Assessment of Resonance Self-shielding Models during Burn-Up Calculations

Various approaches and models are used in deterministic codes to treat the resonance self-shielding behavior of cross-sections.The accuracy of the models used has a significant effect on the precision of calculations;hence it is essential to select the best self-shielding method that yields accurate results within a reasonable computational time.In the present paper,the performance of the statistical subgroup method and the subgroup projection method associated with the DRAGON5 code is assessed during the burnup of a fuel pin.Two types of fuel are investigated:UO2,and PuO2-UO2.The accuracy of the methods is determined by calculating the variation of the infinite multiplication factor and the reaction rates during burnup,and then the results are compared to the stochastic MCNP6 code.It is indicated that the performance of both methods in treating the resonance self-shielding effect is satisfactory and that the subgroup projection method has a better performance during burnup calculations.

Measurement of ^(232)Th(n,γ)cross section at the CSNS Back-n facility in the unresolved resonance region from 4 keV to 100 keV

The neutron capture cross section of ^(232)Th was measured at the neutron time-of-flight facility Back-n of China Spallation Neutron Source(CSNS)for the first time.The measurement was performed with 4 hydrogen-free deuterated benzene C6D6 liquid scintillation detectors,in the ES#2 experiment station on the beam line,at a distance of about 76 m from the neutron-production assembly.The total energy detection principle in combination with the pulse height weighting technique(PHWT)was applied to analyze the measured data.Results of the ^(232)Th(n,γ)reaction cross section in the unresolved resonance region from 4 keV to 100 keV were obtained,which shows a good agreement with the existing experimental data from EXFOR,as well as with the evaluated data from the ENDF/B-VIII.0 and CENDL-3.1.In addition,the excitation function of ^(232)Th(n,γ)^(233)Th reaction in the unresolved resonance region was theoretically calculated by using the code TALYS-1.95.By fitting the experimental cross section and theoretical data,the average parameters in the unresolved resonance region were extracted.

Efficient Calculation of the Radar Cross Section at the Interior Resonance by the Inverse Power Method

It is well known that the incorrect results will be given using either the electric or magnetic field integral equation to calculate the radar cross section (RCS) of a closed body at the interior resonance. In this paper, an effective iterative technique is used to correct the calculated surface current density from the electric field integral equation. The radar cross section is computed for an infinite conducting circular cylinder at the interior resonance, and the obtained results are in good agreement with the analytical results. The backscattering cross section of an infinite triangular cylinder in the vicinity of a resonant frequency is also calculated. It is shown that the presence method is efficient and accurate.

Analysis of the Electric Locomotives Neutral-section Passing Harmonic Resonance

For the further analysis and suppression of the electric locomotives neutral-section passing overvoltage, on the basis of theoretical analysis of the neutral-section passing harmonic resonance conditions, this paper establishes simplified harmonic resonance simulation models of the electric locomotives neutral-section passing using MATLAB/Simulink, and makes the overvoltage simulation analysis of the existing electric locomotives neutral-section passing system in the event of a harmonic resonance. Results show that when the system harmonic resonance occurs, the operating overvoltage of the neutral-section passing is serious intensified by the overvoltage of the harmonic resonance, which will make the voltage of the pantograph collector head exceeding 100kV. This amplitude of the overvoltage will breakdown the air gap, which will be a serious threat to the safety operation of the electric railway. However, this kind of neutral-section passing overvoltage hasn’t cause the attention in the field and theoretical studies, which need more analysis and verification in the further study.

Elastic electron scattering with formamide-(H_(2)O)_(n) complexes(n=1,2):Influence of microsolvation on the π^(*) and σ^(*) resonances

We report elastic cross sections for low-energy electron scattering with formamide-(H_(2)O)n complexes(n=1,2)in the energy region of 0.01-8 eV.The scattering calculations are performed using the R-matrix method in the static-exchange(SE)approximation.We consider three structures of formamide-H_(2)O and six structures of formamide-(H_(2)O)_(2)in the present work.Our purpose is to investigate effects of water molecules hydrogen-bonding to formamide.We focus on the influence of microsolvation on theπ*andσ*resonances of formamide.The scattering result for complexes shows that the position ofπ*resonance appears at lower or higher energies in the cluster than in the isolated formamide depending on the complex structure and the water role in the hydrogen bonding.We explain this behavior according to the net charge of the solute.It is found that the microsolvation environment has a substantial effect on the width ofπ*resonance.Our results indicate that surrounding water molecules may affect the lifetime of the resonances,and hence the process is driven by the anion state,such as the dissociative electron attachment.

A Possible Role of the Gailitis Resonance in Muon Catalyzed Fusion

In a previous JMP article published May 2013, a comprehensive calculation was presented for all properties of a number of long-life s-state Gailitis resonances lying just above the PS(n = 2) formation threshold in a positron-Hydrogen scattering system. The six open-channel calculation was carried out by solving a set of four hundred thousand coupled linear equations. The modified Faddeev equation was used to obtain the wave-amplitude for each of the six open channels. Details can be found in reference [1] 08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000E0000005F005200650066003400300037003200380034003600370034000000 . This note presents some qualitative properties of Gailitis resonances in the scattering systems of d + tu just above the thresholds of the opening of a new channel of the muonic atoms tu(n) or du(n), n > 2 is the principal quantum number. u is a negatively charged muon, d and t are the nuclei of the two isotopes of the Hydrogen atom with one and two neutrons in the nucleus respectively. We study the possible decay channels of some of the long-life Gailitis resonances. Of particular interest is a transition directly from a Gailitis (3-body) resonance to the bound states dtu molecular ions via a radiative emission of a photon or an external auger ejection of a nearby electron. Possible experimental evidence will be presented.

复合助剂对低温喷雾干燥蓝靛果粉理化性质的影响

为保证低温喷雾干燥后蓝靛果粉品质,采用黄金分割法研究复合助剂(麦芽糊精、β-环糊精和乳清蛋白)对喷雾干燥蓝靛果粉理化性质的影响,分析低温进风温度(50~90℃)对蓝靛果粉花青素保留率、集粉率和含水率的影响规律。结果表明,在麦芽糊精、β-环糊精的质量比例为85.4%、14.6%时,集粉率高达37.96%;随进料溶液中麦芽糊精质量比例增加,蓝靛果粉玻璃化转变温度、水溶性指数、堆积密度、亮度L^(*)值、红度a^(*)值和色差值ΔE呈增加趋势,含水率、花青素含量和黄度b^(*)值呈下降趋势;在麦芽糊精、β-环糊精和乳清蛋白质量比例为72.9%、12.5%、14.6%时,集粉率达到最高(40.11%);随料液中乳清蛋白质量比例增加,蓝靛果粉含水率、花青素含量呈上升趋势,其玻璃化转变温度、水溶性指数、亮度L^(*)值、红度a^(*)值、黄度b^(*)值和色差值ΔE等指标呈下降趋势;复合助剂显著提高蓝靛果粉集粉率(P<0.05),对其中的花青素起到较强保护作用,其含水率、水溶性指数、堆积密度等理化指标均接近于最优水平。低温喷雾干燥研究发现,随进风温度上升,集粉率和含水率呈负相关,在进风温度90℃时,集粉率最高的配方中可实现较高花青素保留率(89.94%)。低频核磁共振波谱以及质子密度图像信息分析表明,加入的助剂与蓝靛果果汁中水分通过氢键、静电结合力和疏水作用等分子间作用力,形成稳定性高水合物、增强液滴聚结抵抗力,提高料液玻璃态转换温度,从而实现高集粉率和高花青素保留率的蓝靛果果粉低温喷雾干燥;红外光谱分析表明,复合助剂可在蓝靛果果粉中形成分子间氢键,并对花青素等活性物质进行固定包埋保护。研究结果可为蓝靛果粉喷雾干燥加工生产提供理论支撑和参考依据。

具有尖锐吸收截面和显著增强电场的等离激元-光子混合谐振腔

研究了由二维光子晶体微腔和金纳米天线组成的等离激元-光子混合谐振腔中光学谐振腔对等离激元谐振腔的额外贡献。研究结果表明:与纯等离激元谐振腔相比,混合体系的吸收截面和电场强度均明显增强。特别地,混合谐振腔的吸收截面谱呈现出类Fano线形和尖峰,可以通过改变金纳米天线的数量或金纳米天线与光子晶体微腔之间的共振波长失谐进行调制。此外,混合谐振腔的电场增强因子比金纳米天线高出3个数量级。可为光热探测和光谱增强研究提供新的平台。

腰椎管狭窄与马尾神经冗余关系的MRI形态学定量分析

目的探讨应用MRI分析腰椎管狭窄与马尾神经冗余(redundant nerve roots,RNRs)之间的关系。方法选取我院临床诊断为腰椎管狭窄患者155例的MRI资料。根据矢状位T2WI马尾神经形态将患者分为RNRs阳性组和RNRs阴性组,测量并记录狭窄节段椎管硬膜囊横截面积及硬膜囊前后径,统计分析RNRs阳性组和RNRs阴性组之间硬膜囊横截面积、硬膜囊前后径、椎管狭窄程度的差异,进一步分析RNAs阳性组椎管不同狭窄程度间马尾神经冗余长度的差异。结果腰椎管狭窄患者中马尾神经冗余的发生率为34.2%。RNRs阳性组平均年龄大于RNRs阴性组,腰椎管最窄层面平均硬膜囊横截面积及硬膜囊前后径均小于RNRs阴性组,椎管狭窄程度大于RNRs阴性组,差异均有统计学意义(P均<0.05)。RNRs阳性组女性发生率较男性稍高(56.6%vs 43.4%),但差异无统计学意义(P>0.05);RNRs阳性组椎管不同狭窄程度间马尾神经冗余长度差异具有统计学意义(P<0.05)。结论RNRs是一种特殊的影像学表现,常见于较严重的腰椎管狭窄患者,能够被MRI清晰地展现,为腰椎管狭窄症的明确诊断提供了重要的依据。

磁共振成像对剖宫产术后瘢痕妊娠的诊断价值

目的:探究磁共振成像对剖宫产术后瘢痕妊娠的诊断价值。方法:回顾性分析2016年1月—2023年12月疑似剖宫产术后瘢痕妊娠患者60例的临床资料,患者均进行磁共振成像与超声检查。以病理诊断为“金标准”,观察超声与磁共振成像诊断剖宫产术后瘢痕妊娠结果,分析超声与磁共振成像诊断剖宫产术后瘢痕妊娠的灵敏度、特异度、准确度。结果:病理结果阳性30例,阴性30例。超声检查诊断剖宫产术后子宫瘢痕妊娠41例,与病理结果符合21例;磁共振成像诊断剖宫产术后子宫瘢痕妊娠33例,与病理结果符合27例。超声与磁共振成像诊断剖宫产术后瘢痕妊娠的灵敏度比较,差异无统计学意义(P>0.05);磁共振成像诊断剖宫产术后瘢痕妊娠的特异度、准确度高于超声,差异有统计学意义(P<0.001)。结论:在剖宫产手术后瘢痕妊娠患者的诊断中,磁共振成像技术特异度、准确度高于超声,为早期诊断剖宫产术后瘢痕妊娠提供可靠的鉴别诊断依据。

基于白光中子源的^(197)Au中子辐射俘获截面测量及共振参数分析

中子辐射俘获反应在反应堆运行、核装置设计及核天体物理研究中起重要的作用.4πBaF_(2)探测装置有着高时间分辨能力、低中子灵敏度、高探测效率等优点,适合开展中子辐射俘获反应截面数据的测量.中国原子能科学研究院核数据重点实验室建立了伽马全吸收装置(Gamma total absorption facility,GTAF),该装置用28块六棱BaF_(2)晶体和12块五棱BaF_(2)晶体构成了外径25 cm,内径10 cm的球壳,覆盖了95.2%的立体角.利用GTAF在中国散裂中子源Back-n束线上,测量了197Au(n,γ)的反应截面数据.测量数据通过能量筛选、PSD方法、晶体多重性筛选进行了初步本底扣除,随后结合对^(nat)C及空样品的测量数据对本底进行了分析及扣除,获得了197Au俘获反应的产额,利用SAMMY程序拟合得到了^(197)Au在1—100 e V的共振能量、中子共振宽度和伽马共振宽度参数.实验测量结果与ENDF/B-VIII.0数据库符合良好,其共振参数存在一定差异,分析原因可能与GTAF能量分辨率、Back-n的中子能谱测量精度、以及实验本底扣除方法相关,这也是下一步工作的重点.

表观扩散系数直方图对评估前列腺癌包膜外侵犯的附加价值

目的探讨磁共振表观扩散系数(ADC)直方图对评估前列腺癌包膜外侵犯(EPE)的附加价值。资料与方法回顾性连续纳入2021年1月—2022年12月于解放军总医院第一医学中心行根治性前列腺切除术,并于术前行标准多参数MRI扫描的100例前列腺癌患者,由2名放射科医师使用EPE分级系统独立评估图像,协商后确定评分。应用FireVoxel软件在ADC图上勾画全瘤体,进行直方图分析得到ADC平均值、第1、5、10、25、50、75、90、95和99百分位数ADC值(99th ADC)。比较组间差异,应用多因素Logistic回归筛选评估EPE的独立危险因素,并构建联合模型。采用受试者工作特征曲线评估效能,并比较曲线下面积。结果术后病理证实34例(34%)前列腺癌EPE阳性。ADC直方图分析显示EPE阳性与EPE阴性组间各参数差异有统计学意义(P<0.05)。多因素Logistic回归分析显示,99th ADC(OR=0.609,P=0.008)和EPE分级系统(OR=4.158,P<0.001)是评估EPE的独立危险因素。99th ADC、EPE分级系统及联合模型评估EPE的曲线下面积分别为0.756、0.805和0.856,99th ADC和EPE分级系统评估EPE的效能差异无统计学意义,联合模型的评估效能显著优于两者单独应用(Z=2.223、2.208,均P<0.05)。结论ADC直方图对术前评估EPE具有一定附加价值,99th ADC联合EPE分级系统能有效评估EPE。

基于介质谐振器的薄导电板侧向回射增强设计

该文提出了基于无源介质谐振器腔内磁偶极子谐振的准超方向性再辐射,旨在增强薄导电板受到平面电磁波侧向照射时的后向散射截面。在平面电磁波激励下,设计适当的长方介质体中可诱导产生具有磁偶极子再辐射特征的混合电磁谐振模式。以长方介质体为基本谐振单元,将两个相同的介质体沿入射波传播方向紧密级联以组成一个超单元。超单元的两个介质体中的磁场强度与电场强度矢量均呈现相反的方向且相近的幅度,接近等幅而反相的内部场分布使超单元类似一个二元准超方向性磁偶极子阵列,由此产生的准超方向性再辐射有效地贡献于后向散射截面增强。进一步,由镜像原理,将超单元剖面厚度减半并加载于薄导电板表面。结果表明,剖面厚度仅为0.078λ0的介质谐振器形成基于磁偶极子的准超方向性再辐射,在谐振频率处可显著修改薄导电板的侧向回射特性,进而在相对宽带宽角范围内对侧向入射波实现有效的后向散射截面增强。

磁共振成像在早期剖宫产瘢痕妊娠和不全流产瘢痕停滞的诊断价值

目的探讨早期剖宫产瘢痕妊娠(CSP)和不全流产瘢痕停滞的磁共振成像(MRI)表现及两者之间的鉴别特征。方法收集本院和安阳市妇幼保健院2017年3月至2023年11月经临床及病理证实的53例早期CSP和16例不全流产瘢痕停滞患者的临床资料。用χ^(2)检验对比分析2组MRI征象之间差异是否存在统计学意义。结果CSP的MRI表现:妊娠囊形态规则、饱满48例,囊内信号均匀,囊壁厚薄较一致;35例患者妊娠囊可见尖角状或结节状凸起向瘢痕肌层延伸,14例患者妊娠囊与瘢痕分界模糊,瘢痕处肌层连续性中断;宫体肌层局部增厚突出8例;宫腔积血37例。不全流产瘢痕停滞的MRI表现:13例患者妊娠囊形态不规则,部分囊壁皱缩或塌陷,形态饱满3例;14例患者妊娠囊与瘢痕分界清晰,1例见尖角状凸起,1例分界模糊,肌层连续性中断;宫体肌层局部增厚突出14例;宫腔积血13例。妊娠囊的形态、妊娠囊与瘢痕间的尖角状或结节状凸起及宫体肌层局部明显增厚突出,2组之间差异具有统计学意义(P<0.01)。结论早期CSP和不全流产瘢痕停滞的MRI表现具有一定特征性,妊娠囊的形态、妊娠囊与瘢痕间的尖角状或结节状凸起及宫体肌层局部明显增厚突出对CSP和不全流产瘢痕停滞的诊断和两者之间的鉴别具有重要价值。

Management of a Huge Ovarian Cyst in Pregnancy at the Douala General Hospital, Cameroon: A Case Report and Review of the Literature

Background: Ovarian cysts in pregnancy are common and are usually small benign functional cysts (corpus luteum and theca-lutein cysts) that usually resolve spontaneously between 14 and 16 weeks of gestation. However, large ovarian cysts are rare in pregnancy, with an incidence of 0.2% - 2%, and most of them are benign. The first-line diagnostic modality is ultrasonography. Complications of ovarian cysts in pregnancy include miscarriage, ovarian torsion, cyst rupture, etc. Laparotomy is the treatment modality commonly used in our setting, and histopathologic diagnosis is important for the prognosis of the treatment. Case Presentation: MC is a 32-year-old G3P2002 married housewife of the Bakweri tribe who was referred to our department because of progressive abdominal discomfort and shortness of breath for 1 month’s duration. Her medical history is consistent with two normal vaginal deliveries at term and the use of implants (for contraception) until one month prior to the index pregnancy. Her booking visit was at 16 weeks gestation at a primary (missionary) healthcare facility, and she underwent ultrasonography and was diagnosed with a singleton viable intrauterine pregnancy and a simple septate cystic mass measuring 17 cm situated on top of the uterus, appearing to originate from the left ovary. She was referred to seek the expertise of an obstetrician-gynecologist, but she came to our department at 35 weeks gestation and underwent cesarean birth at 37 weeks gestation. In the pathological review, serous cystadenoma was diagnosed, and there were no positive findings in peritoneal cytology. Conclusion: The ultrasonographic diagnosis of the huge ovarian cyst in the index case was after 16 weeks gestation because of her late booking visit at 16 weeks gestation. The index case deferred referral to the obstetrician because of a lack of finances, came to our department at 35 weeks gestation because of abdominal pain that may have resulted from a torsion of the ovarian cyst, and underwent cesarean birth because of malpresentation and fear of cyst rupture during labor. We recommend cesarean section in such cases because of suboptimal antenatal care uptake and histopathology of the specimen to exclude malignancy. .

一种椭圆形截面拱的气动特性及共振风速研究

以一个椭圆形截面拱为工程背景,对其气动特性和共振风速进行了研究。首先,分别制作了该结构1∶150和1∶300缩尺比的测压与测力试验模型,研究了典型工况下的平均和脉动风压系数、平均气动力系数及Strouhal数等。其次,采用测力试验得到的三个坐标轴方向脉动基底力对应的峰值频率,对该结构的共振风速进行了估算。结果表明:该椭圆截面拱的气流分离点出现在圆周角112.5°附近,最小平均风压系数在0.9左右波动;脉动风压分布受气动外形影响较大,最大脉动风压系数发生在拱顶靠近观光平台的两侧截面气流分离点处,约为0.23;平均气动力系数在拱轴方向沿圆周关于180°风向角反对称,而在垂直于拱轴的方向呈正对称,最大平均阻力系数为0.42左右,远小于圆形截面值;结构三个坐标轴方向的脉动基底气动力功率谱均出现明显的能量峰值,且各峰值对应的频率不同;结构的第一阶振动以垂直于拱轴方向的振动为主,共振风速为38.8 m/s。

基于多频带多特征融合的配电网单相接地故障选段方法

针对现有配电网单相接地故障选段方法存在的通信负担重、阈值设置困难及故障特征量单一等问题,提出一种基于多频带多特征融合的配电网单相接地故障选段方法。首先,利用小波包变换分别对故障后首半个工频周期的零序电压导数和零序电流进行分解和重构,得到原始波形的不同频带分量。其次,根据不同频带分量间的极性关系分别引入伏安特性特征向量与零序功率累加和作为故障特征。最后,筛选特征频带并构造基于特征频带与故障特征融合的选段判据。仿真实验及现场数据验证结果表明,所提方法能够有效实现单相接地故障免阈值就地选段。

等截面高耸烟囱涡激共振时风荷载的风力作用研究

关于锁定区域范围的描述,不同参考文献存在显著的差异。同一类型地形结构发生涡激共振时,横向风向的等效风荷载在基本一致的情况下可能仍存在显著差异。依托实际工程案例,在分析锁定区及横风向等效风荷载的基础上对组合等效风荷载进行确定,结果发现,实例计算检查测试结果与规范之间存在较大差异。

面向轻量级新工具链:GNDS-JSON格式核数据的共振重建

为了验证基于GNDS-JSON格式处理评价核数据能否用于粒子输运模拟,构建了一个新的轻量级工具链。新工具链无须先将ENDF-6或GNDS格式的数据转换为自定义的内部数据结构,可以直接在读入的GNDS-JSON格式数据上进行处理。作为该轻量级工具链的第一步,成功实现了可分辨共振截面重建功能,并在ENDF/B-VIII.0数据库上与NJOY程序进行了比较。计算结果表明,除少数核素外,重建截面的最大相对偏差小于10^(-5),均方根相对偏差约为10^(-6),验证了基于GNDS-JSON打造轻量级新工具链的可行性。同时也发现了自研程序和Fudge程序在处理40 Ca的复杂R-Matrix形式共振参数时的错误。工具链的轻量化可为核数据处理工具的敏捷开发提供参考。

基于同步挤压S变换的谐振接地系统单相接地故障区段定位方法

谐振接地系统单相接地的故障特征微弱,故障区段难以定位。根据健全与故障区段电流低频能量差异大的特点,利用同步挤压S变换挤压、重组低频区段电流,增强故障特征辨识度;计算各区段能量比值,将能量比值最大的判为故障区段,提出基于同步挤压S变换的故障区段定位方法。以全频区段电流重组信号的峭度因子构建保护启动判据。不同故障条件影响下,大量PSCAD仿真测试了所提启动和区段定位方法的性能及可行性,现场数据验证了所提方法的有效性。