时频电磁法在滇西北红山铜钼多金属矿的应用与找矿突破

时频电磁法是一种新兴的电磁勘探方法。它同时采集时间域和频率域的电磁信号,通过对信号中的激发极化信息加以提取及利用,可同时研究地质体的电阻率和极化率信息。它刚开始被广泛应用于油气、页岩气勘探领域,近年来开始大量应用于金属矿山。它在研究构造形态、断裂性质及展布特征等方面具有重要的促进作用。该方法技术不仅丰富了解释参数,还提高了解释的可靠性、准确性,起到了提高钻井见油见矿成功率的效果,赢得了更大的应用范围。在红山铜钼多金属矿深边部找矿中,该方法技术通过强人工电流激发,既压制了矿山的工业干扰源,也能提取和识别矿区岩矿石的电阻率与极化率差异,达到寻找成矿有利部位的目的。该方法技术在红山铜钼多金属矿深边部找矿中取得了理想的效果,在此类矿山找矿进程中具有借鉴意义。

属性多级和项目多级评分的认知诊断模型

认知诊断理论中属性多级和项目多级评分均能极大地丰富项目信息,提高诊断结果准确度.基于此对已有认知诊断模型扩展的属性多级和项目评分多级的认知诊断模型进行介绍,并基于认知诊断模型和相关理论研究视角,对当前认知诊断的发展方向提出思考和建议.

Ground roll attenuation using a time-frequency dependent polarization filter based on the S transform

The ground roll and body wave usually show significant differences in arrival time, frequency content, and polarization characteristics, and conventional polarization filters that operate in either the time or frequency domain cannot consider all these elements. Therefore, we have developed a time-frequency dependent polarization filter based on the S transform to attenuate the ground roll in seismic records. Our approach adopts the complex coefficients of the S transform of the multi-component seismic data to estimate the local polarization attributes and utilizes the estimated attributes to construct the filter function. In this study, we select the S transform to design this polarization filter because its scalable window length can ensure the same number of cycles of a Fourier sinusoid, thereby rendering more precise estimation of local polarization attributes. The results of applying our approach in synthetic and real data examples demonstrate that the proposed polarization filter can effectively attenuate the ground roll and successfully preserve the body wave.

海底与陆地台站背景噪声差异

地震台站按位置可分为陆地台和海底台(Ocean Bottom Seismograph,OBS),为了研究OBS与陆地台站记录的频谱特征差异,采用偏振分析法获得2类记录周期为0.1—100 s的地震背景噪声频谱极化特征。OBS台站与陆地台站的频谱分析结果表现出较大差异。陆地台站均能记录到第一地脉动信号,而OBS台站则不能。陆地台的第二地脉动信号均表现出瑞利波质点运动特征,而OBS台仅个别台站信号显示线性运动特征。台站环境是这一观测结果的主要影响因素,OBS相较于陆地台会受到更多来自海底湍流的影响,而湍流削弱了地脉动信号的信息。

AVO反演预测煤层瓦斯富集区

以赵家寨煤矿为例,对叠前地震数据进行滤波、超道集、保幅等一系列处理,得到高信噪比的叠前地震数据,进而计算出多种AVO(振幅随偏移距的变化Amplitude Versus Offset)属性。通过多种AVO属性与实际钻孔含气量的线性分析,认为极化量属性(PM)具有较好的相关性。对PM属性进行Kriging内插值,最终得到勘探区煤层含气量分布。为验证AVO反演预测煤层瓦斯富集区的准确性,选取矿区14采区18个钻孔进行对比,结果表明,预测的瓦斯含量平均误差为0.95%,最大误差也小于1.5%,均在误差范围内,可见利用AVO反演能够比较准确的圈定瓦斯富集区。

1,3-Dimethyl-2-imidazolidinone: an ideal electrolyte solvent for high-performance Li–O;battery with pretreated Li anode

Electrolytes are widely considered as a key component in Li–O;batteries (LOBs) because they greatly affect the discharge-charge reaction kinetics and reversibility.Herein,we report that 1,3-dimethyl-2-imidazolidinone (DMI) is an excellent electrolyte solvent for LOBs.Comparing with conventional ether and sulfone based electrolytes,it has higher Li_(2)O_(2)and Li_(2)CO_(3)solubility,which on the one hand depresses cathode passivation during discharge,and on the other hand promotes the liquid-phase redox shuttling during charge,and consequently lowers the overpotential and improves the cyclability of the battery.However,despite the many advantages at the cathode side,DMI is not stable with bare Li anode.Thus,we have developed a pretreatment method to grow a protective artificial solid-state electrolyte interface(SEI) to prevent the unfavorable side-reactions on Li.The SEI film was formed via the reaction between fluorine-rich organic reagents and Li metal.It is composed of highly Li^(+)-conducting Li_(x)BO_(y),LiF,Li_(x)NO_(y),Li_(3)N particles and some organic compounds,in which Li_(x)BO_(y)serves as a binder to enhance its mechanical strength.With the protective SEI,the coulombic efficiency of Li plating/stripping in DMI electrolyte increased from 20%to 98.5%and the fixed capacity cycle life of the assembled LOB was elongated to205 rounds,which was almost fivefold of the cycle life in dimethyl sulfoxide (DMSO) or tetraglyme(TEGDME) based electrolytes.Our work demonstrates that molecular polarity and ionic solvation structure are the primary issues to be considered when designing high performance Li–O;battery electrolytes,and cross-linked artificial SEI is effective in improving the anodic stability.

Large family of two-dimensional ferroelectric metals discovered via machine learning

Ferroelectricity and metallicity are usually believed not to coexist because conducting electrons would screen out static internal electric fields.In 1965,Anderson and Blount proposed the concept of"ferroelectric metal",however,it is only until recently that very rare ferroelectric metals were reported.Here,by combining high-throughput ab initio calculations and data-driven machine learning method with new electronic orbital based descriptors,we systematically investigated a large family(2964)of two-dimensional(2D)bimetal phosphates,and discovered 60 stable ferroelectrics with out-of-plane polarization,including 16 ferroelectric metals and 44 ferroelectric semiconductors that contain seven multiferroics.The ferroelectricity origins from spontaneous symmetry breaking induced by the opposite displacements of bimetal atoms,and the full-d-orbital coinage metal elements cause larger displacements and polarization than other elements.For 2D ferroelectric metals,the odd electrons per unit cell without spin polarization may lead to a half-filled energy band around Fermi level and is responsible for the metallicity.It is revealed that the conducting electrons mainly move on a single-side surface of the 2D layer,while both the ionic and electric contributions to polarization come from the other side and are vertical to the above layer,thereby causing the coexistence of metallicity and ferroelectricity.Van der Waals heterostructures based on ferroelectric metals may enable the change of Schottky barrier height or the Schottky-Ohmic contact type and induce a dramatic change of their vertical transport properties.Our work greatly expands the family of 2D ferroelectric metals and will spur further exploration of 2D ferroelectric metals.

Spin-resolved self-doping tunes the intrinsic halfmetallicity of AIN nanoribbons

We present a first-principles theoretical study of electric field- and straincontrolled intrinsic half-metallic properties of zigzagged aluminium nitride （A1N） nanoribbons. We show that the half-metallic property of AIN ribbons can undergo a transition into fully-metallic or semiconducting behavior with application of an electric field or uniaxial strain. An external transverse electric field induces a full charge screening that renders the material semiconducting. In contrast, as uniaxial strain varies from compressive to tensile, a spin-resolved selective self-doping increases the half-metallic character of the ribbons. The relevant strain-induced changes in electronic properties arise from band structure modifications at the Fermi level as a consequence of a spin-polarized charge transfer between p-orbitals of the N and A1 edge atoms in a spin-resolved self-doping process. This band structure tunability indicates the possibility of designing magnetic nanoribbons with tunable electronic structure by deriving edge states from elements with sufficiently different localization properties. Finite temperature molecular dynamics reveal a thermally stable half-metallic nanoribbon up to room temperature.

Carbon-emcoating architecture boosts lithium storage of Nb_(2)O_(5)

Intercalation transition metal oxides (ITMO)have attracted great attention as lithium-ion battery negative electrodes due to high operation safety,high capacity and rapid ion intercalation.However,the intrinsic low electron conductivity plagues the lifetime and cell performance of the ITMO negative electrode.Here we design a new carbon-emcoating architecture through single CO_(2)activation treatment as demonstrated by the Nb_(2)O_(5)/C nanohybrid.Triple structure engineering of the carbon-emcoating Nb_(2)O_(5)/C nanohybrid is achieved in terms of porosity,composition,and crystallographic phase.The carbon-embedding Nb_(2)O_(5)/C nanohybrids show superior cycling and rate performance compared with the conventional carbon coating,with reversible capacity of 387 m A h g(-1)at 0.2 C and 92%of capacity retained after 500cycles at 1 C.Differential electrochemical mass spectrometry(DEMS) indicates that the carbon emcoated Nb_(2)O_(5)nanohybrids present less gas evolution than commercial lithium titanate oxide during cycling.The unique carbon-emcoating technique can be universally applied to other ITMO negative electrodes to achieve high electrochemical performance.