Ivan Stoianov

Bio: Ivan Stoianov is an academic researcher from Imperial College London. The author has contributed to research in topics: Computer science & Mathematical optimization. The author has an hindex of 21, co-authored 77 publications receiving 2352 citations.

PIPENET: A Wireless Sensor Network for Pipeline Monitoring

Abstract: US water utilities are faced with mounting operational and maintenance costs as a result of aging pipeline infrastructures. Leaks and ruptures in water supply pipelines and blockages and overflow events in sewer collectors cost millions of dollars a year, and monitoring and repairing this underground infrastructure presents a severe challenge. In this paper, we discuss how wireless sensor networks (WSNs) can increase the spatial and temporal resolution of operational data from pipeline infrastructures and thus address the challenge of near real-time monitoring and eventually control. We focus on the use of WSNs for monitoring large diameter bulk-water transmission pipelines. We outline a system, PipeNet, we have been developing for collecting hydraulic and acoustic/vibration data at high sampling rates as well as algorithms for analyzing this data to detect and locate leaks. Challenges include sampling at high data rates, maintaining aggressive duty cycles, and ensuring tightly time- synchronized data collection, all under a strict power budget. We have carried out an extensive field trial with Boston Water and Sewer Commission in order to evaluate some of the critical components of PipeNet. Along with the results of this preliminary trial, we describe the results of extensive laboratory experiments which are used to evaluate our analysis and data processing solutions. Our prototype deployment has led to the development of a reusable, field-reprogrammable software infrastructure for distributed high-rate signal processing in wireless sensor networks, which we also describe.

The dynamic effect of pipe-wall viscoelasticity in hydraulic transients. Part II—model development, calibration and verification

Abstract: Un nouveau modele mathematique a ete developpe pour calculer les regimes transitoires hydrauliques des systemes de conduites pressurisees en polyethylene (PE). Ce modele hydraulique (nomme HTS) integre des termes additionnels pour simuler la friction pendant le regime transitoire et l'effet de la viscoelasticite de la conduite. Les resultats numeriques obtenus ont ete compares avec la solution classique du coup de belier et avec les resultats experimentaux collectes a partir d'un systeme de conduites simples en PE construit au Imperial College (Londres, Royaume Unit). Contrairement au modele classique, le modele HTS est capable de predire rigoureusement les fluctuations transitoires de pression dans la conduite de PE ainsi que l'extension de la circonference des parois de la conduite. Le grand challenge de ce travaille est la distinction entre l'effet dynamique de la friction transitoire et l'effet mecanique de la deformation retardee de la conduite. Dans un premier temps, le modele HTS a ete calibre et teste en considerant les deux effets separement. Lorsque la friction en regime transitoire est consideree seule, de grandes differences entre les resultats experimentaux et numeriques sont observees. Si l'effet viscoelastique de la conduite est considere seul, meme avec une bonne correlation entre les resultats experimentaux et numeriques, les fonctions des fluage calibrees varient avec le flux initial. Dans un deuxieme temps, la combinaison de ces deux effets a ete analysee et une bonne correspondance entre les resultats experimentaux et numeriques a ete observee. Enfin, le modele HTS a ete verifie avec succes en utilisant la fonction de fluage mesuree lors d'un test mecanique negligeant la friction en regime transitoire.

Power-Extraction Circuits for Piezoelectric Energy Harvesters in Miniature and Low-Power Applications

Abstract: When a piezoelectric energy harvester is connected to a simple load circuit, the damping force which the piezoelectric element is able to generate is often below the optimal value to maximize electrical power generation Circuits that aim to increase the power output of a piezoelectric energy harvester do so by modifying the voltage onto which the piezoelectric current source drives its charge This paper presents a systematic analysis and comparison of all the principal types of power extraction circuit that allow this damping force to be increased, under both ideal and realistic constraints Particular emphasis is placed on low-amplitude operation A circuit called single-supply prebiasing is shown to harvest more power than previous approaches Most of the analyzed circuits able to increase the power output do so by synchronously inverting or charging the piezoelectric capacitance through an inductor For inductor Q factors greater than around only 2, the single-supply prebiasing circuit has the highest power density of the analyzed circuits The absence of diodes in conduction paths, achievable with a minimum number of synchronous rectifiers, means that the input excitation amplitude is not required to overcome a minimum value before power can be extracted, making it particularly suitable for microscale applications or those with a wide variation in amplitude

The dynamic effect of pipe-wall viscoelasticity in hydraulic transients. Part I—experimental analysis and creep characterization

Abstract: The mechanical behaviour of the pipe material determines the pressure response of a fluid system during the occurrence of transient events. in viscoelastic pipes, typically made of polyethylene (pe), maximum or minimum transient pressures are rapidly attenuated and the overall pressure wave is delayed in time. this is a result of the retarded deformation of the pipe-wall. this effect has been observed in transient data collected in a high-density pe pipe-rig, at imperial college (london, uk). several transient tests were carried out to collect pressure and circumferential strain data. the pipe material presented a typical viscoelastic mechanical behaviour with a sudden pressure drop immediately after the fast valve closure, a major dissipation and dispersion of the pressure wave, and transient mechanical hysteresis. the creep-function of the pipe material was experimentally determined by creep tests, and, its order-of-magnitude was estimated based on pressure-strain data collected from the pipe-rig. a goo...

The dynamic effect of pipe-wall viscoelasticity in hydraulic transients. Part II— model development, calibration and verification L'effet dynamique de la viscoélasticité de la conduite en régimes transitoires hydrauliques. Partie II—développement, calibrage and vérification du modèle mathématique

Abstract: A state-of-the-art mathematical model has been developed to calculate hydraulic transients in pressurized polyethylene (PE) pipe systems. This hydraulic transient solver (HTS) incorporates additional terms to take into account unsteady friction and pipe-wall viscoelasticity. Numerical results obtained were compared with the classic waterhammer solution and with experimental data collected from a PE pipe-rig at Imperial College (London, UK). Unlike the classical model, the developed HTS is capable of accurately predicting transient pressure fluctuations in PE pipes, as well as circumferential strains in the pipe-wall. The major challenge was the distinction between frictional and mechanical dynamic effects. First, the HTS was calibrated and tested considering these two effects separately: if only unsteady friction was considered, a major disagreement between collected data and numerical results was observed; when only the viscoelastic effect was considered, despite the good agreement between data and numerical results, the calibrated creep function depended on the initial flow rate. In a second stage, the combination of these dynamic effects was analysed: creep was calibrated for laminar flow and used to test the solver for turbulent conditions, and a good agreement was observed. Finally, the HTS was tested using creep measured in a mechanical test, neglecting unsteady friction, and a good agreement was obtained.

Survey on Unmanned Aerial Vehicle Networks for Civil Applications: A Communications Viewpoint

Abstract: The days where swarms of unmanned aerial vehicles (UAVs) will occupy our skies are fast approaching due to the introduction of cost-efficient and reliable small aerial vehicles and the increasing demand for use of such vehicles in a plethora of civil applications. Governments and industry alike have been heavily investing in the development of UAVs. As such it is important to understand the characteristics of networks with UAVs to enable the incorporation of multiple, coordinated aerial vehicles into the air traffic in a reliable and safe manner. To this end, this survey reports the characteristics and requirements of UAV networks for envisioned civil applications over the period 2000–2015 from a communications and networking viewpoint. We survey and quantify quality-of-service requirements, network-relevant mission parameters, data requirements, and the minimum data to be transmitted over the network. Furthermore, we elaborate on general networking related requirements such as connectivity, adaptability, safety, privacy, security, and scalability. We also report experimental results from many projects and investigate the suitability of existing communication technologies for supporting reliable aerial networking.

Linear And Nonlinear Programming

Abstract: Thank you for downloading linear and nonlinear programming. As you may know, people have search numerous times for their favorite novels like this linear and nonlinear programming, but end up in malicious downloads. Rather than reading a good book with a cup of tea in the afternoon, instead they juggled with some infectious bugs inside their desktop computer. linear and nonlinear programming is available in our book collection an online access to it is set as public so you can download it instantly. Our digital library spans in multiple locations, allowing you to get the most less latency time to download any of our books like this one. Kindly say, the linear and nonlinear programming is universally compatible with any devices to read.

Flows in Networks

Abstract: In this chapter, you will see how the simplex method simplifies when it is applied to a class of optimization problems that are known as “network flow models.” You will also see that if a network flow model has “integer-valued data,” the simplex method finds an optimal solution that is integer-valued.