科学教育中模型定义及其分类研究述评

模型和建模研究目前已成为国际科学教育的重要研究议题之一,越来越多国家的科学教育标准强调模型和建模的作用,并将其纳入学业要求中。深入理解模型是科学教育研究者和教师有效开展模型和建模研究及进行模型相关教学的重要基础。模型定义和模型分类是认识模型的两个重要方面。模型定义的核心内容为模型是事物的表征,事物的内涵广泛,包括实物、事件、过程、概念、观点和系统等。基于模型功能的视角可以将模型分为八类:尺度模型、类比模型、图像和符号模型、数学模型、不表示数学关系的图表和表格、理论模型、概念-过程模型、系统模型。每类模型的功能和适用范围各不相同,但都可以用于理科教学之中。     

注塑成型充填阶段模拟中的黏度模型比较

阐述了常用的热塑性塑料幂律模型、二阶模流模型、Cross模型和Carreau模型等黏性模型表达式和特点。利用仿真的方法得出不同模型下熔体的填充速度、剪切率、剪切应力与温度这4个参数随时间变化曲线,再利用试验的方法采样得到实测值。把仿真值和实验值相对比,得到不同黏性模型的适用场合。结果表明,幂律模型和Carreau模型描述熔体填充速度时比较准确,在填充初始时描述剪切应力和温度变化率时可应用二阶模流模型、Cross模型或Carreau模型,填充后期采用幂律模型更加准确。该结果为合理选取热塑性塑料注射成型CAE填充模拟时材料的黏性模型提供了依据。     

基于结构方程模型改进ARMA模型参数估计

自回归移动平均模型（ARMA模型）是目前最常用的拟合平稳序列的模型,分为AR模型、MA模型和ARMA模型三大类。通常将自回归模型（AR）、移动平均模型（MA）或自回归移动平均模型（ARMA）,称作ARIMA模型体系,是一个重要的预测工具,成为时间序列分析中许多基本思想的基础。针对时间序列数据分析中ARMA模型的识别、建立和估计问题,提出一种将SEM结构方程应用于ARMA模型参数估计的改进算法,以加快计算的收敛速度和提高模型参数估计的精确度。通过将时间序列数据的协方差式子进行变换,发现其结果满足结构方程对变量协方差的要求。结果表明,可以将SEM结构方程应用于ARMA模型来处理时间序列模型数据。     

使用财务数据进行股权估值的模型及应用

财务数据在进行股权估值时占有极其重要的地位。股权估值模型从原理上可以分为乘数模型和流动模型。乘数模型简单易行,在使用别的模型进行估值后,能帮助我们检验估值的准确性并找到目标公司和比较公司估值的差异。流动模型包括传统的股息折现模型、现金流折现模型和新兴的剩余收益模型等。对这些估值模型的研究能够更好地指导相关模型使用者,对会计和金融交叉领域的探索有着重要意义。     

使用财务数据进行股权估值的模型及应用

财务数据在进行股权估值时占有极其重要的地位。股权估值模型从原理上可以分为乘数模型和流动模型。乘数模型简单易行,在使用别的模型进行估值后,能帮助我们检验估值的准确性并找到目标公司和比较公司估值的差异。流动模型包括传统的股息折现模型、现金流折现模型和新兴的剩余收益模型等。对这些估值模型的研究能够更好地指导相关模型使用者,对会计和金融交叉领域的探索有着重要意义。     

理解“模型认知”素养的不同视角

"模型认知"是化学学科核心素养的重要方面,应从化学模型、认识模型两个视角理解其内涵。从化学模型视角看,"模型认知"包含运用化学模型表征的能力、运用化学模型解释和论证的能力、运用化学模型预测和验证的能力、构建和优化化学模型的能力等;从认识模型视角看,"模型认知"包含运用认识模型将知识认识化、思路化、功能化,运用认识模型助推能力的发展,学习过程中运用认识模型进行自我评价、自我调控等。     

模型认知解读及教学思考——以化学学科为例

模型是人们为了某种特定目的而对认识对象所作的一种简化的描述。按照代表和反映原型的方式,模型可以分为物质模型和思想模型。模型的认知功能主要包括描述、解释、预见、判断。在模型认知的教学中,可以将模型展示与模型建构相结合,提升学生的思维能力;将模型观察与模型制作相结合,提升学生的实践能力;将模型建构与模型演变相结合,培养学生的科学精神;将模型建构与问题解决相结合,培养学生的解题能力。     

中学物理常见模型及解题思路略论

提出中学物理中的几种常用解题的几种模型：物体的动态平衡模型;牛顿运动定律在直线、曲线运动中的模型;运动的合成与分解模型;以能量、动量为核心的综合应用模型;电容器模型等12种模型。实践证明,老师和学生掌握这些模型及其解题思路能很好地提高教与学的效果。     

认知模型研究的新成果及应用

综述认知模型研究近年来取得的成果及应用。研究了粒计算认知模型、动态信任预测认知模型、Bayes信任预测认知模型采用的主要算法,介绍了认知模型在求解认知难题、虚拟人决策训练、多Agent谈判中的应用。指出粒计算认知模型、动态信任预测认知模型、Bayes信任预测认知模型是近年来认知模型的主要研究成果。因此,认知模型的研究具有很高的应用价值。     

IS-LM模型的新发展

IS-LM模型是20世纪下半期西方主流宏观经济学的核心内容之一,这个模型自产生以来就受到各种各样的批评。20世纪80年代以来,西方经济学家们从不同的视角提出了一些新模型来修正或替代IS-LM模型,其中具有代表性的模型有南肯模型、CC-LM模型和AD-PA模型。     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

不同的吃喝玩乐

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/     

漏洞百出的教育

Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help?     

Western and Eastern culture differences in commercial field

The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity.     

只要努力,不要后悔

There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love.     

浅谈移民问题

Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject.     

风的曲线

Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose.     

Sister Carrie, an Adherent of Desires

Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities.     

Improvement of one-cycle controller by use of proportional integral differential controller

1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec…