Composite wood products(i.e.,particleboard,medium density fiberboard,oriented strand board,plywood)used in cabinets,shelving,and base trim express varying degrees of thickness swelling when exposed to a sustained mois...Composite wood products(i.e.,particleboard,medium density fiberboard,oriented strand board,plywood)used in cabinets,shelving,and base trim express varying degrees of thickness swelling when exposed to a sustained moisture source.Thickness swelling occurs when cellulose fibers adsorb water molecules and swell after attaining a moisture content of 29%to 36%.Observations of thickness swelling were made to refine water loss duration estimates.Thickness swell height is the result of several intrinsic factors(wood species,density,adhesive resin,heat pressing conditions).This study examined an extrinsic factor,humidity,at elevated(>95%RH)and ambient(50%RH)conditions.Specimens subjected to moisture for longer periods(8-10 weeks)experienced gradual darkening from accumulated biomass and fungal deterioration of the wood surfaces.The study revealed that high humidity conditions expressed higher rates of thickness swelling and that estimates of water loss duration should consider the influence of ambient humidity during and following a water release.展开更多
The planning of waste management facilities requires a study of design altematives including economic and environmental aspects to determine the optimal solution. Both landfill design and engineering are based on a ge...The planning of waste management facilities requires a study of design altematives including economic and environmental aspects to determine the optimal solution. Both landfill design and engineering are based on a geotechnical risk assessment namely in terms of the stability of the subsoil, the potential of mechanical deformation of the landfill body, and the stability of the interim and final cover considering also seismic events. This contribution introduces sites located in Romania and Estonia with a special focus on the geotechnical risk assessment in the design and construction of new landfills and the closure of old landfills. During the closure of a landfill an appropriate development of the interim cover is of high relevance for the remediation of old landfills, since the settlement processes in the landfill body must be decayed before the final cover can be applied. Depending on the proportion of biodegradable waste in the landfill body, the degree of compaction of the waste as well as the alteration and degree of mineralisation, the degree of the settlements can account for 5 to 15% of the landfill body height. The major settlements can generally last up to three years, depending on the organic inventory of the landfill. The examples from landfill engineering in Estonia and Romania illustrate the relevance of geotechnical assessments during the design phase of a landfill or a landfill closure as well as during the construction period.展开更多
Masonry engineering project is a key part of construction engineering. In the mixed structure, masonry is a load-bearing structure, and in the structural structure, masonry is an enclosure structure. The wall material...Masonry engineering project is a key part of construction engineering. In the mixed structure, masonry is a load-bearing structure, and in the structural structure, masonry is an enclosure structure. The wall materials are connected into a whole according to the mixed mortar to complete the internal and external maintenance, sand prevention, waterproof and shading of the building. Based on the practice of engineering supervision, the key points of engineering supervision and control of brick masonry quality are discussed.展开更多
In the USA,risk-based decision making has not been a common approach to tunnel safety in the past,but this is changing,as concepts such as“equivalency”in the NFPA 502 framework gain acceptance in the USA and elsewhe...In the USA,risk-based decision making has not been a common approach to tunnel safety in the past,but this is changing,as concepts such as“equivalency”in the NFPA 502 framework gain acceptance in the USA and elsewhere.In other regions,in particular in Europe,risk assessment techniques have been used for nearly two decades in many jurisdictions as an additional tool to complement the application of prescriptive guidelines and support decisions related to tunnel safety.After some initial difficulties these methods are meanwhile a well-established element of tunnel safety management.There are several tools available which have been practically applied and further developed over years,such as the Austrian tunnel risk model TuRisMo,or the PIARC owned DG-QRAM model.Whereas TuRisMo is a holistic,system-based model,which is best suited to quantify and assess fire risk and associated mitigation measures,DG-QRAM focusses on the risks related to the transport of hazardous materials.Depending on the objectives and the scope of the investigation and the regulatory environment,tunnel risk assessment tools are in use for different purposes,mainly to demonstrate a sufficient level of safety and to decide on and select(additional)risk mitigation measures.The international experience substantiates that the general approach is flexible and that the methods and tools are mature and can be applied for different problems in different environments.First case studies like the risk study on conditions and permissibility of the transport of hazardous materials through the Eisenhower-Johnson-Memorial Tunnel in Colorado demonstrate the applicability of a risk-based concept for decision making in the US-American environment.展开更多
Iraq covers an area of 437072 km2 in the northeastern part of the Middle East. Its population now is more than 40 million. It relies mainly on its water resources from the Tigris and Euphrates Rivers and their tributa...Iraq covers an area of 437072 km2 in the northeastern part of the Middle East. Its population now is more than 40 million. It relies mainly on its water resources from the Tigris and Euphrates Rivers and their tributaries. Recently, Iraq has been experiencing a severe water scarcity problem. This is mainly due to climate change, increased hydrological projects in riparian countries, and water resources mismanagement inside Iraq itself. To overcome the problem, a new strategy should be implemented. Such strategy should consider two main courses of action: a) serious negotiations with riparian countries to reach an agreement giving Iraq equitable water shares from the Tigris and Euphrates Rivers and their tributaries. b) Prudent water management practices inside Iraq that consider adopting realistic distribution of water between the governorates, rational policies aiming at increased water use efficiencies within Irrigation networks, increased use of non-conventional sources of water, adjustment of water tariffs and their collection procedures, improving agricultural techniques, introduction of intensive guidance and public awareness programs, and promulgation of new legislations, in addition to creation of human resources development programs.展开更多
The past decade has been very busy and exciting times for the underground power cable industry.This paper starts with a brief introduction of the past 100 years and then reviews papers presented at recent JICABLE and ...The past decade has been very busy and exciting times for the underground power cable industry.This paper starts with a brief introduction of the past 100 years and then reviews papers presented at recent JICABLE and CIGRE conferences.Over the past decade both on-line and off-line diagnostics have seen rapid development,HVDC cables have extended interconnection lengths to 600 km and HVAC cables are now commonly installed for distances up to 100 km.And at the same time advanced materials,higher operating voltages and improved cable accessory designs have supported all of these advances.In short,it is an excellent time to review underground power cable technology.展开更多
Natural gases containing sour components exhibit different gas compressibility factor （Z） behavior than do sweet gases. Therefore, a new accurate method should be developed to account for these differences. Several ...Natural gases containing sour components exhibit different gas compressibility factor （Z） behavior than do sweet gases. Therefore, a new accurate method should be developed to account for these differences. Several methods are available today for calculating the Z-factor from an equation of state. However, these equations are more complex than the foregoing correlations, involving a large number of parameters, which require more complicated and longer computations. The aim of this study is to develop a simplified calculation method for a rapid estimating Z-factor for sour natural gases containing as much as 90% total acid gas. In this article, two new correlations are first presented for calculating the pseudo- critical pressure and temperature of the gas mixture as a function of the gas specific gravity. Then, a simple correlation on the basis of the standard gas compressibility factor chart is introduced for a quick estimation of sweet gases＇ compressibility factor as a function of reduced pressure and temperature. Finally, a new corrective term related to the mole fractions of carbon dioxide and hydrogen sulfide is developed.展开更多
Lateral spread of frozen ground crust over liquefied soil has caused extensive bridge foundation damage in the past winter earthquakes.A shake table experiment was conducted to investigate the performance of a model p...Lateral spread of frozen ground crust over liquefied soil has caused extensive bridge foundation damage in the past winter earthquakes.A shake table experiment was conducted to investigate the performance of a model pile in this scenario and revealed unique pile failure mechanisms.The modelling results provided valuable data for validating numerical models.This paper presents analyses and results of this experiment using two numerical modeling approaches： solid-fluid coupled finite element（FE） modeling and the beam-on-nonlinear-Winkler-foundation（BNWF） method.A FE model was constructed based on the experiment configuration and subjected to earthquake loading.Soil and pile response results were presented and compared with experimental results to validate this model.The BNWF method was used to predict the pile response and failure mechanism.A p-y curve was presented for modelling the frozen ground crust with the free-field displacement from the experiment as loading.Pile responses were presented and compared with those of the experiment and FE model.It was concluded that the coupled FE model was effective in predicting formation of three plastic hinges at ground surface,ground crust-liquefiable soil interface and within the medium dense sand layer,while the BNWF method was only able to predict the latter two.展开更多
The effect of macadamia nut shell biochar on nitrogen,potassium,phosphorus,magnesium,calcium and sodium concentrations in potting mix used to grow Eucalyptus nitens seedlings was investigated in a glasshouse experimen...The effect of macadamia nut shell biochar on nitrogen,potassium,phosphorus,magnesium,calcium and sodium concentrations in potting mix used to grow Eucalyptus nitens seedlings was investigated in a glasshouse experiment.The treatments combined two fertiliser rates（50 and 100% rate of the commercial mix commonly used in forestry nurseries） with eight biochar rates(0,2,5,10,20,50,80 and 100 t ha;) arranged in a randomised complete block with three replicates of four sample plants.Nutrients were quantified in the potting mix and seedling leaves at four destructive harvests 135,177,219 and269 days after planting.Biochar significantly increased nitrate-N,Colwell P,Colwell K and exchangeable Na andreduced ammonium-N,Mg and Ca concentrations in the potting mix.Seedling leaf concentrations of P,K and Na were increased by biochar application,while N remained dependent on fertiliser rate only.Mg and Ca leaf concentrations decreased in response to increasing biochar rates.Elevated nitrate-N and decreased ammonium-N concentrations suggest that biochar might have increased nitrification in the potting mix.We presumed that biochar mediated processes that reduced uptake of P and K when high doses of biochar were combined with full fertilisation.Changes in potting mix K,Na,Mg and Ca were consistent with selective adsorption of ions to biochar surfaces.展开更多
The mechanisms of seismically-induced liquefaction of granular soils underhigh confining stresses are still not fully understood.Evaluation of these mechanisms is generallybased on extrapolation of observed behavior a...The mechanisms of seismically-induced liquefaction of granular soils underhigh confining stresses are still not fully understood.Evaluation of these mechanisms is generallybased on extrapolation of observed behavior at shallow depths.Three centrifuge model tests wereconducted at RPI's experimental facility to investigate the effects of confining stresses on thedynamic response of a deep horizontal deposit of saturated sand.Liquefaction was observed at highconfining stresses in each of the tests.A system identification procedure was used to estimate theassociated shear strain and stress time histories.These histories revealed a response marked byshear strength degradation and dilative patterns.The recorded accelerations and pore pressures wereemployed to generate visual animations of the models.These visualizations revealed a liquefactionfront traveling downward and leading to large shear strains and isolation of upper soil layers.展开更多
An inherent problem with natural gas production or transmission is the formation of gas hydrates, which can lead to safety hazards for production/transportation systems, and substantial economic risks. Hydrate inhibit...An inherent problem with natural gas production or transmission is the formation of gas hydrates, which can lead to safety hazards for production/transportation systems, and substantial economic risks. Hydrate inhibition with different inhibitors such as, methanol, ethylene glycol （EG）, triethylene glycol （TEG）, and sodium chloride solution continues to play a critical role in many operations. An understanding of when the hydrates form in the presence of these hydrate inhibitors, is therefore necessary to overcome hydrate problems. Several thermodynamic models have been proposed for predicting the hydrate formation conditions in aqueous solutions containing methanol/glycols and electrolytes. However, available models have limitations that include the types of liquid, compositions of fluids, and inhibitors used. The aim of this study is to develop a simple-to-use correlation for accurate prediction of hydrate-forming pressures of pure alkanes in the presence of different hydrate inhibitors, where the obtained results illustrate good agreement with the reported experimental data.展开更多
The stability of slopes is always of great concern in the field of rock engineering. The geometry and orientation of pre-existing discontinuities show a larger impact on the behavior of slopes that is often used to de...The stability of slopes is always of great concern in the field of rock engineering. The geometry and orientation of pre-existing discontinuities show a larger impact on the behavior of slopes that is often used to describe the measurement of the steepness, incline, gradient, or grade of a straight line. One of the structurally controlled modes of failure in jointed rock slopes is plane failure. There are numerous analytical methods for the rock slope stability including limit equilibrium, stress analysis and stereographic methods. The limiting equilibrium methods for slopes under various conditions against plane failure have been previously proposed by several investigators. However, these methods do not involve water pressure on sliding surfaces assessments due to water velocity and have not yet been validated by case study results. This paper has tried to explore the effects of forces due to water pressure on discontinuity surfaces in plane failure through applying the improved equations. It has studied the effect of water flow velocity on sliding surfaces in safety factor, as well. New equations for considering water velocity (fluid dynamics) are presented. To check the validity of the suggested equations, safety factor for a case study has been determined. Results show that velocity of water flow had significant effect on the amount of safety factor. Also, the suggested equations have higher validity rate compared to the current equations.展开更多
This study examines the performance of integration methods for hybrid simulation of large and complex structural systems in the context of structural collapse due to seismic excitations. The target application is not ...This study examines the performance of integration methods for hybrid simulation of large and complex structural systems in the context of structural collapse due to seismic excitations. The target application is not necessarily for real-time testing, but rather for models that involve large-scale physical sub-structures and highly nonlinear numerical models. Four case studies are presented and discussed. In the first case study, the accuracy of integration schemes including two widely used methods, namely, modified version of the implicit Newmark with fixed-number of iteration （iterative） and the operator-splitting （non-iterative） is examined through pure numerical simulations. The second case study presents the results of 10 hybrid simulations repeated with the two aforementioned integration methods considering various time steps and fixed-number of iterations for the iterative integration method. The physical sub-structure in these tests consists of a single-degree-of-freedom （SDOF） cantilever column with replaceable steel coupons that provides repeatable highly- nonlinear behavior including fracture-type strength and stiffness degradations. In case study three, the implicit Newmark with fixed-number of iterations is applied for hybrid simulations of a 1：2 scale steel moment frame that includes a relatively complex nonlinear numerical substructure. Lastly, a more complex numerical substructure is considered by constructing a nonlinear computational model of a moment frame coupled to a hybrid model ofa 1：2 scale steel gravity frame. The last two case studies are conducted on the same porotype structure and the selection of time steps and fixed number of iterations are closely examined in pre-test simulations. The generated unbalance forces is used as an index to track the equilibrium error and predict the accuracy and stability of the simulations.展开更多
Since the development of the new Austrian tunnelling method(NATM)in the 1960s,this technique has been applied successfully in many tunnels.However,opinions of NATM principles emerged till 2000,i.e.NATM is not a tunnel...Since the development of the new Austrian tunnelling method(NATM)in the 1960s,this technique has been applied successfully in many tunnels.However,opinions of NATM principles emerged till 2000,i.e.NATM is not a tunnelling method,but an approach covering all general principles of tunnelling.To investigate the general principles of the NATM,this study focused on tunnelling practises in the Bolu tunnel,and evaluated the conditions under which the NATM practises could be effective.The Bolu tunnel project was designed following the NATM principles.It is evident that practises adopted in this tunnel are important with respect to the NATM.In addition,it shows that the solutions to the problems encountered in this tunnel are consistent with the NATM principles.Finally,the study determines the ground types of the NATM principles and proposes associated updates.展开更多
Glass fi ber reinforced gypsum(GFRG) wall panels are prefabricated panels with hollow cores, originally developed in Australia and subsequently adopted by India and China for use in buildings. This paper discusses ide...Glass fi ber reinforced gypsum(GFRG) wall panels are prefabricated panels with hollow cores, originally developed in Australia and subsequently adopted by India and China for use in buildings. This paper discusses identifi cation and calibration of a suitable hysteretic model for GFRG wall panels fi lled with reinforced concrete. As considerable pinching was observed in the experimental results, a suitable hysteretic model with pinched hysteretic rule is used to conduct a series of quasi-static as inelastic hysteretic response analyses of GFRG panels with two different widths. The calibration of the pinching model parameters was carried out to approximately match the simulated and experimental responses up to 80% of the peak load in the post peak region. Interestingly, the same values of various parameters(energy dissipation and pinching related parameters) were obtained for all fi ve test specimens.展开更多
This study proposes a novel U-shaped 65Mn steel bumper as the displacement restraining device for base-isolated structures with laminated elastomeric rubber bearings.A series of bumpers with different geometric parame...This study proposes a novel U-shaped 65Mn steel bumper as the displacement restraining device for base-isolated structures with laminated elastomeric rubber bearings.A series of bumpers with different geometric parameters were designed and tested under monotonic and cyclic quasi-static loading protocols.The experimental results from a total of 232 specimens were analyzed to develop an analytical model to calculate the backbone curve and the maximum elastic restoring force for U-shaped 65Mn bumpers.Thus,the analytical equations to calculate the elastic,hardening,and unloading stiffness of U-shaped 65Mn bumpers,as well as their maximum elastic restoring force,are validated by using an additional ten groups of bumpers with varying radiuses.These analytical equations can accurately predict the mechanical parameters of U-shaped 65Mn steel bumpers for a design purpose.展开更多
A simple identification technique is developed to visualize the dynamic deformation mechanisms of centrifuge models of saturated soil and soil-pile systems using the measurements provided by sparsely distributed senso...A simple identification technique is developed to visualize the dynamic deformation mechanisms of centrifuge models of saturated soil and soil-pile systems using the measurements provided by sparsely distributed sensors. Crosscorrelation analyses are employed first to assess the variation of shear wave velocity profile with time as soil experiences stiffness reduction and degradation during dynamic excitations. The corresponding time-dependent modal configurations are determined using the finite-element technique. These configurations are used along with recorded motions to evaluate optimal time histories of displacement and strain fields based on a spectral motion reconstruction. Visualizations of the response of infinite slope and soil-pile centrifuge models revealed salient and complex multi-dimensional deformation patterns, especially at high pore pressure ratios. The developed technique provides an effective tool to visualize and analyze the dynamic response of centrifuge, shake-table and field soil systems.展开更多
In drilling operation, a large saving in time and money would be achieved by reducing the drilling time, since some of the costs are time-dependent. Drilling time could be minimized by raising the penetration rate. In...In drilling operation, a large saving in time and money would be achieved by reducing the drilling time, since some of the costs are time-dependent. Drilling time could be minimized by raising the penetration rate. In the comparative optimization method, by using the records of the first drilled wells and comparing the criteria like penetration rate, cost per foot and specific energy, the drilling parameters of the next wells being drilled can be optimized in each depth interval. In the mathematical optimization technique, some numerical equations to model the penetration rate, bit wear rate and hydraulics would be used to minimize the drilling cost and time as much as possible and improve the results of the primary comparative optimization. In this research, as a case study the Iranian Khangiran gas field has been evaluated to optimize the drilling costs. A combination of the mentioned optimization techniques resulted in an optimal well which reduced the drilling time and cost considerably in comparison with the wells already drilled.展开更多
The most important objective of blasting in open pit mines is rock fragmentation.Prediction of produced boulders(oversized crushed rocks) is a key parameter in designing blast patterns.In this study,the amount of boul...The most important objective of blasting in open pit mines is rock fragmentation.Prediction of produced boulders(oversized crushed rocks) is a key parameter in designing blast patterns.In this study,the amount of boulder produced in blasting operations of Golegohar iron ore open pit mine,Iran was predicted via multiple regression method and artificial neural networks.Results of 33 blasts in the mine were collected for modeling.Input variables were:joints spacing,density and uniaxial compressive strength of the intact rock,burden,spacing,stemming,bench height to burden ratio,and specific charge.The dependent variable was ratio of boulder volume to pattern volume.Both techniques were successful in predicting the ratio.In this study,the multiple regression method was superior with coefficient of determination and root mean squared error values of 0.89 and 0.19,respectively.展开更多
Oxy fuel combustion and conventional cycle(currently working cycle) in Kazeroon plant are modeled using commercial thermodynamic modeling software. Economic evaluation of the two models regarding the resources of tran...Oxy fuel combustion and conventional cycle(currently working cycle) in Kazeroon plant are modeled using commercial thermodynamic modeling software. Economic evaluation of the two models regarding the resources of transport and injection of carbon dioxide into oil fields at Gachsaran for enhanced oil recovery in the various oil price indices is conducted and indices net present value(NPV) and internal rate of return on investment(IRR) are calculated. The results of the two models reveal that gross efficiency of the oxy fuel cycle is more than reference cycle(62% compared to 49.03%), but the net efficiency is less(41.85% compared to 47.92%) because of the high-energy consumption of the components, particularly air separation unit(ASU) in the oxy fuel cycle. In this model, pure carbon dioxide with pressure of 20×105 Pa and purity of 96.84% was captured. NOX emissions also decrease by 4289.7 tons per year due to separation of nitrogen in ASU. In this model, none of the components of oxy fuel cycle is a major engineering challenge. With increasing oil price, economic justification of oxy fuel combustion model increases. With the price of oil at $ 80 per barrel in mind and $ 31 per ton fines for emissions of carbon dioxide in the atmosphere, IRR is the same for both models.展开更多
文摘Composite wood products(i.e.,particleboard,medium density fiberboard,oriented strand board,plywood)used in cabinets,shelving,and base trim express varying degrees of thickness swelling when exposed to a sustained moisture source.Thickness swelling occurs when cellulose fibers adsorb water molecules and swell after attaining a moisture content of 29%to 36%.Observations of thickness swelling were made to refine water loss duration estimates.Thickness swell height is the result of several intrinsic factors(wood species,density,adhesive resin,heat pressing conditions).This study examined an extrinsic factor,humidity,at elevated(>95%RH)and ambient(50%RH)conditions.Specimens subjected to moisture for longer periods(8-10 weeks)experienced gradual darkening from accumulated biomass and fungal deterioration of the wood surfaces.The study revealed that high humidity conditions expressed higher rates of thickness swelling and that estimates of water loss duration should consider the influence of ambient humidity during and following a water release.
文摘The planning of waste management facilities requires a study of design altematives including economic and environmental aspects to determine the optimal solution. Both landfill design and engineering are based on a geotechnical risk assessment namely in terms of the stability of the subsoil, the potential of mechanical deformation of the landfill body, and the stability of the interim and final cover considering also seismic events. This contribution introduces sites located in Romania and Estonia with a special focus on the geotechnical risk assessment in the design and construction of new landfills and the closure of old landfills. During the closure of a landfill an appropriate development of the interim cover is of high relevance for the remediation of old landfills, since the settlement processes in the landfill body must be decayed before the final cover can be applied. Depending on the proportion of biodegradable waste in the landfill body, the degree of compaction of the waste as well as the alteration and degree of mineralisation, the degree of the settlements can account for 5 to 15% of the landfill body height. The major settlements can generally last up to three years, depending on the organic inventory of the landfill. The examples from landfill engineering in Estonia and Romania illustrate the relevance of geotechnical assessments during the design phase of a landfill or a landfill closure as well as during the construction period.
文摘Masonry engineering project is a key part of construction engineering. In the mixed structure, masonry is a load-bearing structure, and in the structural structure, masonry is an enclosure structure. The wall materials are connected into a whole according to the mixed mortar to complete the internal and external maintenance, sand prevention, waterproof and shading of the building. Based on the practice of engineering supervision, the key points of engineering supervision and control of brick masonry quality are discussed.
文摘In the USA,risk-based decision making has not been a common approach to tunnel safety in the past,but this is changing,as concepts such as“equivalency”in the NFPA 502 framework gain acceptance in the USA and elsewhere.In other regions,in particular in Europe,risk assessment techniques have been used for nearly two decades in many jurisdictions as an additional tool to complement the application of prescriptive guidelines and support decisions related to tunnel safety.After some initial difficulties these methods are meanwhile a well-established element of tunnel safety management.There are several tools available which have been practically applied and further developed over years,such as the Austrian tunnel risk model TuRisMo,or the PIARC owned DG-QRAM model.Whereas TuRisMo is a holistic,system-based model,which is best suited to quantify and assess fire risk and associated mitigation measures,DG-QRAM focusses on the risks related to the transport of hazardous materials.Depending on the objectives and the scope of the investigation and the regulatory environment,tunnel risk assessment tools are in use for different purposes,mainly to demonstrate a sufficient level of safety and to decide on and select(additional)risk mitigation measures.The international experience substantiates that the general approach is flexible and that the methods and tools are mature and can be applied for different problems in different environments.First case studies like the risk study on conditions and permissibility of the transport of hazardous materials through the Eisenhower-Johnson-Memorial Tunnel in Colorado demonstrate the applicability of a risk-based concept for decision making in the US-American environment.
文摘Iraq covers an area of 437072 km2 in the northeastern part of the Middle East. Its population now is more than 40 million. It relies mainly on its water resources from the Tigris and Euphrates Rivers and their tributaries. Recently, Iraq has been experiencing a severe water scarcity problem. This is mainly due to climate change, increased hydrological projects in riparian countries, and water resources mismanagement inside Iraq itself. To overcome the problem, a new strategy should be implemented. Such strategy should consider two main courses of action: a) serious negotiations with riparian countries to reach an agreement giving Iraq equitable water shares from the Tigris and Euphrates Rivers and their tributaries. b) Prudent water management practices inside Iraq that consider adopting realistic distribution of water between the governorates, rational policies aiming at increased water use efficiencies within Irrigation networks, increased use of non-conventional sources of water, adjustment of water tariffs and their collection procedures, improving agricultural techniques, introduction of intensive guidance and public awareness programs, and promulgation of new legislations, in addition to creation of human resources development programs.
文摘The past decade has been very busy and exciting times for the underground power cable industry.This paper starts with a brief introduction of the past 100 years and then reviews papers presented at recent JICABLE and CIGRE conferences.Over the past decade both on-line and off-line diagnostics have seen rapid development,HVDC cables have extended interconnection lengths to 600 km and HVAC cables are now commonly installed for distances up to 100 km.And at the same time advanced materials,higher operating voltages and improved cable accessory designs have supported all of these advances.In short,it is an excellent time to review underground power cable technology.
文摘Natural gases containing sour components exhibit different gas compressibility factor （Z） behavior than do sweet gases. Therefore, a new accurate method should be developed to account for these differences. Several methods are available today for calculating the Z-factor from an equation of state. However, these equations are more complex than the foregoing correlations, involving a large number of parameters, which require more complicated and longer computations. The aim of this study is to develop a simplified calculation method for a rapid estimating Z-factor for sour natural gases containing as much as 90% total acid gas. In this article, two new correlations are first presented for calculating the pseudo- critical pressure and temperature of the gas mixture as a function of the gas specific gravity. Then, a simple correlation on the basis of the standard gas compressibility factor chart is introduced for a quick estimation of sweet gases＇ compressibility factor as a function of reduced pressure and temperature. Finally, a new corrective term related to the mole fractions of carbon dioxide and hydrogen sulfide is developed.
基金US Department of Transportation through Alaska University Transportation Centerthe State of Alaska Department of Transportation and Public Facilities(AK DOT&PF)under Project AUTC#410015
文摘Lateral spread of frozen ground crust over liquefied soil has caused extensive bridge foundation damage in the past winter earthquakes.A shake table experiment was conducted to investigate the performance of a model pile in this scenario and revealed unique pile failure mechanisms.The modelling results provided valuable data for validating numerical models.This paper presents analyses and results of this experiment using two numerical modeling approaches： solid-fluid coupled finite element（FE） modeling and the beam-on-nonlinear-Winkler-foundation（BNWF） method.A FE model was constructed based on the experiment configuration and subjected to earthquake loading.Soil and pile response results were presented and compared with experimental results to validate this model.The BNWF method was used to predict the pile response and failure mechanism.A p-y curve was presented for modelling the frozen ground crust with the free-field displacement from the experiment as loading.Pile responses were presented and compared with those of the experiment and FE model.It was concluded that the coupled FE model was effective in predicting formation of three plastic hinges at ground surface,ground crust-liquefiable soil interface and within the medium dense sand layer,while the BNWF method was only able to predict the latter two.
基金Forestry Tasmaniap,BHP Billiton TEMCO Community FoundationTasmanian Community Fund+1 种基金Centre for Renewable Energy and Power Systems(CREPS)Rainbow Bee Eater Project for their support
文摘The effect of macadamia nut shell biochar on nitrogen,potassium,phosphorus,magnesium,calcium and sodium concentrations in potting mix used to grow Eucalyptus nitens seedlings was investigated in a glasshouse experiment.The treatments combined two fertiliser rates（50 and 100% rate of the commercial mix commonly used in forestry nurseries） with eight biochar rates(0,2,5,10,20,50,80 and 100 t ha;) arranged in a randomised complete block with three replicates of four sample plants.Nutrients were quantified in the potting mix and seedling leaves at four destructive harvests 135,177,219 and269 days after planting.Biochar significantly increased nitrate-N,Colwell P,Colwell K and exchangeable Na andreduced ammonium-N,Mg and Ca concentrations in the potting mix.Seedling leaf concentrations of P,K and Na were increased by biochar application,while N remained dependent on fertiliser rate only.Mg and Ca leaf concentrations decreased in response to increasing biochar rates.Elevated nitrate-N and decreased ammonium-N concentrations suggest that biochar might have increased nitrification in the potting mix.We presumed that biochar mediated processes that reduced uptake of P and K when high doses of biochar were combined with full fertilisation.Changes in potting mix K,Na,Mg and Ca were consistent with selective adsorption of ions to biochar surfaces.
基金This research was supported by the National Science Foundation,Grant No.CMS-984754(Dr.C.Astill program manager)the US Army Engineer Research and Development Center.
文摘The mechanisms of seismically-induced liquefaction of granular soils underhigh confining stresses are still not fully understood.Evaluation of these mechanisms is generallybased on extrapolation of observed behavior at shallow depths.Three centrifuge model tests wereconducted at RPI's experimental facility to investigate the effects of confining stresses on thedynamic response of a deep horizontal deposit of saturated sand.Liquefaction was observed at highconfining stresses in each of the tests.A system identification procedure was used to estimate theassociated shear strain and stress time histories.These histories revealed a response marked byshear strength degradation and dilative patterns.The recorded accelerations and pore pressures wereemployed to generate visual animations of the models.These visualizations revealed a liquefactionfront traveling downward and leading to large shear strains and isolation of upper soil layers.
文摘An inherent problem with natural gas production or transmission is the formation of gas hydrates, which can lead to safety hazards for production/transportation systems, and substantial economic risks. Hydrate inhibition with different inhibitors such as, methanol, ethylene glycol （EG）, triethylene glycol （TEG）, and sodium chloride solution continues to play a critical role in many operations. An understanding of when the hydrates form in the presence of these hydrate inhibitors, is therefore necessary to overcome hydrate problems. Several thermodynamic models have been proposed for predicting the hydrate formation conditions in aqueous solutions containing methanol/glycols and electrolytes. However, available models have limitations that include the types of liquid, compositions of fluids, and inhibitors used. The aim of this study is to develop a simple-to-use correlation for accurate prediction of hydrate-forming pressures of pure alkanes in the presence of different hydrate inhibitors, where the obtained results illustrate good agreement with the reported experimental data.
文摘The stability of slopes is always of great concern in the field of rock engineering. The geometry and orientation of pre-existing discontinuities show a larger impact on the behavior of slopes that is often used to describe the measurement of the steepness, incline, gradient, or grade of a straight line. One of the structurally controlled modes of failure in jointed rock slopes is plane failure. There are numerous analytical methods for the rock slope stability including limit equilibrium, stress analysis and stereographic methods. The limiting equilibrium methods for slopes under various conditions against plane failure have been previously proposed by several investigators. However, these methods do not involve water pressure on sliding surfaces assessments due to water velocity and have not yet been validated by case study results. This paper has tried to explore the effects of forces due to water pressure on discontinuity surfaces in plane failure through applying the improved equations. It has studied the effect of water flow velocity on sliding surfaces in safety factor, as well. New equations for considering water velocity (fluid dynamics) are presented. To check the validity of the suggested equations, safety factor for a case study has been determined. Results show that velocity of water flow had significant effect on the amount of safety factor. Also, the suggested equations have higher validity rate compared to the current equations.
基金National Science Foundation(NSF)under grant No.CMMI-0748111
文摘This study examines the performance of integration methods for hybrid simulation of large and complex structural systems in the context of structural collapse due to seismic excitations. The target application is not necessarily for real-time testing, but rather for models that involve large-scale physical sub-structures and highly nonlinear numerical models. Four case studies are presented and discussed. In the first case study, the accuracy of integration schemes including two widely used methods, namely, modified version of the implicit Newmark with fixed-number of iteration （iterative） and the operator-splitting （non-iterative） is examined through pure numerical simulations. The second case study presents the results of 10 hybrid simulations repeated with the two aforementioned integration methods considering various time steps and fixed-number of iterations for the iterative integration method. The physical sub-structure in these tests consists of a single-degree-of-freedom （SDOF） cantilever column with replaceable steel coupons that provides repeatable highly- nonlinear behavior including fracture-type strength and stiffness degradations. In case study three, the implicit Newmark with fixed-number of iterations is applied for hybrid simulations of a 1：2 scale steel moment frame that includes a relatively complex nonlinear numerical substructure. Lastly, a more complex numerical substructure is considered by constructing a nonlinear computational model of a moment frame coupled to a hybrid model ofa 1：2 scale steel gravity frame. The last two case studies are conducted on the same porotype structure and the selection of time steps and fixed number of iterations are closely examined in pre-test simulations. The generated unbalance forces is used as an index to track the equilibrium error and predict the accuracy and stability of the simulations.
基金General Directorate of Highways(KGM)for their supports。
文摘Since the development of the new Austrian tunnelling method(NATM)in the 1960s,this technique has been applied successfully in many tunnels.However,opinions of NATM principles emerged till 2000,i.e.NATM is not a tunnelling method,but an approach covering all general principles of tunnelling.To investigate the general principles of the NATM,this study focused on tunnelling practises in the Bolu tunnel,and evaluated the conditions under which the NATM practises could be effective.The Bolu tunnel project was designed following the NATM principles.It is evident that practises adopted in this tunnel are important with respect to the NATM.In addition,it shows that the solutions to the problems encountered in this tunnel are consistent with the NATM principles.Finally,the study determines the ground types of the NATM principles and proposes associated updates.
文摘Glass fi ber reinforced gypsum(GFRG) wall panels are prefabricated panels with hollow cores, originally developed in Australia and subsequently adopted by India and China for use in buildings. This paper discusses identifi cation and calibration of a suitable hysteretic model for GFRG wall panels fi lled with reinforced concrete. As considerable pinching was observed in the experimental results, a suitable hysteretic model with pinched hysteretic rule is used to conduct a series of quasi-static as inelastic hysteretic response analyses of GFRG panels with two different widths. The calibration of the pinching model parameters was carried out to approximately match the simulated and experimental responses up to 80% of the peak load in the post peak region. Interestingly, the same values of various parameters(energy dissipation and pinching related parameters) were obtained for all fi ve test specimens.
基金National Science Foundation of China for the Financial Support for This Research under Grant Nos.51378047 and 51408027。
文摘This study proposes a novel U-shaped 65Mn steel bumper as the displacement restraining device for base-isolated structures with laminated elastomeric rubber bearings.A series of bumpers with different geometric parameters were designed and tested under monotonic and cyclic quasi-static loading protocols.The experimental results from a total of 232 specimens were analyzed to develop an analytical model to calculate the backbone curve and the maximum elastic restoring force for U-shaped 65Mn bumpers.Thus,the analytical equations to calculate the elastic,hardening,and unloading stiffness of U-shaped 65Mn bumpers,as well as their maximum elastic restoring force,are validated by using an additional ten groups of bumpers with varying radiuses.These analytical equations can accurately predict the mechanical parameters of U-shaped 65Mn steel bumpers for a design purpose.
基金National Science Foundation Under Grant No. CMS-9984754
文摘A simple identification technique is developed to visualize the dynamic deformation mechanisms of centrifuge models of saturated soil and soil-pile systems using the measurements provided by sparsely distributed sensors. Crosscorrelation analyses are employed first to assess the variation of shear wave velocity profile with time as soil experiences stiffness reduction and degradation during dynamic excitations. The corresponding time-dependent modal configurations are determined using the finite-element technique. These configurations are used along with recorded motions to evaluate optimal time histories of displacement and strain fields based on a spectral motion reconstruction. Visualizations of the response of infinite slope and soil-pile centrifuge models revealed salient and complex multi-dimensional deformation patterns, especially at high pore pressure ratios. The developed technique provides an effective tool to visualize and analyze the dynamic response of centrifuge, shake-table and field soil systems.
文摘In drilling operation, a large saving in time and money would be achieved by reducing the drilling time, since some of the costs are time-dependent. Drilling time could be minimized by raising the penetration rate. In the comparative optimization method, by using the records of the first drilled wells and comparing the criteria like penetration rate, cost per foot and specific energy, the drilling parameters of the next wells being drilled can be optimized in each depth interval. In the mathematical optimization technique, some numerical equations to model the penetration rate, bit wear rate and hydraulics would be used to minimize the drilling cost and time as much as possible and improve the results of the primary comparative optimization. In this research, as a case study the Iranian Khangiran gas field has been evaluated to optimize the drilling costs. A combination of the mentioned optimization techniques resulted in an optimal well which reduced the drilling time and cost considerably in comparison with the wells already drilled.
文摘The most important objective of blasting in open pit mines is rock fragmentation.Prediction of produced boulders(oversized crushed rocks) is a key parameter in designing blast patterns.In this study,the amount of boulder produced in blasting operations of Golegohar iron ore open pit mine,Iran was predicted via multiple regression method and artificial neural networks.Results of 33 blasts in the mine were collected for modeling.Input variables were:joints spacing,density and uniaxial compressive strength of the intact rock,burden,spacing,stemming,bench height to burden ratio,and specific charge.The dependent variable was ratio of boulder volume to pattern volume.Both techniques were successful in predicting the ratio.In this study,the multiple regression method was superior with coefficient of determination and root mean squared error values of 0.89 and 0.19,respectively.
文摘Oxy fuel combustion and conventional cycle(currently working cycle) in Kazeroon plant are modeled using commercial thermodynamic modeling software. Economic evaluation of the two models regarding the resources of transport and injection of carbon dioxide into oil fields at Gachsaran for enhanced oil recovery in the various oil price indices is conducted and indices net present value(NPV) and internal rate of return on investment(IRR) are calculated. The results of the two models reveal that gross efficiency of the oxy fuel cycle is more than reference cycle(62% compared to 49.03%), but the net efficiency is less(41.85% compared to 47.92%) because of the high-energy consumption of the components, particularly air separation unit(ASU) in the oxy fuel cycle. In this model, pure carbon dioxide with pressure of 20×105 Pa and purity of 96.84% was captured. NOX emissions also decrease by 4289.7 tons per year due to separation of nitrogen in ASU. In this model, none of the components of oxy fuel cycle is a major engineering challenge. With increasing oil price, economic justification of oxy fuel combustion model increases. With the price of oil at $ 80 per barrel in mind and $ 31 per ton fines for emissions of carbon dioxide in the atmosphere, IRR is the same for both models.
