Cost Flow Research Articles

Demystifying LIFO: Towards Simplification of Inflation-Adjusted Inventory Valuation

The last in, first out (LIFO) method of inventory accounting has been available to taxpayers for more than 50 years. The basic concept of LIFO is relatively simple: it reverses the normal assumed flow of costs (first-in, first-out or FIFO) by matching the costs of the latest purchases or production against current-year sales. During periods of rising costs, LIFO generally results in lower taxable income than the FIFO method because current-year increases in inventory costs are charged to cost of goods sold, rather than accumulated in ending inventory. Thus, LIFO provides protection from the effects on taxable income of rising inventory costs (hereinafter "inflation").Like many other aspects of federal income tax law, the practical implementation of LIFO has often proved to be a complex task. Particularly difficult issues have arisen over the fundamental concept of measuring costs on a comparable basis over time for inventory affected by stylistic, technological, or other changes. The tax law currently lacks objective, determinate standards for ascertaining the proper LIFO cost of inventory items that change. Current standards rely on concepts of similarity, involving fine distinctions that are difficult to apply consistently and resulting in costly and burdensome controversies, with little promise of more determinate results. Moreover, efforts to simplify LIFO have not freed taxpayers from mystifying complexity in this area, as the available simplified methods are far from simple and are not viable alternatives for many taxpayers.

Exergy, exergoeconomic, life cycle, and exergoenvironmental assessments for an engine fueled by diesel–ethanol blends with aluminum oxide and titanium dioxide additive nanoparticles

This study develops energy, exergy, exergoeconomic, exergoenvironmental, and sustainability analyses for a compression ignition (CI) engine fueled with neat diesel (D100), 90 vol% neat diesel + 10 vol% ethanol (D90E10), D90E10 + 100 ppm Al2O3 nanoparticle (D90E10Al2O3), and D90E10 + 100 ppm TiO2 nanoparticle (D90E10TiO2). The experiments were performed on various engine loads (from 3 Nm to 12 Nm with 3 Nm increments) at a fixed crankshaft speed of 2400 rpm. D90E10Al2O3 showed the best energy, exergy, exergoenvironmental, and sustainability results among all fuels. However, according to exergoeconomic analysis, the lowest cost of crankshaft work was obtained with D100, followed by D90E10Al2O3. This means that D90E10Al2O3 presented better exergoeconomic results than its base fuel D90E10 and D90E10TiO2 but worse exergoeconomic results than D100. The addition of ethanol to D100 excessively increased the fuel cost. As a result, the crankshaft work cost flow rate is 0.7645 $/h for D100, 1.1123 $/h for D90E10, 1.1069 $/h for D90E10Al2O3 and 1.1338 $/h for D90E10TiO2. Similarly, the environmental impact rate of work is 250.8 mPt/h for D100, 264.2 mPt/h for D90E10, 245.6 mPt/h for D90E10Al2O3 and 248.7 mPt/h for D90E10TiO2. Increments in the engine load have led to increases in all environmental impact rates due to higher fuel consumption but caused a decrease in the environmental impact rate per exergy unit. In conclusion, it is well noticed that fuel blends with nanoparticles can be used as alternative fuels to their base fuels, but D100 (or an equivalent lower-cost fuel than D100) should be selected for cost-effectiveness purposes.

Rate limits and isotopologue fractionations for microbial methanogenesis examined with combined pathway protein cost and isotopologue flow network models

Microbial methanogenesis produces a range of isotope (13C/12C and D/H) and isotopologue (13CH3D and 12CH2D2) fractionations. Differential reversibility of enzymatic reactions qualitatively explains the isotope and isotopologue fractionations observed in both laboratory cultures and environmental samples. We applied pathway thermodynamics and isotopologue flow network models to quantitatively describe 13C/12C, D/H, 13CH3D, and 12CH2D2 fractionations during hydrogenotrophic methanogenesis. The model consists of the 10 enzymatic reactions of the methanogenesis pathway and tracks mass balance of isotopologues by taking into account the reaction symmetries of singly- and doubly-deuterated isotopologues. Based on the thermodynamics and enzyme kinetic data, the model estimates the reversibilities of 8 reactions from predicted in vivo concentrations of 17 metabolites and cofactors. The isotopologue flow network model calculates the isotopologue composition of product methane as well as all intermediates as a function of reversibilities and prescribed fractionation factors.The model explains a number of observations for laboratory culture experiments, including the range of 13C/12C fractionation up to 80‰ between CH4 and CO2, with increasing magnitudes while decreasing pH2. Relatively constant D/H fractionations of 300 ± 40‰ between methane and water can be explained when methane is produced from three near-equilibrium H in methyl-coenzyme M with the addition of one kinetic D-depleted H during the last step of methanogenesis. Abundances of the doubly substituted isotopologues, 13CH3D and 12CH2D2, reflect kinetic and equilibrium end-members with additional complications due to non-linear mixing and/or combinatorial effect.Our model can make predictions for isotopologue fractionations under slow rates of methanogenesis in energy-limiting deep sedimentary environments, where a large quantity of methane is produced. Near-equilibrium isotopologue ratios, often observed in marine sedimentary environments, are produced when pH2 is less than 10 Pa. Our model results indicate that methanogenesis does not occur or only proceeds at extremely slow rates at this low pH2 because low concentration of methyl-tetrahydromethanopterin limits the rate and thermodynamic feasibility of methanogenesis. Accordingly, it is proposed that near-equilibrium methane isotopologue signals in deep marine sediments are produced by the catalytic reversibility of methyl-coenzyme M reductase, likely from anaerobic methanotrophic archaea performing either anaerobic methane oxidation or net methanogenesis. The pathway thermodynamics and isotopologue flow network model scheme presented herein can be applied and expanded to predict isotopologue fractionations for a range of metabolisms beyond methanogenesis.

Minimum cost flow phase unwrapping method considering range direction slope

In mountainous terrain, the synthetic aperture radar (SAR) interferometry technology causes serious spatial decorrelation due to the shadows and overlaps in the range direction. We propose a minimum cost flow phase unwrapping method considering range direction slope (RDS). The RDS is calculated in the SAR imaging direction, and the RDS is used to divide the high- and low-quality regions of the interferometric phase. In the high-quality area, the residual error between the estimated value of the wrapped phase and the true value is greatly affected by the RDS. The quality map based on the slope in range direction is introduced to limit the number of residuals, at the same time, the quality map is used as the unit cost of the flow to balance the residuals of each node in the minimum cost flow, achieve the minimum cost of the minimum cost flow network, so as to achieve the minimum residual estimation and complete the unwrapping. The phase unwrapping experiments are carried out with the simulated data and the real data from Sentinal-1A in Qinling Mountain in China, and the experimental results show that the root-mean-square error of this method is lower than that of the path tracking method, the least squares method, and the traditional minimum cost flow method. The proposed method is suitable for phase unwrapping in complex mountainous areas.

Probabilistic techno-economic assessment of anaerobic digestion predicts economic benefits to smallholder farmers with quantifiable certainty.

Anaerobic digestion (AD) technology holds numerous potential benefits for farmers, however, challenges persist in terms of implementation costs and sustainability in developing countries. This paper presents a probabilistic techno-economic assessment tool for AD. A clear distinction is made between direct financial feasibility and wider (socio) economic feasibility. The tool identifies the technical- and economic factors influencing the returns of a particular AD process as well as the sensitivity of model predictions to variations in the value of the identified factors using a Monte Carlo approach. The tool is applied to assess the feasibility of a smallholder farm-based AD installation under a variety of substrates and operating conditions as an illustrative case study, where on-going flows of costs and benefits were considered over a 15-year period and discounted at a rate of 8%. The results of the case study revealed that the installation of a 10m3 smallholder farm-based anaerobic digester are likely to be financially and economically viable with a financial benefit-cost ratio of 1.30-1.38 and an economic benefit-cost ratio ranged from 5.49 to 6.01. Risk assessment results confirmed the strong economic feasibility of a smallholder farm-based AD implementation: under the most conservative cost estimates, there is a 73% probability of achieving a financial benefit-cost ratio>1, while there is a 96.6% probability of achieving an economic benefit-cost ratio>1. The case study demonstrated the utility of probabilistic techno-economic assessments for informed decision making, a tool which can be readily generalized to other settings.

Utility-Based Matching of Vehicles and Hybrid Requests on Rider Demand Responsive Systems

In rider demand responsive systems riders submit requests to demand transit services and the incoming requests and vehicles are matched by the system. This demand-responsive transport problem is viewed by existing research as a kind of spatial matching problem between vehicles and riders. However, existing schemes mainly focus on maximizing the number of matching pairs. It neglects other factors like the length of pickup trajectories and riders’ waiting time. And the matching is not revocable, which loses the chance for further optimizations. Moreover, there is still not much work on handling and matching the appointment-based requests that play a key role in the demand-responsive transport market. In this article, we propose an algorithm called BMCF ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Bipartite Minimal-Cost Flow</i> ) to solve the taxi-rider matching problem with appointment-based rider requests on a time-dependent road network. Unlike existing solutions that map the problem into the max flow problem, we transform the optimal matching to a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">minimal cost flow problem</i> which aims to maximize a utility value and could be solved efficiently. Riders and vehicles are modeled as vertices in a bipartite graph, and factors like the length of pickup trajectories, riders’ waiting time, etc. are abstracted as utilities and denoted as weights of the edges which are taken into account during the matching process. To the best of our knowledge, the proposed scheme is the first to efficiently integrate and process both the real-time and appointment-based requests within the same framework, and the assignments between vehicles and requests could be dynamically adjusted and revoked to maximise the overall utility. Experimental results show that the proposed algorithm can effectively increase the appointment-based matching ratio and decrease the riders’ waiting time (> 10.4%) and vacant vehicles’ picking up time (> 60.9%) compared with existing schemes, while at the cost of acceptable increase on the running time.

Программное средство для нахождения оптимальной последовательности технологических операций производственного процесса лесозаготовительного предприятия

The development of a software tool for finding the optimal sequence of technological operations of the production process of a logging enterprise, as well as the principles of its operation, is considered. Planning of logging production is quite a complex process, since it is necessary to determine the optimal strategy of activity, taking into account a large number of factors, increasing revenue and reducing costs. There are many options for organizing the technological process of harvesting and hauling wood. The program is developed on the basis of the algorithm given in the scientific literature for solving the problem of finding the optimal technological sequence of logging operations in order to automate calculations that are time-consuming. The application is created in the Delphi programming language in the Delhi XE2 RAD Studio development environment. The data used for the calculations is presented in an Excel table. To find the minimum cost flow, the program implements the Basaker — Gowan and Ford — Bellman algorithms. The result of the software tool is the optimal technological chain of delivery of wood from the cutting area to the consumer and corresponding costs. The results are displayed on the screen and can be saved to an Excel file. It is possible for the user to get help information about working with the program. With the help of the developed application, the technological chain of operations for the primary processing and transportation of harvested wood from the cutting area to the consumer is determined, which is characterized by a minimum cost for performing all types of work. The testing showed that the software can be used in practical activities by the head of the logging process at the enterprises of the forest industry.

The Influence of Globalization on Insurgency: Boko Haram and Al-Shabaab in the Age of Information Technology

Without a doubt, Africa is presently faced with violence, war, and acts of terrorism arising from the activities of insurgents. This paper examines the ways globalization aids insurgent activities and increasing manipulation of globalization by insurgents. It also looks at the negative impacts of violence and the need to find solutions to the insurgents’ activities that have generated concerns for the contemporary global system. The issues raised are significant considering the need to find solutions to the violence in the continent. This paper argues that just as globalization has encouraged increased technology, lowered transportation cost, increased trade, and capital flow, and the overall economic growth of nation-states; it has also allowed insurgency and terrorism to spread easily; serving as a sanctuary to insurgent groups and aiding the activities of insurgents. Although globalization has been fingered as a factor in some cases of insurgency, it is not itself the main cause of insurgency; however, globalization has dramatically helped transform the strategies, tactics, and the overallactivities of insurgents in the past two decades. This is because insurgents have directly and indirectly manipulated the faceless character of globalization to carry out their activities, especially Al-Shabaab in Kenya and Boko Haram in Nigeria. The paper states that just as insurgents have exploited globalization to perpetrate terror, globalization can also be used as a vital tool in counter-insurgency (COIN) and theWar on Terror (WoT).

The Influence of Globalization on Insurgency: Boko Haram and Al-Shabaab in the Age of Information Technology

Without a doubt, Africa is presently faced with violence, war, and acts of terrorism arising from the activities of insurgents. This paper examines the ways globalization aids insurgent activities and increasing manipulation of globalization by insurgents. It also looks at the negative impacts of violence and the need to find solutions to the insurgents’ activities that have generated concerns for the contemporary global system. The issues raised are significant considering the need to find solutions to the violence in the continent. This paper argues that just as globalization has encouraged increased technology, lowered transportation cost, increased trade, and capital flow, and the overall economic growth of nation-states; it has also allowed insurgency and terrorism to spread easily; serving as a sanctuary to insurgent groups and aiding the activities of insurgents. Although globalization has been fingered as a factor in some cases of insurgency, it is not itself the main cause of insurgency; however, globalization has dramatically helped transform the strategies, tactics, and the overall activities of insurgents in the past two decades. This is because insurgents have directly and indirectly manipulated the faceless character of globalization to carry out their activities, especially Al-Shabaab in Kenya and Boko Haram in Nigeria. The paper states that just as insurgents have exploited globalization to perpetrate terror, globalization can also be used as a vital tool in counter-insurgency (COIN) and the War on Terror (WoT).

ANALISIS USAHATANI LENGKUAS (Alpinia galanga) DI KELURAHAN SUKA MULYA KECAMATAN SEMATANG BORANG KOTA PALEMBANG PROPINSI SUMATERA SELATAN

Analysis of Lengkuas Farming (Alpinia galanga (L) Sw) case study in Sukamulya Subdistrict Sematang District Borang Palembang City.  This study aims to find out how much income and profits galangal farming is implemented in Sukamulya Village District Sematang Borang Palembang City, This study was conducted from February to June 2018.Population in this research is farmer of lengkuas in Sukamulya Subdistrict of Sematang District Borang Palembang as many as 60 farmers. Sampling is using simple random sampling (Simple Random Sampling) of 30% of the total population of 18 farmers as a respondent lengkuas. The calculated operational definitions are fixed costs including land lease fees and equipment depreciation. Variable costs include purchasing seeds, fertilizers, labor in the family. Production of galangal, receipts received by farmers per year, farmer's income and profit galangal farming in Sukamulya Village Sematang District Borang Palembang City. The results showed that the average production cost of sample farmers in Sukamulya village was Rp 49.393.594, -/Ha/Planting season. Receipt of farmers in Sukamulya Village Sukamulya District Borang Palembang City an average of Rp 77.385.000, -/Ha/Planting season. The average income of lengkuas farming in Sukamulya sub-district of Sematang Borang sub-district of Palembang is Rp. 27.991.406, -/Ha/Planting season. The result of analysis of farmer farming system in Sukamulya Village Subdistrict Sematang Borang City Palembang R/C is obtained at the farmer of example of galangal farming of 1.57 means that every Rp 1000, - the cost incurred by farmer, will get the acceptance of Rp 1,570,-. So the cultivated galvanized farming is profitable because R/C &gt;1. Key words : Farming, Lengkuas, Cost and Marketing Flow

Optimization of container traffic distribution on the railway network

The paper considers the problem of optimal redistribution of transit container flows on the railway network. The problem is proposed to be solved as the problem of a multi-commodity flow of minimum cost using the relaxation method. The relaxation method allows choosing the most efficient variant of the next solution at each iteration step. To search for the optimal distribution of container flows on the network, graph theory was used, i.e., the network is presented as a multigraph with a set of vertices and arcs, for which the costs of transporting a unit of production, the maximum and minimum values of the flows between the vertices are given, the conditions for maintaining the flow at the vertices of the graph and restrictions on the amount of flow along the arcs are given. It has been established that in order to implement the task, it is necessary to take into account the unit costs for the movement of container flows between the nodes of the railway network, taking into account the capacity of the branches between the junction stations. The developed mathematical model for the redistribution of container traffic allows you to identify areas with limited throughput, develop options for optimization measures, and, as a result, achieve an economic effect by reducing the cost of transporting containerized cargo.

ОТРАЖЕНИЕ ФИНАНСОВЫХ ПОТОКОВ ИЗ СИСТЕМЫ НАЦИОНАЛЬНЫХ СЧЕТОВ

The main purpose of the work is to show some possibilities and approaches for developing a consolidated financial balance sheet. Such developments are necessary to provide government agencies with information that comprehensively reflects the financial flows of resources and costs of business entities when justifying the plan. The balance of financial resources of a subject of the Russian Federation is the sum of the balance of revenues and expenditures of the budget of the subject of the Russian Federation and the balance of financial resources of municipalities, as well as economic entities in this territory. The development of the balance of financial resources is one of the components of the forecast of socio-economic development of the Russian Federation, the subject of the Russian Federation, and the municipality. The balance of financial resources serves as a tool that allows, at the level of the forecast of macroeconomic development, to determine the expediency of making certain proposals and decisions. Monetary income and expenses of the population are not included in the balance of financial resources. They can be included in the consolidated financial balance sheet as a composite. part of the reproduction balance of gross output as a whole. This is required to achieve and maintain balance: between the supply of consumer goods and the monetary income of the population; between the production of means of production intended for the reimbursement of material costs and capital accumulation, and the corresponding monetary means of producers of material goods and services. Such a balance should be ensured not only by the amount, but also by the structure of the mass of goods produced, intended to satisfy the corresponding needs of all types of activities and households. The consolidated financial balance is closely related to the consolidated material balance and to the Input-output balance of production and distribution of products.

Interval-Valued and Circular Intuitionistic Fuzzy Present Worth Analyses

Present worth (PW) analysis is an important technique in engineering economics for investment analysis. The values of PW analysis parameters such as interest rate, first cost, salvage value and annual cash flow are generally estimated including some degree of uncertainty. In order to capture the vagueness in these parameters, fuzzy sets are often used in the literature. In this study, we introduce interval-valued intuitionistic fuzzy PW analysis and circular intuitionistic fuzzy PW analysis in order to handle the impreciseness in the estimation of PW analysis parameters. Circular intuitionistic fuzzy sets are the latest extension of intuitionistic fuzzy sets defining the uncertainty of membership and non-membership degrees through a circle whose radius is r. Thus, we develop new fuzzy extensions of PW analysis including the uncertainty of membership functions. The methods are given step by step and an application for water treatment device purchasing at a local municipality is illustrated in order to show their applicability. In addition, a multi-parameter sensitivity analysis is given. Finally, discussions and suggestions for future research are given in conclusion section.

Algorithms to Calculate the Most Reliable Maximum Flow in Content Delivery Network

Calculating the most reliable maximum flow (MRMF) from the edge cache node to the requesting node can provide an important reference for selecting the best edge cache node in a content delivery network (CDN). However, SDBA, as the current state-of-the-art MRMF algorithm, is too complex to meet real-time computing needs. This paper proposes a set of MRMF algorithms: NWCD (Negative Weight Community Deletion), SCPDAT (Single-Cycle Preference Deletion Approximation algorithm with Time constraint) and SCPDAP (Single-Cycle Preference Deletion Approximation algorithm with Probability constraint). NWCD draws on the “flow-shifting” algorithm of minimum cost and maximum flow, and further defines the concept of negative weight community. This algorithm continuously deletes the negative weight communities, which can increase reliability while keeping the flow constant in the residual graph. It is proven that when all negative weight communities are deleted, the corresponding maximum flow is the MRMF. SCPDAT tries to approach the optimal solution to the greatest extent possible within the limited time, while SCPDAP tries to reach the probability threshold in the shortest amount of time. Both of these adopt the strategy of first deleting single-cycle communities (which contribute more to the reliability with lower time cost). Experiments show that, compared with SDBA, NWCD combined with the probabilistic pruning achieves an order of magnitude improvement in time cost, while SCPDAT and SCPDAP demonstrate better time performance and increased applicability.

Large-Gradient Interferometric Phase Unwrapping Over Coal Mining Areas Assisted by a 2-D Elliptical Gaussian Function

Phase unwrapping (PU) is a key step in InSAR surface monitoring, which is directly related to the accuracy of the LOS displacement observations. Underground coal mining generally results in large gradient displacements, producing dense and aliasing fringes in interferograms. In this case it is challenging to accurately unwrap interferometric phases using traditional methods. This letter proposes an iterative algorithm to unwrap interferometric phases over underground coal mining areas. Firstly, differential interferogram is unwrapped by the minimum cost flow (MCF) method to obtain unwrapped phases at the edge of the mining subsidence basin. Then, a 2D elliptical Gaussian function, which could approximately describe the spatial shape of mining subsidence basin, is used to iteratively reduce the phase gradients of interferograms, so that residual wrapped phases at more pixel in subsidence basin can be unwrapped. The presented method was tested over Datong coal mine, China, based on 16 TerraSAR-X acquisitions. The result suggests that the accuracy of time-series displacements along the line-of-sight direction solved from the unwrapped phases using the new PU method is 1.1cm, indicating an improvement of 73.2% compared with that of using the traditional MCF method.

Deep-Learning-Based Phase Discontinuity Prediction for 2-D Phase Unwrapping of SAR Interferograms

Phase unwrapping is a critical step of interferometric synthetic aperture radar processing, and its accuracy directly determines the reliability of subsequent applications. Many phase unwrapping methods have been proposed, most of which assume that the phase has spatial continuity, while decorrelation noise and aliasing fringes invalidate the assumptions, resulting in poor performance of these methods. To obtain more reliable unwrapping results, in this article, a deep convolutional neural network, called a discontinuity estimation network (DENet), is proposed for predicting the probabilities of phase discontinuities in interferograms. The main advantages of DENet are: 1) using branching structure to extract detailed and high-level features separately and retain details while making full use of contextual information; 2) using multichannel input, including interferogram, range/azimuthal phase gradients, and residues map, to provide effective guidance for discontinuity prediction; and 3) using a single network to estimate phase discontinuities in both range and azimuth directions simultaneously. To train the network, a dataset simulation strategy is proposed to generate enough training samples. The strategy considers a variety of phase components, such as terrain-related phase, random deformation, atmospheric turbulence, and noise. The phase discontinuity estimated by DENet is then converted to costs in the minimum cost flow (MCF) solver of the statistical-cost, network-flow algorithm for phase unwrapping (SNAPHU) to obtain the final unwrapped phase. Based on validations of simulated and real interferograms, the proposed method exhibits excellent performance compared to traditional and deep learning unwrapping methods. The proposed method can effectively unwrap large-scale, low-quality interferograms, which is expected to significantly improve the accuracy of synthetic aperture radar interferometry (InSAR) applications.

The Existence of Paid Photocopy Services at the Gadjah Mada University (UGM) Library in Era 4.0

The advanced transformation of universities' libraries that is fulfilled by many innovations has offered students an easier way to access collections of sources of information. Even though accessing collections is merely easy, there is a library service area that has restrictions. For instance, reference services frequently include a rule that states that students are only permitted to read materials there and then they are not permitted to borrow collections to read later. Some university libraries offer paid photocopying services despite the limited hours of the library service, which makes it a worthwhile study topic. A qualitative-descriptive research methodology was used for this investigation. In the meantime, the interview approach was employed to obtain the data for this study. The findings demonstrated that students had no other option except to employ copying services in order to fulfill their demands. The availability of these services also fosters a mutually beneficial relationship between users and libraries.For users, there is no need to take notes and go back and forth from the library to refer to the required references. Then for the library, photocopying services provide financial income that supports library development. Its existence, which is still surviving today, helps create a stable cost flow for libraries that can be utilized by library managers and provides time efficiency for users to get the information they need. Although the price of photocopying in the library is more expensive than photocopying outside the library, users are still enthusiastic about using it so that the service continues.

Energy and Material Flow Evaluation with CO2 Emissions in the Glass Production Process

Glass manufacturing is an energy-intensive process with high demands on product quality. The wide usage of glass products results in a high end-product diversity. In the past, many models have been developed to optimize specific process steps, such as glass melting or glass forming. This approach presents a tool for the modeling of the entire glass manufacturing process for container glass, flat glass, and glass fibers. The tool considers detailed bottom-up energy and material balance in each step of the processing route with the corresponding costs and CO2 emissions. Subsequently, it provides the possibility to quantify optimization scenarios in the entire glass manufacturing process in terms of energy, material and cost flow efficiency.

Fuzzy modelling and control of project cash flows

An analysis of the scientific literature on project cash flow control and fuzzy modelling shows that project cash flows are modelled using only basic approaches drawn from fuzzy theory, which may distort the credibility of the model. In this paper, we therefore propose to use the whole spectrum of fuzzy arithmetic, and to select operations that suit the nature of the cash flows in question, their dependencies and the preferences of the project manager. An analysis of the literature also shows that in practically all existing models of project costs and cash flow management, project costs and cash flows are treated at a very high level of generality (without considering the various types of project, factors influencing their variability and signals warning of imminent cash-related problems), and estimations are not updated on an ongoing basis throughout the duration of the project. The results of a survey performed with the participation of 100 project managers show that this simplistic view of project cash flows may be distorting, and cannot guarantee the development of an efficient project cost and cash flow control system. We propose an approach that at least partially compensates for these drawbacks: it differentiates between types of project cash flows and the factors and triggers affecting changes in cash flows. Two case studies are used for a an initial verification of the approach. The paper concludes with suggestions for further research perspectives.

Robust minimum cost flow problem under consistent flow constraints

The robust minimum cost flow problem under consistent flow constraints (RobMCFequiv ) is a new extension of the minimum cost flow (MCF) problem. In the RobMCFequiv problem, we consider demand and supply that are subject to uncertainty. For all demand realizations, however, we require that the flow value on an arc needs to be equal if it is included in the predetermined arc set given. The objective is to find feasible flows that satisfy the equal flow requirements while minimizing the maximum occurring cost among all demand realizations. In the case of a finite discrete set of scenarios, we derive structural results which point out the differences with the polynomial time solvable MCF problem in networks with integral demands, supplies, and capacities. In particular, the Integral Flow Theorem of Dantzig and Fulkerson does not hold. For this reason, we require integral flows in the entire paper. We show that the RobMCFequiv problem is strongly mathcal {NP}-hard on acyclic digraphs by a reduction from the (3, B2)-Sat problem. Further, we demonstrate that the RobMCFequiv problem is weakly mathcal {NP}-hard on series-parallel digraphs by providing a reduction from Partition. If in addition the number of scenarios is constant, we propose a pseudo-polynomial algorithm based on dynamic programming. Finally, we present a special case on series-parallel digraphs for which we can solve the RobMCFequiv problem in polynomial time.