黑河上游地区基流分割及其变化特征分析

基流是枯水期河川径流的主要来源,是一种比较稳定的径流组成部分,对于干旱内流河流域水文模拟和水资源开发利用至关重要。本文基于1979年-2008年莺落峡水文站的实测流量资料,采用数字滤波法中的单参数数字滤波法和递归数字滤波法对内陆河流域黑河上游的流量过程进行了基流分割研究。探讨了黑河上游年基流量和基流指数BFI的年内与年际变化特征,以及不同水平年基流指数BFI变化规律。研究表明,黑河上游基流量年内变化为先增后减,峰值出现在8月份,基流指数则是先减后增,6月份最小。受气温升高和融雪径流影响,黑河上游基流量年际变化呈增加趋势,而基流指数呈减少趋势。在不同水平年,枯水年份的平均基流指数BFI为O．577,平水年为0．551,丰水年为0．521。     

Secondary Students’ Understanding of Basic Ideas of Special Relativity

A major topic that has marked ‘modern physics’ is the theory of special relativity (TSR). The present work focuses on the possibility of teaching the basic ideas of the TSR to students at the upper secondary level in such a way that they are able to understand and learn the ideas. Its aim is to investigate students' learning processes towards the two axioms of the theory (the principle of relativity and the invariance of the speed of light) and their consequences (the relativity of simultaneity, time dilation and length contraction). Based on an analysis of physics college textbooks, on a review of the relevant bibliography and on a pilot study, a teaching and learning sequence consisting of five sessions was developed. To collect the data, experimental interviews (the so-called teaching experiment) were used. The teaching experiment may be viewed as a Piagetian clinical interview that is deliberately employed as a teaching and learning situation. The sample consisted of 40 10th grade students (aged 15–16). The data were collected by taping and transcribing the ‘interviews’, as well as from two open-ended questionnaires filled out by each student, one before and the other after the sessions. Methods of qualitative content analysis were applied. The results show that upper secondary education students are able to cope with the basic ideas of the TSR, but there are some difficulties caused by the following student conceptions: (a) there is an absolute frame of reference, (b) objects have fixed properties and (c) the way events happen is independent of what the observers perceive.     

The effects of an increasing versus constant crank rate on peak physiological responses during incremental arm crank ergometry

Abstract

We examined the effects of concomitant increases in crank rate and power output on incremental arm crank ergometry. Ten healthy males undertook three incremental upper body exercise tests to volitional exhaustion. The first test determined peak minute power. The subsequent tests involved arm cranking at an initial workload of 40% peak minute power with further increases of 10% peak minute power every 2 min. One involved a constant crank rate of 70 rev · min^?1, the other an initial crank rate of 50 rev · min^?1 increasing by 10 rev · min^?1 every 2 min. Fingertip capillary blood samples were analysed for blood lactate at rest and exhaustion. Local (working muscles) and cardiorespiratory ratings of perceived exertion (RPE) were recorded at the end of each exercise stage. Heart rate and expired gas were monitored continuously. No differences were observed in peak physiological responses or peak minute power achieved during either protocol. Blood lactate concentration tended to be greater for the constant crank rate protocol (P = 0.06). Test duration was shorter for the increasing than for the constant crank rate protocol. The relationship between local RPE and heart rate differed between tests. The results of this study show that increasing cadence during incremental arm crank ergometry provides a valid assessment of peak responses over a shorter duration but alters the heart rate–local RPE relationship.     

Trajectory subgroups of perceived emotional support from teachers: Associations with change in mastery climate and intentions to quit upper secondary school

The aims of this three-wave longitudinal study were to identify and describe trajectories of perceived emotional support from teachers and investigate whether these trajectories were related to the development of intentions to quit upper secondary school via change in perceived mastery climate. Among 1379 Norwegian upper secondary school students, three trajectory subgroups were identified: stable high (84.9%), decreasing (7.8%), and low increasing (7.3%). The subgroups differed in levels of achievement ambition and academic self-concept. Further, a parallel process latent growth curve model revealed essential associations with change in intentions to quit school. Specifically, students with high probabilities of membership in the decreasing emotional support subgroup appeared to be at particular risk, perceiving a decrease in mastery climate that was related to a worrying development of intentions to quit school. The results are discussed considering the importance of a sustained supportive learning environment for late adolescents.     

Upper Secondary Schools and Sparsity: The Case of Northern Sweden

Governmental reforms since the early 1990s have acted as a push factor for starting new schools in Sweden and have created options for pupils to choose a school irrespective of municipal borders. This study highlights the upper secondary school system in small municipalities in northern Sweden since the late 1990s. The analysis shows that the reforms led to more schools, and thereby also to more competition in recruiting pupils both within and across municipal borders. When the cohorts started declining, the vulnerability of the school structure became obvious. The competition generated higher costs per capita and fewer available programs in small municipalities. Furthermore, it was noted that fewer pupils attending schools in small municipalities completed their education compared to those in larger municipalities.     

小品《不差钱》中的面子言语行为论略

小品《不差钱》中以大爷为核心形成了与小沈阳的合作与竞争关系、与鸭蛋的亲缘关系以及大爷、鸭蛋和毕福剑之间的"拟亲属化关系",四个人物因角色、目的的不同而在合作与竞争这种特殊的人际关系和争胜与攀附的真假亲缘关系中采取了刻意寻求"给面子"、大肆寻机"伤面子"、精心寻隙"损面子"、巧妙寻衅"撕面子"与居高力导"争面子"、设计铺垫"借面子"等具有戏剧冲突特征的面子言语行为策略,从而既展现了小品的语言艺术魅力,又展示了中华文化中面子观的精神内核和神韵。     

清代汀州两江流域区域经济比较

清代汀州两江流域经济发展并不平衡。由于农耕条件的不同,两江流域不论是在经济作物的种植,还是在工商业活动方面,均表现出明显的差异,闽江流域上游三县比汀江流域诸县逊色得多。     

奇完全数的倒数和

关于奇完全数的存在性问题是一个著名的数学难题,迄今远未解决．在奇完全数存在的条件下,研究了以全部奇完全数的倒数所组成的级数,给出了其和的一个上界．     

E-凸集上的函数的半连续性与E-拟凸性

给出E-凸集上函数的半连续性与E-拟凸性之间的关系：M是R^n中的非空E-凸集,E（M）是凸集,f是M上的上半连续（或下半连续）实值函数,那么f是M上的E-拟凸函数当且仅当存在a∈（0,1）,使得f（aE（x）＋（1-a）E（y））≤max{f（E（x））,f（E（y））},∨x,y∈M．     

浅析元朝蒙古上层崇信藏传佛教之原因

终元一代,元朝蒙古上层对藏传佛教崇信有加,就其原因是多方面的。从主观上讲,元朝蒙古上层一方面利用藏传佛教来达到怀柔吐蕃和统治本国民众之目的,另一方面,蒙古统治者自身对终极关怀的极其重视。从客观上讲,受到内外环境的影响,如西藏佛教领袖、西夏佛教、蒙藏文化的相似以及生物基因等方面的影响。不论从主客观,还是从内外因讲,元朝蒙古上层崇信藏传佛教都是多方面的、多因素的。