Non-steady State Conditions Research Articles

Part-2: Analytical Expressions of Concentrations of Glucose, Oxygen, and Gluconic Acid in a Composite Membrane for Closed-Loop Insulin Delivery for the Non-steady State Conditions.

A mathematical model developed by Abdekhodaie and Wu (J Membr Sci 335:21-31, 2009), which describes a dynamic process involving an enzymatic reaction and diffusion of reactants and product inside glucose-sensitive composite membrane has been discussed. This theoretical model depicts a system of non-linear non-steady state reaction diffusion equations. These equations have been solved using new approach of homotopy perturbation method and analytical solutions pertaining to the concentrations of glucose, oxygen, and gluconic acid are derived. These analytical results are compared with the numerical results, and limiting case results for steady state conditions and a good agreement is observed. The influence of various kinetic parameters involved in the model has been presented graphically. Theoretical evaluation of the kinetic parameters like the maximal reaction velocity (V max) and Michaelis-Menten constants for glucose and oxygen (K g and K ox) is also reported. This predicted model is very much useful for designing the glucose-responsive composite membranes for closed-loop insulin delivery.

Methodological Frontier in Operational Analysis for Roundabouts: A Review

Several studies and researches have shown that modern roundabouts are safe and effective as engineering countermeasures for traffic calming, and they are now widely used worldwide. The increasing use of roundabouts and, more recently, turbo and flower roundabouts, has induced a great variety of experiences in the field of intersection design, traffic safety and capacity modelling. As for unsignalized intersections which represent the starting point to extend knowledge about the operational analysis to roundabouts, the general situation in capacity estimation is still characterized by the discussion between gap acceptance models and empirical regression models. However, capacity modelling must contain both the analytical construction and then solution of the model, and the implementation of driver behavior. Thus, issues on a realistic modelling of driver behavior by the parameters that are included into the models are always of interest for practioners and analysts in transportation and road infrastructure engineering. Based on these considerations, this paper presents a literature review about the key methodological issues in the operational analysis of modern roundabouts. Focus is made on the aspects associated with the gap acceptance behavior, the derivation of the analytical-based models and the calculation of parameters included into the capacity equations, as well as steady state and non-steady state conditions and uncertainty in entry capacity estimation. At last, insights on future developments of the research in this field of investigation will be also outlined.

Cycling of iodine by microalgae: Iodine uptake and release by a microalgae biofilm in a groundwater holding pond

Biological iodine cycling has been widely studied in marine environments, but rarely considered in terrestrial waters. In this work, a microalgae biofilm, with an iodine content of 350±29mgkg−1, is shown to potentially be a significant iodine cycler in a groundwater holding pond. Cultivation of the biofilm in extracted groundwater was carried out at bench scale. In parallel, iodine release from an iodine-rich biofilm kept in the dark was monitored. Iodine uptake and release were found to be proportional to algal growth and decay, with the maximum growth rate and specific decay rate being 0.53±0.05gm−2d−1 and 0.12±0.02d−1 respectively. Iodine update and release in an engineered groundwater holding pond (1m3:1m2×1m) was simulated. The results indicated that bioaccumulation causes non-steady state conditions in such ponds, and in extreme circumstances decay events can elevate iodine concentrations to problematic levels.

Product distribution change in the early stages of carbon monoxide hydrogenation over cobalt magnesium Fischer-Tropsch catalyst

The catalytic hydrogenation of carbon monoxide, known as the Fischer-Tropsch process, is a technologically important, complex multipath reaction which produces long chain hydrocarbons. In order to access the initial kinetics and the mechanism, we developed a reactor that provides information under non-steady state conditions. We tested a CoMgO catalyst and monitored the initial product formation within 2s of exposure to CO as well as the time dependence of high molecular weight products (in a 60s window) and found drastic changes in the product selectivity. The probability for forming branched isomers (C4 and C5) peaks in the first 25s, and within that time frame no unsaturated products were detected. The subsequent decline (at ∼35 to 40s) of branched isomers coincides with the detection of olefins (fromC2 to C5) and the change in carbon coverage at the surface of the catalyst. This indicates a change in the reaction pathway.

Total Harmonic Distortion Estimation, Minimization Inter Harmonic Amplitude and Expanding Bands Rejection in TKF filters

In previous paper a modified Taylor-Kalman-Fourier (TKF) filters was proposed to estimate the dynamic phasor and time varying harmonic components under non-steady state conditions in power systems, In this paper a new TKF filter method to reduce the THD in proposed. A modified multiharmonic signal model leads us to design more robust filters because the frequency response shown that the harmonic bands improve as result of their flatness and interharmonics lobules are minimized. A mathematical signal model is developed with a factor escalate in all set of harmonics, except in the fundamental frequency. Also with proposed method is possible achieve better estimation that the TKF filters when the signal is corrupted by harmonics.

Element diffusion model of bimetallic hot deformation in metallurgical bonding process

The effect of process parameters on the diffusion behavior of different elements in the metallurgical bonding process of bimetallic hot deformation is investigated. The diffusion distance of different elements increases with the effective strain, deformation and holding temperatures, deformation and holding times. On the other hand, it decreases with the increase of effective strain rate. In addition, an element diffusion model considering the influences of different processing parameters on element diffusion behavior is proposed to predict element concentration values near the metallurgical bonding interface. The proposed element diffusion model is based on the Fick's second law for unidirectional flow under non-steady state condition and is applied to the finite element simulation to investigate the diffusion behavior of different elements in metallurgical bonding process. The study shows that the modified model can predict the concentration profile and diffusion distance in the transition zone with a higher accuracy compared with the reference element diffusion model without considering the effects of effective strain and strain rate.

EFFECT OF CRUMB RUBBER ON CONCRETE STRENGTH AND CHLORIDE ION PENETRATION RESISTANCE

This paper present the effect of crumb rubber on its ability to produce concrete with structural strength when it was used directly from the plant without any treatment process. Crumb rubber was added as fine aggregates at 0%, 10%, 15% and 20% of sand volume meanwhile silica fume was added at 10% by cement weight. Three main series of concrete namely rubberized concrete with water-to-cement ratio of 50% and 35% was design and development of compressive strength was observed from day 7 until 91 days. Also, effectiveness of crumb rubber under flexural strength and splitting tensile strength was studied at 28 days curing age. Effect of crumb rubber on durability performance was done on chloride ion penetration resistance performance by migration test and by immersion in salt water. Chloride ion diffusion in rubberized concrete by migration test was carried out under steady state condition using effective diffusion coefficient, De meanwhile, immersion test in salt water was conducted under non-steady state condition using apparent diffusion coefficient, Da. Results showed that compressive strength was decrease with the increasing of crumb rubber in the mixture. Even though the strength were reducing with the inclusion of crumb rubber, the reduction were less than 50% and it achieved acceptable structural strength. Chloride transport characteristics were improved by increasing amount of CR and rubberized concrete with w/c = 0.35 gave better resistance against chloride ion compared to w/c = 0.50 with more than 50% difference. Silica fume provide slightly strength increment compared to normal rubberized concrete and the same behavior was observed during chloride ion diffusion test.

Employing a step-wise titration method under semi-slow reaction regime for evaluating the reactivity of limestone and dolomite in acidic environment

Carbonate rocks are commonly utilized in Wet Flue Gas Desulfurization, WFGD, because of their capability to release calcium ions and precipitate as solid gypsum in an acidic environment. Studies on the reactivity of carbonate rocks and dissolution models can be employed for optimizing the WFGD process. The correct evaluation of limestone reactivity is therefore necessary for the design of the WFGD scrubbing process and for plant operation. In this study, after statistical considerations on evaluating the sample size threshold, a mathematical model and a detailed procedure are given for the estimation of the reaction rate constant and mass transfer coefficient.Results are reported from testing limestone and dolomite samples with different formation periods and geological backgrounds. Samples were tested in a Batch Stirred Tank Reactor (BSTR) with a stepwise titration method using hydrochloric acid and non-steady state conditions. In the experiments particles were shown to be completely immersed in a defined viscous sub-layer. A parametric evaluation for the reaction rate was performed at each titration step using an implemented software procedure that handles hundreds of pH values and more than fifty particle size ranges. The experimental data were accurately fitted to the model. The second order model for dolomite and limestone samples accounts for both mass transfer and reaction rate terms, yielding values for the mass transfer coefficients that are congruent with values estimated by fluid-dynamics inspection.

Experimental study on the characteristics of non-steady state radiation heat transfer in the room with concrete ceiling radiant cooling panels

The dominant heat transfer between ceiling radiant cooling panels (CRCP) and indoor environment is the combined heat transfer of thermal radiation and natural convection. Currently, researchers usually discussed indoor radiation heat transfer under steady state conditions rather than non-steady state conditions. In this study, an experimental chamber was built to investigate the indoor parameter variations during the CRCP start-up process in summer, and a mathematical model was also established for further analysis of non-steady state radiation heat transfer. There was a concrete ceiling radiant cooling panel (C-CRCP) equipped in the chamber, and the panel was a concrete slab with pipes embedded in it. The experimental results showed that the temperature of the ceiling surface suddenly dropped after the C-CRCP started up, but the temperatures of the other inner surfaces and the indoor air decreased gradually with a similar trend. The radiant heat flux of the ceiling reached a trough rapidly, and then increased back to steady status step by step. Moreover, it took 7–9 h to nearly get steady status after the C-CRCP started up because of the thermal inertia and the thermal storage of concrete slab. The ratio of radiation heat transfer in the total heat transfer of the ceiling ranged from 40% to 60%. Based on the useful experimental data obtained in this C-CRCP system, a reliable start-up control strategy was also proposed in this paper.

Evidence for a uniformly small isotope effect of nitrogen leaching loss: results from disturbed ecosystems in seasonally dry climates.

Nitrogen (N) losses constrain rates of plant carbon dioxide (CO2) uptake and storage in many ecosystems globally. N isotope models have been used to infer that ~30% of terrestrial N losses occur via microbial denitrification; however, this approach assumes a small isotope effect associated with N leaching losses. Past work across tropical/sub-tropical forest sites has confirmed this expectation; however, the stable N isotope ratio (δ(15)N) of ecosystem leaching has yet to be systematically evaluated in seasonally dry climates or across major ecosystem disturbances. We here present new measurements of the δ(15)N of total dissolved N (TDN) in small streams, bulk deposition, and soil pools across eight watershed sites in California, including grassland, chaparral, and coastal redwood forest ecosystems, with and without fire, grazing, and forest harvesting. Regardless of the dominant vegetation type or disturbance regime, average δ(15)N of TDN in stream water differed only slightly (<~1‰) from that of bulk soil δ(15)N, revealing a uniformly small isotope effect associated with N leaching losses even under non-steady state conditions. Rather, lower input δ(15)N compared to TDN δ(15)N in streams pointed to fractionations via gaseous loss pathways as the dominant mechanism behind soil δ(15)N enrichment. We conclude that N leaching does not impart a major isotope effect across a broad range of ecosystems and conditions examined, thereby advancing the N gas-loss hypothesis as the principal explanation for variation in bulk soil δ(15)N.

Photosynthesis and photoprotection under drought in the annual desert plant Anastatica hierochuntica

Anastatica hierochuntica is an annual desert plant, which was recently shown to have unusually low nonphotochemical quenching (NPQ) and a high PSII electron transport rate (ETR). In the current study, we examined how these unusual characteristics are related to a lack of CO2 and inhibition of net photosynthetic rate (P N). We compared the photosynthetic and photoprotective response of A. hierochuntica and sunflower (Helianthus annuus), under conditions of photosynthetic inhibition, with either low CO2 or drought. We found that under nonsteady state conditions of low CO2 availability, A. hierochuntica exhibited about half of the NPQ values and almost twice of the ETR values of H. annuus. However, the long-term inhibition of P N under drought caused a similar increase in NPQ and a decrease in ETR in both A. hierochuntica and H. annuus. These results suggest that the unusually low NPQ and high ETR in A. hierochuntica are not directly related to a response to drought conditions.

Evaluation of non-steady state condition contribution to the total emissions of residential wood pellet stove

In order to evaluate non-steady phase contribution to the total emissions of a pellet stove in real domestic operations, particulate matter and gaseous emissions were determined separately for different operating conditions, i.e. ignition, partial load, increase in power and nominal load. TSP (Total suspended particulate) was sampled with a dilution system and characterized for TC (total carbon), PAHs (polycyclic aromatic hydrocarbons), the main soluble ions, Ni, As, Cd and Pb. Gas monitoring shows that CO and NO emission factors in ignition phase markedly differ from other operating conditions: NO emission factor is lower, while CO one is much higher, since it is a product of incomplete combustion. Start-up phase emission factors are also higher for TSP, Cd and other products of incomplete combustion, i.e. TC and PAHs. Despite being a non-steady phase, the increase in power phase emission factors appreciably differ from steady state ones only for PAHs. Moreover, the PAHs emitted in non-steady state phases have a higher toxicological burden. In conclusion, in order to evaluate the real impact of pellet stove on the environment, transient conditions should be taken into account. The ignition phase, even though it lasts only 20 min, can significantly contribute to pollutant emission.

Methodology research on solving non-steady state radiation heat transfer in the room with Ceiling Radiant Cooling Panels

Long wave radiation heat transfer is the dominant cooling mode of the Ceiling Radiant Cooling Panels (CRCP). This unique cooling mode makes the calculation of indoor long wave radiation heat transfer extremely important. Actually, indoor radiation heat transfer is usually under non-steady state conditions. General calculation methodology (simplifying radiation heat transfer or using the equivalent network method of steady state) is complex and less accurate when solving this kind of problem. In addition, general methodology fails to solve the situation that the temperatures of some interior surfaces are lacking but the heat flows are known. This paper provides a calculation methodology improving the Gebhart method for modeling the non-steady state radiation heat transfer between indoor surfaces. Given parameter variations (temperature and net radiant heat flow) of the surfaces are transformed into discrete column vectors of unit time, and then matrix equations are established, which can greatly reduce the work. This methodology has been verified experimentally, which can be regarded as a theoretical basis for solving indoor non-steady state radiation heat transfer of CRCP systems.

Approximate analytical solution for non-linear reaction diffusion equations in a mono-enzymatic biosensor involving Michaelis–Menten kinetics

Here we consider the case where the enzyme reacts with an electroinactive substrate to produce an electroactive product which is quickly oxidized or reduced at the electrode/film interface. This model is based on the system of non-linear reaction diffusion equations containing a nonlinear term related to the Michaelis Menten kinetic of the enzymatic reaction. In this paper the powerful analytical method, called the recent approach of Homotopy analysis method is applied to solve the non-linear reaction diffusion equations in amperometric biosensors. A simple and closed-form of analytical expression for concentrations of substrate, product and corresponding current response in the case of an enzyme immobilized into a planar film onto an electrode have been derived. The effect of various parameters on current density is discussed. Numerical simulation (Matlab) for the concentration profile for non-steady state condition was carried out and compared with the analytical results. A satisfactory agreement is noted. A graphical procedure for estimating the kinetic parameters and sensitivity analysis of the parameters from current density is suggested.

The role of C and Mn at the austenite/pearlite reaction front during non-steady-state pearlite growth in a Fe–C–Mn steel

The role of C and Mn during the growth of pearlite under non-steady state conditions is analyzed by comparing phase compositions of austenite, ferrite and cementite (γ+α+θ) through the use of transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and atom probe tomography (APT) measurements across the austenite/pearlite interface. A local Mn enrichment and C depletion at the austenite/pearlite interface has been measured, which causes a change in the transformation driving force with time during divergent pearlite growth.

Analytical and Experimental Study of Electrochemical Micromilling

Electrochemical micromachining (ECMM) is a non-conventional manufacturing method suitable for the production of microsized components on a wide range of conductive materials. ECMM improves dimensional accuracy and simplifies tool design for machining hard, high strength, heat resistant, and conductive materials into complex shapes. Extremely small interelectrode gaps of the order of few microns are required in ECMM for better dimensional accuracy. However, excessively small interelectrode gaps may lead to complications, such as short-circuiting, which disrupt the stability of ECMM process. This necessitates the need for better understanding of the interelectrode gap dynamics. This paper presents a mathematical model for the analysis of interelectrode gap under non-steady state conditions in micromilling of steel using the ECMM process. Experimental verification of the mathematical model was conducted using an in-house built micro electrochemical machining system. The model is capable of predicting the machining results to within 1- 5 µm error (10- 50%).

Modelling the risk of airborne infectious disease using exhaled air.

In this paper we develop and demonstrate a flexible mathematical model that predicts the risk of airborne infectious diseases, such as tuberculosis under steady state and non-steady state conditions by monitoring exhaled air by infectors in a confined space. In the development of this model, we used the rebreathed air accumulation rate concept to directly determine the average volume fraction of exhaled air in a given space. From a biological point of view, exhaled air by infectors contains airborne infectious particles that cause airborne infectious diseases such as tuberculosis in confined spaces. Since not all infectious particles can reach the target infection site, we took into account that the infectious particles that commence the infection are determined by respiratory deposition fraction, which is the probability of each infectious particle reaching the target infection site of the respiratory tracts and causing infection. Furthermore, we compute the quantity of carbon dioxide as a marker of exhaled air, which can be inhaled in the room with high likelihood of causing airborne infectious disease given the presence of infectors. We demonstrated mathematically and schematically the correlation between TB transmission probability and airborne infectious particle generation rate, ventilation rate, average volume fraction of exhaled air, TB prevalence and duration of exposure to infectors in a confined space.

Analytical expression of transient current-potential for redox enzymatic homogenous system

Abstract Mathematical modeling pertaining to the catalytic response of a redox enzymatic system is discussed. The model proposed herein describes the relationship between the electrochemical responses and the kinetic characteristics of the enzymatic reaction. The analytical expressions corresponding to the concentration of co-substrate for steady and non-steady state conditions have been obtained using a new approach to homotopy perturbation method (HPM). Analytical expressions of the plateau current are also presented for steady and non-steady state conditions. Upon comparison, we found that the analytical results of this work are in excellent agreement with the existing limiting case results. Further, the sensitivity of the parameter in transient current potential was also analyzed due to its importance in predicting the relationship between the input value of the parameter and the model results.

Geochemistry of Tertiary Sequence in Shahbajpur-1 Well, Hatia Trough, Bengal Basin, Bangladesh: Provenance, Source Weathering and Province Affinity

Major and trace element compositions of Neogene sandstones and mudrocks from the Shahbajpur-1 (SB-1) well, Hatia trough, Bengal basin, Bangladesh were determined to examine their geochemical characteristics and provenance, in relation to Himalayan uplift, sediment dispersal, and correlation of coeval successions in a basinal context. Major and trace element abundances in the SB-1 succession vary vertically, with SiO2 content decreasing and Al2O3 increasing from the older (Surma and Tipam Groups) to younger (Dupi Tila Group) sediments. Marked geochemical fractionation between sandstones and mudrocks reflects advanced hydrodynamic sorting, and relative enrichment of several elements (e.g., TiO2, Zr, Ce, Th, Cr) suggests sporadic heavy mineral concentration in some sandstones. Major and trace element provenance discriminants indicate a uniform felsic source (Himalayan detritus and recycled sediments) for the entire succession. Values for the Chemical Index of Alteration (CIA) record moderate weathering in the source, and non-steady state conditions produced by Himalayan uplift. Comparison between the Hatia trough samples and coeval Sylhet trough (P2) sediments shows that the more distal SB-1 succession is compositionally more uniform. Strong similarity in geochemical composition between SB-1 and P2 support the hypothesis that the Hatia trough is an extension of P2, fed by the same dispersal system. DOI: http://dx.doi.org/10.3329/jles.v7i0.20115 J. Life Earth Sci., Vol. 7: 1-13, 2012

Studies on Bubble Column Evaporation in Various Salt Solutions

The physical properties of concentrated salt solutions are an important aspect of many industrial processes. The effects of different salts on the inhibition of bubble coalescence have raised some unexpected observations, because some salts inhibit coalescence while others have no effect over a wide concentration range. Fortunately, many common salts inhibit bubble coalescence and although the mechanism is not fully understood, this effect allows the construction of bubble column evaporators (BCEs) for the efficient transfer of both vapor and heat. In this study the BCE process has been used under steady state conditions to determine the latent heat (enthalpy) of vaporization (ΔH vap) of concentrated solutions of several common salts. In addition, it was found that under non-steady state conditions using high inlet gas temperatures, the rate of vapor transfer, and hence thermal desalination, could be increased using the BCE process. Some new observations on the fundamental mechanism of the bubble coalescence phenomenon are also reported.