The studied rock collapse structure is located on the Liburnian coast (Rijeka Bay, channel zone of the NE Adriatic). The relief of the southern part of this coast, with a length of 6.5 km, is a large ...escarpment with very steep to vertical slopes reaching heights of 100 m above sea level, as a result of tectonic movements along the Kvarner fault zone. These events probably led to a sudden relaxation of the highly fractured rock mass. The progressive expansion occurred at locations where previously favourably oriented faults and fissures had formed a polygonal rock collapse resembling a rock-slide which is the focus of this study. Another aim of this study is to reconstruct and explain the complex morphological evolution of the studied landslide, from the pre-failure deformations, through the failure itself, to post-failure displacements, as well as possible future instabilities. Recent techniques to survey the instability, location and to analyse the evolution of the rupture surface and its dimensions were combined (Unmanned Aerial Vehicle, Side Scan Sonar and Remotely Operated Vehicles). The estimated total volume of displaced rock mass is 950,000 m3. The lower part of the instability phenomenon was submerged during the Holocene sea level rise. Since then, a large part of the displaced rock mass has been in a stable position, with sporadic rock falls. However, given unfavourable orientation and discontinuity characteristics, as well as unfavourable environmental influences, possible instabilities might also be expected in the future.
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Within the shipbuilding process, the outfitting activities are aimed to be deployed within stages before the ship's erection and ship launching as much as possible, where the cost of the working hour ...is lower and work quality higher. High level of ship outfitting before launching is one of the most important goals of today’s modern shipyards. In this work, within the ship equipment process, the most important criteria will be identified, evaluated and ranked according to their impact on the level of ship outfitting before launching. Expert approaches and hierarchical ranking is going to be used along with the creation of a computer application to support the solution which can be applied for different shipyards. The result of the evaluation is the sequence of criteria relevant to their impact on the level of outfitting before launching. Based on such results, the authors are proposing improvement of the ship outfitting process, which is expected to improve the ship's equipment level before launching and thus reduce the cost of the shipbuilding process. In the end, the authors will also indicate the guidelines for continuing the research for the purpose of further improving the ship outfitting process.
In this paper we prove that there does not exist a set of four non-zero polynomials from \(\mathbb{Z}X\), not all constant, such that the product of any two of its distinct elements decreased by ...\(3\) is a square of a polynomial from \(\mathbb{Z}X\).
The development of ecological awareness followed by stringent laws on the protection of natural resources and workers direct the manufacturing industry at the development and implementation of ...alternative methods for cooling and/or lubrication in the machining of metals. The paper investigates the feasibility of using a vortex tube for cooling when turning martensitic stainless steel. Experimental research was conducted to understand the effects of vortex tube cooling on the corrosion resistance of the machined surface and on production costs. It has been determined that the vortex tube cooling has no significant influence on the corrosion resistance and that the tool costs have the most significant influence on the unit production cost. In conclusion, compared to the conventional emulsion cooling in metal cutting, the vortex tube cooling offers a cost-effective solution to the sustainable turning of martensitic stainless steel.
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This study deals with the condition examination of elementary school buildings in Primorje-Gorski Kotar County, Croatia. For schools to be functional and of high quality, adequate maintenance is ...mandatory. Therefore, school maintenance programs need information on the building's condition based on systematic and comprehensive assessments as a primary input. This study aims to establish a framework for assessing the condition of school buildings, based on which information can be obtained quickly and practically regarding the condition of all critical facility elements. To this end, a database on schools and their conditions was created. The conditions of school buildings in terms of damage and defects and their causes were determined. Descriptive and inferential statistical operations were performed on the collected data. A condition assessment of the buildings was performed using a questionnaire survey among the principals, based on the school buildings division model developed in this study; the model presents building elements and a systematic visual condition rating scale. According to the available data, this is Croatia's first condition assessment on elementary school buildings. The main results show that on average, the examined schools are in good condition. Moreover, according to the results, the school building condition is most affected by dilapidation and lack of financial resources.
Cement screed consists of cement, sharp sand and water, laid as a thin layer over the concrete subfloor. Although the screed is strong, it can be additionally reinforced with fibres, most often ...polypropylene fibres. In this study, cotton knitted fabric waste (CKFW) was obtained from a local factory producing underwear to reinforce the cement screed. A total of eight mixtures were made: reference mixture, screed reinforced with polypropylene fibres and six mixtures reinforced with CKFW. CKFW was added in 1,25 %, 2,50 % and 5,00 % of the total volume. Before adding to the mixtures, the first CKFW group was saturated with tap water, whereas, the second CKFW group was saturated with dispersion that improves adhesion. The density and air content of the fresh mixtures were tested, and the compressive strength and flexural strength were determined when the specimens were 28 days old. The specific fracture energy is determined based on the curve from the plot of load vs. displacement. The CKFW increases the ductility of cement screeds, although it has no significant effect on the compressive and flexural strength of the specimens. The CKFW that was saturated with tap water achieved better results.
In this paper we prove that every Diophantine quadruple in ℝ X is regular. In other words, we prove that if {a, b, c, d} is a set of four non-zero elements of ℝX, not all constant, such that the ...product of any two of its distinct elements increased by 1 is a square of an element of ℝX, then
(a+b-c-d)2=4(ab+1)(cd+1).
Some consequences of the above result are that for an arbitrary nℕ there does not exist a set of five non-zero elements from ℤX, which are not all constant, such that the product of any two of its distinct elements increased by n is a square of an element of ℤX. Furthermore, there can exist such a set of four non-zero elements of ℤX if and only if n is a square.
To ensure the better structural integrity and maximum safety of bulk carriers in the ship design phase, an appropriate corrosion margin is introduced by the classification societies, which should ...enable the exploitation of ships during the projected 25-year life cycle. The new Common Structural Rules introduce even higher corrosion margin value to ensure the structural integrity of the ship. This directly affects the increase in hull weight and thus the need for more total installed power and higher fuel consumption. Higher fuel consumption results in increased emissions which directly affects environmental pollution. For these reasons, efforts are being made to introduce alternative energy sources, cleaner fuel, ship weight reduction, and the overall economic efficiency of ships. Therefore, using experimental data collected on aging bulk carriers, the paper explores the corrosion margin reduction potential considering its impact on hull weight. Assuming that the corrosive processes occur after four years of operation, a linear model that describes the percentage of plate wear as a function of the as build-in the thickness of inner bottom plates (IBP) of fuel oil tanks (FOT) located on the double bottom of aging bulk carriers, is analyzed. Over the course of 25 years, the IBP segment was monitored on 36 different ships surveys. In this way, 520 input data describing the depth of corrosion were formed. At the same time, records were kept on the mean thickness of the original metal plate, which enabled systematization of the empirical database and grouping of measured values by intervals of original plate thicknesses, and simple conversion of corrosion depth into adequate percentage values. Depth corrosion percentages were represented by standard linear models known in the literature. Based on this analysis, representative numerical and graphical results were obtained. Conclusions from the paper can assist to optimize corrosion margin and the energy efficiency of future vessels.
In this study, the use of a popular deep reinforcement learning algorithm – deep Q-learning – in developing end-to-end control policies for robotic swarms is explored. Robots only have limited local ...sensory capabilities; however, in a swarm, they can accomplish collective tasks beyond the capability of a single robot. Compared with most automatic design approaches proposed so far, which belong to the field of evolutionary robotics, deep reinforcement learning techniques provide two advantages: (i) they enable researchers to develop control policies in an end-to-end fashion; and (ii) they require fewer computation resources, especially when the control policy to be developed has a large parameter space. The proposed approach is evaluated in a round-trip task, where the robots are required to travel between two destinations as much as possible. Simulation results show that the proposed approach can learn control policies directly from high-dimensional raw camera pixel inputs for robotic swarms.
Volatile compounds (VCs) analysis was performed by solid-phase microextraction-gas chromatography-mass spectrometry. Main groups that define typical cheese flavour formed as a result of the addition ...of a starter culture (SC). The cheesemaking environment, the type of milk (cow, ewe, goat), and the heat treatment of milk were observed. The SC had influenced the total amount of some fatty acids and ketones. Compared to cow and ewe cheeses, goat cheese had higher values of hexanoic and octanoic acids, however, two alcohols, 1-hexanol, 2-ethyl- and hexanol, were only present in cow cheeses. We confirmed that the cheesemaking environment is also an important parameter influencing VC profiles of cheese. Higher amount of esters and the absence of 2-phenylethanol were observed in raw milk cheese, compared to thermised milk cheese where δ-octalactone was present.
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