Influence of the electrolyte conductivity on the critical current density and the breakdown voltage

The work investigates influence of the electrolyte conductivity on the onset of partial contact glow discharge electrolysis(CGDE)in a water electrolysis.Critical current density(CCD)and breakdown voltage were measured together with in situ observation of hydrogen bubble behavior,whose influence has not been focused on.For a fixed current during normal electrolysis,hydrogen coalescence adjacent to cathode surface was invigorated at a lower conductivity.Photographic analyses elucidated the hydrogen coalescence characteristics by quantifying size and population of detached hydrogen bubbles.The CCD increased about 104% within given range of conductivity(11.50-127.48 mS·cm^(-1))due to impaired bubble coalescence,which delays hydrogen film formation on the cathode.Meanwhile,decreasing trend of breakdown voltage was measured with increased conductivity showing maximum drop of 74%.It is concluded that onset of partial CGDE is directly affected by hydrodynamic bubble behaviors,whereas the electrolyte conductivity affects the bubble formation characteristics adjacent to cathode electrode.

Revealing the potential of apparent critical current density of Li/garnet interface with capacity perturbation strategy

Apparent critical current density(j_(Ac)^(a))of garnet all-solid-state lithium metal symmetric cells(ASSLSCs)is a fundamental parameter for designing all-solid-state lithium metal batteries.Nevertheless,how much the possible maximum apparent current density that a given ASSLSC system can endure and how to reveal this potential still require study.Herein,a capacity perturbation strategy aiming to better measure the possible maximum j_(Ac)^(a)is proposed for the first time.With garnet-based plane-surface structure ASSLSCs as an exemplification,the j_(Ac)^(a)is quite small when the capacity is dramatically large.Under a perturbed capacity of 0.001 mA h cm^(-2),the j_(Ac)^(a)is determined to be as high as 2.35 mA cm^(-2)at room temperature.This investigation demonstrates that the capacity perturbation strategy is a feasible strategy for measuring the possible maximum j_(Ac)^(a)of Li/solid electrolyte interface,and hopefully provides good references to explore the critical current density of other types of electrochemical systems.

Effect of the Density of Molten Metal on the Raining Phenomenon in Horizontal Centrifugal Casting

In this work the influence of the density of the molten metal on the emergence of the raining phenomenon in the horizontal centrifugal casting process is numerically studied. Transient 2D numerical simulations were carried out using Computational Fluid Dynamics software. Three molten metals with different density, namely aluminum, iron and lead, and three angular frequencies, namely 50, 66 and 77 rad/s were considered. It is found that the density of the molten metal significantly affects the emergence, transient or permanent, of the rain phenomenon. However, the magnitude and duration of the rain phenomenon depend on the angular frequency of the rotating mold. Likewise, since gravitational forces affect the metal according to its density, the value of the critical rotation speed of the mold is also affected.

Generation of high quality ion beams through the stable radiation pressure acceleration of the near critical density target

In order to generate high quality ion beams through the stable radiation pressure acceleration（RPA） of the near critical density（NCD） target, we propose a new type of target where an ultra-thin high density（HD） layer is attached to the front surface of an NCD target, which has a preferable self-supporting property in the RPA experiments than the ultra-thin foil target. It is found that in one-dimensional particle-in-cell（PIC） simulation, by the block of the HD layer in the new target,there emerges the hole-boring process rather than propagation in the NCD layer when the intense laser pulse impinges on this target. As a result, a typical RPA structure that the compressed electron layer overlaps the ion layer as a whole is formed and a high quality ion beam is obtained, e.g., a circularly polarized laser pulse with normalized amplitude a0= 120 impinges on this new target and a 1.2 GeV monoenergetic ion beam is generated through the RPA of the NCD layer. Similar results are also found in the two-dimensional PIC simulation.

Direct Microwave Synthesis of 11-Type Fe(Te,Se) Polycrystalline Superconductors with Enhanced Critical Current Density

We report a direct microwave synthesis method for the preparation of 11-type high quality Fe(Te,Se) polycrystalline superconductors. The bulk samples are rapidly synthesized under the microwave irradiation during several minutes, with a subsequent annealing process at 400℃. The samples exhibit a nearly single phase of the tetragonal PbO-type crystal structure with minor impurities. Morphology characterization shows high density, tight grain connectivity and large grain sizes around 100 μm with small cavities inside the sample. Resistivity and magnetization measurements both show similar superconducting transitions above 14 K. The magnetic hysteresis measurements display broad and symmetric loops without magnetic background, and a high critical current density J_c about 1.2 × 10~4 A/cm^2 at 2 K and 7 T is estimated by the Bean model. Compared with the solidstate reaction synthesized samples, these superconducting bulks from microwave-assisted synthesis are possibly free of the interstitial Fe due to smaller c-axis, higher T_c in magnetic transitions, better M–H loops without magnetic background and greatly enhanced J_c, and are promising as raw materials for the non-toxic Fe-based superconducting wires for large currents and high field applications.

On a New Equation for Critical Current Density Directly in Terms of the BCS Interaction Parameter, Debye Temperature and the Fermi Energy of the Superconductor

Recasting the BCS theory in the larger framework of the Bethe-Salpeter equation, a new equation is derived for the temperature-dependent critical current density jc(T) of an elemental superconductor (SC) directly in terms of the basic parameters of the theory, namely the dimensionless coupling constant [N(0)V], the Debye temperature θD and, additionally, the Fermi energy EF—unlike earlier such equations based on diverse, indirect criteria. Our approach provides an ab initio theoretical justification for one of the latter, text book equations invoked at T = 0 which involves Fermi momentum;additionally, it relates jc with the relevant parameters of the problem at T ≠ 0. Noting that the numerical value of EF of a high-Tc SC is a necessary input for the construction of its Fermi surface—which sheds light on its gap-structure, we also briefly discuss extension of our approach for such SCs.

Effects of Cold Working and Annealing on the Microstructure and Critical Current Density of Ag-sheathed BiPbSrCaCuO Superconducting Tapes

Ag-sheathed BiPbSrCaO(2223)superconducting tapes prepared by the powder-in-tube technique were inVeSgated. The Mswt of M layCr and the Jc at 77 K are spengly dspendent on the amouDt of cold wotheg and annchg condition. The Jc bo by uhahal tw aha drawing and rolling. The OPbown annwtg theperawt, boe and coohag de tO madrihe Jc vaiueS were in the range 84()-- 850t, 1bo^2bo h and 50-- loot / h, nyhvejy. The mndum tuSPOrt Jt at 77 K under zero mopetic field was l.33 x l04 A / cm2.

Variance of Critical Current Density with Microstructure by a Special Process

A promising method —“powder in tube”technique was used to fabricate Ag-sheathed Bi-2223 superconductive tapes with high critical current density.After a combination processing of pressing and subsequent heat treatment,we obtained tapes with high degree of texture,good compaction and uniform properties.At 77 K in zero field,J_C was higher than 1×10~4 A/cm^2 while the highest J_C was 1.69×10~4 A/cm^2.SEM and XRD was used to detect the tapes texture,and the relationship be- tween J_C and the degree of texture is discussed.In addition,the reason for obstacling the improvement of J_C is also investigated.

A new model analysis of the third harmonic voltage in inductive measurement for critical current density of superconducting films＊

The critical current density Jc is one of the most important parameters of high temperature superconducting films in superconducting applications, such as superconducting filter and superconducting Josephson devices. This paper presents a new model to describe inhomogeneous current distribution throughout the thickness of superconducting films applying magnetic field by solving the differential equation derived from Maxwell equation and the second London equation. Using this model, it accurately calculates the inductive third-harmonic voltage when the film applying magnetic field with the inductive measurement for Jc. The theoretic curve is consistent with the experimental results about measuring superconducting film, especially when the third-harmonic voltage just exceeds zero. The Jc value of superconducting films determined by the inductive method is also compared with results raeasured by four-probe transport method. The agreements between inductive method and transport method are very good.

Effects of Y211 phase contents on the critical current density J_c and microstructural analysis in YBCO bulk superconductors

YBCO bulk superconductors were prepared by the solid state reaction andtop-seed-melt-textured growth (TSMTG) process. By using the AC susceptibility measurement, thecritical transition temperature T_c of samples is 91.5 K for the highest value, and the transitionwidth ΔT_c is less than 1 K. The highest magnetization critical current densities J_c achieved 10~6A/cm^2 under 5 T at 10 K and 1.35X10^4 A/cm^2 under 2 T at 70 K (H//c), respectively. The resultscombining the SEM observation indicate that doping of Y211 particles is more effective in improvingthe growth quality of melt-textured YBCO superconductor and in reducing the micro-cracks ofspecimens. Doping of Y_2O_3 powder forms the rod-shaped Y211 particles, but doping of Y211 particlesdirectly to matrix materials forms the spherical Y211 particles mainly. Combining themicrostructures with J_c measurements shows that the interfaces are most important on flux bundlepinning, in which the gradient of free energy is larger than that of other place between the Y211particles and the Y123 matrix materials.

Critical Temperature of Deconfinement in a Constrained Space Using a Bag Model at Vanishing Baryon Density

The geometry of fireballs in relativistic heavy ion collisions is approximated by a static box,which is infinite in two directions while finite in the other direction.The critical temperature of deconfinement phase transition is calculated explicitly in the MIT bag model at vanishing baryon density.It is found that the critical temperature shifts to a value higher than that in an unconstrained space.

An Inquiry into Two Intriguing Values of the Critical Current Density of Bi-2212

The empirically reported values of the critical current density (jc) of Bi-2212 as 2.4 × 105 (jc1;Sample 1) and 1.0 × 106 A/cm2 (jc2;Sample 2) are intriguing because both of them correspond to the same values of the temperature T = 4.2 K and the applied magnetic field H = 12 × 104 G. This difference is conventionally attributed to such factors—not all of which are quantifiable—as the geometry, dimensions and the nature of dopants and the manners of preparation of the samples which cause their granular structures, grain boundaries, alignment of the grains and so on to differ. Based on the premise that the chemical potential μ subsumes most of these features, given herein is a novel explanation of the said results in terms of the values of μ of the two samples. This paper revisits the problem that was originally addressed in [Malik G.P., Varma V.S. (2020) WJCMP, 10, 53-70] in the more accurate framework of a subsequent paper [Malik G.P., Varma V.S. (2021) JSNM, 34, 1551-1561]. Besides, it distinguishes between the contributions of the electro-electron (e-e) and the hole-hole (h-h) pairs to jc—a feature to which no heed was paid earlier. The essence of our findings is that the jcs of the two samples differ because they are characterized by different values of the primary variables μi and , where is the effective mass of a charge-carrier and me is the free-electron mass and i = 1 and 2 denote Sample 1 and Sample 2, respectively. In the scenario of the charge-carriers being predominantly h-h pairs, the values of these parameters are estimated to be: μ1 ≈ 12.3 meV, η1 ≈ 0.58;μ2 ≈ 22.7 meV, η2 ≈ 0.94. Following from these and similar estimates when the charge-carriers are e-e pairs, given below for each sample are the detailed results for the values of the secondary variables viz. the number density of the charge-carriers and their critical velocity, the number of occupied Landau levels and the magnetic interaction parameter.

Pair-Breaking Critical Current Density of Two-Band Superconductor MgB2

Temperature dependence of the pair-breaking critical current density of MgB2, jd(T), is studied using a two-band Ginzburg-Landau theory. The results are shown to be in good agreement with experimental data for the superconducting magnesium diboride MgB2.

间断级配散粒土侵蚀过程及强度演变机理研究

旨在探究相同应力条件下不同密实度间断级配散粒土管涌侵蚀机理及其侵蚀后强度变化特性,制备干密度为1.80,1.84,1.88 g/cm^(3)的3种土体试样,通过管涌三轴试验深入地探讨了干密度对其破坏临界水力梯度、累计涌砂量、体积变化量及侵蚀后强度变化的影响规律。研究表明:试样破坏临界水力梯度随其干密度增大而增大,且利用Terzaghi公式(F1)、毛昶熙公式(F2)及水利水电科学研究院公式(F3)对其渗流临界水力梯度进行分析,发现在该应力环境下各公式计算结果与试验结果均较接近(优劣度为F2>F3>F1)。试样累计涌砂量与体积变化量均与其干密度呈负相关性变化趋势,其涌砂速率随管涌侵蚀不断发展而逐渐衰减;土的强度受干密度与侵蚀率二者影响,表现为侵蚀后土体强度折减程度随侵蚀进行而逐渐增加,随干密度增大而减小。

Terahertz high-sensitivity SIS mixer based on Nb–AlN–NbN hybrid superconducting tunnel junctions

The terahertz band,a unique segment of the electromagnetic spectrum,is crucial for observing the cold,dark universe and plays a pivotal role in cutting-edge scientific research,including the study of cosmic environments that support life and imaging black holes.High-sensitivity superconductor–insulator–superconductor(SIS)mixers are essential detectors for terahertz astronomical telescopes and interferometric arrays.Compared to the commonly used classical Nb/AlO_(x)/Nb superconducting tunnel junction,the Nb/AlN/NbN hybrid superconducting tunnel junction has a higher energy gap voltage and can achieve a higher critical current density.This makes it particularly promising for the development of ultra-wideband,high-sensitivity coherent detectors or mixers in various scientific research fields.In this paper,we present a superconducting SIS mixer based on Nb/AlN/NbN parallel-connected twin junctions(PCTJ),which has a bandwidth extending up to490 GHz–720 GHz.The best achieved double-sideband(DSB)noise temperature(sensitivity)is below three times the quantum noise level.

High critical current density in Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12) electrolyte via interfacial engineering with complex hydride

Garnet-type solid-state batteries(SSBs)are considered to be one of the most promising candidates to realize next-generation lithium metal batteries with high energy density and safety.However,the dendrite-induced short-circuit and the poor interfacial contact impeded the practical application.Herein,interface engineering to achieve low interfacial resistance without high temperature calcination was developed,which Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)(LLZTO)was simply coated with complex hydride(Li_(4)(BH_(4))_(3)I(3L1L))in various mass ratios n(Li_(4)(BH_(4))_(3)I)-(100−n)LLZTO(10≤n≤40).The interfacial conductivity increases by more than three orders of magnitude from 8.29×10^(−6)S·cm^(−1)to 1.10×10^(−2)S·cm^(−1).Symmetric Li cells exhibit a high critical current density(CCD)of 4.0 mA·cm^(−2) and an excellent cycling stability for 200 h at 4.0 mA·cm^(−2).SSBs with polymeric sulfur-polyacrylonitrile(SPAN)cathode achieve a high discharge capacity of 1149 mAh·g^(−1) with a capacity retention of 91%after 100 cycles(0.2 C).This attempt guides a simple yet efficient strategy for obtaining a stable Li/LLZTO interface,which would promote the development of solid-state batteries.

EuBa_(2)Cu_(3)O_(7-δ)超导带材中掺杂相对He^(+)离子辐照缺陷演化及超导电性的影响

为探究稀土钡铜氧化物(REBCO)第二代高温超导带材中掺杂相对离子辐照缺陷演化及超导电性的影响机理,本文采用能量为1.4 MeV的He^(+)离子对国产化未掺杂和掺杂摩尔分数3.5%BaHfO_(3)(BHO)的EuBa_(2)Cu_(3)O_(7-δ)带材进行三种不同剂量的室温辐照实验并退火.电学性能测试表明,随着辐照剂量的增加,掺杂带材的临界电流密度仍均高于未掺杂带材并且下降程度更小.透射电镜表征结果证明,超导层中通过掺杂BHO纳米相引入局域应变改变了辐照He缺陷的迁移行为,在一定范围内修复了损伤的超导结构,提高了带材载流能力的辐照耐受性.同时BHO纳米柱作为强钉扎中心使得掺杂带材临界电流密度的磁场依赖性和温度依赖性受辐照影响更小.不同于中子或重离子辐照后,通过退火可以恢复材料一定程度的超导电性,本文中大剂量He^(+)离子辐照的两种带材经氧气氛退火后,其电学性能继续恶化.相比于未掺杂带材,掺杂带材中BHO产生的局域应变在高温下抑制了辐照He缺陷在三维方向上的尺寸增长,改变了磁通钉扎特性,延缓了因氦泡长大而造成的超导层结构无序和非晶化.本研究为评估REBCO超导带材在辐照环境下的工况服役行为提供了参考依据.

Effect of fiber-reinforcement on the mechanical behavior of sand approaching the critical state

Several types of ground improvement methods that employ fiber-reinforcement have been developed in recent years.A series of consolidated drained triaxial compression tests has been conducted here to examine the effect of short fibers on the mechanical properties of Toyoura sand.Sand with 0%,0.2%,0.4%,and 1%fiber contents,prepared to yield random distribution,was sheared under several confining pressures and controlled via their initial relative densities.The test results showed that the maximum and residual deviatoric stresses increased,whereas the volumetric expansion decreased with an increase in fiber content.Although the stress ratio h(=q/p′)and specific volume changed depending on the fiber content and confining pressure with shear progression,they each reached the same values for a definite fiber content at the end of shearing,independent of initial relative density.In other words,the unique critical state line can be found for a definite fiber content.Moreover,the greater the fiber content,the larger the slope of the critical state line at the end of shearing.Additionally,as the length of fibers shortened with the same percentage of fiber inclusions in sand,the deviatoric stress and the stress ratio decreased,approaching the shear-strain-volumetric response of unreinforced sand.

A Fermi Energy-Incorporated Framework for Dealing with the Temperature- and Magnetic Field-Dependent Critical Current Densities of Superconductors and Its Application to Bi-2212

It is well known that the critical current density of a superconductor depends on its size, shape, nature of doping and the manner of preparation. It is suggested here that the collective effect of such differences for different samples of the same superconductor is to endow them with different values of the Fermi energy—a single property to which may be attributed the observed variation in their critical current densities. The study reported here extends our earlier work concerned with the generalized BCS equations [Malik, G.P. (2010) Physica B, 405, 3475-3481;Malik, G.P. (2013) WJCMP, 3,103-110]. We develop here for the first time a framework of microscopic equations that incorporates all of the following parameters of a superconductor: temperature, momentum of Cooper pairs, Fermi energy, applied magnetic field and critical current density. As an application of this framework, we address the different values of critical current densities of Bi-2212 for non-zero values of temperature and applied magnetic field that have been reported in the literature.

考虑行车安全事件严重程度和个体差异的驾驶行为风险评估

为解决驾驶行为风险评估方法存在事件危险程度度量缺失及个体行为习惯考虑不足的问题,采集15位被试的自然驾驶试验数据,通过配对T检验和具有噪声的基于密度的聚类方法(DBSCAN),聚类得到行车安全事件中指标偏离正常状态的显著程度和驾驶人风险倾向性等级;选取指标量化单次行车安全事件严重程度,修正驾驶风险权重,构建考虑行车事件严重程度和个体差异的驾驶行为风险评估方法;开展实例分析,使用车头时距(TH)验证模型的有效性。研究结果表明:速度标准差、速度极差、加速度均值和最大值对于驾驶风险评估的重要度较高;使用优化后的评估方法得到的驾驶行为风险评分范围为[21,42.6],均值为32.93,标准差6.62,相较于传统评分方法,该风险评分与实际情况更为接近;采用上述指标评价综合驾驶行为风险,有助于提升驾驶风险辨识准确性。