Downstream Asymmetry Research Articles

Wholesale Price Discrimination and Contract Unobservability

This study examines how wholesale price discrimination (WD) by a supplier affects different parties in a supply chain involving a common supplier distributing homogeneous products through two competing retailers with different costs under wholesale price contracts. Especially, we allow for contract unobservability, where the contract terms between the supplier and each retailer are secret to the rival retailer. Intuitively, given the downstream asymmetry, WD should be more advantageous than the uniform wholesale price (UW) scheme for the supplier. This is true under observable contracts, as we show that WD benefits the supplier and less efficient retailer but hurts the more efficient retailer, supply chain, and consumers. Under unobservability, however, we find that the supplier may be better off by committing to UW. The intuition is that contract unobservability induces the supplier to set lower discretionary wholesale prices, which can outweigh the benefits of pricing flexibility. Consequently, a lack of commitment to UW can benefit both retailers, improve supply chain efficiency, and increase consumer surplus. Our findings suggest that policymakers should be cautious about imposing restrictions on WD. We also consider three extensions for robustness and offer new insights.

Upstream–Downstream Asymmetry in Multiscale Interaction Underlying the Northern Hemisphere Atmospheric Blockings

Abstract The typical blockings over the Pacific, Atlantic, and Ural Mountain regions are investigated for an understanding of their dynamical interactions in a unified treatment with their respective basic flows and high-frequency processes, respectively. Thanks to the localized nature of the new methodology as used in this study, for the first time we identify a dipolar structure (for each of the three regions) in the map of the interscale energy transfer from the basic flow to the composite blocking, with a positive center upstream and a negative center downstream. This indicates the crucial role of the instability of the basic flow in the maintenance of blockings, which has been overlooked due to the bulk nature of the spatially integrated energetics (by summing the transfer over the whole blocking, the two centers essentially cancel out, leaving an insignificant bulk transfer). For the interaction between the blocking and the high-frequency storms, the well-known critical role of the upscale forcing in blocking development is confirmed. But, unexpectedly, except for that over the Atlantic where the forcing exists throughout, over the other two regions the forcing is found to occur mainly downstream. This is quite different from what the classical theory, e.g., the famous eddy strain mechanism of Shutts, would predict.

Sustainable agreements on stochastic river flow

Many river sharing agreements in transboundary river basins are inherently unstable. Due to stochastic river flow, agreements may be broken in case of drought. The objective of this paper is to analyze whether river sharing agreements can be self-enforcing, or sustainable. We do so using an infinitely-repeated sequential game that we apply to several classes of agreements. To derive our main results we apply the equilibrium concepts of subgame-perfect equilibrium and renegotiation-proof equilibrium to the river sharing problem. We show that, given the upstream–downstream asymmetry, sustainable agreements allow downstream agents to reap the larger share of the benefits of cooperation.

The effect of information in a behavioral irrigation experiment

Abstract When governing shared resources, the level and quality of information available to resource users on the actions of others and the state of the environment may have a critical effect on the performance of groups. In the work presented here, we find that lower availability of information does not affect the average performance of the group in terms of their capacity to provide public infrastructure and govern resource use, but it affects the distribution of earnings and the ability to cope with disturbances. We performed behavioral experiments that mimic irrigation dilemmas in which participants need to maintain infrastructure function in order to generate revenue from the use of water. In the experimental design, there is an upstream–downstream asymmetry of access to water that may lead to unequal access to water. We find that inequality of investment in irrigation infrastructure and water appropriation across players is more pronounced in experiments where resource users have limited information about the actions of others. We also find that inequality is linked to the ability of groups to cope with disturbances. Hence a reduced level of information indirectly reduces the adaptive capacity of groups.

Growth patterns of abdominal atherosclerotic calcified deposits from lumbar lateral X-rays

The aim of this study is to investigate new methods for describing the progression of atherosclerosis based on novel information of the growth patterns of individual abdominal aortic calcifications (AACs) over time. Lateral X-ray images were used due to their low cost, fast examination time, and wide-spread use, which facilitates a large statistical model (n > 100) based on longitudinal data. The examined cohort consisted of 103 post-menopausal women aged 62.4 years (± 7.0 years) with an average number of AACs of (4.7 ± 8.0) at baseline. The subjects had X-ray images taken in 1992-1993 (baseline) and again in 2000-2001 (follow-up). The growth patterns of the individual AACs were derived based on registered baseline and follow-up images. Area, height, width, centre of mass position, and movement of the centre of mass, and upper and lower boundary of the matched AACs were measured. The AACs occurred first, mainly, on the posterior aortic wall. The AACs grew on average 41 in the longitudinal direction and 21 in the radial direction. A correlation of 0.48 (P < 0.001) between growth in width and height of the AACs was present. The centre of mass of the AACs moved 0.60 mm (P < 0.001) downstream in the aorta, on average. The growth patterns of AACs may give new insights into the progression of atherosclerosis. The downstream asymmetry in the growth patterns indicates variability in microscopic environments around the AACs.

Assessing morphologic complexity and diversity in river systems using three‐dimensional asymmetry indices for bed elements, bedforms and bar units

AbstractGeomorphologists are becoming increasingly interested in assessing morphologic structure and the diversity and/or complexity in morphologic structure across multiple scales within river systems. Unfortunately, many of our existing tools/variables are unsuitable for this task because they do not work across multiple scales or with changing discharges. Asymmetry is one variable that can be used to either include or exclude variations in flow stage and that can be assessed across multiple scales. Existing asymmetry indices, however, are limited in scope and largely focus on only cross‐sectional form. This study examines three existing asymmetry indices in the cross‐stream and downstream planes (for cross‐sections and riffle or pools, respectively) and develops nine new asymmetry indices that incorporate vertical, cross‐stream and downstream asymmetry for bed elements (e.g. riffle crests, pool troughs, riffle entrance slope), bedforms (pools or riffles) and bar units (pool‐riffle sequences) to investigate the utility of asymmetry as a measure of morphologic structure and diversity in fluvial systems. These 12 indices are field tested on the Embarras River in East Central Illinois, USA. The results of this study indicate that there is considerable morphologic diversity in bed elements, bedforms and bar units both at bankfull and also with varying flow stage. This multi‐scale, multidimensional, multistage variability in morphologic structure highlights the complexity of natural river systems. The highly variable nature of fluvial form within a reach has important implications for river restoration and/or assessments of physical habitat or river health especially in instances where pools, riffles or pool‐riffle sequences are the focus of study. In general the most robust and useful combination of asymmetry indices for most applications includes A* and AL1 for bed elements and bedforms and AL3, AW and AH for bar units. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Multifrequency Instability of Cavitating Inducers

Recent testing of high-speed cavitating turbopump inducers has revealed the existence of more complex instabilities than the previously recognized cavitating surge and rotating cavitation. This paper explores one such instability that is uncovered by considering the effect of a downstream asymmetry, such as a volute on a rotating disturbance similar to (but not identical to) that which occurs in rotating cavitation. The analysis uncovers a new instability that may be of particular concern because it occurs at cavitation numbers well above those at which conventional surge and rotating cavitation occur. This means that it will not necessarily be avoided by the conventional strategy of maintaining a cavitation number well above the performance degradation level. The analysis considers a general surge component at an arbitrary frequency ω present in a pump rotating at frequency Ω and shows that the existence of a discharge asymmetry gives rise not only to beat components at frequencies, Ω−ω and Ω+ω (as well as higher harmonics), but also to rotating as well as surge components at all these frequencies. In addition, these interactions between the frequencies and the surge and rotating modes lead to “coupling impedances” that effect the dynamics of each of the basic frequencies. We evaluate these coupling impedances and show not only that they can be negative (and thus promote instability) but also are most negative for surge frequencies just a little below Ω. This implies potential for an instability involving the coupling of a surge mode with a frequency around 0.9Ω and a low-frequency rotating mode about 0.1Ω. We also examine how such an instability would be manifest in unsteady pressure measurements at the inlet to and discharge from a cavitating pump and establish a “footprint” for the recognition of such an instability.

The global plasma environment of Io as inferred from the Galileo plasma wave observations

We take advantage of a partial and a total occultation of the jovian radio sources observed during the flyby of Io to characterize the plasma environment of this moon. We show that it presents a strong upstream / downstream asymmetry. A dense plasma structure (n &gt; 5 × 104 cm−3) extends far from Io (at least 1000 km) in the wake direction whereas no extended dense region is found upstream. The dense region in the wake could correspond to a the stagnation region of the flow of the corotating plasma.

Input impedance and reflection coefficient in fractal-like models of asymmetrically branching compliant tubes.

A mathematical model is described, based on linear transmission line theory, for the computation of hydraulic input impedance spectra in complex, dichotomously branching networks similar to mammalian arterial systems. Conceptually, the networks are constructed from a discretized set of self-similar compliant tubes whose dimensions are described by an integer power law. The model allows specification of the branching geometry, i.e., the daughter-parent branch area ratio and the daughter-daughter area asymmetry ratio, as functions of vessel size. Characteristic impedances of individual vessels are described by linear theory for a fully constrained thick-walled elastic tube. Besides termination impedances and fluid density and viscosity, other model parameters included relative vessel length and phase velocity, each as a function of vessel size (elastic nonuniformity). The primary goal of the study was to examine systematically the effect of fractal branching asymmetry, both degree and location within the network, on the complex input impedance spectrum and reflection coefficient. With progressive branching asymmetry, fractal model spectra exhibit some of the features inherent in natural arterial systems such as the loss of prominent, regularly-occurring maxima and minima; the effect is most apparent at higher frequencies. Marked reduction of the reflection coefficient occurs, due to disparities in wave path length, when branching is asymmetric. Because of path length differences, branching asymmetry near the system input has a far greater effect on minimizing spectrum oscillations and reflections than downstream asymmetry. Fractal-like constructs suggest a means by which arterial trees of realistic complexity might be described, both structurally and functionally.

Exploratory Flow-Duct Experiments on Combined-Flow Bed Configurations, and Some Implications for Interpreting Storm-Event Stratification

ABSTRACT Experiments were conducted to define equilibrium combined-flow bed configurations developed under a wide range of oscillatory (Uo) and unidirectional (Uu) velocity components, with a constant oscillation period of 8.5 sec and median grain size of 0.09 mm. In the range of flows studied (Uo, 0-0.80 m/sec; Uu, 0-0.25 m/sec) the bed phases are: no movement, small 2D ripples, small 3D ripples, large 3D ripples, and plane bed. Small 2D ripples are stable at low Uo and Uu; by increasing either velocity component the plan-view bed configuration becomes progressively less regular as small 3D ripples develop. Small 3D ripples are stable at low to moderate Uo and a wide r nge of Uu. Under purely oscillatory flow, as Uo increases beyond about 0.40 m/sec, large-scale, hummocky bed forms become stable. When a unidirectional component is applied, these bed forms quickly develop a downstream asymmetry and generally move in the direction of Uu. The dip angles of the lee flanks increase with increasing Uu, although they remain less than the angle of repose. At high oscillatory velocities (Uo, 0.70-0.80 m/sec), plane bed is the stable bed phase when Uu > 0.05 m/sec. Much hummocky cross-stratification shows a preferred dip direction of the coset laminae. Our experiments support the idea that such cross-stratification is produced by combined flow: the large 3D ripples produced at high oscillatory velocities and small to moderate unidirectional velocities would presumably generate what might be called anisotropic hummocky cross-stratification (if we had been able to aggrade the bed during the runs). This would be the case even in dominantly oscillatory flow; the experiments show that even a weak unidirectional current of several centimeters per second superimposed upon a strong oscillatory flow results in bed forms that move predominantly in a single direction and that leave sets of laminae that dip predominantly in that direction. In runs at large Uo, the purely oscillatory large-scale bed forms were quickly planed off as Uu was increased from zero, but a series of almost stationary gentle undulations on the bed surface persisted for indefinitely long times where the original topographic highs were situated, even at the highest unidirectional flow investigated, 0.25 m/sec. This suggests a possible origin for the gentle undulation observed in Cretaceous parallel-laminated shallow-marine sandstones described by Arnott (1987, 1988), with spacings up to a few meters and heights not much more than a centimeter.

Resonance cones in non-Maxwellian plasmas

Resonance cones are studied experimentally in hot drifting plasmas and in various beam–plasma situations. In a drifting plasma the upstream–downstream asymmetry of the main cone is suitable for diagnostics of plasma drifts. The evaluation of electron temperature from the interference pattern is discussed in terms of the low-temperature–low-drift approximation (LTLDA) and by comparing with numerical kinetic theory calculations. In this way the range of applicability of this method is extended above the LTLDA. In a beam–plasma situation, the downstream resonance cone exhibits a new interference pattern, which can be attributed to resonant particle effects. The upstream resonance cone is only slightly affected and is found still applicable for Te and ne diagnostics. As a result of comparison with numerical calculations, in which the actual distribution function is used, the downstream interference pattern is proposed to be useful as a diagnostic method for obtaining the mean beam energy. The waves generated by the beam–plasma interaction are analyzed by digital cross-correlation techniques, and found to propagate obliquely to the magnetic field direction at the resonance cone angle.