一类非对称变分不等式的非精确交替方向法

对一类非对称变分不等式问题提出了一种非精确交替方向法,对其中一个子问题(非线性方程组)的计算仅需要达到一个相对的精度,研究了迭代序列的若干性质,并证明了算法的全局收敛性.     

Germination of stratified and non-stratified seeds of red alder at two germination temperatures

Two- to four-week stratification of red alder seeds slightly increased the speed of germination but did not improve total germination under alternating warm temperatures (30°C/20°C), yet significantly improved speed and total germination under cool temperatures (15°C/5°C) that simulated early spring outdoor nursery bed conditions. Only seeds that received four-week stratification achieved complete germination at the cooler temperatures. Strong seed source variation in response to seed treatments was observed at the cool regime. The Yacolt source germinated well regardless of seed treatments, even without stratification, while five other sources needed two to four weeks of stratification to achieve above 50% germination. Possible reasons for this variation are discussed.     

Magnetic fields-induced modification of DNA content in date palm （Phoenix dactylifera L.）

Plant stress caused by exposure to magnetic fields （MF） induces modifications at molecular level, particularly in DNA synthesis, structure, and function. The objective of this study was to determine the effect of various doses of non-ionizing radiation of magnetic field on date palm （Phoenix dactylifera L.） based on DNA content. Date palm seedlings （cv. Khalas） established for 2 weeks on filter paper were subjected to static magnetic field and alternating magnetic field. Static magnetic fields （SMF） were applied at 10, 50 and 100 mT for 30, 60, 120, 180, 240 and 360 min; while alternating magnetic field applied by magnetic resonance imaging （MRI） at 1500 mT for 1, 5, 10 and 15 min. The seedlings were grown in potting soil following exposure for 4 weeks after which DNA was extracted from leaves and its content was determined. Generally, the exposure to magnetic field caused reduction in the content of DNA. The lowest exposure time tested, 30 rain, was sufficient to induce reduction in DNA content. This was true even at the lowest intensity, 10 mT. This dosage caused the DNA content to decrease from 49 ~tg/g to 45 pg/g. Further, increase of the exposure duration to 60 min caused significant reduction in the DNA content, 36 μg/g. At intensities higher than 10 mT, DNA content decreased significantly even at the shortest exposure of 30 min. At 50 and 100 mT, significant decrease in DNA content was also noticed in response to 30 min exposure; whereas the level of DNA increased after 1 min of MRI exposure to 52 ~g/g, then decreased after 5 min to 46 ~g/g. However, longer durations caused no further decrease in the DNA content. These observations indicate that magnetic fields interact with DNA processes, probably by inhibiting synthesis or stimulating degradation of DNA. This response merits further exploration as a mutational agent for date palm genetic manipulation.     

基于SVM算法的超声波速度-土壤含水率估计模型

为快速准确获取土壤含水率信息,便于农业精准灌溉,引入支持向量机算法（SVM）对4种不同干湿交替处理下超声波速度与土壤含水率进行拟合分析和回归训练优化,构建基于超声波速度的土壤含水率预测模型。结果显示,与传统的烘干法相比较,利用该模型在田间验证土壤含水率,平均相对误差为1.5%左右。研究结果表明,基于SVM模型构建的超声波速度-土壤含水率预测模型能够较好地描述被研究区域内土壤含水率,可为利用超声波特性实现对农田土壤水分的持续监测提供参考。     

Accuracy and precision of aquatic respirometers with emphasis on monophase oxystats

In this paper, the performance of flow-through systems with constant flow rate, alternating open-closed systems, and monophase oxystats for determination of aquatic respiration rates are compared based on computer simulations at steady-state and non steady-state conditions. In most situations, monophase oxystats offer several advantages compared to the other, more frequently used respiratory systems. Monophase oxystats always operates at steady-state dissolved oxygen concentrations and therefore, this principle is less sensitive to noise on oxygen measurements since changes in dissolved oxygen concentration do not need to be measured in order to obtain accurate respiration rates. Furthermore, in monophase oxystats, experiments can be carried out under more precisely defined conditions and experimental animals are allowed better options to adapt to the experimental conditions compared to other respiratory systems. This revised version was published online in July 2006 with corrections to the Cover Date.     

香根草光合特性对水淹-干旱交替胁迫的响应

三峡水库消落带因水位的周期性变化,使其土壤含水量呈干湿交替变化,而大多数原有植物难以适应新的生境,导致生态系统严重破坏。利用盆栽法模拟其水淹条件,以30,60,90和120d为周期进行水淹—干旱交替处理,研究了香根草当年实生幼苗在水淹与干旱交替胁迫下的光合特性及生理生态适应机制。结果表明,不同胁迫周期的水淹—干旱交替胁迫均显著影响香根草幼苗的生长及其光合生理特性。各组幼苗的株高、净光合速率、气孔导度及叶绿素含量等生理生态学指标均随时间变化呈不同幅度的升降变化。而不同组间的各项指标值均随交替周期的增大而减小。但无论何种变化,各处理组最终又都能逐渐恢复或趋于稳定状态,保持较高的存活率。因此,香根草对水淹和干旱均具有良好的耐受力和适应性,可作为三峡库区消落带植被恢复建设的重要植物种类。     

B2010A龙门刨床伺服系统的改造

根据刨床加工工艺特征，采用艾默生公司TD3000变频器、三菱可编程器和Easyview触摸屏组成控制系统，把B2010A龙门刨床原直流驱动改造为交流驱动．改造后机床节电效果明显，工作环境得到优化，稳定性大大提高，故障率大大降低。     

模拟昼夜变温对水稻种子萌发与种苗初期生长的影响

利用人工气候箱,模拟不同昼夜温度(CK:30/30℃;TR1:30/25℃;TR2:30/20℃;TR3:30/15℃;TR4:30/10℃)培养水稻品种粤香占幼苗,研究其对种子萌发及种苗初期生长的影响,旨在为生产上培育壮秧、壮苗提供理论依据。结果表明,昼夜变温可显著提高水稻秧苗素质:株高降低、茎秆变粗、根系发达、干重增加。昼夜变温处理对水稻幼苗的某些生理生化指标产生明显影响。其中,30/20℃(TR2)处理组水稻幼苗淀粉酶活性最高(比对照高17.14%);30/15℃(TR3)处理组水稻幼苗根系活力最高(比对照高12.91%)。     

A new parameter for evaluating waveform distortion of partial discharge signals after de noising

The alternating detail parameter (ADP) is a new parameter to represent waveform micro distortion. It is proposed to overcome the shortcomings of the traditional evaluation parameters, the normalized correlation coefficient (NCC) and the variation trend parameter. This proposal is based on the principle that two discrete waveforms are more similar if the ratio of their corresponding differentials is close to one. ADP is shown to be correct by power spectrum analysis. Simulation research demonstrated that ADP is valid for evaluating the effect on the de noised partial discharge signal by associating NCC with signal noise ratio.     

Harmonic analysis and filtering for alternating current main drive loads

A new analysis and filtering method for the ultra high order harmonic from the alternating current (AC) direct current (DC) AC main drive loads was proposed. The method was based on the practice and the new notation of the ARU（active rectifier unit） main transformer, and the specification of the integrated gate commutated thrusters (IGCT) and injection enhanced gate transistors (IEGT). By analyzing the features of the ultra high order harmonic, the harmfulness to electrical equipment and manufacturing as well as the necessity to filter ultra high order harmonic, indicates it is necessary to set up a higher frequency (HF) type filter. This research serves as a reference for designing and manufacturing the HF type filter in the power supply of rolling mills.