Reliability and validity of the hidden hunger assessment scale in China-revised for high school students

Objective:Hidden hunger remains a severe public health problem that affects millions of people worldwide.In China,challenges related to dietary imbalance and hidden hunger persist.Micronutrient inadequacy deserves more attention among adolescents,given its vital role in their growth and development;however,this problem appears to have been largely ignored.High school students,in particular,are often at a high risk of hidden hunger but have limited assessment tools available.Therefore,this study aims to revise the hidden hunger assessment scale for high school students(HHAS-HSS)in China and assess its reliability and validity.Methods:Based on a literature review,expert consultation,pre-experiment,and formal survey,a hidden hunger assessment scale was revised for high school students.The formal survey involved 9336 high school students in 11 of the 16 cities in Anhui Province,China,and 9038 valid questionnaires were collected and included in the analysis.The item analysis,internal consistency reliability,test-retest reliability,content validity,exploratory factor analysis,and confirmatory factor analysis of the HHAS-HSS were examined.Results:The HHAS-HSS included a total of 4 dimensions and 12 items:"vegetables and food diversity"(three items),"fruits and dairy products"(three items),"micronutrient-dense foods"(four items),and"health condition and eating habits"(two items).The results showed a Cronbach's alpha of 0.758,a split-half reliability of 0.829,and a test-retest reliability of o.793,indicating good internal consistency.Using the Bartlett's test and Kaiser-Meyer-Olkin test(KMO)to test the exploratory factor analysis presented a four-factor model of the HHAS-HSS,the KMO0 value was 0.820(P<0.001),which indicated the possibility for factor confirmatory factor analysis.Using the maximum variance rotation method,four factors were obtained,and the cumulative variance explained rate was 57.974%.Confirmatory factor analysis also supported the division of the scale into four dimensions,and the fitting indices were x^(2)=1417.656,x^(2)/df=29.534,goodness-of-fit index=0.974,adjusted goodnessof-fit index=0.958,parsimonious goodness-of-fit index=0.600,normed fit index=0.938,incremental fit index=0.940,Tucker-Lewis index=0.917,comparative fit index=0.939,and root mean square error of approximation=0.056.Except for x^(2)/df,all the indices reached the fitting standard,and the above results showed that the construct validity of the scale reached an acceptable level.Conclusions:The HHAS-HSS has good validity and reliability for Chinese high school students.It is a convenient self-report measure of hidden hunger risk.

Product reliability assessment based on proportional hazard degradation model

In order to evaluate the reliability of long-lifetime products with degradation data, a new proportional hazard degradation model is proposed. By the similarity between time-degradation data and stress-accelerated lifetime, and the failure rate function of degradation data which is assumed to be proportional to the time covariate, the reliability assessment based on a proportional hazard degradation model is realized. The least squares method is used to estimate the model＇s parameters. Based on the failure rate of the degradation data and the proportion function of the known time, the failure rate and the reliability function under the given time and the predetermined failure threshold can be extrapolated. A long life GaAs laser is selected as a case study and its reliability is evaluated. The results show that the proposed method can accurately describe the degradation process and it is effective for the reliability assessment of long lifetime products.

System reliability assessment based on Wiener process and competing failure analysis

Considering the dependence and competitive relation-ship between traumatic failure and degradation,the reliability assessment of products based on competing failure analysis is studied.The hazard rate of traumatic failure is regarded as a Weibull distribution of the degradation performance,and the Wiener process is used to describe the degradation process.The parameters are estimated with the maximum likelihood estimation（MLE）method.A reliability model based on competing failure analysis is proposed.A case study of the GaAs lasers is given to validate the effectiveness of the model and its solving method.The results indicate that if only the degradation failure is considered,the estimated result will be comparably optimistic.Meanwhile,the correlation between the degradation and traumatic failure has a great influence on the accuracy of reliability assessment.

ON INFORMATION THEORY METHOD FOR RELIABILITY ASSESSMENT OF SYSTEMS CONSISTING OF DIFFERENT SUCCESS FAILURE MODEL UNITS

Using the characteristic of addition of information quantity and the principle of equivalence of information quantity, this paper derives the general conversion formulae of the formation theory method conversion (synthesis) on the systems consisting of different success failure model units. According to the fundamental method of the unit reliability assessment, the general models of system reliability approximate lower limits are given. Finally, this paper analyses the application of the assessment method by examples, the assessment results are neither conservative nor radical and very satisfactory. The assessment method can be popularized to the systems which have fixed reliability structural models.

Handling Uncertainty in Human Cognitive Reliability Method for Safety Assessment Based on DSET

Human Reliability Analysis(HRA)is an important part in safety assessment of a large complex system.Human Cognitive Reliability(HCR)model is a method of evaluating the probability that operators fail to complete during diagnostic decision making within a limited time,which is widely used in HRA.In the application of this method,cognitive patterns of humans are required to be considered and classified,and this process often relies on the evaluation opinions of experts which is highly subjective and uncertain.How to effectively express and process this uncertain and subjective information plays a critical role in improving the accuracy and applicability of HCR.In this paper,a new model was proposed to deal with the uncertain information which exists in the processes of cognitive pattern classification in HCR.First,an evaluation panel was constructed based on expert opinions and processing including setting corresponding anchor points and qualitative indicators of different cognitive patterns,and mapping them to fuzzy numbers and unit intervals.Second,based on the evaluation panel,different analysts judge the cognitive pattern types of actual specific events and provide the level of confidence he or she has in the judgments.Finally,the evaluation opinions of multiple analysts were expressed and fused based on the Dempster-Shafer Evidence Theory(DSET),and the fused results were applied to the HCR model to obtain the Human Error Probability(HEP).A case study was used to demonstrate the procedure and effectiveness of the proposed method.

Integrated Grease-pouring System Design and Reliability Assessment of Engineering Equipment

Because of poor lubrication, the abrasion of the engineering equipment＇s key connection position （the hinge joint and so on） has become the major factor that affects the mechanical benefit. The excavator WY60 is taken as an example in this paper. The automatic grease-pouring, the working state test, and the alarm for fault of every lubricating point on the machine is accomplished by the control sub-system, the lubricating system and other correlated components. The principle and functions of the system are described. The work condition is analyzed. Finally, we present the plan of the software and the hardware of the system, and set up the fuzzy assessment model of reliability of the system.

Improved Reliability Analysis Method Based on the Failure Assessment Diagram

With the uncertainties related to operating conditions,in-service non-destructive testing（NDT） measurements and material properties considered in the structural integrity assessment,probabilistic analysis based on the failure assessment diagram（FAD） approach has recently become an important concern.However,the point density revealing the probabilistic distribution characteristics of the assessment points is usually ignored.To obtain more detailed and direct knowledge from the reliability analysis,an improved probabilistic fracture mechanics（PFM） assessment method is proposed.By integrating 2D kernel density estimation（KDE） technology into the traditional probabilistic assessment,the probabilistic density of the randomly distributed assessment points is visualized in the assessment diagram.Moreover,a modified interval sensitivity analysis is implemented and compared with probabilistic sensitivity analysis.The improved reliability analysis method is applied to the assessment of a high pressure pipe containing an axial internal semi-elliptical surface crack.The results indicate that these two methods can give consistent sensitivities of input parameters,but the interval sensitivity analysis is computationally more efficient.Meanwhile,the point density distribution and its contour are plotted in the FAD,thereby better revealing the characteristics of PFM assessment.This study provides a powerful tool for the reliability analysis of critical structures.

A Global Reliability Assessment Method on Aging Offshore Platforms with Corrosion and Cracks

Corrosion and fatigue cracks are major threats to the structural integrity of aging offshore platforms. For the rational estimation of the safety levels of aging platforms, a global reliability assessment approach for aging offshore platforms with corrosion and fatigue cracks is presented in this paper. The base shear capacity is taken as the global ultimate strength of the offshore platforms. It is modeled as a random process that decreases with time in the presence of corrosion and fatigue crack propagation. And the corrosion and fatigue crack growth rates in the main members and key joints are modeled as random variables. A simulation method of the extreme wave loads which are applied to the structures of offshore platforms is proposed too. Furthermore, the statistics of global base shear capacity and extreme wave loads are obtained by Monte Carlo simulation method. On the basis of the limit state equation of global failure mode, the instantaneous reliability and time dependent reliability assessment methods are both presented in this paper. Finally the instantaneous reliability index and time dependent failure probability of a jacket platform are estimated with different ages in the demonstration example.

Reliability assessment on interfacial failure of thermal barrier coatings

Thermal barrier coatings（TBCs） usually exhibit an uncertain lifetime owing to their scattering mechanical properties and severe service conditions. To consider these uncertainties, a reliability assessment method is proposed based on failure probability analysis. First, a limit state equation is established to demarcate the boundary between failure and safe regions, and then the failure probability is calculated by the integration of a probability density function in the failure area according to the first- or second-order moment.It is shown that the parameters related to interfacial failure follow a Weibull distribution in two types of TBC. The interfacial failure of TBCs is significantly affected by the thermal mismatch of material properties and the temperature drop in service.

Reliability assessment and correlation analysis of evaluating orthodontic treatment outcome in Chinese patients

This study aimed to assess the reliability of experienced Chinese orthodontists in evaluating treatment outcome and to determine the correlations between three diagnostic information sources. Sixty-nine experienced Chinese orthodontic specialists each evaluated the outcome of orthodontic treatment of 108 Chinese patients. Three different information sources： study casts （SC）, lateral cephalometric X-ray images （LX） and facial photographs （PH） were generated at the end of treatment for 108 patients selected randomly from six orthodontic treatment centers throughout China. Six different assessments of treatment outcome were made by each orthodontist using data from the three information sources separately and in combination. Each assessment included both ranking and grading for each patient. The rankings of each of the 69 judges for the 108 patients were correlated with the rankings of each of the other judges yielding 13 873 Spearman rs values, ranging from -0.08 to ＋0.85. Of these, 90% were greater than 0.4, showing moderate-to-high consistency among the 69 orthodontists. In the combined evaluations, study casts were the most significant predictive component （R2=0.86, P〈0.000 1）, while the inclusion of lateral cephalometric films and facial photographs also contributed to a more comprehensive assessment （R2=0.96, P〈0.000 1）. Grading scores for SC＋LX and SC＋PH were highly significantly correlated with those for SC＋LX＋PH （r（SC＋LX）vs.（SC＋LX＋PH）=0.96, r（SC＋PH）vs.（SC＋LX＋PH）=0.97）, showing that either SC＋LX or SC＋PH is an excellent substitute for all three combined assessment,

A New Safety Assessment Method Based on Belief Rule Base With Attribute Reliability

Safety assessment is one of important aspects in health management.In safety assessment for practical systems,three problems exist:lack of observation information,high system complexity and environment interference.Belief rule base with attribute reliability(BRB-r)is an expert system that provides a useful way for dealing with these three problems.In BRB-r,once the input information is unreliable,the reliability of belief rule is influenced,which further influences the accuracy of its output belief degree.On the other hand,when many system characteristics exist,the belief rule combination will explode in BRB-r,and the BRB-r based safety assessment model becomes too complicated to be applied.Thus,in this paper,to balance the complexity and accuracy of the safety assessment model,a new safety assessment model based on BRB-r with considering belief rule reliability is developed for the first time.In the developed model,a new calculation method of the belief rule reliability is proposed with considering both attribute reliability and global ignorance.Moreover,to reduce the influence of uncertainty of expert knowledge,an optimization model for the developed safety assessment model is constructed.A case study of safety assessment of liquefied natural gas(LNG)storage tank is conducted to illustrate the effectiveness of the new developed model.

Bayesian method for system reliability assessment of overlapping pass/fail data

For high reliability and long life systems, system pass/fail data are often rare. Integrating lower-level data, such as data drawn from the subsystem or component pass/fail testing,the Bayesian analysis can improve the precision of the system reliability assessment. If the multi-level pass/fail data are overlapping,one challenging problem for the Bayesian analysis is to develop a likelihood function. Since the computation burden of the existing methods makes them infeasible for multi-component systems, this paper proposes an improved Bayesian approach for the system reliability assessment in light of overlapping data. This approach includes three steps： fristly searching for feasible paths based on the binary decision diagram, then screening feasible points based on space partition and constraint decomposition, and finally simplifying the likelihood function. An example of a satellite rolling control system demonstrates the feasibility and the efficiency of the proposed approach.

Probabilistic seismic response and reliability assessment of isolated bridges

Bridge seismic isolation strategy is based on the reduction of shear forcestransmitted from the superstructure to the piers by two means: shifting natural period andearthquake input energy reduction by dissipation concentrated in protection devices. In this paper,a stochastic analysis of a simple isolated bridge model for different bridge and device parametersis conducted to assess the efficiency of this seismic protection strategy. To achieve this aim, asimple nonlinear softening constitutive law is adopted to model a wide range of isolation devices,characterized by only three essential mechanical parameters. As a consequence of the random natureof seismic motion, a probabilistic analysis is carried out and the time modulated Kanai-Tajimistochastic process is adopted to represent the seismic action. The response covariance in the statespace is obtained by solving the Lyapunov equation for a stochastic linearized system. After asensitivity analysis, the failure probability referred to extreme displacement and the mean value ofdissipated energy are assessed by using the introduced stochastic indices of seismic bridgeprotection efficiency. A parametric analysis for protective devices with different mechanicalparameters is developed for a proper selection of parameters of isolation devices under differentsituations.

System Reliability Analysis of Offshore Strctures and Component Safety Rank Assessment

Offshore structures will encounter serious environmental load, so it is important to study the structural system reliability and to evaluate the structural component safety rank. In this paper, the bracnch-and-bound method is adopted to search the main failure path, and the Ditlevsen bound method is used to calculate the system failure probability. The structure is then assessed by the fuzzy comprehensive assessment method, which evaluates the structural component safety rank. The ultimate equation of the tubular cross- section is analyzed on the basis of ultimate stregnth analysis. The influence of effect coefficients on the structural system failure probability is investigated, and basic results are obtained. A general program for spatial frame structures by means of the above method is developed, and verified by the numerical examples.

Bayesian Assessment for Reliability of Binomial Components Based on Information Fusion of Similar Products

A modified Bayesian reliability assessment method of binomial components was proposed by fusing prior information of similar products.The traditional Bayesian method usually directly used all the prior data,ignoring the differences between them,which might decrease the credibility level of reliability evaluation and result in data submergence.To solve the problem,a revised approach was derived to calculate groups of prior data's quantitative credibility,used for weighted data fusion.Then inheritance factor was introduced to build a mixed beta distribution to illustrate the innovation of new products.However,in many cases,inheritance factor was determined by Chi-square test that could not give out exact result with respect to rare failures.To make the model more precise,Barnard's exact test was suggested being used to calculate the inheritance factor.A numerical example is given to demonstrate that the modified method is successful and rational,while the classical method is too conservative and the traditional Bayesian method is too risky.

Reliability Assessment of Distribution SystemBased on Discrete-event System

Discrete-event system simulation technology is used to analyze distribution system reliability in this paper. A simulation model, including entity state models, system state models, state transition models, reliability criterion model, is established. ‘Next happen event’ is taken as impulse principle of simulator clock to determine the sequence of random event occurrence dynamically. The results show this method is feasible.

PROBABILITY OF RANDOM EVENTS OF INSPECTION AND REPAIR AND MAINTAINING RELIABILITY OF STRUCTURES

Reliability analysis of the inspected and repaired structure requires dealing with a large number of complex random events. Considering many kinds of random factors, a probability of these random events existing possibly in the inspection and repair process and reliability analysis methodologies are proposed. A systematic dynamic reliability model is given for structures in service under the scheduled inspection and repair.

Ageing Assessment, Condition Inspection and Lifetime Evaluation for Safety Related Fuse in Nuclear Power Plant

This paper presents the ageing mechanism of fuse in nuclear power plant in detail. Metal Electromigration is identified as the dominant ageing mechanism. On this basis, the dominant status indicators, temperature and resistance of fuse were ensured, and current-temperature curve was proposed. The infrared thermal imaging technology was used to inspect the ageing condition and prove the current-temperature curve. Finally, the accelerated ageing testing was conducted abiding by the dominant ageing mechanism, and the lifetime was evaluated.

Methods for Reliability Assessment under Irregular Time-Varying-Stress Degradation Testing

Degradation tests are often used to assess the reliability of products with long failure-time or few test units. Much of the previous work on reliability assessment methods has focused on constant-stress degradation test( CSDT) and accelerated degradation test( ADT), mainly under the constant, step or progressive stresses. However,in actual testing environments,some stresses are difficult to control and vary with time irregularly,which are quite different from the three stresses mentioned above. In this paper a new approach was presented for reliability assessment with degradation data under irregular time-varying-stress( ITVS).Firstly,the conventional degradation path modeling method was improved by taking into account the influences of the variable stress on the degradation variable. Then,an example was conducted to show the effectiveness of our improved model.

Probabilistic Methods for Reliability Assessment of Floating Structures Based on Extreme Wave Simulation

With the increasing application of floating platforms in deep waters and harsh environments,a proper assessment of the reliability of floating structures is important to ensure that these structures can operate safely during their design lives.This study outlines a practical methodology for reliability analysis of a semi-submersible platform based estimating the probability distribution of the extreme response in rough sea conditions(survival conditions).The Constrained NewWave(CNW)theory combined with Monte Carlo simulations was first applied to simulate the random wave surface elevation process in the time domain.A Gumbel distribution was the best fitting to describe the dynamically sensitive extreme response statistics under extreme waves(drift and mooring tension).The derived probability distribution of the extreme response was subsequently used in estimation of the associated limit state func-tion,and a reliability analysis of the floating structure was conducted using the Monte Carlo method.A semi-submersible platform in a water depth of 1500 m subjected to extreme wave loads was used to demonstrate the efficiency of the proposed methodology.The probability of failure of the semi-submersible when considering mooring lines tension is greater than considering drift.