An integrated approach for water minimisation in a PVC manufacturing process

This paper presents a water minimisation study carried out for a polyvinyl chloride (PVC) resins manufacturing plant. Due to the complexity of the mixed batch and continuous polymerisation process, an integrated process integration approach, which consists of process synthesis, analysis and optimisation was used for this work. A simulation model was first developed in a batch process simulation software, SuperPro Designer V6.0, based on the operating condition of a PVC manufacturing process. The batch simulation model captured the essential information needed for a water minimisation study, e.g. process duration, water mass flow, etc. Data extracted from the simulation model was later used in the water minimisation study, utilising the widely established process synthesis technique of water pinch analysis. Two water saving scenarios were presented. Scenario 1 reports a fresh water and wastewater reduction of 28.5 and 90.1% respectively, for the maximum water recovery scheme without water storage system. In Scenario 2, higher fresh water and wastewater reduction are reported at 31.7 and 100% respectively, when water storage tank is installed in the water network.     

Hydroxyapatite pattern formation in PVA gels

Sodium hydroxide solution was allowed to diffuse from the edge of an acidic poly(vinyl alcohol) gel sheet containing dissolved calcium and phosphate ions, and calcium phosphate was observed to precipitate as the pH rose. The precipitation pattern changed depending on the solute concentration near the reaction front; precipitate “walls” were formed in areas in which the calcium phosphate concentration was higher or the sodium hydroxide concentration was lower than the conditions for homogeneous precipitation, and within a very limited concentration combination of calcium phosphate and sodium hydroxide, a regular stripe pattern with a pitch of about 100 μm was formed. The calcium phosphate precipitate obtained was a single phase of hydroxyapatite. It was also found that apatite ceramic sheets with periodic porous structures or with undulate patterns could be manufactured by sintering gels with stripe patterns.     

Quality is in the eye of the beholder? An evaluation of impact factors and perception of journal prestige in the UK

A number of proxy measures have been used as indicators of journal quality. The most recent and commonly employed are journal impact factors. These measures are somewhat controversial, although they are frequently referred to in establishing the impact of published journal articles. Within psychology, little is known about the relationship between the ‘objective’ impact factors of journals and the ‘subjective’ ratings of prestige and perceived publishing difficulty amongst academics. In order to address this, a cross-sectional web-based survey was conducted in the UK to investigate research activity and academics’ views of journals within three fields of psychology; cognitive, health and social. Impact factors for each journal were correlated with individual academic’s perceptions of prestige and publishing difficulty for each journal. A number of variables pertaining to the individual academic and their place of work were assessed as predictors of these correlation values, including age, gender, institution type, and a measure of departmental research activity. The implications of these findings are discussed in relation to perceptions of journal prestige and publishing difficulty, higher education in general and the assessment of research activity within academic institutions.     

Disc Stack Centrifuge Operating Parameters and Their Impact on Yeast Physiology

Hydrodynamic stresses imposed on brewing cells of Saccharomyces cerevisiae during beer processing can have a detrimental impact on beer quality. The use of centrifuges has become an efficient way to increase brewery throughput as they decrease clarification times and improve fermenter and tank conditioning efficiency. The effect of a disc stack centrifuge on yeast and beer physical stability has been investigated. In this study, a commercial ale yeast strain has been subjected to different operating conditions during centrifugation. Cell viability and intracellular pH decreased due to processing conditions encountered during yeast cropping with a centrifuge. A relationship has been established that yeast cell wall mannan, an unfilterable haze constituent, as a function of G‐force and centrifugation cycles, is released from the cell wall while concurrently, particle sizes between 0.5‐2.8 μm and beer haze increased. Furthermore, yeast intracellular glycogen and trehalose levels were depleted as a result of centrifugation.     

Walking with increasing acceleration is achieved by tuning ankle torque onset timing and rate of torque development

Understanding the mechanics of torque production about the ankle during accelerative gait is key to designing effective clinical and rehabilitation practices, along with developing functional robotics and wearable assistive technologies. We aimed to explore how torque and work about the ankle is produced as walking acceleration increases from 0 to 100% maximal acceleration. We hypothesized that as acceleration increased, greater work about the ankle would not be solely due to ramping up plantar flexor torque, and instead would be a product of adjustments to relative timing of ankle torque and angular displacement. Fifteen healthy participants performed walking without acceleration (constant speed), as well as low, moderate and maximal accelerations, while motion capture and ground reaction force data were recorded. We employed vector coding in a novel application to overcome limitations of previously employed evaluation methods. As walking acceleration increased, there was reduced negative work and increased positive work about the ankle. Furthermore, early stance dorsiflexion had reducing plantar flexor torque due to delayed plantar flexor torque onset as acceleration increased, while mid-stance ankle plantar flexor torque was substantially increased with minimal ankle dorsiflexion, irrespective of acceleration magnitude. Assistive devices need to account for these changes during accelerative walking to facilitate functional gait.     

REFORMING OF N-OCTANE ON A Pt/Al2O3 CATALYST. II. KINETIC ANALYSIS OF HYDROGEN DEPENDENCE.

The conversion of n-octane on Pt/Al₂O₃ catalyst was found to pass through pronounced maxima with the variation of the partial pressure of hydrogen at temperatures between 420°C-460°C, P_N = 7·63 × 10^-3 atm and W/F = 0·11lg min cm_-3. The products of reaction were hydrocracked products, octane, ethylbenzene, o-.p-,m,-xylene and toluene. The order of appearance of the optimum PH for the various reactions were: Isooctane>Dehydrocyclized products>Hydrocracked products.

A sequence of elementary steps earlier postulated was found to predict the maximum in the n-octane P_H profiles for the three temperatures investigated. The rate determining steps for the two rate equations that were found suitable were conversion of adsorbed isooctane to adsorbed o-xylene and ethylbenzene.     

Comparison between wave generation methods for numerical simulation of bimodal seas

This paper describes an investigation of the generation of desired sea states in a numerical wave model. Bimodal sea states containing energetic swell components can be coastal hazards along coastlines exposed to large oceanic fetches. Investigating the effects of long-period bimodal seas requires large computational domains and increased running time to ensure the development of the desired sea state. Long computational runs can cause mass stability issues due to the Stokes drift and wave reflection, which in turn affect results through the variation of the water level. A numerical wave flume, NEWRANS, was used to investigate two wave generation methods: the wave paddle method, allowing for a smaller domain; and the internal mass source function method, providing an open boundary allowing reflected waves to leave the domain.The two wave generation methods were validated against experimental data by comparing the wave generation accuracy and the variance of mass in the model during simulations. Results show that the wave paddle method not only accurately generates the desired sea state but also provides a more stable simulation, in which mass fluctuation has less of an effect on the water depth during the long-duration simulations. As a result, it is suggested that the wave paddle method with active wave absorption is preferable to the internal wave maker option when investigating intermediate-depth long-period bimodal seas for long-duration simulations.     

Genetic Reinforcement Learning for Neurocontrol Problems

Empirical tests indicate that at least one class of genetic algorithms yields good performance for neural network weight optimization in terms of learning rates and scalability. The successful application of these genetic algorithms to supervised learning problems sets the stage for the use of genetic algorithms in reinforcement learning problems. On a simulated inverted-pendulum control problem, genetic reinforcement learning produces competitive results with AHC, another well-known reinforcement learning paradigm for neural networks that employs the temporal difference method. These algorithms are compared in terms of learning rates, performance-based generalization, and control behavior over time.     

GISMO, a 2 mm Bolometer Camera Optimized for the Study of High Redshift Galaxies

The 2 mm spectral range provides a unique terrestrial window enabling ground based observations of the earliest active dusty galaxies in the universe and thereby allowing a better constraint on the star formation rate in these objects. We have built GISMO (the Goddard-IRAM Superconducting 2-Millimeter Observer), a 2 mm, 128 element superconducting Transition Edge Sensor (TES) based bolometer camera for the IRAM 30 m telescope in Spain. The camera uses an 8×16 planar array of multiplexed TES bolometers, which incorporates our recently designed Backshort Under Grid (BUG) architecture, described elsewhere. The optical design incorporates a 100 mm (4 inches) diameter silicon lens cooled to 4 K, which provides the required fast beam of 0.9 λ/D. With this spatial sampling, GISMO will be very efficient at detecting sources serendipitously in large sky surveys, while the capability for diffraction-limited observations is preserved. With the background limited performance of the detectors, the camera provides significantly greater imaging sensitivity and mapping speed at this wavelength than has previously been possible. The major scientific driver for the instrument is to provide the IRAM 30 m telescope with the capability to rapidly observe galactic and extragalactic dust emission, in particular from high-z Ultra Luminous Infrared Galaxies (ULIRGs) and quasars, even in the summer season. The instrument will fill in the SEDs of high redshift galaxies at the Rayleigh-Jeans part of the dust emission spectrum, even at the highest redshifts. Our source count models predict that GISMO will serendipitously detect one galaxy every four hours on the blank sky, and that one quarter of these galaxies will be at a redshift of z 6.5. We expect to install GISMO at the 30 m telescope in the second half of 2007.