度量经验与量感发展——以人教版教材二年级下册“克与千克”教学为例

量感,主要是指对事物的可测量属性及大小关系的直观感知。量感源于度量,对学生量感的培养应指向度量经验的积累。教师以“克与千克”课例为载体,围绕“对接数感经验,丰富表象感知‘量’”“对比构建标准,具身体验学习‘量’”“推理应用联结,反思辨析内化‘量’”三大策略,借助“十进制”,帮助学生积累克与千克的度量经验,发展学生的量感。

基于数学活动,在度量教学中培育量感

量感是学生形成抽象能力和应用意识的基础,量感的培育有助于学生养成用定量的方法认识和解决问题的习惯,度量教学中的量感培育,应注重引导学生在测量活动中积累度量经验,在想象推理活动中关联度量单位,在估测活动中丰富度量表象。

会计稳健性经验度量模型的批判与发展

如何对会计稳健性实施有效的经验度量,是长期以来困扰会计实证研究的重大难题,Basu提出的不对称及时性概念有效地解决了这一难题,从而极大地促进了有关会计稳健性的实证研究。但Basu模型并非完美无缺,文章的目的就是对该模型提出的背景以及其他学者对该模型的批判与发展做出系统性的回顾与评价。

立足本质 分层建构--《角的度量》教学再思考

《角的度量》一课教学,教师借助学生已有的知识经验,以回顾度量长度和面积的方法为开篇,通过分层设计量角活动,让学生在实际测量的需求中,经历创造量角器模型的过程、认识度量角的本质,从而自主建构运用量角器度量角度的认知结构,形成技能.

Temporal Variations of Water Discharge and Sediment Load of Huanghe River,China

Based on the data from gauging stations, the changes in water discharge and sediment load of the Huanghe （Yellow） River were analyzed by using the empirical mode decomposition （EMD） method. The results show that the periodic oscillation of water discharge and sediment load of the Huanghe River occurs at the interannual, decadal, and multi-decadal scales, caused by the periodic oscillations of precipitation, and E1 Nifio/Southern Oscillation （ENSO） af- fects water discharge by influencing precipitation distribution and contributes to periodic varations in precipitation and water discharge at interannual timescale. The water discharge and sediment load of the Huanghe River have decreased since the 1960s under the influence of precipitation and huamn activities, and human activities attribute more than precipitation to the reduction in the water discharge and sediment load, furthermore, water abstraction and water-soil conservation practices are the main causes of the decrease in water discharge and sediment load, respectively. The reduction in sediment load has directly impacted on the lower reaches of the Huanghe River and the river delta, causing considerable erosion of the river channel in the lower reaches since the 1970s along with River Delta changing siltation into erosion around 2000.

Effective forecast of Northeast Pacific sea surface temperature based on a complementary ensemble empirical mode decomposition–support vector machine method

The sea surface temperature （SST） has substantial impacts on the climate; however, due to its highly nonlinear nature, evidently non-periodic and strongly stochastic properties, it is rather difficult to predict SST. Here, the authors combine the complementary ensemble empirical mode decomposition （CEEMD） and support vector machine （SVM） methods to predict SST. Extensive tests from several different aspects are presented to validate the effectiveness of the CEEMD-SVM method. The results suggest that the new method works well in forecasting Northeast Pacific SST at a 12-month lead time, with an average absolute error of approximately 0.3℃ and a correlation coefficient of 0.85. Moreover, no spring predictability barrier is observed in our experiments.

Relationship Between Upper-Ocean Heat Content in the Tropical Indian Ocean and Summer Precipitation in China

An analysis of the Ishii ocean heat content(OHC) in the tropical Indian Ocean from the surface to 700-m depth shows that the OHC changes dramatically on the interannual timescale in the Indian Ocean.The first mode of empirical orthogonal function(EOF1) of the OHC shows that there is a strong air-sea interaction pattern in the Indian Ocean with a positive(negative) loading in the east and a negative(positive) loading in the west.This seesaw oscillation pattern influences the summer precipitation in China with a North-South reversed distribution.Composite analysis shows that during a positive(negative) OHC episode,an anomalous cyclonic(anticyclonic) circulation over the western Pacific and South China weakens(enhances) the monsoonal northward flow in the lower troposphere;meanwhile,anomalous meridional circulation connects the descending(ascending) branch over the Southeast Indian Ocean and the ascending(descending) branch in South China as well as a descending(ascending) branch over North China.Analysis of the mechanism behind these features suggests that(1) the accumulation of OHC-induced vorticity is related to the wave activity over the mid-latitudes and that(2) the meridional teleconnection induced by the Indo-Pacific air-OHC interaction appears over East Asia and the western Pacific.Both of these patterns can cause summer precipitation anomalies in China.

Estimation of tensile strength of ductile iron friction welded joints using hybrid intelligent methods

A hybrid intelligent method for evaluation of near optimal settings of friction welding process parameters of ductile iron was presented, The optimization of welding parameters was carried out in automatic cycle with the use of support vector regression （SVR）, genetic algorithm （GA） and imperialist competitive algorithm （ICA）. The method suggested was used to determine welding process parameters by which the desired tensile strength was obtained in the friction welding of ductile iron. The highest tensile strength （TS） of 256.93 MPa was obtained using SVR plus GA method for the following friction welding parameters： heating force 40 kN, heating time 300 s and upsetting force 10.12 kN. The samples were welded by friction and subjected to the tensile strength test. The optimized values obtained by means of these hybrid techniques were compared with the experimental results. The application of hybrid intelligent methods allowed to increase the tensile strength joints from 211 to 258 MPa for the friction welder ZT-14 type.

Inter-comparison of seasonal variability and nonlinear trend between AERONET aerosol optical depth and PM10 mass concentrations in Hong Kong

Here we used Empirical Mode Decomposition （EMD） method to study seasonal variability and nonlinear trend of corrected AERONET Aerosol Optical Depth （AOD/Hi） and corrected PM10 mass concentrations （PMmxf（RH）） in Hong Kong during 2005-2011. AODPrli is highly correlated with PMI0xf（RH） in semi-annual and annual time scales （with correlation coefficient 0.67 for semi-annual and 0.79 for annual components, 95% confidence interval）. On the semi-annual scale, both AOD/Hi and PM10xf（RH） can capture the two maxima in March and October, respectively, with much stronger amplitude in March proba- bly due to the long-range transport of dust storm. On the annual cycle, the AOD/Hi and PMI0xf（RH）, which are negatively correlated with the precipitation and solar radiation, vary coherently with the maxima in February. This annual peak occurs about one month earlier than the first peak of the semi-annual variability in March, but with only half amplitude. During 2005-2011, both AOD/Hi and PM10xf（RH） exhibit the pronounced decreasing trend with the mean rate of 14 gg m-3 per year for PM10xf（RH）, which reflects the significant effects of the air pollution control policy in Hong Kong during the past decade. The nonlinear trend analysis indicates that the decreasing of PM10xf（RH） is slower than that of AOD/Hi when the AOD/Hi is less than 0.44 but becomes faster when the AOD/Hi exceeds 0.44. These results illustrate that the AERONET AOD can be used quantitatively to estimate local air-quality variability on the semi-annual, annual, and long-term trend time scales.