从“消极差别化”到“积极差别化”——义务教育资源配置政策的创新逻辑

通过对义务教育政策变迁的"路径依赖"分析,探讨了义务教育城乡失衡问题的制度根源及其破解路径。国家对农村教育和城市教育实行不同的资源分配政策,导致了义务教育发展的城乡失衡。要促进义务教育的均衡发展,必须实行重点向农村倾斜的积极差别化政策,在财政投入、师资力量、资金援助等方面优先考虑农村,以推动农村义务教育的快速发展。

THE STOCHASTIC ESTIMATION OF SATELLITE CLOCK CORRECTION INFORMATION IN WADGPS

Using autocorrelation information of the pseudorange errors generated by se- lective availability (SA) frequency dithering, we have constructed a simple first order stochas- tic model for SA effects. This model has been used in a Kalman filter to account for the stochastic behavior of SA dithering in estimating satellite clock information in wide area dif- ferential GPS. We have obtained fifteen percent improvement in the user positioning using the correlation information on the satellite clock information in a Kalman filter, when comparing the results obtained using a regular least square estimation.

MORPHOLOGICAL STUDY OF FETAL NEOCORTICAL TRANSPLANT GRAFTED TO THE CEREBRAL CORRESPONDING AREA IN YOUNG RATS DIFFERENTIATION OF IMMATURE NEURONS AND RECIPROCAL CONNECTIONS OF FIBERS BETWEEN GRAFT-HOST BRAIN

The fetal neocortical transplant (E15-17 days gestation) of Wistar rat was grafted to the corresponding neocortical region (frontal-parietal lobe) of the same strain in young rats (4-5 weeks old). On the 7th, 15th, 30th, 60th, 150th day after transplantation, the sections cut through the middle area of graft-ost brain were examined by HE, Nissl, Glees stain, immunohistochemical technique for GFAP and NF, Nissl, Glees stain, immunohistochemical technique for GFAP and NF, acetylcholinesterase (AChE) histochemistry as well as horseradish peroxidase (HRP) retrograde tracing with light microscope. Some of the sections were also examined with TEM. The result showed that most immature neurons within the graft can survive, grow, differentiate and mature, and are similar to the structure of the neocortical neurons of host brain. This study also provides patterns of integration of the interface between graft-host brain varying with the proliferation of reactive astrocyte as well as graft-host reciprocal connection of fibers.

An adaptive limited wide area differential protection for power grid with microsources

The operation mode of power grids with intermittent distributed generations(DGs)changes frequently due to the bidirectional power flow.In comparison with the conventional grids,the protection relays in power grids with micro-sources are more difficult to set.To tackle this problem,this paper proposes an extended bus differential protection(EBDP)strategy based on the limited wide area(LWA).In this method,the micro-grids are divided into several protection areas at the core of the bus.The whole protection areas are protected by the wide area current differential relays,which are also configured to protect each component in this protection area.Moreover,the protection areas can be changed adaptively according to the power flow direction.Finally,a micro-grid model with multiple DGs is developed using the PSCAD/EMTDC platform.The simulation results indicate that the proposed adaptive limited wide area differential protection(LWADP)has better performance than the traditional relaying protection in detecting the faulty area in micro-grids and isolating the fault,and can be widely utilized in larger micro-grids.

Influence of the GEO satellite orbit error fluctuation correction on the BDS WADS zone correction

Decimeter-level service is provided by the BeiDou satellite navigation system wide area differential service(BDS WADS)for users who collect carrier phase measurements.However,the fluctuations in Geostationary Earth Orbit(GEO)satellite orbit errors reduce the spatial correlation of orbit errors.These fluctuations not only decrease the accuracy and stability of zone correction service provided by BDS WADS,but also shorten its effective range.In this paper,we proposed an algorithm to weaken the influence of GEO satellite orbit error fluctuations and verified the method using data from eight sparsely distributed zones.The results show that orbit errors can be stabilized using orbit fluctuation corrections,and the positioning precision and stability of the BDS WADS can be improved simultaneously.Under normal circumstances,the horizontal and vertical positioning accuracy of users within 1000 km from the center of the zone can reach 0.19 m and 0.34 m.Furthermore,the effective range is increased.The positioning performance within 1800 km could reach 0.24 m and 0.38 m for the horizontal and vertical components,respectively.