In this paper, the status quo and modeling principles of R/S analysis of non-linear theory are introduced and reviewed. Given the hydro-geological conditions of the Wutongzhuang coal mine, Hurst exponents of mine infl...In this paper, the status quo and modeling principles of R/S analysis of non-linear theory are introduced and reviewed. Given the hydro-geological conditions of the Wutongzhuang coal mine, Hurst exponents of mine inflow for the main shaft, venti- lating shaft and auxiliary shaft were obtained using R/S analysis, which are 0.772 0, 0.824 7 and 0.905 1 respectively. Since all of the three Hurst exponents are larger than 0.5, it can be concluded that the trend of mine inflow are a long-term as well as persistent problem. Based on the level of duration, the shafts can be listed in decreasing order as the auxiliary shaft, the ventilation shaft and the main shaft, which appears identical with the actual situation of the mine inflow. With R/S analysis, a new method for long-term forecasting of mine inflows is provided.展开更多
A Chinese political advisor on Saturday warned a continued over- expectation for the appreciation of the Chinese currency Yuan would bring in more inflows of hot money and worsen the already excessive liquidity.
Prediction of water inflow into a tunnel is a crucial prerequisite for the waterproof and drainage design of mountain tunnels in water-rich areas.Based on the proposed Baiyun Mountain Tunnel project in Guangzhou,a num...Prediction of water inflow into a tunnel is a crucial prerequisite for the waterproof and drainage design of mountain tunnels in water-rich areas.Based on the proposed Baiyun Mountain Tunnel project in Guangzhou,a numerical percolation model of random fractured rock of a tunnel underpassing a water reservoir is established to study the seepage characteristics of surrounding rock,the law of water inflow,and the change of lining water pressure,considering the local artificial boundary conditions for seepage in large rock mass,.In addition,the influences of rock permeability,fracture aperture,grouting circle thickness,and penetration are analyzed.The results show that:(1)Only fractures with aperture wider than 0.1 mm can play a significant role in water conduction in rocks with the permeability lower than 10^(-11)m^(2);(2)The greater the permeability difference between the fractures and rocks,the more remarkable the effects of fractures on the surrounding rock seepage field and cavern water inflow;(3)The sensitivity of grouting waterproof function to grouting circle thickness,grouting ring penetration,and rock permeability is significantly higher than that of tunnel buried depth and fracture aperture;(4)The lining water head is much more sensitive to the grouting circle thickness and penetration than to the tunnel buried depth;(5)With the grouting range enlarging,the impact of grouting circle permeability on the precipitation pressure role of the grouting ring increases;(6)For the interesting tunnel designed to be built at the depth of 70 m,the grouting circle with the thickness of 0.5 m and permeability of 10-^(14)m^(2)is recommended.展开更多
Water inflow into mountain tunnels exhibits high variability and nonlinear seepage behavior,leading to significant prediction inaccuracies and poor pattern recognition when conventional analytical methods are applied....Water inflow into mountain tunnels exhibits high variability and nonlinear seepage behavior,leading to significant prediction inaccuracies and poor pattern recognition when conventional analytical methods are applied.This study proposes a dynamic water inflow prediction method specifically designed for mountain tunnels.The method is based on groundwater dynamics theory,employing nonDarcian law as the governing equation and deriving analytical solutions applicable to both confined and phreatic aquifer conditions.The method incorporates spatiotemporal variations along the tunnel alignment,enabling both short-term and long-term dynamic predictions of water inflow.The study examines the nonlinear characteristics of the seepage field during tunnel water inrush.The research findings indicate that the predictive results are consistent with the hypothesized two-stage water inflow pattern,with relative errors for key parameters,such as maximum water inflow,normal water inflow,and duration of water inflow,remaining within 10%.The magnitude of water inflow is positively correlated with the permeability coefficient,head height;it is negatively correlated with the axial distance to the tunnel face and the non-Darcian influence coefficient.Both water inflow and water pressure are subject to non-Darcian effects within a defined influence zone extending approximately 1.3 times the tunnel diameter.Comparisons with established predictive methods,numerical simulations,and data from existing tunnel projects confirm the effectiveness of the proposed method.Moreover,the method was successfully applied to a mountain tunnel in the Tibet Plateau region in southwestern China,where it achieved prediction errors within 3%to 8%,demonstrating high reliability.展开更多
Based on the Low Frequency Distributed Acoustic Sensing(LF-DAS)fiber optic monitoring and downhole hawk-eye imaging,the fluid and sand distribution and perforation erosion of all clusters during hydraulic fracturing w...Based on the Low Frequency Distributed Acoustic Sensing(LF-DAS)fiber optic monitoring and downhole hawk-eye imaging,the fluid and sand distribution and perforation erosion of all clusters during hydraulic fracturing were evaluated,and then a fully coupled wellbore-perforation-fracture numerical model was established to simulate the whole process of sand-carrying fluid migration and analyze key influencing factors.The proppant and fracturing fluid exhibit divergent flow pathways during multi-staged,multi-cluster fracturing in horizontal wells,resulting in significant heterogeneity in the fluid-proppant distribution among clusters.Perforation erosion is prevalent,and perforation erosion and sand inflow ratio have phase bias.The trajectory of proppant transport is controlled by the combined effects of inertia of particle migration and gravity settlement.The inertial effect is dominant at the wellbore heel,where the fluid flow rate is high,hindering particles turning into perforations and causing uneven sand distribution among clusters.The gravity settlement is more pronounced toward the wellbore toe,where the fluid flow rate is low,leading to enhanced phase-bias of slurry distribution and perforation erosion.Increasing the pumping rate reduces the influence of gravity settlement,mitigating the phase bias of sand inflow and perforation erosion.However,the large pumping rate limits the sand inflow efficiency near the heel clusters,and more proppants accumulate towards the toe clusters.High-viscosity fluids improve particle suspension,achieving more uniform proppant placement within wellbore and fractures.Larger particle sizes exacerbate sand inflow differences among clusters and perforations,limiting the proppant placement range within fractures.展开更多
The muhi-body analysis of the aeroelastic stability of the tiltrotor aircraft is presented. Muhi-body dynamic differential equations are combined with the equations of the unsteady dynamic inflow model to establish th...The muhi-body analysis of the aeroelastic stability of the tiltrotor aircraft is presented. Muhi-body dynamic differential equations are combined with the equations of the unsteady dynamic inflow model to establish the complete unsteadily aeroelastic coupling analytical model of the tiltrotor. The stability of the tiltrotor in the helicopter mode is analyzed aiming at a semi span soft-inplane tihrotor model with an elastic wing. Parametric effects of the lag stiffness of blades and the flight speed are analyzed. Numerical simulations demonstrate that the multibody analytical model can analyze the aeroelastic stability of the tiltrotor aircraft in the helicopter mode.展开更多
WT5 'BZThis paper presents an unsteady and nonlinear wake model based on th e widely used Peters He finite state dynamic wake model with improvements. The swirl component in the tip trace plane (TTP) can be pr...WT5 'BZThis paper presents an unsteady and nonlinear wake model based on th e widely used Peters He finite state dynamic wake model with improvements. The swirl component in the tip trace plane (TTP) can be predicted, nonlinear items are added into the linear theory, and the old small angle assumption use d in matrix prediction is removed. All of these enha ncements are aimed at the low speed flight phase and formulations for the induce d velocity field just in the TTP frame are derived. The corresponding FORTRAN pr ogram is tested and optimized for the real time applications on PCs.展开更多
To improve the rotor off-axis response prediction, aerodynamic models must include the wake distortion effects of the maneuvering rotor. And the crux of the matter is to obtain a precise wake curvature parameter KR. A...To improve the rotor off-axis response prediction, aerodynamic models must include the wake distortion effects of the maneuvering rotor. And the crux of the matter is to obtain a precise wake curvature parameter KR. A Peters-He finite-state wake model is improved to incorporate the operating-state-dependent KR to embody maneuver-induced effects. The curvature parameter KR varies with rotor forward speed, thrust and maneuvering angular rate according to a smoking experiment. Moreover, aerodynamic force/moment experiment indicates that after a quasi-step angular input, both on-axis and off-axis rotor responses show that an overshoot and its amplitude increases with the pitching rate. The comparison between theoretical and experimental results shows that the operating-state-accurate curvature parameter must be adopted to obtain accurate aerodynamic forces/moments, especially for the off-axis response. Additionally, combined with a dynamic wake distortion model, the obtained correlation agrees well with experimental data.展开更多
AIM： To evaluate the clinical outcomes of patients undergoing hepatectomy with hemihepatic vascular occlusion （HHO） compared with total hepatic inflow occlusion （THO）. METHODS： Randomized controlled trials （RCT...AIM： To evaluate the clinical outcomes of patients undergoing hepatectomy with hemihepatic vascular occlusion （HHO） compared with total hepatic inflow occlusion （THO）. METHODS： Randomized controlled trials （RCTs） co- mparing hemihepatic vascular occlusion and total he- patic inflow occlusion were included by a systematic literature search. Two authors independently assessed the trials for inclusion and extracted the data. A meta- analysis was conducted to estimate blood loss, transfu- sion requirement, and liver injury based on the levels of aspartate aminotransferase （AST） and alanine arni- notransferase （ALT）. Either the fixed effects model or random effects model was used. RESULTS- Four RCTs including 338 patients met the predefined inclusion criteria. A total of 167 patients were treated with THO and 171 with HHO. Metaanalysis of AST levels on postoperative day 1 indicated higher levels in the THO group with weighted mean dif- ference （WMD） 342.27; 95% confidence intervals （CI） 217.28-467.26; P = 0.00001; I2 = 16%. Meta-analysis showed no significant difference between THO group and HHO group on blood loss, transfusion requirement, mortality, morbidity, operating time, ischemic duration, hospital stay, ALT levels on postoperative day 1, 3 and 7 and AST levels on postoperative day 3 and 7. CONCLUSION： Hemihepatic vascular occlusion does not offer satisfying benefit to the patients undergoing hepatic resection. However, they have less liver injury after liver resections.展开更多
Summer monsoons （South Asian monsoon, South China Sea monsoon and Subtropical monsoon） are prominent features of summertime climate over southern China. Dif- ferent monsoons carry different inflow moisture into Chin...Summer monsoons （South Asian monsoon, South China Sea monsoon and Subtropical monsoon） are prominent features of summertime climate over southern China. Dif- ferent monsoons carry different inflow moisture into China and control the temporal and spatial distributions of precipitation. Analyses of meteorological data, particularly wind, tempera- ture and pressure anomalies are traditional methods of characterizing moisture sources and transport patterns. Here, we try to utilize the evidence from stable isotopes signatures to trace summer monsoons over southern China. Based on seven CHNIP （Chinese Network of Iso- topes in Precipitation） observatory stations located in southern China, monthly composite precipitation samples have been collected and analyzed for the composition of δ^18O during July, 2005. The results indicated that the spatial distributions of δ^18O in precipitation could properly portray the moisture sources together with their transport pathways. Moreover, the amount effect, altitude effect, temperature effect and the correlation between δ^18O vs. relative humidity were discussed.展开更多
Accurate prediction of the hydrographs of outburst floods induced by landslide dam overtopping failure is necessary for hazard prevention and mitigation. In this study, flume model tests on the breaching of landslide ...Accurate prediction of the hydrographs of outburst floods induced by landslide dam overtopping failure is necessary for hazard prevention and mitigation. In this study, flume model tests on the breaching of landslide dams were conducted. Unconsolidated soil materials with wide grain size distributions were used to construct the dam. The effects of different upstream inflow discharges and downstream bed soil erosion on the outburst peak discharge were investigated. Experimental results reveal that the whole hydrodynamic process of landslide dam breaching can be divided into three stages as defined by clear inflection points and peak discharges. The larger the inflow discharge, the shorter the time it takes to reach the peak discharge, and the larger the outburst flood peak discharge. The scale of the outburst floods was found to be amplified by the presence of an erodible bed located downstream of the landslide dam. This amplification decreases with the increase of upstream inflow. In addition, the results show that the existence of an erodible bed increases the density of the outburst flow, increasing its probability of transforming from a sediment flow to a debris flow.展开更多
AIM:To investigate the clinical significance of hepatic blood inflow occlusion without hemihepatic artery control (BIOwHAC) in the treatment of hepatocellular carcinoma (HCC).METHODS:Fifty-nine patients with HCC were ...AIM:To investigate the clinical significance of hepatic blood inflow occlusion without hemihepatic artery control (BIOwHAC) in the treatment of hepatocellular carcinoma (HCC).METHODS:Fifty-nine patients with HCC were divided into 3 groups based on the technique used for achieving hepatic vascular occlusion:group 1,vascular occlusion was achieved by the Pringle maneuver (n=20);group 2,by hemihepatic vascular occlusion (HVO) (n=20);and group 3,by BIOwHAC (n=19).We compared the procedures among the three groups in term of operation time,intraoperative bleeding,postoperative liver function,postoperative complications,and length of hospital stay.RESULTS:There were no statistically significant differences (P > 0.05) in age,sex,pathological diagnosis,preoperative Child's disease grade,hepatic function,and tumor size among the three groups.No intraoperative complications or deaths occurrred,and there were no significant intergroup differences (P > 0.05) in intraoperative bleeding,hepatic function change 3 and 7 d after operation,the incidence of complications,and length of hospital stay.BIOwHAC and Pringle maneuver required a significantly shorter operation time than HVO;the difference in the serum alanine aminotransferase or aspartate aminotransferase levels before and 1 d after operation was more significant in the BIOwHAC and HVO groups than in the Pringle maneuver group (P < 0.05).CONCLUSION:BIOwHAC is convenient and safe;this technique causes slight hepatic ischemia-reperfusion injury similar to HVO.展开更多
This article proposes a tandem cascade constructed to tackle the thorny problem of designing the high-loaded stator with a supersonic inflow and a large turning angle. The front cascade adopts a supersonic profile to ...This article proposes a tandem cascade constructed to tackle the thorny problem of designing the high-loaded stator with a supersonic inflow and a large turning angle. The front cascade adopts a supersonic profile to reduce the shock wave intensity turning the flow into subsonic,while the rear cascade adopts a subsonic profile with a large camber offering the flow a large turning angle. It is disclosed that the losses would be minimized if the leading edge of the rear cas- cade lies close to the pressure side of the front cascade at a distance of 20% pitch in pitch-wise direction without either axial spacing or overlapping in axial direction. The 2D numerical test results show that,with the inflow Mach number of 1.25 and the turning angle of 52° ,the total pressure loss coefficient of the tandem cascade reaches 0. 106 ,and the diffusion factor 0. 745. Finally,this article has designed and simulated a high-loaded fan stage with the proposed tandem stator,which has the pressure ratio of 3.15 and the efficiency of 86.32% at the rotor tip speed of 495.32 m/s.展开更多
[Objective] To study the characteristics and effects of inorganic nitrogen in east water-source and inflow rivers of Chaohu Lake. [Method] The speciation and distribution characteristics of dissolvable inorganic nitro...[Objective] To study the characteristics and effects of inorganic nitrogen in east water-source and inflow rivers of Chaohu Lake. [Method] The speciation and distribution characteristics of dissolvable inorganic nitrogen （DIN） in east water-source and inflow rivers of Chaohu Lake were investigated, and their effects on water qual- ity were examined. [Result] The concentrations of NH3-N and NO2--N were the high in flood season, and low in non-flood season, while the concentration of NO3--N pre- sented the opposite trend; the concentration of NO3--N was the highest in Shuangqiao estuary, where the pollution was the worst. DIN in Zhegao estuary and Xiaozhegao estuary was mainly caused by domestic sewage and industrial wastewaters; surface runoff and pollution from ships contribute the most to the DIN content in Shuangqiao estuary. [Conclusion] This study provided basic data and theoretical basis for the control and management of eutrophication in Chaohu Lake.展开更多
Currently,the water inrush hazards during tunnel construction,the water leakage during tunnel operation,and the accompanying disturbances to the ecological environment have become the main problems that affect the str...Currently,the water inrush hazards during tunnel construction,the water leakage during tunnel operation,and the accompanying disturbances to the ecological environment have become the main problems that affect the structural safety of tunnels in water-rich regions.In this paper,a tunnel seepage model testing system was used to conduct experiments of the grouting circle and primary support with different permeability coefficients.The influences of the supporting structures on the water inflow laws and the distribution of the water pressure in the tunnel were analyzed.With the decrease in the permeability coefficient of the grouting circle or the primary support,the inflow rate of water into the tunnel showed a non-linear decreasing trend.In comparison,the water inflow reduction effect of grouting circle was much better than that of primary support.With the increase of the permeability coefficient of the grouting ring,the water pressure behind the primary lining increases gradually,while the water pressure behind the grouting ring decreases.Thus,the grouting of surrounding rock during the construction of water-rich tunnel can effectively weaken the hydraulic connection,reduce the influence range of seepage,and significantly reduce the decline of groundwater.Meanwhile,the seepage tests at different hydrostatic heads and hydrodynamic heads during tunnel operation period were also conducted.As the hydrostatic head decreased,the water pressure at each characteristic point decreased approximately linearly,and the water inflow rate also had a gradual downward trend.Under the action of hydrodynamic head,the water pressure had an obvious lagging effect,which was not conducive to the stability of the supporting structures,and it could be mitigated by actively regulating the drainage rate.Compared with the hydrostatic head,the hydrodynamic head could change the real-time rate of water inflow to the tunnel and broke the dynamic balance between the water pressure and water inflow rate,thereby affecting the stress state on the supporting structures.展开更多
Liver transplantation is performed in the recent decades with great improvements not only technically but also conceptually. However, there is still lack of consensus about the optimal hemodynamic characteristics duri...Liver transplantation is performed in the recent decades with great improvements not only technically but also conceptually. However, there is still lack of consensus about the optimal hemodynamic characteristics during liver transplantation. The representative hemodynamic parameters include portal vein pressure, portal vein flow, and hepatic venous pressure gradient; however, there are still others potential valuable parameters, such as total liver inflow and hepatic artery flow. All the parameters are correlated closely and some internal modulating mechanisms, like hepatic arterial buffer response, occur to maintain stable hepatic inflow. To distinguish the unique importance of each hepatic and systemic parameter in different states during liver transplantation, we reviewed the published data and also conducted two transplant cases with different surgical strategies applied to achieve ideal portal inflow and pressure.展开更多
In a karst tunnel, fissures or cracks that are filled with weathered materials are a type of potential water outlet as they are easily triggered and converted into groundwater outlets under the influence of high groun...In a karst tunnel, fissures or cracks that are filled with weathered materials are a type of potential water outlet as they are easily triggered and converted into groundwater outlets under the influence of high groundwater pressure. A terrible water inrush caused by potential water outlets can seriously hinder the project construction. Potential water outlets and water sources that surrounding the tunnel must be detected before water inflow can be treated. This paper provides a successful case of the detection and treatment of water inflow in a karst tunnel and proposes a potential water outlet detection(PWOD) method in which heavy rainfall(>50 mm/d) is considered a trigger for a potential water outlet. The Daba tunnel located in Hunan province, China, has been constructed in a karst stratum where the rock mass has been weathered intensely by the influence of two faults. Heavy rain triggered some potential water outlets, causing a serious water inrush. The PWOD method was applied in this project for the treatment of water inflow, and six potential water outlets in total were identified through three heavy rains. Meanwhile, a geophysical prospecting technique was also used to detect water sources. The connections between water outlets and water sources were identified with a 3-D graphic that included all of them. According to the distribution of water outlets and water sources, the detection area was divided into three sections and separately treated by curtain grouting.展开更多
基金Project 40472146 supported by the National Natural Science Foundation of China
文摘In this paper, the status quo and modeling principles of R/S analysis of non-linear theory are introduced and reviewed. Given the hydro-geological conditions of the Wutongzhuang coal mine, Hurst exponents of mine inflow for the main shaft, venti- lating shaft and auxiliary shaft were obtained using R/S analysis, which are 0.772 0, 0.824 7 and 0.905 1 respectively. Since all of the three Hurst exponents are larger than 0.5, it can be concluded that the trend of mine inflow are a long-term as well as persistent problem. Based on the level of duration, the shafts can be listed in decreasing order as the auxiliary shaft, the ventilation shaft and the main shaft, which appears identical with the actual situation of the mine inflow. With R/S analysis, a new method for long-term forecasting of mine inflows is provided.
文摘A Chinese political advisor on Saturday warned a continued over- expectation for the appreciation of the Chinese currency Yuan would bring in more inflows of hot money and worsen the already excessive liquidity.
文摘Prediction of water inflow into a tunnel is a crucial prerequisite for the waterproof and drainage design of mountain tunnels in water-rich areas.Based on the proposed Baiyun Mountain Tunnel project in Guangzhou,a numerical percolation model of random fractured rock of a tunnel underpassing a water reservoir is established to study the seepage characteristics of surrounding rock,the law of water inflow,and the change of lining water pressure,considering the local artificial boundary conditions for seepage in large rock mass,.In addition,the influences of rock permeability,fracture aperture,grouting circle thickness,and penetration are analyzed.The results show that:(1)Only fractures with aperture wider than 0.1 mm can play a significant role in water conduction in rocks with the permeability lower than 10^(-11)m^(2);(2)The greater the permeability difference between the fractures and rocks,the more remarkable the effects of fractures on the surrounding rock seepage field and cavern water inflow;(3)The sensitivity of grouting waterproof function to grouting circle thickness,grouting ring penetration,and rock permeability is significantly higher than that of tunnel buried depth and fracture aperture;(4)The lining water head is much more sensitive to the grouting circle thickness and penetration than to the tunnel buried depth;(5)With the grouting range enlarging,the impact of grouting circle permeability on the precipitation pressure role of the grouting ring increases;(6)For the interesting tunnel designed to be built at the depth of 70 m,the grouting circle with the thickness of 0.5 m and permeability of 10-^(14)m^(2)is recommended.
基金the financial support provided by the Key Laboratory of Urban Underground Engineering of Ministry of Education,Beijing Jiaotong University(Grant Nos.TUL2024-05)。
文摘Water inflow into mountain tunnels exhibits high variability and nonlinear seepage behavior,leading to significant prediction inaccuracies and poor pattern recognition when conventional analytical methods are applied.This study proposes a dynamic water inflow prediction method specifically designed for mountain tunnels.The method is based on groundwater dynamics theory,employing nonDarcian law as the governing equation and deriving analytical solutions applicable to both confined and phreatic aquifer conditions.The method incorporates spatiotemporal variations along the tunnel alignment,enabling both short-term and long-term dynamic predictions of water inflow.The study examines the nonlinear characteristics of the seepage field during tunnel water inrush.The research findings indicate that the predictive results are consistent with the hypothesized two-stage water inflow pattern,with relative errors for key parameters,such as maximum water inflow,normal water inflow,and duration of water inflow,remaining within 10%.The magnitude of water inflow is positively correlated with the permeability coefficient,head height;it is negatively correlated with the axial distance to the tunnel face and the non-Darcian influence coefficient.Both water inflow and water pressure are subject to non-Darcian effects within a defined influence zone extending approximately 1.3 times the tunnel diameter.Comparisons with established predictive methods,numerical simulations,and data from existing tunnel projects confirm the effectiveness of the proposed method.Moreover,the method was successfully applied to a mountain tunnel in the Tibet Plateau region in southwestern China,where it achieved prediction errors within 3%to 8%,demonstrating high reliability.
基金Supported by National Natural Science Foundation of China Joint Fund for Enterprise Innovation and Development(U24B6002).
文摘Based on the Low Frequency Distributed Acoustic Sensing(LF-DAS)fiber optic monitoring and downhole hawk-eye imaging,the fluid and sand distribution and perforation erosion of all clusters during hydraulic fracturing were evaluated,and then a fully coupled wellbore-perforation-fracture numerical model was established to simulate the whole process of sand-carrying fluid migration and analyze key influencing factors.The proppant and fracturing fluid exhibit divergent flow pathways during multi-staged,multi-cluster fracturing in horizontal wells,resulting in significant heterogeneity in the fluid-proppant distribution among clusters.Perforation erosion is prevalent,and perforation erosion and sand inflow ratio have phase bias.The trajectory of proppant transport is controlled by the combined effects of inertia of particle migration and gravity settlement.The inertial effect is dominant at the wellbore heel,where the fluid flow rate is high,hindering particles turning into perforations and causing uneven sand distribution among clusters.The gravity settlement is more pronounced toward the wellbore toe,where the fluid flow rate is low,leading to enhanced phase-bias of slurry distribution and perforation erosion.Increasing the pumping rate reduces the influence of gravity settlement,mitigating the phase bias of sand inflow and perforation erosion.However,the large pumping rate limits the sand inflow efficiency near the heel clusters,and more proppants accumulate towards the toe clusters.High-viscosity fluids improve particle suspension,achieving more uniform proppant placement within wellbore and fractures.Larger particle sizes exacerbate sand inflow differences among clusters and perforations,limiting the proppant placement range within fractures.
文摘The muhi-body analysis of the aeroelastic stability of the tiltrotor aircraft is presented. Muhi-body dynamic differential equations are combined with the equations of the unsteady dynamic inflow model to establish the complete unsteadily aeroelastic coupling analytical model of the tiltrotor. The stability of the tiltrotor in the helicopter mode is analyzed aiming at a semi span soft-inplane tihrotor model with an elastic wing. Parametric effects of the lag stiffness of blades and the flight speed are analyzed. Numerical simulations demonstrate that the multibody analytical model can analyze the aeroelastic stability of the tiltrotor aircraft in the helicopter mode.
文摘WT5 'BZThis paper presents an unsteady and nonlinear wake model based on th e widely used Peters He finite state dynamic wake model with improvements. The swirl component in the tip trace plane (TTP) can be predicted, nonlinear items are added into the linear theory, and the old small angle assumption use d in matrix prediction is removed. All of these enha ncements are aimed at the low speed flight phase and formulations for the induce d velocity field just in the TTP frame are derived. The corresponding FORTRAN pr ogram is tested and optimized for the real time applications on PCs.
文摘To improve the rotor off-axis response prediction, aerodynamic models must include the wake distortion effects of the maneuvering rotor. And the crux of the matter is to obtain a precise wake curvature parameter KR. A Peters-He finite-state wake model is improved to incorporate the operating-state-dependent KR to embody maneuver-induced effects. The curvature parameter KR varies with rotor forward speed, thrust and maneuvering angular rate according to a smoking experiment. Moreover, aerodynamic force/moment experiment indicates that after a quasi-step angular input, both on-axis and off-axis rotor responses show that an overshoot and its amplitude increases with the pitching rate. The comparison between theoretical and experimental results shows that the operating-state-accurate curvature parameter must be adopted to obtain accurate aerodynamic forces/moments, especially for the off-axis response. Additionally, combined with a dynamic wake distortion model, the obtained correlation agrees well with experimental data.
文摘AIM： To evaluate the clinical outcomes of patients undergoing hepatectomy with hemihepatic vascular occlusion （HHO） compared with total hepatic inflow occlusion （THO）. METHODS： Randomized controlled trials （RCTs） co- mparing hemihepatic vascular occlusion and total he- patic inflow occlusion were included by a systematic literature search. Two authors independently assessed the trials for inclusion and extracted the data. A meta- analysis was conducted to estimate blood loss, transfu- sion requirement, and liver injury based on the levels of aspartate aminotransferase （AST） and alanine arni- notransferase （ALT）. Either the fixed effects model or random effects model was used. RESULTS- Four RCTs including 338 patients met the predefined inclusion criteria. A total of 167 patients were treated with THO and 171 with HHO. Metaanalysis of AST levels on postoperative day 1 indicated higher levels in the THO group with weighted mean dif- ference （WMD） 342.27; 95% confidence intervals （CI） 217.28-467.26; P = 0.00001; I2 = 16%. Meta-analysis showed no significant difference between THO group and HHO group on blood loss, transfusion requirement, mortality, morbidity, operating time, ischemic duration, hospital stay, ALT levels on postoperative day 1, 3 and 7 and AST levels on postoperative day 3 and 7. CONCLUSION： Hemihepatic vascular occlusion does not offer satisfying benefit to the patients undergoing hepatic resection. However, they have less liver injury after liver resections.
基金National Natural Science Foundation of China, No. 40671034 Foundation of Isotopes in Precipitation of Chinese Ecosystem Research Network The authors would like to acknowledge Synthesis Center of Chinese Ecosystem Research Center and National Meteorological Information Center, China Meteorological Administration for providing the meteorological data. We also thank Yang Jinrong and Yuan Jingjing for sample analysis. At the same time, sincerely appreciation is given to all the observatory field stations for the collection of precipitation samples and a tour of their facilities.
文摘Summer monsoons （South Asian monsoon, South China Sea monsoon and Subtropical monsoon） are prominent features of summertime climate over southern China. Dif- ferent monsoons carry different inflow moisture into China and control the temporal and spatial distributions of precipitation. Analyses of meteorological data, particularly wind, tempera- ture and pressure anomalies are traditional methods of characterizing moisture sources and transport patterns. Here, we try to utilize the evidence from stable isotopes signatures to trace summer monsoons over southern China. Based on seven CHNIP （Chinese Network of Iso- topes in Precipitation） observatory stations located in southern China, monthly composite precipitation samples have been collected and analyzed for the composition of δ^18O during July, 2005. The results indicated that the spatial distributions of δ^18O in precipitation could properly portray the moisture sources together with their transport pathways. Moreover, the amount effect, altitude effect, temperature effect and the correlation between δ^18O vs. relative humidity were discussed.
基金the financial support from the National Natural Science Foundation of China (Grant No. 41731283)the Key Research Program of Frontier Sciences, Chinese Academy of Sciences (CAS) (Grant No. QYZDB-SSW-DQC010)the Youth Innovation Promotion Association, Chinese Academy of Sciences (CAS)
文摘Accurate prediction of the hydrographs of outburst floods induced by landslide dam overtopping failure is necessary for hazard prevention and mitigation. In this study, flume model tests on the breaching of landslide dams were conducted. Unconsolidated soil materials with wide grain size distributions were used to construct the dam. The effects of different upstream inflow discharges and downstream bed soil erosion on the outburst peak discharge were investigated. Experimental results reveal that the whole hydrodynamic process of landslide dam breaching can be divided into three stages as defined by clear inflection points and peak discharges. The larger the inflow discharge, the shorter the time it takes to reach the peak discharge, and the larger the outburst flood peak discharge. The scale of the outburst floods was found to be amplified by the presence of an erodible bed located downstream of the landslide dam. This amplification decreases with the increase of upstream inflow. In addition, the results show that the existence of an erodible bed increases the density of the outburst flow, increasing its probability of transforming from a sediment flow to a debris flow.
基金Supported by The Inner Mongolia Science Foundation,Grant No.2009BS1103
文摘AIM:To investigate the clinical significance of hepatic blood inflow occlusion without hemihepatic artery control (BIOwHAC) in the treatment of hepatocellular carcinoma (HCC).METHODS:Fifty-nine patients with HCC were divided into 3 groups based on the technique used for achieving hepatic vascular occlusion:group 1,vascular occlusion was achieved by the Pringle maneuver (n=20);group 2,by hemihepatic vascular occlusion (HVO) (n=20);and group 3,by BIOwHAC (n=19).We compared the procedures among the three groups in term of operation time,intraoperative bleeding,postoperative liver function,postoperative complications,and length of hospital stay.RESULTS:There were no statistically significant differences (P > 0.05) in age,sex,pathological diagnosis,preoperative Child's disease grade,hepatic function,and tumor size among the three groups.No intraoperative complications or deaths occurrred,and there were no significant intergroup differences (P > 0.05) in intraoperative bleeding,hepatic function change 3 and 7 d after operation,the incidence of complications,and length of hospital stay.BIOwHAC and Pringle maneuver required a significantly shorter operation time than HVO;the difference in the serum alanine aminotransferase or aspartate aminotransferase levels before and 1 d after operation was more significant in the BIOwHAC and HVO groups than in the Pringle maneuver group (P < 0.05).CONCLUSION:BIOwHAC is convenient and safe;this technique causes slight hepatic ischemia-reperfusion injury similar to HVO.
基金National Natural Science Foundation of China(10577002)Innovation Foundation of BUAA for PhD Graduates
文摘This article proposes a tandem cascade constructed to tackle the thorny problem of designing the high-loaded stator with a supersonic inflow and a large turning angle. The front cascade adopts a supersonic profile to reduce the shock wave intensity turning the flow into subsonic,while the rear cascade adopts a subsonic profile with a large camber offering the flow a large turning angle. It is disclosed that the losses would be minimized if the leading edge of the rear cas- cade lies close to the pressure side of the front cascade at a distance of 20% pitch in pitch-wise direction without either axial spacing or overlapping in axial direction. The 2D numerical test results show that,with the inflow Mach number of 1.25 and the turning angle of 52° ,the total pressure loss coefficient of the tandem cascade reaches 0. 106 ,and the diffusion factor 0. 745. Finally,this article has designed and simulated a high-loaded fan stage with the proposed tandem stator,which has the pressure ratio of 3.15 and the efficiency of 86.32% at the rotor tip speed of 495.32 m/s.
基金Supported by the Special Fund for the Control and Management of Chaohu Lake of the National Key Technology R&D Program,China(2008ZX07103-005)the Special Fund for the Control and Management of Huaihe River of the National Key Technology R&D Program,China(2008ZX07010-004)+1 种基金National Natural Science Foundation of China(40073030,40972092,41172121)the Natural Science Foundation of Anhui Province,China(090413083)~~
文摘[Objective] To study the characteristics and effects of inorganic nitrogen in east water-source and inflow rivers of Chaohu Lake. [Method] The speciation and distribution characteristics of dissolvable inorganic nitrogen （DIN） in east water-source and inflow rivers of Chaohu Lake were investigated, and their effects on water qual- ity were examined. [Result] The concentrations of NH3-N and NO2--N were the high in flood season, and low in non-flood season, while the concentration of NO3--N pre- sented the opposite trend; the concentration of NO3--N was the highest in Shuangqiao estuary, where the pollution was the worst. DIN in Zhegao estuary and Xiaozhegao estuary was mainly caused by domestic sewage and industrial wastewaters; surface runoff and pollution from ships contribute the most to the DIN content in Shuangqiao estuary. [Conclusion] This study provided basic data and theoretical basis for the control and management of eutrophication in Chaohu Lake.
基金supported by the Chongqing Natural Science Foundation(No.cstc2020jcyjmsxm X0904)the Chongqing Talent Plan(No.CQYC2020058263)+3 种基金the Chongqing Technology Innovation and Application Development Project(No.cstc2021ycjh-bgzxm0246)the China Postdoctoral Science Foundation(No.2021M693739)the Sichuan Science and Technology Program(No.2021YJ0539)the Natural Science foundation of Jiangsu higher education institutions of China(Grant No.19KJD170001)。
文摘Currently,the water inrush hazards during tunnel construction,the water leakage during tunnel operation,and the accompanying disturbances to the ecological environment have become the main problems that affect the structural safety of tunnels in water-rich regions.In this paper,a tunnel seepage model testing system was used to conduct experiments of the grouting circle and primary support with different permeability coefficients.The influences of the supporting structures on the water inflow laws and the distribution of the water pressure in the tunnel were analyzed.With the decrease in the permeability coefficient of the grouting circle or the primary support,the inflow rate of water into the tunnel showed a non-linear decreasing trend.In comparison,the water inflow reduction effect of grouting circle was much better than that of primary support.With the increase of the permeability coefficient of the grouting ring,the water pressure behind the primary lining increases gradually,while the water pressure behind the grouting ring decreases.Thus,the grouting of surrounding rock during the construction of water-rich tunnel can effectively weaken the hydraulic connection,reduce the influence range of seepage,and significantly reduce the decline of groundwater.Meanwhile,the seepage tests at different hydrostatic heads and hydrodynamic heads during tunnel operation period were also conducted.As the hydrostatic head decreased,the water pressure at each characteristic point decreased approximately linearly,and the water inflow rate also had a gradual downward trend.Under the action of hydrodynamic head,the water pressure had an obvious lagging effect,which was not conducive to the stability of the supporting structures,and it could be mitigated by actively regulating the drainage rate.Compared with the hydrostatic head,the hydrodynamic head could change the real-time rate of water inflow to the tunnel and broke the dynamic balance between the water pressure and water inflow rate,thereby affecting the stress state on the supporting structures.
文摘Liver transplantation is performed in the recent decades with great improvements not only technically but also conceptually. However, there is still lack of consensus about the optimal hemodynamic characteristics during liver transplantation. The representative hemodynamic parameters include portal vein pressure, portal vein flow, and hepatic venous pressure gradient; however, there are still others potential valuable parameters, such as total liver inflow and hepatic artery flow. All the parameters are correlated closely and some internal modulating mechanisms, like hepatic arterial buffer response, occur to maintain stable hepatic inflow. To distinguish the unique importance of each hepatic and systemic parameter in different states during liver transplantation, we reviewed the published data and also conducted two transplant cases with different surgical strategies applied to achieve ideal portal inflow and pressure.
基金supported by the National Key Research and Development Project (Grant No.2016YFC0801604)Natural Science Foundation of Shandong Province (Grant No.ZR2017MEE070)
文摘In a karst tunnel, fissures or cracks that are filled with weathered materials are a type of potential water outlet as they are easily triggered and converted into groundwater outlets under the influence of high groundwater pressure. A terrible water inrush caused by potential water outlets can seriously hinder the project construction. Potential water outlets and water sources that surrounding the tunnel must be detected before water inflow can be treated. This paper provides a successful case of the detection and treatment of water inflow in a karst tunnel and proposes a potential water outlet detection(PWOD) method in which heavy rainfall(>50 mm/d) is considered a trigger for a potential water outlet. The Daba tunnel located in Hunan province, China, has been constructed in a karst stratum where the rock mass has been weathered intensely by the influence of two faults. Heavy rain triggered some potential water outlets, causing a serious water inrush. The PWOD method was applied in this project for the treatment of water inflow, and six potential water outlets in total were identified through three heavy rains. Meanwhile, a geophysical prospecting technique was also used to detect water sources. The connections between water outlets and water sources were identified with a 3-D graphic that included all of them. According to the distribution of water outlets and water sources, the detection area was divided into three sections and separately treated by curtain grouting.
