Proportioning is an important part of sintering,as it affects the cost of sintering and the quality of sintered ore.To address the problems posed by the complex raw material information and numerous constraints in the...Proportioning is an important part of sintering,as it affects the cost of sintering and the quality of sintered ore.To address the problems posed by the complex raw material information and numerous constraints in the sintering process,a multi-objective optimisation model for sintering proportioning was established,which takes the proportioning cost and TFe as the optimisation objectives.Additionally,an improved multi-objective beluga whale optimisation(IMOBWO)algorithm was proposed to solve the nonlinear,multi-constrained multi-objective optimisation problems.The algorithm uses the con-strained non-dominance criterion to deal with the constraint problem in the model.Moreover,the algorithm employs an opposite learning strategy and a population guidance mechanism based on angular competition and two-population competition strategy to enhance convergence and population diversity.The actual proportioning of a steel plant indicates that the IMOBWO algorithm applied to the ore proportioning process has good convergence and obtains the uniformly distributed Pareto front.Meanwhile,compared with the actual proportioning scheme,the proportioning cost is reduced by 4.3361¥/t,and the TFe content in the mixture is increased by 0.0367%in the optimal compromise solution.Therefore,the proposed method effectively balances the cost and total iron,facilitating the comprehensive utilisation of sintered iron ore resources while ensuring quality assurance.展开更多
The basic sintering characteristics of Yandi ore from Australia, including assimilation ability, liquid phase fluidity, self-strength of bonding phase, forming ability of silico ferrite of calcium and aluminum （SFCA...The basic sintering characteristics of Yandi ore from Australia, including assimilation ability, liquid phase fluidity, self-strength of bonding phase, forming ability of silico ferrite of calcium and aluminum （SFCA）, and so on, were investigated in detail. Besides, the high temperature behavior and function of sintering were obtained. As a result, the techniques for ore-proportioning in sintering were obtained. The results show that Yandi ore possessing higher assimilation ability, better liquid phase fluidity, lower self-strength of bonding phase, and better forming ability of SFCA, should be mixed with iron ores whose properties are opposite to those of Yandi ore. In the optimization of sintering ore-proportioning, Yandi ore, whose price is relatively low, can be mixed as high as 40wt%.展开更多
With a complicated composition, large rolling sludge has been a focal point concerning neither at home nor abroad have any technologies suitable for bulk utilization of stainless steel cold- production and serious dam...With a complicated composition, large rolling sludge has been a focal point concerning neither at home nor abroad have any technologies suitable for bulk utilization of stainless steel cold- production and serious damage to the environment, stainless steel cold- environmental protection for stainless steel enterprises. Up to now, come into being that are not only proper, safe and economical but also rolling sludge. Based on the characteristics of the stainless steel cold- rolling sludge, orthogonal experiments were carried out on pellet proportioning and high-temperature roasting, and major metallurgical properties of sludge pellets were also tested. As the results show, pellets with 30% addition of cold-rolling sludge are qualified regarding their compressive strength, chemical composition and major metallurgical properties. No adverse impact happens to the blast furnace operation when sludge pellets account for 10% of the blast furnace raw materials. Therefore, the technical route applied in this paper is proved simple, feasible and environmentally friendly for cold-rolling sludge treatment.展开更多
Conventional multilevel inverters often suffer from high harmonic distortion and increased design complexity due to the need for numerous power semiconductor components,particularly at elevated voltage levels.Addressi...Conventional multilevel inverters often suffer from high harmonic distortion and increased design complexity due to the need for numerous power semiconductor components,particularly at elevated voltage levels.Addressing these shortcomings,thiswork presents a robust 15-level PackedUCell(PUC)inverter topology designed for renewable energy and grid-connected applications.The proposed systemintegrates a sensor less proportional-resonant(PR)controller with an advanced carrier-based pulse width modulation scheme.This approach efficiently balances capacitor voltage,minimizes steady-state error,and strongly suppresses both zero and third-order harmonics resulting in reduced total harmonic distortion and enhanced voltage regulation.Additionally,a novel switching algorithm simplifies the design and implementation,further lowering voltage stress across switches.Extensive simulation results validate the performance under various resistive and resistive-inductive load conditions,demonstrating compliance with IEEE-519 THD standards and robust operation under dynamic changes.The proposed sensorless PR-controlled 15-PUC inverter thus offers a compelling,cost-effective solution for efficient power conversion in next-generation renewable energy systems.展开更多
Amyotrophic lateral sclerosis is a rare neurodegenerative disease characterized by the involvement of both upper and lower motor neurons.Early bilateral limb involvement significantly affects patients'daily lives ...Amyotrophic lateral sclerosis is a rare neurodegenerative disease characterized by the involvement of both upper and lower motor neurons.Early bilateral limb involvement significantly affects patients'daily lives and may lead them to be confined to bed.However,the effect of upper and lower motor neuron impairment and other risk factors on bilateral limb involvement is unclear.To address this issue,we retrospectively collected data from 586 amyotrophic lateral sclerosis patients with limb onset diagnosed at Peking University Third Hospital between January 2020 and May 2022.A univariate analysis revealed no significant differences in the time intervals of spread in different directions between individuals with upper motor neuron-dominant amyotrophic lateral sclerosis and those with classic amyotrophic lateral sclerosis.We used causal directed acyclic graphs for risk factor determination and Cox proportional hazards models to investigate the association between the duration of bilateral limb involvement and clinical baseline characteristics in amyotrophic lateral sclerosis patients.Multiple factor analyses revealed that higher upper motor neuron scores(hazard ratio[HR]=1.05,95%confidence interval[CI]=1.01–1.09,P=0.018),onset in the left limb(HR=0.72,95%CI=0.58–0.89,P=0.002),and a horizontal pattern of progression(HR=0.46,95%CI=0.37–0.58,P<0.001)were risk factors for a shorter interval until bilateral limb involvement.The results demonstrated that a greater degree of upper motor neuron involvement might cause contralateral limb involvement to progress more quickly in limb-onset amyotrophic lateral sclerosis patients.These findings may improve the management of amyotrophic lateral sclerosis patients with limb onset and the prediction of patient prognosis.展开更多
Background: Maternal mortality remains a major public health problem worldwide. Objectives: Our study aims to present the results of an analysis of reviews of maternal deaths at HGOPY. Methodology: This was a descript...Background: Maternal mortality remains a major public health problem worldwide. Objectives: Our study aims to present the results of an analysis of reviews of maternal deaths at HGOPY. Methodology: This was a descriptive cross-sectional study with retrospective data collection from archived records and reviewed maternal death reports. Our study lasted 8 months, from October 1, 2023 to May 31, 2024. The study covered maternal death files at the HGOPY over an 8-year period, from 1st of January 2016 to the 31st of December 2023. Data were processed and analyzed using Statitical Paquage for Social Science (SPSS) version 26.0. Results: We counted a total of 160 maternal deaths, of which 97 had been reviewed. We excluded 61 deceased women reviewed and retained 33. We recorded a cumulative total of 160 maternal deaths and 19,651 live births. The peak in the proportion of maternal deaths at the Yaoundé Gynaeco-Obstetric and Paediatric Hospital was in 2021, with a proportion of 0.013. No maternal deaths had been reviewed between 2016 to 2017. Most deaths (64%) occurred between 37 and 40 weeks. The majority (30.5%) were aged between 30 and 35. The data show that 80.6% of maternal deaths were due to direct obstetric causes, while 19.4% were due to indirect causes. Most deaths (69.4%) were preventable. Only 8.3% were not preventable. Conclusion: Concerted efforts must be made to adapt maternal death prevention and management strategies to local contexts in order to significantly reduce these alarming figures.展开更多
Objective:To utilize the VigiAccess database for data mining to analyze the characteristics of adverse reactions induced by mirogabalin,providing critical information for clinical medication use.Method:This study anal...Objective:To utilize the VigiAccess database for data mining to analyze the characteristics of adverse reactions induced by mirogabalin,providing critical information for clinical medication use.Method:This study analyzed data from the VigiAccess database,filtering out adverse reaction reports where mirogabalin was identified as the Primary Suspect Drug(PS).Reporting Odds Ratio(ROR),Proportional Reporting Ratio(PRR),Bayesian Confidence Propagation Neural Network(BCPNN),and Empirical Bayes Geometric Mean(EBGM)methods were employed as data mining algorithms for pharmacovigilance and adverse event monitoring.These methods identify potential drug-adverse event association signals by analyzing the relationship between drug use and adverse event reporting.ROR and PRR focus on calculating reporting ratios,while BCPNN and EBGM use neural networks and empirical Bayes models,respectively,to enhance the accuracy and reliability of signal detection.Results:A total of 734 adverse reaction reports associated with mirogabalin were obtained.The results showed that females reported the highest number of adverse reactions,accounting for 59.67%,while males accounted for 38.83%.In terms of age distribution,the highest number of reports came from individuals over 75 years old,accounting for 33.79%.Adverse reactions mainly involved the nervous system(33.45%),general diseases and reactions at the site of administration(11.62%),and gastrointestinal disorders(10.74%).The most common adverse reactions included dizziness(11.62%),somnolence(8.27%),renal dysfunction(2.90%),and edema(2.82%).Signal intensity analysis revealed that certain adverse reactions(such as renal dysfunction,rhabdomyolysis,and drug-induced liver injury)had significant signal strength,suggesting a strong association with mirogabalin.Conclusion:This study,through signal mining of the VigiAccess database,reveals the characteristics of mirogabalin’s adverse reactions in the real world,particularly in the nervous system and renal function.These findings provide important reference information for clinicians,aiding in the optimization of the safe use of mirogabalin.Future research should further validate the causal relationships of these signals and explore individualized treatment strategies to reduce the incidence of adverse reactions and improve patient outcomes.展开更多
Aiming at the missile avoidance problem of the unmanned aerial vehicle(UAV)in complex obstacle environments,this work proposes a collision-avoidance method based on receding horizon optimization.The proposed method ge...Aiming at the missile avoidance problem of the unmanned aerial vehicle(UAV)in complex obstacle environments,this work proposes a collision-avoidance method based on receding horizon optimization.The proposed method generated a specific trajectory for the UAV to effectively induce the proportional navigation missile to successfully intercept the obstacle,thereby accomplishing the evasive maneuver.The evasive maneuver was divided into two distinct stages,namely the collision-inducing phase and the fast departure phase.The obstacle potential field-based target selection algorithm was employed to identify the most appropriate target obstacle,while the induced trajectory was determined through a combination of receding horizon optimization and the hp-adaptive pseudo-spectral method.Simulation experiments were carried out under three different types of obstacle environments and one multiobstacle environment,and the simulation results show that the method proposed in this paper greatly improves the success rate of UAV evasive maneuvers,proving the effectiveness of this method.展开更多
The abundance of live and dead Oithona similis in Jiaozhou Bay,Shandong,China,was investigated monthly from December 2008 to November 2009 via the neutral red staining method.The annual variation in total abundance wa...The abundance of live and dead Oithona similis in Jiaozhou Bay,Shandong,China,was investigated monthly from December 2008 to November 2009 via the neutral red staining method.The annual variation in total abundance was similar for females,males,and copepodites,with a main numerical peak from February to July and a minor peak in November,but the variations in carcass abundance and death proportion were different.The monthly average abundance of male and copepodite carcasses significantly increased with their total abundance(P<0.001),whereas no such correlation was observed for females.The abundance of female carcasses peaked at 12.4 inds./m^(3) in November but remained below 3.0 inds./m^(3) in all other months.The monthly average death proportion ranged 0.3%-4.9% for females,3.6%-25.7% for males,and 2.6%-8.4% for copepodites.On average,the death proportion of males was 9.2 times greater than that of females and 3.5 times greater than that of copepodites.Therefore,significant sexual difference exists in the non-predatory mortality of O.similis and this difference is an important cause of the female-skewed sex ratios observed in the field.展开更多
The Loess Plateau region in China is characterized by a fragile environment,where vegetation is susceptible to both natural variations and anthropogenic influences.Previous research has indicated a greening trend in v...The Loess Plateau region in China is characterized by a fragile environment,where vegetation is susceptible to both natural variations and anthropogenic influences.Previous research has indicated a greening trend in vegetation across the Loess Plateau over the past two decades.However,the specific contributions of natural and anthropogenic drivers,both individually and interactively,to vegetation distribution remain unclear.To address this gap,we conducted a study using Shaanxi Province as a case area.Utilizing multisource data,we employed the Geographical Detector Model(GDM)to analyze the impacts of natural and human related factors on vegetation distribution.Our analysis revealed that the average NDVI(Normalized Difference Vegetation Index)increased at a rate of 0.006 per year from 2000 to 2021.Notably,88.8%of the region experienced vegetation greening,while 4.5%showed significant declines in NDVI,particularly in areas,such as Xi'an,Weinan,Baoji,Hanzhong,and Ankang.Furthermore,NDVI trend projections suggest that the area undergoing vegetation degradation may surpass the area showing improvement in the future.The study identified that vegetation distribution was influenced by both natural and anthropogenic factors for the whole study area.Precipitation,surface types and land use type were the primary factors with q values above 0.5.During the study period,impacts of GDP,nighttime lights and population density among anthropogenic factors on vegetation distribution increased by 130%,125%and 41%,respectively.Conversely,except for slope and aspect,natural factors'influence on vegetation distribution declined by 5%to 26%.The impact of driving factors on NDVI distribution varied across ecological regions.In Fenwei Basin Agro-Ecoregion(EcoregionⅢ),the influence of anthropogenic factors on vegetation distribution was greater than that in the other three ecoregions.Precipitation primarily affected the vegetation distribution in Loess Plateau Agricultural and Grassland Ecoregion(EcoregionⅡ).Additionally,the combined interactive effects of factors had a stronger influence on NDVI distribution than any single factor.These findings provide valuable insights for local governments in Shaanxi Province to develop targeted ecological restoration and environmental management policies.展开更多
Ternary geopolymers incorporating multiple solid wastes such as steel slag(SS),fly ash(FA),and granulated blast furnace slag(GBFS)are considered environmentally friendly and exhibit enhanced performance.However,the me...Ternary geopolymers incorporating multiple solid wastes such as steel slag(SS),fly ash(FA),and granulated blast furnace slag(GBFS)are considered environmentally friendly and exhibit enhanced performance.However,the mechanisms governing strength development and the design of optimal mixtures are not fully understood due to the complexity of their components.This study presents the development of four machine learning mod-els-Artificial Neural Network(ANN),Support Vector Regression(SVR),Extremely Randomized Tree(ERT),and Gradient Boosting Regression(GBR)-for predicting the unconfined compressive strength(UCS)of ternary geopolymers.The models were trained using a dataset comprising 120 mixtures derived from laboratory tests.Shapley Additive Explanations analysis was employed to interpret the machine learning models and elucidate the influence of different components on the properties of ternary geopolymers.The results indicate that ANN ex-hibits the highest predictive accuracy for UCS(R=0.949).Furthermore,the UCS of ternary geopolymers is most sensitive to the content of GBFS.This study provides valuable insights for optimizing the mix proportions in ternary blended geopolymer mixtures.展开更多
Magnetization convenience is crucial consideration for design of valve magnetic actuators.The existing repulsive-magnetic-coupling of 2D maglev valve is not oriented to the integral-magnetization-processes,resulting i...Magnetization convenience is crucial consideration for design of valve magnetic actuators.The existing repulsive-magnetic-coupling of 2D maglev valve is not oriented to the integral-magnetization-processes,resulting in the high assembly cost.This paper presents a novel tractive-magnetic-coupling(TMC)and its application on a 2D electro-hydraulic proportional flow valve(2D-EHPFV),whose configuration not only fulfill the requirements of 2D valve,but also oriented to integral-magnetization-process.To investigate the output torque of TMC,a detailed analytical model considering leakage flux,edge effect and tooth magnetic saturation is formulated based on the equivalent magnetic circuit method.To facilitate the magnetic saturation calculation,a special magnetic permeability database is established for tooth region of TMC using Ansoft/Maxwell software.Prototype of TMC is machined and an exclusive experimental platform is built.Torque-displacement characteristics under different working airgap and tooth number are measured.The experimental results are in good agreement with the analytical results,which verifies the correctness of the analytical model.Then the TMC is integrated into the 2D-EHPFV by replacing the repulsive-magnetic-coupling.Prototype of 2D-EHPFV is designed and manufactured to test the no-load flow characteristics,load flow characteristics,leakage characteristics,frequency characteristics and step response.Under working pressure of 15 MPa,the maximum no-load flow rate is 82.2 L/min with the hysteresis of 2.6%,and the amplitude and phase frequency width is 21.6 Hz,and 28.9 Hz.The detailed experimental results show that TMC can be applied to 2D valves to form 2D-EHPFV,which can reduce hysteresis and cost,and improve response speed.展开更多
Increasing concerns regarding aquatic ecological health and eutrophication driven by urbanization and human activities have highlighted the need to understand primary productivity(PP)dynamics in aquatic ecosystems. Th...Increasing concerns regarding aquatic ecological health and eutrophication driven by urbanization and human activities have highlighted the need to understand primary productivity(PP)dynamics in aquatic ecosystems. This study investigated the spatial distribution of PP across the Weihe River Basin, China using inverse distance weighting and analyzed the influence of different land uses and water physical-chemical parameters on PP using Mantel test and Spearman analysis. Significantly spatial heterogeneity in PP concentrations, ranging from 0.458 to 3262.807 mg C/(m^(2)·d), was observed with high-PP sites clustered in the middle-lower reaches dominated by farmland-construction land mosaics.Core drivers included light availability(Secchi depth and sunlight duration) and phytoplankton biomass(chlorophyll-a(Chl-a)), while water temperature exhibited threshold-dependent effects. Total organic carbon played dual roles, promoting PP concentrations in low-Chl-a regions, but suppressing it under high-Chl-a regions. Dual-scale buffer analysis(500 and 1000 m buffer zones) revealed PP heterogeneity stemed from interactive land use configurations, rather than isolated types. Balanced construction land-to-farmland ratio(0.467–2.890) elevated PP concentrations in human-dominated basins(the main stem of the Weihe River and Jinghe River), whereas excessive agricultural homogenization reduced PP likely due to fertilizer saturation and algal self-shading. Ecologically sensitive basins(the Beiluohe River Basin) demonstrated distinct patterns, in which PP concentration was regulated through natural-agricultural synergies. These results deepened the understanding of land use effects on aquatic PP,providing a theoretical basis for optimizing land use strategies to reconcile eutrophication control with ecological productivity in human-stressed basins.展开更多
The long transaction latency and low throughput of blockchain are the key challenges affecting the large-scale adoption of blockchain technology. Sharding technology is a primary solution by divides the blockchain net...The long transaction latency and low throughput of blockchain are the key challenges affecting the large-scale adoption of blockchain technology. Sharding technology is a primary solution by divides the blockchain network into multiple independent shards for parallel transaction processing. However, most existing random or modular schemes fail to consider the transactional relationships between accounts, which leads to a high proportion of cross-shard transactions, thereby increasing the communication overhead and transaction confirmation latency between shards. To solve this problem, this paper proposes a blockchain sharding algorithm based on account degree and frequency (DFSA). The algorithm takes into account both account degree and weight relationships between accounts. The blockchain transaction network is modeled as an undirected weighted graph, and community detection algorithms are employed to analyze the correlations between accounts. Strong-correlated accounts are grouped into the same shard, and a multi-shard blockchain network is constructed. Additionally, to further reduce the number of cross-shard transactions, this paper designs a random redundancy strategy based on account correlation, which randomly selects strong-correlated accounts and stores them redundantly in another shard, thus original cross-shard transactions can be verified and confirmed within the same shard. Simulation experiments demonstrate that DFSA outperforms the random sharding algorithm (RSA), modular sharding algorithm (MSA), and label propagation algorithm (LPA) in terms of cross-shard transaction proportion, latency, and throughput. Therefore, DFSA can effectively reduce cross-shard transaction proportion and lower transaction confirmation latency.展开更多
In this paper, a class of discontinuous neutral-type neural networks (NTNNs) with proportional delays is considered. The targets of the paper are to study the problem of periodic solutions and fixed-time (FXT) stabili...In this paper, a class of discontinuous neutral-type neural networks (NTNNs) with proportional delays is considered. The targets of the paper are to study the problem of periodic solutions and fixed-time (FXT) stabilization of the addressed neural networks. In order to complete the targets, based on set-valued map, differential inclusions theory, coincidence theorem and Hölder inequality technique, some new proportional delay-dependent criteria shown by the inequalities are derived. Based on the fact of the existence of solution, further by applying the FXT stability lemmas and equivalent transformation, the zero solution of closed-loop system achieves FXT stabilization and the corresponding settling-times are estimated. Some previous related works on NTNNs are extended. Finally, one typical example is provided to show the effectiveness of the established results.展开更多
Norway spruce(Picea abies(L.)Karst.)in the Harz Mountains National Park(Germany)has experienced widespread mortality(>97%of trees in the study stands)due to infestation with the large spruce bark beetle(Ips typogra...Norway spruce(Picea abies(L.)Karst.)in the Harz Mountains National Park(Germany)has experienced widespread mortality(>97%of trees in the study stands)due to infestation with the large spruce bark beetle(Ips typographus L.).The dead trees(snags)remain standing in the forest for 2-5 years before harvesting.It is important to identify trees that can still produce quality timber,which may be achieved by examining their outer appearance using selected characteristics.The aim of this study was to identify possible correlations between the standing storage duration and defined external characteristics of the snags.The mean tree height at compartment level was calculated using a vegetation height model,based on light detection and ranging data from 2018,to derive the stem breakage proportion.The condition of the crown and the bark and presence of fungi,wood rot,stem cracks and bark stripping damage were also assessed.The majority of the snags were broken at least once.Windthrows were less likely compared to living spruce trees because of reduced resistance to the wind as a result of needle loss and breakage.The mean stem breakage proportion increased significantly with the duration of the standing storage;however,prolonged storage durations did not always lead to complete breakage.The occurrence of fungal fruiting bodies was significantly correlated with a higher proportion of stem breakage,and the longer the storage,the more snags had fungal fruiting bodies.The condition of the crown,assessed by the presence of branchlets,was a good indicator of the duration of the standing storage.If trees had few or no branchlets,they had been standing for at least 4 years.Overall,this initial description of the external appearance of spruce trees that have been stored standing for many years suggests that time significantly influences the tree condition and breakage intensity,which is reflected by certain tree characteristics.Future studies should examine these aspects in greater depth,particularly with regard to utilization options and safety during timber harvesting.展开更多
The Taiji program is focused on achieving space-based gravitational wave detection in the frequency range of 0.1 mHz-1 Hz.To achieve drag-free control,Taiji satellites must be equipped with micro-thrusters that satisf...The Taiji program is focused on achieving space-based gravitational wave detection in the frequency range of 0.1 mHz-1 Hz.To achieve drag-free control,Taiji satellites must be equipped with micro-thrusters that satisfy stringent requirements,including a continuously adjustable thrust,thrust resolution of 0.1μN,thrust noise of 0.1μN·Hz^(-0.5)and response time of less than 100 ms.This paper presents the progress of a variable cold gas micro-thruster being developed for the Taiji program.A series of technologies such as a bidirectional piezoelectric drive,spherical valve core,conical nozzle seal,miniature gas chamber,high thruster integration,combined digital and analogue communication and high-frequency closed-loop thrust control were employed to achieve engineering prototypes of a low-noise and fast-response micro-thruster.Ground performance tests indicate that the micro-thruster achieved a minimum thrust of close to 1.1 nN,a thrust resolution of 0.05μN and a maximum specific impulse of 69.1 s using nitrogen gas as the working fluid.The thrust noise was less than 0.1μN·Hz^(-0.5)in the frequency band of 10 mHz-1 Hz,and the thrust response time was 140 ms.The control parameters were further optimised to achieve a flow response time of 50 ms.The results indicate that the developed micro-thruster essentially met the performance requirements for drag-free control to facilitate space-based gravitational wave detection.展开更多
This study introduces a novel mathematical model to describe the progression of cholera by integrating fractional derivatives with both singular and non-singular kernels alongside stochastic differential equations ove...This study introduces a novel mathematical model to describe the progression of cholera by integrating fractional derivatives with both singular and non-singular kernels alongside stochastic differential equations over four distinct time intervals.The model incorporates three key fractional derivatives:the Caputo-Fabrizio fractional derivative with a non-singular kernel,the Caputo proportional constant fractional derivative with a singular kernel,and the Atangana-Baleanu fractional derivative with a non-singular kernel.We analyze the stability of the core model and apply various numerical methods to approximate the proposed crossover model.To achieve this,the approximation of Caputo proportional constant fractional derivative with Grünwald-Letnikov nonstandard finite difference method is used for the deterministic model with a singular kernel,while the Toufik-Atangana method is employed for models involving a non-singular Mittag-Leffler kernel.Additionally,the integral Caputo-Fabrizio approximation and a two-step Lagrange polynomial are utilized to approximate the model with a non-singular exponential decay kernel.For the stochastic component,the Milstein method is implemented to approximate the stochastic differential equations.The stability and effectiveness of the proposed model and methodologies are validated through numerical simulations and comparisons with real-world cholera data from Yemen.The results confirm the reliability and practical applicability of the model,providing strong theoretical and empirical support for the approach.展开更多
Critical Height Sampling(CHS)estimates stand volume free from any model and tree form assumptions.Despite its introduction more than four decades ago,CHS has not been widely applied in the field due to perceived chall...Critical Height Sampling(CHS)estimates stand volume free from any model and tree form assumptions.Despite its introduction more than four decades ago,CHS has not been widely applied in the field due to perceived challenges in measurement.The objectives of this study were to compare estimated stand volume between CHS and sampling methods that used volume or taper models,the equivalence of the sampling methods,and their relative efficiency.We established 65 field plots in planted forests of two coniferous tree species.We estimated stand volume for a range of Basal Area Factors(BAFs).Results showed that CHS produced the most similar mean stand volume across BAFs and tree species with maximum differences between BAFs of 5-18m^(3)·ha^(−1).Horizontal Point Sampling(HPS)using volume models produced very large variability in mean stand volume across BAFs with the differences up to 126m^(3)·ha^(−1).However,CHS was less precise and less efficient than HPS.Furthermore,none of the sampling methods were statistically interchangeable with CHS at an allowable tolerance of≤55m^(3)·ha^(−1).About 72%of critical height measurements were below crown base indicating that critical height was more accessible to measurement than expected.Our study suggests that the consistency in the mean estimates of CHS is a major advantage when planning a forest inventory.When checking against CHS,results hint that HPS estimates might contain potential model bias.These strengths of CHS could outweigh its lower precision.Our study also implies serious implications in financial terms when choosing a sampling method.Lastly,CHS could potentially benefit forest management as an alternate option of estimating stand volume when volume or taper models are lacking or are not reliable.展开更多
基金supported by the National Key Research and Development Program of China (2022YFB3304700)Hunan Province Natural Science Foundation (2022JJ50132,2022JCYJ05 and 2022JCYJ09).
文摘Proportioning is an important part of sintering,as it affects the cost of sintering and the quality of sintered ore.To address the problems posed by the complex raw material information and numerous constraints in the sintering process,a multi-objective optimisation model for sintering proportioning was established,which takes the proportioning cost and TFe as the optimisation objectives.Additionally,an improved multi-objective beluga whale optimisation(IMOBWO)algorithm was proposed to solve the nonlinear,multi-constrained multi-objective optimisation problems.The algorithm uses the con-strained non-dominance criterion to deal with the constraint problem in the model.Moreover,the algorithm employs an opposite learning strategy and a population guidance mechanism based on angular competition and two-population competition strategy to enhance convergence and population diversity.The actual proportioning of a steel plant indicates that the IMOBWO algorithm applied to the ore proportioning process has good convergence and obtains the uniformly distributed Pareto front.Meanwhile,compared with the actual proportioning scheme,the proportioning cost is reduced by 4.3361¥/t,and the TFe content in the mixture is increased by 0.0367%in the optimal compromise solution.Therefore,the proposed method effectively balances the cost and total iron,facilitating the comprehensive utilisation of sintered iron ore resources while ensuring quality assurance.
文摘The basic sintering characteristics of Yandi ore from Australia, including assimilation ability, liquid phase fluidity, self-strength of bonding phase, forming ability of silico ferrite of calcium and aluminum （SFCA）, and so on, were investigated in detail. Besides, the high temperature behavior and function of sintering were obtained. As a result, the techniques for ore-proportioning in sintering were obtained. The results show that Yandi ore possessing higher assimilation ability, better liquid phase fluidity, lower self-strength of bonding phase, and better forming ability of SFCA, should be mixed with iron ores whose properties are opposite to those of Yandi ore. In the optimization of sintering ore-proportioning, Yandi ore, whose price is relatively low, can be mixed as high as 40wt%.
文摘With a complicated composition, large rolling sludge has been a focal point concerning neither at home nor abroad have any technologies suitable for bulk utilization of stainless steel cold- production and serious damage to the environment, stainless steel cold- environmental protection for stainless steel enterprises. Up to now, come into being that are not only proper, safe and economical but also rolling sludge. Based on the characteristics of the stainless steel cold- rolling sludge, orthogonal experiments were carried out on pellet proportioning and high-temperature roasting, and major metallurgical properties of sludge pellets were also tested. As the results show, pellets with 30% addition of cold-rolling sludge are qualified regarding their compressive strength, chemical composition and major metallurgical properties. No adverse impact happens to the blast furnace operation when sludge pellets account for 10% of the blast furnace raw materials. Therefore, the technical route applied in this paper is proved simple, feasible and environmentally friendly for cold-rolling sludge treatment.
文摘Conventional multilevel inverters often suffer from high harmonic distortion and increased design complexity due to the need for numerous power semiconductor components,particularly at elevated voltage levels.Addressing these shortcomings,thiswork presents a robust 15-level PackedUCell(PUC)inverter topology designed for renewable energy and grid-connected applications.The proposed systemintegrates a sensor less proportional-resonant(PR)controller with an advanced carrier-based pulse width modulation scheme.This approach efficiently balances capacitor voltage,minimizes steady-state error,and strongly suppresses both zero and third-order harmonics resulting in reduced total harmonic distortion and enhanced voltage regulation.Additionally,a novel switching algorithm simplifies the design and implementation,further lowering voltage stress across switches.Extensive simulation results validate the performance under various resistive and resistive-inductive load conditions,demonstrating compliance with IEEE-519 THD standards and robust operation under dynamic changes.The proposed sensorless PR-controlled 15-PUC inverter thus offers a compelling,cost-effective solution for efficient power conversion in next-generation renewable energy systems.
基金supported by the National Natural Science Foundation of China,Nos.82071426,81873784Clinical Cohort Construction Program of Peking University Third Hospital,No.BYSYDL2019002(all to DF)。
文摘Amyotrophic lateral sclerosis is a rare neurodegenerative disease characterized by the involvement of both upper and lower motor neurons.Early bilateral limb involvement significantly affects patients'daily lives and may lead them to be confined to bed.However,the effect of upper and lower motor neuron impairment and other risk factors on bilateral limb involvement is unclear.To address this issue,we retrospectively collected data from 586 amyotrophic lateral sclerosis patients with limb onset diagnosed at Peking University Third Hospital between January 2020 and May 2022.A univariate analysis revealed no significant differences in the time intervals of spread in different directions between individuals with upper motor neuron-dominant amyotrophic lateral sclerosis and those with classic amyotrophic lateral sclerosis.We used causal directed acyclic graphs for risk factor determination and Cox proportional hazards models to investigate the association between the duration of bilateral limb involvement and clinical baseline characteristics in amyotrophic lateral sclerosis patients.Multiple factor analyses revealed that higher upper motor neuron scores(hazard ratio[HR]=1.05,95%confidence interval[CI]=1.01–1.09,P=0.018),onset in the left limb(HR=0.72,95%CI=0.58–0.89,P=0.002),and a horizontal pattern of progression(HR=0.46,95%CI=0.37–0.58,P<0.001)were risk factors for a shorter interval until bilateral limb involvement.The results demonstrated that a greater degree of upper motor neuron involvement might cause contralateral limb involvement to progress more quickly in limb-onset amyotrophic lateral sclerosis patients.These findings may improve the management of amyotrophic lateral sclerosis patients with limb onset and the prediction of patient prognosis.
文摘Background: Maternal mortality remains a major public health problem worldwide. Objectives: Our study aims to present the results of an analysis of reviews of maternal deaths at HGOPY. Methodology: This was a descriptive cross-sectional study with retrospective data collection from archived records and reviewed maternal death reports. Our study lasted 8 months, from October 1, 2023 to May 31, 2024. The study covered maternal death files at the HGOPY over an 8-year period, from 1st of January 2016 to the 31st of December 2023. Data were processed and analyzed using Statitical Paquage for Social Science (SPSS) version 26.0. Results: We counted a total of 160 maternal deaths, of which 97 had been reviewed. We excluded 61 deceased women reviewed and retained 33. We recorded a cumulative total of 160 maternal deaths and 19,651 live births. The peak in the proportion of maternal deaths at the Yaoundé Gynaeco-Obstetric and Paediatric Hospital was in 2021, with a proportion of 0.013. No maternal deaths had been reviewed between 2016 to 2017. Most deaths (64%) occurred between 37 and 40 weeks. The majority (30.5%) were aged between 30 and 35. The data show that 80.6% of maternal deaths were due to direct obstetric causes, while 19.4% were due to indirect causes. Most deaths (69.4%) were preventable. Only 8.3% were not preventable. Conclusion: Concerted efforts must be made to adapt maternal death prevention and management strategies to local contexts in order to significantly reduce these alarming figures.
基金Hubei Provincial Natural Science Foundation Innovation and Development Joint Fund Project(2025AFD278)Three Gorges University Scientific Fund Project(2022kj008)Three Gorges University Special Scientific Fund Project(2023kjzx001)。
文摘Objective:To utilize the VigiAccess database for data mining to analyze the characteristics of adverse reactions induced by mirogabalin,providing critical information for clinical medication use.Method:This study analyzed data from the VigiAccess database,filtering out adverse reaction reports where mirogabalin was identified as the Primary Suspect Drug(PS).Reporting Odds Ratio(ROR),Proportional Reporting Ratio(PRR),Bayesian Confidence Propagation Neural Network(BCPNN),and Empirical Bayes Geometric Mean(EBGM)methods were employed as data mining algorithms for pharmacovigilance and adverse event monitoring.These methods identify potential drug-adverse event association signals by analyzing the relationship between drug use and adverse event reporting.ROR and PRR focus on calculating reporting ratios,while BCPNN and EBGM use neural networks and empirical Bayes models,respectively,to enhance the accuracy and reliability of signal detection.Results:A total of 734 adverse reaction reports associated with mirogabalin were obtained.The results showed that females reported the highest number of adverse reactions,accounting for 59.67%,while males accounted for 38.83%.In terms of age distribution,the highest number of reports came from individuals over 75 years old,accounting for 33.79%.Adverse reactions mainly involved the nervous system(33.45%),general diseases and reactions at the site of administration(11.62%),and gastrointestinal disorders(10.74%).The most common adverse reactions included dizziness(11.62%),somnolence(8.27%),renal dysfunction(2.90%),and edema(2.82%).Signal intensity analysis revealed that certain adverse reactions(such as renal dysfunction,rhabdomyolysis,and drug-induced liver injury)had significant signal strength,suggesting a strong association with mirogabalin.Conclusion:This study,through signal mining of the VigiAccess database,reveals the characteristics of mirogabalin’s adverse reactions in the real world,particularly in the nervous system and renal function.These findings provide important reference information for clinicians,aiding in the optimization of the safe use of mirogabalin.Future research should further validate the causal relationships of these signals and explore individualized treatment strategies to reduce the incidence of adverse reactions and improve patient outcomes.
基金Natural Science Foundation of Heilongjiang Province of China(Grant No.YQ2022F012)the Fundamental Research Funds for the Central Universities(Grant No.HIT.OCEF.2023010)to provide fund for conducting experiments.
文摘Aiming at the missile avoidance problem of the unmanned aerial vehicle(UAV)in complex obstacle environments,this work proposes a collision-avoidance method based on receding horizon optimization.The proposed method generated a specific trajectory for the UAV to effectively induce the proportional navigation missile to successfully intercept the obstacle,thereby accomplishing the evasive maneuver.The evasive maneuver was divided into two distinct stages,namely the collision-inducing phase and the fast departure phase.The obstacle potential field-based target selection algorithm was employed to identify the most appropriate target obstacle,while the induced trajectory was determined through a combination of receding horizon optimization and the hp-adaptive pseudo-spectral method.Simulation experiments were carried out under three different types of obstacle environments and one multiobstacle environment,and the simulation results show that the method proposed in this paper greatly improves the success rate of UAV evasive maneuvers,proving the effectiveness of this method.
基金Supported by the Shandong Provincial Natural Science Foundation(No.ZR2020QC043)。
文摘The abundance of live and dead Oithona similis in Jiaozhou Bay,Shandong,China,was investigated monthly from December 2008 to November 2009 via the neutral red staining method.The annual variation in total abundance was similar for females,males,and copepodites,with a main numerical peak from February to July and a minor peak in November,but the variations in carcass abundance and death proportion were different.The monthly average abundance of male and copepodite carcasses significantly increased with their total abundance(P<0.001),whereas no such correlation was observed for females.The abundance of female carcasses peaked at 12.4 inds./m^(3) in November but remained below 3.0 inds./m^(3) in all other months.The monthly average death proportion ranged 0.3%-4.9% for females,3.6%-25.7% for males,and 2.6%-8.4% for copepodites.On average,the death proportion of males was 9.2 times greater than that of females and 3.5 times greater than that of copepodites.Therefore,significant sexual difference exists in the non-predatory mortality of O.similis and this difference is an important cause of the female-skewed sex ratios observed in the field.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFF0801304)Philosophy and Social Science Foundation of China(Grant No.23BRK011,24CTJ021)+3 种基金the Humanities and Social Sciences Research Planning Fund of the Ministry of Education,China(Grant No.22YJAZH020)Shaanxi Provincial Social Science Foundation(Grant No.2024D041)Graduate Innovation Funds of Xi’an University of Finance and Economics(Grant No.23YC011)the Youth Innovation Team of Shaanxi Universities,China。
文摘The Loess Plateau region in China is characterized by a fragile environment,where vegetation is susceptible to both natural variations and anthropogenic influences.Previous research has indicated a greening trend in vegetation across the Loess Plateau over the past two decades.However,the specific contributions of natural and anthropogenic drivers,both individually and interactively,to vegetation distribution remain unclear.To address this gap,we conducted a study using Shaanxi Province as a case area.Utilizing multisource data,we employed the Geographical Detector Model(GDM)to analyze the impacts of natural and human related factors on vegetation distribution.Our analysis revealed that the average NDVI(Normalized Difference Vegetation Index)increased at a rate of 0.006 per year from 2000 to 2021.Notably,88.8%of the region experienced vegetation greening,while 4.5%showed significant declines in NDVI,particularly in areas,such as Xi'an,Weinan,Baoji,Hanzhong,and Ankang.Furthermore,NDVI trend projections suggest that the area undergoing vegetation degradation may surpass the area showing improvement in the future.The study identified that vegetation distribution was influenced by both natural and anthropogenic factors for the whole study area.Precipitation,surface types and land use type were the primary factors with q values above 0.5.During the study period,impacts of GDP,nighttime lights and population density among anthropogenic factors on vegetation distribution increased by 130%,125%and 41%,respectively.Conversely,except for slope and aspect,natural factors'influence on vegetation distribution declined by 5%to 26%.The impact of driving factors on NDVI distribution varied across ecological regions.In Fenwei Basin Agro-Ecoregion(EcoregionⅢ),the influence of anthropogenic factors on vegetation distribution was greater than that in the other three ecoregions.Precipitation primarily affected the vegetation distribution in Loess Plateau Agricultural and Grassland Ecoregion(EcoregionⅡ).Additionally,the combined interactive effects of factors had a stronger influence on NDVI distribution than any single factor.These findings provide valuable insights for local governments in Shaanxi Province to develop targeted ecological restoration and environmental management policies.
基金support provided by the Natural Science Foundation of China(Grant No.52208240)S&T Program of Hebei(Grant No.E2022202051,236Z3809G)+1 种基金Education Department of Hebei Province(Grant No.:C20220311)Hebei University of Technology(Grant No.:24/424132021).
文摘Ternary geopolymers incorporating multiple solid wastes such as steel slag(SS),fly ash(FA),and granulated blast furnace slag(GBFS)are considered environmentally friendly and exhibit enhanced performance.However,the mechanisms governing strength development and the design of optimal mixtures are not fully understood due to the complexity of their components.This study presents the development of four machine learning mod-els-Artificial Neural Network(ANN),Support Vector Regression(SVR),Extremely Randomized Tree(ERT),and Gradient Boosting Regression(GBR)-for predicting the unconfined compressive strength(UCS)of ternary geopolymers.The models were trained using a dataset comprising 120 mixtures derived from laboratory tests.Shapley Additive Explanations analysis was employed to interpret the machine learning models and elucidate the influence of different components on the properties of ternary geopolymers.The results indicate that ANN ex-hibits the highest predictive accuracy for UCS(R=0.949).Furthermore,the UCS of ternary geopolymers is most sensitive to the content of GBFS.This study provides valuable insights for optimizing the mix proportions in ternary blended geopolymer mixtures.
基金Supported by National Natural Science Foundation of China(Grant Nos.51975524,52375067)Zhejiang Provincial Natural Science Foundation of China(Grant No.Y23E050014).
文摘Magnetization convenience is crucial consideration for design of valve magnetic actuators.The existing repulsive-magnetic-coupling of 2D maglev valve is not oriented to the integral-magnetization-processes,resulting in the high assembly cost.This paper presents a novel tractive-magnetic-coupling(TMC)and its application on a 2D electro-hydraulic proportional flow valve(2D-EHPFV),whose configuration not only fulfill the requirements of 2D valve,but also oriented to integral-magnetization-process.To investigate the output torque of TMC,a detailed analytical model considering leakage flux,edge effect and tooth magnetic saturation is formulated based on the equivalent magnetic circuit method.To facilitate the magnetic saturation calculation,a special magnetic permeability database is established for tooth region of TMC using Ansoft/Maxwell software.Prototype of TMC is machined and an exclusive experimental platform is built.Torque-displacement characteristics under different working airgap and tooth number are measured.The experimental results are in good agreement with the analytical results,which verifies the correctness of the analytical model.Then the TMC is integrated into the 2D-EHPFV by replacing the repulsive-magnetic-coupling.Prototype of 2D-EHPFV is designed and manufactured to test the no-load flow characteristics,load flow characteristics,leakage characteristics,frequency characteristics and step response.Under working pressure of 15 MPa,the maximum no-load flow rate is 82.2 L/min with the hysteresis of 2.6%,and the amplitude and phase frequency width is 21.6 Hz,and 28.9 Hz.The detailed experimental results show that TMC can be applied to 2D valves to form 2D-EHPFV,which can reduce hysteresis and cost,and improve response speed.
基金jointly supported by the National Natural Science Foundation of China (42230513)Key Program of the Shaanxi Key Laboratory of Environmental Monitoring and Forewarning of Trace Pollutants (SHJKFJJ 202307)Research Project on Ecological Protection and High-Quality Development in the Yellow River Basin,China (2022-YRUC-01-0101)。
文摘Increasing concerns regarding aquatic ecological health and eutrophication driven by urbanization and human activities have highlighted the need to understand primary productivity(PP)dynamics in aquatic ecosystems. This study investigated the spatial distribution of PP across the Weihe River Basin, China using inverse distance weighting and analyzed the influence of different land uses and water physical-chemical parameters on PP using Mantel test and Spearman analysis. Significantly spatial heterogeneity in PP concentrations, ranging from 0.458 to 3262.807 mg C/(m^(2)·d), was observed with high-PP sites clustered in the middle-lower reaches dominated by farmland-construction land mosaics.Core drivers included light availability(Secchi depth and sunlight duration) and phytoplankton biomass(chlorophyll-a(Chl-a)), while water temperature exhibited threshold-dependent effects. Total organic carbon played dual roles, promoting PP concentrations in low-Chl-a regions, but suppressing it under high-Chl-a regions. Dual-scale buffer analysis(500 and 1000 m buffer zones) revealed PP heterogeneity stemed from interactive land use configurations, rather than isolated types. Balanced construction land-to-farmland ratio(0.467–2.890) elevated PP concentrations in human-dominated basins(the main stem of the Weihe River and Jinghe River), whereas excessive agricultural homogenization reduced PP likely due to fertilizer saturation and algal self-shading. Ecologically sensitive basins(the Beiluohe River Basin) demonstrated distinct patterns, in which PP concentration was regulated through natural-agricultural synergies. These results deepened the understanding of land use effects on aquatic PP,providing a theoretical basis for optimizing land use strategies to reconcile eutrophication control with ecological productivity in human-stressed basins.
基金supported by the National Natural Science Foundation of China(Grant No.61802301)awarded to J.Lithe Postgraduate Innovation Fund Project of Xi’an Shiyou University(Grant No.YCX2513159).
文摘The long transaction latency and low throughput of blockchain are the key challenges affecting the large-scale adoption of blockchain technology. Sharding technology is a primary solution by divides the blockchain network into multiple independent shards for parallel transaction processing. However, most existing random or modular schemes fail to consider the transactional relationships between accounts, which leads to a high proportion of cross-shard transactions, thereby increasing the communication overhead and transaction confirmation latency between shards. To solve this problem, this paper proposes a blockchain sharding algorithm based on account degree and frequency (DFSA). The algorithm takes into account both account degree and weight relationships between accounts. The blockchain transaction network is modeled as an undirected weighted graph, and community detection algorithms are employed to analyze the correlations between accounts. Strong-correlated accounts are grouped into the same shard, and a multi-shard blockchain network is constructed. Additionally, to further reduce the number of cross-shard transactions, this paper designs a random redundancy strategy based on account correlation, which randomly selects strong-correlated accounts and stores them redundantly in another shard, thus original cross-shard transactions can be verified and confirmed within the same shard. Simulation experiments demonstrate that DFSA outperforms the random sharding algorithm (RSA), modular sharding algorithm (MSA), and label propagation algorithm (LPA) in terms of cross-shard transaction proportion, latency, and throughput. Therefore, DFSA can effectively reduce cross-shard transaction proportion and lower transaction confirmation latency.
基金supported by Social Science Fund of Hunan province(Grant No.22JD074)the Research Foundation of Education Bureau of Hunan province(Grant No.22B0912).
文摘In this paper, a class of discontinuous neutral-type neural networks (NTNNs) with proportional delays is considered. The targets of the paper are to study the problem of periodic solutions and fixed-time (FXT) stabilization of the addressed neural networks. In order to complete the targets, based on set-valued map, differential inclusions theory, coincidence theorem and Hölder inequality technique, some new proportional delay-dependent criteria shown by the inequalities are derived. Based on the fact of the existence of solution, further by applying the FXT stability lemmas and equivalent transformation, the zero solution of closed-loop system achieves FXT stabilization and the corresponding settling-times are estimated. Some previous related works on NTNNs are extended. Finally, one typical example is provided to show the effectiveness of the established results.
基金supported by the German Federal Ministry of Food and Agriculture(BMEL)and the German Federal Ministry for the Environment,Nature Conservation,Nuclear Safety and Consumer Protection(BMUV)via the Agency for Renewable Resources(FNR)(GRANT no.2220WK49E3)。
文摘Norway spruce(Picea abies(L.)Karst.)in the Harz Mountains National Park(Germany)has experienced widespread mortality(>97%of trees in the study stands)due to infestation with the large spruce bark beetle(Ips typographus L.).The dead trees(snags)remain standing in the forest for 2-5 years before harvesting.It is important to identify trees that can still produce quality timber,which may be achieved by examining their outer appearance using selected characteristics.The aim of this study was to identify possible correlations between the standing storage duration and defined external characteristics of the snags.The mean tree height at compartment level was calculated using a vegetation height model,based on light detection and ranging data from 2018,to derive the stem breakage proportion.The condition of the crown and the bark and presence of fungi,wood rot,stem cracks and bark stripping damage were also assessed.The majority of the snags were broken at least once.Windthrows were less likely compared to living spruce trees because of reduced resistance to the wind as a result of needle loss and breakage.The mean stem breakage proportion increased significantly with the duration of the standing storage;however,prolonged storage durations did not always lead to complete breakage.The occurrence of fungal fruiting bodies was significantly correlated with a higher proportion of stem breakage,and the longer the storage,the more snags had fungal fruiting bodies.The condition of the crown,assessed by the presence of branchlets,was a good indicator of the duration of the standing storage.If trees had few or no branchlets,they had been standing for at least 4 years.Overall,this initial description of the external appearance of spruce trees that have been stored standing for many years suggests that time significantly influences the tree condition and breakage intensity,which is reflected by certain tree characteristics.Future studies should examine these aspects in greater depth,particularly with regard to utilization options and safety during timber harvesting.
基金the National Key Research and Development Program of China(Nos.2021YFC2202800 and 2021YFC2202604)the Opening Project of the Key Laboratory of Microgravity of the Chinese Academy of Sciences(No.NML202401)+1 种基金the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2023022)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA1502110105)。
文摘The Taiji program is focused on achieving space-based gravitational wave detection in the frequency range of 0.1 mHz-1 Hz.To achieve drag-free control,Taiji satellites must be equipped with micro-thrusters that satisfy stringent requirements,including a continuously adjustable thrust,thrust resolution of 0.1μN,thrust noise of 0.1μN·Hz^(-0.5)and response time of less than 100 ms.This paper presents the progress of a variable cold gas micro-thruster being developed for the Taiji program.A series of technologies such as a bidirectional piezoelectric drive,spherical valve core,conical nozzle seal,miniature gas chamber,high thruster integration,combined digital and analogue communication and high-frequency closed-loop thrust control were employed to achieve engineering prototypes of a low-noise and fast-response micro-thruster.Ground performance tests indicate that the micro-thruster achieved a minimum thrust of close to 1.1 nN,a thrust resolution of 0.05μN and a maximum specific impulse of 69.1 s using nitrogen gas as the working fluid.The thrust noise was less than 0.1μN·Hz^(-0.5)in the frequency band of 10 mHz-1 Hz,and the thrust response time was 140 ms.The control parameters were further optimised to achieve a flow response time of 50 ms.The results indicate that the developed micro-thruster essentially met the performance requirements for drag-free control to facilitate space-based gravitational wave detection.
文摘This study introduces a novel mathematical model to describe the progression of cholera by integrating fractional derivatives with both singular and non-singular kernels alongside stochastic differential equations over four distinct time intervals.The model incorporates three key fractional derivatives:the Caputo-Fabrizio fractional derivative with a non-singular kernel,the Caputo proportional constant fractional derivative with a singular kernel,and the Atangana-Baleanu fractional derivative with a non-singular kernel.We analyze the stability of the core model and apply various numerical methods to approximate the proposed crossover model.To achieve this,the approximation of Caputo proportional constant fractional derivative with Grünwald-Letnikov nonstandard finite difference method is used for the deterministic model with a singular kernel,while the Toufik-Atangana method is employed for models involving a non-singular Mittag-Leffler kernel.Additionally,the integral Caputo-Fabrizio approximation and a two-step Lagrange polynomial are utilized to approximate the model with a non-singular exponential decay kernel.For the stochastic component,the Milstein method is implemented to approximate the stochastic differential equations.The stability and effectiveness of the proposed model and methodologies are validated through numerical simulations and comparisons with real-world cholera data from Yemen.The results confirm the reliability and practical applicability of the model,providing strong theoretical and empirical support for the approach.
文摘Critical Height Sampling(CHS)estimates stand volume free from any model and tree form assumptions.Despite its introduction more than four decades ago,CHS has not been widely applied in the field due to perceived challenges in measurement.The objectives of this study were to compare estimated stand volume between CHS and sampling methods that used volume or taper models,the equivalence of the sampling methods,and their relative efficiency.We established 65 field plots in planted forests of two coniferous tree species.We estimated stand volume for a range of Basal Area Factors(BAFs).Results showed that CHS produced the most similar mean stand volume across BAFs and tree species with maximum differences between BAFs of 5-18m^(3)·ha^(−1).Horizontal Point Sampling(HPS)using volume models produced very large variability in mean stand volume across BAFs with the differences up to 126m^(3)·ha^(−1).However,CHS was less precise and less efficient than HPS.Furthermore,none of the sampling methods were statistically interchangeable with CHS at an allowable tolerance of≤55m^(3)·ha^(−1).About 72%of critical height measurements were below crown base indicating that critical height was more accessible to measurement than expected.Our study suggests that the consistency in the mean estimates of CHS is a major advantage when planning a forest inventory.When checking against CHS,results hint that HPS estimates might contain potential model bias.These strengths of CHS could outweigh its lower precision.Our study also implies serious implications in financial terms when choosing a sampling method.Lastly,CHS could potentially benefit forest management as an alternate option of estimating stand volume when volume or taper models are lacking or are not reliable.
