A framework for better understanding drinking-water quality in Happy Valley-Goose Bay, Labrador: Implications for optimization and protection of municipally supplied water

This research project was driven by the recurring complaints and concerns voiced in the media by residents living in the Valley area of the community of Happy Valley-Goose Bay, Labrador. Drinking water in this town is supplied by two water treatment plants (a municipality treatment plant and a DND treatment plant), which use raw water from two different sources (groundwater from multiple wells versus surface water from Spring Gulch brook) and use two different processes of drinking-water treatment. In fact, the drinking water supplied in the Valley area has a unique distribution arrangement. To meet demand, the Valley area is served by a blend of treated waters from a storage reservoir (Sandhill reservoir), which is fed by both water treatment plants. Most of the time, treated water from the municipal treatment plant dominates in the mixture. As water travels through the distribution system and household plumbing, specific reactions can occur either in the water itself and/or at the solid–liquid interface at the pipe walls; this is strongly influenced by the physical and chemical characteristics of the water. These reactions can introduce undesirable chemical compounds and/or favor the growth of bacteria in the drinking water, causing the deterioration of the quality of water reaching the consumer taps. In the distribution system in general, these chemical constituents and bacteria may pose potential threats to health or the water’s aesthetic qualities (smell, taste or appearance). Drinking water should be not only safe, but also palatable.

História eruptiva do sistema vulcânico fissural dos picos e avaliação da susceptibilidade a escoadas lávicas (ilha de S. Miguel - Açores)

Tese de Doutoramento, Geologia (Vulcanologia), 18 de Julho 2013, Universidade dos Açores.

AIR SIDE HEAT TRANSFER ENHANCEMENT IN HEAT EXCHANGERS UTILIZING INNOVATIVE DESIGNS AND THE ADDITIVE MANUFACTURING TECHNIQUE

Over the last decade, rapid development of additive manufacturing techniques has allowed the fabrication of innovative and complex designs. One field that can benefit from such technology is heat exchanger fabrication, as heat exchanger design has become more and more complex due to the demand for higher performance particularly on the air side of the heat exchanger. By employing the additive manufacturing, a heat exchanger design was successfully realized, which otherwise would have been very difficult to fabricate using conventional fabrication technologies. In this dissertation, additive manufacturing technique was implemented to fabricate an advanced design which focused on a combination of heat transfer surface and fluid distribution system. Although the application selected in this dissertation is focused on power plant dry cooling applications, the results of this study can directly and indirectly benefit other sectors as well, as the air-side is often the limiting side for in liquid or single phase cooling applications. Two heat exchanger designs were studied. One was an advanced metallic heat exchanger based on manifold-microchannel technology and the other was a polymer heat exchanger based on utilization of prime surface technology. Polymer heat exchangers offer several advantages over metals such as antifouling, anticorrosion, lightweight and often less expensive than comparable metallic heat exchangers. A numerical modeling and optimization were performed to calculate a design that yield an optimum performance. The optimization results show that significant performance enhancement is noted compared to the conventional heat exchangers like wavy fins and plain plate fins. Thereafter, both heat exchangers were scaled down and fabricated using additive manufacturing and experimentally tested. The manifold-micro channel design demonstrated that despite some fabrication inaccuracies, compared to a conventional wavy-fin surface, 15% - 50% increase in heat transfer coefficient was possible for the same pressure drop value. In addition, if the fabrication inaccuracy can be eliminated, an even larger performance enhancement is predicted. Since metal based additive manufacturing is still in the developmental stage, it is anticipated that with further refinement of the manufacturing process in future designs, the fabrication accuracy can be improved. For the polymer heat exchanger, by fabricating a very thin wall heat exchanger (150μm), the wall thermal resistance, which usually becomes the limiting side for polymer heat exchanger, was calculated to account for only up to 3% of the total thermal resistance. A comparison of air-side heat transfer coefficient of the polymer heat exchanger with some of the commercially available plain plate fin surface heat exchangers show that polymer heat exchanger performance is equal or superior to plain plate fin surfaces. This shows the promising potential for polymer heat exchangers to compete with conventional metallic heat exchangers when an additive manufacturing-enabled fabrication is utilized. Major contributions of this study are as follows: (1) For the first time demonstrated the potential of additive manufacturing in metal printing of heat exchangers that benefit from a sophisticated design to yield a performance substantially above the respective conventional systems. Such heat exchangers cannot be fabricated with the conventional fabrication techniques. (2) For the first time demonstrated the potential of additive manufacturing to produce polymer heat exchangers that by design minimize the role of thermal conductivity and deliver a thermal performance equal or better that their respective metallic heat exchangers. In addition of other advantages of polymer over metal like antifouling, anticorrosion, and lightweight. Details of the work are documented in respective chapters of this thesis.

Experimental study on the impact of using a fan coil in the evaluation of contaminant removal effectiveness of common air diffusion strategies

Indoor Air 2016 - The 14th International Conference Indoor Air Quality and Climate

The visibility/invisibility paradox of trust: Developing distributed educational leadership for online communities

A visibility/invisibility paradox of trust operates in the development of distributed educational leadership for online communities. If trust is to be established, the team-based informal ethos of online collaborative networked communities requires a different kind of leadership from that observed in more formal face-to-face positional hierarchies. Such leadership is more flexible and sophisticated, being capable of encompassing both ambiguity and agile response to change. Online educational leaders need to be partially invisible, delegating discretionary powers, to facilitate the effective distribution of leadership tasks in a highly trusting team-based culture. Yet, simultaneously, online communities are facilitated by the visibility and subtle control effected by expert leaders. This paradox: that leaders need to be both highly visible and invisible when appropriate, was derived during research on 'Trust and Leadership' and tested in the analysis of online community case study discussions using a pattern-matching process to measure conversational interactions. This paper argues that both leader visibility and invisibility are important for effective trusting collaboration in online distributed leadership. Advanced leadership responses to complex situations in online communities foster positive group interaction, mutual trust and effective decision-making, facilitated through the active distribution of tasks.

Real-time load-side control of electric power systems

Two trends are emerging from modern electric power systems: the growth of renewable (e.g., solar and wind) generation, and the integration of information technologies and advanced power electronics. The former introduces large, rapid, and random fluctuations in power supply, demand, frequency, and voltage, which become a major challenge for real-time operation of power systems. The latter creates a tremendous number of controllable intelligent endpoints such as smart buildings and appliances, electric vehicles, energy storage devices, and power electronic devices that can sense, compute, communicate, and actuate. Most of these endpoints are distributed on the load side of power systems, in contrast to traditional control resources such as centralized bulk generators. This thesis focuses on controlling power systems in real time, using these load side resources. Specifically, it studies two problems.

(1) Distributed load-side frequency control: We establish a mathematical framework to design distributed frequency control algorithms for flexible electric loads. In this framework, we formulate a category of optimization problems, called optimal load control (OLC), to incorporate the goals of frequency control, such as balancing power supply and demand, restoring frequency to its nominal value, restoring inter-area power flows, etc., in a way that minimizes total disutility for the loads to participate in frequency control by deviating from their nominal power usage. By exploiting distributed algorithms to solve OLC and analyzing convergence of these algorithms, we design distributed load-side controllers and prove stability of closed-loop power systems governed by these controllers. This general framework is adapted and applied to different types of power systems described by different models, or to achieve different levels of control goals under different operation scenarios. We first consider a dynamically coherent power system which can be equivalently modeled with a single synchronous machine. We then extend our framework to a multi-machine power network, where we consider primary and secondary frequency controls, linear and nonlinear power flow models, and the interactions between generator dynamics and load control.

(2) Two-timescale voltage control: The voltage of a power distribution system must be maintained closely around its nominal value in real time, even in the presence of highly volatile power supply or demand. For this purpose, we jointly control two types of reactive power sources: a capacitor operating at a slow timescale, and a power electronic device, such as a smart inverter or a D-STATCOM, operating at a fast timescale. Their control actions are solved from optimal power flow problems at two timescales. Specifically, the slow-timescale problem is a chance-constrained optimization, which minimizes power loss and regulates the voltage at the current time instant while limiting the probability of future voltage violations due to stochastic changes in power supply or demand. This control framework forms the basis of an optimal sizing problem, which determines the installation capacities of the control devices by minimizing the sum of power loss and capital cost. We develop computationally efficient heuristics to solve the optimal sizing problem and implement real-time control. Numerical experiments show that the proposed sizing and control schemes significantly improve the reliability of voltage control with a moderate increase in cost.

Evaluación técnica y económica para analizar la viabilidad del montacargas eléctrico en el sector productivo

Esta tesis pretende demostrar y describir las diferentes características de los montacargas que existen en el mercado, teniendo en cuenta sus ventajas y desventajas, logrando como objetivo analizar la viabilidad de la implementación de los montacargas eléctricos en la industria colombiana a partir de la información brindada sobre las características esenciales de los montacargas eléctricos que hay en el mercado. Así mismo, se quiere mostrar que los montacargas eléctricos generan un ahorro sustancial en comparación con los montacargas convencionales que hay hoy en día en el mercado, logrando así que la industria colombiana reduzca sus gastos en un porcentaje mediante la implementación de las nuevas referencias de montacargas eléctricos los cuales serian una alternativa para las compañías colombianas. Mediante una detallada revisión conceptual, se mostrara la viabilidad de los montacargas eléctricos frente a los otros tipos de montacargas, teniendo como premisa el conocimiento de lo que hoy en día requieren las industrias colombianas, y cumpliendo así con una detallada comparación en donde se enfatice la diferenciación de los montacargas eléctricos con otros tipos que existen y se logre brindar una clara percepción de estos junto con las ventajas de estos vehículos para lograr así brindar mayor información a la industria colombiana sobre las ventajas de la implementación de los montacargas eléctricos en la industria colombiana.

Surface Active Substances in the Cochin Estuarine System

This study focuses on the fractionation and quantification of chlorophenols, the most important and potential pollutant in this category, the distribution and seasonal dynamics of MBAS, phenols and clorophenols and development of a model to describe the chemical reactivity of the estuary are utilizing the dynamics of boron. The CES is highly influenced by various anthropogenic activities like discharge of agricultural, industrial and urban wastes operation of shipyard, oil and other transporting activities, fishing, dredging etc. Seasonal values of MBAS showed high values in the surface water during monsoon compared to premonsoon and postmonsoon. In the Cochin estuary o-chlorophenol and p-chlorophenol showed low values in the surface water compared to bottom water in the northern part of the estuary and higher values in the surface water in the southern part

Distribution of organic-walled dinoflagellate cysts in surface sediments of the Benguela upwelling system

To obtain insight in the relationship between the spatial distribution of organic-walled dinoflagellate cysts (dinocysts) and local environmental conditions, fifty-eight surface sediment samples from the coastal shelf off SW Africa were investigated on their dinocyst content with special focus on the two main river systems and the active upwelling that characterise this region. To avoid possible overprint by species-selective preservation, samples have been selected mainly from shelf sites where high sedimentation rates and/or low bottom water oxygen concentrations prevail. Multivariate ordination analyses have been carried out to investigate the relationship between the distribution patterns of individual species to environmental parameters of the upper water column and sediment transport processes. The main oceanographical variables at the surface (temperature, salinity, nutrients chlorophyll-a) in the region show onshore-offshore gradients. This pattern is reflected in the dinocyst associations with high relative abundances of heterotrophic dinocyst species in neritic regions characterised by high chlorophyll-aand low salinity conditions in surface waters. Phototrophic dinocyst species, notably Operculodinium centrocarpum, dominate in the more oceanic area. Differences in the distribution of phototrophic dinocyst species can be related to sea surface salinity and sea surface temperature gradients and to a lesser extent to chlorophyll-a concentrations. Apart from longitudinal gradients the dinocyst distribution clearly reflects regional environmental features. Six groups of species can be distinguished, characteristic for (1) coastal regions (cysts of Polykrikos kofoidii and Selenopemphix quanta), (2) the vicinity of active upwelling (Brigantedinium spp., Echinidinium aculeatum, Echinidinium spp. and Echinidinium transparantum), (3) river mouths (Lejeunecysta oliva, cysts of Protoperidinium americanum, Selenopemphix nephroides and Votadinium calvum), (4) slope and open ocean sediments (Dalella chathamense, Impagidinium patulum and Operculodinium centrocarpum, (5) the southern Benguela region (south of 24°S) (Spiniferites ramosus) and (6) the northern Benguela region (north of 24°S) (Nematosphaeropsis labyrinthus and Pyxidinopsis reticulata). No indication of overprint of the palaeo-ecological signal by lateral transport of allochthonous species could be observed.

Pore size distribution analysis of activated carbons: Application of density functional theory using nongraphitized carbon black as a reference system

The application of nonlocal density functional theory (NLDFT) to determine pore size distribution (PSD) of activated carbons using a nongraphitized carbon black, instead of graphitized thermal carbon black, as a reference system is explored. We show that in this case nitrogen and argon adsorption isotherms in activated carbons are precisely correlated by the theory, and such an excellent correlation would never be possible if the pore wall surface was assumed to be identical to that of graphitized carbon black. It suggests that pore wall surfaces of activated carbon are closer to that of amorphous solids because of defects of crystalline lattice, finite pore length, and the presence of active centers.. etc. Application of the NLDFT adapted to amorphous solids resulted in quantitative description of N-2 and Ar adsorption isotherms on nongraphitized carbon black BP280 at their respective boiling points. In the present paper we determined solid-fluid potentials from experimental adsorption isotherms on nongraphitized carbon black and subsequently used those potentials to model adsorption in slit pores and generate a corresponding set of local isotherms, which we used to determine the PSD functions of different activated carbons. (c) 2005 Elsevier Ltd. All rights reserved.

Crossing boundaries to explore sustainable architecture by open system design

This paper argues a model of open system design for sustainable architecture, based on a thermodynamics framework of entropy as an evolutionary paradigm. The framework can be simplified to stating that an open system evolves in a non-linear pattern from a far-from-equilibrium state towards a non-equilibrium state of entropy balance, which is a highly ordered organization of the system when order comes out of chaos. This paper is work in progress on a PhD research project which aims to propose building information modelling for optimization and adaptation of buildings environmental performance as an alternative sustainable design program in architecture. It will be used for efficient distribution and consumption of energy and material resource in life-cycle buildings, with the active involvement of the end-users and the physical constraints of the natural environment.

A self-tuning feedforward active noise control system

This paper proposes a self-tuning feedforward active noise control (ANC) system with online secondary path modeling. The step-size parameters of the controller and modeling filters have crucial rule on the system performance. In literature, these parameters are adjusted by trial-and-error. In other words, they are manually initialized before system starting, which require performing extensive experiments to ensure the convergence of the system. Hence there is no guarantee that the system could perform well under different situations. In the proposed method, the appropriate values for the step-sizes are obtained automatically. Computer simulation results indicate the effectiveness of the proposed method.

A coordinated voltage control approach for coordination of OLTC, voltage regulator and DG to regulate voltage in a distribution feeder

Integration of small-scale electricity generators, known as Distributed Generation (DG), into the distribution networks has become increasingly popular at the present. This tendency together with the falling price of synchronous-type generator has potential to give the DG a better chance in participating in the voltage regulation process together with other devices already available in the system. The voltage control issue turns out to be a very challenging problem for the distribution engineers since existing control coordination schemes would need to be reconsidered to take into account the DG operation. In this paper, we propose a control coordination technique, which is able to utilize the ability of the DG as a voltage regulator, and at the same time minimizes interaction with other active devices, such as On-load Tap Changing Transformer (OLTC) and voltage regulator. The technique has been developed based on the concept of control zone, Line Drop Compensation (LDC), as well as the choice of controller's parameters. Simulations carried out on an Australian system show that the technique is suitable and flexible for any system with multiple regulating devices including DG.

A high performance feedback active noise control system

In many active noise control (ANC) applications, an online secondary path modelling method that uses a white noise as a training signal is required. This paper proposes a new feedback ANC system. Here we modified both the FxLMS and the VSS-LMS algorithms to raised noise attenuation and modelling accuracy for the overall system. The proposed algorithm stops injection of the white noise at the optimum point and reactivate the injection during the operation, if needed, to maintain performance of the system. Preventing continuous injection of the white noise increases the performance of the proposed method significantly and makes it more desirable for practical ANC systems. Computer simulation results shown in this paper indicate effectiveness of the proposed method.

Consultant engagement for computer system selection: a pro-active client role in small enterprises

Because of their limited number of senior positions and fewer alternative career paths, small businesses have a more difficult time attracting and retaining skilled information systems (IS) staff and are thus dependent upon external expertise. Small businesses are particularly dependent on outside expertise when first computerizing. Because small businesses suffer from severe financial constraints. it is often difficult to justify the cost of custom software. Hence. for many small businesses, engaging a consultant to help with identifying suitable packaged software and related hardware, is their first critical step toward computerization. This study explores the importance of proactive client involvement when engaging a consultant to assist with computer system selection in small businesses. Client involvement throughout consultant engagement is found to be integral to project success and frequently lacking due to misconceptions of small businesses regarding their role. Small businesses often overestimate the impact of consultant and vendor support in achieving successful computer system selection and implementation. For consultant engagement to be successful, the process must be viewed as being directed toward the achievement of specific organizational results where the client accepts responsibility for direction of the process.