An Embedded Ultra Low Power Nonvolatile Memory in a Standard CMOS Logic Process

This paper proposes an embedded ultra low power nonvolatile memory in a standard CMOS logic process. The memory adopts a bit cell based on the differential floating gate PMOS structure and a novel operating scheme. It can greatly improve the endurance and retention characteristic and make the area/bit smaller. A new high efficiency all-PMOS charge pump is designed to reduce the power consumption and to increase the power efficiency. It eliminates the body effect and can generate higher output voltage than conventional structures for a same stage number. A 32-bit prototype chip is fabricated in a 0.18 mu m 1P4M standard CMOS logic process and the core area is 0.06 mm(2). The measured results indicate that the typical write/erase time is 10ms. With a 700 kHz clock frequency, power consumption of the whole memory is 2.3 mu A for program and 1.2 mu A for read at a 1.6V power supply.

High-output very small aperture laser and its near-field distribution properties - art. no. 60200L

A Very-Small-Aperture Laser with a 250 X 500 nm(2) aperture has been created on a 650nm edge emitting LD. The highest far-field output power is 1.9mW and the power per unit emission area is about 15 MW/mu m(2). The special fabrication process and high output power mechanism are demonstrated respectively. The near-field distribution properties are also analyzed theoretically and experimentally.

processline: visualizing time-series data in process industry

In modern process industry, it is often difficult to analyze a manufacture process due to its umerous time-series data. Analysts wish to not only interpret the evolution of data over time in a working procedure, but also examine the changes in the whole production process through time. To meet such analytic requirements, we have developed ProcessLine, an interactive visualization tool for a large amount of time-series data in process industry. The data are displayed in a fisheye timeline. ProcessLine provides good overviews for the whole production process and details for the focused working procedure. A preliminary user study using beer industry production data has shown that the tool is effective.

Study on pulsed laser ablation and deposition of ZnO thin films by L-MBE

ZnO, as a wide-band gap semiconductor, has recently become a new research focus in the field of ultraviolet optoelectronic semiconductors. Laser molecular beam epitaxy (L-MBE) is quite useful for the unit cell layer-by-layer epitaxial growth of zinc oxide thin films from the sintered ceramic target. The ZnO ceramic target with high purity was ablated by KrF laser pulses in an ultra high vacuum to deposit ZnO thin film during the process of L-MBE. It is found that the deposition rate of ZnO thin film by L-MBE is much lower than that by conventional pulsed laser deposition (PLD). Based on the experimental phenomena in the ZnO thin film growth process and the thermal-controlling mechanism of the nanosecond (ns) pulsed laser ablation of ZnO ceramic target, the suggested effective ablating time during the pulse duration can explain the very low deposition rate of the ZnO film by L-MBE. The unique dynamic mechanism for growing ZnO thin film is analyzed. Both the high energy of the deposition species and the low growth rate of the film are really beneficial for the L-MBE growth of the ZnO thin film with high crystallinity at low temperature.

近60年我国土壤侵蚀科学研究进展

在系统总结我国近60年土壤侵蚀科学研究取得的成就的基础上,通过分析与整合,重点介绍全国土壤侵蚀时空特征与动态变化、土壤侵蚀过程及其调控机制、黄河泥沙来源与粗泥沙集中来源区的界定、风力侵蚀机制及沙漠化防治、侵蚀环境演变与调控等5个对土壤侵蚀学科发展有重大意义的进展,提出了我国土壤侵蚀学科亟待加强的3个领域。

黄土坡面下坡位土壤侵蚀过程的模拟试验

在中国科学院水利部水土保持研究所,采用2个不同坡长小区室内模拟降雨试验方法,对黄土坡面下坡位侵蚀过程进行研究。结果表明:1)坡面下坡位侵蚀模数随降雨过程、降雨强度及坡度的变化均具有大小交错,上下波动的特征,侵蚀模数随降雨过程的变化总体呈先上升后趋于稳定的态势,随降雨强度的增大而增加,随坡度的增大而先增大后减小,再增大再减小;2)坡面上、下坡位侵蚀模数随降雨过程、坡度及降雨强度的变化均具有明显差异,下坡位明显不如上坡位;3)坡面上坡位汇流和下坡位产流与坡面上坡位输沙对坡面下坡位侵蚀模数的影响可用二元线性方程很好地描述,前者的贡献率为47.8%,后者为20.4%;只通过观测分析小区平均侵蚀特征得出的坡面侵蚀过程,掩盖了坡面下坡位的真实侵蚀过程,采取水土保持措施减少坡面上坡位汇流及增加降雨就地入渗,可以有效地治理坡面下坡位的水土流失。

基于GIS的区域土壤侵蚀模型设计

区域土壤侵蚀模型是国家和区域土壤侵蚀调查、水土保持宏观规划的支持工具。借鉴国外区域土壤侵蚀模型,以DEM栅格为空间单元,对区域土壤侵蚀的单元模型进行定量表达,包括降雨、植被截留、入渗,微地形填洼等,并利用GIS功能完成径流传递和汇集部分的计算,建立了区域土壤侵蚀模型。所建立模型在延河流域的试运算,结果接近现实,能反映土壤侵蚀时空分布趋势。模型的建立可为水土保持的宏观决策提供支持。

黄土结皮的发育机理与侵蚀效应研究

了解土壤结皮的发育特征及其对侵蚀的影响作用,是认识土壤侵蚀机理、建立精准侵蚀预报模型的重要理论支持之一。本文通过模拟降雨试验,探讨有无雨滴打击作用下黄土结皮的发育过程以及前期有无结皮时结皮侵蚀效应的动态特征。结果表明:(1)随降雨的进行,黄土结皮发生层容重、抗剪强度(含水率为20%)不断增加,30min内形成厚度约3～4mm稳定结皮层;(2)消除雨滴打击后,黄土结皮发育过程同有雨滴打击时类似,但程度减弱。雨滴打击同湿润作用对黄土结皮形成的贡献作用基本相当;(3)降雨初期有、无结皮处理抗剪强度差别大,随后急剧下降并趋同,因而黄土结皮影响抗蚀性的作用微弱,累积溅蚀量的差异主要由溅蚀起始时间的变化引起;(4)黄土结皮的存在明显的减少入渗、增加径流,但结皮效应随降雨进行逐渐消失。溅蚀效应的函数表达式为C=0.6670ln(t)-3.2459,结合溅蚀量的计算式,可较为准确地预测前期无结皮时某降雨历时的累积溅蚀量。

黄土高原地区水土保持科学研究的重点领域

针对黄土高原地区生态建设的需求与水土保持科学研究现状,分析了黄土高原水土保持科学研究的成就与发展趋势,提出该区未来需加强土壤侵蚀过程、机制及侵蚀模型、植被恢复的潜力及调控、大尺度土壤侵蚀及水土保持的格局与规律、水土流失及治理的环境效应评价理论与模型、水土流失治理的生态服务功能评价和不同尺度水土保持与生态建设模式研究等重点研究领域。

分布式水文模型的误差分析

分布式水文模型以其具有明确物理意义的参数结构和对空间分异性的全面反映,能够准确详尽地描述和模拟流域内真实的降水径流过程而被广泛需求和关注。在模拟土地利用、土地覆盖、水土流失等各种变化过程的水文响应,面源污染、陆面过程、气候变化影响评价等诸多领域都有广泛的应用。模型的预报精度和误差至关重要,决定了模型的应用和推广。在分析分布式水文模型建立和验证过程的基础上,提出了模型的4类误差来源:被排除在外的因素引起的误差,实测历史记录资料的随机或系统误差,参数误差和模型结构误差,讨论了各类误差的分析与计算方法,为模型的发展和成长提供了依据。

森林流域单元水文模型的构建与应用

目前全球缺水、水污染、洪涝灾害以及水土流失仍然非常严重，尤其在我国北方地区。流域水文模型可用来进行不同需水管理的情景分析，为解决我国水问题提供科学依据。分布式水文模型是流域水文模型的发展方向，具有显著特点：1）应用前景广泛，不仅可以模拟流域水文过程，还可以协助模拟泥沙或污染物的运移过程，为水利工程设计、水土保持、环境保护等领域提供技术支持；2）能够预测流域土地利用或气候变化下的流域水文响应过程变化，为管理部门提供决策支持；3）模型所需要的参数全部具有物理意义，可通过实际测量确定，适合模拟实测系列较短或是无观测流域的水文过程；4）对于目前国际水文界的前沿问题—水文尺度转换提供了一种有效的解决途径。 然而分布式水文模型还不完善，如1)真实性问题。对一些水文过程和边界条件还不确定。2)尺度转换问题。目前很少考虑尺度对参数有效性的影响。3)检验问题。还无法判断对有些难以测量的水文状态变量的模拟正确与否。4)计算时间和数据存储的问题。有些分布式水文模型虽然具有很强的水文物理基础和完善的模型结构，但是计算时间过长和(或)数据存储过大，难以应用。上述问题的核心就是对分布式水文模型的核心—单元水文模型的研究不够，需要为进一步完善单元水文模型进行研究。 本文采用饱和入渗理论、Saint-Venant方程、Richards方程、Penman-Monteith方程等等构建了以有限差分法求解的适用于森林流域的单元水文模型，并通过实验室模拟试验和坡地径流场资料进行了验证，主要结论为： 通过不同坡度和不同雨强下的室内坡面产汇流实验模拟，表明：该模型模拟的坡面流和壤中流过程与实测过程基本一致，峰现时间、径流历时、峰值流量、出流总量模拟值与实测值的相对误差均较小，基本小于10%。模型的模拟精度较高，实用性较强，为深入研究壤中流机制和改进流域降雨-径流模型提供了理论依据。 通过坡地径流观测场实测资料的验证，表明：该模型模拟的坡面流过程精度较高，累计流量的精度更高于小时过程的精度，离差系数、效率系数、确定系数均较理想，具有应用价值，有助于改善分布式水文模型在森林流域的模拟效果。

Excitation and dissociation of tungsten hexacarbonyl W(CO)(6): Statistical and nonstatistical dissociation processes

We have studied the excitation and dissociation processes of the molecule W(CO)(6) in collisions with low kinetic energy (3 keV) protons, monocharged fluorine, and chlorine ions using double charge transfer spectroscopy. By analyzing the kinetic energy loss of the projectile anions, we measured the excitation energy distribution of the produced transient dications W(CO)(6)(2+). By coincidence measurements between the anions and the stable or fragments of W(CO)(6)(2+), we determined the energy distribution for each dissociation channel. Based on the experimental data, the emission of the first CO was tentatively attributed to a nonstatistical direct dissociation process and the emission of the second or more CO ligands was attributed to the statistical dissociation processes. The dissociation energies for the successive breaking of the W-CO bond were estimated using a cascade model. The ratio between charge separation and evaporation (by the loss of CO+ and CO, respectively) channels was estimated to be 6% in the case of Cl+ impact. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3523347]

Preparation and characterization of PtSn/C anode electrocatalysts for direct ethanol fuel cell

Highly active PtSn/C catalyst was prepared by a polyol method. The catalyst was reduced in H-2/Ar atmosphere at 600 degreesC for 2 h in order to obtain different metallic phase. TEM images show uniform dispersion of spherical metal nanoparticles with average diameters of 1.8 and 3.9 nm for the as-prepared and treated catalysts, respectively. UV-vis spectrophotometry is employed to monitor the preparation process and the results indicate that Pt-Sn complex formed once the precursors of Pt and Sn were mixed together. The structure properties of the samples were characterized using X-ray diffraction. The results show that after reduction, the catalyst tends to form PtSn alloy. TPR experiment results show that Sn exists in multivalent state in the as-prepared sample while only zero-valence Sn was detected in the treated sample, while it could not be excluded that the multivalent tin existed in the treated sample. Cyclic voltammetry (CV) technique and single direct ethanol fuel cell (DEFC) tests indicate that the as-prepared catalyst possesses superior catalytic activity for ethanol oxidation to the treated sample. The results suggest that Pt and multivalent Sn are the active species for ethanol oxidation. (C) 2004 Elsevier B.V. All rights reserved.

Enhancement on the hydrothermal stability of ZSM-5 zeolites by the cooperation effect of exchanged lanthanum and phosphoric species

It was explored by density functional calculations that exchanged La or P species exert great influence on the local Al sites as well as on the adjacent exchanged species. In partially exchanged La- or P/H-ZSM-5 zeolite, some of the Al sites will fall off from the zeolite framework even more easily than in H-form ZSM-5, consistent with our XRF experiments. However, when exchanged by both La and P species, Al at either of the two exchanged sites shows better stability compared to H-from. zeolite. La and P species will interact strongly with each other, as evidenced by the charge donation process and the shortening of P-O-1 bond length. It was just the cooperation of La and P species that enabled RSCC catalysts worked normally under severe conditions. (C) 2004 Elsevier B.V. All rights reserved.

黄土丘陵区生态修复地不同抗侵蚀植物的消长变化过程

依据黄土丘陵区生态修复过程中植被演替阶段与植物生长型,将抗侵蚀植物分为一年生草本植物,多年生根茎禾草植物,多年生根蘖性草本和半灌木植物、灌木植物和乔木植物5类。一年生草本植物、多年生根茎禾草植物适应土壤侵蚀环境的能力比较强,同时具有一定程度的防止土壤侵蚀的作用;灌木和乔木植物适应土壤侵蚀环境的能力比较弱,而防止土壤侵蚀的作用很强;多年生草本和半灌木植物适应土壤侵蚀环境的能力适中,而防止土壤侵蚀作用的能力优于一年生草本和多年生根茎禾草群落,但不及乔灌木群落。并提出了在天然草本植被恢复的基础上进行人工造林的相关建议。