Low Detection Efficiency Research Articles

Periodic X-ray sources in the Galactic bulge: application of the Gregory–Loredo algorithm

ABSTRACT We present a systematic study of periodic X-ray sources in the Limiting Window (LW), a ∼70 arcmin2 field representative of the inner Galactic bulge and the target of ∼1 Ms Chandra observations. Using the Gregory–Loredo algorithm, which applies Bayes’s theorem to the phase-folded light curve and is well suited for irregularly sampled X-ray data, we detect 25 periodic signals in 23 discrete sources, among which 15 signals are new discoveries and two sources show dual periods. The vast majority of the 23 periodic sources are classified as magnetic cataclysmic variables (CVs), based on their period range, X-ray luminosities, spectral properties, and phase-folded light curves that are characteristic of spin modulation. Meanwhile, there is a paucity of non-magnetic CVs seen as periodic sources, which can be understood as due to a low detection efficiency for eclipsing sources. Under reasonable assumptions about the geometry of magnetic CVs and a large set of simulated X-ray light curves, we estimate the fraction of magnetic CVs in the inner Galactic bulge to be ≲23 per cent, which is similar to that in the solar neighbourhood. There is an apparent lack of long-period (≳3.3 h) CVs in the LW, when contrasted with the range of known CVs in the solar neighbourhood. We suggest that this might be an age effect, in the sense that CVs in the inner bulge are more evolved systems and have substantially shrunk their orbits.

Experimental certification of quantum dimensions and irreducible high-dimensional quantum systems with independent devices

Dimensionality plays an important role in various information-theoretic tasks and can be seen as a key resource for quantum information processing. In this work, for the first time to the best of our knowledge, we report an experimental test of classical and quantum dimensions in a prepare-and-measure scenario through a nonlinear dimension witness (NDW), where the preparer and the measurer have no shared randomness. We propose a theoretical method to certify whether the generated states can be decomposed as products of lower dimensional states with the NDW, certify the dimension of the high-dimensional system, and identify whether the quantum system is irreducible in a unified picture in our experiment. To demonstrate the practicability of this method, we experimentally witness the generation of classical and quantum systems encoded in the high-dimensional orbital angular momentum (OAM) state under the effects of atmospheric turbulence. Our results show that this nonlinear dimension witness is highly robust and can be used in the presence of noise and low detection efficiency; hence, we estimate the dimension in our experiment in a detection-loophole-free manner through the NDW. We believe our work opens new avenues for dimension witnesses, especially for device-independent estimation of quantum systems and quantum communications.

Streaming-enhanced, chip-based biosensor with acoustically active, biomarker-functionalized micropillars: A case study of thrombin detection

Enzyme-linked immunosorbent assay is a widely used analytical technique for detecting and quantifying disease-specific protein biomarkers. Despite recent progresses in disease-specific protein biomarkers detection with microfluidic chips, many devices still suffer from the limited mass transport of target molecules, and consequently low detection efficiency or long incubation time. In this work, we present a novel strategy to significantly enhance the sensing efficiency of a chip-based biosensor by exploiting micro-streaming in an acoustofluidic device, which boosts intermolecular interactions and a hybridization chain reaction to increase the fluorescent signals. This device was made of a microfluidic chip that contains an array of PDMS micropillars in a ship-shaped microchannel. And the inner surface of the channel was functionalized with capture aptamers that bind with thrombin, chosen as a model target molecule. An ultrasonic transducer underneath the chip operating at 150 kHz generates circular micro-streaming flows around the pillars that significantly improves the binding efficiency of thrombin with capture aptamers by 1) increasing the retention time and 2) enhancing mass transport via local convection versus diffusion. The effects of ultrasound parameters, such as operating frequencies and voltages, on the distribution and magnitude of flows were optimized to obtain a better performance of the sensor chip. Under the optimized conditions, the detection limit was increased by one order of magnitude. Although this work has focused on the detection of thrombin as a model molecule, this streaming-enhanced, microstructure-based sensing strategy can be applied to detect a wide range of molecules or even cells.

Research on Detection and Recognition of Abnormal Behavior in Video

In order to solve the problems of low detection efficiency and long working time in traditional video surveillance systems for abnormal behavior detection and recognition methods, a new method for abnormal behavior detection and recognition in video surveillance systems is proposed. This method first completes image preprocessing through four steps: video image noise filtering, image grayscale correction, binarization processing, and image edge detection; then, based on the characteristics of the image abnormal target, the key frame of the abnormal image is detected and the data is dissected to complete the abnormal behavior detection of the video monitoring system; finally analyze the video image rules through adaptive algorithms, and use the computer’s visual detection principle to change with the scene environment to identify the abnormal behavior of the video surveillance system. In order to detect the effect of the method, a comparative experiment was set up. The experimental results show that the new method can accurately detect abnormal behavior in a short time and has a strong working ability.

Deep Learning Based Electric Pylon Detection in Remote Sensing Images

The working condition of power network can significantly influence urban development. Among all the power facilities, electric pylon has an important effect on the normal operation of electricity supply. Therefore, the work status of electric pylons requires continuous and real-time monitoring. Considering the low efficiency of manual detection, we propose to utilize deep learning methods for electric pylon detection in high-resolution remote sensing images in this paper. To verify the effectiveness of electric pylon detection methods based on deep learning, we tested and compared the comprehensive performance of 10 state-of-the-art deep-learning-based detectors with different characteristics. Extensive experiments were carried out on a self-made dataset containing 1500 images. Moreover, 50 relatively complicated images were selected from the dataset to test and evaluate the adaptability to actual complex situations and resolution variations. Experimental results show the feasibility of applying deep learning methods to electric pylon detection. The comparative analysis can provide reference for the selection of specific deep learning model in actual electric pylon detection task.

Toward understanding and optimizing Au-hyperdoped Si infrared photodetectors

Au-hyperdoped Si absorbs near-infrared (NIR) light and recent efforts have successfully produced Si-based NIR photodetectors based on this property but with low detection efficiencies. Here, we investigate the differences between the optical and photocurrent properties of Au-hyperdoped Si. Although defects introduced during fabrication of these materials may not exhibit significant optical absorption, we show that they can produce a measurable photocurrent under NIR illumination. Our results indicate that the optimal efficiency of impurity-hyperdoped Si materials is yet to be achieved and we discuss these opportunities in light of our results. This work thus represents a step forward in demonstrating the viability of using impurity-hyperdoped Si materials for NIR photodetection.

Design on the Inner Wall Crawling and Inspecting Robot for Offshore Platform Leg

Background: The legs are important base mechanism and have a key effect on the stability and security of movable offshore platform. In the application field, the work of defects detection is operated in a manual way for offshore platform leg. The main disadvantages of manual inspection can be summarized as follows: high detection cost and risk, low detection coverage and efficiency, etc. Objective: To develop a robot with an inspecting system that can crawl on the inner wall surface of the offshore platform leg, and inspect the surface defects through the inspecting system. Methods: Based on our patented technologies and the application requirements, the telescopic mechanisms, constituted by motor-screw-nut mechanism, are applied to design the body and legs mechanism of the robot. The vacuum sucker groups are applied to design the adsorption mechanism of the robot. The PLC is applied to design the measurement and movement control system. The laser ranging sensors are applied to realize the function of obstacle detection, robot location and pose analysis. The camera and its driving system are applied to design the image acquisition system. The wireless bridge is applied to design the message remote transmission system. Results: Based on the structure characteristic and the defect inspecting requirement of offshore platform leg, the wall crawling robot and its inspecting system are designed in this study. Conclusion: A series of experiments show that the robot and its inspecting system meet the demand of field applications.

Windowless thin layer electrochemical Raman spectroscopy of Ni-Fe oxide electrocatalysts during oxygen evolution reaction

In-situ Raman spectroelectrochemistry is a powerful tool to understand the structures and reaction mechanisms of electrochemical interfaces yet usually suffers from a low sensitivity and detection efficiency. Herein, we develop a windowless thin layer electrochemical cell design to improve the detection efficiency of in-situ Raman spectroscopy for practical nanoscale electrocatalysts. This was achieved by perforating a hole in the optical window of the cell, which not only eliminates the refraction of light by the window but also induces a meniscus thin electrolyte layer on the working electrode, thus significantly improving the detection efficiency of Raman spectra. We successfully applied this method to conduct in-situ Raman spectroscopy of structural evolutions of two representative Ni-Fe oxide catalysts (layered double hydroxides and spinel oxides) during oxygen evolution reaction (OER) electrocatalysis. It was shown that both catalysts underwent surface transformation to oxyhydroxides and formed active oxygen species at OER relevant potentials. However, the extent of the surface transformation was much lower on the Ni-Fe spinel catalyst, accounting for its lower OER activity. We further show that adding a carbon support can promote the surface transformation of Ni-Fe spinel to oxyhydroxides, thus significantly increasing the electrocatalytic activities. The established windowless thin layer method provides a new way to conduct in-situ electrochemical Raman spectroscopy of a wide range of materials and may be also combined with surface-enhanced Raman spectroscopic methods.

Ship Target Automatic Detection Based on Hypercomplex Flourier Transform Saliency Model in High Spatial Resolution Remote-Sensing Images.

Efficient ship detection is essential to the strategies of commerce and military. However, traditional ship detection methods have low detection efficiency and poor reliability due to uncertain conditions of the sea surface, such as the atmosphere, illumination, clouds and islands. Hence, in this study, a novel ship target automatic detection system based on a modified hypercomplex Flourier transform (MHFT) saliency model is proposed for spatial resolution of remote-sensing images. The method first utilizes visual saliency theory to effectively suppress sea surface interference. Then we use OTSU methods to extract regions of interest. After obtaining the candidate ship target regions, we get the candidate target using a method of ship target recognition based on ResNet framework. This method has better accuracy and better performance for the recognition of ship targets than other methods. The experimental results show that the proposed method not only accurately and effectively recognizes ship targets, but also is suitable for spatial resolution of remote-sensing images with complex backgrounds.

Wide-Field Fluorescence Lifetime Imaging of Single Molecules.

Fluorescence lifetime imaging (FLIM) has become an important microscopy technique in bioimaging. The two most important of its applications are lifetime-multiplexing for imaging many different structures in parallel, and lifetime-based measurements of Förster resonance energy transfer. There are two principal FLIM techniques, one based on confocal-laser scanning microscopy (CLSM) and time-correlated single-photon counting (TCSPC) and the other based on wide-field microscopy and phase fluorometry. Although the first approach (CLSM-TCSPC) assures high sensitivity and allows one to detect single molecules, it is slow and has a small photon yield. The second allows, in principal, high frame rates (by 2-3 orders of magnitude faster than CLSM), but it suffers from low sensitivity, which precludes its application for single-molecule imaging. Here, we demonstrate that a novel wide-field TCSPC camera (LINCam25, Photonscore GmbH) can be successfully used for single-molecule FLIM, although its quantum yield of detection in the red spectral region is only ∼5%. This is due to the virtually absent background and readout noise of the camera, assuring high signal-to-noise ratio even at low detection efficiency. We performed single-molecule FLIM of different red fluorophores, and we use the lifetime information for successfully distinguishing between different molecular species. Finally, we demonstrate single-molecule metal-induced energy transfer (MIET) imaging which is a first step for three-dimensional single-molecule localization microscopy (SMLM) with nanometer resolution.

Sensitivity analysis of radial defect detection of gun barrel based on ultrasonic guided wave

In this paper, aiming at the low efficiency of defect detection of weapon equipment, ultrasonic guided wave non-destructive testing technology is proposed to detect the radial wear defects in gun barrel which have a great impact on its combat effectiveness. At the same time, the sensitivity of different modes of L0,2 and t0,1 ultrasonic guided waves to the detection of such defects is analyzed in this paper, so as to provide theoretical guidance for the mode selection of ultrasonic guided waves in the next practical detection of gun barrel.

Performance Assessment of Amplification and Discrimination Electronic Devices for Passive Neutron Measurements

The assessment of fissile material mass is a key requirement to enhance radioactive waste management and to ensure a high level of safety in the nuclear industry. The assessment of plutonium fissile mass by passive coincidence measurements is usually obtained by detecting the neutrons generated by the spontaneous fissions of Pu isotopes. The detection and the quantification of a fissile mass in the radioactive waste can also be carried out using active neutron interrogation with a pulsed D-T neutron generator. The 14-MeV neutrons are moderated to induce fissions in the uranium and plutonium-contaminated waste. The emitted neutron signal can be analyzed by considering their detection time after the generator pulse. Data are measured according to the principles of the neutron measurement techniques. As proportional counters filled with 3He gas display high neutron detection efficiency and good gamma-ray immunity, they are the reference detector for passive neutron coincidence counting. A charge preamplifier or a current amplifier, depending on applications, collects the electric pulse produced by neutron interaction in the 3He gas, and a threshold discriminator produces a logic pulse used for neutron counting. This article describes the performance assessment of different commercially-available electronics from Mirion Technologies, Precision Data Technology (PDT), Mesytec, as well as MONACO electronics originally developed by CEA LIST for fission chamber measurements in experimental reactors. Comparative passive neutron measurements are carried out with these electronics at CEA/DEN Nuclear Measurement Laboratory in Cadarache. Overall, PDT and Mesytec electronics show similar detection efficiency as the ACH-NA98 charge amplifier, which is commonly used in our laboratory for such applications. However, MONACO electronics have a lower detection efficiency, similar to the Mirion 7820 current amplifier used in specific high-count rate applications. An optimization of MONACO settings would probably be necessary to adapt to 3He counters instead of fission chambers.

Simultaneous Mid-Infrared Gas Sensing and Upconversion Based on Third Harmonic Generation in Cascaded Waveguides

The performance of conventional gas sensors based on light absorption in the mid-infrared are limited by the high-cost and low efficiency of photon detection at these wavelengths. In this paper, cascaded suspended waveguides are proposed and analyzed for mid-infrared gas sensing with enhanced detection limit. The cascaded structure contains two sections in which the first part is optimized for light absorption and the other one is tailored to satisfy the phase matching condition for third harmonic generation toward near-infrared wavelengths. In this configuration, the input mid-infrared light firstly experiences “fingerprint” frequency absorption in the on-chip gas chamber. Consequently, the residuary light produces third harmonic radiation in the second section. Benefiting from the nonlinear relation between pump and harmonic power, the sensitivity of the sensor is significantly improved. Moreover, the signal is up converted from mid-infrared to near-infrared and thus it can be easily detected by efficient near-infrared detectors. The results show that the detection limit can reach the order of nmol/L and the absorption lengths can be reduced to three times shorter comparing to direct mid-infrared detection. The proposed configuration has great potential for high performance on-chip gas sensing.

Measurement of the Acoustic Non-Linearity Parameter of Materials by Exciting Reversed-Phase Rayleigh Waves in Opposite Directions.

The acoustic non-linearity parameter of Rayleigh waves can be used to detect various defects (such as dislocation and micro-cracks) on material surfaces of thick-plate structures; however, it is generally low and likely to be masked by noise. Moreover, conventional methods used with non-linear Rayleigh waves exhibit a low detection efficiency. To tackle these problems, a method of exciting reversed-phase Rayleigh waves in opposite directions is proposed to measure the acoustic non-linearity parameter of materials. For that, two angle beam wedge transducers were placed at the two ends of the upper surface of a specimen to excite two Rayleigh waves of opposite phases, while a normal transducer was installed in the middle of the upper surface to receive them. By taking specimens of 0Cr17Ni4Cu4Nb martensitic stainless steel subjected to fatigue damage as an example, a finite element simulation model was established to test the proposed method of measuring the acoustic non-linearity parameter. The simulation results show that the amplitude of fundamentals is significantly reduced due to offset, while that of second harmonics greatly increases due to superposition because of the opposite phases of the excited signals, and the acoustic non-linearity parameter thus increases. The experimental research on fatigue damage specimens was carried out using this method. The test result was consistent with the simulation result. Thus, the method of exciting reversed-phase Rayleigh waves in opposite directions can remarkably increase the acoustic non-linearity parameter. Additionally, synchronous excitation with double-angle beam wedge transducers can double the detection efficiency.

Time Evolution of Satellite‐Based Optical Properties in Lightning Flashes, and its Impact on GLM Flash Detection

AbstractThe GOES‐16 Geostationary Lightning Mapper (GLM) detection efficiency (DE) is studied over a full year (2018/19) in central Florida using the Kennedy Space Center Lightning Mapping Array (KSC LMA). Mean daily flash DE was 73.8%, and detection was highest during nighttime hours. GLM reported 86.5% of the LMA flashes that had coincident cloud‐to‐ground return strokes reported by the U.S. National Lightning Detection Network. Results also reveal that flash size and duration are critical parameters influencing GLM detection, regardless of the storm type, with 20–40% detection for small and short‐duration flashes and greater than 95% detection for very large and long‐duration flashes.These findings can be explained by examining the time‐evolution of cloud‐top optical emissions observed by the Lightning Imaging Sensor (LIS). Statistical simulations based on long‐term LIS group area observations indicate that about half of the above‐threshold light sources are smaller than a LIS pixel (~ 4 × 4 km) and are smallest during and just after an initial breakdown in IC flashes. This work also demonstrates that for sources smaller than a GLM pixel, the cloud‐top energy detection threshold for GLM is double that for LIS despite GLM's lower energy density threshold. Overall, these findings provide a framework for interpreting GLM performance under varying meteorological conditions, and help explain reports of low flash detection efficiency for storms associated with severe weather, as they typically exhibit high flash rates and resulting small and short‐duration flashes.

Comparisons of Lightning Rates and Properties From the U.S. National Lightning Detection Network (NLDN) and GLD360 With GOES‐16 Geostationary Lightning Mapper and Advanced Baseline Imager Data

AbstractFlash‐level comparisons between the Geostationary Lightning Mapper (GLM; primarily from GOES‐16), the U.S. National Lightning Detection Network (NLDN), and the Global Lightning Dataset GLD360 have been done at quasi‐climatological scale and in smaller samples of both severe and nonsevere thunderstorms. A small sample of data from GOES‐17 has also been analyzed. These comparisons show that the total lightning detection efficiencies of the GLM instruments drop off within about 2,000 km of the edges of their fields of view, particularly over terrestrial areas. In severe storms, low detection efficiency by GLM is clearly associated with very high midaltitude reflectivity, consistent with the idea that large multiple scattering path lengths, together with absorption of the near‐infrared signals by water (in all of its phases), depresses the GLM detection efficiency. This effect appears to be coupled with additional factors, including time of day, flash energetics, and the incident angle at the GLM sensor. The “lightning jump,” the sought‐after signature of severe storms in lightning observations, tends to be poorly correlated between NLDN and GLM unless the storms are fairly isolated, not close to the edge of the GLM field of view, and have moderate midaltitude reflectivity.

Research and Implementation of Transformer Label Detection Algorithm Based on Machine Vision

In order to solve the problem of low efficiency and high false detection rate of transformer label detection in the process of factory production, an algorithm of transformer label detection based on machine vision is proposed in combination with OpenCV function library. In the pre-processing stage, the image noise is filtered and the vertical edge information is highlighted, then the label region is located by morphological processing and contour extraction, and the label image is screened by SVM classifier. Finally, the label character is divided into a single contour and recognized by artificial neural network. The experimental results show that the accuracy of the algorithm is 94.0%, and the average time is 0.334s, which meets the requirements of the factory production line.

Simulation of unidirectional ion ejection in linear ion traps with asymmetric radiofrequency voltage.

Linear ion traps with simplified structure have been widely used in miniaturized mass spectrometers. However, linear ion traps usually have low ion detection efficiency when used in a miniaturized mass spectrometer, in which only one ion detector can be installed. To solve this problem, an asymmetric radiofrequency (RF) voltage was applied to introduce asymmetric electric fields in the trapping volume of linear ion traps, which would lead to unidirectional ion ejection. An asymmetric RF voltage was applied on both half-round-rod electrode and triangular electrode linear ion traps, and their performances including unidirectional ion ejection efficiency and mass resolution were evaluated using computer simulation. The relationship between asymmetric RF voltage difference δ and internal electric field distribution was investigated, and the impact of δ and resonance excitation signal frequency on the unidirectional ion ejection efficiency and mass resolution was also explored. A unidirectional ion ejection efficiency of around 83% and a mass resolution of over 2700 were achieved with δ = 7% in both half-round-rod electrode and triangular electrode linear ion traps. By applying an asymmetric RF voltage, the ion detection efficiency could be significantly improved without any change to the structures of existing linear ion traps. This method provides a simple and general solution for improving the ion detection efficiency and sensitivity of miniaturized linear ion trap mass spectrometers.

Quantum catalysis-based discrete modulation continuous variable quantum key distribution with eight states

How to lengthen the maximum transmission of continuous variable quantum key distribution (CVQKD) has been a notorious hard problem in quantum communications. Here, we propose a simple solution to this problem, i.e., quantum catalyzing CVQKD for discrete modulation with eight states. The quantum catalysis, which can facilitate the conversion of the target ensemble, is used for not only tolerating more excess noise but also lengthening the maximum transmission distance. Security analysis shows that the zero-photon catalysis (ZPC), which is actually seen as a noiseless attenuation can be used as an elegant candidate for the performance improvement of discrete modulation (DM)-CVQKD. The numerical simulations show the ZPC-involved DM-CVQKD protocol outperforms the original DM-CVQKD in terms of maximum transmission distance as well as tolerable noise. Moreover, the ZPC-involved DM-CVQKD protocol can tolerate lower reconciliation efficiency and allow the lower detection efficiency to achieve the same performance.

A Concept Design of TES X-ray Microcalorimeter Array with Different Thickness Absorber Toward the Observation from 50 eV to 15 keV for STEM-EDS

We herein report a concept study of a transition edge sensor (TES) X-ray microcalorimeter array with two different thickness absorbers. We developed an energy-dispersive X-ray spectroscope (EDS) with a 64-pixel TES array and installed it on a scanning transmission electron microscope (STEM) for material analysis. One of the key applications of the proposed system is the microanalysis of astromaterials, for which the relative abundance of light elements such as boron, carbon, and oxygen against silicon are crucial. However, the line sensitivity below sim 500 eV for the our STEM TES EDS system was not enough to detect the X-ray from light elements because of the relatively high continuum emission and low detection efficiency, which occurs due to the X-ray window and the optical blocking filters. A simple solution to increase line sensitivity at low energy is the adoption of thin X-ray absorbers that leads to an improvement in the energy resolution. However, doing so causes the sensitivity to decrease for high energy lines. Utilizing the spot-size dependence of the polycapillary X-ray optics on energy, which are used in the STEM TES EDS system, we studied a design in which thin absorbers are distributed on the outer area of detector. We optimized the design using the raytracing analysis of optics. A thin (300 nm) absorber is placed on the 52 outer pixels, while a thick (3.5 upmum) absorber is placed on the central 12 pixels. The thin pixels detect approximately 50–60% of the total counts in 0.1–2 keV, while the central thick pixels detect approximately 50–80% of the total counts in 2–10 keV. We also demonstrated the fabrication process of two-thickness absorber arrays.