The concrete is considered as one of the most important building materials. Ordinary Portland cement is used as binding material in concrete production. The manufacturing process of cement is accompanied with carbon dioxide emission. The use of green concrete as environmentally friendly material is very important. The local natural pozzolan (LNP) found in volcanic areas in Almadinah Almunawara in Saudi Arabia can be used as partial replacement of cement and sand to produce light weight concrete with special properties and to improve the mechanical properties of environmental friendly concrete. The main objective of this study is to investigate the effect of partial replacement of cement by weight with local natural pozzolan powder in cement mortar cubes to reduce carbon gas emissions and energy in the manufacturing process of cement. The study also includes the effect of partial substitution for sand used in cement mortar with (LNP) and with partial substitution for cement with silica fume on its mechanical properties. The use of pozzolan with special type of cement is recommended by the Saudi Building Code in case of concrete exposed to sulfate and / or chloride with severe exposure. The experimental work is divided into two parts: cement replacement with (LNP) powder and sand replacement with (LNP) in the presence of silica fume. A 84 cement mortar cubes of 50x50x50 mm were made (6 cubes as control specimens, 24 cubes with cement replacement by weight with (LNP) powder at percentages of 10%, 20%, 30% and 40%, 24 cubes with sand replacement by volume with (LNP) at percentages of 10%, 20%, 30% and 40%, without silica fume, 15 cubes with sand replacement by volume with (LNP) at levels of 0%, 10%, 20%, 30% and 40% and with 5% substitution for cement by weight with silica fume, and 15 cubes with sand replacement by volume with (LNP) at replacement levels of 0%, 10%, 20%, 30% and 40% and with 10% replacement of cement by weight with silica fume). The specimens were tested at 28 and 180 days. The utilization of (LNP) and silica fume showed a marked influence on the mechanical properties of cement mortar specially in the case of sand replacement with (LNP).

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Due to the presence of metakaolin in composite cement that consists of Portland Cement and blended cement containing granulated blast furnace slag o, 45% at constant percent at all mix, with OPC 100, 55, 51, 47 and 43 percent and finally metakaolin 0, 0, 4, 8 and 12 % in sea water up to 12 months was investigated. The composite cement pastes which contains cement, granulated blast furnace slag and metakaolin posses higher value of physical properties at 4 and 8% metakaolin such as compressive strength and bulk density than those of OPC and blended cement but opposite direction on apparent porosity and portlandite. By X-ray diffraction indicated that calcium aluminate hydrate and calcium silicate hydrate leading to strengthening the durability of the hardened composite cement pastes.

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This paper deals with the influence of the steel-concrete interface quality and preexisting oxides layer on reinforcement corrosion in passive state. In passive state, steel corrosion rate in concrete is considered null for conventional civil engineering structures due to the relatively short design service life time. On the contrary, for the nuclear waste facilities, due to a very long design life time, this low corrosion rate can become a risk. Previous studies, dealing with chloride induced steel corrosion in concrete, have clearly shown that the quality of the steel-concrete interface is a predominant factor for corrosion propagation. The purpose of this work is to study the influence of steel-concrete interface defaults and preexisting oxides layer on steel passivity and the consequences on the corrosion rate. Electrochemical methods and destructive surface analysis techniques were used to assess the corrosion rate of the embedded steel bars. Results confirm that the quality of the steel-concrete interface and the preexisting oxides layer affect the steel corrosion rate in passive state.

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Ground-penetrating Radar (GPR) is a modern and widely used technology that works to detect buried objects and study surfaces using a non-destructive method by transmitting and receiving electromagnetic waves. This work aims to model radar GPR signals to detect human bodies under the rubble resulting from earthquakes, wars, etc. by the GprMax2d program, which depends on the method FDTD. Many models and simulations have been done using the 500 MHz frequency to detect human bodies, relying on the physical properties of human tissue, such as conductivity and dielectric.

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This article describes the energy intensity of soil excavation and variations of cutting effort constituents acting on manipulator which are required for effective interaction with soil. Internal processes of soil cutting are analyzed upon processing of various soils. The schemes of manipulator interaction with soil are considered since they are important both for analysis of operation of existing earthmoving machinery and for development of new units. Studying volumetric soil cutting by earthmoving manipulator is a contact, elastic and plastic, nonlinear problem with accounting for temperature mode of deformation. The required horizontal and vertical constituents of cutting forces, temperature field, and soil flow rate upon one pass of manipulator have been predicted with accounting for sliding surface. The methods and equations of limit equilibrium theory have been applied resulting in derivation of equations of soil resistance against cutting. The results are confirmed by substantiated use of fundamental dependences, assumptions and limitations, correct formulation of mathematical simulation, application of modern mathematical methods and hardware. The predicted and experimental data on resistance against cutting of various soils are presented with regard to practical range of applied cutting angles for knife manipulators of earthmoving machinery.

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This paper presents the development of an information acquisition and processing system through Wi-Fi wireless communication that allows the programming, capture and sending of data stored in an iButton sensor, to later centralize and store this information in a Web server. The design of the system was structured in three modules and a hardware interface based on the ESP 8266 chip, which was responsible for sensor control and communication. An application for mobile phones was developed to capture the data coming from the hardware application, this application has the option to serve as the programming interface for the iButton sensors and the interface for capturing the data recorded in the internal memory of the same device.

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The investigation data of the formation peculiarities of oxide films on the Ti6A14V alloy in tartaric acid solutions have been given. It is shown that the behavior of alloy forming dependences is conditioned by the anode current density. At ja < 0.5 A·dm–2 the continuous oxide film is not formed on the alloy surface and the preset value of the final voltage on the cell is not reached. With an increase in ja > 0.5 A·dm–2, alloy forming dependences show a linear behavior that is indicative of the formation of low porous films. In these conditions, the oxide film formation rate is in direct proportion to the value of ja. The electrochemical oxidation of Ti6A14V alloy in tartaric acid solutions results in the formation of interference-colored oxide films. The oxide film ultimate thickness and color are defined by the preset voltage and are independent of the current density and electrolyte concentration. The isolating properties of obtained films were studied by way of the cathode polarization of oxidized specimens in the sulfate copper-plating electrolyte. The research done allows us to make a conclusion that electrochemical copper deposition is a convenient tool for the detection of defective spots in oxide films. It is shown that due to the specific features of the reduction kinetics of Cu2+ ions on the oxidized titanium it is reasonable to use for the studies the initial sections of polarization dependences that correspond to ?E = 0.2-0.25 V. The alloy polarization dependences allow us to establish unavailability of apparent dependences between the oxidation current density, the electrolyte concentration, the cell final voltage value and the polarization that occurs during the Cu2+ ion reduction. The anodic connection of copper-coated specimens conditions the reversible dissolution of a greater portion of the specks of copper deposits. It is indicative of the electron conduction of film defects. The obtained data allow us to vary the electrolysis parameters in a wide range with no significant influence of the treatment mode of Ti6A14V alloy on the quality of oxide coatings.

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A compacted soil shows a deterioration in physical properties, affects the availability of water and the growth of plants. The amount of useful water in the soil is a characteristic of it that defines its agricultural aptitude and corresponds to the water that can be absorbed by the plants. This study aims to evaluate the relationship of water parameters, field capacity (FC) and permanent wilting point (PWP), with the optimum moisture content (OMC) in clay soils. The physical properties of the soil, such as texture, real and bulk density, maximum dry density (MDD) value and OMC are analyzed. The Proctor compaction test is used to determine the MDD and its OMC; a Richards Pressure Chamber is utilized to obtain the FC and PWP and a tension table to acquire other moisture retention parameters. The results indicated that in Latossolos (oxisols) of Brazil (LV, LVA) soils, the ratio for FC with water retention value of -100 hPa is 100% of OMC, and in Vertisol soil for -300 hPa is 100% of the OMC. For Latossolos (LV, LVA) soils, the PWP (-15000 hPa) is 80% of the OMC and for Vertisol soil 80% of the OMC. With statistical analyze a polynomial regression model is obtained to relate the water contents to OMC. This regression shows that exist a direct relationship between water retention and OMC values.

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This work presents the results of a series of experiments on heavy oil transformation in a steam-and-air environment at the temperatures and pressures that ensure the presence of water in the steam, the subcritical, and the supercritical states. As a result of heavy oil exposure to water, it has been found that in various thermodynamic conditions, water shows different reactivity and selectivity. In a series of experiments of the hydrothermal effect at temperatures in the range between 360 and 420 °C and the pressures in the range between 4 and 24 MPa, a decrease in the content of aromatic and resinous hydrocarbon compounds and reduced density of liquid end products have been detected. It has been shown that supercritical water provides the most significant formation of light fractions: compared to the source oil, their content increases 2.5 times. Mostly paraffin-naphthenic hydrocarbons are formed on the background of aromatic and resinous hydrocarbons destruction, while subcritical water ensures less significant formation of light fractions (their content increased by 73 %, compared to the source oil); however, it contributes to the most significant reduction in the content of asphaltenes (by 53 rel% compared to the source oil). The greatest degree of sulfur removal is mostly ensured by supercritical water.

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Bioplastics are plastics that can be used just like conventional plastics, but will disintegrate by the activity of microorganisms into water and carbon dioxide. Starch is a natural polymer material that can be used for bioplastic production. The addition of reinforcing particles has been shown to improve the mechanical properties of bioplastics. The aim of this research is to know the potency of mango seed and microparticles of ZnO and clay as filler and glycerol concentration on tensile strength and elongation at break, functional group (FTIR) and surface morphology (SEM). In this study used mango seed starch size of 5 grams, with variation of ZnO mass of 0; 1; 3; and 6% wt, with variation of clay filler mass of 0; 3; 6 and 9 wt%, while mass of glycerol with a variation of 0; 20; 25; 30; and 35% wt. The FTIR analysis shows that no new functional groups are formed. From the analysis of mango starch content obtained 62.82%, 44.0% amilopectin content, amylose content 14.82%, and water content 12.65%. In this study obtained bioplastics with the best conditions on the use of 3% ZnO, 6% clay and 25% glycerol, with a tensile strength of 5,657MPa, percent elongation at breakup 43.431%.

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With a foreseen life of more than 30 years, the future Main Battle Tanks (MBT) will face continuous upgrades in and will challenge ever-changing threats. The armament, the armor, the information and the communication suite will be upgraded/changed depending on the scenario and on the technology available. Like in moder cars, the huge hardware/software/sensors is the most changing package. This continuous upgrade should be included in the design of new vehicle, than should be conceived more as a modular, vehicle family than as a single vehicle. The new battle tank is closer to a car platform that is the base for a family of vehicles, in which a major revision of any single model should be performed every two years. The old option-less approach like the Ford T model, that remained in production from 1908 to 1927, belongs to the past. A very desirable requirement would be to host the new vehicle in the bay of the latest C130 for rapid deployment. Even if it is time to update the venerable C130 to something newer and more capable, the basic concept remains. The always-growing 100-ton pan-tank approach is becoming obsolete, along with the idea to add hardware to improve firepower, protection and battlefield effectiveness. This third part introduces a few concepts to design a new MBT or better, a new MBT family, in which a modular concept makes it possible to adapt the vehicle to a specific scenario and to update it with ease. Flexibility and update capability are the new key words. The old concept of the mobile bunker with tracks should be substituted by a hierarchical protection system. This approach is inherited from the attack helicopters. The best-protected part of the tank should be a very small crew compartment. It should be completely separated from the weapon compartment with the main and secondary armaments equipped with automatic loading systems. The NBC (Nuclear Bacteriological Chemical) air filtering system can then be reduced to serve only the humans. The crew should travel secured by safety belts and should be equipped with ejection seats. Air-bag should be considered to reduce the shock of a direct hit from APFSDS penetrator or other high energy threats. These seats are conceptually different from aircraft ones since they will assure a simple exit from the tank, not a true ejection. A multiengine-multimotor approach may be used for traction with two or more powered sprockets. The small powerpacks will occupy less room inside the vehicle. A drive by wire system with an enhanced stability and direction system should be implemented. The ground pressure should be kept well under 900 kPa. Tracks should be narrow and long to reduce power requirements. Only the frontal arc of the MBT should be protected with passive "direct kill" armor. The remaining part of the vehicle should rely on hard-kill active systems except for "light" automatic fire. Since armor is an accessory, it should be added to the basic MBT structure. The "adding" from the outside approach should be extended to as many items as possible to simplify maintenance, equipment and update. The basic vehicle structure is closer to the frame of an F1 car with all the parts and accessories added to it. Similarly to F1 racing cars, it can be made with lightweight materials and aircraft technologies, like Carbon Fiber Reinforced Plastic or aluminum alloy monocoque structure. Finally, an on-board electronic diagnosis system should be implemented to simplify maintenance and increase availability and reliability.

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Abstract:

This article presents a two-stage second-order stochastic Ruge-Kutta method (RK2-2st) to solve the stochastic equations of point kinetics for a nuclear reactor with Newtonian temperature feedback effects considering step external reactivities. The average values and standard deviations of the neutron density and the population of delayed neutron precursors with a fixed step size are calculated, the Doppler effects considered correspond to the typical adiabatic approximation. The proposed method has a great advantage with respect to other derivative numerical stochastic methods, because it requires fewer derivatives and has low computational cost. The numerical experiments developed indicate that the proposed method has good precision and is very efficient for the study of stochastic point kinetics with Newtonian temperature feedback. The numerical results obtained are compared with deterministic and stochastic methods reported in the literature.

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Abstract:

With the advancements in technology, computers are more capable of solving more and more problems that are integrated into human activity. With sensors, microcontrollers, and processors, one can create a device that uses set theory, artificial intelligence, spatial imaging, data management, and transfer. Devices such as packet sniffers that monitor and analyzes the traffic that passes through a network, obstacle avoiding robots, or getting spied on by hackers, are now possible by using accessible materials. These devices can be the catalyst to the conception of more advanced technologies based on the fundamental concepts and problems that they solve. Such devices, more accurately computer systems, are what connect the physical world to the digital world.

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