Compact Indexes Based on Core Content in Personal Dataspace Management System

A Personal DataSpace Management System is a platform to manage personal data with heterogeneous data types, in which keyword query is a primary query form for users who know little about the structure of the dataspace. Unlike exploratory queries in web search, a user in a personal dataspace usually has a specific search target and wants to find some known items in mind. To improve result quality in terms of query relevance in a personal dataspace, we propose the concept of compact index in this paper. We refer to the most important and representative semantics from documents as core content, and build compact index on it. We propose algorithm for selecting core content from a document based on semantic analysis, which can process English and Chinese documents uniformly. Furthermore, a software platform named Versatile is introduced for flexible personal data management, in which core content is extracted for building compact indexes and generating query-biased snippet efficiently and accurately. Finally, extensive experiments have been conducted to show the effectiveness and feasibility of compact indexes in personal dataspace management system

Editorial: CO 2 -based energy systems for cooling, heating, and power

© 2022 Li, Su, Xu, Dai, Li and Li. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). https://creativecommons.org/licenses/by/4.0/Peer reviewe

Method to delay frost formation under high relative humidity by choosing proper heat exchange temperature difference and air velocity

To delay frost formation and maintain high heat transfer capacity of an evaporator, a closed-loop wind tunnel was designed and constructed to investigate the effect of heat exchange temperature difference (ΔT) and air velocity on frost formation characteristics, refrigerating capacity and water removal of air. The closed-loop wind tunnel provided flowing air at temperature of −18 °C, relative humidity of 85% and velocity from 2 to 5 m/s. During experiment, three obvious stages of frost thickness were found when air initial velocity was 3–5 m/s. With ΔT changing from 7 to 3 °C, the water removal of air through the evaporator decreased by 3–5 times and the high efficient operation time ratio (HETR) increased by 2–3 times. Meanwhile, the average frost mass reduced by about half at any fixed air velocity. When ΔT was 7 °C and air velocity was 2 m/s, the average refrigerating capacity was almost equal to that when ΔT was 3 °C and air velocity was 5 m/s. The combined results showed that smaller ΔT and larger air velocity was useful to forbid frost formation, and to maintain stable high refrigerating capacity and relative humidity

Impacts on the solidification of water on plate surface for cold energy storage using ice slurry

Ice slurry has been widely used for thermal energy storage system due to its high cold energy storage capacity. To effectively improve the efficiency of ice slurry generator, it is essential to have a deeper understanding about the solidification mechanism on the plate surface of ice generator, which is affected by many factors, such as the roughness of surface and the apparent contact angle. This work studies the impacts of roughness and inhibitor concentration on the freezing temperature, subcooling and the heterogeneous nucleation energy at the surface of aluminum, copper and Teflon plates. Results show that both the roughness and the inhibitor concentration can clearly affect the freezing temperature of water droplet and the heterogeneous nucleation energy. In general, the freezing temperature rises and the subcooling and the heterogeneous nucleation energy drop as the surface roughness increases for all studied materials; and the heterogeneous nucleation energy also increases with the increase of inhibitor concentration. Since the heterogeneous nucleation energy is mainly determined by the substance and the roughness, while not by the surface material, it is important to increase the roughness in order to reduce subcooling and save energy, especially for copper and aluminum

Numerical Study of Fin-and-Tube Heat Exchanger in Low-Pressure Environment: Air-Side Heat Transfer and Frictional Performance, Entropy Generation Analysis, and Model Development

Heat transfer and frictional performance at the air-side is predominant for the application and optimization of finned tube heat exchangers. For aerospace engineering, the heat exchanger operates under negative pressure, whereas the general prediction models of convective heat transfer coefficient and pressure penalty for this scenario are rarely reported. In the current study, a numerical model is developed to determine the air-side heat transfer and frictional performance. The influence of air pressure (absolute pressure) is discussed in detail, and the entropy generation considering the effect of heat transfer and pressure drop are analyzed. Furthermore, prediction models of air-side thermal and frictional factors are also developed. The results indicate that both the convective heat transfer coefficient and pressure penalty decrease significantly with decreasing air pressure, and the air-side heat transfer coefficient is decreased by 64.6~73.3% at an air pressure of 25 kPa compared with normal environment pressure. The entropy generation by temperature difference accounts for the highest proportion of the total entropy generation. The prediction correlations of Colburn j-factor and friction factor f show satisfactory accuracy with the absolute mean deviations of 7.48% and 9.42%, respectively. This study can provide a reference for the practical application of fined tube heat exchangers under a negative pressure environment

Electric-field control of magnetic anisotropy in Fe81Ga19/BaTiO3 heterostructure films

We investigate the control of magnetism with an electric field in Fe81Ga19(FeGa)/BaTiO3(BTO) heterostructure films. The as-prepared FeGa/BTO samples present a uniaxial magnetic anisotropy, which is ascribed to be induced by the spontaneous ferroelectric polarization of the BTO substrates. With the electric field applied on the BTO substrates increasing from 0 to 6 kV/cm, the coercivity of FeGa films measured along the BTO[110] direction increases from 28 to 41 Oe, while the squareness of the hysteresis loop decreases from 0.99 to 0.31, which indicates that the easy and hard axes of FeGa films are swapped. The ferroelectric domains of BTO substrates and the magnetic domains of FeGa films exhibit the same dependence on the applied electric fields, manifesting the strong magnetoelectric coupling between the ferroelectricity of BTO substrates and the magnetism of FeGa films

Static and high frequency magnetic properties of FeGa thin films deposited on convex flexible substrates

Magnetostrictive FeGa thin films were deposited on the bowed flexible polyethylene terephthalate (PET) substrates, which were fixed on the convex mold. A compressive stress was induced in FeGa films when the PET substrates were shaped from convex to flat. Due to the effect of magnetostriction, FeGa films exhibit an obvious in-plane uniaxial magnetic anisotropy which could be enhanced by increasing the applied pre-strains on the substrates during growth. Consequently, the ferromagnetic resonance frequency of the films was significantly increased, but the corresponding initial permeability was decreased. Moreover, the films with pre-strains less than 0.78% exhibit a working bandwidth of microwave absorption about 2 GHz. Our investigations demonstrated a convenient method via the pre-strained substrates to tune the high frequency properties of magnetic thin films which could be applied in flexible microwave devices. (C) 2015 AIP Publishing LLC