64 research outputs found
Design of small bulb turbines with unequal specific work distribution of the runner's elementary stages
UzimajuÄi u obzir dosadaÅ”nja saznanja iz oblasti projetovanja turbomaÅ”ina, u ovom radu je prikazan metod projektovanja malih cevnih turbina sa razliÄitim jediniÄnim radovima elementarnih stupnjeva turbinskog kola u okolini glavÄine. Data je funkcija raspodele jediniÄnih radova elementarnih stupnjeva turbinskog kola, pri kojoj osnosimetriÄne strujne povrÅ”ine u turbinskom kolu zanemarljivo malo odstupaju od cilindriÄnih strujnih povrÅ”ina. U datoj funkciji raspodele, jediniÄni rad elementarnog stupnja turbinskog kola može se, uz glavÄinu, smanjiti i na 60% proraÄunskog jediniÄnog rada turbinskog kola, a da strujne povrÅ”ine u obtnom kolu budu priližno cilindriÄne.Regarding the present state of knowledge in the field of the turbo machinery design, the method for designing small bulb turbines with unequal specific work distribution of the turbine runner's elementary stages near the hub is presented in the paper. The distribution function of specific work of all the elementary stages is obtained, according to which the averaged axisymmetric flow surfaces of the turbine runner have a negligibly small deviation from the cylindrical flow surfaces. The specific work of the near-the-hub elementary stages, in the given distribution function, can be reduced up to 60% of the required (design) specific work, still achieving nearly cylindrical flow surfaces
On the Cartan Model of the Canonical Vector Bundles over Grassmannians
We give a representation of canonical vector bundles over Grassmannian
manifolds as non-compact affine symmetric spaces as well as their Cartan model
in the group of the Euclidean motions.Comment: 6 page
Tumori ovarijuma u adolescentkinja i mladih žena
Phenomenon of heterogeneous ovary tumors is probably the result of activity of the whole series of various factors, which play significant role in genesis, development and classification of tumors, In the age of puberty and adolescence, as a transitional period from childhood to adulthood, it is not rarely seen that due to the influence of hormone regulation, social environment and psychophysical stability, the break of correlation of the mentioned factors can imperil reproductive health of young people. That is the moment when the illnesses of reproductive system become noteworthy for the first time. Thus the immense role of juvenile gynecology is to preserve reproductive health of adolescent girls by preventive health education. The most frequent illnesses of ovary are in tight connection with ovary tumor changes, which could have influence on the normal function of the ovary.Pojava raznovrsnih tumora ovarijalnog porekla, verovatno je posledica delovanja Äitavog niza razliÄitih faktora, koji imaju znaÄajnu ulogu u pojavi, razvoju i klasifikaciji tumora. U pubertetu i adolescenciji, kao prelaznom periodu iz detinjstva u zrelo doba, pod uticajem hormonske regulacije, socijalne sredine i psihofiziÄke ravnoteže, najÄeÅ”Äe može doÄi do prekida korelacije pomenutih faktora, a Å”to može da ugrozi reproduktivno zdravije mladih. Bolesti reproduktivnog sistema tada prvi put postaju znaÄajne. Zato je znaÄaj i uloga juvenilne ginekologije da preventivno zdravstveno-vaspitnim radom i pravovremenim leÄenjem saÄuva reproduktivno zdravlje adolescentkinja, jer najÄeÅ”Äa oboljenja ovarijuma su u tesnoj vezi sa tumoroznim promenama, koji mogu da utiÄu na normalnu funkciju ovarijuma
Fizikalne i metalurÅ”ke promjene tijekom zavarivanja trenjem brzoreznog i kaljenog Äelika
This paper outlines the basic principles of welding by friction of high-speed cutting steel and tempered steel from the viewpoint of metallurgic processes that are going on in the material. The bases of welding by friction of different materials are outlined in a theoretical way. The experimental part of the paper also relates to friction welding of samples made of different metals: high-speed cutting steel (HS 6-5-2-5) on one hand and the tempered steel (C60) on the other.Ovaj rad daje osnovne principe zavarivanja trenjem brzoreznog Äelika i kaljenog Äelika s motriÅ”ta metalurÅ”kog procesa koji se odvija u materijalu. Osnove zavarivanja trenjem razliÄitih materijala navedene su teorijski. Eksperimentalni dio rada odnosi se na zavarivanje trenjem uzoraka izraÄenih od razliÄitih metala: brzoreznog Äelika (HS 6-5-2-5) s jedne i kaljenog Äelika (C60) s druge strane
Analiza kvalitete Al-Cu spoja ostvarenog zavarivanjem trenjem
This paper outlines the bases of the friction welding process, especially when it comes to friction welding of different materials. This was illustrated on an example of friction welding of aluminum and copper, which is often applied in electrical engineering. The analysis of influential parameters was conducted based on the data obtained by an experiment, since the data on this topic are very seldom in the available literature.Ovaj Älanak daje osnove procesa zavarivanja trenjem, naroÄito kada je u pitanju zavarivanje trenjem razliÄitih materijala. To je ilustrirano na primjeru zavarivanja trenjem aluminija i bakra, koji se Äesto primjenjuje u elektrotehnici. Analiza utjecajnih parametara provedena je na temelju podataka dobivenih eksperimentom jer su podaci o ovoj temi vrlo rijetko u dostupnoj literaturi
Endometrioza ravnog trbuÅ”nog miÅ”iÄa poslije carskog reza - prikaz sluÄaja
Endometriosis is defined by the presence of functional endometrial tissue outside the uterus, where it is normally located. Endometriosis is one of the most common gynecologic entities affecting 8%-18% of menstrual women. Endometriosis can occur at intra-and extrapelvic localizations. The most common intrapelvic localizations are those involving the ovaries, Douglas\u27 area, pelvic peritoneum, uterus, bladder and rectum. Abdominal endometriosis is the most common localization of extrapelvic endometriosis and usually develops in connective tissue. Extra-pelvic implantation of endometrial tissue may develop in any organ including the skin, lungs, liver, extremities, brain and stomach. Three years after cesarean section, a 35-year-old female was operated on for suspected anterior abdominal hernia at the site of previous section. An egg-sized tumor was removed from the rectus abdominis muscle and referred for histopathologic and immunohistochemical analyses. The results showed endometriosis of the muscle with positive estrogen and progesterone receptors. A year after the procedure, treatment with gonadotropin-releasing hormone analogs was continued due to recurrent pain in the scar area, along with ultrasonography and biochemical marker (carbohydrate antigen 125) follow-up. Clinical diagnosis of scar endometriosis can be made by thorough history and physical, ultrasonography and biochemical examinations. Scar endometriosis should always be considered when the symptoms occur in a cyclic and hormone-dependent pattern, mostly after gynecologic operations, and worsening during menstruation. Definitive diagnosis is based on histopathologic analysis.Endometrioza se definira prisustvom funkcionalnih endometrijalnih žlijezda i strome izvan Å”upljine maternice, gdje je njihova normalna lokalizacija. Endometrioza je jedan od najÄeÅ”Äih ginekoloÅ”kih entiteta, prisutna kod 8%-18% menstrualnih žena. Endometrioza može biti intra-i ekstrapelviÄne lokalizacije. NajÄeÅ”Äi sluÄajevi su intrapelviÄne lokalizacije koje zahvaÄaju ovarijume, zatim Douglasov prostor, pelviÄni peritoneum, veze maternice, mokraÄni mjehur, rektum. Abdominalna endometrioza je najÄeÅ”Äa lokalizacija ekstrapelviÄne endometrioze i obiÄno se razvija na vezivnom tkivu. EkstrapelviÄna implantacija endometrijalnog tkiva može biti na bilo kom organu u organizmu ukljuÄujuÄi i kožu, epiziotomiju, pluÄa, jetru, ekstremitete, mozak i trbuÅ”ni zid. Pacijentica stara 35 godina tri godine poslije carskog reza operirana je zbog pretpostavke da se radi o kili prednjeg trbuÅ”nog zida, na mjestu prethodnog reza, kada je odstranjen tumor veliÄine jajeta na ravnom trbuÅ”nom miÅ”iÄu. HistopatoloÅ”ka i imunohistokemijska analiza tumora pokazala je da se radi o endometriozi dotiÄnog miÅ”iÄa sa pozitivnim estrogenskim i progesteronskim receptorima. Godinu dana poslije procedure pojavila se bol u predjelu ožiljka, bolesnica je stalno lijeÄena analogom hormona za otpuÅ”tanje gonadotropina, uz serijsku kontrolu ultrazvuka i biokemijskog markera, CA 125. KliniÄka dijagnoza ožiljne endometrioze može se postaviti pažljivom anamnezom i fizikalnim pregledom, ultrasonografskim i biokemijskim ispitivanjem. Na ožiljnu endometriozu treba misliti uvijek kada se simptomi javljaju cikliÄno, u zavisnosti od hormona, najÄeÅ”Äe poslije ginekoloÅ”kih operacija, a koji se pogorÅ”avaju tijekom menstruacije. Prava dijagnoza postavlja se histopatoloÅ”kom analizom
DESIGN OF SMALL BULB TURBINES WITH UNEQUAL SPECIFIC WORK DISTRIBUTION OF THE RUNNERāS ELEMENTARY STAGES
Regarding the present state of knowledge in the field of the turbomachinery design, the method for designing small bulb turbines with unequal specific work distribution of the turbine runnerās elementary stages near the hub is presented in the paper. The distribution function of specific work of all the elementary stages is obtained, according to which the averaged axisymmetric flow surfaces of the turbine runner have a negligibly small deviation from the cylindrical flow surfaces. The specific work of the near-the-hub elementary stages, in the given distribution function, can be reduced up to 60% of the required (design) specific work, still achieving nearly cylindrical flow surfaces
Quasi-Chaplygin Systems and Nonholonimic Rigid Body Dynamics
We show that the Suslov nonholonomic rigid body problem can be regarded
almost everywhere as a generalized Chaplygin system. Furthermore, this provides
a new example of a multidimensional nonholonomic system which can be reduced to
a Hamiltonian form by means of Chaplygin reducing multiplier. Since we deal
with Chaplygin systems in the local sense, the invariant manifolds of the
integrable examples are not necessary tori.Comment: minor changes, to appear in Letters in Mathematical Physic
On Elliptical Billiards in the Lobachevsky Space and associated Geodesic Hierarchies
We derive Cayley's type conditions for periodical trajectories for the
billiard within an ellipsoid in the Lobachevsky space. It appears that these
new conditions are of the same form as those obtained before for the Euclidean
case. We explain this coincidence by using theory of geodesically equivalent
metrics and show that Lobachevsky and Euclidean elliptic billiards can be
naturally considered as a part of a hierarchy of integrable elliptical
billiards.Comment: 14 pages, to appear in Journal of Geometry and Physic
Energetic analysis of hard facing and weld cladding of an air powered drop hammer damaged ram
This paper studies problems of hard facing of damaged and initially cracked mechanical engineering heavy parts of complex geometry such as large rams of air powered drop hammers. During long-term exploitation, these parts are subjected to thermal fatigue due to cyclic temperature changes and variable impact compression. Taking into consideration high ram costs and difficulties to purchase ram, the necessity of its reparation becomes obvious. The choices of the most suitable technologies of hard facing and welding of an initially cracked ram are also studied here. Besides the techno-economic analysis, an energetic analysis is performed as an additional criterion in assessment of the proposed technology
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