Possibilities of 3D machining of materials by abrasive water jets

Machining of materials through classical way, i.e. using conventional tools for turning, drilling, milling, grinding and polishing, has some limits that can be overcome applying an abrasive water jet (AWJ). Therefore, some possibilities of 3D machining by AWJ placed on 6 axes robot have been tested. Programming of traverse speeds and tilting angles of cutting head was based on Hlaváč’s theoretical model. Low pressure pump has been used for tests. Because of very low pumping pressure, a selfdesigned and manufactured special mixing chamber was used in the experiments. The article deals with preliminary results and points at the direction of further research

Minimal Detectable Displacement Achievable by GPS-RTK in CZEPOS Network

In this paper we have made a brief study of RTK precision to estimate possibilities of network RTK using CZEPOS for purposes of geotechnic monitoring of landslides in real time. In this paper we describe a testing methodology, which resulted in estimation of point-position precision and describing minimal detectable positional change. Based on our results it is concluded that displacements could be detected with centimetre accuracy even with short-period observations

Mobile IP in MANETs

Práce pojednává o problematice mobility stanic v IP sítích, konkrétně o protokolu Mobile IP. Dále je v ní naznačena problematika sítí MANET, se zaměřením na technologii Motorola MESH a také návrh integrace protokolu Mobile IP v těchto sítích s využitím hardwarových prvků Tropos 5210 MetroMesh router a prvků Cisco (směrovač, přepínač). Dále je popsáno vytvoření a nakonfigurování bezdrátové MESH sítě, její propojení se zařízeními Cisco a implementování protokolu Mobile IP. V dalším pokračování práce pojednává o sestavení bezdrátové sítě za pomoci Cisco bezdrátových přístupových bodů a implementování protokolu Mobile IP do této sítě. V závěrečné části jsou popsány testy funkčnosti a praktických vlastností tohoto uspořádání.This thesis discuss about the problem with mobility of stations in IP networks, concretely protocol Mobile IP and about the problems with this protocol in MANET networks, with the scope on Motorola MESH. First part is about design integration of protocol Mobile IP in this networks with usage Tropos 5210 MetroMesh routers and Cisco components (router, switch) to design and configure wireless MESH network, than connect this network with Cisco components and try to implement Mobile IP into this network. Second part is about design and configure wireless network from Cisco Wireless Access Points and about succesfully implementation of Mobile IP protocol into this network. In the last part is some tests of the function and quality of this topology.

Součty čtverců v číselných tělesech

Cílem práce je studovat totálně reálná kvadratická tělesa Q( √ D), ve kterých pro pevné přirozené číslo m platí, že všechny m-násobky totálně kladných celistvých prvků lze vyjádřit ve tvaru součtu čtverců. Dokazujeme poměrně silné nutné a postačující podmínky k tomu, aby uvažovaná tělesa měla tuto vlastnost. Dále uvádíme rychlý algoritmus, který pro pevné m najde všechna tělesa, ve kterých výše uvedená skutečnost nastává. 1The goal of this thesis is to study real quadratic number fields Q( √ D) such that, for a given rational integer m, all m-multiples of totally positive integers are sums of squares. We prove quite sharp necessary and sufficient conditions for this to happen. Further, we give a fast algorithm that verifies this property for specific m, D and that for a fixed m finds all such fields in polynomial time. 1Department of AlgebraKatedra algebryFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Comparing regional differentiation of land cover changes in natural and administrative regions of the Czech Republic using multivariate statistics

The detection and evaluations of land cover changes represent the major task for landscape transformation studies in post-communistic countries. The results of such evaluation are, however, highly influenced by spatial delimitation of monitored units as natural or administrative regions. Moreover, the objective quantitative assessment of land cover changes and their typologies in different types of regions can be hardly done by traditional map-interpretation approach. The aim of the present research was to evaluate the differences in results of land cover changes in the Czech Republic detected in natural (93 geomorphological units) and administrative (77 districts) regions using multivariate statistics. To analyse land cover (LC) changes we used STATISTICA 9 software. The application of principal component analysis (PCA), factor analysis (FA) and cluster analysis (CA) reveals the main overall trends in land cover changes in the Czech Republic. We applied PCA, CA and FA to land cover data from CORINE projects in 1990, 2000 and 2006. We analyzed LC changes in geomorphological units of Czechia as a whole. We made our calculation based on standardised data for land cover classes. The final number of variables (LC classes) used in the study was 11, drawing upon generalisation of only those land cover classes that are present in Czech landscape. For both sets of territorial units (i.e. natural and administrative), we calculated the Euclidean distance (full connections) between the cases (territorial units). The k-means method and hierarchical clustering were used for clustering. Based on these methods we set the typology of land cover changes in natural and administrative units. Finally, we assessed the differences between these typologies as regards statistical distribution of regions among the individual types. The factors influencing differences between these typologies are discussed, concluding in considerations on a role of spatial delimitation in land cover changes studies

Extremity compartment syndrome: A review with a focus on non-invasive methods of diagnosis

The article deals with an overview of acute extremity compartment syndrome with a focus on the option of non-invasive detection of the syndrome. Acute extremity compartment syndrome (ECS) is an urgent complication that occurs most often in fractures or high-energy injuries. There is still no reliable method for detecting ECS. The only objective measurement method used in clinical practice is an invasive measurement of intramuscular pressure (IMP). The purpose of this paper is to summarize the current state of research into non-invasive measurement methods that could allow simple and reliable continuous monitoring of patients at risk of developing ECS. Clinical trials are currently underway to verify the suitability of the most studied method, near-infrared spectroscopy (NIRS), which is a method for measuring the local oxygenation of muscle compartments. Less explored methods include the use of ultrasound, ultrasound elastography, bioimpedance measurements, and quantitative tissue hardness measurements. Finding a suitable method for continuous non-invasive monitoring of the syndrome would greatly improve the quality of care for patients at risk. ECS must be diagnosed quickly and accurately to prevent irreversible tissue damage that can occur within hours of syndrome onset and may even warrant amputation if neglected.Web of Science10art. no. 80158

Verification and numerical simulation of advanced composite inlet in compliance of airworthiness impact requirements

Bird or hail stone strikes are an important phenomenon which must be considered during aircraft design. Most of major bird or hail strike incidents result from engine ingestion. As engines are the sole thrust providing mechanisms of an aircraft, it is critical to investigate and mitigate the effects of bird or hail strikes on engine inlets and systems to the greatest extent possible. The article presents application of test verified numerical simulation for design and full-scale test verification of advanced composite air inlet for new generation of jet trainer aircraft from point of view of high speed impact resistance. The physical bird and hail impact tests were performed at the Czech Aerospace Research Centre (VZLÚ) according to airworthiness requirements. The measurement during impact test were performed by high-speed camera, Fiber Bragg Grating (FGB) sensors and strain gauges in cooperation with Czech Technical University (CTU) in Prague. The results from full-scale bird and hail strike tests were compared with numerical simulation

Trichoderma longibrachiatum and Aspergillus fischeri Infection as a Cause of Skin Graft Failure in a Patient with Critical Burns after Liver Transplantation

Infectious complications are responsible for the majority of mortalities and morbidities of patients with critical burns. Although bacteria are the predominant etiological agents in such patients, yeasts and fungi have become relatively common causes of infections over the last decade. Here, we report a case of a young man with critical burns on 88% TBSA (total body surface area) arising as a part of polytrauma. The patient's history of orthotopic liver transplantation associated with the patient's need to use combined immunosuppressant therapy was an additional complication. Due to deep burns in the forearm region, we have (after a suitable wound bed preparation) applied a new bi-layered dermal substitute. The patient, however, developed a combined fungal infection in the region of this dermal substitute caused by Trichoderma longibrachiatum and Aspergillus fischeri (the first case ever reported). The infection caused the loss of the split-thickness skin grafts (STSGs); we had to perform repeated hydrosurgical and mechanical debridement and a systemic antifungal treatment prior to re-application of the STSGs. The subsequent skin transplant was successful