电容式束流位置探测器在HIRFL-CSR电子冷却实验中的应用

高效率的电子冷却过程，要求电子束与离子束相互平行，要求电子束与离子束同轴。为了同时测量电子束与离子束的相对位置和夹角，考虑了容式、感式、条带型束流位置探针特点以及电子冷却段实际情况，在HIRFL-CSR电子冷却装置上建立了以容性圆筒形极板为感应电极、NI公司PXI-5105高精度数字化仪为数据采集设备、PET公司P/N AM-4A-000110-11030N型宽带放大器为信号处理电路的束流位置测量系统。通过测量束流通过探针时在极板上产生的脉冲信号，对其进行傅立叶变换得到频谱信号，分析四个不同电极上的频谱信号强度获取束流的位置信息。同时，为了调整电子束与离子束的相对位置和夹角，建立了一套以ADLINK公司的PCI-9113和PCI-6216数据卡为主，针对电子冷却装置中各螺线管电源、静电偏转板电源、校正线圈电源的控制系统，完成了校正线圈、静电偏转板以及螺线管对电子束位置的偏移、扫描，实现了电子束的位置、角度调整。 通过使用位置测量系统、电子束位置调整系统获得了校正线圈、螺线管、静电偏转板对电子束的位置偏移能力以及电子束的流强、电流密度分布、径向尺寸、绝热展开因子对束流位置的影响。在冷却累积过程中进行了改变电子束与离子束相对位置、夹角的实验，观察到了冷却力和离子束流强随相对位置、夹角的变化趋势，进而优化相对位置和夹角，实现高冷却效率。 根据实验数据分析了位置测量系统的系统误差来源和精度，提出了今后提高束流位置测量系统、调整系统稳定性、精确性而需要进行的工作；在此基础上使用测量系统、调整系统进行了电子束、离子束相对位置和角度对冷却效果的影响等电子冷却相关实验工作

峰值幅度分析器的设计和实现

在核物理实验中，能谱测量作为一种主要的测量方式，得到广泛的应用。在能谱测量中，我们最为关心的是信号的幅度信息，而对于幅度信息，我们又最为关心峰值幅度。所以为了使输入到计算机获取系统中的信号的峰值幅度精确不失真，在信号处理的前端电子学部分，不仅要保持信号的幅度信息，还要得到较大的动态范围和较高的计数率，峰值幅度分析电路就是在信号经前端电子学部分（前置放大器和主放大器）对信号进行处理放大成具有高斯或准高斯波形的信号以后，精确地取得信号的峰值幅度，再送往扫描式ADC数据获取卡进行数据获取。在以往的电子学与数据获取系统中，信号峰值幅度分析电路都不是作为一个独立的产品出现的，而是集成在其他的插件中，一般集成在数据获取卡的前端。为了开发新型数据获取系统，其数据获取卡为通用的数据获取卡，并且是基于 PCI 数据总线的数据获取卡。所以我们必须研制峰值幅度分析电路以支持通用的数据获取卡。本电路主要利用了二极管的单向导电性和延时特性以及电容的电荷保持特性再加上其他的辅助电路来实现的。辅助电路包括：加法器，减法器，取样保持脉冲产生电路，隔离电路，缓冲器。其中加法器与减法器的作用是补偿二极管的0.5伏的导通电压和提高电路的线形度而加的，取样脉冲产生电路得到的脉冲控制保持电容的充放电，是为解决信号的堆积效应的。隔离器的作用是避免前后级电路之间的相互影响。缓冲器其实是峰值幅度分析电路与后续数据获取卡的接口电路，为了解决信的处理和信号获取的同步问题，使峰值幅度分析电路对信号的处理与数据获取卡对信号的获取高效有序地工作。本电路在动态范围0-10V之间具有很高的线形度，很高的稳定性，宽的带及高达 500K 的计数率，低成本和很高的集成度。

信号采集与数据处理电路的研究

随着原子核科学技术的发展，无论是对原子核内部特征和规律的研究，或者是对原子核科学技术的应用，都需要对核辐射和原子核所携带的信息进行测量和分析研究。在核电子学测量系统中，核辐射探测器输出信号在经过各种信号处理电路后，通常都要变换成数字信号，再经过数据收集和处理，给出实验的最终结果，因此实验工作的任何进展都要求有相应的数据获取和处理系统的支持。根据实验的实际需求，我们以采集、处理探测器输出的信号为题，开展了一些研究工作，我们先后开展的研究工作包括以下儿个方面：1．激光功率计的变换与显示电路的研制2．基于PCI总线、嵌入8051单片机的计数卡的研制3．数据处理分析软件的设计这三部分的设计工作我们将在论文的第二、第三、第四章分别进行阐述。激光功率计的变换与显示电路把由激光功率计输出的模拟电压量变为数字脉冲输出，并且把该输出脉冲的频率实时定性显示出来。本电路测量精度高，线性好，工作稳定。我们研制开发的计数卡是一种很实用的计数卡，它是一种基于PCI总线，嵌入单片机的高速计数器，最大计数范围为109-1，最高的计数频率为20MHz。该计数卡计数范围宽，计数频率高，具有定时计数、重复计数等功能，可以取代常规的定标器，具有广泛的应用前景。数据处理分析软件包括下位机软件、上位机软件及通讯协议三部分，实现数据的采集与记录，并将读取的数据以Excel电子表格的形式存储，以备查询。下位机的软件采用KeilC编写，上位机软件采用Delphi编写。目前激光功率计的变换与显示电路和计数卡及相应的数据处理软件都设计、调试完成，已经投入使用，获得满意结果，受到好评。

聚(ε-己内酯)/苯乙烯-丙烯腈共聚物共混物的形态研究

本文研究了聚(ε-己内酯)(PCI/苯乙烯-丙烯腈共聚物(SAN)共混物的形态。采用差示扫描量热计(DSC)测量了PCL/SAN共混物中的PCL结晶度随着SAN含量的增加而下降;当SAN浓度达到60wt％。以上时,PCI的结晶度趋于零。通过偏光显微镜可以观察到在含高浓度PCI的共混物中,PCL是以球晶形式存在的。样品是由PCL球晶充满的,但是随着SAN含量的增加,PCL球晶半径减小,球晶结构逐渐变得不规整,而X-射线衍射测试了不同组成的PCL/SAN共混物中PCL的晶胞参数没有改变,说明SAN没有进入到PCL的晶胞内。以小角X-射线散射结果发现PCI片晶之间的距离随着SAN含量的增加而增大。以上说明SAN分子与没有结晶的PCL形成无定形相夹在PCL的片晶之间。

FPGA在偏振耦合测试仪中的应用

在偏振耦合测试仪的PCI接口数据采集系统中,现场可编程门阵列(FieldProgramableGateArray)实现了对模/数器件的控制功能,同时完成了与PCI总线控制器间的数据接口功能。应用自顶向下的设计思想,完成了FPGA内部的逻辑设计,并对其逻辑功能进行了仿真验证,给出了FPGA数据采集时的测试时序图。应用FPGA实现的数据采集系统可以检测出偏振耦合检测仪中的微弱干涉光信号。

Pontos críticos de infecção por fungos, oomicetos e bactérias em tubérculos de batata.

Após a colheita, os tubérculos de batata ficam sujeitos ao ataque de micro-organismos fitopatogênicos que levam ao seu apodrecimento. As ?portas? de entrada desses agentes nos tubérculos, aqui chamadas de pontos críticos de infecção (PCI), podem ser de causa natural ou induzidos durante o manuseio do produto.

Survey of the potential environmental and health impacts in the immediate aftermath of the coal ash spill in Kingston, Tennessee.

An investigation of the potential environmental and health impacts in the immediate aftermath of one of the largest coal ash spills in U.S. history at the Tennessee Valley Authority (TVA) Kingston coal-burning power plant has revealed three major findings. First the surface release of coal ash with high levels of toxic elements (As = 75 mg/kg; Hg = 150 microg/kg) and radioactivity (226Ra + 228Ra = 8 pCi/g) to the environment has the potential to generate resuspended ambient fine particles (< 10 microm) containing these toxics into the atmosphere that may pose a health risk to local communities. Second, leaching of contaminants from the coal ash caused contamination of surface waters in areas of restricted water exchange, but only trace levels were found in the downstream Emory and Clinch Rivers due to river dilution. Third, the accumulation of Hg- and As-rich coal ash in river sediments has the potential to have an impact on the ecological system in the downstream rivers by fish poisoning and methylmercury formation in anaerobic river sediments.

Decadal basin-scale changes in diatoms, dinoflagellates, and phytoplankton color across the North Atlantic

The Continuous Plankton Recorder (CPR) survey has been used to characterize phytoplankton and zooplankton space-time dynamics in the North Sea since 1931 and in the North Atlantic since 1939. Phytoplankton biomass is assessed from these samples by visual assessment of the green color of the silk mesh, the Phytoplankton Color Index (PCI), and the total count of diatoms and dinoflagellates. Species with a frequency of occurrence greater than 1% in the samples are used as indicator species of the community. We investigated (1) long-term fluctuations of phytoplankton biomass, total diatoms, and total dinoflagellates; (2) geographical variation of patterns; (3) the relationship between phytoplankton and climate forcing in the North Atlantic CPR samples; (4) the relative contribution of diatoms and dinoflagellates to the PCI; and (5) the fluctuations of the dominant species over the period of survey to provide more information on the processes linking climate to changes in the phytoplankton community. As a result of the differences in microscopic analysis methods prior to 1958, our analyses were conducted for the period ranging from 1958 to 2002. The North Atlantic was divided into six regions identified through bathymetric criteria and separated along a North-South axis. Based on 12 monthly time series, we demonstrate increasing trends in PCI and total dinoflagellates and a decrease in total diatoms.

Increased blooms of a dinoflagellate in the NW Atlantic

Sampling by the Continuous Plankton Recorder (CPR) over the NW Atlantic from 1960 to 2000 has enabled long-term studies of the larger components of the phytoplankton community, highlighting various changes, particularly during the 1990s. Analysis of an index of phytoplankton biomass, the Phytoplankton Colour Index (PCI) has revealed an increase over the past decade, most marked during the winter (December to February) months. Examination of the structure of the community using multiple linear-regression models indicates that the winter phytoplankton community composition has changed markedly in the 1990s compared to the 1960s. One phytoplankter, the dinoflagellate Ceratium arcticum (Cleve), has undergone dramatic changes in abundance during this period, with pronounced large winter blooms and decreased autumnal levels, and its contribution to the Phytoplankton Colour index values has increased significantly. Other dominant species in the phytoplankton community, both diatoms and dinoflagellates, did not show the same variations over the examined time period. It is suggested that the response of C. arcticum is probably a result of previously reported changes in stratification in the NW Atlantic, due to dynamic hydro-climatic (freshening and cooling) events.

Differential contribution of diatoms and dinoflagellates to phytoplankton biomass in the NE Atlantic Ocean and the North Sea

Sampling by the continuous plankton recorder (CPR) survey over the North Atlantic Ocean and the North Sea has enabled long-term studies of phytoplankton biomass. Analysis of an index of phytoplankton biomass, the phytoplankton colour index (PCI), has previously shown an increase in phytoplankton biomass in the NE Atlantic. In the current study, further investigations were conducted to determine the contribution of diatom and dinoflagellate cell counts to the PCI, their fluctuations over the last 45 yr and their geographical variations in the eastern North Atlantic and the North Sea. An increased contribution of dinoflagellates to the PCI was revealed over the south NE Atlantic and the northern North Sea. In contrast, the contribution of diatoms decreased in the north NE Atlantic and the northern North Sea. No discernible trends were found in the other regions of the North Sea. The relative contributions of diatoms and dinoflagellates to the PCI led to the identification of 3 geographically distinct dynamic regimes in the diatom/dinoflagellate dynamics in the NE Atlantic and the North Sea. Finally, it is stressed that the discrepancy observed in the patterns of PCI and diatom and dinoflagellate cell counts suggests that changes in PCI do not reflect changes in the community structure and that the exclusive use of PCI is not adequate to investigate the long-term trends in the trophic link between phytoplankton and herbivorous zooplankton.

Decadal variability in biogeochemical models: Comparison with a 50-year ocean colour dataset

Assessing the skill of biogeochemical models to hindcast past variability is challenging, yet vital in order to assess their ability to predict biogeochemical change. However, the validation of decadal variability is limited by the sparsity of consistent, long-term biological datasets. The Phytoplankton Colour Index (PCI) product from the Continuous Plankton Recorder survey, which has been sampling the North Atlantic since 1948, is an example of such a dataset. Converting the PCI to chlorophyll values using SeaWiFS data allows a direct comparison with model output. Here we validate decadal variability in chlorophyll from the GFDL TOPAZ model. The model demonstrates skill at reproducing interannual variability, but cannot simulate the regime shifts evident in the PCI data. Comparison of the model output, data and climate indices highlights under-represented processes that it may be necessary to include in future biogeochemical models in order to accurately simulate decadal variability in ocean ecosystems.

A long-term chlorophyll dataset reveals regime shift in North Sea phytoplankton biomass unconnected to nutrient levels

During the 1980s, a rapid increase in the Phytoplankton Colour Index (PCI), a semiquantitative visual estimate of algal biomass, was observed in the North Sea as part of a regionwide regime shift. Two new data sets created from the relationship between the PCI and SeaWiFS chlorophyll a (Chl a) quantify differences in the previous and current regimes for both the anthropogenically affected coastal North Sea and the comparatively unaffected open North Sea. The new regime maintains a 13% higher Chl a concentration in the open North Sea and a 21% higher concentration in coastal North Sea waters. However, the current regime has lower total nitrogen and total phosphorus concentrations than the previous regime, although the molar N: P ratio in coastal waters is now well above the Redfield ratio and continually increasing. Besides becoming warmer, North Sea waters are also becoming clearer (i.e., less turbid), thereby allowing the normally light-limited coastal phytoplankton to more effectively utilize lower concentrations of nutrients. Linear regression analyses indicate that winter Secchi depth and sea surface temperature are the most important predictors of coastal Chl a, while Atlantic inflow is the best predictor of open Chl a; nutrient concentrations are not a significant predictor in either model. Thus, despite decreasing nutrient concentrations, Chl a continues to increase, suggesting that climatic variability and water transparency may be more important than nutrient concentrations to phytoplankton production at the scale of this study.

A 60-year ocean colour data set from the continuous plankton recorder

The phytoplankton colour index (PCI) of the Continuous Plankton Recorder (CPR) survey is an in situ measure of ocean colour, which is considered a proxy of the phytoplankton biomass. PCI has been extensively used to describe the major spatiotemporal patterns of phytoplankton in the North Atlantic Ocean and North Sea since 1931. Regardless of its wide application, the lack of an adequate evaluation to test the PCI's quantitative nature is an important limitation. To address this concern, a field trial over the main production season has been undertaken to assess the numerical values assigned by previous investigations for each category of the greenness of the PCI. CPRs were towed across the English Channel from Roscoff to Plymouth consecutively for each of 8 months producing 76 standard CPR samples, each representing 10 nautical miles of tow. The results of this experiment test and update the PCI methodology, and confirm the validity of this long-term in situ ocean colour data set. In addition, using a 60-year time series of the PCI of the western English Channel, a comparison is made between the previous and the current revised experimental calculations of PCI.