The Experts below are selected from a list of 1683 Experts worldwide ranked by ideXlab platform
Annhelen Osteras - One of the best experts on this subject based on the ideXlab platform.
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historical usage of aqueous film forming foam a case study of the widespread distribution of perfluoroalkyl acids from a Military airport to groundwater lakes soils and fish
Chemosphere, 2015Co-Authors: Marko Filipović, Andreas Woldegiorgis, Karin Norstrom, Momina Bibi, Maria Lindberg, Annhelen OsterasAbstract:Abstract Historical usage of aqueous film forming foams (AFFFs) at Military Airports is a potential source of perfluoroalkyl acids (PFAAs) to the nearby environment. In this study, the distribution of perfluorohexanoic acid (PFHxA), perfluorooctanoic acid (PFOA), perfluorohexane sulfonate (PFHxS) and perfluorooctane sulfonate (PFOS) in soil, groundwater, surface water, tap water well, and fish muscle was investigated at a closed down Military airfield (F18) and its surroundings in Stockholm, Sweden. The presence of PFOS at AFFF training sites was inventoried. One major finding of the study is that a former airfield, abandoned since 1994, may still be a point source of PFAAs to nearby recipients. PFOS and PFOA were ubiquitous in the soil samples at former AFFF training sites with concentrations ranging from 2.18 to 8520 ng g −1 dry weight and −1 dry weight respectively. The sum of PFAAs in the groundwater and surface waters ranged from 738 to 51 000 ng L −1 and −1 , respectively. PFOS in European perch ranged from 76.5 to 370 ng g −1 wet weight muscle tissue which is among the highest previously reported worldwide. Our results provide evidence that the historical use of AFFF at the site have contaminated an aquifer (7500 m 3 d −1 ), that will require constant PFAA purification before being used for drinking water production. Despite the fact that the water turnover time in the investigated recipients (of 4–6 months) suggest a depletion of PFAA-contaminants over a quarter of a decade, abandoned airfields may still pose an environmental and human health concern.
Walter R Barker - One of the best experts on this subject based on the ideXlab platform.
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implementation of a new flexible pavement design procedure for u s Military Airports
2006Co-Authors: Carlos R Gonzalez, Walter R BarkerAbstract:The U.S. Military (Army, Air Force and Navy) thickness design procedures for flexible airport pavements are based the CBR (California Bearing Ratio) method. This method was originally developed in the 1940’s for design of flexible pavements to support the then new heavy bombers. The original airfield design curves were an extrapolation, based on shear stress, of the California pavement design curves for highway pavements. The extrapolated curves were modified and verified by extensive full scale field testing. The classical CBR equation was then developed from these curves. Recent research conducted at the U.S. Army Engineer Research and Development Center revealed that the classic CBR equation can be derived from a stress distribution represented by Frohlich’s stress concentration factor equal to 2. This discovery led to the reformulation of the classical CBR equation into a more general equation in terms vertical stresses as computed with a stress concentration factor. This paper presents the implementation of this new formulation into a more comprehensive design procedure for airport pavements. The paper will present a brief description of the development of the new procedure, flowcharts describing its implementation, and pavement thickness comparison between the old and the new procedures. The importance and positive impact to the U.S. Military by the adoption of this new methodology will also be presented and discussed.
Jinhoon Jeong - One of the best experts on this subject based on the ideXlab platform.
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development of environmental load calculation method for airport concrete pavement design
Journal of The Korean Society of Civil Engineers, 2013Co-Authors: Jooyoung Park, Dongseong Hong, Yeontae Kim, Jinhoon JeongAbstract:ABSTRACTThe environmental load of concrete pavement can be categorized by temperature and moisture loads, which mean temperature distribution, and drying shrinkage and creep in the concrete slab. In this study, a method calculating the environmental load e ssential to mechanistic design of airport concrete pavement was developed. First, target area and design slab thickness were determined. And, the concrete temperature distribution with slab depth was predicted by a pavement temperature prediction program to calculate equivalent linear temperature difference. The concrete drying shrinkage was predicted by improving an existing model to calculate differential shrinkage equivalent linear temperature difference considering regional relative humidity. In addition, the stress relaxation was considered in the drying shrinkage. Eventually, the equivalent linear temperature difference due to temperature and the dif ferential shrinkage equivalent linear temperature difference due to moisture were combined into the total equivalent linear temperature difference as terminal environmental load. The environmental load of eight civilian and two Military Airports which represent d omestic regional weather conditions were calculated and compared by the method developed in this study to show its application.Keywords : Airport concrete pavement, Environmental load, Temperature distribution, Differential shrinkage, Stress relaxation초 록콘크리트 포장의 환경하중은 온도하중과 수분하중으로 구분할 수 있으며, 이는 콘크리트 슬래브 내의 온도분포와 건조수축 및 크리프를 의미한다. 본 연구에서는 공항 콘크리트 포장의 역학적 설계에 필요한 환경하중을 산정할 수 있는 방법을 개발하였다 . 먼저, 대상 지역과 설계 슬래브 두께를 결정한 후, 포장 온도 예측 프로그램을 사용하여 예측된 슬래브 깊이에 따른 콘크리트 온도분포를 등가선형 온도차이로 환산하였다 . 기존 건조수축 예측 모형을 개선하여 지역별 상대습도를 고려하여 콘크리트의 건조수축을 예측한 후 부등건조수축 등가선형 온도차이로 환산하였다. 또한, 응력이완을 건조수축에 반영하였다. 결국, 온도에 의한 등가선형 온도차이와 수분에 의한 부등건조수축 등가선형 온도차이를 합하여 최종 환경하중인 총 등가선형 온도차이를 산정하였다. 적용 예를 보이기 위해 지역별 기상조건을 대표할만한 국내 민간공항 8곳 및 군공항 2곳의 환경하중을 본 연구에서 개발된 방법으로 계산하고 비교하였다.검색어 : 공항 콘크리트 포장, 환경하중, 온도분포, 부등건조수축, 응력이완Highway Engineering
Q U Zhe - One of the best experts on this subject based on the ideXlab platform.
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evaluation of airport cement concrete pavement quality with neural network
Subgrade Engineering, 2010Co-Authors: Q U ZheAbstract:For convenient and effective evaluation of cement concrete pavement quality,network models for pavement evenness,friction coefficient and pavement quality are established with neural network.Through investigation into pavement evenness,friction coefficient and pavement damage condition of 12 Military Airports,the network is exercised with the obtained data as the sample.The result shows that when the target error is 1×10-5,the relative error between calculation value and measured value is less than 0.3 %.This method can be used for evaluation of pavement quality.
Marko Filipović - One of the best experts on this subject based on the ideXlab platform.
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historical usage of aqueous film forming foam a case study of the widespread distribution of perfluoroalkyl acids from a Military airport to groundwater lakes soils and fish
Chemosphere, 2015Co-Authors: Marko Filipović, Andreas Woldegiorgis, Karin Norstrom, Momina Bibi, Maria Lindberg, Annhelen OsterasAbstract:Abstract Historical usage of aqueous film forming foams (AFFFs) at Military Airports is a potential source of perfluoroalkyl acids (PFAAs) to the nearby environment. In this study, the distribution of perfluorohexanoic acid (PFHxA), perfluorooctanoic acid (PFOA), perfluorohexane sulfonate (PFHxS) and perfluorooctane sulfonate (PFOS) in soil, groundwater, surface water, tap water well, and fish muscle was investigated at a closed down Military airfield (F18) and its surroundings in Stockholm, Sweden. The presence of PFOS at AFFF training sites was inventoried. One major finding of the study is that a former airfield, abandoned since 1994, may still be a point source of PFAAs to nearby recipients. PFOS and PFOA were ubiquitous in the soil samples at former AFFF training sites with concentrations ranging from 2.18 to 8520 ng g −1 dry weight and −1 dry weight respectively. The sum of PFAAs in the groundwater and surface waters ranged from 738 to 51 000 ng L −1 and −1 , respectively. PFOS in European perch ranged from 76.5 to 370 ng g −1 wet weight muscle tissue which is among the highest previously reported worldwide. Our results provide evidence that the historical use of AFFF at the site have contaminated an aquifer (7500 m 3 d −1 ), that will require constant PFAA purification before being used for drinking water production. Despite the fact that the water turnover time in the investigated recipients (of 4–6 months) suggest a depletion of PFAA-contaminants over a quarter of a decade, abandoned airfields may still pose an environmental and human health concern.