Reciprocity Violation for Mie Scatterers at the Interface and a Scattering Solar Concentrator

It is shown that reciprocity of the optical path can be violated through asymmetric strength coupling via near-field from resonant Mie scatterers to total internal reflection modes in a dielectric slab. Numerical simulations for silicon nanospheres separated by a nanogap from the glass substrate reveal that at least two orders of magnitude rectification ratio can be realized for such an optical diode configuration. Implementation to a solar light harvesting device, a scattering solar concentrator, is discussed, indicating a similar efficiency is achievable as for the state-of-the-art devices based on luminescence.Comment: 4 pages, 4 figure

Effect of substrate proximity on luminescence yield from Si nanocrystals

The influence of the proximity of a high refractive index substrate on the luminescence of Si nanocrystals was investigated by time-integrated and time-resolved photoluminescence. The luminescence yield was found to be ∼2.5 times larger for emitters distanced from the substrate compared to those in proximity with the substrate, while luminescence decay measurements revealed only a slight increase in the luminescence lifetime (∼15%). Results are discussed in terms of local density of optical modes surrounding a pointlike light emitter with important implications for the collection efficiency of luminescence and the estimation of internal quantum efficiency for a quantum dot.Support for this work was provided by the Swedish Research Council VR and the Australian Research Council ARC

Analytical Description of a Luminescent Solar Concentrator Device

A luminescent solar concentrator focuses solar light spectrallyand spatially to convert it to electricity. Due to a large numberof input parameters and their complex effect on the device efficiency,it is typically described by numerical simulations. Here,an analytical solution is presented, which significantly reducesthe complexity of the optical efficiency evaluation. The equationswere derived using probabilistic approach and validatedby simulations. The implementation by a computer algebra programyields instant results for any set of input parameters. Itallows a higher level of analysis, where an inverse task of findingparameters for a given efficiency can be readily solved. The obtainedexplicit expressions provide a clear standard for theoreticaldescription of such devices.QC 20220201</p

Use of authentic texts to improve students’ discourse competence in Form 10 English lessons

Diplomdarbs “Autentisku tekstu izmantošana skolēnu diskursa kompetences pilnveidē angļu valodas stundās 10.klasē” ir tapis kā vidējās izglītības angļu valodas skolotājas zināšanu un prasmju apliecinājums. Darba autore Liene Lāce strādā Talsu 2.vidusskolā, kur arī tika veikts pētījums zinātniskās vadītājas Sandras Kalniņas, Mg.paed. vadībā. Autore ir izmantojusi kvalitatīvo un kvantitatīvo pētījumu metodes. Gadījuma analīzē autore ir izzinājusi 10.klases skolēnu diskursa kompetenci, kā arī stundās izmanotojusi autentiskas publiskās runas, sagatavojot diskursa un teksta analīzes uzdevumus, pēcāk izvērtējot to devumu skolēnu diskursa kompetences pilnveidē. Pašu skolēnu rakstītās publiskās runas ir analizētas gan kvalitatīvi, gan kvantitatīvi. Pētījumā ir izmantotās datu ievākšanas metodes galvenokārt ir skolēnu publisko runu teksti un to izvērtējums. Autore ir izmantojusi pašas izveidotus kritērijus, lai izvērtētu publisko runu tekstus, kas tapuši pirms un pēc diskursa analīzes uzdevumu izmēģināšanas četrās angļu valodas mācību stundās 10.klasē. Šo stundu laikā tika iegūta atgriezeniskā saite, kas arī ir apkopota un analizēta. Visbeidzot, autore ir intervējusi savu kolēģi - angļu valodas skolotāju Talsu 2.vidusskolā un izveidojusi anketu, lai gūtu priekšstatu par citu angļu valodas skolotāju pieredzi skolēnu diskursa kompetencs pilnveidošanā. Autore secina, ka skolēnu diskursa kompetenci ir iespējams pilnveidot izmantojot rūpīgi izvēlētus autentiskas publiskās runas diskursa izpētei un kā modeli, rezultātā vairums skolēni spēj paši uzrakstīt savas publiskās runas. Publiskās runas pārstāv specifisku žanru, kas sevī apvieno abus diskursa veidus - runā un rakstos. Diemžēl, daļa angļu valodas skolotāju neizmanto publiskās runas savās stundā, jo runu sagatavošana ir laikietilpīgs un sarežģīts uzdevums. Darba atlēgvārdi: diskurss, kompetence, lejupejoša pieeja, autentisks teksts, publiskās runa, publiskās runas teksts.The Diploma Paper „Use of Authentic Texts to Improve Students’ Discourse Competence in Form 10 English Lessons” was written to show the required knowledge and skills to perform as a secondary school English teacher. The author Liene Lāce has been working at Talsi Secondary School No 2 which was also the place of the practical research monitored by the adviser Mg. paed. Sandra Kalniņa. The methods of the research are both qualitative and quantitative. The author has used a case study to find out Form 10 students’ discourse competence and evaluate the impact of using the discourse and text analysis of the authentic speeches in English lessons. The public speeches written by Form 10 students are analysed qualitatively and quantitatively. The methods of the data collection are mainly evaluation and data from the students’ public speech scripts. The author has used a self-designed assessment scale to evaluate the speech scripts prepared before and after the discourse and text analysis tasks of the authentic public speeches were piloted in four English lessons in Form 10. During this process the students’ feedback has been collected and analysed in the research. Finally, the author has interviewed a colleague - another English teacher at Talsi Secondary School No 2 and designed a questionnaire to learn about other English teachers’ experience in improving the learners’ discourse competence. The conclusion is drawn that the students’ discourse competence can be improved by using carefully selected authentic public speeches both to learn about the discourse and looking at them as the models so that the students are able to prepare their own speeches. Public speeches represent a specific genre combining both spoken and written discourse; however, the public speaking is not frequently used in class by a half of English teachers because it is a time consuming and complex task. The key words of the Diploma Paper: discourse, competence, top-down approach, authentic text, public speaking, speech scripts