The proportion of elderly patients in intensive care is increasing, and a significant proportion of them require mechanical ventilation. How to implement safe and effective mechanical ventilation for elderly patients,...The proportion of elderly patients in intensive care is increasing, and a significant proportion of them require mechanical ventilation. How to implement safe and effective mechanical ventilation for elderly patients, and when appropriate off-line is an important issue in the field of critical care medicine. Appropriate sedation can improve patient outcomes, but excessive sedation may lead to prolonged mechanical ventilation and increase the risk of complications. Elderly patients should be closely monitored and evaluated on an individual basis while offline, and the sedation regimen should be dynamically adjusted. This requires the healthcare team to consider the patient’s sedation needs, disease status, and pharmacodynamics and pharmacokinetics of the drug to arrive at the best strategy. Although the current research has provided valuable insights and strategies for sedation and off-line management, there are still many problems to be further explored and solved.展开更多
Ash-rich pyroclastic flows from the cataclysmic eruption of Mount Mazama (~7700 yr. B. P.), Cascade volcanic arc, Oregon, entered and blocked the narrow, bedrock-lined canyon of the Williamson River approximately 35 t...Ash-rich pyroclastic flows from the cataclysmic eruption of Mount Mazama (~7700 yr. B. P.), Cascade volcanic arc, Oregon, entered and blocked the narrow, bedrock-lined canyon of the Williamson River approximately 35 to 44 km from the source volcano. The blockage impounded a body of water which then released producing four stratigraphic units in the downstream debris fan. The four stratigraphic units are a boulder core comprised of locally sourced bedrock boulders and three sand-rich units including a fine-grained sand unit, a sandy pumice gravel (±basalt/hydrovolcanic tuff) unit, and a pumice pebble-bearing, crystal-rich sand unit. Hand-drilled auger holes up to ~1.6 m deep were used to obtain samples of the sand-rich units. Units were delimited using surface and down-hole observations, composition and texture, estimated density, statistical parameters of grain size, and vertical and lateral distribution of properties. Overtopping followed by rapid incision into the ash-rich pyroclastic flows progressively cleared the canyon, but a bedrock knickpoint near the head of the canyon limited the volume of debris available for transport to about 0.04 km<sup>3</sup> to 0.08 km<sup>3</sup>. Co-deposition of bedrock boulders and lithic-rich sand was followed by rapid deposition with minimal reworking of remobilized pyroclastics. Continued draining of the impounded lake sent hyperconcentrated flows onto the debris fan depositing pumice-rich gravels that graded upward to crystal-rich sands.展开更多
Deepwater oil and gas exploration is the key to sustainable breakthroughs in petroleum exploration worldwide.The Central Canyon gas field has confirmed the Lingshui Sag is a hydrocarbon-generating sag,and the deepwate...Deepwater oil and gas exploration is the key to sustainable breakthroughs in petroleum exploration worldwide.The Central Canyon gas field has confirmed the Lingshui Sag is a hydrocarbon-generating sag,and the deepwater reservoirs in the Lingshui Sag still have more fabulous oil and gas exploration potential.Based on drilling data and three-dimensional(3D)seismic data,this paper uses seismic facies analysis,seismic attribute analysis,and coherence slice analysis to identify the types of submarine fans(lobe-shaped and band-shaped submarine fans)that developed in the Lingshui Sag during the Middle Miocene,clarify the source-to-sink system of the submarine fans and discuss the genesis mechanism of the submarine fans.The results show that:(1)the deepwater source-to-sink system of the Lingshui Sag in the Middle Miocene mainly consisted of a“delta(sediment supply)-submarine canyon(sediment transport channel)-submarine fan(deepwater sediment sink)”association;(2)the main factor controlling the formation of the submarine fans developed in the Lingshui Sag was on the relative sea level decline;and(3)the bottom current reworked the lobe-shaped submarine fan that developed in the northern Lingshui Sag and formed the band-shaped submarine fan with a greater sand thickness.This paper aims to provide practical geological knowledge for subsequent petroleum exploration and development in the deepwater area of the Qiongdongnan Basin through a detailed analysis of the Middle Miocene submarine fan sedimentary system developed in the Lingshui Sag.展开更多
树是连通的无圈图,研究树的拉普拉斯矩阵具有重要的图论和实际意义.设G是一个有n个点和m个边的图,A(G)和D(G)分别是图G的邻接矩阵和对角度矩阵,那么G的拉普拉斯矩阵定义为L(G)=D(G)-A(G).LI矩阵定义为LI(G)=L(G)-(2m/n)I_(n),其中I_(n)...树是连通的无圈图,研究树的拉普拉斯矩阵具有重要的图论和实际意义.设G是一个有n个点和m个边的图,A(G)和D(G)分别是图G的邻接矩阵和对角度矩阵,那么G的拉普拉斯矩阵定义为L(G)=D(G)-A(G).LI矩阵定义为LI(G)=L(G)-(2m/n)I_(n),其中I_(n)是单位矩阵.图的LI矩阵的Ky Fan k-范数代表了拉普拉斯特征值和拉普拉斯特征值平均值之间距离的有序和.研究了双星图的LI矩阵的Ky Fan k-范数,证明了双星图的LI矩阵的Ky Fan k-范数满足文献[6]中提出的猜想.展开更多
It is of great significance to study the effects of desert plants on soil enzyme activities and soil organic carbon(SOC)for maintaining the stability of the desert ecosystem.In this study,we studied the responses of s...It is of great significance to study the effects of desert plants on soil enzyme activities and soil organic carbon(SOC)for maintaining the stability of the desert ecosystem.In this study,we studied the responses of soil enzyme activities and SOC fractions(particulate organic carbon(POC)and mineral-associated organic carbon(MAOC))to five typical desert plant communities(Convolvulus tragacanthoides,Ephedra rhytidosperma,Stipa breviflora,Stipa tianschanica var.gobica,and Salsola laricifolia communities)in the proluvial fan in the eastern foothills of the Helan Mountain in Ningxia Hui Autonomous Region,China.We recorded the plant community information mainly including the plant coverage and herb and shrub species,and obtained the aboveground biomass and plant species diversity through sample surveys in late July 2023.Soil samples were also collected at depths of 0–10 cm(topsoil)and 10–20 cm(subsoil)to determine the soil physicochemical properties and enzyme activities.The results showed that the plant coverage and aboveground biomass of S.laricifolia community were significantly higher than those of C.tragacanthoides,S.breviflora,and S.tianschanica var.gobica communities(P<0.05).Soil enzyme activities varied among different plant communities.In the topsoil,the enzyme activities of alkaline phosphatase(ALP)andβ-1,4-glucosidas(βG)were significantly higher in E.rhytidosperma and S.tianschanica var.gobica communities than in other plant communities(P<0.05).The topsoil had higher POC and MAOC contents than the subsoil.Specifically,the content of POC in the topsoil was 18.17%–42.73%higher than that in the subsoil.The structural equation model(SEM)indicated that plant species diversity,soil pH,and soil water content(SWC)were the main factors influencing POC and MAOC.The soil pH inhibited the formation of POC and promoted the formation of MAOC.Conversely,SWC stimulated POC production and hindered MAOC formation.Our study aimed to gain insight into the effects of desert plant communities on soil enzyme activities and SOC fractions,as well as the drivers of SOC fractions in the proluvial fan in the eastern foothills of the Helan Mountain and other desert ecosystems.展开更多
As energy efficiency and indoor comfort increasingly become key standards in modern residential and office environments,research on intelligent fan speed control systems has become particularly important.This study ai...As energy efficiency and indoor comfort increasingly become key standards in modern residential and office environments,research on intelligent fan speed control systems has become particularly important.This study aims to develop a temperature-feedback-based fan speed optimization strategy to achieve higher energy efficiency and user comfort.Firstly,by analyzing existing fan speed control technologies,their main limitations are identified,such as the inability to achieve smooth speed transitions.To address this issue,a BP-PID speed control algorithm is designed,which dynamically adjusts fan speed based on indoor temperature changes.Experimental validation demonstrates that the designed system can achieve smooth speed transitions compared to traditional fan systems while maintaining stable indoor temperatures.Furthermore,the real-time responsiveness of the system is crucial for enhancing user comfort.Our research not only demonstrates the feasibility of temperature-based fan speed optimization strategies in both theory and practice but also provides valuable insights for energy management in future smart home environments.Ultimately,this research outcome will facilitate the development of smart home systems and have a positive impact on environmental sustainability.展开更多
The IAP (Institute of Atmospheric Physics) land-surface model (IAP94) is described. This model is a comprehensive one with detailed description for the processes of vegetation, snow and soil. Particular attention has ...The IAP (Institute of Atmospheric Physics) land-surface model (IAP94) is described. This model is a comprehensive one with detailed description for the processes of vegetation, snow and soil. Particular attention has been paid to the cases with three water phases in the surface media. On the basis of the mixture theory and the theory of fluid dynamics of porous media, the system of universal conservational equations for water and heat of soil, snow and vegetation canopy has been constructed. On this background, all important factors that may affect the water and heat balance in media can be considered naturally, and each factor and term possess distinct physical meaning. In the computation of water content and temperature, the water phase change and the heat transportation by water flow are taken into account. Moreover, particular attention has been given to the water vapor diffusion in soil for arid or semi-arid cases, and snow compaction. In the treatment of surface turbulent fluxes, the difference between aerodynamic and thermal roughness is taken into account. The aerodynamic roughness of vegetation is calculated as a function of canopy density, height and zero-plane displacement. An extrapolation of log linear and exponential relationship is used when calculating the wind profile within canopy. The model has been validated against field measurements in off-line simulations. The desirable model′s performance leads to the conclusion that the IAP94 is able to reproduce the main physical mechanisms governing the energy and water balances in the global land surface. Part II of the present study will concern the validation in a 3-D experiment coupled with the IAP Two-Level AGCM.展开更多
Off-line programming (OLP) system becomes one of the most important programming modules for the robotic belt grinding process, however there lacks research on increasing the grinding dexterous space depending on the...Off-line programming (OLP) system becomes one of the most important programming modules for the robotic belt grinding process, however there lacks research on increasing the grinding dexterous space depending on the OLP system. A new type of grinding robot and a novel robotic belt grinding workcell are forwarded, and their features are briefly introduced. An open and object-oriented off-line programming system is developed for this robotic belt grinding system. The parameters of the trimmed surface are read from the initial graphics exchange specification (IGES) file of the CAD model of the workpiece. The deBoor-Cox basis function is used to sample the grinding target with local contact frame on the workpiece. The numerical formula of inverse kinematics is set up based on Newton's iterative procedure, to calculate the grinding robot configurations corresponding to the grinding targets. After the grinding path is obtained, the OLP system turns to be more effective than the teach-by-showing system. In order to improve the grinding workspace, an optimization algorithm for dynamic tool frame is proposed and performed on the special robotic belt grinding system. The initial tool frame and the interval of neighboring tool frames are defined as the preparation of the algorithm. An optimized tool local frame can be selected to grind the complex surface for a maximum dexterity index of the robot. Under the optimization algorithm, a simulation of grinding a vane is included and comparison of grinding workspace is done before and after the tool frame optimization. By the algorithm, the grinding workspace can be enlarged. Moreover the dynamic tool frame can be considered to add one degree-of-freedom to the grinding kinematical chain, which provides the theoretical support for the improvement of robotic dexterity for the complex surface grinding.展开更多
In order to further understand the land surface processes over the northern Tibetan Plateau, this study produced an off-line simulated examination at the Bujiao site on the northern Tibetan Plateau from June 2002 to A...In order to further understand the land surface processes over the northern Tibetan Plateau, this study produced an off-line simulated examination at the Bujiao site on the northern Tibetan Plateau from June 2002 to April 2004, using the Noah Land Surface Model (Noah LSM) and observed data from the CAMP/Tibet experiment. The observed data were neces- sarily corrected and the number of soil layers in the Noah LSM was changed from 4 to 10 to enable this off-line simulation and analysis. The main conclusions are as follows: the Noah LSM performed well on the northern Tibetan Plateau. The simulated net radiation, upward longwave radiation, and upward shortwave radiation demonstrated the same remarkable annual and seasonal variation as the observed data, especially the upward longwave radiation. The simulated soil temperatures were acceptably close to the observed temperatures, especially in the shallow soil layers. The simulated freezing and melting processes were shown to start from the surface soil layer and spread down to the deep soil layers, but they took longer than the observed processes. However, Noah LSM did not adequately simulate the soil moisture. Therefore, additional high-quality, long-term observations of land surface-atmosphere processes over the Tibetan Plateau will be a key factor in proper adiustments of the model parameters in the future.展开更多
Segmentation of cursive text has been one of the major problems in Arabic writing. The problem is the shape of the letter which is context sensitive, depending on it’s location within a word. Many text recognition sy...Segmentation of cursive text has been one of the major problems in Arabic writing. The problem is the shape of the letter which is context sensitive, depending on it’s location within a word. Many text recognition systems recognize text imagery at the character level and assemble words from the recognized characters. Unfortunately this approach does not work with Arabic text. In this paper we describe a new approach to segment Arabic text imagery at a word level, without analyzing individual characters. This approach avoids the problem of individual characters segmentation, and can overcome local errors in character recognition.展开更多
A study of the interference simulation based on robot welding of the radar pedestal was carried out by using the KUKA Sim Pro simulation software and off-line program technology. Compared with the actual robot welding...A study of the interference simulation based on robot welding of the radar pedestal was carried out by using the KUKA Sim Pro simulation software and off-line program technology. Compared with the actual robot welding process, it was found that the trajectory of the simulated robot welding process in line with that recorded in the actual welding process, and the actual limit and interference appeared at the same place as the simulation process. There was no interference phenomenon on the outside weld-seam; on the internal weld-seam, especially on the weld-joint of support plate connected to the cylinder, a phenomenon of interference appeared. It was helpful to use the simulation method to guide the actual robot welding so as to protect robot from impacting and reduce the weld defects.展开更多
Thick walled curve welding are usually joined by multi-layer and multi-pass welding, which quality and efficiency could be improved by off-line programming of robot welding. However, the precision of off-line programm...Thick walled curve welding are usually joined by multi-layer and multi-pass welding, which quality and efficiency could be improved by off-line programming of robot welding. However, the precision of off-line programming welding path was decreased due to the deviation between the off-line planned welding path and the actual welding path. A path planning algorithm and a path compensation algorithm of multi-layer and multi-pass curve welding seam for off-line programming of robot welding are developed in this paper. Experimental results show that the robot off-line programming improves the welding efftcieney and precision for thick walled curve welding seam.展开更多
Zhao Rukuo's Zhu Fan Zhi in the Southern Song dynasty was the first book in the history of China to systematically describe the “Maritime Silk Road”, recording the geography, products, customs, trade, etc. of mo...Zhao Rukuo's Zhu Fan Zhi in the Southern Song dynasty was the first book in the history of China to systematically describe the “Maritime Silk Road”, recording the geography, products, customs, trade, etc. of more than 50 foreign countries and regions. The book included a large amount of medical literature, introducing medical customs and the production of drugs in various places, as well as the efficacy of some medicine. These materials are of unique value for understanding the medicine trade in the Song dynasty, and even the medical culture along the “Maritime Road of Aromatic Medicine”.展开更多
This study focuses on a single-stage axial flow fan, investigating the effect of three kinds of wave leading edge stator blades on its noise reduction. The DDES method and the duct acoustic analogy theory based on the...This study focuses on a single-stage axial flow fan, investigating the effect of three kinds of wave leading edge stator blades on its noise reduction. The DDES method and the duct acoustic analogy theory based on the penetrable data surface were used for noise prediction. The results showed that the three kinds of wave leading edge blades were effective in reducing the rotor-stator interaction tonal noise and also have a certain inhibitory effect on broadband noise. The A10W15 stator blade can effectively reduce broadband noise in the frequency range of 2200 - 4200 Hz. When the amplitude is increased to 20, the noise reduction effect is further enhanced. However, when the amplitude is increased to 30, the broadband noise reduction effect is no longer significant. Further research shows that the wave leading edge stator blades can significantly change the pressure fluctuation distribution on the leading edge and suction surface, which control the modal energy distribution. Finally, this paper analyzed multiple factors affecting the broadband noise reduction, such as the noise source cut-off and cut-on effect and correlation. The purpose of this paper is to explore the laws of the influence of wave leading edge blades on the duct noise of real fan, and to reveal its noise control mechanism. .展开更多
There are many large-scale Cenozoic sedimentary basins with plentiful river deltas,deep-water fans and carbonate platforms in the southern South China Sea.The Crocker Fan was deposited as a typical submarine fan durin...There are many large-scale Cenozoic sedimentary basins with plentiful river deltas,deep-water fans and carbonate platforms in the southern South China Sea.The Crocker Fan was deposited as a typical submarine fan during the late Eocene–early Miocene,and stretches extensively across the entire Sarawak–Sabah of the northern Borneo area.However,systematic analyses are still lacking regarding its sediment composition and potential source suppliers.No consensus has been reached yet on the provenance evolution and sedimentary infilling processes,which seriously impeded the oil-and-gas exploration undertakings.By combining with sedimentaryfacies identification,heavy mineral assemblages,elemental geochemistry and detrital zircon U-Pb dating,this paper aims to generalize an integrated analysis on the potential provenance terranes and restore source-to-sink pathways of the Crocker Fan.In general,the Crocker Fan was initially formed over the Cretaceous–lower/middle Eocene Rajang Group by an angular Rajang unconformity.The continual southward subduction of the protoSouth China Sea resulted in magmatic activities and subsequent regional deformation and thrusting along the Lupar Line in the northern Borneo.The lowermost Crocker sequence is featured by a thick conglomerate layer sourced from in-situ or adjacent paleo-uplifts.From the late Eocene to the early Miocene,the Crocker Fan was constantly delivered with voluminous detritus from the Malay Peninsula of the western Sundaland.The Zengmu Basin was widely deposited with delta plain and neritic facies sediments,while the Brunei-Sabah Basin,to the farther east,was ubiquitously characterized by turbiditic sequences.The Crocker Fan successions are overall thick layers of modest-grained sandstones,which formed high-quality reservoirs in the southern South China Sea region.展开更多
In this study, we tried to improve the performance by giving a pre-swirling flow to the radial inflow that occurred in the semi-opened axial fan. In addition, the flow fields of rotor outlet were clarified experimenta...In this study, we tried to improve the performance by giving a pre-swirling flow to the radial inflow that occurred in the semi-opened axial fan. In addition, the flow fields of rotor outlet were clarified experimentally, and the effect of pre-swirling flow was considered. The experiment was carried out using a performance test wind tunnel with a square cross section of 880 mm. Three types of casings were prepared, in which the blade tip protruded 0%, 20%, and 40% of the meridional chord length. They were called R25, R15, and R05, respectively, in the casing bellmouth model code. Guide blades for generating a pre-swirling flow were installed on the vertical wall surface of the casing. In addition, a vertical wall was installed 60% upstream of the meridional chord length as an obstacle to prevent axial inflow. The velocity fields of the rotor outlet were measured using a hot-wire anemometer. From the results, the pre-swirling flow did not significantly affect the fan performance. When there was no obstacles wall upstream, there was a partial increase in efficiency, but the difference was not so large. When there was an obstacle wall upstream, the efficiency increased overall in the case of R15, but in the case of R05, the efficiency increased only in the low flow rate region, and conversely decreased in the high flow rate region. By observing the blade outlet flow fields when the performance was improved, it was confirmed that the influence of the tip leakage vortex was weakened.展开更多
Among the common hazards related to alluvial fans,flooding is one of the most important.Nonetheless,in populated alluvial fans,not only the natural processes are effective in floods,but the artificial structures and m...Among the common hazards related to alluvial fans,flooding is one of the most important.Nonetheless,in populated alluvial fans,not only the natural processes are effective in floods,but the artificial structures and modifications can change the behavior of flooding and its potential risks.This study aims to indicate the flood-prone landforms in a set of populated alluvial fans in an arid region and investigate the role of anthropogenic activities in controlling/exacerbating flooding in alluvial fans.To achieve this goal,15 Ground Range Detected in High resolution(GRDH)SAR Sentinel-1 images,covering a total of 24 alluvial fans,were acquired.Pre-processing and post-processing steps were applied to all images to identify flood-prone sections of the studied alluvial fans.The results showed that feeder channels,spreading sites,and wide interfluves are the most flood-prone landforms of alluvial fans.In terms of anthropogenic modifications to mitigate flooding,a rampart system is distributed in the study area.Ramparts are levee like structures formed from the fan material.They aim to mitigate flood hazard on residential areas,infrastructures,and agricultural lands of the study area.Results show that the rampart system can reduce the danger of floods,but it cannot be considered a long-term solution.Therefore,a comprehensive flood protection system distributed throughout the whole alluvial fan system is needed.Results also reveal that in regions where flood monitoring is challenging,SAR images can be used as a freely available data set to monitor and identify flooding hotspots.展开更多
文摘The proportion of elderly patients in intensive care is increasing, and a significant proportion of them require mechanical ventilation. How to implement safe and effective mechanical ventilation for elderly patients, and when appropriate off-line is an important issue in the field of critical care medicine. Appropriate sedation can improve patient outcomes, but excessive sedation may lead to prolonged mechanical ventilation and increase the risk of complications. Elderly patients should be closely monitored and evaluated on an individual basis while offline, and the sedation regimen should be dynamically adjusted. This requires the healthcare team to consider the patient’s sedation needs, disease status, and pharmacodynamics and pharmacokinetics of the drug to arrive at the best strategy. Although the current research has provided valuable insights and strategies for sedation and off-line management, there are still many problems to be further explored and solved.
文摘Ash-rich pyroclastic flows from the cataclysmic eruption of Mount Mazama (~7700 yr. B. P.), Cascade volcanic arc, Oregon, entered and blocked the narrow, bedrock-lined canyon of the Williamson River approximately 35 to 44 km from the source volcano. The blockage impounded a body of water which then released producing four stratigraphic units in the downstream debris fan. The four stratigraphic units are a boulder core comprised of locally sourced bedrock boulders and three sand-rich units including a fine-grained sand unit, a sandy pumice gravel (±basalt/hydrovolcanic tuff) unit, and a pumice pebble-bearing, crystal-rich sand unit. Hand-drilled auger holes up to ~1.6 m deep were used to obtain samples of the sand-rich units. Units were delimited using surface and down-hole observations, composition and texture, estimated density, statistical parameters of grain size, and vertical and lateral distribution of properties. Overtopping followed by rapid incision into the ash-rich pyroclastic flows progressively cleared the canyon, but a bedrock knickpoint near the head of the canyon limited the volume of debris available for transport to about 0.04 km<sup>3</sup> to 0.08 km<sup>3</sup>. Co-deposition of bedrock boulders and lithic-rich sand was followed by rapid deposition with minimal reworking of remobilized pyroclastics. Continued draining of the impounded lake sent hyperconcentrated flows onto the debris fan depositing pumice-rich gravels that graded upward to crystal-rich sands.
基金The National Natural Science Foundation of China under contract No.42372154。
文摘Deepwater oil and gas exploration is the key to sustainable breakthroughs in petroleum exploration worldwide.The Central Canyon gas field has confirmed the Lingshui Sag is a hydrocarbon-generating sag,and the deepwater reservoirs in the Lingshui Sag still have more fabulous oil and gas exploration potential.Based on drilling data and three-dimensional(3D)seismic data,this paper uses seismic facies analysis,seismic attribute analysis,and coherence slice analysis to identify the types of submarine fans(lobe-shaped and band-shaped submarine fans)that developed in the Lingshui Sag during the Middle Miocene,clarify the source-to-sink system of the submarine fans and discuss the genesis mechanism of the submarine fans.The results show that:(1)the deepwater source-to-sink system of the Lingshui Sag in the Middle Miocene mainly consisted of a“delta(sediment supply)-submarine canyon(sediment transport channel)-submarine fan(deepwater sediment sink)”association;(2)the main factor controlling the formation of the submarine fans developed in the Lingshui Sag was on the relative sea level decline;and(3)the bottom current reworked the lobe-shaped submarine fan that developed in the northern Lingshui Sag and formed the band-shaped submarine fan with a greater sand thickness.This paper aims to provide practical geological knowledge for subsequent petroleum exploration and development in the deepwater area of the Qiongdongnan Basin through a detailed analysis of the Middle Miocene submarine fan sedimentary system developed in the Lingshui Sag.
文摘树是连通的无圈图,研究树的拉普拉斯矩阵具有重要的图论和实际意义.设G是一个有n个点和m个边的图,A(G)和D(G)分别是图G的邻接矩阵和对角度矩阵,那么G的拉普拉斯矩阵定义为L(G)=D(G)-A(G).LI矩阵定义为LI(G)=L(G)-(2m/n)I_(n),其中I_(n)是单位矩阵.图的LI矩阵的Ky Fan k-范数代表了拉普拉斯特征值和拉普拉斯特征值平均值之间距离的有序和.研究了双星图的LI矩阵的Ky Fan k-范数,证明了双星图的LI矩阵的Ky Fan k-范数满足文献[6]中提出的猜想.
基金the Key Project of the Natural Science Foundation of Ningxia Hui Autonomous Region,China(2022AAC02020)the Major Strategic Research Project of the Chinese Academy of Engineering and Local Cooperation(2021NXZD8)the Key Research and Development Plan Project of Ningxia Hui Autonomous Region,China(2022004129003).We are grateful to the editors and anonymous reviewers for their insightful comments and suggestions in improving this manuscript.
文摘It is of great significance to study the effects of desert plants on soil enzyme activities and soil organic carbon(SOC)for maintaining the stability of the desert ecosystem.In this study,we studied the responses of soil enzyme activities and SOC fractions(particulate organic carbon(POC)and mineral-associated organic carbon(MAOC))to five typical desert plant communities(Convolvulus tragacanthoides,Ephedra rhytidosperma,Stipa breviflora,Stipa tianschanica var.gobica,and Salsola laricifolia communities)in the proluvial fan in the eastern foothills of the Helan Mountain in Ningxia Hui Autonomous Region,China.We recorded the plant community information mainly including the plant coverage and herb and shrub species,and obtained the aboveground biomass and plant species diversity through sample surveys in late July 2023.Soil samples were also collected at depths of 0–10 cm(topsoil)and 10–20 cm(subsoil)to determine the soil physicochemical properties and enzyme activities.The results showed that the plant coverage and aboveground biomass of S.laricifolia community were significantly higher than those of C.tragacanthoides,S.breviflora,and S.tianschanica var.gobica communities(P<0.05).Soil enzyme activities varied among different plant communities.In the topsoil,the enzyme activities of alkaline phosphatase(ALP)andβ-1,4-glucosidas(βG)were significantly higher in E.rhytidosperma and S.tianschanica var.gobica communities than in other plant communities(P<0.05).The topsoil had higher POC and MAOC contents than the subsoil.Specifically,the content of POC in the topsoil was 18.17%–42.73%higher than that in the subsoil.The structural equation model(SEM)indicated that plant species diversity,soil pH,and soil water content(SWC)were the main factors influencing POC and MAOC.The soil pH inhibited the formation of POC and promoted the formation of MAOC.Conversely,SWC stimulated POC production and hindered MAOC formation.Our study aimed to gain insight into the effects of desert plant communities on soil enzyme activities and SOC fractions,as well as the drivers of SOC fractions in the proluvial fan in the eastern foothills of the Helan Mountain and other desert ecosystems.
文摘As energy efficiency and indoor comfort increasingly become key standards in modern residential and office environments,research on intelligent fan speed control systems has become particularly important.This study aims to develop a temperature-feedback-based fan speed optimization strategy to achieve higher energy efficiency and user comfort.Firstly,by analyzing existing fan speed control technologies,their main limitations are identified,such as the inability to achieve smooth speed transitions.To address this issue,a BP-PID speed control algorithm is designed,which dynamically adjusts fan speed based on indoor temperature changes.Experimental validation demonstrates that the designed system can achieve smooth speed transitions compared to traditional fan systems while maintaining stable indoor temperatures.Furthermore,the real-time responsiveness of the system is crucial for enhancing user comfort.Our research not only demonstrates the feasibility of temperature-based fan speed optimization strategies in both theory and practice but also provides valuable insights for energy management in future smart home environments.Ultimately,this research outcome will facilitate the development of smart home systems and have a positive impact on environmental sustainability.
文摘The IAP (Institute of Atmospheric Physics) land-surface model (IAP94) is described. This model is a comprehensive one with detailed description for the processes of vegetation, snow and soil. Particular attention has been paid to the cases with three water phases in the surface media. On the basis of the mixture theory and the theory of fluid dynamics of porous media, the system of universal conservational equations for water and heat of soil, snow and vegetation canopy has been constructed. On this background, all important factors that may affect the water and heat balance in media can be considered naturally, and each factor and term possess distinct physical meaning. In the computation of water content and temperature, the water phase change and the heat transportation by water flow are taken into account. Moreover, particular attention has been given to the water vapor diffusion in soil for arid or semi-arid cases, and snow compaction. In the treatment of surface turbulent fluxes, the difference between aerodynamic and thermal roughness is taken into account. The aerodynamic roughness of vegetation is calculated as a function of canopy density, height and zero-plane displacement. An extrapolation of log linear and exponential relationship is used when calculating the wind profile within canopy. The model has been validated against field measurements in off-line simulations. The desirable model′s performance leads to the conclusion that the IAP94 is able to reproduce the main physical mechanisms governing the energy and water balances in the global land surface. Part II of the present study will concern the validation in a 3-D experiment coupled with the IAP Two-Level AGCM.
基金supported by National Hi-tech Research and Development Program of China (863 Program, Grant No. 2007AA04Z2443)State Key Laboratory for Man ufacturing Systems Engineering of Xi’an Jiaotong University of China
文摘Off-line programming (OLP) system becomes one of the most important programming modules for the robotic belt grinding process, however there lacks research on increasing the grinding dexterous space depending on the OLP system. A new type of grinding robot and a novel robotic belt grinding workcell are forwarded, and their features are briefly introduced. An open and object-oriented off-line programming system is developed for this robotic belt grinding system. The parameters of the trimmed surface are read from the initial graphics exchange specification (IGES) file of the CAD model of the workpiece. The deBoor-Cox basis function is used to sample the grinding target with local contact frame on the workpiece. The numerical formula of inverse kinematics is set up based on Newton's iterative procedure, to calculate the grinding robot configurations corresponding to the grinding targets. After the grinding path is obtained, the OLP system turns to be more effective than the teach-by-showing system. In order to improve the grinding workspace, an optimization algorithm for dynamic tool frame is proposed and performed on the special robotic belt grinding system. The initial tool frame and the interval of neighboring tool frames are defined as the preparation of the algorithm. An optimized tool local frame can be selected to grind the complex surface for a maximum dexterity index of the robot. Under the optimization algorithm, a simulation of grinding a vane is included and comparison of grinding workspace is done before and after the tool frame optimization. By the algorithm, the grinding workspace can be enlarged. Moreover the dynamic tool frame can be considered to add one degree-of-freedom to the grinding kinematical chain, which provides the theoretical support for the improvement of robotic dexterity for the complex surface grinding.
基金the National Natural Science Foundation of China (Nos. 41075053 and 41275016)
文摘In order to further understand the land surface processes over the northern Tibetan Plateau, this study produced an off-line simulated examination at the Bujiao site on the northern Tibetan Plateau from June 2002 to April 2004, using the Noah Land Surface Model (Noah LSM) and observed data from the CAMP/Tibet experiment. The observed data were neces- sarily corrected and the number of soil layers in the Noah LSM was changed from 4 to 10 to enable this off-line simulation and analysis. The main conclusions are as follows: the Noah LSM performed well on the northern Tibetan Plateau. The simulated net radiation, upward longwave radiation, and upward shortwave radiation demonstrated the same remarkable annual and seasonal variation as the observed data, especially the upward longwave radiation. The simulated soil temperatures were acceptably close to the observed temperatures, especially in the shallow soil layers. The simulated freezing and melting processes were shown to start from the surface soil layer and spread down to the deep soil layers, but they took longer than the observed processes. However, Noah LSM did not adequately simulate the soil moisture. Therefore, additional high-quality, long-term observations of land surface-atmosphere processes over the Tibetan Plateau will be a key factor in proper adiustments of the model parameters in the future.
文摘Segmentation of cursive text has been one of the major problems in Arabic writing. The problem is the shape of the letter which is context sensitive, depending on it’s location within a word. Many text recognition systems recognize text imagery at the character level and assemble words from the recognized characters. Unfortunately this approach does not work with Arabic text. In this paper we describe a new approach to segment Arabic text imagery at a word level, without analyzing individual characters. This approach avoids the problem of individual characters segmentation, and can overcome local errors in character recognition.
基金Funded by Anhui Provincial Natural Science Foundation of China(GFKJ2015B002)Quality Engineering Project of Anhui province(2014zy122)
文摘A study of the interference simulation based on robot welding of the radar pedestal was carried out by using the KUKA Sim Pro simulation software and off-line program technology. Compared with the actual robot welding process, it was found that the trajectory of the simulated robot welding process in line with that recorded in the actual welding process, and the actual limit and interference appeared at the same place as the simulation process. There was no interference phenomenon on the outside weld-seam; on the internal weld-seam, especially on the weld-joint of support plate connected to the cylinder, a phenomenon of interference appeared. It was helpful to use the simulation method to guide the actual robot welding so as to protect robot from impacting and reduce the weld defects.
文摘Thick walled curve welding are usually joined by multi-layer and multi-pass welding, which quality and efficiency could be improved by off-line programming of robot welding. However, the precision of off-line programming welding path was decreased due to the deviation between the off-line planned welding path and the actual welding path. A path planning algorithm and a path compensation algorithm of multi-layer and multi-pass curve welding seam for off-line programming of robot welding are developed in this paper. Experimental results show that the robot off-line programming improves the welding efftcieney and precision for thick walled curve welding seam.
基金financed by the grants from The National Social Science Fund of China,Late Stage Funding (No. 21FZWB005)。
文摘Zhao Rukuo's Zhu Fan Zhi in the Southern Song dynasty was the first book in the history of China to systematically describe the “Maritime Silk Road”, recording the geography, products, customs, trade, etc. of more than 50 foreign countries and regions. The book included a large amount of medical literature, introducing medical customs and the production of drugs in various places, as well as the efficacy of some medicine. These materials are of unique value for understanding the medicine trade in the Song dynasty, and even the medical culture along the “Maritime Road of Aromatic Medicine”.
文摘This study focuses on a single-stage axial flow fan, investigating the effect of three kinds of wave leading edge stator blades on its noise reduction. The DDES method and the duct acoustic analogy theory based on the penetrable data surface were used for noise prediction. The results showed that the three kinds of wave leading edge blades were effective in reducing the rotor-stator interaction tonal noise and also have a certain inhibitory effect on broadband noise. The A10W15 stator blade can effectively reduce broadband noise in the frequency range of 2200 - 4200 Hz. When the amplitude is increased to 20, the noise reduction effect is further enhanced. However, when the amplitude is increased to 30, the broadband noise reduction effect is no longer significant. Further research shows that the wave leading edge stator blades can significantly change the pressure fluctuation distribution on the leading edge and suction surface, which control the modal energy distribution. Finally, this paper analyzed multiple factors affecting the broadband noise reduction, such as the noise source cut-off and cut-on effect and correlation. The purpose of this paper is to explore the laws of the influence of wave leading edge blades on the duct noise of real fan, and to reveal its noise control mechanism. .
基金The National Natural Science Foundation of China under contract Nos 42076066,92055203 and U20A20100。
文摘There are many large-scale Cenozoic sedimentary basins with plentiful river deltas,deep-water fans and carbonate platforms in the southern South China Sea.The Crocker Fan was deposited as a typical submarine fan during the late Eocene–early Miocene,and stretches extensively across the entire Sarawak–Sabah of the northern Borneo area.However,systematic analyses are still lacking regarding its sediment composition and potential source suppliers.No consensus has been reached yet on the provenance evolution and sedimentary infilling processes,which seriously impeded the oil-and-gas exploration undertakings.By combining with sedimentaryfacies identification,heavy mineral assemblages,elemental geochemistry and detrital zircon U-Pb dating,this paper aims to generalize an integrated analysis on the potential provenance terranes and restore source-to-sink pathways of the Crocker Fan.In general,the Crocker Fan was initially formed over the Cretaceous–lower/middle Eocene Rajang Group by an angular Rajang unconformity.The continual southward subduction of the protoSouth China Sea resulted in magmatic activities and subsequent regional deformation and thrusting along the Lupar Line in the northern Borneo.The lowermost Crocker sequence is featured by a thick conglomerate layer sourced from in-situ or adjacent paleo-uplifts.From the late Eocene to the early Miocene,the Crocker Fan was constantly delivered with voluminous detritus from the Malay Peninsula of the western Sundaland.The Zengmu Basin was widely deposited with delta plain and neritic facies sediments,while the Brunei-Sabah Basin,to the farther east,was ubiquitously characterized by turbiditic sequences.The Crocker Fan successions are overall thick layers of modest-grained sandstones,which formed high-quality reservoirs in the southern South China Sea region.
文摘In this study, we tried to improve the performance by giving a pre-swirling flow to the radial inflow that occurred in the semi-opened axial fan. In addition, the flow fields of rotor outlet were clarified experimentally, and the effect of pre-swirling flow was considered. The experiment was carried out using a performance test wind tunnel with a square cross section of 880 mm. Three types of casings were prepared, in which the blade tip protruded 0%, 20%, and 40% of the meridional chord length. They were called R25, R15, and R05, respectively, in the casing bellmouth model code. Guide blades for generating a pre-swirling flow were installed on the vertical wall surface of the casing. In addition, a vertical wall was installed 60% upstream of the meridional chord length as an obstacle to prevent axial inflow. The velocity fields of the rotor outlet were measured using a hot-wire anemometer. From the results, the pre-swirling flow did not significantly affect the fan performance. When there was no obstacles wall upstream, there was a partial increase in efficiency, but the difference was not so large. When there was an obstacle wall upstream, the efficiency increased overall in the case of R15, but in the case of R05, the efficiency increased only in the low flow rate region, and conversely decreased in the high flow rate region. By observing the blade outlet flow fields when the performance was improved, it was confirmed that the influence of the tip leakage vortex was weakened.
文摘Among the common hazards related to alluvial fans,flooding is one of the most important.Nonetheless,in populated alluvial fans,not only the natural processes are effective in floods,but the artificial structures and modifications can change the behavior of flooding and its potential risks.This study aims to indicate the flood-prone landforms in a set of populated alluvial fans in an arid region and investigate the role of anthropogenic activities in controlling/exacerbating flooding in alluvial fans.To achieve this goal,15 Ground Range Detected in High resolution(GRDH)SAR Sentinel-1 images,covering a total of 24 alluvial fans,were acquired.Pre-processing and post-processing steps were applied to all images to identify flood-prone sections of the studied alluvial fans.The results showed that feeder channels,spreading sites,and wide interfluves are the most flood-prone landforms of alluvial fans.In terms of anthropogenic modifications to mitigate flooding,a rampart system is distributed in the study area.Ramparts are levee like structures formed from the fan material.They aim to mitigate flood hazard on residential areas,infrastructures,and agricultural lands of the study area.Results show that the rampart system can reduce the danger of floods,but it cannot be considered a long-term solution.Therefore,a comprehensive flood protection system distributed throughout the whole alluvial fan system is needed.Results also reveal that in regions where flood monitoring is challenging,SAR images can be used as a freely available data set to monitor and identify flooding hotspots.