250 research outputs found

    Quantum phase transitional patterns in the SD-pair shell model

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    Patterns of shape-phase transition in the proton-neutron coupled systems are studied within the SDSD-pair shell model. The results show that some transitional patterns in the SDSD-pair shell model are similar to the U(5)−SU(3)U(5)-SU(3), U(5)−SO(6)U(5)-SO(6) transitions with signatures of the critical point symmetry of the interacting boson model.Comment: 13 pages, 7 figure

    Experimental Research and Theoretical Analysis on Throttling Characteristics of Electronic Expansion Valve in Series with Capillary Tube

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    The mass flow rate of R-32 and volumetric flow rate of dry air in an electronic expansion valves(EEV) , in two different capillary tubes(CT) and in one expansion valve in series with two different capillary tubes were tested, and the theoretical volumetric flow rate of dry air in one EEV in series with different CTs were predicted through a theoretical throttling model built in this paper. The results showed that the mass flow rate of R-32 or volumetric flow rate of dry air of the serial throttling component was lower than but close to that of the EEV in low openings and that of the CT in full opening, respectively, under the same operating conditions. The flow rate ratio of the serial throttling component to the EEV decreased fast with opening increasing, and the flow rate ratio of the refrigerant was obviously lower than that of the dry air. The refrigerant mass flow rate of EEV in series with CT up flow was higher than that of the same EEV in series with the same CT down flow

    Dynamic Investigation of Thermal Behavior in a Hot Water Storage Tank

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    Air Source Heat Pump Water Heater is an environmental –friendly technology with high efficiency. The thermal behavior of water in the storage tank has great importance for designing a more energy-saving control strategy. In this study, the time-dependent temperature distributions during typical transient processes including heating up and tapping processes are studied with a 3D CFD model of the water storage tank in a cyclic heat pump water heater. The simulated temperature profiles in the heating up period were in good agreement with the experimental results. Different initial conditions were tested in the heating up periods, and they had little influence on the final temperature profiles in a practical water tank. The influences of varied flow rates and supply water temperatures were studied in the tapping stages. The thermocline was shortened when the temperatures in the bottom were higher and the flow rates were larger. Finally, the possibility to calculate the flow rates from the temperature changes was discussed

    Experimental Investigation on R245fa Throttling Devices under High Temperature

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    The experiments on mass flow rate characteristics of R245fa refrigerant flowing through throttling devices including seven capillary tubes and the electronic expansion valve were carried out under the high-temperature working conditions. By combining data analysis with flow correlations, the design basis that is applicable to R245fa throttling devices can be obtained. By comparing the experimental mass flow rate with that predicted by Jung Correlation and Kim Correlation, it can be concluded that root mean square deviations of two correlations are 3.2 % and 3.3%, respectively. The root mean square deviation for electronic expansion valve is 4.5%. The conclusions offer high-accuracy design basis for throttling devices selection of high-temperature heat pump systems using R245fa as refrigerant

    High channel count and high precision channel spacing multi-wavelength laser array for future PICs

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    Multi-wavelength semiconductor laser arrays (MLAs) have wide applications in wavelength multiplexing division (WDM) networks. In spite of their tremendous potential, adoption of the MLA has been hampered by a number of issues, particularly wavelength precision and fabrication cost. In this paper, we report high channel count MLAs in which the wavelengths of each channel can be determined precisely through low-cost standard μm-level photolithography/holographic lithography and the reconstruction-equivalent-chirp (REC) technique. 60-wavelength MLAs with good wavelength spacing uniformity have been demonstrated experimentally, in which nearly 83% lasers are within a wavelength deviation of ±0.20 nm, corresponding to a tolerance of ±0.032 nm in the period pitch. As a result of employing the equivalent phase shift technique, the single longitudinal mode (SLM) yield is nearly 100%, while the theoretical yield of standard DFB lasers is only around 33.3%

    Randomized clinical trial comparing abluminal biodegradable polymer sirolimus-eluting stents with durable polymer sirolimus-eluting stents: Nine months angiographic and 5-year clinical outcomes

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    Background: The biodegradable polymer drug-eluting stents (DES) were developed to improve vascular healing. However, further data and longer-term follow-up are needed to confirm safety and efficacy of these stents. This randomized clinical trial aimed to compare safety and efficacy of 2 sirolimus-eluting stents (SES): Cordimax—a novel abluminal biodegradable polymer SES and Cypher Select—a durable polymer SES, at 9 months angiographic and 5-year clinical follow-up. Methods: We randomized 402 patients with coronary artery disease to percutaneous coronary intervention with Cordimax (n = 202) or Cypher select (n = 200). Angiographic follow-up was performed at 9 months after the index procedure and clinical follow-up annually up to 5 years. The primary endpoint was angiographic in-stent late luminal loss (LLL). Secondary endpoints included angiographic restenosis rate, target vessel revascularization (TVR), and major adverse cardiac events (MACEs; defined as cardiac death, myocardial infarction, or TVR) at 5-year follow-up. Results: Cordimax was noninferior to Cypher select for in-stent LLL (0.25 ± 0.47 vs 0.18 ± 0.49 mm; P = 0.587) and in-stent mean diameter stenosis (22.19 ± 12.21% vs 19.89 ± 10.79%; P = 0.064) at 9 months angiographic follow-up. The MACE rates were not different at 1 year (5.9% vs 4.0%, P = 0.376); however, MACE rates from 2 to 5 years were lower in the Cordimax group (6.8% vs 13.1%; P = 0.039). Conclusion: Abluminal biodegradable polymer SES is noninferior to durable polymer SES at 9-month angiographic and 1-year clinical follow-up. However, MACE rates from 2 to 5 years were less in the abluminal biodegradable polymer group.National Key Technology Research and Development Program in the Twelfth Five-year Plan Period of China (No. 2014BAI11B04)

    Intravenous pretreatment with emulsified isoflurane preconditioning protects kidneys against ischemia/reperfusion injury in rats

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    Ordinal logistic regression models have been developed for analysis of epidemiological studies. However, the adequacy of such models for adjustment has so far received little attention. In this article, we reviewed the most important ordinal regression models and common approaches used to verify goodness-of-fit, using R or Stata programs. We performed formal and graphical analyses to compare ordinal models using data sets on health conditions from the National Health and Nutrition Examination Survey (NHANES II).Los modelos de regresión logística ordinal vienen aplicándose con éxito en el análisis de estudios epidemiológicos. Sin embargo, la verificación de la adecuación de cada modelo ha recibido atención limitada. El artículo presenta un breve análisis de los principales modelos de regresión logística ordinal y las estrategias para ajustes, las técnicas de verificación de calidad de ajuste, así como los comandos para ejecución en los softwares R y Stata. La metodología es ilustrada con la aplicación de los datos del Second Nacional Health and Nutrition Examination Survey (NHANES II), el conocido análisis de salud y nutrición.Os modelos de regressão logística ordinal vêm sendo aplicados com sucesso na análise de estudos epidemiológicos. Entretanto, a verificação da adequação de cada modelo tem recebido atenção limitada. O artigo apresenta uma breve análise dos principais modelos de regressão logística ordinal e as estratégias para ajuste s, as técnicas de verificação de qualidade do ajuste, bem como os comandos para execução nos softwares R e Stata. A metodologia é ilustrada com aplicação dos dados do Second National Health and Nutrition Examination Survey (NHANES II), o conhecido levantamento de saúde e nutrição

    Constructing high-order functional connectivity network based on central moment features for diagnosis of autism spectrum disorder

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    The sliding-window-based dynamic functional connectivity network (D-FCN) has been becoming an increasingly useful tool for understanding the changes of brain connectivity patterns and the association of neurological diseases with these dynamic variations. However, conventional D-FCN is essentially low-order network, which only reflects the pairwise interaction pattern between brain regions and thus overlooking the high-order interactions among multiple brain regions. In addition, D-FCN is innate with temporal sensitivity issue, i.e., D-FCN is sensitive to the chronological order of its subnetworks. To deal with the above issues, we propose a novel high-order functional connectivity network framework based on the central moment feature of D-FCN. Specifically, we firstly adopt a central moment approach to extract multiple central moment feature matrices from D-FCN. Furthermore, we regard the matrices as the profiles to build multiple high-order functional connectivity networks which further capture the higher level and more complex interaction relationships among multiple brain regions. Finally, we use the voting strategy to combine the high-order networks with D-FCN for autism spectrum disorder diagnosis. Experimental results show that the combination of multiple functional connectivity networks achieves accuracy of 88.06%, and the best single network achieves accuracy of 79.5%

    Heat Transfer Correlations for Supercritical Water in Vertically Upward Tubes

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    Supercritical pressure water (SCW) has been widely used in many engineering fields and industries, such as fossil fuel-fired power plants, newly developed Gen-IV nuclear power plants and so forth. Heat transfer characteristics of SCW are of great importance for both design and safe operation of the related systems. Many heat transfer correlations have been developed in the history for predicting the heat transfer characteristics of SCW. However, the prediction accuracy of the existing correlations is less than satisfactory, especially in the cases with deteriorated heat transfer (DHT) because of the severe and quick variation in thermal physical properties of SCW in the vicinity of the fluids’ pseudo critical point. It is very necessary to develop new correlations for the heat transfer of SCW to meet the engineering requirements for satisfactory prediction of the heat transfer behavior of SCW. In this chapter, experimental data on heat transfer of SCW are extensively collected from published literatures, and the performance of the existing heat transfer correlations for SCW are reviewed and quantitatively evaluated against the collected experimental data, and then a new heat transfer correlation for SCW with high prediction accuracy is proposed

    Mechanistic Features in Al(I)-Mediated Oxidative Addition of Aryl C-F Bonds: Insights From Density Functional Theory Calculations.

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    The oxidative addition of a range of robust aryl C-F bonds to a single Al(I) center supported by a (NacNac)- bidentate ligand ((NacNac)- = [ArNC(Me)CHC(Me)NAr]- and Ar = 2,6- Pr 2 i C6H3) have been explored by density functional theory calculations. Our calculations demonstrate that the Al(I) center-mediated C-F insertion generally proceeds via the concerted mechanism that involve both the donation ( n Al → σ C - F * ) and back-donation ( σ F ( p ) → π Al ( p ) * ) interactions. In addition, the predicted free energy barriers for the C-F bond activation show good agreement with the experimental information available. Finally, the comparative studies show that B(I) is the most active among group III metals (B, Al, Ga), thus supplying a testable prediction for experiments
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