Determination of smoldering time and thermal characteristics of firebrands under laboratory conditions

The laboratory experiment was conducted to simulate the transfer of smouldering particles produced in forest wildfires by a heated gas flow. The pine bark pieces with the linear dimensions L=(15; 20; 30) mm and a thickness of h=(4−5) mm were selected as model particles. The rate and temperature of the incident flow varied in the range of 1–3 m/s and 80–85 °C, respectively. The temperature of the samples was recorded using a thermal imager. To determine the minimum smouldering temperature of pine bark, the thermal analysis was conducted. The minimum smouldering temperature of pine bark was found to be 190 °C. This temperature will cause thermal decomposition of bark only at the first stage (oxidation of resinous components). In the study the smouldering time, the temperature and the weight of samples were obtained and analyzed under various experimental conditions. The data analysis shows that the increase in the particle size leads to the decrease in their mass loss, and the rate change of the incident flow does not practically influence the mass change. For particles with the linear dimensions of 10 mm and 20 mm, the mass varies from 6% to 25%. The maximum mass loss is observed for the flows with a rate of 1 and 2 m/s. The results have shown that the increase in the particle size leads to the increase in the smouldering time. The position of the particle plays an important role, the effect of which increases with increasing the particle size. The calculations showed that the smouldering time of bark samples is long enough for the particles to serve as new sources of spot fires. The particles were found to be transported to a distance of 218 m from the fire line which can certainly influence the propagation of the fire front.     

Cadmium kinetics in freshwater clams (Unionidae) under field and laboratory conditions.

Cadmium dosing experiments were carried out with the freshwater clam Unio pictorum in flow-through micro-streams in order to obtain additional information on the kinetics of cadmium accumulation and elimination. Accumulation of cadmium in the kidney was rapid and within 3 weeks a concentration factor of 6000 was found. During elimination (29 weeks), the organs lose about one-third of their cadmium content rather rapidly, but no further elimination occurs. It can be concluded that the process of Cd accumulation is rapid and almost irreversible.     

Adhesion of in situ precipitated calcium carbonate in the presence and absence of magnetic field in quiescent conditions on different solid surfaces

Deposition of in situ precipitated calcium carbonate from Na(2)CO(3) and CaCl2 solutions on different substrates, i.e. stainless steel, copper, aluminium, and glass, was investigated at different temperatures, 20 degrees C, 40 degrees C, 60 degrees C and 80 degrees C, both in the absence and presence of S-S 0.1T magnetic field (MF). It was found that in quiescent conditions during 2h the amounts deposited firmly on the surfaces decreased with increasing temperature. If MF was present the deposition was reduced at all temperatures, and depended on the nature of the substrate. The largest MF effect was found on glass at 60 degrees C, which amounted 50% reduction of the deposit. However, at 80 degrees C no deposition was found in the presence of MF on aluminium surface. At this temperature the reproducibility of the experiments was poor, and an additional effect due to the metal surface corrosion (especially that of aluminium and copper) may be thought in alkaline environment of the experiments (pH ca. 10). Based on optical microscope photographs, it was concluded that the amounts of crystallographic forms of CaCO3 depended on the nature of substrate on which the precipitation and then the adhesion took place. To some extent the ratios of CaCO3 forms precipitated were different in the bulk phase than on the substrate surfaces at the same temperature, and this conclusion was based on the X-ray diffractograms. Some possible mechanisms causing MF effects are discussed.     

烟草行业中地坪材料的选择及应用

本文介绍了烟草行业常用的地坪,着重介绍了耐磨地坪、环氧砂浆地坪和环氧石英石地坪的施工和成品保护。并根据烟厂各区域不同的使用要求,对地坪种类的选择进行了说明。结合贵阳卷烟厂易地技术改造项目,对联合工房地坪进行了选型。     

塑料管材应用现状分析及前景展望

结合工程经验和信息资料,分析了我国塑料管在应用中所存在的一些问题,从原材料的生产、产品结构的调整、管理方法的完善等方面介绍了解决问题的措施,以促进塑料管材健康有序地发展.     

特殊条件下无机玻璃钢风管的应用

深圳市市民中心位于深圳市中心区中轴线上,总建筑面积约21万m^2,建筑总高度约78m,由东、中、西三部分组成,并由大屋顶连成一整体。由于大屋顶主要由中区方、圆两个塔楼支撑,因此其外墙均为承重剪力墙。两塔楼建筑功能为大会堂、档案馆及工业展览馆,空调系统以集中供冷的夏季舒适性空调为主。     

Toxicity and bioavailability of atrazine and molinate to the freshwater fish (Melanotenia fluviatilis) under laboratory and simulated field conditions

Acute (96 h) semi-static toxicity tests were conducted by exposing the freshwater fish, Melanotenia fluviatilis, to atrazine and molinate in laboratory and river water both with and without sediment. The 96-h EC50 (imbalance) values of atrazine to M. fluviatilis ranged from 5.6 to 10.4 mg L(-1) while the corresponding values for molinate ranged from 7.9 to 14.8 mg L(-1), respectively. Atrazine was classed as having moderate toxicity while molinate had low to moderate toxicity to M. fluviatilis. Neither the presence of river water nor sediment significantly (P<0.05) reduced the bioavailability of either herbicide to M. fluviatilis. A series of other studies by the authors have found that sediment significantly (P<0.05) reduced the bioavailability of these two chemicals to a variety of organisms. Reasons for sediment having no effect for this species were examined. This lack of effect by sediment is most likely due to the relative rates of absorption into the fish and adsorption onto the sediment. However, contributions to this outcome by resuspended sediment, contaminated food and a combined effect of the herbicides and sediment could not be excluded.     

谈工地试验室组建及运作中应关注的几个问题

工地试验室在工程施工中起着至关重要的作用,从人员、仪器设备、管理体系建立、运行管理等方面阐述了工地试验室组建、运作中应关注的几个问题,提出只有把工地试验室的工作做好,才能为确保工程质量提供科学、公共的技术服务。     

谈钢纤维在桥面铺装现浇混凝土中的应用

从原材料的选择、配合比设计、施工工艺、质量控制等方面对桥面钢纤维混凝土铺装层进行探讨。     

Biodegradation of urea in river waters under controlled laboratory conditions

The biodegradation of urea in river waters has been evaluated under laboratory conditions. Urea will degrade to ammonia at a rate depending on the bacterial state of the river water and on the water temperature. Under normal conditions no breakdown may be expected to occur at temperatures below 8°C for 14 days contact. In river waters with a high suspended solids content, simulating extreme winter river conditions, a maximum breakdown of 3–6 per cent daily of the original urea levels was found for temperatures not exceeding 8°C during the first 7 days contact.     

Performance comparison of laboratory and field produced pervious concrete mixtures

Portland cement pervious concrete (PCPC) is an environmentally friendly paving material that has been increasingly used in parking lots as well as low volume and low speed pavements. Although specifications are available for the mix design and construction of pervious concrete, there still remains a need for laboratory tests to ensure the anticipated performance of laboratory designed pervious concrete. In this study, the performance of laboratory and field produced pervious concrete mixtures as well as field cores were evaluated and compared through laboratory performance tests, including air voids, permeability, compressive and split tensile strengths, as well as Cantabro and freeze–thaw durability tests. Two types of coarse aggregate, limestone and granite, with two gradings, No. 8 and No. 89 specified in ASTM C33, were used to produce the mixtures. Latex, air-entraining admixture (AEA), and high range water reducer (HRWR) were also added to improve the overall performance of pervious concrete. The results indicated that the mixtures made with limestone and latex had lower porosity and permeability, as well as higher strength and abrasion resistance than other mixtures. Even for pervious concrete, the addition of AEA could still help to improve the freeze–thaw resistance. The comparison between laboratory and field mixtures showed that a properly designed and laboratory verified pervious concrete mixture could meet the requirements of permeability, strength, and durability performance in the field.     

Evaluation of a high-volume portable bioaerosol sampler in laboratory and field environments

This study investigated the physical and biological performances of a portable centrifugal sampler for viable bioaerosols, RCS High Flow. The performance of the test sampler in the laboratory and field environments was compared with that of a reference sampler, BioSampler. The laboratory experiments with non-biological particles of KCl, oleic acid, and polystyrene latex showed that the test sampler's collection efficiency is about 22% for 0.5-microm particles, 48% for 1.0-microm particles, and approximately 100% for particles of 2.5 microm and larger. These tests indicated that the sampler's cut-off size (d50) was 1.1 microm. The test sampler's physical performance when collecting the spores and vegetative cells of Bacillus subtilis var. niger (BG) was similar to that when collecting non-biological particles of the same size. In the laboratory tests, the RCS High Flow sampler was found to enumerate approximately 40% of BG spores and cells relative to the reference sampler, BioSampler. A similar ratio was found during testing in an indoor environment. This ratio decreased to below 10% when testing was performed in an outdoor environment. We hypothesize that the test sampler's underperformance compared with the BioSampler could be caused by the damage to sensitive microorganisms during the collection process, test sampler's sensitivity to wind direction and speed as well as break-up of particle aggregates during the impingement process in BioSampler, which resulted in more colony-forming units (CFUs) being counted by the reference sampler than by the test sampler. Overall, when the RCS High Plus is used to sample culturable airborne microorganisms, the results obtained may have to be adjusted to avoid potential underestimation of microorganism concentration in the air. PRACTICAL IMPLICATIONS: The laboratory testing of the RCS High Flow bioaerosol sampler showed that the sampler collects 1 microm particles and larger with an efficiency of 50% and higher; the efficiency reaches approximately 100% for particles of 2.5 microm and larger. When considering this result, most of the airborne fungal spores would be collected with an efficiency between 50 and 100%. The field testing, however, indicated that the RCS High Flow sampler recovered from 41 to 71% of microorganisms collected relative to the reference sampler, Biosampler, and this ratio dropped to below 5% during outdoor testing. Thus, while the RCS High Flow sampler offers certain advantages over other samplers for viable bioaerosols--it is lightweight, battery operated, and collects viable microorganisms at a high flow rate directly on agar media, the results obtained may have to be adjusted to avoid potential underestimation of microorganism concentration in the air, especially if sampling is performed outdoors.     

室外空气计算参数确定方法的研究

介绍了GB 50736—2012《民用建筑供暖通风与空气调节设计规范》室外空气计算参数的确定方法。重点介绍了该方法与发达国家的差异、气象台站的选择原则及统计期的确定思路,分析了气象数据的变化规律:冬季计算温度呈上升趋势,且变化明显;夏季计算温度大部分城市呈上升趋势,但变化较小,部分城市略有降低。     

实验室条件下淡水藻类生长影响因素研究

为研究淡水藻类生长的最适环境条件和各种环境因素对藻类生长的影响,进行了以水体营养盐、水温和光照为影响因素,以叶绿素a含量为评价指标的正交试验.结果表明,在试验所设定的水平范围内,营养盐浓度、水体温度对淡水藻类生长的影响不显著,光照对淡水藻类生长影响显著;三因素对淡水藻类生长的影响大小排序依次为光照>温度>营养盐浓度;在富营养化水平下,水体营养盐浓度在TN＞1.4 mg/L,TP＞0.1 mg/L的条件下,水体营养盐将不是藻类生长的限制性因素.     

塑胶田径运动场施工工艺和质量控制

结合塑胶田径运动场工程建设实践,针对该类工程工序多、精度要求高的特点,总结介绍了塑胶田径跑道建设工程关键工序的管理和全过程质量控制的内容,通过目的明确、程序清晰、措施有效的质量控制,以达到工程质量创优的目标。     

交通建设工程工地试验室管理现状思考

分析了交通建设工程工地试验室管理工作中存在的一些问题,并提出了解决这些问题的相关措施,为保证交通建设工程的质量奠定了基础。     

环氧自流平地坪质量问题分析及处理

结合工程实例,对环氧树脂自流平地坪出现的质量问题进行了分析,提出了解决方案,通过严格控制施工工艺,在实际工程中达到了良好的效果,该施工工艺值得推广应用。     

Large plastic deformation in plane structures: analysis of finned surfaces under in-plane dynamic loads

An analytical model is presented for characterizing finned surfaces as energy absorbing devices for the protection of nuclear components; in particular large irradiated fuel transport packages. The results obtained are compared with the data obtained in a comprehensive experimental programme carried out on stainless steel fin sections and with the results of numerical calculation performed with the MARC code. The comparison indicated the capability of the model to supply useful data, especially from a practical point of view, for the design of the structure under study.