Pattern Scan Laser Photocoagulator on Retinopathy: an annual clinical application summary

Purpose:To evaluate the clinical efficacy of Pattern Scan Laser Photocoagulator (PASCAL) by observing the efficacy of PASCAL on retinopathy.Methods:A total of 92 patients with retinopathy (121 eyes) who underwent PASCAL between December 2008 and February 2009 in our center were retrospectively analyzed to evaluate the visual acuity changes and recovery conditions of the patients from baseline to posterior to the treatment.The retinopathy included:diabetic retinopathy,ischemic retinal vein occlusion.(IRVO),central serous chorioretinopathy (CSC),retinal periphlebitis (Eales disease) and retinal degeneration /holes.Results:The patients were subject to a 12-month follow up after PASCAL.The visual acuity findings were stated as below:for diabetic retinopathy.(73 eyes),10 eyes had improved visual acuity;55 eyes were stabilized and 8 eyes progressed;for IRVO (13 eyes),4 eyes showed improvement,6 eyes were stabilized and 3 eyes progressed;for CSC (9 eyes),6 eyes were alleviated and 3 eyes progressed;for retinal periphlebitis (5 eyes),2 eyes had enhanced visual acuity and 3 eyes showed stable visual acuity;for retinal degeneration /holes (21 eyes),5 eyes presented improved visu-al acuity,16 eyes were stabilized and no eye progressed.Indirect ophthalmoscopic reexamination confirmed secured blockage by laser spots and favorable absorption of the retinal edema and newborn capillaries.No obvious leakage was observed during fundus fluorescein angiography and no laser-related ocular adverse effect was reported.Conclusion:PASCAL is accurate,effective and well-tolerated.The duration of short laser pulse falls within the safety range,ensuring the stabilization and improvement in the pa-tient's visual acuity.The parameters,long-term efficacy and complications of PASCAL should be further demonstrated by performing long-term clinical trials with larger sample size.

Long-term effects of pattern scan laser pan-retinal photocoagulation on diabetic retinopathy in Chinese patients: a retrospective study

●AIM:To evaluate the long-term effects of pattern scan laser(PASCAL)pan-retinal photocoagulation(PRP)on diabetic retinopathy(DR)in Chinese patients.●METHODS:In this retrospective study,we evaluated clinical data of 29 patients(53 eyes)with severe non-proliferative DR(SNPDR)or proliferative DR(PDR)who received PRP and follow-up at our hospital from 2008 to 2013.Sixteen patients(29 eyes)received PASCAL PRP and 13 patients(24 eyes)received 100-ms conventional laser PRP.●RESULTS:After long-term follow-up(mean,min-max days:719.8,290-1666 for PASCAL PRP vs 743.5,240-1348 for conventional PRP,P=0.569),patients receiving PASCAL PRP required fewer photocoagulation sessions than the conventional PRP group(2.6±1.0 vs 3.9±0.9,P<0.01).Best corrected visual acuity(BCVA)was reduced slightly in PASCAL PRP group while reduced significantly in conventional PRP group.At last visit,24 eyes in the PASCAL group(88.9%)and 21 eyes in the conventional group(91.7%)were improved or stable.Two eyes in PASCAL PRP group(7.4%)and 3 eyes in the conventional PRP group(12.5%)developed vitreous hemorrhage or vitreous fibrovascular proliferation.●CONCLUSION:PASCAL PRP is as effective and may be more conducive to maintaining visual acuity with less treatment sessions for DR treatment compared to conventional laser PRP.

Experimental Investigation of Laser Surface Hardening of AISI 4340 Steel Using Different Laser Scanning Patterns

Laser surface transformation hardening becomes one of the most modern processes used to improve fatigue and wear properties of steel surfaces. In this process, the material properties and the heating parameters are the factors that present the most significant effects on the hardened surface attributes. The control of these factors using predictive modeling approaches to achieve desired surface properties leads to conclusive results. However, when the dimensions of the surface to be treated are larger than the cross-section of the laser beam, various laser-scanning patterns are involved. This paper presents an experimental investigation of laser surface hardening of AISI 4340 steel using different laser scanning patterns. This investigation is based on a structured experimental design using the Taguchi method and improved statistical analysis tools. Experiments are carried out using a 3 kW Nd: YAG laser source in order to evaluate the effects of the heating parameters and patterns design parameters on the physical and geometrical characteristics of the hardened surface. Laser power, scanning speed and scanning patterns (linear, sinusoidal, triangular and trochoid) are the factors used to evaluate the hardened depth and the hardened width variations and to identify the possible relationship between these factors and the hardened zone attributes. Various statistical tools such as ANOVA, correlations analysis and response surfaces are applied in order to examine the effects of the experimental factors on the hardened surface characteristics. The results reveal that the scanning patterns do not modify the nature of the laser parameters’ effects on the hardened depth and the hardened width. But they can accentuate or reduce these effects depending on the type of the considered pattern. The results show also that the sinusoidal and the triangular patterns are relevant when a maximum hardened width with an acceptable hardened depth is desired.

Numerical Investigation of Laser Surface Hardening of AISI 4340 Using 3D FEM Model for Thermal Analysis of Different Laser Scanning Patterns

Laser surface hardening is becoming one of the most successful heat treatment processes for improving wear and fatigue properties of steel parts. In this process, the heating system parameters and the material properties have important effects on the achieved hardened surface characteristics. The control of these variables using predictive modeling strategies leads to the desired surface properties without following the fastidious trial and error method. However, when the dimensions of the surface to be treated are larger than the cross section of the laser beam, various laser scanning patterns can be used. Due to their effects on the hardened surface properties, the attributes of the selected scanning patterns become significant variables in the process. This paper presents numerical and experimental investigations of four scanning patterns for laser surface hardening of AISI 4340 steel. The investigations are based on exhaustive modelling and simulation efforts carried out using a 3D finite element thermal analysis and structured experimental study according to Taguchi method. The temperature distribution and the hardness profile attributes are used to evaluate the effects of heating parameters and patterns design parameters on the hardened surface characteristics. This is very useful for integrating the scanning patterns’ features in an efficient predictive modeling approach. A structured experimental design combined to improved statistical analysis tools is used to assess the 3D model performance. The experiments are performed on a 3 kW Nd:Yag laser system. The modeling results exhibit a great agreement between the predicted and measured values for the hardened surface characteristics. The model evaluation reveals also its ability to provide not only accurate and robust predictions of the temperature distribution and the hardness profile as well an in-depth analysis of the effects of the process parameters.

Achieving Directionality and Transmit Diversity via Integrating Beam Pattern Scanning (BPS) Antenna Arrays and OFDM

In this paper, we introduce a novel merger of antenna arrays with scanning beam patterns, and Orthogonal Frequency Division Multiplexing (OFDM) systems. Controlled time varying phase shifts are applied to the antenna array elements mounted at the base station with beam patterns directed toward the desired user. This creates a small beam pattern movement called Beam Pattern Scanning (BPS). In rich scattering environments BPS creates a time varying environment leading to time diversity exploitable at the receiver enhances its probability-of-error performance. Here, we apply OFDM signals to BPS antenna arrays, and we achieve: (1) directionality, which supports Space Division Multiple Access (SDMA);and (2) a time diversity gain, which leads to high performance. We discuss the structure of the base station antenna array and the OFDM receiver that exploits time diversity. We also introduce the merger of BPS and multi-carrier OFDM (MC-OFDM) systems. In MC-OFDM each bit is transmitted over all sub-carriers after serial to parallel conversion. BPS/ MC-OFDM receiver exploits both time diversity inherent in BPS, and frequency diversity inherent in MC-OFDM transmission technique. Simulation results show high Probability-of-error performance is achie- vable via BPS/OFDM and BPS/MC-OFDM schemes comparing to the traditional OFDM and MC-OFDM, respectively. Simulations also reveal that MC-OFDM system as well as its merger with BPS is capable of mitigating large Peak-to-Average Ratio (PAPR) problem in traditional OFDM system. In addition, performance simulations with coded OFDM (COFDM) and coded MC-OFDM (MC-COFDM) and their merger with BPS are studied.

激光后处理实现图案化结构色调控研究

为使人工制备的结构色实现色调的精确调控,本研究以硅片为衬底,采用自组装法制备聚苯乙烯微球(PS微球)的平面六角密堆积结构,通过磁控溅射方法在其上沉积不同厚度的金薄层;再利用532nm脉冲激光后处理,研究不同扫描速度的激光后处理对结构色薄膜呈色性能的影响。结果表明:镀膜时间相同,随激光扫描速度逐渐减小,样品扫描区域颜色的变化为玫红—橙红—橙黄—黄绿—蓝绿—蓝紫,反射光谱中心波长发生蓝移;在此基础上制备了图案化的样品,发现随着观察角度增加,扫描后区域的颜色发生蓝移。

基于激光雷达数据的塔里木河下游胡杨种群空间分布格局和种内竞争关系

【目的】分析胡杨种群在干旱区不同地下水埋深梯度下的空间分布格局及种内竞争强度变化,探究种群空间结构对干旱环境的响应特征。【方法】在塔里木河下游3个断面处离河道1 000 m的范围内等距离布设15个50 m×50 m天然胡杨林样地,利用地面激光雷达(TLS)获取树木三维结构数据,并通过聚集指数(R)、丛生指数(I)、点格局函数g(r)等空间分布指标以及竞争指数(CI),分析空间分布格局和种内竞争强度。【结果】1)R和I指数表明,在下游不同地下水埋深梯度下,胡杨种群空间分布格局整体上呈聚集分布。2)各样地内在0~25 m半径r距离获取的g(r)函数值分析表明,大部分样地胡杨在r<5 m距离内基本呈现聚集分布格局,在r>5 m距离呈随机分布格局。随着地下水埋深增加,树木聚集分布的距离r会缩小。3)点格局函数g_(12)(r)结果表明,不同龄级胡杨树分布格局存在差异,中龄树主要呈聚集分布,其他龄级树呈随机分布;中龄树与幼龄树、成熟树之间存在正关联性,表现出相互促进关系,而其他龄级树木之间未呈现显著关联性。4)平均CI指数随离河道距离增大呈递减趋势,单木CI随胸径增大逐渐递减。【结论】塔里木河下游胡杨种群在小尺度上呈聚集分布格局,随着尺度的增加主要呈现随机分布特征。随离河道距离增大和地下水位逐步降低,导致树木密度降低和种内平均竞争强度变弱,树木呈衰退趋势。

微型光机电二维扫描镜的Lissajous与Linescan扫描对比

在激光扫描显示系统(LSDs)中,MOEMS对激光束的空间调制主要分为Lissajous与Linescan两种模式。为了深入分析各模式的扫描特点,比较各模式之间的优缺,针对每种模式提出了扫描显示分辨率和轨迹均匀性这两个指标进行对比研究。按照仿真分析得出的最小像元划分方法,相同分辨率下,Lissajous模式对MOEMS快轴频率的最低要求要比Linescan模式大约高57%。另外,利用Matlab对不同MOEMS模式进行同一图像的扫描仿真,仿真结果表明,Lissajous扫描轨迹呈现出上下边缘密、中心疏的不均匀特点,而Linescan扫描轨迹则呈现出喇叭状不均匀特点。

扫描雷达未知天线方向图误差下的稀疏目标角超分辨重建方法

扫描雷达角超分辨技术是基于目标与天线方向图的关系,采用解卷积方法获取超越实波束的角分辨能力。目前的角超分辨方法大都是基于理想的无畸变天线方向图,未考虑实际过程中方向图的变化。然而,由于雷达天线罩、天线测量误差与平台非理想运动等因素的影响,天线方向图在实际中往往存在未知的误差,会导致目标分辨能力下降,甚至产生虚假目标。针对此问题,该文提出一种机载扫描雷达未知天线方向图误差下的角超分辨成像方法。首先,基于总体最小二乘(TLS)准则,该文考虑了方向图误差矩阵的影响,导出了相应的目标函数;其次,基于交替迭代的求解思路,利用迭代重加权优化方法实现了目标函数求解;最后,针对算法超参数选取,引入了一种自适应参数选取方法。仿真与实测结果表明,该文方法能实现未知天线误差条件下的超分辨重建,进一步提升了超分辨算法的稳健性。

i-Scan染色与色素内镜技术诊断大肠肿瘤对比研究

目的探讨i-Scan染色内镜技术在大肠肿瘤病变诊断中的应用价值。方法应用高分辨率结肠镜检出大肠息肉样病变180个,应用i-Scan放大观察病变腺管开口类型(PP),预测病变的病理类型,并与染色内镜及病理组织学进行对照研究。结果高分辨率结肠镜i-Scan染色对大肠肿瘤的诊断敏感度为86.2%,特异度为78.9%,准确度为87.4%,阳性预测值为89.8%,阴性预测值为72.5%。色素内镜对大肠肿瘤的诊断敏感度为90.2%,特异度为85.9%,准确度为90.8%,阳性预测值为93.2%,阴性预测值为80.3%。两者对大肠肿瘤诊断敏感度、特异度及准确度比较均无显著性差异(P>0.05)。结论高分辨率结肠镜i-Scan染色能较准确预测大肠肿瘤的病理类型,准确度与色素内镜相当,具有较高的应用价值。

Prophylactic Pattern Scanning Laser Retinal Photocoagulation for Diabetic Retinopathy in Spontaneously Diabetic Torii Fatty Rats: Preliminary Experimental Results

Research Background and Purpose: The number of diabetic patients is rapidly increasing, making it crucial to find methods to prevent diabetic retinopathy (DR), a leading cause of blindness. We investigated the effects of prophylactic pattern scanning laser retinal photocoagulation on DR development in Spontaneously Diabetic Torii (SDT) fatty rats as a new prevention approach. Methods: Photocoagulation was applied to the right eyes of 8-week-old Spontaneously Diabetic Torii (SDT) fatty rats, with the left eyes serving as untreated controls. Electroretinography at 9 and 39 weeks of age and pathological examinations, including immunohistochemistry for vascular endothelial growth factor and glial fibrillary acidic protein at 24 and 40 weeks of age, were performed on both eyes. Results: There were no significant differences in amplitude and prolongation of the OP waves between the right and left eyes in SDT fatty rats at 39 weeks of age. Similarly, no significant differences in pathology and immunohistochemistry were observed between the right and left eyes in SDT fatty rats at 24 and 40 weeks of age. Conclusion: Prophylactic pattern scanning retinal laser photocoagulation did not affect the development of diabetic retinopathy in SDT fatty rats.

Fast Multi-Pattern Matching Algorithm on Compressed Network Traffic

Pattern matching is a fundamental approach to detect malicious behaviors and information over Internet, which has been gradually used in high-speed network traffic analysis. However, there is a performance bottleneck for multi-pattern matching on online compressed network traffic(CNT), this is because malicious and intrusion codes are often embedded into compressed network traffic. In this paper, we propose an online fast and multi-pattern matching algorithm on compressed network traffic(FMMCN). FMMCN employs two types of jumping, i.e. jumping during sliding window and a string jump scanning strategy to skip unnecessary compressed bytes. Moreover, FMMCN has the ability to efficiently process multiple large volume of networks such as HTTP traffic, vehicles traffic, and other Internet-based services. The experimental results show that FMMCN can ignore more than 89.5% of bytes, and its maximum speed reaches 176.470MB/s in a midrange switches device, which is faster than the current fastest algorithm ACCH by almost 73.15 MB/s.

一种贴片天线阵列的测量

阵列接收机是将其前端阵列天线放置于射电望远镜焦平面处,结合后级波束合成网络以形成多个连续波束,用以同时观测一片连续天区、实现更大视场覆盖的接收机技术。本文理论设计了工作在1.25 GHz的十六阵元矩形排布贴片天线阵列,并在该贴片天线阵列样机的基础上进行了实验室测试。在等幅激励、30°设计扫描角度配相下,实测的阵列主波束增益为14.03 dBi、扫描角度约为35°。测量结果显示该贴片天线阵列满足设计指标,相关工作对阵列天线的模拟波束合成及扫描性能验证也具备较好的指导意义。

侧扫声纳图像中央区的自动确定和重建

侧扫声纳是海洋测绘领域的常用设备,为解决侧扫声纳波束模式带来的声纳图像中央区域质量较差的问题,提出了侧扫声纳图像中央区的自动确定和重建方法。首先根据侧扫声纳测量原理,基于波束模式,自动确定侧扫声纳图像的中央区域;然后根据图像强度梯度和像素可靠信息,计算图像重建区域的优先级;最后根据优先级顺序,采用基于样例的方法对中央区进行重建,提高侧扫声纳图像质量。研究表明,重建后的侧扫声纳图像无论是在主观视觉还是客观评价指标方面,都取得了满意的结果。采用本文所提方法得到的重建图像,能够清晰地反映海底特征,具有很好的应用价值。

快乐表情对婴儿面孔种族知觉窄化的影响:眼动证据

本文利用眼动技术,采用改进的视觉配对比较范式,探究快乐表情是否及如何改变中国婴儿的面孔种族知觉窄化。实验一发现,中性条件下,6个月婴儿能识别本族和他族面孔,9个月婴儿仅能识别本族面孔;实验二发现,快乐条件下,9个月婴儿熟悉他族面孔后,能识别他族面孔,并且眼动结果表明,快乐条件下婴儿对他族面孔扫描模式不同于中性条件下,这种差异可能会影响到婴儿对他族面孔的识别。结果为婴儿期面孔知觉-社会加工联结假说提供了证据。

基于三维激光扫描的坡沟系统侵蚀产沙过程研究

为了探究野外自然坡沟系统土壤侵蚀过程,研究于黄土丘陵沟壑区典型流域辛店沟内自然坡面开展5场放水冲刷试验,利用地面三维激光扫描技术(Terrestrial laser scanning, TLS)获取高精度地形信息,并采用DEM of difference(DoD)地形变化监测方法计算产沙量,利用实测产沙量评估TLS的监测精度,并探讨了坡沟系统侵蚀/沉积的变化特征。结果表明:(1)累积场次中,DoD不确定性(即level of detection, LoD)平均值(范围)为16.5 mm(16.2~16.8 mm)。单场次中,LoD值平均值为16.4 mm(16.2~16.6 mm);(2)累积场次中,梁峁坡、沟谷坡、坡沟系统TLS扫描所得产沙量相对误差的平均值(范围)为52.63%(26.06%~106.98%),56.68%(30.26%~75.49%)和56.28%(33.37%~73.28%),与实测数据显著相关(R2>0.9,p<0.05)。单场次TLS扫描相对误差波动范围更大且平均值高于累积场次,其值分别为83.70%(4.08%~190.40%),91.41%(0.95%~225.09%)和87.58%(4.09%~215.55%),与实测值非显著相关(R2<0.57,p>0.05),表明TLS更适合于坡沟系统累积场次侵蚀产沙监测,而单场次监测精度较差;(3)随冲刷次数的增加,梁峁坡、沟谷坡和坡沟系统侵蚀产沙均呈增长趋势,但沟谷坡和坡沟系统沉积量快速增长后趋于平稳。(4)梁峁坡侵蚀区域主要位于梁峁坡上中部,沉积主要分布于梁峁坡中下方,沟谷坡大部分区域侵蚀剧烈,沉积主要分布于沟底,梁峁坡和沟谷坡侵蚀区占地形变化区域的比例均高于79%。结果可为黄土高原土壤侵蚀监测与机理研究提供参考。

基于飞秒激光的高速双光子刻写技术

基于飞秒激光的双光子聚合(two-photon polymerization,TPP)加工技术一直是三维微纳加工技术中的研究热点。随着生命科学、材料工程、微纳光学等领域对复杂、大面积微型三维器件制备需求的提升,TPP加工效率不足的问题日益严重,加工时间过长不仅造成加工结构的不稳定,更是严重阻碍这些重要三维器件的进一步推广应用。本文以TPP加工效率提升方面的研究工作为主线,分别从单光束刻写、并行多光束刻写、面曝光和体曝光四个方式进行总结与对比,阐述相应的光学系统设计、刻写策略、刻写精度与通量等方面的研究情况,总结各种技术的优势与劣势,同时展望未来发展趋势。

四阵元微带天线阵列试制与测试

将阵列天线放置于射电望远镜焦平面处,结合波束合成网络,可以同时观测一片天区,实现更大的视场覆盖。由于需要对各个阵元的幅度和相位进行调控,阵列天线实际就是一个小型相控阵,因此在做阵列设计时,除了需要结合反射面焦面场分布及望远镜拟实现的视场以外,阵列自身的性能验证可以参照传统相控阵进行。设计并加工了工作在1.27 GHz的2×2矩形排布的微带贴片天线阵列,阵元间距为0.7倍波长。经实测,各端口S11均在-10 dB以下,4阵元合成后波束增益为12.54 dBi,通过为对应阵元添加理论偏移30°的延时线,实测阵列的波束扫描角度为28.3°。上述实测数据与仿真结果相比虽略有差异,这和阵列加工及馈电端口焊接有关,但相关工作为之后更多阵元的阵列天线设计、研制及测试积累了经验,尤其对性能验证具有较高的指导意义。

W波段宽带宽角低副瓣类喇叭天线稀布阵

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