The Private Key Capacity of a Cooperative Pairwise-Independent Network

This paper studies the private key generation of a cooperative pairwise-independent network (PIN) with M+2 terminals (Alice, Bob and M relays), M >= 2. In this PIN, the correlated sources observed by every pair of terminals are independent of those sources observed by any other pair of terminal. All the terminals can communicate with each other over a public channel which is also observed by Eve noiselessly. The objective is to generate a private key between Alice and Bob under the help of the M relays; such a private key needs to be protected not only from Eve but also from individual relays simultaneously. The private key capacity of this PIN model is established, whose lower bound is obtained by proposing a novel random binning (RB) based key generation algorithm, and the upper bound is obtained based on the construction of M enhanced source models. The two bounds are shown to be exactly the same. Then, we consider a cooperative wireless network and use the estimates of fading channels to generate private keys. It has been shown that the proposed RB-based algorithm can achieve a multiplexing gain M-1, an improvement in comparison with the existing XOR- based algorithm whose achievable multiplexing gain is about [M]/2.Comment: 5 pages, 3 figures, IEEE ISIT 2015 (to appear

Worldgraph Approach to Yang-Mills Amplitudes from N=2 Spinning Particle

By coupling the N=2 spinning particle to background vector fields, we construct Yang-Mills amplitudes for trees and one loop. The vertex operators are derived through coupling the BRST charge; therefore background gauge invariance is manifest, and the Yang-Mills ghosts are automatically included in loop calculations by worldline ghosts. Inspired by string calculations, we extend the usual worldline approach to incorporate more "generalized" 1D manifolds. This new approach should be useful for constructing higher-point and higher-loop amplitudes.Comment: 21 pages, 4 figures; v2: 22 pages, 5 figures, major changes in section V, typos correcte

Escherichia Coli Removal from Stormwater Using Steel Chips Filter

Media filtration has received increasing attention as an effective technology that can facilitate the removal of particles and dissolved pollutions in the stormwater. However, most traditional media filtration systems are generally ineffective in removing bacteria, causing pollution of groundwater and receiving surface water. In this study, recycled steel chips were evaluated as low-cost filter materials for bacterial removal from stormwater. Laboratory column experiments were conducted to evaluate the impact of steel chips particle size, flow rate, initial E.coli concentration, pH, natural organic matter (NOM), steady and intermittent flow on E.coli removal. The results showed that E.coli removal decreased from 99.4% to 58.1% with increasing steel chip size from 0.5-1.0 mm to 4.0-8.0 mm. The E.coli removal efficiency of 1.0-2.0 mm steel chips varied between 86.5% to 99.2% and was not greatly affected by variations of infiltration rate, influent bacteria concentration, and pH. The competitive adsorption of co-loading NOM can inhibit E.coli adsorption by up to 80.5%. Intermittent flow can lower E.coli adsorption to 54.3% at the beginning of the flow event and gradually increased to 83.2% with the increase of time. The result also showed that less than 0.4% adsorbed E.coli (total adsorbed E.coli=6.7×109 MPN) were desorbed in different conditions (flow rate, NOM). Steel chips also showed high E. coli removal capacity when treating real stormwater. Overall, the results suggest that steel chips are an efficient E.coli adsorption material that can potentially be used for stormwater treatment under a wide range of field conditions

Removal of Disinfection Byproducts in Drinking Water Using Biological Filtration

Drinking water disinfection is essential to protecting public health from waterborne diseases. However, the reaction of disinfectants with natural organic matter (NOM) can form carcinogenic disinfection byproducts (DBPs). Drinking water treatment facilities employ precursor control and alternative disinfectants to minimize regulated DBPs formation to comply with Environmental Protection Agency (EPA) guidelines. Despite their efficacy, some limitations have been observed during the application, such as increased cost of enhanced coagulation, high demand for sludge disposal, inconsistency in precursor removal, and formation of more toxic unregulated and unknown DBPs. Therefore, it is important to develop more efficient and safe strategies for DBPs control. This study proposed a new strategy “pre-chlorine/biofiltration/post-chlorine treatment” to control DBPs formation in drinking water. The main objective of this study is to systematically analyze this strategy on overall DBPs control. The following tasks were performed to achieve the project objective: 1) investigating the potential of biofiltration technology for different groups of DBPs control and evaluating the impact of disinfect switch from chlorine to chloramine on biofilters performance on different DBPs removal; 2) studying the key factors that impact the performance of the biofilter on total organic halogen (TOX), unknown DBPs (UTOX), haloacetic acids (HAAs), dihaloacetonitriles (DHANs) removal, developing kinetic models and temperature activity coefficients to predict different DBPs species removal rates under various conditions; and 3) evaluating the pre-chlorination - DBP biofiltration - post-treatment water treatment strategy in DBPs removal and overall DBPs formation potential control, and investigating the impact of backwash on biofilters performance on DBP removal. The results of long-term biofiltration experiments using the City of Brookings drinking water indicate that biofiltration is an effective technology for DBPs control. Biofilters can consistently remove approximately 52% of the total organic halogens (TOX), 97% of haloacetic acids (HAAs), 14% of trihalomethanes (THMs), and 63% of unknown DBPs (UTOX) in chlorinated drinking water. Biofilters also effectively remove 46% of TOX, 14% of THMs, 96 % of HAAs, and 48% of UTOX from chloraminated drinking water. The two activated carbon biofilters (GAC 300 and 200) exhibited better DBP biofiltration efficiencies than sand and anthracite biofilters. The switch from chlorine to chloramine had little impact on HAAs biodegradation in GAC biofilters. However, it decreased UTOX biodegradation by 15%, indicating that the UTOX formed in the chloraminated water is less biodegradable than those formed in chlorinated water. Moreover, TOX spikes was observed in GAC biofilter effluents after switching to chloraminated water, which was mainly attributed to the leaching of THMs. Therefore, attention should be paid to potential DBPs leaching from GAC biofilters when switching disinfectant from chlorine to chloramine. The DBP biofiltration kinetic study results indicate that a first-order model can adequately describe the degradation of different groups of DBP in GAC biofilters, including HAAs, unknown DBPs, and Dihaloacetonitriles (DHANs), across varied empty bed contact times (EBCTs) (R2 \u3e 0.95). The biodegradation rate constants (k values) for these DBPs increased with increasing temperatures. Extending the EBCT is an effective method to improve DBPs removal, particularly at lower temperatures. In addition, the biodegradation rate constants for the studied DBPs at 5 - 20 °C were 0.106 - 0.273 min-1 for DCAA, 0.081 - 0.235 min-1 for TCAA, 0.020 - 0.046 min-1 for chlorinated UTOX and 0.018 - 0.040 min-1 for chloraminated UTOX. DHANs, including dichloroacetonitrile (DCAN), bromochloroacetonitrile (BCAN), and dibromoacetonitrile (DBAN), show effective biodegradability with k values between 0.098 and 0.427 min-1. In conclusion, the observed biodegradability order of the studied DBPs is: DCAN \u3e BCAN \u3e DBAN \u3e DCAA \u3e TCAA \u3e Cl2-UTOX \u3e NH2Cl-UTOX \u3e Chloroform. The developed first-order model and temperature activity coefficients offer a tool for predicting DBPs biodegradation rates under varying temperatures and EBCTs. Furthermore, the results indicate that the DBP-preformation - biofiltration - post-treatment strategy effectively controls the formation potential of various DBP groups. Biofiltration could remove up to 57% of preformed TOX, mainly attributed to the degradation of unknown DBPs and HAAs. Although post-treatment with chlorine and chloramine would lead to some DBP re-formation, this strategy was able to reduce the overall formation potentials of different groups of DBPs. Compared to pre-chlorine and post-chlorine treatment, the pre-chlorine/biofiltration/post-chlorine treatment reduced 71% of HAAs, 37% of DHANs, 44% of UTOX and 17% of THMs. When post-chloramine was used, the corresponding formation potential reductions were 90% of HAAs, 83% of DHANs, 43% of UTOX and 10% of THMs at an EBCT of 15 min. Therefore, the DBP-preformation - biofiltration - post-treatment strategy can significantly decrease the overall exposure of DBPs within the distribution system