PTW Detector7293种剂量验证方法在调强放射治疗中的对比研究

目的 :对比PTW Detector729 3种验证方法在调强放射治疗(intensity modulated radiation therapy,IMRT)剂量验证中的差异。方法:回顾性选取2022年1—12月于某院完成放射治疗的鼻咽癌、肺癌、乳腺癌、宫颈癌和全脑放射治疗患者共50例,使用PTW Detector729二维电离室矩阵配合PTW RW3固体水与PTW Ocavius 4D旋转模体对50例患者的IMRT计划分别进行归零机架角2D剂量验证、实际机架角2D剂量验证和实际机架角3D剂量验证。将剂量评估阈值设为10%,统计3种验证方法在3%/1 mm、2%/2 mm、3%/2 mm和3%/3 mm 4种评估标准下的γ通过率。采用SPSS 22.0统计学软件进行数据分析。结果:在10%剂量评估阈值标准下,归零机架角2D剂量验证的γ通过率最高,差异有统计学意义(P<0.05);实际机架角2D剂量验证的γ通过率高于实际机架角3D剂量验证,差异有统计学意义(P<0.05)。3种验证方法的γ通过率在3%/1 mm、2%/2 mm、3%/2 mm和3%/3 mm 4种标准下逐渐升高,且在3%/2 mm标准下均超过90%,结果满足临床放射治疗要求。结论:3种验证方法的验证结果均能达到IMRT剂量验证实践指南要求,根据IMRT开展情况选择合适的验证方法,对确保治疗方案安全、有效实施具有重要意义。

Low-noise and low-power pixel sensor chip for gas pixel detectors

Topmetal-M2 is a large-area pixel sensor chip fabricated using the GSMC 130 nm CMOS process in 2021.The pixel array of Topmetal-M2 consists of pixels of 400 rows×512 columns with a pixel pitch of 45μm×45μm.The array is divided into 16 subarrays,with pixels of 400 rows×32 columns per subarray.Each pixel incorporates two charge sensors:a diode sensor and a Topmetal sensor.The in-pixel circuit primarily consists of a charge-sensitive amplifier for energy measurements,a discriminator with a peak-holding circuit,and a time-to-amplitude converter for time-of-arrival measurements.The pixel of Topmetal-M2 has a charge input range of~0-3 k e-,a voltage output range of~0-180 mV,and a charge-voltage conversion gain of~59.56μV∕e-.The average equivalent noise charge of Topmetal-M2,which includes the readout electronic system noise,is~43.45 e-.In the scanning mode,the time resolution of Topmetal-M2 is 1 LSB=1.25μs,and the precision is^()7.41μs.At an operating voltage of 1.5 V,Topmetal-M2 has a power consumption of~49 mW∕cm~2.In this article,we provide a comprehensive overview of the chip architecture,pixel working principles,and functional behavior of Topmetal-M2.Furthermore,we present the results of preliminary tests conducted on Topmetal-M2,namely,alpha-particle and soft X-ray tests.

CVTD: A Robust Car-Mounted Video Text Detector

Text perception is crucial for understanding the semantics of outdoor scenes,making it a key requirement for building intelligent systems for driver assistance or autonomous driving.Text information in car-mounted videos can assist drivers in making decisions.However,Car-mounted video text images pose challenges such as complex backgrounds,small fonts,and the need for real-time detection.We proposed a robust Car-mounted Video Text Detector(CVTD).It is a lightweight text detection model based on ResNet18 for feature extraction,capable of detecting text in arbitrary shapes.Our model efficiently extracted global text positions through the Coordinate Attention Threshold Activation(CATA)and enhanced the representation capability through stacking two Feature Pyramid Enhancement Fusion Modules(FPEFM),strengthening feature representation,and integrating text local features and global position information,reinforcing the representation capability of the CVTD model.The enhanced feature maps,when acted upon by Text Activation Maps(TAM),effectively distinguished text foreground from non-text regions.Additionally,we collected and annotated a dataset containing 2200 images of Car-mounted Video Text(CVT)under various road conditions for training and evaluating our model’s performance.We further tested our model on four other challenging public natural scene text detection benchmark datasets,demonstrating its strong generalization ability and real-time detection speed.This model holds potential for practical applications in real-world scenarios.

Flexibility potential of Cs_(2)BX_(6)(B=Hf,Sn,Pt,Zr,Ti;X=I,Br,Cl)with application in photovoltaic devices and radiation detectors

As interest in double perovskites is growing,especially in applications like photovoltaic devices,understanding their mechanical properties is vital for device durability.Despite extensive exploration of structure and optical properties,research on mechanical aspects is limited.This article builds a vacancyordered double perovskite model,employing first-principles calculations to analyze mechanical,bonding,electronic,and optical properties.Results show Cs_(2)Hfl_(6),Cs_(2)SnBr_(6),Cs_(2)SnI_(6),and Cs_(2)PtBr_(6)have Young's moduli below 13 GPa,indicating flexibility.Geometric parameters explain flexibility variations with the changes of B and X site composition.Bonding characteristic exploration reveals the influence of B and X site electronegativity on mechanical strength.Cs_(2)SnBr_(6)and Cs_(2)PtBr_(6)are suitable for solar cells,while Cs_(2)HfI_(6)and Cs_(2)TiCl_(6)show potential for semi-transparent solar cells.Optical property calculations highlight the high light absorption coefficients of up to 3.5×10^(5) cm^(-1)for Cs_(2)HfI_(6)and Cs_(2)TiCl_(6).Solar cell simulation shows Cs_(2)PtBr_(6)achieves 22.4%of conversion effciency.Cs_(2)ZrCl_(6)holds promise for ionizing radiation detection with its 3.68 eV bandgap and high absorption coefficient.Vacancy-ordered double perovskites offer superior flexibility,providing valuable insights for designing stable and flexible devices.This understanding enhances the development of functional devices based on these perovskites,especially for applications requiring high stability and flexibility.

Design and performance evaluation of a large field-of-view dual-particle time-encoded imager based on a depth-of-interaction detector

Time-encoded imaging is useful for identifying potential special nuclear materials and other radioactive sources at a distance.In this study,a large field-of-view time-encoded imager was developed for gamma-ray and neutron source hotspot imaging based on a depth-of-interaction(DOI)detector.The imager primarily consists of a DOI detector system and a rotary dual-layer cylindrical coded mask.An EJ276 plastic scintillator coupled with two SiPMs was designed as the DOI detector to increase the field of view and improve the imager performance.The difference in signal time at both ends and the log of the signal amplitude ratio were used to calculate the interaction position resolution.The position resolution of the DOI detector was calibrated using a collimated Cs-137 source,and the full width at half maximum of the reconstruction position of the Gaussian fitting curve was approximately 4.4 cm.The DOI detector can be arbitrarily divided into several units to independently reconstruct the source distribution images.The unit length was optimized via Am-Be source-location experiments.A multidetector filtering method is proposed for image denoising.This method can effectively reduce image noise caused by poor DOI detector position resolution.The vertical field of view of the imager was(-55°,55°)when the detector was placed in the center of the coded mask.A DT neutron source at 20 m standoff could be located within 2400 s with an angular resolution of 3.5°.

Self-powered UVC detectors based on α-Ga_(2)O_(3) with enchanted speed performance

Detectors were developed for detecting irradiation in the short-wavelength ultraviolet(UVC)interval using high-quality single-crystallineα-Ga_(2)O_(3) films with Pt interdigital contacts.The films ofα-Ga_(2)O_(3) were grown on planar sapphire substrates with c-plane orientation using halide vapor phase epitaxy.The spectral dependencies of the photo to dark current ratio,responsivity,external quantum efficiency and detectivity of the structures were investigated in the wavelength interval of 200−370 nm.The maximum of photo to dark current ratio,responsivity,external quantum efficiency,and detectivity of the structures were 1.16×10^(4) arb.un.,30.6 A/W,1.65×10^(4)%,and 6.95×10^(15) Hz^(0.5)·cm/W at a wavelength of 230 nm and an applied voltage of 1 V.The high values of photoelectric properties were due to the internal enhancement of the photoresponse associated with strong hole trapping.Theα-Ga_(2)O_(3) film-based UVC detectors can function in self-powered operation mode due to the built-in electric field at the Pt/α-Ga_(2)O_(3) interfaces.At a wavelength of 254 nm and zero applied voltage,the structures exhibit a responsivity of 0.13 mA/W and an external quantum efficiency of 6.2×10−2%.The UVC detectors based on theα-Ga_(2)O_(3) films demonstrate high-speed performance with a rise time of 18 ms in self-powered mode.

Gas microchannel plate-pixel detector for X-ray polarimetry

POLAR-2 is a gamma-ray burst(GRB)polarimeter that is designed to study the polarization in GRB radiation emissions,aiming to improve our knowledge of related mechanisms.POLAR-2 is expected to utilize an on-board polarimeter that is sensitive to soft X-rays(2-10 keV),called low-energy polarization detector.We have developed a new soft X-ray polari-zation detector prototype based on gas microchannel plates(GMCPs)and pixel chips(Topmetal).The GMCPs have bulk resistance,which prevents charging-up effects and ensures gain stability during operation.The detector is composed of low outgassing materials and is gas-sealed using a laser welding technique,ensuring long-term stability.A modulation factor of 41.28%±0.64% is obtained for a 4.5 keV polarized X-ray beam.A residual modulation of 1.96%±0.58% at 5.9 keV is observed for the entire sensitive area.

Probability-Enhanced Anchor-Free Detector for Remote-Sensing Object Detection

Anchor-free object-detection methods achieve a significant advancement in field of computer vision,particularly in the realm of real-time inferences.However,in remote sensing object detection,anchor-free methods often lack of capability in separating the foreground and background.This paper proposes an anchor-free method named probability-enhanced anchor-free detector(ProEnDet)for remote sensing object detection.First,a weighted bidirectional feature pyramid is used for feature extraction.Second,we introduce probability enhancement to strengthen the classification of the object’s foreground and background.The detector uses the logarithm likelihood as the final score to improve the classification of the foreground and background of the object.ProEnDet is verified using the DIOR and NWPU-VHR-10 datasets.The experiment achieved mean average precisions of 61.4 and 69.0 on the DIOR dataset and NWPU-VHR-10 dataset,respectively.ProEnDet achieves a speed of 32.4 FPS on the DIOR dataset,which satisfies the real-time requirements for remote-sensing object detection.

Effect of multiple coulomb scattering on the beam tests of silicon pixel detectors

In the research and development of new silicon pixel detectors,a collimated monoenergetic charged-particle test beam equipped with a high-resolution pixel-beam telescope is crucial for prototype verification and performance evaluation.When the beam energy is low,the effect of multiple Coulomb scattering on the measured resolution of the Device Under Test(DUT)must be considered to accurately evaluate the performance of the pixel chips and detectors.This study aimed to investigate the effect of multiple Coulomb scattering on the measured resolution,particularly at low beam energies.Simulations were conducted using Allpix^(2) to study the effects of multiple Coulomb scattering under different beam energies,material budgets,and telescope layouts.The simulations also provided the minimum energy at which the effect of multiple Coulomb scattering could be ignored.Compared with the results of a five-layer detector system tested with an electron beam at DESY,the simulation results were consistent with the beam test results,confirming the reliability of the simulations.

Study on the Performance of the GRANDProto300 Particle Detector Array by Simulation

The Giant Radio Array for Neutrino Detection(GRAND)is a proposed large-scale observatory designed to detect cosmic rays,gamma-rays,and neutrinos with energies exceeding 100 Pe V.The GRANDProto300 experiment is proposed as the early stage of the GRAND project,consisting of a hybrid array of radio antennas and scintillator detectors.The latter,as a mature and traditional detector,is used to cross-check the nature of the candidate events selected from radio observations.In this study,we developed a simulation software called G4GRANDProto300,based on the Geant4 software package,to optimize the spacing of the scintillator detector array and to investigate its effective area.The analysis was conducted at various zenith angles under different detector spacings,including 300,500,600,700,and 900 m.Our results indicate that,for large zenith angles used to search for cosmic-ray in the GRAND project,the optimized effective area is with a detector spacing of 500 m.The G4GRANDProto300 software that we developed could be used to further optimize the layout of the particle detector array in future work.

Metal-Halide Perovskite Submicrometer-Thick Films for Ultra-Stable Self-Powered Direct X-Ray Detectors

Metal-halide perovskites are revolutionizing the world of X-ray detectors,due to the development of sensitive,fast,and cost-effective devices.Self-powered operation,ensuring portability and low power consumption,has also been recently demonstrated in both bulk materials and thin films.However,the signal stability and repeatability under continuous X-ray exposure has only been tested up to a few hours,often reporting degradation of the detection performance.Here it is shown that self-powered direct X-ray detectors,fabricated starting from a FAPbBr_(3)submicrometer-thick film deposition onto a mesoporous TiO_(2)scaffold,can withstand a 26-day uninterrupted X-ray exposure with negligible signal loss,demonstrating ultra-high operational stability and excellent repeatability.No structural modification is observed after irradiation with a total ionizing dose of almost 200 Gy,revealing an unexpectedly high radiation hardness for a metal-halide perovskite thin film.In addition,trap-assisted photoconductive gain enabled the device to achieve a record bulk sensitivity of 7.28 C Gy^(−1)cm^(−3)at 0 V,an unprecedented value in the field of thin-film-based photoconductors and photodiodes for“hard”X-rays.Finally,prototypal validation under the X-ray beam produced by a medical linear accelerator for cancer treatment is also introduced.

Countermeasure against blinding attack for single-photon detectors in quantum key distribution

Quantum key distribution(QKD),rooted in quantum mechanics,offers information-theoretic security.However,practi-cal systems open security threats due to imperfections,notably bright-light blinding attacks targeting single-photon detectors.Here,we propose a concise,robust defense strategy for protecting single-photon detectors in QKD systems against blinding attacks.Our strategy uses a dual approach:detecting the bias current of the avalanche photodiode(APD)to defend against con-tinuous-wave blinding attacks,and monitoring the avalanche amplitude to protect against pulsed blinding attacks.By integrat-ing these two branches,the proposed solution effectively identifies and mitigates a wide range of bright light injection attempts,significantly enhancing the resilience of QKD systems against various bright-light blinding attacks.This method forti-fies the safeguards of quantum communications and offers a crucial contribution to the field of quantum information security.

High-speed performance self-powered short wave ultraviolet radiation detectors based onκ(ε)-Ga_(2)O_(3)

High-speed solar-blind short wavelength ultraviolet radiation detectors based onκ(ε)-Ga_(2)O_(3)layers with Pt contacts were demonstrated and their properties were studied in detail.Theκ(ε)-Ga_(2)O_(3)layers were deposited by the halide vapor phase epitaxy on patterned GaN templates with sapphire substrates.The spectral dependencies of the photoelectric properties of struc-tures were analyzed in the wavelength interval 200-370 nm.The maximum photo to dark current ratio,responsivity,detectiv-ity and external quantum efficiency of structures were determined as:180.86 arb.un.,3.57 A/W,1.78×10^(12) Hz^(0.5)∙cm·W^(-1) and 2193.6%,respectively,at a wavelength of 200 nm and an applied voltage of 1 V.The enhancement of the photoresponse was caused by the decrease in the Schottky barrier at the Pt/κ(ε)-Ga_(2)O_(3)interface under ultraviolet exposure.The detectors demon-strated could functionalize in self-powered mode due to built-in electric field at the Pt/κ(ε)-Ga_(2)O_(3)interface.The responsivity and external quantum efficiency of the structures at a wavelength of 254 nm and zero applied voltage were 0.9 mA/W and 0.46%,respectively.The rise and decay times in self-powered mode did not exceed 100 ms.

基于InVEST和Geodetector模型的合肥生境质量时空演变及影响因素分析

依据2000年、2010年和2020年3期土地利用数据,运用耦合模型探究合肥2000—2020年间生境质量时空变化特征并对影响因子进行分析。结果表明:2000—2020年合肥生境质量指数平均值分别为0.185、0.181、0.178,呈逐年下降趋势,较低质量区域向低质量区域的转移面积最大。合肥生境质量退化度在2000—2020年逐年下降,呈现出“环状增长”的空间分布特征。高退化度区域主要分布在低值区域外围,呈现非连续性扩张。区域生产总值、坡度以及高程是主要影响因子,双因子增强效应显著,年末总人口和人口密度为主导单因子。

Determination of Benzo[a]pyrene in Edible Oil by High Performance Liquid Chromatography-Fluorescence Detector (HPLC-FL)

In this study, an optimized high performance liquid chromatography-fluorescence detector (HPLC-FL) method for the determination of benzo[a]pyrene in edible oil was established. HPLC was performed with Thermo Fisher Scientific C18 column (250 mm×4.6 mm, 5 μm) as the chromatographic column and acetonitrile and water as the mobile phase, and the excitation wavelength and emission wavelength of fluorescence detector were 286 and 430 nm, respectively. The response was high, and the linear range was 0.5-10.0 ng/ml. The lowest limit of detection was 0.11 ng/ml, and the average recovery was 92.5%. This method is suitable for quantitative analysis of benzo[a]pyrene content in edible oil.

基于运动区域Viola-Jones算法的视频人脸检测

为了进一步提高人脸检测的准确率,本文采用一种基于运动区域的检测方法,该方法主要通过采用帧差法和自适应的滑动平均法相结合的算法,建立提取运动区域的模型,然后通过基于Boxfilter算法的Viola-Jones进行快速人脸检测。自适应的滑动平均法是通过检测光照突变和像素点来实现阈值和更新率的自适应更新,该法提取的前景与帧差法提取的前景进行"与运算"。实验结果表明,该方法可以有效地提取运动区域,从而使人脸检测性能得到进一步的提高,具有一定的应用价值。

基于InVEST&GEO-detectors模型的会仙湿地生境质量变化及影响因素研究

喀斯特湿地是广泛分布在喀斯特地区的一种特殊的湿地类型,其生态地位举足轻重,探索喀斯特湿地生境质量变化的影响因素对喀斯特地区生态建设具有重要的意义。本文基于会仙湿地保护区2000和2020年的土地利用数据,通过InVEST模型评估会仙湿地保护区的生境质量,利用地理探测器探测影响会仙湿地保护区生境质量变化的自然和人为因素。研究结果表明:1)研究区2000至2020年建设用地明显扩张,草地和水体显著减少;2)会仙湿地保护区生境质量总体呈现下降的趋势,生境退化度有所上升,生境质量较差的区域主要集中在研究区的北部、中部和东北部;3)地理探测器识别出会仙湿地保护区生境质量空间变化受自然和人为因子的综合作用,主导影响因子是GDP(q为0.135),其次为夜间灯光指数(DMSP)(q为0.053);交互作用探测结果表明,各因子对生境质量影响呈现出双因子增强效果。研究结果有助于揭示会仙湿地保护区生境质量的时空演变过程,可针对会仙湿地生态建设的问题提出可行的应对策略。

基于Viola-Jones框架人脸检测算法的汽车疲劳驾驶检测

疲劳驾驶导致汽车交通事故逐年增加,为了提升驾车的安全性,需对驾驶员疲劳状态实时监测并及时提醒.为了提高疲劳驾驶判断效率及准确率,本文运用Viola-Jones框架特征矩阵进行人脸预判断;预判断过程中为了减少Haar值计算量并提高人脸识别速度,采用Adaboost算法和级联分析,剔除非人脸的Haar特征值,实现快速人脸识别;根据色彩空间转化实现眼部分割处理,根据PERCLOS值评估驾驶员是否处于疲劳状态并提前予以警示;通过MATLAB仿真软件实现疲劳驾驶检测算法的仿真分析.在多个样本的测试过程中,该方法有效识别出人脸,并能够准确监测驾驶员的疲劳状态.

一种基于Viola-Jones的改进人脸定位算法

Viola-Jones算法能快速定位人脸,但该算法存在对有偏角的人脸出现漏检和对周围环境非人脸区域出现误检的情况。针对该问题,提出一种基于Viola-Jones的改进人脸定位算法。首先将图像中检测到的人脸像素区域排除,再对剩下未被检测出的区域转为YCrCr模式,设定阈值排除大部分环境中非肤色像素的干扰初步筛选出候选人脸区域,再利用形态学方法进一步排除身体其他部位肤色的干扰和环境中近似人脸像素的背景色干扰并对筛选出的区域进行左角度矫正调整和右角度矫正调整,重新检测,准确定位出人脸位置。通过在标准人脸检测库Faces、IMM和AFW上进行实验,结果表明,该算法能有效提高人脸定位的准确性,较原算法在Faces测试库中正确检测率提高5%,在AFW测试库中正确检测率提高9%。

基于Viola-Jones算法的实时人物表情动画的制作

结合计算机图像制作技术,人物表情动画制作有了更先进的方式。本次采用Viola-Jones算法对人脸表情进行实验检测,根据算法实验结果提出表情动画制作的最佳方式。