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Rad sadrži projektni zadatak i poglavlja u kojima se računaju parametri potrebne opreme i odabir iste.

Rad sadrži projektni zadatak i poglavlja u kojima se računaju parametri potrebne opreme i odabir iste.

Posjetiteljski rudnik Sv. Barbara nalazi se u Rudama kod Samobora. U rudniku se planiraju proširenja podzemnih prostora na do sada zatvorene dijelove. Projekt definira izvođenje radova i zaštitnih mjera u skladu sa pravilima za rudarski objekt. Radi potrebe za dodatnim uređajima izrađen je novi projekt elektroinstalacija.

Rad sadrži projektni zadatak i poglavlja u kojima se računaju parametri potrebne opreme i odabir iste.

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When determining firing impulse, electric current through detonator is measured. The current can be measured by measuring voltage drop over known resistance or by magnetic effects of electric current. Shape of current pulse influences the possi-bility to use transducer with magnetic effects. Rise time of pulse limits the possibil- ity to choose a recorder of appropriate bandwidth and necessary resolution. There-fore, the measurement system with possibility to create rectangular and sine shape was assembled, and measurements of firing impulse with both current pulse shapes were conducted on the same type of detonators.

Uređenje starog rudnika željeza u Rudama kod Samobora je u Republici Hrvatskoj jedan od pionirskih pokušaja zaštite i očuvanja tehničke rudarsko-geološke baštine (rudničkih prostorija) u okviru Neighbourhood Programme Slovenia-Hungary-Croatia 2004-2006. Interreg III A. U Hrvatskoj je tek u okviru Parka prirode Medvednica obnovljen i uređen za posjete stari rudnik srebra i olova Zrinski na Medvednici. Nažalost veliki potencijal podzemnih prostorija raških ugljenokopa dosad je nedovoljno iskorišten i valoriziran.

Nowdays the nonelectric systems are used more frequently for blasting activation than the electric systems due to their usage simplicity. The main part of the whole system are the thin tubes that generate and transfer shock wave from the starting point to the nonelectric detonator of the explosive. Depending on the structure and density of the inner "explosion layer" of the tube wall, propagation of the shock wave in tubes is 1900 to 2100 m/s. While setting up complex blasting fields, shock tubes are among themselves connected with nonelectric connectors or bunch connectors, all in order to insure effective blasting. It is necessary that the energy of the shock wave is safely transferred from one to many tubes or to nonelectric detonator. The task is to achieve maximum efficiency while transferring the energy of the shock wave from one tube to the others or to the detonators. Increase of the efficiency could be achieved by resonant construction of connectors adjusted to the spectrum of the shock wave of the tubes. Therefore the determination of the acoustic shock wave characteristics of the shock tubes was examined.

For testing electrical detonators some countries have national standards, members of the European Union have drafts or accepted standards that describe equipment minimal electrical and mechanical properties, preparation of samples to be tested, handling and testing procedures and finally data processing and presentation. In this paper we will consider one alternative method for testing firing current of electrical detonators and compare it to standard method of testing.

Adequate safety measures and their implementation are the essentials to the testing of electrical detonators. It is necessary to do everything possible in order to provide adequate safety measures in protecting human beings and equipment against dangerous impacts during detonators' firing. Most important safety measure is carrying out the explosion in a closed metal container. A container can be either hermetically sealed or half-sealed. If the container is half-sealed, people and equipment are protected against detonators' metal particles, but there is still an existing problem of how to protect people against the noise of explosion. Having constructed and tested a halfsealed testing apparatus, we assessed full justification for additional explosion pulse noise attenuation.

This paper considers the differences in measurement of time necessary for primer mixture initiation of electrical detonator when measured with two different methods. First method is electro&#8211 ; optical where time measurement is electrically triggered but stopped by light of primer mixture flame. Second method is electrical and measures time of current flow through bridge wire. There was significant difference in attained results. Reasons, as well as the influence on application are discussed in this paper.

During standard testing of electrical detonators, some of them require firing likewise. In this process, very high temperature is reached and the noisy explosion of a relatively high level is heard, while parts of metal shell of a detonator are scattered in all directions. This is the reason why the testings are carried out outdoors, accompanied by necessary human and equipment protection measures, or indoors, where the detonators could be tested in a specially designed high-pressured sealed testing apparatus. Outdoors&#8217 ; ; ; areas for testing are selected to be far enough from towns and places, whereas the handling with high-pressured apparatuses is awkward and demands for more time spent in testing. Therefore we undertook to construct the open-testing apparatus, where the effective attenuation of detonator explosion could be applied. This paper gives the results obtained in usage of the constructed open-testing apparatus with the application of standard attenuation elements.

Croatian Radio and Television built two big television studios (1000 m2 and 400 m2) and one big radio studio (400 m2) with control rooms. Because of noise protection requirements, the usual “box in box” design was applied, thus obtaining double and triple dividing walls and double floor and ceiling construction. It was necessary to control the quality of the construction, especially to check if there are any unwanted acoustical bridges. This was done by measuring the transmission of vibration through the partition walls of adjacent rooms. A measuring method with pulse stimulus was developed. A pulse stimulus of a constant and repeatable level was applied on the inner wall and the transmission level was measured on the outer wall. The measuring spots were optimally distributed to provide a statistically acceptable reliability for detection of irregularity in the structure of the studios construction. A test measurement was made on a double wall construction, once with an artificial acoustical bridge, and the next time without it. The difference of acceleration was used as a confident measure for the detection of a possible acoustical bridge.

To transfer audio data via computer networks, it is necessary to make data reduction because of their limited transfer speeds. A common way to do data reduction is using the psychoacoustic model of the human hearing. Nowadays, the fast development of the Internet puts demands on the efficiency of audio coders. A number of objective and subjective experiments have to be done in order to compare different audio coders. This paper compares three different audio coding systems: MPEG-2 Layer III, MPEG-4 AAC and Real Audio G2 by analyzing their THD, S/N ratio, cut-off frequency and impulse response. The MPEG-4 AAC coding system showed the best results.

Godine 1979. napravljen je “ Elaborat o sirovinskoj bazi ležišta arhitektonsko - građevnog kamena Vrsine kraj Trogira” (B.Crnković), a 1992. godine urađen je i “ Elaborat obnova rezervi u ležištu arhitektonsko-građevnog kamena vapnenca Vrsine” (E.Boljat). U cilju utvrđivanja rezervi mineralnih sirovina, sa stanjem 31. prosinac 1997. godine, trgovačko društvo AGAN KAMEN d.d. Split, povjerava izvođaču Rudarsko geološko naftnom fakultetu Sveučilišta u Zagrebu, izradu Elaborata obnove rezervi arhitektonsko građevnog kamena u ležištu “ Vrsine” , koji je izrađen u svibnju 1998. godine (O.Krasić). Obradom postojećih dokumentacijskih podloga, provedbom dodatnih istraživačkih radova trgovačko društvo AGAN KAMEN d.d. Split nastavlja s izradom preostale nužne dokumentacije - Dopunskog rudarskog projekta otkopavanja arhitektonskog građevnog kamena u kamenolomu “ Vrsine” , do ishođenja odobrenja za izvođenje rudarskih radova.

Kamen s otoka, odnosno iz kamenoloma “ Vrnik” plijeni svojim izgledom i bijelosivom do sivožutom bojom. Zahvaljujući mineraloško-petrografskim značajkama, sitnozrnoj strukturi te laganoj obradi čest je i raširen kamen za gradnju. Ekspolatacija, kao i prerada, arhitektonskog građevnog kamena na širem korčulanskom području započela je još u antičko doba. Tijekom starog vijeka Rimljani su eksploatirali kamen iz kamenoloma na otoku Korčuli. U narednom, srednjem vijeku eksploatacija i obrada arhitektonskog građevnog kamena bila je veoma znakovita, osobito u vrijeme vladavine Venecije na ovim prostorima. Tijekom opstojnosti Dubrovačke Republike (poglavito između 14. i 18. st.) izgrađeni su najistaknutiji arhitektonski dijelovi u Dubrovniku (najčešće kamenom iz kamenoloma Vrnik i Kamenjak), kao što je: Knežev dvor, Divone, crkva sv. Spasa, dominikanski samostan, mala Onofrijeva česma (fontana pred Kneževim dvorom) i ostale građevine. Dakako da je, pored dubrovačkih građevina vrijedno spomenuti i druge objekte koji su građeni od arhitektonskog građevnog kamena s otoka Vrnika: Kneževa palača na Cetinju, katedrala sv. Sofije u Carigradu. parlament u Budimpešti, kao i mnoge građevine u zemljama Bliskog istoka. Do izbijanja prvog svjetskog rata klesarski zanat na Korčuli bio je razvijen i u svijetu poznat i priznat. O tome svjedoči i to da je 1900. godine na Međunarodnom sajmu u Parizu, kamen s otoka Vrnika dobio zlatnu nagradu kao najbolji “ vapnenac sredozemnog bazena” . Izbijanjem prvog svjetskog rata klesarska djelatnost dolazi u težak položaj kao i ostale gospodarske djelatnosti na otoku Korčuli. Tijekom rata u eksploataciji su bili samo kamenolomi na Vrniku, Vrbovici i Oskorušici. Do 1921. godine ekspoloatacija arhutektonsko građevnog kamena odvijala se na području Vrnik-Lumbarda, potom u Vrhovici, Oskorušici i Vaji. Radila se uglavnom klesarija za stambene i javne objekte (Stolac, Dubrava, Orebić). Odlaskom Talijana 1921. god. i otvaranjem tržišta prema ostalom primorskom dijelu i unutrašnjosti zemlje povećava se i plasman kamena s otoka Korčule. Klesarski zanat naglo jača i doživljava svoj procvat poglavito u području Lumbarda-Korčula-Žrnovo. U vrijeme drugog svjetskog rata klesarska proizvodnja naglo opada. Jedini radovi iz tog vremena su bili vezani uz gradnju vijećnice u Zadru, korištenjem kamena s Vrnika. Početkom 1946. godine formiraju se dvije klesarske zadruge u istočnom dijelu otoka (Lumbarda i Vrnik), koje rade sve do 1948., kad se formira jedinstveno klesarsko poduzeće sa sjedištem u Gradu Korčuli. U vremenu 1948....1950. godine u ovom dijelu otoka djelovalo je “ GP Vrnik” , koje je objedinjavalo i velik broj klesara s otoka Vrnika. Svi oni kasnije prelaze u prošireno klesarsko poduzeće “ Kamenoklesarsko poduzeće Vrnik” koje eksploatira sljedeće kamenolome: Sutvaru, Vrnik, Badiju, Pelegrin, Vrbovicu i Vaju. Također, 1952./1953. godine poduzeće je počelo nabavljati prvu opremu za piljenje kamenih blokova, te postavlja gatersko postrojenje u luci UŠ, pomoću kojega je izvedeno niz radova, npr. mnoge stambene zgrade u Dubrovniku, Kineski paviljon na Zagrebačkom velesajmu, veći dio luke Ploče, građevine u Zadru i dr. Od 1955. godine klesarska djelatnost je u opadanju. Do likvidacije “ Kamenoklesarskog poduzeća Vrnik” dolazi 15. veljače 1961. godine, jer tada nije postojala perspektiva za njegov daljnji opstanak. Neposredno nakon toga, 16. veljače 1961. godine pristupa se osnivanju “ Kamenoklesarske zanatske radnje” . Poradi velikog broja radnika zadruga nije mogla opstati, te je 14. ožujka 1961. godine preregistrirana u poduzeće “ Klesar” , koje je izvelo niz većih i značajnijih objekata, poput aerodroma u Ćilipima kod Dubrovnika, hotela Bon Repos u Korčuli, upravnih i stambenih zgrada u Pločama. 1971./72. godine poduzeće “ Klesar” se zbog nastalih prilika integrira s “ GP Dubac” iz Dubrovnika. 1974. godine nakon likvidacije “ GP Dubac” , “ Zanatsko građevno poduzeće” postupno preuzima u svoj sastav klesare s istočnog dijela otoka Korčule. Jedan dio klesara radi na gaterskom postrojenju, dok drugi dio radi povremeno u jedinom aktivnom kamenolomu arhitektonsko građevnog kamena “ Humac” . Dio klesara se prekvalificirao, pa radi druge poslove unutar “ Zanatskog građevnog poduzeća” , kasnije “ Komunalne građevinske radne organizacije Korčula” iz Korčule. Novoosnovano trgovačko društvo VRNIK d.o.o. Korčula, želeći nastaviti istraživanja na području lokaliteta otoka Vrnika, naručilo je izradu Elaborata o rezervama arhitektonsko građevnog kamena u ležištu Vrnik (otok Vrnik-Korčula) (Štambuk, S. 1999. godina), od trgovačkog rduštva MRAMOR PROJEKT d.o.o., Zagreb. Obradom postojećih dokumentacijskih podloga, provedbom dodatnih istraživačkih radova, te stjecanjem potrebitog iskustva, trgovačko društvo VRNIK d.o.o. Korčula nastavlja s izradom ostale neophode dokumentacije u cilju ishođenja odobrenja za izvođenje rudarskih radova.

In this paper, the frequency spectra of the CUSA (Cavitation Ultrasonic Surgical Aspirator) probe at its working frequency of 25 kHz were measured in an oval container (simulating the cranium). The measurement was made at few field intensities, using the B&K hydrophone in the container, and the B&K microphone outside it. Cow brain tissue, physiologically similar to human brain was used as a dummy model. The same measurement was repeated in water to examine the spectrum difference in high and low attenuation media. During the measurement, the occurrence of the cavitation was observed by spectra changes.

U novije vrijeme arhitektonski kamen s područja Plano kod Trogira, korišten je pri mnogim graditeljskim zahvatima u RH, bilo da se radilo o obnovi porušenih ili izgradnji novih objekata - toranj Cibona, hotel I, zračna luka (Zagreb), Trg Garibaldi (Rijeka), zračna luka, Marmontova ulica (Split), samostan (Sinj), riva (Baška voda), glavni trg u Kninu i na Lošinju itd. Godine 1979. napravljen je “ Elaborat o sirovinskoj bazi ležišta arhitektonsko - građevnog kamena Plano kraj Trogira” (B.Crnković), a 1992. godine urađen je i “ Elaborat obnova rezervi u ležištu arhitektonskog kamena vapnenca Plano - Trogir” (M.Žižić). U cilju utvrđivanja rezervi mineralnih sirovina, sa stanjem 31. prosinac 1997. godine, trgovačko društvo AGAN KAMEN d.d. Split, povjerava izvođaču Rudarsko geološko naftnom fakultetu Sveučilišta u Zagrebu, izradu Elaborata obnove rezervi arhitektonsko građevnog kamena u ležištu “ Plano” , koji je izrađen u travnju 1998. godine (O.Krasić). Obradom postojećih dokumentacijskih podloga, provedbom dodatnih istraživačkih radova trgovačko društvo AGAN KAMEN d.d. Split nastavlja s izradom preostale nužne dokumentacije - Dopunskog rudarskog projekta otkopavanja arhitektonskog građevnog kamena u kamenolomu “ Plano” , do ishođenja odobrenja za izvođenje rudarskih radova.

The lack of communication channel capacity and erratic behavior of computer networks give audio experts a set of problems whose solving influence the use of internet for real time audio data transfer. Present audio coders (MPEG-1 and MPEG-2 standards) cannot widely vary their transfer speed during net overload which shows that it is necessary to build scalable coders. The development of the MPEG-4 standard went in this direction

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Computer simulation is an adequate way of analysing the ultrasound propagation through the brain occurring during neurosurgical operations. To perform a simulation in real conditions, it is necessary to ensure accurate calculations. Calculation accuracy was checked by measurements on a physical model which confirmed the accuracy of the simulation of sound propagation through air. By introducing known acoustic parameters of the brain tissue in the simulation, it was possible to simulate real situations met during neurosurgical operations by CUSA (Cavitation Ultrasonic Surgical Aspirator).

Computer simulation, if accurate enough, can substitute digital measurements in situations where it is difficult and inconvenient to perform measurements. A good example of such a situation are ultrasound field measurements within the human brain, which occur during ultrasonic brain cancer surgery. The simulation was based on the virtual source model, which ensured accuracy. The source of ultrasound has been described by its position and directivity characteristics. The medium has been described by its absorption coefficient and the velocity of sound in the medium. The reflective surfaces have been described by their geometry and absorption coefficient. The correctness of the mathematical interpretation used in the simulation was checked by measurements on a scaled model specially designed for research. The characteristics of the model were similar to those of the bounded plain. The comparison of the results of the simulation and the measurements on the model confirmed the quality of the computer simulation. Finally, the distribution of acoustic fields in the human cranium was simulated.

Cavitation Ultrasonic Surgical Aspirator (CUSA) used in neurological resectional surgery is a point source of ultrasound which can cause appearance of high ultrasonic field intensities in the parts which are not in the area where resection is being carried out. Brain tissue attenuation is one of the essential parameters for prediction of sound intensities within cranium. Because of low ultrasonic frequency CUSA operates on and because of small tissue sample, determination of brain tissue attenuation can not be carried out with con-ventional method. Using Time-delay Spectrometry (TDS), with careful selection of the reference medium, its dimensions, the measuring sample dimensions and the display of measurement transducers, brain tissue attenuation is measured at the frequency range CUSA operates on. The result shows that trend of attenuation changes within 1-10 MHz range does not continue at frequencies under 1 MHz.

When measuring tissue sample attenuation by TDS it is necessary to be able to reliably distinguish direct sound from its first reflection. While performing measurements, difficulties may arise due to direct sound shifting from one line window to another line window, which is caused by the difference in speed of ultrasound propagation through the reference and measured media. The necessary transducer distance and the allowed thickness of the measured sample must, therefore, be previously defined, to keep the movement, which can not be avoided, within the same line window.

Computer simulation begin as one of the fastest and the most efficient ways of designing and checking is commonly used nowadays. The accuracy of the mathematical interpretation used for simulation should be checked by field measurements or measurements on scaled models. Therefore, the simulation of sound field in bounded plane was checked on a scaled model. The level of sound pressure was measured on the model, especially designed for the presented research. The characteristics of the model are similar to the characteristics of bounded plane. The results of the measurements obtained in this way were compared with those obtained by computer simulation. The performed comparison proves the quality of computer simulation of a sound field.

Computer simulation, being one of the fastest and the most efficient ways of design-ing and checking, is commonly used nowadays. The correctness of mathematical interpretation used for simulation should be checked by measurements in field measurements or measurement on scaled models. Therefore, the simulation of sound field in bounded plane has been checked on scaled model. The level of sound pressure has been measured in a model, specially designed for this research, and it’s characteristics are similar to bounded plain. The results of measurements achieved in this way have been compared with those achieved by computer simulation. The com-parison of the results proves the quality of computer simulation of a sound filed. That is possible only in acoustically determined room and condition.

Standardne metode koje se koriste za mjerenje brzine, prigušenja i apsorpcije nisu upotrebljive za mjerenje nekih parametara na niskim ultrazvučnim frekvencijama i malim uzorcima tkiva mozga. Stoga je pristupljeno razvoju novih mjernih postupaka i sustava koji to omogućuju što je rezultiralo slijedećim izvornim znanstvenim doprinosom: Predloženi su novi mjerni postupci i mjerni sustavi i to: - za mjerenje brtine ultrazvuka kroz male uzorke tkiva mozga pri niskim ultrazvučnim frekvencijama - spektrometrija s vremenskim pomakom u vodi za mjerenje prigušenja kod malih uzoraka tkiva mozga - prilagođena metoda mjerenja s pomoću Kundtove cijevi u vodi za mjerenje apsorpcije malih uzoraka tkiva mozga. Mjerenjem su dobivene: - brzina ultrazvuka kroz mozak - gušenje i apsorpcija tkiva mozga, a sva tri parametra na niskim ultrazvučnim frekvencijama. Potvrđena je korelacija između teoretski dobivenih vrijednosti i rezultata mjerenja dobivenih predloženim mjernim postupcima. Navedeni rezultati omogućuju procjene u raspodjeli intenziteta ultrazvučnog polja u lubanji a time i biranje manje opasnih ultrazvučnih resekcijskih zahvata.