Objective To observe postoperative effect of electroacupuncture（EA） of different frequencies in acupuncture anesthesia combined with drugs on patients undergoing thyroid surgery.Methods One hundred and twenty patien...Objective To observe postoperative effect of electroacupuncture（EA） of different frequencies in acupuncture anesthesia combined with drugs on patients undergoing thyroid surgery.Methods One hundred and twenty patients undergoing thyroid surgery were randomly divided into a 2Hz electroacupuncture anesthesia group（group A）,a 100 Hz electroacupuncture anesthesia group（group B）,a 2Hz/100 Hz electroacupuncture anesthesia group（group C） and a cervical plexus block group（group D） in accordance with the random number table method,with 30 patients in each group.In group A,group B and group C,electroacupuncture was applied at bilateral Futu（扶突 LI 18）,Hegu（合谷 LI 4） and Neiguan（内关 PC 6） at frequencies of 2 Hz,100 Hz and 2 Hz/100 Hz respectively for 30 min.The needles were retained till the end of the surgery.Dolantin and atropine were intramuscularly injected In group D,bilateral cervical plexus block was produced with a mixture of1%lidocaine and 0.375%bupivicaine.Before surgery,pain threshold and threshold of pain tolerance were determined;during surgery,the duration of surgery was recorded;and after surgery,QOLS（Quality Of Life Score） and PHS（Prince-Henry Score） were assessed.Results PHS in group A,group B and group C were lower than that in group D,respectively（0.20±0.41,0.17±0.38,0.10±0.31 vs 0.40±0.50,P〈0.01）,and PHS in group C was lower than those in group A and group B,respectively（both P〈0.01）.QOLS in group A,group B and group C were higher than that in group D,respectively（9.97±1.07,9.97±2.27,10.40±1.45 vs 9.73±1.41,P〈0.05,P〈0.01）,and QOLS in group C was higher than those in group A and group B,respectively（both P〈0.05）.Conclusion Acupuncture anesthesia combined with drugs has better postoperative effect than drug anesthesia.Electroacupuncture of different frequencies can significantly improve general quality of life of patients,so patients recover well after thyroid surgery.As patients in group C suffered from the slightest pain with the highest quality of life,they recovered best within the shortest time.Electroacupuncture at frequency of 2 Hz/100 Hz can better play postoperative analgesic effect.展开更多
The precision of landslide displacement prediction is crucial for effective landslide prevention and mitigation strategies.However,the role of surface monitoring frequency in influencing prediction accuracy has been l...The precision of landslide displacement prediction is crucial for effective landslide prevention and mitigation strategies.However,the role of surface monitoring frequency in influencing prediction accuracy has been largely neglected.This study examined the effect of varying monitoring frequencies on the accuracy of displacement predictions by using the Baijiabao landslide in the Three Gorges Reservoir Area(TGRA)as a case study.We collected surface automatic monitoring data at different intervals,ranging from daily to monthly.The Ensemble Empirical Mode Decomposition(EEMD)algorithm was utilized to dissect the accumulated displacements into periodic and trend components at each monitoring frequency.Polynomial fitting was applied to forecast the trend component while the periodic component was predicted with two state-of-the-art neural network models:Long Short-Term Memory(LSTM)and Gated Recurrent Unit(GRU).The predictions from these models were integrated to derive cumulative displacement forecasts,enabling a comparative analysis of prediction accuracy across different monitoring frequencies.The results demonstrate that the proposed models achieve high accuracy in landslide displacement forecasting,with optimal performance observed at moderate monitoring intervals.Intriguingly,the daily mean average error(MAE)decreases sharply with increasing monitoring frequency,reaching a plateau.These findings were corroborated by a parallel analysis of the Bazimen landslide,suggesting that moderate monitoring intervals of approximately 7 to 15 days are most conducive to achieving enhanced prediction accuracy compared to both daily and monthly intervals.展开更多
Objective To compare the difference in the clinical efficacy on the different frequency hearing damages for the patients with sudden deafness between the comprehensive therapy of electroacupuncture and western medicin...Objective To compare the difference in the clinical efficacy on the different frequency hearing damages for the patients with sudden deafness between the comprehensive therapy of electroacupuncture and western medicine and the simple western medicine comprehensive therapy. Methods Fifty-eight cases were randomized into an acupuncture plus medication group （28 cases, 32 damaged ears） and a western medicine group （30 cases, 34 damaged ears）. In the acupuncture plus medication group, the comprehensive therapy of electroacupuncture and western medicine was used. The main points were ěrmén （耳门 TE 21）, Tīnggōng （听宫 SI 19）, Tīnghuì （听会 GB 2）, Yìfēng （翳风 TE 17）, etc. The western medicine therapy was the comprehensive treatment with vasodilators, the medicines for promoting nerve function and releasing inner ear edema and hyperbaric oxygen. In the western medicine group, the western medicine comprehensive therapy was adopted. 10-day treatment made one session. Two sessions of treatment were required. In 1 or 2 sessions of treatment, the efficacy was observed, the electric audiometry was evaluated. Additionally, the blood routine and liver and kidney functions were detected. Results The total effective rate was 50.0% （16/32） in the acupuncture ＋ medication group and was 55.9% （19/34） in the western medicine group. The efficacies were similar between the two groups （P〉0.05）. In 1 and 2 sessions of treatment, at 250 Hz, 500 Hz and 1 kHz, the electric audiometry values in either group were recovered significantly as compared with those before treatment （all P〈0.01）. At 2 kHz, in 1 and 2 sessions of treatment, the improvements of the electric audiometry values were significant as compared with those before treatment in the acupuncture plus medication group separately （P〈0.05, P〈0.01）. At 4 kHz, the differences were not significant statistically before and after treatment in either group （all P〉0.05）. There were no abnormalities in the blood routine and liver and kidney function detections before and after treatment in either group. Conclusion Either the comprehensive therapy of electroacupuncture and western medicine or the simple western medicine comprehensive therapy is effective in the treatment of low frequency hearing damage of sudden deafness. Either of them has no effect on high frequency hearing damage. But for the middle frequency hearing damage, the efficacy of the comprehensive therapy of electroacupuncture and western medicine is superior to that of the simple western medicine comprehensive therapy.展开更多
Considering the estimation accuracy reduction of Frequency Difference of Arrival （FDOA） caused by relative Doppler companding, a joint Time Difference of Arrival （TDOA）, FDOA and differential Doppler rate estimati...Considering the estimation accuracy reduction of Frequency Difference of Arrival （FDOA） caused by relative Doppler companding, a joint Time Difference of Arrival （TDOA）, FDOA and differential Doppler rate estimation method is proposed and its Cramer-Rao low bound is derived in this paper. Firstly, second-order ambiguity function is utilized to reduce the dimensionality and estimate initial TDOA and differential Doppler rate. Secondly, the TDOA estimation is updated and FDOA is obtained using cross ambiguity function, in which relative Doppler com- panding is compensated by the existing differential Doppler rate. Thirdly, differential Doppler rate estimation is updated using cross estimator. Theoretical analysis on estimation variance and Cramer-Rao low bound shows that the final estimation of TDOA, FDOA and differential Doppler rate performs well at both low and high signal-noise ratio, although the initial estimation accuracy of TDOA and differential Doppler rate is relatively poor under low signal-noise ratio conditions. Simulation results finally verify the theoretical analysis and show that the proposed method can overcome relative Doppler companding problem and performs well for all TDOA, FDOA and differential Doppler rate estimation.展开更多
The marine risers are often subjected to parametric excitations from the fluctuation top tension. The top tension on the riser may fluctuate with multiple frequencies caused by irregular waves. In this paper, the infl...The marine risers are often subjected to parametric excitations from the fluctuation top tension. The top tension on the riser may fluctuate with multiple frequencies caused by irregular waves. In this paper, the influence between different frequency components in the top tension on the riser system is theoretically simulated and analyzed. With the Euler-Bernoulli beam theory, a dynamic model for the vibrations of the riser is established. The top tension is set as fluctuating with time and it has two different frequencies. The influences from the fluctuation amplitudes, circular frequencies and phase angles of these frequency components on the riser system are analyzed in detail. When these two frequencies are fluctuating in the stable regions, the riser system may become unstable because ω1+ω2≈2Ωn. The fluctuation amplitudes of these frequencies have little effect on the components of the vibration frequencies of the riser. For different phase angles, the stability and dynamic behaviors of the riser would be different.展开更多
According to the requirement of multi-parameter time and frequency measurement without frequency normalization,a different frequency synchronization theory is proposed based on Lissajous figure method and the variatio...According to the requirement of multi-parameter time and frequency measurement without frequency normalization,a different frequency synchronization theory is proposed based on Lissajous figure method and the variation lawof Lissajous figure which are used in practice teaching of frequency measurement. The theory can achieve high-precision transmission and comparison of time and frequency and precise locking and tracking of phase and frequency,improve the level of scientific research on time and frequency for postgraduate,and promote practice teaching innovation of time frequency measurement for undergraduate. Utilizing the ratio of horizontal and vertical inflection point of the Lissajous figure,the nominal frequency of the measured signal is precisely calculated.The frequency deviation between the measured frequency and its nominal frequency can be obtained by combining the turning cycle of the Lissajous figure. By observing the phase relationship between the frequency standard signal and the measured signal,the accurate measurement of the frequency is implemented. Experimental results showthat the direct measurement and comparison better than the 10-11 order of magnitude with common frequency source can be finished between any signal frequencies.The frequency measurement method based on the theory has the advantage of simple operation,quick measurement speed,small error,lownoise and high measurement precision. It plays an important role in time synchronization,communications,metrology,scientific research,educational technology practice and equipment and other fields.展开更多
High-efficiency terahertz(THz) wave generation with multiple frequencies by optimized cascaded difference frequency generation(OCDFG) is investigated at 100 K using a nonlinear crystal consisting of a periodically pol...High-efficiency terahertz(THz) wave generation with multiple frequencies by optimized cascaded difference frequency generation(OCDFG) is investigated at 100 K using a nonlinear crystal consisting of a periodically poled lithium niobate(PPLN) part and an aperiodically poled lithium niobate(APPLN) part.Two infrared pump waves with a frequency difference ω_(T1) generate THz waves and a series of cascaded optical waves in the PPLN part by cascaded difference frequency generation(CDFG).The generated cascaded optical waves with frequency interval ω_(T1) then further interact in the APPLN part by OCDFG,yielding the following two advantages.First,OCDFG in the APPLN part is efficiently stimulated by inputting multi-order cascaded optical waves rather than the only two intense infrared pump waves,yielding unprecedented energy conversion efficiencies in excess of 37% at 1 THz at 100 K.Second,THz waves with M timesω_(T1) are generated by mixing the mth-order and the(m+M)th-order cascaded optical waves by designing poling period distributions of the APPLN part.展开更多
Objective: to compare the clinical effect of different frequency hemoperfusion combined with hemodialysis in the treatment of end-stage renal insufficiency. Methods: selected hospital in January 2019 - January 2020 tr...Objective: to compare the clinical effect of different frequency hemoperfusion combined with hemodialysis in the treatment of end-stage renal insufficiency. Methods: selected hospital in January 2019 - January 2020 treatment of 94 patients with end-stage renal failure patients as the research object, randomly divided into 3 groups, all patients were given hemodialysis treatment, three times a week, at the same time give different frequencies of blood perfusion, I group of 32 cases of once every 2 weeks, II group of 31 cases, treatment for 1 times a week. In group III, 31 patients were treated twice a week. After 1 year of treatment, the changes of microinflammatory status indicators in all patients were observed and analyzed. Results: after treatment, the levels of TNF-α, hs-CRP and IL-6 in 3 groups were better than before treatment, and the levels of TNF-α, hs-CRP and IL-6 in group II and III were lower than group I, the differences were statistically significant (P < 0.05). There were no significant differences in TNF-α, hs-CRP and IL-6 levels between group II and group III (P > 0.05). Conclusion: medium and high frequency hemoperfusion combined with hemodialysis in the treatment of end-stage renal insufficiency can fully improve the microinflammatory status of patients, and medium frequency hemoperfusion is more cost-effective and more suitable for clinical treatment.展开更多
BACKGROUND Repetitive transcranial magnetic stimulation(rTMS)entered clinical practice in China after 2000,first used in psychiatric surgery,and then in neurology and other disciplines.The First Hospital of Jiaxing in...BACKGROUND Repetitive transcranial magnetic stimulation(rTMS)entered clinical practice in China after 2000,first used in psychiatric surgery,and then in neurology and other disciplines.The First Hospital of Jiaxing introduced TMS in 2015.In practical applications,it has been found that different models of instruments and technical parameters can lead to differences in therapeutic efficacy.Therefore,our hospital selected the Danish TMS instrument,which ranks second in China,to test patients with schizophrenia from March 2021 to July 2021,with a focus on comparing the results at 5 Hz,10 Hz,and 15 Hz.The testing time is concentrated between 8:30 to 10:30 in the morning.A contingency plan was made for the quality after inspection before testing.Two evaluators independently control the quality of the contingency plan.The data is independently saved and proofread by two evaluators.The purpose of this study is to translate the research results into clinical practice and provide reference basis.AIM To investigate the effects of rehabilitation therapy using rTMS on the negative symptoms and event-related potential component of P300 in chronic schizophrenia.METHODS One hundred and five patients with chronic schizophrenia were randomly allocated to three groups based on the frequency of rTMS(5,10,or 15 Hz).The patients underwent five sessions of rTMS per week for 5 weeks.We compared the pre-and post-treatment P300 latency and scores for the Scale for Assessment of Negative Symptoms(SANS).RESULTS A significant decrease in SANS score after rTMS was observed in the 10-Hz group(P<0.05),which was not observed in the 5-Hz and 15-Hz groups.There was a significant increase in P300 amplitude in the 10-Hz group after rTMS treatment(P<0.05),but there was no significant change in P300 latency(P>0.05).The improvement of SANS score in the 10-Hz rTMS group was related to patient age and disease course.CONCLUSION rTMS at 10 Hz improved negative symptoms and cognitive function in chronic schizophrenia;however,further studies on the mechanism of action are required to validate our observations.展开更多
The radar radiation source signals hold extremely high reconnaissance value.Accurately positioning these signals constitutes one of the key technologies in safeguarding the security of the electromagnetic space.The po...The radar radiation source signals hold extremely high reconnaissance value.Accurately positioning these signals constitutes one of the key technologies in safeguarding the security of the electromagnetic space.The positioning error in multi-station scenarios is influenced not only by the accuracy of positioning parameter estimation but also by the geometric configuration of the positioning platform.This paper focuses on the direction of arrival(DOA),frequency difference of arrival(FDOA),and time difference of arrival(TDOA)methods,analyzing the optimal configuration,optimal detection area,and optimal position dilution of precision in both elevation-known and elevation-unknown scenarios.Specifically,the paper constructs a signal receiving model,establishes the corresponding positioning equations,and performs dimensional normalization on these equations to derive measurement values in meters.Through differential processing,the position dilution of precision is obtained,which is then used as the optimization function to determine the optimal configuration,optimal detection area,and optimal position dilution of precision.Simulation results validate the accuracy of the proposed formulas.展开更多
Acupuncture has been shown to ameliorate cognitive impairment of Alzheimer’s disease.Acupoints and stimulation frequency influence the therapeutic effect of electroacupuncture.Rat models of Alzheimer’s disease were ...Acupuncture has been shown to ameliorate cognitive impairment of Alzheimer’s disease.Acupoints and stimulation frequency influence the therapeutic effect of electroacupuncture.Rat models of Alzheimer’s disease were established by injecting amyloid beta 1–42（Aβ_（1–42））into the bilateral lateral ventricles.Electroacupuncture at 2,30,and 50 Hz was carried out at Baihui（GV20;15°obliquely to a depth of 2mm）and Shenshu（BL23;perpendicularly to 4–6 mm depth）,once a day for 20 minutes（each）,for 15 days,taking a break every 7 days.The Morris water maze test was conducted to assess the learning and memory.The expression levels of glycogen synthase kinase-3β（GSK-3β）,p Ser9-GSK-3β,p Tyr216-GSK-3β,amyloid precursor protein and Aβ_（1–40） in the hippocampus were determined by western blot assay.Results demonstrated that electroacupuncture treatment at different frequencies markedly improved learning and memory ability,increased synaptic curvatures,decreased the width of synaptic clefts,thickened postsynaptic densities,and downregulated the expression of GSK-3β,amyloid precursor protein,and Aβ_（1–40）.pSer9-GSK-3βexpression markedly decreased,while p Tyr216-GSK-3βexpression increased.High-frequency（50 Hz）electroacupuncture was more effective than low（2 Hz）or medium-frequency（30 Hz）electroacupuncture.In conclusion,electroacupuncture treatment exerts a protective effect against Aβ_（1–42）-induced learning and memory deficits and synapse-ultrastructure impairment via inhibition of GSK-3βactivity.Moreover,high-frequency electroacupuncture was the most effective therapy.展开更多
Polarization coding is a specific encoding method by using the polarization state of optical signal carrying coded in- formation. It focuses on nonlinear effects, polarization mode dispersion and other issues in high-...Polarization coding is a specific encoding method by using the polarization state of optical signal carrying coded in- formation. It focuses on nonlinear effects, polarization mode dispersion and other issues in high-speed fiber-optic communi- cations. This paper presents a measurement method for polarization state based on elastic-optic modulator. This method not only retains the original advantages of elastic-optic modulator for polarization measurement, but also overcomes the defects of existing methods including high modulation frequency and invalid collection by using array detector. Matlab simulation and experimental verification scheme are given. The feasibility of this method is verified through theoretical analysis, and simulation and experimental results are carried out. The error analysis of the measurement results shows that the method can meet the measurement requirements and provide conditions for using the polarization encoding in high-speed communication.展开更多
This paper examines the characteristics of a harmonic plane wave in 1D and applies it to a model of an auditorium in the shape of a quarter of an ellipsoid. In the application, this paper will mainly look at transmiss...This paper examines the characteristics of a harmonic plane wave in 1D and applies it to a model of an auditorium in the shape of a quarter of an ellipsoid. In the application, this paper will mainly look at transmission loss, reverberation, disruption of the performers, and differences between different frequencies. The differences between different frequencies will be analyzed on both a macroscopic auditorium level as well as on a microscopic level of a single point in the audience.展开更多
Objective:To observe the effects of electroacupuncture(EA)with varied frequencies on headache and anxiety-depression symptoms in patients with migraine and to screen optimal frequency of EA for patientswith such condi...Objective:To observe the effects of electroacupuncture(EA)with varied frequencies on headache and anxiety-depression symptoms in patients with migraine and to screen optimal frequency of EA for patientswith such conditions.Design:Single-center,randomized,controlled clinical trial was designed,and the outcome assessors and statisticians were blinded.The patients with migraine were randomized into 2 Hz EA group,100 Hz EA group and sham-stimulation group.In each group,the changes in migraine attacks,days with headache,the scores of visual analogy scale(VAS),self-rating anxiety scale(SAS),self-rating depression scale(SDS)and migraine-specific quality-of-life questionnaire(MsQ),as well as the dosage of analgesics were observed at the baseline,during treatment,in 1,2 and 3 months of follow-up separately.Setting:Patients were enrolled in the Third Afiliated Hospital of Zhejiang Chinese Medical University,between 1st August 2018 and 31st July 2021.Participants:Sixty-five migraine patients with or without aura.Interventions:In the EA groups,the acupoints were bilateral Fengchi(GB20),Gongxue(Extra),Sizhukong(TE23),Taiyang(EX-HN5),Shuaigu(GB8),Waiguan(TE5)and Yanglingquan(GB34).Electric stimulation was exerted at GB20 and Gongxue(Extra),with 2 Hz and 100 Hz separately.In the sham-stimulation group,the shallow acupuncture was operated at the sites 1 cm lateral to GB20 and Gongxue(Extra),and on the radial side of TE5 and GB34.The output wires were cut off after attached to the acupoints.The patients in each group received the treatment 3 times weekly,once every two days,for consecutive 4 weeks.The complete intervention was composed of 12 treatments.Main outcome measures:Changes in numbers of migraine attacks at treatment phase(week 1 to week 4)from the baseline(week-4 to week 0)in patients of each group Kesults:(1)Cnangesinmigraineattacks anadays witnneaaacne:intneZ Hz EA anaIuu Hz EA groups the changes of migraine attacks and days of headache were higher significantlyywhencomparedwith that in the sham-stimulation group at the same time stage(P<0.05).There was no statistical difference between two EA groups.(2)Changes of VAS score:In the 2 Hz EA and 100 Hz EA groups,the changes of VAS score were significantly higher when compared with that in the sham-stimulation group during the treatment stage(P<0.05).There was no statistical difference between two EA groups.(3)Assessment of anxiety and depression:The differences in the changes of SAS and sDS scores had no statistical significance among the three groups at each assessment stage(P>0.05).(4)Assessment on the quality of life:Compared with the sham-stimulation group at the same time stage,the MsQ score were increased significantly during treatment in patients of the 2 Hz EA and 100 Hz EA groups(P<0.05).There was no statistical difference between two EA groups.(5)Assessment on safety and compliance:The patients of each group had sound compliance.There was no adverse events during trial,suggesting promising safety of treatment.Conclusion:EA may effectively reduce the migraine attacks,and the days and intensity of headache,presenting promising safety.However,there was no significant improvement on anxiety-depression symptoms,and no significant difference between high and low frequencies of EA treatment in relieving headache and anxiety/depression symptoms in the patients with migraine.展开更多
The localization of a stationary transmitter using moving receivers is considered. The original Direct Position Determination （DPD） methods, with combined Time Difference of Arrival （TDOA） and Frequency Difference...The localization of a stationary transmitter using moving receivers is considered. The original Direct Position Determination （DPD） methods, with combined Time Difference of Arrival （TDOA） and Frequency Difference of Arrival （FDOA）, do not perform well under low Signal-to-Noise Ratio （SNR）, and worse still, the computation cost is difficult to accept when the computational capabilities are limited. To get better positioning performance, we present a new DPD algorithm that proves to be more computationally efficient and more precise for weak signals than the conventional approach. The algorithm partitions the signal received with the same receiver into multiple non-overlapping short-time signal segments, and then uses the TDOA, the FDOA and the coherency among the short-time signals to locate the target. The fast maximum likelihood estimation, one iterative method based on particle filter, is designed to solve the problem of high computation load. A secondary but important result is a derivation of closed-form expressions of the Cramer-Rao Lower Bound （CRLB）. The simulation results show that the algorithm proposed in this paper outperforms the traditional DPD algorithms with more accurate results and higher computational efficiency, and especially at low SNR, it is more close to the CRLB.展开更多
A linear-correction least-squares（LCLS） estimation procedure is proposed for geolocation using frequency difference of arrival （FDOA） measurements only. We first analyze the measurements of FDOA, and further deriv...A linear-correction least-squares（LCLS） estimation procedure is proposed for geolocation using frequency difference of arrival （FDOA） measurements only. We first analyze the measurements of FDOA, and further derive the Cramer-Rao lower bound （CRLB） of geoloeation using FDOA measurements. For the localization model is a nonlinear least squares（LS） estimator with a nonlinear constrained, a linearizing method is used to convert the model to a linear least squares estimator with a nonlinear con- strained. The Gauss-Newton iteration method is developed to conquer the source localization problem. From the analysis of solving Lagrange multiplier, the algorithm is a generalization of linear-correction least squares estimation procedure under the condition of geolocation using FDOA measurements only. The algorithm is compared with common least squares estimation. Comparisons of their estimation accuracy and the CRLB are made, and the proposed method attains the CRLB. Simulation re- sults are included to corroborate the theoretical development.展开更多
By utilizing the time difference of arrival （TDOA） and frequency difference of arrival （FDOA） measurements of signals received at a number of receivers, a constrained least-square （CLS） algorithm for estimating ...By utilizing the time difference of arrival （TDOA） and frequency difference of arrival （FDOA） measurements of signals received at a number of receivers, a constrained least-square （CLS） algorithm for estimating the position and velocity of a moving source is proposed. By utilizing the Lagrange multipliers technique, the known relation between the intermediate variables and the source location coordinates could be exploited to constrain the solution. And without requiring apriori knowledge of TDOA and FDOA measurement noises, the proposed algorithm can satisfy the demand of practical applications. Additionally, on basis of con- volute and polynomial rooting operations, the Lagrange multipliers can be obtained efficiently and robustly allowing real-time imple- mentation and global convergence. Simulation results show that the proposed estimator achieves remarkably better performance than the two-step weighted least square （WLS） approach especially for higher measurement noise level.展开更多
Based on the time differences of arrival(TDOA) and frequency differences of arrival(FDOA) measurements of the given planar stationary radiation source, the joint TDOA/FDOA location algorithm which solves the location ...Based on the time differences of arrival(TDOA) and frequency differences of arrival(FDOA) measurements of the given planar stationary radiation source, the joint TDOA/FDOA location algorithm which solves the location of the target directly is proposed. Compared with weighted least squares(WLS) methods,the proposed algorithm is also suitable for well-posed conditions,and gets rid of the dependence on the constraints of Earth's surface. First of all, the solution formulas are expressed by the radial range. Then substitute it into the equation of the radial range to figure out the radial range between the target and the reference station. Finally use the solution expression of the target location to estimate the location of the target accurately. The proposed algorithm solves the problem that WLS methods have a large positioning error when the number of observation stations is not over-determined. Simulation results show the effectiveness of the proposed algorithm, including effectively increasing the positioning accuracy and reducing the number of observatories.展开更多
This paper considers the problem of geolocating a target on the Earth surface whose altitude is known previously using the target signal time difference of arrival （TDOA） and frequency difference of arrival （FDOA）...This paper considers the problem of geolocating a target on the Earth surface whose altitude is known previously using the target signal time difference of arrival （TDOA） and frequency difference of arrival （FDOA） measurements obtained at satellites. The number of satellites available for the geolocation task is more than sufficient and their locations are subject to random errors. This paper derives the constrained Cramor-Rao lower bound （CCRLB） of the target position, and on the basis of the CCRLB analysis, an approximately efficient constrained maximum likelihood estimator （CMLE） for geolocating the target is established. A new iterative algorithm for solving the CMLE is then proposed, where the updated target position estimate is shown to be the globally optimal solution to a generalized trust region sub-problem （GTRS） which can be found via a simple bisection search. First-order mean square error （MSE） analysis is conducted to quantify the performance degradation when the known target altitude is assumed to be precise but indeed has an unknown but deterministic error. Computer simulations are used to compare the performance of the proposed iterative geolocation technique with those of two benchmark algorithms. They verify the approximate efficiency of the proposed algorithm and the validity of the MSE analysis.展开更多
The source location based on the hybrid time difference of arrival(TDOA)/frequency difference of arrival(FDOA) is a basic problem in wireless sensor networks, and the layout of sensors in the hybrid TDOA/FDOA position...The source location based on the hybrid time difference of arrival(TDOA)/frequency difference of arrival(FDOA) is a basic problem in wireless sensor networks, and the layout of sensors in the hybrid TDOA/FDOA positioning will greatly affect the accuracy of positioning. Using unmanned aerial vehicle(UAV) as base stations, by optimizing the trajectory of the UAV swarm, an optimal positioning configuration is formed to improve the accuracy of the target position and velocity estimation. In this paper, a hybrid TDOA/FDOA positioning model is first established, and the positioning accuracy of the hybrid TDOA/FDOA under different positioning configurations and different measurement errors is simulated by the geometric dilution of precision(GDOP) factor. Second, the Cramer-Rao lower bound(CRLB) matrix of hybrid TDOA/FDOA location under different moving states of the target is derived theoretically, the objective function of the track optimization is obtained, and the track of the UAV swarm is optimized in real time. The simulation results show that the track optimization effectively improves the accuracy of the target position and velocity estimation.展开更多
文摘Objective To observe postoperative effect of electroacupuncture（EA） of different frequencies in acupuncture anesthesia combined with drugs on patients undergoing thyroid surgery.Methods One hundred and twenty patients undergoing thyroid surgery were randomly divided into a 2Hz electroacupuncture anesthesia group（group A）,a 100 Hz electroacupuncture anesthesia group（group B）,a 2Hz/100 Hz electroacupuncture anesthesia group（group C） and a cervical plexus block group（group D） in accordance with the random number table method,with 30 patients in each group.In group A,group B and group C,electroacupuncture was applied at bilateral Futu（扶突 LI 18）,Hegu（合谷 LI 4） and Neiguan（内关 PC 6） at frequencies of 2 Hz,100 Hz and 2 Hz/100 Hz respectively for 30 min.The needles were retained till the end of the surgery.Dolantin and atropine were intramuscularly injected In group D,bilateral cervical plexus block was produced with a mixture of1%lidocaine and 0.375%bupivicaine.Before surgery,pain threshold and threshold of pain tolerance were determined;during surgery,the duration of surgery was recorded;and after surgery,QOLS（Quality Of Life Score） and PHS（Prince-Henry Score） were assessed.Results PHS in group A,group B and group C were lower than that in group D,respectively（0.20±0.41,0.17±0.38,0.10±0.31 vs 0.40±0.50,P〈0.01）,and PHS in group C was lower than those in group A and group B,respectively（both P〈0.01）.QOLS in group A,group B and group C were higher than that in group D,respectively（9.97±1.07,9.97±2.27,10.40±1.45 vs 9.73±1.41,P〈0.05,P〈0.01）,and QOLS in group C was higher than those in group A and group B,respectively（both P〈0.05）.Conclusion Acupuncture anesthesia combined with drugs has better postoperative effect than drug anesthesia.Electroacupuncture of different frequencies can significantly improve general quality of life of patients,so patients recover well after thyroid surgery.As patients in group C suffered from the slightest pain with the highest quality of life,they recovered best within the shortest time.Electroacupuncture at frequency of 2 Hz/100 Hz can better play postoperative analgesic effect.
基金supported by the Open Fund of Key Laboratory of Geological Hazards on Three Gorges Reservoir Area(China Three Gorges University)of the Ministry of Education(Grant Nos.2022KDZ14 and 2022KDZ15)the Open Fund of Badong National Observation and Research Station of Geohazards(Grant No.BNORSG-202304)+3 种基金the Science and Technology Project of Department of Natural Resources of Hubei Province(Grant No.ZRZY2024KJ15)the Natural Science Foundation of Hubei Province(Grant No.2022CFB557)the National Natural Science Foundation of China(Grant No.42107489)the 111 Project of Hubei Province(Grant No.2021EJD026)。
文摘The precision of landslide displacement prediction is crucial for effective landslide prevention and mitigation strategies.However,the role of surface monitoring frequency in influencing prediction accuracy has been largely neglected.This study examined the effect of varying monitoring frequencies on the accuracy of displacement predictions by using the Baijiabao landslide in the Three Gorges Reservoir Area(TGRA)as a case study.We collected surface automatic monitoring data at different intervals,ranging from daily to monthly.The Ensemble Empirical Mode Decomposition(EEMD)algorithm was utilized to dissect the accumulated displacements into periodic and trend components at each monitoring frequency.Polynomial fitting was applied to forecast the trend component while the periodic component was predicted with two state-of-the-art neural network models:Long Short-Term Memory(LSTM)and Gated Recurrent Unit(GRU).The predictions from these models were integrated to derive cumulative displacement forecasts,enabling a comparative analysis of prediction accuracy across different monitoring frequencies.The results demonstrate that the proposed models achieve high accuracy in landslide displacement forecasting,with optimal performance observed at moderate monitoring intervals.Intriguingly,the daily mean average error(MAE)decreases sharply with increasing monitoring frequency,reaching a plateau.These findings were corroborated by a parallel analysis of the Bazimen landslide,suggesting that moderate monitoring intervals of approximately 7 to 15 days are most conducive to achieving enhanced prediction accuracy compared to both daily and monthly intervals.
文摘Objective To compare the difference in the clinical efficacy on the different frequency hearing damages for the patients with sudden deafness between the comprehensive therapy of electroacupuncture and western medicine and the simple western medicine comprehensive therapy. Methods Fifty-eight cases were randomized into an acupuncture plus medication group （28 cases, 32 damaged ears） and a western medicine group （30 cases, 34 damaged ears）. In the acupuncture plus medication group, the comprehensive therapy of electroacupuncture and western medicine was used. The main points were ěrmén （耳门 TE 21）, Tīnggōng （听宫 SI 19）, Tīnghuì （听会 GB 2）, Yìfēng （翳风 TE 17）, etc. The western medicine therapy was the comprehensive treatment with vasodilators, the medicines for promoting nerve function and releasing inner ear edema and hyperbaric oxygen. In the western medicine group, the western medicine comprehensive therapy was adopted. 10-day treatment made one session. Two sessions of treatment were required. In 1 or 2 sessions of treatment, the efficacy was observed, the electric audiometry was evaluated. Additionally, the blood routine and liver and kidney functions were detected. Results The total effective rate was 50.0% （16/32） in the acupuncture ＋ medication group and was 55.9% （19/34） in the western medicine group. The efficacies were similar between the two groups （P〉0.05）. In 1 and 2 sessions of treatment, at 250 Hz, 500 Hz and 1 kHz, the electric audiometry values in either group were recovered significantly as compared with those before treatment （all P〈0.01）. At 2 kHz, in 1 and 2 sessions of treatment, the improvements of the electric audiometry values were significant as compared with those before treatment in the acupuncture plus medication group separately （P〈0.05, P〈0.01）. At 4 kHz, the differences were not significant statistically before and after treatment in either group （all P〉0.05）. There were no abnormalities in the blood routine and liver and kidney function detections before and after treatment in either group. Conclusion Either the comprehensive therapy of electroacupuncture and western medicine or the simple western medicine comprehensive therapy is effective in the treatment of low frequency hearing damage of sudden deafness. Either of them has no effect on high frequency hearing damage. But for the middle frequency hearing damage, the efficacy of the comprehensive therapy of electroacupuncture and western medicine is superior to that of the simple western medicine comprehensive therapy.
基金supported by the National Natural Science Foundation of China(No.61671273)
文摘Considering the estimation accuracy reduction of Frequency Difference of Arrival （FDOA） caused by relative Doppler companding, a joint Time Difference of Arrival （TDOA）, FDOA and differential Doppler rate estimation method is proposed and its Cramer-Rao low bound is derived in this paper. Firstly, second-order ambiguity function is utilized to reduce the dimensionality and estimate initial TDOA and differential Doppler rate. Secondly, the TDOA estimation is updated and FDOA is obtained using cross ambiguity function, in which relative Doppler com- panding is compensated by the existing differential Doppler rate. Thirdly, differential Doppler rate estimation is updated using cross estimator. Theoretical analysis on estimation variance and Cramer-Rao low bound shows that the final estimation of TDOA, FDOA and differential Doppler rate performs well at both low and high signal-noise ratio, although the initial estimation accuracy of TDOA and differential Doppler rate is relatively poor under low signal-noise ratio conditions. Simulation results finally verify the theoretical analysis and show that the proposed method can overcome relative Doppler companding problem and performs well for all TDOA, FDOA and differential Doppler rate estimation.
基金financially supported by the National Natural Science Foundation of China(Grant No.51679167 and 51979193)
文摘The marine risers are often subjected to parametric excitations from the fluctuation top tension. The top tension on the riser may fluctuate with multiple frequencies caused by irregular waves. In this paper, the influence between different frequency components in the top tension on the riser system is theoretically simulated and analyzed. With the Euler-Bernoulli beam theory, a dynamic model for the vibrations of the riser is established. The top tension is set as fluctuating with time and it has two different frequencies. The influences from the fluctuation amplitudes, circular frequencies and phase angles of these frequency components on the riser system are analyzed in detail. When these two frequencies are fluctuating in the stable regions, the riser system may become unstable because ω1+ω2≈2Ωn. The fluctuation amplitudes of these frequencies have little effect on the components of the vibration frequencies of the riser. For different phase angles, the stability and dynamic behaviors of the riser would be different.
基金Supported by the Project of Higher Education Teaching Reform and Practice in Henan Province(2017SJGLX353)the Project of Science and Technology on Electronic Information Control Laboratory,the Science and Technology Innovation Talents in Colleges and Universities of Henan Province(16HASTIT036)+2 种基金the Educational Technology Equipment and Practical Education of Henan Province(GZS028)the National Natural Science Foundation of China(U1304618)the Key Projects of Science And Technology of Henan Province(152102210351)
文摘According to the requirement of multi-parameter time and frequency measurement without frequency normalization,a different frequency synchronization theory is proposed based on Lissajous figure method and the variation lawof Lissajous figure which are used in practice teaching of frequency measurement. The theory can achieve high-precision transmission and comparison of time and frequency and precise locking and tracking of phase and frequency,improve the level of scientific research on time and frequency for postgraduate,and promote practice teaching innovation of time frequency measurement for undergraduate. Utilizing the ratio of horizontal and vertical inflection point of the Lissajous figure,the nominal frequency of the measured signal is precisely calculated.The frequency deviation between the measured frequency and its nominal frequency can be obtained by combining the turning cycle of the Lissajous figure. By observing the phase relationship between the frequency standard signal and the measured signal,the accurate measurement of the frequency is implemented. Experimental results showthat the direct measurement and comparison better than the 10-11 order of magnitude with common frequency source can be finished between any signal frequencies.The frequency measurement method based on the theory has the advantage of simple operation,quick measurement speed,small error,lownoise and high measurement precision. It plays an important role in time synchronization,communications,metrology,scientific research,educational technology practice and equipment and other fields.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61735010,31671580,and 61601183)the Natural Science Foundation of Henan Province,China(Grant No.162300410190)Program for Science&Technology Innovation Talents in Universities of Henan Province,China(Grant No.18HASTIT023)。
文摘High-efficiency terahertz(THz) wave generation with multiple frequencies by optimized cascaded difference frequency generation(OCDFG) is investigated at 100 K using a nonlinear crystal consisting of a periodically poled lithium niobate(PPLN) part and an aperiodically poled lithium niobate(APPLN) part.Two infrared pump waves with a frequency difference ω_(T1) generate THz waves and a series of cascaded optical waves in the PPLN part by cascaded difference frequency generation(CDFG).The generated cascaded optical waves with frequency interval ω_(T1) then further interact in the APPLN part by OCDFG,yielding the following two advantages.First,OCDFG in the APPLN part is efficiently stimulated by inputting multi-order cascaded optical waves rather than the only two intense infrared pump waves,yielding unprecedented energy conversion efficiencies in excess of 37% at 1 THz at 100 K.Second,THz waves with M timesω_(T1) are generated by mixing the mth-order and the(m+M)th-order cascaded optical waves by designing poling period distributions of the APPLN part.
文摘Objective: to compare the clinical effect of different frequency hemoperfusion combined with hemodialysis in the treatment of end-stage renal insufficiency. Methods: selected hospital in January 2019 - January 2020 treatment of 94 patients with end-stage renal failure patients as the research object, randomly divided into 3 groups, all patients were given hemodialysis treatment, three times a week, at the same time give different frequencies of blood perfusion, I group of 32 cases of once every 2 weeks, II group of 31 cases, treatment for 1 times a week. In group III, 31 patients were treated twice a week. After 1 year of treatment, the changes of microinflammatory status indicators in all patients were observed and analyzed. Results: after treatment, the levels of TNF-α, hs-CRP and IL-6 in 3 groups were better than before treatment, and the levels of TNF-α, hs-CRP and IL-6 in group II and III were lower than group I, the differences were statistically significant (P < 0.05). There were no significant differences in TNF-α, hs-CRP and IL-6 levels between group II and group III (P > 0.05). Conclusion: medium and high frequency hemoperfusion combined with hemodialysis in the treatment of end-stage renal insufficiency can fully improve the microinflammatory status of patients, and medium frequency hemoperfusion is more cost-effective and more suitable for clinical treatment.
基金Supported by Key Discipline Construction Project of Neurology of Jiaxing City in Zhejiang Province of China,No.2023-ZC-006.
文摘BACKGROUND Repetitive transcranial magnetic stimulation(rTMS)entered clinical practice in China after 2000,first used in psychiatric surgery,and then in neurology and other disciplines.The First Hospital of Jiaxing introduced TMS in 2015.In practical applications,it has been found that different models of instruments and technical parameters can lead to differences in therapeutic efficacy.Therefore,our hospital selected the Danish TMS instrument,which ranks second in China,to test patients with schizophrenia from March 2021 to July 2021,with a focus on comparing the results at 5 Hz,10 Hz,and 15 Hz.The testing time is concentrated between 8:30 to 10:30 in the morning.A contingency plan was made for the quality after inspection before testing.Two evaluators independently control the quality of the contingency plan.The data is independently saved and proofread by two evaluators.The purpose of this study is to translate the research results into clinical practice and provide reference basis.AIM To investigate the effects of rehabilitation therapy using rTMS on the negative symptoms and event-related potential component of P300 in chronic schizophrenia.METHODS One hundred and five patients with chronic schizophrenia were randomly allocated to three groups based on the frequency of rTMS(5,10,or 15 Hz).The patients underwent five sessions of rTMS per week for 5 weeks.We compared the pre-and post-treatment P300 latency and scores for the Scale for Assessment of Negative Symptoms(SANS).RESULTS A significant decrease in SANS score after rTMS was observed in the 10-Hz group(P<0.05),which was not observed in the 5-Hz and 15-Hz groups.There was a significant increase in P300 amplitude in the 10-Hz group after rTMS treatment(P<0.05),but there was no significant change in P300 latency(P>0.05).The improvement of SANS score in the 10-Hz rTMS group was related to patient age and disease course.CONCLUSION rTMS at 10 Hz improved negative symptoms and cognitive function in chronic schizophrenia;however,further studies on the mechanism of action are required to validate our observations.
基金supported by the National Natural Science Foundation of China(Nos.62027801,62301035).
文摘The radar radiation source signals hold extremely high reconnaissance value.Accurately positioning these signals constitutes one of the key technologies in safeguarding the security of the electromagnetic space.The positioning error in multi-station scenarios is influenced not only by the accuracy of positioning parameter estimation but also by the geometric configuration of the positioning platform.This paper focuses on the direction of arrival(DOA),frequency difference of arrival(FDOA),and time difference of arrival(TDOA)methods,analyzing the optimal configuration,optimal detection area,and optimal position dilution of precision in both elevation-known and elevation-unknown scenarios.Specifically,the paper constructs a signal receiving model,establishes the corresponding positioning equations,and performs dimensional normalization on these equations to derive measurement values in meters.Through differential processing,the position dilution of precision is obtained,which is then used as the optimization function to determine the optimal configuration,optimal detection area,and optimal position dilution of precision.Simulation results validate the accuracy of the proposed formulas.
基金supported by the National Natural Science Foundation of China,No.81373741a grant from the Chinese Medicine and Integrated Medicine Research Projects funded by the Health and Family Planning Commission of Hubei Province of China,No.24a grant from the Hubei Provincial Collaborative Innovation Center of Preventive Treatment by Acupuncture and Moxibustion of China in 2014,No.8
文摘Acupuncture has been shown to ameliorate cognitive impairment of Alzheimer’s disease.Acupoints and stimulation frequency influence the therapeutic effect of electroacupuncture.Rat models of Alzheimer’s disease were established by injecting amyloid beta 1–42（Aβ_（1–42））into the bilateral lateral ventricles.Electroacupuncture at 2,30,and 50 Hz was carried out at Baihui（GV20;15°obliquely to a depth of 2mm）and Shenshu（BL23;perpendicularly to 4–6 mm depth）,once a day for 20 minutes（each）,for 15 days,taking a break every 7 days.The Morris water maze test was conducted to assess the learning and memory.The expression levels of glycogen synthase kinase-3β（GSK-3β）,p Ser9-GSK-3β,p Tyr216-GSK-3β,amyloid precursor protein and Aβ_（1–40） in the hippocampus were determined by western blot assay.Results demonstrated that electroacupuncture treatment at different frequencies markedly improved learning and memory ability,increased synaptic curvatures,decreased the width of synaptic clefts,thickened postsynaptic densities,and downregulated the expression of GSK-3β,amyloid precursor protein,and Aβ_（1–40）.pSer9-GSK-3βexpression markedly decreased,while p Tyr216-GSK-3βexpression increased.High-frequency（50 Hz）electroacupuncture was more effective than low（2 Hz）or medium-frequency（30 Hz）electroacupuncture.In conclusion,electroacupuncture treatment exerts a protective effect against Aβ_（1–42）-induced learning and memory deficits and synapse-ultrastructure impairment via inhibition of GSK-3βactivity.Moreover,high-frequency electroacupuncture was the most effective therapy.
文摘Polarization coding is a specific encoding method by using the polarization state of optical signal carrying coded in- formation. It focuses on nonlinear effects, polarization mode dispersion and other issues in high-speed fiber-optic communi- cations. This paper presents a measurement method for polarization state based on elastic-optic modulator. This method not only retains the original advantages of elastic-optic modulator for polarization measurement, but also overcomes the defects of existing methods including high modulation frequency and invalid collection by using array detector. Matlab simulation and experimental verification scheme are given. The feasibility of this method is verified through theoretical analysis, and simulation and experimental results are carried out. The error analysis of the measurement results shows that the method can meet the measurement requirements and provide conditions for using the polarization encoding in high-speed communication.
文摘This paper examines the characteristics of a harmonic plane wave in 1D and applies it to a model of an auditorium in the shape of a quarter of an ellipsoid. In the application, this paper will mainly look at transmission loss, reverberation, disruption of the performers, and differences between different frequencies. The differences between different frequencies will be analyzed on both a macroscopic auditorium level as well as on a microscopic level of a single point in the audience.
基金Supported by the Foundation of Health Commission of Zhejiang Province:2018ZA060,2020ZB125Scientific research project of Zhejiang Chinese Medical University:2020ZY10。
文摘Objective:To observe the effects of electroacupuncture(EA)with varied frequencies on headache and anxiety-depression symptoms in patients with migraine and to screen optimal frequency of EA for patientswith such conditions.Design:Single-center,randomized,controlled clinical trial was designed,and the outcome assessors and statisticians were blinded.The patients with migraine were randomized into 2 Hz EA group,100 Hz EA group and sham-stimulation group.In each group,the changes in migraine attacks,days with headache,the scores of visual analogy scale(VAS),self-rating anxiety scale(SAS),self-rating depression scale(SDS)and migraine-specific quality-of-life questionnaire(MsQ),as well as the dosage of analgesics were observed at the baseline,during treatment,in 1,2 and 3 months of follow-up separately.Setting:Patients were enrolled in the Third Afiliated Hospital of Zhejiang Chinese Medical University,between 1st August 2018 and 31st July 2021.Participants:Sixty-five migraine patients with or without aura.Interventions:In the EA groups,the acupoints were bilateral Fengchi(GB20),Gongxue(Extra),Sizhukong(TE23),Taiyang(EX-HN5),Shuaigu(GB8),Waiguan(TE5)and Yanglingquan(GB34).Electric stimulation was exerted at GB20 and Gongxue(Extra),with 2 Hz and 100 Hz separately.In the sham-stimulation group,the shallow acupuncture was operated at the sites 1 cm lateral to GB20 and Gongxue(Extra),and on the radial side of TE5 and GB34.The output wires were cut off after attached to the acupoints.The patients in each group received the treatment 3 times weekly,once every two days,for consecutive 4 weeks.The complete intervention was composed of 12 treatments.Main outcome measures:Changes in numbers of migraine attacks at treatment phase(week 1 to week 4)from the baseline(week-4 to week 0)in patients of each group Kesults:(1)Cnangesinmigraineattacks anadays witnneaaacne:intneZ Hz EA anaIuu Hz EA groups the changes of migraine attacks and days of headache were higher significantlyywhencomparedwith that in the sham-stimulation group at the same time stage(P<0.05).There was no statistical difference between two EA groups.(2)Changes of VAS score:In the 2 Hz EA and 100 Hz EA groups,the changes of VAS score were significantly higher when compared with that in the sham-stimulation group during the treatment stage(P<0.05).There was no statistical difference between two EA groups.(3)Assessment of anxiety and depression:The differences in the changes of SAS and sDS scores had no statistical significance among the three groups at each assessment stage(P>0.05).(4)Assessment on the quality of life:Compared with the sham-stimulation group at the same time stage,the MsQ score were increased significantly during treatment in patients of the 2 Hz EA and 100 Hz EA groups(P<0.05).There was no statistical difference between two EA groups.(5)Assessment on safety and compliance:The patients of each group had sound compliance.There was no adverse events during trial,suggesting promising safety of treatment.Conclusion:EA may effectively reduce the migraine attacks,and the days and intensity of headache,presenting promising safety.However,there was no significant improvement on anxiety-depression symptoms,and no significant difference between high and low frequencies of EA treatment in relieving headache and anxiety/depression symptoms in the patients with migraine.
基金supported by the National Natural Science Foundation of China(No.61401513)
文摘The localization of a stationary transmitter using moving receivers is considered. The original Direct Position Determination （DPD） methods, with combined Time Difference of Arrival （TDOA） and Frequency Difference of Arrival （FDOA）, do not perform well under low Signal-to-Noise Ratio （SNR）, and worse still, the computation cost is difficult to accept when the computational capabilities are limited. To get better positioning performance, we present a new DPD algorithm that proves to be more computationally efficient and more precise for weak signals than the conventional approach. The algorithm partitions the signal received with the same receiver into multiple non-overlapping short-time signal segments, and then uses the TDOA, the FDOA and the coherency among the short-time signals to locate the target. The fast maximum likelihood estimation, one iterative method based on particle filter, is designed to solve the problem of high computation load. A secondary but important result is a derivation of closed-form expressions of the Cramer-Rao Lower Bound （CRLB）. The simulation results show that the algorithm proposed in this paper outperforms the traditional DPD algorithms with more accurate results and higher computational efficiency, and especially at low SNR, it is more close to the CRLB.
基金National High-tech Research and Development Program of China (2011AA7072043)National Defense Key Laboratory Foundation of China (9140C860304)Innovation Fund of Graduate School of NUDT (B120406)
文摘A linear-correction least-squares（LCLS） estimation procedure is proposed for geolocation using frequency difference of arrival （FDOA） measurements only. We first analyze the measurements of FDOA, and further derive the Cramer-Rao lower bound （CRLB） of geoloeation using FDOA measurements. For the localization model is a nonlinear least squares（LS） estimator with a nonlinear constrained, a linearizing method is used to convert the model to a linear least squares estimator with a nonlinear con- strained. The Gauss-Newton iteration method is developed to conquer the source localization problem. From the analysis of solving Lagrange multiplier, the algorithm is a generalization of linear-correction least squares estimation procedure under the condition of geolocation using FDOA measurements only. The algorithm is compared with common least squares estimation. Comparisons of their estimation accuracy and the CRLB are made, and the proposed method attains the CRLB. Simulation re- sults are included to corroborate the theoretical development.
基金supported by the National High Technology Research and Development Program of China (863 Program) (2010AA7010422 2011AA7014061)
文摘By utilizing the time difference of arrival （TDOA） and frequency difference of arrival （FDOA） measurements of signals received at a number of receivers, a constrained least-square （CLS） algorithm for estimating the position and velocity of a moving source is proposed. By utilizing the Lagrange multipliers technique, the known relation between the intermediate variables and the source location coordinates could be exploited to constrain the solution. And without requiring apriori knowledge of TDOA and FDOA measurement noises, the proposed algorithm can satisfy the demand of practical applications. Additionally, on basis of con- volute and polynomial rooting operations, the Lagrange multipliers can be obtained efficiently and robustly allowing real-time imple- mentation and global convergence. Simulation results show that the proposed estimator achieves remarkably better performance than the two-step weighted least square （WLS） approach especially for higher measurement noise level.
基金supported by the National Natural Science Foundation of China(6140236561271300)the 13th Five-Year Weaponry PreResearch Project。
文摘Based on the time differences of arrival(TDOA) and frequency differences of arrival(FDOA) measurements of the given planar stationary radiation source, the joint TDOA/FDOA location algorithm which solves the location of the target directly is proposed. Compared with weighted least squares(WLS) methods,the proposed algorithm is also suitable for well-posed conditions,and gets rid of the dependence on the constraints of Earth's surface. First of all, the solution formulas are expressed by the radial range. Then substitute it into the equation of the radial range to figure out the radial range between the target and the reference station. Finally use the solution expression of the target location to estimate the location of the target accurately. The proposed algorithm solves the problem that WLS methods have a large positioning error when the number of observation stations is not over-determined. Simulation results show the effectiveness of the proposed algorithm, including effectively increasing the positioning accuracy and reducing the number of observatories.
基金co-supported by the National Natural Science Foundation of China (Nos. 61304264 and 61305017)the Innovation Foundation of Industry, Education and Research of Jiangsu Province (No. BY2014023-25)
文摘This paper considers the problem of geolocating a target on the Earth surface whose altitude is known previously using the target signal time difference of arrival （TDOA） and frequency difference of arrival （FDOA） measurements obtained at satellites. The number of satellites available for the geolocation task is more than sufficient and their locations are subject to random errors. This paper derives the constrained Cramor-Rao lower bound （CCRLB） of the target position, and on the basis of the CCRLB analysis, an approximately efficient constrained maximum likelihood estimator （CMLE） for geolocating the target is established. A new iterative algorithm for solving the CMLE is then proposed, where the updated target position estimate is shown to be the globally optimal solution to a generalized trust region sub-problem （GTRS） which can be found via a simple bisection search. First-order mean square error （MSE） analysis is conducted to quantify the performance degradation when the known target altitude is assumed to be precise but indeed has an unknown but deterministic error. Computer simulations are used to compare the performance of the proposed iterative geolocation technique with those of two benchmark algorithms. They verify the approximate efficiency of the proposed algorithm and the validity of the MSE analysis.
基金supported by the National Natural Science Foundation of China (61502522)Equipment Pre-Research Field Fund(JZX7Y20190253036101)+1 种基金Equipment Pre-Research Ministry of Education Joint Fund (6141A02033703)Hubei Provincial Natural Scie nce Foundation (2019CFC897)。
文摘The source location based on the hybrid time difference of arrival(TDOA)/frequency difference of arrival(FDOA) is a basic problem in wireless sensor networks, and the layout of sensors in the hybrid TDOA/FDOA positioning will greatly affect the accuracy of positioning. Using unmanned aerial vehicle(UAV) as base stations, by optimizing the trajectory of the UAV swarm, an optimal positioning configuration is formed to improve the accuracy of the target position and velocity estimation. In this paper, a hybrid TDOA/FDOA positioning model is first established, and the positioning accuracy of the hybrid TDOA/FDOA under different positioning configurations and different measurement errors is simulated by the geometric dilution of precision(GDOP) factor. Second, the Cramer-Rao lower bound(CRLB) matrix of hybrid TDOA/FDOA location under different moving states of the target is derived theoretically, the objective function of the track optimization is obtained, and the track of the UAV swarm is optimized in real time. The simulation results show that the track optimization effectively improves the accuracy of the target position and velocity estimation.
