Error field penetration in J-TEXT tokamak based on two-fluid drift-MHD model

An externally generated resonant magnetic perturbation can induce complex non-ideal MHD responses in their resonant surfaces.We have studied the plasma responses using Fitzpatrick's improved two-fluid model and program LAYER.We calculated the error field penetration threshold for J-TEXT.In addition,we find that the island width increases slightly as the error field amplitude increases when the error field amplitude is below the critical penetration value.However,the island width suddenly jumps to a large value because the shielding effect of the plasma against the error field disappears after the penetration.By scanning the natural mode frequency,we find that the shielding effect of the plasma decreases as the natural mode frequency decreases.Finally,we obtain the m/n=2/1 penetration threshold scaling on density and temperature.

Real-time measurement of welding temperature field and closed loop control of penetration

Colormetric method of images by using two different wavelength images is a new measuring method for welding temperature field on the basis of ordinary colorimetric method, which depends little on the measuring distance, emissivity of body etc. In this paper the real time measuring system and measuring principle of welding temperature field are described, the whole welding temperature field is real time measured, so the temperature distribution at the welding direction and its cross section is obtained, then parameters of thermal cycle. With data from the temperature closed loop control system of the parameters of temperature field is developed and tested. Experimental results prove that it has high measurement speed (time of a field within 0.5 s ) and good dynamic response quality. Weld penetration can be controlled satisfactorily under the variation of welding condition such as welding thickness, welding speed and weldment gap etc.

On the Transition Regime of Nonlinear Error Field Penetration in Toroidal Plasmas

The error field penetration is numerically studied in the frame of the visco-resistive magnetohydrodynamics（MHD） model.A transition scaling is obtained to link the Rutherford and Waelbroeck regimes in the nonlinear phase of error field penetration process.Furthermore,a transition density scaling of[br/BT]critne1/2 obtained in accord with recent experimental observations in the J-TEXT tokamak.

An evolutionary adaptive neuro-fuzzy inference system for estimating field penetration index of tunnel boring machine in rock mass

Field penetration index(FPI) is one of the representative key parameters to examine the tunnel boring machine(TBM) performance.Lack of accurate FPI prediction can be responsible for numerous disastrous incidents associated with rock mechanics and engineering.This study aims to predict TBM performance(i.e.FPI) by an efficient and improved adaptive neuro-fuzzy inference system(ANFIS) model.This was done using an evolutionary algorithm,i.e.artificial bee colony(ABC) algorithm mixed with the ANFIS model.The role of ABC algorithm in this system is to find the optimum membership functions(MFs) of ANFIS model to achieve a higher degree of accuracy.The procedure and modeling were conducted on a tunnelling database comprising of more than 150 data samples where brittleness index(BI),fracture spacing,α angle between the plane of weakness and the TBM driven direction,and field single cutter load were assigned as model inputs to approximate FPI values.According to the results obtained by performance indices,the proposed ANFISABC model was able to receive the highest accuracy level in predicting FPI values compared with ANFIS model.In terms of coefficient of determination(R^(2)),the values of 0.951 and 0.901 were obtained for training and testing stages of the proposed ANFISABC model,respectively,which confirm its power and capability in solving TBM performance problem.The proposed model can be used in the other areas of rock mechanics and underground space technologies with similar conditions.

Influence of upstream solar wind on magnetic field distribution in the Martian nightside ionosphere

Using over eight years of Mars Atmosphere and Volatile Evolutio N(MAVEN)data,from November 2014 to May 2023,we have investigated the Martian nightside ionospheric magnetic field distribution under the influence of upstream solar wind drivers,including the interplanetary magnetic field intensity(∣BIMF∣),solar wind dynamic pressure(PS W),solar extreme ultraviolet flux(EUV),and Martian seasons(L s).Our analysis reveals pronounced correlations between magnetic field residuals and both∣BIMF∣and PS W.Correlations observed with EUV flux and Ls were weaker—notably,magnetic field residuals increased during periods of high EUV flux and at Mars perihelion.We find that the IMF penetrates to an altitude of 200 km under a wide range of upstream conditions,penetrating notably deeper under high∣BIMF∣andPSWconditions.Our analysis also indicates that EUV flux and IMF cone angle have minimal impact on IMF penetration depth.Those findings provide useful constraints on the dynamic nature of Martian atmospheric escape processes and their evolution,suggesting that historical solar wind conditions may have facilitated deeper IMF penetration and higher rates of ionospheric escape than are observed now.Moreover,by establishing criteria for magnetic‘quiet’conditions,this study offers new insights into the planet’s magnetic environment under varying solar wind influences,knowledge that should help refine models of the Martian crustal magnetic field.

αDecay in extreme laser fields within a deformed Gamow-like model

In this study, the effect of extreme laser fields on the α decay process of ground-state even–even nuclei was investigated.Using the deformed Gamow-like model, we found that state-of-the-art lasers can cause a slight change in the α decay penetration probability of most nuclei. In addition, we studied the correlation between the rate of change of the α decay penetration probability and angle between the directions of the laser electric field and α particle emission for different nuclei. Based on this correlation, the average effect of extreme laser fields on the half-life of many nuclei with arbitrary α particle emission angles was calculated. The calculations show that the laser suppression and promotion effects on the α decay penetration probability of the nuclei population with completely random α particle-emission directions are not completely canceled.The remainder led to a change in the average penetration probability of the nuclei. Furthermore, the possibility of achieving a higher average rate of change by altering the spatial shape of the laser is explored. We conclude that circularly polarized lasers may be helpful in future experiments to achieve a more significant average rate of change of the α decay half-life of the nuclei population.

Effects of vacuum magnetic field region on the compact torus trajectory in a tokamak plasma

The trajectory of the compact torus(CT)within a tokamak discharge is crucial to fueling.In this study,we developed a penetration model with a vacuum magnetic field region to accurately determine CT trajectories in tokamak discharges.This model was used to calculate the trajectory and penetration parameters of CT injections by applying both perpendicular and tangential injection schemes in both HL-2A and ITER tokamaks.For perpendicular injection along the tokamak's major radius direction from the outboard,CTs with the same injection parameters exhibited a 0.08 reduction in relative penetration depth when injected into HL-2A and a 0.13reduction when injected into ITER geometry when considering the vacuum magnetic field region compared with cases where this region was not considered.In addition,we proposed an optimization method for determining the CT's initial injection velocity to accurately calculate the initial injection velocity of CTs for central fueling in tokamaks.Furthermore,this paper discusses schemes for the tangential injection of CT into tokamak discharges.The optimal injection angle and CT magnetic moment direction for injection into both HL-2A and ITER were determined through numerical simulations.Finally,the kinetic energy loss occurring when the CT penetrated the vacuum magnetic field region in ITER was reduced byΔEk=975.08 J by optimizing the injection angle for the CT injected into ITER.These results provide valuable insights for optimizing injection angles in fusion experiments.Our model closely represents actual experimental scenarios and can assist the design of CT parameters.

RF electric field penetration and power deposition into nonequilibrium planar-type inductively coupled plasmas

The RF electric field penetration and the power deposition into planar-type inductively coupled plasmas in low-pressure discharges have been studied by means of a self-consistent model which consists of Maxwell equations combined with the kinetic equation of electrons. The Maxwell equations are solved based on the expansion of the Fourier-Bessel series for determining the RF electric field. Numerical results show the influence of a non-Maxwellian electron energy distribution on the RF electric field penetration and the power deposition for different coil currents. Moreover, the two-dimensional spatial profiles of RF electric field and power density are also shown for different numbers of RF coil turns.

Investigate the effects of magnetic fields on the penetration ability of a shaped charge jet at different standoffs

The influence of a magnetic field on the stability of a shaped charge jet is experimentally investigated at standoffs of 490,650 and 800 mm.The experimental results without and with the magnetic field are compared in terms of the shaped charge jet form,stability and penetration ability.A theoretical model based on one-dimension fluid dynamics is then developed to assess the depth of penetration of the shaped charge at those three standoffs and magnetic conditions.The results show that the penetration capability can be enhanced in more than 70%by the magnetic field.The theoretical calculations are compared with the experimental results with reasonably good correlation.In addition,the parameters introduced in the theory are discussed together with the experiments at three standoffs studied.

Analysis of Penetration Depth of Pipeline on Cohesive Soil Seabed

This paper conducts laboratory tests to investigate detailedly the soil deformation law around the pipeline and its penetration depth under self-gravity. The seabed model is prepared by consolidating saturated soil using vacuum pressure technology, and the pipeline models are specifically designed to possess different radii. Based on the experimental results and digital images, the soil deformation process is analyzed and summarized, a kinematic admissible velocity field is given and an upper bound solution of pipeline penetration depth and soil reaction force is derived and proposed in this paper. In order to verify the accuracy of the upper bound solution deduced in this paper,a comparison is made among some published results and the solution suggested in this paper, the comparison results confirm that the upper bound solution and the soil failure mode are reasonable. Finally two empirical formulas are given in this paper to estimate the soil reaction force of seabed and the penetration depth of pipeline. The empirical formulas are in agreement with the upper bound solution derived in this paper, and the conclusion of this paper could provide some theoretical reference for the further study of the interaction between the pipeline and the soil.

Magnetic field‐enhanced water splitting enabled by bifunctional molybdenum‐doped nickel sulfide on nickel foam

Herein,we report bifunctional molybdenum-doped nickel sulfide on nickel foam(Mo-NiS_(x)/NF)for magnetic field-enhanced overall water splitting under alkaline conditions.Proper doping of Mo can lead to optimization of the electronic structure of NiS_(x),which accelerates the dissociation of H2O and the adsorption of OH−in the hydrogen evolution reaction(HER)and the oxygen evolution reaction(OER)processes,respectively.In addition,the magnetically active Mo-NiS_(x)/NF can further enhance the HER and OER activity under an applied magnetic field due to the magnetoresistance effect and the ferromagnetic(FM)exchange-field penetration effect.As a result,Mo-NiS_(x)/NF requires low overpotentials of 307 mV at 50mA cm^(−2)(for OER)and 136 mV at 10mA cm^(−2)(for HER)under a magnetic field of 10000 G.Furthermore,the electrolytic cell constructed by the bifunctional Mo-NiS_(x)/NFs as both the cathode and the anode shows a low cell voltage of 1.594 V at 10 mA cm^(−2)with optimal stability over 60 h under the magnetic field.Simultaneous enhancement of the HER and OER processes by an external magnetic field through rational design of electrocatalysts might be promising for overall water splitting applications.

Study of the spectrum effect on the threshold of resonant magnetic perturbation penetration on J-TEXT

The spectrum effect on the penetration of resonant magnetic perturbation(RMP) is studied with upgraded in-vessel RMP coils on J-TEXT.The poloidal spectrum of the RMP field,especially the amplitudes of 2/1 and 3/1 components,can be varied by the phase difference between the upper and lower coil rows,ΔΦ=Φ_(top)-Φ_(bottom),where Φ_(top)and Φ_(bottom)are the toroidal phases of the n=1 field of each coil row.The type of RMP penetration is found to be related to ΔΦ,including the RMP penetration of either 2/1 or 3/1 RMP and the successive penetrations of 3/1 RMP followed by the 2/1 RMP.For cases with penetration of only one RMP component,the penetration thresholds measured by the corresponding resonant component are close for variousΔΦ.However,the 2/1 RMP penetration threshold is significantly reduced if the 3/1 locked island is formed in advance.The changes in the rotation profile due to 3/1 locked island formation could partially contribute to the reduction of the 2/1 thresholds.

Some properties on far-field pattern of scattering by penetrable obstacle in ocean waveguide

This paper is concerned with the properties of propagation fax-field patterns corresponding to the scattering of time harmonic acoustic waves by a bounded penetrable obstacle in an ocean waveguide. The sets of solutions to the transmission problem are constructed such that the restriction of these solutions to the boundary of the penetrable obstacle is dense in a Hilbert space. Then conditions under which a set of propagation far-field patterns is complete in a Hilbert space are determined. These properties are important in investigating inverse transmission problems in an ocean waveguide.

道路地下空洞探地雷达波场和时频特性

根据城市道路地下介质的分布特征和电性参数设计模型,采用时域有限差分法和广义S变换,对道路地下存在的充气空洞、充水空洞、回填不密实、埋藏金属物状态进行探地雷达正演模拟和时频特征提取。结果表明,地下空洞顶界面的反射波同相轴均呈弧形反射形态,但充气空洞的反射波能量强于充水空洞;地下空洞发育区域的中心频率集中在某个低频区间,其余频率成分分布较均匀;埋藏金属物区域出现两簇高幅值能量团,频率分布较分散;回填不密实区域频率未能显示出较明显的规律。最后,通过工程实测验证了数值模拟的可靠性。

On the Role of Chemical Potential in Determining the Temperature Dependent Critical Magnetic Field and the Penetration Depth of Superconductors

Dealing with both elemental and high-Tc superconductors (SCs) - Sn, Nb and Pb belonging to the former category, and MgB2 and different samples of YBCO to the latter - we show that the difference in the values of their critical magnetic field Hc1,c2 and the penetration depth λL(0) is, remarkably, attributable predominantly to the difference in the values of a single parameter, viz., the chemical potential (μ) close to their critical temperatures (Tcs). Based directly on the dynamics of pairing in a magnetic field and the corresponding number equation, our approach relates Hc1,c2 of an SC with the following set of its properties: S1 = {μ, Tc, Debye temperature, effective mass of the electron, magnetic interaction parameter, Landau index}. Hence, it provides an alternative to the approach followed by Talantsev [Mod. Phys. Lett. B 33, 1950195 (2019)] who has shown by ingeniously combining the results of various well-established theories that Hc2 of an SC can be calculated via four different equations, each of which invokes two or more properties from its sample-specific set S2 = {Tc, gap, coherence length, λL(0), jump in sp. ht.}, which is radically different from S1.

高聚物注浆修复的面板堤坝探地雷达波场特征分析

针对高聚物注浆修复堤坝面板脱空病害的修复效果问题,依据实际堤坝面板层间结构和材料介电参数,基于时域有限差分法和完全匹配层边界条件建立了高聚物注浆修复面板脱空堤坝的探地雷达电磁波计算模型,分析了雷达中心频率、面板脱空修复程度及脱空区域大小、面板厚度及配筋等因素对高聚物注浆修复面板脱空堤坝探地雷达波场特征的影响。结果表明:随着激励源中心频率增大,探地雷达剖面图分辨率逐渐增加;随着脱空区域长度增加,探地雷达剖面图中产生的水平状界面反射波增长;随着脱空区域深度增加,探地雷达剖面图水平状反射线之间时间间隔逐渐增大;随着堤坝面板厚度增加,在面板脱空修复区域绕射波和衍射波幅值减小;探地雷达发射的电磁波遇到钢筋时将产生能量较强的绕射波,强绕射波将脱空区域上下分界面的反射波分割开,难以判断反射波的水平长度。根据高聚物注浆修复面板脱空堤坝的探地雷达波场特征,能有效判断堤坝面板脱空区域的高聚物注浆修复效果,有助于解释实际堤坝面板高聚物注浆修复效果的探地雷达图像。

一种用于个人剂量当量H_(p)(0.07)监测的剂量计研制

鉴于目前国内生产的个人剂量当量H_(p)(0.07)剂量计对低能β辐射响应较差,以及对β、γ混合场中H_(p)(0.07)剂量测量误差较大的问题,基于LiF:Mg,Cu,P热释光探测器,结合模拟计算,研制了一种ZF-P7型H_(p)(0.07)剂量计。其性能指标测试结果表明:对于最大能量为225 keV~2.274 MeV的β射线,响应在0.67~0.95之间;对16 keV~1 250 keV的X、γ射线,响应在0.66~1.45之间;在剂量100μSv~1.2 Sv范围内,剂量线性在0.91~1.10范围内;在入射角为0~±60°,对65 keV X射线的角度响应在0.99~1.09范围之内,对^(85)Kr β射线角度响应在0.94~1.11范围之内。经实验验证,ZF-P7型H_(p)(0.07)剂量计的各项指标均满足行业标准EJ/T 1178—2005和检定规程JJG(军工)37—2014要求。由于该ZF-P7型剂量计性能优良,特别是对不同能量的X、γ、β辐射响应较好,可解决混合辐射场作业人员H_(p)(0.07)的剂量准确监测难题,将来可以广泛应用于辐射工作人员的H_(p)(0.07)剂量监测中。

长期运行引水隧洞开裂衬砌受力影响规律与承载特性

衬砌裂缝是引水隧洞中常见的病害之一,衬砌开裂会对隧洞衬砌承载力和安全性造成不同程度的影响。以长期服役的东江水源工程引水隧洞衬砌为研究对象,通过现场检测确定了全洞段裂缝的产状、分布规律和开裂特征。利用ANSYS软件中的软弱薄层单元,建立了开裂衬砌的三维数值模型,得出贯穿型纵向裂缝的位置变化对衬砌结构安全性的影响,系统分析了衬砌的承载特性。结果表明,衬砌开裂条件下,衬砌结构局部开裂区的安全系数降低最为显著,尤其是拱肩位置的裂缝对结构的危害程度远大于边墙、拱顶裂缝;另外,裂缝的产生会对其他未开裂部位的受力特性及稳定性产生影响。数值模拟结果良好地体现了裂损衬砌对隧洞结构的影响规律,与现场检测结果一致,为长期服役下隧洞结构病害防治提供了参考。

冻土抗侵彻试验靶体制备及其冻结温度场模拟研究

不同赋存温度环境下的各类型冻土材料热物理特性存在显著差异,开展高寒高海拔地区多年冻土抗侵彻特性研究时,能制备出满足温度控制要求的冻土靶体并揭示出靶体内冻结温度场的分布规律是后续开展大量侵彻模型试验最为基础而重要的工作。通过研究不同温度下温度场和水分场中热物理参数对冻土靶体制备的耦合影响,获取模型试验所需冻土靶体内部温度梯度分布规律,确定试验靶体达到设定温度时所需要的时间,阐述冻土抗侵彻试验靶体制备技术并对冻结粘土、冻结砂土、冻结粉土等3种典型冻土抗侵彻靶体的温度场进行了数值模拟。研究表明在同等条件下,粉土靶内部温度梯度达到一致所需要的时间最长,粘土靶次之,而砂土靶所需要的时间最短,为后续顺利开展冻土抗侵彻特性模型试验提供依据。

弹丸侵彻混凝土目标的热固耦合数值分析

针对侵彻过程中侵彻深度计算不精准的问题,以弹靶模型为研究对象,基于ANSYS/LS-DYNA软件建立弹靶模型,对35CrMnSi弹丸侵彻C30混凝土靶的侵彻深度进行了计算。以侵彻速度和角度为初始变量设置了33组不同工况,进行了侵彻过程的热固耦合数值分析。提取了弹丸温度场、侵彻深度、侵彻速度衰减等数据进行了深入分析,得出了弹丸侵彻过程中温度升高与侵彻深度之间的关系。结果表明:1)垂直侵彻时,随着侵彻速度的增大,弹头侵蚀加剧,温度变化更显著;2)非垂直侵彻时,温度升高极值点由弹头中心转移至弹丸侧身,弹丸着角增大,温度升高加快,侵彻深度减小;3)侵彻结束时,弹丸温度与侵彻深度成相关比例,相同侵彻角度工况中比例相同。对弹丸侵彻过程中温度场进行分析可提高侵彻深度预测模型的准确性,研究结果可为侵彻引信测试提供参考。