Search

Pharmaceutical pollutants, such as gastrointestinal drugs, pose a significant environmental concern due to their widespread use and potential adverse effects on ecosystems. Insights obtained from computational simulations yielded a more profound grasp of the adsorption mechanism. This study investigated the pH-sensitive adsorption characteristics of two commonly used gastrointestinal drugs, famotidine (FA) and pantoprazole (PA), as pharmaceutical pollutants. The adsorption process was studied using a computational modelling approach, focusing on the Au-doped@ZIF-90-glycerol adsorbent (A@Z/G) as a pivotal adsorbent. This adsorbent demonstrated remarkable adsorption capabilities for both FA and PA. The computational modelling revealed that the adsorption process is highly dependent on the pH of the environment. In protonated form, the adsorbent exhibited a significantly higher affinity towards the drugs, resulting in a more efficient removal of pharmaceutical pollutants. The interactions between the adsorbent and drugs were explored, revealing the crucial role of π–π stacking, electrostatic and van der Waals interactions, and hydrogen bonding. These interactions contributed to the strong adsorption affinity observed between the drugs and the A@Z/G adsorbent. Furthermore, the computational analysis uncovered the pH-sensitive nature of the adsorption process. At lower pH values, the protonation of the adsorbent enhanced its positive charge, leading to increased electrostatic attraction with the negatively charged drug surface. This pH-sensitive behaviour highlights the potential of the A@Z/G adsorbent for the targeted removal of pharmaceutical pollutants under specific pH conditions. [ABSTRACT FROM AUTHOR]

In airlift systems, the difference in gas holdup (εg) between the riser and the downcomer creates the driving force for liquid circulation. This feature can be an interesting approach to using an airlift pump instead of the conventional paddlewheels for simultaneous mixing between phases and supply of air to microalgae in the biomass culture ponds. Before any biomass cultivation, the hydrodynamic behavior of the system must be recognized. Therefore, cold model hydrodynamic characteristics in the air–water system of a novel oval airlift open pond (AOP) are presented by studying gas holdup and riser liquid velocity (Ulr) at different ratios of baffle clearances from the top and bottom (ht/hb) in the AOP. The gas holdup is one of the key parameters to describe the performance of airlift systems, so the effect of riser superficial gas velocity (Ugr), riser liquid velocity, and ht/hb ratios on gas holdup are investigated in this research. The results of this study indicate that superficial gas velocity, riser liquid velocity, and ht/hb ratio have a pronounced effect on the gas holdup. Moreover, due to the lack of gas holdup correlations in the AOP system, new empirical correlations have been developed to predict total gas holdup, riser gas holdup (εgr), and downcomer gas holdup (εgd) with satisfactory accuracy. [ABSTRACT FROM AUTHOR]

Multivariable nature of the flotation process compels advanced control strategies, including Model Predictive Controllers (MPC), leading to robust and effective compensation of disturbances. However, the complexity of calculations and implementation has limited their application in the industry. On the other hand, decoupling methods promise drastic reduction in computation time and complexity, while considering the multivariable relations between the inputs and outputs indirectly. Therefore, in this paper, an Adaptive Decoupling Controller (ADC) was designed and implemented on a pilot flotation column and its control performance was compared to MPC and SISO PID. Results showed that the weak coupling of variables in the studied case (and also reported by other researchers) causes a satisfactory control of the column by ADC, even better than the MPC in terms of Integral Squared Error index (ISE), Mean Squared Error index (MSE) and total energy consumption, with lower costs of computation and implementation. [ABSTRACT FROM AUTHOR]

This paper applies multiple-input multiple-output (MIMO) transmission methods to multiwire communication systems. Using channel matrices generated from a binder MIMO channel model, a performance assessment of digital subscriber line (DSL) technology based on MIMO transmission methods finds that symmetric data rates of more than 1 Gbps are achievable over four twisted pairs (category 3) for a 300 m range. Similar results are also obtained for a "quad" cable. To achieve this data rate, this paper proposes that the source and load be excited using common mode. Index Terms--Digital subscriber line, Gigabit digital subscriber line (GDSL), MIMO systems, twisted pair cables.

This paper introduces a multiple-input multiple-output channel model for the characterization of a binder of telephone lines. This model is based on multiconductor transmission line theory, and uses parameters that can be obtained from electromagnetic theory or measured data. The model generates frequency-dependent channel/binder transfer function matrices as a function of cable type, geometric line-spacing and twist-length parameters, and source-load configurations. The model allows the extraction of the magnitude and the phase of individual near end crosstalk, far end crosstalk, split-pair, and phantom transfer functions from the transfer function matrix of the binder. These individual crosstalk transfer functions are often found to be very sensitive to small imperfections in the binder. Examples of category 3 twisted pair American telephone lines and "quad" telephone cables are also presented. Index Terms--Crosstalk, multiconductor transmission lines (MTLs), multiple-input multiple-output (MIMO) systems, subscriber loops, twisted pair cables.

Upper and lower bounds on the capacity and minimum energy-per-bit for general additive white Gaussian noise (AWGN) and frequency-division AWGN (FD-AWGN) relay channel models are established. First, the max-flow min-cut bound and the generalized block-Markov coding scheme are used to derive upper and lower bounds on capacity. These bounds are never tight for the general AWGN model and are tight only under certain conditions for the FD-AWGN model. Two coding schemes that do not require the relay to decode any part of the message are then investigated. First, it is shown that the "side-information coding scheme" can outperform the block-Markov coding scheme. It is also shown that the achievable rate of the side-information coding scheme can be improved via time sharing. In the second scheme, the relaying functions are restricted to be linear. The problem is reduced to a "single-letter" nonconvex optimization problem for the FD-AWGN model. The paper also establishes a relationship between the minimum energy-per-bit and capacity of the AWGN relay channel. This relationship together with the lower and upper bounds on capacity are used to establish corresponding lower and upper bounds on the minimum energy-per-bit that do not differ by more than a factor of 1.45 for the FD-AWGN relay channel model and 1.7 for the general AWGN model. Index Terms--Additive white Gaussian noise (AWGN) channels, channel capacity, minimum energy-per-bit, relay channel.

Convective heat transfer and effect of nonlinear wall slip are studied analytically in concentric microannulus for viscoelastic fluids obeying the Giesekus constitutive equation. Laminar, thermally, and hydrodynamically fully developed flow is considered. A nonlinear Navier model with nonzero slip critical shear stress is employed for the slip equation at both walls. Critical shear stress will cause three slip flow regimes: no slip condition, slip only at the inner wall, and slip at both walls. Thermal boundary conditions are assumed to be peripherally and axially constant fluxes at the walls. Governing equations are solved to obtain temperature profiles and Nusselt number and effects of slip parameters, elasticity, and Brinkman number are discussed. Two regimes are compared when slip occurs at both walls or only at the inner wall. The results indicate that by increasing slip effect and elasticity, heat transfer between wall and fluid is enhanced, but it decreases by increasing Brinkman number. In the case where the heat flux is dominant in the outer wall, the inner wall Nusselt curve shows a singularity for a critical Brinkman number because at this Brinkman number the bulk temperature will be equal to the wall temperature. [ABSTRACT FROM AUTHOR]