CFB不同密相区形状对固态医疗垃圾颗粒运动特性的影响

提出了不同密相区结构形状(球形、椭球形、方形体)的固态医疗垃圾循环流化床(SMW-CFB),并针对SMW-CFB各段特征,对循环流化床不同密相区形状对固态医疗垃圾颗粒运动特性的影响进行了数值研究,结果表明:密相区为球形体结构比其它结构形状密相区更易出现回流.密相区不同形状时,颗粒运动进入分离器的时间不一样.固态医疗垃圾颗粒在循环流化床内,直径在大于3.5 mm的垃圾颗粒,随烟气上升到一定高度后,落回密相区,而直径小于3.5 mm的颗粒随烟气一同进入分离器,分离器可以捕集直径大于0.025 mm的颗粒,直径小于0.025 mm的颗粒由排气管排出.球形和椭球形密相区有助于垃圾颗粒与风充分混合接触,有利于垃圾颗粒的燃烧.     

切向气流对激光加热金属板非熔化穿孔效应的影响

针对切向气流加载导致激光加热金属板在熔化前的穿孔效应,利用金属薄板的弹性弯曲理论,推导出了两种典型光束（方形和圆形）照射下的弯曲挠度表达式,利用Mises理论给出了非熔化穿孔的破坏判据。研究结果表明：激光加热下材料强度降低是出现非熔化穿孔破坏的主要机理;薄板在光斑区的最大变形与气流速度、光斑直径、板厚与弹性模量（U2a4/Eh3）相关,穿孔破坏温度与气流速度、光斑直径及板厚（Ua/h）2相关;与方形光斑辐照相比,圆形光斑辐照的破坏阈值稍高一些。数值计算结果表明：0.8 Ma切向气流作用下,铝合金壳体的激光破坏能量阈值大大降低（可达40%～50%）,典型不锈钢壳体的破坏阈值降低相对较小（20%左右）,气流作用导致金属板破坏阈值的下降是需特别关注的问题。     

不同脉冲激光波形在打孔实验上的比较与分析

为了获得高质量小孔,克服单脉冲激光打孔的不足,设计了一种能够产生多脉冲激光波形的激光器电源.并在1mm厚的薄钢片上得到直径小于1mm的小孔.多脉冲打孔理论分析表明,多脉冲激光打孔不但减少了熔融物和等离子体的产生,而且降低了激光打孔对高能量的要求,获得的小孔质量优于单脉冲激光打孔.另外脉冲宽度和脉冲间距的选择对激光小孔加工质量起决定性作用,在加工高质量孔的时候,应该选用较短的激光脉冲宽度.实验表明,利用三脉冲激光输出波形打孔所获得的小孔质量要优于单脉冲激光打孔效果,有效脉冲平均能量为350mJ,宽度为100μs,脉冲间距为100μs.     

聚芳亚胺酮空心微球的制备

 利用微流体技术和双重乳液技术对大直径聚芳亚胺亚胺酮空心微球的制备条件进行了讨论。完成了微球壁厚和直径的控制研究,并讨论了密度不匹配对微球质量的影响。获得了直径0.6～2.0 mm,壁厚5.0～20.0 μm的聚合物微球材料,并对微球制备过程中相分离对聚合物微球形貌的影响进行了分析,结果表明：在聚合物微球外表面易于进行spinodal分相,而在内表面易于进行binodal分相,因此微球内外表面具有不同的形貌结构。同批次制备微球中,平均直径±5%范围内的微球数占88%,球形度大于99%。     

球形破片侵彻多层板弹道极限的量纲分析

为了研究Q235钢多层板的抗侵彻性能,进行了直径为9.45 mm的钨合金球形破片侵彻7.2 mm和(3.6+3.6)mm厚Q235钢双层板试验,获得了相应的弹道极限。在此基础上,建立数值仿真模型,研究了钨合金球侵彻接触式等厚3层、4层、5层、6层板的弹道极限。通过量纲分析方法,分析了分层数对靶板弹道极限的影响。结果表明:对于球形破片,总厚度为7.2 mm的等厚双层板的抗侵彻性能高于单层板;当分层数大于2时,接触式多层等厚靶板的弹道极限随着层数的增加而减小,即分层数越多,靶板的抗侵彻性能越低,通过量纲分析方法得到了靶板分层数与破片弹道极限的关系。研究结果可为未来装甲防护设计提供一定的参考。     

激光熔覆Al2O3/Fe901复合涂层的强化机制及耐磨性

为提高金属材料表面涂层的耐磨性,采用激光熔覆工艺制备了Al_2O_3增强Fe901金属陶瓷复合涂层,研究了Al_2O_3陶瓷增强相对Fe基熔覆层组织与性能的影响。利用扫描电镜和X射线衍射仪检测了复合涂层的微观组织和物相;采用显微硬度仪和摩擦磨损试验机分析了复合涂层的显微硬度与耐磨性。结果表明:Fe901涂层的组织以柱状枝晶和等轴枝晶为主,添加的Al_2O_3可促使涂层组织转变为均匀的白色网状晶间组织及其包裹的细小黑色晶粒;复合涂层中的Al_2O_3陶瓷颗粒表面发生微熔,与Fe、Cr结合生成Fe3Al及(Al,Fe)4Cr金属间化合物,起到增加Al_2O_3陶瓷颗粒与金属黏结相结合强度的作用;当Al_2O_3陶瓷颗粒的质量分数为10%时,复合涂层的显微硬度较Fe901涂层增加了16.4%,复合涂层的摩擦磨损质量损失较Fe901涂层降低了50%;添加适量的Al_2O_3陶瓷有助于提高涂层的显微硬度及耐磨性。     

非球形颗粒系粒径分布的机器学习反演算法

动态光散射技术在微米与亚微米级颗粒系粒径分析领域中具有广泛应用,但缺乏非球形颗粒系粒径分布（PSD）的反演模型和算法,限制了其在生物医疗等领域中的应用。基于机器学习方法,设计了基于广义回归神经网络（GRNN）的PSD反演模型和算法,可应用于多角度动态光散射法的粒径分析场景中。以生物医疗领域中的双凹圆饼形和椭球形血红细胞作为典型的非球形颗粒物模型,通过仿真实验测试了所设计的算法。实验结果表明,与传统的正则化Tikhonov算法相比,所设计的反演算法粒径分析准确性更好且耗时更短。对多角度动态光散射法中的散射角度数量进行了仿真实验。结果表明,仅使用2个散射角度处获得的数据依然能实现非球形颗粒系粒径分布的准确反演。     

SOI纳米光波导激光熔凝光整加工温度场的数值模拟及分析北大核心CSCD

激光表面熔凝技术可有效降低纳米光波导侧壁粗糙度进而减小光传输的散射损耗。为明确波导侧壁在KrF准分子激光表面熔凝过程的温度场演化规律,考虑材料参数随温度变化和相变潜热的影响,建立了纳米光波导侧壁激光熔凝的二维有限元数值模型,研究了熔池边界的推进行为与不同工艺参数的映射关系。结果表明:熔池形成于波导上表面与迎光侧壁夹角处;激光入射角度一定时,熔池熔深与平均能量密度正相关;熔池形貌受控于激光入射角度,随着入射角度的减小,熔池形貌由单边U形过渡为单边V形最终呈带钝角单边V形。分析表明,较大激光入射角对应的熔池形貌更有利于波导侧壁的光整加工;据此提出先确定激光入射角度以优化熔池形貌,再选取合适平均能量密度以获得足够熔化深度的工艺方法。     

高温合金活性剂激光微焊接接头的组织性能研究

采用配方均匀设计法,配制了SiO2-MnO2-CaO-TiO2-CaF2-NaF多组元活性剂,利用微型脉冲激光器对500 m厚GH4169高温合金进行了活性剂激光焊接试验。分析并讨论了焊接接头的显微组织和力学性能。试验结果表明,与传统激光焊相比,所配制的20种活性剂均增加了焊缝熔深,并且其中F12系混合活性剂增加熔深能力最为显著,使焊缝深宽比增加了159%,证明通过使用活性剂来增加微激光焊焊缝熔深,降低高温合金板激光焊接的成本是可行的。在活性剂作用下,焊缝显微组织仍由柱状晶和等轴晶组成,接头抗拉强度达到927 MPa,为母材强度的92.7%。     

高温合金活性剂激光微焊接接头的组织性能研究（英文）

采用配方均匀设计法,配制了SiO2-MnO2-CaO-TiO2-CaF2-NaF多组元活性剂,利用微型脉冲激光器对500μm厚GH4169高温合金进行了活性剂激光焊接试验。分析并讨论了焊接接头的显微组织和力学性能。试验结果表明,与传统激光焊相比,所配制的20种活性剂均增加了焊缝熔深,并且其中F12系混合活性剂增加熔深能力最为显著,使焊缝深宽比增加了159%,证明通过使用活性剂来增加微激光焊焊缝熔深,降低高温合金板激光焊接的成本是可行的。在活性剂作用下,焊缝显微组织仍由柱状晶和等轴晶组成,接头抗拉强度达到927 MPa,为母材强度的92.7%。     

三同心球光学系统跟瞄误差分析

针对独有的跟踪方式,具体讨论了激光通信三同心球光学系统的跟瞄方案,并进行了具体规划。通过对通信跟踪光路和通信接收光路的视场和精度分析,给出了二者的相关参数,作为Matlab理论计算跟踪像面轨道的依据。利用Tracepro软件模拟了引入相关误差量后的通信跟踪和通信接收像面光斑质心偏移和光斑大小变化情况。仿真结果显示:随着角度的旋转,通信接收的质心偏差在±4μm范围内,通信跟踪的质心偏差在±50μm范围内;通信接收像面光斑直径小于80μm,通信跟踪像面光斑直径均在400μm以内。系统所引入的误差在允许范围之内,不影响相关跟踪通信功能。     

Monodispersed Spherical Nanoparticles GdxSiyOz:Eu3+ for Magnetic Resonance Tomography and Optical Imaging

Physics of the Solid State - The melt method is used for synthesizing monodispersed spherical silica nanoparticles Gdx-SiyOz:Eu3+. The particle diameter is 450 nm, and the standard deviation does...     

锂离子动力电池极片的激光切割分析

为适应锂离子动力电池行业发展需求,寻求一种高效高质切片方式,本文研究了多种激光器的切片质量。通过影像测量仪和扫描电镜(SEM)对比发现,100 ns脉宽调Q型1 064 nm光纤激光器切割正极铝箔时毛刺和热影响区(HAZ)约为15μm和60μm,切负极铜箔时HAZ约为200μm; 20 ns脉宽的MOPA光纤激光器切割铝箔毛刺10μm,HAZ约为20μm,切铜箔时HAZ约70μm;脉宽为10 ps的固体激光器切割铝箔毛刺和HAZ分别约为6μm和10μm,切铜箔时实现无熔融重凝区; 20 ns脉宽的355 nm紫外和532 nm的绿光固体激光器切割铝箔HAZ分别为10μm和17μm,切铜箔时HAZ则分别为大于70μm和100μm。实验结果表明:脉宽越窄,重复频率越高,切割的极片质量越好,ps激光器切割的极片精度最高,质量最好,是切割极片最理想激光器。而目前,频率高、脉宽相对窄的MOPA光纤激光器切割速度最高,切割的正极片完全满足工业要求,更适合极片切割的工业推广。     

Laser cutting of thick ceramic tile

This paper details developments in the CO₂ laser cutting of thick ceramic tiles, that is thicknesses of 8.5 mm and 9.2 mm. These tiles were cut at a combination of different cutting speeds to determine the necessary cutting parameters for various tile geometries. Different cutting modes were used in conjunction with different cutting speeds to investigate cut quality after laser processing. The work also looked into the effects on cutting through using various shield gases. Multipass cutting and underwater cutting were performed to examine their effects on thermal load during processing.     

柔性变焦镜的理论计算和设计

 设计了由压电陶瓷施压的柔性变焦镜的结构。根据弹性力学建立了相应的数学模型,采用有限元法计算了镜面受力的挠变形值。当柔性变焦镜最大挠度为9μm时,镜面的曲率半径从610mm变至590mm,此时采用环形筋条结构的反射镜镜面和理想球面的面形偏差PV值仅为1μm,面形相对偏差为0.3%。     

On-line determination of average grain size of polycrystalline silicon from melt duration of molten silicon

We demonstrate a method of on-line determination of the average grain size of polycrystalline silicon (poly-Si) deduced from the melt duration of molten silicon during the phase transformation using an in-situ optical measurement system. Optical measurements revealed that the entire phase transformation processes are melting, nucleation, and resolidification. The average grain size of poly-Si can be directly deduced from the melt duration of molten Si under a thickness uniformity of precursor a-Si thin films below ±5%, a pulse-to-pulse variation in the excimer-laser-beam energy below 2% (standard deviation), and a laser-beam spatial homogeneity below 2.5%.     

Effects of processing parameters on laser cutting of aluminium-copper alloys using off-axial supersonic nozzles

Conventional laser cutting involves the utilization of converging coaxial nozzles to inject the assist gas used to remove the molten material. This processing system prevents the utilization of this technique to cut aluminium alloys for aerospace applications. The inefficient removal of molten material by the assist gas produces cuts with poor quality; very rough cuts, with a large amount of dross, and a large heat affected zone (HAZ) are obtained. An alternative to increase the assist gas performance is the utilization of off-axial supersonic nozzles. Removal of molten material is substantially increased and cuts with high quality are obtained. On the other hand, pulsed laser cutting offers superior results during the processing of high reflectivity materials as aluminium alloys. However, there are no experimental studies which explore the pulsed laser cutting of aluminium alloys by means of a cutting head assisted by an off-axis supersonic nozzle.The present work constitutes a quantitative experimental study to determine the influence of processing parameters on the cutting speed and quality criteria during processing by means of off-axial supersonic nozzles. Cutting experiments were performed in pulsed mode and the results explained under the basis of the molten material removal mechanisms. Performed experiments indicate a reduction in cutting speed as compared to continuous wave (CW) mode processing and the existence of two processing regimes as a function of the pulse frequency. Best results are obtained under the high pulse frequency one (f > 100 Hz) because the superior capabilities of molten material removal of the supersonic jets are completely exploited in this processing regime.     

Application of iterative path revision technique for laser cutting with controlled fracture

Laser cutting using the controlled fracture technique has great potential to be employed for the ceramic substrate machining. The heat produced on the surface of a ceramic substrate by the laser separates the substrate controllably along the moving path of the laser beam. Because the extension of the breaking frontier is lager than the movement of the laser spot, the actual fracture trajectory deviates from the desired trajectory when cutting a curve or cutting an asymmetrical straight line. To eliminate this deviation, the iterative learning control method is introduced to obtain the optimal laser beam movement path. The fracture contour image is grabbed by a CCD camera after laser cutting completion. A new image processing system is proposed to detect the deviation between the desired cutting path and the actual fracture trajectory. The laser-movement path for the next trial can then be determined according to the iterative path revision algorithm. The actual fracture trajectory converging to the desired cutting path is assured after a few path revisions. The experimental materials used in these experiments are alumina ceramics and the laser source is CO₂ laser. The proposed system can achieve a machining precision of about 0.1 mm.     

Repeatability characteristics of laser percussion drilling of stainless-steel sheets

An analysis on the repeatability of a laser percussion drilling process is conducted using a flash lamp pumped Nd:YAG laser on 2 mm thick stainless-steel sheets. Laser drilling process is finding increasingly widespread application in the industry and has continually attracted new interests to the industry in recent years. However, the inherent problem of hole geometry repeatability associated with laser percussion drilling is likely to limit the extent of industrial applications of the process. The characteristic of melt ejection is found to be dependent on the parameter setting and is shown to have a significant influence on entrance hole geometry and hence repeatability. The relationship between the percentage standard deviation of entrance hole diameter and the operating parameters is established, and varies between 1.8% and 5.6% in the operating range under this study.     

呼吸性粉尘吸收系数的光声光谱探测

针对呼吸性粉尘浓度连续、可靠、低成本的实时检测需求,实现了光谱应用技术创新,提出了一种基于光声光谱的呼吸性粉尘探测系统,低功率二极管激光器光谱中心波长为403.56 nm及相应的NO₂有效吸收截面为5.948 5×10-19 cm2·mole-1;通过频率扫描拟合得到了1.35 kHz的谐振频率。开展了光声池结构的影响分析,得到了光声池长度参数对本底噪声影响较小但对激光信号影响较大、内径参数对本底噪声存在一定影响但对本底噪声影响较小的结论。在考虑品质因数、加工条件、使用场合和待测对象属性等影响情况下,选用120 mm的长度参数和8 mm的内径参数;基于长度为60 mm、内径为25 mm的缓冲腔结构,开展了缓冲隔板对系统稳定性的影响分析,通过在缓冲腔中设置缓冲隔板,降低了本底噪声、稳定了系统,其幅值及波动由(2.83±0.11) μv稳定为(1.26±0.03) μv。分析得到了NO₂的比吸收系数为195.28 Mm-1·(mg·m-3)-1,利用NO₂气体在405 nm处的吸收对系统进行了标定,得到了拟合斜率为0.0436 8 μv/Mm-1、相关系数为0.998、池常数为300.24 Pa·cm·W-1的结论。同时在1 min平均时间下,得到了系统探测浓度下限及吸收系数为2.30 μg·m-3和0.448 Mm-1。基于标准微球的聚苯乙烯作为气溶胶发生器对象开展了呼吸性粉尘的吸收系数影响分析,进行了5μm以下不同数浓度颗粒及同一数浓度下不同粒径颗粒吸收系数的测试,结果表明：呼吸性粉尘的吸收系数和数浓度成正比,线性拟合后的斜率为10.598±0.641 96,相关系数为0.993;吸收系数曲线的方差在3～4 Mm-1间,不同粒径的颗粒对吸收系数存在着一定的影响;随着粒径增加,吸收系数随之增加。开展了环境大气中NO₂的测量,选用0.2 μm的过滤膜滤除粉尘的干扰,实验结果表明大气NO₂浓度为16.4~61.6 μg·m-3,平均浓度为41.1 μg·m-3。为了证实测量系统的准确性,与课题组自行研发的长光程差分吸收光谱系统(LP-DOAS)进行了对比测试,测试结果显示了本光声光谱系统和LP-DOAS系统测量NO₂浓度的相关性较好,线性拟合后的斜率为1.011 78±0.040 13,相关系数为0.947 81。开展了环境大气中呼吸性粉尘的测量,选用5 μm过滤片过滤环境大气,通过“NO₂+5 μm粉尘”和“NO₂+0.2 μm粉尘”两路测量对象的差分测量,得到了呼吸性粉尘的变化趋势,可以满足自然悬浮状态下的呼吸性粉尘吸收系数实时测量。