It is found that when the parity–time symmetry phenomenon is introduced into the resonant optical gyro system and it works near the exceptional point,the sensitivity can in theory be significantly amplified at low an...It is found that when the parity–time symmetry phenomenon is introduced into the resonant optical gyro system and it works near the exceptional point,the sensitivity can in theory be significantly amplified at low angular rate.However,in fact,the exceptional point is easily disturbed by external environmental variables,which means that it depends on harsh experimental environment and strong control ability,so it is difficult to move towards practical application.Here,we propose a new angular rate sensor structure based on exceptional surface,which has the advantages of high sensitivity and high robustness.The system consists of two fiber-optic ring resonators and two optical loop mirrors,and one of the resonators contains a variable ratio coupler and a variable optical attenuator.We theoretically analyze the system response,and the effects of phase and coupling ratio on the system response.Finally,compared with the conventional resonant gyro,the sensitivity of this exceptional surface angular rate sensor can be improved by about 300 times at low speed.In addition,by changing the loss coefficient in the ring resonator,we can achieve a wide range of 600 rad/s.This scheme provides a new approach for the development of ultra-high sensitivity and wide range angular rate sensors in the future.展开更多
Gaps in compressors are generally unfavorable because they lead to energy loss.However,gaps on diffuser blades can broaden the operation range of a compressor.To broaden the operation range of a centrifugal compressor...Gaps in compressors are generally unfavorable because they lead to energy loss.However,gaps on diffuser blades can broaden the operation range of a compressor.To broaden the operation range of a centrifugal compressor with a tandem diffuser,gaps with different sections and widths on the diffuser blades were examined to determine their influence on the compressor performance.The results show that the compressor’s surge margin increased from 33.28% to 49.2% for a 2.5%tip gap ratio,while its stability margin increased from 44% to 60.5%.However,pressure ratio and efficiency losses of 1.16% and 1.14%,respectively,were incurred.Gap widths less than 5%of the height of the diffuser blade are adequate for broadening the operation range,whereas gap ratios greater than 5%cause more energy loss without broadening the operation range further.Gaps can also reduce the Mach number in the diffuser blade channels and can be influenced by the impeller-tip gap.Moreover,diffuser gaps on the shroud side yield better performance than those on the hub side.An experiment was conducted to investigate the reliability of the calculation and conclusions in this study,and the results proved that the conclusions are valid for different types of centrifugal compressors.展开更多
Traditional operating range prediction methods assume that the atmospheric radiances in a target path and a background path are equal. But they are different in a real-world environment. To solve this problem,the infl...Traditional operating range prediction methods assume that the atmospheric radiances in a target path and a background path are equal. But they are different in a real-world environment. To solve this problem,the influence of atmospheric radiance on operating range prediction is analyzed in this paper. Range estimation model in thermal imaging based on background radiation（ REBR） is proposed. Infrared image radiometric calibration is used to calculate the background radiation of a system entrance pupil. The result shows that,compared with traditional operating range prediction methods,the REBR method is more suitable for the actual atmospheric transmission process and the physical process of infrared imaging.展开更多
We fabricate a three-layer metamaterial of metal patterns/dielectric/metal films. The optical properties associated with Fano resonance of the metamaterials are investigated experimentally and theoretically. The resul...We fabricate a three-layer metamaterial of metal patterns/dielectric/metal films. The optical properties associated with Fano resonance of the metamaterials are investigated experimentally and theoretically. The results indicate that the introduction of Fano resonance due to symmetry breaking leads to a much wider absorption range. Furthermore, the amplitude and phase of reflection can be modulated effectively by adjusting various free parameters using the proposed structure.展开更多
Hollow cathodes are widely used as electron sources and neutralizers in ion and Hall electric propulsion.Special applications such as commercial aerospace and gravitational wave detection require hollow cathodes with ...Hollow cathodes are widely used as electron sources and neutralizers in ion and Hall electric propulsion.Special applications such as commercial aerospace and gravitational wave detection require hollow cathodes with a very wide discharge current range.In this paper,a heater is used to compensate for the temperature drop of the emitter at low current.The self-sustained current can be extended from 0.6 to 0.1 A with a small discharge oscillation and ion energy when the flow rate is constant.This is also beneficial for long-life operation.However,when the discharge current is high(>1 A),heating can cause discharge oscillation,discharge voltage and ion energy to increase,f urther,combined with a rapid decline of pressure inside the cathode and an increase in the temperature in the cathode orifice plate,electron emission in die orifice and outside the orifice increases and the plasma density in the orifice decreases.This leads to a change in the cathode discharge mode.展开更多
The variable cycle engine is distinguished by its highly adjustable compression system,whose aerodynamic characteristic is extremely complex.To explore the regulation range of a double bypass engine compression system...The variable cycle engine is distinguished by its highly adjustable compression system,whose aerodynamic characteristic is extremely complex.To explore the regulation range of a double bypass engine compression system,a multi-dimensional analysis method is developed,through which the coupling mechanism between the compressor component and the bypass is examined.The operation zones of the compressor components and the bypass system are proposed,and the operation range of the compression system is obtained by calculating the overlapping part of the operation zones.The results show that in the double bypass mode,there exists a minimum mode selector valve area and a minimum core driven fan stage stall margin that ensures a feasible bypass flow,the two parameters correspond to each other.Under the given fan and core driven fan stage conditions,the maximum value of the inner bypass ratio is restricted by the upper limit of the forward variable area bypass injector and the maximum Mach number in the total bypass,while the minimum value of the inner bypass ratio depends on the lower limit of the forward variable area bypass injector geometry and the system recirculation margin.The single bypass mode is a unique condition of the double bypass mode,as the operation zone of the compressor component degenerates from a two-dimensional surface to a straight line.There are multiple bypass states available in the single bypass mode,while the regulation range of the bypass ratio is jointly restricted by the operation range of the high pressure compressor and the aerodynamic boundary of the forward variable area bypass injector.展开更多
The current research about the flow ripple of axial piston pump mainly focuses on the effect of the structure of parts on the flow ripple. Therein, the structure of parts are usually designed and optimized at rated wo...The current research about the flow ripple of axial piston pump mainly focuses on the effect of the structure of parts on the flow ripple. Therein, the structure of parts are usually designed and optimized at rated working conditions. However, the pump usually has to work in large-scale and time-variant working conditions. Therefore, the flow ripple characteristics of pump and analysis for its test accuracy with respect to variant steady-state conditions and transient conditions in a wide range of operating parameters are focused in this paper. First, a simulation model has been constructed, which takes the kinematics of oil film within friction pairs into account for higher accuracy. Afterwards, a test bed which adopts Secondary Source Method is built to verify the model. The simulation and tests results show that the angular position of the piston, corresponding to the position where the peak flow ripple is produced, varies with the different pressure. The pulsating amplitude and pulsation rate of flow ripple increase with the rise of pressure and the variation rate of pressure. For the pump working at a constant speed, the flow pulsation rate decreases dramatically with the increasing speed when the speed is less than 27.78% of the maximum speed, subsequently presents a small decrease tendency with the speed further increasing. With the rise of the variation rate of speed, the pulsating amplitude and pulsation rate of flow ripple increase. As the swash plate angle augments, the pulsating amplitude of flow ripple increases, nevertheless the flow pulsation rate decreases. In contrast with the effect of the variation of pressure, the test accuracy of flow ripple is more sensitive to the variation of speed. It makes the test accuracy above 96.20% available for the pulsating amplitude of pressure deviating within a range of ~6% from the mean pressure. However, with a variation of speed deviating within a range of ±2% from the mean speed, the attainable test accuracy of flow ripple is above 93.07%. The model constructed in this research proposes a method to determine the flow ripple characteristics of pump and its attainable test accuracy under the large-scale and time-variant working conditions. Meanwhile, a discussion about the variation of flow ripple and its obtainable test accuracy with the conditions of the pump working in wide operating ranges is given as well.展开更多
If a 3-tuple (A:H_1→H_1,B:H_2→H_1,C:H_2→H_2) of operators on Hilbert spaces is given,we proved that the operator A:= on H=H_1⊕H_2 is≥0 if and only if A≥0,R(B) R(A1/2)and C≥B~* A^+ B, where A^+ is the generalize...If a 3-tuple (A:H_1→H_1,B:H_2→H_1,C:H_2→H_2) of operators on Hilbert spaces is given,we proved that the operator A:= on H=H_1⊕H_2 is≥0 if and only if A≥0,R(B) R(A1/2)and C≥B~* A^+ B, where A^+ is the generalized inverse of A. In general,A^+ is a closed operator,but since R(B) R(A1/2),B~* A^+ B is bounded yet.展开更多
Due to the lack of flexible interconnection devices,power imbalances between networks cannot be relieved effectively.Meanwhile,increasing the penetration of distributed generators exacerbates the temporal power imbala...Due to the lack of flexible interconnection devices,power imbalances between networks cannot be relieved effectively.Meanwhile,increasing the penetration of distributed generators exacerbates the temporal power imbalances caused by large peak-valley load differences.To improve the operational economy lowered by spatiotemporal power imbalances,this paper proposes a two-stage optimization strategy for active distribution networks(ADNs)interconnected by soft open points(SOPs).The SOPs and energy storage system(ESS)are adopted to transfer power spatially and temporally,respectively.In the day-ahead scheduling stage,massive stochastic scenarios against the uncertainty of wind turbine output are generated first.To improve computational efficiency in massive stochastic scenarios,an equivalent model between networks considering sensitivities of node power to node voltage and branch current is established.The introduction of sensitivities prevents violations of voltage and current.Then,the operating ranges(ORs)of the active power of SOPs and the state of charge(SOC)of ESS are obtained from models between networks and within the networks,respectively.In the intraday corrective control stage,based on day-ahead ORs,a receding-horizon model that minimizes the purchase cost of electricity and voltage deviations is established hour by hour.Case studies on two modified ADNs show that the proposed strategy achieves spatiotemporal power balance with lower cost compared with traditional strategies.展开更多
Electroabsorption modulators combining Franz-Keldysh effect and quantum confined Stark effect have been mono-lithically integrated with tunnel-injection quantum-well distributed feedback lasers using a quantum well in...Electroabsorption modulators combining Franz-Keldysh effect and quantum confined Stark effect have been mono-lithically integrated with tunnel-injection quantum-well distributed feedback lasers using a quantum well intermixing method. Superior characteristics such as extinction ratio and temperature insensitivity have been demonstrated at wide temperature ranges.展开更多
The magnetic stabilization flow regime could also be created forGeldart-Bnonmagnetizable particles pro-vided some magnetizable particles are introduced and the magnetic field is applied.This study aimed toexplore the ...The magnetic stabilization flow regime could also be created forGeldart-Bnonmagnetizable particles pro-vided some magnetizable particles are introduced and the magnetic field is applied.This study aimed toexplore the size(d_(pM))and density(ρ_(pM))effects of magnetizable particles on its operating range.The upperlimit(Umb;)could not be determined from the △P_(b)-U_(g)↓curve but could from analyzing the variation of △P_(b)-fluctuation with increasing U_(g).Due to the variation of U_(mfH)(lower limit)with d_(pM) and ppw,both U_(mbH)-U_(mfH) and(U_(mbH)-U_(mfH))/U_(mfH) were used to quantify the operating range of magnetic stabilization.U_(mbH)-U_(mfH) varied hardly with ρ_(pM) but increased significantly with decreasing ρ_(pM).(U_(mbH)-U_(mfH))/U_(mfH)increased as d_(pM) or ρ_(pM) decreased.lt was more difficult for the nonmagnetizable particles to escape fromthe network formed by the smaller/lighter magnetizable particles.For the same magnitude of change,dp had a stronger effect than ρ_(pM) on(U_(mbH)-U_(mfH))/U_(mfH).Neither U_(mbH)-U_(mfH) nor(U_(mbH)-U_(mfH):)/Uma variedmonotonously with the minimum fluidization velocity of the magnetizable particles,indicating that nostraightforward criterion for matching the magnetizable particles to the given nonmagnetizable particlescould be established based on their minimum fluidization velocities to maximize the operating range ofmagnetic stabilization.展开更多
To overcome the drawback of a short operation range and low-resolution of a passive location system using a civil communication signal, the new idea that utilizes code division multiple access （CDMA） signal and repe...To overcome the drawback of a short operation range and low-resolution of a passive location system using a civil communication signal, the new idea that utilizes code division multiple access （CDMA） signal and repeater is disposed off. First, the CDMA passive location model and observation function are given, and the error source and error range are analyzed. Subsequently, the CDMA passive location algorithm in a repeater environment is described and simulated. The simulation result shows that the algorithm can provide the location value with high accuracy.展开更多
Various core memory devices have been proposed for utilization in future inmemory computing technology featuring high energy efficiency.Flash memory is considered as a viable choice owing to its high integration densi...Various core memory devices have been proposed for utilization in future inmemory computing technology featuring high energy efficiency.Flash memory is considered as a viable choice owing to its high integration density,stability,and reliability,which has been verified by commercialized products.However,its high operating voltage and slow operation speed issues caused by the tunneling mechanism make its adoption in in-memory computing applications difficult.In this paper,we introduce a dual-mode memory device named“ferro-floating memory”,fabricated using van der Waals(vdW)materials(h-BN,MoS2,andα-In2Se3).The vdW material,α-In2Se3,acts as a polarization control layer for the ferroelectric memory operation and charge storage layer for the conventional flash memory operation.Compared to the tunnelingbased memory operation,the ferro-floating memory operates 1.9 and 3.3 times faster at 6.7 and 5.8 times lower operating voltages for programming and erasing operations,respectively.The dual-mode operation improves the linearity of conductance change by 5 times and the dynamic range by 48%through achieving conductance variation regions.Furthermore,we assess the effects of the variation in device operating voltage on neural networks and suggest a memory array operating scheme for maximizing the networks'performance through various training/inference simulations.展开更多
In this study,aerodynamic behaviors of swept and leaned blades were investigated.Axial and tangential blade curvatures impacts on compressor's operating parameters were analyzed separately.A commercial CFD program...In this study,aerodynamic behaviors of swept and leaned blades were investigated.Axial and tangential blade curvatures impacts on compressor's operating parameters were analyzed separately.A commercial CFD program which solves the Reynolds-averaged Navier-Stokes equations was used to find out the mentioned impact and the complicated flow field of transonic compressor-rotors.The CFD method that was used for solving flow field's equation was validated by experimental data of NASA Rotor 67.The results showed that the compressor with curved rotors had higher efficiency,rotor pressure ratio and stable operating range compared to the compressor with un-curved rotors.Using curved rotors mostly had higher impact on the overall stable operating range compared to the other operating parameters.Operating range involves choking point and stall point that were changed separately by using of bended blade.For finding the detailed impact of sweep and lean angle on transonic blades,various forms of lean and sweep angles were exerted to basic rotor.It was found that sweep angles increased overall operating range up to 30%,efficiency up to 2%and pressure ratio up to 1%.Leaning the blades increased the safe operating range,the pressure ratio and efficiency by 14%,4%and 2%respectively.展开更多
基金supported in part by the National Natural Science Foundation of China (Grant Nos.62273314,U21A20141,and 51821003)Fundamental Research Program of Shanxi Province (Grant No.202303021224008)Shanxi Province Key Laboratory of Quantum Sensing and Precision Measure-ment (Grant No.201905D121001).
文摘It is found that when the parity–time symmetry phenomenon is introduced into the resonant optical gyro system and it works near the exceptional point,the sensitivity can in theory be significantly amplified at low angular rate.However,in fact,the exceptional point is easily disturbed by external environmental variables,which means that it depends on harsh experimental environment and strong control ability,so it is difficult to move towards practical application.Here,we propose a new angular rate sensor structure based on exceptional surface,which has the advantages of high sensitivity and high robustness.The system consists of two fiber-optic ring resonators and two optical loop mirrors,and one of the resonators contains a variable ratio coupler and a variable optical attenuator.We theoretically analyze the system response,and the effects of phase and coupling ratio on the system response.Finally,compared with the conventional resonant gyro,the sensitivity of this exceptional surface angular rate sensor can be improved by about 300 times at low speed.In addition,by changing the loss coefficient in the ring resonator,we can achieve a wide range of 600 rad/s.This scheme provides a new approach for the development of ultra-high sensitivity and wide range angular rate sensors in the future.
文摘Gaps in compressors are generally unfavorable because they lead to energy loss.However,gaps on diffuser blades can broaden the operation range of a compressor.To broaden the operation range of a centrifugal compressor with a tandem diffuser,gaps with different sections and widths on the diffuser blades were examined to determine their influence on the compressor performance.The results show that the compressor’s surge margin increased from 33.28% to 49.2% for a 2.5%tip gap ratio,while its stability margin increased from 44% to 60.5%.However,pressure ratio and efficiency losses of 1.16% and 1.14%,respectively,were incurred.Gap widths less than 5%of the height of the diffuser blade are adequate for broadening the operation range,whereas gap ratios greater than 5%cause more energy loss without broadening the operation range further.Gaps can also reduce the Mach number in the diffuser blade channels and can be influenced by the impeller-tip gap.Moreover,diffuser gaps on the shroud side yield better performance than those on the hub side.An experiment was conducted to investigate the reliability of the calculation and conclusions in this study,and the results proved that the conclusions are valid for different types of centrifugal compressors.
文摘Traditional operating range prediction methods assume that the atmospheric radiances in a target path and a background path are equal. But they are different in a real-world environment. To solve this problem,the influence of atmospheric radiance on operating range prediction is analyzed in this paper. Range estimation model in thermal imaging based on background radiation（ REBR） is proposed. Infrared image radiometric calibration is used to calculate the background radiation of a system entrance pupil. The result shows that,compared with traditional operating range prediction methods,the REBR method is more suitable for the actual atmospheric transmission process and the physical process of infrared imaging.
基金Supported by the National Natural Science Foundation of China under Grant No 11304002the Natural Science Foundation of Education Bureau of Anhui Province under Grant No KJ2013A136the Natural Science Foundation of Anhui Province under Grant No 1208085MA07
文摘We fabricate a three-layer metamaterial of metal patterns/dielectric/metal films. The optical properties associated with Fano resonance of the metamaterials are investigated experimentally and theoretically. The results indicate that the introduction of Fano resonance due to symmetry breaking leads to a much wider absorption range. Furthermore, the amplitude and phase of reflection can be modulated effectively by adjusting various free parameters using the proposed structure.
文摘Hollow cathodes are widely used as electron sources and neutralizers in ion and Hall electric propulsion.Special applications such as commercial aerospace and gravitational wave detection require hollow cathodes with a very wide discharge current range.In this paper,a heater is used to compensate for the temperature drop of the emitter at low current.The self-sustained current can be extended from 0.6 to 0.1 A with a small discharge oscillation and ion energy when the flow rate is constant.This is also beneficial for long-life operation.However,when the discharge current is high(>1 A),heating can cause discharge oscillation,discharge voltage and ion energy to increase,f urther,combined with a rapid decline of pressure inside the cathode and an increase in the temperature in the cathode orifice plate,electron emission in die orifice and outside the orifice increases and the plasma density in the orifice decreases.This leads to a change in the cathode discharge mode.
基金co-supported by the National Natural Science Foundation of China(No.52206038)the National Science and Technology Major Project,China(No.Y2022-Ⅱ-0003)the Science Center for Gas Turbine Project,China(Nos.P2022-A-Ⅱ-001-001 and P2022-B-Ⅱ-002-001).
文摘The variable cycle engine is distinguished by its highly adjustable compression system,whose aerodynamic characteristic is extremely complex.To explore the regulation range of a double bypass engine compression system,a multi-dimensional analysis method is developed,through which the coupling mechanism between the compressor component and the bypass is examined.The operation zones of the compressor components and the bypass system are proposed,and the operation range of the compression system is obtained by calculating the overlapping part of the operation zones.The results show that in the double bypass mode,there exists a minimum mode selector valve area and a minimum core driven fan stage stall margin that ensures a feasible bypass flow,the two parameters correspond to each other.Under the given fan and core driven fan stage conditions,the maximum value of the inner bypass ratio is restricted by the upper limit of the forward variable area bypass injector and the maximum Mach number in the total bypass,while the minimum value of the inner bypass ratio depends on the lower limit of the forward variable area bypass injector geometry and the system recirculation margin.The single bypass mode is a unique condition of the double bypass mode,as the operation zone of the compressor component degenerates from a two-dimensional surface to a straight line.There are multiple bypass states available in the single bypass mode,while the regulation range of the bypass ratio is jointly restricted by the operation range of the high pressure compressor and the aerodynamic boundary of the forward variable area bypass injector.
基金Supported by National Basic Research Program of China(973 Program,Grant No.2014CB046403)National Key Technology R&D Program of the Twelfth Five-year Plan of China(Grant No.2013BAF07B01)
文摘The current research about the flow ripple of axial piston pump mainly focuses on the effect of the structure of parts on the flow ripple. Therein, the structure of parts are usually designed and optimized at rated working conditions. However, the pump usually has to work in large-scale and time-variant working conditions. Therefore, the flow ripple characteristics of pump and analysis for its test accuracy with respect to variant steady-state conditions and transient conditions in a wide range of operating parameters are focused in this paper. First, a simulation model has been constructed, which takes the kinematics of oil film within friction pairs into account for higher accuracy. Afterwards, a test bed which adopts Secondary Source Method is built to verify the model. The simulation and tests results show that the angular position of the piston, corresponding to the position where the peak flow ripple is produced, varies with the different pressure. The pulsating amplitude and pulsation rate of flow ripple increase with the rise of pressure and the variation rate of pressure. For the pump working at a constant speed, the flow pulsation rate decreases dramatically with the increasing speed when the speed is less than 27.78% of the maximum speed, subsequently presents a small decrease tendency with the speed further increasing. With the rise of the variation rate of speed, the pulsating amplitude and pulsation rate of flow ripple increase. As the swash plate angle augments, the pulsating amplitude of flow ripple increases, nevertheless the flow pulsation rate decreases. In contrast with the effect of the variation of pressure, the test accuracy of flow ripple is more sensitive to the variation of speed. It makes the test accuracy above 96.20% available for the pulsating amplitude of pressure deviating within a range of ~6% from the mean pressure. However, with a variation of speed deviating within a range of ±2% from the mean speed, the attainable test accuracy of flow ripple is above 93.07%. The model constructed in this research proposes a method to determine the flow ripple characteristics of pump and its attainable test accuracy under the large-scale and time-variant working conditions. Meanwhile, a discussion about the variation of flow ripple and its obtainable test accuracy with the conditions of the pump working in wide operating ranges is given as well.
文摘If a 3-tuple (A:H_1→H_1,B:H_2→H_1,C:H_2→H_2) of operators on Hilbert spaces is given,we proved that the operator A:= on H=H_1⊕H_2 is≥0 if and only if A≥0,R(B) R(A1/2)and C≥B~* A^+ B, where A^+ is the generalized inverse of A. In general,A^+ is a closed operator,but since R(B) R(A1/2),B~* A^+ B is bounded yet.
基金supported by the Science and Technology Project of State Grid Corporation of China(No.5400-202199281A-0-0-00)。
文摘Due to the lack of flexible interconnection devices,power imbalances between networks cannot be relieved effectively.Meanwhile,increasing the penetration of distributed generators exacerbates the temporal power imbalances caused by large peak-valley load differences.To improve the operational economy lowered by spatiotemporal power imbalances,this paper proposes a two-stage optimization strategy for active distribution networks(ADNs)interconnected by soft open points(SOPs).The SOPs and energy storage system(ESS)are adopted to transfer power spatially and temporally,respectively.In the day-ahead scheduling stage,massive stochastic scenarios against the uncertainty of wind turbine output are generated first.To improve computational efficiency in massive stochastic scenarios,an equivalent model between networks considering sensitivities of node power to node voltage and branch current is established.The introduction of sensitivities prevents violations of voltage and current.Then,the operating ranges(ORs)of the active power of SOPs and the state of charge(SOC)of ESS are obtained from models between networks and within the networks,respectively.In the intraday corrective control stage,based on day-ahead ORs,a receding-horizon model that minimizes the purchase cost of electricity and voltage deviations is established hour by hour.Case studies on two modified ADNs show that the proposed strategy achieves spatiotemporal power balance with lower cost compared with traditional strategies.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60736036,60706009,60777021 and 60702006)the National Basic Research Program of China (Grant Nos. 2006CB604901 and 2006CB604902)the National High Technology Research and Development Program of China (Grant Nos. 2007AA03Z419,2007AA03Z417 and 2009AA03Z442)
文摘Electroabsorption modulators combining Franz-Keldysh effect and quantum confined Stark effect have been mono-lithically integrated with tunnel-injection quantum-well distributed feedback lasers using a quantum well intermixing method. Superior characteristics such as extinction ratio and temperature insensitivity have been demonstrated at wide temperature ranges.
基金This work was supported by the National Natural Science Foundation of China(No.21808232).
文摘The magnetic stabilization flow regime could also be created forGeldart-Bnonmagnetizable particles pro-vided some magnetizable particles are introduced and the magnetic field is applied.This study aimed toexplore the size(d_(pM))and density(ρ_(pM))effects of magnetizable particles on its operating range.The upperlimit(Umb;)could not be determined from the △P_(b)-U_(g)↓curve but could from analyzing the variation of △P_(b)-fluctuation with increasing U_(g).Due to the variation of U_(mfH)(lower limit)with d_(pM) and ppw,both U_(mbH)-U_(mfH) and(U_(mbH)-U_(mfH))/U_(mfH) were used to quantify the operating range of magnetic stabilization.U_(mbH)-U_(mfH) varied hardly with ρ_(pM) but increased significantly with decreasing ρ_(pM).(U_(mbH)-U_(mfH))/U_(mfH)increased as d_(pM) or ρ_(pM) decreased.lt was more difficult for the nonmagnetizable particles to escape fromthe network formed by the smaller/lighter magnetizable particles.For the same magnitude of change,dp had a stronger effect than ρ_(pM) on(U_(mbH)-U_(mfH))/U_(mfH).Neither U_(mbH)-U_(mfH) nor(U_(mbH)-U_(mfH):)/Uma variedmonotonously with the minimum fluidization velocity of the magnetizable particles,indicating that nostraightforward criterion for matching the magnetizable particles to the given nonmagnetizable particlescould be established based on their minimum fluidization velocities to maximize the operating range ofmagnetic stabilization.
基金the Key Project of Ministry of Education (207097)Education Natural Science Foundation Project of CQCSTC (2006BB2376)
文摘To overcome the drawback of a short operation range and low-resolution of a passive location system using a civil communication signal, the new idea that utilizes code division multiple access （CDMA） signal and repeater is disposed off. First, the CDMA passive location model and observation function are given, and the error source and error range are analyzed. Subsequently, the CDMA passive location algorithm in a repeater environment is described and simulated. The simulation result shows that the algorithm can provide the location value with high accuracy.
基金National Research Foundation of Korea,Grant/Award Numbers:2020M3F3A2A02082436,2020R1A4A2002806,2021R1A2C2010026,2022M3F3A2A01072215Samsung Electronics Co.Ltd.,Grant/Award Number:IO201210-07994-01。
文摘Various core memory devices have been proposed for utilization in future inmemory computing technology featuring high energy efficiency.Flash memory is considered as a viable choice owing to its high integration density,stability,and reliability,which has been verified by commercialized products.However,its high operating voltage and slow operation speed issues caused by the tunneling mechanism make its adoption in in-memory computing applications difficult.In this paper,we introduce a dual-mode memory device named“ferro-floating memory”,fabricated using van der Waals(vdW)materials(h-BN,MoS2,andα-In2Se3).The vdW material,α-In2Se3,acts as a polarization control layer for the ferroelectric memory operation and charge storage layer for the conventional flash memory operation.Compared to the tunnelingbased memory operation,the ferro-floating memory operates 1.9 and 3.3 times faster at 6.7 and 5.8 times lower operating voltages for programming and erasing operations,respectively.The dual-mode operation improves the linearity of conductance change by 5 times and the dynamic range by 48%through achieving conductance variation regions.Furthermore,we assess the effects of the variation in device operating voltage on neural networks and suggest a memory array operating scheme for maximizing the networks'performance through various training/inference simulations.
文摘In this study,aerodynamic behaviors of swept and leaned blades were investigated.Axial and tangential blade curvatures impacts on compressor's operating parameters were analyzed separately.A commercial CFD program which solves the Reynolds-averaged Navier-Stokes equations was used to find out the mentioned impact and the complicated flow field of transonic compressor-rotors.The CFD method that was used for solving flow field's equation was validated by experimental data of NASA Rotor 67.The results showed that the compressor with curved rotors had higher efficiency,rotor pressure ratio and stable operating range compared to the compressor with un-curved rotors.Using curved rotors mostly had higher impact on the overall stable operating range compared to the other operating parameters.Operating range involves choking point and stall point that were changed separately by using of bended blade.For finding the detailed impact of sweep and lean angle on transonic blades,various forms of lean and sweep angles were exerted to basic rotor.It was found that sweep angles increased overall operating range up to 30%,efficiency up to 2%and pressure ratio up to 1%.Leaning the blades increased the safe operating range,the pressure ratio and efficiency by 14%,4%and 2%respectively.
