Selection of prior distributions and multiscale analysis in Bayesian temperature reconstructions based on fossil assemblages

It is possible to reconstruct the past variation of an environmental variable from measured historical indicators when the modern values of the variable and the indicators are known. In a Bayesian statistical approach, the selection of a prior probability distribution for the past values of the environmental variable can then be crucial and the selection therefore should be made carefully. This is particularly the case when the data are noisy and the statistical model used is complex since the influence of the prior on the results can then be especially strong. It can be difficult to elicit the prior probability distribution from the available information, since usually there are no measured data on the past values of the variable one wants to reconstruct and different reconstructions are typically consistent with each other only at a coarse level. To overcome these difficulties we propose to use a non-informative smoothing prior, possibly in combination with an informative prior, that simply penalizes for roughness of the reconstruction as measured by the variability of its values. We believe that it can sometimes be easier to set an overall prior distribution on the roughness than to agree on a prior for the actual values of the reconstructed variable. Note that by using a smoothing prior one incorporates into the model itself the smoothing step usually done before or after the actual numerical reconstruction. Another idea proposed in this paper is to integrate the reconstruction model with a multiscale feature analysis technique known as SiZer. Multiscale analysis of the posterior distribution of the reconstructed variable makes it possible to infer its statistically significant features such as trends, maxima and minima at several different time scales. While only temperature is considered in this paper, the technique can be applied to other environmental variables.     

Holocene thermal optimal and climate variability of East Asian monsoon inferred from forest reconstruction of a subalpine pollen sequence, Taiwan

The East Asian monsoon Holocene optimal period has been debated both about duration and whether conditions were a maximum in thermal conditions or in precipitation. In this study we show Holocene climate variability inferred by a forest reconstruction of a subalpine pollen sequence from peat bog deposits in central Taiwan, based on modern analogues of various altitudinal biomes in the region. A warmer interval occurred between 8 and 4 ka BP (calibrated ¹⁴C years) when the subtropical forests were more extensive. The Holocene thermal optimum is represented by an altitudinal tropical forest at 6.1–5.9 ka BP and 6.9 ka BP and only the latter was accompanied by wet conditions, indicating decoupling of thermal and precipitation mechanism in the middle Holocene. Abrupt and relative severe cold phases, shown by biome changes, occurred at about 11.2–11.0 ka BP; 7.5 ka BP; 7.2 ka BP; 7.1 ka BP; 5.2 ka BP, 5.0 ka BP and 4.9 ka BP. A spectral analysis of pollen of a relatively cold taxon — Salix, reveals that the time series is dominated by a 1500 yr periodicity and similar to the cold cycle reported in the marine records of Indian and western Pacific Oceans. The cold–warm conditions inferred by the change of forests show close relationship to solar energy in comparison with the production rate of Be-10.     

CHANGES IN ICE-MARGIN PROCESSES AND SEDIMENT ROUTING DURING ICE-SHEET ADVANCE ACROSS A MARGINAL MORAINE

Advance of part of the margin of the Greenland ice sheet across a proglacial moraine ridge between 1968 and 2002 caused progressive changes in moraine morphology, basal ice formation, debris release, ice‐marginal sediment storage, and sediment transfer to the distal proglacial zone. When the ice margin is behind the moraine, most of the sediment released from the glacier is stored close to the ice margin. As the margin advances across the moraine the potential for ice‐proximal sediment storage decreases and distal sediment flux is augmented by reactivation of moraine sediment. For six stages of advance associated with distinctive glacial and sedimentary processes we describe the ice margin, the debris‐rich basal ice, debris release from the glacier, sediment routing into the proglacial zone, and geomorphic processes on the moraine. The overtopping of a moraine ridge is a significant glaciological, geomorphological and sedimentological threshold in glacier advance, likely to cause a distinctive pulse in distal sediment accumulation rates that should be taken into account when glacial sediments are interpreted to reconstruct glacier fluctuations.     

基于小波变换的生态综合信息图谱的多尺度结构分析

融合小波分析和逐步回归分析方法,对研究区内不同尺度上决定区域生态信息分异的因素进行研究.结果表明,起伏度在研究区中起总体控制作用,坡度的作用有一定范围,人类作用有明显表现.该方法可有效地分解出不同尺度上各作用因子的作用强度,有可能进一步拓展应用于生态信息研究.     

造山带古地理学——重建区域构造古地理的若干思考

以活动论构造观为指导,尽可能客观地复原地史期间海陆面貌和盆山格局的关键是在给定时间约束之后,于研究区现存的地质记录中发现业已消失了的和后期才出现的构造古地理单元。文章基于大量实例论述了可能导致构造古地理单元消失和后期出现的各种情况,如大陆地块的解体、沉没、俯冲、剥蚀、冲断-推（滑）覆作用、走滑作用、碎裂和被卷入年轻造山带等,特别提出东亚大陆边缘地区自侏罗纪末开始的移置地体拼贴增生是该区的一大特点。构造古地理单元消失和后期出现的发生大都与巨型断裂带（尤其是作为构造边界的巨型断裂带）发育有关。陆内阶段的断裂带活动对盆山格局的变化、盆地发育、沉积演化及其关键地质事件有明显的控制作用,还应注意断裂带解体阶段出现的新生构造对古地理重建的制约。简言之,造山带古地理学的发展是推动构造古地理学前进的关键之一,在恢复古特提斯多岛洋的构造古地理面貌、重建全球古大陆演化尤其是造山带和经受造山运动改造地区的古大陆演化,有着积极的不可或缺的作用。     

低剂量CT心脏成像

采用CT进行心脏成像是CT临床应用中最前沿的进展,心脏扫描中采用较低的螺距使得病人的辐照剂量较高,我们提出一种不同的数据采集和图像重建技术,使病人的辐照剂量减少了50%～89%.该方法的使能技术是64排CT的大容积覆盖范围(40㎜),相对于心脏的平均尺寸是120～140㎜,新的容积CT在3～4步就能够覆盖整个器官.伴随新的数据采集方式,我们也提出了对应的重建算法,克服了不完全投影采样的问题,还进行了广泛的模体和临床实验来阐明所提出方法的有效性.     

Building facade interpretation from uncalibrated wide-baseline image sequences

We propose an approach for building facade interpretation ranging from uncalibrated wide-baseline image sequences to the extraction of windows. The approach comprises several novel features, such as determination of the facade planes by robust least squares matching, learning of implicit shape models for objects, particularly windows, and the determination of the latter by means of Markov Chain Monte Carlo (MCMC) employing an abstraction hierarchy generated via mathematical morphology. Results for the fully automatic approach show its potential and shortcomings.     

单天线SAR运动舰船目标三维形状重构

基于单天线高分辨率机载SAR,研究了运动舰船目标三维形状重构问题。对运动舰船目标回波信号利用KEYSTONE变换和高阶相位拟合法完成距离徙动校正后,利用时频分析方法产生运动舰船目标二维图像序列,尝试着将因子分解法引入到SAR运动目标图像处理领域,通过因子分解法对二维图像序列进行处理,实现运动目标三维形状重构,最后给出了真实SAR数据的运动舰船目标三维重构结果,实验结果表明了该方法的有效性。     

Analysis of Object Depth Effects on Accuracy of Dimensional Shape in X and Y Directions Using Single Non-metric Image

In general, to reconstruct the accurate shape of buildings, we need at least one stereomodel (two photographs) for each building. In most cases, however, only a single non-metric photograph is availabl...     

基于HMRF先验模型的HBE卫星遥感图像超分辨率重建

提出了一种在Bayes概率统计框架下的混合Bayes超分辨率重建算法，该算法采用Huber马尔可夫随机场（Huber Markov random field，HMRF）模型对理想图像进行先验建模，可以较好地突出重建图像的不连续边缘特征信息。实验结果表明，该算法克服了极大后验概率估计（maximum a posteriori，MAP）算法中的若干缺陷，取得了良好的重建结果，图像边缘特征清晰，纹理信息突出。