Flow properties of waxy crude oils,particularly the beneficiated waxy crude oils,are sensitive to shear history that the crude oil experienced,called the shear history effect.To simulate this shear history effect accu...Flow properties of waxy crude oils,particularly the beneficiated waxy crude oils,are sensitive to shear history that the crude oil experienced,called the shear history effect.To simulate this shear history effect accurately is vital to pipeline design and operation.It has been demonstrated by our previous that the energy dissipation or entropy generation due to viscous flow in the shear process is a suitable parameter for simulating the shear history effect.In order to further verify the reliability of this approach,experimental simulations were conducted for three PPD-beneficiated waxy crude oils transported through the China West Crude Oil Pipeline,a most complicated long-distance-crude-oil-pipeline technically and operationally so far in China.The simulations were made by using a stirred vessel and with the energy dissipation of viscous flow as the shear simulation parameter.Comparison between the flow properties of crude oils obtained from field test and experimental simulations,it is found that the gel points and viscosities from experimental simulations are in good agreement with the field data.展开更多
Masonry buildings are primarily constructed out of bricks and mortar which become discrete pieces and cannot sustain horizontal forces created by a strong earthquake.The collapse of masonry walls may cause significant...Masonry buildings are primarily constructed out of bricks and mortar which become discrete pieces and cannot sustain horizontal forces created by a strong earthquake.The collapse of masonry walls may cause significant human casualties and economic losses.To maintain their integrity,several methods have been developed to retrofit existing masonry buildings,such as the constructional RC frame which has been extensively used in China.In this study,a new method using precast steel reinforced concrete(PSRC)panels is developed.To demonstrate its effectiveness,numerical studies are conducted to investigate and compare the collapse behavior of a structure without retrofitting,retrofitted with a constructional RC frame,and retrofitted with external PSRC walls(PSRCW).Sophisticated finite element models(FEM)were developed and nonlinear time history analyses were carried out.The results show that the existing masonry building is severely damaged under occasional earthquakes,and totally collapsed under rare earthquakes.Both retrofitting techniques improve the seismic performance of existing masonry buildings.However,it is found that several occasional earthquakes caused collapse or partial collapse of the building retrofitted with the constructional RC frame,while the one retrofitted by the proposed PSRC wall system survives even under rare earthquakes.The effectiveness of the proposed retrofitting method on existing masonry buildings is thus fully demonstrated.展开更多
We have developed an energy balance equation for the universe. The two system parameters involved in the equation could be “fine-tuned” so that the predicted temperature histories all lead to what is observed in the...We have developed an energy balance equation for the universe. The two system parameters involved in the equation could be “fine-tuned” so that the predicted temperature histories all lead to what is observed in the present cosmic microwave background. We have shown that various combinations of these two parameters are possible;in particular, the present background temperature needs not be the remnant of a very hot temperature in the far distance past. We also solved for the propagation of vortex solitons in optical fibres as contrasting examples to show how electromagnetic wave could be transmitted in a particular waveform under strictly controlled conditions. To avoid singularity, all vortexes have a black centre. We conclude that while numerical techniques can be used to account for an infinite quantity, it is unlikely that such a quantity could exist in reality.展开更多
API RP2AWSD is a design code in practice for design of jacket platforms in the Persian Gulf but is based on the Gulf of Mexico environmental condition. So for the sake of using this code for the Persian Gulf, it is be...API RP2AWSD is a design code in practice for design of jacket platforms in the Persian Gulf but is based on the Gulf of Mexico environmental condition. So for the sake of using this code for the Persian Gulf, it is better to perform a calibration based on this specific region. Analysis and design of jacket platforms based on API code are performed in a static manner and dynamic analysis is not recommended for such structures. Regarding the fact that the real behavior of the offshore jacket platforms is a dynamic behavior, so in this research, dynamic analysis for an offshore jacket platform in the Persian Gulf under extreme environmental condition is performed using random time domain method. Therefore, a new constructed offshore jacket platform in the Persian Gulf is selected and analyzed. Fifteen, 1-h storm, simulations for the water surface elevation is produced to capture the statistical properties of extreme sea condition. Time series of base shear and overturning moment are derived from both dynamic and static responses. By calculating the maximum dynamic amplification factor (DAF) from each simulation and fitting the collected data to Weibull distribution, the most probable maximum extreme (MPME) value for the DAF is achieved. Results show that a realistic value for DAF for this specific platform is 1.06, which is a notable value and is recommended to take into practice in design of fixed jacket platform in the Persian Gulf.展开更多
文摘Flow properties of waxy crude oils,particularly the beneficiated waxy crude oils,are sensitive to shear history that the crude oil experienced,called the shear history effect.To simulate this shear history effect accurately is vital to pipeline design and operation.It has been demonstrated by our previous that the energy dissipation or entropy generation due to viscous flow in the shear process is a suitable parameter for simulating the shear history effect.In order to further verify the reliability of this approach,experimental simulations were conducted for three PPD-beneficiated waxy crude oils transported through the China West Crude Oil Pipeline,a most complicated long-distance-crude-oil-pipeline technically and operationally so far in China.The simulations were made by using a stirred vessel and with the energy dissipation of viscous flow as the shear simulation parameter.Comparison between the flow properties of crude oils obtained from field test and experimental simulations,it is found that the gel points and viscosities from experimental simulations are in good agreement with the field data.
基金Scientific Research Fund of Institute of Engineering Mechanics,CEA under Grant No.2016A06National Key R&D Program of China under Grant Nos.2016YFC0701101 and 2017YFC1500701National Natural Science Foundation of China under Grant No.51678538。
文摘Masonry buildings are primarily constructed out of bricks and mortar which become discrete pieces and cannot sustain horizontal forces created by a strong earthquake.The collapse of masonry walls may cause significant human casualties and economic losses.To maintain their integrity,several methods have been developed to retrofit existing masonry buildings,such as the constructional RC frame which has been extensively used in China.In this study,a new method using precast steel reinforced concrete(PSRC)panels is developed.To demonstrate its effectiveness,numerical studies are conducted to investigate and compare the collapse behavior of a structure without retrofitting,retrofitted with a constructional RC frame,and retrofitted with external PSRC walls(PSRCW).Sophisticated finite element models(FEM)were developed and nonlinear time history analyses were carried out.The results show that the existing masonry building is severely damaged under occasional earthquakes,and totally collapsed under rare earthquakes.Both retrofitting techniques improve the seismic performance of existing masonry buildings.However,it is found that several occasional earthquakes caused collapse or partial collapse of the building retrofitted with the constructional RC frame,while the one retrofitted by the proposed PSRC wall system survives even under rare earthquakes.The effectiveness of the proposed retrofitting method on existing masonry buildings is thus fully demonstrated.
文摘We have developed an energy balance equation for the universe. The two system parameters involved in the equation could be “fine-tuned” so that the predicted temperature histories all lead to what is observed in the present cosmic microwave background. We have shown that various combinations of these two parameters are possible;in particular, the present background temperature needs not be the remnant of a very hot temperature in the far distance past. We also solved for the propagation of vortex solitons in optical fibres as contrasting examples to show how electromagnetic wave could be transmitted in a particular waveform under strictly controlled conditions. To avoid singularity, all vortexes have a black centre. We conclude that while numerical techniques can be used to account for an infinite quantity, it is unlikely that such a quantity could exist in reality.
文摘API RP2AWSD is a design code in practice for design of jacket platforms in the Persian Gulf but is based on the Gulf of Mexico environmental condition. So for the sake of using this code for the Persian Gulf, it is better to perform a calibration based on this specific region. Analysis and design of jacket platforms based on API code are performed in a static manner and dynamic analysis is not recommended for such structures. Regarding the fact that the real behavior of the offshore jacket platforms is a dynamic behavior, so in this research, dynamic analysis for an offshore jacket platform in the Persian Gulf under extreme environmental condition is performed using random time domain method. Therefore, a new constructed offshore jacket platform in the Persian Gulf is selected and analyzed. Fifteen, 1-h storm, simulations for the water surface elevation is produced to capture the statistical properties of extreme sea condition. Time series of base shear and overturning moment are derived from both dynamic and static responses. By calculating the maximum dynamic amplification factor (DAF) from each simulation and fitting the collected data to Weibull distribution, the most probable maximum extreme (MPME) value for the DAF is achieved. Results show that a realistic value for DAF for this specific platform is 1.06, which is a notable value and is recommended to take into practice in design of fixed jacket platform in the Persian Gulf.
