This paper is a review of testing methods dedicated for sandwich type composite structures with honeycomb core. First, information about the composition of sandwich materials structures, their properties, types of core materials and applications in the industry is presented. Mechanical properties were compared in the case of different types of the core material. Later, tests methods needed to describe properties of those materials and normalization organizations which create them were mentioned. The testing methods were divided into two groups: mechanical and physicochemical tests. Mechanical properties are: compressive strength (two types of test), edge compressive strength, shear strength (in two directions) and tension strength (two types of test). Physicochemical properties are: material density, water migration, water absorption and thermal conductivity. Testing methods were described according to American Society for Testing and Materials (ASTM) standards. This article is based on professional literature and the author’s experience.
The paper presents simulation method and results of calculations determining behavior of helicopter and landing site loads which are generated during phase of the helicopter take-off and landing. For helicopter with whirling rotor standing on ground or touching it, the loads of landing gear depend on the parameters of helicopter movement, occurrence of wind gusts and control of pitch angle of the rotor blades. The considered model of helicopter consists of the fuselage and main transmission treated as rigid bodies connected with elastic elements. The fuselage is supported by landing gear modeled by units of spring and damping elements. The rotor blades are modeled as elastic axes with sets of lumped masses of blade segments distributed along them. The Runge-Kutta method was used to solve the equations of motion of the helicopter model. According to the Galerkin method, it was assumed that the parameters of the elastic blade motion can be treated as a combination of its bending and torsion eigen modes. For calculations, data of a hypothetical light helicopter were applied. Simulation results were presented for the cases of landing helicopter touching ground with different vertical speed and for phase of take-off including influence of rotor speed changes, wind gust and control of blade pitch. The simulation method may help to define the limits of helicopter safe operation on the landing surfaces.
The paper attempts to analyze the technical possibilities of using a compressor heat pump to recover waste heat from energy processes implemented by a watercraft. The amount of waste heat that could be used for the heating needs of the vessel was estimated and the hydrothermal potential of the marine waters was assessed. The possibilities of reducing the power of the ship's power plant used to power the ship's heating installation were determined.
Detecting and recognizing text in natural scenes (e.g. streets, restaurants, shops, etc.) could be a part of an artificial intelligence system, especially with regard to the speech synthesis system. Properly detected text is passed to a recognition stage and then to the speech synthesis system, which translates text to speech. Research is carried out for the ‘Toucan Eye’ project — embedded device with artificial intelligence system able to help people with impaired sight. Due to constrained resources and abilities of embedded devices, criteria for text spotting must be met. First criterion is quality of detected and recognized regions with text and the second is time spent on both operations. Particular stages of the system and chosen methods of text spotting under aforementioned constraints are presented.
It is very common for users to create weak passwords. Currently, the majority of websites deploy password strength meters to provide timely feedback. These meters are in wide use and their effects on the security of passwords have been relatively well studied. In this paper another type of feedback is studied: a gamified approach supported by fear appeal. In this approach, users are encouraged to make passwords stronger through the use of visual and textual stories. This approach is supported by data-driven suggestions about how to improve password security as well as by fear appeal. To prove the effectiveness of this gamified password creation process, an experiment was performed in which users changed their passwords in two ways: without any feed-back, and with gamified feedback with fear appeal. To support the initial findings a questionnaire was completed by participants at the end of research.
In this study, the demand of the Iran’s energy carriers is analyzed and modeled for the country’s largest consumer, buildings and related industries, in the status quo and future perspective. To this objective, the building sector is divided into two sections: household section (residential buildings) and services (business-office and service buildings) according to the ISIC classification that each of these sections is divided into sub-sections. In addition, building-related industries include some non-metallic minerals and basic metals industries. Regarding to scenario-based energy planning helps to increase the understanding of different probabilities in the future. The future outlook for the system is modeled with the horizon of 2035 with the LEAP modeling tool in the “reference” scenario, indicating the sustainability of the existing energy system in the future. The results of modeling indicate an increasing demand for energy as expected that energy demand carriers in buildings and related industries from 559.8 million barrels in 2014 reach up to 1040.6 million barrels of crude oil equivalents in 2035. Therefore, in order to reduce energy consumption, solutions are modeled and analyzed according to the scenarios for “Improvement of energy consumption in buildings and related industries”, then the greenhouse gas emissions and their environmental effects are investigated.
The value of a piece of real estate depends on the purpose it is used for and on its function in planning documents. Unfortunately, current land development trends and the provisions of the law that are applicable in these documents often lead to real estate with heterogeneous functions. The valuation of such properties requires a special approach. One method is to divide the prices of real estate similar to the appraised real estate into components that correspond to areas with certain functions. The aim of this paper is to present statistical methods that can facilitate such a solution. The valuation models (parametric and conditional) presented in this article come from geodetic methods for the reconciliation of results. The presented calculations suggest that it is necessary to verify whether the heterogeneous functions of real estate should be considered in its appraisal.
In recent years, the implementations of Micropiles have been increased extensively in large project constructions due to the unique advantages of this method comparing to concrete piles. The results of numerical analysis and centrifuge tests show that the efficiency and importance of micropiles can be considered as an effective solution. This research is designed to compare the newly designed system of microbulb with micropile applying a numerical modeling with finite element software Plaxis 3D foundation v1.6. We also used the FHWA code for a comparative study between micropiles and microbulbs. Then the effective factors were analyzed in order to decide which method is better between these two methods of micropile and microbulb. The results showed that the new microbulb system is an appropriate solution for improvement of mechanical properties of the soil, increase of bearing capacity and settlement decrease.
Geopolymer offers significant promise to the construction world as a possible alternative to ordinary Portland cement (OPC). Like conventional Portland cement concrete, the matrix brittleness in geopolymer composites can be reduced by introducing suitable fibre reinforcement. A few investigations on fibre reinforced geopolymer composites are available. However there is still a gap to comprehend and enhance their performance. This paper describes the effect of incorporating micro polypropylene fibres on the strength and durability characteristics of geopolymer concrete. The engineering and durability properties like workability, compressive strength, split tensile strength, flexural strength, modulus of elasticity, and sorptivity of geopolymer concrete reinforced with micro polypropylene fibres is presented. The effect of the sulfuric acid attack on Geopolymer Concrete reinforced with micro polypropylene fibres is also discussed. The results show that hydrophobic characteristics of the micro polypropylene fibre led to weak contact with the geopolymer binder and hence weakened the mechanical performance of the fly ash based geopolymer matrix. However significant improvements in durability properties were noted.
This research aims to define the degree of enjoyment in regions of Tabriz metropolis through innovative city indicators with an emphasis on the social and cultural indicators. In terms of practical purposes, the present study is of applied research type, and in terms of the nature of methodology, it is a comparative research. In this research, Shannon entropy method for weighing criteria is used to determine the weight of each of the indices under study, and a TOPSIS technique is applied in order to rank the regions of Tabriz metropolis to create the innovative city. Emphasizing on the social and cultural indicators, the findings of the research show that region 8 tops the ranking list and region 10 is ranked the last in terms of enjoyment through innovative city indicators. The result of this research indicates that the social and cultural indicators are not distributed equitably to fit well into an innovative city concept, and there is a focus on spatial distribution of indicators. Moreover, the results of this research indicate the incompatibility of the distribution of social and cultural indicators with the distribution of population across the city. Therefore, since innovation is the key to the development and expansion of cities as well as the equitable and rational distribution of services and facilities necessary for development and progress, the fair distribution of social and cultural indicators is essential for the realization of an innovative city.