Mechanical Performance and Design Criteria of Biodegradable Low-tunnel Films

The overall mechanical behaviour of a series of experimental Mater-Bi made thin low-tunnel films is analysed with respect to the effect of two major factors: the film processing optimisation during manufacturing and the design of the low-tunnels structural system. The analysis of the mechanical behaviour of the biodegradable low-tunnel films, based on the results of extensive full-scale and small-scale experiments, combined with laboratory testing of the mechanical properties of the film, proves that a rather good mechanical behaviour is possible for these films, comparable to the behaviour of conventional agricultural films in terms of strength, provided that two criteria are met: (a) the low tunnel structural design is based on the initial stress at yield value of the film, which represents the asymptotic value of the tensile strength of the film, following its evolution with the time of exposure to real field conditions; (b) the processing of the film is optimised for the particular biodegradable material and film thickness under consideration. It is also confirmed that the stabilisation schemes used with conventional polyethylene films are not suitable for the biodegradable films.

机电产品可靠性研究与探讨

机电产品越来越广泛地应用于社会各个领域,随着自动化、小型化程度的提高,很多机电产品结构越来越复杂,并且其使用条件也越来越严酷,由此产生的产品可靠性问题必然越来越多,可靠性技术也越来越受到重视。本文针对机电产品,从可靠性管理、可靠性设计和分析、可靠性试验和评定三个方面,对可靠性研究工作进行初步探讨。     

Biodegradable Films Based on Blends of Gelatin and Poly (Vinyl Alcohol): Effect of PVA Type or Concentration on Some Physical Properties of Films

The aim of this work was to develop biodegradable films based on blends of gelatin and poly (vinyl alcohol) (PVA), without a plasticizer. Firstly, the effect of five types of PVA with different degree of hydrolysis (DH) on the physical properties of films elaborated with blends containing 23.1% PVA was studied. One PVA type was then chosen for the study of the effect of the PVA concentration on the mechanical properties, color, opacity, gloss, and water solubility of the films. The five types of PVA studied allowed for films with different characteristics, but with no direct relationship with the DH of the PVA. Therefore, the PVA Celvol^®418 with a DH = 91.8% was chosen for the second part, because they produced films with greater tensile strength. The PVA concentration affected all studied properties of films. These results could be explained by the results of the DSC and FTIR analyses, which showed that some interactions between the gelatin and the PVA occurred depending on the PVA concentration, affecting the crystallinity of the films.     

Predictive modelling of dispersion controlled reactive plumes at the laboratory-scale

A model-based interpretation of laboratory-scale experimental data is presented. Hydrolysis experiments carried out using thin glass tanks filled with glass beads to construct a hypothetical and inert, homogeneous porous medium were analysed using a 2D numerical model. A new empirical formula, based upon results for non-reactive (tracer) experiments is used to calculate transversal dispersivity values for a range of grain sizes and any flow velocities. Combined with effective diffusion coefficients calculated from Stokes-Einstein type equations, plume lengths arising from mixing between two solutes can be predicted accurately using numerical modelling techniques. Moreover, pH and ion concentration profiles lateral to the direction of flow of the mixing species can be determined at any given point downstream, without the need for result fitting. In our case, this approach does not lead to overpredictions of lateral mixing, as previously reported when using parameters derived from non-reactive tracer experiments to describe reactive solute transport. The theory is based on the assumption of medium homogeneity.     

基于油水分离的餐饮废水破乳化技术研究

餐饮废水中乳化油的分离处理一直是一个技术难题,文章分别采用物理机械方法和物理化学方法对餐饮废水进行了破乳化研究。通过对比试验结果和分析破乳机理,总结出各方法不同的破乳特点。结果表明,温度越高分离效果越好,但在实际应用中,保持在50～60℃即可。低功率的超声波可以促进破乳效果,但超过30W,又会使溶液发生乳化反应。小分子醇类的加量越多,破乳化作用越强;醇类单链越长,分离效果越好。加入无机盐,在一定程度上可以加快破乳化速度,但效果并不明显。     

How safe are standard certified motorcycle safety helmets? Malaysian postal delivery riders scenario

Objective: The objective of this study was to determine the proportion of motorcycle safety helmets (MSHs) used by postal delivery riders (PDRs) that comply with the Standards and Industrial Research Institute of Malaysia’s (SIRIM) MSH standard guidelines and identify factors that contribute toward compliance of used MSHs with the standards.

Methods: The presence of SIRIM certification label, the status of MSH, type of chinstrap, MSH crash history, and duration of MSH use were observed. The dependent variable was the results of the SIRIM testing procedures (SIRIM tests). MSHs that passed the SIRIM tests were considered “standard certified” MSHs.

Results: The odds of the complimentary MSHs passing all of the SIRIM tests were 3.7 times the odds of the self-purchased MSHs passing the tests. The odds of MSHs with the SIRIM certification label passing all of the SIRIM tests were 24.2 times the odds of MSHs without the SIRIM certification label, and the odds of MSHs used <3?years passing the SIRIM tests were 3.75 times the odds of the MSHs used ≥3.8?years.

Conclusion: PDRs provided with complimentary MSHs with the SIRIM certification label by the employer for their daily delivery routines and duration of MSH used for less than 3 years were found to be safe MSHs for male occupational riders in Malaysia.     

生产工艺参数对高碳钢线材力学性能的影响

用正交试验的方法研究了不同工艺参数对高碳钢力学性能的影响.分析了82MnA钢线材的生产工艺参数.     

七台河矿区采空塌陷引起的地表变形

以实际观测为依据，以七台河地区地质条件为背景，给出该区塌陷变形，诸如不均匀沉降、地面倾斜、曲率变化、移动等力学量的估算。     

兴安落叶松胶合木柱力学性能试验研究

该文以兴安叶松为原料,依据木结构设计规范对国产落叶松动弹性模量和静弹性模量进行研究.采用应力应变片与应力波法分别测定其静态、动态弹性模量,结果表明:静弹性模量是动弹性模量的1.23倍.图2,表4,参9.     

Energy implications of mechanical and mechanical–biological treatment compared to direct waste-to-energy

Primary energy savings potential is used to compare five residual municipal solid waste treatment systems, including configurations with mechanical (MT) and mechanical–biological (MBT) pre-treatment, which produce waste-derived fuels (RDF and SRF), biogas and/or recover additional materials for recycling, alongside a system based on conventional mass burn waste-to-energy and ash treatment. To examine the magnitude of potential savings we consider two energy efficiency levels (state-of-the-art and best available technology), the inclusion/exclusion of heat recovery (CHP vs. PP) and three different background end-use energy production systems (coal condensing electricity and natural gas heat, Nordic electricity mix and natural gas heat, and coal CHP energy quality allocation).The systems achieved net primary energy savings in a range between 34 and 140 MJ_primary/100 MJ_{input waste}, in the different scenario settings. The energy footprint of transportation needs, pre-treatment and reprocessing of recyclable materials was 3–9.5%, 1–18% and 1–8% respectively, relative to total energy savings. Mass combustion WtE achieved the highest savings in scenarios with CHP production, nonetheless, MBT-based systems had similarly high performance if SRF streams were co-combusted with coal. When RDF and SRF was only used in dedicated WtE plants, MBT-based systems totalled lower savings due to inherent system losses and additional energy costs. In scenarios without heat recovery, the biodrying MBS-based system achieved the highest savings, on the condition of SRF co-combustion. As a sensitivity scenario, alternative utilisation of SRF in cement kilns was modelled. It supported similar or higher net savings for all pre-treatment systems compared to mass combustion WtE, except when WtE CHP was possible in the first two background energy scenarios. Recovery of plastics for recycling before energy recovery increased net energy savings in most scenario variations, over those of full stream combustion. Sensitivity to assumptions regarding virgin plastic substitution was tested and was found to mostly favour plastic recovery.