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Barletta, Luca y Arnaldo Spalvieri. "Design of Short, High-Rate DVB-S2-Like Semi-Regular LDPC Codes". Research Letters in Communications 2008 (2008): 1–4. http://dx.doi.org/10.1155/2008/324503.
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This work focuses on high-rate () moderate-length () low-density parity-check codes. High-rate codes allow to maintain good quality of the preliminary decisions that are used in carrier recovery, while a moderate code length allows to keep the latency low. The interleaver of the LDPC matrix that we consider is inspired to the DVB-S2 standard one. A novel approach for avoiding short cycles is analyzed. A modified BP decoding algorithm is applied in order to deal with longer cycles. Simulations and results for the AWGN channel are presented, both for BPSK signalling and for coded modulation based on the partition .
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Văduva, Bogdan y Honoriu Vălean. "Designing a Low-Code CRUD framework". Carpathian Journal of Electronic and Computer Engineering 14, n.º 1 (1 de septiembre de 2021): 11–19. http://dx.doi.org/10.2478/cjece-2021-0003.
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Abstract Nowadays programmers write source code for inserting, editing and deleting records of a relational table. The majority of commercial relational databases include a specific management tool that offers such possibilities and most database programmers take this ability as granted. When it comes to real life applications, programmers use Object Oriented (OO) paradigm to build user friendly windows/screens/forms for database operations. The current work shows a different approach using a Low-code CRUD (Create, Read, Update, Delete) framework. Views and guidelines of how to design a Low-code CRUD framework will be detailed. “Low-code” motivation is due to the fact that the new framework will provide the ability to use less code in order to build fast and efficient complex applications. It will be up to the reader to envision a specific framework.
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Schmidt, K. U. "On cosets of the generalized first-order reed-muller code with low PMEPR". IEEE Transactions on Information Theory 52, n.º 7 (julio de 2006): 3220–32. http://dx.doi.org/10.1109/tit.2006.876252.
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Shridhar, Shreyas. "Analysis of Low Code-No Code Development Platforms in comparison with Traditional Development Methodologies". International Journal for Research in Applied Science and Engineering Technology 9, n.º 12 (31 de diciembre de 2021): 508–13. http://dx.doi.org/10.22214/ijraset.2021.39328.
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Abstract: This paper examines the overview of low-code/no-code development platforms in comparison with traditional development methodologies and examines the benefits and limitations of the same. For several decades, businesses have had multiple options when they demanded new information systems. They could develop a new system using in-house developers, or they could order a system from an external merchant. This offers a close fit to business obligations. However, nowadays, there is a new alternative that is becoming increasingly prevalent. Low code/no code (LC/NC) applications can cater to business requirements efficiently, can be implemented instantly, and the cost is much less than systems developed in-house. Few, if any, programming skills are required. Keywords: Traditional development, No code development, low code development, Low code No code development, Software development life cycle (SDLC)
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Belhadj, Salima, Abdelmounaim Moulay Lakhdar y Ridha Ilyas Bendjillali. "Performance comparison of channel coding schemes for 5G massive machine type communications". Indonesian Journal of Electrical Engineering and Computer Science 22, n.º 2 (1 de mayo de 2021): 902. http://dx.doi.org/10.11591/ijeecs.v22.i2.pp902-908.
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<p><span>Channel coding for the fifth generation (5G) mobile communication is currently facing new challenges as it needs to uphold diverse emerging applications and scenarios. Massive machine-type communication (mMTC) constitute one of the main usage scenarios in 5G systems, which promise to provide low data rate services to a large number of low power and low complexity devices. Research on efficient coding schemes for such use case is still ongoing and no decision has been made yet. Therefore, This paper compares the performance of different coding schemes, namely: tail-biting convolutional code (TBCC), low density parity check codes (LDPC), Turbo code and Polar codes, in order to select the appropriate channel coding technique for 5G-mMTC scenario. The considered codes are evaluated in terms of bit error rate (BER) and block error rate (BLER) for short information block lengths (K ≤ 256). We further investigate their Algorithmic complexity in terms of the number of basic operations. The Simulation results indicate that polar code with CRC-aided successive cancelation list decoder has better performance compared with other coding schemes for 5G-mMTC scenario.</span></p>
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Ganmor, E., R. Segev y E. Schneidman. "Sparse low-order interaction network underlies a highly correlated and learnable neural population code". Proceedings of the National Academy of Sciences 108, n.º 23 (20 de mayo de 2011): 9679–84. http://dx.doi.org/10.1073/pnas.1019641108.
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Ke, Jing, Xiaochun Lu, Xue Wang, Xiaofei Chen y Sheng Tang. "Concatenated Coding for GNSS Signals in Urban Environments". Applied Sciences 10, n.º 18 (14 de septiembre de 2020): 6397. http://dx.doi.org/10.3390/app10186397.
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This work investigated concatenated coding schemes for Global Navigation Satellite System (GNSS) signals in order to increase their error correction capability in urban environments. In particular, a serial concatenated code that combines an outer Reed–Solomon (RS) code with an inner low-density parity-check (LDPC) code was designed, and the performance was investigated over the land mobile satellite (LMS) channel for characterizing multipath and shadow fading in urban environments. The performance of the proposed concatenated coding scheme was compared to that of a B-CNAV1 message, in which two interleaved 64-ary LDPC codes were employed. The simulation results demonstrate that the proposed concatenated code can obtain a similar error correction performance to the two interleaved 64-ary LDPC codes in both the additive white Gaussian noise (AWGN) and LMS channels at a lower complexity level.
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Haah, Jeongwan y Matthew B. Hastings. "Codes and Protocols for Distilling T, controlled-S, and Toffoli Gates". Quantum 2 (7 de junio de 2018): 71. http://dx.doi.org/10.22331/q-2018-06-07-71.
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We present several different codes and protocols to distill T, controlled-S, and Toffoli (or CCZ) gates. One construction is based on codes that generalize the triorthogonal codes, allowing any of these gates to be induced at the logical level by transversal T. We present a randomized construction of generalized triorthogonal codes obtaining an asymptotic distillation efficiency γ→1. We also present a Reed-Muller based construction of these codes which obtains a worse γ but performs well at small sizes. Additionally, we present protocols based on checking the stabilizers of CCZ magic states at the logical level by transversal gates applied to codes; these protocols generalize the protocols of. Several examples, including a Reed-Muller code for T-to-Toffoli distillation, punctured Reed-Muller codes for T-gate distillation, and some of the check based protocols, require a lower ratio of input gates to output gates than other known protocols at the given order of error correction for the given code size. In particular, we find a 512 T-gate to 10 Toffoli gate code with distance 8 as well as triorthogonal codes with parameters [[887,137,5]],[[912,112,6]],[[937,87,7]] with very low prefactors in front of the leading order error terms in those codes.
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Xue, Rui, Tong Wang, Yanbo Sun y Huaiyu Tang. "Optimized Design for NB-LDPC-Coded High-Order CPM: Power and Iterative Efficiencies". Symmetry 12, n.º 8 (13 de agosto de 2020): 1353. http://dx.doi.org/10.3390/sym12081353.
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In this paper, a non-binary low-density parity-check (NB-LDPC) coded high-order continuous phase modulation (CPM) system is designed and optimized to improve power and iterative efficiencies. Firstly, the minimum squared normalized Euclidean distance and the 99% double-sided power bandwidth are introduced to design a competitive CPM, improving its power efficiency under a given code rate and spectral efficiency. Secondly, a three-step method based on extrinsic information transfer (EXIT) and entropy theory is used to design NB-LDPC codes, which reduces the convergence threshold approximately 0.42 and 0.58 dB compared with the candidate schemes. Thirdly, an extrinsic information operation is proposed to address the positive feedback issue in iterative detection and decoding and the value of bit error rate (BER) can approximately be reduced by 5×10−3. Finally, iteration optimization employing the EXIT chart and mutual information between demodulation and decoding is performed to achieve a suitable tradeoff for the communication reliability and iterative decoding delay. Simulation results show that the resulting scheme provides an approximately 3.95 dB coding gain compared to the uncoded CPM and achieves approximately 0.5 and 0.7 dB advantages compared with the candidate schemes. The resulting NB-LDPC-coded high-order CPM for a given code rate and spectral efficiency converges earlier into a turbo cliff region compared with other competitors and significantly improves power and iterative efficiencies.
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Zhao, Dan-feng, Hai Tian y Rui Xue. "Adaptive Rate-Compatible Non-Binary LDPC Coding Scheme for the B5G Mobile System". Sensors 19, n.º 5 (2 de marzo de 2019): 1067. http://dx.doi.org/10.3390/s19051067.
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This paper studies an adaptive coding scheme for B5G (beyond 5th generation) mobile system-enhanced transmission technology. Different from the existing works, the authors develop a class of rate-compatible, non-binary, low-density parity check (RC-NB-LDPC) codes, which expresses the strong connection between the algebra-based and graph-theoretic-based constructions. The constructed codes can not only express rate-compatible (RC) features, but also possess a quasi-cyclic (QC) structure that facilitates the encoding implementation. Further, in order to achieve the code rate-adaptive allocation scheme, the authors propose using the K-means++ clustering algorithm to cluster different channel environments, considering various factors that affect channel characteristics. Finally, in order to present the advantages of the adaptive coding scheme, the authors construct a coding scheme for image transmission. The numerical results demonstrate that the developed code can obtain better waterfall performance in a larger code rate range, which is more suitable for data transmission; the adaptive coding transmission scheme can obtain higher reconstructed image quality compared to the fixed code rate-coding scheme. Moreover, when considering unequal error protection (UEP), the proposed scheme can further improve the reconstructed image quality.
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Sahin, I., J. Crane y K. Watson. "Added Mass Coefficients for Submerged Bodies by a Low-Order Panel Method". Journal of Fluids Engineering 115, n.º 3 (1 de septiembre de 1993): 452–56. http://dx.doi.org/10.1115/1.2910159.
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The added mass coefficients for two and three-dimensional submerged bodies were calculated using a low-order panel code. The source and dipole strengths, and the panel surface area for each panel, were used to compute the integrals needed for added mass in all six degrees of motions. Several applications of this method were used in comparing the results with the theoretical, when available, experimental or other numerical results. The method was found to be successful in predicting the added mass coefficients using relatively low numbers of panels.
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Tian, Yunke, Yong Bai y Dake Liu. "Low-Latency QC-LDPC Encoder Design for 5G NR". Sensors 21, n.º 18 (18 de septiembre de 2021): 6266. http://dx.doi.org/10.3390/s21186266.
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In order to meet the low latency and high throughput requirements of data transmission in 5th generation (5G) New Radio (NR), it is necessary to minimize the low power encoding hardware latency on transmitter and achieve lower base station power consumption within a fixed transmission time interval (TTI). This paper investigates parallel design and implementation of 5G quasi-cyclic low-density parity-check (QC-LDPC) codes encoder. The designed QC-LDPC encoder employs a multi-channel parallel structure to obtain multiple parity check bits and thus reduce encoding latency significantly. The proposed encoder maps high parallelism encoding algorithms to a configurable circuit architecture, achieving flexibility and support for all 5G NR code length and code rate. The experimental results show that under the 800 MHz system frequency, the achieved data throughput ranges from 62 to 257.9 Gbps, and the maximum code length encoding time under base graph 1 (BG1) is only 33.75 ns, which is the critical encoding time of our proposed encoder. Finally, our proposed encoder was synthesized on SMIC 28 nm CMOS technology; the result confirmed the effectiveness and feasibility of our design.
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Asif, Muhammad, Wuyang Zhou, Qingping Yu, Saifullah Adnan, Md Sadek Ali y Muhammad Shahid Iqbal. "Jointly designed quasi-cyclic LDPC-coded cooperation with diversity combining at receiver". International Journal of Distributed Sensor Networks 16, n.º 7 (julio de 2020): 155014772093897. http://dx.doi.org/10.1177/1550147720938974.
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This correspondence proposes a jointly-designed quasi-cyclic (QC) low-density parity-check (LDPC)-coded multi-relay cooperation with a destination node realized by multiple receive antennas. First, a deterministic approach is utilized to construct different classes of binary QC-LDPC codes with no length-4 cycles. Existing methods put some limitations in terms of code length and rate in order to provide high error-correction performance. Therefore, this article gives three classes of QC-LDPC codes based on a combinatoric design approach, known as cyclic difference packing (CDP), with flexibility in terms of code-length and rate selection. Second, the proposed CDP-based construction is utilized to jointly-design QC-LDPC codes for coded-relay cooperation. At the receiver, the destination node is realized by multiple receive antennas, where maximal-ratio combining (MRC) and sum-product algorithm (SPA)-based joint iterative decoding are utilized to decode the corrupted sequences coming from the source and relay nodes. Simulation results show that the proposed QC-LDPC coded-relay cooperations outperform their counterparts with a coding gain of about 0.25 dB at bit-error rate (BER) [Formula: see text] over a Rayleigh fading channel in the presence of additive white Gaussian noise. Furthermore, the extrinsic-information transfer (EXIT) chart analysis has been used to detect the convergence threshold of proposed jointly-designed QC-LDPC codes. Numerical analysis shows that the proposed jointly-designed QC-LDPC codes provide a better convergence as compared to their counterparts under the same conditions.
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Kumari, Annushree. "Channel Coding Technique for 5G to Improve Flexibility". International Journal for Research in Applied Science and Engineering Technology 9, n.º VII (30 de julio de 2021): 2582–89. http://dx.doi.org/10.22214/ijraset.2021.36820.
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5G wireless network will take place after 4G. It will create many new issues. Some problems like, communication with low BER, and performance might be severe issue. In this thesis, coding methods are proposed in order to decrease the signal loss during the transmission process of data. Also, the LDPC system is explained in order to get good results with lower bit error rate over 5G standards by trying to compare it with systems like, LDPC, Convolutional and Turbo code system. Finally, a framework is designed which is a combination of LDPC codes with polar codes in order to improve information transmission efficiency.
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Zhang, Qian Hua y Jian Wu Zhang. "A Construction Method of LDPC Codes for Space Optical Communications Based on Protograph". Applied Mechanics and Materials 631-632 (septiembre de 2014): 791–94. http://dx.doi.org/10.4028/www.scientific.net/amm.631-632.791.
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In order to meet the requirements of low bit error-rate of the channel code in the space optical communication system, a construction method of low density parity check ( LDPC) codes with excellent performance is proposed based on protograph and quasi-cyclic expansion. It can be applied in high-speed encoding and decoding with efficient quasi-cyclic expansion. According to the proposed method, a LDPC ( 8832, 1472) suitable for the space optical communication system is constructed, in which the LDPC codes of the protograph perform very well. Simulation shows that the LDPC codes have superior error-correction performance and show no sign of error floor when the BER is in the order of 10-9, which are suitable for the long-distance space optical communication systems.
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Su, Yang, Peng Han, Zhu Jun Jia y Shi Hua Liang. "Digital Watermarking Based on Two-Way Arnold Transform and QR Code". Advanced Materials Research 591-593 (noviembre de 2012): 2564–67. http://dx.doi.org/10.4028/www.scientific.net/amr.591-593.2564.
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This paper proposes a digital watermarking algorithm based on two-way Arnold transformation and QR code. This algorithm uses the QR barcode as the watermark, and in its pretreatment process it uses the two-way Arnold transformation to broke up the QR code image into blocks which then coded and re-arranged in a specific order. Considering the role of Singular Value Decomposition in watermark embedding, here the watermark information is embedded into the low frequency coefficients of wavelet transform of the carrier image. Simulation results show that the algorithm is robust against attacks such as shearing, the JPEG compression and noise attacking.
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Zong Chen, Dr Joy Iong. "5G Systems with Low Density Parity Check based Chanel Coding for Enhanced Mobile Broadband Scheme". IRO Journal on Sustainable Wireless Systems 2, n.º 1 (25 de marzo de 2020): 42–49. http://dx.doi.org/10.36548/jsws.2020.1.005.
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The 5G mobile communication standard based radio access technology (RAT) is analysed for implementation of several candidate coding schemes in this paper. The third generation partnership project (3GPP) in the 5G scenario based on the Enhanced mobile broadband (eMBB) scheme is considered. Factors like flexibility, complexity of computation, bit error rate (BER), and block error rate (BLER) are considered for the purpose of evaluation of the coding schemes. In order to evaluate the performance various applications and services, a suitable set is of parameters are provided. The candidate schemes considered for this purpose are polar codes, low density parity check (LDPC) and turbo codes. Fair comparison is performed by investigation of block lengths and obtaining suitable rates by proper design. In an additive white Gaussian noise (AWGN) channel, the performance of BLER / BER is obtained for diverse block lengths and code rates based on simulation. The simulation results show that the performance of LDPC is relatively efficient for various code rates and block lengths despite the better performance of polar codes at short block lengths. As an added advantage, LDPC codes also offer relatively low complexity.
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Amerini, Alberto, Leonardo Langone, Riccardo Vadi y Antonio Andreini. "Assessment of a hybrid propulsion system for short-mid range application with a low-order code". E3S Web of Conferences 312 (2021): 11005. http://dx.doi.org/10.1051/e3sconf/202131211005.
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The increase in air traffic expected in the next years must be accompanied by innovation to ensure the lowest possible environmental impact. Hybrid electric-thermal propulsion systems are currently being investigated and could represent a breakthrough for environmental sustainability in the sector. However, the transition to electric propulsion remains challenging due to the current level of energy density related to storage systems, the additional components associated with power conversion and control systems, not to mention the cost of all the associated equipment. The purpose of this study is to carry out a preliminary assessment of a hybrid propulsion system for a short-mid range aircraft. This study investigates the series hybrid configuration, where a turboshaft, a high temperature superconducting (HTS) electric motor, batteries and power converters interact to provide the necessary propulsion for flight. A zero-dimensional procedure is developed to estimate the mass and efficiency of the powertrain components for a selected flight mission. Thermal engines are modeled with the low-order code and coupled with the components of the electric system through a python routine. A comparison in terms of weight and emissions is reported for the designed hybrid propulsion system and the conventional one. The analysis shows that the weight of the two propulsion systems is similar but, the presence of batteries, even considering a higher level of technology than the current one, leads to a significant increase in the weight of the hybrid aircraft. The second part of the study focuses on pollutant emissions, showing that the hybrid system can reduce CO2 emissions by 58% and NOx emissions by 68% compared to the conventional system. Despite the excellent premise, the reduction in payload for the hybrid aircraft causes a reduction in pollutant emissions per passenger only for NOx. For this reason, further technological improvement is needed to make hybrid propulsion advantageous in terms of both payload and pollutant emissions.
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Jin, Ayoung y Younghwan Pan. "A Study on Citizen Developer Competency and Development Process in Low-Code/No-Code Development System". Korean Society of Culture and Convergence 44, n.º 11 (30 de noviembre de 2022): 119–31. http://dx.doi.org/10.33645/cnc.2022.11.44.11.119.
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The era of easy development of apps is opening as the cloud computing environment develops and the need for RPA increases. The development of the low-code/no-code development system has led to the emergence of citizen developers who can create their own apps without little or no coding knowledge. This study investigated the characteristics and types of citizen developers through a survey. The characteristics of citizen developers were identified as marketers, planners, developers, designers, ordinary people, and most of them want to develop RPA apps. The most common types of citizen developers were identified as power users with a little knowledge of coding. In-depth interviews also revealed that the competency required of citizen developers is the most important, and unlike in the past, the order of the development process is very flexible, and the role of app development participants has become very ambiguous.
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Liu, Jie, Xiaojun Tong, Zhu Wang, Jing Ma y Longteng Yi. "An Improved Rao–Nam Cryptosystem Based on Fractional Order Hyperchaotic System and EDF–QC–LDPC". International Journal of Bifurcation and Chaos 29, n.º 09 (agosto de 2019): 1950122. http://dx.doi.org/10.1142/s0218127419501220.
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A Rao–Nam cryptosystem based on error correction code is proposed to provide both security and reliability. Since its security is drastically constrained by the limited error syndromes, in this paper, an improved Rao–Nam cryptosystem based on fractional order hyperchaotic system and Extended Difference Family–Quasi-Cyclic–Low-Density Parity-Check (EDF–QC–LDPC) codes is proposed to improve the security. A four-dimensional fractional order hyperchaotic system is constructed and is used to generate an excellent pseudorandom sequence. By replacing error syndromes with the pseudorandom sequence and permuting the coded message dynamically, the security of the Rao–Nam cryptosystem is enhanced greatly. The ability of the improved Rao–Nam cryptosystem against known attacks is analyzed and the error correction performance with different parameters is simulated. The results show that the proposed cryptosystem has a significant advantage of resisting the chosen-plaintext attack. Moreover, the proposed cryptosystem retains high capacity of error correction.
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Crivellini, A. y F. Bassi. "A Three-Dimensional Parallel Discontinuous Galerkin Solver for Acoustic Propagation Studies". International Journal of Aeroacoustics 2, n.º 2 (abril de 2003): 157–73. http://dx.doi.org/10.1260/147547203322775515.
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The paper presents recent developments of a computational code for the numerical investigation of acoustic propagation. The code solves the three-dimensional linear Euler equations using a Discontinuous Galerkin (DG) method for the spatial discretization and an explicit high-order low-storage Runge-Kutta method for advancing the solution in time. Thanks to DG discretization, high-order accurate numerical solutions on arbitrary unstructured hybrid grids have been easily computed. The code has been parallelized using MPI and preliminary results on a small 10-processor Linux cluster seem very promising.
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Ma, Chao, Li Min Zhang y Jian Xiong Wang. "Blind Estimation of Long Code DSSS Signal Based on Subspace Tracking". Applied Mechanics and Materials 484-485 (enero de 2014): 976–81. http://dx.doi.org/10.4028/www.scientific.net/amm.484-485.976.
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Aiming at solving the blind estimation problem of dispreading spectrum sequence under low SNR, a spread-spectrum estimation algorithm based subspace tracking is studied in this paper. This method avoids the direct eigen decomposition, using the sliding window technique to obtain the code synchronization, then use segmentation subspace tracking method estimate spreading sequence and splice in a certain order to achieve pseudo-code blind estimation. The results show that the algorithm can complete the accurate estimation of PN code sequence in low SNR conditions, reduce the amount of data storage and be easy hardware implementation
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Jorge Fernandez-Mayoralas y Raouia Masmoudi Ghodhbane. "Performance of a parallel Hamming coding in short-frame OFDM sensor's network". ITU Journal on Future and Evolving Technologies 2, n.º 1 (12 de abril de 2021): 77–88. http://dx.doi.org/10.52953/tdhg1720.
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In this paper, we focus on the most relevant Error Correcting Codes (ECCs): the Hamming code and the Reed-Solomon code in order to meet the trade-off between the low implementation complexity and the high error correction capacity in a short-frame OFDM communication system. Moreover, we discuss and validate via simulations this trade-off between complexity (Hamming is the easiest to code) and error correction capability (Reed-Solomon being the most effective). Therefore, we have to either improve the correction capacity of the Hamming code, or decrease the complexity cost for the Reed-Solomon code. Based on this analysis, we propose a new design of parallel Hamming coding. On the one hand, we validate this new model of parallel Hamming coding with numerical results using MATLAB-Simulink tools and BERTool Application which makes easier the Bit Error Rate (BER) performance simulations. On the other hand, we implement the design of this new model on an FPGA mock-up and we show that this solution of a parallel Hamming encoder/decoder uses a few resources (LUTs) and has a higher capability of correcting when compared to the simple Hamming code.
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Yi, Yan. "The Design of 2D Bar Code Recognition Software on Android". Advanced Materials Research 442 (enero de 2012): 453–57. http://dx.doi.org/10.4028/www.scientific.net/amr.442.453.
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In order to promote the application of two dimensional barcode on mobile phone, this paper uses the popular Android technology, and researches QR code format and the decode process of the QR code; and then designs 2D bar code recognition system based on the decode library Zxing. After testing, it is proved that the system has good generality and low resource consuming, and the software of itself is only 140 K.
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Blazewicz, Marek, Ian Hinder, David M. Koppelman, Steven R. Brandt, Milosz Ciznicki, Michal Kierzynka, Frank Löffler, Erik Schnetter y Jian Tao. "From Physics Model to Results: An Optimizing Framework for Cross-Architecture Code Generation". Scientific Programming 21, n.º 1-2 (2013): 1–16. http://dx.doi.org/10.1155/2013/167841.
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Starting from a high-level problem description in terms of partial differential equations using abstract tensor notation, theChemoraframework discretizes, optimizes, and generates complete high performance codes for a wide range of compute architectures. Chemora extends the capabilities of Cactus, facilitating the usage of large-scale CPU/GPU systems in an efficient manner for complex applications, without low-level code tuning. Chemora achieves parallelism through MPI and multi-threading, combining OpenMP and CUDA. Optimizations include high-level code transformations, efficient loop traversal strategies, dynamically selected data and instruction cache usage strategies, and JIT compilation of GPU code tailored to the problem characteristics. The discretization is based on higher-order finite differences on multi-block domains. Chemora's capabilities are demonstrated by simulations of black hole collisions. This problem provides an acid test of the framework, as the Einstein equations contain hundreds of variables and thousands of terms.
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Carter, S., J. M. Bowman y B. J. Braams. "On using low-order Hermite interpolation in `direct dynamics' calculations of vibrational energies using the code `MULTIMODE'". Chemical Physics Letters 342, n.º 5-6 (julio de 2001): 636–42. http://dx.doi.org/10.1016/s0009-2614(01)00656-x.
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Legrady, David, Marton Pukler, Balint Panka y Gabor Tolnai. "Coupling the GUARDYAN code to subchanflow". EPJ Nuclear Sciences & Technologies 9 (2023): 11. http://dx.doi.org/10.1051/epjn/2023002.
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GUARDYAN is a GPU-based dynamic Monte Carlo code developed at the Budapest University of Technology and Economics, Hungary. Dynamic Monte Carlo computes the neutron population evolution by calculating the direct time dependence of the neutron histories in multiplying systems. Some well-established Monte Carlo codes have DMC versions with coupling to Thermal-Hydraulic solvers. GUARDYAN has the computational advantage of applying GPUs, thus calculation burden can be carried by commonly available hardware, and is capable of handling power plant size systems for kinetics problems. GUARDYAN has been recently coupled to the subchannel thermal-hydraulics code SUBCHANFLOW in order to carry out dynamic calculations with TH feedback. This paper describes some convergence studies regarding reaching the initial equilibrium state. A literature-suggested set of TH input settings and high sample numbers resulted in very low statistical errors of the power estimates and stable global measures (L2) of power release, fuel, and coolant temperatures for both static and dynamic convergence. Dynamic mode low-sample simulations provided surprisingly stable global L2 measures, correct fuel temperatures, and power release, while coolant temperatures were off, without any indication of the incorrectness of the result. Static convergence showed an alternating, fluctuating L2 behavior that did not affect the final stable state.
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Righi, Mauro, Vassilios Pachidis, László Könözsy, Fanzhou Zhao y Mehdi Vahdati. "Three-dimensional low-order surge model for high-speed axial compressors". Journal of the Global Power and Propulsion Society 4 (18 de diciembre de 2020): 274–84. http://dx.doi.org/10.33737/jgpps/130790.
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Surge in modern aero-engines can lead to violent disruption of the flow, damage to the blade structures and eventually engine shutdown. Knowledge of unsteady performance and loading during surge is crucial for compressor design, however, the understanding and prediction capability for this phenomenon is still very limited. While useful for the investigation of specific cases, costly experimental tests and high-fidelity CFD simulations cannot be used routinely in the design process of compressor systems. There is therefore an interest in developing a low-order model which can predict compressor performance during surge with sufficient accuracy at significantly reduced computational cost. This paper describes the validation of an unsteady 3D through-flow code developed at Cranfield University for the low-order modelling of surge in axial compressors. The geometry investigated is an 8-stage rig representative of a modern aero-engine IP compressor. Two deep surge events are modelled at part speed and full speed respectively. The results are compared against high-fidelity, full annulus, URANS simulations conducted at Imperial College. Comparison of massflow, pressure and temperature time histories shows a close match between the low-order and the higher-fidelity methods. The low-order model is shown capable of predicting many transient flow features which were observed in the high-fidelity simulations, while reducing the computational cost by up to two orders of magnitude.
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Andreini, A. y B. Facchini. "Gas Turbines Design and Off-Design Performance Analysis With Emissions Evaluation". Journal of Engineering for Gas Turbines and Power 126, n.º 1 (1 de enero de 2004): 83–91. http://dx.doi.org/10.1115/1.1619427.
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Many gas turbines simulation codes have been developed to estimate power plant performance both in design and off-design conditions in order to establish the adequate control criteria or the possible cycle improvements; estimation of pollutant emissions would be very important using these codes in order to determine the optimal performance satisfying legal emission restrictions. This paper present the description of a one-dimensional emission model to simulate different gas turbine combustor typologies, such as conventional diffusion flame combustors, dry-low NOx combustors (DLN) based on lean-premixed technology (LPC) or rich quench lean scheme (RQL) and the new catalytic combustors. This code is based on chemical reactor analysis, using detailed kinetics mechanisms, and it is integrated with an existing power plant simulation code (ESMS Energy System Modular Simulator) to analyze the effects of power plant operations and configurations on emissions. The main goal of this job is the study of the interaction between engine control and combustion system. This is a critical issue for all DLN combustors and, in particular, when burning low-LHV fuel. The objective of this study is to evaluate the effectiveness of different control criteria with regard to pollutant emissions and engine performances. In this paper we present several simulations of actual engines comparing the obtained results with the experimental published data.
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Kuo, F. A. y J. S. Wu. "Implementation of a parallel high-order WENO-type Euler equation solver using a CUDA PTX paradigm". Journal of Mechanics 37 (2021): 496–512. http://dx.doi.org/10.1093/jom/ufab016.
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ABSTRACT This study proposes the optimization of a low-level assembly code to reconstruct the flux for a splitting flux Harten–Lax–van Leer (SHLL) scheme on high-end graphic processing units. The proposed solver is implemented using the weighted essentially non-oscillatory reconstruction method to simulate compressible gas flows that are derived using an unsteady Euler equation. Instructions in the low-level assembly code, i.e. parallel thread execution and instruction set architecture in compute unified device architecture (CUDA), are used to optimize the CUDA kernel for the flux reconstruction method. The flux reconstruction method is a fifth-order one that is used to process the high-resolution intercell flux for achieving a highly localized scheme, such as the high-order implementation of SHLL scheme. Many benchmarking test cases including shock-tube and four-shock problems are demonstrated and compared. The results show that the reconstruction method is computationally very intensive and can achieve excellent performance up to 5183 GFLOP/s, ∼66% of peak performance of NVIDIA V100, using the low-level CUDA assembly code. The computational efficiency is twice the value as compared with the previous studies. The CUDA assembly code reduces 26.7% calculation and increases 37.5% bandwidth. The results show that the optimal kernel reaches up to 990 GB/s for the bandwidth. The overall efficiency of bandwidth and computation performance achieves 127% of the predicted performance based on the HBM2-memory roofline model estimated by Empirical Roofline Tool.
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Hajji, Amine, Christine Coquelet-Pascal y Patrick Blaise. "A hybrid approach for neutronics calculations in the neutron shielding of sodium fast reactors". EPJ Nuclear Sciences & Technologies 7 (2021): 17. http://dx.doi.org/10.1051/epjn/2021016.
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Neutron calculations in the neutron shielding of fast neutron reactors are a complex problem as deterministic schemes are usually not suited for such calculations while Monte-Carlo codes have poor computational performance due to the very low flux levels in neutron shields. In this article, both methods are studied, as well as a hybrid scheme on the neutron shielding of the ASTRID fast reactor benchmark. This hybrid scheme uses a fission source calculated by a deterministic code in order to precisely calculate neutron fluxes in the shielding with a Monte-Carlo code using variance reduction techniques. This provides reference results in order to validate deterministic calculations. Comparisons between deterministic codes and this hybrid reference show that large biases are obtained, up to 50%. Further studies are made to reduce the biases, showing that many physical phenomena should be treated, including anisotropy of the scattering law at high energies and spatial self-shielding inside the boron carbide shielding. These improvements reduce the biases to less than 10%. Finally, some applications to designing criteria for the neutron shielding are presented, such as gas production in the neutron shielding and activation of secondary sodium at the intermediate heat exchanger (IHX).
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Hirata, F. P., R. G. M. de Andrade y J. C. Della Bella. "Comparative analysis between prediction models in codes and test data for shear strength". Revista IBRACON de Estruturas e Materiais 6, n.º 6 (diciembre de 2013): 875–902. http://dx.doi.org/10.1590/s1983-41952013000600004.
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Since the beginning of twentieth century, along with academic publications of Ritter and Mörsch, several studies have been done in order to understand shear strength in reinforced concrete elements. Approximately 1,200 laboratory tests results of reinforced concrete beams under shear stresses were used in a comparative analysis among values from prediction models of codes and laboratory tests results, enabling classification of the codes according to their applicability in several tests intervals. Although the Brazilian Code NBR 6118 (2007) showed good results in usual ranges of parameters, it presented unsatisfactory results on the following cases: low and medium shear transverse reinforcement rate.
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Al-nahari, A. Y., F. E. Abd El-Samie y M. I. Dessouky. "Distributed Space-Time/Frequency Coding Schemes for Single-Carrier Frequency Division Multiple Access Systems". ISRN Communications and Networking 2011 (4 de abril de 2011): 1–10. http://dx.doi.org/10.5402/2011/549706.
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The single carrier-frequency division multiple access (SC-FDMA) system is a new system that was adopted in the standardization of the upcoming 3GPP long-term evolution (LTE). Designing diversity-achieving schemes for the SC-FDMA system is a challenging task. The codes adopted should not affect the peak-to-average power ratio (PAPR) among other constraints. In this paper, we consider the design of cooperative diversity schemes for SC-FDMA systems in the uplink direction. Specifically, two relay-assisted distributed space-time/frequency codes are proposed. The proposed distributed space-frequency code (SFC) achieves full spatial diversity in the uplink fast-fading channels, where a diversity of order three can be achieved. The proposed code keeps a low PAPR, which is a good feature of the system. A minimum mean square error (MMSE) decoder is used at the receiver of the destination node. Moreover, we propose a bandwidth-efficient distributed space-time code (STC) for slow-fading relay channels. A decode-and-forward (DF) protocol is used at the relay node, and the possibility of erroneous decoding is taken into account. Simulation results demonstrate the performance improvement of the proposed schemes.
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Tsoeunyane, Lekhobola, Simon Winberg y Michael Inggs. "Automatic Configurable Hardware Code Generation for Software-Defined Radios". Computers 7, n.º 4 (19 de octubre de 2018): 53. http://dx.doi.org/10.3390/computers7040053.
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The development of software-defined radio (SDR) systems using field-programmable gate arrays (FPGAs) compels designers to reuse pre-existing Intellectual Property (IP) cores in order to meet time-to-market and design efficiency requirements. However, the low-level development difficulties associated with FPGAs hinder productivity, even when the designer is experienced with hardware design. These low-level difficulties include non-standard interfacing methods, component communication and synchronization challenges, complicated timing constraints and processing blocks that need to be customized through time-consuming design tweaks. In this paper, we present a methodology for automated and behavioral integration of dedicated IP cores for rapid prototyping of SDR applications. To maintain high performance of the SDR designs, our methodology integrates IP cores using characteristics of the dataflow model of computation (MoC), namely the static dataflow with access patterns (SDF-AP). We show how the dataflow is mapped onto the low-level model of hardware by efficiently applying low-level based optimizations and using a formal analysis technique that guarantees the correctness of the generated solutions. Furthermore, we demonstrate the capability of our automated hardware design approach by developing eight SDR applications in VHDL. The results show that well-optimized designs are generated and that this can improve productivity while also conserving the hardware resources used.
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Hussein, Yasmeen M., Basman M. Al-Nedawe, Ammar Hussein Mutlag y Ameer K. Jawad. "Application of Error Correction Codes RS and LDPC to Enhance the Dicode Pulse Position Modulation". Journal of Hunan University Natural Sciences 49, n.º 1 (28 de enero de 2022): 161–69. http://dx.doi.org/10.55463/issn.1674-2974.49.1.21.
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Dicode Pulse Position Modulation (DiPPM) has been presented as a new coding technique with several improvements over earlier PPM formats. Few analyses and experimental results have been published because it is a new coding scheme. To overcome the problem of bandwidth utilization in current PPM formats, DiPPM can be employed. The line rate is twice as fast as the original data rate. In order to increase DiPPM's error performance, two types of Forward Error Correction (FEC) codes, Reed-Solomon (RS) code and low-density parity-check (LDPC) code, are investigated in this article. When RS and LDPC function at their optimal parameters, the results show an improvement in DiPPM system error performance. The error performance of an uncoded DiPPM system was compared to that of a DiPPM-encoded LDPC system and a system utilizing the Reed-Solomon algorithm. Transmission efficiency is measured by the number of photons per pulse and bandwidth widening. When the bandwidth is 1x103 times or more than the initial data rate, DiPPM with LDPC code exceeds uncoded DiPPM and DiPPM with RS, using 1.821 x 103 photons per pulse, with a codeword length of 27 and code rate of 0.75.
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Sourkounis, Constantinos y Pavlos Tourou. "Grid Code Requirements for Wind Power Integration in Europe". Conference Papers in Energy 2013 (4 de junio de 2013): 1–9. http://dx.doi.org/10.1155/2013/437674.
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As the capacity of wind power continues to increase globally, stricter requirements regarding grid connection of wind generators are introduced by system operators. The development of wind turbine technology is inevitably affected by the new grid codes, and wind power plants are expected to support the grid and provide ancillary services much like conventional power plants. The most demanding regulations are found in Europe where wind penetration levels are higher. This paper presents the main aspects of current grid code requirements for the integration of wind power in European countries and suggests performance characteristics in order to satisfy the most demanding requirements. The dynamic behavior of wind turbines with doubly fed induction generators is investigated and a solution for low voltage ride through compliance is presented.
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El habti El idrissi, Anas, Rachid El Gouri y Hlou Laamari. "Conception of a new LDPC decoder with hardware implementation on FPGA card". International Journal of Engineering & Technology 3, n.º 4 (18 de septiembre de 2014): 451. http://dx.doi.org/10.14419/ijet.v3i4.3185.
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Low Density Parity-Check codes are one of the hottest topics in coding theory nowadays. Equipped with very fast encoding and decoding algorithms, LDPC codes are very attractive both theoretically and practically. In this paper, A simplified algorithm for decoding Low-Density Parity-Check (LDPC) codes is proposed with a view to reduce the implementation complexity, this algorithm is based on a simple matrix equation which must be resolved in order to calculate all possible solutions of this equation, and then a simple circuit will be used to determine the errors produced during the transmission channel. First, we developed the design of the proposed algorithm second, we generated and simulated the hardware description language source code using Quartus software tools and finally we implemented the new algorithm of LDPC codes on FPGA card. Keywords: Bit-Flipping Algorithm, Error Detection, FPGA Card, LDPC Decoder, Matrix Equation.
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Zhou, You. "Hospital Indoor Navigation System Based on QR Codes". Journal of Electronic Research and Application 5, n.º 6 (30 de noviembre de 2021): 50–54. http://dx.doi.org/10.26689/jera.v5i6.3653.
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With the continuous increase in China’s population, the number of people visiting hospitals are also increasing. In order to meet the needs of patients, hospitals are expanding their scale, and departments are becoming more and more sophisticated. While improving the quality of medical services, it has become more difficult for patients to seek medical consultation. In order to improve the quality of medical services, a indoor navigation system based on QR code has been designed for hospitals, which realizes indoor navigation by scanning a QR code. This low-cost technology has accurate positioning, which brings convenience in locating and navigating departments.
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Vannitsem, S. y L. De Cruz. "A 24-variable low-order coupled ocean–atmosphere model: OA-QG-WS v2". Geoscientific Model Development Discussions 6, n.º 4 (6 de diciembre de 2013): 6569–604. http://dx.doi.org/10.5194/gmdd-6-6569-2013.
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Abstract. A new low-order coupled ocean–atmosphere model for mid-latitudes is derived. It is based on quasi-geostrophic equations for both the ocean and the atmosphere, coupled through momentum transfer at the interface. The systematic reduction of the number of modes describing the dynamics leads to an atmospheric low-order component of 20 ordinary differential equations, already discussed in Reinhold and Pierrehumbert (1982), and an oceanic low-order component of 4 ordinary differential equations, as proposed by Pierini (2012). The coupling terms for both components are derived and all the coefficients of the ocean model are provided. Its dynamics is then briefly explored, through the analysis of its mean field, its variability and its instability properties. The wind-driven ocean displays a decadal variability induced by the atmospheric chaotic wind forcing. The chaotic behavior of the coupled system is highly sensitive to the ocean–atmosphere coupling, for low values of the thermal forcing affecting the atmosphere (corresponding to a weakly chaotic coupled system). But it is less sensitive for large values of the thermal forcing (corresponding to a highly chaotic coupled system). In all the cases explored, the number of positive exponents is increasing with the coupling. A Fortran code of the model integration is provided as Supplement.
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Smith, Robin y Jack Bishop. "A Fast Universal Kinematic Fitting Code for Low-Energy Nuclear Physics: FUNKI_FIT". Physics 1, n.º 3 (26 de noviembre de 2019): 375–91. http://dx.doi.org/10.3390/physics1030027.
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We present an open-source kinematic fitting routine designed for low-energy nuclear physics applications. Although kinematic fitting is commonly used in high-energy particle physics, it is rarely used in low-energy nuclear physics, despite its effectiveness. A FORTRAN and ROOT C++ version of the FUNKI_FIT kinematic fitting code have been developed and published open access. The FUNKI_FIT code is universal in the sense that the constraint equations can be easily modified to suit different experimental set-ups and reactions. Two case studies for the use of this code, utilising experimental and Monte–Carlo data, are presented: (1) charged-particle spectroscopy using silicon-strip detectors; (2) charged-particle spectroscopy using active target detectors. The kinematic fitting routine provides an improvement in resolution in both cases, demonstrating, for the first time, the applicability of kinematic fitting across a range of nuclear physics applications. The ROOT macro has been developed in order to easily apply this technique in standard data analysis routines used by the nuclear physics community.
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Huo, Kejia, Zhuhua Hu y Dake Liu. "Design and Implementation of Shared Memory for Turbo and LDPC Code Interleaver". Wireless Communications and Mobile Computing 2022 (27 de febrero de 2022): 1–9. http://dx.doi.org/10.1155/2022/5782199.
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In 4G turbo and 5G LDPC, in order to realize a flexible, low-power, low-cost shared general-purpose block interleaving hardware module, it faces the challenges of interleaving structure integration, fewer gate circuits, parallel multistream operation, and switching between standards. Facing these challenges, after studying 3GPP TS 36.212 V15.4.0 and 3GPP TS 38.212 V15.4.0 protocols, common part of two major interleaving module standards is found. For the block interleave module in the rate matching of the 4G downlink turbo code and the bit interleave module after the rate matching of the 5G NR downlink LDPC code, this paper first designs a memory and implements the two codes interleaving on it. Then, based on the Altera Quartus prime platform and ModelSim for functional verification. Experimental results show that under SMIC 28 nm, operating frequency 50MHz, after synopsys synthesis, the memory module area is 0.17 μ m 2 , and the power consumption is 6.45 mW. Through the shared design, 32 bits parallel access, and switching between standards, the proposed scheme reduces the hardware cost, power consumption, and clock overhead, and improves the flexibility of 4G LTE and 5G NR communication downlink hardware implementation.
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Sadchenko, А. V., O. A. Kushnirenko, N. P. Kushnirenko, O. V. Sadchenko y O. V. Troyanskiy. "Implementation of Manchester codec for information transmission systems based on AVR and ARM architecture microcontrollers". Технология и конструирование в электронной аппаратуре, n.º 4-6 (2022): 17–24. http://dx.doi.org/10.15222/tkea2022.4-6.17.
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ATmega series AVR microcontrollers (e.g., ATmega8A or ATmega16A) and ARM microcontrollers with a Cortex M3 core (e.g., STM32F103С8T6) are among the most popular controllers used in solving engineering problems related to servicing various fire and security alarm sensors and devices for metering household and industrial power consumption. At the same time, to transfer the data via a twisted pair or AC voltage network, it needs to be encoded using Manchester 1 or Manchester 2 code, and said AVR and ARM microcontroller units (MCU) contain no hardware encoder and decoder for the Manchester code. The study aimed at solving the engineering problem of implementing the codec (encoder-decoder) of the Manchester code based on the hardware interfaces of low-performance microcontrollers. The direct implementation of the encoding algorithm with the Manchester code using a purely software-driven approach significantly decreases the information transfer rate. At the same time, among the hardware interfaces of the MCU, there is always a serial universal asynchronous data transceiver (UART). However, the UART data transfer protocol is not generally suitable for Manchester encoding and, therefore, needs to be software adapted. In order to adapt the UART protocol to the conditions of Manchester encoding, the 8N1 mode is selected at the hardware level, which means 8 data bits, 1 stop and 1 start bit. The software implementation of the encoder consists in the fact that out of the total possible volume of 256 code combinations, 16 are selected that satisfy the Manchester 2 code, while the start and stop conditions for data bytes transmitted in a row also satisfy the structure of the Manchester code. To maximize the efficiency of the program code, all code words are stored in the memory of the MCU in such a way that their serial number corresponds to the decimal interpretation of 4 bits of the input data. The decoding of the received data is also performed as efficiently as possible using the decoding table. The implementation of the software and hardware codec of the Manchester code significantly expands the scope of popular AVR and ARM microcontrollers and reduces the cost of the finished product by excluding any additional units that perform the function of encoding and decoding the Manchester code.
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Prakash K M y G. S. Sunitha. "A Modified-SCD for Optimize Performance Rate at Polar Code". International Journal of Green Computing 10, n.º 1 (enero de 2019): 1–21. http://dx.doi.org/10.4018/ijgc.2019010101.
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The first verified capacity-achieving codes were developed by Arikan called “polar codes.” It has gained significant attention due to their low encoding and decoding process complexity and optimum capacity-achievement process. In the original form of polar codes, the decoder has the inferior performance with finite ‘block-lengths' as compared to the LDPC codes, therefore, the successive cancellation decoder (“SCD”) for the polar codes is a very important element in order to provide a capacity theorem, but it comprises complexity at a larger number of iterations that is not applicable for the point of view of lower latency application. Therefore, in this article we proposed a modified SCD that rearranges the stages but it can cause decoder performance degradation, so we applied a novel design rule of the polar codes in order to match with our MSCD model. In the result analysis section, we show the effectiveness of our proposed model that tends to have higher performance rate as compared to standard SCD.
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Kempka, Thomas. "Verification of a Python-based TRANsport Simulation Environment for density-driven fluid flow and coupled transport of heat and chemical species". Advances in Geosciences 54 (14 de octubre de 2020): 67–77. http://dx.doi.org/10.5194/adgeo-54-67-2020.
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Abstract. Numerical simulation has become an inevitable tool for improving the understanding on coupled processes in the geological subsurface and its utilisation. However, most of the available open source and commercial modelling codes do not come with flexible chemical modules or simply do not offer a straight-forward way to couple third-party chemical libraries. For that reason, the simple and efficient TRANsport Simulation Environment (TRANSE) has been developed based on the Finite Difference Method in order to solve the density-driven formulation of the Darcy flow equation, coupled with the equations for transport of heat and chemical species. Simple explicit, weighted semi-implicit or fully-implicit numerical schemes are available for the solution of the system of partial differential equations, whereby the entire numerical code is composed of less than 1000 lines of Python code, only. A diffusive flux-corrected advection scheme can be employed in addition to pure upwinding to minimise numerical diffusion in advection-dominated transport problems. The objective of the present study is to verify the numerical code implementation by means of benchmarks for density-driven fluid flow and advection-dominated transport. In summary, TRANSE exhibits a very good agreement with established numerical simulation codes for the benchmarks investigated here. Consequently, its applicability to numerical density-driven flow and transport problems is proven. The main advantage of the presented numerical code is that the implementation of complex problem-specific couplings between flow, transport and chemical reactions becomes feasible without substantial investments in code development using a low-level programming language, but the easy-to-read and -learn Python programming language.
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Sugiharto, Setiono. "The Ordinariness of Code-meshing in the Indonesian Linguistic Landscapes". Journal of Language and Literature 22, n.º 2 (26 de septiembre de 2022): 404–12. http://dx.doi.org/10.24071/joll.v22i2.4802.
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Code-meshing as a strategic linguistic practice has been considered a rarity in a high-stake writing practice (e.g. academic writing). Studies in composition scholarship have demonstrated that such a practice needs arduous intellectual endeavors and extra rhetorical efforts to be realized. That is, code-meshing requires an exceptionally high linguistic adeptness, language awareness, and rhetorical sensitivity in order to be performed effectively. As such, the products of code-meshing in scholarly writing are often seen as a marked form of textual realization. This article shows that while strenuous struggles are needed to practice code-meshing in academic writing (i.e. high-stake translingual practice), such a practice can be performed as mundane, ordinary, unremarkable, and relaxed activities (i.e. low-stake translingual practice) in linguistic landscapes or signage displayed in public places. Illustrations of the code-meshed texts in the latter case will be provided, and then examined to account for their ordinariness. In light of the vibrant low-stake translingual practice, I shall develop an important notion of grassroots performativity to suggest the everydayness of quotidian language practices enacted by multilingual language users in their own community.
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PADOVANI, E., E. PRIOLO y G. SERIANI. "LOW AND HIGH ORDER FINITE ELEMENT METHOD: EXPERIENCE IN SEISMIC MODELING". Journal of Computational Acoustics 02, n.º 04 (diciembre de 1994): 371–422. http://dx.doi.org/10.1142/s0218396x94000233.
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The finite element method (FEM) is a numerical technique well suited to solving problems of elastic wave propagation in complex geometries and heterogeneous media. The main advantages are that very irregular grids can be used, free surface boundary conditions can be easily taken into account, a good reconstruction is possible of irregular surface topography, and complex geometries, such as curved, dipping and rough interfaces, intrusions, cusps, and holes can be defined. The main drawbacks of the classical approach are the need for a large amount of memory, low computational efficiency, and the possible appearance of spurious effects. In this paper we describe some experience in improving the computational efficiency of a finite element code based on a global approach, and used for seismic modeling in geophysical oil exploration. Results from the use of different methods and models run on a mini-superworkstation APOLLO DN10000 are reported and compared. With Chebyshev spectral elements, great accuracy can be reached with almost no numerical artifacts. Static condensation of the spectral element's internal nodes dramatically reduces memory requirements and CPU time. Time integration performed with the classical implicit Newmark scheme is very accurate but not very efficient. Due to the high sparsity of the matrices, the use of compressed storage is shown to greatly reduce not only memory requirements but also computing time. The operation which most affects the performance is the matrix-by-vector product; an effective programming of this subroutine for the storage technique used is decisive. The conjugate gradient method preconditioned by incomplete Cholesky factorization provides, in general, a good compromise between efficiency and memory requirements. Spectral elements greatly increase its efficiency, since the number of iterations is reduced. The most efficient and accurate method is a hybrid iterative-direct solution of the linear system arising from the static condensation of high order elements. The size of 2D models that can be handled in a reasonable time on this kind of computer is nowadays hardly sufficient, and significant 3D modeling is completely unfeasible. However the introduction of new FEM algorithms coupled with the use of new computer architectures is encouraging for the future.
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Li, Liangliang, Tao Liang, Huaguo Zhang, Songmao Du y Lin Gao. "A Tensor-Based Approach to Blind Despreading of Long-Code Multiuser DSSS Signals". Electronics 12, n.º 5 (22 de febrero de 2023): 1097. http://dx.doi.org/10.3390/electronics12051097.
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In this paper, a tensor-based approach to blind despreading of long-code multiuser DSSS signals is proposed. We aim to generalize the tensor-based methods originally developed for blind separation of short-code multiuser DSSS signals to long-code cases. Firstly, we model the intercepted long-code multiuser DSSS signals with an antenna-array receiver as a three-order tensor with missing values, and then, the blind separation problem can be formulated as a canonical or parallel factor (CANDECOMP/PARAFAC) decomposition problem of the missing-data tensor, which can be solved using optimum methods. Secondly, a constrained Cramér–Rao Bound (CRB) is also derived to provide a performance benchmark for the proposed approach. Simulation results verify the feasibility of our proposed approach in the case of low signal-to-noise (SNR) conditions.
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Gao, Fan, Tianhe Xu, Xinyue Meng, Nazi Wang, Yunqiao He y Baojiao Ning. "A Coastal Experiment for GNSS-R Code-Level Altimetry Using BDS-3 New Civil Signals". Remote Sensing 13, n.º 7 (3 de abril de 2021): 1378. http://dx.doi.org/10.3390/rs13071378.
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High temporal and spatial resolutions are the key advantages of the global navigation satellites system-reflectometry (GNSS-R) technique, while low precision and instabilities constrain its development. Compared with conventional Ku/C band nadir-looking radar altimetry, the precision of GNSS-R code-level altimetry is restricted by the smaller bandwidth and the lower transmitted power of the signals. Fortunately, modernized GNSS broadcast new open-available ranging codes with wider bandwidth. The Chinese BDS-3 system was built on 31 July 2020; its inclined geostationary orbit and medium circular orbit satellites provide B1C and B2a public navigation service signals in the two frequency bands of B1 and B2. In order to investigate their performance on GNSS-R code-level altimetry, a coastal experiment was conducted on 5 November 2020 at a trestle of Weihai in the Shandong province of China. The raw intermediate frequency data with a 62 MHz sampling rate were collected and post-processed to solve the sea surface height every second continuously for over eight hours. The precisions were evaluated using the measurements from a 26 GHz radar altimeter mounted on the same trestle near our GNSS-R setup. The results show that a centimeter-level accuracy of GNSS-R altimetry—based on B1C code after the application of the moving average—can be achieved, while for B2a code, the accuracy is about 10 to 20 cm.
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Wu, Jian Feng, Cai Hua Wang y Xue Qin Zhang. "The Selection of the Difference Scheme in Numerical Simulation of Low-Rise Gable Roof Surface Pressure". Advanced Materials Research 711 (junio de 2013): 344–47. http://dx.doi.org/10.4028/www.scientific.net/amr.711.344.
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Using the FLUENT software, this paper taking the wind load shape coefficient in the current code for the design of building structures as the comparison standard, have numerical wind tunnel simulation of the wind the surface wind pressure on low layer double slope roof. It focused on the effect of four convective term difference schemes on the numerical simulation, such as First-Order Upwind, Second-Order Upwind, Power Law and Quadratic Upwind Interpolation for ConvectiveKinematics. It provided reasonable reference for selection of convective term difference format.
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Akimova, Elena N., Vladimir E. Misilov, Igor M. Kulikov y Igor G. Chernykh. "OMPEGAS: Optimized Relativistic Code for Multicore Architecture". Mathematics 10, n.º 14 (21 de julio de 2022): 2546. http://dx.doi.org/10.3390/math10142546.
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The paper presents a new hydrodynamical code, OMPEGAS, for the 3D simulation of astrophysical flows on shared memory architectures. It provides a numerical method for solving the three-dimensional equations of the gravitational hydrodynamics based on Godunov’s method for solving the Riemann problem and the piecewise parabolic approximation with a local stencil. It obtains a high order of accuracy and low dissipation of the solution. The code is implemented for multicore processors with vector instructions using the OpenMP technology, Intel SDLT library, and compiler auto-vectorization tools. The model problem of simulating a star explosion was used to study the developed code. The experiments show that the presented code reproduces the behavior of the explosion correctly. Experiments for the model problem with a grid size of 128×128×128 were performed on an 16-core Intel Core i9-12900K CPU to study the efficiency and performance of the developed code. By using the autovectorization, we achieved a 3.3-fold increase in speed in comparison with the non-vectorized program on the processor with AVX2 support. By using multithreading with OpenMP, we achieved an increase in speed of 2.6 times on a 16-core processor in comparison with the vectorized single-threaded program. The total increase in speed was up to ninefold.