Measurement of the high energyγ-rays from heavy ion reactions usingČerenkov detector

The energetic bremsstrahlung photons up to 100 MeV produced in heavy ion collisions can be used as a sensitive probe for short-range correlation in atomic nuclei. The energy of the γ-rays can be measured by collecting the Čerenkov light in the medium induced by the fast electrons generated in the Compton scattering or electromagnetic shower of the incident γray. Two types of detectors based on pure water and lead glass as sensitive materials were designed for this purpose. The γresponse and optical photon propagation in the detectors were simulated based on electromagnetic and optical processes in Geant4. The inherent energy resolutions of 0.022(4) + 0.51(2)∕E^(1/2)_(γ) for water and 0.0026(3) + 0.446(3)∕E^(1/2)_(γ) for lead glass were obtained. The geometry sizes of the lead glass and water were optimized to 30 cm × 30 cm × 30 cm and 60 cm × 60 cm ×120 cm, respectively, to detect high-energy γ-rays at 160 MeV. The Hough transform method was applied to reconstruct the direction of the incident γ-rays, providing the ability to experimentally distinguish the high-energy γ-rays produced in the reactions on the target from random background cosmic-ray muons.

Artificial neural network-based method for discriminating Compton scattering events in high-purity germaniumγ-ray spectrometer

To detect radioactive substances with low activity levels,an anticoincidence detector and a high-purity germanium(HPGe)detector are typically used simultaneously to suppress Compton scattering background,thereby resulting in an extremely low detection limit and improving the measurement accuracy.However,the complex and expensive hardware required does not facilitate the application or promotion of this method.Thus,a method is proposed in this study to discriminate the digital waveform of pulse signals output using an HPGe detector,whereby Compton scattering background is suppressed and a low minimum detectable activity(MDA)is achieved without using an expensive and complex anticoincidence detector and device.The electric-field-strength and energy-deposition distributions of the detector are simulated to determine the relationship between pulse shape and energy-deposition location,as well as the characteristics of energy-deposition distributions for fulland partial-energy deposition events.This relationship is used to develop a pulse-shape-discrimination algorithm based on an artificial neural network for pulse-feature identification.To accurately determine the relationship between the deposited energy of gamma(γ)rays in the detector and the deposition location,we extract four shape parameters from the pulse signals output by the detector.Machine learning is used to input the four shape parameters into the detector.Subsequently,the pulse signals are identified and classified to discriminate between partial-and full-energy deposition events.Some partial-energy deposition events are removed to suppress Compton scattering.The proposed method effectively decreases the MDA of an HPGeγ-energy dispersive spectrometer.Test results show that the Compton suppression factors for energy spectra obtained from measurements on ^(152)Eu,^(137)Cs,and ^(60)Co radioactive sources are 1.13(344 keV),1.11(662 keV),and 1.08(1332 keV),respectively,and that the corresponding MDAs are 1.4%,5.3%,and 21.6%lower,respectively.

Flow Rate Measurement of Gravity Infusion Set and Functional Evaluation of Drop Counter: A Pilot Study

Developing a novel drop counter by introducing the Internet of Things concept has been vigorously conducted in recent years. Understanding the newly introduced drop counter’s flow rate control accuracy and flow rate count feature is essential for improving safety in infusion management. This study aimed to verify if the new drop counters could secure accurate flow rate and drip count by conducting actual flow rate measurements using gravimetry and functional evaluation. A drop counter was attached to each drip chamber of the infusion set, and an IV drip was conducted at the 100 ml/h flow rate. The weight of discharged physiological saline was measured to plot trumpet curves. Next, three different types of drop counters were evaluated to determine if they maintained drip count accuracy according to the changes in their position angles. The flow rate errors in all conditions indicated trumpet-like curves, exhibiting an overall error range within ±10% in all observation windows. Although every drop counter successfully detected and measured dripping, it was challenging in some counters to detect dripping when the drip chamber was tilted. In comparing adult and pediatric IV sets, the adult IV set was found to be less likely to detect dripping in the angled position. No significant differences in results were confirmed between high and low flow rates, suggesting that the drop count function would not be affected by the flow rate in the ranges of typical infusion practices. Doppler sensors have a wide range of measurements and high sensitivity;the dripping was detected successfully even when the drip chamber was tilted, probably due to the advantages of these sensors. In contrast, miscounts occurred in those equipped with infrared sensors, which could not detect light intensity changes in tilted positions. Understanding the tendencies in flow rate errors in infusion can be valuable information for infusion management.

COUNTER Release 5新版本规范分析与研究

本文通过介绍COUNTER规范的历史发展、报告视图、元素属性,并对最新版本的更新与特点进行分析研究,以便国内研究者能更方便快捷地了解和应用COUNTER规范。

Generalization ability of a CNNγ-ray localization model for radiation imaging

Inγ-ray imaging,localization of theγ-ray interaction in the scintillator is critical.Convolutional neural network(CNN)techniques are highly promising for improvingγ-ray localization.Our study evaluated the generalization capabilities of a CNN localization model with respect to theγ-ray energy and thickness of the crystal.The model maintained a high positional linearity(PL)and spatial resolution for ray energies between 59 and 1460 keV.The PL at the incident surface of the detector was 0.99,and the resolution of the central incident point source ranged between 0.52 and 1.19 mm.In modified uniform redundant array(MURA)imaging systems using a thick crystal,the CNNγ-ray localization model significantly improved the useful field-of-view(UFOV)from 60.32 to 93.44%compared to the classical centroid localization methods.Additionally,the signal-to-noise ratio of the reconstructed images increased from 0.95 to 5.63.

The likely counterpart to γ-ray excess from the northwest region of Arp 220

The unknown γ-ray excess in the northwest region of Arp 220 was revisited by analyzing~11.8 years of the Fermi Large Area Telescope(Fermi-LAT) data in this study.We found that its photon flux was approximately three times higher than that of the previous study in the 0.2-100 GeV band,and the corresponding significance level ~8.15σ was approximately four times higher than before.The light curves of 15 and 45 time bins from the whole time all showed two active periods,and the variability of the second period was more significant than that of the first period.The spectral indices from the two active periods were not statistically different and were close to the range of γ-ray flat-spectrum radio quasars observed by Fermi-LAT.Because the position of CRATES J153246+234400 was consistent with the best-fit position of our analysis,we suggest that CRATES J153246+234400 is more likely a γ-ray counterpart for the variational region.For Arp 220,there was no significant variability in the γ-ray emission.

Study on Color Information Degradation Induced byγ-ray Radiation in CMOS Cameras

Theγ-rays are widely and abundantly present in strong nuclear radiation environments,and when they act on the camera equipment used to obtain environmental visual information on nuclear robots,radiation effects will occur,which will degrade the performance of the camera system,reduce the imaging quality,and even cause catastrophic consequences.Color reducibility is an important index for evaluating the imaging quality of color camera,but its degradation mechanism in a nuclear radiation environment is still unclear.In this paper,theγ-ray irradiation experiments of CMOS cameras were carried out to analyse the degradation law of the camera’s color reducibility with cumulative irradiation and reveal the degradation mechanism of the color information of the CMOS camera underγ-ray irradiation.The results show that the spectral response of CMOS image sensor(CIS)and the spectral transmittance of lens after irradiation affect the values of a^(*)and b^(*)in the LAB color model.While the full well capacity(FWC)of CIS and transmittance of lens affect the value of L^(*)in the LAB color model,thus increase color difference and reduce brightness,the combined effect of color difference and brightness degradation will reduce the color reducibility of CMOS cameras.Therefore,the degradation of the color information of the CMOS camera afterγ-ray irradiation mainly comes from the changes in the FWC and spectral response of CIS,and the spectral transmittance of lens.

Comparative Alpha Tracks Counting Using an Optical Microscope and a Spark Counter

In the metrology of radon, an environmental lung carcinogen, the integrated measurements necessary for epidemiological studies are made very often using the tracks detector LR 115 type 2. For dosimetric analysis, the etched tracks from radon alpha particles on this detector are usually counted by means of an optical microscope or a spark counter. An optimal reading of the track densities which must be converted into radon concentrations, can’t be done without a good mastery of the mode of operation and use of these devices. Furthermore, investigations to know as to whether or not each of those can be used to determine radon concentration are necessary. These are the objectives of the present work in which LR 115 samples exposed to radon for at least 3 months, were chemically developed under standard conditions and read. The track densities obtained with the microscope are very much higher than those of the counter for each sample. These results are consistent with those published by other authors. However, each of these devices can be used interchangeably for alpha tracks counting, as both provide radon concentrations with a very good linear correlation coefficient of 0.95 taking into account their respective calibration factors for the reading of this detector. In addition, the saturation phenomenon for the spark counter reading of LR 115 detector occurs beyond 11,000 tr/cm2, a density never reached during our environmental radon measurements.

基于雷达自动目标识别技术的反无人机雷达

面对“低慢小”(Low Slow Small, LSS)无人机威胁挑战,反无人机雷达的关键作用日益凸显。在反无人机系统(Countering-Unmanned Aerial Systems, C-UAS)技术中,反无人机雷达作为C-UAS的核心传感器,承担着关键任务,包括探测和导引等。尽管其重要性显而易见,反无人机雷达设计仍然存在概念上的不清晰,例如如何定义LSS无人机目标,以及为何众多反无人机雷达难以探测无人机等问题。通过探讨雷达自动目标识别(Automatic Target Recognition, ATR)技术在反无人机雷达中的应用,从目标特性和探测技术2个方面明确了关键问题。强调了雷达探测的独立过程,将其分为“信号检测”和“目标识别”,并指出反无人机雷达的主要探测对象是LSS无人机目标。ATR性能等级被明确定义,涵盖了“Detection探测”“Classification分类”“Identification识别”“Description描述”4个等级。整合ATR功能显著提升了无人机的探测距离和识别能力,推动了反无人机雷达系统的性能升级。

Aerodynamic Coupling Analysis of Counter⁃rotating Propfan and Inlet Flow Field

Taking a propfan engine as the research object,the CFD method was used for 3D modeling and unsteady slip flow for numerical calculation.The propfan rotation domain and the nacelle outside flow domain were meshed by using the partition splicing grid technology.Used the Reynolds⁃averaged of N⁃S equation,the Reynolds stress term uses the RNG turbulence model;and based on the slip grid method,numerical calculation of the flow field with different Mach numbers,front and rear blade angles and engine state were carried out;and the change law of propeller fan characteristics and the influence of slip flow on the inlet flow field were analyzed.The blade angle was the key parameter of the propeller fan characteristic conditions.When the blade angle increases from 41°to 50°,the thrust coefficient increases by 31.2%,and the power coefficient increases by 33.4%;in the climbing state of the propeller fan,the maximum total pressure distortion at the inlet port of 6.8%;the cross section is less affected by the slip flow of the propfan;and the pressure distribution is relatively uniform,but the area of the flow channel is small.The research results can provide a solution for the matching of the counter⁃rotating propeller fan and the engine and the arrangement of the air inlet measuring rake.

乡村振兴战略下逆城镇化形成动因与推进策略探析

推进逆城镇化,让社会精英到农村发挥引领作用,是实现乡村振兴的重要举措。从乡村振兴战略视角阐述逆城镇化的概念与作用,并基于社会行为学理论,从外部环境和行为主体两方面解析推进逆城镇化形成的动力因素及其作用关系,以此探析逆城镇化的前因后果。研究认为:促进逆城镇化形成与发展的动力可归纳为四个方面,即政府引导力、城市推动力、农村吸引力和基础支撑力;当前应以政府引导力、农村吸引力为着力点,以产业振兴为中心,推动城乡融合发展。基于上述分析,可以从发挥逆城镇化在乡村振兴中的基础作用、发挥产业振兴在逆城镇化中的核心作用、健全促进逆城镇化发展的政策与机制、创造逆城镇化发展的基础条件等方面着手更好地推进逆城镇化。

利用数字化仪实现放射性气体85Kr核素活度浓度的绝对测量

基于中国计量科学研究院建立的长度补偿法充气正比计数器绝对测量系统,利用CAEN公司开发的DT5730型数字化仪替代多套传统模拟电子学插件,并通过数字化仪对β信号进行采集、重建和数据离线分析,开展85Kr放射性惰性气体活度浓度的绝对测量。实验研究了各种条件的影响,通过对正比计数器端效应、正比计数器壁效应、本底、噪声、死时间漏计数和阈值以下计数进行修正,最终得到85Kr活度浓度绝对测量结果。在相同阈值、主放大倍数100倍、气压50.5 kPa,工作电压1675 V和1700 V的条件下,数字化仪测量和电子学插件测量^(85)Kr放射性活度浓度的相对偏差分别为0.83%和0.74%。测量结果在不确定度范围内一致,证明数字化仪可有效替代传统电子学插件实现放射性惰性气体^(85)Kr活度浓度的绝对测量。

一种基于多变量卡诺图的自启动方法

在时序逻辑电路的分析或设计过程中,都存在自启动的确认环节。以扭环形计数器的自启动电路设计为例,提出一种基于自定义多变量卡诺图的自启动研究方法,分析了电路没有自启动功能的原因所在,并利用卡诺图具有的化简能力,精简优化自启动电路设计。5变量以上的多变量卡诺图应用,使此方法具有更强的工程实用性。同时,此方法可推广到其他类型时序逻辑电路自启动功能的分析、设计工作中。

雷达波形对抗技术发展预见

随着雷达、电子侦察等传感器技术的进步,对电磁空间的操控从能量、频率向更高维度的波形发展,雷达波形对抗应运而生。阐述雷达波形对抗技术产生的背景、概念内涵和发展现状,同时提出可利用博弈思维建立雷达波形“OODA”回路,通过对雷达波形进行伪装、扰乱和利用以达成制造战场迷雾、创造新质杀伤链的效果。此外,介绍实现雷达波形对抗的波形隐匿、波形重建与利用、波形捷变反侦察等关键技术及原理。从波形管控等3个方面提出雷达波形对抗制胜电磁空间的发展建议。

对转螺旋桨气动噪声试验系统设计与试验研究

风洞内对转螺旋桨气动噪声试验存在时间协调难、成本高的问题,依托地面声学环境,研制能够模拟对转螺旋桨地面开车状态的对转螺旋桨气动噪声试验系统。对某穿孔结构的对转螺旋桨和基准桨开展气动噪声试验,对设计的试验系统进行验证,并对穿孔结构对转螺旋桨的降噪效果进行评估。结果表明:在所测试的工况范围内,穿孔结构对转螺旋桨在保证气动性能的前提下能够有效降低噪声;在对飞机舱内影响最显著的90°指向角处,二阶通过频率处降噪量达到5 dB。本文设计的气动噪声试验系统,能够为对转螺旋桨气动噪声评估和降噪设计提供帮助。

小尺寸无静叶对转风扇/压气机气动设计与变工况性能分析研究

无静叶对转风扇/压气机能有效减小发动机陀螺力矩,在轴向长度方面具有优势。然而,无静叶往往导致下游叶片攻角变化较大,变工况性能难以保证,且这一特点随叶尖切线速度的增大而恶化。本文利用小尺寸涡扇发动机风扇叶片根部周向速度较低的特点,尝试对其进行风扇与压气机无静叶对转方案设计。通过速度三角形分析了无静叶对转风扇/压气机的性能特点,开发了无静叶对转风扇/压气机一维设计程序进行参数方案的筛选优化,设计得到小尺寸无静叶对转风扇/压气机构型方案,设计点效率为85.1%,压比为3.16。结果表明,对转压气机的下排叶片相对进口气流角的变化范围较常规转叶+静叶相对进口气流角范围更小,而对转下排叶片的进口速度却将增大1.5~3倍,因此,需要合理选择对转风扇/压气机的轮毂比及转速比,才能保证对转风扇/压气机变转速工况下的设计点效率及失速裕度。减小对转风扇/压气机转速比有利于提高设计点效率和裕度,但本文受发动机总体指标限制,对转速比选择进行了折中。

流气式低本底α/β测量仪的串道特征及干扰修正

研究了一系列α、β金属平面源、粉末源及薄层样法自制面源在流气式低本底α/β测量仪上的串道现象。结果显示:^(90)Sr-^(90)Y金属面源以及 ^(14)C,^(137)Cs,^(90)Sr-^(90)Y, ^(40)K粉末源β对α通道的串道比均在0.1%以下,基本可以忽略不计;α金属平面源串道比大小规律表现为 ^(210)Po<^(209)Po<^(239)Pu<^(239)Pu-^(241)Am混合源<241Am,范围为3.49%~25.4%,发射不同能量粒子的α金属源的串道比差异较大。由于衰变过程产生的内转换电子、俄歇电子以及X射线等在β道产生响应,241Am源的串道比明显高于其他源,241Am粉末源的串道比随单位面积质量厚度增加而增大。α粒子对β通道的串道现象较明显,并与样品制源方式有关,主要是不同制源方式造成的自吸收差异导致的,总体有α粉末源串道比>薄层样法自制α面源>α金属平面源,测量时应重点考虑α粒子对β放射性的串道干扰。通过210Po加标样及牡蛎样品经放化分析制成的电镀源验证,对待测样品源进行一定厚度的铝箔或纸片覆盖,可以有效的减小α粒子对β通道的串道干扰;也可以直接利用串道比对测量计数进行修正,此时需要考虑待测样品源和串道比刻度源的一致性,否则会导致修正结果的偏差较大。

舆论式反恐模式运行探究

舆论式反恐作为重要的反恐模式,在反恐主体、反恐内容和反恐效果等层面具有宣教性,以运行主体、运行旨归和运行影响搭建运行基础,以运行场域、运行逻辑和运行步骤组建运行途径,以运行工具、运行方法和运行保障构建运行手段。有效运行舆论式反恐模式,有利于丰富反恐模式的理论体系,提高反恐主体的反恐能力,推动反恐治理工作的系统性提升。

赫尔德及其同时代人:古典、浪漫、启蒙与反启蒙——乌尔里希·盖尔教授访谈

赫尔德是18世纪德意志重要的思想家,在德意志等西方文学、哲学与其他相关领域享有重要地位。德国康斯坦茨大学盖尔教授是德国著名日耳曼学者,著作等身,长期从事德意志近现代文学研究,尤以在赫尔德研究领域贡献卓著。本文从流派概念出发,围绕赫尔德以及他同时代人,对盖尔教授进行访谈。因为德意志近代文学独具特色,盖尔教授反对用流派概念对这些作家进行标签化的简单划分。而赫尔德在这一独具特色的德意志近代文学中起了举足轻重的作用,对后来德意志文学以及文史哲发展影响深远。

轴流式对旋除尘风机的结构优化与性能研究

为了提高轴流式对旋除尘风机的除尘性能,研究各个参数相互之间的干扰,对其一级叶轮叶片数量、二级叶轮叶片数量、一二级叶轮距离、风筒直径和叶轮至进口距离这5个主要的结构参数进行优化改进和参数匹配。采取正交试验法,通过FLUENT对各结构参数下的风机除尘过程进行模拟仿真试验,分析风机除尘作业时内部流场和进出口速度、压力分布情况,给出综合评价风机除尘性能公式,得到轴流式对旋除尘风机各个参数的影响程度由大到小分别为一级叶轮叶片数量、风筒直径、二级叶轮叶片数量、一二级叶轮距离、叶轮至进口距离,并通过计算分析得到风机结构的最佳参数组合。