LASEK和TransPRK及FS-LASIK术后角膜屈光力及视觉质量比较

目的:比较准分子激光上皮下角膜磨镶术(LASEK)、经上皮准分子激光角膜切削术(TransPRK)、飞秒激光制瓣的准分子激光原位角膜磨镶术(FS-LASIK)三种角膜屈光手术术后角膜屈光力及视觉质量。方法:回顾性研究。选取2021-01/2022-12在我院择期行角膜屈光手术的232例464眼患者作为研究对象,根据患者选择手术方式不同分为LASEK组70例140眼、TransPRK组76例152眼、FS-LASIK组86例172眼。比较三组患者术前,术后1、3 mo时裸眼视力(UCVA)、视觉质量、生物力学稳定性、泪膜破裂时间(BUT)、泪液分泌试验(SⅠt)及生活质量变化情况。结果:术后1、3 mo三组患者裸眼视力较术前均改善,全角膜总高阶像差、球差、水平彗差、垂直彗差均升高,生物学稳定性均降低(均P<0.05)。术后3 mo, TransPRK组、LASEK组生物学稳定性均高于FS-LASIK组(均P<0.05),TransPRK组生活质量评分较LASEK组及FS-LASIK组高(P<0.05)。手术前后三组患者BUT、SⅠt比较均无差异(均P>0.05)。结论:LASEK、TransPRK、FS-LASIK三种角膜屈光手术治疗屈光不正疗效确切,在改善裸眼视力和提高视觉质量方面结果相似,但TransPRK、LASEK较FS-LASIK具有更稳定的生物力学性能,且TransPRK组在改善患者生活质量方面具有更好的效果。

SMILE和WG-FS-LASIK治疗低度无散光近视患者术后早期视觉质量比较

目的比较飞秒激光小切口角膜基质内透镜取出术(SMILE)和波前像差引导的准分子激光原位角膜磨镶术(WG-FS-LASIK)治疗低度无散光近视患者术后的早期视觉质量。方法选择2022年3月至6月在广西壮族自治区人民医院视光中心行SMILE治疗的患者15例(30眼,SMILE组),行WG-FS-LASIK治疗的患者15例(30眼,WG-FS-LASIK组)。所有患者术前无散光且最佳矫正视力所需最低球镜度数均≤-3.00 D。于术前和术后1 d、1周、1个月测量视力、全眼像差(慧差、三叶草像差和球差)、客观散射指数(OSI)、调制传递函数截止频率(MTF_(cut-off))、斯特列尔比(SR)、可预测对比度视力(PVA)(包括PVA 100%、PVA 20%、PVA 9%)。比较两组观察指标测量结果。结果两组术后等效球镜、视力情况均较术前显著改善(P<0.05),但两组各时间点比较差异无统计学意义(P>0.05)。两组术后OSI、SR、PVA 9%均较术前显著改善(P<0.05)。WG-FS-LASIK组在术后1 d、1周、1个月的OSI水平均显著低于SMILE组(P<0.05)。在术后1个月,WG-FS-LASIK组PVA 9%显著高于SMILE组(P<0.05)。SMILE组和WG-FS-LASIK组术后慧差均呈先上升后下降的趋势,但WG-FS-LASIK组变化幅度更小,在术后1 d、1周、1个月,WG-FS-LASIK组慧差小于SMILE组,差异有统计学意义(P<0.05)。结论SMILE和WG-FS-LASIK均能提高低度无散光近视患者术后早期视觉质量,但WG-FS-LASIK早期视力恢复更好,且夜间视觉质量改善更优。

FS-LASIK Xtra治疗中高度近视患者术后2a的矫正效果

目的:评估FS-LASIK Xtra治疗中高度近视患者术后2 a的矫正效果及角膜形态的稳定性。方法:回顾性病例对照研究。纳入2019-08/2020-08在我院拟行屈光手术的中高度近视合并散光患者30例58眼,根据术前角膜地形图中圆锥角膜筛查相关指数行不同手术方式,分为FS-LASIK Xtra组15例29眼,FS-LASIK组15例29眼。术前,术后3 mo,1、2 a观察裸眼视力(UCVA)、最佳矫正视力(BCVA)、等效球镜度(SE)及Sirius三维角膜地形图仪测量的不同直径区域(3、5、7 mm)前后表面角膜曲率。结果:两组患者术后不同时间点UCVA均较术前明显提高(均P<0.01),两组间UCVA和SE比较均无差异(P>0.05)。术后2 a,FS-LASIK Xtra组25眼(86%),FS-LASIK组24眼(83%)残余散光为-0.25-0 D。两组实际矫正SE与预矫正SE均呈正相关(均P<0.05)。两组患者术后3 mo,1、2 a不同直径区域(3、5、7 mm)前后表面角膜曲率均较术前有差异(均P<0.05),术后1、2 a FS-LASIK Xtra组角膜直径3、5 mm后表面曲率均高于FS-LASIK组(P<0.05)。结论:FS-LASIK Xtra治疗中高度近视患者有良好的安全性、有效性及可预测性。

sub-500 fs宽度2μm光纤激光振荡器研究进展(特邀)

2μm波段超快激光持续时间短,峰值功率高,光谱范围宽,同时处在大气窗口,多种有机、无机气体分子的吸收峰和人眼安全波段,已广泛应用于生物医疗、激光雷达和非金属材料加工等领域。利用光纤锁模激光振荡器产生2μm波段超快激光是一种最直接简单的技术方法,具有结构紧凑、光束质量高和成本低等优点。然而,目前关于sub-500 fs的2μm波段的光纤激光振荡器却鲜有报道。基于传统孤子和色散管理孤子两种孤子锁模方式,全面介绍了目前2μm波段sub-500 fs光纤振荡器的研究进展,并总结了实现sub-500 fs脉宽2μm超快激光的关键技术。针对不同的应用领域的具体需求,对2μm超快激光光纤振荡器的未来发展进行展望。

Wedge-shaped HfO_(2) buffer layer-induced field-free spin-orbit torque switching of HfO_(2)/Pt/Co structure

Field-free spin-orbit torque(SOT)switching of perpendicular magnetization is essential for future spintronic devices.This study demonstrates the field-free switching of perpendicular magnetization in an HfO_(2)/Pt/Co/TaO_(x) structure,which is facilitated by a wedge-shaped HfO_(2)buffer layer.The field-free switching ratio varies with HfO_(2)thickness,reaching optimal performance at 25 nm.This phenomenon is attributed to the lateral anisotropy gradient of the Co layer,which is induced by the wedge-shaped HfO_(2)buffer layer.The thickness gradient of HfO_(2)along the wedge creates a corresponding lateral anisotropy gradient in the Co layer,correlating with the switching ratio.These findings indicate that field-free SOT switching can be achieved through designing buffer layer,offering a novel approach to innovating spin-orbit device.

连翘提取物FS-4体外诱导胃癌细胞SGC-7901凋亡作用的研究

为了探讨连翘提取物FS-4体外对胃癌细胞SGC-7901的促凋亡作用,试验采用MTT比色法观察了FS-4对胃癌细胞SGC-7901增殖的抑制情况,AO/EB双荧光染色法和透射电子显微镜观察了细胞凋亡的形态学变化,并通过流式细胞术测定细胞的凋亡率。结果表明:FS-4对胃癌细胞SGC-7901增殖的抑制作用具有剂量和时间依赖性,其36 h的半数抑制浓度(IC_(50))仅为3.23μg/mL;FS-4作用后细胞均出现典型的凋亡细胞形态;FS-4对细胞的诱导凋亡作用呈现明显的浓度依赖性。说明FS-4可抑制胃癌细胞SGC-7901的增殖并具有诱导其凋亡的作用。

Tunable Three-Wavelength Fiber Laser and Transient Switching between Three-Wavelength Soliton and Q-Switched Mode-Locked States

We report a passive mode-locked fiber laser that can realize single-wavelength tuning and multi-wavelength spacing tuning simultaneously.The tuning range is from 1528 nm–1560 nm,and up to three bands of soliton states can be output at the same time.These results are confirmed by a nonlinear Schrodinger equation model based on the split-step Fourier method.In addition,we reveal a way to transform the multi-wavelength soliton state into the Q-switched mode-locked state,which is period doubling.These results will promote the development of optical communication,optical sensing and multi-signal pulse emission.

Switching Frequency Improvement of a High Speed on/off Valve Based on Pre-excitation Control Algorithm

The high-speed on/off valve(HSV)serves as the fundamental component responsible for generating discrete fluids within digital hydraulic systems.As the switching frequency of the HSV increases,the properties of the generated discrete fluid approach those of continuous fluids.Therefore,a higher frequency response characteristic of HSV is the key to ensure the control accuracy of digital hydraulic systems.However,the current research mainly focuses on its dynamic performance,but neglect its FRC.This paper presents a theoretical analysis demonstrating that the FRC of the HSV can be enhanced by minimizing its switching time.The maximum switching frequency(MSF)is mainly determined by opening dynamic performance when HSV operates with low switching duty ratio(SDR),whereas the closing dynamic performance limits the MSF when HSV operates with high SDR.Building upon these findings,the pre-excitation control algorithm(PECA)is proposed to reduce the switching time of the HSV,and consequently enhance its FRC.Experimental results demonstrate that PECA shortens the opening delay time of HSV by 1.12 ms,the closing delay time by 2.54 ms,and the closing moving time by 0.47 ms in comparison to the existing advanced control algorithms.As a result,a larger MSF of 417 Hz and a wider controllable SDR range from 20%to 70%were achieved at a switching frequency of 250 Hz.Thus,the proposed PFCA in this paper has been verified as an effective and promising approach for enhancing the control performance of digital hydraulic systems.

Review of Three-phase Soft Switching Inverters and Challenges for Motor Drives

For electric vehicles (EVs),it is necessary to improve endurance mileage by improving the efficiency.There exists a trend towards increasing the system voltage and switching frequency,contributing to improve charging speed and power density.However,this trend poses significant challenges for high-voltage and high-frequency motor controllers,which are plagued by increased switching losses and pronounced switching oscillations as consequences of hard switching.The deployment of soft switching technology presents a viable solution to mitigate these issues.This paper reviews the applications of soft switching technologies for three-phase inverters and classifies them based on distinct characteristics.For each type of inverter,the advantages and disadvantages are evaluated.Then,the paper introduces the research progress and control methods of soft switching inverters (SSIs).Moreover,it presents a comparative analysis among the conventional hard switching inverters (HSIs),an active clamping resonant DC link inverter (ACRDCLI) and an auxiliary resonant commuted pole inverter (ARCPI).Finally,the problems and prospects of soft switching technology applied to motor controllers for EVs are put forward.

FS复合保温外模板系统与挤塑板薄抹灰系统耐久性研究

FS复合保温外模板系统和挤塑板外保温系统所用保温材料为相同的挤塑板,对FS复合保温外模板系统和挤塑板薄抹灰系统的耐候性试验参照现行国家和行业标准中耐候性试验方法进行研究,通过增加外保温系统耐候性试验中热雨循环和热冷循环的循环次数,同时设置系统耐候性中的热雨循环和热冷循环交替进行,更加符合现实生活中工程现场的实际工况。试验结果表明,随着增加外保温系统耐候性试验中热雨循环和热冷循环的循环次数,外保温系统的耐久性年限也随之增加,但二者并非线性关系。

Chalcogenide Ovonic Threshold Switching Selector

Today’s explosion of data urgently requires memory technologies capable of storing large volumes of data in shorter time frames,a feat unattain-able with Flash or DRAM.Intel Optane,commonly referred to as three-dimensional phase change memory,stands out as one of the most promising candidates.The Optane with cross-point architecture is constructed through layering a storage element and a selector known as the ovonic threshold switch(OTS).The OTS device,which employs chalcogenide film,has thereby gathered increased attention in recent years.In this paper,we begin by providing a brief introduction to the discovery process of the OTS phenomenon.Subsequently,we summarize the key elec-trical parameters of OTS devices and delve into recent explorations of OTS materials,which are categorized as Se-based,Te-based,and S-based material systems.Furthermore,we discuss various models for the OTS switching mechanism,including field-induced nucleation model,as well as several carrier injection models.Additionally,we review the progress and innovations in OTS mechanism research.Finally,we highlight the successful application of OTS devices in three-dimensional high-density memory and offer insights into their promising performance and extensive prospects in emerging applications,such as self-selecting memory and neuromorphic computing.

Resistive switching behavior and mechanism of HfO_(x) films with large on/off ratio by structure design

Different bilayer structures of HfO_(x)/Ti(TiO_(x)) are designed for hafnium-based memory to investigate the switching characteristics. The chemical states in the films and near the interface are characterized by x-ray photoelectron spectroscopy,and the oxygen vacancies are analyzed. Highly improved on/off ratio(~104) and much uniform switching parameters are observed for bilayer structures compared to single layer HfO_(x) sample, which can be attributed to the modulation of oxygen vacancies at the interface and better control of the growth of filaments. Furthermore, the reliability of the prepared samples is investigated. The carrier conduction behaviors of HfO_(x)-based samples can be attributed to the trapping and de-trapping process of oxygen vacancies and a filamentary model is proposed. In addition, the rupture of filaments during the reset process for the bilayer structures occur at the weak points near the interface by the recovery of oxygen vacancies accompanied by the variation of barrier height. The re-formation of fixed filaments due to the residual filaments as lightning rods results in the better switching performance of the bilayer structure.

Model-free Speed Control of Single-phase Flux Switching Motor with an Asymmetrical Rotor

This paper proposes and implements a model-free open-loop iterative learning control(ILC)strategy to realize the speed control of the single-phase flux switching motor(FSM)with an asymmetrical rotor.Base on the proposed winding control method,the asymmetrical rotor enables the motor to generate continuous positive torque for positive rotation,and relatively small resistance torque for negative rotation.An initial iteration coefficient and variable iteration coefficient optimized scheme was proposed based on the characteristics of the hardware circuit,thereby forming the model-free strategy.A series of prototype experiments was carried out.Experimental results verify the effectiveness and practicability of the proposed ILC strategy.

Pure State Feedback Switching Control Based on the Online Estimated State for Stochastic Open Quantum Systems

For the n-qubit stochastic open quantum systems,based on the Lyapunov stability theorem and LaSalle’s invariant set principle,a pure state switching control based on on-line estimated state feedback(short for OQST-SFC)is proposed to realize the state transition the pure state of the target state including eigenstate and superposition state.The proposed switching control consists of a constant control and a control law designed based on the Lyapunov method,in which the Lyapunov function is the state distance of the system.The constant control is used to drive the system state from an initial state to the convergence domain only containing the target state,and a Lyapunov-based control is used to make the state enter the convergence domain and then continue to converge to the target state.At the same time,the continuous weak measurement of quantum system and the quantum state tomography method based on the on-line alternating direction multiplier(QST-OADM)are used to obtain the system information and estimate the quantum state which is used as the input of the quantum system controller.Then,the pure state feedback switching control method based on the on-line estimated state feedback is realized in an n-qubit stochastic open quantum system.The complete derivation process of n-qubit QST-OADM algorithm is given;Through strict theoretical proof and analysis,the convergence conditions to ensure any initial state of the quantum system to converge the target pure state are given.The proposed control method is applied to a 2-qubit stochastic open quantum system for numerical simulation experiments.Four possible different position cases between the initial estimated state and that of the controlled system are studied and discussed,and the performances of the state transition under the corresponding cases are analyzed.

一种应用于探测的可预测电流模式FSBB电路

探测器的能源供给离不开DC-DC变换器,先进的控制方法能提高工作效率。预测电流模式控制相比于传统的PI控制具有动态响应快、易于进行过流保护等优点,因此被广泛应用到电力电子控制领域。由于控制回路的问题,不能通过计算开环增益的方式对负载波动与输出电压变化的闭环传递函数进行有效地设计。因此,提出了一种在不加前馈控制的情况下,基于预测电流模式控制四开关Buck-Boost(four-switch Buck-Boost,FSBB)变换器补偿器的设计方案,该方法能提升负载动态响应,通过实验数据,证明了该方法的有效性。

Machine-Learning Based Packet Switching Method for Providing Stable High-Quality Video Streaming in Multi-Stream Transmission

Broadcasting gateway equipment generally uses a method of simply switching to a spare input stream when a failure occurs in a main input stream.However,when the transmission environment is unstable,problems such as reduction in the lifespan of equipment due to frequent switching and interruption,delay,and stoppage of services may occur.Therefore,applying a machine learning(ML)method,which is possible to automatically judge and classify network-related service anomaly,and switch multi-input signals without dropping or changing signals by predicting or quickly determining the time of error occurrence for smooth stream switching when there are problems such as transmission errors,is required.In this paper,we propose an intelligent packet switching method based on the ML method of classification,which is one of the supervised learning methods,that presents the risk level of abnormal multi-stream occurring in broadcasting gateway equipment based on data.Furthermore,we subdivide the risk levels obtained from classification techniques into probabilities and then derive vectorized representative values for each attribute value of the collected input data and continuously update them.The obtained reference vector value is used for switching judgment through the cosine similarity value between input data obtained when a dangerous situation occurs.In the broadcasting gateway equipment to which the proposed method is applied,it is possible to perform more stable and smarter switching than before by solving problems of reliability and broadcasting accidents of the equipment and can maintain stable video streaming as well.

Improvement of hepatic fibrosis after tenofovir disoproxil fumarate switching to tenofovir alafenamide for three years

BACKGROUND Both tenofovir alafenamide(TAF)and tenofovir disoproxil fumarate(TDF)are the first-line treatments for chronic hepatitis B(CHB).We have showed switching from TDF to TAF for 96 weeks resulted in further alanine aminotransferase(ALT)improvement,but data remain lacking on the long-term benefits of TDF switching to TAF on hepatic fibrosis.AIM To assess the benefits of TDF switching to TAF for 3 years on ALT,aspartate aminotransferase(AST),and hepatic fibrosis improvement in patients with CHB.METHODS A single center retrospective study on 53 patients with CHB who were initially treated with TDF,then switched to TAF to determine dynamic patterns of ALT,AST,AST to platelet ratio index(APRI),fibrosis-4(FIB-4)scores,and shear wave elastography(SWE)reading improvement at switching week 144,and the associated factors.RESULTS The mean age was 55(28-80);45.3%,males;15.1%,clinical cirrhosis;mean baseline ALT,24.8;AST,25.7 U/L;APRI,0.37;and FIB-4,1.66.After 144 weeks TDF switching to TAF,mean ALT and AST were reduced to 19.7 and 21,respectively.From baseline to switching week 144,the rates of ALT and AST<35(male)/25(female)and<30(male)/19(female)were persistently increased;hepatic fibrosis was also improved by APRI<0.5,from 79.2%to 96.2%;FIB-4<1.45,from 52.8%to 58.5%,respectively;mean APRI was reduced to 0.27;FIB-4,to 1.38;and mean SWE reading,from 7.05 to 6.30 kPa after a mean of 109 weeks switching.The renal function was stable and the frequency of patients with glomerular filtration rate>60 mL/min was increased from 86.5%at baseline to 88.2%at switching week 144.CONCLUSION Our data confirmed that switching from TDF to TAF for 3 years results in not only persistent ALT/AST improvement,but also hepatic fibrosis improvement by APRI,FIB-4 scores,as well as SWE reading,the important clinical benefits of long-term hepatitis B virus antiviral treatment with TAF.

基于QFSK调制的DC-DC变换器功率/数据复合传输方法

传统电力线通信方案的硬件设计较为复杂。DC-DC变换器具有发送数据的潜能,可进行功率/数据复合传输。文中提出一种基于四进制频移键控(QFSK)调制的电力电子开关调制方案,通过调制开关频率将数据信息嵌入原始脉宽调制(PWM)信号中,使得电压纹波携带数据的频率特征;再通过基于滑动离散傅里叶变换的解调方案实现数据接收,最终实现功率/数据的同步传输。首先,证明了PWM信号与电压纹波频率一致的关系;然后,给出数据调制与解调的方案;以负载突变工况为例,通过对Buck变换器建模,分析功率变换暂态过程对通信的干扰影响;最后,搭建由两个Buck变换器组成的实验平台,验证了所提方案可实现20 kbit/s的通信速率;并以光伏优化器为应用背景,验证了所提方案的有效性。

Research on Switching Characteristics Based on Optimization Design of SiC MOSFET Drive Circuit

With the increasing emphasis on energy conservation,emission reduction and environmental protection,the application prospect of SiC power devices is becoming more and more broad.In the high frequency application of SiC MOSFET,the change rate of voltage and current in the turn-on and turn-off process increases with the increase of switching frequency.Also,the current and voltage spike oscillation phenomenon is gradually intensified due to the influence of circuit stray parameters.Based on the analysis of SiC MOSFET characteristics,the paper discusses the design requirements and design principles of SiC MOSFET drive circuit.Then,taking the SiC module C2M0080120D of Cree Company as an example,a driver circuit design is realized through the ACPL-355JC optocoupler driver module of Broadcom Company.The circuit not only has the characteristics of fast transmission delay and excellent performance,but also has the functions of overload and short circuit protection.The driving circuit is verified by LTspice simulation software,and the switching characteristics of SiC MOSFET under different working conditions are studied in depth.The experimental results show that the driving circuit can improve the switching time of SiC MOSFET and effectively solve the problem of current and voltage spike oscillation,which lays a foundation for the practical application of SiC MOSFET in the future.

基于FSBB变换器的直流微电网SOC平衡控制策略

针对直流微电网工作时易出现储能单元SOC不平衡的现象,提出一种基于四开关BuckBoost(FSBB)变换器的直流微电网SOC平衡控制策略。使用四开关Buck-Boost变换器替换双向DC/DC变换器与蓄电池相联,既保证功率可以双向流通,又提高储能单元动态响应能力和抗干扰能力;设计了一种基于储能单元SOC平衡的改进下垂控制策略,将蓄电池SOC函数与下垂系数相结合,使各储能单元在充放电过程中按SOC值分配输出电流,实现储能单元SOC平衡和单元间电流合理分配;同时负载跳变时保持母线电压稳定,实现不同模式的平滑切换与功率分配,且无需互联通信,降低系统设计成本。在MATLAB/Simulink中搭建仿真模型,验证了所提控制策略的正确性和可行性。