新疆天然骨料粉煤灰混凝土抗渗性研究

新疆混凝土工程天然骨料料源丰富,水工混凝土骨料几乎全部采用天然骨料,针对这一特点,结合当地原材料情况,通过实验探讨了影响新疆天然骨料粉煤灰混凝土抗渗性的主要因素,提出了天然骨料粉煤灰混凝土提高抗渗性的最大水胶比和粉煤灰掺量上限值等指标。     

最简有效关联规则及其挖掘算法

传统关联规则挖掘算法往往会产生过多规则而难以被决策者所采用。针对该问题,文章从应用的角度提出了最简有效关联规则,其特点是采用以后项为导向的挖掘方式,同时追求规则前后项之间的相关性,在此基础上给出了一种最简有效关联规则挖掘算法。利用该算法得到的最筒有效关联规则集包括的规则数量大为减少且能得出与全部有效关联规则集相同的决策,避免了大量的冗余挖掘及无效挖掘,提高了挖掘效率和应用效果。     

一种电力故障录波数据压缩算法的研究

电力系统故障录波数据是分析电网故障的主要依据,录波数据压缩有益于减小数据存储容量和提高数据传输效率。针对电力故障录波数据的格式及构成特点,提出了一种基于傅里叶变换和小波包变换的数据压缩新算法。采用离散傅里叶变换对录波模拟量通道的B时段数据进行压缩和重构,根据重构误差判断该通道是否为故障通道;对故障通道的暂态扰动时段采用小波包变换进行压缩,对正常通道及故障通道的其他时段采用傅里叶变换进行压缩。大量录波文件的压缩结果和工程实际应用表明,所提算法可以同时获得很高的压缩率和压缩精度,具有广阔的应用前景。     

Assessment of the MODIS LAI product for Australian ecosystems

The leaf area index (LAI) product from the Moderate Resolution Imaging Spectroradiometer (MODIS) is important for monitoring and modelling global change and terrestrial dynamics at many scales. The algorithm relies on spectral reflectances and a six biome land cover classification. Evaluation of the specific behaviour and performance of the product for regions of the globe such as Australia are needed to assist with product refinement and validation. We made an assessment of Collection 4 of the MODIS LAI product using four approaches: (a) assessment against a continental scale Structural Classification of Australian Vegetation (SCAV); (b) assessment against a continental scale land use classification (LUC); (c) assessment against historical field-based measurement of LAI collected prior to the Terra Mission; and (d) direct comparison of MODIS LAI with coincident field measurements of LAI, mostly from hemispherical photography. The MODIS LAI product produced a wide variety of geographically and structurally specific temporal response profiles between different classes and even for sub-groups within classes of the SCAV. Historical and concurrent field measurements indicated that MODIS LAI was giving reasonable estimates for LAI for most cover types and land use types, but that major overestimation of LAI occurs in some eastern Australian open forests and woodlands. The six biome structural land cover classification showed some significant deviations in class allocation compared to the SCAV particularly where grasslands are allocated to shrubland, savanna woodlands are allocated to shrubland, savanna and broadleaf forest, and open forests are allocated to savanna and broadleaf forest. The land cover and LAI products could benefit from some additional examination of Australian data addressing the structural representation of Eucalypt canopies in the “space of canopy realisation” for savanna and broadleaf forest classes.     

基于三菱FX3U系列PLC与MR-J2S-A的通信控制

针对三菱FX3U系列PLC与MR-J2S-A伺服系统的通信方式,对PLC与伺服通信系统之间的系统构成作了介绍,详细描述了MR-J2S-A的通信参数设定及分析其通信数据格式,介绍了MR-J2S-A三菱伺服系统通信控制试运行的流程,实现了FX3U系列PLC对MR-J2S-A伺服系统通信方式的运行控制、参数的修改和监视等功能。     

Microbial polymers in the aquatic environment—II: Isolation from biologically non-purified and purified municipal waste water and analysis

Soluble organic substances in primary and secondary effluents were concentrated by vacuum distillation and the polymers with molecular weights > 10,000 were isolated by dialysis and lyophilization. A concentrated solution of polymers from the secondary effluent was treated by ion-exchange and adsorption chromatography in order to fractionate the polymers into four groups: basic (7.6%), neutral (28.5%), light yellow acid (46.4%) and dark brown acid (14.2%). All isolated and fractionated polymers contained sugars, amino sugars, uronic acids and amino acids. The sum of these compounds, as determined photometrically amounted to 32.8–77.3% of the volatile fraction of the polymers. It has been found that both primary and secondary effluents contain microbial polymers originating in the sewer and in the aeration tank during the waste water purification. Biodegradability tests confirmed that the polymers are refractory having the BOD rate constant of 0.03 d⁻¹.     

Biological reactor resistance to inhibition

The phenomenon of complete substrate conversion within biological reactors in the presence of toxic compounds, called the Reactor Resistance to Inhibition (RRI), has been investigated. It was theoretically demonstrated that the RRI value, which means the highest concentration of inhibitor by which complete substrate conversion is possible, depends on liquid detention time. The excess detention time over that required for complete conversion, imply the existence of a “reserve” reaction potential. The value of this “reserve” can be reduced by inhibitor action with no influence on the observed substrate conversion rate. The influence of detention time on biological denitrification in Packed Bed Reactors in the presence of chromium Cr⁶⁺ was investigated. The RRI value for 1 h detention time was 1.5 mg l⁻¹ Cr⁶⁺. For 3 h detention time the RRI value was 22 mg l⁻¹ Cr⁶⁺. The relationship between the RRI value and detention time was linear.     

Inactivation des virus dans l'eau sur une filiere de production a ozonation etagee

The removal and inactivation of indigenous viruses for individual water treatment processes were investigated both in a pilot (3 m³ h⁻¹) and a full-scale (4000 m³ h⁻¹) plant, treating water from the Seine and Oise rivers respectively.Viruses were recovered by the previously described methods of adsorption-elution using electronegative Balston filters (Joret and Block, 1981) for the pilot plant study or alternatively using either electronegative or electropositive 1 MDS Cuno filters (Sobsey and Glass, 1981) for the full-scale water supply.Depending on the efficiency of filtration, the volumes of water samples concentrated directly in the field varied from 30 to 100 litres for raw, preozonated, stored river water and decanted water, and from 550 to 1000 litres for treated water downstream from the clarification step. BGM cells were used for virus detection by the plaque assay method.During this study, the initial virus concentration in the Seine river water entering the pilot plant, varied from 190 to 1420 PFU/1000 l. The virus removal observed after coagulation-flocculation with 35–50 g m⁻³ of water aluminum chloride (WAC) (a basic aluminum chloride) and settling, was 31–90% effective (130–390 PFU/1000 l. of decanted water), and did not exceed 1–2 logarithms after sand filtration at a rate of 5 m h⁻¹ (83% of 600–800 samples were positive for viruses, maximum concentration = 80 PFU/1000 l.).The preozonation of river water (0.8 ppm during 2–3 min without residual oxidant) inactivated 64–97% of viruses (maximum viral concentration in preozonated water being 300 PFU/1000 l.). Under these conditions, no viruses could be isolated from samples of 550–1000 litres of sand filtered water.The treatment process for the industrial water supply located at Mery sur Oise was preozonation (0.5–1 ppm for 1 min), storage, coagulation-flocculation, settling, sand filtration, second stage ozonation (1.4–1.6 ppm for 10 min, residual oxidant: traces to 0.3 ppm), activated carbon filtration, postozonation (0.4 ppm free residual for 4 min) and chlorine dioxide (0.1 ppm). Nine series of samples were taken after various stages of treatment and tested for viruses. All samples of raw river water yielded positive results with relatively low numbers (10–146 PFU/1000 l.) compared with the number of enterovirus in the Seine river.The efficiency of preozonation before storage could not be evaluated in this study due to its intermittent operation. Enteroviruses were found in 83% of samples after storage (7–100 PFU/1000 l.), 77% after settling and 55% after sand filtration (3–10 PFU/1000 l.). Enteroviruses were not detected after the second stage ozonation in any of the nine samples. The subsequent postozonation and final treatment with chlorine dioxide serves as an additional barrier to ensure virologically safe drinking water.During studies on pilot and full scale water treatment plants, viral isolates are as follows: ECHO virus (49 and 37% respectively), coxsackie B virus (42 and 49% respectively) and poliomyelitis virus (9 and 14% respectively).     

Cadmium in edible crabs (Cancer pagurus L.) from Scottish coastal waters

Concentrations of cadmium in the hepatopancreas (0.1–61.3 mg kg⁻¹), gonad (0.15-11.0 mg kg⁻¹) and gills (0.2–10.7 mg kg⁻¹) of the edible crab Cancer pagurus L. from 16 sampling sites round the Scottish coast are reported, and compared with published elevated concentrations in crabs from the Orkney Islands. Geographical variations in the distribution of cadmium between organs indicate that the dietary uptake of cadmium is predominant in northern mainland and Orkney crabs, but that uptake from the water is more important in the south of Scotland. Mean dissolved cadmium concentrations in eastern coastal water increase from ∼10 ng dm⁻³ in northern waters to ∼25 ng dm⁻³ in the south. It seems likely that a regional contamination of the environment by cadium of geological origin occurs in the extreme north coast of Scotland, and in the Orkney and Shetland areas.     

Effects of Tearing Conditions on the Crack Propagation in a Monolayer Graphene Sheet

The path of crack propagation in a graphene sheet is significant for graphene patterning via the tearing approach. In this study, we evaluate the fracture properties of pre-cracked graphene during the tearing process, with consideration of the effects of the aspect ratio, loading speed, loading direction, and ambient temperatures on the crack propagation in the monolayer sheet. Some remarkable conclusions are drawn based on the molecular dynamic simulation results, i.e., a higher loading speed may result in a complicated path of crack propagation, and the propagation of an armchair crack may be accompanied by sp carbon links at high temperatures. The reason for this is that the stronger thermal vibration reduces the load stress difference near the crack tip and, therefore, the crack tip can pass through the sp link. A crack propagates more easily along the zigzag direction than along the armchair direction. The out-of-plane tearing is more suitable than the in-plane tearing for graphene patterning. The path of crack propagation can be adjusted by changing the loading direction, e.g., a rectangular graphene ribbon can be produced by oblique tearing. This new understanding will benefit the application of graphene patterning via the tearing approach.