Jasmine(Jasminum sambac Aiton)is a well-known cultivated plant species for its fragrant flowers used in the perfume industry and cosmetics.However,the genetic basis of its floral scent is largely unknown.In this study...Jasmine(Jasminum sambac Aiton)is a well-known cultivated plant species for its fragrant flowers used in the perfume industry and cosmetics.However,the genetic basis of its floral scent is largely unknown.In this study,using PacBio,Illumina,10×Genomics and highthroughput chromosome conformation capture(Hi-C)sequencing technologies,a high-quality chromosome-level reference genome for J.sambac was obtained,exploiting a double-petal phenotype cultivar‘Shuangbanmoli’(JSSB).The results showed that the final assembled genome of JSSB is 580.33 Mb in size(contig N50=1.05 Mb;scaffold N50=45.07 Mb)with a total of 39618 predicted protein-coding genes.Our analyses revealed that the JSSB genome has undergone an ancient whole-genome duplication(WGD)event at 91.68 million years ago(Mya).It was estimated that J.sambac diverged from the lineage leading to Olea europaea and Osmanthus fragrans about 28.8 Mya.On the basis of a combination of genomic,transcriptomic and metabolomic analyses,a range of floral scent volatiles and genes were identified involved in the benzenoid/phenylpropanoid and terpenoid biosynthesis pathways.The results provide new insights into the molecular mechanism of its fragrance biosynthesis in jasmine.展开更多
The performance characteristics,particularly the starting performance of direct line-fed induction motors,which are mainly influenced by the design of the rotor,are crucial considerations for end-users.It is quite a c...The performance characteristics,particularly the starting performance of direct line-fed induction motors,which are mainly influenced by the design of the rotor,are crucial considerations for end-users.It is quite a challenging issue for motor manufacturers to enhance the starting performance of existing mass-produced motors with minimal modifications and expenses.In this paper,a simple and cost-effective method to improve the starting performance of a commercial squirrel-cage induction motor(SCIM)is proposed.The influence of geometric parameters of the end-ring on the performance characteristics,including starting(locked rotor)torque,pull-up and break down torque,starting current,rotor electric parameters,current density,power losses,and efficiency have been comprehensively investigated.It has been revealed that among the other end-ring design parameters,the ring thickness has a significant effect on the performance characteristics.An optimal end-ring thickness is determined,and its performance characteristics have been compared to those of its initial counterpart.Numeric and parametric analyses have been conducted using a 2D time-stepping finite element method(FEM).The FEM results were validated using experimental measurements obtained from an 11 kW SCIM prototype.展开更多
The harmonics that appear in the squirrel cage asynchronous machine have been discussed in great detail in the literature for a long time. However, the systematization of the phenomenon is still pending, so we made an...The harmonics that appear in the squirrel cage asynchronous machine have been discussed in great detail in the literature for a long time. However, the systematization of the phenomenon is still pending, so we made an attempt to fill this gap in the previous parts of our study by elaborating formulas for calculation of parasitic torques. It was a general demand among those who work in this field towards the author to verify his formulas with measurements. In the literature, it seems,only one detailed, purposeful series of measurements has been published so far, the purpose of which was to investigate the effect of the number of rotor slots on the torque-speed characteristic curve of the machine. The main goal of this study is to verify the correctness of the formulas by comparing them with the referred series of measurements. Relying on this, the expected synchronous parasitic torques were developed for the frequently used rotor slot numbers-as a design guide for the engineer.Thus, together with our complete table for radial magnetic pull published in our previous work, the designer has all the principles, data and formulas available for the right number of rotor slots for his given machine and for the drive system. This brings this series of papers to an end.展开更多
Flower constancy describes the phenomenon that pollinators tend to successively visit flowers of a single species during foraging,reducing reproductive interference in natural communities.The extent of flower constanc...Flower constancy describes the phenomenon that pollinators tend to successively visit flowers of a single species during foraging,reducing reproductive interference in natural communities.The extent of flower constancy is largely determined by the floral traits of co-flowering species.Both higher inter-specific and lower intraspecific differences of floral traits should contribute to a higher level of flower constancy.However,previous studies mainly focused on interspecific difference,and the intraspecific variation(consistency)of floral traits received much less attention.We hypothesise that selection may favour lower intraspecific floral trait variation in communities composed of multiple co-flowering congeners.We investigated the floral colour variation of three focal Pedicularis species that share pollinators in 19communities composed of either single or multiple Pedicularis species.Colour was quantified using image-based colour analysis as perceived by pollinators.We found that most of the intrapopulation floral colour variation was below the colour discrimination threshold of bumblebees,implying strongly constrained by the visual selection by pollinators.Contrary to the hypothesis,there is no significant difference in intraspecific floral colour variation between different community contexts.It may be due to the relatively large interspecific floral colour differences of most co-flowering species.The influence of community context on intraspecific variation may be reflected in floral traits other than colours.展开更多
Cemented tailings backfill(CTB)not only boosts mining safety and cuts surface environmental pollution but also recovers ores previously retained as pillars,thereby improving resource utilization.The use of alternative...Cemented tailings backfill(CTB)not only boosts mining safety and cuts surface environmental pollution but also recovers ores previously retained as pillars,thereby improving resource utilization.The use of alternative reinforcing products,such as steel fiber(SF),has continuously strengthened CTB into SFCTB.This approach prevents strength decreases over time and reinforces its long-term durability,especially when mining ore in adjacent underground stopes.In this study,various microstructure and strength tests were performed on SFCTB,considering steel fiber ratio and electromagnetic induction strength effects.Lab findings show that combining steel fibers and their distribution dominantly influences the improvement of the fill’s strength.Fill’s strength rises by fiber insertion and has an evident correlation with fiber insertion and magnetic induction strength.When magnetic induction strength is 3×10^(-4) T,peak uniaxial compressive stress reaches 5.73 MPa for a fiber ratio of 2.0vol%.The cracks’expansion mainly started from the specimen’s upper part,which steadily expanded downward by increasing the load until damage occurred.The doping of steel fiber and its directional distribution delayed crack development.When the doping of steel fiber was 2.0vol%,SFCTBs showed excellent ductility characteristics.The energy required for fills to reach destruction increases when steel-fiber insertion and magnetic induction strength increase.This study provides notional references for steel fibers as underground filling additives to enhance the fill’s durability in the course of mining operations.展开更多
The floral organ morphology,pollen morphology,quantity,and viability of Rumex,Rumex hanus F1,Rumex hanus 1,and Rumex hanus 2 were compared and analyzed.The results showed that the longitudinal diameter of petals was n...The floral organ morphology,pollen morphology,quantity,and viability of Rumex,Rumex hanus F1,Rumex hanus 1,and Rumex hanus 2 were compared and analyzed.The results showed that the longitudinal diameter of petals was not significantly different among different varieties of sorrel,and the transverse diameter and corolla diameter showed differences to varying degrees.They all had six stamens and three stigmas.The pollen shape of the four varieties was prolate,and the polar view was trilobated and round.They all had three germinal furrows,and the outer wall of the pollen was decorated with small cavities and spiny patterns,with warty protrusions.The equatorial axis length of pollen of different varieties of sorrel was significantly different(P<0.05).There were no significant differences in pollen amount among different varieties.There were six anthers in a single flower,featuring anther dehiscence.The pollen viability of Rumex hanus 1 was significantly lower than that of the other three varieties(P<0.05).Therefore,through the analysis of the floral organs and morphological characteristics of anthers of sorrel,the varieties of sorrel can be effectively distinguished and identified.展开更多
As the core component of energy conversion for large wind turbines,the output performance of doubly-fed induction generators (DFIGs) plays a decisive role in the power quality of wind turbines.To realize the fast and ...As the core component of energy conversion for large wind turbines,the output performance of doubly-fed induction generators (DFIGs) plays a decisive role in the power quality of wind turbines.To realize the fast and accurate design optimization of DFIGs,this paper proposes a novel hybriddriven surrogate-assisted optimization method.It firstly establishes an accurate subdomain model of DFIGs to analytically predict performance indexes.Furthermore,taking the inexpensive analytical dataset produced by the subdomain model as the source domain and the expensive finite element analysis dataset as the target domain,a high-precision surrogate model is trained in a transfer learning way and used for the subsequent multi-objective optimization process.Based on this model,taking the total harmonic distortion of electromotive force,cogging torque,and iron loss as objectives,and the slot and inner/outer diameters as parameters for optimizing the topology,achieve a rapid and accurate electromagnetic design for DFIGs.Finally,experiments are carried out on a 3MW DFIG to validate the effectiveness of the proposed method.展开更多
Increasing attention has been paid to the efficiency improvement of the induction traction system of high-speed trains due to the high demand for energy saving. In emergency self-propelled mode, however, the dc-link v...Increasing attention has been paid to the efficiency improvement of the induction traction system of high-speed trains due to the high demand for energy saving. In emergency self-propelled mode, however, the dc-link voltage and the traction power of the motor are significantly reduced, resulting in decreased traction efficiency due to the low load and low speed operations. Aiming to tackle this problem, a novel efficiency improved control method is introduced to the emergency mode of high-speed train traction system in this paper. In the proposed method, a total loss model of induction motor considering the behaviors of both iron and copper loss is established. An improved iterative algorithm with decreased computational burden is then introduced, resulting in a fast solving of the optimal flux reference for loss minimization at each control period. In addition, considering the parameter variation problem due to the low load and low speed operations, a parameter estimation method is integrated to improve the controller's robustness. The effectiveness of the proposed method on efficiency improvement at low voltage and low load conditions is demonstrated by simulated and experimental results.展开更多
In this paper,a stable and adaptive sliding mode control(SMC)method for induction motors is introduced.Determining the parameters of this system has been one of the existing challenges.To solve this challenge,a new se...In this paper,a stable and adaptive sliding mode control(SMC)method for induction motors is introduced.Determining the parameters of this system has been one of the existing challenges.To solve this challenge,a new self-tuning type-2 fuzzy neural network calculates and updates the control system parameters with a fast mechanism.According to the dynamic changes of the system,in addition to the parameters of the SMC,the parameters of the type-2 fuzzy neural network are also updated online.The conditions for guaranteeing the convergence and stability of the control system are provided.In the simulation part,in order to test the proposed method,several uncertain models and load torque have been applied.Also,the results have been compared to the SMC based on the type-1 fuzzy system,the traditional SMC,and the PI controller.The average RMSE in different scenarios,for type-2 fuzzy SMC,is 0.0311,for type-1 fuzzy SMC is 0.0497,for traditional SMC is 0.0778,and finally for PI controller is 0.0997.展开更多
Magnetohydrodynamic(MHD)induction pumps are contactless pumps able to withstand harsh environments.The rate of fluid flow through the pump directly affects the efficiency and stability of the device.To explore the inf...Magnetohydrodynamic(MHD)induction pumps are contactless pumps able to withstand harsh environments.The rate of fluid flow through the pump directly affects the efficiency and stability of the device.To explore the influence of induction pump settings on the related delivery speed,in this study,a numerical model for coupled electromagnetic and flow field effects is introduced and used to simulate liquid metal lithium flow in the induction pump.The effects of current intensity,frequency,coil turns and coil winding size on the velocity of the working fluid are analyzed.It is shown that the first three parameters have a significant impact,while changes in the coil turns have a negligible influence.The maximum increase in working fluid velocity within the pump for the parameter combination investigated in this paper is approximately 618%.As the frequency is increased from 20 to 60 Hz,the maximum increase in the mean flow rate of the working fluid is approximately 241%.These research findings are intended to support the design and optimization of these devices.展开更多
This article proposes a dual-negative-objective coordinated control strategy for brushless doubly fed induction generator(BDFIG)based wind power generation system under unbalanced grid voltage.To alleviate the mechani...This article proposes a dual-negative-objective coordinated control strategy for brushless doubly fed induction generator(BDFIG)based wind power generation system under unbalanced grid voltage.To alleviate the mechanical stress and impaction on rotating shaft,the negative control objective(NCO)of machine side converter(MSC)is set to suppress the ripple of electromagnetic torque.While the NCO of grid side converter(GSC)is selected to suppress the oscillation of total output active power or the unbalanced degree of total output current for BDFIG generation system.In comparison with traditional single converter control scheme of the MSC or GSC,dual NCOs can be satisfied at the same time due to the enlarged freedom degree in the proposed improved coordinated control system for back-toback converters.The effectiveness of proposed control strategy is validated by simulation and experimental results on a dual-cagerotor BDFIG(DCR-BDFIG)prototype.展开更多
Objective: The objective of this study was to determine if early rupture of membranes (ROM) in women undergoing induction of labor (IOL) at term is associated with an increased rate of clinical chorioamnionitis. Study...Objective: The objective of this study was to determine if early rupture of membranes (ROM) in women undergoing induction of labor (IOL) at term is associated with an increased rate of clinical chorioamnionitis. Study Design: A retrospective cohort study was performed on women undergoing IOL. Early ROM was defined as ROM at a modified Bishop score less than 5, cervical dilation less than 4 cm, or cervical effacement less than 80%. The rate of clinical chorioamnionitis was compared between women with early and late ROM. Results: The rate of clinical chorioamnionitis was 8.6% (24/279). ROM at an effacement of less than 80% was associated with a rate of clinical chorioamnionitis of 15.4% (12/78) compared to 6.0% (12/201) at an effacement of equal to or greater than 80%, p = 0.017. The rate of cesarean delivery was higher for patients with early ROM by any definition: 32% compared to 17.5% by modified Bishop score (p = 0.031), 32.4% versus 18.2% by cervical dilation (p = 0.049), and 33.3% versus 14.9% by cervical effacement (p = 0.001). Conclusions: In patients undergoing IOL, early ROM may be associated with an increased rate of clinical chorioamnionitis when performed at a cervical effacement of less than 80% and an increased rate of cesarean delivery.展开更多
The induction motor,which converts electrical energy into mechanical energy,has been recognized as the cornerstone of industrialization.The rotor of an induction motor can be either a squirrel cage rotor or a wound-ty...The induction motor,which converts electrical energy into mechanical energy,has been recognized as the cornerstone of industrialization.The rotor of an induction motor can be either a squirrel cage rotor or a wound-type rotor,both existing as magnetless topologies.Three-phase squirrel cage induction motors are frequently utilized in industrial drives because they are dependable,have high starting torque,are selfstarting and affordable.Single-phase induction motors,on the other hand,are commonly used for small loads such as domestic appliances in form of modest fans,pumps and electric power tools.In South Africa,there have been reports of fires and explosions resulting in live and property loss because of induction motors that have not been thoroughly tested or are incorrectly labelled in terms of ratings,electrical safety and performance.The goal of this study is targeted at preventing end-user injuries and failures caused by non-compliant induction motors,by evaluating locally manufactured/imported induction motors based on tests and evaluation from standards(IEC and SANS).The study is conducted using experimental procedures at the Explosion Prevention Technology and Rotating Machines(EPT and RM)laboratory,South African Bureau of Standards(SABS),South Africa.The main finding from the study shows differences in the nameplate characteristics of various induction motors which could have detrimental effects such as production and operational downtime in their end-use industries,at later stages.展开更多
In the context of induction motor control, there are various control strategies used to separately control torque and flux. One common approach is known as Field-Oriented Control (FOC). This technique involves transfo...In the context of induction motor control, there are various control strategies used to separately control torque and flux. One common approach is known as Field-Oriented Control (FOC). This technique involves transforming the three-phase currents and voltages into a rotating reference frame, commonly referred to as the “dq” frame. In this frame, the torque/speed and flux components are decoupled, allowing for independent control, by doing so, the motor’s speed can be regulated accurately and maintain a constant flux which is crucial to ensure optimal motor performance and efficiency. The research focused on studying and simulating a field-oriented control system using fuzzy control techniques for an induction motor. The aim was to address the issue of parameter variations, particularly the change in rotor resistance during motor operation, which causes the control system to deviate from the desired direction. This deviation implies to an increase in the magnetic flux value, specifically the flux component on the q-axis. By employing fuzzy logic techniques to regulate flux vector’s components in the dq frame, this problem was successfully resolved, ensuring that the magnetic flux value remains within the nominal limits. To enhance the control system’s performance, response speed, and efficiency of the motor, sliding mode controllers were implemented to regulate the current in the inner loop. The simulation results demonstrated the proficiency of the proposed methodology.展开更多
The present paper is finalized to show that the Science, even if considered in its two different Phenomenological Approaches at present known, is unable to assert that: “Thinks are like that”. This is because both t...The present paper is finalized to show that the Science, even if considered in its two different Phenomenological Approaches at present known, is unable to assert that: “Thinks are like that”. This is because both the two Scientific Approaches previously mentioned have not the property of “the perfect induction”. Consequently, although they can even reach an experimental confirmation of the theoretical results, and thus a “valid description” of the various phenomena of the surrounding world, such a description has not an “absolute value”. In fact, it always and only has an “operative validity”, that is, it exclusively and solely refers to an “experimental point of view”. This means that such an “operative validity” cannot represent the basis for a logical process characterized by a “perfect induction”. In addition, the Traditional Scientific Approach is also characterized by “Insoluble” Problems, “Intractable Problems”, Problems with “drifts”, which could generally be termed as “side effects”. On the other hand, the same com-possible Scientific Approach based on the Emerging Quality of Self-Organizing Systems, also presents its “Emerging Exits”. Consequently, none of the two mentioned scientific Approaches has the “gift” of “the perfect induction”. However, there are significant differences between the two. Differences that may “suggest” the most appropriate choice among them for an “operative point of view”. This conclusion will be com-proved by considering, with particular reference, both the “side effects”, which are related to the Traditional Approach and, on the other hand, the “Emerging Exits”, which specifically pertain to the new Scientific Approach based on the Emerging Quality of Self-Organizing Systems.展开更多
Drawing upon the electromagnetic conversion formulas in a continuous conductive medium,an extensive examination for total current law and Faraday’s law of electromagnetic induction(Faraday’s law)is undertaken to exp...Drawing upon the electromagnetic conversion formulas in a continuous conductive medium,an extensive examination for total current law and Faraday’s law of electromagnetic induction(Faraday’s law)is undertaken to expound on the laws of electromagnetic induction and conversion.The longitudinal wave term of Faraday’s law is reinstated to render it suitable for theoretical derivation of the LEM(Longitudinal Electromagnetic Wave)equation.Subsequently,we formulate the wave and energy equations for electric P-wave based on reevaluated total current law and modified Faraday’s law;meanwhile proposing a propagation mode that reveals its mechanisms absorbing free energy for LEM waves in a conductor predicated on interaction between scalar electric field and vortex magnetic field.Furthermore,through theoretical derivations based on LEM waves,insights into concealed relationships between electric P-wave and electromagnetism scalar potential are disclosed alongside the constraint equation between the wave velocities of LEM wave and TEM(Transverse Electromagnetic)waves,unveiling the significance of LEM wave.展开更多
基于聚焦性能对经颅磁线圈的影响,针对聚焦型线圈商用不足的问题,设计一种具有高聚焦性的单通道双梯形双层线圈。首先使用球头模型分析不同尺寸、相同结构的线圈性能,得到较优的线圈尺寸;为进一步提升聚焦度,再以中尺寸线圈为研究目标,...基于聚焦性能对经颅磁线圈的影响,针对聚焦型线圈商用不足的问题,设计一种具有高聚焦性的单通道双梯形双层线圈。首先使用球头模型分析不同尺寸、相同结构的线圈性能,得到较优的线圈尺寸;为进一步提升聚焦度,再以中尺寸线圈为研究目标,探讨五种不同结构的双层线圈与两种商用8字形线圈的性能差异,得到最优线圈的结构;最后使用50组存在个体差异性的真实脑模型进行仿真验证,分析球头模型结果的可靠性。仿真结果表明:使用球头模型时,优化后的新型线圈对比70 mm figure-8 coil的聚焦度提升了69.48%,刺激深度减少了27.18%;对比25 mm figure-8 coil的聚焦度提升了44.78%,刺激深度减少了8.5%;使用50组真实脑模型时,优化后的新型线圈对比70 mm figure-8 coil的聚焦度提升了62.07%,刺激深度减少了25.71%;对比25 mm figure-8 coil的聚焦度提升了39.49%,刺激深度减少了9.5%。两种模型仿真数据结果趋于一致,证实了仿真可靠性的同时也证明了新型线圈具有更强的刺激强度和聚焦度,能大大提升TMS治疗的安全性,减少不适感,同时单通道设计易于实现,具有较高的性能优势。展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.31772338)the Basic Scientific Research Business Special Project of Jiangsu Academy of Agricultural Sciences(Grant No.0090756100ZX)。
文摘Jasmine(Jasminum sambac Aiton)is a well-known cultivated plant species for its fragrant flowers used in the perfume industry and cosmetics.However,the genetic basis of its floral scent is largely unknown.In this study,using PacBio,Illumina,10×Genomics and highthroughput chromosome conformation capture(Hi-C)sequencing technologies,a high-quality chromosome-level reference genome for J.sambac was obtained,exploiting a double-petal phenotype cultivar‘Shuangbanmoli’(JSSB).The results showed that the final assembled genome of JSSB is 580.33 Mb in size(contig N50=1.05 Mb;scaffold N50=45.07 Mb)with a total of 39618 predicted protein-coding genes.Our analyses revealed that the JSSB genome has undergone an ancient whole-genome duplication(WGD)event at 91.68 million years ago(Mya).It was estimated that J.sambac diverged from the lineage leading to Olea europaea and Osmanthus fragrans about 28.8 Mya.On the basis of a combination of genomic,transcriptomic and metabolomic analyses,a range of floral scent volatiles and genes were identified involved in the benzenoid/phenylpropanoid and terpenoid biosynthesis pathways.The results provide new insights into the molecular mechanism of its fragrance biosynthesis in jasmine.
文摘The performance characteristics,particularly the starting performance of direct line-fed induction motors,which are mainly influenced by the design of the rotor,are crucial considerations for end-users.It is quite a challenging issue for motor manufacturers to enhance the starting performance of existing mass-produced motors with minimal modifications and expenses.In this paper,a simple and cost-effective method to improve the starting performance of a commercial squirrel-cage induction motor(SCIM)is proposed.The influence of geometric parameters of the end-ring on the performance characteristics,including starting(locked rotor)torque,pull-up and break down torque,starting current,rotor electric parameters,current density,power losses,and efficiency have been comprehensively investigated.It has been revealed that among the other end-ring design parameters,the ring thickness has a significant effect on the performance characteristics.An optimal end-ring thickness is determined,and its performance characteristics have been compared to those of its initial counterpart.Numeric and parametric analyses have been conducted using a 2D time-stepping finite element method(FEM).The FEM results were validated using experimental measurements obtained from an 11 kW SCIM prototype.
文摘The harmonics that appear in the squirrel cage asynchronous machine have been discussed in great detail in the literature for a long time. However, the systematization of the phenomenon is still pending, so we made an attempt to fill this gap in the previous parts of our study by elaborating formulas for calculation of parasitic torques. It was a general demand among those who work in this field towards the author to verify his formulas with measurements. In the literature, it seems,only one detailed, purposeful series of measurements has been published so far, the purpose of which was to investigate the effect of the number of rotor slots on the torque-speed characteristic curve of the machine. The main goal of this study is to verify the correctness of the formulas by comparing them with the referred series of measurements. Relying on this, the expected synchronous parasitic torques were developed for the frequently used rotor slot numbers-as a design guide for the engineer.Thus, together with our complete table for radial magnetic pull published in our previous work, the designer has all the principles, data and formulas available for the right number of rotor slots for his given machine and for the drive system. This brings this series of papers to an end.
基金funded by the West Light Foundation of The Chinese Academy of Sciencesnational youth talent support programYunnan youth talents plan(YNWR-QNBJ-2018-183 to Y.N.)。
文摘Flower constancy describes the phenomenon that pollinators tend to successively visit flowers of a single species during foraging,reducing reproductive interference in natural communities.The extent of flower constancy is largely determined by the floral traits of co-flowering species.Both higher inter-specific and lower intraspecific differences of floral traits should contribute to a higher level of flower constancy.However,previous studies mainly focused on interspecific difference,and the intraspecific variation(consistency)of floral traits received much less attention.We hypothesise that selection may favour lower intraspecific floral trait variation in communities composed of multiple co-flowering congeners.We investigated the floral colour variation of three focal Pedicularis species that share pollinators in 19communities composed of either single or multiple Pedicularis species.Colour was quantified using image-based colour analysis as perceived by pollinators.We found that most of the intrapopulation floral colour variation was below the colour discrimination threshold of bumblebees,implying strongly constrained by the visual selection by pollinators.Contrary to the hypothesis,there is no significant difference in intraspecific floral colour variation between different community contexts.It may be due to the relatively large interspecific floral colour differences of most co-flowering species.The influence of community context on intraspecific variation may be reflected in floral traits other than colours.
基金financially supported by the China’s National Key Research and Development Program(No.2022YFC2905004)the China Postdoctoral Science Foundation(No.2023M742134).
文摘Cemented tailings backfill(CTB)not only boosts mining safety and cuts surface environmental pollution but also recovers ores previously retained as pillars,thereby improving resource utilization.The use of alternative reinforcing products,such as steel fiber(SF),has continuously strengthened CTB into SFCTB.This approach prevents strength decreases over time and reinforces its long-term durability,especially when mining ore in adjacent underground stopes.In this study,various microstructure and strength tests were performed on SFCTB,considering steel fiber ratio and electromagnetic induction strength effects.Lab findings show that combining steel fibers and their distribution dominantly influences the improvement of the fill’s strength.Fill’s strength rises by fiber insertion and has an evident correlation with fiber insertion and magnetic induction strength.When magnetic induction strength is 3×10^(-4) T,peak uniaxial compressive stress reaches 5.73 MPa for a fiber ratio of 2.0vol%.The cracks’expansion mainly started from the specimen’s upper part,which steadily expanded downward by increasing the load until damage occurred.The doping of steel fiber and its directional distribution delayed crack development.When the doping of steel fiber was 2.0vol%,SFCTBs showed excellent ductility characteristics.The energy required for fills to reach destruction increases when steel-fiber insertion and magnetic induction strength increase.This study provides notional references for steel fibers as underground filling additives to enhance the fill’s durability in the course of mining operations.
基金Supported by National Key Research and Development Plan Project of China(2023YFD1301200)。
文摘The floral organ morphology,pollen morphology,quantity,and viability of Rumex,Rumex hanus F1,Rumex hanus 1,and Rumex hanus 2 were compared and analyzed.The results showed that the longitudinal diameter of petals was not significantly different among different varieties of sorrel,and the transverse diameter and corolla diameter showed differences to varying degrees.They all had six stamens and three stigmas.The pollen shape of the four varieties was prolate,and the polar view was trilobated and round.They all had three germinal furrows,and the outer wall of the pollen was decorated with small cavities and spiny patterns,with warty protrusions.The equatorial axis length of pollen of different varieties of sorrel was significantly different(P<0.05).There were no significant differences in pollen amount among different varieties.There were six anthers in a single flower,featuring anther dehiscence.The pollen viability of Rumex hanus 1 was significantly lower than that of the other three varieties(P<0.05).Therefore,through the analysis of the floral organs and morphological characteristics of anthers of sorrel,the varieties of sorrel can be effectively distinguished and identified.
文摘As the core component of energy conversion for large wind turbines,the output performance of doubly-fed induction generators (DFIGs) plays a decisive role in the power quality of wind turbines.To realize the fast and accurate design optimization of DFIGs,this paper proposes a novel hybriddriven surrogate-assisted optimization method.It firstly establishes an accurate subdomain model of DFIGs to analytically predict performance indexes.Furthermore,taking the inexpensive analytical dataset produced by the subdomain model as the source domain and the expensive finite element analysis dataset as the target domain,a high-precision surrogate model is trained in a transfer learning way and used for the subsequent multi-objective optimization process.Based on this model,taking the total harmonic distortion of electromotive force,cogging torque,and iron loss as objectives,and the slot and inner/outer diameters as parameters for optimizing the topology,achieve a rapid and accurate electromagnetic design for DFIGs.Finally,experiments are carried out on a 3MW DFIG to validate the effectiveness of the proposed method.
基金supported in part by the Science Foundation of the Chinese Academy of Railway Sciences under Grant Number:2023QT001。
文摘Increasing attention has been paid to the efficiency improvement of the induction traction system of high-speed trains due to the high demand for energy saving. In emergency self-propelled mode, however, the dc-link voltage and the traction power of the motor are significantly reduced, resulting in decreased traction efficiency due to the low load and low speed operations. Aiming to tackle this problem, a novel efficiency improved control method is introduced to the emergency mode of high-speed train traction system in this paper. In the proposed method, a total loss model of induction motor considering the behaviors of both iron and copper loss is established. An improved iterative algorithm with decreased computational burden is then introduced, resulting in a fast solving of the optimal flux reference for loss minimization at each control period. In addition, considering the parameter variation problem due to the low load and low speed operations, a parameter estimation method is integrated to improve the controller's robustness. The effectiveness of the proposed method on efficiency improvement at low voltage and low load conditions is demonstrated by simulated and experimental results.
基金This research is financially supported by the Ministry of Science and Technology of China(Grant No.2019YFE0112400)the Department of Science and Technology of Shandong Province(Grant No.2021CXGC011204).
文摘In this paper,a stable and adaptive sliding mode control(SMC)method for induction motors is introduced.Determining the parameters of this system has been one of the existing challenges.To solve this challenge,a new self-tuning type-2 fuzzy neural network calculates and updates the control system parameters with a fast mechanism.According to the dynamic changes of the system,in addition to the parameters of the SMC,the parameters of the type-2 fuzzy neural network are also updated online.The conditions for guaranteeing the convergence and stability of the control system are provided.In the simulation part,in order to test the proposed method,several uncertain models and load torque have been applied.Also,the results have been compared to the SMC based on the type-1 fuzzy system,the traditional SMC,and the PI controller.The average RMSE in different scenarios,for type-2 fuzzy SMC,is 0.0311,for type-1 fuzzy SMC is 0.0497,for traditional SMC is 0.0778,and finally for PI controller is 0.0997.
文摘Magnetohydrodynamic(MHD)induction pumps are contactless pumps able to withstand harsh environments.The rate of fluid flow through the pump directly affects the efficiency and stability of the device.To explore the influence of induction pump settings on the related delivery speed,in this study,a numerical model for coupled electromagnetic and flow field effects is introduced and used to simulate liquid metal lithium flow in the induction pump.The effects of current intensity,frequency,coil turns and coil winding size on the velocity of the working fluid are analyzed.It is shown that the first three parameters have a significant impact,while changes in the coil turns have a negligible influence.The maximum increase in working fluid velocity within the pump for the parameter combination investigated in this paper is approximately 618%.As the frequency is increased from 20 to 60 Hz,the maximum increase in the mean flow rate of the working fluid is approximately 241%.These research findings are intended to support the design and optimization of these devices.
基金supported in part by National Natural Science Foundation of China under Grant 61973073supported by Jiangsu Province Higher Education Basic Science (Natural Science) Research Project under Grant 23KJB470022
文摘This article proposes a dual-negative-objective coordinated control strategy for brushless doubly fed induction generator(BDFIG)based wind power generation system under unbalanced grid voltage.To alleviate the mechanical stress and impaction on rotating shaft,the negative control objective(NCO)of machine side converter(MSC)is set to suppress the ripple of electromagnetic torque.While the NCO of grid side converter(GSC)is selected to suppress the oscillation of total output active power or the unbalanced degree of total output current for BDFIG generation system.In comparison with traditional single converter control scheme of the MSC or GSC,dual NCOs can be satisfied at the same time due to the enlarged freedom degree in the proposed improved coordinated control system for back-toback converters.The effectiveness of proposed control strategy is validated by simulation and experimental results on a dual-cagerotor BDFIG(DCR-BDFIG)prototype.
文摘Objective: The objective of this study was to determine if early rupture of membranes (ROM) in women undergoing induction of labor (IOL) at term is associated with an increased rate of clinical chorioamnionitis. Study Design: A retrospective cohort study was performed on women undergoing IOL. Early ROM was defined as ROM at a modified Bishop score less than 5, cervical dilation less than 4 cm, or cervical effacement less than 80%. The rate of clinical chorioamnionitis was compared between women with early and late ROM. Results: The rate of clinical chorioamnionitis was 8.6% (24/279). ROM at an effacement of less than 80% was associated with a rate of clinical chorioamnionitis of 15.4% (12/78) compared to 6.0% (12/201) at an effacement of equal to or greater than 80%, p = 0.017. The rate of cesarean delivery was higher for patients with early ROM by any definition: 32% compared to 17.5% by modified Bishop score (p = 0.031), 32.4% versus 18.2% by cervical dilation (p = 0.049), and 33.3% versus 14.9% by cervical effacement (p = 0.001). Conclusions: In patients undergoing IOL, early ROM may be associated with an increased rate of clinical chorioamnionitis when performed at a cervical effacement of less than 80% and an increased rate of cesarean delivery.
基金supported in part by Explosion Prevention Technology and Rotating Machines(EPT&RM)laboratory,South African Bureau of Standards(SABS),Pretoria,South Africa.
文摘The induction motor,which converts electrical energy into mechanical energy,has been recognized as the cornerstone of industrialization.The rotor of an induction motor can be either a squirrel cage rotor or a wound-type rotor,both existing as magnetless topologies.Three-phase squirrel cage induction motors are frequently utilized in industrial drives because they are dependable,have high starting torque,are selfstarting and affordable.Single-phase induction motors,on the other hand,are commonly used for small loads such as domestic appliances in form of modest fans,pumps and electric power tools.In South Africa,there have been reports of fires and explosions resulting in live and property loss because of induction motors that have not been thoroughly tested or are incorrectly labelled in terms of ratings,electrical safety and performance.The goal of this study is targeted at preventing end-user injuries and failures caused by non-compliant induction motors,by evaluating locally manufactured/imported induction motors based on tests and evaluation from standards(IEC and SANS).The study is conducted using experimental procedures at the Explosion Prevention Technology and Rotating Machines(EPT and RM)laboratory,South African Bureau of Standards(SABS),South Africa.The main finding from the study shows differences in the nameplate characteristics of various induction motors which could have detrimental effects such as production and operational downtime in their end-use industries,at later stages.
文摘In the context of induction motor control, there are various control strategies used to separately control torque and flux. One common approach is known as Field-Oriented Control (FOC). This technique involves transforming the three-phase currents and voltages into a rotating reference frame, commonly referred to as the “dq” frame. In this frame, the torque/speed and flux components are decoupled, allowing for independent control, by doing so, the motor’s speed can be regulated accurately and maintain a constant flux which is crucial to ensure optimal motor performance and efficiency. The research focused on studying and simulating a field-oriented control system using fuzzy control techniques for an induction motor. The aim was to address the issue of parameter variations, particularly the change in rotor resistance during motor operation, which causes the control system to deviate from the desired direction. This deviation implies to an increase in the magnetic flux value, specifically the flux component on the q-axis. By employing fuzzy logic techniques to regulate flux vector’s components in the dq frame, this problem was successfully resolved, ensuring that the magnetic flux value remains within the nominal limits. To enhance the control system’s performance, response speed, and efficiency of the motor, sliding mode controllers were implemented to regulate the current in the inner loop. The simulation results demonstrated the proficiency of the proposed methodology.
文摘The present paper is finalized to show that the Science, even if considered in its two different Phenomenological Approaches at present known, is unable to assert that: “Thinks are like that”. This is because both the two Scientific Approaches previously mentioned have not the property of “the perfect induction”. Consequently, although they can even reach an experimental confirmation of the theoretical results, and thus a “valid description” of the various phenomena of the surrounding world, such a description has not an “absolute value”. In fact, it always and only has an “operative validity”, that is, it exclusively and solely refers to an “experimental point of view”. This means that such an “operative validity” cannot represent the basis for a logical process characterized by a “perfect induction”. In addition, the Traditional Scientific Approach is also characterized by “Insoluble” Problems, “Intractable Problems”, Problems with “drifts”, which could generally be termed as “side effects”. On the other hand, the same com-possible Scientific Approach based on the Emerging Quality of Self-Organizing Systems, also presents its “Emerging Exits”. Consequently, none of the two mentioned scientific Approaches has the “gift” of “the perfect induction”. However, there are significant differences between the two. Differences that may “suggest” the most appropriate choice among them for an “operative point of view”. This conclusion will be com-proved by considering, with particular reference, both the “side effects”, which are related to the Traditional Approach and, on the other hand, the “Emerging Exits”, which specifically pertain to the new Scientific Approach based on the Emerging Quality of Self-Organizing Systems.
文摘Drawing upon the electromagnetic conversion formulas in a continuous conductive medium,an extensive examination for total current law and Faraday’s law of electromagnetic induction(Faraday’s law)is undertaken to expound on the laws of electromagnetic induction and conversion.The longitudinal wave term of Faraday’s law is reinstated to render it suitable for theoretical derivation of the LEM(Longitudinal Electromagnetic Wave)equation.Subsequently,we formulate the wave and energy equations for electric P-wave based on reevaluated total current law and modified Faraday’s law;meanwhile proposing a propagation mode that reveals its mechanisms absorbing free energy for LEM waves in a conductor predicated on interaction between scalar electric field and vortex magnetic field.Furthermore,through theoretical derivations based on LEM waves,insights into concealed relationships between electric P-wave and electromagnetism scalar potential are disclosed alongside the constraint equation between the wave velocities of LEM wave and TEM(Transverse Electromagnetic)waves,unveiling the significance of LEM wave.
文摘基于聚焦性能对经颅磁线圈的影响,针对聚焦型线圈商用不足的问题,设计一种具有高聚焦性的单通道双梯形双层线圈。首先使用球头模型分析不同尺寸、相同结构的线圈性能,得到较优的线圈尺寸;为进一步提升聚焦度,再以中尺寸线圈为研究目标,探讨五种不同结构的双层线圈与两种商用8字形线圈的性能差异,得到最优线圈的结构;最后使用50组存在个体差异性的真实脑模型进行仿真验证,分析球头模型结果的可靠性。仿真结果表明:使用球头模型时,优化后的新型线圈对比70 mm figure-8 coil的聚焦度提升了69.48%,刺激深度减少了27.18%;对比25 mm figure-8 coil的聚焦度提升了44.78%,刺激深度减少了8.5%;使用50组真实脑模型时,优化后的新型线圈对比70 mm figure-8 coil的聚焦度提升了62.07%,刺激深度减少了25.71%;对比25 mm figure-8 coil的聚焦度提升了39.49%,刺激深度减少了9.5%。两种模型仿真数据结果趋于一致,证实了仿真可靠性的同时也证明了新型线圈具有更强的刺激强度和聚焦度,能大大提升TMS治疗的安全性,减少不适感,同时单通道设计易于实现,具有较高的性能优势。