Experimental research on the feature of an x-ray Talbot–Lau interferometer versus tube accelerating voltage

X-ray Talbot-Lau interferometer has been used most widely to perform x-ray phase-contrast imaging with a con- ventional low-brilliance x-ray source, and it yields high-sensitivity phase and dark-field images of samples producing low absorption contrast, thus beating tremendous potential for future clinical diagnosis. In this work, by changing the accel- erating voltage of the x-ray tube from 35 kV to 45 kV, x-ray phase-contrast imaging of a test sample is performed at each integer value of the accelerating voltage to investigate the characteristic of an x-ray Talbot-Lau interferometer （located in the Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Japan） versus tube voltage. Ex- perimental results and data analysis show that within a range this x-ray Talbot-Lau interferometer is not sensitive to the accelerating voltage of the tube with a constant fringe visibility of ~ 44%. This x-ray Talbot-Lau interferometer research demonstrates the feasibility of a new dual energy phase-contrast x-ray imaging strategy and the possibility to collect a refraction spectrum.

Improvements to conventional X-ray tube-based cone-beam computed tomography system

Conventional X-ray tube-based cone-beam computed tomography(CX-CBCT) systems have great potential in industrial applications. Such systems can rapidly obtain a three-dimensional(3D) image of an object.Conventional X-ray tubes fulfill the requirements for industrial applications, because of their high tube voltage and power. Continuous improvements have been made to CX-CBCT systems, such as imaging time shortening,acquisition strategy optimization, and imaging software development, etc. In this study, a CX-CBCT system is developed. Additionally, some improvements to the CX-CBCT system are proposed based on the hardware conditions of the X-ray tube and detector. A near-detector(ND)geometry condition is employed to obtain a sharper image and larger detection area. An improved acquisition strategy is proposed to simplify operations and reduce total imaging time. In the ND geometry condition, a simplified method called FBP slice stacking(SS-FBP) is proposed, which can be applied to 3D image reconstruction. SS-FBP is timesaving relative to traditional methods. Furthermore, imaging software for the CX-CBCT system is developed in the MATLAB environment. Several imaging experiments were performed. The results suggest that the CX-CBCT system works properly, and that the above improvements are feasible and practical.

Effects of Tube Voltage on Phase-Contrast Imaging for Different Microfocus X-Ray Tubes

In the past decade, phase-contrast imaging (PCI) has become a hot research with an increased improvement of the image contrast with respect to conventional absorption radiography. In this paper, effects of tube voltage (kVp) on propagation-based phase-contrast imaging have been investigated with two types of microfocus x-ray tubes, a conventional sealed x-ray tube with the focal spot size of 13 - 20 μm and an open x-ray tube with minimum focal spot size less than 2 μm. A cooled x-ray CCD detector with the pixel size of 24 μm was used to acquire digital images. Two thin plastic sheets with different thickness were used as radiography phantoms. Two different phenomena were observed for the two x-ray tubes. For the open tube, phase-contrast effect has a slight drop with the increasing of tube voltage, however, it is opposite for the sealed tube. A further investigation indicates that the variation of focal spot size causes the abnormal result for the sealed tube. It also shows that phase-contrast effect is more sensitive to focal spot size than tube voltage.

Simulating Medical Imaging X-Ray Tubes with Various Parameters Using BEAMnrc Monte Carlo Software

Context: Medical imaging has a wide range of applications in today’s society. Basic projectional radiography, CT scans, mammograms and a range of other advanced technologies all use x-rays to create a large number of examinations every day across the world. The most essential component of such medical equipment is the x-ray tube, which creates and produces x-rays. Objective: We describe and investigate an abstract model-geometry of a simple x-ray tube utilizing the open-source software package of BEAMnrc of the EGSnrcmp family, which is well validated by several studies over the years, for high and low energy photons generation. Methodology: Our research focuses on two different electron beam energies: 120 keV and 30 keV. The 120 keV is the typical energy for simple projectional radiographic exams and CT examinations, whereas the 30 keV is the typical energy of mammography. Results: Two different anode materials are used for each case, Gold (Au) and Tungsten (W) for 120 keV because these are the most common in projectional radiography and CT;Molybdenum (Mo) and Rhodium (Rh) for 30 keV because with these targets most mammography exams are carried out. The aim of this work is to show how the BEAMnrc software package can simulate effectively x-ray generation of low-energy photons which are utilized in modern medical imaging procedures. We describe useful information on anode-target characteristics, such as anode angle, anode material, and metal filter materials, based on previous quality studies even by using software other than BEAMnrc. Conclusion: We demonstrate that BEAMnrc can be efficiently used for Monte Carlo modeling of low-energy photons.

非周期同心圆弧折叠波导行波管的永磁聚焦系统设计

开展了对非周期折叠波导行波管永磁聚焦系统的研究。基于W波段非周期折叠波导行波管的技术指标,根据理论分析和电磁仿真,设计了一套均匀永磁聚焦的电子光学系统,并进行了实物加工与测试。仿真结果表明,在电子主通道直径0.3 mm,长度为40.5 mm的条件下,阴阳极电压差为6 kV,可以产生120 mA的电流,电子通过率100%。测试结果表明,在阴阳极施加6 kV的电压时,阴极发射电流为120 mA,电子通过率为90%,满足高频结构设计要求。

12Cr2Mo1锻件带极埋弧堆焊Inconel625工艺研究

为保证12Cr2Mo1锻件带极埋弧堆焊Inconel625质量达到设计文件要求,对锻件基材和Inconel625焊接性能进行了分析,模拟承制产品实际生产状态进行堆焊工艺评定试验,采用周向堆焊和直道堆焊相结合的方法制备评定试件,对堆焊层化学成分、弯曲性能、硬度指标、金相组织、耐腐蚀性能进行了检测。试验结果表明,采用EQ62-50/ES200的焊带/焊剂组合可以获得性能优良的堆焊层。对堆焊层进行腐蚀速率检测,其焊态试样腐蚀速率为1.50 mm/a,固溶态试样腐蚀速率为1.17mm/a,两者之比为1.28,满足JB/T 4756—2006标准规定比值小于或等于1.5的要求。根据评定合格的焊接工艺对热高分气/循环氢换热器管板进行了堆焊,堆焊产品已稳定运行三年,未出现焊接缺陷和腐蚀缺陷。

Chemical Analysis of Hydroxyapatite Artificial Bone Powders by Energy Dispersive X-Ray Fluorescence Spectrometry(EDXRF)

Stoichiometric hydroxyapatite(HA)nanoparticles were synthesized by a wet chemical method.Calcium nitrate tetra hydrate used as calcium source and dibasic ammonium phosphate used as phosphorous source.Calcium nitrate tetra hydrate and dibasic ammonium phosphate solutions were prepared by dissolving the salts in distilled water.Stoichiometric hydroxyapatite nanoparticles used by artificial bone powders and synthesized by a wet chemical method were analyzed using EDXRF method.The concentrations of K,Ca,Ti,V,Cr,Fe,Ni,Cu,Sr and Pb for artificial bone powders have been determined.Besides,Calcium contents were evaluated according to the agitation time and temperature in the production process.

Pressure and Arc Voltage Measurement in a 252 kV SF_6 Puffer Circuit Breaker

The pressure distribution in an arcing chamber is critically important for the SF6 puffer circuit breaker design. In this paper, the pressure variation of four locations in the nozzle was measured by piezoresistive and fiber optical pressure sensors at two current levels of 10 kA and 50 kA. An arc voltage measurement was also taken. The results demonstrate that using either type of sensor with a connecting tube is able to detect the fast pressure variation in circuit breakers, however the possible distortion and delay to the pressure transient caused by the tube need further study.

High-Temperature Corrosion of Protective Coatings for Boiler Tubes in Thermal Power Plants

High-temperature corrosion is a serious problem for the water-wall tubes of boilers used in thermal power plants. Oxidation, sulfidation and molten salt corrosion are main corrosion ways.Thereinto, the most severe corrosion occurs in molten salt corrosion environment. Materials rich in oxides formers, such as chromium and aluminum, are needed to resist corrosion in high-temperature and corrosive environment, but processability of such bulk alloys is very limited. High velocity electric arc spraying (HVAS) technology is adopted to produce coatings with high corrosion resistance. By comparison, NiCr (Ni-45Cr-4Ti) is recommended as a promising alloy coating for the water-wall tubes, which can even resist molten salt corrosion attack. In the study of corrosion mechanism, the modern material analysis methods, such as scanning electron microscopy (SEM), X-ray diffractometry (XRD) and energy dispersive spectrometry (EDS), are used. It is found that the corrosion resistances of NiCr and FeCrAI coatings are much better than that of 20g steel, that the NiCr coatings have the best anti-corrosion properties, and that the NiCr coatings have slightly lower pores than FeCrAI coatings.It is testified that corrosion resistance of coatings is mainly determined by chromium content, and the microstructure of a coating is as important as the chemical composition of the material. In addition, the fracture mechanisms of coatings in the cycle of heating and cooling are put forward. The difference of the thermal physical properties between coatings and base metals results in the thermal stress inside the coatings. Consequently, the coatings spall from the base metal.

Naso-jejunal tube insertion-interface between radiology and endoscopy

A survey was performed to identify the practice associated with endoscopic placement of naso-jejunal(NJ) tubes. We had a total of 236 responses, of which 228 responded to the frequency of requesting X-rayafter placing NJ tubes. The responses suggested that there was a strong variation in the practice. The practice was independent on clinicians' area of interest, hospital setting or experience in endoscopy. Currently there are no accepted guidelines on this. Hence, we advise hospitals to have robust local guidelines until there is internationally agreed consensus.

Energy spectrum of multi-radiation of X-rays in a low energy Mather-type plasma focus device

The multi-radiation of X-rays was investigated with special attention to their energy spectrum in a Mather-type plasma focus device （operated with argon gas）. The analysis is based on the effect of anomalous resistances. To study the energy spectrum, a four-channel diode X-ray spectrometer was used along with a special set of filters. The filters were suitable for detection of medium range X-rays as well as hard X-rays with energy exceeding 30 keV. The results indicate that the anomalous resistivity effect during the post pinch phase may cause multi-radiation of X-rays with a total duration of 300 ± 50 ns. The significant contribution of Cu-Kα was due to the medium range X-rays, nonetheless, hard X-rays with energies greater than 15 keV also participate in the process. The total emitted X-ray energy in the forms of Cu-K and Cu-K/3 was around 0.14 ± 0.02 （J/Sr） and 0.04 ±0.01 （J/Sr）, respectively. The total energy of the emitted hard X-ray （〉 15 keV） was around 0.12± 0.02 （J/Sr）.

Synthesis of Crystalline Carbon Nitride Thin Films by Pulsed Arc Discharge at Atmospheric Pressure

The preparation of crystalline C3N4 films was investigated using pulsed arc discharge from mixed methanol and ammonia water at atmospheric pressure. The X-ray diffraction （XRD） patterns of the films prepared at a substrate temperature of 450℃ suggested that the film was composed of α-C3N4 and fl-C3N4 crystallites. Raman spectra exhibited distinct peaks which are in good agreement with those predicted theoretically for C3N4 crystallites.

Influence of Bias on the Properties of Carbon Nitride Films Prepared by Vacuum Cathodic Arc Method

Carbon nitride films have been synthesized in a wide range of biases from 0 to -900 V by vacuum cathodic arc method. The N content was about 12.0-22.0 at. pct. Upon increasing the biases from 0 to -100 V, the N content increased from 15.0 to 22.0 at. pct which could be attributed to the knot-on effect. While the further increasing biases led to the gradual falling of the N content to 12.0 at. pct at -900 V due to the enhancement of the sputtering effect. Below -200 V, with the increasing biases the sp2C fraction in the films decreased, as a result of vvhich the I(D)/I(G) fell in the Raman spectra and the sp peaks also showed the decreasing tendency relative to the s peaks in the VBXPS (valence band X-ray photoelectron spectroscopy). While above -200 V, the sp2C fraction increased and the films became graphitinized gradually, accompanying which the I(D)/I(G) rose from -200 V to -300 V and the Raman spectra even shovved the graphite characteristic above -300 V and the sp peaks rose again relative to the s peak. The carbon nitride films mainly consist of three types of bonding: CC, sp2CN and sp3CN bonds. In the first stage the sp3CN relative ratio rises and falls in the second stage, which corresponded well with the variation of the sp2C in the films. The subpiantation mechanism resulting from the effect of ion energy played an important role in deciding'the variation of the microstructure of the carbon nitride films.

Reducing Radiation Dose by Using Pulse X-Ray Apparatus

Pulse X-ray diagnostics is capable of reducing the radiation exposure considerably. As for pulse X-ray diagnostic machines, which form pulses with the duration of 0.1 μs, using them one can get outstanding results in this area. This fact can be explained by the long period of luminophor persistence in intensifying X-ray luminescent screens. In this paper we present experimental data, comparing radiation doses, measured at pulse X-ray apparatus and apparatus of constant radiation.

Reduction of the Radiation Dose by Decreasing the Tube Current without Degradation of Low-Contrast Detectability on Abdominal Multi-Detector Row CT: A Phantom-Based Study

As use of the lowest acceptable radiation dose during routine diagnostic imaging is important, we determined the optimal tube current without degradation of low-contrast detectability on abdominal multi-detector row CT (MDCT). CT scanning was performed with a Catphan®?500 phantom. The optimal tube current was 300 mA on 64-MDCT and 160 mA on 8-MDCT, with a fixed voltage of 120 kV. Reduction of the radiation dose in abdominal CT scanning by lowering the tube current proved to be feasible.

钛管高速双枪TIG焊电弧和熔池动态行为的数值模拟

采用高速双枪TIG焊制造钛焊管。建立双钨极、双电弧和熔池耦合数学模型,研究温度场分布、电弧等离子体和熔池液态金属流动以及双枪TIG焊系统能量传输行为。电弧极性相同,在电磁力作用下,前后电极下方的电弧等离子体相向流动。熔池Marangoni力远高于电弧剪切力,是熔池上表面液态金属后向流动的主要驱动力。计算的双钨极电弧热效率为79.8%。高速双枪TIG焊可以提高钛焊管的制造效率和质量。

某塑胶U型管注塑模具设计

针对塑胶U型管内壁型芯脱模难度大的特点,将U型管塑件内壁型芯分解为2个直型芯与1个圆弧型芯的拼合结构,在模具动模侧设计了3组油缸驱动抽芯机构完成3个型芯的抽芯动作。2组油缸驱动抽芯机构完成2个直型芯抽芯,其中1组在完成直抽芯过程中,同时驱动动模型腔、摆件板旋转10°,达到共同推动塑件在圆弧型芯上旋转预脱模,防止由摆件板单独推动塑件旋转脱模,引起塑件塑性变形;设计模具二次开模,解决了动模型腔在旋转过程中与相关零件干涉的问题;第3组油缸驱动齿条齿轮传动机构,带动摆件板推动U型管塑件旋转,完成圆弧型芯脱模运动,解决了传统圆弧型芯旋转脱模所需脱模空间大、出现运动干涉,以及圆弧型芯难以冷却等问题。

直流双管式电弧等离子体发生器性能研究

利用实验手段研究了双管式电弧等离子体发生器的特性,包括旋流进气特性、伏安特性和运行热效率等,建立了基于双管式电弧等离子体发生器的数学模型。结果表明,旋流流速对电极烧蚀速率有较大影响,电弧电压降和发生器热效率随电流增加而下降,发生器热效率随气流量增大而增大。根据相似理论建立的数学模型能够准确模拟等离子体发生器的负电弧动态电阻伏安特性。以上研究可为大功率、长寿命双管式电弧等离子体发生器的开发及其在材料制备和环境保护领域的应用提供参考。

一种直流插座的设计

为了保证直流用电,特别是高电压大电流的用电安全,对配电单元的保护能力提出了更高的要求,尤其是日常使用的插座,主要对直流插座的工作原理、设计参数、结构设计展开分析。实验证明:所设计插座为符合交流86规格和日常用电习惯的大功率直流插座。此产品在满足现有86型墙壁插座底盒规格的前提下,实现了高直流电压、大电流带载下的随意拔插。

钛表面掺钴-钙磷涂层成血管作用的体外研究

目的探讨钛掺钴(cobalt,Co)-钙磷(Ca/P)涂层的成血管作用。方法通过微弧氧化(micro-arc oxidation,MAO)方法在钛表面制备掺钴涂层组(Co组)和掺钴-钙磷涂层组(Co-Ca/P组),以未经MAO处理的纯钛试件作为对照组(Ti组)。通过扫描电镜(scanning electron microscope,SEM)观察涂层表面微观形貌,并通过能谱分析仪检测涂层表面元素成分与含量。应用内皮细胞培养基(endothelial cell medium,ECM)制备各组试件标准浸提液,用于成血管实验。人脐静脉内皮细胞(human umbilical vein endothelial cells,HUVECs)接种于基质胶表面并加入不同浸提液体外培养;于第4、8 h观察新生血管形态与数目,并用Image J软件对新生血管环数和血管节点数进行定量分析。结果SEM观察显示,Co组、Co-Ca/P组涂层表面均出现不规则晶体沉积,直径<2μm,Co-Ca/P组晶体更多且均匀;而Ti组只观察到打磨留下的划痕。能谱分析仪分析显示,Co、Ca、P三种元素被成功掺入到Co-Ca/P组涂层中,Co组只有Co元素掺入,而Ti组未检测到上述三种元素。Co-Ca/P组浸提液中HUVECs形成血管环数和节点数显著高于Co组(P<0.05),而这两组成血管效果显著优于Ti组(P<0.05)。结论掺Co-Ca/P微弧氧化涂层具有较好的体外促血管生成能力,对新型高生物活性种植体涂层研发具有一定价值。