The settling flux of biodeposition affects the environmental quality of cage culture areas and determines their environmental carrying capacity.Simple and effective simulation of the settling flux of biodeposition is ...The settling flux of biodeposition affects the environmental quality of cage culture areas and determines their environmental carrying capacity.Simple and effective simulation of the settling flux of biodeposition is extremely important for determining the spatial distribution of biodeposition.Theoretically,biodeposition in cage culture areas without specific emission rules can be simplified as point source pollution.Fluent is a fluid simulation software that can simulate the dispersion of particulate matter simply and efficiently.Based on the simplification of pollution sources and bays,the settling flux of biodeposition can be easily and effectively simulated by Fluent fluid software.In the present work,the feasibility of this method was evaluated by simulation of the settling flux of biodeposition in Maniao Bay,Hainan Province,China,and 20 sampling sites were selected for determining the settling fluxes.At sampling sites P1,P2,P3,P4,P5,Z1,Z2,Z3,Z4,A1,A2,A3,A4,B1,B2,C1,C2,C3 and C4,the measured settling fluxes of biodeposition were 26.02,15.78,10.77,58.16,6.57,72.17,12.37,12.11,106.64,150.96,22.59,11.41,18.03,7.90,19.23,7.06,11.84,5.19 and 2.57 g d^(−1)m^(−2),respectively.The simulated settling fluxes of biodeposition at the corresponding sites were 16.03,23.98,8.87,46.90,4.52,104.77,16.03,8.35,180.83,213.06,39.10,17.47,20.98,9.78,23.25,7.84,15.90,6.06 and 1.65 g d^(−1)m^(−2),respectively.There was a positive correlation between the simulated settling fluxes and measured ones(R=0.94,P=2.22×10^(−9)<0.05),which implies that the spatial differentiation of biodeposition flux was well simulated.Moreover,the posterior difference ratio of the simulation was 0.38,and the small error probability was 0.94,which means that the simulated results reached an acceptable level from the perspective of relative error.Thus,if nonpoint source pollution is simplified to point source pollution and open waters are simplified based on similarity theory,the setting flux of biodeposition in the open waters can be simply and effectively simulated by the fluid simulation software Fluent.展开更多
Efficient numerical schemes were presented for the steady state solutions of towed marine cables. For most of towed systems,the steady state problem can be resolved into two-point boundary-value problem,or initial val...Efficient numerical schemes were presented for the steady state solutions of towed marine cables. For most of towed systems,the steady state problem can be resolved into two-point boundary-value problem,or initial value problem in some special cases where the initial values are available directly.A new technique was proposed and attempted to solve the two-point boundary-value problem rather than the conventional shooting method due to its algorithm complexity and low efficiency.First,the boundary conditions are transformed into a set of nonlinear governing equations about the initial values,then bisection method is employed to solve these nonlinear equations with the aid of 4th order Runge-Kutta method.In common sense,non-uniform (sheared) current is assumed,which varies in magnitude and direction with depth.The schemes are validated through the DE Zoysa's example,then several numerical examples are also presented to illustrate the numerical schemes.展开更多
In marine wireless sensor networks(MWSNs),an appropriate routing protocol is the key to the collaborative collection and efficient transmission of massive data.However,designing an appropriate routing protocol under t...In marine wireless sensor networks(MWSNs),an appropriate routing protocol is the key to the collaborative collection and efficient transmission of massive data.However,designing an appropriate routing protocol under the condition of sparse marine node deployment,highly dynamic network topology,and limited node energy is complicated.Moreover,the absence of continuous endto-end connection introduces further difficulties in the design of routing protocols.In this case,we present a novel energy-efficient opportunistic routing(Novel Energy-Efficient Opportunistic Routing,NEOR)protocol for MWSNs that is based on compressed sensing and power control.First,a lightweight time-series prediction method-weighted moving average method is proposed to predict the packet advancement value such that the number of location information that is exchanged among a node and its neighbor nodes can be minimized.Second,an adaptive power control mechanism is presented to determine the optimal transmitting power and candidate nodeset on the basis of node mobility,packet advancement,communication link quality,and remaining node energy.Subsequently,a timer-based scheduling algorithm is utilized to coordinate packet forwarding to avoid packet conflict.Furthermore,we introduce the compressed sensing theory to compress perceptual data at source nodes and reconstruct the original data at sink nodes.Therefore,energy consumption in the MWSNs is greatly reduced due to the decrease in the amount of data perception and transmission.Numerical simulation experiments are carried out in a wide range of marine scenarios to verify the superiority of our approach over selected benchmark algorithms.展开更多
Nitrogen(N) and potassium(K) are essential elements for rice growth. When N and K are in deficient rice, specific symptoms appear on the leaves that are similar and difficult to distinguish with the naked eye.
To study the applicability of biodiesel in marine engines,this research investigated the performance,combustion characteristics,and emission characteristics of biodiesel(B100),diesel,and a 50%volume blend of the two f...To study the applicability of biodiesel in marine engines,this research investigated the performance,combustion characteristics,and emission characteristics of biodiesel(B100),diesel,and a 50%volume blend of the two fuels(B50)in a marine engine.This study was conducted on a 4-cylinder,520 mm-bore,two-stroke,low-speed marine engine with a common rail fuel and exhaust gas charge system.The three fuels were tested at different loads from 25%–100%with a step size of 25%.Results showed that the fuel consumption of pure biodiesel increased by about 13.5%and 3.8%relative to that of diesel at 25%and 100%loads,respectively,and by about 6%at 50%and 75%loads.In-cylinder combustion pressure was slightly reduced when the engine ran on biofuel,and black carbon emissions from biodiesel were reduced by an average of 54.7%.Compared with those from diesel,the carbon CO and total hydrocarbon emissions from B100 were reduced by 11.3%and 39%,respectively.Nitroxide emissions were elevated for B100 and B50 under all loading conditions.The properties of B50 blended diesel lie between those of B100 and diesel.In terms of combustion characteristics and emissions,biodiesel can be used without changing the engine parameters and can effectively reduce pollution,such as black carbon and carbon monoxide.展开更多
This study investigates the underwater radiated noise(URN)of a manned submersible support mother ship.To this end,a detailed finite element model of the hull and outflow field is established,and the vibration wet mode...This study investigates the underwater radiated noise(URN)of a manned submersible support mother ship.To this end,a detailed finite element model of the hull and outflow field is established,and the vibration wet mode of the scientific research ship is calculated.A combination of finite element and boundary element methods is used to analyze the spectral features of ship low-frequency URN.The URN source is comprehensively analyzed,the vibration energy is considered the basic parameter to describe the vibration,and the medium-and high-frequency URN of the ship are calculated using the statistical energy analysis.To obtain the full frequency-band URN of the ship,the risk position of exceeding the standard is determined,and the contribution of each main noise source in the ship to the URN is analyzed.The URN level of the ship is comprehensively measured in the free navigation state.The accuracy of the URN control evaluation model,and the method of the ship are verified.The data support for the ship to apply for the classification society certificate provides a scheme reference for the URN control of other scientific research ship in the future.展开更多
It is well known that outer rise bending-assisted oceanic plate hydration is an important mechanism for transporting substantial amounts of water into the mantle.A key question is:Are there other equally or more impor...It is well known that outer rise bending-assisted oceanic plate hydration is an important mechanism for transporting substantial amounts of water into the mantle.A key question is:Are there other equally or more important water transport mechanisms?Here we propose,for the first time,that subducting passive continental margins,particularly those with crustal(ultra)mafic intrusions,play a critical role in recycling water back into the mantle.Evidence for this mechanism is the exceptionally high outer rise seismicity observed in a subducting passive continental margin(i.e.,the northeastern South China Sea continental margin)near the northern Manila trench,characterized by a high-velocity lower crust that has been attributed to(ultra)mafic intrusions.Our interpretation of this correlation between high outer rise seismicity and lower crust(ultra)mafic intrusions is that(ultra)mafic intrusions alter the crustal rheology and increase brittle deformation in the lower crust in this region,thereby promoting lithospheric fracturing and plate hydration,which is evidenced by increased outer rise seismicity.展开更多
In order to develop a anchoring operation simulation system and improve safety during anchoring operations,a relatively accurate mathematical model of anchoring operations needs to be established.In this paper,the str...In order to develop a anchoring operation simulation system and improve safety during anchoring operations,a relatively accurate mathematical model of anchoring operations needs to be established.In this paper,the stress condition of anchor chain under environmental and subsea geological conditions is further studied and the stress condition of anchor chain is analyzed based on the previous research.In this paper,a quasi-static model based on catenary method is used as the basis of dynamic analysis,and the dynamic model of anchor chain is established based on the concentrated mass method,which fully considers the influence of anchor chain weight,hydrodynamic force,ocean current and interaction with the seabed.The fourth-order Runge Kutta method was used to solve the model numerically,and a calculation procedure was developed.The accuracy of the model was verified by comparing the calculated results with the experimental results,indicating that the constructed anchor chain dynamics model has a high accuracy.展开更多
Out-of-plane mechanical properties of the riveted joints restrict the performance of the wing box assembly of airplane.It is necessary to investigate the pull-through performance of the composite/metal riveted joints ...Out-of-plane mechanical properties of the riveted joints restrict the performance of the wing box assembly of airplane.It is necessary to investigate the pull-through performance of the composite/metal riveted joints in order to guide the riveting design and ensure the safety of the wing box assembly.The progressive failure mechanism of composite/aluminum riveted joint subjected to pull-through loading was investigated by experiments and finite element method.A progressive damage model based on the Hashin-type criteria and zero-thickness cohesive zone method was developed by VUMAT subroutine,which was validated by both open-hole tensile test and three-point bending test.Predicted load-displacement response,failure modes and damage propagation were analysed and compared with the results of the pull-through tests.There are 4 obvious characteristic stages on the load-displacement curve of the pull-through test and that of the finite element model:first load take-up stage,damage stage,second load take-up stage and failure stage.Relative error of stiffness,first load peak and second load peak between finite element method and experiments were 8.1%,-3.3%and 10.6%,respectively.It was found that the specimen was mainly broken by rivet-penetration fracture and delamination of plies of the composite laminate.And the material within the scope of the rivet head is more dangerous with more serious tensile damages than other regions,especially for 90°plies.This study proposes a numerical method for damage prediction and reveals the progressive failure mechanism of the hybrid material riveted joints subjected to the pull-through loading.展开更多
The freshwater species,Euplotes mazeii n.sp.,and the marine species,E.balteatus(Dujardin,1841)Diesing,1850 were collected from China and investigated based on their living morphology,ciliary pattern,and small subunit ...The freshwater species,Euplotes mazeii n.sp.,and the marine species,E.balteatus(Dujardin,1841)Diesing,1850 were collected from China and investigated based on their living morphology,ciliary pattern,and small subunit ribosomal RNA(SSU rRNA)gene sequence data.Euplotes mazeii n.sp.was characterized by its small cell size((40-55)μm×(25-35)μm),nine frontoventral cirri,one marginal and two caudal cirri,seven dorsal kineties,and a double-eurystomus type of dorsal silverline system.Phylogenetic analyses based on molecular data confirmed the branching position of this new taxa within the genus Euplotes,with 5.01%(84 nucleotides)sequence variation,supporting the identification of a new species.We re-examined all described and supposedly conspecific populations and give a review of Euplotes balteatus.E.balteatus has been reported frequently;however,E.balteatus sensu Agamaliev,1968 is different from other populations in the number of marginal cirri or the type of silverline system,which suggests there might be a misidentification.The SSU rRNA gene sequences of two populations of E.balteatus from the studies of Chen et al.(2013)and Pan et al.(2012)differ from each other by more than 135 nucleotides,implying that the identity of the species currently associated with the SSU rRNA gene sequence in molecular databases requires further confirmation.展开更多
Widespread species that inhabit diverse environments possess large population sizes and exhibit a high capacity for environmental adaptation,thus enabling range expansion.In contrast,narrow-range species are confined ...Widespread species that inhabit diverse environments possess large population sizes and exhibit a high capacity for environmental adaptation,thus enabling range expansion.In contrast,narrow-range species are confined to restricted geographical areas and are ecologically adapted to narrow environmental conditions,thus limiting their ability to expand into novel environments.However,the genomic mechanisms underlying the differentiation between closely related species with varying distribution ranges remain poorly understood.The Niviventer niviventer species complex(NNSC),consisting of highly abundant wild rats in Southeast Asia and China,offers an excellent opportunity to investigate these questions due to the presence of both widespread and narrow-range species that are phylogenetically closely related.In the present study,we combined ecological niche modeling with phylogenetic analysis,which suggested that sister species cannot be both widespread and dominant within the same geographical region.Moreover,by assessing heterozygosity,linkage disequilibrium decay,and Tajima's D analysis,we found that widespread species exhibited higher genetic diversity than narrow-range species.In addition,by exploring the“genomic islands of speciation”,we identified 13 genes in highly divergent regions that were shared by the two widespread species,distinguishing them from their narrow-range counterparts.Functional annotation analysis indicated that these genes are involved in nervous system development and regulation.The adaptive evolution of these genes likely played an important role in the speciation of these widespread species.展开更多
This article reports a particle image velocimetry study and the comparative results of a numerical simulation into the hydrodynamic characteristics around an artificial reef.We reveal the process of flow separation an...This article reports a particle image velocimetry study and the comparative results of a numerical simulation into the hydrodynamic characteristics around an artificial reef.We reveal the process of flow separation and vortex evolution,and compare the force terms generated by our artificial reef model.The numerical simulation agrees well with experimental results,showing the applicability of computational fluid dynamics to the hydrodynamics of an artificial reef.Furthermore,we numerically simulate the hydrodynamics of the reef model for seven velocities.The results show that the drag coefficient is approximately 1.21 in a self-modeling region for Reynolds numbers between 2.123×104and 9×104.Therefore,the upwelling height and current width of the flow field do not change significantly when the inflow velocity increases.Our study indicates that computational fluid dynamics can be applied to study the hydrodynamics of an artificial reef and offer clues to its construction.展开更多
The hydrodynamic forces and flow field of artificial reef models in steady flow were numerically investigated using the RNG k–εturbulent model.The numerical simulation results are consistent with results observed by...The hydrodynamic forces and flow field of artificial reef models in steady flow were numerically investigated using the RNG k–εturbulent model.The numerical simulation results are consistent with results observed by experimental means.A comparative study indicates that the corresponding errors of forces between calculated values and values observed in the experiment vary in the range of 2.3%–11.2%and that the corresponding errors of velocities vary in the range of 1.3%–15.8%. The flow field numerical results show that upstream and vortices exist when the current passes over and through the surface of the reef model.This study suggests that the numerical simulation method can be applied to predict the forces and flow field associated with artificial reefs.展开更多
A three-dimensional numerical model was established to simulate the hydrodynamics within an octagonal tank of a recirculating aquaculture system.The realizable k-s turbulence model was applied to describe the flow,the...A three-dimensional numerical model was established to simulate the hydrodynamics within an octagonal tank of a recirculating aquaculture system.The realizable k-s turbulence model was applied to describe the flow,the discrete phase model(DPM) was applied to generate particle trajectories,and the governing equations are solved using the finite volume method.To validate this model,the numerical results were compared with data obtained from a full-scale physical model.The results show that:(1) the realizable k-e model applied for turbulence modeling describes well the flow pattern in octagonal tanks,giving an average relative error of velocities between simulated and measured values of 18%from contour maps of velocity magnitudes;(2) the DPM was applied to obtain particle trajectories and to simulate the rate of particle removal from the tank.The average relative error of the removal rates between simulated and measured values was 11%.The DPM can be used to assess the self-cleaning capability of an octagonal tank;(3) a comprehensive account of the hydrodynamics within an octagonal tank can be assessed from simulations.The velocity distribution was uniform with an average velocity of 15 cm/s;the velocity reached0.8 m/s near the inlet pipe,which can result in energy losses and cause wall abrasion;the velocity in tank corners was more than 15 cm/s,which suggests good water mixing,and there was no particle sedimentation.The percentage of particle removal for octagonal tanks was 90%with the exception of a little accumulation of <5 mm particle in the area between the inlet pipe and the wall.This study demonstrated a consistent numerical model of the hydrodynamics within octagonal tanks that can be further used in their design and optimization as well as promote the wide use of computational fluid dynamics in aquaculture engineering.展开更多
Based on the field survey data of four cruises in 2011,all phytoplankton communities in the southern Yellow Sea (SYS) were investigated for the species composition,dominant species,abundance and diversity indices.A to...Based on the field survey data of four cruises in 2011,all phytoplankton communities in the southern Yellow Sea (SYS) were investigated for the species composition,dominant species,abundance and diversity indices.A total of 379 species belonging to9 phyla were identified,of which the most abundant group was Bacillariophyta (60.9%) ,followed by Pyrrophyta (23.7%) and Haptophyta (6.9%) .The seasonal distribution of abundance was:summer (4137.1×103ind m 3) >spring (3940.4×103ind m 3) >winter (3010.6×103ind m 3) >autumn (340.8×103ind m 3) ,while the horizontal distribution showed a decreasing tendency from inshore to offshore regions.The dominant species of phytoplankton varied in different seasons.The dominant species were Thalassiosira pacifica,Skeletoema spp.and Chaetoceros cinctus in spring,Chaetoceros debbilis,Chaetoceros pseudocurvisetus and Chaetoceros curvisetus in summer,Thalassiosira curviseriata,Alexandrium catenella and Ceratium fusus in autumn,Paralia sulcata,Phaeocystis sp.and Bacillaria paradoxa in winter,respectively.In SYS,the group of temperate coastal species was the major ecotype,and the groups of the central SYS species and oceanic species were also important constituents.The average values of Shannon-Weaver diversity index (H’) and Pielou evenness index (J) were 2.37 and 0.65 respectively.The indices H’and J in the open sea were higher than those in coastal waters.Obvious co-variation tendencies between H’and J were observed in all but the summer cruise of this survey.展开更多
The orifice plate energy dissipater is an economic and highly efficient dissipater.However,there is a risk of cavitaion around the orifice plate flow.In order to provide references for engineering practice,we examined...The orifice plate energy dissipater is an economic and highly efficient dissipater.However,there is a risk of cavitaion around the orifice plate flow.In order to provide references for engineering practice,we examined the cavitation mechanism around the orifice plate and its influencing factors by utilizing mathematical analysis methods to analyze the flow conditions around the orifice plate in view of gas bubble dynamics.Through the research presented in this paper,the following can be observed:The critical radius and the critical pressure of the gas nucleus in orifice plate flow increase with its initial state parameter τ0 ;the development speed of bubbles stabilizes at a certain value after experiencing a peak value and a small valley value;and the orifice plate cavitation is closely related to the distribution of the gas nucleus in flow.For computing the orifice plate cavitation number,we ought to take into account the effects of pressure fluctuation.The development time of the gas nucleus from the initial radius to the critical radius is about 10-7-10-5 s;therefore,the gas nucleus has sufficient time to develop into bubbles in the negative half-cycle of flow fluctuation.The orifice critical cavitation number is closely related to the orifice plate size,and especially closely related with the ratio of the orifice plate radius to the tunnel radius.The approximate formula for the critical cavitation number of the square orifice plate that only considers the main influencing factor was obtained by model experiments.展开更多
The performance of six statistical approaches,which can be used for selection of the best model to describe the growth of individual fish,was analyzed using simulated and real length-at-age data.The six approaches inc...The performance of six statistical approaches,which can be used for selection of the best model to describe the growth of individual fish,was analyzed using simulated and real length-at-age data.The six approaches include coefficient of determination(R2),adjusted coefficient of determination(adj.-R2),root mean squared error(RMSE),Akaike's information criterion(AIC),bias correction of AIC(AICc) and Bayesian information criterion(BIC).The simulation data were generated by five growth models with different numbers of parameters.Four sets of real data were taken from the literature.The parameters in each of the five growth models were estimated using the maximum likelihood method under the assumption of the additive error structure for the data.The best supported model by the data was identified using each of the six approaches.The results show that R2 and RMSE have the same properties and perform worst.The sample size has an effect on the performance of adj.-R2,AIC,AICc and BIC.Adj.-R2 does better in small samples than in large samples.AIC is not suitable to use in small samples and tends to select more complex model when the sample size becomes large.AICc and BIC have best performance in small and large sample cases,respectively.Use of AICc or BIC is recommended for selection of fish growth model according to the size of the length-at-age data.展开更多
In order to reduce the resistance and improve the hydrodynamic performance of a ship, two hull form design methods are proposed based on the potential flow theory and viscous flow theory. The flow fields are meshed us...In order to reduce the resistance and improve the hydrodynamic performance of a ship, two hull form design methods are proposed based on the potential flow theory and viscous flow theory. The flow fields are meshed using body-fitted mesh and structured grids. The parameters of the hull modification function are the design variables. A three-dimensional modeling method is used to alter the geometry. The Non-Linear Programming(NLP) method is utilized to optimize a David Taylor Model Basin(DTMB) model 5415 ship under the constraints, including the displacement constraint. The optimization results show an effective reduction of the resistance. The two hull form design methods developed in this study can provide technical support and theoretical basis for designing green ships.展开更多
基金support from the National Key Research and Development Program of China(No.2018YFD0900704)the National Natural Science Foundation of China(No.31972796).
文摘The settling flux of biodeposition affects the environmental quality of cage culture areas and determines their environmental carrying capacity.Simple and effective simulation of the settling flux of biodeposition is extremely important for determining the spatial distribution of biodeposition.Theoretically,biodeposition in cage culture areas without specific emission rules can be simplified as point source pollution.Fluent is a fluid simulation software that can simulate the dispersion of particulate matter simply and efficiently.Based on the simplification of pollution sources and bays,the settling flux of biodeposition can be easily and effectively simulated by Fluent fluid software.In the present work,the feasibility of this method was evaluated by simulation of the settling flux of biodeposition in Maniao Bay,Hainan Province,China,and 20 sampling sites were selected for determining the settling fluxes.At sampling sites P1,P2,P3,P4,P5,Z1,Z2,Z3,Z4,A1,A2,A3,A4,B1,B2,C1,C2,C3 and C4,the measured settling fluxes of biodeposition were 26.02,15.78,10.77,58.16,6.57,72.17,12.37,12.11,106.64,150.96,22.59,11.41,18.03,7.90,19.23,7.06,11.84,5.19 and 2.57 g d^(−1)m^(−2),respectively.The simulated settling fluxes of biodeposition at the corresponding sites were 16.03,23.98,8.87,46.90,4.52,104.77,16.03,8.35,180.83,213.06,39.10,17.47,20.98,9.78,23.25,7.84,15.90,6.06 and 1.65 g d^(−1)m^(−2),respectively.There was a positive correlation between the simulated settling fluxes and measured ones(R=0.94,P=2.22×10^(−9)<0.05),which implies that the spatial differentiation of biodeposition flux was well simulated.Moreover,the posterior difference ratio of the simulation was 0.38,and the small error probability was 0.94,which means that the simulated results reached an acceptable level from the perspective of relative error.Thus,if nonpoint source pollution is simplified to point source pollution and open waters are simplified based on similarity theory,the setting flux of biodeposition in the open waters can be simply and effectively simulated by the fluid simulation software Fluent.
文摘Efficient numerical schemes were presented for the steady state solutions of towed marine cables. For most of towed systems,the steady state problem can be resolved into two-point boundary-value problem,or initial value problem in some special cases where the initial values are available directly.A new technique was proposed and attempted to solve the two-point boundary-value problem rather than the conventional shooting method due to its algorithm complexity and low efficiency.First,the boundary conditions are transformed into a set of nonlinear governing equations about the initial values,then bisection method is employed to solve these nonlinear equations with the aid of 4th order Runge-Kutta method.In common sense,non-uniform (sheared) current is assumed,which varies in magnitude and direction with depth.The schemes are validated through the DE Zoysa's example,then several numerical examples are also presented to illustrate the numerical schemes.
基金The authors appreciate the project support from China Scholarship Council, and the National Natural Science Foundation of China （51579143, 51379121, 61304230）, Shanghai Shuguang Plan Project （No： 15SG44） and China Postdoctoral Foundation （No. 2015M581585）.
基金supported by the National Natural Science Foundation of China(Nos.52201403,52201401,52071200,52102397,61701299,51709167)the National Key Research and Development Program(No.2021YFC2801002)+4 种基金the China Postdoctoral Science Foundation(Nos.2021M 700790,2022M712027)the Fund of National Engineering Research Center for Water Transport Safety(No.A2022003)the Foundation for Jiangsu Key Laboratory of Traffic and Transportation Security(No.TTS2021-05)the Fund of Hubei Key Laboratory of Inland Shipping Technology(No.NHHY2021002)the Top-Notch Innovative Program for Postgraduates of Shanghai Maritime University(Nos.2019YBR006,2019YBR002).
文摘In marine wireless sensor networks(MWSNs),an appropriate routing protocol is the key to the collaborative collection and efficient transmission of massive data.However,designing an appropriate routing protocol under the condition of sparse marine node deployment,highly dynamic network topology,and limited node energy is complicated.Moreover,the absence of continuous endto-end connection introduces further difficulties in the design of routing protocols.In this case,we present a novel energy-efficient opportunistic routing(Novel Energy-Efficient Opportunistic Routing,NEOR)protocol for MWSNs that is based on compressed sensing and power control.First,a lightweight time-series prediction method-weighted moving average method is proposed to predict the packet advancement value such that the number of location information that is exchanged among a node and its neighbor nodes can be minimized.Second,an adaptive power control mechanism is presented to determine the optimal transmitting power and candidate nodeset on the basis of node mobility,packet advancement,communication link quality,and remaining node energy.Subsequently,a timer-based scheduling algorithm is utilized to coordinate packet forwarding to avoid packet conflict.Furthermore,we introduce the compressed sensing theory to compress perceptual data at source nodes and reconstruct the original data at sink nodes.Therefore,energy consumption in the MWSNs is greatly reduced due to the decrease in the amount of data perception and transmission.Numerical simulation experiments are carried out in a wide range of marine scenarios to verify the superiority of our approach over selected benchmark algorithms.
基金funded by the National Natural Science Foundation of China(Grant Nos.31801255 and 52071200)。
文摘Nitrogen(N) and potassium(K) are essential elements for rice growth. When N and K are in deficient rice, specific symptoms appear on the leaves that are similar and difficult to distinguish with the naked eye.
基金Ministry of Industry and Information Technology High-tech Ship Research Project(Grant No.MC-202019-C08)Shanghai Ship Intelligent Operation and Maintenance and Energy Efficiency Monitoring Engineering Technology Research Center,Shanghai Science and Technology Program(Grant No.20DZ2252300).
文摘To study the applicability of biodiesel in marine engines,this research investigated the performance,combustion characteristics,and emission characteristics of biodiesel(B100),diesel,and a 50%volume blend of the two fuels(B50)in a marine engine.This study was conducted on a 4-cylinder,520 mm-bore,two-stroke,low-speed marine engine with a common rail fuel and exhaust gas charge system.The three fuels were tested at different loads from 25%–100%with a step size of 25%.Results showed that the fuel consumption of pure biodiesel increased by about 13.5%and 3.8%relative to that of diesel at 25%and 100%loads,respectively,and by about 6%at 50%and 75%loads.In-cylinder combustion pressure was slightly reduced when the engine ran on biofuel,and black carbon emissions from biodiesel were reduced by an average of 54.7%.Compared with those from diesel,the carbon CO and total hydrocarbon emissions from B100 were reduced by 11.3%and 39%,respectively.Nitroxide emissions were elevated for B100 and B50 under all loading conditions.The properties of B50 blended diesel lie between those of B100 and diesel.In terms of combustion characteristics and emissions,biodiesel can be used without changing the engine parameters and can effectively reduce pollution,such as black carbon and carbon monoxide.
基金The National Key R&D Plan(Grant No.2016YFC03000704)National Key R&D Plan(Grant No.2018YFC03009202).
文摘This study investigates the underwater radiated noise(URN)of a manned submersible support mother ship.To this end,a detailed finite element model of the hull and outflow field is established,and the vibration wet mode of the scientific research ship is calculated.A combination of finite element and boundary element methods is used to analyze the spectral features of ship low-frequency URN.The URN source is comprehensively analyzed,the vibration energy is considered the basic parameter to describe the vibration,and the medium-and high-frequency URN of the ship are calculated using the statistical energy analysis.To obtain the full frequency-band URN of the ship,the risk position of exceeding the standard is determined,and the contribution of each main noise source in the ship to the URN is analyzed.The URN level of the ship is comprehensively measured in the free navigation state.The accuracy of the URN control evaluation model,and the method of the ship are verified.The data support for the ship to apply for the classification society certificate provides a scheme reference for the URN control of other scientific research ship in the future.
基金funded by the National Natural Science Foundation of China(Grant Nos.42276049,91858205,42076068).
文摘It is well known that outer rise bending-assisted oceanic plate hydration is an important mechanism for transporting substantial amounts of water into the mantle.A key question is:Are there other equally or more important water transport mechanisms?Here we propose,for the first time,that subducting passive continental margins,particularly those with crustal(ultra)mafic intrusions,play a critical role in recycling water back into the mantle.Evidence for this mechanism is the exceptionally high outer rise seismicity observed in a subducting passive continental margin(i.e.,the northeastern South China Sea continental margin)near the northern Manila trench,characterized by a high-velocity lower crust that has been attributed to(ultra)mafic intrusions.Our interpretation of this correlation between high outer rise seismicity and lower crust(ultra)mafic intrusions is that(ultra)mafic intrusions alter the crustal rheology and increase brittle deformation in the lower crust in this region,thereby promoting lithospheric fracturing and plate hydration,which is evidenced by increased outer rise seismicity.
基金supported by the National Natural Science Foundation of China(Grant No.52071200)the Science and Technology Commission of Shanghai Munici-pality.(Grant No.23010501900)。
文摘In order to develop a anchoring operation simulation system and improve safety during anchoring operations,a relatively accurate mathematical model of anchoring operations needs to be established.In this paper,the stress condition of anchor chain under environmental and subsea geological conditions is further studied and the stress condition of anchor chain is analyzed based on the previous research.In this paper,a quasi-static model based on catenary method is used as the basis of dynamic analysis,and the dynamic model of anchor chain is established based on the concentrated mass method,which fully considers the influence of anchor chain weight,hydrodynamic force,ocean current and interaction with the seabed.The fourth-order Runge Kutta method was used to solve the model numerically,and a calculation procedure was developed.The accuracy of the model was verified by comparing the calculated results with the experimental results,indicating that the constructed anchor chain dynamics model has a high accuracy.
基金National Natural Science Foundation of China(Grant Nos.U21A20165,52205515,52105431)Applied Basic Research Program of Liaoning Province of China(Grant No.2022JH2/101300221)+2 种基金Dalian Science and Technology Innovation Fund of China(Grant No.2022JJ12GX033)National Key Research and Development Project of China(Grant No.2020YFB2009805)China Postdoctoral Science Foundation(Grant Nos.2020M680937,2020M670734)。
文摘Out-of-plane mechanical properties of the riveted joints restrict the performance of the wing box assembly of airplane.It is necessary to investigate the pull-through performance of the composite/metal riveted joints in order to guide the riveting design and ensure the safety of the wing box assembly.The progressive failure mechanism of composite/aluminum riveted joint subjected to pull-through loading was investigated by experiments and finite element method.A progressive damage model based on the Hashin-type criteria and zero-thickness cohesive zone method was developed by VUMAT subroutine,which was validated by both open-hole tensile test and three-point bending test.Predicted load-displacement response,failure modes and damage propagation were analysed and compared with the results of the pull-through tests.There are 4 obvious characteristic stages on the load-displacement curve of the pull-through test and that of the finite element model:first load take-up stage,damage stage,second load take-up stage and failure stage.Relative error of stiffness,first load peak and second load peak between finite element method and experiments were 8.1%,-3.3%and 10.6%,respectively.It was found that the specimen was mainly broken by rivet-penetration fracture and delamination of plies of the composite laminate.And the material within the scope of the rivet head is more dangerous with more serious tensile damages than other regions,especially for 90°plies.This study proposes a numerical method for damage prediction and reveals the progressive failure mechanism of the hybrid material riveted joints subjected to the pull-through loading.
基金supported by the National Natural Science Foundation of China(Nos.32030015,32111530116)the China Postdoctoral Science Foundation Grant(No.2021M701993)the Fundamental Research Funds for the Central Universities(No.GK202207019)。
文摘The freshwater species,Euplotes mazeii n.sp.,and the marine species,E.balteatus(Dujardin,1841)Diesing,1850 were collected from China and investigated based on their living morphology,ciliary pattern,and small subunit ribosomal RNA(SSU rRNA)gene sequence data.Euplotes mazeii n.sp.was characterized by its small cell size((40-55)μm×(25-35)μm),nine frontoventral cirri,one marginal and two caudal cirri,seven dorsal kineties,and a double-eurystomus type of dorsal silverline system.Phylogenetic analyses based on molecular data confirmed the branching position of this new taxa within the genus Euplotes,with 5.01%(84 nucleotides)sequence variation,supporting the identification of a new species.We re-examined all described and supposedly conspecific populations and give a review of Euplotes balteatus.E.balteatus has been reported frequently;however,E.balteatus sensu Agamaliev,1968 is different from other populations in the number of marginal cirri or the type of silverline system,which suggests there might be a misidentification.The SSU rRNA gene sequences of two populations of E.balteatus from the studies of Chen et al.(2013)and Pan et al.(2012)differ from each other by more than 135 nucleotides,implying that the identity of the species currently associated with the SSU rRNA gene sequence in molecular databases requires further confirmation.
基金supported by the Guangdong Provincial Key R&D Program (2022B1111040001)the Second Tibetan Plateau Scientific Expedition and Research Program (2019QZKK0402/2019QZKK0501)National Natural Science Foundation of China (32170426)。
文摘Widespread species that inhabit diverse environments possess large population sizes and exhibit a high capacity for environmental adaptation,thus enabling range expansion.In contrast,narrow-range species are confined to restricted geographical areas and are ecologically adapted to narrow environmental conditions,thus limiting their ability to expand into novel environments.However,the genomic mechanisms underlying the differentiation between closely related species with varying distribution ranges remain poorly understood.The Niviventer niviventer species complex(NNSC),consisting of highly abundant wild rats in Southeast Asia and China,offers an excellent opportunity to investigate these questions due to the presence of both widespread and narrow-range species that are phylogenetically closely related.In the present study,we combined ecological niche modeling with phylogenetic analysis,which suggested that sister species cannot be both widespread and dominant within the same geographical region.Moreover,by assessing heterozygosity,linkage disequilibrium decay,and Tajima's D analysis,we found that widespread species exhibited higher genetic diversity than narrow-range species.In addition,by exploring the“genomic islands of speciation”,we identified 13 genes in highly divergent regions that were shared by the two widespread species,distinguishing them from their narrow-range counterparts.Functional annotation analysis indicated that these genes are involved in nervous system development and regulation.The adaptive evolution of these genes likely played an important role in the speciation of these widespread species.
基金Supported by the National Natural Science Foundation of China(Nos.31072246,31272703)
文摘This article reports a particle image velocimetry study and the comparative results of a numerical simulation into the hydrodynamic characteristics around an artificial reef.We reveal the process of flow separation and vortex evolution,and compare the force terms generated by our artificial reef model.The numerical simulation agrees well with experimental results,showing the applicability of computational fluid dynamics to the hydrodynamics of an artificial reef.Furthermore,we numerically simulate the hydrodynamics of the reef model for seven velocities.The results show that the drag coefficient is approximately 1.21 in a self-modeling region for Reynolds numbers between 2.123×104and 9×104.Therefore,the upwelling height and current width of the flow field do not change significantly when the inflow velocity increases.Our study indicates that computational fluid dynamics can be applied to study the hydrodynamics of an artificial reef and offer clues to its construction.
基金Supported by the National High Technology Research and Development Program of China(863 Programs)(No.2006AA100301)Science and Technology Development Program of Shandong Province(No.2005GG3205102)
文摘The hydrodynamic forces and flow field of artificial reef models in steady flow were numerically investigated using the RNG k–εturbulent model.The numerical simulation results are consistent with results observed by experimental means.A comparative study indicates that the corresponding errors of forces between calculated values and values observed in the experiment vary in the range of 2.3%–11.2%and that the corresponding errors of velocities vary in the range of 1.3%–15.8%. The flow field numerical results show that upstream and vortices exist when the current passes over and through the surface of the reef model.This study suggests that the numerical simulation method can be applied to predict the forces and flow field associated with artificial reefs.
基金Supported by the Application Research Project of Post-Doctoral Researchers in Qingdao(No.ZQ51201415037)the Modern Agriculture Industry System Construction of Special Funds(No.CARS-50-G10)+1 种基金the Special Project about Independent Innovation and Achievement Transformation of Shandong Province(No.2014ZZCX07102)the Key R&D Program of Jiangsu Province(No.BE2015328)
文摘A three-dimensional numerical model was established to simulate the hydrodynamics within an octagonal tank of a recirculating aquaculture system.The realizable k-s turbulence model was applied to describe the flow,the discrete phase model(DPM) was applied to generate particle trajectories,and the governing equations are solved using the finite volume method.To validate this model,the numerical results were compared with data obtained from a full-scale physical model.The results show that:(1) the realizable k-e model applied for turbulence modeling describes well the flow pattern in octagonal tanks,giving an average relative error of velocities between simulated and measured values of 18%from contour maps of velocity magnitudes;(2) the DPM was applied to obtain particle trajectories and to simulate the rate of particle removal from the tank.The average relative error of the removal rates between simulated and measured values was 11%.The DPM can be used to assess the self-cleaning capability of an octagonal tank;(3) a comprehensive account of the hydrodynamics within an octagonal tank can be assessed from simulations.The velocity distribution was uniform with an average velocity of 15 cm/s;the velocity reached0.8 m/s near the inlet pipe,which can result in energy losses and cause wall abrasion;the velocity in tank corners was more than 15 cm/s,which suggests good water mixing,and there was no particle sedimentation.The percentage of particle removal for octagonal tanks was 90%with the exception of a little accumulation of <5 mm particle in the area between the inlet pipe and the wall.This study demonstrated a consistent numerical model of the hydrodynamics within octagonal tanks that can be further used in their design and optimization as well as promote the wide use of computational fluid dynamics in aquaculture engineering.
基金supported by the grants from the National Basic Research Program of China(No.2010CB428903)the National Marine Public Welfare Research Project of China(Nos.201205015 and 201305009)+5 种基金the National Natural Science Foundation of China(No.41206103)the Basic Scientific Research of SIO,SOA(No.JG1222)the National Natural Science Foundation of China(No.41306112)the Zhejiang Provincial Natural Science Foundation(No.LY13D060004)the Basic Scientific Research Fund of SIO,China(No.JG1311)the Marine Science Foundation of State Oceanic Administration for Youth(No.2013140)
文摘Based on the field survey data of four cruises in 2011,all phytoplankton communities in the southern Yellow Sea (SYS) were investigated for the species composition,dominant species,abundance and diversity indices.A total of 379 species belonging to9 phyla were identified,of which the most abundant group was Bacillariophyta (60.9%) ,followed by Pyrrophyta (23.7%) and Haptophyta (6.9%) .The seasonal distribution of abundance was:summer (4137.1×103ind m 3) >spring (3940.4×103ind m 3) >winter (3010.6×103ind m 3) >autumn (340.8×103ind m 3) ,while the horizontal distribution showed a decreasing tendency from inshore to offshore regions.The dominant species of phytoplankton varied in different seasons.The dominant species were Thalassiosira pacifica,Skeletoema spp.and Chaetoceros cinctus in spring,Chaetoceros debbilis,Chaetoceros pseudocurvisetus and Chaetoceros curvisetus in summer,Thalassiosira curviseriata,Alexandrium catenella and Ceratium fusus in autumn,Paralia sulcata,Phaeocystis sp.and Bacillaria paradoxa in winter,respectively.In SYS,the group of temperate coastal species was the major ecotype,and the groups of the central SYS species and oceanic species were also important constituents.The average values of Shannon-Weaver diversity index (H’) and Pielou evenness index (J) were 2.37 and 0.65 respectively.The indices H’and J in the open sea were higher than those in coastal waters.Obvious co-variation tendencies between H’and J were observed in all but the summer cruise of this survey.
基金supported by the National Natural Science Foundation of China (Grant No.50879021)
文摘The orifice plate energy dissipater is an economic and highly efficient dissipater.However,there is a risk of cavitaion around the orifice plate flow.In order to provide references for engineering practice,we examined the cavitation mechanism around the orifice plate and its influencing factors by utilizing mathematical analysis methods to analyze the flow conditions around the orifice plate in view of gas bubble dynamics.Through the research presented in this paper,the following can be observed:The critical radius and the critical pressure of the gas nucleus in orifice plate flow increase with its initial state parameter τ0 ;the development speed of bubbles stabilizes at a certain value after experiencing a peak value and a small valley value;and the orifice plate cavitation is closely related to the distribution of the gas nucleus in flow.For computing the orifice plate cavitation number,we ought to take into account the effects of pressure fluctuation.The development time of the gas nucleus from the initial radius to the critical radius is about 10-7-10-5 s;therefore,the gas nucleus has sufficient time to develop into bubbles in the negative half-cycle of flow fluctuation.The orifice critical cavitation number is closely related to the orifice plate size,and especially closely related with the ratio of the orifice plate radius to the tunnel radius.The approximate formula for the critical cavitation number of the square orifice plate that only considers the main influencing factor was obtained by model experiments.
基金Supported by the High Technology Research and Development Program of China (863 Program,No2006AA100301)
文摘The performance of six statistical approaches,which can be used for selection of the best model to describe the growth of individual fish,was analyzed using simulated and real length-at-age data.The six approaches include coefficient of determination(R2),adjusted coefficient of determination(adj.-R2),root mean squared error(RMSE),Akaike's information criterion(AIC),bias correction of AIC(AICc) and Bayesian information criterion(BIC).The simulation data were generated by five growth models with different numbers of parameters.Four sets of real data were taken from the literature.The parameters in each of the five growth models were estimated using the maximum likelihood method under the assumption of the additive error structure for the data.The best supported model by the data was identified using each of the six approaches.The results show that R2 and RMSE have the same properties and perform worst.The sample size has an effect on the performance of adj.-R2,AIC,AICc and BIC.Adj.-R2 does better in small samples than in large samples.AIC is not suitable to use in small samples and tends to select more complex model when the sample size becomes large.AICc and BIC have best performance in small and large sample cases,respectively.Use of AICc or BIC is recommended for selection of fish growth model according to the size of the length-at-age data.
基金financially supported by the National P&D Program of China(Grant No.2016YFB0300700)the National Natural Science Foundation of China(Grant Nos.51779135 and 51009087)the Natural Science Foundation of Shanghai(Grant No.14ZR1419500)
文摘In order to reduce the resistance and improve the hydrodynamic performance of a ship, two hull form design methods are proposed based on the potential flow theory and viscous flow theory. The flow fields are meshed using body-fitted mesh and structured grids. The parameters of the hull modification function are the design variables. A three-dimensional modeling method is used to alter the geometry. The Non-Linear Programming(NLP) method is utilized to optimize a David Taylor Model Basin(DTMB) model 5415 ship under the constraints, including the displacement constraint. The optimization results show an effective reduction of the resistance. The two hull form design methods developed in this study can provide technical support and theoretical basis for designing green ships.
