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Laboratory and field tests were performed on sandy soils from six Pleistocene-age sites in the South Carolina coastal region to investigate the age-related resistance to liquefaction. Stress-controlled cyclic triaxial tests were used to determine the cyclic strength of soils with geologic ages ranging from approximately 59,000 to 1,200,000 years. Three sites have evidence of liquefaction in the form of sand blows that are 467 to 4,185 years old as determined from C14 dating of embedded organic material. The other three sites show no indications of liquefaction. Cyclic stress ratios ranging from 0.095 to 0.225 were applied to undisturbed and reconstituted soil specimens that were consolidated to an effective stress equal to 100 kPa. Soil specimen liquefaction was defined to occur when the excess pore pressure was equal to the confining effective stress. Estimates of the at-rest earth pressure coefficient were determined using measurements from the flat plate dilatometer and the cone penetrometer and were applied to the laboratory cyclic stress ratio occurring at the 15th loading cycle to determine the laboratory–field equivalent cyclic resistance ratio. The age-dependent liquefaction resistance was determined using additional data from the inner coastal plain of South Carolina and assessing the cyclic resistance ratios and their associated KDR ratios relative to the base data and applying one of the more recently developed liquefaction triggering model. It was found that the development of the aging factor should be independent of the liquefaction triggering model. Subsequently, the aging factor is developed using an offset that is constrained at 20 years and a KDR=1.0 , and was found to range from 1.00 at 20 years to 1.45 at 1.0 Ma for the original deposition ages of the soils and 1.00 at 20 years to 1.51 at 1.0 Ma for the data set consisting of the last disturbance and original deposition ages of the soils. [ABSTRACT FROM AUTHOR]

The use of blended cements enables the production of concretes with low embodied carbon and improved resistance to chloride penetration compared to general-purpose (GP) cement concrete. This paper reports the chloride diffusion characteristics in terms of the apparent diffusion coefficient (Da), surface chloride concentration (Cs), and corresponding aging factors (a and b) of low-carbon concrete (LCC) derived from up to 9-year long-term exposure of small reinforced concrete slabs in both laboratory-simulated and field marine tidal conditions. LCC with either 30% fly ash or 50% slag provides slightly to significantly lower 28-day compressive strength than GP cement concrete at the same water-binder ratio but significantly better resistance to chloride penetration. The longterm chloride profile necessary to determine the concrete cover where the chloride threshold is reached can be determined with the Da.t0, Cs.t0, and corresponding age factors a and b, where t0 is the 1-year time of exposure. The improved resistance to chloride penetration by the use of fly ash and slag as cement replacements was largely due to their intrinsic influence on the microstructure of the concrete. The results highlight that the difference in chloride penetration arises from the change in test methods, thus the importance of calibration when data obtained from laboratory concrete were used as inputs for service-life design. [ABSTRACT FROM AUTHOR]

Bone drilling is a routine operation in surgeries, such as neurosurgery and orthopedics. However, the excessive drilling temperature may cause severe thermal damage to the bone tissue. Therefore, the drilling temperature determination of bone tissue can reduce the harm caused by thermal damage. A time-varying temperature field simulation model of bone drilling was set up by ABAQUS software in this paper, based on the Johnson-Cook model. Then it was validated with experiments by drilling cortical bone of fresh bovine shaft of the femur. The relative error between the experimental values and the theoretical values within 7.67% showed a good consistency. Furthermore, the aging factor is also considered to evaluate the temperature field of bone drilling. The results showed that the drilling temperature near the bone-drill area increased significantly. The drilling temperature of cortical bone decreases sharply with the radial distance and exhibits a hysteresis lag in the axial distribution. The aging factor mainly affects the peak of drilling temperature. The peak of drilling temperature tends to increase with age. The peak drilling temperature in the elderly (70y) was up to 6.8% higher than that in the young (20y), indicating that the elderly is more prone to excessive drilling temperature. Therefore, special attention should be paid to the temperature control of elderly bone tissue.

During the long-term operation of high-voltage cross-linked polyethylene (XLPE) cables, the cable will gradually deteriorate under the effect of various aging factors. Thermal aging is one of the key factors directly related to the long-term operation reliability of the XLPE cables. In this paper, the thermal aging samples are prepared for PDC measurement. Based on the polymer trap theory and the extended Debye model, the shape of PDC curve, depolarization charge, parameters of the extended Debye model, aging factor (A), elongation at break retention rate (EB%) and their relationships under different thermal aging degrees are analyzed. The results show that the depolarization current curve and the depolarization charge can preliminarily judge the aging condition of the XLPE, but it is not accurate enough. $R_{3}$ and $\tau _{3}$ of the branch, with the largest time constant must be the most sensitive to cable aging. With the increase of aging degree, the A shows an upward trend, and has a nonlinear relationship with EB%. Under the aging temperature of 140 °C, after 15–25 days of aging, the A suggests the samples are in the moderate to severe aging stage, and the PDC test should be performed on carried out for the cables with that have been used for 21 years of operation to evaluate the insulation aging condition. The study reveals that the PDC-based parameters can be serviced as an effective tool for the aging condition prediction of XLPE cable insulation.

Increasing penetration of distributed generation (DG) is imminent in the new age of power distribution networks, which are smarter than the conventional grids. They enable the integration of DG into the power distribution network. This paper presents an assessment methodology for determining the optimal capacity and location of DG to ensure high reliability in a radial distribution network. The approach considers cost and the impact of aging on the DG and network topology for interconnection using genetic algorithm, which is a robust technique with wide solution space searchability and can potentially find global optima with fewer chances of getting trapped into local optima. A case study is simulated using three different scenarios to evaluate the impact of DG interconnection on the 13.8 kV power distribution network. The scenarios comprise of situations without any DG, with DG interconnection and optimization of DG interconnection. The case study shows that the penetration of DG increases the reliability of the distribution network while reducing the expected energy not supplied (EENS). Although, the difference between EENS in the optimized DG integration and non-optimized DG integration is not very significant in a small network, however, it becomes apparent with the aging curve that optimized allocation of DG possesses significant benefits.

Abstract Background At present, many laboratories and hospitals all over the world are attempting and exploring the clinical transformation of this tissue engineered bone graft (TEBG) strategy. Many successful cases of bone tissue engineering (BTE) repair were based on young individuals. But there are little studies about the effectiveness of TEBG strategy in physiological aged individuals. Methods In this research, we studied whether aging factor has influence on the skull repair effect of Fetal-TEBG, at the level of the large animal models. We used the fetal bone marrow stromal cells (Fetal-BMSCs) as the seed cells, combining the decalcified bone matrix (DBM) scaffolds, to repair the skull defects of the aged goats and the young goats. The repair effects on both aged goat and young goat were compared by Micro-CT and histology examination. Results The skull defects of the young goats could be repaired better than that of the aged goats after 6 months by Fetal-TEBG; In the aged goats, although not completely repaired, the defects repaired by Fetal-TEBG was better than that repaired by the Control DBM scaffold. Conclusions Aging factor has impact on the bone repair effect of Fetal-TEBG; and the BTE strategy is still efficacious even in the aged individuals. The improvement of the aged state may promote the repair effect of the BTE in the aged individuals.

Selective catalytic reduction (SCR) systems have been widely used to meet the emission regulations and two-cell SCR systems have shown the advantages of high NO $_{x}$ conversion efficiency and low NH $_{3}$ slip simultaneously. However, it is noteworthy that the catalyst performance of SCR device would degrade over the service time gradually. If the performance degrading is not well-compensated, the NO $_{x}$ conversion efficiency would reduce significantly. Different from detecting the aging issue in the laboratory, a practical method is to design an observer to estimate the aging factor online such that the urea injection can be modified accordingly. In this paper, we aim to construct an aging-factor observer for two-cell SCR systems. In order to reduce the algorithm computational load and guarantee the implementation performance, we propose a dual time-scale algorithm based on two-cell SCR model and unscented Kalman filter. There is a fast time scale and a slow time scale in the algorithm. Two simulation studies of constant aging factor and time-varying aging factor are investigated in the simulation environment of MATLAB/SIMULINK. The simulation results indicate that the proposed dual time-scale observer works well under different conditions and the calculational load is reduced significantly. [ABSTRACT FROM AUTHOR]

Foamed asphalt typically relies on water as a foaming agent because water becomes gaseous at elevated temperatures, generating numerous tiny bubbles in the asphalt and causing spontaneous foaming. In this study, ethanol was used as a potential alternative to water as a foaming agent. Ethanol is expected to be a physical blowing agent in the same manner as water, except it requires less energy to foam due to its 78 °C boiling point. This study compares the performance of water and ethanol as foaming agents through the measurements of rotational viscosity, the reduction in temperature during foaming, and volatile loss. The ethanol-foamed asphalt binders were prepared at 80 °C and 100 °C, while the water-foamed asphalt binders were prepared at 100 °C and 120 °C. Additionally, the rolling thin film oven (RTFO) was used to generate short-term aging of the foamed asphalt binders. A rotational viscometer was used to determine the viscosity of the asphalt binders at 80 °C, 100 °C, 120 °C, 140 °C, and 160 °C. Overall, ethanol can function in the same manner as water but requires less energy to foam. It is proven based on the smaller drop in temperature of the asphalt binder foamed using ethanol compared with that prepared with water. This is due to the lower latent heat capacity of ethanol, which requires less energy to vaporize compared with water. Through the rotational viscometer test, ethanol performs better in lowering the viscosity of asphalt binders, which is essential in allowing production processes at low temperatures, as well as a better workability and aggregate coating. Ethanol can be expelled from the foamed asphalt binders at a higher rate due to its lower boiling point and latent heat.

In this work it is established for the first time that the internal parameters of the electrical equivalent circuit of vanadium redox flow battery (VRFB) are variable not only with flow rate and stack current but also the state of charge (SOC) and operational cycle number. The dynamic internal circuit parameters are extracted by using the charge-discharge characteristics of a practical 1 kW 6 h VRFB system as input to the proposed model. The role of temperature on the VRFB internal parameters is also discussed. It is further demonstrated that the average error in estimation of VRFB stack voltage using dynamic parameters reduces by 28% (charging) and 14% (discharging) compared to that of using static internal parameters. The proposed model exhibits robustness and validity for large scale applications as evidenced by further extracting the internal parameters of a 125 kW 2 h VRFB system. Another significant contribution of this paper is the optimization of flow rate by considering both the stack internal power loss and pump power loss simultaneously to achieve optimal performance of the VRFB system. The proposed model involving dynamic parameter extraction and loss optimization is very useful for designing suitable battery management system (BMS) for interfacing VRFB with renewable energy sources. [ABSTRACT FROM AUTHOR]

Laser-induced breakdown spectroscopy (LIBS) is a method for atomic emission analysis that can be used to analyze the chemical composition of samples in the forensic investigations. The combined effort of extracting, analyzing, and restoring latent fingerprints at crime scenes is an important step toward successful arrests, and hence, the purpose of this research is to estimate the temporal sequence at which a fingerprint was imprinted from an individual. The difference in the laser spectrum from a latent fingerprint at times from 0 to 60 min after it was left was analyzed using LIBS and Raman spectroscopy, both of which require no chemical pre-treatment of the sample. We found that the signal intensity changes with time, 60 min after the imprint was made for the wavelengths of CN band, fatty acid, amino acid, and oil components. Based on these preliminary findings, the chemometric analysis was performed on the spectrum data obtained from 60 min of exposure time and the time-sequenced overlapping fingerprints were distinguished, which were imprinted at intervals of 10, 20, 30, and 40 min using SIMCA and PLS-DA classification methods. [ABSTRACT FROM AUTHOR]

With the increasing of service years, failure happens more frequently than before, which is consistent with the failure rate of equipment during the wear-out life period. On the base of continuous time Markov model for multistate elements during the useful life period, aging factor is introduced to establish a non-homogenous continuous time Markov model during the wear-out life period. To obtain the reliability of a multi-state element, universal generating function is applied to combine its performance levels and probability functions. Through a combination operator determined by series-parallel logic relations, universal generating function of a multi-state system can be obtained. At last, a compressor of an engine is taken for example. The reliability of the system and its elements considering aging factor are relatively lower than that during the useful life period. And to maintain a reliability level at 80% under the demand of 50%, two days will be reduced from the planned maintenance cycle. [ABSTRACT FROM AUTHOR]

Evolution strategies traditionally employ the comma or the plus scheme for selection. The concept of intermediate selection schemes was introduced in 1995, in which individuals may survive limited but more than one generation; however, research on this topic has remained dormant. During the recent decade, the comma scheme has emerged as the preferred choice at least for continuous optimization. The objective of this article is to explore pros and cons of both extreme as well as intermediate selection schemes in coping with different types of difficulties that may arise in global optimization of multimodal functions. A specific test suite is developed which allows for studying different selection schemes when facing particular challenges. A modified variant of the previously proposed intermediate selection scheme in which fitness of survivors iteratively degrades is proposed. The degrading rate is controlled by a strategy parameter, called the aging factor. The resulting algorithm is tested on the whole suite using different values of the aging factor. The comparison of results reveals the drastic problem dependence of the optimal aging factor; however, when all situations are considered, an intermediate selection scheme significantly outperforms both the comma and the plus schemes. [ABSTRACT FROM AUTHOR]

The nozzle-head intersection of a nuclear steam generator (SG) has gained great attention due to its special location and prone to cracks. For the purpose of estimating and ensuring the integrity of the SG structure, the fracture evaluation of nozzle-head intersection after a period of operation needs to be analyzed under a variety of loading conditions. In this paper, stress intensity factors (SIFs) of external surface cracks postulated at the nozzle-head intersection of a SG subjected to pressure, bending, and thermal loadings are evaluated using finite element method. Comparing to the SIFs of cracked pipe described in the RSE-M code, it is found that SIF calculation method of cracked pipe can be conservatively applied to the external surface cracks at the nozzle-head intersection of the SG. Using the conservative SIF solution, the fatigue crack growth and fracture assessment of the postulated cracks are evaluated according to the RSE-M code considering the material aging. Finally, the critical crack size and allowable initial crack size for the life of 40 years are given for the nozzle-head intersection of the SG. • The SIF solution of pipe in RSE-M can be conservatively used to the external surface cracks at the nozzle-head intersection. • The initial size of a *2 c = 10*30 mm will be unsafefor 40 years life with RT NDT = 50 °C using the conservative method. • The conservative critical crack size and allowable initial crack size are given for the life of 40 years with various RT NDT. [ABSTRACT FROM AUTHOR]

This paper presents a methodology to estimate the effects of heating and lifetime in Low Voltage conductors (LV) due to the presence of stationary power quality disturbances. Conductor overheating and cable insulation accelerated aging can be caused by temporary increases in the RMS values of the voltages and currents due to stationary disturbances. Waveform distortion, unbalance and phase displacements can be considered among the stationary disturbances. For disturbances with short duration, there are no significant reductions in the insulation lifetime, but disturbances acting for long time periods will cause cumulative and detrimental effects. Currently valid models for insulation aging are employed; the expected power quality disturbance levels are extracted from power quality databases. A discussion about the effects on insulation lifetime is presented. [ABSTRACT FROM AUTHOR]

Although a budding yeast culture can be propagated eternally, individual yeast cells age and eventually die. The detailed knowledge of this unicellular eukaryotic species as well as the powerful tools developed to study its physiology makes budding yeast an ideal model organism to study the mechanisms involved in aging. Considering both detrimental and positive aspects of age, we review changes occurring during aging both at the whole-cell level and at the intracellular level. The possible mechanisms allowing old cells to produce rejuvenated progeny are described in terms of accumulation and inheritance of aging factors. Based on the dynamic changes associated with age, we distinguish different stages of age: early age, during which changes do not impair cell growth; intermediate age, during which aging factors start to accumulate; and late age, which corresponds to the last divisions before death. For each aging factor, we examine its asymmetric segregation and whether it plays a causal role in aging. Using the example of caloric restriction, we describe how the aging process can be modulated at different levels and how changes in different organelles might interplay with each other. Finally, we discuss the beneficial aspects that might be associated with age. [ABSTRACT FROM AUTHOR]

It is feasible to survey actual performances of degradation for 550 kV transformers by a preventive test. By means of condition monitoring, it is possible to forecast the transformers? lifetime. Such data, particularly in an application where few or no failures are expected, can provide considerably more information than the failure-time data from a traditional accelerated life test. In order to develop a life model for 550 kV transformers, the effect of temperature on a thermal aging factor is taken into account since it is associated with various degradation performances of a transformer. With the aid of measurement, the thermal aging factor is analysed by the probability plot and the least-squares fitting of data so that all unknown parameters of the life model are estimated. The method will extrapolate the lifetime of large power transformers from a preventive test in practice. [ABSTRACT FROM PUBLISHER]

Highlights: [•] The paper addresses the effects of curing regimes, compositions and exposure time on the resistivity of concrete. [•] The aging factor of the different concrete mixes was calculated from the resistivity values measured. [•] The aging factors for concrete mixes with FA and with FA+SF was found not to be constant with time. [•] It is inferred from the above that the aging factor for diffusivity for these types of mixes is not constant with time. [•] Time dependent aging factors comprised of an initial phase with time-dependent values followed by an almost constant value. [ABSTRACT FROM AUTHOR]

Six typical China soils with different properties were selected and added with seven concentrations of ZnCl2 to study the effects of different aging time (14, 90, 180, 360, and 540 days) on the form transformation and eco-toxicity threshold (ECx) of added Zn in the soils, with the main affecting factors analyzed. The results indicated that with the increase of aging time, the fraction of 0.01 mol x L(-1) CaCl2-extracted Zn in the soils decreased sharply initially, then slowed down, and reached the dynamic balance after 540 d incubation. The eco-toxicity thresholds (ECx, x = 10, 50) of Zn to bok choy increased significantly with aging time (P < 0.05), which implied the marked decrease of the phyto-toxicity of Zn. The measured aging factors AF10 and AF50 of Zn ranged from 1.077-1.743 and 1.174-1.441, respectively, and increased with aging time. The balanced concentration of Zn in the soils was significantly negatively correlated with soil pH, CEC, and organic carbon (Org-C) content, and soil pH was the most important controlling factor, followed by CEC and Org-C. It took shorter time to reach Zn balance in the soils with higher pH. The prediction model of the ECx of Zn was developed based on the aging factors and the main soil properties, and could be well validated by the measured ECx under field condition. This study would provide theoretical basis for the normalization of the eco-toxicity thresholds of added Zn in different soils and the formulation of the environmental criterion of Zn in China soils. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a hybrid prognosis approach of age-dependent hidden Markov model (HMM) and grey model (GM) for prediction of engineering asset health. Age-dependent HMM allows modeling the time duration of the hidden states and therefore is capable of prognosis. The estimated state duration probability distributions can be used to predict the remaining useful life (RUL) of the assets. The previous HMM based prognosis method assumed that the transition probabilities are only state-dependent. That is, the probability of making transition to a less healthy state does not increase with the age. In the proposed method, in order to characterize a deteriorating asset, an aging factor that discounts the probabilities of staying at current state while increasing the probabilities of transitions to less healthy states will be introduced. After the estimation of the aging factor, a grey model is used to compute the expected residual life (ERL) by redefining the hazard rate. With the asset health prognosis, the behavior of the asset condition can be predicted. [Copyright &y& Elsevier]

Abstract: Health monitoring and prognostics of equipment is a basic requirement for condition-based maintenance (CBM) in many application domains. This paper presents an age-dependent hidden semi-Markov model (HSMM) based prognosis method to predict equipment health. By using hazard function (h.f.), CBM is based on a failure rate which is a function of both the equipment age and the equipment conditions. The state values of the equipment condition considered in CBM, however, are limited to those stochastically increasing over time and those having non-decreasing effect on the hazard rate. The previous HSMM based prognosis algorithm assumed that the transition probabilities are only state-dependent, which means that the probability of making transition to a less healthy state does not increase with the age. In the proposed method, in order to characterize the deterioration of equipment, three types of aging factors that discount the probabilities of staying at current state while increasing the probabilities of transitions to less healthy states are integrated into the HSMM. With an iteration algorithm, the original transition matrix obtained from the HSMM can be renewed with aging factors. To predict the remaining useful life (RUL) of the equipment, hazard rate is introduced to combine with the health-state transition matrix. With the classification information obtained from the HSMM, which provides the current health state of the equipment, the new RUL computation algorithm could be applied for the equipment prognostics. The performances of the HSMMs with aging factors are compared by using historical data colleted from hydraulic pumps through a case study. [Copyright &y& Elsevier]

Aging is a complex phenomenon of functional decay in a biological organism. Although the effects of aging are readily recognizable in a wide range of organisms, the cause(s) of aging are ill defined and poorly understood. Experimental methods on model organisms have driven significant insight into aging as a process, but have not provided a complete model of aging. Computational biology offers a unique opportunity to resolve this gap in our knowledge by generating extensive and testable models that can help us understand the fundamental nature of aging, identify the presence and characteristics of unaccounted aging factor(s), demonstrate the mechanics of particular factor(s) in driving aging, and understand the secondary effects of aging on biological function. In this review, we will address each of the above roles for computational biology in aging research. Concurrently, we will explore the different applications of computational biology to aging in single-celled versus multicellular organisms. Given the long history of computational biogerontological research on lower eukaryotes, we emphasize the key future goals of gradually integrating prior models into a holistic map of aging and translating successful models to higher-complexity organisms. [ABSTRACT FROM AUTHOR]