聚焦超声消融肝癌时大血管位置对热场分布的影响

采用有限元方法研究了聚焦超声消融肝脏肿瘤时，大血管存在于肿瘤附近不同位置对温度分布以及热剂量分布的影响．建立基于大血管对流效应的生物传热模型，基于不同的加热方案进行3-D温度瞬态仿真．仿真针对四种情况进行计算：模型中无血管，血管分别距离肿瘤1mm、2mm、3mm．仿真结果表明使用聚焦超声进行快速加热可以使能量集中在目标治疗区域．但是当肿瘤组织的近距离内（1mm）存在大血管且加热时间较长时（〉2s），肿瘤组织靠近血管的边界部分仍然会受到大血管冷却效应的影响，这种影响会导致肿瘤治疗不彻底．当肿瘤距离大血管3ram以上时，大血管在聚焦超声治疗中的冷却效应不再明显．     

高强度聚焦超声治疗中基于电阻抗相对变化的组织温度监测技术

高强度聚焦超声(HIFU)通过聚焦超声的声热效应对肿瘤组织进行局部快速的热疗,是一种非侵入性的无创肿瘤治疗新技术,而其治疗过程中温度监测是HIFU治疗中剂量精准控制的关键.本文基于HIFU的声传播基本原理,建立了HIFU治疗和组织电阻抗测量的模型,数值模拟了治疗过程中焦域的声场、温度场和电导率分布,并通过电势和电流密度分布的变化,计算了模型的电阻抗的整体变化,结果表明在一个规定的HIFU声功率作用下,组织模型的电阻抗相对变化和治疗时间呈线性关系,其电阻抗相对变化率和HIFU声功率也呈线性关系.按照仿真条件,建立了HIFU治疗和电阻抗实时测量的联合实验系统,在不同声功率和治疗时间条件下,对组织模型的电阻抗相对变化进行了测量,实验结果和理论仿真结果基本一致.研究结果证明用电阻抗相对变化进行HIFU治疗中焦域温度监控的可行性,为其疗效检测和剂量控制提供了新方法.     

血管对HIFU治疗焦域影响的实验研究

通过实验测量高强度聚焦超声辐照下仿组织体模中焦域附近特定点的温度变化以及形成焦域大小分析血管对HIFU治疗焦域的影响.当血管位置和血流速度分别不同时利用热电偶探针测量几何焦点上方2 mm处温度,采用Matlab编程计算焦域体积.在血管前方聚焦时,焦域附近峰值温度较高,形成焦域体积较大;在血管后方聚焦时,焦域体积随远离血管距离的增大而增大;无血流时,焦域附近峰值温度较高,焦域体积较大;加入血流之后,焦域附近峰值温度明显降低,但血流速度差异性对峰值温度和焦域大小影响不明显.血管位置和血流速度影响HIFU治疗焦域温度分布,在临床治疗焦域附近有血管时应当考虑血管的影响.     

HIFU焦域的温度分布模拟及其疗效分析

高强度聚焦超声(HIFU)是一种非侵入性、对正常组织无损伤且不易引起癌细胞转移的肿瘤治疗手段,对其治疗过程中的疗效以及肿瘤周围正常组织破坏情况的监测是实现HIFU治疗剂量精准控制的关键.本文首先从HIFU局部组织加热出发,建立了HIFU治疗系统模型,利用有限元数值模拟了HIFU焦域的声场以及温度场分布,并研究了换能器参数、超声功率、治疗时间对焦域温度分布的影响.结果表明,随着治疗时间的增长,焦点温度上升,逐渐形成椭球状的焦域;在达到治疗疗效时,即焦域径向±0.4 mm椭球范围内的组织温度达到了343 K(70℃)时,随着换能器结构系数(半径/焦距)的减小,所需要的治疗时间增长,所形成的焦域不断扩大,其轴向宽度与径向宽度比值增大,焦域变得细长,焦点处的温度逐渐降低.本研究对已知结构系数的聚焦换能器的焦域温度场仿真,可以为HIFU治疗中的温度估计和监控提供新方法,也可为疗效评估和剂量控制提供新技术.     

青藏高原地表参数的被动微波遥感反演研究

利用被动微波遥感数据TMI和GAMB-Tibet加强观测期的地面观测数据，改进和发展了一个被动微波遥感反演地表温度、土壤湿度和植被含水量的三维查表算法(3-D LUT)，并在青藏高原中部中尺度范围内进行了反演试验．对1998年7月1日的数据进行了个例处理，给出了3个地表参数的空间分布结果．进一步考虑了高原对流云对反演结果的影响，对5个月的TMI数据进行了10天的合成处理，利用合成图像运行算法得到了10天平均的结果．结果显示1998年5～9月5个月的土壤湿度反演结果的时空分布与实际情况符合较好；从选取的几个测站的数据比较看，去云处理后得到的土壤湿度反演结果有了明显改善．     

二维弹性锥形血管模型的有限元分析及数值模拟

通过运用任意拉格朗日一欧拉方法（ALE方法）,能够对二维下的弹性条件下的锥形血管中的速度场和压力场进行分析．假设血管的锥度角为小锥度角,来获得血液在血管内流动的速度、压力分布,并与无锥度角的血管和刚性条件下的血管内的血液流动情况作比较．结论：血液在血管内的流动的速度分布和压力分布与血管的弹性性质无关,但和锥度角的大小有关系．锥度角越大,那么压力变化的幅值就越大,径向速度变化越显著,却又不会影响径向速度分布的最大值位置．     

三维动脉血管树的模拟与分析

进行血液动力学模拟和血液传热计算需要先建立血管网络,为此,借鉴强制结构优化(CCO)方法,提出了基于分支法则、Poiseuilles’law及质量守恒原则,直接在模拟区域上生成动脉血管树的新方法及相应的半径比计算公式和分支点确定步骤.模型采用根血管半径已知和末端压力未知作为定解条件,并使用了变化的分支指数.根据该方法建立了球形血管树;分析了搜索数组最佳大小随末端数的变化规律;计算了变化的分支指数对生成血管树直径分布的影响.结果表明:末端数越多,需要的搜索数组越大;由变指数得到的血管直径分布优于常指数的结果.     

乳腺组织温度分布的数值模拟研究

基于正常乳腺的解剖学结构和生理学特征,建立了一个乳腺组织多维热传递模型,采用有限元法求解热传导方程,获得乳腺组织的稳态温度分布.结果表明:乳腺浅表或深部组织的血液灌注和代谢产热等参数的变化均在一定程度上影响乳腺组织的温度分布,但相比之下,血液灌注的变化,尤其是浅表组织血液灌注的变化对乳腺皮表温度的影响更为显著.研究结果有望为乳腺热图像分析提供重要的参考.     

有关罗非鱼血液试样处理条件的研究

为了探讨罗非鱼的血液健康诊断技术，作者对采血方法、溶血以及血浆分离前血液的放置时间和温度对血浆成分量的影响进行了研究．结果表明，1）血管采血法产生的人为误差较少，尾柄切断法切断时有肌肉混入．导致某些成分量的升高；2）溶血明显地影响血浆成分量，使用血样时应该避免使用溶血试样；3）血浆分离前血液放置时间与温度对血浆多数成分的定量有影响，采血后，应该立即分离，来不及分离时应该低温保存.     

激光诱导间质热疗中血流冷却效应的模拟

为研究激光诱导间质热疗过程中血管冷却对于生物组织内温度场和损伤度的影响,建立了包含单根血管的双层模型。由M on te C arlo模拟方法得到组织内的激光能量分布,采用有限差分法求解Pennes生物传热方程和血流换热能量方程得到组织内温度场,通过A rrhen ius速率过程方程得到组织损伤度。利用此模型,比较研究了不同血管情况下组织的温度场和损伤度。模拟结果表明,血管直径及血流速度是影响热疗中血管附近组织温度场和损伤度的重要因素。在模拟的5W功率条件下,当血管直径大于1mm时,如果仍采用与无血管情况下相同的治疗方案将可能导致无法完全杀死肿瘤而使热疗失去疗效。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that