A color image encryption scheme based on a 2D coupled chaotic system and diagonal scrambling algorithm

A novel color image encryption scheme is developed to enhance the security of encryption without increasing the complexity. Firstly, the plain color image is decomposed into three grayscale plain images, which are converted into the frequency domain coefficient matrices(FDCM) with discrete cosine transform(DCT) operation. After that, a twodimensional(2D) coupled chaotic system is developed and used to generate one group of embedded matrices and another group of encryption matrices, respectively. The embedded matrices are integrated with the FDCM to fulfill the frequency domain encryption, and then the inverse DCT processing is implemented to recover the spatial domain signal. Eventually,under the function of the encryption matrices and the proposed diagonal scrambling algorithm, the final color ciphertext is obtained. The experimental results show that the proposed method can not only ensure efficient encryption but also satisfy various sizes of image encryption. Besides, it has better performance than other similar techniques in statistical feature analysis, such as key space, key sensitivity, anti-differential attack, information entropy, noise attack, etc.

Reformatted method for two-dimensional detector arrays measurement data in proton pencil beam scanning

The spatial resolution of a commercial two-dimensional(2D)ionization chamber(IC)array is limited by the size of the individual detector and the center-to-center distance between sensors.For dose distributions with areas of steep dose gradients,inter-detector dose values are derived by the interpolation of nearby detector readings in the conventional mathematical interpolation of 2D IC array measurements.This may introduce significant errors,particularly in proton spot scanning radiotherapy.In this study,by combining logfile-based reconstructed dose values and detector measurements with the Laplacian pyramid image blending method,a novel method is proposed to obtain a reformatted dose distribution that provides an improved estimation of the delivered dose distribution with high spatial resolution.Meanwhile,the similarity between the measured original data and the downsampled logfilebased reconstructed dose is regarded as the confidence of the reformatted dose distribution.Furthermore,we quantify the performance benefits of this new approach by directly comparing the reformatted dose distributions with 2D IC array detector mathematically interpolated measurements and original low-resolution measurements.The result shows that this new method is better than the mathematical interpolation and achieves gamma pass rates similar to those of the original low-resolution measurements.The reformatted dose distributions generally yield a confidence exceeding 95%.

ASME 2013 NDE中有关相控阵超声成像检测的要点评析 第二部分:计算机成像技术

探讨ASME最新版(2013)第Ⅴ卷《无损检测》第四章中有关承压设备相控阵超声成像检测的主要规定。评析承压设备焊接接头体积检测必须采用的CI(计算机成像)技术,突出相控阵超声检测扫查的典型模式,探测布图的典型示例,以及典型缺陷的相控阵读谱精要。意在对照国标国情,找差距、纠偏误,使中国企业正确执行ASME有关规范的水平更上一个台阶。

Light trapping enhanced broadband photodetection and imaging based on MoSe_(2)/pyramid Si vdW heterojunction

Two-dimensional(2D)layered materials have been considered promising candidates for next-generation optoelectronics.However,the performance of 2D photodetectors still has much room for improvement due to weak light absorption of planar 2D materials and lack of high-quality heterojunction preparation technology.Notably,2D materials integrating with mature bulk semiconductors are a promising pathway to overcome this limitation and promote the practical application on optoelectronics.In this work,we present the patterned assembly of MoSe_(2)/pyramid Si mixed-dimensional van der Waals(vdW)heterojunction arrays for broadband photodetection and imaging.Benefited from the light trapping effect induced enhanced optical absorption and high-quality vdW heterojunction,the photodetector demonstrates a wide spectral response range from 265 to 1550 nm,large responsivity up to 0.67 A·W^(-1),high specific detectivity of 1.84×10^(13)Jones,and ultrafast response time of 0.34/5.6μs at 0 V.Moreover,the photodetector array exhibits outstanding broadband image sensing capability.This study offers a novel development route for high-performance and broadband photodetector array by MoSe_(2)/pyramid Si mixed-dimensional heterojunction.

Image-Based Feature Extraction Technique for Inclined Crack Quanti cation Using Pulsed Eddy Current

Existing eddy current non-destructive testing(NDT) techniques generally do not consider the inclination angle of inclined cracks, which potentially harms a larger region of a tested structure. This work proposes the use of 2 D scan images generated by using pulsed eddy current(PEC) non-destructive testing(NDT) technique in the quantification of the inclination and depth of inclined cracks. The image-based feature extraction technique e ectively identifies the crack axis, which consequently enables extraction of features from the extracted linear scans. The technique extracts linear scans from the images to allow the extraction of three novel image-based features, namely the length of extracted linear scans(LLS), the linear scan skewness(LSS), and the highest value on linear scan(LSmax). The correlation of the three features to surface crack inclination angles and depths were analysed and found to be highly dependent on the crack depths, while only LLS and LSS are correlated to the crack inclination angles.

Bi_(2)O_(2)Se nanoplates for broadband photodetector and full-color imaging applications

Broadband light detection and sensing are widely applied in modern technology.As a promising candidate for next-generation two-dimensional(2D)optoelectronic material,bismuth oxyselenide(Bi_(2)O_(2)Se)nanoplates exhibit many prospects in the application of visible light detection due to their peculiar properties.In this work,we report the photodetection performance of single-crystal 2D Bi_(2)O_(2)Se nanoplates grown on SiO_(2)based on a ternary-alloy growth model by utilizing chemical vapor deposition(CVD).The Bi_(2)O_(2)Se nanoplates were found to have an even and uniform square shape with side lengths up to 15μm and an approximate thickness of 15 nm.A visible-light photodetector was fabricated based on a CVD-grown Bi_(2)O_(2)Se nanoplate,and characterized by a set of illumination experiments using a 400 nm laser at temperatures ranging from 77 to 370 K.The device exhibited superior performance at the temperature of 77 K,with a responsivity of 523 A/W,a specific detectivity of 1.37×10^(11)Jones,a response time of 0.2175 ms,an external quantum efficiency of 162,119.44%,resulting in high-quality and fullcolor imaging in the visible spectrum.These results indicate that the single-crystalline Bi_(2)O_(2)Se nanoplates have excellent potential in broadband photodetection and non-cryogenic imaging.

Layer-dependent signatures for exciton dynamics in monolayer and multilayer WSe2 revealed by fluorescence lifetime imaging measurement

Two-dimensional(2D)transition-metal dichalcogenide(TMD)materials have aroused noticeable interest due to their distinguished electronic and optical properties.However,little is known about their complex exciton properties together with the exciton dynamics process which have been expected to influence the performance of optoelectronic devices.The process of fluorescence can well reveal the process of exciton transition after excitation.In this work,the room-temperature layer-dependent exciton dynamics properties in layered WSe2 are investigated by the fluorescence lifetime imaging microscopy(FLIM)for the first time.This paper focuses on two mainly kinds of excitons including the direct transition neutral excitons and trions.Compared with the lifetime of neutral excitons(<0.3 ns within four-layer),trions possess a longer lifetime(~6.6 ns within four-layer)which increases with the number of layers.We attribute the longer-lived lifetime to the increasing number of trions as well as the varieties of trion configurations in thicker WSe2.Besides,the whole average lifetime increases over 10%when WSe2 flakes added up from monolayer to four-layer.This paper provides a novel tuneable layer-dependent method to control the exciton dynamics process and finds a relatively longer transition lifetime of trions at room temperature,enabling to investigate in the charge transport in TMD-based optoelectronics devices in the future.

Radial Hahn Moment Invariants for 2D and 3D Image Recognition

Recently, orthogonal moments have become efficient tools for two-dimensional and three-dimensional（2D and 3D） image not only in pattern recognition, image vision, but also in image processing and applications engineering. Yet, there is still a major difficulty in 3D rotation invariants. In this paper, we propose new sets of invariants for 2D and 3D rotation, scaling and translation based on orthogonal radial Hahn moments. We also present theoretical mathematics to derive them. Thus, this paper introduces in the first case new 2D radial Hahn moments based on polar representation of an object by one-dimensional orthogonal discrete Hahn polynomials, and a circular function. In the second case, we present new 3D radial Hahn moments using a spherical representation of volumetric image by one-dimensional orthogonal discrete Hahn polynomials and a spherical function. Further 2D and 3D invariants are derived from the proposed 2D and 3D radial Hahn moments respectively, which appear as the third case. In order to test the proposed approach, we have resolved three issues： the image reconstruction, the invariance of rotation, scaling and translation, and the pattern recognition. The result of experiments show that the Hahn moments have done better than the Krawtchouk moments, with and without noise. Simultaneously, the mentioned reconstruction converges quickly to the original image using 2D and 3D radial Hahn moments, and the test images are clearly recognized from a set of images that are available in COIL-20 database for 2D image, and Princeton shape benchmark（PSB） database for 3D image.

Two-dimensional transition metal chalcogenide nanomaterials for cancer diagnosis and treatment

For more than a decade,the exfoliation of graphene and other layered materials has led to a tremendous amount of research in two-dimensional(2D)materials,among which 2D transition metal chalcogenides(TMCs)nanomaterials have attracted much attention in a wide range of applications including photoelectric devices,lithium-ion batteries,catalysis,and energy conversion and storage owing to their unique photoelectric physical properties.With such large specific surface area,strong near-infrared(NIR)absorption and abundant chemical element composition,2D TMCs nanomaterials have become good candidates in biomedical imaging and cancer treatment.This review systematically summarizes recent progress on 2D TMCs nanomaterials,which includes their synthesis methods and applications in cancer treatment.At the end of this review,we also highlight the future prospects and challenges of 2D TMCs nanomaterials.It is expected that this work can provide the readers with a detailed overview of the synthesis of 2D TMCs and inspire more novel functional biomaterials based on 2D TMCs for cancer treatment in the future.

半导体激光扫描二维成像系统研制

介绍一种基于激光主动扫描物体，记录物体表面反射光强，然后重现物体二维图像的激光成像系统。该系统是进一步发展机器视觉三维距离成像的基础。

被动太赫兹成像二维扫描技术

太赫兹成像受探测器像元数少和无法进行大规模面阵集成的限制,大视场成像不可避免地要用到二维扫描。45°镜具有尺寸小,稳定性好,幅宽大等特点,可以用来实现被动太赫兹二维扫描成像。详细分析了45°镜扫描成像的工作原理和扫描方式,提出了绕Z轴摆动实现水平扫描,绕Y轴摆动实现垂直步进的扫描方案,计算了扫描轨迹,边沿视场成像畸变约3.2%,并通过成像实验对扫描方案进行了验证,得到了大视场下的被动太赫兹二维扫描图像。

航空遥感相机光学系统设计

地球静止轨道区域凝视成像监视的目的就是为了及时发现和生成地面目标特征和参数,光学成像遥感技术是现代对地观测的一个重要手段。通常长焦距、大视场遥感系统的光学系统设计是通过提高光学成像遥感器的质量、加长焦距、提高记录介质的分辨力、提高系统的传递函数等措施提高其性能的。介绍焦距为36 m,视场角达到0.75°的三反射式光学系统的设计过程,给出了设计结果。该系统实现了范围为90 km×90 km的瞬时对地扫描,摆动后能够对地面900 km×450 km区域实现凝视成像。

Tiny 2D silicon quantum sheets:a brain photonic nanoagent for orthotopic glioma theranostics

We report that atomically thin two-dimensional silicon quantum sheets(2D Si QSs),prepared by a scalable approach coupling chemical delithiation and cryo-assisted exfoliation,can serve as a highperformance brain photonic nanoagent for orthotopic glioma theranostics.With the lateral size of approximately 14.0 nm and thickness of about 1.6 nm,tiny Si QSs possess high mass extinction coefficient of 27.5 Lg^(-1)cm^(-1)and photothermal conversion efficiency of 47.2%at 808 nm,respectively,concurrently contributing to the best photothermal performance among the reported 2 D mono-elemental materials(Xenes).More importantly,Si QSs with low toxicity maintain the trade-off between stability and degradability,paving the way for practical clinical translation in consideration of both storage and action of nanoagents.In vitro Transwell filter experiment reveals that Si QSs could effectively go across the b End.3 cells monolayer.Upon the intravenous injection of Si QSs,orthotopic brain tumors are effectively inhibited under the precise guidance of photoacoustic imaging,and the survival lifetime of brain tumor-bearing mice is increased by two fold.Atomically thin Si QSs with strong light-harvesting capability are expected to provide an effective and robust 2D photonic nanoplatform for the management of brain diseases.

Single and multi domain buckled germanene phases on Al(111)surface

The simultaneous formati on of single domain(3×3)and multi domai n(√7×√7)R(±19.1°)germa nene phases on Al(111)surface in thesub-monolayer range was studied using seanning tunneling microscopy(STM)and density functional theory(DFT)based simulations.Experimental results revealed that both germa nene phases nu cleate and grow in dependently from each other and regardless of Al substratetemperature within significantly expanded range Ts=27-200℃.Our results unambiguously showed that STM images with hexagonalcontrast yield correct-resolved structure for both germanene phases,while honeycomb contrast is a result of an artificial tip-induced STM resolution.First-principles calculations suggested atomic models with strongly buckled germanene(2×2)/Al(111)(3×3)and(√3×√3)R30°/Al(111)(√7×√7)R(±19.1°)with one of eight and one of six Ge atoms protruding upward respectively,that consistently describe the experimentally observed STM images both for single and multi domai n surface phases.According to the DFT based simulati ons both germa nene(2×2)and(√3×√3)R30°superstructures have a stretched lattice strain with respect to the ideal free-standing germa nene by 6.2%and 13.9%,respectively.Hence,numerous small domains separated by domain boundaries in the(√3×√3)R30°/Al(111)(√7×√7)R(±19.1°)germanenephase tend to reduce the surface energy and prevent the formation of extended single domains,in contrast to the(2×2)/Al(111)(3×3)phase.However,our experimental results showed that the nucleation and growth of germa nene on Al(111)surface yield strong modifications of Alsurface even at room temperature(RT),which may be contributed to the formation of Al-Ge alloy due to Ge surface solid-states reactivitythat was ignored in recent studies.It is already evident from our present findings that the role of Al atoms in the formation of(3×3)and(√7×√7)R(±19.1°)germa nene phases is worthy to be carefully studied in the future,which could be an important knowledge for large-quantityfabrication of germanene on aluminum.

Real-time decay of fluorinated fullerene molecules on Cu（001） surface controlled by initial coverage

In this study, the evolution of C60F18 molecules on a Cu（001） surface was studied by means of scanning tunneling microscopy and density functional theory calculations. The results showed that fluorinated fuUerenes （tortoise-shaped polar C60F18） decay on Cu（001） surfaces by a step-by-step detachment of F atoms from the C60 cage. The most favorable adsorption configuration was realized when the F atoms of C60F18 pointed towards the Cu surface and six F atoms were detached from it. The results also showed that a further decay of C60F12 molecules strongly depended on the initial C60F18 coverage. The detached F atoms initially formed a two-dimensional （2D） gas phase which then slowly transformed into F-induced surface structures. The degree of contact between the C60F12 molecules and the Cu（001） surface depended on the density of the 2D gas phase. Hence, the life-time of fluorinated fullerenes was determined by the density of the 2D gas phase, which was affected by the formation of new F-induced structures and the decay of C60F12 molecules.

合成孔径激光成像雷达(Ⅳ):统一工作模式和二维数据收集方程

提出了合成孔径激光成像雷达(SAIL)的一种统一的工作模式,即激光雷达运动的同时进行光束扫描。同时推导了点目标激光雷达方程,据此还定义了SAIL二维数据收集方程,二维数据收集方程组是合成孔径激光雷达的数据产生和收集过程中的完整数学表达,并给出了统一模式的二维数据收集方程。从统一工作模式可以分解出条带扫描模式、聚束模式、滑动聚束模式和光束扫描模式,及其相应的简化二维数据收集方程。上述的光束扫描模式是一种激光雷达和被观察面之间相对静止而只采用光束扫描实现孔径合成成像的新方法,具有特殊的应用范围。

The potentially crucial role of quasi-particle interferences for the growth of silicene on graphite

A comprehensive picture of the initial stages of silicene growth on graphite is drawn.Evidence is shown that quasiparticle interferences play a crucial role in the formation of the observed silicene configurations.We propose,on one hand,that the charge modulations caused by those quantum interferences serve as templates and guide the incoming Si atoms to self-assemble to the unique(√3 x√3)R30°honeycomb atomic arrangement.On the other hand,their limited extension limits the growth to about 150 Si atoms under our present deposition conditions.The here proposed electrostatic interaction finally explains the unexpected stability of the observed silicene islands over time and with temperature.Despite the robust guiding nature of those quantum interferences during the early growth phase,we demonstrate that the window of experimental conditions for silicene growth is quite narrow,making it an extremely challenging experimental task.Finally,it is shown that the experimentally observed threedimensional silicon clusters might very well be the simple result of the end of the silicene growth resulting from the limited extent of the quasi-particle interferences.