Comparison of visual effects of FS-LASIK for myopia centered on the coaxially sighted corneal light reflex or the line of sight

AIM：To compare visual quality after femtosecond laser in situ keratomileusis（FS-LASIK）,between the coaxially sighted corneal light reflex（CSCLR） group and conventional ablation line of sight（LOS） group.METHODS：In total,243 eyes（122 patients） were treated with centration on the CSCLR（visual axis） and 238 eyes（119 patients） treated with centration on the pupil center（LOS）.Postoperative outcomes [uncorrected visual acuity（UCVA）,best spectacle-corrected visual acuity（BSCVA）],safety index,efficacy index,refractive outcome,ablation center distance from the visual axis,corneal high-order aberrations,subjective discomfort glare and shadowing incidence rate,and contrast sensitivity at 1,3,and 6mo were measured and compared.RESULTS：The mean age was 27.77±7.1y in the CSCLR group and 26.03±7.70 y in the LOS group.Preoperatively,the manifest refraction spherical equivalent（MRSE） was-6.68±2.60 D in the CSCLR group and-6.65±2.68 D in the LOS group.The postoperative UCVA,BSCVA,MRSE（-0.03±0.263 D in the CSCLR group,-0.05±0.265 D in the LOS group）,efficacy index（1.04,1.03）,and safety index（1.09,1.08） were not significantly different between the groups（all P〉0.05）.In total,3% lost one line and more of BSCVA in the CSCLR group,as 9% in the LOS group postoperatively（P〈0.05）.The ablation center deviation was 0.20±0.15 mm from the visual axis（Pentacam system default setting;range,0-0.75 mm） in the CSCLR group,and 0.43±0.22 mm（range,0-1.32 mm） in the LOS group（P〈0.0001）.Statistically significant greater augmentationof total corneal higher-order aberrations（0.15±0.10 μm and 0.20±0.12 μm respectively,P=0.03） and vertical and horizontal coma（P〈0.0001） were noted in the LOS group.Subjective discomfort glare and shadowing incidence rates were 8.59% and 17.5% in the CSCLR and LOS groups,respectively（P〈0.05）.The 1-month postoperative contrast sensitivity visual acuity in the CSCLR group was significantly higher than that in the LOS group on contrast（100%,25%,10%） with a dark background,but there was no significant difference between the groups at 3 or 6m.CONCLUSION：Myopic LASIK centered on the CSCLR achieves significantly lower induction of loss of BSCVA,corneal high-order aberrations,and lower risk of subjective discomfort glare and shadowing,and lower decline in early contrast sensitivity by comparison with centration on the LOS,giving advantages in visual quality postoperatively.

Netro-非视距(Non Line Of Sight)固定无线架构的灵活性

成功地部署一个固定宽带无线(FBW)网络取决于两个关键因素：射频网络规划的灵活性和视距(LOS)／非视距(NLOS)情况。因为在视距(LOS)情况下要求在发射机和接收器之间没有阻挡，运营商在规划和部署一个视距(LOS)的固定宽带无线(FBW)网络时，需面对许多技术和业务上的困难；事实上第……

Efficiency Effect of Obstacle Margin on Line-of-Sight in Wireless Networks

Line-of-sight clarity and assurance are essential because they are considered the golden rule in wireless network planning,allowing the direct propagation path to connect the transmitter and receiver and retain the strength of the signal to be received.Despite the increasing literature on the line of sight with different scenarios,no comprehensive study focuses on the multiplicity of parameters and basic concepts that must be taken into account when studying such a topic as it affects the results and their accuracy.Therefore,this research aims to find limited values that ensure that the signal reaches the future efficiently and enhances the accuracy of these values’results.We have designed MATLAB simulation and programming programs by Visual Basic.NET for a semi-realistic communication system.It includes all the basic parameters of this system,taking into account the environment’s diversity and the characteristics of the obstacle between the transmitting station and the receiving station.Then we verified the correctness of the system’s work.Moreover,we begin by analyzing and studying multiple and branching cases to achieve the goal.We get several values from the results,which are finite values,which are a useful reference for engineers and designers of wireless networks.

An Optimization Approach of IoD Deployment for Optimal Coverage Based on Radio Frequency Model

Recently,Internet of Drones(IoD)has garnered significant attention due to its widespread applications.However,deploying IoD for area coverage poses numerous limitations and challenges.These include interference between neighboring drones,the need for directional antennas,and altitude restrictions for drones.These challenges necessitate the development of efficient solutions.This research paper presents a cooperative decision-making approach for an efficient IoDdeployment to address these challenges effectively.The primary objective of this study is to achieve an efficient IoDdeployment strategy thatmaximizes the coverage regionwhile minimizing interference between neighboring drones.In deployment problem,the interference increases as the number of deployed drones increases,resulting in bad quality of communication.On the other hand,deploying a few drones cannot satisfy the coverage demand.To accomplish this,an enhanced version of a concise population-based meta-heuristic algorithm,namely Improved Particle SwarmOptimization(IPSO),is applied.The objective function of IPSO is defined based on the coverage probability,which is primarily influenced by the characteristics of the antennas and drone altitude.A radio frequency(RF)model is derived to evaluate the coverage quality,considering both Line of Sight(LOS)and Non-Line of Sight(NLOS)down-link coverage probabilities for ground communication.It is assumed that each drone is equipped with a directional antenna to optimize coverage in a given region.Extensive simulations are conducted to assess the effectiveness of the proposed approach.Results demonstrate that the proposed method achieves maximum coverage with minimum transmission power.Furthermore,a comparison is made against Collaborative Visual Area Coverage Approach(CVACA),and a game-based approach in terms of coverage quality and convergence speed.The simulation results reveal that our approach outperforms both CVACA and the gamebased schemes in terms of coverage and convergence speed.Comparisons validate the superiority of our approach over existing methods.To assess the robustness of the proposed RFmodel,we have considered two distinct ranges of noise:range1 spanning from−120 to−90 dBm,and range2 spanning from−90 to−70 dBmfor different numbers of UAVs.In summary,this research presents a cooperative decision-making approach for efficient IoD deployment to address the challenges associatedwith area coverage and achieves an optimal coveragewithminimal interference.

Line-of-Sight MIMO for Next-Generation Microwave Transmission Systems

Line-of-sight MIMQ （LoS MIMO） is not applicable in scattering wireless transmission scenarios, but it may be applied in LoS microwave transmission scenarios if antenna spacing （within transmit and/or receive arrays） is suitable and there is one hop distance. LoS MIMQ can improve channel capacity and performance of a transmission system. In this paper, we discuss factors affecting channel capacity and performance in LoS MIMO. We also discuss the feasibility LoS MIMO applications.

Outage Probability Analysis of Free Space Communication System Using Diversity Combining Techniques

Recently,free space optical(FSO)communication is gaining much attention towards the research community.The reason for this attention is the promises of high data-rate,license-free deployment,and non-interfering links.It can,however,give rise to major system difficulties concerning alignment and atmospheric turbulence.FSO is the degradation in the signal quality because of atmospheric channel impairments and conditions.The worst effect is due to fog particles.Though,Radio Frequency(RF)links are able to transmit the data in foggy conditions but not in rain.To overcome these issues related to both the FSO and RF links.A free space communication system(FSCS)is proposed,in which the hybrid technology is based on the individual FSO and RF channel.FSCS is a capable solution to overcome the difficulties of the existing systems(FSO and RF)as well as to enhance the overall link reliability and availability.In this paper,FSCS is investigated in terms of performance throughput(i.e.,outage probability and bit-error-rate(BER))by implementing the receive diversity combining techniques.An analysis of the outage probability of the proposed system along with the individual FSO and RF system is developed.Simulation results are presented to support the analysis.It is shown that the proposed system outperforms the individual FSO andRF system and gives a power gain of 3dB over a distinct number of receive antennas.

Codebook design for uplink of densely small cells

The shrinking of cell-size brings significant changes to the wireless uplink of densely small cells （DSCs）. A codebook design is proposed that utilizes the strong line of sight （LOS） chan- nel component existing in a DSC system for uplink of the DSC system. To further improve the uplink performance, the high-rank codebook is designed based on singular value decomposition （SVD） due to the unnecessary preservation of strict constant modulus in the DSC system. And according to the simulation result, the proposed codebook leads to significant sum-rate gain and appreciable block error rate （BLER） performance improvement in the DSC system.

Study of Wireless Sensor Network Based on Optical Communication:Research Challenges and Current Results

With the rapid developments of commercial demands,a majority of ad­vanced researches have been investigated for the applications of underwa­ter wireless sensor(WSN)networks.Recently optical communication has been considered for underwater wireless sensor network.An experimental set-up for testing optical communication underwater has been provided and designed in present papers to maximize the energy coupled from these displacements to the transduction mechanism that converts the mechanical energy into electrical.The true case has been considered by measuring dif­fuse attenuation coefficients in different seas.One stand out potential opti­cal communication method,Visible Light Communication(VLC)has been talked and several communication methods are compared from many points of view,for example attenuation in salt water.The evaluation of modula­tion techniques for underwater wireless optical communications has been displayed,and further how the data collection and storage with an under­water WSN is introduced.In this paper current researches for an(UWSN)based on optical communication are studied,in particular the potential VLC method and comparisons of VLC with other optical communication approaches.Underwater challenges would be analyzed by comparing a sort of communication methods,applied in underwater.Future work will be de­veloped at last.

Spatial sight analysis of Hangzhou Xiaoyingzhou based on tourists’landscape preference

Tourist preferences are important for the high-quality planning and design of recreation spaces.The famous scenic locale of West Lake in Hangzhou,China,is used as an example in this study.Based on multi-source data(e.g.,online comments,and tourist photographs),we used content analysis,kernel density estimation,and image semantic segmentation technology to determine the spatial distribution of tourists’landscape preferences.We analyzed these spatial sight characteristics from the viewpoint,sight distance,and perspectives.The results show that tourists’landscape preferences are mainly concentrated on landscape architecture for recreation.The viewpoints of these preferences are concentrated in the north-south embankmentdfar beyond that of the east-west embankment.The preferences also show a spatial sequence in terms of sight distance,and the best visual effect is the open platform at the north and south islands of Xiaoyingzhou.From the perspective of vision,the degree of spatial openness in the tourists’landscape preferences is proportional to the distance of vision;the two factors have a convergent relationship.The discussion of the characteristics of tourists’landscape preference and space sight creation in Xiaoyingzhou provides a reference for the quality improvement of island recreation space.

A novel estimation algorithm for torpedo tracking in undersea environment

A novel estimation algorithm is introduced to handle the popular undersea problem called torpedo tracking with angle-only measurements with a better approach compared to the existing filters. The new algorithm produces a better estimate from the outputs produced by the traditional nonlinear approaches with the assistance of simple noise minimizers like maximum likelihood filter or any other algorithm which belongs to their family. The introduced method is extended to the higher version in two ways. The first approach extracts a better estimate and covariance by enhancing the count of the intermediate filters, while the second approach accepts more inputs so as to attain improved performance without enhancement of the intermediate filter count. The ideal choice of the placement of towed array sensors to improve the performance of the proposed method further is suggested as the one where the line of sight and the towed array are perpendicular. The results could get even better by moving the ownship in the direction of reducing range. All the results are verified in the MATLAB environment.

LoS sensing-based superimposed CSI feedback for UAV-assisted mmWave systems

In Unmanned Aerial Vehicle(UAV)-assisted millimeter Wave(mmWave)systems,Channel State Information(CSI)feedback is critical for the selection of modulation schemes,resource management,beamforming,etc.However,traditional CSI feedback methods lead to significant feedback overhead and energy consumption of the UAV transmitter,therefore shortening the system operation time.To tackle these issues,inspired by superimposed feedback and Integrated Sensing and Communications(ISAC),a Line of Sight(LoS)sensing-based superimposed CSI feedback scheme is proposed.Specifically,on the UAV transmitter side,the Ground-to-UAV(G2U)CSI is superimposed on the UAV-to-Ground(U2G)data to feed back to the ground Base Station(gBS).At the gBS,the dedicated LoS Sensing Network(LoS-SenNet)is designed to sense the U2G CSI in LoS and NLoS scenarios.With the sensed result of LoS-SenNet,the determined G2U CSI from the initial feature extraction will work as the priori information to guide the subsequent operation.Specifically,for the G2U CSI in NLoS,a CSI Recovery Network(CSI-RecNet)and superimposed interference cancellation are developed to recover the G2U CSI and U2G data.As for the LoS scenario,a dedicated LoS Aid Network(LoS-Aid Net)is embedded before the CSI-RecNet and the block of superimposed interference cancellation to highlight the feature of the G2U CSI.Compared with other methods of superimposed CSI feedback,simulation results demonstrate that the proposed feedback scheme effectively improves the recovery accuracy of the G2U CSI and U2G data.Besides,against parameter variations,the proposed feedback scheme presents its robustness.

Centration axis in refractive surgery

The human eye is an asymmetric optical system and the real cornea is not a rotationally symmetrical volume.Each optical element in the eye has its own optical and neural axes.Defining the optimum center for laser ablation is difficult with many available approaches.We explain the various centration approaches(based on these reference axes)in refractive surgery and review their clinical outcomes.The line-of-sight(LOS)(the line joining the entrance pupil center with the fixation point)is often the recommended reference axis for representing wavefront aberrations of the whole eye(derived from the definition of chief ray in geometrical optics);however pupil centration can be unstable and change with the pupil size.The corneal vertex(CV)represents a stable preferable morphologic reference which is the best approximate for alignment to the visual axis.However,the corneal light reflex can be considered as non-constant,but dependent on the direction of gaze of the eye with respect to the light source.A compromise between the pupil and CV centered ablations is seen in the form of an asymmetric offset where the manifest refraction is referenced to the CV while the higher order aberrations are referenced to the pupil center.There is a need for a flexible choice of centration in excimer laser systems to design customized and non-customized treatments optimally.

Ideal proportional navigation for exoatmospheric interception

Ideal proportional navigation （IPN） is a natural choice for exoatmospheric interception for its mighty capture capability and ease of implementation. The closed-form solution of two- dimensional ideal proportional navigation was conducted in previous public literature, whereas the practical interception happens in the three-dimensional space. A novel set of relative dynamic equations is adopted in this paper, which is with the advantage of decoupling relative motion in the instantaneous rotation plane of the line of sight from the rotation of this plane. The dimension-reduced IPN is constructed in this instantaneous plane, which functions as a three-dimensional guidance law. The trajectory features of dimension-reduced IPN are explored, and the capture regions of dimension-reduced IPN with limited acceleration against nonmaneuvering and maneuvering targets are analyzed by using phase plane method. It is proved that the capture capability of IPN is much stronger than true proportional navigation （TPN）, no matter the target maneuvers or not. Finally, simulation results indicate that IPN is more effective than TPN in exoatmospheric interception scenarios.