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The pulsation modes of the pre-white dwarf PG 1159-035
Costa, J. E. S.,Kepler, S. O.,Winget, D. E.,O'Brien, M. S.,Kawaler, S. D.,Costa, A. F. M.,Giovannini, O.,Kanaan, A.,Mukadam, A. S.,Mullally, F.,Nitta, A.,Provenç,al, J. L.,Shipman, H.,Wood, M. A EDP Sciences 2008 Astronomy and astrophysics Vol.477 No.2
Reed, M. D.,Harms, S. L.,Poindexter, S.,Zhou, A.‐,Y.,Eggen, J. R.,Morris, M. A.,Quint, A. C.,McDaniel, S.,Baran, A.,Dolez, N.,Kawaler, S. D.,Kurtz, D. W.,Moskalik, P.,Riddle, R.,Zola, S.,Østense Blackwell Publishing Ltd 2011 Monthly notices of the Royal Astronomical Society Vol.412 No.1
<P><B>ABSTRACT</B></P><P>KPD 1930+2752 is a short‐period pulsating subdwarf B (sdB) star. It is also an ellipsoidal variable with a known binary period of 2.3 h. The companion is most likely a white dwarf and the total mass of the system is close to the Chandresekhar limit. In this paper, we report the results of Whole Earth Telescope (WET) photometric observations during 2003 and a smaller multisite campaign of 2002. From 355 h of WET data, we detect 68 pulsation frequencies and suggest an additional 13 frequencies within a crowded and complex temporal spectrum between 3065 and 6343 μHz (periods between 326 and 157 s). We examine pulsation properties including phase and amplitude stability in an attempt to understand the nature of the pulsation mechanism. We examine a stochastic mechanism by comparing amplitude variations with simulated stochastic data. We also use the binary nature of KPD 1930+2752 for identifying pulsation modes via multiplet structure and a tidally induced pulsation geometry. Our results indicate a complicated pulsation structure that includes short‐period (≈16 h) amplitude variability, rotationally split modes, tidally induced modes and some pulsations which are geometrically limited on the sdB star.</P>
Experimental Study of Domestic Refrigerator Performance Improvement with Evaporative Condenser
Kawal Preet Singh Khalsa,Sayan Sadhu 대한설비공학회 2021 International Journal Of Air-Conditioning and Refr Vol.29 No.2
Evaporation of defrosted water in household refrigerators and condenser waste heat utilization has been reported by many researchers but limited literature is available on the study of evaporative cooling in domestic refrigerators (condenser waste heat utilization for defrost water evaporation) with helical coil heat exchangers. This paper is concerned with evaluating domestic refrigerator performance by employing an evaporative helical coil heat exchanger before hot wall condenser which is utilized for evaporation of defrost water and reducing the superheated refrigerant temperature to condensing temperature to reduce the condenser load and improve the overall performance of a domestic refrigerator. Results show that evaporative cooling increases COP of the system by 25.3%, reduces the energy consumption of the refrigerator by 7.3% and the compressor run time by 10.6%. These experimental results also revealed that using two different thermal conductivity tube materials for evaporative helical coil condenser (Copper tube and Zinc coated steel tube) provided with less wall thickness (0.2mm) PVC coating results in good agreement for the same evaporation rate of defrosted water.
Se-Jun Yim,Ki-Won Gyak,Sanket A. Kawale,Amirreza Mottafegh,Chae-Hyeon Park,Yoonseok Ko,In Kim,Sang Soo Jee,Dong-Pyo Kim 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.123 No.-
As semiconductor technology becomes rapidly advanced, semiconductor packaging materials demandcritical characteristics in various aspects. Besides, the development of these new epoxy mold compounds(EMC) by batch reaction process requires time-consuming experimentation and the multi-step chemistryfurther reduces the efficiency of the synthetic process. We report a one-flow multi-step process for thesynthesis of newly developed Np-C4-Np, which comprises two mesogenic units connected with a flexiblespacer, as a monomeric precursor of semiconductor packaging material. Graphical convolution neuralnetwork (GCNN), a deep learning model, predicts a common solvent for three-step reactions, therebyenabling serial esterification-deprotection-epoxidation integrated with in-situ multi-phasic separationsthat were accomplished within 76 min in flow over the long batch process (>20 h excluding separationstep). Eventually, the Np-C4-Np is synthesized rapidly with higher space–time yield compared to thebatch system, thus confirming benefits in terms of productivity. Moreover, we prevent the deteriorationof electronic circuits during the semiconductor packaging process by lowering the molding temperature(126 C) of EMC and quickly dissipating the heat generated from semiconductor chip by increasing thethermal conductivity (0.34 W m1 K1) of EMC.