Based on analyzing the limit of Ziolkowski's bubble oscillation formulation,a new model with various physical factors is established to simulate air gun signatures fo marine seismic exploration.The practical effects ...Based on analyzing the limit of Ziolkowski's bubble oscillation formulation,a new model with various physical factors is established to simulate air gun signatures fo marine seismic exploration.The practical effects of physical factors,such as heat transfe across the bubble wall,air gun port throttling,vertical rise of the bubble,fluid viscosity,and the existence of the air gun body were all taken into account in the new model.Compared with Ziolkowski's model,the signatures simulated by the new model,with small peak amplitude and rapid decay of bubble oscillation,are more consistent with actual signatures The experiment analysis indicates:(1)gun port throttling controls the peak amplitude of ai gun pulse;(2)since the hydrostatic pressure decreases when the bubble rises,the bubble oscillation period changes;(3)heat transfer and fluid viscosity are the main factors tha explain the bubble oscillation damping.展开更多
Objective To observe the therapeutic effect of acupuncture for collagen-induced arthritis (CIA) in Cx43 knock-out mice and its underlying immunological mechanism.Methods Heterozygote (Cx43^+/-) mice (n=64) and ...Objective To observe the therapeutic effect of acupuncture for collagen-induced arthritis (CIA) in Cx43 knock-out mice and its underlying immunological mechanism.Methods Heterozygote (Cx43^+/-) mice (n=64) and wild-type (Cx43^+/+) mice (n=46) were used in the present study.CIA model was es- tablished by intracutaneous injection of bovine collagenⅡ(immunonization).Acupuncture of Zúsānlǐ(足三里ST36) was carried out from the 4^th week on after the initial immunization,once a day for 3 weeks.Arthritis score and days of onset of CIA were recorded.Intracellular contents of Th subgroups of splenic lymphocytes were detected with flow cytometry.Results The incidence rate of CIA and arthritis score in Cx43^+/- mice were significantly lower than those in Cx43^+/+ mice (P〈0.05).In Cx43^+/+ mice,3 weeks after acupuncture treatment,the score of arthritis symptoms and signs in acupuncture group was significantly lower than that in model group (P〈0.01),while in Cx43^+/- mice,no significant difference was found between model group and acupuncture group in arthritis score (P〉0.05).In comparison with control group,percentages of both Thl and Th2 and Th1/Th2 increased significantly in 0x43^+/+ CIA model group (P〈0.05),while compared with model group,the percentage of Th1,Th2 and Th1/Th2 in acupuncture group decreased evidently (P〈0.05) or moderately,showing that acupuncture can effectively suppress arthritis-induced increase of Thl in Cx43^+/+ mice.In 0x43^+/- mice,Th1 level and Th1/Th2 of CIA model group increased considerably in comparison with control group (P〈0.05),while compared with model group,the Th1,Th2 and Th1/Th2 of acupuncture group had no significant changes (P〉0.05),indicating that the effect of acupuncture in suppressing increase of Th1 percent and Th1/Th2 was eliminated.Conclusion Acupuncture of Zúsānlǐ(足三里ST 36) can effectively relieve CIA symptoms and signs and inhibit increase of splenic Th1 in Cx43^+/+ mice but has no any effect on CIA score,Th1,Th2 and Th1/Th2 in Cx43^+/- mice.It shows the effect of acupuncture in improving CIA is closely related to Cx43 gene.展开更多
With the continuous improvement of living standards, there is an increasingly concerned about food quality and safety issues. Especially in recent years,food safety incidents, breaking out frequently, have become the ...With the continuous improvement of living standards, there is an increasingly concerned about food quality and safety issues. Especially in recent years,food safety incidents, breaking out frequently, have become the focus of people's attention, putting forward new demands on the regulation of food safety. This paper reviewed the Food Safety Supervision in China from food safety supervision mode,regulatory system defects and circulation supervision system, and also proposed the future research trends of food safety regulations for the wholesale market of Chinese agricultural products.展开更多
With the in-situ temperature and salinity observations taken seasonally in the Northern Yellow Sea area during the National 908 Water Investigation and Research Project from 2006 to 2007, the characteristics of the No...With the in-situ temperature and salinity observations taken seasonally in the Northern Yellow Sea area during the National 908 Water Investigation and Research Project from 2006 to 2007, the characteristics of the Northern Yellow Sea cold water mass (NYSCWM) were studied, including both its spatial pattern over the whole bottom and historically typical section from Dalian to Chengshantou. Seasonal evolution as well as its spatial distribution was analyzed to further understand the NYSCWM, as a result, some new features about the NYSCWM had been found. Compared to the previous studies, the center of colder water mass in summer moved eastward, but sharing the similar peak values for both temperature and salinity with historical data. In spring, the axis of 32.8 psu saltier moves westward approximately 75 km and the high salinity areas beyond 123.5° E were largely impaired comparing to that in winter. In winter, the NYSCWM almost disappeared due to the reinforced wind-induced mixing and the Yellow Sea Warm Currents (YSWC) moved northward and controlled most of the Northern Yellow Sea region. In autumn, two cold centers with the peak value of 9℃ were found inside the attenuated NYSCWM.展开更多
The current research of the aerostatic thrust bearing mainly focuses on the porous material bearing and inherent compensated air bearing, which aims at obtaining small physical dimension and large load capacity. Altho...The current research of the aerostatic thrust bearing mainly focuses on the porous material bearing and inherent compensated air bearing, which aims at obtaining small physical dimension and large load capacity. Although porous material bearing appears larger load capacity, materials anisotropy itself and void content distortion caused in heat-treating, and machining processes add greater complexity to internal flow transfer process. Inherent compensated air bearing has the advantages of simple structure and good stability, but its load capacity and static stiffness is not worth somewhat. In this paper, based on hydrostatic lubrication theory, finite volume method is presented for taking entrance effects into account in computing pressure distribution, load capacity and mass flow rates of circular aerostatic thrust bearings. Technical analysis, numerical simulations and laboratory demonstration tests of influence of pocket diameter and pocket depth on loading capacity of aerostatic thrust bearing are carried out on simple orifice compensated air bearings with feeding pockets. The static parameters, such as air consumption and pressure distributions, are measured as a function of supply pressure and air gap height for several different orifices and pockets size. Entrance effects are described in term of typical throttling types, and the effect of pocket diameter and pocket depth on load capacity is systematically described respectively. The proposed research results uncover the causation of throttling action of the orifice compensated air bearing with feed pocket and further develop and improve the design theory of air bearing.展开更多
Auto cascade refrigeration(ACR) cycle with phase separators is widely used in the cryogenic system. The composition of mixed refrigerant has a great effect on the performance of the system. Based on the assumption of ...Auto cascade refrigeration(ACR) cycle with phase separators is widely used in the cryogenic system. The composition of mixed refrigerant has a great effect on the performance of the system. Based on the assumption of infinite volume of phase separator, ACR system with one phase separator is simulated in this paper. The variation of refrigerant composition under different valves opening is obtained. A related experimental system is set up to verify the variation. The result shows that when the valve opening connected to the evaporator increases or the valve opening under the phase separator decreases, the low-boiling component concentration of the working mixture passing through the compressor and condenser increases, while the high-boiling component concentration decreases. Furthermore, the variations of condensation pressure and evaporation pressure under different valves opening are also observed. This paper is helpful to deepen the understanding of ACR system.展开更多
Flotation column is widely used as the separation equipment for fine mineral due to its high selectivity. However, this device may be unsuitable for the coarse particle flotation and has high handling ability. A two-s...Flotation column is widely used as the separation equipment for fine mineral due to its high selectivity. However, this device may be unsuitable for the coarse particle flotation and has high handling ability. A two-stage flotation column with dimensions of 2 000 mm×1 000 mm×4 000 mm was designed to enhance the column flotation process. The energy input was modified by adjusting the flow rate and the head of circulating pump. The flotation column was designed with low energy input in the first stage(speed flotation stage) to recover easy-to-float materials quickly, and high energy input in the second stage(recovery stage) to recover difficult-to-float minerals compulsorily. Contrast experiments on the throughput and coarse coal recovery of high ash coal from the Kailuan Mine were conducted using conventional single-stage flotation column and the two-stage flotation column. The results show that the combustible matter recovery of the two-stage flotation column is 5.25% higher than that of the conventional single-stage flotation column. However, the ash contents of clean coal for both columns are similar. Less coarse coals with low ash are obtained using the two-stage flotation column than that using the single-stage column flotation with the same handling ability. The two-stage flotation column process can enhance coal flotation compared with the conventional single-stage column flotation.展开更多
Hydraulic butterfly valves have been widely applied in marine engineering because of their large switching torque, low pressure loss and suitability for large and medium diameter pipelines. Due to control problems res...Hydraulic butterfly valves have been widely applied in marine engineering because of their large switching torque, low pressure loss and suitability for large and medium diameter pipelines. Due to control problems resulting from switching angular speeds of the hydraulic butterfly valve, a throttle-governing control mode has been widely adopted, and detailed analysis has been carried out worldwide on the structural principle concerning speed-regulation and the load torque on the shaft while opening or closing a hydraulic butterfly valve. However relevant reports have yet been published on the change law, the error and the influencing factors of the rotational angular velocity of the hydraulic butterfly valve while opening and closing. In this article, research was based on some common specifications of a hydraulic butterfly valve with a symmetrical valve flap existing in a marine environment. The throttle governing system supplied by the accumulator to achieve the switching of the hydraulic control valve was adopted, and the mathematical models of the system were established in the actual conditions while the numerical simulations took place. The simulation results and analysis show that the rotational angular velocity and the error of the hydraulic butterfly valve while switching is influenced greatly by the drainage amount of the accumulator, resulting in pressure loss in the pipeline, the temperature of hydraulic medium and the load of the hydraulic butterfly valve. The simulation results and analysis provide a theoretical basis for the choice of the total capacity of the accumulator and pipeline diameters in a throttle governing system with a hydraulic butterfly valve.It also determines the type and specification of the hydraulic butterfly valve and the design of motion parameters of the transported fluid.展开更多
Groundwater reservoir is a kind of important engineering, which can optimize water resources arran- gement by means of artificial regulation. Regulated water is the blood and value performance of groundwater reservoir...Groundwater reservoir is a kind of important engineering, which can optimize water resources arran- gement by means of artificial regulation. Regulated water is the blood and value performance of groundwater reservoir. To resolve the problem of real-time quantification of regulated water, the paper analyzed sources and compositions of regulated water in detail. Then, under the conditions of satisfying water demand inside research area, the paper analyzed quantity available and regulation coefficient of different regulated water and established a formula to calculate regulated water. At last, based on a pore groundwater reservoir in the middle reaches of the Yinma River, Jilin Province, the paper calculated regulated water with the formula and the result shows that the method is feasible. With some constraint conditions, the formula can be adopted in other similar areas.展开更多
In order to balancing based on data achieve dynamic load flow level, in this paper, we apply SDN technology to the cloud data center, and propose a dynamic load balancing method of cloud center based on SDN. The appro...In order to balancing based on data achieve dynamic load flow level, in this paper, we apply SDN technology to the cloud data center, and propose a dynamic load balancing method of cloud center based on SDN. The approach of using the SDN technology in the current task scheduling flexibility, accomplish real-time monitoring of the service node flow and load condition by the OpenFlow protocol. When the load of system is imbalanced, the controller can allocate globally network resources. What's more, by using dynamic correction, the load of the system is not obvious tilt in the long run. The results of simulation show that this approach can realize and ensure that the load will not tilt over a long period of time, and improve the system throughput.展开更多
An iterative optimization strategy for fed-batch fermentation process is presented by combining a run-to-run optimization with swarm energy conservation particle swarm optimization (SEC-PSO). SEC-PSO, which is designe...An iterative optimization strategy for fed-batch fermentation process is presented by combining a run-to-run optimization with swarm energy conservation particle swarm optimization (SEC-PSO). SEC-PSO, which is designed with the concept of energy conservation, can solve the problem of premature convergence frequently appeared in standard PSO algorithm by partitioning its population into several sub-swarms according to the energy of the swarm and is used in the optimization strategy for parameter identification and operation condition optimization. The run-to-run optimization exploits the repetitive nature of fed-batch processes in order to deal with the optimal problems of fed-batch fermentation process with inaccurate process model and unsteady process state. The kinetic model parameters, used in the operation condition optimization of the next run, are adjusted by calculating time-series data obtained from real fed-batch process in the run-to-run optimization. The simulation results show that the strategy can adjust its kinetic model dynamically and overcome the instability of fed-batch process effectively. Run-to-run strategy with SEC-PSO provides an effective method for optimization of fed-batch fermentation process.展开更多
Objective: To evaluate the efficacy of dynamic multi-slice spiral computed tomography (MSCT) for providing quantitative information about blood flow patterns of solitary pulmonary nodules (SPNs). Methods: Sevent...Objective: To evaluate the efficacy of dynamic multi-slice spiral computed tomography (MSCT) for providing quantitative information about blood flow patterns of solitary pulmonary nodules (SPNs). Methods: Seventy-eight patients with SPNs (diameter 〈 4 cm; 68 malignant; 10 active inflammatory) were underwent multi-location dynamic contrast material-enhanced serial CT (nonionic contrast material was administrated via the antecubital vein at a rate of 4 mLJs by using an autoinjector, 4 × 5 mm or 4 × 2.5 mm transverse scanning mode with stable table were performed). Sixteen series CT scans (16 scans each for the first and second series and one scan each for the rest series) were obtained during 9 min scanning period. Precontrast and postcontrast attenuation on every scan was recorded. Perfusion, peak height and ratio of peak height of the SPN to that of the aorta were calculated. Perfusion was calculated from the maximum gradient of the time-attenuation curve and the peak height of the aorta. Results: No statistically significant difference in the peak height was found between malignant (35.79 ± 10.76 Hu) and active inflammatory (39.76 ± 4.59 Hu) (t = 1.148, P = 0.255 〉 0.05). SPN-to-aorta ratio (14.27% ± 4.37) and perfusion value (30.18 mL/min/100 g ± 9.58) in malignant SPNs were significantly lower than those of active inflammatory (18.51% ± 2.71, 63.44 mL/min/100 g ± 43.87) (t = 2.978, P = 0.004 〈 0.05; t = 5.590, P 〈 0.0001). Conclusion: The quantitative information about blood flow patterns of malignant and active inflammatory SPNs is different. SPN-to-aorta ratio and perfusion value are helpful in differentiating malignant nodules from active inflammatory.展开更多
Datasets of equivalent temperature of black body (TBB) and sea surface temperature (SST)ranging from 1980 to 1997 are used to diagnose and analyze the characteristics of frequency spectrum andstrength of intraseasonal...Datasets of equivalent temperature of black body (TBB) and sea surface temperature (SST)ranging from 1980 to 1997 are used to diagnose and analyze the characteristics of frequency spectrum andstrength of intraseasonal variation of convection. The relationship between the strength of intraseasonaloscillation of convection, strength of convection itself and SST in the South China Sea (SCS) is studied. It isshown that, there are distinguishable annual, interannual and interdecadal variations in both strength andfrequency spectrum of intraseasonal variation of convection in SCS. There are connections between strength ofconvection, strength of ISO1 in the summer half (s.h.) year and SST in ensuing winter half (w.h.) year in SCS.The strong (weak) convection and strong (weak) ISO1 are associated with negative (positive) bias of SST inensuing w.h. year in SCS.展开更多
On the basis of a comprehensive literature review and data analysis of global influenza surveillance, a transmission theory based numerical model is developed to understand the causative factors of influenza seasonali...On the basis of a comprehensive literature review and data analysis of global influenza surveillance, a transmission theory based numerical model is developed to understand the causative factors of influenza seasonality and the biodynamical mechanisms of seasonal flu. The model is applied to simulate the seasonality and weekly activity of influenza in different areas across all continents and climate zones around the world. Model solution and the good matches between model output and actual influenza indexes affirm that influenza activity is highly auto-correlative and relies on determinants of a broad spectrum. Internal dynamic resonance; variations of meteorological elements (solar radiation, precipitation and dewpoint); socio-behavioral influences and herd immunity to circulating strains prove to be the critical explanatory factors of the seasonality and weekly activity of influenza. In all climate regions, influenza activity is proportional to the exponential of the number of days with precipitation and to the negative exponential of quarter power of sunny hours. Influenza activity is a negative exponential function of dewpoint in temperate and arctic regions and an exponential function of the absolute deviation of dewpoint from its annual mean in the tropics. Epidemics of seasonal influenza could be deemed as the consequence of the dynamic resonance and interactions of determinants. Early interventions (such as opportune vaccination, prompt social distancing, and maintaining incidence well below a baseline) are key to the control and prevention of seasonal influenza. Moderate amount of sunlight exposure or Vitamin D supplementation during rainy and short-day photoperiod seasons, more outdoor activities, and appropriate indoor dewpoint deserve great attention in influenza prevention. To a considerable degree, the study reveals the mechanism of influenza seasonality, demonstrating a potential for influenza activity projection. The concept and algorithm can be explored for further applications.展开更多
基金supported by the National 973 Program(Grant No.2007CB209608)National 863 Program(Grant No.2007AA06Z218)
文摘Based on analyzing the limit of Ziolkowski's bubble oscillation formulation,a new model with various physical factors is established to simulate air gun signatures fo marine seismic exploration.The practical effects of physical factors,such as heat transfe across the bubble wall,air gun port throttling,vertical rise of the bubble,fluid viscosity,and the existence of the air gun body were all taken into account in the new model.Compared with Ziolkowski's model,the signatures simulated by the new model,with small peak amplitude and rapid decay of bubble oscillation,are more consistent with actual signatures The experiment analysis indicates:(1)gun port throttling controls the peak amplitude of ai gun pulse;(2)since the hydrostatic pressure decreases when the bubble rises,the bubble oscillation period changes;(3)heat transfer and fluid viscosity are the main factors tha explain the bubble oscillation damping.
文摘Objective To observe the therapeutic effect of acupuncture for collagen-induced arthritis (CIA) in Cx43 knock-out mice and its underlying immunological mechanism.Methods Heterozygote (Cx43^+/-) mice (n=64) and wild-type (Cx43^+/+) mice (n=46) were used in the present study.CIA model was es- tablished by intracutaneous injection of bovine collagenⅡ(immunonization).Acupuncture of Zúsānlǐ(足三里ST36) was carried out from the 4^th week on after the initial immunization,once a day for 3 weeks.Arthritis score and days of onset of CIA were recorded.Intracellular contents of Th subgroups of splenic lymphocytes were detected with flow cytometry.Results The incidence rate of CIA and arthritis score in Cx43^+/- mice were significantly lower than those in Cx43^+/+ mice (P〈0.05).In Cx43^+/+ mice,3 weeks after acupuncture treatment,the score of arthritis symptoms and signs in acupuncture group was significantly lower than that in model group (P〈0.01),while in Cx43^+/- mice,no significant difference was found between model group and acupuncture group in arthritis score (P〉0.05).In comparison with control group,percentages of both Thl and Th2 and Th1/Th2 increased significantly in 0x43^+/+ CIA model group (P〈0.05),while compared with model group,the percentage of Th1,Th2 and Th1/Th2 in acupuncture group decreased evidently (P〈0.05) or moderately,showing that acupuncture can effectively suppress arthritis-induced increase of Thl in Cx43^+/+ mice.In 0x43^+/- mice,Th1 level and Th1/Th2 of CIA model group increased considerably in comparison with control group (P〈0.05),while compared with model group,the Th1,Th2 and Th1/Th2 of acupuncture group had no significant changes (P〉0.05),indicating that the effect of acupuncture in suppressing increase of Th1 percent and Th1/Th2 was eliminated.Conclusion Acupuncture of Zúsānlǐ(足三里ST 36) can effectively relieve CIA symptoms and signs and inhibit increase of splenic Th1 in Cx43^+/+ mice but has no any effect on CIA score,Th1,Th2 and Th1/Th2 in Cx43^+/- mice.It shows the effect of acupuncture in improving CIA is closely related to Cx43 gene.
文摘With the continuous improvement of living standards, there is an increasingly concerned about food quality and safety issues. Especially in recent years,food safety incidents, breaking out frequently, have become the focus of people's attention, putting forward new demands on the regulation of food safety. This paper reviewed the Food Safety Supervision in China from food safety supervision mode,regulatory system defects and circulation supervision system, and also proposed the future research trends of food safety regulations for the wholesale market of Chinese agricultural products.
文摘With the in-situ temperature and salinity observations taken seasonally in the Northern Yellow Sea area during the National 908 Water Investigation and Research Project from 2006 to 2007, the characteristics of the Northern Yellow Sea cold water mass (NYSCWM) were studied, including both its spatial pattern over the whole bottom and historically typical section from Dalian to Chengshantou. Seasonal evolution as well as its spatial distribution was analyzed to further understand the NYSCWM, as a result, some new features about the NYSCWM had been found. Compared to the previous studies, the center of colder water mass in summer moved eastward, but sharing the similar peak values for both temperature and salinity with historical data. In spring, the axis of 32.8 psu saltier moves westward approximately 75 km and the high salinity areas beyond 123.5° E were largely impaired comparing to that in winter. In winter, the NYSCWM almost disappeared due to the reinforced wind-induced mixing and the Yellow Sea Warm Currents (YSWC) moved northward and controlled most of the Northern Yellow Sea region. In autumn, two cold centers with the peak value of 9℃ were found inside the attenuated NYSCWM.
基金supported by Basic Scientific Research Project of National Natural Science Foundation of China (Grant No. k1402040202)
文摘The current research of the aerostatic thrust bearing mainly focuses on the porous material bearing and inherent compensated air bearing, which aims at obtaining small physical dimension and large load capacity. Although porous material bearing appears larger load capacity, materials anisotropy itself and void content distortion caused in heat-treating, and machining processes add greater complexity to internal flow transfer process. Inherent compensated air bearing has the advantages of simple structure and good stability, but its load capacity and static stiffness is not worth somewhat. In this paper, based on hydrostatic lubrication theory, finite volume method is presented for taking entrance effects into account in computing pressure distribution, load capacity and mass flow rates of circular aerostatic thrust bearings. Technical analysis, numerical simulations and laboratory demonstration tests of influence of pocket diameter and pocket depth on loading capacity of aerostatic thrust bearing are carried out on simple orifice compensated air bearings with feeding pockets. The static parameters, such as air consumption and pressure distributions, are measured as a function of supply pressure and air gap height for several different orifices and pockets size. Entrance effects are described in term of typical throttling types, and the effect of pocket diameter and pocket depth on load capacity is systematically described respectively. The proposed research results uncover the causation of throttling action of the orifice compensated air bearing with feed pocket and further develop and improve the design theory of air bearing.
基金Supported by the China Postdoctoral Science Foundation(2014M552195)the State Key Laboratory Foundation of Subtropical Building,South China University of Technology(2013ZC13)the Guangdong Province Key Laboratory of Efficient and Clean Energy Utilization,South China University of Technology(2013A061401005)
文摘Auto cascade refrigeration(ACR) cycle with phase separators is widely used in the cryogenic system. The composition of mixed refrigerant has a great effect on the performance of the system. Based on the assumption of infinite volume of phase separator, ACR system with one phase separator is simulated in this paper. The variation of refrigerant composition under different valves opening is obtained. A related experimental system is set up to verify the variation. The result shows that when the valve opening connected to the evaporator increases or the valve opening under the phase separator decreases, the low-boiling component concentration of the working mixture passing through the compressor and condenser increases, while the high-boiling component concentration decreases. Furthermore, the variations of condensation pressure and evaporation pressure under different valves opening are also observed. This paper is helpful to deepen the understanding of ACR system.
基金Project(2012CB214905)supported by the National Basic Research Program of ChinaProject(51074157)supported by the National Natural Science Foundation of China
文摘Flotation column is widely used as the separation equipment for fine mineral due to its high selectivity. However, this device may be unsuitable for the coarse particle flotation and has high handling ability. A two-stage flotation column with dimensions of 2 000 mm×1 000 mm×4 000 mm was designed to enhance the column flotation process. The energy input was modified by adjusting the flow rate and the head of circulating pump. The flotation column was designed with low energy input in the first stage(speed flotation stage) to recover easy-to-float materials quickly, and high energy input in the second stage(recovery stage) to recover difficult-to-float minerals compulsorily. Contrast experiments on the throughput and coarse coal recovery of high ash coal from the Kailuan Mine were conducted using conventional single-stage flotation column and the two-stage flotation column. The results show that the combustible matter recovery of the two-stage flotation column is 5.25% higher than that of the conventional single-stage flotation column. However, the ash contents of clean coal for both columns are similar. Less coarse coals with low ash are obtained using the two-stage flotation column than that using the single-stage column flotation with the same handling ability. The two-stage flotation column process can enhance coal flotation compared with the conventional single-stage column flotation.
文摘Hydraulic butterfly valves have been widely applied in marine engineering because of their large switching torque, low pressure loss and suitability for large and medium diameter pipelines. Due to control problems resulting from switching angular speeds of the hydraulic butterfly valve, a throttle-governing control mode has been widely adopted, and detailed analysis has been carried out worldwide on the structural principle concerning speed-regulation and the load torque on the shaft while opening or closing a hydraulic butterfly valve. However relevant reports have yet been published on the change law, the error and the influencing factors of the rotational angular velocity of the hydraulic butterfly valve while opening and closing. In this article, research was based on some common specifications of a hydraulic butterfly valve with a symmetrical valve flap existing in a marine environment. The throttle governing system supplied by the accumulator to achieve the switching of the hydraulic control valve was adopted, and the mathematical models of the system were established in the actual conditions while the numerical simulations took place. The simulation results and analysis show that the rotational angular velocity and the error of the hydraulic butterfly valve while switching is influenced greatly by the drainage amount of the accumulator, resulting in pressure loss in the pipeline, the temperature of hydraulic medium and the load of the hydraulic butterfly valve. The simulation results and analysis provide a theoretical basis for the choice of the total capacity of the accumulator and pipeline diameters in a throttle governing system with a hydraulic butterfly valve.It also determines the type and specification of the hydraulic butterfly valve and the design of motion parameters of the transported fluid.
基金Under the auspices of Scientific & Technological Development Project of Science & Technology Office, JilinProvince (No. 200104032)
文摘Groundwater reservoir is a kind of important engineering, which can optimize water resources arran- gement by means of artificial regulation. Regulated water is the blood and value performance of groundwater reservoir. To resolve the problem of real-time quantification of regulated water, the paper analyzed sources and compositions of regulated water in detail. Then, under the conditions of satisfying water demand inside research area, the paper analyzed quantity available and regulation coefficient of different regulated water and established a formula to calculate regulated water. At last, based on a pore groundwater reservoir in the middle reaches of the Yinma River, Jilin Province, the paper calculated regulated water with the formula and the result shows that the method is feasible. With some constraint conditions, the formula can be adopted in other similar areas.
基金supported by the National Natural Science Foundation of China(No.61163058No.61201250 and No.61363006)Guangxi Key Laboratory of Trusted Software(No.KX201306)
文摘In order to balancing based on data achieve dynamic load flow level, in this paper, we apply SDN technology to the cloud data center, and propose a dynamic load balancing method of cloud center based on SDN. The approach of using the SDN technology in the current task scheduling flexibility, accomplish real-time monitoring of the service node flow and load condition by the OpenFlow protocol. When the load of system is imbalanced, the controller can allocate globally network resources. What's more, by using dynamic correction, the load of the system is not obvious tilt in the long run. The results of simulation show that this approach can realize and ensure that the load will not tilt over a long period of time, and improve the system throughput.
基金Supported by the National Natural Science Foundation of China (20676013)
文摘An iterative optimization strategy for fed-batch fermentation process is presented by combining a run-to-run optimization with swarm energy conservation particle swarm optimization (SEC-PSO). SEC-PSO, which is designed with the concept of energy conservation, can solve the problem of premature convergence frequently appeared in standard PSO algorithm by partitioning its population into several sub-swarms according to the energy of the swarm and is used in the optimization strategy for parameter identification and operation condition optimization. The run-to-run optimization exploits the repetitive nature of fed-batch processes in order to deal with the optimal problems of fed-batch fermentation process with inaccurate process model and unsteady process state. The kinetic model parameters, used in the operation condition optimization of the next run, are adjusted by calculating time-series data obtained from real fed-batch process in the run-to-run optimization. The simulation results show that the strategy can adjust its kinetic model dynamically and overcome the instability of fed-batch process effectively. Run-to-run strategy with SEC-PSO provides an effective method for optimization of fed-batch fermentation process.
文摘Objective: To evaluate the efficacy of dynamic multi-slice spiral computed tomography (MSCT) for providing quantitative information about blood flow patterns of solitary pulmonary nodules (SPNs). Methods: Seventy-eight patients with SPNs (diameter 〈 4 cm; 68 malignant; 10 active inflammatory) were underwent multi-location dynamic contrast material-enhanced serial CT (nonionic contrast material was administrated via the antecubital vein at a rate of 4 mLJs by using an autoinjector, 4 × 5 mm or 4 × 2.5 mm transverse scanning mode with stable table were performed). Sixteen series CT scans (16 scans each for the first and second series and one scan each for the rest series) were obtained during 9 min scanning period. Precontrast and postcontrast attenuation on every scan was recorded. Perfusion, peak height and ratio of peak height of the SPN to that of the aorta were calculated. Perfusion was calculated from the maximum gradient of the time-attenuation curve and the peak height of the aorta. Results: No statistically significant difference in the peak height was found between malignant (35.79 ± 10.76 Hu) and active inflammatory (39.76 ± 4.59 Hu) (t = 1.148, P = 0.255 〉 0.05). SPN-to-aorta ratio (14.27% ± 4.37) and perfusion value (30.18 mL/min/100 g ± 9.58) in malignant SPNs were significantly lower than those of active inflammatory (18.51% ± 2.71, 63.44 mL/min/100 g ± 43.87) (t = 2.978, P = 0.004 〈 0.05; t = 5.590, P 〈 0.0001). Conclusion: The quantitative information about blood flow patterns of malignant and active inflammatory SPNs is different. SPN-to-aorta ratio and perfusion value are helpful in differentiating malignant nodules from active inflammatory.
基金"Research on the monitoring and service of South China Sea monsoons", a public welfareproject from the Ministry of Science and Technology (2002RKT01)"Response of interdecadal changes of SouthChina Sea summer monsoon to global change", a project from the Natural Science Foundation of China(902110110)
文摘Datasets of equivalent temperature of black body (TBB) and sea surface temperature (SST)ranging from 1980 to 1997 are used to diagnose and analyze the characteristics of frequency spectrum andstrength of intraseasonal variation of convection. The relationship between the strength of intraseasonaloscillation of convection, strength of convection itself and SST in the South China Sea (SCS) is studied. It isshown that, there are distinguishable annual, interannual and interdecadal variations in both strength andfrequency spectrum of intraseasonal variation of convection in SCS. There are connections between strength ofconvection, strength of ISO1 in the summer half (s.h.) year and SST in ensuing winter half (w.h.) year in SCS.The strong (weak) convection and strong (weak) ISO1 are associated with negative (positive) bias of SST inensuing w.h. year in SCS.
文摘On the basis of a comprehensive literature review and data analysis of global influenza surveillance, a transmission theory based numerical model is developed to understand the causative factors of influenza seasonality and the biodynamical mechanisms of seasonal flu. The model is applied to simulate the seasonality and weekly activity of influenza in different areas across all continents and climate zones around the world. Model solution and the good matches between model output and actual influenza indexes affirm that influenza activity is highly auto-correlative and relies on determinants of a broad spectrum. Internal dynamic resonance; variations of meteorological elements (solar radiation, precipitation and dewpoint); socio-behavioral influences and herd immunity to circulating strains prove to be the critical explanatory factors of the seasonality and weekly activity of influenza. In all climate regions, influenza activity is proportional to the exponential of the number of days with precipitation and to the negative exponential of quarter power of sunny hours. Influenza activity is a negative exponential function of dewpoint in temperate and arctic regions and an exponential function of the absolute deviation of dewpoint from its annual mean in the tropics. Epidemics of seasonal influenza could be deemed as the consequence of the dynamic resonance and interactions of determinants. Early interventions (such as opportune vaccination, prompt social distancing, and maintaining incidence well below a baseline) are key to the control and prevention of seasonal influenza. Moderate amount of sunlight exposure or Vitamin D supplementation during rainy and short-day photoperiod seasons, more outdoor activities, and appropriate indoor dewpoint deserve great attention in influenza prevention. To a considerable degree, the study reveals the mechanism of influenza seasonality, demonstrating a potential for influenza activity projection. The concept and algorithm can be explored for further applications.