Articles de revues : « 1D code »

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Matem, Rima, S. A. Aljunid, M. N Junita, C. B. M Rashidi et Israa Shihab Aqrab. « Enhancement of optical code division multiple access system based on 2D ZCC/MD spectral/spatial code ». Indonesian Journal of Electrical Engineering and Computer Science 14, n^o 2 (1 mai 2019) : 661. http://dx.doi.org/10.11591/ijeecs.v14.i2.pp661-667.

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<span>The combination of 1D zero cross correlation (ZCC) and 1D Multi Diagonal (MD) results a new two dimensional hybrid called 2D ZCC/MD code for spectral/spatial OCDMA system. The proposed code aims to enhance the functional qualities of Optical Code Division Multiple Access (OCDMA) and to overcome the limitations of one dimensional codes. In this paper, 2D ZCC/MD is evaluated at data rate; 622Mbps. A comparison of the proposed 2D ZCC/MD code to 1D Random Diagonal (RD) and 1D Modified Double Weight (MDW) highlight that 2D ZCC/MD can support a large number of active users even at the higher user bit rate. Furthermore, in term of effective power 2D ZCC/MD can achieve lower effective power.</span>

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Matem, Rima, S. A. Aljunid, M. N. Junita, C. B. M. Rashidi et Israa Shihab Aqrab. « Performance analysis of spectral/spatial of OCDMA system using 2D hybrid ZCC/MD code ». Indonesian Journal of Electrical Engineering and Computer Science 13, n^o 2 (1 février 2019) : 569. http://dx.doi.org/10.11591/ijeecs.v13.i2.pp569-574.

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This paper proposes a new spectral/spatial code for Spectral Amplitude Coding in Optical Coding Division Multiple Access (SAC-OCDMA) called two-Dimensional hybrid ZCC/MD code. The new code combines two of the one –dimensional codes which are Zero Cross Correlation (1D ZCC) and Multi-Diagonal code (1D MD). Moreover, it produces a zero cross correlation property for each code. The main goal of this proposed code is to mitigate Phase Induced Intensity Noise and eliminate Multiple Access Interference (MAI). This proposed code can provide a better performance comparing to other codes as 2D FCC/MDW and 2D DPDC according to the obtained numerical analysis.

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WANG, KONGQIAO, YANMING ZOU et HAO WANG. « 1D BAR CODE READING ON CAMERA PHONES ». International Journal of Image and Graphics 07, n^o 03 (juillet 2007) : 529–50. http://dx.doi.org/10.1142/s0219467807002805.

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The availability of camera phones provides people with a mobile platform for decoding bar codes, whereas conventional scanners lack mobility. However, using a normal camera phone in such applications is challenging due to the out-of-focus problem. In this paper, we present the research effort on the bar code reading algorithms using a VGA camera phone, NOKIA 7650. EAN-13, a widely used 1D bar code standard, is taken as an example to show the efficiency of the method. A wavelet-based bar code region location and knowledge-based bar code segmentation scheme is applied to extract bar code characters from poor-quality images. All the segmented bar code characters are input to the recognition engine, and based on the recognition distance, the bar code character string with the smallest total distance is output as the final recognition result of the bar code. In order to train an efficient recognition engine, the modified Generalized Learning Vector Quantization (GLVQ) method is designed for optimizing a feature extraction matrix and the class reference vectors. 19 584 samples segmented from more than 1000 bar code images captured by NOKIA 7650 are involved in the training process. Testing on 292 bar code images taken by the same phone, the correct recognition rate of the entire bar code set reaches 85.62%. We are confident that auto focus or macro modes on camera phones will bring the presented method into real world mobile use.

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Yeh, Bih-Chyun. « Noncoherent Spectral Optical CDMA System Using 1D Active Weight Two-Code Keying Codes ». Mathematical Problems in Engineering 2016 (2016) : 1–9. http://dx.doi.org/10.1155/2016/3724843.

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We propose a new family of one-dimensional (1D) active weight two-code keying (TCK) in spectral amplitude coding (SAC) optical code division multiple access (OCDMA) networks. We use encoding and decoding transfer functions to operate the 1D active weight TCK. The proposed structure includes an optical line terminal (OLT) and optical network units (ONUs) to produce the encoding and decoding codes of the proposed OLT and ONUs, respectively. The proposed ONU uses the modified cross-correlation to remove interferences from other simultaneous users, that is, the multiuser interference (MUI). When the phase-induced intensity noise (PIIN) is the most important noise, the modified cross-correlation suppresses the PIIN. In the numerical results, we find that the bit error rate (BER) for the proposed system using the 1D active weight TCK codes outperforms that for two other systems using the 1D M-Seq codes and 1D balanced incomplete block design (BIBD) codes. The effective source power for the proposed system can achieve −10 dBm, which has less power than that for the other systems.

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Sécher, Matthieu, Philippe Ung, Eric Valette, Magali Jodeau et Nicole Goutal. « COURLIS : a 1D suspension and bedload code ». E3S Web of Conferences 40 (2018) : 05038. http://dx.doi.org/10.1051/e3sconf/20184005038.

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COURLIS is a 1D sedimentology module coupled with MASCARET, 1D hydraulic code of the TELEMAC-MASCARET open source system. The code has been developed for more than 10 years, mainly for suspension sediment transport. Recently, the need of a 1D bedload code has been identified to model the long term evolution of rivers and reservoirs (several decades). New numerical schemes were implemented, some improvements were done in the geometry evolution algorithms. In terms of performance and robustness, the best scheme implemented is a finite volume upwind/downwind scheme. Several solutions are implemented to reduce calculation time. This new version of COURLIS for bedload transport was validated successfully on test-cases (Soni and Newton experiments). A real case has been simulated during an 11 year period. The calculation time is very similar to those obtained with codes tested in the benchmark and the results are in a good agreement with measurements and other code results. COURLIS (suspension and bedload transport) will be released in the next version of the TELEMAC-MASCARET open source system and so, it will be freely available for sedimentology community. Further developments are planned in 2018.

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Sharma, Teena, Abdellah Chehri, Paul Fortier, Hassan Yousif Ahmed, Medien Zeghid et Waqas A. Imtiaz. « Optical Code Construction of 2D Spectral/Spatial BIBD Codes for SAC-OCDMA Systems ». Applied Sciences 11, n^o 2 (15 janvier 2021) : 783. http://dx.doi.org/10.3390/app11020783.

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Optical code division multiple access (OCDMA) shows limitations in terms of the inefficient bandwidth utilization and low spectral density with one-dimensional (1D) codes. To overcome these limitations, a novel design is presented using a two dimensional (2D) spectral/spatial multiwavelength coding scheme. The proposed code is constructed using a 1D balanced incomplete block design (BIBD) technique. Theoretical and analytical results indicate that the proposed code provided improvement in the number of simultaneous users, code construction, and cross-correlation and minimized noise. Moreover, the bandwidth requirements can be minimized, and it can provide flexibility in addressing code sequences. Finally, results were compared with existing spectral-spatial 2D codes such as diagonal eigenvalue unity (DEU) and 2D diluted perfect difference (DPD). It was observed that the 2D-BIBD code fulfilled optical transmission needs with minimum effective source power (Psr = −27.5 dBm) when compared to 2D-DEU (−26.5 dBm) and 2D-DPD (−25.5 dBm) codes. Overall, our results suggested that the performance of BER for the proposed code was 72% and 22% higher than the existing 2D-DPD and 2D-DEU codes, respectively.

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Vidal, Jean-Philippe, Sabine Moisan, Jean-Baptiste Faure et Denis Dartus. « Towards a reasoned 1D river model calibration ». Journal of Hydroinformatics 7, n^o 2 (1 mars 2005) : 91–104. http://dx.doi.org/10.2166/hydro.2005.0009.

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Model calibration remains a critical step in numerical modelling. After many attempts to automate this task in water-related domains, questions about the actual need for calibrating physics-based models are still open. This paper proposes a framework for good model calibration practice for end-users of 1D hydraulic simulation codes. This framework includes a formalisation of objects used in 1D river hydraulics along with a generic conceptual description of the model calibration process. It was implemented within a knowledge-based system integrating a simulation code and expert knowledge about model calibration. A prototype calibration support system was then built up with a specific simulation code solving subcritical unsteady flow equations for fixed-bed rivers. The framework for model calibration is composed of three independent levels related, respectively, to the generic task, to the application domain and to the simulation code itself. The first two knowledge levels can thus easily be reused to build calibration support systems for other application domains, like 2D hydrodynamics or physics-based rainfall–runoff modelling.

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Yen, Chih-Ta, et Chih-Ming Chen. « BER Analysis Using Beat Probability Method of 3D Optical CDMA Networks with Double Balanced Detection ». Mathematical Problems in Engineering 2015 (2015) : 1–6. http://dx.doi.org/10.1155/2015/456829.

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This study proposes novel three-dimensional (3D) matrices of wavelength/time/spatial code for code-division multiple-access (OCDMA) networks, with a double balanced detection mechanism. We construct 3D carrier-hopping prime/modified prime (CHP/MP) codes by extending a two-dimensional (2D) CHP code integrated with a one-dimensional (1D) MP code. The corresponding coder/decoder pairs were based on fiber Bragg gratings (FBGs) and tunable optical delay lines integrated with splitters/combiners. System performance was enhanced by the low cross correlation properties of the 3D code designed to avoid the beat noise phenomenon. The CHP/MP code cardinality increased significantly compared to the CHP code under the same bit error rate (BER). The results indicate that the 3D code method can enhance system performance because both the beating terms and multiple-access interference (MAI) were reduced by the double balanced detection mechanism. Additionally, the optical component can also be relaxed for high transmission scenery.

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Balaž, Antun, Ivana Vidanović, Danica Stojiljković, Dušan Vudragović, Aleksandar Belić et Aleksandar Bogojević. « SPEEDUP Code for Calculation of Transition Amplitudes via the Effective Action Approach ». Communications in Computational Physics 11, n^o 3 (mars 2012) : 739–55. http://dx.doi.org/10.4208/cicp.131210.180411a.

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AbstractWe present Path Integral Monte Carlo C code for calculation of quantum mechanical transition amplitudes for 1D models. The SPEEDUP C code is based on the use of higher-order short-time effective actions and implemented to the maximal order p=18 in the time of propagation (Monte Carlo time step), which substantially improves the convergence of discretized amplitudes to their exact continuum values. Symbolic derivation of higher-order effective actions is implemented in SPEEDUP Mathematica codes, using the recursive Schrödinger equation approach. In addition to the general 1D quantum theory, developed Mathematica codes are capable of calculating effective actions for specific models, for general 2D and 3D potentials, as well as for a general many-body theory in arbitrary number of spatial dimensions.

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Gupta, Sumit, et Aditya Goel. « Design of Multiservice Code (MS) in Spectral/Temporal/Spatial Domain for OCDMA System ». Journal of Optical Communications 41, n^o 3 (28 avril 2020) : 305–17. http://dx.doi.org/10.1515/joc-2017-0180.

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AbstractThis paper explores the design of multiservice code (MS) in spectral, time spreading and wavelength domains (3-Dimensional). The proposed 3D code is designed in such a manner that follows the ideal in phase unit cross correlation in spectral, time spreading and wavelength domains. The proposed encoder generates the MS code effectively in 3D domain and decoder suppresses the multi-user interferences successfully. Performance analyses are carried out by considering the all noises such as phase induce intensity noise(PIIN), shot noise and thermal noise. The analysis of 3D-MS code for variable code length is also performed for measurement of variation in bit error rate against the received power and number of active users in the design. The observed performances are also compared with existing codes such as 2D-MDW, 3D-PDC and 1D-MS code and the proposed code shows the better performance. The analysis of bit error rate of proposed code is carried out against the number of users at 0.622Gbits/s data rate and 0 dBm received power and comparison is also formed with the existing code such as 3D PD(M=21, N=3, P=3), 2DMDW(M=63, P=3), PDC(M=57, P=3) and 1D MS Code. It is noted that 3D MS code shows the better performance than the existing methods. Analysis is also evaluated for variable weight and variable length codes in order to observe the variation in bit error rate with variation in received power and number of simultaneous users.

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Glisson, Allen W., et Atef Z. Elsherbeni. « An interactive 1D Matlab FDTD code for education ». Computer Applications in Engineering Education 9, n^o 2 (2001) : 136–47. http://dx.doi.org/10.1002/cae.1015.

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Matem, Rima, S. A. Aljunid, M. N. Junita, C. B. M. Rashidi et Israa Shihab Ahmed. « Influence of Code Size Variation on the Performance of 2D Hybrid ZCC/MD in OCDMA System ». MATEC Web of Conferences 150 (2018) : 06018. http://dx.doi.org/10.1051/matecconf/201815006018.

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Several two dimensional OCDMA have been developed in order to overcome many problems in optical network, enhancing cardinality, suppress Multiple Access Interference (MAI) and mitigate Phase Induced Intensity Noise (PIIN). This paper propose a new 2D hybrid ZCC/MD code combining between 1D ZCC spectral encoding where M is its code length and 1D MD spatial spreading where N is its code length. The spatial spreading (N) code length offers a good cardinality so it represents the main effect to enhance the performance of the system compared to the spectral (M) code length according to the numerical results.

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Rahmani, Mohamed, Abdelhamid Cherifi, Abdullah S. Karar, Ghoutia Naima Sabri et Boubakar S. Bouazza. « Contribution of New Three-Dimensional Code Based on the VWZCC Code Extension in Eliminating Multiple Access Interference in Optical CDMA Networks ». Photonics 9, n^o 5 (3 mai 2022) : 310. http://dx.doi.org/10.3390/photonics9050310.

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In order to solve the problem of one-dimensional code length, two-dimensional code spatial length, phase induced intensity noise PIIN effect, improved system capacity, and increased the number of simultaneous users, a new three-dimensional spectral/time/spatial variable weight zero cross correlation code for non-coherent spectral amplitude coding-optical code division multiple access (3D-VWZCC-SAC-OCDMA) is proposed in this paper. Its construction is based on a one-dimensional (1D) spectral sequence and two-dimensional (2D) temporal/spatial sequences, which are characterized by the property of zero cross correlation ZCC. The simulation results demonstrate that our code proves high immunity against PIIN noise and shot noise, it increases multiplexing ability when the passage is from (1D) and (2D) to (3D) up to 5.112 and 2.248 times, and it saves −7.04 dBm and −5.9 dBm of the receiver power due to simple detection at the receiver; furthermore, the 3D-VWZCC system capacity has outperformed the 3D-PD, 3D-PD/MD and 3D-DCS/MD codes, which reach 3686, 2908, and 3234 times, respectively. Moreover, our code offers better performance, in terms of data rates, with up to 2 Gbps compared to previous codes, which makes the system meet the requirements of optical communication networks. Further, 3D-VWZCC is also simulated in Optisystem software, where our code offers a transmission quality Q reaching 11.56 with a bit error rate BER of 1.99 × 10−31 despite a high number of users.

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Karrach, Ladislav, Elena Pivarčiová et Yury Rafailovich Nikitin. « Comparing the impact of different cameras and image resolution to recognize the data matrix codes ». Journal of Electrical Engineering 69, n^o 4 (1 août 2018) : 286–92. http://dx.doi.org/10.2478/jee-2018-0040.

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Abstract Data matrix codes are two-dimensional (2D) matrix bar codes, which are the descendants of the well known 1D bar codes. However, compared to 1D bar codes, they allow to store much more information in the same area. Comparing data matrix codes with QR codes, for example, we find them much more effective in marking small objects or in the case that you have only a very small area for placing a code in. Their capacity and ability of decoding also a code that is partly damaged make them an appropriate solution for industrial applications. In the following paper we compare the impact of various cameras on the detection and decoding of data matrix codes in real scene images. The location of the code is based on the fact that typical bordering of a data matrix code forms a region of connected points which create “L”, the so-called finder pattern, and the parallel dotting, the so-called timing pattern. In the first step, we try to locate the finder pattern using adaptive thresholding and connecting neighbouring points to continuous regions. Then we search for the regions where 3 outer boundary points form a isosceles right triangle that could represent the finder pattern. In the second step, we have to verify the timing pattern. We look for an even number of crossings between the background and foreground. Experimental results show that the algorithm we have proposed provides better results than competitive solutions.

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Bouarfa, A., M. Kandouci, A. Garadi et H. Djellab. « PIIN Cancellation Using a Novel Receiving Architecture for Spectral/Spatial SAC-OCDMA System ». Journal of Optical Communications 41, n^o 3 (28 avril 2020) : 295–304. http://dx.doi.org/10.1515/joc-2017-0179.

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AbstractIncreasing the number of users presents a limitation in one-dimensional (1D) spectral amplitude coding (SAC) for Optical Code Division Multiple Access (OCDMA) system. In order to overcome this disadvantage, a new architecture of the two-dimensional wavelength/spatial SAC-OCDMA system using the multi-diagonal (MD) code has been proposed. The 2D-MD code possesses the same properties of 1D-MD code, which leads to total suppression of the multiple access interference. Unlike conventional receivers used in precedent studies, where the phase-induced intensity noise (PIIN) is a drawback, the suggested structure not only eliminates PIIN but reduces the system architecture. The results show that the user’s number reached by the proposed system is the user number’s multiplication of the 1D system and the couplers’ number. Moreover, the new 2D-MD system presents good performances at the high data rate.

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Fijalkow, Eric. « Numerical solution to the Vlasov equation : The 1D code ». Computer Physics Communications 116, n^o 2-3 (février 1999) : 329–35. http://dx.doi.org/10.1016/s0010-4655(98)00147-7.

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Glasser, Alan H., et Kenneth Smith. « POS - A 1D time-dependent H+ ion source code ». Computer Physics Communications 55, n^o 3 (octobre 1989) : 409–24. http://dx.doi.org/10.1016/0010-4655(89)90135-5.

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Karrach, Ladislav, Elena Pivarčiová et Pavol Bozek. « Recognition of Perspective Distorted QR Codes with a Partially Damaged Finder Pattern in Real Scene Images ». Applied Sciences 10, n^o 21 (4 novembre 2020) : 7814. http://dx.doi.org/10.3390/app10217814.

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QR (Quick Response) codes are one of the most famous types of two-dimensional (2D) matrix barcodes, which are the descendants of well-known 1D barcodes. The mobile robots which move in certain operational space can use information and landmarks from environment for navigation and such information may be provided by QR Codes. We have proposed algorithm, which localizes a QR Code in an image in a few sequential steps. We start with image binarization, then we continue with QR Code localization, where we utilize characteristic Finder Patterns, which are located in three corners of a QR Code, and finally we identify perspective distortion. The presented algorithm is able to deal with a damaged Finder Pattern, works well for low-resolution images and is computationally efficient.

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Kamenski, I. V., et G. G. Borg. « A 1D cylindrical kinetic wave code for helicon plasma sources ». Computer Physics Communications 113, n^o 1 (septembre 1998) : 10–32. http://dx.doi.org/10.1016/s0010-4655(98)00077-0.

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Napp, Diego, Ricardo Pereira, Raquel Pinto et Paula Rocha. « Realization of 2D (2,2)–Periodic Encoders by Means of 2D Periodic Separable Roesser Models ». International Journal of Applied Mathematics and Computer Science 29, n^o 3 (1 septembre 2019) : 527–39. http://dx.doi.org/10.2478/amcs-2019-0039.

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Abstract It is well known that convolutional codes are linear systems when they are defined over a finite field. A fundamental issue in the implementation of convolutional codes is to obtain a minimal state representation of the code. Compared with the literature on one-dimensional (1D) time-invariant convolutional codes, there exist relatively few results on the realization problem for time-varying 1D convolutional codes and even fewer if the convolutional codes are two-dimensional (2D). In this paper we consider 2D periodic convolutional codes and address the minimal state space realization problem for this class of codes. This is, in general, a highly nontrivial problem. Here, we focus on separable Roesser models and show that in this case it is possible to derive, under weak conditions, concrete formulas for obtaining a 2D Roesser state space representation. Moreover, we study minimality and present necessary conditions for these representations to be minimal. Our results immediately lead to constructive algorithms to build these representations.

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Koten, Hasan, Mustafa Yilmaz et M. Zafer Gul. « Compressed Biogas-Diesel Dual-Fuel Engine Optimization Study for Ultralow Emission ». Advances in Mechanical Engineering 6 (1 janvier 2014) : 571063. http://dx.doi.org/10.1155/2014/571063.

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The aim of this study is to find out the optimum operating conditions in a diesel engine fueled with compressed biogas (CBG) and pilot diesel dual-fuel. One-dimensional (1D) and three-dimensional (3D) computational fluid dynamics (CFD) code and multiobjective optimization code were employed to investigate the influence of CBG-diesel dual-fuel combustion performance and exhaust emissions on a diesel engine. In this paper, 1D engine code and multiobjective optimization code were coupled and evaluated about 15000 cases to define the proper boundary conditions. In addition, selected single diesel fuel (dodecane) and dual-fuel (CBG-diesel) combustion modes were modeled to compare the engine performances and exhaust emission characteristics by using CFD code under various operating conditions. In optimization study, start of pilot diesel fuel injection, CBG-diesel flow rate, and engine speed were optimized and selected cases were compared using CFD code. CBG and diesel fuels were defined as leading reactants using user defined code. The results showed that significantly lower NOx emissions were emitted under dual-fuel operation for all cases compared to single-fuel mode at all engine load conditions.

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M P, Shreya, et Dr Anitha R. « A REVIEW ON STEGANOGRAPHY AND DATA HIDING IN QR CODE ». International Research Journal of Computer Science 8, n^o 8 (30 août 2021) : 165–68. http://dx.doi.org/10.26562/irjcs.2021.v0808.001.

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In comparison to 1D barcodes, a two-dimensional matrix is regarded as a Quick-Response (QR) code which is a programme that contains a vast quantity of data. QR codes offer quick scanning, omnidirectional reading, and a variety of other benefits, such as error correction. Barcode scanners can readily reveal the content of QR codes. In reality, however, gratified QR apps could contain confidential information, like an electronic-ticket or an electronic-coupon. To safeguard quick response essence from unauthorized users or scanners, it should be password protected. We'll look at QR codes and different sorts of QR barcode steganography mechanisms in this article.

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Morel, P. « The Evolutionary Code Cesam : Numerical Techniques ». International Astronomical Union Colloquium 137 (1993) : 445–47. http://dx.doi.org/10.1017/s0252921100018200.

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AbstractCESAM is a consistent set of programs and routines designed for the calculations of stellar evolution. Untill now it allows the computation of the evolution from PMS or ZAMS to helium flash for stellar masses of some solar mass. It is constructed in such a way that all the physics works as external routines. The numerical techniques are based on the B-spline formalism. This formalism used both for the integration of the differential equations and for 1D and 2D interpolation schemes of various tables of physical data.

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Hursin, Mathieu, et Tatjana Jevremovic. « Agent code : Neutron transport benchmark example and extension to 3D lattice geometry ». Nuclear Technology and Radiation Protection 20, n^o 2 (2005) : 10–16. http://dx.doi.org/10.2298/ntrp0502010h.

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The general methodology be hind 2D arbitrary geometry neutron transport AGENT code is the theory of R-functions, which al lows for simple modeling of complex geometries, and the method of characteristics, which solves the integral transport equation along characteristic neutron trajectories. This paper focuses on the extension of the methodology to ac count for 3D lattice geometries. Since the direct application of method of characteristics to 3D non-homogenized core con figuration may re quire a tremendous amount of memory and computing time, an alternative approximate solution based on coupling 2D method of characteristics and 1D diffusion solution is developed. The planar 2D method of characteristics and axial 1D diffusion solutions are coupled through the trans verse leak age. The use of a lower order 1D solution in the axial direction is justified by the fact that more heterogeneity in current PWR and BWR reactor cores occurs in the radial direction than in the axial one. In order to demonstrate the versatility and accuracy of the AGENT code, a 2D heterogeneous lattice problem, C5G7 is described in details. A theoretical description of the coupling methodology for 3D method of characteristics solution is followed by preliminary validation in comparison to the DeCART code.

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Teodosio, Luigi, Dino Pirrello et Luca Marchitto. « 1D numerical study on hydrogen injection enabling ultra-lean combustion in a small gasoline Spark Ignition engine ». E3S Web of Conferences 197 (2020) : 06001. http://dx.doi.org/10.1051/e3sconf/202019706001.

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This paper deals with the effects of hydrogen port injection on combustion evolution, efficiency and exhaust emissions of a small turbocharged gasoline Spark-Ignition engine through a 1D numerical code. First, the experiments on the base engine architecture are performed at different speeds and at low/medium loads. The experimental findings are used to validate a 1D model of the whole engine, developed within a commercial code. 1D model is also refined with “user-defined” sub-models for an accurate description of the in-cylinder phenomena, namely turbulence, combustion, heat transfer, and emissions. In a second step, 1D model is virtually modified through the installation of an hydrogen injector in each intake runner, while the combustion sub-model also accounts for the impact of hydrogen addition on the laminar flame speed through a dedicated correlation. 1D simulations are performed at low/medium loads and fixed speed of 2250 rpm with 5% of hydrogen by volume in the intake air. Numerical investigations show that hydrogen addition to gasoline/air mixtures allows relevant efficiency benefits (up to a maximum percent gain of 19%), while the NO emissions are almost eliminated. Consequently, hydrogen-boosted combustion represents a potential solution to achieve very high efficiency and reduced pollutant emissions of gasoline spark ignition engines equipped with a conventional combustion system.

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Freschi, Rosa, Agapi Bakogianni, David John Rajendran, Eduardo Anselmi Palma, Lorenzo Talluri et Ioannis Roumeliotis. « Flow Field Explorations in a Boundary Layer Pump Rotor for Improving 1D Design Codes ». Designs 7, n^o 1 (3 février 2023) : 29. http://dx.doi.org/10.3390/designs7010029.

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Boundary layer pumps, although attractive due to their compactness, robustness and multi-fluid and phase-handling capability, have been reported to have low experimental efficiencies despite optimistic predictions from analytical models. A lower-order flow-physics-based analytical model that can be used as a 1D design code for sizing and predicting pump performance is described. The rotor component is modelled by means of the Navier–Stokes equations as simplified using velocity profiles in the inter-disk gap, while the volute is modelled using kinetic-energy-based coefficients inspired by centrifugal pumps. The code can predict the rotor outlet and overall pump pressure ratio with an around 3% and 10% average error, respectively, compared to the reference experimental data for a water pump. Moreover, 3D RANS flow-field explorations of the rotor are carried out for different inter-disk gaps to provide insights concerning the improvement of the 1D design code for the better prediction of the overall pump performance. Improvements in volute loss modelling through the inclusion of realistic flow properties at the rotor outlet rather than the detailed resolution of the velocity profiles within the rotor are suggested as guidelines for improved predictions. Such improved design codes could close the gap between predictions and experimental values, thereby paving the way for the appropriate sizing of boundary layer pumps for several applications, including aircraft thermal management.

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Gallagher, A. J., M. Bergemann, R. Collet, B. Plez, J. Leenaarts, M. Carlsson, S. A. Yakovleva et A. K. Belyaev. « Observational constraints on the origin of the elements ». Astronomy & ; Astrophysics 634 (février 2020) : A55. http://dx.doi.org/10.1051/0004-6361/201936104.

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Context. The pursuit of more realistic spectroscopic modelling and consistent abundances has led us to begin a new series of papers designed to improve current solar and stellar abundances of various atomic species. To achieve this, we have begun updating the three-dimensional (3D) non-local thermodynamic equilibrium (non-LTE) radiative transfer code, MULTI3D, and the equivalent one-dimensional (1D) non-LTE radiative transfer code, MULTI 2.3. Aims. We examine our improvements to these codes by redetermining the solar barium abundance. Barium was chosen for this test as it is an important diagnostic element of the s-process in the context of galactic chemical evolution. New Ba II + H collisional data for excitation and charge exchange reactions computed from first principles had recently become available and were included in the model atom. The atom also includes the effects of isotopic line shifts and hyperfine splitting. Methods. A grid of 1D LTE barium lines were constructed with MULTI 2.3 and fit to the four Ba II lines available to us in the optical region of the solar spectrum. Abundance corrections were then determined in 1D non-LTE, 3D LTE, and 3D non-LTE. A new 3D non-LTE solar barium abundance was computed from these corrections. Results. We present for the first time the full 3D non-LTE barium abundance of A(Ba) = 2.27 ± 0.02 ± 0.01, which was derived from four individual fully consistent barium lines. Errors here represent the systematic and random errors, respectively.

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Prošek, Andrej, et Ovidiu-Adrian Berar. « BETHSY 9.1b test calculation with TRACE using 3D vessel component ». Journal of Energy - Energija 62, n^o 1-4 (18 juillet 2022) : 93–103. http://dx.doi.org/10.37798/2013621-4221.

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Recently, several advanced multidimensional computational tools for simulating reactor system behavior during real and hypothetical transient scenarios were developed. One of such advanced, best-estimate reactor systems codes is TRAC/RELAP Advanced Computational Engine (TRACE), developed by the U.S. Nuclear Regulatory Commission. The advanced TRACE comes with a graphical user interface called SNAP (Symbolic Nuclear Analysis Package). It is intended for pre- and post-processing, running codes, RELAP5 to TRACE input deck conversion, input deck database generation etc. The TRACE code is still not fully development and it will have all the capabilities of RELAP5. The purpose of the present study was therefore to assess the 3D capability of the TRACE on BETHSY 9.1b test. The TRACE input deck was semi-converted (using SNAP and manual corrections) from the RELAP5 input deck. The 3D fluid dynamics within reactor vessel was modeled and compared to 1D fluid dynamics. The TRACE 3D calculation was compared both to TRACE 1D calculation and RELAP5 calculation. Namely, the geometry used in TRACE is basically the same, what gives very good basis for the comparison of the codes. The only exception is 3D reactor vessel model in case of TRACE 3D calculation. The TRACE V5.0 Patch 1 and RELAP5/MOD3.3 Patch 4 were used for calculations. The BETHSY 9.1b test (International Standard Problem no. 27 or ISP-27) was 5.08 cm equivalent diameter cold leg break without high pressure safety injection and with delayed ultimate procedure. BETHSY facility was a 3-loop replica of a 900 MWe FRAMATOME pressurized water reactor. In general, all presented code calculations were in good agreement with the BETHSY 9.1b test. The TRACE 1D calculation results are comparable to RELAP5 calculated results. For some parameters they are better, this is mostly due to better tuning of the break flow, what influences timing of the transient. When comparing TRACE 1D and TRACE 3D calculation, the latter is slightly better. One reason for comparable results is already good agreement of 1D calculations and there was not much space to further improve the results. The other reason may be that in the facility the phenomena were mostly one dimensional (for example, external downcomer was used for reactor vessel modeling). However, when 3D behavior of the heater rod temperatures was investigated, the advantage of three dimensional treatment was clearly demonstrated.

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Otsubo, Yuhei, Akira Otsuka, Mamoru Mimura et Takeshi Sakaki. « o-glasses : Visualizing X86 Code From Binary Using a 1D-CNN ». IEEE Access 8 (2020) : 31753–63. http://dx.doi.org/10.1109/access.2020.2972358.

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Barrera, Marcela, Francisco Rubinelli, Ignacio Rey-Stolle et Juan Plá. « Numerical simulation of Ge solar cells using D-AMPS-1D code ». Physica B : Condensed Matter 407, n^o 16 (août 2012) : 3282–84. http://dx.doi.org/10.1016/j.physb.2011.12.087.

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Jackson, Z. J., J. R. Nicholas et P. T. Ireland. « Development of a 1D thermofluid code for divertor target plate modeling ». Fusion Engineering and Design 147 (octobre 2019) : 111237. http://dx.doi.org/10.1016/j.fusengdes.2019.06.010.

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Hien, Nghiem Manh. « Stress-independent parameters for stress-strain relationship and damping in nonlinear one-dimensional seismic site response analysis ». Journal of Science and Technology in Civil Engineering (STCE) - NUCE 15, n^o 1 (22 janvier 2021) : 14–29. http://dx.doi.org/10.31814/stce.nuce2021-15(1)-02.

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The modulus reduction and damping curves represent the nonlinear behavior of soil under cyclic load. In the literature, those curves were produced from lab tests of soil at particular confining stresses. This study developed a set of parameters that can be used to normalize the modulus reduction and damping curves to be stress-independent. The proposed formulations for the stress-independent parameters were implemented in the finite element code SRAP and validated through producing shear modulus reduction and damping curves that match the existed ones. Nonlinear 1D seismic site response analyses were conducted for centrifuge experiments to verify the developed computer code. Comparisons of the analysis results between SRAP and another computer code were presented in terms of maximum and minimum displacement, peak ground acceleration, maximum shear strain profiles, and response spectra. Keywords: backbone curve; hysteretic damping; dynamic soil model; stress-independent parameters; finite element method; nonlinear 1D seismic site response analysis.

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Yousif Ahmed, Hassan, Medien Zeghid, Waqas A.Imtiaz, Teena Sharma, Abdellah Chehri et Paul Fortier. « Two-Dimensional Permutation Vectors’ (PV) Code for Optical Code Division Multiple Access Systems ». Entropy 22, n^o 5 (20 mai 2020) : 576. http://dx.doi.org/10.3390/e22050576.

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In this paper, we present a new algorithm to generate two-dimensional (2D) permutation vectors’ (PV) code for incoherent optical code division multiple access (OCDMA) system to suppress multiple access interference (MAI) and system complexity. The proposed code design approach is based on wavelength-hopping time-spreading (WHTS) technique for code generation. All possible combinations of PV code sets were attained by employing all permutations of the vectors with repetition of each vector weight (W) times. Further, 2D-PV code set was constructed by combining two code sequences of the 1D-PV code. The transmitter-receiver architecture of 2D-PV code-based WHTS OCDMA system is presented. Results indicated that the 2D-PV code provides increased cardinality by eliminating phase-induced intensity noise (PIIN) effects and multiple user data can be transmitted with minimum likelihood of interference. Simulation results validated the proposed system for an agreeable bit error rate (BER) of 10−9.

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Karrach, Ladislav, Elena Pivarčiová et Pavol Božek. « Identification of QR Code Perspective Distortion Based on Edge Directions and Edge Projections Analysis ». Journal of Imaging 6, n^o 7 (10 juillet 2020) : 67. http://dx.doi.org/10.3390/jimaging6070067.

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QR (quick response) Codes are one of the most popular types of two-dimensional (2D) matrix codes currently used in a wide variety of fields. Two-dimensional matrix codes, compared to 1D bar codes, can encode significantly more data in the same area. We have compared algorithms capable of localizing multiple QR Codes in an image using typical finder patterns, which are present in three corners of a QR Code. Finally, we present a novel approach to identify perspective distortion by analyzing the direction of horizontal and vertical edges and by maximizing the standard deviation of horizontal and vertical projections of these edges. This algorithm is computationally efficient, works well for low-resolution images, and is also suited to real-time processing.

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Suresh Babu, Sumith Babu, et R. Kumar. « Multigroup Synchronization in 1D-Bernoulli Chaotic Collaborative CDMA ». Wireless Communications and Mobile Computing 2017 (2017) : 1–7. http://dx.doi.org/10.1155/2017/7561757.

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Code-division multiple access (CDMA) has played a remarkable role in the field of wireless communication systems, and its capacity and security requirements are still being addressed. Collaborative multiuser transmission and detection are a contemporary technique used in CDMA systems. The performance of these systems is governed by the proper accommodation of the users and by proper synchronization schemes. The major research concerns in the existing multiuser overloaded CDMA schemes are (i) statistically uncorrelated PN sequences that cause multiple-access interference (MAI) and (ii) the security of the user’s data. In this paper, a novel grouped CDMA scheme, the 1D-Bernoulli chaotic collaborative CDMA (BCC-CDMA), is introduced, in which mutually orthogonal chaotic sequences spread the users’ data within a group. The synchronization of multiple groups in this scheme has been analyzed under MAI limited environments and the results are presented. This increases the user capacity and also provides sufficient security as a result of the correlation properties possessed by the chaotic codes. Multigroup synchronization is achieved using a 1D chaotic pilot sequence generated by the Bernoulli Map. The mathematical model of the proposed system is described and compared with the theoretical model of the synchronization in CDMA, the simulation results of which are presented.

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Bonifacio, P., E. Caffau, H. G. Ludwig et M. Steffen. « LTE Model Atmospheres : MARCS, ATLAS and CO5BOLD ». Proceedings of the International Astronomical Union 7, S282 (juillet 2011) : 213–20. http://dx.doi.org/10.1017/s1743921311027402.

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AbstractIn this talk, we review the basic assumptions and physics covered by classical 1D LTE model atmospheres. We will focus on ATLAS and MARCS models of F-G-K stars and describe what resources are available through the web, both in terms of codes and model-atmosphere grids. We describe the advances made in hydrodynamical simulations of convective stellar atmospheres with the CO5BOLD code and what grids and resources are available, with a prospect of what will be available in the near future.

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Nool, Margreet, et Rony Keppens. « Amrvac : a Multidimensional Grid-adaptive Magnetofluid Dynamics Code ». Computational Methods in Applied Mathematics 2, n^o 1 (2002) : 92–109. http://dx.doi.org/10.2478/cmam-2002-0005.

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Abstract We present the results obtained with AMRVAC, a software package designed for solution-adaptive time-accurate (magneto)hydrodynamic simulations. In any dimensionality, the grid adjusts to capture shocks and other sharp flow features accurately following an automated Adaptive Mesh Refinement [AMR] strategy. This grid adaptation algorithm is incorporated with the Versatile Advection Code [VAC], so that it can be used to time-advance sets of conservation laws with options for the spatial discretization employed. We demonstrate and evaluate the efficiency achievable by AMR for 1D, 2D, and 3D test problems and describe the employed data structures.

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Liu, Rong, Jianin Liu, Jianxin Wang, Zhuo Liu et Rongwen Guo. « 1D electromagnetic response modeling with arbitrary source-receiver geometry based on vector potential and its implementation in MATLAB ». GEOPHYSICS 85, n^o 3 (1 mai 2020) : F27—F38. http://dx.doi.org/10.1190/geo2019-0224.1.

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The calculation of 1D electromagnetic (EM) responses of dipole sources is considered as a fundamental computation kernel in several geophysical applications, ranging from EM sensitivity analysis to high-dimensional EM forward modeling and inversion. To solve the EM responses caused by electric and magnetic dipoles with different orientations, we have developed an open-source MATLAB code for a complete treatment, which allows for an arbitrary transmitter-receiver geometry in the multilayered earth. A complete derivation of the EM field expressions with simplified exponent terms for all traditional dipole sources is accomplished based on the vector potential differential equations. The quadrature-with-extrapolation algorithm is adapted for calculating the integration of Bessel functions to produce EM responses with a desired accuracy. The MATLAB digit functions are used to alleviate the instability problem caused by the exponent terms. The accuracy of our code is verified by comparing the results with the published data and self-checks on an infinite thin sheet. A layered model is designed to test the capability of our code for all traditional dipole sources by placing the receiver at different depths. In the end, we apply our code to marine and airborne controlled-source EM explorations. The results indicate that our code is accurate and can potentially be used to calculate 1D EM responses for general EM problems.

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Leboeuf, Jean-Noel G., Viktor K. Decyk, David E. Newman et Raul Sanchez. « Implementation of 2D Domain Decomposition in the UCAN Gyrokinetic Particle-in-Cell Code and Resulting Performance of UCAN2 ». Communications in Computational Physics 19, n^o 1 (janvier 2016) : 205–25. http://dx.doi.org/10.4208/cicp.070115.030715a.

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AbstractThe massively parallel, nonlinear, three-dimensional (3D), toroidal, electrostatic, gyrokinetic, particle-in-cell (PIC), Cartesian geometry UCAN code, with particle ions and adiabatic electrons, has been successfully exercised to identify non-diffusive transport characteristics in present day tokamak discharges. The limitation in applying UCAN to larger scale discharges is the 1D domain decomposition in the toroidal (or z-) direction for massively parallel implementation using MPI which has restricted the calculations to a few hundred ion Larmor radii or gyroradii per plasma minor radius. To exceed these sizes, we have implemented 2D domain decomposition in UCAN with the addition of the y-direction to the processor mix. This has been facilitated by use of relevant components in the P2LIB library of field and particle management routines developed for UCLA's UPIC Framework of conventional PIC codes. The gyro-averaging specific to gyrokinetic codes is simplified by the use of replicated arrays for efficient charge accumulation and force deposition. The 2D domain-decomposed UCAN2 code reproduces the original 1D domain nonlinear results within round-off. Benchmarks of UCAN2 on the Cray XC30 Edison at NERSC demonstrate ideal scaling when problem size is increased along with processor number up to the largest power of 2 available, namely 131,072 processors. These particle weak scaling benchmarks also indicate that the 1 nanosecond per particle per time step and 1 TFlops barriers are easily broken by UCAN2 with 1 billion particles or more and 2000 or more processors.

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Jensen, Rune, Jesper Larsen, Kasper Lassen, Matthias Mandø et Anders Andreasen. « Implementation and Validation of a Free Open Source 1D Water Hammer Code ». Fluids 3, n^o 3 (3 septembre 2018) : 64. http://dx.doi.org/10.3390/fluids3030064.

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This paper presents a free code for calculating 1D hydraulic transients in liquid-filled piping. The transient of focus is the Water Hammer phenomenon which may arise due to e.g., sudden valve closure, pump start/stop etc. The method of solution of the system of partial differential equations given by the continuity and momentum balance is the Method of Characteristics (MOC). Various friction models ranging from steady-state and quasi steady-state to unsteady friction models including Convolution Based models (CB) as well as an Instantaneous Acceleration Based (IAB) model are implemented. Furthermore, two different models for modelling cavitation/column separation are implemented. Column separation may occur during low pressure pulses if the pressure decreases below the vapour pressure of the fluid. The code implementing the various models are compared to experiments from the literature. All experiments consist of an upstream reservoir, a straight pipe and a downstream valve.

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Haugen, Nils Erland L., Øyvind Langørgen et Sigurd Sannan. « Nonlinear simulations of combustion instabilities with a quasi-1D Navier–Stokes code ». Journal of Sound and Vibration 330, n^o 23 (novembre 2011) : 5644–59. http://dx.doi.org/10.1016/j.jsv.2011.06.023.

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Nosakare Ogunbo, Jide. « MATLAB code for data-driven initial model of 1D Schlumberger sounding curve ». GEOPHYSICS 83, n^o 2 (1 mars 2018) : F21—F28. http://dx.doi.org/10.1190/geo2016-0631.1.

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A MATLAB code automatically performs partial curve matching of 1D apparent resistivity data recorded with the Schlumberger electrode array configuration. The two-layer master and auxiliary curves are used to systematically match through the branches of data extracting the corresponding model properties. Partial curve matching is a classical interpretation procedure of the sounding curve, which has been done manually. Results from the manual and automatic procedures are compared. The matched geoelectric models from the automatic process are retrieved more quickly, and these results are consistent because the process is digitalized and are not dependent on human numerical accuracy judgment. Magnitudes of random noise affect the final matched model parameters, yet these values are sufficient to be initial models for subsequent nonlinear inversion. It is hoped that for an inversion workflow, the code can be included to automatically find an initial resistivity model.

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Muscato, O., S. Rinaudo et P. Falsaperla. « Calibration of a One Dimensional Hydrodynamic Simulator with Monte Carlo Data ». VLSI Design 8, n^o 1-4 (1 janvier 1998) : 515–20. http://dx.doi.org/10.1155/1998/47467.

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In this paper we use the code Exemplar for matching a hydrodynamic 1D, time-dependent simulator and the transport coefficients obtained by the Monte Carlo simulator Damocles. This code is based on the Least Square method and it does not require any a priori knowledge about the simulator (analytical form of the equations etc.). The stationary electron flow in a one dimensional n+−n−n+ submicron silicon diode is simulated.

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Peng, Ronghua, Bo Han, Yajun Liu et Xiangyun Hu. « EM3DANI : A Julia package for fully anisotropic 3D forward modeling of electromagnetic data ». GEOPHYSICS 86, n^o 5 (1 septembre 2021) : F49—F60. http://dx.doi.org/10.1190/geo2020-0489.1.

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Forward modeling is vital for 3D inversion and interpretation of electromagnetic (EM) data in anisotropic media, which is one of the major challenges in the field of EM geophysics. However, there are few freely available 3D codes that are capable of modeling EM responses in fully anisotropic media. In addition, most existing 3D EM codes are written in low-level languages (LLs) such as C and Fortran, making them difficult to read, maintain, and extend. Taking advantage of recent progress in computer technology and numerical methods, we have developed an open-source package for forward modeling of frequency-domain EM fields in a fully 3D anisotropic earth (EM3DANI) using the Julia language, a relatively young, high-level programming language with a focus on high performance. Based on a mimetic finite-volume discretization of the governing equations, the modeling algorithm is expressed in an abstract form in terms of matrices/vectors and thus can be easily implemented by using any high-level language commonly used for numerical computing. Existing libraries written in LLs can be easily integrated into a Julia code without the so-called two-language problem; thus, we have exploited several mature third-party packages to deal with computationally intensive parts of the forward modeling, which guarantees high stability and efficiency. We have elaborated the structure of the package, paying special attention to code usability, readability, and extendability, while striving to retain versatility and high performance. The effectiveness of the code is demonstrated through two 1D synthetic examples for magnetotelluric and controlled-source EM (CSEM) problems, respectively. High accuracy and efficiency can be achieved for both 1D examples. Furthermore, we have developed a 3D example mimicking a marine CSEM survey scenario for hydrocarbon exploration. The simulation results indicate that the effect of the anisotropy on forward responses is significant and can be comparable to that of the target reservoir.

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Osuský, Filip, Branislav Vrban, Peter Ballo, Štefan Čerba, Jakub Lüley et Gabriel Farkas. « NUMERICAL MULTIGROUP TRANSIENT ANALYSIS OF SLAB NUCLEAR REACTOR WITH THERMAL FEEDBACK ». Acta Polytechnica CTU Proceedings 4 (16 décembre 2016) : 62. http://dx.doi.org/10.14311/ap.2016.4.0062.

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The paper describes a new numerical code for multigroup transient analyses with thermal feedback. The code is developed at Institute of Nuclear and Physical Engineering. It is necessary to carefully investigate transient states of fast neutron reactors, due to recriticality issues after accident scenarios. The code solves numerical diffusion equation for 1D problem with possible neutron source incorporation. Crank-Nicholson numerical method is used for the transient states. The investigated cases are describing behavior of PWR fuel assembly inside of spent fuel pool and with the incorporated neutron source for better illustration of thermal feedback.

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Pérez Mañes, Jorge, Victor Hugo Sánchez Espinoza, Sergio Chiva et Robert Stieglitz. « A New Coupled CFD/Neutron Kinetics System for High Fidelity Simulations of LWR Core Phenomena : Proof of Concept ». Science and Technology of Nuclear Installations 2014 (2014) : 1–13. http://dx.doi.org/10.1155/2014/294648.

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The Institute for Neutron Physics and Reactor Technology (INR) at the Karlsruhe Institute of Technology (KIT) is investigating the application of the meso- and microscale analysis for the prediction of local safety parameters for light water reactors (LWR). By applying codes like CFD (computational fluid dynamics) and SP3 (simplified transport) reactor dynamics it is possible to describe the underlying phenomena in a more accurate manner than by the nodal/coarse 1D thermal hydraulic coupled codes. By coupling the transport (SP3) based neutron kinetics (NK) code DYN3D with NEPTUNE-CFD, within a parallel MPI-environment, the NHESDYN platform is created. The newly developed system will allow high fidelity simulations of LWR fuel assemblies and cores. In NHESDYN, a heat conduction solver, SYRTHES, is coupled to NEPTUNE-CFD. The driver module of NHESDYN controls the sequence of execution of the solvers as well as the communication between the solvers based on MPI. In this paper, the main features of NHESDYN are discussed and the proof of the concept is done by solving a single pin problem. The prediction capability of NHESDYN is demonstrated by a code-to-code comparison with the DYNSUB code. Finally, the future developments and validation efforts are highlighted.

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Cretignier, M., J. Francfort, X. Dumusque, R. Allart et F. Pepe. « RASSINE : Interactive tool for normalising stellar spectra ». Astronomy & ; Astrophysics 640 (août 2020) : A42. http://dx.doi.org/10.1051/0004-6361/202037722.

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Aims. We provide an open-source code allowing an easy, intuitive, and robust normalisation of spectra. Methods. We developed RASSINE, a Python code for normalising merged 1D spectra through the concepts of convex hulls. The code uses six parameters that can be easily fine-tuned. The code also provides a complete user-friendly interactive interface, including graphical feedback, that helps the user to choose the parameters as easily as possible. To facilitate the normalisation even further, RASSINE can provide a first guess for the parameters that are derived directly from the merged 1D spectrum based on previously performed calibrations. Results. For HARPS spectra of the Sun that were obtained with the HELIOS solar telescope, a continuum accuracy of 0.20% on line depth can be reached after normalisation with RASSINE. This is three times better than with the commonly used method of polynomial fitting. For HARPS spectra of α Cen B, a continuum accuracy of 2.0% is reached. This rather poor accuracy is mainly due to molecular band absorption and the high density of spectral lines in the bluest part of the merged 1D spectrum. When wavelengths shorter than 4500 Å are excluded, the continuum accuracy improves by up to 1.2%. The line-depth precision on individual spectrum normalisation is estimated to be ∼0.15%, which can be reduced to the photon-noise limit (0.10%) when a time series of spectra is given as input for RASSINE. Conclusions. With a continuum accuracy higher than the polynomial fitting method and a line-depth precision compatible with photon noise, RASSINE is a tool that can find applications in numerous cases, for example stellar parameter determination, transmission spectroscopy of exoplanet atmospheres, or activity-sensitive line detection.

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Ketata, Ahmed, Zied Driss et Mohamed Salah Abid. « 1D gas dynamic code for performance prediction of one turbocharger radial turbine with different finite difference schemes ». Mechanics & ; Industry 20, n^o 6 (2019) : 627. http://dx.doi.org/10.1051/meca/2019073.

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The turbine, a key component of a turbocharger, is usually characterized by steady flow solutions. This method seems to be physically unrealistic as the fluid flow within a turbine is strongly unsteady due to the pulsating nature of the flow in the exhaust manifold of a reciprocating engine. This paper presents a new 1D gas dynamic code, written in the FORTRAN language, to characterize a radial turbine of one turbocharger embedded to a small gasoline engine. This code presents the novelty of meanline-1D coupling and the feature of numerical schemes choice. In this study, the turbocharger turbine is simulated with six different finite difference schemes. The computed distribution of the downstream mass flow rate, from the different cases, is compared to test data in order to choose the most suitable scheme. Test data are gathered from a developed test facility. Based on the computed results, unsteady performance of the turbine has been computed and discussed for the different schemes at two engine frequencies of 50 and 83.33 Hz. The results showed a significant impact of the numerical scheme on the 1D prediction of the turbine performance. Results indicated that the MR2LW finite-difference scheme has led to the minimum deviation of the numerical results to test data compared to the other considered schemes.

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Mahmoud, Mostafa, et S. Shaaban. « Sensitivity analysis of centrifugal compressors aerodynamic losses using 1D-mean streamline prediction technique ». Journal of Physics : Conference Series 2128, n^o 1 (1 décembre 2021) : 012029. http://dx.doi.org/10.1088/1742-6596/2128/1/012029.

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Abstract One-dimensional modeling and prediction of the centrifugal compressor performance are challenging as they require conservation equations and empirical and semi-empirical correlations. Therefore, there is a need to perform a consolidated study of the compressor aerodynamic loss models to conclude the importance of each loss to the compressor performance modeling. Accordingly, the purpose of this paper is to examine the effect of each aerodynamic loss on the compressor performance and explore more about which loss could have a negligible effect on the compressor performance. A MATLAB code was developed to predict the performance of five different small turbocharger centrifugal compressors at different geometric and operating conditions. The developed code was validated using the available experimental data of the investigated compressors. A sensitivity analysis methodology was performed using the validated code to check the effect of ten aerodynamic losses for the impeller and volute sections on the compressor performance. This paper concludes that impeller disk friction, blade loading, and clearance losses have a negligible effect on the small turbocharger vanless diffuser compressor performance.

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Juvela, Mika. « LOC program for line radiative transfer ». Astronomy & ; Astrophysics 644 (décembre 2020) : A151. http://dx.doi.org/10.1051/0004-6361/202039456.

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Context. Radiative transfer (RT) modelling is part of many astrophysical simulations. It is used to make synthetic observations and to assist the analysis of observations. We concentrate on modelling the radio lines emitted by the interstellar medium. In connection with high-resolution models, this can be a significant computationally challenge. Aims. Our aim is to provide a line RT program that makes good use of multi-core central processing units (CPUs) and graphics processing units (GPUs). Parallelisation is essential to speed up computations and to enable large modelling tasks with personal computers. Methods. The program LOC is based on ray-tracing (i.e. not Monte Carlo) and uses standard accelerated lambda iteration methods for faster convergence. The program works on 1D and 3D grids. The 1D version makes use of symmetries to speed up the RT calculations. The 3D version works with octree grids, and to enable calculations with large models, is optimised for low memory usage. Results. Tests show that LOC results agree with other RT codes to within ∼2%. This is typical of code-to-code differences, which are often related to different interpretations of the model set-up. LOC run times compare favourably especially with those of Monte Carlo codes. In 1D tests, LOC runs were faster by up to a factor ∼20 on a GPU than on a single CPU core. In spite of the complex path calculations, a speed-up of up to ∼10 was also observed for 3D models using octree discretisation. GPUs enable calculations of models with hundreds of millions of cells, as are encountered in the context of large-scale simulations of interstellar clouds. Conclusions. LOC shows good performance and accuracy and is able to handle many RT modelling tasks on personal computers. It is written in Python, with only the computing-intensive parts implemented as compiled OpenCL kernels. It can therefore also a serve as a platform for further experimentation with alternative RT implementation details.

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