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| Inicialni Eksploziv |
Inicialni eksplozivInicialni eksploziv je eksploziv, ki jih uporabljamo, da izzovejo eksplozijo pri drugih eksplozivih.
Zelo so občutljivi na raznovrstne zunanje vplive (udarec, trenje, iskra, vlaga,...) in so neprimerni in nevarni za uporabo. Predvsem jih uporabljamo kot polnitev vžigalnikov oz detonatorjev.
Seznam
- srebrov fulminat
- svinčev azid
- tricinat
Kategorija:Eksplozivi
EksplozivEksplozívi oziroma detonacíjske eksplozívne snoví so kemične eksplozivne snovi, pri katerih se energija za aktiviranje molekul prenaša od sloja do sloja z udarnim valom nadzvočne hitrosti.
Delitev
- inicialni eksploziv
- brizantni eksploziv
- potisni eksploziv
- pirotehnična zmes
-
ja:火薬
TrenjeTrênje je pojav, da deluje telo, po katerem drsi drugo telo, na slednjega deluje s silo trenja, ki ima nasprotno smer od smeri gibanja. Zaradi trenja se del mehanske energije pretvori v notranjo energijo, zato silo trenja uvrščamo med nekonservativne sile.
Sila trenja Ft je premo sorazmerna z normalno komponento sile Fn, s katero pritiska prvo telo na stično ploskev. Sorazmernostni koeficient je koeficient trenja kt:
:
Koeficient trenja je odvisen od snovi, iz katerih sta mejni ploskvi teles, od njune hrapavosti oziroma obdelave, od morebitnih nečistoč, ter tudi od relativne hitrosti drsenja enega telesa glede na drugo. Največjo vrednost ima pri hitrosti nič, ko telesi mirujeta. V tem primeru govorimo o koeficientu lepenja, sam pojav pa imenujemo lepenje. Koeficient trenja je neodvisen od velikosti stične površine.
Vrste trenja
Koeficient trenja je odvisen od vrste trenja. V splošnem ločimo tri vrste trenja:
- lepenje imenujemo trenje v limitnem primeru, ko telesi v stiku mirujeta eno glede na drugo. koeficient lepenja navadno označujemo s kl. Sila lepenja je tista, ki preprečuje, da bi radirka zdrsnila po gladki nagnjeni površini.
- trenje imenujemo pojav, kadar telesi drsita eno glede na drugo. Zgled za trenje je gibanje sani po snegu.
- kotalno trenje imenujemo trenje, pri katerem se eno telo kotali po drugem, kot denimo kolo po vozišču. Kotalno trenje je v splošnem manjše od drsnega trenja, kar izkoriščamo pri krogličnih ležajih.
Koeficient trenja je mogoče določiti le empirično z meritvijo in ga ni mogoče izračunati vnaprej.
Posledice trenja
Posledica trenja je deformacija teles. Ta je včasih zaželena, kot denimo pri poliranju, največkrat pa ne, saj vodi v obrabo. Trenje zmanjšujemo z mazivom na stiku površin, s čimer močno zmanjšamo koeficient trenja. Pri grafitu so nedavno odkrili supermazivnost, pojav, da dve površini v stiku drsita ena ob drugi brez trnja, kar ustreza koeficientu trenja, enakem nič. Veda, ki preučuje maziva in njihove lastnosti, se imenuje tribologija.
Namesto maziv se lahko za zmanjševanje trenja uporablja tudi akustično mazanje: zvok povzroči vibracije plasti v stiku, s čimer se zmanjša trenje med njimi. Pojav so uporabljali nemški tanki med drugo svetovno vojno, pri katerih je za akustično »mazanje« tankovskih gosenic skrbelo njihovo lastno cviljenje.
Delo sile trenja se sprošča kot toplota, ki nadalje lahko vodi v deformacijo telesa in lahko dolgoročno spremeni njegove specifikacije. V izjemnih primerih lahko trenje povzroči tudi taljenje snovi v stiku.
Izraz trenje praviloma uporabljamo za opis pojava na stiku dveh trdnih teles. S podobnim pojavom imamo opraviti tudi na stiku trdnine in tekočine ali dveh tekočin, kjer pa namesto o trenju govorimo o uporu.
Glej tudi
- notranje trenje
Kategorija:Mehanika
ja:摩擦
ko:마찰력
IskraIskra lahko označuje:
- svetel drobec goreče snovi
- slovensko podjetje Iskra (podjetje), ki je razpadlo v 80. letih 20. stoletja
- Iskra - srbski časopis (1898-1912)
- Iskra - ruski časopis (1900-1905)
Svinčev azidSvinčev azid je predstavnik eksplozivov.
Sestavine
- svinec,
- dušik.
Uporaba
Je nadomestek za živosrebrni fulminat.
Lastnosti
Za aktiviranje svinčevega azida je potrebna netilka (vžigalna kapica) ali detonatorska kapica. Je občutljiv na tresljaje.
V stiku z večino kovin tvori azide teh kovin, ki pa so še bolj občutljivi na segrevanje in udarce kot svinčev azid. Kovina, s katero ne tvori kovinskega azida, je aluminij, kar je razlog, da so detonatorske kapice, ki vsebujejo svinčev azid, narejene iz aluminija.
Zunanje povezave
- http://filebox.gimb.org/~pirnakle/svincev_azid.htm
- http://www.geocities.com/pirotehnicni_raj/podatki.htm
Kategorija:Eksplozivi Association of IdeasIn psychology and marketing, two concepts or stimuli are associated when the experience of one leads to the effects of another, due to repeated pairing. This is sometimes called Pavlovian association for Ivan Pavlov's pioneering of classical conditioning.
Association is a widely used memory trick. Associating a new item (an object, a picture, a smell or anything else a person may wish to recall) to another, more easily-remembered item can allow you to think of them both.
See also
- Associationism
- Conditioning
External link
- [http://etext.lib.virginia.edu/cgi-local/DHI/dhi.cgi?id=dv1-19 Dictionary of the History of Ideas:] Association of Ideas
Category:Psychology
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