Z-pinch X射线时间分辨多幅图像诊断系统

介绍了为"强光一号"设计的ns级时间分辨软X射线多幅图像诊断系统,分析了系统的主要性能指标,给出并分析了利用该系统诊断"强光一号"高功率脉冲Z pinch等离子体辐射源的最新的实验结果。

复数射线时间叙事与小说叙事立体空间的建构

外部环境的变化,以及人们对世界认知的变化,使小说传统的线性叙事面临着危机这种叙事显得把世界简单化了。但是另一方面,小说叙事的特质又是线性的。近年来在长篇小说叙事中,一种新的,我称之为复数射线时间叙事模式兴起,这种叙事模式中,在一条主叙事轴上会存在多个分叉叙事,从而对主叙事轴进行了有效的丰富。通过这种复数射线时间叙事模式,小说有效建构起一个立体叙事空间,从而呈现了更为复杂的现实。

最小时间两点射线追踪

陈裕明 ,李晶 ,唐湘蓉 ,张海燕 .最小时间两点射线追踪 .石油地球物理勘探 ,2 0 0 2 ,37(5 ) :4 5 5～ 4 5 9 本文利用费马原理提出了一种快速、有效的射线追踪方法——最小时间射线追踪方法。首先利用三次样条函数详细描述地质模型 ,根据费马原理导出微分形式的射线路径方程组。为确保算法的鲁棒性和精确度 ,本文提出在保证一定运算速度的情况下 ,尽可能同时提供多种解法 ,以确保成功地得到射线路径 ,并且给出多组不同的初始值 ,以解决多解问题 ;然后以利用梯度法为例简单介绍了求解的过程 ,推导了梯度法的主要数值计算公式。模型试算结果表明 ,本文所提出的方法具有精确、适用于复杂地质模型的特点 ,其运算速度与打靶法相比提高了两个数量级。

经桡动脉入路(TRA)与经股动脉入路(TFA)全脑血管造影术临床应用观察

研究全脑血管造影术中,经桡动脉入路(TRA)、经股动脉入路(TFA)的应用价值。方法 选取2021年04月-2023年09月,医院总脑血管造影术例数632例,TRA全脑血管造影312例(TRA组),TFA全脑血管造影320例(TFA组)。采用SPSS25.0版本统计学软件,对比两组造影时间、射线时间、术后恢复时长、曝光时间、造影前后的血清氧化应激因子、并发症发生率。结果 TRA组、TFA组曝光时间、造影时间、射线时间以及术后恢复时长显示前者更短,差异有统计学意义(P<0.05);与TFA组相比,TRA组造影后的血清氧化应激因子较低,差异有统计学意义(P<0.05);TFA组并发症发生率较TRA组高,差异有统计学意义(P<0.05)。结论 TRA全脑血管造影实施价值及安全性高,实施后患者并发症发生率较低,可以有效抑制血清氧化应激因子,缩短造影、射线时间,加快患者术后恢复速度,具有较高的推广及应用价值。

整体多毛细管X光透镜在扩展X射线吸收精细结构分析技术中的应用(英文)

为了将整体多毛细管X光透镜应用到扩展X射线吸收精细结构分析技术中,对整体多毛细管X光透镜的功率密度增益、光斑稳定性、高能滤波性质等进行了系统表征。通过实验可知,利用基于整体多毛细管X光透镜的扩展X射线吸收精细结构分析设备可对样品进行微区分析,其空间分辨为25μm左右;利用整体多毛细管X光透镜会聚激光等离子体发出的X射线进行超快时间分辨扩展X射线吸收精细结构分析时,透镜的功率密度增益约为3000。实验结果证明,整体多毛细管X光透镜可以改善扩展X射线吸收精细结构分析设备的性能。

三维标测系统在射频消融治疗阵发性室上性心动过速中的研究现状

三维标测系统作为一种新型标测手段,因其独特的有效性和准确性,已被广泛应用于复杂性心律失常的射频消融治疗中。随着对三维标测系统的进一步认识和熟练掌握三维标测技术,其在导管消融治疗阵发性室上性心动过速中的优势逐渐显露,现有研究显示三维标测系统引导下结合短暂X射线透视,可明显减少阵发性室上性心动过速射频消融术中X射线透视时间和曝光剂量,具有同样高的成功率,三维标测系统在阵发性室上性心动过速射频消融中展示出的安全性及有效性,使快速性心律失常的射频消融治疗进入了一个新时代。

Enhanced Photoelectrochemical Property of Zn Loaded TiO2 Nanotube Arrays Electrode

TiO2 nanotube arrays （TNTs） electrode loaded with Zn nanoparticles was prepared by anodization and the size of Zn nanoparticle loaded on TNTs electrode was controlled by chronoamperometry deposition time. Results of SEM and XRD analysis show that Zn nanoparticles had a diameter of about 15-25 nm when the deposition time was 3-5 s. The UV-Vis diffuse reflectance spectra show the Zn loaded harvest light with 480-780 nm more effectively than the unloaded sample. The photocurrent response of Zn loaded TNTs electrodes were studied, the results showed that TNTs electrodes loaded with Zn nanoparti-cles has 50% increased photocurrent response under high-pressure mercury lamp irradiation compared with unloaded TNTs electrode.

时间分辨原位同步X射线衍射技术在分子筛研究中的应用

介绍了时间分辨原位同步 X射线衍射技术 (in situ TR XRSD)的原理。该技术以其原位测量性和时间分辨性为特征 ,广泛应用于分子筛研究的各个领域。举例阐述了该技术在水热合成条件的优化、结晶动力学参数测定、成核机理探索、转晶过程和机理。

Microstructure comparison of ZK60 alloy under casting,twin roll casting and hot compression

The microstructures of ZK60 alloy under conventional direct as-casting (DC),twin roll casting (TRC) and twin roll casting followed by hot compression (TRC-HC) were analyzed by optical morphology (OM),electron backscatter diffraction (EBSD) and X-ray diffraction (XRD).The deformation condition of hot compression is 350 ℃,0.1 s?1.The microstructural evolution under TRC-HC deformation followed by annealing at different temperatures and time was discussed.The results show that TRC provides more modified microstructure compared with DC.Twins are found in TRC processing;dynamic recrystallization (DRX),shear bands and twins are found in TRC-HC.A short annealing time has little effect on hardness,while during a long time annealing,it is found that low annealing temperatures increase the micro-hardness and high temperature decreases it.

压力感应导管在环肺静脉消融中的优势

环肺静脉隔离术的持久稳定与很多参数有关,其中包括:导管尖端电极的尺寸和组成、导管尖端的方向、温度、射频导管消融时间、功率、血流以及导管与组织的接触。新的压力感应导管射频导管消融的发展已可满足在射频导管消融术中测量出导管尖端与组织的压力。现就心房颤动射频导管消融中使用压力感应导管的经验,特别是在术中的参数(手术时间和X射线透视时间)做一综述。

Electroless nickel plating on the surface of carbon fibers

The electroless nickel plating on the surface of carbon fibers was prepared by pretreating the carbon fibers in order to increase their conductivity,and consequently enhance the EMI shielding effectiveness of the composites.The relationship between the performance of depositing coat and pH value,temperature,reaction time and the way of agitation was studied.Results show that the depositing quality is stable under pH between 4.5 and 5.0,temperature between 75 ℃ and 85 ℃,reaction time for 10 min and air agitation.The uniform and compact nickel layer deposited on carbon fibers was proved by XRD and SEM,and the electrical resistivity of carbon fibers with nickel coating was tested.Results indicate that the electrical resistivity of carbon fibers with electroless nickel plating is decreased by an order of magnitude compared with that of carbon fibers.It means that nickel coating can greatly improve the electromagnetic interference shielding properties of carbon fibers.

Preparation of ZAO film by low-temperature hydrothermal approach and its electrical property

Al-doped ZnO (ZAO) films were successfully deposited on the surface of common glasses by using low-temperature hydrothermal approach. In the reaction solution, the molar ratio of Al3+ to Zn2+ was 1∶100, the annealing temperature and time were 200 ℃ and 2-6 h, respectively. The structure of the thin films was identified by X-ray diffraction (XRD), the surface morphology and thickness of the thin films were observed by scanning electron microscopy (SEM), and the electrical performance of the thin films was measured by four-point probes. It was shown that the films with an average particle size of 27.53 nm had a preferential orientation along (002), Al3+ had replaced the position of Zn2+ in the lattice without forming the Al2O3 phase and its thickness was 20-25 μm. With the increased annealing time, the intensity of diffraction peaks was decreased, the film exhibited irregular surface morphology gradually, and the resistivity of ZAO films was increased. The lowest resistivity obtained in this study was 3.45×10-5Ω·cm.

锗dc到β-Sn结构的压致相变动力学研究

室温常压下锗是一种具有高载流子迁移率和窄带隙的半导体材料。在高压下,锗具有多种与硅相似的晶相,其有趣的高压行为如压致金属化和超导电性转变引起了高压研究领域的广泛关注。然而,其核心的高压相变动力学机制却鲜有深入研究。利用先进同步辐射光源的高通量X射线衍射结构诊断手段,结合基于金刚石压砧的快速动态压缩技术,研究了锗在高压相变过程中的结构演化机理。采用气膜与压电陶瓷相结合的快速加载方法,实现了数十太帕每秒的压缩速率。采用第三代同步辐射高通量粉光X射线衍射技术,实现了数十微秒时间分辨的结构解析。在相变过程中,新旧相中不同晶面的衍射强度变化存在一定的先后顺序,证实了锗的半导体相(金刚石立方结构)到金属相(β-Sn结构)的转变是位移型相变。此外,通过与静态压缩X射线衍射数据的对比,证实了在此相变过程中不同晶面消失/出现存在先后顺序的行为只能通过动态压缩和动态探测手段观察。

地震资料的九类成象方法

本文给出了九类成象方法，分析了共中心点迭加方武的弊病，叙述了共反射点迭加对成象精度的改善，提出了一种依赖于时间与倾角的NMO-DMO速度分析方法，指出这种方法可以克服速度谱解释的多解性。在简要比较了迭前全偏移与达前部分偏移后，说明了对横向变速介质使用深度偏移的必要性以及深度偏移在实用中的困难所在。最后叙述了全三维处理的基本内容，给出了一个实用的三维处理流程，并对各种成象技术给予了简要评价。

Short-Wave Emission and Microdischarges during Self-Propagating High-Temperature Synthesis

Emission in the X-ray and ultraviolet （200-300 nanometers） region of spectrum is found out during combustion of heterogeneous systems with the formation of condensed products, and pulses from microwave emission with short duration are recorded as well. Combustion of a Ti-B powder system showed that self-propagating high-temperature synthesis （SHS） is accompanied by two types of X-ray radiation. Radiation of the first type has the maximum quantum energy - 5 keV. It is supposed that this type is caused by micro-breakdowns due to the charge separation in combustion products. Runaway electrons and soft X-ray radiation are generated due to the concentration of electric field on microparticles during breakdown. Radiation of the second type has the quantum energy up to - 15 keV. It is supposed that it is caused by exoemission of photons. UV radiation in the region of 200-300 nm is recorded during SHS in different gases （He, Ar, N2）. This radiation is shown to have the highest intensity in helium at the pressure - 25 x 103 Pa.

Single-versus multi-fraction radiation treatment for metastatic spinal cord compression:functional outcome study

Objective:The optimal treatment of patients with metastatic spinal cord compression(MSCC) is still being debated.This randomized trial was planned to compare the functional outcome and its related prognostic factors,toxicity and in-field recurrence of the three schedules of radiotherapy.Methods:Two hundred and eighty five patients enrolled in the study of which 95 received 1 × 8 Gy,100 received 10 x 3 Gy and 90 received the radiation treatment of 20 × 2 Gy.Irradiation was performed with 6-10 Mv linear accelerators or cobalt-60 units by single posterior field or parallel opposed fields according to depth of irradiation spines.Premedication with dexamethasone was started from the first day of clinico-radiologic diagnosis till 4-5 days after the end of radiotherapy(RT) then tapered off during 10 days.Potential prognostic factors were evaluated with respect to functional outcome.Results:All groups were balanced for patient's characteristics and potential prognostic factors.No statistically significant difference was observed between the 3 groups as regard functional outcome and toxicity while single fraction was associated with higher in-field recurrences(22.8%) with statistically significant difference between the 3 groups(P = 0.01).Functional outcome was significantly better with younger age(≤ 60 y),Eastern Cooperative Oncology Group performance status(ECOG-PS) of 1-2,involved vertebra of 1-2,favorable tumor type,absence of visceral or other bone metastasis,decreased time of developing motor deficit before radiotherapy,long interval between cancer diagnosis to metastatic spinal cord compression,and normal ambulatory status.Conclusion:The three schedules provided similar functional outcome.Single-radiation dose was associated with higher in-field recurrence.To minimize treatment time and costs,the dose of 1 × 8 Gy is recommended for patients with poor predicated survival and 10 × 3 Gy for other patients.

A Forward-Secure Multi-Receiver Signcryption Scheme

In order to protect historical ciphertext when the private key leaked in the broadcasting system,the forward-secure multi-receiver signcryption scheme is designed based on the generic graded multilinear mapping encoding structure,which effectively prevents illegal access from intruder to the ciphertext in the past time period when the private key in current time period is revealed.Through the generalization of the existing multilinear mapping encoding system,it proposes the generic graded multilinear mapping encoding structure and the generic graded decision Diffie-Hellman problem.Because of the generic graded multilinear mapping encoding system adopted,almost all candidate multilinear mapping encoding systems can automatically adapt to our scheme.Under the assumption of generic graded decision Diffie-Hellman problem,it has proved that the scheme has the information confidentiality and unforgeability in the current time period.After putting forward the security model of forward-secure multi-receiver signcryption scheme,and under the assumption of generic graded decision Diffie-Hellman problem,it has proved that the scheme has the message forward-confidentiality and forward-unforgeability.Compared with other forward-secure public key encryption schemes,the relationship between our scheme and time periods is sub-linear,so it is less complex.

Radio variability for OJ287 and 3C279

Based on the new data from the database of the University of Michigan Radio Astronomy Observatory （UMRAO）, we analyze the spectral index and optical variability of OJ287 and 3C279. The main results show that 1） the time delay among three radio bands （4.8, 8, and 14.5 GHz） shows： r8-14.5 = 31 d, r4.8-8 = 41 d for OJ287, but no time delay lying in 3C279; 2） strong correlation lies in the polarization and flux density at 8 GHz for OJ287 and at 8, 14.5 GHz for 3C279; 3） the logarithmic brightness temperature log（TB） = 14.l K for OJ287 is 14.1 K, log（TB） = 15.1 K for 3C279.

Comparison between the time-integrated spectrum and the peak time spectrum of gamma-ray bursts and possible implications

The mono-frequency peak luminosity and the corresponding photon energy of the time-integrated （L~, Eg） and peak time （L~, ffp） vfv spectra were derived for a sample of 38 redshift-known Fermi GRBs by fitting the spectra with the Band function. It was found that Ept is generally consistent with Ep, and Lp is averagely three times larger than Lp. The slope of the Lp1 -Etp relation was consistent with that of the Lps - Eps relation. The photon indices in the peak time spectrum, particularly, the index of the low energy end was, were statistically larger than that in the time-integrated spectrum. These results indicate that Lp and Ep are dominated by Lp1 and Ept, respectively. The difference of the spectral indices between the time-integrated and peak time spectra may be because of the overlap effect of a series of time-resolved spectra within a GRB. Our simulations, which were based on the observed spectral evolution and correlation between the energy flux and the peak energy within individual GRBs support our speculations. The Lt - Et, relation may be less contaminated by the overla!a effect, and it would may be an intrinsic feature of radiation ohvsics.

Quasi-periodic variations of low energy cosmic rays

Cosmic rays(CR)play an important role in space weather-related studies.Their temporal variability,both of a quasi-periodic character as well as an irregular one,has been studied from ground-based direct measurements,as well as from cosmogenic nuclides,over a long time.We attempt to describe the current knowledge of selected quasi-periodicities in CR flux in the energy range above the atmospheric threshold,from direct measurements.The power spectrum density(PSD)of the CR time series as measured by neutron monitors(NMs)and by muon detectors has a rather complicated character.Along with the shape(slope)of the PSD,knowledge of the contribution of quasi-periodic variations(q-per)to the CR signal is of importance for the modulation,as well as for checking the links of CR to space weather,and/or to space climate effects.The rotation of the Earth and solar rotation cause two types of mechanisms behind the certain q-per observed in secondary CR on the Earth’s surface.Solar activity and solar magnetic field cyclicities contribute to the q-per signals in CR if studied over a longer time.The complexity of the spatial structure of the interplanetary magnetic field(IMF)and its evolution within the heliosphere,in addition to the changes in the geomagnetic field,cause variability in contributions of the q-per in CR.Wavelet spectra are useful tools for checking the fine structure of q-per and their temporal behaviour.Over a long time NMs and muon telescopes provide information about q-per in CR.