Supply Streams Research Articles

Geostatistical methods in the assessment of the spatial variability of the quality of river water

The research was conducted in the agricultural catchment in north–eastern Poland. The aim of this study was to check how geostatistical analysis can be useful for the detection zones and forms of supply stream by water from different sources. The work was included the implementation of hydrochemical profiles. These profiles were made by measuring the electrical conductivity (EC) values and temperature along the river. On the basis of these results, the authors calculated the coefficient of Moran I and performed semivariogram and found that the EC values are correlated on a stretch of about 140 m. This means that the spatial correlation between samples of water in the stream is readable over a distance of about 140 meters. Therefore it is believed that the degree of water mineralization on this section is shaped by water entering the river channel migration in different ways: through tributaries, leachate drainage and surface runoff. In the case of the analyzed catchment, the potential sources of pollution were drainage systems. Therefore, the spatial analysis allowed the identification pollution sources in a catchment, especially in drained agricultural catchments.

Modeling grain size adjustments in the downstream reach following run‐of‐river development

AbstractDisruptions to sediment supply continuity caused by run‐of‐river (RoR) hydropower development have the potential to cause downstream changes in surface sediment grain size which can influence the productivity of salmon habitat. The most common approach to understanding the impacts of RoR hydropower is to study channel changes in the years following project development, but by then, any impacts are manifest and difficult to reverse. Here we use a more proactive approach, focused on predicting impacts in the project planning stage. We use a one‐dimensional morphodynamic model to test the hypothesis that the greatest risk of geomorphic change and impact to salmon habitat from a temporary sediment supply disruption exists where predevelopment sediment supply is high and project design creates substantial sediment storage volume. We focus on the potential impacts in the reach downstream of a powerhouse for a range of development scenarios that are typical of projects developed in the Pacific Northwest and British Columbia. Results indicate that increases in the median bed surface size (D50) are minor if development occurs on low sediment supply streams (<1 mm for supply rates 1 × 10−5 m2 s−1 or lower), and substantial for development on high sediment supply streams (8–30 mm for supply rates between 5.5 × 10−4 and 1 × 10−3 m2 s−1). However, high sediment supply streams recover rapidly to the predevelopment surface D50 (∼1 year) if sediment supply can be reestablished.

Structure and dynamics of edge flames in the near wake of unequal merging shear flows

We examine in this study the structure and dynamic properties of an edge flame formed in the near-wake of two initially separated shear flows, one containing fuel and the other oxidiser. A comprehensive study is carried out within the diffusive-thermal framework where the flow field, computed a-priori, is used for the determination of the combustion field. Our focus is on the effects of three controlling parameters: the Damköhler number controlling the overall flow rate, the oxidiser-to-fuel strain rate ratio of the supply streams that determines the extent of oxidiser entrainment towards the mixing zone, and the Lewis number, assumed equal for the fuel and oxidiser, that depends on the mixture composition. Response curves, representing the edge flame standoff distance as a function of Damköhler number, exhibit two distinct shapes: C-shaped and U-shaped curves characterising the response of low and high Lewis number flames, respectively. Stability considerations show that the upper solution branch of the C-shaped response curve is unstable and hence corresponds to physically unrealistic states, but due to heat conduction toward the cold plate the lower solution branch is always stable. The states forming this solution branch correspond to flame attachment, where the edge flame remains practically attached to the tip of the plate until it is blown off by the flow when the velocity exceeds a critical value. The U-shaped response, on the other hand, consists of equilibrium states that are globally stable. Thus, high Lewis number flames can be always stabilised near the splitter plate, with the edge held stationary or undergoing a back and forth motion, or lifted and stabilised downstream by the flow. Insight into the distinct stabilisation characteristics, exhibited by the different Lewis number cases, is given by examining the relationship between the local flow velocity and the edge propagation speed.

Extending the newsvendor model to account for uncontrolled inventory transfers

In this paper we consider the single-period newsvendor model with uncontrolled inventory transfers. The newsvendor or buyer places a single order for identical items. Independently of the order, the buyer can also receive an additional random amount of the same item in the same time period via “transfer”. Thus, there is uncertainty associated with both the demand and the quantity that is transferred. We formulate this problem as a newsvendor problem with two independent supply streams (one deterministic and one random) and compare our analytical results for different demand distribution/transfer distribution combinations to analytical results associated with the classic newsvendor model. Uncontrolled inventory transfers present a challenging problem in the health care industry with respect to the management of blood inventory. However, the proposed extension can be generalized and applied to any situation where perishable items are transferred from satellite locations to a centralized location in order to increase the probability that the items will be sold before they expire.

Sensing Abnormal Resource Flow Using Adaptive Limit Process Charts in a Complex Supply Network*

ABSTRACTSupply networks are becoming increasingly complex with multiple overlapping relationships between firms that may span across industries. Consequently, inventory management is becoming more difficult as managers have to cope with variability in the supply flows that originate from different parts of the network. Managers that quickly sense abnormal flows may intervene and adapt their inventory policies in response to system changes. In this article, we present a framework for sensing abnormal flows originating within the upstream supply network of a focal organization. Our framework combines time series modeling with process charts to identify abnormal flow patterns in the incoming supply streams. It is a flexible framework that uses off‐the‐shelf technology to provide managers with a process that can be employed for monitoring multiple individual or aggregated data streams originating within any complex system such as complex adaptive supply networks. We illustrate our framework on four years of longitudinal supply data from the second largest food bank in the United States. We identify multiple instances of abnormal supply flows and validate our results through rigorous inventory analysis as well as field‐based expert interviews. We discuss the implications of our findings for inventory management in complex supply networks, both from academic and practitioner points of view.

Management of Supply Chain: X-to-order Concepts vs Make-to-stock Model

In a challenging market, companies’ ability to act faster is considered a basic advantage. From a value chain aspect, when a company cannot change its internal production processes and the external supply streams according to the demand requirements, this may lead to sales reduction or stock left-overs. X-to-order concepts [where X=Α(ssemble), Μ(ake)/Β(uilt) and Ε(ngineer)], are key types of supply chain planning, where the production process starts after the orders are placed. Those methods have caught the attention of both researchers and businesses because of the advantages they offer in business procedures and the customization of consumers needs. The aim of this paper is to present the framework of supply chain management of the X-to-order concepts in comparison to the make-to-stock model and depict the main differences between these two approaches.

Channel-reach morphology controls of headwater streams based in flysch geologic structures: An example from the Outer Western Carpathians, Czech Republic

A detailed measurement of 93 channel reaches that were classified with an adjusted Montgomery–Buffington (1997) reach-scale system provided comprehensive information of approximately 9 at-a-reach parameters: the channel gradient, the bankfull width, the bankfull depth, d90, the percentage of resistant rocks in the bed sediment, the number of pieces of large woody debris, valley confinement, direct sediment inputs and the presence of fluvial accumulations in the stream channel. In addition, the quantified intensity of sediment transport (i.e. ratio between sediment supply and transport capacity in longitudinal stream profiles) during flood events has been estimated by the one-dimensional bedload transport model (TOMSED), which was validated in two local streams. The principal component analysis of the at-a-reach parameters did not reveal significant groups of channel-reach morphologies; thus, the selected parameters that exclude sediment transport dynamics within stream longitudinal profile cannot reliably distinguish or predict individual channel reach morphologies. Nevertheless, the channel gradient represented the most significant single explanatory variable for stepped-bed morphologies. The addition of bedload transport parameters demonstrated that limited sediment supply streams and streams with limited transport capacities featured different successions of the channel reach morphologies in terms of the channel gradient and, subsequently, the fluvial continuity. The bedrock-cascades and step-pools were significant for the first case, whereas cascade and step-rapid morphology often occurred in higher sediment supply conditions.

ISASMELT™ for the Recycling of E-Scrap and Copper in the U.S. Case Study Example of a New Compact Recycling Plant

As living standards around the world improve and metal consumption increases, extracting raw materials will likely become more challenging in the future. Although already part of the general metal supply stream, metal recycling has to increase if we are to build a more sustainable society. With the recent widespread adoption of a range of consumer and industrial electronics, the recycling of the so-called electronic scrap (“e-scrap”) has also increased in importance. One of the leading technologies for the recycling of e-scrap and copper scrap is the ISASMELT™ Top Submerged Lance technology. This article describes new opportunities for the U.S. recycling industry to yield full value from collected, sorted, and separated waste metals, in particular, e-scrap and lower grade copper scrap by the use of ISASMELT™ technology. The article includes the description of a case study example of a regional, compact ISASMELT™ plant in the United States treating a blend of e-scrap and copper scrap, having a total feed capacity of 75000 t/year of feed. Plants of higher or lower capacity are also discussed.

Formaldehyde transfer in residential energy recovery ventilators

The rotary enthalpy wheel design used in many energy recovery ventilators (ERVs) is designed to transfer heat and moisture between supply and exhaust air streams. The wheel, however, can also transfer formaldehyde and other indoor contaminants from the exhaust stream to the supply stream through air leakage, entrainment in the porous wheel, and adsorption/desorption to the filter medium. This contaminant transfer reduces the benefit of the mechanical ventilation provided by the device. Field and chamber experiments were used to quantify the formaldehyde transfer efficacy (the fraction of formaldehyde transferred from the exhaust stream to the supply stream) in a common ERV model under varied conditions. In field experiments, the transfer efficacy was approximately 29%. Chamber tests showed formaldehyde transfer efficacy between 10 and 29%. The bulk of the transfer was due to air leakage and entrainment within the wheel, with up to 30% of the transfer attributed adsorption/desorption from the filter medium. The transfer efficacy decreased with increasing air exchange rate and supply air temperature. The transfer efficacy increased as the supply and exhaust streams were unbalanced in flow rate. Overall, the air leakage through the device substantially exceeded the product rating of 10%, with 27–28% air leakage measured in field experiments and 12–19% air leakage in chamber experiments.

Supply Streams

A supply stream is a continuous version of a supply chain. It is like a series inventory system, but stock can be held at any point along a continuum, not just at discrete stages. We assume stationary parameters and aim to minimize the long-run average total cost. We show that a stationary continuous-stage echelon base-stock policy is optimal. That is, at each geographic point along the supply stream, there is a target echelon inventory level, and the optimal policy at all times is to order and dispatch material so as to move the echelon inventory position as close as possible to this target. We establish this result by showing that the solutions to certain discrete-stage systems converge monotonically to a limit, as the distances between the stages become small, and this limit solves the continuous-stage system. With demand approximated by a Brownian motion, we show that, in the continuous-stage limit, the supply stream model is equivalent to one describing first-passage times. This linkage leads to some interesting and useful results. Specifically, we obtain a partial differential equation that characterizes the optimal cost function, and we find a closed-form expression for the optimal echelon base-stock levels in a certain special case, the first in the inventory literature. These expressions demonstrate that the well-known square-root law for safety stock does not apply in this context.

Factors affecting storm event turbidity in a New York City water supply stream

Stream turbidity levels tend to increase during high stream discharge events, and it is important to quantify the suspended sediment flux during these events that could potentially lead to water quality problems. Here, a case study for estimating suspended sediment loads (as a product of turbidity and stream discharge) in streams that are part of the New York City (NYC) water supply in the Catskill region of New York State is presented. Over the 8 year study period 80% of the suspended sediment load was transported during less than 4% of the time, indicating the importance of estimating storm event suspended sediment loads. The objective of this study was to understand the underlying factors controlling the uncertainty in the discharge vs turbidity relationship at the outlet of the watershed draining into the NYC Ashokan Reservoir. High frequency (15-min) automated monitoring of stream turbidity was combined with stream discharge measurements of a similar frequency to provide an estimate of the true suspended sediment load that could be used for model testing and verification at two time scales; daily and events. Multivariate statistical analyses indicate that average daily stream turbidity during storm events can be influenced by the spatial variability in runoff, antecedent conditions, and season. A predictive relationship of event mean stream turbidity based on stream discharge alone led to a strong predictive relationship (r 2 = 0.81), but also a 10% underestimation of the cumulative measured event mean suspended sediment load. Inclusion of information on the time between events improved the regression equation (r 2 = 0.89), and reduced the cumulative difference between estimated and measured event mean suspended sediment loads to 7% underestimation. ► High frequency (15-min) automated monitoring of stream turbidity ► Factors causing variability in discharge–turbidity relationship ► Influence of spatial variability in runoff, antecedent conditions, and season

Efficient water recirculation for portable direct methanol fuel cells using electroosmotic pumps

We present an efficient water recirculation method for air-breathing direct methanol fuel cells (DMFC) by utilizing so-called electroosmotic (EO) pumps. The fuel management system includes three EO pumps for the delivery of methanol solution, pure methanol, and pure water, respectively. Water recirculates from the fuel cell back to the fuel supply stream with the aid of these pump systems. We characterized the performance of the air-breathing DMFC for 2 M and 4 M methanol solutions using a syringe pump and EO pumps, respectively. The DMFC performance is similar for both types of pumps as long as the EO pump operates with the applied voltage of 6 V or higher. The maximum net power density (fuel cell power generation minus pump power consumption) was 50 mW cm−2 for 2 M methanol solution and the applied pump potential of 8 V. The minimum parasitic power ratio (pump power consumption divided by fuel cell power generation) was merely 2.1% for 4 M methanol solution and the applied pump potential of 6 V. We successfully demonstrated that the air-breathing DMFC integrated with the EO pumps operated in a stable condition in 1-h galvanostatic measurement.

Market Liquidity and Adverse Permanent Effects in Hedging Equity & Interest Rates Derivatives

This work presents a review of modeling techniques for pricing in incomplete markets and managing liquidity costs. We go through a variety of financial models and mathematical aspects related to market liquidity. We present in Chapter 1 the temporary liquidity modeling proposed by Cetin, Jarrow and Protter (2004). We extend this framework to limit order books with liquidity supply and consumption streams. In Chapter 2, we present our main contribution that consists in generalizing Almgren et al. (2011)’s liquidity adverse impacts modeling and hedging strategies from standards of short-term high-frequency trading to the general economy of financial markets. This allows us to introduce, in Chapter 3, a new paradigm to model both temporary and permanent liquidity costs for the Fixed-Income market. Numerical aspects about stochastic control and Backward Stochastic Differential Equations (BSDE) are discussed in Chapter 4. Conclusions are addressed afterward.This work is elaborated in partial fulfillment of the requirements for the degree of Master of Science (DEA) in Quantitative Finance and Mathematical Engineering of the Ecole Nationale des Ponts et Chaussees (Paris, France).

Life Expectancy Study of Small Diameter Type E, K, and N Mineral-Insulated Thermocouples Above 1000 °C in Air

Very little if any current data is available for the life expectancy of very small diameter thermocouples operating at high temperatures, greater than 1000 °C. Over the past 10 years significant changes in the supply stream of the materials used to manufacture base metal thermocouples have occurred. In many industrial applications, small diameter thermocouples are the only solution for high-temperature measurements. This study has been undertaken to assess the performance of small diameter magnesium oxide insulated metal sheathed thermocouple sensors at or above 1000 °C. Three different American Society of Testing and Materials (ASTM) standard letter designation thermocouple types have been included in this study, Types E, K, and N. Inconel 600 and 316 stainless, for three different sizes, 0.5 mm, 1.0 mm, and 1.5 mm, have been tested for different thermocouple types. Each group of sensors was placed in an equalization block in air for a maximum of 500 h or until failure. The performance of 0.5 mm diameter thermocouples varies widely depending on the thermocouple type, sheath material, and test temperature. Larger diameter Type K and N thermocouples show very little drift up to 500 h at 1100 °C. The data for each test was collected at 10 s intervals for the entire duration of the test. Data for the sensor drift and subsequent failure are presented.

Study on the Bounded Inventory Model with Returning Items and Disposals

This paper addresses a dynamic lot sizing problem with mixed returning items and disposals and bounded inventory. The returning items mean that returns are in good enough condition to re-enter the inventory supply stream. The producing, the holding, backlogging and disposals cost functions are concave cost functions. Furthermore, backlogging level and inventory level at each period is limited. The goal is to minimize the total cost of production, inventory holding/backlogging and disposal. A dynamic programming algorithm with complexity O(T3) is developed to solve this model, where T is the length of the planning horizon.

Run-Around Energy Recovery System for Air-to-Air Applications Using Cross-Flow Exchangers Coupled with a Porous Solid Desiccant—Part I: Model Development and Verification

Heat and moisture transfer between supply and exhaust air streams are investigated for a run-around system in which the coupling material is a desiccant coated solid that is transported between two exchangers. The finite volume method is used to solve the governing partial differential equations of the cross-flow heat exchangers in the supply and exhaust ducts under steady state operating conditions. The outlet air properties are calculated for several inlet air operating conditions and desiccant properties. The accuracy of the model is verified by comparing the simulations with well-known theoretical solutions for a single cross flow heat exchanger and a liquid coupled run-around system. The difference between the analytical predictions and numerical model for sensible effectiveness for each exchanger and the run-around system were found to be less than 1% over a range of operating conditions. The model is also verified by modifying the boundary conditions to represent a counter flow energy wheel and comparing the calculated sensible, latent and total effectiveness values with correlations in the literature. Part II of this paper will investigate the sensible, latent and total effectivenesses during simultaneous heat and moisture transfer.

Modular Syncrude Conversion Drives Oilfield GTL Solution for Associated Gas

Technology Update The associated gas that accompanies oil to the surface in a producing well can be a great advantage and valuable revenue stream, if your oil field is near a pipeline that feeds into a gas market. However, as oil fields move into deeper and more remote areas, away from population centers and gas infrastructure, the options for handling associated gas have become restricted and the question of what to do with it often difficult. The industry is crying out for a solution. Historically, where there was no local market or available pipeline, associated gas was flared. However, this is now both environmentally and politically unacceptable, and in many countries banned. The alternative of gas reinjection is expensive and can cause reservoir damage, which adversely affects production and reserves. Seeking a solution that avoids either of these alternatives, the industry for years has experimented with a variety of technologies. For example, in areas with large associated gas volumes, the gas can be commingled into gathering systems and supply nearby specially constructed liquefied natural gas (LNG), methanol, or ammonia plants. However, this solution comes with a couple of major requirements.High gas volumes must be com-mitted in advance to justify the substantial plant-building cost.Commonly, supplementary nonassociated gas also must be available to offset supply fluctuations, including the eventual decline of field production. One example of how this supply-balancing requirement can work is the Bonny Island LNG plant in Nigeria, which ran on nonassociated gas until gathering systems were built that allowed associated gas to replace part of the original supply stream. Without both of these prerequisites, commingling is not an option. With oil fields getting smaller and more remote, there will commonly not be sufficient reserves of associated gas to justify installing gas infrastructure or gas-processing plants. Even in areas such as the North Sea, where extensive gas infrastructure and a ready local market exist, small fields with short lives of 4 years or so cannot justify the expense of installing a gas export pipeline. Other solutions proposed for dealing with associated gas that cannot be exported by pipeline have involved locating a gas-processing plant adjacent to the oil field and using technologies such as floating LNG, gas-to-liquids (GTL), methanol production, or gas-to-wire electrical power generation. These too tend to require large supplies of gas and considerable investment. For example, a standalone facility capable of consuming 100 to 150 MMscf/D of gas would have a capital expenditure of more than USD 1 billion. In addition, a facility would need a steady nondeclining gas stream, which often can only be achieved by combining associated gas with nonassociated gas from other fields. As such, this has led to these large facilities focusing on stranded gas with reserves of 0.5 Tcf or greater, rather than associated gas.

Suministro de antirretrovirales en Argentina: Programa Nacional de Lucha contra los Retrovirus del Humano, SIDA y ETS

To evaluate the supply cycle of antiretroviral (ARV) drugs, overseen by the National Program to Combat Human Retroviruses, AIDS, and STDs, through its order fulfillment indicators, and to obtain input from supply chain stakeholders. A study was carried out from April-September 2005 in the pharmacies of two hospitals in Rosario, Argentina, involving both a quantitative analysis of indicators and secondary sources and a qualitative evaluation using semistructured interviews. The indicators reveal the impact that interruptions in ARV supply stream from the Program (central level) have and the overstocking that takes place at the pharmacies (local level) to manage the shortages. Changes in ARV treatment account for over 50% of the prescriptions. Fulfillments fall short of the reference value. The interviewees shared possible strategies for overcoming the communication gaps between levels, for building-up stock, for guaranteeing availability, and for shortening waiting times; reached informal agreements to deal with the lack of policies and the shortage of staff; acknowledged the challenges facing the jurisdictions (central, intermediate, and local/community); and recognized local efforts to improve management. These challenges could be the starting point for building teams to work on effectively decentralizing the entire supply chain and allowing the Program to fulfill its much-needed oversight role.

Use of supply relationships to recycle secondary materials

The reverse logistics function in supply chain management has received increasing attention in recent years as the value of the activity, the awareness of its potential and the legal requirements for its presence have increased. Reverse logistics has two dominant end purposes for returned materials–reconditioning (high-value recovery) or recycling (low to no value recovery). Much of the material generated by reverse logistics activity falls into this second category of low to no value. This can create a significant material management problem for many organisations. Several large organisations have successfully created recycling empires around the more primary materials that feed readily into raw material supply streams–such as metals, timbers and paper. For individual firms, however, the likelihood of investing effort in identifying both materials that could be recycled and a potential market for them has seemed frequently out of reach. This study highlights an under-researched phenomenon whereby firms engage with one another to seek economical recycling of low value and often complex secondary materials. Using eight case studies of manufacturing firms, the study identifies several examples of innovative and valuable recycling solutions occurring between supply chain members. Supply relationships are proposed to provide a critical enabler for improving firm knowledge of material value, recycling options, previously un-considered buyers or markets for a material, and for aggregating resources and improving the economy of recycling.

Determination of Soot Formation Rate from Laminar Smoke Point Measurements

In order to develop soot formation models for fuels in fires, a global Arrhenius equation for soot formation rate has been studied in terms of the mixture fraction, the fuel concentration in the fuel supply stream, the local gas density and the gas temperature. A procedure relying on modelling and experimental data determines the parameters for the soot formation rate by exploiting the physics and results in laminar smoke point flames corresponding to a given fuel. The main advantages of such an approach are its simplicity and applicability to fuels (solids or liquids) in fires as long as their smoke point height is known, whereas most of the previous studies focused on pure hydrocarbons.