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Polymer blends have been widely used as tribological materials for replacements of traditional metals and ceramics. Polymer blends consist of the reinforced phase, the matrix phase and interfaces between reinforced and matrix phase. Although the interface structure of polymer blends is usually small in size, it is one of the key factors for deciding the physical and tribological properties of polymer blends. Thus, this review highlights the most recent trends in the field of influences of interface structure on tribological properties of engineering polymer blends. Emphasis is given to the improvement methods of interfacial compatibility of polymer blends and the behavior variation of interface structure during friction process.

Purpose This paper aims to investigate the thermal oxidation behavior of trimethylolpropane trioleate (TMPTO) base oil when exposed to Fe surfaces. Design/methodology/approach Samples of TMPTO bulk oil were placed in Fe vessels and heated in an oven to accelerate the oxidation at different time intervals, while others were placed in glass vessels and used as experimental controls. Subsequently, the physicochemical properties of the oxidized TMPTOs, including the kinematic viscosity and acid value, were measured and a structural analysis was conducted using the Raman and Fourier transform infrared (FTIR) techniques. Findings The results demonstrate that the TMPTO bulk oil exhibited an exponential increase in the kinematic viscosity along with the increasing acid value over the oxidation time. The Fe surface significantly increased the kinematic viscosity of TMPTO, while only mildly impacting its acid value compared with the experimental controls. The structural analysis results of the TMPTO suggest that the C = C and = C-H bonds were the vulnerable sites. Furthermore, the results suggest that the Fe surface evidently accelerates the chemical reactions of the C = C and the = C-H bonds, and less alcohols and more carbonyl products were identified in the oil samples that were heated in the Fe vessels. Originality/value The results demonstrate that the Fe surfaces affected the oxidation behavior of the TMPTO base oil, and an interaction mechanism between the Fe and the TMPTO is developed.

To prepare a high-performance anti-friction and wear-resistant composite material for friction sub-components in marine equipment, a modification was made by adding different amounts sodium polyacrylate (PAANa) to ultra-high molecular weight polyethylene (UHMWPE). PAANa/UHMWPE-blended powders were prepared at individual weight ratios of 0/100, 3/97, 5/95, 8/92, 13/87, and 18/82 with hot-press molding. In seawater, experiments of PAANa/UHMWPE composites sliding against GCr15 have been conducted with a ball-on-disk configuration in this study. The results show the surface hardness of composites was almost the same with the increase in PAANa proportion, however, the friction coefficient and wear scars of PAANa/UHMWPE composites/GCr15 sliding pairs firstly decrease and then increase. Scanning electron microscopy (SEM) results show that wear mechanism of the composites is mainly plastic deformation and spalling. The composites with PAANa content of 3% and 5% achieves better tribological properties than the pure UHMWPE material.

Purpose The purpose of this paper is to synthesize amines/phenolic antioxidants by a new method and to characterize the influence of antioxidants on thermo-oxidative degradation in trimethylolpropane trioleate (TMPTO) base oil. Design/methodology/approach The molecule structures of antioxidants and lubricants were confirmed using Fourier transform infrared spectroscopy (FTIR). The oxidative stability of antioxidants and lubricants was evaluated by pressurized differential scanning calorimetry (PDSC). Findings These findings suggested that butyl-octyl-diphenylamine has obvious advantage on kinematic viscosity inhibition, and amine-phenol combination antioxidant has a slightly better suppression of total acid in TMPTO under thermal oxidation at 200°C for 96 h. The FTIR characterizations showed that all antioxidants could protect the basic structure of TMPTO in the early stage of thermal degradation. Originality/value Under the action of butyl-octyl-diphenylamine, the dehydrogenation of TMPTO is easily met with the alkenyl hydrogen = C–H bond in the unsaturated C = C. Meanwhile, as octadecyl 3-(3, 5-di-tert-butyl-4-hydroxyphenyl)propionate protects TMPTO, the unsaturated C = C bond in the base oil molecule easily breaks down during transition.

This study attempts to use ionic liquids (ILs) as oil additives to lubricate oxygen-diffusion (OD) case-hardened titanium for improved friction and wear behavior. Four oil-soluble ILs were used as additives in a base oil for boundary lubrication of an OD-treated Ti-6Al-4V surface sliding against a bearing steel ball. The ILs improved the friction behavior to various extents and the two phosphate ILs clearly outperformed the conventional ZDDP. Unlike ZDDP that adversely caused a higher material loss, ILs exhibited excellent wear protection suggesting good material-chemical compatibility. Particularly, the carboxylate IL protected the OD-Ti surface from any measurable wear. The morphology and chemical composition of the worn surfaces and tribofilms were examined to gain insights of the anti-wear mechanism.

Purpose This paper aims to investigate the thermal oxidation characteristics of the unsaturated bonds (C=C) of trimethylolpropane trioleate (TMPTO) and to reveal the high temperature oxidation decay mechanism of unsaturated esters and the nature of the anti-oxidation properties of the additives. Design/methodology/approach Using a DXR laser microscopic Raman spectrometer and Linkam FTIR600 temperature control platform, the isothermal oxidation experiments of TMPTO with or without 1.0 wt. % of different antioxidants were performed. Findings The results indicated that the Raman peaks of =C-H, C=C and -CH2- weaken gradually with prolonged oxidation time, and the corresponding Raman intensities drop rapidly at higher temperatures. The aromatic amine antioxidant can decrease the attenuation of peak intensity, as it significantly reduces the rate constant of C=C thermal oxidation. The hindered phenolic antioxidant has a protective effect during the early stages of oxidation (induction period), but it may accelerate the oxidation of C=C afterwards. Originality/value Research on the structure changes of synthetic esters during oxidation by Raman spectroscopy will be of great importance in promoting the use of Raman spectroscopy to analyze the oxidation of lubricants.

Recently, unprecedented extreme drought has appeared around the world. As the most direct signal of drought, evapotranspiration deserves a more systematic and comprehensive study. Further depicting their divergence of potential (ETp) and actual evapotranspiration (ETa) will help to explore the limitation of evapotranspiration. In this paper, the multi-source remote sensing datasets from the Climate Research Unit (CRU), Gravity Recovery and Climate Experiment (GRACE) and its follow-on experiment (GRACE-FO), the Global Land Data Assimilation System (GLDAS), and the Moderate Resolution Imaging Spectroradiometer (MODIS) during 2002 to 2020 were employed to explore the influence of meteorological, hydrological and botanical factors on ETp, ETa and their divergence – reduction of evapotranspiration (Er) which represents regional vegetation and water limitations. According to the Pearson correlation analysis and the Boruta Algorithm based on Random Forest, the temperature is the first decisive promoter of evapotranspiration in the most area while the sparse vegetation is the primary or second determinant limiting the evapotranspiration in 61.84% of the world. In addition, the Coupled Model Intercomparison Project (CMIP6) data from 2030 to 2090 and the support vector machine regression (SVMR) model were applied to predict the future global ETp, ETa and Er on the pixel scale. Predicted results of the model considering the water change not only can highly improve the model performance (with higher R2), but also can simulate the drought in Europe and the more intense ETa in Africa. Thus, Er proposed in this study provide a good reference for regional ETa except for ETp. The future evapotranspiration value derived by introducing the water storage changes into the machine learning model in this study is also valuable for climate change adaptation and drought warning.

The condition of the motor oil in civilian cars is difficult to monitor; hence, we propose a method to evaluate the degree of degradation of motor oil using an on-board diagnostic (OBD) system. Three civilian cars and four motor oils (containing mineral oils and synthetic oils) were subjected to five groups of road tests under urban traffic and high-way conditions. The operation information, oil service time, mileage, engine operation time, idle time of the engine, and number of start-ups of the engine were obtained using the proposed OBD system. Physiochemical properties and changes in the components of motor oils during road tests were analyzed in laboratory. The theoretical model of the comprehensive indicators of driving parameters and oil properties were established. The proposed method was successfully applied to different cars, motor oils, and operating conditions in road tests. All the theoretical models had high accuracy and precision. Herein, we provide a method to monitor the oil condition with real-time driving parameters and provide a reference for end users to change their motor oil reasonably.

In this study, it is tried to establish a theoretical model based on oil oxidation stability to evaluate the motor oil life. Five civilian cars and five motor oils were taken to eight road tests. The road tests contained two experiments taken in two test cars with the same car model, synthetic motor oil and test time, and three experiments taken in one test car with the same mineral oil to study the reliability and repeatability of the proposed method. The change characteristics of oxidation onset temperature, total acid number, and kinematic viscosity of test oils were analyzed. A theoretical model was established with the oxidation onset temperature and column chromatography method. The results showed the established theoretical model has the potential to quantitatively determine the remaining service time and operation mileage of the test oils with high accuracy and reliability. The test synthetic oils are able to operate approximately 11,000–13,000 km in 534–686 days in the typical urban traffic condition of China. The test mineral oils are capable of operating approximately 8200 km with 40 km/day or capable of operating 5723 km in 410 days. The proposed approach can provide some reference for end-users to drain their motor oil reasonably.

Purpose This paper aims to investigate the tribological behavior and online infrared spectra of three types of lubricating oils containing dinonyl diphenylamine (DNDA) antioxidant, which are mineral oil (MO), poly alpha olefin (PAO) and trimethylolpropane trioleate (TMPTO), during the friction process at high temperature (temperature rising at first and isothermal holding afterwards). Design/methodology/approach A platform of low speed four-ball tribometer equipped with a temperature controller combined with infrared spectrometer was established. MO, PAO and TMPTO base oils were mixed with 1.0 Wt.% DNDA antioxidant, coded as MOa, PAOa and TMPTOa in sequence. The friction coefficient and online infrared spectra of the oils were tested during the friction process of temperature rising at first and isothermal holding afterwards, and the wear tracks of the upper balls were measured using a confocal scanning optical microscope. Findings The results indicated that the DNDA antioxidant was depleted to reduce the generation of alcohols and carbonyl products, and the depletion rate of DNDA followed the sequence of MOa > PAOa > TMPTOa. In the temperature rising friction process, the critical transition of friction coefficient was confirmed. The addition of DNDA antioxidant reduced the temperature of the oils at the critical transition of friction coefficient, and the temperature followed the sequence of TMPTOa > PAOa > MOa. After the critical transition, the friction coefficient was first increased and then declined to a steady value; the friction coefficient of MOa increased and declined first, followed by PAOa and TMPTOa. In the steady stage of friction, there was no obvious effect of DNDA on the friction coefficient of the oils. Moreover, DNDA enhanced the wear properties of MOa and PAOa; no obvious improvement was revealed for the wear property of TMPTOa. Originality/value The established platform of low speed four-ball tribometer combined with infrared spectrometer successfully realized online testing of the structure changes of lubricating oil during high temperature friction, which can give some reference on the oxidation and friction researches of lubricating oil.

Although the reason is not clear, mileage is commonly recommended as an indicator to evaluate the oil drain interval of a car. This paper tries to investigate whether the mileage is the most suitable indicator to evaluate the oil drain interval based on scientific experiments and data analysis method. Three civilian cars and motor oils (contained mineral oil, semisynthetic oil, and synthetic oil) were subjected to road tests under urban traffic condition. The real-time driving parameters comprising speed, mileage, idle time, engine operation time, and number of starts were obtained by on-board diagnostic system. Synchronous oil samples were collected about every 30 days. The physicochemical properties and component changes of experimental oils were analyzed in laboratory. The effects of driving parameters on oil properties were studied with the improved grey relational analysis method. The results show that the influencing factors of driving parameters on motor oil degradation were different in different experimental cars. The influence of mileage on oil degradation was not obvious. The idle time of engine, engine operation time, and number of starts were the three most significantly influential factors on oil deterioration after comprehensive analysis of the three experimental cars.

Polymeric materials have a short history of employment as tribological materials in liquid-propellant rocket engines, but they hold promise for the future. Even those polymer materials served already in rocket engines are based on inaccurate or unsubstantiated data. For these reasons, aging tests of polyformaldehyde (POM) and ultra-high molecular weight polyethylene (UHMWPE) in rocket-grade hydrogen peroxide solution were carried out, and then tribological experiments were conducted in this work. The objective is to provide a sound foundation of further selecting or developing polymeric materials for tribological application in rocket-grade hydrogen peroxide environment. The micrographs of polymer specimen with various aging time indicate that POM has poorer aging resistance in hydrogen peroxide solution than UHMWPE. A new absorption peak assigned to hydroxyl group appears on FTIR spectra of POM after aging test due to the oxidation by hydrogen peroxide solution. It is deduced from thermoanalysis that the amorphous regions is the main area influenced by hydrogen peroxide solution. Results of tribological experiments display that the friction coefficients of both POM and UHMWPE decrease with the increase in aging time from 0 to 240 h. However, the wear rates of POM and UHMWPE present different trends with the increase of aging time; the wear rate of POM decreases, whereas the wear rate of UHMWPE increases.

Molecular models were established to predict the miscibility of polyimide/polythene mixing systems and the enhancing effects of compatibilizer addition of maleic anhydride grafted polythene (MAH-g-PE). Molecular dynamics simulations were applied to investigate radial distribution functions and Flory-Huggins parameters of the mixing systems. Results show that polyimide/polythene is miscible to a certain degree, and the miscibility gets better after adding MAH-g-PE. Dissipative particle dynamics (DPD) simulations display that micro-phase separation occurs in the polyimide/polythene mixing systems, however, effective interfaces appear between polyimide and polythene phases after adding MAH-g-PE. The results of molecular mechanics simulations indicate that the ability of mixing systems to resist stretch, compression and shear deformation increases after adding MAH-g-PE. This work offers a promising technique to predict miscibility properties for polyimide/polythene system prior to actual production and attempt to find a suitable compatibilizer for that system.

Experiments of polyimide/UHMWPE composites sliding against tin-bronze counterfaces under seawater condition have been conducted with a pin-on-disk configuration in this study, aiming at developing matched materials for the bushing of seawater lubricated bearing. As the results, the friction efficient of composite/bronze sliding pairs decreases with the increase in polyimide proportion; however, the wear rate and optimum surface roughness of polyimide/UHMWPE composites firstly decrease and then increase. Mesoscale simulation results show that phase segregation has important effects on wear mechanism. The composite with 50 wt.% polyimide has the lowest wear rate and optimum surface roughness.

Polyimide-modified ultrahigh molecular weight polyethylene (UHMWPE) composites were fabricated by hot-press molding process. Mesoscopic morphologies of polyimide/UHMWPE blending systems show high c...

Baiyangdian Lake, the largest freshwater body in Northern China, is facing water shortage and eutrophication problems that threaten the lake&rsquo, s ecosystem. Environmental water releases from upstream reservoirs to the lake are important measures to provide the freshwater resources demanded by the lake ecosystem. However, knowledge is limited regarding the influences of such water allocations on the water quality of the upstream rivers that receive the reservoir water and transport it into Baiyangdian Lake. To improve our understanding of possible influences of environmental water releases from upstream reservoirs, the spatial variation of water quality in rivers upstream of the lake during environmental water release periods from reservoirs was explored in this study. Water samples were collected along the two routes of water allocation: the WangKuai reservoir route (WKR) and the XiDaYang reservoir route (XDYR) and water quality parameters related to organic pollutants, nitrogen and phosphorus were analyzed. In the WKR, the pollutant concentrations generally increased from upstream to downstream. Chemical oxygen demand, total nitrogen, and total phosphorous at the sampling site closest to Baiyangdian Lake could not meet the water quality target of the water function zone. For the XDYR, pollutant concentrations peaked downstream of the major urban region of Baoding city and then decreased or remained at a similar level further downstream and only the total nitrogen concentration was worse than the target. The dissimilarities in spatial variation patterns of water quality may be caused by the different spatial distribution of wastewater treatment plants in the two routes.

Sustainable management strategies for water resources rely on accurate knowledge about the dynamics of hydrological processes, especially in drylands, where freshwater is the limiting factor for the development of human society and ecosystems. The populated Loess Plateau (LP) in North China is a typical semi-arid region where competition for water between people and nature is worth noting because of afforestation promoted by the Grain to Green Program. In this study, changes in key components of terrestrial water storage (TWS) in the LP were explored using a multi-satellite approach, including Gravity Recovery and Climate Experiment (GRACE) observations and Earth observations of precipitation, evapotranspiration and soil moisture. By integrating data on human water use from different sources with satellite observations, we were able to examine the mechanisms driving these changes. The results demonstrated that, according to an evaluation based on reproducing TWS computed from the regional water balance in the LP, the mascon solution of the Center for Space Research (CSR) at University of Texas at Austin performed best out of the commonly used GRACE products. Regional TWS derived from the CSR mascon solution in the LP decreased significantly for the period 2003-2015. Significant decreases were also detected for regional ground water storage (GWS) estimated by decomposing the GRACE TWS using multi-sources remote sensing data. GWS made the greatest contribution to the changes in TWS. Increased plant transpiration was one reason for the decreasing trend of GWS. Because changes in precipitation, soil moisture and water consumed by irrigation were minor at regional scales, we concluded that the increase of transpiration is driven by deep-rooted trees planted, which use the part of precipitation that previously recharged groundwater. The findings from this study are valuable for water resource management and ecological restoration in semi-arid regions with high populations. (C) 2019 Elsevier B.V. All rights reserved.

Long developing period and cumbersome evaluation for the lubricating materials performance seriously jeopardize the successful development and application of any database system in tribological field. Such major setback can be solved effectively by implementing approaches with high throughput calculation. However, it often involves with vast number of output files, which are computed on the basis of first principle computation, having different data format from that of their experimental counterparts. Commonly, the input, storage and management of first principle calculation files and their individually test counterparts, implementing fast query and display in the database, adding to the use of physical parameters, as predicted with the performance estimated by first principle approach, may solve such setbacks. Investigation is thus performed for establishing database website specifically for lubricating materials, which satisfies both data: (i) as calculated on the basis of first principles and (ii) as obtained by practical experiment. It further explores preliminarily the likely relationship between calculated physical parameters of lubricating oil and its respectively tribological and anti-oxidative performance as predicted by lubricant machine learning model. Success of the method facilitates in instructing the obtainment of optimal design, preparation and application for any new lubricating material so that accomplishment of high performance is possible.

Baiyangdian Lake, the largest shallow lake in the North China Plain, is essential for maintaining ecosystem functioning in this highly populated region. To explore the influences of human activities on the lake’s water quality, an improved Water Quality Index (WQI) method and multivariate statistical techniques were adopted to assess the temporal and spatial variations of the lake’s water quality and explore the dominant factors of these variations. Datasets for 11 water quality parameters from six monitoring stations were used to evaluate the period spanning from 2006 to 2016. Assessment of the annual WQI showed that the water quality of the lake has generally improved over the past decade. Cluster analysis divided 12 months into the dry and wet periods and the six monitoring stations into those located in the western and eastern parts of the lake. Discriminant analysis demonstrated that with only two parameters (water temperature and fluoride) and six parameters (dissolved oxygen, ammonia nitrogen, total nitrogen, total phosphorus, anionic surfactant, and fecal coliform), 96.0% and 93.8% of the water quality data can be classified into the correct spatial and temporal clusters, respectively. For the principal component analysis and factor analysis, the varifactors detected for the two temporal clusters were similar, and varifactors related to pollution explained more variance in the water quality variation than the ones representing natural factors. For the two spatial clusters, the varifactors were different, indicating they are influenced by different types of anthropogenic activities. Correlation analysis between lake water level and water quality indicated that environmental water allocation to the lake generally improve water quality. These findings provide a more thorough understanding of driving mechanism of water quality and may be helpful for making environmental management decisions in Baiyangdian Lake and other large, shallow lakes in highly populated dryland regions.

In this study, a multi-phenol antioxidant 2,4,6-tris(3,5-di-tert-butyl-4-hydroxyphenylthio)-1,3,5-triazine (THA) was synthesized. The thermal stability of THA and its oxidation resistance in triisodecyl trimellitate (TDTM) ester oil were evaluated compared with several commercial phenol antioxidants. Further investigations on the oxidation resistance and tribological performance of THA with dinonyl diphenylamine (Am) and ZDDP composites were conducted to determine the additive compatibility in TDTM. The results indicate that the THA possesses higher thermal stability and more effectiveness of oxidation resistance than the commercial phenol antioxidants. The synergistic anti-oxidative effect is confirmed for the THA/Am mixtures in TDTM ester oil. However, the addition of THA alone or THA/Am mixtures shows no improvement for the tribological performance of TDTM. Excitingly, the THA/Am/ZDDP composite additives not only have the superior oxidation resistance, but exhibit the effective friction and wear reductions. It suggests the excellent compatibility of the synthesized THA antioxidant with Am and ZDDP additives in TDTM ester oil.

Available model of 3D-quantitative structure-activity relationship (3D-QSAR, the method of TopomerCoMFA) has been used to establish relationship between antioxidant performances of lubricating oil (trimethylolpropane trioleate, TMPTO) with 15 kinds of amine additives and its molecular structure. Correlation coefficient of the cross-validation (include internal q 2 and external q pred 2 ) and conventional correlation coefficient showed the model to be both stable and good predictive. The electron-donating group and larger steric effects group are adopted at the para-position or meta-position of amido on the benzene ring, and suitably decreasing the branch chain near the para-position, these indicate that the antioxidant performance of amine additives can be enhanced. The results not only can help us understanding the rule of antioxidant performance, but also providing guidance(s) to predict antioxidant performance of existing amine additives and to design or modify new amine additives in lubricating oil.

The objective of this paper is to integrate stochastic approaches in the life cycle cost analysis of sewer pipes. It is generally accepted that costs are of the greatest interest to the decision maker. The selection procedure primarily depends on the material availability as well as empirical information. Afterward costs in the maintenance phase lack consideration, which is mainly constrained by data availability and analysis techniques. This study focuses on the rigid pipe and evaluates the comparable application of reinforced concrete pipe (RCP), non-reinforced concrete pipe (NRCP), and vitrified clay pipe (VCP) in sewer systems. The life cycle cost analysis is performed throughout the material manufacturing, construction and maintenance phases. Particularly, the Markov chain model is used to predict systems' conditions that are used as a guidance for management in the maintenance phase. Under a given strategy, the cost estimate is extended to the steady state, providing a new cost comparison perspective. In addition, methods to evaluate the model uncertainty are also presented. Applying the bootstrapping approach, the analysis reveals that the Markov chains model demonstrates decent robustness. In the case study of a 24-in. pipe application, results show that NRCP demands the least initial building cost, while RCP is more cost effective considering longer service life time. Cost comparison and specific examples are also presented to demonstrate practical applications. This integrated approach allows decision-makers and stakeholders to understand and compare economic costs during alternative selections in practice. The methodology developed may also be applied in the life cycle analysis of other critical infrastructure systems.

PI/UHMWPE blends are going to be used as the bush material of sliding bearings under high speed dry condition in one project. Prior to the fabrication of these bearings, the tribological properties PI/UHMWPE blends with various component ratio under the specific service condition was investigated by using a pin-on-disk tribometer. The results revealed that the compression modulus of PI/UHMWPE blends increases with the increase in PI content. Furthermore, the coefficient of friction and wear rate decrease firstly and then increase slightly with the increase in PI content, both of which reach the minimum value when PI content is 70%. The analyses of transfer membrane indicate that both of UHMWPE and PI can transfer to the metal counterface, while the increase of PI content is more conducive to the increase of transfer membrane.

The Great Lakes watershed is home to over 40 million people (Canadian and U.S.) who depend on a healthy Great Lakes ecosystem for economic, societal, and personal vitality. The challenge to policymakers and the public is to balance economic benefits with the need to conserve and replenish regional natural resources in a manner that ensures long term prosperity. Nine critical broad-spectrum stressors of ecological services are identified, which include pollution and contamination, agricultural erosion, non-native species, degraded recreational resources, loss of wetlands habitat, climate change, risk of clean water shortage, vanishing sand dunes, and population overcrowding. Many of these stressors overlap. For example, mining activities alone can create stress in at least five of these categories. The focus groups were conducted to examine the public’s awareness of, concern with, and willingness to expend resources on these stressors. This helped generate a grouping of stressors that the public is especially concerned about, those they care little about, and everything else in between. Stressors that the respondents have direct contact with tend to be the most important to them. This approach of using focus groups is a critical first step in helping natural resource managers such as Trustees and NGOs understand what subsequent steps to take and develop policy measures that are of most interest and value to the public. Skipping or glossing over this key first task could lead to difficulties with respect to survey design and model development in a non-market valuation study. The focus group results show that concern related to pollution and contamination is much higher than for any of the others. It is thus clear that outreach programs may be necessary to educate the public about the severity of some low-ranked stressors including climate change.

The objective of this research is to develop and implement a stochastic method that can be applied to characterize random failures in critical infrastructure systems. We particularly focus on blockage failures in sewer systems that are nonmechanistic and result from combination of external factors, including deterioration in condition. The method was implemented using a data set consisting of sewer blockage failure records from a small municipality. Statistical tests were conducted to: (1) ensure that available data set is representative and (2) estimate parameters of distributions that appropriately characterize failure event arrival pattern. Failure trends were also analyzed to identify the influence of local factors and justify the choice of the distributions used to characterize interarrival times. Based on the analysis, we explored the challenges in developing a reliability model across the life cycle of a sewer system. In addition, specific examples were also presented to illustrate how the method can be applied to support system maintenance decisions. The results of this study illustrate how the memoryless property can be assumed in analyzing failure events, while explicitly considering context specific influences. Finally, the methods described in this paper are extensible and can be applied generally to analyzing random failures in other infrastructure systems as well.

A system dynamics method to assess carrying capacity of a defined natural environment is presented. The proposed method seeks to relate per capita resource usage to ranges of population and per capita consumption beyond which the system is not viable relative to population dependent resource constraints. It provides a platform to investigate system behavior through system dynamics simulations where populations change, natural resources decay due to stressor impacts, and feedback occurs via implementation of policy. Application of the model to a case study of Total Maximum Daily Load (TMDL) of phosphorous in Bear Lake, a Lake Michigan estuary (USA), shows the major total phosphorous (P) loading contribution is anthropogenic land use development. Three scenarios are quantitatively explored by assuming changes in land use and/or loading rates. Simulation results show tradeoffs between reduction of total P and land use; economic development can be flexibly evaluated against targets of loading reduction trajectories.

Condition states of civil infrastructure such as pavements and bridges are usually indexed on discrete scales, and Markov chain models are often used to estimate transition rates from one state to another, as well as sojourn times in any given state. Such models tend to assume homogenous transition rates between states, even though the models should account for heterogeneity to improve the accuracy of the predicted outcomes. Therefore, the objective of this study is to evaluate variations in model predictions when transition rates between condition states vary. Building on existing research, this paper considers a Monte Carlo simulation of a non-homogeneous Markov chain model for condition prediction of infrastructure systems. The method considers two scenarios (i) when transition rates are regressed according to a Weibull probability density function, and (ii) when transition rates are sampled as random values from interval estimates. For each scenario, multiple cases are further investigated to quantitatively describe variations in model predictions generated from variable transition rates. For the first scenario, simulations demonstrated that the accuracy of the model predictions is sensitive to the shape parameter for the Weibull distribution. Similarly, for the second scenario simulations illustrated that the interval estimates when chosen correctly can be used to establish confidence intervals for the transition rate parameter. Methods developed in this study can be used to test the accuracy of performance predictions for infrastructure systems, thus improving a decision-maker’s confidence in using the models to optimize infrastructure maintenance schedules.

This paper describes a novel image registration method that combines log-polar transform and SIFT to recover similarity transformations (rotation/ scale/ translation). We extracts SIFT feature points in the two images firstly. Then, we use threshold Euclidean distance to coarsely match the feature points. After that, the log-polar transform is applied to compute the rotation and scale parameters. And we can obtain the translation parameter by the location relationship of the feature points.

The objective of this research is to analyze historical records of random nonmechanistic failures in civil infrastructure systems. In this paper, we particularly focus on blockage failures in sewer systems that result from combination of external factors, such as variations in usage loads, construction quality and soil characteristics. The study uses historical blockage failure records maintained by municipalities. However, such datasets often tend to be incomplete and/or not representative of failure patterns. We discuss the application of statistical tests – specifically the Kolmogorov-Smirnov (KS) test and Anderson-Darling (AD) goodness-of-fit test – to estimate (i) if the datasets are complete and representative enough, and (ii) estimate parameters of distributions that appropriately characterize failure event arrival pattern. A dataset consisting of sewer blockage failures for ten years from a small municipality in the State of Michigan was used. The methods discussed in this paper can be used to implement reliability models of other related infrastructure systems as well.

In cases where an open channel needs bed and bank protection riprap is a common lining material, of which riprap size is the main design parameter needing determination. The current solution procedure is a cumbersome iterative one. A direct solution (one not needing iteration) is proposed here that improves computation time by 98% and adds less than 8% error.