Acoustic models of railway vehicles in standstill and pass-by conditions can be used as part of a virtual certification process for new trains.For each piece of auxiliary equipment,the sound power measured on a test b...Acoustic models of railway vehicles in standstill and pass-by conditions can be used as part of a virtual certification process for new trains.For each piece of auxiliary equipment,the sound power measured on a test bench is combined with meas-ured or predicted transfer functions.It is important,however,to allow for installation effects due to shielding by fairings or the train body.In the current work,fast-running analytical models are developed to determine these installation effects.The model for roof-mounted sources takes account of diffraction at the corner of the train body or fairing,using a barrier model.For equipment mounted under the train,the acoustic propagation from the sides of the source is based on free-field Green’s functions.The bottom surfaces are assumed to radiate initially into a cavity under the train,which is modelled with a simple diffuse field approach.The sound emitted from the gaps at the side of the cavity is then assumed to propagate to the receivers according to free-field Green’s functions.Results show good agreement with a 2.5D boundary element model and with measurements.Modelling uncertainty and parametric uncertainty are evaluated.The largest variability occurs due to the height and impedance of the ground,especially for a low receiver.This leads to standard deviations of up to 4 dB at low frequencies.For the roof-mounted sources,uncertainty over the location of the corner used in the equivalent barrier model can also lead to large standard deviations.展开更多
This paper puts forward a valuation model for the flexibility of revamping urea plants based on the substitutability of switching between the internationally accepted fertilizer feedstock fuel oil and natural gas. The...This paper puts forward a valuation model for the flexibility of revamping urea plants based on the substitutability of switching between the internationally accepted fertilizer feedstock fuel oil and natural gas. The paper first builds a stochastic mean-reversion model for fuel oil prices and natural gas prices respectively, then estimates and tests the parameters using the fuel oil and natural gas prices data from the U.S. market. This paper also conducts a sensitivity analysis with important parameters. The results show that the real option method can be applied successfully to evaluate the flexibility in decision- making for revamping installations in fertilizer plants or other similar plants.展开更多
Wind power has made rapid progress and should gain significance as an energy resource,given growing interest in renewable energy and clean energy.Offshore wind energy resources have attracted significant attention,as,...Wind power has made rapid progress and should gain significance as an energy resource,given growing interest in renewable energy and clean energy.Offshore wind energy resources have attracted significant attention,as,compared with land-based wind energy resources,offshore wind energy resources are more promising candidates for development.Sea winds are generally stronger and more reliable and with improvements in technology,the sea has become a hot spot for new designs and installation methods for wind turbines.In the present paper,based on experience building offshore wind farms,recommended foundation styles have been examined.Furthermore,wave effects have been investigated.The split installation and overall installation have been illustrated.Methods appropriate when installing a small number of turbines as well as those useful when installing large numbers of turbines were analyzed.This investigation of installation methods for wind turbines should provide practical technical guidance for their installation.展开更多
The offshore pipeline network in the U.S. Gulf of Mexico is the largest and most transparent system in the world. A review of deepwater projects in the region provides insight into construction cost and installation m...The offshore pipeline network in the U.S. Gulf of Mexico is the largest and most transparent system in the world. A review of deepwater projects in the region provides insight into construction cost and installation methods and the evolution of contract strategies. Pipeline projects are identified as export systems, infield flowline systems, and combined export and infield systems, and three dozen deepwater pipeline installations from 1980–2014 are described based on Offshore Technology Conference(OTC) and Society of Petroleum Engineers(SPE) industry publications and press release data. Export lines and infield flowlines are equally represented and many projects used a combination of J-lay, S-lay and reel methods with rigid steel, flexible line, and pipe-in-pipe systems. The average 2014 inflation-adjusted cost for pipeline projects based on OTC/SPE publications was $2.76 million/mi and ranged from $520 000/mi to $12.94 million/mi. High cost pipelines tend to be short segments or specialized pipeline. Excluding the two cost endpoints, the majority of projects ranged from $1 to $6 million/mi. The average inflation-adjusted cost to install deepwater pipelines in the U.S. Gulf of Mexico based on available public data is estimated at $3.1 million/mi.展开更多
In this paper,a numerical investigation of a float-over installation for an offshore platform is presented to verify the feasibility of the actual installation.The hydrodynamic performance of a T-barge is investigated...In this paper,a numerical investigation of a float-over installation for an offshore platform is presented to verify the feasibility of the actual installation.The hydrodynamic performance of a T-barge is investigated in the frequency domain,and the coupled motions are analyzed in the time domain.We then compare with those of the model test and determine that the response amplitude operator and the time series agree quite well.The barge exhibits favorable hydrodynamic behavior in the considered sea state,and the equipment loads are allowable.Themooring systemand sway fender forces are within the permissible range.Based on these results,we can verify that the actual installation of the offshore platform is feasible.We accurately simulated many important factors and effectively reduced the risk associated with the offshore installation,which is of great importance.As such,we demonstrate that the numerical simulation of the float-over installation for offshore platforms has practical engineering significance.展开更多
An electric-arc plasma installation operated in the hidden anode arrangement is constructed and used for the preparation of carbon nanostructures. A contracted plasma arc generated by a plasma torch using an inert gas...An electric-arc plasma installation operated in the hidden anode arrangement is constructed and used for the preparation of carbon nanostructures. A contracted plasma arc generated by a plasma torch using an inert gas is used as heat source. The average mass temperature of arc is higher than 10^4 K, while its power density, which is directly transferred onto the electrode （anode）, is - 2 kW/mm^2. The anode contact area formed on the electrode moves against the arc by way of shifting the electrode and is hidden completely in the interior of plasma gas stream moving towards it. As a result of both the direct plasma attack and the opposite movement of streams in the hidden anode contact area, a temperature higher than 6000 K is reached. Thus, intensive vaporization takes place, which forms a saturated plasma-gas-aerosol phase of the initial material of electrode （anode）. This gas phase is mixed in and carried by the plasma stream. Over that mixed plasma stream, a controlled process of quenching （fixation） is carried out by twisted turbulent fluid streams. After the fixation, the resultant carbon nano-structures are caught by a filter and collected in a bunker.展开更多
A subsea flowline jumper （FJ） is a basic connected component for the wet oil tree, subsea pipeline and riser base, and it plays an irreplaceable role in the subsea production system. During the installation of FJ, c...A subsea flowline jumper （FJ） is a basic connected component for the wet oil tree, subsea pipeline and riser base, and it plays an irreplaceable role in the subsea production system. During the installation of FJ, collisions often happen between FJ and other equipment, which may cause serious damage. Besides, as the operating water depth increases, the demand for the installation equipments, such as the crane and winch, will increase. The research of deepwater FJ installation in China is still in the primary stage, thus an installation method for the deepwater FJ is proposed in this paper. Finite element models of a typical M-shaped FJ installation system are built to simulate the installation procedures. Analysis results show that the installation steps designed are feasible and valid for the deepwater FJ. In order to ensure the safety of the installation process, the collision-sensitive analysis for the FJ is conducted, and results show that it is necessary to set the pick up speed at a proper value, in order to avoid collision in the installation process. Besides, the mechanical characteristics of FJ during the installation are investigated under a range of environmental conditions and it is found that the maximum stress of the FJ always happens at its central position. The basic requirements for the installation equipment are also obtained through the analysis of the main installation steps.展开更多
We investigated the behaviors of an active control system of two-stage vibration isolation with the actuator installed in parallel with either the upper passive mount or the lower passive isolation mount. We revealed ...We investigated the behaviors of an active control system of two-stage vibration isolation with the actuator installed in parallel with either the upper passive mount or the lower passive isolation mount. We revealed the relationships between the active control force of the actuator and the parameters of the passive isolators by studying the dynamics of two-stage active vibration isolation for the actuator at the foregoing two positions in turn. With the actuator installed beside the upper mount, a small active force can achieve a very good isolating effect when the frequency of the stimulating force is much larger than the natural frequency of the upper mount; a larger active force is required in the low-frequency domain; and the active force equals the stimulating force when the upper mount works within the resonance region, suggesting an approach to reducing wobble and ensuring desirable installation accuracy by increasing the upper-mount stiffness. In either the low or the high frequency region far away from the resonance region, the active force is smaller when the actuator is beside the lower mount than beside the upper mount.展开更多
基金The work described here has been supported by the TRANSIT project(funded by EU Horizon 2020 and the Europe’s Rail Joint Undertaking under grant agreement 881771).
文摘Acoustic models of railway vehicles in standstill and pass-by conditions can be used as part of a virtual certification process for new trains.For each piece of auxiliary equipment,the sound power measured on a test bench is combined with meas-ured or predicted transfer functions.It is important,however,to allow for installation effects due to shielding by fairings or the train body.In the current work,fast-running analytical models are developed to determine these installation effects.The model for roof-mounted sources takes account of diffraction at the corner of the train body or fairing,using a barrier model.For equipment mounted under the train,the acoustic propagation from the sides of the source is based on free-field Green’s functions.The bottom surfaces are assumed to radiate initially into a cavity under the train,which is modelled with a simple diffuse field approach.The sound emitted from the gaps at the side of the cavity is then assumed to propagate to the receivers according to free-field Green’s functions.Results show good agreement with a 2.5D boundary element model and with measurements.Modelling uncertainty and parametric uncertainty are evaluated.The largest variability occurs due to the height and impedance of the ground,especially for a low receiver.This leads to standard deviations of up to 4 dB at low frequencies.For the roof-mounted sources,uncertainty over the location of the corner used in the equivalent barrier model can also lead to large standard deviations.
文摘This paper puts forward a valuation model for the flexibility of revamping urea plants based on the substitutability of switching between the internationally accepted fertilizer feedstock fuel oil and natural gas. The paper first builds a stochastic mean-reversion model for fuel oil prices and natural gas prices respectively, then estimates and tests the parameters using the fuel oil and natural gas prices data from the U.S. market. This paper also conducts a sensitivity analysis with important parameters. The results show that the real option method can be applied successfully to evaluate the flexibility in decision- making for revamping installations in fertilizer plants or other similar plants.
基金Supported by 111 Project Foundation under Grant No.B07019the National Natural Science Foundation of China under Grand No.50979020
文摘Wind power has made rapid progress and should gain significance as an energy resource,given growing interest in renewable energy and clean energy.Offshore wind energy resources have attracted significant attention,as,compared with land-based wind energy resources,offshore wind energy resources are more promising candidates for development.Sea winds are generally stronger and more reliable and with improvements in technology,the sea has become a hot spot for new designs and installation methods for wind turbines.In the present paper,based on experience building offshore wind farms,recommended foundation styles have been examined.Furthermore,wave effects have been investigated.The split installation and overall installation have been illustrated.Methods appropriate when installing a small number of turbines as well as those useful when installing large numbers of turbines were analyzed.This investigation of installation methods for wind turbines should provide practical technical guidance for their installation.
基金provided through the U.S. Department of the Interior, Bureau of Ocean Energy Management
文摘The offshore pipeline network in the U.S. Gulf of Mexico is the largest and most transparent system in the world. A review of deepwater projects in the region provides insight into construction cost and installation methods and the evolution of contract strategies. Pipeline projects are identified as export systems, infield flowline systems, and combined export and infield systems, and three dozen deepwater pipeline installations from 1980–2014 are described based on Offshore Technology Conference(OTC) and Society of Petroleum Engineers(SPE) industry publications and press release data. Export lines and infield flowlines are equally represented and many projects used a combination of J-lay, S-lay and reel methods with rigid steel, flexible line, and pipe-in-pipe systems. The average 2014 inflation-adjusted cost for pipeline projects based on OTC/SPE publications was $2.76 million/mi and ranged from $520 000/mi to $12.94 million/mi. High cost pipelines tend to be short segments or specialized pipeline. Excluding the two cost endpoints, the majority of projects ranged from $1 to $6 million/mi. The average inflation-adjusted cost to install deepwater pipelines in the U.S. Gulf of Mexico based on available public data is estimated at $3.1 million/mi.
基金supported by Marine Engineering Equipment Scientific Research Project of Ministry of Industry and Information Technology of PRC and the Application of float-over installation simulation in Wangchang Project of CNOOC Technology ProjectThe Fundamental Research Funds for the Central Universities(HEUCF170102)
文摘In this paper,a numerical investigation of a float-over installation for an offshore platform is presented to verify the feasibility of the actual installation.The hydrodynamic performance of a T-barge is investigated in the frequency domain,and the coupled motions are analyzed in the time domain.We then compare with those of the model test and determine that the response amplitude operator and the time series agree quite well.The barge exhibits favorable hydrodynamic behavior in the considered sea state,and the equipment loads are allowable.Themooring systemand sway fender forces are within the permissible range.Based on these results,we can verify that the actual installation of the offshore platform is feasible.We accurately simulated many important factors and effectively reduced the risk associated with the offshore installation,which is of great importance.As such,we demonstrate that the numerical simulation of the float-over installation for offshore platforms has practical engineering significance.
文摘An electric-arc plasma installation operated in the hidden anode arrangement is constructed and used for the preparation of carbon nanostructures. A contracted plasma arc generated by a plasma torch using an inert gas is used as heat source. The average mass temperature of arc is higher than 10^4 K, while its power density, which is directly transferred onto the electrode （anode）, is - 2 kW/mm^2. The anode contact area formed on the electrode moves against the arc by way of shifting the electrode and is hidden completely in the interior of plasma gas stream moving towards it. As a result of both the direct plasma attack and the opposite movement of streams in the hidden anode contact area, a temperature higher than 6000 K is reached. Thus, intensive vaporization takes place, which forms a saturated plasma-gas-aerosol phase of the initial material of electrode （anode）. This gas phase is mixed in and carried by the plasma stream. Over that mixed plasma stream, a controlled process of quenching （fixation） is carried out by twisted turbulent fluid streams. After the fixation, the resultant carbon nano-structures are caught by a filter and collected in a bunker.
基金Supported by the Numerical Simulation and Experimental Investigation of FPSO and Offloading System(2011ZX05030-006-002)
文摘A subsea flowline jumper （FJ） is a basic connected component for the wet oil tree, subsea pipeline and riser base, and it plays an irreplaceable role in the subsea production system. During the installation of FJ, collisions often happen between FJ and other equipment, which may cause serious damage. Besides, as the operating water depth increases, the demand for the installation equipments, such as the crane and winch, will increase. The research of deepwater FJ installation in China is still in the primary stage, thus an installation method for the deepwater FJ is proposed in this paper. Finite element models of a typical M-shaped FJ installation system are built to simulate the installation procedures. Analysis results show that the installation steps designed are feasible and valid for the deepwater FJ. In order to ensure the safety of the installation process, the collision-sensitive analysis for the FJ is conducted, and results show that it is necessary to set the pick up speed at a proper value, in order to avoid collision in the installation process. Besides, the mechanical characteristics of FJ during the installation are investigated under a range of environmental conditions and it is found that the maximum stress of the FJ always happens at its central position. The basic requirements for the installation equipment are also obtained through the analysis of the main installation steps.
基金the Natural Science Foundation of China under Grant No. 50075029
文摘We investigated the behaviors of an active control system of two-stage vibration isolation with the actuator installed in parallel with either the upper passive mount or the lower passive isolation mount. We revealed the relationships between the active control force of the actuator and the parameters of the passive isolators by studying the dynamics of two-stage active vibration isolation for the actuator at the foregoing two positions in turn. With the actuator installed beside the upper mount, a small active force can achieve a very good isolating effect when the frequency of the stimulating force is much larger than the natural frequency of the upper mount; a larger active force is required in the low-frequency domain; and the active force equals the stimulating force when the upper mount works within the resonance region, suggesting an approach to reducing wobble and ensuring desirable installation accuracy by increasing the upper-mount stiffness. In either the low or the high frequency region far away from the resonance region, the active force is smaller when the actuator is beside the lower mount than beside the upper mount.
