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Operating speed models for curved segments of highways in plateau regions 被引量:2
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作者 Wang Chenzhu Chen Fei +4 位作者 Xu Wensheng Wu Yutao Zhang Yunlong Bo Wu Zhang Ping 《Journal of Southeast University(English Edition)》 EI CAS 2022年第1期85-91,共7页
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
关键词 plateau areas operating speed stepwise regression method prediction model
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Spatial and Temporal Variations in the Atmospheric Age Distribution of Primary and Secondary Inorganic Aerosols in China
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作者 Xiaodong Xie Qi Ying +1 位作者 Hongliang Zhang Jianlin Hu 《Engineering》 SCIE EI CAS CSCD 2023年第9期117-129,共13页
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
关键词 Atmospheric age PM_(2.5) CMAQ model Control strategy
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Experimental Study on the Use of Trass as a Supplementary Cementitious Material in Pervious Concrete
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作者 Alireza Joshaghani Alireza Moazenian Richard Abubakar Shuaibu 《Journal of Environmental Science and Engineering(A)》 2017年第1期39-52,共14页
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
关键词 Pervious concrete TRASS supplementary cementitious material PERMEABILITY STRENGTH natural pozzolans.
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PATIENT EXPERIENCE WITH HOSPITAL CARE-COMPARISON OF A SAMPLE OF GREEN HOS PITALS AND NON-GREEN HOSPITALS
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作者 Hessam Sadatsafavi John Walewski Michael Taborn 《Journal of Green Building》 2015年第1期169-185,共17页
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
关键词 green hospitals patient experiences with hospital care HOSPITAL Compare patient survey
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COMPARISON OF A SAMPLE OF GREEN HOSPITALS WITH NON-GREEN HOSPITALS WITH RESPECT TO OPERATING EXPENSES AND PATIENT REVENUE
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作者 Hessam Sadatsafavai John Walewski Michael Taborn 《Journal of Green Building》 2014年第3期163-188,共26页
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
关键词 LEED-certified hospitals financial performance hospital cost report Center for Medicare and Medicaid Services
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基于可解释机器学习框架的快速路立交出口风险预测及致因解析 被引量:9
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作者 赵晓华 亓航 +3 位作者 姚莹 郭淼 国景枫 张云龙 《东南大学学报(自然科学版)》 EI CAS CSCD 北大核心 2022年第1期152-161,共10页
为实现城市快速路立交出口安全风险防控,提升城市道路整体安全性,对快速路立交出口风险水平进行预测,并探究运行状态、控制设施、道路属性、天气等因素对立交出口安全风险的影响.基于导航数据和实地调查数据,以交通秩序指数作为事故替... 为实现城市快速路立交出口安全风险防控,提升城市道路整体安全性,对快速路立交出口风险水平进行预测,并探究运行状态、控制设施、道路属性、天气等因素对立交出口安全风险的影响.基于导航数据和实地调查数据,以交通秩序指数作为事故替代指标,采用极限梯度提升(XGBoost)算法构建交通秩序预测模型,并利用可解释机器学习框架SHAP解析安全风险致因.结果表明:XGboost算法能够精准预测立交出口安全风险,准确率93.69%,精确率93.73%,召回率93.69%;拥堵指数是立交出口安全风险的重要影响因素;缓解拥堵,减少交通分流合流以及降低天气的影响对提升道路安全均有积极效应;不同拥堵状态下的预告标志数或车道数对交通秩序指数具有差异化影响. 展开更多
关键词 快速路立交出口 交通安全风险 风险预测 致因解析 可解释机器学习
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煤炭矿区植被冠层光谱土地复垦敏感性分析 被引量:8
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作者 赵恒谦 张文博 +4 位作者 朱孝鑫 毕银丽 李瑶 赵学胜 金倩 《光谱学与光谱分析》 SCIE EI CAS CSCD 北大核心 2019年第6期1858-1863,共6页
煤矿区土地复垦及复垦监测工作,对于我国土地利用和生态环境治理具有重要意义。微生物复垦技术能够促进植物吸收利用矿质养分和水分,增强土壤肥力,对矿区生态恢复具有显著作用。监测和评价土地复垦效应对植物生长影响的传统方法,通常采... 煤矿区土地复垦及复垦监测工作,对于我国土地利用和生态环境治理具有重要意义。微生物复垦技术能够促进植物吸收利用矿质养分和水分,增强土壤肥力,对矿区生态恢复具有显著作用。监测和评价土地复垦效应对植物生长影响的传统方法,通常采用野外采集植物和土壤样本并进行室内分析,但这些方法不仅破坏植物根系原状土壤,造成植株损伤,而且耗费人力、物力,时效性差。高光谱遥感技术具有数据获取速度快、信息量大、精度高且无须离体破坏植株等优点,对于土地复垦监测有非常大的潜力。目前,土地复垦效应遥感监测相关研究仍以观测盆栽大豆、玉米等作物的叶片光谱分析为主。实际上,卫星遥感数据观测到的是冠层光谱,并非叶片光谱,但目前还没有通过植被冠层光谱对矿区土地复垦进行监测的研究成果出现。植被冠层光谱不仅受到叶片光谱的影响,还受到植株长势、下垫面等其他因素的影响,光谱特征变化更为复杂。矿区植被冠层光谱特征对于土地复垦效应的敏感度分析,是对矿区植被理化参量进行定量反演的基础,也是限制高光谱技术应用于大面积土地复垦监测的主要瓶颈。于煤炭矿区土地复垦实验基地开展野外冠层光谱观测实验,获取了接菌组和对照组野外植株冠层光谱数据,并从光谱波形变化和光谱特征参量变化两方面综合分析了植被冠层光谱对土地复垦的敏感性。冠层光谱波形方面,分别采用标准差和光谱敏感度作为组内和组间光谱波形差异的有效指标;冠层光谱特征参量方面,选取了植被红边、黄边、蓝边、绿峰、红谷等典型光谱特征,计算获取其位置、斜率、面积等特征参量,并通过描述性统计和单因素方差分析研究了这些冠层光谱特征参量对土地复垦效应的敏感性,挑选出矿区土地复垦监测的有效特征参量。研究表明,接菌组和对照组冠层光谱的主要波形变化趋势一致,但接菌组植株的生长状况更稳定,不同植株之间差异较小,且绿峰和红谷两个特征更突出。这说明土地复垦能够减少植株间冠层光谱差异,增强植被典型光谱特征,而绿峰和红谷对土地复垦有较高的光谱敏感度。光谱特征参量方面,绿峰、红谷、红边波长在土地复垦作用下显著向长波方向移动,而此前叶片光谱研究中对土地复垦较敏感的红边、蓝边斜率变化并不显著。这说明,野外植被冠层光谱分析结果与实验室植被叶片光谱分析的结果并不完全一致,这可能和植被类型、生长周期、土壤背景光谱干扰等因素相关。在采用卫星或航拍遥感数据进行矿区植被环境监测时,所获取的都是植被冠层光谱,因此本研究所得到的结论具有更强的参考意义和实际应用价值。 展开更多
关键词 高光谱 土地复垦 煤炭矿区 植被冠层 敏感性分析
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A worldwide SPT-based soil liquefaction triggering analysis utilizing gene expression programming and Bayesian probabilistic method 被引量:3
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作者 Maral Goharzay Ali Noorzad +1 位作者 Ahmadreza Mahboubi Ardakani Mostafa Jalal 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2017年第4期683-693,共11页
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
关键词 LIQUEFACTION Soft computing technique Gene expression programming(GEP) Deterministic model Bayes' theorem
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Estimating walking access area for rail transit station based on discrete choice model 被引量:1
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作者 Zhang Ning Shi Zhuangbin +1 位作者 Zhang Yunlong Zhang Xiaojun 《Journal of Southeast University(English Edition)》 EI CAS 2018年第3期377-385,共9页
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
关键词 walking access area urban rail transit discretechoice model walking environment competing trafficmodes passenger transportation demand
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Homogenization in clay barriers and seals:Two case studies
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作者 A.Gens B.Valleján +1 位作者 M.T.Zandarín M.Sánchez 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2013年第3期191-199,共9页
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
关键词 Nuclear waste disposal Clay barriers Clay seals HETEROGENEITY Compacted soils Coupled analyses Unsaturated soils
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Examining Potential Travel Time Savings Benefits Due to Toll Rates That Vary by Lane
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作者 Negin Alemazkoor Mark Burris 《Journal of Transportation Technologies》 2014年第3期267-276,共10页
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
关键词 Differential TOLL Rates TRAVEL TIME SAVINGS Value of TRAVEL TIME
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Modeling and simulating the impact of forgetting and communication errors on delays in civil infrastructure shutdowns
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作者 Zhe SUN Pingbo TANG Cheng ZHANG 《Frontiers of Engineering Management》 2021年第1期109-121,共13页
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
关键词 NPP outage human error team cognition handoff modeling
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Removal of arsenite by reductive precipitation in dithionite solution activated by UV light 被引量:4
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作者 Bahngmi Jung Aya Safan +3 位作者 Yuhang Duan Vishakha Kaushik Bill Batchelor Ahmed Abdel-Wahab 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2018年第12期168-176,共9页
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
关键词 ARSENITE Sodium dithionite Reductive precipitation and Ultraviolet light
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Cropping pattern optimization considering uncertainty of water availability and water saving potential 被引量:2
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作者 Lina Hao Xiaoling Su Vijay P.Singh 《International Journal of Agricultural and Biological Engineering》 SCIE EI CAS 2018年第1期178-186,共9页
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
关键词 cropping pattern optimization irrigation water-saving potential different scenarios water availability water use efficiency particle swarm optimization(PSO)
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Innovative seismic retrofitting strategy of added stories isolation system 被引量:1
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作者 Min-Ho CHEY J.Geoffrey CHASE +1 位作者 John B.MANDER Athol J.CARR 《Frontiers of Structural and Civil Engineering》 SCIE EI CSCD 2013年第1期13-23,共11页
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
关键词 added stories seismic isolation tuned mass damper parametric optimization statistical method
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Physical and chemical processes of wintertime secondary nitrate aerosol formation
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作者 Qi YING 《Frontiers of Environmental Science & Engineering》 SCIE EI CSCD 2011年第3期348-361,共14页
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
关键词 secondary nitrate aerosol N_(2)O_(5)heterogeneous reaction process analysis
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Nonstationarities and At-site Probabilistic Forecasts of Seasonal Precipitation in the East River Basin, China
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作者 Peng Sun Qiang Zhang +4 位作者 Xihui Gu Peijun Shi Vijay P.Singh Changqing Song Xiuyu Zhang 《International Journal of Disaster Risk Science》 SCIE CSCD 2018年第1期100-115,共16页
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
关键词 China ENSO regimes GAMLSS model Nonstationarity Probabilistic precipitation forecasting
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基于模糊集合理论和集对原理的径流丰枯分类方法 被引量:11
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作者 丁小玲 周建中 +2 位作者 陈璐 赵云发 李晖 《水力发电学报》 EI CSCD 北大核心 2015年第5期4-9,共6页
在分析现有基于集对分析的年径流丰枯分类方法不足的基础上,考虑径流等级划分的模糊性和径流的年内分布特性,提出模糊化径流分级标准,并引入基于径流分布的年内丰枯贡献权重因子,得到年径流对于各个等级的综合隶属度,进而利用集对分析... 在分析现有基于集对分析的年径流丰枯分类方法不足的基础上,考虑径流等级划分的模糊性和径流的年内分布特性,提出模糊化径流分级标准,并引入基于径流分布的年内丰枯贡献权重因子,得到年径流对于各个等级的综合隶属度,进而利用集对分析方法判断年径流的丰枯等级。利用所提方法对溪洛渡径流丰枯等级进行分析,结果表明该方法较于单一的集对分析方法能更好的描述径流丰枯状态。 展开更多
关键词 水文学 年径流分类 模糊集合 集对分析 溪洛渡 丰枯贡献权重
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大气氧化性及其对二次污染物形成的贡献 被引量:11
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作者 王芃 朱盛强 +3 位作者 张梦媛 邵田 Qi Ying 张宏亮 《科学通报》 EI CAS CSCD 北大核心 2022年第18期2069-2078,共10页
大气氧化性(atmospheric oxidation capacity,AOC)是指大气化学过程对一次污染物的氧化能力,一般用氧化剂的浓度或者总反应速率来表征.AOC对二次污染的形成起重要的作用,是研究二次污染物的重要指标.本研究利用三维空气质量模式(Communi... 大气氧化性(atmospheric oxidation capacity,AOC)是指大气化学过程对一次污染物的氧化能力,一般用氧化剂的浓度或者总反应速率来表征.AOC对二次污染的形成起重要的作用,是研究二次污染物的重要指标.本研究利用三维空气质量模式(Community Multi-scale Air Quality model,CMAQ)模拟了2013和2020年我国主要大气氧化剂(HO_(2)、OH和NO_(3)自由基)与二次污染物(臭氧和二次颗粒物)及其前体物,并结合观测数据,综合讨论了AOC对二次污染物生成的作用.结果表明,从2013~2020年,颗粒物浓度显著下降,而AOC水平并未明显降低,甚至在华北平原(NCP)和珠江三角洲(PRD)地区还略有上升.主要氧化剂浓度呈现一定的区域特征,HO_(x)(OH+HO_(2))在四川盆地浓度水平较高,而NO_(3)自由基在华北平原的浓度水平较高.O_(3)光解过程是生成AOC最主要的来源,而OH自由基和二氧化氮生成硝酸的过程是AOC最主要的汇.AOC与二次污染物浓度关系密切,在O_(3)重污染情况下,AOC的浓度水平与年均值相比增幅明显(最高可达475%);同时,在高AOC水平下,二次有机气溶胶(secondary organic aerosol,SOA)的浓度也有显著升高.因为二次无机气溶胶(secondary inorganic aerosol,SIA)的生成过程包含气相和其他相位过程,并且受排放的季节性变化影响较大,因此总浓度与AOC关系不直接.此外,通过情景模拟分析了AOC和二次污染物浓度对不同污染物减排的响应.在夏季,减少氮氧化物(NO_(x))排放可以降低AOC,而在冬季AOC对排放调整的响应较为复杂,呈现较强的区域差异性特征.研究表明,在减少一次排放的同时要控制AOC的升高,才能高效地实现空气质量的提升和细颗粒物(PM_(2.5))与O_(3)协同控制的目标. 展开更多
关键词 大气氧化性 二次污染物 三维空气质量模式 臭氧 减排政策
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Aseismic smart building isolation systems under multi-level earthquake excitations: Part II, energy-dissipation and damage reduction 被引量:2
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作者 Min-Ho CHEY J. Geoffrey CHASE +1 位作者 John B. MANDER Athol J. CARR 《Frontiers of Structural and Civil Engineering》 CSCD 2015年第3期297-306,共10页
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
关键词 smart building isolation story and structural ENERGY-DISSIPATION damage assessment
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