生物教学中多媒体技术与合作学习模式的互补应用

近年来国内引入一系列国外效果较好的教学理论以进行新一轮课程改革.其中多媒体技术成为学生感性认识生物的有利工具,合作学习成为培养学生自主学习能力的有效模式.两者在国内教学推广中效果显著,但其中存在着不可忽略的问题.本文将分析两者在高中生物教学应用中各自出现的问题,提出两者恰当结合解决问题的策略,以期高中生物教学更好地达到新课改的目标.     

位移性在拉普拉斯变换中的应用

本文利用位移性,通过变量代换将非零初始条件转化零初始条件,拓宽了拉普拉斯变换法的使用范围.     

一类无非平凡有理整点的椭圆曲线y~2=x(x-p)(x-q)

令p、q为两个素数,且p+4=q。本文证明了椭圆曲线y2=x(x-p)(x-q)没有非平凡有理整点.同时得到了一类无整解的负Pell方程组和一类无整解的四次丢番图方程.     

文科生大学数学学习情况调查研究

通过对文科大一与大三学生的抽样调查,采用问卷调查、课堂观察和深度访谈这三种方法,对其数学学习情况进行了具体的分析研究,由此发现文科教材中存在的问题:中学与大学的过渡环节较为欠缺以及教材内容的构成成分有待完善.     

Effect of Ce addition on hot tearing behavior of AZ91 alloy

A small amount of cerium (below 1.0 wt%) addition to AZ91 alloy have been investigated on the hot tearing susceptibility (HTS) at a cooling rate of 1.5Ks^?1. The HTS increased to a maximum value with a cerium addition of 0.6 wt% and then decreased to a stable status as cerium was gradually added. Due to high chemical activity, cerium into the melts can react with aluminum to form an Al₁₁Ce₃ intermetallic compound. X–ray diffraction results also confirmed the existence of Al₁₁Ce₃. The Al₁₁Ce₃ increased with the presence of the needle-like and block morphology. As cerium levels increased, the amount of Mg₁₇Al₁₂ decreased. The variations between Mg₁₇Al₁₂ and Al₁₁Ce₃ resulted in a similar normal distribution of the HTS in AZ91 alloy. The findings were further verified through the microstructure evolution and the surface morphology of fracture.     

毛花猕猴桃果实发育过程中理化性质的变化研究

为深入了解猕猴桃果实生长发育规律及果实商品价值,本研究以四川地区野生毛花猕猴桃果实为材料,采用田间取样和实验室测定相结合的方法测定其果实发育过程中理化性质变化.结果显示果实重量、纵横径和干物质积累呈单‘S’型曲线.果实淀粉积累时间短,果糖和葡萄糖从盛花期(DAA)105 d开始急剧上升,果实成熟时生成少量的蔗糖和麦芽糖.苹果酸和柠檬酸浓度整体呈上升趋势,而奎宁酸在90 DAA前保持相对恒定,105 DAA时下降到最低,后保持稳定.VC含量高,整体呈下降趋势.以上结果说明毛花猕猴桃果树园艺性状好,其果实有机酸含量高,特别是VC,是天然维生素库.     

New rapid transfer alignment method for SINS of airborne weapon systems

Transfer alignment is an effective alignment method for the strapdown inertial navigation system （SINS） of airborne weapon systems. The traditional transfer alignment methods for large misalignment angles alignment use nonlinear transfer align- ment models and incorporate nonlinear filtering. A rapid transfer alignment method with linear models and linear filtering for ar- bitrary misalignment angles is presented. Through the attitude quaternion decomposition, the purpose of transfer alignment is converted to estimate a constant quaternion. Employing special manipulations on measurement equation, velocity and attitude linear measurement equations are derived. Then the linear trans- fer alignment model for arbitrary misalignment angles is built. An adaptive Kalman filter is developed to handle modeling errors of the measurement noise statistics. Simulation results show feasibili- ty and effectiveness of the proposed method, which provides an alternative rapid transfer alignment method for airborne weapons.     

（1-uv）-CONSTACYCLIC CODES OVER Fp＋uFp＋vFp＋uvFp

Constacyclic codes are an important class of linear codes in coding theory.Many optimal linear codes are directly derived from constacyclic codes.In this paper,（1 — uv）-constacyclic codes over the local ring Fp ＋ uFp ＋ vFp ＋ uvFp are studied.It is proved that the image of a（1 — uv）-constacyclic code of length n over Fp ＋ uFp ＋ vFp ＋ uvFp under a Gray map is a distance invariant quasi-cyclic code of index p2 and length p3n over Fp.Several examples of optimal linear codes over Fp from（1 — uv）-constacyclic codes over Fp ＋ uFp ＋ vFp ＋ uvFp are given.     

“盗窃符号”类别、特点及理论性分析初探

随着我国盗窃犯罪日渐专业化,"盗窃符号"开始在社会中广泛显现,并日益威胁着社会治安与居民安全感。对"盗窃符号"的概念进行了类别划分,总结出"盗窃符号"具有总体数量多、增长趋势明显、城市间差异大、区域性明显、隐蔽性高这五个特点。结合犯罪社会学相关理论进行分析,发现其反映出理性选择理论与日常活动理论的丰富内涵,并显现出犯罪专业化的趋势,提出了相关的防控对策。