Effects of the Active Hold-off Technique in 1.55-µm Single-photon Detection

BOUZID,박준범,문성 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.5

We investigate the effects of the active hold-off technique in single-photon detector (SPD) based on InGaAs/InP avalanche photodiodes (APDs). The concept of this technique is to hold-off an appropriate number of gate pulses after each recorded detection in order to wait for the trapping levels to empty. We found that at almost a 1-MHz repetition rate of the gate, such a hold-off mechanism must block at least two gate pulses after each photon click event to reduce the afterpulsing effect and does not significantly affect the count probability per gate. For higher repetition frequencies, the number of hold-off gates must be increased.

Curvature ductility of confined HSC beams

Bouzid Haytham,Idriss Rouaz,Sahnoune Ahmed,Benferhat Rabia,Tahar Hassaine Daouadji 국제구조공학회 2024 Structural Engineering and Mechanics, An Int'l Jou Vol.89 No.6

Tahar Hassaine Daouadji2,4 The present paper investigates the curvature ductility of confined reinforced concrete (RC) beams with normal (NSC) and high strength concrete (HSC). For the purpose of predicting the curvature ductility factor, an analytical model was developed based on the equilibrium of internal forces of confined concrete and reinforcement. In this context, the curvatures were calculated at first yielding of tension reinforcement and at ultimate when the confined concrete strain reaches the ultimate value. To best simulate the situation of confined RC beams in flexure, a modified version of an ancient confined concrete model was adopted for this study. In order to show the accuracy of the proposed model, an experimental database was collected from the literature. The statistical comparison between experimental and predicted results showed that the proposed model has a good performance. Then, the data generated from the validated theoretical model were used to train the artificial neural network (ANN) prediction model. The R² values for theoretical and experimental results are equal to 0.98 and 0.95, respectively which proves the high performance of the ANN model. Finally, a parametric study was implemented to analyze the effect of different parameters on the curvature ductility factor using theoretical and ANN models. The results are similar to those extracted from experiments, where the concrete strength, the compression reinforcement ratio, the yield strength, and the volumetric ratio of transverse reinforcement have a positive effect. In contrast, the ratio and the yield strength of tension reinforcement have a negative effect.

Characterization of a single-photon detector at 1.55 μm operated with an active hold-off technique for quantum key distribution

Bouzid, A.,Park, J.B.,Kim, S.M.,Kwak, S.,Moon, S. Elsevier 2011 Current Applied Physics Vol.11 No.3

To better understand how the active hold-off technique in single-photon detectors (SPDs) based on InGaAs/InP avalanche photodiodes (APDs) enhances the performance of a quantum key distribution (QKD) system based on the BB84 protocol, we have evaluated the dependence of the raw key creation rate (R<SUB>raw</SUB>) as well as the quantum bit error rate (QBER) on the number of active hold-off gates. The results of our analysis reveal that at 10 MHz repetition rate of the gate, by holding-off 200 gate pulses immediately following an avalanche event, the afterpulse contribution to the QBER drops down to 2.35% without noticeable decrease in the R<SUB>raw</SUB>w.

Single-Photon Detector at Telecommunication Wavelengths Using an Analog Integrator for Ultra Small Avalanche Discrimination

Bouzid, A.,Han, S.-W.,Lee, M.-S.,Moon, S. JAPAN SOCIETY OF APPLIED PHYSICS 2013 Applied physics express Vol.6 No.5

Curvature ductility prediction of high strength concrete beams

Bouzid, Haytham,Kassoul, Amar Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.66 No.2

From the structural safety point of view, ductility is an important parameter, a relatively high level of curvature ductility would provide to the structure an increased chance of survival against accidental impact and seismic attack. The ductility of reinforced concrete beams is very important, because it is the property that allows structures to dissipate energy in seismic zone. This paper presents a revision of an earlier formula for predicting the curvature ductility factor of unconfined HSC beams to make it simpler in the use. The new formula is compared with the earlier formula and other numerical and experimental results. The new formula regroups all parameters can affecting the curvature ductility of unconfined HSC beams and it has the same domain of application as the earlier formula.

Winkler Springs (p-y curves) for pile design from stress-strain of soils: FE assessment of scaling coefficients using the Mobilized Strength Design concept

Bouzid, Dj. Amar,Bhattacharya, S.,Dash, S.R. Techno-Press 2013 Geomechanics & engineering Vol.5 No.5

In practice, analysis of laterally loaded piles is carried out using beams on non-linear Winkler springs model (often known as p-y method) due to its simplicity, low computational cost and the ability to model layered soils. In this approach, soil-pile interaction along the depth is characterized by a set of discrete non-linear springs represented by p-y curves where p is the pressure on the soil that causes a relative deformation of y. p-y curves are usually constructed based on semi-empirical correlations. In order to construct API/DNV proposed p-y curve for clay, one needs two values from the monotonic stress-strain test results i.e., undrained strength ($s_u$) and the strain at 50% yield stress (${\varepsilon}_{50}$). This approach may ignore various features for a particular soil which may lead to un-conservative or over-conservative design as not all the data points in the stress-strain relation are used. However, with the increasing ability to simulate soil-structure interaction problems using highly developed computers, the trend has shifted towards a more theoretically sound basis. In this paper, principles of Mobilized Strength Design (MSD) concept is used to construct a continuous p-y curves from experimentally obtained stress-strain relationship of the soil. In the method, the stress-strain graph is scaled by two coefficient $N_C$ (for stress) and $M_C$ (for strain) to obtain the p-y curves. $M_C$ and $N_C$ are derived based on Semi-Analytical Finite Element approach exploiting the axial symmetry where a pile is modelled as a series of embedded discs. An example is considered to show the application of the methodology.

Hygro-thermo-mechanical bending response of FG plates resting on elastic foundations

Bouzid Merazka,Abdelhakim Bouhadra,Abderrahmane Menasria,Mahmoud M. Selim,Abdelmoumen Anis Bousahla,Fouad Bourada,Abdeldjebbar Tounsi,Kouider Halim Benrahou,Abdelouahed Tounsi,Mesfer Mohammad Al-Zahra 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.39 No.5

The aim of this work is to study the hygro-thermo-mechanical bending responses of simply supported FG plate resting on a Winkler-Pasternak elastic foundation. The effect transverse shear strains is taken into account in which the zero transverse shear stress condition on the top and bottom surfaces of the plate is ensured without using any shear correction factors. The developed model contains only four unknowns variable which is reduced compared to other HSDTs models. The material properties of FG-plate are supposed to vary across the thickness of the plate according to power-law mixture. The differential governing equations are derived based on the virtual working principle. Numerical outcomes of bending analysis of FG plates under hygro-thermo-mechanical loads are performed and compared with those available in the literature. The effects of the temperature, moisture concentration, elastic foundation parameters, shear deformation, geometrical parameters, and power-law-index on the dimensionless deflections, axial and transverse shear stresses of the FG-plate are presented and discussed.

Curvature ductility of high strength concrete beams according to Eurocode 2

Haytham Bouzid,Amar Kassoul 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.58 No.1

Recently, the high-strength concrete is increasingly used in the construction of reinforced concrete structures due to its benefits, but this use is influenced negatively on the local ductility of structural elements. The objective of this study is the prediction of a new approach to evaluate the curvature ductility factor of high strength concrete beams according to Eurocode 2. After the presentation of the Constitutive laws of materials and the evaluation method of curvature ductility according to the Eurocode 2, we conduct a parametric study on the factors influencing the curvature ductility of inflected sections. The calibrating of the obtained results allows predicting a very simple approach for estimating the curvature ductility factor. The proposed formula allows to calculate the curvature ductility factor of high strength concrete beams directly according to the concrete strength fck, the yield strength of steel fyk and the ratio of tension and compression reinforcements ρ and ρ' respectively, this proposed formula is validated by theoretical and experimental results of different researchers.

Characterization of a single-photon detector at 1.55 mm operated with an active hold-off technique for quantum key distribution

Abdessattar Bouzid,Jun-Bum Park,Se Min Kim,Sean Kwak,Sung Moon 한국물리학회 2011 Current Applied Physics Vol.11 No.3

To better understand how the active hold-off technique in single-photon detectors (SPDs) based on InGaAs/InP avalanche photodiodes (APDs) enhances the performance of a quantum key distribution (QKD) system based on the BB84 protocol, we have evaluated the dependence of the raw key creation rate (R_raw) as well as the quantum bit error rate (QBER) on the number of active hold-off gates. The results of our analysis reveal that at 10 MHz repetition rate of the gate, by holding-off 200 gate pulses immediately following an avalanche event, the afterpulse contribution to the QBER drops down to 2.35%without noticeable decrease in the R_raw.

Finite element analysis of a piled footing under horizontal loading

Amar Bouzid, Dj. Techno-Press 2011 Geomechanics & engineering Vol.3 No.1

In this paper a semi-analytical approach is proposed to study the lateral behavior of a piled footing under horizontal loading. As accurate computation of stresses is usually needed at the interface separating the footing (pile) and the soil, this important location should be appropriately modeled as zero-thickness joint element. The piled footing is embedded in elastic soil with either homogeneous modulus or modulus proportional to depth (Gibson's soil). As the pile is the principal element in the piled footing system, a limited parametric study is carried out in order to investigate the influence of footing dimensions and the interface conditions on the lateral behavior of the pile. Hence, the pile behavior is examined through its main governing parameters, namely, the lateral displacement profiles, the bending moments, the shear forces and the soil reactions. The numerical results are presented for Poisson's ratio of 0.2 to represent a large variety of sands and Poisson's ratio of 0.5 to represent undrained clays.