods: Our retrospective study included 8218 consecutive adult patients with suspected chronic liver diseases. In each patient, LSMs were performed with a FibroScan{sup ®} device (Echosens, France), with the M probe. Failure of TE measurements was defined if no valid measurement was obtained after at least 10 shots and unreliable if fewer than 10 valid shots were obtained, success rate (SR) <60% and/or interquartile range interval/median value (IQR/Med) ≥30%. Results: From the 8218 patients, failed and unreliable LSMs were observed in 29.2% of cases. In univariant analysis, the following risk factors were associated with failed and unreliable measurements: age over 50 years (OR 2.04; 95%CI 1.84–2.26), female gender (OR 1.32; 95%CI 1.20–1.45), BMI > 27.7 kg/m{sup 2} (OR 2.89, 95%CI 2.62–3.19), weight > 77 kg (OR 2.17; 95%CI 1.97–2.40) and height < 162 cm (OR 1.26; 95%CI 1.14–1.40). In multivariate analysis all the factors mentioned above were independently associated with the risk of failed and unreliable measurements. If all the negative predictive factors were present (woman, older than 50 years, with BMI > 27.7 kg/m{sup 2}, heavier than 77 kg and shorter than 162 cm), the rate of failed and unreliable measurements was 58.5%. In obese patients (BMI ≥ 30 kg/m{sup 2}), the rate of failed and unreliable measurements was 49.5%. Conclusion: Failed and unreliable LSMs were observed in 29.1% of patients. Female gender, older age, higher BMI, higher weight and smaller height were significantly associated with failed and unreliable LSMs.
Reliability of Wave Energy Converters
DEFF Research Database (Denmark)
Ambühl, Simon
. Structural reliability considerations and optimizations impact operation and maintenance (O&M) costs as well as the initial investment costs. Furthermore, there is a control system for WEC applications which defines the harvested energy but also the loads onto the structure. Therefore, extreme loads but also...... WEPTOS. Calibration of safety factors are performed for welded structures at theWavestar device including different control systems for harvesting energy from waves. In addition, a case study of different O&M strategies for WECs is discussed, and an example of reliability-based structural optimization......There are many different working principles for wave energy converters (WECs) which are used to produce electricity from waves. In order for WECs to become successful and more competitive to other renewable electricity sources, the consideration of the structural reliability of WECs is essential...
Yuen, Mantak; Lau, Patrick S Y; Shek, Daniel T L; Lam, Man-Ping
2002-12-01
In 1995 Chan and Hui examined the responses of a sample of Chinese teachers on the Maslach Burnout Inventory and recommended a possible 2-factor rather than the original 3-factor model for the assessment of burnout among Chinese teachers. In the present study, the factor structure of responses to the Chinese version of the Maslach Burnout Inventory in a sample of 1,398 Chinese secondary school guidance teachers was examined using the EQS approach to confirmatory factor analysis. The results showed that a 3-factor model (Emotional Exhaustion, Depersonalization, and Personal Accomplishment) provided the best fit, with the first two factors highly correlated (r = .80). Internal consistencies for the subscales ranged from .80 to .88.
Reliability and Efficiency Factors in Decision Making for Rehabilitation of Pipelines
Directory of Open Access Journals (Sweden)
Alonso-Guzmán Carlos Daniel
2013-10-01
Full Text Available The methodology that has been developed suggests a sequence of interventions in the water distribution network, identifying the hierarchy of groups of pipes that must be renewed, taking into consideration all the factors associated, both endogenous and exogenous, and the technical limitations in the functioning of the water network considering the annual budget available for the rehabilitation of pipelines. The aim of this work is to develop a model to facilitate the decision-making to the managers of water distribution systems, considering a budget constraint, the amount of linear meters of each group of pipes that provides a maximum benefit in relation to the valuation of influence factors, the benefits and the cost of the rehabilitation. To ac- complish this, we use the genetic algorithms tool through Evolver and fuzzy logic, using EPANET to determine the cost of "saving" electricity and the recovered leak- age flow. This model is applied to a case study in the city of Celaya, Guanajuato, Mexico.
Structural Factors Affecting Health Examination Behavioral Intention
National Research Council Canada - National Science Library
Huang, Hui-Ting; Kuo, Yu-Ming; Wang, Shiang-Ru; Wang, Chia-Fen; Tsai, Chung-Hung
2016-01-01
.... Here, we used the health belief model as a foundation and integrated social psychological factors and investigated the factors influencing health examination behavioral intention among the public in Taiwan...
Human factors perspective on the reliability of NDT in nuclear applications
Energy Technology Data Exchange (ETDEWEB)
Bertovic, Marija; Mueller, Christina [Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin (Germany); Fahlbruch, Babette [TUEV NORD SysTec GmbH und Co. KG, Berlin (Germany)
2013-04-01
A series of research studies have been conducted over the course of five years venturing into the fields of in-service inspections (ISI) in nuclear power plants (NPPs) and inspection of manufactured components to be used for permanent nuclear waste disposal. This paper will provide an overview of four research studies, present selected experimental results and suggest ways for optimization of the NDT process, procedures, and training. The experimental results have shown that time pressure and mental workload negatively influence the quality of the manual inspection performance. Noticeable were influences of the organization of the working schedule, communication, procedures, supervision, and demonstration task. Customized Failure Mode and Effects Analysis (FMEA) was used to identify potential human risks, arising during acquisition and evaluation of NDT data. Several preventive measures were suggested and furthermore discussed, with respect to problems that could arise from their application. Experimental results show that implementing human redundancy in critical tasks, such as defect identification, as well as using an automated aid (software) to help operators in decision making about the existence and size of defects, could lead to other kinds of problems, namely social loafing and automation bias that might affect the reliability of NDT in an undesired manner. Shifting focus from the operator, as the main source of errors, to the organization, as the underlying source, is a recommended approach to ensure safety. (orig.) [German] Der Artikel beschreibt eine arbeitspsychologische Analyse des Einflusses der menschlichen Faktoren auf die Zuverlaessigkeit zerstoerungsfreier Pruefungen (ZfP). Im Zeitraum von 5 Jahren wurde eine Serie von Untersuchungen zur wiederkehrenden Pruefung in Kernkraftwerken sowie zur Pruefung von Komponenten fuer die Endlagerung von radioaktivem Abfall durchgefuehrt. Dieser Beitrag gibt einen Ueberblick ueber vier Studien, diskutiert
关于结构非概率可靠性模型的安全评估%SAFETY EVALUATION OF NON-PROBABILISTIC RELIABILITY MODEL OF STRUCTURES
Institute of Scientific and Technical Information of China (English)
樊建平; 李世军; 漆伟; 陈旭勇
2012-01-01
With the consideration of interval variables in non-probabilistic reliability model,three kinds of parameters, including reliability index, safety factor and set-theoretic reliability measurement, were a-dopted to represent the reliability and safety measurement of the structures. The physical means of the three kinds of parameters were described through geometric representation and the value range and practi cal region were suggested. Furthermore,the differentiation among three kinds of parameters was investigated in design concept, measurement and representation formation, so that the function relationship among them was then built up. The present results extend the non-probabilistic theory for structure design. The optimal scheme has been demonstrated through examples and results were discussed.%考虑区间变量非概率可靠性模型,采用非概率可靠性指标、安全系数和集合可靠度三类确定性参数描述结构的可靠性和安全程度.通过儿何描述,明确地给出了三类参数的物理意义,指出了各自的取值范围和实用区间.从设计思想、度量方法及表现形式方面分析了三类度量的区别,并建立了它们之间的函数关系.研究结果拓展了结构非概率设计理论,并通过具体优化算例对三类度量所得到的结果进行了讨论.
Reliability based topology optimization for continuum structures with local failure constraints
DEFF Research Database (Denmark)
Luo, Yangjun; Zhou, Mingdong; Wang, Michael Yu
2014-01-01
-related) target performance constraints. In order to overcome the stress singularity phenomenon caused by the combined stress and reliability constraints, a reduction strategy on target reliability index is proposed and utilized together with the ε-relaxation approach. Meanwhile, an enhanced aggregation method......This paper presents an effective method for stress constrained topology optimization problems under load and material uncertainties. Based on the Performance Measure Approach (PMA), the optimization problem is formulated as to minimize the objective function under a large number of (stress...... is employed to aggregate the selected active constraints using a general K–S function, which avoids expensive computational cost from the large-scale nature of local failure constraints. Several numerical examples are given to demonstrate the validity of the present method....
Directory of Open Access Journals (Sweden)
Leszek CHYBOWSKI
2012-04-01
Full Text Available In the paper the concept of a system structure with particular emphasis on the reliability structure has been presented. Advantages and disadvantages of modeling the reliability structure of a system using reliability block diagrams (RBD have been shown. RBD models of a marine steam‐water system constructed according to the concept of ‘multi‐component’, ‘one component’ and mixed models have been discussed. Critical remarks on the practical application of models which recognize only the structural surplus have been dealt with. The significant value of the model by professors Smalko and Jaźwiński called by them ‘default reliability structure’ has been pointed out. The necessity of building a new type of models: quality‐quantity, useful in the methodology developed by the author's multi-criteria analysis of importance of elements in the reliability structure of complex technical systems.
Testing the factor structure of the beliefs about language learning inventory.
Hsiao, Tsung-Yuan; Chiang, Steve
2010-12-01
This preliminary study examined the factor structure of the Beliefs About Language Learning Inventory in two samples of about 750 college students of English as a foreign language in Taiwan. Results of confirmatory factor analysis lend partial support to Horwitz's theoretical five-factor belief model. Subsequent exploratory and confirmatory factor analyses of data show that a four-factor model represented by only 12 items performed better than other models both theoretically and empirically. This model consists of two dimensions already theorized in the inventory: Difficulty of Language Learning and Foreign Language Aptitude, and two newly interpreted dimensions, Importance of Spoken Language and Analytical Approaches to Language Learning. Although this four-factor model could be replicated in an independent sample, the factors are not reliable, suggesting the need to search for a more representative set of beliefs to tap specific aspects of language learning.
Directory of Open Access Journals (Sweden)
Nasrin Jalilian
2012-11-01
Full Text Available Introduction: Objective structured clinical examination (OSCE is used for the evaluation of the clinical competence in medicine for which it is essential to measure validity and reliability. This study aimed to investigate the validity and reliability of OSCE for residents of obstetrics and gynecology at Kermanshah University of Medical Sciences in 2011.Methods: A descriptive-correlation study was designed and the data of OSCE for obstetrics and gynecology were collected via learning behavior checklists in method stations and multiple choice questions in question stations. The data were analyzed through Pearson correlation coefficient and Cronbach's alpha, using SPSS software (version 16. To determine the criterion validity, correlation of OSCE scores with scores of resident promotion test, direct observation of procedural skills, and theoretical knowledge was determined; for reliability, however, Cronbach's alpha was used. Total sample consisted of 25 participants taking part in 14 stations. P value of less than 0.05 was considered as significant.Results: The mean OSCE scores was 22.66 (±6.85. Criterion validity of the stations with resident promotion theoretical test, first theoretical knowledge test, second theoretical knowledge, and direct observation of procedural skills (DOPS was 0.97, 0.74, 0.49, and 0.79, respectively. In question stations, criterion validity was 0.15, and total validity of OSCE was 0.77.Conclusion: Findings of the present study indicated acceptable validity and reliability of OSCE for residents of obstetrics and gynecology.
Rose, Kevin A; Babajanian, Jesika
2016-10-01
The objective structured practical examination (OSPE) is a case-based assessment that can be used to assess the clinical reasoning ability of students. The reliability of using an OSPE for this purpose has not been reported in the literature. The objective of this study was to determine the interrater reliability of the OSPE in measuring the clinical reasoning ability of chiropractic students. Two examiners tested each student simultaneously when enough were available as a check for interrater reliability. The scores for students over 4 exam administrations were compiled, and we calculated an intraclass correlation coefficient (ICC) using 1-way random single measures. Paired scores were available for 133 students. The ICC was .685, showing a fair-to-good level of agreement for faculty in assessing the clinical reasoning ability of chiropractic students using an OSPE. The OSPE can be a valuable tool for testing clinical reasoning abilities because it can simulate the decision-making process that needs to be implemented in clinical practice. Faculty members at our chiropractic college were able to achieve an acceptable level of reliability in measuring the clinical reasoning abilities of students using an OSPE. Other health professional programs may consider using this tool for assessing the clinical reasoning skills of their students.
The Disgust Scale: Item Analysis, Factor Structure, and Suggestions for Refinement
Olatunji, Bunmi O.; Williams, Nathan L.; Tolin, David F.; Abramowitz, Jonathan S.; Sawchuk, Craig N.; Lohr, Jeffrey M.; Elwood, Lisa S.
2007-01-01
In the 4 studies presented (N = 1,939), a converging set of analyses was conducted to evaluate the item adequacy, factor structure, reliability, and validity of the Disgust Scale (DS; J. Haidt, C. McCauley, & P. Rozin, 1994). The results suggest that 7 items (i.e., Items 2, 7, 8, 21, 23, 24, and 25) should be considered for removal from the DS.…
Safety factors for structural design-history and developments
Straalen, IJ.J. van
2000-01-01
The design of structures is concemed with the generation of solutions and the verification of the reliability. potential design solutions are a result of a process of problem formulation, definition of objeciive functions, conceptual design and optimization. To control this process, many strategies
Energy Technology Data Exchange (ETDEWEB)
Huang, Shichun [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Geng, Rongli [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
2015-09-01
Reliable acceleration of low- to medium-beta proton or heavy ion species is needed for future high-current superconducting radio frequency (SRF) accelerators. Due to the high-Q nature of an SRF resonator, it is sensitive to many factors such as electron loading (from either the accelerated beam or from parasitic field emitted electrons), mechanical vibration, and liquid helium bath pressure fluctuation etc. To increase the stability against those factors, a mechanically strong and stable RF structure is desirable. Guided by this consideration, multi-fold symmetry element-loaded SRF structures (MFSEL), cylindrical tanks with multiple (n>=3) rod-shaped radial elements, are being explored. The top goal of its optimization is to improve mechanical stability. A natural consequence of this structure is a lowered ratio of the peak surface electromagnetic field to the acceleration gradient as compared to the traditional spoke cavity. A disadvantage of this new structure is an increased size for a fixed resonant frequency and optimal beta. This paper describes the optimization of the electro-magnetic (EM) design and preliminary mechanical analysis for such structures.
Paueksakon, Paisit; Fogo, Agnes B; Sethi, Sanjeev
2014-07-01
We investigated the role of leukocyte chemotactic factor (LECT2) immunohistochemical staining in the diagnosis of type of renal amyloidosis. Fifty renal amyloidosis cases with available paraffin blocks in our 2002 to 2012 renal biopsy files were reviewed. Patients were designated as a defined amyloid, including amyloid light chain (AL) and amyloid-associated amyloid (AA), or a non-AL/non-AA amyloid group. LECT2-specific antibody immunohistochemistry was performed in all 50 cases. Laser microdissection and mass spectrometry (LMD/MS) were performed in 10 cases. Forty-five patients had amyloid classified as either AL (44) or AA (1), and 5 had undetermined amyloid. Three of the five non-AL/non-AA group patient biopsies showed positive LECT2 immunohistochemical staining, and of these, LECT2 was also identified by LMD/MS in 1 patient, fibrinogen-α was identified in 1 patient, and apolipoprotein IV was identified in 1 patient. Two of these non-AL/non-AA patients showed negative LECT2 staining, and LMD/MS showed apolipoprotein IV as a major protein component. Five of the 44 AL amyloid patients showed weakly positive LECT2 staining. However, LECT2 was not identified by LMD/MS in any of these 5 cases. The single patient with AA amyloid was negative for LECT2 by immunohistochemical staining. Among 5 non-AL and non-AA amyloidosis patients in our study, 1 had LECT2, 1 had fibrinogen-α, and 3 had apolipoprotein IV as a major protein component. The data from this study show that weak LECT2 staining should be regarded as indeterminate or a negative result and does not per se allow diagnosis of specific amyloid type. The diagnosis of LECT2 renal amyloidosis may require LMD/MS confirmation.
Reliability in Single, Double and N2R Ring Network Structures
DEFF Research Database (Denmark)
Jørgensen, T.; Pedersen, L.; Pedersen, Jens Myrup
This paper studies the properties of single, double and N2R ring network structures during link errors. The structure of the network infrastructure must be redesigned in order to fulfil the requirements of services using the Internet in the future; hence, N2R structures have been suggested. N2R...
Reliability in single, double and N2R ring network structures
DEFF Research Database (Denmark)
Jørgensen, T.; Pedersen, L.; Pedersen, Jens Myrup
2005-01-01
This paper studies the properties of single, double and N2R ring network structures during link errors. The structure of the network infrastructure must be redesigned in order to fulfil the requirements of services using the Internet in the future; hence, N2R structures have been suggested. N2R...
基于环结构的可靠检测机制%Reliable detection mechanism based on ring structure
Institute of Scientific and Technical Information of China (English)
李俊锋; 杨英杰; 张国强
2013-01-01
为了解决层次式失效检测方法中检测点单点失效问题,为系统提供一种可靠检测点,提出基于环结构的可靠检测机制(BR_RD).该机制采用环检测算法迅速发现可疑失效节点,利用随机半元确认算法定位出环内的失效节点,通过选举算法产生新的可靠节点来替代失效节点以保持环结构完整性.其有效性和可靠性在失效注入实验中得到验证.%To solve the single failure point in hierarchical failure detection model and supply a reliable detecting point for the detection system, reliable detection mechanism based on ring structure (BR_ RD) is presented, which consists of multiple points. The loop detection algorithm is to find suspect failure points, then random semi-confirmation algorithm is to locate the failure points in the ring, and election algorithm is to maintenance the integrity of the ring structure by updating the failed points. Its validity and reliability is verified by failure injection experiments.
Reliability Analysis on Structural Integrity of Propel l ant Grains%药柱结构完整性的可靠性分析
Institute of Scientific and Technical Information of China (English)
王铮
2001-01-01
在药柱结构应力分析和推进剂伸长主曲线处理的基础上，讨论药柱结构完整性、可靠性的计算方法.并对计算结果与传统的安全系数方法进行比较，二者的趋势是一样的。%Based on the structural stress (stain) analysis of grains and the treatment of the master elongation curve of propellant, the reliability analysis methods of the structural integrity of solid propellant grains are discussed. In comparison of the calculated results with those given by the traditional methods of safety factor,the tendencies are identical
Factor Structure of the Exercise Self-Efficacy Scale
Cornick, Jessica E.
2015-01-01
The current study utilized exercise self-efficacy ratings from undergraduate students to assess the factor structure of the Self-Efficacy to Regulate Exercise Scale (Bandura, 1997, 2006). An exploratory factor analysis (n = 759) indicated a two-factor model solution and three separate confirmatory factor analyses (n = 1,798) supported this…
McFadyen, A K; Maclaren, W M; Webster, V S
2007-08-01
The original 4 sub-scale version of the Interdisciplinary Education Perception Scale (IEPS) was published by Luecht et al. (1990, Journal of Allied Health, 181 - 191). There appears however to be a lack of evidence of the stability of the original instrument and of the test-retest reliability of the items and sub-scales when used with undergraduates. Given that during its development only 143 subjects completed the questionnaire which contained 18 items the generalizability of the instrument should perhaps have been investigated further. The Interprofessional Learning Group (IPL) at Glasgow Caledonian University has been using both the IEPS and the Readiness for Interprofessional Learning Scale (RIPLS) (Parsell & Bligh, 1999, Medical Education, 33, 95 - 100) to monitor changes in attitudes and perceptions of undergraduate students from eight different health and social care programmes. This paper reports the development of an alternative sub-scale model for the IEPS based on a sample of 308 students. Various aspects of the reliability of this revised model based on a subsequent data set of 247 students are also reported. This revised model appears to be stable for use with undergraduate students yielding Cronbach Alpha values for two of the sub-scales greater than 0.80 and test-retest weighted kappa values for items being fair to moderate.
Structural Testing of the Blade Reliability Collaborative Effect of Defect Wind Turbine Blades
Energy Technology Data Exchange (ETDEWEB)
Desmond, M. [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Hughes, S. [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Paquette, J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2015-06-08
Two 8.3-meter (m) wind turbine blades intentionally constructed with manufacturing flaws were tested to failure at the National Wind Technology Center (NWTC) at the National Renewable Energy Laboratory (NREL) south of Boulder, Colorado. Two blades were tested; one blade was manufactured with a fiberglass spar cap and the second blade was manufactured with a carbon fiber spar cap. Test loading primarily consisted of flap fatigue loading of the blades, with one quasi-static ultimate load case applied to the carbon fiber spar cap blade. Results of the test program were intended to provide the full-scale test data needed for validation of model and coupon test results of the effect of defects in wind turbine blade composite materials. Testing was part of the Blade Reliability Collaborative (BRC) led by Sandia National Laboratories (SNL). The BRC seeks to develop a deeper understanding of the causes of unexpected blade failures (Paquette 2012), and to develop methods to enable blades to survive to their expected operational lifetime. Recent work in the BRC includes examining and characterizing flaws and defects known to exist in wind turbine blades from manufacturing processes (Riddle et al. 2011). Recent results from reliability databases show that wind turbine rotor blades continue to be a leading contributor to turbine downtime (Paquette 2012).
A reliability analysis of the revised competitiveness index.
Harris, Paul B; Houston, John M
2010-06-01
This study examined the reliability of the Revised Competitiveness Index by investigating the test-retest reliability, interitem reliability, and factor structure of the measure based on a sample of 280 undergraduates (200 women, 80 men) ranging in age from 18 to 28 years (M = 20.1, SD = 2.1). The findings indicate that the Revised Competitiveness Index has high test-retest reliability, high inter-item reliability, and a stable factor structure. The results support the assertion that the Revised Competitiveness Index assesses competitiveness as a stable trait rather than a dynamic state.
Directory of Open Access Journals (Sweden)
Tomislav Car
1989-12-01
Full Text Available Statistical approach is one of methods offering us some quantitative indications of structure security and basic techno-economics criterion of their applications. The basis of that approach is determination of the probability of error occurrence in different interactive relationship between natural forces and structure properties. Results of that analyse are the basis for quantitative definition of the techno-economics optimum for structure and system application (the paper is published in Croatian.
Examining the factor structure of the Multiple Sclerosis Impact Scale.
Fitzgerald, Shawn M; Li, Jian; Rumrill, Phillip D; Merchant, William; Bishop, Malachy
2014-01-01
The purpose of this study was to investigate the factor structure of the Multiple Sclerosis Impact Scale (MSIS-29) to assess its suitability for modeling the impact of MS on a nation-wide sample of individuals from the United States. Investigators completed a Confirmatory Factor Analysis (CFA) to examine the two-factor structure proposed by Hobart et al. [17]. Although the original MSIS-29 factor structure did not fit the data exactly, the hypothesized two-factor model was partially supported in the current data. Implications for future instrument development and rehabilitation practice are discussed.
Highly Reliable Structural Health Monitoring of Smart Composite Vanes for Jet Engine Project
National Aeronautics and Space Administration — Intelligent Fiber Optic Systems and Auburn University propose a Fiber Bragg Grating (FBG) integrated Structural Health Monitoring (SHM) sensor system capable of...
Highly Reliable Structural Health Monitoring of Smart Composite Vanes for Jet Engine Project
National Aeronautics and Space Administration — In Phase 1, Intelligent Fiber Optic Systems (IFOS) successfully demonstrated a Fiber Bragg Grating (FBG) based integrated Structural Health Monitoring (SHM) sensor...
Human Reliability Program Overview
Energy Technology Data Exchange (ETDEWEB)
Bodin, Michael
2012-09-25
This presentation covers the high points of the Human Reliability Program, including certification/decertification, critical positions, due process, organizational structure, program components, personnel security, an overview of the US DOE reliability program, retirees and academia, and security program integration.
On the reliability, validity, and cognitive structure of the Thurstone Word Fluency Test.
Cohen, M J; Stanczak, D E
2000-04-01
The Thurstone Word Fluency Test (TWFT) is a widely used neuropsychological instrument. However, data regarding its psychometric properties are lacking. The results of the present study suggest that the TWFT possesses excellent test-retest and inter-rater reliability, in addition to good construct validity. However, its criterion validity is limited by its lack of specificity and sensitivity. The present study also suggests that the TWFT is a complex cognitive task, and that successful TWFT performance depends upon a constellation of cognitive abilities, including attention/concentration, psychomotor speed, and memory. Finally, the relationship between verbal IQ and TWFT letter association value was examined. While the TWFT appears to be useful in detecting the presence of cerebral dysfunction, it is of less value in localizing such dysfunction. It is argued that the TWFT should not be used as a neuropsychological screening instrument, but rather, is best used within the context of a thorough neuropsychological examination.
Mooring System Diagnosis and Structural Reliability Control for Position Moored Vessels
DEFF Research Database (Denmark)
Fang, Shaoji; Blanke, Mogens; Leira, Bernt J.
2015-01-01
Early diagnosis and fault-tolerant control are essential for safe operation of oating platforms where mooring systems maintain vessel position and must withstand environmental loads. This paper considers two critical faults, line breakage and loss of a buoyancy element and employs vector statisti......Early diagnosis and fault-tolerant control are essential for safe operation of oating platforms where mooring systems maintain vessel position and must withstand environmental loads. This paper considers two critical faults, line breakage and loss of a buoyancy element and employs vector...... for monitoring the safety level of each mooring line and, a set-point chasing algorithm accommodates the eects of line failure, as an integral part of the reliability- based set-point chasing control algorithm. The feasibility of the diagnosis and of the fault-tolerant control strategy is veried in model basin...
Directory of Open Access Journals (Sweden)
Maria Valeria Piras
2015-01-01
Full Text Available Fuzzy logic applied to the visual inspection of existing buildings has been proposed in relation to simple structures. Isostatic structures are characterized by a unique and known collapse mechanism, which does not vary with geometry or load change. In this paper we apply fuzzy logic to visual inspection for complex structures such as hyperstatic ones in which the collapse mechanism depends not only on the geometry but also on the size and disposition of loads. The goal of this paper is to give relevant weight, in the fuzzy analysis, not only to the single expression of degradation, due to its localization within the element, but also to the structural element itself by assigning a different resistance to the various elements. The underlying aim of the proposed method is to manage, evaluate, and process all the information coming from visual inspections in order to realize a management information system for the evaluation of the safety level of even complex structures.
Smith, Martin M; Saklofske, Donald H
2016-08-05
Evidence suggests perfectionism is a multidimensional construct composed of 2 higher order factors: perfectionistic strivings and perfectionistic concerns. However, the substantial overlap between perfectionistic strivings and perfectionistic concerns is problematic, as are the unanswered questions regarding the structure of perfectionism following removal of common variance. This research addressed this through bifactor modeling. Three student samples (N = 742) completed Hewitt and Flett's ( 1991 ) Multidimensional Perfectionism Scale, Frost, Marten, Lahart, and Rosenblate's ( 1990 ) Multidimensional Perfectionism Scale, and Slaney, Rice, Mobley, Trippi, and Ashby's ( 2001 ) Almost Perfect Scale-Revised. Greater support was consistently found for the bifactor model, relative to the 2-factor model. Results suggest the bifactor model best represents the structure of perfectionism and provide preliminary support for the use of a general factor score. Researchers are cautioned that removal of general variance may render the reliability of specific factors (i.e., perfectionistic strivings and perfectionistic concerns) suspect.
Factor structure underlying components of allostatic load.
Directory of Open Access Journals (Sweden)
Jeanne M McCaffery
Full Text Available Allostatic load is a commonly used metric of health risk based on the hypothesis that recurrent exposure to environmental demands (e.g., stress engenders a progressive dysregulation of multiple physiological systems. Prominent indicators of response to environmental challenges, such as stress-related hormones, sympatho-vagal balance, or inflammatory cytokines, comprise primary allostatic mediators. Secondary mediators reflect ensuing biological alterations that accumulate over time and confer risk for clinical disease but overlap substantially with a second metric of health risk, the metabolic syndrome. Whether allostatic load mediators covary and thus warrant treatment as a unitary construct remains to be established and, in particular, the relation of allostatic load parameters to the metabolic syndrome requires elucidation. Here, we employ confirmatory factor analysis to test: 1 whether a single common factor underlies variation in physiological systems associated with allostatic load; and 2 whether allostatic load parameters continue to load on a single common factor if a second factor representing the metabolic syndrome is also modeled. Participants were 645 adults from Allegheny County, PA (30-54 years old, 82% non-Hispanic white, 52% female who were free of confounding medications. Model fitting supported a single, second-order factor underlying variance in the allostatic load components available in this study (metabolic, inflammatory and vagal measures. Further, this common factor reflecting covariation among allostatic load components persisted when a latent factor representing metabolic syndrome facets was conjointly modeled. Overall, this study provides novel evidence that the modeled allostatic load components do share common variance as hypothesized. Moreover, the common variance suggests the existence of statistical coherence above and beyond that attributable to the metabolic syndrome.
A Confirmatory Factor Analysis of the Structure of Abbreviated Math Anxiety Scale
Directory of Open Access Journals (Sweden)
Farahman Farrokhi
2011-06-01
Full Text Available "nObjective: The aim of this study is to explore the confirmatory factor analysis results of the Persian adaptation of Abbreviated Math Anxiety Scale (AMAS, proposed by Hopko, Mahadevan, Bare & Hunt. "nMethod: The validity and reliability assessments of the scale were performed on 298 college students chosen randomly from Tabriz University in Iran. The confirmatory factor analysis (CFA was carried out to determine the factor structures of the Persian version of AMAS. "nResults: As expected, the two-factor solution provided a better fit to the data than a single factor. Moreover, multi-group analyses showed that this two-factor structure was invariant across sex. Hence, AMAS provides an equally valid measure for use among college students. "nConclusions: Brief AMAS demonstrates adequate reliability and validity. The AMAS scores can be used to compare symptoms of math anxiety between male and female students. The study both expands and adds support to the existing body of math anxiety literature.
Reliability and factorial structure of an Arabic translation of the Self-Consciousness Scale.
Bendania, A; Abed, A S
1997-12-01
An Arabic translation of Fenigstein, Scheier, and Buss's 1975 Self-consciousness scale was administered to 254 United Arab Emirates University undergraduate students, 99 men and 155 women with a mean age of 24 years. A factor analysis of the intercorrelations indicated the same general factors as in the original and other replicating studies. This study, however, differed from them in item loadings and distribution of items within the three factors of the scale. Other factor solutions were also tried and reported. Differences between men and women were also noted. In contrast with previous studies, the Arabic version showed differences in the magnitude of correlations among subscales. These differences were discussed in the light of cross-cultural and Arabic studies showing the influence of culture.
Directory of Open Access Journals (Sweden)
Sara Mortaz Hejri
2013-01-01
Full Text Available Background: One of the methods used for standard setting is the borderline regression method (BRM. This study aims to assess the reliability of BRM when the pass-fail standard in an objective structured clinical examination (OSCE was calculated by averaging the BRM standards obtained for each station separately. Materials and Methods: In nine stations of the OSCE with direct observation the examiners gave each student a checklist score and a global score. Using a linear regression model for each station, we calculated the checklist score cut-off on the regression equation for the global scale cut-off set at 2. The OSCE pass-fail standard was defined as the average of all station′s standard. To determine the reliability, the root mean square error (RMSE was calculated. The R2 coefficient and the inter-grade discrimination were calculated to assess the quality of OSCE. Results: The mean total test score was 60.78. The OSCE pass-fail standard and its RMSE were 47.37 and 0.55, respectively. The R2 coefficients ranged from 0.44 to 0.79. The inter-grade discrimination score varied greatly among stations. Conclusion: The RMSE of the standard was very small indicating that BRM is a reliable method of setting standard for OSCE, which has the advantage of providing data for quality assurance.
Directory of Open Access Journals (Sweden)
Conversano Ciro
2008-01-01
Full Text Available Abstract Background DSM-IV identifies three stress response disorders (acute stress Disorder (ASD, post-traumatic stress Disorder (PTSD and adjustment disorders (AD that derive from specific life events. An additional condition of complicated grief (CG, well described in the literature, is triggered by bereavement. This paper reports on the reliability and validity of the Structured Clinical Interview for Trauma and Loss Spectrum (SCI-TALS developed to assess the spectrum of stress response. The instrument is based on a spectrum model that emphasizes soft signs, low-grade symptoms, subthreshold syndromes, as well as temperamental and personality traits comprising clinical and subsyndromal manifestations. Methods Study participants, enrolled at 6 Italian Departments of Psychiatry located at six sites, included consecutive patients with PTSD, 44 with CG and a comparative group of 48 unselected controls. Results We showed good reliability and validity of the SCI-TALS. Domain scores were significantly higher in participants with PTSD or CG compared to controls. There were high correlations between specific SCI-TALS domains and corresponding scores on established measures of similar constructs. Participants endorsing grief and loss events reported similar scores on all instruments, except those with CG who scored significantly higher on the domain of grief reactions. Conclusion These findings provide strong support for the internal consistency, the discriminant validity and the reliability of the SCI-TALS. These results also support the existence of a specific grief-related condition and the proposal that different forms of stress response have similar manifestations.
Institute of Scientific and Technical Information of China (English)
ZHANG; Yimin; (张义民); WANG; Shun; (王; 顺); LIU; Qiaoling; (刘巧伶); WEN; Bangchun; (闻邦椿)
2003-01-01
Based on the generalized probabilistic finite element method, this paper presents an approximate solution technique for general multi-degree-of-freedom nonlinear random vibration systems with random parameters. The fourth-moment technique, maximum entropy theory and incomplete probability information theory are employed to systematically develop a reliability analysis method for dynamic random structural systems with correlation failure modes under unavailable joint probability density functions of basic random variables. The first passage problem of multi-degree-of-freedom nonlinear random vibration systems is solved.
Factor structure of the Spanish version of the Object-Spatial Imagery and Verbal Questionnaire.
Campos, Alfredo; Pérez-Fabello, María José
2011-04-01
The reliability and factor structure of the Spanish version of the Object-Spatial Imagery and Verbal Questionnaire (OSIVQ) were assessed in a sample of 213 Spanish university graduates. The questionnaire measures three types of processing preferences (verbal, object imagery, and spatial imagery). Principal components analysis with varimax rotation identified three factors, corresponding to the three scales proposed in the original version, explaining 33.1% of the overall variance. Cronbach's alphas were .72, .77, and .81 for the verbal, object imagery, and spatial imagery scales, respectively.
NAC transcription factors: structurally distinct, functionally diverse
DEFF Research Database (Denmark)
Olsen, Addie Nina; Ernst, Heidi A; Leggio, Leila Lo;
2005-01-01
NAC proteins constitute one of the largest families of plant-specific transcription factors, and the family is present in a wide range of land plants. Here, we summarize the biological and molecular functions of the NAC family, paying particular attention to the intricate regulation of NAC protei...
A Study of Quasicrystal Structure Factors by Using Quantitative CBED
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
The procedure of simulating convergent beam electron diffraction (CBED) pattern of quasicrystals by dynamical theory is described. The simulated patterns are generally coincide with the experimental patterns. The variations of intensity distribution in CBED pattern with the amplitude and phase of the structure factor of quasicrystai are caiculated with dynamical theory. The sensitivity of intensity distribution to the structure factor is investigated.
Structural Genomics of Bacterial Virulence Factors
2006-05-01
structure of pXO1-118 shown in its 2fo-fc electron density map. Arginine 74 and the two visible conformations of Phenylalanine 19 are shown. B...the methane monooxygenase hydroxylase from Methylococcus capsulatus (Bath): implications for substrate gating and component interac- tions. Proteins
Aloba, Olutayo; Olabisi, Oluseyi; Aloba, Tolulope
2016-01-01
The 10-item Connor-Davidson Resilience Scale (CD-RISC) has demonstrated satisfactory psychometric properties as a measure of resilience in all the previous studies conducted in developed countries. The objective of this study was to explore the psychometric characteristics of the 10-item CD-RISC among students nurses in southwestern Nigeria. This descriptive cross-sectional study involved a total of 449 student nurses who completed the 10-item CD-RISC in addition to measures of self-esteem, depression, religiosity, and psychological distress. The scale demonstrated adequate reliability (Cronbach's α = .81) and satisfactory validity with significant correlations with the measures of self-esteem, depression, religiosity, and psychological distress. Factor analyses revealed that resilience was best explained by a two-factor construct. The scale is a valid measure of resilience among Nigerian student nurses. © The Author(s) 2016.
Factor Structure of Attention Capacities Measured With Eye-Tracking Tasks in 18-Month-Old Toddlers.
de Jong, M.; Verhoeven, Marjolein; Hooge, I.T.C.; van Baar, A.L.
2016-01-01
Objective: Attention capacities are critical for adaptive functioning and development. Reliable assessment measures are needed for the study of attention capacities in early childhood. In the current study, we investigated the factor structure of the Utrecht Tasks of Attention in Toddlers Using
Factor Structure of Attention Capacities Measured With Eye-Tracking Tasks in 18-Month-Old Toddlers.
de Jong, M.; Verhoeven, Marjolein; Hooge, I.T.C.; van Baar, A.L.
2016-01-01
Objective: Attention capacities are critical for adaptive functioning and development. Reliable assessment measures are needed for the study of attention capacities in early childhood. In the current study, we investigated the factor structure of the Utrecht Tasks of Attention in Toddlers Using Eye-
System Reliability of Timber Trusses Based on Non-Linear Structural Modelling
DEFF Research Database (Denmark)
Hansson, Martin; Ellegaard, Peter
2006-01-01
Structural design is today concerned with single component performance where each limit state is related to a single mode of failure of a single component. Further, in limit state codes the strength variables are related to a deterministic value (usually the 5-percentile). However, in a structure...... spruce (Picea abies). Most studies found in the literature are based on linear-elastic theory and the variability within members is neglected mainly because of lack of data. The FE calculations are performed by TrussLab - a toolbox for MATLAB developed at Aalborg University. TrussLab considers contact...
Demographic Correlates and Factor Structure of the Family Environment Scale.
Boake, Corwin; Salmon, Paul G.
1983-01-01
Factor analyzed the Family Environment Scale (FES) subscale scores of 204 families and correlated them with family demographic characteristics. The obtained factor structure showed two major factors similar to "control" and "acceptance-rejection" dimensions in previous research. Results support the FES as part of multimethod…
Factor Structure of the TOEFL Internet-Based Test
Sawaki, Yasuyo; Stricker, Lawrence J.; Oranje, Andreas H.
2009-01-01
This construct validation study investigated the factor structure of the Test of English as a Foreign Language[TM] Internet-based test (TOEFL[R] iBT). An item-level confirmatory factor analysis was conducted for a test form completed by participants in a field study. A higher-order factor model was identified, with a higher-order general factor…
Reliability-Based Optimal Design of Experiment Plans for Offshore Structures
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Faber, M. H.; Kroon, I. B.
1993-01-01
Design of cost optimal experiment plans on the basis of a preposterior analysis is discussed. In particular the planning of on-site response measurements on offshore structures in order to update probabilistic models for fatigue life estimation is addressed. Special emphasis is given to modelling...
Reliable and More Powerful Methods for Power Analysis in Structural Equation Modeling
Yuan, Ke-Hai; Zhang, Zhiyong; Zhao, Yanyun
2017-01-01
The normal-distribution-based likelihood ratio statistic T[subscript ml] = nF[subscript ml] is widely used for power analysis in structural Equation modeling (SEM). In such an analysis, power and sample size are computed by assuming that T[subscript ml] follows a central chi-square distribution under H[subscript 0] and a noncentral chi-square…
Unascertained Factor Method of Dynamic Characteristic Analysis for Antenna Structures
Institute of Scientific and Technical Information of China (English)
ZHU Zeng-qing; LIANG Zhen-tao; CHEN Jian-jun
2008-01-01
The dynamic characteristic analysis model of antenna structures is built, in which the structural physical parameters and geometrical dimensions are all considered as unascertained variables, And a structure dynamic characteristic analysis method based on the unascertained factor method is given. The computational expression of structural characteristic is developed by the mathematics expression of unascertained factor and the principles of unascertained rational numbers arithmetic. An example is given, in which the possible values and confidence degrees of the unascertained structure characteristics are obtained. The calculated results show that the method is feasible and effective.
Optimization of Measurements on Dynamically Sensitive Structures Using a Reliability Approach
DEFF Research Database (Denmark)
Kirkegaard, Poul Henning; Sørensen, John Dalsgaard; Brincker, Rune
1990-01-01
Design of measuring program devoted to parameter identification of structural dynamic systems described by random fields is considered. The design problem is formulated as an optimization problem to minimize the total expected costs due to failure and costs of masuring program. Design variables...... are the numbers of measuring points, the locations of these points and the required number of sample records. An example with a simply supported plane, vibrating beam is considered and tentative results are presented....
Optimization of Measurements on Dynamically Sensitive Structures Using a Reliability Approach
DEFF Research Database (Denmark)
Kirkegaard, Poul Henning; Sørensen, John Dalsgaard; Brincker, Rune
Design of a measuring program devoted to parameter identification of structural dynamic systems described by random fields is considered. The design problem is formulated as an optimization problem to minimize the total expected costs due to failure and costs of a measuring program. Design...... variables are the numbers of measuring points, the locations of these points and the required number of sample records. An example with a simply supported plane, vibrating beam is considered and tentative results are presented....
1994-06-30
uniaxial yield strength of HY80 steels . The following is a description of a potential flow pattern of the database data retrieval program. i) The...Emphasis is placed on strength and toughness properties of marine steels and their welds. The format developed and reported in the SSC report 352 was...Parent M aterial ................................... 58 5.1.1 A Hierarchy for Pooling Tensile Data of Marine Structural Steels (Appendix B
Lee, Kangjoo; Lina, Jean-Marc; Gotman, Jean; Grova, Christophe
2016-07-01
Functional hubs are defined as the specific brain regions with dense connections to other regions in a functional brain network. Among them, connector hubs are of great interests, as they are assumed to promote global and hierarchical communications between functionally specialized networks. Damage to connector hubs may have a more crucial effect on the system than does damage to other hubs. Hubs in graph theory are often identified from a correlation matrix, and classified as connector hubs when the hubs are more connected to regions in other networks than within the networks to which they belong. However, the identification of hubs from functional data is more complex than that from structural data, notably because of the inherent problem of multicollinearity between temporal dynamics within a functional network. In this context, we developed and validated a method to reliably identify connectors and corresponding overlapping network structure from resting-state fMRI. This new method is actually handling the multicollinearity issue, since it does not rely on counting the number of connections from a thresholded correlation matrix. The novelty of the proposed method is that besides counting the number of networks involved in each voxel, it allows us to identify which networks are actually involved in each voxel, using a data-driven sparse general linear model in order to identify brain regions involved in more than one network. Moreover, we added a bootstrap resampling strategy to assess statistically the reproducibility of our results at the single subject level. The unified framework is called SPARK, i.e. SParsity-based Analysis of Reliable k-hubness, where k-hubness denotes the number of networks overlapping in each voxel. The accuracy and robustness of SPARK were evaluated using two dimensional box simulations and realistic simulations that examined detection of artificial hubs generated on real data. Then, test/retest reliability of the method was assessed
Long, Kim Chenming
Real-world engineering optimization problems often require the consideration of multiple conflicting and noncommensurate objectives, subject to nonconvex constraint regions in a high-dimensional decision space. Further challenges occur for combinatorial multiobjective problems in which the decision variables are not continuous. Traditional multiobjective optimization methods of operations research, such as weighting and epsilon constraint methods, are ill-suited to solving these complex, multiobjective problems. This has given rise to the application of a wide range of metaheuristic optimization algorithms, such as evolutionary, particle swarm, simulated annealing, and ant colony methods, to multiobjective optimization. Several multiobjective evolutionary algorithms have been developed, including the strength Pareto evolutionary algorithm (SPEA) and the non-dominated sorting genetic algorithm (NSGA), for determining the Pareto-optimal set of non-dominated solutions. Although numerous researchers have developed a wide range of multiobjective optimization algorithms, there is a continuing need to construct computationally efficient algorithms with an improved ability to converge to globally non-dominated solutions along the Pareto-optimal front for complex, large-scale, multiobjective engineering optimization problems. This is particularly important when the multiple objective functions and constraints of the real-world system cannot be expressed in explicit mathematical representations. This research presents a novel metaheuristic evolutionary algorithm for complex multiobjective optimization problems, which combines the metaheuristic tabu search algorithm with the evolutionary algorithm (TSEA), as embodied in genetic algorithms. TSEA is successfully applied to bicriteria (i.e., structural reliability and retrofit cost) optimization of the aircraft tail structure fatigue life, which increases its reliability by prolonging fatigue life. A comparison for this
Hojka, Vladimir; Stastny, Petr; Rehak, Tomas; Gołas, Artur; Mostowik, Aleksandra; Zawart, Marek; Musálek, Martin
2016-09-01
While tests of basic motor abilities such as speed, maximum strength or endurance are well recognized, testing of complex motor functions such as agility remains unresolved in current literature. Therefore, the aim of this review was to evaluate which main factor or factor structures quantitatively determine agility. In methodological detail, this review focused on research that explained or described the relationships between latent variables in a factorial model of agility using approaches such as principal component analysis, factor analysis and structural equation modeling. Four research studies met the defined inclusion criteria. No quantitative empirical research was found that tried to verify the quality of the whole suggested model of the main factors determining agility through the use of a structural equation modeling (SEM) approach or a confirmatory factor analysis. From the whole structure of agility, only change of direction speed (CODS) and some of its subtests were appropriately analyzed. The combination of common CODS tests is reliable and useful to estimate performance in sub-elite athletes; however, for elite athletes, CODS tests must be specific to the needs of a particular sport discipline. Sprinting and jumping tests are stronger factors for CODS than explosive strength and maximum strength tests. The authors suggest the need to verify the agility factorial model by a second generation data analysis technique such as SEM.
The validation of the Polish version of the Posttraumatic Diagnostic Scale and its factor structure
Directory of Open Access Journals (Sweden)
Wojciech Ł. Dragan
2012-08-01
Full Text Available Background: Posttraumatic Diagnostic Scale (PDS is a self-descriptive measure developed to provide information regarding posttraumatic stress disorder (PTSD diagnosis and symptom severity. Objectives: The aim of this article is to report on the validation of the Polish version of PDS and to test its factor structure with reference to two models: an original three-factor model (Reexperiencing, Avoidance, and Arousal and alternative five-factor model (Reexperiencing, Avoidance, Numbing, Dysphoric Arousal, and Anxious Arousal. Method: The validation procedure included three studies conducted on samples of separate populations: university-level students (n=507, individuals who had experienced various traumas (n=320, and treatment-seeking survivors of motor vehicle accidents (MVA (n=302. Various other measures of trauma-related psychopathology were administered to participants, as well as the PTSD module of the Structured Clinical Interview (SCID in the case of MVA patients. Results: PDS showed high internal consistency and test–retest reliability, good diagnostic agreement with SCID, good sensitivity but relatively low specificity. The satisfactory convergent validity was supported by a large number of significant correlations with other measures of trauma-related psychopathology. Confirmatory factor analysis (CFA generally confirmed both the three-factor structure and the alternative five-factor structure of the questionnaire. Conclusions: The results show generally good psychometric properties of the Polish version of PDS.
Chiu, Weisheng; Rodriguez, Fernando M; Won, Doyeon
2016-10-01
This study examines the factor structure of the shortened version of the Leadership Scale for Sport, through a survey of 201 collegiate swimmers at National Collegiate Athletic Association Division II and III institutions, using both exploratory structural equation modeling and confirmatory factor analysis. Both exploratory structural equation modeling and confirmatory factor analysis showed that a five-factor solution fit the data adequately. The sizes of factor loadings on target factors substantially differed between the confirmatory factor analysis and exploratory structural equation modeling solutions. In addition, the inter-correlations between factors of the Leadership Scale for Sport and the correlations with athletes' satisfaction were found to be inflated in the confirmatory factor analysis solution. Overall, the findings provide evidence of the factorial validity of the shortened Leadership Scale for Sport.
Directory of Open Access Journals (Sweden)
Oppert Jean-Michel
2010-05-01
Full Text Available Abstract Background A questionnaire to assess physical activity related environmental factors in the European population (a 49-item and an 11-item version was created as part of the framework of the EU-funded project "Instruments for Assessing Levels of PHysical Activity and fitness (ALPHA". This paper reports on the development and assessment of the questionnaire's test-retest stability, predictive validity, and applicability to European adults. Methods The first pilot test was conducted in Belgium, France and the UK. In total 190 adults completed both forms of the ALPHA questionnaire twice with a one-week interval. Physical activity was concurrently measured (i by administration of the long version of the International Physical Activity Questionnaire (IPAQ by interview and (ii by accelerometry (Actigraph™ device. After adaptations, the second field test took place in Belgium, the UK and Austria; 166 adults completed the adapted questionnaire at two time points, with minimum one-week interval. In both field studies intraclass correlation coefficients (ICC and proportion of agreement were computed to assess the stability of the two test scores. Predictive validity was examined in the first field test by correlating the results of the questionnaires with physical activity data from accelerometry and long IPAQ-last 7 days. Results The reliability scores of the ALPHA questionnaire were moderate-to good in the first field testing (ICC range 0.66 - 0.86 and good in the second field testing (ICC range 0.71 - 0.87. The proportion of agreement for the ALPHA short increased significantly from the first (range 50 - 83% to the second field testing (range 85 - 95%. Environmental scales from both versions of the ALPHA questionnaire were significantly associated with self-reported minutes of transport-related walking, and objectively measured low intensity physical activity levels, particularly in women. Both versions were easily administered with an
Investigating the factor structure of the Questionnaire on Smoking Urges-Brief (QSU-Brief).
Toll, Benjamin A; Katulak, Nicole A; McKee, Sherry A
2006-07-01
This study was designed to investigate the proposed two-factor structure of the 10-item Questionnaire on Smoking Urges-Brief (QSU-Brief) and to provide evidence for the psychometric properties of this questionnaire using the seven-point scoring set from the original QSU study [Tiffany, S.T., Drobes, D.J. (1991). The development and initial validation of a questionnaire on smoking urges. British Journal of Addiction, 86, 1467-1476.]. The study sample (N=576) was comprised of smokers presenting for treatment. Although an initial exploratory factor analysis appeared to replicate the original factor analytic findings of Cox et al. [Cox, L.S., Tiffany, S.T., Christen, A.G. (2001). Evaluation of the brief questionnaire of smoking urges (QSU-Brief) in laboratory and clinical settings. Nicotine and Tobacco Research, 3, 7-16.], when subjected to confirmatory factor analyses, a five-item, two-factor model using the most robust items from the original QSU-Brief factor analysis was the best explanation of the data in the present study. Good internal consistency reliability estimates were also obtained with this model. These results suggest that this shortened form of the QSU-Brief can be used with the original seven-point scoring set as a reliable assessment of the dual nature of smoking urges in a treatment-seeking population.
Indian Academy of Sciences (India)
Sunil Dutta
2001-04-01
The importance of high fracture toughness and reliability in Si3N4, and SiC-based structural ceramics and ceramic matrix composites is reviewed. The potential of these ceramics and ceramic matrix composites for high temperature applications in defence and aerospace applications such as gas turbine engines, radomes, and other energy conversion hardware have been well recognized. Numerous investigations were pursued to improve fracture toughness and reliability by incorporating various reinforcements such as particulate-, whisker-, and continuous fibre into Si3N4 and SiC matrices. All toughening mechanisms, e.g. crack deflection, crack branching, crack bridging, etc essentially redistribute stresses at the crack tip and increase the energy needed to propagate a crack through the composite material, thereby resulting in improved fracture toughness and reliability. Because of flaw insensitivity, continuous fibre reinforced ceramic composite (CFCC) was found to have the highest potential for higher operating temperature and longer service conditions. However, the ceramic fibres should display sufficient high temperature strength and creep resistance at service temperatures above 1000°C. The greatest challenge to date is the development of high quality ceramic fibres with associate coatings able to maintain their high strength in oxidizing environment at high temperature. In the area of processing, critical issues are preparation of optimum matrix precursors, precursor infiltration into fibre array, and matrix densification at a temperature, where grain crystallization and fibre degradation do not occur. A broad scope of effort is required for improved processing and properties with a better understanding of all candidate composite systems.
Directory of Open Access Journals (Sweden)
Jiaobo Duan
Full Text Available The English version of the Caregiver Quality of Life Index-Cancer (CQOLC was translated into simplified Chinese (CQOLC-C, following cultural translation, back-translation and pretest steps. Three hundred and sixty one cancer caregivers participated in this study. Cronbach's alpha was used to assess CQOLC-C reliability. Exploratory factor analyses (EFA was used to generate two models of the measure's factor structure, and confirmatory factor analyses (CFA were used to test each model, such that the best model to explain the latent structure of the CQOLC-C was identified. EFA using different factor extraction methods yielded two models including four and eight factors. According to the CFA results, model 2 was better fit for the original study data, based on the RMSEA criterion [0.058(90% CI = 0.051-0.065], χ2 (531 = 853.92, p < 0.0001; CFI (0.96, NNFI (0.96, IFI (0.97, and NFI (0.92. We also examined the effect of removing three items on the CQOLC-C factor structure and discuss the resulting differences from other versions. These results indicate that the CQOLC-C's factor structure does not fully fit the original theorized model. This study provides preliminary support for further use of the CQOLC-C. However, the present work provides only partial support for the relevance and construct validity of the scale for Chinese caregivers.
DOProC-based reliability assessment of steel structures exposed to fatigue
Directory of Open Access Journals (Sweden)
Martin Krejsa
2016-03-01
For probabilistic calculation of fatigue crack progression was used the original and new probabilistic methods – the Direct Optimized Probabilistic Calculation (“DOProC”, which uses a purely numerical approach without any simulation techniques. This provides more accurate solutions to probabilistic tasks, and, in some cases, to considerably faster completion of computations. FCProbCalc code has been developed using the aforementioned techniques. By means of FCProbCalc (which stands for Fatigue Crack Probability Calculation, it is possible to carry out the probabilistic modelling of propagation of fatigue cracks in a user friendly environment and to propose a system of regular inspections which should reveal damage to the structure, using the described computational procedures.
Energy Technology Data Exchange (ETDEWEB)
Guest, Daniel A.; Cairns, Douglas S.
2014-02-01
The increased use and interest in wind energy over the last few years has necessitated an increase in the manufacturing of wind turbine blades. This increase in manufacturing has in many ways out stepped the current understanding of not only the materials used but also the manufacturing methods used to construct composite laminates. The goal of this study is to develop a list of process parameters which influence the quality of composite laminates manufactured using vacuum assisted resin transfer molding and to evaluate how they influence laminate quality. Known to be primary factors for the manufacturing process are resin flow rate and vacuum pressure. An incorrect balance of these parameters will often cause porosity or voids in laminates that ultimately degrade the strength of the composite. Fiber waviness has also been seen as a major contributor to failures in wind turbine blades and is often the effect of mishandling during the lay-up process. Based on laboratory tests conducted, a relationship between these parameters and laminate quality has been established which will be a valuable tool in developing best practices and standard procedures for the manufacture of wind turbine blade composites.
Infrared spectroscopy of CO sub 2 --D(H)Br: Molecular structure and its reliability
Energy Technology Data Exchange (ETDEWEB)
Zeng, Y.P.; Sharpe, S.W.; Shin, S.K.; Wittig, C.; Beaudet, R.A. (Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482 (United States))
1992-10-15
A high resolution rovibrational absorption spectrum of the weakly bonded CO{sub 2}--DBr complex has been recorded in the 2350 cm{sup {minus}1} region by exciting the CO{sub 2} asymmetric stretch vibration with a tunable diode laser. The CO{sub 2}--DBr band origin associated with this mode is 2348.2710 cm{sup {minus}1}, red-shifted by 0.87 cm{sup {minus}1} from uncomplexed CO{sub 2}. The position of the hydrogen atom is determined from differences in moments-of-inertia between CO{sub 2}--DBr and CO{sub 2}--HBr, i.e., by using the Kraitchman method. From this, we conclude that ground state CO{sub 2}--H(D)Br has an average geometry that is planar and inertially T-shaped, with essentially parallel HBr and CO{sub 2} axes. Average values of intermolecular parameters are: {ital R}{sub cm}=3.58 A, {theta}{sub BrCO}=79.8{degree}, and {theta}{sub HBrC}=93.1{degree}. The validity of using the Kraitchman method, which was designed for use with rigid molecules, with a floppy complex like CO{sub 2}--HBr is discussed. The experimental structure is corroborated qualitatively by results from Moller--Plesset second-order perturbation calculations, corrected for basis set superposition errors. The theoretical equilibrium geometry for the inertially T-shaped complex is planar with structural parameters: {ital R}{sub CBr}=3.62 A, {theta}{sub BrCO}=89{degree}, and {theta}{sub HBrC}=86{degree}. A number of cuts on the four dimensional intermolecular potential surface confirm large zero-point amplitudes, which are known to be characteristic of such systems, and these cuts are used to estimate tunneling splittings. Tunneling is shown to occur by out-of-plane rotation of the H atom, in accord with the experimental observations of Rice {ital et} {ital al}. There is no significant in-plane tunneling.
Infrared spectroscopy of CO2-D(H)Br: Molecular structure and its reliability
Zeng, Y. P.; Sharpe, S. W.; Shin, S. K.; Wittig, C.; Beaudet, R. A.
1992-10-01
A high resolution rovibrational absorption spectrum of the weakly bonded CO2-DBr complex has been recorded in the 2350 cm-1 region by exciting the CO2 asymmetric stretch vibration with a tunable diode laser. The CO2-DBr band origin associated with this mode is 2348.2710 cm-1, red-shifted by 0.87 cm-1 from uncomplexed CO2. The position of the hydrogen atom is determined from differences in moments-of-inertia between CO2-DBr and CO2-HBr, i.e., by using the Kraitchman method. From this, we conclude that ground state CO2-H(D)Br has an average geometry that is planar and inertially T-shaped, with essentially parallel HBr and CO2 axes. Average values of intermolecular parameters are: Rcm=3.58 Å, θBrCO=79.8°, and θHBrC=93.1°. The validity of using the Kraitchman method, which was designed for use with rigid molecules, with a floppy complex like CO2-HBr is discussed. The experimental structure is corroborated qualitatively by results from Møller-Plesset second-order perturbation calculations, corrected for basis set superposition errors. The theoretical equilibrium geometry for the inertially T-shaped complex is planar with structural parameters: RCBr=3.62 Å, θBrCO=89°, and θHBrC=86°. A number of cuts on the four dimensional intermolecular potential surface confirm large zero-point amplitudes, which are known to be characteristic of such systems, and these cuts are used to estimate tunneling splittings. Tunneling is shown to occur by out-of-plane rotation of the H atom, in accord with the experimental observations of Rice et al. There is no significant in-plane tunneling. A quasilinear hingelike isomer (OCO-HBr) with ROH=2.35 Å at equilibrium is calculated to be as stable as the T-shaped complex; however, this species has yet to be observed experimentally. Photoinitiated reactions in CO2-HX complexes are discussed.
Verheul, R.; Andrea, H.; Berghout, C.C.; Dolan, C.V.; Busschbach, J.J.V.; Kroft, P.J.A.; Batemen, A.W.; Fonagy, P.
2008-01-01
This article describes a series of studies involving 2,730 participants on the development and validity testing of the Severity Indices of Personality Problems (SIPP), a self-report questionnaire covering important core components of (mal)adaptive personality functioning. Results show that the 16 fa
Development of the Career Indecision Profile: Factor Structure, Reliability, and Validity
Hacker, Jason; Carr, Andrea; Abrams, Matthew; Brown, Steven D.
2013-01-01
Prior research using a 167-item measure of career indecision (Career Indecision Profile-167 [CIP-167]) has suggested that career choice difficulties may be associated with four major sources of career indecision: neuroticism/negative affectivity, choice/commitment anxiety, lack of readiness, and interpersonal conflicts. The purpose of this study…
'Mum never loved me.' How structural factors influence adolescent ...
African Journals Online (AJOL)
How structural factors influence adolescent sexual and reproductive health ... Research in high income countries shows parent–child connectedness to be ... to young people's low self-esteem and risky sexual behaviour while unplanned ...
Maximum Likelihood Factor Structure of the Family Environment Scale.
Fowler, Patrick C.
1981-01-01
Presents the maximum likelihood factor structure of the Family Environment Scale. The first bipolar dimension, "cohesion v conflict," measures relationship-centered concerns, while the second unipolar dimension is an index of "organizational and control" activities. (Author)
Matrix factorization method for the Hamiltonian structure of integrable systems
Indian Academy of Sciences (India)
S Ghosh; B Talukdar; S Chakraborti
2003-07-01
We demonstrate that the process of matrix factorization provides a systematic mathematical method to investigate the Hamiltonian structure of non-linear evolution equations characterized by hereditary operators with Nijenhuis property.
Bacterial Sigma Factors and Anti-Sigma Factors: Structure, Function and Distribution
Paget, Mark S.
2015-01-01
Sigma factors are multi-domain subunits of bacterial RNA polymerase (RNAP) that play critical roles in transcription initiation, including the recognition and opening of promoters as well as the initial steps in RNA synthesis. This review focuses on the structure and function of the major sigma-70 class that includes the housekeeping sigma factor (Group 1) that directs the bulk of transcription during active growth, and structurally-related alternative sigma factors (Groups 2–4) that control ...
[Factor structure validity of the social capital scale used at baseline in the ELSA-Brasil study].
Souto, Ester Paiva; Vasconcelos, Ana Glória Godoi; Chor, Dora; Reichenheim, Michael E; Griep, Rosane Härter
2016-07-21
This study aims to analyze the factor structure of the Brazilian version of the Resource Generator (RG) scale, using baseline data from the Brazilian Longitudinal Health Study in Adults (ELSA-Brasil). Cross-validation was performed in three random subsamples. Exploratory factor analysis using exploratory structural equation models was conducted in the first two subsamples to diagnose the factor structure, and confirmatory factor analysis was used in the third to corroborate the model defined by the exploratory analyses. Based on the 31 initial items, the model with the best fit included 25 items distributed across three dimensions. They all presented satisfactory convergent validity (values greater than 0.50 for the extracted variance) and precision (values greater than 0.70 for compound reliability). All factor correlations were below 0.85, indicating full discriminative factor validity. The RG scale presents acceptable psychometric properties and can be used in populations with similar characteristics.
Shabakhty, N.
2004-01-01
A variety of factors is governing the operational conditions of jack-up platforms. The platforms are moved to different locations, which are causing changes in water depth, environmental and seabed conditions, drilling depths, payload etc. Insight should be gained in how the different factors affect
Directory of Open Access Journals (Sweden)
Eleanor Raffan
2015-09-01
Full Text Available Background. Dogs are compelling models in which to study obesity since the condition shares many characteristics between humans and dogs. Differences in eating behaviour are recognised to contribute to obesity susceptibility in other species but this has not been systematically studied in dogs.Aim. To develop and validate an owner-reported measure of canine eating behaviour and owner or dog related factors which can alter the development of obesity. Further, to then test variation in food-motivation in dogs and its association with obesity and owner management.Methods. Owner interviews, a literature review and existing human appetite scales were used to identify relevant topics and generate items for the questionnaire. Following a pilot phase, a 75 item online questionnaire was distributed via social media. Responses from 302 dog/owner dyads were analysed and factor structure and descriptive statistics calculated. Results were compared with descriptions of dog behaviour and management from a subset of respondents during semi-structured interviews. The optimum questions were disseminated as a 34 item final questionnaire completed by 213 owners, with a subset of respondents repeating the questionnaire 3 weeks later to assess test–retest reliability.Results. Analysis of responses to the final questionnaire relating to 213 dog/owner dyads showed a coherent factor structure and good test–retest reliability. There were three dog factors (food responsiveness and satiety, lack of selectivity, Interest in food, four owner factors (owner motivation to control dog weight, owner intervention to control dog weight, restriction of human food, exercise taken and two dog health factors (signs of gastrointestinal disease, current poor health. Eating behaviour differed between individuals and between breed groups. High scores on dog factors (high food-motivation and low scores on owner factors (less rigorous control of diet/exercise were associated with
Raffan, Eleanor; Smith, Stephen P; O'Rahilly, Stephen; Wardle, Jane
2015-01-01
Background. Dogs are compelling models in which to study obesity since the condition shares many characteristics between humans and dogs. Differences in eating behaviour are recognised to contribute to obesity susceptibility in other species but this has not been systematically studied in dogs. Aim. To develop and validate an owner-reported measure of canine eating behaviour and owner or dog related factors which can alter the development of obesity. Further, to then test variation in food-motivation in dogs and its association with obesity and owner management. Methods. Owner interviews, a literature review and existing human appetite scales were used to identify relevant topics and generate items for the questionnaire. Following a pilot phase, a 75 item online questionnaire was distributed via social media. Responses from 302 dog/owner dyads were analysed and factor structure and descriptive statistics calculated. Results were compared with descriptions of dog behaviour and management from a subset of respondents during semi-structured interviews. The optimum questions were disseminated as a 34 item final questionnaire completed by 213 owners, with a subset of respondents repeating the questionnaire 3 weeks later to assess test-retest reliability. Results. Analysis of responses to the final questionnaire relating to 213 dog/owner dyads showed a coherent factor structure and good test-retest reliability. There were three dog factors (food responsiveness and satiety, lack of selectivity, Interest in food), four owner factors (owner motivation to control dog weight, owner intervention to control dog weight, restriction of human food, exercise taken) and two dog health factors (signs of gastrointestinal disease, current poor health). Eating behaviour differed between individuals and between breed groups. High scores on dog factors (high food-motivation) and low scores on owner factors (less rigorous control of diet/exercise) were associated with obesity. Owners of
Structure factor determination of amorphous materials by neutron diffraction
Energy Technology Data Exchange (ETDEWEB)
Cuello, Gabriel J [Institut Laue Langevin, 6 rue Jules Horowitz, BP 156, F-38042 Grenoble Cedex 9 (France)], E-mail: cuello@ill.eu
2008-06-18
An introduction is given to structure factor determination by means of neutron diffraction. The method of isotopic substitution, which allows us to separate the partial correlation functions, is also presented. Suitable instruments, the experimental procedures, and corrections are described. Other less-conventional techniques such as isomorphic substitution and anomalous dispersion are also discussed. Finally, examples of the structure factor determination in chalcogenide, molecular, telluride and phosphate glasses are discussed in order to illustrate the usefulness of the neutron diffraction technique.
Directory of Open Access Journals (Sweden)
Ajay Kumar Bakhla
2013-01-01
Full Text Available Background: As there are no instruments to measure psychological wellness or distress in visually impaired students, we studied internal consistency and factor structure of GHQ-12 in visually impaired children. Materials and Methods: Internal consistency analysis (Cronbach′s alpha and item total correlation and exploratory factor analysis (principal component analysis were carried out to identify factor structure of 12-item general health questionnaire (GHQ-12. Results: All items of GHQ-12 were significantly associated with each other and the Cronbach′s alpha coefficient for the scale was 0.7. On analysis of principal component, three-factor solution was found that accounted for 47.92% of the total variance. The factors included, ′general well-being′, ′depression′ and ′cognitive′, with Cronbach′s alpha coefficients being 0.70, 0.59, and 0.34, respectively. Conclusion: Our study findings suggest GHQ-12 is a reliable with adequate internal consistency scale and multidimensional factor structure in visually impaired students.
Structure and regulatory function of plant transcription factors
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
The expression of inducible genes in plants is regulated byspecific transcription factors at the transcriptional level. A typical transcription factor usually contains a DNA-binding domain, a transcription regulation domain, a dimerization site and a nuclear localization domain. These functional domains define the characteristic, localization and regulatory role of a transcription factor. Transcription factors recognize and bind to specific cis-acting elements or interact with other proteins, and then activate or repress the transcription of target genes by their functional domains. In recent years, elucidation on the structure and function of transcription factors has become an important subject in plant molecular biology.
Energy Technology Data Exchange (ETDEWEB)
Broas, M., E-mail: mikael.broas@aalto.fi; Mattila, T. T.; Paulasto-Kröckel, M. [Department of Electrical Engineering and Automation, Aalto University, Espoo, P.O. Box 13500, FIN-00076 Aalto (Finland); Liu, X.; Ge, Y. [Department of Materials Science and Engineering, Aalto University, Espoo, P.O. Box 16200, FIN-00076 Aalto (Finland)
2015-06-28
This paper describes a reliability assessment and failure analysis of a poly-Si/non-stoichiometric silicon nitride thin film composite structure. A set of poly-Si/SiN{sub x} thin film structures were exposed to a mixed flowing gas (MFG) environment, which simulates outdoor environments, for 90 days, and an elevated temperature and humidity (85 °C/95% R.H.) test for 140 days. The mechanical integrity of the thin films was observed to degrade during exposure to the chemically reactive atmospheres. The degree of degradation was analyzed with nanoindentation tests. Statistical analysis of the forces required to initiate a fracture in the thin films indicated degradation due to the exposure to the MFG environment in the SiN{sub x} part of the films. Scanning electron microscopy revealed a porous-like reaction layer on top of SiN{sub x}. The morphology of the reaction layer resembled that of galvanically corroded poly-Si. Transmission electron microscopy further clarified the microstructure of the reaction layer which had a complex multi-phase structure extending to depths of ∼100 nm. Furthermore, the layer was oxidized two times deeper in a 90 days MFG-tested sample compared to an untested reference. The formation of the layer is proposed to be caused by galvanic corrosion of elemental silicon in non-stoichiometric silicon nitride during hydrofluoric acid etching. The degradation is proposed to be due uncontrolled oxidation of the films during the stress tests.
Exploring the factor structure of neurocognitive measures in older individuals.
Santos, Nadine Correia; Costa, Patrício Soares; Amorim, Liliana; Moreira, Pedro Silva; Cunha, Pedro; Cotter, Jorge; Sousa, Nuno
2015-01-01
Here we focus on factor analysis from a best practices point of view, by investigating the factor structure of neuropsychological tests and using the results obtained to illustrate on choosing a reasonable solution. The sample (n=1051 individuals) was randomly divided into two groups: one for exploratory factor analysis (EFA) and principal component analysis (PCA), to investigate the number of factors underlying the neurocognitive variables; the second to test the "best fit" model via confirmatory factor analysis (CFA). For the exploratory step, three extraction (maximum likelihood, principal axis factoring and principal components) and two rotation (orthogonal and oblique) methods were used. The analysis methodology allowed exploring how different cognitive/psychological tests correlated/discriminated between dimensions, indicating that to capture latent structures in similar sample sizes and measures, with approximately normal data distribution, reflective models with oblimin rotation might prove the most adequate.
Exploring the factor structure of neurocognitive measures in older individuals.
Directory of Open Access Journals (Sweden)
Nadine Correia Santos
Full Text Available Here we focus on factor analysis from a best practices point of view, by investigating the factor structure of neuropsychological tests and using the results obtained to illustrate on choosing a reasonable solution. The sample (n=1051 individuals was randomly divided into two groups: one for exploratory factor analysis (EFA and principal component analysis (PCA, to investigate the number of factors underlying the neurocognitive variables; the second to test the "best fit" model via confirmatory factor analysis (CFA. For the exploratory step, three extraction (maximum likelihood, principal axis factoring and principal components and two rotation (orthogonal and oblique methods were used. The analysis methodology allowed exploring how different cognitive/psychological tests correlated/discriminated between dimensions, indicating that to capture latent structures in similar sample sizes and measures, with approximately normal data distribution, reflective models with oblimin rotation might prove the most adequate.
Factor Structure of Japanese Versions of Two Emotional Intelligence Scales
Fukuda, Eriko; Saklofske, Donald H.; Tamaoka, Katsuo; Fung, Tak Shing; Miyaoka, Yayoi; Kiyama, Sachiko
2011-01-01
This article reports the psychometric properties of two emotional intelligence measures translated into Japanese. Confirmatory factor analysis (CFA) was conducted to examine the factor structure of a Japanese version of the Wong and Law Emotional Intelligence Scale (WLEIS) completed by 310 Japanese university students. A second study employed CFA…
RELIABILITY-BASED ON OPTIMIZATION FOR FRAME STRUCTURES WITH DISCRETE VARIABLES%离散变量框架结构的可靠性优化
Institute of Scientific and Technical Information of China (English)
蔡迎建; 孙焕纯
2001-01-01
Based on the requirement of engineering practice, a structure is designed by the determinism method according to economic and safety criteria, this is the aim of traditional structural design. It is more practical to understand the structural safety sense from the probability point of view. Based upon this idea people find a reasonable method to design the optimum structural member size, this is the reliability-based on structural optimization method. The traditional optimization procedure is to make the objective function to be maximum or minimum, subjected to a set of constraint conditions, and no matter whether the objective function or constarint conditions are all unconcerned with the reliability concept. Therefore it is inevitable that the traditional optimal structure design exists two defects: the first is that the optimum structure obtained by the traditional optimum design method can't be guaranteed having the necessary reliability level,the second is that in the traditional optimum design the randomnes of the parameters of material's mechanical behaviours and member's geometric properties are neglected, so the safety index is indefinite. Therefore the requirement of reliability should be added in the mathematic model of optimum design. The optimum structure obtained by this model is called reliability-based on optimization. In this paper, the relative difference quotient method is used to the reliability-based on optimization for frame structures with discrete variables, and an iteration scheme to find the optimum solution is presented. Some examples show that the method is effective and practica%以框架结构系统的可靠性分析为基础，给出离散变量框架结构可靠性优化的柏对差商方法及迭代格式，并用算例证明了该法的有效性及实用性.
Influence of environmental factors on corrosion damage of aircraft structure
Institute of Scientific and Technical Information of China (English)
无
2011-01-01
Corrosion is one of the important structural integrity concerns of aging aircraft, and it is estimated that a significant portion of airframe maintenance budgets is directed towards corrosion-related problems for both military and commercial aircraft. In order to better understand how environmental factors influence the corrosion damage initiation and propagation on aircraft structure and to predict pre-corrosion test pieces of fatigue life and structural integrity of an effective approach, this paper uses ...