101 research outputs found
Electron Heat Fluxes for the Global Ionospheric Networks
Get PDFAbstract This paper proposes an alternative approach for calculating electron heat fluxes by combining the Belgian 3D Plasmaspheric Model (Pierrard, Botek, & Darrouzet, 2021, https://doi.org/10.3389/fspas.2021.681401) and an analytical electron temperature formalism developed by Khazanov (2011), https://doi.org/10.1007/978‐1‐4419‐6797‐8. Such information is essential for 3D ionospheric modeling networks, which use the heat flux parameter as an upper boundary condition to calculate electron temperature, Te, at altitudes below 700–800 km. The theoretical approach presented in this letter does not identify the nature of the magnetospheric cold electron temperature heating sources. Instead, it relies on the empirical thermal structure that is incorporated in the Belgian plasmasphere model and their calculation of total plasmaspheric cold plasma content. We also extended our results to plasmaspheric altitudes and provided cold electron heating rates along the geomagnetic field lines from the southern to the northern hemisphere for different magnetic and solar activities
Theoretical Design of Substituted Tetrathia-[7]-Helicenes with Large Second-Order Nonlinear Optical Responses
No full textIncreasing response: Semiempirical calculations show that substituting tetrathia-[7]-helicene in positions 7 and 8 (see graphic) as well as in positions 2 and 13 by adequate donor/acceptor pairs can lead to a substantial increase of the second-order nonlinear optical response
Theoretical and experimental investigation of electric field induced second harmonic generation in tetrathia 7 helicenes
No full textIn this paper, we report the first systematic experimental and theoretical investigation of the electric field induced second harmonic response of some tetrathia[7]helicene-based NLOphores. We studied six model compounds carrying the NO2, CH=CHCN, and COCF3 units as accepting groups on both the terminal thiophene positions as well as on the central benzene ring of the helicene backbone. These groups, known to be of medium and medium-strong accepting strength, allow tuning of both the electronic and structural properties of the helicenes studied. This experimental/theoretical study should set a milestone in addressing new structure-properties relationship of this class of nonconventional chiral chromophores able to show second order as well as third order NLO phenomena
The role of plasmasphere in the formation of electron heat fluxes
Get PDFPlasmasphere plays an important role in the magnetospheric physics, defining many important inputs to the ionosphere from the middle to the auroral latitudes. Among them are electron thermal heat fluxes resulting from the Coulomb interaction of superthermal electrons (SE) and cold plasmaspheric electrons. These fluxes define the electron temperature at the upper ionospheric altitudes and are the input to the global ionospheric modeling networks. As was previously found from the calculation of lower energy SE and thermal heat fluxes, the knowledge of field-aligned cold plasma distribution in the plasmasphere is a very sensitive parameter that introduces the most uncertainties in the calculation of these values. To verify the previously used SuperThermal Electron Transport code assumptions regarding plasmaspheric field-aligned density structure ∼[B(s)/Bo]a, we used the latest version of 3D plasmaspheric model developed by Pierrard, Botek, and Darrouzet (2021, https://doi.org/10.3389/fspas.2021.681401). Such an assumption is found to be very reasonable in the calculations of electron thermal heat fluxes entering upper ionospheric altitudes and the associated electron temperature formation for the two selected dayside and nightside electron precipitation events driven by whistler-mode wave activity
From molecular to macroscopic engineering: shaping H-bonded organic nanomaterials.
No full textThe self-assembly and self-organization behavior of chromophoric acetylenic scaffolds bearing 2,6-bis(acetylamino) pyridine (1, 2) or uracyl-type (3-9) terminal groups has been investigated by photophysical and microscopic methods. Systematic absorption and luminescence studies show that 1 and 2, thanks to a combination of solvophilic/solvophobic forces and pi-pi stacking interactions, undergo self-organization in apolar solvents (i.e., cyclohexane) and form spherical nanoparticles, as evidenced by wide-field optical microscopy, TEM, and AFM analysis. For the longer molecular module, 2, a more uniform size distribution is found (80-200 nm) compared to 1 (20-1000 nm). Temperature scans in the range 283-353 K show that the self-organized nanoparticles are reversibly formed and destroyed, being stable at lower temperatures. Molecular modules 1 and 2 were then thoroughly mixed with the complementary triply hydrogen-bonding units 3-9. Depending on the specific geometrical structure of 3-9, different nanostructures are evidenced by microscopic investigations. Combination of modules 1 or 2 with 3, which bears only one terminal uracyl unit, leads to the formation of vesicular structures; instead, when 1 is combined with bis-uracyl derivative 4 or 5, a structural evolution from nanoparticles to nanowires is observed. The length of the wires obtained by mixing 1 and 4 or 1 and 5 can be controlled by addition of 3, which prompts transformation of the wires into shorter rods. The replacement of linear system 5 with the related angular modules 6 and 7 enables formation of helical nanostructures, unambiguously evidenced by AFM. Finally, thermally induced self-assembly was studied in parallel with modules 8 and 9, in which the uracyl recognition sites are protected with tert-butyloxycarbonyl (BOC) groups. This strategy allows further control of the self-assembly/self-organization process by temperature, since the BOC group is completely removed on heating. Microscopy studies show that the BOC-protected ditopic modules 8 self-assemble and self-organize with 1 into ordered linear nanostructures, whereas BOC-protected tritopic system 9 gives rise to extended domains of circular nano-objects in combination with 1
Ontological models for web portals<br>
No full textCílem této diplomové práce je aplikovat formální konceptuální analýzu na oblast e-commerce. Diplomová práce je rozdělena na teoretickou a praktickou část. Teoretická část se zabývá stručným přehledem a základními pojmy teorie svazů, zejména pak uzávěrovými operátory na úplných svazech a jejich vlastnostmi. Dále jsou v teoretické části uvedeny základy formální konceptuální analýzy, její matematický aparát a grafická reprezentace (konceptuální svaz). Praktická část diplomové práce se zabývá analýzou internetových obchodů z hlediska jejich rozdělení a typů. Dále následuje konkrétní postup návrhu a realizace internetového obchodu. Závěrečná část diplomové práce se zabývá zpracováním webových analytik na e-bussines systémech.The objective of this thesis is to apply the formal concept analysis in the area of e-commerce. The thesis is divided into the theoretical and the practical parts. The theoretical part deals with a brief survey and basic terms of lattice theory, especially with closure operators on complete lattices and their properties. Further in the theoretical part there are fundamentals of formal concept analysis, its mathematical apparatus and graphic representation (concept lattice). The practical part if this thesis deals with the analysis of internet business from the point of view of its division and types. It is followed by a particular procedure of proposal and realization of internet business. The final part of the thesis deals with web analytics processing in e-business systems.Ústav počítačových a komunikačních systémůobhájen
Digital Photography in a Hobbies Class in a Secondary School
No full textDiplomová práce se zabývá problematikou digitální fotografie na střední škole. Cílem práce bylo zjistit, jakým způsobem a za pomoci jakých softwarových nástrojů je tato problematika vyučována, a navrhnout zájmový kroužek, včetně všech náležitostí s ohledem na výuku, pro žáky středních škol zaměřený na tuto problematiku. Úvodní část práce je zaměřena pedagogicky, pojednává o všech záležitostech, na které je nutné brát při tvorbě kroužku ohled a které jsou během výuky využívány. Jelikož jde o práci zaměřenou na digitální fotografii, i ta je v teoretické části nastíněna. Praktická část je již zaměřena na výzkum výuky problematiky digitální fotografie na středních školách a na samotný návrh zájmového kroužku, včetně pedagogických dokumentů, podkladů pro výuku či samostatných cvičení pro žáky. Poslední kapitolu tvoří zhodnocení tohoto navrhovaného kroužku jak autorem práce, tak učitelem z praxe.Master's thesis deals with problematics of digital photography on a high school level. The main idea of the thesis is to find out how and with which software tools is these problematics teached. Second aim of the thesis suggesting the optional subject for high schools with all necessary documents needed for creating this course and for the teaching. Introductory part is aimed for pedagogical concept, it deals with all issues needed for creating the course and for using it during the course. This thesis is about digital photography, also this topic is described in the theoretical part. The practical part is focused on the research of problematics of digital photography at high schools and on the suggestion of the course. Exemplary pedagogical documents as well the base documents for teaching or individual exercises for students are included. The last chapter is the evaluation of this suggested course both by the author of the thesis and by the high school teacher.Ústav informatiky a umělé inteligenc
Synthesis of tetrathia[7]helicenes promoted by Pd-catalysed cross coupling reactions
No full textTetrathia[7]helicenes (7-TH), formed by thiophene and benzene rings ortho-fused in an alternating fashion, are emerging as one of the most popular class of chiral helical-shaped molecules [1], thanks to their unique electronic and optical properties suitable for applications in optoelectronics [2], biomolecular recognition [3], and asymmetric catalysis [4]. Despite all these potential advantages, most of the synthetic methodologies to prepare 7-TH systems involve oxidative photochemical cyclization processes, which require specific equipment, highly diluted solutions, and can limit the scale-up of the synthesis of these derivatives. In our ongoing studies on the preparation of 7-TH derivatives, we have set up an innovative and non-photochemical synthesis of 7,8-diaryl substituted 7-TH compounds, exploiting Suzuki-type reactions and Pd-catalysed annulation with diaryl alkynes. [1] Dova, D.; Cauteruccio, S.; Prager, S.; Dreuw, A.; Graiff, C.; Licandro E. J. Org. Chem. ASAP (DOI: 10.1021/acs.joc.5b00243)
[2] Bossi, A.; Licandro, E.; Maiorana, S.; Rigamonti, C.; Righetto, S.; Stephenson, G. R.; Spassova, M.; Botek, E.; Champagne, B. J. Phys. Chem. C 2008, 112, 7900.
[3] Cauteruccio, S.; Bartoli, C.; Carrara, C.; Dova, D.; Errico, C.; Ciampi, G.; Dinucci, D.; Licandro, E.; Chiellini, F. Chem. Plus. Chem. 2015, 80, 490.
[4] Cauteruccio, S.; Dova, D.; Benaglia, M.; Genoni, A.; Orlandi, M.; Licandro, E. Eur. J. Org. Chem. 2014, 2694
Syvänreiänporaus
Get PDFTämän opinnäytetyön aiheena oli perehtyä Konepaja Häkkinen Oy:n
uuden syvänreiänporakoneen hankintaan liittyviin porausmenetelmiin
ja työstökoneen hankintaprosessin vaiheisiin. Työn pääpaino oli syvänreiänporauksen
valmistusmenetelmissä. Valmistusmenetelmissä
käsitellään porausmenetelmiä ja laitteistoja sekä porausprosessiin
vaikuttavia tekijöitä. Uusi työstökonehankinta laajentaa yrityksen menetelmärakennetta.
Laajemmalla menetelmärakenteella pystytään
palvelemaan asiakasta laadukkaammin.
Työ suoritettiin yhteistyössä Konepaja Häkkinen Oy:n, TACCHI Giacomo
e Figli SpA:n ja Botekin ammattilaisten kanssa. Koneen vastaanotoista
ja loppuhyväksynnästä vastasi Konepaja Häkkinen Oy,
työstökonetta koskevista tiedoista sekä koekäytöstä vastasi TACCHI
Giacomo e Figli SpA ja työkalusovelluksista vastasi Botek.
Tuloksena työstä saatiin kattavat tiedot syvänreiänporausmenetelmistä
ja laitteistoista. Vastaanottohyväksytyllä työstökoneella suoritettu
koeporaus antoi arvokasta tietoa onnistuneesta porausmenetelmän
ja -laitteiston valinnasta
Quantum-chemistry simulations of second-harmonic and sum-frequency generation of organic layers
No full textBy using quantum-chemistry approaches, the second-order nonlinear optical responses of molecules and two-dimensional molecular arrays containing the p-nitroaniline chromophore are evaluated in order to highlight key features of the simulation of the second-harmonic and sum-frequency generation spectra of organic layers. For the electronic component, which dominates the second-harmonic generation response and which constitutes the weakly frequency-dependent background contribution to the vibrational sum-frequency generation phenomenon, the time-dependent Hartree-Fock scheme based on the semi-empirical AM1 parameterization is suitable for predicting the microscopic responses as well as for accounting for the surrounding effects within a simple multiplicative scheme. For the vibrational resonant part of the sum-frequency generation response, ab initio density functional theory approaches turn out to be necessary for locating the resonances and estimating their intensities.</p
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