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.     

污泥化学调理和机械脱水方面的研究进展

综述了近几年来国内外有关化学药剂单独或联合调理对污泥脱水性能的影响。污泥颗粒尺寸、污泥化学组成对污泥脱水性能的影响。以及污泥化学调理的静电作用过程、污泥离心脱水过程、污泥过滤和挤压固化脱水过程等方面的研究进展。汇总了实验研究中常用的参数指标．并展望今后在污泥调理和机械脱水方面的发展动态。     

某城市地下车库联络通道的消防安全研究

城市地下车库联络通道作为一种新型的地下交通联络通道,可净化地面交通,提高土地利用率,解决城市交通拥堵问题。然而这种通道兼有地下车库和城市交通隧道的特点,结构复杂,一旦发生火灾,损失较大。其防火设计的难点在于如何定性并选择合适的规范条文,因此有必要系统研究其消防安全问题并提出有效解决方案。以某城市地下车库联络通道为例,研究该通道的火灾危险性,提出防火分隔、探测报警、排烟以及人员安全疏散等消防设计方案和管理对策,并通过数值模拟方法验证了该方案的有效性和可行性。     

机械设备可靠性分析与工程安全

指出了机械设备的可靠性对工程安全的重要意义。根据可靠性理论,对机械应力损伤和组织变化损伤这两种最常见的降低设备可靠性的损伤形式进行了讨论,并结合实例详细分析了判定机械设备工作状态的各种物理现象,以及估算剩余寿命的基本方法。     

Strength and workability of masonry mortars manufactured with ladle furnace slag

Ladle furnace basic slag (LFS) is a by-product of the steelmaking process. It has rarely been recovered in the past and is usually disposed of in landfill sites. Despite containing stable chemical substances of great quality, some of which are potentially hydraulic, its practical applications have been limited. This paper discusses the attractive option of using LFS in the manufacture of masonry mortars for use in the construction industry, which requires an analysis of the principal characteristics of such mortars, i.e. workability and mechanical strength. It reports on a comparative study, using standard commercial admixtures, between conventional masonry mortars and mortars manufactured with LFS as a partial replacement for sand and cement, the results of which imply considerable economic savings in sand and cement, improvements in the properties of the mortars and in overall sustainability, by avoiding disposal and conserving natural resources.     

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.     

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.     

水压在隧道工程水环境中的力学效应机理初探

隧道工程水环境和隧道工程的设计、施工及维护密切相关 ,往往是诱发工程事故的主要原因 ,其中水压是最重要的基本要素之一 ,对工程的影响主要通过其力学效应表现出来。笔者通过所建立的数学模型 ,初步解释了水压对于隧道工程力学效应 ,评价了其对隧道工程设计、施工和维护的影响     

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.