Innovations in titanium powder processing

One way of reducing the cost of titanium components is to use near-net shape powder-metallurgy techniques. This article describes a number of new approaches to producing components using the powder-metallurgy method for the aerospace, industrial, and consumer marketplaces. For more information, contact F.H. Froes, Institute for Materials and Advanced Processes, University of Idaho, Mines Building, Room 321, Moscow, Idaho 83844-3026; (208) 885-7989; fax (208) 885-4009; e-mail imap@uidaho.edu.     

Regimes of Two-Phase Flow in Short Rectangular Channel

Experimental study of two-phase flow in the short rectangular horizontal channel with height 440 μm has been performed. Characteristics of liquid motion inside the channel have been registered and measured by the Laser Induced Fluorescence technique. New information has allowed determining more precisely the characteristics of churn regime and boundaries between different regimes of two-phase flow. It was shown that formation of some two-phase flow regimes and transitions between them are determined by instability of the flow in the lateral parts of the channel.     

Chiral carbon nanoscrolls with a polygonal cross-section

Carbon nanoscrolls with a unique polygonal cross-section have been discovered in films synthesized by chemical vapor deposition in a hydrogen-methane gas mixture activated by a direct current discharge. The structure type has been revealed by high resolution transmission electron microscopy (TEM) combined with selected area electron diffraction patterning. The peculiarities observed in the TEM diffraction contrast have allowed for the identification of the nanoscroll shape as a twisted polygon. A three-dimensional atomic structure model of these complex nanocarbon species is based on a tilting series and the electron diffraction patterns. The proposed model adequately describes the structure of the nanoscrolls and the formation mechanism of the characteristic diffraction contrast in their corresponding electron microscopy images. The results point to the specific features of the electronic properties of nanoscrolls.     

Design and testing of a 9.5 kWe proton exchange membrane fuel cell–supercapacitor passive hybrid system

The design and test of a 9.5 kWe proton exchange membrane fuel cell passively coupled with a 33 × 1500 F supercapacitor pack is presented. Experimental results showed that the system reduced dynamic loads on the fuel cell without the need for additional DC/DC converters. Fuel efficiency gains of approximately 5% were achieved by passive hybridisation in addition to addressing two main operational degradation mechanisms: no-load idling and rapid load cycling.     

A numerical investigation of the refrigerant maldistribution from a header towards parallel channels in an evaporator of automotive air conditioning system

Evaporators in automotive air conditioning are designed as compact heat exchangers with the aim to cool outside air for the widest possible range of weather conditions. Under low operating loads a non-uniformity of the refrigerant liquid and gas phase distribution from the evaporator headers towards the evaporating channels leads to a decrease of the evaporator efficiency and a temperature stratification in the exit stream of cooled air. This malfunction is investigated by numerical simulations and analyses with the Computational Multi-Fluid Dynamic code. The applied numerical approach is validated for available experimental conditions. In order to eliminate the air exit temperature stratification, numerical experiments are performed with design changes of the evaporator header and the effectiveness of applied measures is demonstrated.     

Asymptotically stable detection of a weak signal

To design highly efficient and robust detectors of a weak signal, an asymptotic approach to stable estimation exploiting redescending score functions is used. Two new indicators of robustness of detection, the detection error sensitivity and detection stability, are introduced. The optimal Neyman–Pearson rules maximizing detection efficiency under the guaranteed level of detection stability are written out. Under heavy‐tailed noise distributions, the proposed asymptotically stable detectors based on redescending score functions, namely, the minimum error sensitivity and the radical ones, outperform conventional linear bounded Huber's and redescending Hampel's detectors both on small and large samples. Copyright © 2013 John Wiley & Sons, Ltd.     

Assessment of process parameters on the production of diglycerides rich in omega-3 fatty acids through the enzymatic glycerolysis of fish oil

The main objective of this work is to present new experimental information concerning the effect of relevant process parameters related to the production of diglycerides by enzymatic glycerolysis of fish oil. Reaction products can be applied as ingredients in food industry, joining the emulsifying properties of partial glycerides along with the nutritional benefits attributed to the omega-3 fatty acids. From preliminary reactions, conversion was higher for a solvent- and surfactant-free system but the long time to reach appreciable amounts of diglycerides may be a drawback for practical purposes. To overcome this problem, the addition of tert-butanol revealed to be relevant, leading to high diglycerides contents in short times. The system containing Tween 65 led to the highest amount of diglycerides. This study described the feasibility of enzymatic synthesis of diglycerides rich in EPA and DHA in short reaction times as well by using a more environmentally friendly process.