Investigation of water displacement following large CO2 sequestration operations

The scale of CO2 injection into the subsurface required to address CO2 atmospheric concentrations is unprecedented. Multiple injection sites injecting into multiple formations will create a large excess pressure zone extending far beyond the limited volume where CO2 is present. In a closed system, additional mass is accommodated by the compressibility of system components, an increase in fluid pressure, and possibly an uplift of the land surface. In an open system, as assumed in this analysis, another coping mechanism involves fluid flux out of the boundaries of the system, in which case the fresh-water-bearing outcrop areas, corresponding to the up-dip sections of the down-dip formations into which CO2 is injected, could be impacted. A preliminary study using a MODFLOW groundwater model extending far down-dip shows that injecting a large amount of fluid does have an impact some distance away from the injection area but most likely only in localized areas. A major assumption of this preliminary work was that multiphase processes do not matter some distance away from the injection zones. In a second step, presented in this paper, to demonstrate that a simplified model can yield results as useful as those of a more sophisticated multiphase-flow compositional model, we model the same system using CMG-GEM software. Because the chosen software lacks the ability to deal easily with unconfined water flow, we compare fluxes through time, as given by MODFLOW and CMG-GEM models at the confined/unconfined interface.Bureau of Economic Geolog

Criminology in Action: Examining Corruption in Russia Under the Lens of Criminological Theories

The purpose of this research paper is to investigate whether there exist alterative methods ofexamining the widespread nature of corruption in Russia. According to Transparency International’s most recently published Corruption Perceptions Index 2012, Russia ranks 133 out of 176 countries and territories, indicating that Russia’s public sector is perceived to be a corrupt as those of the Comoros, Guyana, Honduras, Iran, and Kazakhstan. This paper advocates the view that what is currently needed most is not solutions or prescriptive measures to curb such high levels of reported corruption in Russia. Rather, this paper seeks to ultimately gain a better understanding of the conditions behind Russia’s consistently low-ranking with regards to its high levels of perceived corruption. To achieve this aim, a method of examining corruption under the lens of criminological theories is proposed. Corruption is defined as the acceptance of bribes in Russia’s civil service system. Based on a review of relevant criminological theories and an examination of the supporting body of academic literature, criminological theories deemed most applicable to the study of corruption in Russia’s civil service system are rational choice theory, social control theory, and strain theory. In contrast, theories requiring further research before any direct applications can be established include critical theory, biological theory, and labeling theory. The paper ends by highlighting several areas that deserve further study in order to advance with this newly proposed method of examining corruption in Russia

Structural and magnetic properties of FeMnx_x (x=x=1...6) chains supported on Cu2_2N / Cu (100)

Heterogeneous atomic magnetic chains are built by atom manipulation on a Cu$_2$N/Cu (100) substrate. Their magnetic properties are studied and rationalized by a combined scanning tunneling microscopy (STM) and density functional theory (DFT) work completed by model Hamiltonian studies. The chains are built using Fe and Mn atoms ontop of the Cu atoms along the N rows of the Cu$_2$N surface. Here, we present results for FeMn$_x$ ($x$=1...6) chains emphasizing the evolution of the geometrical, electronic, and magnetic properties with chain size. By fitting our results to a Heisenberg Hamiltonian we have studied the exchange-coupling matrix elements $J$ for different chains. For the shorter chains, $x \leq 2$, we have included spin-orbit effects in the DFT calculations, extracting the magnetic anisotropy energy. Our results are also fitted to a simple anisotropic spin Hamiltonian and we have extracted values for the longitudinal-anisotropy $D$ and transversal-anisotropy $E$ constants. These parameters together with the values for $J$ allow us to compute the magnetic excitation energies of the system and to compare them with the experimental data.Comment: 10 pages 8 figure

Weibull-type limiting distribution for replicative systems

The Weibull function is widely used to describe skew distributions observed in nature. However, the origin of this ubiquity is not always obvious to explain. In the present paper, we consider the well-known Galton-Watson branching process describing simple replicative systems. The shape of the resulting distribution, about which little has been known, is found essentially indistinguishable from the Weibull form in a wide range of the branching parameter; this can be seen from the exact series expansion for the cumulative distribution, which takes a universal form. We also find that the branching process can be mapped into a process of aggregation of clusters. In the branching and aggregation process, the number of events considered for branching and aggregation grows cumulatively in time, whereas, for the binomial distribution, an independent event occurs at each time with a given success probability.Comment: 6 pages and 5 figure

Dynamic modelling of a fractionation process for a liquid mixture using supercritical carbon dioxide

This work presents a simple dynamic modelling of a process of separation of a quaternary mixture using supercritical CO2. Thermodynamic description is accomplished using efficient available models (SRK equation of state with MHV2 mixing rules). An approximate approach was compared to the rigorous resolution of the system of algebro-differential equations, and was shown to enable a correct description of the dynamic behaviour. The modelling was compared to experiments performed on a small pilot composed of one 200-ml contactor and a cascade of three cyclonic separators. Good results were obtained for the contactor, although they were not very satisfactory for the description of the fractionation in the cyclonic separators. Even if discrepancies between experimental and calculated results may probably originate from the experimental procedure, the hydrodynamic description of the separators here is likely to be oversimplified. The cyclonic separator cannot be regarded as a simple theoretical stage (TSM), and we have proposed an alternate description (EPSM), that, although more suitable, still needs to be improved

MuON: Epidemic based mutual anonymity in unstructured P2P networks

A mutual anonymity system enables communication between a client and a service provider without revealing their identities. In general, the anonymity guarantees made by the protocol are enhanced when a large number of participants are recruited into the anonymity system. Peer-to-peer (P2P) systems are able to attract a large number of nodes and hence are highly suitable for anonymity systems. However, the churn (changes in system membership) within P2P networks, poses a significant challenge for low-bandwidth reliable anonymous communication in these networks. This paper presents MuON, a protocol to achieve mutual anonymity in unstructured P2P networks. MuON leverages epidemic-style data dissemination to deal with churn. Simulation results and security analysis indicate that MuON provides mutual anonymity in networks with high churn, while maintaining predictable latencies, high reliability, and low communication overhead

Mitigating radiation damage of single photon detectors for space applications

Single-photon detectors in space must retain useful performance characteristics despite being bombarded with sub-atomic particles. Mitigating the effects of this space radiation is vital to enabling new space applications which require high-fidelity single-photon detection. To this end, we conducted proton radiation tests of various models of avalanche photodiodes (APDs) and one model of photomultiplier tube potentially suitable for satellite-based quantum communications. The samples were irradiated with 106 MeV protons at doses approximately equivalent to lifetimes of 0.6 , 6, 12 and 24 months in a low-Earth polar orbit. Although most detection properties were preserved, including efficiency, timing jitter and afterpulsing probability, all APD samples demonstrated significant increases in dark count rate (DCR) due to radiation-induced damage, many orders of magnitude higher than the 200 counts per second (cps) required for ground-to-satellite quantum communications. We then successfully demonstrated the mitigation of this DCR degradation through the use of deep cooling, to as low as -86 degrees C. This achieved DCR below the required 200 cps over the 24 months orbit duration. DCR was further reduced by thermal annealing at temperatures of +50 to +100 degrees C.Comment: The license has been corrected. Note that the license of v2 was incorrect and not valid. No other changes since v