AIM： To evaluate the efficacy of non-sequential narrow band imaging （NBI） for a better recognition of gastric intestinal metaplasia （GIM）. METHODS： Previously diagnosed GIM patients underwent targeted biopsy fro...AIM： To evaluate the efficacy of non-sequential narrow band imaging （NBI） for a better recognition of gastric intestinal metaplasia （GIM）. METHODS： Previously diagnosed GIM patients underwent targeted biopsy from areas with and without GIM, as indicated by NBI, twice at an interval of 1 year. The authors compared the endoscopic criteria such as light blue crest （LBC）, villous pattern （VP）, and large long crest （LLC） with standard histology. The results from two surveillance endoscopies were compared with histology results for sensitivity, specificity, positive predic-tive value （PPV）, negative predictive value （NPV）, and likelihood ratio of positive test （LR＋）. The number of early gastric cancer cases detected was also reported. RESULTS： NBI targeted biopsy was performed in 38 and 26 patients during the first and second surveillance endoscopies, respectively. There were 2 early gastric cancers detected in the first endoscopy. No cancer was detected from the second study. Surgical and endoscopic resections were successfully performed in each patient. Sensitivity, specificity, PPV, NPV, and LR＋ of all 3 endoscopic criteria during the first/second surveillances were 78.8%/91.3%, 82.5%/89.1%, 72.8%/77.8%, 86.8%/96.1, and 4.51/8.4, respectively. LBC provided the highest LR＋ over VP and LLC. CONCLUSION： Nonequential NBI is useful for GIM targeted biopsy. LBC provides the most sensitive reading. However, the optimal duration between two surveillances requires further study.展开更多
AIM:To evaluate the accuracy and predictability of ray tracing-assisted intraocular lens(IOL) calculation function in Sirius internal software and further improve the accuracy by optimizing the calculation of predicte...AIM:To evaluate the accuracy and predictability of ray tracing-assisted intraocular lens(IOL) calculation function in Sirius internal software and further improve the accuracy by optimizing the calculation of predicted lens position(PLP).METHODS:This retrospective study recruited 52 eyes of 49 patients.All of the cases with cataract had undergone phacoemulsification combined with IOL implantation.SRK-T,Haigis formula,and Sirius ray-tracing method were all used for each eye’s IOL calculation.The mean absolute value of prediction error(prediction error=predicted refraction-postoperative refraction) was defined as mean absolute prediction error(MAPE) and was determined for each method.Calculation of PLP was optimized by effective lens position(ELP).Optimized PLP was entered to Sirius internal software again to verify whether the method was improved.RESULTS:Compared with SRK-T and Haigis formulas,less accuracy was shown in Sirius ray-tracing method(P=0.001).The ELP of the IOL moved forward compared to PLP(P<0.001).The MAPE of the ELP-inputted Sirius ray-tracing method was reduced.ELP and PLP were well correlated.Taking ELP as y and PLP given by Sirius soft as x,a linear regression formula y=0.1637 x+3.1741 was concluded(R^(2)=0.1066,P=0.018).It was shown that the optimized Sirius ray-tracing method(optimized PLP entered),compared with SRK-T and Haigis formulas,worked with the same accuracy(P=0.038).CONCLUSION:The original Sirius ray tracing method is not satisfactory enough.However,in normal eyes,the optimized Sirius ray-tracing method in IOL calculation was as accurate as SRK-T and Haigis formulas.展开更多
A new seismic ray-tracing method is put forward based on parabolic travel-time interpolation(PTI) method, which is more accurate than the linear travel-time interpolation (LTI) method. Both PTI method and LTI method a...A new seismic ray-tracing method is put forward based on parabolic travel-time interpolation(PTI) method, which is more accurate than the linear travel-time interpolation (LTI) method. Both PTI method and LTI method are used to compute seismic travel-time and ray-path in a 2-D grid cell model. Firstly, some basic concepts are introduced. The calculations of travel-time and ray-path are carried out only at cell boundaries. So, the ray-path is always straight in the same cells with uniform velocity. Two steps are applied in PTI and LTI method, step 1 computes travel-time and step 2 traces ray-path. Then, the derivation of LTI formulas is described. Because of the presence of refraction wave in shot cell, the formula aiming at shot cell is also derived. Finally, PTI method is presented. The calculation of PTI method is more complex than that of LTI method, but the error is limited. The results of numerical model show that PTI method can trace ray-path more accurately and efficiently than LTI method does.展开更多
Beginning with the method of whole path iterative ray-tracing and according to the positive definiteness of the coefficient matrix of the systems of linear equations, a symmetry olock tridiagonal matrix was decomposed...Beginning with the method of whole path iterative ray-tracing and according to the positive definiteness of the coefficient matrix of the systems of linear equations, a symmetry olock tridiagonal matrix was decomposed into the product of block bidiagonal triangular matrix and its transpose by means of Cholesky decomposition. Then an algorithm for solving systems of block bidiagonal triangular linear equations was given, which is not necessary to treat with the zero elements out of banded systems. A fast algorithm for solving the systems of symmetry block tridiagonal linear equations was deduced, which can quicken the speed of ray-tracing. Finally, the simulation based on this algorithm for ray-tracing in three dimensional media was carried out. Meanwhile, the segmentally-iterative ray-tracing method and banded method for solving the systems of block tridiagonal linear equations were compared in the same model mentioned above. The convergence condition was assumed that the L-2 norm summation for mk, 1 and mk. 2 in the whole ray path was limited in 10-6. And the calculating speeds of these methods were compared. The results show that the calculating speed of this algorithm is faster than that of conventional method and the calculated results are accurate enough. In addition, its precision can be controlled according to the requirement of ray-tracing.展开更多
Electron dynamics during non-sequential double ionization(NSDI) is one of the most attractive areas of research in the field of laser–atom or laser–molecule interaction. Based on the classic two-dimensional model, w...Electron dynamics during non-sequential double ionization(NSDI) is one of the most attractive areas of research in the field of laser–atom or laser–molecule interaction. Based on the classic two-dimensional model, we study the process of NSDI of argon atoms driven by a few-cycle orthogonal two-color laser field composed of 800 nm and 400 nm laser pulses. By changing the relative phase of the two laser pulses, a localized enhancement of NSDI yield is observed at 0.5πand 1.5π, which could be attributed to a rapid and substantial increase in the number of electrons returning to the parent ion within extremely short time intervals at these specific phases. Through the analysis of the electron–electron momentum correlations within different time windows of NSDI events and the angular distributions of emitted electrons in different channels, we observe a more pronounced electron–electron correlation phenomenon in the recollision-induced ionization(RII) channel. This is attributed to the shorter delay time in the RII channel.展开更多
The effect of initial longitudinal velocity of the tunnelled electron on the non-sequential double ionization （NSDI） process in an elliptically polarized laser field is studied by a semiclassical model. We find that...The effect of initial longitudinal velocity of the tunnelled electron on the non-sequential double ionization （NSDI） process in an elliptically polarized laser field is studied by a semiclassical model. We find that the non-zero initial longitudinal velocity has a suppressing effect on single-return collision （SRC） events in the double ionization process, more specifically, it results in an obvious reduction in the center part of the correlation momentum distributions in the direction of the major polarization axis （z axis） and makes the distribution of single-return collision in the minor polarization axis （x axis） become narrower.展开更多
By using a two-dimensional Monte-Carlo classical ensemble method, we investigate the double ionization（DI） process of the CS_2 molecule with different bond lengths in an 800-nm intense laser field. The double ioniza...By using a two-dimensional Monte-Carlo classical ensemble method, we investigate the double ionization（DI） process of the CS_2 molecule with different bond lengths in an 800-nm intense laser field. The double ionization probability presents a ＂knee＂ structure with equilibrium internuclear distance R = 2.9245 a.u.（a.u. is short for atomic unit）. As the bond length of CS increases, the DI probability is enhanced and the ＂knee＂ structure becomes less obvious. In addition,the momentum distribution of double ionized electrons is also investigated, which shows the momentum mostly distributed in the first and third quadrants with equilibrium internuclear distance R = 2.9245 a.u. As the bond length of CS increases,the electron momentum becomes evenly distributed in the four quadrants. Furthermore, the energy distributions and the corresponding trajectories of the double-ionized electrons versus time are also demonstrated, which show that the bond length of CS in the CS_2 molecule plays a key role in the DI process.展开更多
The smart meter communication system has substantial application value for the construction and upgrading of the entire power system.The deployment of the transmitter(Tx)of the smart meter system in the residential sc...The smart meter communication system has substantial application value for the construction and upgrading of the entire power system.The deployment of the transmitter(Tx)of the smart meter system in the residential scenarios is vexed by the need for more theoretical support.This paper mainly studies the communication channel between the Tx at semibasement and receiver(Rx)at outdoor.The design of an effective communication system relies on an accurate understanding of channel characteristics.Channel measurements and ray-tracing channel modeling are conducted to obtain channel data.The influence of different positions at same semi-basement is studied.Typical channel characteristics are analyzed,such as power delay profile(PDP),power angular profile(PAP),root-mean-square(RMS)delay spread(DS),channel capacity,received power,and path loss.The influence of different semi-basement placements and different floor heights is also compared.Besides,the channel measurements and simulation data fit well,which can illustrate the validity and reliability of the acquired channel data.This paper can provide theoretical support for the design and optimization of smart meter communication systems in semi-basement scenarios.展开更多
Canopy photosynthesis,rather than leaf photosynthesis,is highly related to plant biomass and yield formation.Studying canopy photosynthesis and identifying the parameters that control it can help optimize agricultural...Canopy photosynthesis,rather than leaf photosynthesis,is highly related to plant biomass and yield formation.Studying canopy photosynthesis and identifying the parameters that control it can help optimize agricultural management and achieve crop yield potential.Compared with traditional parameters,canopy occupation volume(COV)offers an integrative parameter on canopy architecture related to canopy photosynthetic rates.In this study,we developed a high-throughput method to derive COV for different rice varieties.We first used multi-perspective two-dimensional imaging to reconstruct three-dimensional point clouds of rice plants and developed a suite of pipelines to calculate plant height,leaf number,tiller number,and biomass,with R^(2) values of 91.8%,95.9%,82.3%,and 94.3%,respectively.We further employed point cloud data to reconstruct the surfaces of rice plants and construct a virtual canopy model of the rice population.Light distribution was simulated using a ray-tracing algorithm and canopy photosynthetic rates were simulated via photosynthetic rate-incident light intensity curve fitting.Furthermore,we systematically explored the relationships between canopy phenotypes and photosynthetic rates,and found that COV was the most effective predictor of canopy photosynthesis,achieving an R^(2) value of 92.1%.Adjustment in atmospheric transmittance showed that COV strongly correlated with canopy photosynthesis under different light conditions,with higher accuracy observed under diffuse light.Variations in planting density confirmed that this correlation remained strong at the community level.In summary,this study demonstrates that COV is closely linked to simulated canopy photosynthesis and the developed pipeline can support future agronomic and breeding research.展开更多
Using a recognition model of atmospheric gravity waves(AGWs),we identified 519 AGW events from the OH airglow images observed at the Dandong and Lhasa stations from 2015 to 2017.The 317 AGW events detected at the Dand...Using a recognition model of atmospheric gravity waves(AGWs),we identified 519 AGW events from the OH airglow images observed at the Dandong and Lhasa stations from 2015 to 2017.The 317 AGW events detected at the Dandong station have wavelengths ranging from 30 to 60 km,periods from 14 to 20 min,horizontal speeds from 30 to 60 m/s,and relative intensities from 0.4%to 0.6%,respectively.The parameters of 202 events recorded at the Lhasa station mainly vary within 15-35 km in horizontal wavelength,4-6 min in period,40-100 m/s in horizontal velocity,and 0.1%-0.3%in relative intensity.The occurrence rate peaks in winter and summer at Dandong and the peak in summer are absent at Lhasa because of the lack of convective weather.The seasonal propagation directions of the waves are influenced by both the wind field-filtering effect and the distribution of wave sources.In spring,because of the southeastward background wind field,fewer southeastward events are observed at the Dandong station.The situation at the Lhasa station is similar.In summer,both the Lhasa and Dandong stations are dominated by northeastward AGWs,which can be attributed to the southwestward wind.In autumn,ray-tracing results show that the events at Dandong mainly originate from wind shear,whereas the events at the Lhasa station are triggered by convective weather.The location of the wave sources determines the trend of the propagation directions at the Dandong and Lhasa stations in autumn.In winter,because of the eastward wind,more events are propagating to the southwest at the Dandong station.展开更多
Radar cross section(RCS)plays a critical role in modeling target scattering characteristics and enhancing the precision of target detection and localization in integrated sensing and communication(ISAC)systems.This pa...Radar cross section(RCS)plays a critical role in modeling target scattering characteristics and enhancing the precision of target detection and localization in integrated sensing and communication(ISAC)systems.This paper investigates the human body RCS at 26 GHz via multiangle channel measurements under different clothing conditions.Based on calibrated electromagnetic(EM)parameters,the RCS characteristics of the human body in far-field conditions are analyzed using ray-tracing(RT)simulations.Some suggestions for the design of ISAC systems are also discussed.The results provide a solid theoretical foundation and practical reference for the modeling of target scattering characteristics for ISAC channels.展开更多
Lightning-generated whistler(LGW)is an important electromagnetic wave in the magnetosphere,causing energetic electron losses.Here we analyze the LGW distribution and propagation using Van Allen Probes data and ray-tra...Lightning-generated whistler(LGW)is an important electromagnetic wave in the magnetosphere,causing energetic electron losses.Here we analyze the LGW distribution and propagation using Van Allen Probes data and ray-tracing simulation.The statistics show that LGW occurs more frequently at L<2.5 with higher amplitudes in the northern hemisphere.The Poynting flux demonstrates that LGW originates from both hemispheres within L~2.5,and propagates into the space as the wave power decays.The wave normal angle distributions indicate that LGW propagates quasi-parallel to the field line near its source and becomes oblique as the magnetic latitude decreases.Furthermore,we use the ray-tracing model to simulate the LGW propagation,and statistically analyze the propagation characteristics of LGW,which are consistent with the observational data.This paper presents the latitudinal distribution and propagation properties of LGW based on statistics for the first time,providing new insights into the LGW generation and evolution in the magnetosphere.展开更多
Narrow-band imaging （NBI） is an innovative optical technology that modifies the center wavelength and bandwidth of an endoscope＇s light into narrow-band illumination of 415 ：1： 30 nm. NBI markedly improves capill...Narrow-band imaging （NBI） is an innovative optical technology that modifies the center wavelength and bandwidth of an endoscope＇s light into narrow-band illumination of 415 ：1： 30 nm. NBI markedly improves capillary pattern contrast and is an in vivo method for visualizing microvessel morphological changes in superficial neoplastic lesions. The scientific basis for NBI is that short wavelength light falls within the hemoglobin absorption band, thereby facilitating clearer visualization of vascular structures. Several studies have reported advantages and limitations of NBI colonoscopy in the colorectum. One difficulty in evaluating results, however, has been nonstandardization of NBI systems （Sequential and nonsequential）. Utilization of NBI technology has been increasing worldwide, but accurate pit pattern analysis and sufficient skill in magnifying colonoscopy are basic fundamentals required for proficiency in NBI diagnosis of colorectal lesions. Modern optical technology without proper image interpretation wastes resources, confuses untrained endoscopists and delays interinstitutional validation studies. Training in the principles of ＂optical image-enhanced endoscopy＂ is needed to close the gap between technological advancements and their clinical usefulness. Currently available evidence indicates that NBI constitutes an effective and reliable alternative to chromocolonoscopy for in vivo visualization of vascular structures, but further study assessing reproducibility and effectiveness in the colorectum is ongoing at various medical centers.展开更多
A three-dimensional laser absorption model based on ray tracing was established to describe the coupled interaction of a laser beam with particles in the powder layers of pure tungsten(W)material processed by selectiv...A three-dimensional laser absorption model based on ray tracing was established to describe the coupled interaction of a laser beam with particles in the powder layers of pure tungsten(W)material processed by selective laser melting(SLM).The influence of particle size on the powder-to-laser absorptivity and underlying absorption behavior was investigated.An intrinsic relationship between the absorption,distribution of absorbed irradiance within the powder layers,and surface morphology and geometric characteristics(e.g.,contact angle,width and height of tracks,and remelted depth)of the laser scanning tracks is presented here.Simulation conclusions indicate that the absorptivity of the powder layers considerably exceeds the single powder particle value or the dense solid material value.With an increase in particle size,the powder layer absorbs less laser energy.The maximum absorptivity of theWpowder layers reached 0.6030 at the particle size of 5 lm.The distribution of laser irradiance on the particle surface was sensitive to particle size,azimuthal angle,and the position of the powder particles on the substrate.The maximum irradiance in the powder layers decreased from 1.117×10^–3 to 0.85×10^–3W·μm^-2 and the contour of the irradiance distribution in the center of the irradiated area gradually contracted when the particle size increased from 5 to 45 lm.An experimental study on the surface morphologies and cross-sectional geometric characteristics of SLM-fabricated W material was performed,and the experimental results validated the mechanisms of the powder-to-laser-absorption behavior that were obtained in simulations.This work provides a scientific basis for the application of the ray-tracing model to predict the wetting and spreading ability of melted tracks during SLM additive manufacturing in order to yield a sound laser processability.展开更多
The sixth generation(6G)of mobile communication system is witnessing a new paradigm shift,i.e.,integrated sensing-communication system.A comprehensive dataset is a prerequisite for 6G integrated sensing-communication ...The sixth generation(6G)of mobile communication system is witnessing a new paradigm shift,i.e.,integrated sensing-communication system.A comprehensive dataset is a prerequisite for 6G integrated sensing-communication research.This paper develops a novel simulation dataset,named M3SC,for mixed multi-modal(MMM)sensing-communication integration,and the generation framework of the M3SC dataset is further given.To obtain multimodal sensory data in physical space and communication data in electromagnetic space,we utilize Air-Sim and WaveFarer to collect multi-modal sensory data and exploit Wireless InSite to collect communication data.Furthermore,the in-depth integration and precise alignment of AirSim,WaveFarer,andWireless InSite are achieved.The M3SC dataset covers various weather conditions,multiplex frequency bands,and different times of the day.Currently,the M3SC dataset contains 1500 snapshots,including 80 RGB images,160 depth maps,80 LiDAR point clouds,256 sets of mmWave waveforms with 8 radar point clouds,and 72 channel impulse response(CIR)matrices per snapshot,thus totaling 120,000 RGB images,240,000 depth maps,120,000 LiDAR point clouds,384,000 sets of mmWave waveforms with 12,000 radar point clouds,and 108,000 CIR matrices.The data processing result presents the multi-modal sensory information and communication channel statistical properties.Finally,the MMM sensing-communication application,which can be supported by the M3SC dataset,is discussed.展开更多
With the research of the upcoming sixth generation(6 G) systems, new technologies will require wider bandwidth, larger scale antenna arrays and more diverse wireless communication scenarios on the future channel model...With the research of the upcoming sixth generation(6 G) systems, new technologies will require wider bandwidth, larger scale antenna arrays and more diverse wireless communication scenarios on the future channel modeling. Considering channel model is prerequisite for system design and performance evaluation of 6 G technologies, we face a challenging task: how to accurately and efficiently model 6 G channel for various scenarios? This paper tries to answer it. Firstly, the features of cluster-nuclei(CN) and principle of cluster-nuclei based channel model(CNCM) are introduced. Then, a novel modeling framework is proposed to implement CNCM,which consists four steps: propagation environment reconstruction, cluster-nuclei identification, multipath parameters generation, and channel coefficients generation. Three-dimensional environment with material information is utilized to map CN with scatterers in the propagation pathway. CN are identified by geometrical and electric field calculation based on environmental mapping, and multipath components within CN are calculated by statistical characteristics of angle, power and delay domains. Finally, we present a three-level verification structure to investigate the accuracy and complexity of channel modeling comprehensively. Simulation results reveal that CNCM can perform higher accuracy than geometrybased stochastic model while lower complexity compared with ray-tracing model for practical propagation environment.展开更多
To establish a theoretical basis for providing a better design method of multielement optical systems, we have developed a third-order geometric theory of a plane-symmetric multielement optical system that consists of...To establish a theoretical basis for providing a better design method of multielement optical systems, we have developed a third-order geometric theory of a plane-symmetric multielement optical system that consists of a planar light source, an arbitrary number of ellipsoidal gratings, and an image plane. Analytic formulas of spot diagrams are derived for the system by analytically following a ray-tracing formalism. With these formulas, coma, spherical aberration, and resultant aberration are discussed. To make the theory practical, we determine the aberration coefficients numerically, rather than analytically, with the aid of ray tracing that takes into account the angular distribution of rays originating from a given light source. A merit function is defined so as to represent closely the variance of the spots formed when an infinite number of rays are traced and to take into account the dimensions of the source and the last optical element. The theory is also applicable to mirror-grating or mirror systems.展开更多
In the present reported study, the vertical distributions of local atmospheric refractivity were retrieved from ground- based GPS observations at low elevation angles. An improved optimization method was implemented a...In the present reported study, the vertical distributions of local atmospheric refractivity were retrieved from ground- based GPS observations at low elevation angles. An improved optimization method was implemented at altitudes of 0-10 km to search for a best-fit refractivity profile that resulted in atmospheric delays most similar to the delays calculated from the observations. A ray-tracing model was used to simulate neutral atmospheric delays corresponding to a given refractivity profile. We initially performed a ＂theoretical retrieval＂, in which no observation data were involved, to verify the optimization method. A statistical relative error of this ＂theoretical retrieval＂ （-2% to 2%） indicated that such a retrieval is effective. In a practical retrieval, observations were obtained using a dual-frequency GPS receiver, and its initial value was provided by CIRA86aQ_UoG data. The statistical relative errors of the practical retrieval range from -3% to 5% were compared with co-located radiosonde measurements, Results clearly revealed diurnal variations in local refractivity prc,files, The results also suggest that the general vertical distribution of refractivity can be derived with a high temporal resolution. However, further study is needed to describe the vertical refractivity gradient clearly.展开更多
This article describes the task of optical designers to achieve a better design. This is followed by some discussions on the necessity of total design that takes all the elements into account from its light source to ...This article describes the task of optical designers to achieve a better design. This is followed by some discussions on the necessity of total design that takes all the elements into account from its light source to the final image plane. Methods are given to simulate rays from a bending magnet and an undulator, surface figure errors, and thermal deformations. Some examples are given for an undulator beamline and an EUVL optical system, together with tolerance estimates of the figure error and thermal deformation.展开更多
In the solar atmosphere, there exist two frequently-observed phenomena, Moreton waves and EIT(extreme-ultraviolet imaging telescope) waves, whose physical nature is still under debate. In this work, we perform a three...In the solar atmosphere, there exist two frequently-observed phenomena, Moreton waves and EIT(extreme-ultraviolet imaging telescope) waves, whose physical nature is still under debate. In this work, we perform a three-dimensional ray-tracing simulation for the propagation of fast magnetoacoustic waves. We build a stratified solar atmosphere model and take partial ionization into consideration to give an exact description of chromosphere and transition region. The calculated result is compared with a flare event observation in which both Moreton waves and EIT waves were present. In agreement with observations, the calculated wavefront show different kinematical characteristics in different propagation directions during different times.Moreton waves and EIT waves have higher propagation speeds near the active region where the magnetic field strength is strong. The result suggests that both Moreton waves and EIT waves of this event can be interpreted as the fast magnetoacoustic waves propagating at different heights in the solar atmosphere.展开更多
基金Supported by The Gastroenterological Association of Thailand: grant for Gastroenterology Fellow 2007
文摘AIM： To evaluate the efficacy of non-sequential narrow band imaging （NBI） for a better recognition of gastric intestinal metaplasia （GIM）. METHODS： Previously diagnosed GIM patients underwent targeted biopsy from areas with and without GIM, as indicated by NBI, twice at an interval of 1 year. The authors compared the endoscopic criteria such as light blue crest （LBC）, villous pattern （VP）, and large long crest （LLC） with standard histology. The results from two surveillance endoscopies were compared with histology results for sensitivity, specificity, positive predic-tive value （PPV）, negative predictive value （NPV）, and likelihood ratio of positive test （LR＋）. The number of early gastric cancer cases detected was also reported. RESULTS： NBI targeted biopsy was performed in 38 and 26 patients during the first and second surveillance endoscopies, respectively. There were 2 early gastric cancers detected in the first endoscopy. No cancer was detected from the second study. Surgical and endoscopic resections were successfully performed in each patient. Sensitivity, specificity, PPV, NPV, and LR＋ of all 3 endoscopic criteria during the first/second surveillances were 78.8%/91.3%, 82.5%/89.1%, 72.8%/77.8%, 86.8%/96.1, and 4.51/8.4, respectively. LBC provided the highest LR＋ over VP and LLC. CONCLUSION： Nonequential NBI is useful for GIM targeted biopsy. LBC provides the most sensitive reading. However, the optimal duration between two surveillances requires further study.
基金Supported by the Basic Scientific Research Project of Wenzhou (No.2020Y0599)。
文摘AIM:To evaluate the accuracy and predictability of ray tracing-assisted intraocular lens(IOL) calculation function in Sirius internal software and further improve the accuracy by optimizing the calculation of predicted lens position(PLP).METHODS:This retrospective study recruited 52 eyes of 49 patients.All of the cases with cataract had undergone phacoemulsification combined with IOL implantation.SRK-T,Haigis formula,and Sirius ray-tracing method were all used for each eye’s IOL calculation.The mean absolute value of prediction error(prediction error=predicted refraction-postoperative refraction) was defined as mean absolute prediction error(MAPE) and was determined for each method.Calculation of PLP was optimized by effective lens position(ELP).Optimized PLP was entered to Sirius internal software again to verify whether the method was improved.RESULTS:Compared with SRK-T and Haigis formulas,less accuracy was shown in Sirius ray-tracing method(P=0.001).The ELP of the IOL moved forward compared to PLP(P<0.001).The MAPE of the ELP-inputted Sirius ray-tracing method was reduced.ELP and PLP were well correlated.Taking ELP as y and PLP given by Sirius soft as x,a linear regression formula y=0.1637 x+3.1741 was concluded(R^(2)=0.1066,P=0.018).It was shown that the optimized Sirius ray-tracing method(optimized PLP entered),compared with SRK-T and Haigis formulas,worked with the same accuracy(P=0.038).CONCLUSION:The original Sirius ray tracing method is not satisfactory enough.However,in normal eyes,the optimized Sirius ray-tracing method in IOL calculation was as accurate as SRK-T and Haigis formulas.
文摘A new seismic ray-tracing method is put forward based on parabolic travel-time interpolation(PTI) method, which is more accurate than the linear travel-time interpolation (LTI) method. Both PTI method and LTI method are used to compute seismic travel-time and ray-path in a 2-D grid cell model. Firstly, some basic concepts are introduced. The calculations of travel-time and ray-path are carried out only at cell boundaries. So, the ray-path is always straight in the same cells with uniform velocity. Two steps are applied in PTI and LTI method, step 1 computes travel-time and step 2 traces ray-path. Then, the derivation of LTI formulas is described. Because of the presence of refraction wave in shot cell, the formula aiming at shot cell is also derived. Finally, PTI method is presented. The calculation of PTI method is more complex than that of LTI method, but the error is limited. The results of numerical model show that PTI method can trace ray-path more accurately and efficiently than LTI method does.
基金Project(40674071) supported by the National Natural Science Foundation of ChinaProject(KFAS2002-2003) supported by the Korea Foundation for Advanced Studies
文摘Beginning with the method of whole path iterative ray-tracing and according to the positive definiteness of the coefficient matrix of the systems of linear equations, a symmetry olock tridiagonal matrix was decomposed into the product of block bidiagonal triangular matrix and its transpose by means of Cholesky decomposition. Then an algorithm for solving systems of block bidiagonal triangular linear equations was given, which is not necessary to treat with the zero elements out of banded systems. A fast algorithm for solving the systems of symmetry block tridiagonal linear equations was deduced, which can quicken the speed of ray-tracing. Finally, the simulation based on this algorithm for ray-tracing in three dimensional media was carried out. Meanwhile, the segmentally-iterative ray-tracing method and banded method for solving the systems of block tridiagonal linear equations were compared in the same model mentioned above. The convergence condition was assumed that the L-2 norm summation for mk, 1 and mk. 2 in the whole ray path was limited in 10-6. And the calculating speeds of these methods were compared. The results show that the calculating speed of this algorithm is faster than that of conventional method and the calculated results are accurate enough. In addition, its precision can be controlled according to the requirement of ray-tracing.
基金partly supported by the National Natural Science Foundation of China (Grant Nos. 12034008,12250003, and 11727810)the Program of Introducing Talents of Discipline to Universities 111 Project (B12024)。
文摘Electron dynamics during non-sequential double ionization(NSDI) is one of the most attractive areas of research in the field of laser–atom or laser–molecule interaction. Based on the classic two-dimensional model, we study the process of NSDI of argon atoms driven by a few-cycle orthogonal two-color laser field composed of 800 nm and 400 nm laser pulses. By changing the relative phase of the two laser pulses, a localized enhancement of NSDI yield is observed at 0.5πand 1.5π, which could be attributed to a rapid and substantial increase in the number of electrons returning to the parent ion within extremely short time intervals at these specific phases. Through the analysis of the electron–electron momentum correlations within different time windows of NSDI events and the angular distributions of emitted electrons in different channels, we observe a more pronounced electron–electron correlation phenomenon in the recollision-induced ionization(RII) channel. This is attributed to the shorter delay time in the RII channel.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11074026 and 11074155)the Program for New Century Excellent Talents in University of the Ministry of Education of China (Grant No. NCET-08-0883)
文摘The effect of initial longitudinal velocity of the tunnelled electron on the non-sequential double ionization （NSDI） process in an elliptically polarized laser field is studied by a semiclassical model. We find that the non-zero initial longitudinal velocity has a suppressing effect on single-return collision （SRC） events in the double ionization process, more specifically, it results in an obvious reduction in the center part of the correlation momentum distributions in the direction of the major polarization axis （z axis） and makes the distribution of single-return collision in the minor polarization axis （x axis） become narrower.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11574117 and11604131)
文摘By using a two-dimensional Monte-Carlo classical ensemble method, we investigate the double ionization（DI） process of the CS_2 molecule with different bond lengths in an 800-nm intense laser field. The double ionization probability presents a ＂knee＂ structure with equilibrium internuclear distance R = 2.9245 a.u.（a.u. is short for atomic unit）. As the bond length of CS increases, the DI probability is enhanced and the ＂knee＂ structure becomes less obvious. In addition,the momentum distribution of double ionized electrons is also investigated, which shows the momentum mostly distributed in the first and third quadrants with equilibrium internuclear distance R = 2.9245 a.u. As the bond length of CS increases,the electron momentum becomes evenly distributed in the four quadrants. Furthermore, the energy distributions and the corresponding trajectories of the double-ionized electrons versus time are also demonstrated, which show that the bond length of CS in the CS_2 molecule plays a key role in the DI process.
基金supported by the Natural Science Foundation of Shandong Province under Grant ZR2024MF062the open research fund of National Mobile Communications Research Laboratory,Southeast University under Grants 2025D03+1 种基金the Future Plan Program for Young Scholars of Shandong University,and the Innovation and Technology Support Program for Young Scholars of Colleges and Universities in Shandong Province under Grant 2022KJ009The B6G R&D Group in Shandong University is greatly thanked for channel measurements.
文摘The smart meter communication system has substantial application value for the construction and upgrading of the entire power system.The deployment of the transmitter(Tx)of the smart meter system in the residential scenarios is vexed by the need for more theoretical support.This paper mainly studies the communication channel between the Tx at semibasement and receiver(Rx)at outdoor.The design of an effective communication system relies on an accurate understanding of channel characteristics.Channel measurements and ray-tracing channel modeling are conducted to obtain channel data.The influence of different positions at same semi-basement is studied.Typical channel characteristics are analyzed,such as power delay profile(PDP),power angular profile(PAP),root-mean-square(RMS)delay spread(DS),channel capacity,received power,and path loss.The influence of different semi-basement placements and different floor heights is also compared.Besides,the channel measurements and simulation data fit well,which can illustrate the validity and reliability of the acquired channel data.This paper can provide theoretical support for the design and optimization of smart meter communication systems in semi-basement scenarios.
基金supported by the National Natural Science Foundation of China(Grant Nos.32201654 and U22A20464)National Key Research and Development Program from the Ministry of Science and Technology of China(Grant No.2020YFA0907600)the 2115 Talent Development Program of China Agricultural University.
文摘Canopy photosynthesis,rather than leaf photosynthesis,is highly related to plant biomass and yield formation.Studying canopy photosynthesis and identifying the parameters that control it can help optimize agricultural management and achieve crop yield potential.Compared with traditional parameters,canopy occupation volume(COV)offers an integrative parameter on canopy architecture related to canopy photosynthetic rates.In this study,we developed a high-throughput method to derive COV for different rice varieties.We first used multi-perspective two-dimensional imaging to reconstruct three-dimensional point clouds of rice plants and developed a suite of pipelines to calculate plant height,leaf number,tiller number,and biomass,with R^(2) values of 91.8%,95.9%,82.3%,and 94.3%,respectively.We further employed point cloud data to reconstruct the surfaces of rice plants and construct a virtual canopy model of the rice population.Light distribution was simulated using a ray-tracing algorithm and canopy photosynthetic rates were simulated via photosynthetic rate-incident light intensity curve fitting.Furthermore,we systematically explored the relationships between canopy phenotypes and photosynthetic rates,and found that COV was the most effective predictor of canopy photosynthesis,achieving an R^(2) value of 92.1%.Adjustment in atmospheric transmittance showed that COV strongly correlated with canopy photosynthesis under different light conditions,with higher accuracy observed under diffuse light.Variations in planting density confirmed that this correlation remained strong at the community level.In summary,this study demonstrates that COV is closely linked to simulated canopy photosynthesis and the developed pipeline can support future agronomic and breeding research.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFF0711402)the Specialized Research Fund for State Key Laboratories。
文摘Using a recognition model of atmospheric gravity waves(AGWs),we identified 519 AGW events from the OH airglow images observed at the Dandong and Lhasa stations from 2015 to 2017.The 317 AGW events detected at the Dandong station have wavelengths ranging from 30 to 60 km,periods from 14 to 20 min,horizontal speeds from 30 to 60 m/s,and relative intensities from 0.4%to 0.6%,respectively.The parameters of 202 events recorded at the Lhasa station mainly vary within 15-35 km in horizontal wavelength,4-6 min in period,40-100 m/s in horizontal velocity,and 0.1%-0.3%in relative intensity.The occurrence rate peaks in winter and summer at Dandong and the peak in summer are absent at Lhasa because of the lack of convective weather.The seasonal propagation directions of the waves are influenced by both the wind field-filtering effect and the distribution of wave sources.In spring,because of the southeastward background wind field,fewer southeastward events are observed at the Dandong station.The situation at the Lhasa station is similar.In summer,both the Lhasa and Dandong stations are dominated by northeastward AGWs,which can be attributed to the southwestward wind.In autumn,ray-tracing results show that the events at Dandong mainly originate from wind shear,whereas the events at the Lhasa station are triggered by convective weather.The location of the wave sources determines the trend of the propagation directions at the Dandong and Lhasa stations in autumn.In winter,because of the eastward wind,more events are propagating to the southwest at the Dandong station.
基金supported by the National Natural Science Foundation of China under Grant No.62271043Ministry of Education of China under Grant No.8091B032123Beijing Natural Science Foundation under Grant No.L212029。
文摘Radar cross section(RCS)plays a critical role in modeling target scattering characteristics and enhancing the precision of target detection and localization in integrated sensing and communication(ISAC)systems.This paper investigates the human body RCS at 26 GHz via multiangle channel measurements under different clothing conditions.Based on calibrated electromagnetic(EM)parameters,the RCS characteristics of the human body in far-field conditions are analyzed using ray-tracing(RT)simulations.Some suggestions for the design of ISAC systems are also discussed.The results provide a solid theoretical foundation and practical reference for the modeling of target scattering characteristics for ISAC channels.
基金supported by the National Natural Science Foundation of China(Grant Nos.42422406,42174185,42474209)the Science and Technology Development Fund,Macao SAR(Grant Nos.0042/2024/RIA1,0176/2023/RIA3,0008/2024/AKP and 002/2024/SKL)the Guangdong Basic and Applied Basic Research Foundation(Grant No.2024A1515012093)。
文摘Lightning-generated whistler(LGW)is an important electromagnetic wave in the magnetosphere,causing energetic electron losses.Here we analyze the LGW distribution and propagation using Van Allen Probes data and ray-tracing simulation.The statistics show that LGW occurs more frequently at L<2.5 with higher amplitudes in the northern hemisphere.The Poynting flux demonstrates that LGW originates from both hemispheres within L~2.5,and propagates into the space as the wave power decays.The wave normal angle distributions indicate that LGW propagates quasi-parallel to the field line near its source and becomes oblique as the magnetic latitude decreases.Furthermore,we use the ray-tracing model to simulate the LGW propagation,and statistically analyze the propagation characteristics of LGW,which are consistent with the observational data.This paper presents the latitudinal distribution and propagation properties of LGW based on statistics for the first time,providing new insights into the LGW generation and evolution in the magnetosphere.
文摘Narrow-band imaging （NBI） is an innovative optical technology that modifies the center wavelength and bandwidth of an endoscope＇s light into narrow-band illumination of 415 ：1： 30 nm. NBI markedly improves capillary pattern contrast and is an in vivo method for visualizing microvessel morphological changes in superficial neoplastic lesions. The scientific basis for NBI is that short wavelength light falls within the hemoglobin absorption band, thereby facilitating clearer visualization of vascular structures. Several studies have reported advantages and limitations of NBI colonoscopy in the colorectum. One difficulty in evaluating results, however, has been nonstandardization of NBI systems （Sequential and nonsequential）. Utilization of NBI technology has been increasing worldwide, but accurate pit pattern analysis and sufficient skill in magnifying colonoscopy are basic fundamentals required for proficiency in NBI diagnosis of colorectal lesions. Modern optical technology without proper image interpretation wastes resources, confuses untrained endoscopists and delays interinstitutional validation studies. Training in the principles of ＂optical image-enhanced endoscopy＂ is needed to close the gap between technological advancements and their clinical usefulness. Currently available evidence indicates that NBI constitutes an effective and reliable alternative to chromocolonoscopy for in vivo visualization of vascular structures, but further study assessing reproducibility and effectiveness in the colorectum is ongoing at various medical centers.
文摘A three-dimensional laser absorption model based on ray tracing was established to describe the coupled interaction of a laser beam with particles in the powder layers of pure tungsten(W)material processed by selective laser melting(SLM).The influence of particle size on the powder-to-laser absorptivity and underlying absorption behavior was investigated.An intrinsic relationship between the absorption,distribution of absorbed irradiance within the powder layers,and surface morphology and geometric characteristics(e.g.,contact angle,width and height of tracks,and remelted depth)of the laser scanning tracks is presented here.Simulation conclusions indicate that the absorptivity of the powder layers considerably exceeds the single powder particle value or the dense solid material value.With an increase in particle size,the powder layer absorbs less laser energy.The maximum absorptivity of theWpowder layers reached 0.6030 at the particle size of 5 lm.The distribution of laser irradiance on the particle surface was sensitive to particle size,azimuthal angle,and the position of the powder particles on the substrate.The maximum irradiance in the powder layers decreased from 1.117×10^–3 to 0.85×10^–3W·μm^-2 and the contour of the irradiance distribution in the center of the irradiated area gradually contracted when the particle size increased from 5 to 45 lm.An experimental study on the surface morphologies and cross-sectional geometric characteristics of SLM-fabricated W material was performed,and the experimental results validated the mechanisms of the powder-to-laser-absorption behavior that were obtained in simulations.This work provides a scientific basis for the application of the ray-tracing model to predict the wetting and spreading ability of melted tracks during SLM additive manufacturing in order to yield a sound laser processability.
基金This work was supported in part by the Ministry National Key Research and Development Project(Grant No.2020AAA0108101)the National Natural Science Foundation of China(Grants No.62125101,62341101,62001018,and 62301011)+1 种基金Shandong Natural Science Foundation(Grant No.ZR2023YQ058)the New Cornerstone Science Foundation through the XPLORER PRIZE.The authors would like to thank Mengyuan Lu and Zengrui Han for their help in the construction of electromagnetic space in Wireless InSite simulation platform and Weibo Wen,Qi Duan,and Yong Yu for their help in the construction of phys ical space in AirSim simulation platform.
文摘The sixth generation(6G)of mobile communication system is witnessing a new paradigm shift,i.e.,integrated sensing-communication system.A comprehensive dataset is a prerequisite for 6G integrated sensing-communication research.This paper develops a novel simulation dataset,named M3SC,for mixed multi-modal(MMM)sensing-communication integration,and the generation framework of the M3SC dataset is further given.To obtain multimodal sensory data in physical space and communication data in electromagnetic space,we utilize Air-Sim and WaveFarer to collect multi-modal sensory data and exploit Wireless InSite to collect communication data.Furthermore,the in-depth integration and precise alignment of AirSim,WaveFarer,andWireless InSite are achieved.The M3SC dataset covers various weather conditions,multiplex frequency bands,and different times of the day.Currently,the M3SC dataset contains 1500 snapshots,including 80 RGB images,160 depth maps,80 LiDAR point clouds,256 sets of mmWave waveforms with 8 radar point clouds,and 72 channel impulse response(CIR)matrices per snapshot,thus totaling 120,000 RGB images,240,000 depth maps,120,000 LiDAR point clouds,384,000 sets of mmWave waveforms with 12,000 radar point clouds,and 108,000 CIR matrices.The data processing result presents the multi-modal sensory information and communication channel statistical properties.Finally,the MMM sensing-communication application,which can be supported by the M3SC dataset,is discussed.
基金supported by National Science Fund for Distinguished Young Scholars (No.61925102)Beijing University of Posts and TelecommunicationsChina Mobile Research Institute Joint Innovation Center。
文摘With the research of the upcoming sixth generation(6 G) systems, new technologies will require wider bandwidth, larger scale antenna arrays and more diverse wireless communication scenarios on the future channel modeling. Considering channel model is prerequisite for system design and performance evaluation of 6 G technologies, we face a challenging task: how to accurately and efficiently model 6 G channel for various scenarios? This paper tries to answer it. Firstly, the features of cluster-nuclei(CN) and principle of cluster-nuclei based channel model(CNCM) are introduced. Then, a novel modeling framework is proposed to implement CNCM,which consists four steps: propagation environment reconstruction, cluster-nuclei identification, multipath parameters generation, and channel coefficients generation. Three-dimensional environment with material information is utilized to map CN with scatterers in the propagation pathway. CN are identified by geometrical and electric field calculation based on environmental mapping, and multipath components within CN are calculated by statistical characteristics of angle, power and delay domains. Finally, we present a three-level verification structure to investigate the accuracy and complexity of channel modeling comprehensively. Simulation results reveal that CNCM can perform higher accuracy than geometrybased stochastic model while lower complexity compared with ray-tracing model for practical propagation environment.
文摘To establish a theoretical basis for providing a better design method of multielement optical systems, we have developed a third-order geometric theory of a plane-symmetric multielement optical system that consists of a planar light source, an arbitrary number of ellipsoidal gratings, and an image plane. Analytic formulas of spot diagrams are derived for the system by analytically following a ray-tracing formalism. With these formulas, coma, spherical aberration, and resultant aberration are discussed. To make the theory practical, we determine the aberration coefficients numerically, rather than analytically, with the aid of ray tracing that takes into account the angular distribution of rays originating from a given light source. A merit function is defined so as to represent closely the variance of the spots formed when an infinite number of rays are traced and to take into account the dimensions of the source and the last optical element. The theory is also applicable to mirror-grating or mirror systems.
基金supported by the National Basic Research Program of China (973 Program) under Grant No. 2010CB428601the Open Fund of the State Key Laboratory of Satellite Ocean Environment Dynamics under Contract No. SOED0705the China Postdoctoral Science Foundation
文摘In the present reported study, the vertical distributions of local atmospheric refractivity were retrieved from ground- based GPS observations at low elevation angles. An improved optimization method was implemented at altitudes of 0-10 km to search for a best-fit refractivity profile that resulted in atmospheric delays most similar to the delays calculated from the observations. A ray-tracing model was used to simulate neutral atmospheric delays corresponding to a given refractivity profile. We initially performed a ＂theoretical retrieval＂, in which no observation data were involved, to verify the optimization method. A statistical relative error of this ＂theoretical retrieval＂ （-2% to 2%） indicated that such a retrieval is effective. In a practical retrieval, observations were obtained using a dual-frequency GPS receiver, and its initial value was provided by CIRA86aQ_UoG data. The statistical relative errors of the practical retrieval range from -3% to 5% were compared with co-located radiosonde measurements, Results clearly revealed diurnal variations in local refractivity prc,files, The results also suggest that the general vertical distribution of refractivity can be derived with a high temporal resolution. However, further study is needed to describe the vertical refractivity gradient clearly.
文摘This article describes the task of optical designers to achieve a better design. This is followed by some discussions on the necessity of total design that takes all the elements into account from its light source to the final image plane. Methods are given to simulate rays from a bending magnet and an undulator, surface figure errors, and thermal deformations. Some examples are given for an undulator beamline and an EUVL optical system, together with tolerance estimates of the figure error and thermal deformation.
基金the National Natural Science Foundation of China(Grant Nos.41274174,41422405,41274169&41421063)the Fundamental Research Funds for the Central Universities(Grant No.WK2080000077)
文摘In the solar atmosphere, there exist two frequently-observed phenomena, Moreton waves and EIT(extreme-ultraviolet imaging telescope) waves, whose physical nature is still under debate. In this work, we perform a three-dimensional ray-tracing simulation for the propagation of fast magnetoacoustic waves. We build a stratified solar atmosphere model and take partial ionization into consideration to give an exact description of chromosphere and transition region. The calculated result is compared with a flare event observation in which both Moreton waves and EIT waves were present. In agreement with observations, the calculated wavefront show different kinematical characteristics in different propagation directions during different times.Moreton waves and EIT waves have higher propagation speeds near the active region where the magnetic field strength is strong. The result suggests that both Moreton waves and EIT waves of this event can be interpreted as the fast magnetoacoustic waves propagating at different heights in the solar atmosphere.
