Humans can perceive our complex world through multi-sensory fusion.Under limited visual conditions,people can sense a variety of tactile signals to identify objects accurately and rapidly.However,replicating this uniq...Humans can perceive our complex world through multi-sensory fusion.Under limited visual conditions,people can sense a variety of tactile signals to identify objects accurately and rapidly.However,replicating this unique capability in robots remains a significant challenge.Here,we present a new form of ultralight multifunctional tactile nano-layered carbon aerogel sensor that provides pressure,temperature,material recognition and 3D location capabilities,which is combined with multimodal supervised learning algorithms for object recognition.The sensor exhibits human-like pressure(0.04–100 kPa)and temperature(21.5–66.2℃)detection,millisecond response times(11 ms),a pressure sensitivity of 92.22 kPa^(−1)and triboelectric durability of over 6000 cycles.The devised algorithm has universality and can accommodate a range of application scenarios.The tactile system can identify common foods in a kitchen scene with 94.63%accuracy and explore the topographic and geomorphic features of a Mars scene with 100%accuracy.This sensing approach empowers robots with versatile tactile perception to advance future society toward heightened sensing,recognition and intelligence.展开更多
Current power systems face significant challenges in supporting large-scale access to new energy sources,and the potential of existing flexible resources needs to be fully explored from the power supply,grid,and custo...Current power systems face significant challenges in supporting large-scale access to new energy sources,and the potential of existing flexible resources needs to be fully explored from the power supply,grid,and customer perspectives.This paper proposes a multi-objective electricity consumption optimization strategy considering the correlation between equipment and electricity consumption.It constructs a multi-objective electricity consumption optimization model that considers the correlation between equipment and electricity consumption to maximize economy and comfort.The results show that the proposed method can accurately assess the potential for electricity consumption optimization and obtain an optimal multi-objective electricity consumption strategy based on customers’actual electricity consumption demand.展开更多
In many existing multi-view gait recognition methods based on images or video sequences,gait sequences are usually used to superimpose and synthesize images and construct energy-like template.However,information may b...In many existing multi-view gait recognition methods based on images or video sequences,gait sequences are usually used to superimpose and synthesize images and construct energy-like template.However,information may be lost during the process of compositing image and capture EMG signals.Errors and the recognition accuracy may be introduced and affected respectively by some factors such as period detection.To better solve the problems,a multi-view gait recognition method using deep convolutional neural network and channel attention mechanism is proposed.Firstly,the sliding time window method is used to capture EMG signals.Then,the back-propagation learning algorithm is used to train each layer of convolution,which improves the learning ability of the convolutional neural network.Finally,the channel attention mechanism is integrated into the neural network,which will improve the ability of expressing gait features.And a classifier is used to classify gait.As can be shown from experimental results on two public datasets,OULP and CASIA-B,the recognition rate of the proposed method can be achieved at 88.44%and 97.25%respectively.As can be shown from the comparative experimental results,the proposed method has better recognition effect than several other newer convolutional neural network methods.Therefore,the combination of convolutional neural network and channel attention mechanism is of great value for gait recognition.展开更多
Objective: To examine the association between lymph node status and recurrence patterns in completely resected gastric adenocarcinoma.Methods: We retrospectively assessed 1,694 patients who underwent curative gastrect...Objective: To examine the association between lymph node status and recurrence patterns in completely resected gastric adenocarcinoma.Methods: We retrospectively assessed 1,694 patients who underwent curative gastrectomy from January 2010 to August 2014. Patients stratified according to lymph node status and recurrence patterns among different subgroups were compared.Results: Of all, 517(30.5%) patients developed recurrent disease, and complete data of recurrence could be obtained in 493(95.4%) patients. For p^(N0) patients, the patterns of recurrence were different according to p T stage: locoregional recurrence was most common in patients with p T1-2 disease(57.1%), distant recurrence was most common in patients with p T3 disease(57.1%), and peritoneal recurrence was most common in patients with p T4 a disease(66.7%). For p^(N+) patients, distant metastasis was most common pattern irrespective of p T stage. The site-specific trend of recurrence showed that locoregional recurrence increased within 5 years in patients with p^(N0)-2 disease but plateaued 3 years after surgery in patients with p N3 disease. Time to recurrence was significantly longer for the p^(N0) patients compared with the p^(N+) patients(median: 25 vs. 16 months, P=0.001).Moreover, post-recurrence survival was significantly better for the p^(N0) patients than for the p^(N+) patients(median:12 vs. 6 months, P<0.001), especially in patients with non-peritoneal recurrence, late recurrence, single recurrence,and receipt of potential curative treatment.Conclusions: Among clinicopathologic factors, lymph node status is the most important factor associated with recurrence patterns after curative gastrectomy. Lymph node status may be used as an adjunct in clinical decisionmaking about postoperative therapeutic and follow-up strategies.展开更多
We propose a high-sensitivity bidirectional torsion sensor using a helical seven-core fiber taper embedded in multimode fiber(MHSTM).Sensors with different taper waists and helical pitches are fabricated,and their tra...We propose a high-sensitivity bidirectional torsion sensor using a helical seven-core fiber taper embedded in multimode fiber(MHSTM).Sensors with different taper waists and helical pitches are fabricated,and their transmission spectra are obtained and analyzed.The waist and length of the sandwiched seven-core fiber are finally determined to be 68 μm and3 mm,respectively.The experimental results show that the clockwise and counterclockwise torsion sensitivities of the proposed sensor are 2.253 nm/(rad/m) and-1.123 nm/(rad/m),respectively.When tapered waist diameter reduces to48 μm,a superior torsion sensitivity of 5.391 nm/(rad/m) in the range of 0-4.24 nm/(rad/m) is obtained,which is 46 times as large as the traditional helical seven-core fiber structure.In addition,the MHSTM structure is also relatively stable to temperature variations.展开更多
In this study,an improved delayed detached eddy simulation(IDDES)method based on the shear-stress transport(SST)k-ωturbulence model has been used to investigate the underbody flow characteristics of a high-speed trai...In this study,an improved delayed detached eddy simulation(IDDES)method based on the shear-stress transport(SST)k-ωturbulence model has been used to investigate the underbody flow characteristics of a high-speed train operating at lower temperatures with Reynolds number Re=1.85×10^(6).The accuracy of the numerical method has been validated by wind tunnel tests.The aerodynamic drag of the train,pressure distribution on the surface of the train,the flow around the vehicle,and the wake flow are compared for four temperature values:+15℃,0℃,−15℃,and−30℃.It was found that lower operating t emperatures significantly increased the aerodynamic drag force of the train.The drag overall at low temperatures increased by 5.3%(0℃),11.0%(−15℃),and 17.4%(−30℃),respectively,relative to the drag at+15℃.In addition,the low temperature e nhances the positive and negative pressures around and on the surface of the car body,raising the peak positive and negative pressure values in areas susceptible to impingement flow and to rapid changes in flow velocity.The range of train-induced winds around the car body is significantly reduced,the distribution area of vorticity moves backwards,and the airflow velocity in the bogie cavity is significantly increased.At the same time,the temperature causes a significant velocity reduction in the wake flow.It can be seen that the temperature reduction can seriously disturb the normal operation of the train while increasing the aerodynamic drag and energy consumption,and significantly interfering with the airflow characteristics around the car body.展开更多
Quantum squeezing is an important quantum resource for quantum metrology as it can improve the measurement precision.By enhancing the quantum squeezing level,the measurement precision can be further improved.Here,we e...Quantum squeezing is an important quantum resource for quantum metrology as it can improve the measurement precision.By enhancing the quantum squeezing level,the measurement precision can be further improved.Here,we experimentally implement quantum squeezing enhancement based on phase-sensitive cascaded four-wave mixing(CFWM)processes.The intensitydifference squeezing(IDS)between the two outputs of the phase-sensitive CFWM processes is enhanced to about 7.42 dB compared with IDS generated by the single four-wave mixing(FWM)process(about 3.31 or 4.01 dB).Such enhancement is enabled by both the intrinsic interference nature of phase-sensitive CFWM processes and the contribution of more gain from the two FWM processes.In addition,we measure IDS levels generated by phase-sensitive CFWM processes at different internalphase-locking points,which shows that the internal phase plays an important role in IDS enhancement.Our scheme provides a new method for improving the degree of IDS and may find potential applications in enhancing the measurement precision in quantum metrology.展开更多
Nemadectin, a macrocyclic lactone antibiotic, is produced by Streptomyces cyaneogriseus ssp. noncyanogenus. A methoxime derivative of nemadectin, moxdectin, has been widely used to control insect and helminth in anima...Nemadectin, a macrocyclic lactone antibiotic, is produced by Streptomyces cyaneogriseus ssp. noncyanogenus. A methoxime derivative of nemadectin, moxdectin, has been widely used to control insect and helminth in animal health. Despite the importance of nemadectin, little attention has been paid to the regulation of nemadectin biosynthesis, which has hindered efforts to improve nemadectin production via genetic manipulation of regulatory genes. Here, we characterize the function of nemR, the cluster-situated regulatory gene encoding a LAL-family transcriptional regulator, in the nemadectin biosynthesis gene cluster of S. cyaneogriseus ssp. noncyanogenus NMWT1. NemR is shown to be essential for nemadectin production and found to directly activate the transcription of nemA1-1/A1-2/A2, nemC and nemA4/A3/E/D operons, but indirectly activate that of nemG and nemF. A highly conserved sequence 5′-TGGGGTGKATAGGGGGTA-3′(K=T/G) is verified to be essential for NemR binding.Moreover, four novel targets of NemR, including genes encoding an SsgA-like protein(TU94_12730), a methylmalonyl-CoA mutase(TU94_19950), a thioesterase of oligomycin biosynthesis(TU94_22425) and a MFS family transporter(TU94_24835)are identified. Overexpression of nemR significantly increased nemadectin production by 79.9%, in comparison with NMWT1,suggesting that nemR plays an important role in the nemadectin biosynthesis.展开更多
Magnetic polyphosphazene(MPZS) particles coated by Ag nanoparticles(MPZS-Ag) have been developed as surface enhanced Raman spectroscopy(SERS) substrates for sensitive detection of melamine in aqueous solutions and mil...Magnetic polyphosphazene(MPZS) particles coated by Ag nanoparticles(MPZS-Ag) have been developed as surface enhanced Raman spectroscopy(SERS) substrates for sensitive detection of melamine in aqueous solutions and milk samples.5,5’-Dithiobis-(2-nitrobenzoic acid)(DTNB) was used as model analyte to test the SERS activity of the MPZS-Ag particles.The prepared MPZS-Ag particles possess both magnetic responsiveness and excellent SERS properties.SERS detection of different concentrations of melamine aqueous solutions and spiked milk samples were performed by the MPZS-Ag particles.The limit of detection(LOD) of the melamine in aqueous solutions was 10^-7 mol/L(0.0126 mg/L) and 0.6 mg/L in real milk samples using the MPZS-Ag particles as SERS substrates.The LOD of the melamine are much lower than the safety values of Food and Drug Administration and Codex Alimentarius Commission.These results indicate that the MPZS-Ag particles have promising application prospect for SERS analysis in food safety fields.展开更多
Short-Term Memory (STM) is a primary capability of the human brain. Humans use STM to remember a small amount of information, like someone's phone number, for a short period of time. Usually the duration of STM is ...Short-Term Memory (STM) is a primary capability of the human brain. Humans use STM to remember a small amount of information, like someone's phone number, for a short period of time. Usually the duration of STM is less than 1 minute. Synapses, the connections between neurons, are of vital importance to memory in biological brains. For mimicking the memory function of synapses, Carbon Nanotube (CNT) networks based thin- film transistors with Electric Double Layers (EDL) at the dielectric/channel interface were researched in this work. A response characteristic of pre-synaptic potential pulses on the gate electrode of this CNT synaptic transistor was shown remarkably similar to Excitatory Post-Synaptic Current (EPSC) of biological synapses. Also a multi-level modulatable STM of CNT synaptic transistors was investigated. Post-synaptic current was shown with tunable peak values, on-off ratio, and relaxation time.展开更多
Compared to conventional distributed winding configurations,the fractional-slot non-overlapping(concentrated)windings exhibit advantages such as short end-winding length,high copper packing factor(particularly with se...Compared to conventional distributed winding configurations,the fractional-slot non-overlapping(concentrated)windings exhibit advantages such as short end-winding length,high copper packing factor(particularly with segmented stator structure),low cogging torque,good field weakening capability owing to relatively large d-axis inductance,and better fault tolerant capability due to low mutual inductance.However,one of the key problems of employing concentrated windings in Permanent-magnet Synchronous Machines(PMSMs)is the high eddy-current losses in rotor magnets and/or rotor iron due to the presence of a large number of lower and higher order space harmonics in the stator Magneto-Motive Force(MMF).These MMF harmonics also result in other undesirable effects,such as acoustic noise and vibrations,and localized core saturation which tend to reduce reluctance torque.This paper reviews the current state-of-the-art of the MMF harmonic reduction techniques for concentrated winding configurations in PMSMs,including winding split and shift,delta-star connected windings,multiple 3-phase windings,multilayer windings,uneven turn numbers,and stator flux barriers.Their concepts,advantages and disadvantages are presented and assessed.展开更多
When a short-circuit fault occurs in a phase,the faulty phase needs to be removed artificially from the system because of the loss of the capability to generate torque.In this case,both the short-circuit current and p...When a short-circuit fault occurs in a phase,the faulty phase needs to be removed artificially from the system because of the loss of the capability to generate torque.In this case,both the short-circuit current and phase-loss fault would generate additional torque ripples.In this study,a novel fault-tolerant control strategy is introduced to achieve low torque ripple operation of five-phase fault-tolerant permanent magnet synchronous motors with trapezoidal back electromotive force(FTPMSM-TEMF)in the event of a short-circuit fault.The key concept of this method is to compensate for the torque ripples caused by the short-circuit current and the adverse effect of the phase-loss.Based on the torque expression under fault conditions,the torque ripple caused by the short-circuit current can be offset by injecting a certain pulsating component into the torque expression in the phase-loss condition.This would result in smooth operation under fault conditions.Moreover,to track the fault-tolerant alternating currents,the model of the deadbeat current predictive control is extended and restructured for the fault condition.The effectiveness and feasibility of the proposed fault-tolerant strategy are verified by experimental results.展开更多
The mile range of an electric vehicle(EV)may be reduced significantly in cold weather owing to the energy demand for meeting thermal comfort in the vehicle cabin,as waste heat from a combustion engine is not available...The mile range of an electric vehicle(EV)may be reduced significantly in cold weather owing to the energy demand for meeting thermal comfort in the vehicle cabin,as waste heat from a combustion engine is not available for this purpose.Various heat pump-based heating,ventilation,and air conditioning(HVAC)systems can be employed to absorb the heat energy from the surroundings and/or the waste heat from the electrical powertrain to facilitate cabin thermal comfort,thereby extending the EV mile range.However,there is a lack of research on the electro-thermally coupled modelling and evaluation of the thermal performance of HVAC systems.This paper proposes electro-thermally coupled models for the electrical machine and inverter by modelling the key electromagnetic quantities as functions of the torque and speed based on offline parameter extraction from two-dimensional electromagnetic finite element analysis.The proposed electro-thermally coupled models,which are computationally efficient,are integrated into HVAC thermofluid simulation.Comparative studies of three heat pump-based HVAC architectures(conventional ambient heat only,waste heat only,and dual heat source)are performed using the proposed electro-thermally coupled models.The dual heat source HVAC architecture exhibits superior thermal performance over its counterparts in cold weather conditions.展开更多
基金the National Natural Science Foundation of China(Grant No.52072041)the Beijing Natural Science Foundation(Grant No.JQ21007)+2 种基金the University of Chinese Academy of Sciences(Grant No.Y8540XX2D2)the Robotics Rhino-Bird Focused Research Project(No.2020-01-002)the Tencent Robotics X Laboratory.
文摘Humans can perceive our complex world through multi-sensory fusion.Under limited visual conditions,people can sense a variety of tactile signals to identify objects accurately and rapidly.However,replicating this unique capability in robots remains a significant challenge.Here,we present a new form of ultralight multifunctional tactile nano-layered carbon aerogel sensor that provides pressure,temperature,material recognition and 3D location capabilities,which is combined with multimodal supervised learning algorithms for object recognition.The sensor exhibits human-like pressure(0.04–100 kPa)and temperature(21.5–66.2℃)detection,millisecond response times(11 ms),a pressure sensitivity of 92.22 kPa^(−1)and triboelectric durability of over 6000 cycles.The devised algorithm has universality and can accommodate a range of application scenarios.The tactile system can identify common foods in a kitchen scene with 94.63%accuracy and explore the topographic and geomorphic features of a Mars scene with 100%accuracy.This sensing approach empowers robots with versatile tactile perception to advance future society toward heightened sensing,recognition and intelligence.
文摘Current power systems face significant challenges in supporting large-scale access to new energy sources,and the potential of existing flexible resources needs to be fully explored from the power supply,grid,and customer perspectives.This paper proposes a multi-objective electricity consumption optimization strategy considering the correlation between equipment and electricity consumption.It constructs a multi-objective electricity consumption optimization model that considers the correlation between equipment and electricity consumption to maximize economy and comfort.The results show that the proposed method can accurately assess the potential for electricity consumption optimization and obtain an optimal multi-objective electricity consumption strategy based on customers’actual electricity consumption demand.
基金This work was supported by the Natural Science Foundation of China(No.61902133)Fujian natural science foundation project(No.2018J05106)Xiamen Collaborative Innovation projects of Produces study grinds(3502Z20173046)。
文摘In many existing multi-view gait recognition methods based on images or video sequences,gait sequences are usually used to superimpose and synthesize images and construct energy-like template.However,information may be lost during the process of compositing image and capture EMG signals.Errors and the recognition accuracy may be introduced and affected respectively by some factors such as period detection.To better solve the problems,a multi-view gait recognition method using deep convolutional neural network and channel attention mechanism is proposed.Firstly,the sliding time window method is used to capture EMG signals.Then,the back-propagation learning algorithm is used to train each layer of convolution,which improves the learning ability of the convolutional neural network.Finally,the channel attention mechanism is integrated into the neural network,which will improve the ability of expressing gait features.And a classifier is used to classify gait.As can be shown from experimental results on two public datasets,OULP and CASIA-B,the recognition rate of the proposed method can be achieved at 88.44%and 97.25%respectively.As can be shown from the comparative experimental results,the proposed method has better recognition effect than several other newer convolutional neural network methods.Therefore,the combination of convolutional neural network and channel attention mechanism is of great value for gait recognition.
基金supported by Scientific and Technological Innovation Joint Capital Projects of Fujian Province, China (No. 2017Y9011)Minimally Invasive Medical Center of Fujian Province (No. [2017]171)+1 种基金Project supported by the Science Foundation of the Fujian Province, China (No. 2018J01307)Joint Funds for the innovation of science and Technology, Fujian province (No. 2018Y9041)。
文摘Objective: To examine the association between lymph node status and recurrence patterns in completely resected gastric adenocarcinoma.Methods: We retrospectively assessed 1,694 patients who underwent curative gastrectomy from January 2010 to August 2014. Patients stratified according to lymph node status and recurrence patterns among different subgroups were compared.Results: Of all, 517(30.5%) patients developed recurrent disease, and complete data of recurrence could be obtained in 493(95.4%) patients. For p^(N0) patients, the patterns of recurrence were different according to p T stage: locoregional recurrence was most common in patients with p T1-2 disease(57.1%), distant recurrence was most common in patients with p T3 disease(57.1%), and peritoneal recurrence was most common in patients with p T4 a disease(66.7%). For p^(N+) patients, distant metastasis was most common pattern irrespective of p T stage. The site-specific trend of recurrence showed that locoregional recurrence increased within 5 years in patients with p^(N0)-2 disease but plateaued 3 years after surgery in patients with p N3 disease. Time to recurrence was significantly longer for the p^(N0) patients compared with the p^(N+) patients(median: 25 vs. 16 months, P=0.001).Moreover, post-recurrence survival was significantly better for the p^(N0) patients than for the p^(N+) patients(median:12 vs. 6 months, P<0.001), especially in patients with non-peritoneal recurrence, late recurrence, single recurrence,and receipt of potential curative treatment.Conclusions: Among clinicopathologic factors, lymph node status is the most important factor associated with recurrence patterns after curative gastrectomy. Lymph node status may be used as an adjunct in clinical decisionmaking about postoperative therapeutic and follow-up strategies.
基金the National Natural Science Foundation of China(Grant Nos.52078199 and 51905547)the Young Elite Scientists Sponsorship Program by CAST(Grant No.2020QNRC001)+2 种基金the financial support received from the National Key R&D Program of China(Grant No.2020YFA0710903-C)the China National Railway Group Limited(Grant No.P2021J036)the Self-exploration and Innovation Project for Graduate Students of Central South University and Hunan Province(Grant Nos.2022ZZTS0158 and CX20220244).
基金supported in part by the Joint Research Fund in Astronomy under Cooperative Agreement between the National Natural Science Foundation of China(NSFC) and the Chinese Academy of Sciences(CAS)(Nos.U2031132 and U2031130)the National Natural Science Foundation of China(No.12103015)the Fundamental Research Funds for the Central Universities to the Harbin Engineering University。
文摘We propose a high-sensitivity bidirectional torsion sensor using a helical seven-core fiber taper embedded in multimode fiber(MHSTM).Sensors with different taper waists and helical pitches are fabricated,and their transmission spectra are obtained and analyzed.The waist and length of the sandwiched seven-core fiber are finally determined to be 68 μm and3 mm,respectively.The experimental results show that the clockwise and counterclockwise torsion sensitivities of the proposed sensor are 2.253 nm/(rad/m) and-1.123 nm/(rad/m),respectively.When tapered waist diameter reduces to48 μm,a superior torsion sensitivity of 5.391 nm/(rad/m) in the range of 0-4.24 nm/(rad/m) is obtained,which is 46 times as large as the traditional helical seven-core fiber structure.In addition,the MHSTM structure is also relatively stable to temperature variations.
基金supported by the National Natural Science Foundation of China(Nos.52172363 and 52202429)the National Key Research and Development Program of China(No.2020YFF0304103-03)the Independent Exploration of Graduate Students of Central South University(No.2019zzts268),China.
文摘In this study,an improved delayed detached eddy simulation(IDDES)method based on the shear-stress transport(SST)k-ωturbulence model has been used to investigate the underbody flow characteristics of a high-speed train operating at lower temperatures with Reynolds number Re=1.85×10^(6).The accuracy of the numerical method has been validated by wind tunnel tests.The aerodynamic drag of the train,pressure distribution on the surface of the train,the flow around the vehicle,and the wake flow are compared for four temperature values:+15℃,0℃,−15℃,and−30℃.It was found that lower operating t emperatures significantly increased the aerodynamic drag force of the train.The drag overall at low temperatures increased by 5.3%(0℃),11.0%(−15℃),and 17.4%(−30℃),respectively,relative to the drag at+15℃.In addition,the low temperature e nhances the positive and negative pressures around and on the surface of the car body,raising the peak positive and negative pressure values in areas susceptible to impingement flow and to rapid changes in flow velocity.The range of train-induced winds around the car body is significantly reduced,the distribution area of vorticity moves backwards,and the airflow velocity in the bogie cavity is significantly increased.At the same time,the temperature causes a significant velocity reduction in the wake flow.It can be seen that the temperature reduction can seriously disturb the normal operation of the train while increasing the aerodynamic drag and energy consumption,and significantly interfering with the airflow characteristics around the car body.
基金supported by the National Natural Science Foundation of China(Grant Nos.12225404,11874155,91436211,11374104,and 12174110)the Innovation Program of Shanghai Municipal Education Commission(Grant No.2021-01-07-00-08-E00100)+7 种基金the Program of Shanghai Academic Research Leader(Grant No.22XD1400700)the Basic Research Project of Shanghai Science and Technology Commission(Grant No.20JC1416100)the Natural Science Foundation of Shanghai(Grant No.17ZR1442900)the Minhang Leading Talents(Grant No.201971)the Shanghai Sailing Program(Grant No.21YF1410800)the Natural Science Foundation of Chongqing(Grant No.CSTB2022NSCQ-MSX0893)the Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)the 111 Project(Grant No.B12024).
文摘Quantum squeezing is an important quantum resource for quantum metrology as it can improve the measurement precision.By enhancing the quantum squeezing level,the measurement precision can be further improved.Here,we experimentally implement quantum squeezing enhancement based on phase-sensitive cascaded four-wave mixing(CFWM)processes.The intensitydifference squeezing(IDS)between the two outputs of the phase-sensitive CFWM processes is enhanced to about 7.42 dB compared with IDS generated by the single four-wave mixing(FWM)process(about 3.31 or 4.01 dB).Such enhancement is enabled by both the intrinsic interference nature of phase-sensitive CFWM processes and the contribution of more gain from the two FWM processes.In addition,we measure IDS levels generated by phase-sensitive CFWM processes at different internalphase-locking points,which shows that the internal phase plays an important role in IDS enhancement.Our scheme provides a new method for improving the degree of IDS and may find potential applications in enhancing the measurement precision in quantum metrology.
基金supported by grants from the National Natural Science Foundation of China (31372006 and 31401814)
文摘Nemadectin, a macrocyclic lactone antibiotic, is produced by Streptomyces cyaneogriseus ssp. noncyanogenus. A methoxime derivative of nemadectin, moxdectin, has been widely used to control insect and helminth in animal health. Despite the importance of nemadectin, little attention has been paid to the regulation of nemadectin biosynthesis, which has hindered efforts to improve nemadectin production via genetic manipulation of regulatory genes. Here, we characterize the function of nemR, the cluster-situated regulatory gene encoding a LAL-family transcriptional regulator, in the nemadectin biosynthesis gene cluster of S. cyaneogriseus ssp. noncyanogenus NMWT1. NemR is shown to be essential for nemadectin production and found to directly activate the transcription of nemA1-1/A1-2/A2, nemC and nemA4/A3/E/D operons, but indirectly activate that of nemG and nemF. A highly conserved sequence 5′-TGGGGTGKATAGGGGGTA-3′(K=T/G) is verified to be essential for NemR binding.Moreover, four novel targets of NemR, including genes encoding an SsgA-like protein(TU94_12730), a methylmalonyl-CoA mutase(TU94_19950), a thioesterase of oligomycin biosynthesis(TU94_22425) and a MFS family transporter(TU94_24835)are identified. Overexpression of nemR significantly increased nemadectin production by 79.9%, in comparison with NMWT1,suggesting that nemR plays an important role in the nemadectin biosynthesis.
基金the financial support of the National Natural Science Foundation of China(Nos.51503040,31771893)the Natural Science Foundation of Fujian Province,China(No. 2018J01766)the Outstanding Youth Research Talent Cultivation Program of Universities in Fujian Province,China (No.601936)
文摘Magnetic polyphosphazene(MPZS) particles coated by Ag nanoparticles(MPZS-Ag) have been developed as surface enhanced Raman spectroscopy(SERS) substrates for sensitive detection of melamine in aqueous solutions and milk samples.5,5’-Dithiobis-(2-nitrobenzoic acid)(DTNB) was used as model analyte to test the SERS activity of the MPZS-Ag particles.The prepared MPZS-Ag particles possess both magnetic responsiveness and excellent SERS properties.SERS detection of different concentrations of melamine aqueous solutions and spiked milk samples were performed by the MPZS-Ag particles.The limit of detection(LOD) of the melamine in aqueous solutions was 10^-7 mol/L(0.0126 mg/L) and 0.6 mg/L in real milk samples using the MPZS-Ag particles as SERS substrates.The LOD of the melamine are much lower than the safety values of Food and Drug Administration and Codex Alimentarius Commission.These results indicate that the MPZS-Ag particles have promising application prospect for SERS analysis in food safety fields.
基金supported by the National Natural Science Foundation of China(Nos.61574083 and 61434001)the National Key Basic Research and Development(973)Program of China(No.2015CB352100)+3 种基金the National Key Project of Science and Technology(No.2011ZX02403-002)Special Fund for Agroscientic Research in the Public Interest of China(No.201303107)Thankful for the support of the Independent Research Program(2014Z01006)of Tsinghua UniversityAdvanced Sensor and Integrated System Lab of Tsinghua University Graduate School at Shenzhen under project No.ZDSYS20140509172959969
文摘Short-Term Memory (STM) is a primary capability of the human brain. Humans use STM to remember a small amount of information, like someone's phone number, for a short period of time. Usually the duration of STM is less than 1 minute. Synapses, the connections between neurons, are of vital importance to memory in biological brains. For mimicking the memory function of synapses, Carbon Nanotube (CNT) networks based thin- film transistors with Electric Double Layers (EDL) at the dielectric/channel interface were researched in this work. A response characteristic of pre-synaptic potential pulses on the gate electrode of this CNT synaptic transistor was shown remarkably similar to Excitatory Post-Synaptic Current (EPSC) of biological synapses. Also a multi-level modulatable STM of CNT synaptic transistors was investigated. Post-synaptic current was shown with tunable peak values, on-off ratio, and relaxation time.
文摘Compared to conventional distributed winding configurations,the fractional-slot non-overlapping(concentrated)windings exhibit advantages such as short end-winding length,high copper packing factor(particularly with segmented stator structure),low cogging torque,good field weakening capability owing to relatively large d-axis inductance,and better fault tolerant capability due to low mutual inductance.However,one of the key problems of employing concentrated windings in Permanent-magnet Synchronous Machines(PMSMs)is the high eddy-current losses in rotor magnets and/or rotor iron due to the presence of a large number of lower and higher order space harmonics in the stator Magneto-Motive Force(MMF).These MMF harmonics also result in other undesirable effects,such as acoustic noise and vibrations,and localized core saturation which tend to reduce reluctance torque.This paper reviews the current state-of-the-art of the MMF harmonic reduction techniques for concentrated winding configurations in PMSMs,including winding split and shift,delta-star connected windings,multiple 3-phase windings,multilayer windings,uneven turn numbers,and stator flux barriers.Their concepts,advantages and disadvantages are presented and assessed.
基金the National Natural Science Foundation of China(52077097,52025073,and 51991383)in part by the Natural Science Research Project of Higher Education Institutions of Jiangsu Province(20KJA470003)in part by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘When a short-circuit fault occurs in a phase,the faulty phase needs to be removed artificially from the system because of the loss of the capability to generate torque.In this case,both the short-circuit current and phase-loss fault would generate additional torque ripples.In this study,a novel fault-tolerant control strategy is introduced to achieve low torque ripple operation of five-phase fault-tolerant permanent magnet synchronous motors with trapezoidal back electromotive force(FTPMSM-TEMF)in the event of a short-circuit fault.The key concept of this method is to compensate for the torque ripples caused by the short-circuit current and the adverse effect of the phase-loss.Based on the torque expression under fault conditions,the torque ripple caused by the short-circuit current can be offset by injecting a certain pulsating component into the torque expression in the phase-loss condition.This would result in smooth operation under fault conditions.Moreover,to track the fault-tolerant alternating currents,the model of the deadbeat current predictive control is extended and restructured for the fault condition.The effectiveness and feasibility of the proposed fault-tolerant strategy are verified by experimental results.
基金Supported by the European Commission Horizon 2020-Optimised and Systematic Energy Management in Electric Vehicles,under Grant 653514.
文摘The mile range of an electric vehicle(EV)may be reduced significantly in cold weather owing to the energy demand for meeting thermal comfort in the vehicle cabin,as waste heat from a combustion engine is not available for this purpose.Various heat pump-based heating,ventilation,and air conditioning(HVAC)systems can be employed to absorb the heat energy from the surroundings and/or the waste heat from the electrical powertrain to facilitate cabin thermal comfort,thereby extending the EV mile range.However,there is a lack of research on the electro-thermally coupled modelling and evaluation of the thermal performance of HVAC systems.This paper proposes electro-thermally coupled models for the electrical machine and inverter by modelling the key electromagnetic quantities as functions of the torque and speed based on offline parameter extraction from two-dimensional electromagnetic finite element analysis.The proposed electro-thermally coupled models,which are computationally efficient,are integrated into HVAC thermofluid simulation.Comparative studies of three heat pump-based HVAC architectures(conventional ambient heat only,waste heat only,and dual heat source)are performed using the proposed electro-thermally coupled models.The dual heat source HVAC architecture exhibits superior thermal performance over its counterparts in cold weather conditions.