Thermal Generation of Residual Stress Fields for Purpose of Distortion Minimization

Thermal treatments of steel components with the goal of hardening often result in distortion by releasing the residual stresses which were brought into the specimen during the preceding processing steps. The goal of the presented work is the minimization of this distortion. By generating definite residual stress fields and investigating the resulting distortion, the distortion mechanism can be observed in detail. A flexible and reproducible way to generate such residual stress fields inside a specimen is by means of local thermal treatment with a laser beam. Computer simulations as well as experiments were carried out using an idealized tooth of a gearwheel (finger sample) as a model system. The deformation of the samples due to the laser heat treatment and the stress fields generated inside the samples were determined with respect to different process parameters.     

Influence of the silicon surface treatment by plasma etching and scratching on the nucleation of diamond grown in HFCVD - a comparative study

A comparative study for the nucleation of diamond was carried out using surface treatment like (i) surface scratching with 1 μm diamond paste and (ii) surface etching using chlorine plasma at different RF powers (50, 100 and 150 W). Atomic force microscopic study shows variation in roughness from 31 nm to 110 nm. Scratching results in random scratches, whereas plasma etches a surface uniformly. Scanning electron microscopic observations show well faceted crystallites with a predominance of angular shaped grains corresponding to 〈100〉 and 〈110〉 crystallite surfaces for the scratched as well as plasma etched substrate. Surface etching at 150 W plasma power results in a better growth in comparison with 50 and 100 W plasma powers. Chlorine-radical is found responsible for the changes in the growth morphology. Raman spectroscopy shows a sharp peak at 1,332 cm⁻¹ and a peak at ∼1,580 cm⁻¹ for both samples.     

Electrokinetic remediation of soils contaminated with heavy metals

This paper describes the results obtained from an electrokinetic treatment of a real soil polluted by lead acetate. Powdered soil samples were pressed with a consolidometer till 100 kPa to obtain cylindrical specimens with the same characteristics as a subsoil. Tests were carried out in a Perspex electrochemical cell where soil specimens were introduced with a hollow punch. A low intensity direct current was applied in order to remove contaminants, due to electrophoresis and electroosmosis phenomena. The water flow, conductivity, apparent electroosmotic coefficient, as well as other characteristic parameters, were measured throughout the test. The water content and degree of pore saturation were estimated at the beginning and end of the test. The soil slab was divided into four slices and the Pb concentration profile determined. The main factor governing the extraction of contaminant was found to be the pH in the acidic range. Indeed, under these conditions high removal efficiencies could be reached. These results could lead to the design of a new electrochemical treatment cell equipped with a cationic membrane to expand the region of favourable pH within the soil.     

Sequentially Enhanced Electrokinetic Remediation of Heavy Metals in Low Buffering Clayey Soils

This paper presents the results of an experimental investigation undertaken to evaluate different purging solutions to enhance the removal of multiple heavy metals, particularly chromium, nickel, and cadmium, from a low buffering clay, specifically kaolin, during electrokinetic remediation. Experiments were conducted on kaolin spiked with Cr(VI), Ni(II), and Cd(II) in concentrations of 1,000, 500, and 250 mg/kg, respectively, which simulate typical electroplating waste contamination. A total of five different tests were performed to investigate the effect of different electrode purging solutions on the electrokinetic remedial efficiency. A constant DC voltage gradient of 1 V/cm was applied for all the tests. The removal of heavy metals from the soil using tap water as the purging solution was very low. When 1 M acetic acid was used as the purging solution in the cathode, the removal of chromium, nickel, and cadmium was increased to 20, 19, and 13%, respectively. Using 0.1 M ethylene diamine tetraacetic acid as the purging solution in the cathode, 83% of the initial Cr was removed; however, the nickel and cadmium removal was very low. A sequentially enhanced electrokinetic remediation approach involving the use of water as a purging solution at both the anode and cathode initially, followed by the use of acetic acid as the cathode purging solution and a NaOH alkaline solution as the anode purging solution was tested. This sequential approach resulted in a maximum removal of chromium, nickel, and cadmium of 68–71, 71–73, and 87–94%, respectively. This study shows that the sequential use of appropriate electrode purging solutions, rather than a single electrode purging solution, is necessary to remediate multiple heavy metals in soils using electrokinetics.     

Lipid damage in farmed rainbow trout (Oncorhynchus mykiss) after slaughtering and chilled storage

The flow ice system including ozone (OFI condition) was tested for slaughtering and storage (up to 16 days) of farmed rainbow trout (Oncorhynchus mykiss). Lipid damage analyses were carried out and compared to sensory acceptance and instrumental colour changes. Comparison to individuals processed with the flow ice system in the absence of ozone (FI condition) was undertaken. Rainbow trout slaughtered and chilled under FI and OFI conditions showed a low lipid damage development, according to lipid oxidation and hydrolysis events and lipid composition (polyunsaturated fatty acids, phospholipids and endogenous antioxidants) changes. Additionally, both icing conditions led to largely good quality and shelf life times and to the absence of changes in colour properties. It is concluded that flow ice as such, or including the presence of ozone, can be considered as ideal strategy to be employed as slaughtering and storage system during the commercialisation of the actual farmed species. The ozone presence has shown some profitable effects as leading to an extended shelf life time by quality retention of several sensory parameters; in contrast, some negligible negative effects could be observed on the secondary and tertiary lipid oxidation development. However, the oxidation values reached by individuals kept under OFI conditions cannot be considered as particularly high.     

夜视系统鉴别率测试的新方法

用室内低光照高对比鉴别率取代野外探测目标距离作为衡量夜视系统性能优劣的标准,将给验收工作带来方便。本文给出一种实验室内测试夜视系统鉴别率的方法。文中导出了夜视系统鉴别率的一种新的表达式,从而提出了一种改进后的物理模型及其实验方案。分析表明,采用新方案,即在实验室中人为增加环境照度,由此测得的系统工作鉴别率,用以取代野外探测目标距离,其可信度可望得到明显的提高。     

基于GRNN网络模型的土壤重金属空间分布的研究

以江苏省南通市为研究区,利用采样点实测数据,借助GRNN神经网络模型并结合3S技术对农田土壤重金属的空间动态分布进行了深入研究。结果表明,GRNN神经网络模型能够智能地学习各个采样点的空间位置与该点各重金属含量之间的映射关系,并能够稳健地对各个空间插值点处的土壤重金属含量进行预测;结果显示南通市农田土壤重金属污染总体较轻,但也存在局部地区的严重污染。在运用GRNN神经网络模型进行空间插值了解重金属空间动态分布的基础上,可以根据污染的状况确定农产品的生产布局和规划。     

计算机在热处理工艺编制中的应用

利用计算机强大的数据处理功能 ,对热处理工艺中的各种数据进行记录和处理 ,并制成各种图表 ,掌握其中的各种规律。使热处理工艺的编制不再是一种经验积累式的工作 ,而是依照其规律制定一次合格的规范的热处理工艺卡片 ,并为将来计算机工艺自动生成的工作打下基础     

膜淤塞对微滤的油水分离性能的影响

本文报道了用微滤分离乳化含油废水的研究，利用微滤过程中膜淤塞的特点，显著地提高了油水的分离效率，同时维持较高的水透过率。文章讨论了油水分离的机理，并根据实验结果提出流体中适当的油粒粒径分布，是获得较好分离效果的重要条件。本研究表明了在一定下，可以用水透过率较高、操作成本降低的微滤取代超滤。     

Engineering practice and economic analysis of ozone oxidation wet denitrification technology

SO₂ and NO emitted from coal-fired power plants have caused serious air pollution in China. In this study, a test system for NO oxidation using O₃ is established. The basic characteristics of NO oxidation and products forms are studied. A separate test system for the combined removal of SO₂ and NO_x is also established, and the absorption characteristics of NO_x are studied. The characteristics of NO oxidation and NO_x absorption were verified in a 35 t·h^-1 industrial boiler wet combined desulfurization and denitrification project. The operating economy of ozone oxidation wet denitrification technology is analyzed. The results show that O₃ has a high rate and strong selectivity for NO oxidation. When O₃ is insufficient, the primary oxidation product is NO₂. When O₃ is present in excess, NO₂ continues to get oxidized to N₂O₅ or NO₃. The removal efficiency of NO₂ in alkaline absorption system is low (only about 15%). NO_x removal efficiency can be improved by oxidizing NO_x to N₂O₅ or NO₃ by increasing ozone ratio. When the molar ratio of O₃/NO is 1.77, the NO_x removal efficiency reaches 90.3%, while the operating cost of removing NO_x per kilogram is 6.06 USD (NO₂).