UNMANNED SURFACE VEHICLE – TRITOR Ljulj, Andrija; Slapničar, Vedran; Brigić, Juraj
Brodogradnja,
2022, Letnik:
73, Številka:
3
Journal Article, Paper
Recenzirano
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This paper presents an unmanned surface vehicle Tritor that was developed, constructed, and tested within an innovative, multi-purpose, multidisciplinary, low-budget and environmentally friendly ...solution. The idea behind this work was trying to invent a new concept of a miniature surface vehicle that will be unmanned, remotely controlled and autonomous, with electric propulsion, and with an innovative Three Slender Cylinders Hull (3SCH) form gaining advantages in comparison to existing surface vehicles. This initial work is focused on vehicle prototype design, propulsion system development and optimization, control design, and trials, while research related to advantages of the vehicle in terms of naval architecture criteria such as drag and power, stability, seakeeping, and maneuverability will be investigated in further work. In addition, the paper intends to contribute to a new trend in developing vehicles with electrical propulsion that could use renewable sources of energy such as wind and solar energy. The potential usage of the vehicle can be civilian or military, and further work will be focused on larger models, improved based on the experience got during the development of the vehicle. Tritor vehicle was successfully designed, constructed, and tested in real environmental conditions. The preliminary results show that the vehicle has required performances and potential for improvements in the future. The main scientific contribution of this work is advanced surface vehicle development with a focus on a new hull form and the integration of electric propulsion in it.
Technology development allows the design and standardization of manual work in human activities which are yet to be observed, especially those of low-volume discrete production, such as in ear, nose ...and throat (ENT) surgery, particularly endoscopic sinus surgery (ESS). The paper considers the possibilities of developing an approach that would be useful for specific ESS manual work analysis and design and its automation in a future. The consideration includes, beside other aspects, initial steps, such as the traditional work motion capture by camera and experiments by Leap Motion Controller, Perception Neuron 2.0 and Emotiv Epoc+.
Recently, an increasing attention is given to preservation and popularization of Croatian traditional boat building, which plays an important role in Croatian cultural and national heritage. ...Reconstruction and revitalization projects of individual historical vessels are key factors within preservation process, where the lack of technical documentation is one of the main issues. In this paper, a simple and efficient procedure for taking offsets of a traditional fishing vessel guc is presented to document and preserve the traditional Croatian vessel form. A 3D model of a guc is generated using the points on the hull surface obtained by the manual measurement and a fairing process. Numerical simulations of the resistance test for a fishing vessel are carried out for a wide range of speeds, and the curve of effective power as a function of vessel speed is provided.
Accidents in Facilities for Storing Hazardous Materials Tepic, Goran; Sremac, Sinisa; Moraca, Slobodan ...
Operational Research in Engineering Sciences: Theory and Applications,
08/2019, Letnik:
2, Številka:
2
Journal Article
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The vital elements of numerous industrial plants include the process equipment which, depending on the nature of the technological process, can be exposed to internal pressure in the general case of ...a variable size. The typical examples of process equipment are available at LPG stations (distribution centers), fuel tanks, gas boilers, combustion plants, etc. Practical experience and the analysis of the cause of accidents have shown that damage to process equipment is most often followed by the explosions of the tanks in which the flammable substances, such as LPG, petrol, diesel and jet fuel, oils, etc. are stored. The explosion of a tank cannot occur spontaneously, but only results from external factors. This means that the explosion of process equipment is preceded by the primary events whose harmful effects are manifested through the following phenomena: the weakening of the strength of a tank, an increase in pressure above the nominal value, or a combination of the two preceding cases.
An approach to converting general cargo ship to cement carrier is analysed in the present study, emphasising the structural aspects of the conversion. A comprehensive re-appraisal of the conditions ...of the ship hull, considering her history and present condition of the structure, is provided. Two case studies are presented where the strength assessment has been performed using 2D sectional and 3D finite element models, generated according to the available hull drawings and thickness measurement reports. The results of the two studies are interpreted with respect to the structural modifications carried out during the conversion process, and some general conclusions are drawn.
Computational model was developed to investigate aerodynamic forces acting on a closed-wheel race car. A particular focus was on the effects of ground clearance and rake angle on aerodynamic drag and ...lift forces. Computations were performed for a steady viscous fluid flow using the realizable k-ε turbulence model and non-equilibrium wall functions. The computational results indicate a strong influence of ground clearance and rake angle on aerodynamic loading of a race car. The largest drag force coefficient was obtained for the largest ground clearance. The drag force coefficient for the squatting car is larger by 5% compared to the reference case, where the both front and rear ground clearances are 100 mm. For the nose-diving car, the drag force coefficient is equal to the reference case. Increasing the ground clearance caused a negligible increase in the lift force coefficient in comparison with the reference case. A decrease in the ground clearance yielded an increase in the lift force coefficient. The largest positive lift force coefficient was obtained for a squatting car, whereas the largest negative lift force coefficient was observed for a nose-diving car. While the favorable aerodynamic downforce acting on front wheels is larger for a nose-diving car, for rear wheels it is larger for a squatting car.
Hilly terrain may considerably influence energy yield and structural loading of wind turbines. Wind energy developers are therefore required to accurately predict wind characteristics at the wind ...farm site already in the designing phase. It is necessary to determine how particular hill shape and size affect wind characteristics at the location of wind turbines operating in the wake of a hill. In order to address this complex issue, small-scale laboratory experiments were carried out in a boundary layer wind tunnel (BLWT). The focus was on characteristics of the flow at the same position downstream of the hill and the wind turbine models studied on various sizes and shapes of the hill model. Three hill models (a small and a large hill with laterally uniform heights and a hill with a bay) were exposed to the thermally neutrally stratified atmospheric boundary layer (ABL) simulation. In each experiment, there was only one hill model in the BLWT test section. The configuration without the hill, i.e. the flat terrain model, was tested as a reference case. Downstream of the hill model, there was a single (alone-standing) wind turbine model. Flow characteristics were studied downstream (behind) the wind turbine model. The wind turbine model was in the parking position in order to study wind characteristics in the situation with a strong wind when there is no rotation of rotor blades. The experimental results indicate a velocity decrease and stronger turbulence in the wind turbine wake in the presence of a hill, which trend is more pronounced in the case of larger hills. Strong velocity gradients are observed around the hub height in the large hill configuration, while this velocity deficit is the smallest in the hill with a bay configuration due to flow channeling. The velocity power spectra reveal the characteristic peak due to the vortex shedding from the hill ridge. The obtained results provide a new insight into the turbulent wake characteristics of a single wind turbine placed downstream of a hill with a potential to serve as a validation tool for computational studies.
Suppose G is a graph with the vertex set V (G). A set D ⊆ V (G) is a total k-dominating set if every vertex v ∈ V (G) has at least k neighbours in D. The total k-domination number γkt(G) is the size ...of the smallest total k-dominating set. When k = 2 the total 2-dominating set is referred to as a double total dominating set. In this work we compute the exact values for double total domination number on H-phenylenic nanotubes HPH(m,n), m,n ≥ 2 and H-naphtalenic nanotubes HN(m,n), n = 2k, m,n ≥ 2. As all vertices have a degree 2 or 3, there is no total k-domination for k ≥ 3 for H-phenylenic and H-naphtalenic nanotubes, and the double total domination is the maximum possible.
Greenhouse gases reduction through waste management in Croatia Anić-Vučinić, A., Faculty of Mechanical Engineering and Naval Architecture, Zagreb (Croatia); Hublin, A., EKONERG - Energy and Environmental Protection Institute, Zagreb (Croatia); Ružinski, N., Faculty of Mechanical Engineering and Naval Architecture, Zagreb (Croatia)
Thermal science,
(2010), 2010-00-00, 20100101, Letnik:
14, Številka:
3
Journal Article
Recenzirano
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The climate change policy is one of the key factors in the achievement of sustainable development in the Republic of Croatia. Control and mitigation of green house gases is correlated with all ...economy activities. Waste management is one of the main tasks of environmental protection in Croatia. The Waste Management Strategy of the Republic of Croatia and the Waste Management Plan in the Republic of Croatia define the concept of waste management hierarchy and direct and indirect measures as criteria for sustainable waste management establishment. The main constituent of this system is avoiding and minimizing waste, as well as increasing the recycling and recovery level of waste and land fill gas, which also represent green house gases mitigation measures. The Waste Management Plan consists of several direct and indirect measures for green house gases emission reduction and their implementation also affects the green house gases emissions. The contribution of the methane emission from land fills amounts to about 2% of the total green house gases emissions in Croatia. The climate change control and mitigation measures as an integral part of waste management sector strategies represent the measures of achieving the national objectives to wards green house gases emission reduction which Croatia has accepted in the frame work of the Kyoto Protocol.
The presented research shows the time dependent temperature distribution and thermal time constant within a typical industrial X-ray computed tomography (XCT) system used for dimensional metrology. ...Temperature effects can significantly affect measurement results of XCT scans either by directly changing the dimensions of the measurement object, or by indirectly changing the geometry of XCT scanner. In either case, the effect is not known well enough to be used for correction of measurement results or estimation of measurement uncertainty. In order to determine these effects, traceable temperature measurements were performed with a custom measurement system designed for this application. The influence of temperature fluctuations on length errors was determined by correlation of the measured temperature fluctuations with measurement deviations of a reference standard in repeated CT scans at different X-ray power levels. After experimental determination of X-ray focal spot displacement due to thermal expansion, a simple mathematical model of X-ray source displacement as a function of its temperature was developed and validated for a selected X-ray power level.
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