Design of Custom Made Prosthesis of the Hip

Replacement of a natural hip joint with an artificial is one of the most commonly used surgical procedures in orthopaedic surgery. This paper describes the methodology of the hip joint prosthesis design, which presents the foundation for the automation of all stages of the development of custom-made prostheses. A general mathematical model based mostly on B-spline surfaces is used in order to define the prosthesis geometry. In order to verify the method, a software solution was developed and used for designing prostheses based on ten diagnostic images obtained by various methods. The results of the analysis of the ten designed prostheses, out of which five manufactured, show that deviations from the desired values are less than the errors caused by diagnostic imaging

Copyright Protection of 3D Digitized Artistic Sculptures by Adding Unique Local Inconspicuous Errors by Sculptors

In recent years, digitization of cultural heritage objects, for the purpose of creating virtual museums, is becoming increasingly popular. Moreover, cultural institutions use modern digitization methods to create three-dimensional (3D) models of objects of historical significance to form digital libraries and archives. This research aims to suggest a method for protecting these 3D models from abuse while making them available on the Internet. The proposed method was applied to a sculpture, an object of cultural heritage. It is based on the digitization of the sculpture altered by adding local clay details proposed by the sculptor and on sharing on the Internet a 3D model obtained by digitizing the sculpture with a built-in error. The clay details embedded in the sculpture are asymmetrical and discreet to be unnoticeable to an average observer. The original sculpture was also digitized and its 3D model created. The obtained 3D models were compared and the geometry deviation was measured to determine that the embedded error was invisible to an average observer and that the watermark can be extracted. The proposed method simultaneously protects the digitized image of the artwork while preserving its visual experience. Other methods cannot guarantee this

The Design and Simulation of an Astronomical Clock

This paper describes and explains the synthesis of an astronomical clock mechanism which displays the mean position of the Sun, the Moon, the lunar node and zodiac circle as well as the Moon phases and their motion during the year as seen from the Earth. The clock face represents the stereographic projection of the celestial equator, celestial tropics, zodiac circle (ecliptic) and horizon for the latitude of Belgrade from the north celestial pole to the equator plane. The observed motions of celestial objects are realized by a set of clock gear trains with properly calculated gear ratios. The method of continued fraction is applied in the computation of proper and practically applicable gear ratios of the clock gear trains. The fully operational 3D model of the astronomical clock is created and the motion study of its operation is accomplished by using the SolidWorks 2016 application. The simulation results are compared with the ephemeris data and the detected differences are used to evaluate the long-term accuracy of the astronomical clock operation. The presented methods of the clock mechanism synthesis can be useful for the design, maintenance and conservation of large-scale city astronomical clocks since these clocks represent a precious historical and cultural heritage of European civilization

Configuring a machine tool based on hybrid O-X glide mechanism

The application of computer technologies based on enhanced geometric interpretation of the product in terms of virtual prototype is considered as the basis for product development in the XXI century. This enables integrated development of products that includes the conception, design, optimization, production planning and the manufacture of machine tool as a product of complex mechatronic structure. This paper describes the configuration of the new machine tool with a hybrid kinematic structure based on the original O-X glide mechanism, which includes analyses of kinematics, workspace, virtual prototype simulation and planning of the control system for the management and programming

Configuring a machine tool based on hybrid O-X glide mechanism

The application of computer technologies based on enhanced geometric interpretation of the product in terms of virtual prototype is considered as the basis for product development in the XXI century. This enables integrated development of products that includes the conception, design, optimization, production planning and the manufacture of machine tool as a product of complex mechatronic structure. This paper describes the configuration of the new machine tool with a hybrid kinematic structure based on the original O-X glide mechanism, which includes analyses of kinematics, workspace, virtual prototype simulation and planning of the control system for the management and programming

The Design and Simulation of an Astronomical Clock

This paper describes and explains the synthesis of an astronomical clock mechanism which displays the mean position of the Sun, the Moon, the lunar node and zodiac circle as well as the Moon phases and their motion during the year as seen from the Earth. The clock face represents the stereographic projection of the celestial equator, celestial tropics, zodiac circle (ecliptic) and horizon for the latitude of Belgrade from the north celestial pole to the equator plane. The observed motions of celestial objects are realized by a set of clock gear trains with properly calculated gear ratios. The method of continued fraction is applied in the computation of proper and practically applicable gear ratios of the clock gear trains. The fully operational 3D model of the astronomical clock is created and the motion study of its operation is accomplished by using the SolidWorks 2016 application. The simulation results are compared with the ephemeris data and the detected differences are used to evaluate the long-term accuracy of the astronomical clock operation. The presented methods of the clock mechanism synthesis can be useful for the design, maintenance and conservation of large-scale city astronomical clocks since these clocks represent a precious historical and cultural heritage of European civilization

Copyright Protection of 3D Digitized Artistic Sculptures by Adding Unique Local Inconspicuous Errors by Sculptors

In recent years, digitization of cultural heritage objects, for the purpose of creating virtual museums, is becoming increasingly popular. Moreover, cultural institutions use modern digitization methods to create three-dimensional (3D) models of objects of historical significance to form digital libraries and archives. This research aims to suggest a method for protecting these 3D models from abuse while making them available on the Internet. The proposed method was applied to a sculpture, an object of cultural heritage. It is based on the digitization of the sculpture altered by adding local clay details proposed by the sculptor and on sharing on the Internet a 3D model obtained by digitizing the sculpture with a built-in error. The clay details embedded in the sculpture are asymmetrical and discreet to be unnoticeable to an average observer. The original sculpture was also digitized and its 3D model created. The obtained 3D models were compared and the geometry deviation was measured to determine that the embedded error was invisible to an average observer and that the watermark can be extracted. The proposed method simultaneously protects the digitized image of the artwork while preserving its visual experience. Other methods cannot guarantee this

The Design – in Faults as a Causes of the High Performance Machines Failures

High capacities and key roles in the technological processes cause the extremely high financial losses in the case of high performance machines failures. This paper presents case studies of bucket wheel excavators, stackers and bucket chain reclaimers failures caused by design – in faults. Besides that, paper gives a redesign solutions which are developed by University of Belgrade – Faculty of Mechanical Engineering

Experimental modal analysis of cross-laminated timber floors

Cross-laminated timber (CLT) floors have gained in popularity due to their outstanding strength, aesthetic appeal, good fire resistance, and high level of prefabrication. However, due to their high stiffness-to-weight ratio, CLT floors are highly susceptible to pedestrian-induced vibrations. In design practice, vibration serviceability is usually assessed by assuming a floor as a set of CLT panels with no inter-panel connections, which leads to overestimation of the vibration response. In this paper, an experimental dynamic testing was carried out to identify modal properties and pedestrian-induced response of two CLT floors with different number of panels in a floor assembly. Influence of the inter-panel connections on the floor modal properties and pedestrian-induced vibration response is particularly studied and discussed

Strength analysis of bucket wheel excavator’s eight wheel equalizing system

This paper presents the results of the study dedicated to the problem of the bucket wheel excavator equalizing system (ES) strength. Finite element analysis of two wheel (TWB), four wheel (FWB) and eight wheel (EWB) bogies were conducted in order to determine weak points in ES structure. Strength and carrying capacity of FWB and EWB structures might be jeopardized due to their insufficient strength under lateral forces acting during curve travel. Severe failure of similar TWB structure is also presented and certain paraleles were made