等离子吸收器

基于金属-电介质-金属表面等离子谐振原理的电磁波吸收器,可以实现多波长及宽波段入射电磁波吸收,其电磁波敏感波长决定于微纳结构的阵列形式、单元结构尺寸。从材料特性和结构匹配角度讨论了表面等离子电磁波吸收器的吸收机理;重点介绍不同微纳结构单元及阵列形式的吸收器的发展;介绍了微纳结构阵列吸收器在选择性热辐射、生物检测以及光电探测方面的应用;最后探讨了吸收器的谐振频谱可调性、以及提高吸收效率和能量转换等问题。     

表面等离子电磁波吸收器发展及应用

基于金属-电介质-金属表面等离子谐振原理的电磁波吸收器,可以实现多波长及宽波段入射电磁波吸收,其电磁波敏感波长决定于微纳结构的阵列形式、单元结构尺寸。从材料特性和结构匹配角度讨论了表面等离子电磁波吸收器的吸收机理;重点介绍不同微纳结构单元及阵列形式的吸收器的发展;介绍了微纳结构阵列吸收器在选择性热辐射、生物检测以及光电探测方面的应用;最后探讨了吸收器的谐振频谱可调性、以及提高吸收效率和能量转换等问题。     

飞秒激光正交线扫描诱导表面微纳结构

通过控制激光偏振与扫描方向,利用飞秒脉冲激光正交线扫描的微加工方式,在硅和不锈钢表面诱导出了规则分布的复合表面微纳结构并分析了激光能量密度对微纳表面结构形成的影响。实验显示:当激光的能量密度接近材料烧蚀阈值时,在硅表面诱导出了周期条纹嵌套纳米孔的双层复合二维结构,在不锈钢表面则诱导出了依赖于激光偏振方向的纳米点阵列分布,分析认为纳米点阵列是由周期条纹结构边缘发生断裂而生成的。另外,当激光的能量密度大于材料烧蚀阈值时,在硅和不锈钢表面会烧蚀出规则分布的微米级孔洞结构。实验结果表明:第一次扫描诱导出的表面微纳结构增加了对入射激光的吸收,促进入射激光与表面等离子体波的耦合,加强了后扫描的烧蚀效果,使得后扫描诱导出的微纳结构占主导。文中提出的正交线扫描的加工方式为微纳表面结构的制备提供了新的思路。     

可见光和近红外区域宽带超材料吸收器的设计

电磁波吸收器是一种能够吸收和湮灭电磁波的装置,广泛应用于军事、科技和人民生活的各个领域。基于超材料的吸收器由于其强大的吸收电磁波的能力、超薄特性以及设计的灵活性而受到广泛关注。但此类吸收器存在带宽窄的问题,因此,设计了一种基于金属–介电–金属（metal-dielectric-metal,MDM）结构的宽带超材料吸收器。对其吸收原理和物理机制进行了分析,并对其结构参数进行了仿真模拟。结果表明,超材料吸收器对于490～1 790 nm的入射光的吸收率高于80%,平均吸收率可达90%,最佳工作角度为30°。此外,通过修改单元结构的对称性,可以实现偏振相关调控。所提出的超材料吸收器非常适合于太阳能光伏、光通信、滤波和传感等方面的应用。     

金属纳米线阵列红外偏振器

本文用电磁场理论推导了多排金属纳米线有序阵列的光学损耗表达式，并进行了数值模拟。采用电化学沉积工艺将金属银电镀到氧化铝的孔中，得到含银纳米线氧化铝膜有序阵列复合结构，测量了含银纳米线氧化铝膜的光学损耗。理论和实验研究表明，含银纳米线氧化铝膜有序阵列的光学损耗显著依赖于光的偏振方向，在红外波段表现出良好的偏振特性，是一种新型红外微偏振器。     

基于等效层理论的薄膜滤光片中心波长消偏振膜系设计

针对薄膜滤光片倾斜入射时产生的偏振光中心波长分离现象和偏振相关损耗,本文利用等效层理论设计了倾斜入射下中心波长消偏振的100GHz信道间隔滤光片膜系结构,实现了薄膜滤光片的角度和波长调谐。首先通过相位关系分析,计算了滤光片间隔层的消偏振等效折射率,实现了不同偏振光中心波长的对准。然后,根据等效层理论,设计三层对称膜层结构实现了对间隔层中心波长消偏振等效折射率的替换。与原有的五层规整低偏振薄膜滤光片相比,本文提出的膜系结构更为简单,对消偏振等效折射率的替换更为精确。仿真和实验结果表明:该膜系结构的薄膜滤光片能实现0~20°倾斜入射的偏振光中心波长对准,偏振光波长偏离度小于0.03nm,波长调谐范围能达到35nm。     

曲面上化学气相沉积的二维材料研究

过渡金属硫系化合物二维材料因其体积小、直接带隙发光等特点,可作为微纳光学结构的优异介质材料而受到广泛关注。通过转移法得到的二维材料微纳光学结构,如光学微腔、微纳传感器等,容易引起材料污染和破损,对结构的功能特性影响很大。通过化学气相沉积法（CVD）,将硒化钨直接沉积在6 μm直径的二氧化硅（SiO₂）微球上,对微球上的材料进行成分表征,证明在微球上生长出了二维材料硒化钨,且证明了通过化学气相沉积法在曲面上沉积二维材料是可行的。这种化学气相沉积法直接生长的二维材料微纳球腔,有望应用于高性能光学传感器和微纳光源器件中。     

超构表面红外分光阵列设计

超构表面阵列分光具有高透射、低损耗、高集成度的特点,是当前微纳结构领域的研究热点.本文提出了一种由Si和SiO2组成的超构表面红外分光阵列.以不同波长的红外光入射单元,仅改变圆柱半径,分别计算不同波长的透射率和出射相位随半径的变化.根据广义斯涅尔定律,选择具有不同圆柱半径的若干单元组成超构表面分光周期.该周期对不同波长...     

飞轮组件微振动对高分辨率光学卫星光轴的影响

为了研究高分辨率光学卫星星上飞轮的微振动对卫星成像质量的影响,分别建立了飞轮扰动模型和整星结构动力学模型。首先,对飞轮组件系统进行了地面扰动测试,对实测扰动数据的分析表明,飞轮组件在与转速相关的一阶频率50Hz处产生一次谐波,在190Hz与280Hz左右存在与转速无关的一系列峰值。然后,对整星进行了单位正弦激励,获得了光轴角位移响应,并对其与飞轮实测扰动数据进行了集成分析。分析结果表明:整星在50~80 Hz和230~280Hz的角位移响应有较多的谐振响应频率成分,沿光轴方向和垂直光轴方向整星光轴的角位移最大谐振响应幅值分别为2.718″、2.739″,在245Hz左右存在较多幅值为0.5″量级的谐波。分析显示飞轮组件微振动对高分辨率光学卫星成像质量影响较大,得到的结果可为整星系统的优化设计和隔振补偿措施提供参考依据。     

仿生楔形阵列制备方法与方向性黏附特性研究

针对一次性蜡模或光刻工艺制备方向性黏附阵列效率低且工艺复杂的问题,提出了基于微纳3D打印技术的楔形微结构阵列高效制备工艺,制备的仿生楔形阵列材料具有良好的黏附性能和方向性黏附特性。首先,仿生设计了具有方向性特性的楔形阵列黏附结构。然后,利用微纳3D打印技术加工了相应的微结构阵列模具,发展了仿生黏附材料制备工艺,分析了楔形结构的轮廓精度。最后,搭建了实验测试平台,研究了剪切方向、剪切距离、预压力、脱附速度等因素对黏附性能的影响规律。结果表明,仿生楔形阵列黏附材料具有显著的方向性黏附特性,验证了微纳3D技术用于制备仿生方向性干黏附材料的可行性。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.