For the purpose of improving efficiency and realizing start–stop function, an electric oil pump(EOP) is integrated into an 8-speed automatic transmission(AT). A mathematical model is built to calculate the transmissi...For the purpose of improving efficiency and realizing start–stop function, an electric oil pump(EOP) is integrated into an 8-speed automatic transmission(AT). A mathematical model is built to calculate the transmission power loss and the hydraulic system leakage. Based on this model, a flow-based control strategy is developed for EOP to satisfy the system flow requirement. This control strategy is verified through the forward driving simulation. The results indicate that there is a best combination for the size of mechanical oil pump(MOP) and EOP in terms of minimum energy consumption. In order to get a quick and smooth starting process, control strategies of the EOP and the on-coming clutch are proposed. The test environment on a prototype vehicle is built to verify the feasibility of the integrated EOP and its control strategies. The results show that the selected EOP can satisfy the flow requirement and a quick and smooth starting performance is achieved in the start–stop function. This research has a high value for the forward design of EOP in automatic transmissions with respect to efficiency improvement and start–stop function.展开更多
Mooring systems play an important role for semi-submersible rigs that drill in deepwater.A detailed analysis was carried out on the mooring of a semi-submersible rig that conducted a trial well drilling at a deepwater...Mooring systems play an important role for semi-submersible rigs that drill in deepwater.A detailed analysis was carried out on the mooring of a semi-submersible rig that conducted a trial well drilling at a deepwater location in the South China Sea in 2009.The rig was 30 years old and had a shallow platform with a designed maximum operating water depth of 457 m.Following the mooring analysis,a mooring design was given that requires upgrading of the rig’s original mooring system.The upgrade included several innovations,such as installing eight larger anchors,i.e.replacing the original anchors and inserting an additional 600 m of steel wires with the existing chains.All this was done to enhance the mooring capability of the rig in order for the rig to be held in position to conduct drilling at a water depth of 476 m.The overall duration of the drilling was 50 days and the upgraded mooring system proved to be efficient in achieving the goal of keeping the rig stationary while it was drilling the trial well in the South China Sea.This successful campaign demonstrates that an older semi-submersible rig can take on drilling in deep water after careful design and proper upgrading and modification to the original mooring system.展开更多
In the literature, many works on determining inspection interval by the delay time concept generally assumed that the time of inspection span and the time of failure renewal are negligible. However, in realistic cases...In the literature, many works on determining inspection interval by the delay time concept generally assumed that the time of inspection span and the time of failure renewal are negligible. However, in realistic cases, the above time should not be neglected for both the time itself and its effect. In order to model the effect of the possible overlapping of inspection span with failure downtime on determining the optimal inspection interval, we propose a block-based inspection model for a single component-based on delay time concept. We further compare this model with the age-based model to show the practical sense. The developed models are also demonstrated by numerical examples.展开更多
In view of the reduction of hovering efficiency near high tension when a helicopter rotor hovers,a numerical simulation method of lifting rotor hovering aerodynamic characteristics based on leading edge droop is estab...In view of the reduction of hovering efficiency near high tension when a helicopter rotor hovers,a numerical simulation method of lifting rotor hovering aerodynamic characteristics based on leading edge droop is established in this paper. It is dominated by Reynolds average N-S equation in integral form. Firstly,VR-12 airfoil is taken as the research object,and the influence of leading edge droop angle on the aerodynamic characteristics of two-dimensional airfoil is studied. Secondly,the modified 7 A rotor is taken as the research object,and the effects of different leading edge droop angles at the position of blade r/R=0.75—1 on the aerodynamic characteristics in hover are explored. It is found that the leading edge droop can significantly improve the aerodynamic characteristics of two-dimensional airfoil and three-dimensional hovering rotor near high angle of attack,and can effectively inhibit the generation of stall vortex.展开更多
An optimal maintenance policy tor deteriorating components based on quasi renew-process model is presented. In this policy, the first N - 1 failures of a component are maintained by repairs and the N'h failure is mai...An optimal maintenance policy tor deteriorating components based on quasi renew-process model is presented. In this policy, the first N - 1 failures of a component are maintained by repairs and the N'h failure is maintained by replacement. The policy takes replacement actions at component lev- el by considering the fact that more and more components are designed to be field replaceable and maintenance activities are setting free from system halt. Concerning system structure impact, impor- tance measure is employed in the optimization procedure which aims at maximizing the long-rnn prof- it per unit time. Two example series parallel systems are taken to illustrate the policy and it is proved to work well. According to importance analysis, components are classified into important ones and unimportant ones based on the system behavior under their failures. Simulation results show that the presented policy makes a clear distinction between them and takes effective mainte- nance actions to compensate the deteriorating of components.展开更多
Downtime due to adverse wave conditions for vessels at berth is an important commercial aspect in the planning and development of a sea port or a berthing terminal. This paper describes a practical technique for preli...Downtime due to adverse wave conditions for vessels at berth is an important commercial aspect in the planning and development of a sea port or a berthing terminal. This paper describes a practical technique for preliminary assessment of operational downtime at a proposed bulk terminal. Time-series wind and wave data at an offshore location was purchased. Numerical modelling was then carried out using the MIKE21 SW (spectral wave) model developed by DHI (Deutsches Hydrographisches Institut) to transform these offshore waves into inshore in order to derive wave conditions at the berth. Both wind-waves and swell-waves were considered. Waves affecting the head and beam of a vessel were considered separately for a wide range of vessel sizes with DT (displacement tonnage) ranging from 5,000 tons to 〉 200,000 tons. The limiting wave height H5% was used. Operational downtime was also calculated using significant wave height, Hs as a criterion with limits ofHs = 1.0 m for beam seas and Hs = 1.5 m for head seas. The methodology and lessons learnt from the study can be applied for the development of any sea port worldwide.展开更多
The White Tiger is Aravind Adiga's first novel just like Son of the Native Soil which is Shadrach Ambanasom's first oeuvre. The two novels address two major social concerns (the caste system and tribal loyalty) th...The White Tiger is Aravind Adiga's first novel just like Son of the Native Soil which is Shadrach Ambanasom's first oeuvre. The two novels address two major social concerns (the caste system and tribal loyalty) that impair national cohesion in India and Cameroon respectively. Briefly speaking, the caste refers to the classification of peoples in India (and other South Asian countries) into in-marrying hereditary social classes of the privileged and the underprivileged while tribal loyalty refers to selfish attachment to a tribe or clan to the detriment of community or national feeling. The two concepts are related in the sense that the word "caste" derives from the Spanish or Portuguese "casta" meaning race, lineage, breed or clan. In both cases therefore, the issues of sectionalism, division, discrimination, selfishness, marginalization, and hegemony (amongst others) are at play--issues that impede the notion of nationhood. Read principally from the Marxist perspective of power dynamics and class struggle, the paper argues that Adiga and Ambanasom through skillful manipulation of symbols, time, characters and events, try to imagine the deconstruction of caste and ethnic loyalty in India and Cameroon respectively, which to the two authors, are only historically and socially erected edifices rather than natural order. For the two authors, although global forces may seem to play in favor of a more equitable human society, a necessarily violent revolution might be required to dismantle a blighted body politico-modus operandi that has operated in the people's psyche for a long time, as characters and events in the two novels reveal.展开更多
RLWI (Riserless Light Well Intervention) technology has the advantage of utilizing a special subsea lubricator to perform intervention activities in water depths of up to 1,200 m without the need for the marine rise...RLWI (Riserless Light Well Intervention) technology has the advantage of utilizing a special subsea lubricator to perform intervention activities in water depths of up to 1,200 m without the need for the marine risers. Utilizing the technology, oil companies have been able to save up to 50% on the intervention costs. However, in the last five years, it has seen up to 25% downtime due to waiting on weather (wow). Thus, in this manuscript, it is attempted to identify the critical elements of the module deployment system and analyze their significance in the objective of raising the operational weather limit. Critical failure modes were found to be failure of crane wire due to excess loading, failure of the lower cursor system due to the impact loading and clashing of the module with the moonpool walls. Analysis of the module deployment system against these failure modes was ensued by using Orcaflex. The results showed the moonpool sea state to be the defining parameter. Although, changing moonpool dimensions affect hydrodynamics positively, however it's significance is small due to dependency on the vessel's breadth. Based on these results and the available data for the analysis, a recommended system particular was tested. Significance improvement, in lowering the risk of failure was observed.展开更多
Generally, lightning damage has mainly been to home appliances and telephones, towers and power transmission and generation equipment mal functions and damage due to strikes on power lines. With the adoption of wind p...Generally, lightning damage has mainly been to home appliances and telephones, towers and power transmission and generation equipment mal functions and damage due to strikes on power lines. With the adoption of wind power generation equipment, however, lightning damage is also increasing in this area. Through his dimensional characteristics, the wind power system is more exposed in the nature compared to all others systems. Lightning damage is the single largest cause of unplanned downtime in wind turbines, and that downtime is responsible for the loss of countless megawatts of power generation. The wind turbines are important structures, since they can easily attract the wrath of storms hits heights close, they can also capture the most distant. The rotation of the blades may also trigger lightning and result in considerable increase in the number of strikes to a wind turbine unit. Since wind turbines are tall structures, the lightning currents that are injected by return strokes into the turbines will be affected by reflections at the top, at the bottom, and at the junction of the blades with the static base of the turbine. We present our contribution in this paper to study lightning strokes and their effects on the wind turbines with the aim to enrich the work and to suggest more effective means of protection against lightning.展开更多
In order to evaluate the operational reliability of Japanese FBR (fast breeder reactor) MONJU, frequencies of important intermediate events and equipment failures resulting during reactor automatic trip are predicte...In order to evaluate the operational reliability of Japanese FBR (fast breeder reactor) MONJU, frequencies of important intermediate events and equipment failures resulting during reactor automatic trip are predicted using FTA (fault tree analysis) technique for the plant system model. The targeted devices are the following: PHTS (primary heat transport system), SHTS (secondary heat transport system), WS (water and steam system), PPS (plant protection system) and PCS (plant control system). In this paper, the frequency of automatic reactor trips was estimated by extracting and analyzing the important intermediate events and equipment failures covering all the derived fault trees of these systems. The analyses predicted 1.2/RY (reactor year) the value of unplanned shut down frequency by the internal factor of the system. The largest contributed event was function failure of SHTS accounting for 42.6% of total events followed by PHTS with 40.1%. The contribution factor of WS was only 4.4%.展开更多
AIM: To explore the relationship between the level of proinsulin with cardiovascular risk factors and sleep snoring.METHODS: Based on the random stratified sampling principle, 1 193 Chinese residents in Pizhou City, J...AIM: To explore the relationship between the level of proinsulin with cardiovascular risk factors and sleep snoring.METHODS: Based on the random stratified sampling principle, 1 193 Chinese residents in Pizhou City, Jiangsu Province (530 males and 663 females, aged 35-59 years with an average age of 46.69 years) were recruited. Their sleep snoring habits were investigated. Biotin-avidin based double mAbs ELISA was used to detect specific insulin and proinsulin, and a risk factor score was established to evaluate the individuals according to the number of their risk factors.RESULTS: The results of Spearman correlation analysis and covariate ANOVA analysis after age and sex were controlled, indicated that not only the level of proinsulin (r = 0.156, P = 0.000, F= 5.980 P = 0.000), but also cardiovascular risk factors score (r = 0.194, P = 0.000,F= 11.135, P = 0.000) significantly associated with the frequency of sleep snoring, and the significant relationship between true insulin and frequency of sleep snoring was only shown in the covariate ANOVA analysis (F = 2.868,P = 0.022). The result of multivariate stepwise logistic regression after age, sex, body mass index, waist circumference and true insulin were controlled showed that proinsulin (division by interval of quartile) was an independent risk factor for sleep snoring (OR = 1.220,95%CI: 1.085-1.373, P = 0.001).CONCLUSION: The interaction of cardiovascular risk factors clustering, high proinsulin level and sleep breathing disorder may be a syndrome, which has not been recognized in human beings so far.展开更多
According to Brazilian reports of large trucks accidents on Federal Highway, fatigue and speeding are the major contributors to those accidents in which drivers are trying to meet short delivery deadlines for long hau...According to Brazilian reports of large trucks accidents on Federal Highway, fatigue and speeding are the major contributors to those accidents in which drivers are trying to meet short delivery deadlines for long hauls. A new federal law has been approved to limit truck drivers' working times, including maximum continuous driving time and maximum daily and weekly on-duty time. We present a study that aims at analyzing whether the existing resting areas on federal highways have sufficient capacity to meet current and future demand for truck stops. We have established the following method: In the first step, we review and study different models found in the literature and evaluate their potential application to Brazilian conditions; In the next step, we develop our own model and, finally, validate it using data from BR-101 Federal Highway, in Santa Catarina State. Tests made using part of collected data (which were subjected to statistical treatment) showed satisfactory results, indicating that the demand behavior was consistent with that observed in the field and the answers provided by truck drivers in the interviews. The research has yet to complete processing all data and it also must be repeated in other regions with different characteristics.展开更多
To evaluate the particle dynamics and estimate the POC (particulate organic carbon) export flux from the euphotic zone in the western Arctic Ocean,234 Th238 U disequilibrium was applied during the second Chinese Natio...To evaluate the particle dynamics and estimate the POC (particulate organic carbon) export flux from the euphotic zone in the western Arctic Ocean,234 Th238 U disequilibrium was applied during the second Chinese National Arctic Research Expedition (July 15-September 26,2003).The POC export fluxes are estimated from the measured profiles of the 234 Th/238 U activity ratios and the POC/PTh ratios.The average residence times of the particulate and dissolved 234 Th in the euphotic zone are 33 d and 121 d,and their average export fluxes are 480 dpm/m 2 d and 760 dpm/m 2 d,respectively.The scavenging and removal processes of particle reactive elements are active in the upper layer of the Chukchi Sea.The average residence time of 234 Th increases from shelf to basin,while the export fluxes of 234 Th decrease.The estimated POC export fluxes from the euphotic zone vary from 2.1 to 20.3 mmol/m 2 d,indicating that the western Arctic Ocean is an important carbon sink in summer due to efficient biological pump.展开更多
In the paper,we obtain the SRC lifting of a right continuous, left upper semi-continuous random process on a Loeb space.And show the existence of S-optimal stopping of an internal process,construct the S-optimal stopp...In the paper,we obtain the SRC lifting of a right continuous, left upper semi-continuous random process on a Loeb space.And show the existence of S-optimal stopping of an internal process,construct the S-optimal stopping. Finally we prove the fact that the standard part of the S-optimal stopping of a SRC lifting is the optimal stopping of the corresponding standard process,which generalizes the conclusions in [8]on a Loeb space.展开更多
This paper studies for ward-back ward differential equations with Poisson jumps and with stopping time as termination. Under some weak monotonicity conditions and for non-Lipschitzian coefficients, the existence and u...This paper studies for ward-back ward differential equations with Poisson jumps and with stopping time as termination. Under some weak monotonicity conditions and for non-Lipschitzian coefficients, the existence and uniqueness of solutions are proved via a purely probabilistic approach, while a priori estimate is given. Here, we allow the forward equation to be degenerate.展开更多
The authors study the continuous properties of square integrable g-martingales via backward stochastic differential equations (shortly BSDEs) and get a general upcrossing inequality and an optional stopping theorem fo...The authors study the continuous properties of square integrable g-martingales via backward stochastic differential equations (shortly BSDEs) and get a general upcrossing inequality and an optional stopping theorem for g-martingales.展开更多
Delirium is an acute and fluctuating change in mental status, with inattention and altered levels of consciousness. It is a common comorbidity in intensive care units (ICU), resulting in delayed withdrawal of mechan...Delirium is an acute and fluctuating change in mental status, with inattention and altered levels of consciousness. It is a common comorbidity in intensive care units (ICU), resulting in delayed withdrawal of mechanical ventilation, prolonged length of stay in ICU, increased ICU mortality and impaired long-term cognitive function of the survivors. Narcotic or psychoactive medication is one of the major risk factors that contribute to ICU delirium. Surveys conducted in several countries indicated that delirium in ICU was inad- equately monitored, underdiagnosed and lacked standardized treatment. In order to improve the prevention and treatment of ICU delirium, it is imperative that the ICU professionals should enrich their knowledge about this comorbidity, familiarize themselves with its screening and management, as well as standardize the administration of narcotic and psychoactive medications.展开更多
Obstructive sleep apnea syndrome (OSAS) is characterized by recurrent collapses of the upper airway, which lead to repetitive transient hypoxia, arousals and finally sleep fragmentation. Both anatomical and neuromuscu...Obstructive sleep apnea syndrome (OSAS) is characterized by recurrent collapses of the upper airway, which lead to repetitive transient hypoxia, arousals and finally sleep fragmentation. Both anatomical and neuromuscular factors may play key roles in the pathophysiology of OSAS. The purpose of this paper was to study the control mechanism of OSAS from the mechanical point of view. A three-dimensional finite element model was developed, which not only reconstructed the realistic anatomical structure of the human upper airway, but also included surrounding structures such as the skull, neck, hyoid, cartilage and soft tissues. The respiration process during the normal and apnea states was simulated with the fluid-structure interaction method (FSI) and the computational fluid dynamics method (CFD). The airflow and deformation of the upper airway obtained from the FSI and the CFD method were compared and the results obtained under large negative pressure during an apnea episode were analyzed. The simulation results show that the FSI method is more feasible and effective than the CFD method. The concave configuration of the upper airway may accelerate the collapse of the upper airway in a positive feedback mechanism, which supplies meaningful information for clinical treatment and further research of OSAS.展开更多
基金Project(51405010)supported by the National Natural Science Foundation of ChinaProject(2011BAG09B00)supported by the National Science and Technology Support Program of China
文摘For the purpose of improving efficiency and realizing start–stop function, an electric oil pump(EOP) is integrated into an 8-speed automatic transmission(AT). A mathematical model is built to calculate the transmission power loss and the hydraulic system leakage. Based on this model, a flow-based control strategy is developed for EOP to satisfy the system flow requirement. This control strategy is verified through the forward driving simulation. The results indicate that there is a best combination for the size of mechanical oil pump(MOP) and EOP in terms of minimum energy consumption. In order to get a quick and smooth starting process, control strategies of the EOP and the on-coming clutch are proposed. The test environment on a prototype vehicle is built to verify the feasibility of the integrated EOP and its control strategies. The results show that the selected EOP can satisfy the flow requirement and a quick and smooth starting performance is achieved in the start–stop function. This research has a high value for the forward design of EOP in automatic transmissions with respect to efficiency improvement and start–stop function.
文摘Mooring systems play an important role for semi-submersible rigs that drill in deepwater.A detailed analysis was carried out on the mooring of a semi-submersible rig that conducted a trial well drilling at a deepwater location in the South China Sea in 2009.The rig was 30 years old and had a shallow platform with a designed maximum operating water depth of 457 m.Following the mooring analysis,a mooring design was given that requires upgrading of the rig’s original mooring system.The upgrade included several innovations,such as installing eight larger anchors,i.e.replacing the original anchors and inserting an additional 600 m of steel wires with the existing chains.All this was done to enhance the mooring capability of the rig in order for the rig to be held in position to conduct drilling at a water depth of 476 m.The overall duration of the drilling was 50 days and the upgraded mooring system proved to be efficient in achieving the goal of keeping the rig stationary while it was drilling the trial well in the South China Sea.This successful campaign demonstrates that an older semi-submersible rig can take on drilling in deep water after careful design and proper upgrading and modification to the original mooring system.
文摘In the literature, many works on determining inspection interval by the delay time concept generally assumed that the time of inspection span and the time of failure renewal are negligible. However, in realistic cases, the above time should not be neglected for both the time itself and its effect. In order to model the effect of the possible overlapping of inspection span with failure downtime on determining the optimal inspection interval, we propose a block-based inspection model for a single component-based on delay time concept. We further compare this model with the age-based model to show the practical sense. The developed models are also demonstrated by numerical examples.
基金supported by the National Natural Science Foundation of China(No.11972190)the Aeronautical Science Foundation of China(No. 20185752)
文摘In view of the reduction of hovering efficiency near high tension when a helicopter rotor hovers,a numerical simulation method of lifting rotor hovering aerodynamic characteristics based on leading edge droop is established in this paper. It is dominated by Reynolds average N-S equation in integral form. Firstly,VR-12 airfoil is taken as the research object,and the influence of leading edge droop angle on the aerodynamic characteristics of two-dimensional airfoil is studied. Secondly,the modified 7 A rotor is taken as the research object,and the effects of different leading edge droop angles at the position of blade r/R=0.75—1 on the aerodynamic characteristics in hover are explored. It is found that the leading edge droop can significantly improve the aerodynamic characteristics of two-dimensional airfoil and three-dimensional hovering rotor near high angle of attack,and can effectively inhibit the generation of stall vortex.
基金Supported by the National High Technology Research and Development Programme of China(No.2008AA01A204)the National Natural Science Foundation of China(No.61003047,61173020)International Science & Technology Cooperation Project(No.2010DFA14400)
文摘An optimal maintenance policy tor deteriorating components based on quasi renew-process model is presented. In this policy, the first N - 1 failures of a component are maintained by repairs and the N'h failure is maintained by replacement. The policy takes replacement actions at component lev- el by considering the fact that more and more components are designed to be field replaceable and maintenance activities are setting free from system halt. Concerning system structure impact, impor- tance measure is employed in the optimization procedure which aims at maximizing the long-rnn prof- it per unit time. Two example series parallel systems are taken to illustrate the policy and it is proved to work well. According to importance analysis, components are classified into important ones and unimportant ones based on the system behavior under their failures. Simulation results show that the presented policy makes a clear distinction between them and takes effective mainte- nance actions to compensate the deteriorating of components.
文摘Downtime due to adverse wave conditions for vessels at berth is an important commercial aspect in the planning and development of a sea port or a berthing terminal. This paper describes a practical technique for preliminary assessment of operational downtime at a proposed bulk terminal. Time-series wind and wave data at an offshore location was purchased. Numerical modelling was then carried out using the MIKE21 SW (spectral wave) model developed by DHI (Deutsches Hydrographisches Institut) to transform these offshore waves into inshore in order to derive wave conditions at the berth. Both wind-waves and swell-waves were considered. Waves affecting the head and beam of a vessel were considered separately for a wide range of vessel sizes with DT (displacement tonnage) ranging from 5,000 tons to 〉 200,000 tons. The limiting wave height H5% was used. Operational downtime was also calculated using significant wave height, Hs as a criterion with limits ofHs = 1.0 m for beam seas and Hs = 1.5 m for head seas. The methodology and lessons learnt from the study can be applied for the development of any sea port worldwide.
文摘The White Tiger is Aravind Adiga's first novel just like Son of the Native Soil which is Shadrach Ambanasom's first oeuvre. The two novels address two major social concerns (the caste system and tribal loyalty) that impair national cohesion in India and Cameroon respectively. Briefly speaking, the caste refers to the classification of peoples in India (and other South Asian countries) into in-marrying hereditary social classes of the privileged and the underprivileged while tribal loyalty refers to selfish attachment to a tribe or clan to the detriment of community or national feeling. The two concepts are related in the sense that the word "caste" derives from the Spanish or Portuguese "casta" meaning race, lineage, breed or clan. In both cases therefore, the issues of sectionalism, division, discrimination, selfishness, marginalization, and hegemony (amongst others) are at play--issues that impede the notion of nationhood. Read principally from the Marxist perspective of power dynamics and class struggle, the paper argues that Adiga and Ambanasom through skillful manipulation of symbols, time, characters and events, try to imagine the deconstruction of caste and ethnic loyalty in India and Cameroon respectively, which to the two authors, are only historically and socially erected edifices rather than natural order. For the two authors, although global forces may seem to play in favor of a more equitable human society, a necessarily violent revolution might be required to dismantle a blighted body politico-modus operandi that has operated in the people's psyche for a long time, as characters and events in the two novels reveal.
文摘RLWI (Riserless Light Well Intervention) technology has the advantage of utilizing a special subsea lubricator to perform intervention activities in water depths of up to 1,200 m without the need for the marine risers. Utilizing the technology, oil companies have been able to save up to 50% on the intervention costs. However, in the last five years, it has seen up to 25% downtime due to waiting on weather (wow). Thus, in this manuscript, it is attempted to identify the critical elements of the module deployment system and analyze their significance in the objective of raising the operational weather limit. Critical failure modes were found to be failure of crane wire due to excess loading, failure of the lower cursor system due to the impact loading and clashing of the module with the moonpool walls. Analysis of the module deployment system against these failure modes was ensued by using Orcaflex. The results showed the moonpool sea state to be the defining parameter. Although, changing moonpool dimensions affect hydrodynamics positively, however it's significance is small due to dependency on the vessel's breadth. Based on these results and the available data for the analysis, a recommended system particular was tested. Significance improvement, in lowering the risk of failure was observed.
文摘Generally, lightning damage has mainly been to home appliances and telephones, towers and power transmission and generation equipment mal functions and damage due to strikes on power lines. With the adoption of wind power generation equipment, however, lightning damage is also increasing in this area. Through his dimensional characteristics, the wind power system is more exposed in the nature compared to all others systems. Lightning damage is the single largest cause of unplanned downtime in wind turbines, and that downtime is responsible for the loss of countless megawatts of power generation. The wind turbines are important structures, since they can easily attract the wrath of storms hits heights close, they can also capture the most distant. The rotation of the blades may also trigger lightning and result in considerable increase in the number of strikes to a wind turbine unit. Since wind turbines are tall structures, the lightning currents that are injected by return strokes into the turbines will be affected by reflections at the top, at the bottom, and at the junction of the blades with the static base of the turbine. We present our contribution in this paper to study lightning strokes and their effects on the wind turbines with the aim to enrich the work and to suggest more effective means of protection against lightning.
文摘In order to evaluate the operational reliability of Japanese FBR (fast breeder reactor) MONJU, frequencies of important intermediate events and equipment failures resulting during reactor automatic trip are predicted using FTA (fault tree analysis) technique for the plant system model. The targeted devices are the following: PHTS (primary heat transport system), SHTS (secondary heat transport system), WS (water and steam system), PPS (plant protection system) and PCS (plant control system). In this paper, the frequency of automatic reactor trips was estimated by extracting and analyzing the important intermediate events and equipment failures covering all the derived fault trees of these systems. The analyses predicted 1.2/RY (reactor year) the value of unplanned shut down frequency by the internal factor of the system. The largest contributed event was function failure of SHTS accounting for 42.6% of total events followed by PHTS with 40.1%. The contribution factor of WS was only 4.4%.
基金Supported by the National Natural Science Foundation of China,No. 30400173
文摘AIM: To explore the relationship between the level of proinsulin with cardiovascular risk factors and sleep snoring.METHODS: Based on the random stratified sampling principle, 1 193 Chinese residents in Pizhou City, Jiangsu Province (530 males and 663 females, aged 35-59 years with an average age of 46.69 years) were recruited. Their sleep snoring habits were investigated. Biotin-avidin based double mAbs ELISA was used to detect specific insulin and proinsulin, and a risk factor score was established to evaluate the individuals according to the number of their risk factors.RESULTS: The results of Spearman correlation analysis and covariate ANOVA analysis after age and sex were controlled, indicated that not only the level of proinsulin (r = 0.156, P = 0.000, F= 5.980 P = 0.000), but also cardiovascular risk factors score (r = 0.194, P = 0.000,F= 11.135, P = 0.000) significantly associated with the frequency of sleep snoring, and the significant relationship between true insulin and frequency of sleep snoring was only shown in the covariate ANOVA analysis (F = 2.868,P = 0.022). The result of multivariate stepwise logistic regression after age, sex, body mass index, waist circumference and true insulin were controlled showed that proinsulin (division by interval of quartile) was an independent risk factor for sleep snoring (OR = 1.220,95%CI: 1.085-1.373, P = 0.001).CONCLUSION: The interaction of cardiovascular risk factors clustering, high proinsulin level and sleep breathing disorder may be a syndrome, which has not been recognized in human beings so far.
文摘According to Brazilian reports of large trucks accidents on Federal Highway, fatigue and speeding are the major contributors to those accidents in which drivers are trying to meet short delivery deadlines for long hauls. A new federal law has been approved to limit truck drivers' working times, including maximum continuous driving time and maximum daily and weekly on-duty time. We present a study that aims at analyzing whether the existing resting areas on federal highways have sufficient capacity to meet current and future demand for truck stops. We have established the following method: In the first step, we review and study different models found in the literature and evaluate their potential application to Brazilian conditions; In the next step, we develop our own model and, finally, validate it using data from BR-101 Federal Highway, in Santa Catarina State. Tests made using part of collected data (which were subjected to statistical treatment) showed satisfactory results, indicating that the demand behavior was consistent with that observed in the field and the answers provided by truck drivers in the interviews. The research has yet to complete processing all data and it also must be repeated in other regions with different characteristics.
基金Supported by the National Natural Science Foundation of China (No.40531007)the China Action Plan of the International Polar Year (Nos.2009DFA22920 and 2008Po5040014-03)+1 种基金the International Science and Technology Cooperation (Nos. 2008DFA20420 and 2009DFA22920)the Polar Atmospheric Environment Remote Sensing Monitoring Technique of the National High Technology Research and DevelopmentProgram of China (863 Program) (No. N2008DFA20420)
文摘To evaluate the particle dynamics and estimate the POC (particulate organic carbon) export flux from the euphotic zone in the western Arctic Ocean,234 Th238 U disequilibrium was applied during the second Chinese National Arctic Research Expedition (July 15-September 26,2003).The POC export fluxes are estimated from the measured profiles of the 234 Th/238 U activity ratios and the POC/PTh ratios.The average residence times of the particulate and dissolved 234 Th in the euphotic zone are 33 d and 121 d,and their average export fluxes are 480 dpm/m 2 d and 760 dpm/m 2 d,respectively.The scavenging and removal processes of particle reactive elements are active in the upper layer of the Chukchi Sea.The average residence time of 234 Th increases from shelf to basin,while the export fluxes of 234 Th decrease.The estimated POC export fluxes from the euphotic zone vary from 2.1 to 20.3 mmol/m 2 d,indicating that the western Arctic Ocean is an important carbon sink in summer due to efficient biological pump.
文摘In the paper,we obtain the SRC lifting of a right continuous, left upper semi-continuous random process on a Loeb space.And show the existence of S-optimal stopping of an internal process,construct the S-optimal stopping. Finally we prove the fact that the standard part of the S-optimal stopping of a SRC lifting is the optimal stopping of the corresponding standard process,which generalizes the conclusions in [8]on a Loeb space.
文摘This paper studies for ward-back ward differential equations with Poisson jumps and with stopping time as termination. Under some weak monotonicity conditions and for non-Lipschitzian coefficients, the existence and uniqueness of solutions are proved via a purely probabilistic approach, while a priori estimate is given. Here, we allow the forward equation to be degenerate.
基金Project supported by the National Natural Science Foundation of China (No.79790130).
文摘The authors study the continuous properties of square integrable g-martingales via backward stochastic differential equations (shortly BSDEs) and get a general upcrossing inequality and an optional stopping theorem for g-martingales.
文摘Delirium is an acute and fluctuating change in mental status, with inattention and altered levels of consciousness. It is a common comorbidity in intensive care units (ICU), resulting in delayed withdrawal of mechanical ventilation, prolonged length of stay in ICU, increased ICU mortality and impaired long-term cognitive function of the survivors. Narcotic or psychoactive medication is one of the major risk factors that contribute to ICU delirium. Surveys conducted in several countries indicated that delirium in ICU was inad- equately monitored, underdiagnosed and lacked standardized treatment. In order to improve the prevention and treatment of ICU delirium, it is imperative that the ICU professionals should enrich their knowledge about this comorbidity, familiarize themselves with its screening and management, as well as standardize the administration of narcotic and psychoactive medications.
基金supported by the Beijing Natural Science Foundation(3122020)
文摘Obstructive sleep apnea syndrome (OSAS) is characterized by recurrent collapses of the upper airway, which lead to repetitive transient hypoxia, arousals and finally sleep fragmentation. Both anatomical and neuromuscular factors may play key roles in the pathophysiology of OSAS. The purpose of this paper was to study the control mechanism of OSAS from the mechanical point of view. A three-dimensional finite element model was developed, which not only reconstructed the realistic anatomical structure of the human upper airway, but also included surrounding structures such as the skull, neck, hyoid, cartilage and soft tissues. The respiration process during the normal and apnea states was simulated with the fluid-structure interaction method (FSI) and the computational fluid dynamics method (CFD). The airflow and deformation of the upper airway obtained from the FSI and the CFD method were compared and the results obtained under large negative pressure during an apnea episode were analyzed. The simulation results show that the FSI method is more feasible and effective than the CFD method. The concave configuration of the upper airway may accelerate the collapse of the upper airway in a positive feedback mechanism, which supplies meaningful information for clinical treatment and further research of OSAS.