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排序方式: 共有4203条查询结果,搜索用时 15 毫秒
1.
Due to the growing energy requirements, the proportion of external thermal insulation composite systems (ETICS) installed has increased significantly during the past 50 years. Due to the longevity of these systems, ETICS waste is currently accumulating. Owing to the complex construction as well as a multitude of differently installed materials and substances of the past generations, there are many uncertainties and problems with the clean and low-pollutant processing of such systems. In the frame of this work, the ETICS were processed and sorted before being screened for ingredients or pollutants as well as for the purity of the recovered material fractions.  相似文献   
2.
将Copulas理论引入文本特征词关联模式挖掘,提出融合Copulas理论和关联规则挖掘的查询扩展算法.从初检文档集中提取前列n篇文档构建伪相关反馈文档集或用户相关反馈文档集,利用基于Copulas理论的支持度和置信度对相关反馈文档集挖掘含有原查询词项的特征词频繁项集和关联规则模式,从这些规则模式中提取扩展词,实现查询扩展.在NTCIR-5 CLIR中英文本语料上的实验表明,文中算法可有效遏制查询主题漂移和词不匹配问题,改善信息检索性能,提升扩展词质量,减少无效扩展词.  相似文献   
3.
Bioactive ceramic scaffolds for bone regeneration consisting of a three-dimensional mesh of interpenetrating struts with square section were fabricated via Digital Light Processing (DLP). The ability of the technique to manufacture 3D porous structures from β-tricalcium phosphate (β-TCP) powders with different dimensions of struts and pores was evaluated, identifying the possibilities and limitations of the manufacturing process. Small pore sizes were found to seriously complicate the elimination of excess slurry from the scaffold’s innermost pores. The effect of the strut/pore size on the mechanical performance of the scaffolds under compressive stresses was also evaluated, but no significant influence was found. Under compressive stresses, the structures resulted weaker when tested perpendicularly to the printing plane due to interlayer shear failure. Interlayer superficial grooves are proposed as potential failure-controlling defects, which could also explain the lack of a Weibull size effect on the mechanical strength of the fabricated DLP scaffolds.  相似文献   
4.
《Ceramics International》2021,47(19):27032-27041
The scaffold of bone repair needs a variety of material combinations to meet its intended performance; a typical single material such as zirconia has excellent mechanical properties, while hydroxyapatite and calcium silicate are bioactive materials with different degradation rates. In this paper, porous zirconia scaffolds were fabricated using 3D printing technology. The surface of the scaffold was coated by dipping with different contents of calcium silicate and hydroxyapatite to improve the biological activity and mechanical properties. Mechanical tests show that the coating material can effectively fill the pores of the porous scaffold, increasing its compressive strength by an average of 55%. The simulated body fluid (SBF) test showed that the higher calcium silicate in the coating increased the degradation rate. Cell experiments showed that the coated scaffolds exhibited good cytocompatibility and were beneficial to the proliferation and differentiation of cells. In conclusion, coated scaffolds have potential applications in the field of bone repair.  相似文献   
5.
通过定量与定性相结合的方式全面分析了深度学习在自然语言处理领域的研究情况。采用CiteSpace和VOSviewer对深度学习在自然语言处理领域的研究国家、机构、期刊分布、关键词共现、共被引网络聚类及时间轴视图等进行知识图谱绘制,理清研究脉络。通过深入挖掘领域内的重要文献,总结深度学习在自然语言处理领域的研究趋势、存在的主要问题或发展瓶颈,并给出相应的解决办法与思路。对于如何跟踪深度学习在自然语言处理领域的研究成果给出建议,为该领域的后续研究与发展提供参考。  相似文献   
6.
One of the main challenges in the laser powder bed fusion (LPBF) process is making dense and defect-free components. These porosity defects are dependent upon the melt pool geometry and the processing conditions. Power-velocity (PV) processing maps can aid in visualizing the effects of LPBF processing variables and mapping different defect regimes such as lack-of-fusion, under-melting, balling, and keyholing. This work presents an assessment of existing analytical equations and models that provide an estimate of the melt pool geometry as a function of material properties. The melt pool equations are then combined with defect criteria to provide a quick approximation of the PV processing maps for a variety of materials. Finally, the predictions of these processing maps are compared with experimental data from the literature. The predictive processing maps can be computed quickly and can be coupled with dimensionless numbers and high-throughput (HT) experiments for validation. The present work provides a boundary framework for designing the optimal processing parameters for new metals and alloys based on existing analytical solutions.  相似文献   
7.
Understanding aqueous dispersion, rheological properties and colloidal stabilisation mechanisms of hierarchically assembled ceramic powders is important for progress in the fields of catalysis, separation and/or adsorption. The present study was designed to evaluate the rheological and sedimentation behaviour of highly loaded aqueous suspensions (up to φA = 0.126) containing AlN-powder-hydrolysis-derived, micron-sized, mesoporous, gamma alumina (MA) particulates with a high surface area (~180 m2/g) dispersed with sodium polyacrylate (NaPAA). The as-prepared suspensions were prone to sedimentation and segregation. However, when divalent cations (Mg2+, Ca2+) or cellulose nanofibers were added, the formation of interparticle association networks in the aqueous suspensions containing MA particles was triggered, facilitating their long-term resistance to sedimentation lasting more than 12 weeks.  相似文献   
8.
万向轴动不平衡主要体现在万向轴振动信号的转频及其倍频上,为了更准确地提取动不平衡振动特征,引入具有完备理论基础、窄带滤波特性和最优解的信号分解方法——变分模态分解法来提取动不平衡振动特征。然而,变分模态分解的结果对两个参数(模态数量、惩罚因子)的设置很敏感。因此,提出应用傅里叶谱的均方根分布与其局部峭度值确定变分模态分解的模态数量,利用傅里叶谱峭度增量对惩罚因子进行最优选择。建立万向轴动不平衡的自适应提取模型,应用试验台实测数据对该检测方法和模型的有效性进行了验证。  相似文献   
9.
谢晖 《云南化工》2019,(4):152-153
塑料在目前的经济社会生活中呈现出高速发展的趋势,,对塑料进行成型加工是完成塑料制品一个最终的过程。对塑料成型加工的不同方法进行了研究,分析不同技术存在的特点,了解塑料成型加工不同的发展趋势,促进塑料制品发展。  相似文献   
10.
目的 开发与优化即食液熏鲍鱼生产工艺。方法 以感官评分为指标,通过正交实验,研究液熏液配方和浸渍烘干工艺参数对即食液熏鲍鱼品质的影响。结果 即食液熏鲍鱼最佳生产工艺为[液熏液配方为食用盐添加量(2 %)、白砂糖添加量(10 %)、酱油添加量(3.5 %)、烟熏香味料添加量(0.2 %)和浸渍烘干工艺参数为浸渍时间(2 h)、浸渍温度(60 ℃)、烘干时间(2 h)、烘干温度(80 ℃)];在此最佳生产工艺下加工而成的即食液熏鲍鱼的理化、微生物及污染物指标符合相关食品安全国家标准。结论 开发并优化了一种即食液熏鲍鱼生产工艺,为鲍鱼休闲食品的深加工提供了参考依据。  相似文献   
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