Conceptualizations of slope in Mexican intended curriculum

Slope is a fundamental mathematics concept in middle and high school that transcends to the university level. An understanding of slope is needed at the university level since slope plays an important role in understanding problems involving variation and change. In this study Mexican curricula documents were examined to determine which conceptualizations of slope are addressed in the intended mathematics curriculum. To explain the results, we use conceptualizations of slope identified in previous research. Our findings reveal that, to a certain extent, the conceptualizations proposed in the Mexican intended mathematics curriculum differ slightly in terms of the emphasis and timing of instruction from what others have identified in the U.S., with slope as a geometric ratio receiving less emphasis in the Mexican curriculum. There was also noted discontinuity within the Mexican curriculum in introducing slope in grade 9 and subsequently introducing of linear functions in grade 10 without explicit mention of slope. Suggestions are made for future studies, both to consider the conceptualizations of slope promoted in the Mexican textbooks and the impact they have in classroom instruction and student learning of slope.     

内蒙古河套灌区土壤盐分光谱定量分析研究

研究盐碱化土壤的光谱特性是利用遥感技术实现在区域尺度上进行土壤盐碱化监测和评价的工作基础。为了实现对内蒙古河套灌区土壤盐分的定量反演,于2007年7～8月间采集了河套灌区土壤样品,进行土壤化学成分及其光谱反射特性的测量。基于统计分析的方法,建立了土壤盐分与高光谱数据的偏最小二乘回归(PLSR)模型,对土壤中主要盐分参数进行了反演实验。独立验证结果表明,对全盐(S%)、硫酸根离子(SO2-₄)、pH值以及钾、钠总含量(Ka++Na+)有较好的反演精度,验证数据的决定系数R2分别是0.728,0.801,0.715和0.734,预测方差比(RDP)分别是1.79,1.87,1.64,1.63。将以上参数的PLSR模型回归系数聚合在TM的可见光(蓝色、绿色、红色)和近红外波段时,回归系数在数值上均有显著反应。研究结果为在航空航天遥感尺度上实现土壤盐分的定量反演提供了理论基础和实验依据。     

Measurement of Slopes of a Deformed Object Corresponding to Different Directions with Digital Holography

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｓｔｒｅｓｓａｎａｌｙｓｔｓａｒｅｏｆｔｅｎｉｎｔｅｒｅｓｔｅｄｉｎｔｈｅｄｅｒｉｖａｔｉｖｅｓｏｆｔｈｅｄｉｓｐｌａｃｅｍｅｎｔｒａｔｈｅｒｔｈａｎｔｈｅｄｉｓｐｌａｃｅｍｅｎｔｉｔｓｅｌｆ ,ｂｅｃａｕｓｅｓｔｒａｉｎｓａｎｄｈｅｎｃｅｓｔｒｅｓｓｅｓａｒｅｆｉｒｓｔ ｏｒｄｅｒｄｅｒｉｖａｔｉｖｅｓｏｆｄｉｓｐｌａｃｅｍｅｎｔ.Ｔｈｅｄｅｒｉｖａｔｉｖｅｓｃａｎｂｅｏｂｔａｉｎｅｄｎｕｍｅｒｉｃａｌｌｙｆｒｏｍｔｈｅｄｉｓｐｌａｃｅｍｅｎｔｄａｔａｂｕｔｔｈｅｐ…     

有限外尺度对大气湍流统计特征测量的影响

有限外尺度影响下的相位结构函数和孔径平均的斜率相关函数的表达式,结果表明有限的大气外尺度对大气流流统计特征的测量有很大的影响,尤其对大尺寸的望远镜和子孔径更是如此。基于科尔莫戈罗夫模型的大气相位结构函数和相干长度仅仅是本文推导结果的近似。对结果的分析表明,测量得到的对大气湍流科尔莫戈罗夫模型的偏离有可能是大气外尺度的影响,而不完全是真正的偏离。     

土壤非光滑表面电渗粘附的试验优化技术研究

阎备战等．土壤非光滑表面电渗粘附的试验优化技术研究．数理统计与管理，１９９８，１７（２），１７～２１．本文应用正交多项式试验优化技术，对非光滑表面电渗原理进行了试验设计，探讨了非光滑表面电渗技术的两个重要影响因素对土壤粘附产生的影响作用，揭示了一定条件下直流电渗电压与电渗时间对粘附力的影响规律。     

秩协方差分析及应用

吴占鹏．秩协方差分析及应用．数理统计与管理，１９９８，１７（３），７～１０．在随机区组试验中，区组内往往存在土壤梯度差异，使试验误差增大。为此，本文提出秩协方差分析方法，即把土壤差异εｉｊ分解成Δ·ｘｉｊ和δｉｊ两个成份，从中剔除土壤梯度差异Δ·ｘｉｊ对试验精度的影响，以提高试验结果的可靠性     

直立顺层边坡的黏弹性稳定分析

直立边坡的失稳与岩体的流变性质密切相关，其在一定载荷作用下失稳表现出延迟特性。采用自重作用下的梁柱力学模型，考虑岩石的流变性，给出了不同材料模型下直立边坡的极限坡高及其分析方法。     

Overwinter changes to near-surface bulk density, penetration resistance and infiltration rates in compacted soil

Previous studies at Yakima Training Center (YTC), in Washington State, suggest freeze-thaw (FT) cycles can ameliorate soil compacted by tracked military vehicles [J. Terramechanics 38 (2001) 133]. However, we know little about the short-term effects of soil freezing over a single winter. We measured bulk density (BD), soil penetration resistance (SPR), and steady-state runoff rates in soil newly tracked by an Abrams tank and in uncompacted soil, before and after a single winter at YTC. We similarly measured BD, SPR and saturated hydraulic conductivity (k_fs) in simulated tank tracks at another site near Lind Washington. Average BD was significantly greater in tank ruts at YTC and in simulated tracks at the Lind site than in uncompacted soil soon after tracking and did not change significantly during the winter of 1997–1998. Measurements of SPR were strongly influenced by soil moisture. When soil was moist or tracks were newly formed, SPR was significantly higher in tank ruts than in uncompacted soil from the surface to a depth of about 10–15 cm. The greatest average SPR in compacted soil was observed between 4 and 6 cm depth. We observed less difference in SPR between tank ruts and uncompacted soil near-surface at YTC as the time after trafficking increased. We observed highest SPR ratios (compacted rut:undisturbed) in fresh tracks near the surface, with lower ratios associated with increasing track age or soil depth, indicating that some recovery had occurred at YTC near-surface. However, we did not observe a similar over-winter change in SPR profiles at the Lind site. Rainfall simulator data from YTC showed higher steady-state runoff rates in tank ruts than over uncompacted soil both before and after winter. However, more time was required to reach steady-state flow in tank ruts and the proportion of runoff was slightly lower in May 1998 than in August 1997. At the Lind site, k_fs was lower in newly compacted soil than in one-year old compacted soil or uncompacted soil. Our data suggest that indices of water infiltration such as steady-state runoff rates or k_fs, are more sensitive indicators of soil recovery after compaction than are BD or SPR.     

应用特征波段和反射变形差的方法进行土壤属性估算

传统的土壤分析是昂贵的、费时的并且可能带来环境污染问题。应用近红外光谱分析技术测定土壤参数具有快速、花费少和非破坏性的特点。利用GPS野外定位,在江西省的红壤站、鄱阳湖站和千烟州站周边共取得41个耕层(0～20 cm)土壤样品。通过对土壤样品高光谱反射率的室内分析测定,研究了土壤在紫外/可见光/近红外波段光谱的反射特性。研究的目的是应用波谱反射建立一个新的研究方法来估算土壤属性含量值。随后应用多元线性逐步回归方法对反射光谱数据进行分析,“B22+H13”光谱数据作为自变量,土壤属性含量作为因变量,建立了土壤属性含量的高光谱预测模型, 并对模型的稳定性和预测能力进行了检验。结果是土壤的pH、有机碳、全氮、全磷、阳离子代换量和碱解氮的相关系数都达到了0.80,而TK、速效磷、速效钾的相关系数在0.68左右。结果表明,应用此方法估算一些土壤属性含量是可行的。     

旋转锥镜相机研测动态曲率和斜率

采用旋转锥镜相机，进行激光散斑剪切照相，研测缓慢变形物体的动态曲率和斜率。拍摄一张散斑图即可获得曲率和斜率动态变化的全过程。