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The nucleation and growth of cavitation bubbles few micrometers in size in water generated by a 60 ps 515 nm fiber laser is observed and visualized near nucleation threshold. The study is performed by monitoring the plasma size, the cavitation bubble size and the emitted shock waves. The latter two aspects are supported by the Gilmore model using a Noble-Abel-stiffened-gas (NASG) equations of state. For the first time, two types of cavitation events are identified and visualized that exhibit a difference of more than two orders of magnitude in the excitation energy converted to mechanical effects with minimal change in excitation laser pulse energy. The result is localized cavitation and reduced mechanical stress on water-based media with potentially positive implications for laser treatments of biological tissue.

U ovom diplomskom radu biti će obrađene ne destruktivne metode ispitivanja nosivih konstrukcija. Napravljena će biti usporedba između destruktivnih i ne destruktivnih metoda, te opisan proces tehničke dijagnoze na konstrukciji. Pojasniti će se trajnost betonske konstrukcije koja se mora ostvariti odgovarajućim planiranjem, projektiranjem i dimenzioniranjem, ali i također i odabirom građevnih proizvoda i izvođenjem radova. Tema rada je ne destruktivna Impact-echo metoda. Ista je teoretski obrađena, te su objašnjene teoretske postavke na temelju kojih funkcionira uređaj i način ispitivanja. Proračunima će biti dokazana ispravnost metode i svih njezinih segmenata. U praktičnom dijelu zadatka uređajem će se ispitati oštećeni most, te će se dijagnosticirati oštećenja, lokacija kao i težina oštećenja. In this master work, will be discussed non - destructive methods of testing load - bearing structures. A comparison between destructive and non-destructive methods will be made, and the process of technical diagnosis on the structure will be described. The durability of the concrete structure will be clarified, which must be achieved by appropriate planning, design and dimensioning, but also by the selection of construction products and execution of works. The topic of the this master work is the non-destructive Impact-echo method. It is theoretically processed, and the theoretical settings on the basis of which the device operates and the test method are explained. The calculations will prove the correctness of the method and all its segments.

Uvod: Lateralni epikondilitis ali tudi teniški komolec je boleče stanje, ki nastane zaradi prekomerne rabe ekstenzornih mišic zapestja. Težave pacientov se kažejo kot močna bolečina okoli lateralnega epikondila nadlaktnice, kar lahko vpliva na funkcijo in kakovost življenja posameznika. Simptomi se pojavijo med kontrakcijami ali palpacijo ekstenzornih mišic zapestja. Namen: Namen diplomskega dela je bil pri pacientih z lateralnim epikondilitisom komolca s pregledom literature primerjati učinkovitost zdravljenja z udarnimi globinskimi valovi in ultrazvokom. Metode dela: Literatura je bila iskana v podatkovni zbirki Pubmed. Vključene so bile raziskave, ki niso bile starejše od 10 let, so bile prosto dostopne, v angleškem jeziku in v katerih so primerjali izbrana postopka zdravljenja. Literaturo smo iskali v s kombinacijami ključnih besed: »tennis elbow«, »lateral epicondylitis«, »shockwave therapy«, »ultrasound therapy«. Rezultati: V pregled literature je bilo glede na vključitvene kriterije analiziranih šest raziskav. V vseh so primerjali udarne valove z ultrazvokom, vendar so se uporabljeni merilni protokoli razlikovali. Razlikovali so se načini zapisov rezultatov, v dveh raziskavah so uporabili mediano, v štirih povprečje. Obe terapiji sta bili uspešni pri zmanjšanju bolečine, merjeno z vizualno analogno lestvico in algometerom, ekstenzijo zapestja proti uporu, funkcijskim testom, močjo prijema in vprašalniki za oceno funkcionalnosti in kakovosti življenja. Med primerjavo terapij je bilo ugotovljeno, da so udarni valovi uspešnejši kot ultrazvok, predvsem v daljšem časovnem obdobju. Razprava in zaključek: Ker so bili pri terapiji uporabljeni različni parametri in različni merilni protokoli, je bilo raziskave med seboj težko primerjati. Stranski učinki ter denarna dostopnost terapije sta dva dejavnika, za katere menimo, da jih pri izbiri terapije moramo upoštevati. Zaradi nasprotujočih si rezultatov raziskav in nezadostnih podatkov o izbiti optimalnih parametrov za terapijo z udarnimi valovi ali ultrazvokom je za zdravljenje pacientov z lateralnim epikondilitisom komolca potrebno nadaljnje raziskovanje. Introduction: Lateral epicondylitis, or tennis elbow, is a painful condition, which results from overuse of wrist extensors muscles. Problems manifest as severe pain around the lateral epicondyle of the upper arm, which affects an individual's function and quality of life. Symptoms occur during contractions or palpation of the wrist extensors muscles. Purpose: The purpose of the diploma work was to compare the effectiveness of shock wave and ultrasound treatment in patients with lateral epicondylitis of the elbow joint by reviewing the scientific literature. Methods: Literature was searched in the PubMed online database. Studies that were not older than 10 years, were full freely available, in English language, and compared selected treatment methods were included. We searched the literature with combinations of keywords: "tennis elbow", "lateral epicondylitis", "shockwave therapy", "ultrasound therapy". Results: In the literature review, six studies were analyzed according to inclusion criteria. In all studies, shock waves were compared with ultrasound, but the measurement protocols used differed. Methods of recording results differed, with a median used in two studies and an average in four. Both therapies were successful in reducing pain as measured by a visual analog scale and algometer, wrist extension against resistance, function tests, grip strength, and questionnaires to assess functionality and quality of life. During the comparison of therapies, it was found that shock waves are more successful than ultrasound especially over a longer period of time. Discussion and conclusion: Due to different therapy parameters and different measurement protocols, research is more difficult to compare with each other. Side effects and the affordability of therapy are two things that we believe should be considered when choosing therapy. Due to the contradictory results of other research and insufficient data on the choice of optimal parameters for therapy, additional research should be done in this area.

Naloga obravnava problematiko postavitve za slikanje lasersko povzročenih udarnih valov v tekočini. Slikanje teh valov zaradi njihove velike hitrosti ni enostavno, razlike v lomnem količniku, ki jih ti povzročijo, pa ne moremo zaznati s klasičnimi metodami slikanja. Metodi schlieren in senčne fotografije omogočata zaznavanje majhnih sprememb lomnega količnika. Na podlagi zahtev obeh metod smo v programu Solidworks izdelali model sistema, ki lahko z večkratno osvetlitvijo senzorja tekom časa ekspozicije zajame ostre slike udarnih valov. Prilagojen je svetlobi z valovno dolžino 800 nm in lahko zajame vidno polje premera 24 mm. Vključuje zaslonko z ostrim robom za potrebe schliren fotografije, z njeno odstranitvijo pa lahko sistem uporabljamo tudi po metodi senčne fotografije. S sistemom lahko slikamo tudi druge pojave, ki spremenijo lomni količnik v transparentnem mediju, kot so na primer kavitacijski mehurčki, mešanje fluidov in konvektivni prenos toplote. Komponente sistema so modularne in jih lahko prilagodimo našim potrebam. The thesis deals with the problem of setup for imaging laser-induced shock waves in a fluid. Imaging of these waves is difficult due to their high speed, and the differences in the refractive index they cause cannot be detected by classical imaging methods. The schlieren and shadowgraphy methods enable us to detect small changes of the refractive index. Based on the requirements of both methods, we have built a Solidworks model of an optical system that can capture sharp images of shock waves, by repeatedly illuminating the sensor during its exposure time. It is designed for the light with the wavelength of 800 nm and can capture a field of view with a diameter of 24 mm. It includes a knife-edge insert for the needs of schlieren photography, and by removing it, the system can also be used for shadowgraphy. The system can also be used to image other phenomena that change the refractive index in a transparent medium, such as cavitation bubbles, fluid mixing and convective heat transfer. The components of the system are modular and can be adapted to our needs.

Upon cavitation cloud collapse an omnidirectional shock wave is emitted. It then travels through the flow field, causing a cascade of events resulting in erosion, noise, vibration and the cavitation shedding process. Despite that the accumulated data points evidently to the presence of the shock waves, the direct measurements hardly exist - and even then, they are very expensive and time consuming to perform. In the present paper, the possibility of detecting shock waves inside cavitating flow is shown. The methodology bases on using two conventional high speed cameras. With the first one cavitating flow from a distance is observed, determining the position of the wave, while the second camera with a microscopic lens enables a close-up view to determine the number and size change of air bubbles as a shock wave passed them. By calibration and reference measurements the amplitude of the shock waves was determined. This relatively simple approach enabled the first observation of shockwaves which occur at the cavitation cloud collapse (downstream of the attached cavity). Several examples of shock wave dynamics are shown and how they influence the general cavitation cloud behaviour. Shock wave front velocities and local pressure waves caused by cloud collapse were estimated from visualization, reaching values to more than 700 m/s and over 5 MPa respectively.

Comparative analysis of pressure wave propagation, following laser-induced ablation of the human cornea, was performed. Evolution of the pressure field as well as temporal and spatial dependencies of the transient pressure amplitudes created at various input laser parameters, corresponding to different typical procedures of laser eye surgery, is presented comprehensively. The computations were performed with the next generation of the acoustic eye model, previously validated against existing measurements. The analysis allows the assessment of potentially problematic regions within the eye where the resultant positive and/or negative pressure may exceed values which are considered safe for the patient. Izvedena je bila primerjalna analiza širjenja tlačnega vala po laserski ablaciji človeške roženice. Izčrpno je predstavljeno širjenje tlačnega polja ter časovne in prostorske odvisnosti amplitud tlaka, ustvarjenih z različnimi vhodnimi laserskimi parametrih, ki ustrezajo različnim značilnim postopkom laserskih operacij oči. Izračuni so bili izvedeni z naslednjo generacijo akustičnega modela očesa, predhodno potrjenim z naslombo na obstoječe meritve. Analiza omogoča oceno potencialno problematičnih področij v očesu, kjer lahko pozitivni in/ali negativni tlak preseže vrednosti, ki veljajo za varne za pacienta.

An adaptable, laser-diode-based illumination system was developed to simultaneously visualize the dynamics of slow and fast phenomena in optically transparent media. The system can be coupled with still or high-speed cameras and makes it possible to generate an arbitrary train of illumination pulses with a variable pulse duration, pulse energy, and an intrapulse delay with a temporal resolution of 12.5 ns. Its capabilities are presented with selected illustrative visualizations of the dynamics of the shock waves and the cavitation entities generated after the laser-induced breakdown in water.

The paper presents a novel method for automatic segmentation of the low-contrast shadowgraphs that are acquired during the examination of the laser-induced shockwaves evolution. The method is based on two-stage, active-contour algorithms. First stage ensures global robustness, but it is locally inaccurate. It is implemented by traditional snake based on texture cues. The outcome serves as initialization to the second refining stage detection. In the second stage the detection is robust only locally and improves local accuracy. To do this, we introduce a greedy-snake algorithm. Local optimum is searched with respect to responses of steerable filtering and edge orientation similarity by exploiting the Bayesian formalism. The paper presents validation of the method on large data set of low-contrast shadowgraphs by comparison to the manual segmentation technique. The obtained results demonstrate overall good performance, robustness, high accuracy, and objectivity of the method.

Uporaba laserjev ima pomembno vlogo v oftalmologiji. Za varno izvajanje posegov, ki temeljijo na fotodisrupciji, je potrebno dobro razumeti optični preboj v kapljevinah in spremljajoče fizikalne pojave. V kadici z destilirano vodo, ki predstavlja poenostavljen model očesa, smo z 1 ns laserskimi bliski diodno črpanega trdninskega laserja povzročali preboj. Z odklonsko sondo, PZT senzorjem in hitro kamero smo zaznavali kavitacijske mehurčke in udarne valove. Določili smo energijske pragove za preboj in maksimalne polmere mehurčkov pri različnih oddaljenostih mesta preboja od stene kadice. Opazovali smo dinamiko mehurčkov v bližini trdne meje in proste površine ter odboje udarnih valov. Ugotovili smo, da so uporabljene detekcijske metode ustrezne in zanesljive ter omogočajo ponovljive meritve. Lasers are an important instrument in ophthalmology. To provide safe photodisruption-based procedures, laser-induced breakdown in liquids and corresponding physical phenomena must be well understood. We used a diode-pumped solid-state laser with 1 ns pulses to induce breakdown in distilled water in a cell. Cavitation bubbles and shock waves were detected using beam-deflection probe, PZT sensor and high-speed camera. We determined threshold energies for laser-induced breakdown and maximal bubble radii at different distances between the breakdown volume and the cell wall. We analyzed bubble and shock wave dynamics near a solid boundary and a free surface. We established, that the used detection methods are suitable and reliable.

Oblikovanje metala eksplozivom jedna je od mlađih grana oblikovanja metala deformiranjem. Razlikuje se od konvencionalnih metoda oblikovanja jer se primjenjuje energija eksploziva za oblikovanje obradka. U radu su obrađeni temeljni zakoni obrade metala deformiranjem, čimbenici koji utječu na uspješnost oblikovanja te metode i sustavi koji se koriste pri oblikovanju metala eksplozivom.

Terapija udarnim valovima

Razmatrano je impulzivno širenje sfernog i cilindričnog ustrojstva kao pokretača magnetohidrodinamičkih (MHD) udarnih valova. Pretpostavilo se da se površina izvora valova tijekom određenog vremena ubrzava dok ne postigne maksimalnu brzinu. Takva ekspanzija stvara val velike amplitude u okolnoj plazmi. Nelinearni razvoj valne fronte uzrokuje ustrmljavanje valnog profila koji dovodi do nastanka diskontinuiteta, tj. udarnog vala. Ispitivalo se kako vrijeme i položaj nastanka diskontinuiteta ovisi o raznim početnim parametrima: trajanju akceleracijske faze, maksimalne brzine ekspanzije (definira također i akceleraciju), Alfvénove brzine (time je definiran i Mach-ov broj), početne veličine strukture. Navedeni model je proširenje jedno-dimenzionalnog modela Vršnak and Lulić (2000). Temeljna razlika se sastoji u tro-dimenzionalnoj evoluciji modela, u kojem se mora uzeti u obzir smanjenje valne amplitude s udaljenošću. Osnovni cilj analize bio je odrediti i usporediti vremena i udaljenosti nastanka diskontinuiteta u okolinama niske i visoke vrijednosti plazmenog parametra beta.

Obrađen je fenomen spektralnih promjena koje se dešavaju prilikom prolaska udarnih valova kroz određena sredstva.