Optimized compressive sampling for passive millimeter-wave imaging

In this paper, we briefly describe a single detector passive millimeter-wave imaging system, which has been previously presented. The system uses a cyclic sensing matrix to acquire incoherent measurements of the observed scene and then reconstructs the image using a Bayesian approach. The cyclic nature of the sensing matrix allows for the design of a single unified and compact mask that provides all the required random masks in a convenient way, such that no mechanical mask exchange is needed. Based on this setup, we primarily propose the optimal adaptive selection of sampling submasks out of the full cyclic mask to obtain improved reconstruction results. The reconstructed images show the feasibility of the imaging system as well as its improved performance through the proposed sampling scheme.     

Three-dimensional sensing based on a dynamically focused laser optical feedback imaging technique

A new method analogous to three-dimensional confocally based sensing is proposed. This method uses the technique of laser optical feedback imaging, which takes advantage of the resonant sensitivity of a short-cavity laser to frequency-shifted optical feedback for highly sensitive detection, making it ideal for surface and volume measurements of noncooperative targets. Rapid depth scanning is made possible by use of an electrically controlled variable-focus lens. The system is able to detect height discontinuities, and because detection occurs along the axis of projection the system does not have problems of shadow. Preliminary results for a depth range of 15 mm and a resolution of 100 mum are presented.     

Implementation of vibro-acoustography on a clinical ultrasound system

Vibro-acoustography is an ultrasound-based imaging modality that uses two ultrasound beams of slightly different frequencies to produce images based on the acoustic response caused by harmonic ultrasound radiation force excitation at the difference frequency between the two ultrasound frequencies. Vibro-acoustography has demonstrated feasibility and usefulness in imaging of breast and prostate tissue. However, previous studies have been performed either in controlled water tank settings or a prototype breast scanner equipped with a water tank. To make vibro-acoustography more accessible and relevant to clinical use, we report here on the implementation of vibro-acoustography on a General Electric Vivid 7 ultrasound scanner. In this paper, we will describe software and hardware modifications that were performed to make vibro- acoustography functional on this system. We will discuss aperture definition for the two ultrasound beams and beamforming using a linear-array transducer. Experimental results from beam measurements and phantom imaging studies will be shown. The implementation of vibro-acoustography provides a step toward clinical translation of this imaging modality for applications in various organs including breast, prostate, thyroid, kidney, and liver.     

A linearised hp–finite element framework for acousto‐magneto‐mechanical coupling in axisymmetric MRI scanners

We propose a new computational framework for the treatment of acousto‐magneto‐mechanical coupling that arises in low‐frequency electro‐magneto‐mechanical systems such as magnetic resonance imaging scanners. Our transient Newton–Raphson strategy involves the solution of a monolithic system obtained from the linearisation of the coupled system of equations. Moreover, this framework, in the case of excitation from static and harmonic current sources, allows us to propose a simple linearised system and rigorously motivate a single‐step strategy for understanding the response of systems under different frequencies of excitation. Motivated by the need to solve industrial problems rapidly, we restrict ourselves to solving problems consisting of axisymmetric geometries and current sources. Our treatment also discusses in detail the computational requirements for the solution of these coupled problems on unbounded domains and the accurate discretisation of the fields using hp–finite elements. We include a set of academic and industrially relevant examples to benchmark and illustrate our approach. Copyright © 2017 The Authors. International Journal for Numerical Methods in Engineering Published by John Wiley & Sons, Ltd.     

Variable Focusing Microlens Chip for Potential Sensing Applications

A variable focusing microlens chip, which has the capability of adjusting its focal length over a wide range without any mechanical driving parts, is reported in this paper. The packaged microlens chip consists of a flexible polymer lens, a fluidic chamber, an integrated sensor, and an actuator. A thermal actuator is introduced into this variable focusing microlens to obtain relatively large actuation force and displacement. The hemispheric convex polymer lens provides an initial focal point without being actuated. The focal length change is controlled by varying the voltage applied to the thermal actuator. A 1.9-mm-diameter polymer lens is made to test the performance of the device. The focal length of this chip varies from 14.658 to 2.782 mm, which corresponds to the change of numerical aperture from 0.078 to 0.412. Based on the working mechanism and constructing method of the single lens chip, a variable focusing microlenses array has been fabricated for future testing and application. Potential sensing applications for single lens and array include cell detection and immobilization, optical sensors, lab-on-a-chip, ophthalmic lens systems, microphotonics, high throughput scanning, and confocal imaging system     

Remote sensing of mechanical properties of materials using a novel ultrasound transducer and signal processing

An ultrasound-based remote sensing method to evaluate the mechanical properties of materials is presented. This method consists of a disk-shaped, piezoelectric transducer, operating at its resonance frequency, and a phase-shifted, feedback circuit. Mechanical parameters are derived by analyzing the signal contained in the phase-shifted values of the reflected signal. It is concluded that, using this novel transducer system and signal processing, remote mechanical measurements can be made. Such measurements obviate the need to apply the force-deformation approach and may be used to enable stiffness imaging.     

Light‐Activated Nanoprobes for Biosensing and Imaging

Fluorescent nanoprobes are indispensable tools to monitor and analyze biological species and dynamic biochemical processes in cells and living bodies. Conventional nanoprobes have limitations in obtaining imaging signals with high precision and resolution because of the interference with biological autofluorescence, off‐target effects, and lack of spatiotemporal control. As a newly developed paradigm, light‐activated nanoprobes, whose imaging and sensing activity can be remotely regulated with light irradiation, show good potential to overcome these limitations. Herein, recent research progress on the design and construction of light‐activated nanoprobes to improve bioimaging and sensing performance in complex biological systems is introduced. First, recent innovative strategies and their underlying mechanisms for light‐controlled imaging are reviewed, including photoswitchable nanoprobes and phototargeted nanosystems. Subsequently, a short highlight is provided on the development of light‐activatable nanoprobes for biosensing, which offer possibilities for the remote control of biorecognition and sensing activity in a precise manner both temporally and spatially. Finally, perspectives and challenges in light‐activated nanoprobes are commented.     

Nanodiamonds That Swim

Nanodiamonds are emerging as nanoscale quantum probes for bio‐sensing and imaging. This necessitates the development of new methods to accurately manipulate their position and orientation in aqueous solutions. The realization of an “active” nanodiamond (ND) swimmer in fluids, composed of a ND crystal containing nitrogen vacancy centers and a light‐driven self‐thermophoretic micromotor, is reported. The swimmer is propelled by a local temperature gradient created by laser illumination on its metal‐coated side. Its locomotion—from translational to rotational motion—is successfully controlled by shape‐dependent hydrodynamic interactions. The precise engineering of the swimmer's geometry is achieved by self‐assembly combined with physical vapor shadow growth. The optical addressability of the suspended ND swimmers is demonstrated by observing the electron spin resonance in the presence of magnetic fields. Active motion at the nanoscale enables new sensing capabilities combined with active transport including, potentially, in living organisms.     

大型平行光管像质实时监测的可行性论证

针对目前大型平行光管成像质量监测的现状,本文提出了一种对平行光管进行实时监测的新方法,验证了这种监测方法的可行性.该方法根据光管自准检测原理,采用小平面镜对光管像质进行实时监测,计算了在一个焦深范围内小平面镜转角误差大小.实验结果证明在一个焦深范围内用精度0.02"的自准直仪,可将小平面镜转角误差控制在0.2"以内,对大型平行光管起到了进行实时监测的作用.大型平行光管在空间遥感设备中运用广泛,此检测光管像质的方法在工程上将起到积极的作用.     

Stereopsis-Inspired 3D Visual Imaging System Based on 2D Ruddlesden–Popper Perovskite

Stereopsis is of great important functions for humans to perceive and interact with the world. To realize the function of stereoscopic imaging, optoelectronic sensors shall possess good photoresponsive performance, multidirectional sensing, and 3D building capabilities. However, the current imaging sensors are mainly focused on 2D imaging, limiting their practical application scenarios. In this study, a stereopsis-inspired flexible 3D visual imaging system (VIS) based on 2D Ruddlesden–Popper perovskite is demonstrated. The 3D-VIS consists of 800 device units, each of which demonstrates excellent photoresponse performance, mechanical characteristics, and environmental stability. In addition to the capability of detecting 2D reflective images, the 3D-VIS realizes the function of detecting the depth of field and fusing object projections of two directions to invert the 3D image by utilizing voxels to rebuild the spatial structure of the object. In the future, the 3D-VIS will have broad application prospects in medical imaging, virtual reality, industrial automation, and other fields.     

A Novel Design of Multi‐Mechanoresponsive and Mechanically Strong Hydrogels

A newly developed polyacrylamide‐co ‐methyl acrylate/spiropyran (SP) hydrogel crosslinked by SP mechanophore demonstrates multi‐stimuli‐responsive and mechanically strong properties. The hydrogels not only exhibit thermo‐, photo‐, and mechano‐induced color changes, but also achieve super‐strong mechanical properties (tensile stress of 1.45 MPa, tensile strain of ≈600%, and fracture energy of 7300 J m^?2). Due to a reversible structural transformation between spiropyran (a ring‐close) and merocyanine (a ring‐open) states, simple exposure of the hydrogels to white light can reverse color changes and restore mechanical properties. The new design approach for a new mechanoresponsive hydrogel is easily transformative to the development of other mechanophore‐based hydrogels for sensing, imaging, and display applications.     

我国果蔬低温贮藏保鲜发展状况与展望

综述我国果蔬低温贮藏保鲜发展状况,包括机械冷藏、机械气调冷藏、机械减压冷藏、机械湿冷冷藏和机械冰库冷藏等冷藏场所及设施。介绍数字化与智能化控制、环境友好型制冷工质及制氮方法及多种温度和气调使用形式等保鲜科技及技术支持与新技术开发。提出研究果蔬物流保鲜全程控制体系、完善果蔬冷链流通体系和冷藏库建设以物流现代化为基础的展望。     

基于运动补偿的机械扫描式高频超声成像技术

由于高频相控阵超声成像系统和多阵元高频超声探头工艺复杂,成本较高、实现难度大,单阵元的机械扫描式高频超声成像探头因其结构简单、实现方便、成本低的特点仍具有较高的理论研究和实际应用价值。但目前机械扫描式成像系统的机械扫描的非均匀性是阻碍其性能进一步提升的主要问题,因此文章设计了一种高精度运动补偿的机械扫描式高频超声成像探头和系统,通过理论计算分析、运动系统结构设计加工、扫描成像系统搭建实现了高精度的扫描成像。最后,线靶和仿体的成像实验结果显示,经运动补偿后,系统能够有效克服传统机械扫描成像的伪影和失真,实现的横向几何位置精度误差为1.34%,纵向几何位置精度误差为1.33%,面积测量精度误差为3.15%,为高精度、高频超声成像算法和系统研究提供了一种有效的手段。     

Application of infrared imaging to the study of controlled failure of thermal barrier coatings

A technique that uses high resolution infrared (IR) imaging was developed to track and analyze damage evolution of thermal barrier coatings (TBCs) during controlled mechanical testing of a TBC specimen. Coating debonding and spallation were examined during a monotonic load-to-TBC-failure test. The infrared imaging, in concert with a controlled thermal gradient in the specimen, was particularly effective in identifying and tracking localized damage evolution because the damage in the TBC was always associated with a measurable surface-temperature change. It is demonstrated that the combined use of high-resolution infrared imaging and controlled mechanical testing of TBCs is an effective method to characterize the evolution of their failure.     

Chemiluminescence imaging immunoassay of multiple tumor markers for cancer screening

A sensitive chemiluminescence (CL) imaging immunoassay method for detection of multiple tumor markers with high throughput, easy operation, and low cost was developed. The immunosensor array was prepared by covalently immobilizing capture antibodies on corresponding sensing sites on a silanized disposable glass chip. Gold nanoparticle-based bioconjugates with a high molar ratio of horseradish peroxidase (HRP) to detection antibodies were used for signal amplification. Under a sandwich immunoassay, the CL signals triggered by HRP captured on each sensing cell were collected by a charge-coupled device for simultaneous measurement of biomarkers and combination diagnosis of certain tumors. As a proof of concept, the immunosensor array was applied to detect α-fetoprotein, carcinoma antigen 125, carbohydrate antigen 153, and carcinoembryonic antigen and to screen patients with liver, breast, or ovarian cancers. This method showed wide linear ranges over 5 orders of magnitude and much lower detection limits than previously reported multiplexed immunoassays. The high throughput and acceptable stability, reproducibility, and accuracy showed good applicability of the proposed multiplex CL imaging immunoassay in clinical diagnosis.     

An optical fiber sensor for remote pH sensing and imaging

A fiber-optical probe for pH sensing and real-time imaging is successfully fabricated by connecting a polymer imaging fiber and a gradient index (GRIN) lens rod which was modified with a sensing film. By employing an improved metallographic microscope, an optical system is designed to cooperate with the probe. This novel technique has high-quality imaging capabilities for observing remote samples while measuring pH. The linear range of the probe is pH 1.2-3.5. This technique overcomes the difficulty that high-quality images cannot be obtained when directly using conventional imaging bundles for pH sensing and imaging. As preliminary applications, the corrosion behavior of an iron screw and the reaction process of rust were investigated in buffer solutions of pH 2.0 and 2.9, respectively. The experiment demonstrated that the pH values of the analytes' surface were higher than that of buffer solutions due to the chemical reaction. It provides great potential for applications in optical multifunctional detection, especially in chemical sensing and biosensing.     

Durable metal-enhanced fluorescence flexible platform by in-situ growth of micropatterned Ag nanospheres

Here, we demonstrate an in-situ growth of micropatterned silver nanospheres(Ag NS) array on transparent polyimide(PI), namely PI-Ag substrate, applied as a flexible platform for metal-enhanced fluorescence(MEF). The scheme proposed here can easily control the grid formation of Ag NSs and the particle size inside, thus achieving patterned fluorescence imaging and MEF efficiency optimization. Meanwhile, the magnitude of enhanced intensity, relying on the distance between Ag NSs and emissive molecules, was systematically investigated by exploring diverse polyethyleneimine(PEI) spacer thickness. Consequently,an optimal enhancement factor of 7.9 and a pattern of grid fluorescence imaging was obtained with an insertion of 10 nm PEI on the PI-Ag(25 nm) platform. Moreover, owing to robust adhesion between Ag NSs and PI film by in-situ growth, this flexible PI-Ag MEF platform maintained a stable MEF efficiency even after taking mechanical bending for 1000 cycles. This new surface-confined micropatterned Ag NSs PI film provides a promising candidate in design flexible MEF platforms for future analytical and clinical sensing applications.     

A Multimodal Tomography System Based on ECT Sensors

A new noninvasive system for multimodal electrical tomography based on electrical capacitance tomography (ECT) sensor hardware is proposed. Quasistatic electromagnetic fields are produced by ECT sensors and used for interrogating the sensing domain. The new system is noninvasive and based on capacitance measurements for permittivity and power balance measurements for conductivity (impedance) imaging. A dual sensitivity map of perturbations in permittivity and conductivity is constructed. The measured data along with the sensitivity matrix are used for the actual image reconstruction. The new multimodal tomography system has the advantage of using already established reconstruction techniques, and the potential for combination with new reconstruction techniques by taking advantage of combined conductivity/permittivity data. Moreover, it does not require direct contact between the sensor and the region of interest. The system performance has been tested on representative data, producing good results     

Pd nanowires as new biosensing materials for magnified fluorescent detection of nucleic acid

The designed synthesis of new nanomaterials with controlled shape, composition, and structure is critical for tuning their physical and chemical properties, and further developing interesting analytical sensing devices. Herein, we presented that Pd nanowires (NWs) can be used as a new biosensing platform for high-sensitivity nucleic acid detection. The general sensing concept is based on the fact that Pd NWs can adsorb the fluorescently labeled single-stranded DNA probe and lead to substantial fluorescence quenching of dye, followed by specific hybridization with the complementary region of the target DNA sequence. This results in desorption of double-stranded DNA from Pd NWs surface and subsequent recovery of fluorescence. Furthermore, an amplification strategy based on Pd NWs for nucleic acid detection by using exonuclease III (Exo III) was demonstrated. The present dual-magnification sensing system combined Pd NWs with Exo III has a detection range of 1.0 nM to 2.0 μM with the detection limit of 0.3 nM (S/N = 3), which is about 20-fold higher than that of traditional unamplified homogeneous assays.     

Investigation of absorbed radiation dose in refraction-enhanced breast tomosynthesis by a Laue case analyser

An early diagnosis system for breast cancer using refraction-enhanced breast tomosynthesis is under development. Tomograms of breast specimens based on refraction-contrast were demonstrated using the simplest shift-and-add tomosynthesis algorithm. Raw projection image data of breast specimens for tomosynthesis were acquired for a total of 51 views over an angle of 50°, in increments of 1°, by rotating the object. The incident X ray was monochromatic synchrotron radiation with 20 keV. The purpose of this study was to estimate the absorbed dose of a new X-ray imaging method. As breast cancer almost always arises in glandular breast tissue, the average absorbed dose in such glandular tissue should be measured to estimate the radiation risk associated with mammography. The absorbed dose of the mammary gland due to monochromatic X rays was calculated by the Monte Carlo method, and the optimal X ray energy range for refraction-enhanced breast tomosynthesis was investigated through actual measurements. Compared with the conventional method, it was found to be below one-sixth per inspection.