In this paper, sinking and growth of apexes and mid-stems of Myriophyllum spicatum L., Hydrilla verticillata （L.f.） Royle and Ceratophyllum demersum L. in concrete ponds containing eutrophic water and sediment were ...In this paper, sinking and growth of apexes and mid-stems of Myriophyllum spicatum L., Hydrilla verticillata （L.f.） Royle and Ceratophyllum demersum L. in concrete ponds containing eutrophic water and sediment were investigated. Sinking rates of apexes and mid-stems reached 34.8% and 4.4% at the 6 th day and 91.1% and 66.7% at the 22 nd day for M. spicatum, 57.8% and 55.6% at the 6 th day and 100% and 97.8% at the 22 nd day for H. vertieillata, 18.9% and 86.7% at the 6 th day and 95.6% and 100% at the 22 nd day for C. demersum, respectively. Most sunken fragments established themselves successfully with significant growth. Total shoot length ofplantlets developed from apexes and mid-stems increased by 399% and 61% for M. spicatum, 593% and 256% for H. vertieillata and 114% and 104% for C. demersum, respectively. The results showed that it was feasible to establish submersed macrophytes via sinking and colonization of shoot fragments clipped off manually.展开更多
The oxidative degradation of 4-chlorophenol （4-CP） in aqueous solution induced by plasma with submersed glow discharge has been investigated. The concentration of 4-CP and the reaction intermediates were determined ...The oxidative degradation of 4-chlorophenol （4-CP） in aqueous solution induced by plasma with submersed glow discharge has been investigated. The concentration of 4-CP and the reaction intermediates were determined by high performance liquid chromatography （HPLC）. Various influencing factors such as the initial pH, the concentration of 4-CP and the catalytic action of Fe^2＋ were examined. The results indicate that 4-CP is eventually degraded into inorganic ion, dioxide carbon and water. The attack of hydroxyl radicals on the benzene rings of 4-CP in the initial stage of oxidative reactions is presumed to be a key step. They also suggest that the reaction is of a pseudo-first order kinetic reaction and the proposed method is an efficient way for the 4-CP degradation,展开更多
An experiment was conducted to investigate the response of periphyton biomass to addition of phosphorus (P) in an aquatic ecosystem dominated by submersed plants. Aquatic ecosystems dominated by Hydrilla verticillata ...An experiment was conducted to investigate the response of periphyton biomass to addition of phosphorus (P) in an aquatic ecosystem dominated by submersed plants. Aquatic ecosystems dominated by Hydrilla verticillata (L.f.) Royle and Vallisneria natans (Lour.) Hara were constructed in mesocosm aquaria. Mesocosms were dosed weekly with different P loads (0 μg/L/Week and 100 μg/L/Week) for 17 weeks. Total P (TP), total soluble P (TSP), and soluble reactive P (SRP) concentrations in the waters of mesocosms added with P were significantly higher as opposed to the unenriched control mesocosms. The biomass of the attached periphyton and the cover of floating periphyton remained abundant in P-unenriched control mesocosms throughout the test period with a TP, TSP, and SRP concentration ranging of 0.021 - 0.049 mg/L, 0.004 - 0.024 mg/L, and 0.003 - 0.018 mg/L, respectively. P addition caused the decline of attached periphyton biomass to a low level and loss of floating periphyton. Results indicate that P enrichment in an aquatic ecosystem dominated by submersed plants could reduce attached periphyton biomass and eliminate floating periphyton. The research would be useful to maintain periphyton by reducing excessive P in aquatic ecosystem dominated by submersed plants.展开更多
Plant competition has been recognized as one of the most important factors influencing the soructure and function of lake ecosystems. Competition from plants of dissimilar growth form may have profound effects on shal...Plant competition has been recognized as one of the most important factors influencing the soructure and function of lake ecosystems. Competition from plants of dissimilar growth form may have profound effects on shallow lakes＇. An experiment was conducted to investigate the effects of competitive interactions of submersed plants with dis- similar growth forms on the biomass allocations. Hydrilla verticitlata and Vallisneria natans were selected and were planted in a single-species monoculture and a mixed-species pattern, Results showed that the growth of E natans was＇ significantly affected by the tt, verticillata and caused a sharp reduction of biomass, but the root：shoot ratio of E ha- tans was not affected significantly and there was a minimal increase in mixture： while for H. verticillata, the biomass and the root：shoot ratio were not significantly changed by the competitive interactions ore natans, there was minimal increase of biomass and minimal decrease of the root：shoot ratio. These results may indicate that theplant which can develop a dense mat or canopy at the water surface would be a stronger competitor relative to the plant that depends more on light availability near the sediment.展开更多
1.Introduction As China’s first floating production platform in ultra-deepwater,the“Deep Sea No.1”energy station is a milestone in China’s deepwater resource utilization.The energy station is located in the LS17-2...1.Introduction As China’s first floating production platform in ultra-deepwater,the“Deep Sea No.1”energy station is a milestone in China’s deepwater resource utilization.The energy station is located in the LS17-2 gas field,150 km off the southeast coast of Hainan Island,China.It is a semi-submersible platform(Fig.1)with a displacement of 101 thousand tonnes and an operational draft of 35 to 40 m.The platform is permanently moored in 1422 m water by 16 chain-polyester-chain mooring lines in a 4×4 pattern,and six steel catenary risers(SCRs)are attached to the platform.It is the world’s first and only semi-submersible platform with the function of condensate storage,so it can be regarded as a floating production storage and offloading(FPSO)unit.With the ability to produce 3 billion m3 of natural gas each year(enough for over 10 million families),the Deep Sea No.1 energy station is a key step toward China’s energy independence.The LS17-2 gas field,where the Deep Sea No.1 energy station is located,was discovered in 2014.Plans for its development were made in 2015,followed by research and a preliminary design.Deep Sea No.1 went into operation on June 25,2021,and will operate onsite continuously without dry-docking for 30 years.展开更多
Scientific and precise evaluations of the megafaunal and landform characteristics of seamounts are important guides for their protection and study.A series of manned and unmanned submersibles have provided invaluable ...Scientific and precise evaluations of the megafaunal and landform characteristics of seamounts are important guides for their protection and study.A series of manned and unmanned submersibles have provided invaluable observational imaging data for the ecological study of seamounts.However,traditional methods of artificial observation of seamount imaging data cannot accurately and efficiently determine the characteristics of megafauna and landforms.This research harnesses data-driven technology to systematically investigate the distributional traits and morphological features of megafaunal organisms,as well as the topographical characteristics,in the Caiwei Guyot region of the western Pacific’s Magellan Seamounts.To construct the landform and megafauna dataset of the Caiwei Guyot region,we used a data preprocessing technology based on image enhancement to provide high-quality imaging data for data-driven technologies.A megafaunal identification and counting algorithm based on YOLOv5(You Only Look Once Version 5)was developed to efficiently assess the abundance,variety,and dominant species of megafauna.Simultaneously,a landform three-dimensional(3D)reconstruction algorithm based on PatchmatchNet was developed to reconstruct the 3D form of the terrain accurately.This study pioneers the application of data-driven technology to deep-sea imaging within the Caiwei Guyot region,offering an innovative approach to accurately and efficiently characterize the region’s unique megafauna and landforms.展开更多
Internal solitary waves(ISWs) are a common phenomenon beneath the ocean surface and represent a significant environmental hazard that must be considered for the safe navigation of submersibles. A numerical simulation ...Internal solitary waves(ISWs) are a common phenomenon beneath the ocean surface and represent a significant environmental hazard that must be considered for the safe navigation of submersibles. A numerical simulation model for the interaction of solitary waves with submersibles at a large scale has been developed. The Miyata-ChoiCamassa(MCC) equation serves as the basis for generating ISWs. The impacts of the submergence depth, wave amplitude, and advancing velocity on the motion response and load characteristics of the submersible are examined in detail. This study elucidates the governing laws and mechanisms underlying the impact of ISWs on submersibles.The research findings indicate that shorter distances to the undisturbed surface, higher wave amplitudes, and fasteradvancing speeds result in greater effects on submersibles. For a submersible operating in the lower layer, both the alteration in density near the wave interface and the dynamic pressure induced by ISWs can reduce its lift, potentially resulting in a rapid descent. It is imperative to pay considerable attention to the impact of ISWs, as they have the potential to precipitate a loss of control of the submersible.展开更多
Polymethyl methacrylate(PMMA)has the advantages of good transparency,corrosion resistance and light weight and can be used as the preferred material for pressure-resistant cabins of fully transparent submersibles.In t...Polymethyl methacrylate(PMMA)has the advantages of good transparency,corrosion resistance and light weight and can be used as the preferred material for pressure-resistant cabins of fully transparent submersibles.In this study,based on the fracture mechanics method,a calculation method for estimating the residual fatigue life of a PMMA manned cabin is proposed by improving the small-time scale fatigue crack growth rate model.This improved model is verified by the experimental data of the PMMA material.Then,through the Weibull and Gumbel combined distribution functions,the fatigue load spectrum suitable for the fully transparent manned cabin is fitted according to the dive data.A parametric analysis of the residual fatigue life of the fully transparent manned cabin under various initial crack sizes and dwell time is conducted,yielding valuable results.This study aims to increase the safety of fully transparent pressure-resistant cabins and offer insights for fatigue analysis of underwater structures utilizing PMMA materials.展开更多
Tunisia’s coastal alluvial plains are fragile areas exposed to occasional disturbances(including storms,submersion,and floods)and serious imbalances,such as rising sea level,erosion,and salinisation of soils.Their se...Tunisia’s coastal alluvial plains are fragile areas exposed to occasional disturbances(including storms,submersion,and floods)and serious imbalances,such as rising sea level,erosion,and salinisation of soils.Their sensitivity tends to increase under the impact of strong anthropogenic pressures:population growth,rapid urbanisation,and concentration of economic activities.With the acceleration of climate change and the associated rise in sea level,these areas are facing a new challenge.At the interface between land and sea,scattered across these coastal alluvial plains are wetlands that are predisposed to marine submersion due to a combination of factors.Diachronic analysis of cartographic documents has made it possible to produce geodynamic maps.These were used in the current study to assess sea level rise and flooding,as well as their impact on the future development of coastal alluvial plains,particularly during exceptional weather and sea conditions.The findings show that a poor understanding of the mechanisms specific to these environments has often resulted in short-sighted sectoral approaches to land use planning.Sabkhas and lagoons alone account for more than half of all submerged areas.Coastal wetland ecosystems will be threatened by changes in living conditions,as the rather saline biocenosis will be transformed into a euryhaline lagoon biocenosis.展开更多
China Launches“Blue Whale”-World’s First High-speed Uncrewed Submersible.The"Blue Whale,"a cutting-edge high-speed submersible unmanned surface vessel,was launched on April 28 in Zhuhai,south China's ...China Launches“Blue Whale”-World’s First High-speed Uncrewed Submersible.The"Blue Whale,"a cutting-edge high-speed submersible unmanned surface vessel,was launched on April 28 in Zhuhai,south China's Guangdong Province.展开更多
The electric submersible pump(ESP) is a crucial apparatus utilized for lifting in the oil extraction process.Its lifting capacity is enhanced by the multi-stage tandem structure, but variations in energy characteristi...The electric submersible pump(ESP) is a crucial apparatus utilized for lifting in the oil extraction process.Its lifting capacity is enhanced by the multi-stage tandem structure, but variations in energy characteristics and internal flow across stages are also introduced. In this study, the inter-stage variability of energy characteristics in ESP hydraulic systems is investigated through entropy production(EP) analysis,which incorporates numerical simulations and experimental validation. The EP theory facilitates the quantification of energy loss in each computational subdomain at all ESP stages, establishing a correlation between microscopic flow structure and energy dissipation within the system. Furthermore, the underlying causes of inter-stage variability in ESP hydraulic systems are examined, and the advantages and disadvantages of applying the EP theory in this context are evaluated. Consistent energy characteristics within the ESP, aligned with the distribution of internal flow structure, are provided by the EP theory, as demonstrated by our results. The EP theory also enables the quantitative analysis of internal flow losses and complements existing performance analysis methods to map the internal flow structure to hydraulic losses. Nonetheless, an inconsistency between the energy characterization based on EP theory and the traditional efficiency index when reflecting inter-stage differences is identified. This inconsistency arises from the exclusive focus of the EP theory on flow losses within the flow field, disregarding the quantification of external energy input to the flow field. This study provides a reference for the optimization of EP theory in rotating machinery while deeply investigating the energy dissipation characteristics of multistage hydraulic system, which has certain theoretical and practical significance.展开更多
This paper introduces current four categories of submersible standards in China. It also analyzes the progress of submersible standardization, and expounds on the future direction of standards for submersibles and thr...This paper introduces current four categories of submersible standards in China. It also analyzes the progress of submersible standardization, and expounds on the future direction of standards for submersibles and three development paths, which will help consolidate China's advanced technology with independent intellectual property rights and enhance the influence of China's deep-sea equipment in the global market. It provides reference for related standardization workers as well.展开更多
CHINA Jiaolong Completes 300th Dive Jiaolong,China’s manned deep-sea submersible,on 18 August completed its 300th dive since its maiden mission in August 2009.Jiaolong,with a crew of one scientist and two submariners...CHINA Jiaolong Completes 300th Dive Jiaolong,China’s manned deep-sea submersible,on 18 August completed its 300th dive since its maiden mission in August 2009.Jiaolong,with a crew of one scientist and two submariners,conducted the dive in the Western Pacific Ocean.It was the first of 18 planned dives in an ongoing scientific expedition.展开更多
Submersed macrophytes decay is an important natural process and has important role in mass and energy flow in aquatic ecosystems.However,little is known about the dynamical changes in nutrients release and bacterial c...Submersed macrophytes decay is an important natural process and has important role in mass and energy flow in aquatic ecosystems.However,little is known about the dynamical changes in nutrients release and bacterial community during submersed macrophyte decay in natural environment.In this study,a field observation was conducted in a wetland dominated with Hydrilla verticillata for 36 days.Increase of H2O2 and malondialdehyde(MDA)content and decrease of soluble proteins concentration were detected in leaves during H.verticillata decay.Meanwhile,ammonium-N,soluble microbial products(SMP)and TOC concentration increased in overlying water.According to bacterial 16 S r RNA Illumina sequencing analysis,the Shannon values were lower in epiphytic biofilms than deciduous layer sediments.The relative abundances of Proteobacteria,Cyanobacteria and Actinobacteria were higher in epiphytic biofilms than in deciduous layer sediments(P<0.05).Co-occurrence network analyses showed that a total of 578 and 845 pairs of correlations(|r|>0.6)were identified from 122 and 112 genera in epiphytic biofilms and deciduous layer sediments,respectively.According to co-occurrence patterns,eight hubs were mainly from phyla Proteobacteria,Acidobacteria and Parcubacteria in epiphytic biofilms;while 37 hubs from the 14 phyla(Proteobacteria,Bacteroidetes,Acidobacteria,Chloroflexi,et al.)were detected in deciduous layer sediments.Our results indicate that bacterial community in deciduous layer sediments was more susceptible than in epiphytic biofilms during decay process.These data highlight the role of microbial community in deciduous layer sediments on nutrients removal during H.verticillata decay and will provide useful information for wetland management.展开更多
The competition between submersed plants has been recognized as an important factor influencing the structure of plant communities in shallow lakes.The ability of different species to take up and store nutrients from ...The competition between submersed plants has been recognized as an important factor influencing the structure of plant communities in shallow lakes.The ability of different species to take up and store nutrients from the surrounding ambience varies,and hence plant community structure might be expected to affect the cycling of nutrients in lake ecosystems.In this study,the uptake of phosphorus by Hydrilla verticillata and Vallisneria natans was studied and compared in monoculture and competitive mixed-culture plantings.Results showed that for both studied species the phosphorus concentrations of different tissues and of whole plants was unaffected by competition.However,the quantity of phosphorus accumulated by whole plants of 1-1.verticillata was significantly higher in mixture culture than in monoculture,while that of V.natans was lower in the mixed culture.The results indicated that 11.verticillata has a competitive advantage over V.natans,when the two species are grown in competition,and is able to accumulate a greater quantity of phosphorus.展开更多
Regime shifts from submersed macrophyte dominance to phytoplankton dominance have been widely reported in small-to medium-sized shallow lakes.However,alternative stable states in large shallow lakes(surface area>50...Regime shifts from submersed macrophyte dominance to phytoplankton dominance have been widely reported in small-to medium-sized shallow lakes.However,alternative stable states in large shallow lakes(surface area>500 km^(2))remain unconfirmed.To understand the alternative stable states and the main influencing factors of submersed macrophytes in large lakes,the ecosystem states from monitoring data from 1959 to 2019 in large shallow Taihu Lake(2338 km^(2)in average depth of 2.12 m)in China were examined.Changes in submersed macrophyte coverage(C_(Mac))and phytoplankton chlorophyll a(Chl a)in the time series and their relationships with environmental factors were analyzed.During the field investigation from August 2018 to May 2019,nutrients and Chl a showed obvious heterogeneity across the lake,being generally higher in the western and northern areas and lower in the southeast area,while C_(Mac)was only observed in the eastern areas,e.g.,East Taihu Lake,Xukou Bay,and Gonghu Bay.During the long-term monitoring from 1959 to 2019 in the Central Region,Meiliang Bay,and East Taihu Lake,Chl a increased significantly in the time series.C_(Mac)varied slightly among different subareas,always at low levels(<10%)in the Central Region and Meiliang Bay but at relatively high levels in East Taihu Lake(10%–90%).Frequency distributions of response variables had no multimodality except for C_(Mac)in East Taihu Lake,with two peaks between 15%and 20%and between 55%and 60%.A dual relationship was found between Chl a and total phosphorus(TP)in the areas with and without macrophytes,while C_(Mac)showed no relationship with TP,and submersed macrophytes did not flourish in the Central Region and Meiliang Bay even when TP was at very low levels(≈10 mg/m3).Taihu Lake had similar algal turbidity(TurbAlg)as small-to mediumsized lakes but generally presented with higher values of nonalgal turbidity(TurbNonAlg),as did their contribution to total turbidity as a percentage.This study suggested that large shallow Taihu Lake may have no alternative stable states,but more evidence is needed for East Taihu Lake,which was dominated by macrophytes,as it remains unknown whether hysteresis occurs between the processes of eutrophication and oligotrophication.Unfavorable conditions caused by wind might be the main reason due to the absence of submersed macrophytes in Taihu Lake.These results demonstrate that stricter nutrient control is needed to maintain a healthy state or to recover from a decayed state for large lakes.展开更多
A controlled experiment was designed to resolve the influence of nitrogen abundance on sediment organic matters in macrophyte-dominated lakes using fluorescence analysis.Macrophyte biomass showed coincident growth tre...A controlled experiment was designed to resolve the influence of nitrogen abundance on sediment organic matters in macrophyte-dominated lakes using fluorescence analysis.Macrophyte biomass showed coincident growth trends with time, but different variation rates with nitrogen treatment. All plant growth indexes with nitrogen addition（N, NH4Cl100, 200, 400 mg/kg, respectively） were lower than those of the control group. Four humiclike components, two autochthonous tryptophan-like components, and one autochthonous tyrosine-like component were identified using the parallel factor analysis model. The results suggested that the relative component changes of fluorescence in the colonized sediments were in direct relation to the change of root biomass with time. In the experiment, the root formation parameters of the plants studied were significantly affected by adding N in sediments, which may be related to the reason that the root growth was affected by N addition.Adding a low concentration of N to sediments can play a part in supplying nutrients to the plants. However, the intensive uptake of NH4^＋may result in an increase in the intracellular concentration of ammonia, which is highly toxic to the plant cells. Hence, our experiment results manifested that organic matter cycling in the macrophyte-dominated sediment was influenced by nitrogen enrichment through influencing vegetation and relevant microbial activity.展开更多
Aquatic macrophytic growth and its distribution in eutrophic lakes are described in relation to its sediment type and irradiance. Hence, it is necessary to characterize the response of macrophytic growth to lake sedim...Aquatic macrophytic growth and its distribution in eutrophic lakes are described in relation to its sediment type and irradiance. Hence, it is necessary to characterize the response of macrophytic growth to lake sediment and its re-suspension. We conducted two independent experiments to measure the effects of sediment and its re-suspension on the growth of Vallisneria asiatica Miki. Based on our study, we conclude that the amount of total biomass of V. asiatica is related, in important ways, to the type of sediment and its re-suspension. According to our comparison, plants and biomass cultured on lake sediments are 2.1 times and 1.5 times greater than that on brown clay from nearby places beside Lake Taihu. The number of plants and the amount of biomass in a turbid water column are smaller than those in a clear water column. The results indicate that the nutrient-rich lake sediments have promoted the growth of V. asiatica, while the re-suspension of the sediment leads to a high turbid level and low light penetration which has a negative impact on the growth of V. asiatica.展开更多
This paper presents a theoretic implementation method of Morphing Unmanned Submersible Aerial Vehicle （MUSAV）, which can both submerge in the water and fly in the air. Two different shapes are put forward so that th...This paper presents a theoretic implementation method of Morphing Unmanned Submersible Aerial Vehicle （MUSAV）, which can both submerge in the water and fly in the air. Two different shapes are put forward so that the vehicle can suit both submergence and flight, considering the tremendous differences between hydrodynamic configuration and aerodynamic configuration of a vehicle. The transition of the two shapes can be achieved by using morphing technology. The water-to-air process, including water-exit, morphing, take-off and steady flight, is analyzed. The hydrodynamic and aerodynamic model of the vehicle exiting the water surface obliquely and then taking off into the air has been founded. The control strategy after morphing is analyzed and the control method is given. Numerical method is used to validate the motion model of the water-exit process. Results of simulations show the validity of the proposed model and the feasibility of MUSAV in theory.展开更多
Given the recent success in the development of several submersibles in China, people's interest in the history of submersible development is increasing. This paper presents the history of submersible development i...Given the recent success in the development of several submersibles in China, people's interest in the history of submersible development is increasing. This paper presents the history of submersible development in China, which can be briefly divided into three periods. The first one is the early period of hardship(1971–2000). Many prototype submersibles of HOVs, ROVs, and AUVs were developed at this time, but the main achievement was the establishment of special research organizations and the training of research and development personnel. The second period can be regarded as the quick development period(2001–2015). All currently used submersibles were developed during this period. The most remarkable achievement was the successful development of 7000 m-deep manned submersible "Jiaolong." The third period aims to develop 11 000 m submersibles for challenging the full ocean depth(2016–2020). In this period, two unmanned submersibles and two manned submersibles will be the significant indicators of achievement. If this 5-year plan can be successfully completed, China can play a significant role in the investigation of the deepest part of the oceans, namely, the hadal trenches(6500–11 000 m).展开更多
基金Supported by the National Natural Science Foundation of China (39925007)the High Technology Research and Development Program of China (2002AA60l021)the Knowledge Innovation Program Key Project of Chinese Academy of Sciences (KSCX2-SW-102)
文摘In this paper, sinking and growth of apexes and mid-stems of Myriophyllum spicatum L., Hydrilla verticillata （L.f.） Royle and Ceratophyllum demersum L. in concrete ponds containing eutrophic water and sediment were investigated. Sinking rates of apexes and mid-stems reached 34.8% and 4.4% at the 6 th day and 91.1% and 66.7% at the 22 nd day for M. spicatum, 57.8% and 55.6% at the 6 th day and 100% and 97.8% at the 22 nd day for H. vertieillata, 18.9% and 86.7% at the 6 th day and 95.6% and 100% at the 22 nd day for C. demersum, respectively. Most sunken fragments established themselves successfully with significant growth. Total shoot length ofplantlets developed from apexes and mid-stems increased by 399% and 61% for M. spicatum, 593% and 256% for H. vertieillata and 114% and 104% for C. demersum, respectively. The results showed that it was feasible to establish submersed macrophytes via sinking and colonization of shoot fragments clipped off manually.
基金The project partially supported by the Project of Key Science and Technology of Education Ministry (00250), the Natural ScienceFoundation of Gansu Province (3ZS041-A25-028), and the Project of KJCXGC-01, NWNU, China
文摘The oxidative degradation of 4-chlorophenol （4-CP） in aqueous solution induced by plasma with submersed glow discharge has been investigated. The concentration of 4-CP and the reaction intermediates were determined by high performance liquid chromatography （HPLC）. Various influencing factors such as the initial pH, the concentration of 4-CP and the catalytic action of Fe^2＋ were examined. The results indicate that 4-CP is eventually degraded into inorganic ion, dioxide carbon and water. The attack of hydroxyl radicals on the benzene rings of 4-CP in the initial stage of oxidative reactions is presumed to be a key step. They also suggest that the reaction is of a pseudo-first order kinetic reaction and the proposed method is an efficient way for the 4-CP degradation,
文摘An experiment was conducted to investigate the response of periphyton biomass to addition of phosphorus (P) in an aquatic ecosystem dominated by submersed plants. Aquatic ecosystems dominated by Hydrilla verticillata (L.f.) Royle and Vallisneria natans (Lour.) Hara were constructed in mesocosm aquaria. Mesocosms were dosed weekly with different P loads (0 μg/L/Week and 100 μg/L/Week) for 17 weeks. Total P (TP), total soluble P (TSP), and soluble reactive P (SRP) concentrations in the waters of mesocosms added with P were significantly higher as opposed to the unenriched control mesocosms. The biomass of the attached periphyton and the cover of floating periphyton remained abundant in P-unenriched control mesocosms throughout the test period with a TP, TSP, and SRP concentration ranging of 0.021 - 0.049 mg/L, 0.004 - 0.024 mg/L, and 0.003 - 0.018 mg/L, respectively. P addition caused the decline of attached periphyton biomass to a low level and loss of floating periphyton. Results indicate that P enrichment in an aquatic ecosystem dominated by submersed plants could reduce attached periphyton biomass and eliminate floating periphyton. The research would be useful to maintain periphyton by reducing excessive P in aquatic ecosystem dominated by submersed plants.
基金sponsored by China Postdoctoral Science Foundation (Grant No.20090461149)the Postdoctoral Science Foundation of Jiangsu Province (Grant No. 0802029C)the Youth Science Foundation of JINAN Univeristy (Grant No. 51208026)
文摘Plant competition has been recognized as one of the most important factors influencing the soructure and function of lake ecosystems. Competition from plants of dissimilar growth form may have profound effects on shallow lakes＇. An experiment was conducted to investigate the effects of competitive interactions of submersed plants with dis- similar growth forms on the biomass allocations. Hydrilla verticitlata and Vallisneria natans were selected and were planted in a single-species monoculture and a mixed-species pattern, Results showed that the growth of E natans was＇ significantly affected by the tt, verticillata and caused a sharp reduction of biomass, but the root：shoot ratio of E ha- tans was not affected significantly and there was a minimal increase in mixture： while for H. verticillata, the biomass and the root：shoot ratio were not significantly changed by the competitive interactions ore natans, there was minimal increase of biomass and minimal decrease of the root：shoot ratio. These results may indicate that theplant which can develop a dense mat or canopy at the water surface would be a stronger competitor relative to the plant that depends more on light availability near the sediment.
文摘1.Introduction As China’s first floating production platform in ultra-deepwater,the“Deep Sea No.1”energy station is a milestone in China’s deepwater resource utilization.The energy station is located in the LS17-2 gas field,150 km off the southeast coast of Hainan Island,China.It is a semi-submersible platform(Fig.1)with a displacement of 101 thousand tonnes and an operational draft of 35 to 40 m.The platform is permanently moored in 1422 m water by 16 chain-polyester-chain mooring lines in a 4×4 pattern,and six steel catenary risers(SCRs)are attached to the platform.It is the world’s first and only semi-submersible platform with the function of condensate storage,so it can be regarded as a floating production storage and offloading(FPSO)unit.With the ability to produce 3 billion m3 of natural gas each year(enough for over 10 million families),the Deep Sea No.1 energy station is a key step toward China’s energy independence.The LS17-2 gas field,where the Deep Sea No.1 energy station is located,was discovered in 2014.Plans for its development were made in 2015,followed by research and a preliminary design.Deep Sea No.1 went into operation on June 25,2021,and will operate onsite continuously without dry-docking for 30 years.
基金The Key Research and Development Program of Shandong Province of China under contract No.2020JMRH0101the National Key Research and Development Project of China under contract No.2021YFC2802100the Qingdao Natural Science Foundation under contract No.24-4-4-zrij-127-jch.
文摘Scientific and precise evaluations of the megafaunal and landform characteristics of seamounts are important guides for their protection and study.A series of manned and unmanned submersibles have provided invaluable observational imaging data for the ecological study of seamounts.However,traditional methods of artificial observation of seamount imaging data cannot accurately and efficiently determine the characteristics of megafauna and landforms.This research harnesses data-driven technology to systematically investigate the distributional traits and morphological features of megafaunal organisms,as well as the topographical characteristics,in the Caiwei Guyot region of the western Pacific’s Magellan Seamounts.To construct the landform and megafauna dataset of the Caiwei Guyot region,we used a data preprocessing technology based on image enhancement to provide high-quality imaging data for data-driven technologies.A megafaunal identification and counting algorithm based on YOLOv5(You Only Look Once Version 5)was developed to efficiently assess the abundance,variety,and dominant species of megafauna.Simultaneously,a landform three-dimensional(3D)reconstruction algorithm based on PatchmatchNet was developed to reconstruct the 3D form of the terrain accurately.This study pioneers the application of data-driven technology to deep-sea imaging within the Caiwei Guyot region,offering an innovative approach to accurately and efficiently characterize the region’s unique megafauna and landforms.
基金financially supported by the National Natural Science Foundation of China (Grant No. 52201380)Fundamental Research Funds for the Central Universities (Grant No. D5000230080)+2 种基金Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University (Grant Nos. CX 2024049 and CX2023006)the Chunhui Program of Ministry of Education of China (Grant No. HZKY20220538)the Practice and Innovation Funds for Graduate Students of Northwestern Polytechnical University (Grant No. PF2023057)。
文摘Internal solitary waves(ISWs) are a common phenomenon beneath the ocean surface and represent a significant environmental hazard that must be considered for the safe navigation of submersibles. A numerical simulation model for the interaction of solitary waves with submersibles at a large scale has been developed. The Miyata-ChoiCamassa(MCC) equation serves as the basis for generating ISWs. The impacts of the submergence depth, wave amplitude, and advancing velocity on the motion response and load characteristics of the submersible are examined in detail. This study elucidates the governing laws and mechanisms underlying the impact of ISWs on submersibles.The research findings indicate that shorter distances to the undisturbed surface, higher wave amplitudes, and fasteradvancing speeds result in greater effects on submersibles. For a submersible operating in the lower layer, both the alteration in density near the wave interface and the dynamic pressure induced by ISWs can reduce its lift, potentially resulting in a rapid descent. It is imperative to pay considerable attention to the impact of ISWs, as they have the potential to precipitate a loss of control of the submersible.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFC2800600)the National Natural Science Foundation of China(Grant No.52071203).
文摘Polymethyl methacrylate(PMMA)has the advantages of good transparency,corrosion resistance and light weight and can be used as the preferred material for pressure-resistant cabins of fully transparent submersibles.In this study,based on the fracture mechanics method,a calculation method for estimating the residual fatigue life of a PMMA manned cabin is proposed by improving the small-time scale fatigue crack growth rate model.This improved model is verified by the experimental data of the PMMA material.Then,through the Weibull and Gumbel combined distribution functions,the fatigue load spectrum suitable for the fully transparent manned cabin is fitted according to the dive data.A parametric analysis of the residual fatigue life of the fully transparent manned cabin under various initial crack sizes and dwell time is conducted,yielding valuable results.This study aims to increase the safety of fully transparent pressure-resistant cabins and offer insights for fatigue analysis of underwater structures utilizing PMMA materials.
基金supported by the Deanship of Scientific Research,Vice Presidency for Graduate Studies and Scientific Research,King Faisal University,Saudi Arabia(Grant No.KFU241778).
文摘Tunisia’s coastal alluvial plains are fragile areas exposed to occasional disturbances(including storms,submersion,and floods)and serious imbalances,such as rising sea level,erosion,and salinisation of soils.Their sensitivity tends to increase under the impact of strong anthropogenic pressures:population growth,rapid urbanisation,and concentration of economic activities.With the acceleration of climate change and the associated rise in sea level,these areas are facing a new challenge.At the interface between land and sea,scattered across these coastal alluvial plains are wetlands that are predisposed to marine submersion due to a combination of factors.Diachronic analysis of cartographic documents has made it possible to produce geodynamic maps.These were used in the current study to assess sea level rise and flooding,as well as their impact on the future development of coastal alluvial plains,particularly during exceptional weather and sea conditions.The findings show that a poor understanding of the mechanisms specific to these environments has often resulted in short-sighted sectoral approaches to land use planning.Sabkhas and lagoons alone account for more than half of all submerged areas.Coastal wetland ecosystems will be threatened by changes in living conditions,as the rather saline biocenosis will be transformed into a euryhaline lagoon biocenosis.
基金financially supported by the China Postdoctoral Science Foundation(Grant No.2023M732979 and No.2022TQ0127)the Cooperative Research Project of the Ministry of Education's "Chunhui Program"(Grant No.HZKY20220117)+1 种基金the Natural Science Foundation of Jiangsu Province(Grant No.BK20220587)the National Natural Science Foundation of China(Grant No.52309112)。
文摘The electric submersible pump(ESP) is a crucial apparatus utilized for lifting in the oil extraction process.Its lifting capacity is enhanced by the multi-stage tandem structure, but variations in energy characteristics and internal flow across stages are also introduced. In this study, the inter-stage variability of energy characteristics in ESP hydraulic systems is investigated through entropy production(EP) analysis,which incorporates numerical simulations and experimental validation. The EP theory facilitates the quantification of energy loss in each computational subdomain at all ESP stages, establishing a correlation between microscopic flow structure and energy dissipation within the system. Furthermore, the underlying causes of inter-stage variability in ESP hydraulic systems are examined, and the advantages and disadvantages of applying the EP theory in this context are evaluated. Consistent energy characteristics within the ESP, aligned with the distribution of internal flow structure, are provided by the EP theory, as demonstrated by our results. The EP theory also enables the quantitative analysis of internal flow losses and complements existing performance analysis methods to map the internal flow structure to hydraulic losses. Nonetheless, an inconsistency between the energy characterization based on EP theory and the traditional efficiency index when reflecting inter-stage differences is identified. This inconsistency arises from the exclusive focus of the EP theory on flow losses within the flow field, disregarding the quantification of external energy input to the flow field. This study provides a reference for the optimization of EP theory in rotating machinery while deeply investigating the energy dissipation characteristics of multistage hydraulic system, which has certain theoretical and practical significance.
文摘This paper introduces current four categories of submersible standards in China. It also analyzes the progress of submersible standardization, and expounds on the future direction of standards for submersibles and three development paths, which will help consolidate China's advanced technology with independent intellectual property rights and enhance the influence of China's deep-sea equipment in the global market. It provides reference for related standardization workers as well.
文摘CHINA Jiaolong Completes 300th Dive Jiaolong,China’s manned deep-sea submersible,on 18 August completed its 300th dive since its maiden mission in August 2009.Jiaolong,with a crew of one scientist and two submariners,conducted the dive in the Western Pacific Ocean.It was the first of 18 planned dives in an ongoing scientific expedition.
基金supported by the National Natural Science Foundation of China(Nos.E51879084 and E51579075)Major Science and Technology Program for Water Pollution Con-trol and Treatment of China(No.2018ZX07208-4)。
文摘Submersed macrophytes decay is an important natural process and has important role in mass and energy flow in aquatic ecosystems.However,little is known about the dynamical changes in nutrients release and bacterial community during submersed macrophyte decay in natural environment.In this study,a field observation was conducted in a wetland dominated with Hydrilla verticillata for 36 days.Increase of H2O2 and malondialdehyde(MDA)content and decrease of soluble proteins concentration were detected in leaves during H.verticillata decay.Meanwhile,ammonium-N,soluble microbial products(SMP)and TOC concentration increased in overlying water.According to bacterial 16 S r RNA Illumina sequencing analysis,the Shannon values were lower in epiphytic biofilms than deciduous layer sediments.The relative abundances of Proteobacteria,Cyanobacteria and Actinobacteria were higher in epiphytic biofilms than in deciduous layer sediments(P<0.05).Co-occurrence network analyses showed that a total of 578 and 845 pairs of correlations(|r|>0.6)were identified from 122 and 112 genera in epiphytic biofilms and deciduous layer sediments,respectively.According to co-occurrence patterns,eight hubs were mainly from phyla Proteobacteria,Acidobacteria and Parcubacteria in epiphytic biofilms;while 37 hubs from the 14 phyla(Proteobacteria,Bacteroidetes,Acidobacteria,Chloroflexi,et al.)were detected in deciduous layer sediments.Our results indicate that bacterial community in deciduous layer sediments was more susceptible than in epiphytic biofilms during decay process.These data highlight the role of microbial community in deciduous layer sediments on nutrients removal during H.verticillata decay and will provide useful information for wetland management.
基金supported by the State Key Development Program of Basic Research of China(No.2008CB418104)the National Major Science and Technology Program for Water Pollution Control and Management(No.2008ZX07211-003)+1 种基金the China Post-doctoral Science Foundation(No.20090461149)the Fundamental Research Funds for Central Universities
文摘The competition between submersed plants has been recognized as an important factor influencing the structure of plant communities in shallow lakes.The ability of different species to take up and store nutrients from the surrounding ambience varies,and hence plant community structure might be expected to affect the cycling of nutrients in lake ecosystems.In this study,the uptake of phosphorus by Hydrilla verticillata and Vallisneria natans was studied and compared in monoculture and competitive mixed-culture plantings.Results showed that for both studied species the phosphorus concentrations of different tissues and of whole plants was unaffected by competition.However,the quantity of phosphorus accumulated by whole plants of 1-1.verticillata was significantly higher in mixture culture than in monoculture,while that of V.natans was lower in the mixed culture.The results indicated that 11.verticillata has a competitive advantage over V.natans,when the two species are grown in competition,and is able to accumulate a greater quantity of phosphorus.
基金Supported by the National Key Research and Development Program of China(No.2021YFC3200103)the Major Science and Technology Program for Water Pollution Control and Treatment of China(No.2017ZX07302-002)+2 种基金the State Key Laboratory of Freshwater Ecology and Biotechnology(No.2019FBZ01)the Wuhan Science and Technology Plan Project(No.2020020602012152),the Research Project of Wuhan Municipal Construction Group Co.,Ltd.(No.wszky202014)Haijun WANG was supported by the Youth Innovation Association of Chinese Academy of Sciences as an excellent member(No.Y201859)。
文摘Regime shifts from submersed macrophyte dominance to phytoplankton dominance have been widely reported in small-to medium-sized shallow lakes.However,alternative stable states in large shallow lakes(surface area>500 km^(2))remain unconfirmed.To understand the alternative stable states and the main influencing factors of submersed macrophytes in large lakes,the ecosystem states from monitoring data from 1959 to 2019 in large shallow Taihu Lake(2338 km^(2)in average depth of 2.12 m)in China were examined.Changes in submersed macrophyte coverage(C_(Mac))and phytoplankton chlorophyll a(Chl a)in the time series and their relationships with environmental factors were analyzed.During the field investigation from August 2018 to May 2019,nutrients and Chl a showed obvious heterogeneity across the lake,being generally higher in the western and northern areas and lower in the southeast area,while C_(Mac)was only observed in the eastern areas,e.g.,East Taihu Lake,Xukou Bay,and Gonghu Bay.During the long-term monitoring from 1959 to 2019 in the Central Region,Meiliang Bay,and East Taihu Lake,Chl a increased significantly in the time series.C_(Mac)varied slightly among different subareas,always at low levels(<10%)in the Central Region and Meiliang Bay but at relatively high levels in East Taihu Lake(10%–90%).Frequency distributions of response variables had no multimodality except for C_(Mac)in East Taihu Lake,with two peaks between 15%and 20%and between 55%and 60%.A dual relationship was found between Chl a and total phosphorus(TP)in the areas with and without macrophytes,while C_(Mac)showed no relationship with TP,and submersed macrophytes did not flourish in the Central Region and Meiliang Bay even when TP was at very low levels(≈10 mg/m3).Taihu Lake had similar algal turbidity(TurbAlg)as small-to mediumsized lakes but generally presented with higher values of nonalgal turbidity(TurbNonAlg),as did their contribution to total turbidity as a percentage.This study suggested that large shallow Taihu Lake may have no alternative stable states,but more evidence is needed for East Taihu Lake,which was dominated by macrophytes,as it remains unknown whether hysteresis occurs between the processes of eutrophication and oligotrophication.Unfavorable conditions caused by wind might be the main reason due to the absence of submersed macrophytes in Taihu Lake.These results demonstrate that stricter nutrient control is needed to maintain a healthy state or to recover from a decayed state for large lakes.
基金supported by the National Basic Research Program (973) of China (No. 2012CB417004)the National Natural Science Foundation of China (Nos. U1202235,41173118, 41301544)the Shandong Provincial Natural Science Foundation (No. ZR2012DQ003)
文摘A controlled experiment was designed to resolve the influence of nitrogen abundance on sediment organic matters in macrophyte-dominated lakes using fluorescence analysis.Macrophyte biomass showed coincident growth trends with time, but different variation rates with nitrogen treatment. All plant growth indexes with nitrogen addition（N, NH4Cl100, 200, 400 mg/kg, respectively） were lower than those of the control group. Four humiclike components, two autochthonous tryptophan-like components, and one autochthonous tyrosine-like component were identified using the parallel factor analysis model. The results suggested that the relative component changes of fluorescence in the colonized sediments were in direct relation to the change of root biomass with time. In the experiment, the root formation parameters of the plants studied were significantly affected by adding N in sediments, which may be related to the reason that the root growth was affected by N addition.Adding a low concentration of N to sediments can play a part in supplying nutrients to the plants. However, the intensive uptake of NH4^＋may result in an increase in the intracellular concentration of ammonia, which is highly toxic to the plant cells. Hence, our experiment results manifested that organic matter cycling in the macrophyte-dominated sediment was influenced by nitrogen enrichment through influencing vegetation and relevant microbial activity.
基金Projects KZCX1-SW-12 supported by the Key Project of CAS 2002AA601011-04 by the Hi-tech Research and Development Program of China
文摘Aquatic macrophytic growth and its distribution in eutrophic lakes are described in relation to its sediment type and irradiance. Hence, it is necessary to characterize the response of macrophytic growth to lake sediment and its re-suspension. We conducted two independent experiments to measure the effects of sediment and its re-suspension on the growth of Vallisneria asiatica Miki. Based on our study, we conclude that the amount of total biomass of V. asiatica is related, in important ways, to the type of sediment and its re-suspension. According to our comparison, plants and biomass cultured on lake sediments are 2.1 times and 1.5 times greater than that on brown clay from nearby places beside Lake Taihu. The number of plants and the amount of biomass in a turbid water column are smaller than those in a clear water column. The results indicate that the nutrient-rich lake sediments have promoted the growth of V. asiatica, while the re-suspension of the sediment leads to a high turbid level and low light penetration which has a negative impact on the growth of V. asiatica.
基金financially supported by the National Natural Science Foundation of China(Grant No.51541905)
文摘This paper presents a theoretic implementation method of Morphing Unmanned Submersible Aerial Vehicle （MUSAV）, which can both submerge in the water and fly in the air. Two different shapes are put forward so that the vehicle can suit both submergence and flight, considering the tremendous differences between hydrodynamic configuration and aerodynamic configuration of a vehicle. The transition of the two shapes can be achieved by using morphing technology. The water-to-air process, including water-exit, morphing, take-off and steady flight, is analyzed. The hydrodynamic and aerodynamic model of the vehicle exiting the water surface obliquely and then taking off into the air has been founded. The control strategy after morphing is analyzed and the control method is given. Numerical method is used to validate the motion model of the water-exit process. Results of simulations show the validity of the proposed model and the feasibility of MUSAV in theory.
基金supported by the State Key Program of National Natural Science of China "Structural Reliability Analysis on the Spherical Hull of Deep Sea MSs"(Grant No.51439004)the Scientific Innovation Program Project of "Key technology research and experimental validation of deep MS" by the Shanghai Committee of Science and Technology(Grant No.15DZ1207000)
文摘Given the recent success in the development of several submersibles in China, people's interest in the history of submersible development is increasing. This paper presents the history of submersible development in China, which can be briefly divided into three periods. The first one is the early period of hardship(1971–2000). Many prototype submersibles of HOVs, ROVs, and AUVs were developed at this time, but the main achievement was the establishment of special research organizations and the training of research and development personnel. The second period can be regarded as the quick development period(2001–2015). All currently used submersibles were developed during this period. The most remarkable achievement was the successful development of 7000 m-deep manned submersible "Jiaolong." The third period aims to develop 11 000 m submersibles for challenging the full ocean depth(2016–2020). In this period, two unmanned submersibles and two manned submersibles will be the significant indicators of achievement. If this 5-year plan can be successfully completed, China can play a significant role in the investigation of the deepest part of the oceans, namely, the hadal trenches(6500–11 000 m).
