Relationship between suspended sediment load, channel geometry and land area increment in the Yellow River Delta

The annual river discharges and suspended sediment loads into the Yellow River Delta show a declining tendency with some distinct fluctuations over the last 50 years. The decrease of river discharge and suspended sediment load and the change in the river channel must influence the evolution of the Yellow River Delta. During this period several new river mouths formed via channel switch at the river delta, and the old watercourse was gradually abandoned. Recently, in years with very low annual suspended load, erosion of land area has been recorded for the delta. The aims of this work are (1) to determine what is the critical suspended sediment load needed in order to maintain the land balance of the Yellow River Delta for two periods before and after 1976 (the last time the channel shifted), and (2) to examine the variation in the channel geometry and gradient in response to changes in suspended sediment load and delta area at the river mouth. In order to estimate these critical values, we used statistical method to analyze the relationships between land area increment, and suspended sediment load and channel geometry. In order to examine the variation in the channel geometry, the channel cross-sections of the Q1 and Q6 were compared. The results show that to maintain the land area balance between 1953 and 1973, when the river mouth was the Diaokouhe, the critical annual suspended sediment load entering the delta was 4.21  10⁸ tonnes/a. After the main channel switched to Qingshuigou in 1976, the critical value to maintain the Qingshuigou mouth between 1976 and 1997 was 1.51  10⁸ tonnes/a. To maintain the land area balance for the entire Yellow River Delta between 1976 and 1997 the critical suspended sediment load was 3.18  10⁸ tonnes/a. The annual mean channel thalweg elevation and channel gradient at the river delta increase with increasing land area increment at the Qingshuigou mouth. The critical channel gradient at the channel reach between cross sections Q1 and Q6 is 0.000095. The channel has narrowed during the time period from 1976 to 1997. Also, lateral channel migration has decreased remarkably, resulting in enhanced hydraulic efficiency of the deltaic channel and artificial levees. This channel geometry evolution was influenced by river adjustment and human activities. These results are of importance for the management of the lower Yellow River channel and the delta. Future water diversion or river damming should consider the balance between suspended sediment delivery and delta growth.     

马尾松人工林直径分布神经网络模型研究

该文首先以相对直径为输入变量,以累积频率为输出变量,构建了1∶S∶1的林分直径分布BP神经网络模型. 用1块具有代表性、26年生、全林伐倒测定每木胸径、树高生长过程的马尾松人工林标准地直径分布数据,作为马尾松人工林的期望分布,对所建模型进行训练、用定性与定量相结合的方法,选出既符合林分直径分布规律,又具有较高拟合准确度的网络模型结构为1∶2∶1,网络对象名为FRdnet2 该模型的总体累积频率拟合准确度达99.5%,径阶累积频率拟合准确度最低93%、最高99.9%、平均99%,径阶频率拟合准确度最低82%、最高99%、平均95%. 神经网络建模技术的拟合准确度好,可作为有效的林分直径分布模拟技术.      

ULTRASONOGRAPHIC APPEARANCE OF JEJUNAL LYMPH NODES IN DOGS WITHOUT CLINICAL SIGNS OF GASTROINTESTINAL DISEASE

The jejunal lymph nodes of 57 dogs without clinical signs of gastrointestinal disease were examined to characterize their ultrasonographic appearance on B-mode and power Doppler examination, and to obtain ultrasonographic measurements. The lymph nodes were mildly hypoechoic to the mesentery in 71% of dogs and isoechoic in 29%. All dogs, 6 years of age or older had jejunal lymph nodes of uniform echogenicity. In dogs less than 6 years of age, nonuniform lymph nodes with different echopatterns were observed. Although most lymph nodes had no blood flow based on power Doppler examination, hilar blood flow was detected in 33% of dogs, which were generally less than 2 years of age. The median maximum thickness of the jejunal lymph nodes was 3.9 mm (range 1.6–8.2 mm), and their median maximum width 7.5 mm (range 2.6–14.7 mm). There was a significant correlation between larger lymph node diameter and younger age and higher body weight. We concluded that patient age should be considered when interpreting the echopattern and vascularity of jejunal lymph nodes in dogs, and that the jejunal lymph nodes of dogs without clinical signs of gastrointestinal disease may exceed the previously stated upper limit of 5–6 mm thickness.     

V带传动的计算机辅助设计

运用AutoCAD软件支持的AutoLISP程序设计语言和DCL对话框设计语言,对V带传动的计算机辅助设计系统的开发进行初步探讨。     

A comparison of needle retention on Japanese black pine and Japanese red pine

Needle retention (number of needle sets), needle density, height increment and radial increment were surveyed on seven Japanese black pines (Pinus thunbergii Parl.) and seven Japanese red pines (Pinus densiflora Sieb. et Zucc.) growing on the same site. Number of needle sets on branches with respect to whorl position was estimated visually. In 1999, maximum summer needle retention was observed on the fifth and sixth whorl from the top, with values of 3.4 needle sets for the black pines and 2.4 needle sets for the red pines, respectively. The needle trace method (NTM) was used to determine needle retention and needle density along the main stems retrospectively for the years 1968–1998. The long-term mean summer needle retention along the main stem was 3.7 needle sets for the black pines and 2.2 needle sets for the red pines. In both pine species, the number of needle sets varied from year to year. However, the long-term budget between newly born and annually shed needle sets was in equilibrium. The long-term average of needle density per cm of stem shoot was 9.4 needle pairs for the black pines and 7.4 needle pairs for the red pines. The results showed clear intra-specific and inter-specific similarities in needle retention, height increment and radial increment trends. The values for number of needle sets, height increment and radial increment positively increased with favorable growing conditions, whereas the value of needle density had an opposite tendency.     

小麦草蘑菇培养料发酵技术研究简报

不同发酵方式制备的小麦草蘑菇培养料的质量及蘑菇的产员有较大的差异。试验结果表明,在其它条件相同的情况下,室内二次发酵的培养料比室外一次发酵的增产40.8％;室外堆制发酵翻堆两次后,改小堆进行空心发酵的培养料比室外一次发酵的增产33.8%,其增产幅度同室内二次发酵的较为接近,且耗资少,省工简便。     

基于茎直径变化的作物水分状况监测研究进展

对“利用茎直径变化监测作物水分”的研究进行了综述。自20世纪60年代开始,基于茎直径变化的作物水分状况监测指标体系研究经历了两个阶段,即茎直径变化与作物水势关系的定性研究阶段;考虑环境变化和植株正常生长的茎直径变化—作物水势之间动态量化阶段。此方法通过对作物体内水分的动态监测,并与计算机应用相配合,可以用于温室和大田条件下指导适时灌溉。     

Recurrent 3‐day cycles of water deprivation for over a month depress mating behaviour but not semen characteristics of adult rams

This study aimed to investigate the effect of water deprivation (WD) on reproductive traits of rams. Ten mature rams were used and allocated to two groups balanced for body weight. Control (C) rams had free access to drinking water, while water‐restricted rams (WD) were deprived from water for 3 consecutive days and early on the morning of day 4, they had ad libitum access to water for 24 h, similar to C animals. The experiment lasted 32 days, that is eight 4‐day cycles of water deprivation and subsequent watering. Feed and water intake were significantly affected by water deprivation; in comparison with C rams, WD rams reduced their feed intake by 18%. During the watering day of the deprivation cycle, WD rams consumed more water than C rams on the same day (11.8 (SD = 3.37) and 8.4 (SD = 1.92) l respectively; p < 0.05). Glucose, total protein and creatinine were increased as a result of water deprivation. However, testosterone levels were lowered as a result of water deprivation and average values were 10.9 and 6.2 (SEM 1.23) ng/ml for C and WD rams respectively (p < 0.05). Semen traits were less affected by treatment; WD rams consistently had superior sperm concentrations than C animals; and statistical significances were reached in cycles 5 and 8 of water deprivation. Several mating behaviour traits were modified as a result of water deprivation. When compared to controls, WD rams had a more prolonged time to first mount attempt (p < 0.001), their frequency of mount attempts decreased [6.8 vs. 5.2 (SEM 0.1); p < 0.001] and their flehmen reaction intensity was negatively affected (p < 0.05). Water deprivation may have practical implications reducing the libido and therefore the serving capacity of rams under field conditions.     

Morphological indicators of stock quality and field performance of red oak (Quercus rubra L.) seedlings underplanted in a central Ontario shelterwood

The value of initial stem diameter near the root collar, shoot length and number of first-order lateral roots (FOLR) as morphological indicators of stock quality and field performance was examined for bareroot (1+0, undercut) red oak (Quercus rubra L.) underplanted in a shelterwood in central Ontario. These three attributes were measured on more than 400 seedlings prior to planting, and their relationship with height and basal diameter growth two years after planting was determined using correlation and regression analysis. Initial diameter, shoot length and number of FOLR were positively and significantly correlated with second-year height and diameter. These relationships were strongest for diameter, but this variable explained less than 25% of the total variation in growth. Of the three indicators, diameter was also the best predictor of several physical characteristics of root systems two years after planting. Initial diameter was significantly correlated with root volume, root area and lateral root, taproot and total root dry mass. Weaker relationships existed between initial shoot length and number of FOLR and second-year root system features. Stem diameter two years after planting was more strongly related to root volume, area and dry mass than was initial diameter, the probable result of adjustment in root-shoot balance of planting stock to the shelterwood environment.     

乳化剂和共乳化剂对甲维盐水乳剂乳液稳定性的影响

在筛选出合适的乳化剂和共乳化剂的基础上,研究了乳化剂亲水亲油平衡值(HLB)、含量以及共乳化剂含量对1%甲氨基阿维菌素苯甲酸盐水乳剂乳液体系稳定性的影响,以及乳化剂在54℃热贮2周的稳定性.结果表明,乳化剂的HLB可以为水乳剂的乳液稳定性提供参考依据,乳液的粒径和表面张力随着乳化剂含量的升高而减小,当乳化剂含量增大到一...