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Evaluation of the new coastal protection scheme at Mamaia Bay in the nearshore of the Black Sea
Niculescu, Dragos M.,Rusu, Eugen V.C. Techno-Press 2018 Ocean systems engineering Vol.8 No.1
The target area of the proposed study, Mamaia beach, is a narrow stretch of sand barrier island that sits between the Siutghiol Lake and the Black Sea. In the northern part of the bay, is located the Midia Port, where between 1966 and 1971 a long extension of 5 km of the offshore was built. Because of this extension, the natural flow of sediments has been significantly changed. Thus, the southern part of the Mamaia Bay had less sand nourishment which meant that the coast was eroding and to prevent it a protection of six dikes was built. After approximately forty years of coastal erosion, the south of the Mamaia Bay had in 2016 a new protection scheme, which includes first of all the beach nourishment and a new dike structure (groins scheme for protection) to protect it. From this perspective, the objective of the proposed study is to evaluate the effectiveness of the old Master plan against the new one by modeling the outcome of the two scenarios and to perform a comparison with a third one, in which the protection dikes do not exist and only the artificial nourishment has been done. In order to assess the wave processes and the current patterns along the shoreline, a complex computational framework has been applied in the target area. This joins the SWAN spectral phase averaged model with the 1D surf model. Furthermore, new UAV technology was also used to map out, chart and validate the numerical model outputs within the target zone for a better evaluation of the trends expected in the shoreline dynamics.
Laser-induced diamagnetic anisotropy of coaxial nanowires
E.C. Niculescu,A. Radu 한국물리학회 2010 Current Applied Physics Vol.10 No.5
The diamagnetic susceptibility of the hydrogenic impurity in coaxial quantum well wires under high frequency laser field has been investigated taking into account the laser dressing effect on both the impurity Coulomb potential and confinement potential. The analysis revealed that a laser beam which is linearly polarized along the wire radial direction destroys the cylindrical symmetry of the donor Hamiltonian, leading to a strong dependence of the electron probability density on the laser field amplitude and orientation of the applied magnetic field. Thus, the direction of the magnetic field can be used as a tunable parameter in the variation of the diamagnetic susceptibility in low-dimensional structures under intense laser radiation. This phenomenon gives an additional degree of freedom in device applications.
CLAS Collaboration,Pereira, S.A.,Mirazita, M.,Rossi, P.,De Sanctis, E.,Niculescu, G.,Niculescu, I.,Stepanyan, S.,Adhikari, K.P.,Aghasyan, M.,Anghinolfi, M.,Baghdasaryan, H.,Ball, J.,Battaglieri, M.,Be North-Holland Pub. Co 2010 Physics letters: B Vol.688 No.4
<P>Differential cross sections of the reaction gamma d -> K+Sigma(-)(p) have been measured with the CLAS detector at Jefferson Lab using incident photons with energies between 1.1 and 3.6 GeV. This is the first complete set of strangeness photoproduction data on the neutron covering a broad angular range. At energies close to threshold and up to E-gamma similar to 1.8 GeV. the shape of the angular distribution is suggestive of the presence of s-channel production mechanisms. For E-gamma > 1.8 GeV, a clear forward peak appears and becomes more prominent as the photon energy increases, suggesting contributions from t-channel production mechanisms. These data can be used to constrain future analysis of this reaction. (c) 2010 Elsevier B.V. All rights reserved.</P>
Gateway Strategies for VoIP Traffic over Wireless Multihop Networks
( Kyungtae Kim ),( Dragos Niculescu ),( Sangjin Hong ) 한국인터넷정보학회 2011 KSII Transactions on Internet and Information Syst Vol.5 No.1
When supporting both voice and TCP in a wireless multihop network, there are two conflicting goals: to protect the VoIP traffic, and to completely utilize the remaining capacity for TCP. We investigate the interaction between these two popular categories of traffic and find that conventional solution approaches, such as enhanced TCP variants, priority queues, bandwidth limitation, and traffic shaping do not always achieve the goals. TCP and VoIP traffic do not easily coexist because of TCP aggressiveness and data burstiness, and the (self-) interference nature of multihop traffic. We found that enhanced TCP variants fail to coexist with VoIP in the wireless multihop scenarios. Surprisingly, even priority schemes, including those built into the MAC such as RTS/CTS or 802.11e generally cannot protect voice, as they do not account for the interference outside communication range. We present VAGP (Voice Adaptive Gateway Pacer) - an adaptive bandwidth control algorithm at the access gateway that dynamically paces wired-to-wireless TCP data flows based on VoIP traffic status. VAGP continuously monitors the quality of VoIP flows at the gateway and controls the bandwidth used by TCP flows before entering the wireless multihop. To also maintain utilization and TCP performance, VAGP employs TCP specific mechanisms that suppress certain retransmissions across the wireless multihop. Compared to previous proposals for improving TCP over wireless multihop, we show that VAGP retains the end-to-end semantics of TCP, does not require modifications of endpoints, and works in a variety of conditions: different TCP variants, multiple flows, and internet delays, different patterns of interference, different multihop topologies, and different traffic patterns.
Predictor-Corrector Type Multi-Rate Sample Hold for Continuous Estimated Outputs
정주노,Silviu-Iulian Niculescu,Frederic Mazenc 제어·로봇·시스템학회 2012 International Journal of Control, Automation, and Vol.10 No.1
A novel predictor-corrector hold (PCH) that yields continuous estimates for all instances is proposed for multi-rate control systems. The principle, characteristic, and performance of the PCH are analyzed. Through a comparison with other conventional holds, the efficacy of the proposed PCH is validated.
Physically Based Collaborative Simulations under Ring-Like Network Configurations
Joono Cheong,Jongwoo Park,Niculescu, S.-I. IEEE 2009 IEEE computer graphics and applications Vol.29 No.4
<P>A state-synchronization method for physically based simulations provides equivalent visual scenes at remote sites on ring-like networks. The simulation runs independently on each participating site so that sites can immediately process and display any local user's action, allowing high responsiveness.</P>
Bogdan Liacu,Cesar Mendez-Barrios,Silviu-Iulian Niculescu,Sorin Olaru 제어로봇시스템학회 2010 제어로봇시스템학회 국제학술대회 논문집 Vol.2010 No.10
This paper addresses the “rade-off” between transparency and stability of some specific bilateral teleoperation systems including communication time-delays. Using a geometric approach, we derive a simple method to study the fragility of the proposed controller for a general 4-channel architecture for bilateral teleoperation with time-delays such that the closed-loop stability as well as the transparency are guaranteed for the overall scheme. Illustrative examples complete the presentation.
Some Remarks on the Fragility of Smith Predictors used in Haptics
Bogdan Liacu,Irinel-Constantin Mor?rescu,Claude Andriot,Silviu-Iulian Niculescu,Didier Dumur,Patrick Boucher,Frederic Colledani 제어로봇시스템학회 2011 제어로봇시스템학회 국제학술대회 논문집 Vol.2011 No.10
In this paper, we propose a method to study the fragility of Smith predictor-based controllers used in haptics. Using a geometric approach, we derive a simple approach to examine the fragility of Smith predictors for two cases - constant and uncertain delays. Illustrative examples complete the presentation.
Collision avoidance and path following for multi-agent dynamical systems
Ionela Prodan,Sorin Olaru,Cristina Stoica,Silviu-Iulian Niculescu 제어로봇시스템학회 2010 제어로봇시스템학회 국제학술대회 논문집 Vol.2010 No.10
This paper deals with collision avoidance problems while following an optimal trajectory for a group of agents operating in open space. The basic idea is to use the Model Predictive Control (MPC) technique to solve a realtime optimization problem with non-convex constraints over a finite time horizon. Both centralized and decentralized MPC formulations are presented. In a second stage it is shown that velocity constraints can be added to the collision avoidance restrictions in the optimization problem. Following a specified trajectory, the agents move in the same direction and end up eventually in a particular formation. A primer ingredient in the control design is the generation of a flat trajectory, planned in the physical open space. This allows the agents to maneuver successfully in a dynamic environment and to reach a common objective.
Road condition estimation and longitudinal control for electric vehicles
Marcel Stefan Geamanu,Arben Cela,Guenael LeSolliec,Hugues Mounier,Silviu-Iulian Niculescu 제어로봇시스템학회 2011 제어로봇시스템학회 국제학술대회 논문집 Vol.2011 No.10
This paper presents a road condition estimator based on the wheel acceleration and a torque controller for a vehicle equipped with an electric motor. In the first step, the instantaneous friction coefficient and the maximum friction coefficient between the wheel and the road are estimated, without knowing a priori the road conditions. Next, a longitudinal controller is set up to ensure the two main functions : braking with anti-skidding function and traction control using the electric motor torque as a unique actuator. Unlike the torque generated by classic internal combustion engines, the torque of electric motors is available almost instantaneously. In addition, it can be measured on-line which means that advanced control techniques can be applied. The approach presented in this paper relies on recent algebraic techniques for numerical differentiation and diagnosis, and a feedback sliding mode control scheme to ensure the vehicle is operated at the maximum friction zone in both acceleration and braking phases, along with a given reference speed to track.