Several untypical trigonometric equations

U radu je riješeno nekoliko netipičnih trigonometrijski jednadžbi, koje osim trigonometrije zahtijevaju i neka druga matematička znanja. Takav tip jednadžbi često se susreće na matematičkim natjecanjima kao i na klasifikacijskim ispitima za upis na fakultet.Several untypical trigonometric equations have been solved in the paper, which, in addition to trigonometry, demand a knowledge of some other mathematical branches. Such type of equations is often present at various mathematics competitions as well as entrance exams selecting students for admission to faculties

Spectrographic Trace Analysis of Tin in the Presence of Large Amounts of Iron

It is possible to lower the inferior limit of spectrographic trace analysis of Sn in iron and steel1 if the Sn is separated by coprecipitation from the solution obtained by dissolving the sample in a mineral acid. The coprecipitation of Sn2+ 2•3 was in these experiments tested with CdS which is formed in the investigated solution. The amount of Cd2+ must be known because the spectrographic lines of Cd were used as reference lines, i. e. as an internal standard

New materials and technologies in aero and space research

Space technology plays an integral and indispensable role in our daily lives. Whether we are talking about live broadcasts of World Cup matches, satellite-assisted emergency management efforts, or the nightly weather forecast, one thing is true: our lives would be very different without satellite images or satellite-based communication and navigation systems. Space technology is key to our modern, knowledge-based society. Today space makes a vital contribution when it comes to promoting research and development, education and innovation, economic growth, providing highly qualified jobs, improving our quality of life, protecting the Earth, ensuring our security and defence and furthering international cooperation. Military platforms—such as ships, aircraft, and ground vehicles— rely on advanced materials to make them lighter, stronger, and more resistant to harsh environmental conditions. Currently, the process for developing new materials frequently takes longer than a decade. This lengthy process often means that developers of new military platforms are forced to rely on decades-old, mature materials, because potentially more advanced materials are still being developed and tested and are considered too large a risk to be implemented into platform designs. Al alloys have been the primary material for the structural parts of aircraft because of their well known performance, well established design methods, manufacturing and reliable inspection techniques. Fiber reinforced polymer composites have been increasingly used in aerospace. Fiber Metal Laminate (FML) is a new kind of hybrid composite. Materials used to construct spacecraft and protective gear—including the International Space Station and space suits for astronauts—must be lightweight yet strong enough to guard against cosmic dust that travels at hypervelocity

The Effects of Aggressive Environments on the Properties of Fly Ash based Geopolymers

This paper analyzes the effects of two different aggressive environments, concentrated ammonium nitrate solution (480 g/dm(3)) and sodium sulphate solution (50 g/dm(3)), on the structure and mechanical strength of fly ash based geopolymers. Geopolymer samples were subjected to the aggressive solutions over a period of 365 days. It was found that exposure to the NH4NO3 and Na2SO4 solutions caused small decrease in geopolymer strength (10-20 %). The most valuable insight into the structural changes caused by testing of the geopolymer samples in the aggressive solutions was provided by means of Si-29 MAS NMR. It was found that the immersion of geopolymer samples in the NH4NO3 solution caused breaking of Si-O-Al bonds in the aluminosilicate geopolymer gel structure. On the other hand, treatment of the geopolymer samples with the Na2SO4 solution resulted in breaking of Si-O-Si bonds in geopolymer gel structure and leaching of Si. It was concluded that the major changes in the geopolymer structure were associated with the changes in the pH values of aggressive solutions during the testing

Tribological Aspects of the Process of Winding the Steel Rope Around the Winch Drum

Proper winding of the steel rope around the winch drum is great importance, mostly for: prolonging the service life of the rope, reduction of deformations of the body and the sides of the drum if the winding of the rope is multilayered, increasing of the safety factors, easier unwinding of the rope while lowering the load, even running of the drive unit, etc. The focus of this paper is on the analysis of the friction which occurs in the process of winding and unwinding the rope around the winch drum. Friction force is in its highest intensity when the rope passes from one layer to another, if the winding of the rope is multilayered. As the result of the research, certain mechanisms of winding of the rope from the aspects of the friction force were obtained, and the effects of the forces on the sides of the drum were analyzed

Electrical properties of doped BaTiO3 Ceramics

The electrical resistivity and PTCR (Positive Temperature Coefficient of Resistivity) effect doped BaTiO3 ceramics with different dopant were investigated in this paper, The content of additive in doped samples were ranged from 0.01 to 1.0 at% Er/Yb. The samples were prepared by a conventional solid state sintering procedure and sintered at 1320 °C for 4 hours. For samples doped with Er2O3 (0.01 at% Er/Yb), SEM analysis shows abnormal grain growth with the average size range between 20 μm - 40 μm. For samples doped with Yb2O3 the average size was from 30 μm - 50 μm. With increase of dopants concentration the average grain size decreases, and for samples doped with 1.0 at% Er/Yb, grain size range between 3 μm - 20 μm for samples doped with Er and between 1 μm - 10 μm for samples doped with Yb2O3. The specific electrical resistance were measured in temperature range from 25 °C to 170°C at different frequencies, ranged from 100Hz to 1MHz. To a temperature of 120 °C, resistance has a slight increase with increasing of temperature, but above this temperature the resistance rapidly increasing. The value of the specific electrical resistance decreases with increasing concentration of Er/Yb, reached the minimum at certain dopant content (0.5 at% Er/Yb), then increased rapidly with dopant content in high doping level

The Rare-Earths influences on doped BaTiO3-Ceramics Microstructure and Electric Characteristics

The influence of rare-earth additive content on microstructure and electric properties of doped BaTiO3 ceramics is investigated. The concentration of Er2O3 and Yb2O3 in the doped samples range from 0.01 to 1.0at % . The samples are prepared by the conventional solid state reaction, and sintered at 1320° and 1350°C in air atmosphere for 4 hours. SEM analysis shows that all samples are characterized by polygonal grains. The uniform and homogeneous microstructure with grain size ranged from 20 to 45μm is the main low doped samples characteristics. For the samples doped with the higher dopant concentration (0.5 and 1.0 at%) the average grains size is ranged from 5 to 10μm. Dielectric measurements are carried out as a function of temperature up to 180°C at different frequencies. The low doped samples display the high value of dielectric permittivity at room temperature. A nearly flat permittivity-temperature response is obtained in specimens with higher additive content. The Curie temperature of doped samples were ranged from 126 to 130°C. The Curie constant for all series of samples decrease with increment of dopant concentration and the lowest values is mesured from samples doped with 0.01 wt% of aditive. The obtained value of γ pointed out that the specimens have almost sharp phase transition. Also, the specific electrical resistance is measured in function of temperature at the different frequencies from 100Hz to 1MHz. With increasing additives concentration, the electrical resistance decreases to the concentration of 0.5 at% and then increases

Benchmark based on application signature to analyze and predict their behavior

Currently, there are benchmark sets that measure the performance of HPC systems under specific computing and communication properties. These benchmarks represent the kernels of applications that measure specific hardware components. If the user’s application is not represented by any benchmark, it is not possible to obtain an equivalent performance metric. In this work, we propose a benchmark based on the signature of an MPI application obtained by the PAS2P method. PAS2P creates the application signature in order to predict the execution time, which we believe will be very adjusted in relation to the execution time of the full application. The signature has two performance qualities: the bounded time to execute it (a benchmark property) and the quality of prediction. Therefore, we propose to extend the signature by giving the benchmark capacities such as the efficiency of the application over the HPC system. The performance metrics will be performed by the benchmark proposed. The experimentation validates our proposal with an average error of prediction close to 7%.Instituto de Investigación en Informátic