Linear magnetoresistance and structural distortion in layered SrCu_(4-x)P_(2) single crystals

We report a systematic study on layered metal SrCu_(4-x)P_(2) single crystals via transport, magnetization, thermodynamic measurements and structural characterization. We find that the crystals show large linear magnetoresistance without any sign of saturation with a magnetic field up to 30T. We also observe a phase transition with significant anomalies in resistivity and heat capacity at T_(p)~140 K. Thermal expansion measurement reveals a subtle lattice parameter variation near Tp, i.e.,?L_(c)/L_(c)~0.062%. The structural characterization confines that there is no structure transition below and above T_(p). All these results suggest that the nonmagnetic transition of SrCu_(4-x)P_(2) could be associated with structural distortion.

Bulging Distortion of Austenitic Stainless Steel Sheet on the Partially Penetrated Side of Non-Penetration Lap Laser Welding Joint

Non-penetration laser welding of lap joints in austenitic stainless steel sheets is commonly preferred in fields where the surface quality is of utmost importance.However,the application of non-penetration welded austenitic stainless steel parts is limited owing to the micro bulging distortion that occurs on the back surface of the partial penetration side.In this paper,non-penetration lap laser welding experiments,were conducted on galvanized and SUS304 austenitic stainless steel plates using a fiber laser,to investigate the mechanism of bulging distortion.A comparative experiment of DC01 galvanized steel-Q235 carbon steel lap laser welding was carried out,and the deflection and distortion profile of partially penetrated side of the sheets were measured using a noncontact laser interferometer.In addition,the cold-rolled SUS304 was subjected to heat holding at different temperatures and water quenching after bending to characterize its microstructure under tensile and compressive stress.The results show that,during the heating stage of the thermal cycle of laser lap welding,the partial penetration side of the SUS304 steel sheet generates compressive stress,which extrudes the material in the heat-affected zone to the outside of the back of the SUS304 steel sheet,thereby forming a bulge.The findings of these experiments can be of great value for controlling the distortion of the partial penetrated side of austenitic stainless steel sheet during laser non-penetration lap welding.

Computational Quantification of Map Projection Distortion by Fractal Dimension of Coastlines

Maps, essential tools for portraying the Earth’s surface, inherently introduce distortions to geographical features. While various quantification methods exist for assessing these distortions, they often fall short when evaluating actual geographic features. In our study, we took a novel approach by analyzing map projection distortion from a geometric perspective. We computed the fractal dimensions of different stretches of coastline before and after projection using the divide-and-conquer algorithm and image processing. Our findings revealed that map projections, even when preserving basic shapes, inevitably stretch and compress coastlines in diverse directions. This analysis method provides a more realistic and practical way to measure map-induced distortions, with significant implications for cartography, geographic information systems (GIS), and geomorphology. By bridging the gap between theoretical analysis and real-world features, this method greatly enhances accuracy and practicality when evaluating map projections.

DISTORTIONAL PROPERTIES OF THE BIJECTIVE PATTERN MAP (PART I: DISTORTION IN LENGTH)

The Bijective Pattern Map maps the 3D surface patch to the 2D flat pattern. The bijection property has been proved. However, since the 3D Algebraic Mannequin is not developeable, meaning that it is not isometric to the 2D plane, the intrinsic geometry of the 3D surface patches is different from their images on the 2D plane. Consequently, distortion exists. The distortional property of the Bijective Pattern Map is discussed in this article.

Distortional Properties of the Bijective Pattern Map (Part II: Change of Reference)

This is the part n of the study of distortion property of the Bijective Pattern Map maps. In part I, the generic distortion was presented. In this article, the distortion using different set of reference points and pre - image is compared with the result in part I. Moreover, the distortion induced by a change of reference is illustrated with examples. The formulation of the relationship between the distortion and the Gaussian curvature will be followed.

Correction of distorted X-ray absorption spectra collected with capillary sample cell

In certain exceptional cases,capillary samples must be used to measure X-ray absorption spectra(XAS).However,the inho-mogeneous thickness of capillary samples causes XAS distortion.This study discusses the distortion and correction of the XAS curve caused by the inhomogeneous thickness of capillary samples.The relationship between the distorted XAS curveμ′d_(eq)(measured values)and the real absorption coefficientμ_(s)d_(eq)(true values)of the sample was established.The distortion was slight and negligible when the vertical size(2h)of the X-ray beam spot was smaller than 60%of the capillary tube’s inner diameter(2R_(in)).When h/R_(in)>1,X-ray leakage is inevitable and should be avoided during measurement.Partial X-ray leakage caused by an X-ray beam spot size larger than the inner diameter of the capillary tube leads to serious compressed distortion of the XAS curve.When h/R_(in)<1,the distorted XAS data were well corrected.Possible errors and their influence on the corrected XAS are also discussed.Simulations and corrections for distortions verify the feasibility and effectiveness of the corrected method.

DISTORTION THEOREMS FOR CLASSES OF g-PARAMETRIC STARLIKE MAPPINGS OF REAL ORDER IN C^(n)

In this paper,we define the class S_(g)^(BX)of g-parametric starlike mappings of real order γ on the unit ball BX in a complex Banach space X,where g is analytic and satisfies certain conditions.By establishing the distortion theorem of the Fr´echet-derivative type of S_(g)^(BX)with a weak restrictive condition,we further obtain the distortion results of the Jacobi-determinant type and the Fr´echet-derivative type for the corresponding classes(compared with S_(g)^(BX))defined on the unit polydisc(resp.unit ball with the arbitrary norm)in the space of n-dimensional complex variables,n≥2.Our results extend the classic distortion theorem of holomorphic functions from the case in one-dimensional complex space to the case in the higher dimensional complex space.The main theorems also generalize and improve some recent works.

Out-of-plane weak ferromagnetism at room temperature in lattice-distortion non-collinear antiferromagnet of single-crystal Mn_(3)Sn

Out-of-plane weak ferromagnetic(OWFM)spin arrangements with topological properties can realize a series of interesting physical properties.However,this spin structure tends to exist at low temperatures.The OWFM structure can also be induced at room temperature by hydrostatic pressure,whereas this isotropic approach tends to form helical AFM structures.We report the OWFM spin arrangement in single crystal Mn_(3)Sn by an anisotropic strategy of high-stressconstrained compression deformation at room temperature.Both experimental and theoretical simulation results show that the alignment of the OWFM spin structure is due to the distortion of the atomic scale caused by the strain energy during deformation.The OWFM spin arrangement can significantly change the magnetic property of Mn_(3)Sn.As a result,the remanent magnetization M_(r)for the deformed sample(0.056μ_(B)/f.u.)is about eleven times that for the pre-deformed sample(0.005μ_(B)/f.u.),and the coercivity(H_(c))increases from 0 k Oe(pre-deformed sample)to 6.02 k Oe(deformed sample).Our findings provide a way to generate the OWFM spin structure at room temperature and may give fresh ideas for creating antiferromagnetic materials with excellent physical properties.

Distortion Evaluation of EMP Sensors Using Associated-Hermite Functions

Electromagnetic pulse(EMP)is a kind of transient electromagnetic phenomenon with short rise time of the leading edge and wide spectrum,which usually disrupts communications and damages electronic equipment and system.It is challenging for an EMP sensor to measure a wideband electromagnetic pulse without distortion for the whole spectrum.Therefore,analyzing the distortion of EMP measurement is crucial to evaluating the sensor distortion characteristics and correcting the measurement results.Waveform fidelity is usually employed to evaluate the distortion of an antenna.However,this metric depends on specific signal waveforms,thus is unsuitable for evaluating and analyzing the distortion of EMP sensors.In this paper,an associated-hermite-function based distortion analysis method including system transfer matrices and distortion rates is proposed,which is general and independent from individual waveforms.The system transfer matrix and distortion rate can be straightforwardly calculated by the signal orthogonal transformation coefficients using associated-hermite functions.Distortion of a sensor vs.frequency is then visualized via the system transfer matrix,which is convenient in quantitative analysis of the distortion.Measurement of a current probe,a coaxial pulse voltage probe and a B-field sensor were performed,based on which the feasibility and effectiveness of the proposed distortion analysis method is successfully verified.

Distortion product otoacoustic emissions in newborn babies with and without late-term maternal iron deficiency anaemia

Background:Studies on animals have demonstrated that maternal iron deficiency anaemia(IDA)could result in decreased cochlear sensory hair cells and reduced amplitudes of distortion-product otoacoustic emissions(DPOAEs)of young guinea pigs.Thus,it is essential to study the functioning of cochlear hair cells using DPOAEs in human newborn babies with maternal IDA.The current study explores maternal IDA’s effect on DPOAEs in newborn babies.Method:A total of 110 newborn babies with gestational age≥34 weeks were considered and a‘betweensubjects’design was used.The participants were divided into 3 groups-“Normal”(61 babies without maternal IDA),“Mild”(28 babies with mild maternal IDA)and“Moderate”(21 babies with moderate maternal IDA).The cord blood was collected and the DPOAEs were recorded for each baby for a range of frequencies(1 k 8 kHz)and a range of intensities(7040 dB SPL in 10 dB steps).Results:The analysis of both DP-gram and DP input-output(I/O)function showed that there was no significant difference(p>0.05)across the normal,mild,and moderate groups in the overall presence of DPOAEs as well as the amplitude across frequencies or intensities(7040 dB SPL).Also,the overall correlation of RBC indices with DPOAE amplitude across frequencies as well as the slope of the I/O function showed no relationship.Conclusion:The current study concludes that there is no effect of late-term maternal IDA on the DPOAEs of newborn babies.

基于光纤传感器的视频图像几何失真校正方法

视频图像在传播过程中会出现信息畸变,致使图像几何失真,为此提出基于光纤传感器的视频图像几何失真校正方法。分析视频图像像素节点在光敏区域分布情况,提取亚像素视差信息,通过面阵CCD图像传感器获取畸变视频图像;利用畸变曲线近似模型计算出视频图像畸变率,确定畸变图像坐标,并结合双线性灰度插值算法推导校正参数,实现视频图像的几何失真校正。实验结果表明,所提方法能够有效校正不同种类的视频图像几何畸变,校正后的图像与原图像相似度高超过0.97,图像边缘模糊程度降低,提高了图像的视觉观测效果。

液晶空间光调制器及其在自适应光学中的应用

液晶空间光调制器(LC-SLM)通过对液晶折射率的调制来实现对光程的控制,在自适应光学中起着重要的作用。文章梳理了国内外LC-SLM的发展现状,对LC-SLM的工作原理和相位标定原理进行了详细介绍,针对LC-SLM在自适应光学中的应用,对国内外LC-SLM关键技术研究状况进行了讨论,分析总结了西安理工大学在该领域的实验研究。最后展望了LC-SLM的应用前景。

矩形上全组合偏差的极值问题

根据Kalaj在圆环上给出的全组合偏差定义,给出了矩形上全组合偏差和组合偏差的定义.同时,在从矩形到矩形上并保持端点的所有同胚映射类中,分别考虑了组合偏差和全组合偏差的极值问题,利用面积长度方法和均值不等式证明了仿射映射为此两类极值问题的唯一解.该结果推广了相关文献的结果.

胎儿脑中线弯曲的产前诊断及妊娠结局分析

目的分析胎儿脑中线弯曲的超声和磁共振成像(MRI)表现及妊娠结局,探讨胎儿脑中线弯曲对严重神经系统异常的提示价值。方法选取2018年3月至2023年4月于首都医科大学附属北京妇产医院产前常规超声检查发现胎儿脑中线弯曲的孕妇,分析其超声和MRI影像学资料、遗传学检查结果及妊娠结局。结果12例为胎儿脑中线整体弯曲,6例为胎儿脑中线局部弯曲。整体弯曲的12例中11例为颅内多发异常,主要异常包括2例半侧巨脑畸形、3例脑皮质发育异常、3例双侧脑室重度增宽、2例单侧脑室重度增宽、1例疑似颅内出血及1例颅板下蛛网膜囊肿,其中1例合并颅外异常即法洛四联症。6例脑中线局部弯曲的病例中,5例诊断为脑皮质发育异常,1例诊断为颅内占位;5例脑皮质发育异常的病例中3例通过产前超声诊断,余2例通过MRI诊断;6例胎儿均未发现合并其他系统异常。脑中线整体弯曲的病例中4例进行遗传学检查,核型均未见异常。脑中线局部弯曲的病例中3例进行遗传学检查,包括1例核型及拷贝数变异(CNV)未见异常;1例CNV未见异常;1列核型及CNV未见异常,而全外显子检测显示TUBB3基因新发突变。12例脑中线整体弯曲的病例中8例选择终止妊娠,2例失访,2例继续妊娠并分娩,其中1例患儿在11月龄时行法洛四联症矫正手术时死亡,另1例患儿出生后行颅内囊肿分流术,术后新生儿生长发育正常。而6例脑中线局部弯曲的病例均选择终止妊娠。结论脑中线弯曲通常合并严重的颅内异常,与不良妊娠结局相关。脑中线局部弯曲是提示脑皮质发育异常的重要超声指标。产前如发现脑中线弯曲,必须进行胎儿神经学超声及头颅MRI检查以明确诊断,并尽量完善遗传学检查。

基于均匀相位采样提高阻抗谱测量精度的研究

周期性信号采样中,等效采样利用较低采样频率的A/D转换实现高频周期信号的采集,一定程度上弥补欠采样测量精度低的缺陷。为了有效地提高高频测量中阻抗谱测量精度与稳定性,提出一种基于等效采样思想的均匀相位采样的阻抗谱测量方法。利用单片机共时钟基准的模/数转换器(digital to analog convertor,DAC)与数/模转换器(analog to digital convertor,ADC)模块,在完成激励信号产生、输入输出信号同步采集的基础上,合理设计激励信号频率、采集频率与信号重构方法,实现高频信号单周期内均匀相位分布的等效高频采样,同时为克服常规A/D转换速度条件下难以准确实现高频阻抗谱测量的问题提供了新思路。从误差假设与拟合算法的角度,理论上分析证明了该方法降低误差的原因。并通过两种等效电路模型的阻抗谱测量对比实验,表明该方法在所设计的20~100 kHz高频段上,阻抗测量精度与稳定性得到了显著的提高。

考虑约束扭转二次剪力流影响的箱梁畸变效应分析

为了揭示箱梁约束扭转和畸变之间的耦联关系,研究约束扭转对箱梁畸变效应的影响,根据约束扭转二次剪力流形成的畸变荷载,建立了考虑约束扭转的箱梁畸变控制微分方程.基于乌曼斯基第二理论,提出约束扭转剪力流是基于约束扭转引起的畸变效应修正后的总扭矩布雷特剪力流,并通过Ansys有限元模型和能量法计算结果对理论公式进行了验证.数值算例结果表明:2种不同约束扭转剪力流分解方法计算所得结果完全一致;不同计算点处的约束扭转剪应力与Ansys有限元法计算结果吻合良好;扭转畸变翘曲总正应力、畸变翘曲正应力均与按能量法计算所得结果吻合良好,误差不超过10%.计入约束扭转二次剪应力的影响能够更准确地计算箱梁畸变效应.

工程降水对钻孔应变的干扰特征及干扰机制研究

抽水干扰在钻孔应变观测中常见且影响显著,为了能真实捕捉到地震前兆信息,须对其干扰机制进行研究.随着城市化进程,基坑工程及其伴随的工程降水逐步增多,工程降水对钻孔应变的干扰比普通单井抽水干扰更为严重.工程降水对钻孔应变观测有何干扰特征、干扰机制如何、干扰数据能否修复等问题对地震异常的探测具有重要意义.本文基于莱阳体应变受到附近御龙湾项目工程降水干扰的观测案例,研究了工程降水的干扰特征,修复了干扰畸变,通过数值模拟确定了干扰机制.结果表明:(1)工程降水在干扰体应变趋势变化的基础上叠加了方向明确、量级稳定的固体潮畸变,可以通过一阶差分逆运算进行修复.修复固体潮畸变并扣除背景速率后,工程降水干扰量级达-15.65×10^(-9)/d;(2)通过建立基于集中载荷模型的网格算法,模拟出工程降水在体应变异常初期和后期分别产生6.61×10^(9) N和1.73×10^(10) N的集中力载荷,干扰量级明显大于常见的单井抽水干扰,压性干扰集中于体应变仪与抽水井连线的垂直方向;(3)通过固体潮畸变特征及力学机制分析确定了工程降水造成固体潮畸变的干扰机制为"抽水引起压性趋势下降—抽水暂停引起张性台阶上升—抽水引起压性趋势下降"周期行为,固体潮畸变时间间隔(频次)和钻孔水位之间呈显著同步特征,线性系数为0.737.

山地地震勘探中的静校正对成像质量的影响及改进策略

在山地地震勘探中,地震数据常常被校正到固定基准面上进行偏移成像,从而造成成像失真。本文从数学上直接推导公式,证明了静校正后从基准面进行偏移会造成倾角误差;通过山地起伏地表正演模型,说明了静校正后从基准面偏移会扭曲波场,导致严重的偏移成像失真。此外,应用四川南部山区的实际案例,分别从基准面偏移及从起伏地表偏移,叠前时间偏移和深度偏移结果均表明,在复杂的山地地形中,剧烈的高差变化会导致固定基准面偏移成像失真,应用起伏地表偏移能改进山地地震勘探资料的成像质量。本文的研究结果对理论研究和实际地震数据处理具有重要意义。

城市土地要素配置扭曲与产业结构升级研究

在当前要素市场化改革背景下,土地作为最基本的要素单元,其市场化配置程度以及对产业结构升级的影响,深刻影响着经济的高质量发展,对于加快完善社会主义市场经济体制具有重大意义。本文在构建土地要素配置扭曲模型基础上,测算了全国105个城市的土地要素配置扭曲值,并采用工具变量法分析2000—2019年全国以及三个经济圈城市土地要素配置扭曲程度对产业结构升级的影响。结果显示,土地要素在工业和服务业部门间的配置扭曲值近年来趋缓,且不同区域间存在异质性;土地要素配置扭曲不利于产业结构升级,而且长三角和珠三角经济圈土地要素扭曲配置对产业结构升级的负面影响,在2008年金融危机后逐渐变强,说明现行城市建设用地配置不仅存在效率低下问题,还进一步制约了产业升级的步伐。为加快产业结构升级,地方政府应转变“以地谋发展”的方式,完善土地要素市场化配置运行机制,因地制宜地优化城市用地供应结构。

光储备池通感一体通信噪声抑制方案(封面文章·特邀)

通感一体技术可利用已大范围铺设的光纤网实现智能传感,具备智能识别、信息融合优势。在同波长通感共传信道中,通感信号串扰及光纤传输噪声严重影响通信信号质量,需提升发射功率来保证低误码率,但增大了非线性噪声和功耗。提出了基于光储备池计算神经网络的通感共传信道通信失真均衡方法,搭建了信道均衡仿真系统,实现了低发射功率下前向通信信号噪声均衡。周期线性调频光和56 Gb/s四电平脉冲幅度调制信号分别用于分布式瑞利散射传感和数据通信。仿真结果表明,在5~14 dBm入纤功率时,与未均衡信号相比该方法可提供高于3个数量级以上的误码率优化。此方法在短距离模块间15~24 km光纤传输和0.5~2.0 GHz带宽线性调频感测脉冲下均实现了2个数量级以上的误码率下降。依托光储备池计算芯片的低能耗和低延时优势,该方法可为进一步提升通感一体系统中噪声抑制能力提供理论支撑。