Filtry
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Wyniki wyszukiwania dla: failure
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Assessment of Thermal Stresses in Asphalt Mixtures at Low Temperatures Using the Tensile Creep Test and the Bending Beam Creep Test
PublikacjaThermal stresses are leading factors that influence low-temperature cracking behavior of asphalt pavements. During winter, when the temperature drops to significantly low values, tensile thermal stresses develop as a result of pavement contraction. Creep test methods can be suitable for the assessment of low-temperature properties of asphalt mixtures. To evaluate the influence of creep test methods on the obtained low-temperature...
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A continual model of a damaged medium used for analyzing fatigue life of polycrystalline structural alloys under thermal–mechanical loading
PublikacjaThe main physical laws of thermal–plastic deformation and fatigue damage accumulation processes in polycrystalline structural alloys under various regimes of cyclic thermal–mechanical loading are considered. Within the framework of mechanics of damaged media, a mathematical model is developed that describes thermal–plastic deformation and fatigue damage accumulation processes under low-cycle loading. The model consists of three...
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Development and performance analysis of a novel multiphase doubly-fed induction generator
PublikacjaThis paper presents the research into the design and performance analysis of a novel five-phase doubly-fed induction generator (DFIG). The designed DFIG is developed based on standard induction motor components and equipped with a five-phase rotor winding supplied from the five-phase inverter. This approach allows the machine to be both efficient and reliable due to the ability of the five-phase rotor winding to operate during...
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Consideration of the safety of bungee jumping in relation to mechanical properties of the instalation based on a jump accident in Gdynia
PublikacjaThis paper considers a bungee jumping accident that took place in July 2019 in Gdynia, Poland. The authors conducted an investigation to determine the cause of the bungee rope failure. It was based on mechanical tests concerning the strength of the rope as well as the calculation of the force induced in the rope during the jump. Based on the theoretical and experimental results, the rope safety factor was estimated. It appeared...
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The Reference Model of Tools Adaptation in the Perspective of Technological Agile Transformaton in IT Organizations
PublikacjaThe scientific aim of the presented paper is the analysis of agile transformation processes in IT organizations in technological perspective of such transformation. The phenomenon of agile transformation becomes a complex challenge for an IT organization, since it has not been analysed in detail so far. There is not any research on the readiness of IT organizations for the realization of agile transformation processes, and such...
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Numerical investigations on early indicators of fracture in concrete at meso-scale.
PublikacjaFracture is a major reason of the global failure of concretes. The understanding of fracture is important to ensure the safety of structures and to optimize the material behaviour. In particular an early prediction possibility of fracture in concretes is of major importance. In this paper, concrete fracture under bending was numerically analysed using the Discrete Element Method (DEM). The real mesoscopic structure of a concrete...
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Sensitivity analysis of simple random beam models by means of Monte Carlo Methods using Variance Reductions Techniques
PublikacjaA probabilistic sensitivity analysis of two nonlinear bar structures is presented. The analysis is carried out on the basis of the Monte Carlo method. The imperfections of the structures and the applied loads are adapted as random variables. Based on all of the generated input variables, an output response of the system is sought. Afterwards, a coefficient responsible for the structure failure is calculated and the limit state...
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Voice Multilateration System
PublikacjaThis paper presents an innovative method of locating airplanes, which uses only voice communication between an air traffic controller and the pilot of an aircraft. The proposed method is described in detail along with its practical implementation in the form of a technology demonstrator (proof of concept), included in the voice communication system (VCS). A complete analysis of the performance of the developed method is presented,...
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Remote Health Monitoring of Wind Turbines Employing Vibroacoustic Transducers and Autoencoders
PublikacjaImplementation of remote monitoring technology for real wind turbine structures designed to detect potential sources of failure is described. An innovative multi-axis contactless acoustic sensor measuring acoustic intensity as well as previously known accelerometers were used for this purpose. Signal processing methods were proposed, including feature extraction and data analysis. Two strategies were examined: Mel Frequency Cepstral...
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Numerical simulation of the influence of the selected factors on the performance of a concrete road barrier H2/W5/B
PublikacjaThis paper discuss the influence of selected factors on the performance of a concrete road barrier H2/W5/B. Modelling techniques of a concrete road safety system were briefly discussed. Comparison to the full scale crash test results has been shown. The concrete road safety barrier has been investigated for evaluation of the overall damage after collision under various initial conditions. The failure assessment criterion has been...
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Mechanical Properties of a Dike Formed from a Soil-ash Composite
PublikacjaThe paper presents the research results on application of composite soils for dike construction. The composite soil is produced by mixing bottom ash (by-product of energetics) with dredged material (sand) taken from the mouth of The Vistula river. The optimum composite for dike core was chosen with respect to mechanical parameters: high internal friction angle, good compaction and reduced hydraulic conductivity. The test dike was...
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Influence of an applied bearing system on behaviour of multi-span footbridge
PublikacjaThe cycle overpass in Gdynia is a box structure over 300 metres long, 10-span. It was opened for bicycle traffic in the second half of 2013. At the end of its construction, there was failure due to excessive horizontal displacement of the system. A number of bearings exceeded the range of permissible transverse shifts thus it was necessary to temporarily protect the spans from slipping. The FEM analysis of the original solution...
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Analysis of Ceramic Elements with Ring-Crack Defects in Lubricated Rolling Contact
PublikacjaThe properties of ceramics, specifically low density, high hardness, high temperature capability and low coefficient of thermal expansion are of most interest to rolling element manufacturers. Surface ring cracks on lubricating rolling contact fatigue failure has been studied using numerical fracture analysis. Such cracks are very often found on ceramic bearing balls and decrease fatigue life rapidly. The numerical calculations...
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The correlation of fractal dimension to fracture surface slope for fatigue crack initiation analysis under bending-torsion loading in high-strength steels
PublikacjaIn this study, the fractal dimension of fatigue fracture surfaces is investigated in order to find an alternative failure loading indicator. Some of many metrological factors are generalized by reducing the fracture surface structure to one factor and develop an entire fracture surface procedure by analyzing the impact of surface slope and calculation resolution. Three notched geometries are studied under cyclic bending-torsion:...
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Meso‐scale analyses of size effect in brittle materials using DEM
PublikacjaThe paper describes numerical meso-scale results of a size effect on strength, brittleness and fracture in brittle materials like concrete. The discrete element method (DEM) was used to simulate the size effect during quasi-static splitting tension with the experimental-based meso-structure. The two-dimensional (2D) calculations were carried out on concrete cylindrical specimens with two diameters wherein two different failure...
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A theoretical framework for understanding trust and distrust in internet voting
PublikacjaEach and every case of success and failure in the implementation of internet voting is permeated by a common element: the concept of trust. Several researchers highlighted the relevance of creating trust for the successful implementation of technology [15] and, in particular, of internet voting [13]. But the concept itself is complex and challenging to define, for one fundamental reason: it is a concept of everyday social use...
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Optimization model of agile team’s cohesion
PublikacjaTeam’s cohesion is one of the most important factors of IT project execution effectiveness. Optimization of team’s cohesion gives the possibility of reducing the risk of project failure. It also allows to increase the teamwork efficiency and thus optimize time of tasks execution, increase the guarantee of maintaining the scope of the project and the chance of achieving a given level of products quality. This article presents determination...
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Experimental Tests Of Sandwich Beams In The Design Process Of GFRP Shell Footbridge Structure
PublikacjaThe paper includes selected aspects of the study to elaborate architectural, material and construction design of pedestrian footbridge spans made of composite materials. The considered footbridge is a sandwich-type shell structure. The cooperation of PET foam core with outer lining surfaces is crucial for its load bearing capacity. The paper is aimed to experimental investigation of sandwich beams subjected to bending loading....
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ECG-based prediction of ventricular fibrillation by means of the PCA
PublikacjaA Sudden Cardiac Death (SCD) is a death resulting from cardiac failure with no significant symptoms earlier than one hour before occurrence. It is the cause of for approximately 400000 deaths per year in United States and millions of deaths worldwide. The proposed system, including two-stage algorithm and wearable diagnostic device allows for SCD risk estimation and continuous monitoring of high risk patients. A single channel...
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Crack Mouth Opening Displacement for EH36 Shipbuilding Steel Measurements
PublikacjaThe dataset titled EH36 steel for shipbuilding (plate thicnkness 50mm) - CMOD - force record, a0/W = 0.6 contains CMOD (Crack Mouth Opening Displacement) - Force record which is the base for evaluation of fracture toughness of structural steel. Bend specimens witch Bx2B section (B= 50mm), and relative initial crack length a0 / W = 0.60 were used. The test was carried out at ambient temperature in accordance to ISO 12135 standard....
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Analysis of load carrying capacity and destruction mechanism of an intermediate anchorage steel plate for pillar jib crane
PublikacjaPillar jib cranes are often mounted to existing floors with the use of an intermediate anchorage steel plate instead of using independent foundations, what is shown in the figure. Standards for steel design provide only basic rules for the design of such an intermediate plate. This study presents a simple design approach by using a numerical model in order to analyze different parameters that have significant influence in the anchorage...
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Smart heating system for home extending utilization of renewable energy sources
PublikacjaIn the paper a modern approach to smart home heating is presented. Proposed solution utilizes at least two low-polluting energy source technologies. The main idea is to connect well known ecological energy sources in a way that they can support each other and minimize risks of failure when using single system or even both of them but managed in separate way. Considered energy technologies, used separatelly, have disadvan-tages,...
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Modal analysis of cylindrical steel tanks
PublikacjaCylindrical steel tanks are very popular structures used for storage of products of chemical and petroleum industries. Their safety and reliability is crucial because any failure could have serious consequences. The aim of present paper is to show the results of the first phase of investigation of seismic behaviour such structures. Modal analysis using Finite Element Method (FEM) for three models of real tanks used in Poland has...
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Numerical analysis of crack propagation in silicone nitride
PublikacjaThe properties of ceramics, specifically low density, high hardness, high temperature capability and low coefficient of thermal expansion are of most interest to rolling element manufacturers. The influence of ring crack size on rolling contact fatigue failure has been studied using numerical fracture analysis. Such cracks are very often found on ceramic bearing balls and decrease fatigue life rapidly. The numerical calculation...
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Mechanical compatibility of implants used in hernia repair with abdominal wall
PublikacjaThe paper deals with a membrane model of a synthetic surgical mesh for treatment of abdominal hernia. The authors analyse the compatibility of two implant types with the human wall: Dualmesh Gore and Proceed. The finite element method is applied to simulate tjhe behavior of the proposed model. Due fact that recurrences are usually caused by connection failure, this study is focused on reaction forces in supports representing the...
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Future research directions in design of reliable communication systems
PublikacjaIn this position paper on reliable networks, we discuss new trends in the design of reliable communication systems. We focus on a wide range of research directions including protection against software failures as well as failures of communication systems equipment. In particular, we outline future research trends in software failure mitigation, reliability of wireless communications, robust optimization and network design, multilevel...
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Experimental determination of dynamic properties of cylindrical steel tank model filled with liquid
PublikacjaIn technical branches, such as chemical or petroleum industries, cylindrical steel tanks are essential structures used for storage of liquid products. Any failure might have disastrous consequences, therefore their safety and reliability is essential. The aim of the present paper is to show the results of the experimental study which has been conducted on a scaled model of a real tank used in Poland. The investigation was carried...
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Reliability Analysis of Sea Cliff Slope Stability by Point Estimate Method
PublikacjaThe paper presents a reliability analysis of a sea cliff slope. The cliff, located in Jastrzębia Góra, is characterised by a complicated geological structure. Although currently stable, it is in fact close to the limit state. The objective of this paper is to present the point estimate method (PEM) of determining the mean value and standard deviation of the safety factor of the slope. Assuming its normal distribution, these statistical...
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Crack Mouth Opening Displacement for EH36 Shipbuilding Steel Measurements Dataset
PublikacjaThe dataset titled EH36 steel for shipbuilding (plate thickness 50 mm) – CMOD – force record, a0/W=0.6 contains a CMOD (Crack Mouth Opening Displacement) – Force record which is the base for evaluation of the fracture toughness of structural steel. Bend specimens with a Bx2B section (B = 50 mm), and relative initial crack length a0/W=0.60 were used. The test was carried out at ambient temperature in accordance with the ISO 12135...
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Effect of bitumen characteristics obtained according to EN and Superpave specifications on asphalt mixture performance in low-temperature laboratory tests
PublikacjaThe paper aims to identify those characteristics of bitumen which have the greatest impact on asphalt mixture low-temperature performance. It was observed that stiffness and m-value of bitumen from BBR test were moderately related to stiffness and m-value of asphalt mixture obtained from 3 PB test. Simultaneously those rheological properties significantly impact on cryogenic stresses induced during TSRST test. The multiple regression...
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Reliability Analysis of Sea Cliff Slope Stability by Point Estimate Method
PublikacjaThe paper presents a reliability analysis of a sea cliff slope. The cliff, located in Jastrzębia Góra, is characterised by a complicated geological structure. Although currently stable, it is in fact close to the limit state. The objective of this paper is to present the point estimate method (PEM) of determining the mean value and standard deviation of the safety factor of the slope. Assuming its normal distribution, these statistical...
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Dynamics of mechanical model of implant-tissue system in ventral hernia repair
PublikacjaThe paper deals with a finite element modelling of implants in the problem of ventral hernia repair. The synthetic mesh implanted in the abdomen during surgery is here modelled as a membrane structure. Thesystem undergoes the internal abdominal pressure that occurs during the postoperative cough, the load identified in the literature as the main cause of the connection failure and hernia recurrence. The model can be used to estimate...
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Research on causes of corrosion in the municipal water supply system
PublikacjaThis paper presents results of failure analysis study to characterize the corrosion damage that occurred in the water supply system in Krakow. This analysis includes: electrochemical noise, linear polarization and resistometric measurements. Water aggressiveness of four water intakes was defined using Langelier and Ryznar indices. Results from this indices did not reveal the causes of considerable corrosion losses in water systems....
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Akaike's final prediction error criterion revisited
PublikacjaWhen local identification of a nonstationary ARX system is carried out, two important decisions must be taken. First, one should decide upon the number of estimated parameters, i.e., on the model order. Second, one should choose the appropriate estimation bandwidth, related to the (effective) number of input-output data samples that will be used for identification/ tracking purposes. Failure to make the right decisions results...
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Project Management Cycle in the Construction Industry Augmented by Collaborative Innovation Network Software
PublikacjaProject management is a very broad concept that has in recent times is growing rapidly. Management is especially complex in the construction sector, among the other sectors, due to the high uncertainty of workmanship and complexity of construction projects. Proper project management skills are an important factor in the success of projects, leading to reduced costs and shorten the time of investment. Nevertheless, most of the projects...
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BEARING SYSTEMS OF WIND TURBINES – MAINTENANCE PROBLEMS
PublikacjaW praktyce eksploatacyjnej turbin wiatrowych o tradycyjnej konstrukcji (przekładniowych) obserwowana jest duża awaryjność przekładni, a zwłaszcza łożysk tocznych szybkoobrotowych wałów przekładni. W Polsce na zlecenie właściciela dużej farmy wiatrowej, firmy Energa Wytwarzanie S.A., Politechnika Gdańska we współpracy z Politechniką Poznańską i Akademią Górniczo Hutniczą podjęły badania mające na celu diagnozowanie przyczyn uszkodzeń...
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Trwałość spawanych instalacji wodnych wykonanych z nierdzewnych stali austenitycznych
PublikacjaW artykule przedstawiono dwa przypadki przedwczesnych uszkodzeń spawanych instalacji wodnych wykonanych ze stali odpornych na korozję. W celu ustalenia przyczyn uszkodzenia instalacji przeprowadzono badania metalograficzne, makro - i mikroskopowe oraz mikroanalizę składu chemicznego EDS na próbkach pobranych z reprezentatywnych miejsc. Wykazano, że głównymi przyczynami awarii rurociągów wody pitnej były niezgodności spawalnicze,...
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Application of spectroscopy to the measurement of blood parameters
PublikacjaSpectroscopy is the study of formation and interpretation of the spectra arising from the interactions of all types of radiation on matter, understood as a collection of atoms and molecules. This is a very important department of optics which gives us many opportunities to measure various parameters such as material blood parameters. Among the diseases that are associated significantly with changes in rheological properties of...
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Automatic Correction of Non-Anechoic Antenna Measurements using Low-Pass Filters
PublikacjaPrototype measurements belong to key steps in the development of antenna structures. They are normally performed in expensive facilities, such as anechoic chambers (ACs). Alternatively, antenna performance can be extracted (at a low cost) in non-anechoic conditions upon appropriate post-processing. Unfortunately, existing correction algorithms are difficult to set up and prone to failure, which limits their practical usefulness....
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Modeling, simulation, and validation of a TB41 crash test of the H2/W5/B concrete vehicle restraint system
PublikacjaThe paper addresses numerical simulations of a concrete vehicle restraint system. The model is described in detail. The advanced material law of the continuous surface cap model was used to analyze the damage locations in concrete barrier segments. The results were validated against the TB41 full-scale crash test. The test was conducted in compliance with European standard EN 1317, and the validation was performed in accordance...
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Markov Model of Disease Development and Recovery
PublikacjaMarkov models are commonly used to simulate diseases and allow modeling of multiple health states and outcomes. Starting with the well known Le Bras multistate model (cascading failure model) with time-independent transitions we will see how simple Markov mortality models may be pressed into the service of survival and event history analysis. We will focus on more complex models which will be able to take into account remission,...
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Flexural behaviour of concrete slabs reinforced with FRP bars in experiments and according to aci ACI 440.1R guide
PublikacjaThe paper presents research conducted on two concrete slabs reinforced with the carbon composite bars and two other concrete slabs reinforced with basalt composite bars. The carbon bars were plain, while the basalt ones were ribbed. The slabs were experimentally investigated in the flexural state of effort with the concentrated forces applied. The results are compared with the analytical solution proposed in the guide ACI 440.1R-06...
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Pedestrian and bicycle bridges as examples of safe collision-free road crossings
PublikacjaPedestrians are most at risk when they are crossing the road. This represents a significant proportion of all fatalities among pedestrians, amounting respectively to 50% in non-built-up areas and 75% in built-up areas. The most frequent reason for this accident is failure to give way. What is most terrible is that 30% of pedestrian accidents occurred at marked pedestrian crossings. Therefore, an important part of pedestrian safety...
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Effect of Thermal Shock During Legionella Bacteria Removal on the Corrosion Properties of Zinc-Coated Steel Pipes
PublikacjaThe purpose of this investigation was to conduct the failure analysis of a water-supply system made from zinc-coated steel. The observed corrosion process had an intense and complex character. The brownish deposits and perforations were present after 2-3 years of exploitation. The electrochemical study based on the Tafel polarization, corrosion potential monitoring, and electrochemical impedance spectroscopy together with microscopic...
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Micro-cracking pattern recognition of hybrid CNTs/GNPs cement pastes under three-point bending loading using acoustic emission technique
PublikacjaThe generation of microcracks has an important influence on the behaviour of concrete structures. In this study, the acoustic emission (AE) technique was used to investigate the fracture phenomena and micro-cracking behavior of hybrid carbon nanotubes (CNTs, the 1-D allotrope of carbon atoms) and graphene nanoplatelets (GNPs, 2D monolayer of sp2-hybridized carbon atoms), cement composites under three-point bending loading. In...
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Why do Open Government Data initiatives fail in developing countries? A root cause analysis of the most prevalent barriers and problems
PublikacjaOpen government data (OGD) include the provision of government data, which have so far been reserved for the provision of public utilities and services, wherein different stakeholders may create value out of the same source. Recently, OGD initiatives around the world have dampened or were found to be inadequate for one or other reasons. The present study seeks to underline the root causes behind these inadequate or stalled initiatives...
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Activated Tungsten Inert Gas Weld Characteristics of P91 Joint for Advanced Ultra Supercritical Power Plant Applications
PublikacjaActivated Tungsten Inert Gas (A-TIG) welding, a variant of tungsten inert gas (TIG) welding, was used for welding P91. In Generation IV power plants, P91 welds are prone to premature failure due to the presence and formation of brittle phases and creep at high temperatures. When performing A-TIG welding, the flux composition plays a role in the reversal of the Marangoni flow in the weld pool, which ultimately determines the level...
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Numerical analysis of lumbar spine injury during road safety barrier collision
PublikacjaPurpose: Enhancing road safety is a critical goal worldwide, necessitating the development of clear standards for road safety systems. This study focuses on lumbar spine (L-spine) compression injuries during collisions with concrete road safety barriers (RSBs). It aims to analyze internal forces during impact to understand L-spine injury biomechanics in such accidents. Methods: The research included a literature review, analyzing...
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Microcracking monitoring and damage detection of graphene nanoplatelets-cement composites based on acoustic emission technology
PublikacjaThis study aims to identify the micro-cracking pattern and structural applications of cement composites replaced with 0 wt%, 0.04 wt%, and 0.08 wt% contents of graphene nanoplatelets (GNPs) over cement weight through acoustic emission (AE) monitoring under mechanical degradation. The ultraviolet-visible spectroscopy (UV–vis) results showed that at 60 min sonication period, GNP-4 showed maximum absorbance rate of 16.15% compared...
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Traffic-induced vibrations. The impact on buildings and people
PublikacjaTraffic-induced vibrations have recently been of major concern to engineers as one of the aspects of so called physical environmental pollution. The interest is related to the observations of serious negative effects of such kind of vibrations on buildings and their inhabitants. Traffic-induced vibrations may cause plaster cracks, structural damage and even failure and collapse of the structure. They may also be the reason of serious...