It was approved by the State Council in I984 to establish economicand technological development zones in 14 coastal port cities tofunction as windows for those cities to attract foreign investment,introduce advanced t...It was approved by the State Council in I984 to establish economicand technological development zones in 14 coastal port cities tofunction as windows for those cities to attract foreign investment,introduce advanced technology and management methods andexpand the export-oriented economy.Since 1992,18 other developmentzones have been approved by the Council,increasing the number ofsuch zones to 32.展开更多
This paper discusses China＇s relatively new structure of dual onshore and offshore RMB markets. Its distinguishingJeature is both offshore trading at exchange rates that are market determined and onshore trading at e...This paper discusses China＇s relatively new structure of dual onshore and offshore RMB markets. Its distinguishingJeature is both offshore trading at exchange rates that are market determined and onshore trading at exchange rates anchored at the official spot rate with capital account inconvertibility. We note that thus far the CNH and CNY spot rates have largely tracked each other, suggesting that the shadow priee on the convertibility constraint onshore and also the offshore diversification benefit is close to zero. However, this could change in the future. We discuss the potentialJbr the offshore RMB market to grow with trade settlement and bilateral ,swap arrangements in RMB, which would provide a big enough pool ofliquidityforthe RMB to become a vehicle currency and reserve c^rrency. These potential developments will be restrained by onshore inconvertibility, but moving to convertibility seemingly implies major change in China ＂s financial structure and the offshore RMB arrangements are only a small first step along this path. Crucial in this evolution of arrangements will be fi^ture Chinese growth performance and the relative attractiveness of onshore inconvertible but offshore marketable RA4B relative to the debt laden and slow growth currencies of the USA, the EU and Japan.展开更多
The global adoption of Electric Vehicles(EVs)is on the rise due to their advanced features,with projections indicating they will soon dominate the private vehicle market.However,improper management of EV charging can ...The global adoption of Electric Vehicles(EVs)is on the rise due to their advanced features,with projections indicating they will soon dominate the private vehicle market.However,improper management of EV charging can lead to significant issues.This paper reviews the development of high-power,reliable charging solutions by examining the converter topologies used in rectifiers and converters that transfer electricity from the grid to EV batteries.It covers technical details,ongoing developments,and challenges related to these topologies and control strategies.The integration of rapid charging stations has introduced various Power Quality(PQ)issues,such as voltage fluctuations,harmonic distortion,and supra-harmonics,which are discussed in detail.The paper also highlights the benefits of controlled EV charging and discharging,including voltage and frequency regulation,reactive power compensation,and improved power quality.Efficient energy management and control strategies are crucial for optimizing EV battery charging within microgrids to meet increasing demand.Charging stations must adhere to specific converter topologies,control strategies,and industry standards to function correctly.The paper explores microgrid architectures and control strategies that integrate EVs,energy storage units(ESUs),and Renewable Energy Sources(RES)to enhance performance at charging points.It emphasizes the importance of various RES-connected architectures and the latest power converter topologies.Additionally,the paper provides a comparative analysis of microgrid-based charging station architectures,focusing on energy management,control strategies,and charging converter controls.The goal is to offer insights into future research directions in EV charging systems,including architectural considerations,control factors,and their respective advantages and disadvantages.展开更多
This paper presents a new type of triangular Sharp Eagle wave energy converter(WEC)platform.On the basis of the linear potential flow theory and the finite element analysis method,the hydrodynamic performance and stru...This paper presents a new type of triangular Sharp Eagle wave energy converter(WEC)platform.On the basis of the linear potential flow theory and the finite element analysis method,the hydrodynamic performance and structural response of the platform are studied,considering the actual platform motion and free surface rise under extreme sea states.First,the effects of the wave frequency and direction on the wave-induced loads and dynamic responses were examined.The motion at a wave direction angle of 0°is relatively low.On this basis,the angle constrained by the two sides of the Sharp Eagle floaters should be aligned with the main wave direction to avoid significant platform motion under extreme sea states.Additionally,the structural response of the platform,including the wave-absorbing floaters,is investigated.The results highlighted that the conditions or locations where yielding,buckling,and fatigue failures occur were different.In this context,the connection area of the Sharp Eagle floaters and platform is prone to yielding failure under oblique wave action,whereas the pontoon and side of the Sharp Eagle floaters are prone to buckling failure during significant vertical motion.Additionally,fatigue damage is most likely to occur at the connection between the middle column on both sides of the Sharp Eagle floaters and the pontoons.The findings of this paper revealed an intrinsic connection between wave-induced loads and the dynamic and structural responses of the platform,which provides a useful reference for the improved design of WECs.展开更多
The four-level nested neutral-point-clamped(4L-NNPC)inverter is a competitive topology among the various medium-voltage multilevel converters,and its main issue is flying-capacitor voltage unbalance.In this article,a ...The four-level nested neutral-point-clamped(4L-NNPC)inverter is a competitive topology among the various medium-voltage multilevel converters,and its main issue is flying-capacitor voltage unbalance.In this article,a novel carrier-interleaved pulse width modulation(CIPWM)method that satisfies the volt-sec balance principle is proposed with an advanced carrier distribution rule.By adopting the proposed CIPWM method,the redundant switching states of 4L-NNPC inverters can be evenly distributed into the output PWM waveform in each carrier period,and natural flying-capacitor voltage balance can be achieved.Furthermore,an active balancing strategy is also proposed to eliminate the voltage unbalance caused by nonideal factors,which is realized by simply adjusting the duty cycle and with no need to adjust the redundant switching states for 4L-NNPC inverters.The simulation and experimental results verify the effectiveness of the proposed CIPWM method and the flying-capacitor voltage balancing strategy.展开更多
With the depletion of fossil fuels and increasing environmental concerns,the development of renewable energy,such as wave energy,has become a critical component of global energy strategies.However,challenges persist i...With the depletion of fossil fuels and increasing environmental concerns,the development of renewable energy,such as wave energy,has become a critical component of global energy strategies.However,challenges persist in the field testing methodologies for wave energy converters(WECs).In this paper,a numerical wave field of the Dawanshan Island Sea Area in Zhuhai City is constructed based on the MIKE21 SW wave model and by using an NCEP wind field driving model.In conjunction with the IEC-62600-100 standard,by taking site testing of the“Wanshan”wave energy converter on which a sea trial has been conducted in Dawanshan Island of Zhuhai city as an example,research on-site testing method for a wave energy converter has been carried out.The wave measurement position for the“Wanshan”converter was determined by combining statistically analyzed field data with a validated numerical wave model.By comparing a valid wave height at the position where a wave rider is located with a valid wave height at the position where the“Wanshan”wave energy converter is situated,the correlation coefficient between simulation and observed data reached 0.90,with a root-mean-square error of 0.19.The representativeness of wave measurement data during site testing is verified and can be used as a basis for calculating the input energy of the“Wanshan”wave energy converter.展开更多
An in-pixel histogramming time-to-digital converter(hTDC)based on octonary search and 4-tap phase detection is presented,aiming to improve frame rate while ensuring high precicion.The proposed hTDC is a 12-bit two-ste...An in-pixel histogramming time-to-digital converter(hTDC)based on octonary search and 4-tap phase detection is presented,aiming to improve frame rate while ensuring high precicion.The proposed hTDC is a 12-bit two-step converter consisting of a 6-bit coarse quantization and a 6-bit fine quantization,which supports a time resolution of 120 ps and multiphoton counting up to 2 GHz without a GHz reference frequency.The proposed hTDC is designed in 0.11μm CMOS process with an area consumption of 6900μm^(2).The data from a behavioral-level model is imported into the designed hTDC circuit for simulation verification.The post-simulation results show that the proposed hTDC achieves 0.8%depth precision in 9 m range for short-range system design specifications and 0.2%depth precision in 48 m range for long-range system design specifications.Under 30×10^(3) lux background light conditions,the proposed hTDC can be used for SPAD-based flash LiDAR sensor to achieve a frame rate to 40 fps with 200 ps resolution in 9 m range.展开更多
Virescent rice is a type of non-lethal chlorophyll deficient mutant generated by natural mutation, genetically known as mutation of nuclear genes. Under normal growing conditions, virescent rices can develop from whit...Virescent rice is a type of non-lethal chlorophyll deficient mutant generated by natural mutation, genetically known as mutation of nuclear genes. Under normal growing conditions, virescent rices can develop from white seedlings to green seedlings through a half-white stage (white leaves with green strips) and therefore possess the convertibility. This differs definitely from the lethal albino mutant of rice, such as those derived from anther culture. It has been known that the generation of albino pollen plants is due to展开更多
Power converters are essential components in modern life,being widely used in industry,automation,transportation,and household appliances.In many critical applications,their failure can lead not only to financial loss...Power converters are essential components in modern life,being widely used in industry,automation,transportation,and household appliances.In many critical applications,their failure can lead not only to financial losses due to operational downtime but also to serious risks to human safety.The capacitors forming the output filter,typically aluminumelectrolytic capacitors(AECs),are among the most critical and susceptible components in power converters.The electrolyte in AECs often evaporates over time,causing the internal resistance to rise and the capacitance to drop,ultimately leading to component failure.Detecting this fault requires measuring the current in the capacitor,rendering the method invasive and frequently impractical due to spatial constraints or operational limitations imposed by the integration of a current sensor in the capacitor branch.This article proposes the implementation of an online noninvasive fault diagnosis technique for estimating the Equivalent Series Resistance(ESR)and Capacitance(C)values of the capacitor,employing a combination of signal processing techniques(SPT)and machine learning(ML)algorithms.This solution relies solely on the converter’s input and output signals,therefore making it a non-invasive approach.The ML algorithm used was linear regression,applied to 27 attributes,21 of which were generated through feature engineering to enhance the model’s performance.The proposed solution demonstrates an R^(2) score greater than 0.99 in the estimation of both ESR and C.展开更多
The top-bottom combined blowing converter mainly adopts the blowing method of top-blowing oxygen and bottom-blowing nitrogen.In the production process,there are some disadvantages,such as a significant temperature dif...The top-bottom combined blowing converter mainly adopts the blowing method of top-blowing oxygen and bottom-blowing nitrogen.In the production process,there are some disadvantages,such as a significant temperature difference between the top and bottom of the molten pool,inadequate gas permeability of bottom blowing,and low decarburization efficiency.Therefore,we propose a novel bottom-blowing gas doped oxygen process to enhance the smelting conditions in the converter.The 500 kg medium frequency induction furnace with top and bottom-blowing function was used to explore the influence of the proportion of bottom-blowing gas doped oxygen on the smelting effect in different smelting cycles.Subsequently,industrial experimental verification was carried out on a 60 t converter.The results of intermediate frequency furnace experiments demonstrate that the bottom-blowing gas doped oxygen process exhibits a superior heating rate and decarburization efficiency during the initial and final stages of blowing compared to pure N2 used for bottom-blowing.Simultaneously,the dephosphorization efficiency exhibited an initial increase followed by a subsequent decrease as the bottom-blowing oxygen content increased.The industrial test of 60 t converter validates the findings above.Moreover,when the oxygen content in bottom-blowing gas is 5%,the average blowing time reduces by 54 s,and the minimum endpoint carbon-oxygen equilibrium reaches 0.00219 under this condition.The results demonstrate that the appropriate amount of oxygen doped in bottom-blowing gas can effectively enhance the metallurgical conditions of the converter and improve production efficiency.展开更多
Through an example of a main transformer switch-in with load during the reverse transmission of a 750 kV power plan,the paper introduces the basic principle of transformer switch-in with load.EMTPE program that is use...Through an example of a main transformer switch-in with load during the reverse transmission of a 750 kV power plan,the paper introduces the basic principle of transformer switch-in with load.EMTPE program that is used to establish a calculation model,at the same time mainly considers the excitation characteristics of the transformer,the transient model of the circuit breaker,and the model of high voltage transformer,and calculated the inrush current with transformer switch-in with load in this plan.During system debugging in the plan,the two sets of main transformers passed the closing and opening test,and the data of inrush current in the test are recorded and analyzed.The simulation calculation and measured data show that the results are consistent.The simulation calculation also shows that it is not recommended to perform on-load closing of the transformer except for special circumstances,because of the influence of hysteresis characteristic when the transformer was switched in with load or the terminal voltage of the transformer resumed normal level from a low one after an external near-end fault was cleared,which various transformer differential protection using the characteristics of inrush to implement block scheme may mal-operate.展开更多
Efficient battery charging requires a power conversion system capable of providing precise voltage regulation tailored to the battery’s needs.This study develops a buck converter with a 36 V input for charging a 14 V...Efficient battery charging requires a power conversion system capable of providing precise voltage regulation tailored to the battery’s needs.This study develops a buck converter with a 36 V input for charging a 14 V battery using the Constant Voltage(CV)method.The system is designed to ensure safe and efficient charging while protecting the battery from overcharging and extending its lifespan.In the proposed design,the converter maintains a constant output voltage while the charging current decreases as the battery approaches full capacity.Pulse Width Modulation(PWM)is used as a control strategy to modify the duty cycle of the converter.This keeps the voltage output stable whenever the load changes.The design process involves simulation and experimental validation to evaluate the system’s performance and efficiency.The test results show the significant impact of Proportional-Integral-Derivative(PID)control on the stability of the output voltage to meet the requirements for 14 V battery charging and the efficiency of the battery charging process.The output voltage becomes more stable,with reduced oscillation and minimal steadystate error.The State of Charge(SOC)increases more stably,controllably,and efficiently thanks to the PID controller’s ability to adjust the duty cycle in real time based on system feedback.This dynamic adjustment ensures that the output current and voltage remain within the optimal range,which directly improves the battery charging process.In addition,PID control significantly improves the dynamic response of the system,reducing overshoot and settling time while maintaining precise voltage regulation.This speeds up the battery charging process and contributes to better energy efficiency,reduced power loss,and extended battery life.This research provides a reliable and cost-effective solution for applications in electric vehicles,renewable energy systems,and other battery-powered devices.展开更多
Safety,high protein content,and the numerous health benefits make Spirulina an outstanding source of bioactive peptides.Peptides from Spirulina,which exhibit antioxidant,anti-inflammatory,and antihypertensive effects,...Safety,high protein content,and the numerous health benefits make Spirulina an outstanding source of bioactive peptides.Peptides from Spirulina,which exhibit antioxidant,anti-inflammatory,and antihypertensive effects,may assist in the management of cardiovascular diseases(CVDs).Here,we present the optimization of enzyme-digested hydrolysates derived from Spirulina sp.by using response surface methodology(RSM).We also evaluated the biological activity of Spirulina protein hydrolysates(SPHs)in contributing to the amelioration of hypertension and associated cardiovascular diseases.Our findings suggest that Spirulina protein extracts contain a complex proteinaceous composition with phycocyanin being the dominant protein,as evidenced by both SDS-PAGE and LC-MS/MS profiling.Alkaline protease,protease K,andα-chymotrypsin exhibited a substantial hydrolytic effect on Spirulina protein,taking into account their degree of hydrolysis(DH),peptide yield,and molecular weight distribution.Single-factor experiments identified pH,temperature,and enzyme/substrate ratio as the key factors influencing DH.Moreover,optimal hydrolysis conditions for the proteases were determined via RSM,leading to a considerable enhancement of the actual DH.Bioassays showed that SPHs have strong antioxidant activity against various free radicals,with a higher ability to scavenge hydroxyl radicals.Furthermore,SPHs inhibited macrophage nitric oxide secretion and significantly inhibited angiotensin I-converting enzyme in vitro at 400μg/mL.It is worth noting that SPHs prepared with protease K exhibited a potent anti-hypertensive effect in vivo.The findings indicate the potential usefulness of including dietary SPHs in preventing hypertension and associated CVDs.This research could be valuable in guiding the development of health-promoting foods within the Spirulina industry.展开更多
With the continuous improvement of signal processing accuracy requirements in modern electronic systems,the demand for high-precision analog-to-digital converters(ADCs)is increasing.Sigma-Delta modulator,as the most i...With the continuous improvement of signal processing accuracy requirements in modern electronic systems,the demand for high-precision analog-to-digital converters(ADCs)is increasing.Sigma-Delta modulator,as the most important component of high-precision ADC,is widely used in high-quality audio,high-precision instrument measurement,and other fields due to its advantages of high precision,strong noise resistance,and low hardware cost.This article designs a discrete structure third-order four-bit high-precision Sigma-Delta modulator through modeling,with an oversampling rate set to 512.Under ideal conditions,the simulation results show that the SDNR reaches 152.7db and the ENOB is 25.24bits.After introducing non-ideal noise,the system performance has decreased.The simulation results show that the SDNR is as high as 124.5db and the ENOB is 20.39bits.This indicates that the design can achieve high-precision conversion and provide assistance for further research in the future.展开更多
This review paper examines the various types of electrical generators used to convert wave energy into electrical energy.The focus is on both linear and rotary generators,including their design principles,operational ...This review paper examines the various types of electrical generators used to convert wave energy into electrical energy.The focus is on both linear and rotary generators,including their design principles,operational efficiencies,and technological advancements.Linear generators,such as Induction,permanent magnet synchronous,and switched reluctance types,are highlighted for their direct conversion capability,eliminating the need for mechanical gearboxes.Rotary Induction generators,permanent magnet synchronous generators,and doubly-fed Induction generators are evaluated for their established engineering principles and integration with existing grid infrastructure.The paper discusses the historical development,environmental benefits,and ongoing advancements in wave energy technologies,emphasizing the increasing feasibility and scalability of wave energy as a renewable source.Through a comprehensive analysis,this review provides insights into the current state and future prospects of electrical generators in wave energy conversion,underscoring their potential to significantly reduce reliance on fossil fuels and mitigate environmental impacts.展开更多
Scientists have introduced new methods for capturing energy from ocean waves.Specifically,scientists have focused on a type of wave energy converter(WEC)that is nonbuoyant(i.e.,a body that cannot float).Typically,the ...Scientists have introduced new methods for capturing energy from ocean waves.Specifically,scientists have focused on a type of wave energy converter(WEC)that is nonbuoyant(i.e.,a body that cannot float).Typically,the WEC is most effective when it is in resonance,which occurs when the natural frequency of the WEC aligns with that of the ocean waves.Therefore,accurately predicting the movement of the WEC is crucial for adjusting its system to resonate with the incoming waves for optimal performance.In this study,artificial intelligence techniques,such as random forest,extra trees(ET),and support vector machines,are created to forecast the vertical movement of a nonbuoyant WEC.The developed models require two variables as input,namely,the water wave height and its time period.A total of approximately 4500 data points,which include nonlinear water wave height and duration ob-tained from a laboratory experiment,are used as the input for these models,with the resulting vertical movement as the output.When comparing the three models based on their processing speed and accuracy,the ET model stands out as the most efficient.Ultimately,the ET model is tested using data from a real ocean setting.展开更多
Analysis of the energy balance of various parts during the basic oxygen furnace(BOF)steelmaking is of vital importance for revealing the blowing characteristics of the swirl-type oxygen lance.The energy transfer behav...Analysis of the energy balance of various parts during the basic oxygen furnace(BOF)steelmaking is of vital importance for revealing the blowing characteristics of the swirl-type oxygen lance.The energy transfer behavior between the oxygen jet and the molten bath in the top-blowing steelmaking process was investigated using the volume of fluid method.The energy of the reflected jet and the slag was introduced,and the energy balance model of the BOF converter was modified.The influences of lance height and operation pressure on energy transfer were analyzed.Compared with the traditional oxygen lance,the energy of reflected jet,splashing,and cavity formation of the swirl-type oxygen lance was decreased.However,the energy of jet attenuation,slag,and molten steel increased.The energy proportion of the reflected jet was about 8%,while the energy of slag was 15%of molten steel.The maximum energy was transferred from the jet to the slag and molten steel at H=40de(H is lance height and de is outlet diameter).When the operation pressure increased from 0.8P0 to 1.2P0(P0 is the designed pressure),the energy of slag and molten steel was increased by 33%and 25.9%,respectively.展开更多
In multi-component oil and gas exploration using ocean bottom nodes,converted wave data is rich in lithological and fracture information.One of the urgent problems to be solved is how to construct an accurate shear wa...In multi-component oil and gas exploration using ocean bottom nodes,converted wave data is rich in lithological and fracture information.One of the urgent problems to be solved is how to construct an accurate shear wave velocity model of the shallow sea bottom by leveraging the seismic wave information at the fluid-solid interface in the ocean,and improve the lateral resolution of marine converted wave data.Given that the dispersion characteristics of surface waves are sensitive to the S-wave velocity of subsurface media,and that Scholte surface waves,which propagate at the interface between liquid and solid media,exist in the data of marine oil and gas exploration,this paper proposes a Scholte wave inversion and modeling method based on oil and gas exploration using ocean bottom nodes.By using the method for calculating the Scholte wave dispersion spectrum based on the Bessel kernel function,the accuracy of dispersion spectrum analysis is improved,and more accurate dispersion curves are picked up.Through the adaptive weighted least squares Scholte wave dispersion inversion algorithm,the Scholte wave dispersion equation for liquid-solid media is solved,and the shear wave velocity model of the shallow sea bottom is calculated.Theoretical tests and applications of realdata have proven that this method can significantly improve the lateral resolution of converted wave data,provide high-quality data for subsequent inversion of marine multi-component oil and gas exploration data and reservoir reflection information,and contribute to the development of marine oil and gas exploration technology.展开更多
Submodule capacitor aging poses significant challenges to the safe operation of modular multilevel converter(MMC)systems.Traditional detection methods rely predominantly on offline tests,lacking real-time evaluation c...Submodule capacitor aging poses significant challenges to the safe operation of modular multilevel converter(MMC)systems.Traditional detection methods rely predominantly on offline tests,lacking real-time evaluation capabilities.Moreover,existing online approaches require additional sampling channels,thereby increasing system complexity and costs.To address these issues,this paper proposes an online evaluation method for submodule capacitor aging based on CapAgingNet.Initially,an MMC system simulation platform is developed to examine the effects of submodule capacitor aging on system operational characteristics and to create a dataset of submodule capacitor switching states.Subsequently,the CapAgingNet model is introduced,incorporating key technical modules to enhance performance:the Deep Stem module,which extracts larger receptive fields through multiple convolution layers and mitigates the impact of data sparsity in capacitor aging on feature extraction;the efficient channel attention(ECA)module,utilizing onedimensional convolution for dynamic weighting to adjust the importance of each channel,thereby enhancing the ability of the model to process high-dimensional features in capacitor aging data;and the multiscale feature fusion(MSF)module,which integrates capacitor aging information across different scales by combining fine-grained and coarse-grained features,thus improving the capacity of the model to capture high-frequency variation characteristics.The experimental results reveal that the CapAgingNet model achieves a TOP-1 accuracy of 95.32%and a macro-averaged F1 score of 95.49%on the test set,thereby providing effective technical support for online monitoring of submodule capacitor aging.展开更多
In the novel fully dry converter gas recovery process,a novel circumfluent cyclone separator with an evaporation heating surface can simultaneously realize the dust removal and sensible heat recovery of converter gas....In the novel fully dry converter gas recovery process,a novel circumfluent cyclone separator with an evaporation heating surface can simultaneously realize the dust removal and sensible heat recovery of converter gas.For this equipment,the distributions of internal flow and wall heat transfer affect the efficiency of dust removal and sensible heat recovery.In this study,based on on-site operation tests,the distributions of internal flow and wall heat transfer in the circumfluent cyclone separator are studied by numerical simulation.The results indicate that the flow rate proportions in different regions of the circumfluent cyclone separator remain constant during the steelmaking process,approximately 80.1%of the converter gas flows through the cone chamber,and 15.4%of the converter gas flows through the annular chamber.The heat transfer rate proportions on the walls of different regions of the circumfluent cyclone separator remain constant during the steelmaking process,and the heat transfer rate proportions on the walls of the cone chamber,straight shell,shell head and outlet pipe are 40.2%,27.0%,17.6%and 15.2%,respectively.展开更多
文摘It was approved by the State Council in I984 to establish economicand technological development zones in 14 coastal port cities tofunction as windows for those cities to attract foreign investment,introduce advanced technology and management methods andexpand the export-oriented economy.Since 1992,18 other developmentzones have been approved by the Council,increasing the number ofsuch zones to 32.
文摘This paper discusses China＇s relatively new structure of dual onshore and offshore RMB markets. Its distinguishingJeature is both offshore trading at exchange rates that are market determined and onshore trading at exchange rates anchored at the official spot rate with capital account inconvertibility. We note that thus far the CNH and CNY spot rates have largely tracked each other, suggesting that the shadow priee on the convertibility constraint onshore and also the offshore diversification benefit is close to zero. However, this could change in the future. We discuss the potentialJbr the offshore RMB market to grow with trade settlement and bilateral ,swap arrangements in RMB, which would provide a big enough pool ofliquidityforthe RMB to become a vehicle currency and reserve c^rrency. These potential developments will be restrained by onshore inconvertibility, but moving to convertibility seemingly implies major change in China ＂s financial structure and the offshore RMB arrangements are only a small first step along this path. Crucial in this evolution of arrangements will be fi^ture Chinese growth performance and the relative attractiveness of onshore inconvertible but offshore marketable RA4B relative to the debt laden and slow growth currencies of the USA, the EU and Japan.
文摘The global adoption of Electric Vehicles(EVs)is on the rise due to their advanced features,with projections indicating they will soon dominate the private vehicle market.However,improper management of EV charging can lead to significant issues.This paper reviews the development of high-power,reliable charging solutions by examining the converter topologies used in rectifiers and converters that transfer electricity from the grid to EV batteries.It covers technical details,ongoing developments,and challenges related to these topologies and control strategies.The integration of rapid charging stations has introduced various Power Quality(PQ)issues,such as voltage fluctuations,harmonic distortion,and supra-harmonics,which are discussed in detail.The paper also highlights the benefits of controlled EV charging and discharging,including voltage and frequency regulation,reactive power compensation,and improved power quality.Efficient energy management and control strategies are crucial for optimizing EV battery charging within microgrids to meet increasing demand.Charging stations must adhere to specific converter topologies,control strategies,and industry standards to function correctly.The paper explores microgrid architectures and control strategies that integrate EVs,energy storage units(ESUs),and Renewable Energy Sources(RES)to enhance performance at charging points.It emphasizes the importance of various RES-connected architectures and the latest power converter topologies.Additionally,the paper provides a comparative analysis of microgrid-based charging station architectures,focusing on energy management,control strategies,and charging converter controls.The goal is to offer insights into future research directions in EV charging systems,including architectural considerations,control factors,and their respective advantages and disadvantages.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFC3003805)Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.2022356)Guangzhou Basic and Applied Basic Research Project(Grant No.2023A04J0955).
文摘This paper presents a new type of triangular Sharp Eagle wave energy converter(WEC)platform.On the basis of the linear potential flow theory and the finite element analysis method,the hydrodynamic performance and structural response of the platform are studied,considering the actual platform motion and free surface rise under extreme sea states.First,the effects of the wave frequency and direction on the wave-induced loads and dynamic responses were examined.The motion at a wave direction angle of 0°is relatively low.On this basis,the angle constrained by the two sides of the Sharp Eagle floaters should be aligned with the main wave direction to avoid significant platform motion under extreme sea states.Additionally,the structural response of the platform,including the wave-absorbing floaters,is investigated.The results highlighted that the conditions or locations where yielding,buckling,and fatigue failures occur were different.In this context,the connection area of the Sharp Eagle floaters and platform is prone to yielding failure under oblique wave action,whereas the pontoon and side of the Sharp Eagle floaters are prone to buckling failure during significant vertical motion.Additionally,fatigue damage is most likely to occur at the connection between the middle column on both sides of the Sharp Eagle floaters and the pontoons.The findings of this paper revealed an intrinsic connection between wave-induced loads and the dynamic and structural responses of the platform,which provides a useful reference for the improved design of WECs.
基金supported by Beijing Natural Science Foundation under Grant L242006.
文摘The four-level nested neutral-point-clamped(4L-NNPC)inverter is a competitive topology among the various medium-voltage multilevel converters,and its main issue is flying-capacitor voltage unbalance.In this article,a novel carrier-interleaved pulse width modulation(CIPWM)method that satisfies the volt-sec balance principle is proposed with an advanced carrier distribution rule.By adopting the proposed CIPWM method,the redundant switching states of 4L-NNPC inverters can be evenly distributed into the output PWM waveform in each carrier period,and natural flying-capacitor voltage balance can be achieved.Furthermore,an active balancing strategy is also proposed to eliminate the voltage unbalance caused by nonideal factors,which is realized by simply adjusting the duty cycle and with no need to adjust the redundant switching states for 4L-NNPC inverters.The simulation and experimental results verify the effectiveness of the proposed CIPWM method and the flying-capacitor voltage balancing strategy.
基金supported by the“National Ocean Technology Center Innovation Fund”under Project No.N3220Z002,led by Ning Jia.The official website of the National Ocean Technology Center is accessible at:http://www.notcsoa.org.cn/.
文摘With the depletion of fossil fuels and increasing environmental concerns,the development of renewable energy,such as wave energy,has become a critical component of global energy strategies.However,challenges persist in the field testing methodologies for wave energy converters(WECs).In this paper,a numerical wave field of the Dawanshan Island Sea Area in Zhuhai City is constructed based on the MIKE21 SW wave model and by using an NCEP wind field driving model.In conjunction with the IEC-62600-100 standard,by taking site testing of the“Wanshan”wave energy converter on which a sea trial has been conducted in Dawanshan Island of Zhuhai city as an example,research on-site testing method for a wave energy converter has been carried out.The wave measurement position for the“Wanshan”converter was determined by combining statistically analyzed field data with a validated numerical wave model.By comparing a valid wave height at the position where a wave rider is located with a valid wave height at the position where the“Wanshan”wave energy converter is situated,the correlation coefficient between simulation and observed data reached 0.90,with a root-mean-square error of 0.19.The representativeness of wave measurement data during site testing is verified and can be used as a basis for calculating the input energy of the“Wanshan”wave energy converter.
基金National Key Research and Development Program of China(2022YFB2804401)。
文摘An in-pixel histogramming time-to-digital converter(hTDC)based on octonary search and 4-tap phase detection is presented,aiming to improve frame rate while ensuring high precicion.The proposed hTDC is a 12-bit two-step converter consisting of a 6-bit coarse quantization and a 6-bit fine quantization,which supports a time resolution of 120 ps and multiphoton counting up to 2 GHz without a GHz reference frequency.The proposed hTDC is designed in 0.11μm CMOS process with an area consumption of 6900μm^(2).The data from a behavioral-level model is imported into the designed hTDC circuit for simulation verification.The post-simulation results show that the proposed hTDC achieves 0.8%depth precision in 9 m range for short-range system design specifications and 0.2%depth precision in 48 m range for long-range system design specifications.Under 30×10^(3) lux background light conditions,the proposed hTDC can be used for SPAD-based flash LiDAR sensor to achieve a frame rate to 40 fps with 200 ps resolution in 9 m range.
文摘Virescent rice is a type of non-lethal chlorophyll deficient mutant generated by natural mutation, genetically known as mutation of nuclear genes. Under normal growing conditions, virescent rices can develop from white seedlings to green seedlings through a half-white stage (white leaves with green strips) and therefore possess the convertibility. This differs definitely from the lethal albino mutant of rice, such as those derived from anther culture. It has been known that the generation of albino pollen plants is due to
文摘Power converters are essential components in modern life,being widely used in industry,automation,transportation,and household appliances.In many critical applications,their failure can lead not only to financial losses due to operational downtime but also to serious risks to human safety.The capacitors forming the output filter,typically aluminumelectrolytic capacitors(AECs),are among the most critical and susceptible components in power converters.The electrolyte in AECs often evaporates over time,causing the internal resistance to rise and the capacitance to drop,ultimately leading to component failure.Detecting this fault requires measuring the current in the capacitor,rendering the method invasive and frequently impractical due to spatial constraints or operational limitations imposed by the integration of a current sensor in the capacitor branch.This article proposes the implementation of an online noninvasive fault diagnosis technique for estimating the Equivalent Series Resistance(ESR)and Capacitance(C)values of the capacitor,employing a combination of signal processing techniques(SPT)and machine learning(ML)algorithms.This solution relies solely on the converter’s input and output signals,therefore making it a non-invasive approach.The ML algorithm used was linear regression,applied to 27 attributes,21 of which were generated through feature engineering to enhance the model’s performance.The proposed solution demonstrates an R^(2) score greater than 0.99 in the estimation of both ESR and C.
基金supported by the National Natural Science Foundation of China(No.U21A20317)the National Key Research and Development Program of China(No.2017YFB0304201).
文摘The top-bottom combined blowing converter mainly adopts the blowing method of top-blowing oxygen and bottom-blowing nitrogen.In the production process,there are some disadvantages,such as a significant temperature difference between the top and bottom of the molten pool,inadequate gas permeability of bottom blowing,and low decarburization efficiency.Therefore,we propose a novel bottom-blowing gas doped oxygen process to enhance the smelting conditions in the converter.The 500 kg medium frequency induction furnace with top and bottom-blowing function was used to explore the influence of the proportion of bottom-blowing gas doped oxygen on the smelting effect in different smelting cycles.Subsequently,industrial experimental verification was carried out on a 60 t converter.The results of intermediate frequency furnace experiments demonstrate that the bottom-blowing gas doped oxygen process exhibits a superior heating rate and decarburization efficiency during the initial and final stages of blowing compared to pure N2 used for bottom-blowing.Simultaneously,the dephosphorization efficiency exhibited an initial increase followed by a subsequent decrease as the bottom-blowing oxygen content increased.The industrial test of 60 t converter validates the findings above.Moreover,when the oxygen content in bottom-blowing gas is 5%,the average blowing time reduces by 54 s,and the minimum endpoint carbon-oxygen equilibrium reaches 0.00219 under this condition.The results demonstrate that the appropriate amount of oxygen doped in bottom-blowing gas can effectively enhance the metallurgical conditions of the converter and improve production efficiency.
文摘Through an example of a main transformer switch-in with load during the reverse transmission of a 750 kV power plan,the paper introduces the basic principle of transformer switch-in with load.EMTPE program that is used to establish a calculation model,at the same time mainly considers the excitation characteristics of the transformer,the transient model of the circuit breaker,and the model of high voltage transformer,and calculated the inrush current with transformer switch-in with load in this plan.During system debugging in the plan,the two sets of main transformers passed the closing and opening test,and the data of inrush current in the test are recorded and analyzed.The simulation calculation and measured data show that the results are consistent.The simulation calculation also shows that it is not recommended to perform on-load closing of the transformer except for special circumstances,because of the influence of hysteresis characteristic when the transformer was switched in with load or the terminal voltage of the transformer resumed normal level from a low one after an external near-end fault was cleared,which various transformer differential protection using the characteristics of inrush to implement block scheme may mal-operate.
文摘Efficient battery charging requires a power conversion system capable of providing precise voltage regulation tailored to the battery’s needs.This study develops a buck converter with a 36 V input for charging a 14 V battery using the Constant Voltage(CV)method.The system is designed to ensure safe and efficient charging while protecting the battery from overcharging and extending its lifespan.In the proposed design,the converter maintains a constant output voltage while the charging current decreases as the battery approaches full capacity.Pulse Width Modulation(PWM)is used as a control strategy to modify the duty cycle of the converter.This keeps the voltage output stable whenever the load changes.The design process involves simulation and experimental validation to evaluate the system’s performance and efficiency.The test results show the significant impact of Proportional-Integral-Derivative(PID)control on the stability of the output voltage to meet the requirements for 14 V battery charging and the efficiency of the battery charging process.The output voltage becomes more stable,with reduced oscillation and minimal steadystate error.The State of Charge(SOC)increases more stably,controllably,and efficiently thanks to the PID controller’s ability to adjust the duty cycle in real time based on system feedback.This dynamic adjustment ensures that the output current and voltage remain within the optimal range,which directly improves the battery charging process.In addition,PID control significantly improves the dynamic response of the system,reducing overshoot and settling time while maintaining precise voltage regulation.This speeds up the battery charging process and contributes to better energy efficiency,reduced power loss,and extended battery life.This research provides a reliable and cost-effective solution for applications in electric vehicles,renewable energy systems,and other battery-powered devices.
基金Supported by the Science and Technology Project of Fujian Province(Nos.2023T3034,2020N3011)the Innovation Academy for Drug Discovery and DevelopmentChinese Academy of Sciences。
文摘Safety,high protein content,and the numerous health benefits make Spirulina an outstanding source of bioactive peptides.Peptides from Spirulina,which exhibit antioxidant,anti-inflammatory,and antihypertensive effects,may assist in the management of cardiovascular diseases(CVDs).Here,we present the optimization of enzyme-digested hydrolysates derived from Spirulina sp.by using response surface methodology(RSM).We also evaluated the biological activity of Spirulina protein hydrolysates(SPHs)in contributing to the amelioration of hypertension and associated cardiovascular diseases.Our findings suggest that Spirulina protein extracts contain a complex proteinaceous composition with phycocyanin being the dominant protein,as evidenced by both SDS-PAGE and LC-MS/MS profiling.Alkaline protease,protease K,andα-chymotrypsin exhibited a substantial hydrolytic effect on Spirulina protein,taking into account their degree of hydrolysis(DH),peptide yield,and molecular weight distribution.Single-factor experiments identified pH,temperature,and enzyme/substrate ratio as the key factors influencing DH.Moreover,optimal hydrolysis conditions for the proteases were determined via RSM,leading to a considerable enhancement of the actual DH.Bioassays showed that SPHs have strong antioxidant activity against various free radicals,with a higher ability to scavenge hydroxyl radicals.Furthermore,SPHs inhibited macrophage nitric oxide secretion and significantly inhibited angiotensin I-converting enzyme in vitro at 400μg/mL.It is worth noting that SPHs prepared with protease K exhibited a potent anti-hypertensive effect in vivo.The findings indicate the potential usefulness of including dietary SPHs in preventing hypertension and associated CVDs.This research could be valuable in guiding the development of health-promoting foods within the Spirulina industry.
文摘With the continuous improvement of signal processing accuracy requirements in modern electronic systems,the demand for high-precision analog-to-digital converters(ADCs)is increasing.Sigma-Delta modulator,as the most important component of high-precision ADC,is widely used in high-quality audio,high-precision instrument measurement,and other fields due to its advantages of high precision,strong noise resistance,and low hardware cost.This article designs a discrete structure third-order four-bit high-precision Sigma-Delta modulator through modeling,with an oversampling rate set to 512.Under ideal conditions,the simulation results show that the SDNR reaches 152.7db and the ENOB is 25.24bits.After introducing non-ideal noise,the system performance has decreased.The simulation results show that the SDNR is as high as 124.5db and the ENOB is 20.39bits.This indicates that the design can achieve high-precision conversion and provide assistance for further research in the future.
文摘This review paper examines the various types of electrical generators used to convert wave energy into electrical energy.The focus is on both linear and rotary generators,including their design principles,operational efficiencies,and technological advancements.Linear generators,such as Induction,permanent magnet synchronous,and switched reluctance types,are highlighted for their direct conversion capability,eliminating the need for mechanical gearboxes.Rotary Induction generators,permanent magnet synchronous generators,and doubly-fed Induction generators are evaluated for their established engineering principles and integration with existing grid infrastructure.The paper discusses the historical development,environmental benefits,and ongoing advancements in wave energy technologies,emphasizing the increasing feasibility and scalability of wave energy as a renewable source.Through a comprehensive analysis,this review provides insights into the current state and future prospects of electrical generators in wave energy conversion,underscoring their potential to significantly reduce reliance on fossil fuels and mitigate environmental impacts.
文摘Scientists have introduced new methods for capturing energy from ocean waves.Specifically,scientists have focused on a type of wave energy converter(WEC)that is nonbuoyant(i.e.,a body that cannot float).Typically,the WEC is most effective when it is in resonance,which occurs when the natural frequency of the WEC aligns with that of the ocean waves.Therefore,accurately predicting the movement of the WEC is crucial for adjusting its system to resonate with the incoming waves for optimal performance.In this study,artificial intelligence techniques,such as random forest,extra trees(ET),and support vector machines,are created to forecast the vertical movement of a nonbuoyant WEC.The developed models require two variables as input,namely,the water wave height and its time period.A total of approximately 4500 data points,which include nonlinear water wave height and duration ob-tained from a laboratory experiment,are used as the input for these models,with the resulting vertical movement as the output.When comparing the three models based on their processing speed and accuracy,the ET model stands out as the most efficient.Ultimately,the ET model is tested using data from a real ocean setting.
基金financially supported by the Natural Science Foundation of Liaoning Province,China(Grant No.2024-BS-219)the Education Department Project of Liaoning Province(JYTMS20230932)+3 种基金the National Natural Science Foundation of China(U20A20272)the Department of Science&Technology of Liaoning Province(Grant No.2022JH2/101300079)the Fundamental Research Funds for the Liaoning Universities(LJ212410146002)the National Natural Science Foundation of China(NSFC52074151).
文摘Analysis of the energy balance of various parts during the basic oxygen furnace(BOF)steelmaking is of vital importance for revealing the blowing characteristics of the swirl-type oxygen lance.The energy transfer behavior between the oxygen jet and the molten bath in the top-blowing steelmaking process was investigated using the volume of fluid method.The energy of the reflected jet and the slag was introduced,and the energy balance model of the BOF converter was modified.The influences of lance height and operation pressure on energy transfer were analyzed.Compared with the traditional oxygen lance,the energy of reflected jet,splashing,and cavity formation of the swirl-type oxygen lance was decreased.However,the energy of jet attenuation,slag,and molten steel increased.The energy proportion of the reflected jet was about 8%,while the energy of slag was 15%of molten steel.The maximum energy was transferred from the jet to the slag and molten steel at H=40de(H is lance height and de is outlet diameter).When the operation pressure increased from 0.8P0 to 1.2P0(P0 is the designed pressure),the energy of slag and molten steel was increased by 33%and 25.9%,respectively.
基金financially supported by the Scientific Research and Technology Development Project of China National Petroleum Corporation(No.2021ZG02)titled"Development of Seismic Data Processing Software for Ocean Nodes(OBN)"。
文摘In multi-component oil and gas exploration using ocean bottom nodes,converted wave data is rich in lithological and fracture information.One of the urgent problems to be solved is how to construct an accurate shear wave velocity model of the shallow sea bottom by leveraging the seismic wave information at the fluid-solid interface in the ocean,and improve the lateral resolution of marine converted wave data.Given that the dispersion characteristics of surface waves are sensitive to the S-wave velocity of subsurface media,and that Scholte surface waves,which propagate at the interface between liquid and solid media,exist in the data of marine oil and gas exploration,this paper proposes a Scholte wave inversion and modeling method based on oil and gas exploration using ocean bottom nodes.By using the method for calculating the Scholte wave dispersion spectrum based on the Bessel kernel function,the accuracy of dispersion spectrum analysis is improved,and more accurate dispersion curves are picked up.Through the adaptive weighted least squares Scholte wave dispersion inversion algorithm,the Scholte wave dispersion equation for liquid-solid media is solved,and the shear wave velocity model of the shallow sea bottom is calculated.Theoretical tests and applications of realdata have proven that this method can significantly improve the lateral resolution of converted wave data,provide high-quality data for subsequent inversion of marine multi-component oil and gas exploration data and reservoir reflection information,and contribute to the development of marine oil and gas exploration technology.
基金supported by China Yangtze Power Co.,Ltd.(No.ZSF2502001).
文摘Submodule capacitor aging poses significant challenges to the safe operation of modular multilevel converter(MMC)systems.Traditional detection methods rely predominantly on offline tests,lacking real-time evaluation capabilities.Moreover,existing online approaches require additional sampling channels,thereby increasing system complexity and costs.To address these issues,this paper proposes an online evaluation method for submodule capacitor aging based on CapAgingNet.Initially,an MMC system simulation platform is developed to examine the effects of submodule capacitor aging on system operational characteristics and to create a dataset of submodule capacitor switching states.Subsequently,the CapAgingNet model is introduced,incorporating key technical modules to enhance performance:the Deep Stem module,which extracts larger receptive fields through multiple convolution layers and mitigates the impact of data sparsity in capacitor aging on feature extraction;the efficient channel attention(ECA)module,utilizing onedimensional convolution for dynamic weighting to adjust the importance of each channel,thereby enhancing the ability of the model to process high-dimensional features in capacitor aging data;and the multiscale feature fusion(MSF)module,which integrates capacitor aging information across different scales by combining fine-grained and coarse-grained features,thus improving the capacity of the model to capture high-frequency variation characteristics.The experimental results reveal that the CapAgingNet model achieves a TOP-1 accuracy of 95.32%and a macro-averaged F1 score of 95.49%on the test set,thereby providing effective technical support for online monitoring of submodule capacitor aging.
基金funded by the Strategic Priority Research Program of the Chinese Academy of Sciences,Grant Number XDA29020503.
文摘In the novel fully dry converter gas recovery process,a novel circumfluent cyclone separator with an evaporation heating surface can simultaneously realize the dust removal and sensible heat recovery of converter gas.For this equipment,the distributions of internal flow and wall heat transfer affect the efficiency of dust removal and sensible heat recovery.In this study,based on on-site operation tests,the distributions of internal flow and wall heat transfer in the circumfluent cyclone separator are studied by numerical simulation.The results indicate that the flow rate proportions in different regions of the circumfluent cyclone separator remain constant during the steelmaking process,approximately 80.1%of the converter gas flows through the cone chamber,and 15.4%of the converter gas flows through the annular chamber.The heat transfer rate proportions on the walls of different regions of the circumfluent cyclone separator remain constant during the steelmaking process,and the heat transfer rate proportions on the walls of the cone chamber,straight shell,shell head and outlet pipe are 40.2%,27.0%,17.6%and 15.2%,respectively.
