Impact Of Irreversibility Research Articles

Irreversibility analysis of an unsteady micropolar CNT-blood nanofluid flow through a squeezing channel with activation energy-Application in drug delivery

Background and objectiveDue to the low toxicity, unique physiochemical properties, and appropriate surface modifications, Carbon Nanotubes (CNTs) are used as target carriers in drug delivery systems. In the present problem, we have considered both single-walled and multi-walled CNTs to study the impact of irreversibility on the micropolar nanofluid flow through a squeezing channel with the base fluid blood. The blood is considered a micropolar fluid in the presence of different blood cells and their rotational nature. Further, blood is influenced by the external magnetic field parallel to the microrotation along with viscous and Joule dissipations. MethodHighly coupled and nonlinear partial differential equations are solved with Homotopy Analysis Method (HAM) after simplified equations using similarity transformation. Further, we have concluded the minimum squared residual errors to show the method's accuracy. A comparison made with the existing literature and shows a good agreement. ResultsThe angular velocity of the fluid particles is enhanced by increasing the squeezing number. In the case of the squeezing, volume fraction has improved the viscous drag and is found high for MWCNT embedded nanofluid. The heat transfer rate is higher for the MWCNT embedded nanofluid than the SWCNT embedded nanofluid. A descent found in entropy generation boosts up with the Brinkman parameter while opposite phenomena appear for radiation and Hartman number and vortex viscosity. Both Bejan number and entropy generation profiles are restricted with an increase in vortex viscosity. ConclusionSWCNTs are showed to be more effective and efficient than the MWCNTs in elevating velocity, temperature and irreversibility of the system. Outcomes of this problem will help to understand the implementation of the drug carrier and irreversibility phenomena during drug delivery.

Life cycle environmental impact of system irreversibility based on advanced exergy analysis: A case study

Optimizing system irreversibility has been a major concern for the global environmental impacts of production, use, and disposal of goods in international value chains. However, the life cycle environmental impact of system irreversibility based on advanced exergy analysis is still opened problem. Using coal-to-SNG as a case study, this study conducted an integrated assessment of advanced exergy analysis and life cycle environmental impact to provide more insight into system optimization. Based on advanced exergy analysis, SNG production system still has considerable improvement potential because 61.88% of exergy destruction is avoidable. Using life cycle assessment with inventory modified by advanced exergy analysis, the improvement potentials of life cycle environmental impacts can be identified by the near-, mid-, and long-term technological optimization scenarios of SNG production process. The results show that acidification potential, global warming potential, and ozone layer depletion potential throughout the life cycle will continue to decrease, while the optimization potentials of abiotic depletion, eutrophication and human toxicity will gradually become flattened with continuous technology optimization. The potentials for reducing life cycle environmental impacts brought by improving system irreversibility are limited (15%–25%), but they are also indispensable. The results may be helpful to understand the life cycle environmental impact of system irreversibility improvement and optimize environmental performance of industrial systems.

Quantitative analysis of the irreversible membrane fouling of forward osmosis during wastewater reclamation: Correlation with the modified fouling index

In this study, the fouling behavior in the long-term performance of the forward osmosis (FO)-based osmotic dilution process was systematically explored by assessing the impact of irreversibility. The effects of physical cleaning, scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) analyses, and foulant distributions were systematically investigated to control irreversible organic foulants on the membrane surface. It was observed that specific foulants in the secondary wastewater effluent impeded the long-term performance of FO fouling reversibility and final flux. A strong correlation between irreversible foulant concentrations, especially that of protein-like biopolymer, and physical fouling reversibility was observed, which caused continual irreversible fouling in the FO process. Multiple modified fouling indexes (MFIs) were measured to evaluate the fouling potential of the feed water with size fractionation. It was confirmed that the MFI-UF employing a 300 kDa ultrafiltration (UF) membrane is an appropriate water quality index for studying irreversible membrane fouling. It is expected that the application of MFI in predicting the fouling potential of FO intake water will significantly contribute toward the development of operational guidelines for FO plants.

Time Integrated Flux Analysis: Exploiting the Concentration Measurements Directly for Cost-Effective Metabolic Network Flux Analysis

Background: Flux analyses, such as Metabolic Flux Analysis (MFA), Flux Balance Analysis (FBA), Flux Variability Analysis (FVA) or similar methods, can provide insights into the cellular metabolism, especially in combination with experimental data. The most common integration of extracellular concentration data requires the estimation of the specific fluxes (/rates) from the measured concentrations. This is a time-consuming, mathematically ill-conditioned inverse problem, raising high requirements for the quality and quantity of data. Method: In this contribution, a time integrated flux analysis approach is proposed which avoids the error-prone estimation of specific flux values. The approach is adopted for a Metabolic time integrated Flux Analysis and (sparse) time integrated Flux Balance/Variability Analysis. The proposed approach is applied to three case studies: (1) a simulated bioprocess case studying the impact of the number of samples (experimental points) and measurements’ noise on the performance; (2) a simulation case to understand the impact of network redundancies and reaction irreversibility; and (3) an experimental bioprocess case study, showing its relevance for practical applications. Results: It is observed that this method can successfully estimate the time integrated flux values, even with relatively low numbers of samples and significant noise levels. In addition, the method allows the integration of additional constraints (e.g., bounds on the estimated concentrations) and since it eliminates the need for estimating fluxes from measured concentrations, it significantly reduces the workload while providing about the same level of insight into the metabolism as classic flux analysis methods.

Temporal asymmetry in precipitation time series and its influence on flow simulations in combined sewer systems

A property of natural processes is temporal irreversibility. However, this property cannot be reflected by most statistics used to describe precipitation time series and, consequently, is not considered in most precipitation models. In this paper, a new statistic, the asymmetry measure, is introduced and applied to precipitation enabling to detect and quantify irreversibility. It is used to analyze two different data sets of Singapore and Germany. The data of both locations show a significant asymmetry for high temporal resolutions. The asymmetry is more pronounced for Singapore where the climate is dominated by convective precipitation events. The impact of irreversibility on applications is analyzed on two different hydrological sewer system models. The results show that the effect of the irreversibility can lead to biases in combined sewer overflow statistics. This bias is in the same order as the effect that can be achieved by real time control of sewer systems. Consequently, wrong conclusion can be drawn if synthetic time series are used for sewer systems if asymmetry is present, but not considered in precipitation modeling.

How Asset Irreversibility Influences the Investment-Uncertainty Relationship

This paper examines how industry-specific uncertainty affects firms’ investments for varying degrees of asset irreversibility (i.e. the wedge between purchase price and liquidation value of an asset). To identify more or less irreversible capital goods, we exploit unique survey data on German manufacturing firms over the sample period 2004 to 2012 in which managers provide information on investments’ purpose (capacity expansion, replacement, restructuring, rationalization, and other). We find that uncertainty only depresses capacity expansion investments, while non-capacity expansion investments such as replacement, restructuring and rationalization investments are not affected. Our results indicate that only investments into the most irreversible capital goods will decrease if uncertainty raises. We provide several tests confirming the robust impact of asset irreversibility on the investment-uncertainty relationship as we analyze several competing channels explaining the negative investment-uncertainty relation, such as the financial friction or the market power channel.

Mission-Integrated Exergy Analysis for Hypersonic Vehicles: Methodology and Application

Recently developed theoretical work in which energy (the first law of thermodynamics) and entropy (the second law of thermodynamics) considerations are consistently applied to aerospace vehicles is used to provide a detailed exergy (availability) and performance analysis for an airbreathing hypersonic vehicle. An acceleration and climb mission at constant freestream dynamic pressure is performed with detailed instantaneous and time-integrated audits of entropy generation in and over the vehicle and in the vehicle wake. Entropy generation in the vehicle wake ranges from five to eight times the total entropy generation in and over the vehicle. The impact of irreversibility occurring in and over the vehicle itself on the total entropy generation in the wake is a small fraction of the overall wake losses. Fifteen percent of the overall energy input during the mission actually goes into productive acceleration and climb. The remainder is associated with the generation of entropy due to irreversibility in and over the vehicle and in the vehicle wake. The propulsion system is responsible for almost all entropy generation associated solely with the vehicle (excluding the overwhelmingly dominant contribution of the vehicle wake), and entropy generation in the combustor alone represents 85% of the total propulsion system loss.

Impact of Irreversibility and Uncertainty on the Timing of Infrastructure Projects

This paper argues that because of the irreversibility and uncertainty associated with Build-Operate-Transfer (BOT) infrastructure projects, their nancial evaluation should also routinely include the determination of the value of the option to defer the construction start-up. This ensures that project viability is comprehensively assessed before any revenue or loan guarantees are considered by project sponsors to support the project. We show that the framework can be used even in the context of the intuitive binomial lattice model. This requires estimating volatility directly from the evolution of the net operating income whilst accounting for the correlation between the revenue and costs functions. This approach ensures that the uncertainties usually associated with toll revenues, in particular, are thoroughly investigated and their impact on project viability is thoroughly assessed. We illustrate the usefulness of our framework with data from an actual (BOT) toll road project. The results show that by postponing the project for a couple of years the project turns out to be viable, whilst it was not, without the deferral. The evaluation approach proposed therefore provides a better framework for determining when and the extent of government nancial support, if any, that may

Investment Under Tax Policy Uncertainty: A Neoclassical Approach

This article studies the impact of investment irreversibility, delivery lags, and adjustment costs on the firm’s optimal investment policy in a world of uncertainty. The source of uncertainty is a future change in the corporate profits tax where both the timing of this event and the size of associated adjustment in the tax benefit of investing are random. Such a tax uncertainty is particularly evident in reform economies whose authorities consider significant reductions in the corporate tax rate to stimulate business life. It is shown that greater transparency on tax policy promotes the firm’s expected net worth and the capital accumulation process.

Real Estate and the Economy: Aggregate Implications of Irreversible Investment

While significant effort has been devoted to characterizing the role that irreversibility plays in individual agents' investment behavior, very little has been devoted to the aggregate economic implications of investment irreversibility. Yet irreversibility prevents the continual allocation of capital to its most productive use, with first-order economic consequences. Moreover, the asymmetric nature of the friction, which prevents disinvestment in bad times but allows investment in good times, means its impact varies over the business cycle. In order to study the aggregate effects of irreversibility, this paper introduces a general equilibrium model with two consumption goods and irreversible investment. After characterizing the optimal investment strategy of competitive heterogeneous developers, we show that this behavior endogenously generates a business cycle: periods of more intensive real estate development are associated with greater consumption growth, even when fundamental shocks are stationary. We also consider an array of business cycle-dependent macroeconomic implications, including the impact of irreversibility on the term structures of interest rates and interest rate volatility, consumption risk premia, forward prices and forward price volatilities, and the expected returns to real assets. Finally, we consider the role that irreversibility plays in both the time-series and cross-section of investment, generating lumpy investment at the firm level and heterogeneity across firms. There is less heterogeneity, in equilibrium, than is socially optimal. Competitive pressures drive developers to build too soon, and consequently on too small a scale, to efficiently utilize resources diverted to the housing sector.

AN EMPIRICAL EXAMINATION OF THE HANGOVER EFFECT OF IRREVERSIBILITY ON INVESTMENT

ABSTRACTIrreversibility does not only raise the user cost of capital and discourage new investment but also hinders disinvestment because of the hangover effect. This paper derives a theoretical model that separates the impact of conventional convex adjustment costs from the impact of irreversibility, based on which we test the hangover effect of irreversibility by using a panel of Dutch listed firms during 1985–2000. We find that the sample firms cut both the capital stock and the inventory stock facing shocks to sales and cash flow, but they cut the inventory stock by a larger magnitude than they cut the capital stock. Given that fixed investment is more irreversible than inventory investment, the result suggests that the diminished impact of irreversibility provides the firm with more flexibility in responding to uncertainty, which lends support for the hangover effect of irreversibility on investment.

The Impact of Market Structure and Irreversibility on Investment under Uncertainty: An Empirical Analysis

The empirical literature of investment under uncertainty has vastly neglected to account for the role played by market structure. Recently the theory has however started to merge real options theory with game theory to offer alternative explanations to strategic investment behaviour. This paper estimates an error correction model of investment under product price uncertainty for 23 French industries during the period 1977-1997 and represents the first empirical work that includes variables of market structure (in terms of degree of competition) in a model of investment under uncertainty. It is also one of the very first attempts to make explicit the empirical relationship between investment and uncertainty under different degrees of irreversibility. Although I find evidence that in general uncertainty has a negative impact on investment, the results show that the more concentrated industries are not significantly affected. Irreversibility, as predicted by theory, has a significant negative impact on investment, but when degree of competition and irreversibility are considered together it appears that the more concentrated industries can shield from the negative impact of uncertainty notwithstanding the presence of downward adjustment costs of capital. This seems in line with some of the recent developments proposed by the theory.

Investment, irreversibility, and options: An empirical framework

The paper presents an empirical test of the impact of irreversibility on threshold return levels and on investment. These tests permit an examination of a key concept and some predictions of irreversible investment theory, which links the option pricing approach with Tobin's q theory. A key feature of the paper is that estimates of the threshold return levels required for investment, which account for both options to invest and disinvest, are obtained internally from the empirical model. The study employs a panel data set consisting of U.S. manufacturing firms and finds that irreversibility, through its negative impact on marginal put options and the resulting increase in threshold returns, reduces investment in two of the four groups of firms studied.

The impact of uncertainty and irreversibility on investments in online learning

Uncertainty and irreversibility are central to online learning projects, but have been neglected in the existing educational cost-benefit analysis literature. This paper builds some simple illustrative models of the impact of irreversibility and uncertainty, and shows how different types of cost and demand uncertainty can have substantial impacts on investment decisions. The techniques used are drawn from the financial option pricing literature. In some situations uncertainty should lead decision makers to delay projects which would be accepted under the usual rule "invest if the net present value (NPV) is positive," and in other situations it suggests that projects with negative NPVs should be undertaken. The application of one of these models will then be illustrated in relation to a new online course: the Master of Educational Technology offered by the University of British Columbia.

Impact and nature of irreversibility and uncertainty on investment decisions : a survey on Italian manufacturing firms

In this paper we investigate on the empirical ground the core of the real option theory. Using data drawn from a specific survey on Italian manufacturing firms, on spring 1998, we focus on how much irreversibility of capital and uncertainty about future may generate large changes in investment spending. We find a considerable heterogeneity in the irreversibility-uncertainty correlation, depending on the firms’ size, their geographical location, and their productive sector. In accordance with the option theory it has been shown that with irreversible equipment an increasing uncertainty can discourage new investments. Then, our data confirm that irreversibility increases the minimum expected rate of return necessary to implement new project. (Keywords : Investment ; Uncertainty ; Irreversibility. JEL Classification : D80, E22)

Econometric Modelling of UK Aggregate Investment: The Role of Profits and Uncertainty

This paper focuses on the determinants of aggregate investment spending in the UK for the industrial and commercial companies (ICC) sector. It complements recent work by Cuthbertson and Gasparro, who study an augmented Tobin’s q model of investment in the manufacturing sector. Important focal points of our analysis are a role for real profits (internal funds), which allow firms to combat liquidity constraints when access to capital markets is not perfect, and the impact of irreversibility and uncertainty in determining aggregate investment spending. Earlier work on manufacturing investment by Bean developed a dynamic error‐correction specification based on the flexible accelerator model. Following Cuthbertson and Gasparro we use multivariate cointegration techniques to discover a parsimonious dynamic model, which can explain the investment experience of the ICC sector in the 1980s and early 1990s. Our results show that a model based on investment and output alone does not cointegrate, and a short‐run dynamic model of these variables suffers from heteroscedasticity. This may be consistent with the idea that increased (uncontrolled for) uncertainty has led to increased volatility in investment. The possibility that movements in the real price of gold reflect uncertainty in financial and other traded commodity markets is explored. Investigation of this more general model indicates that real profits and the real price of gold can enhance the explanation of investment spending by the ICC sector.

The Impact of Irreversibility, Uncertainty and Timing Options on Deprival Valuations and the Detection of Monopoly Profits

This paper has two purposes. The first is to derive rules identifying the deprival value of an asset (i) which is irreversible to one extent or another; (ii) the benefit stream of which is subject to continuing uncertainty; and (iii) for which an option to wait exists as to when to reacquire should the owner be deprived of it. The second is to consider whether accounting rates of return employing these deprival value rules can be developed to help in the detection of monopoly profits in circumstances where investment decision-making takes place in the presence of irreversibility, uncertainty and the existence of timing options. The ‘new’ deprival value rules for an asset differ from the ‘conventional’ ones in that present value less the value of the option to reinvest in the asset appears in the ‘new’ rules wherever present value appears in the ‘conventional’ rules. Examples are provided which suggest that ‘new’ and ‘conventional’ deprival value rules can differ materially. A further result is that accounting rates of return can be developed using the ‘new’ deprival value rules that are, in principle, useful in the detection of monopoly profits. Nonetheless, in practice such use requires a level of information that renders the result superfluous in the sense that the provision of replacement cost balance sheet data, combined with the level of information needed, is sufficient to reveal the presence of monopoly profits directly.