一种基于单电子晶体管的全加器电路设计

基于单电子晶体管的I-V特性和传输晶体管的设计思想,用多栅单电子晶体管作为传输晶体管,设计了一个由5个SET构成的全加器,相对于静态互补逻辑设计的全加器,本文设计的全加器在器件数量上大大减少,有利于大规模电路的设计,仿真结果表明,本文设计的全加器电路具有高速与低功耗的特性.     

一种SET/CMOS混合器件模型的建立及特性分析

本文基于一种单电子晶体管数学模型（改进的MIB模型），实现其SPICE宏模型。提出一种改进型SET／CMOS混合器件模型，并用SPICE对其I-V特性进行了仿真验证，仿真结果证实了电流与电压具有线性关系。此混合模型的线性电流区可以在积分器以及滤波器电路中得到应用。     

程控单结晶体管PUT的原理及应用

PUT 是负阻器件,常用来作控制晶闸管的触发和张弛振荡器。PUT 的触发可程控。PUT 比单结晶体管应用更广泛,更经济。本文详介PUT 的原理,结构,特性参数及几种主要应用。     

单电子隧穿结电路在图像轮廓检测中的应用

对细胞神经网络增强单电子电路的鲁棒性的机理进行了理论分析,构建了一种新型的基于细胞神经网络的单电子电路模型,并将其应用到图像检测方面,对单电子细胞神经网络在图像边缘检测方面的应用给出了实验结果。结果证明细胞神经网络是构建单电子电路的可靠网络,这为未来单电子电路鲁棒性的提高和其在图像处理方面的应用做了铺垫。     

基于射频单电子晶体管的超灵敏电荷计的模拟研究

集成单电子晶体管(single electron transistor, SET)与射频共振电路的射频单电子晶体管(radio frequency single electron transistor, RF SET)是一种高速高灵敏的电荷计。本文通过建立RF SET的等效电路模型,对共振电路及其与射频传输线的集成进行模拟分析,得到了SET阻抗的最佳匹配,获得了所需的谐振频率、品质因子和对SET阻抗的灵敏度。结果表明,受电荷调制的SET阻抗直接影响着共振电路的品质因子、阻抗和射频透射/反射系数。射频信号随着SET的阻抗降低而减小,峰位基本不变。在SET阻抗小于200 k?时,共振信号幅度随阻抗的变化率较大。透射式与反射式两种结构相比,前者共振频率及品质因子更高,后者则具有更高的灵敏度优势。     

基于混合SET/MOSFET的比较器

基于双输入单电子晶体管与MOSFET的混合结构I-V特性和数字电路的逻辑设计思想,提出了一种由5个双栅极SET和6个MOSFET构成的一位比较器电路结构.该比较器有以下优点:利用双栅极SET和MOSFET构成逻辑块使电路结构大为简化;减少了管子的数日;电压兼容性好,驱动性能高;输入和输出高低电平都接近于1V和0V;静态总功耗低,为nW级.仿真结果验证了它的正确性.     

室温单电子晶体管制备进展

单电子晶体管由于其纳米级的器件尺寸和超低功耗等优点被广泛认为是当前最有应用前景的纳米电子器件之一,实现室温下的正常工作和器件结构的精确控制是其实用化的关键。室温单电子晶体管的主流制备方法为自顶向下工艺和自底向上工艺。自顶向下工艺便于器件集成,但纳米尺度下的制备工艺误差较大,室温单电子晶体管的性质难以稳定;自底向上工艺能够比较容易地制备出室温单电子晶体管,但同样有耦合结构误差较大的问题。在结合自顶向下工艺和自底向上工艺的基础上,引进纳米结构制备的新技术来提高工艺过程的可控性,是下一步室温单电子晶体管制备的研究重点。     

基于压控单元的单电子晶体管宏模型

采用等效电路的方法,将单电子晶体管(SET)等效为由电容、电阻、多个压控电压源和压控电流源构成的电路,并从SET的结构出发,利用正统理论和量子力学理论,得到了单电子晶体管的电压与电流的关系.该模型可以较好模拟SET稳态时的工作状态,并可以由此出发,研究SET反相器和存储器电路,解决SET/MOS混合电路仿真的问题,对未来单电子电路的研究会有一定的帮助.     

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).