UBET-based numerical modeling of bulk deformation processes

The paper summarizes the development of numerical procedures for modeling bulk deformation process and preform designing techniques based on the upper bound elemental technique (UBET). UBET has a unique place where an approximate, but faster solution is needed for decision making. In designing and optimizing multistage forging and profile ring-rolling processes, an approximate solution can be used to identify the most influential process parameters. Once an optimum combination of process conditions are determined, computationally intensive, but more accurate finite element analysis can be used to verify and refine results. In this paper, UBET procedures for closed-die forging and profile ring rolling are high-lighted. Experimental investigations are used to validate the model predictions. Also, the UBET-based preform design tool is presented as a process and die design tool for multistage forging processes. Application of these techniques is presented with evidence of effective material usage and extended overall die-life.     

FISA-2009 Conference on Euratom Research and Training Activities: Nuclear Fission - Past, Present and Future (Generation-II, -III and -IV + Partitioning and Transmutation)

This paper is an introduction to the research and training activities carried out under the Euratom 7th Framework Programme (FP7, 2007-2011) in the field of nuclear fission science and technology, covering in particular nuclear systems and safety, and including innovative reactor systems and partitioning and transmutation. It is based on the more than 40 invited lectures that were delivered by Euratom project coordinators and keynote speakers at the FISA-2009 Conference (FISA, 2009), organised by the European Commission DG Research, 22-24 June 2009, Prague, Czech Republic.The Euratom programme must be considered in the context of current and future nuclear technology and the respective research effort:

•

Generation-II (i.e. yesterday, NPP construction 1970-2000): safety and reliability of nuclear facilities and energy independence in order to ensure security of supply worldwide;

•

Generation-III (i.e. today, construction 2000-2040+): continuous improvement of safety and reliability, and increased industrial competitiveness in a growing energy market;

•

Generation-IV (i.e. tomorrow, construction from 2040) for increased sustainability though optimal utilisation of natural resources and waste minimisation, and increased proliferation resistance.

Consequently, the focus of the lectures devoted to Generation-II and -III is on the major scientific challenges and technological developments needed to guarantee safety and reliability, in particular issues associated with plant lifetime extension and operation.The focus of the lectures devoted to Generation-IV is on the design objectives and associated research issues that have been agreed upon internationally, in particular the ambitious criteria and technology goals established at the international level by the Generation-IV International Forum (GIF). In the future, electricity must continue to be produced competitively, and in addition high temperature process heat may also be required, while exploiting a maximum of fissile and fertile material and recycling all actinides, both safely and reliably. Scientific viability studies and technological performance tests for each Generation-IV system are now being carried out in many European Union (EU) Member States, in collaboration with other laboratories worldwide as part of the inter-governmental GIF agreement. The ultimate phase of commercial deployment will be from 2040, but no one can predict accurately when industry and investors will make firm, often difficult decisions regarding the construction of these very innovative Generation-IV systems. However, to be deployed commercially, it must first be demonstrated that Generation-IV technology can be a beneficial, responsible and sustainable response to the long-term challenges faced by society to establish a low-carbon economy.     

Inhibition of Bacterial and Filamentous Fungal Growth in High Moisture,Nonsterile Corn with Intermittent Pumping of Trans‐2‐Hexenal Vapor

Trans‐2‐hexenal (T2H), a plant‐produced aldehyde, was intermittently pumped over a 7 d period into a small, bench top model of stored corn (nonsterile, moisture content about 23%). Naturally occurring bacteria and fungi, including added Aspergillus flavus, grew rapidly on corn not treated with T2H vapor. However, intermittently pumped T2H (30 min per 2 h or 30 min per 12 h) significantly reduced bacterial and fungal viable populations, with nearly 100% fungal viability loss observed after either (1) one day of pumping at the 30 min per 2 h rate or (2) pumping cycles of 30 min per 12 h period over the initial 48 to 72 h of incubation. Data suggest that short‐term intermittent fumigation of stored corn with T2H could prevent growth of bacteria and mycotoxigenic fungi such as A. flavus.     

Electrical characteristics of schottky barriers on 4H-SiC: The effects of barrier height nonuniformity

Electrical properties, including current-voltage (I-V) and capacitance-voltage (C-V) characteristics, have been measured on a large number of Ti, Ni, and Pt-based Schottky barrier diodes on 4H-SiC epilayers. Various nonideal behaviors are frequently observed, including ideality factors greater than one, anomalously low I-V barrier heights, and excess leakage currents at low forward bias and in reverse bias. The nonidealities are highly nonuniform across individual wafers and from wafer to wafer. We find a pronounced linear correlation between I-V barrier height and ideality factor for each metal, while C-V barrier heights remain constant. Electron beam induced current (EBIC) imaging strongly suggests that the nonidealities result from localized low barrier height patches. These patches are related to discrete crystal defects, which become visible as recombination centers in the EBIC images. Alternative explanations involving generation-recombination current, uniform interfacial layers, and effects related to the periphery are ruled out.     

Risk intermediation in supply chains

This paper demonstrates that an important role of intermediaries in supply chains is to reduce the financial risk faced by retailers. It is well known that risk averse retailers when faced by the classical single-period inventory (newsvendor) problem will order less than the expected value maximizing (newsboy) quantity. We show that in such situations a risk neutral distributor can offer a menu of mutually beneficial contracts to the retailers. We show that a menu can be designed to simultaneously: (i) induce every risk averse retailer to select a unique contract from it; (ii) maximize the distributor's expected profit; and (iii) raise the order quantity of the retailers to the expected value maximizing quantity. Thus inefficiency created due to risk aversion on part of the retailers can be avoided. We also investigate the influence of product/market characteristics on the offered menu of contracts.     

Properties of nylon 12 balloons after thermal and liquid carbon dioxide treatments

Critical design attributes of angioplasty balloons include the following: tear resistance, high burst pressures, controlled compliance, and high fatigue. Balloons must have tear resistance and high burst pressures because a calcified stenosis can be hard and nominal pressures of up to 16 atm can be used to expand the balloon. The inflated balloon diameter must be a function of the inflation pressure, thus compliance is predictable and controlled. Reliable compliance is necessary to prevent damage to vessel walls, which may be caused by over-inflation. Balloons are often inflated multiple times in a clinical setting and they must be highly resistant to fatigue. These design attributes are dependent on the mechanical properties and polymer morphology of the balloon. The effects of residual stresses on shrinkage, crystallite orientation, balloon compliance, and mechanical properties were studied for angioplasty nylon 12 balloons. Residual stresses of these balloons were relieved by oven heat treatment and liquid CO₂ exposure. Residual stresses were measured by quantifying shrinkage at 80 °C of excised balloon samples using a dynamic mechanical analyzer. Shrinkage was lower after oven heat treatment and liquid CO₂ exposure compared to the as-received balloons, in the axial and radial directions. As-received, oven heat treated, and liquid CO₂-exposed balloon samples exhibited similar thermal properties (T_g, T_m, X_t). Crystallite orientation was not observed in the balloon cylindrical body using X-ray scattering and polarized light microscopy, which may be due to balloon fabrication conditions. Significant differences were not observed between the stress–strain curves, balloon compliance, and average burst pressures of the as-received, oven heat treated, and liquid CO₂-exposed balloons.     

Four degree of freedom liquid dispenser for direct write capillary self-assembly with sub-nanoliter precision

Capillary forces provide a ubiquitous means of organizing micro- and nanoscale structures on substrates. In order to investigate the mechanism of capillary self-assembly and to fabricate complex ordered structures, precise control of the meniscus shape is needed. We present a precision instrument that enables deposition of liquid droplets spanning from 2 nl to 300 μl, in concert with mechanical manipulation of the liquid-substrate interface with four degrees of freedom. The substrate has sub-100 nm positioning resolution in three axes of translation, and its temperature is controlled using thermoelectric modules. The capillary tip can rotate about the vertical axis while simultaneously dispensing liquid onto the substrate. Liquid is displaced using a custom bidirectional diaphragm pump, in which an elastic membrane is hydraulically actuated by a stainless steel syringe. The syringe is driven by a piezoelectric actuator, enabling nanoliter volume and rate control. A quantitative model of the liquid dispenser is verified experimentally, and suggests that compressibility in the hydraulic line deamplifies the syringe stroke, enabling sub-nanoliter resolution control of liquid displacement at the capillary tip. We use this system to contact-print water and oil droplets by mechanical manipulation of a liquid bridge between the capillary and the substrate. Finally, we study the effect of droplet volume and substrate temperature on the evaporative self-assembly of monodisperse polymer microspheres from sessile droplets, and demonstrate the formation of 3D chiral assemblies of micro-rods by rotation of the capillary tip during evaporative assembly.     

Development of ashless multifunctional additives from cashew nutshell liquid

Aminodi(alkylphenyl) phosphorodithioates have been synthes‐ised by the condensation of di (alkylphenyl) phosphorodithioic acid, which was derived from a renewable, biodegradable, low‐cost, naturally occurring vegetable product, cashew nutshell liquid, with various amines. These ashless aminodi (alkyl‐phenyl) phosphorodithioates have been evaluated as anti‐oxidant, antiwear, friction‐modifying, and extreme‐pressure additives in lubricant compositions.