基于原木断层图像的三维重构技术研究

利用OpenGL和VC＋＋平台进行原木断层图像三维重构的研究。首先对断层图像进行轮廓形状插值,然后对轮廓线进行连续性处理,最后使用双三次B样条插值曲面来实现轮廓线的三维重构。实验结果表明,本文提供的方法可以很好的将一组原木腐朽断层图像还原为三维立体图,为原木缺陷检测、立木健康评价等方面提供应用理论基础和科学依据。     

脑脓肿57例临床分析

随着CT及MRI的广泛应用,细菌培养技术的提高,有效抗生素的日益增多及适当手术时机和方法的选择,脑脓肿的发病率及死亡率均明显下降,其治愈率,尤其是微创手术治愈率明显提高1.本文总结分析了我院应用CT确诊的57例脑脓肿的诊治情况,现报道如下.     

快速充盈型肝海绵状血管瘤的CT表现及特点

目的探讨快速充盈型肝海绵状血管瘤（ffHCH）的动态增强CT表现特征。方法回顾性分析13例共15个ffHCH病灶的强CT资料,观察病灶部位、大小、三期动态（动脉期、门静脉期及延迟期）强化模式,以及是否伴有动脉-门静脉分流（APS）、假包膜征及肝包膜回缩征等表现。结果ffHCH病灶好发于肝右叶近包膜下区域;直径（2.42±0.64）cm;动脉期病灶完全强化呈高密度,病灶平均CT值明显高于同期正常肝实质（P〈0.05）;门静脉期病灶呈高或等密度,病灶平均CT值仍明显高于肝实质（P〈0.05）;延迟期病灶呈等或稍高密度,但其强化程度与肝实质无统计学意义（P〉0.05）;部分病灶可见APS,发生率33.33%;无假包膜征及肝包膜回缩征。结论ffHCH三期增强CT表现在病灶位置、大小、增强方式和伴发APS等方面有一定特征,有助于该病的诊断。     

Identification of selected internal wood characteristics in computed tomography images of black spruce: a comparison study

The feasibility of identifying internal wood characteristics in computed tomography (CT) images of black spruce was investigated using two promising classifiers: the maximum likelihood classifier (MLC) and the back propagation (BP) artificial neural network (ANN) classifier. Nine image features including one spectral feature (gray level values), a distance feature, and seven textural features were employed to develop the classifiers. The selected internal wood characteristics to be identified included heartwood, sapwood, bark, and knots. Twenty cross-sectional CT images of a black spruce log were randomly selected to develop the two classifiers. The results suggest that both classifiers produced high classification accuracy. Compared with the MLC classifier (80.9% overall accuracy), the BP ANN classifier had better classification performance (97.6% overall accuracy). Moreover, statistical analysis reveals that the heartwood of the black spruce log used in this study is the easiest to identify by either classifier compared with the other three log features. The results also suggest that the separability of one wood characteristic from the other wood characteristics in black spruce CT images is mainly related to moisture content.     

Moisture content measurements in wood using dual-energy CT scanning – a feasibility study

Currently computed tomography (CT) scanning provides a non-destructive method to determine moisture content in wood in three dimensions. With the current methodology two measurements are needed, one with the scanned piece of wood’s moist state and one after drying. Then the difference of the images can be calculated. The drawback and challenge is that dimensional changes due to shrinkage of wood in the drying process have to be compensated for by image processing. In this study a dual-energy CT scanning method is tested based on the consecutive scanning of wood samples at different energy levels to differentiate water from wood, without the necessity to dry the sample and thus without the need for complex image correction. Not quantified but visible differentiations due to moisture content were obtained on small cubical pine samples of different densities by quick consecutives scans at 60 and 200?kV. The results suggest that given that the pixels in the CT images are representing absorption coefficients it should be possible to directly measure moisture content in wood non-destructively in small volume elements inside solid wood in three dimensions. Further applications of this technique in industrial CT scanning of wood are discussed.     

基于CT图像的岩石破裂过程裂纹分形特征分析

岩石材料存在不同阶次随机分布的微观孔隙和裂纹,其受载后的宏观断裂失稳和破坏与内部微裂纹的分布以及微裂纹的产生、扩展和贯通有密切关系.通过对岩石CT图像中各点材料进行分析,清晰地看到岩石材料中孔洞及裂纹区域的大小分布随应力的变化过程.利用分形维数对裂纹扩展至破裂过程进行分析,揭示岩石裂纹从萌生、扩展到贯通的细观破损机理....     

肾透明细胞癌CT与病理的对照分析

目的 探讨肾透明细胞癌的CT征象与病理表现之间的关系,并对两者进行对照分析.方法 对我院2006-09-2010-09月44例经手术后病理证实的肾透明细胞癌病例术前CT征象及术后病理结果,进行回顾对照分析.结果 CT平扫8例病灶为高密度,17例为低密度,19例为混杂密度.CT强化皮质期43例肿瘤实体强化幅度超过正常肾实...     

Tillage system effect on nitrogen rhizodeposited by faba bean and chickpea

The quantification of the below-ground N of legumes is a key to understand its effect on soil N fertility and the N economy of subsequent legume-based rotations. Significant amounts of the N fixed by legumes are incorporated into the soil as fallen leaves and stems. However, the N from roots, nodules and root exudates has rarely been quantified under field conditions, nor have the management effects been evaluated. This study measured the effects of tillage system [no-tillage (NT) and conventional tillage (CT)] on N rhizodeposition in faba bean (Vicia faba L.) and chickpea (Cicer arietinum L.) during a 3-year period (2003–2004, 2005–2006 and 2006–2007) in a Vertisol under rainfed Mediterranean conditions. Faba bean and chickpea plants were labelled in situ with ¹⁵N using stem feeding and leaf feeding, respectively. NT increased the N derived from rhizodeposition (NdfR) with respect to CT (135 vs. 68 kg N ha⁻¹ in faba bean and 115 vs. 97 kg N ha⁻¹ in chickpea). Such differences between tillage methods can be attributed to the more favourable conditions for root growth produced by NT. NdfR was significantly influenced by depth; in faba bean, the greatest amount (70%) was found in the 0–30 cm layer, whereas in chickpea, 41% of the NdfR was concentrated in the 30–60 cm depth. The 54% and 61% of total plant N was NdfR (in faba bean and chickpea, respectively) representing 90% of the below-ground plant N in both crops. Our results show that the N derived from rhizodeposition is an important source for N balance and is a key to soil fertility in rain-fed Mediterranean cropping systems.     

冻融条件下黑土大孔隙结构特征研究

冻融作用会改变土壤微观结构,孔隙特征的变化是其结构性改变的重要体现。研究冻融作用对开展黑土区侵蚀机理研究及合理利用黑土资源具有重要意义。本研究旨在对冻融条件下原状土样的三维结构进行分析,获取孔隙特征的定量指标,进而分析冻融循环对土壤大孔隙的影响,为进一步揭示黑土区季节性冻融对黑土结构的影响提供证据。通过室内冻融循环试验结合CT扫描技术研究黑土原状土体大孔隙在7种冻融循环次数以及两组含水率下的变化规律,探讨在冻融循环作用下原状土体大于1.25 mm的孔隙变化特征。结果表明:在15次冻融循环内,随着冻融循环次数的增多,土壤孔隙度不断增大,在7次冻融循环后增长尤为显著;孔隙数量随冻融循环次数的增多而减小;规则孔隙度(RP)持续减小,不规则孔隙度(IRP)呈减小趋势而加长孔隙度(EP)呈增大趋势;孔径随冻融循环次数的增多而增大,孔径大于3 mm的孔隙孔隙度不断增大;冻融作用使孔隙出现大量分支,冻融循环次数越多分支占比越大。在冻融温差一定时,冻融循环后高含水率土壤比低含水率土壤的上述孔隙特征变化更为显著。研究成果为阐明冻融侵蚀机理、合理评价及利用寒区农田提供理论依据。     

A retrobulbar meningioma as a cause of unilateral exophthalmos and blindness in a horse

This report describes the unusual diagnosis of a retrobulbar syncytial meningioma in a 16‐year‐old Thoroughbred gelding. The horse initially presented with unilateral left sided exophthalmos and apparent blindness characterised by unilaterally absent menace and pupillary light responses. Magnetic resonance imaging (MRI) identified a well‐defined soft tissue mass intimately associated with the optic nerve. Based on the characteristic MRI appearance, a meningioma was suspected. The eye was enucleated under general anaesthesia and partial excision of the mass was achieved. Histopathology confirmed the diagnosis and the horse underwent a course of adjuvant radiotherapy. Twelve months following surgery the horse is back in work, no neurological abnormalities have been detected and follow‐up computed tomographic imaging of the skull has revealed mild bone sclerosis with no remnants of the mass identified.