Prioritized data synchronization with applications

We are interested on the problem of synchronizing data on two distinct devices with differed priorities using minimum communication. A variety of distributed sys- tems require communication efficient and prioritized synchronization, for example, where the bandwidth is limited or certain information is more time sensitive than others. Our particular approach, P-CPI, involving the interactive synchronization of prioritized data, is efficient both in communication and computation. This protocol sports some desirable features, including (i) communication and computational com- plexity primarily tied to the number of di erences between the hosts rather than the amount of the data overall and (ii) a memoryless fast restart after interruption. We provide a novel analysis of this protocol, with proved high-probability performance bound and fast-restart in logarithmic time. We also provide an empirical model for predicting the probability of complete synchronization as a function of time and symmetric differences. We then consider two applications of our core algorithm. The first is a string reconciliation protocol, for which we propose a novel algorithm with online time com- plexity that is linear in the size of the string. Our experimental results show that our string reconciliation protocol can potentially outperform existing synchroniza- tion tools such like rsync in some cases. We also look into the benefit brought by our algorithm to delay-tolerant networks(DTNs). We propose an optimized DTN routing protocol with P-CPI implemented as middleware. As a proof of concept, we demonstrate improved delivery rate, reduced metadata and reduced average delay

Quantum information with continuous variables

Quantum information is a rapidly advancing area of interdisciplinary research. It may lead to real-world applications for communication and computation unavailable without the exploitation of quantum properties such as nonorthogonality or entanglement. We review the progress in quantum information based on continuous quantum variables, with emphasis on quantum optical implementations in terms of the quadrature amplitudes of the electromagnetic field.Comment: accepted for publication in Reviews of Modern Physic

The Security of Practical Quantum Key Distribution

Quantum key distribution (QKD) is the first quantum information task to reach the level of mature technology, already fit for commercialization. It aims at the creation of a secret key between authorized partners connected by a quantum channel and a classical authenticated channel. The security of the key can in principle be guaranteed without putting any restriction on the eavesdropper's power. The first two sections provide a concise up-to-date review of QKD, biased toward the practical side. The rest of the paper presents the essential theoretical tools that have been developed to assess the security of the main experimental platforms (discrete variables, continuous variables and distributed-phase-reference protocols).Comment: Identical to the published version, up to cosmetic editorial change

Using mathematical models to track phosphorus in a full-scale wastewater treatment plant

The challenges associated with pollution, declining nutrients and water shortage, resulted in the need for strategies towards cost effective recovery of nutrients from waste types fed to wastewater treatment systems, to forms that are usable and possibly marketable, while ensuring maintenance of good effluent quality from the plant. To address these challenges, the plant wide model (PWM_SA) of Ikumi et al. (2015) was utilized to evaluate and propose operational strategies for Zeekoegat WWTW of the City of Tshwane to help with future design or optimized operation of the system. This goal was achieved by (i) acquisition of all necessary data from Zekoegat WWTP, (ii) Reconciliation of measured data and subsequent characterization of the influent WW using widely documented protocol to run an excel steady state model which uses explicit mass balanced equations and (iii) setting up Zeekoegat WWTW virtually within the WEST® dynamic simulation environment and ensuring that confidence is achieved in virtual replication of the plant before testing operational scenarios. The two operational strategies were simulated and evaluated using performance indices (PI's: operational cost index (OCI) and effluent quality index (EQI)) derived from a previous investigation by the International Water Association (IWA) benchmark simulation modelling task group (Copp, 2002, Nopenset al., 2010). These PI's were modified by De Ketele et al. (2018) and later extended by Coothen (2021) and they proved to be a useful approach to evaluating the environmental (EQI) and economic (OCI) impact of a WWTP based on any operational strategy implemented i.e., optimizing water resource recovery (WRRFs) and troubleshooting problems to improve our wastewater treatment systems in South Africa

Local governmental audit and accounting manual, as of March 1, 1991: a nonauthoritative practice aid

https://egrove.olemiss.edu/aicpa_guides/1211/thumbnail.jp

Dynamic modelling of anaerobic digestion of Fischer-Tropsch reaction water.

Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2013.Fischer-Tropsch Reaction Water (FTRW) is a high organic strength wastewater produced as a by-product in Sasol’s Fischer-Tropsch Reactors. Typically it has an organic load of 18000 mgCOD/L and is highly acidic with a pH of approximately 3.8. It is deficient in nutrients (N and P and other micronutrients). This dissertation deals with the biological and physico-chemical model development of a dynamic anaerobic digestion model, and explores two different approaches to representing the physico-chemical processes that complement and interact with the bioprocesses. The performances of the resultant two dynamic models (ADFTRW1 & AD-FTRW2) were compared in order to assess to what extent the more detailed and rigorous ionic speciation modeling in AD-FTRW2 addressed the shortcomings attributed to the simplified physicochemical modeling in AD-FTRW1. The ionic speciation model used in AD-FTRW2 uses a classic equilibrium formulation along the same lines as in the UCTADM2 model for anaerobic digestion of municipal wastewater sludges (Brouckaert et al., 2010), while AD-FTRW1 uses a simplification of the approach developed by Musvoto et al. (2000) in order to represent short chain fatty acid (SCFA) dissociation and the weak acid base chemistry of the inorganic carbon system. A 44 day extract from a 700 day laboratory-scale dataset (Van Zyl et al. 2008) was used as the basis for comparing the models. During this period the membrane bio-reactor was subjected to varying flow and load conditions. To validate the models, the experimentally measured and model predicted process variables of reactor alkalinity, reactor pH, biogas production and effluent SCFA concentration were compared. It was found that AD-FTRW2 provided superior agreement with pH data, but predictions of alkalinity, gas production rate and effluent short-chain fatty acids were not significantly improved in AD-FTRW2 relative to AD-FTRW1. This outcome was hypothesized since pH is strongly dependent on physico-chemical processes such as ionic interactions in solution and gas exchange which were the components to the models (AD-FTRW1 versus AD-FTRW2) which differed most significantly. Alkalinity, which is also highly influenced by physico-chemical model representations showed substantial improvement however statistical analysis could not show this improvement to be significant. The other two variables that were compared, biogas production and effluent SCFA concentration, displayed very similar agreement with experimental data. These variables depend more on mass balance effects and biological kinetics and were therefore not significantly altered by the more rigorous handling of aqueous chemistry in AD-FTRW2. It was concluded that AD-FTRW2 constitutes an improvement in model predictive power over AD-FTRW1 at a small cost in computing time

Local governmental audit and accounting manual, as of March 1, 1990 : a nonauthoritative practice aid

https://egrove.olemiss.edu/aicpa_guides/1210/thumbnail.jp

Improved tracking of phosphorus in wastewater treatment works through anaerobic digestion of p-rich sludge

This research aims at improving the tracking of phosphorus (P) in wastewater treatment works (WWTWs) by developing a model which accurately explains the intracellular processes of phosphorus accumulating organisms (PAOs). Two major models: the “Comeau-Wentzel” model (Comeau et al., 1987) and the “Mino” model (Mino et al., 1988) were developed to explain PAO intracellular processes but the failure of these models to achieve data reconciliation when modelling the anaerobic digestion of PAOs show that they are still incomplete. Ikumi and Ekama (2019) generated stoichiometry to help model PAO intracellular processes and hypothesised that an energy transfer between the activated sludge (AS) system and the anaerobic digester (AD) might take place. This research generated a steady state (SS) anaerobic digestion model (an extension of Sӧtemann et al.'s (2005) model) to model the treatment of sludge from nitrifying-denitrifying enhanced biological phosphorus removal (NDEBPR) system and assess, through data reconciliation, which of Ikumi and Ekama's (2019) stoichiometry best models PAO behaviour. The AD model generated achieved a high degree of correlation with experimental data but was unable to conclusively identify a single biochemical pathway for PAO processes