P-V-T Behavior of 2,3,3,3-Tetrafluoroprop-1-ene (HFO-1234yf) in the Vapor Phase from (243 to 373) K

The P-V-T properties of 2,3,3,3-tetrafluoroprop-1-ene (CF 3 CFdCH 2 , HFO-1234yf), an environmentally friendly refrigerant, were measured using a constant volume apparatus. Measurements were carried out at temperatures from (243 to 373) K and at pressures from (84 to 3716) kPa. A total of 136 experimental points, taken along 12 isochores, were obtained. Our experimental results were compared with a preliminary equation of state. The measurements were also regressed to the Martin-Hou equation of state. No other data on this fluid were found in the literature for the superheated region

Carbon Dioxide + Fluoromethane and Nitrous Oxide + Fluoromethane: Solid−Liquid Equilibria Measurements

A recently built experimental setup was employed for the estimation of the solid-liquid equilibria (SLE) of alternative refrigerant systems. The behavior of two binaries, that is, carbon dioxide + fluoromethane (CO2 + R41) and nitrous oxide + fluoromethane (N2O + R41), was measured down to temperatures of 126.5 K. To confirm the reliability of the apparatus, the triple points of the pure fluids constituent of the binary systems were measured. All triple-point data measured revealed a generally good consistency with the literature. The results obtained for the mixtures were corrected by the Rossini method and interpreted by means of the Schröder equation. © 2010 American Chemical Society

Identification of UNIQUAC binary interaction parameters in liquid-liquid equilibrium

An algorithm is presented for the estimation of the UNIQUAC interaction parameters for liquid-liquid equilibrium of ternary systems. The algorithm is based on two optimization levels. In the inner level the algorithm performs the minimization of an objective function based on the isoactivity conditions. The outer level aims to minimize the error between calculated and experimental compositions. The Common Tangent Plane condition is checked at the end to guarantee a thermodynamically consistent representation of the phase behavior of ternary liquid systems. The algorithm is challenged with a historical Type 1 ternary liquid-liquid equilibrium system from the seminal study of Anderson and Prausnitz in which the authors showed the limitations of the original UNIQUAC model and justified its amendment in the modified UNIQUAC model. The present algorithm makes available single temperature and temperature-dependent interaction parameters enabling accurate and thermodynamically correct description of the experimental data with the original UNIQUAC model, therefore without the need of any model modification. This outcome does not change when the interaction parameters from the binary partially miscible constituent pair are first regressed and kept constant during the estimation of the remaining parameters on ternary equilibrium data. This investigation confirms that a model cannot be judged if the correctness of the model parameters has not been proved first

A CFD-based virtual test-rig for rotating heat exchangers

Rotating heat exchangers are used in steel industry, air conditioning and thermal power plants to pre-heat air used in steam generators or for waste heat recovery. Here we focus on a rotating heat exchanger on a so-called Ljungström arrangement operated in thermal power plants to pre-heat the air fed to the steam generators. In these devices the heat exchange between two fluids is achieved through a rotating matrix that gets in contact alternatively with the two fluid streams and acts as a thermal accumulator. To increase the heat capacity and the overall exchange surface, the rotating matrix is filled by a series of folded metal sheets. In the paper we de-scribe a methodology to account for the effects of the Ljungström in a virtual test-rig implemented in a Computational Fluid Dynamics environment. To this aim, a numerical model based on the work of Molinari and Cantiano was derived and implemented in the OpenFOAM library. RANS numerical results were compared with those of a mono-dimensional tool used by ENEL to design Ljungström heat exchangers and validated against available measurements in a real configuration of a thermal power plant

R&D ALLIANCE PARTNER ATTRIBUTES AND INNOVATION PERFORMANCE: A FUZZY SET QUALITATIVE COMPARATIVE ANALYSIS

Because R&D alliances are important means for fostering firm innovation performance, research has investigated their key drivers. However, multiple configurations of R&D alliance drivers may lead to firm innovation performance. Drawing upon the knowledge-based view of alliances, we investigate configurations of R&D alliance factors leading to high innovation performance in allied firms by focusing on partner attributes (i.e., technological relatedness, competitive overlap, experience, relative size). Then, using a fuzzy set qualitative comparative analysis, we dissect the configurations of these factors in 27 R&D alliances formed by 54 telecom firms worldwide. We find that good R&D alliance partners are technologically related competitors with no experience in forming R&D alliances. Alternatively, competitors can achieve high innovation performance when they have experience in doing R&D alliances and are not technologically related. Drawing on these findings, we submit a set of propositions with relevant implications for the knowledge-based view of alliances and coopetition research

Spontaneous Opinion Swings in the Voter Model with Latency

The cognitive process of opinion formation is often characterized by stubbornness or resistance of agents to changes of opinion. To capture such a feature we introduce a constant latency time in the standard voter model of opinion dynamics: after switching opinion, an agent must keep it for a while. This seemingly simple modification drastically changes the stochastic diffusive behavior of the original model, leading to deterministic dynamical oscillations in the average opinion of the agents. We explain the origin of the oscillations and develop a mathematical formulation of the dynamics that is confirmed by extensive numerical simulations. We further characterize the rich phase space of the model and its asymptotic behavior. Our work offers insights into understanding and modeling opinion swings in diverse social contexts

Erythropoietin: Recent Developments in the Treatment of Spinal Cord Injury

Erythropoietin (EPO), originally identified for its critical function in regulating production and survival of erythrocytes, is a member of the type 1 cytokine superfamily. Recent studies have shown that EPO has cytoprotective effects in a wide variety of cells and tissues. Here is presented the analysis of EPO effects on spinal cord injury (SCI), considering both animal experiments concerning to mechanisms of neurodegeneration in SCI and EPO as a neuroprotective agent, and some evidences coming from ongoing clinical trials. The evidences underling that EPO could be a promising therapeutic agent in a variety of neurological insults, including trauma, are mounting. In particular, it is highlighted that administration of EPO or other recently generated EPO analogues such as asialo-EPO and carbamylated-EPO demonstrate interesting preclinical and clinical characteristics, rendering the evaluation of these tissue-protective agents imperative in human clinical trials. Moreover the demonstration of rhEPO and its analogues' broad neuroprotective effects in animal models of cord lesion and in human trial like stroke, should encourage scientists and clinicians to design clinical trials assessing the efficacy of these pharmacological compounds on SCI