基于改进Marching Cubes算法的雷达气象数据三维重建

在气象领域中,多普勒天气雷达探测到的气象数据采用以雷达站点为原点的三维极坐标系进行存储,具有形状不规则、数据量大等特征。Marching Cubes(MC)算法是三维重建中的经典算法,但应用于气象领域时存在重建效率低下和不能直接处理气象数据的缺点。为了实现气象数据的三维重建,基于MC算法提出雷达数据归一化处理与状态标记判别算法NBV-MC。该算法根据雷达基数据文件的特点对其进行归一化预处理,使用雷达基数据构建拟梯形六面体体素,对每一个六面体体素进行状态标记,在遍历六面体体素时动态判别其是否需要处理。实验结果表明,NBV-MC算法不仅解决了由于气象数据具有不规则性而不能直接用于MC算法的问题,而且可以在保证数据真实性和重建效果的情况下有效减少绘制等值面所需要的三角面片数量,提高重建速度。与MC算法相比,NBV-MC算法的重建效率提升了77.70%以上,有利于实时场景交互,便于气象研究人员直接分析雷达数据。

CUBE自动滤波在远海多波束测深中的应用

为提升远海多波束测深数据标准化处理能力,验证CUBE自动滤波在远海海域的实际应用效果,选取远海海域3个典型深度测区,使用优选的CUBE自动处理参数组,对多波束测深数据进行自动滤波处理,并从处理用时、逐点标记以及交叉点水深差值3个方面,将处理结果与多名作业人员的手工处理结果进行对比分析。实验结果表明,使用CUBE自动处理与人工处理结果基本相同,且少量处理不同之处产生的水深成果差值均在测量误差允许范围之内,且CUBE自动处理在处理效率、成果标准一致性方面均优于人工处理。本文成果对于提升远海多波束测深数据标准化处理能力具有较强的实践指导意义。

Failure mechanisms and destruction characteristics of cemented coal gangue backfill under compression effect of non-uniform load

Backfill mining is one of the most important technical means for controlling strata movement and reducing surface subsidence and environmental damage during exploitation of underground coal resources. Ensuring the stability of the backfill bodies is the primary prerequisite for maintaining the safety of the backfilling working face, and the loading characteristics of backfill are closely related to the deformation and subsidence of the roof. Elastic thin plate model was used to explore the non-uniform subsidence law of the roof, and then the non-uniform distribution characteristics of backfill bodies’ load were revealed. Through a self-developed non-uniform loading device combined with acoustic emission (AE) and digital image correlation (DIC) monitoring technology, the synergistic dynamic evolution law of the bearing capacity, apparent crack, and internal fracture of cemented coal gangue backfills (CCGBs) under loads with different degrees of non-uniformity was deeply explored. The results showed that: 1) The uniaxial compressive strength (UCS) of CCGB increased and then decreased with an increase in the degree of non-uniformity of load (DNL). About 40% of DNL was the inflection point of DNL-UCS curve and when DNL exceeded 40%, the strength decreased in a cliff-like manner;2) A positive correlation was observed between the AE ringing count and UCS during the loading process of the specimen, which was manifested by a higher AE ringing count of the high-strength specimen. 3) Shear cracks gradually increased and failure mode of specimens gradually changed from “X” type dominated by tension cracks to inverted “Y” type dominated by shear cracks with an increase in DNL, and the crack opening displacement at the peak stress decreased and then increased. The crack opening displacement at 40% of the DNL was the smallest. This was consistent with the judgment of crack size based on the AE b-value, i. e., it showed the typical characteristics of “small b-value-large crack and large b-value-small crack”. The research results are of significance for preventing the instability and failure of backfill.

Study of the pressure transient behavior of directional wells considering the effect of non-uniform flux distribution

During the production,the fluid in the vicinity of the directional well enters the wellbore with different rates,leading to non-uniform flux distribution along the directional well.However,in all existing studies,it is oversimplified to a uniform flux distribution,which can result in inaccurate results for field applications.Therefore,this paper proposes a semi-analytical model of a directional well based on the assumption of non-uniform flux distribution.Specifically,the direction well is discretized into a carefully chosen series of linear sources,such that the complex well trajectory can be captured and the nonuniform flux distribution along the wellbore can be considered to model the three-dimensional flow behavior.By using the finite difference method,we can obtain the numerical solutions of the transient flow within the wellbore.With the aid of Green's function method,we can obtain the analytical solutions of the transient flow from the matrix to the wellbore.The complete flow behavior of a directional well is perfectly represented by coupling the above two types of transient flow.Subsequently,on the basis of the proposed model,we conduct a comprehensive analysis of the pressure transient behavior of a directional well.The computation results show that the flux variation along the direction well has a significant effect on pressure responses.In addition,the directional well in an infinite reservoir may exhibit the following flow regimes:wellbore afterflow,transition flow,inclined radial flow,elliptical flow,horizontal linear flow,and horizontal radial flow.The horizontal linear flow can be observed only if the formation thickness is much smaller than the well length.Furthermore,a dip region that appears on the pressure derivative curve indicates the three-dimensional flow behavior near the wellbore.

The Mechanism of Cube Texture Formation in Ni-7 at%W Substrate

In order to obtain the sharp cube texture,a new process,the intermediate annealing rolling technique,has been introduced to prepare the Ni7W substrate.In this paper,a cubic texture content up to 98.5%within 10°of the standard cubic orientation is obtained in the final substrate and the influence of this improved rolling technique on the cube texture formation has been discussed.The results show that the increased cube texture in the Ni7W substrate is caused by the optimized deformation texture and the increased nucleated fraction of the cube grains.

An Improved Framework of Massive Superpoly Recovery in Cube Attacks Against NFSR-Based Stream Ciphers

A critical problem in the cube attack is how to recover superpolies efficiently.As the targeting number of rounds of an iterative stream cipher increases,the scale of its superpolies becomes larger and larger.Recently,to recover massive superpolies,the nested monomial prediction technique,the algorithm based on the divide-and-conquer strategy,and stretching cube attacks were proposed,which have been used to recover a superpoly with over ten million monomials for the NFSR-based stream ciphers such as Trivium and Grain-128AEAD.Nevertheless,when these methods are used to recover superpolies,many invalid calculations are performed,which makes recovering superpolies more difficult.This study finds an interesting observation that can be used to improve the above methods.Based on the observation,a new method is proposed to avoid a part of invalid calculations during the process of recovering superpolies.Then,the new method is applied to the nested monomial prediction technique and an improved superpoly recovery framework is presented.To verify the effectiveness of the proposed scheme,the improved framework is applied to 844-and 846-round Trivium and the exact ANFs of the superpolies is obtained with over one hundred million monomials,showing the improved superpoly recovery technique is powerful.Besides,extensive experiments on other scaled-down variants of NFSR-based stream ciphers show that the proposed scheme indeed could be more efficient on the superpoly recovery against NFSR-based stream ciphers.

Effect of non-uniform swelling on coal multiphysics during gas injection: The triangle approach

In current dual porosity/permeability models,there exists a fundamental assumption that the adsorption-induced swelling is distributed uniformly within the representative elementary volume (REV),irrespective of its internal structures and transient processes.However,both internal structures and transient processes can lead to the non-uniform swelling.In this study,we hypothesize that the non-uniform swelling is responsible for why coal permeability in experimental measurements is not only controlled by the effective stress but also is affected by the adsorption-induced swelling.We propose a concept of the swelling triangle composed of swelling paths to characterize the evolution of the non-uniform swelling and serve as a core link in coupled multiphysics.A swelling path is determined by a dimensionless volumetric ratio and a dimensionless swelling ratio.Different swelling paths have the same start and end point,and each swelling path represents a unique swelling case.The swelling path as the diagonal of the triangle represents the case of the uniform swelling while that as the two perpendicular boundaries represents the case of the localized swelling.The paths of all intermediate cases populate inside the triangle.The corresponding relations between the swelling path and the response of coal multiphysics are established by a non-uniform swelling coefficient.We define this method as the triangle approach and corresponding models as swelling path-based ones.The proposed concept and models are verified against a long-term experimental measurement of permeability and strains under constant effective stress.Our results demonstrate that during gas injection,coal multiphysics responses have a close dependence on the swelling path,and that in both future experiments and field predictions,this dependence must be considered.

Quasi-static and dynamic compressive behaviour of additively manufactured Menger fractal cube structures

This paper presents the first-ever investigation of Menger fractal cubes'quasi-static compression and impact behaviour.Menger cubes with different void ratios were 3D printed using polylactic acid(PLA)with dimensions of 40 mm×40 mm×40 mm.Three different orders of Menger cubes with different void ratios were considered,namely M1 with a void ratio of 0.26,M2 with a void ratio of 0.45,and M3with a void ratio of 0.60.Quasi-static Compression tests were conducted using a universal testing machine,while the drop hammer was used to observe the behaviour under impact loading.The fracture mechanism,energy efficiency and force-time histories were studied.With the structured nature of the void formation and predictability of the failure modes,the Menger geometry showed some promise compared to other alternatives,such as foams and honeycombs.With the increasing void ratio,the Menger geometries show force-displacement behaviour similar to hyper-elastic materials such as rubber and polymers.The third-order Menger cubes showed the highest energy absorption efficiency compared to the other two geometries in this study.The findings of the present work reveal the possibility of using additively manufactured Menger geometries as an energy-efficient system capable of reducing the transmitting force in applications such as crash barriers.

Pressure transient characteristics of non-uniform conductivity fractured wells in viscoelasticity polymer flooding based on oil-water two-phase flow

Polymer flooding in fractured wells has been extensively applied in oilfields to enhance oil recovery.In contrast to water,polymer solution exhibits non-Newtonian and nonlinear behavior such as effects of shear thinning and shear thickening,polymer convection,diffusion,adsorption retention,inaccessible pore volume and reduced effective permeability.Meanwhile,the flux density and fracture conductivity along the hydraulic fracture are generally non-uniform due to the effects of pressure distribution,formation damage,and proppant breakage.In this paper,we present an oil-water two-phase flow model that captures these complex non-Newtonian and nonlinear behavior,and non-uniform fracture characteristics in fractured polymer flooding.The hydraulic fracture is firstly divided into two parts:high-conductivity fracture near the wellbore and low-conductivity fracture in the far-wellbore section.A hybrid grid system,including perpendicular bisection(PEBI)and Cartesian grid,is applied to discrete the partial differential flow equations,and the local grid refinement method is applied in the near-wellbore region to accurately calculate the pressure distribution and shear rate of polymer solution.The combination of polymer behavior characterizations and numerical flow simulations are applied,resulting in the calculation for the distribution of water saturation,polymer concentration and reservoir pressure.Compared with the polymer flooding well with uniform fracture conductivity,this non-uniform fracture conductivity model exhibits the larger pressure difference,and the shorter bilinear flow period due to the decrease of fracture flow ability in the far-wellbore section.The field case of the fall-off test demonstrates that the proposed method characterizes fracture characteristics more accurately,and yields fracture half-lengths that better match engineering reality,enabling a quantitative segmented characterization of the near-wellbore section with high fracture conductivity and the far-wellbore section with low fracture conductivity.The novelty of this paper is the analysis of pressure performances caused by the fracture dynamics and polymer rheology,as well as an analysis method that derives formation and fracture parameters based on the pressure and its derivative curves.

An improved non-uniform fast Fourier transform method for radio imaging of coronal mass ejections

Radioheliographs can obtain solar images at high temporal and spatial resolution,with a high dynamic range.These are among the most important instruments for studying solar radio bursts,understanding solar eruption events,and conducting space weather forecasting.This study aims to explore the effective use of radioheliographs for solar observations,specifically for imaging coronal mass ejections(CME),to track their evolution and provide space weather warnings.We have developed an imaging simulation program based on the principle of aperture synthesis imaging,covering the entire data processing flow from antenna configuration to dirty map generation.For grid processing,we propose an improved non-uniform fast Fourier transform(NUFFT)method to provide superior image quality.Using simulated imaging of radio coronal mass ejections,we provide practical recommendations for the performance of radioheliographs.This study provides important support for the validation and calibration of radioheliograph data processing,and is expected to profoundly enhance our understanding of solar activities.

基于X-CUBE-AI的神经网络手语识别系统设计

手语交流是聋哑人与他人交流的主要方法,设计了一款基于STM32的神经网络手语识别系统,采用TensorFlow和Keras机器学习框架训练网络模型,由于训练数据的局限性,加入L2正则化以解决训练过拟合问题。使用意法半导体推出的STM32Cube.AI工具包在STM32嵌入式平台上部署神经网络,搭载OV2640摄像头采集图像并进行缩放处理,将图像数据传入网络进行推理可获得识别结果。经测试,网络模型获得了较好的鲁棒性和适应性,在STM32上运行平均每帧推理时间为15.8 ms,平均准确率达92.3%。使用STM32作为手语识别终端,极大地提高了设备的便携性,节约成本,反应迅速。为聋哑人与正常人交流提供了一种新的解决方案,具有较高的实际应用价值。

MRI 3D CUBE T_(2)序列检查在踝关节外伤患者韧带损伤诊断中的价值

目的:研究MRI 3D CUBE T_(2)序列检查在踝关节外伤患者韧带损伤诊断中的价值。方法:选择2020年4月—2023年4月于白银市第一人民医院就诊的226例踝关节外伤拟行手术术前患者作为研究对象,按照不同检查方式将患者分为观察组(n=126)与对照组(n=100)。观察组采用MRI 3D CUBE T_(2)序列检查,对照组采取常规MRI检查。比较两组患侧、健侧距腓前韧带测量结果、诊断效能。结果:两组患侧、健侧距腓前韧带宽度及厚度比较,差异无统计学意义(P>0.05)。观察组Ⅰ级踝关节外伤患者韧带损伤诊断准确度、敏感度、特异度、阳性预测值、阴性预测值高于对照组,Ⅱ级患者准确度、敏感度、阴性预测值高于对照组,Ⅲ级患者准确度、特异度、阳性预测值高于对照组,差异有统计学意义(P<0.05)。结论:MRI 3D CUBE T_(2)序列检查踝关节外伤患者韧带损伤诊断效能高于常规MRI检查,可作为治疗效果评价及康复治疗的重要依据。

Efficient electrocatalytic conversion of N_(2) to NH_(3) using oxygen-rich vacancy lithium niobate cubes

Instead of the energy-intensive Haber-Bosch process,the researchers proposed a way to produce ammonia using water and nitrogen as feedstock,powered by electricity,without polluting the environment.Nevertheless,how to design efficient electrocatalyst for electrocatalytic nitrogen reduction reaction(NRR)is still urgent and challenging.Herein,a strategy is proposed to adjust the morphology and surface electronic structure of electrocatalyst by optimizing material synthesis method.LiNbO3(lithium niobate,LN)cubes with oxygen-rich vacancy and regular morphology were synthesized by hydrothermal synthesis and followed molten salt calcination process,which were used for electrocatalytic NRR under mild conditions.Compared with LN nanoparticles synthesized by solid phase reaction,LN cubes exhibit better NRR performance,with the highest ammonia yield rate(13.74μg.h^(-1).mg^(-1))at the best potential of-0.45V(vs.reversible hydrogen electrode,RHE)and the best Faradaic efficiency(85.43%)at-0.4 V.Moreover,LN cubes electrocatalyst also demonstrates high stability in 7 cycles and 18 h current-time tests.Further investigation of the reaction mechanism confirmed that the structure of oxygen vacancy could adjust the electronic structure of the electrocatalyst,which was conducive to the adsorption and activation of N_(2) molecule and also increased the ECSA of electrocatalyst,thus providing more active sites for the NRR process.

基于SPH的新型人工块体TB-CUBE设计优化和水动力特性数值模拟

为探究高透空性新型人工块体TB-CUBE的最优结构尺寸型式及其水动力特性,利用基于光滑粒子方法(smoothed particle hydrodynamics,SPH)的DualSPHysics开源代码开展斜坡堤新型人工块体TB-CUBE数值模拟研究,探究其在规则波作用下的爬高和越浪等水动力特性及波浪变化规律。结果表明:数学模型模拟的爬高和越浪与物理模型试验的实测值误差分别在6%和9%以内,可较好地刻画波浪在人工块体上的演变过程。基于此验证模型,分析不同细部尺寸参数下块体的水动力特性,综合块体爬高、反射系数、越浪、块体孔隙率和材料用量等因素,得到最优消浪效果所对应TB-CUBE块体的球相对半径R1、圆柱相对半径R2与块体边长h的关系。在此基础上,以优化后的TB-CUBE块体为对象,分析其爬高和越浪的过程,揭示出该块体的消浪机理主要为相邻块体之间的圆孔对波浪的爬高和回落均有阻滞作用,且块体内部孔隙可以容纳水体并形成紊流效能,可以相应地减少波浪的爬高。此外,研究斜坡坡度、堤前水深、入射波高和波周期等对波浪爬高的影响,得到TB-CUBE块体爬高随入射波高和波坦的增大而增大,而随坡度的变化呈现单峰曲线的变化趋势。进一步考虑不同波浪破碎形态对波浪爬高的影响,拟合得出TB-CUBE块体的爬高经验公式,公式拟合值与模型计算值相关系数达0.981,能够真实反映该块体的爬高情况,为今后该块体在海岸工程中的实践运用提供科学依据。

JOHN-NIRENBERG-Q SPACES VIA CONGRUENT CUBES

To shed some light on the John-Nirenberg space,the authors of this article introduce the John-Nirenberg-Q space via congruent cubes,JNQp,qα(Rn),which,when p=∞and q=2,coincides with the space Qα(Rn)introduced by Essen,Janson,Peng and Xiao in[Indiana Univ Math J,2000,49(2):575-615].Moreover,the authors show that,for some particular indices,JNQp,qα(Rn)coincides with the congruent John-Nirenberg space,or that the(fractional)Sobolev space is continuously embedded into JNQp,qα(Rn).Furthermore,the authors characterize JNQp,qα(Rn)via mean oscillations,and then use this characterization to study the dyadic counterparts.Also,the authors obtain some properties of composition operators on such spaces.The main novelties of this article are twofold:establishing a general equivalence principle for a kind of’almost increasing’set function that is here introduced,and using the fine geometrical properties of dyadic cubes to properly classify any collection of cubes with pairwise disjoint interiors and equal edge length.

Hierarchical Datacubes

Many approaches have been proposed to pre-compute data cubes in order to efficiently respond to OLAP queries in data warehouses. However, few have proposed solutions integrating all of the possible outcomes, and it is this idea that leads the integration of hierarchical dimensions into these responses. To meet this need, we propose, in this paper, a complete redefinition of the framework and the formal definition of traditional database analysis through the prism of hierarchical dimensions. After characterizing the hierarchical data cube lattice, we introduce the hierarchical data cube and its most concise reduced representation, the closed hierarchical data cube. It offers compact replication so as to optimize storage space by removing redundancies of strongly correlated data. Such data are typical of data warehouses, and in particular in video games, our field of study and experimentation, where hierarchical dimension attributes are widely represented.

Robust and Reusable Fuzzy Extractors from Non-Uniform Learning with Errors Problem

Afuzzy extractor can extract an almost uniformrandom string from a noisy source with enough entropy such as biometric data.To reproduce an identical key from repeated readings of biometric data,the fuzzy extractor generates a helper data and a random string from biometric data and uses the helper data to reproduce the random string from the second reading.In 2013,Fuller et al.proposed a computational fuzzy extractor based on the learning with errors problem.Their construction,however,can tolerate a sub-linear fraction of errors and has an inefficient decoding algorithm,which causes the reproducing time to increase significantly.In 2016,Canetti et al.proposed a fuzzy extractor with inputs from low-entropy distributions based on a strong primitive,which is called digital locker.However,their construction necessitates an excessive amount of storage space for the helper data,which is stored in authentication server.Based on these observations,we propose a new efficient computational fuzzy extractorwith small size of helper data.Our scheme supports reusability and robustness,which are security notions that must be satisfied in order to use a fuzzy extractor as a secure authentication method in real life.Also,it conceals no information about the biometric data and thanks to the new decoding algorithm can tolerate linear errors.Based on the non-uniform learning with errors problem,we present a formal security proof for the proposed fuzzy extractor.Furthermore,we analyze the performance of our fuzzy extractor scheme and provide parameter sets that meet the security requirements.As a result of our implementation and analysis,we show that our scheme outperforms previous fuzzy extractor schemes in terms of the efficiency of the generation and reproduction algorithms,as well as the size of helper data.

Radial Basis Approximations Based BEMD for Enhancement of Non-Uniform Illumination Images

An image can be degraded due to many environmental factors like foggy or hazy weather,low light conditions,extra light conditions etc.Image captured under the poor light conditions is generally known as non-uniform illumination image.Non-uniform illumination hides some important information present in an image during the image capture Also,it degrades the visual quality of image which generates the need for enhancement of such images.Various techniques have been present in literature for the enhancement of such type of images.In this paper,a novel architecture has been proposed for enhancement of poor illumination images which uses radial basis approximations based BEMD(Bi-dimensional Empirical Mode Decomposition).The enhancement algorithm is applied on intensity and saturation components of image.Firstly,intensity component has been decomposed into various bi-dimensional intrinsic mode function and residue by using sifting algorithm.Secondly,some linear transformations techniques have been applied on various bidimensional intrinsic modes obtained and residue and further on joining the transformed modes with residue,enhanced intensity component is obtained.Saturation part of an image is then enhanced in accordance to the enhanced intensity component.Final enhanced image can be obtained by joining the hue,enhanced intensity and enhanced saturation parts of the given image.The proposed algorithm will not only give the visual pleasant image but maintains the naturalness of image also.

Image Non-Uniformity Correction in 3T Gd-EOB-DTPA-Enhanced Magnetic Resonance Imaging: Comparison among Different Software Versions

Background: Non-uniformity in signal intensity occurs commonly in magnetic resonance (MR) imaging, which may pose substantial problems when using a 3T scanner. Therefore, image non-uniformity correction is usually applied. Purpose: To compare the correction effects of the phased-array uniformity enhancement (PURE), a calibration-based image non-uniformity correction method, among three different software versions in 3T Gd-EOB-DTPA-enhanced MR imaging. Material and Methods: Hepatobiliary-phase images of a total of 120 patients who underwent Gd-EOB-DTPA-enhanced MR imaging on the same 3T scanner were analyzed retrospectively. Forty patients each were examined using three software versions (DV25, DV25.1, and DV26). The effects of PURE were compared by visual assessment, histogram analysis of liver signal intensity, evaluation of the spatial distribution of correction effects, and evaluation of quantitative indices of liver parenchymal enhancement. Results: The visual assessment indicated the highest uniformity of PURE-corrected images for DV26, followed by DV25 and DV25.1. Histogram analysis of corrected images demonstrated significantly larger variations in liver signal for DV25.1 than for the other two versions. Although PURE caused a relative increase in pixel values for central and lateral regions, such effects were weaker for DV25.1 than for the other two versions. In the evaluation of quantitative indices of liver parenchymal enhancement, the liver-to-muscle ratio (LMR) was significantly higher for the corrected images than for the uncorrected images, but the liver-to-spleen ratio (LSR) showed no significant differences. For corrected images, the LMR was significantly higher for DV25 and DV26 than for DV25.1, but the LSR showed no significant differences among the three versions. Conclusion: There were differences in the effects of PURE among the three software versions in 3T Gd-EOB-DTPA-enhanced MR imaging. Even if the non-uniformity correction method has the same brand name, correction effects may differ depending on the software version, and these differences may affect visual and quantitative evaluations.

神奇的立方宝贝--CUBE BABY AC

这次我为大家推荐的是来自笙科智能公司的CUBE BABY AC,相比国际上的大品牌,例如雅马哈、罗兰、Korg,国内这家珠海的科技公司确实是名不见经传。毕竟市场的份额就这么多,想做出有创新的产品,就必须投入大量的研发精力。而这家公司的运营方式很奇特,只做中低端市场,以最便宜的价格拿到更有“性价比”的产品。那在乐器行业中什么是“性价比”呢?是售价低廉还是音质越级,是做工出色还是极致创新?在搜索引擎上。