Actual Lifetime Research Articles

Concentration and health risk assessment of polycyclic aromatic hydrocarbons in commercial tea and coffee samples marketed in Iran.

The aim of the current study was to evaluate the probabilistic health risk and the concentration of 16 polycyclic aromatic hydrocarbons (PAHs) in commercial tea and coffee samples. For determining the mentioned contaminants in sixty-four samples, a reliable and sensitive technique was validated and developed. The technique is established on magnetic solid-phase extraction and gas chromatography-mass spectrometry analysis (MSPE/GC-MS). The maximum mean of ƩPAHs in coffee samples was 13.75 ± 2.90 μg kg-1, while the minimum mean ƩPAHs in tea samples was 4.77 ± 1.01 μg kg-1. The mean concentration of benzo(a)pyrene (BaP) in samples ranged from 0.64 to 2.07 μg kg-1 which was lower than that of standard levels (10 μg kg-1) established by the European Union (EU). The Monte Carlo simulation results showed that the actual target hazard quotient (THQ) for the adult and children was equal to 1.63E-04 and 1.67E-04, respectively; hence, non-carcinogenic health risk for consumers is negligible. The result of actual incremental lifetime cancer risk (ILCR) was lower than the limits of safe risk (1E-4), indicating no notable possibility of cancer risk due to the digestion of tea and coffee for children and adults. Therefore, it can be concluded that the amount of contamination of popular commercial coffee and tea available in the Iranian market with PAHs is often similar to that found in other countries and was lower than the standard of EU. Thus, the processing conditions of these products must be controlled to prevent the formation of PAHs due to the suspicion of carcinogenicity and mutation.

Increasing the Reliability of Dust Collector Machine IDC001 Using Preventive Maintenance with Continuous Monitoring Activity in Automotive Company

As one of the main vital for automotive company, the maintenance of machine is very vital to be maintained and controlled to prevent any meaningless downtime. But during January 2015 until November 2018, machine is the highest downtime contributor for molding line with total downtime 2320.49 hours. Especially for dust collector machine IDC001 that contribute the highest downtime of the machines. It is caused by the current preventive maintenance schedule still not considering the machine reliability. The schedule also cannot represent the actual lifetime of its critical components which are dust tube, shaft, v-belt, and bearing. Moreover, there is no any data recorded about the components performance that make the maintenance team cannot predict the component lifetime accurately. The objectives of this research are to achieve 80% reliability and to get more data of component performance by proposing the new preventive maintenance schedule and continuous monitoring activity. After several failure functions calculation, then the new preventive maintenance schedule is established. Through the analysis of what the current maintenance system needs today, there are vibration monitoring and dust concentration monitoring activities that will be proposed to get more data to predict the component lifetime in the future. By implementing the proposed preventive maintenance schedule and continuous monitoring activities, the maintenance team able to get more data to predict the component lifetime and the reliability of each component will increase into 80% with total savings IDR 830,645,805.

A novel approach to evaluating the business potential of intellectual properties: A machine learning-based predictive analysis of patent lifetime

Because most patent holders are likely to retain their patents only when the profits created are larger than the maintenance fee, the patent lifetime has been used as a proxy of a patent’s business potential in a patent evaluation. In this paper, we propose an approach to evaluate the business potential of individual patents by applying a machine learning algorithm to predict the likelihood that a patent will survive until its maximum expiration date. A total of 24 indicators and historical maintenance fee event data obtained from a large number of patents were used for learning a feed-forward neural network (FFNN) model. Consequently, the FFNN model outperformed other algorithms and interesting trends were identified, namely, the recall is higher than precision irrespective of the models used, and the predicted business potential grade of a patent has a strong positive correlation with the actual lifetime of the patent. An advantage of the approach is its wide applicability in dealing with patents with few or no forward citations. This approach can be employed for examining patents with high business potential to uncover hidden core technologies of competitive firms or identifying newly issued patents with a high business potential to predict emerging technologies.

A Laboratory Astrophysics Problem: The Lifetime of Very Long-Lived Levels in Low-Charge Ions

Emission lines of singly charged ions populate many astrophysical spectra. However, the interpretation of the line intensities (usually line ratios) often depends on the transition rates of the decays of very long-lived low-lying levels. For example, the line ratio of two electric-dipole forbidden transitions in the 3s 2 3p 3 ground configuration of singly ionized sulfur (ion S + , spectrum S II) has been interpreted in terms of a density diagnostic for planetary nebulae, i.e., for densities in the order of 10 4 cm − 3 . The predicted lifetimes of the 2 D 3 / 2 , 5 / 2 o levels are in the order of one hour. Modeling indicates that a 10% uncertainty of the lifetime determination in this case corresponds to a 50% uncertainty of the density diagnostic. The available theoretical lifetime predictions scatter by much more than 10%. Considerations about an experimental approach are presented with the goal of instigating a measurement of the actual level lifetimes.

Network Lifetime and Coverage Fraction Analysis for Wireless Sensor Networks

In Wireless Sensor Networks, two crucial parameters are lifetime of the network and optimal coverage for sensed region. This paper addresses the issues and challenges pertaining to these parameters for further investigation, and provides a method to approximate the energy utilization and optimal coverage inside the bottleneck zone for wireless sensor networks. The proposed analytical framework calculates correctly the network lifetime upper bound of wireless sensor networks. The derivation of the network lifetime upper bound is carried out using (i) network coding and (ii) network coding with duty cycle. Based on that, an approximate derivation is made and the corresponding results are obtained from the simulation study. The comparison of the results of the previous study and those obtained in this paper reveals that the actual network lifetime upper bound is lower in the present case. This is due to the assumption made by authors of previous work, on coder nodes’ presence throughout the bottleneck zone instead of only one hop distance away from the sink. In addition, the effect of coverage fraction in case of node failure, on network lifetime upper bound is derived for the previously reported and present model. The simulated results obtained from new derivation show that the coverage fraction is lesser than that obtained by previous model.

Copula models for one-shot device testing data with correlated failure modes

Copula models have become one of the most popular tools, especially in finance and insurance, for modeling multivariate distributions in the past few decades, and they have recently received increasing attention for data analysis in reliability engineering and survival analysis. This paper considers two Archimedean copula models — the Gumbel-Hougaard copula and Frank copula — for analyzing one-shot device data with two correlated failure modes, which are collected from constant-stress accelerated life tests. A one-shot device is a unit that cannot be used again after a test, e.g., munitions, rockets, and automobile airbags. Only either left- or right-censored data are collected instead of the actual lifetimes of the devices under test. With the aid of Kendall’s tau correlation coefficient, initial values of the dependence parameter for the copula models are presented to determine maximum likelihood estimates of model parameters through a numerical approach. Furthermore, the proposed model can be used to examine whether the correlation between times to failure modes changes over stress levels. Real data from a survival experiment are also re-analyzed to illustrate the proposed methods.

Predictive analytics as a way to smart maintenance of hydraulic turbines

Today, most energy companies face serious problems with the reliability and safety of large power equipment due to the long-term operation at off-design modes. This is especially true for hydraulic units that are traditionally used to ensure the required level of energy output and maintain the stability of a power grid due to their maneuverability. Off-design operational modes cause increased loads and stresses in the unit’s components, accelerate the growth of defects, stimulate premature failures, and can lead to a grave accident with large losses.Standard diagnostic systems for hydraulic units usually do not allow tracking hazardous defects such as fatigue cracks in the runner blades, guide vines, shaft, etc. The individuality of hydraulic units also excludes the use of any statistical methods to determine the time when the equipment will go to the limit state and its operation will become unreasonably dangerous. Therefore, the predictive analytics system is proposed as an additional approach to forecasting the appearance and growth of dangerous operational defects. The system realizes an analytical algorithm based on evaluating the fatigue strength of hydraulic unit elements under variable operating conditions and allows summing up damage from various external loads and in different time ranges.Input data for this predictive system is information about the actual operating time at every working mode and expected regime parameters for the upcoming period. The output data is information about actual and residual lifetime. All individual features are taken into account by the digital model which is a multidimensional matrix of equipment’s response to external influences. Data is generated in the cells for each unit’s elements with reference to the operating parameters and time scale.The proposed predictive analytics system allows not only to reduce the risk of accidents and unplanned shutdowns but it also is a way to smart maintenance of hydraulic turbines due to the development of the most effective, most reasonable, most lifetime-saving strategy of using the equipment.

Degradation of PVC Waterproofing Membrane containing Plasticizers

Durability and repairability are one of the basic conditions for the economically efficient use of building materials. The actual lifetime of PVC waterproofing membrane is not only affected by the ageing of the materials, but also by the ageing of the joints. Thus, a significant phenomenon in the evaluation of the lifetime of roof cladding is its realisation - welding. Plasticizers are used for the production of PVC waterproofing membrane. The migration of the plasticizers and the quantity of non-combustible residues (fillers) influence the service life (durability) and the possibility of subsequent repair. Methods used to determine the quantity of non-combustible residues and quantity of plasticizers are described in the paper. Samples were taken from roofs with degrading roofing layer. Based on the results, the lifetime of the PVC waterproofing membrane was determined in dependence on the plasticizers.

Optimal design of simple step-stress accelerated life tests for one-shot devices under Weibull distributions

One-shot devices, such as rockets, airbags of automobiles, and electro-explosive devices, can be used only once and will be extensively destroyed. The actual lifetimes of the devices cannot be observed, no matter whether the outcomes are successful or not. Step-stress accelerated life tests, which are useful for shortening the lifetimes of devices and quickly collecting lifetime data in a limited time, are widely adopted in engineering reliability studies. However, optimal designs of step-stress accelerated life tests for one-shot devices have not been well studied. This paper provides a procedure of determining optimal designs of simple step-stress accelerated life tests for one-shot devices by minimizing the asymptotic variance of the maximum likelihood estimate of reliability at normal operating conditions under Weibull distributions, with respect to inspection times and sample allocations. Comprehensive simulation studies are carried out to study the optimal designs under Weibull distributions with various hazard rates, showing that the optimal designs can maintain the simulated standard deviations at the nominal level of standard error. Besides, sensitivity analysis is conducted to evaluate the robustness of determined designs when mis-specification on planning values of model parameters exists. Finally, an application in grease-based magnetorheological fluids is presented to illustrate the optimal designs.

Modeling Lifetime Earnings Paths: Hypothetical versus Actual Workers

To assess the distributional effects of social security reform proposals, it is essential to have good information on real-world workers' lifetime earnings trajectories. Until recently, however, policymakers have relied on hypothetical earnings profiles for policy analysis. We use actual lifetime earnings data from the Health and Retirement Study (HRS) to compare actual workers' covered earnings profiles to these hypothetical profiles. We show that the hypothetical profiles do not track earnings patterns of current retirees; thus lifetime pay levels are much higher than for most HRS workers. Therefore, using hypothetical profiles could misrepresent benefits paid and taxes collected under such reforms.

Field study on operational performance and economics of lithium-polymer and lead-acid battery systems for consumer load management

This paper presents long-term field test results of lithium-polymer and advanced lead-acid battery systems for consumer load management. The battery systems aimed to minimize electricity bills of an industrial consumer by shifting its load to lower priced time-zones and regulating its peak. Annual and daily peak reduction effects and operating revenues are examined under a time-of-use tariff and battery promotional incentive. Capacity degradations of the batteries are calculated to estimate the actual lifetime. Based on actually earned revenue during the field test and predicted service life for the each type of the batteries, total expected revenue per unit installation capacity is estimated and compared with investment cost per capacity to perform the economics of the tested battery systems for consumer load. This analysis found that the profitability cannot be assured under the considered time-of-use pricing alone but can be expected when adequate incentive is provided. It is also revealed that the batteries in real use conditions lose their capacity considerably quicker than suggested by manufacturers. Therefore, it is recommended to consider actual fading pattern of the battery for accurate economic evaluation at the design stage and to reflect the battery degrading cost into the charge-discharge scheduling model to optimize operating revenue.

Effect of multi-walled carbon nanotubes addition on MnOx/Ti electrode prepared by spraying–calcination method for electro-catalytic oxidation of Acid Red B

The titanium-based electrodes with MnOx nanoparticles coating (MnOx/Ti) and MnOx nanoparticles mixed with multi-walled carbon nanotubes (MnOx–CNTs/Ti) were fabricated by spraying–calcination method. The physicochemical properties of electrodes were investigated by SEM, XRD and XPS, which indicated that the surface coating of MnOx–CNTs/Ti, with MnOx nanoparticles dispersed uniformly on the CNTs, was smoother and with higher integrity than MnOx/Ti. Acid Red B was used as model pollutant to investigate the electro-catalytic activity of the electrodes, and the results revealed that the removal efficiency of Acid Red B reached 93.6% and 98.0% by MnOx/Ti and MnOx–CNTs/Ti, respectively, and the cell potential during the process of degradation by MnOx–CNTs/Ti was relatively low and stable. The electrochemical results confirmed that MnOx–CNTs/Ti possessed smaller charge transfer resistance and higher oxygen evolution current compared with MnOx/Ti, which can enhance the electro-catalytic activity and reduce the energy consumption by accelerating the transfer of electrons on the electrode surface. The accelerated lifetime tests of electrodes were carried out and showed that actual service lifetimes of MnOx–CNTs/Ti were 38 times of that for MnOx/Ti calculated by the experienced formula, which demonstrated that the durability of MnOx-based electrode was significantly promoted by addition of CNTs on Ti substrate.

Development of a durability evaluation model to optimize rare-earth-element-based thermal barrier coatings

Abstract A reliable technique for evaluating the durability of the double-ceramic-layered thermal barrier coatings will enhance the design process by increasing efficiency and lowering costs. In this study, a failure index was proposed, and a numerical model to evaluate the durability of the coating system was developed. The failure index is a factor that indirectly expresses durability by considering fracture toughness, thermal stress, and the specifications of the system. This approach was used in extensive parametric studies on the top coating material and the thickness ratio of coating systems exposed to temperatures in the range of 1200–1500 °C . For the reliability of the study, La2Zr2O7, La2Ce2O7, LaTi2Al9O10, and Sr(Zr0.8Yb0.1)O2.95 were considered as the material for top-coats. In addition, the heating/cooling condition was carefully determined to reflect an actual engine condition. The minimum thickness, the average shielding performance of the materials, and the failure indexes were calculated in this parametric study. The La2Ce2O7-based system and LaTi2Al9O10-based system were found to be the most effective insulation system and the most durable system, respectively. Finally, experimental studies on four kinds of materials were collected from the references. From the collected data, the failure index of each case was calculated and compared with the actual lifetime. As a result, we have confirmed that the log-scaled lifetime and failure indexes are in a linear relationship. Using the linear relationships, the failure index from the parametric study was converted to a lifetime, allowing for an intuitive durability comparison. In terms of converted life expectancy, the LaTi2Al9O10-based system was again found to be the most durable. In conclusion, the proposed failure index is a useful factor to express the durability of double-ceramic-layered thermal barrier coatings and its practicality can be enhanced by comparisons with experimental data.

Sliding mode and SDRE control laws on a tethered satellite system to de-orbit space debris

Since space debris is a problem that has been continuously increasing, removal missions should be considered. Tethered space system (TSS) has wide application prospects in the future on-orbit missions such as debris removal. However, it is rather complex and difficult for TSS to realize stabilization of tumbling combinations after connecting to the debris. In this paper, the stabilization problem of this combination is studied.An adaptive sliding mode and State-Dependent Riccati Equation control methods are applied on a TSS to stabilize the system and de-orbit the space debris. The tether tension and stability of the in-plane and out-of-plane libration angles of the system are taken into account. The tether can only resist axial stretching. The thrusters, which are the sources of the system inputs are equipped on the satellite. The controllers regulate the tether to remain fully stretched and to decrease the altitude of the orbit continuously. The numerical simulation validates the proposed control schemes for de-orbiting the debris and put it in lower altitude orbit. This makes the debris retrieve to the atmosphere in less time than the actual orbit lifetime. The comparison between two control schemes is discussed.

Defects and their range in pure bismuth irradiated with swift Xe ions studied by positron annihilation techniques

Investigations of defects and their spatial distribution in Bi irradiated with 167 MeV Xe26+ ions of different doses have been performed using conventional positron lifetime spectroscopy and variable energy positron beam. In an implanted layer, in which ions are traveling, interacting with atoms and stopping, only clusters which consist of more than eight vacancies were found. It was assigned from ab initio theoretical calculations of positron lifetime in vacancy clusters in Bi. The thickness of this layer corresponds to the range of implanted ions calculated from the SRIM code. However, beyond this layer, an extended layer with such defects has also been found. Its thickness is comparable to the thickness of the implanted layer and it depends on the dose. Defects induced by implantation are also present near the entrance surface, and their concentration depends on the dose of implanted ions as well. Three methods for reconstructing the actual mean positron lifetime and thus the induced depth defect distribution have been proposed, two of them are used in current research.

Conservative estimations of irradiation embrittlement of reactor pressure vessel steels for WWER-1000 lifetime prediction

PurposeThe purpose of this paper is to consider a procedure of water-water energetic reactor (WWER) reactor pressure vessel (RPV) lifetime prediction at the stages of design and lifetime extension using the standard irradiation embrittlement parameters as defined in regulatory documents. A comparison is made of the brittle fracture resistance (BFR) values evaluated using two criteria: shift in the critical brittleness temperature ΔTc or shift in the brittle-to-ductile transition temperature ΔTp and without shifts (Tc and Tp).Design/methodology/approachThe radiation resistance was determined using the following three approaches: calculation based on standard values ΔTc and Tc0 or ΔTp and Tp0 (a level of excessive conservatism); calculation based on standard value ΔTc and actual value Tc0 or actual values ΔTp and Tp0 (the level of realistic conservatism); or calculation based on actual values of Tc and Tc0 or Tp and Tp0 (the level of actual conservatism). The BFR was evaluated based on the results of testing the specimens subjected to irradiation in research reactors as well as surveillance specimens subjected to irradiation immediately under operating conditions.FindingsThe excessive conservatism in determining the actual lifetime of nuclear reactor vessel materials can be eliminated by using the immediate values of critical brittleness temperature and ductile-to-brittle transition temperature.Originality/valueObtained results can be applied to extend WWER vessel operating time at the stages of designing and operation due to substantiated decrease in conservatism. And it will allow carrying out a statistical substantiated assessment of the resistance to brittle fracture of the RPV steels.

Implication of our technological species being first and early: The anthropic selection effect of our technological youth

AbstractIn the previous paper (Whitmire 2017; hereafter Paper I) arguments were given which suggest that the typical technological species is short-lived and that their demise coincides with the extinction of their planetary biosphere. This conclusion is based on two observations and one primary assumption. The observations are: (1) Our own technological species is the first such species to evolve on Earth and (2) we are early in the potential evolution of a technological species. The primary assumption is that we are a typical member (in age) of the reference class of all extant technological species in the universe. In this Letter, I thoroughly discuss the anthropic selection effect that the predicted lifetime of the typical technological species would most likely first be made when a technological species is young, thus guaranteeing a predicted short lifetime, regardless of the actual typical lifetime. I argue here that this selection effect is equivalent to narrowly redefining the reference class to be only early technological species and, although true, it is a logical tautology, correct by definition and does not invalidate the application of the Principle of Mediocrity assumption to the expanded reference class of all technological species, as was done in Paper I. Several simple analogies are given to illustrate this point.

An intelligent prognostic model for electrolytic capacitors health monitoring: A design of experiments approach

In the world of fast-growing technology, the electronic gadgets become obsolete with the invention of advanced technology. Reuse of electronic components is a philosophy now being applied to all manufacturing industries to achieve the goal of reuse technology. The accurate assessment of residual life is of great significance for reuse as well as the successful operation of the application. The prediction of failure before it occurs will, in turn, reduce the repairing cost and strengthen the reputation of the manufacturer in real-time market. This article reports a novel technique to explore the residual life of electrolytic capacitor and validates it, using accelerated life testing. The optimization and evaluation of proposed technology are accomplished using design of experiments methodology, that is, Taguchi’s approach to designing the experiments. Prediction of residual life of capacitor is done using regression and artificial neural networks technique. A decision support system is prepared using fuzzy logic, which monitors the current health status of the capacitor and directs the user accordingly. Using six environmental stress and electrical parameters, the actual lifetime of the electrolytic capacitor is accessed, which has been proven as a valid and accurate technique, exhibiting error rate of 2.99%.

Performance analysis of field-exposed multicrystalline silicon photovoltaic modules over 30 years

In this paper, we present the energy performance and degradation of multicrystalline silicon photovoltaic (PV) modules after a 30-year operation under hot and humid climatic conditions. A comprehensive analysis was conducted by visual inspection, electrical performance evaluation, and system final yield evaluation. Visual inspection revealed the yellowing and delamination of ethylene vinyl acetate (EVA), and cracks in the backsheet were found to be the most frequent defects. It is possible to perform a comparison between final and initial parameters. The average performance degradation over 30 years from 1986 to 2016 is 6.51%. The annual average degradation has been found to be only 0.22%/year. System output power and performance ratio (PR) were also analyzed, giving an annual PR of 69.72%. These results indicate that the actual lifetime of PV modules is significantly longer than the warranty periods of 25 years, and still with good performance and reliability.

Elevating the use of sugar-free chewing gum in Germany: cost saving and caries prevention

Objective: To analyse the lifetime monetary and health related effects of the consumption of sugar-free chewing gum.Material and methods: Using a Markov model we assumed that the German consumption of sugar-free chewing gum (111 gums/year) could be elevated to the level of Finland (202 gums/year). The calculation was based on a model patient representing the development of oral health from the age of 12 to 74 years and clinical data on the effectiveness of chewing sugar-free gum. Lifetime and yearly costs for the ‘Finland-scenario’ were determined and compared with the actual German expenses of the statutory health insurance companies for dental health.Results: The actual total lifetime expenditures of the statutory health insurance companies are 17,199.96€ per capita and would be 12,188.94€ in the scenario with elevated consumption of sugar-free chewing gum in Germany. Thus, 5011.02€ per capita could be saved in a lifetime and 80.82€ per year.Conclusions: On a national scale, the elevation of the consumption of sugar-free chewing gum in Germany to the level of Finland would lead to a considerable benefit for cost saving and oral health for the statutory health insurance companies.