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Integral equations for Rost's reversed barriers: existence and uniqueness results

We establish that the boundaries of the so-called Rost’s reversed barrier are the unique couple of left-continuous monotonic functions solving a suitable system of nonlinear integral equations of Volterra type. Our result holds for atom-less target distributions μ of the related Skorokhod embedding problem. The integral equations we obtain here generalise the ones often arising in optimal stopping literature and our proof of the uniqueness of the solution goes beyond the existing results in the field

Device for changing tires with foam inserts

Käesoleva magistritöö eesmärgiks on konstrueerida uudne rakis vahtkummist sisekummidega rehvide vahetamiseks. Vahtkummist sisekumm on ringikujulise ristlõikega rõngas, mille kärgkonstruktsioon on valmistatud butüülkummist ning tühimikud täidetud lämmastikuga. Sellise sisekummiga rehvide vahetus on keeruline protseduur, mis vajab spetsiaalseid tööriistu ja töövõtteid. Protseduuri keerukus seisneb asjaolus, et vahtkummis ei ole õhku, mille saaks välja lasta. Seega võib võrrelda seda olukorraga, kus rehv tuleb paigaldada täis pumbatud õhukummiga. Töö koostamisel tehti koostööd mitmete enduuro- ja motokrossisõitjatega. Hea lähtepositsiooni parema rakise konstrueerimiseks andis seadme potentsiaalse kasutajaskonna vajaduste ja ootuste välja selgitamine. Olemasolevate rehvivahetusrakiste tehnikataseme analüüsi käigus tuvastati erinevate konstruktsioonide funktsionaalsed ja ergonoomilised puudused ning tugevused. Kogutud info põhjal koostati projekteerimisülesanne - esitati nõuded konstrueeritavale rakisele ning valiti eelistatud konstruktsioonimaterjalid. Projekteerimisülesandest lähtuvalt töötas töö autor välja mitmeid erinevaid eskiislahendusi rakisest. Konstruktsiooni lihtsuse printsiibi järgi valiti välja 2 erinevat konstruktsiooni, millest ehitati prototüübid. Testimisel ilmnes mõlema katseeksemplari juures rida probleeme, mille sünteesi tulemusena konstrueeriti parandatud versioon. Kolmanda prototüübi katsetused päädisid 20 eksemplari tootmisega. Need eksponeeriti maailma suurimal enduurovõistlusel Saksamaal. Ürituse raames proovis uudset rehvivahetusrakist ligemale 100 mootorratturit ning kogutud tagasiside põhjal täiustati rakise konstruktsiooni. Käesoleva magistritöö tulemuseks on uudse konstruktsiooniga rehvivahetusrakis, mille funktsionaalsed- ja ergonoomilised omadused on saanud positiivse hinnangu suurelt hulgalt sõitjatelt üle maailma. Konstrueeritud rakis on kasutusele võetud mootorrattatootjate tehasemeeskondade poolt ning pälvinud kiidusõnu auhinnatud tippsõitjatelt. Tegu on kõige kompaktsema rakisega, mis on mõeldud vahtkummist sisekummide vahetamiseks. Töö on esitatud 95 leheküljel, millest 40 on lisad. Tekstiosa sisaldab 29 tekstisisest joonist ja 4 tabelit. Kirjanduses on 15 nimetust. Lisades on üks A1 formaadis, 5 A3 formaadi ja 26 A4 formaadis joonist.Aim of this master’s thesis is to develop a new device for changing tires with foam inserts. Foam insert is a ring of butyl honeycomb foam with its cells filled with nitrogen. It is used as an inner tube on off-road motorcycles. Fitting and removing a tire with foam insert is a complex procedure that requires special equipment and correct techniques. Consumer survey shows that large number of riders would like to take foam inserts into use, but have not done it due to the complexity of the tire changing procedure. Group of motorcycle riders were involved throughout the product development process. Defining their needs and expectations for a tire changing device helped to established the functional requirements. Testing and analyzing existing devices gave a good understanding of different design’s advantages and weaknesses. Different drafts of devices geometry and joints were sketched. Proposed solutions were selected according to constructions simplicity and two different prototypes were drawn and manufactured. Designs weak spots were detected through testing. Synthesis of conclusions led up to an improved design. As a result a new tire changing device with great functional and ergonomic features was constructed. Device can be easily assembled and has a carry-bag for compact storage. The product has received positive feedback from motorcycle riders and is used by factory racing teams. Technical drawings of the device are included in Appendices

UNTERSUCHUNG VON KORROSIONSINHIBITOREN SÄURIGER BEIZLÖSUNGEN IN DER ANWESENHEIT VON KOMPLEXBILDERN

Corrosion of Soviet and Hungarian carbon steels has been examined in 6% solution of hydrochloric acid. The virtual activation energy and the frequency coefficient have been determined with the help of the Arrhenius equation. The corrosion effect of the Fe(III)-ions, furtheron the inhibitor effect of oxalic acid, sulfosalycilic acid, sodium triphosphate and sodium fluoride have been investigated

КОРРОЗИОННАЯ СТОЙКОСТЬ И ИЗНОСОСТОЙКОСТЬ ПОРОШКОВЫХ ТВЕРДЫХ СПЛАВОВ НА ОСНОВЕ КАРБИДА ТИТАНА И ХРОМИСТОЙ СТАЛИ. Korrozionnaâ stojkost' i iznosostojkost' poroškovyh tverdyh splavov na osnove karbida titana i hromistnj stali

TiC-Fe-Cr alloys prepared from titanium-carbide and steel basis metal by powder metallurgy were studied with concerning their corrosion and abrasion resistance in water. Such alloys is used for preparing of pieces exposed to corrosion. Our experiments have indicated that the abrasion is not independent for corrosion resistance. By weak corrosion resistance abrasion decreases too because that the corroded metal do not bound together the hard titanium-carbide grains. Good abrasion is only by good corrosion resistance attainable. The corrosive abrasion is dependent on the hardness only in the case of suitable corrosion resistance of the solid alloys

КОРРОЗИОННАЯ СТОЙКОСТЬ НЕРЖАВЕЮЩИХ ПОРОШКОВЫХ ТВЕРДЫХ СПЛАВОВ TiC-СТАЛЬ. Korrozionnaâ stojkost' neržaveůşih poroškovyh tverdyh splavov TiC-stal'

Corrosion properties of powder metallurgical solidy alloys made of high wear resistance TiC and of corrosion-proof steel has been investigated in NaOH solution of 20% conc., in 10% HNO3, in 3% H2SO4 and in 44% H3PO4 solutions. The corrosion of solid alloys is deteriorating not only the metal, but also reduces its wear resistance. Our preliminary experiments performed with some corrosion-proof steels disclosed that the corrosion resistance of solid alloys made of nickel-free steels with high chrome content is poor. Solid alloys produced of austenite chromonickel steels with TiC proved to be acceptable. These solid alloys did not corrode at all in NaOH, as well as in acidic solutions. In the presence of inhibitors their corrosion resistance is further improved