10,066 research outputs found

    Computation diversity in emerging networking paradigms

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    Nowadays, computation is playing an increasingly more important role in the future generation of computer and communication networks, as exemplified by the recent progress in SDN for wired networks as well as C-RAN and mobile cloud computing (MCC) for wireless networks. This article proposes a unified concept (i.e., computation diversity) to describe the impact and diverse forms of the computation resources on both wired and wireless communications. By linking the computation resources to the communication networks based on quality of service requirements, we can show how computation resources influence the networks. Moreover, by analyzing the different functionalities of computation resources in SDN, C-RAN, and MCC, we can show the diverse and flexible forms that the computation resources present in different networks. The study of computation diversity can provide guidance in future networks design as far as how to allocate the resources jointly between computation (e.g., CPU capacity) and communication (e.g., bandwidth), thereby saving system energy and improving users' experiences

    New Terms for the Compact Form of Electroweak Chiral Lagrangian

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    The compact form of the electroweak chiral Lagrangian is a reformulation of its original form and is expressed in terms of chiral rotated electroweak gauge fields, which is crucial for relating the information of underlying theories to the coefficients of the low-energy effective Lagrangian. However the compact form obtained in previous works is not complete. In this letter we add several new chiral invariant terms to it and discuss the contributions of these terms to the original electroweak chiral Lagrangian.Comment: 3 pages, references adde

    A review towards finding a simplified approach for modelling the kinetics of the soluble microbial products (SMP) in an integrated mathematical model of membrane bioreactor (MBR)

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    Soluble microbial products (SMPs) tend to accumulate in the membrane bioreactor (MBR) systems as a consequence of high membrane rejection and apparently low biodegradability within the wastewater treatment system. The extension of the activated sludge models (ASMs) with SMPs, therefore, has received crucial importance in recent days, particularly considering their potential use as indicators of the membrane fouling propensity. This paper presents a critical review of the formation and degradation kinetics of SMP subdivisions that have so far been used for the mathematical modelling of MBR. The paper identified a simplified approach to incorporate the kinetics of the SMP formation and degradation in the general mathematical models of MBR. It suggested that the inclusion of only four additional linear differential equations in the ASM1-SMP integrated mathematical model could simulate well the effluent quality and membrane fouling prediction. The model would also serve as a useful tool in optimizing operation conditions for better treatability and fouling control. © 2013 Elsevier Ltd

    A laboratory study using maple leaves as a biosorbent for lead removal from aqueous solutions

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    This study tested the ability of maple leaf powder (MLP) to reduce the level of Pb(II) ions in aqueous solutions. As a biosorbent, MLP has a larger specific surface area (10.94 m2/g) and contains Pb(II) binding functional groups. The highest Pb(II) removals were achieved at pH of 6.2, particle size of less than 75 μm, dose of 0.5 g, initial concentration of 10 mg/l and equilibrium time of >15 minutes. Thermodynamic results indicated that the Pb(II) adsorption process was spontaneous and exothermic. MLP biosorbent could be reused for five cycles after successfully recovery by 0.1N H2SO4. Both adsorption and desorption data fit well with Langmuir and Sips isotherm models (R2 ≈ 0.961-1.00). The Pb(II) adsorption and desorption capacities (qm) of MLP were up to 50.27 mg/g and 40.06 mg/g, respectively, for a 1 g dose at room temperature. Kinetics processes were rate controlling step and showed good fitness with the pseudo-second order and intraparticle diffusion models. Results suggest that multiple mechanisms (chelating bond, physisorption and chemisorption) are involved to adsorb the Pb(II) ions on to MLP. Higher Pb(II) removal revealed the practical applicability of MLP in water and wastewater treatment systems. © IWA Publishing 2014

    Evaluation of energy-distribution of a hybrid microbial fuel cell-membrane bioreactor (MFC-MBR) for cost-effective wastewater treatment

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    © 2015 Elsevier Ltd. A low-cost hybrid system integrating a membrane-less microbial fuel cell (MFC) with an anoxic/oxic membrane bioreactor (MBR) was studied for fouling mitigation. The appended electric field in the MBR was supplied by the MFC with continuous flow. Supernatant from an anaerobic reactor with low dissolved oxygen was used as feed to the MFC in order to enhance its performance compared with that fed with synthetic wastewater. The voltage output of MFC maintained at 0.52 ± 0.02 V with 1000 Ω resister. The electric field intensity could reach to 0.114 V cm-1. Compared with the conventional MBR (CMBR), the contents rather than the components of foulants on the cake layer of fouled MFC-MBR system was significantly reduced. Although only 0.5% of the feed COD was translated into electricity and applied to MBR, the hybrid system showed great feasibility without additional consumption but extracting energy from waste water and significantly enhancing the membrane filterability

    Performance of a microbial fuel cell-based biosensor for online monitoring in an integrated system combining microbial fuel cell and upflow anaerobic sludge bed reactor

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    © 2016. A hybrid system integrating a microbial fuel cell (MFC)-based biosensor with upflow anaerobic sludge blanket (UASB) was investigated for real-time online monitoring of the internal operation of the UASB reactor. The features concerned were its rapidity and steadiness with a constant operation condition. In addition, the signal feedback mechanism was examined by the relationship between voltage and time point of changed COD concentration. The sensitivity of different concentrations was explored by comparing the signal feedback time point between the voltage and pH. Results showed that the electrical signal feedback was more sensitive than pH and the thresholds of sensitivity were S = 3 × 10-5 V/(mg/L) and S = 8 × 10-5 V/(mg/L) in different concentration ranges, respectively. Although only 0.94% of the influent COD was translated into electricity and applied for biosensing, this integrated system indicated great potential without additional COD consumption for real-time monitoring

    New functional biocarriers for enhancing the performance of a hybrid moving bed biofilm reactor-membrane bioreactor system

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    © 2016 Elsevier Ltd. In this study, new sponge modified plastic carriers for moving bed biofilm reactor (MBBR) was developed. The performance and membrane fouling behavior of a hybrid MBBR-membrane bioreactor (MBBR-MBR) system were also evaluated. Comparing to the MBBR with plastic carriers (MBBR), the MBBR with sponge modified biocarriers (S-MBBR) showed better effluent quality and enhanced nutrient removal at HRTs of 12 h and 6 h. Regarding fouling issue of the hybrid systems, soluble microbial products (SMP) of the MBR unit greatly influenced membrane fouling. The sponge modified biocarriers could lower the levels of SMP in mixed liquor and extracellular polymeric substances in activated sludge, thereby mitigating cake layer and pore blocking resistances of the membrane. The reduced SMP and biopolymer clusters in membrane cake layer were also observed. The results demonstrated that the sponge modified biocarriers were capable of improving overall MBBR performance and substantially alleviated membrane fouling of the subsequent MBR unit

    Characterization and sulfonamide antibiotics adsorption capacity of spent coffee grounds based biochar and hydrochar.

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    A large amount of spent coffee grounds is produced as a processing waste each year during making the coffee beverage. Sulfonamide antibiotics (SAs) are frequently detected in the environment and cause pollution problems. In this study, biochar (BC) and hydrochar (HC) were derived from spent coffee grounds through pyrolysis and hydrothermal carbonization, respectively. Their characteristics and sulfonamide antibiotics adsorption were investigated and compared with reference to adsorption capacity, adsorption isotherm and kinetics. Results showed BC possessed more carbonization and less oxygen-containing functional groups than HC when checked by Elemental Analysis, X-ray diffraction, X-ray photoelectron spectrometry and Fourier transform infrared. These groups affected the adsorption of sulfonamide antibiotics and adsorption mechanism. The maximum adsorption capacities of BC for sulfadiazine (SDZ) and sulfamethoxazole (SMX) were 121.5 μg/g and 130.1 μg/g at 25 °C with the initial antibiotic concentration of 500 μg/L, respectively. Meanwhile the maximum adsorption capacities of HC were 82.2 μg/g and 85.7 μg/g, respectively. Moreover, the adsorption mechanism for SAs adsorbed onto BC may be dominated by π-π electron donor-acceptor interactions, yet the SAs adsorption to HC may be attributed to hydrogen bonds. Further analysis of the adsorption isotherms and kinetics, found that physical and chemical interactions were involved in the SAs adsorption onto BC and HC. Overall, results suggested that: firstly, pyrolysis was an effective thermochemical conversion of spent coffee grounds; and secondly, BC was the more promising adsorbent for removing sulfonamide antibiotics

    Large-scale multi-stage constructed wetlands for secondary effluents treatment in northern China: Carbon dynamics

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    © 2017 Elsevier Ltd Multi-stage constructed wetlands (CWs) have been proved to be a cost-effective alternative in the treatment of various wastewaters for improving the treatment performance as compared with the conventional single-stage CWs. However, few long-term full-scale multi-stage CWs have been performed and evaluated for polishing effluents from domestic wastewater treatment plants (WWTP). This study investigated the seasonal and spatial dynamics of carbon and the effects of the key factors (input loading and temperature) in the large-scale seven-stage Wu River CW polishing domestic WWTP effluents in northern China. The results indicated a significant improvement in water quality. Significant seasonal and spatial variations of organics removal were observed in the Wu River CW with a higher COD removal efficiency of 64–66% in summer and fall. Obvious seasonal and spatial variations of CH4 and CO2 emissions were also found with the average CH4 and CO2 emission rates of 3.78–35.54 mg m−2 d−1 and 610.78–8992.71 mg m−2 d−1, respectively, while the higher CH4 and CO2 emission flux was obtained in spring and summer. Seasonal air temperatures and inflow COD loading rates significantly affected organics removal and CH4 emission, but they appeared to have a weak influence on CO2 emission. Overall, this study suggested that large-scale Wu River CW might be a potential source of GHG, but considering the sustainability of the multi-stage CW, the inflow COD loading rate of 1.8–2.0 g m−2 d−1 and temperature of 15–20 °C may be the suitable condition for achieving the higher organics removal efficiency and lower greenhouse gases (GHG) emission in polishing the domestic WWTP effluent. The obtained knowledge of the carbon dynamics in large-scale Wu River CW will be helpful for understanding the carbon cycles, but also can provide useful field experience for the design, operation and management of multi-stage CW treatments
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