FGL-3型γ射线料位计及其应用

1.γ射线料位计基本原理γ射线料位计是基于放射性同位素所激发出来的γ射线而制成的料位计。它是一种非接触式仪器,可以用来测量化工各种贮罐、容器和塔器中的液体或固体料位。当γ射线穿过被测物料时,其射线强度被物料吸收而减弱。这种射线强度变化符合下列方程式:     

放射性γ射线料位计在石化行业中的典型应用

本文介绍了放射性γ射线料位计的测量原理及测量系统的构成。讨论了放射性γ射线料位计在石油化工行业的4种典型应用。     

基于LORA在线式γ辐射监测系统

针对γ辐射监测过程中核辐射对工作人员的伤害,本文介绍了一种基于LORA在线式γ辐射监测系统,该系统有效地减少了监测过程中γ射线对人体的照射。本文基于碘化钠探测器对γ射线进行监测,由单片机作为控制核心完成对脉冲信号的模数转换,获取现场辐射计数总量,经LORA无线通信技术将监测数据传输至上位机,上位机软件完成人机交互。结果表明：该系统实现了γ射线监测数据的无线传输和可视化实时监测,且运行稳定,安全性和实时性高,可以满足使用过程中的实际需求。     

一种新型的γ—射线涡轮变送器

本文介绍一种新型的γ—射线涡轮变送器,该变送器采用γ—射线检测涡轮的转速,用不锈钢表面镀氮化钛薄层作轴承,可用于高温流体的流量测量。文中简明地阐述了γ—射线涡轮变送器的结构和原理,并给出了石墨轴承和不锈钢镀氮化钛轴承的流量系数实际标定结果。图5表2。     

低能γ射线反散射法测量塑料薄膜厚度的研究

本文叙述了低能γ射线反散射法测量塑料薄膜的可能性，建立了塑料薄膜厚度与反散射γ射线强度的关系式。研制了一套测量装置，并对测量误差进行了分析。     

γ射线对塔设备体外不停工监测的软件系统

本文在IBM PC/XT个人微型计算机上,开发了γ射线对塔设备体外不停工监测的软件系统,实现了γ射线对塔设备体外不停工监测过程的控制、数据采集和数据处理、绘图。本文着重介绍了该系统的结构与性能。本文所涉及的技术内容经实验验证是切实可行的,该系统的开发成功为将γ射线体外不停工监测技术运用于工业实践提供了基础。     

利用γ射线辐照苹果花粉提高座果率的试验

受小剂量γ射线处理植物种子和柞蚕卵提高生命力的启示,1978年我们用137铯—γ射线照射量:5γ、10γ、10γ、20γ处理苹果花粉,并对幼果期、初果期、盛果期三种树龄果树进行授粉试验。经过多次重复和统计分析结果表明:5γ照射花粉是促进提高花粉发芽率和花序花朵座果率的最佳照射量,用5γ处理花粉,小区试验花粉发芽率平均提高62％,生产对比试验发芽率提高12～89％。用5γ照射花粉分别对幼果期、初果期、盛果期三种树龄果树授粉试验,花序花朵座果率分别提高4～10％,12～24％,生产对比试验花序花朵座果率分别提高4～16％,10～56％。     

管道内离散物料流量相关计量装置的研究

根据γ射线检测和相关测速技术设计了管道内物料流量相关计量装置，建立了用点γ射线源和充气高压电离室检测固体物料等效质量面积的数学模型及算法。     

自然􀀁射线方法检测放顶煤开采中的煤矸混合度研究

根据煤与矸石中的自然γ射线放射性含量具有显著差异这一物理特性，提出了利用煤与矸石中的自然γ射线的差异来检测放顶煤过程中煤、矸混合度的方法。推导出煤矸混合体中的矸石含量与检测仪器自然7射线计数率的数学关系。分析了检测仪器探头在液压支架尾梁上的合理安装方式及安装位置。地面模拟采煤工作面的实验数据表明煤矸混合度检测方法是可行和可靠的。     

基于蒙特卡罗模拟的BGO探测器探测效率研究

基于蒙特卡罗模拟方法,对比分析了圆柱型闪烁体探测器NaI(Tl)、LaBr3(Ce)及锗酸铋(BGO)对γ射线的探测效率,研究了晶体尺寸、入射γ射线能量、放射源与探测器间距离、包壳材料厚度对探测效率的影响。在相同条件下,BGO的绝对探测效率、全能峰探测效率及本征探测效率均大于LaBr3(Ce)及NaI(Tl)。对于BGO探测器,探测效率与晶体尺寸呈正相关关系;绝对探测效率及全能峰探测效率随γ射线能量的增加呈现先上升后下降趋势,本征探测效率与γ射线能量呈负相关关系;绝对探测效率及全能峰探测效率与放射源与探测器间距离呈负相关关系;包壳材料厚度对本征探测效率几乎无影响,越薄的铝制外壳可达到越好的绝对探测效率及全能峰探测效率。该研究结果能够为闪烁体探测器几何设计、产品研发和无源效率刻度提供一定参考。     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.     

Editorial: Special issue on recent advances in hybrid control theory and applications

正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where     

Information for Authors

正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere.     

Enhancing a leaf radiative transfer model to estimate concentrations and in vivo specific absorption coefficients of total carotenoids and chlorophylls a and b from single-needle reflectance and transmittance

The relative concentrations of different pigments within a leaf have significant physiological and spectral consequences. Photosynthesis, light use efficiency, mass and energy exchange, and stress response are dependent on relationships among an ensemble of pigments. This ensemble also determines the visible characteristics of a leaf, which can be measured remotely and used to quantify leaf biochemistry and structure. But current remote sensing approaches are limited in their ability to resolve individual pigments. This paper focuses on the incorporation of three pigments—chlorophyll a, chlorophyll b, and total carotenoids—into the LIBERTY leaf radiative transfer model to better understand relationships between leaf biochemical, biophysical, and spectral properties.Pinus ponderosa and Pinus jeffreyi needles were collected from three sites in the California Sierra Nevada. Hemispheric single-leaf visible reflectance and transmittance and concentrations of chlorophylls a and b and total carotenoids of fresh needles were measured. These data were input to the enhanced LIBERTY model to estimate optical and biochemical properties of pine needles. The enhanced model successfully estimated reflectance (RMSE = 0.0255, BIAS = 0.00477, RMS%E = 16.7%), had variable success estimating transmittance (RMSE = 0.0442, BIAS = 0.0294, RMS%E = 181%), and generated very good estimates of carotenoid concentrations (RMSE = 2.48 µg/cm², BIAS = 0.143 µg/cm², RMS%E = 20.4%), good estimates of chlorophyll a concentrations (RMSE = 10.7 µg/cm², BIAS = − 0.992 µg/cm², RMS%E = 21.1%), and fair estimates of chlorophyll b concentrations (RMSE = 7.49 µg/cm², BIAS = − 2.12 µg/cm², RMS%E = 43.7%). Overall root mean squared errors of reflectance, transmittance, and pigment concentration estimates were lower for the three-pigment model than for the single-pigment model. The algorithm to estimate three in vivo specific absorption coefficients is robust, although estimated values are distorted by inconsistencies in model biophysics. The capacity to invert the model from single-leaf reflectance and transmittance was added to the model so it could be coupled with vegetation canopy models to estimate canopy biochemistry from remotely sensed data.     

Mr. Twinn’s bombes

This article discusses the history and design of the special versions of the bombe key-finding machines used by Britain’s Government Code & Cypher School (GC&CS) during World War II to attack the Enigma traffic of the Abwehr (the German military intelligence service). These special bombes were based on the design of their more numerous counterparts used against the traffic of the German armed services, but differed from them in important ways that highlight the adaptability of the British bombe design, and the power and flexibility of the diagonal board. Also discussed are the changes in the Abwehr indicating system that drove the development of these machines, the ingenious ways in which they were used, and some related developments involving the bombes used by the U.S. Navy’s cryptanalytic unit (OP-20-G).