关于函数值域的概念及其应用

函数值域是函数的三大要素之一，有许多文章对函数值域的求法作了专门的分类和探讨，其中有一种十分常见的方法是“逆求法”．笔者认为从本质上讲逆求法有所不妥．本文将从函数值域概念入手说明“逆求法”的不当性．并通过几个例子说明值域概念的应用．     

例谈函数值域的几种解法

函数是中学数学的一个重点，特别是到了高中，函数的类型多了，如何求函数的值域是一个重点也是一个难点，而函数值域（最值）的求解方法在高考中更是一个常考点。因此，能熟练掌握其值域（最值）求法就显得十分重要，本文旨在通过对典型例题的分析求解来归纳函数值域（最值）的求法。     

例谈含二次根式的函数值域的常用求法

求合有二次根式的函数值域问题是高中数学中常见的题型，它的形式多种多样，求法也灵活多变，几乎涵盖了所有的函数值域的求法，正因它含有二次根式，因而求有关此类值域时，也就有它独特的一面，现介绍几类此题的方法，以飧读．     

函数定义域和值域的常见求法

构成函数的三要素是：定义域、对应关系和值域，因此，理解一个函数的定义域和值域显得尤其重要。下面介绍关于函数的定义域和值域的求法。     

函数值域的一点思考

在函数的三要素中,定义域和值域起决定作用,而值域是由定义域和对应法则共同确定的.关于函数值域的求法,是高中数学教学中的一个难点,也是一个重点.确定函数的值域是研究函数不可缺少的重要一环.对于如何求函数的值域,若方法运用适当,就能起到简化运算过程,避繁就简,事半功倍的作用.本文就函数值域求法谈一点认识.     

分式函数值域的求法

函数的值域是中学数学的重要内容,值域的求法很多,本文基于数学思想:方程思想及数形结合思想给出了分式函数值域的两种求法.     

函数值域求法

函数值域的求法是高中教学的难点,本文总结了函数值域的最常见的求法,旨在帮助学生克服难点,提高函数的学习效率.     

函数值域的求法

在函数问题中,往往需要求函数的值域,然而求函数值域的方法灵活多样,本文试图通过实例对函数值域的求法做一个归纳小结,以便同学们掌握．     

例谈含二次根式的函数值域的常用求法

求含有二次根式的函数值域问题是高中数学中常见的题型,它的形式多种多样,求法也灵活多变,几乎涵盖了所有的函数值域的求法,正因它含有二次根式,因而求有关此类值域时,也就有它独特的一面,现介绍几类此题的方法,以飧读者.一、利用基本函数的值域法有些含有二次根式的函数结构并     

浅谈求函数的值域的方法

求函数的值域是高中函数学习中的重要内容之一，它有着广泛的应用，因此，熟练掌握求函数值域的方法是非常重要的．在熟悉求函数值域的常用方法的基础上，还应注意关注和积累一些特殊类型函数的值域求法，具体情况如下：     

Conceptualizing Counseling Theories: A Content Analysis of Process and Goal Statements

This research effort presents (a) a model for viewing counseling theories and (b) data regarding the similarities and differences among selected counseling theorists on two dimensions: a process dimension and a goal dimension. Two instruments were used to tap the process and goal statements of selected theorists. Thirty-seven graduate students in two counseling theory classes completed the instruments, and their statement ratings were used to plot the selected theorists on the proposed model. Analysis of variance procedures were used to test differences among the theorists. The F ratios for both the process and goal statements were found to be significant at or beyond the .05 level. Theorist clusters were obtained by a post hoc probing process where the process clusters are as follows: (a) Williamson, Wolpe, Krumboltz; (b) Ellis, Thorne, Dreikurs, and Dollard and Miller; (c) Frankl, Alexander; (d) Rogers. The goal clusters are: (a) Wolpe, Krumboltz; (b) Williamson, Dollard and Miller; (c) Dreikurs, Thorne, Ellis, Alexander; (d) Rogers; (e) Frankl.     

The Stability of IRT b Values

This study investigated possible explanations for an observed change in Rasch item parameters (b values) obtained from consecutive administrations of a professional licensure examination. Considered in this investigation were variables related to item position, item type, item content, and elapsed time between administrations of the item. An analysis of covariance methodology was used to assess the relations between these variables and change in item b values, with the elapsed time index serving to control for differences that could be attributed to average or pool changes in b values over time. A series of analysis of covariance models were fitted to the data in an attempt to identify item characteristics that were significantly related to the change in b values after the time elapsed between item administrations had been controlled. The findings indicated that the change in item b values was not related either to item position or to item type. A small, positive relationship between this change and elapsed time indicated that the pool b values were increasing over time. A test of simple effects suggested the presence of greater change for one of the content categories analyzed. These findings are interpreted, and suggestions for future research are provided.     

Perspectives on a whole class mindfulness programme

This study sought to establish pupil and teacher views about a six-hour, whole-class mindfulness programme called Paws.b. Pupil post-intervention focus groups and teacher semi-structured interviews were used to ascertain what was interesting and useful about Paws.b, and how it could be developed. Audio recordings were transcribed and thematically analysed. Findings indicated the vast majority of pupils enjoyed Paws.b and it was deemed to be both accessible to pupils and feasible for teachers to deliver. A number of themes highlighted the impact of Paws.b upon pupils’ attention but also on their metacognition and social/emotional functioning, both within and beyond the classroom. Several potentially fruitful adaptations were also proposed. Findings are discussed relative to mindfulness and educational psychology literature, and future directions for research are outlined.     

Silencing of DsbA-L gene impairs the PPARγ agonist function of improving insulin resistance in a high-glucose cell model

Disulfide-bond A oxidoreductase-like protein (DsbA-L) is a molecular chaperone involved in the multimerization of adiponectin. Recent studies have found that DsbA-L is related to metabolic diseases including gestational diabetes mellitus (GDM), and can be regulated by peroxisome proliferator-activated receptor γ (PPARγ) agonists; the specific mechanism, however, is uncertain. Furthermore, the relationship between DsbA-L and the novel adipokine chemerin is also unclear. This article aims to investigate the role of DsbA-L in the improvement of insulin resistance by PPARγ agonists in trophoblast cells cultured by the high-glucose simulation of GDM placenta. Immunohistochemistry and western blot were used to detect differences between GDM patients and normal pregnant women in DsbA-L expression in the adipose tissue. The western blot technique was performed to verify the relationship between PPARγ agonists and DsbA-L, and to explore changes in key molecules of the insulin signaling pathway, as well as the effect of chemerin on DsbA-L. Results showed that DsbA-L was significantly downregulated in the adipose tissue of GDM patients. Both PPARγ agonists and chemerin could upregulate the level of DsbA-L. Silencing DsbA-L affected the function of rosiglitazone to promote the phosphatidylinositol 3-kinase (PI3K)-protein kinase B (PKB)/AKT pathway. Therefore, it is plausible to speculate that DsbA-L is essential in the environment of PPARγ agonists for raising insulin sensitivity. Overall, we further clarified the mechanism by which PPARγ agonists improve insulin resistance.     

Performance Improvement of DCF Supporting Multi-Rate in IEEE 802.11b Wireless LAN

Inrecent years ,IEEE802.11 wirelesslocal area net-work (WLAN) has emerged as a prevailing technology forthe (indoor) broadband wireless access to internet for themobile/portable devices . In IEEE 802.11 standards ,802.11b has become the most widely used v…     

特殊环形框架结构施工技术

双坡斜墙面与扇形大楼梯组成的特殊环形框架结构,复合地基处理,竹胶模板体系,钢筋绑扎、混凝土浇灌的新施工方法.     

Prevalence and correlates of multiple victimization in a nation-wide adolescent sample

Objectives

Adolescents often experience different types of victimization across a specified period of time in different situations. These multiple victimization experiences can have a number of deleterious effects on psychosocial well-being. To expand on research gathered primarily from US samples, the current study estimated the prevalence of multiple victimization in a nationally representative sample of Canadian adolescents. We also expanded on past research by adopting an ecological approach to identify correlates of multiple victimization.

Methods

Cross-sectional data from the 2000-2001 cycle of the National Longitudinal Survey of Children and Youth (NLSCY) were used to estimate the prevalence of multiple victimization (verbal harassment, threat of and actual physical assault, school social exclusion, discrimination) in 1,036 13-16 year olds. We also examined household (e.g., parental education), family (e.g., parenting practices), and adolescent (e.g., friendship quality) correlates of multiple victimization for the whole sample and separately by sex.

Results

Among the 6 in 10 adolescents who reported at least 1 victimization experience, 30.5% reported 2 types of victimization whereas 23.7% reported 3 or more types. There was an increased probability of multiple victimization (2 or more types) in adolescents who reported greater parental rejection, who engaged in more frequent out-of-school activities, and who experienced non-victimization adversity. The probability decreased if adolescents reported greater friendship quality.

Conclusions

The clustering of different types of victimization is common among adolescents. For both males and females, a difficult parent-child relationship characterized as rejecting is important when considering risk for multiple victimization, as is the adolescent's functioning outside of the home in the context of friendship quality and involvement in out-of-school activities. Non-victimization adversity (e.g., death of a loved one) also emerged as a significant multiple victimization correlate.

Practice implications

Non-physically invasive types of victimization (although adolescents also endorsed physical assault) are a reality for a number of adolescents. As such, we need to inquire about such experiences as school social exclusion, discrimination, and verbal threats in applied contexts. Moreover, in order to better identify adolescents who may be vulnerable to multiple forms of victimization, we need to adopt an ecological approach that considers individual, family, and household functioning.     

鸟类mtDNA中cytb基因及在系统进化研究中的应用

本文着重介绍了鸟类mtDNA中cytb基因的结构、功能、特点及其在鸟类系统进化研究领域中的主要应用。