陕西汉中出土商代四足铜鬲的科学分析研究

陕西汉中曾出土大量商代青铜器,其中城固县龙头出土的一件商代四足铜鬲,造型独特,纹饰精美,是迄今所见唯一一件。分析了该器物的化学成分、金相组织和铅同位素比值。结果表明,该四足铜鬲为高铅铅锡合金,铸造成型;微量元素中银的含量较高,可能由铅矿引入;其铅同位素比值为商代常见的高放射成因铅,所用铅矿的产地与郑州、盘龙城、殷墟等遗址出土铜器相同,说明与商文化存在密切的关系。并从合金技术和铅同位素比值的角度讨论了汉中四足铜鬲的年代和来源。     

Bioinspired Multifunctional Cellular Plastics with a Negative Poisson’s Ratio for High Energy Dissipation

Cellular plastics have been widely used in transportation, aerospace, and personal safety applications owing to their excellent mechanical, thermal, and acoustic properties. It is highly desirable to impart them with a complex porous structure and composition distribution to obtain specific functionality for various engineering applications, which is challenging with conventional foaming technologies. Herein, it is demonstrated that this can be achieved through the controlled freezing process of a monomer/water emulsion, followed by cryopolymerization and room temperature thawing. As ice is used as a template, this method is environmentally friendly and capable of producing cellular plastics with various microstructures by harnessing the numerous morphologies of ice crystals. In particular, a cellular plastic with a radially aligned structure shows a negative Poisson’s ratio under compression. The rigid plastic shows a much higher energy dissipation capability compared to other materials with similar negative Poisson’s ratios. Additionally, the simplicity and scalability of this approach provides new possibilities for fabricating high-performance cellular plastics with well-defined porous structures and composition distributions.     

Bacterial source tracking from diverse land use catchments by sterol ratios

Water samples from sites potentially impacted by septic tanks, cattle, sewage treatment plant (STP) and natural forests were collected at regular monthly intervals and within 48 h of rainfall events between October 2004 and June 2006. All samples (n=296) were analysed for faecal coliforms and faecal sterols including coprostanol, epicoprostanol, cholestanol, cholesterol and 24-ethylcoprostanol. Faecal sterol ratios were used to assign human and/or herbivore contamination sources and to estimate their percentage relative contributions in water samples. The catchments had significantly different profiles of designated contamination origins (p<0.05), which were consistent with land use patterns. The STP impacted site had the highest incidence of human contamination assignations and the highest mean levels of coprostanol, whilst the forested site had the highest incidence of uncontaminated samples and the lowest mean concentration of coprostanol. Coprostanol concentrations were not always correlated with faecal coliform counts.     

Relationship between outdoor and indoor air quality in eight French schools

In the frame of the French national research program PRIMEQUAL (inter-ministry program for better air quality in urban environments), measurements of outdoor and indoor pollution have been carried out in eight schools in La Rochelle (France) and its suburbs. The buildings were naturally ventilated by opening the windows, or mechanically ventilated, and showed various air permeabilities. Ozone, nitrogen oxides (NO and NO(2)), and airborne particle (particle counts within 15 size intervals ranging from 0.3 to 15 mum) concentrations were continuously monitored indoors and outdoors for two 2-week periods. The indoor humidity, temperature, CO(2) concentration (an indicator of occupancy), window openings and building permeability were also measured. The temporal profiles of indoor and outdoor concentrations show ozone and nitrogen oxides behave differently: NO and NO(2) indoor/outdoor concentration ratios (I/O) were found to vary in a range from 0.5 to 1, and from 0.88 to 1, respectively, but no correlation with building permeability was observed. On the contrary, I/O ratios of ozone vary in a range from 0 to 0.45 and seem to be strongly influenced by the building air-tightness: the more airtight the building envelope, the lower the ratio. Occupancy, through re-suspension of previously deposited particles and possible particle generation, strongly influences the indoor concentration level of airborne particles. However, this influence decreases with particle size, reflecting the way deposition velocities vary as a function of size. The influence of particle size on deposition and penetration across the building envelope is also discussed by analyzing the I/O ratios measured when the buildings were unoccupied, by comparing the indoor concentrations measured when the buildings were occupied and when they were not (O/U ratios), and by referring to previously published studies focussing on this topic. Except one case, I/O were found to vary in the range from 0.03 to 1.79. All O/U are greater than one and increase up to 100 with particle size. PRACTICAL IMPLICATIONS: Assessing children's total exposure requires the knowledge of outdoor and indoor air contaminant concentrations. The study presented here provides data on compared outdoor and indoor concentration levels in school buildings, as well as information on the parameters influencing the relationship between outdoor and indoor air quality. It may be used as a basis for estimating indoor concentrations from outdoor concentrations data, or as a first step in designing buildings sheltering children against atmospheric pollution.     

The Synthesis of Polymer Supports

Conventional polymer supports (polymeric reagents, functional polymers) such as polyacrylamides and polystyrene are based on either strongly polar or nonpolar chemical structures. As a result, these polymers may show low reactivity and poor performance due to their relatively limited ranges of solvent and substrate compatibility. More-recently introduced products are designed on the basis of copolymer structures, which incorporate both polar and nonpolar (hydrophilic and hydrophobic) residues and possess general solvent and substrate compatibility. Due to their ease of production, general solvent and substrate compatibility and improved performance, these new “amphiphilic” copolymers provide new impetus in the study and applications of polymer supports and functional polymers.     

Insights into the Organotemplate-Free Synthesis of Zeolite Catalysts

As the most important nanoporous material, zeolites, which have intricate micropores, are essential heterogeneous catalysts in industrial processes. Zeolites are generally synthesized with organic templates under hydrothermal conditions; however, this method is environmentally unfriendly and costly due to the formation of harmful gases and polluted water. This article briefly summarizes the role of organic templates and describes designed routes for the organotemplate-free synthesis of zeolites, aided by zeolite seeds and zeolite seeds solution. Furthermore, this review explicates that the micropore volume decreases with an increase of the Si/Al ratios in the organotemplate-free synthesis of zeolite products, where Na⁺ exists as an alkali cation. This feature is very important in directing the synthesis of zeolite catalysts with controllable Si/Al ratios under organotemplate-free conditions, and is thus important for the efficient design of zeolites.     

An evidential analysis of Altman Z-score for financial predictions: Case study on solar energy companies

Altman Z-score has been a well-accepted model of predicting survivals and failures of manufactures since 1968. However, short of an underpinning theory causes a wide gap between asking and responding sides, which still has no effective solution. This research proposes a rough set approach to inducing granular evidence and solving evidential coefficients of financial ratios for the distressed companies. Empirically, the proposed approach is applied to a financial database, Taiwan Economic Journal, to analyze the solar energy industry during 2009–2014. The result shows the inferential evidence successfully serves as a basis for financial analysis and discloses that the profit efficiency of the distressed companies in Taiwan's solar energy industry had been declining.     

EnergIoT: A solution to improve network lifetime of IoT devices

Internet of Things (IoT) is a novel paradigm attracting significant attention in the modern wireless telecommunications field. However, in some scenarios, the performance of IoT network is limited by energy-constrained devices. In order to improve the energy efficiency of such IoT devices, researchers have proposed several approaches based on duty cycle operation (switching devices between sleeping and active mode). However, current solutions adopting duty cycle (i.e., the fraction of time in which a node is active) have three issues: (i) they assign the same duty cycle ratio to all the nodes without balancing energy consumption; or (ii) they distribute different duty cycle ratios without considering the energy consumption during network construction phase; or (iii) their network structure models are based on concentric corona, instead of clustering structure.In this paper, we propose EnergIoT, a hierarchical clustering approach based on duty cycle ratio to maximize network lifetime of battery-powered IoT devices. In particular, we assign different duty cycle ratios to devices according to their distance from the sink, since different duty cycle ratios balance the energy consumption among devices at different layers. Furthermore, we calculate the energy consumption of IoT devices, considering both network construction phase and data processing phase. We evaluate EnergIoT through extensive simulation analyses on the OMNet++ platform. The result shows that EnergIoT is not only feasible but also efficient. Moreover, EnergIoT improves the network lifetime by 32%, compared to the uniform duty cycle approach, without sacrificing the network performance (i.e., end-to-end delay).     

Effects of equivalence ratios on the normal and inverse diffusion flame of acid gas combustion in the pure oxygen atmosphere

The experimental studies on the effect of equivalence ratios to the acid gas (H₂S and CO₂) combustion in the pure oxygen atmosphere was presented in a coaxial jet double channel burner. Three equivalence ratios (Φ = 0.8, 1.0 and 1.5) are examined to analyze the distribution of the flame temperature and gas composition in the normal and inverse diffusion flame along central axial (R = 0.0) and axial line at 3 mm (R = 0.75) in radial direction. The results revealed that acid gas combustion mainly occurred chemical decomposition of H₂S and oxidation of H₂S and H₂ at R = 0.0, while mainly occurred H₂S and H₂ oxidation at R = 0.75 in the normal diffusion flame. Reducing Φ increased the flame temperature and it is higher at R = 0 than that at R = 0.75 because of heat loss. It also increased the volume fraction of CO, H₂ and COS in the flame combustion area, while decreased downstream reactor because of occurring oxidation. CO was formed by the reaction of CO₂ and H, and H₂ primarily derived from chemical decomposition of H₂S. COS was generated by the reaction of CO₂ with SH, H₂S and S as well as the reaction of CO with SO and SH at R = 0.0, while was mainly formed by the reaction of CO with SO and SH at R = 0.75. H₂S mainly occurred the oxidation in the inverse diffusion flame. The temperature at R = 0.0 was still higher than that at R = 0.75, and it was higher than that in the normal diffusion flame in the combustion area. Increasing Φ promoted the formation of CO, H₂ and COS, and each gas under Φ of 1.5 was higher significantly. The Φ had no significant effect on the distribution of SO₂ compared to the normal diffusion flame, but changed the distribution of CO, H₂ and COS. It can be inferred that the content of CO, H₂ and COS will be more higher under Claus condition in the inverse diffusion flame.     

A simplified method of computing the effectiveness of tests in selection.

The Taylor-Russell method of predicting the number of successful workers, for various validities and selection ratios, is compared with a direct method in which the number successful is predicted from the data used to obtain the validity coefficient. Four sets of data are presented in which the predicted percent successful is compared with the percent actually successful, as determined from follow-up groups. "While the average errors of the Taylor-Russell method were… slightly less than the average errors of the direct method, the differences were small." (PsycINFO Database Record (c) 2010 APA, all rights reserved)