Showing papers by "Curtin University published in 2005"

Assessing the generality of global leaf trait relationships

Abstract: Summary • Global-scale quantification of relationships between plant traits gives insight into the evolution of the world’s vegetation, and is crucial for parameterizing vegetation‐ climate models. • A database was compiled, comprising data for hundreds to thousands of species for the core ‘leaf economics’ traits leaf lifespan, leaf mass per area, photosynthetic capacity, dark respiration, and leaf nitrogen and phosphorus concentrations, as well as leaf potassium, photosynthetic N-use efficiency (PNUE), and leaf N : P ratio. • While mean trait values differed between plant functional types, the range found within groups was often larger than differences among them. Future vegetation‐ climate models could incorporate this knowledge. • The core leaf traits were intercorrelated, both globally and within plant functional types, forming a ‘leaf economics spectrum’. While these relationships are very general, they are not universal, as significant heterogeneity exists between relationships fitted to individual sites. Much, but not all, heterogeneity can be explained by variation in sample size alone. PNUE can also be considered as part of this trait spectrum, whereas leaf K and N : P ratios are only loosely related.

Modulation of leaf economic traits and trait relationships by climate

Abstract: Aim Our aim was to quantify climatic influences on key leaf traits and relationships at the global scale. This knowledge provides insight into how plants have adapted to different environmental pressures, and will lead to better calibration of future vegetation‐climate models. Location The data set represents vegetation from 175 sites around the world. Methods For more than 2500 vascular plant species, we compiled data on leaf mass per area (LMA), leaf life span (LL), nitrogen concentration (N mass ) and photosynthetic capacity (A mass ). Site climate was described with several standard indices. Correlation and regression analyses were used for quantifying relationships between single leaf traits and climate. Standardized major axis (SMA) analyses were used for assessing the effect of climate on bivariate relationships between leaf traits. Principal components analysis (PCA) was used to summarize multidimensional trait variation. Results At hotter, drier and higher irradiance sites, (1) mean LMA and leaf N per area were higher; (2) average LL was shorter at a given LMA, or the increase in LL was less for a given increase in LMA (LL‐LMA relationships became less positive); and (3) A mass was lower at a given N mass , or the increase in A mass was less for a given increase in N mass . Considering all traits simultaneously, 18% of variation along the principal multivariate trait axis was explained by climate.

Transdermal drug delivery: penetration enhancement techniques.

Abstract: There is considerable interest in the skin as a site of drug application both for local and systemic effect. However, the skin, in particular the stratum corneum, poses a formidable barrier to drug penetration thereby limiting topical and transdermal bioavailability. Skin penetration enhancement techniques have been developed to improve bioavailability and increase the range of drugs for which topical and transdermal delivery is a viable option. This review describes enhancement techniques based on drug/vehicle optimisation such as drug selection, prodrugs and ion-pairs, supersaturated drug solutions, eutectic systems, complexation, liposomes, vesicles and particles. Enhancement via modification of the stratum corneum by hydration, chemical enhancers acting on the structure of the stratum corneum lipids and keratin, partitioning and solubility effects are also discussed. The mechanism of action of penetration enhancers and retarders and their potential for clinical application is described.

Fly Ash-Based Geopolymer Concrete

Abstract: In recent years, attempts to increase the utilisation of fly ash to partially replace the use of Portland cement in concrete are gathering momentum. Geopolymer concrete is a ‘new’ material that does not need the presence of Portland cement as a binder. Instead, activating the source materials such as fly ash that are rich in Silicon (Si) and Aluminium (Al) using high alkaline liquids produces the binder required to manufacture the concrete. Hence, concrete with no cement.This paper presents information on fly ash-based geopolymer concrete. The paper covers the material and the mixture proportions, the manufacturing process, and the influence of various parameters on the properties of fresh and hardened concrete.

Activity recognition and abnormality detection with the switching hidden semi-Markov model

Abstract: This paper addresses the problem of learning and recognizing human activities of daily living (ADL), which is an important research issue in building a pervasive and smart environment. In dealing with ADL, we argue that it is beneficial to exploit both the inherent hierarchical organization of the activities and their typical duration. To this end, we introduce the switching hidden semi-markov model (S-HSMM), a two-layered extension of the hidden semi-Markov model (HSMM) for the modeling task. Activities are modeled in the S-HSMM in two ways: the bottom layer represents atomic activities and their duration using HSMMs; the top layer represents a sequence of high-level activities where each high-level activity is made of a sequence of atomic activities. We consider two methods for modeling duration: the classic explicit duration model using multinomial distribution, and the novel use of the discrete Coxian distribution. In addition, we propose an effective scheme to detect abnormality without the need for training on abnormal data. Experimental results show that the S-HSMM performs better than existing models including the flat HSMM and the hierarchical hidden Markov model in both classification and abnormality detection tasks, alleviating the need for presegmented training data. Furthermore, our discrete Coxian duration model yields better computation time and generalization error than the classic explicit duration model.

A survey of digital image watermarking techniques

Abstract: Watermarking, which belong to the information hiding field, has seen a lot of research interest. There is a lot of work begin conducted in different branches in this field. Steganography is used for secret communication, whereas watermarking is used for content protection, copyright management, content authentication and tamper detection. In this paper we present a detailed survey of existing and newly proposed steganographic and watermarking techniques. We classify the techniques based on different domains in which data is embedded. We limit the survey to images only.

A critical analysis of decision support systems research

Abstract: This paper critically analyses the nature and state of decision support systems (DSS) research. To provide context for the analysis, a history of DSS is presented which focuses on the evolution of a number of sub-groupings of research and practice: personal DSS, group support systems, negotiation support systems, intelligent DSS, knowledge management-based DSS, executive information systems/business intelligence, and data warehousing. To understand the state of DSS research an empirical investigation of published DSS research is presented. This investigation is based on the detailed analysis of 1,020 DSS articles published in 14 major journals from 1990 to 2003. The analysis found that DSS publication has been falling steadily since its peak in 1994 and the current publication rate is at early 1990s levels. Other findings include that personal DSS and group support systems dominate research activity and data warehousing is the least published type of DSS. The journal DSS is the major publishing outlet; US ‘Other’ journals dominate DSS publishing and there is very low exposure of DSS in European journals. Around two-thirds of DSS research is empirical, a much higher proportion than general IS research. DSS empirical research is overwhelming positivist, and is more dominated by positivism than IS research in general. Design science is a major DSS research category. The decision support focus of the sample shows a well-balanced mix of development, technology, process, and outcome studies. Almost half of DSS papers did not use judgement and decision-making reference research in the design and analysis of their projects and most cited reference works are relatively old. A major omission in DSS scholarship is the poor identification of the clients and users of the various DSS applications that are the focus of investigation.

A review of synergistic effect of photocatalysis and ozonation on wastewater treatment

Abstract: For the treatment of wastewater that contain recalcitrant organic compounds, such as organo-halogens, organic pesticides, surfactants, and colouring matters, wastewater engineers are now required to develop advanced treatment processes. A promising way to perform the mineralization of this type of substance is the application of an advanced oxidation process (AOP). Photocatalytic oxidation and ozonation appear to be the most popular treatment technologies compared with other advanced oxidation processes (AOPs) as shown by the large amount of information available in the literature. The principal mechanism of AOPs function is the generation of highly reactive free radicals. Consequently, combination of two or more AOPs expectedly enhances free radical generation, which eventually leads to higher oxidation rates. The use of combine photocatalysis and ozonation is an attractive route because of the enhancement of the performance for both agents by means of the hydroxyl radical generation, a powerful oxidant agent that can oxidize completely the organic matter present in the aqueous system. The scope of this paper is to review recently published work in the field of integrated photocatalysis and ozonation on wastewater treatment. In this review the chemical effects of various variables on the rate of degradation of different pollutants are discussed. The mechanism and kinetics has also been reported. It can be concluded that photocatalytic oxidation in the presence of ozone is a process that is qualitatively and quantitatively different from the well-known photocatalytic oxidation with oxygen and the ozonation without photocatalyst. The reason for the higher oxidation rate is probably a photocatalytic induced decay of ozone, initiated by the combination of titanium dioxide and UV-A radiation.

Learning and detecting activities from movement trajectories using the hierarchical hidden Markov model

Abstract: Directly modeling the inherent hierarchy and shared structures of human behaviors, we present an application of the hierarchical hidden Markov model (HHMM) for the problem of activity recognition. We argue that to robustly model and recognize complex human activities, it is crucial to exploit both the natural hierarchical decomposition and shared semantics embedded in the movement trajectories. To this end, we propose the use of the HHMM, a rich stochastic model that has been recently extended to handle shared structures, for representing and recognizing a set of complex indoor activities. Furthermore, in the need of real-time recognition, we propose a Rao-Blackwellised particle filter (RBPF) that efficiently computes the filtering distribution at a constant time complexity for each new observation arrival. The main contributions of this paper lie in the application of the shared-structure HHMM, the estimation of the model's parameters at all levels simultaneously, and a construction of an RBPF approximate inference scheme. The experimental results in a real-world environment have confirmed our belief that directly modeling shared structures not only reduces computational cost, but also improves recognition accuracy when compared with the tree HHMM and the flat HMM.

Development and Validation of an Instrument for Assessing Distance Education Learning Environments in Higher Education: The Distance Education Learning Environments Survey (DELES).

Abstract: The purpose of this study was to develop and validate a new learning environments instrument designed to aid investigators and practitioners in measuring and researching the psychosocial learning environment in post-secondary distance education. Using a three-stage approach, the Distance Education Learning Environments Survey (DELES) was developed, field-tested with 680 distance education students, and then validated. The DELES has 34 items allocated to six scales: (1) Instructor Support; (2) Student Interaction and Collaboration; (3) Personal Relevance; (4) Authentic Learning; (5) Active Learning; and (6) Student Autonomy. An additional scale of Enjoyment was included in this study to explore associations between the psychosocial learning environment and student affective traits. Each learning environment item had a factor loading of at least 0.50 with its own scale, and less than 0.50 with all other scales. The alpha reliability coefficient for each scale ranged from 0.75 to 0.94. Simple correlations between Enjoyment and the DELES scales ranged from 0.12 to 0.31, with the scale of Personal Relevance having the strongest correlation with Enjoyment when all other scales were mutually controlled. The DELES, an online instrument that can be utilized by students at any location, eliminates data transfer errors and does not allow for non-responses, adding to the overall validity of the instrument. The development of DELES relied extensively on literature pertaining to high-quality distance education and expert content validation techniques. It treats distance learning as having a distinct social-psychological climate unlike those found in other post-secondary classroom environments.