Taking Qinling, Ann River lead-zinc mining area and ore dressing area as the research scope,through field investigation and sampling surface water and sediments,this paper tested 5 heavy metals' contents,including Cu,Pb,Zn,Cd and Cr,by atomic absorption spectroscopy(AAS),and determined the form contents of the heavy metal.The enrichment and migration of heavy metals in surface water and sediments were analyzed to give the comprehensive assessment of heavy metal pollution degree.The results showed that:the surface water and sediments of mine channel had been seriously polluted,which the heavy metal elements accumulated from upstreatn to downstream.Heavy metal content in downstream was out of the range of field irrigation water quality.The pollution indexes of sediments in mid-downstream were Ⅲ grade,the main pollutants were Pb and Zn.In sediments,the available heavy metals had a higher proportion,which showed direct injection characteristics and caused direct threat to environment.
Dynamic compression experiments on cubic polymethyl methacrylate (PMMA) specimens and two kinds of trapezoid PMMA specimens are carried by changing the transmission bars into steel bar and aluminum bar on the experimental device of split Hopkinson pressure bar (SHPB). The compression processes of PMMA specimens are recorded by high-speed photography, and the breakage processes of PMMA specimens are analyzed based on the force displacement curves and high-speed images. The evolutions of deformation and diffusion resistances of PMMA specimens under impact loading are discussed. The results show that the failure of the sample is caused mainly by the partial failure front at the contact end, and then the failure front propagates to the inside of the sample, s leading the sample to break. The failure front of cubic sample is generated preferentially at the transmission end under low speed impact and at the incident end under the higher speed impact. After changing the shape of the specimen and the material of the transmission bar, the relaxation phenomenon is prominent, and the failure front occurs only at the incident end. The compressive deformation of the trapezoid sample before breakage is non-uniform, and the stress and strain in the sample gradually decrease with the increase of the cross section, and show a linear diffusion distribution. The strain distribution and shear activation diffusion equation are used to obtain the generalized diffusion resistance distribution of the failure front. The generalized diffusion resistance increases first in front of the failure front and decreases after the failure front, and the amplitude of the generalized diffusion resistance is related to the release of local strain energy.
The Duobaoshan area is located in Zhalantun-Duobaoshan island arc tectonic belt in the eastern section of Xing'an-Mongolian orogenic belt, with the Early Paleozoic geological bodies developed and closely related to regional mineralization. The formation age, tectonic setting and mineralization are discussed based on the study of petrography, lithogeochemistry and isotopic chronology of the Middle Ordovician intrusive rocks in Duobaoshan area. The LA-MC-ICP-MS zircon U-Pb age of granodiorites is 488±3 Ma, indicating that the granodiorites were formed in the Middle Ordovician. The magma source is mainly mantle origin with some crust-derived materials. With intensive tectonic thermal events and magmatic intrusion-eruption activities, a large number of deep fluids bring metallogenic elements such as Au and Cu to form Duobaoshan Cu-Mo deposit under favorable minerogenetic conditions and expanded space.
taiwan1 In order to investigate the influence of different explosives type on the blasting effects, three kinds of explosives with the same quality were used to carry out blasting test on iron ore samples. The fractal dimension of surface crack and fragment size distribution of specimens were comparatively studied, and then the damage degree and blasting effects of specimens were quantitatively compared and evaluated. At the same time, the differences of blasting effects are analyzed theoretically from the angle of explosion stress wave superposition, energy release and energy transfer. The results show that: (1) Both loose charge and mixed charge will cause the uniformity of the explosion stress field distribution to deteriorate; (2) The greater the explosion heat, the greater the energy released after explosion; the higher the wave impedance matching, the higher the energy transfer efficiency after explosive explosion; (3) In the selection of explosives in blasting engineering, three parameters of explosive including density, explosion heat and detonation velocity should be considered; Explosives with a high degree of wave impedance matching and appropriate explosion heat should be selected so that the bulk and small pieces generated after blasting are less.
The corrosion of metals can be induced by different environmental and operational conditions, and protecting metals from corrosion is a serious concern in many applications. The development of new materials and/or technologies to improve the efficiency of anti-corrosion coatings has attracted renewed interest. In this study, we develop a protective coating composed of a bilayer structure of reduced graphene oxide (RGO)/graphene oxide (GO) applied to Cu plates by spray-coating and subsequent annealing. The annealing of the GO/Cu plates at 120 ℃ produces a bilayer structure of RGO/GO by the partial reduction of the spray-coated GO layer. This induces superior corrosion resistance and adhesion strength compared to those of GO/Cu and RGO/Cu plates because of the hydrophobic nature of the RGO surface exposed to the surroundings and the formation of Cu-O bonds with the O-based functional groups of GO. This approach provides a viable and scalable route for using graphene coatings to protect metal surfaces from corrosion.
We explore the coherent perfect absorption of light in a nonlocal metal-dielectric composite film in which metallic nanoparticles (gold) are randomly embedded in the dielectric host medium (silica). The two coherent light beams illuminate the gold-silica composite slab respectively from the left and right sides at the same angle of incidence and the conditions required for coherent perfect absorption are investigated each as a function of different system parameters. Under different system parameters, we study the coherent perfect absorption of a nonlocal particle composite medium. A nonlocal effective medium theory is proposed to approximately describe the metal-dielectric composite film. The effective permittivity and effective permeability of the composite medium are approximated by using the effective medium theory under the model of coated sphere with core and shell. According to the effective dielectric parameters of the composite medium, we can obtain the transmission coefficient and reflection coefficient of the plan wave incident on the slab. By comparing and analyzing the coherent perfect absorptions of the composite medium under nonlocal and local conditions, we find that under the influence of nonlocal effect when the size of particle is very small, the frequency range of incident light that produces the coherent perfect absorption of the composite medium increases and the small size can also cause the coherent perfect absorption to occur in wider frequency range. Especially, we pay attention to the choosing of physical parameters in the design of coherent perfect absorption with macroscopic composite slab when we take the nonlocal effect (or spatial dispersion) into account. In the further calculation, the coherent perfect absorption of the composite medium can be realized by changing the system parameters such as the thickness of composite slab, the wavelength of incident light, the volume fraction of metal particles, etc. We also bring about the coherent perfect absorption at a small volume fraction which satisfies all the conditions. Finally, according to these results, we can realize the control of the coherent perfect absorption with nonlocal effect. Huaniushan map-sheet, Gansu, has been developed basically in accordance with DD 2019-02 Technical Specification for Mineral Geological Survey (1:50 000), guided by the “trinity” survey area prospecting prediction theory, building on original data and information from the previous 1:50 000 regional geological survey on Huaniushan map-sheet, sGansuB (including original data map, profile and record book) and applying fully new results from this 1∶50 000 mineral geological mapping of the Huaniushan map-sheet. The latest geographical data from the National Survey and Mapping Geographical Information Bureau are used in the geographical base map. Existing technical standards and computer software such as the digital mapping system (DGSS) and MapGIS are applied for data processing.
Trapping sets significantly influence the performance of low-density parity-check codes. An $ (a, b) $ elementary trapping set (ETS) causes high decoding failure rate and exert a strong influence on the error floor of the code, where $ a $ and $ b $ denote the size and the number of unsatisfied check-nodes in the ETS, respectively. The smallest size of an ETS in $ (3, n) $-regular LDPC codes with girth 6 is 4. In this paper, we provide sufficient conditions to construct fully connected $ (3, n) $-regular algebraic-based QC-LDPC codes with girth 6 whose Tanner graphs are free of $ (a, b) $ ETSs with $ a\leq5 $ and $ b\leq2 $. We apply these sufficient conditions to the exponent matrix of a new algebraic-based QC-LDPC code with girth at least 6. As a result, we obtain the maximum size of a submatrix of the exponent matrix which satisfies the sufficient conditions and yields a Tanner graph free of those ETSs with small size. Some algebraic-based QC-LDPC code constructions with girth 6 in the literature are special cases of our construction. Our experimental results show that removing ETSs with small size contribute to have better performance curves in the error floor region.
I11111ncreasing atmospheric CO2 concentration leads to ocean acidification, which might affect phytoplankton to varying degrees. Phytoplankton in coastal waters may be affected by seawater acidification and alkalization. In this experiment, Thalassoosira punctigera (diatom) was used to investigate its growth, photosynthesis, dark respiration, cell size, chlorophyll a content, biogenic silica content and chlorophyll fluorescence at seven pCO2 levels (25, 50, 100, 200, 400, 800, 1600 μatm). The results showed that, compared with 400 μatm, the growth rate and chlorophyll a content in seawater acidification (pCO2 > 400 μatm) and alkalization (pCO2 < 400 μatm) treatments were significantly reduced, but the degree of decrease was greater under the condition of alkalization. In addition, cells showed lower photosynthesis rates and maximum quantum yield of PSII (Fv/Fm) and relative maximum electron transport rate (rETRmax) under alkalization conditions. However, there was no significant changes in biogenic silica content and cell size among different pCO2 levels. We found both seawater alkalization and acidification could inhibit the physiological activities of T. punctigera, and seawater alkalization had much more inhibited effects. Our results showed that the cell grown at current pCO2 level (400 μatm) had the optical physiological performance. Moreover, among the pCO2 levels set in this study, seawater alkalization has a more significant effect on T. punctigera. The present study provides a theoretical basis for studying the effects of changing seawater carbonate chemistry on the marine primary productivity in coastal waters.
Broadband and omnidirectional antireflection coating is generally an effective way to improve solar cell efficiency, because the destructive interference between the reflected and incident light can maximize the light transmission into the absorption layer. In this paper, we report the incident quantum efficiency
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