Dynamic tidal power is a new way of capturing tidal energy by building a water head using a dike perpendicular to the coast. This study explored the hydrodynamic mechanism of the water head across an intended dynamic ...Dynamic tidal power is a new way of capturing tidal energy by building a water head using a dike perpendicular to the coast. This study explored the hydrodynamic mechanism of the water head across an intended dynamic tidal power dike system using the Delft3 D-FLOW software module. The propagating wave was simulated in a rectangular domain with a horizontal sea bottom at a 30-m depth. A significant water head was created across the dike by blocking the water. The water head increased with increasing dike length and increasing undisturbed tidal current acceleration. The maximum water head for the dike with a length of 50 km, located 900 km from the western boundary, was 2.15 m,which exceeded the undisturbed tidal range. The time series of the water head behaved in a manner identical to the undisturbed tidal current acceleration. The distribution of the water head over the dike assumed an elliptical shape. A parasitic wave was generated at the attachment and scattered outward. The phase lag across the dike did not behave as a linear function of the detour distance.展开更多
Completely weathered phyllite(CWP)soil is a kind of special soil with high swell potential,while red clay is a special soil with high shrinkage.This means that these two kinds of special soils are usually not suitable...Completely weathered phyllite(CWP)soil is a kind of special soil with high swell potential,while red clay is a special soil with high shrinkage.This means that these two kinds of special soils are usually not suitable for direct use as subgrade fill.To reduce the swell index of the CWP soil and the shrinkage of red clay at the same time,it was proposed to blend the CWP soil with red clay to improve their basic characteristics.A series of swell index tests and dry-wet cycle tests of the blended soils have been carried out at varying blending ratios,compaction coefficients and moisture contents.The test results show that the free swell index of the blended soil decreases with the increase of red clay,moisture content and compaction coefficient,respectively.The fissure density of the blended soil first decreases and then increases with the blending ratio,with the lowest being zero when the blending ratio is ranging from 20%to 40%.Through particle microscopic analysis and elemental composition analysis,it is found that the neutralization effect,the dilution effect of swell minerals,and the partition effect of coarse particles play an important role in restraining expansion and shrinkage deformation of the blended soil.Based on the liquid limit requirement of Chinese Railway Design Code(TB 10001-2016),the optimal blending ratio of red clay has been proposed to be 50%.Compared with the CWP soil,the free load swell index of the blended soil is reduced by 45.0%and the fissure density is reduced by 99.3%compared with that of red clay.Therefore,it is feasible to improve the CWP soil by blending it with red clay at an optimal ratio of 50%by using the neutralization effect of the expansion of CWP and shrinkage of red clay.展开更多
This paper presents results of a study on the mechanical properties of sandy and gravely soils within the Cordillera Blanca, Peru. The soils were divided into groups according to their origin(glacial, fluvial, or debr...This paper presents results of a study on the mechanical properties of sandy and gravely soils within the Cordillera Blanca, Peru. The soils were divided into groups according to their origin(glacial, fluvial, or debris flow). The grain size distribution of forty three soil samples was used to classify the soils according to the scheme of the Unified Soil Classification System(USCS). These distributions have then been used to estimate shear strength and hydraulic properties of the soils. There are clear differences between the soils which reflect their divergent origins. The glacial soils normally fit within one of two distinctive groups according to the proportion of fines(Group A, 7%-21.5%; Group B, 21%-65%). The estimation of shear strength at constant volume friction angle and peak shear strength of the glacial sediments with low content of fines was made using published data relating to the measured shear strength characteristics of soils with similar origins and grain size distributions. The estimated values were supported by measurements of the angle of repose taken from fourteen samples from two moraines and by shear tests on samples from one locality. The results of the grain size distribution werealso used to estimate the average hydraulic conductivity using the empirical Hazen formula which results were verified by field infiltration tests at two localities.展开更多
The paper gives two examples of larger construction projects with typical stability problems. The first example is from Sakhalin Island in the Russian Far East. It is connected with a construction of oil and gas pipel...The paper gives two examples of larger construction projects with typical stability problems. The first example is from Sakhalin Island in the Russian Far East. It is connected with a construction of oil and gas pipelines through the mountainous terrain in Makarov region. The region has an active geotectonic history and is highly affected by uncontrolled erosion and extensive landslips. Basic principles of landslide hazard mitigation are presented. The second example is from a motorway construction in Azerbaijan. This motorway leads from Baku to Russia through a seismo-tectonically active area at the toe of Caucasian mountains and in some places is situated in deep cuts at the toe of high slopes. This unsuitable routing, together with seismic activity, led to a slope stability failure of a slope affected by recent tectonic movements near the village of Devechi. Stability conditions and designed remedy measures are presented.展开更多
Completely weathered phyllite(CWP)has the characteristics of difficult compaction,low shear strength after compaction and large settlement after construction.The traditional improvement method using a single agent of ...Completely weathered phyllite(CWP)has the characteristics of difficult compaction,low shear strength after compaction and large settlement after construction.The traditional improvement method using a single agent of red clay or cement for CWP satisfies the subgrade requirements for ordinary railway,but cannot meet the requirements of immediate strength and long-term post-construction settlement of high-speed railway at the same time.A series of experimental investigations were undertaken for the blended CWP soils,with three additives used.The first additive was red clay,the second was cement and the third was a combination of both red clay and cement at various portions.Results of consolidation test and shear strength test carried out for the treated CWP soils show that:1)The effect of cement on improving the compression modulus of CWP is much better than that of red clay;2)The settlement of an embankment of 10 m high formed by blended soil of CWP with 3%cement can be controlled within 15 mm,while the settlement will be 25.15 mm for the same embankment of blended soil of CWP with 40%red clay;3)The shear strength and ultimate bearing capacity of CWP improved by red clay are much better than those of 5%cement;4)The ultimate bearing capacity of CWP improved by 40%red clay is 3.42 times of that by 3%cement and 2.95 times by 5%cement.Furthermore,the bearing capacity of CWP when improved by red clay can meet railway subgrade requirements immediately after compaction,while cement improved CWP needs a curing time of 1 day or longer.This is an impediment to rapid construction process.The improvement mechanism of red clay is mainly filling effect and grading improvement effect,while the improvement mechanism of cement is mainly hardening reaction,which produces high strength material to cement.It is found that 40%red clay and 3%cement treated CWP,which is considered to be optimum,can meet the subgrade requirements of both immediate bearing capacity and long-term post-construction settlement for the high-speed railway.展开更多
Despite efforts to end homelessness in the United States,student homelessness is gradually growing over the past decade.Homelessness creates physical and psychological disadvantages for students and often disrupts sch...Despite efforts to end homelessness in the United States,student homelessness is gradually growing over the past decade.Homelessness creates physical and psychological disadvantages for students and often disrupts school access.Research suggests that students who experience prolonged dislocation and school disruption after a dis-aster are primarily from low-income households and under-resourced areas.This study develops a framework to predict post-disaster trajectories for kindergarten through high school(K-12)students faced with a major disaster;the framework includes an estimation on the households with children who recover and those who experience long-term homelessness.Using the National Center for Education Statistics school attendance boundaries,resi-dential housing inventory,and U.S.Census data,the framework first identifies students within school boundaries and links schools to students to housing.The framework then estimates dislocation induced by the disaster sce-nario and tracks the stage of post-disaster housing for each dislocated student.The recovery of dislocated students is predicted using a multi-state Markov chain model,which captures the sequences that households transition through the four stages of post-disaster housing(i.e.,emergency shelter,temporary shelter,temporary housing,and permanent housing)based on the social vulnerability of the household.Finally,the framework predicts the number of students experiencing long-term homelessness and maps the students back to their pre-disaster school.The proposed framework is exemplified for the case of Hurricane Matthew-induced flooding in Lumberton,North Carolina.Findings highlight the disparate outcomes households with children face after major disasters and can be used to aid decision-making to reduce future disaster impacts on students.展开更多
Both intake volumetric flow and through-screen velocity （the velocity of water as it passes through the screen） are important variables affecting fish impingement at industrial water intake structures including thos...Both intake volumetric flow and through-screen velocity （the velocity of water as it passes through the screen） are important variables affecting fish impingement at industrial water intake structures including those at power plants. However, there are limited data available on quantitative assessments of impingement following changes in power plant operation such as reduced volumetric flow and intake velocity. Impingement studies were conducted at Bay Shore Power Plant in 2005-2006 （baseline） and again in 2013-2014 following fish protection mitigation which included reduced intake volumetric flows （from 33.5 m^3·s^-1 to 9.1 cm·s^-1）, a reduced through-screen velocity （from approximately 79.2 cm·s^-1 to 11.6 cm·s^-1）, modified traveling screens and installation of a fish-return system to gently and quickly remove any fish that were impinged back into the waterbody. A comparison of baseline and post-mitigation results suggested that with this mitigation in place, impingement reductions can exceed 90% for robust dominant fish species in the area.展开更多
The effectiveness of an injection-based remediation strategy is primarily governed by accurate understanding of reagent delivery and ensuring uniform distribution within the reactive zone. In IRZ （in situ reactive z...The effectiveness of an injection-based remediation strategy is primarily governed by accurate understanding of reagent delivery and ensuring uniform distribution within the reactive zone. In IRZ （in situ reactive zone） design, the required reagent strength, injection volumes, injection rates, injection frequency, injection and monitoring well spacing, and the cost and time to achieve remediation goals are governed by the hydrogeology of the site. A properly designed tracer test is capable of providing critical above mentioned site-specific information, to assist with full scale design of an IRZ. This paper describes that implementing tracer testing to support remedial design can result in enhanced design efficiency, added assurance in full-scale implementation and ultimately resulted in substantial cost savings. Therefore, it is recommended that the broader practitioner community adopt this technique as a best practice for effective and optimum in situ remediation system design.展开更多
Underground storage systems are currently being used worldwide for the geological storage of natural gas （CH4）, the geological disposal of CO2, in geothermal energy, or radioactive waste disposal. We introduce a com...Underground storage systems are currently being used worldwide for the geological storage of natural gas （CH4）, the geological disposal of CO2, in geothermal energy, or radioactive waste disposal. We introduce a complex approach to the risks posed by induced bedrock instabilities in deep geological underground storage sites. Bedrock instability owing to underground openings has been studied and discussed for many years. The Bohemian Massif in the Czech Republic （Central Europe） is geologically and tectonically complex. However, this setting is ideal for leaming about the instability state of rock masses. Longterm geological and mining studies, natural and induced seismicity, radon emanations, and granite properties as potential storage sites for disposal of radioactive waste in the Czech Republic have provided useful information. In addition, the Czech Republic, with an average concentration radon of 140 Bq m-3, has the highest average radon concentrations in the world. Bedrock instabilities might emerge from microscale features, such as grain size and mineral orientation, and microfracturing. Any underground storage facility construction has to consider the stored substance and the geological settings. In the Czech Republic, granites and granitoids are the best underground storage sites. Microcrack networks and migration properties are rock specific and vary considerably. Moreover, the matrix porosity also affects the mechanical properties of the rocks. Any underground storage site has to be selected carefully. The authors suggest to study the complex set of parameters from micro to macroscale for a particular place and type of rock to ensure that the storage remains safe and stable during construction, operation, and after closure.展开更多
Unbalanced bidding is a cash flow management strategy that is recognized as an illegal/disqualifying practice by public owners;and unethical practice by most private owners. This practice provides the awarded bidder w...Unbalanced bidding is a cash flow management strategy that is recognized as an illegal/disqualifying practice by public owners;and unethical practice by most private owners. This practice provides the awarded bidder with unjustified advantages at the expense of the owner. Unfortunately, limited tools and techniques are currently available to identify and detect unbalanced bids during the evaluation process. This paper presents an innovative detection tool to identify unbalanced bids in unit price contracts during the bid evaluation process. The proposed technique develops BMDI graphs to visualize total markup variation patterns during the project lifetime to detect unbalanced bids. The proposed method also uses Monte Carlo simulation to take in consideration the impact of cost uncertainties and risks. An illustrative example was presented to show the capabilities and features of the proposed method in determining the status of submitted bids during the evaluation process.展开更多
Excessive growth of population and urbanization in the developing countries set an increasing demand of mobility services. To meet this demand, public transport plays a significant role by providing an easy and afford...Excessive growth of population and urbanization in the developing countries set an increasing demand of mobility services. To meet this demand, public transport plays a significant role by providing an easy and affordable mobility service. Public transport service is a process evolving over time nevertheless is not always directly responsive to the changing demand of the passengers. Recently in developing countries, the unpleasant experience in public transport services is seen as one of the main reasons behind increased passenger car share, which eventually lead to traffic congestion. However, the situation can be ameliorated if the features of the public transport are improved by addressing the users’ demand. In this study, the primary features desired and demanded by the passengers of a developing country are identified by three phase survey. These identified features are also categorized based on public responses. And finally, the required features in an appropriate public transport mode are prioritized by using a common Multi Criteria Decision Making approach (AHP—Analytic Hierarchy Process). The study suggests that residents of the developing city are not that much concern on the outlook and ambience of the service rather they are concerned about finishing their trips safely in time at an affordable rate. The findings of this research will help planners and decision makers to make the best use of the investment in public transport services and infrastructure to promote these modes over privately owned vehicle.展开更多
Traffic micro-simulation is a widely accepted tool in many countries for the evaluation and assessment of alternative design schemes.However,for several developing countries,replicating heterogeneous,non-lane based tr...Traffic micro-simulation is a widely accepted tool in many countries for the evaluation and assessment of alternative design schemes.However,for several developing countries,replicating heterogeneous,non-lane based traffic in a micro-simulation framework is gaining increased importance and still remains a challenge due to its complexity.The present study demonstrates a methodology to calibrate a traffic micro-simulation model giving due consideration to vehicle-class specific driver behavior in an urban Indian scenario for a midblock section and an intersection approach in Kolkata.The sensitive parameters affecting the driver behavior were identified for every vehicle type using Latin Hyper cube design,taking vehicle class specific travel time as a performance measure.Linear regression models were developed for each vehicle class considering the sensitive driving behavior parameters.The models highlight that the dependency of measure of effectiveness(MOE)of one vehicle type is not only limited to its own driver behavior but also on parameters of other vehicle classes.A genetic algorithm based optimization was adopted to obtain optimal parameter sets for different vehicle classes.The optimum values were found to vary significantly across all vehicle classes at a 95%confidence level.Single and multi-criteria calibration principles are also implemented to yield much more realistic results and subsequently minimizing weighted error for all vehicle classes.展开更多
This study develops and evaluates models to estimate annual average daily traffic(AADT)at non-coverage or out-of-network locations.The non-coverage locations are those where counts are performed very infrequently,but ...This study develops and evaluates models to estimate annual average daily traffic(AADT)at non-coverage or out-of-network locations.The non-coverage locations are those where counts are performed very infrequently,but an up-to-date and accurate estimate is needed by state departments of transportation.Two types of models are developed,one is that simply uses the nearby known AADT to provide an estimate,the other is that requires road-way features(e.g.,type of median,presence of left-turn lane).The advantage of the former type is that no additional data collection is needed,thereby saving time and money for state highway agencies.A natural question that this study seeks to answer is:can this type of model provide equally as good or better estimates than the latter type?The models developed belonging to the first type include hybrid-kriging and Gaussian process regres-sion GPR model(GPR-no-feature),and the models developed belonging to the second type include point-based model,ordinary regression model,quantile regression model,and GPR model(GPR-with-features).The performance of these models is compared against one another using South Carolina data from 2019 to 2021.The results indicate that the GPR-with-features model yields the lowest root mean squared error(RMSE)and lowest mean absolute percentage error(MAPE).It outperforms the hybrid-kriging model by 6.45%in RMSE,GPR without features model by 4.25%,point-based model by 4.69%,regular regres-sion model by 11.35%,and quantile regression model by 4.25%.Similarly,the GPR-with-features model outperforms the hybrid-kriging model by 25.21%in MAPE,GPR without features model by 17.81%,point-based model by 22.26%,regular regression model by 26.36%,and quantile regression model by 21.07%.展开更多
Shipping fairways in estuaries are continuously dredged to maintain access for large vessels to major ports.However,several estuaries worldwide show adverse side effects to dredging activities,in particular affecting ...Shipping fairways in estuaries are continuously dredged to maintain access for large vessels to major ports.However,several estuaries worldwide show adverse side effects to dredging activities,in particular affecting morphology and ecologically valuable habitats.We used physical scale experiments,field assessments of the Western Scheldt estuary(the Netherlands),and morphodynamic model runs to analyse the effects of dredging and future stresses(climate and sediment management)on a multi-channel system and its ecologically valuable intertidal flats.All methods indicate that dredging and disposal strategies are unfavourable to long-term morphology because dredging creates and propagates the imbalance between shallow and deeper parts of the estuary,causing a loss of valuable connecting channels and fixation of the tidal flats and main channel positions,while countering adverse effects by disposal strategy has limited effectiveness.Changing the disposal strategy towards main channel scour disposal can be economically and ecologically beneficial for the preservation of the multi-channel system.Further channel deepening will accelerate the adverse side effects,whereas future sea-level rise may revive the multi-channel system.展开更多
基金supported by the National Key R&D Program of China(Grant No.2017YFC1404200)the National Natural Science Foundation of China(Grants No.51520105014 and 51509168)the National Special Funds for Basic Scientific Research for Research Institutes(Grant No.Y218008)
文摘Dynamic tidal power is a new way of capturing tidal energy by building a water head using a dike perpendicular to the coast. This study explored the hydrodynamic mechanism of the water head across an intended dynamic tidal power dike system using the Delft3 D-FLOW software module. The propagating wave was simulated in a rectangular domain with a horizontal sea bottom at a 30-m depth. A significant water head was created across the dike by blocking the water. The water head increased with increasing dike length and increasing undisturbed tidal current acceleration. The maximum water head for the dike with a length of 50 km, located 900 km from the western boundary, was 2.15 m,which exceeded the undisturbed tidal range. The time series of the water head behaved in a manner identical to the undisturbed tidal current acceleration. The distribution of the water head over the dike assumed an elliptical shape. A parasitic wave was generated at the attachment and scattered outward. The phase lag across the dike did not behave as a linear function of the detour distance.
基金This work is supported by the National Natural Science Foundation of China(Grant Nos.52068027,51668018,51768021).
文摘Completely weathered phyllite(CWP)soil is a kind of special soil with high swell potential,while red clay is a special soil with high shrinkage.This means that these two kinds of special soils are usually not suitable for direct use as subgrade fill.To reduce the swell index of the CWP soil and the shrinkage of red clay at the same time,it was proposed to blend the CWP soil with red clay to improve their basic characteristics.A series of swell index tests and dry-wet cycle tests of the blended soils have been carried out at varying blending ratios,compaction coefficients and moisture contents.The test results show that the free swell index of the blended soil decreases with the increase of red clay,moisture content and compaction coefficient,respectively.The fissure density of the blended soil first decreases and then increases with the blending ratio,with the lowest being zero when the blending ratio is ranging from 20%to 40%.Through particle microscopic analysis and elemental composition analysis,it is found that the neutralization effect,the dilution effect of swell minerals,and the partition effect of coarse particles play an important role in restraining expansion and shrinkage deformation of the blended soil.Based on the liquid limit requirement of Chinese Railway Design Code(TB 10001-2016),the optimal blending ratio of red clay has been proposed to be 50%.Compared with the CWP soil,the free load swell index of the blended soil is reduced by 45.0%and the fissure density is reduced by 99.3%compared with that of red clay.Therefore,it is feasible to improve the CWP soil by blending it with red clay at an optimal ratio of 50%by using the neutralization effect of the expansion of CWP and shrinkage of red clay.
基金Financial support for the contribution was provided by Grant Agency of the Czech Republic (Project No. GACR P209/11/1000)
文摘This paper presents results of a study on the mechanical properties of sandy and gravely soils within the Cordillera Blanca, Peru. The soils were divided into groups according to their origin(glacial, fluvial, or debris flow). The grain size distribution of forty three soil samples was used to classify the soils according to the scheme of the Unified Soil Classification System(USCS). These distributions have then been used to estimate shear strength and hydraulic properties of the soils. There are clear differences between the soils which reflect their divergent origins. The glacial soils normally fit within one of two distinctive groups according to the proportion of fines(Group A, 7%-21.5%; Group B, 21%-65%). The estimation of shear strength at constant volume friction angle and peak shear strength of the glacial sediments with low content of fines was made using published data relating to the measured shear strength characteristics of soils with similar origins and grain size distributions. The estimated values were supported by measurements of the angle of repose taken from fourteen samples from two moraines and by shear tests on samples from one locality. The results of the grain size distribution werealso used to estimate the average hydraulic conductivity using the empirical Hazen formula which results were verified by field infiltration tests at two localities.
文摘The paper gives two examples of larger construction projects with typical stability problems. The first example is from Sakhalin Island in the Russian Far East. It is connected with a construction of oil and gas pipelines through the mountainous terrain in Makarov region. The region has an active geotectonic history and is highly affected by uncontrolled erosion and extensive landslips. Basic principles of landslide hazard mitigation are presented. The second example is from a motorway construction in Azerbaijan. This motorway leads from Baku to Russia through a seismo-tectonically active area at the toe of Caucasian mountains and in some places is situated in deep cuts at the toe of high slopes. This unsuitable routing, together with seismic activity, led to a slope stability failure of a slope affected by recent tectonic movements near the village of Devechi. Stability conditions and designed remedy measures are presented.
基金This work is supported by the National Natural Science Foundation of China(Grant Nos.52068027,51668018,51768021).
文摘Completely weathered phyllite(CWP)has the characteristics of difficult compaction,low shear strength after compaction and large settlement after construction.The traditional improvement method using a single agent of red clay or cement for CWP satisfies the subgrade requirements for ordinary railway,but cannot meet the requirements of immediate strength and long-term post-construction settlement of high-speed railway at the same time.A series of experimental investigations were undertaken for the blended CWP soils,with three additives used.The first additive was red clay,the second was cement and the third was a combination of both red clay and cement at various portions.Results of consolidation test and shear strength test carried out for the treated CWP soils show that:1)The effect of cement on improving the compression modulus of CWP is much better than that of red clay;2)The settlement of an embankment of 10 m high formed by blended soil of CWP with 3%cement can be controlled within 15 mm,while the settlement will be 25.15 mm for the same embankment of blended soil of CWP with 40%red clay;3)The shear strength and ultimate bearing capacity of CWP improved by red clay are much better than those of 5%cement;4)The ultimate bearing capacity of CWP improved by 40%red clay is 3.42 times of that by 3%cement and 2.95 times by 5%cement.Furthermore,the bearing capacity of CWP when improved by red clay can meet railway subgrade requirements immediately after compaction,while cement improved CWP needs a curing time of 1 day or longer.This is an impediment to rapid construction process.The improvement mechanism of red clay is mainly filling effect and grading improvement effect,while the improvement mechanism of cement is mainly hardening reaction,which produces high strength material to cement.It is found that 40%red clay and 3%cement treated CWP,which is considered to be optimum,can meet the subgrade requirements of both immediate bearing capacity and long-term post-construction settlement for the high-speed railway.
基金supported by the Center for Risk-Based Community Resilience Planning.The Center for Risk-Based Community Resilience Planning is a NIST-funded Center of Excellence.Funding for this study was provided as part of the Center’s cooperative agreement between the U.S.National Institute of Standards and Technology and Colorado State University(Grant Number 70NANB15H044)。
文摘Despite efforts to end homelessness in the United States,student homelessness is gradually growing over the past decade.Homelessness creates physical and psychological disadvantages for students and often disrupts school access.Research suggests that students who experience prolonged dislocation and school disruption after a dis-aster are primarily from low-income households and under-resourced areas.This study develops a framework to predict post-disaster trajectories for kindergarten through high school(K-12)students faced with a major disaster;the framework includes an estimation on the households with children who recover and those who experience long-term homelessness.Using the National Center for Education Statistics school attendance boundaries,resi-dential housing inventory,and U.S.Census data,the framework first identifies students within school boundaries and links schools to students to housing.The framework then estimates dislocation induced by the disaster sce-nario and tracks the stage of post-disaster housing for each dislocated student.The recovery of dislocated students is predicted using a multi-state Markov chain model,which captures the sequences that households transition through the four stages of post-disaster housing(i.e.,emergency shelter,temporary shelter,temporary housing,and permanent housing)based on the social vulnerability of the household.Finally,the framework predicts the number of students experiencing long-term homelessness and maps the students back to their pre-disaster school.The proposed framework is exemplified for the case of Hurricane Matthew-induced flooding in Lumberton,North Carolina.Findings highlight the disparate outcomes households with children face after major disasters and can be used to aid decision-making to reduce future disaster impacts on students.
文摘Both intake volumetric flow and through-screen velocity （the velocity of water as it passes through the screen） are important variables affecting fish impingement at industrial water intake structures including those at power plants. However, there are limited data available on quantitative assessments of impingement following changes in power plant operation such as reduced volumetric flow and intake velocity. Impingement studies were conducted at Bay Shore Power Plant in 2005-2006 （baseline） and again in 2013-2014 following fish protection mitigation which included reduced intake volumetric flows （from 33.5 m^3·s^-1 to 9.1 cm·s^-1）, a reduced through-screen velocity （from approximately 79.2 cm·s^-1 to 11.6 cm·s^-1）, modified traveling screens and installation of a fish-return system to gently and quickly remove any fish that were impinged back into the waterbody. A comparison of baseline and post-mitigation results suggested that with this mitigation in place, impingement reductions can exceed 90% for robust dominant fish species in the area.
文摘The effectiveness of an injection-based remediation strategy is primarily governed by accurate understanding of reagent delivery and ensuring uniform distribution within the reactive zone. In IRZ （in situ reactive zone） design, the required reagent strength, injection volumes, injection rates, injection frequency, injection and monitoring well spacing, and the cost and time to achieve remediation goals are governed by the hydrogeology of the site. A properly designed tracer test is capable of providing critical above mentioned site-specific information, to assist with full scale design of an IRZ. This paper describes that implementing tracer testing to support remedial design can result in enhanced design efficiency, added assurance in full-scale implementation and ultimately resulted in substantial cost savings. Therefore, it is recommended that the broader practitioner community adopt this technique as a best practice for effective and optimum in situ remediation system design.
基金supported by the long-term conceptual development research organization RVO grant 67985891the Ministry of Industry and Trade of the Czech Republic (FR-TI1/367)
文摘Underground storage systems are currently being used worldwide for the geological storage of natural gas （CH4）, the geological disposal of CO2, in geothermal energy, or radioactive waste disposal. We introduce a complex approach to the risks posed by induced bedrock instabilities in deep geological underground storage sites. Bedrock instability owing to underground openings has been studied and discussed for many years. The Bohemian Massif in the Czech Republic （Central Europe） is geologically and tectonically complex. However, this setting is ideal for leaming about the instability state of rock masses. Longterm geological and mining studies, natural and induced seismicity, radon emanations, and granite properties as potential storage sites for disposal of radioactive waste in the Czech Republic have provided useful information. In addition, the Czech Republic, with an average concentration radon of 140 Bq m-3, has the highest average radon concentrations in the world. Bedrock instabilities might emerge from microscale features, such as grain size and mineral orientation, and microfracturing. Any underground storage facility construction has to consider the stored substance and the geological settings. In the Czech Republic, granites and granitoids are the best underground storage sites. Microcrack networks and migration properties are rock specific and vary considerably. Moreover, the matrix porosity also affects the mechanical properties of the rocks. Any underground storage site has to be selected carefully. The authors suggest to study the complex set of parameters from micro to macroscale for a particular place and type of rock to ensure that the storage remains safe and stable during construction, operation, and after closure.
文摘Unbalanced bidding is a cash flow management strategy that is recognized as an illegal/disqualifying practice by public owners;and unethical practice by most private owners. This practice provides the awarded bidder with unjustified advantages at the expense of the owner. Unfortunately, limited tools and techniques are currently available to identify and detect unbalanced bids during the evaluation process. This paper presents an innovative detection tool to identify unbalanced bids in unit price contracts during the bid evaluation process. The proposed technique develops BMDI graphs to visualize total markup variation patterns during the project lifetime to detect unbalanced bids. The proposed method also uses Monte Carlo simulation to take in consideration the impact of cost uncertainties and risks. An illustrative example was presented to show the capabilities and features of the proposed method in determining the status of submitted bids during the evaluation process.
文摘Excessive growth of population and urbanization in the developing countries set an increasing demand of mobility services. To meet this demand, public transport plays a significant role by providing an easy and affordable mobility service. Public transport service is a process evolving over time nevertheless is not always directly responsive to the changing demand of the passengers. Recently in developing countries, the unpleasant experience in public transport services is seen as one of the main reasons behind increased passenger car share, which eventually lead to traffic congestion. However, the situation can be ameliorated if the features of the public transport are improved by addressing the users’ demand. In this study, the primary features desired and demanded by the passengers of a developing country are identified by three phase survey. These identified features are also categorized based on public responses. And finally, the required features in an appropriate public transport mode are prioritized by using a common Multi Criteria Decision Making approach (AHP—Analytic Hierarchy Process). The study suggests that residents of the developing city are not that much concern on the outlook and ambience of the service rather they are concerned about finishing their trips safely in time at an affordable rate. The findings of this research will help planners and decision makers to make the best use of the investment in public transport services and infrastructure to promote these modes over privately owned vehicle.
文摘Traffic micro-simulation is a widely accepted tool in many countries for the evaluation and assessment of alternative design schemes.However,for several developing countries,replicating heterogeneous,non-lane based traffic in a micro-simulation framework is gaining increased importance and still remains a challenge due to its complexity.The present study demonstrates a methodology to calibrate a traffic micro-simulation model giving due consideration to vehicle-class specific driver behavior in an urban Indian scenario for a midblock section and an intersection approach in Kolkata.The sensitive parameters affecting the driver behavior were identified for every vehicle type using Latin Hyper cube design,taking vehicle class specific travel time as a performance measure.Linear regression models were developed for each vehicle class considering the sensitive driving behavior parameters.The models highlight that the dependency of measure of effectiveness(MOE)of one vehicle type is not only limited to its own driver behavior but also on parameters of other vehicle classes.A genetic algorithm based optimization was adopted to obtain optimal parameter sets for different vehicle classes.The optimum values were found to vary significantly across all vehicle classes at a 95%confidence level.Single and multi-criteria calibration principles are also implemented to yield much more realistic results and subsequently minimizing weighted error for all vehicle classes.
基金supported by the South Carolina Department of Transportation under the State Planning and Research grant(No.SPR 749).
文摘This study develops and evaluates models to estimate annual average daily traffic(AADT)at non-coverage or out-of-network locations.The non-coverage locations are those where counts are performed very infrequently,but an up-to-date and accurate estimate is needed by state departments of transportation.Two types of models are developed,one is that simply uses the nearby known AADT to provide an estimate,the other is that requires road-way features(e.g.,type of median,presence of left-turn lane).The advantage of the former type is that no additional data collection is needed,thereby saving time and money for state highway agencies.A natural question that this study seeks to answer is:can this type of model provide equally as good or better estimates than the latter type?The models developed belonging to the first type include hybrid-kriging and Gaussian process regres-sion GPR model(GPR-no-feature),and the models developed belonging to the second type include point-based model,ordinary regression model,quantile regression model,and GPR model(GPR-with-features).The performance of these models is compared against one another using South Carolina data from 2019 to 2021.The results indicate that the GPR-with-features model yields the lowest root mean squared error(RMSE)and lowest mean absolute percentage error(MAPE).It outperforms the hybrid-kriging model by 6.45%in RMSE,GPR without features model by 4.25%,point-based model by 4.69%,regular regres-sion model by 11.35%,and quantile regression model by 4.25%.Similarly,the GPR-with-features model outperforms the hybrid-kriging model by 25.21%in MAPE,GPR without features model by 17.81%,point-based model by 22.26%,regular regression model by 26.36%,and quantile regression model by 21.07%.
基金supported by the Dutch Technology Foundation TTW under project No.STW-Vici-016.140.316/13710(granted to M.G.Kleinhans)which is part of the Netherlands Organisation for Scientific Research(NWO)+1 种基金M.R.Hiatt was supported by an ERC Consolidator Grant(agreement 647570)awarded to M.G.KleinhansW.Sonke and B.Speckmann were supported by the Netherlands Organisation for Scientific Research(NWO)under project No.639.023.208(Vici granted to B.Speckmann),K.Verbeek under project No.639.021.541.
文摘Shipping fairways in estuaries are continuously dredged to maintain access for large vessels to major ports.However,several estuaries worldwide show adverse side effects to dredging activities,in particular affecting morphology and ecologically valuable habitats.We used physical scale experiments,field assessments of the Western Scheldt estuary(the Netherlands),and morphodynamic model runs to analyse the effects of dredging and future stresses(climate and sediment management)on a multi-channel system and its ecologically valuable intertidal flats.All methods indicate that dredging and disposal strategies are unfavourable to long-term morphology because dredging creates and propagates the imbalance between shallow and deeper parts of the estuary,causing a loss of valuable connecting channels and fixation of the tidal flats and main channel positions,while countering adverse effects by disposal strategy has limited effectiveness.Changing the disposal strategy towards main channel scour disposal can be economically and ecologically beneficial for the preservation of the multi-channel system.Further channel deepening will accelerate the adverse side effects,whereas future sea-level rise may revive the multi-channel system.
