A novel Mg-Gd-Y-Zn-Cu-Ni alloy with excellent combination of strength and dissolution via peak-aging treatment

Inferior absolute strength and dissolution properties are the main bottlenecks for the widespread application of dissolvable magnesium alloys in complex working environments for unconventional oil and gas resources.Here,a novel functional peak-aged Mg-9.5Gd-2.7Y-0.9Zn-0.8Cu-0.4Ni(wt.%) alloy for fracturing tools is reported,and it possesses an ultimate tensile strength of 457.6 MPa,ultimate compressive strength of 620.7 MPa and dissolution rate of ~43.7 mg·cm^(-2)·h^(-1) in 3 wt.% KCl solutions at 93℃.The excellent strength of the agedalloy is primarily attributed to the combination of grain refinement,long-period stacking ordered(LPSO) strengthening,and precipitation strengthening induced by stacking fault and β’ phase,among which the precipitation strengthening is dominant.Further investigations confirm that the corrosion is triggered from the micro-galvanic coupling between the Mg matrix and the cathodic lamellar and block LPSO phases.Strip-shaped corrosion pits along with LPSO phases are subsequently formed,significantly accelerating corrosion.The β’ precipitates can effectively improve the strength without compromising the dissolution rate because of their nanoscale size.This study provides an excellent material selection for dissolvable fracturing tools and presents a strategy by which a synergistic combination of strength and dissolution rate is achieved via peak-aging treatment.

The Lobster Eye Imager for Astronomy Onboard the SATech-01 Satellite

The Lobster Eye Imager for Astronomy(LEIA),a pathfinder of the Wide-field X-ray Telescope of the Einstein Probe mission,was successfully launched onboard the SATech-01 satellite of the Chinese Academy of Sciences on2022 July 27.In this paper,we introduce the design and on-ground test results of the LEIA instrument.Using stateof-the-art Micro-Pore Optics(MPO),a wide field of view of 346 square degrees(18.6°×18.6°)of the X-ray imager is realized.An optical assembly composed of 36 MPO chips is used to focus incident X-ray photons,and four large-format complementary metal-oxide semiconductor(CMOS)sensors,each of size 6 cm×6 cm,are used as the focal plane detectors.The instrument has an angular resolution of 4’-8’(in terms of FWHM)for the central focal spot of the point-spread function,and an effective area of 2-3 cm^(2) at 1 keV in essentially all the directions within the field of view.The detection passband is 0.5-4 keV in soft X-rays and the sensitivity is2-3×10^(-11) erg s^(-1) cm^(-2)(about 1 milliCrab)with a 1000 s observation.The total weight of LEIA is 56 kg and the power is 85 W.The satellite,with a design lifetime of 2 yr,operates in a Sun-synchronous orbit of 500 km with an orbital period of 95 minutes.LEIA is paving the way for future missions by verifying in flight the technologies of both novel focusing imaging optics and CMOS sensors for X-ray observation,and by optimizing the working setups of the instrumental parameters.In addition,LEIA is able to carry out scientific observations to find new transients and to monitor known sources in the soft X-ray band,albeit with limited useful observing time available.

Possible Detection of a Flare-associated Coronal Mass Ejection on an M-dwarf

We here report a probable detection of a stellar coronal mass ejection(CME)in active M dwarf KIC 8093473 by performing an analysis on its time resolved X-ray spectra observed by the XMM-Newton satellite.Compared to the value at the quiescent state and the interstellar one,our spectral modeling returns a marginal(and probably evolving)excess of hydrogen column density in the flare state at a significance level of 1σ,which can be understood by an additional absorption due to a flare-associate CME.The CME mass is then estimated to be∼7×10^(18)–2×10^(20)g according to the ice cream cone model.

Effect of Matching Algorithm and Profile Shape on Pulsar Pulse Time of Arrival Uncertainties

For high-precision pulsar timing analysis and low-frequency gravitational wave detection,it is essential to accurately determine pulsar pulse times of arrival(ToAs)and associated uncertainties.To measure the ToAs and their uncertainties,various cross-correlation-based techniques can be employed.We develop methodologies to investigate the impact of the template-matching method,profile shape,signal-to-noise ratio of both template and observation on ToA uncertainties.These methodologies are then applied to data from the International Pulsar Timing Array.We demonstrate that the Fourier domain Markov chain Monte Carlo method is generally superior to other methods,while the Gaussian interpolation shift method outperforms other methods in certain cases,such as profiles with large duty cycles or smooth profiles without sharp features.However,it is important to note that our study focuses solely on ToA uncertainty,and the optimal method for determining both ToA and ToA uncertainty may differ.

GPS实时监测和预报电离层电子含量

GPS能高精度地实时监测电离层总电子含量(TEC)变化,对纠正单频GPS接收机电离层延迟和监测电离层活动及其所反映的太阳活动规律具有重要意义。上海地区GPS综合应用网的建立,为监测长江三角洲地区电离层变化提供了宝贵的资料,利用这些双频GPS接收机的连续观测资料,可近实时地监测和预报该地区电离层总电子含量,其内外符精度和外推预报30分钟的精度均优于0.4m。

激光修整圆柱形CBN砂轮中偏焦量对能量分布的影响

激光束偏焦量是修整圆柱形砂轮的重要参数,它影响光斑形状及其能量密度,因而影响激光修整砂轮的质量。介绍了用数控Nd:YAG激光系统修整圆柱形CBN砂轮过程中,偏焦量对光斑作用能量分布的影响与其修整作用的基本原理,建立了激光偏焦量作用于圆柱形砂轮上任意一点的光斑面积数学模型;给出了调整激光偏焦量修整圆柱形砂轮的关系与参数范围;采用计算与试验结合的方法,得到激光偏焦量、输入能量密度及激光修整参数的对应关系。研究结果为进一步提高激光修整圆柱形陶瓷结合剂CBN砂轮的质量提供了理论与试验依据。

分子束外延生长Al掺杂n型ZnS_(1-x)Tex的类DX中心

应用光致发光 (PL )、电容 -电压 (C- V)、深能级瞬态谱 (DL TS)和光电导 (PC)技术系统研究 Al掺杂 Zn S1 - xTex 中与 Al有关的类 DX中心 .实验结果表明 ,Zn S1 - x Tex 中存在与 - 族半导体 DX中心相类似的性质 .获得与 Al有关的类 DX中心光离化能 Ei (～ 1.0 e V和 2 .0 e V)和发射势垒 Ee (0 .2 1e V和 0 .39e V) ,这表明 Zn S1 - x Tex大晶格弛豫的出现是由类

一种车辆主动悬架系统的数学模型及最优控制力的确定

对一种车辆主动悬架装置进行了研究。首先对该主动悬架系统进行了分析并建立了该主动悬架系统的数学模型,然后应用线性二次型最优控制方法设计了全状态反馈控制器,以获得最优的主动控制力。对控制器参数的物理意义进行了分析。最后,按主动悬架和被动悬架方式对系统进行了仿真,结果表明:在车辆性能改善方面主动系统优于被动系统。

我国不同类型烟叶烟碱向降烟碱转化研究

对我国不同类型烟叶生物碱含量和烟碱向降烟碱转化的株间变异研究表明,白肋烟和沙姆逊香料烟降烟碱占总生物碱比例高,不同样品间变化幅度和变异性大,烟碱向降烟碱转化问题比较突出。单株分析表明,白肋烟JB80和TN9O群体中转化株比例分别为20.0%和18.3%,且50%以上的转化株为转化率在20%以上的高转化株。烤烟转化株比例和转化程度较低。去除转化株后的纯化群体,其生物碱组成得到优化。

Effect of trace Ni addition on microstructure,mechanical and corrosion properties of the extruded Mg-Gd-Y-Zr-Ni alloys for dissoluble fracturing tools

Magnesium alloys,a novel functional material for the fabrication of fracturing tools,are being paid more and more attentions recently due to their relatively high mechanical properties and fast dissolubility ability after fracturing.In this study,the novel extruded Mg-10Gd-3Y-0.3Zr-xNi alloys will be reported and their microstructure,mechanical and corrosion behaviors will be also studied.The results show that Ni contents influence phase precipitation behaviors.With adding 0.2 wt%Ni,a large amount of Zr_(7)Ni_(10)phases will be precipitated insidesα-Mg matrix,directly leading to degradation of strength and large corrosion rate.With further increasing Ni contents,the precipitation phases can be changed from Mg_(5)RE to 18R-LPSO structure,resulting in higher mechanical properties and faster corrosion rate.Moreover,adding Ni element also change the texture orientation by influencing the precipitation behavior of the alloys.The alloys invented in this paper have attained the highest compressive and tensile properties among all the reported dissoluble magnesium alloys.This work is beneficial in understanding the role of Ni in the magnesium alloys and provides more materials alternatives for the fabrication of dissoluble fracturing tools.

Effects of effective stress and temperature on permeability of sandstone from CO2-plume geothermal reservoir

Rock is generally complex and heterogeneous,therefore the heterogeneity effects of effective stress and temperature on permeability should be taken into account.In this study,two-part Hooke’s model（TPHM） is introduced to understand the influences of effective stress and temperature on permeability of soft and hard parts（two parts） of rock based on coupling thermo-hydro-mechanical tests.Under a fixed temperature level（25 ℃.35 ℃.50 ℃.65 ℃.80 ℃.90 ℃ and 95 ℃）.the tests were carried out in a conventional triaxial system whereas the confining pressure was remained at 50 MPa.and the pore pressure was increased to the specified levels step by step.i.e.8 MPa,18 MPa.28 MPa.38 MPa.41 MPa,44 MPa.46 MPa and 48 MPa.The temperature-dependent relationships for two parts permeabilities are proposed on the basis of the initial test results.We point out that temperature of 65 ℃-90 ℃ is the threshold for the development of CO2-plume geothermal（CPC） reservoir sandstone cracking under low effective stress（2-9 MPa） based on the relationship between temperature and soft part permeability.Furthermore,we discuss the effect of temperature on the two parts in the rock.The results indicate that as the temperature increases from 25 ℃ to 65 ℃.the flow channel in the hard part has a stronger response to temperature than that in the soft part at a fixed effective stress level,which is opposite to the situation of effective stress.Considering that natural rock is generally heterogeneous with non-uniform pore structure,we suggest a physical interpretation of the phenomenon that before the thermal cracking threshold the two parts have different responses to temperature.

Synthesis of Ni nanowires via a hydrazine reduction route in aqueous ethanol solutions assisted by external magnetic fields

One-dimensional Ni nanostructures were synthesized via a hydrazine reduction route under external magnetic fields. The mixture of de-ionized water and ethanol was used as the reaction solvent and hydrazine hydrate as reducing agents. The morphology and properties of Ni nanostructures were characterized by X-ray diffractometer(XRD), scanning electron microscopy(SEM), and vibrating sample magnetometer(VSM). It was found that the magnetic field strength, concentration of Ni ions,reaction time and temperature as well as p H values played key roles on formation, microstructures and magnetic properties of Ni nanowires. The optimal wires have diameter of ~200 nm and length up to ~200 μm. And their coercivity is ~260 Oe, which is much larger than the commercial Ni powders of 31 Oe. This work presents a simple, low-cost, environment-friendly and large-scale production approach to fabricate one-dimensional magnetic materials. The resulting materials may have potential applications in conductive filters, magnetic sensors and catalytic agents.

颈动脉斑块形态和组成:1.5 T和3.0 T磁场强度间的初步对照性研究

目的前瞻性地比较1．5T和3．0TMR在诊断和定量观察颈动脉壁的形态学和斑块组成的异同。方法20例病人[平均年龄（69．8±10．5）岁，75％为男性]入选研究，经多普勒血管超声证实颈动脉狭窄程度16％～79％。入选病人均采用双侧四通道相控阵表面线圈行1．5T和3．0TMR扫描。本研究符合HIPAA的要求，经学术审查委员会批准并取得所有病人书面的知情同意。成像序列包括横断面T1WI、T2WI、质子像、TOF和增强T1WI，并保持不同成像设备之间的信噪比基本一致。记录管腔区域、管壁区域、血管总面积、

EFFECTS OF Pb COMPOUND ADDITIVES ON THE PROPERTIES OF YBa_2Cu_3O_(7-δ)

The melting temperature and critical transition temperature Tc of YBa2Cu3O7-δ with deferent content additives of PbO and BaPbO3 were studied. When PbO was doped in YBa2Cu3O7-δ, the melting temperature of YBa2Cu3O7-δ was reduced, however its superconductivity was weakened. From the XRD pattern of the sintered mixture of YBa2Cu3O7-δ and PbO, it was known that there was a reaction between YBa2Cu3O7-δ and PbO, and the product was BaPbO3. Hence different contents of BaPbO3 (10mass%, 20mass% and 30mass%) were added in YBa2Cu3O7-δ. It was proved that there were no reactions between YBa2Cu3O7-δ and BaPbO3. And the superconductivity of the mixtures was much better than that of the samples with PbO additive.

Preparation and growth mechanism of nickel nanowires under applied magnetic field

Nickel nanowires with large aspect ratio of up to 300 have been prepared by a hydrazine hydrate reduction method under applied magnetic field. The diameter of nickel nanowires is about 200 nm and length up to 60 μm. The role of magnetic field on the growth of magnetic nanowires is discussed and a magnetic nanowire growth mechanism has been proposed. Nickel ions are firstly reduced to nickel atoms by hydrazine hydrates in a strong alkaline solution and grow into tiny spherical nanoparticles. Then, these magnetic particles will align under a magnetic force and form linear chains. Furthermore, the as-formed chains can enhance the local magnetic field and attract other magnetic particles nearby, resulting finally as linear nanowires. The formation and the size of nanowires depend strongly on the magnitude of applied magnetic field.

CRYSTAL STRUCTURE AND MORPHOLOGY OF NASCENT SAMPLES OF SYMMETRIC AROMATIC POLYESTERS——Ⅰ.POLY(P-PHENYLENE TEREPHTHALATE)

The morphology and crytal structure of poly(p-phenylene terephthalate) (PPT), prepared by confined thin filmmelt (CTFMP) and solution (CTFSP) and bulk solution polymerization, were characterized by transmission electronmicroscopy, electron dimaction and molecular modeling. The unit cell is monoclinic (P2_1/a space group) with parameters a =7.89, b = 5.49, c = 12.65 A, α=γ= 90°, β=100.33°, density = 1.48 g/cm^3, the a, b and β values differing slightly from thosereported previously in the literature. A degree of variation in relative intensities of hk0 reflections in, apparently, untilted[001] ED patterns was observed from a given sample, suggesting some variation in molecular packing. ED evidence wasfound for a second phase, with [001] appearing the same as for phase Ⅱ of the related poly(p-oxybenzoate) (PpOBA)polymer. CTFMP crystals polymerized above 220℃ (up to 370℃) and CTFSP crystals polymerized at 300℃ consisted oflamellae 100-200 A thick.

THE EFFECTS OF NEGATIVE BIAS AND FLUX RATIO ON THE PROPERTIES OF TiN THIN FILMS FORMED BY FILTERED CATHODIC ARC PLASMA TECHNIQUE

The filtered cathodic vacuum-arc (FCVA) technique is a supplementary and alterna tive technique with respect to convendtional physical and chemical vapour deposi tion which can remove macro-particles effectively and make the deposition proces s at ambient temperature. In this work, high quality TiN thin films were deposi ted on silicon substrates at low temperature using the improved filtered cathodi c arc plasma (FCAP) technique. AFM, XRD, TEM were employed to characterize the T iN thin films. The effects of the negative substrate bias on the grain size, pre ferred crystalline orientation, surface roughness of TiN thin films were discuss ed.

B3 0749+460A: A New Repeat “Changing-look” Active Galactic Nucleus Associated with X-Ray Spectral Slope Variations

Here we report an identification of B3 0749+460 A as a new double-peaked local "changing-look" active galactic nucleus(CL-AGN) in terms of our multi-epoch spectroscopic analysis. By comparing our new spectra taken in 2021 with the ones taken by the Sloan Digital Sky Survey in 2004, BOSS in 2013 and Ma NGA in 2016, we reveal type transitions of Seyfert(Sy) 1.9 → Sy1.8 → Sy1.9. In the transitions, the classical broad Hα emission fades away after 2013 and disappears in our 2021 spectrum, although the absence of broad Hβ can be traced back to at least 2016. A follow-up observation in X-rays by the Swift/XRT reveals that(1) the X-ray emission level gradually decreased since 2005;and(2)the X-ray spectrum is soft in the optical "turn-off" state and hard in the "turn-on" state. We argue that the disappearance of the classical broad Hα emission can be likely explained by the disk-wind broad-line-region model, in which the CL phenomenon is sensitive to luminosity in individual AGNs.

RECRYSTALLIZATION BEHAVIOR AND PRIOR AUSTENITE GRAIN BOUNDARY CORROSION IN THE PLANE STRAIN COMPRESSION CONDITION FOR A LOW CARBON X70 PIPELINE STEEL

Recrystallization behavior of a low carbon X70 pipeline steel was studied in the plane strain compression condition. It was found that the dynamic recovery but no dynamic recrystal- lization occurred in the current experimental condition. A method for examining the prior austenite grain boundary corrosion was supposed.

车削加工时屑流模型的建立

文中介绍用圆弧刀尖车刀斜角车削时，预断屑流方向的模型。执行该模型时仅需知道刀刃几何形状和切削条件（进给量和切削速度）。试验结果证实，屑流模型预测的结果和试验结果相当一致。