20CrMnTi钢元素偏析和疏松研究

应用金属原位统计分布分析技术研究了20CrMnTi钢中C、Si、Mn、Cr和Ti元素的偏析规律,样品的统计致密度较好,疏松程度较小;Si、Mn元素分布较均匀,偏析程度较小;Cr元素总体偏析程度不大,但分布不均匀;C、Ti元素偏析程度较大,中心存在负偏析。该方法能在较大范围内对钢材质量进行全面分析,对产品质量控制和工艺优化具有指导意义。     

帘线钢72A连铸坯的原位统计分布分析

为了更好地了解铸坯中元素偏析、疏松和夹杂物分布规律,采用金属原位分析仪对帘线钢72A连铸坯进行了原位成分统计分布分析,并探讨了铸坯中C、Si、Mn、P、S和Al元素分布规律,发现C、Si、Mn和P元素在铸坯中心都存在明显的偏析,且中心区域的偏析程度比边部严重。Mn元素含量的分布规律与C元素相似,在铸坯边部附近,C、Mn元素有明显的负偏析带,在铸坯中心区域元素出现了明显的正偏析带,整体上,Mn元素成分分布比C元素更均匀;比较这几种元素的成分分布,发现Si元素成分分布较均匀,而P元素成分分布较不均匀。帘线钢中Al、S元素基本上都以夹杂物的形式存在,两种元素分布规律极其相似,且中心夹杂物的含量明显比边部多。由于铸坯中心存在明显的缩孔,导致铸坯表观致密度下降,表观致密度为0.869 0。     

船板钢连铸坯中心偏析的原位统计分布分析

采用原位统计分布分析技术对船板钢连铸坯的中心偏析的特性进行了研究.提出了各元素含量三维分布图、二维等高图、频度分布图、统计均匀度、统计偏析度以及统计疏松度等各种参数,定量表征了船板钢连铸坯的纵剖面以及沿厚度中心线(相当于偏析带)的剖面中各元素的含量的统计分布.船板钢连铸坯的纵剖面中C、Si、Ni等元素的最大偏析位置处于铸坯纵剖面X=4mm附近的偏析带上;Mn、S、P等元素的最大偏析位置处于X=21mm附近的偏析带上.沿板坯厚度中心线剖面的采用原位统计分布分析结果指出在厚度中心线剖面上没有偏析带,硫呈云状(或称团簇状)分布.最大偏析度的数值与纵剖面相当,最大偏析点的位置无规律.沿该板坯厚度中心线剖面上C、S二元素的统计均匀度及统计偏析度的数值与板坯纵剖面上的统计均匀度及统计偏析度数值相当.     

管线钢连铸板坯横截面元素的原位统计分布分析

管线钢作为石油、天然气等管道运输的主要材料,其元素分布及组织结构对管线钢强度和韧性有较大影响。实验采用原位统计分布分析技术对管线钢连铸板坯板宽中心到板宽1/4处的中心区域中C、Mn、P、S、V、Ti、Nb元素的偏析和分布状态进行了定量统计分析研究。采用最大偏析度、统计偏析度、统计均匀度等指标对各元素的偏析分布进行了定量表征。研究结果表明,C、Mn、P、S、V、Nb元素的偏析分布形式基本类似,都在板厚中心线附近和板宽1/4处的厚度方向存在由局部富集区域组成的带状偏析带。其中,C、P、S元素的偏析较为严重,统计偏析度达到20%以上。Ti元素没有观察到明显的偏析,在整个分析区域分布比较均匀。     

原位统计分布技术分析汽车大梁钢坯

采用金属原位分析技术对汽车大梁钢坯横截面上各元素的成分分布、中心偏析、疏松、夹杂等进行质量分析。并采用最大偏析度以及统计偏析度等指标对各元素的偏析程度进行了定量表征。从大梁钢坯横截面整体的原位统计分布二维成分等高图可以直观的看出,在连铸坯横截面上中心部位,硫形成一条较连续的"带状"偏析,磷形成一条不连续的"带状"偏析,其它元素中心"带状"偏析不明显。结果表明,被测连铸大梁钢坯横截面内弧侧有明显的疏松现象,在内弧侧的缺陷位置(缩孔)处富集了少量铝和钙。此技术的应用有利于连铸坯的质量控制和工艺条件改进。     

不同拉速工艺下连铸板坯横截面中心偏析和夹杂物分布分析

采用原位统计分布分析技术对不同拉速工艺下连铸板坯中心横截面的偏析特性和夹杂物分布进行了研究.通过对3.0m/min和4.2m/min拉速条件下C、Si、Mn、P、S及Al系夹杂物在连铸板坯中心横截面的分布规律的对比,发现在低拉速工艺下的样品C、Mn、P等元素在连铸板坯中心横截面的统计均匀性好于高拉速工艺下样品,Si、S等元素则呈现相反的规律;低拉速工艺下的样品中S、P、C等元素易形成"点状"偏析,呈不连续分散分布的特点;高拉速工艺下的样品中S、P、C等元素易形成"带状"偏析,呈连续分布的特点,并位于板厚中心线附近.高拉速工艺下的Al系夹杂物分布不均匀,粒度大,靠近板坯的上下表面;低拉速工艺下的Al系夹杂物分布均匀,粒度小.     

不同拉速工艺下连铸板坯横截面中心偏析和夹杂物的原位统计分布分析

采用原位统计分布分析技术对不同拉速工艺条件下连铸板坯中心横截面的偏析特性和夹杂物分布进行了研究。通过对3.0 m/min和4.2 m/min拉速条件下C,Si,Mn,P,S及Al系夹杂物含量在连铸板坯中心横截面的分布规律对比,发现在低拉速工艺条件下,样品中C,Mn,P等元素在连铸板坯横截面的统计均匀性好于高拉速工艺条件下样品,Si,S等元素则呈现相反的规律,S,P,C等元素易形成“点状”偏析,呈不连续分散分布的特点,Al系夹杂物分布均匀,粒度小;高拉速工艺条件下,样品中S,P,C等元素易形成“带状”偏析,     

原位统计分布分析技术分析不同中低合金钢连铸板坯横截面上碳、硅、锰、磷、硫、铌、钛、钒

采用金属原位统计分布分析（OPA）技术考察了不同生产工艺条件下不同厚度的中低合金钢连铸板坯横截面上C、Si、Mn、P、S、Nb、Ti、V等元素的分布、富集及中心偏析形态。观察并描述了几种典型的中心偏析形式,如断续的、连续的以及正负偏析呈交错分布状等;发现大多元素的中心偏析模式相对固定,即在沿拉速方向一定厚度范围内具有稳定性;给出了最大偏析度、统计偏析度等定量表征元素分布状态的原位技术特征值;讨论了各元素在板坯中形成偏析的难易程度及常见的分布模式。硫元素的偏析分析结果和传统分析硫偏析的方法-硫印也基本一致。研究表明,原位统计分布分析技术能有效地应用于较宽含量范围内、不同厚度尺寸的中低合金钢板坯的成分分布分析和偏析分析,且其分析结果具有很好的重复性和可靠性。     

原位统计分布分析技术分析不同中低合金钢连铸板坯横截面上碳、硅、锰、磷、硫、铌、钛、钒

采用金属原位统计分布分析（OPA）技术考察了不同生产工艺条件下不同厚度的中低合金钢连铸板坯横截面上C、Si、Mn、P、S、Nb、Ti、V等元素的分布、富集及中心偏析形态。观察并描述了几种典型的中心偏析形式,如断续的、连续的以及正负偏析呈交错分布状等;发现大多元素的中心偏析模式相对固定,即在沿拉速方向一定厚度范围内具有稳定性;给出了最大偏析度、统计偏析度等定量表征元素分布状态的原位技术特征值;讨论了各元素在板坯中形成偏析的难易程度及常见的分布模式。硫元素的偏析分析结果和传统分析硫偏析的方法-硫印也基本一致。研究表明,原位统计分布分析技术能有效地应用于较宽含量范围内、不同厚度尺寸的中低合金钢板坯的成分分布分析和偏析分析,且其分析结果具有很好的重复性和可靠性。     

GCr15轴承钢连铸方坯与电渣重熔铸锭的 原位统计分布分析

GCr15轴承钢作为高碳钢,其元素偏析尤其是碳元素的偏析对于钢的组织和性能有很大影响。实验应用原位统计分布分析技术对GCr15轴承钢连铸方坯整个横截面以及GCr15电渣锭的中心区域进行了对比分析,并重点研究了C和Cr元素的偏析情况以及试样表面的疏松情况。通过C和Cr元素含量二维等高图以及统计偏析度的对比分析可知,连铸方坯横截面的C和Cr元素都存在严重的中心偏析现象,同时在中心偏析区域外围观察到由于树枝晶搭桥而造成的环状、不连续的C元素负偏析带;GCr15电渣锭中心区域的C和Cr元素分布则较为均匀,即偏析现象得到明显改善。此外,电渣重熔前后试样表面的统计致密度和统计疏松度表明,电渣锭的致密程度要明显优于连铸方坯。     

Cost-utility analysis

Decisions have to be made about allocating health resources. Currently the best economic evaluation method for doing this is cost-utility analysis. This compares the costs of different procedures with their outcomes measured in "utility based" units--that is, units that relate to a person's level of wellbeing. The most commonly used unit is the quality adjusted life year (QALY). QALYs are calculated by estimating the total life years gained from a procedure and weighting each year to reflect the quality of life in that year. To compare outcomes of different programmes the Rosser index is one measure that is widely used to assign quality of life scores to patients. Combined with a measure of life years gained from a procedure, this enables QALYs to be calculated and procedures ranked according to cost per QALY gained. In this article Ray Robinson explains the measures used and discusses how QALY league tables can be used to guide decisions on resource allocation.     

Sonoclot analysis

Assessment of perioperative bleeding disorders, especially those related to platelet dysfunction, remains a clinical challenge. The management of the bleeding patient in the operating theatre or on the postoperative ward is often empirical with little scientific basis. Much of the reason for this is that conventional clotting studies are not immediately available and there is a perceived urgency, particularly among trainee doctors, to treat bleeding disorders without first establishing the exact nature of the coagulopathy. SCT provides useful information on platelet function, particularly in patients after cardiopulmonary bypass, and has enabled practitioners to rationalize the management of bleeding disorders and not expose their patients to the risks of unnecessary transfusion of blood products. Undoubtedly further studies are required before this instrument can be used reliably in the clinical setting but it may prove to be a useful addition to the available techniques for monitoring perioperative bleeding disorders.     

Cost-effectiveness analysis

When different health care interventions are not expected to produce the same outcomes both the costs and the consequences of the options need to be assessed. This can be done by cost-effectiveness analysis, whereby the costs are compared with outcomes measured in natural units--for example, per life saved, per life year gained, and per pain or symptom free day. Many cost-effective analyses rely on existing published studies for effectiveness data as it is often too costly or time consuming to collect data on cost and effectiveness during a clinical trial. Where there is uncertainty about the costs and effectiveness of procedures sensitivity analysis can be used, which examines the sensitivity of the results to alternative assumptions about key variables. In this article Ray Robinson describes these methods of analysis and discusses possibilities for how the benefits of alternative interventions should be valued.     

Timing waveform analysis

PURPOSE: To determine the diagnostic yield of routine admission chest radiographs in patients with acute gastrointestinal (GI) hemorrhage and clinical predictors of radiographic abnormalities. PATIENTS AND METHODS: The study was a retrospective series of 202 adult patients with GI hemorrhage admitted to intensive care units at an academic medical center. Routine admission chest radiographs were obtained in 161 patients. These radiographs were reviewed by a study radiologist blinded to the study purpose. The radiologist scored radiographic abnormalities into categories of "minor" or "major," "new" or "previously known," and "with an intervention" or "without an intervention." Nominal logistic regression explored the data for clinical features that identified patients with major new radiographic abnormalities with or without an intervention. RESULTS: Minor radiographic abnormalities were noted in 23 (14.3%) patients, of whom 17 (10.6%) patients had "new" (previously unknown) abnormalities. No minor abnormality prompted a therapeutic or diagnostic intervention. Major radiographic abnormalities were detected in 21 (13.0%) patients, of whom 19 (11.8%) had new findings. Major new findings prompted interventions in only 9 (5.6%) of patients. A history of lung disease and an abnormal lung physical examination predicted major new radiographic findings (P = 0.0001, sensitivity 79%, negative predictive value 96%). These variables also identified major new abnormalities that prompted interventions (P = 0.007, sensitivity 89%, negative predictive value 99%). Use of the logistic regression model to select patients for admission chest radiographs decreased charges from $1,068 to $580 for each detected major new radiographic abnormality and from $2,254 to $1,087 for major new radiographic abnormalities that prompted an intervention. CONCLUSION: These data indicate that routine chest radiographs have a low yield in detecting major new radiographic abnormalities in patients with acute GI hemorrhage. Clinical criteria, available at the time of admission, may be useful for selecting patients for chest radiographic evaluations.     

Theatre utilization analysis

A method of analysing operating theatre utilization is presented as a management information system applicable to medical administration.The operating theatre plant represents an item of considerable expenditure in a hospital budget. This aspect of hospital activity requires maximized utilization to ensure an appropriate cost benefit. Extraction of information in such a form provides a basis for exact comparisons of performance of the personnel involved and determining needs for additional resources.     

一种新型稳定平台的运动学和工作空间分析

针对某些精密设备在运输过程中的颠簸、倾斜等问题,设计了一种采用液压缸驱动方式的水平稳定平台,并对该平台进行了结构、运动学分析,计算出了机构运动的自由度,建立了运动学数学模型,使用Matlab软件对机构进行了仿真计算,为伺服液压缸的设计计算提供了依据.通过对工作空间的分析,得出了稳定平台的工作空间范围.仿真结果表明,该稳定平台不存在干涉现象.