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关键词： 加工特征识别   点云   神经网络   Point Transformer  

摘要： 加工特征识别在计算机辅助设计(CAD)和制造(CAM)中至关重要,是连接CAD和CAM系统的重要环节。研究者们提出了基于规则和基于学习的2类加工特征识别方法,其中基于学习的方法表现更出色且备受关注。然而,现有识别方法面临着几何信息利用不足、加工特征定位不精准、实例分割过程复杂等挑战。针对这些问题,提出PT-MFR,一种基于Point Transformer的CAD模型加工特征识别方法,它执行语义分割和实例分割2个任务,分别预测模型每个面的加工特征语义类别并计算面相似度以分割加工特征实例,综合2个任务得到加工特征识别结果。实验结果表明,提出的方法性能优于现有的其他方法。

关键词： 3D printing   CAD/CAM post   Relined fibre post   Customised post   Internal adaptation   Micro-CT   Push-out bond strength  

摘要： This study assessed the internal adaptation and push-out bond strength (PBS) of customised CAD/CAM 3D-printed (Varseosmile Crown Plus, Bego, Germany - 3DP) and milled (Enamic, Vita, Germany - MP) resin-based posts vs prefabricated fiber posts relined with resin composite (RelyX fiber post and Filtek Bulkfil Composite, 3M Health Care, USA - RFP).

关键词： 四氯双酚A   四溴双酚A   液相色谱-串联质谱   纺织品   同位素内标  

摘要： 建立了液相色谱-串联质谱法测定纺织品中四氯双酚A(TCBPA)和四溴双酚A(TBBPA)的残留方法。样品采用乙腈/水(50/50)超声提取,提取液用HLB固相萃取小柱净化,以水-乙腈为流动相,选择C18色谱柱(100 mm×2.1 mm, 1.7μm)进行梯度分离。采用电喷雾负离子电离模式(ESI-)和多反应监测(MRM)扫描模式,同位素内标法定量。结果显示,TCBPA在0.2~20.0μg/L和TBBPA在0.5~40.0μg/L浓度范围内呈良好线性关系,相关系数(r)均大于0.999,检出限(S/N=3)分别为0.03、0.07μg/kg,平均加标回收率分别为97.4%和94.8%,相对标准偏差范围分别为4.1%~6.3%和4.2%~5.7%。所建方法灵敏度高,特异性强,适用于纺织品中TCBPA和TBBPA的测定,可为纺织品中其他双酚化合物残留检测提供技术方案。

关键词： 3D reconstruction   boundary marking   CAD   geometric accuracy   photogrammetry   reverse engineering  

摘要： Photogrammetric modelling, a widely used technique for reconstructing 3D models from photographic data, relies on achieving high geometric accuracy to minimize post-processing efforts. This study proposes an enhancement to the photogrammetric reconstruction workflow through the introduction of the Boundary Marking Technique. By visibly marking the edges surrounding object surfaces, this method aims to improve edge definition and overall reconstruction quality. The technique was applied to both metal and plastic objects of identical geometry. 3D models were generated using close-range photogrammetry for both marked and unmarked versions, and deviation analyses were conducted against their CAD references. A total of 16 analyses comprising one 3D and three 2D per object were performed using computer-aided comparison tools. Results indicate that the Boundary Marking Technique significantly enhances geometric accuracy, particularly along edges and adjacent surfaces, ultimately improving model topology and dimensional fidelity across the entire reconstruction.

关键词： Functional estimation   minimax optimality   convex optimization and duality   modulus of continuity   linear programming  

摘要： Le Cam's method (or the two-point method) is a commonly used tool for obtaining statistical lower bound and especially popular for functional estimation problems. This work aims to explain and give conditions for the tightness of Le Cam's lower bound in functional estimation from the perspective of convex duality. Under a variety of settings, it is shown that the maximization problem that searches for the best two-point lower bound, upon dualizing, becomes a minimization problem minimizing an upper bound on the quadratic risk over a family of estimators. Since by the minimax theorem two problems have the same value, this value also characterizes (up to a universal factor) the optimal estimation rate. For estimating linear functionals of a distribution, our work strengthens prior results of Donoho-Liu (Ann. Statist. 19 (1991) 633-667) (for quadratic loss) by dropping the H & ouml;lderian assumption on the modulus of continuity. For exponential families, our results extend those of Juditsky-Nemirovski (Ann. Statist. 37 (2009) 2278-2300) by characterizing the minimax risk for the quadratic loss under weaker assumptions on the exponential family. We also provide an extension to the high-dimensional setting for estimating separable functionals. An application of our methodology to the area of "estimating the unseens" is provided in the companion paper (Polyanskiy and Wu (2023)), resolving the optimal rates (within logarithmic factors) of the distinct elements problem and Fisher's species problem.

关键词： 3D printing   bonding   CAD/CAM   denture base   denture tooth   milling  

摘要： Objective: This in-vitro study examined the bond between denture teeth (milled, printed, and prefabricated) and milled, printed, and autopolymerized denture bases. Method and materials: In total, 88 specimens (11 groups, n = 8 per group) of denture teeth and denture base resins were fabricated using systems of three different manufacturers (Vita Zahnfabrik, Ivoclar Vivadent, and Formlabs). The groups consisted of combinations of six different teeth, five different denture base materials, and four different adhesive bonding options. Teeth were either printed, milled, or prefabricated, while denture bases were either conventionally polymerized, milled, or printed. In addition, two dentures were milled from industrially pre-polymerized blocks. After 24 hours of storage in distilled water, all specimens were loaded to failure to determine fracture forces. The fracture pattern was classified according to adhesive, cohesive, and mixed failures. Statistical analysis was performed using one-way analysis of variance and the Bonferroni test for post-hoc analysis. The level of significance (a) was set to .05. Results: Mean fracture forces ranged between 34.6 N and 649.3 N. The monobloc dentures Formlabs (459.0 +/- 82.5 N) and Ivoclar (649.3 +/- 32.3 N) featured the significantly highest fracture forces (P < .001). For adhesively luted teeth, the conventional base-conventional tooth group showed the highest bond strength (289.5 +/- 44.3 N), while the printed base-printed tooth group had the lowest (34.6 +/- 12.7 N). The milled base group showed intermediate values (236.5 +/- 56.4 N). Conclusion: Bond strength between denture teeth and denture base depends on the fabrication process. Monolithic systems demonstrated optimal bond strength. Among all other combinations, the conventionally polymerized denture base combined with prefabricated teeth showed the best results. Prefabricated teeth and milled teeth in combination with milled denture bases showed similarly good results. Pri

关键词： Dissection   Stroke   Risk Factors  

关键词： Dissection   Stroke   Stroke Or Other Cerebrovascular Disease  

关键词： Complementary and alternative medicine   CAM   depoliticisation   political participation   voting   survey  

摘要： The increasing cultural prevalence and appeal of complementary and alternative medicine (CAM) have raised concerns about its potential depoliticising effects. Due to its focus on the self, CAM is believed to cultivate individualism and orient transformative energies towards self-improvement rather than the collective struggle for social justice. However, despite these concerns, few quantitative studies have examined CAM from the perspective of the depoliticisation thesis. This article aims to address this gap by studying the association between political participation and CAM with data from the European Social Survey (ESS). These data enable us to capture a diverse range of CAM practices and to scrutinise both institutionalised forms of political participation, such as voting, and non-institutionalised participation taking place in civil society. Contrary to the depoliticisation thesis, our results show that CAM users either engage more actively in voting or do not significantly differ in their voting behaviour compared to non-users, depending on the specific CAM modalities considered. Moreover, CAM users participate more actively in non-institutionalised activities than non-users across all types of CAM modalities. This article offers valuable insights into the relationship between CAM and political engagement and challenges prevailing assumptions about the depoliticising effects of CAM.

关键词： Random access memory   Circuits   Logic   Transistors   Optimization   Nonvolatile memory   Integrated circuit reliability   MOS devices   Layout   Arrays   Content addressable memory (CAM)   embedded dynamic random access memory (eDRAM)   logic-in-memory   Boolean logic operation  

摘要： Content-addressable memory (CAM) is regarded as an attractive solution for data-intensive applications with high-density search demands. To further improve functional flexibility yet at a low cost, several CAM macros have been developed to support multiple bit-wise logic operations. However, conventional SRAM-based CAM designs are constrained by the large bitcell area, posing significant challenges to achieve higher density. To address this issue, we propose a complementary 3T (C3T) based embedded dynamic random access memory (eDRAM) macro for high-density dual-direction CAM searching and logic-in-memory operations. First, we propose a compact C3T bitcell featuring a pair of complementary decoupled read ports, enabling dual-port read and efficient CAM operations. Second, we present a compact dynamic-circuit-based sense amplifier (DSA) to optimize the area of readout peripheral circuitry while mitigating the read bit line saturation issue. Additionally, we implement dual-direction CAM searching and logic-in-memory operations exploiting the C3T-based eDRAM macro. A 4 Kb C3T-based eDRAM macro has been validated in a commercial 40-nm CMOS process. Post-layout results demonstrate a 53% reduction in the bitcell area and a 58.1% reduction in the macro area compared to the state-of-the-art 6T compute SRAM. Moreover, the proposed design achieves a maximum frequency of 578 MHz for binary CAM (BCAM) searching operations and 694 MHz for logic operations, with energy consumption of 1.12 fJ/bit and 26.8 fJ/bit, respectively.