BEING CREATIVE WITH THE TRUTH? SELF-EXPRESSION AND ORIGINALITY IN PUPILS' MATHEMATICS

Whenever one justification for learning mathematics is questioned, educationists have usually been ready to offer an alternative rationale. Often this involves presenting (or re-presenting) the subject in a new light. This paper will consider the implications of trying to invoke creativity in mathematics. We shall argue that 'creativity' is a complex notion and should only be applied to mathematics with caution and attention to meaning.     

Open problems and conjectures

In this section we present some open problems and conjectures about some interesting types of difference equations. Please submit your problems and conjectures with all relavant information to G.Ladas     

Improving LED Efficiency with the New Polymorph β-Ca1−xSrxAlSiN3:Eu2+

Innovative materials for phosphor-converted white light-emitting diodes (pc-LEDs) are much sought after due to the huge potential of the LED technology to reduce energy consumption worldwide. One of the main levers for further improvements are the conversion phosphors. The system Ca_1−xSr_xAlSiN₃:Eu²⁺ currently provides one of the most important red-emitting phosphors for pc-LEDs. We report the discovery of the new polymorph β-Ca_1−xSr_xAlSiN₃:Eu²⁺ which allows for significant improvements to LED efficacies. It crystallizes in the orthorhombic space group Pbcn with lattice parameters a=982.43(10) pm, b=575.2(1) pm and c=516.12(5) pm. Compared to α-Ca_1−xSr_xAlSiN₃:Eu²⁺, its emission shows a significantly reduced spectral full-width at half maximum (FWHM). With that, we demonstrated 3 % efficacy increase for white light-emitting pc-LEDs. The new polymorph can easily be industrialised, because the synthesis works on the same equipment as α-Ca_1−xSr_xAlSiN₃:Eu²⁺.     

消费类应用市场概览

市场概述消费类市场应用范围宽广,而且由于有创新产品如平板电脑等的推出,其应用范围还在不断演变。由于难以论及所有消费应用,本文将重点探讨传统"家庭娱乐"类消费应用,如电视、机顶盒(STB)及数字视频播放机(如DVD、DVR等,简称DVx)。过去几年来,这些应用的变化颇大,功率电子设计工程师需要特别注意。这些应用中变化最大的就是