外伤危急症患者腹部急诊增强CT扫描的诊断价值分析     

明建中  刘涛  相呈县  仇容  吴京兰 《CT理论与应用研究》2017,26(2):247-252

目的:分析多层增强CT检查对外伤危急症患者腹部损伤的诊断价值。方法:回顾性分析15例外伤危急症患者的多层CT急诊平扫和增强检查资料。结果:15例外伤危急症患者中,骨盆骨折8例(CT增强显示:1伴动脉血管破裂出血:1例左侧髂总动脉破裂,5例伴一侧髂内动脉分支破裂出血,2例双侧髂内动脉分支破裂出血;2伴肝破裂出血2例,脾破裂出血3例,肾破裂1例);小肠及系膜损伤并多发断裂1例伴肝脾破裂;肝破裂1例;脾破裂4例;左侧臀上动脉破裂1例。增强CT可直接显示造影剂外溢及脏器破口外伤改变。结论:多层增强CT与单纯平扫CT比较,在显示血管破裂及脏器出血定位方面有重要的临床应用价值,有条件的医院可积极应用推广。   相似文献   

不同造影剂注射速率对下腔静脉直接法CTV成像图像质量的影响          下载免费PDF全文

曹宏伟  邢媛媛  仇恒志  张丹  曹振东  万立野  王胜林 《CT理论与应用研究》2017,26(6):775-782

目的:通过改变造影剂注射速率的方式,进行多排螺旋CT直接法下腔静脉成像并对图像质量的优劣对比,寻找造影剂速率的最佳注射方案。方法:采用Siemens公司的64排螺旋CT,对临床疑诊疾为下腔静脉疾病的患者30例行直接法多排螺旋CT下腔静脉扫描,随机分为5组,在相同造影剂浓度(1:4)、液体量(单侧液体量200 m L)、延迟扫描时间(30 s)及不结扎下肢浅静脉等同一条件下,每组造影剂注射速率分别采用2.5,3.0,3.5,4.0和4.5 m L/s,比较各组图像质量优劣。结果:所有患者均顺利完成检查,秩和检验各组间图像质量不完全相同(χ2=21.254,P<0.001),3.5~4.0 m L/s造影剂注射速率的图像质量主要为良及以上,达到临床诊断要求,为最佳流速范围。两组间行χ2检验,χ2=1.588,P>0.05,两组间图像质量总体分布无显著差异。结论:下腔静脉多排螺旋CT直接法成像切实可行,在相同造影剂浓度(1:4)、液体量(单侧液体量200 m L)、延迟扫描时间(30 s)、不结扎下肢浅静脉等条件下,最佳造影剂注射速率3.5~4.0 m L/s。   相似文献   

数值模式的预报策略和方法研究进展   总被引：17，自引：1，他引：16  

任宏利  丑纪范 《地球科学进展》2007,22(4):376-385

数值预报经历了半个多世纪的发展,已成为当前主要的客观预报工具。在模式和资料状况给定的情况下,预报效果的改善很大程度上依赖于所采用的预报策略和方法。为此,全面回顾了国内外基于数值模式的预报策略和方法研究进展,认为采取统计—动力相结合、从历史资料中提炼信息的预报策略是提高数值预报水平的可行之路。最后在总结前人工作基础上,着重介绍了动力相似预报策略和方法的相关研究,特别是实际预报中的试验情况。  相似文献   

基于交通振动环境下建筑结构损伤机理及减振隔振的研究现状          下载免费PDF全文

丑亚玲  刘文高  乔雄  倪伟淋 《地震工程学报》2021,43(3):654-662,686

随着交通建设的发展,越来越多的公路要临近已有建筑物通过,而由于建设或重车通行引起的振动对周边建筑结构产生了很大的安全威胁,严重的甚至造成了建筑结构的损坏.论文通过对交通振动下建筑结构的振动控制标准和在振动中的损伤机理进行综述,系统总结了交通振动对建筑影响的方法,介绍了目前交通振动对建筑结构安全性影响的研究现状和方法,分...  相似文献   

Application of an Economy--Climate Model to Assess the Impact of Climate Change   总被引：1，自引：0，他引：1  

CHOU Jieming  DONG Wenjie  FENG Guolin 《大气科学进展》2010,27(4):957-965

An interdisciplinary investigation was conducted to assess the impact of climate change on grain yields using an economy--climate model (C-D-C). The model was formulated by incorporating climate factors into the classic Cobb-Douglas (C-D) economic production function model. The economic meanings of the model output elasticities are described and elucidated. The C-D-C model was applied to the assessment of the impact of climate change on grain yields in China during the past 20 years, from 1983 through 2002. In the study, the land of China was divided into eight regions, and both the C-D-C and C-D models were applied to each individual region. The results suggest that the C-D-C model is superior to the classic C-D model, indicating the importance of climate factors. Prospective applications of the C-D-C model are discussed.  相似文献   

两种四维SVD同化方法的比较及误差分析   总被引：3，自引：3，他引：0  

王金成  李建平  丑纪范 《大气科学》2008,32(2):277-288

4DSVD是最近提出的一种新的资料同化方法。目前还存在一些需要解决的问题,比如如何选取样本,如何得到支撑大气吸引子的基向量以及选取基向量的个数问题等等。作者利用奇异值分解(SVD)与经验正交函数分解(EOF)两种方法来获得支撑大气吸引子的基向量,推导了基于这两种方法的4DSVD分析场的理论公式,并用简单的数值试验比较了基于这两种方法的4DSVD分析场的空间相关系数和误差,初步分析了分析场与基向量个数的关系以及与样本选取的关系和分析误差的来源及各种误差对分析误差影响的相对大小。结果表明,用SVD方法作为获得支撑大气吸引子基向量的方法得到的分析场较EOF方法稳定,分析场与基向量个数有密切关系,观测误差、模式误差和观测代表性误差是分析误差的主要来源,且其引起的分析误差随着基向量个数增多而增大。  相似文献   

A forecast error correction method in numerical weather prediction by using recent multiple-time evolution data     

薛海乐  沈学顺  丑纪范 《大气科学进展》2013,30(5):1249-1259

The initial value error and the imperfect numerical model are usually considered as error sources of numerical weather prediction (NWP). By using past multi-time observations and model output, this study proposes a method to estimate imperfect numerical model error. This method can be inversely estimated through expressing the model error as a Lagrange interpolation polynomial, while the coefficients of polynomial are determined by past model performance. However, for practical application in the full NWP model, it is necessary to determine the following criteria: (1) the length of past data sufficient for estimation of the model errors, (2) a proper method of estimating the term "model integration with the exact solution" when solving the inverse problem, and (3) the extent to which this scheme is sensitive to the observational errors. In this study, such issues are resolved using a simple linear model, and an advection-diffusion model is applied to discuss the sensitivity of the method to an artificial error source. The results indicate that the forecast errors can be largely reduced using the proposed method if the proper length of past data is chosen. To address the three problems, it is determined that (1) a few data limited by the order of the corrector can be used, (2) trapezoidal approximation can be employed to estimate the "term" in this study; however, a more accurate method should be explored for an operational NWP model, and (3) the correction is sensitive to observational error.  相似文献   

Delayed Seasonal Transition of Tropical Wave Activity in the CMIP3 Global Climate Models          下载免费PDF全文

HUANG Ping  Chia CHOU  Chia-Hui CHUNG  HUANG Rong-Hui 《大气和海洋科学快报》2013,6(1):33-38

This study evaluates the seasonal cycle of the activity of convectively coupled equatorial waves(CCEWs),including mixed Rossby-gravity(MRG) and tropical depression-type(TD-type) waves,based on the twentieth century experiments of 18 global climate models(GCMs) from the Coupled Model Intercomparison Project phase 3(CMIP3).The ensemble result of the 18 GCMs shows that the observed seasonal cycle of MRG and TD-type wave activity cannot be well reproduced.The seasonal transition of wave activity from the southern hemisphere to the northern hemisphere is delayed from April in the observations to May in the simulations,indicating that the simulated active season of tropical waves in the northern hemisphere is delayed and shortened.This delayed seasonal transition of tropical wave activity is associated with a delayed seasonal transition of simulated mean precipitation.The mean precipitation in April and May shows a double-ITCZ problem,and the horizontal resolution is important to the delayed seasonal transition of wave activity.Because of the coincident seasonal cycle of MRG and TD-type wave activity and tropical cyclone(TC) geneses,the delayed seasonal transition of wave activity may imply a similar problem of TC genesis in the GCMs,namely,a delayed and shortened TC season in the northern hemisphere.  相似文献   

Re-equilibration of CO₂ fluid inclusions at controlled hydrogen fugacities     

G. B. MORGAN VI  I-MING CHOU  J. D. PASTERIS  S. N. OLSEN 《Journal of Metamorphic Geology》1993,11(1):155-164

Abstract Natural, pure CO₂ inclusions in quartz and olivine (c. Fo₉₀) were exposed to controlled f_H2 conditions at T= 718–728°C and P_total= 2 kbar; their compositions were monitored (before and after exposures) by microsampling Raman spectroscopy (MRS) and microthermometry. In both minerals exposed at the graphite–methane buffer (f_H2= 73 bar), fluid speciations record the diffusion of hydrogen into the inclusions. In quartz, room-temperature products in euhedral isolated (EI type) inclusions are carbonic phases with molar compositions of c. CO₂(60) + CH₄(40) plus graphite (Gr) and H₂O, whereas anhedral inclusions along secondary fractures (AS type) are Gr-free and contain H₂O plus carbonic phases with compositions in the range c. CO₂(60) + CH₄(40) to CO₂(10) + CH₄(90). EI type inclusions in olivine evolved to c. CO₂(90–95) + CH₄(5–10) without Gr, whereas AS type inclusions have a range of compositions from CO₂(90) + CH₄(10) ± Gr to CH₄(50) + H₂(50) ± Gr; neither H₂O nor any hydrous species was detected by optical microscopy or MRS in the olivine-hosted products. Differences in composition between and among the texturally distinct populations of inclusions in both minerals probably arise from variations in initial fluid densities, as all inclusions apparently equilibrated with the ambient f_H2. These relations suggest that compositional variability among inclusions in a given natural sample does not require the entrapment of multiple generations of fluids. In addition, the absence of H₂O in the olivine-hosted inclusions would require the extraction of oxygen from the fluids, in which case re-equilibration mechanisms may be dependent on the composition and structure of the host mineral. Many of the same samples were re-exposed to identical P–T conditions using Ar as the pressure medium, yielding ambient f_H2= 0.06 bar. In most inclusions, the carbonic fluids returned to pure CO₂ and graphite persisted in the products. Reversal of the mechanisms from the prior exposure at f_H2= 73 bar did not occur in any inclusions but the AS types in olivine, in which minor CO₂ was produced at the expense of CH₄ and/or graphite. The observed non-reversibility of previous mechanisms may be attributed to: (1) slower fluid–solid reactions compared to reactions in the homogeneous fluid phase; (2) depressed activities of graphite due to poor ordering; and/or (3) low ambient f_O2 at the conditions of the second run.  相似文献   

深圳湾福田红树林保护区生态系统健康评价     

胡涛  丑庆川  徐华林  史秀华 《湿地科学与管理》2015,(1):16-20

基于PSR模型建立了深圳湾福田红树林保护区生态系统健康评价体系,运用层次分析法对保护区健康状况进行评价。结果表明:保护区生态系统的压力、状态、响应在体系中的比例分别为53.89%、29.73%、16.38%,健康指数分别为0.4080、0.5891、0.6037;保护区综合健康指数为0.4939,处于健康等级Ⅲ级(亚健康状态)。造成以上结果的主要原因为:1近30年来城市化发展导致保护区生态系统丧失部分生态功能,健康水平不断下降;2水污染、人工引种植物和病虫害等对保护区造成巨大外界压力;3建筑施工和人类活动影响保护区自然状态的恢复。  相似文献