Retail Pricing Behavior for Perishable Produce Products in the US with Implications for Farmer Welfare

The typical model of retail pricing for produce products assumes retailers set price equal to the farm price plus a certain markup. However, observations from scanner data indicate a large degree of price dispersion in the grocery retailing market. In addition to markup pricing behavior, we document three alternative leading pricing patterns: fixed (constant) pricing, periodic sale, and high-low pricing. Retail price variations under these alternative pricing regimes in general have little correlation with the farm price. How do retailers’ alternative pricing behaviors affect farmers’ welfare? Using markup pricing as the baseline case, we parameterize the model to reflect a prototypical fresh produce market and carry out a series of simulations under different pricing regimes. Our study shows that if harvest cost is sufficiently low, retail prices adjusting only partially, or not at all, to supply shocks tends to diminish farm income and exacerbate farm price volatility relative to the baseline case. However, we also find that if harvest cost is sufficiently large and the harvest-cost constraint places a lower bound on the farm price, increased farm price volatility induced by retailers’ alternative pricing strategies may result in higher farm income, compared to markup pricing. Our study is the first to evaluate the welfare implications for producers of the diversified pricing strategies that retailers utilize in practice and the resulting attenuation of the relationship between prices at retail and at the farm gate.Agribusiness, Demand and Price Analysis,

"Asymmetric Market Shares, Advertising, and Pricing: Equilibrium with an Information Gatekeeper"

We analyze the impact of market share on advertising and pricing decisions by firms that sell to loyal, non-shopping customers and can advertise to shoppers through an information intermediary or "gatekeeper." In equilibrium the firm with the smaller loyal market advertises more aggressively but prices less competitively than the firm with the larger loyal market, and there is no equilibrium in which both firms advertise with probability 1. The results differ significantly from earlier literature which assumes all prices are revealed to shoppers and finds that the firm with the smaller loyal market adopts a more competitive pricing strategy. The predictions of the model are consistent with advertising and pricing behavior observed on price comparison websites such as Shopper.com.online markets, E-commerce, market share, information gatekeeper, equilibrium price dispersion, advertising

NMDA Receptors Enhance the Fidelity of Synaptic Integration

Excitatory synaptic transmission in many neurons is mediated by two coexpressed ionotropic glutamate receptor subtypes, AMPA and NMDA receptors, that differ in kinetics, ion selectivity, and voltage-sensitivity. AMPA receptors have fast kinetics and are voltage-insensitive, while NMDA receptors have slower kinetics and increased conductance at depolarized membrane potentials. Here, we report that the voltage dependency and kinetics of NMDA receptors act synergistically to stabilize synaptic integration of EPSPs across spatial and volt- age domains. Simulations of synaptic integration in simplified and morphologically realistic dendritic trees re- vealed that the combined presence of AMPA and NMDA conductances reduce the variability of somatic responses to spatiotemporal patterns of excitatory synaptic input presented at different initial membrane poten- tials and/or in different dendritic domains. This moderating effect of the NMDA conductance on synaptic integra- tion was robust across a wide range of AMPA-to-NMDA ratios, and results from synergistic interaction of NMDA kinetics (which reduces variability across membrane potential) and voltage dependence (which favors stabiliza- tion across dendritic location). When combined with AMPA conductance, the NMDA conductance compensates for voltage-dependent and impedance-dependent changes in synaptic driving force, and distance-dependent at- tenuation of synaptic potentials arriving at the axon, to increase the fidelity of synaptic integration and EPSP- spike coupling across both neuron state (i.e., initial membrane potential) and dendritic location of synaptic input. Thus, synaptic NMDA receptors convey advantages for synaptic integration that are independent of, but fully compatible with, their importance for coincidence detection and synaptic plasticity

Simultaneously encoding movement and sEMG-based stiffness for robotic skill learning

Transferring human stiffness regulation strategies to robots enables them to effectively and efficiently acquire adaptive impedance control policies to deal with uncertainties during the accomplishment of physical contact tasks in an unstructured environment. In this work, we develop such a physical human-robot interaction (pHRI) system which allows robots to learn variable impedance skills from human demonstrations. Specifically, the biological signals, i.e., surface electromyography (sEMG) are utilized for the extraction of human arm stiffness features during the task demonstration. The estimated human arm stiffness is then mapped into a robot impedance controller. The dynamics of both movement and stiffness are simultaneously modeled by using a model combining the hidden semi-Markov model (HSMM) and the Gaussian mixture regression (GMR). More importantly, the correlation between the movement information and the stiffness information is encoded in a systematic manner. This approach enables capturing uncertainties over time and space and allows the robot to satisfy both position and stiffness requirements in a task with modulation of the impedance controller. The experimental study validated the proposed approach

Ensuring Readability and Data-fidelity using Head-modifier Templates in Deep Type Description Generation

A type description is a succinct noun compound which helps human and machines to quickly grasp the informative and distinctive information of an entity. Entities in most knowledge graphs (KGs) still lack such descriptions, thus calling for automatic methods to supplement such information. However, existing generative methods either overlook the grammatical structure or make factual mistakes in generated texts. To solve these problems, we propose a head-modifier template-based method to ensure the readability and data fidelity of generated type descriptions. We also propose a new dataset and two automatic metrics for this task. Experiments show that our method improves substantially compared with baselines and achieves state-of-the-art performance on both datasets.Comment: ACL 201

La estrategia china de Felipe II: la vía castellana

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Filosofía y Letras, Departamento de Historia Moderna. Fecha de lectura: 11-05-2018Esta tesis tiene embargado el acceso al texto completo hasta el 11-11-2019Nuestra tesis doctoral lleva por el título: La estrategia china de Felipe II: la vía castellana (1556-1581), y por tanto, se van presentando y desarrollando en ella, los acontecimientos según la evolución del plan diseñado por el Prudente en relación con los asuntos vinculados con la China de la dinastía Ming (1368-1640). Antes de presentar esta estrategia de Felipe II formalmente, dedicamos la primera parte de la tesis a recuperar los conocimientos -vagos o precisos- que había tenido el príncipe Felipe con respecto a China, los cuales le permitirían iniciar una serie de decisiones y acciones para crear relación con aquel imperio oriental. En cuanto a las consideraciones y a las políticas del monarca hispano con respecto a aquel imperio oriental entre 1556 y 1581, las presentamos por tres partes y cada una se corresponde a una etapa de la estrategia china -el preludio, el inicio y el apogeo- del rey Prudente. A través de las fuentes históricas que hemos recuperado y utilizado en la tesis, podemos contemplar que durante el reinado de Felipe II, el interés por China iba creciendo dentro del imperio hispano. Es más, la estrategia del monarca sobre aquel imperio oriental se mostró como un proceso complejo y dilatado en el que confluyen múltiples factores dentro o fuera de su imperio. Por tanto, Felipe II, relativo a China, sostuvo siempre el acercamiento pacífico y diplomático para crear relación oficial con el imperio oriental, culminando con las dos cartas regias -en 1580 y 1581 respectivamente- enviadas desde Castilla con destino al mandatario Ming

Numerical Modeling of Multiphase Flows with Applications to the Automotive Industry

Multiphase flows have become an issue of deep concern in the automotive industry. Two specific problems of concern to the ABC Group and Ford Motor Company have shown that the current multiphase models available in commercial software are not able to satisfy the requirements of the automotive industry for numerical simulations: namely, the need to solve complex industrial problems and the need to provide accurate solutions for these problems. The first problem of concern involves degassing in coolant surge tanks. Bubbles mixed in the coolant constitute a risk factor that influences the cooling performance, and the degree of mixing needs to be strictly controlled. Therefore, simulating the degassing rate accurately is of critical importance for the design of a coolant surge tank. The second case of concern focuses on a multiphase-flow-induced vibration and noise problem in a dynamic valve. This problem relates directly to the noise, vibration and harshness (NVH) performance of a hybrid vehicle. The dynamic motion of a dynamic valve, which is controlled by a balance between the spring force and the pressure force of the diesel-air multiphase flow acting on the valve, results in a complicated generation and propagation of mechanical and fluid-dynamic noise. This is a complex problem that combines multiphase flows and fluid-structure interaction (FSI). Motivated by these two problems posed by our industrial collaborators, this research has been conducted specifically in order to improve both the predictive accuracy of and degree of complexity of problems that can be addressed by the multiphase flow models presently available in commercial software. Moreover, the improvements obtained here are used to solve the two industrial problems described above. Towards this purpose, the ANSYS-FLUENT software is utilized for the current research because of its overall computational capabilities, its ease of use, and its widespread application in the automotive industry. However, to address the two aforementioned problems, it was necessary to improve the modeling capabilities of the ANSYS-FLUENT software. For this purpose, a number of model improvements were implemented in this study. Firstly, a multiphase flow model in ANSYS-FLUENT was improved through the utilization of user-defined functions (UDFs). Secondly, UDFs were also implemented to generalize the solution procedures in the FSI model. Thirdly, a Scheme command file was used to the FSI model to provide a significantly improved solution algorithm based on an implicit solver that is capable of addressing problems requiring the strong coupling between the flow solver and the FSI solver. Validations of the key methodologies (viz., the multiphase flow, the dynamic meshing capability and the FSI) of the integrated modeling system were carried out before being applied to the two specific problems of concern described above. Firstly, a bubbly turbulent flow in a vertical pipe was simulated and then compared with the experimental measurements in order to validate the improved multiphase flow model. The new multiphase flow model is based on the original Eulerian model (sometimes referred to as the two-fluid model in the literature) in ANSYS-FLUENT, but this model incorporates a number of new interfacial force models which were implemented using a UDF. The "wall peak'' observed in the radial distribution of the gas volume fraction and the shift of this peaks towards the core (center) of the flow (to give a "core peak'') as the volume fraction of the gas increases are captured correctly in our simulations, in contrast to the simulation results reported by other researchers. The immiscible model was also tested and found to be able to capture the major features of the bubbly flow in the vertical pipe. A turbulent flow over a square cylinder with a prescribed motion was used as the second benchmark test case. The purpose of this test was to validate the capability and accuracy of the dynamic (or moving) mesh model in ANSYS-FLUENT. Two methods (namely, smoothing and layering) were used to generate the dynamic mesh. Both of these dynamic meshing methods yielded good performance in terms of the mesh quality. The predicted shedding of the Karman vortex street behind the cylinder and the “lock-in” phenomena over a small range of reduced velocities agreed well with the experimental measurements. The layering method for dynamic mesh generation was found to give a higher computational efficiency than the smoothing method. Validation of the FSI model was more complicated than that of multiphase flow model, as models for FSI depend critically on the specific physical characteristics of the problem and these characteristics dictate whether a weak coupling or strong coupling is required for the solution. To validate the model for a weak-coupling FSI problem, a turbulent flow over and past an autonomous-oscillating square cylinder was used as the benchmark test case. The vortex-induced vibration occurring behind the square cylinder for this case constitutes the classic weak-coupling FSI problem. A UDF was implemented to simulate the FSI using a dynamic mesh. A layering method was used to generate the dynamic mesh. The predicted shedding of the Karman vortex street behind the cylinder and the ``lock-in'' phenomenon over a small range of reduced velocities was found to agree well with the experimental measurements. For a strong-coupling FSI validation, we used a laminar flow in a heart valve as a benchmark test case. This valve has a free rotating leaflet controlled by periodic variations of the unsteady inlet velocity. To address this case, a new implicit solution methodology was proposed and implemented using a command file (written in Scheme) in order to solve this large-displacement problem. Simulation results indicate that the periodic motion of the leaflet was predicted fairly accurately even when friction was ignored. The resulting implicit FSI model demonstrates the capability of the new modeling tool in solving strongly coupled FSI problems similar to that associated with the operation of a dynamic valve. The improved and validated multiphase flow model was applied firstly to a simulation of the degassing problem in a coolant surge tank. Grid sensitivity tests and time step sensitivity tests were conducted in order to determine optimal values for various parameters to be used in the simulation. Parametric tests, including inlet velocity tests, bubble diameter tests and liquid viscosity tests were undertaken. A degassing rate was proposed and defined as a metric for the degassing process. Geometries for a single-chamber and three connected chambers were simulated. It was found that bubbles are degassed stage by stage owing to the buoyancy effect. The degassing rate is a dynamic variable related to many physical properties, such as the inlet velocity, the liquid viscosity and the bubble size. A larger inlet velocity, a greater liquid viscosity, and a smaller bubble size result in a lower degassing rate. The effect the drag force models is not obvious although the drag force is the most important interfacial force influencing the degas rate. The effect of the lift force models is even weaker than that of drag force for determination of the phase interaction. It is concluded that our proposed integrated modeling system provides reasonably good results for the degassing process in a surge tank. Finally, the multiphase-flow-induced vibration and noise problem in a dynamic valve was simulated using our proposed integrated modeling system. For a two-phase flow through the valve, the simulations showed that the deformation and breakup of gas bubbles in the gap between the poppet and the valve seat generate vibrations that arises primarily from the force imbalance between the spring and the two-phase fluid-flow-induced forces on the poppet. A spectral analysis of the transient pressure force on the poppet revealed the presence of a strong cyclical behavior consisting of two major components. There was a low-frequency peak located at about 87 Hz and associated with the frequency of the poppet vibration (and which we interpret to be the source of the mechanical noise) and a high-frequency peak located at about 450--970 Hz which is associated with compressibility effects and the unsteady vortex motions in the spring chamber. The poppet vibration and noise are influenced by various factors such as the flow condition, the spring system properties, and the geometry of the valve. Larger bubbles and a lower inlet velocity result in larger displacements in the poppet in a non-equilibrium condition and induce a greater loading on the spring due to the higher pressures. These pressures in turn amplify the poppet vibration and noise. The detailed simulations and subsequent analysis of the complex interactions that occur in the turbulent multiphase fluid motion through a moving poppet valve allowed deeper physical insights and an improved understanding of both the source and properties of the vibration and noise generated in this complicated dynamic system