列车轮群激励的频谱

本文提出：由于列车的运行，线路在通过列车轮群周期性力作用下强迫振动，因而，线路振动是不可避免的。通过对列车轮群激励的频谱分析，指出了它们主要集中在数十赫芝以内，对线路自振动频率较低的下部结构物特别有害，在设计高速铁路线路和旧线提速改造时对它们的破坏作用应予以重视。

基于间歇式的簇首选择的WSNs分层路由

为了降低无线传感网络(Wireless Sensor Networks, WSNs)中分簇路由的能耗,提出基于间歇式的簇头选择的能量感知的分簇路由(Intermittent Cluster Head Selection-based energy-aware clustering protocol, ICHS-CP)。ICHS-CP引用集中式分簇路由思想,它仅在每个轮群(Group of Rounds, GOR)的开始选择簇头,而不是传统集中协议每轮选择簇头,降低了重复CHs选择过程的能量成本。同时,基站保证了轮群的固定的簇头数,并基于六边形网络拓扑均衡簇头分布。仿真结果表明,提出的ICHS-CP协议提高了能量效率,延长了第一个失效节点的发生时间。

Recurrent Selection for Improving Quality Characters of Male Sterile Restorer Lines of Brassica napus

[Objective] This study aimed to improve the quality characters of the male sterile restorer lines of Brassica napus by recurrent selection. [Method] The dominant male sterile alleles were used as outcross medium to be transformed with the favourable genes from thirteen materials, and finally excellent restorer materials were bred by recurrent selection. After that, the genetic diversity, genetic gains, fatty acid chain length and unsaturarion ratios of the improved populations were analyzed. [Result] The genetic diversity and genetic gains were obviously improved by the recurrent selection. Nine materials whose oil content exceeding 50% and 14 materials whose protein content exceeding 30% were acquired, and crossed with sterile lines. The comparative experiment showed that there were 11 combinations whose oil content was obviously enhanced compared with the control. [Conclusion] Recurrent selection is an effective way to improve the quality characters of the objective pop- ulations and breed favourable male sterile restorer lines of B. napus.

Numerical Hydrodynamics Study Around Turbine Array of Tidal Stream Farm in Zhoushan, China

In recent decades,great efforts have been made to efficiently explore tidal stream energy due to its unique advantages of easy prediction and great potential.China recently launched a national tidal stream farm demonstration project in the waterway between Putuoshan and Hulu Islands in the Zhoushan area.Before deployment of the turbine array,it is necessary to understand the hydrodynamic changes associated with the construction of a turbine array.In this study,we developed a depth-averaged hydrodynamics model that solves the shallow water governing equations to simulate the tidal hydrodynamics around the Zhoushan Archipelago.The simulation results agree with field data in terms of the water elevation and stream velocity.We considered two types of turbine arrays in this study and investigated their impacts on the local hydrodynamics.In general,the stream velocity in the northern and southern areas is reduced due to the power take-off of the turbine array,whereas stream velocity in the western and eastern areas is slightly increased due to the blockage impact of the turbine array.

Rotifer community structure and assessment of water quality in Yangcheng Lake

Rotifer community structure was investigated in Yangcheng Lake in 2008. Dominant species and species diversity indices were determined and QB/T was used to assess water quality. The annual average density and biomass of the rotifers in Yangcheng Lake was 2 894＋ 1 006 indYL and 12.47± 10.28 mg/L, respectively. The highest densities were observed in the western portion of the lake in March, but the highest biomass occurred in inflowing creeks in September. Within a year of monitoring in Yangcheng Lake, 93 species were identified and the dominant species were found to be Polyarthra trigla, Brachionus angularis, Keratella eochlearis, Keratella valga, Brachionus calyciflorus, and Filinia major. Of the species recorded, 75 were pollution indicator species. Density and biomass exhibited significant positive correlations with water temperature （R=0,209, P=0.003; R=0.446, P=0.000）, but the peak density showed two lags in response to chl a. According to the Jaccard similarity index （S0, the greatest similarity among dominant species occurred between creeks and the eastern part of the lake. The annual average Shannon-Wiener diversity index H＇, Margalef richness index D and Pielou evenness index J were 1.96±0.34, 1.61±0.50 and 0.77±0.10, respectively. In all four areas of Yangcheng Lake, β- mesosaprobic species comprised the largest share of pollution indicator species. These data suggest that Yangcheng Lake is mesosaprobic.

Bacterial Flora of Water and Rotifers in Outdoor Mass Culture Tanks Fed with Different Microalagal Diets

Investigations were carried out on the bacterial flora of water and the quality of rotifers in outdoor mass culture tanks. Brachionus plicatilis and B. rotundiformis were cultured in 10 numbers of 1 tonne tanks and the physico-chemical parameters and microbial loads of water, and total bacterial and Vibrio loads of microalgae and rotifers, during the period 2014-15, were studied. The study revealed a significant variation of the ammonia levels and total bacterial loads with different diets （P 〈 0.05）. A positive correlation was observed between the total bacterial loads of algal concentrations and loads of rotifers, but no correlation was observed between Vibrio loads of water and rotifers. The prevalence of Vibrio loads of rotifers was low in tanks fed with Nannochloropsis oculata and maximum Vibrio loads were recorded in Chaetoceros calcitrans fed rotifers. The Vibrio loads significantly varied with days of culture and also with the algal diets. A positive correlation was observed between the total Vibrio loads of water and rotifers.

Monitoring method of gear teeth failure of hydraulic gear pump based on improved VMD and DBN-DNN of electrical signal

Abundant system operation state information is included in the electrical signal of the hydraulic system motor.How to accurately extract and classify the operation information of electrical signal is the key to realize the condition monitoring of hydraulic system.The early fault characteristics of hydraulic gear pump hidden in the motor current signal are weak and difficult to extract by traditional time-frequency analysis.Based on the correlation coefficient and artificial bee colony algorithm(ABC),the parameter optimization of variational mode decomposition(VMD)is realized in this paper.At the same time,the principle of maximum signal correlation coefficient and kurtosis value is adopted to determine the effective intrinsic mode function(IMF).Moreover,the permutation entropy(PE)and root mean square(RMS)of the effective IMF components are input into the deep belief network(DBN-DNN)as high-dimensional feature vectors.The operation state of gear pump is monitored.The results show that the weak characteristics of current signal of gear pump fault are accurately and stably extracted by this method.The running state of gear pump is monitored and the accuracy of gear fault diagnosis is improved.

The Effect of Crop Rotation on Soil Nematode Community Composition in a Greenhouse

[Objective] The aim was to identify changes in a nematode community in response to crop rotation and to determine the appropriate catch crop for a greenhouse. [Method] The experiment was carried out in a typical 6-year-old greenhouse,in which cucumber crops were cultivated twice each year(in spring and autumn),and catch crops were planted in summer. The total number of nematodes was counted and nematode community indices were calculated after collecting soil samples in different stages. [Result] Total nematode abundance was decreased in the soils of catch crop in contrast with former crops(cucumber crops). The abundance of the nematode community was reduced in the treatment of crop rotation compared to the soils of catch crop. In addition, the number of nematode taxa was significantly reduced by the treatment of crown daisy compared to the treatments of following crops. Crop rotation regulated the functional composition of the nematode community by increasing the omnivores-predators functional group and decreasing the relative abundance of root herbivores. [Conclusion] These results indicate that crop rotation affects the nematode community in abundance, diversity and functional composition of the nematode community and crown daisy can be served as the most appropriate catch crop in the greenhouse.

Vegetation Recovery in Karst Areas in Central Guizhou, China

Due to the unique environment of karst landscapes, there are many uncertainties regarding the recovery of vegetation following human disturbance. Through standard wood parsing and growth ring investigation in Puding county in Guizhou province, China, we studied the process of vegetation restoration in karst areas. According to our results, during the recovery of karst vegetation height increases and ground diameter enlargement of tree layers occurred. Increases in the height and ground diameter followed logarithmic and growth curves, respectively. The development time of trees showed continuity, and growth points were randomly distributed. However, with large propagule quantities, vegetation can be directly restored and developed into a secondary high forest without a grass filling stage, and the recovery time is shortened.