A hybrid process for manufacturing surgical-grade knife blade cutting edges from bulk metallic glass

The demand for precision surgical knives is enormous. Currently, diamond knives have been the preferred choice among surgeons for use in precision surgeries, owing to the extreme hardness of diamond and the sharpness that can be achieved in single crystal diamond blades, but material and processing costs are high. Bulk metallic glass (BMG) has the potential to be an economically viable material of similar performance for use in precision surgical knives. To this end, a novel hybrid manufacturing process integrating thermally assisted micro-molding and micro-drawing has been developed for producing BMG surgical-grade knife blade cutting edges with edge radii <50 nm. A hybrid process testbed was designed and used to successfully run tests over a range of the key process variables. Through this testing the deformation of BMG under different strain rates and temperatures was studied in terms of the quality of edge formation. The hybrid process was shown to be capable of producing cutting edges of radius at or below 100 nm.     

Rotary ultrasonic machining of potassium dihydrogen phosphate (KDP) crystal: An experimental investigation on surface roughness

Potassium dihydrogen phosphate (KDP) crystal, widely used for important electro-optic parts, is a typical hard-to-machine material because of its soft, brittle, and anisotropic properties. High quality is usually required for machined surfaces on KDP parts. Reported machining methods for KDP crystal include diamond turning, grinding, magnetorheological finishing, and polishing. Each of these methods has its limitations. Therefore, it is desirable to develop new machining methods for KDP crystal. This paper presents an experimental investigation on surface roughness in rotary ultrasonic machining (RUM) of KDP. It was found that the surface roughness obtained when using a tool with a chamfered corner was lower than that obtained using tools with right-angle corners. Other process variables (spindle speed, feedrate, and ultrasonic power) also affected the surface roughness obtained.     

Mathematical model for abrasive content estimation in a pulse-electroplated abrasive microtool

A mathematical model was developed to estimate the weight percent of diamond abrasive particles incorporated in nickel binder matrix during abrasive microtool fabrication by pulse-plating process. The proposed model is based on the hypothesis that, embedment of an inert micro abrasive diamond particle on the substrate will only occur when a few nickel ions from the adsorbed ionic cloud are chemically reduced at the cathode by hydrogen ions present in the diffusion layer. Experimental verification of the model developed was performed by pulse electroplating of diamond abrasive particles on tungsten micro tool shank using an in-house built experimental setup. The predictive model developed was found to estimate diamond abrasive content in nickel binder matrix within 1–7 wt% of experimental results for different pulse-plating conditions.     

Nitrogen source-receptor matrices and model results for eastern Canada

The long-range transport sulphur/nitrogen model of the Atmospheric Environment Service of Environment Canada was used to compute nitrogen source-receptor matrices for 1980 at 12 receptor sites in eastern Canada and 3 in the eastern U.S.A. There were 40 emission regions used to produce the 40 × 15 matrices of concentration and deposition of nitrogen species. The model used nonlinear chemical reactions and the nonlinear effects could be estimated by running each emission region regions combined. For wet deposition the nonlinear effects were less than 10%. For the total annual deposition (wet and dry), the nonlinearity was less than 5%.At each receptor, the matrices showed the contribution to nitrogen concentration and deposition from each emission region. The Canadian contribution to nitrogen concentration/deposition was greatest at Gander, Newfoundland (60–70%) and least at Algoma, Ontario (7–12%). Of the total North American emissions, Canada contributed about 8–9%. Model results that were compared to the limited amount of observed data showed reasonably good agreement (within factors of 2–3).In spite of the model nonlinearities, deficiencies and uncertainties, these matrices provide a first quantitative estimate of the magnitude and relative contributions of Canadian and U.S. source regions to the nitrogen concentration and deposition at several receptors in eastern Canada.     

Tool wear of coated drills in drilling CFRP

This study aimed to investigate the wear of certain coated drills when drilling carbon fiber reinforced composites (CFRP). Three different drills were used in the drilling experiments: uncoated, diamond coated and AlTiN coated carbide (WC–Co) drills. The tool wear in CFRP machining was quite different from that in conventional metal machining. The primary wear type was a dulling or blunting of the cutting edge, which has been referred to as edge rounding wear or edge recession. In this paper, a hypothesis has been developed to explain the edge rounding wear in CFRP machining. Due to the fracture-based chip formation of CFRP, there is lack of the work material stagnation zone in front of the cutting edge, which normally prevents the edge wear in metal machining. Series of wear lead to rapid dulling of the cutting edge. The resistance to edge rounding wear on the coated as well as uncoated drills has been investigated. The diamond coating significantly reduces the edge rounding wear. However, AlTiN coated drills showed no visible improvement over the uncoated carbide drill, despite of their high hardness, thus not protecting the drill. The wear mechanisms of the uncoated carbide drill and coatings are discussed. It is believed that the 2-body and 3-body abrasive wear fail to explain the observed tool wear in CFRP drilling. However, the wear of the coatings and uncoated carbide substrate from tribo-meter tests correlated well with the tool wear in the CFRP drilling. Therefore, the tribo-meter test can be used to screen the prospective tool materials before carrying drilling experiment.     

AFM probe based nano mechanical scribing of soda-lime glass

In recent years, demands for miniature components have increased due to their reduced size, weight and energy consumption. In particular, brittle materials such as glass can provide high stiffness, hardness, corrosion resistance and high-temperature strength for various biomedical and high-temperature applications. In this study, cutting properties and the effects of machining parameters on the ductile cutting of soda-lime glass are investigated through the nano-scale scratching process. In order to understand the fundamentals of the material removal mechanism at the atomic scale, such as machined surface quality, cutting forces and the apparent friction, theoretical investigation along with experimental study are needed. Scribing tests have been performed using a single crystal diamond atomic force microscope (AFM) probe as the scratching tool, in order to find the cutting mechanism of soda-lime glass in the nano-scale. The extended lateral force calibration method is proposed to acquire accurate lateral forces. The experimental thrust and cutting forces are obtained and apparent friction coefficients are deduced. The effects of feed rates and the ploughing to shearing transition of soda-lime glass have been investigated.     

磁性氧化石墨电催化活性及净化印染废水效能

采用高铁酸钾作为铁前驱体和氧化剂氧化石墨矿物,原位合成磁性氧化石墨(MGO)催化剂.磁性氧化石墨与碳黑(CB)混合在碳纤维布基底上制备阴极(MGO/CB),将溶解氧还原生成活性氧(ROS)氧化处理含活性红X-3B染料的模拟废水,并采用扫描电子显微镜、X-射线衍射仪、X-射线光电子能谱、电化学手段表征磁性氧化石墨催化剂的...     

A comparative study of the interaction between microhole sidewall and the plasma generated by nanosecond and femtosecond laser ablation of deep microholes

High-aspect-ratio microholes have many industrial applications, but are difficult to produce. Femtosecond (fs) and nanosecond (ns) laser ablation may produce potential manufacturing solutions. However, the laser-induced plasma–microhole sidewall interaction has not been well understood for laser ablation of deep microholes, which may significantly affect the hole size and/or quality. This interaction has been investigated in this paper. Due to the huge challenges involved in direct experimental observations, a physics-based model is applied as the research tool, which has been verified by measurements from literatures on laser ablation of flat targets (without deep microholes) that are relatively easy to perform. The study shows that under the same laser pulse fluence, the fs laser-induced plasma generates larger transient peak heat flux to the sidewall than the ns laser pulse. However, the high-heat-flux region moves up very rapidly in the hole, and hence the sidewall temperature is not significantly raised and sidewall melting does not occur under the studied conditions. On the other hand, for the ns laser pulse, the induced plasma maintains a relatively high heat flux to the sidewall near the hole bottom for a much longer time, which yields obvious sidewall melting and surface vaporization. The results are consistent with the previously observed sidewall surface morphology for microholes drilled by fs and ns laser pulses in air with the same pulse energy.     

Aero-lap polishing of poly crystalline diamond inserts using Multicon media

Increasing use of poly crystalline diamond (PCD) inserts as cutting tools and wear parts is vividly seen in automobile, aerospace, marine and precision engineering applications. The PCD inserts undergo series of manufacturing processes such as: grinding that forms the required shape and polishing that gives a fine finish. These operations are not straight forward as PCD is extremely resistant to grinding and polishing. Single crystal diamond can easily be polished by choosing a direction of easy abrasion, but polishing a PCD imposes serious difficulties as the grains are randomly oriented. Prior research on polishing of PCD inserts includes electro discharge grinding (EDG), dynamic friction polishing and grinding by a vitrified bonded diamond wheel. The surface textures of PCD produced using an EDG process often contains: micro cavities, particle pullout, micro-grooves, chipped edges, cracks and gouch marks. While applying the dynamic friction polishing method the PCD material undergoes phase transformation and hence increased polishing rate was apparently seen. However the phase transformation of PCD deteriorates the strength of the insert. Furthermore the inserts produced using the dynamic polishing method often exhibits cracks, chip off and edge damage while using as a cutting tool. Therefore, a new method “aero-lap polishing” was attempted as it applies controlled amount of impinging force by which the surface damage can be significantly reduced. The study did establish an improvement of surface finish of PCD from R_a = 0.55 μm, R_t = 4.5 μm to R_a = 0.29 μm, R_t = 1.6 μm within 15–25 min of polishing time along with significant reduction in surface defects.     

Orthogonal machining of single-crystal and coarse-grained aluminum

Orthogonal machining of single-crystal and coarse-grained (i.e., grain size considerably larger than the uncut chip thickness) materials has been a subject to many studies in the literature. The first part of this paper presents background on machining single-crystal materials, including experimental and modeling attempts. The second part briefly describes more recent modeling results from the authors, and presents new experimental results on planing and plunge-turning of single-crystal and coarse-grained aluminum using diamond tools. The experiments indicate that (1) cutting across grains of a coarse-grained aluminum workpiece produces distinctly varying forces and surface roughness from one grain to another, (2) plunge-turning and planing of single crystal aluminum provide equivalent force data for large rake angles, (3) forces alter between two distinct levels while cutting single crystals with small rake angles, and (4) with small rake angles, subsurface damage on single-crystal aluminum is extensive, reaching depths comparable to the uncut chip thickness.     

Recovery of Cu and Fe from Printed Circuit Board waste sludge by ultrasound: Evaluation of industrial application

The paper presents a novel cleaner process for metal recovery from the Printed Circuit Board (PCB) waste sludge by assistance of ultrasound. The process can effectively recover heavy metals at low cost with high separation and recovery efficiency, produce high quality products and also achieve zero waste discharge with operation at industrial scale. With the PCB waste sludge containing (wet content) 3.14–4.85% copper and 3.71–4.23% iron, copper recovery efficiency of 95.2–97.5% and iron recovery efficiency of 97.1–98.5% were achieved, while the purity of copper sulfate produced by the process was 98.0% and the produced ferric chloride had a satisfied quality for using as a coagulant material for the plant on-site wastewater treatment. The process had been successfully scaled up to the industrial scaled applications in a heavy metal recovery plant in city of Huizhou, China for more than two years. The novel cleaner heavy metal recovery process has a great prospect on the applications of resources recovery and environmental protection practices.     

中国旅游业绿色发展效率时空演变特征及影响机理

绿色发展是旅游业可持续发展理念的重要组成部分,是旅游业奉行以人为本、生态至上和全面发展的新价值观。在梳理旅游业绿色发展概念及内涵基础上,构建旅游业绿色发展效率评价体系,运用SBM-Undersirable模型、核密度估计、空间马尔科夫链等方法,探讨2008—2018年中国31个省（市、自治区）旅游业绿色发展效率（TGDE）时空演化特征及影响机理。研究发现：（1）时间和空间变化方面,TGDE总体处于中等偏下水平,时间上呈“W”型变化形态,“下降—上升—调整”阶段特征显著;空间呈“东—中—西”递减分布,内部差异为西部地区>东部地区>中部地区,低、中、高效率由“金字塔”向“菱形”结构转变,高效率地区集中于东部沿海,中等效率多分布于中西部地区,低效率位于胡焕庸线两侧。（2）动态演进方面,TGDE始终存在两极分化现象,但区域协调性逐步增强,具有较强平稳性,难以实现跨越式发展,空间向上转移省份比较集中,以中西部为主,向下调整省份较少,且存在明显的空间溢出效应,溢出影响具有不对称性。（3）影响机理方面,总体上,经济水平、产业结构、政府规制、教育水平和旅游资源影响因子与TGDE间存在显著的正向关系,对外开放程度的作用不显著,但各因子的影响程度、作用机理及条件具有较强地域性。     

论石材工业废渣中人造金刚石的回收

人造金刚石是锯切石材最理想的材料。通过对锯片金刚石脱落及金刚石在废渣中赋存状态的分析，论述从废渣中回收金刚石的必要性、可能性和客观条件；利用金刚石特有的物理化学性质及其与造岩矿物之间的物性差异，采用筛分祛清洗废渣、矿物分离、金刚石提纯、选形分级等方法，可获得纯度为99％以上的人造金刚石，回收率可达10％一15％；通过对回收金刚石强度的测定和再利用，证明完全具有重新使用价值。从废渣中回收人造金刚石的方法可靠，工艺合理，成本约占产值的30％左右，具有较好的社会经济效益。在国内外属首创的回收入造金刚石方法具有良好的推广应用价值。     

Human Enteric Viruses in Groundwater

Waterborne outbreaks of enteric viruses are a major public health concern. The present study has been carried out to assess the presence of enteric viruses responsible for human acute gastroenteritis (AGE) in groundwater intended for drinking and produce washing. In total, 62 samples from groundwater for drinking and produce washing collected from Dec 2007 to Dec 2008 in Seoul were tested for enteric viruses using conventional RT–PCR, ELISA, and real-time RT–PCR. Our results showed that enteric viruses were detected in 7 (8.8%) groundwater samples. Rotaviruses were detected in 3 (4.8%) of the samples by ELISA; human adenoviruses were detected in 2 (3.2%) of the samples by ELISA; and nested RT–PCR detected noroviruses in 2 (3.2%) of the samples. In one of the groundwater sample, the norovirus RNA was detected by conventional RT–PCR which was confirmed positive by real-time RT–PCR. Additionally, real-time RT–PCR successfully detected norovirus RNA in five out of 62 water samples (8.1%). The data demonstrate that real-time RT–PCR will be useful as a rapid and sensitive method for detecting norovirus in water samples. Phylogenetic analysis revealed that the noroviruses detected in two of the groundwater samples belonged to GII-4. These studies can provide important information for the prevalence of enteric viruses in Korean groundwater.     

汽车排气管焊缝断裂的失效分析

某汽车用排气管使用不久焊缝处断裂。对失效排气管焊缝进行化学成分、金相组织和断口的微观分析。发现该排气管焊缝柱状组织粗大,断口微观形貌为沿晶断裂,柱状晶贯穿整个断裂面,断口有较明显的脆性特征。分析认为该排气管属于早期失效,是由于薄壁的排气管焊接时温度过高,导致焊缝柱状组织粗大,加之薄壁管冷却又快,致使焊缝产生较大的内应力。建议改进焊接工艺,控制较低的层间温度,使焊缝组织细化,解决焊缝断裂问题。     

Enhanced struvite recovery from wastewater using a novel cone-inserted fluidized bed reactor

The feasibility of struvite recovery at low （12.5 mg/L） and high （120 mg[L） phosphorus concentrations was studied by constructing a novel fluidized bed reactor with cones （FBRwc） and without cones （FBRwoc）. The crystallization process was continuously operated for 133 days under different hydraulic retention times （HRT = 1-10 hr）, pH （7.5-10）, and molar ratios of Mg/P （0.75-1.75）, N/P （1-10） and Ca/Mg （0-2）. The optimum operating conditions of HRT, pH, Mg/P and N/P molar ratios were found to be 2 hr, 9, 1.25, and 7.5, respectively. Under these optimum conditions, the phosphorus precipitation efficiencies of FBRwc were 93% for low and 98% for high phosphorus influent; however, the efficiencies were 78% and 81% for FBRwoc, respectively. Due to crystal losses at each junction （17%-31%）, the crystal recovery efficiency of FBRwoc was relatively low （47%-65%） for both influent concentrations. However, the losses were minimal in FBRwc, which showed 75% and 92% crystal recovery for low and high phosphorus concentrations, respectively. At low calcium concentration, crystal chemical analysis showed the product to be pure struvite （〉 99%）. The scanning electron microscope and X-ray diffraction results further confirmed that the crystal recovered from FBRwc contained pure struvite, which could be considered a high quality fertilizer. Except HRT, all parameters （pH, Mg/P, N/P and Ca/Mg） were found to be influencing factors for FBRwc performance. Overall, inserting cones in each part of the reactor played a significant role in enhancing struvite recovery from a wide range of phosphorus-containing wastewater.     

New developments in diamond geology

New occurrences of kimberlite are reviewed together with the occurrences of diamond in nonkimberlitic volcanic rocks, in xenoliths within kimberlite and in orogenic peridotites occurring within fold mountain belts; and the various types of inclusions found within diamonds are then reviewed. Various arguments for the two main hypotheses of diamond formation (phenocrystal v. xenocrystal) are presented and it is concluded that diamonds are not precipitated from ascending melts. It is also concluded that diamond may form in a wide range of chemical environments and that the speed of ascent for the preservation of diamond during its ascent to the surface from its stability field depth is perhaps not as important as formerly believed.     

A streamlined life cycle assessment on the fabrication of WC–Co cermets

Tungsten carbide–cobalt (WC–Co) cermets have been widely used because of their high hardness and excellent wear-resistant properties. In this study, the environmental burdens related to WC–Co component fabrication were evaluated to compare the Laser Engineered Net Shaping (LENS^®) process and the conventional powder metallurgy (P/M) process. Sensitivity analysis revealed that choice of weighting scheme does not significantly affect the final result; the LENS^® process is more preferable if powder recycling is applied, part size is small, or part shape is complex; and the P/M process provides more benefits to produce large parts of simple shape.     

华南板块的内部结构和原生金刚石的地质意义

华南板块的构造格局与太平洋板块和印度板块的共同作用相关.华南板块中,由于绍兴-鹰潭-藤县-北海断裂带内中元古代蛇绿混杂岩的确认并恢复为消减的大洋,其两侧古老的扬子地块和华夏地块及其演化历史的追溯也日见清晰.它们是在两个克拉通地块基础上发展起来的.1998年在浙江省龙游首次发现的原生金刚石,产于这条深断裂旁侧白垩纪盆地中的似金伯利岩岩管内,含矿岩管生成深度大,构造部位有利;金刚石呈八面体外形、纯度高;类似的岩管有100多个,但研究程度较低,因而具有良好的找矿前景.     

脱色酶TpmD在大肠杆菌中的高效表达及纯化

用PCR方法从嗜水气单胞菌DN322基因组中扩增出编码三苯基甲烷类染料脱色酶TpmD的基因,与表达载体pET-22b(+)连接构建成重组质粒pET22-tpmD,转化大肠杆菌BL21(DE3)得到重组工程菌株.结果表明,经IPTG诱导,脱色酶基因可高效表达,粗酶液降解结晶紫、孔雀石绿、碱性品红、灿烂绿的比活力达到569.5,386.9,516.1,273.0U/g.表达产物经Ni-NTA亲和层析法一步纯化,蛋白纯度达94.05%.对4种染料的比活力分别达到1075.3,1042.8,903.9,484.3U/g,重组质粒稳定存在于工程菌中,便于规模化发酵生产.