Engineering analysis of biological variables: an example of blood pressure over 1 day

Almost all variables in biology are nonstationarily stochastic. For these variables, the conventional tools leave us a feeling that some valuable information is thrown away and that a complex phenomenon is presented imprecisely. Here, we apply recent advances initially made in the study of ocean waves to study the blood pressure waves in the lung. We note first that, in a long wave train, the handling of the local mean is of predominant importance. It is shown that a signal can be described by a sum of a series of intrinsic mode functions, each of which has zero local mean at all times. The process of deriving this series is called the "empirical mode decomposition method." Conventionally, Fourier analysis represents the data by sine and cosine functions, but no instantaneous frequency can be defined. In the new way, the data are represented by intrinsic mode functions, to which Hilbert transform can be used. Titchmarsh [Titchmarsh, E. C. (1948) Introduction to the Theory of Fourier Integrals (Oxford Univ. Press, Oxford)] has shown that a signal and i times its Hilbert transform together define a complex variable. From that complex variable, the instantaneous frequency, instantaneous amplitude, Hilbert spectrum, and marginal Hilbert spectrum have been defined. In addition, the Gumbel extreme-value statistics are applied. We present all of these features of the blood pressure records here for the reader to see how they look. In the future, we have to learn how these features change with disease or interventions.     

Binding and lysing of blood clots using MRX-408

RATIONALE AND OBJECTIVES: A thrombus-specific ultrasound contrast agent, MRX-408, has been developed recently. This agent consists of phospholipid-coated microbubbles with a ligand capable of targeting the GPIIb/IIIa receptor, thereby allowing the microbubbles to bind with thrombi rich in activated platelets. In vitro and in vivo animal experiments have been conducted to examine imaging enhancement and sonothrombolysis using this agent compared with a nontargeted agent. METHODS: For clot binding, blood-smeared slides were incubated with microbubbles and examined under a light microscope. Change in backscatter signals from the blood clots after binding was examined by both an ultrasound scanner and two single-element transducers arranged in a transmitter-receiver pair. For clot lysis, either 1-MHz or 20-KHz ultrasound was used to enhance the lysing effects of MRX-408 with or without urokinase. RESULTS: Evidence of binding was demonstrated under a microscope. In vitro experiments showed that the "acoustic signature", or properties, of blood clots changed after binding. Clots became more echogenic and nonlinear. In vivo fundamental ultrasound imaging confirmed that as a result of binding, blood clots were more visible, the area of detection was improved, and shadowing behind clots was more noticeable. Under 1-MHz ultrasound and 30 minutes of treatment, lysis efficiency reached 34% with MRX-408, whereas there was no visible clot lysis with saline. CONCLUSION: The results of these preliminary studies show that as a contrast agent, MRX-408 enhanced clots under ultrasound imaging and facilitated sonothrombolysis with or without thrombolytic drugs.     

电站 F/A 异种钢接头早期失效及其防治措施

扼要归纳了Ｆ／Ａ异种钢接头早期失效的特征,分析了导致早期失效的因素,提出可用焊后高温回火和适当增加铁素体侧坡口角的办法降低钢１０２／Ｉｎｃｏｎｅｌ１８２／ＴＰ３４７Ｈ接头的早期失效倾向．文章列出的高温持久强度试验、高温承载加速模拟试验、残余应力测试等结果以及热应力的有限元分析都证明了上述措施是有效的．     

灰口铸铁HT100及其补焊焊缝断裂韧性的研究

采用短棒试样测定了普通灰口铸铁及其补焊焊缝的平面应变断裂韧性ＫＩＣ。结果表明：ＨＴ１００灰口铸铁ＫＩＣ值可达２５ＭＰａｍ,经手工电弧焊或气焊补焊后的ＫＩＣ值明显下降,这在重要铸铁件的补焊过程中应引起注意     

数值模拟技术在气体辅助注射成型过程中的应用

基于粘性流体力学基本方程,针对气体辅助注射成型的特点,提出合理的假设并进行必要的简化,建立描述气体辅助注射成型充模流动过程的数学模型,进而采用有限元／有限差分混合算法进行数值求解。在对移动边界的处理采用控制体积法对充模过程中的两类移动边界：熔体前沿、熔体—气体边界进行跟踪,从而实现气体辅助注射成型充模过程的数值模拟。     

快速凝固 Al-Fe 合金中准晶相的研究

在快速凝固Ａｌ－Ｆｅ－Ｖ－Ｓｉ合金棒材中发现了１种圆形准晶相,尺寸为０２～０５μｍ,成分为Ａｌ－８０ａｔ％Ｆｅ－２．１ａｔ％Ｖ－３．２ａｔ％Ｓｉ。对此准晶进行了透射电镜、Ｘ－光衍射结构分析,并对准晶的形成机制进行了讨论。     

一种新型加工中心加工球面的研究

介绍一种采用 STEWART机构的新型加工中心 .对这种加工中心加工球面时各“腿”长度变化的规律进行了分析 .结果表明 :各“腿”长度呈正 (余 )弦规律变化 ,且其变化周期与幅度均相同 ;它们的变化曲线依次相差 1 2 0°到达峰顶 ,其顺序与加工球面上截面圆各点的逆时针顺序相互对应 .导出的各“腿”长度变化的公式可用于指导数控编程     

混沌系统在保密通信中的应用

混沌保密通信是当今研究热门课题之一。本文就混沌系统应用于保密通信中的基本理论, 编码方式和密钥等内容作一简要讨论, 并采用一次一密密码体制,用损耗调制ＣＯ２ 激光器混沌系统的输出作为密钥分别对文本文件、图形文件进行加密和解密。这种一次一密加密方式是不可破译的     

热喷涂技术在水轮机修复中的应用研究

本文对多泥沙水白沙河电站水轮机过流部件的快速失效进行了分析,并针对损坏的水轮机采用国家推广的热喷涂技术,选用抗磨蚀的合金粉末对水轮机进行修复,取得了明显的效果。