336 research outputs found
Performance analysis of RIS-assisted downlink NOMA wireless systems under D2D interference
No full textReconfigurable intelligent surfaces (RISs) are considered a key paradigm to improve the coverage of beyond-fifth-generation (B5G) networks as signal reflectors. Moreover, device-to-device (D2D) communications and non-orthogonal multiple-access (NOMA) schemes will enable networks with a large number of devices for the Internet of Things. This paper analyzes the performance of the downlink of B5G network, where both a NOMA-empowered BS and a RIS support cellular communications co-existing with inband D2D transmissions. We derive approximate expressions of the outage probability, the cumulative distribution function (CDF), and the probability density function (PDF) of the signal-to-noise-plus-interference ratio (SINR) of the NOMA-connected users and the D2D receivers. We further derive similar expressions under orthogonal multiple access (OMA) transmission for comparison purpose. Then, we numerically compute the ergodic rate of each user for a given power allocation. The derived expressions are validated by extensive simulations
Physical Layer Authentication With Simultaneous Reflecting and Sensing RIS
No full textHybrid reconfigurable intelligent surfaces (H-RISs) are panels of metamaterial elements that can be electrically reconfigured to reflect radio signals in the desired direction. At the same time, they can also act as receiving antennas. We propose to use an H-RIS to authenticate radio signals, i.e., to enable a receiver Bob to authenticate signals received by a legitimate transmitter Alice rather than an impersonating attacker Eve. Such a decision is made on the basis of the channel response estimated from the received signal, which operates as a signature in this physical-layer authentication (PLA) mechanism. We consider two attacks, where Eve can transmit signals either through the H-RIS to Bob (as she is close to Alice) or directly to Bob (as she is close to Bob). As the H-RIS can receive signals, the authentication test is performed jointly at Bob and at the H-RIS, significantly improving the distinguishability of the legitimate and attack scenarios. In particular, the optimal attack strategy and a generalized likelihood ratio test for authentication are derived
New results on networked control systems with non-stationary packet dropouts
No full textIn this study, an improved observer-based stabilising controller has been designed for networked systems involving both random measurement and actuation delays and subject to non-stationary packet dropouts. The developed control algorithm is suitable for networked systems with any type of delays. By the simultaneous presence of binary random delays and making full use of the delay information in the measurement model and controller design, new and less conservative stabilisation conditions for networked control systems are derived. The criterion is formulated in terms of linear matrix inequalities. Detailed simulation studies on representative systems are provided to show the applicability of the developed design technique. © 2012 The Institution of Engineering and Technology.M.S. Mahmoud, S.Z. Selim, P. Shi, M.H. Bai
The role of different dietary Zn sources in modulating heat stress-related effects on some thermoregulatory parameters of New Zealand white rabbit bucks
No full textThe present work was conducted to assess the effect of diets supplementation to heat-stressed buck rabbits with different zinc (Zn) sources on the thermoregulatory and hematobiochemical parameters, and antioxidant status. A total of 24 mature buck rabbits (32–36 weeks of age) were randomly distributed into four groups (6 each). Group 1, non-heat-stressed control (NHSC), was reared in the absence of heat stress (HS) conditions and received the basal diet only. The other three groups (groups 2, 3 and 4) were kept in HS conditions. Group 2, heat-stressed control (HSC), received the basal diet only. The diet supplemented with 75mg Zn/kg diet either in the inorganic form (Zn sulfate) or in the organic form (Zn picolinate) for groups 3 and 4, respectively. Zn supplementation to rabbits’ diets lowered the heat stress-related increase of serum urea, alanine transaminase and malondialdehyde (MDA) concentration. These supplementations also increased the concentration of
testosterone under HS conditions. Zn picolinate was more effective than Zn sulfate in restoring serum concentrations of urea, testosterone, and MDA. In conclusion, Zn addition to rabbits’ diets from different sources, especially Zn picolinate, exhibits an ameliorative effect against the harmful impact of HS on hematobiochemical parameters and antioxidant status
The revitalization of endangered heritage buildings in developing countries: A Decision-making framework for investment and determining highest and best use in Egypt
No full textEgypt's major cities, especially Alexandria and Cairo, have been losing heritage and historical buildings due to neglect and misuse, prompting non-governmental organizations, academic institutions, and researchers to advocate for adaptive reuse strategies to preserve the cities' heritage and identity. Adaptive reuse involves changing, modifying, or repurposing an existing space based on multiple factors, such as community needs, the business model, location, and proximity to facilities and services. This study identifies the benefits and methodology of investing in heritage buildings and the factors that help investors decide on project function, type, scale, and category. Investing in heritage buildings has many tangible and non-tangible benefits, many of which can be debated on relevance and priority, but what is certain is that they all contribute significantly to the financial return for such projects, making them challenging yet feasible and attractive for investors with a vision and appreciation of the value introduced by authenticity, uniqueness, and sustainability. Also, the basis of asset evaluation in terms of the above factors and how it could be achieved based on different analyses on different levels, such as understanding market value, old and current property prices and sales, market demand and direction, specific acquisition opportunities, target clients, age groups, and socioeconomic status, This paper addresses Egyptian case studies, identifies stakeholder roles, and concludes with establishing development guidelines and decision-making parameters that significantly influence architectural project design and functions in buildings, creating the ideal mixed-use development.The findings of this research are guidelines for the investment in heritage buildings and a developed framework for the decision-making process that assists different stakeholders in determining the highest and best use for adaptive reuse projects in downtown areas in Egypt in particular and in developing countries in general, as such a framework was intended to be generalized in order to potentially be implemented in different settings.The data provided in this dataset includes:- All figures seen in the research paper- Detailed data from the case studies (Avierino, Little Venice, and Ouzonnian building) such as drawings and photos from before and after development- Maps and their sources (Photoshop) of the downtown areas of the major cities of Alexandria and Cairo- Axonometric diagrams for the 3 case studies and their source (pptx)Please contact the author if you require any further information or have any inquiries at [email protected]
Notched Beam Test for SHCC-Concrete Interface
No full textThe number of hybrid concrete structures is increasing due to the need for repairing/strengthening existing structures and the development of new hybrid concrete systems. The structural response of these hybrid structures might be governed by the strength of the interface between the two concretes, making it essential to characterize the mechanical response of the interface. In this research, a notch beam tests is proposed to investigate the structural behavior of the interface. Hybrid beams consisting of Strain Hardening Cementitious Composites (SHCC) and conventional concrete are designed with a notch at mid-span and are tested under a four-point bending configuration. The effect of interface treatment (i.e. surface roughness) and the curing condition is tested using two sets of hybrid beams. The first set has three beams which are cured in sealed conditions until the day of testing and the interface is varied between smooth, profiled and roughened. The second set has two beams with smooth interface where one beam is seal cured and the other one is exposed to drying in the laboratory. The opening of the interface is visualized using Digital Image Correlation (DIC) and quantified using Linear Variable Differential Transformers (LVTDs) during testing of the hybrid beams. It is observed that increasing the roughness of the interface leads to higher load-bearing capacity and controlled opening of the interface. The beam exposed to drying showed somewhat reduced capacity, possibly due to the pre-damage caused by differential shrinkage of the two concretes.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Concrete Structure
Strain Hardening Cementitious Composite in Reinforced Concrete Cover Zone for Crack Width Control
No full textIn the current study, experiments were carried out to investigate the cracking behaviour of reinforced concrete beams consisting of 1-cm-thick layer of Strain Hardening Cementitious Composite (SHCC) in the concrete cover zone. The hybrid SHCC/concrete beams with different types of interfaces were tested and compared with control reinforced concrete beams without a SHCC layer. A new SHCC/concrete interface that features a weakened chemical adhesion but an enhanced mechanical bonding was also developed to facilitate the activation of SHCC. The beams were tested in four-point bending configuration, while Digital Image Correlation (DIC) was used to evaluate crack pattern development and crack widths. Results show that hybrid beams possessed similar load bearing capacity but exhibited an improved cracking behaviour as compared to the control beam. The maximum crack width of the best performing hybrid beams exceeded 0.3 mm at approximately 53.3 kN load, whereas in the control beam it exceeded 0.3 mm at only 32.5 kN load. It is thus expected that the hybrid beams developed in the current study will possess an improved durability and enhanced self-healing potential as a result of having smaller cracks, leading to an extended service life at the expense of minimal additional cost.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Materials and EnvironmentConcrete Structure
Experimental and Numerical Assessment of Historical Steel-Concrete Composite Bridge Decks Without Mechanical Connectors
No full textIn old Dutch inner cities like Amsterdam a large number of steel-concrete bridge decks built between 1880 and 1960 remain in service nowadays and currently need assessment of their bearing capacity. A significant number of these decks were designed without any mechanical connectors like shear studs in the interface between concrete and steel. Moreover, the concrete decks were designed with only shrinkage reinforcement in both directions on the top layer of concrete. No additional transverse reinforcement was placed that can ensure proper (re)distribution of loads after cracking. In order to study the bearing capacity of this deck typology, two specimens of an existing bridge were taken to the Stevin Lab of TU Delft and tested until failure. In this work, the experimental results of both tests are presented. Then, finite element models including nonlinear behaviour of the materials and the interface are presented and compared with the experimental observations. Experimental results show that the bearing capacity is achieved after yielding of the steel beams. Nevertheless, the ductility and transverse load distribution of the elements is affected by the interface behaviour and the poor detailing. The finite element simulation strategy used shows good agreement with the experiment and can be used for future assessments.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Concrete Structure
Dynamic Characterization of a Real-Scale Prestressed Concrete Beam Tested Until Failure
No full textIn this work, dynamic characterization of a simply supported beam is carried out during different steps in a failure load test. The main goal of this work is to evaluate the evolution of the structural dynamic parameters of the beam with different status of damage. Real-scale prestressed concrete beams are tested to investigate its shear behaviour as a part of a large research program at TU Delft. Four dynamic tests are performed at different damage status of the beam: firstly in the initial or undamaged condition; secondly after the first flexural cracks; then, after shear cracking; and finally in the full damaged condition. The dynamic excitation is performed with an impact load at fixed location on the top of the beam and the vibration data is recorded by three different systems. The first one is a cost-effective and open source monitoring equipment, consisting of seven low-cost accelerometers. The second system is based on five trusted high performance accelerometers. The last one is a commercial alternative consisting of four high accuracy piezoelectric accelerometers. Acceleration data is analysed afterwards using Operational Modal Analysis techniques to obtain modal frequencies, modal shapes and damping of the structure in the different states. The obtained dynamic behaviour of the structure and its results are discussed and compared. It is concluded that a change in the frequency of the first flexural mode is only observed when the damage in the beam is very significant, while no changes are observed with the occurrence of flexural and shear cracks.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Concrete Structure
Measurement of Restraint Moment Effect on Lab Specimens with Precast Girders Made Continuous
No full textTypically precast girders are designed and utilized as simple supported members. Alternatively, the precast girders can be made continuous at the intermediate support using cast-in-place concrete topping. Once the girders are made continuous, time-dependent restraint moments will occur. The magnitude of the restraint moment is mainly affected by the creep and shrinkage behaviour of the concrete and the age of the girders at continuity. The developing restraint moment may affect the stress conditions near the support region and, in extreme cases, result in the loss of the integrity of the structural member. Currently, full-scale experimental campaign is underway on the shear behaviour precast continuous girders at Delft University of Technology. Inverted T girders are individually cast and later made continuous after a certain period. To investigate the influence of restrained action and quantify the prestress losses, fiber optic sensors (FOS) are embedded in the girders. By utilizing the FOS, the evolution of the concrete strain is monitored. This paper presents the measurement of the time-dependent strains. Furthermore, the concrete strains are analysed to evaluate the prestress loss and time-dependent restraint moment effect.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Concrete Structure
- …
