Alternating Direction Finite Volume Element Methods for Three-Dimensional Parabolic Equations

This paper presents alternating direction finite volume element methods for three-dimensional parabolic partial differential equations and gives four computational schemes, one is analogous to Douglas finite difference scheme with second-order splitting error, the other two schemes have third-order splitting error, and the last one is an extended LOD scheme. The L2 norm and H1 semi-norm error estimates are obtained for the first scheme and second one, respectively. Finally, two numerical examples are provided to illustrate the efficiency and accuracy of the methods.

Science Letters:Dynamic concision for three-dimensional reconstruction of human organ built with virtual reality modelling language (VRML)

This research studies the process of 3D reconstruction and dynamic concision based on 2D medical digital images using virtual reality modelling language (VRML) and JavaScript language, with a focus on how to realize the dynamic concision of 3D medical model with script node and sensor node in VRML. The 3D reconstruction and concision of body internal organs can be built with such high quality that they are better than those obtained from the traditional methods. With the function of dynamic concision, the VRML browser can offer better windows for man-computer interaction in real-time environment than ever before. 3D reconstruction and dynamic concision with VRML can be used to meet the requirement for the medical observation of 3D reconstruction and have a promising prospect in the fields of medical imaging.

Obstacle avoidance method of three-dimensional obstacle spherical cap

Focusing on obstacle avoidance in three-dimensional space for unmanned aerial vehicle(UAV), the direct obstacle avoidance method in dynamic space based on three-dimensional velocity obstacle spherical cap is proposed, which quantifies the influence of threatening obstacles through velocity obstacle spherical cap parameters. In addition, the obstacle avoidance schemes of any point on the critical curve during the multi-obstacles avoidance are given. Through prediction, the insertion point for the obstacle avoidance can be obtained and the flight path can be replanned. Taking the Pythagorean Hodograph(PH) curve trajectory re-planning as an example, the three-dimensional direct obstacle avoidance method in dynamic space is tested. Simulation results show that the proposed method can realize the online obstacle avoidance trajectory re-planning, which increases the flexibility of obstacle avoidance greatly.

Wide color gamut switchable autostereoscopic 3D display based on directional quantum-dot backlight

A switchable autostereoscopic 3-dimensional(3D) display device with wide color gamut is introduced in this paper. In conjunction with a novel directional quantum-dot(QD) backlight, the precise scanning control strategy, and the eye-tracking system, this spatial-sequential solution enables our autostereoscopic display to combine all the advantages of full resolution,wide color gamut, low crosstalk, and switchable 2D/3D. And also, we fabricated an autostereoscopic display prototype and demonstrated its performances effectively. The results indicate that our system can both break the limitation of viewing position and provide high-quality 3D images. We present two working modes in this system. In the spatial-sequential mode,the crosstalk is about 6%. In the time-multiplexed mode, the viewer should wear auxiliary and the crosstalk is about 1%,just next to that of a commercial 3D display(BENQ XL2707-B and View Sonic VX2268 WM). Additionally, our system is also completely compatible with active shutter glasses and its 3D resolution is same as its 2D resolution. Because of the excellent properties of the QD material, the color gamut can be widely extended to 77.98% according to the ITU-R recommendation BT.2020(Rec.2020).

Experimental Study on the Wavelengths of Two-Dimensional and Three-Dimensional Freak Waves

Freak waves are commonly characterized by strong-nonlinearity, and the wave steepness, which is calculated from the wavelength, is a measure of the degree of the wave nonlinearity. Moreover, the wavelength can describe the locally spatial characteristics of freak waves. Generally, the wavelengths of freak waves are estimated from the dispersion relations of Stokes waves. This paper concerns whether this approach enables a consistent estimate of the wavelength of freak waves. The two-(unidirectional, long-crested) and three-dimensional(multidirectional, shortcrested) freak waves are simulated experimentally through the dispersive and directional focusing of component waves, and the wavelengths obtained from the surface elevations measured by the wave gauge array are compared with the results from the linear, 3rd-order and 5th-order Stokes wave theories. The comparison results suggest that the 3rd-order theory estimates the wavelengths of freak waves with higher accuracy than the linear and 5th-order theories. Furthermore, the results allow insights into the dominant factors. It is particularly noteworthy that the accuracy is likely to depend on the wave period, and that the wavelengths of longer period freak waves are overestimated but the wavelengths are underestimated for shorter period ones. In order to decrease the deviation, a modified formulation is presented to predict the wavelengths of two-and three-dimensional freak waves more accurately than the 3rd-order dispersion relation, by regression analysis. The normalized differences between the predicted and experimental results are over 50% smaller for the modified model suggested in this study compared with the 3rd-order dispersion relation.

Methods for Setting up a Three-Dimensional Industrial Surveying System of “Building Blocks Type”

This paper is to advance some relevant techniques to set up a three-dimensional industrial surveying system of “building blocks type”, making use of the electronic theodolite, standard ruler and portable computer.

Situation Prior to the Trade Mark Directive

introduce the situation prior to the trade mark directive.

3D Echocardiogram Reconstruction Employing a Flip Directional Texture Pyramid

Three dimensional(3D)echocardiogram enables cardiologists to visua-lize suspicious cardiac structures in detail.In recent years,this three-dimensional echocardiogram carries important clinical value in virtual surgical simulation.However,this 3D echocardiogram involves a trade-off difficulty between accu-racy and efficient computation in clinical diagnosis.This paper presents a novel Flip Directional 3D Volume Reconstruction(FD-3DVR)method for the recon-struction of echocardiogram images.The proposed method consists of two main steps:multiplanar volumetric imaging and 3D volume reconstruction.In the crea-tion of multiplanar volumetric imaging,two-dimensional(2D)image pixels are mapped into voxels of the volumetric grid.As the obtained slices are discontin-uous,there are some missing voxels in the volume data.To restore the structural and textural information of 3D ultrasound volume,the proposed method creates a volume pyramid in parallel with theflip directional texture pyramid.Initially,the nearest neighbors of missing voxels in the multiplanar volumetric imaging are identified by 3D ANN(Approximate Nearest Neighbor)patch matching method.Furthermore,aflip directional texture pyramid is proposed and aggregated with distance in patch matching tofind out the most similar neighbors.In the recon-struction step,structural and textural information obtained from differentflip angle directions can reconstruct 3D volume well with the desired accuracy.Com-pared with existing 3D reconstruction methods,the proposed Flip Directional 3D Volume Reconstruction(FD-3DVR)method provides superior performance for the mean peak signal-to-noise ratio(40.538 for the proposed method I and 39.626 for the proposed method II).Experimental results performed on the cardi-ac datasets demonstrate the efficiency of the proposed method for the reconstruc-tion of echocardiogram images.

OpenMP-Based PCG Solver for Three-Dimensional Heat Equation

As one of the most important mathematics-physics equations, heat equation has been widely used in engineering area and computing science research. Large-scale heat problems are difficult to solve due to computational intractability. The parallelization of heat equation is available to improve the simulation model efficiency. In order to solve the three-dimensional heat problems more rapidly, the OpenMP was adopted to parallelize the preconditioned conjugate gradient （PCG） algorithm in this paper. A numerical experiment on the three-dimensional heat equation model was carried out on a computer with four cores. Based on the test results, it is found that the execution time of the original serial PCG program is about 1.71 to 2.81 times of the parallel PCG program executed with different number of threads. The experiment results also demonstrate the available performance of the parallel PCG algorithm based on OpenMP in terms of solution quality and computational performance.

Direct loading of atoms from a macroscopic quadrupole magnetic trap into a microchip trap

We demonstrate the direct loading of cold atoms into a microchip 2-mm Z-trap, where the evaporative cooling can be performed efficiently, from a macroscopic quadrupole magnetic trap with a high loading efficiency. The macroscopic quadrupole magnetic trap potential is designed to be moveable by controlling the currents of the two pairs of anti-Helrnholtz coils. The cold atoms are initially prepared in a standard six-beam magneto-optical trap and loaded into the macroscopic quadrupole magnetic trap, and then transported to the atom chip surface by moving the macroscopic trap potential. By means of a three-dimensional absorption imaging system, we are able to optimize the position alignment of the atom cloud in the macroscopic trap and the microchip Z-shaped wire. Consequently, with a proper magnetic transfer scheme, we load the cold atoms into the microchip Z-trap directly and efficiently. The loading efficiency is measured to be about 50%. This approach can be used to generate appropriate ultracold atoms sources, for example, for a magnetically guided atom interferometer based on atom chip.

A novel method for geometric quality assurance of rock joint replicas in direct shear testing-Part 2:Validation and mechanical replicability

Each rock joint is unique by nature which means that utilization of replicas in direct shear tests is required in experimental parameter studies.However,a method to acquire knowledge about the ability of the replicas to imitate the shear mechanical behavior of the rock joint and their dispersion in direct shear testing is lacking.In this study,a novel method is presented for geometric quality assurance of replicas.The aim is to facilitate generation of high-quality direct shear testing data as a prerequisite for reliable subsequent analyses of the results.In Part 1 of this study,two quality assurance parameters,smf and V_(Hp100),are derived and their usefulness for evaluation of geometric deviations,i.e.geometric reproducibility,is shown.In Part 2,the parameters are validated by showing a correlation between the parameters and the shear mechanical behavior,which qualifies the parameters for usage in the quality assurance method.Unique results from direct shear tests presenting comparisons between replicas and the rock joint show that replicas fulfilling proposed threshold values of σ_(mf)<0.06 mm and
|V_(Hp100)|
<0.2 mm have a narrow dispersion and imitate the shear mechanical behavior of the rock joint in all aspects apart from having a slightly lower peak shear strength.The wear in these replicas,which have similar morphology as the rock joint,is in the same areas as in the rock joint.The wear is slightly larger in the rock joint and therefore the discrepancy in peak shear strength derives from differences in material properties,possibly from differences in toughness.It is shown by application of the suggested method that the quality assured replicas manufactured following the process employed in this study phenomenologically capture the shear strength characteristics,which makes them useful in parameter studies.

砂土-混凝土接触面剪切带细观变形特征的试验研究

接触面剪切带的细观变形特征是研究结构物与土体相互作用的核心问题。为探明砂土-混凝土接触面剪切带变形特征,利用大型直剪仪开展砂土-混凝土接触面直剪试验,采用灌砂变形标记法实测砂土变形,依据标记线剪应变沿竖向的变化特征对砂土变形区域进行划分。在此基础上,研究粗糙度、法向应力和密实度对砂土-混凝土接触面剪切带细观变形特征的影响规律。研究结果表明:1)砂土可分为非剪切区、过渡区和应变集中区,应变集中区仅存在剪切面之上。2)规则型接触面的上剪切带厚度均值为33D_(50),远大于下剪切带9D_(50)和“光滑”接触面剪切带厚度20.4D_(50)。3)密实度对剪切带及其过渡区厚度的影响微弱,而粗糙度对其影响显著;法向应力、密实度对应变集中区厚度影响有限,应变集中区厚度随粗糙度的增大近似线性增大;应变集中区长度随粗糙度的增大先增大后减小,随密实度的增大近似线性增大,随法向应力增大而减小。4)随剪切位移增大,上剪切带厚度不断增大而下剪切带厚度先增大后保持基本不变,应变集中区的长度增大,但剪切位移对应变集中区厚度的影响有限。5)获得归一化剪切带厚度取值h_(t)/D_(50)与D_(50)的关系,在有限元模拟规则型结构与砂土的相互作用时,建议砂土体细化网格单元的范围不小于最大剪切带厚度37D_(50)。研究成果深化了砂土-规则型接触面剪切带变形特征的认识,可为大粗糙度、带肋桩的承载变形特性的精细化有限元模拟分析提供重要参考和依据。

Radiological Concentration Distribution of ¹³¹I, ¹³²I, ¹³³I, ¹³⁴I, and ¹³⁵I Due to a Hypothetical Accident of TRIGA Mark-II Research Reactor

The present work gives a methodology for assessing radiological concentration of 131I, 132I, 133I, 134I, and 135I due to a hypothetical accident of TRIGA Mark-II research Reactor at AERE, Savar, Bangladesh. The concentrations were estimated through different pathways like ingestion of vegetation, milk, and meat from air and ground deposition. The maximum air concentrations for all 16 directions were found at 110 m distance from the core of the reactor and it was found to be highest in the southern (S) direction. The maximum ground concentration occurred immediately just after the accident in different directions. In all pathways, the most concentration was found to be in S-direction. The concentrations in vegetation of 131I, 133I, 135I were significant, while no concentrations of 132I and 134I were observed. The concentration in vegetation for 131I was found to be highest than all other isotopes of iodine. The concentrations of 133I were found to be higher and concentrations of 134I were observed to be lower in both milk and meat compared to other radio isotopes of iodine. In the case of a radiological accident, the results of the present study will be a valuable guide for adopting radiological safety measures for radiation protection against the ingestion of vegetables, milk and meat from around the research reactor at AERE, Savar, Bangladesh.

家蚕素斑品种菁松的茶斑限性定向转育

为在家蚕现行素斑品种菁松的幼虫发育早期进行雌雄性别鉴别,实现雌雄分养分缫差异化利用目的,用普斑限性品系云蚕7A的雌与茶斑品系Cb的雄杂交后,再分别与现行素斑品系菁松A、菁松B杂交,其后代连续数次回交素斑亲本后自交,结合分类选择进行个体和蛾区选择淘汰,将云蚕7A的普斑限性基因和Cb的茶斑基因转入现行素斑品种菁松中,定向转育得到菁A茶限和菁B茶限。结果表明:转育过程中,幼虫斑纹分化成颜色与形状易于分辨的茶斑与非茶斑2种类型,转育得到的菁A茶限和菁B茶限幼虫在3龄初期就会呈现茶斑颜色深浅明显不同的分化,能准确分辨雌雄,其虫蛹率分别为96.91%和96.40%,全茧量分别为1.62 g和1.56 g,茧层率分别为23.78%和23.26%,经济性状与其轮回亲本的差异较小,表现出健康好养、茧质优良等特性。研究结果可为创建特殊性状的育种材料、差异化利用雌雄蚕,以及降低雄蚕种繁育成本奠定基础。

电化学发光法和直接化学发光法测定12项肿瘤标志物指标的相关性和一致性评价

目的:评估电化学发光法和直接化学发光法测定12项肿瘤标志物的相关性和一致性。方法:选取2023年3-8月首都医科大学附属北京天坛医院体检血清标本2426例,在12项肿瘤标志物中甲胎蛋白(AFP)446例、癌胚抗原(CEA)284例、糖类抗原72-4(CA72-4)289例、糖类抗原19-9(CA19-9)87例、糖类抗原125(CA125)205例、糖类抗原15-3(CA15-3)216例、总前列腺特异性抗原(TPSA)292例、游离前列腺特异性抗原(FPSA)292例、细胞角蛋白19片段(Cyfra21-1)84例、神经元特异性烯醇化酶(NSE)84例、鳞状细胞癌相关抗原(SCC)84例、胃泌素释放肽前体(PROGrp)63例。分别采用电化学发光法和直接化学发光法对12项肿瘤标志物指标进行检测,分析两种检测方法的相关性与及一致性。结果:Pearson和Spearman相关性分析显示,电化学发光和直接化学发光法检测肿瘤标志物的AFP、CEA、CA72-4、CA19-9、CA125、CA15-3、TPSA、FPSA、Cyfra21-1、NSE、SCC和PROGrp12项指标均具有显著正相关性(r=0.971、0.934、0.945、0.975、0.900、0.948、0.994、0.984、0.982、0.828、0.879、0.922,P<0.05);两种方法检测总符合率分别为98.21%、98.24%、98.27%、98.85%、97.07%、99.54%、99.66%、99.32%、92.86%、92.86%、95.24%和96.83%,除CA15-3和NSE因数据原因无法计算Kappa值外,其余均有一致性(Kappa=0.848、0.728、0.930、0.794、0.485、0.887、0.664、0.540、0.477、0.652,P<0.05)。结论:电化学发光法和直接化学发光法检测肿瘤标志物中AFP、CA72-4、CA19-9、TPSA相关性及一致性较好,CEA、CA125、FPSA、Cyfra21-1、SCC、PROGrp相关性较好,但一致性一般,CA15-3、NSE相关性较好。临床在参考实验室检测结果时应注意检测方法的不同可能存在着结果差异。

Direct Radiative Effects of Dust Aerosols over Northwest China Revealed by Satellite-Derived Aerosol Three-Dimensional Distribution

Northwest China is recognized as a main source and a major transport channel of dust aerosols in East Asia.With a fragile ecological environment,this region is quite sensitive to global climate change.Based on the satellite-derived aerosol three-dimensional distribution,the direct radiative effects of dust aerosols over Northwest China are evaluated.Aerosols over Northwest China are mainly distributed in the Tarim Basin,Junggar Basin,Gobi Desert,and Loess Plateau.The aerosol extinction coefficients are greater than 0.36 km-1 over the Tarim Basin and 0.16 km^(-1) over the Gobi Desert and Loess Plateau,decreasing with height.Aerosols over Northwest China are mainly composed of pure dust and polluted dust.These dust aerosols can modify the horizontal temperature gradient,vertical thermodynamic structure,and diurnal temperature range by absorbing and scattering shortwave radiation and emitting longwave radiation.For the column atmosphere,the radiative effect of dust aerosols shows heating effect of approximately 0.3 K day^(-1) during the daytime and cooling effect of approximately-0.4 K day^(-1) at night.In the vertical direction,dust aerosols can heat up the lower atmosphere(0.5–1.5 K day^(-1))and cool down the upper atmosphere(about-1.0 K day^(-1))during the daytime,while they cool down the lower atmosphere(-3 to-1.5 K day^(-1))and heat up the upper atmosphere(1–1.5 K day^(-1))at night.There are also significant lateral and vertical variations in the dust radiative effects corresponding to their spatial distributions.This study provides some scientific basis for reducing uncertainty in the investigation of aerosol radiative effects and provides observation evidence for simulation studies.

Three-dimensional porous electrodes for direct formate fuel cells

The dual-layer electrode for fuel cells is typically prepared by binding discrete catalyst nanoparticles onto a diffusion layer.Such a random packing forms a dense catalyst layer and thus creates a barrier for mass/ion transport,particularly for direct liquid fuel cells.Three-dimensional porous electrodes,a thin nano-porous catalyst layer uniformly distributed on the matrix surface of a foam-like structure,are typically employed to improve the mass/ion transport.Such a three-dimensional porous structure brings two critical advantages:(i)reduced mass/ion transport resistance for the delivery of the reactants via shortening the transport distance and(ii)enlarged electrochemical surface area,via reducing the dead pores,isolated particles and severe aggregations,for interfacial reactions.Moreover,the three-dimensional design is capable of fabricating binder-free electrodes,thereby eliminating the use of ionomers/binders and simplifying the fabrication process.In this work,three types of three-dimensional porous electrode are fabricated,via different preparation methods,for direct formate fuel cells:(i)Pd/C nanoparticles coating on the nickel foam matrix surface(Pd-C/NF)via a dip-coating method,(ii)Pd nanoparticles depositing on the nickel foam matrix surface(Pd/NF)via reduction reaction deposition,and(iii)Pd nanoparticles embedding in the nickel foam matrix(Pd/(in)NF)via replacement reaction deposition.The latter two are binder-free three-dimensional porous electrodes.As a comparison,a conventional dual-layer design,Pd/C nanoparticles painting on the nickel foam layer(Pd-C//NF),is also prepared via direct painting method.It is shown that the use of the three-dimensional Pd-C/NF electrode as the anode in a direct formate fuel cell results in a peak power density of 45.0 mW cm^(-2)at 60℃,which is two times of that achieved by using a conventional dual-layer design(19.5 mW cm^(-2)).This performance improvement is mainly attributed to the unique three-dimensional structure design,which effectively enhances the mass/ion transport through the porous electrode and enlarges the electrochemical surface area(accessible active area)for interfacial reactions.In addition,the delivery of the fuel solution is still sufficient even when the flow rate is as low as 2.0 mL min^(-1).It is also demonstrated that direct formate fuel cells using two binder-free electrodes yield the peak power densities of 13.5 mW cm^(-2)(Pd/(in)NF)and 14.0 mW cm^(-2)(Pd/NF)at 60℃,respectively,both of which are much lower than the power density achieved by using the Pd-C/NF electrode.This is because the electrochemical surface areas of two binderfree electrodes are much smaller than the Pd/C-based electrodes,since the specific area of Pd/C nanoparticles is much larger.

直接激光标刻和二维条码技术在刀具标识中的应用研究

针对目前刀具标识与信息追踪方面存在的不足,采用直接激光标刻和二维条码技术实现了刀具的直接标识。在大量试验研究的基础上,重点探讨了刀具直接激光标刻对刀具识别可靠性、刀具识别时间以及刀具力学性能的影响。该研究为刀具和在制品的标识以及信息追踪提供了新的方法和技术,有利于提高刀具库存管理的效率,缩短刀具准备时间,实现刀具生产过程信息采集和信息追踪。

刀具直接标刻与识别技术研究

为解决刀具在库存管理和生产过程追踪管理中的标识问题,提出了激光标刻与二维条码相结合的刀具直接标识方法。研究了条码划伤和刀具储存等对识别可靠性的影响,以及条码标刻深度、表面粗糙度和热影响区等对表面质量的影响。从条码的微观组织、疲劳寿命试验、动平衡试验中分析了对刀具疲劳寿命和动平衡的影响。通过编码,实现了条码识别设备和刀具管理系统的集成。研究表明,该方法对刀具的表面质量、刀具的疲劳强度和刀具的动平衡没有影响,识别可靠性高,为刀具的全生命周期管理和信息追踪提供了有效的技术手段。

DPM技术标准化发展探析

直接零件标识DPM(Direct part marking)技术是实现产品标识的重要于段之一,其与二维条码技术的结合日益密切,已应用于电子与半导体制造、汽车及汽车零部件制造、航空航天制造、军队枪械和资产管理、制药和医疗保健等行业的产品质量追溯和跟踪管理。本文研究了DPM技术标准化发展现状,并对我国DPM技术的标准化提出了建议。