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1.
Retrieving 3D shapes with 2D images has become a popular research area nowadays, and a great deal of work has been devoted to reducing the discrepancy between 3D shapes and 2D images to improve retrieval performance. However, most approaches ignore the semantic information and decision boundaries of the two domains, and cannot achieve both domain alignment and category alignment in one module. In this paper, a novel Collaborative Distribution Alignment (CDA) model is developed to address the above existing challenges. Specifically, we first adopt a dual-stream CNN, following a similarity guided constraint module, to generate discriminative embeddings for input 2D images and 3D shapes (described as multiple views). Subsequently, we explicitly introduce a joint domain-class alignment module to dynamically learn a class-discriminative and domain-agnostic feature space, which can narrow the distance between 2D image and 3D shape instances of the same underlying category, while pushing apart the instances from different categories. Furthermore, we apply a decision boundary refinement module to avoid generating class-ambiguity embeddings by dynamically adjusting inconsistencies between two discriminators. Extensive experiments and evaluations on two challenging benchmarks, MI3DOR and MI3DOR-2, demonstrate the superiority of the proposed CDA method for 2D image-based 3D shape retrieval task.  相似文献   
2.
超临界二氧化碳是一种特殊的流体,具有粘度低、扩散系数大、密度大和溶解性较好等特点,因此被认为是第四代核反应堆能量传递的首选材料。由于核反应堆的工作环境十分苛刻,超临界二氧化碳应用于核反应堆系统中易造成材料腐蚀,为确保核反应堆安全有效地运行,对超临界二氧化碳腐蚀行为进行系统研究,介绍了核反应堆的发展历程,重点探讨超临界二氧化碳对合金材料腐蚀的机理,详细阐述了温度、压力、杂质和流速等因素对材料在超临界二氧化碳中腐蚀行为的影响,针对目前的研究提出了亟待解决的问题。  相似文献   
3.
黑钨矿极易发生泥化现象,导致其有效浮选仍是一个难题。本研究在实验室球磨机中,探讨了不同尺寸的钢球作为介质对黑钨矿细度和形状的影响,在干磨条件下进行了6种不同球径(20、30、40、50、60、70 mm)的磨矿试验。结果如下所示:各磨矿条件下获得的产品粒径均随磨矿时间的增加而减小。以70 mm钢球为磨矿介质时,大颗粒含量最低,-10μm过磨颗粒含量最高。这些粒径比x80/x20随着产品尺寸的减小先增大后减小,每一个球的粒径都趋于平缓。中值粒径x50随球径的减小先减小后增大,其中40mm球径最小(0.06 mm);但当球直径小于40 mm时,破碎混合颗粒物料的粉碎能力减弱。在相同的磨矿时间下,粒径比x80/x20随球径的减小先增大后减小,其中40mm球的粒径比最大;对于40mm钢球,产品的细度和宽度不一致,因此选择钢球直径不容易。当球直径小于40 mm时,粒径比x90/x10越来越大。粒径比(x90-x10)/x50随着产品粒径的减小先增大后减小,减小趋势随着球径的减小而趋于平缓,在x50为0.075 mm-0.085 mm范围内达到最大;另一方面,20毫米球下,(x90-x10)/x50磨矿产品尺寸几乎是不变的,为20.66。当产品粒径小于1 mm时,产品颗粒的球形度急剧增加,且随着球直径的减小,球形度增加的更快。当产品粒径小于0.04 mm时,产品颗粒球形度的变化趋势趋于平缓,这可能是在磨机内表面和球表面形成粘附颗粒层。0.8 ~ 0.3 mm的球形度变化趋势小于0.3 mm以下的球形度变化趋势。  相似文献   
4.
5.
PurposeThis prospective study assessed the influence of wearing and then discontinuing orthokeratology (OK) lenses on retinal shape and peripheral refraction in myopic children.MethodsFifty-eight myopic children (age 8–12 years) were equally divided into an OK group and a single vision spectacles (SVS) group. After 12 months of OK, it was discontinued for 1 month. Peripheral eye length (PEL), relative peripheral refraction (RPR), and corneal parameters were measured in the right eye on the nasal and temporal retinal sides at baseline, 6 months, and 12 months (13 months in OK group) visits.ResultsIn the SVS group, faster elongation of the temporal side PEL made the eyes more asymmetric and prolate, developing a temporal pointed shape. In the OK group, the nasal retinal side PEL grew faster, the nasal RPR developed less hyperopic defocus, and the eye shape became more symmetric and less prolate. The central cornea became thinner and flattened, while the peripheral cornea became steeper. Changes in corneal thickness, relative peripheral corneal power, and K-values were no significant differences for the OK and SVS groups at 12 months.ConclusionsThe cornea reverted to be no difference with myopic children with SVS after 1 month discontinuation of OK. The retinal shape of SVS eyes became more asymmetric and prolate with myopia progression. OK remodelled retinal shape to be less asymmetric and less prolate.  相似文献   
6.
利用Ansys数值模拟软件,对含埋藏缺陷的承压管道进行磁记忆检测有限元模拟,分析磁记忆信号值在不同缺陷参数、不同应力状态下的变化规律。结果表明,磁记忆信号可以对管道埋藏型裂纹及气孔产生的应力集中进行表征,随着缺陷埋深的减小与内压载荷的增加,磁记忆信号变化幅度增大,法向梯度极值增加。通过法向和切向信号协同分析,可以实现对缺陷信号的量化。  相似文献   
7.
An important difficulty associated with alkaline water electrolysis is the rise in anode overpotential attributable to bubble coverage of the electrode surface. For this study, a system with a high-speed video camera was developed, achieving in-situ observation of bubble generation on an electrode surface, monitoring an area of 1.02 mm2 at 6000 frames per second. The relation between polarization curve (current density up to 3.0 A cm?2) and oxygen bubble generation behavior on nickel electrodes having cylindrical wires and rectangular wires of different sizes (100–300 μm) was clarified. The generated bubbles slide upward, contacting the electrode surface and detaching at the top edge. Observations indicate that small electrodes have short bubble residence time and thin bubble covering layer on the electrode. As a result, the small electrode diameter contributes to smaller overpotential at high current density.  相似文献   
8.
Intermetallic materials are bestowed by diverse ordered superlattice structures together with many unusual properties. In particular, the advent of chemically complex intermetallic alloys (CCIMAs) has received considerable attention in recent years and offers a new paradigm to develop novel metallic materials for advanced structural applications. These newly emerged CCIMAs exhibit synergistic modulations of structural and chemical features, such as self-assembled long-range close-packed ordering, complex sublattice occupancy, and interfacial disordered nanoscale layer, potentially allowing for superb physical and mechanical properties that are unmatched in conventional metallic materials. In this paper, we critically review the historical developments and recent advances in ordered intermetallic materials from the simple binary to chemically complex alloy systems. We are focused on the unique multicomponent superlattice microstructures, nanoscale grain-boundary segregation, and disordering, as well as the various extraordinary mechanical and functional properties of these newly developed CCIMAs. Finally, perspectives on the future research orientation, challenges, and opportunities of this new frontier are provided.  相似文献   
9.
Interface shear strength of geosynthetic clay liners (GCL) with the sand particles is predominantly influenced by the surface characteristics of the GCL, size and shape of the sand particles and their interaction mechanisms. This study brings out the quantitative effects of particle shape on the interaction mechanisms and shear strength of GCL-sand interfaces. Interface direct shear tests are conducted on GCL in contact with a natural sand and a manufactured sand of identical gradation, eliminating the particle size effects. Results showed that manufactured sand provides effective particle-fiber interlocking compared to river sand, due to the favorable shape of its grains. Further, the role of particle shape on the hydration of GCL is investigated through interface shear tests on GCL-sand interfaces at different water contents. Bentonite hydration is found to be less in tests with manufactured sand, leading to better interface shear strength. Grain shape parameters of sands, surface changes related to hydration and particle entrapment in GCL are quantified through image analysis on sands and tested GCL surfaces. It is observed that the manufactured sand provides higher interface shear strength and causes lesser hydration related damages to GCL, owing to its angular particles and low permeability.  相似文献   
10.
RM3 compounds (R = rare earth metals, M = transition metals) have rarely been studied for gaseous hydrogen storage applications because of unfavorable thermodynamics. In this work, the hydrogen storage properties of a single-phase YFe3 alloy were improved by non-stoichiometric composition and alloying with Sc and Zr. Only the Y1.1–yScyFe3 (y = 0.22, 0.33) alloys consist of a single rhombohedral phase. The Sc substitution for Y leads to the reduction in the unit cell volume of the YFe3 phase, and thus significantly increases the dehydriding equilibrium pressure and decreases the dehydrogenation temperature. The alloy Y0.77Sc0.33Fe3 delivers a decomposition enthalpy change of 33.54 kJ/mol and a lowest dehydrogenation temperature of 135 °C, in comparison with 38.99 kJ/mol and 165 °C for the alloy Y1.1Fe3. The Zr substitution causes a similar thermodynamic destabilization effect, but the composition and microstructure of Y–Zr–Fe alloys need to be further optimized.  相似文献   
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