Two-dimensional Code Research Articles

Assessing high fidelity multi-component models to facilitate safeguards at Gas Centrifuge Enrichment Plants

The International Atomic Energy Agency (IAEA) inspectors routinely carry out environmental sampling (ES) as a verification method. Collection of environmental swipe samples at various locations in Gas Centrifuge Enrichment Plants (GCEPs) is an important process in detecting misuse of a declared facility and possibly the existence of undeclared nuclear material. These samples are measured for isotopic composition in uranium containing particles by Thermal Ionization Mass Spectrometry (TIMS) or Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Even though ES is highly effective in detecting the absolute value of enrichments and their deviations from the declared values, it cannot explain the cause of those changes. Several potential explanations can serve as possibilities for particles detected above or other than the declared enrichment. These include normal and non-malicious events such as the design of the enrichment cascades, unintentional failures of the machines, or overshoot during startup of a cascade. It can also be the result of deliberate misuse by the facility operators. The primary objective of this work is to understand how these factors affect the enrichments produced by a cascade and quantify anticipated multi-isotopic concentrations for each case. The following methodology is employed to determine signatures at a particular facility.1)Utilize a new two-dimensional multi-component diffusion code to obtain centrifuge performance data and use that information to design and perform cascade analysis. Compare and contrast the results with previous 1-D radially averaged solutions from the Pancake code.2)Design a GCEP cascade with the production goal of 19.75% 235U for each set of machine data above. Investigate two cascade scenarios that include enrichment of natural uranium (NU) feed to 19.75% 235U in a single cascade compared to a two-step process of NU to 5% and then 5% to 19.75%.3)Simulate the intentional vs unintentional off-normal scenarios in the cascades to assess the differences in isotopic concentrations.A non-ideal squared-off cascade model developed at the University of Virginia is used to calculate flow rates and isotopic concentrations of the process gas. The analysis is performed using the Rome machine model operated at 600 m/s rotor speed. The upper and lower bounds of normal and abnormal enrichments in a typical facility are used in conjunction with ES results to understand the root causes of such observations.

Numerical simulation of mesomechanical properties of limestone containing dissolved hole and persistent joint

In order to reveal the complex mechanical properties and mesoscopic failure behavior of limestone rock mass containing both dissolved hole defect and persistent joint, numerical models are developed using the two-dimensional particle flow code (PFC2D) to carry out the uniaxial compressive strength (UCS) tests. The stress–strain, contact force chain, vertical stress field, and crack evolution characteristics of limestone samples containing circular holes and different dip angles persistent joints were analyzed. The results show that the UCS and elastic modulus of the rock samples can be reduced by the circular hole and the persistent joint, and the persistent joints with steep dip angles have a more obvious control effect on the mechanical properties of the rock samples. With the increase in loading stress level, the contact force chain in the hole-joint combination model gradually deflects slightly along the joint dip angle from the left and right sides of the hole and gradually spreads outward. Under uniaxial compression, the initiation cracks in persistent joints and rock blocks are primarily tensile cracks. The initiation positions first appear in the persistent joint, and the initiation positions in the rock block change from the upper and lower vertices of the circular hole to the junction below the joint with the increase of the joint dip angle. The crack initiation stress in the persistent joint is smaller than that in the corresponding rock block, and the control effect of the joint dip angle on the crack initiation stress of the whole rock sample is reduced.

The influence of intra-cortical microstructure on the contrast in ultrasound images of the cortex of long bones: A 2D simulation study

Decreased thickness of the bone cortex due to bone loss in the course of ageing and osteoporosis is associated with reduced bone strength. Cortical thickness measurement from ultrasound images was recently demonstrated in young adults. This requires the identification of both the outer (periosteum) and inner (endosteum) surfaces of the bone cortex. However, with bone loss, the cortical porosity and the size of the vascular pores increase resulting in enhanced ultrasound scattering which may prevent the detection of the endosteum. The aim of this work was to study the influence of cortical bone microstructure variables, such as porosity and pore size, on the contrast of the endosteum in ultrasound images. We wanted to estimate the range of these variables for which ultrasound imaging of the endosteum is feasible. We generated synthetic data using a two-dimensional time-domain code to simulate the propagation of elastodynamic waves. A synthetic aperture imaging sequence with an array transducer operating at a center frequency of 2.5 MHz was used. The numerical simulations were conducted for 105 cortical microstructures obtained from high resolution X-ray computed tomography images of ex vivo bone samples with a porosity ranging from 2% to 24 %. Images were reconstructed using a delay-and-sum (DAS) algorithm with optimized f-number, correction of refraction at the periosteum, and sample-specific wave-speed. We observed a range variation of 18 dB of endosteum contrast in our data set depending on the bone microstructure. We found that as porosity increases, speckle intensity inside the bone cortex increases whereas the intensity of the signal from the endosteum decreases. Also, a microstructure with large pores (diameter >250 μm) was associated with poor endosteum visibility, compared with a microstructure with equal porosity but a more narrow distribution of pore sizes. These findings suggest that ultrasound imaging of the bone cortex with a probe operating at a central frequency of 2.5 MHz using refraction-corrected DAS is capable of detecting the endosteum of a cortex with moderate porosity (less than about 10%) if the largest pores remain smaller than about 200 μm.

Analysis of Combination of Parking System with Face Recognition and QR Code using Histogram of Oriented Gradient Method

Security is very important everywhere, including in the campus environment. To provide security and comfort for those who park their vehicles, a parking application is needed that can provide vehicle security while undergoing academic activities on campus. QR code (Quick Response Code) is a technology for converting written data into a two-dimensional code, which is printed on a more compact medium capable of storing various types of data. The most common individual part used to identify a person is the face because it has the unique characteristics of everyone. Histogram of Oriented Gradient (HOG) is a feature extraction used for face identification based on histogram of gradient orientation and gradient magnitude. This application is implemented using the Dlib library for facial recognition. The implementation of this method is expected to improve parking security and provide a record of parked vehicles. The results of testing the implementation of facial recognition methods into android applications show very satisfactory results. With the results of testing the QR code scanning accuracy of 100% and an accuracy of 90% for a 7% damage rate and an accuracy of 85% for a 15% damage rate, and the results of facial recognition testing of 90% on face photos wearing helmets and an accuracy of 92% on photo of face without helmet.

Galaxy And Mass Assembly (GAMA): bulge-disc decomposition of KiDS data in the nearby Universe

ABSTRACT We derive single Sérsic fits and bulge-disc decompositions for 13 096 galaxies at redshifts z < 0.08 in the GAMA II equatorial survey regions in the Kilo-Degree Survey (KiDS) g, r, and i bands. The surface brightness fitting is performed using the Bayesian two-dimensional profile fitting code ProFit. We fit three models to each galaxy in each band independently with a fully automated Markov chain Monte Carlo analysis: a single Sérsic model, a Sérsic plus exponential and a point source plus exponential. After fitting the galaxies, we perform model selection and flag galaxies for which none of our models are appropriate (mainly mergers/Irregular galaxies). The fit quality is assessed by visual inspections, comparison to previous works, comparison of independent fits of galaxies in the overlap regions between KiDS tiles and bespoke simulations. The latter two are also used for a detailed investigation of systematic error sources. We find that our fit results are robust across various galaxy types and image qualities with minimal biases. Errors given by the MCMC underestimate the true errors typically by factors 2–3. Automated model selection criteria are accurate to $\gt 90{{\ \rm per\ cent}}$ as calibrated by visual inspection of a subsample of galaxies. We also present g−r component colours and the corresponding colour–magnitude diagram, consistent with previous works despite our increased fit flexibility. Such reliable structural parameters for the components of a diverse sample of galaxies across multiple bands will be integral to various studies of galaxy properties and evolution. All results are integrated into the GAMA database.

Numerical analyses of coupled thermo-mechanical behaviors of cement sheath in geothermal wells

The stability of cement sheath under high temperature and high pressure is one of the most critical issues for the durability of geothermal well systems. In this study, a two-dimensional plane-strain finite element code was developed to investigate the coupled thermo-mechanical behaviors of the casing-cement-formation system. Different from previous linear elastic analyses, a thermoelasto-plastic constitutive model based on the thermodynamic theory was adopted for the cement sheath. It is shown that the finite element simulations using the proposed model provide a more accurate and realistic prediction of stress–strain responses of the cement sheath under high temperature. The results demonstrate that the radial stress concentration and the tensile strain concentration occur at both the cement–casing interface and the cement–formation interface, where the cement sheath is most likely to fail. High strength and low stiffness in the cement sheath and the formation are preferred for the integrity of the system. Both large thermal cycles and large differences between the internal fluid pressure and the external pressure should be avoided during operation. The new code is an alternative tool for guiding the geothermal well design. The finite element framework described herein is universal for other thermo-mechanical applications, such as energy foundations and energy tunnels.

Improve cardinality with two-dimensional unipolar (optical) orthogonal codes for multiple access interference

Abstract Optical code division multiple access (OCDMA) is one of the promising technologies to be implemented using all-optical networks. The OCDMA system performance is substantially determined by the particular encoding codes. Due to the different transmitter and receiver design considerations, selecting the right code family and code dimension is critical. In this research, 2D codes based on permutation vectors’ (PV) codes are presented to overcome the Multiple Access Interference (MAI) problem and system complexity. Consequently, the research work focused on two-dimensional unipolar codes to mitigate the probability error and cardinality of the optical CDMA system. A fast wavelength-hopping/time-spreading (FWHTS) is introduced as an encoding technique. The FWHTS is used for code construction design, and it achieves cardinality in upper bound theory without sacrificing good auto-and-cross correlation properties. Accordingly, hybrid codes with serial elimination interference receivers are presented to estimate the error probability of 2D optical codes. The proposed method is simulated using Python software. The performance metrics are flexibility, bit rate, minimum temporal length, computational complexity, cardinality and wavelength. The proposed method is compared with the existing 2D balanced incomplete block design (BIBD) technique and multidiagonal (MD) codes. The performance of the proposed method is approximately 4% higher than these existing methods. Subsequently, in the future work, a SAC-OCDMA code construction design shall be presented and the decoding techniques can be introduced, which can reduce the receiver noise and other phase intensity induced noise, respectively.

Shear characteristics and shear strength model of rock mass structural planes

Accurately determining the shear strength of structural planes is crucial for evaluating the stability of rock masses. The shear test using the sawtooth structural plane usually captures the main influencing factors of its shear characteristics. In this study, the two-dimensional particle flow code (PFC2D) numerical simulation method was used to conduct shear tests on the sawtooth structural planes of rock masses with undulant angles of 10°, 20°, and 30°, respectively. With the increase in normal stress and the undulant angle, the shear failure of the structural planes was found to no longer be pure slip failure or shear failure but accompanied by a compression-induced fracture phenomenon. Based on the analysis of the shear test results, a peak shear strength model considering different undulant angles and normal stresses was proposed, and the hyperbolic function post-peak shear strength model was improved. The peak shear strength obtained from the physical direct shear tests was compared with those calculated using the proposed model, Parton model, and Shen model. The calculation error under low and high normal stress of the proposed method was found to be within an acceptable range. Additionally, when calculating the peak shear strength of a structural plane under high normal stress, applying the calculation method proposed in this study is a better option than applying the other models. Furthermore, although the variation trend of the post-peak shear strength was similar to that of the experimental results, the values obtained using the hyperbolic variation model were too large. The variation trend of the post-peak shear strength obtained using the improved function was essentially consistent with the experimental results, and the calculated values were close to the experimental results. The systematic research on the shear strength calculation model of rock mass structural planes contributes to the theoretical research of rock mass mechanics, and this study can act as a guide for landslide prediction and control projects.

Entanglement Estimation in Tensor Network States via Sampling

We introduce a method for extracting meaningful entanglement measures of tensor network states in general dimensions. Current methods require the explicit reconstruction of the density matrix, which is highly demanding, or the contraction of replicas, which requires an effort exponential in the number of replicas and which is costly in terms of memory. In contrast, our method requires the stochastic sampling of matrix elements of the classically represented reduced states with respect to random states drawn from simple product probability measures constituting frames. Even though not corresponding to physical operations, such matrix elements are straightforward to calculate for tensor network states, and their moments provide the Rényi entropies and negativities as well as their symmetry-resolved components. We test our method on the one-dimensional critical XX chain and the two-dimensional toric code in a checkerboard geometry. Although the cost is exponential in the subsystem size, it is sufficiently moderate so that—in contrast with other approaches—accurate results can be obtained on a personal computer for relatively large subsystem sizes.4 MoreReceived 21 March 2022Accepted 15 June 2022DOI:https://doi.org/10.1103/PRXQuantum.3.030312Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasEntanglement detectionEntanglement measuresQuantum information theoryTechniquesProjected entangled pair statesReplica methodsTensor network methodsQuantum InformationCondensed Matter, Materials & Applied Physics

Quantum to classical mapping of the two-dimensional toric code in an external field

Kitaev's toric code Hamiltonian in dimension D=2 has been extensively studied for its topological properties, including its quantum error correction capabilities. While the Hamiltonian is quantum, it lies within the class of models that admits a D+1-dimensional classical representation. In these notes, we provide details of a Suzuki-Trotter expansion of the partition function of the toric code Hamiltonian in the presence of an external magnetic field. By coupling additional degrees of freedom in the form of a matter field that can subsequently be gauged away, we explicitly derive a classical Hamiltonian on a cubic lattice which takes the form of a non-isotropic 3D Ising gauge theory.

A note on two-dimensional cyclic and constacyclic codes

During the study of the two-dimensional cyclic (TDC) codes of length $n=ls$ over a finite field $\mathbb{F}_q$ where $s=2^k$, Sepasdar and Khashyarmanesh (2016, [11]) arose a problem that the technique used by them to characterize TDC codes of length $n=ls$ does not work for TDC codes of length $3l$. It naturally motivates us to study the TDC codes of other lengths together with $3l$. Further, $(\lambda_1,\lambda_2)$-constacyclic codes are the generalization of constacyclic codes. Thus, we study two-dimensional cyclic codes of length $3l$ and $(\lambda_1,\lambda_2)$-constacyclic codes of length $2l$, respectively over finite fields. Here, the generating set of polynomials for these two-dimensional codes and their duals are obtained. Finally, with the help of our derived results, we have constructed many MDS codes corresponding to the two-dimensional codes.

Mitigating laser imprint with a foam overcoating

In direct-drive inertial confinement fusion, laser imprint can cause areal density perturbations on the target shell that seed the Rayleigh–Taylor instability and further degrade the implosion. To mitigate the effect of laser imprint, a foam overcoating layer outside the target shell has been suggested to increase the thermal smoothing of the conduction region (between the ablation front and the critical density surface) and mass ablation of the ablation front. In this paper, we use a two-dimensional radiation hydrodynamic code FLASH to investigate the laser imprint mitigation performance and find other physical mechanisms of foam overcoatings. First, radiation ablation dynamically modulates density distribution not only to increase the frequency of the perturbed ablation front oscillation but also to decrease the amplitude of the oscillation. Second, a larger length of the shocked compression region reduces the amplitude of the perturbed shock front oscillation. The areal density perturbations decrease with the decrease in the perturbations of the ablation front and shock front. Based on the abovementioned physical mechanisms, we propose the optimal ranges of foam parameters to mitigate laser imprint with the aid of dimensional analysis: the foam thickness is about two to three times that of the perturbation wavelength, and the foam density is about 1/2–3/2 times that of the critical density.

QR Code Detection

Due to the incorrect image collecting approach, QR code identification frequently confronts obstacles such as uneven backdrop fluctuations, inadequate illuminations, and distortions. As a result, identifying QR codes is difficult, and artificial intelligence-based methods were developed to address this challenge. This article uses an improved adaptive median filter technique and a QR code distortion correction method based on backpropagation (BP) neural networks to increase the identification rate of QR image codes. The distorted QR image can be fitted into the geometric deformation pattern using this combination of artificial intelligence methods, and QR code identification is possible. This paper addresses two-dimensional code distortion, which has been a critical research topic in present software systems. The research findings, which focused on the picture preprocessing step, demonstrated a significant improvement of 14 percent in the reading rate of QR image codes following processing using the system algorithm described in this article. The artificial intelligence technique used improves the recognition rate of the two-dimensional code image to some extent.

Dual-emitting ZIF-8⊃4-MU@Zn2GeO4:Mn2+ nanocomposites for ratiomertic luminescent thermometer and information encryption

Dual-emitting ratiometric optical thermometers with the advantages of excellent self-calibration and high-sensitivity have become a research hot spot. Herein, a dual-emissive 4-methylumbelliferone encapsulated ZIF-8 (ZIF-8⊃4-MU) modified Zn2GeO4:Mn2+ nanocomposite was simply prepared by adding Zn2GeO4:Mn2+ nanorods into a methanol solution containing 4-methylumbelliferone (4-MU), zinc (II) nitrate hexahydrate, and 2-methylimidazole. Accompanying with the self-assembly of ZIF-8⊃4-MU, the binding affinity of Zn2+ ions to the surface of Zn2GeO4:Mn2+ nanorods enables the formation of ZIF-8⊃4-MU@Zn2GeO4:Mn2+ nanocomposite. The photoluminescence violet-blue (420 nm) and green emissions (531 nm) of the nanocomposite can be ascribed to the two independent luminescent centers of 4-MU dyes confined in ZIF-8 and the characteristic transition of 4T1-6A1 for Mn2+ ions doped in Zn2GeO4, respectively. The fluorescent intensity ratios (FIRs) of 4-MU to Mn2+ (I420 nm/I531 nm) showed excellent self-calibrating temperature monitoring functions with a maximum relative sensitivity (Sr) of 1.82%·oC−1 and stable reusability in the temperature range of 20–100 °C. Also, the ZIF-8⊃4-MU@Zn2GeO4:Mn2+ hybridized polyvinyl alcohol (PVA) transparent film showed a similar multi-emitting behavior, as well as good processability and tensile properties. Benefiting from the excitation-dependent emitting property of ZIF-8⊃4-MU@Zn2GeO4:Mn2+, a multiple optical encryption of digital information was successfully realized based on a two-dimensional code, achieving an enhanced security level for preventing counterfeiting. This proof-of-concept study offers a feasible assembled way in fabricating multi-mode luminescent nanocomposites for ratiometric temperature sensing and information encryption.

Two-Dimensional Error Correction Code for Spin-Transfer Torque Magnetic Random-Access Memory (STT-MRAM) Caches

Spin-Transfer Torque Magnetic Random-Access Memory (STT-MRAM) is an emerging nonvolatile memory (NVM) technology that can replace conventional cache memory in computer systems. STT-RAM has many desirable properties such as high writing and reading speed, non-volatility, and low power consumption. Since the cache requires a high speed of writing and reading speed, a single-error correction and double error detection (SEC - DED) are applicable to improve the reliability of the cache. However, the process variation and thermal fluctuation of STT-MRAM cause errors. For example, writing ‘1’ bits has more errors than writing ‘0’ bits. We then design the weight reduction code to reduce the error caused by writing ‘1’ bits. Moreover, the performance of an SEC-DED code is improved by constructing an SED-DED code as the product code. The simulation results demonstrate that the two-dimensional error correction code consisting of product code and weight reduction code is roughly 5.67 × 10−4 lower than the SEC-DED code when the error rate of writing ‘1’ bits is equal to 6 × 10−3.

Design of Cigarette QR Code Decoding System Based on STM32

This paper mainly studies the design method of the hardware and software of the cigarette strip QR code decoding based on STM32 microprocessor. This paper expounds the principle of hardware circuit design with STM32F407 microprocessor as the core, analyzes the steps of analyzing the QR code decoding algorithm based on the modular programming idea of C language, and analyzes the result of cigarette-bar QR code decoding. The results of field application show that the system can meet the design requirements of cigarette QR code decoding and improve the recognition rate of two-dimensional code, which has high application value.

Quantum phase transitions in the K -layer Ising toric code

We investigate the quantum phase diagram of the $K$-layer Ising toric code corresponding to $K$ layers of two-dimensional toric codes coupled by Ising interactions. While for small Ising interactions the system displays ${\mathbb{Z}}_{2}^{K}$ topological order originating from the toric codes in each layer, the system shows ${\mathbb{Z}}_{2}$ topological order in the high-Ising limit. The latter is demonstrated for general $K$ by deriving an effective low-energy model in $K\mathrm{th}$-order degenerate perturbation theory, which is given as an effective anisotropic single-layer toric code in terms of collective pseudospins 1/2 referring to the two ground states of isolated Ising chain segments. For the specific cases $K=3$ and $K=4$ we apply high-order series expansions to determine the gap series in the low- and high-Ising limit. Extrapolation of the elementary energy gaps gives convincing evidence that the ground-state phase diagram consists of a single quantum critical point and our findings suggest a quantum phase transition in the 3D Ising* universality class for both $K$ separating both types of topological order, which is consistent with former findings for the bilayer Ising toric code.

Behaviour of Horseshoe-Shaped Tunnel Subjected to Different In Situ Stress Fields

At great depths, tunnel openings experience a tectonic stress field rather than overburden stress. This paper aims to examine the impact of different in situ stress ratios and multiple tunnel depths below the surface on the excavation induced-stresses and displacements around tunnel openings. Thus, a series of models has been built, using a two-dimensional elasto-plastic finite-elements code, RS2D, to conduct parametric stability analysis. The performance of tunnel opening is examined by evaluating the induced stress-deformation around the opening. The results indicate that ratio of wall convergence, roof sag and floor heave increase as in situ stress ratio and tunnel depth below surface increase. Additionally, the induced-stresses increase as depth and state of in situ stress increase. In addition, the extent of yielding zones into rock mass around tunnel roof and floor deteriorates as tunnel depth and in situ stress ratio increase. Moreover, the normal stress along rock joints is sharply dropped when joints pass in the vicinity of tunnel opening (e.g., centre of opening). As well, the direction of shear stress along joints is reversed. Consequently, inward shear displacement of rock, on the underside of the weakness plane, is produced as a result of slip occurrence.

A Family of Optimal Multiple-Weight Optical Orthogonal Codes for Fiber-Optic Networks.

Optical orthogonal codes (OOCs) were designed for multimedia optical CDMA systems with quality of service requirements in optical fiber networks. Two-dimensional (2-D) multiple-weight optical orthogonal codes have been invested as they can overcome the drawbacks of nonlinear effects in large spreading sequences. In this paper, we reveal the combinatorial properties of optimal 2-D OOCs and focus our attention on the constructions for a family of optimal 2-D multiple-weight optical orthogonal codes by combinatorial methods, such as incomplete difference matrix, h-perfect cyclic packing, and skew starter. In particular, an improved construction of skew starters with multiple weights is also proposed to solve the existence of optimal multiple-weight optical orthogonal codes. Our numerical examples demonstrate that the proposed construction is very helpful for optimizing the utilization of optical network effectively.

TECED: A Two-Dimensional Error-Correction Codes Based Energy-Efficiency SRAM Design

The reliability of memory is an important issue. The rapid development of transistor technology makes the memory more prone to soft errors. Several recent efforts have proposed various designs to avoid the corruption of stored data by using Error Correction Codes (ECC). However, these designs tend to focus on one indicator, which means they cannot balance the electrical timing, area and power consumption constraints with the increasing of the chip-scale and the operating frequency. In this paper, we propose a design named TECED: A Two-Dimensional Error-Correction Codes Based Energy-Efficiency SRAM Design. We achieve higher energy-efficiency and lower hardware cost by using a two-dimensional error correction codes, and evaluate the design by considering the overall system performance. Comparing with the traditional Hamming code, the evaluation shows that the TECED reduces most of fifty percent of the area overhead and twenty-eight point five percent power consumption of the memory at a specific storage capacity.