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Biomechanica Hungarica7. évf. 2. sz.

Tartalom

Előszó

  • Borbás Lajos ,
    Kiss Rita :
    Előszó [56.62 kB - PDF]EPA-02271-00012-0010

Eredeti közlemények

  • Bocskai Imre Zoltán ,
    Kiss Zoltán ,
    Sándor László Gábor ,
    Bojtár Imre ,
    Nagy Zsolt Zoltán :

    The mechanical behaviour of the zonular apparatus greatly affects the accommodation process because it moves out from the ciliary muscle and runs into the lens capsule. The zonular fi bres convey the force between the ciliary body and the crystalline lens. For the measurement of the mechanical properties of zonular fi bres is necessary to know its geometry. In this paper we analyzed the network of porcine zonular fi bres with scanning electron and optical microscope. We manifested that the porcine zonular fi bre system differs from human and monkey eyes. The thickness of the apparatus of intertwined zonular fi bres is approximately 45 um and the length from the origin to the insertion is about 1.5 mm. Based on these informations the input parameters of numerical modelling can be more precise to clarify the accommodation process.

  • Simonovics János ,
    Bujtár Péter ,
    Váradi Károly ,
    Szűcs Attila ,
    Fejér Zsolt :

    Nowadays the examination of implants from engineering point of view is becoming more and more supported in the medical fi eld. Instead of the more problematic cadaver examination, the computer based simulations are growing more popular. The examinations must be validated to be able to stay with the realistic situation. Using these engineering methods it became possible to do measurements on the reconstructions of a human resectioned mandible. The creation of the bone models is one of the most varying fi elds in the biomechanical simulation. In the literature a wide range of Young modulus for the bone cortical layers can be found and these values are actively used even in different further fi nite element simulation researches. However the proper modeling of the cortical layer thickness and correctly calibrated mechanical parameter settings bare key importance regarding the stability and connection of the implants and the fi xing screws. The values of the Young modulus are depending on many factors, for example gender or even the age, not even mentioning further different infl uencing factors. In this study destructive biomechanical examinations were carried out on bones received from dead people. The samplings of the bone were conducted from the area of the screwing used in the mandible reconstruction. Considering the results it can be concluded that the values in the literature are often not as accurate. Regarding orthotropic values of the mandible, so far has only been a small segment of information was covered. The measured values are lower than the ones in the literature. In case of the highest value it is still 3.5 GPa Young modulus in the axial direction. The results can be used in order to create a more reliable model combined with a more realistic Young modulus for the fi nite element simulation of the bone models. On these models

  • Simonovics János ,
    Bujtár Péter ,
    Váradi Károly ,
    Szűcs Attila ,
    Fejér Zsolt :

    The number of patients diagnosed with cancer is reaching a scarily high number worldwide. This is no different in the area of mandible cancer. Unfortunately Hungary is quite high up in the ladder. The registered known number of patients with mandible cancer and the associated number of death occurrences are also showing signifi cant data in the country. However it is easy to diagnose, alcohol consumption and smoking or just bad oral hygiene really pushes the statistics. Inside the oral cavity, in case of mandible cancer and late diagnosis the only viable solution is the bone resection. To determine the extent of the cancer and to carefully plan the surgery procedure or in case of models which were created for biomechanical examinations, the medical science more and more often uses the image based processes and tools. Next to the realistically built models a more punctual mechanical parameter simulation becomes possible. It is highly important that the necessary information is extracted from the patients with the least stress. With the shortest time and smallest radiation the image must be made in a way that the scan can be well evaluated and it is usable. Within the current examination in the medical fi eld of imaging methods a gold standard MSCT and a specifi cally in the head-neck region used CBCT methods will be compared specifi cally from biomechanical modelling point of view. During the comparison the gray value was examined by the use of a cadaver head. The results show that the gray values provided by CBCT differs slightly from the MSCT values that is considered as reference. The more extent absolute error occurs with less frequency. Based on these facts the CBCT can be used for the density based material comparison for biomechanical models with less radiation dose.

  • Závodszky Gábor ,
    Paál György :

    Thrombus formation is a thoroughly researched area, posing several unanswered questions. Quite many of the underlying processes are still not well understood. This uncertainty arises from the fact that the blood clotting mechanism in our bodies involves a rather complex reaction cascade with plenty of components. These underlying dynamic processes stretch over the domains of several disciplines (as there are biomechanical and biochemical reactions as well as fl uid dynamical components). In this study the factors thought to be the most infl uential were selected and coupled with the transient fl ow fi eld that reacts not only to the cardiac pressure waves but also to the changing geometry of the vessel due to the clot formation. Although the number of degrees of freedom is reduced heavily, this model is already capable of qualitatively reproducing the results of in-vivo measured hemostasis.

  • Závodszky Gábor ,
    Paál György :

    According to popular consideration prolonged sitting posture in work can cause pain at different regions of the back. Many researches aiming to defi ne the relationship between these two, and as a result of noticing the problem many design solutions can be found, some of which are considered as alternative. Healthy sitting posture should be mean that with anterior rotation of the pelvis the curve of the lumbar spine would be neutral or more preferably lordotic. In sitting the muscle balance changes thus there is more muscle activity needed for erection of the trunk and anterior rotation of the pelvis. In this study muscle activity in standing and in two different sitting postures is estimated as a difference of the two moments acting on the pelvis, which are the upper body weight moment and the passive elastic moment. Further investigation of the effects of hip-fl exing thigh muscles or other passive tissues on pelvic range of motion is warranted.

  • Bálint Magyar ,
    Gábor Stépán ,
    I-Ming Chen :

    This paper presents the application of the Dynamic Time Warping (DTW) algorithm in the analysis of human functional movements in activities of daily living (ADLs). Dynamic Time Warping was originally developed for automatic speech recognition, though the method has been adopted by several fi elds of biomechanics. As a part of the post-stroke rehabilitation project COSMOSYS, the aim is to quantify the ADL performances of hemiparetic subjects, hence to be able to track their progress during physiotherapy.