39 research outputs found
Effects of ATF cladding properties on PWR responses to an SBO accident: A sensitivity analysis
No full textTo investigate the effects of ATF cladding properties on the plant responses to severe accidents, shortterm station blackout simulations and sensitivity analyses on hypothetical cladding materials were performed using MAAP code. For sensitivity analyses, 7 hypothetical cladding materials were used. Hypo-0 was the reference cladding whose properties are anticipated to show the poorest fuel performance during an STSBO. The input property values for Hypo-1 through Hypo-6 were selected by changing each variable independently while keeping the others at their reference values. The onset times for core uncovery and cladding oxidation were similar for all the simulation cases, implying that single property cannot affect the event times. A main conclusion is that a large enthalpy of cladding can delay the increase in temperatures of fuel and cladding by playing a role as a heat sink after the core uncovery occurs, resulting in the delayed hot leg rupture. (c) 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Porovnávací studie a analýza směrovacích protokolů pro bezdrátové mobilní sítě
No full textThe process of selecting the routing protocols is one of the most important decisions to be made in the design of an Ad hoc network. There are many characteristics that mainly affect the network, and the most important characteristics represented by routing protocol are: strengthen robustness, scalability, and quality of service (QoS) of a network. Additionally, the chosen protocol has to be optimal in terms of data transfer and data integrity. The process of examining protocols and their performances is a highly important step while choosing the proper protocols for any network. The aim of this paper is to evaluate the performance of the major routing protocols used in mobile ad hoc network, namely AODV, DSD, and DSR. We performed a simulation based comparative analysis of the ad hoc for reactive and proactive routing protocols. Results showed that DSDV has a better performance in terms of packet drop rate, throughput, energy consumption and end to end delay comparing to other analysed protocols.Výběr směrovacích protokolů je důležité rozhodnutí při návrhu ad hoc sítě. Síť ovlivňuje řada vlastností směrovacího protokolu, především robustnost, škálovatelnost a kvalita služeb sítě. Dále musí být protokol optimální z hlediska přenosu dat a zajištění jejich integrity. Proto je proces zhodnocení výkonnosti síťových protokolů vždy důležitý při jejich výběru. Cílem příspěvku je zhodnotit výkonnost klíčových směrovacích protokolů používaných v ad hoc mobilních sítích, jmenovitě AODV, DSDV a DS
The physico-mechanical properties of concrete with red-mud at high temperatures
Get PDFReuse of treated waste can provide significant environmental, social and economic benefits. It is necessary to use it in the right places while keeping the properties of the waste in mind. Aluminum-rich wastes such as red mud derived from bauxite may be used in places exposed to high temperatures. This article discusses the effects of high temperatures of 25, 200, 300, 400, 600 and 800°C and 3 hours of exposure on concrete samples replaced by red mud at 0, 10, 15 and 20%. To study the concrete’s mechanical and permeability properties, loss in weight, compressive strength, splitting tensile strength, capillary water absorption and water permeability tests were performed for all mixes. Results were closer to those of the control specimen, which ultimately supported the use of red mud at a ratio of 10%
Performance and statistical analysis of ant colony route in mobile ad-hoc networks
Get PDFResearch on mobile ad-hoc networks (MANETs) is increasing in popularity due to its rapid, budget-friendly, and easily altered implementation, and relevance to emergencies such as forest firefighting and health care provisioning. The main concerns that ad-hoc networks face is dynamic topology, energy usage, packet drop rate, and throughput. Routing protocol selection is a critical point to surmount alterations in topology and maintain quality in MANET networks. The effectiveness of any network can be vastly enhanced with a well-designed routing protocol. In recent decades, standard MANET protocols have not been able to keep pace with growing demands for MANET applications. The current study investigates and contrasts ant colony optimization (ACO) with various routing protocols. This paper compares ad-hoc on-demand multi-path distance vector (AOMDV), dynamic source routing protocol (DSR), ad-hoc on-demand distance vector routing (AODV), and AntHocNet protocols regarding the quality of service (QoS) and statistical analysis. The current research aims to study the behavior of the state-of-the-art MANET protocols with the ACO technique. The ACO technique is a hybrid technique, integrating a reactive route maintaining technique with a proactive method. The reason and motivation for including the ACO algorithm in the current study is to improve by using optimization algorithms proved in other domains. The ACO algorithm appears to have substantial use in large-scale MANET simulation
THE MECHANICAL PROPERTIES OF CONCRETE WITH RED MUD (BAUXITE RESIDUE) AND NANO-Al2O3 AT HIGH TEMPERATURES
No full textThis study was carried out in order to produce a concrete with better performance by examining the effect of red mud, which is a waste material, and Nanopowder (Nano-A1203) additives on the mechanical properties of concrete under the influence of high temperature. Samples were made by replacing 10% of the cement with red mud and adding Nano-A1203 into the concrete in the ratios 0.5%, 1%, and 1.25%, respectively. The test specimens were exposed to temperatures of 200, 400 and 600 C, for 3 hours. Residual stresses and tensile strength, as well as weight loss values, were determined after high-temperature exposures. As a result, it can be said that the combination of red mud and Nano-A1203 under high temperature had positive effects on the concrete, and the optimum ratio was 10% red mud and 0.5% Nano A1203. A significant reduction in the mechanical properties of concrete normally occurs with increasing temperature; however, the use of red mud waste material in addition to Nanopowder under the effect of high temperature produces a concrete with a better performance
Modification of the AODV Routing Discovery Mechanism in Wireless Mesh Networks
No full textThis thesis offers a comprehensive analysis of Wireless Mesh Networks (WMNs), crucial in the evolution of advanced wireless technologies like Wireless Sensor Networks, the Internet of Things, and the Internet of Vehicles. It highlights WMNs? unique characteristics, such as self-configuration and scalability, while addressing their dynamic nature, posing challenges for routing protocols. The thesis explores the limitations of the Ad hoc On-Demand Distance Vector (AODV) protocol and introduces the Fuzzy Control Energy Efficient (FCEE) routing protocol as a solution. FCEE, integrating fuzzy logic with AODV, enhances network efficiency and longevity, demonstrating superiority over traditional protocols in terms of throughput, energy efficiency, and quality of service metrics.
This work stands out for its innovative approach to applying informatics principles to wireless communications, mainly designing adaptive routing lutions for WMNs. This thesis effectively demonstrates the FCEE protocol?s advantages through rigorous simulations, showing its potential to improve link stability and network performance. This thesis is significant for its contribution to the field of wireless communications and Applied Informatics, offering a novel perspective on tackling routing challenges in WMNs and highlighting the importance of data-driven decision-making in modern networking environments. It sets a precedent for future research at the intersection of networking and informatics.Disertační práce komplexně analyzuje bezdrátové mesh sítě (WMN), které jsou klíčové pro další vývoj pokročilých bezdrátových technologií, například bezdrátové senzorové sítě, Internet věcí a Internet vozidel. Jsou zdůrazněny jedinečné vlastnosti WMN, jako je autokonfigurace a škálovatelnost, a je charakterizována jejich dynamická povaha, které je výzvou pro směrovací protokoly. Dále práce zkoumá omezení protokolu Ad Hoc On-Demand istance Vector (AODV) a představuje protokol Fuzzy Control Energy Efficient (FCEE) jako nově navržené řešení. Protokol FCEE, který integruje fuzzy logiku s ODV, zvyšuje efektivitu a životnost sítě, poskytuje lepší výsledky ve srovnání s tradičními protokoly v následujících metrikách kvality služby: propustnost
a energetická efektivita. Tato práce se nabízí inovativní přístup k aplikaci principů informatiky v oblasti bezdrátové komunikace, zejména tím, že avrhuje adaptivní řešení směrování pro WMN. Výhody protokolu FCEE jsou názorně ukázány pomoci simulací, které demonstrují potenciál protokolu FCEE vylepšit stabilitu spojení a výkon sítě. Tímto práce přispívá k rozvoji bezdrátových technologií a aplikované informatiky, nabízí nový pohled na řešení výzev směrování ve WMN a zdůrazňuje důležitost datově řízeného rozhodování v moderních síťových prostředích.Fakulta ekonomicko-správníStudent za použití powerpointové prezentace představil téma své disertační práce. V úvodu hovořil o motivaci a teoretických východiscích, z nichž vyplývá cíl disertační práce. Součástí prezentace bylo i představení výzkumných metod a použitých dat. Druhá část prezentace obsahovala výsledky disertačního výzkumu a jejich vysvětlení. V závěru nechyběly praktické přínosy a implikace.
Následovalo představení posudků jednotlivými oponenty. Dotazy, jež byly položeny, jsou uvedeny v posudcích. Na tyto dotazy student odpověděl uspokojivě.
V rámci veřejné rozpravy k disertační práci byly položeny tyto dotazy:
You introduced your fuzzy logics system in your work - did you experience any critical delay?
How many literature sources have you used in your dissertation? PRISMA usage experience - usability.
Would you consider to implement other scenario ratios?
In FCEE protocol a broadcast is used. Can you discuss the possibilities of multicast utilization.
Can you discuss current trends in AODV protocols. Can you discuss the convergence time or resource utilization.
Have you considered the multitask (not only broadcast) in your work? Would you consider the AODV and extensions?
How would you define the set in case of membership? Do you estimate the remaining energy?
Precision of definition of set in fasification.
Student úspěšně odpověděl i na položené dotazy v rámci veřejné rozpravy.Dokončená práce s úspěšnou obhajobo
Mechanical properties of polymer composites reinforced by silica-based materials of various sizes
No full textPolymer composites have good mechanical, friction, durability, and wear performance after being reinforced with waste or nanofiller. These features make them flexible in many structural applications. This study was carried out to improve the mechanical performance of polymer composites using silica-based, waste, and nanomaterials. To achieve this, marble dust of millimeter size, silica fume of micrometer size, and Nano-SiO(2)of nanometer size were added separately or in combination to the polymer matrix. The samples were tested to obtain the compressive strength, tensile strength, ultrasonic pulse wave velocity, dynamic modulus of elasticity, toughness, and density of reinforced polymer composites. The results of the tests on the polymer composites indicated that the best ratios were 30%, 5% and 1% for separately added marble dust, silica fume and nano-silica groups, respectively, while the contribution of nano-silica to marble dust/silica fume was the optimum when added by 1%. Moreover, the results showed that adding marble dust to polymer composites increased ductility while adding silica fume and nano-silica reduced the ductility of the samples. Additionally, the microstructural properties of the polymer composites with waste marble dust and silica fume, and nano-SiO(2)additives were evaluated using a scanning electron microscope (SEM) to provide a close relationship between the morphological structure and mechanical properties. This study opens up a new way for added value using waste materials like marble dust/silica fume as well as nanomaterials in polymer composite applications
Experimental and numerical study on the mechanical properties of reinforced polyester composites
No full textPolyester composites play a vital role in civil engineering applications, especially in bridge and car park structures. Therefore, the addition of waste silica-based fillers will both improve the mechanical and durability performance of composites and produce an environmentally friendly material. In this study, the mechanical performance of polyester composites was investigated experimentally and numerically by adding micro and nanosized silica-based fillers, marble powder, silica fume and nano-silica. 24 cubes for the compression test and 18 prisms for the flexural test were produced in six different groups containing 30% marble powder, 5% silica fume and 1% nano-silica by weight. SEM/EDS testing was used to investigate the distribution of filler particles in the matrix. Experimentally collected results were used to validate tests in the Abaqus software. Additionally, the Extended Finite Element Method (XFEM) was used to estimate the fracture process for the flexural test. The results show that the added silica fume, marble powder and nano silica improves the compressive strength of polyester composites by 32-38% and the flexural tensile strength by 10-60% compared to pure polyester composite. The numerically obtained results matched well with the experimental data, demonstrating the accuracy and feasibility of the calibrated finite element model
Long-term durability of red mud-modified cement mortars: Effects of high temperature and freeze-thaw cycles
Get PDFThe use of industrial by-products such as red mud in cementitious materials addresses sustainability by reducing environmental impact and improving performance. As a hazardous waste from aluminium production, red mud offers a promising solution for waste management and improves the mechanical and durability properties of mortar when used as a partial cement replacement. This study investigates the long-term mechanical and durability properties of cement mortars modified with red mud, a by-product of alumina production. Red mud was incorporated at substitution percentages of 5%, 10%, 15%, 20%, 25%, 30% and 35% by weight of cement. The mortars were subjected to harsh environmental conditions such as high temperatures (200°C to 600°C), freeze-thaw cycles (50 and 100 cycles), and normal curing conditions at 365 days of age. The study showed that partial replacement of cement with red mud significantly affected the mechanical and durability properties of the mortars. The optimum red mud replacement level of 10% showed that microstructural compactness and hardness were improved by increasing the ultrasonic pulse velocity, dynamic modulus of elasticity and flexural strength. Durability tests showed improved thermal resistance at moderate levels of red mud content, while higher levels adversely affected freeze-thaw performance. These findings confirm that a 10% red mud substitution offers the best balance between strength, durability, and sustainability
The impact of design approach and contracting practices on cost and execution period of school buildings
Get PDFMore than two million school-age children in Yemen are unable to enroll in education because of a shortage of school buildings. This is one of the reasons the country missed the Millennium Development Goal of achieving Education for all by 2015. The struggle to afford school accommodation will continue, because of the lack of resources and high unit cost. Construction cost as time schedule for an identical school building vary by the implementing agency. This paper aims to study in-depth this multi-dimensional issue to find out the factors that lead to this variation, as well as the reasons for the high unit cost and lengthy periods of construction. To achieve this objective, comprehensive raw data that was resourced from agencies that are assigned to implement the largest part of the construction program along with data collected through questionnaires and semi-structured interviews were utilized. Complete sets of design and contracting documents of representative schools were used for deeper analysis and evaluation. The analysis shows that the employed design approaches lead to large structural elements and consequently to longer implementation period and 30% increase in cost. It also shows that contractors add up to 20% for the client’s procurement procedure, approvals, and payment cycle. Additionally, bidders price risks related to accessibility to building sites, availability of building materials, and how trouble-prone is the region. The findings are of relevance to researchers, education planners, and practitioners as they are of high importance to policy makers and financiers whose main concern is to meet the growing need for school accommodation
