Design of small bulb turbines with unequal specific work distribution of the runner's elementary stages

Uzimajući u obzir dosadašnja saznanja iz oblasti projetovanja turbomašina, u ovom radu je prikazan metod projektovanja malih cevnih turbina sa različitim jediničnim radovima elementarnih stupnjeva turbinskog kola u okolini glavčine. Data je funkcija raspodele jediničnih radova elementarnih stupnjeva turbinskog kola, pri kojoj osnosimetrične strujne površine u turbinskom kolu zanemarljivo malo odstupaju od cilindričnih strujnih površina. U datoj funkciji raspodele, jedinični rad elementarnog stupnja turbinskog kola može se, uz glavčinu, smanjiti i na 60% proračunskog jediničnog rada turbinskog kola, a da strujne površine u obtnom kolu budu priližno cilindrične.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 čitavog niza različitih faktora, koji imaju značajnu 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 psihofizičke ravnoteže, najčešće može doći do prekida korelacije pomenutih faktora, a što može da ugrozi reproduktivno zdravije mladih. Bolesti reproduktivnog sistema tada prvi put postaju značajne. Zato je značaj i uloga juvenilne ginekologije da preventivno zdravstveno-vaspitnim radom i pravovremenim lečenjem sačuva reproduktivno zdravlje adolescentkinja, jer najčešća oboljenja ovarijuma su u tesnoj vezi sa tumoroznim promenama, koji mogu da utiču na normalnu funkciju ovarijuma

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 članak daje osnove procesa zavarivanja trenjem, naročito kada je u pitanju zavarivanje trenjem različitih materijala. To je ilustrirano na primjeru zavarivanja trenjem aluminija i bakra, koji se često primjenjuje u elektrotehnici. Analiza utjecajnih parametara provedena je na temelju podataka dobivenih eksperimentom jer su podaci o ovoj temi vrlo rijetko u dostupnoj literaturi

Fizikalne i metalurške promjene tijekom zavarivanja trenjem brzoreznog i kaljenog čelika

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 čelika i kaljenog čelika s motrišta metalurškog procesa koji se odvija u materijalu. Osnove zavarivanja trenjem različitih materijala navedene su teorijski. Eksperimentalni dio rada odnosi se na zavarivanje trenjem uzoraka izrađenih od različitih metala: brzoreznog čelika (HS 6-5-2-5) s jedne i kaljenog čelika (C60) s druge strane

Endometrioza ravnog trbušnog mišića poslije carskog reza - prikaz slučaja

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 šupljine maternice, gdje je njihova normalna lokalizacija. Endometrioza je jedan od najčešćih ginekoloških entiteta, prisutna kod 8%-18% menstrualnih žena. Endometrioza može biti intra-i ekstrapelvične lokalizacije. Najčešći slučajevi su intrapelvične lokalizacije koje zahvaćaju ovarijume, zatim Douglasov prostor, pelvični peritoneum, veze maternice, mokraćni mjehur, rektum. Abdominalna endometrioza je najčešća lokalizacija ekstrapelvične endometrioze i obično se razvija na vezivnom tkivu. Ekstrapelvična implantacija endometrijalnog tkiva može biti na bilo kom organu u organizmu uključujući i kožu, epiziotomiju, pluća, jetru, ekstremitete, mozak i trbušni zid. Pacijentica stara 35 godina tri godine poslije carskog reza operirana je zbog pretpostavke da se radi o kili prednjeg trbušnog zida, na mjestu prethodnog reza, kada je odstranjen tumor veličine jajeta na ravnom trbušnom mišiću. Histopatološka i imunohistokemijska analiza tumora pokazala je da se radi o endometriozi dotičnog mišića sa pozitivnim estrogenskim i progesteronskim receptorima. Godinu dana poslije procedure pojavila se bol u predjelu ožiljka, bolesnica je stalno liječena analogom hormona za otpuštanje gonadotropina, uz serijsku kontrolu ultrazvuka i biokemijskog markera, CA 125. Klinička 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 ciklično, u zavisnosti od hormona, najčešće poslije ginekoloških operacija, a koji se pogoršavaju tijekom menstruacije. Prava dijagnoza postavlja se histopatološkom analizom

DESIGN OF SMALL BULB TURBINES WITH UNEQUAL SPECIFIC WORK DISTRIBUTION OF THE RUNNER’S 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 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

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