Evaluation of cutting quality of PMMA using CO2 lasers

Polymethyl methacrylate (PMMA) is a versatile thermoplastic that is well suited for engineering and many common applications. This article presents a study to evaluate the effect of the processing parameters (laser power and cutting velocity) under the quality of the cut of PMMA. A plan of experiments was established considering CO₂ laser cutting with prefixed processing parameters in plates of PMMA with 6 mm thickness. The objective was to evaluate the quality of the cut (surface roughness, dimensional precision and heat affected zone-HAZ) in linear and complex 2D cutting. The obtained results show that PMMA in complex 2D cutting presents dimension of HAZ between 0.12 to 0.37 mm, without burr and low surface roughness Ra?<?1 μm. The results present good repeatability.     

Methanol-induced biological nutrient removal kinetics in a full-scale sequencing batch reactor

The primary goal of this research was to determine the potential for denitrification and phosphorus removal of a full-scale sequencing batch reactor (SBR), with and without the use of methanol as an external carbon source. The control SBR, without methanol addition, achieved negligible denitrification. Two denitrification rates were observed in the experimental SBR, with methanol addition, an initial fast rate and a slower second rate. The denitrification rate during the first rate period increased with increasing methanol concentration, until a maximum denitrification rate of approximately 19 mg NOx-N/g MLVSS/day was attained. Following the depletion of the methanol, denitrification reactions probably continued by using the available natural carbon in the influent, resulting in a slower, second denitrification rate. Biological phosphorus uptake and release was significant only in the SBR with methanol addition. Methanol was probably not utilized as the carbon source for the enhanced biological phosphorus removal (EBPR) process. However, methanol addition was critical, since it depleted the available nitrates and thus allowed EBPR to take place.     

Indoor gaseous air pollutants determinants in office buildings—The OFFICAIR project

The aim of this study was to identify determinants of aldehyde and volatile organic compound (VOC) indoor air concentrations in a sample of more than 140 office rooms, in the framework of the European OFFICAIR research project. A large field campaign was performed, which included (a) the air sampling of aldehydes and VOCs in 37 newly built or recently retrofitted office buildings across 8 European countries in summer and winter and (b) the collection of information on building and offices’ characteristics using checklists. Linear mixed models for repeated measurements were applied to identify the main factors affecting the measured concentrations of selected indoor air pollutants (IAPs). Several associations between aldehydes and VOCs concentrations and buildings’ structural characteristic or occupants’ activity patterns were identified. The aldehyde and VOC determinants in office buildings include building and furnishing materials, indoor climate characteristics (room temperature and relative humidity), the use of consumer products (eg, cleaning and personal care products, office equipment), as well as the presence of outdoor sources in the proximity of the buildings (ie, vehicular traffic). Results also showed that determinants of indoor air concentrations varied considerably among different type of pollutants.     

A Reconfigurable Posit Tensor Unit with Variable-Precision Arithmetic and Automatic Data Streaming

Journal of Signal Processing Systems - The increased adoption of DNN applications drove the emergence of dedicated tensor computing units to accelerate multi-dimensional matrix multiplication...     

Low-cost silicon neural probe: fabrication,electrochemical characterization and in vivo validation

Microsystem Technologies - This paper presents the fabrication of a silicon neural probe using low-cost microfabrication technologies, such as thin-films deposition, blade dicing, and...     

斜屋顶钢框架的弹性屈曲及二阶受力性能

该文工作有双重目的：（i）介绍考虑了弹性平面内稳定和二阶受力性能的无支撑单层斜屋顶钢框架的研究结果;（ii）提出、验证并阐述一种有效方法如何用于这种常用类型框架的设计。在完成了（i）给出相应的框架屈曲模式和P-△二阶效应的特点;（ii）给出了计算相应的分支荷载和二阶弯矩的精确方法和近似方法等工作之后,该文将这些概念融合到一种有效的设计方法中。特别要指出的是,很明显,由于椽子的坡度,