R-factor Pseudo-circular Extension Method

The extension methods of finite length signals for sub band coding associated with wavelet transformation are investigated.Considering the weakness of the existing extension methods,an extension method is presented which is named r factor pseudo circular extension method.It turns out theoretically that the input signal can be reconstructed exactly from the truncated section of the analyzed signals by our method and the method is better than other existing extension methods,as shown in many examples.A new valid way is provided for wavelet transform application in data compression.     

宁夏银北排水项目暗管排水外包滤料试验研究

采用一维和二维渗透模型对土工织物作为农田暗管排水外包滤料进行了试验研究。试验用的 2种土壤取自宁夏银北暗管排水区 ,对 1 2种不同土工织物的透水效果进行了测定和对比分析 ,其初选结果将用于野外现场作进一步观测评价 ,并最终为宁夏银北暗管排水滤料选择提供依据     

Simulated rainfall evaluation of revegetation/mulch erosion control in the Lake Tahoe basin—3: soil treatment effects

Revegetation, or other erosion control treatments of disturbed soil slopes in forested areas and along highways of the Lake Tahoe basin are directed at reduction of sediment loading to waterways reaching the lake. However, following treatment, little vegetation monitoring, or hydrologic evaluation has been conducted either to determine if the various treatments are successful or to assess the duration of erosion control anticipated in the field. Here, we build upon results from use of the portable rainfall simulator (RS) described in the first two papers of this series to evaluate cover and revegetation treatment effects on runoff rates and sediment concentrations and yields from disturbed granitic and volcanic soils in the basin. The effects of slope on rainfall runoff, infiltration and erosion rates were determined at several revegetated road cut and ski run sites. Rainfall simulation (∼60 mm h⁻¹, approximating a 100‐year, 15‐minute storm) had a mean drop size of ∼2·1 mm and approximately 70 per cent of ‘natural’ rainfall kinetic energy. Measurements of: time to runoff; infiltration; runoff amount; sediment yield; and average sediment concentration were obtained. Runoff sediment concentrations and yields from sparsely covered volcanic and bare granitic soils can be correlated to slope. Sediment concentrations and yields from nearly bare volcanic soils exceeded those from granitic soils by an order of magnitude across slopes ranging from 30–70 per cent. Revegetation, or application of pine‐needle mulch covers to both soil types dramatically decreased sediment concentrations and yields. Incorporation of woodchips or soil rehabilitation that includes tillage, use of amendments (biosol, compost) and mulch covers together with plant seeding resulted in little or no runoff or sediment yield from both soils. Repeated measurements of sediment concentrations and yields in the subsequent two years following woodchip or soil rehabilitation treatments continued to result in little or no runoff. Revegetation treatments involving only use of grasses to cover the soils were largely ineffective due to sparse sustainable coverage (< 35 per cent) and inadequate infiltration rates. Copyright © 2005 John Wiley & Sons, Ltd.     

Least limiting water range and crop yields as affected by crop rotations and tillage

Crop rotation and the maintenance of plant residues over the soil can increase soil water storage capacity. Root access to water and nutrients depends on soil physical characteristics that may be expressed in the Least Limiting Water Range (LLWR) concept. In this work, the effects of crop rotation and chiselling on the soil LLWR to a depth of 0.1 m and crop yields under no‐till were studied on a tropical Alfisol in São Paulo state, Brazil, for 3 yr. Soybean and corn were grown in the summer in rotation with pearl millet (Pennisetum glaucum, Linneu, cv. ADR 300), grain sorghum (Sorghum bicolor, L., Moench), congo grass (Brachiaria ruziziensis, Germain et Evrard) and castor bean (Ricinus comunis, Linneu) during fall/winter and spring, under no‐till or chiselling. The LLWR was determined right after the desiccation of the cover crops and before soybean planting. Soil physico‐hydraulic conditions were improved in the uppermost soil layers by crop rotations under zero tillage, without initial chiselling, from the second year and on, resulting in soil quality similar to that obtained with chiselling. In seasons without severe water shortage, crop yields were not limited by soil compaction, however, in a drier season, the rotation with congo grass alone or intercropped with castor resulted in the greatest cover crop dry matter yield. Soybean yields did not respond to modifications in the LLWR.     

西瓜新品种农科大5号的选育

农科大5号是以自交系M18为母本,自交系F23为父本配制而成的西瓜新品种一代杂种。早熟,果实发育期28～30d(天),全生育期90～92d(天);易坐果,果实圆形,果形指数1.1;果皮深绿色,覆墨绿色中细条带,皮厚0.93cm,硬韧,耐贮运;果肉红色,肉质沙细,汁多纤维少,口感佳,品质优,中心折光糖含量12.4%,中边糖梯度小;田间调查表明对蔓枯病的抗性强于对照京欣2号,枯萎病零星发生,未见炭疽病和白粉病发生;单瓜质量5.9kg,产量3200kg·(667m2)-1。适宜在陕西及同类生态区早春设施西瓜种植区种植。     

电动汽车用内置式永磁同步电动机精确转矩控制方法

提出一种基于转矩观测器的电动汽车内置式永磁同步电动机精确转矩闭环控制方法。通过内置式永磁同步电动机数学模型的建立,分析了基于Popov超稳定理论的模型参考自适应参数辨识方法,为了提高系统的响应速度,提出和采用了极点配置法。研究了自适应模型控制参数对MRAI系统响应时间的影响,并进行了验证和理论分析。仿真和实验结果表明辨识出的永磁体磁通和定子电阻较为准确,转矩观测器可以根据辨识出的永磁体磁通对实际的转矩进行估算,以此和转矩命令值构成转矩闭环控制,从而在永磁体磁通发生变化时提高驱动系统的转矩控制精度,改善电动汽车驱动系统的性能。     

四轮转向汽车操纵性和稳定性联合优化及仿真研究

首先在考虑汽车和驾驶员等不确定性因索，以厦已有的驾驶员一汽车闭环系统的操纵性评价指标、稳定性评价指标的基础上，提出了同时考虑四轮转向汽车操纵性和稳定性的加权操纵稳定性指标J0；然后考虑各种车速的重要性，提出了考虑车速影响的驾驶员-汽车闭环系统操纵稳定性综合评价指标J。最后对操纵性和稳定性进行联合优化，从理论上指导四轮转向汽车相关结构参数设计，对汽车动力学厦其控制系统的研究也具有一定的借鉴价值。     

Short‐term environmental changes in Lake Morenito (41°S, 71°W,Patagonia, Argentina) from the analysis of sub‐fossil chironomids

• 1. A short sediment core from Lake Morenito was studied to assess the impact of environmental changes on chironomid communities occurring during the last ca 100 yr.
• 2. Lake Morenito (41°S, 71°W) is located 20 km west of the city of Bariloche, in northern Patagonia, Argentina. Before 1960, this lake was a branch of Lake Moreno; by that time, an artificial dam closed the system, establishing the new lake. Another human disturbance that took place during the time span of the core was the introduction of salmonids to the area ca 1910.
• 3. The most important natural events that occurred in the area during the last 100 yr were related to volcanic episodes. One of them, occured in Chile in 1960 affecting the Argentinian side, coincided with the dam's construction.
• 4. Changes in the chironomid community were recorded by studying the sub‐fossil remains (the chitinized head capsule of the larvae) present in the sedimentary sequence. The results show that volcanic tephra layers deposited along the core led to a sharp instantaneous drop in the diversity and abundance of chironomid assemblages. Human activities are also associated with a change in chironomid community composition.
• 5. Chironomus reached its maximum abundance values in 1910 and 1960. The organic matter content also increased at the same time. The increase of Chironomus after 1910 is clearly related to an increase in the trophic status of the lake. However, owing to the synchronicity of events in 1960, i.e. the volcanic event and the dam's construction, it is difficult to establish whether the change in the chironomid assemblage was in response to an increase in trophic enrichment, to natural disturbance, or both.

Copyright © 2004 John Wiley & Sons, Ltd.     

Performance of Sugarcane (Saccharum officinarum L.) Under Surface Drip, Sub Surface Drip (Biwall) and Furrow Methods of Irrigation

Field experiments were conducted at the Sugarcane Breeding Institute, Coimbatore, India during 1989–93 to study the productivity and water use efficiency of sugarcane under different methods of irrigation. The results showed that there could be a 44 % saving in water with higher water use efficiency in drip irrigation compared to conventional furrow irrigation. Among drip irrigation systems in the plant crop, sub surface drip (Biwall) at 40/140 cm spacing recorded a significantly higher number of millable canes, cane length and single cane weight compared to either conventional furrow irrigation or furrow irrigation based on IW/CPE (Irrigation Water Cumulative Pan Evaporation) ratio. In ratoon crop, Biwall irrigation at 60/120 cm gave significantly higher cane length and single cane weight compared to any other methods of irrigation. However, cane and sugar yields in Biwall irrigations were on par with conventional furrow irrigation but superior to either surface drip or furrow irrigation based in IW/CPE ratio.     

亚二倍体嵌合体母猪及其子代染色体组型分析

报告了 1头亚二倍体嵌合体的母猪 (4 0 3号 ) .在所检查的 19个中期相细胞中 ,染色体组型为 36,XX ,- 4D , 2rob(15 ;17)的核型有 4个 (2 1% ) ;37,XX ,- 2D , rob(15 ;17)的核型有 15个(79% ) .对其所产的 10头仔猪进行染色体检查 ,发现其中有 1头雄性仔猪 (4 87号 )为 36,XY ,- 4D , 2rob(15 ;17)的纯合子 ,有 1头雌性仔猪 (5 79号 )为亚二倍体 二倍体嵌合体 ,在其被检的 16个细胞中 ,有 2个为 36,XX ,- 4D , 2rob(15 ;17) (12 .5 % ) ,14个为 38,XX(87.5 % ) .其余 8头仔猪及配种公猪的染色体检查均为正常二倍体 38,XX(XY)核型