Aspects of nerve conduction

Myelinated axons have been developed as a solution to the problem of increasing the velocity of conduction of the action potential (AP) along the axon while keeping the axon diameter small. In the best engineering tradition, the solution is simple, elegant, and highly effective. The article explores this and other aspects of nerve conduction that are of interest from an engineering standpoint.     

Three-Stage Spray Drying: New Process Involving Instant Controlled Pressure Drop

The goal of this article is to define a new industrial operation called three-stage spray drying that can increase the specific surface area of powder while reducing the amount of fine dust. Because of their compact structure, spray-dried granules have an exchange surface limited to their surface area. We performed experiments inserting the instant controlled pressure drop (DIC®) treatment between the atomization (first stage of spray drying) and the final drying stage. As a high-temperature, short time (HTST) process, DIC treatment expanded granule texture at a rate depending on pore distribution, mesopore volume, and the mean porosity thus generated; the cumulative specific surface area thus induced evolved as a function of the DIC treatment conditions: the higher the DIC steam pressure, the higher the expansion rate. Both specific surface area and mean particle diameter may then simultaneously increase. Technological properties were investigated in order to compare DIC textured powders and conventional spray-dried powders and optimize the treatment; such an optimization can include the rate of decontamination thus generated.     

Application of a micro computer in investment decisions using dynamic programming

Organizations and individuals are often faced with the problem of allocation of limited resources to a number of competing projects. The tendency in the past has been towards the use of cost-benefit analysis which is unsuitable for handling indivisible projects or ventures. The acceptance of much more appropriate mathematical programming techniques such as dynamic programming has been slow due to their relative computational difficulty. This paper presents an interactive microcomputer program, MAXRETURN, applicable to all types of projects, indivisible or otherwise, using dynamic programming techniques. It does not require the user to have prior knowledge of dynamic programming or optimization techniques. Use of the program is illustrated with an example.     

Application of California Puff (CALPUFF) model: a case study for Oman

Oil Refineries surrounding the gulf are the largest source of environmental pollution in the region. Air dispersion models are powerful tools for assessing the consequences of environmental air pollutant concentrations. This study was carried out to investigate the transport and dispersion patterns of SO₂ originating from Mina Al-Fahal refinery, in the Sultanate Oman by employing California Puff (CALPUFF) dispersion modeling system. The major goal of this study is to make a comparison of the results produced by this modeling system with a previous study which was conducted for the same area using Industrial Source Complex Short Term (ISCST) model. In order to obtain the meteorological fields of the study area the CALPUFF modeling system was coupled with Weather Research and Forecasting (WRF), a prognostic meteorological model. The results indicated that the performance of the CALPUFF was better than that of ISCST; however, a difference in magnitudes of predicted and measured concentrations of SO₂ was found. This difference can be reduced using high-resolution terrain elevation data, site-specific observational meteorological data and buoy data. The complex geography and variable wind regimes played an important role in distribution of SO₂ in and around the refinery. The land–sea interaction also influenced the predicted results.     

Evaluation of scheduling rules for single- and dual-dock automated storage/retrieval system

The effect of the number of pick-up delivery stations (or docks or input/output points) is analyzed and compared for three different unit load automated storage and retrieval (AS/R) systems operating under dual command cycle. The AS/R system layouts differ in the number of docks per aisle, and the relationship between the storage and retrieval sources. A simulation model was used to evaluate the systems on three performance criteria—system throughput, mean waiting time and maximum waiting time. The efficiency of the AS/R system can be improved by the introduction of two docks per aisle with the input/output pallets for each dock being independent of each other, the input pallet storage based on closest open location policy, and output pallet withdrawal based on a nearest neighbour policy (or its variant, with a maximum waiting time limit).     

An Alternative Empirical Formula for Positive Corona Discharge I-V Characteristics in Point-to-Plate Electrode Geometry

Experimental data are presented for a study on the dependence of the I-V character- istics of the corona discharge on pressure and electrode spacing using point-to-plane electrode con- figuration. These experimental data are obtained by a fast, automatic computer data-acquisition system. The data are used to suggest an alternative dimensionally self-consistent empirical equa- tion for the parameterization of the I-V curves. The formula eliminates the need for any prior assumptions concerning the inception voltage, as is customary in this type of work.     

Swell Drying: Coupling Instant Controlled Pressure Drop DIC to Standard Convection Drying Processes to Intensify Transfer Phenomena and Improve Quality—An Overview

Increasing globalization is driving agricultural production in developing countries toward better recovery levels and high additional value. A great opportunity is thus offered to emerging economies. By adopting appropriate and improved methods that allow better preservation, transport, and storage and that conform to the rigorous requirements and standards of organoleptic and nutritional quality as well as stringent hygienic criteria, emerging economies can derive significant benefits.

Drying of biological materials usually results in shrinkage. The impact of shrinkage is often highly prejudicial for both the function and use of these materials. On the one hand, shrinkage results in a sharp decrease in water diffusivity through the porous structure (for dehydration and rehydration processes). On the other hand, the compact structure of dried biological material is usually unsuitable in terms of organoleptic quality and is inadequate for grinding. Thus, it is becoming very important to include retexturing and structure-expanding processes in standard drying processes. To this end, the instant controlled pressure drop (DIC) technology has been proposed and successfully tested as a texturing process for partially dried materials, which should normally intensify the whole operation. The quality of the final product as well as the performance of the drying process can also be dramatically improved. Finally, for a large category of dried fruits and vegetables, and even freeze-dried materials, microbiological contamination and the presence of insects and larvae are serious problems. DIC technology can be used as an ultra-high-temperature treatment for a controlled decontamination. Such dried, expanded, and completely decontaminated products can be used as highly nutritional snacks. They can easily be ground to produce expanded granulated powders with excellent sensory, nutritional, functional, and textural properties.     

Adsorption mechanism of cationic surfactants onto acid- and heat-activated sepiolites

Systematic adsorption tests were carried out to determine the uptake of typical quaternary amines, dodecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide and a primary amine, dodecylamine hydrochloride by sepiolite. Bottle adsorption tests conducted with untreated, acid- and heat-activated sepiolites exhibit two distinct regions. The first stage is characterized by low rate and governed through an ion exchange process between ammonium ions and magnesium ions in the octahedral sheet. The second stage is ascribed to a combination of chain-chain interactions through Van der Waals forces and ion exchange process. Despite several-fold increases in surface areas upon activation, surprisingly no improvement in adsorption is observed. The observed differences are explained on the basis of partial collapse of the sepiolite crystal structure, the removal of zeolitic and bound waters and modification of the pore size distribution of sepiolite upon treatments.     

Economic modelling and sensitivity analysis of alternative power plant designs

This paper presents a summary of the methodology employed in investigating the economic feasibility of constructing small (10 MW_e) biomass-fueled electric generating plants, specifically, the development of an interactive computer program designed for the calculation of levelized bus bar power costs and the application of this program to perform economic sensitivity analyses.