As cataract surgery progresses from “restoration of sight” to “refractive correction”, precise prediction of intraocular lens (IOL) power is critical for enhancing postoperative visual quality in patients. IOL pow...As cataract surgery progresses from “restoration of sight” to “refractive correction”, precise prediction of intraocular lens (IOL) power is critical for enhancing postoperative visual quality in patients. IOL power calculation methods have evolved and innovated throughout time, from early theoretical and regression formulas to nonlinear formulas for estimating effective lens position (ELP), multivariable formulas, and innovative formulas that use optical principles and AI-based online formulas. This paper thoroughly discusses the development and iteration of traditional IOL calculation formulas, the emergence of new IOL calculation formulas, and the selection of IOL calculation formulas for different patients in the era of refractive cataract surgery, serving as a reference for “personalized” IOL implantation in clinical practice.展开更多
AIM:To investigate the effect of pharmacological pupil alterations on intraocular lens(IOL)power calculations.METHODS:A systematic review and Meta-analysis of studies published before December 2023 in the PubMed,Embas...AIM:To investigate the effect of pharmacological pupil alterations on intraocular lens(IOL)power calculations.METHODS:A systematic review and Meta-analysis of studies published before December 2023 in the PubMed,Embase,and Cochrane library databases on the accuracy of pharmacological pupil changes on IOL power calculation was performed.The primary outcome was the results of IOL power calculations before and after the use of medications.Subgroup analyses were performed based on participants’basic characteristics,such as age,axial length(AL),and whether miosis or mydriasis were used as classification criteria for further analyses.Each eligible study was evaluated for potential risk of bias by the AHRQ assessment scale.The study was registered on PROSPERO(CRD 42024497535).RESULTS:A total of 3062 eyes from 21 studies were eligible.There was no significant difference in the IOL power calculation before and after pharmacological pupil changes using any of the Hoffer Q(WMD=0.055,95%CI=-0.046–0.156;P=0.29),SRK/T(WMD=0.003,95%CI=-0.073–0.080;P=0.93),Haigis(WMD=-0.030,95%CI=-0.176–0.116;P=0.69),Holladay 2(WMD=-0.042,95%CI=-0.366–0.282;P=0.80),and Barrett Universal Ⅱ(WMD=0.033,95%CI=-0.061–0.127;P=0.49)formulas.On the measurement of parameters related to IOL power calculation,for either miosis or mydriasis AL(P=0.98 and 0.29,respectively),lens thickness(P=0.96 and 0.13,respectively),and mean keratometry(P=0.90 and 0.86,respectively)did not present significant differences,while anterior chamber depth(P=0.07 and<0.01,respectively)and white-to-white distance(P=0.01 and 0.04,respectively)changed significantly between the two measurements prior and posterior.At the same time,despite there being some participants with the difference between the before and after calculations greater than 0.5 diopter,there was no significant difference in the incidence rate between these formulas.CONCLUSION:There is no significant effect of pharmacological pupil changes on the IOL power calculation.It will considerably reduce the visit time burden for patients who require cataract surgery.展开更多
AIM: To evaluate the accuracy of three commonly used biometric formulae across different axial lengths(ALs) at one United States Veterans Affairs teaching hospital.METHODS: A retrospective chart review was conducted f...AIM: To evaluate the accuracy of three commonly used biometric formulae across different axial lengths(ALs) at one United States Veterans Affairs teaching hospital.METHODS: A retrospective chart review was conducted from November 2013 to May 2018. One eye of each patient who underwent cataract surgery with a monofocal intraocular lens(IOL) was included. The range of postoperative follow-up period was from 3 wk to 4 mo. The Holladay 2, Barrett Universal II, and Hill-Radial Basis Function(Hill-RBF) formulae were used to predict the postoperative refraction for all cataract surgeries. For each formula, we calculated the prediction errors [including mean absolute prediction error(MAE)] and the percentage of eyes within ±0.25 diopter(D) and ±0.5 D of predicted refraction. We performed subgroup analyses for short(AL<22.0 mm), medium(AL 22.0-25.0 mm), and long eyes(AL>25.0 mm).RESULTS: A total of 1131 patients were screened, and 909 met the inclusion criteria. Resident ophthalmologists were the primary surgeons in 710(78.1%) cases. We found no statistically significant difference in predictive accuracy among the three formulae over the entire AL range or in the short, medium, and long eye subgroups. Across the entire AL range, the Hill-RBF formula resulted in the lowest MAE(0.384 D) and the highest percentage of eyes with postoperative refraction within ±0.25 D(42.7%) and ±0.5 D(75.5%) of predicted. All three formulae had the highest MAEs(>0.5 D) and lowest percentage within ±0.5 D of predicted refraction(<55%) in short eyes.CONCLUSION: In cataract surgery patients at our teaching hospital, three commonly used biometric formulae demonstrate similar refractive accuracy across all ALs. Short eyes pose the greatest challenge to predicting postoperative refractive error.展开更多
Purpose To evaluate the refractive prediction error of common intraocular lens(IOL)power calculation formulae in patients who underwent intrascleral IOL fixation using two different techniques.Methods This is a prospe...Purpose To evaluate the refractive prediction error of common intraocular lens(IOL)power calculation formulae in patients who underwent intrascleral IOL fixation using two different techniques.Methods This is a prospective,randomized,longitudinal,single-site,single-surgeon study.Patients who underwent intrascleral IOL implantation using the Yamane or the Carlevale technique were followed up for a period of six months postoperatively.Refraction was measured using the best-corrected visual acuity at 4 m(EDTRS chart).Lens decentration,tilt and effective lens position(ELP)were assessed using an anterior segment optical coherence tomography(AS-OCT).The prediction error(PE)and the absolute error(AE)were evaluated for the SRK/T,Hollayday1 and Hoffer Q formula.Subsequently,correlations between the PE and axial length,keratometry,white to white and ELP were assessed.Results In total,53 eyes of 53 patients were included in the study.Twenty-four eyes of 24 patients were in the Yamane group(YG)and 29 eyes of 29 patients were in the Carlevale group(CG).In the YG,the Holladay 1 and Hoffer Q formulae resulted in a hyperopic PE(0.02±0.56 D,and 0.13±0.64 D,respectively)while in the SRK/T formula the PE was slightly myopic(−0.16±0.56 D).In the CG,SRK/T and Holladay 1 formulae led to a myopic PE(−0.1±0.80 D and−0.04±0.74 D,respectively),Hoffer Q to a hyperopic PE(0.04±0.75 D).There was no difference between the PE of the same formulae across both groups(P>0.05).In both groups the AE differed significantly from zero in each evaluated formula.The AE error was within±0.50 D in 45%–71%and was within±1.00 D in 72%–92%of eyes depending on the formula and surgical method used.No significant differences were found between formulae within and across groups(P>0.05).Intraocular lens tilt was lower in the CG(6.45±2.03°)compared to the YG(7.67±3.70°)(P<0.001).Lens decentration was higher in the YG(0.57±0.37 mm)than in the CG(0.38±0.21 mm),though the difference was not statistically significant(P=0.9996).Conclusions Refractive predictability was similar in both groups.IOL tilt was better in the CG,however this did not influence the refractive predictability.Though not significant,Holladay 1 formula seemed to be more probable than the SRK/T and Hoffer Q formulae.However,significant outliers were observed in all three different formulae and therefore remain a challenging task in secondary fixated IOLs.展开更多
Background:The accuracy of using total keratometry(TK)value in recent IOL power calculation formulas in highly myopic eyes remained unknown.Methods:Highly myopic patients who underwent uneventful cataract surgery were...Background:The accuracy of using total keratometry(TK)value in recent IOL power calculation formulas in highly myopic eyes remained unknown.Methods:Highly myopic patients who underwent uneventful cataract surgery were prospectively enrolled in this prospective comparative study.At one month postoperatively,standard deviation(SD)of the prediction errors(PEs),mean and median absolute error(MedAE)of 103 highly myopic eyes were back-calculated and compared among ten formulas,including XGboost,RBF 3.0,Kane,Barrett Universal II,Emmetropia Verifying Optical 2.0,Cooke K6,Haigis,SRK/T,and Wang-Koch modifications of Haigis and SRK/T formulas,using either TK or standard keratometry(K)value.Results:In highly myopic eyes,despite good agreement between TK and K(P>0.05),larger differences between the two were associated with smaller central corneal thickness(P<0.05).As to the refractive errors,TK method showed no differences compared to K method.The XGBoost,RBF 3.0 and Kane ranked top three when considering SDs of PEs.Using TK value,the XGboost calculator was comparable with the RBF 3.0 formula(P>0.05),which both presented smaller MedAEs than others(all P<0.05).As for the percentage of eyes within±0.50 D or±0.75 D of PE,the XGBoost TK showed comparable percentages with the RBF 3.0 TK formula(74.76%vs.66.99%,or 90.29%vs.87.38%,P>0.05),and statistically larger percentages than the other eight formulas(P<0.05).Conclusions:Highly myopic eyes with thinner corneas tend to have larger differences between TK and K.The XGboost enhancement calculator and RBF 3.0 formula using TK showed the most promising outcomes in highly myopic eyes.展开更多
Forward scattering micro radar is used for situation awareness; its operational range is relatively short because of the battery power and local horizon, the free space propagation model is not appropriate. The ground...Forward scattering micro radar is used for situation awareness; its operational range is relatively short because of the battery power and local horizon, the free space propagation model is not appropriate. The ground moving targets, such as humans, cars and tanks, have only comparable size with the transmitted signal wavelength; the point target model and the linear change of observation angle are not applicable. In this paper, the signal model of ground moving target is developed based on the case of forward scattering micro radar, considering the two-ray propagation model and area target model, and nonlinear change of observation angle as well as high order phase error. Furthermore, the analytical form of the received power from moving target has been obtained. Using the simulated forward scattering radar cross section, the received power of theoretical calculation is near to that of measured data. In addition, the simulated signal model of ground moving target is perfectly matched with the experimented data. All these results show the correctness of analytical calculation completely.展开更多
In order to enhance the stability of single-phase microgrid,virtual synchronous generator(VSG)control method is investigated in this paper.Its electromagnetic model and electromechanical model are established to illus...In order to enhance the stability of single-phase microgrid,virtual synchronous generator(VSG)control method is investigated in this paper.Its electromagnetic model and electromechanical model are established to illustrate the performance of VSG.Considering the 2 nd fluctuation of fundamental-frequency in the output power,an instantaneous power calculation strategy is proposed based on the intrinsic frequency of single-phase VSG.Besides,a virtual power calculation method is presented to achieve islanded/grid-connected seamless transition.Stability analysis and comparison simulation results demonstrate the correctness of the presented power calculation method.At last,the effectiveness of the proposed approach is verified by comparison experiments of islanded/gridconnected operations in a 500 VA single-phase inverter.展开更多
Background:To compare the accuracy of intraocular lens power calculation formulae after laser refractive surgery in myopic eyes.Methods:We searched the databases on PubMed,EMBASE,Web of Science and the Cochrane librar...Background:To compare the accuracy of intraocular lens power calculation formulae after laser refractive surgery in myopic eyes.Methods:We searched the databases on PubMed,EMBASE,Web of Science and the Cochrane library to select relevant studies published between Jan 1st,2009 and Aug 11th,2019.Primary outcomes were the percentages of refractive prediction error within±0.5 D and±1.0 D.Results:The final meta-analysis included 16 studies using seven common methods(ASCRS average,Barrett True-K no history,Double-K SRK/T,Haigis-L,OCT formula,Shammas-PL,and Wang-Koch-Maloney).ASCRS average yielded significantly higher percentage of refractive prediction error within±0.5 D than Haigis-L,Shammas-PL and WangKoch-Maloney(P=0.009,0.01,0.008,respectively).Barrett True-K no history also yielded significantly higher percentage of refractive prediction error within±0.5 D than Shammas-PL and Wang-Koch-Maloney(P=0.01,P<0.0001,respectively),and a similar result was found when comparing OCT formula with Haigis-L and Shammas-PL(P=0.03,P=0.01,respectively).Conclusion:The ASCRS average or Barrett True-K no history should be used to calculate the intraocular lens power in eyes after myopic laser refractive surgery.The OCT formula if available,can also be a good alternative choice.展开更多
Background:To compare the accuracy of intraocular lens power calculation formulae after laser refractive surgery in myopic eyes.Methods:We searched the databases on PubMed,EMBASE,Web of Science and the Cochrane librar...Background:To compare the accuracy of intraocular lens power calculation formulae after laser refractive surgery in myopic eyes.Methods:We searched the databases on PubMed,EMBASE,Web of Science and the Cochrane library to select relevant studies published between Jan 1st,2009 and Aug 11th,2019.Primary outcomes were the percentages of refractive prediction error within±0.5 D and±1.0 D.Results:The final meta-analysis included 16 studies using seven common methods(ASCRS average,Barrett True-K no history,Double-K SRK/T,Haigis-L,OCT formula,Shammas-PL,and Wang-Koch-Maloney).ASCRS average yielded significantly higher percentage of refractive prediction error within±0.5 D than Haigis-L,Shammas-PL and Wang,Koch-Maloney(P=0.009,0.01,0.008,respectively).Barrett True-K no history also yielded significantly higher percentage of refractive prediction error within±0.5 D than Shammas-PL and Wang-Koch-Maloney(P=0.01,P<0.0001,respectively),and a similar result was found when comparing OCT formula with Haigis-L and Shammas-PL(P=0.03,P=0.01,respectively).Conclusion:The ASCRS average or Barrett True-K no history should be used to calculate the intraocular lens power in eyes after myopic laser refractive surgery.The OCT formula if available,can also be a good alternative choice.展开更多
Background:To examine the effectiveness of the use of machine learning for adapting an intraocular lens(IOL)power calculation for a patient group.Methods:In this retrospective study,the clinical records of 1,611 eyes ...Background:To examine the effectiveness of the use of machine learning for adapting an intraocular lens(IOL)power calculation for a patient group.Methods:In this retrospective study,the clinical records of 1,611 eyes of 1,169 Japanese patients who received a single model of monofocal IOL(SN60WF,Alcon)at Miyata Eye Hospital were reviewed and analyzed.Using biometric metrics and postoperative refractions of 1211 eyes of 769 patients,constants of the SRK/T and Haigis formulas were optimized.The SRK/T formula was adapted using a support vector regressor.Prediction errors in the use of adapted formulas as well as the SRK/T,Haigis,Hill-RBF and Barrett Universal II formulas were evaluated with data from 395 eyes of 395 distinct patients.Mean prediction errors,median absolute errors,and percentages of eyes within±0.25 D,±0.50 D,and±1.00 D,and over+0.50 D of errors were compared among formulas.Results:The mean prediction errors in the use of the SRT/K and adapted formulas were smaller than the use of other formulas(P<0.001).In the absolute errors,the Hill-RBF and adapted methods were better than others.The performance of the Barrett Universal II was not better than the others for the patient group.There were the least eyes with hyperopic refractive errors(16.5%)in the use of the adapted formula.Conclusions:Adapting IOL power calculations using machine learning technology with data from a particular patient group was effective and promising.展开更多
Background:To examine the effectiveness of the use of machine learning for adapting an intraocular lens(IOL)power calculation for a patient group.Methods:In this retrospective study,the clinical records of 1,611 eyes ...Background:To examine the effectiveness of the use of machine learning for adapting an intraocular lens(IOL)power calculation for a patient group.Methods:In this retrospective study,the clinical records of 1,611 eyes of 1,169 Japanese patients who received a single model of monofocal IOL(SN60WF,Alcon)at Miyata Eye Hospital were reviewed and analyzed.Using biometric metrics and postoperative refractions of 1211 eyes of 769 patients,constants of the SRK/T and Haigis formulas were optimized.The SRK/T formula was adapted using a support vector regressor.Prediction errors in the use of adapted formulas as well as the SRK/T,Haigis,Hill-RBF and Barrett Universal II formulas were evaluated with data from 395 eyes of 395 distinct patients.Mean prediction errors,median absolute errors,and percentages of eyes within±0.25 D,±0.50 D,and±1.00 D,and over+0.50 D of errors were compared among formulas.Results:The mean prediction errors in the use of the SRT/K and adapted formulas were smaller than the use of other formulas(P<0.001).In the absolute errors,the Hill-RBF and adapted methods were better than others.The performance of the Barrett Universal II was not better than the others for the patient group.There were the least eyes with hyperopic refractive errors(16.5%)in the use of the adapted formula.Conclusions:Adapting IOL power calculations using machine learning technology with data from a particular patient group was effective and promising.展开更多
Based on the general methods in power flow calculation of power system and on conceptions and classifications of parallel algorithm, a new approach named Dynamic Asynchronous Parallel Algorithm that applies to the onl...Based on the general methods in power flow calculation of power system and on conceptions and classifications of parallel algorithm, a new approach named Dynamic Asynchronous Parallel Algorithm that applies to the online analysis and real-time dispatching and controlling of large-scale power network was put forward in this paper. Its performances of high speed and dynamic following have been verified on IEEE-14 bus system.展开更多
We present a theoretic model to calculate skin depths and eddy-current power losses for a magnetic position sensor. Eddy-current, arised from the operation of an alternating-current excitation, induces secondary curre...We present a theoretic model to calculate skin depths and eddy-current power losses for a magnetic position sensor. Eddy-current, arised from the operation of an alternating-current excitation, induces secondary currents and fields between magnetic material and magnetic position sensor. In this paper, a magnetic position sensor system is simplified to be an outer-winding coil along the axial direction of a low carbon steel bar. The analytical model is derived from basic field and circuit theory considering a linear approximation for a nonlinear permeability. Thus the skin depths and eddy-current power losses from the model in eddy-current modeling techniques at various frequencies of an excited current source can be calculated. The proposed configuration is capable of predicting the skin depths and eddy-current power losses for a magnetic position sensor and has a consistence with experiments.展开更多
AIM:To investigate the influence of postoperative intraocular lens(IOL)positions on the accuracy of cataract surgery and examine the predictive factors of postoperative biometry prediction errors using the Barrett Uni...AIM:To investigate the influence of postoperative intraocular lens(IOL)positions on the accuracy of cataract surgery and examine the predictive factors of postoperative biometry prediction errors using the Barrett Universal II(BUII)IOL formula for calculation.METHODS:The prospective study included patients who had undergone cataract surgery performed by a single surgeon from June 2020 to April 2022.The collected data included the best-corrected visual acuity(BCVA),corneal curvature,preoperative and postoperative central anterior chamber depths(ACD),axial length(AXL),IOL power,and refractive error.BUII formula was used to calculate the IOL power.The mean absolute error(MAE)was calculated,and all the participants were divided into two groups accordingly.Independent t-tests were applied to compare the variables between groups.Logistic regression analysis was used to analyze the influence of age,AXL,corneal curvature,and preoperative and postoperative ACD on MAE.RESULTS:A total of 261 patients were enrolled.The 243(93.1%)and 18(6.9%)had postoperative MAE<1 and>1 D,respectively.The number of females was higher in patients with MAE>1 D(χ^(2)=3.833,P=0.039).The postoperative BCVA(logMAR)of patients with MAE>1 D was significantly worse(t=-2.448;P=0.025).After adjusting for gender in the logistic model,the risk of postoperative refractive errors was higher in patients with a shallow postoperative anterior chamber[odds ratio=0.346;95% confidence interval(CI):0.164,0.730,P=0.005].CONCLUSION:Risk factors for biometry prediction error after cataract surgery include the patient’s sex and postoperative ACD.Patients with a shallow postoperative anterior chamber are prone to have refractive errors.展开更多
Purpose–The traction cable is paralleled with the existing traction network of electrified railway through transverse connecting line to form the scheme of long distance power supply for the traction network.This pap...Purpose–The traction cable is paralleled with the existing traction network of electrified railway through transverse connecting line to form the scheme of long distance power supply for the traction network.This paper aims to study the scheme composition and power supply distance(PSD)of the scheme.Design/methodology/approach–Based on the structure of parallel traction network(referred to as“cable traction network(CTN)”),the power supply modes(PSMs)are divided into cableþdirect PSM and cableþautotransformer(AT)PSM(including Japanese mode,French mode and new mode).Taking cableþJapanese AT PSM as an example,the scheme of long distance power supply for CTN under the PSMs of co-phase and out-of-phase power supply are designed.On the basis of establishing the equivalent circuit model and the chain circuit model of CTN,taking the train working voltage as the constraint condition,and based on the power flow calculation of multiple train loads,the calculation formula and process for determining the PSD of CTN are given.The impedance and PSD of CTN under the cableþAT PSM are simulated and analyzed,and a certain line is taken as an example to compare the scheme design.Findings–Results show that the equivalent impedance of CTN under the cableþAT PSM is smaller,and the PSD is about 2.5 times of that under the AT PSM,which can effectively increase the PSD and the flexibility of external power supply location.Originality/value–The research content can effectively improve the PSD of traction power supply system and has important reference value for the engineering application of the scheme.展开更多
Power flow calculation is the basis of power grid planning and many system analysis tasks require convergent power flow conditions.To address the unsolvable power flow problem caused by the reactive power imbalance,a ...Power flow calculation is the basis of power grid planning and many system analysis tasks require convergent power flow conditions.To address the unsolvable power flow problem caused by the reactive power imbalance,a method for adjusting reactive power flow convergence based on deep reinforcement learning is proposed.The deep reinforcement learning method takes switching parallel reactive compensation as the action space and sets the reward value based on the power flow convergence and reactive power adjustment.For the non-convergence power flow,the 500 kV nodes with reactive power compensation devices on the low-voltage side are converted into PV nodes by node type switching.And the quantified reactive power non-convergence index is acquired.Then,the action space and reward value of deep reinforcement learning are reasonably designed and the adjustment strategy is obtained by taking the reactive power non-convergence index as the algorithm state space.Finally,the effectiveness of the power flow convergence adjustment algorithm is verified by an actual power grid system in a province.展开更多
Purpose:This prospective cohort study aimed to assess the influence of tear film stability on corneal refractive power measurement and surgical planning in cataract patients.Methods:Participants were divided into tear...Purpose:This prospective cohort study aimed to assess the influence of tear film stability on corneal refractive power measurement and surgical planning in cataract patients.Methods:Participants were divided into tear film instability(tear film stability level 2)and control(level 0–1)groups based on Keratograph 5M results.Using IOL Master 700,two consecutive measurements were obtained with a 10-min interval.Parameters including standard keratometry(Kf,Ks and K),keratometric corneal astigmatism(KCA),total keratometry(TKf,TKs and TK)and total corneal astigmatism(TCA)were recorded.IOL power was calculated using SRK-T,SRK-T TK,Haigis,Haigis TK,Barrett Universal II,and Barrett Universal II TK formulas.Results:The results showed significantly higher differences between two measurements in Kf,K,KCA,TKf,TK,and TCA,as well as the vector variability of corneal astigmatism in the tear film instability group(all P<0.05).Of all formulas,only the SRK-T formula displayed significantly higher variability in IOL power calculations in the tear film instability group compared to the control group(P<0.05).Conclusions:This study highlights that tear film instability can lead to deviations in corneal refractive power and astigmatism measurements,contributing to increased prediction errors in IOL power calculation,particularly with the SRK-T formula.展开更多
Expanding photovoltaic(PV)resources in rural-grid areas is an essential means to augment the share of solar energy in the energy landscape,aligning with the“carbon peaking and carbon neutrality”objectives.However,ru...Expanding photovoltaic(PV)resources in rural-grid areas is an essential means to augment the share of solar energy in the energy landscape,aligning with the“carbon peaking and carbon neutrality”objectives.However,rural power grids often lack digitalization;thus,the load distribution within these areas is not fully known.This hinders the calculation of the available PV capacity and deduction of node voltages.This study proposes a load-distribution modeling approach based on remote-sensing image recognition in pursuit of a scientific framework for developing distributed PV resources in rural grid areas.First,houses in remote-sensing images are accurately recognized using deep-learning techniques based on the YOLOv5 model.The distribution of the houses is then used to estimate the load distribution in the grid area.Next,equally spaced and clustered distribution models are used to adaptively determine the location of the nodes and load power in the distribution lines.Finally,by calculating the connectivity matrix of the nodes,a minimum spanning tree is extracted,the topology of the network is constructed,and the node parameters of the load-distribution model are calculated.The proposed scheme is implemented in a software package and its efficacy is demonstrated by analyzing typical remote-sensing images of rural grid areas.The results underscore the ability of the proposed approach to effectively discern the distribution-line structure and compute the node parameters,thereby offering vital support for determining PV access capability.展开更多
In this paper, it is discussed that two tests for varying dispersion of binomial data in the framework of nonlinear logistic models with random effects, which are widely used in analyzing longitudinal binomial data. O...In this paper, it is discussed that two tests for varying dispersion of binomial data in the framework of nonlinear logistic models with random effects, which are widely used in analyzing longitudinal binomial data. One is the individual test and power calculation for varying dispersion through testing the randomness of cluster effects, which is extensions of Dean(1992) and Commenges et al (1994). The second test is the composite test for varying dispersion through simultaneously testing the randomness of cluster effects and the equality of random-effect means. The score test statistics are constructed and expressed in simple, easy to use, matrix formulas. The authors illustrate their test methods using the insecticide data (Giltinan, Capizzi & Malani (1988)).展开更多
Medium-voltage distribution systems(MVDSs)mainly consist of a feeder head,lines,distribution transformers,and the equivalent load or power supply interfaced with the distribution transformers.The information of such l...Medium-voltage distribution systems(MVDSs)mainly consist of a feeder head,lines,distribution transformers,and the equivalent load or power supply interfaced with the distribution transformers.The information of such load or power supply can be measured via the three-wattmeter method(THM)and the two-wattmeter method(TWM).The measurements can be used to perform the control of the power supply and simulate the characteristics of the load,so the models of the load and the power supply need to consider the measurement characteristics.Existing research works on three-phase power flow(PF)just consider the measurement characteristics of THM.Hence,the PF equation of the bus measured via TWM is firstly built.Based on conventional measurements,an accurate and general model of the grounded and ungrounded slack bus is proposed.Furthermore,the influence arising from the connection type and angle shift of distribution transformers on the admittance matrix is considered,and thus a general three-phase transformer model is summarized,which is applicable for all the transformers mentioned herein.Finally,Newton's method is adopted to solve the PF calculation,and the performance of the proposed PF model is demonstrated through designed tests.展开更多
文摘As cataract surgery progresses from “restoration of sight” to “refractive correction”, precise prediction of intraocular lens (IOL) power is critical for enhancing postoperative visual quality in patients. IOL power calculation methods have evolved and innovated throughout time, from early theoretical and regression formulas to nonlinear formulas for estimating effective lens position (ELP), multivariable formulas, and innovative formulas that use optical principles and AI-based online formulas. This paper thoroughly discusses the development and iteration of traditional IOL calculation formulas, the emergence of new IOL calculation formulas, and the selection of IOL calculation formulas for different patients in the era of refractive cataract surgery, serving as a reference for “personalized” IOL implantation in clinical practice.
基金Supported by Beijing Natural Science Foundation from Beijing Municipal Government(No.7202030).
文摘AIM:To investigate the effect of pharmacological pupil alterations on intraocular lens(IOL)power calculations.METHODS:A systematic review and Meta-analysis of studies published before December 2023 in the PubMed,Embase,and Cochrane library databases on the accuracy of pharmacological pupil changes on IOL power calculation was performed.The primary outcome was the results of IOL power calculations before and after the use of medications.Subgroup analyses were performed based on participants’basic characteristics,such as age,axial length(AL),and whether miosis or mydriasis were used as classification criteria for further analyses.Each eligible study was evaluated for potential risk of bias by the AHRQ assessment scale.The study was registered on PROSPERO(CRD 42024497535).RESULTS:A total of 3062 eyes from 21 studies were eligible.There was no significant difference in the IOL power calculation before and after pharmacological pupil changes using any of the Hoffer Q(WMD=0.055,95%CI=-0.046–0.156;P=0.29),SRK/T(WMD=0.003,95%CI=-0.073–0.080;P=0.93),Haigis(WMD=-0.030,95%CI=-0.176–0.116;P=0.69),Holladay 2(WMD=-0.042,95%CI=-0.366–0.282;P=0.80),and Barrett Universal Ⅱ(WMD=0.033,95%CI=-0.061–0.127;P=0.49)formulas.On the measurement of parameters related to IOL power calculation,for either miosis or mydriasis AL(P=0.98 and 0.29,respectively),lens thickness(P=0.96 and 0.13,respectively),and mean keratometry(P=0.90 and 0.86,respectively)did not present significant differences,while anterior chamber depth(P=0.07 and<0.01,respectively)and white-to-white distance(P=0.01 and 0.04,respectively)changed significantly between the two measurements prior and posterior.At the same time,despite there being some participants with the difference between the before and after calculations greater than 0.5 diopter,there was no significant difference in the incidence rate between these formulas.CONCLUSION:There is no significant effect of pharmacological pupil changes on the IOL power calculation.It will considerably reduce the visit time burden for patients who require cataract surgery.
文摘AIM: To evaluate the accuracy of three commonly used biometric formulae across different axial lengths(ALs) at one United States Veterans Affairs teaching hospital.METHODS: A retrospective chart review was conducted from November 2013 to May 2018. One eye of each patient who underwent cataract surgery with a monofocal intraocular lens(IOL) was included. The range of postoperative follow-up period was from 3 wk to 4 mo. The Holladay 2, Barrett Universal II, and Hill-Radial Basis Function(Hill-RBF) formulae were used to predict the postoperative refraction for all cataract surgeries. For each formula, we calculated the prediction errors [including mean absolute prediction error(MAE)] and the percentage of eyes within ±0.25 diopter(D) and ±0.5 D of predicted refraction. We performed subgroup analyses for short(AL<22.0 mm), medium(AL 22.0-25.0 mm), and long eyes(AL>25.0 mm).RESULTS: A total of 1131 patients were screened, and 909 met the inclusion criteria. Resident ophthalmologists were the primary surgeons in 710(78.1%) cases. We found no statistically significant difference in predictive accuracy among the three formulae over the entire AL range or in the short, medium, and long eye subgroups. Across the entire AL range, the Hill-RBF formula resulted in the lowest MAE(0.384 D) and the highest percentage of eyes with postoperative refraction within ±0.25 D(42.7%) and ±0.5 D(75.5%) of predicted. All three formulae had the highest MAEs(>0.5 D) and lowest percentage within ±0.5 D of predicted refraction(<55%) in short eyes.CONCLUSION: In cataract surgery patients at our teaching hospital, three commonly used biometric formulae demonstrate similar refractive accuracy across all ALs. Short eyes pose the greatest challenge to predicting postoperative refractive error.
文摘Purpose To evaluate the refractive prediction error of common intraocular lens(IOL)power calculation formulae in patients who underwent intrascleral IOL fixation using two different techniques.Methods This is a prospective,randomized,longitudinal,single-site,single-surgeon study.Patients who underwent intrascleral IOL implantation using the Yamane or the Carlevale technique were followed up for a period of six months postoperatively.Refraction was measured using the best-corrected visual acuity at 4 m(EDTRS chart).Lens decentration,tilt and effective lens position(ELP)were assessed using an anterior segment optical coherence tomography(AS-OCT).The prediction error(PE)and the absolute error(AE)were evaluated for the SRK/T,Hollayday1 and Hoffer Q formula.Subsequently,correlations between the PE and axial length,keratometry,white to white and ELP were assessed.Results In total,53 eyes of 53 patients were included in the study.Twenty-four eyes of 24 patients were in the Yamane group(YG)and 29 eyes of 29 patients were in the Carlevale group(CG).In the YG,the Holladay 1 and Hoffer Q formulae resulted in a hyperopic PE(0.02±0.56 D,and 0.13±0.64 D,respectively)while in the SRK/T formula the PE was slightly myopic(−0.16±0.56 D).In the CG,SRK/T and Holladay 1 formulae led to a myopic PE(−0.1±0.80 D and−0.04±0.74 D,respectively),Hoffer Q to a hyperopic PE(0.04±0.75 D).There was no difference between the PE of the same formulae across both groups(P>0.05).In both groups the AE differed significantly from zero in each evaluated formula.The AE error was within±0.50 D in 45%–71%and was within±1.00 D in 72%–92%of eyes depending on the formula and surgical method used.No significant differences were found between formulae within and across groups(P>0.05).Intraocular lens tilt was lower in the CG(6.45±2.03°)compared to the YG(7.67±3.70°)(P<0.001).Lens decentration was higher in the YG(0.57±0.37 mm)than in the CG(0.38±0.21 mm),though the difference was not statistically significant(P=0.9996).Conclusions Refractive predictability was similar in both groups.IOL tilt was better in the CG,however this did not influence the refractive predictability.Though not significant,Holladay 1 formula seemed to be more probable than the SRK/T and Hoffer Q formulae.However,significant outliers were observed in all three different formulae and therefore remain a challenging task in secondary fixated IOLs.
基金supported by research grants from the National Natural Science Foundation of China(Grant Nos.82122017,81870642,81970780 and 81670835)Science and Technology Innovation Action Plan of Shanghai Science and Technology Commission(Grant Nos.19441900700 and 21S31904900)+1 种基金Clinical Research Plan of Shanghai Shenkang Hospital Development Center(Grant Nos.SHDC2020CR4078 and SHDC12019X08)the Fudan University“Outstanding 2025”Program.
文摘Background:The accuracy of using total keratometry(TK)value in recent IOL power calculation formulas in highly myopic eyes remained unknown.Methods:Highly myopic patients who underwent uneventful cataract surgery were prospectively enrolled in this prospective comparative study.At one month postoperatively,standard deviation(SD)of the prediction errors(PEs),mean and median absolute error(MedAE)of 103 highly myopic eyes were back-calculated and compared among ten formulas,including XGboost,RBF 3.0,Kane,Barrett Universal II,Emmetropia Verifying Optical 2.0,Cooke K6,Haigis,SRK/T,and Wang-Koch modifications of Haigis and SRK/T formulas,using either TK or standard keratometry(K)value.Results:In highly myopic eyes,despite good agreement between TK and K(P>0.05),larger differences between the two were associated with smaller central corneal thickness(P<0.05).As to the refractive errors,TK method showed no differences compared to K method.The XGBoost,RBF 3.0 and Kane ranked top three when considering SDs of PEs.Using TK value,the XGboost calculator was comparable with the RBF 3.0 formula(P>0.05),which both presented smaller MedAEs than others(all P<0.05).As for the percentage of eyes within±0.50 D or±0.75 D of PE,the XGBoost TK showed comparable percentages with the RBF 3.0 TK formula(74.76%vs.66.99%,or 90.29%vs.87.38%,P>0.05),and statistically larger percentages than the other eight formulas(P<0.05).Conclusions:Highly myopic eyes with thinner corneas tend to have larger differences between TK and K.The XGboost enhancement calculator and RBF 3.0 formula using TK showed the most promising outcomes in highly myopic eyes.
基金the Electro-Magnetic Remote Sensing Defence Technology Centre (EMRS DTC)established by the UK Ministry of Defence (Grant No. 1-27)+1 种基金the Program for New Century Excellent Talents in University (Grant No. NCET-06-0162)the National Natural Science Foundation of China (Grant Nos. 60890071-17, 60890072-13, 60890073)
文摘Forward scattering micro radar is used for situation awareness; its operational range is relatively short because of the battery power and local horizon, the free space propagation model is not appropriate. The ground moving targets, such as humans, cars and tanks, have only comparable size with the transmitted signal wavelength; the point target model and the linear change of observation angle are not applicable. In this paper, the signal model of ground moving target is developed based on the case of forward scattering micro radar, considering the two-ray propagation model and area target model, and nonlinear change of observation angle as well as high order phase error. Furthermore, the analytical form of the received power from moving target has been obtained. Using the simulated forward scattering radar cross section, the received power of theoretical calculation is near to that of measured data. In addition, the simulated signal model of ground moving target is perfectly matched with the experimented data. All these results show the correctness of analytical calculation completely.
基金supported by the National Basic Research Program of China(973 Program)(No.2013CB02708201)
文摘In order to enhance the stability of single-phase microgrid,virtual synchronous generator(VSG)control method is investigated in this paper.Its electromagnetic model and electromechanical model are established to illustrate the performance of VSG.Considering the 2 nd fluctuation of fundamental-frequency in the output power,an instantaneous power calculation strategy is proposed based on the intrinsic frequency of single-phase VSG.Besides,a virtual power calculation method is presented to achieve islanded/grid-connected seamless transition.Stability analysis and comparison simulation results demonstrate the correctness of the presented power calculation method.At last,the effectiveness of the proposed approach is verified by comparison experiments of islanded/gridconnected operations in a 500 VA single-phase inverter.
基金This study was supported by the Technology Foundation of Tianjin Municipal Health Bureau of China(grant no.2014KY37 to Jun Li)the Natural Science Foundation of the Tianjin Science and Technology Committee of China(grant no.18JCZDJC36400 to Li Nan).
文摘Background:To compare the accuracy of intraocular lens power calculation formulae after laser refractive surgery in myopic eyes.Methods:We searched the databases on PubMed,EMBASE,Web of Science and the Cochrane library to select relevant studies published between Jan 1st,2009 and Aug 11th,2019.Primary outcomes were the percentages of refractive prediction error within±0.5 D and±1.0 D.Results:The final meta-analysis included 16 studies using seven common methods(ASCRS average,Barrett True-K no history,Double-K SRK/T,Haigis-L,OCT formula,Shammas-PL,and Wang-Koch-Maloney).ASCRS average yielded significantly higher percentage of refractive prediction error within±0.5 D than Haigis-L,Shammas-PL and WangKoch-Maloney(P=0.009,0.01,0.008,respectively).Barrett True-K no history also yielded significantly higher percentage of refractive prediction error within±0.5 D than Shammas-PL and Wang-Koch-Maloney(P=0.01,P<0.0001,respectively),and a similar result was found when comparing OCT formula with Haigis-L and Shammas-PL(P=0.03,P=0.01,respectively).Conclusion:The ASCRS average or Barrett True-K no history should be used to calculate the intraocular lens power in eyes after myopic laser refractive surgery.The OCT formula if available,can also be a good alternative choice.
基金supported by the Technology Foun dation of Tianjin Municipal Health Bureau of China(Grant No.2014KY37)the Natural Science Foundation of the Tianjin Science and Technology Committee of China(Grant No.18JCZDJC36400).
文摘Background:To compare the accuracy of intraocular lens power calculation formulae after laser refractive surgery in myopic eyes.Methods:We searched the databases on PubMed,EMBASE,Web of Science and the Cochrane library to select relevant studies published between Jan 1st,2009 and Aug 11th,2019.Primary outcomes were the percentages of refractive prediction error within±0.5 D and±1.0 D.Results:The final meta-analysis included 16 studies using seven common methods(ASCRS average,Barrett True-K no history,Double-K SRK/T,Haigis-L,OCT formula,Shammas-PL,and Wang-Koch-Maloney).ASCRS average yielded significantly higher percentage of refractive prediction error within±0.5 D than Haigis-L,Shammas-PL and Wang,Koch-Maloney(P=0.009,0.01,0.008,respectively).Barrett True-K no history also yielded significantly higher percentage of refractive prediction error within±0.5 D than Shammas-PL and Wang-Koch-Maloney(P=0.01,P<0.0001,respectively),and a similar result was found when comparing OCT formula with Haigis-L and Shammas-PL(P=0.03,P=0.01,respectively).Conclusion:The ASCRS average or Barrett True-K no history should be used to calculate the intraocular lens power in eyes after myopic laser refractive surgery.The OCT formula if available,can also be a good alternative choice.
文摘Background:To examine the effectiveness of the use of machine learning for adapting an intraocular lens(IOL)power calculation for a patient group.Methods:In this retrospective study,the clinical records of 1,611 eyes of 1,169 Japanese patients who received a single model of monofocal IOL(SN60WF,Alcon)at Miyata Eye Hospital were reviewed and analyzed.Using biometric metrics and postoperative refractions of 1211 eyes of 769 patients,constants of the SRK/T and Haigis formulas were optimized.The SRK/T formula was adapted using a support vector regressor.Prediction errors in the use of adapted formulas as well as the SRK/T,Haigis,Hill-RBF and Barrett Universal II formulas were evaluated with data from 395 eyes of 395 distinct patients.Mean prediction errors,median absolute errors,and percentages of eyes within±0.25 D,±0.50 D,and±1.00 D,and over+0.50 D of errors were compared among formulas.Results:The mean prediction errors in the use of the SRT/K and adapted formulas were smaller than the use of other formulas(P<0.001).In the absolute errors,the Hill-RBF and adapted methods were better than others.The performance of the Barrett Universal II was not better than the others for the patient group.There were the least eyes with hyperopic refractive errors(16.5%)in the use of the adapted formula.Conclusions:Adapting IOL power calculations using machine learning technology with data from a particular patient group was effective and promising.
文摘Background:To examine the effectiveness of the use of machine learning for adapting an intraocular lens(IOL)power calculation for a patient group.Methods:In this retrospective study,the clinical records of 1,611 eyes of 1,169 Japanese patients who received a single model of monofocal IOL(SN60WF,Alcon)at Miyata Eye Hospital were reviewed and analyzed.Using biometric metrics and postoperative refractions of 1211 eyes of 769 patients,constants of the SRK/T and Haigis formulas were optimized.The SRK/T formula was adapted using a support vector regressor.Prediction errors in the use of adapted formulas as well as the SRK/T,Haigis,Hill-RBF and Barrett Universal II formulas were evaluated with data from 395 eyes of 395 distinct patients.Mean prediction errors,median absolute errors,and percentages of eyes within±0.25 D,±0.50 D,and±1.00 D,and over+0.50 D of errors were compared among formulas.Results:The mean prediction errors in the use of the SRT/K and adapted formulas were smaller than the use of other formulas(P<0.001).In the absolute errors,the Hill-RBF and adapted methods were better than others.The performance of the Barrett Universal II was not better than the others for the patient group.There were the least eyes with hyperopic refractive errors(16.5%)in the use of the adapted formula.Conclusions:Adapting IOL power calculations using machine learning technology with data from a particular patient group was effective and promising.
文摘Based on the general methods in power flow calculation of power system and on conceptions and classifications of parallel algorithm, a new approach named Dynamic Asynchronous Parallel Algorithm that applies to the online analysis and real-time dispatching and controlling of large-scale power network was put forward in this paper. Its performances of high speed and dynamic following have been verified on IEEE-14 bus system.
文摘We present a theoretic model to calculate skin depths and eddy-current power losses for a magnetic position sensor. Eddy-current, arised from the operation of an alternating-current excitation, induces secondary currents and fields between magnetic material and magnetic position sensor. In this paper, a magnetic position sensor system is simplified to be an outer-winding coil along the axial direction of a low carbon steel bar. The analytical model is derived from basic field and circuit theory considering a linear approximation for a nonlinear permeability. Thus the skin depths and eddy-current power losses from the model in eddy-current modeling techniques at various frequencies of an excited current source can be calculated. The proposed configuration is capable of predicting the skin depths and eddy-current power losses for a magnetic position sensor and has a consistence with experiments.
基金Supported by the Innovation&Transfer Fund of Peking University Third Hospital(No.BYSYZHKC2021108).
文摘AIM:To investigate the influence of postoperative intraocular lens(IOL)positions on the accuracy of cataract surgery and examine the predictive factors of postoperative biometry prediction errors using the Barrett Universal II(BUII)IOL formula for calculation.METHODS:The prospective study included patients who had undergone cataract surgery performed by a single surgeon from June 2020 to April 2022.The collected data included the best-corrected visual acuity(BCVA),corneal curvature,preoperative and postoperative central anterior chamber depths(ACD),axial length(AXL),IOL power,and refractive error.BUII formula was used to calculate the IOL power.The mean absolute error(MAE)was calculated,and all the participants were divided into two groups accordingly.Independent t-tests were applied to compare the variables between groups.Logistic regression analysis was used to analyze the influence of age,AXL,corneal curvature,and preoperative and postoperative ACD on MAE.RESULTS:A total of 261 patients were enrolled.The 243(93.1%)and 18(6.9%)had postoperative MAE<1 and>1 D,respectively.The number of females was higher in patients with MAE>1 D(χ^(2)=3.833,P=0.039).The postoperative BCVA(logMAR)of patients with MAE>1 D was significantly worse(t=-2.448;P=0.025).After adjusting for gender in the logistic model,the risk of postoperative refractive errors was higher in patients with a shallow postoperative anterior chamber[odds ratio=0.346;95% confidence interval(CI):0.164,0.730,P=0.005].CONCLUSION:Risk factors for biometry prediction error after cataract surgery include the patient’s sex and postoperative ACD.Patients with a shallow postoperative anterior chamber are prone to have refractive errors.
基金funded by Youth Science Foundation Fund Project of National Natural Science Foundation of China(51607148)Science and Technology R&D Program of China State Railway Group Co.,Ltd.(SY2020G001)Project of Sichuan Science and Technology Program(2021YJ0028)。
文摘Purpose–The traction cable is paralleled with the existing traction network of electrified railway through transverse connecting line to form the scheme of long distance power supply for the traction network.This paper aims to study the scheme composition and power supply distance(PSD)of the scheme.Design/methodology/approach–Based on the structure of parallel traction network(referred to as“cable traction network(CTN)”),the power supply modes(PSMs)are divided into cableþdirect PSM and cableþautotransformer(AT)PSM(including Japanese mode,French mode and new mode).Taking cableþJapanese AT PSM as an example,the scheme of long distance power supply for CTN under the PSMs of co-phase and out-of-phase power supply are designed.On the basis of establishing the equivalent circuit model and the chain circuit model of CTN,taking the train working voltage as the constraint condition,and based on the power flow calculation of multiple train loads,the calculation formula and process for determining the PSD of CTN are given.The impedance and PSD of CTN under the cableþAT PSM are simulated and analyzed,and a certain line is taken as an example to compare the scheme design.Findings–Results show that the equivalent impedance of CTN under the cableþAT PSM is smaller,and the PSD is about 2.5 times of that under the AT PSM,which can effectively increase the PSD and the flexibility of external power supply location.Originality/value–The research content can effectively improve the PSD of traction power supply system and has important reference value for the engineering application of the scheme.
基金This work was partly supported by the Technology Project of State Grid Jiangsu Electric Power Co.,Ltd.,China,under Grant No.J2022095.
文摘Power flow calculation is the basis of power grid planning and many system analysis tasks require convergent power flow conditions.To address the unsolvable power flow problem caused by the reactive power imbalance,a method for adjusting reactive power flow convergence based on deep reinforcement learning is proposed.The deep reinforcement learning method takes switching parallel reactive compensation as the action space and sets the reward value based on the power flow convergence and reactive power adjustment.For the non-convergence power flow,the 500 kV nodes with reactive power compensation devices on the low-voltage side are converted into PV nodes by node type switching.And the quantified reactive power non-convergence index is acquired.Then,the action space and reward value of deep reinforcement learning are reasonably designed and the adjustment strategy is obtained by taking the reactive power non-convergence index as the algorithm state space.Finally,the effectiveness of the power flow convergence adjustment algorithm is verified by an actual power grid system in a province.
基金supported by the 2022 Science and Technology Project of Tianjin Binhai New Area Health Commission(2022BWKQ008)Tianjin Medical University"Clinical Talent Training 123 Climbing Plan"and Tianjin Medical University Eye Hospital High-level Innovative Talent Programmer(YDYYRCXM-E2023-05).
文摘Purpose:This prospective cohort study aimed to assess the influence of tear film stability on corneal refractive power measurement and surgical planning in cataract patients.Methods:Participants were divided into tear film instability(tear film stability level 2)and control(level 0–1)groups based on Keratograph 5M results.Using IOL Master 700,two consecutive measurements were obtained with a 10-min interval.Parameters including standard keratometry(Kf,Ks and K),keratometric corneal astigmatism(KCA),total keratometry(TKf,TKs and TK)and total corneal astigmatism(TCA)were recorded.IOL power was calculated using SRK-T,SRK-T TK,Haigis,Haigis TK,Barrett Universal II,and Barrett Universal II TK formulas.Results:The results showed significantly higher differences between two measurements in Kf,K,KCA,TKf,TK,and TCA,as well as the vector variability of corneal astigmatism in the tear film instability group(all P<0.05).Of all formulas,only the SRK-T formula displayed significantly higher variability in IOL power calculations in the tear film instability group compared to the control group(P<0.05).Conclusions:This study highlights that tear film instability can lead to deviations in corneal refractive power and astigmatism measurements,contributing to increased prediction errors in IOL power calculation,particularly with the SRK-T formula.
基金supported by the State Grid Science&Technology Project of China(5400-202224153A-1-1-ZN).
文摘Expanding photovoltaic(PV)resources in rural-grid areas is an essential means to augment the share of solar energy in the energy landscape,aligning with the“carbon peaking and carbon neutrality”objectives.However,rural power grids often lack digitalization;thus,the load distribution within these areas is not fully known.This hinders the calculation of the available PV capacity and deduction of node voltages.This study proposes a load-distribution modeling approach based on remote-sensing image recognition in pursuit of a scientific framework for developing distributed PV resources in rural grid areas.First,houses in remote-sensing images are accurately recognized using deep-learning techniques based on the YOLOv5 model.The distribution of the houses is then used to estimate the load distribution in the grid area.Next,equally spaced and clustered distribution models are used to adaptively determine the location of the nodes and load power in the distribution lines.Finally,by calculating the connectivity matrix of the nodes,a minimum spanning tree is extracted,the topology of the network is constructed,and the node parameters of the load-distribution model are calculated.The proposed scheme is implemented in a software package and its efficacy is demonstrated by analyzing typical remote-sensing images of rural grid areas.The results underscore the ability of the proposed approach to effectively discern the distribution-line structure and compute the node parameters,thereby offering vital support for determining PV access capability.
基金The project supported by NNSFC (19631040), NSSFC (04BTJ002) and the grant for post-doctor fellows in SELF.
文摘In this paper, it is discussed that two tests for varying dispersion of binomial data in the framework of nonlinear logistic models with random effects, which are widely used in analyzing longitudinal binomial data. One is the individual test and power calculation for varying dispersion through testing the randomness of cluster effects, which is extensions of Dean(1992) and Commenges et al (1994). The second test is the composite test for varying dispersion through simultaneously testing the randomness of cluster effects and the equality of random-effect means. The score test statistics are constructed and expressed in simple, easy to use, matrix formulas. The authors illustrate their test methods using the insecticide data (Giltinan, Capizzi & Malani (1988)).
基金supported in part by the National Natural Science Foundation of China(No.52177071).
文摘Medium-voltage distribution systems(MVDSs)mainly consist of a feeder head,lines,distribution transformers,and the equivalent load or power supply interfaced with the distribution transformers.The information of such load or power supply can be measured via the three-wattmeter method(THM)and the two-wattmeter method(TWM).The measurements can be used to perform the control of the power supply and simulate the characteristics of the load,so the models of the load and the power supply need to consider the measurement characteristics.Existing research works on three-phase power flow(PF)just consider the measurement characteristics of THM.Hence,the PF equation of the bus measured via TWM is firstly built.Based on conventional measurements,an accurate and general model of the grounded and ungrounded slack bus is proposed.Furthermore,the influence arising from the connection type and angle shift of distribution transformers on the admittance matrix is considered,and thus a general three-phase transformer model is summarized,which is applicable for all the transformers mentioned herein.Finally,Newton's method is adopted to solve the PF calculation,and the performance of the proposed PF model is demonstrated through designed tests.
