This study investigated the operation features of a dropshaft-tunnel system under varying downstream water levels through a large-scale physical model.In the experiments,the air pressure distribution in the system was...This study investigated the operation features of a dropshaft-tunnel system under varying downstream water levels through a large-scale physical model.In the experiments,the air pressure distribution in the system was measured,and the flow pattern was recorded by cameras.The results revealed that the air pressure in the drop-shaft increased with increasing water flow rate under free outflow conditions but changed little when the outflow was submerged,even when the flow rate further increased.Additionally,there was a wavy flow in the tunnel un-der free outflow conditions,whereas plug flow with air pockets occurred under submerged outflow conditions.The downstream water level was found to affect the system through changing the linkage between the drop-shaft and tunnel and the resistance to air release downstream.The findings of this study contribute to a more comprehensive understanding of the operation of deep tunnel systems.展开更多
Hydrogen peroxide(H_(2)O_(2))production via electrochemical two-electron oxygen reduction reaction(ORR)holds a great promise for sustainable energy storage.However,the issues such as high energy consumption and diffic...Hydrogen peroxide(H_(2)O_(2))production via electrochemical two-electron oxygen reduction reaction(ORR)holds a great promise for sustainable energy storage.However,the issues such as high energy consumption and difficult extraction of thermodynamically unstable H_(2)O_(2) still need to be resolved.Herein,we reported a unified system for energy-out production and downstream conversion of H_(2)O_(2).By replacing the sluggish oxygen evolution reaction with a hydrazine oxidation reaction(HzOR),the cell of twoelectron ORR coupled with HzOR achieves the co-generation of electricity energy and valuable H_(2)O_(2).By employing Ru single atoms anchored on cobalt hydroxide(for HzOR)and NiSe_(2)(for ORR)as electrocatalysts,both exhibiting onset potentials near the theoretical values for their respective reactions,the ORR‖HzOR cell exhibits an energy output of 3.58 mW cm^(-2) and generates 0.66 kWh of electricity per kg of H_(2)O_(2).with a production rate of 583 mmol h^(-1) H_(2)O_(2).The produced H_(2)O_(2) was subsequently in-situ upgraded via three downstream conversion pathways to yield value-added products of sodium percarbonate,sodium peroxyborate,and ethylene glycol.A techno-economic analysis confirmed the economic viability of this ORR‖HzOR coupled with downstream conversion system.展开更多
The research selected three typical areas for plant investigation, including upper reaches of Gangnan Reservoir, the area between Gangnan and downstream of Huangbizhuang Reservoir, and Huangbizhuang Reservoir. The res...The research selected three typical areas for plant investigation, including upper reaches of Gangnan Reservoir, the area between Gangnan and downstream of Huangbizhuang Reservoir, and Huangbizhuang Reservoir. The results showed that affected by water, plant species, species diversity and species richness were all decreasing in varying degrees as the distance with watercourse upper reaches was increasing, but the ratio of Anthropochory plants was growing. The research finally proposed countermeasures, including increasing wetland area, constructing forests and artificial water landscape of Hutuo River and reinforcing watercourse compre- hensive management.展开更多
Large language models(LLMs)have demonstrated significant capabilities in semantic understanding and code generation.However,cybersecurity tasks often require prompting the adaptation of open-source models to this doma...Large language models(LLMs)have demonstrated significant capabilities in semantic understanding and code generation.However,cybersecurity tasks often require prompting the adaptation of open-source models to this domain.Despite their effectiveness,large-parameter LLMs incur substantial memory usage and runtime costs during task inference and downstreamfine-tuning for cybersecurity applications.In this study,we fine-tuned six LLMs with parameters under 4 billion using LoRA(Low-Rank Adaptation)on specific cybersecurity instruction datasets,employing evaluation metrics similar to Hackmentor.Results indicate that post-fine-tuning,smaller models achieved victory or parity rates up to 85%against larger models like Qwen-1.5-14B on cybersecurity test datasets,with the best model reaching a 90%win or tie rate compared to SecGPT.Additionally,these smaller models required significantly less computational resources,reducing fine-tuning times by up to 53%and enhancing efficiency in downstream tasks.Further validation showed that withminimal fine-tuning,our models achieved a performance gain of 21.66%to 31.32%in tactical extraction and 30.69%to 40.42%in technical extraction tasks,significantly outperforming ChatGPT.These findings highlight the potential of smaller parameter LLMs for optimizing performance and resource utilization in cybersecurity applications including methods such as technique and tactic extraction.It will facilitate future research on the application of small-parameter large language models in the cybersecurity domain.展开更多
River Tano, located in the Brong Ahafo region of Ghana, has a number of socio-ecological functions. Anthropogenic activities such as farming, washing, and discharge of industrial effluents into the river pose serious ...River Tano, located in the Brong Ahafo region of Ghana, has a number of socio-ecological functions. Anthropogenic activities such as farming, washing, and discharge of industrial effluents into the river pose serious threat to human health. In view of this, water quality campaign was carried out for a period of 12 months by taking samples from the source and the downstream end of the river and analysing for some physico-chemical parameters. The results showed that most of the physico-chemical parameters such as pH, fluoride, nitrite, manganese and temperature were not within the regulatory safe limit. Although the levels of total alkalinity, total iron, ammonia and phosphate kept fluctuating along the course of the river, the difference were not statistically significant apart from fluoride and phosphate which showed significant difference between the upstream and downstream levels. This may be attributed to anthropogenic activities such as farming and washing in the river which implies that human activities have impacted slightly on the water quality. It is recommended that the relevant stakeholders should come together to enforce the environmental laws regarding protection of water bodies and do continuous monitoring for early detection of any change in quality of the River Tano.展开更多
Gezhouba hydroproject was impounded and put into operation in 1981. In order to analyse the impact on the downstream river course, Jingjiang Hydrologic and Water Resources Survey Bureau of Changjiang Water Resources C...Gezhouba hydroproject was impounded and put into operation in 1981. In order to analyse the impact on the downstream river course, Jingjiang Hydrologic and Water Resources Survey Bureau of Changjiang Water Resources Commission has conducted prototype observation on the Yichang-Chenglingji river stretch. On basis of the observed data, the change in river regime and scour-sedimentation evolution and water surface profile below the dam are analysed systematically. The results show that the scouring of downstream river course mainly stretches from Yichang to Ouchikou, mainly occurring in 1980～1987; the scourring mainly takes place in the river channel and the water surface profile drops significantly in dry season,but not quite in high flood season.展开更多
In this study,the nonplanar post-buckling behavior of a simply supported fluid-conveying pipe with an axially sliding downstream end is investigated within the framework of a three-dimensional(3 D)theoretical model.Th...In this study,the nonplanar post-buckling behavior of a simply supported fluid-conveying pipe with an axially sliding downstream end is investigated within the framework of a three-dimensional(3 D)theoretical model.The complete nonlinear governing equations are discretized via Galerkin’s method and then numerically solved by the use of a fourth-order Runge-Kutta integration algorithm.Different initial conditions are chosen for calculations to show the nonplanar buckling characteristics of the pipe in two perpendicular lateral directions.A detailed parametric analysis is performed in order to study the influence of several key system parameters such as the mass ratio,the flow velocity,and the gravity parameter on the post-buckling behavior of the pipe.Typical results are presented in the form of bifurcation diagrams when the flow velocity is selected as the variable parameter.It is found that the pipe will stay at its original straight equilibrium position until the critical flow velocity is reached.Just beyond the critical flow velocity,the pipe would lose stability by static divergence via a pitchfork bifurcation,and two possible nonzero equilibrium positions are generated.It is shown that the buckling and post-buckling behaviors of the pipe cannot be influenced by the mass ratio parameter.Unlike a pipe with two immovable ends,however,the pinned-pinned pipe with an axially sliding downstream end shows some different features regarding post-buckling behaviors.The most important feature is that the buckling amplitude of the pipe with an axially sliding downstream end would increase first and then decrease with the increase in the flow velocity.In addition,the buckled shapes of the pipe varying with the flow velocity are displayed in order to further show the new post-buckling features of the pipe with an axially sliding downstream end.展开更多
The Yalong River is an important river that runs across the abruptly changing terrain of the SE Tibetan Plateau. The terraces and Quaternary sediments in its valleys preserve the information of tectonic uplift, climat...The Yalong River is an important river that runs across the abruptly changing terrain of the SE Tibetan Plateau. The terraces and Quaternary sediments in its valleys preserve the information of tectonic uplift, climate changes, and landform evolution since the Middle Pleistocene. Based on geomorphological, sedimentological, and chronological investigations, 6-8 terraces are identified in the lower reaches of Yalong catchment and its tributary--the Anning River. The electron spin resonance （ESR） or optically stimulated luminescence （OSL） data on the alluvial sediments in the upper portion of terraces indicate that they formed in 1.10, 0.90, 0.72, 0.06-0.04, 0.03-0.02, and 0.01 Ma. Tectonic uplift and the climatic cycle controlled the formation of the Yalong River terraces. The former dominated the dissection depths and incision rates, whereas the latter controlled the transformation between accumulation, which developed during the glacial period, and incision, which developed during the glacial-interglacial transition. The Yalong downstream incised rapidly from 1.10 to 0.72 Ma and rapidly from 0.06 Ma until the present; the terraces developed during these two periods. The incision rates in space during the two periods indicate the uplifting extent of the Jinpingshan area, which decreases toward the east and the south. The results reveal two rapidly uplifting stages in the SE Tibetan Plateau, including an accelerated uplifting since 0.06 Ma. Since the Middle Pleistocene, the tectonic uplift of the SE and NE parts of the Tibetan Plateau is synchronous, according to the same development stages of the river terraces of the Yalong downstream and the Yellow River in the Lanzhou area of the NE Tibetan Plateau. The difference in the horizontal displacement between the Xianshuihe Fault and the Anninghe Fault bend resulted in the rapid uplift of the Jinpingshan area. The incision rate for the spatial distribution of the Yalong downstream is the geomorphologicai response of crustal shortening and uplift differences in the SE margin block of the Tibetan Plateau. The southeastward diffusion process of the Tibetan Plateau was recorded.展开更多
Elucidating the influence of dams on fluvial processes can inform river protection and basin management. However, relatively few studies have focused on how multiple factors interact to affect the morphological evolut...Elucidating the influence of dams on fluvial processes can inform river protection and basin management. However, relatively few studies have focused on how multiple factors interact to affect the morphological evolution of meandering reaches. Using hydrological and topographical data, we analyzed the factors that influence and regulate the meandering reaches downstream the Three Gorges Dam （TGD）. Our conclusions are as follows. （1） The meandering reaches can be classified into two types based on their evolution during the pre-dam period： G1 reaches, characterized by convex point bar erosion and concave channel deposition （CECD）, and G2 reaches, characterized by convex point bar deposition and concave channel erosion （CDCE）. Both reach types exhibited CECD features during the post-dam period, （2） Flow processes and sediment transport are the factors that caused serious erosion of the low beaches located in the convex point bars. However, changes in the river regime, river boundaries and jacking of Dongting Lake do not act as primary controls on the morphological evolution of the meandering reaches. （3） Flood discharges ranging from 20,000 to 25,000 m^3/s result in greater erosion of convex point bars. The point bars become scoured if the durations of these flows, which are close to bankfull discharge, exceed 20 days. In addition, the reduction in bedload causes the decreasing of point bar siltation in the water-falling period. （4） During the post-dam period, flood abatement, the increased duration of discharges ranging from 20,000 to 25,000 m^3/s, and a significant reduction in sediment transport are the main factors that caused meandering reaches to show CECD features. Our results are relevant to other meandering reaches, where they can inform estimates of riverbed change, river management strategies and river protection.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52300122).
文摘This study investigated the operation features of a dropshaft-tunnel system under varying downstream water levels through a large-scale physical model.In the experiments,the air pressure distribution in the system was measured,and the flow pattern was recorded by cameras.The results revealed that the air pressure in the drop-shaft increased with increasing water flow rate under free outflow conditions but changed little when the outflow was submerged,even when the flow rate further increased.Additionally,there was a wavy flow in the tunnel un-der free outflow conditions,whereas plug flow with air pockets occurred under submerged outflow conditions.The downstream water level was found to affect the system through changing the linkage between the drop-shaft and tunnel and the resistance to air release downstream.The findings of this study contribute to a more comprehensive understanding of the operation of deep tunnel systems.
基金the National Natural Science Foundation of China(U21A20286 to Y.H.,22206054 to Y.H.,and 22478310 to J.Z.)the Fundamental Research Funds for the Central China Normal University(CCNU)。
文摘Hydrogen peroxide(H_(2)O_(2))production via electrochemical two-electron oxygen reduction reaction(ORR)holds a great promise for sustainable energy storage.However,the issues such as high energy consumption and difficult extraction of thermodynamically unstable H_(2)O_(2) still need to be resolved.Herein,we reported a unified system for energy-out production and downstream conversion of H_(2)O_(2).By replacing the sluggish oxygen evolution reaction with a hydrazine oxidation reaction(HzOR),the cell of twoelectron ORR coupled with HzOR achieves the co-generation of electricity energy and valuable H_(2)O_(2).By employing Ru single atoms anchored on cobalt hydroxide(for HzOR)and NiSe_(2)(for ORR)as electrocatalysts,both exhibiting onset potentials near the theoretical values for their respective reactions,the ORR‖HzOR cell exhibits an energy output of 3.58 mW cm^(-2) and generates 0.66 kWh of electricity per kg of H_(2)O_(2).with a production rate of 583 mmol h^(-1) H_(2)O_(2).The produced H_(2)O_(2) was subsequently in-situ upgraded via three downstream conversion pathways to yield value-added products of sodium percarbonate,sodium peroxyborate,and ethylene glycol.A techno-economic analysis confirmed the economic viability of this ORR‖HzOR coupled with downstream conversion system.
基金Supported by Hebei Provincial Natural Science Foundation(D2012302007)Science and Technology Project of Hebei Academy of Sciences(14111)~~
文摘The research selected three typical areas for plant investigation, including upper reaches of Gangnan Reservoir, the area between Gangnan and downstream of Huangbizhuang Reservoir, and Huangbizhuang Reservoir. The results showed that affected by water, plant species, species diversity and species richness were all decreasing in varying degrees as the distance with watercourse upper reaches was increasing, but the ratio of Anthropochory plants was growing. The research finally proposed countermeasures, including increasing wetland area, constructing forests and artificial water landscape of Hutuo River and reinforcing watercourse compre- hensive management.
文摘Large language models(LLMs)have demonstrated significant capabilities in semantic understanding and code generation.However,cybersecurity tasks often require prompting the adaptation of open-source models to this domain.Despite their effectiveness,large-parameter LLMs incur substantial memory usage and runtime costs during task inference and downstreamfine-tuning for cybersecurity applications.In this study,we fine-tuned six LLMs with parameters under 4 billion using LoRA(Low-Rank Adaptation)on specific cybersecurity instruction datasets,employing evaluation metrics similar to Hackmentor.Results indicate that post-fine-tuning,smaller models achieved victory or parity rates up to 85%against larger models like Qwen-1.5-14B on cybersecurity test datasets,with the best model reaching a 90%win or tie rate compared to SecGPT.Additionally,these smaller models required significantly less computational resources,reducing fine-tuning times by up to 53%and enhancing efficiency in downstream tasks.Further validation showed that withminimal fine-tuning,our models achieved a performance gain of 21.66%to 31.32%in tactical extraction and 30.69%to 40.42%in technical extraction tasks,significantly outperforming ChatGPT.These findings highlight the potential of smaller parameter LLMs for optimizing performance and resource utilization in cybersecurity applications including methods such as technique and tactic extraction.It will facilitate future research on the application of small-parameter large language models in the cybersecurity domain.
文摘River Tano, located in the Brong Ahafo region of Ghana, has a number of socio-ecological functions. Anthropogenic activities such as farming, washing, and discharge of industrial effluents into the river pose serious threat to human health. In view of this, water quality campaign was carried out for a period of 12 months by taking samples from the source and the downstream end of the river and analysing for some physico-chemical parameters. The results showed that most of the physico-chemical parameters such as pH, fluoride, nitrite, manganese and temperature were not within the regulatory safe limit. Although the levels of total alkalinity, total iron, ammonia and phosphate kept fluctuating along the course of the river, the difference were not statistically significant apart from fluoride and phosphate which showed significant difference between the upstream and downstream levels. This may be attributed to anthropogenic activities such as farming and washing in the river which implies that human activities have impacted slightly on the water quality. It is recommended that the relevant stakeholders should come together to enforce the environmental laws regarding protection of water bodies and do continuous monitoring for early detection of any change in quality of the River Tano.
文摘Gezhouba hydroproject was impounded and put into operation in 1981. In order to analyse the impact on the downstream river course, Jingjiang Hydrologic and Water Resources Survey Bureau of Changjiang Water Resources Commission has conducted prototype observation on the Yichang-Chenglingji river stretch. On basis of the observed data, the change in river regime and scour-sedimentation evolution and water surface profile below the dam are analysed systematically. The results show that the scouring of downstream river course mainly stretches from Yichang to Ouchikou, mainly occurring in 1980～1987; the scourring mainly takes place in the river channel and the water surface profile drops significantly in dry season,but not quite in high flood season.
基金Project supported by the National Natural Science Foundation of China(Nos.11622216,11602090,and 11672115)the Natural Science Foundation of Hubei Province(No.2017CFB429)the fundamental Research Funds for the Central Universities of China(No.2017KFYXJJ135)
文摘In this study,the nonplanar post-buckling behavior of a simply supported fluid-conveying pipe with an axially sliding downstream end is investigated within the framework of a three-dimensional(3 D)theoretical model.The complete nonlinear governing equations are discretized via Galerkin’s method and then numerically solved by the use of a fourth-order Runge-Kutta integration algorithm.Different initial conditions are chosen for calculations to show the nonplanar buckling characteristics of the pipe in two perpendicular lateral directions.A detailed parametric analysis is performed in order to study the influence of several key system parameters such as the mass ratio,the flow velocity,and the gravity parameter on the post-buckling behavior of the pipe.Typical results are presented in the form of bifurcation diagrams when the flow velocity is selected as the variable parameter.It is found that the pipe will stay at its original straight equilibrium position until the critical flow velocity is reached.Just beyond the critical flow velocity,the pipe would lose stability by static divergence via a pitchfork bifurcation,and two possible nonzero equilibrium positions are generated.It is shown that the buckling and post-buckling behaviors of the pipe cannot be influenced by the mass ratio parameter.Unlike a pipe with two immovable ends,however,the pinned-pinned pipe with an axially sliding downstream end shows some different features regarding post-buckling behaviors.The most important feature is that the buckling amplitude of the pipe with an axially sliding downstream end would increase first and then decrease with the increase in the flow velocity.In addition,the buckled shapes of the pipe varying with the flow velocity are displayed in order to further show the new post-buckling features of the pipe with an axially sliding downstream end.
基金supported by the Project of China Geological Survey (grant nos.1212011120071,201211077-3 and 1212011120182)
文摘The Yalong River is an important river that runs across the abruptly changing terrain of the SE Tibetan Plateau. The terraces and Quaternary sediments in its valleys preserve the information of tectonic uplift, climate changes, and landform evolution since the Middle Pleistocene. Based on geomorphological, sedimentological, and chronological investigations, 6-8 terraces are identified in the lower reaches of Yalong catchment and its tributary--the Anning River. The electron spin resonance （ESR） or optically stimulated luminescence （OSL） data on the alluvial sediments in the upper portion of terraces indicate that they formed in 1.10, 0.90, 0.72, 0.06-0.04, 0.03-0.02, and 0.01 Ma. Tectonic uplift and the climatic cycle controlled the formation of the Yalong River terraces. The former dominated the dissection depths and incision rates, whereas the latter controlled the transformation between accumulation, which developed during the glacial period, and incision, which developed during the glacial-interglacial transition. The Yalong downstream incised rapidly from 1.10 to 0.72 Ma and rapidly from 0.06 Ma until the present; the terraces developed during these two periods. The incision rates in space during the two periods indicate the uplifting extent of the Jinpingshan area, which decreases toward the east and the south. The results reveal two rapidly uplifting stages in the SE Tibetan Plateau, including an accelerated uplifting since 0.06 Ma. Since the Middle Pleistocene, the tectonic uplift of the SE and NE parts of the Tibetan Plateau is synchronous, according to the same development stages of the river terraces of the Yalong downstream and the Yellow River in the Lanzhou area of the NE Tibetan Plateau. The difference in the horizontal displacement between the Xianshuihe Fault and the Anninghe Fault bend resulted in the rapid uplift of the Jinpingshan area. The incision rate for the spatial distribution of the Yalong downstream is the geomorphologicai response of crustal shortening and uplift differences in the SE margin block of the Tibetan Plateau. The southeastward diffusion process of the Tibetan Plateau was recorded.
基金National Natural Science Foundation of China, No.51479146 Doctoral Foundation of Northwest A＆F University No.2452015337 National Key Research and Development Plan, No.2016YFC0402303, No.2016YFC0402101
文摘Elucidating the influence of dams on fluvial processes can inform river protection and basin management. However, relatively few studies have focused on how multiple factors interact to affect the morphological evolution of meandering reaches. Using hydrological and topographical data, we analyzed the factors that influence and regulate the meandering reaches downstream the Three Gorges Dam （TGD）. Our conclusions are as follows. （1） The meandering reaches can be classified into two types based on their evolution during the pre-dam period： G1 reaches, characterized by convex point bar erosion and concave channel deposition （CECD）, and G2 reaches, characterized by convex point bar deposition and concave channel erosion （CDCE）. Both reach types exhibited CECD features during the post-dam period, （2） Flow processes and sediment transport are the factors that caused serious erosion of the low beaches located in the convex point bars. However, changes in the river regime, river boundaries and jacking of Dongting Lake do not act as primary controls on the morphological evolution of the meandering reaches. （3） Flood discharges ranging from 20,000 to 25,000 m^3/s result in greater erosion of convex point bars. The point bars become scoured if the durations of these flows, which are close to bankfull discharge, exceed 20 days. In addition, the reduction in bedload causes the decreasing of point bar siltation in the water-falling period. （4） During the post-dam period, flood abatement, the increased duration of discharges ranging from 20,000 to 25,000 m^3/s, and a significant reduction in sediment transport are the main factors that caused meandering reaches to show CECD features. Our results are relevant to other meandering reaches, where they can inform estimates of riverbed change, river management strategies and river protection.
