The use of staged scouring aeration to reduce energy for membrane fouling was studied using one pilot-scale submerged membrane bioreactor to treat municipal wastewater. The experiments were conducted by varying each of permeate fluxes, scouring air scouring intensities and sequence during both permeation and relaxation periods while keeping other factors same. The critical and recoverable fluxes were measured by the stepwise flux method. Mixed liquor, permeate and filtrate was characterized by analysing COD, cTOC, SMP contents, etc. The recorded transmembrane pressure data were used to calculate the fouling resistance after relaxation and fouling rate of each cycle. The results showed that when operated at relatively high permeate flux rate, membrane fouling could be effectively controlled by using relatively lower air scouring intensity and/or less infrequent aeration sequence during the permeation combined subsequently with more vigorous and frequent air scouring during the relaxation. At lower permeate flux rate with good permeability sludge, membrane fouling was effectively controlled by relatively low air scouring intensity and/or relatively infrequent aeration sequence during both permeation and relaxation periods. For each sludge condition, an optimal combination of cyclic air scouring intensity and sequence existed which could minimize the aeration energy consumption while maintaining effective fouling control. The frequency of aeration sequence plays a more dominant role than the air scouring intensity during the permeation in aeration optimization. / GE Water & Process Technologies Natural Sciences and Engineering Research Council of Canada

Magistro baigiamaje darbe nagrinėjama plačiai naudojamų asimetrinių ir simetrinių šifrų bei maišos funkcijų įtaka mobilių įrenginių energijos suvartojimui. Darbe ištirti AES, Camellia ir Serpent simetriniai blokiniai ir RC4 simetrinis srautinis šifras. Tirti asimetriniai šifrai: RSA, DSA, ECDSA ir ElGamal bei MD5, SHA1, SHA2 ir Whirlpool maišos funkcijos. Suformuluotas ir pasiūlytas baterijos elgsenos matematinis modelis. Skirtingi kriptoalgoritmai palyginti energijos sąnaudų atžvilgiu ir atrinkti našiausi kiekvieno tipo šifrai. / Main topic of Master thesis is analysis on how widely used asymmetric and symmetric ciphers and hash functions influence energy consumption then used on mobile devices. In this paper AES, Camellia and Serpent block ciphers and RC4 stream cipher are being analyzed. There were RSA, DSA, ECDSA and ElGamal asymmetric ciphers and MD5, SHA1, SHA2 and Whirlpool hash function analyzed too. Proposed mathematical model of battery behaviour. Different ciphers were compared to each other and energy-wise best one are pointed out from each cipher type.

Multihop Cellular Networks (MCNs) form combined wireless paradigm that carries the advantages of both traditional cellular networks and wireless multihop relay. Cellular networks depend on a fixed infrastructure to provide wide area coverage for users with high mobility profile. Multihop relay networks depend on wireless devices inside the network to relay signals through multiple hops from source to destination. MCNs were proposed to overcome inherent drawbacks in cellular networks like congestion and dead spots. These gains build on the characteristics of multihop relay that result in increased capacity, decrease energy depletion and virtually extended coverage. But while these gains have been widely accepted and advocated, they have not been verified in rigor. A realistic need therefore exists to quantify these gains in order to realize more capable network management functionalities for this new paradigm. In this thesis, we present an analytical framework for MCNs. We quantify the capacity and energy consumption in MCNs, while considering various call distributions, network loads and transmission power. We apply our framework to Code Division Multiple Access (CDMA) cellular networks, which are very dependent on interference levels in their performance. Our results show that capacity can be increased in CDMA cellular networks using multihop relay by increasing either the number of simultaneous calls or data rates. We also demonstrate that consumed energy is decreased in MCNs, especially in environments with high path loss. We validate that multihop relay is most rewarding when calls tend to originate near cell borders. Beyond verifying basic claims, we explore other potential gains of MCNs. We investigate the viability of congestion relief and load balancing and substantiate the benefits for congested cells neighbored by lightly loaded cells. Load balancing has also been shown to increase data rates and fairness in user allocations. Lastly, we explore enabling multimedia applications in MCNs and study the application of data rate adaptations given multiple classes of service. A key advantage of our work is that, while applied to CDMA in this thesis, the presented analytical framework can be extended to other technologies. The framework also accommodates both mobile and fixed network relay elements, expanding its applicability to next generation cellular networks. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2009-01-30 09:34:39.735

No description available.

Wireless Sensor Networks (WSN), a new class of devices, has the potential to revolutionize the capturing, processing, and communication of critical data at low cost. Sensor networks consist of small, low-power, and low-cost devices with limited computational and wireless communication capabilities. These sensor nodes can only transmit a finite number of messages before they run out of energy. Thus, reducing the energy consumption per node for end-to-end data transmission is an important design consideration for WSNs. The Medium Access Control (MAC) protocols aim at providing collision-free access to the wireless medium. MAC protocols also provide the most direct control over the utilization of the transceiver, which consumes most of the energy of the sensor nodes. The major part of this thesis is based on a proposed MAC protocol called Distributed Receiver-oriented MAC (DRMACSN) protocol for code division multiple access (CDMA) based WSNs. The proposed MAC protocol employs the channel load blocking scheme to reduce energy consumption in the network. The performance of the proposed MAC protocol is verified through simulations for average packet throughput, average delay and energy consumption. The performance of the proposed MAC protocol is also compared to the IEEE 802.15.4 MAC and the MAC without the channel load sensing scheme via simulations. An analytical model is derived to analyse the average packet throughput and average energy consumption performance for the DRMACSN MAC protocol. The packet success probability, the message success and blocking probabilities are derived for the DRMACSN MAC protocol. The discrete-time multiple vacation queuing models are used to model the delay behaviour of the DRMACSN MAC protocol. The Probability Generating Functions (PGF) of the arrivals of new messages in sleep, back-off and transmit states are derived. The PGF of arrivals of retransmitted packets of a new message are also derived. The queue length and delay expressions for both the Bernoulli and Poisson message arrival models are derived. Comparison between the analytical and simulation results shows that the analytical model is accurate. The proposed MAC protocol is aimed at having an improved average packet throughput, a reduced packet delay, reduced energy consumption performance for WSN. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

Energy efficiency is an issue currently generating huge interest as a potentially costeffective solution to the twin challenges of environmental pollution from energy production, and the increasing scarcity of energy resources. This research aims to interrogate the practicalities of regulation of energy efficiency to ask what scope there is for public-led encouragement of greater energy savings in industry. Shortcomings of current theory addressed include a discounting of the impact of heterogeneity of industrial activity on prospects to effectively regulate for energy efficiency, and a conflation of the different aspects of societal functioning to which energy efficiency regulations and incentives can be applied. The research argues that the scope for energy savings has been exaggerated and the factors which drive pursuit of energy efficiency within firms of different sizes poorly understood and articulated. The Voluntary Agreement form of environmental regulation is assessed for its applicability to regulating for energy efficiency in the context of these characteristics of energy efficiency in industrial settings. An in-depth interview approach with core participants in an example of a Voluntary Agreement for energy efficiency in South Africa, the Energy Efficiency Accord (Accord), reveals the difficulties of regulating for specific technologies, the generally targeted nature of energy efficiency incentive schemes which provide household and commercial-type programmes to heavy industry, and the fact that environmental objectives and capacities are highly developed within firms interviewed and in most cases precede participation in Accord activities. The inference is that participation at this stage of the Accord's existence is driven by the need to develop and maintain relations between key stakeholders, and to exploit opportunities to influence the form of energy efficiency regulation enacted as opposed to the need to obtain forms of technical guidance. The particular pattern of participation in the Accord is argued to result in part from the historical dominance of large, energy-intensive firms in South Africa, and to be consistent with the theory that the more energy-intensive firms in a society will be motivated to participate in voluntary initiatives such as the Accord. / Thesis (M.A.)-University of KwaZulu-Natal, Durban, 2008.

As South Africa's electricity consumption increases, Eskom is promoting Demand Side Management (DSM) to aid control of both the electricity consumption and its more effective usage, thereby delaying the need to construct new power stations, which pose large economic and environmental problems. Eskom has investigated various DSM strategies, such as load shifting, co-generation, alternative fuels and energy efficient processes, and has targeted the areas of load shifting and energy efficiency as prime areas for energy savings as they are relatively inexpensive and easy to implement. Pumps and fans form a large part of the industrial load. By improving the power usage of these devices with the use of variable speed drives, large energy savings may be achieved. To enable the energy usage of industrial loads to be evaluated, a test bed system which enables a variable speed drive to be loaded with a configurable load, was constructed. The test bed system forms a tool for evaluating and demonstrating the energy savings that are possible, by replacing fixed speed drives with variable speed drives when controlling the flow rate of pumps and fans. Results from the test bed system show that by using variable speed operation of pumps and fans, some energy savings are achievable when compared to existing methods of flow control. The achievable energy savings are dependent on the system properties and the duty cycle of the pump or fan system. / Thesis (M.Sc.)-University of Natal, Durban, 2001.

The following report investigates district cooling systems. This form of technology provides an alternative means of providing cooling. In a traditional cooling system each building would include cooling equipment to serve only that building. District cooling differs in that water is chilled at one location and pumped to two or more buildings. District cooling has many benefits over traditional cooling systems. This report, however, aims to determine the economic benefits (if any) of district cooling systems. The location chosen as a model for this study was the University of Natal (Durban) campus. This campus currently operates a district cooling system serving six buildings. This study is hypothetical in nature, as the cooling system is already finalized and operational. The aim of this dissertation is to answer the question of which would be the more attractive alternative if the University were in a position of having to install a completely cooling system. One of the most important steps in this process is the calculation of cooling loads. The cooling load was estimated for each of the buildings associated with the district cooling system. The LOADEST software package was used to derive these cooling loads. The accuracy of LOADEST software was also validated in this study. The bulk of this report is composed of the preliminary work required to obtain capital and operating costs for cooling systems, including validation of cooling load calculation software. It was felt that this prelimiinary work justified inclusion in the final report to provide accurate representation of the steps taken before any economic evaluation could be reached. The capital and operating costs of the district cooling system and a more traditional system were compared. It was found that the district cooling system reduces operating costs significantly, although it's capital cost is higher than the traditional system against which it was compared. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2003.

Sustainable manufacturing involves utilizing energy resources efficiently. Currently, the state of sustainability for a given manufacturing process is described by most in a qualitative sense as opposed to using quantitative metrics. This thesis offers a segment of analysis needed to understand the state of sustainability in the context of energy resource utilization. This was accomplished by measuring the order of magnitude difference between the energy consumption of a manufacturing process vs. the theoretical minimum amount of energy required to complete the same task (aluminum T-joint bond). This analysis was completed for a TIG welding process and a controlled atmosphere brazing (CAB) process. Also, the energy Sankey diagram was constructed for the TIG welding process. The TIG welding process and CAB process consumed an average of 136.1 ± 16.5 kJ and 6,830 ± 77 kJ respectively to bond the same sample. The TIG welding process consumed O(102 kJ) more than the theoretical minimum amount needed to complete the same bond while the CAB process consumed O(104 kJ) more than the theoretical minimum. In the context of energy consumption, there are sizable margins for improvement for both metal joining processes analyzed in this study.

This study addresses 5 uncertainties that exist in the operation of HVAC systems, which will presumably affect the actual energy consumption of the HVAC system in comparison to the consumption under idealized bahavior. We consequently add these parameters and their uncertainty range into the source code, eventually resulting in an EnergyPlus program in which the HVAC operation uncertainty is embedded as so-called model form uncertainty. The upgraded EnergyPlus is tested for each parameter uncertainty separately, and to show the impact of each uncertainty albeit for hypothetical uncertainty ranges of the parameters.