In situ observations from Argo profiling floats combined with satellite retrieved SST and rain rate are used to investigate an upper ocean response to Typhoon Bolaven from 20 through 29 August 2012. After the passage ...In situ observations from Argo profiling floats combined with satellite retrieved SST and rain rate are used to investigate an upper ocean response to Typhoon Bolaven from 20 through 29 August 2012. After the passage of Typhoon Bolaven, the deepening of mixed layer depth（MLD）, and the cooling of mixed layer temperature（MLT） were observed. The changes in mixed layer salinity（MLS） showed an equivalent number of increasing and decreasing because the typhoon-induced salinity changes in the mixed layer were influenced by precipitation, evaporation, turbulent mixing and upwelling of thermocline water. The deepening of the MLD and the cooling of the MLT indicated a significant rightward bias, whereas the MLS was freshened to the left side of the typhoon track and increased on the other side. Intensive temperature and salinity profiles observed by Iridium floats make it possible to view response processes in the upper ocean after the passage of a typhoon. The cooling in the near-surface and the warming in the subsurface were observed by two Iridium floats located to the left side of the cyclonic track during the development stage of the storm, beyond the radius of maximum winds relative to the typhoon center. Water salinity increases at the base of the mixed layer and the top of the thermocline were the most obvious change observed by those two floats. On the right side of the track and near the typhoon center when the typhoon was intensified, the significant cooling from sea surface to a depth of 200×10^4 Pa, with the exception of the water at the top of the thermocline, was observed by the other Iridium float. Owing to the enhanced upwelling near the typhoon center, the water salinity in the near-surface increased noticeably. The heat pumping from the mixed layer into the thermocline induced by downwelling and the upwelling induced by the positive wind stress curl are the main causes for the different temperature and salinity variations on the different sides of the track. It seems that more time is required for the anomalies in the subsurface to be restored to pretyphoon conditions than for the anomalies in the mixed layer.展开更多
Critical Path Method (CPM) Scheduling has proven to be an effective project management tool. However, teaching the topic has proven difficult to include all elements of CPM yet keep it simple enough for students to un...Critical Path Method (CPM) Scheduling has proven to be an effective project management tool. However, teaching the topic has proven difficult to include all elements of CPM yet keep it simple enough for students to understand. In an effort to simplify the teaching of critical path method scheduling, the issue of two total floats in an activity does not get the attention necessary to address its occurrence. The objective of this paper is to present a mathematical method to show multiple total floats are possible for an activity. Also presented are suggestions for schedule crashing when multiple total floats are found. Two totals floats can be found if constraints (Lag or Lead) or non-Finish-to-Start (FS) relationships, or both are used in a network diagram. Situations are possible where an activity may have a start total float (STF) of zero but have a finish total float (FTF) greater than zero, or vice versa. Because the critical path generally follows the zero total float, these situations, where either the STF or the FTF is critical while the other is not, determines how the critical path activity must be controlled and crashed. This paper will present approaches of how to crash the schedule when a portion of the activity, either start or finish, is critical. Also presented will be methods to teach the subject matter with or without the use of scheduling software. Critical Path Method was revisited to see what the minimal conditions are needed to have activities with two total float. Generalized crashing methods were studied to see if the methods can be used when two total floats exist.展开更多
The three dimensional structure of the western boundary current east of the Vietnam coast was determined from measurements by Argo profiling floats which deployed near the east of the Vietnam Coast in October 2007. Th...The three dimensional structure of the western boundary current east of the Vietnam coast was determined from measurements by Argo profiling floats which deployed near the east of the Vietnam Coast in October 2007. The trajectories of the Argo floats provided robust evidence that there does exist southward flowing current along the Vietnam coast. The southward current begins at about 15°N, 111°E, flowing along the 1 000 m isobath and extending to 5°N south. The estimated surface and parking depth velocities obtained from the floats suggest that this southward current can extend to 1 000 m depth. The mean surface velocity of the western boundary current is about 49 cm/s, with the maximum speed exceeding 100 cm/s occurring at 11.6°N, 109.5°E in the direction of 245°. The mean parking depth （1 000 m） velocity is 12-16 cm/s with the maximum speed of 36 cm/s occurring at 12.1°N, 109.7°E in the direction of 239°. The water mass analysis suggests that the Kuroshio surface water and NPIW are not apparent in the western boundary current although this time was the favored season for the Kuroshio intrusion into Luzon Strait. The mean geostrophic currents suggest that the Kuroshio intrusion into Luzon Strait during October to December 2007 is very weak, as most of the intruding water was carried eastward at 14°N near the western boundary and little flowed southward along the western boundary, providing an explanation for the absence of Kuroshio surface water and NPIW in the water mass analysis. There is a strong cyclonic circulation in the SSCS during this time, which induces a strong mixing in the western boundary companied by a homogeneous salinity layer between 300 600 m in the salinity vertical distribution. No reversal undercurrent occurred at the intermediate depth along the western boundary east of the Vietnam coast during October to December 200%展开更多
Ecological floating bed is an important biological remediation method for water pollution control.During the removal of excess nutrients and pollutants,changes in environmental factors affect the characteristics of mi...Ecological floating bed is an important biological remediation method for water pollution control.During the removal of excess nutrients and pollutants,changes in environmental factors affect the characteristics of microorganisms in aquatic ecosystems.To understand the influences of ecological floating beds on size-fractionated microorganisms,we investigated the community assembly and nitrogen metabolic characteristics of three size-fractionated microorganism groups in the ecological floating bed area,using 18S rDNA,16S rDNA metabarcoding,and metagenomic sequencing techniques.Firstly,we discovered substantial differences between size-fractionated groups in the diversity and compositions of both microeukaryotic and bacterial communities,as well as the influences of floating beds on specific groups.The floating beds appeared to provide more habitats for heterotrophs and symbiotes while potentially inhibiting the growth of certain phytoplankton(cyanobacteria).Secondly,we observed that microeukaryotic and bacterial communities were predominantly influenced by stochastic and deterministic processes,respectively,and they both exhibited distinct patterns across different size-fractionated groups.Notably,microeukaryotic community assembly demonstrated a greater sensitivity to ecological floating beds,as indicated by an increase in dispersal limitation processes.Finally,the nitrogen metabolism functional genes revealed that microbes associated with large-sized particles played a crucial role in dissimilatory nitrate reduction to ammonium(DNRA)and denitrification processes within the floating bed area,thereby facilitating the removal of excess nitrogen nutrients from the water.In contrast,freeliving microorganisms from small-sized groups were linked mainly to the genes involved in nitrogen assimilation and assimilatory nitrate reduction to ammonium(ANRA)processes.These findings help understand the impact of ecological floating beds on the diversity and functional characteristics of microorganism communities in different size-fractionated groups.展开更多
During the hoisting process of the offshore substation,changes in the hoisting speed can affect the hoisting system.Therefore,this study set four different speed conditions for the lifting and lowering stages of the i...During the hoisting process of the offshore substation,changes in the hoisting speed can affect the hoisting system.Therefore,this study set four different speed conditions for the lifting and lowering stages of the installation process,and studied the impact of different lifting and lowering speeds on the hoisting system under the same environmental conditions through numerical simulation.The results show that during the lifting operation,as the lifting speed increases,the swing motion of the substation and the installation vessel tends to decrease,and the faster the hoisting speed,the more obvious the swing suppression of the substation and the installation vessel,and the smaller the fluctuation in the tension amplitude of the slings and mooring lines.In contrast,during the lowering operation,as the lowering speed increases,the swing motion of the substation and the installation vessel tends to increase,and the faster the lowering speed,the more obvious the swing amplification effect of the substation and the installation vessel.Therefore,during hoisting operations,increasing the lifting speed and reducing the lowering speed can mitigate the motion performance of the hoisting coupling system,reduce the tension amplitude variation of the sling and mooring,and ensure the smooth progress of the hoisting operation.展开更多
Floating ring bearings are widely used in high-speed turbomachinery such as turbochargers and turbogenerators.Research-ers have recently explored various surface texturing strategies on the inner surface of floating r...Floating ring bearings are widely used in high-speed turbomachinery such as turbochargers and turbogenerators.Research-ers have recently explored various surface texturing strategies on the inner surface of floating rings to enhance bearing performance.In this study,the herring patterns are textured on the inner surface of the floating ring.This pattern is inspired by the secondary flight feathers of the Indian pigeon,which aid the bird in reducing viscous drag during flight.The result-ing Herringbone Textured Floating Ring Bearing(HTFRB)is investigated for its potential application in locomotive turbo-chargers.The HTFRB is numerically modeled using the Reynolds equation to evaluate the bearing's pressure distribution and static characteristics,including load-carrying capacity,power loss,and side leakage.Dynamic characteristics are determined by solving the zeroth-and first-order perturbed Reynolds equation.A Sobol sensitivity analysis is conducted to quantify the influence of groove parameters-helix angle,groove depth,groove width ratio,and number of grooves-on bearing performance metrics.An artificial intelligence-based optimization framework,integrating artificial neural networks and adaptive neuro-fuzzy inference systems,is developed to maximize load carrying capacity while minimiz-ing power loss,side leakage,and friction coefficient.The optimized texture parameters obtained from this framework are employed to validate the ANN model and evaluate the static and dynamic characteristics of the HTFRB.The dynamic coefficients of the HTFRB are further employed to evaluate the stability and robustness of the turbocharger rotor-HTFRB system.This study underscores the potential of combining bio-inspired texture design with numerical modeling and AI-based optimization to develop high-performance HTFRB.展开更多
The meso-scale circulation at the intermediate depth east of Mindanao is studied using Argo profiling floats observations.The trajectories and the parking-depth velocities of Argo floats show that the intermediate-dep...The meso-scale circulation at the intermediate depth east of Mindanao is studied using Argo profiling floats observations.The trajectories and the parking-depth velocities of Argo floats show that the intermediate-depth circulation east of Mindanao contains significant meso-scale features that are highly variable both in space and in time.Both cyclonic and anticyclonic eddies at the intermediate depth(1000–2000 m)are indicated by the trajectories east of Mindanao.The mean tangential velocities of these eddies are about 10 cm/s at 2000 m and over 20 cm/s at 1000 m,which indicates that the geostrophic calculation may contain large errors due to the vigorous eddy activity at the reference levels.The analyses also suggest that these eddies might play an important role in mass and vorticity balances of the intermediate-depth circulation east of Mindanao.展开更多
This paper presents an overview of the recent developments in hybrid wind-wave energy.With the focus on floating concepts,the possible configurations introduced in the literature are categorized and depicted,and the m...This paper presents an overview of the recent developments in hybrid wind-wave energy.With the focus on floating concepts,the possible configurations introduced in the literature are categorized and depicted,and the main conclusions obtained from the references are summarized.Moreover,offshore wind and wave resources are discussed in terms of complementarity and supplementarity,offering a new perspective to developing hybrid wind-wave energy systems that look for synergies not limited to maximizing power output.Then,the feasibility of the concepts under development is discussed in detail,with focus on technical feasibility,dynamic feasibility and limitations of the methods employed.The hybrid configurations that surpassed the experimental validation phase are highlighted,and the experimental results are summarized.By compiling more than 40 floating wind turbine concepts,new relations are drawn between power,wind turbine dimensions,platforms’draft and displacement,which are further related to the payload allowance of the units to accommodate wave devices and onboard power take-off systems.Bearing in mind that it is a challenge to model the exact dynamics of hybrid floating wind-wave platforms,this paper elucidates the current research gaps,limitations and future trends in the field.Lastly,based on the overview and topics discussed,several major conclusions are drawn concerning hybrid synergies,dynamics and hydrodynamics of hybrid platforms,feasibility of concepts,among other regards.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
This study employed a computational fluid dynamics model with an overset mesh technique to investigate the thrust and power of a floating offshore wind turbine(FOWT)under platform floating motion in the wind–rain fie...This study employed a computational fluid dynamics model with an overset mesh technique to investigate the thrust and power of a floating offshore wind turbine(FOWT)under platform floating motion in the wind–rain field.The impact of rainfall on aerodynamic performance was initially examined using a stationary turbine model in both wind and wind–rain conditions.Subsequently,the study compared the FOWT’s performance under various single degree-of-freedom(DOF)motions,including surge,pitch,heave,and yaw.Finally,the combined effects of wind–rain fields and platform motions involving two DOFs on the FOWT’s aerodynamics were analyzed and compared.The results demonstrate that rain negatively impacts the aerodynamic performance of both the stationary turbines and FOWTs.Pitch-dominated motions,whether involving single or multiple DOFs,caused significant fluctuations in the FOWT aerodynamics.The combination of surge and pitch motions created the most challenging operational environment for the FOWT in all tested scenarios.These findings highlighted the need for stronger construction materials and greater ultimate bearing capacity for FOWTs,as well as the importance of optimizing designs to mitigate excessive pitch and surge.展开更多
This study applies a double snap-through mechanism on a box-type oscillating buoy(OB)wave energy converter(WEC)-floating breakwater integrated system(OB WEC-FB)to simultaneously achieve efficient wave energy conversio...This study applies a double snap-through mechanism on a box-type oscillating buoy(OB)wave energy converter(WEC)-floating breakwater integrated system(OB WEC-FB)to simultaneously achieve efficient wave energy conversion and nearshore protection within a low-frequency bandwidth.This mechanism consists of four oblique springs and can operate in mono-stable,bi-stable,and tri-stable modes.A viscous-flow-based numerical model is established to investigate the hydrodynamic performance and dynamic behavior of the proposed multi-stable breakwater.The operational performance of the breakwater at different dynamic modes is first compared.The effects of the springs’original length and stiffness coefficient are then analyzed.The results show that the tri-stable breakwater has a wider resonance frequency tuning range than the bi-stable one,both of which outperform the mono-stable and linear ones in shifting the effective bandwidth to a lower frequency range.For a tri-stable breakwater,a large distance between outermost potential wells is conducive to tuning resonance frequency,whereas shallow potential wells limit this effect.The increase in spring stiffness distinctly causes a higher potential barrier and thus constrains the motion response of the breakwater.A well-designed double snap-through mechanism can excite large-amplitude inter-well motion,tune the resonance frequency of breakwater from 3.98 to 1.96 rad/s,and decrease the lower limit of the effective transmission bandwidth from 3.75 to 3.00 rad/s.It is crucial for improving the power absorption and wave attenuation capabilities of multi-stable OB WEC-FB.This study contributes to the limited research on the implementation of a double snap-through mechanism on multifunctional marine structures.It establishes the underlying connection between nonlinear dynamic behaviors and hydrodynamic coefficients.展开更多
Complicated loads encountered by floating offshore wind turbines(FOWTs)in real sea conditions are crucial for future optimization of design,but obtaining data on them directly poses a challenge.To address this issue,w...Complicated loads encountered by floating offshore wind turbines(FOWTs)in real sea conditions are crucial for future optimization of design,but obtaining data on them directly poses a challenge.To address this issue,we applied machine learning techniques to obtain hydrodynamic and aerodynamic loads of FOWTs by measuring platform motion responses and wave-elevation sequences.First,a computational fluid dynamics(CFD)simulation model of the floating platform was established based on the dynamic fluid body interaction technique and overset grid technology.Then,a long short-term memory(LSTM)neural network model was constructed and trained to learn the nonlinear relationship between the waves,platform-motion inputs,and hydrodynamic-load outputs.The optimal model was determined after analyzing the sensitivity of parameters such as sample characteristics,network layers,and neuron numbers.Subsequently,the effectiveness of the hydrodynamic load model was validated under different simulation conditions,and the aerodynamic load calculation was completed based on the D'Alembert principle.Finally,we built a hybrid-scale FOWT model,based on the software in the loop strategy,in which the wind turbine was replaced by an actuation system.Model tests were carried out in a wave basin and the results demonstrated that the root mean square errors of the hydrodynamic and aerodynamic load measurements were 4.20%and 10.68%,respectively.展开更多
Mooring cable tension is a crucial parameter for evaluating the safety and reliability of a floating platform mooring system.The real-time mooring tension in an actual marine environment has always been essential data...Mooring cable tension is a crucial parameter for evaluating the safety and reliability of a floating platform mooring system.The real-time mooring tension in an actual marine environment has always been essential data that mooring system designers aim to acquire.To address the need for long-term continuous monitoring of mooring tension in deep-sea marine environments,this paper presents a mooring cable tension monitoring method based on the principle of direct mechanical measurement.The developed tension monitoring sensors were installed and applied in the mooring system of the"Yongle"scientific experimental platform.Over the course of one year,a substantial amount of in-situ tension monitoring data was obtained.Under wave heights of up to 1.24 m,the mooring tension on the floating platform reached 16.5 tons.Through frequency domain and time domain analysis,the spectral characteristics of mooring tension,including waveinduced force,slow drift force,and mooring cable elastic restoring force,were determined.The mooring cable elastic restoring force frequency was approximately half of that of the wave signal.Due to the characteristics of the hinge connection structure of the dual module floating platform,under some specific working conditions the wave-induced force was the maximum of the three different frequency forces,and restoring force was the smallest.展开更多
Modular floating structures(MFS)offer a sustainable pathway towards the expansion of coastal cities in adaptation tofilooding and sea level rise driven by climate change.It is therefore necessary to develop analytical...Modular floating structures(MFS)offer a sustainable pathway towards the expansion of coastal cities in adaptation tofilooding and sea level rise driven by climate change.It is therefore necessary to develop analytical methods easily accessible to architects or structural engineers for the rapid prototyping of MFS designs.This work develops novel closed‑form expressions describing the rigid body dynamics of symmetrically loaded rectangular pontoons across all six degrees of freedom(DOF)excited by surface waves approaching from any arbitrary direction.The derivations were based on Airy wave theory assuming frequency‑independent added mass and damping.When benchmarked against numerical solutions from ANSYS/AQWA for two MFS prototypes,the analytical approach proved capable of predicting the response amplitude operators(RAO)across all DOFs,wave directions,and structural confiigurations.However,while the response of mass‑dominated DOFs(surge,sway,and yaw)were well captured,the damping ratio for stiffness‑dominated DOFs(heave,roll,and pitch)must be judiciously selected to yield accurate RAO results.A parametric investigation further elucidated the contribution of structural geometry and wave directionality on the critical accelerations experienced by an idealizedfiloating structure founded upon a square pontoon under realistic sea states.It was discovered that the largest accelerations were triggered by waves approaching orthogonally to the pontoon.Ultimately,this work facilitates a more streamlined approach for the dynamic analysis of compliantfiloating bodies to supplement detailed modeling efforts via numerical methods.展开更多
Interest in understanding the structural behavior of marine floating photovoltaic(FPV)systems has grown significantly over the last decade.Numerical models are the preferred approach for understanding FPV responses un...Interest in understanding the structural behavior of marine floating photovoltaic(FPV)systems has grown significantly over the last decade.Numerical models are the preferred approach for understanding FPV responses under environmental loads,but they require validation.Several methods are commonly used to validate numerical results,such as comparison with analytical,field data,and experimental data.The use of analytical approaches to validate numerical results can sometimes be inaccurate due to the complexity of the problems;nevertheless,field data is commonly restricted and frequently unavailable for numerical model validation.Thus,physical models play a crucial role in validating numerical results.This study focuses on the two-dimensional(2-D)modeling process and sensors development for an FPV system with taut mooring,aiming to investigate wave-structure interaction while considering hydroelastic effects.The model is developed in accordance with the Froude-Cauchy similitude law and is made from composite materials to capture structural stiffness.Structural motions,specifically heave and pitch,are measured using an Inertial Measurement Unit(IMU),while strain gauges measure structural stress and mooring tension.The sensors provide precise measurements for strain and pitch;however,heave,as a result of time-domain integration from acceleration,requires further validation.The motion responses of the model align with reference results.展开更多
For the development of an integrated rounded rectangular wellhead platform with a bucket foundation,a model test was conducted to study the towing motion response of such a structure under still water and wave conditi...For the development of an integrated rounded rectangular wellhead platform with a bucket foundation,a model test was conducted to study the towing motion response of such a structure under still water and wave conditions.The influence of various factors on the floating stability of the structure was investigated through alterations of the towing conditions(draft,towing point position,and wave conditions),and the related influencing mechanism was analyzed.Comparison and analysis were performed to determine the changes in the structure motion pattern and various effects of towing conditions on the structure during towing in still water and regular waves.Moreover,the influence of each factor on the structure’s motion response during towing was analyzed using the Apriori algorithm.In addition,for the simulation of the towing process under actual sea conditions,a towing test was performed under irregular waves,and the stability of towing in irregular waves was compared with that in regular waves.展开更多
Offshore floating photovoltaic systems have tremendous potential to address the energy crisis.As a novel type of float-ing photovoltaic system,membrane structures are increasingly applied due to their advantages of be...Offshore floating photovoltaic systems have tremendous potential to address the energy crisis.As a novel type of float-ing photovoltaic system,membrane structures are increasingly applied due to their advantages of being lightweight and cost-effective.A 1:40 scaled model for laboratory experiments was designed and developed,considering Ocean Sun’s membrane structure.The study aims to investigate the hydrodynamic characteristics of the membrane structure under wave loading by testing its various mo-tion responses and mooring forces at different wave heights and periods.The conclusions indicate that as the wave period decreases within the range of 1.75 to 1.25 s,the heave motion response of the structure decreases,whereas pitch,surge motion response,heave acceleration,and mooring force increase.The amplitudes of various motions and mooring forces of the structure decrease with de-creasing wave height.The hydrodynamic responses under irregular and regular waves follow similar patterns,but the responses and mooring forces induced by irregular waves are more significant.The structure should be designed based on the actual wave height.In addition,the same frequency resonance phenomenon is avoided because the movement period of each degree of freedom is close to the wave period.展开更多
Siwa Oasis,one of Egypts most remote settlements,is also a popular tourist destination thanks to the beautiful salt pools with water that people can float in.Salt is both a blessing and a curse in Siwa.Years ago,peopl...Siwa Oasis,one of Egypts most remote settlements,is also a popular tourist destination thanks to the beautiful salt pools with water that people can float in.Salt is both a blessing and a curse in Siwa.Years ago,people started realizing that there was money to be made in the salt trade,and salt mining operations created the salt lakes that the oasis is now famous for.展开更多
As a typical in-memory computing hardware design, nonvolatile ternary content-addressable memories(TCAMs) enable the logic operation and data storage for high throughout in parallel big data processing. However,TCAM c...As a typical in-memory computing hardware design, nonvolatile ternary content-addressable memories(TCAMs) enable the logic operation and data storage for high throughout in parallel big data processing. However,TCAM cells based on conventional silicon-based devices suffer from structural complexity and large footprintlimitations. Here, we demonstrate an ultrafast nonvolatile TCAM cell based on the MoTe2/hBN/multilayergraphene (MLG) van der Waals heterostructure using a top-gated partial floating-gate field-effect transistor(PFGFET) architecture. Based on its ambipolar transport properties, the carrier type in the source/drain andcentral channel regions of the MoTe2 channel can be efficiently tuned by the control gate and top gate, respectively,enabling the reconfigurable operation of the device in either memory or FET mode. When working inthe memory mode, it achieves an ultrafast 60 ns programming/erase speed with a current on-off ratio of ∼105,excellent retention capability, and robust endurance. When serving as a reconfigurable transistor, unipolar p-typeand n-type FETs are obtained by adopting ultrafast 60 ns control-gate voltage pulses with different polarities.The monolithic integration of memory and logic within a single device enables the content-addressable memory(CAM) functionality. Finally, by integrating two PFGFETs in parallel, a TCAM cell with a high current ratioof ∼10^(5) between the match and mismatch states is achieved without requiring additional peripheral circuitry.These results provide a promising route for the design of high-performance TCAM devices for future in-memorycomputing applications.展开更多
基金The National Basic Research Program(973 Program)of China under contract No.2013CB430301the National Natural Science Foundation of China under contract No.41206022the Ministry of Science and Technology of China under contract No.2012FY112300
文摘In situ observations from Argo profiling floats combined with satellite retrieved SST and rain rate are used to investigate an upper ocean response to Typhoon Bolaven from 20 through 29 August 2012. After the passage of Typhoon Bolaven, the deepening of mixed layer depth（MLD）, and the cooling of mixed layer temperature（MLT） were observed. The changes in mixed layer salinity（MLS） showed an equivalent number of increasing and decreasing because the typhoon-induced salinity changes in the mixed layer were influenced by precipitation, evaporation, turbulent mixing and upwelling of thermocline water. The deepening of the MLD and the cooling of the MLT indicated a significant rightward bias, whereas the MLS was freshened to the left side of the typhoon track and increased on the other side. Intensive temperature and salinity profiles observed by Iridium floats make it possible to view response processes in the upper ocean after the passage of a typhoon. The cooling in the near-surface and the warming in the subsurface were observed by two Iridium floats located to the left side of the cyclonic track during the development stage of the storm, beyond the radius of maximum winds relative to the typhoon center. Water salinity increases at the base of the mixed layer and the top of the thermocline were the most obvious change observed by those two floats. On the right side of the track and near the typhoon center when the typhoon was intensified, the significant cooling from sea surface to a depth of 200×10^4 Pa, with the exception of the water at the top of the thermocline, was observed by the other Iridium float. Owing to the enhanced upwelling near the typhoon center, the water salinity in the near-surface increased noticeably. The heat pumping from the mixed layer into the thermocline induced by downwelling and the upwelling induced by the positive wind stress curl are the main causes for the different temperature and salinity variations on the different sides of the track. It seems that more time is required for the anomalies in the subsurface to be restored to pretyphoon conditions than for the anomalies in the mixed layer.
文摘Critical Path Method (CPM) Scheduling has proven to be an effective project management tool. However, teaching the topic has proven difficult to include all elements of CPM yet keep it simple enough for students to understand. In an effort to simplify the teaching of critical path method scheduling, the issue of two total floats in an activity does not get the attention necessary to address its occurrence. The objective of this paper is to present a mathematical method to show multiple total floats are possible for an activity. Also presented are suggestions for schedule crashing when multiple total floats are found. Two totals floats can be found if constraints (Lag or Lead) or non-Finish-to-Start (FS) relationships, or both are used in a network diagram. Situations are possible where an activity may have a start total float (STF) of zero but have a finish total float (FTF) greater than zero, or vice versa. Because the critical path generally follows the zero total float, these situations, where either the STF or the FTF is critical while the other is not, determines how the critical path activity must be controlled and crashed. This paper will present approaches of how to crash the schedule when a portion of the activity, either start or finish, is critical. Also presented will be methods to teach the subject matter with or without the use of scheduling software. Critical Path Method was revisited to see what the minimal conditions are needed to have activities with two total float. Generalized crashing methods were studied to see if the methods can be used when two total floats exist.
基金Supported by the Knowledge Innovation Projects of Chinese Academy of Sciences(Nos. KZCX2-YW-214, KZCX2-YW-Q11-02)NSFC (No. 40806010)+1 种基金the National Basic Research Program of China "973 Program" (No.2006CB403600)the CAS Key projects, and by the "Hundreds-Talent Program" project of CAS
文摘The three dimensional structure of the western boundary current east of the Vietnam coast was determined from measurements by Argo profiling floats which deployed near the east of the Vietnam Coast in October 2007. The trajectories of the Argo floats provided robust evidence that there does exist southward flowing current along the Vietnam coast. The southward current begins at about 15°N, 111°E, flowing along the 1 000 m isobath and extending to 5°N south. The estimated surface and parking depth velocities obtained from the floats suggest that this southward current can extend to 1 000 m depth. The mean surface velocity of the western boundary current is about 49 cm/s, with the maximum speed exceeding 100 cm/s occurring at 11.6°N, 109.5°E in the direction of 245°. The mean parking depth （1 000 m） velocity is 12-16 cm/s with the maximum speed of 36 cm/s occurring at 12.1°N, 109.7°E in the direction of 239°. The water mass analysis suggests that the Kuroshio surface water and NPIW are not apparent in the western boundary current although this time was the favored season for the Kuroshio intrusion into Luzon Strait. The mean geostrophic currents suggest that the Kuroshio intrusion into Luzon Strait during October to December 2007 is very weak, as most of the intruding water was carried eastward at 14°N near the western boundary and little flowed southward along the western boundary, providing an explanation for the absence of Kuroshio surface water and NPIW in the water mass analysis. There is a strong cyclonic circulation in the SSCS during this time, which induces a strong mixing in the western boundary companied by a homogeneous salinity layer between 300 600 m in the salinity vertical distribution. No reversal undercurrent occurred at the intermediate depth along the western boundary east of the Vietnam coast during October to December 200%
基金Supported by the National Natural Science Foundation of China(Nos.42141003,42176147)the National Key Research and Development Program of China(No.2022YFF0802204)the Xiamen Key Laboratory of Urban Sea Ecological Conservation and Restoration(USER)(Nos.USER2021-1,USER2021-5)。
文摘Ecological floating bed is an important biological remediation method for water pollution control.During the removal of excess nutrients and pollutants,changes in environmental factors affect the characteristics of microorganisms in aquatic ecosystems.To understand the influences of ecological floating beds on size-fractionated microorganisms,we investigated the community assembly and nitrogen metabolic characteristics of three size-fractionated microorganism groups in the ecological floating bed area,using 18S rDNA,16S rDNA metabarcoding,and metagenomic sequencing techniques.Firstly,we discovered substantial differences between size-fractionated groups in the diversity and compositions of both microeukaryotic and bacterial communities,as well as the influences of floating beds on specific groups.The floating beds appeared to provide more habitats for heterotrophs and symbiotes while potentially inhibiting the growth of certain phytoplankton(cyanobacteria).Secondly,we observed that microeukaryotic and bacterial communities were predominantly influenced by stochastic and deterministic processes,respectively,and they both exhibited distinct patterns across different size-fractionated groups.Notably,microeukaryotic community assembly demonstrated a greater sensitivity to ecological floating beds,as indicated by an increase in dispersal limitation processes.Finally,the nitrogen metabolism functional genes revealed that microbes associated with large-sized particles played a crucial role in dissimilatory nitrate reduction to ammonium(DNRA)and denitrification processes within the floating bed area,thereby facilitating the removal of excess nitrogen nutrients from the water.In contrast,freeliving microorganisms from small-sized groups were linked mainly to the genes involved in nitrogen assimilation and assimilatory nitrate reduction to ammonium(ANRA)processes.These findings help understand the impact of ecological floating beds on the diversity and functional characteristics of microorganism communities in different size-fractionated groups.
基金support from the National Natural Science Foundation of China(No.52271287)funding from the State Key Laboratory of Hydraulic Engineering Intelligent Construction and Operation,Tianjin University。
文摘During the hoisting process of the offshore substation,changes in the hoisting speed can affect the hoisting system.Therefore,this study set four different speed conditions for the lifting and lowering stages of the installation process,and studied the impact of different lifting and lowering speeds on the hoisting system under the same environmental conditions through numerical simulation.The results show that during the lifting operation,as the lifting speed increases,the swing motion of the substation and the installation vessel tends to decrease,and the faster the hoisting speed,the more obvious the swing suppression of the substation and the installation vessel,and the smaller the fluctuation in the tension amplitude of the slings and mooring lines.In contrast,during the lowering operation,as the lowering speed increases,the swing motion of the substation and the installation vessel tends to increase,and the faster the lowering speed,the more obvious the swing amplification effect of the substation and the installation vessel.Therefore,during hoisting operations,increasing the lifting speed and reducing the lowering speed can mitigate the motion performance of the hoisting coupling system,reduce the tension amplitude variation of the sling and mooring,and ensure the smooth progress of the hoisting operation.
文摘Floating ring bearings are widely used in high-speed turbomachinery such as turbochargers and turbogenerators.Research-ers have recently explored various surface texturing strategies on the inner surface of floating rings to enhance bearing performance.In this study,the herring patterns are textured on the inner surface of the floating ring.This pattern is inspired by the secondary flight feathers of the Indian pigeon,which aid the bird in reducing viscous drag during flight.The result-ing Herringbone Textured Floating Ring Bearing(HTFRB)is investigated for its potential application in locomotive turbo-chargers.The HTFRB is numerically modeled using the Reynolds equation to evaluate the bearing's pressure distribution and static characteristics,including load-carrying capacity,power loss,and side leakage.Dynamic characteristics are determined by solving the zeroth-and first-order perturbed Reynolds equation.A Sobol sensitivity analysis is conducted to quantify the influence of groove parameters-helix angle,groove depth,groove width ratio,and number of grooves-on bearing performance metrics.An artificial intelligence-based optimization framework,integrating artificial neural networks and adaptive neuro-fuzzy inference systems,is developed to maximize load carrying capacity while minimiz-ing power loss,side leakage,and friction coefficient.The optimized texture parameters obtained from this framework are employed to validate the ANN model and evaluate the static and dynamic characteristics of the HTFRB.The dynamic coefficients of the HTFRB are further employed to evaluate the stability and robustness of the turbocharger rotor-HTFRB system.This study underscores the potential of combining bio-inspired texture design with numerical modeling and AI-based optimization to develop high-performance HTFRB.
基金supported by National Basic Research Program of China(Grant Nos.2007CB816002 and 2006CB403600)National Natural Science Foundation of China(Grant No.40806010)
文摘The meso-scale circulation at the intermediate depth east of Mindanao is studied using Argo profiling floats observations.The trajectories and the parking-depth velocities of Argo floats show that the intermediate-depth circulation east of Mindanao contains significant meso-scale features that are highly variable both in space and in time.Both cyclonic and anticyclonic eddies at the intermediate depth(1000–2000 m)are indicated by the trajectories east of Mindanao.The mean tangential velocities of these eddies are about 10 cm/s at 2000 m and over 20 cm/s at 1000 m,which indicates that the geostrophic calculation may contain large errors due to the vigorous eddy activity at the reference levels.The analyses also suggest that these eddies might play an important role in mass and vorticity balances of the intermediate-depth circulation east of Mindanao.
基金supported by the Portuguese Foundation for Science and Technology(Fundação para a Ciência e Tecnologia-FCT)it contributes to the Strategic Research Plan of the Centre for Marine Technology and Ocean Engineering(Grant No.UIDB/UIDP/00134/2020)funded the first author for his PhD Scholarship(Grant No.SFRH/BD/145602/2019).
文摘This paper presents an overview of the recent developments in hybrid wind-wave energy.With the focus on floating concepts,the possible configurations introduced in the literature are categorized and depicted,and the main conclusions obtained from the references are summarized.Moreover,offshore wind and wave resources are discussed in terms of complementarity and supplementarity,offering a new perspective to developing hybrid wind-wave energy systems that look for synergies not limited to maximizing power output.Then,the feasibility of the concepts under development is discussed in detail,with focus on technical feasibility,dynamic feasibility and limitations of the methods employed.The hybrid configurations that surpassed the experimental validation phase are highlighted,and the experimental results are summarized.By compiling more than 40 floating wind turbine concepts,new relations are drawn between power,wind turbine dimensions,platforms’draft and displacement,which are further related to the payload allowance of the units to accommodate wave devices and onboard power take-off systems.Bearing in mind that it is a challenge to model the exact dynamics of hybrid floating wind-wave platforms,this paper elucidates the current research gaps,limitations and future trends in the field.Lastly,based on the overview and topics discussed,several major conclusions are drawn concerning hybrid synergies,dynamics and hydrodynamics of hybrid platforms,feasibility of concepts,among other regards.
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Supported by the National Natural Science Foundation of China(51679080 and 51379073)the Fundamental Research Funds for the Central Universities(B230205020).
文摘This study employed a computational fluid dynamics model with an overset mesh technique to investigate the thrust and power of a floating offshore wind turbine(FOWT)under platform floating motion in the wind–rain field.The impact of rainfall on aerodynamic performance was initially examined using a stationary turbine model in both wind and wind–rain conditions.Subsequently,the study compared the FOWT’s performance under various single degree-of-freedom(DOF)motions,including surge,pitch,heave,and yaw.Finally,the combined effects of wind–rain fields and platform motions involving two DOFs on the FOWT’s aerodynamics were analyzed and compared.The results demonstrate that rain negatively impacts the aerodynamic performance of both the stationary turbines and FOWTs.Pitch-dominated motions,whether involving single or multiple DOFs,caused significant fluctuations in the FOWT aerodynamics.The combination of surge and pitch motions created the most challenging operational environment for the FOWT in all tested scenarios.These findings highlighted the need for stronger construction materials and greater ultimate bearing capacity for FOWTs,as well as the importance of optimizing designs to mitigate excessive pitch and surge.
基金supported by the National Natural Science Foundation of China Program(No.51739010).
文摘This study applies a double snap-through mechanism on a box-type oscillating buoy(OB)wave energy converter(WEC)-floating breakwater integrated system(OB WEC-FB)to simultaneously achieve efficient wave energy conversion and nearshore protection within a low-frequency bandwidth.This mechanism consists of four oblique springs and can operate in mono-stable,bi-stable,and tri-stable modes.A viscous-flow-based numerical model is established to investigate the hydrodynamic performance and dynamic behavior of the proposed multi-stable breakwater.The operational performance of the breakwater at different dynamic modes is first compared.The effects of the springs’original length and stiffness coefficient are then analyzed.The results show that the tri-stable breakwater has a wider resonance frequency tuning range than the bi-stable one,both of which outperform the mono-stable and linear ones in shifting the effective bandwidth to a lower frequency range.For a tri-stable breakwater,a large distance between outermost potential wells is conducive to tuning resonance frequency,whereas shallow potential wells limit this effect.The increase in spring stiffness distinctly causes a higher potential barrier and thus constrains the motion response of the breakwater.A well-designed double snap-through mechanism can excite large-amplitude inter-well motion,tune the resonance frequency of breakwater from 3.98 to 1.96 rad/s,and decrease the lower limit of the effective transmission bandwidth from 3.75 to 3.00 rad/s.It is crucial for improving the power absorption and wave attenuation capabilities of multi-stable OB WEC-FB.This study contributes to the limited research on the implementation of a double snap-through mechanism on multifunctional marine structures.It establishes the underlying connection between nonlinear dynamic behaviors and hydrodynamic coefficients.
基金This work is supported by the National Key Research and Development Program of China(No.2023YFB4203000)the National Natural Science Foundation of China(No.U22A20178)
文摘Complicated loads encountered by floating offshore wind turbines(FOWTs)in real sea conditions are crucial for future optimization of design,but obtaining data on them directly poses a challenge.To address this issue,we applied machine learning techniques to obtain hydrodynamic and aerodynamic loads of FOWTs by measuring platform motion responses and wave-elevation sequences.First,a computational fluid dynamics(CFD)simulation model of the floating platform was established based on the dynamic fluid body interaction technique and overset grid technology.Then,a long short-term memory(LSTM)neural network model was constructed and trained to learn the nonlinear relationship between the waves,platform-motion inputs,and hydrodynamic-load outputs.The optimal model was determined after analyzing the sensitivity of parameters such as sample characteristics,network layers,and neuron numbers.Subsequently,the effectiveness of the hydrodynamic load model was validated under different simulation conditions,and the aerodynamic load calculation was completed based on the D'Alembert principle.Finally,we built a hybrid-scale FOWT model,based on the software in the loop strategy,in which the wind turbine was replaced by an actuation system.Model tests were carried out in a wave basin and the results demonstrated that the root mean square errors of the hydrodynamic and aerodynamic load measurements were 4.20%and 10.68%,respectively.
文摘Mooring cable tension is a crucial parameter for evaluating the safety and reliability of a floating platform mooring system.The real-time mooring tension in an actual marine environment has always been essential data that mooring system designers aim to acquire.To address the need for long-term continuous monitoring of mooring tension in deep-sea marine environments,this paper presents a mooring cable tension monitoring method based on the principle of direct mechanical measurement.The developed tension monitoring sensors were installed and applied in the mooring system of the"Yongle"scientific experimental platform.Over the course of one year,a substantial amount of in-situ tension monitoring data was obtained.Under wave heights of up to 1.24 m,the mooring tension on the floating platform reached 16.5 tons.Through frequency domain and time domain analysis,the spectral characteristics of mooring tension,including waveinduced force,slow drift force,and mooring cable elastic restoring force,were determined.The mooring cable elastic restoring force frequency was approximately half of that of the wave signal.Due to the characteristics of the hinge connection structure of the dual module floating platform,under some specific working conditions the wave-induced force was the maximum of the three different frequency forces,and restoring force was the smallest.
文摘Modular floating structures(MFS)offer a sustainable pathway towards the expansion of coastal cities in adaptation tofilooding and sea level rise driven by climate change.It is therefore necessary to develop analytical methods easily accessible to architects or structural engineers for the rapid prototyping of MFS designs.This work develops novel closed‑form expressions describing the rigid body dynamics of symmetrically loaded rectangular pontoons across all six degrees of freedom(DOF)excited by surface waves approaching from any arbitrary direction.The derivations were based on Airy wave theory assuming frequency‑independent added mass and damping.When benchmarked against numerical solutions from ANSYS/AQWA for two MFS prototypes,the analytical approach proved capable of predicting the response amplitude operators(RAO)across all DOFs,wave directions,and structural confiigurations.However,while the response of mass‑dominated DOFs(surge,sway,and yaw)were well captured,the damping ratio for stiffness‑dominated DOFs(heave,roll,and pitch)must be judiciously selected to yield accurate RAO results.A parametric investigation further elucidated the contribution of structural geometry and wave directionality on the critical accelerations experienced by an idealizedfiloating structure founded upon a square pontoon under realistic sea states.It was discovered that the largest accelerations were triggered by waves approaching orthogonally to the pontoon.Ultimately,this work facilitates a more streamlined approach for the dynamic analysis of compliantfiloating bodies to supplement detailed modeling efforts via numerical methods.
基金funded by the Center for Higher Education Funding and Assessment(Pusat Pelayanan Pembiayaan dan Asesmen Pendidkan Tinggi)-Ministry of Higher Education,Science,and Technology of Republic Indonesia.
文摘Interest in understanding the structural behavior of marine floating photovoltaic(FPV)systems has grown significantly over the last decade.Numerical models are the preferred approach for understanding FPV responses under environmental loads,but they require validation.Several methods are commonly used to validate numerical results,such as comparison with analytical,field data,and experimental data.The use of analytical approaches to validate numerical results can sometimes be inaccurate due to the complexity of the problems;nevertheless,field data is commonly restricted and frequently unavailable for numerical model validation.Thus,physical models play a crucial role in validating numerical results.This study focuses on the two-dimensional(2-D)modeling process and sensors development for an FPV system with taut mooring,aiming to investigate wave-structure interaction while considering hydroelastic effects.The model is developed in accordance with the Froude-Cauchy similitude law and is made from composite materials to capture structural stiffness.Structural motions,specifically heave and pitch,are measured using an Inertial Measurement Unit(IMU),while strain gauges measure structural stress and mooring tension.The sensors provide precise measurements for strain and pitch;however,heave,as a result of time-domain integration from acceleration,requires further validation.The motion responses of the model align with reference results.
基金support from the National Natural Science Foundation of China(No.52171274)。
文摘For the development of an integrated rounded rectangular wellhead platform with a bucket foundation,a model test was conducted to study the towing motion response of such a structure under still water and wave conditions.The influence of various factors on the floating stability of the structure was investigated through alterations of the towing conditions(draft,towing point position,and wave conditions),and the related influencing mechanism was analyzed.Comparison and analysis were performed to determine the changes in the structure motion pattern and various effects of towing conditions on the structure during towing in still water and regular waves.Moreover,the influence of each factor on the structure’s motion response during towing was analyzed using the Apriori algorithm.In addition,for the simulation of the towing process under actual sea conditions,a towing test was performed under irregular waves,and the stability of towing in irregular waves was compared with that in regular waves.
基金supported by the National Natural Science Foundation of China(No.52271287).
文摘Offshore floating photovoltaic systems have tremendous potential to address the energy crisis.As a novel type of float-ing photovoltaic system,membrane structures are increasingly applied due to their advantages of being lightweight and cost-effective.A 1:40 scaled model for laboratory experiments was designed and developed,considering Ocean Sun’s membrane structure.The study aims to investigate the hydrodynamic characteristics of the membrane structure under wave loading by testing its various mo-tion responses and mooring forces at different wave heights and periods.The conclusions indicate that as the wave period decreases within the range of 1.75 to 1.25 s,the heave motion response of the structure decreases,whereas pitch,surge motion response,heave acceleration,and mooring force increase.The amplitudes of various motions and mooring forces of the structure decrease with de-creasing wave height.The hydrodynamic responses under irregular and regular waves follow similar patterns,but the responses and mooring forces induced by irregular waves are more significant.The structure should be designed based on the actual wave height.In addition,the same frequency resonance phenomenon is avoided because the movement period of each degree of freedom is close to the wave period.
文摘Siwa Oasis,one of Egypts most remote settlements,is also a popular tourist destination thanks to the beautiful salt pools with water that people can float in.Salt is both a blessing and a curse in Siwa.Years ago,people started realizing that there was money to be made in the salt trade,and salt mining operations created the salt lakes that the oasis is now famous for.
基金supported by the National Key Research&Development Projects of China(Grant No.2022YFA1204100)National Natural Science Foundation of China(Grant No.62488201)+1 种基金CAS Project for Young Scientists in Basic Research(YSBR-003)the Innovation Program of Quantum Science and Technology(2021ZD0302700)。
文摘As a typical in-memory computing hardware design, nonvolatile ternary content-addressable memories(TCAMs) enable the logic operation and data storage for high throughout in parallel big data processing. However,TCAM cells based on conventional silicon-based devices suffer from structural complexity and large footprintlimitations. Here, we demonstrate an ultrafast nonvolatile TCAM cell based on the MoTe2/hBN/multilayergraphene (MLG) van der Waals heterostructure using a top-gated partial floating-gate field-effect transistor(PFGFET) architecture. Based on its ambipolar transport properties, the carrier type in the source/drain andcentral channel regions of the MoTe2 channel can be efficiently tuned by the control gate and top gate, respectively,enabling the reconfigurable operation of the device in either memory or FET mode. When working inthe memory mode, it achieves an ultrafast 60 ns programming/erase speed with a current on-off ratio of ∼105,excellent retention capability, and robust endurance. When serving as a reconfigurable transistor, unipolar p-typeand n-type FETs are obtained by adopting ultrafast 60 ns control-gate voltage pulses with different polarities.The monolithic integration of memory and logic within a single device enables the content-addressable memory(CAM) functionality. Finally, by integrating two PFGFETs in parallel, a TCAM cell with a high current ratioof ∼10^(5) between the match and mismatch states is achieved without requiring additional peripheral circuitry.These results provide a promising route for the design of high-performance TCAM devices for future in-memorycomputing applications.
