To examine the influence of the harsh environment in plateau areas on the operating speed of vehicles,advanced speed prediction models for curved segments are established based on observed actual speed data.First,the ...To examine the influence of the harsh environment in plateau areas on the operating speed of vehicles,advanced speed prediction models for curved segments are established based on observed actual speed data.First,the speed characteristics at the starting,mid,and end points of a plane curve were observed on Lalin Highway and China National Highway 318 with Bushnell s handheld radar speedometer 10-1911CN.Second,the stepwise regression method was proposed to determine the significant parameters and propose the prediction models of the operating speed of cars and large vehicles for the two highways.Finally,reserved test group data were utilized to prove the validity and practicality of the proposed models.Compared with traditional methods,the established models can produce more accurate prediction results and deeply examine the nonlinear relationships between parameters and the predicted operating speed.This study provides a considerate direction and basis for the operating speed prediction model for other segments in plateau regions.展开更多
The aging timescale of particles is a key parameter in determining their impacts on air quality,human health,and climate.In this study,a one-year simulation of the age distributions of the primary and secondary inorga...The aging timescale of particles is a key parameter in determining their impacts on air quality,human health,and climate.In this study,a one-year simulation of the age distributions of the primary and secondary inorganic fine particulate matter(PM_(2.5))components was conducted over China using an age-resolved Community Multiscale Air Quality(CMAQ)model.The results indicate that primary PM_(2.5)(PPM)and ammonium mainly originate from fresh local emissions,with approximately 60%-80%concentrated in 0-24 h age bins in most of China throughout the year.The average age is about15-25 h in most regions in summer,but increases to 40-50 h in southern region of China and the Sichuan Basin(SCB)in winter.Sulfate is more aged than PPM,indicating an enhanced contribution from regional transport.Aged sulfate with atmospheric age>48 h account for 30%-50%of total sulfate in most regions and seasons,and the concentrations in the>96 h age bin can reach up to 15μg·m-3 in SCB during winter.Dramatic seasonal variations occur in the Yangtze River Delta,Pearl River Delta,and SCB,with highest average age of 60-70 h in winter and lowest of 40-45 h in summer.The average age of nitrate is 20-30 h in summer and increases to 40-50 h in winter.The enhanced deposition rate of nitric acid vapor combined with the faster chemical reaction rate of nitrogen oxides leads to a lower atmospheric age in summer.Additionally,on pollution days,the contributions of old age bins(>24 h)increase notably for both PPM and secondary inorganic aerosols in most cities and seasons,suggesting that regional transport plays a vital role during haze events.The age information of PM_(2.5),provided by the age-resolved CMAQ model,can help policymakers design effective emergent emission control measures to eliminate severe haze episodes.展开更多
Abstract: The purpose of this paper is to evaluate the suitability of using trass as a supplementary cementing material in pervious concrete. OPC (Ordinary Portland Cement) was replaced in the concrete mix by 15%, ...Abstract: The purpose of this paper is to evaluate the suitability of using trass as a supplementary cementing material in pervious concrete. OPC (Ordinary Portland Cement) was replaced in the concrete mix by 15%, 25% and 35% weight percentages and the results were compared with reference mixtures with 100% Portland cement. The variables in this study were trass content, aggregate size and water to cement ratio. Sixteen eases of concrete mixtures were tested to study physical and mechanical properties of hardened concrete, including porosity, permeability, compressive strength, splitting-tensile strength and flexural strength at various ages. Results indicated that mechanical properties of the pervious concrete marginally decreased with the increased content of trass when compared to the reference mixtures. However, at later ages the differences were insignificant.展开更多
Although the sustainability movement in the healthcare sector was initiated in response to ecological concerns,green hospitals are expected to outperform traditional hospitals on a variety of levels.The impacts of env...Although the sustainability movement in the healthcare sector was initiated in response to ecological concerns,green hospitals are expected to outperform traditional hospitals on a variety of levels.The impacts of environmental quality on patients and caregivers are demonstrated in numerous studies.However,there is still a lack of evidence on the benefits of green hospitals with respect to different dimensions of patients’experiences.In this study,data from the public Hospital Consumer Assessment of Health Plans Survey is used to compare the performance of green hospitals with the average performance of traditional hospitals.This study included 19 green hospitals and found that patients hospitalized in green facilities reported overall higher ratings than those in traditional hospitals when compared to the average performance of traditional hospitals of similar sizes and locations.Additionally,patients in green hospitals were more likely to recommend the hospital to their friends and family.However,relationships between specific green building features and patient experiences were not identified in this study.展开更多
Concerns regarding the environmental impacts of hospitals have made the healthcare sector one of the most prominent settings for the green building movement.Despite these environmental concerns,the number of studies t...Concerns regarding the environmental impacts of hospitals have made the healthcare sector one of the most prominent settings for the green building movement.Despite these environmental concerns,the number of studies that document the benefits of sustainable healthcare facilities is limited.In this study,the authors used the Medicare and Medicaid cost report data to compare the financial performance of 14 Leadership in Energy and Environmental Design(LEED)certified hospitals against the average performance of non-green facilities.In line with studies conducted in other settings,the authors found that there are low and high performers among green hospitals.For this study,green hospitals had higher facility operating expenses than an average non-green hospital and spent more on plant operations.While green hospitals included in this study generated more revenue,the incomes were not high enough to validate the high operating expenses.展开更多
In this context,two different approaches of soil liquefaction evaluation using a soft computing technique based on the worldwide standard penetration test(SPT) databases have been studied.Gene expression programming(G...In this context,two different approaches of soil liquefaction evaluation using a soft computing technique based on the worldwide standard penetration test(SPT) databases have been studied.Gene expression programming(GEP) as a gray-box modeling approach is used to develop different deterministic models in order to evaluate the occurrence of soil liquefaction in terms of liquefaction field performance indicator(LI) and factor of safety(FS) in logistic regression and classification concepts.The comparative plots illustrate that the classification concept-based models show a better performance than those based on logistic regression.In the probabilistic approach,a calibrated mapping function is developed in the context of Bayes’ theorem in order to capture the failure probabilities(PL) in the absence of the knowledge of parameter uncertainty.Consistent results obtained from the proposed probabilistic models,compared to the most well-known models,indicate the robustness of the methodology used in this study.The probability models provide a simple,but also efficient decision-making tool in engineering design to quantitatively assess the liquefaction triggering thresholds.展开更多
The discrete choice model is used to estimate the walking access area of rail transit stations while considering the influence of existing competition from other traffic modes. The acceptable walking access area is de...The discrete choice model is used to estimate the walking access area of rail transit stations while considering the influence of existing competition from other traffic modes. The acceptable walking access area is determined according to the willingness of passengers to walk who prefer rail transit compared with bus and automobile. Empirical studies were conducted using the survey data of six stations from the rail transit in Nanjing, China. The results indicate that the rail transit is more preferable compared with bus and private automobile in this case when excluding the influence of individual and environmental factors. It is found that passengers tend to underestimate their willingness to walk. The acceptable walking access area of every rail transit station is different from each other. Suburban stations generally have a larger walking access area than downtown stations. In addition, a better walking environment and a scarcer surrounding traffic environment can also lead to a larger walking area. The model was confirmed to be effective and reasonable according to the model validation. This study can be of benefit to the passenger transportation demand estimation in the location planning and evaluation of rail transit stations.展开更多
The paper presents two case studies that provide information on the process of homogenization of initially heterogeneous clay barriers and seals. The first case is the canister retrieval test performed in the Asp0 Har...The paper presents two case studies that provide information on the process of homogenization of initially heterogeneous clay barriers and seals. The first case is the canister retrieval test performed in the Asp0 Hard Rock Laboratory (Sweden). The heterogeneity arises from the use of a combination of blocks and pellets to construct the engineered barrier. The degree of homogenization achieved by the end of the tests is evaluated from data obtained during the dismantling of the test. To assist in the interpretation of the test, a fully coupled thermo-hydro-mechanical (THM) analysis has been carried out. The second case involves the shaft sealing test performed in the HADES underground research laboratory (URL) in Mol (Belgium). Here the seal is made up of a heterogeneous mixture of bentonite pellets and bentonite powders. In addition to the full scale test, the process of homogenization of the mixture has also been observed in the laboratory using X-ray tomography. Both field test and laboratory tests are successfully modelled by a coupled hydro-mechanical (HM) analysis using a double structure constitutive law. The paper concludes with some considerations on the capability of highly expansive materials to provide a significant degree of homogenization upon hydration.展开更多
By assigning different toll rates to different lanes during peak traffic hours, the demand for each lane of a road can be optimized. Lanes with lower travel times charge higher toll rates which are paid by those drive...By assigning different toll rates to different lanes during peak traffic hours, the demand for each lane of a road can be optimized. Lanes with lower travel times charge higher toll rates which are paid by those drivers who have higher values of travel time (VTT) and who want to avoid congestion in the other lanes. Conversely, travel time for those drivers with lower values of travel times will increase as they select the lower priced and slower lanes. This research examines toll rates that minimize the total value of travel time spent on the road under such a scenario. The optimum toll rates are dependent on the total road volume and distribution of VTT. The results show that total saved value of travel time can easily reach 11% of the total value of time spent traveling on the lanes when compared to a toll road with a uniform toll rate for all lanes. These savings vary based on many factors including the number of travelers on urgent trips.展开更多
Handoff processes during civil infrastructure operations are transitions between sequential tasks.Typical handoffs constantly involve cognitive and communication activities among operations personnel,as well as travel...Handoff processes during civil infrastructure operations are transitions between sequential tasks.Typical handoffs constantly involve cognitive and communication activities among operations personnel,as well as traveling activities.Large civil infrastructures,such as nuclear power plants(NPPs),provide critical services to modem cities but require regular or unexpected shutdowns(i.e.,outage)for maintenance.Handoffs during such an outage contain interwoven workflows and communication activities that pose challenges to the cognitive and communication skills of handoff participants and constantly result in delays.Traveling time and changing field conditions bring additional challenges to effective coordination among multiple groups of people.Historical NPP records studied in this research indicate that even meticulous planning that takes six months before each outage could hardly guarantee sufficient back-up plans for handling various unexpected events.Consequently,delays frequently occur in NPP outages and bring significant socioeconomic losses.A synthesis of previous studies on the delay analysis of accelerated maintenance schedules revealed the importance and challenges of handoff modeling.However,existing schedule representation methods could hardly represent the interwoven communication,cognitive,traveling,and working processes of multiple participants collaborating on completing scheduled tasks.Moreover,the lack of formal models that capture how cognitive,waiting,traveling,and communication issues affect outage workflows force managers to rely on personal experiences in diagnosing delays and coordinating multiple teams involved in outages.This study aims to establish formal models through agent-based simulation to support the analytical assessment of outage schedules with full consideration of cognitive and communication factors involved in handoffs within the NPP outage workflows.Simulation results indicate that the proposed handoff modeling can help predict the impact of cognitive and communication issues on delays propagating throughout outage schedules.Moreover,various activities are flilly considered,including traveling between workspaces and waiting.Such delay prediction capability paves the path toward predictive and resilience outage control of NPPs.展开更多
This study investigates the removal of arsenite(As(III)) from water using dithionite activated by UV light. This work evaluated the removal kinetics of As(III) under UV light irradiation as affected by dithionit...This study investigates the removal of arsenite(As(III)) from water using dithionite activated by UV light. This work evaluated the removal kinetics of As(III) under UV light irradiation as affected by dithionite dose and light intensity, and characterized the nature of the precipitated solids using XPS and SEM-EDS. Photolysis of dithionite was observed by measuring dithionite concentration using UV absorbance at 315 nm. This study also investigated the effect of UV light path length on soluble As concentrations to understand resolubilization mechanisms. Total soluble As concentrations were observed to decrease with reaction time due to reduction of arsenite to form solids having a yellow-orange color.The removal mechanism was found to be reductive precipitation that formed solids of elemental arsenic or arsenic sulfide. However, these solids were observed to resolubilize at later times after dithionite had been consumed. Resolubilization of As was prevented and additional As removal was obtained by frequent dosing of dithionite throughout the experiment. As(III) removal is attributed to photolysis of dithionite by UV light and production of reactive radicals that reduce As(III) and convert it to solid forms.展开更多
In arid and semi-arid areas,the profitability of irrigated agriculture mainly depends on the availability of water resources and optimal cropping patterns of irrigation districts.In this study,an integrated agricultur...In arid and semi-arid areas,the profitability of irrigated agriculture mainly depends on the availability of water resources and optimal cropping patterns of irrigation districts.In this study,an integrated agricultural cropping pattern optimization model was developed with considering the uncertainty of water availability and water saving potential in the future,aiming to maximize agricultural net benefit per unit of irrigation water.The available water which was based on the uncertainty of runoff was divided into five scenarios.The irrigation water-saving potential in the future was quantified by assuming an increase in the rate irrigation water-saving of 10% and 20%.The model was applied to the middle reaches of Heihe River basin,in Gansu Province,China.Results showed that if the irrigation water-saving rate was assumed to increase by 10%,then the net water-saving quantity would increase by 21.5-22.5 million m3 and the gross water-saving quantity would increase by 275.7-303.0 million m3.Similarly,if the irrigation water-saving rate increased by 20%,then the net water-saving quantity would increase by 43.0-45.1 million m3 and the gross water-saving quantity would increase by 331.7-383.2 million m3.If the agricultural cropping pattern was optimized,the optimal water and cultivated area allocation for maize would be greater than those for other crops.Under the premise that similar volume of irrigation water quantity was available in different scenarios,results showed differences in system benefit and net benefit per unit of irrigation water,for the distribution of available irrigation water was diverse in different irrigation districts.展开更多
The seismic performance of“added stories isolation”(ASI)systems are investigated for 12-story moment resisting frames.The newly added and isolated upper stories on the top of the existing structure are rolled to act...The seismic performance of“added stories isolation”(ASI)systems are investigated for 12-story moment resisting frames.The newly added and isolated upper stories on the top of the existing structure are rolled to act as a large tuned mass damper(TMD)to overcome the limitation of the size of tuned mass,resulting to“12+2”and“12+4”stories building configurations.The isolation layer,as a core design strategy,is optimally designed based on optimal TMD design principle,entailing the insertion of passive flexible laminated rubber bearings to segregate two or four upper stories from a conventionally constructed lower superstructure system.Statistical performance metrics are presented for 30 earthquake records from the 3 suites of the SAC project.Time history analyses are used to compute various response performances and reduction factors across a wide range of seismic hazard intensities.Results show that ASI systems can effectively manage seismic response for multi-degree-of freedom(MDOF)systems across a broader range of ground motions without requiring burdensome extra mass.Specific results include the identification of differences in the number of added story by which the suggested isolation systems remove energy.展开更多
The UCD/CIT model was modified to include a process analysis(PA)scheme for gas and particulate matter(PM)to study the formation of secondary nitrate aerosol during a stagnant wintertime air pollution episode during th...The UCD/CIT model was modified to include a process analysis(PA)scheme for gas and particulate matter(PM)to study the formation of secondary nitrate aerosol during a stagnant wintertime air pollution episode during the California Regional PM_(2.5)/PM_(10) Air Quality Study(CRPAQS)where detailed measurements of PM components are available at a few sites.Secondary nitrate is formed in the urban areas from near the ground to a few hundred meters above the surface during the day with a maximum modeled net increase rate of 4μg·m^(-3)·d^(-1) during the study episode.The secondary nitrate formation rate in rural areas is lower due to lower NO_(2).In the afternoon hours,near-surface temperature can be high enough to evaporate the particulate nitrate.In the nighttime hours,both the gas phase N_(2)O_(5) reactions with water vapor and the N_(2)O_(5) heterogeneous reactions with particle-bound water are important for secondary nitrate formation.The N_(2)O_(5) reactions are most import near the surface to a few hundred meters above surface with a maximum modeled net secondary nitrate increase rate of 1μg·m^(-3)·d^(-1) and are more significant in the rural areas where the O3 concentrations are high at night.In general,vertical transport during the day moves the nitrate formed near the surface to higher elevations.During the stagnant days,process analysis indicates that the nitrate concentration in the upper air builds up and leads to a net downward flux of nitrate through vertical diffusion and a rapid increase of surface nitrate concentration.展开更多
Seasonal precipitation changes under the influence of large-scale climate oscillations in the East River basin were studied using daily precipitation data at 29 rain stations during 1959–2010. Seasonal and global mod...Seasonal precipitation changes under the influence of large-scale climate oscillations in the East River basin were studied using daily precipitation data at 29 rain stations during 1959–2010. Seasonal and global models were developed and evaluated for probabilistic precipitation forecasting. Generalized additive model for location,scale, and shape was used for at-site precipitation forecasting. The results indicate that:(1) winter and spring precipitation processes at most stations are nonstationary,while summer and autumn precipitation processes at few of the stations are stationary. In this sense, nonstationary precipitation processes are dominant across the studyregion;(2) the magnitude of precipitation is influenced mainly by the Arctic Oscillation, the North Pacific Oscillation, and the Pacific Decadal Oscillation(PDO). The El Nin? o/Southern Oscillation(ENSO) also has a considerable effect on the variability of precipitation regimes across the East River basin;(3) taking the seasonal precipitation changes of the entire study period as a whole, the climate oscillations influence precipitation magnitude, and this is particularly clear for the PDO and the ENSO. The latter also impacts the dispersion of precipitation changes; and(4) the seasonal model is appropriate for modeling spring precipitation, but the global model performs better for summer, autumn, and winter precipitation.展开更多
Based on the performance results of the previously suggested smart building isolation systems (lst companion paper), this following study verifies the control effects of the systems from the view point of energy dis...Based on the performance results of the previously suggested smart building isolation systems (lst companion paper), this following study verifies the control effects of the systems from the view point of energy dissipation and damage level metrics. Several different model cases of the strategically isolated multi-story building structures utilizing passive dampers and semi-active resettable devices are analyzed and the energy-based target indices are compared. Performance comparisons are conducted on statistically calculated story/structural hysteretic energy and story/structural damage demands over realistic suites of earthquake ground motion records, representing seismic excitations of specific return period probability. Again, the semi-active solutions show significant promise for applications ofresettable device, offering advantages over passive systems in the consistent damage reductions. The specific results of this study include the identification of differences in the mechanisms by which smart building isolation systems remove energy, based on the differences in the devices used. Less variability is also seen for the semi-active isolation systems, indicating an increased robustness.展开更多
基金The National Natural Science Foundation of China(No.51768063,51868068)。
文摘To examine the influence of the harsh environment in plateau areas on the operating speed of vehicles,advanced speed prediction models for curved segments are established based on observed actual speed data.First,the speed characteristics at the starting,mid,and end points of a plane curve were observed on Lalin Highway and China National Highway 318 with Bushnell s handheld radar speedometer 10-1911CN.Second,the stepwise regression method was proposed to determine the significant parameters and propose the prediction models of the operating speed of cars and large vehicles for the two highways.Finally,reserved test group data were utilized to prove the validity and practicality of the proposed models.Compared with traditional methods,the established models can produce more accurate prediction results and deeply examine the nonlinear relationships between parameters and the predicted operating speed.This study provides a considerate direction and basis for the operating speed prediction model for other segments in plateau regions.
基金supported by the National Key Research and Development(R&D)Program of China(2019YFA0606802)the National Natural Science Foundation of China(41975162 and 42021004)the Jiangsu Environmental Protection Research Project(2016015)。
文摘The aging timescale of particles is a key parameter in determining their impacts on air quality,human health,and climate.In this study,a one-year simulation of the age distributions of the primary and secondary inorganic fine particulate matter(PM_(2.5))components was conducted over China using an age-resolved Community Multiscale Air Quality(CMAQ)model.The results indicate that primary PM_(2.5)(PPM)and ammonium mainly originate from fresh local emissions,with approximately 60%-80%concentrated in 0-24 h age bins in most of China throughout the year.The average age is about15-25 h in most regions in summer,but increases to 40-50 h in southern region of China and the Sichuan Basin(SCB)in winter.Sulfate is more aged than PPM,indicating an enhanced contribution from regional transport.Aged sulfate with atmospheric age>48 h account for 30%-50%of total sulfate in most regions and seasons,and the concentrations in the>96 h age bin can reach up to 15μg·m-3 in SCB during winter.Dramatic seasonal variations occur in the Yangtze River Delta,Pearl River Delta,and SCB,with highest average age of 60-70 h in winter and lowest of 40-45 h in summer.The average age of nitrate is 20-30 h in summer and increases to 40-50 h in winter.The enhanced deposition rate of nitric acid vapor combined with the faster chemical reaction rate of nitrogen oxides leads to a lower atmospheric age in summer.Additionally,on pollution days,the contributions of old age bins(>24 h)increase notably for both PPM and secondary inorganic aerosols in most cities and seasons,suggesting that regional transport plays a vital role during haze events.The age information of PM_(2.5),provided by the age-resolved CMAQ model,can help policymakers design effective emergent emission control measures to eliminate severe haze episodes.
文摘Abstract: The purpose of this paper is to evaluate the suitability of using trass as a supplementary cementing material in pervious concrete. OPC (Ordinary Portland Cement) was replaced in the concrete mix by 15%, 25% and 35% weight percentages and the results were compared with reference mixtures with 100% Portland cement. The variables in this study were trass content, aggregate size and water to cement ratio. Sixteen eases of concrete mixtures were tested to study physical and mechanical properties of hardened concrete, including porosity, permeability, compressive strength, splitting-tensile strength and flexural strength at various ages. Results indicated that mechanical properties of the pervious concrete marginally decreased with the increased content of trass when compared to the reference mixtures. However, at later ages the differences were insignificant.
文摘Although the sustainability movement in the healthcare sector was initiated in response to ecological concerns,green hospitals are expected to outperform traditional hospitals on a variety of levels.The impacts of environmental quality on patients and caregivers are demonstrated in numerous studies.However,there is still a lack of evidence on the benefits of green hospitals with respect to different dimensions of patients’experiences.In this study,data from the public Hospital Consumer Assessment of Health Plans Survey is used to compare the performance of green hospitals with the average performance of traditional hospitals.This study included 19 green hospitals and found that patients hospitalized in green facilities reported overall higher ratings than those in traditional hospitals when compared to the average performance of traditional hospitals of similar sizes and locations.Additionally,patients in green hospitals were more likely to recommend the hospital to their friends and family.However,relationships between specific green building features and patient experiences were not identified in this study.
文摘Concerns regarding the environmental impacts of hospitals have made the healthcare sector one of the most prominent settings for the green building movement.Despite these environmental concerns,the number of studies that document the benefits of sustainable healthcare facilities is limited.In this study,the authors used the Medicare and Medicaid cost report data to compare the financial performance of 14 Leadership in Energy and Environmental Design(LEED)certified hospitals against the average performance of non-green facilities.In line with studies conducted in other settings,the authors found that there are low and high performers among green hospitals.For this study,green hospitals had higher facility operating expenses than an average non-green hospital and spent more on plant operations.While green hospitals included in this study generated more revenue,the incomes were not high enough to validate the high operating expenses.
文摘In this context,two different approaches of soil liquefaction evaluation using a soft computing technique based on the worldwide standard penetration test(SPT) databases have been studied.Gene expression programming(GEP) as a gray-box modeling approach is used to develop different deterministic models in order to evaluate the occurrence of soil liquefaction in terms of liquefaction field performance indicator(LI) and factor of safety(FS) in logistic regression and classification concepts.The comparative plots illustrate that the classification concept-based models show a better performance than those based on logistic regression.In the probabilistic approach,a calibrated mapping function is developed in the context of Bayes’ theorem in order to capture the failure probabilities(PL) in the absence of the knowledge of parameter uncertainty.Consistent results obtained from the proposed probabilistic models,compared to the most well-known models,indicate the robustness of the methodology used in this study.The probability models provide a simple,but also efficient decision-making tool in engineering design to quantitatively assess the liquefaction triggering thresholds.
基金The Scientific Research Foundation of Graduate School of Southeast University(No.YBJJ1838)the Fundamental Research Funds for the Central Universities(No.KYLX16_0270)the Foundation of China Scholarship Council(No.201606090240)
文摘The discrete choice model is used to estimate the walking access area of rail transit stations while considering the influence of existing competition from other traffic modes. The acceptable walking access area is determined according to the willingness of passengers to walk who prefer rail transit compared with bus and automobile. Empirical studies were conducted using the survey data of six stations from the rail transit in Nanjing, China. The results indicate that the rail transit is more preferable compared with bus and private automobile in this case when excluding the influence of individual and environmental factors. It is found that passengers tend to underestimate their willingness to walk. The acceptable walking access area of every rail transit station is different from each other. Suburban stations generally have a larger walking access area than downtown stations. In addition, a better walking environment and a scarcer surrounding traffic environment can also lead to a larger walking area. The model was confirmed to be effective and reasonable according to the model validation. This study can be of benefit to the passenger transportation demand estimation in the location planning and evaluation of rail transit stations.
基金co-funded by ANDRA,CIEMAT,ONDRAF-NIRAS and the European Commission (EC contracts FIKWCT-2000-00010 and STRP-036458)The support of the Spanish Ministry of Science and Innovation trough grant BIA2011-27217 is also gratefully acknowledged
文摘The paper presents two case studies that provide information on the process of homogenization of initially heterogeneous clay barriers and seals. The first case is the canister retrieval test performed in the Asp0 Hard Rock Laboratory (Sweden). The heterogeneity arises from the use of a combination of blocks and pellets to construct the engineered barrier. The degree of homogenization achieved by the end of the tests is evaluated from data obtained during the dismantling of the test. To assist in the interpretation of the test, a fully coupled thermo-hydro-mechanical (THM) analysis has been carried out. The second case involves the shaft sealing test performed in the HADES underground research laboratory (URL) in Mol (Belgium). Here the seal is made up of a heterogeneous mixture of bentonite pellets and bentonite powders. In addition to the full scale test, the process of homogenization of the mixture has also been observed in the laboratory using X-ray tomography. Both field test and laboratory tests are successfully modelled by a coupled hydro-mechanical (HM) analysis using a double structure constitutive law. The paper concludes with some considerations on the capability of highly expansive materials to provide a significant degree of homogenization upon hydration.
文摘By assigning different toll rates to different lanes during peak traffic hours, the demand for each lane of a road can be optimized. Lanes with lower travel times charge higher toll rates which are paid by those drivers who have higher values of travel time (VTT) and who want to avoid congestion in the other lanes. Conversely, travel time for those drivers with lower values of travel times will increase as they select the lower priced and slower lanes. This research examines toll rates that minimize the total value of travel time spent on the road under such a scenario. The optimum toll rates are dependent on the total road volume and distribution of VTT. The results show that total saved value of travel time can easily reach 11% of the total value of time spent traveling on the lanes when compared to a toll road with a uniform toll rate for all lanes. These savings vary based on many factors including the number of travelers on urgent trips.
基金This research is supported by the US Department of Energy(DOE),Nuclear Engineering University Program(NEUP)under Award No.DENE0008403.
文摘Handoff processes during civil infrastructure operations are transitions between sequential tasks.Typical handoffs constantly involve cognitive and communication activities among operations personnel,as well as traveling activities.Large civil infrastructures,such as nuclear power plants(NPPs),provide critical services to modem cities but require regular or unexpected shutdowns(i.e.,outage)for maintenance.Handoffs during such an outage contain interwoven workflows and communication activities that pose challenges to the cognitive and communication skills of handoff participants and constantly result in delays.Traveling time and changing field conditions bring additional challenges to effective coordination among multiple groups of people.Historical NPP records studied in this research indicate that even meticulous planning that takes six months before each outage could hardly guarantee sufficient back-up plans for handling various unexpected events.Consequently,delays frequently occur in NPP outages and bring significant socioeconomic losses.A synthesis of previous studies on the delay analysis of accelerated maintenance schedules revealed the importance and challenges of handoff modeling.However,existing schedule representation methods could hardly represent the interwoven communication,cognitive,traveling,and working processes of multiple participants collaborating on completing scheduled tasks.Moreover,the lack of formal models that capture how cognitive,waiting,traveling,and communication issues affect outage workflows force managers to rely on personal experiences in diagnosing delays and coordinating multiple teams involved in outages.This study aims to establish formal models through agent-based simulation to support the analytical assessment of outage schedules with full consideration of cognitive and communication factors involved in handoffs within the NPP outage workflows.Simulation results indicate that the proposed handoff modeling can help predict the impact of cognitive and communication issues on delays propagating throughout outage schedules.Moreover,various activities are flilly considered,including traveling between workspaces and waiting.Such delay prediction capability paves the path toward predictive and resilience outage control of NPPs.
基金possible by grants from the Qatar National Research Fund under its National Priorities Research Program award number NPRP 6-729-2-301 and NPRP 8-1406-2-605
文摘This study investigates the removal of arsenite(As(III)) from water using dithionite activated by UV light. This work evaluated the removal kinetics of As(III) under UV light irradiation as affected by dithionite dose and light intensity, and characterized the nature of the precipitated solids using XPS and SEM-EDS. Photolysis of dithionite was observed by measuring dithionite concentration using UV absorbance at 315 nm. This study also investigated the effect of UV light path length on soluble As concentrations to understand resolubilization mechanisms. Total soluble As concentrations were observed to decrease with reaction time due to reduction of arsenite to form solids having a yellow-orange color.The removal mechanism was found to be reductive precipitation that formed solids of elemental arsenic or arsenic sulfide. However, these solids were observed to resolubilize at later times after dithionite had been consumed. Resolubilization of As was prevented and additional As removal was obtained by frequent dosing of dithionite throughout the experiment. As(III) removal is attributed to photolysis of dithionite by UV light and production of reactive radicals that reduce As(III) and convert it to solid forms.
基金We acknowledge that this work was financially supported by the National Natural Science Fund in China(Grant No.91425302,91325201)National Key Research and Development Program during the 13th Five-year Plan in China(Grant No.2016YFC0401306).
文摘In arid and semi-arid areas,the profitability of irrigated agriculture mainly depends on the availability of water resources and optimal cropping patterns of irrigation districts.In this study,an integrated agricultural cropping pattern optimization model was developed with considering the uncertainty of water availability and water saving potential in the future,aiming to maximize agricultural net benefit per unit of irrigation water.The available water which was based on the uncertainty of runoff was divided into five scenarios.The irrigation water-saving potential in the future was quantified by assuming an increase in the rate irrigation water-saving of 10% and 20%.The model was applied to the middle reaches of Heihe River basin,in Gansu Province,China.Results showed that if the irrigation water-saving rate was assumed to increase by 10%,then the net water-saving quantity would increase by 21.5-22.5 million m3 and the gross water-saving quantity would increase by 275.7-303.0 million m3.Similarly,if the irrigation water-saving rate increased by 20%,then the net water-saving quantity would increase by 43.0-45.1 million m3 and the gross water-saving quantity would increase by 331.7-383.2 million m3.If the agricultural cropping pattern was optimized,the optimal water and cultivated area allocation for maize would be greater than those for other crops.Under the premise that similar volume of irrigation water quantity was available in different scenarios,results showed differences in system benefit and net benefit per unit of irrigation water,for the distribution of available irrigation water was diverse in different irrigation districts.
文摘The seismic performance of“added stories isolation”(ASI)systems are investigated for 12-story moment resisting frames.The newly added and isolated upper stories on the top of the existing structure are rolled to act as a large tuned mass damper(TMD)to overcome the limitation of the size of tuned mass,resulting to“12+2”and“12+4”stories building configurations.The isolation layer,as a core design strategy,is optimally designed based on optimal TMD design principle,entailing the insertion of passive flexible laminated rubber bearings to segregate two or four upper stories from a conventionally constructed lower superstructure system.Statistical performance metrics are presented for 30 earthquake records from the 3 suites of the SAC project.Time history analyses are used to compute various response performances and reduction factors across a wide range of seismic hazard intensities.Results show that ASI systems can effectively manage seismic response for multi-degree-of freedom(MDOF)systems across a broader range of ground motions without requiring burdensome extra mass.Specific results include the identification of differences in the number of added story by which the suggested isolation systems remove energy.
基金This research was partially supported by the California Air Resources Board and the San Joaquin Valleywide Air Pollution Study Agency under contract 2000-2005 PM.
文摘The UCD/CIT model was modified to include a process analysis(PA)scheme for gas and particulate matter(PM)to study the formation of secondary nitrate aerosol during a stagnant wintertime air pollution episode during the California Regional PM_(2.5)/PM_(10) Air Quality Study(CRPAQS)where detailed measurements of PM components are available at a few sites.Secondary nitrate is formed in the urban areas from near the ground to a few hundred meters above the surface during the day with a maximum modeled net increase rate of 4μg·m^(-3)·d^(-1) during the study episode.The secondary nitrate formation rate in rural areas is lower due to lower NO_(2).In the afternoon hours,near-surface temperature can be high enough to evaporate the particulate nitrate.In the nighttime hours,both the gas phase N_(2)O_(5) reactions with water vapor and the N_(2)O_(5) heterogeneous reactions with particle-bound water are important for secondary nitrate formation.The N_(2)O_(5) reactions are most import near the surface to a few hundred meters above surface with a maximum modeled net secondary nitrate increase rate of 1μg·m^(-3)·d^(-1) and are more significant in the rural areas where the O3 concentrations are high at night.In general,vertical transport during the day moves the nitrate formed near the surface to higher elevations.During the stagnant days,process analysis indicates that the nitrate concentration in the upper air builds up and leads to a net downward flux of nitrate through vertical diffusion and a rapid increase of surface nitrate concentration.
基金financially supported by the Fund for Creative Research Groups of the National Natural Science Foundation of China(Grant No.41621061)the National Science Foundation for Distinguished Young Scholars of China(Grant No.51425903)+1 种基金the National Science Foundation of China(Grant Nos.4160102341401052)
文摘Seasonal precipitation changes under the influence of large-scale climate oscillations in the East River basin were studied using daily precipitation data at 29 rain stations during 1959–2010. Seasonal and global models were developed and evaluated for probabilistic precipitation forecasting. Generalized additive model for location,scale, and shape was used for at-site precipitation forecasting. The results indicate that:(1) winter and spring precipitation processes at most stations are nonstationary,while summer and autumn precipitation processes at few of the stations are stationary. In this sense, nonstationary precipitation processes are dominant across the studyregion;(2) the magnitude of precipitation is influenced mainly by the Arctic Oscillation, the North Pacific Oscillation, and the Pacific Decadal Oscillation(PDO). The El Nin? o/Southern Oscillation(ENSO) also has a considerable effect on the variability of precipitation regimes across the East River basin;(3) taking the seasonal precipitation changes of the entire study period as a whole, the climate oscillations influence precipitation magnitude, and this is particularly clear for the PDO and the ENSO. The latter also impacts the dispersion of precipitation changes; and(4) the seasonal model is appropriate for modeling spring precipitation, but the global model performs better for summer, autumn, and winter precipitation.
文摘Based on the performance results of the previously suggested smart building isolation systems (lst companion paper), this following study verifies the control effects of the systems from the view point of energy dissipation and damage level metrics. Several different model cases of the strategically isolated multi-story building structures utilizing passive dampers and semi-active resettable devices are analyzed and the energy-based target indices are compared. Performance comparisons are conducted on statistically calculated story/structural hysteretic energy and story/structural damage demands over realistic suites of earthquake ground motion records, representing seismic excitations of specific return period probability. Again, the semi-active solutions show significant promise for applications ofresettable device, offering advantages over passive systems in the consistent damage reductions. The specific results of this study include the identification of differences in the mechanisms by which smart building isolation systems remove energy, based on the differences in the devices used. Less variability is also seen for the semi-active isolation systems, indicating an increased robustness.