Exotic behaviour of angular dispersion of weakly bound nucleus F-17 at small angles

The differential cross sections of F-17 and O-17 elastic scattering products on Pb-208 have been measured at the Radioactive Ion Beam Line at Lanzhou (RIBLL). Two angular dispersion plots of ln(d sigma/d theta) versus theta 2 are obtained from the angular distribution of the elastic scattering differential cross sections. The angular dispersion plot exhibits a clear turning point for F-17 in the range of small scattering angles 6 degrees-20 degrees due to its exotic structure, but for O-17, the turning point is not observed in the same angular range. The experimental results have been compared with previous data of other groups. Systematical analysis on the available data supports the above conclusion that there is an exotic behaviour of the angular dispersion plot of weakly bound nuclei with halo or skin structure as compared with that of the ordinary nuclei near stable line. Therefore the turning point of the angular dispersion plot appears at small angle for weakly bound nuclei with halo or skin structure, and can be used as a new probe to investigate the halo and skin phenomena of weakly bound nuclei.

低碳:国家可持续发展实验区建设的重要方向

<正>经过20多年的建设与发展,国家可持续发展实验区依靠科技进步、机制创新,在协调社会经济发展与环境资源关系、促进经济发展、提高居民生活质量、探索新型工业化道路等诸多方面进行了积极的探索和实践,极大地推动了区域经济社会的协调发展,已成为实施国家可持续发展战略的

试论东北地区农业节水与农业水资源可持续利用

针对振兴东北老工业基地大背景下的东北地区水资源紧缺状况 ,通过对农业水资源和农业节水潜力的系统分析 ,提出了东北地区的系统农业节水战略 .根据东北地区农业生产特点和农业发展需求 ,进行节水农业分区 ,确定不同农业类型区节水高效栽培模式与关键集成技术体系 .论述了东北地区农业水资源可持续利用系统学方略和实施系统节水治水工程的必要性 ,以及农业节水研究的发展趋势 .

脱落酸对UV-C胁迫下小麦幼苗光合特性及抗氧化酶活性的影响

研究了UV-C辐射下短期和长期脱落酸(ABA)处理对小麦幼苗CO2同化作用、羧化效率、光合CO2响应以及抗氧化酶活性等的影响.结果表明,在无UV-C辐射情况下,短期和长期ABA处理能提高光合速率,比对照增加14·69%和20·46%,降低气孔导度,比对照降低14·74%和17·31%,但对胞间CO2浓度和羧化效率影响不大.当受到UV-C辐射时,光合速率、羧化效率、气孔导度和胞间CO2浓度逐渐降低.长期ABA处理变化最小,其次为ABA短期处理,对照降低最大.ABA处理能够提高小麦光合对CO2的响应,UV-C辐射抑制光合对CO2的响应.ABA处理能够提高小麦抗氧化酶(CAT、SOD、POD)活性而降低MDA含量.在UV-C辐射下,CAT活性先升高随后降低,在辐射处理1h时活性达最大值,ABA处理的SOD和POD活性先升高后降低,且ABA长期处理比短期处理增加明显,对照则逐渐降低.ABA处理可能通过提高小麦CO2同化作用和抗氧化酶活性增强对UV-C胁迫的抗性,且ABA长期处理比短期处理效果更明显.

钐与磷酸二甲酯配合物的合成和结构

合成了钐与磷酸二甲酯的配合物,该配合物的组成为Sm〔(CH_3O)_2PO_2〕_3,测定了该配合物的红外和拉曼光谱。x射线单晶衍射法测定配合物的晶体属单斜晶系,P2_(1/c)空间群,α=10.434(4)A,b=16.541(3)A,c=10.804(4)A,β=111.75(3)°,V=1731.7(9)A~3,Z=4。钐与6个氧原子配位,每2个相邻的钐原子通过双“O—P—O”桥相连接,形成奇特的“双桥24元环”的环套环网状结构。钐氧配位多面体为稍微扭曲的正八面体。

Terpenes and polybromoindoles from the marine red alga Laurencia decumbens (Rhodomelaceae)

Two new brominated diterpenes, namely, laurendecumtriol (1) and 11-O-deacetylpinnaterpene C (2), one new polybromoindole, 2,3,4,6-tetrabromo-1-methyl-1H-indole (7), and six known natural products were isolated and identified from the marine red alga Laurencia decumbens. Their structures were elucidated on the basis of detailed spectroscopic and mass-spectrometric analysis as well as by comparison with literature data. Based on 2D-NMR experiments, the previously reported NMR data for pinnaterpene C (3) were reassigned.

一种基于 PSD 的机器人动态轨迹测量系统的研制

本文介绍了一个基于 PSD 的机器人动态位置测量系统,描述了系统的构成,并对该系统中的标定方法,数据处理方法和为提高系统的性能所采取的硬件措施进行探讨,本系统通过长期考机和初步应用,表明了它具有良好的可靠性和有效性.

黔中喀斯特地区的景观变化及其生态效应

为了解喀斯特地区景观变化过程及相应的生态效应,利用遥感影像数据对黔中地区1995 —2000 年的景观格局与动态进行分析。结果显示:研究区以灌木林地、坡耕地、中覆盖度荒草地占据着景观中的优势地位。旱地、林地和荒草坡的转换关系复杂,退耕还林还草与毁林毁草开荒同时并存,植被恢复与退化并存,整体景观尚处于一种波动状态,区域土地利用生态价值并未有明显提高,而呈下降趋势。研究区景观格局特征是岩性、地貌和人为活动共同作用的结果,景观斑块的转化主要受人文因素的影响,耕地的变化主要是被建设用地占用。在1995 —2000 年的土地利用变化中,研究区的生态既有恢复,又存在继续恶化的趋势。

学习不良青少年学业情绪研究：特点、影响学业成就的机制及干预

学业情绪是指在教学或学习过程中，与学生学业相关的各种情绪体验。采用问卷、访谈、实验室实验、自然实验等多种方法，从学习不良青少年学业情绪的特点和影响因素出发，重点考察了学业情绪对学习不良青少年学业成就及选择性注意和持续性注意的影响。在此基础上，制定了学业情绪整合性干预措施，对学习不良青少年进行了学业情绪的干预。结果表明： 1、以1731名初一到高三学生为被试，通过三次取样测试，编制的《青少年学业情绪问卷》具有较好的理论构想和信、效度指标，是研究青少年学业情绪问题的一个有效工具。 2、采用问卷法，比较了学习不良青少年和一般青少年在学业情绪上的特点，被试为普通初中与高中学生1034人，其中学习不良学生506人。结果表明，学习不良青少年比一般青少年有更少的积极学业情绪、更多的消极学业情绪。学习不良青少年与一般青少年在学业情绪上的差异主要体现在初一、初二和高二、高三年级。总体上，消极学业情绪有随着学业时间的延续而增强的趋势，积极学业情绪有随着学业时间延续而降低的趋势。男生的积极学业情绪多于女生，女生的消极学业情绪多于男生。学习不良青少年的学业情绪受人际、学业、课堂、个人等多方面因素的影响，其中人际因素是最主要的因素。 3、以1209名青少年为被试，采用结构方程模型检验了学业情绪对学业成就的影响模式。结果发现，积极高唤醒学业情绪通过成就目标、学业效能、学习策略间接影响学业成就；积极低唤醒、消极低唤醒和消极高唤醒学业情绪对学业成就有直接影响。学业情绪影响学习不良青少年学业成就的模式形态与一般青少年相同。 4、学业情绪对学习不良青少年的选择性注意和持续性注意有一定影响。对70名高一学习不良青少年研究的结果表明，对积极低唤醒学业情绪下选择性注意的反应时成绩优于消极学业情绪。对69名高二学习不良青少年研究的结果表明，消极高唤醒的学业情绪能够增加持续性注意的虚报率，降低抑制能力，而积极高唤醒的学业情绪能够提高判断标准，占用更多的心理资源。 5、以358名高中学生为被试（其中学习不良学生52人），通过学业情绪的整合性教育干预发现，该干预能够有效促进学习不良青少年及全体青少年学业情绪的改善；短期内对学习不良及全体青少年的学业成就提高有积极作用。

Intelligence in Scientific Computing

Combining numerical techniques with ideas from symbolic computation and with methods incorporating knowledge of science and mathematics leads to a new category of intelligent computational tools for scientists and engineers. These tools autonomously prepare simulation experiments from high-level specifications of physical models. For computationally intensive experiments, they automatically design special-purpose numerical engines optimized to perform the necessary computations. They actively monitor numerical and physical experiments. They interpret experimental data and formulate numerical results in qualitative terms. They enable their human users to control computational experiments in terms of high-level behavioral descriptions.

Comparison Between Subsonic Flow Simulation and Physical Measurements of Flue Pipes

Direct simulations of wind musical instruments using the compressible Navier Stokes equations have recently become possible through the use of parallel computing and through developments in numerical methods. As a first demonstration, the flow of air and the generation of musical tones inside a soprano recorder are simulated numerically. In addition, physical measurements are made of the acoustic signal generated by the recorder at different blowing speeds. The comparison between simulated and physically measured behavior is encouraging and points towards ways of improving the simulations.

A Computational Model for the Acquisition and Use of Phonological Knowledge

Does knowledge of language consist of symbolic rules? How do children learn and use their linguistic knowledge? To elucidate these questions, we present a computational model that acquires phonological knowledge from a corpus of common English nouns and verbs. In our model the phonological knowledge is encapsulated as boolean constraints operating on classical linguistic representations of speech sounds in term of distinctive features. The learning algorithm compiles a corpus of words into increasingly sophisticated constraints. The algorithm is incremental, greedy, and fast. It yields one-shot learning of phonological constraints from a few examples. Our system exhibits behavior similar to that of young children learning phonological knowledge. As a bonus the constraints can be interpreted as classical linguistic rules. The computational model can be implemented by a surprisingly simple hardware mechanism. Our mechanism also sheds light on a fundamental AI question: How are signals related to symbols?

Sparse Representations for Fast, One-Shot Learning

Humans rapidly and reliably learn many kinds of regularities and generalizations. We propose a novel model of fast learning that exploits the properties of sparse representations and the constraints imposed by a plausible hardware mechanism. To demonstrate our approach we describe a computational model of acquisition in the domain of morphophonology. We encapsulate phonological information as bidirectional boolean constraint relations operating on the classical linguistic representations of speech sounds in term of distinctive features. The performance model is described as a hardware mechanism that incrementally enforces the constraints. Phonological behavior arises from the action of this mechanism. Constraints are induced from a corpus of common English nouns and verbs. The induction algorithm compiles the corpus into increasingly sophisticated constraints. The algorithm yields one-shot learning from a few examples. Our model has been implemented as a computer program. The program exhibits phonological behavior similar to that of young children. As a bonus the constraints that are acquired can be interpreted as classical linguistic rules.