Pre-service mathematics teachers’ concept images of radian

This study investigates pre-service mathematics teachers’ concept images of radian and possible sources of such images. A multiple-case study was conducted for this study. Forty-two pre-service mathematics teachers completed a questionnaire, which aims to assess their understanding of radian. Six of them were selected for individual interviews on the basis of theoretical sampling. The data indicated that participants’ concept images of radian were dominated by their concept images of degree. As the data in this study suggested, pre-service mathematics teachers were reluctant to accept trigonometric functions with the inputs of real numbers but rather they use value in degrees. More interestingly, they have two distinct images of π : π as an angle in radian and π as an irrational number.     

A report on the introduction of a multiple choice examination for a first year university engineering mathematics course

The paper is an account of the experience of introducing a multiple choice mathematics examination paper for the first year engineering mathematics course at Nottingham University. The form of the paper is described, as is a system for providing the candidates with feedback on their performance without the publication of the examination paper.     

A mathematics support programme for first-year engineering students

This article describes a mathematics support programme at the University of Queensland, targeted at first-year engineering students identified as having a high risk of failing a first-year mathematics course in calculus and linear algebra. It describes how students were identified for the programme and the main features of the programme. The success of the programme was evaluated using student feedback as well as a comparison of the performance of students who participated in the support programme with those of a similar background who briefly attended or did not attend the programme. The pass rate in the supported group of regular attendees was 79% compared with 43% and 46% in the briefly supported and unsupported groups, respectively. Both student feedback and statistical data indicate that the programme was highly successful in improving the performance of those who regularly engaged with it.     

An Automatic Hollow-Cathode Light Source Device for Emission Spectrochemical Analysis

The construction and operation of the ZKG-I automatic hollow-cathode hight source device for the emission spectrochemical analysis of trace elements in steels, superalloys, nonferrous metals and super-high-purity substances are presented in this booklet. The questions discussed include high voltage electrical source unit for steady current and steady voltage supply, dynamic equilibrium-type vacuum system, programme control unit of the light source, and the comparison of the effect of He and Ar to be used as carrier gas in the hollow-cathode lamp on the limit of detection for different elements. The different methods for the detection of trace elements in superalloys, super-high-purity substances, pure metals, and oxides of pure metals are also listed.     

Determination of Silver in Plants by Flameless Atomic Absorption Spectrometry and Neutron Activation Analysis

Abstract

Three analytical techniques suitable for determining silver concentrations in plants are presented and compared. Graphite furnace atomic absorption spectrometry performed directly on sample digests was the most sensitive and convenient. Neutron activation analysis, measuring ^110mAg gave good reproducibility, but lower sensitivity. A cyclic activation scheme to generate and detect the short-lived isotope ¹¹⁰Ag was useful as a quick reconnaissance technique, but interference from ⁷⁶As reduced its effectiveness.

Data are presented on the silver content of terrestrial plants. Background silver concentrations for lichens and bryophytes collected from Wales, U.K. were <0.07μgg^?1. Samples collected from areas contaminated by derelict metal mines contained between 0.1-1.0μAgg^?1. The aerial portions of vascular species usually contained less silver than bryophytes growing on the same substrate. Fungi are shown to bioconcentrate silver to a greater extent than cadmium, copper or lead.     

CHERNE: prehistory and early days of the network

ABSTRACT

While the founding members of CHERNE gradually retire, the memory of the early steps of the network should not be lost. CHERNE (‘Cooperation for Higher Education on Radiological and Nuclear Engineering’) is the product of a specific Erasmus activity possible in the early 2000s: the intensive programmes (IP). The first step was a collaboration of three partners (Czech Technical University CTU, Institut Supérieur Industriel de Bruxelles ISIB, Universitat Politècnica de València UPV) organising in 2002 the 3-year IP ‘PAN: Practical Approach to Nuclear techniques’, soon integrating two other partners (Aachen University of Applied Science AcUAS, XIOS Hogeschool Limburg). A second IP ‘SPERANSA: Stimulating Practical Expertise in RAdiation and Nuclear SAfety’ was first organised without Erasmus support in 2005. A workshop was held in 2005 at UPV, including colleagues from other universities. Its main goal was to put in contact professors and researchers from European Institutions in order to share experiences in education and research in Radiation Protection and Nuclear Engineering. The creation of an informal group of universities to develop activities for the benefit of students was discussed. With the addition of Università degli Studi di Bologna (UniBo) to the initial group, the CHERNE network was created. It attracted rapidly more members (6 adhesions in 2006). CHERNE was conceived as a non-formal wide-scope open network, easily integrating new members, offering affordable activities to the students and mostly relying on Erasmus subsidies. The main goal was still the organisation of Erasmus IP’s based on practical activities, benefitting of the access to big experimental facilities offered by several partners, like reactors, accelerators, or a radiochemical laboratory. SPERANSA was organised from 2006 to 2008, ‘JUNCSS: JÜlich Nuclear Chemistry Summer School’ from 2007 to 2011 and ‘RAPIX-NOCOS: Radiation protection in non-conventional sectors’ in 2007 and 2008 without Erasmus support. The annual workshops triggered exchanges between partners and attracted more institutions. The first workshops saw intense discussions about the network organisation and the types of activities that could be organised. A kind of maturity was reached from 2008.     

非凸函数极小问题的BFGS算法

本对于非凸函数的无约束优化问题，给出一类修正的BFGS算法。算法的思想是对非凸函数的近似Hesse矩阵进行修正，得到下降方向，并且保证拟牛顿条件成立，当步长采用线性搜索一般模型时，证明了该算法的局部收敛性。     

基于科学论证视角的职前科学教师培养研究述评

目前基于科学论证的教学设计研究成果缺乏,且科学教师论证水平普遍较低,且未养成习惯。通过文献法,关注国际本主题相关实证研究成果,发现职前科学教师对科学论证具有不同的理解,科学论证对职前科学教师科学本质观、科学概念和论证能力有影响。基于文献总结,从培养论证能力的专业课程设置、社会性科学议题教学和学科知识强化等3个方面提出建议。     

Analytical chemistry of the persistent organic pollutants identified in the Stockholm Convention: A review

Persistent organic pollutants (POPs) are major environmental concern due to their persistence, long-range transportability, bio-accumulation and potentially adverse effects on living organisms. Analytical chemistry plays an essential role in the measurement of POPs and provides important information on their distribution and environmental transformations. Much effort has been devoted during the last two decades to the development of faster, safer, more reliable and more sensitive analytical techniques for these pollutants. Since the Stockholm Convention (SC) on POPs was adopted 12 years ago, analytical methods have been extensively developed. This review article introduces recent analytical techniques and applications for the determination of POPs in environmental and biota samples, and summarizes the extraction, separation and instrumental analyses of the halogenated POPs. Also, this review covers important aspects for the analyses of SC POPs (e.g. lipid determination and quality assurance/quality control (QA/QC)), and finally discusses future trends for improving the POPs analyses and for potential new POPs.