Detection Unit Research Articles

SNR-Net OCT: brighten and denoise low-light optical coherence tomography images via deep learning.

Low-light optical coherence tomography (OCT) images generated when using low input power, low-quantum-efficiency detection units, low exposure time, or facing high-reflective surfaces, have low bright and signal-to-noise rates (SNR), and restrict OCT technique and clinical applications. While low input power, low quantum efficiency, and low exposure time can help reduce the hardware requirements and accelerate imaging speed; high-reflective surfaces are unavoidable sometimes. Here we propose a deep-learning-based technique to brighten and denoise low-light OCT images, termed SNR-Net OCT. The proposed SNR-Net OCT deeply integrated a conventional OCT setup and a residual-dense-block U-Net generative adversarial network with channel-wise attention connections trained using a customized large speckle-free SNR-enhanced brighter OCT dataset. Results demonstrated that the proposed SNR-Net OCT can brighten low-light OCT images and remove the speckle noise effectively, with enhancing SNR and maintaining the tissue microstructures well. Moreover, compared to the hardware-based techniques, the proposed SNR-Net OCT can be of lower cost and better performance.

Calibration Facility for Detector Strings for the KM3NeT/ARCA Neutrino Telescope at the Capacity Laboratory

KM3NeT is a network of submarine Cherenkov neutrino telescopes under construction at two different sites in the Mediterranean Sea. ARCA, near Sicily in Italy, is optimised for the detection of cosmic neutrinos while ORCA, near Toulon in France, is optimized for atmospheric neutrinos. ARCA and ORCA are both arrays of thousands of optical sensors (Digital Optical Modules - DOMs), each consisting of 31 small photomultipliers (PMTs) housed inside a glass sphere, which detect the Cherenkov light produced by the secondary particles generated in the neutrino interactions. 18 DOMs are arranged on flexible strings, referred to as vertical Detection Units (DUs), anchored to the sea floor. Once completed, ARCA and ORCA will consist of 230 and 115 DUs, respectively. Each DOM of a string communicates at a dedicated wavelength to the shore station via a network of optical fibers transmitting optical and acoustic signal information as well as orientation information. Before the deployment, each DU is tested and calibrated in a dark room. The test bench is equipped with a full data acquisition system for communication, data processing, and time synchronisation. Several steps are needed to accomplish the DU calibration, including the High-Voltage (HV) tuning of the PMTs, checking of the acoustic receivers and calibration light sources in the DOM, and time calibration using laser signals distributed to all DOMs. Here, we describe the DU test and calibration facility at the CAPACITY laboratory (Campania AstroPArtiCle InfrastrucTure facilitY) in Caserta, focusing on the functional tests and calibrations performed at the end of the DU integration.

Application of modern technical systems for automation of radioactive waste sorting process

The paper describes the technical design and composition of a robotic radioactive waste (RW) sorting and certifica-tion unit, which combines a technical vision system (TVS) to determine the position of RW fragments and assess their morphology, detection units to determine the radionuclide composition and a manipulation system for moving and sorting the RW fragments themselves into containers in accordance with the parameters measurements. Such an approach will allow sorting of RW by the method of their subsequent processing, as well as reduce the total cost of subsequent disposal of RW by reducing the total waste class.

Thermal bubble-driven impedance-based high-throughput cell counting chip design

Cell identification and enumeration are important methods within clinical and research laboratories for rapid diagnosis of relevant diseases. However, there are still many shortcomings in the current cell counting methods. In order to improve the performance of cell counting, a novel impedance-based cell counting chip based on thermal bubble drive was designed in this study. The chip is fabricated by whole-wafer processing and provides the driving force for cells through a combination of thermal bubble nozzles and microfluidic channels, integrating 100 individual detection units on a 38 mm2 size chip. Experimental and theoretical analyses have demonstrated that the chip can achieve high throughput detection of 45 000 beads/s under extreme conditions. A fourfold difference in detection voltage was obtained for both 14 and 7 µm diameter polystyrene beads. The linear fit coefficient of determination between the cell number measured by the chip and the cell number observed in reality was above 0.999 for both polystyrene beads and 211H cells, and the counting accuracy exceeded previous studies. It turns out that the chip achieves portable, low-cost, high-throughput, and high-accuracy cell counting, which is conducive to the development of impedance cell counting.

Finite-key security analysis of differential-phase-shift quantum key distribution

Differential-phase-shift (DPS) quantum key distribution (QKD) is one of the major QKD protocols that can be implemented with a simple setup using a laser source and a passive detection unit. Recently, an information-theoretic security proof of this protocol has been established in [npj Quant. Inf. 5, 87 (2019)] assuming the infinitely large number of emitted pulses. To implement the DPS protocol in a real-life world, it is indispensable to analyze the security with the finite number of emitted pulses. The extension of the security proof to the finite-size regime requires the accommodation of the statistical fluctuations to determine the amount of privacy amplification. In doing so, Azuma's inequality is often employed, but unfortunately we show that in the case of the DPS protocol, this results in a substantially low key rate. This low key rate is due to a loose estimation of the sum of probabilities regarding three-photon emission whose probability of occurrence is very small. The main contribution of our work is to show that this obstacle can be overcome by exploiting the recently found novel concentration inequality, Kato's inequality. As a result, the key rate of the DPS protocol is drastically improved. For instance, assuming typical experimental parameters, a 3 Mbit secret key can be generated over 77 km for 8.3 hours, which shows the feasibility of DPS QKD under a realistic setup.

Methods for express assessment of the radiation situation using a mobile laboratory in emergency situations

Methods for express assessment of the radiation situation in situ with the use of a mobile laboratory have been developed. During making decisions on protective measures application in the acute period of a radiological accident, the proposed methods make it possible to promptly assess the values of the volumetric activity of air in the breathing zone (Bq·m-3) and the contamination density of the territory with gamma-emitting radionuclides (Bq·m-2). These methods also allow to determine the activity (Bq) of the detected local radiation source. The scope of application has been expanded and the uncertainty of the previously developed method used for radiological survey of agricultural lands contaminated with cesium-137 without sampling has been reduced. It has been established that in the presence of not only caesium-137, but also caesium-134, cobalt-60, and iodine-131 on the radioactive trace, the proposed methodological approach makes it possible to quickly select the appropriate spectral regions for each pollutant and calibrate the detection units for the current radionuclide composition.

Ultra-stable, sensitive and broadband photodetector based on large-area 2D bismuth oxyselenide film for multiband image sensing

Two-dimensional (2D) materials have proven to be a highly promising candidate for applications in electronic and optoelectronic devices due to their attractive structure and properties. However, the micron-scale dimensions, random distribution on the substrate, and complex transfer processes of 2D materials inevitably cause difficulties in device integration, which limits practical applications in photodetection. Herein, high-quality 2D Bi2O2Se film (2×2 cm) composed of numerous single crystal nanosheets on SrTiO3 substrate was prepared employing the chemical vapor deposition method. The layered Bi2O2Se film features a perfect atomic alignment free of lattice mismatch and a sharp interface with the SrTiO3 substrate. Afterward, a broadband photodetector based on 2D Bi2O2Se film was directly constructed, which covered the ultraviolet, visible and infrared range from 365 to 940 nm and demonstrated a fast response speed of 32 ms and 44 ms, maximum responsivity and detectivity of 136 mA/W and 2×109 Jones. Importantly, fast on/off behavior for 100 cycles and reliable photoresponse after storage in air for 1 year confirmed the excellent cycling stability and air stability of the Bi2O2Se photodetector. Furthermore, the Bi2O2Se photodetector as a single point sensing pixel was capable to perform high-resolution imaging of “H, I, T” patterns. This research affirms the huge potential of Bi2O2Se photodetectors to perform as reliable multi-band detection units in complex systems.

A detailed infrared detectors systems overview of MOONS VLT instrument

MOONS is a multi‐object spectrograph that will be installed at the Nasmyth focus of the VLT ESO Telescopes in Chile. The instrument has the capacity to deploy approximately 1000 fibers over a field of view of 500 square arcminutes, with a total wavelength coverage of from 0.6 to 1.8 m, offering both low‐ and medium‐resolution modes. The high demand for fast and large optics in all spectral channels prompted the use of similar Schmidt cameras. As a result, the Detector Unit (DU) must be located within the optical beam and its footprint must be minimized to reduce vignetting. The instrument consists of four H4RG‐15um pixel detectors and two fully depleted LBNL CCDs. This article provides a comprehensive description of the detector systems, focusing particularly on the H4RG‐15, including a brief overview of the newly developed cryogenic pre‐amplifier for 64‐output operation, and a detailed discussion of the woven cable technology used for signal routing. Some results of the characterization of three H4RG detectors are presented, with a focus on crosstalk and buffer output performance. The use of the buffer output for the H4RG results in a glow‐per‐read observed at the bottom of the detectors. This article also describes the trade‐offs and alternatives used to optimize detector performance in this situation.

Deep Learning-Assisted OFDM Channel Estimation and Signal Detection Technology

The orthogonal frequency division multiplexing (OFDM) technique has received wide attention because of its high spectrum utilization. However, the drawback of inter-subcarrier interference in OFDM systems makes the channel estimation and signal detection performance of OFDM systems with few pilots and short cyclic prefixes (CP) poor. In this paper, we use deep learning to assist OFDM in recovering nonlinearly distorted transmission data. Specifically, we use a self-normalizing network (SNN) for channel estimation, combined with a convolutional neural network (CNN) and a bidirectional gated recurrent unit (BiGRU) for signal detection, thus proposing a novel SNN-CNN-BiGRU network structure (SCBiGNet). The simulation results show that the SCBiGNet model outperforms the existing techniques for the different numbers of pilots and lengths of CPs. The BER performance is improved by 0.2~9 dB.

The single-layer readout electronics design and development for CEPC scintillator analog hadronic calorimeter prototype

With the progress in modern high-energy physics, the Standard Model is constantly being refined. As the last brick of the Standard Model, the Higgs boson was confirmed to be discovered in the Large Hadron Collider (LHC) in 2012. For the further exploration of the Higgs boson, the Circular Electron Positron Collider (CEPC) is proposed. The baseline detector concept of CEPC is guided by the particle flow principle. The Particle Flow Algorithm (PFA) reconstructs a list of low-level particles and associates every detector hit with these particles. The high granularity hadronic calorimeter (HCAL) represents an essential component of PFA-based detectors. This paper mainly presents the single-layer electronics design and development for the scintillator analog hadronic calorimeter prototype (AHCAL). The single-layer readout electronics consists of front-end electronics board (FEB) and data interface (DIF) board. The FEB carries the silicon photomultipliers (SiPM), plastic scintillators, and the SiPM signal readout circuit. A single SiPM coupled with a scintillator constitute the basic detection unit. The size of scintillator used here is 4 cm×4 cm. A sensitive area of 72×72 cm2 can be covered by the design presented here. 324 SiPMs coupled with scintillators are mounted on each FEB. Besides the huge sensitive area, The AHCAL prototype must also meet strict requirements on the integration and robustness of the electronics. This paper develops a complete single-layer readout electronics design that meets the requirements for use in the AHCAL. The results of beam test shows that the peak of the minimum ionizing particle (MIP) is separated from the pedestal evidently and the signal-to-noise ratio (SNR) is better than 20. The volume required for the electronics is less than 4 cm3 per channel. In addition, the FEB is sufficiently robust to avoid damage during intercontinental transportation. The development of the single-layer electronics represents significant progress in the design of a prototype device that meets the requirement for use in the CEPC.

First observation of the cosmic ray shadow of the Moon and the Sun with KM3NeT/ORCA

This article reports the first observation of the Moon and the Sun shadows in the sky distribution of cosmic-ray induced muons measured by the KM3NeT/ORCA detector. The analysed data-taking period spans from February 2020 to November 2021, when the detector had 6 Detection Units deployed at the bottom of the Mediterranean Sea, each composed of 18 Digital Optical Modules. The shadows induced by the Moon and the Sun were detected at their nominal position with a statistical significance of 4.2sigma and 6.2sigma , and an angular resolution of sigma _{res}=0.49^circ and sigma _{res}=0.66^circ , respectively, consistent with the prediction of 0.53^circ from simulations. This early result confirms the effectiveness of the detector calibration, in time, position and orientation and the accuracy of the event direction reconstruction. This also demonstrates the performance and the competitiveness of the detector in terms of pointing accuracy and angular resolution.

POWTEX visits POWGEN.

The high-intensity time-of-flight (TOF) neutron diffractometer POWTEX for powder and texture analysis is currently being built prior to operation in the eastern guide hall of the research reactor FRM II at Garching close to Munich, Germany. Because of the world-wide 3He crisis in 2009, the authors promptly initiated the development of 3He-free detector alternatives that are tailor-made for the requirements of large-area diffractometers. Herein is reported the 2017 enterprise to operate one mounting unit of the final POWTEX detector on the neutron powder diffractometer POWGEN at the Spallation Neutron Source located at Oak Ridge National Laboratory, USA. As a result, presented here are the first angular- and wavelength-dependent data from the POWTEX detector, unfortunately damaged by a 50g shock but still operating, as well as the efforts made both to characterize the transport damage and to successfully recalibrate the voxel positions in order to yield nonetheless reliable measurements. Also described is the current data reduction process using the PowderReduceP2D algorithm implemented in Mantid [Arnold et al. (2014). Nucl. Instrum. Methods Phys. Res. A, 764, 156-166]. The final part of the data treatment chain, namely a novel multi-dimensional refinement using a modified version of the GSAS-II software suite [Toby & Von Dreele (2013). J. Appl. Cryst.46, 544-549], is compared with a standard data treatment of the same event data conventionally reduced as TOF diffraction patterns and refined with the unmodified version of GSAS-II. This involves both determining the instrumental resolution parameters using POWGEN's powdered diamond standard sample and the refinement of a friendly-user sample, BaZn(NCN)2. Although each structural parameter on its own looks similar upon comparing the conventional (1D) and multi-dimensional (2D) treatments, also in terms of precision, a closer view shows small but possibly significant differences. For example, the somewhat suspicious proximity of the a and b lattice parameters of BaZn(NCN)2 crystallizing in Pbca as resulting from the 1D refinement (0.008 Å) is five times less pronounced in the 2D refinement (0.038 Å). Similar features are found when comparing bond lengths and bond angles, e.g. the two N-C-N units are less differently bent in the 1D results (173 and 175°) than in the 2D results (167 and 173°). The results are of importance not only for POWTEX but also for other neutron TOF diffractometers with large-area detectors, like POWGEN at the SNS or the future DREAM beamline at the European Spallation Source.

Visual/quantitative SERS biosensing chip based on Au-decorated polystyrene sphere microcavity arrays

A microfluidic chip was designed and fabricated to achieve visual and quantitative sensing for the biomarker of Epstein-barr virus antibody (EBV IgG) based on TMB chromogenic unit and Raman detection unit. The biosensor was composed of polystyrene/Au nanoparticles (PS/AuNPs) microsphere arrays on a quartz substrate, where the initial SERS signal was amplified ten times than pure AuNPs through synergetic coupling between the optical field of PS whispering gallery microcavity and plasmon of AuNPs. Meanwhile, we introduced a signal probe by assembling horseradish peroxidase with high catalytic activity to TMB and Raman reporter rhodamine 6 G, in which TMB turned from colorless to blue and gradually deepened with increasing amount of EBV IgG being captured while the unique fingerprint information of rhodamine 6 G provided the accurate Raman signal for point-of-care testing of target. In sum, an integrated microchip that allows visual prediction under the assistance of TMB color as well as SERS responses with a wide dynamic linear range of 10−1∼105 pg·mL−1 and detection limit as low as 0.045 pg·mL−1 were obtained simultaneously, this lab-on-a-chip design offers a powerful model system for the early diagnosis of various cancer markers in peripheral blood.

Tetraphenylethene-Based cis/trans Isomers for Targeted Fluorescence Sensing and Biomedical Applications.

Molecular probes which can be modulated, functionalized and used to visualize the processes are highly desirable for understanding and manipulating biological systems. Geometric cis and trans isomers of tetraphenylethene (TPE) emerge as attractive candidates to fulfill these tasks thanks to the unique aggregation-induced emission properties, tailorable structures, and responsiveness to external stimuli. This minireview focuses on cis and trans isomers of TPE derivatives that are functionalized with molecular recognition units for fluorescence detection, bioimaging and cancer therapy. The effects of molecular geometry on fluorescence property, target binding ability and biological activity are summarized. The feasibility to in vitro and in vivo switch molecular configuration and thus bio-activity is discussed. Finally, the future development and challenges are discussed in view of TPE-based stereoisomers for targeted sensing and imaging-guided modulation of biological processes.

Accident Detection and Flow Prediction for Connected and Automated Transport Systems

Effective accident detection and traffic flow forecasting are of great importance for quick respond, impact elimination and intelligent control of the traffic flow consisting of autonomous vehicles. This paper proposes a traffic accident detection method for connected and automated transport systems by conducting a grid-based parameter extracting and SVC-based traffic state classification. Allowing for the dynamic spread of traffic flow over time, from upstream to downstream and from accident lanes to other lanes, a spatiotemporal Markov model is established to predict the evolution of traffic flow after accident by introducing the grid as state detection unit and fitting the spatiotemporal evolution with the parameter space mean speed to match the need of both detection accuracy and monitoring scope. Compared with actual accident data, the validation results indicate that the proposed methods present a good performance in accident detection with the accident detection rate as 87.72% and a higher precision rate than both SVM (support vector machine) and ANN (artificial neural network) models in traffic flow prediction. With the active traffic accident identification and dynamic traffic flow prediction, it is beneficial to shorten detection time, reduce possible impacts of traffic accidents and carbon emissions from congestion. The methods can be implied to traffic state recognition and traffic flow prediction, which is one of the significant sections of connected and automated transport systems, and serve as references for accident handling and urban traffic management.

A Miniaturized 3D-Printed Quartz-Enhanced Photoacoustic Spectroscopy Sensor for Methane Detection with a High-Power Diode Laser.

In this invited paper, a highly sensitive methane (CH4) trace gas sensor based on quartz-enhanced photoacoustic spectroscopy (QEPAS) technique using a high-power diode laser and a miniaturized 3D-printed acoustic detection unit (ADU) is demonstrated for the first time. A high-power diode laser emitting at 6057.10 cm-1 (1650.96 nm), with the optical power up to 38 mW, was selected as the excitation source to provide a strong excitation. A 3D-printed ADU, including the optical and photoacoustic detection elements, had a dimension of 42 mm, 27 mm, and 8 mm in length, width, and height, respectively. The total weight of this 3D-printed ADU, including all elements, was 6 g. A quartz tuning fork (QTF) with a resonant frequency and Q factor of 32.749 kHz and 10,598, respectively, was used as an acoustic transducer. The performance of the high-power diode laser-based CH4-QEPAS sensor, with 3D-printed ADU, was investigated in detail. The optimum laser wavelength modulation depth was found to be 0.302 cm-1. The concentration response of this CH4-QEPAS sensor was researched when the CH4 gas sample, with different concentration samples, was adopted. The obtained results showed that this CH4-QEPAS sensor had an outstanding linear concentration response. The minimum detection limit (MDL) was found to be 14.93 ppm. The normalized noise equivalent absorption (NNEA) coefficient was obtained as 2.20 × 10-7 cm-1W/Hz-1/2. A highly sensitive CH4-QEPAS sensor, with a small volume and light weight of ADU, is advantageous for the real applications. It can be portable and carried on some platforms, such as an unmanned aerial vehicle (UAV) and a balloon.

Ultrasonic sensor-based automatic control volume sprayer for pesticides and growth regulators application in vineyards

A study was conducted to design a sensor-based control volume sprayer for vineyard cultivation. The study aimed to develop cluster-specific pesticide and growth regulator application systems with improved penetration and minimum off-target losses, thus saving chemicals and overall cost. For the determination of design values of the control volume unit, physical properties (cluster length, width, and level of compactness) of grape clusters from seventeen major genotypes selected from vineyard research farm ICAR-IARI New Delhi were studied. For the design of the grape cluster detection unit, two different types of sensors, i.e., ultrasonic sensor (HC SR-04) and infrared proximity sensor (B0115NCT4U), were evaluated for their ability to detect the target (grape cluster) and the response time. The design of the spraying unit for the control volume sprayer also involved selecting suitable nozzles and operational parameters. The developed sprayer was evaluated for application of plant growth hormone (Gibberellic acid), and the performance was assessed in terms of droplet size, chemical application per cluster, cluster and berry growth characteristics, sprayer application rate, uniformity coefficient, and application time. The data on the physical properties of grape clusters revealed a maximum cluster length and width of 24.00 ± 0.91 cm and 18.80 ± 0.15 cm, respectively. The ultrasonic sensor had a comparatively higher sensing range, beam angle, and lower price than the infrared sensor. The spray uniformity for the hollow cone and flat fan nozzle varied significantly for the operating pressure range of 2–4.5 kg.cm−2. The developed sprayer consisted of a 3D printed control volume unit, ultrasonic sensor, two flat fan nozzles, microcontroller (Atmega 328P), relay switch, voltage converter, spray tank of 16-liter capacity, and 12 VDC battery. In case of developed sensor-based control volume sprayer, 30% and 35.48% saving in chemical use and application time, respectively, were observed compared to the conventional dipping method. The PGR application method has significant interaction with cluster length and berry growth as the main effect; however, failed to show a significant interaction with cluster width. Maximum cluster growth (16.89 ± 1.72 mm) was observed in PGR application with a developed sprayer.

An adaptive link training based hybrid circuit topology for full‐duplex on‐chip interconnects

SummaryThis work proposes a link training based half‐rate dynamic current‐steering echo‐cancellation hybrid circuit topology for full‐duplex signaling that performs echo cancellation by deploying a bit error detection unit and backchannel adaptation. In addition, this work proposes a power‐efficient half‐rate dynamic current‐steering logic hybrid circuit for full‐duplex signaling over on‐chip interconnects for simultaneous transmission and reception. The half‐rate dynamic current‐steering hybrid circuit topology has low static power consumption compared with traditional current‐mode circuit topology implementations, thanks to the discrete nature of the current‐steering hybrid topology. The proposed scheme is implemented in 1.2 V, 65‐nm complementary metal‐oxide semiconductor (CMOS). The performance results show that the link training scheme sets the control bits for both the transmitter driver and hybrid circuit topology when the backchannel adaptation loop gets locked for 1‐ and 3‐mm interconnects for process, voltage, and temperature (PVT) variations. The proposed hybrid circuit topology is able to receive the required far‐end transmitted data with the link training scheme and has the differential recovered received signal voltage swing of 1.2 V for both 1‐ and 3‐mm interconnect at the 10‐Gb/s data rate. The total power consumption of the hybrid is 3 and 3.5 mW for 1‐ and 3‐mm interconnect with an energy efficiency of 0.6 and 0.7 pJ/bit, respectively, at 10‐Gb/s full‐duplex operation.

VioNets: efficient multi-modal fusion method based on bidirectional gate recurrent unit and cross-attention graph convolutional network for video violence detection

Recent research on video violence detection has made great progress with the development of multi-modal fusion techniques. However, existing approaches still pose huge challenges in real-time violence detection due to fusion features being fixed and not able to be further fine tuned. We aim to address this challenge by exploring the multi-modal fusion method for analyzing multiple modal violent information, i.e., audio, optical flows, and RGB images. We propose a unified network called VioNets, which contains both a cross-attention graph convolutional network (GCN) module and a bidirectional gate recurrent unit (Bi-GRU) module for fusing different modalities of information. First, the cross-attention GCN module is utilized to extract the cross-modal spatial–temporal features. The Bi-GRU module is then applied to accurately capture both past and future context features for each time step of the single-modal features. As a result, the model retains important single-modal information in the extracted features while using the cross-modal features to improve the detection accuracy. Experiments conducted on the XD-Violence dataset show that the proposed method achieves an average precision of 80.59% and an inference time of 0.16 s with 1.82 M parameters.

A new multi-piezoelectric input synchronized switch harvesting on inductor circuit

This paper has proposed a multi-piezoelectric input synchronized switch harvesting on inductor (MI-SSHI) circuit. The MI-SSHI circuit is mainly composed of an extreme detector unit and synchronized switch harvesting on inductor (SSHI) units. The extreme detector unit generates real-time control signals. Since the principle of SSHI circuit, each voltage on piezoelectric element can be switched at different instant in a period. In this paper, two piezoelectric element inputs are selected as an example. The experimental result validates that the output power of the MI-SSHI circuit is improved by 11.67%, in comparison to the traditional S-SSHI circuit.