Active brazed ceramic cemented carbide compound drills for machining lamellar graphite cast iron

The optimum and efficient way of machining is linked to the choice of the most appropriate cutting tool and cutting tool material. High performance cutting ceramics are characterized by excellent hardness properties at elevated temperatures. For this reason, cutting ceramics meet the requirements for machining with high cutting speeds to increase process productivity. Whereas cutting ceramics are widely used in turning and milling operations, their use in drilling processes, using ceramic insert tipped tools, is limited to larger diameter applications due to design restrictions. Beyond small diameters, solid ceramic tools were of negligible interest for industrial applications owing to their excessive tool manufacturing costs. This paper presents a new tool concept which addresses this challenge and permits a more productive machining process for drilling small diameter holes using ceramics as the cutting material. An active brazed compound drill combines the advantageous properties of ceramics and cemented carbide as the cutting tool material and basic holder material, respectively. The investigations presented here describe the manufacturing chain as well as the application of a compound drill, and compares it to a widely used industrial reference tool.     

Five-axis grinding of wear-resistant,thermally sprayed coatings on free-formed surfaces

The abrasive wear resistance of tribologically stressed free-formed surfaces can be increased with thermally sprayed tungsten carbide coatings. In order to improve the surface topographies and shape accuracies, the workpieces must be finished prior to industrial application. A suitable machining process is NC grinding on five-axis machining centres using abrasive mounted points. However, the high hardness of the applied coatings and the small diameter of the utilized tools pose a great challenge for the process design. In this paper both, the results of fundamental investigations on the grinding of tungsten carbide coatings as well as a process optimization for the finishing of a coated forming tool are presented. This includes the heat transfer into the coating and the tool wear during the grinding process as well as the wear behaviour of the coating in dependence of the generated surface topography. In order to achieve a smooth surface, elastic-bonded diamond tools were used during polishing in a multi-stage machining process.     

Does it make sense to modify tropical cyclones? A decision-analytic assessment

Recent dramatic increases in damages caused by tropical cyclones (TCs) and improved understanding of TC physics have led DHS to fund research on intentional hurricane modification. We present a decision analytic assessment of whether it is potentially cost-effective to attempt to lower the wind speed of TCs approaching South Florida by reducing sea surface temperatures with wind-wave pumps. Using historical data on hurricanes approaching South Florida, we develop prior probabilities of how storms might evolve. The effects of modification are estimated using a modern TC model. The FEMA HAZUS-MH MR3 damage model and census data on the value of property at risk are used to estimate expected economic losses. We compare wind damages after storm modification with damages after implementing hardening strategies protecting buildings. We find that if it were feasible and properly implemented, modification could reduce net losses from an intense storm more than hardening structures. However, hardening provides "fail safe" protection for average storms that might not be achieved if the only option were modification. The effect of natural variability is larger than that of either strategy. Damage from storm surge is modest in the scenario studied but might be abated by modification.     

Effect of particle size on arsenic bioaccessibility in gold mine tailings of Nova Scotia

Tailings samples from the Goldenville and Montague abandoned gold mines in Nova Scotia, Canada were subjected to bioaccessibility tests to examine the effects of the choice of particle size fraction on the bioaccessibility of arsenic. The proportion of finer grains (< 150 μm) in this sample set varied from 6.0 to 66 wt.%. Samples were sieved to < 250, < 150, and < 45 μm particle size fractions. The arsenic bioaccessibility ranged from less than 1.0 to 48%, but no systematic variation was observed (p > 0.13) precluding the association of greater percent arsenic bioaccessibility with a specific particle size fraction, method or site. On the other hand, the highest bioaccessible arsenic concentrations (up to 5200 mg kg^− 1) were consistently observed in samples sieved to the < 45 μm particle size, for both the physiologically based extraction test and a glycine-buffered bioaccessibility method (in 89 and 87% of samples tested, respectively). This was due to higher total arsenic concentrations in the same particle size fraction. Grain maps obtained by X-ray absorption spectroscopy indicate that samples with the highest percent arsenic bioaccessibility contain amorphous pentavalent arsenic distributed throughout the sample as well as grains coated with pentavalent arsenic. Arsenic bioaccessibilities lower than 10% were found in samples with encapsulated arsenopyrite and some grains composed primarily of pentavalent arsenic. The < 45 μm particle size fraction appears to yield conservative (protective) estimates of the bioaccessible dose of arsenic, but wide variations exist in particle size distribution and arsenic bioaccessibility between samples. As well, sieving to < 45 μm may exclude potentially relevant particles by restricting the study to an average particle size that is smaller than the average size of particles found on human hands, and may unduly influence the resulting bioaccessibility measurements.     

The Sweetness Concentration‐Response of R,R‐Monatin,a Naturally Occurring High‐Potency Sweetener

Abstract: Monatin, known by the common and usual name arruva, is a zero‐calorie, high‐potency sweetener naturally occurring in the plant Sclerochiton ilicifolius A.Meeuse. The sweetness concentration‐response (C‐R) behavior of the most potent isomer (R,R‐) in room‐temperature (21 °C) water was determined using two‐alternative forced choice discrimination tests with a minimum of 69 tasters. Results were processed by a method previously published to obtain isosweet concentrations of sucrose for 8 monatin concentrations up to 240 mg/L. These were used to construct a C‐R plot. The equation for the resultant hyperbolic curve relating sucrose equivalent (SE,%) to monatin concentration ([monatin], mg/L) was SE = 26.7 ×[monatin]/(69.6 +[monatin]). R,R‐monatin has a potency above 3000 at 5% sucrose equivalent, making it one of the most potently sweet naturally occurring substances known. Practical Application: Monatin is a naturally occurring, zero‐calorie, high‐potency sweetener. We have measured the sweetness of monatin over a range of concentrations. This information will help developers of zero‐, low‐ and reduced‐calorie products formulate with monatin.     

Investigations on the Corrosion Behaviour and Structural Characteristics of Low Temperature Nitrided and Carburised Austenitic Stainless Steel

The wear resistance of austenitic stainless steels can be improved by thermo-chemical surface treatment with nitrogen and carbon. However, it is possible that the corrosion resistance will be impaired by the precipitation of chromiumnitrid or -carbide. The present contribution deals with investigations of the corrosion behaviour and structural characteristics of a low temperature nitrided and carburised austenitic stainless steel.The material investigated was AISI 316L (X2CrNiMol7-12-2) austenitic stainless steel. A commercial plasma-nitriding unit (pulsed dc) was used for the nitriding and carburising process. Additional samples were treated by the gasoxinitriding process for a comparison between plasma- and gasoxinitriding. The nitrided and carburised layer of austenitic stainless steel consists of the nitrogen or carbon S-phase (expanded austenite), respectively. X-ray diffraction investigations show the typical shift of the peaks to lower angles, indicating expansion of the fcc lattice. Also the X-ray diffraction technique was employed to study the residual stresses in the nitrogen and carbon S-phase. The corrosion behaviour of surface engineered samples was investigated with electrochemical methods. Anodic potentiodynamic polarisation curves were recorded for testing the resistance against general corrosion (in H2SO4) and pitting corrosion (in NaCl).     

Kinetics of deformation processes in high-alloyed cast transformation-induced plasticity/twinning-induced plasticity steels determined by acoustic emission and scanning electron microscopy: Influence of austenite stability on deformation mechanisms

The austenite stability and the stacking fault energy of high-alloyed metastable transformation-induced plasticity/twinning-induced plasticity (TRIP/TWIP) steels, both depending on the chemical composition, have a strong influence on the deformation processes and stress/strain-induced martensitic phase transformation. Aiming at a better understanding of the kinetics of TRIP/TWIP-assisted plastic deformation, acoustic emission (AE) measurements were performed during room temperature tensile deformation of high-alloyed cast model steels with different austenite stability. The real-time AE investigations were complemented by detailed scanning electron microscopy investigations of deformed microstructures using electron backscattered diffraction to determine the martensitic phase transformation and electron channelling contrast to visualize dislocations and their arrangements. The quantitative AE analysis revealed different AE patterns at different plastic strains, which were correlated with underlying deformation mechanisms and microstructural transformations.     

Travel Plans in Public Transit Networks Using Artificial Intelligence Planning Models

Users of public transit networks require tools that generate travel plans to traverse them. The main issue is that public transit networks are time and space dependent. Travel plans depend on the current location of users and transit units, along with a set of user preferences and time restrictions. In this work, we propose the design and development of artificial intelligence (AI) planning models for engineering travel plans for such networks. The proposed models consider temporal actions, bus locations, and user preferences as constraints, to restrict the set of travel plans generated. Our approach decouples model design from algorithm construction, providing a greater level of flexibility and richness of solutions. We also introduce an integer linear programming formulation, and a fast preprocessing procedure, to evaluate the quality of the solutions returned by the proposed planning models. Experimental results show that AI planning models can efficiently generate close to optimal solutions. Furthermore, our analysis identifies user preferences as the most critical factor that increases solution complexity for planning models.     

Maternal representations of past and current attachment relationships, and emotional experience across the transition to motherhood: A longitudinal study.

Sad and anxious feelings are known to increase in the immediate postpartum period, whereas studies on new mothers' other emotional qualities such as anger are scarce. In laboratory studies, attachment security was found to be associated with effective emotion regulation in challenging situations. This study investigated attachment representations of experiences with parents and of current experiences with the partner as predictors of sad, anxious, and angry feelings across the transition to motherhood. Seventy-seven pregnant women in their third trimester were administered the Adult Attachment Interview and the Current Relationship Interview. The Differential Emotions Scale was given in pregnancy and at the infant's ages of 2 weeks, 2, 4, and 6 months, asking both mothers and fathers about maternal emotional experience. Sadness and anxiety increased 2 weeks postpartum and returned to below baseline over the following months, while anger did not change. Contrary to mothers with an insecure representation of their couple relationship, those with a secure representation reported and displayed increased sadness and anxiety 2 weeks after giving birth, from which they quickly recovered. For mothers secure in their representation of past attachment relationships with parents, an increase of low-level anger emerged 4 months postpartum, which did not occur in insecure participants and receded quickly. It can be concluded that secure representations of current and past attachment relationships help new mothers express and recover from negative emotions. These findings further elucidate the associations between attachment status and emotion regulation while adding a couple perspective. (PsycINFO Database Record (c) 2011 APA, all rights reserved)