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Purpose The aim of the present study was to determine whether plates with only 1 screw pair can be used for Le Fort I fracture management. Good postoperative results motivated the direct application of mandible fixation principles to the fractured midface region without additional experimental research. However, the amount and distribution of the forces in the midface region is different from those on the mandible. Materials and Methods Testing was conducted on plastic anatomic models. The validity of the experimental model was tested before the fixation techniques were compared. Standard miniplates and miniscrews were used for fixation of the maxilla. The model surface strain analysis was conducted using the noncontact object grating method, which enabled the surface strain measurement without direct influence on the measured model. Results In 2 screw pair fixation, the outer screw pair has little effect on the local strain distribution, but it lowers the contact forces along the crack. One screw pair fixation is stable enough for fixation, but it has a greater strain peak at the crack edges. Conclusion Our results showed that 1 screw pair per plate was enough for stable fixation, and 2 or more screw pairs should only be used when the bone fragment at the fracture site cannot sufficiently transmit forces along the crack.

How to correctly locate and uniquely index the same image point during the optical measurements is known as the correspondence problem. It occurs when there is a need for tracking features in all of the recorded images, regardless of the number of used cameras and the number of recorded images. In this paper, we have compared the correspondence problem solutions for the passive and active single, stereo and multi-camera systems, with a special focus to the active multi-camera system, for which we present the absolute method for unique stereo pair indexing. By using a modified projection approach, we have showed that it is possible to eliminate the need for the epipolar principle from the correspondence problem solving. With the new indexing method, each pixel can be used as a separate measuring point since it has been indexed with two independent absolute phases. Searching for stereo pairs has also been reduced from the two-dimensional image domain to a one-dimensional array, where the next stereo pair is most likely the nearest neighbor to the observed one., Problem lociranja i jednoznačnog prepoznavanja jedne te iste točke na više uzastopno ili istovremeno snimljenih slika tijekom optičkih mjerenja oblika ili deformacija poznat je pod pojmom jednoznačnosti. Javlja se kada postoji potreba za praćenjem neke optičke karakteristike u svim snimljenim slikama, neovisno o broju korištenih kamera i broju snimljenih slika. U ovom su radu kritički uspoređena rješenja problema jednoznačnosti kod pasivnih i aktivnih sustava s jednom kamerom, stereo sustava s dvije kamere i vlastito razvijenog sustava s više kamera. Posebno je za aktivni sustav s više kamera razvijena apsolutna metoda za jednoznačno indeksiranje stereoparova. Korištenjem modificiranog projekcijskog pristupa pokazano je kako je iz postupka za rješavanje problema jednoznačnosti moguće eliminirati potrebu primjene epipolarnog principa. Nova metoda indeksiranja omogućava da svaki piksel u kameri postaje zasebna mjerna točka, jer je indeksirana s dvije međusobno neovisne apsolutne faze. Ovom modifikacijom je pretraga cijele dvodimenzijske domene slike svedena na pretragu jednodimenzijskog reda kod kojega je sljedeći traženi stereopar susjed trenutno promatranoj točki.

Development of the flexible multi-camera optical surface digitization system which projects non coherent coded light in two perpendicular directions is presented. By the introduction of the absolute method for stereopairs indexing the need for twofold searching through the phase images is eliminated, as well as the influence of discontinuities. Critical areas responsible for outlier generation are eliminated prior to triangulation by combining the modulation filtering of phase images and gradient filtering of the absolute phase images. Sequential triangulation process enabled triangulation of points that are not visible in all the cameras, thus providing means for digitization of partially occluded areas. Free form calibration object eliminated the need for specialized planar calibration objects, which combined with variable external camera parameters resulted in a system that can be adjusted depending on the measurement problem. In comparison to the commercial single and stereo camera systems our approach reduces the number of projections for the digitization of the complete objects., Razmatrana je problematika razvoja fleksibilnog optičkog sustava s proizvoljnim brojem slobodnih kamera koji digitalizaciju oblika površine provodi dvostrukim projiciranjem nekoherentnog kodiranog svjetla. Apsolutnom metodom određivanja stereoparova eliminirana je potreba za dvostrukim pretraživanjem faznih slika, te utjecaj diskontinuiteta. Kombinacijom amplitudnog filtriranja slike parcijalnih faza i gradijentnog filtriranja slike apsolutnih faza eliminirana su kritična područja, te smanjen broj pogrešno identificiranih stereoparova. Uvođenjem slijednog postupka triangulacije omogućeno je trianguliranje i onih točaka koje nisu istovremeno vidljive u svim kamerama, odnosno uvedena je mogućnost digitalizacije površina djelomično zasjenjenih površinskim artefaktima. Kroz kalibraciju slobodnim kalibrom eliminirana je potreba za specijalnim planarnim kalibracijskim objektima, u sprezi sa varijabilnim vanjskim parametrima kalibracije sustav postaje prilagodljiv mjernom zadatku. U odnosu na komercijalno dostupne sustave s jednom i dvije kamere novi sustav omogućava smanjenje broja potrebnih projekcija za digitalizaciju kompletnog mjernog volumena.

Standard fracture toughness tests require standard specimens with the presumption that mechanical properties are uniform in the crack growth direction. Standards for CTOD fracture tests prescribe remote crack mouth opening displacement-CMOD, which can lead to in-adequate results in the case of heterogeneous materials properties. This paper describes the application of an object grating method on the fracture behaviour of a heterogeneous specimen. Fracture behaviour is described by measuring deformation on the surface of a specimen, in terms of crack tip opening displacement and, consequently, by strain determination. An object grating method is advantageously used when measuring modified CTOD tests on two specimens with an initial crack in a macroscopic heterogeneous welded joint. Results significantly show that fracture behaviour depends on the material in the vicinity of the crack tip concerning the direction of crack propagation.

Mechanical properties of cereal (starch-based) extrudates are perceived by the final consumer as criteria of quality. We investigate one of the important characteristics of extrudates, mechanical hardness, which is one of the main texture parameters. Texture quality has an influence on taste sensory evaluation, and thus on the acceptability of the product. Characteristics that have great influence on acceptability are crispness, elasticity, hardness and softness. These attributes are narrowly related to, and affected by, the process parameters. A 2-level– 4-factor factorial experimental design was used to investigate the influence of temperature of expansion, screw speed, feed moisture content and feed rate, and their interactions, on the mechanical hardness of extrudates. Feed moisture content, screw speed and temperature are found to influence, while feed rate does not have significant effect on extrudate hardness. Mechanical properties of specimens were measured by means of compression testing, based on the concept of nominal stress, using a universal testing machine and special grips that were constructed for this purpose.