Sediment-associated metals levels along the sewer-natural treatment wetland continuum,Phnom Penh,Cambodia

Sediment deposited within open sewers of Phnom Penh and the natural wetland that treats the waste was sampled and analyzed by X-ray fluorescence (XRF). Mean levels of Pb, Zn (P < 0.05), and Cu (P = 0.08) were greater in the sewer samples than the wetland, while As was not different (P>0.2), and Mn was greater (P < 0.06) in the wetland. Pb, Cu, and Zn levels generally were lower at the wetland outlet and in quiescent areas, suggesting deposition occurs along the sewer/wetland continuum. Background (natural) levels of Mn and As are higher in soils/sediments of this region and levels in the wetland likely reflect these background levels than enrichment from anthropogenic activity. Although 60% of all metals levels in the wetland samples exceeded USEPA threshold effect concentrations, results of recent studies that analyzed fish and vegetables from the wetland showed a small health risk associated with consumption. The XRF was a good tool for environmental analysis in a developing country.     

使用θ-θ/Ψ测角仪测定钢中残余奥氏体的原理与方法

介绍了X射线衍射法测定钢中残余奥氏体含量的原理。给出了使用θ-θ/Ψ测角仪测定钢中残余奥氏体的方法,并通过实例阐述了测试技术要点和注意事项。     

In situ evaluation of dynamic precipitation during plastic straining of an Al-Zn-Mg-Cu alloy

The coupling between precipitation and plasticity has been systematically investigated in an Al-Zn-Mg-Cu alloy using in situ small-angle X-ray scattering measurements during thermomechanical tests. Material pre-aged to two different initial precipitate conditions has been examined. Each pre-aged condition has been strained at 160 °C and we show that the plasticity induces an accelerated coarsening kinetics, which we characterize in terms of the evolution of the precipitate size. This acceleration is correlated with the degree of plastic strain, but does not depend markedly on strain rate. The experimental data strongly suggests that the accelerated kinetics is mainly linked with the accumulation of a supersaturation of vacancies during plastic flow that increases the effective diffusion constant.     

Electrical disintegration and micro-focus X-ray CT observations of cement paste samples with dispersed mineral particles

Electrical disintegration is an effective liberation technique in mineral processing where the liberation ratio depends on the mineralogical properties of the mineral grains. However elucidation of the liberation behavior is difficult since the fragments after the electrical disintegration are fine and complex. This study applies electrical disintegration to cement paste samples with various dispersed mineral particles (calcite, quartz, albite, and pyrite) and the disintegrated products are observed with a micro-focus X-ray CT scanner. Current channels and crack extension behavior from the channels are identified by cross sectional CT and three dimensional reconstructed images. A classification of the crack patterns was carried out and compared with the results of liberation ratio measurements of the products.     

Crystal structure and thermoelectric properties of Cu2Cd1−xZnxSnSe4 solid solutions

Cu₂Cd_1–xZn_xSnSe₄ solid solutions were synthesized, and their phase constitutions and thermoelectric properties were investigated. The solid solutions crystallized in the stannite-type structure for Zn contents x up to 0.65 and in the kesterite-type structure for 0.7 ≤ x ≤ 1.0. The lattice parameter a and cell volume V of the compounds decreased linearly with increasing x for both the stannite-type (0 ≤ x ≤ 0.65) and the kesterite-type (0.7 ≤ x ≤ 1) structures. The lattice parameter c decreased with increasing x for the compounds with the kesterite-type structure but increased for the compounds with the stannite-type structure. The c/a ratio increased with increasing Zn content, which indicated an weakening of the lattice distortion. The Seebeck coefficient tended to decrease with increasing Zn content, whereas the electrical conductivity and thermal conductivity increased. The figure of merit ZT increased with increasing x over the composition range of 0 ≤ x ≤ 0.60 and then fluctuated with a further increase in x. A maximum ZT of 0.23 was achieved for Cu₂Cd_0.4Zn_0.6SnSe₄ at 720 K.     

变频节能技术在山煤国际澄蓉选煤厂的应用

随着国家对环保、节能降耗要求的提高,以重介工艺为主的选煤厂大力响应国家的环保政策,实现节能降耗。山煤国际能源澄蓉选煤厂对合格介质泵304(450 kW)、精磁泵328(200 kW)、中矸泵(90 kW)、浮选入料泵402(185 kW)、循环水泵604(200 kW)等大功率电机(占全厂总容量33.3%)采用美国圣诺变频器进行调控,仅电能一项每年就为公司节省了近200万元。采用变频器来控制大功率的泵类设备,还可以降低电机的噪音污染、减少管路阀门的机械磨损、延长泵的使用寿命,节省了人力和物力。     

Boundary-based object segmentation in X-ray imaging using spiral search

In this paper, we propose a boundary-based method for object segmentation by using only the edge information. The proposed method is especially applied to object segmentation of dangerous firearms and knives in the X-ray images of baggage, where no colour or texture features are available to describe the target object. The Canny edge detector is used to extract edge points from the X-ray image. These edges have cluttered backgrounds and may be discontinuous. A fast spiral search is proposed to connect neighbouring points, either continuous or discontinuous, and form closed contours for individual objects. The distance and direction angle of an edge point in the search process can be obtained from a pre-constructed spiral look-up-table. No computation of the geometric features is required. Thus, the search of the coherent neighbouring points for edge connection is very fast. The experimental results have shown that the proposed method can effectively and efficiently segment a variety of firearms and knives of different shapes and sizes in the X-ray images of baggage.     

Nanocomposites of triazole functionalized multi-walled carbon nanotube with chemically grafted polyimide: preparation,characterization, and properties

In order to improve the dispersion of multi-walled carbon nanotubes (MWCNTs) in polyimide (PI) matrix and the interfacial interaction between MWCNTs and PI, 3,5-diamino-N-(1H-[1,2,4]triazol-3-yl)-benzamide (DTB)-functionalized MWCNTs (DTB-MWCNTs) were synthesized by amidation reaction. The DTB-MWCNTs were analyzed by several techniques. DTB-MWCNTs were used as a platform for the grafting of a DTB-based PI in N,N′-dimethylformamide solution with different loadings of DTB-MWCNTs to produce PI-grafted MWCNT (PI-g-MWCNT) composites. The thermal, mechanical, and electrical properties of the PI-g-MWCNT composites were improved compared with PI due to the homogeneous dispersion of DTB-MWCNTs and strong interfacial covalent bonds between DTB-MWCNTs and the PI chain.     

Effect of NOx on AgI formation in Ag-mordenite

Ag loaded mordenite can be used as a trap for radio-iodine arising from nuclear reprocessing operations. Typically, iodine is trapped in the Ag loaded mordenite by the formation of AgI in the pores of the mordenite, through a solid-vapour reaction. In the presence of NO_x and water vapour, AgI is most likely formed by liquid-vapour reaction between AgNO₃ and I₂. This reaction results in the formation of large aggregates of AgI crystals on the surface of the mordenite, also leading to a yellow colouration of the mordenite, which is not observed when NO_x and water vapour is absent.     

The control of spontaneous emission from a three-level atom in an anisotropic photonic crystal with two asymmetric bands

We theoretically investigate the spontaneous emission light of an excited three-level atom embedded in an anisotropic photonic crystal with two asymmetric bands. The property of spontaneous emission relating to the atomic position in a unit cell of the crystal is described with a position-dependent phase difference. The atomic transition in free space can be manipulated by the other associated transition coupling to photonic crystal. The result shows that the spontaneous emission spectra are effectively shifted and tuned by the atomic position-dependent phase, which results in the asymmetric distribution of the photonic density of states between two bands, and the increasing band can push the emitted light towards the other band. The physical process can be further illuminated through analyzing the emitted field in photonic crystal. The result perhaps offers an interesting route towards tunable photonic devices.