控制滇池生态环境的关键

滇池水污染、生态恶化 ,近 10年综合治理仍未能逆转。认为导致滇池生态恶化的原因主要有三方面 :一是入湖污染物量超过水环境承载能力 ,水污染和水体富营养化 ;二是城市发展超过水资源承载能力 ,难以保证生态环境用水 ;三是滇池逐步演化成半封闭湖泊 ,加上数十年污染负荷剧增 ,加速了生态环境变化由量变到质变的进程。改善滇池生态环境的关键措施有 :综合治理 ,有效控制污染物 ;引水济昆 ,缓解流域水资源匮乏 ,从根本上提高滇池流域水资源及水环境承载能力。     

冻融作用下活化煤矸石粉混凝土损伤劣化规律

为促进寒冷地区煤矸石在混凝土中的应用,通过机械-微波方式对煤矸石进行复合活化,从表观形貌、质量损失率、相对动弹性模量、抗压强度和劈裂抗拉强度等方面对煤矸石粉混凝土的损伤劣化规律进行了研究,并使用扫描电子显微镜、核磁共振波谱仪和X射线衍射仪等研究了活化煤矸石粉对混凝土抗冻性能的改性机理。结果表明:20%(质量分数)掺量下活化煤矸石粉对混凝土抗冻性能改善效果最好,且经300次冻融循环后,质量损失率和相对动弹性模量分别为2.32%和91.32%,抗压强度和劈裂抗拉强度分别下降了16.40%和26.12%;活化煤矸石粉能填充、细化孔隙,且其二次水化能消耗水泥水化产物Ca(OH)₂,产生C-S-H和C-A-S-H,提升水泥石密实程度,改善孔结构,使大孔占比减少。     

Aerobic deterioration in maize silage stored in a bunker silo under farm conditions in a subtropical climate

Whole maize plants at the milk and dough maturation stages were ensiled in August and October 1984, for periods of 45 and 40 days, respectively. Thirteen net bags containing herbage samples were buried at different locations within the silo to determine changes and losses during the conservation period. Thermocouple wires and small-diameter plastic pipes were connected to every bag for temperature and gas measurements. Air penetration in the upper layer was much faster than in the inner parts. Losses in dry matter of 3.9-7.4% were found in well sealed sites in the bunkers, and of up to 36% at locations where air penetrated. The rate of air penetration into the silage and temperature at various sites in the bunker were recorded. Correlation between CO₂, and N₂, contents in the silage was very high (r² = 0.995) whereas oxygen levels were close to zero.     

Risk-based life-cycle maintenance strategies for corroded reinforced concrete buildings located in the region with high seismic hazard

In this study, several developed models have been adopted to investigate deterioration induced by chloride ingress by considering uncertainty in order to estimate the initiation and rate of corrosion. Besides, the structural capacity and serviceability of RC buildings, i.e. the shear capacity, bending strength and width of cracking or spalling of columns and beams with corroded reinforcing bars, were also calculated using simple formulas developed from previous experiments. Based on the information of annual spalling/cracking and failure probabilities, the deterioration risk of an RC building attacked by chloride can be evaluated using the concept of reliability of a series system. In order to find the optimal maintenance plan, probabilistic effect assessment models for repair/retrofit strategies (five repair/retrofit strategies were selected) that consider the recurrence of deterioration in repaired areas and the deterioration proceeding in unrepaired areas were developed in this research. These models reflect the effects of the maintenance strategies on the failure and spalling probability directly and can be used to estimate the life-cycle performance and cost of RC buildings. Finally, on the basis of the minimal life-cycle cost, the optimal life-cycle maintenance strategy can also be identified by using the genetic algorithm; case studies were used to discuss the applicability of this system.     

The relationship of silage temperature with the microbiological status of the face of corn silage bunkers

A method is proposed to quantify aerobic deterioration of corn silage forage quality as related to the temperature of silage mass in the bunker. Aerobic deterioration, apart from causing nutritional value losses, affects the hygienic quality of silages through the accumulation of pathogenic organisms and their toxins. A survey was carried out in northern Italy that involved a detailed examination of silage bunker from each of 54 dairy farms. Samples from the core, the peripheral areas within 1 m from the silo walls, and the molded spots, when present, were collected. The sample and silage temperatures across the working face were measured at depths of 200 mm at 11 locations and at 7 elevations. The temperature of the central zone of the silo was defined as the reference temperature (T_ref40). The difference between the temperature of the silage sample and the T_ref40 was used as a heating index associated with aerobic deterioration (dT_ref40). The working face area with visible molds was measured. The samples were analyzed for DM content; pH; water activity; nitrates; lactic, acetic, and butyric acids; and microbiological count of yeasts, molds, and clostridia spores. The core samples always showed a pH below 4.0 and a dT_ref40 below 2°C, whereas the silages from the peripheral areas were split into 2 groups, one that had a pH lower than 4 and a dT_ref40 lower than 3.5°C (53%) and one that had a pH higher than 4 and a dT_ref40 higher than 5°C (47%). Most of the silages from the peripheral areas (94%) and all the silages from the moldy spots that have a dT_ref40 above 5°C had a pH higher than 4.5. Furthermore, a positive dT_ref40 higher than 5°C corresponds to a higher yeast count than 5 log cfu/g in most of the silages from the peripheral areas (93% of samples) and in almost all the silages from the molded spots. The evaluation of the extension of the visible molded areas combined with temperature measurement at 200 mm behind the feed-out face could offer a good indication of the health status of silage during consumption. Furthermore, this method could be useful to detect early stages of the aerobic deterioration process and to improve silage management.     

Effect of gelatin dip on the oxidative and colour stability of cooked ham and bacon pieces during frozen storage

Summary Samples of cooked ham and bacon were dipped in water or 2, 4 or 6% gelatin solutions. Samples were then packed in oxygen permeable or vacuum packaging film and stored at −18 °C for seven months. Lipid oxidation (TBARS) and colour stability (Hunter a* values) were assessed monthly. The gelatin coating exerted beneficial effects on oxidative and colour stability.     

Testing for reliability improvement or deterioration in repairable systems

This paper reviews the derivation and application of the reverse arrangement test which is used to assess whether a system has improved or deteriorated in a reliability sense. Because the well-known and published table of statistics for this test is erroneous, the prime objective of this paper is to provide the correct statistical table. A secondary aim, however, is to demonstrate how this table can be applied when there is a paucity of failure data for each individual system and to show how a more meaningful reliability assessment can be obtained by pooling results, from the reverse arrangement test, for several systems.     

Improvement of partial discharge (PD) resistance of epoxy resin by using sulfur-containing additives

In the field of high-voltage engineering, it has been desired for a long time to improve the internal PD resistance of epoxy resin without lowering other properties. Recently, the authors discovered that some sulfur compound as curing agents or simple additives improved the PD resistance of rubber markedly, and here an attempt has been made to apply this fact to the case of epoxy resin. As was expected, some sulfur compounds containing SS-bond suppress the deterioration of epoxy resin due to internal partial discharges, and the larger the molecular weight of organic group combining the SS-bond, the longer the effective life of additives. Moreover, to make full use of these additives, it is very important to restrict moisture in the insulation systems. From this study, the authors have proposed the chemical formulation of the suppressive effect of additives for deterioration of epoxy resin due to internal partial discharges.     

Comparison of the contribution of formaldehyde and lipid oxidation products to protein denaturation and texture deterioration during frozen storage of minced ice-fish fillet (Champsocephalus gunnari and Pseudochaenichthys georgianus)

Fillets of the ice-fish Champsocephalus gunnari and Pseudochaenichthys georgianus were minced and mixed with various additives to induce the formation of formaldehyde and oxidation of lipids. The mixtures were frozen and stored for several months and protein denaturation and changes in texture were measured. Samples containing high concentrations of formaldehyde were very tough in texture. However it was found that even severe lipid oxidation (up to 14 mg of malonaldehyde per kg wet mass) had only a slight influence on texture.     

中国城市建设的可持续发展问题分析

在大量调查、分析与研究的基础上，结合中国经济发展中城市快速发展面临的一系列地质灾害，采用自然科学与社会科学相互交叉的方法。分析了城市地质灾害的危险性及对城市发展的影响，根据中国城市发展的实际情况和2001年以后的远景目标，因地制宜地提出了整治城市地质灾害的基本对策与管理措施，为国家在制定城市发展远影规划和奋斗，目标提供基本思路。