Block Structure Research Articles

Toward a classification of PT-symmetric quantum systems: From dissipative dynamics to topology and wormholes

Studies of many-body non-Hermitian parity-time (PT)-symmetric quantum systems are attracting a lot of interest due to their relevance in research areas ranging from quantum optics and continuously monitored dynamics to Euclidean wormholes in quantum gravity and dissipative quantum chaos. While a symmetry classification of non-Hermitian systems leads to 38 universality classes, we show that, under certain conditions, PT-symmetric systems are grouped into 24 universality classes. We identify 14 of them in a coupled two-site Sachdev-Ye-Kitaev (SYK) model and confirm the classification by spectral analysis using exact diagonalization techniques. Intriguingly, in 4 of these 14 universality classes, AIIIν, BDIν†, BDI++ν, and CI−−ν, we identify a basis in which the SYK Hamiltonian has a block structure in which some blocks are rectangular, with ν∈N the difference between the number of rows and columns. We show analytically that this feature leads to the existence of ν robust purely eigenvalues, whose level statistics follow the predictions of Hermitian random matrix theory for classes A, AI, BDI, and CI, respectively. We have recently found that this ν is a topological invariant, so these classes are topological. By contrast, nontopological real eigenvalues display a crossover between Hermitian and non-Hermitian level statistics. Similarly to the case of Lindbladian dynamics, the reduction of universality classes leads to unexpected results, such as the absence of Kramers degeneracy in a given sector of the theory. Another novel feature of the classification scheme is that different sectors of the PT-symmetric Hamiltonian may have different symmetries. Published by the American Physical Society 2024

PFedBASC: Personalized Federated Learning with Blockchain-Assisted Semi-Centralized Framework

As network technology advances, there is an increasing need for a trusted new-generation information management system. Blockchain technology provides a decentralized, transparent, and tamper-proof foundation. Meanwhile, data islands have become a significant obstacle for machine learning applications. Although federated learning (FL) ensures data privacy protection, server-side security concerns persist. Traditional methods have employed a blockchain system in FL frameworks to maintain a tamper-proof global model database. In this context, we propose a novel personalized federated learning (pFL) with blockchain-assisted semi-centralized framework, pFedBASC. This approach, tailored for the Internet of Things (IoT) scenarios, constructs a semi-centralized IoT structure and utilizes trusted network connections to support FL. We concentrate on designing the aggregation process and FL algorithm, as well as the block structure. To address data heterogeneity and communication costs, we propose a pFL method called FedHype. In this method, each client is assigned a compact hypernetwork (HN) alongside a normal target network (TN) whose parameters are generated by the HN. Clients pull together other clients’ HNs for local aggregation to personalize their TNs, reducing communication costs. Furthermore, FedHype can be integrated with other existing algorithms, enhancing its functionality. Experimental results reveal that pFedBASC effectively tackles data heterogeneity issues while maintaining positive accuracy, communication efficiency, and robustness.

Monofilaments of isosorbide-based tetrapolyesters with enhanced (bio)degradability prepared by a solid-state drawing process: Synthesis and struture-property relations

To enhance the degradation rate of poly (butylene adipate-co-terephthalate) (PBAT) in the natural environment and to investigate the effect of modified monomers on the molding and structure of copolyester fibers, a series of isosorbide modified PBAT (PBIAT) tetrapolyesters were synthesized and monofilaments were prepared by solid-state drawing in this work. The experimental results revealed that the introduction of isosorbide formed a partial block structure in the molecular chain, and that a significant improvement in the properties of heat resistance and degradability of the copolyester was observed with the introduction of isosorbide. In the research of fiber forming and structure-property relationship by isosorbide, it was found that although the monofilament orientation process was affected by the V-shape structure of isosorbide, the change of the crystal structure under stress was similar to that of polybutylene terephthalate (PBT). The PBIAT monofilaments showed a decrease in the strength at break affected by the introduction of isosorbide but they still met the requirements for textile applications.

A comparative study of streamlined flow channels with water drop block configurations and their effects on temperature profiles, mass transport characteristics, and performance in PEM fuel cell

The problems of temperature distribution, mass transport, and drainage performance in flow field channels (FFCs) become the most significant effects on PEMFC performance. In order to solve the above problems, this study proposes five distinct streamlined block architectures of flow channels that consider interface contact resistance (ICR) and gas diffusion layer (GDL) face permeability effect on temperature profiles to enhance mass transport and cell performance of PEMFC. The streamlined block structures of flow channels considering ICR and GDL face permeability were comparatively evaluated. The results show that the temperature profiles exhibit a distinctive "Ʌ" shape with an approximate increase of 0.19ᵒC at CN 2 compared to CN1. Besides, CN6 has current density, power density, and the best removal water saturation of 6.94 %, 12.27 %, and 7.18 %, respectively, are higher than CN1 (conventional model) when the voltage is 0.4 V. Consequently, the streamlined imitated water-drop block (WDB) models applied in the flow channels with considering both suitable ICR and GDL face permeability for PEM fuel cell can improve the mass transport capacity, enhance the speed of the electrochemical reaction, and provide better cell performance.

Efficient inter partitioning of versatile video coding based on supervised contrastive learning

Nowadays, Versatile Video Coding (VVC) has achieved a superior performance than previous video coding standard (High Efficiency Video Coding). The Quadtree with Nested Multi-Type Tree (QTMT) coding block structure can enhance the coding performance. Nevertheless, this technique also leads to the significantly increasing complexity of VVC inter coding. Therefore, complexity optimization is an urgent problem to be optimized in the market application of VVC. To solve this issue, we propose a Supervised-Contrastive-Learning-based Inter Partitioning (SCLIP) method in this paper. Firstly, we define the above complexity optimization problem as a supervised classification task. Next, we develop a SCLIP Estimation Network (SCLIPEst-Net) with a supervised contrastive learning module and a classification module. After training on a newly established dataset, the SCLIPEst-Net can reasonably predict the mode partitioning. Finally, we propose an overall SCLIP algorithm that effectively determines the inter partitions of VVC with a low computational overhead. Experimental results indicate that our method achieves 45.14% average Time Saving (TS) with a 2.40% Bjøntegaard Delta Bit Rate (BDBR) in Random Access (RA), outperforming the benchmarks.

Broué's abelian defect group conjecture for blocks with cyclic hyperfocal subgroups

AbstractIn this paper, we prove that the hyperfocal subalgebra of a block with an abelian defect group and a cyclic hyperfocal subgroup is Rickard equivalent to the group algebra of the semidirect of the hyperfocal subgroup by the inertial quotient of the block. In particular, the hyperfocal subalgebra is a Brauer tree algebra, which is analogous to the structure of blocks with cyclic defect groups. As a consequence, we show that Broué's abelian defect group conjecture holds for blocks with cyclic hyperfocal subgroups.

Lithology and subsurface structures related to gold mineralisation in the Kibati prospect, Mozambique belt in eastern Tanzania, with implications for gold exploration

This paper provides an insight into the structures, lithologies, and potential zones and their relationships to gold mineralisation that were investigated to decipher the controls of gold mineralisation at the Kibati Gold Prospect within the Mozambique Belt. Although the Kibati area is located within the gold mineralised zone, lithology and subsurface geological structures associated with gold mineralisation are not well studied. The available high-resolution aeromagnetic data have not yet also been analysed and interpreted to derive geological features that are useful in mineral exploration. The investigation of the structures and lithologies was accomplished through integrated interpretation of high-resolution aeromagnetic data, ground magnetic data, geological mapping, and rock sampling. Aeromagnetic and ground magnetic results reveal the presence of two structural systems, which were previously not identified that trend in NW–SE and NE–SW, with the NW–SE being the dominant control of gold mineralisation. The subsurface structure with NW–SE trending controls the mineralised fluids as a consequence of gold mineralisation in the surface lithologies. Petrography and geological mapping show that granitic gneiss, garnet-biotite quartzo-feldspathic gneiss, dolerite, and amphibolite are the main exposed outcrops where the first two identified types of gneisses, based on their protolith, were previously not specified. Based on the gold assay results, which are persistent and collinear to the structural trend of NW–SE picked out by magnetic data, two (2) potential blocks (A and B) were identified. The trend of the structure in blocks A and B when overlaid with gold anomalies indicates that most of the gold concentrations are located in block B and the highest value of gold concentrations is located in block A where gold values range from 10.19 to 19.680 g/t in block A and 0.0623 to 4.419 g/t in block B. The difference in gold values between blocks A and B is due to the variation in the degree of alteration. The integration of the results indicates that the gold mineralisation in the Kibati area is structurally controlled and concentrated in shear zones. The findings therefore, indicate that the Mozambique Belt is potential for gold mineralisation and provide a warrant for future plan for gold exploration.

Fast Coding Unit Partitioning Algorithm for Video Coding Standard Based on Block Segmentation and Block Connection Structure and CNN

The recently introduced Video Coding Standard, VVC, presents a novel Quadtree plus Nested Multi-Type Tree (QTMTT) block structure. This structure enables a more flexible block partition and demonstrates enhanced compression performance compared to its predecessor, HEVC. However, The introduction of the new structure has led to a more complex partition search process, resulting in a considerable increase in time complexity. The QTMTT structure yields diverse Coding Unit (CU) block sizes, posing challenges for CNN model inference. In this study, we propose a representation structure termed Block Segmentation and Block Connection (BSC), rooted in texture features. This ensures that partial CU blocks are uniformly represented in size. To address different-sized CUs, various levels of CNN models are designed for prediction. Moreover, we introduce a post-processing method and a multi-thresholding scheme to further mitigate errors introduced by CNNs. This allows for flexible and adjustable acceleration, achieving a trade-off between coding time complexity and performance. Experimental results indicate that, in comparison to VTM-10.0, our “Fast” scheme reduces the average complexity by 57.14% with a 1.86% increase in BDBR. Meanwhile, the “Moderate” scheme reduces average complexity by 50.14% with only a 1.39% increase in BDBR.

Adaptive HEVC video steganograhpy based on PU partition modes

High EfficiencyVideoCoding (HEVC) −based steganography has gained attention as a prominent research focus. Especially, block structure based HEVC video steganography has received increasing attention due to commendable performance. However, current block structure- based steganography algorithms confront with challenges such as reduced coding efficiency and limited capacity. To avoid these problems, an adaptive video steganography algorithm based on Prediction Unit (PU) partition mode in I-frames is proposed. This is done through the analysis of the block division process and the visual distortion resulting from the modification of the PU partition mode in HEVC. The PU block structure is utilized as steganographic covers, and the Rate Distortion Optimization (RDO) technique is introduced to establish an adaptive distortion function for Syndrome-trellis code (STC). Further comparison is performed between the proposed method and the state-of-the-art steganography algorithms, confirming its advantages in embedding capacity, compression efficiency, visual quality, and resistance to video steganalysis.

The effect of annealing and multilayer structure on promoting the electrochemical performance of Al/Si thin film anodes

C/(Al/Si)n/TiO2 multilayer thin films with the controllable number of (Al/Si) layers (n = 1, 2, 3, 4) were prepared by magnetron sputtering. The effect of the inserted Al layers and annealing process on the electrochemical performance of the anodes have been discussed. Among the samples before annealing, C/(Al/Si)4/TiO2 thin film anode exhibits a better capacity retention rate after 500 cycles. The annealing process was performed to facilitate the diffusion of Al and Si layers in the film, improving the conductivity of the anode. The result is a decrease in the resistance and an increase in the Li+ diffusion rate of the anode. The annealing process also forms the Al-Si phase. During the cycling process, the Al-Si phase reacts with the electrolyte to form a Li-Al-Si ternary phase, which can improve the stability of the solid electrolyte interphase (SEI) layer. C/(Al/Si)4/TiO2 thin film anode annealed at 300 °C for 30 min (C/(Al/Si)4/TiO2-30 min) forms a stable block structure during cycling, which can alleviate volume expansion, enhance Li+ diffusion rate and exhibit adaptability to high current densities of the thin film anode. It is shown that C/(Al/Si)4/TiO2-30 min thin film anode obtains an initial discharge capacity of 2419 mA h g−1 and a capacity retention of 80.5 % after 500 cycles. In addition, this thin film anode exhibits superior rate performance, maintaining a capacity of 1453 mA h g−1 after 500 cycles at 5 A/g and a capacity above 1463 mAhg−1 even at 30 A/g.

A UAV-Based Single-Lens Stereoscopic Photography Method for Phenotyping the Architecture Traits of Orchard Trees

This article addresses the challenges of measuring the 3D architecture traits, such as height and volume, of fruit tree canopies, constituting information that is essential for assessing tree growth and informing orchard management. The traditional methods are time-consuming, prompting the need for efficient alternatives. Recent advancements in unmanned aerial vehicle (UAV) technology, particularly using Light Detection and Ranging (LiDAR) and RGB cameras, have emerged as promising solutions. LiDAR offers precise 3D data but is costly and computationally intensive. RGB and photogrammetry techniques like Structure from Motion and Multi-View Stereo (SfM-MVS) can be a cost-effective alternative to LiDAR, but the computational demands still exist. This paper introduces an innovative approach using UAV-based single-lens stereoscopic photography to overcome these limitations. This method utilizes color variations in canopies and a dual-image-input network to generate a detailed canopy height map (CHM). Additionally, a block structure similarity method is presented to enhance height estimation accuracy in single-lens UAV photography. As a result, the average rates of growth in canopy height (CH), canopy volume (CV), canopy width (CW), and canopy project area (CPA) were 3.296%, 9.067%, 2.772%, and 5.541%, respectively. The r2 values of CH, CV, CW, and CPA were 0.9039, 0.9081, 0.9228, and 0.9303, respectively. In addition, compared to the commonly used SFM-MVS approach, the proposed method reduces the time cost of canopy reconstruction by 95.2% and of the cost of images needed for canopy reconstruction by 88.2%. This approach allows growers and researchers to utilize UAV-based approaches in actual orchard environments without incurring high computation costs.

Alternating block linearized Bregman iterations for regularized nonnegative matrix factorization

In this paper, we propose an alternating block variant of the linearized Bregman iterations for a class of regularized nonnegative matrix factorization (NMF) problems. The proposed method exploits the block structure of NMF, utilizes the smooth adaptable property of the loss function based on the Bregman distance, and at the same time follows the iterative regularization idea of the linearized Bregman iterations method. Theoretically, we show that the proposed method is a descent method by adjusting the involved parameters. Finally, we end with several illustrative numerical experiments.

Adaptive fast multiplication of ℋ²-matrices

Hierarchical matrices approximate a given matrix by a decomposition into low-rank submatrices that can be handled efficiently in factorized form. H 2 \mathcal {H}^2 -matrices refine this representation following the ideas of fast multipole methods in order to achieve linear, i.e., optimal complexity for a variety of important algorithms. The matrix multiplication, a key component of many more advanced numerical algorithms, has been a challenge: the only linear-time algorithms known so far either require the very special structure of HSS-matrices or need to know a suitable basis for all submatrices in advance. In this article, a new and fairly general algorithm for multiplying H 2 \mathcal {H}^2 -matrices in linear complexity with adaptively constructed bases is presented. The algorithm consists of two phases: first an intermediate representation with a generalized block structure is constructed, then this representation is re-compressed in order to match the structure prescribed by the application. The complexity and accuracy are analyzed and numerical experiments indicate that the new algorithm can indeed be significantly faster than previous attempts.

Study on the Effect of Bifurcation Position on Spontaneous Ignition and Shock Wave Propagation Characteristics in High-pressure Hydrogen Leakage Tubes

Hydrogen safety issues constrain the development and diffusion of hydrogen energy technologies. The current research on tube types in high-pressure hydrogen storage and transportation links is insufficient. In this paper, the spontaneous combustion law and the propagation characteristics of the shock wave in the tube after accidental leakage of high-pressure hydrogen in a bifurcated tube with a blocking structure are investigated by experimental means. By changing the relative position of the bifurcation structure, it is found that moving the bifurcation position upstream can effectively reduce the intensity of the shock wave at the nozzle of the tube, the propagation velocity of the shock wave inside the tube and the critical ignition pressure. There are three ignition possibilities in the bifurcated tube with blocking structure, and quenching can be realized in the tube under lower pressure.

Regulation of Two-Dimensional Platelet Micelles with Tunable Core Composition Distribution via Coassembly Seeded Growth Approach.

Seeded growth termed "living" crystallization-driven self-assembly (CDSA) has been identified as a powerful method to create one- or two-dimensional nanoparticles. Epitaxial crystallization is usually regarded as the growth mechanism for the formation of uniform micelles. From this perspective, the unimer depositing rate is largely related to the crystallization temperature, which is a key factor to determine the crystallization rate and regulate the core composition distribution among nanoparticles. In the present work, the coassembly of two distinct crystallizable polymers is explored in detail in a one-pot seeded growth protocol. Results have shown that polylactone containing a larger number of methylene groups (-CH2-) in their repeating units such as poly(η-octalactone) (POL) has a faster crystallization rate compared to poly(ε-caprolactone) (PCL) with a smaller number of -CH2- at ambient temperature (25 °C), thus a block or blocky platelet structure with heterogeneous composition distribution is formed. In contrast, when the crystallization temperature decreases to 4 °C, the difference of crystallization rate between both cores become negligible. Consequently, a completely random component distribution within 2D platelets is observed. Moreover, we also reveal that the core component of seed micelles is also paramount for the coassembly seeded growth, and a unique structure of flower-like platelet micelle is created from the coassembly of PCL/POL using POL core-forming seeds. This study on the formation of platelet micelles by one-pot seeded growth using two crystallizable components offers a considerable scope for the design of 2D polymer nanomaterials with a controlled core component distribution.

Design and Application of a Credit Bank Based on Blockchain Technology

Credit banks are an important way to build a lifelong learning system and a learning society. At present, various types of credit banks in China generally have limitations such as low efficiency in learning achievement certification and conversion, difficulty in ensuring the quality of learning achievement certification, and vague identification of credit banks. Blockchain technology has the characteristics of openness, consensus, transparent transactions, anonymity, tamper resistance, and traceability, which can effectively solve the centralized governance problems faced by the current construction of credit banks. This article elaborates on the current development status and characteristics of credit banks at home and abroad, analyzes the feasibility of combining credit banks with blockchain, and designs a blockchain based credit bank system architecture and processing flow to address the challenges of inconsistent credit conversion standards, low conversion efficiency, and data security risks in traditional credit banks. It proposes using block structure design to achieve secure and tamper proof credit data, proposes a smart contract based credit recognition and conversion method to achieve decentralized governance of credit banks, and establishes a blockchain based credit bank certification, conversion, and other application design models, which can provide technical support for the large-scale application of credit banks in the future.

Enhanced heat transfer in vented square enclosures with block structures: Exploring iso-perimetric shapes and multigrid approach for mixed convection of nano-fluids

A Multigrid approach was employed to examine the fluid flow and heat transfer features of a nano-fluid undergoing mixed convection within a vented enclosure featuring a variety of iso-perimetric-shaped obstacles. Concerning the cavity, the inlet port is situated at the lower left corner, while the outlet port is located at the upper right corner. The study involved conducting simulations with a range of control parameters by employing the higher-order mixed finite element technique. To capture key physical processes like mass transfer, fluid flow, and heat transfer within the model, we employed a numerical technique called finite element discretization. Specifically, we used a stable combination of cubic and quadratic (P3 ∕P2) approximations on a hybrid grid to discretize the governing equations, ensuring accurate and reliable results. The study examines the influence of governing parameters within specified ranges, including nanoparticle volume fraction (0 % ≤ φ ≤ 10 %), the Richardson number (0.01 ≤ Ri ≤ 5), and obstacle positions (0.3 ≤ C ≤ 0.7). Adding more nanoparticles to a liquid makes it better at conducting heat, which helps the liquid transfer heat more efficiently. The findings indicate that, in all instances, isothermal obstacles lead to a more significant increase in the average Nusselt number compared to adiabatic obstacles.

Identification of calcium chelating peptides from peanut protein hydrolysate and absorption activity of peptide-calcium complex.

Peanut peptides have good chelating ability with metal ions. However, there are few studies on the chelation mechanism of peanut peptides with calcium and absorption properties of peptide-calcium complex. Peptides with high calcium chelating rate were isolated and purified from peanut protein hydrolysate (PPH), and the chelation rate of component F21 was higher (81.4 ± 0.8%). Six peptides were identified from component F21 by liquid chromatography-tandem mass spectrometry, and the frequency of acidic amino acids and arginine in the amino acid sequence was higher in all six peptides. Peanut peptide-calcium complex (PPH21-Ca) was prepared by selecting component F21 (PPH21). Ultraviolet analysis indicated that the chelate reaction occurred between peanut peptide and calcium ions. Fourier transform infrared analysis showed that the chelating sites were carboxyl and amino groups on the amino acid residues of peptides. Scanning electron microscopy revealed that the surface of peanut peptide had a smooth block structure, but the surface of the complex had a granular morphology. Caco-2 cell model tests revealed that the bioavailability of PPH21-Ca was 58.4 ± 0.5%, which was significantly higher than that of inorganic calcium at 37.0 ± 0.4%. Peanut peptides can chelate calcium ions by carboxyl and amino groups, and the peptide-calcium complex had higher bioavailability. This study provides a theoretical basis for the development of new calcium supplement products that are absorbed easily. © 2024 Society of Chemical Industry.

Access to Stereoblock Polyesters via Irreversible Chain-Transfer Ring-Opening Polymerization (ICT-ROP).

Precise control over polymer microstructure can enable the molecular tunability of material properties and represents a significant challenge in polymer chemistry. Stereoblock copolymers are some of the simplest stereosequenced polymers, yet the synthesis of stereoblock polyesters from prochiral or racemic monomers outside of "simple" isotactic stereoblocks remains limited. Herein, we report the development of irreversible chain-transfer ring-opening polymerization (ICT-ROP), which overcomes the fundamental limitations of single catalyst approaches by using transmetalation (e.g., alkoxide-chloride exchange) between two catalysts with distinct stereoselectivities as a means to embed temporally controlled multicatalysis in ROP. Our combined small-molecule model and catalytic polymerization studies lay out a clear molecular basis for ICT-ROP and are exploited to access the first examples of atactic-syndiotactic stereoblock (at-sb-st) polyesters, at-sb-st polyhydroxyalkanoates (PHAs). We achieve high levels of control over molecular weight, tacticity, monomer composition, and block structures in a temporally controlled manner and demonstrate that stereosequence control leads to polymer tensile properties that are independent of thermal properties.

Enhancing structural resilience by using 3D printed complex polymer reinforcement for high damage tolerant structures

Conventional cementitious structures demonstrate high compressive strength, yet they are inherently prone to brittleness. The development of materials or building blocks with high damage tolerance is essential for constructing robust buildings and structures, capable of withstanding various forms of damage. In this study, we introduce a novel approach that involves incorporating 3D printed complex schwarzites and zeolite based biodegradable polymer porous structures (soft phase) as a reinforcement medium within cement matrices (brittle phase). In the case of composite using primitive schwarzites and primitive gyroids, the specific resilience increases by 128.1% and 121.30%, respectively, compared to the control 3D printed structures. The most remarkable enhancement was observed in zeolites based structures, where the specific resilience was improved by 125.63% w.r.t the cement cube and an 505.33% compared to the control pristine 3D printed structure, respectively. This transformation effectively would mitigate the inherent brittleness of cement blocks, imparting a more ductile and damage-tolerant charecteristic to the composite material. These findings highlight the superior resilient structure and energy absorption capabilities of the composite blocks with different 3D printed polymer structures compared to pure cement cubes.