One-sided Model Research Articles

Parallelized, Automated, and Predictive Imprint Cooling Model for Combustion Systems

A novel parallelized, automated, and predictive imprint cooling model (PAPRICO) was developed for modeling of combustor liners using Reynolds-averaged Navier–Stokes (RANS). The methodology involves removing the film and effusion cooling jet geometry from the liner while retaining the cooling hole imprints on the liner. The PAPRICO can operate under two modalities, viz., two-sided and one-sided. For the two-sided PAPRICO model, the imprints are kept on the plenum and combustor sides of the liner. For the one-sided PAPRICO model, the imprints are retained only on the combustor side of the liner and there is no need for a plenum. The PAPRICO model neither needs a priori knowledge of the cooling flow rates through various combustor liner regions nor specific mesh partitioning. The imprint mass flow rate, momentum, enthalpy, turbulent kinetic energy, and eddy dissipation rate are included in the governing equations as volumetric source terms in cells adjacent to the liner on the combustor side. Additionally, the two-sided PAPRICO model includes corresponding volumetric sinks in cells adjacent to the liner on the plenum side. A referee combustor liner was simulated using PAPRICO under nonreacting flow conditions. The PAPRICO results were compared against predictions of nonreacting flow results of a resolved liner geometry, against a combustor liner with prescribed mass and enthalpy source terms (simplified liner) and against measurements. The results clearly conclude that PAPRICO can qualitatively and quantitatively emulate the local turbulent flow field with a reduced mesh size. The simplified liner fails to emulate the local turbulent flow field.

Fostering Dialogue or Monologue? Estonian Party Websites During the 2009 European Parliament Elections

This paper presents data from the analyses of political party web pages during the 2009 European Parliament elections in Estonia. It examines the presence and absence of web 2.0 features on the sites and aims to find out whether interactivity-based applications are used by parties to increase participation and to foster deliberative politics. Estonia as a small ex-Soviet country has emerged after the Soviet Union collapse as one of the most advanced e-societies in the world. Therefore, Estonia is chosen as a case study to explore whether and how decision makers use web 2.0 elements for fostering Habermasian dialogue between the citizens and the power holders in the society where technical obstacles for deliberative politics do not exist any longer. The results show that the Estonian parties still focus on the one-sided or top-down model of communication, based on web 1.0 features, even though all conditions for deliberation from the technical and infrastructural side in Estonia are fulfilled. The paper concludes with a discussion on the possible reasons parties might not be interested in using web 2.0 elements in their web campaign and how it might be linked to the conditions where citizens’ participation and interest in politics is low. There is also emphasis on the need for further systematic comparative research in order to draw conclusions on the changes in the online campaigning and political communication process in the era of cyber-democracy.

Net Neutrality: A Fast Lane to Understanding the Trade-offs

The last decade has seen a strident public debate about the principle of “net neutrality.” The economic literature has focused on two definitions of net neutrality. The most basic definition of net neutrality is to prohibit payments from content providers to internet service providers; this situation we refer to as a one-sided pricing model, in contrast with a two-sided pricing model in which such payments are permitted. Net neutrality may also be defined as prohibiting prioritization of traffic, with or without compensation. The research program then is to explore how a net neutrality rule would alter the distribution of rents and the efficiency of outcomes. After describing the features of the modern internet and introducing the key players, (internet service providers, content providers, and customers), we summarize insights from some models of the treatment of internet traffic, framing issues in terms of the positive economic factors at work. Our survey provides little support for the bold and simplistic claims of the most vociferous supporters and detractors of net neutrality. The economic consequences of such policies depend crucially on the precise policy choice and how it is implemented. The consequences further depend on how long-run economic trade-offs play out; for some of them, there is relevant experience in other industries to draw upon, but for others there is no experience and no consensus forecast.

Truthful budget constrained auction for device-to-device relaying packet allocation

Taking advantage of peer-to-peer transmission underlying cellular networks, device-to-device (D2D) communications offer various benefits such as coverage extension, traffic offloading, and improved energy efficiency. In this paper, we focus on a promising scenario where a D2D local area network is formed to relay packets for an out-of-coverage source device. A one-sided auction model is formulated from a unique perspective in which the source device decides the allocation of its packets among the helpers and charges reserve payments to the helpers according to their bids. The winning helpers only collect rewards from the source's deposit at the base station when the assigned packets are successfully relayed. In this model, we further take into account the budget constraints of the helpers to capture the helpers' resource limits and the risks that the helpers are willing to take. Based on this model, we propose three auction mechanisms targeting economic properties such as individual rationality, efficiency, and truthfulness. An enhanced Martello & Toth algorithm is first developed for the VCG-based auction to determine packet allocation that optimizes the source's quality of service. The probabilistic entrance auction mechanism uses sequential second price auction to achieve a low computational cost. The randomized mechanism involves a randomization over the above two mechanisms to satisfy certain requirement for social welfare while minimizing the computational time. We also conduct extensive simulations to examine the performance of the proposed mechanisms.

Argument-Counterargument Structure in Indonesian EFL Learners’ English Argumentative Essays: A Dialogic Concept of Writing

This study investigates the potential use of the argument-counterargument structure in English L2 essays written by Indonesian EFL learners. It examines whether L2 proficiency affects the use of opposing views in their essays, and measures whether there is a correlation between the use of the rhetorical structure and the participants’ overall essay quality. In order to achieve this purpose, the study asks participants to write an English argumentative essay and measures their English L2 proficiency. The researcher also requests that the participants write in Indonesian (L1) and uses the data to measure whether there is consistency in terms of the use of the argument-counterargument structure in their L1 and L2 essays. The results show that the majority of the students developed a one-sided model of argumentation in their L1 and L2 essays by focusing only on how to state their main claim and providing relevant justification for it. The students’ relatively low L2 proficiency was found to be one of the possible factors behind their inability to include other-side views in their essays. In addition, the participants’ use of rhetorical features affected the overall quality of their essays. Pedagogical implications of these findings will be discussed.

Importance of wave-number dependence of Biot numbers in one-sided models of evaporative Marangoni instability: Horizontal layer and spherical droplet.

A one-sided model of the thermal Marangoni instability owing to evaporation into an inert gas is developed. Two configurations are studied in parallel: a horizontal liquid layer and a spherical droplet. With the dynamic gas properties being admittedly negligible, one-sided approaches typically hinge upon quantifying heat and mass transfer through the gas phase by means of transfer coefficients (like in the Newton's cooling law), which in dimensionless terms eventually corresponds to using Biot numbers. Quite a typical arrangement encountered in the literature is a constant Biot number, the same for perturbations of different wavelengths and maybe even the same as for the reference state. In the present work, we underscore the relevance of accounting for its wave-number dependence, which is especially the case in the evaporative context with relatively large values of the resulting effective Biot number. We illustrate the effect in the framework of the Marangoni instability thresholds. As a concrete example, we consider HFE-7100 (a standard refrigerant) for the liquid and air for the inert gas.

Noisy 1-bit compressive sensing: models and algorithms

The compressive sensing (CS) method allows us to recover a sparse signal from a small number of its linear measurements relative to the dimension of the signal space. The classic CS method assumes the measurements to have infinite bit precisions, which cannot be satisfied in practice. Quantization of the measurements is a crucial issue in CS. An extreme quantization, which preserves the signs of the measurements only, attracted much attention recently. The corresponding CS problem is called the 1-bit CS problem since each measurement is quantized to 1 bit. Many models and algorithms were proposed for solving the 1-bit CS problem. Some of them work well when there is no noise (sign flips) in the measurements and a recently proposed algorithm works well when the noise level is known. However, the noise level is not always known in practice. In this paper, we propose a robust one-sided ℓ0 objective model for the 1-bit CS problem by applying the maximum a posteriori (MAP) estimation. In the proposed model, the noise factor is considered without knowing the noise level. We also provide an upper bound of the reconstruction error for the proposed model. To solve the proposed model, we first approximate the objective function of the one-sided ℓ0 model by a continuous function utilizing the Moreau envelope. This leads to an approximate model whose objective function is non-smooth and non-convex. We prove that such an objective function has a finite number of local minimizers. We develop a system of fixed-point equations whose solutions are local minimizers of the approximate model and show that global minimizers of the approximate model are solutions of the fixed-point equations, based on which we propose a fixed-point proximity algorithm for finding local minimizers of the approximate model. We prove that the sequence generated from the algorithm converges to a local minimizer of the approximate model and the sequence of the corresponding objective function values is non-increasing and converges. Furthermore, we prove that the sequence generated from the algorithm converges to a global minimizer of the approximate model as long as the initial guess is sufficiently close to a global minimizer of the approximate model. Numerical results are presented to demonstrate the accuracy of the proposed method.

Binary Power Allocation in Symmetric Wyner-Type Interference Networks

The Wyner interference network is a popular model used in research on cellular networks due to its simplicity and analytical tractability. In this paper, the optimal power allocation strategies in symmetric one- and two-sided Wyner models are investigated. We determine a sufficient condition for binary power control (BPC) to be optimal that can be applied to the one-sided symmetric model. We consider binary power schemes for the symmetric two-sided Wyner network. Using a method of grouping links and performing a piecewise comparison of the group rates, we are able to determine the optimal power policy that maximizes the network sum rate. The result of the optimization can be expressed as follows for both types of networks: When the interfering channel gain √ϵ is small, it is optimal (in the class of binary schemes) to have all links on; otherwise, alternate links are switched off to remove interference. We characterize the critical values of ϵ where the transitions occur.

The affected and contralateral kidney morphological changes in course of one-sided rat pyelonephiritis model

The research aimed to identify presence and severity of contralateral kidney tissue changes while opposite kidney inflammation progresses. Our own model was used for disease evoking in rats. The observation period lasted 10 days. Starting from the 3rd day, signs of hematogenous dissemination of infection/inflammation into contralateral kidney were registered. Starting from the 5th day urinogenous dissemination process was observed. By the 3rd day of study a cortical hyperemia in contralateral kidney was seen, which possibly was of compensatory origin. Based on research results, a primarily bilateral urinary tract inflammation/infection can be suspected.

Bringing communication up to agency: UNESCO reforms its visibility

This article is the first to discuss the recent and significant reforms of United Nations Educational, Scientific and Cultural Organization’s (UNESCO) communications. I analyse the major measures such as bringing together communication and political workers in one sector, assembling all communicators and web services in one division and introducing monthly media reports. I examine issues such as opening the brand, clearance of press releases, use of languages, professionalisation, press agentry and the need to adopt a more conversational and multiple-voice approach. UNESCO’s communications reform has advanced only halfway in two respects. First, changes have not resulted in a comprehensive communication strategy. Despite refurbishing its web site and introducing various social media, the organisation is still using the one-sided model of public information. It is lacking the new media agents who can engage UNESCO’s diverse constituency in online sharing and networking. Second, the restructuring has partly empowered the communicators and made them more professional. The reform, however, is not accomplished. The functionalist, old-bureaucratic notion that communication is an organisational ‘silo’, and that changes should affect only those who are appointed to communicate, is redundant. For a full success, not only the communications of the organisation, but also the organisation that communicates needs to change.

The influence of evaporation on long-wavelength instabilities in liquid layer with insoluble surfactant

We investigate the long-wavelength Marangoni instability in an evaporating horizontal liquid layer with insoluble surfactant absorbed on the free deformable surface. The insoluble surfactant hinders the evaporation of the liquid into a vapor. The mass flux depends on the difference between the actual surface temperature and the equilibrium one. Different kinetics limited regimes of evaporation are considered. Density, viscosity, and thermal conductivity of the vapor are smaller than those of the liquid, and a one-sided model is applied. The layer is subjected to a heat flux at its bottom. We assume a small heat transfer coefficient at the interface. The linear stability analysis of this system for different values of kinetic resistance parameter is performed. Instability thresholds are determined and critical Marangoni numbers for monotonic, as well as for oscillatory mode, are found.

Paradoxes of Prosperity in China's New Capitalism

This article gives a broad characterization of China's political economy, as well as specific aspects of its socio-economic instabilities. With a focus on China's export-oriented industry sectors, concepts from comparative and international political economy are applied to show how the Chinese economy can be understood as a variegated form of state-permeated capitalism that at the same time is deeply integrated into world economic processes. The article goes on to portray the socio-economic dynamics, as well as the instabilities of China's new capitalism, that are at the root of the state leadership's attempts to turn away from a one-sided model of export and investment-driven growth. Thereby, a number of obstacles are revealed for the “rebalancing” of the economy: a continued dependence on exports, a lack of domestic consumer demand which impedes a significant “social” upgrading, the ongoing low-wage model for which there is no end in sight, the limits of the state's steering capacity and the weaknesses of its fragmented, competition-driven structure.

Instabilities in evaporating liquid layer with insoluble surfactant

The stability of an evaporating liquid layer with insoluble surfactant distributed over the free deformable surface is studied theoretically. The insoluble surfactant hinders the evaporation, and mass flux through the interface is a decreasing function of surfactant concentration. Density, viscosity, and thermal conductivity of the gaseous phase are assumed to be small compared with those of the liquid phase, and a one-sided model is applied. A system of nonlinear equations is obtained using the long-wave approximation and the assumption of a slow time evolution. These equations incorporate basic physical effects which take place in the system. Linear stability analysis of the base state is performed for long-wave disturbances in the framework of the frozen interface approximation. The cases of quasi-equilibrium evaporation (when the interfacial temperature equals the equilibrium one) and nonequilibrium evaporation are considered. In addition to a monotonic instability mode, an oscillatory mode has been found.

Well-posedness of a needle crystal growth problem with anisotropic surface tension

We study an initial value problem for two-dimensional needle crystal growth with anisotropic surface tension. The initial value problem is derived from the so called one-sided model based on complex variables method. We then obtain the existence and uniqueness of local solution in Sobolev spaces for the needle crystal problem with arbitrary initial interface. Furthermore, we obtain that, on average in time, the solution gains derivative of smoothness in spatial variable compared to the initial data. The continuous dependence on the initial data of the solution map is also established.

Singularity-free description of moving contact lines for volatile liquids

For a liquid advancing or receding on a flat bare solid in a vapor atmosphere, we show that no singularities in fact arise at the contact (triple) line. Contrary to common expectations, this does not require any "regularizing" microscopic effect (such as slip at the substrate, disjoining pressure or precursor films). The key here is the Kelvin effect, i.e., a curvature-induced variation of saturation conditions. Importantly, no evaporation-related singularities appear either. We proceed within the lubrication approximation and a classical one-sided model for zero or finite contact angle.

A thin film on a porous substrate: A two-sided model, dynamics and stability

A two-sided model (TLM) is employed to investigate the dynamics and stability of a thin film of Newtonian fluid overlying a porous substrate; the model consists of a free fluid interfacing a Brinkman-type porous transition layer, which overlies a porous medium described by the Darcy equation. The model explicitly describes the transition flow at the top of the porous medium. A nonlinear evolution equation for the free surface of the film is derived through long-wave approximation. A linear stability analysis of the base flow is performed and the critical condition for the onset of instability is obtained. It is observed that the stability characteristics of the film are influenced by the permeability, the porosity of the porous medium and the ratio of the porous to liquid layer thickness d^. Further, the conditions under which the two-sided model (TLM) can be replaced by an effective one-sided slip model (SM) is analyzed and the corresponding slip length is computed in terms of the porous layer characteristics. A weakly nonlinear stability analysis is performed and the range of preferred wave numbers for which the disturbances reach finite equilibrium amplitude or an explosive state is obtained. The nonlinear equation is then numerically solved as an initial value problem on a periodic domain and different scenarios of surface structures are captured. The long-time wave forms are shown to agree very well with the corresponding stationary solutions of the evolution equation. The results show that the long-time wave forms are either time-independent waves that propagate or time-dependent modes that oscillate slightly in amplitude. The fundamental modes dominate the stationary solution for shorter periods and the higher modes dominate as the period increases. Further, for certain bands of the period, the steady state is observed to lose its stability to oscillations.

The role of electrical coupling in the decision to initiate swimming in young frog tadpoles

Most neuronal networks are very complex and detailed information on the neurons and their connections is lacking. To investigate the significance of electrical coupling it is therefore necessary to find simpler networks for study. At hatching, Xenopus laevis tadpoles show two modes of locomotion; fictive swimming and struggling, making it an interesting model animal for studying relatively simple network dynamics[1]. Experiments have shown that fictive swimming can be generated by a central pattern generating (CPG) network of approximately 2000 neurons in the caudal hindbrain and the rostral spinal cord[1]. The neurons can be distinguished into groups, based on anatomy, morphology and firing characteristics[1]. During swimming, a particular group of neurons with descending axons (dINs) are the first neurons to fire on each side and act as 'trigger' neurons; synchronizing firing in each side of the CPG[2]. These neurons are electrically coupled, probably via gap junctions between their axons. Blocking this coupling makes the generation of swimming unreliable[3]. Since it is only possible to record from a limited number of neurons simultaneously and dINs are electrically coupled, electrophysiological investigation into dINs is difficult. Modelling allows us to test hypotheses and ask questions which are experimentally impossible. Tadpoles respond to stimulation to the head by starting to swim. Recent work (Buhl et al. submitted) has defined a three step pathway from the headskin to the CPG network. The headskin is innervated by trigeminal afferent neurons. These synapse onto a population of ~20 trigeminal interneurons (tINs), which then synapse onto the population of dINs in the hindbrain. In life, in response to stimulation, the tadpole will either not react or will start swimming. We show that the electrical coupling plays an important role in converting a continuously variable input signal (headskin stimulation) into a discrete decision (initiation of swimming). We first built multi-compartmental models of an individual dIN with an axon using Hodgkin-Huxley style current models from voltage-clamp data. Next, a model of a column of 30 dINs was built, with an anatomically realistic layout of somata and axons in the hindbrain. We investigated biologically feasible mechanisms for distributing gap junctions between the axons, which produced coupling coefficients between neurons similar to those measured physiologically. Next, a model of the synaptic input from the tINs onto the dIN network was built, converting a 'stimulation level' into a set of input spike times. We show that the presence or absence of electrical coupling plays an important role in the dynamics of group recruitment; with electrical coupling, increasing the chemical synaptic input to the network in small steps leads to an abrupt switch in behaviour, from few dINs firing to the entire population firing. Modelling was done in a high-level Python API for simulating small networks of multi-compartmental neurons, using the NEURON simulator as a backend[4]. Using the one-sided model as a foundation; we will explore a fuller, bilateral model of the CPG; in particular investigating the roles of reciprocal inhibition, background NMDA excitation, and electrical coupling on the initiation of swimming in the tadpole.

Evaporation-driven Contact Angles in a Pure-vapor Atmosphere : the Effect of Vapor Pressure Non-uniformity

A small vicinity of a contact line, with well-defined (micro)scales (henceforth the “microstructure”), is studied theoretically for a system of a perfectly wetting liquid, its pure vapor and a superheated flat substrate. At one end, the microstructure terminates in a non-evaporating microfilm owing to the disjoining-pressure-induced Kelvin effect. At the other end, for motionless contact lines, it terminates in a constant film slope (apparent contact angle as seen on a larger scale), the angle being non-vanishing despite the perfect wetting due to an overall dynamic situation engendered by evaporation. Here we go one step beyond the standard one-sided model by incorporating the effect of vapor pressure non-uniformity as caused by a locally intense evaporation flow, treated in the Stokes approximation. Thereby, the film dynamics is primarily affected through thermodynamics (shift of the local saturation temperature and evaporation rate), the direct mechanical impact being rather negligible. The resulting integro-differential lubrication film equation is solved by handling the newly introduced effect (giving rise to the “integro” part) as a perturbation. In the ammonia (at 300 K) example dealt with here, it proves to be rather weak indeed: the contact angle decreases while the integral evaporation flux increases just by a few percent for a superheat of ~1 K. However, the numbers grow (roughly linearly) with the superheat.

Stability of liquid films on a porous vertical cylinder

The stability of liquid films flowing down a vertical porous cylinder is investigated in this paper. Fluids in the porous medium are assumed to be governed by Darcy's law. The Beaver-Joseph conditions on the liquid-porous surface are applied, and the influence of the porous medium reduces as a slip condition on the cylinder, which leads to the one-sided model. A Benney-type equation governing the interfacial shape is derived to study the nonlinear behavior of liquid films. Linear stability analysis shows that the film flow system on a porous vertical cylinder is more unstable than that on a solid impermeable vertical cylinder and that increasing the permeability of the porous medium enhances the destabilizing effect. Nonlinear studies examine our linear stability analysis. We find that, for Reynolds number Re=0, as the permeability parameter increases, the rupture time of film decreases; for Re>0, Rayleigh-Plateau instability is suppressed, and disturbances evolve to saturated traveling waves. By increasing the permeability parameter, the amplitude of traveling wave increases, and the wave speed increases too. Aside from that, the wave speed increases with increasing Re.

Estimating Platform Market Power in Two-Sided Markets with an Application to Magazine Advertising

In this paper I develop a structural model of platform demand in two-sided markets and use it to estimate platform market power and predict price changes in post-merger markets. My model and estimation procedure are applicable to settings where (1) agents on each side care about the presence of agents on the other side and (2) platforms charge access fees on both sides. Using data on TV magazines in Germany I show that the magazines typically set copy prices below marginal costs and make profits from selling advertising space. I also show that platform mergers are much less harmful to consumers (readers and advertisers) than what the one-sided market model predicts.