The Relation Between Upper Limb Muscle and Brain Activity in Two Precision Levels of Repetitive Light Tasks

A study was conducted to investigate the effects of repetitive light tasks of low and high precision on upper limb muscles and brain activities. Surface electromyography (EMG) and electroencephalography (EEG) were used to measure the muscle and brain activity of 10 subjects. The results show that the root-meansquare (RMS) and mean power frquency (MPF) of the muscle activity and the mean power of the EEG alpha bands were higher on the high-precision task than on the low-precision one. There was also a high and significant correlation between upper limb muscle and brain activity during the tasks. The longer the time and the more precise the task, the more the subjects become fatigued both physically and mentally. Thus, these results could be potentially useful in managing fatigue, especially fatique related to muscle and mental workload.     

用"3S"技术在低湿地区域提取高精度水灾信息--若干问题讨论

低湿地区域因其经济发达,财富密度大,故对于水灾损失评估,水灾信息的高精度提取显得尤为重要.作为水灾信息表征的两个重要方面:淹没范围和水深,是我们研究的重点.首先,论述了研究低湿地区域水灾的重要性;提出了研究应用“3S“技术提取高精度水灾信息的必要性,然后,综述了“3S“技术在水灾信息提取中的研究进展,指出了目前研究存在的问题;最后,阐明了今后在低湿地水灾信息高精度提取中应优先开展的研究课题.     

A Comparison of Protocols and Observer Precision for Measuring Physical Stream Attributes1

Abstract: Stream monitoring programs commonly measure physical attributes to assess the effect of land management on stream habitat. Variability associated with the measurement of these attributes has been linked to a number of factors, but few studies have evaluated variability due to differences in protocols. We compared six protocols, five used by the U.S. Department of Agriculture Forest Service and one by the U.S. Environmental Protection Agency, on six streams in Oregon and Idaho to determine whether differences in protocol affect values for 10 physical stream attributes. Results from Oregon and Idaho were combined for groups participating in both states, with significant differences in attribute means for 9 out of the 10 stream attributes. Significant differences occurred in 5 of 10 in Idaho, and 10 of 10 in Oregon. Coefficients of variation, signal‐to‐noise ratio, and root mean square error were used to evaluate measurement precision. There were differences among protocols for all attributes when states were analyzed separately and as a combined dataset. Measurement differences were influenced by choice of instruments, measurement method, measurement location, attribute definitions, and training approach. Comparison of data gathered by observers using different protocols will be difficult unless a core set of protocols for commonly measured stream attributes can be standardized among monitoring programs.     

对影响测定水中矿物油结果相关因素的研究

在紫外分光光度法测定水中矿物油中 ,存在着标准油品、石油醚纯度、石油醚萃取液体积定容等相关因素影响测定结果的准确度。本研究对上述因素进行实验对比 ,明确影响因素 ,提出改进建议     

一种新型的机械除尘技术——旋流除尘离心机

简要介绍了一项高效、经济的机械除尘技术,一种新型的旋流除尘离心机,给出了这种离心机除尘性能指标等的中期试验结果,指出了它的技术特点。     

含油污泥离心脱水中离心机参数的选择

通过对含油污泥离心脱水的批量处理和连续处理的研究，取得了含油污泥水固两相离心分离的满意效果。实验表明，适宜的操作参数可提高离心脱水效果。对LWD-430卧式螺旋离心机，当离心速度在1200～1400r／min之间，处理量在1，3m^3／h之间，差转速（转鼓与螺旋推料器的转速差）为20r／min时，离心液体积和COD均达到最佳状况。离心速度过高，会使絮体中的油离解出来，从而使离心液COD增加。差转速增加能明显改善“三泥”的离心脱水效果。     

土壤空间变异性研究评述

在研究方法上，土壤空间变异性研究经历了由定性描述到传统统计学、再到地统计学的不断改进过程，而研究内容也由对单一特性的研究逐渐转向多特性的研究。土壤空间变异性研究虽取得了明显的进展，但也存在地统计学方法在实际应用中主观性太强，土壤综合特性的空间变异性研究、时空结合的变异性研究以及与数学模型有机结合研究不够深入等问题。文章在分析国内外研究现状的基础上，提出了亟待深入研究的若干问题，对这些问题的研究有助于“数字土壤”、“精准农业”和生态环境建设的实施。     

Evaluation of Metric Precision for a Riparian Forest Survey

This article evaluates the performance of a protocol to monitor riparian forests in western Oregon, United States based on thequality of the data obtained from a field survey. Precision isthe criteria used to determine the quality of 19 field and 6 derived metrics. The derived metrics were calculated from thefield data. The survey consisted of 110 riparian sites on publicand private lands that were sampled during the summers of 1996 and 1997. In order to calculate metric precision, some of the field plots were re-measured. Metric precision was defined in terms of the coefficient of variability (CV) and standard deviation and then compared with a pre-defined data quality objective (DQO). A metric was considered precise if the CV met or exceeded the DQO. The geomorphology metrics were not precisewhile the forest stand inventory metrics and forest cover metrics, with some exceptions, were precise. The precision formany of the field and derived metrics compared favorably withthe level of precision for similar metrics reported in the literature. Recommendations are made to improve the precision for some metrics and they include changing the way precision is calculated, re-defining the field protocol, or improving field training.     

氯化亚锡还原光度法测定总磷的改进

用氯化亚锡还原光度法测定总磷时, 实验条件要求比较苛刻。克拉玛依市环境科研中心监测站对延长SnCl2、KH2PO4试剂的使用保存期、提高显色的稳定度、降低空白值的方法做了大量试验。试验表明:SnCl2-40%丙三醇溶液、KH2PO4使用液均有很好的稳定性,使用期达到2个月;钼酸铵溶液中,加入酒石酸锑钾钼蓝显色有良好的稳定性。用本方法和标准方法测定水样的结果无显著差异,其准确度与精密度均能达到要求。     

基于ZJU400土工离心机的CFD模拟方法

目的给出可靠的CFD模拟方法,用于土工离心机风阻功率估算,得到流场及温度场模拟结果。方法针对ZJU400中高速大型土工离心机,利用结构化网格划分使转臂及内壁面处的y+值<30,使其满足湍流模型边界层厚度要求。利用k-omega SST湍流模型和MRF多参考系方法对ZJU400土工离心机进行数值模拟,对模拟所得风阻功率、流场和温度场进行对比验证。结果模拟所得风阻功率与ZJU400实测数据偏差<10%,模拟所得流场与文献[8]中的结果吻合,温度场与实测数据吻合。结论针对ZJU400中高速大型土工离心机的CFD模拟方法取得了精度较高的模拟结果,通过仿真模拟弥补了大型土工离心机实验数据缺乏问题,减少了对实验数据的依赖,为制造设计和研究大型土工离心机提供了CFD模拟方法。