CBCT测量磨牙根管工作长度的实验研究

目的:评价CBCT测量根管工作长度的准确性,为临床应用提供实验依据。方法:选取外形完整、根尖发育完成或接近完成、无龋坏、无充填及牙髓病治疗史的上下颌磨牙40颗(共计136个根管)。应用CBCT测量各磨牙根管工作长度,以直视下测量的根管工作长度为标准,判断测量方法的准确性,并且和RVG、根管长度电测仪测量结果比较。结果:CBCT(根管腔测量法;根长度测量法)的准确率分别是84.56%、91.91%,而RVG、根管长度电测仪的准确率分别是58.09%、86.03%。经统计学检验,CBCT测量的准确率与根管长度电测仪差异无统计学意义(P>0.05),RVG测量与其他两种方法的准确率差异有统计学意义(P<0.01)。结论:CBCT与根管长度电测仪测量磨牙根管工作长度的准确率均较高,但各有其优缺点,CBCT可作为临床根管测量方法的一种有效的补充,而在RVG图像上测量根管长度的准确率不高。     

CBCT测量磨牙根管工作长度的实验研究

目的:评价CBCT测量根管工作长度的准确性,为临床应用提供实验依据.方法:选取外形完整、根尖发育完成或接近完成、无龋坏、无充填及牙髓病治疗史的上下颌磨牙40颗(共计136个根管).应用CBCT测量各磨牙根管工作长度,以直视下测量的根管工作长度为标准,判断测量方法的准确性,并且和RVG、根管长度电测仪测量结果比较.结果:CBCT(根管腔测量法;根长度测量法)的准确率分别是84.56％、91.91％,而RVG、根管长度电测仪的准确率分别是58.09％、86.03％.经统计学检验,CBCT测量的准确率与根管长度电测仪差异无统计学意义(P＞0.05),RVG测量与其他两种方法的准确率差异有统计学意义(P＜0.01).结论:CBCT与根管长度电测仪测量磨牙根管工作长度的准确率均较高,但各有其优缺点,CBCT可作为临床根管测量方法的一种有效的补充,而在RVG图像上测量根管长度的准确率不高.     

CBCT技术在多生牙诊断中的意义

目的:探讨CBCT诊断及定位多生牙的临床应用价值。方法:选取有完整病史资料的123例多生牙病例的CBCT影像,水平截面和任意截面T:0.43mm,S:0.5mm;曲面断层T:15mm,D:1.0mm。利用CBCT三维重建影像,观察多生牙的好发部位、数目以及对牙列的影响,并对图像进行测量分析。结果:CBCT能清晰显示多生牙的数目、大小、位置、与邻近组织的关系等。结论:CBCT扫描能够全面地提供多生牙的影像信息,有利于治疗方案的制定与实施。     

锥束CT技术在口腔临床中的应用

将锥束CT应用于口腔部位的三维成像,是近年来CT研究人员和口腔医生共同关注的一个热点.特别是随着牙齿种植技术的兴起,利用CBCT进行牙齿种植计划和手术导板的设计已成为一项新的研究方向.本文综述了口腔CBCT的成像原理和临床应用,比较了CBCT与传统CT在口腔成像中的特点,并总结了当前的关键技术和研究热点,供相关的技术及医学研究人员参考.     

基于耳石微化学的长江靖江段长颌鲚与短颌鲚生境履历重建

为了解长江靖江段两种刀鲚生态型长颌鲚与短颌鲚的生境履历的不同,利用X射线电子探针微区分析技术研究采集自长江靖江江段的长颌鲚和短颌鲚个体耳石的锶和钙微化学特征.定量分析结果显示,短颌鲚个体的耳石锶、钙比值(即Sr/Ca×10~3)稳定在2.00左右,反映了其在纯淡水生活的习性;而长颌鲚的锶、钙比值波动显著,不仅具有对应淡水生活的低值(1.18±0.48~2.11±0.94),还具有对应半咸水生活的高值(3.39±0.60~6.79±1.13),反映了其溯河洄游的生活习性.短颌鲚因在淡水生活,其淡水系数(FC)值均为1.00,2013年和2014年长颌鲚的FC值分别为0.36±0.06和0.50±0.11,证明了长颌鲚与短颌鲚群体间存在差异,而且长颌鲚不同年份群体间也并不相同.长颌鲚和短颌鲚的洄游模式存在显著差异,同时不同年份间的长颌鲚也存在生境履历差异.靖江段长颌鲚资源群可能来自不同出生地起源及生活史背景不同的群体.该江段是两类刀鲚的重要栖息地或洄游通道.     

CBCT在牙中牙诊断和治疗中的临床应用

目的：探讨CBCT在牙中牙诊断及治疗中的临床应用价值。方法：对3例经x线根尖片或曲面体层摄片发现的牙中牙病例进行CBCT扫描。利用CBCT三维重建影像,观察牙中牙的根管腔形态、内陷牙的数目和内陷牙髓腔的形状以及治疗后牙中牙内腔隙的封闭情况,并且与x线根尖片、曲面体层摄片比较。结果：CBCT能清晰显示牙中牙的根管腔形态、内陷牙的数目和内陷牙髓腔的形状以及治疗后牙中牙内腔隙的封闭情况等。结论：CBCT扫描能够全面地提供牙中牙治疗前后的影像信息,有利于牙中牙的诊断和治疗。     

应用模式识别定量划分潜在震源区

本文以陕西关中及部分邻区为例,考虑地质构造、地震活动及地球物地场等因素,采用不同的模式识别方法和多种计算方案,以定量判定潜在震源区。其结果表明,模式识别方法有利于地质、地震活动及地球物理场等多种因素综合应用,并能选择和显示判定潜有震源区的主要特征。不同模式识别方法的比较和多种试验方案的综合,则可提高潜在震源区判定的可靠性和稳定性。     

口腔锥形束CT剂量评估模式的研究现状?

基于平板探测器的口腔锥形束计算机断层成像（CBCT）具有X射线Z方向（本文中指平行于CT旋转轴的方向）宽准直、180°至360°投影角度范围可选、扫描视野尺寸可调节、全扇束或半扇束偏置模式可选等特点。受检者头部的吸收剂量分布与传统多排探测器CT （MDCT）和其他临床CBCT （例如放射治疗图像引导的CBCT、介入手术的CBCT等）的吸收剂量分布相比更加复杂。因此,至今还没有有效的、取得国际共识的口腔CBCT剂量评估模式。本文调研了CT剂量评估的相关研究,将口腔CBCT剂量评估模式总结为由相互联系的剂量表征量和受检者医疗照射剂量（本文中指基于人群平均数据的有效剂量和受检者特异的组织器官吸收剂量）两个层面构成。同时指出,口腔CBCT剂量表征量研究的关键问题是如何准确地描述口腔CBCT扫描一个均匀圆柱体模时,体模的垂直于Z方向的中间平面的吸收剂量分布规律,目前,面平均吸收剂量是最有潜力解决该问题的剂量表征量;口腔CBCT可以直接采用MDCT的受检者医疗照射剂量评估原理,但还需要解决的关键问题是如何提供准确的受检者对X射线的衰减情况;同时,口腔CBCT的剂量评估模式研究还应该探讨锥形束X射线阳极效应、锥角效应的影响。      

我国重力测量在地震预报研究中的作用和问题

本文是全国重力测量用于地震预报研究的清理攻关工作的综合报告概要。主要从重力台网的布局、干扰因素、测量技术、观测精度、质量评定、预报方法等几方面的清理工作来评价和论述重力手段在地震预报应用中所取得的成果和意义,以及今后的主攻方向。     

地震海洋学回顾与展望

地震海洋学是利用反射地震勘探方法来研究海洋水体温盐结构的一门新兴学科.相对于传统的物理海洋学测量手段,其主要优势在于该方法有效的提高了水平方向的分辨率,并具有短时间内对整条海水剖面进行快速成像的特点.本文论述了地震海洋学在温盐反演、海洋内波、涡旋、海洋混合参数提取等方面的研究成果及发展趋势,并就水体的浅层结构地震影像分析及地球固液系统相互作用进行了探讨.今后地震海洋学有望在温盐剖面反演新算法、浅层水体结构信息的探索、固体地球与海水层之间相互作用的研究等方面取得进展,而新时期的地震海洋学研究有赖于不同观测手段的联合调查与分析.     

数学形态学在地震信号处理中的应用研究

数学形态学是一门新兴科学,它建立在严格的数学理论基础之上,是研究数字信号（图像）形态结构特征及其快速并行处理方法的理论,已经成功应用于图像处理、医学信号处理和语音信号处理等领域.地震信号去噪处理和裂缝检测的研究一直都是地质学家和油气藏工程学家感兴趣的问题.本文将数学形态学与地震信号处理相结合,重点探讨了数学形态学在地震信号处理中的应用,针对地震信号的特点,设计了形态滤波器,应用于合成地震资料,得到了理想的结果.在此基础上,本文研究并构造了形态学边缘检测算子,通过理论和实际资料检验,该方法具有良好适用性.以上研究表明,基于形态学的地震信号处理是可行的,具有推广应用前景.     

基于CT图像分析建立岩土材料数值模型的方法研究

根据材料内部真实结构建立数值计算模型是岩土力学研究的一个热点。本文针对不同材料内部结构特征,介绍了等效图形法与边缘矢量化两种建模方法,并以自制孔隙岩土材料和混凝土的CT图像为例,说明了两种建模步骤。分析表明:当图像的灰度直方图具有明显双峰或多峰结构时,特征区域易分割;而当灰度直方图为单峰结构时,可以通过数学形态学的top-hat方法进行图像增强,以方便特征区域的提取。对于孔隙结构,可以利用等效圆或等效椭圆表征,建立相应的数值模型;而当内部结构复杂时,可利用特征边缘矢量化方法进行建模。本研究为如何建立反映岩土材料内部真实结构数值模型提供了方法。     

Evaluating river morphology change with a geomorphic form variation approach

Geomorphic river design strives for natural resilience by encouraging geomorphic form complexity and morphological processes linked to greater habitat diversity. Increasing availability of high-resolution topographic data and spatial feature mapping methods provide advantages for morphological analysis and river restoration planning. We propose and evaluate an approach to quantifying topographic variability of geomorphic form and pixel-level surface roughness resulting from channel planform geometry differences using spatially continuous variety computation applied to component metrics including flow direction, aspect and planform curvature. We define this as the geomorphic form variation (GFV) approach and found it scalable, repeatable and a multi-stage analytical metric for quantifying physical aspects of river-bed topographic variability. GFV may complement process-based morphological feature mapping applications, hydraulic assessment indices and spatial habitat heterogeneity metrics commonly used for ecological quality evaluation and river restoration. The GFV was tested on controlled synthetic channels derived from River Builder software and quasi-controlled sinuous planform flume experiment channels. Component variety metrics respond independently to specific geometric surface changes and are sensitive to multi-scaled morphology change, including coarser-grained sediment distributions of pixel-level surface roughness. GFV showed systematic patterns of change related to the effects of channel geometry, vertical bed feature (pool-bar) frequency and amplitude, and bar size, shape and orientation. Hotspot analysis found that bar margins were major components of topographic complexity, whereas grain-scale variety class maps further supported the multi-stage analytical capability and scalability of the GFV approach. The GFV can provide an overall variety value that may support river restoration decision-making and planning, particularly when geomorphic complexity enhancement is a design objective. Analysing metric variety values with statistically significant hotspot cluster maps and complementary process-based software and mapping applications allows variety correspondence to systematic feature changes to be assessed, providing an analytical approach for river morphology change comparison, channel design and geomorphic process restoration.     

Corroded cobbles in Southern Death Valley: Their relationship to honeycomb weathering and lake shorelines

In southern Death Valley, pits similar in morphology to honeycomb weathering (herein referred to as corrosion pits) occur on the surfaces of cobbles that are associated with wave-produced benches. The pitted cobbles include a variety of igneous, metamorphic, and siliciclastic rocks; corrosion pits are rare to absent in limestones or dolomites. Pit morphology is controlled by cobble lithology. In massive rocks the pits are arcuate, elongate, and gently tapering; corrosion of laminated or foliated rocks has produced irregular, more jagged pits. The presence of desert varnish has strongly inhibited the corrosion process. The corroded cobbles are inferred to reflect both chemical and physical weathering of rocks along Pleistocene lacustrine strandlines. Corrosion took place through salt-weathering and/or heat-moisture expansion processes and through chemical dissolution of selected minerals as a result of splash-zone wetting and drying. The ancient lake waters may have had high pH and high total dissolved solids contents. The recognition of corroded cobbles may be important in the reconstruction of the position of ancient shorelines for certain types of alkaline lakes and in the reconstruction of their ancient chemistries.     

Quantification of clay minerals by combined EWA/XRD method

Illite has been considered the main constraint on permeability in the Morecambe Gas Field, East Irish Sea, UK. Previous research has emphasized the morphology rather than the amount of clay minerals. By applying a new method of clay mineral quantification, EWA/XRD, and applying statistical analysis methods, we are able to establish a quantitative model of illite distribution in the field. The result also leads to a better understanding of permeability distribution in reservoir sandstones.     

Improved petrographic-coded model and its evaluation to determine a thermal conductivity log

Thermal conductivity is one of the crucial properties for thermal modelling as well as tunnelling or geological modelling. Available data are mainly from laboratory measurements. Therefore, additional ways, such as correlations with other properties to derive the petrophysical parameter, will be an advantage. The research presented here continues and improves the petrographic-coded model concept with an increased set of data, including a variety of lithologies, and, furthermore, the correlations, including the electrical resistivity. Input parameters are no longer taken from the literature, but are derived directly from measurements. In addition, the results are compared with other published approaches. Results show good correlations with measured data. The comparison with the multi-linear regression method shows acceptable outcome, in contrast to a geometric-mean method, where data scatter. In summary, it can be said that the improved model delivers for both correlation (compressional wave velocity and electrical resistivity with thermal conductivity) positive results.     

数学形态滤波与大地电磁噪声压制

数学形态滤波是一种新型的非线性滤波方法.介绍了形态学滤波的基本原理,针对大地电磁信号表现出的非线性、非平稳性和非最小相位特性,综合结构元素特征我们提出一种基于数学形态滤波的大地电磁噪声压制方法.为了有效抑制目标信号中的噪声干扰及修正统计偏倚现象,通过选用合理的结构元素及形态开-闭、闭-开组合,将正、负结构元素级联构造组合广义形态滤波器对实测大地电磁信号进行噪声压制.实验结果表明,该方法是切实可行的,有效地剔除了大尺度干扰及基线漂移,较好地还原了大地电磁信号的原始特征,修正了标准形态算子所产生的统计偏倚现象,去噪精度高.该方法计算速度快,具有潜在优势,为矿集区海量大地电磁信号与强干扰的分离提供了一条新的途径,应用前景广阔.     

Sensitivity of a hydraulic model to channel erosion uncertainty during extreme flooding

Recent research into flood modelling has primarily concentrated on the simulation of inundation flow without considering the influences of channel morphology. River channels are often represented by a simplified geometry that is implicitly assumed to remain unchanged during flood simulations. However, field evidence demonstrates that significant morphological changes can occur during floods to mobilize the boundary sediments. Despite this, the effect of channel morphology on model results has been largely unexplored. To address this issue, the impact of channel cross‐section geometry and channel long‐profile variability on flood dynamics is examined using an ensemble of a 1D–2D hydraulic model (LISFLOOD‐FP) of the ~1 : 2000 year recurrence interval floods in Cockermouth, UK, within an uncertainty framework. A series of simulated scenarios of channel erosional changes were constructed on the basis of a simple velocity‐based model of critical entrainment. A Monte‐Carlo simulation framework was used to quantify the effects of this channel morphology together with variations in the channel and floodplain roughness coefficients, grain size characteristics and critical shear stress on measures of flood inundation. The results showed that the bed elevation modifications generated by the simplistic equations reflected an approximation of the observed patterns of spatial erosion that enveloped observed erosion depths. The effect of uncertainty on channel long‐profile variability only affected the local flood dynamics and did not significantly affect the friction sensitivity and flood inundation mapping. The results imply that hydraulic models generally do not need to account for within event morphodynamic changes of the type and magnitude of event modelled, as these have a negligible impact that is smaller than other uncertainties, e.g. boundary conditions. Instead, morphodynamic change needs to happen over a series of events to become large enough to change the hydrodynamics of floods in supply limited gravel‐bed rivers such as the one used in this research. Copyright © 2014 John Wiley & Sons, Ltd.     

IDENTIFICATION OF PALEO-EARTHQUAKES OF LUOYUNSHAN PIEDMONT FAULT BY QUANTITATIVE MORPHOLOGY OF LIMESTONE FAULT SURFACES

The quantitative analysis of morphologic characteristics of bedrock fault surface is a useful approach to study faulting history and identify paleo-earthquake. It is an effective complement to trenching technique, specially to identifying paleo-earthquakes in a bedrock area where the trenching technique cannot be applied. This paper focuses on the Luoyunshan piedmont fault, which is an active normal fault extending along the eastern boundary of the Shanxi Graben, China. There are a lot of fault scarps along the fault zone, which supply plentiful samples to be selected to our research, that is, to study faulting history and identify paleo-earthquakes in bedrock area by the quantitative analysis of morphologic characteristics of fault surfaces. In this paper, we calculate the 2D fractal dimension of two bedrock fault surfaces on the Luoyunshan piedmont fault in the Shanxi Graben, China using the isotropic empirical variance function, which is a popular method in fractal geometry. Results indicate that the fractal dimension varies systematically with height above the base of the fault surface exposures, indicating segmentation of the fault surface morphology. The 2D fractal dimension on a fault surface shows a ‘stair-like’ vertical segmentation, which is consistent with the weathering band and suggests that those fault surfaces are outcropped due to periodic faulting earthquakes. However, compared to the results of gneiss obtained by the former researchers, the characteristic fractal value of limestone shows an opposite evolution trend. 1)The paleo-earthquake study of the bedrock fault surface can be used as a supplementary method to study the activity history of faults in specific geomorphological regions. It can be used to fill the gaps in the exploration of the paleo-earthquake method in the bedrock area, and then broaden the study of active faults in space and scope. The quantitative analysis of bedrock fault surface morphology is an effective method to study faulting history and identify paleo-earthquake. The quantitative feature analysis method of the bedrock fault surface is a cost-effective method for the study of paleo-earthquakes in the bedrock fault surface. The number of weathered bands and band height can be identified by the segment number and segment height of the characteristic fractal dimension, and then the paleoearthquake events and the co-seismic displacement can be determined; 2)The exposure of the fault surface of the Luoyunshan bedrock is affected and controlled by both fault activity and erosion. A strong fault activity(ruptured earthquake)forms a segment of fault surface which is equivalent to the vertical co-seismic displacement of the earthquake. After the segment is cropped out, it suffers from the same effect of weathering and erosion, and thus this segment has approximately the same fractal dimension. Multiple severe fault activities(ruptured earthquake)form multiple fault surface topography. The long-term erosion under weak hydrodynamic conditions at the base of the fault cliff between two adjacent fault activities(intermittent period)will form a gradual slow-connect region where the fractal dimension gradually changes with the height of the fault surface. Based on the segmentation of quantitative morphology of the two fault surfaces on the Luoyunshan piedmont fault, we identified four earthquake events. Two sets of co-seismic displacement of about 3m and 1m on the fault are obtained; 3)The relationship between the fault surface morphology parameters and the time is described as follows:The fractal dimension of the limestone area decreases with the increase of the exposure time, which reflects the gradual smoothing characteristics after exposed. The phenomenon is opposite to the evolution of the geological features of gneiss faults acquired by the predecessors on the Huoshan piedmont fault; 4)Lithology plays an important role in morphology evolution of fault surface and the two opposite evolution trends of the characteristic fractal value on limestone and gneiss show that the weathering mechanism of limestone is different from that of the gneiss.     

Removal of Selected Micropollutants from Synthetic Wastewater by Electrooxidation Using Oxidized Titanium and Graphite Electrodes

Micropollutants cover a variety of compounds that mainly originate from the pharmaceutical and agricultural sectors. Even at trace concentrations, the discharge of micropollutants into water bodies pose a serious threat to the environment and human health. Their removal from wastewaters at treatment plants before their discharge into the environment has become one of the leading topics of research. Physical, chemical, and biological treatment methods have been listed in the literature for efficient removal of a variety of pollutants. In this study, seven micropollutants, namely 4‐tert‐octylphenol, atrazine, 2,4,6‐trichlorophenol, fluoxetine, estrone, penconazole, and di‐n‐octyl phthalate, are spiked into municipal simulated synthetic wastewater and treated by a laboratory‐scale electrooxidation (EO) system using oxidized titanium and graphite electrode as anode and cathode, respectively. Sensitive determination of the selected micropollutants by gas chromatography–mass spectrometry (GC‐MS) before and after treatment is performed after their pre‐concentration using an eco‐friendly switchable solvent liquid‐phase microextraction method (SSLPME). The pH value, applied current, and reaction period are optimized to enhance the removal efficiency of micropollutants. Results show that the highest removal efficiency of all micropollutants is obtained at pH 3, 20 min reaction period, and 3 A applied current. The operational costs are also investigated in this study.