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.

Thermodynamic,Economic,and Environmental Analyses and Multi-Objective Optimization of Dual-Pressure Organic Rankine Cycle System with Dual-Stage Ejector

A novel dual-pressure organic Rankine cycle system(DPORC)with a dual-stage ejector(DE-DPORC)is proposed.The system incorporates a dual-stage ejector that utilizes a small amount of extraction steam from the highpressure expander to pressurize a large quantity of exhaust gas to performwork for the low-pressure expander.This innovative approach addresses condensing pressure limitations,reduces power consumption during pressurization,minimizes heat loss,and enhances the utilization efficiency of waste heat steam.A thermodynamic model is developed with net output work,thermal efficiency,and exergy efficiency(W_(net,ηt,ηex))as evaluation criteria,an economicmodel is established with levelized energy cost(LEC)as evaluation index,anenvironmentalmodel is created with annual equivalent carbon dioxide emission reduction(AER)as evaluation parameter.A comprehensive analysis is conducted on the impact of heat source temperature(T_(S,in)),evaporation temperature(T_(2)),entrainment ratio(E_(r1),E_(r2)),and working fluid pressure(P_(5),P_(6))on system performance.It compares the comprehensive performance of the DE-DPORC system with that of the DPORC system at TS,in of 433.15 K and T2 of 378.15 K.Furthermore,multi-objective optimization using the dragonfly algorithm is performed to determine optimal working conditions for the DE-DPORC system through the TOPSIS method.The findings indicate that the DEDPORC system exhibits a 5.34%increase inWnet andηex,a 58.06%increase inηt,a 5.61%increase in AER,and a reduction of 47.67%and 13.51%in the heat dissipation of the condenser andLEC,compared to theDPORCsystem,highlighting the advantages of this enhanced system.The optimal operating conditions are TS,in=426.74 K,T_(2)=389.37 K,E_(r1)=1.33,E_(r2)=3.17,P_(5)=0.39 MPa,P_(6)=1.32 MPa,which offer valuable technical support for engineering applications;however,they are approaching the peak thermodynamic and environmental performance while falling short of the highest economic performance.

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.

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.

Effect of an Internal Heat Exchanger on the Performances of a Double Evaporator Ejector Refrigeration Cycle

A theoretical investigation is presented about a double evaporator ejector refrigeration cycle(DEERC).Special attention is paid to take into account the influence of the sub-cooling and superheating effects induced by an internal heat exchanger(IHX).The ejector is introduced into the baseline cycle in order to mitigate the throttling process losses and increase the compressor suction pressure.Moreover,the IHX has the structure of a concentric counter-flow type heat exchanger and is intentionally used to ensure that the fluid at the compressor inlet is vapor.To assess accurately the influence of the IHX on the DEERC performance,a mathematical model is derived in the frame of the dominant one-dimensional theory for ejectors.The model also accounts for the friction effect in the ejector mixing section.The equations of this model are solved using an Engineering Equation Solver(EES)for different fluids.These are:R134a as baseline fluid and other environment friendly refrigerants used for comparison,namely,R1234yf,R1234ze,R600,R600a,R290,R717 and R1270.The simulation results show that the DEERC with an IHX can achieve COP(the coefficient of performance)improvements from 5.2 until 10%.

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.

改良成人经口气管插管机械通气患者口腔护理方法及应用

目的探讨改良成人经口气管插管机械通气患者口腔护理方法的应用效果。方法便利抽样选取2021年1月1日至2021年12月30日四川省人民医院神外监护室经口气管插管机械通气患者220例为对照组,口腔护理方法为冲洗+擦拭+吸痰管连接负压吸引;2022年1月1日至2022年12月30日经口气管插管机械通气患者163例为观察组,口腔护理方法为擦拭+冲洗+吸唾管连接负压吸引。比较两组患者口腔异味发生率、口腔污垢残留、操作时口腔内污液溢出及吸唾管/吸痰管滑出情况、呼吸机相关性肺炎发生率。结果两组患者呼吸机相关性肺炎发生率比较差异无统计学意义(P>0.05);两组口腔异味发生率、口腔污垢残留、操作时口腔内污液溢出及吸唾管/吸痰管滑出、操作耗时等比较,差异有统计学意义(P<0.05);100%操作人员愿意选择观察组的吸唾管连接负压吸引口腔护理废液(P<0.05)。结论改良成人经口气管插管机械通气患者口腔护理方法,能提高口腔护理质量、提高患者舒适度,节约成本、提高工作效率,有一定的推广应用价值。

碎纸机收纳桶塑件的注塑模具设计

根据碎纸机收纳桶产品的外形特征与成型要求,设计了一副包括定模隧道滑块油缸抽芯机构、推板带斜顶抽芯机构、斜顶内带司筒和弹针顶出结构的复杂注塑模具。其中,推板带斜顶抽芯机构用于脱出塑件内观面上的两个倒扣,斜顶内带司筒和弹针顶出结构成功解决塑件内部的4个柱子倒扣的脱模问题,设置的定模隧道滑块油缸抽芯机构用于脱出塑件外观面上的倒扣。推板带动斜顶抽芯的同时完成塑件的顶出,在模具结构上省去了顶针板结构。模具在制作调试过程中,各项顶出抽芯机构无干涉,针对塑件成型时易出现的问题,通过进一步的模具结构优化设计加以解决。在模具投入使用后,已生产塑件产品达3万件,塑件尺寸精度及外观质量要求符合预期。

基于CFD和响应面法的引射器优化设计

针对质子交换膜燃料电池(Proton Exchange Membrane Fuel Cell, PEMFC)氢气引射器优化研究中优化精度低、忽视多结构耦合作用的问题,采用CFD和响应面法结合优化引射器结构参数。通过单因素仿真试验研究各结构对引射比的影响,在此基础上设计正交试验构建响应面分析多结构参数交互作用。研究结果表明:喷嘴距和等压混合室直径的响应p值小于0.05,存在耦合作用且对引射性能具有显著影响,通过响应面法优化后引射器最大引射比达到3.62,相比于单因素优化结果提升了25.69%并且预测模型误差仅为4.93%。

乏汽供热用大型蒸汽射汽器性能试验与研究

对乏汽供热用大型射汽器的性能进行了全面分析和研究。结合射汽器的固有特性,在300 MW等级机组的乏汽供热系统中对射汽器变工况性能进行了试验研究,得到了不同机组背压、动力蒸汽压力和出口压力下射汽器的性能曲线。建立了一种射汽器全工况特性的性能参数求解方法。结果表明:性能参数求解结果与试验数据吻合度高。

冷却通道对引射器红外辐射特性影响的研究

为降低燃气轮机排气系统中的引射器排气温度,从而减少排出燃气的红外辐射强度,本文提出了一种具有冷却通道的亚音速引射器结构,并提出了评价冷却通道引射器的综合系数。在原有的引射器喷嘴内增加冷却通道,使冷气直接与主流中心位置的高温气体掺混,破坏排气包覆性分布,达到提高主流温度均匀性、降低中心温度的目的。本文运用数值模拟的方法,研究引射器内冷却通道数量、冷却通道进深和排气通道的排布对引射器内阻力特性、换热特性、出口温度分布特性的综合影响。研究结果表明:单排冷却通道排布时,通道数量与换热特性成正比,与阻力损失成反比;双排冷却通道排布时,阻力损失降低。双排12通道引射器可有效降低出流总温,均匀主流温度,综合系数最高。

结构参数对气液下喷式喷射器性能的影响研究

喷射环流反应器是一种新型的气液或气液固接触反应装置,其中的喷射器结构会对反应器性能产生重要影响。文章采用计算流体力学方法,建立了文丘里型喷射器的数学模型,分析了吸气室、喉部和扩散段等结构对喷射器吸气量的影响规律。模拟结果表明:吸气室直径和气相入口方式对吸气量影响不大;喷嘴与喉部之间距离越小,喉部长度越短,吸气量越高;扩散段扩散角度在2~4°之间时吸气量存在最大值。

异形分流管热流道家族注塑模具设计

介绍了某款异形分流管零件热流道注塑模具的设计过程。模具设计中,首先,分析了注塑件的零件特征和生产要求,确定了模具的基本结构方案;再利用Moldflow软件分析模具注塑成型过程,预测零件的成型时间、翘曲变形量、熔接痕位置等,最终完成整套模具的设计。模具采用两板式热流道冷浇口注塑成型,浇口选择潜伏式点浇口形式,开模时自动拉断与注塑件分离;模具定模型腔设计了1个弹性脱模镶件,保证了开模时塑件紧贴型芯侧;模具分型面上共分布了5个侧抽芯滑块结构,由弯销导向并延时开模。对常用型弯销滑块机构进行了改进,将两段式弯销改进为三段式弯销,有效地避免了常用弯销滑块机构容易出现卡死和锁闭不紧的问题。模具经过实际生产验证可知,结构合理可靠,制备得到的零件尺寸精度满足设计要求。

机载水稻抛秧装置输送顶出机构优化设计及仿真

水稻抛秧具有效率高、秧苗损伤小等优势。基于此,设计一种连续型秧苗自动输送及顶出机构,对输送机构进行设计及受力分析,得到中间仿形架受力最大约为23.47 N,静力学分析得出仿形架最大应力为36 MPa,最大位移变形量为0.6 mm,最大应变为0.012。对钵体顶出及斜抛过程进行受力分析,计算出钵体质心到底面距离为9.71 mm,得出钵体脱盘时的最小翻滚角度与翻滚角速度、下落垂直距离的关系。对顶针进行参数优化,当顶针总长为50 mm,凸台长度为5 mm时,钵体顶出完整性较好。以顶针安装角、顶出力为试验因素,以钵体顶出后的二维空间位移为指标,进行ADAMS运动学仿真试验及正交试验,当仿真试验水平和竖直位移达到最小值时,顶针安装角为25°、顶出力为1.5 N;进行正交试验验证仿真结果,当试验因素水平一致时,水平和竖直位移达到最小值。通过分析得出安装角对指标影响极显著,顶出力对指标影响较显著。研究结果可为水稻抛秧装置设计和作业参数优化提供重要参考。

基于夹点的带喷射器CO_(2)热泵系统性能分析

为了研究带喷射器的跨临界CO_(2)内部过冷热泵系统(TCISE),基于夹点建立了TCISE的热力学模型,分析了冷却水进出水温度及流量对系统性能的影响。研究表明:冷却水进水温度从25℃降低到15℃时,最优高压压力从9.3 MPa降至8.8 MPa,降低了5.4%,最大COP从3.83提升至4.27,提高了11.49%;TCISE存在临界冷却水出水温度和临界冷却水质量流量,当冷却水进水温度一定时,在出水温度低于临界出水温度或质量流量高于临界质量流量时,系统COP保持不变。

引射器真空度的设计与研究

为满足大型电解槽精准出铝、减少电解槽散热要求,需要提高引射器的真空度。本文参考了目前理论研究的最新结果并结合经验数据,设计出引射器的内部结构。根据减少动能损失而提高真空度的原理提出了调整压缩空气压力、喷嘴至收缩段的距离和喷嘴直径这三个主要参数值的方法,按此最佳参数值设计出的引射器经试验测试当进口压缩空气压力为0.65 MPa时,真空度最大达到-0.068 MPa。

塑料外壳注射模设计

按照塑件结构设计了1副两板注射模,为了降低模具制造成本,将定模板适当增厚,省去定模座板,为了减少塑件表面的流痕和方便修剪浇口凝料,将塑件上浇口对应的位置设计成凹形。针对塑件侧面的扣位结构,采用由斜导柱驱动的侧滑块机构脱模,对模具两侧的滑块设置减速弹簧,降低滑块在合模时的速度,以减少滑块对模具零件的撞击。斜推杆与安装座之间通过圆弧形扣位相连,简化了模具结构,根据塑件结构,采用推管与推杆相结合的推出方式脱模,并根据模具结构设置“直通+隔片式水井”相结合的多个冷却回路的随形冷却系统。

宽工况下水蒸气喷射制冷系统试验研究

针对低品位余热资源热负荷的不稳定性,开展研究利用低品位余热资源的水蒸气喷射制冷系统性能变化规律。通过搭建水蒸气喷射制冷试验平台,对蒸汽喷射器的引射系数与系统性能进行了试验研究。结果表明:当发生温度为设计温度140 ℃时,蒸汽喷射器引射系数与系统性能最佳,分别为0.34和0.33,当发生温度高于设计温度时,系统性能和蒸汽喷射器引射系数要比发生温度低于设计温度时更优;随着蒸发温度从2 ℃上升到22 ℃时,蒸汽喷射器引射系数由0.17上升到了0.22,增加了25%,系统性能从0.17上升到了0.24,提高了41%,因此较高的蒸发温度对系统的性能有所提升;系统存在1个临界冷凝温度,当超过临界冷凝温度时,蒸汽喷射器引射系数与系统性能急剧下降。研究结果为水蒸气喷射制冷的模拟研究提供了试验验证,对水蒸气喷射制冷系统的优化具有重要意义。

Study on γ-Ray Irradiation Mutation of Bacillus subtilis NCD-2

[Objective] To study the effect of 60Co γ-rays irradiation on Botrytis cinerea biocontrol strains—Bacillus subtilis NCD-2. [Method] NCD-2 cells were irradiated at different doses of γ-rays from 100 to 2 000 Gy. The strains were screened by plate confrontation method and Oxford cup diffusion. [Result] The curves of the relationship of irradiation dose and mutation and lethal rate were obtained. The results showed that lethal rate increased with the increasing of irradiation dose. The lethal rate of 1 000 Gy irradiation dose reached 99.50%. The mutation rate increased below 500 Gy and decreased above 500 Gy. The highest mutation rate occurred when the irradiation dose was between 400 and 700 Gy, and the average mutation rate was above 15%. The optimal irradiation dose was 500 Gy, when the average mutation rate was 26.51% and lethal rate was 77.71%. [Conclusion] This study provided references for γ-rays irradiation mutation of Bacillus subtilis.

车用燃料电池引射器设计及测试评价方法研究

在研究开发车用燃料电池引射器时,湿氢流量监测困难、台架技术难度大、试验成本高,并且存在安全隐患和能源浪费问题。为此,在推导空气与氢气、空气与100%RH的氢在相同工作条件下的流量变化关系式的基础上,针对110 kW燃料电池,试制引射器进行空气和氢气测试,并结合数值仿真分析。结果发现:车用燃料电池引射器引射流体中水蒸气质量分数达到40%~50%;在相同工作条件下,空气与氢气的体积和质量流量分别等于其气体常数比值的平方根和比值倒数的平方根,其中空气与氢气的体积和质量流量之比分别为3.786和0.2641。工作、引射和混合流体质量流量的空气实测与仿真数据之间的平均相对误差分别为4.48%、4.54%和2.78%;空气实测数据经折算后与氢气测试数据相吻合,与湿氢的仿真数据平均偏差率分别为5.4%和6.11%;氢气测试数据经折算也与湿氢仿真数据相吻合。因此,空气测试数据经处理可以用于车用燃料电池引射器特性研究。