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Wyszukujesz frazę "bond length" wg kryterium: Temat


Wyświetlanie 1-5 z 5
Tytuł:
N-N Bond Lengths and Initiation Reactivity of Nitramines
Autorzy:
Zeman, Svatopluk
Atalar, Taner
Růžička, Aleš
Powiązania:
https://bibliotekanauki.pl/articles/358441.pdf
Data publikacji:
2020
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
bond length
impact sensitivity
nitramines
reactivity
thermal decomposition
X-ray analysis
Opis:
For the 16 selected nitramines, it is shown that an increase in the energy content of these molecules (represented by enthalpies of formation) is connected with an increase in the lengths of the longest N–N bonds in the molecules. These lengths are directly proportional to the activation energies of the low-temperature thermal decomposition of the pure nitramines in all states of matter for this reaction. Raising the energy content also leads to reductions in the rate constants of thermal decomposition. Both of these facts are in contrast to expectations and also with similar published findings concerning thermal decomposition of nitramines in solution, which can be explained by the solvation effect and termination of the emerging aza-radicals in solutions. The calculated dissociation energies of the weakest N–N bonds yielded a relatively good reciprocal conformity with the lengths of the longest N–N bonds of the nitramines studied, especially when using the UB3LYP/6-31G* method. The relationship between the impact sensitivity of these nitramines and the lengths of their longest N–N bond is not completely clear. Such lengths cannot be a measure of impact reactivity, because the longest N–N bond might be stabilized in some cases by suitable intermolecular interactions with adjacent molecules in the crystal lattice.
Źródło:
Central European Journal of Energetic Materials; 2020, 17, 2; 169-200
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study of conceptual knowledge and mode of reasoning relating to the characteristics of covalent bonds in future algerian physics teachers
Autorzy:
Hazzi, Salah
Djouahra, Idris
Dumon, Alain
Powiązania:
https://bibliotekanauki.pl/articles/2175228.pdf
Data publikacji:
2022
Wydawca:
Towarzystwo Chemii i Inżynierii Ekologicznej
Tematy:
covalent bond
orbital overlap
bond stability
bond length
localised system
conjugated system
wiązania kowalencyjne
stabilność wiązania
długość wiązania
układ miejscowy
układy sprzężone
Opis:
In this study we tried to analyse how future teachers of Ecole Normale Supérieure (ENS) school who are at the end of education have integrated the specifications of covalent bonds in the different bond orders in terms of symmetry, stability, length, localisation (in the case of structures of ethane, ethylene and acetylene) or delocalisation of electrons (case of benzene). The analysis of responses to a written questionnaire shows that the majority of students have only integrated some knowledge, which may be termed as procedural, on the structural elements of molecules such as stability and the length of bonds. Although possessing some conceptual knowledge, students tend to use an alternative way of reasoning arising from the mental representation that single and multiple bonds are independent entities: the single bond is a ”σ bond” while the double bond is considered only as a ”π bond”.
Źródło:
Chemistry-Didactics-Ecology-Metrology; 2022, 27, 1-2; 105--121
2084-4506
Pojawia się w:
Chemistry-Didactics-Ecology-Metrology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Strength of the Bond of Structural Steel S235JR to Bronze SAE660 Produced by Casting in Pre-Mold
Autorzy:
Zaheri, M.
Vahdat, S. E.
Powiązania:
https://bibliotekanauki.pl/articles/380357.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
casting in pre-mold
bond length
strength of the bond
thrust bearing
weld
odlew wstępny
czas wiązania
wytrzymałość połączenia
łożysko
spawanie
Opis:
Different methods are used for production of bronze bearings. In terms of technical specifications, the success of each of these methods depends on the bond’s strength and in terms of economic, the production method is important. In this study, the aim is to study the strength and microstructure of steel-bronze thrust bearing bond that has been produced through the casting using pre-mold. In this study, in order to bond, the raw metals are chemically washed with sulfuric acid solution for five minutes at first. Then, the molten bronze SAE660 is cast in a structural steel S235JR pre-mold. The bond’s strength has been measured using the shear test three times; the measurement of bond’s length has been done using field emission scanning electron microscope (FESEM). The results indicate that the strength of the bond is at least 94.8 MPa and bond’s length is 0.45 micrometers. Therefore, this method was successful for trust bearing application.
Źródło:
Archives of Foundry Engineering; 2017, 17, 3; 149-154
1897-3310
2299-2944
Pojawia się w:
Archives of Foundry Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Chemia kwantowa w molekularnej optyce nieliniowej
Quantum chemistry in molecular nonlinear optics
Autorzy:
Wielgus, M.
Kozłowska, J.
Bartkowiak, W.
Powiązania:
https://bibliotekanauki.pl/articles/172421.pdf
Data publikacji:
2012
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
polaryzowalność
hiperpolaryzowalność
przekrój czynny
rezonansowe zjawiska optyczne
nierezonansowe zjawiska optyczne
metoda sumowania po stanach
model dwustanowy
model trójstanowy
wewnątrzcząsteczkowe przeniesienie ładunku
nielinowa odpowiedź optyczna
parametr alternacji wiązania
hyperpolarizability
two-photon absorption cross section (TPA)
resonant optical processes
nonresonant optical processes
sum-over-states method
two-state model
three-state model
charge transfer
nonlinear optical response
bond length alternation (BLA)
Opis:
We review quantum-chemical methodologies based on simple two- and three- state models for molecular hyperpolarizabilities and two-photon cross-sections. In this article we show that simplified few-state models, obtained from sum -over-states formalism, are important tools for investigations structure-property relationships for various type of đ-conjugated compounds. These relationships are important for rational design of molecules with large nonlinear optical response
Źródło:
Wiadomości Chemiczne; 2012, 66, 1-2; 1-18
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Assessment of the casting position factor in reinforced concrete elements in view of experimental studies
Autorzy:
Dybeł, P.
Furtak, K.
Powiązania:
https://bibliotekanauki.pl/articles/230739.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
układanie betonu
przyczepność zbrojenia
miejsce zabetonowania
długość zakotwienia
beton wysokowartościowy
concreting
bond of reinforcement
casting position
anchorage length
high performance concrete
Opis:
The paper presents the results of experimental investigations performed by the authors on the casting position factor. It was proved that at the height of reinforced concrete elements there are different bond conditions. Moreover, the bond depends on concrete mechanical properties, element height as well as concrete mix composition and consistency. The experiments also showed the advisability of determining the casting position factor separately for bars from normal concrete and those from high–performance concrete (HPC). The analysis of investigation results has shown that “good” bond conditions are a relative concept and depend on, among other things, element height. The higher the element the better the concrete to lower bars bond. Consequently, elements of considerable height (higher than 600 mm) demonstrate a bigger difference between concrete to upper bars bond and concrete to lower bars bond.
Źródło:
Archives of Civil Engineering; 2014, 60, 2; 209-221
1230-2945
Pojawia się w:
Archives of Civil Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-5 z 5

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