APPARATUS FOR THE MEASUREMENT OF DECOMPRESSION WAVE FRONT VELOCITY BASED SOUND SPEEDS AND OF ASSOCIATED DENSITIES AND ISOTHERMAL COMPRESSIBILITY COEFFICIENTS IN MODERATELY DENSE GASES

An apparatus containing a T-shaped tube fitted with a rupture diaphragm was developed in order to generate simultaneously two decompression waves traveling in opposite directions through a gas. The speeds of decompression wave fronts observed at ideal gas densities were found to be precisely equal to the calculated values of the speed of sound of equilibrium thermodynamics. Accordingly, the observed speed of the wave front is adopted as the speed of sound at all gas densities. Wave front speeds are determined from transit-times between two piezoelectric transducers mounted face-on to the waves and average speed of the two wave fronts is recorded at the speed of sound at a chosen pressure and temperature. The gas density is determined by discharging the contents of a small side-chamber filled with the gas at this state into a pre-evacuated chamber sufficiently large that the mass of discharged gas is provided with precision by the ideal gas law. The compressibility coefficient is measured at slightly higher pressures and is determined from the isothermal decrease in pressure resulting from a controlled leak of the gas in the T-tube to the small side-chamber. All gas-containing vessels were maintained at constant temperature to within ±0,1°C by immersion in a suitable bath.     

Threshold value for the number of cells in group technology

The similarity coefficient methods are more flexible in incorporating manufacturing data into the machine cells formation process in group technology. When threshold value is applied it is impossible to consider the restriction of number of cells or pact family. This paper discusses how a function is defined on Similarity coefficients and generates a threshold value which specifies an upper band on number of cells.     

Novel computational methods for high‐dimensional stochastic sensitivity analysis

This paper presents three new computational methods for calculating design sensitivities of statistical moments and reliability of high‐dimensional complex systems subject to random input. The first method represents a novel integration of the polynomial dimensional decomposition (PDD) of a multivariate stochastic response function and score functions. Applied to the statistical moments, the method provides mean‐square convergent analytical expressions of design sensitivities of the first two moments of a stochastic response. The second and third methods, relevant to probability distribution or reliability analysis, exploit two distinct combinations built on PDD: the PDD‐saddlepoint approximation (SPA) or PDD‐SPA method, entailing SPA and score functions; and the PDD‐Monte Carlo simulation (MCS) or PDD‐MCS method, utilizing the embedded MCS of the PDD approximation and score functions. For all three methods developed, the statistical moments or failure probabilities and their design sensitivities are both determined concurrently from a single stochastic analysis or simulation. Numerical examples, including a 100‐dimensional mathematical problem, indicate that the new methods developed provide not only theoretically convergent or accurate design sensitivities, but also computationally efficient solutions. A practical example involving robust design optimization of a three‐hole bracket illustrates the usefulness of the proposed methods. Copyright © 2014 John Wiley & Sons, Ltd.     

An efficient memetic algorithm for 3D shape matching problems

Shape representation plays a vital role in any shape optimization exercise. The ability to identify a shape with good functional properties is dependent on the underlying shape representation scheme, the morphing mechanism and the efficiency of the optimization algorithm. This article presents a novel and efficient methodology for morphing 3D shapes via smart repair of control points. The repaired sequence of control points are subsequently used to define the 3D object using a B-spline surface representation. The control points are evolved within the framework of a memetic algorithm for greater efficiency. While the authors have already proposed an approach for 2D shape matching, this article extends it further to deal with 3D shape matching problems. Three 3D examples and a real customized 3D earplug design have been used as examples to illustrate the performance of the proposed approach and the effectiveness of the repair scheme. Complete details of the problems are presented for future work in this direction.     

Reducing the greenhouse gas footprint of primary metal production: Where should the focus be?

The mineral processing and metal production sector is endeavouring to identify opportunities to improve the sustainability of its operations and reduce its greenhouse gas footprint, with improved energy efficiency receiving increased attention. However, if truly sustainable outcomes are to be obtained it is essential that a life cycle approach be adopted in evaluating these opportunities. In this paper, life cycle assessment methodology is used to indicate where in the metal production life cycle this focus on energy efficiency should be and to evaluate a number of potential opportunities for reducing the greenhouse gas footprint of primary metal production.Results from life cycle assessments of the main primary metal production processes, together with current and predicted global metal production rates, ore grades and grind or liberation size, have been used in a broad analysis to indicate that endeavours to improve the energy efficiency of primary metal production should focus mainly on the metal extraction stage, particularly for steel and aluminium. Declining ore grades and more complex ore bodies anticipated in the future can be expected to significantly increase the energy required for comminution of the main metal ores and will present opportunities for improving the energy efficiency of primary metal production. However, these opportunities will still be appreciably less than potential energy efficiency improvements in the extraction stage for these metals.     

An improved resource allocation scheme for plane cover multiple access using genetic algorithm

An improved resource allocation scheme is proposed in this paper which uses genetic algorithms (GAs) in conjunction with the recently developed plane cover multiple-access (PCMA) scheme in order to maximize the attainable capacity of packet-based wireless cellular networks. The studied problem has been proven to be in the class of nondeterministic polynomial (NP)-hard problem, therefore, the powerful search capability of the GA is a key factor in improving the performance of cellular resource allocation. Computer simulation results suggest that the proposed approach outperforms the "uniform" and the "greedy" algorithm-based "min " methods in terms of the number of serviced users.     

Self-regulating network utilization in mobile ad hoc wireless networks

In mobile ad hoc wireless LANs, it is very difficult to maintain a targeted network utilization due to the time-varying nature of the contention-based medium access control protocol and the lack of a central control. Furthermore, previous research has been mainly focusing on the aspect of optimizing the performance at each station. But doing so may result in a very low overall network utilization. Therefore, self-regulating network utilization is very important to provide quality-of-service (QoS) in mobile ad hoc wireless networks. Through self-disciplining its own behaviors locally, each station will optimize its protocol parameters to meet the targeted overall network utilization, which is very important for QoS provisioning to multimedia services. This paper proposes and evaluates a fully distributed scheme for each station to self-regulate its behaviors through adapting the local protocol parameters to meet the targeted overall network utilization with the changes in the network environment such as the number of stations and channel quality.     

Development of amine–acid cured Annona squamosa oil epoxy anticorrosive polymeric coatings

Forecasts for exhaustion of depleting petroleum resources in the years to come and escalating prices of petro-based chemicals, advocate the utilization of monomers/polymers derived from sustainable resources as an alternative. Oils of certain seeds may hold considerable promise as a source of unsaturated hydrocarbon, an excellent starting material for epoxidation and subsequent polymer production. Seeds of Annona squamosa (oil content 42–45%), go as a natural waste. Oil obtained from these seeds contains good amount of unsaturation; however, it has not been reported to be epoxidised, yet. Thus, epoxidation of A. squamosa oil (AOE) has been carried out in our effort to utilize a sustainable resource through the development of an anticorrosive coating material. AOE was further cured with different curing agent systems (ethylenediamine/phthalic acid (EDA–PA), 1,3-propanediamine/phthalic acid (PDA–PA), ethylenediamine/adipic acid (EDA–AA), 1,3-propanediamine/adipic acid (PDA–AA), p-phenylenediamine/adipic acid (PhDA–AA). AOE and AOE curing agent systems were subjected to structural elucidation by spectroscopic techniques (IR and ¹H NMR) and physico-chemical characterization (refractive index, specific gravity, iodine value, saponification value, hydroxyl value) involving standard methods. Thermal stability of these resins was investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Coatings of oil epoxy curing agent combinations prepared on Fe- and Al-alloys (mild steel and aluminium-24345) were subjected to physico-mechanical and anticorrosive tests in various corrosive media (water, saline water, acid and alkali) along with abrasion and steam resistance, light fastness, water vapour transmission, gloss, salt fog and humidity tests. These systems apprise satisfactory performance under different corrosive environments. The approach offers an alternate way for resource utilization and overcomes the drawbacks (poor load-bearing capacity and hardness) of oil epoxy-based coatings.