Methods for ice velocity mapping in West Antarctica using historical optical satellite images

The Antarctic Ice Sheet harbors more than 90%of the Earth ice mass,with significant losses experienced through dynamic thinning,particularly in West Antarctica.The crucial aspect of investigating ice mass balance in historical periods preceding 1990 hinges on the utilization of ice velocities derived from optical satellite images.We employed declassified satellite images and Landsat images with normalized cross correlation based image matching,adopting an adaptive combination of skills and methods to overcome challenges encountered during the mapping of historical ice velocity in West Antarctica.A basin-wide synthesis velocity map encompassing the coastal regions of most large-scale glaciers and ice shelves in West Antarctica has already been successfully generated.Our results for historical ice velocities cover over 70%of the grounding line in most of the West Antarctic basins.Through adjustments,we uncovered overestimations in ice velocity measurements over an extended period,transforming our ice velocity map into a spatially deterministic,temporally average version.Among all velocity measurements,Thwaites Glacier exhibited a notable spatial variation in the fastest ice flowline and velocity distribution.Overestimation distributions on Thwaites Glacier displayed a clear consistency with the positions of subsequent front calving events,offering insights into the instabilities of ice shelves.

Velocity Correction and Measurement Uncertainty Analysis of Light Screen Velocity Measuring Method

Light screen velocity measuring method with unique advantages has been widely used in the velocity measurement of various moving bodies.For large air resistance and friction force which the big moving bodies are subjected to during the light screen velocity measuring,the principle of velocity correction was proposed and a velocity correction equation was derived.A light screen velocity measuring method was used to measure the velocity of big moving bodies which have complex velocity attenuation,and the better results were gained in practical tests.The measuring uncertainty after the velocity correction was calculated.

An Intermediate Reference Datum Static Correction Technique and Its Applications

Static corrections using the conventional method are basically conducted in two steps, the weathering correction followed by the correction from the top of the sub-weathering to the unified datum. However, the conventional method fails to well deal with statics problems in case the top of the sub-weathering is sharply undulated and the lateral velocity of the sub-weathering varies significantly. This brings us to the introduction of a smooth intermediate reference datum （IRD） located under the top of the sub-weathering, which helps to further increase the accuracy of statics based on the weathering corrections, and ensures the imaging quality. Good results based on the IRD technique have been achieved in the complex areas in western China. This paper discusses the IRD functions, its application requirements, and selection of related parameters. Some typical sections for comparison are also given in this paper.

Correction of seabed layer thickness in processing subbottom profile data

The subbottom profiling is an important means of marine engineering survey, hazardous geology study and continental shelf scientific research. The accuracy of subbottom profile data interpretation has a direct impact on the research and investigation results. Because some of profilers’ transducer and hydrophone are separately installed, when the survey area is very shallow, distortion of shallow layers will be caused if it is seen as a self-excited and self-collected single-channel seismic system. According to the principle of subbottom profiler, the distortion correction formula is deduced and analyzed, providing actual value to using C-View software to interpret such subbottom profile data more accurately. In addition, the seabed sediments sound velocity is one of the key parameters when acquiring and processing the subbottom profile data. On the basis of comparing some sound velocity forecasting empirical equations, the LU Bo’s equation was considered the most appropriate to predict the seabed sediments, sound velocity at near-shore of China. In a survey of an artificial island site, the LU Bo’s equation and the porosity data obtained from geological drilling were utilized to predict the sediments sound velocity, and the sound velocity structure profile was plotted, which was applied in processing the subbottom profile data of the artificial island investigation. The method of using porosity data to predict sediments sound velocity in processing subbottom profile data can improve the interpretation accuracy and it’s of practical significance.

Baseline correction for digital strong-motion records by using the pre-event portion

Baseline offset in digital strong-motion acceleration record and initial velocity can produce unrealistic results for ground velocity and displacement derived from the acceleration by integration. A new method is proposed for the baseline correction and initial velocity calculation. It is based on linear least-squares fitting of the pre-event portion of velocity derived from the uncorrected acceleration data. Compared with the conventional method,which is based on removing the mean values of the pre-event portions of the acceleration and velocity traces,this method has clearer physical meaning and better stability.

Problems and Solutions of Velocity Modeling in Natural Gas Exploration

Recently, velocity prediction and modeling have been focus of the geophysical exploration in the high temperature and high pressure of the south China sea area, especially for new offshore exploratory areas. The error is large with great difficulty owing to fewer exploratory wells and misunderstanding. Firstly, on the basis of three typical velocity prediction and modeling examples in Ying-Qiong basin, it’s easy to put forward the corresponding not common but urgent problem in each instance, then combined with the velocity problem and misunderstanding to expand method discussion and solution, which include geological model to guide the velocity interpretation and analysis, the establishment of forward velocity of the auxiliary model explaining and constructing high precision velocity model. This research basically solves existing velocity problems in gas exploration of south China sea in recent years, and proposes corresponding solution and application, which is of great significance to the further exploration and productive practice.

Can a Michelson-Morley Experiment Designed with Current Solar Velocity Distinguish between Non-Relativistic and Relativistic Theories?

If Michelson were to answer the question posed in the title, given the line of reasoning he used in 1881, Michelson would seat at his desktop computer to calculate the expected fringeshifts for several solar speeds around 400 km/s and various directions of motion. Present author did exactly the same in 2001 to plan his repetition of Michelson and Morley’s (MM) 1887 experiment. The paper sketchedly summarizes the procedure to calculate expected fringeshifts in the MM interferometer for solar speeds available at Miller’s epoch. In a pre-relativistic context, amplitudes of several fringeshifts may be expected in both MM and Miller experiments. However, all interferometer experiments up to 1930 were designed under the (incorrect from a modern viewpoint) assumption that fringeshifts would be smaller than one fringe-width. The inescapable conclusion is that those experiments were not appropriate to measure the true value of solar motion, always yielding a small, but lower than expected, value for solar speed. The ensuing “negative” interpretation led to the birth of relativity theory and to a new series of experiments implicitly designed to test the relativistic hypothesis of length-contraction, while the earlier “positive” experiments were designed to test a different hypothesis: whether the motion of Earth relative to some preferred frame can be measured using an interferometer of constant dimensions. With the benefit of hindsight this writer repeated the MM experiment, correcting main weaknesses identified up to the Michelson-Morley-Miller (MMM) measurements at Mount Wilson from April 1925 to February 1926. A new possible reinterpretation of the MMM data as a sequence of stationary measurements is pointed out. Our Michelson-Morley-Miller-Munera (MMMM) experiment at Bogota (Colombia) from January 2003 to June 2005 gave values for solar absolute velocity in the same range as those obtained by astronomical means. Surprisingly, our results are compatible with modern third-party MM-type experiments designed and interpreted within relativistic contexts. Thus, a so far unexplored possibility arises: can interferometric experiments distinguish between pre-relativistic and relativistic theories? Our answer is negative.

真地表速度建模技术在复杂山地地震资料成像中的应用

传统的叠前深度偏移成像技术将偏移成像和静校正问题分开处理,在复杂山地资料处理中,由于地表条件复杂、近地表横向速度变化剧烈、高速层出露等问题,基于地表一致性假设的静校正处理会引起波场畸变,导致旅行时计算误差较大,影响深度偏移成像效果。因此,提出了一种基于真地表偏移面的全深度建模与成像技术方案,从地表高程面开始速度建模,计算旅行时,将静校正问题隐含在偏移成像过程中,在复杂山地资料处理中取得了较好的应用效果。

基于自适应ZUPT与航向角误差修正的INS约束算法

为提高行人惯性导航系统(INS)的定位精度,提出了一种基于自适应零速修正算法(ZUPT)与航向角误差修正的INS约束算法。首先,利用基于广义似然比的零速检测阈值与检验统计量的特征值建立关系式,实现对零速检测阈值的自适应调整。然后,对INS解算位置建立线性回归模型,结合主航向与解算航向的航向差,根据行人运动类型构建观测向量和观测矩阵,对INS误差进行修正。最后,经实验验证,当行人在复杂路线变速运动时,相较于固定阈值的零速检测算法和主航向修正算法,所提算法的解算轨迹更接近真实轨迹,平均闭环误差从3.31%D减小至1.45%D,有效提高了INS定位精度,具有较好的工程应用价值。

混凝土不同形态裂纹对声发射波传播特性影响

混凝土中裂纹的尺寸与形态参数对损伤声发射信号传播存在不可忽视的影响,为研究不同形态裂纹对声发射波传播特性的影响,进而研究不同形态裂纹存在对损伤信号的定位修正模型;试验基于不同形态裂纹的混凝土试件声发射试验的基础上,研究裂纹角度、裂纹距声发射源距离、裂纹数量和裂纹深度对声发射波传播特性的影响规律。研究表明:不同形态裂纹对声发射信号传播的损伤程度不同,裂纹距声发射源距离和裂纹角度对声发射信号的损伤较大,最大损伤达到66.44%和48.43%;裂纹数量和裂纹深度对其的损伤相对较小,最大损伤达到38.00%和24.71%;基于不同形态裂纹影响规律,建立了考虑不同形态裂纹影响的修正波速关系模型,与传统时差定位方法相比,基于不同裂纹形态的修正波速定位方法对声发射源的定位更精确。

风速传感器风洞校准的阻塞影响及修正方法研究

为研究阻塞现象的形成原理及其对风速校准结果的影响,建立高阻塞比和低阻塞比工况对应的气象风速校准流场仿真模型,分析不同阻塞比工况对圆柱形结构和长方体结构风洞试验段流场影响。现有理论模型和比较法使用单一的修正系数修正所有校准点风速示值,导致低风速校准点风速传感器示值修正存在偏差,针对该问题提出一种各校准点独立计算阻塞修正系数的分段修正方法。结合EC9-1型、EL15-1A型和ZQZ-TF型等常用气象风速传感器校准数据,分析分段修正法与既有理论模型和比较法对传感器测量特性的影响。实验结果表明,3种阻塞修正方法都可改善风速传感器示值误差和频率方程等测量特性,使传感器示值、频率方程的斜率和截距更接近标准风洞的校准数据,分段修正法对传感器偏离程度的改善效果最为显著,经分段修正法修正后的传感器偏离程度最接近标准风洞测得值。

一种基于运动平台的测控设备测速修正新方法

针对传统的船载测控设备船速修正方法过程复杂、计算量大的缺点,直接从速度的物理意义出发,建立数学模型,采用数学推导的方法,提出一种适用于船载、车载、机载等运动平台下的测控设备测速修正的新方法。结合校飞数据与传统修正方法进行比对,结果表明,相对于传统的测速修正方法,修正精度相当,但算法大大简化,时间代价降低54.9%。

“断层阴影”识别与校正方法——以松辽盆地升平构造为例

地层错断往往引起速度横向突变,导致在时间域地震资料中出现“断层阴影”现象,影响地质解释结果及圈闭评价等。为此,以松辽盆地升平构造为例,分析“断层阴影”现象,提出了正演模拟法、井震结合地层对比法和平均速度成图法三种识别方法;在此基础上,针对“断层阴影”,提出了高精度速度场校正和时间域层位校正两种校正方法。结果表明,高精度速度场校正法可以实现数据体的校正,适应性更广;时间域层位校正法可以实现层位的校正,具有快速、简便的优势。该方法对类似地区具有借鉴意义。

泊松比变化对基于波速混凝土损伤计算的影响

利用超声波波速计算材料损伤的方法有广泛的应用,然而现有研究中常忽略泊松比的变化。研究了泊松比变化对基于波速混凝土损伤计算结果的影响。首先,通过理论分析,在基于波速的损伤计算公式中引入泊松比修正系数;其次,通过对混凝土柱试件进行轴压试验,验证了考虑泊松比变化的必要性;最后,在试验数据的基础上提出了泊松比修正系数实用计算方法。结果表明:忽略泊松比变化的影响时,基于波速的混凝土损伤计算值与真实值的平均相对误差高达73%;采用泊松比修正系数后,该误差减小至21%。基于波速进行混凝土损伤计算时宜计入泊松比修正系数以提高计算精度。

破片撞击裸药柱临界起爆速度判据的研究

为了获得破片以不同入射角撞击不同曲率半径裸药柱的冲击起爆判据,以Held提出的判据为基础,考虑破片入射角和裸药柱曲率半径2个因素,采用Autodyn软件对球形破片撞击裸药柱的过程展开了数值仿真计算,得到了30种工况下炸药装药的临界起爆速度,获得了破片入射角、裸药柱曲率半径对炸药临界起爆速度的影响规律,通过Matlab软件拟合得到修正项,建立了关于破片入射角和裸药柱曲率半径的炸药临界起爆速度修正判据。结果显示建立的修正判据和数值仿真结果吻合较好,表明该修正判据可以较好地预测裸药柱的冲击起爆条件。

半分离式斜腹板双箱梁大跨单肋拱桥颤振临界风速分析

为研究低扭弯频率比大跨度桥梁的颤振性能,以某主跨180 m的半分离式斜腹板双箱梁大跨单肋拱桥为背景(主梁扭弯频率比接近1.0),进行颤振临界风速分析。采用有限元法分析该桥动力特性,计算桥梁颤振稳定性;对比《公路桥梁抗风设计规范》(JTG/T 3360-01—2018)推荐的3组理想平板颤振临界风速估算公式,基于Scanlan半逆解法的理想平板颤振临界风速,考虑主梁形状与攻角修正系数确定颤振临界风速范围;采用强迫振动数值模拟识别颤振导数,获得精确颤振临界风速,进一步计算半分离式斜腹板双箱梁的形状和攻角系数。结果表明:该桥主梁扭弯频率比较低,颤振稳定性低于500 m级大跨度双肋拱桥;规范推荐的理想平板颤振临界风速估算公式在小扭弯频率比时差异较大;半分离式斜腹板双箱梁形状修正系数小于分离式双箱梁而大于P-K梁、带斜腹板箱梁,攻角修正系数略大于这3种形式主梁。

落速约束条件下滑翔飞行器制导律设计

针对滑翔飞行器末端速度约束条件下的制导问题,本文在分析侧向过载对速度的控制作用后提出了两种制导方法。首先,建立侧向机动模型,分析侧向机动运动对飞行器能量耗散的作用,提出利用侧向机动控制飞行器落速;其次,为准确控制飞行器末端速度,分别提出基于速度修正和神经网络的制导方法,并进行了六自由度仿真计算。仿真结果表明:本文所提出的制导方法能够在落角约束条件下准确控制飞行器末端速度;基于速度修正的制导方法在工程上易于实现,基于神经网络的制导方法具有更好的速度控制效果,具备在线实施的能力。本文所提出的落速约束制导方法具有较好的工程实用性,对此类飞行器的制导系统设计具有一定的参考意义。

基于全波形反演速度约束的叠后地震反演方法

对于井数较少或者沉积相变化较快的地层,利用测井曲线建立的反演低频模型难以控制反演弹性参数的空间变化趋势。据此笔者发展了基于FWI速度约束的叠后地震反演方法,该方法充分利用了FWI速度的真三维信息,据此得到反演弹性参数的空间变化趋势。对于叠后地震反演所需要的纵波阻抗低频模型,提出了基于测井岩石物理拟合关系将FWI速度转换为FWI纵波阻抗的方法。另外,针对FWI纵波阻抗和测井纵波阻抗存在一定差异的问题,提出了FWI纵波阻抗均值校正方法,据此可得到较为准确的纵波阻抗低频模型。单井和实际工区应用表明,纵波阻抗反演结果和井上结果匹配性较高,因此笔者提出的基于FWI速度约束的叠后地震反演方法较为有效,可为储层预测提供较为有利的技术支持。

钢筋混凝土梁不同受载等级对声发射波速的影响研究

为了研究钢筋混凝土梁结构不同受载等级对声发射波速的影响,对2根混凝土强度等级为C30、C50的钢筋混凝土梁试件进行静力分级加载试验和声发射试验,同时分析了钢筋混凝土梁不同受载等级对声发射声源的定位问题。结果表明,随着受载等级的增加,声发射波速呈现先缓慢衰减,之后快速衰减,最后缓慢衰减三个阶段。通过对受载的钢筋混凝土梁结构进行定位分析,利用考虑受载等级的修正波速时差定位法将定位误差精确到2%以内。

中医体质调理对早期无症状型糖尿病周围神经病变的影响

【目的】观察基于“治未病”理论的中医体质调理对早期无症状型糖尿病周围神经病变(diabetic peripheral neuropathy,DPN)的影响及安全性。【方法】将87例早期无症状型DPN患者随机分为对照组43例和试验组44例,对照组仅予糖尿病的规范饮食、运动及药物治疗,试验组在对照组的基础上,根据患者的主要体质类型给予相应的中医体质调养方案进行调理,疗程为48周。观察2组患者干预前后中医体质转化情况、体质量指数(BMI)、收缩压(SBP)、舒张压(DBP)、空腹血糖(FPG)、糖化血红蛋白(HbA1c)、总胆固醇(TC)、甘油三酯(TG)、高密度脂蛋白胆固醇(HDL-C)、低密度脂蛋白胆固醇(LDL-C)水平以及神经传导速度(NCV)的变化情况,并评价2组患者的安全性。【结果】(1)干预结束后,试验组有17例患者转化为平和质,而对照组仅有5例患者转化为平和质,2组患者的中医体质分布比较,差异有统计学意义(P<0.05)。(2)干预前,2组患者的BMI、SBP、DBP、FPG、HbA1c、TC、TG、HDL-C、LDL-C水平比较,差异均无统计学意义(P>0.05),具有可比性。干预后,2组患者的BMI、SBP、DBP水平以及试验组的HbA1c、TC、TG、LDL-C水平均较干预前下降(P<0.05或P<0.01),对照组的FPG、HDL-C水平则较干预前升高(P<0.05或P<0.01);组间比较,试验组的FPG、HbA1c、TG、LDL-C水平均较对照组明显降低,差异均有统计学意义(P<0.05或P<0.01)。(3)干预结束后,对照组有10例出现DPN临床典型症状,试验组仅有6例出现DPN临床症状。干预前,2组患者的双侧胫神经及腓总神经运动传导速度(MNCV)、双侧腓肠神经及腓浅神经感觉传导速度(SNCV)比较,差异均无统计学意义(P>0.05),具有可比性。干预后,对照组的双侧胫神经及腓总神经MNCV、双侧腓肠神经及腓浅神经SNCV均较干预前减慢(P<0.01),而试验组的以上神经传导速度虽较干预前有轻微上升,但与干预前比较差异均无统计学意义(P>0.05);组间比较,试验组的双侧胫神经MNCV、双侧腓肠神经及腓浅神经SNCV均较对照组高,差异均有统计学意义(P<0.05)。(4)干预过程中,2组患者均未出现明显不良反应,具有较高的安全性。【结论】中医体质调理可以调整早期无症状型DPN患者的失衡体质,同时对患者的糖脂代谢、胫神经运动传导速度、双侧腓肠神经及腓浅神经的感觉传导速度具有一定的保护作用。