Solidification structure variation of single phase alloy with undercooling prior to nucleation has been widely studied. The progress, especially during the last decade, is reviewed so as to give a comprehensive knowle...Solidification structure variation of single phase alloy with undercooling prior to nucleation has been widely studied. The progress, especially during the last decade, is reviewed so as to give a comprehensive knowledge for it, in which the emphases are laid on the structure evolution mechanism and the potential application. Lastly, the future interesting subjects are presented.展开更多
A series of single phase,warm white light emitting phosphors,Gd(P_(x)V_(1−x))O_(4):y at%Sm^(3+),with 1 at%Bi^(3+) doping concentration were synthesized by high temperature solid state method in this work.The experimen...A series of single phase,warm white light emitting phosphors,Gd(P_(x)V_(1−x))O_(4):y at%Sm^(3+),with 1 at%Bi^(3+) doping concentration were synthesized by high temperature solid state method in this work.The experimental results indicate broadband cyan emission of Bi^(3+)and characteristic orange-red emission of Sm^(3+)can be effectively tuned by changing the ratios of PO^(3−)_(4)/VO^(3−)_(4) in Gd(P_(x)V_(1−x))O_(4):1 at%Sm^(3+),1 at%Bi^(3+),and the energy transfer process among VO^(3−)_(4),Sm^(3+),Bi^(3+) also can be adjusted.Based on this,warm white light emitting can be realized by further optimizing the doping concentration of Sm^(3+) in the phosphors.At 423 K,the PL intensity of Gd(P_(0.7)V_(0.3))O_(4):2 at%Sm^(3+),1 at%Bi^(3+) remains~84.3%of the initial value at 293 K,while the measured quantum efficiency is 67.8%.EL spectrum analysis results of the fabricated white light emitting diode(wLED)based on a 310 nm UV-chip and Gd(P_(0.7)V_(0.3))O4:2 at%Sm^(3+),1 at%Bi^(3+)phosphors imply low correlated color temperature(3132 K)and appropriate color-rending index(R_(a)=82.7).These results demonstrate that Gd(P_(0.7)V_(0.3))O4:2 at%Sm^(3+),1 at%Bi^(3+)is a good candidate for manufacturing UV-activated warm white light emitting diodes.展开更多
When, in a coal mine distribution network whose neutral point is grounded by an arc suppression coil (ASC), a fault occurs in the ASC, compensation cannot be properly realized. Furthermore, it can damage the safe and ...When, in a coal mine distribution network whose neutral point is grounded by an arc suppression coil (ASC), a fault occurs in the ASC, compensation cannot be properly realized. Furthermore, it can damage the safe and reliable run of the network. We first introduce a three-phase five-column arc suppression coil (TPFCASC) and discuss its autotracking compensation theory. Then we compare the single phase to ground fault of the coal mine distribution network with an open phase fault at the TPFCASC using the Thévenin theory, the symmetrical-component method and the complex sequence network respectively. The results show that, in both types of faults, zero-sequence voltage of the network will appear and the maximum magnitude of this zero-sequence voltage is different in both faults. Based on this situation, a protection for the open phase fault at the TPFCASC should be estab-lished.展开更多
Most of traditional traveling wave piezoelectric transducers are driven by two phase different excitation signals,leading to a complex control system and seriously limiting their applications in industry.To overcome t...Most of traditional traveling wave piezoelectric transducers are driven by two phase different excitation signals,leading to a complex control system and seriously limiting their applications in industry.To overcome these issues,a novel traveling wave sandwich piezoelectric transducer with a single-phase drive is proposed in this study.Traveling waves are produced in two driving rings of the transducer while the longitudinal vibration is excited in its sandwich composite beam,due to the coupling property of the combined structure.This results in the production of elliptical motions in the two driving rings to achieve the drive function.An analytical model is firstly developed using the transfer matrix method to analyze the dynamic behavior of the proposed transducer.Its vibration characteristics are measured and compared with computational results to validate the effectiveness of the proposed analytical model.Besides,the driving concept of the transducer is investigated by computing the motion trajectory of surface points of the driving ring and the quality of traveling wave of the driving ring.Additionally,application example investigations on the driving effect of the proposed transducer are carried out by constructing and assembling a tracked mobile system.Experimental results indicated that 1)the assembled tracked mobile system moved in the driving frequency of 19410 Hz corresponding to its maximum mean velocity through frequency sensitivity experiments;2)motion characteristic and traction performance measurements of the system prototype presented its maximum mean velocity with 59 mm/s and its maximum stalling traction force with 1.65 N,at the excitation voltage of 500 V_(RMS).These experimental results demonstrate the feasibility of the proposed traveling wave sandwich piezoelectric transducer.展开更多
In this paper, a regression method of estimation has been used to derive the mean estimate of the survey variable using simple random sampling without replacement in the presence of observational errors. Two covariate...In this paper, a regression method of estimation has been used to derive the mean estimate of the survey variable using simple random sampling without replacement in the presence of observational errors. Two covariates were used and a case where the observational errors were in both the survey variable and the covariates was considered. The inclusion of observational errors was due to the fact that data collected through surveys are often not free from errors that occur during observation. These errors can occur due to over-reporting, under-reporting, memory failure by the respondents or use of imprecise tools of data collection. The expression of mean squared error (MSE) based on the obtained estimator has been derived to the first degree of approximation. The results of a simulation study show that the derived modified regression mean estimator under observational errors is more efficient than the mean per unit estimator and some other existing estimators. The proposed estimator can therefore be used in estimating a finite population mean, while considering observational errors that may occur during a study.展开更多
In industrial drives, electric motors are extensively utilized to impart motion control and induction motors are the most familiar drive at present due to its extensive performance characteristic similar with that of ...In industrial drives, electric motors are extensively utilized to impart motion control and induction motors are the most familiar drive at present due to its extensive performance characteristic similar with that of DC drives. Precise control of drives is the main attribute in industries to optimize the performance and to increase its production rate. In motion control, the major considerations are the torque and speed ripples. Design of controllers has become increasingly complex to such systems for better management of energy and raw materials to attain optimal performance. Meager parameter appraisal results are unsuitable, leading to unstable operation. The rapid intensification of digital computer revolutionizes to practice precise control and allows implementation of advanced control strategy to extremely multifaceted systems. To solve complex control problems, model predictive control is an authoritative scheme, which exploits an explicit model of the process to be controlled. This paper presents a predictive control strategy by a neural network predictive controller based single phase induction motor drive to minimize the speed and torque ripples. The proposed method exhibits better performance than the conventional controller and validity of the proposed method is verified by the simulation results using MATLAB software.展开更多
This paper signifies the study of modeling and simulation of a single phase matrix converter for induction heating system. The working principle and the control method, using PID are revealing in detail. The performan...This paper signifies the study of modeling and simulation of a single phase matrix converter for induction heating system. The working principle and the control method, using PID are revealing in detail. The performance of the system is carried out in MATLAB/Simulink environment with pulse width modulation switching strategy by varying the duty cycle. PID control is employed to obtain the better performance for a specified input supply for various output frequencies. The proposed control strategy of AC to AC converter has been discussed with a wide range of operating frequencies and results in low Total Harmonic Distortion.展开更多
Current literature lacks simple ways to predict whether a given halide perovskite solid solution forms a single-phase system.Examining existing data suggests that single-phase A-site solid solutions are preferably for...Current literature lacks simple ways to predict whether a given halide perovskite solid solution forms a single-phase system.Examining existing data suggests that single-phase A-site solid solutions are preferably formed when substituent cations are larger and have more N–H bonds than the host cation.展开更多
Organic light-emitting diodes(OLEDs)used in virtual and augmented reality displays require micrometer-scale red-green-blue(RGB)pixel patterns in the emissive layer(EML).However,conventional patterning methods based on...Organic light-emitting diodes(OLEDs)used in virtual and augmented reality displays require micrometer-scale red-green-blue(RGB)pixel patterns in the emissive layer(EML).However,conventional patterning methods based on evaporation and shadow masks can only produce patterns larger than tens of micrometers owing to the geometric constraint of the mask.Herein,an indirect method for photopatterning solution-processed OLED EMLs is proposed,which can be used to form micrometer-scale RGB pixel patterns without involving direct exposure to UV radiation or harsh etching processes on EMLs.EMLs can be patterned byⅰ)forming a sacrificial photoresist(PR)pattern,ⅱ)spin-coating an EML film,ⅲ)converting the EML film into a single-phase network(SPN)structure by crosslinking vinylbenzyl-group-appended hosts and dopants at a low temperature,andⅳ)stripping the pre-formed PR pattern.Furthermore,repeating the process thrice results in the formation of RGB EML patterns.During the repeated process,the sacrificial PR pattern serves as a protective layer for the underlying EML pattern,effectively preventing the EML pattern from being exposed to solutions in subsequent processes.Using a conventional photolithography setup,we produced sets of RGB EML patterns with densities exceeding 3000 patterns/in.,which indicated the potential of the method for industrial use.展开更多
The solution of the intermetallic phase and the homogenization of composition are important for Mg alloy biomaterials.A single-phase Mg-6Zn alloy with the average grain size of about 20μm was prepared by ECAP process...The solution of the intermetallic phase and the homogenization of composition are important for Mg alloy biomaterials.A single-phase Mg-6Zn alloy with the average grain size of about 20μm was prepared by ECAP processed for six passes at 320°C.It indicated that the ECAP could significantly promote the process of solid solution in Mg-Zn alloy.The results showed that complete dissolution of the intermetallic phase improved the corrosion resistance of Mg-6Zn alloy in 0.9%NaCl solution by turning the corrosion behavior into uniform corrosion and increased the hardness in combination with its smaller grain size.展开更多
Mg–Zn–Ag alloys have been extensively studied in recent years for potential biodegradable implants due to their unique mechanical properties,biodegradability and biocompatibility.In the present study,Mg–3Zn-x Ag（w...Mg–Zn–Ag alloys have been extensively studied in recent years for potential biodegradable implants due to their unique mechanical properties,biodegradability and biocompatibility.In the present study,Mg–3Zn-x Ag（wt%,x=0.2,0.5 and0.8）alloys with single-phase crystal structure were prepared by backward extrusion at 340°C.The addition of Ag element into Mg–3Zn slightly influences the ultimate tensile strength and microstructure,but the elongation firstly increases from12%to 19.8%and then decreases from 19.8%to 9.9%with the increment of Ag concentration.The tensile yield strength,ultimate tensile strength and elongation of Mg–3Zn–0.2Ag alloy reach up to 142,234 MPa and 19.8%,respectively,which are the best mechanical performance of Mg–Zn–Ag alloys in the present work.The extruded Mg–3Zn–0.2Ag alloy also possesses the best corrosion behavior with the corresponding corrosion rate of 3.2 mm/year in immersion test,which could be explained by the single-phase and uniformly distributed grain structure,and the fewer twinning.展开更多
A speaker driver applied to class G/classⅠwith a single phase power supply is presented.Gain expanding and compressing technology are employed in the signal processing circuit to optimize power dissipation.The circui...A speaker driver applied to class G/classⅠwith a single phase power supply is presented.Gain expanding and compressing technology are employed in the signal processing circuit to optimize power dissipation.The circuit is implemented in 0.18μm N-well CMOS.Experimental results show that the speaker driver has a good audio sound quality and power efficiency.Less than 0.006%THD at a low power range and less than 0.4%at a medium power range can be obtained with a 1 kHz sine wave signal.Maximum output power of 360 mW can be gained at a load of 8Ω.The power efficiency is about twice that of a traditional class AB driver at the power range of 80 mW and shows more than 18%improvement at the higher output power range.展开更多
A novel controller is proposed to regulate the DC-link voltage of a single phase active power filter （SPAPF）. The proposed switched fractional controller （SFC） consists of a conventional PI controller, a fractiona...A novel controller is proposed to regulate the DC-link voltage of a single phase active power filter （SPAPF）. The proposed switched fractional controller （SFC） consists of a conventional PI controller, a fractional order PI （FO-PI） controller and a decision maker that switches between them. Commonly, the conventional PI controller is used in regulation loops due to its advantages in steady-state but it is limited in transient state. On the other hand, the FO-PI controller overcomes these draw- backs but it causes dramatic degradation in control performances in steady-state because of the fractional calculus theory and the approximation method used to implement this kind of controller. Thus, the purpose of this paper is to switch to the PI controller in steady-state to obtain the best power quality and to switch to the FO-PI controller when external disturbances are detected to guarantee a fast transient state. To investigate the efficiency and accuracy of the SFC considering all robustness tests, an experimental setup has been established. The results of the SFC fulfill the requirements, confirm its high performances in steady and transient states and demon- strate its feasibility and effectiveness. The experiment results have satisfied the limit specified by the IEEE harmonic standard 519.展开更多
The generation of electricity based on renewable energy sources,parti-cularly Photovoltaic(PV)system has been greatly increased and it is simply insti-gated for both domestic and commercial uses.The power generated fr...The generation of electricity based on renewable energy sources,parti-cularly Photovoltaic(PV)system has been greatly increased and it is simply insti-gated for both domestic and commercial uses.The power generated from the PV system is erratic and hence there is a need for an efficient converter to perform the extraction of maximum power.An improved interleaved Single-ended Primary Inductor-Converter(SEPIC)converter is employed in proposed work to extricate most of power from renewable source.This proposed converter minimizes ripples,reduces electromagnetic interference due tofilter elements and the contin-uous input current improves the power output of PV panel.A Crow Search Algo-rithm(CSA)based Proportional Integral(PI)controller is utilized for controlling the converter switches effectively by optimizing the parameters of PI controller.The optimized PI controller reduces ripples present in Direct Current(DC)vol-tage,maintains constant voltage at proposed converter output and reduces over-shoots with minimum settling and rise time.This voltage is given to single phase grid via 1�Voltage Source Inverter(VSI).The command pulses of 1�VSI are produced by simple PI controller.The response of the proposed converter is thus improved with less input current.After implementing CSA based PI the efficiency of proposed converter obtained is 96%and the Total Harmonic Distor-tion(THD)is found to be 2:4%.The dynamics and closed loop operation is designed and modeled using MATLAB Simulink tool and its behavior is performed.展开更多
Open phase in three phase induction motors is a common fault that can occur as a result of a fuse blowing or a pro- tective device failing on one phase of the motor. This paper introduces a new method,which is based o...Open phase in three phase induction motors is a common fault that can occur as a result of a fuse blowing or a pro- tective device failing on one phase of the motor. This paper introduces a new method,which is based on the transient mea- surement and can distinguish the fault of one phase connecting ground. The method has been proved to be in correspondence with the simulation results by Matlab and LabVIEW in practice, The method has merits of simplicity, accuracy and ease of USe.展开更多
In the synthesis of highly applicable metal-organic frameworks(MOFs),obtaining pure phases poses a great challenge since some MOFs have diverse phases with the same metal sources and ligands.Among such MOFs,PCN-223 an...In the synthesis of highly applicable metal-organic frameworks(MOFs),obtaining pure phases poses a great challenge since some MOFs have diverse phases with the same metal sources and ligands.Among such MOFs,PCN-223 and PCN-221 can easily be formed together in a one-pot reaction,making it hard to separate them in a single phase.It is known that some PCN series have a kinetic relationship in the early stages of their formation mechanisms.Thus,we have dedicated our efforts to finding the kinetic relationship between PCN-223 and PCN-221 by utilizing the chemical bath deposition(CBD)method to establish reaction parameters for their pure phases.We found that one out of the two phases can be transformed into the other phase by varying the Zr precursors,water amount,modulators,substrates,and reaction time.Furthermore,the pure phase of PCN-221 with a distinct open-pore channel of 100 nm,which has not been obtained previously,can be synthesized through the CBD method.In this work,we successfully demonstrate that the CBD method is a versatile method for synthesizing phase-pure and uniform MOFs by controlling their nucleation stage and pore structures.展开更多
Single-phase white light phosphors for phosphor-converted white light-emitting diodes(pc-WLEDs)have become a hot spot and attracted considerable attention.However,the unsatisfactory luminous efficiency and colour rend...Single-phase white light phosphors for phosphor-converted white light-emitting diodes(pc-WLEDs)have become a hot spot and attracted considerable attention.However,the unsatisfactory luminous efficiency and colour rendering index of this kind of device hinder their large-scale applications in the field of lighting.Herein,a novel multi-centre activated single-phase white light phosphor,Gd_(2)Sr_(3)B_(4)O_(12):Ce^(3+),Tb^(3+),Sm^(3+),has been designed and prepared.The crystal structures of the host and the doped samples are characterized with XRD and Rietveld refinements.The band gap of the host calculated with the density functional theory is consistent with the value obtained from the UV-Vis reflection spectrum.Benefiting from the energy transfer paths of Ce^(3+)–Tb^(3+),Ce^(3+)–Sm^(3+)and Tb^(3+)–Sm^(3+),which are quantitatively evaluated with photoluminescence spectra and decay curves,the intensities of the characteristic emission peaks of the three dopants are found to be closely interlocked and the emission colour of the phosphors can be precisely tuned by adjusting the relative ratio of the three ions.Under the excitation of near-UV light,the two phosphors of Gd_(2)Sr_(3)B_(4)O_(12):0.03Ce^(3+),0.18Tb^(3+),0.05Sm^(3+)and Gd_(2)Sr_(3)B_(4)O_(12):0.03Ce^(3+),0.22Tb^(3+),0.07Sm^(3+)emit white light with CIE coordinates of(0.32,0.35)and(0.34,0.34),and the quantum efficiencies are 46.8%and 34.9%,respectively.The temperature-dependent photoluminescence spectra of the phosphors show that the quenching temperature(T50%)is as high as 450 K.Finally,WLED devices with maximal colour rendering index of 87.5 are obtained by fabricating the two single-phase white light phosphors with 365 nm LED chips.The balanced and preferable comprehensive performances of Gd_(2)Sr_(3)B_(4)O_(12):Ce^(3+),Tb^(3+),Sm^(3+)demonstrate that the as-prepared single-phase white light phosphor can be a promising candidate for fabricating near-UV chip-based WLEDs.展开更多
Analysing the heat states of transformers under DC bias requires careful consideration of their own structural and material characteristics.Although the 3D finite element method(FEM)is a reliable way of simulating all...Analysing the heat states of transformers under DC bias requires careful consideration of their own structural and material characteristics.Although the 3D finite element method(FEM)is a reliable way of simulating all the details of transformers,it may be time-consuming or have encountered convergence difficulties due to the complex internal structure of the transformer.To address the issues,this paper proposes a fast calculation model for estimating the top-oil temperature rise and the winding hotspot temperature rise of single-phase three-limb transformers under DC bias.This model is based on the coupling principle of electric circuits,magnetic circuits and thermal circuits,and it considers the winding loss and core loss of the transformer under DC bias as key factors linking electromagnetic and thermal effects.All the model parameters can be obtained from nameplate data and regular test data to ensure the method's engineering practicality.The results were compared with 3D FEM,demonstrating favourable performance in terms of computational speed and availability.展开更多
Single-phase ordered body-centered cubic or B2 multi-principal element intermetallics(MPEIs)have garnered significant attention due to their exceptional mechanical and functional properties.However,their discovery in ...Single-phase ordered body-centered cubic or B2 multi-principal element intermetallics(MPEIs)have garnered significant attention due to their exceptional mechanical and functional properties.However,their discovery in complex compositional spaces is challenging due to the lack of high-dimensional phase diagrams and the inefficiency of traditional trial-and-error methods.In this study,we developed a physics-informed machine learning(ML)framework that integrates a conditional variational autoencoder(CVAE)with an artificial neural network(ANN).This approach effectively addresses the challenges of data limitation and imbalance,enabling the high-throughput generation of B2 MPEIs.Using this framework,we successfully identified a wide range of B2 complex alloys,spanning quaternary to senary systems,with superior mechanical performance.This work not only demonstrates a significant advancement in the discovery of B2 MPEIs but also provides an accelerated pathway for their design and development.展开更多
基金This work was supported by the National Natural Science Foundation of China under grant No. 50171043 and the Open Foundation from State Key Laboratory of Solidification Process-ing.
文摘Solidification structure variation of single phase alloy with undercooling prior to nucleation has been widely studied. The progress, especially during the last decade, is reviewed so as to give a comprehensive knowledge for it, in which the emphases are laid on the structure evolution mechanism and the potential application. Lastly, the future interesting subjects are presented.
基金Project supported by the National Natural Science Foundation of China(51972181,61705231)Major Basic Research Projects of Shandong Natural Science Foundation(ZR2018ZB0650)+2 种基金China Postdoctoral Science Foundation(2015M580573)High Quality Course Construction Project of Graduate Education in Shandong Province(SDYKC18051)Postgraduate Tutor Ability Improvement Project of Shandong Province(SDYY17179)。
文摘A series of single phase,warm white light emitting phosphors,Gd(P_(x)V_(1−x))O_(4):y at%Sm^(3+),with 1 at%Bi^(3+) doping concentration were synthesized by high temperature solid state method in this work.The experimental results indicate broadband cyan emission of Bi^(3+)and characteristic orange-red emission of Sm^(3+)can be effectively tuned by changing the ratios of PO^(3−)_(4)/VO^(3−)_(4) in Gd(P_(x)V_(1−x))O_(4):1 at%Sm^(3+),1 at%Bi^(3+),and the energy transfer process among VO^(3−)_(4),Sm^(3+),Bi^(3+) also can be adjusted.Based on this,warm white light emitting can be realized by further optimizing the doping concentration of Sm^(3+) in the phosphors.At 423 K,the PL intensity of Gd(P_(0.7)V_(0.3))O_(4):2 at%Sm^(3+),1 at%Bi^(3+) remains~84.3%of the initial value at 293 K,while the measured quantum efficiency is 67.8%.EL spectrum analysis results of the fabricated white light emitting diode(wLED)based on a 310 nm UV-chip and Gd(P_(0.7)V_(0.3))O4:2 at%Sm^(3+),1 at%Bi^(3+)phosphors imply low correlated color temperature(3132 K)and appropriate color-rending index(R_(a)=82.7).These results demonstrate that Gd(P_(0.7)V_(0.3))O4:2 at%Sm^(3+),1 at%Bi^(3+)is a good candidate for manufacturing UV-activated warm white light emitting diodes.
文摘When, in a coal mine distribution network whose neutral point is grounded by an arc suppression coil (ASC), a fault occurs in the ASC, compensation cannot be properly realized. Furthermore, it can damage the safe and reliable run of the network. We first introduce a three-phase five-column arc suppression coil (TPFCASC) and discuss its autotracking compensation theory. Then we compare the single phase to ground fault of the coal mine distribution network with an open phase fault at the TPFCASC using the Thévenin theory, the symmetrical-component method and the complex sequence network respectively. The results show that, in both types of faults, zero-sequence voltage of the network will appear and the maximum magnitude of this zero-sequence voltage is different in both faults. Based on this situation, a protection for the open phase fault at the TPFCASC should be estab-lished.
基金Supported by the National Science Foundation of China(Grants Nos.51905262 and U2037603)the Natural Science Foundation of Jiangsu Province(Grant No.BK20190398)the State Key Laboratory of Mechanical System and Vibration(Grant No.MSV202011).
文摘Most of traditional traveling wave piezoelectric transducers are driven by two phase different excitation signals,leading to a complex control system and seriously limiting their applications in industry.To overcome these issues,a novel traveling wave sandwich piezoelectric transducer with a single-phase drive is proposed in this study.Traveling waves are produced in two driving rings of the transducer while the longitudinal vibration is excited in its sandwich composite beam,due to the coupling property of the combined structure.This results in the production of elliptical motions in the two driving rings to achieve the drive function.An analytical model is firstly developed using the transfer matrix method to analyze the dynamic behavior of the proposed transducer.Its vibration characteristics are measured and compared with computational results to validate the effectiveness of the proposed analytical model.Besides,the driving concept of the transducer is investigated by computing the motion trajectory of surface points of the driving ring and the quality of traveling wave of the driving ring.Additionally,application example investigations on the driving effect of the proposed transducer are carried out by constructing and assembling a tracked mobile system.Experimental results indicated that 1)the assembled tracked mobile system moved in the driving frequency of 19410 Hz corresponding to its maximum mean velocity through frequency sensitivity experiments;2)motion characteristic and traction performance measurements of the system prototype presented its maximum mean velocity with 59 mm/s and its maximum stalling traction force with 1.65 N,at the excitation voltage of 500 V_(RMS).These experimental results demonstrate the feasibility of the proposed traveling wave sandwich piezoelectric transducer.
文摘In this paper, a regression method of estimation has been used to derive the mean estimate of the survey variable using simple random sampling without replacement in the presence of observational errors. Two covariates were used and a case where the observational errors were in both the survey variable and the covariates was considered. The inclusion of observational errors was due to the fact that data collected through surveys are often not free from errors that occur during observation. These errors can occur due to over-reporting, under-reporting, memory failure by the respondents or use of imprecise tools of data collection. The expression of mean squared error (MSE) based on the obtained estimator has been derived to the first degree of approximation. The results of a simulation study show that the derived modified regression mean estimator under observational errors is more efficient than the mean per unit estimator and some other existing estimators. The proposed estimator can therefore be used in estimating a finite population mean, while considering observational errors that may occur during a study.
文摘In industrial drives, electric motors are extensively utilized to impart motion control and induction motors are the most familiar drive at present due to its extensive performance characteristic similar with that of DC drives. Precise control of drives is the main attribute in industries to optimize the performance and to increase its production rate. In motion control, the major considerations are the torque and speed ripples. Design of controllers has become increasingly complex to such systems for better management of energy and raw materials to attain optimal performance. Meager parameter appraisal results are unsuitable, leading to unstable operation. The rapid intensification of digital computer revolutionizes to practice precise control and allows implementation of advanced control strategy to extremely multifaceted systems. To solve complex control problems, model predictive control is an authoritative scheme, which exploits an explicit model of the process to be controlled. This paper presents a predictive control strategy by a neural network predictive controller based single phase induction motor drive to minimize the speed and torque ripples. The proposed method exhibits better performance than the conventional controller and validity of the proposed method is verified by the simulation results using MATLAB software.
文摘This paper signifies the study of modeling and simulation of a single phase matrix converter for induction heating system. The working principle and the control method, using PID are revealing in detail. The performance of the system is carried out in MATLAB/Simulink environment with pulse width modulation switching strategy by varying the duty cycle. PID control is employed to obtain the better performance for a specified input supply for various output frequencies. The proposed control strategy of AC to AC converter has been discussed with a wide range of operating frequencies and results in low Total Harmonic Distortion.
基金supported by the Fundação de AmparoàPesquisa do Estado de São Paulo(FAPESP Project:2017/13769-1)the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior(CAPES-PRINT Project:88881.310513/2018-01)the Conselho Nacional de Desenvolvimento Científico e Tecnológico(151319/2023-5).
文摘Current literature lacks simple ways to predict whether a given halide perovskite solid solution forms a single-phase system.Examining existing data suggests that single-phase A-site solid solutions are preferably formed when substituent cations are larger and have more N–H bonds than the host cation.
基金supported by the National R&D Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(NRF-2023R1A2C3006550,2021R1A2C2008332,and RS-2024-00445116)。
文摘Organic light-emitting diodes(OLEDs)used in virtual and augmented reality displays require micrometer-scale red-green-blue(RGB)pixel patterns in the emissive layer(EML).However,conventional patterning methods based on evaporation and shadow masks can only produce patterns larger than tens of micrometers owing to the geometric constraint of the mask.Herein,an indirect method for photopatterning solution-processed OLED EMLs is proposed,which can be used to form micrometer-scale RGB pixel patterns without involving direct exposure to UV radiation or harsh etching processes on EMLs.EMLs can be patterned byⅰ)forming a sacrificial photoresist(PR)pattern,ⅱ)spin-coating an EML film,ⅲ)converting the EML film into a single-phase network(SPN)structure by crosslinking vinylbenzyl-group-appended hosts and dopants at a low temperature,andⅳ)stripping the pre-formed PR pattern.Furthermore,repeating the process thrice results in the formation of RGB EML patterns.During the repeated process,the sacrificial PR pattern serves as a protective layer for the underlying EML pattern,effectively preventing the EML pattern from being exposed to solutions in subsequent processes.Using a conventional photolithography setup,we produced sets of RGB EML patterns with densities exceeding 3000 patterns/in.,which indicated the potential of the method for industrial use.
基金The authors gratefully acknowledge financial support from the National Natural Science Foundation of China(Grant no.51301151)Jiangsu Province Natural Science Foundation of China(Grant nos.BK20130447 and BK20160869).
文摘The solution of the intermetallic phase and the homogenization of composition are important for Mg alloy biomaterials.A single-phase Mg-6Zn alloy with the average grain size of about 20μm was prepared by ECAP processed for six passes at 320°C.It indicated that the ECAP could significantly promote the process of solid solution in Mg-Zn alloy.The results showed that complete dissolution of the intermetallic phase improved the corrosion resistance of Mg-6Zn alloy in 0.9%NaCl solution by turning the corrosion behavior into uniform corrosion and increased the hardness in combination with its smaller grain size.
基金supported by the National Natural Science Foundation of China (Nos. 51371046 and 51525101)the National Key Research and Development Program of China (No. 2016YFB0701202)the Fundamental Research Funds of the Central Universities (No. N141008001)
文摘Mg–Zn–Ag alloys have been extensively studied in recent years for potential biodegradable implants due to their unique mechanical properties,biodegradability and biocompatibility.In the present study,Mg–3Zn-x Ag（wt%,x=0.2,0.5 and0.8）alloys with single-phase crystal structure were prepared by backward extrusion at 340°C.The addition of Ag element into Mg–3Zn slightly influences the ultimate tensile strength and microstructure,but the elongation firstly increases from12%to 19.8%and then decreases from 19.8%to 9.9%with the increment of Ag concentration.The tensile yield strength,ultimate tensile strength and elongation of Mg–3Zn–0.2Ag alloy reach up to 142,234 MPa and 19.8%,respectively,which are the best mechanical performance of Mg–Zn–Ag alloys in the present work.The extruded Mg–3Zn–0.2Ag alloy also possesses the best corrosion behavior with the corresponding corrosion rate of 3.2 mm/year in immersion test,which could be explained by the single-phase and uniformly distributed grain structure,and the fewer twinning.
文摘A speaker driver applied to class G/classⅠwith a single phase power supply is presented.Gain expanding and compressing technology are employed in the signal processing circuit to optimize power dissipation.The circuit is implemented in 0.18μm N-well CMOS.Experimental results show that the speaker driver has a good audio sound quality and power efficiency.Less than 0.006%THD at a low power range and less than 0.4%at a medium power range can be obtained with a 1 kHz sine wave signal.Maximum output power of 360 mW can be gained at a load of 8Ω.The power efficiency is about twice that of a traditional class AB driver at the power range of 80 mW and shows more than 18%improvement at the higher output power range.
文摘A novel controller is proposed to regulate the DC-link voltage of a single phase active power filter （SPAPF）. The proposed switched fractional controller （SFC） consists of a conventional PI controller, a fractional order PI （FO-PI） controller and a decision maker that switches between them. Commonly, the conventional PI controller is used in regulation loops due to its advantages in steady-state but it is limited in transient state. On the other hand, the FO-PI controller overcomes these draw- backs but it causes dramatic degradation in control performances in steady-state because of the fractional calculus theory and the approximation method used to implement this kind of controller. Thus, the purpose of this paper is to switch to the PI controller in steady-state to obtain the best power quality and to switch to the FO-PI controller when external disturbances are detected to guarantee a fast transient state. To investigate the efficiency and accuracy of the SFC considering all robustness tests, an experimental setup has been established. The results of the SFC fulfill the requirements, confirm its high performances in steady and transient states and demon- strate its feasibility and effectiveness. The experiment results have satisfied the limit specified by the IEEE harmonic standard 519.
文摘The generation of electricity based on renewable energy sources,parti-cularly Photovoltaic(PV)system has been greatly increased and it is simply insti-gated for both domestic and commercial uses.The power generated from the PV system is erratic and hence there is a need for an efficient converter to perform the extraction of maximum power.An improved interleaved Single-ended Primary Inductor-Converter(SEPIC)converter is employed in proposed work to extricate most of power from renewable source.This proposed converter minimizes ripples,reduces electromagnetic interference due tofilter elements and the contin-uous input current improves the power output of PV panel.A Crow Search Algo-rithm(CSA)based Proportional Integral(PI)controller is utilized for controlling the converter switches effectively by optimizing the parameters of PI controller.The optimized PI controller reduces ripples present in Direct Current(DC)vol-tage,maintains constant voltage at proposed converter output and reduces over-shoots with minimum settling and rise time.This voltage is given to single phase grid via 1�Voltage Source Inverter(VSI).The command pulses of 1�VSI are produced by simple PI controller.The response of the proposed converter is thus improved with less input current.After implementing CSA based PI the efficiency of proposed converter obtained is 96%and the Total Harmonic Distor-tion(THD)is found to be 2:4%.The dynamics and closed loop operation is designed and modeled using MATLAB Simulink tool and its behavior is performed.
文摘Open phase in three phase induction motors is a common fault that can occur as a result of a fuse blowing or a pro- tective device failing on one phase of the motor. This paper introduces a new method,which is based on the transient mea- surement and can distinguish the fault of one phase connecting ground. The method has been proved to be in correspondence with the simulation results by Matlab and LabVIEW in practice, The method has merits of simplicity, accuracy and ease of USe.
基金supported by grants(NRF-2018R1D1A1B07050671 and NRF-2017R1A2B4006352)of the National Research Foundation of Korea(NRF)funded by the Korea Government(Ministry of Science and ICT)and by Industrial Core Technology Development Program(no.20005342,‘Development of VOC oxidation system’)funded by the Ministry of Trade,Industry&Energy(MI,Korea)supported by the Hankuk University of Foreign Studies Research Fund of 2019support of the Korea Institute of Industrial Technology(Project No.EE-19-0022).
文摘In the synthesis of highly applicable metal-organic frameworks(MOFs),obtaining pure phases poses a great challenge since some MOFs have diverse phases with the same metal sources and ligands.Among such MOFs,PCN-223 and PCN-221 can easily be formed together in a one-pot reaction,making it hard to separate them in a single phase.It is known that some PCN series have a kinetic relationship in the early stages of their formation mechanisms.Thus,we have dedicated our efforts to finding the kinetic relationship between PCN-223 and PCN-221 by utilizing the chemical bath deposition(CBD)method to establish reaction parameters for their pure phases.We found that one out of the two phases can be transformed into the other phase by varying the Zr precursors,water amount,modulators,substrates,and reaction time.Furthermore,the pure phase of PCN-221 with a distinct open-pore channel of 100 nm,which has not been obtained previously,can be synthesized through the CBD method.In this work,we successfully demonstrate that the CBD method is a versatile method for synthesizing phase-pure and uniform MOFs by controlling their nucleation stage and pore structures.
基金financially supported by grants from the National Natural Science Foundation of China(NSFC No.51972347 and 21771195)the joint projects of NSFC with Guangdong Province(No.U22A20135 and U1301242).
文摘Single-phase white light phosphors for phosphor-converted white light-emitting diodes(pc-WLEDs)have become a hot spot and attracted considerable attention.However,the unsatisfactory luminous efficiency and colour rendering index of this kind of device hinder their large-scale applications in the field of lighting.Herein,a novel multi-centre activated single-phase white light phosphor,Gd_(2)Sr_(3)B_(4)O_(12):Ce^(3+),Tb^(3+),Sm^(3+),has been designed and prepared.The crystal structures of the host and the doped samples are characterized with XRD and Rietveld refinements.The band gap of the host calculated with the density functional theory is consistent with the value obtained from the UV-Vis reflection spectrum.Benefiting from the energy transfer paths of Ce^(3+)–Tb^(3+),Ce^(3+)–Sm^(3+)and Tb^(3+)–Sm^(3+),which are quantitatively evaluated with photoluminescence spectra and decay curves,the intensities of the characteristic emission peaks of the three dopants are found to be closely interlocked and the emission colour of the phosphors can be precisely tuned by adjusting the relative ratio of the three ions.Under the excitation of near-UV light,the two phosphors of Gd_(2)Sr_(3)B_(4)O_(12):0.03Ce^(3+),0.18Tb^(3+),0.05Sm^(3+)and Gd_(2)Sr_(3)B_(4)O_(12):0.03Ce^(3+),0.22Tb^(3+),0.07Sm^(3+)emit white light with CIE coordinates of(0.32,0.35)and(0.34,0.34),and the quantum efficiencies are 46.8%and 34.9%,respectively.The temperature-dependent photoluminescence spectra of the phosphors show that the quenching temperature(T50%)is as high as 450 K.Finally,WLED devices with maximal colour rendering index of 87.5 are obtained by fabricating the two single-phase white light phosphors with 365 nm LED chips.The balanced and preferable comprehensive performances of Gd_(2)Sr_(3)B_(4)O_(12):Ce^(3+),Tb^(3+),Sm^(3+)demonstrate that the as-prepared single-phase white light phosphor can be a promising candidate for fabricating near-UV chip-based WLEDs.
基金supported by the National Natural Science Foundation of China Joint Fund Key Project(Grant U22B20118).
文摘Analysing the heat states of transformers under DC bias requires careful consideration of their own structural and material characteristics.Although the 3D finite element method(FEM)is a reliable way of simulating all the details of transformers,it may be time-consuming or have encountered convergence difficulties due to the complex internal structure of the transformer.To address the issues,this paper proposes a fast calculation model for estimating the top-oil temperature rise and the winding hotspot temperature rise of single-phase three-limb transformers under DC bias.This model is based on the coupling principle of electric circuits,magnetic circuits and thermal circuits,and it considers the winding loss and core loss of the transformer under DC bias as key factors linking electromagnetic and thermal effects.All the model parameters can be obtained from nameplate data and regular test data to ensure the method's engineering practicality.The results were compared with 3D FEM,demonstrating favourable performance in terms of computational speed and availability.
基金supported by university grants council(RGC),the Hong Kong government,through the general research fund(GRF)with the grant numbers of CityU 11201721 and CityU 11202924supported by the National Natural Science Foundation of China(Grant No.U20A20236).
文摘Single-phase ordered body-centered cubic or B2 multi-principal element intermetallics(MPEIs)have garnered significant attention due to their exceptional mechanical and functional properties.However,their discovery in complex compositional spaces is challenging due to the lack of high-dimensional phase diagrams and the inefficiency of traditional trial-and-error methods.In this study,we developed a physics-informed machine learning(ML)framework that integrates a conditional variational autoencoder(CVAE)with an artificial neural network(ANN).This approach effectively addresses the challenges of data limitation and imbalance,enabling the high-throughput generation of B2 MPEIs.Using this framework,we successfully identified a wide range of B2 complex alloys,spanning quaternary to senary systems,with superior mechanical performance.This work not only demonstrates a significant advancement in the discovery of B2 MPEIs but also provides an accelerated pathway for their design and development.
