Simulation of humidity control and greenhouse temperature tracking in a growth chamber using a passive air conditioning unit

In this paper, we define a dynamic discrete model of a passive air conditioning unit, without the more typical compression or absorption-refrigeration cycle. The unit is composed of heat exchangers, a positioning system and humid corrugated pads. The aim of the study was to follow the temperature in a greenhouse and to replicate it with a desired and stable relative humidity in a ventilated growth chamber. A control law, based on a quadratic criterion and dynamic programming, taking output error and energy consumption minimisation into account, was used to control the behaviour of the unit in spite of air intake disturbances. The results of the simulation indicate that the air conditioning unit can produce a variable climate in the growth chamber, with a wide range of relative humidity setpoints.     

Software process improvement as emergent change: A structurational analysis

This paper presents a framework that draws on Structuration theory and dialectical hermeneutics to explicate the dynamics of software process improvement (SPI) in a packaged software organisation. Adding to the growing body of qualitative research, this approach overcomes some of the criticisms of interpretive studies, especially the need for the research to be reflexive in nature.Our longitudinal analysis of the case study shows SPI to be an emergent rather than a deterministic activity: the design and action of the change process are shown to be intertwined and shaped by their context. This understanding is based upon a structurational perspective that highlights how the unfolding/realisation of the process improvement (intent) are enabled and constrained by their context. The work builds on the recognition that the improvements can be understood from an organisational learning perspective. Fresh insights to the improvement process are developed by recognising the role of the individual to influence the improvement through facilitating or resisting the changes. The understanding gained here can be applied by organisations to enable them to improve the effectiveness of their SPI programmes, and so improve the quality of their software.     

Effect of charge trapping species of cupric ions on the photocatalytic oxidation of resorcinol

The photocatalytic oxidation of resorcinol, a potent endocrine disrupting chemical, in oxygenated aqueous suspensions of pure and cupric ions modified Degussa P25 titanium dioxide has been investigated at pH 3.0 ± 0.5. The initial rate of photocatalytic oxidation of resorcinol increased until an optimum dissolved cupric ions concentration was reached at 1.04 mM. At the optimum concentration of cupric ions, the initial rate of photocatalytic mineralisation and degradation of resorcinol was improved by 400%. The observed beneficial effect of cupric ions on the initial rate of resorcinol oxidation could be attributed to the formation of complex and its participation in the photoredox cyclic reaction.Two of the initial oxidation intermediates detected were 1,2,3-trihydroxybenzene and 1,2,4-trihydroxybenzene. These intermediates were formed via hydroxylation of the aromatic ring of resorcinol. Evidences have revealed that 1,2,4-trihydroxybenzene interacted strongly with cupric ions forming copper(II)-trihydroxybenzoate complexes that possessed good adsorption onto TiO₂ surface. These dual-effects help to draw the metal ions closer to the photocatalyst surface and subsequently trigger the electron trapping mechanism by cupric ions. As a result, this improved the charge carriers’ separation. Furthermore, in the presence of oxygen, reoxidation of photoreduced cupric ions occurred and this eliminated the possibility of copper photodeposition, while inducing a photoredox cyclic reaction to regenerate copper species that may potentially act as co-catalyst for the oxidation of 1,2,4-trihydroxybenzene. In contrast, no obvious complex formation was seen between 1,2,3-trihydroxybenzene and cupric ions. This pointed to an intriguing finding which indicates that the positioning of functional group on benzene ring influences the role of cupric ions.     

Applying data mining to learn system dynamics in a biological model

Data mining consists of a set of powerful methods that have been successfully applied to many different application domains, including business, engineering, and bioinformatics. In this paper, we propose an innovative approach that uses genetic algorithms to mine a set of temporal behavior data output by a biological system in order to determine the kinetic parameters of the system. Analyzing the behavior of a biological network is a complicated task. In our approach, the machine learning method is integrated with the framework of system dynamics so that its findings are expressed in a form of system dynamics model. An application of the method to the cell division cycle model has shown that the method can discover approximate parametric values of the system and reproduce the input behavior.     

Detection of acylated homoserine lactones in gram-negative proteolytic psychrotrophic bacteria isolated from cooled raw milk

Through a mechanism called quorum sensing, bacteria are able to express specific genes in response to population density. Cell-to-cell communication in bacteria is mediated by signal molecules such as acylated homoserine lactones (AHLs). This work aimed to detect AHL production in Gram-negative psychrotrophic bacteria isolated from raw milk. A total of 84.9% of the bacteria were identified as AHL producers eliciting a diversity of responses in the AHL-monitor systems. These results demonstrate that AHL-production is common among psychrotrophic bacteria isolated from milk, and indicate that quorum sensing may play an important role in the spoilage of this product.     

Desktop inkjet printer as a tool to print conducting polymers

In order to exploit mechanical flexibility of organic-based electronic devices, conducting polymer anodes, such as polyaniline or poly(3,4-ethylenedioxy)-thiophene-poly(styrene sulfonate) (PEDOT-PSS), have been extensively studied. Along with the use of solution based processing techniques, conducting polymers can simplify the device fabrication procedure and yield themselves easily to printing techniques. In this paper, we present the results of utilizing desktop inkjet printer as a tool for direct printing and patterning of conducting polymer. Design of printable patterns and adjustment of printing parameters can be performed using any software such as Power Point. PEDOT-PSS suspension can be loaded into an inkjet cartridge and deposited on a given substrate in any designed pattern. The gray-scale color scheme can be employed to control the layer thickness and sheet resistivity of the inkjet printed layers. These layers are then used as anodes in organic light-emitting devices (OLEDs).     

Computational modeling of reactive multi-phase flows in porous media: Applications to metals extraction and environmental recovery processes

A computational modeling framework is described for the analysis of multi-phase flows in reactive porous media targeted at the metals recovery through stockpile leaching and in environmental recovery processes. These systems involve a complex suite of interacting fluid, thermal and chemical reaction physics in complex geometries, which in the case of heap leaching actually grow with time, and varying environmental conditions. The computational models of such processes need to account for variably saturated liquid flow in porous media, gas flow through porous media, together with the transport of many species in one of these fluid phases plus multi-phase heat transfer and mass transfer arising from a range of phase change and gas–liquid–solid chemical reaction processes. This contribution describes just such a development of a three dimensional modeling framework which is applied to the heap leaching of gold, silver and copper in a variety of contexts.