强化制种基地管理 保障玉米良种有效供给

近年来,随着玉米品种审定制度的变化,审定渠道增加、速度加快,带来玉米新品种审定数量多、基地制种生产面积多、供应市场种子数量多,导致玉米种子严重过剩,供大于求。供需关系决定价格,由于供应量大且都急于销售,互相压价倾销,导致销售市场无序竞争,加上农民鉴别能力差,购买种子全凭经销商推荐,优质产品不能实现优价,其结果是种子质量良莠不齐,种子企业经营量上去了利润却在下降,最后导致经营困难,研发创新能力不足。因此要强化玉米制种生产基地管理,从种子生产源头抓起,进行供给侧改革,尽量减少制种品种,合理降低生产面积,严格管理提高产品质量,科学谋划稳定供给,才能促进种子行业良性健康发展。

Flyash properties and analysis of flyash dam stability under seismic load

This article discusses the flyash mechanical properties and analyzes stability of two flyash dams under earthquake by finite element methods. It is studied whether the mixture of flyash and clay can be used as the fill for a dam located in an earthquake region.

An Experimental Investigation on the Stability of Foundation of Composite Vertical Breakwaters

A series of 2D model tests were conducted to assess the foundation stability of composite vertical breakwaters. In this paper, the results from the experimental study are presented conjointly with a formula to estimate the stability number of foundation, which is the most important parameter for evaluation of foundation stability of such structures. The influences of wave height, wave period and the berm width on the stability of compo^ite breakwaters with different armor stone sizes were investigated. Forty-five tests were performed to cover the influences of these parameters. According to the present research, berm width is a significant parameter concerning erosion of armor foundation. As the berm width increases, the amount of berm erosion decreases. Comparisons are made between results of present study and the estimated stability number proposed by Kimura et al. （1994）, which is extension of Tanimoto formula. Results show that the later formula underestimates the stability number. However, by applying an enhancement factor about 1.7 meters to Kimura et al. formula, results correlated with the present experimental results..

Map-based control method for vehicle stability enhancement

This work proposes a map-based control method to improve a vehicle's lateral stability, and the performance of the proposed method is compared with that of the conventional model-referenced control method. Model-referenced control uses the sliding mode method to determine the compensated yaw moment; in contrast, the proposed map-based control uses the compensated yaw moment map acquired by vehicle stability analysis. The vehicle stability region is calculated by a topological method based on the trajectory reversal method. A 2-DOF vehicle model and Pacejka's tire model are used to evaluate the proposed map-based control method. The properties of model-referenced control and map-based control are compared under various road conditions and driving inputs. Model-referenced control uses a control input to satisfy the linear reference model, and it generates unnecessary tire lateral forces that may lead to worse performance than an uncontrolled vehicle with step steering input on a road with a low friction coefficient. However, map-based control determines a compensated yaw moment to maintain the vehicle within the stability region,so the typical responses of vehicle enable to converge rapidly. The simulation results with sine and step steering show that map-based control provides better the tracking responsibility and control performance than model-referenced control.

Stress and Displacement Distribution of Soft Clay Slope with 2D and 3D Elastoplastic Finite Element Method

Based on elastoplastic model, 2D and 3D finite element method （FEM） are used to calculate the stress and displacement distribution in the soft clay slope under gravity and uniform load at the slope top. Stability analyses indicate that 3D boundary effect varies with the stress level of the slope. When the slope is stable, end effect of 3D space is not remarkable. When the stability decreases, end effect occurs; when the slope is at limit state, end effect reaches maximum. The energy causing slope failure spreads preferentially along y-z section, and when the failure resistance capability reaches the limit state, the energy can extend along x-axis direction. The 3D effect of the slope under uniform load on the top is related to the ratio of load influence width to slope height, and the effect is remarkable with the decrease of the ratio.

Pre-evaluation on stability of proposed expressway embankment with existing geothermal regulation measures in permafrost regions

Embankment stability is the primary problem for the expressway construction in permafrost regions.The proposed Qinghai-Tibet Expressway(QTE)is planned to construct along the Qinghai-Tibet Project Corridor.Confronted with harsh environmental condition and intense heat exchange between earth and atmosphere,it is necessary to predict and evaluate the stability of the proposed QTE.In this study,the factors affecting the embankment stability are analyzed firstly.And then,a scheme for the stability evaluation of the embankment is established.Finally,the evaluation scheme is used for the pre-evaluation of the stability for the proposed QTE with different geothermal regulation measures(GRMs).The results indicate that the influencing factors include climatic environment,permafrost property,engineering condition and geological condition,and among them,engineering condition and permafrost property are the main influence factors for embankment stability.The stability of the proposed QTE varies greatly in the different geomorphological regions.The application effect and contribution to embankment stability of the existing GRMs are different,and using GRMs cannot completely overcome the influence of various factors on expressway stability.In the construction process,different GRMs should be adopted depending on the geomorphological environment where the embankment is located to ensure the embankment stability.

Application of probability integral method in ground deformation prediction

In order to study the law of mining subsidence and ground movement, to provide the basis of coal mining under building, railway and water, we used the probability integration method to make comprehensive evaluation of ground stability. Take Yingcheng Coal Mine of Jiutai as an example. Mining-induced movement and horizontal movement are analyzed on the basis of the measurement data. The resuhs of prediction can pro- vide reference and basis for prevention of coal mining subsidence and future restoration and treatment.

Influence of filling velocity on stability of subgrade with marine soft soil

Filling velocity and thickness of soft layer are major factors affecting subgrade stability according to an example study by means of finite element stress method(FESM). A case is studied and shows that the subgrade was slided because of excessive filling velocity. To determine a reasonable filling velocity is a key problem to a subgrade with marine soft soil.

Stability Study on Hydroelectric Production Site Using Eigenvalues Analysis Method

The eigenvalues analysis method is generally applied to synchronous machines by using d, q-components. This paper presents the application of this method on an equivalent model for the synchronous machine based on phase variables a, b, c instead of d, q-components. The advantages of this approach, essential for programs using phase variables as state variables, are presented. The application of this method to a complete hydroelectric production site including hydraulic components （pump-turbine, penstock, gallery, reservoir...） permits the study and analysis of the interactions between the hydraulic, electric and regulation parts of the system. Results coming from the proposed eigenvalues analysis method and the numerical simulations confirm the interest of the presented approach.

Histone 3 lysine 36 to methionine mutations stably interact with and sequester SDG8 in Arabidopsis thaliana

Post-transcriptional modifications of histones play important roles in various biological processes. Here, we report that Arabidopsis plants overexpressing histone H3 lysine to methionine mutations at histone H3.1K36(H3.1K36M) and H3.3K36(H3.3K36M) have serious developmental defects with early-flowering and change in the modifications of endogenous histone H3, including acetylation at lysine 9(H3K9ac), trimethylation at lysine 27(H3K27me3), di-and tri-methylation at lysine 36(H3K36me2 and H3K36me3). In addition, H3K36M mutation alters its subcellular localization and interacts with H3K36 methyltransferase SDG8. Our results support a model in which H3K36M stably interacts with SDG8, and inhibits the activity of SDG8 by sequestering SDG8, resulting in a dominant negative effect to affect the proper expression levels of a variety of genes and plant development.

Timing,scale and mechanism of the destruction of the North China Craton

The North China Craton (NCC) is a classical example of ancient destroyed cratons.Since the initiation of the North China Craton Destruction Project by the National Natural Science Foundation of China,numerous studies have been conducted on the timing,scale,and mechanism of this destruction through combined interdisciplinary research.Available data suggest that the destruction occurred mainly in the eastern NCC,whereas the western NCC was only locally modified.The sedimentation,magmatic activities and structural deformation after cratonization at ～1.8 Ga indicate that the NCC destruction took place in the Mesozoic with a peak age of ca 125 Ma.A global comparison suggests that most cratons on Earth are not destroyed,although they have commonly experienced lithospheric thinning;destruction is likely to occur only when the craton has been disturbed by oceanic subduction.The destruction of the NCC was coincident with globally active plate tectonics and high mantle temperatures during the Cretaceous.The subducted Pacific slab destabilized mantle convection beneath the eastern NCC,which resulted in cratonic destruction in the eastern NCC.Delamination and/or thermal-mechanical-chemical erosion resulted from the destabilization of mantle convection.